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Sample records for dynamic weight bearing

  1. Dynamic weight-bearing assessment of pain in knee osteoarthritis

    DEFF Research Database (Denmark)

    Klokker, Louise; Christensen, Robin; Osborne, Richard

    2015-01-01

    PURPOSE: To evaluate the reliability, agreement and smallest detectable change in a measurement instrument for pain and function in knee osteoarthritis; the Dynamic weight-bearing Assessment of Pain (DAP). METHODS: The sample size was set to 20 persons, recruited from the outpatient osteoarthritis...

  2. Dynamic weight-bearing assessment of pain in knee osteoarthritis

    DEFF Research Database (Denmark)

    Klokker, Louise; Christensen, Robin; Wæhrens, Eva Elisabet Ejlersen

    2016-01-01

    BACKGROUND: The Osteoarthritis Research Society International (OARSI) has suggested to asses pain after specific activities consistently in clinical trials on knee OA. The Dynamic weight-bearing Assessment of Pain (DAP) assesses pain during activity (30 s of performing repeated deep knee-bends from...

  3. Dynamic weight-bearing assessment of pain in knee osteoarthritis

    DEFF Research Database (Denmark)

    Klokker, Louise; Christensen, Robin; Wæhrens, Eva E;

    2016-01-01

    BACKGROUND: The Osteoarthritis Research Society International (OARSI) has suggested to asses pain after specific activities consistently in clinical trials on knee OA. The Dynamic weight-bearing Assessment of Pain (DAP) assesses pain during activity (30 s of performing repeated deep knee-bends fr....... A change of 2.4 or more can be interpreted as clinically relevant. The DAP is a promising alternative to using 'pain on walking' as a clinical trial inclusion criterion/outcome....

  4. Upright, weight-bearing, dynamic-kinetic MRI of the spine: initial results.

    Science.gov (United States)

    Jinkins, J Randy; Dworkin, Jay S; Damadian, Raymond V

    2005-09-01

    The potential relative beneficial aspects of upright, weight-bearing (pMRI), dynamic-kinetic (kMRI) spinal imaging over that of recumbent MRI (rMRI) include the revelation of occult spinal disease dependent on true axial loading, the unmasking of kinetic-dependent spinal disease and the ability to scan the patient in the position of clinically relevant signs and symptoms. This imaging unit under study also demonstrated low claustrophobic potential and yielded comparatively high resolution images with little motion/magnetic susceptibility/chemical shift artifact. Overall, it was found that rMRI underestimated the presence and maximum degree of gravity-dependent spinal pathology and missed altogether pathology of a dynamic nature, factors that are optimally revealed with p/kMRI. Furthermore, p/kMRI enabled optimal linkage of the patient's clinical syndrome with the medical imaging abnormality responsible for the clinical presentation, thereby allowing for the first time an improvement at once in both imaging sensitivity and specificity.

  5. Upright, weight-bearing, dynamic-kinetic MRI of the spine: initial results

    Energy Technology Data Exchange (ETDEWEB)

    Jinkins, J. Randy [State University of New York, Department of Radiology, Downstate Medical Center, Brooklyn, NY (United States); Fonar Corporation, Melville, NY (United States); Dworkin, Jay S.; Damadian, Raymond V. [Fonar Corporation, Melville, NY (United States)

    2005-09-01

    The potential relative beneficial aspects of upright, weight-bearing (pMRI), dynamic-kinetic (kMRI) spinal imaging over that of recumbent MRI (rMRI) include the revelation of occult spinal disease dependent on true axial loading, the unmasking of kinetic-dependent spinal disease and the ability to scan the patient in the position of clinically relevant signs and symptoms. This imaging unit under study also demonstrated low claustrophobic potential and yielded comparatively high resolution images with little motion/magnetic susceptibility/chemical shift artifact. Overall, it was found that rMRI underestimated the presence and maximum degree of gravity-dependent spinal pathology and missed altogether pathology of a dynamic nature, factors that are optimally revealed with p/kMRI. Furthermore, p/kMRI enabled optimal linkage of the patient's clinical syndrome with the medical imaging abnormality responsible for the clinical presentation, thereby allowing for the first time an improvement at once in both imaging sensitivity and specificity. (orig.)

  6. Effects of auditory feedback during gait training on hemiplegic patients' weight bearing and dynamic balance ability.

    Science.gov (United States)

    Ki, Kyong-Il; Kim, Mi-Sun; Moon, Young; Choi, Jong-Duk

    2015-04-01

    [Purpose] This study examined the effects of auditory feedback during gait on the weight bearing of patients with hemiplegia resulting from a stroke. [Subjects] Thirty hemiplegic patients participated in this experiment and they were randomly allocated to an experimental group and a control group. [Methods] Both groups received neuro-developmental treatment for four weeks and the experimental group additionally received auditory feedback during gait training. In order to examine auditory feedback effects on weight bearing during gait, a motion analysis system GAITRite was used to measure the duration of the stance phase and single limb stance phase of the subjects. [Results] The experimental group showed statistically significant improvements in the duration of the stance phase and single limb stance phase of the paretic side and the results of the Timed Up and Go Test after the training. [Conclusion] Auditory feedback during gait training significantly improved the duration of the stance phase and single limb stance phase of hemiplegic stroke patients.

  7. Gait Measures and Dynamic Weight bearing in Young and Elder Trans-tibal Amputee using PTB Prosthesis with SACH foot

    Directory of Open Access Journals (Sweden)

    Prasanna K. Lenka

    2008-12-01

    Full Text Available Objective: to investigate the changes associated with age in gait characteristics and dynamic weight bearing pattern of sound and prosthetic limb of persons with unilateral amputation. Participant: two groups of seven young (24±3.8 years and seven elderly unilateral amputee (71±6 years were selected for this study. Setting: both groups walked at their self selected speed over a 20 second duration plane surface walk way in trans-tibial prosthesis with PTB socket and SACH foot. The raw data of force and EMG sensors of gait analyzer were filtered, processed and analyzed with help of ‘matlab 7.0. A blue tooth enabled heart rate telemetry system was used for calculating gait efficiency in terms of physiological cost index (PCI. Results: significant differences were found in stride duration, (p=0.003, step duration sound limb (p<0.002, stance duration sound limb (p=0.002, stance duration prosthetic limb (p=0.006 and cadence (p=0.001<0.05, however no difference was found in EMG pattern of vastus lateralis between the two groups. The dynamic weight distribution showed more normalized load on anterior parts of heel and minimum load at calcaneal max in elderly group. The results of vertical ground reaction force found the prosthetic side of elderly group takes more weight than young group during loading response. In comparison, PCI was observed to be greater in case of elderly group. Conclusion: most of difference between two groups could be explained by speed variations and biomechanical limitation of ankle joint due to natural aging process.

  8. Weight-bearing recommendations after operative fracture treatment-fact or fiction? Gait results with and feasibility of a dynamic, continuous pedobarography insole.

    Science.gov (United States)

    Braun, Benedikt J; Veith, Nils T; Rollmann, Mika; Orth, Marcel; Fritz, Tobias; Herath, Steven C; Holstein, Jörg H; Pohlemann, Tim

    2017-08-01

    Rehabilitation after lower-extremity fractures is based on the physicians' recommendation for non-, partial-, or full weight-bearing. Clinical studies rely on this assumption, but continuous compliance or objective loading rates are unknown. The purpose of this study was to determine the compliance to weight-bearing recommendations by introducing a novel, pedobarography system continuously registering postoperative ground forces into ankle, tibial shaft and proximal femur fracture aftercare and test its feasibility for this purpose. In this prospective, observational study, a continuously measuring pedobarography insole was placed in the patients shoe during the immediate post-operative aftercare after ankle, tibial shaft and intertrochanteric femur fractures. Weight-bearing was ordered as per the institutional standard and controlled by physical therapy. The insole was retrieved after a maximum of six weeks (28 days [range 5-42 days]). Non-compliance was defined as a failure to maintain, or reach the ordered weight-bearing within 30%. Overall 30 patients were included in the study. Fourteen (47%) of the patients were compliant to the weight-bearing recommendations. Within two weeks after surgery patients deviated from the recommendation by over 50%. Sex, age and weight did not influence the performance (p > 0.05). Ankle fracture patients (partial weight-bearing) showed a significantly increased deviation from the recommendation (p = 0.01). Our study results show that, despite physical therapy training, weight-bearing compliance to recommended limits was low. Adherence to the partial weight-bearing task was further decreased over time. Uncontrolled weight-bearing recommendations should thus be viewed with caution and carefully considered as fiction. The presented insole is feasible to determine weight bearing continuously, could immediately help define real-time patient behaviour and establish realistic, individual weight-bearing recommendations.

  9. LIGHT-WEIGHT LOAD-BEARING STRUCTURE

    DEFF Research Database (Denmark)

    2009-01-01

    The invention relates to a light-weight load-bearing structure (1) with optimized compression zone (2), where along one or more compression zones (2) in the structure (1) to be cast a core (3) of strong concrete is provided, which core (3) is surrounded by concrete of less strength (4) compared...... to the core (3) of strong concrete. The invention also relates to a method of casting of light-weight load-bearing structures (1) with optimized compression zone (2) where one or more channels, grooves, ducts, pipes and/or hoses (5) formed in the load-bearing structure (1) serves as moulds for moulding one...... or more cores (3) of strong concrete in the light-weight load-bearing structure (1)....

  10. Dynamic measurement of patello-femoral joint alignment using weight-bearing magnetic resonance imaging (WB-MRI).

    Science.gov (United States)

    Mariani, Silvia; La Marra, Alice; Arrigoni, Francesco; Necozione, Stefano; Splendiani, Alessandra; Di Cesare, Ernesto; Barile, Antonio; Masciocchi, Carlo

    2015-12-01

    Aim of our work was to compare standard and weight-bearing WB-MRI to define their contribution in unmasking patello-femoral (PF) maltracking and to define what measurement of patellar alignment is the most reliable. We prospectively collected 95 non consecutive patients, clinically divided into 2 groups: group A (the control group), including 20 patients (negative for patellar maltracking), and group B including 75 patients (positive for patellar maltracking). The patients underwent a dedicated 0.25 T MRI, in supine and WB position, with knee flexion of 12-15°. The following measurements were performed: Insall-Salvati index (IS), lateral patellar displacement (LPD), lateral patello-femoral angle (LPA) and lateral patellar tilt (LPT). Quantitative and qualitative statistical analyses were performed to compare the results obtained before and after WB-MRI. Measurements were subsequently performed on both groups. Group A patients showed no statistically significant variations at all measurements both on standard and WB-MRI. On the basis of measurements made on standard MRI, group B patients were divided into group B1 (23 patients) (negative or positive at 1 measurement) and group B2 (52 patients) (positive at 2 or more measurements). After WB-MRI, group B1 patients were divided into group B1a (6 patients), in case they remained positive at 0/1 measurement, and group B1b (17 patients), in case they became positive at 2 or more measurements. All group B2 patients confirmed to be positive at 2 or more measurements at WB-MRI. Quantitative statistical analysis showed that LPT and LPA were the most reproducible and clinically useful measurements. Qualitative statistical analysis performed on standard and WB-MRI demonstrated that LPT was the best predictive measurement. This study demonstrates both the high diagnostic value of WB-MRI in unmasking PF-maltracking and the best predictive value of LPT measurement. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  11. The effects of dynamic ankle-foot orthoses on functional ambulation activities, weight bearing and spatio-temporal characteristics of hemiparetic gait.

    Science.gov (United States)

    Suat, Erel; Fatma, Uygur; Nilgün, Bek

    2011-01-01

    To investigate the effects of dynamic ankle-foot orthoses (DAFOs) on functional ambulation activities, weight bearing and spatio-temporal characteristics of hemiparetic gait and to inquire whether wearing a DAFO for 3 months has a carryover effect. Fourteen chronic hemiparetic patients who could walk independently with or without a cane were the subjects of the study. Patients were assessed initially with tennis shoes and were given custom fabricated DAFOs which they wore for three months and were retested under two conditions: with tennis shoes only and with DAFOs worn in these shoes. All patients were assessed for weight bearing percentage of the affected side, cadence, step length of the involved and uninvolved sides, step width, functional reach, timed up and go, timed down stairs, timed up stairs, physiologic cost index and velocity. Comparison of initial and third month assessments with shoes only condition showed that there was no significant improvement for the measured parameters. When comparison was made at the third month while patients were wearing tennis shoes only and when they were wearing DAFO's in their shoes there was a significant difference in favour of the condition where patients were wearing DAFOs. The benefits of using DAFOs in chronic hemiparetic patients are lost when the patients are not wearing their orthoses.

  12. Hypolocomotion, asymmetrically directed behaviors (licking, lifting, flinching, and shaking and dynamic weight bearing (gait changes are not measures of neuropathic pain in mice

    Directory of Open Access Journals (Sweden)

    Schorscher-Petcu Ara

    2010-06-01

    Full Text Available Abstract Background Spontaneous (non-evoked pain is a major clinical symptom of neuropathic syndromes, one that is understudied in basic pain research for practical reasons and because of a lack of consensus over precisely which behaviors reflect spontaneous pain in laboratory animals. It is commonly asserted that rodents experiencing pain in a hind limb exhibit hypolocomotion and decreased rearing, engage in both reflexive and organized limb directed behaviors, and avoid supporting their body weight on the affected side. Furthermore, it is assumed that the extent of these positive or negative behaviors can be used as a dependent measure of spontaneous chronic pain severity in such animals. In the present study, we tested these assumptions via blinded, systematic observation of digital video of mice with nerve injuries (chronic constriction or spared nerve injury, and automated assessment of locomotor behavior using photocell detection and dynamic weight bearing (i.e., gait using the CatWalk® system. Results We found no deficits in locomotor activity or rearing associated with neuropathic injury. The frequency of asymmetric (ipsilaterally directed behaviors were too rare to be seriously considered as representing spontaneous pain, and in any case did not statistically exceed what was blindly observed on the contralateral hind paw and in control (sham operated and unoperated mice. Changes in dynamic weight bearing, on the other hand, were robust and ipsilateral after spared nerve injury (but not chronic constriction injury. However, we observed timing, pharmacological, and genetic dissociation of mechanical allodynia and gait alterations. Conclusions We conclude that spontaneous neuropathic pain in mice cannot be assessed using any of these measures, and thus caution is warranted in making such assertions.

  13. Neuromuscular Fatigue and Tibiofemoral Joint Biomechanics When Transitioning From Non–Weight Bearing to Weight Bearing

    Science.gov (United States)

    Schmitz, Randy J.; Kim, Hyunsoo; Shultz, Sandra J.

    2015-01-01

    Context: Fatigue is suggested to be a risk factor for anterior cruciate ligament injury. Fatiguing exercise can affect neuromuscular control and laxity of the knee joint, which may render the knee less able to resist externally applied loads. Few authors have examined the effects of fatiguing exercise on knee biomechanics during the in vivo transition of the knee from non–weight bearing to weight bearing, the time when anterior cruciate ligament injury likely occurs. Objective: To investigate the effect of fatiguing exercise on tibiofemoral joint biomechanics during the transition from non–weight bearing to early weight bearing. Design: Cross-sectional study. Setting: Research laboratory. Patients or Other Participants: Ten participants (5 men and 5 women; age = 25.3 ± 4.0 years) with no previous history of knee-ligament injury to the dominant leg. Intervention(s): Participants were tested before (preexercise) and after (postexercise) a protocol consisting of repeated leg presses (15 repetitions from 10°–40° of knee flexion, 10 seconds' rest) against a 60% body-weight load until they were unable to complete a full bout of repetitions. Main Outcome Measure(s): Electromagnetic sensors measured anterior tibial translation and knee-flexion excursion during the application of a 40% body-weight axial compressive load to the bottom of the foot, simulating weight acceptance. A force transducer recorded axial compressive force. Results: The axial compressive force (351.8 ± 44.3 N versus 374.0 ± 47.9 N; P = .018), knee-flexion excursion (8.0° ± 4.0° versus 10.2° ± 3.7°; P = .046), and anterior tibial translation (6.7 ± 1.7 mm versus 8.2 ± 1.9 mm; P knee-joint stabilization during weight acceptance, leading to greater accessory motion at the knee and the potential for greater anterior cruciate ligament loading. PMID:25375932

  14. Neuromuscular fatigue and tibiofemoral joint biomechanics when transitioning from non-weight bearing to weight bearing.

    Science.gov (United States)

    Schmitz, Randy J; Kim, Hyunsoo; Shultz, Sandra J

    2015-01-01

    Fatigue is suggested to be a risk factor for anterior cruciate ligament injury. Fatiguing exercise can affect neuromuscular control and laxity of the knee joint, which may render the knee less able to resist externally applied loads. Few authors have examined the effects of fatiguing exercise on knee biomechanics during the in vivo transition of the knee from non-weight bearing to weight bearing, the time when anterior cruciate ligament injury likely occurs. To investigate the effect of fatiguing exercise on tibiofemoral joint biomechanics during the transition from non-weight bearing to early weight bearing. Cross-sectional study. Research laboratory. Ten participants (5 men and 5 women; age = 25.3 ± 4.0 years) with no previous history of knee-ligament injury to the dominant leg. Participants were tested before (preexercise) and after (postexercise) a protocol consisting of repeated leg presses (15 repetitions from 10°-40° of knee flexion, 10 seconds' rest) against a 60% body-weight load until they were unable to complete a full bout of repetitions. Electromagnetic sensors measured anterior tibial translation and knee-flexion excursion during the application of a 40% body-weight axial compressive load to the bottom of the foot, simulating weight acceptance. A force transducer recorded axial compressive force. The axial compressive force (351.8 ± 44.3 N versus 374.0 ± 47.9 N; P = .018), knee-flexion excursion (8.0° ± 4.0° versus 10.2° ± 3.7°; P = .046), and anterior tibial translation (6.7 ± 1.7 mm versus 8.2 ± 1.9 mm; P knee-joint stabilization during weight acceptance, leading to greater accessory motion at the knee and the potential for greater anterior cruciate ligament loading.

  15. Effect of Dynamic Platform Lateral Step-Up versus Stable Platform Lateral Step-Up Weight Bearing Exercise in Hip Abductor Strengthening on Healthy Male Volunteers - Randomized Clinical Trial

    Directory of Open Access Journals (Sweden)

    Jagatheesan Alagesan

    2011-07-01

    Full Text Available Objective & Background: To determine the effect of the dynamic platform lateral step-up and stable platform lateral step-up weight bearing standing exercise in strengthening of hip abductor. Many researchers have reported that strengthening of hip muscles as important component especially hip abductors in lower extremity rehabilitation program. Study Design: Single blinded randomized comparative clinical trial. Methodology: Sixty five healthy college going male subjects (Age group of 18 – 24 years volunteered for this study. They were randomly assigned to one of the 2 groups. One group received the dynamic platform lateral step-up and the other received stable platform lateral step-up weight bearing standing exercise. The strength measurements were recorded using hand held dynamometer. Results: The results indicate that both groups had a positive effect on the outcome measures. The strength of hip abductors in dynamic platform group improved from a mean value (SD of 19.47(3.59 to 26.93(3.19 and in stable platform group from 19.07(2.32 to 22.67(2.46. Significant difference is also observed between the two groups at p value .05. Conclusion: The study shows that dynamic platform lateral step-up exercise is more beneficial than stable platform lateral step-up weight bearing standing exercise in improving hip abductor muscle strength.

  16. Shaft Center Orbit in Dynamically Loaded Bearings

    DEFF Research Database (Denmark)

    Klit, Peder

    The aim of this work is to demonstrate how to utilize the bearings damping coefficients to estimate the orbit for a dynamically loaded journal bearing. The classical method for this analysis was developed by Booker in 1965 and described further in 1972. Several authors have refined this method over...... Jorgen W. Lund pointed out in lecture notes that the dynamic damping coefficients of the bearing could be used to find the shaft orbit for dynamically loaded bearings. For simplicity the "Short-Width-Journal-Bearing Theory" is used as a basis for finding the damping coefficients in this work...

  17. Dynamic Weighted Data Structures.

    Science.gov (United States)

    1982-06-01

    and Bonnie Hampton, who taught me much more than how to play the cello . Finally, for hours of artistic satisfaction, I thank Johannes Brahms, Ludwig...van "j Beethoven, Igor Stravinsky, Glan-Carlo Menotti, and Johann Sebastian Bach . Dynamic Weighted Data Structures Samuel W. Bent This thesis discusses...34I find It a matter of some difficulty to arrange these cards In a manner suited to my needs.’ I glanced at the cards and noticed each was labelled

  18. [Partial weight-bearing in rehabilitation. Strategies for instruction and limitations].

    Science.gov (United States)

    Klöpfer-Krämer, I; Augat, P

    2010-01-01

    Following trauma or surgery on the musculoskeletal system the primary aim is always as complete a restitution of mobility as possible. By mobilization with partial weight-bearing this is possible. The preferred way of teaching partial weight-bearing is the use of conventional bathroom scales. This method proves to be simple as well as time and cost-saving, but the transferability to the patient's daily life is questionable. Training and control of partial weight-bearing under dynamic conditions, such as normal walking, and walking up and down stairs seem to be very important. Different investigations have shown that the minority of subjects recruited could manage to maintain the given load of partial weight-bearing. Furthermore, the actual resulting moments within the joints, caused by muscles, fascia and tendons, are not considered in presets of partial weight-bearing, as only external forces (ground reaction forces) are measured. However, the problems in teaching partial weight-bearing have to be contrasted with the as yet unexplained issue of postoperative partial versus full weight-bearing.

  19. early weight-bearing after ankle fracture fixation: a prospective ...

    African Journals Online (AJOL)

    I then determined to study and compare the functional benefit of early weight- bearing as compared ... management strategies after surgical treatment which have included ..... compensation expectations or concurrent medical comorbidity were ...

  20. Shaft Center Orbit in Dynamically Loaded Bearings

    DEFF Research Database (Denmark)

    Klit, Peder

    2005-01-01

    The aim of this work is to demonstrate how to utilize the bearings damping coe±cients to estimate the orbit for a dynamically loaded journal bearing. The classical method for this analysis was developed by Booker in 1965 [1]and described further in 1972 [2]. Several authors have re¯ned this method...... seventies Jorgen W. Lund pointed out in lecture notes that the dynamic damping coe±cients of the bearing could be used to ¯nd the shaft orbit for dynamically loaded bearings. For simplicity the "Short-Width-Journal-Bearing Theory" is used as a basis for ¯nding the damping coe±cients in this work...

  1. Foot Loading Characteristics of Different Graduations of Partial Weight Bearing

    Science.gov (United States)

    Gusinde, Johannes; Pauser, Johannes; Swoboda, Bernd; Gelse, Kolja; Carl, Hans-Dieter

    2011-01-01

    Limited weight bearing of the lower extremity is a commonly applied procedure in orthopaedic rehabilitation after reconstructive forefoot surgery, trauma surgery and joint replacement. The most frequent limitations are given as percentage of body weight (BW) and represent 10 or 50% BW. The extent of foot loading under these graduations of partial…

  2. Biofeedback in Partial Weight Bearing: Validity of 3 Different Devices.

    Science.gov (United States)

    van Lieshout, Remko; Stukstette, Mirelle J; de Bie, Rob A; Vanwanseele, Benedicte; Pisters, Martijn F

    2016-11-01

    Study Design Controlled laboratory study to assess criterion-related validity, with a cross-sectional within-subject design. Background Patients with orthopaedic conditions have difficulties complying with partial weight-bearing instructions. Technological advances have resulted in biofeedback devices that offer real-time feedback. However, the accuracy of these devices is mostly unknown. Inaccurate feedback can result in incorrect lower-limb loading and may lead to delayed healing. Objectives To investigate validity of peak force measurements obtained using 3 different biofeedback devices under varying levels of partial weight-bearing categories. Methods Validity of 3 biofeedback devices (OpenGo science, SmartStep, and SensiStep) was assessed. Healthy participants were instructed to walk at a self-selected speed with crutches under 3 different weight-bearing conditions, categorized as a percentage range of body weight: 1% to 20%, greater than 20% to 50%, and greater than 50% to 75%. Peak force data from the biofeedback devices were compared with the peak vertical ground reaction force measured with a force plate. Criterion validity was estimated using simple and regression-based Bland-Altman 95% limits of agreement and weighted kappas. Results Fifty-five healthy adults (58% male) participated. Agreement with the gold standard was substantial for the SmartStep, moderate for OpenGo science, and slight for SensiStep (weighted ± = 0.76, 0.58, and 0.19, respectively). For the 1% to 20% and greater than 20% to 50% weight-bearing categories, both the OpenGo science and SmartStep had acceptable limits of agreement. For the weight-bearing category greater than 50% to 75%, none of the devices had acceptable agreement. Conclusion The OpenGo science and SmartStep provided valid feedback in the lower weight-bearing categories, and the SensiStep showed poor validity of feedback in all weight-bearing categories. J Orthop Sports Phys Ther 2016;46(11):-1. Epub 12 Oct 2016. doi:10

  3. Patellar position in weight-bearing radiographs compared with non-weight-bearing: significance for the detection of osteoarthritis.

    Science.gov (United States)

    Skou, Nikolaj; Egund, Niels

    2017-03-01

    Background Diagnosis and treatment of patellofemoral disorders including osteoarthritis are currently often based on imaging and clinical assessment with patients in the supine position. Purpose To evaluate differences in patellar position in the trochlear groove and to assess the detection of medial and lateral patellofemoral (PF) osteoarthritis (OA) on axial radiographs in supine and standing positions, respectively. Material and Methods Thirty-five women and 23 men (mean age, 56 years; age range, 18-87 years) referred for routine radiographic examinations of the knees were included. Axial radiographs of the PF joint in both supine non-weight-bearing and standing weight-bearing position in 30° knee flexion were obtained of 111 knees. Measurements performed on the radiographs: patellar tilt, patellar displacement, joint space width, and grade of OA according to Ahlbäck. Results From supine to standing position the patella moved medially and medial joint space width and lateral patellar tilt angle decreased ( P < 0.0001 for the three measured parameters). In the standing position, medial PF OA was observed in 19 knees compared to three knees in the supine position. Fourteen knees had lateral PF OA with almost unchanged grade of OA irrespective of position. Conclusion In weight-bearing positions, the patella is positioned medially in the trochlear groove compared to supine non-weight-bearing positions. Therefore, this study suggests that the common occurrence of medial PF OA can generally not be detected on axial radiographs in supine non-weight-bearing positions and confirms the importance of imaging the PF joint in standing weight-bearing positions.

  4. Weight bearing or non-weight bearing after surgically fixed ankle fractures, the WOW! Study : study protocol for a randomized controlled trial

    NARCIS (Netherlands)

    Briet, Jan Paul; Houwert, Roderick M; Smeeing, Diederik P J; Pawiroredjo, Janity S; Kelder, Johannes C; Lansink, Koen W; Leenen, Luke P H; van der Zwaal, Peer; van Zutphen, Stephan W A M; Hoogendoorn, Jochem M; van Heijl, Mark; Verleisdonk, Egbert J M M; van Lammeren, Guus W; Segers, Michiel J; Hietbrink, Falco

    2015-01-01

    BACKGROUND: The optimal post-operative care regimen after surgically fixed Lauge Hansen supination exorotation injuries remains to be established. This study compares whether unprotected weight bearing as tolerated is superior to protected weight bearing and unprotected non-weight bearing in terms o

  5. Immediate Weight-Bearing after Ankle Fracture Fixation

    Directory of Open Access Journals (Sweden)

    Reza Firoozabadi

    2015-01-01

    Full Text Available We believe that a certain subset of surgical ankle fracture patients can be made weight-bearing as tolerated immediately following surgery. Immediate weight-bearing as tolerated (IWBAT allows patients to return to ambulation and activities of daily living faster and may facilitate rehabilitation. A prospectively gathered orthopaedic trauma database at a Level 1 trauma center was reviewed retrospectively to identify patients who had ORIF after unstable ankle injuries treated by the senior author. Patients were excluded if they were not IWBAT based on specific criteria or if they did meet followup requirement. Only 1/26 patients was noted to have loss of fixation. This was found at the 6-week followup and was attributed to a missed syndesmotic injury. At 2-week followup, 2 patients had peri-incisional erythema that resolved with a short course of oral antibiotics. At 6-week followup, 20 patients were wearing normal shoes and 6 patients continued to wear the CAM Boot for comfort. To conclude, IWBAT in a certain subset of patients with stable osteosynthesis following an ankle fracture could potentially be a safe alternative to a period of protected weight-bearing.

  6. Eccentric exercise training as a countermeasure to non-weight-bearing soleus muscle atrophy

    Science.gov (United States)

    Kirby, Christopher R.; Ryan, Mirelle J.; Booth, Frank W.

    1992-01-01

    This investigation tested whether eccentric resistance training could prevent soleus muscle atrophy during non-weight bearing. Adult female rats were randomly assigned to either weight bearing +/- intramuscular electrodes or non-weight bearing +/- intramuscular electrodes groups. Electrically stimulated maximal eccentric contractions were performed on anesthetized animals at 48-h intervals during the 10-day experiment. Non-weight bearing significantly reduced soleus muscle wet weight (28-31 percent) and noncollagenous protein content (30-31 percent) compared with controls. Eccentric exercise training during non-weight bearing attenuated but did not prevent the loss of soleus muscle wet weight and noncollagenous protein by 77 and 44 percent, respectively. The potential of eccentric exercise training as an effective and highly efficient counter-measure to non-weight-bearing atrophy is demonstrated in the 44 percent attenuation of soleus muscle noncollagenous protein loss by eccentric exercise during only 0.035 percent of the total non-weight-bearing time period.

  7. Eccentric exercise training as a countermeasure to non-weight-bearing soleus muscle atrophy

    Science.gov (United States)

    Kirby, Christopher R.; Ryan, Mirelle J.; Booth, Frank W.

    1992-01-01

    This investigation tested whether eccentric resistance training could prevent soleus muscle atrophy during non-weight bearing. Adult female rats were randomly assigned to either weight bearing +/- intramuscular electrodes or non-weight bearing +/- intramuscular electrodes groups. Electrically stimulated maximal eccentric contractions were performed on anesthetized animals at 48-h intervals during the 10-day experiment. Non-weight bearing significantly reduced soleus muscle wet weight (28-31 percent) and noncollagenous protein content (30-31 percent) compared with controls. Eccentric exercise training during non-weight bearing attenuated but did not prevent the loss of soleus muscle wet weight and noncollagenous protein by 77 and 44 percent, respectively. The potential of eccentric exercise training as an effective and highly efficient counter-measure to non-weight-bearing atrophy is demonstrated in the 44 percent attenuation of soleus muscle noncollagenous protein loss by eccentric exercise during only 0.035 percent of the total non-weight-bearing time period.

  8. Shaft centre orbit for dynamically loaded radial bearings

    DEFF Research Database (Denmark)

    Klit, Peder; Vølund, Anders

    2002-01-01

    The aim of this work is to demonstrate how to utilize the bearings damping coefficients to estimate the orbit for a dynamically loaded journal bearing. The classical method for this analysis was developed by Booker in 1965 Booker1 and described further in 1972 Booker2. Several authors have refined...... seventies Jorgen W. Lund pointed out in lecture notes that the dynamic damping coefficients of the bearing could be used to find the shaft orbit for dynamically loaded bearings. For simplicity the "Short-Width-Journal-Bearing Theory" is used as a basis for finding the damping coefficients in this work...

  9. [Management of weight-bearing area fracture of acetabulum].

    Science.gov (United States)

    Zhang, Yun-tong; Wang, Pan-feng; Zhang, Chun-cai

    2011-02-01

    Acetabulum, as the important factor for weight bearing of the upper body, has its unique anatomic features and complicated physiological function. The integrity and stability of the lunata articular surface in the dome region of acetabulum, is the important base to bear the physiological function of acetabulum. The fracture related to this part will cause relation change of contact area and stress between head of femur and acetabulum. Furthermore, the deep anatomical position of the dome region, the complicated surrounding anatomical relation, and the irregular bony structure will also increase the difficulty of surgical treatment. Especially for some complicated comminuted or compressed fracture, even with good explosions, it is hard to get satisfied anatomical reduction. Consequently,forward traumatic arthritis has greater probability of occurrence. Therefore, the clinical research on the fracture in the dome region of acetabulum was getting more and more attention worldly. This paper intended to review the relation of fracture classifications and anatomic features, physiological function,diagnostic criteria,and also its clinical treating countermeasure.

  10. Upright Cone CT of the hindfoot: Comparison of the non-weight-bearing with the upright weight-bearing position

    Energy Technology Data Exchange (ETDEWEB)

    Hirschmann, Anna; Pfirrmann, Christian W.A.; Buck, Florian M. [University of Zurich, Department of Radiology, Orthopaedic University Hospital Balgrist, Zurich (Switzerland); Klammer, Georg; Espinosa, Norman [University of Zurich, Department of Orthopedic Surgery, Orthopaedic University Hospital Balgrist, Zurich (Switzerland)

    2014-03-15

    To prospectively compare computed tomography (CT) of the hindfoot in the supine non-weight-bearing position (NWBCT) with upright weight-bearing position (WBCT). Institutional review board approval and informed consent of all patients were obtained. NWBCT and WBCT scans of the ankle were obtained in 22 patients (mean age, 46.0 ± 17.1 years; range 19-75 years) using a conventional 64-row CT for NWBCT and a novel cone-beam CT for WBCT. Two musculoskeletal radiologists independently performed the following measurements: the hindfoot alignment angle, fibulocalcaneal and tibiocalcaneal distances, lateral talocalcaneal joint space width, talocalcaneal overlap and naviculocalcaneal distance. Significant changes between NWBCT and WBCT were sought using Wilcoxon signed-rank test. P values <0.05 were considered statistically significant. Significant differences were found for all measurements except the hindfoot alignment angle and tibiocalcaneal distance. Significant measurement results were as follows (NWBCT/WBCT reader 1; NWBCT/WBCT reader 2, mean ± standard deviation): fibulocalcaneal distance 3.6 mm ± 5.2/0.3 mm ± 6.0 (P = 0.006); 1.4 mm ± 6.3/-1.1 mm ± 6.3 (P = 0.002), lateral talocalcaneal joint space width 2.9 mm ± 1.7/2.2 mm ± 1.1 (P = 0.005); 3.4 mm ± 1.9/2.4 mm ± 1.3 (P = 0.001), talocalcaneal overlap 4.1 mm ± 3.9/1.4 mm ± 3.9 (P = 0.001); 4.5 mm ± 4.3/1.4 mm ± 3.7 (P < 0.001) and naviculocalcaneal distance 13.5 mm ± 4.0/15.3 mm ± 4.7 (P = 0.037); 14.0 mm ± 4.4/15.7 mm ± 6.2 (P = 0.100). Interreader agreement was good to excellent (ICC 0.48-0.94). Alignment of the hindfoot significantly changes in the upright weight-bearing CT position. Differences can be visualised and measured using WBCT. (orig.)

  11. Interchangeable Bearings for Profile and Weight Trade Studies Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Air-Lock, Incorporated is proposing to design fully sealed shoulder and arm bearings with interchangeable bearing housings. The interchangeable housings shall be...

  12. Nonlinear dynamic behaviors of ball bearing rotor system

    Institute of Scientific and Technical Information of China (English)

    WANG Li-qin; CUI Li; ZHENG De-zhi; GU Le

    2009-01-01

    Nonlinear forces and moments caused by ball bearing were calculated based on relationship of displacement and deflection and quasi-dynamic model of bearing. Five-DOF dynamic equations of rotor supported by ball bearings were estimated. The Newmark-β method and Newton-Laphson method were used to solve the equations. The dynamic characteristics of rotor system were studied through the time response, the phase portrait, the Poincar? maps and the bifurcation diagrams. The results show that the system goes through the quasiperiodic bifurcation route to chaos as rotate speed increases and there are several quasi-periodic regions and chaos regions. The amplitude decreases and the dynamic behaviors change as the axial load of ball bearing increases; the initial contact angle of ball bearing affects dynamic behaviors of the system obviously. The system can avoid non-periodic vibration by choosing structural parameters and operating parameters reasonably.

  13. Dynamic balance of unsymmetrical rotor-bearing system

    Institute of Scientific and Technical Information of China (English)

    黄森林; 刘占生; 苏杰先

    2003-01-01

    The formula is derived for calculating correction weights from motion equations of unsymmetrical ro-tor-bearing system. Two trial weights are required in two trial operations for ea ch balancing plane, and forwardprecession of trial responses are used to calculate the correction weights. Comparative experiments between thismethod and the conventional method are carried out on the test bench. Moreover, this method was used to bal-ance a 600 MW generator-bearing system, it decreased the balancing time and improved the balance accuracy.This method has been proved valid for balancing unsymmetrical rotor-bearing system.

  14. Identification of dynamic stiffness matrix of bearing joint region

    Institute of Scientific and Technical Information of China (English)

    Feng HU; Bo WU; Youmin HU; Tielin SHI

    2009-01-01

    The paper proposes an identification method of the dynamic stiffness matrix of a bearing joint region on the basis of theoretical analysis and experiments. The author deduces an identification model of the dynamic stiffness matrix from the synthetic substructure method. The dynamic stiffness matrix of the bearing joint region can be identified by measuring the matrix of frequency response function (FRFs) of the substructure (axle) and whole structure (assembly of the axle, bearing, and bearing housing) in different positions. Considering difficulty in measuring angular displacement, applying moment, and directly measuring relevant FRFs of rotational degree of freedom, the author employs an accurately calibrated finite element model of the unconstrained structure for indirect estimation. With experiments and simulation analysis, FRFs related with translational degree of freedom, which is estimated through the finite element model, agrees with experimental results, and there is very high reliability in the identified dynamic stiffness matrix of the bearing joint region.

  15. External pneumatic compression device prevents fainting in standing weight-bearing MRI

    DEFF Research Database (Denmark)

    Hansen, Bjarke Brandt; Bouert, Rasmus; Bliddal, Henning

    2013-01-01

    To investigate if a peristaltic external pneumatic compression device attached to the legs, while scanning, can reduce a substantial risk of fainting in standing weight-bearing magnetic resonance imaging (MRI).......To investigate if a peristaltic external pneumatic compression device attached to the legs, while scanning, can reduce a substantial risk of fainting in standing weight-bearing magnetic resonance imaging (MRI)....

  16. Immediate weight-bearing after osteosynthesis of proximal tibial fractures may be allowed

    DEFF Research Database (Denmark)

    Haak, Karl Tobias; Palm, Henrik; Holck, Kim;

    2012-01-01

    Immediate weight-bearing following osteosynthesis of proximal tibial fractures is traditionally not allowed due to fear of articular fracture collapse. Anatomically shaped locking plates with sub-articular screws could improve stability and allow greater loading forces. The purpose of this study...... was to investigate if immediate weight-bearing can be allowed following locking plate osteosynthesis of proximal tibial fractures....

  17. Effect of unaccustomed eccentric exercise on proprioception of the knee in weight and non-weight bearing tasks.

    Science.gov (United States)

    Vila-Chã, Carolina; Riis, Simone; Lund, Ditte; Møller, Anders; Farina, Dario; Falla, Deborah

    2011-02-01

    The study investigates the effects of eccentric exercise of the quadriceps on proprioception of the knee in weight and non-weight bearing tasks. Proprioception of the exercised leg was assessed at 120° and 150° of knee extension in 15 healthy adults (age 25.0 ± 3.6 yrs) before, immediately after, and 24h following eccentric exercise of the quadriceps. Three tests of proprioception were performed: 1. matching the position of the exercised leg (right leg) to the reference leg (left leg) in sitting (non-weight bearing matching task); 2. repositioning the exercised leg after active movement in sitting (non-weight bearing repositioning task); 3. repositioning the exercised leg after active movement in standing (weight bearing task). Maximum knee extension force was reduced by 77.0 ± 12.3 % immediately after the exercise, and by 82.7 ± 16.2% 24h post exercise, with respect to baseline (Peccentric exercise (12.3 ± 5.6, Pexercise (8.1 ± 4.5, Pexercise (5.2 ± 3.0°, Peccentric exercise by adopting a more extended knee position of the exercised limb. Furthermore, the subjects showed higher variability in their performance immediately post exercise (Peccentric exercise did not affect the repositioning errors in the weight bearing task. In conclusion, eccentric exercise of the quadriceps impairs proprioception of the knee both immediately after and 24h post exercise, but only in non-weight bearing tasks.

  18. Lower Profile, Lighter Weight Space Suit Bearings Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Air-Lock will deliver a final report based on the follwoing: 1. Historical summary of bearing design evolution throughout the life of the EMU Program 2. Material...

  19. Handling Dynamic Weights in Weighted Frequent Pattern Mining

    Science.gov (United States)

    Ahmed, Chowdhury Farhan; Tanbeer, Syed Khairuzzaman; Jeong, Byeong-Soo; Lee, Young-Koo

    Even though weighted frequent pattern (WFP) mining is more effective than traditional frequent pattern mining because it can consider different semantic significances (weights) of items, existing WFP algorithms assume that each item has a fixed weight. But in real world scenarios, the weight (price or significance) of an item can vary with time. Reflecting these changes in item weight is necessary in several mining applications, such as retail market data analysis and web click stream analysis. In this paper, we introduce the concept of a dynamic weight for each item, and propose an algorithm, DWFPM (dynamic weighted frequent pattern mining), that makes use of this concept. Our algorithm can address situations where the weight (price or significance) of an item varies dynamically. It exploits a pattern growth mining technique to avoid the level-wise candidate set generation-and-test methodology. Furthermore, it requires only one database scan, so it is eligible for use in stream data mining. An extensive performance analysis shows that our algorithm is efficient and scalable for WFP mining using dynamic weights.

  20. Haptic biofeedback for improving compliance with lower-extremity partial weight bearing.

    Science.gov (United States)

    Fu, Michael C; DeLuke, Levi; Buerba, Rafael A; Fan, Richard E; Zheng, Ying Jean; Leslie, Michael P; Baumgaertner, Michael R; Grauer, Jonathan N

    2014-11-01

    After lower-extremity orthopedic trauma and surgery, patients are often advised to restrict weight bearing on the affected limb. Conventional training methods are not effective at enabling patients to comply with recommendations for partial weight bearing. The current study assessed a novel method of using real-time haptic (vibratory/vibrotactile) biofeedback to improve compliance with instructions for partial weight bearing. Thirty healthy, asymptomatic participants were randomized into 1 of 3 groups: verbal instruction, bathroom scale training, and haptic biofeedback. Participants were instructed to restrict lower-extremity weight bearing in a walking boot with crutches to 25 lb, with an acceptable range of 15 to 35 lb. A custom weight bearing sensor and biofeedback system was attached to all participants, but only those in the haptic biofeedback group were given a vibrotactile signal if they exceeded the acceptable range. Weight bearing in all groups was measured with a separate validated commercial system. The verbal instruction group bore an average of 60.3±30.5 lb (mean±standard deviation). The bathroom scale group averaged 43.8±17.2 lb, whereas the haptic biofeedback group averaged 22.4±9.1 lb (Pbiofeedback group averaged 14.5±6.3% (Pbiofeedback to improve compliance with lower-extremity partial weight bearing, haptic biofeedback was superior to conventional physical therapy methods. Further studies in patients with clinical orthopedic trauma are warranted.

  1. Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig

    Science.gov (United States)

    Morrison, Carlos R.; Provenza, Andrew; Kurkov, Anatole; Mehmed, Oral; Johnson, Dexter; Montague, Gerald; Duffy, Kirsten; Jansen, Ralph

    2005-01-01

    The Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig is an apparatus for vibration testing of turbomachine blades in a vacuum at rotational speeds from 0 to 40,000 rpm. This rig includes (1) a vertically oriented shaft on which is mounted an assembly comprising a rotor holding the blades to be tested, (2) two actively controlled heteropolar radial magnetic bearings at opposite ends of the shaft, and (3) an actively controlled magnetic thrust bearing at the upper end of the shaft. This rig is a more capable successor to a prior apparatus, denoted the Dynamic Spin Rig (DSR), that included a vertically oriented shaft with a mechanical thrust bearing at the upper end and a single actively controlled heteropolar radial magnetic bearing at the lower end.

  2. Nonlinear Analyses of the Dynamic Properties of Hydrostatic Bearing Systems

    Institute of Scientific and Technical Information of China (English)

    LIU Wei(刘伟); WU Xiujiang(吴秀江); V.A. Prokopenko

    2003-01-01

    Nonlinear analyses of hydrostatic bearing systems are necessary to adequately model the fluid-solid interaction. The dynamic properties of linear and nonlinear analytical models of hydrostatic bearings are compared in this paper. The analyses were based on the determination of the aperiodic border of transient processes with external step loads. The results show that the dynamic properties can be most effectively improved by increasing the hydrostatic bearing crosspiece width and additional pocket volume in a bearing can extend the load range for which the transient process is aperiodic, but an additional restrictor and capacitor (RC) chain must be introduced for increasing damping. The nonlinear analyses can also be used to predict typical design parameters for a hydrostatic bearing.

  3. Kinematic Changes of Gait in Patients with Knee Osteoarthritis by Different Weight bearings

    Directory of Open Access Journals (Sweden)

    Margareth Lorena Alfonso-Mora

    2014-09-01

    Full Text Available Objective: To describe the differences in kinematic gait variables in women over sixty years of age with knee osteoarthritis by different weight bearings. Material and Methods: Phanel longitudinal research design with convenience sampling probabilistic n = 16 women, aged > 60 years, obesity and knee osteoarthritis, control weight bearing was performed by a locomotive rehabilitation platform that measured gait three times with weights of 100%, 90% and 80%. Results: The movement ranges in certain gait phases were different for bearings of used weight p < 0.05; for angular speed and acceleration no statistically significant differences were found. Conclusions: The different weight bearings for this research represented a variable that significantly change the kinematic gait variables.

  4. Dynamic Analysis of a Rotor-Bearing-SFD System with the Bearing Inner Race Defect

    Directory of Open Access Journals (Sweden)

    Junhong Zhang

    2017-01-01

    Full Text Available In this paper, the dynamic behavior of a rotor-bearing-SFD system with the inner race defect of bearing is investigated. The contact force between the rolling element and the race is calculated in Hertzian contact and elastohydrodynamic lubrication condition. The supporting force of the SFD is simulated by integrating the pressure distribution derived from Reynolds’s equation. The equations of motion of the rotor-bearing-SFD system are derived and solved using the fourth-order Runge-Kutta method. The dynamic behavior and the fault characteristics are analyzed with two configurations of the SFD: (1 mounted on the unfaulted bearing and (2 mounted on the faulty bearing. According to the analysis of time-frequency diagram, waterfall plot, and spectral diagram, the results show that the characteristics of inner race defects on bearing frequencies are related to the characteristic multiple frequency of the inner race defect and the fundamental frequency. The speed and defect width have different influence on the distribution and amplitude of frequency. The SFD can enhance the system stability under the bearing fault but the enhancement decreases with the increasing speed. Meanwhile, the beneficial effect of the SFD varies according to the mounted position in the rotor system.

  5. State Space Formulation of Nonlinear Vibration Responses Collected from a Dynamic Rotor-Bearing System: An Extension of Bearing Diagnostics to Bearing Prognostics

    Directory of Open Access Journals (Sweden)

    Peter W. Tse

    2017-02-01

    Full Text Available Bearings are widely used in various industries to support rotating shafts. Their failures accelerate failures of other adjacent components and may cause unexpected machine breakdowns. In recent years, nonlinear vibration responses collected from a dynamic rotor-bearing system have been widely analyzed for bearing diagnostics. Numerous methods have been proposed to identify different bearing faults. However, these methods are unable to predict the future health conditions of bearings. To extend bearing diagnostics to bearing prognostics, this paper reports the design of a state space formulation of nonlinear vibration responses collected from a dynamic rotor-bearing system in order to intelligently predict bearing remaining useful life (RUL. Firstly, analyses of nonlinear vibration responses were conducted to construct a bearing health indicator (BHI so as to assess the current bearing health condition. Secondly, a state space model of the BHI was developed to mathematically track the health evolution of the BHI. Thirdly, unscented particle filtering was used to predict bearing RUL. Lastly, a new bearing acceleration life testing setup was designed to collect natural bearing degradation data, which were used to validate the effectiveness of the proposed bearing prognostic method. Results show that the prediction accuracy of the proposed bearing prognostic method is promising and the proposed bearing prognostic method is able to reflect future bearing health conditions.

  6. Cranial acetabular retroversion is common in developmental dysplasia of the hip as assessed by the weight bearing position

    DEFF Research Database (Denmark)

    Troelsen, Anders; Mikkelsen, Lone Rømer; Jacobsen, Steffen;

    2010-01-01

    The appearance of acetabular version differs between the supine and weight bearing positions in developmental dysplasia of the hip. Weight bearing radiographic evaluation has been recommended to ensure the best coherence between symptoms, functional appearance, and hip deformities. Previous preva...

  7. Bearing problems’ effects on the dynamic performance of pumping stations

    Directory of Open Access Journals (Sweden)

    Mostafa A. Abu-Zeid

    2013-09-01

    Pumping stations use large number of bearings with different types and applications. These bearings have a clear effect on the performance and efficiency of the pumps. Pump bearings in the arid regions are greatly affected by temperature, water quality, lubricants, and maintenance operations. This research focuses on analysis of damaged rolling element bearings of pumping system. The objective of the research is to enhance and control dynamic performance of pumping stations by avoiding damage and failure of bearings. The research proves that damaged bearings generate periodic, non-periodic, and transient forces causing high amplitude of vibration at high frequencies and increasing energy consumption. Bearing faults increase vibration level 85%, where power consumption increases 14% and pump efficiency decreases 18%. It is very important to take care of bearings during installation, alignment, balancing, and maintenance to assure safe and efficient pump operation for long period. As pump efficiency decreases, water power decreases and/or consumed power increases affecting water distribution and management system. Bearing faults break pumping system for long period affecting irrigation system. Optimum operation of pumping stations helps to save and manage water requirement for development and extension projects in arid regions. The measurements are performed on full scale model in the field, which proves reliable results on similar pumping stations.

  8. Correlation of psychomotor findings and the ability to partially weight bear

    Directory of Open Access Journals (Sweden)

    Ruckstuhl Thomas

    2012-02-01

    Full Text Available Abstract Background Partial weight bearing is thought to avoid excessive loading that may interfere with the healing process after surgery of the pelvis or the lower extremity. The object of this study was to investigate the relationship between the ability to partially weight bear and the patient's psychomotor skills and an additional evaluation of the possibility to predict this ability with a standardized psychomotor test. Methods 50 patients with a prescribed partial weight bearing at a target load of 15 kg following surgery were verbally instructed by a physical therapist. After the instruction and sufficient training with the physical therapist vertical ground reaction forces using matrix insoles were measured while walking with forearm crutches. Additionally, psychomotor skills were tested with the Motorische Leistungsserie (MLS. To test for correlations Spearman's Rank correlation was used. For further comparison of the two groups a Mann-Withney test was performed using Bonferroni correction. Results The patient's age and body weight significantly correlated with the ability to partially weight bear at a 15 kg target load. There were significant correlations between several subtests of the MLS and ground reaction forces measured while walking with crutches. Patients that were able to correctly perform partial weight bearing showed significant better psychomotor skills especially for those subtests where both hands had to be coordinated simultaneously. Conclusions The ability to partially weight bear is associated with psychomotor skills. The MLS seems to be a tool that helps predicting the ability to keep within the prescribed load limits.

  9. Femur rotation and patellofemoral joint kinematics: a weight-bearing magnetic resonance imaging analysis

    National Research Council Canada - National Science Library

    Souza, Richard B; Draper, Christie E; Fredericson, Michael; Powers, Christopher M

    2010-01-01

    ...) and pain-free controls using weight-bearing kinematic magnetic resonance imaging. Recently, it has been recognized that patellofemoral malalignment may be the result of femoral motion as opposed to patella motion...

  10. Feasibility of Applying Controllable Lubrication to Dynamically Loaded Journal Bearings

    DEFF Research Database (Denmark)

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    A multibody dynamic model of the main mechanical components of a hermetic reciprocating compressor is presented in this work. Considering that some of the mechanical elements are interconnected via thin fluid films, the multibody dynamic model is coupled to the equations from the dynamics...... levels, wear and power losses of the system components. From the point of view of actively controlled lubrication and specifically for the case of dynamically loaded journal bearings, the injection pressure should be controlled in time domain. However, taking into account that the gas pressure...... and reaction forces in a reciprocating compressor have a cyclic behavior, periodic oil pressure injection rules based on the instantaneous crank angle and load bearing condition can be established. In this paper, several bearing configurations working under different oil pressure injection rules conditions...

  11. Path Minima Queries in Dynamic Weighted Trees

    DEFF Research Database (Denmark)

    Davoodi, Pooya; Brodal, Gerth Stølting; Satti, Srinivasa Rao

    2011-01-01

    In the path minima problem on a tree, each edge is assigned a weight and a query asks for the edge with minimum weight on a path between two nodes. For the dynamic version of the problem, where the edge weights can be updated, we give data structures that achieve optimal query time\\todo{what about...

  12. Is it correct to always consider weight-bearing asymmetrically distributed in individuals with hemiparesis?

    Science.gov (United States)

    Martins, Emerson Fachin; de Araujo Barbosa, Paulo Henrique Ferreira; de Menezes, Lidiane Teles; de Sousa, Pedro Henrique Côrtes; Costa, Abraão Souza

    2011-11-01

    Injuries may cause unilateral deterioration of brain areas related to postural control resulting in lateralized motor disability with abnormal asymmetry in weight-bearing distribution. Although overloading toward the nonaffected limb has been described as the preferred posture among individuals with hemiparesis, characterization of the weight-bearing asymmetry is poorly and indirectly described. Therefore, this study aimed to describe weight-bearing distribution during upright stance, establishing criteria to consider asymmetry in hemiparesis when analyzed within the limits defined by controls matched by age and gender. Forty subjects with (n = 20) or without hemiparesis (n = 20) were included in procedures to record weight-bearing values between hemibodies, and these values were used to calculate a symmetry ratio. Control presented 95% confidence interval (CI) of the mean for symmetry ratio ranging from 0.888 to 1.072, defining limits to symmetry. Four subjects with hemiparesis (20%) had symmetry ratios inside limits defined by controls (i.e., weight-bearing symmetrically distributed), and 11 (55%) subjects without hemiparesis showed symmetry ratios outside the limits, suggesting asymmetrical weight-bearing distribution. It was concluded that asymmetry, when present in a control group, was more frequently overloading nonpredominantly used hemibody (nondominant side), differing from a hemiparesis group commonly forced to assume the nonaffected side as the predominantly used hemibody and where the overload was observed.

  13. Effect of Bearing Housings on Centrifugal Pump Rotor Dynamics

    Science.gov (United States)

    Yashchenko, A. S.; Rudenko, A. A.; Simonovskiy, V. I.; Kozlov, O. M.

    2017-08-01

    The article deals with the effect of a bearing housing on rotor dynamics of a barrel casing centrifugal boiler feed pump rotor. The calculation of the rotor model including the bearing housing has been performed by the method of initial parameters. The calculation of a rotor solid model including the bearing housing has been performed by the finite element method. Results of both calculations highlight the need to add bearing housings into dynamic analyses of the pump rotor. The calculation performed by modern software packages is more a time-taking process, at the same time it is a preferred one due to a graphic editor that is employed for creating a numerical model. When it is necessary to view many variants of design parameters, programs for beam modeling should be used.

  14. Numerical Analysis of Turbocharger’s Bearing using Dynamic Mesh

    Directory of Open Access Journals (Sweden)

    J. Moradi Cheqamahi

    2016-01-01

    Full Text Available Journal bearings are widely used in different machineries. Reynolds equation is the governing equation to predict pressure distribution and load bearing capacity in journal bearings. There are many analytical and numerical methods for solving this equation. The main disadvantage of these methods is their inability to analyze complex geometries. In this paper, a comprehensive method based on dynamic mesh method is developed to solve the conservation equations of mass, momentum and energy. This method has smaller error compared to other techniques. To verify the accuracy of this method, the bearings with different length to diameter ratios are analytically and numerically analyzed under different loads and compared with each other. In continue, the turbocharger’s bearing is numerically simulated and the effects of rotational speed change are studied. Finally, the turbocharger’s bearing with four axial grooves are simulated. The simulations results show that adding grooves to the turbocharger’s bearing causes the bearing eccentricity ratio and lubricant flow rate to increase and the attitude angle, rate of temperature rise and frictional torque to decrease.

  15. Dynamic behavior of a magnetic bearing supported jet engine rotor with auxiliary bearings

    Science.gov (United States)

    Flowers, George T.; Xie, Huajun; Sinha, S. C.

    1995-01-01

    This paper presents a study of the dynamic behavior of a rotor system supported by auxiliary bearings. The steady-state behavior of a simulation model based upon a production jet engine is explored over a wide range of operating conditions for varying rotor imbalance, support stiffness, and damping. Interesting dynamical phenomena, such as chaos, subharmonic responses, and double-valued responses, are presented and discussed.

  16. Strength dynamics of weighted evolving networks

    Institute of Scientific and Technical Information of China (English)

    Wu Jian-Jun; Gao Zi-You; Sun Hui-Jun

    2007-01-01

    In this paper, a simple model for the strength dynamics of weighted evolving networks is proposed to characterize the weighted networks. By considering the congestion effects, this approach can yield power law strength distribution appeared on the many real weighted networks, such as traffic networks, internet networks. Besides, the relationship between strength and degree is given. Numerical simulations indicate that the strength distribution is strongly related to the strength dynamics decline. The model also provides us with a better description of the real weighted networks.

  17. The effects of a 12-week program of static upper extremity weight bearing exercises on weight bearing in children with hemiplegic type of cerebral palsy

    Directory of Open Access Journals (Sweden)

    P. Jayaraman

    2010-02-01

    Full Text Available The  major  objective  of  this  study  was  to  quantify  the  effects  of a  12-week  program  of  weight  bearing  exercises  on  weight  borne  through  the hand and grip pressures in children with hemiplegic cerebral palsy. This study also sought to monitor the change in spasticity immediately following weight-bearing  exercises.  A  quasi-experimental,  one  group  pre-test,  post-test  study  was used. Eleven children with hemiplegic type of cerebral palsy from a special school in KwaZulu Natal participated after fully informed written consent. The intervention consisted of a 12-week program of weight bearing. The Tekscan Grip system was used to quantify weight borne through the hand during extended arm prone and quadruped positions and whilst holding a pencil and a tumbler. The modified Ashworth grading of spasticity was used to monitor spasticity. The data was analysed using the random effects GLS model Wald Chi Square test. Significant increases in contact pressure in extended arms prone (p=0,012 and quadruped (p=0,002 and when holding a pencil (p=0,045 was noted post-test compared to pre-test. Significant increases in contact area of the hand was also noted in prone (p=0,000, quadruped (p=0, 03 at assessment 7 and when holding a pencil (p=0,035.  A significant decrease in spasticity during elbow extension (p=0,004, and wrist flexion (p=0,026 and extension (p=0,004 was noted. An overall significant effect of static weight bearing exercises on weight borne through the hands, grip strength and spasticity justifies the use of static weight-bearing in therapy.

  18. Leg muscle activity during walking with assistive devices at varying levels of weight bearing.

    Science.gov (United States)

    Clark, Brian C; Manini, Todd M; Ordway, Nathaniel R; Ploutz-Snyder, Lori L

    2004-09-01

    To evaluate the muscle activation patterns at varying levels of weight-bearing forces during assisted walking with an axillary crutch and a recently designed device that allows weight transfer through the pelvic girdle (ED Walker). Descriptive, repeated measures. University-based research laboratory. Twelve healthy volunteers (age, 39.6+/-13.6 y). Not applicable. Electromyographic activity was recorded from the anterior tibialis, soleus, biceps femoris, and vastus lateralis muscles on a test leg during assisted axillary crutch and ED Walker ambulation. Force platform readings measured weight-bearing load (non, light, heavy). These values were normalized to normal walking gait. In the vastus lateralis and soleus muscles, both devices allowed for approximately 50% and 65% reductions in electromyographic activity during the non-weight-bearing condition. During crutch ambulation, electromyographic activity of the soleus was significantly reduced compared with that required for normal walking at all levels of weight-bearing load. In the vastus lateralis for the weight-bearing conditions, the ED Walker required significantly higher electromyographic activity than crutch ambulation (light: 105.0%+/-12.3% vs 72.7%+/-10.1%; heavy: 144.8%+/-23.5% vs 100.0%+/-13.5%). Both devices required similar peak vertical ground reaction forces during the heavy weight-bearing conditions (crutch: 75%+/-1.6%; ED Walker: 73%+/-1.8%), whereas axillary crutch gait produced less force than the ED Walker in the light condition (32%+/-2.0% vs 48%+/-1.6%). During walking with assistive devices, muscle activation patterns varied with weight-bearing load. The leg extensor muscles appeared to incur a greater reduction in muscle activity when compared with their flexor counterparts. Additionally, the ED Walker and axillary crutch differed with respect to their muscle activity levels and weight-bearing characteristics. Clinically, knowledge of these muscle activity and force characteristics may aid in

  19. Weight-bearing shifts of hemiparetic and healthy adults upon stepping on stairs of various heights.

    Science.gov (United States)

    Laufer, Y; Dickstein, R; Resnik, S; Marcovitz, E

    2000-04-01

    To examine and compare the effect of stepping on stairs of various heights on lower extremity weight bearing in hemiparetic patients. Flieman Geriatric Rehabilitation Hospital, Haifa, Israel. Fifteen ambulatory hemiparetic patients following an acute cerebrovascular accident, and 16 age-matched healthy controls. Each subject was tested twice on two consecutive days in five weight-bearing positions which included level stance and stepping with either leg on 10-cm- and 17-cm-high steps. Data concerning weight distribution on the lower extremities were collected by two computerized forceplates. Weight borne by each foot expressed as percentage of overall body weight. In the attempted symmetrical level stance, the percentage of body weight borne by the paretic limb of the stroke patients was significantly lower than that of the nonparetic limb. Placing one foot on a step induced a weight shift to the foot placed on the floor regardless of step height. Weight shifting to the paretic limb was, however, significantly lower than to the nonparetic limb. Weight shifting to the nonparetic limb was significantly lower than to the corresponding limb of healthy individuals. Step height had no significant effect on weight distributions on the feet. Raising a foot on a step appears to be an appropriate strategy for weight shift training of stroke patients. Since weight shifting to both the paretic and nonparetic limb of stroke patients is impaired, treatment strategies should include training in weight shifting to both lower extremities.

  20. Lower-extremity weight-bearing compliance is maintained over time after biofeedback training.

    Science.gov (United States)

    Hustedt, Joshua W; Blizzard, Daniel J; Baumgaertner, Michael R; Leslie, Michael P; Grauer, Jonathan N

    2012-11-01

    Previous studies have shown immediate compliance with weight-bearing instructions to be better after biofeedback training than after verbal or scale training. This study assessed retention of biofeedback training to determine potential clinical applicability. Twelve participants were enrolled in a prospective clinical study at an academic orthopedic center. Participants were trained with a biofeedback device to comply with touch-down weight-bearing instructions (25 lb). Immediately following the training session, weight bearing was assessed for each participant. The retention of this training was then reassessed at 2 to 4, 6 to 8, and 22 to 24 hours. Two control participants were given no biofeedback training (verbal instructions only) and were followed similarly. Following initial biofeedback training at 25 lb, participants bore an average of 20.4±2.12 lb. Retention tests during the 24-hour period showed no significant difference from the original testing, with 2- to 4-hour retention of 19.98±4.75 lb, 6- to 8-hour retention of 25.07±6.60 lb, and 22- to 24-hour retention of 21.75±4.58 lb. Participants who only received verbal instructions consistently bore several-fold greater weight than instructed. Biofeedback training has previously been shown to have a strong immediate effect on partial weight-bearing compliance. This study demonstrated that this effect lasts up to 24 hours. This maintained weight-bearing compliance after biofeedback training suggests that this method may be an effective way to train patients to comply with given instructions for limited weight bearing.

  1. Dynamic characteristics of polymer faced tilting pad journal bearings

    DEFF Research Database (Denmark)

    Simmons, Gregory F.; Cerda Varela, Alejandro Javier; Santos, Ilmar

    2014-01-01

    Dynamic characteristics of polymer faced tilting pad journal bearings are presented. Investigations are conducted using a single pad, load on pad configuration over a range of shaft speeds and loads. Two polyether ether ketone (PEEK) faced pads, one polytetrafluoroethylene (PTFE) faced pad and tw...

  2. Discontinuity effects in dynamically loaded tilting pad journal bearings

    DEFF Research Database (Denmark)

    Thomsen, Kim; Klit, Peder; Vølund, Anders

    2011-01-01

    This paper describes two discontinuity effects that can occur when modelling radial tilting pad bearings subjected to high dynamic loads. The first effect to be treated is a pressure build-up discontinuity effect. The second effect is a contact-related discontinuity that disappears when a contact...

  3. Seismic velocities for hydrate-bearing sediments using weighted equation

    Science.gov (United States)

    Lee, M.W.; Hutchinson, D.R.; Collett, T.S.; Dillon, William P.

    1996-01-01

    A weighted equation based on the three-phase time-average and Wood equations is applied to derive a relationship between the compressional wave (P wave) velocity and the amount of hydrates filling the pore space. The proposed theory predicts accurate P wave velocities of marine sediments in the porosity range of 40-80% and provides a practical means of estimating the amount of in situ hydrate using seismic velocity. The shear (S) wave velocity is derived under the assumption that the P to S wave velocity ratio of the hydrated sediments is proportional to the weighted average of the P to S wave velocity ratios of the constituent components of the sediment. In the case that all constituent components are known, a weighted equation using multiphase time-average and Wood equations is possible. However, this study showed that a three-phase equation with modified matrix velocity, compensated for the clay content, is sufficient to accurately predict the compressional wave velocities for the marine sediments. This theory was applied to the laboratory measurements of the P and S wave velocities in permafrost samples to infer the amount of ice in the unconsolidated sediment. The results are comparable to the results obtained by repeatedly applying the two-phase wave scattering theory. The theory predicts that the Poisson's ratio of the hydrated sediments decreases as the hydrate concentration increases and the porosity decreases. In consequence, the amplitude versus offset (AVO) data for the bottom-simulating reflections may reveal positive, negative, or no AVO anomalies depending on the concentration of hydrates in the sediments.

  4. Bear

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The famous physicist made for his scholars this riddle. A fellow encountered a bear in a wasteland. There was nobody else there. Both were frightened and ran away. Fellow to the north, bear to the west. Suddenly the fellow stopped, aimed his gun to the south and shot the bear. What colour was the bear?

  5. Effects of body weight and season on serum lipid concentrations in sloth bears (Melursus ursinus ursinus).

    Science.gov (United States)

    Shanmugam, Arun Attur; Kumar, Jadav Kajal; Selvaraj, Illayaraja; Selvaraj, Vimal

    2011-09-01

    Serum lipid levels were measured in 66 healthy sloth bears (Melursus ursinus ursinus) living under semicaptive conditions with access to natural food resources in the Bannerghatta Biological Park (Karnataka, India), a portion of their native habitat range in the Indian peninsula. Total cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein cholesterol levels were analyzed. The effects of age, body weight, and season on these lipid parameters were statistically evaluated. There were no correlations between age and any of the serum lipid parameters analyzed. Positive correlations of body weight to both triglyceride and HDL cholesterol levels in these bears were identified. In addition, seasonal trends in physiological serum lipid values, potentially due to variations in the sloth bear diet, were identified. Serum triglyceride levels were higher during postmonsoon season and cholesterol levels were higher during winter compared to other seasons. Serum lipid values obtained from sloth bears in this study were also compared to previously published data on other members of the family Ursidae. This is the first report of serum lipid values as a reference for sloth bears. These values can be used as sensitive predictors of overall health and nutritional status to aid in the captive management and feeding of these bears.

  6. A Dynamic Analysis of Hydrodynamic Wave Journal Bearings

    Science.gov (United States)

    Ene, Nicoleta M.; Dimofte, Florin; Keith, Theo G.

    2008-01-01

    The purpose of this paper is to study the dynamic behavior of a three-wave journal bearing using a transient approach. The transient analysis permits the determination of the rotor behavior after the fractional frequency whirl appears. The journal trajectory is determined by solving a set of nonlinear equations of motion using the Runge-Katta method. The fluid film forces are computed by integrating the transient Reynolds equation at each time step location of the shaft with respect to the bearing. Because of the large values of the rotational speeds, turbulent effects were included in the computations. The influence of the temperature on the viscosity was also considered. Numerical results were compared to experimenta1 results obtained at the NASA Glenn Research Center. Comparisons of the theoretical results with experimental data were found to be in good agreement. The numerical and experimental results showed that the fluid film of a three-wave journal bearing having a diameter of 30 mm, a length of 27 mm, and a wave amplitude ratio greater than 0.15 is stable even at rotational speeds of 60,000 RPM. For lower wave amplitude ratios, the threshold speed at which the fluid film becomes unstable depends on the wave amplitude and on the supply pocket pressure. Even if the fluid film is unstable, the wave bearing maintains the whirl orbit inside the bearing clearance.

  7. Influence of backup bearings and support structure dynamics on the behavior of rotors with active supports

    Science.gov (United States)

    Flowers, George T.

    1995-02-01

    This semiannual status report lists specific accomplishments made on the research of the influence of backup bearings and support structure dynamics on the behavior of rotors with active supports. Papers have been presented representing work done on the T-501 engine model; an experimental/simulation study of auxiliary bearing rotordynamics; and a description of a rotordynamical model for a magnetic bearing supported rotor system, including auxiliary bearing effects. A finite element model for a foil bearing has been developed. Additional studies of rotor/bearing/housing dynamics are currently being performed as are studies of the effects of sideloading on auxiliary bearing rotordynamics using the magnetic bearing supported rotor model.

  8. Weighted Kernel Entropy Component Analysis for Fault Diagnosis of Rolling Bearings

    Science.gov (United States)

    Zhou, Hongdi; Shi, Tielin; Liao, Guanglan; Xuan, Jianping; Duan, Jie; Su, Lei; He, Zhenzhi; Lai, Wuxing

    2017-01-01

    This paper presents a supervised feature extraction method called weighted kernel entropy component analysis (WKECA) for fault diagnosis of rolling bearings. The method is developed based on kernel entropy component analysis (KECA) which attempts to preserve the Renyi entropy of the data set after dimension reduction. It makes full use of the labeled information and introduces a weight strategy in the feature extraction. The class-related weights are introduced to denote differences among the samples from different patterns, and genetic algorithm (GA) is implemented to seek out appropriate weights for optimizing the classification results. The features based on wavelet packet decomposition are derived from the original signals. Then the intrinsic geometric features extracted by WKECA are fed into the support vector machine (SVM) classifier to recognize different operating conditions of bearings, and we obtain the overall accuracy (97%) for the experimental samples. The experimental results demonstrated the feasibility and effectiveness of the proposed method. PMID:28335480

  9. Comparisons of weight-bearing and non-weight-bearing tests of knee proprioception performed by patients with patello-femoral pain syndrome and asymptomatic individuals.

    Science.gov (United States)

    Kramer, J; Handfield, T; Kiefer, G; Forwell, L; Birmingham, T

    1997-04-01

    To compare non-weight-bearing (sitting) and weight-bearing (standing, with approximately 95% of body weight on the test leg) tests of knee proprioception performed by patients with patello-femoral pain syndrome (PFPS) and asymptomatic individuals. A repeated measures design, repeated on two occasions. Athletic injuries clinic. Seven men and 17 women with PFPS, and age- and sex-matched asymptomatic individuals. With their eyes closed, subjects extended their knee in sitting, or flexed their knees in standing, attempting to replicate target angles (15 degrees, 30 degrees, 45 degrees, and 60 degrees knee flexion) measured using an electrogoniometer. Observed angle of knee flexion during joint angle replication tests. Test-retest reliability coefficients (0.17-0.79) and between-session measurement error (+/-2.0 degrees to +/-6.4 degrees) varied widely. There was a tendency for reliability coefficients to be greater and between-session measurement error to be lower, for PFPS subjects, and for sitting tests. No significant differences were observed between the scores of the PFPS and asymptomatic subjects, at any of the four target knee angles. Scores in sitting should not be compared with those in standing. Clinically, the low reliability coefficients, large between-session measurement error, and finding of no statistically significant difference between PFPS and asymptomatic subjects suggest that the diagnostic value of the proprioceptive tests used is questionable. Further research is required to develop more precise tests of knee proprioception and to determine if the present results are applicable to other pathologies.

  10. Dynamic Carrying Capacity Analysis of Double-Row Four-Point Contact Ball Slewing Bearing

    Directory of Open Access Journals (Sweden)

    Yunfeng Li

    2015-01-01

    Full Text Available Carrying capacity is the most important performance index for slewing bearings. Maximizing the carrying capacity of slewing bearing is one pursuing goal for the bearing designer; this is usually realized by optimizing the design parameters. A method of analyzing the carrying capacity of double-row four-point contact ball slewing bearing by using dynamic carrying capacity surfaces was proposed in this paper. Based on the dynamic load carrying capacity surface of the slewing bearing, the effect of changes of the bearing design parameters, such as axial clearance, raceway groove radius coefficient, and contact angle, on the dynamic carrying capacity of the slewing bearing was researched; the trend and the degree of the effect of the micro changes of the bearing design parameters on the dynamic load carrying capacity of the bearing were discussed, and the results provide the basis for optimizing the design parameter of this type of slewing bearing.

  11. Dynamic Carrying Capacity Analysis of Double-Row Four-Point Contact Ball Slewing Bearing

    OpenAIRE

    Yunfeng Li; Di Jiang

    2015-01-01

    Carrying capacity is the most important performance index for slewing bearings. Maximizing the carrying capacity of slewing bearing is one pursuing goal for the bearing designer; this is usually realized by optimizing the design parameters. A method of analyzing the carrying capacity of double-row four-point contact ball slewing bearing by using dynamic carrying capacity surfaces was proposed in this paper. Based on the dynamic load carrying capacity surface of the slewing bearing, the effect...

  12. Biofeedback in Partial Weight Bearing : Usability of Two Different Devices from a Patient's and Physical Therapist's Perspective

    NARCIS (Netherlands)

    van Lieshout, Remko; Pisters, Martijn F; Vanwanseele, Benedicte; de Bie, Rob A; Wouters, Eveline J; Stukstette, Mirelle J

    2016-01-01

    BACKGROUND: Partial weight bearing is frequently instructed by physical therapists in patients after lower-limb trauma or surgery. The use of biofeedback devices seems promising to improve the patient's compliance with weight-bearing instructions. SmartStep and OpenGo-Science are biofeedback devices

  13. Compliant Foil Journal Bearings - Investigation of Dynamic Properties

    DEFF Research Database (Denmark)

    Larsen, Jon Steffen; Santos, Ilmar

    a Bubnow-Galerkin approach. This constitutes the main original contribution of this work, considering the fact that the finite difference method is commonly used and thouroughly investigated in the literature. The finite element method leads to a set of non-linear equations for the static fluid film....../compliance of the foil structure is presented. The compliance of the foil structure is incorporated implicitly in the Reynolds equation which is accomplished through a modification of the film gap function [8]. The resulting non-linear equation is perturbed and solved by use of the finite element method following...... and dynamic coefficients, of the compliant foil bearing together with an efficient solution method, which can be easily adopted and implemented by mechanical engineers. A theoretical model of a radial compliant foil bearing that incorporates compressibility of the lubricating gas and flexibility...

  14. Inadequate thickness of the weight-bearing surface of claws in ruminants.

    Science.gov (United States)

    Shakespeare, A S

    2009-12-01

    The term 'thin soles' refers to the suboptimal thickness of the weight-bearing surface of claws in ruminants. These palmar/plantar surfaces of the claws support the weight of the animal and consist of the distal wall horn, the sole proper, the heel and the minute white line area. The sole should normally only bear weight on uneven or undulating surfaces. A decrease in the thickness of the weight-bearing claw surface will decrease the protective function of this structure and may alter the proportion of weight-bearing by each section with possible detrimental effects on hoof function. Horn tissue readily absorbs water and becomes softer which can lead to increased wear rates. Growth rates normally match wear rates but, unlike the latter, time is needed for the growth rate response to adapt to changes in wear rate. Concrete surfaces can be abrasive and dairy cows that spend their lactation cycle on these floors should be let out to pasture in the dry period so that their claws can recoup lost horn. Frictional coefficient is a measure of the'slipperiness' of hooves on various surfaces. Newly laid or fresh concrete is not only abrasive but the thin surface suspension of calcium hydroxide that forms has a very alkaline pH which causes keratin degradation and is mostly responsible for the excessive claw wear that occurs. Four case studies are used to illustrate the importance of the distal wall horn, the dangers of over-trimming and the effects of disease and concrete on horn growth and wear rates.

  15. The energy expenditure of non-weight bearing crutch walking on the level and ascending stairs.

    Science.gov (United States)

    Moran, Jonathan; Murphy, Alexandra; Murphy, David; Austin, Andy; Moran, Danielle; Cronin, Caitriona; Guinan, Emer; Hussey, Juliette

    2015-06-01

    Crutches are commonly prescribed to patients with lower limb dysfunction during rehabilitation to assist with mobility. The aim of this study was to determine the energy expenditure for non-weight bearing crutch walking on level ground and ascending stairs at a self selected speed in a healthy adult population. Thirty-one healthy male and female adults (mean±SD: age 21.6±1.2 years; height 170.8±10.8 cm; weight 70.8±11.4 kg) mobilised non-weight bearing with elbow crutches along a 30 m corridor and (with one crutch) up a flight of 13 stairs. Energy expenditure for each activity was measured by indirect calorimetry using the COSMED K4b(2) portable ergospirometry system. The established VO2 values were 16.4ml/kg/min for crutch walking on level ground and 17.85 ml/kg/min for stair climbing. Non-weight bearing crutch walking at a self selected speed on the level ground and up a flight of stairs resulted in a MET value of 4.57 and 5.06 respectively. The mean heart rate (HR) for crutch walking along the flat was 117.06±20.54 beats per minute (bpm), while the mean HR for ambulating upstairs with crutches was 113.91±19.32 bpm. The increased energy demands of non-weight bearing crutch walking should be considered by physical therapists when instructing patients on crutch use. Further investigation to determine the implications of these results in populations with chronic disease is warranted.

  16. Inadequate thickness of the weight-bearing surface of claws in ruminants : clinical review

    Directory of Open Access Journals (Sweden)

    A.S. Shakespeare

    2009-05-01

    Full Text Available The term 'thin soles' refers to the suboptimal thickness of the weight-bearing surface of claws in ruminants. These palmar / plantar surfaces of the claws support the weight of the animal and consist of the distal wall horn, the sole proper, the heel and the minute white line area. The sole should normally only bear weight on uneven or undulating surfaces. A decrease in the thickness of the weight-bearing claw surface will decrease the protective function of this structure and may alter the proportion of weight-bearing by each section with possible detrimental effects on hoof function. Horn tissue readily absorbs water and becomes softer which can lead to increased wear rates. Growth rates normally match wear rates but, unlike the latter, time is needed for the growth rate response to adapt to changes in wear rate. Concrete surfaces can be abrasive and dairy cows that spend their lactation cycle on these floors should be let out to pasture in the dry period so that their claws can recoup lost horn. Frictional coefficient is a measure of the 'slipperiness' of hooves on various surfaces. Newly laid or fresh concrete is not only abrasive but the thin surface suspension of calcium hydroxide that forms has a very alkaline pH which causes keratin degradation and is mostly responsible for the excessive claw wear that occurs. Four case studies are used to illustrate the importance of the distal wall horn, the dangers of over-trimming and the effects of disease and concrete on horn growth and wear rates.

  17. Automatic Weight Selection Algorithm for Designing H Infinity controller for Active Magnetic Bearing

    Directory of Open Access Journals (Sweden)

    Sarath S Nair

    2011-01-01

    Full Text Available In recent times active magnetic bearing has got wide acceptance in industries and other special systems. Current researches focus on improving the disturbance rejection properties of magnetic bearings towork well in industrial environment. So far many controllers have been developed to control the system, of which the H∞ controller is found to guarantee robustness and performance. In this paper an automatic weight selection algorithm is proposed to design robust H Infinity controller automatically for active magnetic bearing system and detailed disturbance analysis is done. This paper focuses on the controller implementation point of view and analyses the variation in control current, peak responses and steady state error of the developed controller. Comparison with a well tuned PID controller shows the efficacy of H infinity controller designed using the proposed algorithm.

  18. The impact of adding weight-bearing exercise versus nonweight bearing programs to the medical treatment of elderly patients with osteoporosis

    Directory of Open Access Journals (Sweden)

    Alsayed A Shanb

    2014-01-01

    Full Text Available Background: Osteoporosis is a major public health problem affecting the elderly population, particularly women. The objective of the study was to evaluate the effects of adding weight-bearing exercise as opposed to nonweight-bearing programs to the medical treatment of bone mineral density (BMD and health-related quality of life (HRQoL of elderly patients with osteoporosis. Materials and Methods: Participating in the study were 40 elderly osteoporotic patients (27 females and 13 males, with ages ranging from 60 to 67 years, who were receiving medical treatment for osteoporosis. They were assigned randomly into two groups: Group-I: Twenty patients practiced weight-bearing exercises. Group-II: Twenty patients did nonweight-bearing exercises. All patients trained for 45-60 min/session, two sessions/week for 6 months. BMD of the lumbar spine, right neck of femur, and right distal radial head of all patients were measured by dual-energy X-ray absorptiometry before and after both treatment programs. In addition, the QoL was measured by means of the HRQoL "ECOS-16" questionnaire. Results: T-tests proved that mean values of BMD of the lumbar spine, right neck of femur and right distal radial head were significantly increased in both groups with greater improvement in the weight-bearing group. The QoL was significantly improved in both groups, but the difference between them was not significant. Conclusion: Addition of weight-bearing exercise program to medical treatment increases BMD more than nonweight-bearing exercise in elderly subjects with osteoporosis. Furthermore, both weight-bearing and nonweight-bearing exercise programs significantly improved the QoL of patients with osteoporosis.

  19. Lesion of the anterior cruciate ligament and sagittal disalignment of the knee in weight-bearing

    Energy Technology Data Exchange (ETDEWEB)

    Egund, N.; Friden, T.

    Twenty-nine patients with late reconstructive surgery for anterior cruciate ligament lesions had a clinical and radiologic follow-up ten years after injury. Anterior sagittal displacement of the tibia was recorded on the routine standing radiographs in 16 knees all having a normal femoro-tibial alignment in the non-weight-bearing position. Five of eleven patients with sagittal displacement of between 10 and 19 mm had early osteoarthrosis, which was confirmed by magnetic resonance imaging in four cases; their ages ranged from 23 to 38 years. No radiographic signs of osteoarthrosis were observed in those with displacements of less than 10 mm. In some patients there was a discrepancy between the clinical and radiographic measurements of instability. In addition to the clinical tests of instability standing rather than non-weight-bearing lateral radiographs are suggested for the routine assessment of cruciate ligament injuries.

  20. Lumbar stenosis rates in symptomatic patients using weight-bearing and recumbent magnetic resonance imaging.

    Science.gov (United States)

    Gilbert, John W; Martin, J Chad; Wheeler, Greg R; Storey, Benjamin B; Mick, Gregory E; Richardson, Gay B; Herder, Stephanie L; Gyarteng-Dakwa, Kwadwo

    2011-10-01

    The purpose of this study was to determine the rate of lumbar stenosis detected via magnetic resonance imaging (MRI) in patients with symptomatic foraminal stenosis, lateral recess stenosis, or central stenosis. A retrospective review was performed on 1983 MRI scans from a 2-year period on 1486 symptomatic patients. Of these patients, 761 were scanned in the recumbent position using low-field (0.3 T, Airis II; Hitachi, Twinsburg, Ohio) MRI, and 725 were scanned in an upright sitting position using midfield (0.6 T) open Upright MRI (Fonar Corp, Melville, NY). In total, 986 serial scans (recumbent) and 997 serial scans (weight-bearing) were performed. Of scans performed in the recumbent position, stenoses were identified in 382 scans (38.8%), central stenosis in 119 scans (12%), lateral recess stenosis in 91 scans (9.2%), and foraminal stenosis in 327 scans (33.2%). Of scans performed in a weight-bearing position, stenoses were identified in 565 scans (56.7%), central stenosis in 136 scans (13.6%), lateral recess stenosis in 206 scans (20.7%), and foraminal stenosis in 524 scans (52.6%). The stenosis rates as indicated by MRI interpretation ranged between 38.5% (recumbent) and 56.7% (weight-bearing). These rates are higher than those reported in the medical literature for asymptomatic patients. Further study is needed to determine whether weight-bearing, compared with recumbent, MRI better informs the clinician in the diagnosis of spinal stenosis. Copyright © 2011 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.

  1. Sclerostin antibody inhibits skeletal deterioration in mice exposed to partial weight-bearing

    Science.gov (United States)

    Spatz, J. M.; Ellman, R.; Cloutier, A. M.; Louis, L.; van Vliet, M.; Dwyer, D.; Stolina, M.; Ke, H. Z.; Bouxsein, M. L.

    2017-02-01

    Whereas much is known regarding the musculoskeletal responses to full unloading, little is known about the physiological effects and response to pharmacological agents in partial unloading (e.g. Moon and Mars) environments. To address this, we used a previously developed ground-based model of partial weight-bearing (PWB) that allows chronic exposure to reduced weight-bearing in mice to determine the effects of murine sclerostin antibody (SclAbII) on bone microstructure and strength across different levels of mechanical unloading. We hypothesize that treatment with SclAbII would improve bone mass, microarchitecture and strength in all loading conditions, but that there would be a greater skeletal response in the normally loaded mice than in partially unloaded mice suggesting the importance of combined countermeasures for exploration-class long duration spaceflight missions. Eleven-week-old female mice were assigned to one of four loading groups: normal weight-bearing controls (CON) or weight-bearing at 20% (PWB20), 40% (PWB40) or 70% (PWB70) of normal. Mice in each group received either SclAbII (25 mg/kg) or vehicle (VEH) via twice weekly subcutaneous injection for 3 weeks. In partially-unloaded VEH-treated groups, leg BMD decreased -5 to -10% in a load-dependent manner. SclAbII treatment completely inhibited bone deterioration due to PWB, with bone properties in SclAbII-treated groups being equal to or greater than those of CON, VEH-treated mice. SclAbII treatment increased leg BMD from +14 to +18% in the PWB groups and 30 ± 3% in CON (p antibody therapy in preventing astronaut bone loss during terrestrial solar system exploration.

  2. Bone loss during partial weight bearing (1/6th gravity) is mitigated by resistance and aerobic exercise in mice

    Science.gov (United States)

    Boudreaux, R. D.; Metzger, C. E.; Macias, B. R.; Shirazi-Fard, Y.; Hogan, H. A.; Bloomfield, S. A.

    2014-06-01

    Astronauts on long duration missions continue to experience bone loss, as much as 1-2% each month, for up to 4.5 years after a mission. Mechanical loading of bone with exercise has been shown to increase bone formation, mass, and geometry. The aim of this study was to compare the efficacy of two exercise protocols during a period of reduced gravitational loading (1/6th body weight) in mice. Since muscle contractions via resistance exercise impart the largest physiological loads on the skeleton, we hypothesized that resistance training (via vertical tower climbing) would better protect against the deleterious musculoskeletal effects of reduced gravitational weight bearing when compared to endurance exercise (treadmill running). Young adult female BALB/cBYJ mice were randomly assigned to three groups: 1/6 g (G/6; n=6), 1/6 g with treadmill running (G/6+RUN; n=8), or 1/6 g with vertical tower climbing (G/6+CLB; n=9). Exercise was performed five times per week. Reduced weight bearing for 21 days was achieved through a novel harness suspension system. Treadmill velocity (12-20 m/min) and daily run time duration (32-51 min) increased incrementally throughout the study. Bone geometry and volumetric bone mineral density (vBMD) at proximal metaphysis and mid-diaphysis tibia were assessed by in vivo peripheral quantitative computed tomography (pQCT) on days 0 and 21 and standard dynamic histomorphometry was performed on undemineralized sections of the mid-diaphysis after tissue harvest. G/6 caused a significant decrease (P<0.001) in proximal tibia metaphysis total vBMD (-9.6%). These reductions of tibia metaphyseal vBMD in G/6 mice were mitigated in both G/6+RUN and G/6+CLB groups (P<0.05). After 21 days of G/6, we saw an absolute increase in tibia mid-diaphysis vBMD and in distal metaphysis femur vBMD in both G/6+RUN and G/6+CLB mice (P<0.05). Substantial increases in endocortical and periosteal mineralizing surface (MS/BS) at mid-diaphysis tibia in G/6+CLB demonstrate that

  3. A prospective study comparing attempted weight bearing in fiberglass below-knee casts and prefabricated pneumatic braces.

    Science.gov (United States)

    Mason, Lyndon W; Dodds, Alex

    2010-04-01

    Partial weight bearing is commonly advised after fracture of the lower extremity. Research has determined this to be inaccurate both in its instruction and its reproducibility. Many trauma departments are commonly using alternatives to plaster in the splintage of fractures, such as fiberglass and the prefabricated pneumatic braces. This study's null hypothesis is that there is no difference between partial weight bearing through a fiberglass cast as compared with a pneumatic walker. A prospective study was conducted in our department including all patients who had metatarsal or ankle fractures and could partially weight bear. Patients were excluded if they were not allowed to bear weight, had received operative fixation of their fracture, or were younger than age 16 years. The patients' total weight was measured first, and then they were trained to place 50% of their weight through the splinted limb. Three measurements were taken of their attempted weight bearing at 50%, and they were blinded to the results. Over a 16-month period, 117 patients were enrolled for this study: 72 in the pneumatic walker group and 45 in the fiberglass group. There was no significant difference in sex, age, or fracture type. There was a significant difference in percentage of weight placed through the splinted limb, with the pneumatic brace group placing much greater force than the fiberglass group. This may have been caused by altered proprioception from the walker. It is important to realize this when prescribing partial weight bearing in a particular splint as this may result in avoidable complications.

  4. Knee angle-specific MVIC for triceps surae EMG signal normalization in weight and non weight-bearing conditions.

    Science.gov (United States)

    Hébert-Losier, Kim; Holmberg, Hans-Christer

    2013-08-01

    Varying the degree of weight-bearing (WB) and/or knee flexion (KF) angle during a plantar-flexion maximal voluntary isometric contraction (MVIC) has been proposed to alter soleus and/or gastrocnemius medialis and lateralis activation. This study compared the surface EMG signals from the triceps surae of 27 men and 27 women during WB and non weight bearing (NWB) plantar-flexion MVICs performed at 0° and 45° of KF. The aim was to determine which condition was most effective at eliciting the greatest EMG signals from soleus, gastrocnemius medialis, and gastrocnemius lateralis, respectively, for subsequent use for the normalization of EMG signals. WB was more effective than NWB at eliciting the greatest signals from soleus (p=0.0021), but there was no difference with respect to gastrocnemius medialis and lateralis (p⩾0.2482). Although the greatest EMG signals during MVICs were more frequently elicited at 0° of KF from gastrocnemius medialis and lateralis, and at 45° from soleus (ptriceps surae muscle.

  5. A new nonlinear dynamic model of the rotor-bearing system considering preload and varying contact angle of the bearing

    Science.gov (United States)

    Zhang, Xuening; Han, Qinkai; Peng, Zhike; Chu, Fulei

    2015-05-01

    A great deal of research work has been done on the dynamic behaviors of the rotor-bearing system. However, the important effects of load and variation of contact angle on the bearing performance have not been focused on sufficiently. In this paper, a five-degree-of-freedom load distribution model is set up considering the bearing preload and the loads due to the rotor imbalance. Utilizing this model, the variation of the bearing contact angle is investigated thoroughly. The comparisons of the obtained contact angle against the results from literature validate that the proposed load distribution model is effective. With this model, the static ball deformations are obtained considering variation of the contact angle. Through resolving the dynamic displacements of the rotor, the dynamic ball deformations could also be obtained. Then the total restoring forces and moments of the bearings could be formulated. By introducing these nonlinear forces and moments into the rotating system, a new dynamic model considering the preload and the variation of contact angle is set up. The present analyses indicate that the bearing contact angle will be changed remarkably with the effect of bearing load. The deflection vibration of the rotor-bearing system will be underestimated without considering the varying contact angle. With the effect of varying contact angle, the ball passage frequency and its combinations with the shaft rotating frequency become more noticeable. The main resonance regions for the rotor-bearing system shift to the lower speed ranges when the variation of contact angle is taken into account.

  6. Weight-bearing passive dorsiflexion of the hallux in standing is not related to hallux dorsiflexion during walking.

    Science.gov (United States)

    Halstead, Jill; Redmond, Anthony C

    2006-08-01

    Case control study. To explore the validity of the assumptions underpinning the Hubscher maneuver of hallux dorsiflexion in relaxed standing, by comparing the relationship between static and dynamic first metatarsophalangeal (MTP) joint motions in groups differentiated by normal and abnormal clinical test findings. Limitation of motion at the first MTP joint during gait may be due to either structural or functional factors. Functional hallux limitus (FHL) has been proposed as a term to describe the situation in which the first MTP joint shows no limitation when non-weight bearing, but shows limited dorsiflexion during gait. One clinical test of first MTP joint limitation during standing (the Hubscher maneuver or Jack's test) has become widely used in physical therapy, orthopedic, and podiatric assessments, supposedly to assess for the presence of hallux limitations during gait. The utility of the test is based on an assumption that restriction during the static maneuver is predictive of functional limitation at this joint during gait. Despite a lack of evidence for the validity of such an assumption, the outcome of the static test is often used to infer risk of overuse injury or as an outcome for functional therapy. This paper examines the validity of the assumptions supporting this widely used static test. First-MTP-joint motion was assessed using an electromagnetic motion tracking system in cases (n = 15) demonstrating clinically limited passive hallux dorsiflexion in relaxed standing, and in 15 controls matched for age and gender and demonstrating a clinically normal Hubscher maneuver. Maximum hallux dorsiflexion was measured with the subject non-weight bearing (seated), during relaxed standing, and during normal walking. Hallux dorsiflexion was similar in cases and controls when motions were measured non-weight bearing (cases mean +/- SD, 55.0 degrees +/- 11.0 degrees; controls mean + SD, 55.0 degrees +/- 10.7 degrees), confirming the absence of structural

  7. Rotor-Bearing Dynamics Technology Design Guide. Part 4. Cylindrical Roller Bearings

    Science.gov (United States)

    1979-12-01

    ýbluck ,,lb.,mb i Tapered Roller Bearings Roller Beating Stiffness Tapered Roller Bearing Stiffness Turbine Bearings VRoller Bearings Rotordynamics ...input for rotordynamic response programs. The complete stiffness matrix is calculated including centrifugal effects. Considerations such as elastohydro...those parts directly connected with preparation of input for the rotordynamic response programs (Part 1(5) of the revised series) were retained. The

  8. Effects of obesity on weight-bearing versus weight-supported exercise testing in patients with COPD.

    Science.gov (United States)

    Maatman, Robbert C; Spruit, Martijn A; van Melick, Paula P; Peeters, Jos P I; Rutten, Erica P A; Vanfleteren, Lowie E G W; Wouters, Emiel F M; Franssen, Frits M E

    2016-04-01

    Obesity is associated with increased dyspnoea and reduced health status in patients with chronic obstructive pulmonary disease (COPD). Studies on the effects of obesity on exercise capacity showed divergent results. The objective of this study is to investigate the impact of obesity on weight-bearing versus weight-supported exercise tolerance in obese and normal weight patients, matched for age, gender and degree of airflow limitation. Retrospective analyses of data obtained during pre-pulmonary rehabilitation assessment in 108 obese COPD patients (OB) (age: 61.2 ± 5.3y, FEV1 : 43.2 ± 7.4%, BMI: 34.1 ± 3.9 kg/m(2) ,) and 108 age and FEV1 -matched normal weight COPD patients (NW) (age: 61.7 ± 3.6y, FEV1 : 41.5 ± 8.4%, BMI: 22.9 ± 1.2 kg/m(2) ,). Cardiopulmonary exercise test (CPET) and 6 min walk test (6MWT) were performed, Borg scores for dyspnoea and leg fatigue were recorded, before and after the tests. Six-minute walk distance differed between OB (398 ± 107 m) and NW patients (446 ± 109 m, P exercise load was comparable (OB: 75 ± 29 W, NW: 70 ± 25 W, ns). Dyspnoea (OB 3.2 ± 2.0 vs NW 3.1 ± 1.7, ns) and leg fatigue (OB 2.4 ± 2.3 vs NW 1.9 ± 1.7, ns) were not significantly different in OB compared with NW after 6MWT, or after CPET (dyspnoea: OB 5.1 ± 2.4 vs NW 5.4 ± 2.2, ns; leg fatigue: OB 4.0 ± 2.3 vs NW 4.0 ± 2.7, ns). In contrast to weight-supported exercise, obesity has a negative impact on weight-bearing exercise capacity, despite comparable exercise-related symptoms. The results of this study enhance the understanding of the impact of obesity on physical performance in COPD. © 2015 Asian Pacific Society of Respirology.

  9. KINEMATICS AND DYNAMICS MODELS OF CYLINDRICAL ROLLER BEARING OF RAILWAY TRANSPORT

    Directory of Open Access Journals (Sweden)

    A. V. Gaydamaka

    2014-05-01

    Full Text Available Purpose. Lack of kinematics models and imperfection of the known dynamics models of the roller bearings of railway rolling stock axle-boxes do not allow designing the optimal structure of bearing cages, providing the required service life and reliability of bearing units of wheel sets for cars and locomotives. The studies of kinematics and dynamics of roller bearings of axle boxes for cars and locomotives and modeling of their parts interaction to create the analytical method of bearing cages calculation are necessary. Methodology. This purpose has been achieved due to the modeling of kinematics of the ideal (without gaps and real (taking account the gaps, manufacturing and installation errors bearings, substantiation of the transfer mechanism of motion from the rollers to bearing cage, modeling the dynamics of rolling, research of interaction forces of the rollers with bearing cage. Findings. It is established that the kinematics of ideal bearing is determined by the contact deformations of the rollers and rings, when the kinematics of real bearing depends mainly on the side gaps in the windows of the bearing cage. On the basis of studies of the real bearing kinematics the dynamics models of the rollers and bearing cage interaction were constructed. The conducted studies of kinematics and dynamics of rolling bearings have changed our view of them as of the planetary mechanism, explained the reason of bearing cage loading, and confirmed the possibility of destruction during operation. Originality. It was first proposed a mechanism for motion transfer from the rollers to the bearing cage of roller bearings, consisting in that the side gap in the bearing cage window is reduced gradually multiple of the number of rollers of radial loading area according to the bearing cage motion. The models of roller bearing dynamics, which allow calculating the interaction forces of parts for all modes of operation, were improved. Practical value. Use of the

  10. Is Weight-Bearing Asymmetry Associated with Postural Instability after Stroke? A Systematic Review

    Directory of Open Access Journals (Sweden)

    Jip F. Kamphuis

    2013-01-01

    Full Text Available Introduction. Improvement of postural stability is an important goal during poststroke rehabilitation. Since weight-bearing asymmetry (WBA towards the nonparetic leg is common, training of weight-bearing symmetry has been a major focus in post-stroke balance rehabilitation. It is assumed that restoration of a more symmetrical weight distribution is associated with improved postural stability. Objective. To determine to what extent WBA is associated with postural instability in people after stroke. Methods. Electronic databases were searched (Cochrane, MEDLINE, EMBASE, and CINAHL until March 2012. Main Eligibility Criteria. (1 Participants were people after stroke. (2 The association between WBA and postural stability was reported. Quality of reporting was assessed with the STROBE checklist and a related tool for reporting of confounding. Results. Nine observational studies met all criteria. Greater spontaneous WBA was associated with higher center of pressure (COP velocity and with poorer synchronization of COP trajectories between the legs (two and one studies, resp.. Evidence for associations between WBA and performance on clinical balance tests or falls was weak. Conclusion. Greater WBA after stroke was associated with increased postural sway, but the current literature does not provide evidence for a causal relationship. Further studies should investigate whether reducing WBA would improve postural stability.

  11. On the Modulation of Brain Activation During Simulated Weight Bearing in Supine Gait-Like Stepping.

    Science.gov (United States)

    Jaeger, Lukas; Marchal-Crespo, Laura; Wolf, Peter; Luft, Andreas R; Riener, Robert; Michels, Lars; Kollias, Spyros

    2016-01-01

    To date, the neurophysiological correlates of muscle activation required for weight bearing during walking are poorly understood although, a supraspinal involvement has been discussed in the literature for many years. The present study investigates the effect of simulated ground reaction forces (0, 20, and 40% of individual body weight) on brain activation in sixteen healthy participants. A magnetic resonance compatible robot was applied to render three different levels of load against the feet of the participants during active and passive gait-like stepping movements. Brain activation was analyzed by the means of voxel-wise whole brain analysis as well as by a region-of-interest analysis. A significant modulation of brain activation in sensorimotor areas by the load level could neither be demonstrated during active nor during passive stepping. These observations suggest that the regulation of muscle activation under different weight-bearing conditions during stepping occurs at the level of spinal circuitry or the brainstem rather than at the supraspinal level.

  12. A study on compliant layers and its influence on dynamic response of a hydrodynamic journal bearing

    DEFF Research Database (Denmark)

    Thomsen, Kim; Klit, Peder

    2011-01-01

    For some hydrodynamic bearing applications polymer-lined bearings are chosen over traditional metal alloy bearings due to their better wear and friction properties when operating at very thin films, e.g. in the mixed lubrication region. The introduction of a compliant layer also affects the dynamic...

  13. Weighted low-rank sparse model via nuclear norm minimization for bearing fault detection

    Science.gov (United States)

    Du, Zhaohui; Chen, Xuefeng; Zhang, Han; Yang, Boyuan; Zhai, Zhi; Yan, Ruqiang

    2017-07-01

    It is a fundamental task in the machine fault diagnosis community to detect impulsive signatures generated by the localized faults of bearings. The main goal of this paper is to exploit the low-rank physical structure of periodic impulsive features and further establish a weighted low-rank sparse model for bearing fault detection. The proposed model mainly consists of three basic components: an adaptive partition window, a nuclear norm regularization and a weighted sequence. Firstly, due to the periodic repetition mechanism of impulsive feature, an adaptive partition window could be designed to transform the impulsive feature into a data matrix. The highlight of partition window is to accumulate all local feature information and align them. Then, all columns of the data matrix share similar waveforms and a core physical phenomenon arises, i.e., these singular values of the data matrix demonstrates a sparse distribution pattern. Therefore, a nuclear norm regularization is enforced to capture that sparse prior. However, the nuclear norm regularization treats all singular values equally and thus ignores one basic fact that larger singular values have more information volume of impulsive features and should be preserved as much as possible. Therefore, a weighted sequence with adaptively tuning weights inversely proportional to singular amplitude is adopted to guarantee the distribution consistence of large singular values. On the other hand, the proposed model is difficult to solve due to its non-convexity and thus a new algorithm is developed to search one satisfying stationary solution through alternatively implementing one proximal operator operation and least-square fitting. Moreover, the sensitivity analysis and selection principles of algorithmic parameters are comprehensively investigated through a set of numerical experiments, which shows that the proposed method is robust and only has a few adjustable parameters. Lastly, the proposed model is applied to the

  14. Upright CT of the knee: the effect of weight-bearing on joint alignment

    Energy Technology Data Exchange (ETDEWEB)

    Hirschmann, Anna [Orthopedic University Hospital Balgrist, University of Zurich, Department of Radiology, Zurich (Switzerland); University of Basel Hospital, Clinic of Radiology and Nuclear Medicine, Basel (Switzerland); Buck, Florian M.; Pfirrmann, Christian W.A. [Orthopedic University Hospital Balgrist, University of Zurich, Department of Radiology, Zurich (Switzerland); Fucentese, Sandro F. [Orthopedic University Hospital Balgrist, University of Zurich, Orthopedic Surgery, Zurich (Switzerland)

    2015-11-15

    To prospectively compare patellofemoral and femorotibial alignment in supine non-weight-bearing computed tomography (NWBCT) and upright weight-bearing CT (WBCT) and assess the differences in joint alignment. NWBCT and WBCT images of the knee were obtained in 26 patients (mean age, 57.0 ± 15.9 years; range, 21-81) using multiple detector CT for NWBCT and cone-beam extremity CT for WBCT. Two musculoskeletal radiologists independently quantified joint alignment by measuring femorotibial rotation, tibial tuberosity-trochlear groove distance (TTTG), lateral patellar tilt angle, lateral patellar shift, and medial and lateral femorotibial joint space widths. Significant differences between NWBCT and WBCT were sought using Wilcoxon signed-rank test (P-value < 0.05). Significant differences were found for femorotibial rotation (the NWBCT mean changed from 2.7 ± 5.1 (reader 1)/2.6 ± 5.6 (reader 2) external rotation to WBCT 0.4 ± 7.7/0.2 ± 7.5 internal rotation; P = 0.009/P = 0.004), TTTG decrease from NWBCT (13.8 mm ± 5.1/13.9 mm ± 3.9) to WBCT (10.5 mm ± 5.0/10.9 mm ± 5.2; P = 0.008/P = 0.002), lateral patellar tilt angle decrease from NWBCT (15.6 ± 6.7/16.9 ± 7.4) to WBCT (12.5 ± 7.7/15.0 ± 6.2; P = 0.011/P = 0.188). The medial femorotibial joint space decreased from NWBCT (3.9 mm ± 1.4/4.5 mm ± 1.3) to WBCT (2.9 mm ± 2.2/3.5 mm ± 2.2; P = 0.003/P = 0.004). Inter-reader agreement ranged from 0.52-0.97. Knee joint alignment changes significantly in the upright weight-bearing position using CT when compared to supine non-weight-bearing CT. (orig.)

  15. Kurtosis based weighted sparse model with convex optimization technique for bearing fault diagnosis

    Science.gov (United States)

    Zhang, Han; Chen, Xuefeng; Du, Zhaohui; Yan, Ruqiang

    2016-12-01

    The bearing failure, generating harmful vibrations, is one of the most frequent reasons for machine breakdowns. Thus, performing bearing fault diagnosis is an essential procedure to improve the reliability of the mechanical system and reduce its operating expenses. Most of the previous studies focused on rolling bearing fault diagnosis could be categorized into two main families, kurtosis-based filter method and wavelet-based shrinkage method. Although tremendous progresses have been made, their effectiveness suffers from three potential drawbacks: firstly, fault information is often decomposed into proximal frequency bands and results in impulsive feature frequency band splitting (IFFBS) phenomenon, which significantly degrades the performance of capturing the optimal information band; secondly, noise energy spreads throughout all frequency bins and contaminates fault information in the information band, especially under the heavy noisy circumstance; thirdly, wavelet coefficients are shrunk equally to satisfy the sparsity constraints and most of the feature information energy are thus eliminated unreasonably. Therefore, exploiting two pieces of prior information (i.e., one is that the coefficient sequences of fault information in the wavelet basis is sparse, and the other is that the kurtosis of the envelope spectrum could evaluate accurately the information capacity of rolling bearing faults), a novel weighted sparse model and its corresponding framework for bearing fault diagnosis is proposed in this paper, coined KurWSD. KurWSD formulates the prior information into weighted sparse regularization terms and then obtains a nonsmooth convex optimization problem. The alternating direction method of multipliers (ADMM) is sequentially employed to solve this problem and the fault information is extracted through the estimated wavelet coefficients. Compared with state-of-the-art methods, KurWSD overcomes the three drawbacks and utilizes the advantages of both family

  16. Identification of dynamic properties of radial air-foil bearings

    NARCIS (Netherlands)

    Arora, V.; Hoogt, van der P.J.M.; Aarts, R.G.K.M.; Boer, de A.

    2010-01-01

    Air-foil bearings (AFBs) are self acting hydrodynamic bearings made from sheet metal foils comprised of at least two layers. The innermost “top foil” layer traps a gas pressure film that supports a load while the layer or layers underneath provide an elastic foundation. Air-foil bearings are current

  17. Identification of dynamic properties of radial air-foil bearings

    NARCIS (Netherlands)

    Arora, V.; Hoogt, van der P.J.M.; Aarts, R.G.K.M.; Boer, de A.

    2010-01-01

    Air-foil bearings (AFBs) are self acting hydrodynamic bearings made from sheet metal foils comprised of at least two layers. The innermost ‘‘top foil’’ layer traps a gas pressure film that supports a load while the layer or layers underneath provide an elastic foundation. Air-foil bearings are curre

  18. A Canine Non-Weight-Bearing Model with Radial Neurectomy for Rotator Cuff Repair.

    Directory of Open Access Journals (Sweden)

    Xiaoxi Ji

    Full Text Available The major concern of using a large animal model to study rotator cuff repair is the high rate of repair retears. The purpose of this study was to test a non-weight-bearing (NWB canine model for rotator cuff repair research.First, in the in vitro study, 18 shoulders were randomized to 3 groups. 1 Full-width transections repaired with modified Mason-Allen sutures using 3-0 polyglactin suture, 2 Group 1 repaired using number 2 (#2 polyester braid and long-chain polyethylene suture, and 3 Partial-width transections leaving the superior 2 mm infraspinatus tendon intact without repair. In the in vivo study of 6 dogs, the infraspinatus tendon was partially transected as the same as the in vitro group 3. A radial neurectomy was performed to prevent weight bearing. The operated limb was slung in a custom-made jacket for 6 weeks.In the in vitro study, mean ultimate tensile load and stiffness in Group 2 were significantly higher than Group 1 and 3 (p<0.05. In the in vivo study, gross inspection and histology showed that the preserved superior 2-mm portion of the infraspinatus tendon remained intact with normal structure.Based on the biomechanical and histological findings, this canine NWB model may be an appropriate and useful model for studies of rotator cuff repair.

  19. A Canine Non-Weight-Bearing Model with Radial Neurectomy for Rotator Cuff Repair

    Science.gov (United States)

    Ji, Xiaoxi; Bao, Nirong; An, Kai-Nan; Amadio, Peter C.; Steinmann, Scott P.; Zhao, Chunfeng

    2015-01-01

    Background The major concern of using a large animal model to study rotator cuff repair is the high rate of repair retears. The purpose of this study was to test a non-weight-bearing (NWB) canine model for rotator cuff repair research. Methods First, in the in vitro study, 18 shoulders were randomized to 3 groups. 1) Full-width transections repaired with modified Mason-Allen sutures using 3-0 polyglactin suture, 2) Group 1 repaired using number 2 (#2) polyester braid and long-chain polyethylene suture, and 3) Partial-width transections leaving the superior 2 mm infraspinatus tendon intact without repair. In the in vivo study of 6 dogs, the infraspinatus tendon was partially transected as the same as the in vitro group 3. A radial neurectomy was performed to prevent weight bearing. The operated limb was slung in a custom-made jacket for 6 weeks. Results In the in vitro study, mean ultimate tensile load and stiffness in Group 2 were significantly higher than Group 1 and 3 (pinfraspinatus tendon remained intact with normal structure. Conclusions Based on the biomechanical and histological findings, this canine NWB model may be an appropriate and useful model for studies of rotator cuff repair. PMID:26107616

  20. A Canine Non-Weight-Bearing Model with Radial Neurectomy for Rotator Cuff Repair.

    Science.gov (United States)

    Ji, Xiaoxi; Bao, Nirong; An, Kai-Nan; Amadio, Peter C; Steinmann, Scott P; Zhao, Chunfeng

    2015-01-01

    The major concern of using a large animal model to study rotator cuff repair is the high rate of repair retears. The purpose of this study was to test a non-weight-bearing (NWB) canine model for rotator cuff repair research. First, in the in vitro study, 18 shoulders were randomized to 3 groups. 1) Full-width transections repaired with modified Mason-Allen sutures using 3-0 polyglactin suture, 2) Group 1 repaired using number 2 (#2) polyester braid and long-chain polyethylene suture, and 3) Partial-width transections leaving the superior 2 mm infraspinatus tendon intact without repair. In the in vivo study of 6 dogs, the infraspinatus tendon was partially transected as the same as the in vitro group 3. A radial neurectomy was performed to prevent weight bearing. The operated limb was slung in a custom-made jacket for 6 weeks. In the in vitro study, mean ultimate tensile load and stiffness in Group 2 were significantly higher than Group 1 and 3 (pinfraspinatus tendon remained intact with normal structure. Based on the biomechanical and histological findings, this canine NWB model may be an appropriate and useful model for studies of rotator cuff repair.

  1. Appearance of the weight-bearing lateral radiograph in retrocalcaneal bursitis

    Science.gov (United States)

    Muller, Bart; Maas, Mario; Sierevelt, Inger N; van Dijk, C Niek

    2010-01-01

    Background and purpose A retrocalcaneal bursitis is caused by repetitive impingement of the bursa between the Achilles tendon and the posterosuperior calcaneus. The bursa is situated in the posteroinferior corner of Kager's triangle (retrocalcaneal recess), which is a radiolucency with sharp borders on the lateral radiograph of the ankle. If there is inflammation, the fluid-filled bursa is less radiolucent, making it difficult to delineate the retrocalcaneal recess. We assessed whether the radiographic appearance of the retrocalcaneal recess on plain digital (filmless) radiographs could be used in the diagnosis of a retrocalcaneal bursitis. Methods Whether or not there was obliteration of the retrocalcaneal recess (yes/no) on 74 digital weight-bearing lateral radiographs of the ankle was independently assessed by 2 observers. The radiographs were from 24 patients (25 heels) with retrocalcaneal bursitis (confirmed on endoscopic calcaneoplasty); the control group consisted of 50 patients (59 heels). Results The sensitivity of the test was 83% for observer 1 and 79% for observer 2. Specificity was 100% and 98%, respectively. The kappa value of the interobserver reliability test was 0.86. For observer 1, intraobserver reliability was 0.96 and for observer 2 it was 0.92. Interpretation On digital weight-bearing lateral radiographs of a retrocalcaneal bursitis, the retrocalcaneal recess has a typical appearance. PMID:20450438

  2. Electromyographic analysis of the three subdivisions of gluteus medius during weight-bearing exercises

    Directory of Open Access Journals (Sweden)

    O'Sullivan Kieran

    2010-07-01

    Full Text Available Abstract Background Gluteus medius (GM dysfunction is associated with many musculoskeletal disorders. Rehabilitation exercises aimed at strengthening GM appear to improve lower limb kinematics and reduce pain. However, there is a lack of evidence to identify which exercises best activate GM. In particular, as GM consists of three distinct subdivisions, it is unclear if GM activation is consistent across these subdivisions during exercise. The aim of this study was to determine the activation of the anterior, middle and posterior subdivisions of GM during weight-bearing exercises. Methods A single session, repeated-measures design. The activity of each GM subdivision was measured in 15 pain-free subjects using surface electromyography (sEMG during three weight-bearing exercises; wall squat (WS, pelvic drop (PD and wall press (WP. Muscle activity was expressed relative to maximum voluntary isometric contraction (MVIC. Differences in muscle activation were determined using one-way repeated measures ANOVA with post-hoc Bonferroni analysis. Results The activation of each GM subdivision during the exercises was significantly different (interaction effect; p Discussion Posterior GM displayed higher activation across all three exercises than both anterior and middle GM. The WP produced the highest %MVIC activation for all GM subdivisions, and this was most pronounced for posterior GM. Clinicians may use these results to effectively progress strengthening exercises for GM in the rehabilitation of lower extremity injuries.

  3. Non-weight-bearing neural control of a powered transfemoral prosthesis.

    Science.gov (United States)

    Hargrove, Levi J; Simon, Ann M; Lipschutz, Robert; Finucane, Suzanne B; Kuiken, Todd A

    2013-06-19

    Lower limb prostheses have traditionally been mechanically passive devices without electronic control systems. Microprocessor-controlled passive and powered devices have recently received much interest from the clinical and research communities. The control systems for these devices typically use finite-state controllers to interpret data measured from mechanical sensors embedded within the prosthesis. In this paper we investigated a control system that relied on information extracted from myoelectric signals to control a lower limb prosthesis while amputee patients were seated. Sagittal plane motions of the knee and ankle can be accurately (>90%) recognized and controlled in both a virtual environment and on an actuated transfemoral prosthesis using only myoelectric signals measured from nine residual thigh muscles. Patients also demonstrated accurate (~90%) control of both the femoral and tibial rotation degrees of freedom within the virtual environment. A channel subset investigation was completed and the results showed that only five residual thigh muscles are required to achieve accurate control. This research is the first step in our long-term goal of implementing myoelectric control of lower limb prostheses during both weight-bearing and non-weight-bearing activities for individuals with transfemoral amputation.

  4. Biomechanical effects of lateral and medial wedge insoles on unilateral weight bearing.

    Science.gov (United States)

    Sawada, Tomonori; Kito, Nobuhiro; Yukimune, Masaki; Tokuda, Kazuki; Tanimoto, Kenji; Anan, Masaya; Takahashi, Makoto; Shinkoda, Koichi

    2016-01-01

    [Purpose] Lateral wedge insoles reduce the peak external knee adduction moment and are advocated for patients with knee osteoarthritis. However, some patients demonstrate adverse biomechanical effects with treatment. In this study, we examined the immediate effects of lateral and medial wedge insoles under unilateral weight bearing. [Subjects and Methods] Thirty healthy young adults participated in this study. The subjects were assessed by using the foot posture index, and were divided into three groups: normal foot, pronated foot, and supinated foot groups. The knee adduction moment and knee-ground reaction force lever arm under the studied conditions were measured by using a three-dimensional motion capture system and force plates. [Results] In the normal and pronated groups, the change in knee adduction moment significantly decreased under the lateral wedge insole condition compared with the medial wedge insole condition. In the normal group, the change in the knee-ground reaction force lever arm also significantly decreased under the lateral wedge insole condition than under the medial wedge insole condition. [Conclusion] Lateral wedge insoles significantly reduced the knee adduction moment and knee-ground reaction force lever arm during unilateral weight bearing in subjects with normal feet, and the biomechanical effects varied according to individual foot alignment.

  5. Effect of simulated early weight bearing on micromotion and pullout strength of uncemented distal femoral stems.

    Science.gov (United States)

    Barr, Jennifer S; White, Jedediah K; Punt, Stephanie E W; Conrad, Ernest U; Ching, Randal P

    2015-05-01

    The effect of simulated early weight bearing on both micromotion and pullout strength of uncemented distal femoral stems was evaluated in this study. The effect of stem endosteal contact and bone quality on implant pullout strength was also analyzed. A randomized matched-pair study was performed using 8 bilateral pairs of fresh human cadaveric femoral specimens. Each specimen pair was dual-energy x-ray absorptiometry scanned, uniformly implanted, fluoroscopically imaged, and randomly assigned to the cycled or uncycled group. The cycled group received 5000 cycles of axial compressive loading (to 700 N) and the contralateral side was not cycled. Micromotion was monitored during cycling and compared with a failure threshold (150 µm), and all implants underwent direct axial distraction (pullout) testing. During cycling, minimal micromotion was observed with an asymptotic decrease in differential motion between the first and last 50 cycles. Both cycled and uncycled groups demonstrated no statistical difference in average pullout force (4888±2124 N vs 4367±1154 N; P=.43). The percentage of cortical contact for each implant was determined from panoramic fluoroscopy images using digital image analysis software. Contact area for the distal third of the stem showed the highest correlation with pullout force and with predicting pullout force. Bone quality did not correlate with pullout force (r(2)=0.367) or stem contact area (r(2)=0.394). In sum, press-fit uncemented femoral stems did not loosen or demonstrate decreased pullout strength with early weight bearing simulated by cyclical axial compressive loading.

  6. Feasibility of Applying Active Lubrication to Dynamically Loaded Fluid Film Bearings

    DEFF Research Database (Denmark)

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    The feasibility of modifying the dynamics of the thin fluid films of dynamically loaded journal bearings, using different strategies of active lubrication is studied in this work. A significant reduction in the vibration levels, wear and power friction losses, is expected. Particularly, the focus...... of this study is on the analysis of main crankshaft bearings, where the conventional hydrodynamic lubrication is modified by injecting oil at actively controllable pressures, through orifices circumferentially located along the bearing surface....

  7. Characteristics of the Main Journal Bearings of an Engine Based on Non-linear Dynamics

    Institute of Scientific and Technical Information of China (English)

    NI Guangjian; ZHANG Junhong; CHENG Xiaoming

    2009-01-01

    Many simple nonlinear main journal bearing models have been studied theoretically, but the connection to existing engineering system has not been equally investigated. The consideration of the characteristics of engine main journal bearings may provide a prediction of the bearing load and lubrication. Due to the strong non-linear features in bearing lubrication procedure, it is difficult to predict those characteristics. A non-linear dynamic model is described for analyzing the characteristics of engine main journal bearings. Components such as crankshaft, main journals and con rods are found by applying the finite element method. Non-linear spring/dampers are introduced to imitate the constraint and supporting functions provided by the main bearing and oil film. The engine gas pressure is imposed as excitation on the model via the engine piston, con rod, etc. The bearing reaction force is calculated over one engine cycle, and meanwhile, the oil film thickness and pressure distribution are obtained based on Reynolds differential equation. It can be found that the maximum bearing reaction force always occurs when the maximum cylinder pressure arises in the cylinder adjacent to that bearing. The simulated minimum oil film thickness, which is 3 μm, demonstrates the reliability of the main journal bearings. This non-linear dynamic analysis may save computing efforts of engine main bearing design and also is of good precision and close connection to actual engine main journal bearing conditions.

  8. Influence of biofeedback weight bearing training in sit to stand to sit and the limits of stability on stroke patients.

    Science.gov (United States)

    Yang, Dae Jung

    2016-11-01

    [Purpose] The purpose of this study is to observe the influence of biofeedback weight bearing training in sit to stand to sit and limits of stability on stroke patients. [Subjects and Methods] For subjects of this study, 30 stroke patients were randomly divided into two groups of 15, a biofeedback weight bearing training group and a functional weight bearing training group. Biofeedback weight bearing training was conducted for 30 minutes, five times a week for eight weeks, using Biorescue. Analysis of sit to stand to sit was done with LUKOtronic while the analysis of limits of stability was done with Biorescue. [Results] In a comparison of sit to stand to sit and limits of stability between the two groups before and after intervention, Group I showed significant difference in sit to stand to sit and limits of stability when compared to Group II. [Conclusion] This study concludes that biofeedback weight bearing training is more effective in improving sit to stand to sit and limits of stability in stroke patients.

  9. Dynamics of Permanent-Magnet Biased Active Magnetic Bearings

    Science.gov (United States)

    Fukata, Satoru; Yutani, Kazuyuki

    1996-01-01

    Active magnetic radial bearings are constructed with a combination of permanent magnets to provide bias forces and electromagnets to generate control forces for the reduction of cost and the operating energy consumption. Ring-shaped permanent magnets with axial magnetization are attached to a shaft and share their magnet stators with the electromagnets. The magnet cores are made of solid iron for simplicity. A simplified magnetic circuit of the combined magnet system is analyzed with linear circuit theory by approximating the characteristics of permanent magnets with a linear relation. A linearized dynamical model of the control force is presented with the first-order approximation of the effects of eddy currents. Frequency responses of the rotor motion to disturbance inputs and the motion for impulsive forces are tested in the non-rotating state. The frequency responses are compared with numerical results. The decay of rotor speed due to magnetic braking is examined. The experimental results and the presented linearized model are similar to those of the all-electromagnetic design.

  10. A Frequency-Weighted Energy Operator and complementary ensemble empirical mode decomposition for bearing fault detection

    Science.gov (United States)

    Imaouchen, Yacine; Kedadouche, Mourad; Alkama, Rezak; Thomas, Marc

    2017-01-01

    Signal processing techniques for non-stationary and noisy signals have recently attracted considerable attentions. Among them, the empirical mode decomposition (EMD) which is an adaptive and efficient method for decomposing signals from high to low frequencies into intrinsic mode functions (IMFs). Ensemble EMD (EEMD) is proposed to overcome the mode mixing problem of the EMD. In the present paper, the Complementary EEMD (CEEMD) is used for bearing fault detection. As a noise-improved method, the CEEMD not only overcomes the mode mixing, but also eliminates the residual of added white noise persisting into the IMFs and enhance the calculation efficiency of the EEMD method. Afterward, a selection method is developed to choose relevant IMFs containing information about defects. Subsequently, a signal is reconstructed from the sum of relevant IMFs and a Frequency-Weighted Energy Operator is tailored to extract both the amplitude and frequency modulations from the selected IMFs. This operator outperforms the conventional energy operator and the enveloping methods, especially in the presence of strong noise and multiple vibration interferences. Furthermore, simulation and experimental results showed that the proposed method improves performances for detecting the bearing faults. The method has also high computational efficiency and is able to detect the fault at an early stage of degradation.

  11. Torsion of undescended testis in a 14-month-old child refusing to bear weight.

    Science.gov (United States)

    Knight, Ryan M; Cuenca, Peter J

    2011-11-01

    In this report, we discuss a case of a 14-month-old male presenting in the emergency department with refusal to bear weight on his left leg. Plain radiographic studies revealed no evidence of effusion, fracture, or dislocation. Laboratory studies were significant for an elevated white blood cell count, erythrocyte sedimentation rate, and C-reactive protein. Further studies included unremarkable ultrasound of the left hip and normal magnetic resonance imaging (MRI) of both hips. An incidental finding on MRI was a left inguinal mass concerning an incarcerated hernia. Ultrasound of this mass demonstrated a left undescended testis within the inguinal canal and possible incarcerated paratesticular inguinal hernia. The final pathologic diagnosis of a torsed gangrenous left testicle within the inguinal canal was confirmed during surgery.

  12. Bone compaction enhances fixation of weight-bearing hydroxyapatite-coated implants

    DEFF Research Database (Denmark)

    Kold, Søren; Rahbek, Ole; Vestermark, Marianne;

    2006-01-01

    The effect of bone compaction vs conventional drilling on the fixation of hydroxyapatite-coated implants was examined in a weight-bearing canine model. In each dog, one knee joint had the implant cavity prepared with drilling, the other with compaction. Eight dogs were euthanized after 2 weeks...... and 8 dogs after 4 weeks. Femoral condyles from additional 7 dogs represented time 0. Compacted specimens had significantly higher bone implant contact and energy absorption at time 0. Compaction significantly increased ultimate shear strength at 0 and 2 weeks. There was no significant difference...... in implant fixation after 4 weeks. The results of this study suggest that compaction may be beneficial in optimizing the crucial initial implant stability, even when hydroxyapatite-coated implants with osteoconductive properties are inserted in vivo....

  13. DYNAMIC AND VERIFIABLE SECRET SHARING AMONG WEIGHTED PARTICIPANTS

    Institute of Scientific and Technical Information of China (English)

    Yanshuo ZHANG; Zhuojun LIU

    2007-01-01

    A secret sharing scheme permits a secret to be shared among participants in such a way that only qualified subsets of participants can recover the secret. Secret sharing is useful in management of cryptographic keys. Based on identity, we analyze the secret sharing scheme among weighted participants. Then we present a dynamic scheme about secret sharing among weighted participants. At last, we analyze the secret sharing scheme among weighted participants, which can make all weighted participants verifiable and dynamic.

  14. Acetabular roof arc angles and anatomic biomechanical superior acetabular weight bearing area

    Directory of Open Access Journals (Sweden)

    Thossart Harnroongroj

    2014-01-01

    Full Text Available Background: Acetabular fracture involves whether superior articular weight bearing area and stability of the hip are assessed by acetabular roof arc angles comprising medial, anterior and posterior. Many previous studies, based on clinical, biomechanics and anatomic superior articular surface of acetabulum showed different degrees of the angles. Anatomic biomechanical superior acetabular weight bearing area (ABSAWBA of the femoral head can be identified as radiographic subchondral bone density at superior acetabular dome. The fracture passes through ABSAWBA creating traumatic hip arthritis. Therefore, acetabular roof arc angles of ABSAWBA were studied in order to find out that the most appropriate degrees of recommended acetabular roof arc angles in the previous studies had no ABSAWBA involvement. Materials and Methods: ABSAWBA of femoral head was identified 68 acetabular fractures and 13 isolated pelvic fractures without unstable pelvic ring injury were enrolled. Acetabular roof arc angle was measured on anteroposterior, obturator and iliac oblique view radiographs of normal contralateral acetabulum using programmatic automation controller digital system and measurement tools. Results: Average medial, anterior and posterior acetabular roof arc angles of the ABSAWBA of 94 normal acetabulum were 39.09 (7.41, 42.49 (8.15 and 55.26 (10.08 degrees, respectively. Conclusions: Less than 39°, 42° and 55° of medial, anterior and posterior acetabular roof arc angles involve ABSAWBA of the femoral head. Application of the study results showed that 45°, 45° and 62° from the previous studies are the most appropriate medial, anterior and posterior acetabular roof arc angles without involvement of the ABSAWBA respectively.

  15. Reliability and minimal detectable change of the weight-bearing lunge test: A systematic review.

    Science.gov (United States)

    Powden, Cameron J; Hoch, Johanna M; Hoch, Matthew C

    2015-08-01

    Ankle dorsiflexion range of motion (DROM) is often a point of emphasis during the rehabilitation of lower extremity pathologies. With the growing popularity of weight-bearing DROM assessments, several versions of the weight-bearing lunge (WBLT) test have been developed and numerous reliability studies have been conducted. The purpose of this systematic review was to critically appraise and synthesize the studies which examined the reliability and responsiveness of the WBLT to assess DROM. A systematic search of PubMed and EBSCO Host databases from inception to September 2014 was conducted to identify studies whose primary aim was assessing the reliability of the WBLT. The Quality Appraisal of Reliability Studies assessment tool was utilized to determine the quality of included studies. Relative reliability was examined through intraclass correlation coefficients (ICC) and responsiveness was evaluated through minimal detectable change (MDC). A total of 12 studies met the eligibility criteria and were included. Nine included studies assessed inter-clinician reliability and 12 included studies assessed intra-clinician reliability. There was strong evidence that inter-clinician reliability (ICC = 0.80-0.99) as well as intra-clinician reliability (ICC = 0.65-0.99) of the WBLT is good. Additionally, average MDC scores of 4.6° or 1.6 cm for inter-clinician and 4.7° or 1.9 cm for intra-clinician were found, indicating the minimal change in DROM needed to be outside the error of the WBLT. This systematic review determined that the WBLT, regardless of method, can be used clinically to assess DROM as it provides consistent results between one or more clinicians and demonstrates reasonable responsiveness. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Modeling of dynamically loaded hydrodynamic bearings at low Sommerfeld numbers

    DEFF Research Database (Denmark)

    Thomsen, Kim

    . The challenging main bearing operation conditions in a wind turbine pose a demanding development task for the design of a hydrodynamic bearing. In general these conditions include operation at low Reynolds numbers with frequent start and stop at high loads as well as difficult operating conditions dictated...

  17. Dynamic behaviour of ball bearing applications with constrained damping layers

    NARCIS (Netherlands)

    Tillema, Hetzer G.

    2001-01-01

    Rolling bearing noise has become an aspect of increasing importance for the performance of rotating machinery, like electric motors and gearboxes. Generally, two aspects are important with regard to bearing noise, i.e. the transmission characteristics and the vibration generation characteristics. A

  18. Dynamic interaction between rotor and axially-magnetized passive magnetic bearing considering magnetic eccentricity

    DEFF Research Database (Denmark)

    Enemark, Søren; Santos, Ilmar

    2014-01-01

    Passive magnetic bearings are known due to the excellent characteristics in terms of friction and no requirement of additional energy sources to work. However, passive magnetic bearings do not provide damping, are not stable and, depending on their design, may also introduce magnetic eccentricity....... Such magnetic eccentricities are generated by discrepancies in magnet fabrication. In this framework the main focus of the work is the theoretical as well as experimental investigation of the nonlinear dynamics of a rotor-bearing system with strong emphasis on the magnetic eccentricities and non......-linear stiffness. In this investigation passive magnetic bearings using axially- aligned neodymium cylinder magnets are investigated. The cylinder magnets are axially magnetised for rotor as well as bearings. Compared to bearings with radial magnetisation, the magnetic stiffness of axially-aligned bearings...

  19. The value of Weight-Bearing CT scan in the evaluation of subtalar distraction bone block arthrodesis: Case report.

    Science.gov (United States)

    Welck, M J; Myerson, M S

    2015-12-01

    Subtalar distraction arthrodesis is performed in certain situations where there is loss of subtalar height, reduced talar declination and evidence of anterior tibiotalar impingement. Standard evaluation includes the assessment of the lateral talocalcaneal angle, calcaneal pitch, talocalcaneal height and talar declination angle on a weight bearing lateral radiograph. We present a case of erosive valgus subtalar osteoarthritis with subtalar collapse managed with a subtalar distraction arthrodesis. A weight bearing CT (WB-CT) scan was used in the assessment. The value of WB-CT for this indication is discussed, along with a discussion on surgical technique, complications and future directions. Copyright © 2015 European Foot and Ankle Society. All rights reserved.

  20. Dynamic Performance Characteristics of a Curved Slider Bearing Operating with Ferrofluids

    Directory of Open Access Journals (Sweden)

    Udaya P. Singh

    2012-01-01

    Full Text Available In the present theoretical investigation, the effect of ferrofluid on the dynamic characteristics of curved slider bearings is presented using Shliomis model which accounts for the rotation of magnetic particles, their magnetic moments, and the volume concentration in the fluid. The modified Reynolds equation for the dynamic state of the bearing is obtained. The results of dynamic stiffness and damping characteristics are presented. It is observed that the effect of rotation of magnetic particles improves the stiffness and damping capacities of the bearings.

  1. Effect of Magnetohydrodynamic Couple Stresses on Dynamic Characteristics of Exponential Slider Bearing

    Directory of Open Access Journals (Sweden)

    N.B. Naduvinamani

    2017-05-01

    Full Text Available The effect of couple stresses on static and dynamic characteristics of exponential slider bearing in the presence of magnetic field considering squeeze action is theoretically analyzed in this paper. The modified magnetohydrodynamic couple stress Reynolds type equation is derived on the basis of Stokes couple stress model and closed form expressions are obtained for static and dynamic character coefficients. Comparing with bearing lubricated with non-conducting Newtonian lubricants, the magnetohydrodynamic couple stress lubrication provides the higher steady load carrying capacity, dynamic stiffness and damping coefficient. The exponential bearing shows higher efficiency for small film thickness at higher value of couple stress parameter and Hartmann number.

  2. Experimental Identification of Dynamic Coefficients of Tilting-Pad Bearings with Active Lubrication

    DEFF Research Database (Denmark)

    Salazar, Jorge Andrés González; Cerda Varela, Alejandro Javier; Santos, Ilmar

    This article presents the experimental identification of the equivalent dynamic coefficients of an activelylubricated bearing under different lubrication regimes, namely: passive (no injection flow), hybrid (constant injection flow) and feedback-controlled (variable injection flow) lubrication. T...

  3. Assessment of Brown Bear\\'s (Ursus arctos syriacus Winter Habitat Using Geographically Weighted Regression and Generalized Linear Model in South of Iran

    Directory of Open Access Journals (Sweden)

    A. A. Zarei

    2016-03-01

    Full Text Available Winter dens are one of the important components of brown bear's (Ursus arctos syriacus habitat, affecting their reproduction and survival. Therefore identification of factors affecting the habitat selection and suitable denning areas in the conservation of our largest carnivore is necessary. We used Geographically Weighted Logistic Regression (GWLR and Generalized Linear Model (GLM for modeling suitability of denning habitat in Kouhkhom region in Fars province. In the present research, 20 dens (presence locations and 20 caves where signs of bear were not found (absence locations were used as dependent variables and six environmental factors were used for each location as independent variables. The results of GLM showed that variables of distance to settlements, altitude, and distance to water were the most important parameters affecting suitability of the brown bear's denning habitat. The results of GWLR showed the significant local variations in the relationship between occurrence of brown bear dens and the variable of distance to settlements. Based on the results of both models, suitable habitats for denning of the species are impassable areas in the mountains and inaccessible for humans.

  4. Dynamic Finite Element Analysis of Mobile Bearing Type Knee Prosthesis under Deep Flexional Motion

    Directory of Open Access Journals (Sweden)

    Mohd Afzan Mohd Anuar

    2014-01-01

    Full Text Available The primary objective of this study is to distinguish between mobile bearing and fixed bearing posterior stabilized knee prostheses in the mechanics performance using the finite element simulation. Quantifying the relative mechanics attributes and survivorship between the mobile bearing and the fixed bearing prosthesis remains in investigation among researchers. In the present study, 3-dimensional computational model of a clinically used mobile bearing PS type knee prosthesis was utilized to develop a finite element and dynamic simulation model. Combination of displacement and force driven knee motion was adapted to simulate a flexion motion from 0° to 135° with neutral, 10°, and 20° internal tibial rotation to represent deep knee bending. Introduction of the secondary moving articulation in the mobile bearing knee prosthesis has been found to maintain relatively low shear stress during deep knee motion with tibial rotation.

  5. Bifurcation and Nonlinear Dynamic Analysis of Externally Pressurized Double Air Films Bearing System

    Directory of Open Access Journals (Sweden)

    Cheng-Chi Wang

    2014-01-01

    Full Text Available This paper studies the chaotic and nonlinear dynamic behaviors of a rigid rotor supported by externally pressurized double air films (EPDAF bearing system. A hybrid numerical method combining the differential transformation method and the finite difference method is used to calculate pressure distribution of EPDAF bearing system and bifurcation phenomenon of rotor center orbits. The results obtained for the orbits of the rotor center are in good agreement with those obtained using the traditional finite difference approach. The results presented summarize the changes which take place in the dynamic behavior of the EPDAF bearing system as the rotor mass and bearing number are increased and therefore provide a useful guideline for the bearing system.

  6. Fluid Compressibility Effects on the Dynamic Response of Hydrostatic Journal Bearings

    Science.gov (United States)

    Sanandres, Luis A.

    1991-01-01

    A theoretical analysis for the dynamic performance characteristics of laminar flow, capillar/orifice compensated hydrostatic journal bearings is presented. The analysis considers in detail the effect of fluid compressibility in the bearing recesses. At high frequency excitations beyond a break frequency, the bearing hydrostatic stiffness increases sharply and it is accompanied by a rapid decrease in direct damping. Also, the potential of pneumatic hammer instability (negative damping) at low frequencies is likely to occur in hydrostatic bearing applications handling highly compressible fluids. Useful design criteria to avoid undesirable dynamic operating conditions at low and high frequencies are determined. The effect of fluid recess compressibility is brought into perspective, and found to be of utmost importance on the entire frequency spectrum response and stability characteristics of hydrostatic/hybrid journal bearings.

  7. STUDY ON THE METHOD OF FATIGUE STRENGTH DESIGN FOR DYNAMICALLY LOADED JOURNAL BEARING

    Institute of Scientific and Technical Information of China (English)

    FanXun; MengHuirong

    1996-01-01

    In this paper, a novel design method, which is different from the traditional and empirical one (i. e. , taking p and pv as the basic checking parameters) is presented for the fatigue strength design of dynamically loaded journal bearings. The method makes it possible that dynamically loaded bearings can be designed as same as other machine elements hy stress-strength criterion. The practical design results show that the method has high accuracy and reliability, and may open a new vista in bearing fatigue designs.

  8. On the tribological characteristics of dynamically loaded journal bearing with micropolar fluids

    Institute of Scientific and Technical Information of China (English)

    WANG; Xiaoli; WANG; Kongying; ZHU; Keqin

    2004-01-01

    The addition of the additives to the lubricant oil to enhance the characteristics of the lubricant will influence the performance of the bearings. Based on the theory of micropolar fluids, the tribological characteristics of a dynamically-loaded journal bearing are numerically studied. Comparisons are made between the Newtonian fluids and the micropolar fluids. It is shown that for a dynamically-loaded journal bearing, the micropolar fluids yield an increase not only in the friction force, but also in the friction coefficient. In addition, the oil film pressure and the oil film thickness are obviously higher than that of Newtonian fluids.

  9. Dynamical Systems On Weighted Lattices: General Theory

    OpenAIRE

    Maragos, Petros

    2016-01-01

    In this work a theory is developed for unifying large classes of nonlinear discrete-time dy- namical systems obeying a superposition of a weighted maximum or minimum type. The state vectors and input-output signals evolve on nonlinear spaces which we call complete weighted lat- tices and include as special cases the nonlinear vector spaces of minimax algebra. Their algebraic structure has a polygonal geometry. Some of the special cases unified include max-plus, max- product, and probabilistic...

  10. Compliant Foil Journal Bearings - Investigation of Dynamic Properties

    DEFF Research Database (Denmark)

    Larsen, Jon Steffen; Santos, Ilmar

    Through the past three decades gas bearings have found way into an increasing number of industrial applications within high speed rotating machinery. Especially the compliant foil type of bearings has gained large popularity. Much theoretical and experimental work has been conducted...... a Bubnow-Galerkin approach. This constitutes the main original contribution of this work, considering the fact that the finite difference method is commonly used and thouroughly investigated in the literature. The finite element method leads to a set of non-linear equations for the static fluid film...

  11. Vertical weight-bearing MRI provides an innovative method for standardizing Spurling test.

    Science.gov (United States)

    Yan, Jun; Wang, Yi; Liu, Xiaofeng; Li, Jian; Jin, Zhigao; Zheng, Zugen

    2010-12-01

    Although Spurling test, a foraminal compression test, is commonly used in clinical practice in patients with a suspected cervical radiculopathy, its protocol is still obscure. In undergoing this test, patients extend, laterally flex and slightly rotate neck to the symptomatic side, and then a pressure is applied on the top of patient's head by examiner. The test is scored as positive if it causes pain or tingling that starts in the shoulder and radiates distally to the elbow. But the range of neck motion and level of load are not clearly defined. Magnetic resonance imaging (MRI) has proved to be an excellent method of assessing the situation of cervical intervertebral foramen. Unfortunately the conventional MRI system is not able to fully achieve this goal because it can only examine patient in supine position while Spurling test needs to be performed in a sitting position. Here we hypothesize that vertical weight-bearing MRI provides an innovative method for researching and standardizing the protocols of Spurling test. The result will provide better knowledge of the mechanism of Spurling test. Standardization of the test will improve its sensitivity and rate of reproducibility.

  12. A palmar pressure sensor for measurement of upper limb weight bearing by the hands during transfers by paraplegics.

    Science.gov (United States)

    Kunju, Nissan; Ojha, Rajdeep; Devasahayam, Suresh R

    2013-10-01

    Paraplegic patients have to effect transfer from one seat to another by using their upper limbs. In this process the hands bear almost the entire weight of the body in at least some phases of the transfer. It is desirable to train patients, especially those who are elderly and otherwise weak, to distribute their weight so as to avoid large forces being sustained on any one hand for an extended period. It is also desirable to evaluate the effectiveness of assistive devices like lower limb FES in sharing the load on the hand. This study presents a simple and versatile method of measuring palmar hand force during transfers by paraplegic patients. It is important that this force sensor should not interfere with the grasping and stabilizing properties of the hands and should permit normal transferring. The force sensor comprises an air-filled pouch or pillow that can be placed on any surface. This pneumatic sensor feels like upholstery padding on the surface on which it is placed. The sensor integrates the total pressure applied to the surface of the pouch, thereby obtaining the total force exerted by the palm/hand. The fabrication of the sensor is described, as well as the associated measurement circuit. The static calibration shows that the sensor is linear up to 350 N and the dynamic calibration shows that it has a bandwidth of 13 Hz. The sensor was fabricated using an inflated inelastic airbag attached to a pressure transducer. An automatic offset correction circuit in the preamplifier module ensures that any offset due to initial pressure or sensor drift is removed and the output is zero under no load condition. The key to this sensor arrangement is the ease of fitting it into the intended location without disturbing the existing arrangement for the subject's activities of daily living (ADL).

  13. Toward a 3D dynamic model of a faulty duplex ball bearing

    Science.gov (United States)

    Kogan, Gideon; Klein, Renata; Kushnirsky, Alex; Bortman, Jacob

    2015-03-01

    Bearings are vital components for safe and proper operation of machinery. Increasing efficiency of bearing diagnostics usually requires training of health and usage monitoring systems via expensive and time-consuming ground calibration tests. The main goal of this research, therefore, is to improve bearing dynamics modeling tools in order to reduce the time and budget needed to implement the health and usage monitoring approach. The proposed three-dimensional ball bearing dynamic model is based on the classic dynamic and kinematic equations. Interactions between the bodies are simulated using non-linear springs combined with dampers described by Hertz-type contact relation. The force friction is simulated using the hyperbolic-tangent function. The model allows simulation of a wide range of mechanical faults. It is validated by comparison to known bearing behavior and to experimental results. The model results are verified by demonstrating numerical convergence. The model results for the two cases of single and duplex angular ball bearings with axial deformation in the outer ring are presented. The qualitative investigation provides insight into bearing dynamics, the sensitivity study generalizes the qualitative findings for similar cases, and the comparison to the test results validates model reliability. The article demonstrates the variety of the cases that the 3D bearing model can simulate and the findings to which it may lead. The research allowed the identification of new patterns generated by single and duplex bearings with axially deformed outer race. It also enlightened the difference between single and duplex bearing manifestation. In the current research the dynamic model enabled better understanding of the physical behavior of the faulted bearings. Therefore, it is expected that the modeling approach has the potential to simplify and improve the development process of diagnostic algorithms. • A deformed outer race of a single axially loaded bearing is

  14. Use of weight-bearing MRI for evaluating wheelchair cushions based on internal soft-tissue deformations under ischial tuberosities

    Directory of Open Access Journals (Sweden)

    Amit Gefen, PhD

    2010-03-01

    Full Text Available Deep tissue injury (DTI is a severe type of pressure ulcer, in which damage initiates under intact skin, in soft tissues that are mechanically deformed by load-bearing bony prominences. Sitting-acquired DTI typically occurs in the gluteus muscles that could sustain deformations by the weight-bearing ischial tuberosities (ITs. No clinical method currently exists for measuring internal tissue deformations; so design and selection of wheelchair cushions are based mostly on meas-uring sitting pressures. Our objective was to evaluate the influence of different commercial cushions on internal soft-tissue deformations under the ITs, using weight-bearing magnetic resonance imaging (MRI. We specifically compared muscle, superficial fat, and effective (muscle and fat together tissue deformations while subjects (n = 10 sat on four cushions (two viscoelastic and two foam and directly on a rigid support. Deformations were maximal in muscle tissue (mean ~70%, twice more the amount than in fat (~30%. Effective soft-tissue deformations were ~50% to ~60%. Although cushions mildly reduced muscle deformations in the order of 10%, theoretically, our interpretation suggests that this deformation level adds safe sitting time. This study demonstrated that weight-bearing MRI is applicable for evaluating wheelchair cushions and, in the future, may be a tool to systematically support cushion design and selection.

  15. Influence of unbalance levels on nonlinear dynamics of a rotor-backup rolling bearing system

    Science.gov (United States)

    Fonseca, Cesar A.; Santos, Ilmar F.; Weber, Hans I.

    2017-04-01

    Rotor drops in magnetic bearing and unbalance in rotors have been objective of study for many years. The combination of these two well-known phenomena led to an interesting chaotic response, when the rotor touches the inner race of the back-up bearing. The present work explores the nonlinear rotor backup bearing dynamics both theoretically and experimentally using a fully instrumented test rig, where the position of shaft, its angular velocity and the contact forces between the shaft and the backup bearing are sampled at 25 kHz. The test rig is built by a removable passive magnetic bearing, which allows for simulation of magnetic bearing failure (loss of carrying capacity and rotor fall). The rotor is studied numerically as well as experimentally. A theoretical approach is given beforehand and supplies the basis of the study. Finally the presented results are commented on the point of view of nonlinear dynamics applied to the practical use. The theoretical and numerical analyses are shown through orbit plots, phase plans, Poincaré maps, force response in time and double sided spectrum. The latter is important to characterize the condition at different levels of unbalance between forward and backward whirl. Our preliminary results indicate that for smaller amount of unbalance the rotor swings at the bottom of the bearing, the more the unbalance increases, other dynamical behavior occur and some can be extremely harmful, since the rotor can be lifted from the contact state and return, starting to impact innumerable times without reaching a steady state.

  16. Nonlinear Dynamics Behaviors of a Rotor Roller Bearing System with Radial Clearances and Waviness Considered

    Institute of Scientific and Technical Information of China (English)

    Wang Liqin; Cui Li; Zheng Dezhi; Gu Le

    2008-01-01

    A rotor system supported by roller bearings displays very complicated nonlinear behaviors due to nonlinear Hertzian contact forces, radial clearances and bearing waviness. This paper presents nonlinear bearing forces of a roller bearing under four-dimensional loads and establishes 4-DOF dynamics equations of a rotor roller bearing system. The methods of Newmark-β and of Newton-Laphson are used to solve the nonlinear equations. The dynamics behaviors of a rigid rotor system are studied through the bifurcation, the Poincar bility caused by the quasi-periodic bifurcation, the periodic-doubling bifurcation and chaos routes as the rotational speed increases.Clearances, outer race waviness, inner race waviness, roller waviness, damping, radial forces and unbalanced forces-all these bring a significant influence to bear on the system stability. As the clearance increases, the dynamics behaviors become complicated with the number and the scale of instable regions becoming larger. The vibration frequencies induced by the roller bearing waviness and the orders of the waviness might cause severe vibrations. The system is able to eliminate non-periodic vibration by reasonable choice and optimization of the parameters.

  17. A non-linear mathematical model for dynamic analysis of spur gears including shaft and bearing dynamics

    Science.gov (United States)

    Ozguven, H. Nevzat

    1991-01-01

    A six-degree-of-freedom nonlinear semi-definite model with time varying mesh stiffness has been developed for the dynamic analysis of spur gears. The model includes a spur gear pair, two shafts, two inertias representing load and prime mover, and bearings. As the shaft and bearing dynamics have also been considered in the model, the effect of lateral-torsional vibration coupling on the dynamics of gears can be studied. In the nonlinear model developed several factors such as time varying mesh stiffness and damping, separation of teeth, backlash, single- and double-sided impacts, various gear errors and profile modifications have been considered. The dynamic response to internal excitation has been calculated by using the 'static transmission error method' developed. The software prepared (DYTEM) employs the digital simulation technique for the solution, and is capable of calculating dynamic tooth and mesh forces, dynamic factors for pinion and gear, dynamic transmission error, dynamic bearing forces and torsions of shafts. Numerical examples are given in order to demonstrate the effect of shaft and bearing dynamics on gear dynamics.

  18. A non-linear mathematical model for dynamic analysis of spur gears including shaft and bearing dynamics

    Science.gov (United States)

    Özgüven, H. N.

    1991-03-01

    A six-degree-of-freedom non-linear semi-definite model with time varying mesh stiffness has been developed for the dynamic analysis of spur gears. The model includes a spur gear pair, two shafts, two inertias representing load and prime mover, and bearings. As the shaft and bearing dynamics have also been considered in the model, the effect of lateral-torsional vibration coupling on the dynamics of gears can be studied. In the non-linear model developed several factors such as time varying mesh stiffness and damping, separation of teeth, backlash, single- and double-sided impacts, various gear errors and profile modifications have been considered. The dynamic response to internal excitation has been calculated by using the "static transmission error method" developed. The software prepared (DYTEM) employs the digital simulation technique for the solution, and is capable of calculating dynamic tooth and mesh forces, dynamic factors for pinion and gear, dynamic transmission error, dynamic bearing forces and torsions of shafts. Numerical examples are given in order to demonstrate the effect of shaft and bearing dynamics on gear dynamics.

  19. Role of weighting in the dynamics of front propagation

    Energy Technology Data Exchange (ETDEWEB)

    Zekri, Nouredine, E-mail: zekri@univ-usto.dz [Université des Sciences et de la Technologie d' Oran Mohamed Boudiaf, Département de Physique, LEPM, BP 1505 El Mnaouer, Oran (Algeria); Khelloufi, Khadidja; Zekri, Lotfi [Université des Sciences et de la Technologie d' Oran Mohamed Boudiaf, Département de Physique, LEPM, BP 1505 El Mnaouer, Oran (Algeria); Porterie, Bernard; Kaiss, Ahmed; Clerc, Jean-Pierre [Aix-Marseille Université, CNRS, IUSTI UMR 7343, 13453, Marseille (France)

    2012-07-30

    Non-equilibrium front propagation in a two-dimensional network modelling wildfire propagation was studied. The model includes deterministic long-range interactions due to radiation and a time weighting procedure. Three weight-dependent propagation regimes were found: dynamical, static, and non-propagative. The dynamical regime shows saturation for small weight values and a percolation transition area depending on the weight and size of the interaction domain. From the scaling interface exponents, the model seems to belong to the dynamical percolation universality class. In the limit of static regime it belongs to the random deposition class. -- Highlights: ► Percolation model used includes the weighting procedure and long-range interactions (an interaction domain). The interaction strength is chosen to decrease inversely with the square distance. ► There is a weight threshold R{sub c} above which the front cannot propagate. ► At R{sub c} the percolation is static (usual percolation), and below this threshold it becomes dynamic. ► A generalized dependence of the percolation threshold on both the interaction size n{sub y} and the weight parameter R is proposed. ► A further study of the front dynamic scaling is added to this version and dynamic exponents determined.

  20. The cavitation erosion damage process of dynamically loaded journal bearings

    Institute of Scientific and Technical Information of China (English)

    MA Yan-yan; CHENG Xian-hua

    2006-01-01

    The cavitation damage model was built using finite element analysis software MSC.Marc.This paper attempted to numerically analyze the action process based on damage mechanics when a jet created by bubble collapse acted on the bearing surface in the process of cavitation erosion.The numerical results show that the values of equivalent plastic strain and void volume fraction increase with time.The values of damage scalar are higher on the bearing surface and subsurface,and decrease when it approaches the interface of overlay and nickel layer.The strain history and damage evolvement of beating material acted on by jet impact load can be calculated efficiently using the proposed method,which develops a new method of analyzing cavitation erosion failure of thebearing surface.

  1. Nonlinear Dynamics Analysis of Tilting Pad Journal Bearing-Rotor System

    Directory of Open Access Journals (Sweden)

    Jiayang Ying

    2011-01-01

    Full Text Available The nonlinear dynamics theory is increasingly applied in the dynamics analysis of tilting pad journal bearing-rotor system. However, extensive work on system dynamics done previously neglects the influence caused by the moment of inertia of the pad. In this paper, a comparison is made between the responses of the rotor in the bearings with and without pad inertia effect. Taking the Jeffcott rotor system as an example, the characteristics of bearing-rotor system, such as bifurcation diagram, cycle response, frequency spectrum, phase trajectories, and Poincaré maps, were attained within a certain rotation rate range. The pivotal oil-film force of tilting pad journal bearing was calculated by database method. The results directly demonstrate that considering the influence of the pad moment of inertia, system dynamics characteristics are found more complicated when rotor-bearing system works around natural frequency and system bifurcation is observed forward when rotor-bearing system works on high-speed range.

  2. A model for the dynamics of human weight cycling

    Indian Academy of Sciences (India)

    Albert Goldbeter

    2006-03-01

    The resolution to lose weight by cognitive restraint of nutritional intake often leads to repeated bouts of weight loss and regain, a phenomenon known as weight cycling or ``yo-yo dieting”. A simple mathematical model for weight cycling is presented. The model is based on a feedback of psychological nature by which a subject decides to reduce dietary intake once a threshold weight is exceeded. The analysis of the model indicates that sustained oscillations in body weight occur in a parameter range bounded by critical values. Only outside this range can body weight reach a stable steady state. The model provides a theoretical framework that captures key facets of weight cycling and suggests ways to control the phenomenon. The view that weight cycling represents self-sustained oscillations has indeed specific implications. In dynamical terms, to bring weight cycling to an end, parameter values should change in such a way as to induce the transition of body weight from sustained oscillations around an unstable steady state to a stable steady state. Maintaining weight under a critical value should prevent weight cycling and allow body weight to stabilize below the oscillatory range.

  3. Development and in vitro characterization of galactosylated low molecular weight chitosan nanoparticles bearing doxorubicin.

    Science.gov (United States)

    Jain, Nitin K; Jain, Sanjay K

    2010-06-01

    The aim of the present research was to evaluate the potential of galactosylated low molecular weight chitosan (Gal-LMWC) nanoparticles bearing positively charged anticancer, doxorubicin (DOX) for hepatocyte targeting. The chitosan from crab shell was depolymerized, and the lactobionic acid was coupled with LMWC using carbodiimide chemistry. The depolymerized and galactosylated polymers were characterized. Two types of Gal-LMWC(s) with variable degree of substitution were employed to prepare the nanoparticles using ionotropic gelation with pentasodium tripolyphosphate anions. Factors affecting nanoparticles formation were discussed. The nanoparticles were characterized by transmission electron microscopy and photon correlation spectroscopy and found to be spherical in the size range 106-320 nm. Relatively higher percent DOX entrapment was obtained for Gal-LMWC(s) nanoparticles than for LMWC nanoparticles. A further increase in drug entrapment was found with nanoparticles prepared by Gal-LMWC with higher degree of substitution. A hypothesis which correlates the ionic concentration of DOX in nanoparticles preparation medium and percent DOX entrapment in cationic polymer has been proposed to explain the enhanced DOX entrapment. In-vitro drug release study demonstrated an initial burst release followed by a sustained release. The targeting potential of the prepared nanoparticles was assessed by in vitro cytotoxicity study using the human hepatocellular carcinoma cell line (HepG(2)) expressing the ASGP receptors on their surfaces. The enthusiastic results showed the feasibility of Gal-LMWC(s) to entrap the cationic DOX and targeting potential of developed Gal-LMWC(s) nanoparticles to HepG(2) cell line.

  4. Relative weights approach to dynamical fermions at finite densities

    CERN Document Server

    Greensite, Jeff

    2016-01-01

    The method of relative weights, coupled with mean field theory, is applied to the problem of simulating gauge theories with dynamical staggered fermions at finite densities. We present initial results and discuss issues so far encountered.

  5. Experimental identification of dynamic coefficients of lightly loaded tilting-pad bearings under several lubrication regimes

    DEFF Research Database (Denmark)

    Salazar, Jorge G.; Santos, Ilmar F.

    2016-01-01

    This paper presents the identified dynamic coefficients of a lightly loaded actively lubricated bearing under three lubrication regimes: passive, hybrid and feedback-controlled. The goal is to experimentally demonstrate the feasibility of modifying the bearing dynamic properties via active...... lubrication. Dominated by the latest two regimes, the bearing properties become adjustable or controllable due to the injection of either a constant or variable pressurized oil flow. Such a flow is regulated by a hydraulic control system composed of (a) a high-pressure oil supply unit, (b) servovalves, (c......) radial injection nozzles, (d) displacement sensors and (e) well-tuned digital controllers. A scaled-down industrial rotor featuring active lubrication, composed of a flexible rotor supported by a four-rocker load-between-pads tilting-pad bearing under light load condition, is used for this objective...

  6. Lateral Dynamics of Flexible Rotors Supported by Controllable Gas Bearings Theory & Experiment

    DEFF Research Database (Denmark)

    Pierart Vásquez, Fabián Gonzalo; Santos, Ilmar

    2015-01-01

    Active gas bearings might represent a mechatronic answer to the growing industrial need for high performance turbomachinery. In this framework, the paper gives a theoretical and experimental contribution to the improvement of lateral dynamics of rotating machines. The work aims at demonstrating...... theoretically as well as experimentally the feasibility of applying active lubrication to gas journal bearings. The operation principle is to generate active forces by regulating the radial injection of a compressible lubricant (gas) by means of piezoelectric actuators mounted on the back of the bearing sleeve...

  7. Study of nonlinear dynamic characteristics of rotor-bearing systems

    Institute of Scientific and Technical Information of China (English)

    焦映厚; 陈照波; 曲秀全

    2004-01-01

    Based on the short-bearing model, the stability of a rigid Jeffcott rotor system is studied in a relatively wide parameter range by using Poincare maps and the numerical intrgration method. The results of the calculation show that the period doubling bifurcation, quasi-periodic and chaotic motions may occur. In some typical system are acquired with the numerical integration method. They demonstrate some motion state of the system.The fractal dimension concept is used to determine whether the system is in a state of chaotic motion. The analysis result of this paper provides the theoretical basis for qualitatively controlling the stable operating states ofthe rotors.

  8. Effect of recovery from muscle strength imbalance in lower limb using four point weight bearing reduction system.

    Science.gov (United States)

    Yu, Chang Ho; Kang, Seung Rok; Jeong, Ho Choon; Kim, Kyung; Kwon, Tae Kyu

    2014-01-01

    This study was performed to assess the improvement of muscle strength imbalance in the lower limbs using a four point weight bearing reduction system with a two-belt treadmill. Participants, each having differences in muscle function of the left and right legs of over 20%, were divided into two groups of ten. The participants were involved in experiments progressing 40 minutes per day, 3 days per week, during a period of 4 weeks. The maximal peak torque and average power were measured for testing joint torque in the hip, knee and ankle. The results showed the improvement of muscle imbalance as assessed by the maximal muscle strength was the most effective in the hip joint, while the improvement of muscular reaction was the most effective in the knee joint. We suggest that the method of weight bearing reduction could be sufficient to reduce muscle imbalance in the lower limbs.

  9. A do-it-yourself membrane-activated auditory feedback device for weight bearing and gait training: a case report.

    Science.gov (United States)

    Batavia, M; Gianutsos, J G; Vaccaro, A; Gold, J T

    2001-04-01

    An augmented auditory feedback device comprised of a thin membrane switch mini-buzzer, and battery is described as a modification of a previously described feedback device. The membrane switch can be customized for the patient and is designed to fit inside a patient's shoe without altering the heel height. Its appeal lies in its simplicity of construction, low cost, and ease of implementation during a patient's training for weight bearing and gait. An ever-present source of information, it provides performance-relevant cues to both patient and clinician about the occurrence, duration, and location of a force component of motor performance. The report includes suggested applications of the device, instructions to construct it, and a case report in which the device was used to improve weight bearing and gait in a cognitively healthy person with spina bifida.

  10. Dynamic characteristics of hard disk drive spindles supported by hydrodynamic bearings

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Most hard disk spindles currently used are supported by grease lubricated deep-groove ball bearings.However, in the trend of increasing spindle speed and reducing size and cost, the shortcomings of ball bearing spin-dles, such as high non-repeatable run out, high acoustic noise and short life time at high running speed, make themunsuitable for high performance hard disk drives (HDD). On the contrary, the dynamic characteristics of hydrody-namic bearing spindles are superior to that of ball bearing spindles. Therefore, they are considered to be the substi-tute of ball bearing spindles in HDD. In this paper, a simulative setup of HDD is build up. The dynamic characteristicsof liquid lubricated spiral groove bearing(SGB) spindles are studied. The effects of both operating condition andbearing clearance are investigated. It is found that running speed of the spindle has significant influence on its dy-namic performance, while the load has little influence. The effect of clearance is also evident.

  11. Effect of modified constraint induced movement therapy on weight bearing and protective extension in children with hemiplegic cerebral palsy

    Directory of Open Access Journals (Sweden)

    Masoud Gharib

    2012-01-01

    Full Text Available Background: Constraint induced movement therapy is one of the new therapeutic interventions that limits the performance of intact upper limb with increased use of the affected limb. Aim of this study was to investigate the effects of modified constraint induced movement therapy on weight bearing & protective extension in children with hemiplegic cerebral palsy.Methods: 21 hemiplegic children were selected and randomly divided into experimental and control groups. Common Practices of Occupational Therapy applied for 6 weeks in both groups equally and test group received constrain induced movement therapy for three hours every day. Weight-bearing and protective extension was measured based on quality of test skills of upper limbs (QUEST. Data analyzed using appropriated statistical methods. Results: 11 children in the experimental group (7 girls, 4 boys with mean age 47.2 ± 55.5 months and 10 children in the control group (5 girls, 5 boys with mean age 19.2 ± 10.5 months were studied. No significant difference observed before and after six weeks intervention between two groups (P>0.05. There was a significant change before and after six weeks intervention in both subscales (P<0.05.Conclusion: This study showed that modified constraint induced movement therapy may affect weight bearing, but has no effect on the protective extension.

  12. Effect of smoking and ABO blood groups on maternal age at child bearing and on birth weight.

    Science.gov (United States)

    Gloria-Bottini, F; Cozzoli, E; Neri, A; Bottini, E; Magrini, A

    2011-11-01

    The negative effects of cigarette smoking on human reproduction and on birth weight are well documented. On the other hand ABO system, encoding for glycosyltransferases, contributes to biosynthesis of antigens and oligosaccharide structures involved in blastocyst adhesion and intrauterine selection. In this paper we have searched for possible interaction between ABO system and smoking concerning their effects on maternal age at child bearing and on birth weight. We have studied 395 consecutive healthy puerperae from the White Caucasian population of Rome. ABO blood group was determined by standard laboratory methods. Three-way contingency table analysis was performed according to Sokal and Rohlf and Chi square test of independence by SPSS programs. The proportion of smokers is higher in A phenotype than in other ABO types among young puerperae (≤ 24 years) while it is lower in A phenotype than in other types among older women. The negative effects of smoke on birth weight is much more evident in women with A blood group than in women carrying other ABO phenotypes. The interaction between smoking and ABO blood groups concerning their effects on birth weight is influenced by gender of newborn and by maternal age. ABO blood groups and smoking could have a joint influence on maternal age at child bearing and on birth weight. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  13. Relaxation Dynamics in Condensation on Weighted Scale-Free Networks

    Institute of Scientific and Technical Information of China (English)

    MENG Xin-He; TANG Ming; WANG Peng; LIU Zong-Hua

    2008-01-01

    Most of the realistic networks are weighted scale-free networks. How this structure influences the conden-sation on it is a challenging problem. Recently, we make a first step to discuss its condensation [Phys. Rev. E 74 (2006) 036101] and here we focus on its evolutionary process of phase transition. In order to show how the weighted transport influences the dynamical properties, we study the relaxation dynamics in a zero range process on weighted scale-free networks. We find that there is a hierarchical relaxation dynamics in the evolution and there is a scaling relation between the relaxation time and the jumping exponent. The relaxation dynamics can be illustrated by a mean-field equation. The theoretical predictions are confirmed by our numerical simulations.

  14. Theoretical and experimental studies on dynamics of double-helical gear system supported by journal bearings

    Directory of Open Access Journals (Sweden)

    Minghu Yin

    2016-05-01

    Full Text Available The dynamic behaviour of a double-helical gear system supported by journal bearings is theoretically and experimentally investigated in this study. A bending–torsional–axial coupling model for dynamic analysis of double-helical gear system is developed. Influence of the time-varying mesh stiffness and damping is considered. Oil film stiffness and damping of the supporting journal bearing are supposed to be time-varying, and the time-varying oil film stiffness and damping are predicted by a back propagation neural network, which is optimized by genetic algorithm. A double-helical gear–rotor–journal bearing system test rig is also established to carry out the experimental investigations, such as the dynamic transmission errors of gear pairs. The comparisons between theoretical and experimental results show that the time-varying oil film dynamic coefficients of journal bearings are an important internal excitation. The theoretical model with time-varying oil film stiffness and damping can predict the gear dynamics more accurate than the model with time-invariant oil film stiffness and damping, and the neural network optimized by genetic algorithm can obtain the time-varying oil film stiffness and damping efficiently and accurately for the dynamic analysis of double-helical gear system.

  15. Study of journal bearing dynamics using 3-dimensional motion picture graphics

    Science.gov (United States)

    Brewe, D. E.; Sosoka, D. J.

    1985-01-01

    Computer generated motion pictures of three dimensional graphics are being used to analyze journal bearings under dynamically loaded conditions. The motion pictures simultaneously present the motion of the journal and the pressures predicted within the fluid film of the bearing as they evolve in time. The correct prediction of these fluid film pressures can be complicated by the development of cavitation within the fluid. The numerical model that is used predicts the formation of the cavitation bubble and its growth, downstream movement, and subsequent collapse. A complete physical picture is created in the motion picture as the journal traverses through the entire dynamic cycle.

  16. Dynamic Model and Fault Feature Research of Dual-Rotor System with Bearing Pedestal Looseness

    Directory of Open Access Journals (Sweden)

    Nanfei Wang

    2016-01-01

    Full Text Available The paper presents a finite element model of dual-rotor system with pedestal looseness stemming from loosened bolts. Dynamic model including bearing pedestal looseness is established based on the dual-rotor test rig. Three-degree-of-freedom (DOF planar rigid motion of loose bearing pedestal is fully considered and collision recovery coefficient is also introduced in the model. Based on the Timoshenko beam elements, using the finite element method, rigid body kinematics, and the Newmark-β algorithm for numerical simulation, dynamic characteristics of the inner and outer rotors and the bearing pedestal plane rigid body motion under bearing pedestal looseness condition are studied. Meanwhile, the looseness experiments under two different speed combinations are carried out, and the experimental results are basically the same. The simulation results are compared with the experimental results, indicating that vibration displacement waveforms of loosened rotor have “clipping” phenomenon. When the bearing pedestal looseness fault occurs, the inner and outer rotors vibration spectrum not only contains the difference and sum frequency of the two rotors’ fundamental frequency but also contains 2X and 3X component of rotor with loosened support, and so forth; low frequency spectrum is more, containing dividing component, and so forth; the rotor displacement spectrums also contain fewer combination frequency components, and so forth; when one side of the inner rotor bearing pedestal is loosened, the inner rotor axis trajectory is drawn into similar-ellipse shape.

  17. High-speed motion picture camera experiments of cavitation in dynamically loaded journal bearings

    Science.gov (United States)

    Hamrock, B. J.; Jacobson, B. O.

    1983-01-01

    A high-speed camera was used to investigate cavitation in dynamically loaded journal bearings. The length-diameter ratio of the bearing, the speeds of the shaft and bearing, the surface material of the shaft, and the static and dynamic eccentricity of the bearing were varied. The results reveal not only the appearance of gas cavitation, but also the development of previously unsuspected vapor cavitation. It was found that gas cavitation increases with time until, after many hundreds of pressure cycles, there is a constant amount of gas kept in the cavitation zone of the bearing. The gas can have pressures of many times the atmospheric pressure. Vapor cavitation bubbles, on the other hand, collapse at pressures lower than the atmospheric pressure and cannot be transported through a high-pressure zone, nor does the amount of vapor cavitation in a bearing increase with time. Analysis is given to support the experimental findings for both gas and vapor cavitation. Previously announced in STAR as N82-20543

  18. Dynamic force response of spherical hydrostatic journal bearing for cryogenic applications

    Science.gov (United States)

    Sanandres, Luis

    1994-01-01

    Hydrostatic Journal Bearings (HJB's) are reliable and resilient fluid film rotor support elements ideal to replace roller bearings in cryogenic turbomachinery. HJB' will be used for primary space-power applications due to their long lifetime, low friction and wear, large load capacity, large direct stiffness, and damping force coefficients. An analysis for the performance characteristics of turbulent flow, orifice compensated, spherical hydrostatic journal bearings (HJB's) is presented. Spherical bearings allow tolerance for shaft misalignment without force performance degradation and have also the ability to support axial loads. The spherical HJB combines these advantages to provide a bearing design which could be used efficiently on high performance turbomachinery. The motion of a barotropic liquid on the thin film bearing lands is described by bulk-flow mass and momentum equations. These equations are solved numerically using an efficient CFD method. Numerical predictions of load capacity and force coefficients for a 6 recess, spherical HJB in a LO2 environment are presented. Fluid film axial forces and force coefficients of a magnitude about 20% of the radial load capacity are predicted for the case analyzed. Fluid inertia effects, advective and centrifugal, are found to affect greatly the static and dynamic force performance of the bearing studied.

  19. Weight Identification of a Weighted Bipartite Graph Complex Dynamical Network with Coupling Delay

    Directory of Open Access Journals (Sweden)

    Jia Zhen

    2010-01-01

    Full Text Available Abstract We propose a network model, a weighted bipartite complex dynamical network with coupling delay, and present a scheme for identifying the weights of the network. Based on adaptive synchronization technique, weight trackers are designed for identifying the edge weights between nodes of the network by monitoring the dynamical evolution of the synchronous networks with drive-response structure. The conclusion is proved theoretically by Lyapunovs stability theory and LaSalle's invariance principle. Compared with the similar works, taking into consideration the structural characteristics of the network, the tracking devices designed in our paper are more effective and more easy to implement. Finally, numerical simulations show the effectiveness of the proposed method.

  20. Nonlinear dynamic modeling of rotor system supported by angular contact ball bearings

    Science.gov (United States)

    Wang, Hong; Han, Qinkai; Zhou, Daning

    2017-02-01

    In current bearing dynamic models, the displacement coordinate relations are usually utilized to approximately obtain the contact deformations between the rolling element and raceways, and then the nonlinear restoring forces of the rolling bearing could be calculated accordingly. Although the calculation efficiency is relatively higher, the accuracy is lower as the contact deformations should be solved through iterative analysis. Thus, an improved nonlinear dynamic model is presented in this paper. Considering the preload condition, surface waviness, Hertz contact and elastohydrodynamic lubrication, load distribution analysis is solved iteratively to more accurately obtain the contact deformations and angles between the rolling balls and raceways. The bearing restoring forces are then obtained through iteratively solving the load distribution equations at every time step. Dynamic tests upon a typical rotor system supported by two angular contact ball bearings are conducted to verify the model. Through comparisons, the differences between the nonlinear dynamic model and current models are also pointed out. The effects of axial preload, rotor eccentricity and inner/outer waviness amplitudes on the dynamic response are discussed in detail.

  1. Effect of Different Bearing Ratios on the Friction between Ultrahigh Molecular Weight Polyethylene Ski Bases and Snow.

    Science.gov (United States)

    Rohm, Sebastian; Knoflach, Christoph; Nachbauer, Werner; Hasler, Michael; Kaserer, Lukas; van Putten, Joost; Unterberger, Seraphin H; Lackner, Roman

    2016-05-18

    The purpose of this study was to analyze the effect of surfaces with different bearing ratios, but similar roughness heights, on the friction between ultrahigh molecular weight polyethylene (UHMWPE) and snow. On a linear tribometer positioned inside a cold chamber, the different samples were tested over a wide range of velocities and snow temperatures. The surface roughness was measured with a focus variation microscope and analyzed using the bearing ratio curve and its parameters. The surface energy was investigated by measuring the contact angles of a polar (water) and nonpolar (diiodmethane) liquid. The friction tests showed that the bearing ratio had a major effect on the friction between UHMWPE and snow. For temperatures close to the melting point a surface with wide grooves and narrow plateaus (nonbearing surface) performed well. For cold conditions, the friction was less for a surface with narrow grooves and wide plateaus (bearing surface). Interpretations of the results are given on the basis of mixed friction, with lubricated friction being dominant at higher snow temperatures and solid-solid interaction at lower ones.

  2. Nonlinear dynamics of flexible rotor supported on the gas foil journal bearings

    Science.gov (United States)

    Bhore, Skylab P.; Darpe, Ashish K.

    2013-09-01

    Investigation on nonlinear dynamics of a flexible rotor supported on the gas foil journal bearings is attempted. A time domain orbit simulation is carried out that couples the equations of rotor motion, unsteady Reynolds equation and foil deformation. The unsteady Reynolds equation is solved using control volume formulation with power law hybrid scheme and Gauss-Seidel method. The nonlinear dynamic response is analyzed using disc center and journal center trajectories, Poincaré maps, Fast Fourier transforms and bifurcation plots. The analysis is carried out for different system parameters, namely, rotating speed, unbalance eccentricity, compliance and loss factor of gas foil bearing. The analysis reveals highly nonlinear behavior with periodic, multi-periodic and quasiperiodic motion of the disc and the journal center. The present analysis can be useful in designing and selection of suitable operating parameters of rotor bearing system.

  3. Cortical and Trabecular Bone Microstructure Did Not Recover at Weight-Bearing Skeletal Sites and Progressively Deteriorated at Non-Weight-Bearing Sites During the Year Following International Space Station Missions.

    Science.gov (United States)

    Vico, Laurence; van Rietbergen, Bert; Vilayphiou, Nicolas; Linossier, Marie-Thérèse; Locrelle, Hervé; Normand, Myriam; Zouch, Mohamed; Gerbaix, Maude; Bonnet, Nicolas; Novikov, Valery; Thomas, Thierry; Vassilieva, Galina

    2017-06-02

    Risk for premature osteoporosis is a major health concern in astronauts and cosmonauts; the reversibility of the bone lost at the weight-bearing bone sites is not established, although it is suspected to take longer than the mission length. The bone three-dimensional structure and strength that could be uniquely affected by weightlessness is currently unknown. Our objective is to evaluate bone mass, microarchitecture, and strength of weight-bearing and non-weight-bearing bone in 13 cosmonauts before and for 12 months after a 4-month to 6-month sojourn in the International Space Station (ISS). Standard and advanced evaluations of trabecular and cortical parameters were performed using high-resolution peripheral quantitative computed tomography. In particular, cortical analyses involved determination of the largest common volume of each successive individual scan to improve the precision of cortical porosity and density measurements. Bone resorption and formation serum markers, and markers reflecting osteocyte activity or periosteal metabolism (sclerostin, periostin) were evaluated. At the tibia, in addition to decreased bone mineral densities at cortical and trabecular compartments, a 4% decrease in cortical thickness and a 15% increase in cortical porosity were observed at landing. Cortical size and density subsequently recovered and serum periostin changes were associated with cortical recovery during the year after landing. However, tibial cortical porosity or trabecular bone failed to recover, resulting in compromised strength. The radius, preserved at landing, unexpectedly developed postflight fragility, from 3 months post-landing onward, particularly in its cortical structure. Remodeling markers, uncoupled in favor of bone resorption at landing, returned to preflight values within 6 months, then declined farther to lower than preflight values. Our findings highlight the need for specific protective measures not only during, but also after spaceflight, because

  4. Dynamic Characteristics of the Herringbone Groove Gas Journal Bearings: Numerical Simulations

    Directory of Open Access Journals (Sweden)

    Bin Wang

    2016-01-01

    Full Text Available Dynamic characteristics of the herringbone grooved gas journal bearings (HGGJB under fluid-structure interactions are systematically investigated using the finite element method. Stability and bearing capacity of the HGGJB are estimated and compared with those of the plain gas journal bearings (PGJB. Influences of the structural parameters, including the spiral angle, the groove number, the groove depth, the pressure relief hole diameter, the bearing radial clearance, the length to diameter ratio, and the rotating speed, on dynamic characteristics of HGGJB are analyzed. To verify the numerical simulation results, pressure nephograms and cross-section pressure curves of the same rotor model, calculated by the numerical simulation and the theoretical method, respectively, are compared. Similar results are obtained. Compared to the common constrained boundary conditions in the previous numerical simulations, boundary conditions adopted in this paper are complete self-absorption and the change of the gas inlet and outlet depends on the rotating state of the rotor, which are more accordant with the real dynamic characteristics of the HGGJB. In all, the results presented in this paper provide a deeper and better understanding of the dynamic characteristics of the HGGJB under fluid-structure interactions.

  5. Influence of the Mechanical Seals on the Dynamic Performance of Rotor-Bearing Systems

    Institute of Scientific and Technical Information of China (English)

    XU Hua; ZHU Jun

    2006-01-01

    In this Paper,to consider the effects of mechanical seals.a lumped-mass modeJ and the transfer matric method are used to establish the equations for the dynamics performance of rotor-bearing system.The general inverted iteration method is also used to solve the eigenvalue problem of these equations.To check the response of the rotorbearing system under unbalance motivation,the Gauss method is used to calculate the dynamic response of the constrained vibration.The results,based on the dynamic properties calculation of a typical mechanical spiral seal,such as stiffness coefficients and damping coefficients.exert the influence of the mechanical seal on the rotorbeating system of the high-speed machinery.Meanwhile,some structure parameters that may affect the dynamic performance and forced vibration under unbalance motiVation of the rotor-bearing system considering mechanical seals are analyzed in the Paper.The analysis results show that the mechanical seal more or less has effects on the rotor-bearing system.The mechanical seal has much more effects on the flexible rotor-bearing system than on the rigid one.For instance,in a certain case,ifthe effects of the mechanical seal were taken into account,the system's critical speed may increase by 70-80%.

  6. Potassium chloride-bearing ice VII and ice planet dynamics

    Science.gov (United States)

    Frank, Mark R.; Scott, Henry P.; Aarestad, Elizabeth; Prakapenka, Vitali B.

    2016-02-01

    Accurate modeling of planetary interiors requires that the pressure-volume-temperature (PVT) properties of phases present within the body be well understood. The high-pressure polymorphs of H2O have been studied extensively due to the abundance of ice phases in icy moons and, likely, vast number of extra-solar planetary bodies, with only select studies evaluating impurity-laden ices. In this study, ice formed from a 1.6 mol percent KCl-bearing aqueous solution was studied up to 32.89 ± 0.19 GPa and 625 K, and the incorporation of K+ and Cl- ionic impurities into the ice VII structure was documented. The compression data at 295 K were fit with a third order Birch-Murnaghan equation of state and yielded a bulk modulus (KT0), its pressure derivative (KT0‧), and zero pressure volume (V0) of 24.7 ± 0.9 GPa, 4.44 ± 0.09, and 39.2 ± 0.2 Å3, respectively. The impurity-laden ice was found to be 6-8% denser than ice VII formed from pure H2O. Thermal expansion coefficients were also determined for several isothermal compression curves at elevated temperatures, and a PVT equation of state was obtained. The melting curve of ice VII with incorporated K+ and Cl- was estimated by fitting experimental data up to 10.2 ± 0.4 GPa, where melting occurred at 625 K, to the Simon-Glatzel equation. The melting curve of this impurity-laden ice is systematically depressed relative to that of pure H2O by approximately 45 K and 80 K at 4 and 11 GPa, respectively. A portion of the K+ and Cl- contained within the ice VII structure was observed to exsolve with increasing temperature. This suggests that an internal differentiating process could concentrate a K-rich phase deep within H2O-rich planets, and we speculate that this could supply an additional source of heat through the radioactive decay of 40K. Our data illustrate ice VII can incorporate significant concentrations of K+ and Cl- and increasing the possibility of deep-sourced and solute-rich plumes in moderate to large sized H2O

  7. Identification Methods and Test Results for Tilting Pad and Fixed Geometry Journal Bearing Dynamic Coefficients – A Review

    Directory of Open Access Journals (Sweden)

    T.W. Dimond

    2009-01-01

    Full Text Available Fluid film journal bearings (FFBs are used to support high-speed rotors in turbomachinery which often operate above the rotor first bending critical speed. The FFBs provide both lateral support and dynamic coefficients: stiffness, damping, and mass terms, related to machine vibrations. Detailed numerical values of the bearing dynamic characteristics are necessary for proper design and operation of rotating machinery.

  8. A high-precision instrument for analyzing nonlinear dynamic behavior of bearing cage

    Science.gov (United States)

    Yang, Z.; Chen, H.; Yu, T.; Li, B.

    2016-08-01

    The high-precision ball bearing is fundamental to the performance of complex mechanical systems. As the speed increases, the cage behavior becomes a key factor in influencing the bearing performance, especially life and reliability. This paper develops a high-precision instrument for analyzing nonlinear dynamic behavior of the bearing cage. The trajectory of the rotational center and non-repetitive run-out (NRRO) of the cage are used to evaluate the instability of cage motion. This instrument applied an aerostatic spindle to support and spin test the bearing to decrease the influence of system error. Then, a high-speed camera is used to capture images when the bearing works at high speeds. A 3D trajectory tracking software tema Motion is used to track the spot which marked the cage surface. Finally, by developing the matlab program, a Lissajous' figure was used to evaluate the nonlinear dynamic behavior of the cage with different speeds. The trajectory of rotational center and NRRO of the cage with various speeds are analyzed. The results can be used to predict the initial failure and optimize cage structural parameters. In addition, the repeatability precision of instrument is also validated. In the future, the motorized spindle will be applied to increase testing speed and image processing algorithms will be developed to analyze the trajectory of the cage.

  9. A high-precision instrument for analyzing nonlinear dynamic behavior of bearing cage.

    Science.gov (United States)

    Yang, Z; Chen, H; Yu, T; Li, B

    2016-08-01

    The high-precision ball bearing is fundamental to the performance of complex mechanical systems. As the speed increases, the cage behavior becomes a key factor in influencing the bearing performance, especially life and reliability. This paper develops a high-precision instrument for analyzing nonlinear dynamic behavior of the bearing cage. The trajectory of the rotational center and non-repetitive run-out (NRRO) of the cage are used to evaluate the instability of cage motion. This instrument applied an aerostatic spindle to support and spin test the bearing to decrease the influence of system error. Then, a high-speed camera is used to capture images when the bearing works at high speeds. A 3D trajectory tracking software tema Motion is used to track the spot which marked the cage surface. Finally, by developing the matlab program, a Lissajous' figure was used to evaluate the nonlinear dynamic behavior of the cage with different speeds. The trajectory of rotational center and NRRO of the cage with various speeds are analyzed. The results can be used to predict the initial failure and optimize cage structural parameters. In addition, the repeatability precision of instrument is also validated. In the future, the motorized spindle will be applied to increase testing speed and image processing algorithms will be developed to analyze the trajectory of the cage.

  10. A knee brace alters patella position in patellofemoral osteoarthritis: a study using weight bearing magnetic resonance imaging.

    Science.gov (United States)

    Callaghan, M J; Guney, H; Reeves, N D; Bailey, D; Doslikova, K; Maganaris, C N; Hodgson, R; Felson, D T

    2016-12-01

    To assess using weight bearing magnetic resonance imaging (MRIs), whether a patellar brace altered patellar position and alignment in patellofemoral joint (PFJ) osteoarthritis (OA). Subjects age 40-70 years old with symptomatic and a radiographic Kellgren-Lawrence (K-L) evidence of PFJOA. Weight bearing knee MRIs with and without a patellar brace were obtained using an upright open 0.25 T scanner (G-Scan, Easote Biomedica, Italy). Five aspects of patellar position were measured: mediolateral alignment by the bisect offset index, angulation by patellar tilt, patellar height by patellar height ratio (patellar length/patellar tendon length), lateral patellofemoral (PF) contact area and finally a measurement of PF bony separation of the lateral patellar facet and the adjacent surface on the femoral trochlea (Fig. 1). Thirty participants were recruited (mean age 57 SD 27.8; body mass index (BMI) 27.8 SD 4.2); 17 were females. Four patients had non-usable data. Main analysis used paired t tests comparing within subject patellar position with and without brace. For bisect offset index, patellar tilt and patellar height ratio there were no significant differences between the brace and no brace conditions. However, the brace increased lateral facet contact area (P = .04) and decreased lateral PF separation (P = .03). A patellar brace alters patellar position and increases contact area between the patella and femoral trochlea. These changes would lower contact stress at the PFJ. Such changes in patella position in weight bearing provide a possible biomechanical explanation for the success of the PFJ brace in clinical trials on PFJOA. Copyright © 2016. Published by Elsevier Ltd.

  11. The effect of weight bearing on bone mineral density and bone growth in children with cerebral palsy

    Science.gov (United States)

    Han, Eun Young; Choi, Jung Hwa; Kim, Sun-Hyun; Im, Sang Hee

    2017-01-01

    Abstract Background: The present study aims to explore the effect of weight bearing exercise on bone mineral density (BMD) and bone growth in children with cerebral palsy (CP). Methods: Twelve children with CP of functional level of gross motor functional classification scale (GMFCS) V and 6 healthy children (control group) were included in the study. Participants underwent a dual-energy X-ray absorptiometry scan to measure the BMD of the femur and full-length anteroposterior radiography to measure the bone length of the femur and tibia at baseline and after 6 months. Patients were randomly divided into 2 groups: group A with programmed standing exercises and assisted standing for more than 2 hours a day, more than 5 days a week; and group B with conventional physiotherapy with a standing program for 20 minutes a day, 2 to 3 days a week. Results: A 6-month follow-up showed significantly increased BMD on the femur neck in the control group. Although the changes in BMD were not significant in both groups, group A demonstrated an increased trend of BMD, whereas group B showed a decreased trend. Bone length was significantly increased in all 3 groups at the 6-month follow-up. Although this increase was not significant, the change in bone length was greatest in the control group. The smallest changes were observed in group B. Conclusions: Weight bearing exercise may play an important role in increasing or maintaining BMD in children with CP and is also expected to promote bone growth. Programmed standing may be used as an effective treatment method to increase BMD in children with CP. However, further studies with a larger cohort and longer follow-up period are required to reveal further information on the benefit of weight bearing exercise and to develop a detailed program. PMID:28272197

  12. Polar bear population dynamics in the southern Beaufort Sea during a period of sea ice decline

    Science.gov (United States)

    Bromaghin, Jeffrey F.; McDonald, Trent L.; Stirling, Ian; Derocher, Andrew E.; Richardson, Evan S.; Regehr, Eric V.; Douglas, David C.; Durner, George M.; Atwood, Todd C.; Amstrup, Steven C.

    2015-01-01

    In the southern Beaufort Sea of the United States and Canada, prior investigations have linked declines in summer sea ice to reduced physical condition, growth, and survival of polar bears (Ursus maritimus). Combined with projections of population decline due to continued climate warming and the ensuing loss of sea ice habitat, those findings contributed to the 2008 decision to list the species as threatened under the U.S. Endangered Species Act. Here, we used mark–recapture models to investigate the population dynamics of polar bears in the southern Beaufort Sea from 2001 to 2010, years during which the spatial and temporal extent of summer sea ice generally declined. Low survival from 2004 through 2006 led to a 25–50% decline in abundance. We hypothesize that low survival during this period resulted from (1) unfavorable ice conditions that limited access to prey during multiple seasons; and possibly, (2) low prey abundance. For reasons that are not clear, survival of adults and cubs began to improve in 2007 and abundance was comparatively stable from 2008 to 2010, with ~900 bears in 2010 (90% CI 606–1212). However, survival of subadult bears declined throughout the entire period. Reduced spatial and temporal availability of sea ice is expected to increasingly force population dynamics of polar bears as the climate continues to warm. However, in the short term, our findings suggest that factors other than sea ice can influence survival. A refined understanding of the ecological mechanisms underlying polar bear population dynamics is necessary to improve projections of their future status and facilitate development of management strategies.

  13. The influence of a weight-bearing platform on the mechanical behavior of two Ilizarov ring fixators: tensioned wires vs. half-pins

    Directory of Open Access Journals (Sweden)

    Gessmann Jan

    2011-12-01

    Full Text Available Abstract Background A weight-bearing platform applied at the distal end of an Ilizarov external frame allows patients with hindfoot transfixations, foot deformities or plantar skin lesions to bear weight. This leads to an indirect loading of the fracture or osteotomy site. However, the effect on the fracture/osteotomy site's motion or compressive loads is unknown. The aim of this study was to analyze the mechanical effects of a weight-bearing platform on the traditional all-wire, four-ring frame in comparison to a two-ring frame consisting of half-pins. Methods Two frame configurations, with either anatomically positioned wires or half-pins, were analyzed with and without a weight-bearing platform applied underneath the distal ring. Composite tibiae with a mid-diaphyseal osteotomy of 3.5 mm were used in all the experiments. An axial load was applied with the use of a universal test machine (UTS®. Interfragmentary movements, the relative movements of bone fragments and movements between rings were recorded using displacement transducers. Compressive loads at the osteotomy site were recorded with loading cells. Results Indirect loading with a weight-bearing platform altered the force transmission through the osteotomy. Indirect loading of the tibiae decreased the extent of the axial micro-motion by 50% under the applied weight load when compared to direct weight loading (p Conclusions A weight-bearing platform has substantial influence on the biomechanical performance of an Ilizarov external fixator. Half-pins induce greater stiffness to the Ilizarov external fixator and allow the usage of only one ring per bone segment, but shear stresses at the osteotomy under axial loading should be considered. The results allow an estimation of the size and direction of interfragmentary movements based on the extent of weight bearing.

  14. Dynamic Analysis of Flexible Cage of High-speed Angular Contact Ball Bearing

    Institute of Scientific and Technical Information of China (English)

    邓四二; 谢鹏飞; 杨海生; 高银涛

    2012-01-01

    A dynamics formula was established for the flexible cage of high-speed angular contact ball bearing. A modified Craig-Bampton component mode synthetic method was used to establish the formula with regard to the flexibility of cage and based on a dynamic analysis of angular contact ball bearing, and a rigid-flexible multi-body dynamic analysis program was developed using ADAMS, which is verified by a computation example of Gupta. The results show that it' s not likely to keep the rotation smoothness of cage when the ratio of pocket clearance to guiding clearance and the ratio of radial load to axial load become too large or too small. By comparison, the flexible cage runs more smoothly than the rigid cage.

  15. Dynamics analysis of a cracked dual-disk over-hung rotor-bearing system

    Institute of Scientific and Technical Information of China (English)

    CHEN Hong; LI He; ZHANG Xiao-wei; WEN Bang-chun

    2006-01-01

    A dynamic model of a dual-disk vertical over-hung rotor-bearing system is developed,taking into account nonlinear oil-film force.Its dynamic behaviors are investigated by numerical Runge-Kutta method.Its bifurcation and chaos characteristics are analyzed with crack fault and without crack fault.By analyzing the bifurcation plot,Poincare section plots and amplitude spectra,we found that the crack greatly influences the dynamic characteristics of the rotor-bearing system.Because of the strong effect of the nonlinear oil-film force and crack to the system,1/2 times,1/3 times frequency components appear in the response spectrum map.The results may bring up theoretical references for fault diagnosis of rotor-beating systems.

  16. Characteristics analysis and dynamic responses of micro-gas-lubricated journal bearings with a new slip model

    Science.gov (United States)

    Zhang, Wen-Ming; Meng, Guang; Huang, Hai; Zhou, Jian-Bin; Chen, Jie-Yu; Chen, Di

    2008-08-01

    In this paper, a new slip model based on kinetic theory of gases for gas-lubricated journal bearings in micro-electro-mechanical systems (MEMS) is applied using a physical approach. The corresponding modified governing equation and mathematic model are presented and the flow rate is plotted versus the inverse Knudsen number. Pressure distributions along the gas bearing at various Knudsen numbers and bearing numbers are plotted and the load carrying capacities are also obtained. A numerical analysis of a rigid rotor supported by gas-lubricated journal bearings is presented for dynamic behaviour. The slip flow effect on the properties, including pressure distribution, load carrying capacity and dynamic coefficients, of the micro-gas-lubricated journal bearings and dynamic responses of the micro rotor-bearing system are estimated and analysed in detail. It is shown that the dynamic coefficients increase with increasing bearing number except for two damping coefficients and the rotor-bearing system runs at a much higher rotating speed to keep stable when slip flow occurs. Moreover, the oscillation period of the rotor operating with the slip model is longer than that with the continuum flow. In addition, the whirl frequency is reduced from 0.422 to 0.079 under the slip effect. Therefore, the results of this study contribute to a further understanding of the characteristics and nonlinear dynamics of gas-film rotor-bearing systems in MEMS.

  17. Effects of Floating Ring Bearing Manufacturing Tolerance Clearances on the Dynamic Characteristics for Turbocharger

    Institute of Scientific and Technical Information of China (English)

    WANG Longkai; BIN Guangfu; LI Xuejun; ZHANG Xuefeng

    2015-01-01

    The inner and outer oil film dynamic characteristic coefficients of floating ring bearings(FRBs) change due to the manufacturing tolerance of the floating ring, journal and intermediate, which leads to high-speed turbocharger’s vibration too large and even causes nonlinear vibration accident. However, the investigation of floating ring bearing manufacturing tolerance clearance on the rotordynamic characteristics is less at present. In order to study the influence law of inner and outer clearance on turbocharger vibration, the rotor dynamic motion equations of turbocharger supported in FRBs are derived by analyzing the size relations between floating ring, journal and intermediate for the inner and outer oil film clearances, the time transient response analysis for combination of FRBs clearance are developed. A realistic turbocharger is taken as a research object, the FE model of the turbocharger with FRBs is modeled. Under the conditions of four kinds of limit state bearing clearances for inner and outer oil film, the nonlinear transient analyses are performed based on the established FE dynamic models of the nonlinear rotor-FRBs system applied incentive combinations of gravity and unbalance force, respectively. From the waterfall, the simulation results show that the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different under the four kinds of bearing manufacturing tolerance limit clearances, and fractional frequency does not appear in the turbocharger and the amplitude is minimum under the ODMin/IDMax bearing manufacturing tolerance clearances. The turbocharger vibration is reduced by controlling the manufacturing tolerance clearance combinations of FRBs, which is helpful for the dynamic design and production-manufacturing of high-speed turbocharger.

  18. Weighted Networks Model Based on Traffic Dynamics with Local Perturbation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In the study of weighted complex networks, the interplay between traffic and topology have been paid much attention. However, the variation of topology and weight brought by new added vertices or edges should also be considered. In this paper, an evolution model of weighted networks driven by traffic dynamics with local perturbation is proposed. The model gives power-law distribution of degree, weight and strength, as confirmed by empirical measurements. By choosing appropriate parameters W and δ, the exponents of various power law distributions can be adjusted to meet real world networks. Nontrivial clustering coefficient C, degree assortativity coefficient r, and strength-degree correlation are also considered. What should be emphasized is that, with the consideration of local perturbation, one can adjust the exponent of strength-degree correlation more effectively. It makes our model more general than previous ones and may help reproducing real world networks more appropriately.

  19. A Comparison Study of Magnetic Bearing Controllers for a Fully Suspended Dynamic Spin Rig

    Science.gov (United States)

    Choi, Benjamin; Johnson, Dexter; Morrison, Carlos; Mehmed, Oral; Huff, Dennis (Technical Monitor)

    2002-01-01

    NASA Glenn Research Center (GRC) has developed a fully suspended magnetic bearing system for the Dynamic Spin Rig (DSR) that is used to perform vibration tests of turbomachinery blades and components under spinning conditions in a vacuum. Two heteropolar radial magnetic bearings and a thrust bearing and the associated control system were integrated into the DSR to provide noncontact magnetic suspension and mechanical excitation of the 35 lb vertical rotor with blades to induce turbomachinery blade vibration. A simple proportional-integral-derivative (PID) controller with a special feature for multidirectional radial excitation worked very well to both support and shake the shaft with blades. However, more advanced controllers were developed and successfully tested to determine the optimal controller in terms of sensor and processing noise reduction, smaller rotor orbits, and energy savings for the system. The test results of a variety of controllers we demonstrated up to the rig's maximum allowable speed of 10,000 rpm are shown.

  20. Shape memory alloys applied to improve rotor-bearing system dynamics - an experimental investigation

    DEFF Research Database (Denmark)

    Enemark, Søren; Santos, Ilmar; Savi, Marcelo A.

    2015-01-01

    tor-bearing systems have critical speeds and to pass through them is an ongoing challenge in the field of mechanical engineering. The incorporation of shape memory alloys in rotating systems has an increasing importance to improve system performance and to avoid potential damaging situations when...... passing through critical speeds. In this work, the feasibility of applying shape memory alloys to a rotating system is experimentally investigated. Shape memory alloys can change their stiffness with temperature variations and thus they may change system dynamics. Shape memory alloys also exhibit...... hysteretic stress-strain relations which may be utilized for damping purposes. These ideas are tested in this study on a dedicated test-rig, consisting of a rigid shaft and disc held vertically by passive magnetic bearings, where the damping is low. The bearing housings is flexibly supported by shape memory...

  1. Non-linear dynamics of a geared rotor-bearing system with multiple clearances

    Science.gov (United States)

    Kahraman, A.; Singh, R.

    1991-02-01

    Non-linear frequency response characteristics of a geared rotor-bearing system are examined in this paper. A three-degree-of-freedom dynamic model is developed which includes non-linearities associated with radial clearances in the radial rolling element bearings and backlash between a spur gear pair; linear time-invariant gear meshing stiffness is assumed. The corresponding linear system problem is also solved, and predicted natural frequencies and modes match with finite element method results. The bearing non-linear stiffness function is approximated for the sake of convenience by a simple model which is identical to that used for the gear mesh. This approximate bearing model has been verified by comparing steady state frequency spectra. Applicability of both analytical and numerical solution techniques to the multi-degree-of-freedom non-linear problem is investigated. Satisfactory agreement has been found between our theory and available experimental data. Several key issues such as non-linear modal interactions and differences between internal static transmission error excitation and external torque excitation are discussed. Additionally, parametric studies are performed to understand the effect of system parameters such as bearing stiffness to gear mesh stiffness ratio, alternating to mean force ratio and radial bearing preload to mean force ratio on the non-linear dynamic behavior. A criterion used to classify the steady state solutions is presented, and the conditions for chaotic, quasi-periodic and subharmonic steady state solutions are determined. Two typical routes to chaos observed in this geared system are also identified.

  2. Combined magnetic resonance imaging approach for the assessment of in vivo knee joint kinematics under full weight-bearing conditions.

    Science.gov (United States)

    Al Hares, Ghaith; Eschweiler, Jörg; Radermacher, Klaus

    2015-06-01

    The development of detailed and specific knowledge on the biomechanical behavior of loaded knee structures has received increased attention in recent years. Stress magnetic resonance imaging techniques have been introduced in previous work to study knee kinematics under load conditions. Previous studies captured the knee movement either in atypical loading supine positions, or in upright positions with help of inclined supporting backrests being insufficient for movement capture under full-body weight-bearing conditions. In this work, we used a combined magnetic resonance imaging approach for measurement and assessment in knee kinematics under full-body weight-bearing in single legged stance. The proposed method is based on registration of high-resolution static magnetic resonance imaging data acquired in supine position with low-resolution data, quasi-static upright-magnetic resonance imaging data acquired in loaded positions for different degrees of knee flexion. The proposed method was applied for the measurement of tibiofemoral kinematics in 10 healthy volunteers. The combined magnetic resonance imaging approach allows the non-invasive measurement of knee kinematics in single legged stance and under physiological loading conditions. We believe that this method can provide enhanced understanding of the loaded knee kinematics. © IMechE 2015.

  3. Effect of gradual weight-bearing on regenerated articular cartilage after joint distraction and motion in a rabbit model.

    Science.gov (United States)

    Nishino, Tomofumi; Ishii, Tomoo; Chang, Fei; Yanai, Takaji; Watanabe, Arata; Ogawa, Takeshi; Mishima, Hajime; Nakai, Kenjiro; Ochiai, Naoyuki

    2010-05-01

    The purpose of this study was to clarify the effect of gradual weight bearing (GWB) on regenerating cartilage. We developed a novel external fixation device (EFD) with a controllable weight-bearing system and continuous passive motion (CPM). A full-thickness defect was created by resection of the entire articular surface of the tibial plateau after the EFD was fixed in the rabbit's left knee. In the GWB group (n=6), GWB was started 6 weeks after surgery. In the CPM group (n=6), CPM with EFD was applied in the same manner without GWB. The control group (n=5) received only joint distraction. All rabbits were sacrificed 9 weeks after surgery. The central one-third of the regenerated tissue was assessed and scored blindly using a grading scale modified from the International Cartilage Repair Society visual histological assessment scale. The areas stained by Safranin-O and type II collagen antibody were measured, and the percentage of each area was calculated. There was no significant difference in the histological assessment scale among the groups. The percentage of the type II collagen-positive area was significantly larger in the GWB group than in the CPM group. The present study suggests that optimal mechanical stress, such as GWB, may affect regeneration of cartilage, in vivo.

  4. Measurement of tibial nerve excursion during ankle joint dorsiflexion in a weight-bearing position with ultrasound imaging

    Directory of Open Access Journals (Sweden)

    Carroll Matthew

    2012-03-01

    Full Text Available Abstract Background The ability of peripheral nerves to stretch and slide is thought to be of paramount importance to maintain ideal neural function. Excursion in peripheral nerves such as the tibial can be measured by analysis of ultrasound images. The aim of this study was to assess the degree of longitudinal tibial nerve excursion as the ankle moved from plantar flexion to dorsiflexion in a standardised weight-bearing position. The reliability of ultrasound imaging to measure tibial nerve excursion was also quantified. Methods The tibial nerve was imaged over two separate sessions in sixteen asymptomatic participants in a weight-bearing position. Longitudinal nerve excursion was calculated from a three-second video loop captured by ultrasound imaging using frame-by-frame cross-correlation analysis. Intraclass correlation coefficients (ICC with 95% confidence intervals (CI were used to assess the intra-rater reliability. Standard error of the measurement (SEM and smallest real difference (SRD were calculated to assess measurement error. Results Mean nerve excursion was 2.99 mm SEM ± 0.22 mm. The SRD was 0.84 mm for session 1 and 0.66 mm for session 2. Intra-rater reliability was excellent with an ICC = 0.93. Conclusions Assessment of real-time ultrasound images of the tibial nerve via frame-by-frame cross-correlation analysis is a reliable non-invasive technique to assess longitudinal nerve excursion. The relationship between foot posture and nerve excursion can be further investigated.

  5. Research and Development of a Chaotic Signal Synchronization Error Dynamics-Based Ball Bearing Fault Diagnostor

    Directory of Open Access Journals (Sweden)

    Ying-Che Kuo

    2014-10-01

    Full Text Available This paper describes the fault diagnosis in the operation of industrial ball bearings. In order to cluster the very small differential signals of the four classic fault types of the ball bearing system, the chaos synchronization (CS concept is used in this study as the chaos system is very sensitive to a system’s variation such as initial conditions or system parameters. In this study, the Chen-Lee chaotic system was used to load the normal and fault signals of the bearings into the chaos synchronization error dynamics system. The fractal theory was applied to determine the fractal dimension and lacunarity from the CS error dynamics. Extenics theory was then applied to distinguish the state of the bearing faults. This study also compared the proposed method with discrete Fourier transform and wavelet packet analysis. According to the results, it is shown that the proposed chaos synchronization method combined with extenics theory can separate the characteristics (fractal dimension vs. lacunarity completely. Therefore, it has a better fault diagnosis rate than the two traditional signal processing methods, i.e., Fourier transform and wavelet packet analysis combined with extenics theory.

  6. Effects of upright weight bearing and the knee flexion angle on patellofemoral indices using magnetic resonance imaging in patients with patellofemoral instability.

    Science.gov (United States)

    Becher, Christoph; Fleischer, Benjamin; Rase, Marten; Schumacher, Thees; Ettinger, Max; Ostermeier, Sven; Smith, Tomas

    2017-08-01

    This study analysed the effects of upright weight bearing and the knee flexion angle on patellofemoral indices, determined using magnetic resonance imaging (MRI), in patients with patellofemoral instability (PI). Healthy volunteers (control group, n = 9) and PI patients (PI group, n = 16) were scanned in an open-configuration MRI scanner during upright weight bearing and supine non-weight bearing positions at full extension (0° flexion) and at 15°, 30°, and 45° flexion. Patellofemoral indices included the Insall-Salvati Index, Caton-Deschamp Index, and Patellotrochlear Index (PTI) to determine patellar height and the patellar tilt angle (PTA), bisect offset (BO), and the tibial tubercle-trochlear groove (TT-TG) distance to assess patellar rotation and translation with respect to the femur and alignment of the extensor mechanism. A significant interaction effect of weight bearing by flexion angle was observed for the PTI, PTA, and BO for subjects with PI. At full extension, post hoc pairwise comparisons revealed a significant effect of weight bearing on the indices, with increased patellar height and increased PTA and BO in the PI group. Except for the BO, no such changes were seen in the control group. Independent of weight bearing, flexing the knee caused the PTA, BO, and TT-TG distance to be significantly reduced. Upright weight bearing and the knee flexion angle affected patellofemoral MRI indices in PI patients, with significantly increased values at full extension. The observations of this study provide a caution to be considered by professionals when treating PI patients. These patients should be evaluated clinically and radiographically at full extension and various flexion angles in context with quadriceps engagement. Explorative case-control study, Level III.

  7. First Operating Results of a Dynamic Gas Bearing Turbine in AN Industrial Hydrogen Liquefier

    Science.gov (United States)

    Bischoff, S.; Decker, L.

    2010-04-01

    Hydrogen has been brought into focus of industry and public since fossil fuels are depleting and costs are increasing dramatically. Beside these issues new high-tech processes in the industry are in need for hydrogen at ultra pure quality. To achieve these requirements and for efficient transportation, hydrogen is liquefied in industrial plants. Linde Gas has commissioned a new 5.5 TPD Hydrogen liquefier in Leuna, Germany, which has been engineered and supplied by Linde Kryotechnik. One of the four expansion turbines installed in the liquefaction process is equipped with dynamic gas bearings. Several design features and operational characteristics of this application will be discussed. The presentation will include results of efficiency and operational reliability that have been determined from performance tests. The advantages of the Linde dynamic gas bearing turbine for future use in hydrogen liquefaction plants will be shown.

  8. Orthostatic Tremor and Orthostatic Myoclonus: Weight-bearing Hyperkinetic Disorders: A Systematic Review, New Insights, and Unresolved Questions

    Science.gov (United States)

    Hassan, Anhar; van Gerpen, Jay A.

    2016-01-01

    Background Orthostatic tremor (OT) and orthostatic myoclonus (OM) are weight-bearing hyperkinetic movement disorders most commonly affecting older people that induce “shaky legs” upon standing. OT is divided into “classical” and “slow” forms based on tremor frequency. In this paper, the first joint review of OT and OM, we review the literature and compare and contrast their demographic, clinical, electrophysiological, neuroimaging, pathophysiological, and treatment characteristics. Methods A PubMed search up to July 2016 using the phrases “orthostatic tremor,” “orthostatic myoclonus,” “shaky legs,” and “shaky legs syndrome” was performed. Results OT and OM should be suspected in older patients reporting unsteadiness with prolonged standing and/or who exhibit cautious, wide-based gaits. Surface electromyography (SEMG) is necessary to verify the diagnoses. Functional neuroimaging and electrophysiology suggest the generator of classical OT lies within the cerebellothalamocortical network. For OM, and possibly slow OT, the frontal, subcortical cerebrum is the most likely origin. Clonazepam is the most useful medication for classical OT, and levetiracetam for OM, although results are often disappointing. Deep brain stimulation appears promising for classical OT. Rolling walkers reliably improve gait affected by these disorders, as both OT and OM attenuate when weight is transferred from the legs to the arms. Discussion Orthostatic hyperkinesias are likely underdiagnosed, as SEMG is often unavailable in clinical practice, and thus may be more frequent than currently recognized. The shared weight-bearing induction of OT and OM may indicate a common pathophysiology. Further research, including use of animal models, is necessary to better define the prevalence and pathophysiology of OT and OM, in order to improve their treatment, and provide additional insights into basic balance and gait mechanisms.

  9. A novel dynamical community detection algorithm based on weighting scheme

    Science.gov (United States)

    Li, Ju; Yu, Kai; Hu, Ke

    2015-12-01

    Network dynamics plays an important role in analyzing the correlation between the function properties and the topological structure. In this paper, we propose a novel dynamical iteration (DI) algorithm, which incorporates the iterative process of membership vector with weighting scheme, i.e. weighting W and tightness T. These new elements can be used to adjust the link strength and the node compactness for improving the speed and accuracy of community structure detection. To estimate the optimal stop time of iteration, we utilize a new stability measure which is defined as the Markov random walk auto-covariance. We do not need to specify the number of communities in advance. It naturally supports the overlapping communities by associating each node with a membership vector describing the node's involvement in each community. Theoretical analysis and experiments show that the algorithm can uncover communities effectively and efficiently.

  10. Hash function construction using weighted complex dynamical networks

    Institute of Scientific and Technical Information of China (English)

    Song Yu-Rong; Jiang Guo-Ping

    2013-01-01

    A novel scheme to construct a hash function based on a weighted complex dynamical network (WCDN) generated from an original message is proposed in this paper.First,the original message is divided into blocks.Then,each block is divided into components,and the nodes and weighted edges are well defined from these components and their relations.Namely,the WCDN closely related to the original message is established.Furthermore,the node dynamics of the WCDN are chosen as a chaotic map.After chaotic iterations,quantization and exclusive-or operations,the fixed-length hash value is obtained.This scheme has the property that any tiny change in message can be diffused rapidly through the WCDN,leading to very different hash values.Analysis and simulation show that the scheme possesses good statistical properties,excellent confusion and diffusion,strong collision resistance and high efficiency.

  11. Dynamic airspace configuration method based on a weighted graph model

    Directory of Open Access Journals (Sweden)

    Chen Yangzhou

    2014-08-01

    Full Text Available This paper proposes a new method for dynamic airspace configuration based on a weighted graph model. The method begins with the construction of an undirected graph for the given airspace, where the vertices represent those key points such as airports, waypoints, and the edges represent those air routes. Those vertices are used as the sites of Voronoi diagram, which divides the airspace into units called as cells. Then, aircraft counts of both each cell and of each air-route are computed. Thus, by assigning both the vertices and the edges with those aircraft counts, a weighted graph model comes into being. Accordingly the airspace configuration problem is described as a weighted graph partitioning problem. Then, the problem is solved by a graph partitioning algorithm, which is a mixture of general weighted graph cuts algorithm, an optimal dynamic load balancing algorithm and a heuristic algorithm. After the cuts algorithm partitions the model into sub-graphs, the load balancing algorithm together with the heuristic algorithm transfers aircraft counts to balance workload among sub-graphs. Lastly, airspace configuration is completed by determining the sector boundaries. The simulation result shows that the designed sectors satisfy not only workload balancing condition, but also the constraints such as convexity, connectivity, as well as minimum distance constraint.

  12. Dynamic airspace configuration method based on a weighted graph model

    Institute of Scientific and Technical Information of China (English)

    Chen Yangzhou; Zhang Defu

    2014-01-01

    This paper proposes a new method for dynamic airspace configuration based on a weighted graph model. The method begins with the construction of an undirected graph for the given airspace, where the vertices represent those key points such as airports, waypoints, and the edges represent those air routes. Those vertices are used as the sites of Voronoi diagram, which divides the airspace into units called as cells. Then, aircraft counts of both each cell and of each air-route are computed. Thus, by assigning both the vertices and the edges with those aircraft counts, a weighted graph model comes into being. Accordingly the airspace configuration problem is described as a weighted graph partitioning problem. Then, the problem is solved by a graph par-titioning algorithm, which is a mixture of general weighted graph cuts algorithm, an optimal dynamic load balancing algorithm and a heuristic algorithm. After the cuts algorithm partitions the model into sub-graphs, the load balancing algorithm together with the heuristic algorithm trans-fers aircraft counts to balance workload among sub-graphs. Lastly, airspace configuration is com-pleted by determining the sector boundaries. The simulation result shows that the designed sectors satisfy not only workload balancing condition, but also the constraints such as convexity, connec-tivity, as well as minimum distance constraint.

  13. Couple-Stress Fluid Improves Dynamic Response of Gear-Pair System Supported by Journal Bearings

    Directory of Open Access Journals (Sweden)

    Cai-Wan Chang-Jian

    2012-01-01

    Full Text Available A systematic analysis of the dynamic behavior of a gear-bearing system with nonlinear suspension, couple-stress fluid flow effect, nonlinear oil-film force, and nonlinear gear mesh force is performed in the present study. The dynamic orbits of the system are observed using bifurcation diagrams plotted using the dimensionless rotational speed ratio as a control parameter. The onset of chaotic motion is identified from the phase diagrams, power spectra, Poincaré maps, Lyapunov exponents and fractal dimension of the gear-bearing system. The numerical results reveal that the system exhibits a diverse range of periodic, subharmonic, quasiperiodic, and chaotic behaviors. The couple-stress fluid would be a useful lubricating fluid to suppress nonlinear dynamic responses and improve the steady of the systems. The results presented in this study provide some useful insights into the design and development of a gear-bearing system for rotating machinery that operates in highly rotational speed and highly nonlinear regimes.

  14. Fully Suspended, Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig With Forced Excitation

    Science.gov (United States)

    Morrison, Carlos R.; Provenza, Andrew; Kurkov, Anatole; Montague, Gerald; Duffy, Kirsten; Mehmed, Oral; Johnson, Dexter; Jansen, Ralph

    2004-01-01

    The Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig, a significant advancement in the Dynamic Spin Rig (DSR), is used to perform vibration tests of turbomachinery blades and components under rotating and nonrotating conditions in a vacuum. The rig has as its critical components three magnetic bearings: two heteropolar radial active magnetic bearings and a magnetic thrust bearing. The bearing configuration allows full vertical rotor magnetic suspension along with a feed-forward control feature, which will enable the excitation of various natural blade modes in bladed disk test articles. The theoretical, mechanical, electrical, and electronic aspects of the rig are discussed. Also presented are the forced-excitation results of a fully levitated, rotating and nonrotating, unbladed rotor and a fully levitated, rotating and nonrotating, bladed rotor in which a pair of blades was arranged 180 degrees apart from each other. These tests include the bounce mode excitation of the rotor in which the rotor was excited at the blade natural frequency of 144 Hz. The rotor natural mode frequency of 355 Hz was discerned from the plot of acceleration versus frequency. For nonrotating blades, a blade-tip excitation amplitude of approximately 100 g/A was achieved at the first-bending critical (approximately 144 Hz) and at the first-torsional and second-bending blade modes. A blade-tip displacement of 70 mils was achieved at the first-bending critical by exciting the blades at a forced-excitation phase angle of 908 relative to the vertical plane containing the blades while simultaneously rotating the shaft at 3000 rpm.

  15. Positional pelvic organ prolapse (POP) evaluation using open, weight-bearing magnetic resonance imaging (MRI).

    Science.gov (United States)

    Friedman, Boris; Stothers, Lynn; Lazare, Darren; Macnab, Andrew

    2015-01-01

    Magnetic resonance imaging (MRI) of patients with pelvic organ prolapse (POP) is completed in the supine position. Open magnetic resonance imaging (MRO) uses vertical magnets, allowing imaging in a variety of upright postures. This pilot study used MRO to evaluate the change of prolapse in different positions compared to non-prolapsed images. In total, 11 women (6 POP, 5 controls) aged 24 to 65 years had 12 MRO images (midline sagittal pelvic line) consecutively when supine, sitting and standing with a full and empty bladder. Lengths between the lowest point of the bladder to the pubococcygeal (PC) and pubopromontoreal (PP) lines in each image were compared, and the ratio of bladder area under the PC and PP lines to the total bladder area. Significant elongation between the PC line and lowest point of the bladder was evident in subjects with POP comparing supine and standing images (p = 0.03), but not controls (p = 0.07). Similarly, this axis was significantly longer in cystocele subjects versus controls only in the standing position. Bladder area under the PC line was significantly increased between supine and standing positions only among subjects with cystocele (p bearing on the staging of POP. Imaging patients when sitting and standing identified that significant changes occur in the maximal descent of the bladder.

  16. Non-weight-bearing status compromises the functional level up to 1 yr after hip fracture surgery

    DEFF Research Database (Denmark)

    Ariza-Vega, Patrocinio; Jiménez-Moleón, José Juan; Kristensen, Morten Tange

    2014-01-01

    OBJECTIVE: The aim of this study was to examine the influence of weight-bearing (WB) status after hip fracture surgery on 1-yr functional outcome. DESIGN: This was a prospective cohort study, carried out in a public acute hospital trauma service. The 194 patients (36 men and 158 women), with a mean...... (SD) age of 81.4 (6.1) yrs, were admitted with a hip fracture within 2009 and were followed for 1 yr thereafter. The influence of postoperative WB status on the 1-yr functional outcome was assessed using the Functional Independence Measure (18-126 points), adjusting for other known factors by multiple...... linear regression. RESULTS: Seventy-five patients (39%) were not allowed WB for a period of 2-4 wks after surgery. Improved functional outcomes were associated positively with prefracture functional level and having a trochanteric fracture during the first year after fracture (P ≤ 0.01). Non-WB status...

  17. Metric analysis of loading magnitudes at articular and non-articular weight-bearing surfaces in human calcaneus.

    Science.gov (United States)

    Mahato, Niladri Kumar; Murthy, S Sathiya Narayana

    2013-03-01

    The calcaneus is axially loaded at its articular interface with the talus. A large bulk of this load is transmitted to the ground across the non-articular tubercles at the plantar surface of the bone. A small part of the incumbent load sustained by the calcaneus is directed towards the forefoot at the calcaneo-cuboid junction. This study investigates the proportion of load distributed across the articular and non-articular surfaces of the calcaneus. The present study demonstrates strong and significant correlation between some of the load bearing variables and suggests the need for further investigations to understand the effect of angular aspects of axial loading on the calcaneus. Accounting for the relative distribution of weight across the articular and non-articular areas may enable us to appreciate the internal trabecular structure of the calcaneus in light of its clinical importance.

  18. Vibration Propagation of Gear Dynamics in a Gear-Bearing-Housing System Using Mathematical Modeling and Finite Element Analysis

    Science.gov (United States)

    Parker, Robert G.; Guo, Yi; Eritenel, Tugan; Ericson, Tristan M.

    2012-01-01

    Vibration and noise caused by gear dynamics at the meshing teeth propagate through power transmission components to the surrounding environment. This study is devoted to developing computational tools to investigate the vibro-acoustic propagation of gear dynamics through a gearbox using different bearings. Detailed finite element/contact mechanics and boundary element models of the gear/bearing/housing system are established to compute the system vibration and noise propagation. Both vibration and acoustic models are validated by experiments including the vibration modal testing and sound field measurements. The effectiveness of each bearing type to disrupt vibration propagation is speed-dependent. Housing plays an important role in noise radiation .It, however, has limited effects on gear dynamics. Bearings are critical components in drivetrains. Accurate modeling of rolling element bearings is essential to assess vibration and noise of drivetrain systems. This study also seeks to fully describe the vibro-acoustic propagation of gear dynamics through a power-transmission system using rolling element and fluid film wave bearings. Fluid film wave bearings, which have higher damping than rolling element bearings, could offer an energy dissipation mechanism that reduces the gearbox noise. The effectiveness of each bearing type to disrupt vibration propagation in explored using multi-body computational models. These models include gears, shafts, rolling element and fluid film wave bearings, and the housing. Radiated noise is mapped from the gearbox surface to surrounding environment. The effectiveness of rolling element and fluid film wave bearings in breaking the vibro-acoustic propagation path from the gear to the housing is investigated.

  19. Human growth and body weight dynamics: an integrative systems model.

    Science.gov (United States)

    Rahmandad, Hazhir

    2014-01-01

    Quantifying human weight and height dynamics due to growth, aging, and energy balance can inform clinical practice and policy analysis. This paper presents the first mechanism-based model spanning full individual life and capturing changes in body weight, composition and height. Integrating previous empirical and modeling findings and validated against several additional empirical studies, the model replicates key trends in human growth including A) Changes in energy requirements from birth to old ages. B) Short and long-term dynamics of body weight and composition. C) Stunted growth with chronic malnutrition and potential for catch up growth. From obesity policy analysis to treating malnutrition and tracking growth trajectories, the model can address diverse policy questions. For example I find that even without further rise in obesity, the gap between healthy and actual Body Mass Indexes (BMIs) has embedded, for different population groups, a surplus of 14%-24% in energy intake which will be a source of significant inertia in obesity trends. In another analysis, energy deficit percentage needed to reduce BMI by one unit is found to be relatively constant across ages. Accompanying documented and freely available simulation model facilitates diverse applications customized to different sub-populations.

  20. Gender and weight shape brain dynamics during food viewing.

    Directory of Open Access Journals (Sweden)

    Ulrike Toepel

    Full Text Available Hemodynamic imaging results have associated both gender and body weight to variation in brain responses to food-related information. However, the spatio-temporal brain dynamics of gender-related and weight-wise modulations in food discrimination still remain to be elucidated. We analyzed visual evoked potentials (VEPs while normal-weighted men (n = 12 and women (n = 12 categorized photographs of energy-dense foods and non-food kitchen utensils. VEP analyses showed that food categorization is influenced by gender as early as 170 ms after image onset. Moreover, the female VEP pattern to food categorization co-varied with participants' body weight. Estimations of the neural generator activity over the time interval of VEP modulations (i.e. by means of a distributed linear inverse solution [LAURA] revealed alterations in prefrontal and temporo-parietal source activity as a function of image category and participants' gender. However, only neural source activity for female responses during food viewing was negatively correlated with body-mass index (BMI over the respective time interval. Women showed decreased neural source activity particularly in ventral prefrontal brain regions when viewing food, but not non-food objects, while no such associations were apparent in male responses to food and non-food viewing. Our study thus indicates that gender influences are already apparent during initial stages of food-related object categorization, with small variations in body weight modulating electrophysiological responses especially in women and in brain areas implicated in food reward valuation and intake control. These findings extend recent reports on prefrontal reward and control circuit responsiveness to food cues and the potential role of this reactivity pattern in the susceptibility to weight gain.

  1. Dynamic Model for Hydro-Turbine Generator Units Based on a Database Method for Guide Bearings

    Directory of Open Access Journals (Sweden)

    Yong Xu

    2013-01-01

    Full Text Available A suitable dynamic model of rotor system is of great significance not only for supplying knowledge of the fault mechanism, but also for assisting in machine health monitoring research. Many techniques have been developed for properly modeling the radial vibration of large hydro-turbine generator units. However, an applicable dynamic model has not yet been reported in literature due to the complexity of the boundary conditions and exciting forces. In this paper, a finite element (FE rotor dynamic model of radial vibration taking account of operating conditions is proposed. A brief and practical database method is employed to model the guide bearing. Taking advantage of the method, rotating speed and bearing clearance can be considered in the model. A novel algorithm, which can take account of both transient and steady-state analysis, is proposed to solve the model. Dynamic response for rotor model of 125 MW hydro-turbine generator units in Gezhouba Power Station is simulated. Field data from Optimal Maintenance Information System for Hydro power plants (HOMIS are analyzed compared with the simulation. Results illustrate the application value of the model in providing knowledge of the fault mechanism and in failure diagnosis.

  2. A novel test rig for the dynamic characterization of large size tilting pad journal bearings

    Science.gov (United States)

    Forte, P.; Ciulli, E.; Saba, D.

    2016-09-01

    The present work concerns the realization of a test bench for the dynamic characterization of high performance tilting pad journal bearings, within a collaboration between the Department of Civil and Industrial Engineering of Pisa, GE Oil&Gas and AM Testing. The objective is to cover journal diameters of interest of GE, from 150 to 300 mm, with peripheral speeds up to 150 m/s, static load up to 270 kN, dynamic loads up to 30 kN and frequencies up to 350 Hz, performances that make the apparatus very competitive worldwide. The adopted configuration has the test article (TA) floating at the mid-span of a rotor supported by two rolling bearings. The TA is statically loaded by a hydraulic actuator and excited dynamically by two orthogonal hydraulic actuators. Construction was recently concluded and preliminary tests are under way. In order to assess in advance the possible accuracy of the tests, a dynamic lumped parameter model of the test bench was developed to perform virtual experiments, including several possible sources of experimental errors and uncertainties. The model was implemented using reduced stiffness and mass matrices obtained from Finite Element Analysis by Component Modal Synthesis.

  3. WEIGHTS STAGNATION IN DYNAMIC LOCAL SEARCH FOR SAT

    Directory of Open Access Journals (Sweden)

    Abdelraouf Ishtaiwi

    2016-05-01

    Full Text Available Since 1991, tries were made to enhance the stochastic local search techniques (SLS. Some researchers turned their focus on studying the structure of the propositional satisfiability problems (SAT to better understand their complexity in order to come up with better algorithms. Other researchers focused in investigating new ways to develop heuristics that alter the search space based on some information gathered prior to or during the search process. Thus, many heuristics, enhancements and developments were introduced to improve SLS techniques performance during the last three decades. As a result a group of heuristics were introduced namely Dynamic Local Search (DLS that could outperform the systematic search techniques. Interestingly, a common characteristic of DLS heuristics is that they all depend on the use of weights during searching for satisfiable formulas. In our study we experimentally investigated the weights behaviors and movements during searching for satisfiability using DLS techniques, for simplicity, DDFW DLS heuristic is chosen. As a results of our studies we discovered that while solving hard SAT problems such as blocks world and graph coloring problems, weights stagnation occur in many areas within the search space. We conclude that weights stagnation occurrence is highly related to the level of the problem density, complexity and connectivity.

  4. Kinematic Analysis of Healthy Hips during Weight-Bearing Activities by 3D-to-2D Model-to-Image Registration Technique

    Directory of Open Access Journals (Sweden)

    Daisuke Hara

    2014-01-01

    Full Text Available Dynamic hip kinematics during weight-bearing activities were analyzed for six healthy subjects. Continuous X-ray images of gait, chair-rising, squatting, and twisting were taken using a flat panel X-ray detector. Digitally reconstructed radiographic images were used for 3D-to-2D model-to-image registration technique. The root-mean-square errors associated with tracking the pelvis and femur were less than 0.3 mm and 0.3° for translations and rotations. For gait, chair-rising, and squatting, the maximum hip flexion angles averaged 29.6°, 81.3°, and 102.4°, respectively. The pelvis was tilted anteriorly around 4.4° on average during full gait cycle. For chair-rising and squatting, the maximum absolute value of anterior/posterior pelvic tilt averaged 12.4°/11.7° and 10.7°/10.8°, respectively. Hip flexion peaked on the way of movement due to further anterior pelvic tilt during both chair-rising and squatting. For twisting, the maximum absolute value of hip internal/external rotation averaged 29.2°/30.7°. This study revealed activity dependent kinematics of healthy hip joints with coordinated pelvic and femoral dynamic movements. Kinematics’ data during activities of daily living may provide important insight as to the evaluating kinematics of pathological and reconstructed hips.

  5. DYNAMIC CHARACTERISTIC ANALY- SIS OF PRECISE LONG STROKE LINEAR MOTOR WITH AIR-BEARING IN OPTICAL LITHOGRAPHY

    Institute of Scientific and Technical Information of China (English)

    CHEN Xuedong; YU Xianzhong; HE Xueming; YAN Tianhong

    2008-01-01

    Dynamic characteristic is presented by identifying the model and the dynamic parameters of a precise long stroke linear motor (PLSLM) with the air-bearing in optical lithography. The PLSLM is supported by air-bearing on the stator, and is driven by on-board two large linear motors in a cross-configuration. Firstly, a model of the PLSLM is established by finite element method (FEM). Secondly, based on the model, the natural frequencies and model shapes are discussed. And the contribution of each active mode is evaluated by computing the modal participation factors (MPF), which indicates the major vibration direction. Furthermore, by the experimental modal analysis, the experimental results are in agreement with simulation results, which it is sure that the FEM is reasonable. What's more, comparing with the effects on the frequency due to the air-bearing stiffness, the relations of the natural frequencies with the air-bearing stiffness are found. It is found that the frequency response curve is fluctuant with the air-bearing stiffness in each direction. Finally, it is conclusion that the natural frequency of the PLSLM is largely affected by the air-bearing stiffness variety. This research is contributed to the dynamic characteristics resulted from the air-bearing stiffness. Further work will include better optimization on the dynamic parameter in the controller design through the control algorithm for the precise long stroke motor.

  6. Approximating the maximum weight clique using replicator dynamics.

    Science.gov (United States)

    Bomze, I R; Pelillo, M; Stix, V

    2000-01-01

    Given an undirected graph with weights on the vertices, the maximum weight clique problem (MWCP) is to find a subset of mutually adjacent vertices (i.e., a clique) having the largest total weight. This is a generalization of the classical problem of finding the maximum cardinality clique of an unweighted graph, which arises as a special case of the MWCP when all the weights associated to the vertices are equal. The problem is known to be NP-hard for arbitrary graphs and, according to recent theoretical results, so is the problem of approximating it within a constant factor. Although there has recently been much interest around neural-network algorithms for the unweighted maximum clique problem, no effort has been directed so far toward its weighted counterpart. In this paper, we present a parallel, distributed heuristic for approximating the MWCP based on dynamics principles developed and studied in various branches of mathematical biology. The proposed framework centers around a recently introduced continuous characterization of the MWCP which generalizes an earlier remarkable result by Motzkin and Straus. This allows us to formulate the MWCP (a purely combinatorial problem) in terms of a continuous quadratic programming problem. One drawback associated with this formulation, however, is the presence of "spurious" solutions, and we present characterizations of these solutions. To avoid them we introduce a new regularized continuous formulation of the MWCP inspired by previous works on the unweighted problem, and show how this approach completely solves the problem. The continuous formulation of the MWCP naturally maps onto a parallel, distributed computational network whose dynamical behavior is governed by the so-called replicator equations. These are dynamical systems introduced in evolutionary game theory and population genetics to model evolutionary processes on a macroscopic scale.We present theoretical results which guarantee that the solutions provided by

  7. Dynamic characteristics of a flywheel energy storage system using superconducting magnetic bearings

    CERN Document Server

    Kim, J S

    2003-01-01

    The high-temperature superconducting magnetic bearing flywheel energy storage system (SMB-FESS) is proposed as an efficient energy storage system. It is important to identify the dynamic behaviour and the characteristics of the SMB-FESS. First, a new method for identifying SMB characteristics has been suggested. The suggested modelling method is verified by comparing the experimental and analytical frequency response functions. In this study, the analyses of critical speed and unbalance response are performed using the analytical model. The experimental test has been carried out to verify the result of simulation. A good agreement has been observed between the experiment and the simulation result.

  8. Dynamic behavior of dissymmetric rotor bearings modelled with a periodic coefficient large system

    Science.gov (United States)

    Guilhen, P. M.; Berthier, P.; Ferraris, G.; Lalanne, M.

    1987-01-01

    The instability and unbalance response of dissymmetric rotor-bearing systems containing periodic coefficients when modeling produces matrices with a large number of degrees of freedom are discussed. It is important to solve the equations and then predict the dynamic behavior of the system. This can be done knowing the instability areas and the unbalance response in the stable areas. One deals here with a large number of equations and a reduction of the number of degrees of freedom of the system is achieved through a pseudo modal method. This method is shown to give satisfactory results.

  9. Control Study for Five-axis Dynamic Spin Rig Using Magnetic Bearings

    Science.gov (United States)

    Choi, Benjamin; Johnson, Dexter; Provenza, Andrew; Morrison, Carlos; Montague, Gerald

    2003-01-01

    The NASA Glenn Research Center (GRC) has developed a magnetic bearing system for the Dynamic Spin Rig (DSR) with a fully suspended shaft that is used to perform vibration tests of turbomachinery blades and components under spinning conditions in a vacuum. Two heteropolar radial magnetic bearings and a thrust magnetic bearing and the associated control system were integrated into the DSR to provide magnetic excitation as well as non-contact mag- netic suspension of a 15.88 kg (35 lb) vertical rotor with blades to induce turbomachinery blade vibration. For rotor levitation, a proportional-integral-derivative (PID) controller with a special feature for multidirectional radial excitation worked well to both support and shake the shaft with blades. However, more advanced controllers were developed and successfully tested to determine the optimal controller in terms of sensor and processing noise reduction, smaller rotor orbits, more blade vibration amplitude, and energy savings for the system. The test results of a variety of controllers that were demonstrated up to 10.000 rpm are shown. Furthermore, rotor excitation operation and conceptual study of active blade vibration control are addressed.

  10. The Dynamic Characteristic Analysis of the Water Lubricated Bearing-Rotor System in Seawater Desalination Pump

    Directory of Open Access Journals (Sweden)

    Xiaoyan Ye

    2014-05-01

    Full Text Available In order to study the water lubricated bearing-rotor system in seawater desalination pump, this paper is based on the coupling between the lubricating flow field and the rotor dynamics. The fluid-solid interaction (FSI method, Rigid Body, was adopted to study the journal orbit of the bearing-rotor system under the periodic unbalancing load. The influences of geometric and working parameter to the journal orbit were combined to analyze the stability and reliability of the bearing-rotor system. The result shows that increasing the rotating speed would increase the journal whirling amplitude and the system sensitivity to the external excitation and unbalancing load were promoted; increasing the aspect ratio would reduce the journal whirling amplitude and cause the system to be more unstable; increasing the inlet pressure would reduce the journal whirling amplitude and cause the system to be more unstable; increasing the unbalancing load would reduce the stability margin and the system is easy to be unstable if obstructed; increasing the radial clearance would reduce the journal whirling amplitude and cause the system to be more unstable. The attitude angle has no influence on the journal whirling amplitude but would influence the stability of system and the value of attitude angle should not be large.

  11. Modeling and Analysis of Coupling Performance of Dynamic Stiffness Models for a Novel Combined Radial-Axial Hybrid Magnetic Bearing

    Directory of Open Access Journals (Sweden)

    Bangcheng Han

    2014-01-01

    Full Text Available The combined radial-axial magnetic bearing (CRAMB with permanent magnet creating bias flux can reduce the size, cost, and mass and save energy of the magnetic bearing. The CRAMB have three-degree-of-freedom control ability, so its structure and magnetic circuits are more complicated compared to those of the axial magnetic bearing (AMB or radial magnetic bearing (RMB. And the eddy currents have a fundamental impact on the dynamic performance of the CRAMB. The dynamic stiffness model and its cross coupling problems between different degrees of freedom affected for the CRAMB are proposed in this paper. The dynamic current stiffness and the dynamic displacement stiffness models of the CRAMB are deduced by using the method of equivalent magnetic circuit including eddy current effect, but the dynamic current stiffness of the RMB unit is approximately equal to its static current stiffness. The analytical results of an example show that the bandwidth of the dynamic current stiffness of the AMB unit and the dynamic displacement stiffness of the CRAMB is affected by the time-varying control currents or air gap, respectively. And the dynamic current stiffness and the dynamic displacement stiffness between the AMB unit and the RMB unit are decoupled due to few coupling coefficients.

  12. Rotor-Bearing Dynamics Technology Design Guide. Part 1. Flexible Rotor Dynamics

    Science.gov (United States)

    1980-06-01

    program, which replaces AFAPL/SFL Programs No. 100, 01l, and 1117. ha-, then cApabiity t0 perfllavar’iety of rotordynamics analyses. These analyses...released by the authors in November 1979. rI MI / ] iii : . o t"’V- TABLE OF CONTENTS Page I. INTRODUCTION 1 II, ROTORDYNAMIC ANALYSIS AND CAPABILITIES...Characteristics of the Bearings 11. 2.4 Producing the Rotordynamics Analyses 12 III. DESCRIPTION OF COMPUTER PROGRAM 15 3.1 Input Data 15 3.2 ’iTput Samples 35

  13. Effects of ankle strengthening exercises combined with motor imagery training on the timed up and go test score and weight bearing ratio in stroke patients.

    Science.gov (United States)

    Kim, Sung Shin; Lee, Hyung Jin; You, Young Youl

    2015-07-01

    [Purpose] The purpose of the present study was to compare the effects of ankle strengthening exercises combined with motor imagery training and those of ankle strengthening exercises alone in stroke patients. [Subjects and Methods] Thirty stroke patients were randomly assigned to one of the following two groups: experimental group (15 patients) and control group (15 patients). The experimental group underwent motor imagery training for 15 minutes and ankle joint strengthening exercises for 15 minutes, while the control group underwent only ankle joint strengthening exercises for 30 minutes. Each session and training program was implemented four times a week for 4 weeks. The timed up and go (TUG) test score, affected-side weight bearing ratio, and affected-side front/rear weight bearing ratio were assessed. [Results] Both groups demonstrated improvement on the TUG test, and in the affected-side weight bearing ratios, affected-side front/rear weight bearing ratios, and balance errors. The experimental group demonstrated greater improvement than the control group in all variables. [Conclusion] Motor imagery training is an effective treatment method for improving static balance ability in stroke patients.

  14. The difference between actual and prescribed weight bearing of total hip patients with a trochanteric osteotomy: long-term vertical force measurements inside and outside the hospital

    NARCIS (Netherlands)

    H.L.P. Hurkmans (Henri); J.B.J. Bussmann (Hans); R.W. Selles (Ruud); E. Benda (Eric); H.J. Stam (Henk); J.A.N. Verhaar (Jan)

    2007-01-01

    textabstractOBJECTIVE: To determine whether patients load the operated leg at a prescribed weight-bearing target load during postoperative recovery. DESIGN: A descriptive prospective study. SETTING: Orthopedic clinic and patients' homes. PARTICIPANTS: Fifty patients who had undergone total hip arthr

  15. NONLINEAR DYNAMIC CHARACTERISTICS OF HYDRODYNAMIC JOURNAL BEARING-FLEXIBLE ROTOR SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Lu Yanjun; Yu Lie; Liu Heng

    2005-01-01

    The nonlinear dynamic behaviors of flexible rotor system with hydrodynamic bearing supports are analyzed. The shaft is modeled by using the finite element method that takes the effect of inertia and shear into consideration. According to the nonlinearity of the hydrodynamic journal bearing-flexible rotor system, a modified modal synthesis technique with free-interface is represented to reduce degrees-of-freedom of model of the flexible rotor system. According to physical character of oil film, variational constrain approach is introduced to continuously revise the variational form of Reynolds equation at every step of dynamic integration and iteration. Fluid lubrication problem with Reynolds boundary is solved by the isoparametric finite element method without the increasing of computing efforts. Nonlinear oil film forces and their Jacobians are simultaneously calculated and -Newton-Floquet (PNF) method. A method, combining the predictor-corrector mechanism to the PNF method, is presented to calculate the bifurcation point of periodic motions to be subject to change of system parameters. The local stability and bifurcation behaviors of periodic motions are obtained by Floquet theory. The chaotic motions of the beating-rotor system are investigated by power spectrum.The numerical examples show that the scheme of this study saves computing efforts but also is of good precision.

  16. [Metabolic effects of physical countermeasures against deficient weight-bearing in an experiment with 7-day immersion].

    Science.gov (United States)

    Markin, A A; Zhuravleva, O A; Morukov, B V; Zabolotskaia, I V; Vostrikova, L V; Kuzichkin, D S

    2011-01-01

    Metabolic effects of physical countermeasures against deficient weight-loading were studied in three groups of 21-30 y.o. volunteers for 7-d dry immersion. Blood serum was investigated for 38 biochemical parameters that characterize myocardium, skeletal musculature, hepatobiliary system, kidney, pancreas, GI tract, prostate, and protein-nucleic, carbohydrate, electrolyte and mineral metabolism. Seven-day DI w/o countermeasures (n = 5) increased concentration of conjugated bilirubin, suppressed activities of muscular (creatine phosphokinase MM) and myocardial enzymes (CPK MB, OBDH), and caused an upward trend in cholesterol, its atherogenic LDP fraction and triglycerides. Mechanic sole stimulation (n = 6) intensified, within the physiological norm, erythrocyte hematolysis raising total bilirubin and potassium. Despite the stimulation, activity of muscle and myocardial enzymes made a decrease. Blood creatinine decreased to a less extent than in the immersed group w/o stimulation, however, lipid parameters did not rise. High-frequency stimulation of the lower leg and hip muscles in the course of immersion (n = 5) was noted to heighten the activity of muscle enzymes and potassium level in blood beyond the physiological norm. Change in creatinine did not reach a statistical significance and lipid metabolism parameters were not different from baseline values. Application of these physical methods of counteracting deficiency of weight bearing did not interfere with redistribution of body liquids due to immersion. Values of the parameters under study were mostly within the normal limits throughout the experimental exposure suggesting absence of pathological developments during DI or in consequence of physical stimulation. Therefore, the reactions were obviously of normal adaptive character.

  17. Weight-bearing locomotion in the developing opossum, Monodelphis domestica following spinal transection: remodeling of neuronal circuits caudal to lesion.

    Directory of Open Access Journals (Sweden)

    Benjamin J Wheaton

    that although following injury the isolated segment of the spinal cord retains some capability of rhythmic movement the mechanisms involved in weight-bearing locomotion are distinct.

  18. Rotor-Bearing Dynamics Technology Design Guide. Part 8. A computerized Data Retrieval System for Fluid Film Bearings

    Science.gov (United States)

    1980-10-01

    eccentricity ratio of assembled bearing iviscosity coefficient of lubricant (Reyns) v frequency of oscillation (radians/sec) w rotational speed...IKHGE 1 5?A &G TE &3 FF = 1(FE 6020 COTIU 2492IF (SEL 0 3)00 1 2219 FF = 0D+O~ FENE 40 TO 249 !FI IF (KPAGE-GE.57) GO TO f6025 WRITE(KU,2331 ) KPAGE =KPAGE

  19. Effects of calcaneal eversion on three-dimensional kinematics of the hip, pelvis and thorax in unilateral weight bearing.

    Science.gov (United States)

    Tateuchi, Hiroshige; Wada, Osamu; Ichihashi, Noriaki

    2011-06-01

    Understanding the kinematic chain from foot to thorax will provide a better basis for assessment of malalignment of the body. The purpose of this study was to investigate the effects of induced calcaneal eversion on the kinematics of the hip, pelvis and thorax in three dimensions under unilateral weight-bearing. Twenty-eight healthy males were requested to stand on one leg under three conditions: normal (standing directly on the floor), and on wedges producing 5° and 10° calcaneal eversion. Recorded kinematic parameters included the angles of the hip joint, pelvis, and thorax in three dimensions. Eversion induced by wedges produced significant increases in hip flexion, hip medial rotation, pelvic anterior tilt, and thoracic lateral tilt and axial rotation to the standing side. In the frontal plane, pelvic lateral tilt to the standing side was decreased in 5° eversion condition compared with normal condition; conversely, it was increased in 10° eversion condition compared with 5° eversion condition. Arch height was negatively correlated with change in thoracic axial rotation to standing side from the normal to 10° eversion (r=-.528, pthorax through the hip joint and the pelvis. Copyright © 2011 Elsevier B.V. All rights reserved.

  20. The effect of motor control training on abdominal muscle contraction during simulated weight bearing in elite cricketers.

    Science.gov (United States)

    Hides, Julie A; Endicott, Timothy; Mendis, M Dilani; Stanton, Warren R

    2016-07-01

    To investigate whether motor control training alters automatic contraction of abdominal muscles in elite cricketers with low back pain (LBP) during performance of a simulated unilateral weight-bearing task. Clinical trial. 26 male elite-cricketers attended a 13-week cricket training camp. Prior to the camp, participants were allocated to a LBP or asymptomatic group. Real-time ultrasound imaging was used to assess automatic abdominal muscle response to axial loading. During the camp, the LBP group performed a staged motor control training program. Following the camp, the automatic response of the abdominal muscles was re-assessed. At pre-camp assessment, when participants were axially loaded with 25% of their own bodyweight, the LBP group showed a 15.5% thicker internal oblique (IO) muscle compared to the asymptomatic group (p = 0.009). The post-camp assessment showed that participants in the LBP group demonstrated less contraction of the IO muscle in response to axial loading compared with the asymptomatic group. A trend was found in the automatic recruitment pattern of the transversus abdominis (p = 0.08). Motor control training normalized excessive contraction of abdominal muscles in response to a low load task. This may be a useful strategy for rehabilitation of cricketers with LBP. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Instantaneous screws of weight-bearing knee: what can the screws tell us about the knee motion.

    Science.gov (United States)

    Wolf, Alon

    2014-07-01

    There are several ways to represent a given object's motion in a 3D space having 6DOF i.e., three translations and three rotations. Some of the methods that are used are mathematical and do not provide any geometrical insight into the nature of the motion. Screw theory is a mathematical, while at the same time, geometrical method in which the 6DOF motion of an object can be represented. We describe the 6DOF motion of a weight-bearing knee by its screw parameters, that are extracted from 3D Optical Reflective motion capture data. The screw parameters which describe the transformation of the shank with respect to the thigh in each two successive frames, is represented as the instantaneous screw axis of the motion given in its Plücker line coordinate, along with its corresponding pitch and intensity values. Moreover, the Striction curve associated with the motion provides geometrical insight into the nature of the motion and its repeatability. We describe the theoretical background and demonstrate what the screw can tell us about the motion of healthy subjects' knee.

  2. Classification and mass production technique for three-quarter shoe insoles using non-weight-bearing plantar shapes.

    Science.gov (United States)

    Sun, Shuh-Ping; Chou, Yi-Jiun; Sue, Chun-Chia

    2009-07-01

    We have developed a technique for the mass production and classification of three-quarter shoe insoles via a 3D anthropometric measurement of full-size non-weight-bearing plantar shapes. The plantar shapes of fifty 40-60-year-old adults from Taiwan were categorized and, in conjunction with commercially available flat or leisure shoe models, three-quarter shoe-insole models were generated using a CAD system. Applying a rapid prototype system, these models were then used to provide the parameters for manufacturing the shoe insoles. The insoles developed in this study have been classified into S, M and L types that offer user-friendly options for foot-care providers. We concluded that these insoles can mate tightly with the foot arch and disperse the pressure in the heel and forefoot over the foot arch. Thus, practically, the pressure difference over the plantar region can be minimised, and the user can experience comfort when wearing flat or leisure shoes.

  3. A comparison between the dimensions of positive transtibial residual limb molds prepared by air pressure casting and weight-bearing casting methods

    Science.gov (United States)

    Hajiaghaei, Behnam; Ebrahimi, Ismail; Kamyab, Mojtaba; Saeedi, Hassan; Jalali, Maryam

    2016-01-01

    Background: Creating a socket with proper fit is an important factor to ensure the comfort and control of prosthetic devices. Several techniques are commonly used to cast transtibial stumps but their effect on stump shape deformation is not well understood. This study compares the dimensions, circumferences and volumes of the positive casts and also the socket comfort between two casting methods. Our hypothesis was that the casts prepared by air pressure method have less volume and are more comfortable than those prepared by weight bearing method. Methods: Fifteen transtibial unilateral amputees participated in the study. Two weight bearing and air pressure casting methods were utilized for their residual limbs. The diameters and circumferences of various areas of the residual limbs and positive casts were compared. The volumes of two types of casts were measured by a volumeter and compared. Visual Analogue Scale (VAS) was used to measure the sockets fit comfort. Results: Circumferences at 10 and 15 cm below the patella on the casts were significantly smaller in air pressure casting method compared to the weight bearing method (p=0.00 and 0.01 respectively). The volume of the cast in air pressure method was lower than that of the weight bearing method (p=0.006). The amputees found the fit of the sockets prepared by air pressure method more comfortable than the weight bearing sockets (p=0.015). Conclusion: The air pressure casting reduced the circumferences of the distal portion of residual limbs which has more soft tissue and because of its snug fit it provided more comfort for amputees, according to the VAS measurements. PMID:27390711

  4. Dynamic characteristics of the rotor in a magnetically suspended control moment gyroscope with active magnetic bearing and passive magnetic bearing.

    Science.gov (United States)

    Tang, Jiqiang; Xiang, Biao; Zhang, Yongbin

    2014-07-01

    For a magnetically suspended control moment gyroscope, stiffness and damping of magnetic bearing will influence modal frequency of a rotor. In this paper the relationship between modal frequency and stiffness and damping has been investigated. The mathematic calculation model of axial passive magnetic bearing (PMB) stiffness is developed. And PID control based on internal model control is introduced into control of radial active magnetic bearing (AMB), considering the radial coupling of axial PMB, a mathematic calculation model of stiffness and damping of radial AMB is established. According to modal analysis, the relationship between modal frequency and modal shapes is achieved. Radial vibration frequency is mainly influenced by stiffness of radial AMB; however, when stiffness increases, radial vibration will disappear and a high frequency bending modal will appear. Stiffness of axial PMB mainly affects the axial vibration mode, which will turn into high-order bending modal. Axial PMB causes bigger influence on torsion modal of the rotor. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

  5. Controllability of Weighted and Directed Networks with Nonidentical Node Dynamics

    Directory of Open Access Journals (Sweden)

    Linying Xiang

    2013-01-01

    Full Text Available The concept of controllability from control theory is applied to weighted and directed networks with heterogenous linear or linearized node dynamics subject to exogenous inputs, where the nodes are grouped into leaders and followers. Under this framework, the controllability of the controlled network can be decomposed into two independent problems: the controllability of the isolated leader subsystem and the controllability of the extended follower subsystem. Some necessary and/or sufficient conditions for the controllability of the leader-follower network are derived based on matrix theory and graph theory. In particular, it is shown that a single-leader network is controllable if it is a directed path or cycle, but it is uncontrollable for a complete digraph or a star digraph in general. Furthermore, some approaches to improving the controllability of a heterogenous network are presented. Some simulation examples are given for illustration and verification.

  6. Effects of tooth profile modification on dynamic responses of a high speed gear-rotor-bearing system

    Science.gov (United States)

    Hu, Zehua; Tang, Jinyuan; Zhong, Jue; Chen, Siyu; Yan, Haiyan

    2016-08-01

    A finite element node dynamic model of a high speed gear-rotor-bearing system considering the time-varying mesh stiffness, backlash, gyroscopic effect and transmission error excitation is developed. Different tooth profile modifications are introduced into the gear pair and corresponding time-varying mesh stiffness curves are obtained. Effects of the tooth profile modification on mesh stiffness are analyzed, and the natural frequencies and mode shapes of the gear-rotor-bearing transmission system are given. The dynamic responses with respect to a wide input speed region including dynamic factor, vibration amplitude near the bearing and dynamic transmission error are obtained by introducing the time-varying mesh stiffness in different tooth profile modification cases into the gear-rotor-bearing dynamic system. Effects of the tooth profile modification on the dynamic responses are studied in detail. The numerical simulation results show that both the short profile modification and the long profile modification can affect the mutation of the mesh stiffness when the number of engaging tooth pairs changes. A short profile modification with an appropriate modification amount can improve the dynamic property of the system in certain work condition.

  7. Merge-Weighted Dynamic Time Warping for Speech Recognition

    Institute of Scientific and Technical Information of China (English)

    张湘莉兰; 骆志刚; 李明

    2014-01-01

    Obtaining training material for rarely used English words and common given names from countries where English is not spoken is difficult due to excessive time, storage and cost factors. By considering personal privacy, language-independent (LI) with lightweight speaker-dependent (SD) automatic speech recognition (ASR) is a convenient option to solve the problem. The dynamic time warping (DTW) algorithm is the state-of-the-art algorithm for small-footprint SD ASR for real-time applications with limited storage and small vocabularies. These applications include voice dialing on mobile devices, menu-driven recognition, and voice control on vehicles and robotics. However, traditional DTW has several limitations, such as high computational complexity, constraint induced coarse approximation, and inaccuracy problems. In this paper, we introduce the merge-weighted dynamic time warping (MWDTW) algorithm. This method defines a template confidence index for measuring the similarity between merged training data and testing data, while following the core DTW process. MWDTW is simple, efficient, and easy to implement. With extensive experiments on three representative SD speech recognition datasets, we demonstrate that our method outperforms DTW, DTW on merged speech data, the hidden Markov model (HMM) significantly, and is also six times faster than DTW overall.

  8. Estimating Allee dynamics before they can be observed: polar bears as a case study.

    Directory of Open Access Journals (Sweden)

    Péter K Molnár

    Full Text Available Allee effects are an important component in the population dynamics of numerous species. Accounting for these Allee effects in population viability analyses generally requires estimates of low-density population growth rates, but such data are unavailable for most species and particularly difficult to obtain for large mammals. Here, we present a mechanistic modeling framework that allows estimating the expected low-density growth rates under a mate-finding Allee effect before the Allee effect occurs or can be observed. The approach relies on representing the mechanisms causing the Allee effect in a process-based model, which can be parameterized and validated from data on the mechanisms rather than data on population growth. We illustrate the approach using polar bears (Ursus maritimus, and estimate their expected low-density growth by linking a mating dynamics model to a matrix projection model. The Allee threshold, defined as the population density below which growth becomes negative, is shown to depend on age-structure, sex ratio, and the life history parameters determining reproduction and survival. The Allee threshold is thus both density- and frequency-dependent. Sensitivity analyses of the Allee threshold show that different combinations of the parameters determining reproduction and survival can lead to differing Allee thresholds, even if these differing combinations imply the same stable-stage population growth rate. The approach further shows how mate-limitation can induce long transient dynamics, even in populations that eventually grow to carrying capacity. Applying the models to the overharvested low-density polar bear population of Viscount Melville Sound, Canada, shows that a mate-finding Allee effect is a plausible mechanism for slow recovery of this population. Our approach is generalizable to any mating system and life cycle, and could aid proactive management and conservation strategies, for example, by providing a priori

  9. Characterization of the High-Speed-Stage Bearing Skidding of Wind Turbine Gearboxes Induced by Dynamic Electricity Grid Events

    Energy Technology Data Exchange (ETDEWEB)

    Helsen, Jan; Guillaume, Patrick; Guo, Yi; Keller, Jonathan

    2016-07-01

    Bearing behavior is an important factor for wind turbine drivetrain reliability. Extreme loads and dynamic excitations pose challenges to the bearing design and therefore its performance. Excessive skidding of the bearing rollers should be avoided because it can cause scuffing failures. Excitations coming from wind and the electricity grid can subject the drivetrain to fluctuating torque and nontorque loads. Wind-induced excitations have been investigated predominantly in literature. However, modern wind turbines are subjected more and more to grid-induced loads because of stricter electricity grid regulations. For example, during fault-ride-through events, turbines are required to stay connected for a longer period of time during the grid failure. This work investigates the influence of electrically induced excitations on the skidding behaviour of the tapered roller bearings on the high-speed stage of a wind turbine gearbox. This skidding behaviour during dynamic events is described as a potential bearing failure initiator by many researchers; however, only limited full-scale dynamic testing is documented. Therefore, a dedicated gridloss-type event is defined in the paper and conducted in a dynamometer test on a full-scale wind turbine nacelle. During the event, a complete electricity grid failure is simulated while the turbine is at rated speed and predefined torque levels. Particular focus is on the characterization of the high-speed shaft tapered roller bearing slip behavior. Strain-gauge bridges in grooves along the circumference of the outer ring are used to characterize the bearing load zone in detail. It is shown that during the torque reversals of the transient event, roller slip can be induced. This indicates the potential of the applied load case to go beyond the preload of the tapered roller bearing. Furthermore, the relation between the applied torque and skidding level is studied.

  10. Characterization of the High-Speed-Stage Bearing Skidding of Wind Turbine Gearboxes Induced by Dynamic Electricity Grid Events: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Helsen, Jan; Guillaume, Patrick; Guo, Yi; Keller, Jonathan

    2016-05-18

    Bearing behavior is an important factor for wind turbine drivetrain reliability. Extreme loads and dynamic excitations pose challenges to the bearing design and therefore its performance. Excessive skidding of the bearing rollers should be avoided because it can cause scuffing failures. Excitations coming from wind and the electricity grid can subject the drivetrain to fluctuating torque and nontorque loads. Wind-induced excitations have been investigated predominantly in literature. However, modern wind turbines are subjected more and more to grid-induced loads because of stricter electricity grid regulations. For example, during fault-ride-through events, turbines are required to stay connected for a longer period of time during the grid failure. This work investigates the influence of electrically induced excitations on the skidding behaviour of the tapered roller bearings on the high-speed stage of a wind turbine gearbox. This skidding behaviour during dynamic events is described as a potential bearing failure initiator by many researchers; however, only limited full-scale dynamic testing is documented. Therefore, a dedicated gridloss-type event is defined in the paper and conducted in a dynamometer test on a full-scale wind turbine nacelle. During the event, a complete electricity grid failure is simulated while the turbine is at rated speed and predefined torque levels. Particular focus is on the characterization of the high-speed shaft tapered roller bearing slip behavior. Strain-gauge bridges in grooves along the circumference of the outer ring are used to characterize the bearing load zone in detail. It is shown that during the torque reversals of the transient event, roller slip can be induced. This indicates the potential of the applied load case to go beyond the preload of the tapered roller bearing. Furthermore, the relation between the applied torque and skidding level is studied.

  11. Computational Analysis of Static and Dynamic Behaviour of Magnetic Suspensions and Magnetic Bearings

    Science.gov (United States)

    Britcher, Colin P. (Editor); Groom, Nelson J.

    1996-01-01

    Static modelling of magnetic bearings is often carried out using magnetic circuit theory. This theory cannot easily include nonlinear effects such as magnetic saturation or the fringing of flux in air-gaps. Modern computational tools are able to accurately model complex magnetic bearing geometries, provided some care is exercised. In magnetic suspension applications, the magnetic fields are highly three-dimensional and require computational tools for the solution of most problems of interest. The dynamics of a magnetic bearing or magnetic suspension system can be strongly affected by eddy currents. Eddy currents are present whenever a time-varying magnetic flux penetrates a conducting medium. The direction of flow of the eddy current is such as to reduce the rate-of-change of flux. Analytic solutions for eddy currents are available for some simplified geometries, but complex geometries must be solved by computation. It is only in recent years that such computations have been considered truly practical. At NASA Langley Research Center, state-of-the-art finite-element computer codes, 'OPERA', 'TOSCA' and 'ELEKTRA' have recently been installed and applied to the magnetostatic and eddy current problems. This paper reviews results of theoretical analyses which suggest general forms of mathematical models for eddy currents, together with computational results. A simplified circuit-based eddy current model proposed appears to predict the observed trends in the case of large eddy current circuits in conducting non-magnetic material. A much more difficult case is seen to be that of eddy currents in magnetic material, or in non-magnetic material at higher frequencies, due to the lower skin depths. Even here, the dissipative behavior has been shown to yield at least somewhat to linear modelling. Magnetostatic and eddy current computations have been carried out relating to the Annular Suspension and Pointing System, a prototype for a space payload pointing and vibration

  12. Optimizing ankle performance when taped: Effects of kinesiology and athletic taping on proprioception in full weight-bearing stance.

    Science.gov (United States)

    Long, Zhi; Wang, Renwei; Han, Jia; Waddington, Gordon; Adams, Roger; Anson, Judith

    2017-03-01

    To explore the effects of kinesiology taping (KT) and athletic taping (AT) on ankle proprioception when tested in functional, full weight-bearing stance. Cross-sectional study. Twenty-four healthy university students participated. Proprioception was measured using the Active Movement Extent Discrimination Apparatus (AMEDA). The three testing conditions: no-taping, KT, AT, and foot tested were randomly assigned. Perceived comfort, support and proprioceptive performance under two taping conditions were recorded. Proprioceptive discrimination scores with 95% CIs for no-taping, KT and AT were 0.81 (0.79-0.84), 0.81 (0.79-0.83), and 0.79 (0.77-0.81). Repeated measures ANOVA showed neither any significant difference associated with taping compared with no-taping (p=0.30), nor any difference between KT and AT (p=0.19). The group was then divided, according to their no-taping scores, into two sub-groups: with scores below the no-taping mean (n=13), and above the mean (n=11). ANOVA revealed a significant interaction (p=0.008) indicating that above-average no-taping performers proprioception scores were worse when taped, whereas below-average performers improved. For both KT and AT, only ratings of perceived comfort when taped were significantly associated with actual proprioceptive performance (both r>0.44, p≤0.03). Other perception ratings (support and performance) were significantly inter-correlated (both r>0.42, p0.31). Taping of the foot and ankle may amplify sensory input in a way that enhances proprioception of poor performers but produces an input overload that impairs proprioception in those who originally performed well when no-taping. Screening of ankle proprioception may identify those who would benefit most from taping. Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  13. Dynamic Spin Rig Upgraded With a Five- Axis-Controlled Three-Magnetic-Bearing Support System With Forward Excitation

    Science.gov (United States)

    Morrison, Carlos R.; Mehmed, Oral

    2003-01-01

    The NASA Glenn Research Center Dynamic Spin Rig is used for experimental evaluation of vibration analysis methods and dynamic characteristics for rotating systems. Measurements are made while rotors are spun and vibrated in a vacuum chamber. The rig has been upgraded with a new active magnetic bearing rotor support and excitation system. This design is expected to provide operational improvements over the existing rig. The rig will be able to be operated in either the old or new configuration. In the old configuration, two ball bearings support the vertical shaft of the rig, with the test article located between the bearings. Because the bearings operate in a vacuum, lubrication is limited to grease. This limits bearing life and speed. In addition, the old configuration employs two voice-coil electromagnetic shakers to apply oscillatory axial forces or transverse moments to the rotor shaft through a thrust bearing. The excitation amplitudes that can be imparted to the test article with this system are not adequate for components that are highly damped. It is expected that the new design will overcome these limitations.

  14. Dynamic Behavior and Function of Foxp3+ Regulatory T Cells in Tumor Bearing Host

    Institute of Scientific and Technical Information of China (English)

    F. Xiao-Feng Qin

    2009-01-01

    Regulatory T cells (Tregs) expressing forkhead/winged-helix transcription factor Foxp3 represent a distinct lineage of lymphocytes which play a central role in protecting the host from autoimmune diseases. However, Tregs also pose a major problem to anti-tumor immunity. Growing body of evidence from both laboratory and clinical investigations has demonstrated that expansion and accumulation of these immunosuppressive cells correlates with advanced tumor growth and predicts poor disease prognosis. How tumor development subverts normal self-tolerance function of Tregs thereby thwarts host anti-tumor immunity remains elusive. This review will discuss our current knowledge in understanding the dynamics and plasticity of Foxp3+ Treg activation and induction in tumor bearing hosts and their interaction with various antigen presenting cells (APCs) in tumor microenvironment leading to the establishment of active local and systemic immune suppression.

  15. Active magnetic bearings dynamic parameters identification from experimental rotor unbalance response

    Science.gov (United States)

    Xu, Yuanping; Zhou, Jin; Di, Long; Zhao, Chen

    2017-01-01

    Active magnetic bearings (AMBs) support rotors using electromagnetic force rather than mechanical forces. It is necessary to accurately identify the AMBs force coefficients since they play a critical role in the rotordynamic analysis including system stability, bending critical speeds and modes of vibrations. This paper proposes a rotor unbalance response based approach to identifying the AMBs stiffness and damping coefficients during rotation. First, a Timoshenko beam finite element (FE) rotor model is created. Second, an identification procedure based on the FE model is proposed. Then based on the experimental rotor unbalance response data from 1200 rpm to 30,000 rpm, the AMBs dynamic force parameters (stiffness and damping) are obtained. Finally, the identified results are verified by comparing the estimated and experimental rotor unbalance responses, which shows high accuracy.

  16. Magnetic Bearing

    Science.gov (United States)

    1996-01-01

    AVCON, Inc. produces advanced magnetic bearing systems for industrial use, offering a unique technological approach based on contract work done at Marshall Space Flight Center and Lewis Research Center. Designed for the turbopump of the Space Shuttle main engine, they are now used in applications such as electric power generation, petroleum refining, machine tool operation and natural gas pipelines. Magnetic bearings support moving machinery without physical contact; AVCON's homopolar approach is a hybrid of permanent and electromagnets which are one-third the weight, smaller and more power- efficient than previous magnetic bearings.

  17. Effects of age, sex, and treatment on weight-loss dynamics in overweight people

    National Research Council Canada - National Science Library

    Rojo-Tirado, Miguel A; Benito, Pedro J; Atienza, David; Rincon, Emiliano; Calderon, Francisco J

    2013-01-01

    The objective of this work was to evaluate how sex, age, and the kind of treatment followed affect weight loss in overweight men and women, as well as to develop an explanation for the evolution of weight-loss dynamics...

  18. Evaluating sustainability of truck weight regulations: A system dynamics view

    Directory of Open Access Journals (Sweden)

    Pei Liu

    2015-11-01

    Full Text Available Purpose: Targeting the problem of overload trucking in Highway Transportation of iron ore from Caofeidian to Tangshan (HTCT, this paper aims to assess long-term effects of alternative Truck Weight Regulation (TWR policies on sustainability of HTCT. Design/methodology/approach: A system dynamics model was established for policy evaluation. The model, composed of six interrelating modules, is able to simulate policies effects on trucking issues such as freight flow, truck traffic flow, pavement performance, highway transport capacity and trucking time, and further on the Cumulative Economic Cost (CEC including transport cost and time cost of freight owners and the Cumulative Social Cost (CSC including pavement maintenance cost, green house gas emission cost, air pollutants emission cost and traffic accidents cost, so the effects of TWR policies on sustainability of HTCT could be evaluated. Findings: According to different values of overload ratio which a TWR policy allows, alternative TWR policies are classified into three types, which are The Rigid Policy (TRP, The Moderate Policy (TMP and The Tolerant Policy (TTP. Results show that the best policy for sustainability of HTCT depends on the importance of CSC which is expected by the local government. To be specific, (1 if CSC is considered much less important than CEC, the local government should continue implementing the current TTP with the maximum overload ratio; (2 if CSC is considered much more important than CEC, then TRP is recommended; and (3 if CSC is considered slightly more important than CES, TMP with overload ratio of 80% is the best. Practical implications: Conclusions of this paper may help the local government design appropriate TWR policies to achieve sustainability of HTCT. Originality/value: To the best of our knowledge, this is the first effort to evaluate TWR policies on sustainability of regional freight transportation based on system dynamics modeling.

  19. Dynamics of intertidal foraging by coastal brown bears in Southwestern Alaska

    Science.gov (United States)

    Smith, T.S.; Partridge, Steven T.

    2004-01-01

    Shoreline areas provide early season foraging opportunities for coastal bears in Alaska. We investigated use by brown bears (Ursus arctos) of soft-shelled (Mya arenaria) and Pacific razor (Siliqua patula) clams at Katmai National Park, Alaska, USA, to identify the potential importance of these clams to bears. We used direct observations of bear foraging behavior in the summers of 1998, 1999, and 2001 to model the nutritional importance of clamming behavior. We also used previously described models to estimate the relative importance of clamming and vegetative foraging in meeting the maintenance requirements of bears. At the harvest rate that we observed (0.69 ?? 0.46 clams/min), bears achieved higher rates of digestible energy intake than those foraging on vegetation. Although clams are available for only a few hours per day, bears could significantly reduce their total daily foraging time by utilizing clams. Smaller single bears and females with dependent young were the most represented groups of bears using intertidal areas. Large male bears, faced with higher energy requirements, likely are unable to efficiently exploit these intertidal resources. Depending on the relationship between clam size and tissue mass, the relative quality of clams differed by species. Bears foraging on Pacific razor clams required the fewest hours to meet maintenance, followed by bears consuming soft-shelled clams. Our findings highlight the significance of intertidal habitats for coastal bears, especially females.

  20. LIGHT-WEIGHT LOAD-BEARING STRUCTURES REINFORCED BY CORE ELEMENTS MADE OF SEGMENTS AND A METHOD OF CASTING SUCH STRUCTURES

    DEFF Research Database (Denmark)

    2009-01-01

    The invention relates to a light-weight load-bearing structure, reinforced by core elements (2) of a strong material constituting one or more compression or tension zones in the structure to be cast, which core (2) is surrounded by or adjacent to a material of less strength compared to the core (2......), where the core (2) is constructed from segments (1) of core elements (2) assembled by means of one or more prestressing elements (4). The invention further relates to a method of casting of light-weight load-bearing structures, reinforced by core elements (2) of a strong material constituting one...... or more compression or tension zones in the structure to be cast, which core (2) is surrounded by or adjacent to a material of less strength compared to the core (2), where the core (2) is constructed from segments (1) of core elements (2) assembled and hold together by means of one or more prestressing...

  1. LIGHT-WEIGHT LOAD-BEARING STRUCTURES REINFORCED BY CORE ELEMENTS MADE OF SEGMENTS AND A METHOD OF CASTING SUCH STRUCTURES

    DEFF Research Database (Denmark)

    2009-01-01

    The invention relates to a light-weight load-bearing structure, reinforced by core elements (2) of a strong material constituting one or more compression or tension zones in the structure to be cast, which core (2) is surrounded by or adjacent to a material of less strength compared to the core (2...... or more compression or tension zones in the structure to be cast, which core (2) is surrounded by or adjacent to a material of less strength compared to the core (2), where the core (2) is constructed from segments (1) of core elements (2) assembled and hold together by means of one or more prestressing......), where the core (2) is constructed from segments (1) of core elements (2) assembled by means of one or more prestressing elements (4). The invention further relates to a method of casting of light-weight load-bearing structures, reinforced by core elements (2) of a strong material constituting one...

  2. Plantar fascia evaluation with a dedicated magnetic resonance scanner in weight-bearing position: our experience in patients with plantar fasciitis and in healthy volunteers.

    Science.gov (United States)

    Sutera, R; Iovane, A; Sorrentino, F; Candela, F; Mularo, V; La Tona, G; Midiri, M

    2010-03-01

    This study assessed the usefulness of upright weight-bearing examination of the ankle/hind foot performed with a dedicated magnetic resonance (MR) imaging scanner in the evaluation of the plantar fascia in healthy volunteers and in patients with clinical evidence of plantar fasciitis. Between January and March 2009, 20 patients with clinical evidence of plantar fasciitis (group A) and a similar number of healthy volunteers (group B) underwent MR imaging of the ankle/hind foot in the upright weight-bearing and conventional supine position. A 0.25-Tesla MR scanner (G-Scan, Esaote SpA, Genoa, Italy) was used with a dedicated receiving coil for the ankle/hind foot. Three radiologists, blinded to patients' history and clinical findings, assessed in consensus morphological and dimensional changes and signal intensity alterations on images acquired in both positions, in different sequences and in different planes. In group A, MR imaging confirmed the diagnosis in 15/20 cases; in 4/15 cases, a partial tear of the plantar fascia was identified in the upright weight-bearing position alone. In the remaining 5/20 cases in group A and in all cases in group B, the plantar fascia showed no abnormal signal intensity. Because of the increased stretching of the plantar fascia, in all cases in group A and B, thickness in the proximal third was significantly reduced (pbearing compared with the supine position. Imaging the ankle/hind foot in the upright weight-bearing position with a dedicated MR scanner and a dedicated coil might enable the identification of partial tears of the plantar fascia, which could be overlooked in the supine position.

  3. Radiographic and functional results in the treatment of early stages of Charcot neuroarthropathy with a walker boot and immediate weight bearing

    Directory of Open Access Journals (Sweden)

    Maria Candida Ribeiro Parisi

    2013-10-01

    Full Text Available Background: One of the most common gold standards for the treatment of Charcot neuroarthropathy (CN in the early Eichenholtz stages I and II is immobilization with the total contact casting and lower limb offloading. However, the total amount of offloading is still debatable. Objectives: This study evaluates the clinical and radiographic findings in the treatment of early stages of CN (Eichenholtz stages I and II with a walker boot and immediate total weight-bearing status. Methods: Twenty-two patients with type 2 diabetes mellitus (DM and CN of Eichenholtz stages I and II were selected for non-operative treatment. All patients were educated about their condition, and full weight bearing was allowed as tolerated. Patients were monitored on a fortnightly basis in the earlier stages, with clinical examination, temperature measurement, and standardized weight-bearing radiographs. Their American Orthopedic Foot and Ankle Society (AOFAS scores were determined before and after the treatment protocol. Results: No cutaneous ulcerations or infections were observed in the evaluated cases. The mean measured angles at the beginning and end of the study, although showing relative increase, did not present a statistically significant difference (p > 0.05. Mean AOFAS scores showed a statistically significant improvement by the end of the study (p < 0.005. Conclusion: The treatment of early stages of CN (Eichenholtz stages I and II with emphasis on walker boot and immediate weight bearing has shown a good functional outcome, non-progressive deformity on radiographic assessment, and promising results as a safe treatment option.

  4. The effects of ankle mobilization and active stretching on the difference of weight-bearing distribution, low back pain and flexibility in pronated-foots subjects.

    Science.gov (United States)

    Yoon, Ki-Seok; Park, Seong-Doo

    2013-04-01

    The purpose of this study was designed to analyze the effects mobilization and active stretching on the difference of weight-bearing distribution, low back pain, and flexibility in pronated-foot subjects. The subjects of this study were 16 chronic low back pain patients. They were randomly divided into the control and experimental group. The experimental group had used the model of ankle mobilization and calf muscle active stretching three times per week, for 4 weeks. The control group did same method without an ankle mobilization. The range of flexion and extension motion of the lumbar vertebrae and low back pain degree and difference of weight-bearing were measured before and after the experiment. The model of ankle mobilization and calf muscle stretching of pronated-foot significantly improved the range of flexion and extension motion of the vertebrae. And the visual analogue scale and distribution of weight-bearing were decreased in both of two groups. In other word, the exercise of this study showed that the model of ankle mobilization and calf muscle stretching of pronated-foot had positive effects on improving the range of flexion and extension motion of the vertebrae. The calf muscle stretching was easy and it is effective in therapy that patients by themselves and helped to recover the balance of the vertebrae to combine ankle mobilization and muscle stretching.

  5. ELECTROMYOGRAPHIC ACTIVITY OF THE VASTUS MEDIALIS OBLIQUE AND VASTUS LATERALIS DURING MAXIMUM VOLUNTARY ISOMETRICS IN DIFFERENT WEIGHT BEARING POSITIONS OF THE FOOT

    Directory of Open Access Journals (Sweden)

    Sreekar Kumar Reddy.R

    2014-09-01

    Full Text Available Background: Patellofemoral pain syndrome is a very common disorder. 90% of the general population has some degree of pathologic changes of the patellofemoral joint. Knowledge regarding the cause and prevention of patellofemoral pain syndrome is essential. Therefore the purpose of this study is intended to know whether different foot positions alter Vastus Medialis Oblique and Vastus Lateralis that leads to dysfunctions of knee joint. Method: 30 subjects are included in study and investigated foot in different foot positions are in neutral, pronated and supinated foot positions and performed maximum voluntary isometric contractions are recorded with electromyography. Results: EMG amplitudes (microvolts of VL and VMO at three different weight bearing positions of foot during maximum voluntary contraction analysis by using one-way Analysis of Variance. Mean amplitudes of foot positions in pronation shown significant difference while comparing with neutral and supination. Conclusion: The VMO and VL activity shows significant difference in the pronated foot weight bearing position compared to the neutral and supinated foot. Performing the maximum voluntary isometric contractions of VMO and VL with pronated foot elicited significantly higher EMG activity compared to Neutral or supinated weight bearing positions of foot. The results of this study also suggested that for patellofemoral pain which is caused by pronated foot can be treat with by using the soft foot orthoses

  6. American Society of Biomechanics Clinical Biomechanics Award 2013: tibiofemoral contact location changes associated with lateral heel wedging--a weight bearing MRI study.

    Science.gov (United States)

    Barrance, Peter J; Gade, Venkata; Allen, Jerome; Cole, Jeffrey L

    2014-11-01

    Vertically open magnetic resonance imaging permits study of knee joint contact during weight bearing. Lateral wedging is a low cost intervention for knee osteoarthritis that may influence load distribution and contact. This study assessed the ability of feedback-assisted weight bearing magnetic resonance imaging to detect changes in tibiofemoral contact associated with lateral wedging. One knee in each of fourteen subjects with symptomatic knee osteoarthritis was studied, without specification of compartmental involvement. Knees were imaged during upright standing and at 20° knee flexion. Bilateral external heel wedges were used to provide non-wedged and 5° lateral wedging conditions. Computer modeling was used to measure the medial and lateral compartment contact patch center coordinates on the tibial plateau and the respective contact areas. Lateral heel wedging in flexion was associated with a significant anterior shift of the contact patch of the lateral femoral condyle. Changes with knee flexion were similar to previous reports: both medial and lateral contact centers moved posteriorly with flexion, and lateral condyle contact also moved laterally. Lateral condyle contact area significantly reduced with flexion, while lateral wedging did not significantly affect contact areas. In symptomatic knee osteoarthritis patients standing in knee flexion, weight bearing magnetic resonance imaging recorded an anterior shift of lateral condyle contact in response to lateral heel wedging. Future studies may investigate lateral wedging effects more specifically in candidates for this clinical intervention. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Feasibility of Influencing the Dynamic Fluid Film Coefficients of a Multirecess Journal Bearing by means of Active Hybrid Lubrication

    DEFF Research Database (Denmark)

    Santos, Ilmar; Watanabe, F. Y.

    2003-01-01

    and control techniques. The feasibility of influencing the dynamic fluid film coefficients (stiffness and damping) by means of a controllable fluid injection into opposed bearing recesses is investigated. By controlling the pressure and flow injection using servo control systems, it is possible to obtain...... significant modifications of active hybrid forces, which can be useful while reducing vibration and stabilizing rotating machines....

  8. Nonlinear dynamic behaviour of a rotor-foundation system coupled through passive magnetic bearings with magnetic anisotropy - Theory and experiment

    DEFF Research Database (Denmark)

    Enemark, Søren; Santos, Ilmar F.

    2016-01-01

    In this work, the nonlinear dynamic behaviour of a vertical rigid rotor interacting with a flexible foundation by means of two passive magnetic bearings is quantified and evaluated. The quantification is based on theoretical and experimental investigation of the non-uniformity (anisotropy) of the...

  9. Normalisation method can affect gluteus medius electromyography results during weight bearing exercises in people with hip osteoarthritis (OA): a case control study.

    Science.gov (United States)

    French, Helen P; Huang, Xiaoli; Cummiskey, Andrew; Meldrum, Dara; Malone, Ailish

    2015-02-01

    Surface electromyography (sEMG) is used to assess muscle activation during therapeutic exercise, but data are significantly affected by inter-individual variability and requires normalisation of the sEMG signal to enable comparison between individuals. The purpose of this study was to compare two normalisation methods, a maximal method (maximum voluntary isometric contraction (MVIC)) and non-maximal peak dynamic method (PDM), on gluteus medius (GMed) activation using sEMG during three weight-bearing exercises in people with hip osteoarthritis (OA) and healthy controls. Thirteen people with hip OA and 20 controls performed three exercises (Squat, Step-Up, Step-Down). Average root-mean squared EMG amplitude based on MVIC and PDM normalisation was compared between groups for both involved and uninvolved hips using Mann-Whitney tests. Using MVIC normalisation, significantly higher normalised GMed EMG amplitudes were found in the OA group during all Step-up and down exercises on the involved side (p=0.02-0.001) and most of the Step exercises on the uninvolved side (p=0.03-0.04), but not the Squat (p>0.05), compared to controls. Using PDM normalisation, significant between-group differences occurred only for Ascending Squat (p=0.03) on the involved side. MVIC normalisation demonstrated higher inter-trial relative reliability (ICCs=0.78-0.99) than PDM (ICCs=0.37-0.84), but poorer absolute reliability using Standard Error of Measurement. Normalisation method can significantly affect interpretation of EMG amplitudes. Although MVIC-normalised amplitudes were more sensitive to differences between groups, there was greater variability using this method, which raises concerns regarding validity. Interpretation of EMG data is strongly influenced by the normalisation method used, and this should be considered when applying EMG results to clinical populations.

  10. An Optimized Weighted Association Rule Mining On Dynamic Content

    CERN Document Server

    Velvadivu, P

    2010-01-01

    Association rule mining aims to explore large transaction databases for association rules. Classical Association Rule Mining (ARM) model assumes that all items have the same significance without taking their weight into account. It also ignores the difference between the transactions and importance of each and every itemsets. But, the Weighted Association Rule Mining (WARM) does not work on databases with only binary attributes. It makes use of the importance of each itemset and transaction. WARM requires each item to be given weight to reflect their importance to the user. The weights may correspond to special promotions on some products, or the profitability of different items. This research work first focused on a weight assignment based on a directed graph where nodes denote items and links represent association rules. A generalized version of HITS is applied to the graph to rank the items, where all nodes and links are allowed to have weights. This research then uses enhanced HITS algorithm by developing...

  11. Food intake, tumor growth, and weight loss in EP2 receptor subtype knockout mice bearing PGE2-producing tumors

    OpenAIRE

    Iresjö, Britt‐Marie; Wang, Wenhua; Nilsberth, Camilla; Andersson, Marianne; LÖNNROTH, CHRISTINA; Smedh, Ulrika

    2015-01-01

    Previous studies in our laboratory have demonstrated that prostaglandin (PG) E2 is involved in anorexia/cachexia development in MCG 101 tumor‐bearing mice. In the present study, we investigate the role of PGE receptor subtype EP2 in the development of anorexia after MCG 101 implantation in wild‐type (EP2+/+) or EP2‐receptor knockout (EP2−/−) mice. Our results showed that host absence of EP2 receptors attenuated tumor growth and development of anorexia in tumor‐bearing EP2 knockout mice compar...

  12. On diagnosis measurement under dynamic loading of ball bearing using numerical thermal analysis and infrared thermography

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Dong Pyo; Kim, Ho Jong [School of Mechanical System Engineering, Chonbuk Nationa University, Jeonju (Korea, Republic of); Kim, Won Tae [School of Mechanical and Automotive Engineering, Kongju National University, Kongju (Korea, Republic of)

    2013-08-15

    With the modern machinery towards the direction of high-speed development, the thermal issues of mechanical transmission system and its components is increasingly important. Ball bearing is one of the main parts in rotating machinery system, and is a more easily damaged part. In this paper, bearing thermal fault detection is investigated in details Using infrared thermal imaging technology to the operation state of the ball bearing, a preliminary thermal analysis, and the use of numerical simulation technology by finite element method(FEM) under thermal conditions of the bearing temperature field analysis, initially identified through these two technical analysis, bearing a temperature distribution in the normal state and failure state. It also shows the reliability of the infrared thermal imaging technology with valuable suggestions for the future bearing fault detection.

  13. Effects of Talocrural Mobilization with Movement on Ankle Strength, Mobility, and Weight-Bearing Ability in Hemiplegic Patients with Chronic Stroke: A Randomized Controlled Trial.

    Science.gov (United States)

    An, Chang-Man; Jo, Shin-Ok

    2017-01-01

    In general, adequate movement of the ankle joint is known to play an important role in functional activities. Stroke survivors frequently have limited range of motion of the ankle, leading to dysfunctional weight transfer toward the paretic lower limb during standing or gait. The purpose of this study was to investigate the effects of talocrural mobilization with movement (MWM) on ankle strength, dorsiflexion passive range of motion (DF-PROM), and weight-bearing ability on the paretic limb during standing or gait in stroke patients with limited ankle dorsiflexion. Twenty-six participants with chronic hemiplegia (>6 months post stroke) were divided into 2 groups: MWM group (n = 13) and control group (n = 13). Both groups attended conventional physiotherapy sessions 3 times a week for 5 weeks. Additionally, the MWM group underwent talocrural MWM 3 times a week for 5 weeks. Isokinetic ankle strength, DF-PROM, and weight-bearing ability measures included the limit of stability (LOS); gait parameters were evaluated before and after interventions. Plantarflexors peak torque and DF-PROM significantly increased in the MWM group. In addition, forward and forward-paretic direction LOS significantly increased in the MWM group. Paretic direction LOS, single-limb support phase of the paretic limb significantly increased and double limb support phase significantly decreased within the MWM group. This study demonstrates that talocrural MWM has an augmented effect on ankle strength, mobility, and weight-bearing ability in chronic stroke patients with limited ankle motion when added to conventional therapy. Copyright © 2017 National Stroke Association. Published by Elsevier Inc. All rights reserved.

  14. Some Experimental and Simulation Results on the Dynamic Behaviour of Spur and Helical Geared Transmissions with Journal Bearings

    Directory of Open Access Journals (Sweden)

    R. Fargère

    2012-01-01

    Full Text Available Some interactions between the dynamic and tribological behaviour of geared transmissions are examined, and a number of experimental and simulation results are compared. A model is introduced which incorporates most of the possible interactions between gears, shafts and hydrodynamic journal bearings. It combines (i a specific element for wide-faced gears that includes the normal contact conditions between actual mating teeth, that is, with tooth shape deviations and mounting errors, (ii shaft finite elements, and (iii the external forces generated by journal bearings determined by directly solving Reynolds' equation. The simulation results are compared with the measurement obtained on a high-precision test rig with single-stage spur and helical gears supported by hydrodynamic journal bearings. The experimental and simulation results compare well thus validating the simulation strategy both at the global and local scales.

  15. The influence of external dynamic loads on the lifetime of rolling element bearings: Experimental analysis of the lubricant film and surface wear

    Science.gov (United States)

    Jacobs, William; Van Hooreweder, Brecht; Boonen, Rene; Sas, Paul; Moens, David

    2016-06-01

    Precise prediction of the lifetime of rolling element bearings is a crucial step towards a reliable design of many rotating machines. For bearings subjected to highly varying loads, recent research emphasises a strong reduction of the actual bearing lifetime w.r.t. the classically calculated bearing lifetime. This paper experimentally analyses the influence of external dynamic loads on the lifetime of rolling element bearings. A novel bearing test rig is introduced. The test rig is able to apply a fully controlled multi-axial static and dynamic load on a single test bearing. Also, different types and sizes of bearings can be tested. Two separate investigations are conducted. First, the behaviour of the lubricant film between the rolling elements and raceways is analysed. Increased metallic contact or breakdown of the film during dynamic excitation is investigated based on the measured electrical resistance through the bearing. The study shows that the lubricant film thickness follows the imposed variations of the load. Variations of the lubricant film thickness are similar to the variations when the magnitude of the static bearing load is changed. Second, wear of the raceway surfaces is analysed. Surface wear is investigated after a series of accelerated lifetime tests under high dynamic load. Due to sliding motion between asperities of the contacting surfaces in the bearing, polishing of the raceway honing structure occurs. This polishing is clearly observed on SEM images of the inner raceway after a test duration of only 0.5% of the calculated L10 life. Polishing wear of the surfaces, such as surface induced cracks and material delamination, is expected when the bearing is further exposed to the high dynamic load.

  16. Enhanced model of gear transmission dynamics for condition monitoring applications: Effects of torque, friction and bearing clearance

    Science.gov (United States)

    Fernandez-del-Rincon, A.; Garcia, P.; Diez-Ibarbia, A.; de-Juan, A.; Iglesias, M.; Viadero, F.

    2017-02-01

    Gear transmissions remain as one of the most complex mechanical systems from the point of view of noise and vibration behavior. Research on gear modeling leading to the obtaining of models capable of accurately reproduce the dynamic behavior of real gear transmissions has spread out the last decades. Most of these models, although useful for design stages, often include simplifications that impede their application for condition monitoring purposes. Trying to filling this gap, the model presented in this paper allows us to simulate gear transmission dynamics including most of these features usually neglected by the state of the art models. This work presents a model capable of considering simultaneously the internal excitations due to the variable meshing stiffness (including the coupling among successive tooth pairs in contact, the non-linearity linked with the contacts between surfaces and the dissipative effects), and those excitations consequence of the bearing variable compliance (including clearances or pre-loads). The model can also simulate gear dynamics in a realistic torque dependent scenario. The proposed model combines a hybrid formulation for calculation of meshing forces with a non-linear variable compliance approach for bearings. Meshing forces are obtained by means of a double approach which combines numerical and analytical aspects. The methodology used provides a detailed description of the meshing forces, allowing their calculation even when gear center distance is modified due to shaft and bearing flexibilities, which are unavoidable in real transmissions. On the other hand, forces at bearing level were obtained considering a variable number of supporting rolling elements, depending on the applied load and clearances. Both formulations have been developed and applied to the simulation of the vibration of a sample transmission, focusing the attention on the transmitted load, friction meshing forces and bearing preloads.

  17. Improvement of Dynamic Performance of Hybrid Gas Bearings via Adjustable Lubrication

    DEFF Research Database (Denmark)

    Pierart Vásquez, Fabián Gonzalo; Santos, Ilmar

    2013-01-01

    the aerodynamic effect with the addition of external pressurization in a hybrid gas bearing. This study uses a mathematical model for hybrid lubrication of a compressible fluid film journal bearing with adjustable control of the external pressure, developed previously in [12]. The model is based on a compressible...

  18. Influence of unbalance levels on nonlinear dynamics of a rotor-backup rolling bearing system

    DEFF Research Database (Denmark)

    Fonseca, Cesar A.; Santos, Ilmar; Weber, Hans I.

    2017-01-01

    Rotor drops in magnetic bearing and unbalance in rotors have been objective of study for many years. The combination of these two well-known phenomena led to an interesting chaotic response, when the rotor touches the inner race of the back-up bearing. The present work explores the nonlinear roto...

  19. Effects of ankle joint mobilization with movement and weight-bearing exercise on knee strength, ankle range of motion, and gait velocity in patients with stroke: a pilot study

    National Research Council Canada - National Science Library

    An, Chang-Man; Won, Jong-Im

    2016-01-01

    [Purpose] The purpose of this study was to investigate the effects of ankle joint mobilization with movement on knee strength, ankle range of motion, and gait velocity, compared with weight-bearing exercise in stroke patients...

  20. The effect of frog pressure and downward vertical load on hoof wall weight-bearing and third phalanx displacement in the horse - an in vitro study : research communication

    Directory of Open Access Journals (Sweden)

    A. Olivier

    2001-07-01

    Full Text Available A shoe was designed to combine the advantages of a reverse shoe and an adjustable heart bar shoe in the treatment of chronic laminitis. This reverse even frog pressure (REFP shoe applies pressure uniformly over a large area of the frog solar surface. Pressure is applied vertically upward parallel to the solar surface of the frog and can be increased or decreased as required. Five clinically healthy horses were humanely euthanased and their dismem-bered forelimbs used in an in vitro study. Frog pressure was measured by strain gauges applied to the ground surface of the carrying tab portion of the shoe. A linear variable distance transducer (LVDT was inserted into a hole drilled in the dorsal hoof wall. The LVDT measured movement of the third phalanx (P3 in a dorsopalmar plane relative to the dorsal hoof wall. The vertical component of hoof wall compression was measured by means of unidirectional strain gauges attached to the toe, quarter and heel of the medial hoof wall of each specimen. The entire limb was mounted vertically in a tensile testing machine and submitted to vertical downward compressive forces of 0 to 2500 Nat a rate of 5 cm/minute. The effects of increasing frog pressure on hoof wall weight-bearing and third phalanx movement within the hoof were determined. Each specimen was tested with the shoe under the following conditions: zero frog pressure; frog pressure used to treat clinical cases of chronic laminitis (7 N-cm; frog pressure clinically painful to the horse as determined prior to euthanasia; frog pressure just alleviating this pain. The specimens were also tested after shoe removal. Total weight-bearing on the hoof wall at zero frog pressure was used as the basis for comparison. Pain-causing and pain-alleviating frog pressures decreased total weight-bearing on the hoof wall (P < 0.05. Frog pressure of 7 N-cm had no statistically significant effect on hoof wall weight-bearing although there was a trend for it to decrease as

  1. EFFICACY OF WEIGHT BEARING DISTAL TIBIOFIBULAR JOINT MOBILIZATION WITH MOVEMENT (MWM IN IMPROVING PAIN, DORSIFLEXION RANGE AND FUNCTION IN PATIENTS WITH POSTACUTE LATERAL ANKLE SPRAIN

    Directory of Open Access Journals (Sweden)

    Kumari Nisha

    2014-06-01

    Full Text Available Background: Various treatments in physiotherapy are available for ankle sprain with no consensus like taping, bracing, splinting, cryotherapy, electrotherapy modality like ultrasound, laser therapy, interferential therapy and HVGS, joint mobilization. Mulligan’s mobilizations-with movement (MWM have been proposed as novel manual therapy technique to improve joint ROM by combining physiological and accessory joint movements. He developed a suite of treatment techniques on the basis of his theory of positional faults and altered joint kinematics following injuries affecting spinal and peripheral joints. Objective: To find out the efficacy of distal tibiofibular joint MWM in conjunction with conventional treatment over conventional treatment alone for improving pain , dorsiflexion range and lower extremity function in patients with post acute lateral ankle sprain. Subject and methods: 30 lateral ankle sprain subjects were randomized into 2 groups:- Group 1(n=15 were received distal tibiofibular joint MWM along with conventional treatment and Group 2 (n=15 subjects were received conventional treatment only. Treatment consist of 3 sessions spread over 1 week, each session 48 hours apart and data is recorded at beginning and end of treatment regimen. Results: Independent t-test showed statistical significant improvement in only weight bearing lunge measure for dorsiflexion (p=0.008 in group 1 over group 2 and paired t-test was used for within group analysis which showed significant improvement in both the groups in all the outcome variables (p=0.000 Discussion and conclusion: Both the groups demonstrated significant improvement in pain, range and lower extremity function in lateral ankle sprain and distal tibiofibular joint mobilization with movement in conjunction with conventional treatment will be significantly more effective than conventional treatment alone in improving weight bearing ankle dorsiflexion range (Weight bearing lunge measure in

  2. Effect of weight-bearing exercise and calcium supplement on cortical and trabecular bone in the proximal tibia metaphyseal- an experimental protocol in ovariectomized rats

    Directory of Open Access Journals (Sweden)

    Valliollah Dabidy Roshan1

    2009-01-01

    Full Text Available (Received 4 April, 2009; Accepted 17 June, 2009AbstractBackground and purpose: Osteoporotic fractures are much more common in older post-menopausal women and account for significant morbidity and mortality. Although age is an independent risk factor for fractures, bone micro-architecture is the predictor of subsequent fractures. Adequate calcium and Weight-bearing exercise are known to affect skeletal development, however, the effects of calcium supplement and treadmill endurance running on bone micro-architecture are not well known. The objective of this study was to determine the effects of treadmill endurance running training and calcium supplement, on micro-architectures of cortical and trabecular bone in the proximal tibia metaphyseal in ovariectomized Sprague Dawley rats.Materials and methods: Forty-three rats were randomly divided into endurance running training, calcium supplement, control, pre-test and base groups. The rats in the treadmill running group performed the progressive running exercise in 12 to 20 m/minutes for a total of 10 to 60 minutes, 5 times a week. Calcium group received ca supplement using Gavage (35 mg/kg/day for 8 weeks. After 8 weeks, micro-architecture parameters in the proximal tibia metaphyseal were measured by using a semi-automated image analysis system.Results: The ovariectomay was associated with a significant decrease in the trabecular volume and thickness, while separation insignificantly decreased in the cortical volume and thickness in the proximal tibia metaphyseal. The treadmill running exercise and calcium supplement significantly increased cortical or trabecular volume and also thickness and the trabecular separation compared with age-matched controls. Furthermore, the micro-architectures of cortical and trabecular bone in the proximal tibia metaphyseal was insignificant between the treadmill endurance running and calcium supplement groups.Conclusion: Skeletal benefits can be obtained by changes in

  3. Influence of Bearing Stiffness on the Nonlinear Dynamics of a Shaft-Final Drive System

    Directory of Open Access Journals (Sweden)

    Xu Jinli

    2016-01-01

    Full Text Available The bearing stiffness has a considerable influence on the nonlinear coupling vibration characteristics of the shaft-final drive system. A 14-DOF nonlinear coupled vibration model was established by employing the lumped mass method so as to identify the coupling effects of the bearing stiffness to the vibration response of the shaft-final drive system. The engine’s torque ripple, the alternating load from the universal joint (U-joint, and the time-varying mesh parameters of hypoid gear of the shaft-final drive system were also considered for accurate quantitative analysis. The numerical analysis of the vibration response of the coupled system was performed and the experimental measurements were carried out for the validation test. Results show that, at the given driving speed, improving the bearing stiffness can reduce the vibration response of the given coupled system; however, when the bearing stiffness increases to a critical value, the effects of bearing stiffness on the vibration reduction become insignificant; when the driving speed changes, the resonance regions of the coupled system vary with the bearing stiffness. The results are helpful to determine the proper bearing stiffness and the optimum control strategy for the shaft-final drive system. It is hoped that the optimal shaft-final drive system can provide good vibration characteristics to achieve the energy saving and noise reduction for the vehicle application.

  4. Some Experimental and Simulation Results on the Dynamic Behaviour of Spur and Helical Geared Transmissions with Journal Bearings

    OpenAIRE

    2012-01-01

    Some interactions between the dynamic and tribological behaviour of geared transmissions are examined, and a number of experimental and simulation results are compared. A model is introduced which incorporates most of the possible interactions between gears, shafts and hydrodynamic journal bearings. It combines (i) a specific element for wide-faced gears that includes the normal contact conditions between actual mating teeth, that is, with tooth shape deviations and mounting errors, (ii) shaf...

  5. The influence of synaptic weight distribution on neuronal population dynamics.

    Directory of Open Access Journals (Sweden)

    Ramakrishnan Iyer

    2013-10-01

    Full Text Available The manner in which different distributions of synaptic weights onto cortical neurons shape their spiking activity remains open. To characterize a homogeneous neuronal population, we use the master equation for generalized leaky integrate-and-fire neurons with shot-noise synapses. We develop fast semi-analytic numerical methods to solve this equation for either current or conductance synapses, with and without synaptic depression. We show that its solutions match simulations of equivalent neuronal networks better than those of the Fokker-Planck equation and we compute bounds on the network response to non-instantaneous synapses. We apply these methods to study different synaptic weight distributions in feed-forward networks. We characterize the synaptic amplitude distributions using a set of measures, called tail weight numbers, designed to quantify the preponderance of very strong synapses. Even if synaptic amplitude distributions are equated for both the total current and average synaptic weight, distributions with sparse but strong synapses produce higher responses for small inputs, leading to a larger operating range. Furthermore, despite their small number, such synapses enable the network to respond faster and with more stability in the face of external fluctuations.

  6. Static, Dynamic, and Thermal Properties of Compressible Fluid Film Journal Bearings

    DEFF Research Database (Denmark)

    Paulsen, Bo Terp; Morosi, Stefano; Santos, Ilmar

    2011-01-01

    fluid film journal bearing, in order to identify when this type of analysis should be of concern. Load capacity, stiffness, and damping coefficients are determined by the solution of the standard Reynolds equation coupled to the energy equation. Numerical investigations show how bearing geometry......Modern turbo-machinery applications, high-speed machine tools, and laboratory equipment require ever-growing rotational speeds and high degree of precision and reliability. Gas journal bearings are often employed because they meet the demands of high-speed performance, in a clean environment...

  7. TEHL analysis of high-speed and heavy-load roller bearing with quasi-dynamic characteristics

    Directory of Open Access Journals (Sweden)

    Shi Xiujiang

    2015-08-01

    Full Text Available In this paper, the aero-engine mainshaft roller bearing D1842926 under typical operating conditions is taken as a case study, a new integrated numerical algorithm of quasi-dynamics and thermal elastohydrodynamic lubrication (TEHL is put forward, which can complete the bearing lubricated analysis from global dynamic performance to local TEHL state and break out of the traditional analysis way carried out independently in their own field. The 3-D film thickness distributions with different cases are given through integrated numerical algorithm, meanwhile the minimum film thickness of quasi-dynamic analysis, integrated numerical algorithm and testing are compared, which show that integrated numerical results have good agreements with the testing data, so the algorithm is demonstrated available and can judge the lubrication state more accurately. The parameter effects of operating and structure on pv value, cage sliding rate, TEHL film pressure, thickness and temperature are researched, which will provide an important theoretical basis for the structure design and optimization of aero-engine mainshaft roller bearing.

  8. Wayside Bearing Fault Diagnosis Based on Envelope Analysis Paved with Time-Domain Interpolation Resampling and Weighted-Correlation-Coefficient-Guided Stochastic Resonance

    Directory of Open Access Journals (Sweden)

    Yongbin Liu

    2017-01-01

    Full Text Available Envelope spectrum analysis is a simple, effective, and classic method for bearing fault identification. However, in the wayside acoustic health monitoring system, owing to the high relative moving speed between the railway vehicle and the wayside mounted microphone, the recorded signal is embedded with Doppler effect, which brings in shift and expansion of the bearing fault characteristic frequency (FCF. What is more, the background noise is relatively heavy, which makes it difficult to identify the FCF. To solve the two problems, this study introduces solutions for the wayside acoustic fault diagnosis of train bearing based on Doppler effect reduction using the improved time-domain interpolation resampling (TIR method and diagnosis-relevant information enhancement using Weighted-Correlation-Coefficient-Guided Stochastic Resonance (WCCSR method. First, the traditional TIR method is improved by incorporating the original method with kinematic parameter estimation based on time-frequency analysis and curve fitting. Based on the estimated parameters, the Doppler effect is removed using the TIR easily. Second, WCCSR is employed to enhance the diagnosis-relevant period signal component in the obtained Doppler-free signal. Finally, paved with the above two procedures, the local fault is identified using envelope spectrum analysis. Simulated and experimental cases have verified the effectiveness of the proposed method.

  9. Characteristics and dynamic response of 3-D component base isolation system using ball bearings and air springs

    Energy Technology Data Exchange (ETDEWEB)

    Tsutsumi, Hideaki; Yamada, Hiroyuki; Mori, Kazunari; Ebisawa, Katsumi; Shibata, Katsuyuki [Seismic Emergency Information System Research Team, Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan)

    2001-02-01

    Introduction of the base isolation technique into the seismic design of nuclear power plant components as well as buildings has been expected as one of effective countermeasure to reduce the seismic force applied to components. A research program on the base isolation of nuclear components has been carried out at the Japan Atomic Energy Research Institute (JAERI) since 1991. A methodology and a computer code (EBISA: Equipment Base Isolation System Analysis) for evaluating the failure frequency of the nuclear component with the base isolation were developed. In addition, a test program, which is concerned with the above development, aiming at improvement of failure frequency analysis models in the code has been conducted since 1996 to investigate the dynamic behavior and to verify the effectiveness of component base isolation systems. Two base isolation test systems with different characteristics were fabricated and static and dynamic characteristics were measured by static loading and free vibration tests. One which consists of ball bearings and air springs was installed on the test bed to observe the dynamic response under natural earthquake motion. The effect of base isolation system has been observed under several earthquakes. Three-dimensional response and effect of base isolation of another system using multi-layer-rubber-bearings and coil springs has been investigated against various large earthquake motions by shaking table test. This report describes the design specification of the base isolation system using ball bearings and air springs, dynamic characteristics, dynamic response against natural seismic motion and results of dynamic response analysis considering the various characteristics of isolation devices. (author)

  10. Foil bearings

    Science.gov (United States)

    Elrod, David A.

    1993-01-01

    The rolling element bearings (REB's) which support many turbomachinery rotors offer high load capacity, low power requirements, and durability. Two disadvantages of REB's are: (1) rolling or sliding contact within the bearing has life-limiting consequences; and (2) REB's provide essentially no damping. The REB's in the Space Shuttle Main Engine (SSME) turbopumps must sustain high static and dynamic loads, at high speeds, with a cryogenic fluid as lubricant and coolant. The pump end ball bearings limit the life of the SSME high pressure oxygen turbopump (HPOTP). Compliant foil bearing (CFB) manufacturers have proposed replacing turbopump REB's with CFB's CFB's work well in aircraft air cycle machines, auxiliary power units, and refrigeration compressors. In a CFB, the rotor only contracts the foil support structure during start up and shut down. CFB damping is higher than REB damping. However, the load capacity of the CFB is low, compared to a REB. Furthermore, little stiffness and damping data exists for the CFB. A rotordynamic analysis for turbomachinery critical speeds and stability requires the input of bearing stiffness and damping coefficients. The two basic types of CFB are the tension-dominated bearing and the bending-dominated bearing. Many investigators have analyzed and measured characteristics of tension-dominated foil bearings, which are applied principally in magnetic tape recording. The bending-dominated CFB is used more in rotating machinery. This report describes the first phase of a structural analysis of a bending-dominated, multileaf CFB. A brief discussion of CFB literature is followed by a description and results of the present analysis.

  11. Foil bearings

    Science.gov (United States)

    Elrod, David A.

    1993-11-01

    The rolling element bearings (REB's) which support many turbomachinery rotors offer high load capacity, low power requirements, and durability. Two disadvantages of REB's are: (1) rolling or sliding contact within the bearing has life-limiting consequences; and (2) REB's provide essentially no damping. The REB's in the Space Shuttle Main Engine (SSME) turbopumps must sustain high static and dynamic loads, at high speeds, with a cryogenic fluid as lubricant and coolant. The pump end ball bearings limit the life of the SSME high pressure oxygen turbopump (HPOTP). Compliant foil bearing (CFB) manufacturers have proposed replacing turbopump REB's with CFB's CFB's work well in aircraft air cycle machines, auxiliary power units, and refrigeration compressors. In a CFB, the rotor only contracts the foil support structure during start up and shut down. CFB damping is higher than REB damping. However, the load capacity of the CFB is low, compared to a REB. Furthermore, little stiffness and damping data exists for the CFB. A rotordynamic analysis for turbomachinery critical speeds and stability requires the input of bearing stiffness and damping coefficients. The two basic types of CFB are the tension-dominated bearing and the bending-dominated bearing. Many investigators have analyzed and measured characteristics of tension-dominated foil bearings, which are applied principally in magnetic tape recording. The bending-dominated CFB is used more in rotating machinery. This report describes the first phase of a structural analysis of a bending-dominated, multileaf CFB. A brief discussion of CFB literature is followed by a description and results of the present analysis.

  12. Local Events and Dynamics on Weighted Complex Networks

    Institute of Scientific and Technical Information of China (English)

    ZHAO Hui; GAO Zi-You

    2006-01-01

    @@ We examine the weighted networks grown and evolved by local events, such as the addition of new vertices and links and we show that depending on frequency of the events, a generalized power-law distribution of strength can emerge. Continuum theory is used to predict the scaling function as well as the exponents, which is in good agreement with the numerical simulation results. Depending on event frequency, power-law distributions of degree and weight can also be expected. Probability saturation phenomena for small strength and degree in many real world networks can be reproduced. Particularly, the non-trivial clustering coefficient, assortativity coefficient and degree-strength correlation in our model are all consistent with empirical evidences.

  13. Nano-level instrumentation for analyzing the dynamic accuracy of a rolling element bearing

    Science.gov (United States)

    Yang, Z.; Hong, J.; Zhang, J.; Wang, M. Y.; Zhu, Y.

    2013-12-01

    The rotational performance of high-precision rolling bearings is fundamental to the overall accuracy of complex mechanical systems. A nano-level instrument to analyze rotational accuracy of high-precision bearings of machine tools under working conditions was developed. In this instrument, a high-precision (error motion spindle was applied to spin the test bearing. Operating conditions could be simulated effectively because of the large axial loading capacity. An air-cylinder, controlled by a proportional pressure regulator, was applied to drive an air-bearing subjected to non-contact and precise loaded axial forces. The measurement results on axial loading and rotation constraint with five remaining degrees of freedom were completely unconstrained and uninfluenced by the instrument's structure. Dual capacity displacement sensors with 10 nm resolution were applied to measure the error motion of the spindle using a double-probe error separation method. This enabled the separation of the spindle's error motion from the measurement results of the test bearing which were measured using two orthogonal laser displacement sensors with 5 nm resolution. Finally, a Lissajous figure was used to evaluate the non-repetitive run-out (NRRO) of the bearing at different axial forces and speeds. The measurement results at various axial loadings and speeds showed the standard deviations of the measurements' repeatability and accuracy were less than 1% and 2%. Future studies will analyze the relationship between geometrical errors and NRRO, such as the ball diameter differences of and the geometrical errors in the grooves of rings.

  14. Some dynamic generalized information measures in the context of weighted models

    Directory of Open Access Journals (Sweden)

    S. S. Maya

    2013-05-01

    Full Text Available In this paper, we study some dynamic generalized information measures between a true distribution and an observed (weighted distribution, useful in life length studies. Further, some bounds and inequalities related to these measures are also studied.

  15. Some dynamic generalized information measures in the context of weighted models

    OpenAIRE

    S. S. Maya; S. M. Sunoj

    2013-01-01

    In this paper, we study some dynamic generalized information measures between a true distribution and an observed (weighted) distribution, useful in life length studies. Further, some bounds and inequalities related to these measures are also studied.

  16. Effects of Functional Limb Overloading on Symmetrical Weight Bearing, Walking Speed, Perceived Mobility, and Community Participation among Patients with Chronic Stroke.

    Science.gov (United States)

    Alabdulwahab, Sami S; Ahmad, Fuzail; Singh, Harpreet

    2015-01-01

    Background. Stroke is a leading cause for long-term disability that often compromises the sensorimotor and gait function accompanied by spasticity. Gait abnormalities persist through the chronic stages of the condition and only a small percentage of these persons are able to walk functionally in the community. Material and Method. Patients with chronic stroke were recruited from outpatient rehabilitation unit at Department of Neurology & Neurosurgery, All India Institute of Medical Sciences, having a history of first stroke at least six months before recruitment, with unilateral motor deficits affecting gait. The patients were randomly assigned to either the functional limb overloading (FLO) or Limb Overloading Resistance Training (LORT) group and provided four weeks of training. Result. We found that there was an improvement in gait performance, weight bearing on affected limb, and perceived mobility and community participation. Conclusion. To the best of our knowledge, this is the first study that has evaluated the effects of functional limb overloading training on symmetric weight bearing, walking ability, and perceived mobility and participation in chronic hemiplegic population. The study demonstrated a beneficial effect of training on all the outcomes, suggesting that the functional limb overloading training can be a useful tool in the management of gait problems in chronic stroke patients.

  17. Dynamic monitoring of weight data at the pen vs at the individual level

    DEFF Research Database (Denmark)

    Jensen, Dan Børge; Toft, Nils; Kristensen, Anders Ringgaard

    recorded weight data from finisher pigs. Data are collected at insertion and at the exit of the first pigs in the pen, and in few pens, the weight is recorded weekly. Dynamic linear models are fitted on the weight data, at the pig level (univariate), at the double pen level using averaged weight...... (univariate) and using individual pig values as parameters in a hierarchical (multivariate) model including section, double pen, and individual level. Variance components of the different models are estimated using the Expectation Maximization algorithm. The difference of information obtained...... at the individual vs. pen level is thereafter assessed. Whereas weight data is usually monitored after a batch is being sent to the slaughter house, this method provides with weekly updating of the data. Perspectives of application include dynamic monitoring of weight data in relation to events such as diarrhoea...

  18. Dynamic monitoring of weight data at the pen vs at the individual level

    DEFF Research Database (Denmark)

    Jensen, Dan; Toft, Nils; Kristensen, A. R. K.

    recorded weight data from finisher pigs. Data are collected at insertion and at the exit of the first pigs in the pen, and in few pens, the weight is recorded weekly. Dynamic linear models are fitted on the weight data, at the pig level (univariate), at the double pen level using averaged weight...... (univariate) and using individual pig values as parameters in a hierarchical (multivariate) model including section, double pen, and individual level. Variance components of the different models are estimated using the Expectation Maximization algorithm. The difference of information obtained...... at the individual vs pen level is thereafter assessed. Whereas weight data is usually monitored after a batch is being sent to the slaughter house, this method provides weekly updating of the data. Perspectives of application include dynamic monitoring of weight data in relation to events such as diarrhoea, tail...

  19. Hominin-bearing caves and landscape dynamics in the Cradle of Humankind, South Africa

    Science.gov (United States)

    Dirks, Paul H. G. M.; Berger, Lee R.

    2013-02-01

    sediment traps on the landscape. Caves in the CoH are distributed along lithological boundaries and NNE and ESE fractures. Fossil-bearing caves have a distinct distribution pattern, with different directional controls, a high degree of clustering, a characteristic spacing of 1700 m or 3400 m, and a characteristic bi-model fractal distribution best explained by a combination of geological and biological controls. It is suggested that clustering of fossil-bearing caves reflects a Lévy flight patterns typical for foraging behavior in animals. The controlling element in this behavior could have been availability of water in or near groups of caves, resulting in preferential occupation of these caves with accumulation of diverse faunal fossil assemblages. The tectonic drivers shaping the dynamic landscape of the CoH did not involve large, seismically active fault lines, but complex interactions between multiple smaller fractures and joints activated in a far field stress controlled by uplift. The landscape of the CoH, with its caves and water sources and dissected landscape provided a setting favored by many animals including hominins. A modern day analog for what the CoH would have looked like 2 My ago is found 50 km east of Johannesburg, near the SE margin of the Johannesburg Dome.

  20. 主动电磁轴承系统的动力学性能分析%Analysis on Dynamic Performance for Active Magnetic Bearing-Rotor System

    Institute of Scientific and Technical Information of China (English)

    严慧燕; 汪希平; 朱礼进; 张直明; 万金贵

    2001-01-01

    In the application of active magnetic bearings (AMB), one of the key problems to be solved is the safety and stability in the sense of rotor dynamics. The project related to the present paper deals with the method for analyzing bearing rotor systems with high rotation speed and specially supported by active magnetic bearings, and studies its rotor dynamics performance, including calculation of the natural frequencies with their distribution characteristics, and the critical speeds of the system. One of the targets of this project is to formulate a theory and method valid for the analysis of the dynamic performance of the active magnetic bearing-rotor system by combining the traditional theory and method of rotor dynamics with the analytical theory and design method based on modern control theory of the AMB system.

  1. Application of laser interferometry to the evaluation of the dynamic characteristics of rolling bearings and comparison with piezoelectric device measurements

    Science.gov (United States)

    Vela Arvizo, Dagoberto; Rodríguez Lelis, José Maria; Vargas Treviño, Marciano; Flores Gil, Aarón; May Alarcón, Manuel; Villanueva Luna, Adrián E.

    2007-03-01

    Bearings are elements of rotating machinery that are widely used as low friction joint elements between other machine elements. Like any other machine element they posses a finite life which is dependent on a number of factors, among them manufacture, assembling, maintenances, load, etc. Bearing failures are amongst the principal causes of machinery overhaul. They by themselves are a source of vibration which is a function of surface conditions, clearances, misalignment, etc. Each of these defects present a specific dynamic signature, and can be analyzed by a number of techniques already in used, among them the laser vibrometry. This is a non-contact, non-disturbing method commonly used for measurements of vibrations on static objects. The technique offers the possibility to measure vibrations on thin-walled (light), and rotating objects as well as sound fields. Common vibration signal analysis in rotating machinery are restricted to low frequencies, up to 3000 Hz, and in some cases when analyzing contact problems and fatigue at 7000 up to 15000 Hz. In this work, are presented the primary results to employ laser interferometry to study the dynamic signals generated by rolling bearings, and the feasibility to employ it to study high frequency problems of these machine elements.

  2. Nonlinear Dynamic Analysis of Coupled Gear-Rotor-Bearing System with the Effect of Internal and External Excitations

    Institute of Scientific and Technical Information of China (English)

    ZHOU Shihua; SONG Guiqiu; REN Zhaohui; WEN Bangchun

    2016-01-01

    Extensive studies on nonlinear dynamics of gear systems with internal excitation or external excitation respectively have been carried out. However, the nonlinear characteristics of gear systems under combined internal and external excitations are scarcely investigated. An eight-degree-of-freedom(8-DOF) nonlinear spur gear-rotor-bearing model, which contains backlash, transmission error, eccentricity, gravity and input/output torque, is established, and the coupled lateral-torsional vibration characteristics are studied. Based on the equations of motion, the coupled spur gear-rotor-bearing system(SGRBS) is investigated using the Runge-Kutta numerical method, and the effects of rotational speed, error fluctuation and load fluctuation on the dynamic responses are explored. The results show that a diverse range of nonlinear dynamic characteristics such as periodic motion, quasi-periodic motion, chaotic behaviors and impacts exhibited in the system are strongly attributed to the interaction between internal and external excitations. Significantly, the changing rotational speed could effectively control the vibration of the system. Vibration level increases with the increasing error fluctuation. Whereas the load fluctuation has an influence on the nonlinear dynamic characteristics and the increasing excitation force amplitude makes the vibration amplitude increase, the chaotic motion may be restricted. The proposed model and numerical results can be used for diagnosis of faults and vibration control of practical SGRBS.

  3. Nonlinear dynamic analysis of coupled gear-rotor-bearing system with the effect of internal and external excitations

    Science.gov (United States)

    Zhou, Shihua; Song, Guiqiu; Ren, Zhaohui; Wen, Bangchun

    2016-03-01

    Extensive studies on nonlinear dynamics of gear systems with internal excitation or external excitation respectively have been carried out. However, the nonlinear characteristics of gear systems under combined internal and external excitations are scarcely investigated. An eight-degree-of-freedom(8-DOF) nonlinear spur gear-rotor-bearing model, which contains backlash, transmission error, eccentricity, gravity and input/output torque, is established, and the coupled lateral-torsional vibration characteristics are studied. Based on the equations of motion, the coupled spur gear-rotor-bearing system(SGRBS) is investigated using the Runge-Kutta numerical method, and the effects of rotational speed, error fluctuation and load fluctuation on the dynamic responses are explored. The results show that a diverse range of nonlinear dynamic characteristics such as periodic motion, quasi-periodic motion, chaotic behaviors and impacts exhibited in the system are strongly attributed to the interaction between internal and external excitations. Significantly, the changing rotational speed could effectively control the vibration of the system. Vibration level increases with the increasing error fluctuation. Whereas the load fluctuation has an influence on the nonlinear dynamic characteristics and the increasing excitation force amplitude makes the vibration amplitude increase, the chaotic motion may be restricted. The proposed model and numerical results can be used for diagnosis of faults and vibration control of practical SGRBS.

  4. Reliability of the measures of weight-bearing distribution obtained during quiet stance by digital scales in subjects with and without hemiparesis.

    Science.gov (United States)

    de Araujo-Barbosa, Paulo Henrique Ferreira; de Menezes, Lidiane Teles; Costa, Abraão Souza; Couto Paz, Clarissa Cardoso Dos Santos; Fachin-Martins, Emerson

    2015-05-01

    Described as an alternative way of assessing weight-bearing asymmetries, the measures obtained from digital scales have been used as an index to classify weight-bearing distribution. This study aimed to describe the intra-test and the test/retest reliability of measures in subjects with and without hemiparesis during quiet stance. The percentage of body weight borne by one limb was calculated for a sample of subjects with hemiparesis and for a control group that was matched by gender and age. A two-way analysis of variance was used to verify the intra-test reliability. This analysis was calculated using the differences between the averages of the measures obtained during single, double or triple trials. The intra-class correlation coefficient (ICC) was utilized and data plotted using the Bland-Altman method. The intra-test analysis showed significant differences, only observed in the hemiparesis group, between the measures obtained by single and triple trials. Excellent and moderate ICC values (0.69-0.84) between test and retest were observed in the hemiparesis group, while for control groups ICC values (0.41-0.74) were classified as moderate, progressing from almost poor for measures obtained by a single trial to almost excellent for those obtained by triple trials. In conclusion, good reliability ranging from moderate to excellent classifications was found for participants with and without hemiparesis. Moreover, an improvement of the repeatability was observed with fewer trials for participants with hemiparesis, and with more trials for participants without hemiparesis.

  5. Dynamics of phase oscillators with generalized frequency-weighted coupling

    Science.gov (United States)

    Xu, Can; Gao, Jian; Xiang, Hairong; Jia, Wenjing; Guan, Shuguang; Zheng, Zhigang

    2016-12-01

    Heterogeneous coupling patterns among interacting elements are ubiquitous in real systems ranging from physics, chemistry to biology communities, which have attracted much attention during recent years. In this paper, we extend the Kuramoto model by considering a particular heterogeneous coupling scheme in an ensemble of phase oscillators, where each oscillator pair interacts with different coupling strength that is weighted by a general function of the natural frequency. The Kuramoto theory for the transition to synchronization can be explicitly generalized, such as the expression for the critical coupling strength. Also, a self-consistency approach is developed to predict the stationary states in the thermodynamic limit. Moreover, Landau damping effects are further revealed by means of linear stability analysis and resonance poles theory below the critical threshold, which turns to be far more generic. Our theoretical analysis and numerical results are consistent with each other, which can help us understand the synchronization transition in general networks with heterogenous couplings.

  6. Nano-level instrumentation for analyzing the dynamic accuracy of a rolling element bearing

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Z.; Hong, J.; Zhang, J.; Wang, M. Y. [State Key Laboratory for Manufacturing Systems Engineering, Xi' an Jiaotong University, Xi' an (China); Zhu, Y. [Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi' an Jiaotong University, Xi' an (China)

    2013-12-15

    The rotational performance of high-precision rolling bearings is fundamental to the overall accuracy of complex mechanical systems. A nano-level instrument to analyze rotational accuracy of high-precision bearings of machine tools under working conditions was developed. In this instrument, a high-precision (error motion < 0.15 μm) and high-stiffness (2600 N axial loading capacity) aerostatic spindle was applied to spin the test bearing. Operating conditions could be simulated effectively because of the large axial loading capacity. An air-cylinder, controlled by a proportional pressure regulator, was applied to drive an air-bearing subjected to non-contact and precise loaded axial forces. The measurement results on axial loading and rotation constraint with five remaining degrees of freedom were completely unconstrained and uninfluenced by the instrument's structure. Dual capacity displacement sensors with 10 nm resolution were applied to measure the error motion of the spindle using a double-probe error separation method. This enabled the separation of the spindle's error motion from the measurement results of the test bearing which were measured using two orthogonal laser displacement sensors with 5 nm resolution. Finally, a Lissajous figure was used to evaluate the non-repetitive run-out (NRRO) of the bearing at different axial forces and speeds. The measurement results at various axial loadings and speeds showed the standard deviations of the measurements’ repeatability and accuracy were less than 1% and 2%. Future studies will analyze the relationship between geometrical errors and NRRO, such as the ball diameter differences of and the geometrical errors in the grooves of rings.

  7. Nonlinear dynamic analysis of a rotor-bearing-seal system under two loading conditions

    Science.gov (United States)

    Ma, Hui; Li, Hui; Niu, Heqiang; Song, Rongze; Wen, Bangchun

    2013-11-01

    The operating speed of the rotating machinery often exceeds the second or even higher order critical speeds to pursue higher efficiency. Thus, how to restrain the higher order mode instability caused by the nonlinear oil-film force and seal force at high speed as far as possible has become more and more important. In this study, a lumped mass model of a rotor-bearing-seal system considering the gyroscopic effect is established. The graphite self-lubricating bearing and the sliding bearing are simulated by a spring-damping model and a nonlinear oil-film force model based on the assumption of short bearings, respectively. The seal is simulated by Muszynska nonlinear seal force model. Effects of the seal force and oil-film force on the first and second mode instabilities are investigated under two loading conditions which are determined by API Standard 617 (Axial and Centrifugal Compressors and Expander-compressors for Petroleum, Chemical and Gas Industry Services, Seventh Edition). The research focuses on the effects of exciting force forms and their magnitudes on the first and second mode whips in a rotor-bearing-seal system by using the spectrum cascades, vibration waveforms, orbits and Poincaré maps. The first and second mode instability laws are compared by including and excluding the seal effect in a rotor system with single-diameter shaft and two same discs. Meanwhile, the instability laws are also verified in a rotor system with multi-diameter shaft and two different discs. The results show that the second loading condition (out-of-phase unbalances of two discs) and the nonlinear seal force can mainly restrain the first mode instability and have slight effects on the second mode instability. This study may contribute to a further understanding about the higher order mode instability of such a rotor system with fluid-induced forces from the oil-film bearings and seals.

  8. Deep Learning with Dynamic Spiking Neurons and Fixed Feedback Weights.

    Science.gov (United States)

    Samadi, Arash; Lillicrap, Timothy P; Tweed, Douglas B

    2017-03-01

    Recent work in computer science has shown the power of deep learning driven by the backpropagation algorithm in networks of artificial neurons. But real neurons in the brain are different from most of these artificial ones in at least three crucial ways: they emit spikes rather than graded outputs, their inputs and outputs are related dynamically rather than by piecewise-smooth functions, and they have no known way to coordinate arrays of synapses in separate forward and feedback pathways so that they change simultaneously and identically, as they do in backpropagation. Given these differences, it is unlikely that current deep learning algorithms can operate in the brain, but we that show these problems can be solved by two simple devices: learning rules can approximate dynamic input-output relations with piecewise-smooth functions, and a variation on the feedback alignment algorithm can train deep networks without having to coordinate forward and feedback synapses. Our results also show that deep spiking networks learn much better if each neuron computes an intracellular teaching signal that reflects that cell's nonlinearity. With this mechanism, networks of spiking neurons show useful learning in synapses at least nine layers upstream from the output cells and perform well compared to other spiking networks in the literature on the MNIST digit recognition task.

  9. Effects of age, sex, and treatment on weight-loss dynamics in overweight people.

    Science.gov (United States)

    Rojo-Tirado, Miguel A; Benito, Pedro J; Atienza, David; Rincón, Emiliano; Calderón, Francisco J

    2013-09-01

    The objective of this work was to evaluate how sex, age, and the kind of treatment followed affect weight loss in overweight men and women, as well as to develop an explanation for the evolution of weight-loss dynamics. The study consisted of 119 overweight participants (18-50 years old, body mass index >25 and exercised 3 times per week for 24 weeks, and their daily diet was restricted to a specific protocol during the testing period and controlled carefully. Body weight changes in the participants were evaluated every 15 days. Based on this study, we developed and validated different sets of equations to accurately capture the weight-loss dynamics. There were no significant differences in terms of global body weight changes from the statistical viewpoint, either regarding the carried out treatment or the individuals' ages. However, significant differences in weight-loss tendency were found depending on participant sex. We concluded that the effectiveness of different possible treatments for weight loss varies by sex and, based on our experimental observations, a quadratic function provides the most accurate model for capturing specific weight-loss dynamics. This trial is registered at Clinical Trials Gov.: number NCT01116856.

  10. The calciotropic hormone response to omega-3 supple-mentation during long-term weight-bearing exercise training in post menopausal women.

    Science.gov (United States)

    Tartibian, Bakhtiar; Maleki, Behzad Hajizadeh; Abbasi, Asghar

    2010-01-01

    The purpose of this study was to examine the effects of ingestion of omega-3 (n-3) and aerobic exercise intervention on the calcium regulating hormones in healthy postmenopausal women. To this end, 56 healthy sedentary postmenopausal women with mean age 57.7 ± 3.5 yrs participated in this study. Participants were randomly divided into exercise plus supple-ment (E+S; n = 14), exercise (E; n = 14), supplement (S; n = 14) and control (Con, n = 14) groups. The subjects in E+S and E groups performed aerobic exercise training (walking and jog-ging) up to 65% of exercise HRmax, three times a week for 16 weeks. Subjects in E+S and S groups were asked to consume 1000 mg/d omega-3 for 16 weeks. The blood ionized Calcium (Ca(+2)), Parathyroid hormone (PTH), estrogen and Calcitonin (CT) were measured before and after 16 weeks of exercise training. Results indicated that consuming 1000 mg·day(-1) omega-3 during 16 weeks and or the aerobic exercise, significantly increased CT (p = 0.001) in E+S, E and S groups and significantly decreased PTH (p = 0.001) levels in E+S and E groups, also significantly increased estrogen (p = 0.024) levels in E+S and E groups, but had no significant effects on blood Ca(+2) (p = 0.619) levels. The results of present study demonstrate that omega-3 in combination with regular aerobic exercise training have significant effects on serum CT, estrogen and PTH in non-athletic post-menopausal women, suggesting that participating in moderate intensity weight-bearing exercise and incorporating sources of omega-3 in the diet a possible intervention to help slow the loss of bone that occurs following menopause. Key pointsLong-term weight-bearing exercise was shown to prove positive effects on bone metabolism.Serum calciotropic hormone levels and Ca(+2) can be affected by exercise intensity as well as dura-tion.There is a good relationship between dietary omega-3 (n-3) and bone metabolism in post-menopausal women.Omega-3 in combination with long-term weight-bearing

  11. Growth hormone, IGF-I, and exercise effects on non-weight-bearing fast muscles of hypophysectomized rats

    Science.gov (United States)

    Grossman, E. J.; Grindeland, R. E.; Roy, R. R.; Talmadge, R. J.; Evans, J.; Edgerton, V. R.

    1997-01-01

    The effects of growth hormone (GH) or insulin-like growth factor I (IGF-I) with or without exercise (ladder climbing) in countering the effects of unweighting on fast muscles of hypophysectomized rats during 10 days of hindlimb suspension were determined. Compared with untreated suspended rats, muscle weights were 16-29% larger in GH-treated and 5-15% larger in IGF-I-treated suspended rats. Exercise alone had no effect on muscle weights. Compared with ambulatory control, the medial gastrocnemius weight in suspended, exercised rats was larger after GH treatment and maintained with IGF-I treatment. The combination of GH or IGF-I plus exercise in suspended rats resulted in an increase in size of each predominant fiber type, i.e., types I, I + IIa and IIa + IIx, in the medial gastrocnemius compared with untreated suspended rats. Normal ambulation or exercise during suspension increased the proportion of fibers expressing embryonic myosin heavy chain in hypophysectomized rats. The phenotype of the medial gastrocnemius was minimally affected by GH, IGF-I, and/or exercise. These results show that there is an IGF-I, as well as a GH, and exercise interactive effect in maintaining medial gastrocnemius fiber size in suspended hypophysectomized rats.

  12. Growth hormone, IGF-I, and exercise effects on non-weight-bearing fast muscles of hypophysectomized rats

    Science.gov (United States)

    Grossman, E. J.; Grindeland, R. E.; Roy, R. R.; Talmadge, R. J.; Evans, J.; Edgerton, V. R.

    1997-01-01

    The effects of growth hormone (GH) or insulin-like growth factor I (IGF-I) with or without exercise (ladder climbing) in countering the effects of unweighting on fast muscles of hypophysectomized rats during 10 days of hindlimb suspension were determined. Compared with untreated suspended rats, muscle weights were 16-29% larger in GH-treated and 5-15% larger in IGF-I-treated suspended rats. Exercise alone had no effect on muscle weights. Compared with ambulatory control, the medial gastrocnemius weight in suspended, exercised rats was larger after GH treatment and maintained with IGF-I treatment. The combination of GH or IGF-I plus exercise in suspended rats resulted in an increase in size of each predominant fiber type, i.e., types I, I + IIa and IIa + IIx, in the medial gastrocnemius compared with untreated suspended rats. Normal ambulation or exercise during suspension increased the proportion of fibers expressing embryonic myosin heavy chain in hypophysectomized rats. The phenotype of the medial gastrocnemius was minimally affected by GH, IGF-I, and/or exercise. These results show that there is an IGF-I, as well as a GH, and exercise interactive effect in maintaining medial gastrocnemius fiber size in suspended hypophysectomized rats.

  13. Determination of Dynamic Characteristics of the Frame Bearing Structures of the Vibrating Separating Machines

    Science.gov (United States)

    Piven, V. V.; Umanskaya, O. L.

    2016-08-01

    Within the vibrating separating machines the vibration displacement of the members is transferred to a frame bearing structure, and over it the movement is transferred again to the suspension brackets of the sieve separating surfaces and to the foundation, on which the machine is fixed. The forced oscillations of the sieve separating surfaces ensure the separation process, and the vibration, transferred from the frame structure, disturbs this process. It is necessary to ensure the vibration displacement of the separating surfaces within the fixed limitations by means of optimal design of the frame bearing surfaces. The aim of the work is to decrease adverse vibrations towards the technological separation process. The calculated and graphical relations, acquired according to the presented methods, enable to estimate the influence of various structure solutions on vibration displacements of the structure elements at the stage of design.

  14. Investigation of journal orbit and flow pattern in a dynamically loaded journal bearing

    DEFF Research Database (Denmark)

    Christiansen, Christian Kim; Walther, Jens Honore; Klit, Peder

    2017-01-01

    A hydrodynamic journal bearing has been investigated using both the traditional two-dimensional (2D) Reynolds equation, and the full solution being the three-dimensional (3D) Navier-Stokes equations. The two approaches are compared by performing an investigation of two inlet groove designs......: the axial and the circumferential groove, respectively, on a bearing with length-to-diameter ratio of 0.5 exposed to a sinusoidal load pattern. Pressure distributions, journal orbits and frictional losses are compared. The modelling of grooves by pressure boundary conditions versus geometric conditions...... is examined. It is investigated if the presence of a groove increases frictional losses and the increase relates to groove dimensions. Furthermore, the influence of the groove design on the flow field is studied using the 3D solution....

  15. On the nonlinear dynamics of two types of backup bearings - Theoretical and experimental aspects

    DEFF Research Database (Denmark)

    Lahriri, Said; Santos, Ilmar F.; Weber, Hans I.

    2012-01-01

    The possible contact between rotor and stator can for some cases be considered a serious malfunction that may lead to catastrophic failure. Rotor rub is considered a secondary phenomenon caused by a primary source that leads to a disruption of the normal operational condition. It arises from sudd...... at impact is forced to the center of the backup bearing and the lateral motion is mitigated. As a result of this, the rotor spin is kept constant. © 2012 American Society of Mechanical Engineers....

  16. Shape memory alloys applied to improve rotor-bearing system dynamics - an experimental investigation

    OpenAIRE

    2015-01-01

    tor-bearing systems have critical speeds and to pass through them is an ongoing challenge in the field of mechanical engineering. The incorporation of shape memory alloys in rotating systems has an increasing importance to improve system performance and to avoid potential damaging situations when passing through critical speeds. In this work, the feasibility of applying shape memory alloys to a rotating system is experimentally investigated. Shape memory alloys can change their stiffness with...

  17. Structural Dynamic Topology Optimisation of a Direct-Drive Single Bearing Wind Turbine Generator

    NARCIS (Netherlands)

    Kirschneck, M.; Polinder, H.; Van Ostayen, R.A.J.; Van Kempen, F.C.M.; Rixen, D.J.

    2015-01-01

    Reducing weight of off-shore wind turbine nacelles is currently a key driver of innovation within the wind turbine industry. Weight reduction will not only lead to smaller loads and thus smaller towers of the turbine, but also reduce logistic costs during the turbine’s installation. This holds even

  18. Diffusion-weighted imaging and dynamic contrast-enhanced MRI of experimental breast cancer bone metastases – A correlation study with histology

    Energy Technology Data Exchange (ETDEWEB)

    Merz, Maximilian [Department of Medical Physics in Radiology, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg (Germany); Department of Hematology, Oncology and Rheumatology, Heidelberg University Hospital, Im Neuenheimer Feld 410, 69120 Heidelberg (Germany); Seyler, Lisa; Bretschi, Maren; Semmler, Wolfhard [Department of Medical Physics in Radiology, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg (Germany); Bäuerle, Tobias, E-mail: tobias.baeuerle@uk-erlangen.de [Department of Medical Physics in Radiology, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg (Germany); Institute of Radiology, University Medical Center Erlangen, Palmsanlage 5, 90154 Erlangen (Germany)

    2015-04-15

    Purpose: To validate imaging parameters from diffusion-weighted imaging and dynamic contrast-enhanced MRI with immunohistology and to non-invasively assess microstructure of experimental breast cancer bone metastases. Materials and methods: Animals bearing breast cancer bone metastases were imaged in a clinical 1.5 T MRI scanner. HASTE sequences were performed to calculate apparent diffusion coefficients. Saturation recovery turbo FLASH sequences were conducted while infusing 0.1 mmol/l Gd–DTPA for dynamic contrast-enhanced MRI to quantify parameters amplitude A and exchange rate constant k{sub ep}. After imaging, bone metastases were analyzed immunohistologically. Results: We found correlations of the apparent diffusion coefficients from diffusion-weighted imaging with tumor cellularity as assessed with cell nuclei staining. Histological vessel maturity was correlated negatively with parameters A and k{sub ep} from dynamic contrast-enhanced MRI. Tumor size correlated inversely with cell density and vessel permeability as well as positively with mean vessel calibers. Parameters from the rim of bone metastases differed significantly from values of the center. Conclusion: In vivo diffusion-weighted imaging and dynamic contrast-enhanced MRI in experimental bone metastases provide information about tumor cellularity and vascularity and correlate well with immunohistology.

  19. Nonlinear Dynamic Response of an Unbalanced Flexible Rotor Supported by Elastic Bearings Lubricated with Piezo-Viscous Polar Fluids

    Directory of Open Access Journals (Sweden)

    Mustapha Lahmar

    2015-04-01

    Full Text Available On the basis of the V. K. Stokes micro-continuum theory, the effects of couple stresses on the nonlinear dynamic response of the unbalanced Jeffcott’s flexible rotor supported by layered hydrodynamic journal bearings is presented in this paper. A nonlinear transient modified Reynolds’ equation is derived and discretized by the finite element method to obtain the fluid-film pressure field as well as the film thickness by means of the implicit Euler method. The nonlinear orbits of the rotor center are determined by solving the nonlinear differential equations of motion with the explicit Euler’s scheme taking into account the flexibility of rotor. According to the obtained results, the combined effects of couple stresses due to the presence of polymer additives in lubricant and the pressure dependent viscosity on the nonlinear dynamic response of the rotor-bearing system are significant and cannot be ignored or overlooked. As expected, these effects are more noticeable for polymers characterized by higher length molecular chains.

  20. Scheduling Performance Evaluation of Logistics Service Supply Chain Based on the Dynamic Index Weight

    Directory of Open Access Journals (Sweden)

    Weihua Liu

    2014-01-01

    Full Text Available Scheduling is crucial to the operation of logistics service supply chain (LSSC, so scientific performance evaluation method is required to evaluate the scheduling performance. Different from general project performance evaluation, scheduling activities are usually continuous and multiperiod. Therefore, the weight of scheduling performance evaluation index is not unchanged, but dynamically varied. In this paper, the factors that influence the scheduling performance are analyzed in three levels which are strategic environment, operating process, and scheduling results. Based on these three levels, the scheduling performance evaluation index system of LSSC is established. In all, a new performance evaluation method proposed based on dynamic index weight will have three innovation points. Firstly, a multiphase dynamic interaction method is introduced to improve the quality of quantification. Secondly, due to the large quantity of second-level indexes and the requirements of dynamic weight adjustment, the maximum attribute deviation method is introduced to determine weight of second-level indexes, which can remove the uncertainty of subjective factors. Thirdly, an adjustment coefficient method based on set-valued statistics is introduced to determine the first-level indexes weight. In the end, an application example from a logistics company in China is given to illustrate the effectiveness of the proposed method.

  1. Rotor-bearing system integrated with shape memory alloy springs for ensuring adaptable dynamics and damping enhancement-Theory and experiment

    DEFF Research Database (Denmark)

    Enemark, Søren; Santos, Ilmar F.

    2016-01-01

    Helical pseudoelastic shape memory alloy (SMA) springs are integrated into a dynamic system consisting of a rigid rotor supported by passive magnetic bearings. The aim is to determine the utility of SMAs for vibration attenuation via their mechanical hysteresis, and for adaptation of the dynamic ...

  2. The Research of Influence of Blood upon the Dynamics of Artificial Ventricle Rotor on Active Magnetic Bearings

    Directory of Open Access Journals (Sweden)

    E. E. Ovsiannikova

    2015-01-01

    Full Text Available The article studies dynamics of rotor on active magnetic bearings within the mathematical model development of rotor in artificial ventricle. The problem of stabilization of rigid titanium rotor with magnetic inserts on active magnetic bearings is analyzed.The relevance of the research field is caused by high percent of people who are suffering from heart disease. The purposes of work are to create a mathematical model of the rigid rotor and position its center to meet specified requirements for displacement of no more than 0.2 millimeter while rotating with the speed from 5 000 rpm to 10 000 rpm in constant blood flow. The work of AMBs is based on the principle of active magnetic pendant of ferromagnetic solid. The stabilization in adjusted position is accomplished by magnetic forces, which affect the solid from the control electromagnets.The article presents initial data, design scheme, assumptions accepted to solve the problem and derivation of dynamic equation of rotating rigid rotor on AMBs. The decentralized control of magnetic pendant was implemented. The PD control – proportional differential control - was chosen as the base of control system. Its application is widespread due to the simplicity, industrial use and operation stability. The use of decentralized control in dynamics modeling of a rigid rotor in AMBs is physically occurred and has some advantages. One of the most important advantages is the calculation of control parameters by selection of appropriate values of rigidity and damping parameters.The analysis of rotor dynamics was conducted in MATLAB© software package.The modeling was performed to allow observing the system action while the parameters were varied.The conducted research showed that to meet the specified requirements of maximal rotor displacement no more than 0.2 mm the following values of coefficients were required:                                       and The stabilization of the rotor

  3. Additional weight bearing during exercise and estrogen in the rat: the effect on bone mass, turnover, and structure.

    Science.gov (United States)

    Tromp, A M; Bravenboer, N; Tanck, E; Oostlander, A; Holzmann, P J; Kostense, P J; Roos, J C; Burger, E H; Huiskes, R; Lips, P

    2006-12-01

    Mechanical loading and estrogen play important roles in bone homeostasis. The aim of this study was to evaluate the effects of mechanical loading on trabecular bone in the proximal femur of ovariectomized rats. We hypothesized that mechanical loading suppresses bone resorption and increases bone formation, which differs from the suppressive effects of estrogen on both resorption and formation. Furthermore, we expected to find changes in trabecular architecture elicited by the effects of mechanical loading and estrogen deficiency. Sixty female Wistar rats, 12 weeks old, were assigned to either the sedentary groups sham surgery (SED), ovariectomy (SED+OVX), and ovariectomy with estrogen replacement (SED+OVX+E2) or to the exercise groups EX, EX+OVX, EX+OVX+E2. Following ovariectomy, 5 microg 17beta-estradiol was given once weekly to the estrogen replacement groups. Exercise consisted of running with a backpack (load +/-20% of body weight) for 15 minutes/day, 5 days/week, for 19 weeks. Dual-energy X-ray absorptiometry (DXA) scans were performed before (T0), during (T6), and after (T19) the exercise period to obtain bone mineral content (BMC) and bone mineral density (BMD) data. After the exercise program, all rats were killed and right and left femora were dissected and prepared for micro-CT scanning and histomorphometric analysis of the proximal femoral metaphysis. After 19 weeks, increases in BMC (P = 0.010) and BMD (P = 0.031) were significant. At T19, mechanical loading had a significant effect on BMC (P = 0.025) and BMD (P = 0.010), and an interaction between mechanical loading and estrogen (P = 0.023) was observed. Bone volume and trabecular number decreased significantly after ovariectomy, while trabecular separation, mineralizing surface, bone formation rate, osteoclast surface, degree of anisotropy, and structure model index increased significantly after ovariectomy (P exercise. Estrogen deficiency resulted in a less dense and more oriented trabecular bone

  4. Dynamic modeling for rigid rotor bearing systems with a localized defect considering additional deformations at the sharp edges

    Science.gov (United States)

    Liu, Jing; Shao, Yimin

    2017-06-01

    Rotor bearing systems (RBSs) play a very valuable role for wind turbine gearboxes, aero-engines, high speed spindles, and other rotational machinery. An in-depth understanding of vibrations of the RBSs is very useful for condition monitoring and diagnosis applications of these machines. A new twelve-degree-of-freedom dynamic model for rigid RBSs with a localized defect (LOD) is proposed. This model can formulate the housing support stiffness, interfacial frictional moments including load dependent and load independent components, time-varying displacement excitation caused by a LOD, additional deformations at the sharp edges of the LOD, and lubricating oil film. The time-varying displacement model is determined by a half-sine function. A new method for calculating the additional deformations at the sharp edges of the LOD is analytical derived based on an elastic quarter-space method presented in the literature. The proposed dynamic model is utilized to analyze the influences of the housing support stiffness and LOD sizes on the vibration characteristics of the rigid RBS, which cannot be predicted by the previous dynamic models in the literature. The results show that the presented method can give a new dynamic modeling method for vibration formulation for a rigid RBS with and without the LOD on the races.

  5. DYNAMICS OF THE WEIGHTED AVERAGE CUSTOMS FARE AND ITS INFLUENCE ON COMPETITIVENESS OF RUSSIAN MANUFACTURERS

    Directory of Open Access Journals (Sweden)

    Syromyatnikov D. A.

    2013-12-01

    Full Text Available The article presents an analysis of the dynamics of the weighted average customs fare on the competitiveness of economic subjects. The characteristic of the current state of competitiveness of Russian companies after joining the World Trade Organization is given

  6. Measurement of brain oxygenation changes using dynamic T1-weighted imaging

    DEFF Research Database (Denmark)

    Haddock, Bryan; Larsson, Henrik B W; Hansen, Adam E

    2013-01-01

    Magnetic resonance imaging (MRI) has proven useful in evaluating oxygenation in several types of tissue and blood. This study evaluates brain tissue oxygenation changes between normoxia and hyperoxia in healthy subjects using dynamic T1 and T2*-weighted imaging sequences. The change in FiO2 induced...... in the brain with a potential to provide quantitative information on tissue oxygenation....

  7. Fiducial marker-based correction for involuntary motion in weight-bearing C-arm CT scanning of knees. II. Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jang-Hwan [Department of Radiology, Stanford University, Stanford, California 94305 and Department of Mechanical Engineering, Stanford University, Stanford, California 94305 (United States); Maier, Andreas; Keil, Andreas; McWalter, Emily J.; Gold, Garry E.; Fahrig, Rebecca [Department of Radiology, Stanford University, Stanford, California 94305 (United States); Pal, Saikat [Biomedical Engineering Department, California Polytechnic State University, San Luis Obispo, California 93407 (United States); Beaupré, Gary S. [Musculoskeletal Research Laboratory, VA Palo Alto Health Care System, Palo Alto, California 94304 (United States)

    2014-06-15

    Purpose: A C-arm CT system has been shown to be capable of scanning a single cadaver leg under loaded conditions by virtue of its highly flexible acquisition trajectories. In Part I of this study, using the 4D XCAT-based numerical simulation, the authors predicted that the involuntary motion in the lower body of subjects in weight-bearing positions would seriously degrade image quality and the authors suggested three motion compensation methods by which the reconstructions could be corrected to provide diagnostic image quality. Here, the authors demonstrate that a flat-panel angiography system is appropriate for scanning both legs of subjectsin vivo under weight-bearing conditions and further evaluate the three motion-correction algorithms using in vivo data. Methods: The geometry of a C-arm CT system for a horizontal scan trajectory was calibrated using the PDS-2 phantom. The authors acquired images of two healthy volunteers while lying supine on a table, standing, and squatting at several knee flexion angles. In order to identify the involuntary motion of the lower body, nine 1-mm-diameter tantalum fiducial markers were attached around the knee. The static mean marker position in 3D, a reference for motion compensation, was estimated by back-projecting detected markers in multiple projections using calibrated projection matrices and identifying the intersection points in 3D of the back-projected rays. Motion was corrected using three different methods (described in detail previously): (1) 2D projection shifting, (2) 2D deformable projection warping, and (3) 3D rigid body warping. For quantitative image quality analysis, SSIM indices for the three methods were compared using the supine data as a ground truth. Results: A 2D Euclidean distance-based metric of subjects’ motion ranged from 0.85 mm (±0.49 mm) to 3.82 mm (±2.91 mm) (corresponding to 2.76 to 12.41 pixels) resulting in severe motion artifacts in 3D reconstructions. Shifting in 2D, 2D warping, and 3D

  8. Application of the segment weight dynamic movement method to the normalization of gait EMG amplitude.

    Science.gov (United States)

    Nishijima, Y; Kato, T; Yoshizawa, M; Miyashita, M; Iida, H

    2010-06-01

    This study aims at determining the applicability of a segment weight dynamic movement (SWDM) method as an alternative for normalizing gait EMGs in comparison with the conventional isometric maximal voluntary contraction (MVC) method. The SWDM method employs reference exercises, each being a dynamic, repetitive movement of a joint under the load of the segment weight (i.e., the total weight of all segments distal to the joint). EMG amplitudes of 28 healthy male subjects walking at 120 steps/min were normalized by the two methods. CV and VR were used to assess the inter-individual variability of both the normalized gait EMG for 8 muscles. The CV and VR values attained with the two methods were close to each other, as well as to those obtained by other researchers using the isometric MVC method. These results suggest that the SWDM method has a comparable level of applicability to gait EMG normalization as the isometric MVC method.

  9. Dynamic Optimal CCI Weight Channel Pre-evaluative Assignment in Adaptive Array Antenna System

    Institute of Scientific and Technical Information of China (English)

    MENG Weixiao; ZHANG Naitong

    2001-01-01

    Dynamic Channel Assignment (DCA)together with Adaptive Array Antenna (AAA) takes an important part in cellular mobile communication system. In this paper, a conception of co-channel in terference (CCI) quantification is advanced in multicell 8-element circular adaptive array antenna system.Normalized CCI weight relational expression, which is concerned in distance and look angle difference is sublimed from experiential sampling, induction and non-linear fitting. Then an algorithm of optimal CCI weight channel pre-evaluation is proposed as a solution of dynamic channel assignment. The least sum of weight value before assignment is used to pre-evaluate the performance of all the channels. Based on an approached practical cellular model, a series of systemclassed simulations are accomplished. Simulation resuits show that this algorithm is quite effective: system capacity is increased greatly; traffic block probabilities are decreased remarkably; nice channel quality is maintained; the reliability of DCA is enhanced; the higher frequency utilization efficiency is also obtained.

  10. Effect of PEO molecular weight on the miscibility and dynamics in epoxy/PEO blends.

    Science.gov (United States)

    Lu, Shoudong; Zhang, Rongchun; Wang, Xiaoliang; Sun, Pingchuan; Lv, Weifeng; Liu, Qingjie; Jia, Ninghong

    2015-11-01

    In this work, the effect of poly(ethylene oxide) (PEO) molecular weight in blends of epoxy (ER) and PEO on the miscibility, inter-chain weak interactions and local dynamics were systematically investigated by multi-frequency temperature modulation DSC and solid-state NMR techniques. We found that the molecular weight (M(w)) of PEO was a crucial factor in controlling the miscibility, chain dynamics and hydrogen bonding interactions between PEO and ER. A critical PEO molecular weight (M(crit)) around 4.5k was found. PEO was well miscible with ER when the molecular weight was below M(crit), where the chain motion of PEO was restricted due to strong inter-chain hydrogen bonding interactions. However, for the blends with high molecular weight PEO (M(w) > M(crit)), the miscibility between PEO and ER was poor, and most of PEO chains were considerably mobile. Finally, polarization inversion spin exchange at magic angle (PISEMA) solid-state NMR experiment further revealed the different mobility of the PEO in ER/PEO blends with different molecular weight of PEO at molecular level. Based on the DSC and NMR results, a tentative model was proposed to illustrate the miscibility in ER/PEO blends.

  11. REGULAR PATTERN MINING (WITH JITTER ON WEIGHTED-DIRECTED DYNAMIC GRAPHS

    Directory of Open Access Journals (Sweden)

    A. GUPTA

    2017-02-01

    Full Text Available Real world graphs are mostly dynamic in nature, exhibiting time-varying behaviour in structure of the graph, weight on the edges and direction of the edges. Mining regular patterns in the occurrence of edge parameters gives an insight into the consumer trends over time in ecommerce co-purchasing networks. But such patterns need not necessarily be precise as in the case when some product goes out of stock or a group of customers becomes unavailable for a short period of time. Ignoring them may lead to loss of useful information and thus taking jitter into account becomes vital. To the best of our knowledge, no work has been yet reported to extract regular patterns considering a jitter of length greater than unity. In this article, we propose a novel method to find quasi regular patterns on weight and direction sequences of such graphs. The method involves analysing the dynamic network considering the inconsistencies in the occurrence of edges. It utilizes the relation between the occurrence sequence and the corresponding weight and direction sequences to speed up this process. Further, these patterns are used to determine the most central nodes (such as the most profit yielding products. To accomplish this we introduce the concept of dynamic closeness centrality and dynamic betweenness centrality. Experiments on Enron e-mail dataset and a synthetic dynamic network show that the presented approach is efficient, so it can be used to find patterns in large scale networks consisting of many timestamps.

  12. Sea Surface Temperature Modeling using Radial Basis Function Networks With a Dynamically Weighted Particle Filter

    KAUST Repository

    Ryu, Duchwan

    2013-03-01

    The sea surface temperature (SST) is an important factor of the earth climate system. A deep understanding of SST is essential for climate monitoring and prediction. In general, SST follows a nonlinear pattern in both time and location and can be modeled by a dynamic system which changes with time and location. In this article, we propose a radial basis function network-based dynamic model which is able to catch the nonlinearity of the data and propose to use the dynamically weighted particle filter to estimate the parameters of the dynamic model. We analyze the SST observed in the Caribbean Islands area after a hurricane using the proposed dynamic model. Comparing to the traditional grid-based approach that requires a supercomputer due to its high computational demand, our approach requires much less CPU time and makes real-time forecasting of SST doable on a personal computer. Supplementary materials for this article are available online. © 2013 American Statistical Association.

  13. Fixed versus dynamic co-occurrence windows in TextRank term weights for information retrieval

    DEFF Research Database (Denmark)

    Lu, Wei; Cheng, Qikai; Lioma, Christina

    2012-01-01

    TextRank is a variant of PageRank typically used in graphs that represent documents, and where vertices denote terms and edges denote relations between terms. Quite often the relation between terms is simple term co-occurrence within a fixed window of k terms. The output of TextRank when applied...... iteratively is a score for each vertex, i.e. a term weight, that can be used for information retrieval (IR) just like conventional term frequency based term weights. So far, when computing TextRank term weights over co-occurrence graphs, the window of term co-occurrence is always fixed. This work departs from...... this, and considers dynamically adjusted windows of term co-occurrence that follow the document structure on a sentence- and paragraph-level. The resulting TextRank term weights are used in a ranking function that re-ranks 1000 initially returned search results in order to improve the precision...

  14. MODELING AND ANALYSIS OF DYNAMICS IN BEARING SYSTEM OF DRILLING, MILLING AND BORING MACHINE WITH MONO-COLUMN

    Directory of Open Access Journals (Sweden)

    Yu. V. Vasilevich

    2015-01-01

    Full Text Available  FEM-analysis of dynamics in the bearing system of a heavy-duty machine tool has been carried out in the paper. This is a prospective variant for a large-size multi-purpose machine tool with a horizontal sliding ram. A saddle and a ram are moving vertically along a subtle mono-column. A rigid double-column is used in the existing analog machine tool. A static, modal and harmonic analysis of the bearing system with the mono-column has been made in the paper. It has been done with the help of FEM-simulation prior to fabrication of a prototype sample. Previously conducted calculations for the analog machine tool have shown good compatibility of FEM-calculation with experiments.Six common machine tool resonances have been revealed for the bearing system. Their oscillating cutting forces are actively exciting three-four resonance modes. Ranges of a flexure-torsion resonance (20–40 Hz and nose-diving resonances (70–90 Hz have been determined in the paper. The paper shows that the range of multi-wave resonances starts significantly higher from 140 Hz. These resonances are interconnected with bending oscillations of the ram and bucklings of the column walls which are matched with the oscillations. The paper demonstrates stability in resonance pattern. The torsional resonance of the column on the frequency of nearly 40 Hz is considered as the more dangerous one. Spindle rigidity goes down up to 3.8 Н/μm. It is possible to observe self-stabilization of the torsional resonance. Frequency of the torsional oscillations is practically unchangeable when there is a lifting or lowering down of the saddle and the ram. It is related to the migration of dynamical axis of torsion.Frequency-response characteristics of the bearing system have been constructed for various saddle positions on the column. Three frequency intervals that make it possible to carry out machining operation have been determined in the paper. The first interval is a static one. The

  15. Effects of Unbalance Location on Dynamic Characteristics of High-speed Gasoline Engine Turbocharger with Floating Ring Bearings

    Institute of Scientific and Technical Information of China (English)

    WANG Longkai; BIN Guangfu; LI Xuejun; LIU Dingqu

    2016-01-01

    For the high-speed gasoline engine turbocharger rotor, due to the heterogeneity of multiple parts material, manufacturing and assembly errors, running wear in impeller and uneven carbon of turbine, the random unbalance usually can be developed which will induce excessive rotor vibration, and even lead to nonlinear vibration accidents. However, the investigation of unbalance location on the nonlinear high-speed turbocharger rotordynamic characteristics is less. In order to discuss the rotor unbalance location effects of turbocharger with nonlinear floating ring bearings(FRBs), the realistic turbocharger of gasoline engine is taken as a research object. The rotordynamic equations of motion under the condition of unbalance are derived by applied unbalance force and nonlinear oil film force of FRBs. The FE model of turbocharger rotor-bearing system is modeled which includes the unbalance excitation and nonlinear FRBs. Under the conditions of four different applied locations of unbalance, the nonlinear transient analyses are performed based on the rotor FEM. The differences of dynamic behavior are obvious to the turbocharger rotor systems for four conditions, and the bifurcation phenomena are different. From the results of waterfall and transient response analysis, the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different from the different unbalance locations, and the non-synchronous vibration does not occur in the turbocharger and the amplitude is relative stable and minimum under the condition 4. The turbocharger vibration and non-synchronous components could be reduced or suppressed by controlling the applied location of unbalance, which is helpful for the dynamic design, fault diagnosis and vibration control of the high-speed gasoline engine turbochargers.

  16. Image-based compensation for involuntary motion in weight-bearing C-arm cone-beam CT scanning of knees

    Science.gov (United States)

    Unberath, Mathias; Choi, Jang-Hwan; Berger, Martin; Maier, Andreas; Fahrig, Rebecca

    2015-03-01

    We previously introduced four fiducial marker-based strategies to compensate for involuntary knee-joint motion during weight-bearing C-arm CT scanning of the lower body. 2D methods showed significant reduction of motion- related artifacts, but 3D methods worked best. However, previous methods led to increased examination times and patient discomfort caused by the marker attachment process. Moreover, sub-optimal marker placement may lead to decreased marker detectability and therefore unstable motion estimates. In order to reduce overall patient discomfort, we developed a new image-based 2D projection shifting method. A C-arm cone-beam CT system was used to acquire projection images of five healthy volunteers at various flexion angles. Projection matrices for the horizontal scanning trajectory were calibrated using the Siemens standard PDS-2 phantom. The initial reconstruction was forward projected using maximum-intensity projections (MIP), yielding an estimate of a static scan. This estimate was then used to obtain the 2D projection shifts via registration. For the scan with the most motion, the proposed method reproduced the marker-based results with a mean error of 2.90 mm +/- 1.43 mm (compared to a mean error of 4.10 mm +/- 3.03 mm in the uncorrected case). Bone contour surrounding modeling clay layer was improved. The proposed method is a first step towards automatic image-based, marker-free motion-compensation.

  17. Electromyographic preactivation pattern of the gluteus medius during weight-bearing functional tasks in women with and without anterior knee pain.

    Science.gov (United States)

    Nakagawa, Theresa H; Muniz, Thiago B; Baldon, Rodrigo M; Maciel, Carlos D; Amorim, César F; Serrão, Fábio V

    2011-01-01

    Proximal factors have been proposed to influence the biomechanics of the patellofemoral joint. A delayed or diminished gluteus medius (GM) activation, before the foot contact on the ground during functional activities could lead to excessive femur adduction and internal rotation and be associated with anterior knee pain (AKP). There are few studies on this topic and the results were inconclusive, therefore, it is necessary to investigate the GM preactivation pattern during functional activities. To compare the GM electromyographic (EMG) preactivation pattern during walking, descending stairs and in single leg jump task in women with and without AKP. Nine women clinically diagnosed with AKP and ten control subjects with no history of knee injury participated in this study. We evaluated GM EMG linear envelope before the foot contact on the ground during walking and GM onset time and EMG linear envelope during descending stairs as well as in a single leg vertical jump. Mann-Whitney U tests were used to determine the between-group differences in GM EMG preactivation pattern. No between-group differences were observed in GM linear envelope during walking (P=0.41), GM onset time and linear envelope during descending stairs (P=0.17 and P=0.15) and single leg jump (P=0.81 and P=0.33). Women with AKP did not demonstrated altered GM preactivation pattern during functional weight bearing activities. Our results did not support the hypothesis that poor GM preactivation pattern could be associated with AKP.

  18. Dynamic Mesh Adaptation for Front Evolution Using Discontinuous Galerkin Based Weighted Condition Number Mesh Relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Greene, Patrick T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Schofield, Samuel P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Nourgaliev, Robert [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-06-21

    A new mesh smoothing method designed to cluster mesh cells near a dynamically evolving interface is presented. The method is based on weighted condition number mesh relaxation with the weight function being computed from a level set representation of the interface. The weight function is expressed as a Taylor series based discontinuous Galerkin projection, which makes the computation of the derivatives of the weight function needed during the condition number optimization process a trivial matter. For cases when a level set is not available, a fast method for generating a low-order level set from discrete cell-centered elds, such as a volume fraction or index function, is provided. Results show that the low-order level set works equally well for the weight function as the actual level set. Meshes generated for a number of interface geometries are presented, including cases with multiple level sets. Dynamic cases for moving interfaces are presented to demonstrate the method's potential usefulness to arbitrary Lagrangian Eulerian (ALE) methods.

  19. Dynamic mesh adaptation for front evolution using discontinuous Galerkin based weighted condition number relaxation

    Science.gov (United States)

    Greene, Patrick; Schofield, Sam; Nourgaliev, Robert

    2016-11-01

    A new mesh smoothing method designed to cluster cells near a dynamically evolving interface is presented. The method is based on weighted condition number mesh relaxation with the weight function being computed from a level set representation of the interface. The weight function is expressed as a Taylor series based discontinuous Galerkin (DG) projection, which makes the computation of the derivatives of the weight function needed during the condition number optimization process a trivial matter. For cases when a level set is not available, a fast method for generating a low-order level set from discrete cell-centered fields, such as a volume fraction or index function, is provided. Results show that the low-order level set works equally well for the weight function as the actual level set. The method retains the excellent smoothing capabilities of condition number relaxation, while providing a method for clustering mesh cells near regions of interest. Dynamic cases for moving interfaces are presented to demonstrate the method's potential usefulness as a mesh relaxer for arbitrary Lagrangian Eulerian (ALE) methods. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  20. Dynamic analysis of double-row self-aligning ball bearings due to applied loads, internal clearance, surface waviness and number of balls

    Science.gov (United States)

    Zhuo, Yaobin; Zhou, Xiaojun; Yang, Chenlong

    2014-11-01

    In this paper, a three degrees of freedom (dof) model was established for a double-row self-aligning ball bearing (SABB) system, and was applied to study the dynamic behavior of the system during starting process and constant speed rotating process. A mathematical model was developed concerning stiffness and damping characteristics of the bearing, as well as three-dimensional applied load, rotor centrifugal force, etc. Balls and races were all considered as nonlinear springs, and the contact force between ball and race was calculated based on classic Hertzian elastic contact deformation theory and deformation compatibility theory. The changes of each ball's contact force and loaded angle of each row were taken into account. In order to solve the nonlinear dynamical equilibrium equations of the system, these equations were rewritten as differential equations and the fourth order Runge-Kutta method was used to solve the equations iteratively. In order to verify accuracy of the dynamical model and correctness of the numerical solution method, a kind of SABB-BRF30 was chosen for case studies. The effects of several important governing parameters, such as radial and axial applied loads, normal internal, inner and outer races waviness, and number of balls were investigated. These parametric studies led to a complete characterization of the shaft-bearing system vibration transmission. The research provided a theoretical reference for new type bearing design, shaft-bearing system kinetic analysis, optimal design, etc.

  1. The Dynamics Simulation of the Deep Groove Ball Bearing Based on LS-DYNA%基于LS-DYNA深沟球轴承的动力学仿真

    Institute of Scientific and Technical Information of China (English)

    康晓晨; 乔长帅; 吴楠

    2013-01-01

    基于ANSYS/LS-DYNA建立了深沟球轴承的有限元模型,有效处理了考虑摩擦条件的接触问题,实现了深沟球轴承显式动力学的运动过程仿真。并以6203深沟球轴承为例,进行了动力学仿真与分析。%The finite element model of deep groove ball bearing was established based on ANSYS/LS-DYNA, effectively deal with the contact problem with friction condition,the explicit dynamic simulation of deep groove ball bearing was realized. Taking the 6203 deep groove ball bearing as an example,the dynamics simulation and analysis is carried out.

  2. Management of weight-bearing area fracture of acetabulum%涉及臼顶负重区髋臼骨折的诊疗与对策

    Institute of Scientific and Technical Information of China (English)

    章云童; 王攀峰; 张春才

    2011-01-01

    Acetabulum, as the important factor for weight bearing of the upper body, has its unique anatomic features and complicated physiological function.The integrity and stability of the lunata articular surface in the dome region of acetabulum,is the important base to bear the physiological function of acetabulum.The fracture related to this part will cause relation change of contact area and stress between head of femur and acetabulum.Furthermore,the deep anatomical position of the dome region ,the complicated surrounding anatomical relation,and the irregular bony structure will also increase the difficulty of surgical treatment.Especially for some complicated comminuted or compressed fracture,even with good explosions, it is hard to get satisfied anatomical reduction.Consequently ,forward traumatic arthritis has greater probability of occurrence.Therefore,the clinical research on the fracture in the dome region of acetabulum was getting more and more attention worldly.This paper intended to review the relation of fracture classifications and anatomic features, physiological function, diagnostic criteria, and also its clinical treating countermeasure.%髋臼作为承载上半身体重的重要关节,具有独特的解剖学特点及复杂的生理功能,而臼顶区月状关节面的完整性与稳定性是承担髋臼生理功能的重要基础,涉及此处骨折会导致股骨头与髋臼之间的接触面积和应力等关系发生改变,加之臼项区解剖位置深在,周围解剖关系复杂,骨性结构不规则,手术治疗难度较大,特别是一些复杂的粉碎压缩骨折,即使达到良好暴露也难以达到满意的解剖复位,从而使远期创伤性关节炎的发生概率大大增加.因此涉及臼顶负重区的髋臼骨折的基础及临床研究在国内外的重视程度逐年增高,本文就其解剖学特点及生理功能、诊断标准与骨折分型的关系、临床治疗对策等做一综述.

  3. Dynamic Optimization Method on Electromechanical Coupling System by Exponential Inertia Weight Particle Swarm Algorithm

    Institute of Scientific and Technical Information of China (English)

    LI Qiang; WU Jianxin; SUN Yan

    2009-01-01

    Dynamic optimization of electromechanical coupling system is a significant engineering problem in the field of mechatronics. The performance improvement of electromechanical equipment depends on the system design parameters. Aiming at the spindle unit of refitted machine tool for solid rocket, the vibration acceleration of tool is taken as objective function, and the electromechanical system design parameters are appointed as design variables. Dynamic optimization model is set up by adopting Lagrange-Maxwell equations, Park transform and electromechanical system energy equations. In the procedure of seeking high efficient optimization method, exponential function is adopted to be the weight function of particle swarm optimization algorithm. Exponential inertia weight particle swarm algorithm(EPSA), is formed and applied to solve the dynamic optimization problem of electromechanical system. The probability density function of EPSA is presented and used to perform convergence analysis. After calculation, the optimized design parameters of the spindle unit are obtained in limited time period. The vibration acceleration of the tool has been decreased greatly by the optimized design parameters. The research job in the paper reveals that the problem of dynamic optimization of electromechanical system can be solved by the method of combining system dynamic analysis with reformed swarm particle optimization. Such kind of method can be applied in the design of robots, NC machine, and other electromechanical equipments.

  4. Modeling Topology and Nonlinear Dynamical Behavior of the Weighted Scale-Free Networks

    Institute of Scientific and Technical Information of China (English)

    YANG Qiu-Ying; ZHANG Gui-Qing; ZHANG Ying-Yue; CHEN Tian-Lun

    2008-01-01

    An improved weighted scale-free network,which has two evolution mechanisms:topological growth and strength dynamics,has been introduced.The topology structure of the model will be explored in details in this work.The evolution driven mechanism of Olami-Feder-Christensen (OFC) model is added to our model to study the self-organized criticality and the dynamical behavior.We also.consider attack mechanism and the study of the model with attack is also investigated in this paper.We find there axe differences between the model with attack and without attack.

  5. A dynamical model for describing behavioural interventions for weight loss and body composition change.

    Science.gov (United States)

    Navarro-Barrientos, J-Emeterio; Rivera, Daniel E; Collins, Linda M

    2011-01-12

    We present a dynamical model incorporating both physiological and psychological factors that predicts changes in body mass and composition during the course of a behavioral intervention for weight loss. The model consists of a three-compartment energy balance integrated with a mechanistic psychological model inspired by the Theory of Planned Behavior (TPB). The latter describes how important variables in a behavioural intervention can influence healthy eating habits and increased physical activity over time. The novelty of the approach lies in representing the behavioural intervention as a dynamical system, and the integration of the psychological and energy balance models. Two simulation scenarios are presented that illustrate how the model can improve the understanding of how changes in intervention components and participant differences affect outcomes. Consequently, the model can be used to inform behavioural scientists in the design of optimised interventions for weight loss and body composition change.

  6. 球轴承涡轮增压器轴承-转子系统动力学分析与应用∗%Analysis and Application of Rotor Dynamics of Bearing-rotor System of Ball Bearing Turbocharger

    Institute of Scientific and Technical Information of China (English)

    刘大诚; 史立伟

    2014-01-01

    相比于普遍使用的浮动轴承,在涡轮增压器中使用球轴承具有机械效率高和加速响应快的优势。以车用球轴承涡轮增压器为研究对象,用有限元法对轴承-转子系统进行了转子动力学特性的研究,对轴承-转子系统的临界转速进行了计算与分析,这是判断转子工作转速是否稳定和涡轮增压器工作是否可靠的重要依据;建立了增压器模型,并对比了计算结果和试验结果,证明了方法的可行性。通过整机试验表明,球轴承涡轮增压器能够满足当前车用发动机的需求,能够提高发动机的工作性能。%Turbochargers in ball bearings have much advantage than floating busing bearings,such as high mechanical efficiency and fast accelerate response.The paper studied obj ect that was ball bearing turbocharger of vehicle,researched on rotor dynamic characteristics of bearing-rotor system,and used finite element method to analyze the critical speed of bearing-rotor system which is the very important basis to j udging whether the rotor work is stable and turbocharger work is reliable. Comparing and analyzing the computing and experimental results,it proves the feasibility and accuracy of setting up model on bearing-rotor system of ball bearing turbocharger.After the test of prototype,it was proved that ball bearing turbo-charger can meet the current needs of vehicle engine and improve the working performance of the engine.

  7. Therapeutic Effect of Weight Bearing Exercise on Stroke Patients with Osteoporosis%承重运动对脑卒中患者骨质疏松症的疗效

    Institute of Scientific and Technical Information of China (English)

    徐东红; 尚霄东; 王培良; 王惠芳

    2014-01-01

    Objective:To confirm the therapeutic effect of weight-bearing exercise on bone mineral density and low back pain in stroke patients with Osteoporosis .Methods:174 stroke patients with osteoporosis ,who were treated in Shanghai yangzhi rehabilitation hospital during January 2011 and October 2013 ,were randomly divided into control group (n=60 ,conventional therapy) ,weight-bearing exercise group 1(n=56 ,weight-bearing exercise of moderate in-tensity for 40 minutes daily)and weight-bearing exercise group 2(n=58 ,weight-bearing exercise of moderate intensity for 80 minutes daily) .All patients were treated with weight bearing exercise for 8 months .The BMD of all patients were measured by Dual energy X-ray absorptiometry and the assessment of low back pain was done by Visual Analog Scale (VAS) before and after treatment .Results:Both the BMD and symptom of patients treated with weight-bearing exercise for 80 minutes daily improved significantly .Neither the BMD nor the symptom of low back pain in both con-ventional therapy patients and 40 minutes weight-bearing exercise patients was improved .Conclusion:Weight bearing exercise had no obvious effect either on the increasing of bone mineral density in femoral neck or lightening the symp-tom of low back pain unless it continues for enough time .%目的:明确承重运动疗法对脑卒中患者骨质疏松症的疗效。方法:选择2011年1月-2013年10月我院收治的脑卒中合并骨质疏松症患者174例,随机分为承重运动治疗组1(56例,承重运动40min/d)、承重运动治疗组2(58例,承重运动80min/d)与对照组(60例,常规治疗),干预8个月。治疗前、后用双能X线骨密度仪检查患者股骨颈骨密度值(BMD),视觉模拟评分法(VAS法)评估患者腰背痛症状。结果:每日行80min承重运动疗法的患者股骨颈BMD较治疗前明显提升,腰背痛症状明显改善;每日行40min承重运动及常规治疗不能提升股骨

  8. Tide forecasting method based on dynamic weight distribution for operational evaluation

    Institute of Scientific and Technical Information of China (English)

    Shao-wei QIU; Zeng-chuan DONG; Fen XU; Li SUN; Sheng CHEN

    2009-01-01

    Through analysis of operational evaluation factors for tide forecasting, the relationship between the evaluation factors and the weights of forecasters was examined. A tide forecasting method based on dynamic weight distribution for operational evaluation was developed, and multiple-forecaster synchronous forecasting was realized while avoiding the instability cased by only one forecaster. Weights were distributed to the forecasters according to each one's forecast precision. An evaluation criterion for the professional level of the forecasters was also built. The eligibility rates of forecast results demonstrate the skill of the forecasters and the stability of their forecasts. With the developed tide forecasting method, the precision and reasonableness of tide forecasting are improved. The application of the present method to tide forecasting at the Huangpu Park tidal station demonstrates the validity of the method.

  9. Decrease in dynamic viscosity and average molecular weight of alginate from Laminaria digitata during alkaline extraction

    OpenAIRE

    Vauchel, Peggy; Arhaliass, Abdellah; Legrand, Jack; Kaas, Raymond; Baron, Regis

    2008-01-01

    Alginates are natural polysaccharides that are extracted from brown seaweeds and widely used for their rheological properties. The central step in the extraction protocol used in the alginate industry is the alkaline extraction, which requires several hours. In this study, a significant decrease in alginate dynamic viscosity was observed after 2 h of alkaline treatment. Intrinsic viscosity and average molecular weight of alginates from alkaline extractions 1-4 h in duration were determined, i...

  10. Dynamic Particle Weight Remapping in Hybrid PIC Hall-effect Thruster Simulation

    Science.gov (United States)

    2015-05-01

    International Electric Propulsion Conference and 6th Nano-satellite Symposium Hyogo-Kobe, Japan July 410, 2015 Robert Martin∗ ERC Incorporated, Huntsville...Algorithms, . 8Koo, J. and Martin, R., Pseudospectral model for hybrid PIC Hall -eect thruster simulation, 34th Int. Electric Propul- sion Conf...Paper 3. DATES COVERED (From - To) May 2015-July 2015 4. TITLE AND SUBTITLE Dynamic Particle Weight Remapping in Hybrid PIC Hall -effect Thruster

  11. Dynamic mesh adaptation for front evolution using discontinuous Galerkin based weighted condition number relaxation

    Science.gov (United States)

    Greene, Patrick T.; Schofield, Samuel P.; Nourgaliev, Robert

    2017-04-01

    A new mesh smoothing method designed to cluster cells near a dynamically evolving interface is presented. The method is based on weighted condition number mesh relaxation with the weight function computed from a level set representation of the interface. The weight function is expressed as a Taylor series based discontinuous Galerkin projection, which makes the computation of the derivatives of the weight function needed during the condition number optimization process a trivial matter. For cases when a level set is not available, a fast method for generating a low-order level set from discrete cell-centered fields, such as a volume fraction or index function, is provided. Results show that the low-order level set works equally well as the actual level set for mesh smoothing. Meshes generated for a number of interface geometries are presented, including cases with multiple level sets. Dynamic cases with moving interfaces show the new method is capable of maintaining a desired resolution near the interface with an acceptable number of relaxation iterations per time step, which demonstrates the method's potential to be used as a mesh relaxer for arbitrary Lagrangian Eulerian (ALE) methods.

  12. Dynamic modeling of methylprednisolone effects on body weight and glucose regulation in rats

    Science.gov (United States)

    Fang, Jing; DuBois, Debra C.; He, Yang; Almon, Richard R.

    2012-01-01

    Influences of methylprednisolone (MPL) and food consumption on body weight (BW), and the effects of MPL on glycemic control including food consumption and the dynamic interactions among glucose, insulin, and free fatty acids (FFA) were evaluated in normal male Wistar rats. Six groups of animals received either saline or MPL via subcutaneous infusions at the rate of 0.03, 0.1, 0.2, 0.3 and 0.4 mg/kg/h for different treatment periods. BW and food consumption were measured twice a week. Plasma concentrations of MPL and corticosterone (CST) were determined at animal sacrifice. Plasma glucose, insulin, and FFA were measured at various times after infusion. Plasma MPL concentrations were simulated by a two-compartment model and used as the driving force in the pharmacodynamic (PD) analysis. All data were modeled using ADAPT 5. The MPL treatments caused reduction of food consumption and body weights in all dosing groups. The steroid also caused changes in plasma glucose, insulin, and FFA concentrations. Hyper-insulinemia was achieved rapidly at the first sampling time of 6 h; significant elevations of FFA were observed in all drug treatment groups; whereas only modest increases in plasma glucose were observed in the low dosing groups (0.03 and 0.1 mg/kg/h). Body weight changes were modeled by dual actions of MPL: inhibition of food consumption and stimulation of weight loss, with food consumption accounting for the input of energy for body weight. Dynamic models of glucose and insulin feedback interactions were extended to capture the major metabolic effects of FFA: stimulation of insulin secretion and inhibition of insulin-stimulated glucose utilization. These models of body weight and glucose regulation adequately captured the experimental data and reflect significant physiological interactions among glucose, insulin, and FFA. These mechanism-based PD models provide further insights into the multi-factor control of this essential metabolic system. PMID:21394487

  13. Ultrafast excited state dynamics of Pt(II) chromophores bearing multiple infrared absorbers.

    Science.gov (United States)

    Glik, Elena A; Kinayyigit, Solen; Ronayne, Kate L; Towrie, Michael; Sazanovich, Igor V; Weinstein, Julia A; Castellano, Felix N

    2008-08-04

    The paper reports the synthesis, structural characterization, electrochemistry, ultrafast time-resolved infrared (TRIR) and transient absorption (TA) spectroscopy associated with two independent d (8) square planar Pt(II) diimine chromophores, Pt(dnpebpy)Cl 2 ( 1) and Pt(dnpebpy)(C[triple bond]Cnaph) 2 ( 2), where dnpebpy = 4,4'-(CO 2CH 2- (t) Bu) 2-2,2'-bipyridine and CCnaph = naphthylacetylide. The neopentyl ester substitutions provided markedly improved complex solubility relative to the corresponding ethyl ester which facilitates synthetic elaboration as well as spectroscopic investigations. Following 400 nm pulsed laser excitation in CH 2Cl 2, the 23 cm (-1) red shift in the nu C=O vibrations in 1 are representative of a complex displaying a lowest charge-transfer-to-diimine (CT) excited state. The decay kinetics in 1 are composed of two time constants assigned to vibrational cooling of the (3)CT excited-state concomitant with its decay to the ground state (tau = 2.2 +/- 0.4 ps), and to cooling of the formed vibrationally hot ground electronic state (tau = 15.5 +/- 4.0 ps); we note that an assignment of the latter to a ligand field state cannot be excluded. Ultrafast TA data quantitatively support these assignments yielding an excited-state lifetime of 2.7 +/- 0.4 ps for the (3)CT excited-state of 1 and could not detect any longer-lived species. The primary intention of this study was to develop a Pt (II) complex ( 2) bearing dual infrared spectroscopic tags (C[triple bond]C attached to the metal and CO (ester) attached to the diimine ligand) to independently track the movement of charge density in different segments of the molecule following pulsed light excitation. Femtosecond laser excitation of 2 in CH 2Cl 2 at 400 nm simultaneously induces a red-shift in both the nu C=O (-30 cm (-1)) and the nu C[triple bond]C (-61 cm (-1)) vibrations. The TRIR data in 2 are consistent with a charge transfer assignment, and the significant decrease of the energy of the nu

  14. Effects of spaceflight on the murine mandible: Possible factors mediating skeletal changes in non-weight bearing bones of the head.

    Science.gov (United States)

    Ghosh, Payal; Stabley, John N; Behnke, Bradley J; Allen, Matthew R; Delp, Michael D

    2016-02-01

    Spaceflight-induced remodeling of the skull is characterized by greater bone volume, mineral density, and mineral content. To further investigate the effects of spaceflight on other non-weight bearing bones of the head, as well as to gain insight into potential factors mediating the remodeling of the skull, the purpose of the present study was to determine the effects of spaceflight on mandibular bone properties. Female C57BL/6 mice were flown 15d on the STS-131 Space Shuttle mission (n=8) and 13d on the STS-135 mission (n=5) or remained as ground controls (GC). Upon landing, mandibles were collected and analyzed via micro-computed tomography for tissue mineralization, bone volume (BV/TV), and distance from the cemento-enamel junction to the alveolar crest (CEJ-AC). Mandibular mineralization was not different between spaceflight (SF) and GC mice for either the STS-131 or STS-135 missions. Mandibular BV/TV (combined cortical and trabecular bone) was lower in mandibles from SF mice on the STS-131 mission (80.7±0.8%) relative to that of GC (n=8) animals (84.2±1.2%), whereas BV/TV from STS-135 mice was not different from GC animals (n=7). The CEJ-AC distance was shorter in mandibles from STS-131 mice (0.217±0.004mm) compared to GC animals (0.283±0.009mm), indicating an anabolic (or anti-catabolic) effect of spaceflight, while CEJ-AC distance was similar between STS-135 and GC mice. These findings demonstrate that mandibular bones undergo skeletal changes during spaceflight and are susceptible to the effects of weightlessness. However, adaptation of the mandible to spaceflight is dissimilar to that of the cranium, at least in terms of changes in BV/TV.

  15. Association between bone stiffness and nutritional biomarkers combined with weight-bearing exercise, physical activity, and sedentary time in preadolescent children. A case-control study.

    Science.gov (United States)

    Herrmann, Diana; Pohlabeln, Hermann; Gianfagna, Francesco; Konstabel, Kenn; Lissner, Lauren; Mårild, Staffan; Molnar, Dénes; Moreno, Luis A; Siani, Alfonso; Sioen, Isabelle; Veidebaum, Toomas; Ahrens, Wolfgang

    2015-09-01

    Physical activity (PA) and micronutrients such as calcium (Ca), vitamin D (25OHD), and phosphate (PO) are important determinants of skeletal development. This case-control study examined the association of these nutritional biomarkers and different PA behaviours, such as habitual PA, weight-bearing exercise (WBE) and sedentary time (SED) with bone stiffness (SI) in 1819 2-9-year-old children from the IDEFICS study (2007-2008). SI was measured on the calcaneus using quantitative ultrasound. Serum and urine Ca and PO and serum 25OHD were determined. Children's sports activities were reported by parents using a standardised questionnaire. A subsample of 1089 children had accelerometer-based PA data (counts per minute, cpm). Moderate-to-vigorous PA (MVPA) and SED were estimated. Children with poor SI (below the 15th age-/sex-/height-specific percentile) were defined as cases (N=603). Randomly selected controls (N=1216) were matched by age, sex, and country. Odds ratios (OR) for poor SI were calculated by conditional logistic regression for all biomarkers and PA behaviour variables separately and combined (expressed as tertiles and dichotomised variables, respectively). ORs were adjusted for fat-free mass, dairy product consumption, and daylight duration. We observed increased ORs for no sports (OR=1.39, pnutritional biomarkers appear to play a minor role compared to the osteogenic effect of PA and WBE, it is noteworthy that the highest risk for poor SI was observed for no sports or low MVPA combined with lower serum Ca (<2.5 mmol/l) or lower 25OHD (<43.0 nmol/l).

  16. Weight-bearing MR imaging as an option in the study of gravitational effects on the vocal tract of untrained subjects in singing phonation.

    Science.gov (United States)

    Traser, Louisa; Burdumy, Michael; Richter, Bernhard; Vicari, Marco; Echternach, Matthias

    2014-01-01

    Magnetic Resonance Imaging (MRI) of subjects in a supine position can be used to evaluate the configuration of the vocal tract during phonation. However, studies of speech phonation have shown that gravity can affect vocal tract shape and bias measurements. This is one of the reasons that MRI studies of singing phonation have used professionally trained singers as subjects, because they are generally considered to be less affected by the supine body position and environmental distractions. A study of untrained singers might not only contribute to the understanding of intuitive singing function and aid the evaluation of potential hazards for vocal health, but also provide insights into the effect of the supine position on singers in general. In the present study, an open configuration 0.25 T MRI system with a rotatable examination bed was used to study the effect of body position in 20 vocally untrained subjects. The subjects were asked to sing sustained tones in both supine and upright body positions on different pitches and in different register conditions. Morphometric measurements were taken from the acquired images of a sagittal slice depicting the vocal tract. The analysis concerning the vocal tract configuration in the two body positions revealed differences in 5 out of 10 measured articulatory parameters. In the upright position the jaw was less protruded, the uvula was elongated, the larynx more tilted and the tongue was positioned more to the front of the mouth than in the supine position. The findings presented are in agreement with several studies on gravitational effects in speech phonation, but contrast with the results of a previous study on professional singers of our group where only minor differences between upright and supine body posture were observed. The present study demonstrates that imaging of the vocal tract using weight-bearing MR imaging is a feasible tool for the study of sustained phonation in singing for vocally untrained subjects.

  17. THE CALCIOTROPIC HORMONE RESPONSE TO OMEGA-3 SUPPLE-MENTATION DURING LONG-TERM WEIGHT-BEARING EXERCISE TRAINING IN POST MENOPAUSAL WOMEN

    Directory of Open Access Journals (Sweden)

    Bakhtiar Tartibian

    2010-06-01

    Full Text Available The purpose of this study was to examine the effects of ingestion of omega-3 (n-3 and aerobic exercise intervention on the calcium regulating hormones in healthy postmenopausal women. To this end, 56 healthy sedentary postmenopausal women with mean age 57.7 ± 3.5 yrs participated in this study. Participants were randomly divided into exercise plus supple-ment (E+S; n = 14, exercise (E; n = 14, supplement (S; n = 14 and control (Con, n = 14 groups. The subjects in E+S and E groups performed aerobic exercise training (walking and jog-ging up to 65% of exercise HRmax, three times a week for 16 weeks. Subjects in E+S and S groups were asked to consume 1000 mg/d omega-3 for 16 weeks. The blood ionized Calcium (Ca+2, Parathyroid hormone (PTH, estrogen and Calcitonin (CT were measured before and after 16 weeks of exercise training. Results indicated that consuming 1000 mg·day-1 omega-3 during 16 weeks and or the aerobic exercise, significantly increased CT (p = 0.001 in E+S, E and S groups and significantly decreased PTH (p = 0.001 levels in E+S and E groups, also significantly increased estrogen (p = 0.024 levels in E+S and E groups, but had no significant effects on blood Ca+2 (p = 0.619 levels. The results of present study demonstrate that omega-3 in combination with regular aerobic exercise training have significant effects on serum CT, estrogen and PTH in non-athletic post-menopausal women, suggesting that participating in moderate intensity weight-bearing exercise and incorporating sources of omega-3 in the diet a possible intervention to help slow the loss of bone that occurs following menopause

  18. Shifty: A Weight-Shifting Dynamic Passive Haptic Proxy to Enhance Object Perception in Virtual Reality.

    Science.gov (United States)

    Zenner, Andre; Kruger, Antonio

    2017-04-01

    We define the concept of Dynamic Passive Haptic Feedback (DPHF) for virtual reality by introducing the weight-shifting physical DPHF proxy object Shifty. This concept combines actuators known from active haptics and physical proxies known from passive haptics to construct proxies that automatically adapt their passive haptic feedback. We describe the concept behind our ungrounded weight-shifting DPHF proxy Shifty and the implementation of our prototype. We then investigate how Shifty can, by automatically changing its internal weight distribution, enhance the user's perception of virtual objects interacted with in two experiments. In a first experiment, we show that Shifty can enhance the perception of virtual objects changing in shape, especially in length and thickness. Here, Shifty was shown to increase the user's fun and perceived realism significantly, compared to an equivalent passive haptic proxy. In a second experiment, Shifty is used to pick up virtual objects of different virtual weights. The results show that Shifty enhances the perception of weight and thus the perceived realism by adapting its kinesthetic feedback to the picked-up virtual object. In the same experiment, we additionally show that specific combinations of haptic, visual and auditory feedback during the pick-up interaction help to compensate for visual-haptic mismatch perceived during the shifting process.

  19. The Distribution Dynamics of Carbon Dioxide Emissions Intensity across Chinese Provinces: A Weighted Approach

    Directory of Open Access Journals (Sweden)

    Jian-Xin Wu

    2017-01-01

    Full Text Available This paper examines the distribution dynamics of carbon dioxide (CO2 emissions intensity across 30 Chinese provinces using a weighted distribution dynamics approach. The results show that CO2 emissions intensity tends to diverge during the sample period of 1995–2014. However, convergence clubs are found in the ergodic distributions of the full sample and two sub-sample periods. Divergence, polarization, and stratification are the dominant characteristics in the distribution dynamics. Weightings with economic and population sizes have important impacts on current distributions and hence long-run steady distributions. Neglecting the size of the economy may underestimate the deterioration in the long-run steady state. The result also shows that conditioning on space and income cannot eliminate the multimodality in the long-run distribution. However, capital intensity has an important impact on the formation of convergence clubs. Our findings will contribute to an understanding of the spatial dynamic behaviors of CO2 emissions across Chinese provinces, and have important policy implications for CO2 emissions reduction in China.

  20. Nurse Scheduling System based on Dynamic Weighted Maximal Constraint Satisfaction Problem

    Science.gov (United States)

    Hattori, Hiromitsu; Isomura, Atsushi; Ito, Takayuki; Ozono, Tadachika; Shintani, Toramatsu

    Scheduling has been an important research field in Artificial Intelligence. Because typical scheduling problems could be modeled as a Constraint Satisfaction Problem(CSP), several constraint satisfaction techniques have been proposed. In order to handle the different levels of importance of the constraints, solving a problem as a Weighted Maximal Constraint Satisfaction Problem(W-MaxCSP) is an promising approach. However, there exists the case where unexpected events are added and some sudden changes are required, i.e., the case with dynamic changes in scheduling problems. In this paper, we describe such dynamic scheduling problem as a Dynamic Weighted Maximal Constraint Satisfaction Problem(DW-MaxCSP) in which constraints would changes dynamically. Generally, it is undesirable to determine vastly modified schedule even if re-scheduling is needed. A new schedule should be close to the current one as much as possible. In order to obtain stable solutions, we propose the methodology to maintain portions of the current schedule using the provisional soft constraints, which explicitly penalize the changes from the current schedule. We have experimentally confirmed the efficacy of re-scheduling based on our method with provisional constraints. In this paper, we construct the nurse scheduling system for applying the proposed scheduling method.

  1. Dynamic weighted voting for multiple classifier fusion: a generalized rough set method

    Institute of Scientific and Technical Information of China (English)

    Sun Liang; Han Chongzhao

    2006-01-01

    To improve the performance of multiple classifier system, a knowledge discovery based dynamic weighted voting (KD-DWV) is proposed based on knowledge discovery. In the method, all base classifiers may be allowed to operate in different measurement/feature spaces to make the most of diverse classification information. The weights assigned to each output of a base classifier are estimated by the separability of training sample sets in relevant feature space. For this purpose, some decision tables (DTs) are established in terms of the diverse feature sets. And then the uncertainty measures of the separability are induced, in the form of mass functions in Dempster-Shafer theory (DST), from each DTs based on generalized rough set model. From the mass functions, all the weights are calculated by a modified heuristic fusion function and assigned dynamically to each classifier varying with its output. The comparison experiment is performed on the hyperspectral remote sensing images. And the experimental results show that the performance of the classification can be improved by using the proposed method compared with the plurality voting (PV).

  2. Characterization of Fault Size in Bearings

    Science.gov (United States)

    2014-12-23

    0.3 and 1.2 mm into the outer-race of the bearing, which simulates realistic faults that often can be found in damaged bearings. A 3D dynamic model ...3 4. MODEL DESCRIPTION A 3D dynamic ball bearing model was developed to study the effect of faults on the bearing dynamic behavior. The aim of the...understanding of the effects of fault size on the bearing dynamics. The research methodology combines dynamic modeling of the faulty bearing with

  3. Characterizing system dynamics with a weighted and directed network constructed from time series data

    Science.gov (United States)

    Sun, Xiaoran; Small, Michael; Zhao, Yi; Xue, Xiaoping

    2014-06-01

    In this work, we propose a novel method to transform a time series into a weighted and directed network. For a given time series, we first generate a set of segments via a sliding window, and then use a doubly symbolic scheme to characterize every windowed segment by combining absolute amplitude information with an ordinal pattern characterization. Based on this construction, a network can be directly constructed from the given time series: segments corresponding to different symbol-pairs are mapped to network nodes and the temporal succession between nodes is represented by directed links. With this conversion, dynamics underlying the time series has been encoded into the network structure. We illustrate the potential of our networks with a well-studied dynamical model as a benchmark example. Results show that network measures for characterizing global properties can detect the dynamical transitions in the underlying system. Moreover, we employ a random walk algorithm to sample loops in our networks, and find that time series with different dynamics exhibits distinct cycle structure. That is, the relative prevalence of loops with different lengths can be used to identify the underlying dynamics.

  4. Effects of ankle joint mobilization with movement and weight-bearing exercise on knee strength, ankle range of motion, and gait velocity in patients with stroke: a pilot study.

    Science.gov (United States)

    An, Chang-Man; Won, Jong-Im

    2016-01-01

    [Purpose] The purpose of this study was to investigate the effects of ankle joint mobilization with movement on knee strength, ankle range of motion, and gait velocity, compared with weight-bearing exercise in stroke patients. [Subjects and Methods] Thirty subjects with chronic stroke were divided into three groups: MWM (n = 12), WBE (n = 8), and control (n = 10). All groups attended physical therapy sessions 3 times a week for 5 weeks. Subjects in the MWM group performed mobilization with movement exercises, whilst participants in the WBE group performed weight-bearing exercises. Knee peak torque, ankle range of motion, and spatiotemporal gait parameters were evaluated before and after the interventions. [Results] Knee extensor peak torque increased significantly in both MWM and WBE groups. However, only the MWM group showed significant improvement in passive and active ankle range of motion and gait velocity, among the three groups. [Conclusion] Ankle joint mobilization with movement intervention is more effective than simple weight-bearing intervention in improving gait speed in stroke patients with limited ankle motion.

  5. Dynamical Associative Memory: The Properties of the New Weighted Chaotic Adachi Neural Network

    Science.gov (United States)

    Luo, Guangchun; Ren, Jinsheng; Qin, Ke

    A new training algorithm for the chaotic Adachi Neural Network (AdNN) is investigated. The classical training algorithm for the AdNN and it's variants is usually a “one-shot” learning, for example, the Outer Product Rule (OPR) is the most used. Although the OPR is effective for conventional neural networks, its effectiveness and adequateness for Chaotic Neural Networks (CNNs) have not been discussed formally. As a complementary and tentative work in this field, we modified the AdNN's weights by enforcing an unsupervised Hebbian rule. Experimental analysis shows that the new weighted AdNN yields even stronger dynamical associative memory and pattern recognition phenomena for different settings than the primitive AdNN.

  6. Characteristics of metal and ceramic total hip bearing surfaces and their effect on long-term ultra high molecular weight polyethylene wear.

    Science.gov (United States)

    Davidson, J A

    1993-09-01

    The micromechanics of ultra high molecular weight polyethylene (UHMWPE) wear in total hip replacement are very complex. Polyethylene wear from the metal head and debris formation are two common types of wear. There are additional wear-related processes occurring at the metal-bearing surfaces that are not well-known, however. This study outlines these processes, including (1) surface wettability changes, (2) oxidative wear of metal surfaces, (3) microabrasion of metal surfaces from oxide film damage, and (4) surface abrasion from three-body polymethylmethacrylate and bone debris. These processes can contribute to metal ion release and a gradual increase in the roughness of the metal surfaces. This can lead to increased long-term UHMWPE wear. Of the metal alloys currently used in total hip replacements, Co-Cr-Mo alloy is significantly more resistant to roughening processes. Hard, stable, oxide: ceramic surfaces articulating against UHMWPE are essentially immune to these surface-roughening processes, however. In addition, they provide a more wettable surface, further minimizing polyethylene wear relative to metal surfaces. By analyzing metal release rates from metal-polyethylene wear tests, it is shown here that Co-Cr-Mo is gradually removed at a rate of about 0.1 micron per year (10(6) cycles), whereas 316L stainless steel is removed on the order of 0.2 microns per year and Ti-6Al-4V on the order of 1 micron per year. The wear rate of Co-Cr-Mo articulating against itself is reported to be still greater, at about 2-4 microns per year after an initial wear-in period. Because metal is gradually removed with articulation time, surface-hardening methods such as nitrogen ion implantation can be expected to provide only temporary resistance to these metal removal and surface-roughening processes. Hard, stable ceramic surfaces such as Al2O3 and ZrO2, however, can be expected to maintain their initial surface finish and thus minimize UHMWPE wear in the long term.

  7. Relative weights approach to SU(3) gauge theories with dynamical fermions at finite density

    CERN Document Server

    Höllwieser, Roman

    2016-01-01

    We derive effective Polyakov line actions for SU(3) gauge theories with staggered dynamical fermions, for a small sample of lattice couplings, lattice actions, and lattice extensions in the time direction. The derivation is via the method of relative weights, and the theories are solved at finite chemical potential by mean field theory. We find in some instances that the long-range couplings in the effective action are very important to the phase structure, and that these couplings are responsible for long-lived metastable states in the effective theory. Only one of these states corresponds to the underlying lattice gauge theory.

  8. On the dynamic estimation of relative weights for observation and forecast in numerical weather prediction

    Science.gov (United States)

    Wahba, Grace; Deepak, A. (Editor)

    1988-01-01

    The problem of merging direct and remotely sensed (indirect) data with forecast data to get an estimate of the present state of the atmosphere for the purpose of numerical weather prediction is examined. To carry out this merging optimally, it is necessary to provide an estimate of the relative weights to be given to the observations and forecast. It is possible to do this dynamically from the information to be merged, if the correlation structure of the errors from the various sources is sufficiently different. Some new statistical approaches to doing this are described, and conditions quantified in which such estimates are likely to be good.

  9. REGULAR PATTERN MINING (WITH JITTER) ON WEIGHTED-DIRECTED DYNAMIC GRAPHS

    OpenAIRE

    Gupta, A.; H. K. THAKUR; Gupta, T.; Yadav, S.

    2017-01-01

    Real world graphs are mostly dynamic in nature, exhibiting time-varying behaviour in structure of the graph, weight on the edges and direction of the edges. Mining regular patterns in the occurrence of edge parameters gives an insight into the consumer trends over time in ecommerce co-purchasing networks. But such patterns need not necessarily be precise as in the case when some product goes out of stock or a group of customers becomes unavailable for a short period of time. Ignoring them ...

  10. On-line Weighted Least Squares Kernel Method for Nonlinear Dynamic Modeling

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Support vector machines (SVM) have been widely used in pattern recognition and have also drawn considerable interest in control areas. Based on rolling optimization method and on-line learning strategies, a novel approach based on weighted least squares support vector machines (WLS-SVM) is proposed for nonlinear dynamic modeling.The good robust property of the novel approach enhances the generalization ability of kernel method-based modeling and some experimental results are presented to illustrate the feasibility of the proposed method.

  11. Weighted-ensemble Brownian dynamics simulation: sampling of rare events in nonequilibrium systems.

    Science.gov (United States)

    Kromer, Justus A; Schimansky-Geier, Lutz; Toral, Raul

    2013-06-01

    We provide an algorithm based on weighted-ensemble (WE) methods, to accurately sample systems at steady state. Applying our method to different one- and two-dimensional models, we succeed in calculating steady-state probabilities of order 10(-300) and reproduce the Arrhenius law for rates of order 10(-280). Special attention is payed to the simulation of nonpotential systems where no detailed balance assumption exists. For this large class of stochastic systems, the stationary probability distribution density is often unknown and cannot be used as preknowledge during the simulation. We compare the algorithm's efficiency with standard Brownian dynamics simulations and the original WE method.

  12. The influence of climate variability on polar bear (Ursus maritimus) and ringed seal (Pusa hispida) population dynamics

    DEFF Research Database (Denmark)

    Rosing-Asvid, A.

    2006-01-01

    Unusually high polar bear (Ursus maritimus Phipps, 1774) predation on ringed seal (Pusa hispida (Schreber, 1775)) pups and increased survival of polar bear cubs during mild springs is documented in published articles. Strong predation on newborn ringed seal pups in early spring, however, is likely...... to lower the overall energy intake of polar bears if ringed seal pups are their main food, because the energetic value of ringed seal pups increases 7-8 times during the 6 week lactation period. So although hunting success in early spring increases cub survival during the period after den emergence......,when they are most vulnerable, it is likely to increase the number of starving bears later in the season. This negative-feedback effect of strong spring predation will not occur in areas where other seal species are abundant during summer, and polar bears in such areas are likely to exhibit population growth during...

  13. Body Weight Dynamics Following Intentional Weight Loss and Physical Performance: The Look AHEAD Movement and Memory Study.

    Science.gov (United States)

    Beavers, Kristen M; Neiberg, Rebecca H; Houston, Denise K; Bray, George A; Hill, James O; Jakicic, John M; Johnson, Karen C; Kritchevsky, Stephen B

    2015-10-01

    To explore the impact of body weight change following intentional weight loss on measures of physical performance in adults with diabetes. 450 individuals with type 2 diabetes (age: 59.0±6.9 years, BMI: 35.5±5.9 kg/m(2)) who participated in the Look AHEAD Movement and Memory Study and lost weight one year after being randomized to an intensive lifestyle intervention were assessed. Body weight was measured annually, and participants were categorized as continued losers/maintainers, regainers, or cyclers based on a ±5% annual change in weight. Objective measures of physical performance were measured at the year 8/9 visit. Forty-four, 38 and 18% of participants were classified as regainers, cyclers, and continued losers/maintainers. In women, weight cycling and regain was associated with worse follow-up expanded physical performance battery score (1.46±0.07 and 1.48±0.07 vs. 1.63±0.07, both p≤0.02) and slower 20-meter walking speed (1.10±0.04 and 1.08±0.04 m/s vs. 1.17±0.04 m/s, both pweight loss. Male cyclers presented with weaker grip strength compared to regainers or continued losers/maintainers (30.12±2.21 kg versus 34.46±2.04 and 37.39±2.26 kg; both pWeight cycling and regain following intentional weight loss in older adults with diabetes was associated with worse physical function in women and grip strength in men.

  14. A contribution on the investigation of the dynamic behavior of rotating shafts with a Hybrid Magnetic Bearing Concept (HMBC) for blower application

    Energy Technology Data Exchange (ETDEWEB)

    Gronek, Martin, E-mail: MGronek@hs-zigr.d [HOCHSCHULE ZITTAU/GOERLITZ-University of Applied Sciences, Institute of Process Technology, Process Automation and Measuring Technology (IPM), Department Mechatronical Systems, Theodor-Koerner-Allee 16, 02763 Zittau (Germany); Rottenbach, Torsten; Worlitz, Frank [HOCHSCHULE ZITTAU/GOERLITZ-University of Applied Sciences, Institute of Process Technology, Process Automation and Measuring Technology (IPM), Department Mechatronical Systems, Theodor-Koerner-Allee 16, 02763 Zittau (Germany)

    2010-10-15

    Within a subproject of the RAPHAEL-Program, which was part of the 6th EURATOM Framework Program supervised by the European Commission, it was investigated whether the use of a Hybrid Magnetic Bearing Concept (HMBC) will be beneficial for a blower application. Within the RAPHAEL program, the subproject 'Component Development' is dealing with R and D of components of High Temperature Reactor Technology (HTR), where a major focus is on safety- and reliability-related issues. That implies special requirements for the support of high speed rotating shafts in HTR-Applications that only can be satisfied by using Active Magnetic Bearings (AMB). Regarding safety and competitiveness, AMBs are considered to be key components for the support of rotating HTR-components due to their technical features. AMBs are characterized by an electromagnetic actuator that is generating the bearing force depending on the clearance between stator and rotor, in which the rotor is levitated. Therefore an active control of the coil current is necessary. Furthermore, Touch Down Bearings (TDB) are needed to avoid damages in case of an emergency shut down or in case of energy supply losses. This contribution provides an internal insight on the advantages of a Hybrid Magnetic Bearing Concept that is characterized by a completely Active Magnetic Bearing-supported vertical arranged rotor and an additional permanent magnetic radial orientated bearing. One benefit of the HMBC is an additional radial guidance of the shaft that may reduce the loads while dropping into the Touch Down Bearings e.g. in case of energy supply losses of the AMBs. Reduced loads on the TDBs will increase their life cycle and the availability of the AMB supported component. The scope of this R and D-Project, which will be described more detailed in this contribution, includes: the analytical modeling and simulation of the dynamic behavior of the Hybrid Magnetic Bearing System; the modification of the completely AMB

  15. Sexual dimorphic regulation of body weight dynamics and adipose tissue lipolysis.

    Science.gov (United States)

    Benz, Verena; Bloch, Mandy; Wardat, Sami; Böhm, Christian; Maurer, Lukas; Mahmoodzadeh, Shokoufeh; Wiedmer, Petra; Spranger, Joachim; Foryst-Ludwig, Anna; Kintscher, Ulrich

    2012-01-01

    Successful reduction of body weight (BW) is often followed by recidivism to obesity. BW-changes including BW-loss and -regain is associated with marked alterations in energy expenditure (EE) and adipose tissue (AT) metabolism. Since these processes are sex-specifically controlled, we investigated sexual dimorphisms in metabolic processes during BW-dynamics (gain-loss-regain). Obesity was induced in C57BL/6J male (m) and female (f) mice by 15 weeks high-fat diet (HFD) feeding. Subsequently BW was reduced (-20%) by caloric restriction (CR) followed by adaptive feeding, and a regain-phase. Measurement of EE, body composition, blood/organ sampling were performed after each feeding period. Lipolysis was analyzed ex-vivo in gonadal AT. Male mice exhibited accelerated BW-gain compared to females (relative BW-gain m:140.5±3.2%; f:103.7±6.5%; pregain faster in males than in females. The present study shows sex-specific dynamics during BW-gain-loss-regain. Female mice responded to CR with an increase in lipolytic activity, and augmented lipid-oxidation leading to more efficient weight loss. These processes likely involve ERα-dependent signaling in AT and sexual dimorphic regulation of genes involved in lipid metabolism.

  16. Weight loss and lipolysis promote a dynamic immune response in murine adipose tissue

    Science.gov (United States)

    Kosteli, Aliki; Sugaru, Eiji; Haemmerle, Guenter; Martin, Jayne F.; Lei, Jason; Zechner, Rudolf; Ferrante, Anthony W.

    2010-01-01

    Obesity elicits an immune response characterized by myeloid cell recruitment to key metabolic organs, including adipose tissue. However, the response of immune cells to nonpathologic metabolic stimuli has been less well studied, and the factors that regulate the metabolic-dependent accumulation of immune cells are incompletely understood. Here we characterized the response of adipose tissue macrophages (ATMs) to weight loss and fasting in mice and identified a role for lipolysis in ATM recruitment and accumulation. We found that the immune response to weight loss was dynamic; caloric restriction of high-fat diet–fed mice led to an initial increase in ATM recruitment, whereas ATM content decreased following an extended period of weight loss. The peak in ATM number coincided with the peak in the circulating concentrations of FFA and adipose tissue lipolysis, suggesting that lipolysis drives ATM accumulation. Indeed, fasting or pharmacologically induced lipolysis rapidly increased ATM accumulation, adipose tissue chemoattractant activity, and lipid uptake by ATMs. Conversely, dietary and genetic manipulations that reduced lipolysis decreased ATM accumulation. Depletion of macrophages in adipose tissue cultures increased expression of adipose triglyceride lipase and genes regulated by FFA, and increased lipolysis. These data suggest that local lipid fluxes are central regulators of ATM recruitment and that once recruited, ATMs form lipid-laden macrophages that can buffer local increases in lipid concentration. PMID:20877011

  17. Fracture-driven methane bubble ascent within shallow fine-grained clay-bearing aquatic sediments: dynamics and controlling factors

    Science.gov (United States)

    Tarboush Sirhan, Shahrazad; Katsman, Regina; Ten Brink, Uri

    2017-04-01

    Mature methane gas bubbles in the fine-grained, clay-bearing (cohesive) aquatic sediments, found at many locations throughout the world, are much larger than the characteristic pore size. When gas pressure within the bubble is high enough to overcome compression, friction, and cohesion at grain contacts, gas migrates upward driven by buoyancy, by pushing the grains apart and fracturing the fine-grained sediments. Fracturing of the fine-grained cohesive sediments by the migrating bubbles destabilizes sediment and might result in slope failure. Migrating methane bubbles may bypass processes of oxidation in the upper sediment layers due to their fast rise velocity, release to the water column and eventually to the atmosphere. In this study we use coupled macroscopic single-bubble mechanical/reaction-transport numerical model to explore bubble ascent under various ambient concentration profiles, associated with bio-chemical processes of methane production and consumption below sediment-water interface, as it occurs in nature. Modeling results show that changes in the ambient dissolved-methane concentrations strongly affect bubble ascent velocity. It is demonstrated that bubble migration scenario within fine-grained muddy sediments is controlled dominantly by the internal bubble pressure that manages solute exchange with adjacent porewater. It is significantly affected by the total hydrostatic pressure. For shallow water depths two sequential bubble propagation patterns were observed: (1) Stable (saw-tooth) fracturing, followed by (2) Dynamic (unstable, rising line) fracturing, leading to an ultimate release of the bubble to the water column. However, for a higher water depth, bubble propagation pattern is characterized by stable fracturing only. In this pattern the bubble becomes more sensitive to the ambient field of methane concentrations and may stop below sediment-water interface due solute release caused by the local methanotrophy.

  18. Journal bearing

    Science.gov (United States)

    Menke, John R.; Boeker, Gilbert F.

    1976-05-11

    1. An improved journal bearing comprising in combination a non-rotatable cylindrical bearing member having a first bearing surface, a rotatable cylindrical bearing member having a confronting second bearing surface having a plurality of bearing elements, a source of lubricant adjacent said bearing elements for supplying lubricant thereto, each bearing element consisting of a pair of elongated relatively shallowly depressed surfaces lying in a cylindrical surface co-axial with the non-depressed surface and diverging from one another in the direction of rotation and obliquely arranged with respect to the axis of rotation of said rotatable member to cause a flow of lubricant longitudinally along said depressed surfaces from their distal ends toward their proximal ends as said bearing members are rotated relative to one another, each depressed surface subtending a radial angle of less than 360.degree., and means for rotating said rotatable bearing member to cause the lubricant to flow across and along said depressed surfaces, the flow of lubricant being impeded by the non-depressed portions of said second bearing surface to cause an increase in the lubricant pressure.

  19. Characteristics and dynamic response analysis of 3-D component base isolation system using multi-layer-rubber-bearings and coil springs

    Energy Technology Data Exchange (ETDEWEB)

    Tsutsumi, Hideaki; Yamada, Hiroyuki; Ebisawa, Katsumi; Shibata, Katsuyuki [Seismic Emergency Information System Research Team, Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan)

    2000-07-01

    Introduction of the base isolation technique into the seismic design of nuclear power plant components as well as buildings has been expected as one of effective countermeasure to reduce the seismic force applied to components. A research program of the base isolation of nuclear components has been carried out at Japan Atomic Energy Research Institute(JAERI) since 1991. A methodology and a computer code (EBISA: Equipment Base Isolation System Analysis) for evaluating the failure frequency of the nuclear component with the base isolation were developed. In addition, a test program, which is concerned with the above development, i.e., improvement of failure frequency analysis models in the code has been conducted since 1996 to investigate the dynamic behavior and to verify the effectiveness of component base isolation systems. Two kinds of base isolation test systems with different characteristic were fabricated and static and dynamic characteristics were measured by static loading and free vibration tests. One which consists of ball bearings and air springs was installed on the test bed to observe the dynamic response under natural earthquake motion. The effect of base isolation system has been observed under several earthquakes. Another system which consists of multi-layer-rubber-bearings and coil springs has been investigated three-dimensional dynamic behavior and effect of base isolation against various large earthquake motions by shaking table test. This report describes the design specification of the base isolation system which consists of multi-layer-rubber-bearings and coil springs, static and dynamic characteristics, analysis model based on the characteristics, results of shaking table test and the dynamic response analysis (author)

  20. Obtaining Arbitrary Prescribed Mean Field Dynamics for Recurrently Coupled Networks of Type-I Spiking Neurons with Analytically Determined Weights

    Directory of Open Access Journals (Sweden)

    Wilten eNicola

    2016-02-01

    Full Text Available A fundamental question in computational neuroscience is how to connect a network of spiking neurons to produce desired macroscopic or mean field dynamics. One possible approach is through the Neural Engineering Framework (NEF. The NEF approach requires quantities called decoders which are solved through an optimization problem requiring large matrix inversion. Here, we show how a decoder can be obtained analytically for type I and certain type II firing rates as a function of the heterogeneity of its associated neuron. These decoders generate approximants for functions that converge to the desired function in mean-squared error like 1/N, where N is the number of neurons in the network. We refer to these decoders as scale-invariant decoders due to their structure. These decoders generate weights for a network of neurons through the NEF formula for weights. These weights force the spiking network to have arbitrary and prescribed mean field dynamics. The weights generated with scale-invariant decoders all lie on low dimensional hypersurfaces asymptotically. We demonstrate the applicability of these scale-invariant decoders and weight surfaces by constructing networks of spiking theta neurons that replicate the dynamics of various well known dynamical systems such as the neural integrator, Van der Pol system and the Lorenz system. As these decoders are analytically determined and non-unique, the weights are also analytically determined and non-unique. We discuss the implications for measured weights of neuronal networks

  1. Measurement and calculation of dynamic coefficients in hydrodynamic bearings of gas films; Medicion y calculo de coeficientes dinamicos en cojinetes hidrodinamicos de peliculas de gas

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz, Rafael O.; Di Liscia, Marcelo H.; Diaz, Sergio E. [Universidad Simon Bolivar, Sartendejas, Baruta (Venezuela)

    2007-11-15

    The identification of the dynamic coefficients in air bearings is fundamental for a suitable roto-dynamic analysis. The present paper shows the development of an algorithm that allows the direct obtaining of the dynamic coefficients in hydrodynamic air bearings as much of numerical form as experimental. The testing bench used consists of two magnetic bearings, which support the rotor in their ends and work as well as actuators allowing inducing controlled orbits in the rotor. The test bearing is located between the magnetic bearings. The dynamic forces generated in the air bearing are registered from three load cells. The algorithm was developed in a commercial code of graphical programming, through which the signals can be collected, controlled and processed. The nonlinear behavior of this type of bearings makes difficult the calculation of the dynamic coefficients, therefore the processing of the signals in frequencial space facilitates, in a certain way, its handling. On the other hand, the numerical model was compared with the experimental results obtaining acceptable approaches in magnitude as well as in behavior. The numerical dynamic coefficients calculation was realized solving the Reynolds differential equation for a compressible fluid in the thickness of the gas film, taking into consideration the fluid mass flow that is introduced, as well as the pressure loss suffered by the same in passing through the feeding orifices. The numerical methods utilized include the solution of the differential equation of Reynolds for finite differences, the calculation of the profile realizing successive iterations and the calculation of the hydrodynamics forces through the Simpson numerical integration. The numerical dynamic coefficients were found applying a minimum squared technique to the hydrodynamic stresses generated in simulating an orbit of the rotor at a determined frequency and velocity, allowing in this way the calculation of the synchronous and asynchronous

  2. Measurement and calculation of dynamic coefficients in hydrodynamic bearings of gas films; Medicion y calculo de coeficientes dinamicos en cojinetes hidrodinamicos de peliculas de gas

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz, Rafael O.; Di Liscia, Marcelo H.; Diaz, Sergio E. [Universidad Simon Bolivar, Sartendejas, Baruta (Venezuela)

    2007-11-15

    The identification of the dynamic coefficients in air bearings is fundamental for a suitable roto-dynamic analysis. The present paper shows the development of an algorithm that allows the direct obtaining of the dynamic coefficients in hydrodynamic air bearings as much of numerical form as experimental. The testing bench used consists of two magnetic bearings, which support the rotor in their ends and work as well as actuators allowing inducing controlled orbits in the rotor. The test bearing is located between the magnetic bearings. The dynamic forces generated in the air bearing are registered from three load cells. The algorithm was developed in a commercial code of graphical programming, through which the signals can be collected, controlled and processed. The nonlinear behavior of this type of bearings makes difficult the calculation of the dynamic coefficients, therefore the processing of the signals in frequencial space facilitates, in a certain way, its handling. On the other hand, the numerical model was compared with the experimental results obtaining acceptable approaches in magnitude as well as in behavior. The numerical dynamic coefficients calculation was realized solving the Reynolds differential equation for a compressible fluid in the thickness of the gas film, taking into consideration the fluid mass flow that is introduced, as well as the pressure loss suffered by the same in passing through the feeding orifices. The numerical methods utilized include the solution of the differential equation of Reynolds for finite differences, the calculation of the profile realizing successive iterations and the calculation of the hydrodynamics forces through the Simpson numerical integration. The numerical dynamic coefficients were found applying a minimum squared technique to the hydrodynamic stresses generated in simulating an orbit of the rotor at a determined frequency and velocity, allowing in this way the calculation of the synchronous and asynchronous

  3. Frequency-weighted feedforward control for dynamic compensation in ionic polymer-metal composite actuators

    Science.gov (United States)

    Shan, Yingfeng; Leang, Kam K.

    2009-12-01

    Ionic polymer-metal composites (IPMCs) are innovative materials that offer combined sensing and actuating ability in lightweight and flexible package. IPMCs have been exploited in robotics and a wide variety of biomedical devices, for example, as sensors for teleoperation, as actuators for positioning in active endoscopy, as fins for propelling aquatic robots, and as an injector for drug delivery. In the actuation mode, one of the main challenges is precise position control. In particular, IPMC actuators exhibit relaxation behavior and nonlinearities; and at relatively high operating frequencies dynamic effects limit accuracy and positioning bandwidth. A frequency-weighted feedforward controller is designed to account for the IPMC's structural dynamics to enable fast positioning. The control method is applied to a custom-made Nafion-based IPMC actuator. The controller takes into account the magnitude of the control input to avoid generating excessively large voltages which can damage the IPMC actuator. To account for unmodeled effects not captured by the dynamics model, a feedback controller is integrated with the feedforward controller. Experimental results show a significant improvement in the tracking performance when feedforward control is used. For instance, the feedforward controller shows over 75% reduction in the tracking error compared to the case without feedforward compensation. Finally, the integrated feedforward and feedback control system reduces the tracking error to less than 10% for tracking an 18-Hz triangle-like trajectory. Some of the advantages of feedforward control as well as its limitations are also discussed.

  4. Damper bearing rotordynamics

    Science.gov (United States)

    Elrod, David A.

    1990-01-01

    High side loads reduce the life of the Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbopump (HPOTP) bearings. High stiffness damper seals were recommended to reduce the loads on the pump and turbine end bearings in the HPOTP. The seals designed for use on the pump end are expected to adequately reduce the bearing loads; the predicted performance of the planned turbine end seal is marginal. An alternative to the suggested turbine end seal design is a damper bearing with radial holes from the pressurized center of the turbopump rotor, feeding a smooth land region between two rough-stator/smooth-rotor annular seals. An analysis was prepared to predict the leakage and rotor dynamic coefficients (stiffness, damping, and added mass) of the damper bearing. Governing equations of the seal analysis modified to model the damper bearing; differences between the upstream conditions of the damper bearing and a typical annular seal; prediction of the damper bearing analysis; and assumptions of the analysis which require further investigation are described.

  5. Seismic ultimate bearing capacity of strip footings on slope

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The influence of earthquake forces on ultimate bearing capacity of foundations on sloping ground was studied. A solution to seismic ultimate bearing capacity of strip footings on slope was obtained by utilizing pseudo-static analysis method and taking the effect of intermediate principal stress into consideration. Based on limit equilibrium theory, the formulae for computing static bearing capacity factors, Nq, Nc, Nγ, and dynamic bearing capacity factors, Nqd, Ncd, Nγd, which are associated with surcharge, cohesion and self-weight of soils respectively, were presented. A great number of analysis calculations were carried out to obtain the relationship curves of the static and dynamic bearing capacity factors versus various calculation parameters. The curves can serve as the practical engineering design. The calculation results also show that when the values of horizontal and vertical seismic coefficients are 0.2, the dynamic bearing capacity factors Nqd, Ncd and Nγd, in which the effects of intermediate principal stress are taken into consideration, increase by 4%-42%, 3%-27% and 34%-57%, respectively.

  6. Polyakov line actions from SU(3) lattice gauge theory with dynamical fermions via relative weights

    CERN Document Server

    Höllwieser, Roman

    2016-01-01

    We extract an effective Polyakov line action from an underlying SU(3) lattice gauge theory with dynamical fermions via the relative weights method. The center-symmetry breaking terms in the effective theory are fit to a form suggested by effective action of heavy-dense quarks, and the effective action is solved at finite chemical potential by a mean field approach. We show results for a small sample of lattice couplings, lattice actions, and lattice extensions in the time direction. We find in some instances that the long-range couplings in the effective action are very important to the phase structure, and that these couplings are responsible for long-lived metastable states in the effective theory. Only one of these states corresponds to the underlying lattice gauge theory.

  7. Public and health professionals’ misconceptions about the dynamics of body weight gain/loss

    Science.gov (United States)

    Abdel-Hamid, Tarek; Ankel, Felix; Battle-Fisher, Michele; Gibson, Bryan; Gonzalez-Parra, Gilberto; Jalali, Mohammad; Kaipainen, Kirsikka; Kalupahana, Nishan; Karanfil, Ozge; Marathe, Achla; Martinson, Brian; McKelvey, Karma; Sarbadhikari, Suptendra Nath; Pintauro, Stephen; Poucheret, Patrick; Pronk, Nicolaas; Qian, Ying; Sazonov, Edward; Van Oorschot, Kim; Venkitasubramanian, Akshay; Murphy, Philip

    2014-01-01

    Human body energy storage operates as a stock-and-flow system with inflow (food intake) and outflow (energy expenditure). In spite of the ubiquity of stock-and-flow structures, evidence suggests that human beings fail to understand stock accumulation and rates of change, a difficulty called the stock–flow failure. This study examines the influence of health care training and cultural background in overcoming stock–flow failure. A standardized protocol assessed lay people’s and health care professionals’ ability to apply stock-and-flow reasoning to infer the dynamics of weight gain/loss during the holiday season (621 subjects from seven countries). Our results indicate that both types of subjects exhibited systematic errors indicative of use of erroneous heuristics. Stock–flow failure was found across cultures and was not improved by professional health training. The problem of stock–flow failure as a transcultural global issue with education and policy implications is discussed. PMID:25620843

  8. Adaptive polarization image fusion based on regional energy dynamic weighted average

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yong-qiang; PAN Quan; ZHANG Hong-cai

    2005-01-01

    According to the principle of polarization imaging and the relation between Stokes parameters and the degree of linear polarization, there are much redundant and complementary information in polarized images. Since man-made objects and natural objects can be easily distinguished in images of degree of linear polarization and images of Stokes parameters contain rich detailed information of the scene, the clutters in the images can be removed efficiently while the detailed information can be maintained by combining these images. An algorithm of adaptive polarization image fusion based on regional energy dynamic weighted average is proposed in this paper to combine these images. Through an experiment and simulations,most clutters are removed by this algorithm. The fusion method is used for different light conditions in simulation, and the influence of lighting conditions on the fusion results is analyzed.

  9. Weighted fractional permutation entropy and fractional sample entropy for nonlinear Potts financial dynamics

    Science.gov (United States)

    Xu, Kaixuan; Wang, Jun

    2017-02-01

    In this paper, recently introduced permutation entropy and sample entropy are further developed to the fractional cases, weighted fractional permutation entropy (WFPE) and fractional sample entropy (FSE). The fractional order generalization of information entropy is utilized in the above two complexity approaches, to detect the statistical characteristics of fractional order information in complex systems. The effectiveness analysis of proposed methods on the synthetic data and the real-world data reveals that tuning the fractional order allows a high sensitivity and more accurate characterization to the signal evolution, which is useful in describing the dynamics of complex systems. Moreover, the numerical research on nonlinear complexity behaviors is compared between the returns series of Potts financial model and the actual stock markets. And the empirical results confirm the feasibility of the proposed model.

  10. Sexual Dimorphic Regulation of Body Weight Dynamics and Adipose Tissue Lipolysis

    Science.gov (United States)

    Benz, Verena; Bloch, Mandy; Wardat, Sami; Böhm, Christian; Maurer, Lukas; Mahmoodzadeh, Shokoufeh; Wiedmer, Petra; Spranger, Joachim; Foryst-Ludwig, Anna; Kintscher, Ulrich

    2012-01-01

    Background Successful reduction of body weight (BW) is often followed by recidivism to obesity. BW-changes including BW-loss and -regain is associated with marked alterations in energy expenditure (EE) and adipose tissue (AT) metabolism. Since these processes are sex-specifically controlled, we investigated sexual dimorphisms in metabolic processes during BW-dynamics (gain-loss-regain). Research Design Obesity was induced in C57BL/6J male (m) and female (f) mice by 15 weeks high-fat diet (HFD) feeding. Subsequently BW was reduced (-20%) by caloric restriction (CR) followed by adaptive feeding, and a regain-phase. Measurement of EE, body composition, blood/organ sampling were performed after each feeding period. Lipolysis was analyzed ex-vivo in gonadal AT. Results Male mice exhibited accelerated BW-gain compared to females (relative BW-gain m:140.5±3.2%; f:103.7±6.5%; plipolysis in AT associated with significantly higher glycerol concentrations, lower RER-values, and increased AT expression of adipose triglyceride lipase (ATGL) and hormone sensitive lipase (HSL). Analysis of AT lipolysis in estrogen receptor alpha (ERα)–deficient mice revealed a reduced lipolytic rate in the absence of ERα exclusively in females. Finally, re-feeding caused BW-regain faster in males than in females. Conclusion The present study shows sex-specific dynamics during BW-gain-loss-regain. Female mice responded to CR with an increase in lipolytic activity, and augmented lipid-oxidation leading to more efficient weight loss. These processes likely involve ERα-dependent signaling in AT and sexual dimorphic regulation of genes involved in lipid metabolism. PMID:22662224

  11. Nonoperative dynamic treatment of acute achilles tendon rupture

    DEFF Research Database (Denmark)

    Barfod, Kristoffer Weisskirchner; Bencke, Jesper; Bloch Lauridsen, Hanne

    2014-01-01

    BACKGROUND: Dynamic rehabilitation has been suggested to be an important part of nonoperative treatment of acute Achilles tendon rupture that results in functional outcome and rerupture rates comparable with those of operative treatment. However, the optimal role of weight-bearing during early...... rehabilitation remains unclear. The purpose of this study was to compare immediate weight-bearing with non-weight-bearing in a nonoperative dynamic treatment protocol for Achilles tendon rupture. METHODS: The study was conducted as a blinded, randomized, controlled, parallel superiority trial. Patients eighteen...... to sixty years of age were eligible for inclusion. Both groups were treated nonoperatively with controlled early motion. The intervention group was allowed full weight-bearing from day one, and the control group was non-weight-bearing for six weeks. The primary outcome was the Achilles tendon Total Rupture...

  12. Grizzly bear

    Science.gov (United States)

    Schwartz, C.C.; Miller, S.D.; Haroldson, M.A.; Feldhamer, G.; Thompson, B.; Chapman, J.

    2003-01-01

    The grizzly bear inspires fear, awe, and respect in humans to a degree unmatched by any other North American wild mammal. Like other bear species, it can inflict serious injury and death on humans and sometimes does. Unlike the polar bear (Ursus maritimus) of the sparsely inhabited northern arctic, however, grizzly bears still live in areas visited by crowds of people, where presence of the grizzly remains physically real and emotionally dominant. A hike in the wilderness that includes grizzly bears is different from a stroll in a forest from which grizzly bears have been purged; nighttime conversations around the campfire and dreams in the tent reflect the presence of the great bear. Contributing to the aura of the grizzly bear is the mixture of myth and reality about its ferocity. unpredictable disposition, large size, strength, huge canines, long claws, keen senses, swiftness, and playfulness. They share characteristics with humans such as generalist life history strategies. extended periods of maternal care, and omnivorous diets. These factors capture the human imagination in ways distinct from other North American mammals. Precontact Native American legends reflected the same fascination with the grizzly bear as modern stories and legends (Rockwell 1991).

  13. Molecular weight effects on interfacial properties of linear and ring polymer melts: A molecular dynamics study

    Science.gov (United States)

    Meddah, Chahrazed; Milchev, Andrey; Sabeur, Sid Ahmed; Skvortsov, Alexander M.

    2016-11-01

    Using molecular dynamics simulations, we study and compare the pressure, P, and the surface tension, γ , of linear chains and of ring polymers at the hard walls confining both melts into a slit. We examine the dependence of P and γ on the length (i.e., molecular weight) N of the macromolecules. For linear chains, we find that both pressure and surface tension are inversely proportional to the chain length, P (N ) -P (N →∞ ) ∝N-1,γ (N ) -γ (N →∞ ) ∝N-1 , irrespective of whether the confining planes attract or repel the monomers. In contrast, for melts comprised of cyclic (ring) polymers, neither the pressure nor the surface tension is found to depend on molecular weight N for both kinds of wall-monomer interactions. While other structural properties as, e.g., the probability distributions of trains and loops at impenetrable walls appear quantitatively indistinguishable, we observe an amazing dissimilarity in the probability to find a chain end or a tagged monomer of a ring at a given distance from the wall in both kinds of polymeric melts. In particular, we demonstrate that the conformational equivalence of linear chains in a confined melt to a single chain under conditions of critical adsorption to a planar surface, established two decades ago, does also hold for ring polymers in a melt of linear chains. This analogy does not hold, however, for linear and ring chains in a confined melt of ring chains.

  14. Ultra-light weight undamped tuned dynamic absorber for cryogenically cooled infrared electro-optic payload

    Science.gov (United States)

    Veprik, Alexander; Babitsky, Vladimir

    2017-04-01

    Attenuation of tonal cryocooler induced vibration in infrared electro-optical payloads may be achieved by using of Tuned Dynamic Absorber (TDA) which is, generally speaking, a passive, weakly damped mass-spring system the resonant frequency of which is precisely matched with the driving frequency. Added TDA results in a favorable modification of the frequency response functions of combined structure. In particular, a favorable antiresonant notch appears at the frequency of tonal excitation along with the adjacent secondary resonance, the width and depth of which along with its closeness to the secondary resonance are strongly dependent on the mass and damping ratios. Using heavier TDA favorably results in wider and deeper antiresonant notch along with increased gap between antiresonant and resonant frequencies. Lowering damping in TDA favorably results in deepening the antiresonant notch. The weight of TDA is usually subjected to tight design constrains. Use of lightweight TDA not only diminishes the attainable performance but also complicates the procedure of frequency matching. Along these lines, even minor frequency deviations may negate the TDA performance and even result in TDA failure in case of resonant build up. The authors are presenting theoretical and practical aspects of designing and constructing ultra-light weight TDA in application to vibration attenuation of electro-optical infrared payload relying on Split Stirling linear cryocooler, the driving frequency of which is fixed and may be accurately tuned and maintained using a digital controller over the entire range of working conditions and lifetime; the lack of mass ratio is compensated by minimizing the damping ratio. In one particular case, in excess of 100-fold vibration attenuation has been achieved by adding as little as 5% to the payload weight.

  15. Tracking lung tumour motion using a dynamically weighted optical flow algorithm and electronic portal imaging device

    Science.gov (United States)

    Teo, P. T.; Crow, R.; Van Nest, S.; Sasaki, D.; Pistorius, S.

    2013-07-01

    This paper investigates the feasibility and accuracy of using a computer vision algorithm and electronic portal images to track the motion of a tumour-like target from a breathing phantom. A multi-resolution optical flow algorithm that incorporates weighting based on the differences between frames was used to obtain a set of vectors corresponding to the motion between two frames. A global value representing the average motion was obtained by computing the average weighted mean from the set of vectors. The tracking accuracy of the optical flow algorithm as a function of the breathing rate and target visibility was investigated. Synthetic images with different contrast-to-noise ratios (CNR) were created, and motions were tracked. The accuracy of the proposed algorithm was compared against potentiometer measurements giving average position errors of 0.6 ± 0.2 mm, 0.2 ± 0.2 mm and 0.1 ± 0.1 mm with average velocity errors of 0.2 ± 0.2 mm s-1, 0.4 ± 0.3 mm s-1 and 0.6 ± 0.5 mm s-1 for 6, 12 and 16 breaths min-1 motions, respectively. The cumulative average position error reduces more rapidly with the greater number of breathing cycles present in higher breathing rates. As the CNR increases from 4.27 to 5.6, the average relative error approaches zero and the errors are less dependent on the velocity. When tracking a tumour on a patient's digitally reconstructed radiograph images, a high correlation was obtained between the dynamically weighted optical flow algorithm, a manual delineation process and a centroid tracking algorithm. While the accuracy of our approach is similar to that of other methods, the benefits are that it does not require manual delineation of the target and can therefore provide accurate real-time motion estimation during treatment.

  16. Polar Bear Optimization Algorithm: Meta-Heuristic with Fast Population Movement and Dynamic Birth and Death Mechanism

    Directory of Open Access Journals (Sweden)

    Dawid Połap

    2017-09-01

    Full Text Available In the proposed article, we present a nature-inspired optimization algorithm, which we called Polar Bear Optimization Algorithm (PBO. The inspiration to develop the algorithm comes from the way polar bears hunt to survive in harsh arctic conditions. These carnivorous mammals are active all year round. Frosty climate, unfavorable to other animals, has made polar bears adapt to the specific mode of exploration and hunting in large areas, not only over ice but also water. The proposed novel mathematical model of the way polar bears move in the search for food and hunt can be a valuable method of optimization for various theoretical and practical problems. Optimization is very similar to nature, similarly to search for optimal solutions for mathematical models animals search for optimal conditions to develop in their natural environments. In this method. we have used a model of polar bear behaviors as a search engine for optimal solutions. Proposed simulated adaptation to harsh winter conditions is an advantage for local and global search, while birth and death mechanism controls the population. Proposed PBO was evaluated and compared to other meta-heuristic algorithms using sample test functions and some classical engineering problems. Experimental research results were compared to other algorithms and analyzed using various parameters. The analysis allowed us to identify the leading advantages which are rapid recognition of the area by the relevant population and efficient birth and death mechanism to improve global and local search within the solution space.

  17. Shaking table test and dynamic response analysis of 3-D component base isolation system using multi-layer rubber bearings and coil springs

    Energy Technology Data Exchange (ETDEWEB)

    Tsutsumi, Hideaki; Yamada, Hiroyuki; Ebisawa, Katsumi; Shibata, Katsuyuki [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Fujimoto, Shigeru [Toshiba Corp., Tokyo (Japan)

    2001-06-01

    Introduction of the base isolation technique into the seismic design of nuclear power plant components as well as buildings has been expected as one of the effective countermeasure to reduce the seismic force applied to components. A research program on the base isolation of nuclear components has been carried out at the Japan Atomic Energy Research Institute (JAERI) since 1991. A methodology and a computer code (EBISA: Equipment Base Isolation System Analysis) for evaluating the failure frequency of the nuclear component with the base isolation were developed. In addition, a test program, which is concerned with the above development, aiming at improvement of failure frequency analysis models in the code has been conducted since 1996 to investigate the dynamic behavior and to verify the effectiveness of component base isolation systems. Two base isolation test systems with different characteristics were fabricated and static and dynamic characteristics were measured by static loading and free vibration tests. One which consists of ball bearings and air springs was installed on the test bed to observe the dynamic response under natural earthquake motion. The effect of base isolation system has been observed under several earthquakes. Three-dimensional response and effect of base isolation of another system using multi-layer-rubber-bearings and coil springs has been investigated under various large earthquake motions by shaking table test. This report describes the results of the shaking table tests and dynamic response analysis. (author)

  18. Balancing the Rates of New Bone Formation and Polymer Degradation Enhances Healing of Weight-Bearing Allograft/Polyurethane Composites in Rabbit Femoral Defects

    Science.gov (United States)

    2014-10-03

    and Pelo, S. Cranial reshaping using methyl methacrylate: technical note. J Craniofac Surg 20, 184, 2009. 13. Moreira Gonzalez, A., Jackson, I.T...trabecular bone from the femur, and some factors affecting the shear strength of the cement bone interface. Arch Orthop Trauma Surg 92, 19, 1978. Epub 1978...bearing protocol. Orthopaedic Trauma Association, Balti more, MD, 2010. 54. Kim, S.S., Sun Park, M., Jeon, O., Yong Choi, C., and Kim, B.S. Poly(lactide

  19. Dynamic analysis of centrifugal machines rotors supported on ball bearings by combined application of 3D and beam finite element models

    Science.gov (United States)

    Pavlenko, I. V.; Simonovskiy, V. I.; Demianenko, M. M.

    2017-08-01

    This research paper is aimed to investigating rotor dynamics of multistage centrifugal machines with ball bearings by using the computer programs “Critical frequencies of the rotor” and “Forced oscillations of the rotor,” which are implemented the mathematical model based on the use of beam finite elements. Free and forces oscillations of the rotor for the multistage centrifugal oil pump NPS 200-700 are observed by taking into account the analytical dependence of bearing stiffness on rotor speed, which is previously defined on the basis of results’ approximation for the numerical simulation in ANSYS by applying 3D finite elements. The calculations found that characteristic and constrained oscillations of rotor and corresponded to them forms of vibrations, as well as the form of constrained oscillation on the actual frequency for acceptable residual unbalance are determined.

  20. Weighted fractional permutation entropy and fractional sample entropy for nonlinear Potts financial dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Kaixuan, E-mail: kaixuanxubjtu@yeah.net; Wang, Jun

    2017-02-26

    In this paper, recently introduced permutation entropy and sample entropy are further developed to the fractional cases, weighted fractional permutation entropy (WFPE) and fractional sample entropy (FSE). The fractional order generalization of information entropy is utilized in the above two complexity approaches, to detect the statistical characteristics of fractional order information in complex systems. The effectiveness analysis of proposed methods on the synthetic data and the real-world data reveals that tuning the fractional order allows a high sensitivity and more accurate characterization to the signal evolution, which is useful in describing the dynamics of complex systems. Moreover, the numerical research on nonlinear complexity behaviors is compared between the returns series of Potts financial model and the actual stock markets. And the empirical results confirm the feasibility of the proposed model. - Highlights: • Two new entropy approaches for estimation of nonlinear complexity are proposed for the financial market. • Effectiveness analysis of proposed methods is presented and their respective features are studied. • Empirical research of proposed analysis on seven world financial market indices. • Numerical simulation of Potts financial dynamics is preformed for nonlinear complexity behaviors.

  1. Dynamic considerations in pavement layers moduli evaluation using falling weight deflectometer

    Science.gov (United States)

    Shoukry, Samir N.; Martinelli, David R.; Selezneva, Olga I.

    1996-11-01

    Falling weight deflectometer (FWD) test is employed by many state highway agencies for the nondestructive evaluation of pavement layers moduli. The accuracy of test results changes significantly for different pavement systems and may results in misleading conclusions. In this study, explicit finite element analysis was used to investigate the behavior of pavement layers under the action of an impact load. The time dependent dynamic responses of origin and flexible pavements were compared and significant differences in behavior were observed. Analysis of the time-histories of vertical deformations propagating through the pavement depth reveals that the displacements measured on the surface layer at standard FWD sensors' positions may not be indicative of the displacements of underlying layers. Computer results are provided for the extreme cases of fully bonded and unbonded pavement layers' interfaces. The results of the analysis reveal that the dynamic displacement patterns are much more complicated than the static ones. Animation of the model results indicates that near-surface pavement layers may behave as a set of composite plates resting on an elastic foundation in absence of bonds between the layers interfaces. If there are strong bonds, the near surface layers behave as a single composite solid resting on elastic foundation.

  2. Aerospace applications of magnetic bearings

    Science.gov (United States)

    Downer, James; Goldie, James; Gondhalekar, Vijay; Hockney, Richard

    1994-01-01

    Magnetic bearings have traditionally been considered for use in aerospace applications only where performance advantages have been the primary, if not only, consideration. Conventional wisdom has been that magnetic bearings have certain performance advantages which must be traded off against increased weight, volume, electric power consumption, and system complexity. These perceptions have hampered the use of magnetic bearings in many aerospace applications because weight, volume, and power are almost always primary considerations. This paper will review progress on several active aerospace magnetic bearings programs at SatCon Technology Corporation. The magnetic bearing programs at SatCon cover a broad spectrum of applications including: a magnetically-suspended spacecraft integrated power and attitude control system (IPACS), a magnetically-suspended momentum wheel, magnetic bearings for the gas generator rotor of a turboshaft engine, a vibration-attenuating magnetic bearing system for an airborne telescope, and magnetic bearings for the compressor of a space-rated heat pump system. The emphasis of these programs is to develop magnetic bearing technologies to the point where magnetic bearings can be truly useful, reliable, and well tested components for the aerospace community.

  3. Dynamic interfacial behavior of viscoelastic aqueous hyaluronic acid: effects of molecular weight, concentration and interfacial velocity.

    Science.gov (United States)

    Vorvolakos, Katherine; Coburn, James C; Saylor, David M

    2014-04-07

    An aqueous hyaluronic acid (HA(aq)) pericellular coat, when mediating the tactile aspect of cellular contact inhibition, has three tasks: interface formation, mechanical signal transmission and interface separation. To quantify the interfacial adhesive behavior of HA(aq), we induce simultaneous interface formation and separation between HA(aq) and a model hydrophobic, hysteretic Si-SAM surface. While surface tension γ remains essentially constant, interface formation and separation depend greatly on concentration (5 ≤ C ≤ 30 mg mL(-1)), molecular weight (6 ≤ MW ≤ 2000 kDa) and interfacial velocity (0 ≤ V ≤ 3 mm s(-1)), each of which affect shear elastic and loss moduli G′ and G′′, respectively. Viscoelasticity dictates the mode of interfacial motion: wetting-dewetting, capillary necking, or rolling. Wetting-dewetting is quantified using advancing and receding contact angles θ(A) and θ(R), and the hysteresis between them, yielding data landscapes for each C above the [MW, V] plane. The landscape sizes, shapes, and curvatures disclose the interplay, between surface tension and viscoelasticity, which governs interfacial dynamics. Gel point coordinates modulus G and angular frequency ω appear to predict wetting-dewetting (G 200ω0.075). Dominantly dissipative HA(aq) sticks to itself and distorts irreversibly before separating, while dominantly elastic HA(aq) makes contact and separates with only minor, reversible distortion. We propose the dimensionless number (G′V)/(ω(r)γ), varying from 10(-5) to 10(3) in this work, as a tool to predict the mode of interface formation-separation by relating interfacial kinetics with bulk viscoelasticity. Cellular contact inhibition may be thus aided or compromised by physiological or interventional shifts in [C, MW, V], and thus in (G′V)/(ω(r)γ), which affect both mechanotransduction and interfacial dynamics. These observations, understood in terms of physical properties, may be broadened to probe

  4. Eruptive dynamics and hazards associated with obsidian bearing ignimbrites of the Geghama Volcanic Highland, Central Armenia: a textural insight

    Science.gov (United States)

    Matthews, Zoe; Manning, Christina J.

    2017-04-01

    The Geghama Volcanic highland in central Armenia is an ideal setting to study the young ( 750-25 ka [1]) volcanism that characterises the Lesser Caucasus region. The volcanism in the area is bimodal in composition: the eastern highlands are dominated by numerous monogenetic scoria cones, whilst the west shows more evolved volcanism centered on two obsidian bearing, polygenetic domes (Hatis and Gutanasar) [2]. Activity at Hatis and Gutanasar is thought to have spanned 550ka-200ka [3] and produced a range of products including obsidian flows, ignimbrites and basaltic scoria cones, consistent with long lived and complex magma storage systems. During a similar time period there is evidence for the presence of hominin groups in the surrounding region [3] and it is likely that at least some of the volcanic activity at Hatis and Gutanasar impacted on their distribution [4]. A better understanding of the eruptive behaviour of these volcanoes during this period could therefore shed light on the effect of volcanic activity on the dispersal of man through this period. Whilst large regional studies have striven to better understand the timing and source of volcanism in Armenia, there have been few detailed studies on single volcanoes. Obsidian is ubiquitous within the volcanic material of both Gutanasar and Hatis as lava flows, dome deposits and within ignimbrites. This study aims to better understand the eruptive history of Gutanasar, with specific focus upon the determination of the petrogenetic history of obsidian lenses observed within the ignimbrite deposits. Identification of these obsidians as the result of welding or in-situ melting will help constrain eruptive volumes and flow thickness, important for the reconstruction of palaeo-volcanic hazards. In order to interpret how this obsidian was deposited, macro textural analysis is combined with micro textural measurements of microlite crystals. Quantitative measurements of microlites in obsidian can provide significant

  5. Flexible Multibdoy Contact Dynamics Analysis on Angular Contact Ball Bearings%角接触球轴承柔性多体接触动力学分析

    Institute of Scientific and Technical Information of China (English)

    姚廷强; 谭阳; 王里达

    2011-01-01

    在考虑套圈结构弹性变形和边界条件的影响下,提出并系统地研究一种以多体动力学方法和有限元方法相结合的角接触球轴承动力学混合计算分析方法.应用ADAMS软件编制了动态接触力和约束方程的用户自定义计算程序,建立了运转过程中考虑钢球和套圈动态接触关系的角接触球轴承柔性多体接触动力学分析模型.在承受不同载荷以及考虑转速、接触角和离心力影响的条件下,分别计算讨论了动态接触力、接触角、振动位移和套圈动态接触应力的变化规律.动力学分析模型较好地模拟了角接触球轴承的柔性多体接触动力学特性,为重载荷、冲击载荷或其他复杂载荷作用下的角接触球轴承的设计、寿命预测和工程应用提供了参考方法.%With the effect of structural elastic deformation of rings and boundary conditions, the paper tried to propose a new dynamics hybrid computing method on angular contact ball bearings based on combining finite element method and dynamics of multibody system. Considering dynamic contact between balls and ring's races, the new multi-flexible bodies contact dynamics analysis models of angular contact ball bearings were established by ADAMS. The calculation programme was written for dynamic contact force based on penalty method. Considering the effect of different load parameters, rotate speed and centrifugal force, the distributions and rules of dynamic contact force,contact angle, vibration displacements, dynamic contact stress and strain were discussed. The new dynamic analysis model and simulation results have significances in guiding the design, analysis and application of angular ball bearings with the purpose of vibration and fatigue life with heavy loads, impact loads or complex loads.

  6. Pathogenesis of foot blisters caused by weight-bearing march%负重徒步致足部水疱的发病机制研究

    Institute of Scientific and Technical Information of China (English)

    陈聪; 周维均; 刘明华; 曾凡杰; 田铸; 郭国宁

    2016-01-01

    Objective To analyze the related factors of foot blisters caused by long-distance weight-bearing march and to explore the pathogenesis of foot blisters to provide a useful way for the prevention and treatment.Methods After the 300 km march,counted the number who had accomplished the march,and then recorded the number of foot blisters,location of blisters,and abrasion of sole.Collected the data of gender,age,body mass index (BMI),hand dominance,and whether had bliters before the march through questionnaire.And the data were coded for analysis with SPSS 13.0 statistical package.Results The 7 cases who complete the whole march and 17 cases who already had foot blisters before the march were ruled out of the final statistics.Among the remaining 590 cases,there were 554 cases (93.9%)suffered from foot blisters.And there were 1 282 blisters in total,among which the plantar blisters occupied 98% (1 257 cases).The analysis showed that the incidence of foot blisters had no significant correlation with gender,left/right foot,hand dominance,BMI and age.The predilection sites of blisters were the second and third metatarsals (28.2%),the hallux (21.3%),the fifth metatarsal (18.1%),and the calcaneus (15.8%)of the left foot.The predilection sites of blisters were the second and third metatarsals (33.3%),the hallux (22.4%),the fifth metatarsal (18.6%),and the calcaneus (14.5%)of the right foot.In terms of the abrasion of sole,the lateral heel was worn out the most (34.6% on the left and 34.2% on the right).Conclusion The study confirmed that the incidence of foot blisters had no significant correla-tion with gender,left/right foot,hand dominance,BMI and age,which may be affected by the particularity of this march.Most of the foot blisters occurred in the planta,and the predilection sites of blisters were in accord with sites of of the abrasion of sole and the distribution of plantar shear force,which demonstrated the shear force is the most critical factor on the pathogenesis of

  7. A new modal-based approach for modelling the bump foil structure in the simultaneous solution of foil-air bearing rotor dynamic problems

    Science.gov (United States)

    Bin Hassan, M. F.; Bonello, P.

    2017-05-01

    Recently-proposed techniques for the simultaneous solution of foil-air bearing (FAB) rotor dynamic problems have been limited to a simple bump foil model in which the individual bumps were modelled as independent spring-damper (ISD) subsystems. The present paper addresses this limitation by introducing a modal model of the bump foil structure into the simultaneous solution scheme. The dynamics of the corrugated bump foil structure are first studied using the finite element (FE) technique. This study is experimentally validated using a purpose-made corrugated foil structure. Based on the findings of this study, it is proposed that the dynamics of the full foil structure, including bump interaction and foil inertia, can be represented by a modal model comprising a limited number of modes. This full foil structure modal model (FFSMM) is then adapted into the rotordynamic FAB problem solution scheme, instead of the ISD model. Preliminary results using the FFSMM under static and unbalance excitation conditions are proven to be reliable by comparison against the corresponding ISD foil model results and by cross-correlating different methods for computing the deflection of the full foil structure. The rotor-bearing model is also validated against experimental and theoretical results in the literature.

  8. Ejection of iron-bearing giant-impact fragments and the dynamical and geochemical influence of the fragment re-accretion

    Science.gov (United States)

    Genda, Hidenori; Iizuka, Tsuyoshi; Sasaki, Takanori; Ueno, Yuichiro; Ikoma, Masahiro

    2017-07-01

    The Earth was born in violence. Many giant collisions of protoplanets are thought to have occurred during the terrestrial planet formation. Here we investigated the giant impact stage by using a hybrid code that consistently deals with the orbital evolution of protoplanets around the Sun and the details of processes during giant impacts between two protoplanets. A significant amount of materials (up to several tens of percent of the total mass of the protoplanets) is ejected by giant impacts. We call these ejected fragments the giant-impact fragments (GIFs). In some of the erosive hit-and-run and high-velocity collisions, metallic iron is also ejected, which comes from the colliding protoplanets' cores. From ten numerical simulations for the giant impact stage, we found that the mass fraction of metallic iron in GIFs ranges from ∼1 wt% to ∼25 wt%. We also discussed the effects of the GIFs on the dynamical and geochemical characteristics of formed terrestrial planets. We found that the GIFs have the potential to solve the following dynamical and geochemical conflicts: (1) The Earth, currently in a near circular orbit, is likely to have had a highly eccentric orbit during the giant impact stage. The GIFs are large enough in total mass to lower the eccentricity of the Earth to its current value via their dynamical friction. (2) The concentrations of highly siderophile elements (HSEs) in the Earth's mantle are greater than what was predicted experimentally. Re-accretion of the iron-bearing GIFs onto the Earth can contribute to the excess of HSEs. In addition, Iron-bearing GIFs provide significant reducing agent that could transform primitive CO2-H2O atmosphere and ocean into more reducing H2-bearing atmosphere. Thus, GIFs are important for the origin of Earth's life and its early evolution.

  9. Monitoring ankylosing spondylitis therapy by dynamic contrast-enhanced and diffusion-weighted magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Gaspersic, Natasa [University Medical Centre, Department of Rheumatology, Ljubljana (Slovenia); Sersa, Igor [Jozef Stefan Institute, Ljubljana (Slovenia); Jevtic, Vladimir [Medical Faculty, Department of Radiology, Ljubljana (Slovenia); Tomsic, Matija; Praprotnik, Sonja [University Medical Centre, Department of Rheumatology, Ljubljana (Slovenia)

    2008-02-15

    The effects of different therapies on enthesitis/osteitis in active ankylosing spondylitis (AS) were evaluated by magnetic resonance imaging (MRI). The aim was to assess the role of quantitative MRI in the evaluation of AS treatment efficacy. Thirty patients with active spondylitis or bilateral sacroilitis were selected and followed up for 1 year. Ten of the patients were treated only with non-steroidal anti-inflammatory drugs, 10 patients additionally received at baseline an intravenous pulse of glucocorticoids and 10 patients were treated with regular infusions of infliximab. Disease activity was measured according to clinical instruments and laboratory tests. For each patient, one selected inflamed lesion was followed from baseline through control visits quantitatively by diffusion-weighted imaging (DWI) measuring the apparent diffusion coefficient (ADC) and by dynamic contrast-enhanced imaging (DCEI) with evaluation of the enhancement factor (f{sub enh}) and enhancement gradient (g{sub enh}). Clinical and quantitative MRI parameters diminished significantly with regression of the inflammatory activity. The improvement in AS was most pronounced in patients treated with infliximab; after 12 months the ADC diminished from an average of 1.31 to 0.88 x 10{sup -3} mm{sup 2}/s, f{sub enh} from 1.85 to 0.60, and g{sub enh} from 3.09 to 1.40 %/s. Diffusion-weighted imaging and DCEI were shown to be effective in quantifying changes in inflammation in skeletal lesions during the treatment of AS, and could therefore be convenient for assessing treatment efficacy. To the best of our knowledge this is the first time DWI was used to evaluate the activity of skeletal inflammation in rheumatic diseases such as AS. (orig.)

  10. A 100-kW wind turbine blade dynamics analysis, weight-balance, and structural test results

    Science.gov (United States)

    Anderson, W. D.

    1975-01-01

    The results of dynamic analyses, weight and balance tests, static stiffness tests, and structural vibration tests on the 60-foot-long metal blades for the ERDA-NASA 100-kW wind turbine are presented. The metal blades are shown to be free from structural or dynamic resonance at the wind turbine design speed. Aeroelastic instabilities are unlikely to occur within the normal operating range of the wind turbine.

  11. Sexual dimorphic regulation of body weight dynamics and adipose tissue lipolysis.

    Directory of Open Access Journals (Sweden)

    Verena Benz

    Full Text Available BACKGROUND: Successful reduction of body weight (BW is often followed by recidivism to obesity. BW-changes including BW-loss and -regain is associated with marked alterations in energy expenditure (EE and adipose tissue (AT metabolism. Since these processes are sex-specifically controlled, we investigated sexual dimorphisms in metabolic processes during BW-dynamics (gain-loss-regain. RESEARCH DESIGN: Obesity was induced in C57BL/6J male (m and female (f mice by 15 weeks high-fat diet (HFD feeding. Subsequently BW was reduced (-20% by caloric restriction (CR followed by adaptive feeding, and a regain-phase. Measurement of EE, body composition, blood/organ sampling were performed after each feeding period. Lipolysis was analyzed ex-vivo in gonadal AT. RESULTS: Male mice exhibited accelerated BW-gain compared to females (relative BW-gain m:140.5±3.2%; f:103.7±6.5%; p<0.001. In consonance, lean mass-specific EE was significantly higher in females compared to males during BW-gain. Under CR female mice reached their target-BW significantly faster than male mice (m:12.2 days; f:7.6 days; p<0.001 accompanied by a sustained sex-difference in EE. In addition, female mice predominantly downsized gonadal AT whereas the relation between gonadal and total body fat was not altered in males. Accordingly, only females exhibited an increased rate of forskolin-stimulated lipolysis in AT associated with significantly higher glycerol concentrations, lower RER-values, and increased AT expression of adipose triglyceride lipase (ATGL and hormone sensitive lipase (HSL. Analysis of AT lipolysis in estrogen receptor alpha (ERα-deficient mice revealed a reduced lipolytic rate in the absence of ERα exclusively in females. Finally, re-feeding caused BW-regain faster in males than in females. CONCLUSION: The present study shows sex-specific dynamics during BW-gain-loss-regain. Female mice responded to CR with an increase in lipolytic activity, and augmented lipid

  12. Comparação entre medidas de descarga, simetria e transferência de peso em indivíduos com e sem hemiparesia Comparison between bearing, symmetry, and transfer weight measurements in subjects with or without hemiparesis

    Directory of Open Access Journals (Sweden)

    Emerson Fachin Martins

    2011-09-01

    Full Text Available Avaliação da Simetria e Transferência de Peso (ASTP foi indicada para se fazer associação entre simetria e atividades funcionais nas hemiparesias, apontando simétricos como mais capacitados. Contudo, tais relações não são claras e divergem com evidências que sugerem assimetrias como estratégias funcionais. Assim, objetivou-se verificar se as medidas subjetivamente determinadas pela ASTP concordam com medidas calculas pela descarga de peso entre os pés. Realizou-se estudo observacional do tipo transversal para amostra de sujeitos com hemiparesia (n=20 pareados por idade e gênero a controles (n=20. Os participantes submeteram-se a procedimentos para obtenção de escore determinado pela ASTP e para cálculo da razão de simetria (RS na descarga de peso entre os pés obtido por meio de duas balanças digitais. Os resultados obtidos pela ASTP identificaram apenas um sujeito com hemiparesia apresentando simetria, dentre os quatro sujeitos identificados pela RS como simétricos. Ainda, a ASTP não diferenciou assimetrias com sobrecarga para o lado afetado e apresentou correlação significativa somente quando os escores foram analisados com os valores de RSAssessment of symmetry and weight-transfer (ASWT was indicated to relate symmetry and functional activity in the hemiparesis, pointing as the most qualified symmetrical. However, such relationships are not clear and disagree with evidences suggesting asymmetries as strategies for functional strategies. Then, it was proposed to verify the measurements subjectively determined by ASWT agree with measurements calculated by weight-bearing distribution for each foot. It was applied observational study with transversal design for sample of subjects with hemiparesis (n=20 matched by age and gender with controls (n=20. Participants were included in procedures toobtain scores by ASWT and to calculate symmetry ratio (SR in the weight-bearing between feet by digital scales. The results obtained by

  13. Re-evaluation of Yellowstone grizzly bear population dynamics not supported by empirical data: response to Doak & Cutler

    Science.gov (United States)

    van Manen, Frank T.; Ebinger, Michael R.; Haroldson, Mark A.; Harris, Richard B.; Higgs, Megan D.; Cherry, Steve; White, Gary C.; Schwartz, Charles C.

    2014-01-01

    Doak and Cutler critiqued methods used by the Interagency Grizzly Bear Study Team (IGBST) to estimate grizzly bear population size and trend in the Greater Yellowstone Ecosystem. Here, we focus on the premise, implementation, and interpretation of simulations they used to support their arguments. They argued that population increases documented by IGBST based on females with cubs-of-the-year were an artifact of increased search effort. However, we demonstrate their simulations were neither reflective of the true observation process nor did their results provide statistical support for their conclusion. They further argued that survival and reproductive senescence should be incorporated into population projections, but we demonstrate their choice of extreme mortality risk beyond age 20 and incompatible baseline fecundity led to erroneous conclusions. The conclusions of Doak and Cutler are unsubstantiated when placed within the context of a thorough understanding of the data, study system, and previous research findings and publications.

  14. Experimental quantification of dynamic forces and shaft motion in two different types of backup bearings under several contact conditions

    DEFF Research Database (Denmark)

    Lahriri, Said; Santos, Ilmar

    2013-01-01

    This paper treats the experimental study on a shaft impacting its stator for different cases. The paper focuses mainly on the measured contact forces and the shaft motion in two different types of backup bearings. As such, the measured contact forces are thoroughly studied. These measured contact....... The analyses show that by use of a conventional annular guide, the shaft undergoes a direct transition from normal operation to a full annular backward whirling state for the case of external excitation. However, in a self-excited vibration case, where the speed is gradually increased and decreased through...... the first critical speed, the investigation revealed that different paths initiated the onset of backward whip and whirling motion. In order to improve the whirling and the full annular contact behavior, an unconventional pinned backup bearing is realized. The idea is to utilize pin connections that center...

  15. Molecular dynamics simulations on the interactions of low molecular weight natural organic acids with C60.

    Science.gov (United States)

    Sun, Qian; Xie, Hong-Bin; Chen, Jingwen; Li, Xuehua; Wang, Zhuang; Sheng, Lianxi

    2013-07-01

    As an important part of dissolved organic matter (DOM), low molecular weight organic acids (LOAs) may play a key role in the process for DOM stabilizing carbon nanomaterials (e.g. C60) suspensions in aquatic environment. In addition, both LOAs and C60 have been detected in the troposphere and therefore have a chance to interact with each other in the gaseous phase. However, the mechanism for LOAs-C60 interactions and their environmental implications need further investigations. In this study, molecular dynamics (MD) simulation was employed to investigate the interactions between both neutral and ionic LOAs with C60 in vacuum and water. The results showed that the adsorptions of all LOAs on C60 in energy are favorable, and the aromatic acids have stronger interactions with C60 than the aliphatic acids in vacuum and water. The interaction energies (Eint) of the LOA anions with C60 were weaker than those of their corresponding neutral LOA molecules. The models were also developed to predict and interpret Eint based on the results from MD simulations. Dispersion, induction and hydrophobic interactions were found to be the dominating factor in Eint. These findings indicate that cost-efficient MD simulation can be employed as an important tool to predict the adsorption behavior of LOAs on carbon nanomaterials. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Coherence and spectral weight transfer in the dynamic structure factor of cold lattice bosons

    Science.gov (United States)

    Zaleski, T. A.; Kopeć, T. K.

    2017-01-01

    Ultracold atoms have been used to create novel correlated quantum phases allowing to address many solid-state physics problems using the quasi-particle concept, which is the foundation of our understanding of many-body quantum systems. For bosons, the simplest kinds of excited states involve two particles and they are connected to the dynamic structure factor S (k , ω) , measured using Bragg spectroscopy, similarly to the angle-resolved photoemission spectroscopy (ARPES) in solid state physics - a major tool in the study of high-Tc cuprates. Calculation of S (k , ω) requires a significant numerical effort to determine multidimensional convolutions of momentum and frequency dependent constituents functions, which we achieve using parallelized fast Fourier transform. As a result, we are able to show that spectral weight transfer between low and high energies is an intrinsic property of the strongly correlated Bose system in close analogy to the doped Mott-Hubbard electronic insulator. Furthermore, the appearance of sharp coherence peaks in the superfluid phase of the cold bosons closely resembles the formation of sharply defined quasiparticle excitations below Tc in cuprates suggesting an intimate connection between the intrinsic nature of these seemingly different systems.

  17. [The actions of diffusion weighted imaging (DWI) and dynamic contrast enhanced MRI in differentiating breast tumors].

    Science.gov (United States)

    Luo, Yi; Yu, Jianqun; Chen, Dongdong; Xu, Zhongzi; Zeng, Hanjiang

    2013-12-01

    We studied the actions of diffusion weighted imaging (DWI) and dynamic contrast enhanced (DCE) magnetic resonance imaging (MRI) in differentiating breast tumors. From January 2010 to February 2012, we retrospectively analyzed data of 95 cases with breast tumor pathologically confirmed from DWI and DCE-MRI. We compared the ADC value, time-intensity curve (TIC) and DCE-MRI parameters between breast tumors, and calculated the sensitivity and specificity for differentiating breast tumors. The results were as follows: (1) On DWI, mean ADC value of malignant tumor was lower than that of benign tumor (P value of time to peak (Tpeak) and maximal enhancement ratio (SImax) were lower than that of benign tumor (all P < 0.05). As for TIC, type II and III were more frequently seen in malignant tumor than in benign tumor whereas type I was more common in benign tumor than in malignant tumor (all P < 0.05). For differentiating breast malignant tumors from benign neoplasm, DCE-MRI obtained a sensitivity of 89.7% and specificity of 70.3%. (3) For differentiating breast malignant tumors from benign neoplasm, ADC value together with TIC obtained a sensitivity of 79.3% and specificity of 78.4%. Malignant or benign breast tumors could have their own unique characteristics on DWI and DCE-MRI. These characteristics might be helpful for differentiating these tumors.

  18. Robust dynamic myocardial perfusion CT deconvolution using adaptive-weighted tensor total variation regularization

    Science.gov (United States)

    Gong, Changfei; Zeng, Dong; Bian, Zhaoying; Huang, Jing; Zhang, Xinyu; Zhang, Hua; Lu, Lijun; Feng, Qianjin; Liang, Zhengrong; Ma, Jianhua

    2016-03-01

    Dynamic myocardial perfusion computed tomography (MPCT) is a promising technique for diagnosis and risk stratification of coronary artery disease by assessing the myocardial perfusion hemodynamic maps (MPHM). Meanwhile, the repeated scanning of the same region results in a relatively large radiation dose to patients potentially. In this work, we present a robust MPCT deconvolution algorithm with adaptive-weighted tensor total variation regularization to estimate residue function accurately under the low-dose context, which is termed `MPD-AwTTV'. More specifically, the AwTTV regularization takes into account the anisotropic edge property of the MPCT images compared with the conventional total variation (TV) regularization, which can mitigate the drawbacks of TV regularization. Subsequently, an effective iterative algorithm was adopted to minimize the associative objective function. Experimental results on a modified XCAT phantom demonstrated that the present MPD-AwTTV algorithm outperforms and is superior to other existing deconvolution algorithms in terms of noise-induced artifacts suppression, edge details preservation and accurate MPHM estimation.

  19. Estimating kinetic parameters from dynamic contrast-enhanced T(1)-weighted MRI of a diffusable tracer: standardized quantities and symbols

    DEFF Research Database (Denmark)

    Tofts, P.S.; Brix, G; Buckley, D.L.

    1999-01-01

    We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast-enhanced T(1)-weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd-DTPA). These include a) the volume transfer constant K...

  20. Fixed versus dynamic co-occurrence windows in textrank term weights for information retrieval

    DEFF Research Database (Denmark)

    Lu, Wei; Cheng, Qikai; Lioma, Christina

    2012-01-01

    iteratively is a score for each vertex, i.e. a term weight, that can be used for information retrieval (IR) just like conventional term frequency based term weights. So far, when computing TextRank term weights over co-occurrence graphs, the window of term co-occurrence is always fixed. This work departs from...

  1. Fault Tolerant Magnetic Bearing for Turbomachinery

    Science.gov (United States)

    Choi, Benjamin; Provenza, Andrew

    2001-01-01

    NASA Glenn Research Center (GRC) has developed a Fault-Tolerant Magnetic Bearing Suspension rig to enhance the bearing system safety. It successfully demonstrated that using only two active poles out of eight redundant poles from each radial bearing (that is, simply 12 out of 16 poles dead) levitated the rotor and spun it without losing stability and desired position up to the maximum allowable speed of 20,000 rpm. In this paper, it is demonstrated that as far as the summation of force vectors of the attracting poles and rotor weight is zero, a fault-tolerant magnetic bearing system maintained the rotor at the desired position without losing stability even at the maximum rotor speed. A proportional-integral-derivative (PID) controller generated autonomous corrective actions with no operator's input for the fault situations without losing load capacity in terms of rotor position. This paper also deals with a centralized modal controller to better control the dynamic behavior over system modes.

  2. Concepts of flywheels for energy storage using autostable high-T(sub c) superconducting magnetic bearings

    Science.gov (United States)

    Bornemann, Hans J.; Zabka, R.; Boegler, P.; Urban, C.; Rietschel, H.

    1994-01-01

    A flywheel for energy storage using autostable high-T(sub c) superconducting magnetic bearings has been built. The rotating disk has a total weight of 2.8 kg. The maximum speed is 9240 rpm. A process that allows accelerated, reliable and reproducible production of melt-textured superconducting material used for the bearings has been developed. In order to define optimum configurations for radial and axial bearings, interaction forces in three dimensions and vertical and horizontal stiffness have been measured between superconductors and permanent magnets in different geometries and various shapes. Static as well as dynamic measurements have been performed. Results are being reported and compared to theoretical models.

  3. Dynamic contrast-enhanced quantitative perfusion measurement of the brain using T-1-weighted MRI at 3T

    DEFF Research Database (Denmark)

    Larsson, H.B.W.; Hansen, A.E.; Berg, H.K.;

    2008-01-01

    Purpose: To develop a method for the measurement of brain perfusion based on dynamic contrast-enhanced T-1-weighted MR imaging. Materials and Methods: Dynamic imaging of the first pass of a bolus of a paramagnetic contrast agent was performed using a 3T whole-body magnet and a T-1-weighted fast...... field echo sequence. The input function was obtained from the internal carotid artery. An initial T-1 measurement was performed in order to convert the MR signal to concentration of the contrast agent. Pixelwise and region of interest (ROI)based calculation of cerebral perfusion (CBF) was performed...... inside the infarct core was, 9 mL/100g/min in one of the stroke patients. The other stroke patient had postischemic hyperperfusion and CBF was 140 mL/100g/min. Conclusion: Absolute values of brain perfusion can be obtained using dynamic contrast-enhanced MRI. These values correspond,to expected values...

  4. Hydrostatic and hybrid bearing design

    CERN Document Server

    Rowe, W B

    1983-01-01

    Hydrostatic and Hybrid Bearing Design is a 15-chapter book that focuses on the bearing design and testing. This book first describes the application of hydrostatic bearings, as well as the device pressure, flow, force, power, and temperature. Subsequent chapters discuss the load and flow rate of thrust pads; circuit design, flow control, load, and stiffness; and the basis of the design procedures and selection of tolerances. The specific types of bearings, their design, dynamics, and experimental methods and testing are also shown. This book will be very valuable to students of engineering des

  5. Dynamic Characteristic Analysis of High-speed Spherical Ball Bearing%高速滚珠关节轴承的动力学特性分析

    Institute of Scientific and Technical Information of China (English)

    卓耀彬; 周晓军

    2015-01-01

    The dynamics balance equation of spherical ball bearing under combined loads and high-speed revolution condition is established, during using the outer ring raceway control theory, considering the influence of ball's gyroscopic couple and centrifugal force, and analyzing several factors, such as overall force balance of spherical ball bearing, relationship of geometric structure, curvature of contact point, change of contact angle, relationship of elastic deformation, rotation and revolution of ball, force balance of ball, etc. After analyzing the solution method of the dynamics balance equation, obtaining the change rules of the unknown variables’ feasible regions, and setting up the optimization objective equations, solving method and procedure of optimization equation basing on the complex-constrain genetic algorithm is presented. As an example of spherical bearing BRF30, its dynamics balance equation is established and solved, the change laws of several important bearing statuses are obtained, such as relative displacement between inner ring and outer ring, stiffness of bearing, contact angle, distribution of contact angle, distribution of loads, ratio of revolution, etc. The research provides theoretical basis for designing and analyzing of the bearing, such as standardization of its structural size parameters and characteristic parameters, calculations of equivalent loads and work life, optimal design, etc.%应用外圈滚道控制理论,考虑滚珠陀螺力矩和离心力的影响,分析高速滚珠关节轴承的整体受力平衡、结构尺寸关系、接触点的综合曲率、接触角的变化、弹性变形关系、滚珠的自转和公转、滚珠受力平衡等因素,建立滚珠关节轴承在联合载荷及高速旋转工况下的动力学平衡方程。对动力学平衡方程的求解方法进行分析,得到未知变量可行域的变化规律,建立优化目标方程,提出基于复合形法约束处理遗传算法的优化方

  6. To Compare the Effect of Pre and Post Weight Bearing Anxiety, Depression in Conventional and Modular Prosthesis on Unilateral Transtibial Amputees

    Directory of Open Access Journals (Sweden)

    R. Raja

    2014-01-01

    Full Text Available Aims and Objectives: To compare the effect of anxiety and depression on unilateral trans tibial amputees those who are using conventional and modular patellar tendon bearing (PTB prosthesis with stump exercises. Material and Methods: A sample of 40 persons with below knee amputation who were trained to wear prosthesis were studied with an experimental comparative study design. Patients who were admitted at Kempegowda Institute of Medical Sciences and Research Centre, Bangalore, K. S. Hegde Medical Academy and Research Centre Mangalore, (N=150 who underwent unilateral transtibial, transfemoral and other amputations between August 2009 - December 2011. To find out peri and postoperative prosthetic fitting, anxiety and depression level of transtibial amputees who wear conventional and modular PTB prosthesis. 3 years of experimental comparative study reveals that the outcome measures of peri and post-operative anxiety and depression level while using conventional PTB prosthesis with stump exercises and modular PTB prosthesis with stump exercises on unilateral transtibial amputees. Results: The unilateral transtibial amputees who were trained with modular prosthesis along with stump exercises group patients anxiety and depression levels are reduced as compared to the unilateral transtibial amputees who were trained with conventional PTB prosthesis along with stump exercises. There is no significant difference seen in both the groups while giving stump exercises alone. Conclusion: The unilateral transtibial amputees who were trained with modular prosthesis along with stump exercises group, patient’s anxiety and depression levels are reduced drastically.

  7. Computational design of rolling bearings

    CERN Document Server

    Nguyen-Schäfer, Hung

    2016-01-01

    This book comprehensively presents the computational design of rolling bearings dealing with many interdisciplinary difficult working fields. They encompass elastohydrodynamics (EHD), Hertzian contact theory, oil-film thickness in elastohydrodynamic lubrication (EHL), bearing dynamics, tribology of surface textures, fatigue failure mechanisms, fatigue lifetimes of rolling bearings and lubricating greases, Weibull distribution, rotor balancing, and airborne noises (NVH) in the rolling bearings. Furthermore, the readers are provided with hands-on essential formulas based on the up-to-date DIN ISO norms and helpful examples for computational design of rolling bearings. The topics are intended for undergraduate and graduate students in mechanical and material engineering, research scientists, and practicing engineers who want to understand the interactions between these working fields and to know how to design the rolling bearings for automotive industry and many other industries.

  8. Evaluation of knee-joint cartilage and menisci ten years after isolated and combined ruptures of the medial collateral ligament. Investigation by weight-bearing radiography, MR imaging and analysis of proteoglycan fragments in the joint fluid

    Energy Technology Data Exchange (ETDEWEB)

    Lundberg, M. [Univ. Hospital, Linkoeping (Sweden). Dept. of Orthopaedics and Sports Medicine (Sweden); Thuomas, K.Aa. [Univ. Hospital, Linkoeping (Sweden). Dept. of Diagnostic Radiology; Messner, K. [Univ. Hospital, Linkoeping (Sweden). Dept. of Orthopaedics and Sports Medicine (Sweden)

    1997-01-01

    Purpose: To compare radiography, MR imaging, and chemical analysis in posttraumatic knees. Material and Methods: Ten matched pairs with either isolated partial rupture of the medial collateral ligament or combined medial collateral ligament/anterior cruciate ligament rupture were compared with matched controls 10 years after trauma. Weight-bearing radiographys and MR examinations were compared with proteoglycan fragment concentrations in the joint fluid. Results: The chemical analyses were similar in both trauma groups. The radiographs showed mild signs of arthrosis in half the patients with combined injury. MR images showed almost all injuried knees to have degenerative changes of various degrees in the cartilage and menisci. More frequent and more advanced changes were found after combined injury than after isolated injury (p<0.01). There were no changes in the controls. Conclusion: MR imaging is the best method for detecting and differentiating early posttraumatic knee arthrosis. (orig.).

  9. Journal and Wave Bearing Impedance Calculation Software

    Science.gov (United States)

    Hanford, Amanda; Campbell, Robert

    2012-01-01

    The wave bearing software suite is a MALTA application that computes bearing properties for user-specified wave bearing conditions, as well as plain journal bearings. Wave bearings are fluid film journal bearings with multi-lobed wave patterns around the circumference of the bearing surface. In this software suite, the dynamic coefficients are outputted in a way for easy implementation in a finite element model used in rotor dynamics analysis. The software has a graphical user interface (GUI) for inputting bearing geometry parameters, and uses MATLAB s structure interface for ease of interpreting data. This innovation was developed to provide the stiffness and damping components of wave bearing impedances. The computational method for computing bearing coefficients was originally designed for plain journal bearings and tilting pad bearings. Modifications to include a wave bearing profile consisted of changing the film thickness profile given by an equation, and writing an algorithm to locate the integration limits for each fluid region. Careful consideration was needed to implement the correct integration limits while computing the dynamic coefficients, depending on the form of the input/output variables specified in the algorithm.

  10. Hydrodynamic bearings

    CERN Document Server

    Bonneau, Dominique; Souchet, Dominique

    2014-01-01

    This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.

  11. Synchronization-based topology identification of weighted general complex dynamical networks with time-varying coupling delay

    Science.gov (United States)

    Wu, Xiaoqun

    2008-02-01

    Many existing papers investigated the geometric features, control and synchronization of complex dynamical networks provided with certain topology. However, the exact topology of a network is sometimes unknown or uncertain. Based on LaSalle’s invariance principle, we propose an adaptive feedback technique to identify the exact topology of a weighted general complex dynamical network model with time-varying coupling delay. By receiving the network nodes evolution, the topology of such a kind of network with identical or different nodes, or even with varying topology can be monitored. In comparison with previous methods, time delay is taken into account in this simple, analytical and systematic synchronization-based technique. Particularly, the weight configuration matrix is not necessarily symmetric or irreducible, and the inner-coupling matrix need not be symmetric. Illustrative simulations are provided to verify the correctness and effectiveness of the proposed scheme.

  12. PHASE SEPARATION IN BIMODAL MOLECULAR WEIGHT HIGH DENSITY POLYETHYLENE WITH DIFFERING BRANCH CONTENTS BY MOLECULAR DYNAMICS AND MESODYN SIMULATION

    Institute of Scientific and Technical Information of China (English)

    Zhi-jie Zhang; Zhong-yuan Lu; Ze-sheng Li

    2009-01-01

    The phase behavior of bimodal molecular weight high density polyethylene (BHDPE) in solid state was investigated. Hildebrand solubility parameters (δ) were calculated for the models of blends of higher molecular weight branch polyethylene (HBPE) with different branch contents and lower molecular weight linear polyethylene (LLPE), by using molecular dynamics (MD) simulations. These δ values were then used to calculate the corresponding Flory-Huggins interaction parameter (χ) between HBPE and LLPE models. In order to better understand the compatibility between LLPE and various HBPE, Mesodyn simulations were used to show the density profiles of the blends of LLPE with various HBPE at different compositions. The results indicated that the phase behavior of BHDPE was influenced by both the global branch content of the system and the local branch content, I.e., the branch content of HBPE.

  13. Perfusion-weighted imaging and dynamic 4D angiograms for the estimation of collateral blood flow in lacunar infarction.

    Science.gov (United States)

    Förster, Alex; Mürle, Bettina; Böhme, Johannes; Al-Zghloul, Mansour; Kerl, Hans U; Wenz, Holger; Groden, Christoph

    2016-10-01

    Although lacunar infarction accounts for approximately 25% of ischemic strokes, collateral blood flow through anastomoses is not well evaluated in lacunar infarction. In 111 lacunar infarction patients, we analyzed diffusion-weighted images, perfusion-weighted images, and blood flow on dynamic four-dimensional angiograms generated by use of Signal Processing In NMR-Software. Blood flow was classified as absent (type 1), from periphery to center (type 2), from center to periphery (type 3), and combination of type 2 and 3 (type 4). On diffusion-weighted images, lacunar infarction was found in the basal ganglia (11.7%), internal capsule (24.3%), corona radiata (30.6%), thalamus (24.3%), and brainstem (9.0%). In 58 (52.2%) patients, perfusion-weighted image showed a circumscribed hypoperfusion, in one (0.9%) a circumscribed hyperperfusion, whereas the remainder was normal. In 36 (62.1%) patients, a larger perfusion deficit (>7 mm) was observed. In these, blood flow was classified type 1 in four (11.1%), 2 in 17 (47.2%), 3 in 9 (25.0%), and 4 in six (16.7%) patients. Patients with lacunar infarction in the posterior circulation more often demonstrated blood flow type 2 and less often type 3 (p = 0.01). Detailed examination and graduation of blood flow in lacunar infarction by use of dynamic four-dimensional angiograms is feasible and may serve for a better characterization of this stroke subtype.

  14. Dynamics of Weight Change and Temperature of Apis mellifera (Hymenoptera: Apidae) Colonies in a Wintering Building With Controlled Temperature.

    Science.gov (United States)

    Stalidzans, E; Zacepins, A; Kviesis, A; Brusbardis, V; Meitalovs, J; Paura, L; Bulipopa, N; Liepniece, M

    2017-01-04

    Honey bee wintering in a wintering building (indoors) with controlled microclimate is used in some cold regions to minimize colony losses due to the hard weather conditions. The behavior and possible state of bee colonies in a dark room, isolated from natural environment during winter season, was studied by indirect temperature measurements to analyze the expression of their annual rhythm when it is not affected by ambient temperature, rain, snow, wind, and daylight. Thus, the observed behavior in the wintering building is initiated solely by bee colony internal processes. Experiments were carried out to determine the dynamics of temperature above the upper hive body and weight dynamics of indoors and outdoors wintered honey bee colonies and their brood-rearing performance in spring. We found significantly lower honey consumption-related weight loss of indoor wintered colonies compared with outdoor colonies, while no significant difference in the amount of open or sealed brood was found, suggesting that wintering building saves food and physiological resources without an impact on colony activity in spring. Indoor wintered colonies, with or without thermal insulation, did not have significant differences in food consumption and brood rearing in spring. The thermal behavior and weight dynamics of all experimental groups has changed in the middle of February possibly due to increased brood-rearing activity. Temperature measurement above the upper hive body is a convenient remote monitoring method of wintering process. Predictability of food consumption in a wintering building, with constant temperature, enables wintering without oversupply of wintering honey.

  15. A study of passive weight-bearing lower limb exercise effects on local muscles and whole body oxidative metabolism: a comparison with simulated horse riding, bicycle, and walking exercise.

    Science.gov (United States)

    Shimomura, Kohsuke; Murase, Norio; Osada, Takuya; Kime, Ryotaro; Anjo, Mikiko; Esaki, Kazuki; Shiroishi, Kiyoshi; Hamaoka, Takafumi; Katsumura, Toshihito

    2009-11-10

    We have developed an exercise machine prototype for increasing exercise intensity by means of passively exercising lower limb muscles. The purpose of the present study was to compare the passive exercise intensity of our newly-developed machine with the intensities of different types of exercises. We also attempted to measure muscle activity to study how these forms of exercise affected individual parts of the body. Subjects were 14 healthy men with the following demographics: age 30 years, height 171.5 cm, weight 68.3 kg. They performed 4 types of exercise: Passive weight-bearing lower limb exercise (PWLLE), Simulated horse riding exercise (SHRE), Bicycle exercise, and Walking exercise, as described below at an interval of one week or longer. Oxygen uptake, blood pressure, heart rate, and electromyogram (EMG) were measured or recorded during exercise. At rest prior to exercise and immediately after the end of each exercise intensity, the oxygenated hemoglobin levels of the lower limb muscles were measured by near-infrared spectroscopy to calculate the rate of decline. This rate of decline was obtained immediately after exercise as well as at rest to calculate oxygen consumption of the lower limb muscles as expressed as a ratio of a post-exercise rate of decline to a resting one. The heart rate and oxygen uptake observed in PWLLE during maximal intensity were comparable to that of a 20-watt bicycle exercise or 2 km/hr walking exercise. Maximal intensity PWLLE was found to provoke muscle activity comparable to an 80-watt bicycle or 6 km/hr walking exercise. As was the case with the EMG results, during maximal intensity PWLLE, the rectus femoris muscle consumed oxygen in amounts identical to that of an 80-watt bicycle or a 6 km/hr walking exercise. Passive weight-bearing lower limb exercise using our trial machine could provide approximately 3 MET of exercise and the thigh exhibited muscle activity equivalent to that of 80-watt bicycle or 6 km/hr walking exercise

  16. Correlação entre simetria corporal na descarga de peso e alcance funcional em hemiparéticos crônicos Relationships between body symmetry during weight-bearing and functional reach among chronic hemiparetic patients

    Directory of Open Access Journals (Sweden)

    Laura C. Pereira

    2010-06-01

    Full Text Available CONTEXTUALIZAÇÃO: O controle postural está frequentemente prejudicado nas condições de hemiparesias. Quando na posição em pé, sujeitos hemiparéticos oscilam mais do que sujeitos sem hemicorpo afetado, adotando posturas assimétricas com maior descarga de peso na perna não afetada. OBJETIVO: Analisar o alcance funcional e a dependência por dispositivo de apoio em hemiparéticos crônicos, verificando correlações entre deslocamentos de alcance funcional e valores de simetria de descarga de peso durante a posição em pé. MÉTODOS: Quatorze hemiparéticos classificados em dependentes ou independentes de dispositivo de apoio foram incluídos nos procedimentos experimentais para registro de deslocamento de alcance funcional e valores de simetria. RESULTADOS: Nenhuma diferença significativa foi obtida entre os dependentes e os independentes de dispositivo de apoio para todas as variáveis. Porém, quando a descarga de peso ocorreu no lado não afetado, os mais altos deslocamentos foram significativamente correlacionados com os hemiparéticos mais assimétricos. CONCLUSÃO: A simetria não favorece o alcance funcional nem a independência de dispositivo de apoio em hemiparéticos.BACKGROUND: Postural control is often impaired in hemiparetic patients. During upright stance, hemiparetic subjects sway more than subjects with an unaffected hemibody, and they assume asymmetrical postures to place less weight on the affected side. OBJECTIVE: To analyze functional reach and dependence on support devices among people with chronic hemiparesis and to investigate the relationships between displacements of functional reach and weight-bearing symmetry during upright stance. METHODS: Fourteen participants with hemiparesis, classified as dependent on support devices or independent from them, were included in experimental procedures to record functional reach displacements and symmetry values. RESULTS: No significant differences were found between the

  17. A Dynamic Laplacian for Identifying Lagrangian Coherent Structures on Weighted Riemannian Manifolds

    Science.gov (United States)

    Froyland, Gary; Kwok, Eric

    2017-06-01

    Transport and mixing in dynamical systems are important properties for many physical, chemical, biological, and engineering processes. The detection of transport barriers for dynamics with general time dependence is a difficult, but important problem, because such barriers control how rapidly different parts of phase space (which might correspond to different chemical or biological agents) interact. The key factor is the growth of interfaces that partition phase space into separate regions. The paper Froyland (Nonlinearity 28(10):3587-3622, 2015) introduced the notion of dynamic isoperimetry: the study of sets with persistently small boundary size (the interface) relative to enclosed volume, when evolved by the dynamics. Sets with this minimal boundary size to volume ratio were identified as level sets of dominant eigenfunctions of a dynamic Laplace operator. In this present work we extend the results of Froyland (Nonlinearity 28(10):3587-3622, 2015) to the situation where the dynamics (1) is not necessarily volume preserving, (2) acts on initial agent concentrations different from uniform concentrations, and (3) occurs on a possibly curved phase space. Our main results include generalised versions of the dynamic isoperimetric problem, the dynamic Laplacian, Cheeger's inequality, and the Federer-Fleming theorem. We illustrate the computational approach with some simple numerical examples.

  18. Steady state characteristics of an adjustable hybrid gas bearing – Computational fluid dynamics, modified Reynolds equation and experimental validation

    DEFF Research Database (Denmark)

    Pierart Vásquez, Fabián Gonzalo; Santos, Ilmar

    2015-01-01

    for compressible fluid against computational fluid dynamics (CFD) model is presented in terms of pressure and flow rate considering pressurization levels, journal eccentricities and angular velocities. Correction factors for the jet discharge coefficients are necessary and calculated added by CFD model...

  19. Interpreting lateral dynamic weight shifts using a simple inverted pendulum model.

    Science.gov (United States)

    Kennedy, Michael W; Bretl, Timothy; Schmiedeler, James P

    2014-01-01

    Seventy-five young, healthy adults completed a lateral weight-shifting activity in which each shifted his/her center of pressure (CoP) to visually displayed target locations with the aid of visual CoP feedback. Each subject's CoP data were modeled using a single-link inverted pendulum system with a spring-damper at the joint. This extends the simple inverted pendulum model of static balance in the sagittal plane to lateral weight-shifting balance. The model controlled pendulum angle using PD control and a ramp setpoint trajectory, and weight-shifting was characterized by both shift speed and a non-minimum phase (NMP) behavior metric. This NMP behavior metric examines the force magnitude at shift initiation and provides weight-shifting balance performance information that parallels the examination of peak ground reaction forces in gait analysis. Control parameters were optimized on a subject-by-subject basis to match balance metrics for modeled results to metric values calculated from experimental data. Overall, the model matches experimental data well (average percent error of 0.35% for shifting speed and 0.05% for NMP behavior). These results suggest that the single-link inverted pendulum model can be used effectively to capture lateral weight-shifting balance, as it has been shown to model static balance. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Astrocytic tumour grading: a comparative study of three-dimensional pseudocontinuous arterial spin labelling, dynamic susceptibility contrast-enhanced perfusion-weighted imaging, and diffusion-weighted imaging

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Hua-Feng [302 Hospital of Chinese People' s Liberation Army, Department of Radiology, Beijing (China); Chen, Zhi-Ye; Wang, Yu-Lin; Wang, Yan; Ma, Lin [People' s Liberation Army General Hospital, Department of Radiology, Beijing (China); Lou, Xin [People' s Liberation Army General Hospital, Department of Radiology, Beijing (China); University of California, Department of Neurology, Los Angeles, CA (United States); Gui, Qiu-Ping [People' s Liberation Army General Hospital, Department of Pathology, Beijing (China); Shi, Kai-Ning; Zhou, Zhen-Yu; Zheng, Dan-Dan [General Electric Healthcare (China) Co., Ltd., Beijing; Wang, Danny J.J. [University of California, Department of Neurology, Los Angeles, CA (United States)

    2015-12-15

    We hypothesized that three-dimensional pseudocontinuous arterial spin labelling (pCASL) may have similar efficacy in astrocytic tumour grading as dynamic susceptibility contrast-enhanced perfusion-weighted imaging (DSC-PWI), and the grading accuracy may be further improved when combined with apparent diffusion coefficient (ADC) values. Forty-three patients with astrocytic tumours were studied using diffusion weighted imaging (DWI), pCASL, and DSC-PWI. Histograms of ADC and normalized tumour cerebral blood flow values (nCBF on pCASL and nrCBF on DSC-PWI) were measured and analyzed. The mean 10 % ADC value was the DWI parameter that provided the best differentiation between low-grade astrocytoma (LGA) and high-grade astrocytoma (HGA). The nCBF and nrCBF (1.810 ± 0.979 and 2.070 ± 1.048) in LGA were significantly lower than those (4.505 ± 2.270 and 5.922 ± 2.630) in HGA. For differentiation between LGA and HGA, the cutoff values of 0.764 x 10{sup -3} mm{sup 2}/s for mean 10 % ADC, 2.374 for nCBF, and 3.464 for nrCBF provided the optimal accuracy (74.4 %, 86.1 %, and 88.6 %, respectively). Combining the ADC values with nCBF or nrCBF could further improve the grading accuracy to 97.7 % or 95.3 %, respectively. pCASL is an alternative to DSC-PWI for astrocytic tumour grading. The combination of DWI and contrast-free pCASL offers a valuable choice in patients with risk factors. (orig.)

  1. Dynamics in the length-weight parameters of the mudskipper Periophthalmus barbarus (Gobiidae), in Imo River estuary, Nigeria

    Science.gov (United States)

    King, Richard P.; Udo, Mfon T.

    1998-06-01

    Seasonal and intersexual dynamics in parameters of the length-weight relationship of the mudskipper Periophthalmus barbarus, from Imo River estuary, Nigeria, were studied. The proportionality constant or intercept (a) was aseasonal in males, but in females it was significantly higher in the dry season (November April) than during the rains (May October) due to heightened breeding activity. The length exponent (b) depicted seasonal isometry in males. In females, isometry was evident in the dry season while a positive allometry occurred during the wet season. The sizes of the smallest and largest specimens examined did not regulate variations in the magnitudes of (a) and (b) in both sexes. The insignificant intersexual variation in the length-weight parameters suggests the possibility of using a single predictive length-weight equation for the population. However, the sexes exhibited different monthly rank-orders of (a) and (b), thus making such composite estimates unreliable for a study spanning up to a year. Values of (a) and (b) were inversely correlated in both sexes. The population dynamics implications of the results are discussed.

  2. 转子-轴承-密封系统的多因素动力行为研究%Research on the Dynamic Properties of Rotor-Bearing-Seals System with Different Factors

    Institute of Scientific and Technical Information of China (English)

    王弢; 帅健; 刘焰明

    2012-01-01

    The dynamic systems, such as generator rotors and ship propulsion shafts, include transmission shafts, bearings and seals, which is a typical rotor-bearing-seal dynamic system. When the system is running, some factors, including shaft mass eccentricity, bearing lubrication properties and seal force, change the system running stability and make it into different movement conditions. The dynamic equations are given in the paper. With the numerical integral method, the influences of shaft mass eccentricity, bearing lubrication properties and seal force on the dynamic system are investigated. Some relationships between the factors with the system running stability are offered in the paper, which are very significant in theory.%建立了转子-轴承-密封动力学模型,通过数值积分模拟方法,研究了轴系对中偏心、轴承支承润滑特性、密封力等动态因素对系统振动的影响,其运动行为和各因素对系统运动稳定性的影响,得出了各种因素与系统运动行为之间的相互关系.

  3. Dynamics of a forced 2 dof piece-wise linear system by consideration of the weight

    Directory of Open Access Journals (Sweden)

    Dimitrijevic Z.

    2012-07-01

    Full Text Available Energy pumping phenomenon between a linear system and a non-smooth system by taking into account the weight of the system is studied. The system faces bifurcation when it reaches to its unstable border and then according to external forcing term it can follow lower stable branch or to face strongly modulated response by hysteresis jumps between its stable branches.

  4. 左侧带权凸二分图动态权值匹配%Dynamic Weight Matchings in Left Weighted Convex Bipartite Graphs

    Institute of Scientific and Technical Information of China (English)

    祖佺; 张苗苗; 刘静

    2016-01-01

    .The existing algorithm for dynamic cardinality matching in convex bipartite graphs cannot solve dynamic maximum weighted matching.And this paper researches dynamic maximum weight matching in left weighted convex bipartite graphs.To solve this problem,we propose a framework that is maintaining the set of vertices participating in the matching in the update operations,and based on the set,computing the matching information in the query operations.We define the concept of replaceable set,i.e.,the set of matched vertices reachable by alternating paths from an unmatched vertex,and prove that the computation for replaceable sets is sufficient to maintain the matched vertex set. We then define the concept of tight subgraph,and prove that computing a replaceable set is equivalent to finding a certain tight subgraph.Thus,the traditional way of computing matchings via finding alternating paths is reduced to our approach of computing matchings via finding a subgraph structure.Utilizing the convexity property of a convex bipartite graph,we further put forward a method to find a tight subgraph by searching for the maximum or minimum y vertices in the subgraph.The method can be efficiently implemented in an augmented balanced binary search tree data structure with the implicit representation of the subgraph.Then we design algorithms that maintain the update operations in O (log2|V|)amortized time and the query operations in worst-case linear time, which achieves the same time bound as the best known solution to the dynamic cardinality matching problem in the unweighted situation.

  5. Dynamic quality of service differentiation using fixed code weight in optical CDMA networks

    Science.gov (United States)

    Kakaee, Majid H.; Essa, Shawnim I.; Abd, Thanaa H.; Seyedzadeh, Saleh

    2015-11-01

    The emergence of network-driven applications, such as internet, video conferencing, and online gaming, brings in the need for a network the environments with capability of providing diverse Quality of Services (QoS). In this paper, a new code family of novel spreading sequences, called a Multi-Service (MS) code, has been constructed to support multiple services in Optical- Code Division Multiple Access (CDMA) system. The proposed method uses fixed weight for all services, however reducing the interfering codewords for the users requiring higher QoS. The performance of the proposed code is demonstrated using mathematical analysis. It shown that the total number of served users with satisfactory BER of 10-9 using NB=2 is 82, while they are only 36 and 10 when NB=3 and 4 respectively. The developed MS code is compared with variable-weight codes such as Variable Weight-Khazani Syed (VW-KS) and Multi-Weight-Random Diagonal (MW-RD). Different numbers of basic users (NB) are used to support triple-play services (audio, data and video) with different QoS requirements. Furthermore, reference to the BER of 10-12, 10-9, and 10-3 for video, data and audio, respectively, the system can support up to 45 total users. Hence, results show that the technique can clearly provide a relative QoS differentiation with lower value of basic users can support larger number of subscribers as well as better performance in terms of acceptable BER of 10-9 at fixed code weight.

  6. Delaunay-Object-Dynamics: cell mechanics with a 3D kinetic and dynamic weighted Delaunay-triangulation.

    Science.gov (United States)

    Meyer-Hermann, Michael

    2008-01-01

    Mathematical methods in Biology are of increasing relevance for understanding the control and the dynamics of biological systems with medical relevance. In particular, agent-based methods turn more and more important because of fast increasing computational power which makes even large systems accessible. An overview of different mathematical methods used in Theoretical Biology is provided and a novel agent-based method for cell mechanics based on Delaunay-triangulations and Voronoi-tessellations is explained in more detail: The Delaunay-Object-Dynamics method. It is claimed that the model combines physically realistic cell mechanics with a reasonable computational load. The power of the approach is illustrated with two examples, avascular tumor growth and genesis of lymphoid tissue in a cell-flow equilibrium.

  7. Array Pattern Synthesis Using Particle Swarm Optimization with Dynamic Inertia Weight

    Directory of Open Access Journals (Sweden)

    Chuang Han

    2016-01-01

    Full Text Available A Feedback Particle Swarm Optimization (FPSO with a family of fitness functions is proposed to minimize sidelobe level (SLL and control null. In order to search in a large initial space and converge fast in local space to a refined solution, a FPSO with nonlinear inertia weight algorithm is developed, which is determined by a subtriplicate function with feedback taken from the fitness of the best previous position. The optimized objectives in the fitness function can obtain an accurate null level independently. The directly constrained SLL range reveals the capability to reduce SLL. Considering both element positions and complex weight coefficients, a low-level SLL, accurate null at specific directions, and constrained main beam are achieved. Numerical examples using a uniform linear array of isotropic elements are simulated, which demonstrate the effectiveness of the proposed array pattern synthesis approach.

  8. Fast Dynamic Meshing Method Based on Delaunay Graph and Inverse Distance Weighting Interpolation

    Science.gov (United States)

    Wang, Yibin; Qin, Ning; Zhao, Ning

    2016-06-01

    A novel mesh deformation technique is developed based on the Delaunay graph mapping method and the inverse distance weighting (IDW) interpolation. The algorithm maintains the advantages of the efficiency of Delaunay-graph-mapping mesh deformation while possess the ability for better controlling the near surface mesh quality. The Delaunay graph is used to divide the mesh domain into a number of sub-domains. On each of the sub-domains, the inverse distance weighting interpolation is applied to build a much smaller sized translation matrix between the original mesh and the deformed mesh, resulting a similar efficiency for the mesh deformation as compared to the fast Delaunay graph mapping method. The paper will show how the near-wall mesh quality is controlled and improved by the new method while the computational time is compared with the original Delaunay graph mapping method.

  9. Estimating the Effects of Obesity and Weight Change on Mortality Using a Dynamic Causal Model

    OpenAIRE

    Bochen Cao

    2015-01-01

    Background A well-known challenge in estimating the mortality risks of obesity is reverse causality attributable to illness-associated and smoking-associated weight loss. Given that the likelihood of chronic and acute illnesses rises with age, reverse causality is most threatening to estimates derived from elderly populations. Methods I analyzed data from 12,523 respondents over 50 years old from a nationally representative longitudinal dataset, the Health and Retirement Study (HRS). The effe...

  10. Vibration Characteristics of Hydrodynamic Fluid Film Pocket Journal Bearings

    Directory of Open Access Journals (Sweden)

    N. S. Feng

    2010-01-01

    Full Text Available Theoretical analyses of hydrodynamic fluid film bearings with different bearing profiles rely on solutions of the Reynolds equation. This paper presents an approach used for analysing the so-called pocket bearings formed from a combination of offset circular bearing profiles. The results show that the variation of the dynamic bearing characteristics with different load inclinations for the pocket bearings is less than that for the elliptic bearing counterpart. It is shown that the natural frequencies as well as the critical speeds, and hence the vibrational behaviour, can also be significantly different for an industrial rotor supported by the different bearings.

  11. Convergence of Weighted Min-Sum Decoding Via Dynamic Programming on Trees

    CERN Document Server

    Jian, Yung-Yih

    2011-01-01

    Applying the max-product (and belief-propagation) algorithms to loopy graphs is now quite popular for best assignment problems. This is largely due to their low computational complexity and impressive performance in practice. Still, there is no general understanding of the conditions required for convergence and/or the optimality of converged solutions. This paper presents an analysis of both attenuated max-product (AMP) decoding and weighted min-sum (WMS) decoding for LDPC codes which guarantees convergence to a fixed point when a weight parameter, {\\beta}, is sufficiently small. It also shows that, if the fixed point satisfies some consistency conditions, then it must be both the linear-programming (LP) and maximum-likelihood (ML) solution. For (dv,dc)-regular LDPC codes, the weight must satisfy {\\beta}(dv-1) \\leq 1 whereas the results proposed by Frey and Koetter require instead that {\\beta}(dv-1)(dc-1) 1 is also given. Finally, connections are explored with recent work by Arora et al. on the threshold of...

  12. Real-time Classification of Non-Weight Bearing Lower-Limb Movements Using EMG to Facilitate Phantom Motor Execution: Engineering and Case Study Application on Phantom Limb Pain

    Directory of Open Access Journals (Sweden)

    Eva Lendaro

    2017-09-01

    Full Text Available Phantom motor execution (PME, facilitated by myoelectric pattern recognition (MPR and virtual reality (VR, is positioned to be a viable option to treat phantom limb pain (PLP. A recent clinical trial using PME on upper-limb amputees with chronic intractable PLP yielded promising results. However, further work in the area of signal acquisition is needed if such technology is to be used on subjects with lower-limb amputation. We propose two alternative electrode configurations to conventional, bipolar, targeted recordings for acquiring surface electromyography. We evaluated their performance in a real-time MPR task for non-weight-bearing, lower-limb movements. We found that monopolar recordings using a circumferential electrode of conductive fabric, performed similarly to classical bipolar recordings, but were easier to use in a clinical setting. In addition, we present the first case study of a lower-limb amputee with chronic, intractable PLP treated with PME. The patient’s Pain Rating Index dropped by 22 points (from 32 to 10, 68% after 23 PME sessions. These results represent a methodological advancement and a positive proof-of-concept of PME in lower limbs. Further work remains to be conducted for a high-evidence level clinical validation of PME as a treatment of PLP in lower-limb amputees.

  13. Use of an arm weight-bearing combined with upper-limb reaching apparatus to facilitate motor paralysis recovery in an incomplete spinal cord injury patient: a single case report

    Science.gov (United States)

    Hoei, Takashi; Kawahira, Kazumi; Fukuda, Hidefumi; Sihgenobu, Keizo; Shimodozono, Megumi; Ogura, Tadashi

    2017-01-01

    [Purpose] Training using an arm weight-bearing device combined with upper-limb reaching apparatus to facilitate motor paralysis recovery, named the “Reaching Robot”, as well as Repetitive Facilitation Exercise were applied to a patient with severe impairment of the shoulder and elbow due to incomplete spinal cord injury and the effects were examined. [Subjects and Methods] A 66-year-old man with incomplete spinal cord injury participated in an upper extremity rehabilitation program involving a Reaching Robot. The program was comprised of active motor suspension, continuous low amplitude neuromuscular electrical stimulation and functional vibratory stimulation, as well as Repetitive Facilitation Exercise combined with continuous low amplitude neuromuscular electrical stimulation. This protocol used a crossover design following an A1-B1-A2-B2. “A” consisted of 2 weeks of Repetitive Facilitation Exercise, and “B” consisted of 2 weeks of Reaching Robot training. [Results] Improvements were observed after all sessions. Active range of motion for shoulder flexion improved after 2 weeks of Reaching Robot sessions only. There were no adverse events. [Conclusion] Reaching Robot training for severe paretic upper-extremity after incomplete spinal cord injury was a safe and effective treatment. Reaching Robot training may be useful for rehabilitation of paretic upper-extremity after incomplete spinal cord injury. PMID:28210068

  14. Using gait analysis to assess weight bearing in rats with Freund׳s complete adjuvant-induced monoarthritis to improve predictivity: Interfering with the cyclooxygenase and nerve growth factor pathways.

    Science.gov (United States)

    Ängeby Möller, Kristina; Berge, Odd-Geir; Finn, Anja; Stenfors, Carina; Svensson, Camilla I

    2015-06-01

    Lack of predictive power for drug effects has been a major criticism against animal pain models. It is therefore important to define the utility and limitations of different models. The aim of this study was to extend previous work on gait analysis as a tool to investigate pharmacological effects in monoarthritic rats, specifically to test the hypothesis that monoarthritis induced by Freund׳s complete adjuvant (FCA) provides a better estimate of overall analgesic efficacy of established, and novel, clinically effective and ineffective therapeutic approaches. Male rats injected intra-articularly into one ankle joint with FCA (1.0mg/ml) were treated with the monoclonal antibody to nerve growth factor (NGF), MEDI-578, the inhibitors of tropomyosin receptor kinases A, B and C (pan-Trk) AZ6623 or AZ7092, the transient receptor potential vanilloid 1 (TRPV1) inhibitor AZD1386, or the cyclooxygenase (COX) inhibitors naproxen, ibuprofen, valdecoxib or rofecoxib. Effects on weight bearing during locomotion were tested using video capture of print images. The apparent efficacy in this model was Trk inhibitors≥anti-NGF antibody>COX inhibitors. The TRPV1 inhibitor was ineffective. Together with previous data, the results support using gait-related parameters in the monoarthritis model. FCA as induction agent seems to provide a good overall prediction of analgesic efficacy in disorders with inflammatory joint pain.

  15. Biological characteristics and clinical application of artificial hip joint weight-bearing surface materials%人工髋关节负重面材料的生物特性及其临床应用

    Institute of Scientific and Technical Information of China (English)

    唐焜

    2012-01-01

    背景:人工髋关节假体材料对髋关节置换的成功率及对患者治愈率起到决定性作用.目的:评价不同组合方式髋关节负重面材料的性能及置入体内与机体的生物相容性.方法:以"全髋关节置换,人工髋关节,金属,陶瓷,聚乙烯,生物相容性,临床应用;total hip replacement,Artificialhip,prosthetic materials,Biocompatibility,clinical application"为关键词,应用计算机检索2001-01/2011-12 万方数据库、PubMed 数据库有关人工髋关节负重面生物材料与宿主生物相容性的文章.结果与结论:金属-超高分子量聚乙烯组合是目前常用的组合,也是衡量其他组合的金标准,但其磨损颗粒引起周围组织反应导致骨溶解和无菌性假体松动;金属-高交联聚乙烯、金属-金属、陶瓷-陶瓷和陶瓷-聚乙烯组合均在一定程度上减少了磨损,但金属离子毒性、陶瓷脆性、造价高等仍然是需要解决的问题.理想的负重面材料应具有良好生物相容、耐蚀性、耐磨性、耐疲劳性、强韧性好等特点,目前人工髋关节负重面组合材料各有优缺点.因此,临床医师针对不同的患者,采取个体化治疗原则,综合患者病情和经济状况等多方面因素,选择合适假体组合类型,以期达到最佳临床疗效.%BACKGROUND: Artificial hip prosthesis materials play a decisive role in the success rates of hip replacement and the recovery rate for patientsOBJECTIVE: To evaluate the properties of hip joint weight-bearing surface materials with different combinations, as well as the biocompatibihty of the materials and the host after implanted in vivoMETHODS: The keyword of "total hip replacement, artificial hip joint, metal, ceramic, polyethylene, biocompatibihty, clinical application" in Chinese and "total hip replacement, artificial hip, prosthetic materials, biocompatibihty, clinical application" in English were used to retrieve the articles published from January 2001 to

  16. Effect of weight-bearing activity on the center of rotation in the lower lumbar vertebrae%负重状态对下腰椎椎体间旋转中心的影响

    Institute of Scientific and Technical Information of China (English)

    刘佳男; 夏群; 苗军; 李宏达; 魏冬

    2016-01-01

    BACKGROUND:Epidemiologic reports have indicated that excessive weight-bearing exercise is one of important risk factors for lumbar degeneration, but the effects of weight-bearing activity on normal lumbar motion pattern are stil not clear. OBJECTIVE:To measure the changing characteristics and rules of position at the center of rotation of the lower lumbar spine during a weight-lifting activity of normal person. METHODS: Fourteen asymptomatic subjects with a mean age of (25±5) years were recruited for this study. The L4-5 and L5-S1 segments of each subject were CT-scanned to construct 3D models using dual X-ray imaging system and spiral CT examination combined technology in the aid of computer software. The physiological load and lumbar spinal 3D motion under the loading condition were reproduced when matching the flexion, neutrality and extension in the dual X-ray imaging system and on dual oblique lumbar X-ray image. Coordinate systems were established at the vertebral body of L4-S1 to obtain the center of rotation during flexion-to-neutral, neutral-to-extension and the ful flexion-extension motion. RESULTS AND CONCLUSION: (1) Under physiological load, the center of rotation of L4-5 of normal person was located about 1.0 mm anterior to the central axis of the vertebral body, and the center of rotation of L5-S1 was located about 0.7 mm anterior to the central axis of the vertebral body. (2) With weight loading, the center of rotation of both two segments shifted backward about 0.5 mm. There was no statistical difference between these two loading conditions. (3) When the center of rotation in flexion and extension was calculated respectively, the moving range of the center of rotation at both L4-5and L5-S1 became larger due to taking loads of 10 kg (P < 0.05). In flexion, the center of rotation at L5-S1 significantly shifted forward during a weight-lifting activity (P < 0.05). (4) These results confirm that compared with non-weight-bearing condition, the trajectory

  17. Nonlinear Analysis of Rotors Supported by Air Foil Journal Bearings – Theory and Experiments

    DEFF Research Database (Denmark)

    Larsen, Jon Steffen

    Direct driven compressors supported by air foil bearings (AFB) are gaining increasing popularity, for example within the waste water treatment industry where the demand for larger machines up to 250 kW is growing. In order to keep production costs low, the shaft and bearing design need to be simple...... and allow manufacturing using conventional materials and production facilities. As a consequence, the assembled rotor weight can be up to 50 kg. The compressors are operated at variable speed and load and are subjected to several starts and stops per day. Therefore, the rotor bearing design must be robust...... with a good margin of rotordynamical stable operation. To ensure this, good mathematical models, capable of accurately predicting the dynamic behaviour of the rotor-bearing system, are required at the design stage. This thesis focuses on developing and improving existing mathematical models for predicting...

  18. The Avoidance of Saturation Limits in Magnetic Bearing Systems During Transient Excitation

    Science.gov (United States)

    Rutland, Neil K.; Keogh, Patrick S.; Burrows, Clifford R.

    1996-01-01

    When a transient event, such as mass loss, occurs in a rotor/magnetic bearing system, optimal vibration control forces may exceed bearing capabilities. This will be inevitable when the mass loss is sufficiently large and a conditionally unstable dynamic system could result if the bearing characteristic become non-linear. This paper provides a controller design procedure to suppress, where possible, bearing force demands below saturation levels while maintaining vibration control. It utilizes H(sub infinity) optimization with appropriate input and output weightings. Simulation of transient behavior following mass loss from a flexible rotor is used to demonstrate the avoidance of conditional instability. A compromise between transient control force and vibration levels was achieved.

  19. Dynamic crystallization experiments bearing on the origin of textures in impact-generated liquids. [for lunar rock formation

    Science.gov (United States)

    Lofgren, G. E.

    1977-01-01

    Dynamic crystallization experiments on a synthetic glass of 14310 composition show that the density and distribution of crystals present at the initiation of cooling can drastically affect the texture of the crystallized product. Experiments were performed in one-atmosphere gas-mixing furnaces at an oxygen fugacity slightly below iron-wustite, and precooling crystallization, cooling history, and melt history were systematically varied. When cooled from a complete liquid, the experimental charges were porphyritic with 1-2 mm phenocrysts set in a very fine-grained matrix (less than 0.1 mm). This result suggests that 14310 did not cool from a complete melt. When cooled from a crystal-liquid mixture, the experimental charges had widely varying textures depending on the density and distribution of crystals that act as nucleation sites. It is suggested that the close spatial association of widely divergent textures in the matrices of some breccias and rocks might arise in this manner; local variations in cooling rates are not required.

  20. Progressive Time-Weighted Dynamic Energy Efficiency, Energy Decoupling Rate, and Decarbonization: An Empirical Study on G7 and BRICS

    Directory of Open Access Journals (Sweden)

    Chia-Jung Tu

    2016-09-01

    Full Text Available Energy is a critical factor of economic growth, but the overuse of it results in global warming and climate change. Hence, energy efficiency improvement can help mitigate climate change and prevent economic losses or even ecological extinction. The data envelopment analysis (DEA approach has been extensively applied for energy efficiency estimation, but past studies of this estimation employ a static mode that does not consider consecutive periods and the carry-over effect. This study estimates energy efficiency under a weight-restricted dynamic DEA (WrD-DEA model, creates a weight-restricted dynamic energy efficiency (WrD-EE indicator, and discusses issues concerning the energy decoupling rate and decarbonization. We utilize members in the Group of Seven (G7 and BRICS (Brazil, China, India, Russia, and South Africa for our experimental observations. The main results herein are: (1 BRICS has larger room for improvement to achieve the standard ratio of the energy decoupling rate than the G7; (2 the G7 and BRICS do not converge to decarbonization; and (3 BRICS exhibits more rapid improvement on energy efficiency than the G7.

  1. Dynamic interplay among homeostatic, hedonic, and cognitive feedback circuits regulating body weight.

    Science.gov (United States)

    Hall, Kevin D; Hammond, Ross A; Rahmandad, Hazhir

    2014-07-01

    Obesity is associated with a prolonged imbalance between energy intake and expenditure, both of which are regulated by multiple feedback processes within and across individuals. These processes constitute 3 hierarchical control systems-homeostatic, hedonic, and cognitive-with extensive interaction among them. Understanding complex eating behavior requires consideration of all 3 systems and their interactions. Existing models of these processes are widely scattered, with relatively few attempts to integrate across mechanisms. We briefly review available empirical evidence and dynamic models, discussing challenges and potential for better integration. We conclude that developing richer models of dynamic interplay among systems should be a priority in the future study of obesity and that systems science modeling offers the potential to aid in this goal.

  2. Temporal weighting of binaural information at low frequencies: Discrimination of dynamic interaural time and level differences.

    Science.gov (United States)

    Diedesch, Anna C; Stecker, G Christopher

    2015-07-01

    The importance of sound onsets in binaural hearing has been addressed in many studies, particularly at high frequencies, where the onset of the envelope may carry much of the useful binaural information. Some studies suggest that sound onsets might play a similar role in the processing of binaural cues [e.g., fine-structure interaural time differences (ITD)] at low frequencies. This study measured listeners' sensitivity to ITD and interaural level differences (ILD) present in early (i.e., onset) and late parts of 80-ms pure tones of 250-, 500-, and 1000-Hz frequency. Following previous studies, tones carried static interaural cues or dynamic cues that peaked at sound onset and diminished to zero at sound offset or vice versa. Although better thresholds were observed in static than dynamic conditions overall, ITD discrimination was especially impaired, regardless of frequency, when cues were not available at sound onset. Results for ILD followed a similar pattern at 1000 Hz; at lower frequencies, ILD thresholds did not differ significantly between dynamic-cue conditions. The results support the "onset" hypothesis of Houtgast and Plomp [(1968). J. Acoust. Soc. Am. 44, 807-812] for ITD discrimination, but not necessarily ILD discrimination, in low-frequency pure tones.

  3. Dynamic relations between fast-food restaurant and body weight status: a longitudinal and multilevel analysis of Chinese adults

    Science.gov (United States)

    Xu, Hongwei; Short, Susan E; Liu, Tao

    2013-01-01

    Background Mixed findings have been reported on the association between Western fast-food restaurants and body weight status. Results vary across study contexts and are sensitive to the samples, measures and methods used. Most studies have failed to examine the temporally dynamic associations between community exposure to fast-food restaurants and weight changes. Methods Bayesian hierarchical regressions are used to model changes in body mass index, waist-to-height ratio (WHtR) and waist-to-hip ratio (WHpR) as a function of changes in Western fast-food restaurants in 216 communities for more than 9000 Chinese adults followed up multiple times between 2000 and 2009. Results Number of Western fast-food restaurants is positively associated with subsequent increases in WHtR and WHpR among rural population. More fast-food restaurants are positively associated with a future increase in WHpR for urban women. Increased availability of fast food between two waves is related to increased WHtR for urban men over the same period. A past increase in number of fast-food restaurants is associated with subsequent increases in WHtR and WHpR for rural population. Conclusions The associations between community exposure to Western fast food and weight changes are temporally dynamic rather than static. Improved measures of exposure to community environment are needed to achieve more precise estimates and better understanding of these relationships. In light of the findings in this study and China’s rapid economic growth, further investigation and increased public health monitoring is warranted since Western fast food is likely to be more accessible and affordable in the near future. PMID:22923769

  4. Geochemical speciation and dynamic of copper in tropical semi-arid soils exposed to metal-bearing mine wastes.

    Science.gov (United States)

    Perlatti, Fabio; Otero, Xosé Luis; Macias, Felipe; Ferreira, Tiago Osório

    2014-12-01

    The potentially hazardous effects of rock wastes disposed at open pit in three different areas (Pr: Ore processing; Wr: Waste rock and Bd: Border) of an abandoned copper mine were evaluated in this study, with emphasis on acid drainage generation, metal contamination and copper geochemical dynamics in soils. Samples of waste rock were analyzed by Energy dispersive X-ray fluorescence (XRF), scanning electron microscopy with microanalysis (SEM-EDS) and X-ray diffraction (XRD). Soil samples were analyzed to determine the total metal contents (XRF), mineralogy (XRD), pH (H2O and H2O2), organic and inorganic carbon, % of total N, S and P, particle size, and a sequential extraction procedure was used to identify the different copper fractions. As a result of the prevalence of carbonates over sulphides in the wastes, the soil pH remained close to neutral, with absence of acid mine drainage. The geochemical interaction between these mineral phases seems to be the main mechanism to release Cu(2)(+) ions. Total Cu in soils from the Pr area reached 11,180mg.kg(-1), while in Wr and Bd areas the values reached, on average, 4683 and 1086mg.kg(-1), respectively, indicating a very high level of soil contamination. In the Pr and Wr, the Cu was mainly associated with carbonates and amorphous iron oxides. In the Bd areas, the presence of vegetation has influenced the geochemical behavior of copper by increasing the dissolution of carbonates, affecting the buffer capacity of soils against sulphide oxidation, reducing the pH levels and enhancing the proportion of exchangeable and organic bound Cu. The present findings show that the use of plants or organic amendments in mine sites with high concentration of Cu carbonate-containing wastes should be viewed with caution, as the practice may enhance the mobilization of copper to the environment due to an increase in the rate of carbonates dissolution. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Geochemical speciation and dynamic of copper in tropical semi-arid soils exposed to metal-bearing mine wastes

    Energy Technology Data Exchange (ETDEWEB)

    Perlatti, Fabio [Department of Environmental Technology, National Department of Mineral Production – DNPM, Rua Dr. José Lourenço, 90560115-280 Fortaleza, CE (Brazil); Graduate Course of Ecology and Natural Resources, Department of Biology, Federal University of Ceará – UFC, Building 906, 60455-760, Fortaleza, CE (Brazil); Otero, Xosé Luis; Macias, Felipe [Department of Edaphology and Agricultural Chemistry, Faculty of Biology, University of Santiago de Compostela – USC, Rúa Lope Gómez de Marzoa, s/n. Campus sur, 15782 Santiago de Compostela (Spain); Ferreira, Tiago Osório, E-mail: toferreira@usp.br [Department of Soil Science, University of São Paulo (ESALQ/USP), Av. Pádua Dias, 11, 13418-900, Piracicaba, SP (Brazil); Graduate Course of Ecology and Natural Resources, Department of Biology, Federal University of Ceará – UFC, Building 906, 60455-760, Fortaleza, CE (Brazil)

    2014-12-01

    The potentially hazardous effects of rock wastes disposed at open pit in three different areas (Pr: Ore processing; Wr: Waste rock and Bd: Border) of an abandoned copper mine were evaluated in this study, with emphasis on acid drainage generation, metal contamination and copper geochemical dynamics in soils. Samples of waste rock were analyzed by Energy dispersive X-ray fluorescence (XRF), scanning electron microscopy with microanalysis (SEM-EDS) and X-ray diffraction (XRD). Soil samples were analyzed to determine the total metal contents (XRF), mineralogy (XRD), pH (H2O and H2O2), organic and inorganic carbon, % of total N, S and P, particle size, and a sequential extraction procedure was used to identify the different copper fractions. As a result of the prevalence of carbonates over sulphides in the wastes, the soil pH remained close to neutral, with absence of acid mine drainage. The geochemical interaction between these mineral phases seems to be the main mechanism to release Cu{sup 2+} ions. Total Cu in soils from the Pr area reached 11,180 mg.kg{sup −1}, while in Wr and Bd areas the values reached, on average, 4683 and 1086 mg.kg{sup −1}, respectively, indicating a very high level of soil contamination. In the Pr and Wr, the Cu was mainly associated with carbonates and amorphous iron oxides. In the Bd areas, the presence of vegetation has influenced the geochemical behavior of copper by increasing the dissolution of carbonates, affecting the buffer capacity of soils against sulphide oxidation, reducing the pH levels and enhancing the proportion of exchangeable and organic bound Cu. The present findings show that the use of plants or organic amendments in mine sites with high concentration of Cu carbonate-containing wastes should be viewed with caution, as the practice may enhance the mobilization of copper to the environment due to an increase in the rate of carbonates dissolution. - Highlights: • The hazardous effects of mine waste rocks at

  6. Disentangling density-dependent dynamics using full annual cycle models and Bayesian model weight updating

    Science.gov (United States)

    Robinson, Orin J.; McGowan, Conor; Devers, Patrick K.

    2017-01-01

    Density dependence regulates populations of many species across all taxonomic groups. Understanding density dependence is vital for predicting the effects of climate, habitat loss and/or management actions on wild populations. Migratory species likely experience seasonal changes in the relative influence of density dependence on population processes such as survival and recruitment throughout the annual cycle. These effects must be accounted for when characterizing migratory populations via population models.To evaluate effects of density on seasonal survival and recruitment of a migratory species, we used an existing full annual cycle model framework for American black ducks Anas rubripes, and tested different density effects (including no effects) on survival and recruitment. We then used a Bayesian model weight updating routine to determine which population model best fit observed breeding population survey data between 1990 and 2014.The models that best fit the survey data suggested that survival and recruitment were affected by density dependence and that density effects were stronger on adult survival during the breeding season than during the non-breeding season.Analysis also suggests that regulation of survival and recruitment by density varied over time. Our results showed that different characterizations of density regulations changed every 8–12 years (three times in the 25-year period) for our population.Synthesis and applications. Using a full annual cycle, modelling framework and model weighting routine will be helpful in evaluating density dependence for migratory species in both the short and long term. We used this method to disentangle the seasonal effects of density on the continental American black duck population which will allow managers to better evaluate the effects of habitat loss and potential habitat management actions throughout the annual cycle. The method here may allow researchers to hone in on the proper form and/or strength of

  7. Segmented Hybrid Gasostatic Bearing Optimization

    Directory of Open Access Journals (Sweden)

    Prodan Nikolay Vasilevich

    2014-07-01

    Full Text Available The purpose of research-development of methods of numerical optimization rotatable support pads gasostatic hybrid bearing. In the world‘s aerospace engineering the gas-dynamic bearings are currently most common. They are characterized by the supporting layer of different designs, which ensures the workability of the rotors during starts and stops. The main problem of this bearing type, apart from the construction complexity is the wear of this supporting layer. Gas-static bearing has no such defect, since there is no physical contact between solid surfaces. This study presents the results of the hybrid bearing’s calculation, combining both technologies. The slotted nozzle of non-conventional shape that mirrors the solution of Reynolds equation’s isoline is studied. The dependences of the main parameters on the speed of the shaft’s rotation are discussed. The aerodynamic resistance of pads for different regimes of operation is investigated.

  8. 拼接软件在负重位全下肢及全脊柱中的应用%Application of Image Splicing Software for Whole Low Extremities and Total Spine Radiography at Weight Bearing Position

    Institute of Scientific and Technical Information of China (English)

    王鑫; 张博; 常冬梅; 龚建平; 赵春阳; 田岚

    2012-01-01

    目的:探讨拼接软件在负重位全下肢及全脊柱摄影中的应用.方法:利用日本岛津公司的D-Vison Plus设备系统和具有拼接功能的后处理工作站(E-PACS 2000),60例患者在负重立位下分次进行全下肢正位(双侧髋关节至踝关节,30例)和全脊柱(C3至S1,30例)摄影,然后进行图像拼接和影像质量对比评价.结果:60例全下肢和全脊柱影像全部成功拼接,拼接前后甲片率差异无统计学差异(P=0.51>0.05).拼接后的影像诸骨结构、下肢力线以及脊柱侧弯的cobb角测量点均能清晰显示,密度也基本一致.结论:应用拼接软件对负重位下分段拍摄及全下肢和全脊柱影像进行后处理,使全下肢和全脊柱能同时在一张照片上完整无缝地呈现,更有利于外科医生对脊柱和下肢的整体观察与计算测量,有利于手术方式的选择和疗效的判断.%Objective To discuss the application of image splicing software to the photography of the whole low extremities and total spine at weight bearing position. Methods With Shimadzu Corporation D-Vision Plus system and a post-processing workstation with full-splicing function, 30 cases went through radiology examination of whole low extremities, and another 30 ones through total spine radiology, then image splicing and quality comparison were performed. Results Sixty cases of whole low extremities and total spine radiographs were completely mosaiced, and there were no statistically significant differences between the rates of first-class radiograph(P=0.51>0.05). The radiographs before and after splicing were very clear to show all the bones, the lower limb alignment, and the cobb angle in scoliosis. Also the densities of radiograph were uniform on the whole. Conchusion The splicing software can be used in the post processing of the photographs of the whole low extremities and total spine at weight bearing position, which can make the whole low extremities and total spine seamlessly

  9. Effect of Weight-bearing Too Early in Lower Limbs on Extensor Muscle Spasm and Knee Hyperextension of Affected Limb in Acute Stroke Patients with Hemiplegia%急性脑卒中患者过早下肢负重与患肢伸肌痉挛及膝过伸的关系研究

    Institute of Scientific and Technical Information of China (English)

    谭永霞; 刘建国; 戚晓昆

    2012-01-01

    Objective: To investigate the effect of weight-bearing too early in the lower limbs on extensor muscle spasm and knee hyperextension of affected limbs in acute stroke patients with hemiplegia. Methods; Eighty acute stroke patients with hemiplegia were recruited and the clinical data was analyzed. Results: All the cases were divided into control and weight-bearing groups according to their compliance in rehabilitation training. All the cases were given canonical rehabilitation program for 2 months, and the cases in the weight-bearing group started weight-bearing too early. Results: The number of cases with extensor muscle spasm and knee hyperextension of affected limbs in the weight-bearing group was higher than that in the control group (P<0. 05) after 2 months of treatment. Conclusion: Weight-bearing too early could increase the risk of extensor muscle spasm and knee hyperextension in acute stroke patients with hemiplegia.%目的:研究下肢过早负重对脑卒中偏瘫患者下肢功能的影响.方法:急性脑卒中患者80例,对全部患者的临床资料进行回顾性分析.结果:根据患者康复过程中的依从性,分为规范康复组和过早负重组,各40例,2组均接受康复治疗2个月,但过早负重组患者康复治疗期间过早下肢负重;治疗2个月后,过早负重组患者下肢出现伸肌痉挛及膝过伸的例数均高于规范康复组(P<0.05).结论:过早下肢负重容易使脑卒中偏瘫患者下肢出现伸肌痉挛及膝过伸.

  10. Redox dynamics in multicomponent, iron-bearing silicate melts and glasses: Application to the float-glass processing of high-temperature silicate glassmelts

    Science.gov (United States)

    Cook, Glen Bennett

    Processing high-strain-point glasses by the float process is challenged by the relative thermochemical properties of glassmelts and the liquid-metal float medium. As the chemical reaction between the glassmelt and the float metal involves dynamic reduction of the glassmelt, this research has examined the constraints on high-temperature float processing of glassmelts by combining metal-alloy/oxide reaction thermodynamics and Wagnerian kinetic models for redox reactions in silicate melts. The dynamic response of Fe-bearing, p-type (polaronic) semiconducting amorphous silicates to a chemical potential gradient of oxygen has been shown to be rate-limited by the chemical diffusion of network-modifying cations. The persistence of this mechanism to very low Fe concentrations in Fe-doped magnesium aluminosilicate glasses was proven with Rutherford backscattering spectroscopy. Three glasses, with 0.1, 0.5, and 1.25 mol. % FeO were reacted with air at temperatures from 710-845sp°C. For all compositions and temperatures, oxidation was dominated by network modifier diffusion; an activation energy of 475 kJ*molsp{-1} characterized the process. Chemical dynamics in a high-temperature float environment were characterized on liquid-liquid reaction couples between two low-Fe sodium-aluminoborosilicate (NABS) glassmelts (0.01 and 0.08 mol. % FeO) and Au-30Sn and Au-28Ge (atomic basis) alloys. Experiments were performed in the temperature range 1250-1450sp°C for 30 min; wavelength-dispersive and Rutherford backscattering spectroscopies were employed. These exothermic liquid-metal alloys display large negative deviations from ideal solution behavior, with significantly depressed chemical activities. Diffusion of Sn or Ge in the NABS glassmelts (depth and concentration) was limited at all temperatures to levels comparable to conventional soda-lime (NCS) float glass (˜2 min on pure Sn at 1100sp°C). Incorporation of Sn or Ge was reduced significantly in the higher-Fe-content NABS

  11. Electromechanical properties of radial active magnetic bearings

    OpenAIRE

    Antila, Matti

    1998-01-01

    Nonideal properties of the electromagnetic actuators in radial active magnetic bearings are studied. The two dimensional nonlinear stationary finite element method is used to determine the linearised parameters of a radial active magnetic bearing. The method is verified on two test machines. The accuracy is 10-15 % in the magnetic saturation region. The effect of magnetic saturation on the bearing dynamics is studied based on the root locus diagrams of the closed loop system. These diagrams s...

  12. 磁悬浮飞轮储能系统机电耦合动力学特性研究%Investigation on the Dynamics Character of Electromechanical Coupling for Flywheel Energy Storage System Based on Active Magnetic Bearing

    Institute of Scientific and Technical Information of China (English)

    陈峻峰; 刘昆; 肖凯; 王昊泽

    2012-01-01

    根据永磁电机结构,采用解析法分析了转子偏心时气隙磁感强度分布,推导出了储能飞轮系统充放电时受到的不平衡磁吸力和洛伦兹力表达式。构建了电机-磁轴承机电耦合动力学仿真模型,分析了电机产生的不平衡力与磁悬浮飞轮动力学性能的耦合影响。在不平衡力分析基础上,设计了磁轴承系统,抑制了机电耦合的影响。研究结果表明:当系统的电机尺寸较大且应用于高能放电领域时,转子偏心引起电机产生不平衡力较大,飞轮动力学性能变化显著,合理设计磁轴承可以抑制机电耦合。%The coupling between the generator and active magnetic bearing affects the stable operation of flywheel system in flywheel energy storage system based on active magnetic bearing,and restricts the control system design of active magnetic bearing.According to the structure of the generator,an analytical method is adopted to analyse the magnetic flux density distribution in the airgap region considering the rotor eccentricity,and the expressions of the unbalanced magnetic force and the unbalanced Lorentz force are educed when the flywheel energy storage system is charged or discharged.The dynamics simulation model of electromechanical coupling between the generator and active magnetic bearing is established,and the coupling effects between the unbalanced force brought by generator and the flywheel dynamics performance based on active magnetic bearing are analysed.Based on the analysis,an active magnetic bearing system is designed to restrain the electromechanical coupling.The results indicate that when the generator has a big size and the system is used in high electric-power field,the unbalanced force brought by rotor eccentricity in the generator is large,and have obvious impact on the performance of flywheel dynamics.The active magnetic bearing system can be reasonably designed to restrain the electromechanical coupling.

  13. The application of Dynamic Linear Bayesian Models in hydrological forecasting: Varying Coefficient Regression and Discount Weighted Regression

    Science.gov (United States)

    Ciupak, Maurycy; Ozga-Zielinski, Bogdan; Adamowski, Jan; Quilty, John; Khalil, Bahaa

    2015-11-01

    A novel implementation of Dynamic Linear Bayesian Models (DLBM), using either a Varying Coefficient Regression (VCR) or a Discount Weighted Regression (DWR) algorithm was used in the hydrological modeling of annual hydrographs as well as 1-, 2-, and 3-day lead time stream flow forecasting. Using hydrological data (daily discharge, rainfall, and mean, maximum and minimum air temperatures) from the Upper Narew River watershed in Poland, the forecasting performance of DLBM was compared to that of traditional multiple linear regression (MLR) and more recent artificial neural network (ANN) based models. Model performance was ranked DLBM-DWR > DLBM-VCR > MLR > ANN for both annual hydrograph modeling and 1-, 2-, and 3-day lead forecasting, indicating that the DWR and VCR algorithms, operating in a DLBM framework, represent promising new methods for both annual hydrograph modeling and short-term stream flow forecasting.

  14. Whole-body MRI, dynamic contrast-enhanced MRI, and diffusion-weighted imaging for the staging of multiple myeloma

    Energy Technology Data Exchange (ETDEWEB)

    Dutoit, Julie C.; Verstraete, Koenraad L. [Ghent University Hospital, Department of Radiology, Ghent (Belgium)

    2017-06-15

    Magnetic resonance imaging (MRI) is the most sensitive imaging technique for the detection of bone marrow infiltration, and has therefore recently been included in the new diagnostic myeloma criteria, as proposed by the International Myeloma Working Group. Nevertheless, conventional MRI only provides anatomical information and is therefore only of limited use in the response assessment of patients with multiple myeloma. The additional information from functional MRI techniques, such as diffusion-weighted imaging and dynamic contrast-enhanced MRI, can improve the detection rate of bone marrow infiltration and the assessment of response. This can further enhance the sensitivity and specificity of MRI in the staging of multiple myeloma patients. This article provides an overview of the technical aspects of conventional and functional MRI techniques with practical recommendations. It reviews the diagnostic performance, prognostic value, and role in therapy assessment in multiple myeloma and its precursor stages. (orig.)

  15. Transient Vibration Prediction for Rotors on Ball Bearings Using Load-dependent Non-linear Bearing Stiffness

    Science.gov (United States)

    Fleming, David P.; Poplawski, J. V.

    2002-01-01

    Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus an accurate rotordynamic transient analysis requires bearing forces to be determined at each step of the transient solution. Analyses have been carried out to show the effect of accurate bearing transient forces (accounting for non-linear speed and load dependent bearing stiffness) as compared to conventional use of average rolling-element bearing stiffness. Bearing forces were calculated by COBRA-AHS (Computer Optimized Ball and Roller Bearing Analysis - Advanced High Speed) and supplied to the rotordynamics code ARDS (Analysis of Rotor Dynamic Systems) for accurate simulation of rotor transient behavior. COBRA-AHS is a fast-running 5 degree-of-freedom computer code able to calculate high speed rolling-element bearing load-displacement data for radial and angular contact ball bearings and also for cylindrical and tapered roller beatings. Results show that use of nonlinear bearing characteristics is essential for accurate prediction of rotordynamic behavior.

  16. Design of a Weighted-Rotor Energy Harvester Based on Dynamic Analysis and Optimization of Circular Halbach Array Magnetic Disk

    Directory of Open Access Journals (Sweden)

    Yu-Jen Wang

    2015-03-01

    Full Text Available This paper proposes the design of a weighted-rotor energy harvester (WREH in which the oscillation is caused by the periodic change of the tangential component of gravity, to harvest kinetic energy from a rotating wheel. When a WREH is designed with a suitable characteristic length, the rotor’s natural frequency changes according to the wheel rotation speed and the rotor oscillates at a wide angle and high angular velocity to generate a large amount of power. The magnetic disk is designed according to an optimized circular Halbach array. The optimized circular Halbach array magnetic disk provides the largest induced EMF for different sector-angle ratios for the same magnetic disk volume. This study examined the output voltage and power by considering the constant and accelerating plate-rotation speeds, respectively. This paper discusses the effects of the angular acceleration speed of a rotating wheel corresponding to the dynamic behaviors of a weighted rotor. The average output power is 399 to 535 microwatts at plate-rotation speeds from 300 to 500 rpm, enabling the WREH to be a suitable power source for a tire-pressure monitoring system.

  17. Diffusion-weighted MRI, dynamic susceptibility contrast MRI and ultrasound perfusion quantification of denervated muscle in rabbits

    Energy Technology Data Exchange (ETDEWEB)

    Goyault, G.; Beregi, J.P. [University Hospital, Department of Cardiovascular imaging, Cardiologic Hospital, Lille (France); Bierry, G.; Holl, N.; Dietemann, J.L.; Kremer, S. [University Hospital, Department of Neuroradiology, Strasbourg (France); Lhermitte, B. [University Hospital, Department of Pathology, Strasbourg (France)

    2012-01-15

    The purpose of this study was to assess denervated muscle perfusion using dynamic susceptibility contrast MRI (DSCMRI) and contrast-enhanced ultrasound (CEUS), and to measure denervated muscle apparent diffusion coefficient (ADC) on b1000 diffusion-weighted MRI (DWMRI) at 3 T in order to clarify whether muscle denervation leads to an increase in the extracellular extravascular space, or an increase in blood flow - or both. Axotomy of the right sciatic nerve of six white rabbits was performed at day 0. At day 9, hind limb muscles MRI and CEUS were performed to assess the consequences of denervation and both semimembranosus muscles of each rabbit were explanted for histological studies. Signal intensity on T2- and T1-weighted MRI, ADC on DWMRI, maximum signal drop (MSD) on DSCMRI and the area under the curve (AUC) on CEUS were measured over circular regions of interest (ROI), in both semimembranosus muscles. Non-parametric Wilcoxon matched-pairs tests were used to assess the mean differences between denervated and normal muscles. T2 fat-saturated (FS) MRI studies showed a strong signal in the right semimembranosus muscles compared with the left side, and gadolinium enhancement was observed on T1 FS MRI. Denervated muscles show a significant increase in ADC on DWMRI (p < 0.01) and a significant signal enhancement on DSCMR imaging (p < 0.05) and on first-pass CEUS (p < 0.05). The results of this study - based on perfusion- and diffusion-weighted images - suggest that, after denervation, both increased blood flow through muscle tissue and expansion of the extracellular water volume are present. (orig.)

  18. Prostate cancer transrectal HIFU ablation: detection of local recurrences using T2-weighted and dynamic contrast-enhanced MRI

    Energy Technology Data Exchange (ETDEWEB)

    Rouviere, Olivier; Lyonnet, Denis [Hopital Edouard Herriot, Hospices Civils de Lyon, Department of Urinary and Vascular Radiology, Lyon (France); Universite de Lyon, Lyon (France); Universite de Lyon 1, Faculte de medecine Lyon Nord, Lyon (France); Inserm, U556, Lyon (France); Girouin, Nicolas; Glas, Ludivine; Ben Cheikh, Alexandre [Hopital Edouard Herriot, Hospices Civils de Lyon, Department of Urinary and Vascular Radiology, Lyon (France); Universite de Lyon, Lyon (France); Universite de Lyon 1, Faculte de medecine Lyon Nord, Lyon (France); Gelet, Albert [Hopital Edouard Herriot, Hospices Civils de Lyon, Department of Urology, Lyon (France); Inserm, U556, Lyon (France); Mege-Lechevallier, Florence [Hopital Edouard Herriot, Hospices Civils de Lyon, Department of Pathology, Lyon (France); Rabilloud, Muriel [Hospices Civils de Lyon, Department of Biostatistics, Lyon (France); Universite de Lyon 1, UMR CNRS, Laboratoire Biostatistiques-Sante, Pierre-Benite (France); Chapelon, Jean-Yves [Inserm, U556, Lyon (France)

    2010-01-15

    The objective was to evaluate T2-weighted (T2w) and dynamic contrast-enhanced (DCE) MRI in detecting local cancer recurrences after prostate high-intensity focused ultrasound (HIFU) ablation. Fifty-nine patients with biochemical recurrence after prostate HIFU ablation underwent T2-weighted and DCE MRI before transrectal biopsy. For each patient, biopsies were performed by two operators: operator 1 (blinded to MR results) performed random and colour Doppler-guided biopsies (''routine biopsies''); operator 2 obtained up to three cores per suspicious lesion on MRI (''targeted biopsies''). Seventy-seven suspicious lesions were detected on DCE images (n=52), T2w images (n=2) or both (n=23). Forty patients and 41 MR lesions were positive at biopsy. Of the 36 remaining MR lesions, 20 contained viable benign glands. Targeted biopsy detected more cancers than routine biopsy (36 versus 27 patients, p=0.0523). The mean percentages of positive cores per patient and of tumour invasion of the cores were significantly higher for targeted biopsies (p<0.0001). The odds ratios of the probability of finding viable cancer and viable prostate tissue (benign or malignant) at targeted versus routine biopsy were respectively 3.35 (95% CI 3.05-3.64) and 1.38 (95% CI 1.13-1.63). MRI combining T2-weighted and DCE images is a promising method for guiding post-HIFU biopsy towards areas containing recurrent cancer and viable prostate tissue. (orig.)

  19. Coupling analysis of dynamic and tribological behavior of angle-contact ball bearings for electric spindle%电主轴角接触球轴承摩擦学和动力学耦合分析

    Institute of Scientific and Technical Information of China (English)

    胡赤兵; 黄丛领; 王保民

    2013-01-01

    Based on elastic hydrodynamic lubrication theory and dynamic theory,the coupling investigation of tribological and dynamics characteristics of angle-contact ball bearing (spindle bearings) was conducted.The dynamic simulation model was established with software Ansys and taking into consideration the tribological characteristics of the spindle bearings.The Reynolds equation and elastic equation of elastohydrodynamic lubrication were solved by using finite difference method to get the solution of the oil film reaction force.The dynamic simulation was carried out with Ansys and the characteristic curves of all motional parameters of the bearing parts were output.It was shown by the research that the speed was the important factor influencing the elastic hydrodynamic lubrication oil film within the spindle bearings.Under the same load,contact angle and other working conditions,the inner ball track oil film thickness of ceramic angle-contact ball bearing would increase first and then gradually reduce as speed increased,and the outer ball track oil film thickness would not change significantly with rotation speed at first and then decrease noticeably.%基于弹性流体动力润滑理论和动力学理论,对角接触球轴承(主轴轴承)进行摩擦学特性和动力学特性耦合研究.在Ansys软件中建立考虑主轴轴承摩擦学特性的动力学仿真模型,利用有限差分法求解弹流润滑的Reynolds方程和弹性方程,求解轴承油膜反力,在Ansys中进行动力学仿真,输出轴承零件各种运动参数特性曲线.研究表明,速度是影响主轴轴承内部弹流油膜的重要因素,在相同的预载荷、接触角等工况条件下,陶瓷角接触球轴承的内圈油膜厚度随转速增大先增大后逐渐减小,外圈油膜厚度随转速增大开始变化不明显,随后明显减小.

  20. Fatigue life analysis and research on rod end spherical plain bearings under dynamic stress%杆端向心关节轴承动应力下疲劳寿命分析研究

    Institute of Scientific and Technical Information of China (English)

    苏高峰; 薄玉成; 孔静静; 曲振森; 徐煜星

    2013-01-01

    针对QG325型切管机液压缸杆端向心关节轴承工作时主要是向心内外圈疲劳磨损破坏问题,采用Solidworks 建立了简化的杆端向心关节轴承三维模型;通过ANSYS workbench 13.0瞬态动力分析模块对其进行实际工况下动应力分析,找出了杆端向心关节轴承最大应力集中处.在此基础上利用ANSYS workbench 13.0的疲劳分析模块实现对杆端向心关节轴承的接触疲劳寿命分析,获取杆端向心关节轴承在实际工况下的接触疲劳寿命,有效预测零件的工作寿命.%This paper focuses on the problem of concentric inner and outer rings fatigue wear damage that mainly produced from the type of QG325 pipe cutting machine hydraulic cylinder rod end spherical plain bearings working, and it has built the simplified three-dimensioned model of rod ends spherical plain bearings by Solidworks. By using the transient dynamic analysis module of AN-SYS workbench1 3. 0, which can analyze its actual conditions of dynamic stress and find out the maximum stress concentration of the rod ends spherical plain bearing. On this basis, it has realized contact fatigue life analysis of rod ends spherical plain bearing by using ANSYS workbenchl3. 0 fatigue analysis module, and getting the contact fatigue life of rod end spherical plain bearing in actual operating conditions, which can predict the working life of the parts effectively.

  1. Performance Evaluation and Impact of Weighting Factors on an Energy and Delay Aware Dynamic Source Routing Protocol

    CERN Document Server

    Rekik, Jihen Drira; Ghezala, Henda Ben

    2011-01-01

    Typical applications of the mobile ad-hoc network, MANET, are in disaster recovery operations which have to respect time constraint needs. Since MANET is affected by limited resources such as power constraints, it is a challenge to respect the deadline of a real-time data. This paper proposes the Energy and Delay aware based on Dynamic Source Routing protocol, ED-DSR. ED-DSR efficiently utilizes the network resources such as the intermediate mobile nodes energy and load. It ensures both timeliness and energy efficiency by avoiding low-power and overloaded intermediate mobile nodes. Through simulations, we compare our proposed routing protocol with the basic routing protocol Dynamic Source Routing, DSR. Weighting factors are introduced to improve the route selection. Simulation results, using the NS-2 simulator, show that the proposed protocol prolongs the network lifetime (up to 66%), increases the volume of packets delivered while meeting the data flows real-time constraints and shortens the endto- end delay...

  2. Lubricant replacement in rolling element bearings for weapon surety devices

    Energy Technology Data Exchange (ETDEWEB)

    Steinhoff, R.; Dugger, M.T.; Varga, K.S. [Sandia National Laboratories, Albuquerque, NM (United States)

    1996-05-01

    Stronglink switches are a weapon surety device that is critical to the nuclear safety theme in modem nuclear weapons. These stronglink switches use rolling element bearings which contain a lubricant consisting of low molecular weight polytetrafluoroethylene (PTFE) fragments. Ozone-depleting solvents are used in both the manufacture and application of this lubricant. An alternate bearing lubrication for stronglink switches is needed that will provide long-term chemical stability, low migration and consistent performance. Candidates that were evaluated include bearings with sputtered MoS{sub 2} on the races and retainers, bearings with TiC-coated balls, and bearings with Si{sub 3}N{sub 4} balls and steel races. These candidates were compared to the lubricants currently used which are bearings lubricated with PTFE fragments of low molecular weight in a fluorocarbon solvent. The candidates were also compared to bearings lubricated with a diester oil which is representative of bearing lubricants used in industrial applications. Evaluation consisted of cycling preloaded bearings and subjecting them to 23 gRMS random vibration. All of the candidates are viable substitutes for low load application where bearing preload is approximately 1 pound. For high load applications where the bearing preload is approximately 10 pounds, bearings with sputtered MoS{sub 2} on the races and retainers appear to be the best substitutes. Bearings with TiC-coated balls also appear to be a viable candidate but these bearings did not perform as well as the sputtered MoS{sub 2}.

  3. Polar bear research in Alaska, spring 1982

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — An investigation of the ecology and population dynamics of Alaskan polar bears has continued since 1967. As part of that program, U.S. Fish and Wildlife Service...

  4. Polar bear research in Alaska, spring 1981

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — An investigation of the ecology and population dynamics of Alaskan polar bears has continued since 1967. As part of that program, U.S. Fish and Wildlife Service...

  5. Analysis of dynamic characteristics of self-aligning ball bearing%调心球轴承动态特性参数分析

    Institute of Scientific and Technical Information of China (English)

    袁丁; 蒋书运

    2010-01-01

    基于Jones-Harris方法建立了调心球轴承的动力学模型,应用Newton-Raphson方法对轴承动力学方程组进行了求解,开发了相应的计算程序.完成了该轴承的离心力、陀螺力矩、接触载荷、接触角、径向变形与径向刚度等动态特性参数分析.分析结果表明:转速与载荷是影响接触角大小与接触载荷分布最主要的2个因素;滚子的离心力与陀螺力矩随着转速的上升而增大,在此影响下外圈接触载荷增大而内圈接触载荷减小;受离心力的影响,外圈的接触角减小而内圈的接触角增大,且随着转速的增加,内外圈接触角的差值越来越大;轴承的径向刚度随着转速的上升而下降,而滚道沟曲率系数也对轴承径向刚度有一定程度的影响.%A dynamics model of the self-aligning ball bearing is proposed based on the Jones-Harris method (JHM), and a computer program is developed to solve the equations by using the Newton-Raphson method. A parametric analysis of the centrifugal force and the gyroscopic moment, the contact loads, the contact angles, the radial deformation and the radial stiffness is carried out. The analytical results show that the applied loads and the rotational speed are two main factors that can influence the distributions of the contact loads and values of the contact angles. The centrifugal force and the gyroscopic moment increase with the increase in the rotational speed, resulting in the decrease of the inner raceway contact load and the increase of the outer raceway contact load. The outer raceway contact angle increases under the centrifugal force; on the contrary, the inner raceway contact angle decreases. Furthermore, the differences between the inner and the outer contact angles increase with the increase in the rotational speed. The higher rotational speed results in the decrease in radial stiffness for the self-aligning ball bearing, and the raceway curvature coefficient, to some extent, also

  6. Effectiveness of elastic band-type ankle–foot orthoses on postural control in poststroke elderly patients as determined using combined measurement of the stability index and body weight-bearing ratio

    Directory of Open Access Journals (Sweden)

    Kim JH

    2015-11-01

    Full Text Available Jong Hyun Kim, Woo Sang Sim, Byeong Hee Won Usability Evaluation Technology Center, Advanced Biomedical and Welfare R&D Group, Korea Institute of Industrial Technology, Cheonan-si, Chungcheongnam-do, South Korea Purpose: Poor recovery of postural stability poststroke is the primary cause of impairment in activities and social participation in elderly stroke survivors. The purpose of our study was to experimentally evaluate the effectiveness of our new elastic ankle–foot orthosis (AFO, compared to a traditional AFO fabricated with hard plastic, in improving postural stability in elderly chronic stroke survivors. Patients and methods: Postural stability was evaluated in ten chronic stroke patients, 55.7±8.43 years old. Postural stability was evaluated using the standardized methods of the Biodex Balance System combined with a foot pressure system, under three experimental conditions, no AFO, rigid plastic AFO, and elastic AFO (E-AFO. The following dependent variables of postural stability were analyzed: plantar pressure under the paretic and nonparetic foot, area of the center of balance (COB and % time spent in each location, distance traveled by the COB away from the body center, distance traveled by the center of pressure, and calculated index of overall stability, as well as indices anterior–posterior and medial–lateral stability. Results: Both AFO designs improved all indices of postural stability. Compared to the rigid plastic AFO, the E-AFO produced additional positive effects in controlling anterior–posterior body sway, equalizing weight bearing through the paretic and nonparetic limbs, and restraining the displacement of the center of pressure and of the COB. Conclusion: Based on our outcomes, we recommend the prescription of E-AFOs as part of a physiotherapy rehabilitation program to promote recovery of postural stability poststroke. When possible, therapeutic outcomes should be documented using the Biodex Balance System and

  7. Influence of Preload and Speed on Dynamic Contact Characteristics of High Speed Angular Contact Ball Bearings%预紧及转速对角接触球轴承动态接触特性的影响*

    Institute of Scientific and Technical Information of China (English)

    罗小百; 肖曙红; 雷枝武; 吴利杰

    2013-01-01

    基于拟动力学、套圈控制理论建立了角接触球轴承的刚度、旋滚比数学模型。以此为基础利用Matlab编程,计算了轴承钢球与套圈的接触角、陀螺力矩、旋滚比和轴承刚度,分析了高速工况下预紧载荷、转速对轴承各接触参数的影响规律。%Based on the sub-dynamics analysis theory and race’ s control theory, this paper introduces the mathematic model of the angular contact bearing rigidity and ratio of revolution and rolling firstly. Then calculates the ball contact angle, gyro moment, ratio of revolution and rolling, and bearing rigidity by programming in Matlab, and the numerical method. Finally analyzes the influence of the preload and rotary speed on the dynamic parameters of high speed angular contact ball bearings.

  8. Rotational characteristics in the resonance state of the HTSC-permanent magnet hybrid magnetic bearing

    Energy Technology Data Exchange (ETDEWEB)

    Morii, Y.; Sukedai, M. [Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan); Ohashi, S., E-mail: ohashi@kansai-u.ac.jp [Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan)

    2011-11-15

    The hybrid magnetic bearing has been developed. In the hybrid system, effect of the pinning force becomes smaller. Influence of the vibration and the gradient angle in the resonance state is large. The resonance frequency becomes small in the hybrid bearing system. The hybrid magnetic bearing using permanent magnets and the high-Tc bulk superconductor (HTSC) has been developed. Repulsive force of the permanent magnet is introduced to increase the load weight of the magnetic bearing. Effect of the hybrid system has been shown. In this paper, influence of the hybrid system on the dynamic characteristics of the rotor is studied. The rotational characteristics in the mechanical resonance state are studied, and the equivalent magnetic spring coefficient is estimated from the experimental results of the load weight. The resonance frequency is measured by the rotation experiments. The rotor achieves stable levitation even in the resonance state. In the hybrid system, effect of the pinning force becomes smaller than that of the lateral force generated by the repulsive force between the two permanent magnets at the smaller air gap. Thus influence of the lateral vibration and the gradient angle in the resonance state becomes larger at a smaller air gap. The equivalent magnetic spring coefficient becomes also small, and the resonance frequency becomes small in the hybrid bearing system.

  9. A Novel Strategy for Speed up Training for Back Propagation Algorithm via Dynamic Adaptive the Weight Training in Artificial Neural Network

    Directory of Open Access Journals (Sweden)

    Mohameed Sarhan Al_Duais

    2015-01-01

    Full Text Available The drawback of the Back Propagation (BP algorithm is slow training and easily convergence to the local minimum and suffers from saturation training. To overcome those problems, we created a new dynamic function for each training rate and momentum term. In this study, we presented the (BPDRM algorithm, which training with dynamic training rate and momentum term. Also in this study, a new strategy is proposed, which consists of multiple steps to avoid inflation in the gross weight when adding each training rate and momentum term as a dynamic function. In this proposed strategy, fitting is done by making a relationship between the dynamic training rate and the dynamic momentum. As a result, this study placed an implicit dynamic momentum term in the dynamic training rate. This αdmic = f(1/&etadmic . This procedure kept the weights as moderate as possible (not to small or too large. The 2-dimensional XOR problem and buba data were used as benchmarks for testing the effects of the ‘new strategy’. All experiments were performed on Matlab software (2012a. From the experiment’s results, it is evident that the dynamic BPDRM algorithm provides a superior performance in terms of training and it provides faster training compared to the (BP algorithm at same limited error.

  10. 齿轮耦合的转子-轴承系统的非线性模型%A Nonlinear Model for Dynamic Analysis of a Geared Rotor-Bearing System

    Institute of Scientific and Technical Information of China (English)

    张锁怀; 石守红; 丘大谋

    2001-01-01

    在考虑滑动轴承非线性油膜力、齿轮时变啮 合刚度、齿面间的摩擦力以及齿侧间隙的情况下,推导出了齿轮耦合的转子-轴承系统的非 线性动力学模型,该模型是一个包含强非线性项的非自治系统,蕴含着丰富的动力学内容。%Considering nonlinear fluid film forces of a journal bearing, the time-varying mesh stiffness of the gears, friction effect between tooth pairs, and backlash clearance, a geared rotor-bearing system is modeled. It is shown that the motion equation of the system is a nonautonomous differential equation with strong nonlinearity. It contains plenty of dynamic phenomena.

  11. A visão do ortopedista brasileiro sobre a descarga parcial de peso em ortostase nas fraturas expostas da diáfise da tíbia após osteossíntese The view of Brazilian orthopedists on partial weight bearing in open fractures of the tibial shaft following osteosynthesis

    Directory of Open Access Journals (Sweden)

    Valéria R. G. Sella

    2009-12-01

    Full Text Available CONTEXTUALIZAÇÃO: As fraturas da diáfise da tíbia são as mais frequentes dentre as dos ossos longos. Há descrições na literatura, de acordo com o método e dispositivo de tratamento, com recomendações que vão desde a descarga total até a proibição do suporte de peso corporal em ortostase. Existem estudos comparando os dispositivos de osteossíntese e os diversos aspectos cirúrgicos, porém não são encontradas referências que descrevam como e quando se deve liberar a descarga sobre o membro acometido na posição ortostática. OBJETIVOS: Verificar, entre os ortopedistas brasileiros, qual ou quais são os métodos de osteossíntese adotados para o tratamento de fraturas expostas de tíbia, se indicam o tratamento fisioterápico, quando e quais fatores influem para liberar a descarga parcial em ortostase, tanto para a função quanto para a fisioterapia. MÉTODOS: 235 ortopedistas responderam a um questionário durante o XIV Congresso Brasileiro de Trauma Ortopédico. RESULTADOS: Os resultados mostraram que, no Brasil, o dispositivo de osteossíntese mais utilizado é o fixador externo (FE, porém a descarga de peso em pé ocorre mais precocemente quando são utilizadas as hastes intramedulares. A grande maioria dos ortopedistas indica fisioterapia, e o período para liberação de descarga de peso parcial em ortostatismo varia de acordo com o material de síntese utilizado. Conclusões: Concluiu-se que há preferência pelos FEs, a grande maioria indica tratamento fisioterápico e o material de síntese influencia o tempo de liberação de descarga parcial de peso em ortostatismo.BACKGROUND: Tibial shaft fractures are the most frequent among long bone fractures. They are described in the literature according to the device and method of treatment, with recommendations that range from full weight bearing to non-weight bearing restrictions. There are studies comparing osteosynthesis devices and surgical aspects, but no references

  12. The role of dynamic contrast-enhanced and diffusion weighted magnetic resonance imaging in the female pelvis

    Energy Technology Data Exchange (ETDEWEB)

    Sala, Evis, E-mail: es220@radiol.cam.ac.uk [University Department of Radiology, Box 218, Level 5, Addenbrooke' s Hospital, Hills Road, Cambridge CB2 0QQ (United Kingdom); Rockall, Andrea, E-mail: Andrea.Rockall@bartsandthelondon.nhs.uk [Department of Radiology, St Bartholomew' s Hospital, West Smithfield, London EC1A 7ED (United Kingdom); Rangarajan, Deepa, E-mail: rdrangarajan@googlemail.com [Department of Radiology, Box 218, Addenbrooke' s Hospital, Hills Road, Cambridge CB2 0QQ (United Kingdom); Kubik-Huch, Rahel A., E-mail: rahel.kubik@ksb.ch [Institute of Radiology, Department of Medical Services, Kantonsspital Baden Im Ergel, CH-5404 Baden (Switzerland)

    2010-12-15

    Functional imaging by means of dynamic multiphase contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion weighted magnetic resonance imaging (DW-MRI) is now part of the standard imaging protocols for evaluation of the female pelvis. DCE-MRI and DW-MRI are important MR imaging techniques which enable the radiologist to move from morphological to functional assessment of diseases of the female pelvis. This is mainly due to the limitations of morphologic imaging, particularly in lesion characterization, accurate lymph node staging, assessment of tumour response and inability to differentiate post-treatment changes from tumour recurrence. DCE-MRI improves the accuracy of T2WI in staging of endometrial cancer. It also helps differentiate tumour recurrence from radiation fibrosis in patients with cervical cancer. DCE-MRI improves characterization of cystic adnexal lesions and detection of small peritoneal implants in patients with ovarian cancer. DW-MRI is valuable in preoperative staging of patients with endometrial and cervical cancer, especially in detection of extra-uterine disease. It does increase reader's confidence for detection of recurrent disease in gynaecological malignancies and improves detection of small peritoneal implants in patients with ovarian cancer. In this review article we give an overview of both DCE-MRI and DW-MRI techniques, concentrating on their main clinical application in the female pelvis, and present a practical approach of the added value of these techniques according to the main pathological conditions, highlighting the pearls and pitfalls of each technique.

  13. Diffusion-weighted and dynamic contrast-enhanced imaging as markers of clinical behavior in children with optic pathway glioma

    Energy Technology Data Exchange (ETDEWEB)

    Jost, Sarah C. [Swedish Neuroscience Institute, Department of Neurosurgery, Seattle, WA (United States); Ackerman, Joseph W. [Washington University School of Medicine, Department of Radiology, 660 South Euclid Ave., Box 8131, St. Louis, MO (United States); Garbow, Joel R. [Washington University School of Medicine, Department of Radiology, 660 South Euclid Ave., Box 8131, St. Louis, MO (United States); Alvin J. Siteman Cancer Center, St. Louis, MO (United States); Manwaring, Linda P. [Washington University School of Medicine, Department of Pediatrics, St. Louis, MO (United States); Washington University School of Medicine, Department of Genetics and Genomic Medicine, St. Louis, MO (United States); Gutmann, David H. [Washington University School of Medicine, Department of Neurology, St. Louis, MO (United States); Alvin J. Siteman Cancer Center, St. Louis, MO (United States); McKinstry, Robert C. [Washington University School of Medicine, Department of Radiology, 660 South Euclid Ave., Box 8131, St. Louis, MO (United States); Washington University School of Medicine, Department of Pediatrics, St. Louis, MO (United States)

    2008-12-15

    Optic pathway gliomas (OPGs) are common pediatric brain tumors that pose significant clinical challenges with regard to predicting which tumors are likely to become symptomatic and require treatment. These tumors can arise sporadically or in the context of the inherited cancer predisposition syndrome neurofibromatosis type 1 (NF1). Few studies have suggested biological or imaging markers that predict the clinical course of this disease. In this cross-sectional study, we hypothesized that the clinical behavior of OPGs in children can be differentiated by diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) MRI. A total of 27 children with OPG were studied using DW and DCE MRI protocols. Diffusivity and permeability were calculated and correlated with the clinical behavior the OPG. Mean diffusivity values of 1.39 {mu}m{sup 2}/ms and mean permeability values of 2.10 ml/min per 100 cm{sup 3} of tissue were measured. Clinically aggressive OPGs had significantly higher mean permeability values (P = 0.05) than clinically stable tumors. In addition, there was a strong correlation between clinical aggressiveness and the absence of NF1 (P < 0.01). These results suggest that DCE MRI might be a useful biomarker for clinically aggressive OPG, which should be confirmed in larger prospective longitudinal studies. (orig.)

  14. Evaluation of T2-weighted and dynamic contrast-enhanced MRI in localizing prostate cancer before repeat biopsy

    Energy Technology Data Exchange (ETDEWEB)

    Cheikh, Alexandre Ben; Girouin, Nicolas [Hopital Edouard Herriot, Hospices Civils de Lyon, Department of Urinary and Vascular Radiology, Lyon (France)]|[Universite de Lyon, Lyon (France)]|[Universite de Lyon 1, faculte de medecine Lyon Nord, Lyon (France); Colombel, Marc; Marechal, Jean-Marie [Hopital Edouard Herriot, Hospices Civils de Lyon, Department of Urology, Lyon (France); Gelet, Albert [Hopital Edouard Herriot, Hospices Civils de Lyon, Department of Urology, Lyon (France)]|[Inserm, U556, Lyon (France); Bissery, Alvine; Rabilloud, Muriel [Hospices Civils de Lyon, Department of Biostatistics, Lyon (France)]|[Universite de Lyon 1, UMR CNRS 5558, Laboratoire Biostatistiques-Sante, Pierre-Benite (France); Lyonnet, Denis [Hopital Edouard Herriot, Hospices Civils de Lyon, Department of Urinary and Vascular Radiology, Lyon (France)]|[Universite de Lyon, Lyon (France)]|[Universite de Lyon 1, faculte de medecine Lyon Nord, Lyon (France)]|[Inserm, U556, Lyon (France); Rouviere, Olivier [Hopital Edouard Herriot, Hospices Civils de Lyon, Department of Urinary and Vascular Radiology, Lyon (France)]|[Universite de Lyon, Lyon (France)]|[Universite de Lyon 1, faculte de medecine Lyon Nord, Lyon (France)]|[Inserm, U556, Lyon (France)]|[Hopital Edouard Herriot, Department of Urinary and Vascular Radiology, Pavillon P Radio, Lyon Cedex 03 (France)

    2009-03-15

    We assessed the accuracy of T2-weighted (T2w) and dynamic contrast-enhanced (DCE) 1.5-T magnetic resonance imaging (MRI) in localizing prostate cancer before transrectal ultrasound-guided repeat biopsy. Ninety-three patients with abnormal PSA level and negative prostate biopsy underwent T2w and DCE prostate MRI using pelvic coil before repeat biopsy. T2w and DCE images were interpreted using visual criteria only. MR results were correlated with repeat biopsy findings in ten prostate sectors. Repeat biopsy found prostate cancer in 23 patients (24.7%) and 44 sectors (6.6%). At per patient analysis, the sensitivity, specificity, positive and negative predictive values were 47.8%, 44.3%, 20.4% and 79.5% for T2w imaging and 82.6%, 20%, 24.4% and 93.3% for DCE imaging. When all suspicious areas (on T2w or DCE imaging) were taken into account, a sensitivity of 82.6% and a negative predictive value of 100% could be achieved. At per sector analysis, DCE imaging was significantly less specific (83.5% vs. 89.7%, p < 0.002) than T2w imaging; it was more sensitive (52.4% vs. 32.1%), but the difference was hardly significant (p = 0.09). T2w and DCE MRI using pelvic coil and visual diagnostic criteria can guide prostate repeat biopsy, with a good sensitivity and NPV. (orig.)

  15. Effects of a multidisciplinary body weight reduction program on static and dynamic thoraco-abdominal volumes in obese adolescents.

    Science.gov (United States)

    LoMauro, Antonella; Cesareo, Ambra; Agosti, Fiorenza; Tringali, Gabriella; Salvadego, Desy; Grassi, Bruno; Sartorio, Alessandro; Aliverti, Andrea

    2016-06-01

    The objective of this study was to characterize static and dynamic thoraco-abdominal volumes in obese adolescents and to test the effects of a 3-week multidisciplinary body weight reduction program (MBWRP), entailing an energy-restricted diet, psychological and nutritional counseling, aerobic physical activity, and respiratory muscle endurance training (RMET), on these parameters. Total chest wall (VCW), pulmonary rib cage (VRC,p), abdominal rib cage (VRC,a), and abdominal (VAB) volumes were measured on 11 male adolescents (Tanner stage: 3-5; BMI standard deviation score: >2; age: 15.9 ± 1.3 years; percent body fat: 38.4%) during rest, inspiratory capacity (IC) maneuver, and incremental exercise on a cycle ergometer at baseline and after 3 weeks of MBWRP. At baseline, the progressive increase in tidal volume was achieved by an increase in end-inspiratory VCW (p obese adolescents adopt a thoraco-abdominal operational pattern characterized by abdominal rib cage hyperinflation as a form of lung recruitment during incremental cycle exercise. Additionally, a short period of MBWRP including RMET is associated with improved exercise performance, lung and chest wall volume recruitment, unloading of respiratory muscles, and reduced dyspnea.

  16. Solution of dynamic characteristics of journal bearing based on two phase flow theory%基于两相流理论滑动轴承动力特性求解

    Institute of Scientific and Technical Information of China (English)

    孙丹; 张楚; 郭瑞; 杨建刚

    2012-01-01

    将计算流体动力学(CFD)两相流与动网格技术应用于滑动轴承动力特性数值求解,建立了基于CFD两相流滑动轴承动力特性求解模型,该模型无需设定油膜破裂边界条件且更能准确模拟滑动轴承流场特性.比较了单相流与两相流滑动轴承压力分布特性,计算分析了滑动轴承气穴分布特征及其影响因素,研究了两相流模型对滑动轴承动力特性的影响.计算结果表明:气化比例随着转速、偏心率和气化压力的增加而迅速增大,随进口压力的增加而缓慢减小.考虑两相流后,直接刚度系数增加,交叉刚度系数减小,直接与交叉阻尼系数均减小.随着偏心率的增加,单相流与两相流动力特性系数求解结果偏差增大.%The computational fluid dynamics(CFD) two phase flow and dynamic mesh technologies were applied to the numerical calculation of dynamic characteristics of journal bearing.A new journal bearing dynamic characteristic solving model using the two phase flow theory of CFD model was established.The two phase flow theory of computational fluid dynamics for the journal bearing dynamic characteristics did not need to define the oil film rupture boundary condition,and it can generate more complementary and more accurate flow information.The pressure distribution characteristics of the sliding bearing were compared,and the cavitation characteristics and the effects of the journal bearing were calculated.Finally,the effect of the two phase flow theory of CFD model on dynamic characteristics of journal bearing was analyzed.Calculation results show that the cavitation ratio increases significantly with the increase of rotating speed,eccentricity,and vaporization pressure,and decreases slowly with the increase of inlet pressure.Using two phase flow,calculation results also show that the direct stiffness increases,the cross stiffness decreases and the direct and cross dampings decrease.The deviation between the

  17. Measurement of brain perfusion, blood volume, and blood-brain barrier permeability, using dynamic contrast-enhanced T(1)-weighted MRI at 3 tesla

    DEFF Research Database (Denmark)

    Larsson, Henrik B W; Courivaud, Frédéric; Rostrup, Egill

    2009-01-01

    Assessment of vascular properties is essential to diagnosis and follow-up and basic understanding of pathogenesis in brain tumors. In this study, a procedure is presented that allows concurrent estimation of cerebral perfusion, blood volume, and blood-brain permeability from dynamic T(1)-weighted...

  18. Dynamics and stability of rigid rotors levitated by passive cylinder-magnet bearings and driven/supported axially by pointwise contact clutch

    DEFF Research Database (Denmark)

    Andersen, Søren Bøgh; Enemark, Søren; Santos, Ilmar

    2013-01-01

    A stable rotor—supported laterally by passive magnetic bearings and longitudinally by magnetic forces and a clutch—loses suddenly its contact to the clutch and executes abruptly longitudinal movements away from its original equilibrium position as a result of small increases in angular velocity. ...

  19. Effect of fluid compressibility on journal bearing performance

    Energy Technology Data Exchange (ETDEWEB)

    Dimofte, F. (NASA, Lewis Research Center, Cleveland, OH (United States))

    1993-07-01

    An analysis was undertaken to determine the effect of fluid film compressibility on the performance of fluid film bearings. A new version of the Reynolds equation was developed, using a polytropic expansion, for both steady-state and dynamic conditions. Polytropic exponents from 1 (isothermal) to 1000 (approaching an incompressible liquid) were evaluated for two bearing numbers, selected from a range of practical interest for cryogenic application, and without cavitation. Bearing loads were insensitive to fluid compressibility for low bearing numbers, as was expected. The effect of compressibility on attitude angle was significant, even when the bearing number was low. A small amount of fluid compressibility was enough to obtain stable running conditions. Incompressible liquid lacked stability at all conditions. Fluid compressibility can be used to control the bearing dynamic coefficients, thereby influencing the dynamic behavior of the rotor-bearing system. 14 refs.

  20. A Comparison of Experimental and Theoretical Results for Magnetic Bearings

    Science.gov (United States)

    Hibbs, Robert I., Jr.; Scharrer, Joseph K.; Galvin, Bonnie A.; Galvin, Mark W.

    2000-01-01

    A comprehensive program was undertaken to experimentally characterize the static and dynamic characteristics of a heteropolar magnetic bearing and to develop nonlinear theoretical models capable of accurately predicting magnetic bearing performance. This paper presents the results for the static characteristics of the magnetic bearing and a comparison with the predictions from the analytical model. The results indicate that the nonlinear theoretical model can accurately predict the static characteristics of the magnetic bearing.

  1. Comprehensive Indicator Weight Determination and Application Based on Dynamic Weight%基于动态权重的综合指标权重确定及应用

    Institute of Scientific and Technical Information of China (English)

    闫滨; 钱静宇; 郭超

    2014-01-01

    为使不确定事件评价中指标的筛选更加准确,借助数据挖掘的聚类思想来刻画两个指标间的相似程度,将相似程度归一化获得表现相互支持度的动态权重,再将静态权重和动态权重按比例系数分配,求得综合权重。将此权重确定方法运用到土石坝坝坡失稳预警指标体系中,结果表明:管涌权重最大,其次是滑坡、流土和裂缝,亦即管涌对坝坡失稳影响最为突出。并通过实例验证了该方法的可行性和实用性。%In order to make a more accurate selection of indicators in uncertain events' assessment, the similarity degree between two indicators was described with the help of date mining clustering ideas, so as to reflect the degree of mutual support between these indicators. Dynamic weights which represent the mutual support were obtained by normalizing the degree of similarity. Then the static weights and dynamic weights were allocated a proportional coefficient to get the comprehensive weight. The method was applied to dam slop instability early warning index system of an earth and rockfill dam. The calculation results showed that piping's weight is larger than landslide, soil flow and crack, which means that piping index is highlight in dam instability early warning. The feasibility and practicality of the method were also verified.

  2. Estimating the effects of a calorie-based sugar-sweetened beverage tax on weight and obesity in New York City adults using dynamic loss models.

    Science.gov (United States)

    Ruff, Ryan Richard; Zhen, Chen

    2015-05-01

    Sugar-sweetened beverages (SSBs) contribute to weight gain and increase the risk of obesity. In this article, we determine the effects of an innovative SSB tax on weight and obesity in New York City adults. Dynamic weight loss models were used to estimate the effects of an expected 5800-calorie reduction resulting from an SSB tax on weight and obesity. Baseline data were derived from the New York City Community Health S