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Sample records for helical rotary screw

  1. Helical Screw Expander Evaluation Project. Final report

    Energy Technology Data Exchange (ETDEWEB)

    McKay, R.

    1982-03-01

    A functional 1-MW geothermal electric power plant that featured a helical screw expander was produced and then tested in Utah in 1978 to 1979 with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing operation on two-phase geothermal fluids. The Project also produced a computer-equipped data system, an instrumentation and control van, and a 1000-kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Additional testing was performed in Mexico in 1980 under a cooperative test program using the same test array, and machine efficiency was measured at 62% maximum with the rotors partially coated with scale, compared with approximately 54% maximum in Utah with uncoated rotors, confirming the importance of scale deposits within the machine on performance. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  2. Studies on positive conveying in helically channeled single screw extruders

    OpenAIRE

    L. Pan; M. Y. Jia; Jin, Z. M.; Wang, K. J.; Xue, P

    2012-01-01

    A solids conveying theory called double-flight driving theory was proposed for helically channeled single screw extruders. In the extruder, screw channel rotates against static barrel channel, which behaves as cooperative embedded twin-screws for the positive conveying. They turn as two parallel arc plates, between which an arc-plate solid-plug was assumed. By analyzing the forces on the solid-plug in the barrel channel and screw channel, the boundary conditions when the solid-plug is waived ...

  3. Studies on positive conveying in helically channeled single screw extruders

    Directory of Open Access Journals (Sweden)

    L. Pan

    2012-07-01

    Full Text Available A solids conveying theory called double-flight driving theory was proposed for helically channeled single screw extruders. In the extruder, screw channel rotates against static barrel channel, which behaves as cooperative embedded twin-screws for the positive conveying. They turn as two parallel arc plates, between which an arc-plate solid-plug was assumed. By analyzing the forces on the solid-plug in the barrel channel and screw channel, the boundary conditions when the solid-plug is waived of being cut off on barrel wall, were found to have the capacity of the positive conveying. Experimental data were obtained using a specially designed extruder with a helically channeled barrel in the feeding zone and a pressure-adjustable die. The effects of the barrel channel geometry and friction coefficients on the conveying mechanism were presented and compared with the experimental results. The simulations showed that the positive conveying could be achieved after optimizing extruder designs. Compared with the traditional design with the friction-drag conveying, the throughput is higher while screw torque and energy consumption are decreased. Besides, the design criteria of the barrel channel were also discussed.

  4. Analysis of Eyring-Powell Fluid in Helical Screw Rheometer

    Directory of Open Access Journals (Sweden)

    A. M. Siddiqui

    2014-01-01

    Full Text Available This paper aims to study the flow of an incompressible, isothermal Eyring-Powell fluid in a helical screw rheometer. The complicated geometry of the helical screw rheometer is simplified by “unwrapping or flattening” the channel, lands, and the outside rotating barrel, assuming the width of the channel is larger as compared to the depth. The developed second order nonlinear differential equations are solved by using Adomian decomposition method. Analytical expressions are obtained for the velocity profiles, shear stresses, shear at wall, force exerted on fluid, volume flow rates, and average velocity. The effect of non-Newtonian parameters, pressure gradients, and flight angle on the velocity profiles is noticed with the help of graphical representation. The observation confirmed the vital role of involved parameters during the extrusion process.

  5. Analysis of Eyring-Powell fluid in helical screw rheometer.

    Science.gov (United States)

    Siddiqui, A M; Haroon, T; Zeb, M

    2014-01-01

    This paper aims to study the flow of an incompressible, isothermal Eyring-Powell fluid in a helical screw rheometer. The complicated geometry of the helical screw rheometer is simplified by "unwrapping or flattening" the channel, lands, and the outside rotating barrel, assuming the width of the channel is larger as compared to the depth. The developed second order nonlinear differential equations are solved by using Adomian decomposition method. Analytical expressions are obtained for the velocity profiles, shear stresses, shear at wall, force exerted on fluid, volume flow rates, and average velocity. The effect of non-Newtonian parameters, pressure gradients, and flight angle on the velocity profiles is noticed with the help of graphical representation. The observation confirmed the vital role of involved parameters during the extrusion process.

  6. Analysis of Third-Grade Fluid in Helical Screw Rheometer

    Directory of Open Access Journals (Sweden)

    M. Zeb

    2013-01-01

    Full Text Available The steady flow of an incompressible, third-grade fluid in helical screw rheometer (HSR is studied by “unwrapping or flattening” the channel, lands, and the outside rotating barrel. The geometry is approximated as a shallow infinite channel, by assuming that the width of the channel is large as compared to the depth. The developed second-order nonlinear coupled differential equations are reduced to single differential equation by using a transformation. Using Adomian decomposition method, analytical expressions are calculated for the the velocity profiles and volume flow rates. The results have been discussed with the help of graphs as well. We observed that the velocity profiles are strongly dependant on non-Newtonian parameter (β~, and with the increase in β~, the velocity profiles increase progressively, which conclude that extrusion process increases with the increase in β~. We also observed that the increase in pressure gradients in x- and z-direction increases the net flow inside the helical screw rheometer, which increases the extrusion process. We noticed that the flow increases as the flight angle increase.

  7. Prototype and test of a novel rotary magnetorheological damper based on helical flow

    Science.gov (United States)

    Yu, Jianqiang; Dong, Xiaomin; Wang, Wen

    2016-02-01

    To increase the output damping torque of a rotary magnetorheological (MR) damper with limited geometrical space, a novel rotary MR damper based on helical flow is proposed. A new working mode, helical flow mode, is discussed and applied to enlarge the flow path of MR fluids. The helical flow can improve the performance of the rotary damper by enlarging the length of the active region. Based on the idea, a rotary MR damper is designed. The rotary MR damper contains a spiral piston, dual-coil core, a rotating cylinder and a stator cylinder. Based on the Bingham model, the output damping torque of the damper is analytically derived. The finite element method (FEM) is applied to calculate the magnetic field of the active region. The multi-objective optimal design method is adopted to obtain the optimal geometric parameters. A prototype is fabricated based on the optimal results. To validate the proposed rotary MR damper, two types of experiments including the low rotation speed and the high rotation speed are investigated. The results show that the proposed rotary MR damper has high torque density and compact structure. The helical flow mode can increase the output damping torque with limited space.

  8. Integrated Status and Effectiveness Monitoring Program - Entiat River Snorkel Surveys and Rotary Screw Trap, 2007.

    Energy Technology Data Exchange (ETDEWEB)

    Nelle, R.D.

    2008-01-01

    The USFWS Mid-Columbia River Fishery Resource Office conducted snorkel surveys at 24 sites during the summer and fall periods of 2006 survey periods as part of the Integrated Status and Effectiveness Monitoring Program in the Entiat River. A total of 37,938 fish from 15 species/genera and an unknown category were enumerated. Chinook salmon were the overall most common fish observed and comprised 15% of fish enumerated followed by rainbow trout (10%) and mountain whitefish (7%). Day surveys were conducted during the summer period 2007 (August), while night surveys were conducted during the fall 2007 (October) surveys. The USFWS Mid-Columbia River Fishery Resource Office (MCFRO) operated two rotary screw traps on the Entiat River as part of the Integrated Status and Effectiveness Monitoring Program (ISEMP) program from August through November of 2007. Along with the smolt traps, juvenile emigrants were also captured at remote locations throughout the Entiat watershed and its major tributary, the Mad River. A total of 999 wild Oncorhynchus mykiss and 5,107 wild run O. tshawytscha were PIT tagged during the study period. Rotary screw trap efficiencies averaged 22.3% for juvenile O. tshawytscha and 9.0% for juvenile O. mykiss. Rotary screw traps operated 7 days a week and remote capture operations were conducted when flow and temperature regimes permitted. This is third annual progress report to Bonneville Power Administration for the snorkel surveys conducted in the Entiat River as related to long-term effectiveness monitoring of restoration programs in this watershed. The objective of this study is to monitor the fish habitat utilization of planned in-stream restoration efforts in the Entiat River by conducting pre- and post-construction snorkel surveys at selected treatment and control sites.

  9. A rotary drum screen with internal screw flights for Eri silkworm pupae

    Directory of Open Access Journals (Sweden)

    Kanjanawanishkul Kiattisin

    2015-01-01

    Full Text Available Eri silkworm pupae (Samia ricini are very interesting creatures since they can be developed as a sustainable high protein food source for human beings and animals, and their cocoons can be used for silk production. At present, Thai silk is very famous for its special qualities, whereas the requirement of pupae as food grows increasingly, in particular, canned pupae with seasoning favors. Like other food products, size uniformity is required. Therefore, in this paper, a rotary drum screen with internal screw flights was designed and constructed for separating Eri silkworm pupae into two groups with different sizes. The experiments were conducted to evaluate its effectiveness. The results show that the optimal angular speed of the screen was 20 rpm and the screw pitch value was 10 cm. These parameters resulted in the accuracy percentage of pupa screening of 94.3% and the working capacity of 8.6 kg/h.

  10. New helical-shape magnetic pole design for Magnetic Lead Screw enabling structure simplification

    DEFF Research Database (Denmark)

    Lu, Kaiyuan; Xia, Yongming; Wu, Weimin

    2015-01-01

    Magnetic lead screw (MLS) is a new type of high performance linear actuator that is attractive for many potential applications. The main difficulty of the MLS technology lies in the manufacturing of its complicated helical-shape magnetic poles. Structure simplification is, therefore, quite essent......-shape magnetic poles. The performance of the new structure is compared with a MLS with ideal helical-shape magnetic poles using 3-D finite-element analysis. Halbach and flux concentration designs using the new approach are introduced....

  11. Integrated Status and Effectiveness Monitoring Program - Entiat River Rotary Screw Traps, Snorkel Surveys, and Steelhead Redd Surveys, 2008-2009.

    Energy Technology Data Exchange (ETDEWEB)

    Nelle, R.D.; Desgroseillier, Tom; Cotter, Michael [U.S. Fish and Wildlife Service

    2009-04-14

    The USFWS Mid-Columbia River Fishery Resource Office (MCRFRO) operated two rotary screw traps on the Entiat River as part of the Integrated Status and Effectiveness Monitoring Program from March through November of 2008. Along with the smolt traps, juvenile emigrants were also captured at remote locations throughout the Entiat watershed and its major tributary, the Mad River. A total of 16,782 wild salmonids were PIT tagged during the study period. Of this, 3,961(23.6%) were wild Oncorhynchus mykiss, 6,987 (41.6%) were wild spring run O. tshawytscha, and 5,591 (33.3%) were identified as wild O. tshawytscha of unknown run. Rotary screw trap efficiencies averaged 40.3% at the upper (Rkm 11.0) trap and 7.8% for the lower (Rkm 2.0) trap. These efficiencies were pooled for emigrant O. tshawytscha and O. mykiss. The MCRFRO conducted effectiveness monitoring snorkel surveys at 24 sites during the winter period and 30 sites during the summer and fall periods of 2008 as part of the Integrated Status and Effectiveness Monitoring Program in the Entiat River. The 2008 steelhead spawning grounds surveys were conducted weekly in the main Entiat River from rkm 1.1 to 44.2. A total of 222 steelhead redds were identified over the period from February 28 to June 16 2008 with April being the peak spawning month. Approximately 80% of the steelhead redds were located downstream of the rkm 26.

  12. Integrated Status and Effectiveness Monitoring Program - Entiat River Rotary Screw Traps,Snorkel Surveys, and Steelhead Redd Surveys, 2008.

    Energy Technology Data Exchange (ETDEWEB)

    Nelle, R.D.; Desgroseiller, Tom; Cotter, Michael (U.S. Fish and Wildlife Service)

    2009-02-17

    The USFWS Mid-Columbia River Fishery Resource Office (MCRFRO) operated two rotary screw traps on the Entiat River as part of the Integrated Status and Effectiveness Monitoring Program from March through November of 2008. Along with the smolt traps, juvenile emigrants were also captured at remote locations throughout the Entiat watershed and its major tributary, the Mad River. A total of 16,782 wild salmonids were PIT tagged during the study period. Of this, 3,961(23.6%) were wild Oncorhynchus mykiss, 6,987 (41.6%) were wild spring run O. tshawytscha, and 5,591 (33.3%) were identified as wild O. tshawytscha of unknown run. Rotary screw trap efficiencies averaged 40.3% at the upper (Rkm 11.0) trap and 7.8% for the lower (Rkm 2.0) trap. These efficiencies were pooled for emigrant O. tshawytscha and O. mykiss. The MCRFRO conducted effectiveness monitoring snorkel surveys at 24 sites during the winter period and 30 sites during the summer and fall periods of 2008 as part of the Integrated Status and Effectiveness Monitoring Program in the Entiat River. The 2008 steelhead spawning grounds surveys were conducted weekly in the main Entiat River from rkm 1.1 to 44.2. A total of 222 steelhead redds were identified over the period from February 28 to June 16 2008 with April being the peak spawning month. Approximately 80% of the steelhead redds were located downstream of the rkm 26.

  13. A Biomechanical Study Comparing Helical Blade with Screw Design for Sliding Hip Fixations of Unstable Intertrochanteric Fractures

    Directory of Open Access Journals (Sweden)

    Qiang Luo

    2013-01-01

    Full Text Available Dynamic hip screw (DHS is a well-established conventional implant for treating intertrochanteric fracture. However, revision surgery sometimes still occurs due to the cutting out of implants. A helical blade instead of threaded screw (DHS blade was designed to improve the fixation power of the osteoporotic intertrochanteric fracture. In this study, the biomechanical properties of DHS blade compared to the conventional DHS were evaluated using an unstable AO/OTA 31-A2 intertrochanteric fracture model. Fifty synthetic proximal femoral bone models with such configuration were fixed with DHS and DHS blade in five different positions: centre-centre (CC, superior-centre (SC, inferior-center (IC, centre-anterior (CA, and centre-posterior (CP. All models had undergone mechanical compression test, and the vertical and rotational displacements were recorded. The results showed that DHS blade had less vertical or rotational displacement than the conventional DHS in CC, CA, and IC positions. The greatest vertical and rotational displacements were found at CP position in both groups. Overall speaking, DHS blade was superior in resisting vertical or rotational displacement in comparison to conventional DHS, and the centre-posterior position had the poorest performance in both groups.

  14. Statistical Capability Study of a Helical Grinding Machine Producing Screw Rotors

    Science.gov (United States)

    Holmes, C. S.; Headley, M.; Hart, P. W.

    2017-08-01

    Screw compressors depend for their efficiency and reliability on the accuracy of the rotors, and therefore on the machinery used in their production. The machinery has evolved over more than half a century in response to customer demands for production accuracy, efficiency, and flexibility, and is now at a high level on all three criteria. Production equipment and processes must be capable of maintaining accuracy over a production run, and this must be assessed statistically under strictly controlled conditions. This paper gives numerical data from such a study of an innovative machine tool and shows that it is possible to meet the demanding statistical capability requirements.

  15. Data on mixing of viscous fluids by helical screw impellers in cylindrical vessels

    Directory of Open Access Journals (Sweden)

    Houari Ameur

    2016-09-01

    Full Text Available In this article, the data assembled regarding the mixing of Newtonian and shear thinning fluids by screw impellers in a cylindrical tank is disclosed. The data summarizing some information on the efficiency of such impellers are obtained via 3D calculations of velocities and viscous dissipation in the whole vessel volume. The data presented herein may be useful for those who want to outline the mixing characteristics in terms of fluid circulation and power consumption for this kind of impellers, therefore, avoiding a great effort for achieving a high number of experiments.

  16. Enumeration of Juvenile Salmonids in the Okanogan Basin Using Rotary Screw Traps, Performance Period: March 15, 2006 - July 15, 2006.

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Peter N.; Rayton, Michael D.

    2007-05-01

    The Colville Tribes identified the need for collecting baseline census data on the timing and abundance of juvenile salmonids in the Okanogan River basin for the purpose of documenting local fish populations, augmenting existing fishery data and assessing natural production trends of salmonids. This report documents and assesses the pilot year of rotary trap capture of salmonid smolts on the Okanogan River. The project is a component of the Colville Tribes Okanogan Basin Monitoring and Evaluation Program (OBMEP) which began in 2004. Trapping for outmigrating fish began on 14 March 2006 and continued through 11 July 2006. Anadromous forms of Oncorhynchus, including summer steelhead (O. mykiss), Chinook (O. tshawytscha), and sockeye (O. nerka), were targeted for this study; all have verified, natural production in the Okanogan basin. Both 8-ft and 5-ft rotary screw traps were deployed on the Okanogan River from the Highway 20 Bridge and typically fished during evening hours or 24 hours per day, depending upon trap position and discharge conditions. Juvenile Chinook salmon were the most abundant species trapped in 2006 (10,682 fry and 2,024 smolts), followed by sockeye (205 parr and 3,291 smolts) and steelhead (1 fry and 333 smolts). Of the trapped Chinook, all fry were wild origin and all but five of the smolts were hatchery-reared. All trapped sockeye were wild origin and 88% of the steelhead smolts were hatchery-reared. Mark-recapture experiments were conducted using Chinook fry and hatchery-reared steelhead smolts (sockeye were not used in 2006 because the peak of the juvenile migration occurred prior to the onset of the mark-recapture experiments). A total of 930 chinook fry were marked and released across eight separate release dates (numbers of marked Chinook fry released per day ranged from 34 to 290 fish). A total of 11 chinook fry were recaptured for an overall trap efficiency of 1.18%. A total of 710 hatchery-reared steelhead were marked and released across

  17. A new geometrical model for mixing of highly viscous fluids by combining two-blade and helical screw agitators

    Directory of Open Access Journals (Sweden)

    Hadjeb Abdessalam

    2017-09-01

    Full Text Available Mixing processes are becoming today a huge concern for industrialists in various domains like the pharmaceutical production, oil refining, food industry and manufacture of cosmetic products especially when the processes are related to the mixing of highly viscous products. So the choice of a stirring system for this category of products or fluids must be rigorously examined before use because of the flows which are laminar in the most cases, something that is not good to obtain homogeneous particles or suspensions after the mixing operation. This CFD study allows developing a new geometrical model of mechanical agitator with high performance for mixing of highly viscous fluids. It consists of a combination of two bladed and helical screw agitators. The investigations of the flow structure generated in the vessel are made by using the computer code ANSYS CFX (version 13.0, which allows us to realize and test the effectiveness of the new stirrer on the resulting mixture and power consumption.

  18. Designing of monitoring setup for vibration signature analysis of steam turbine driven high capacity rotary screw compressor

    Energy Technology Data Exchange (ETDEWEB)

    Pyne, T.; Vinod, J. [Birla VXL Ltd., Porbandar (India)

    1997-12-31

    Tracking the behaviour by signature analysis of machines like Screw Compressor having large number of auxiliaries, high power transmissions, variation of process gas properties, changes of load condition, fluctuating revolutions is truly a challenging job. These unavoidable process conditions often disturb the whole setup and there is every possibility to miss important and relevant information. Standards for overall monitoring as well as for peak-amplitudes responsible for root cause identification are not always available because these machines are `custom designed` and manufacturer`s standards are of paramount importance to consider. The health of these machines cannot be assessed by simply comparing with the international standards unlike most common machines such as fans, pumps, motors etc. with minimum number of auxiliaries. There may also be limitations in the features of the instruments used for the purpose. In this presentation, an attempt has been made to setup a monitoring approach for screw compressor which will help the industries initially setting base-line data to implement vibration analysis based off-line predictive maintenance programme either with the help of an analyser or with a latest software. (orig.) 3 refs.

  19. Test and demonstration of a 1-MW wellhead generator: helical screw expander power plant, Model 76-1. Final report to the International Energy Agency

    Energy Technology Data Exchange (ETDEWEB)

    1985-07-04

    A 1-MW geothermal wellhead power plant incorporating a Lysholm or helical screw expander (HSE) was field tested between 1980 and 1983 by Mexico, Italy, and New Zealand with technical assistance from the United States. The objectives were to provide data on the reliability and performance of the HSE and to assess the costs and benefits of its use. The range of conditions under which the HSE was tested included loads up to 933 kW, mass flowrates of 14,600 to 395, 000 lbs/hr, inlet pressures of 64 to 220 psia, inlet qualities of 0 to 100%, exhaust pressures of 3.1 to 40 psia, total dissolved solids up to 310,000 ppM, and noncondensible gases up to 38% of the vapor mass flow. Typical machine efficiencies of 40 to 50% were calculated. For most operations efficiency increased approximately logarithmically with shaft power, while inlet quality and rotor speed had only small effects. The HSE was designed with oversized internal clearances in the expectation that adherent scale would form during operation. Improvements in machine efficiency of 3.5 to 4 percentage points were observed over some test periods with some scale deposition. A comparison with a 1-MW back-pressure turbine showed that the HSE can compete favorably under certain conditions. The HSE was found to be a rugged energy conversion machine for geothermal applications, but some subsystems were found to require further development. 7 refs., 28 figs., 5 tabs.

  20. On the helical arrangements of protein molecules.

    Science.gov (United States)

    Dauter, Zbigniew; Jaskolski, Mariusz

    2017-12-01

    Helical structures are prevalent in biology. In the PDB, there are many examples where protein molecules are helically arranged, not only according to strict crystallographic screw axes but also according to approximate noncrystallographic screws. The preponderance of such screws is rather striking as helical arrangements in crystals must preserve an integer number of subunits per turn, while intuition and simple packing arguments would seem to favor fractional helices. The article provides insights into such questions, based on stereochemistry, trigonometry, and topology, and illustrates the findings with concrete PDB structures. Updated statistics of Sohncke space groups in the PDB are also presented. © 2017 The Protein Society.

  1. Unidirectional rotary motion in achiral molecular motors

    NARCIS (Netherlands)

    Kistemaker, Jos C. M.; Stacko, Peter; Visser, Johan; Feringa, Ben L.

    2015-01-01

    Control of the direction of motion is an essential feature of biological rotary motors and results from the intrinsic chirality of the amino acids from which the motors are made. In synthetic autonomous light-driven rotary motors, point chirality is transferred to helical chirality, and this governs

  2. Rotary Transformer

    Science.gov (United States)

    McLyman, Colonel Wm. T.

    1996-01-01

    None given. From first Par: Many spacecraft (S/C) and surface rovers require the transfer of signals and power across rotating interfaces. Science instruments, antennas and solar arrays are elements needing rotary power transfer for certain (S/C) configurations. Delivery of signal and power has mainly been done by using the simplest means, the slip ring approach. This approach, although simple, leaves debris generating noise over a period of time...The rotary transformer is a good alternative to slip rings for signal and power transfer.

  3. Determinación de perfiles para rotores de compresores de tornillo con perfil simétrico. // Profiles determination for screw compressors rotors with symmetrical profile.

    Directory of Open Access Journals (Sweden)

    A. Rivera Torres

    2005-05-01

    Full Text Available Los compresores rotativos de tornillo, constituyeron el acontecimiento histórico más relevante del siglo XX en el campodel proceso de compresión. Dentro de los elementos fundamentales de los compresores rotativos de tornillo se encuentranlos rotores, los cuales tienen lóbulos o canales helicoidales con perfiles con formas simétricas o asimétricas.En este articulo se presenta un método para el diseño de los perfiles de rotores para compresores o bombas de tornillo, conperfil circular, a partir del empleo de una curva de cuarto orden y la condición de conjugación de los engranajes, sin incluirel empleo de cicloides en la generación de dichos perfiles, lográndose características similares a la de los perfiles SRM.Palabras claves: Rotores, rotor macho, rotor hembra._____________________________________________________________________________Abstract:Rotary screw compressors constitute the most relevant historic event of the twentieth century in the field of the process ofcompression. The most fundamental elements of rotary screw compressors are the rotors, which have helical lobes or canalsand symmetrical or asymmetrical profiles.This paper presents a method of circular profile design for screw compressors or pumps, based on fourth order curves andthe conjugation of gears, which does not include the application of cycloids in profile generation but have similarcharacteristics to SRM profiles.Key words: rotors, male rotor, female rotor.

  4. Rotary capacitor

    CERN Multimedia

    1971-01-01

    The rotating wheel of the rotary capacitor representing the most critical part of the new radio-frequency system of the synchro-cyclotron. The three rows of teeth on the circumference of the wheel pass between four rows of stator blades with a minimum clearance of 1 mm at a velocity of 1700 rev/min.

  5. Rotary ATPases

    Science.gov (United States)

    Stewart, Alastair G.; Sobti, Meghna; Harvey, Richard P.; Stock, Daniela

    2013-01-01

    Rotary ATPases are molecular rotary motors involved in biological energy conversion. They either synthesize or hydrolyze the universal biological energy carrier adenosine triphosphate. Recent work has elucidated the general architecture and subunit compositions of all three sub-types of rotary ATPases. Composite models of the intact F-, V- and A-type ATPases have been constructed by fitting high-resolution X-ray structures of individual subunits or sub-complexes into low-resolution electron densities of the intact enzymes derived from electron cryo-microscopy. Electron cryo-tomography has provided new insights into the supra-molecular arrangement of eukaryotic ATP synthases within mitochondria and mass-spectrometry has started to identify specifically bound lipids presumed to be essential for function. Taken together these molecular snapshots show that nano-scale rotary engines have much in common with basic design principles of man made machines from the function of individual “machine elements” to the requirement of the right “fuel” and “oil” for different types of motors. PMID:23369889

  6. ROTARY SWITCH

    Science.gov (United States)

    Watterberg, J.P.E.

    1960-03-15

    BS>A compact rotary-type switoh was designed wherein an insulating shell carries circumferentially spaced contacts exposed to its interior and also carries, on a re-entrant portion, resilient contact arms having contact portions aligned wth and biased toward the spaced contacts. A dielectric rotor with a movable wall between the contacts and contact arms has an aperture that may be turned into or out of registry with the contacts so as to establish or interrupt circuits.

  7. Unidirectional rotary motion in achiral molecular motors.

    Science.gov (United States)

    Kistemaker, Jos C M; Štacko, Peter; Visser, Johan; Feringa, Ben L

    2015-11-01

    Control of the direction of motion is an essential feature of biological rotary motors and results from the intrinsic chirality of the amino acids from which the motors are made. In synthetic autonomous light-driven rotary motors, point chirality is transferred to helical chirality, and this governs their unidirectional rotation. However, achieving directional rotary motion in an achiral molecular system in an autonomous fashion remains a fundamental challenge. Here, we report an achiral molecular motor in which the presence of a pseudo-asymmetric carbon atom proved to be sufficient for exclusive autonomous disrotary motion of two appended rotor moieties. Isomerization around the two double bonds enables both rotors to move in the same direction with respect to their surroundings--like wheels on an axle--demonstrating that autonomous unidirectional rotary motion can be achieved in a symmetric system.

  8. Helicity scalings

    Energy Technology Data Exchange (ETDEWEB)

    Plunian, F [ISTerre, CNRS, Universite Joseph Fourier, Grenoble (France); Lessinnes, T; Carati, D [Physique Statistique et Plasmas, Universite Libre de Bruxelles (Belgium); Stepanov, R, E-mail: Franck.Plunian@ujf-grenoble.fr [Institute of Continuous Media Mechanics of the Russian Academy of Science, Perm (Russian Federation)

    2011-12-22

    Using a helical shell model of turbulence, Chen et al. (2003) showed that both helicity and energy dissipate at the Kolmogorov scale, independently from any helicity input. This is in contradiction with a previous paper by Ditlevsen and Giuliani (2001) in which, using a GOY shell model of turbulence, they found that helicity dissipates at a scale larger than the Kolmogorov scale, and does depend on the helicity input. In a recent paper by Lessinnes et al. (2011), we showed that this discrepancy is due to the fact that in the GOY shell model only one helical mode (+ or -) is present at each scale instead of both modes in the helical shell model. Then, using the GOY model, the near cancellation of the helicity flux between the + and - modes cannot occur at small scales, as it should be in true turbulence. We review the main results with a focus on the numerical procedure needed to obtain accurate statistics.

  9. Kinematics and Dynamic Evaluation of the Screw Conveyor of a ...

    African Journals Online (AJOL)

    This paper presents the volumetric performance of a horizontal enclosed screw conveyor with reference to the influence of vortex motion. Vortex motion is as a result of internal friction, friction between the granular material and surface of the helical blade, and the variable helix angle of the helical flight from the outer ...

  10. Discrete element modelling of screw conveyor-mixers

    Directory of Open Access Journals (Sweden)

    Jovanović Aca

    2015-01-01

    Full Text Available Screw conveyors are used extensively in food, plastics, mineral processing, agriculture and processing industries for elevating and/or transporting bulk materials over short to medium distances. Despite their apparent simplicity in design, the transportation action is very complex for design and constructors have tended to rely heavily on empirical performance data. Screw conveyor performance is affected by its operating conditions (such as: the rotational speed of the screw, the inclination of the screw conveyor, and its volumetric fill level. In this paper, horizontal, several single-pitch screw conveyors with some geometry variations in screw blade was investigated for mixing action during transport, using Discrete Element Method (DEM. The influence of geometry modifications on the performance of screw conveyor was examined, different screw designs were compared, and the effects of geometrical variations on mixing performances during transport were explored. During the transport, the particle tumbles down from the top of the helix to the next free surface and that segment of the path was used for auxiliary mixing action. The particle path is dramatically increased with the addition of three complementary helices oriented in the same direction as screw blades (1458.2 mm compared to 397.6 mm in case of single flight screw conveyor Transport route enlarges to 1764.4 mm, when installing helices oriented in the opposite direction from screw blades. By addition of straight line blade to single flight screw conveyor, the longest particle path is being reached: 2061.6 mm [Projekat Ministarstva nauke Republike Srbije, br. TR-31055

  11. Ultrasonic rotary-hammer drill

    Science.gov (United States)

    Bar-Cohen, Yoseph (Inventor); Badescu, Mircea (Inventor); Sherrit, Stewart (Inventor); Bao, Xiaoqi (Inventor); Kassab, Steve (Inventor)

    2010-01-01

    A mechanism for drilling or coring by a combination of sonic hammering and rotation. The drill includes a hammering section with a set of preload weights mounted atop a hammering actuator and an axial passage through the hammering section. In addition, a rotary section includes a motor coupled to a drive shaft that traverses the axial passage through the hammering section. A drill bit is coupled to the drive shaft for drilling by a combination of sonic hammering and rotation. The drill bit includes a fluted shaft leading to a distal crown cutter with teeth. The bit penetrates sampled media by repeated hammering action. In addition, the bit is rotated. As it rotates the fluted bit carries powdered cuttings helically upward along the side of the bit to the surface.

  12. Rotary filtration system

    Science.gov (United States)

    Herman, David T [Aiken, SC; Maxwell, David N [Aiken, SC

    2011-04-19

    A rotary filtration apparatus for filtering a feed fluid into permeate is provided. The rotary filtration apparatus includes a container that has a feed fluid inlet. A shaft is at least partially disposed in the container and has a passageway for the transport of permeate. A disk stack made of a plurality of filtration disks is mounted onto the shaft so that rotation of the shaft causes rotation of the filtration disks. The filtration disks may be made of steel components and may be welded together. The shaft may penetrate a filtering section of the container at a single location. The rotary filtration apparatus may also incorporate a bellows seal to prevent leakage along the shaft, and an around the shaft union rotary joint to allow for removal of permeate. Various components of the rotary filtration apparatus may be removed as a single assembly.

  13. Inducing achiral aliphatic oligoureas to fold into helical conformations.

    Science.gov (United States)

    Wechsel, Romina; Maury, Julien; Fremaux, Juliette; France, Scott P; Guichard, Gilles; Clayden, Jonathan

    2014-12-11

    The ability of urea-linked oligomers of achiral diamines (achiral analogues of the well-established chiral oligourea foldamers) to adopt helical conformations was explored spectroscopically. Up to four achiral units were ligated either to a well-formed helical trimer or to a single chiral diamine, and the extent to which they adopted a screw-sense preference was determined by NMR and CD. In the best performing cases, a trimeric chiral oligourea and even a single cis-cyclohexanediamine monomer induced folding into a helical conformation.

  14. Sacroiliac Screw Fixation

    NARCIS (Netherlands)

    E.W. van den Bosch

    2003-01-01

    textabstractThe aim of this thesis is to evaluate three major aspects of the use of sacroiliac screws in patients with unstable pelvic ring fractures: the optimal technique for sacroiliac screw fixation, the reliability of peroperative fluoroscopy and the late results. We focused on the questions

  15. Rotary Series Elastic Actuator

    Science.gov (United States)

    Ihrke, Chris A. (Inventor); Mehling, Joshua S. (Inventor); Parsons, Adam H. (Inventor); Griffith, Bryan Kristian (Inventor); Radford, Nicolaus A. (Inventor); Permenter, Frank Noble (Inventor); Davis, Donald R. (Inventor); Ambrose, Robert O. (Inventor); Junkin, Lucien Q. (Inventor)

    2013-01-01

    A rotary actuator assembly is provided for actuation of an upper arm assembly for a dexterous humanoid robot. The upper arm assembly for the humanoid robot includes a plurality of arm support frames each defining an axis. A plurality of rotary actuator assemblies are each mounted to one of the plurality of arm support frames about the respective axes. Each rotary actuator assembly includes a motor mounted about the respective axis, a gear drive rotatably connected to the motor, and a torsion spring. The torsion spring has a spring input that is rotatably connected to an output of the gear drive and a spring output that is connected to an output for the joint.

  16. Rotary mechanical latch

    Science.gov (United States)

    Spletzer, Barry L.; Martinez, Michael A.; Marron, Lisa C.

    2012-11-13

    A rotary mechanical latch for positive latching and unlatching of a rotary device with a latchable rotating assembly having a latching gear that can be driven to latched and unlatched states by a drive mechanism such as an electric motor. A cam arm affixed to the latching gear interfaces with leading and trailing latch cams affixed to a flange within the drive mechanism. The interaction of the cam arm with leading and trailing latch cams prevents rotation of the rotating assembly by external forces such as those due to vibration or tampering.

  17. Rotary drum separator system

    Science.gov (United States)

    Barone, Michael R. (Inventor); Murdoch, Karen (Inventor); Scull, Timothy D. (Inventor); Fort, James H. (Inventor)

    2009-01-01

    A rotary phase separator system generally includes a step-shaped rotary drum separator (RDS) and a motor assembly. The aspect ratio of the stepped drum minimizes power for both the accumulating and pumping functions. The accumulator section of the RDS has a relatively small diameter to minimize power losses within an axial length to define significant volume for accumulation. The pumping section of the RDS has a larger diameter to increase pumping head but has a shorter axial length to minimize power losses. The motor assembly drives the RDS at a low speed for separating and accumulating and a higher speed for pumping.

  18. Rotary jagas stipendiume

    Index Scriptorium Estoniae

    2009-01-01

    Pärnu Rotary klubi aastapäevapeol 11. mail Ammende villas anti stipendium viiele Pärnumaa noorele, teiste seas pälvis preemia Pärnu Ülejõe Gümnaasiumi muusikaõpetaja Fred Rõigas ja Pärnu Muusikakoolis trompetit õppiv Chris Sommer

  19. Rotary magnetic heat pump

    Science.gov (United States)

    Kirol, Lance D.

    1988-01-01

    A rotary magnetic heat pump constructed without flow seals or segmented rotor accomplishes recuperation and regeneration by using split flow paths. Heat exchange fluid pumped through heat exchangers and returned to the heat pump splits into two flow components: one flowing counter to the rotor rotation and one flowing with the rotation.

  20. Rotary shaft sealing assembly

    Science.gov (United States)

    Dietle, Lannie L.; Schroeder, John E.; Kalsi, Manmohan S.; Alvarez, Patricio D.

    2010-09-21

    A rotary shaft sealing assembly in which a first fluid is partitioned from a second fluid in a housing assembly having a rotary shaft located at least partially within. In one embodiment a lip seal is lubricated and flushed with a pressure-generating seal ring preferably having an angled diverting feature. The pressure-generating seal ring and a hydrodynamic seal may be used to define a lubricant-filled region with each of the seals having hydrodynamic inlets facing the lubricant-filled region. Another aspect of the sealing assembly is having a seal to contain pressurized lubricant while withstanding high rotary speeds. Another rotary shaft sealing assembly embodiment includes a lubricant supply providing a lubricant at an elevated pressure to a region between a lip seal and a hydrodynamic seal with a flow control regulating the flow of lubricant past the lip seal. The hydrodynamic seal may include an energizer element having a modulus of elasticity greater than the modulus of elasticity of a sealing lip of the hydrodynamic seal.

  1. Rotary slot dog

    Science.gov (United States)

    Cutburth, Ronald W.; Smauley, David A.

    1987-01-01

    A clamp or dog is disclosed which preferably comprises a slotted stepped cylindrical body which is inserted into a hole in a workpiece and then fastened to a base or fixture using a screw which is inserted through the slot. The stepped configuration provides an annular clamping surface which securely clamps the workpiece against the base or fixture. The slotted cylindrical configuration permits adjustment of the workpiece and retaining clamp in any direction, i.e., over 360.degree., relative to the mounting position of the screw in the base or fixture.

  2. DLC screw preload. Loosening prevention

    Directory of Open Access Journals (Sweden)

    Ivete Aparecida de Mattias Sartori

    2008-01-01

    Full Text Available The screw loosening is a reason to prosthetic rehabilitation failure. However, the DLC (Diamond-like carbon screw treatment lead thefriction decrease and sliding between the components, which increases the screw preload benefit and decreases the chance of looseningoccurrence. This case shows a clinical indication of the association of the correct preload applied and the DLC screw, which can be considered an optimized protocol to solve screw loosening recidivate of unitary prosthesis in anterior maxillary site.

  3. Cascades in helical turbulence

    CERN Document Server

    Ditlevsen, P D

    2001-01-01

    The existence of a second quadratic inviscid invariant, the helicity, in a turbulent flow leads to coexisting cascades of energy and helicity. An equivalent of the four-fifth law for the longitudinal third order structure function, which is derived from energy conservation, is easily derived from helicity conservation cite{Procaccia,russian}. The ratio of dissipation of helicity to dissipation of energy is proportional to the wave-number leading to a different Kolmogorov scale for helicity than for energy. The Kolmogorov scale for helicity is always larger than the Kolmogorov scale for energy so in the high Reynolds number limit the flow will always be helicity free in the small scales, much in the same way as the flow will be isotropic and homogeneous in the small scales. A consequence is that a pure helicity cascade is not possible. The idea is illustrated in a shell model of turbulence.

  4. Design and analysis of a field modulated magnetic screw for artificial heart

    Science.gov (United States)

    Ling, Zhijian; Ji, Jinghua; Wang, Fangqun; Bian, Fangfang

    2017-05-01

    This paper proposes a new electromechanical energy conversion system, called Field Modulated Magnetic Screw (FMMS) as a high force density linear actuator for artificial heart. This device is based on the concept of magnetic screw and linear magnetic gear. The proposed FMMS consists of three parts with the outer and inner carrying the radially magnetized helically permanent-magnet (PM), and the intermediate having a set of helically ferromagnetic pole pieces, which modulate the magnetic fields produced by the PMs. The configuration of the newly designed FMMS is presented and its electromagnetic performances are analyzed by using the finite-element analysis, verifying the advantages of the proposed structure.

  5. Development of a Piezoelectric Rotary Hammer Drill

    Science.gov (United States)

    Domm, Lukas N.

    2011-01-01

    The Piezoelectric Rotary Hammer Drill is designed to core through rock using a combination of rotation and high frequency hammering powered by a single piezoelectric actuator. It is designed as a low axial preload, low mass, and low power device for sample acquisition on future missions to extraterrestrial bodies. The purpose of this internship is to develop and test a prototype of the Piezoelectric Rotary Hammer Drill in order to verify the use of a horn with helical or angled cuts as a hammering and torque inducing mechanism. Through an iterative design process using models in ANSYS Finite Element software and a Mason's Equivalent Circuit model in MATLAB, a horn design was chosen for fabrication based on the predicted horn tip motion, electromechanical coupling, and neutral plane location. The design was then machined and a test bed assembled. The completed prototype has proven that a single piezoelectric actuator can be used to produce both rotation and hammering in a drill string through the use of a torque inducing horn. Final data results include bit rotation produced versus input power, and best drilling rate achieved with the prototype.

  6. The fate of syndesmotic screws.

    Science.gov (United States)

    Stuart, Kyle; Panchbhavi, Vinod K

    2011-05-01

    A standard protocol for the management of syndesmosis injuries has yet to be established. Debate persists regarding number of screws, screw diameter, number of cortices purchased, and the need for and timing of screw removal. The purpose of this study was to identify factors related to screw fixation that may lead to the ultimate failure of syndesmosis fixation defined as a loss of reduction of the syndesmosis, screw breakage, screw loosening, or widening of the medial clear space. A retrospective assessment of 137 consecutive patients who underwent open reduction and internal fixation of the distal tibiofibular joint at a single institution from 2004 to 2008 was performed. Clinical and radiographic data were recorded regarding problems with questionable clinical significance (number of syndesmotic screws, number of cortices, screw diameter, screw location, hardware failure) and loss of syndesmosis reduction. A series of Fisher's exact tests were used to evaluate outcomes. A p value of 0.05 defined as significant. The 3.5-mm diameter screws were statistically more likely to break than 4- or 4.5-mm screws, but there was no difference in frequency of loss of reduction of the syndesmosis as a function of screw diameter; however, a power study revealed an n value of 1656 would be required to show a significant difference. Screw diameter may have an effect on screw breakage but clinical significance of hardware failure itself is unknown including whether or not it results in a loss of reduction or failure of syndesmotic fixation.

  7. Piezoelectric Rotary Tube Motor

    Science.gov (United States)

    Fisher, Charles D.; Badescu, Mircea; Braun, David F.; Culhane, Robert

    2011-01-01

    A custom rotary SQUIGGLE(Registered TradeMark) motor has been developed that sets new benchmarks for small motor size, high position resolution, and high torque without gear reduction. Its capabilities cannot be achieved with conventional electromagnetic motors. It consists of piezoelectric plates mounted on a square flexible tube. The plates are actuated via voltage waveforms 90 out of phase at the resonant frequency of the device to create rotary motion. The motors were incorporated into a two-axis postioner that was designed for fiber-fed spectroscopy for ground-based and space-based projects. The positioner enables large-scale celestial object surveys to take place in a practical amount of time.

  8. Rotary deformity in degenerative spondylolisthesis

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Sung Gwon; Kim, Jeong; Kho, Hyen Sim; Yun, Sung Su; Oh, Jae Hee; Byen, Ju Nam; Kim, Young Chul [Chosun University College of Medicine, Gwangju (Korea, Republic of)

    1994-05-15

    We studied to determine whether the degenerative spondylolisthesis has rotary deformity in addition to forward displacement. We have made analysis of difference of rotary deformity between the 31 study groups of symptomatic degenerative spondylolisthesis and 31 control groups without any symptom, statistically. We also reviewed CT findings in 15 study groups. The mean rotary deformity in study groups was 6.1 degree(the standard deviation is 5.20), and the mean rotary deformity in control groups was 2.52 degree(the standard deviation is 2.16)(p < 0.01). The rotary deformity can be accompanied with degenerative spondylolisthesis. We may consider the rotary deformity as a cause of symptomatic degenerative spondylolisthesis in case that any other cause is not detected.

  9. Influence of a Number of Screw and Nut Thread Starts of Planetary Roller-Screw Mechanisms on Their Main Parameters

    Directory of Open Access Journals (Sweden)

    D. S. Blinov

    2016-01-01

    Full Text Available One of the most important requirements imposed to the modern mechanisms is economic feasibility. Therefore, considered as advanced are mechanical transducers of rotary motion to translational one, where rolling friction is mainly realized. They include planetary roller-screw mechanisms (PRSM.PRSM has a large variety of features. The design feature of PRSM is multiple starts of screw and nut thread. Rollers, as a rule, are made single-threaded. Number of screw thread starts which equals to a number of nut thread starts, has an effect on almost all performance characteristics of PRSM.This article covers comprehensively enough the influence of screw thread starts quantity on: kinematical parameters of PRSM, transfer function, mechanism radial dimensions, efficiency, power values, required characteristics of electric motor. As a result of investigations the graphs of dimensionless parameters vs. number of screw thread starts have been plotted, which are demonstrative and common.Being high enough the PRSM efficiency can vary within 20…25% and more. It depends on a variety of mechanism part parameters; primarily on geometrical ones, as well as on a number of screw thread starts. Previously the methods of PRSM design calculation consisted in determination of the main geometric parameters of mechanism parts, then in determination of mechanism efficiency. At that, it was not always possible to design the economically feasible PRSM structure.Introduction of a dimensionless value – a relation of PRSM part thread pitch to average screw thread diameter – contributed to successive plotting of the assemblage of curves for relation of efficiency to the indicated ratio and a number of screw thread starts. By taking this assemblage of curves as a basis, the method of economically feasible PRSM structures calculation and design was proposed.  The essence of the developed method lies in that selection or definition of a number of screw thread starts helps to

  10. BIOMATERIALS FOR ROTARY BLOOD PUMPS

    NARCIS (Netherlands)

    VANOEVEREN, W

    Rotary blood pumps are used for cardiac assist and cardiopulmonary support since mechanical blood damage is less than with conventional roller pumps. The high shear rate in the rotary pump and the reduced anticoagulation of the patient during prolonged pumping enforces high demands on the

  11. Design of Nano Screw Pump for Water Transport and its Mechanisms

    Science.gov (United States)

    Wang, LiYa; Wu, HengAn; Wang, FengChao

    2017-01-01

    Nanopumps conducting fluids through nanochannels have attracted considerable interest for their potential applications in nanofiltration, water desalination and drug delivery. Here, we demonstrate by molecular dynamics (MD) simulations that a nano screw pump is designed with helical nanowires embedded in a nanochannel, which can be used to drive unidirectional water flow. Such helical nanowires have been successfully synthesized in many experiments. By investigating the water transport mechanism through nano screw pumps with different configuration parameters, three transport modes were observed: cluster-by-cluster, pseudo-continuous, and linear-continuous, in which the water flux increases linearly with the rotating speed. The influences of the nanowires’ surface energy and the screw’s diameter on water transport were also investigated. Results showed that the water flux rate increases as the decreasing wettability of helical nanowires. The deviation in water flux in screw pumps with smaller radius is attributed to the weak hydrogen bonding due to space confinement and the hydrophobic blade. Moreover, we also proposed that such screw pumps with appropriate diameter and screw pitch can be used for water desalination. The study provides an insight into the design of multifunctional nanodevices for not only water transport but water desalination in practical applications. PMID:28155898

  12. Theoretical and experimental loss and efficiency studies of a magnetic lead screw

    DEFF Research Database (Denmark)

    Berg, Nick Ilsø; Holm, Rasmus Koldborg; Rasmussen, Peter Omand

    2013-01-01

    This paper investigates mechanical and magnetic losses in a magnetic lead screw (MLS). The MLS converts a low speed high force linear motion of a translator into a high speed low torque rotational motion of a rotor through helically shaped magnets. Initial tests performed with a novel 17 k...

  13. A new type of axial-flux magnetic lead screw with inherent spring characteristic

    DEFF Research Database (Denmark)

    Lu, Kaiyuan; Xia, Yongming; Pan, Haipeng

    2016-01-01

    Magnetic Lead Screw (MLS) can transfer slow linear motion into fast rotary motion offering much higher force density than that of traditional linear permanent magnet machines. It has been developed for ocean wave energy harvester and active damper for electrical vehicles. In this paper, a new typ...... in the same shape reducing the manufacturing cost while maintaining good force density. In addition, it has another advantage of inherent spring characteristic that is preferred for e.g. working under resonance condition for achieving the best system efficiency.......Magnetic Lead Screw (MLS) can transfer slow linear motion into fast rotary motion offering much higher force density than that of traditional linear permanent magnet machines. It has been developed for ocean wave energy harvester and active damper for electrical vehicles. In this paper, a new type...

  14. Helicity of the Neutrino

    Indian Academy of Sciences (India)

    IAS Admin

    Helicity for a particle is defined as the projection of the particle's spin along its direction of motion. For a massive particle, the sign of its helicity depends on the frame of reference ... A team of three scientists at Brookhaven National Lab- oratory, M Goldhaber, L Grodzins and A W Sunyar set about to rectify the situation.

  15. Rotary shaft seal

    Science.gov (United States)

    Langebrake, C.O.

    1984-01-01

    The invention is a novel rotary shaft seal assembly which provides positive-contact sealing when the shaft is not rotated and which operates with its sealing surfaces separated by a film of compressed ambient gas whose width is independent of the speed of shaft rotation. In a preferred embodiment, the assembly includes a disc affixed to the shaft for rotation therewith. Axially movable, non-rotatable plates respectively supported by sealing bellows are positioned on either side of the disc to be in sealing engagement therewith. Each plate carries piezoelectric transucer elements which are electrically energized at startup to produce films of compressed ambient gas between the confronting surfaces of the plates and the disc. Following shutdown of the shaft, the transducer elements are de-energized. A control circuit responds to incipient rubbing between the plate and either disc by altering the electrical input to the transducer elements to eliminate rubbing.

  16. NUT SCREW MECHANISMS

    Science.gov (United States)

    Glass, J.A.F.

    1958-07-01

    A reactor control mechanism is described wherein the control is achieved by the partial or total withdrawal of the fissile material which is in the form of a fuel rod. The fuel rod is designed to be raised and lowered from the reactor core area by means of two concentric ball nut and screw assemblies that may telescope one within the other. These screw mechanisms are connected through a magnetic clutch to a speed reduction gear and an accurately controllable prime motive source. With the clutch energized, the fuel rod may be moved into the reactor core area, and fine adjustments may be made through the reduction gearing. However, in the event of a power failure or an emergency signal, the magnetic clutch will become deenergized, and the fuel rod will drop out of the core area by the force of gravity, thus shutting down the operation of the reactor.

  17. Handedness preference and switching of peptide helices. Part II: Helices based on noncoded α-amino acids.

    Science.gov (United States)

    Crisma, Marco; De Zotti, Marta; Formaggio, Fernando; Peggion, Cristina; Moretto, Alessandro; Toniolo, Claudio

    2015-03-01

    In this second part of our review article on the preferred screw sense and interconversion of peptide helices, we discuss the most significant computational and experimental data published on helices formed by the most extensively investigated categories of noncoded α-amino acids. They are as follows: (i) N-alkylated Gly residues (peptoids), (ii) C(α) -alkylated α-amino acids, (iii) C(α,β) -sp(2) configurated α-amino acids, and (iv) combinations of residues of types (ii) and (iii). With confidence, the large body of interesting papers examined and classified in this editorial effort will stimulate the development of helical peptides in many diverse areas of biosciences and nanosciences. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.

  18. Magnetic helical micromachines.

    Science.gov (United States)

    Peyer, Kathrin E; Tottori, Soichiro; Qiu, Famin; Zhang, Li; Nelson, Bradley J

    2013-01-02

    Helical microrobots have the potential to be used in a variety of application areas, such as in medical procedures, cell biology, or lab-on-a-chip. They are powered and steered wirelessly using low-strength rotating magnetic fields. The helical shape of the device allows propulsion through numerous types of materials and fluids, from tissue to different types of bodily fluids. Helical propulsion is suitable for pipe flow conditions or for 3D swimming in open fluidic environments. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Internally geared screw machines with ported end plates

    Science.gov (United States)

    Read, M. G.; Smith, I. K.; Stosic, N.

    2017-08-01

    It is possible to design cylindrical helical gearing profiles such that an externally lobed inner gear rotates inside an internally lobed outer gear while maintaining continuous lines of contact between the gears. The continuous contact between the inner and outer rotors (analogous to the main and gate rotors in a conventional screw machine) creates a series of separate working chambers. In this type of machine the rotors have parallel axes of rotation, and if both rotors are free to rotate about their own axes, these axes can be fixed in space. The use of ported end plates is proposed to control the period during which fluid is allowed to enter or leave the working chambers of the internally geared screw machine. As with conventional screw machines, these internally geared rotors can then be used to achieve compression or expansion of a trapped mass of fluid, and the machine geometry can be designed in order to optimise performance for particular applications. This paper describes the geometrical analysis of some simple rotor profiles and explores the effect on rotor torques for particular applications of this novel screw configuration.

  20. Predicting rolling screw mechanisms service life

    Directory of Open Access Journals (Sweden)

    D. S. Blinov

    2015-01-01

    Full Text Available Ball screw mechanisms (BSM and planetary roller screw mechanisms (PRSM belong to promising energy-saving mechanisms converting rotary motion into linear motion. To calculate and design these mechanisms the static and dynamic load capacities are used. In case a standard size of the mechanism to be designed is available in manufacturer’s catalog, the specified load capacities can be taken from the catalog, and if not, then the static load for the mechanism being designed can be calculated. To determine the dynamic load capacity, long-term and costly experimental studies are to be conducted. Therefore, the crucial task is to forecast the BSM and PRSM dynamic load capacity and, further, the service life of these mechanisms. As follows from the analysis of information provided in manufacturers’ catalogs, there were established correlative relationships of static and dynamic load capacities for BSM and PRSM with the parameters determining their standard sizes. Using these relationships and methods of power regression enable us to obtain empirical dependences linking the factor equal to the ratio of static load capacity to dynamic load capacity with parameters defining standard sizes of the mechanisms. To predict BSM and PRSM service lives the said ratio is calculated using the empirical dependence, static load capacity of the mechanism being designed is determined by means of calculation using known procedures, and then dynamic load capacity is determined as the quotient of static load capacity division by the said factor. Then, having determined the equivalent load acting on the mechanism being designed the service life value is predicted based on known procedures. The developed procedure for predicting dynamic load capacity and service life can be used for calculation of newly developed BSM and PRSM designs when determining reasonable parameters of these mechanisms and their parts. The article cites an example of forecasting PRSM service life

  1. SCREW SELECTION FOR SCREW OPERATION USING EXPERT SYSTEM APPROACH

    Directory of Open Access Journals (Sweden)

    Hüdayim BAŞAK

    1999-01-01

    Full Text Available In this study, a expert system has been developed using Leonardo expert system package programming for screw operation, According to DIN standard norm. The designed program decide the most suitable screw type considering to material, cutting speed, working condition etc. This program also directs to user.

  2. 21 CFR 872.4840 - Rotary scaler.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Rotary scaler. 872.4840 Section 872.4840 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Surgical Devices § 872.4840 Rotary scaler. (a) Identification. A rotary scaler is an...

  3. Large Helical Device project

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-05-01

    In this book, the results of the scientific research on the design, trial manufacture and manufacturing processes of the Large Helical Device which was constructed in National Institute for Fusion Science are summarized. The LHD is the largest helical device in the world, and the largest superconducting system in the world. It possesses the following features: the optimization of heliotron magnetic field coordination, the adoption of superconducting magnets for 2 helical magnetic field coils and 6 poloidal coils, the adoption of helical diverter which enables steady plasma experiment, the flexible specification as the experimental facility and so on. The construction has been carried out smoothly, and in March, 1998, first plasma was generated. The outline of the Large Helical Device project, the physical design, the equipment design, the research and development of superconductivity and low temperature system, the design and manufacture of the superconducting and low temperature systems, the design and manufacture of the power source and superconducting bus-line, vacuum vessel and others, electron cyclotron heating, neutral beam injection and ion cyclotron RF heating, measurement system, control and data processing, safety management, the theory and analysis of LHD plasma, the visualization of the result of theoretical analysis, the analysis of the experimental data, and the experiment plan are described. (K.I.)

  4. Helical plasma thruster

    Energy Technology Data Exchange (ETDEWEB)

    Beklemishev, A. D., E-mail: bekl@bk.ru [Budker Institute of Nuclear Physics SB RAS, Novosibirsk (Russian Federation)

    2015-10-15

    A new scheme of plasma thruster is proposed. It is based on axial acceleration of rotating magnetized plasmas in magnetic field with helical corrugation. The idea is that the propellant ionization zone can be placed into the local magnetic well, so that initially the ions are trapped. The E × B rotation is provided by an applied radial electric field that makes the setup similar to a magnetron discharge. Then, from the rotating plasma viewpoint, the magnetic wells of the helically corrugated field look like axially moving mirror traps. Specific shaping of the corrugation can allow continuous acceleration of trapped plasma ions along the magnetic field by diamagnetic forces. The accelerated propellant is expelled through the expanding field of magnetic nozzle. By features of the acceleration principle, the helical plasma thruster may operate at high energy densities but requires a rather high axial magnetic field, which places it in the same class as the VASIMR{sup ®} rocket engine.

  5. A screwing device for handling and assembly of micro screws

    DEFF Research Database (Denmark)

    Gegeckaite, Asta; Hansen, Hans Nørgaard; Eriksson, Torbjörn Gerhard

    2007-01-01

    specific requirements for the torque and displacement regarding precision and repeatability. Micro screws are used as critical mechanical components in micro assemblies such as watches, dials, computers and hearing aids. These miniature parts normally require manual assembly processes under magnification...

  6. The pullout performance of pedicle screws

    CERN Document Server

    Demir, Teyfik

    2015-01-01

    This brief book systematically discusses all subjects that affect the pullout strength of pedicle screws. These screws are used in spinal surgeries to stabilize the spine. The holding strength of the pedicle screw is vital since loosening of the pedicle screws can cause revision surgeries. Once the pedicle screw is pulled out, it is harder to obtain same stabilization for the fused vertebrae. The book reviews the effect of screw designs, application techniques, cement augmentation, coating of the screw and test conditions on the pullout strength. The studies with finite element analysis were also included.

  7. Designing screws for polymer compounding in twin-screw extruders =

    Science.gov (United States)

    Teixeira, Cristina Ferreira

    Considering its modular construction, co-rotating twin screw extruders can be easily adapted to work with polymeric systems with more stringent specifications. However, their geometrical flexibility makes the performance of these machines strongly dependent on the screw configuration. Therefore, the definition of the adequate screw geometry to use in a specific polymer system is an important process requirement which is currently achieved empirically or using a trial-and-error basis. The aim of this work is to develop an automatic optimization methodology able to define the best screw geometry/configuration to use in a specific compounding/reactive extrusion operation, reducing both cost and time. This constitutes an optimization problem where a set of different screw elements are to be sequentially positioned along the screw in order to maximize the extruder performance. For that, a global modeling program considering the most important physical, thermal and rheological phenomena developing along the axis of an intermeshing co-rotating twin screw extruder was initially developed. The accuracy and sensitivity of the software to changes in the input parameters was tested for different operating conditions and screw configurations using a laboratorial Leistritz LSM 30.34 extruder. Then, this modeling software was integrated into an optimization methodology in order to be possible solving the Twin Screw Configuration Problem. Multi-objective versions of local search algorithms (Two Phase Local Search and Pareto Local Search) and Ant Colony Optimization algorithms were implemented and adapted to deal with the combinatorial, discrete and multi-objective nature of the problem. Their performance was studied making use of the hypervolume indicator and Empirical Attainment Function, and compared with the Reduced Pareto Search Genetic Algorithm (RPSGA) previously developed and applied to this problem. In order to improve the quality of the results and/or to decrease the

  8. Rotary condenser for SC2

    CERN Multimedia

    1975-01-01

    During 1975 the SC2 performance was improved among other things by redesigning some of the elements of the ROTCO (Annual Report 1975, p. 55). The photo shows an interior wiew of the housing of the rotary condenser and of the sixteen sets of shaped stator blades.

  9. Rotary reactor and use thereof

    NARCIS (Netherlands)

    Bakker Wridzer, J.W.; Kapteijn, F.; Moulijn, J.A.

    1998-01-01

    The invention relates to a rotary reactor consisting of a number of tubular reaction compartments (A), each provided with a first end and a second end, a ceramic first reactor end plate (B) in which said first ends are received, and a second end plate (B) in which said second ends are received,

  10. Rotary ultrasonic bone drilling: Improved pullout strength and reduced damage.

    Science.gov (United States)

    Gupta, Vishal; Pandey, Pulak M; Silberschmidt, Vadim V

    2017-03-01

    Bone drilling is one of the most common operations used to repair fractured parts of bones. During a bone drilling process, microcracks are generated on the inner surface of the drilled holes that can detrimentally affect osteosynthesis and healing. This study focuses on the investigation of microcracks and pullout strength of cortical-bone screws in drilled holes. It compares conventional surgical bone drilling (CSBD) with rotary ultrasonic bone drilling (RUBD), a novel approach employing ultrasonic vibration with a diamond-coated hollow tool. Both techniques were used to drill holes in porcine bones in an in-vitro study. Scanning electron microscopy was used to observe microcracks and surface morphology. The results obtained showed a significant decrease in the number and dimensions of microcracks generated on the inner surface of drilled holes with the RUBD process in comparison to CSBD. It was also observed that a higher rotational speed and a lower feed rate resulted in lower damage, i.e. fewer microcracks. Biomechanical axial pullout strength of a cortical bone screw inserted into a hole drilled with RUBD was found to be much higher (55-385%) than that for CSBD. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

  11. Surgeon perception of cancellous screw fixation.

    Science.gov (United States)

    Stoesz, Michael J; Gustafson, Peter A; Patel, Bipinchandra V; Jastifer, James R; Chess, Joseph L

    2014-01-01

    The ability of surgeons to optimize screw insertion torque in nonlocking fixation constructs is important for stability, particularly in osteoporotic and cancellous bone. This study evaluated screw torque applied by surgeons during synthetic cancellous fixation. It evaluated the frequency with which screws were stripped by surgeons, factors associated with screw stripping, and ability of surgeons to recognize it. Ten surgeons assembled screw and plate fixation constructs into 3 densities of synthetic cancellous bone while screw insertion torque and axial force were measured. For each screw, the surgeon recorded a subjective rating as to whether or not the screw had been stripped. Screws were then advanced past stripping, and stripped screws were identified by comparing the insertion torque applied by the surgeon to the measured stripping torque. Surgeons stripped 109 (45.4%) of 240 screws and did not recognize stripping 90.8% of the time when it occurred. The tendency to strip screws was highly variable among individual surgeons (stripping ranging from 16.7% to 83.3%, P perception is not reliable at preventing and detecting screw stripping at clinical torque levels in synthetic cancellous bone. Less aggressive insertion or standardized methods of insertion may improve the stability of nonlocking screw and plate constructs.

  12. Dynamic control of chirality and self-assembly of double-stranded helicates with light.

    Science.gov (United States)

    Zhao, Depeng; van Leeuwen, Thomas; Cheng, Jinling; Feringa, Ben L

    2017-03-01

    Helicity switching in biological and artificial systems is a fundamental process that allows for the dynamic control of structures and their functions. In contrast to chemical approaches to responsive behaviour in helicates, the use of light as an external stimulus offers unique opportunities to invert the chirality of helical structures in a non-invasive manner with high spatiotemporal precision. Here, we report that unidirectional rotary motors with connecting oligobipyridyl ligands, which can dynamically change their chirality upon irradiation, assemble into metal helicates that are responsive to light. The motor function controls the self-assembly process as well as the helical chirality, allowing switching between oligomers and double-stranded helicates with distinct handedness. The unidirectionality of the light-induced motion governs the sequence of programmable steps, enabling the highly regulated self-assembly of fully responsive helical structures. This discovery paves the way for the future development of new chirality-dependent photoresponsive systems including smart materials, enantioselective catalysts and light-driven molecular machines.

  13. Dynamic control of chirality and self-assembly of double-stranded helicates with light

    Science.gov (United States)

    Zhao, Depeng; van Leeuwen, Thomas; Cheng, Jinling; Feringa, Ben L.

    2017-03-01

    Helicity switching in biological and artificial systems is a fundamental process that allows for the dynamic control of structures and their functions. In contrast to chemical approaches to responsive behaviour in helicates, the use of light as an external stimulus offers unique opportunities to invert the chirality of helical structures in a non-invasive manner with high spatiotemporal precision. Here, we report that unidirectional rotary motors with connecting oligobipyridyl ligands, which can dynamically change their chirality upon irradiation, assemble into metal helicates that are responsive to light. The motor function controls the self-assembly process as well as the helical chirality, allowing switching between oligomers and double-stranded helicates with distinct handedness. The unidirectionality of the light-induced motion governs the sequence of programmable steps, enabling the highly regulated self-assembly of fully responsive helical structures. This discovery paves the way for the future development of new chirality-dependent photoresponsive systems including smart materials, enantioselective catalysts and light-driven molecular machines.

  14. Helices and vector bundles

    CERN Document Server

    Rudakov, A N

    1990-01-01

    This volume is devoted to the use of helices as a method for studying exceptional vector bundles, an important and natural concept in algebraic geometry. The work arises out of a series of seminars organised in Moscow by A. N. Rudakov. The first article sets up the general machinery, and later ones explore its use in various contexts. As to be expected, the approach is concrete; the theory is considered for quadrics, ruled surfaces, K3 surfaces and P3(C).

  15. An Improved Rotary Interpolation Based on FPGA

    Directory of Open Access Journals (Sweden)

    Mingyu Gao

    2014-08-01

    Full Text Available This paper presents an improved rotary interpolation algorithm, which consists of a standard curve interpolation module and a rotary process module. Compared to the conventional rotary interpolation algorithms, the proposed rotary interpolation algorithm is simpler and more efficient. The proposed algorithm was realized on a FPGA with Verilog HDL language, and simulated by the ModelSim software, and finally verified on a two-axis CNC lathe, which uses rotary ellipse and rotary parabolic as an example. According to the theoretical analysis and practical process validation, the algorithm has the following advantages: firstly, less arithmetic items is conducive for interpolation operation; and secondly the computing time is only two clock cycles of the FPGA. Simulations and actual tests have proved that the high accuracy and efficiency of the algorithm, which shows that it is highly suited for real-time applications.

  16. Design of a new separable rotary transformer

    Science.gov (United States)

    Gong, X. F.; Zhang, L.; Feng, E. J.

    2017-09-01

    A new-type separable rotary transformer which can be used in rotary steerable drilling is designed to deliver power efficiently from a stationary primary source to a rotary secondary load over a relatively large air gap via magnetic coupling. In this paper, E-type magnetic cores are reasonably distributed so that rotation of the rotary secondary has the least influence on reluctance of magnetic coupling. The influence of different winding layouts and connection modes on self-inductance and coupling coefficient is studied. By analysing the influence of the different geometrical shapes of cores on magnetic path, a design principle is proposed.

  17. comparative effects of screw press for honey

    African Journals Online (AJOL)

    2013-03-01

    . Different local methods of honey extraction, their strengths and weaknesses were discussed. A screw press was fabricated to facilitate honey extraction. The fabricated screw honey extractor is good alternative to the existing ...

  18. Effect of surface coating on the screw loosening of dental abutment screws

    Science.gov (United States)

    Park, Chan-Ik; Choe, Han-Cheol; Chung, Chae-Heon

    2004-12-01

    Regardless of the type of performed restoration, in most cases, a screw connection is employed between the abutment and implant. For this reason, implant screw loosening has remained a problem in restorative practices. The purpose of this study was to compare the surface of coated/plated screws with titanium and gold alloy screws and to evaluate the physical properties of coated/plated material after scratch tests via FE-SEM (field emission scanning electron microscopy) investigation. GoldTite, titanium screws provided by 3i (Implant Innovation, USA) and TorqTite, titanium screws by Steri-Oss (Nobel Biocare, USA) and gold screws and titanium screws by AVANA (Osstem Implant, Korea) were selected for this study. The surface, crest, and root of the abutment screws were observed by FE-SEM. A micro-diamond needle was also prepared for the scratch test. Each abutment screw was fixed, and a scratch on the surface of the head region was made at constant load and thereafter the fine trace was observed with FE-SEM. The surface of GoldTite was smoother than that of other screws and it also had abundant ductility and malleability compared with titanium and gold screws. The scratch tests also revealed that teflon particles were exfoliated easily in the screw coated with teflon. The titanium screw had rough surface and low ductility. The clinical use of gold-plated screws is recommended as a means of preventing screw loosening.

  19. Arthroscopic Screw Removal After Arthroscopic Latarjet Procedure

    OpenAIRE

    Lafosse, Thibault; Amsallem, Lior; Delgrande, Damien; Gerometta, Antoine; Lafosse, Laurent

    2017-01-01

    Arthroscopic Latarjet procedure is an efficient and reliable approach for the treatment of shoulder instability. Nevertheless, the screws fixing the bone block may sometimes be responsible for pain and uncomfortable snapping in the shoulder that is triggered during active external rotation. We propose an all-arthroscopic technique for screw removal in cases of complications involving the screws from a Latarjet procedure. The all-arthroscopic screw removal is reliable and efficient. This proce...

  20. Using Ultrasound to Prevent Screw Penetration.

    Science.gov (United States)

    Balfour, George W

    2016-03-01

    Ultrasound is a readily available, inexpensive, easy-to-use, and rapid diagnostic tool. Physicians can use ultrasound to identify excessively long screws or screw penetration into joints. This article illustrates ultrasound identification of problem screws. Copyright © 2016 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

  1. Helical CT for lumbosacral spinal

    Energy Technology Data Exchange (ETDEWEB)

    Tatsuno, Satoshi; Fukuda, Kunihiko [Jikei Univ., Tokyo (Japan). School of Medicine

    1996-10-01

    The aim of this study was to investigate the efficacy of helical CT for lumbosacral pathology. We performed helical CT with multiplanar reconstruction, including the formation of oblique transaxial and coronal images, in 62 patients with various lumboscral disorders, including 32 non-enhanced CT and 36 CT after myelography. We correlated the appearance of the stenotic spinal canal and neoplastic disease with the findings on MRI obtained at nearly the same time. We obtained helical CT images in all cases in about 30 seconds. The diagnostic ability of helical CT was roughly equal to that of MRI in patients with spondylosis deformans, spondylolisthesis and herniated nucleus pulposus. There was no significant difference in diagnostic value for degenerative lumbosacral disease with canal and foraminal stenosis between non-enhanced and post-myelography helical CT. However, non-enhanced helical CT could not clearly demonstrate neoplastic disease because of the poor contrast resolution. Helical CT was useful in evaluating degenerative disorder and its diagnostic value was nearly equal to that of MRI. We considered that helical CT may be suitable for the assessment of patients with severe lumbago owing to the markedly shortened examination time. However, if helical CT is used as a screening method for lumbosacral disease, one must be careful of its limitations, for example, poor detectability of neoplastic disease, vascular anomalies and so on. (author)

  2. The rotary subwoofer: a controllable infrasound source.

    Science.gov (United States)

    Park, Joseph; Garcés, Milton; Thigpen, Bruce

    2009-04-01

    The rotary subwoofer is a novel acoustic transducer capable of projecting infrasonic signals at high sound pressure levels. The projector produces higher acoustic particle velocities than conventional transducers which translate into higher radiated sound pressure levels. This paper characterizes measured performance of a rotary subwoofer and presents a model to predict sound pressure levels.

  3. Rotary-atomizer electric power generator

    NARCIS (Netherlands)

    Nguyen, Trieu; Tran, Tuan; de Boer, Hans L.; van den Berg, Albert; Eijkel, Jan C.T.

    2015-01-01

    We report experimental and theoretical results on a ballistic energy-conversion method based on a rotary atomizer working with a droplet acceleration-deceleration cycle. In a rotary atomizer, liquid is fed onto the center of a rotating flat surface, where it spreads out under the action of the

  4. DEMES rotary joint: theories and applications

    Science.gov (United States)

    Wang, Shu; Hao, Zhaogang; Li, Mingyu; Huang, Bo; Sun, Lining; Zhao, Jianwen

    2017-04-01

    As a kind of dielectric elastomer actuators, dielectric elastomer minimum energy structure (DEMES) can realize large angular deformations by small voltage-induced strains, which make them an attractive candidate for use as biomimetic robotics. Considering the rotary joint is a basic and common component of many biomimetic robots, we have been fabricated rotary joint by DEMES and developed its performances in the past two years. In this paper, we have discussed the static analysis, dynamics analysis and some characteristics of the DEMES rotary joint. Based on theoretical analysis, some different applications of the DEMES rotary joint were presented, such as a flapping wing, a biomimetic fish and a two-legged walker. All of the robots are fabricated by DEMES rotary joint and can realize some basic biomimetic motions. Comparing with traditional rigid robot, the robot based on DEMES is soft and light, so it has advantage on the collision-resistant.

  5. Magnetic helicity and higher helicity invariants as constraints for dynamo action

    Science.gov (United States)

    Sokoloff, Dmitry; Akhmetyev, Peter; Illarionov, Egor

    2018-01-01

    We consider classical magnetic helicity (a Gauss invariant of magnetic lines) and higher helicity invariants as nonlinear constraints for dynamo action. We argue that the Gauss invariant has several properties absent from higher helicity invariants which prevents use of the latter to constrain dynamo action. We consider other helicities (hydrodynamic helicity and cross helicity) in the context of the dynamo problem.

  6. Metallurgical examination of gun barrel screws

    Energy Technology Data Exchange (ETDEWEB)

    Bird, E.L.; Clift, T.L.

    1996-06-01

    The examination was conducted to determine the extent of degradation that had occurred after a series of firings; these screws prevent live rounds of ammunition from being loaded into the firing chamber. One concern is that if the screw tip fails and a live round is accidentally loaded into the chamber, a live round could be fired. Another concern is that if the blunt end of the screw begins to degrade by cracking, pieces could become small projectiles during firing. All screws used in firing 100 rounds or more exhibited some degree degradation, which progressively worsened as the number of rounds fired increased. (SEM, metallography, x-ray analysis, and microhardness were used.) Presence of cracks in these screws after 100 fired rounds is a serious concern that warrants the discontinued use of these screws. The screw could be improved by selecting an alloy more resistant to thermal and chemical degradation.

  7. Rotating Optical Tubes: An Archimedes' Screw for Atoms

    CERN Document Server

    Rsheed, Anwar Al; Aldossary, Omar M; Lembessis, Vassilis E

    2016-01-01

    The classical dynamics of a cold atom trapped inside a vertical rotating helical optical tube (HOT) is investigated by taking also into account the gravitational field. The resulting equations of motion are solved numerically. The rotation induces a vertical motion for an atom initially at rest. The motion is a result of the action of two inertial forces, namely the centrifugal force and the Coriolis force. Both inertial forces force the atom to rotate in a direction opposite to that of the angular velocity of the HOT. The frequency and the turning points of the atom's global oscillation can be controlled by the value and the direction of the angular velocity of the HOT. However, at large values of the angular velocity of the HOT the atom can escape from the global oscillation and be transported along the axis of the HOT. In this case, the rotating HOT operates as an Optical Archimedes' Screw (OAS) for atoms.

  8. Topology of helical fluid flow

    DEFF Research Database (Denmark)

    Andersen, Morten; Brøns, Morten

    2014-01-01

    Considering a coordinate-free formulation of helical symmetry rather than more traditional definitions based on coordinates, we discuss basic properties of helical vector fields and compare results from the literature obtained with other approaches. In particular, we discuss the role of the stream...

  9. Helicity in dynamic atmospheric processes

    Science.gov (United States)

    Kurgansky, M. V.

    2017-03-01

    An overview on the helicity of the velocity field and the role played by this concept in modern research in the field of geophysical fluid dynamics and dynamic meteorology is given. Different (both previously known in the literature and first presented) formulations of the equation of helicity balance in atmospheric motions (including those with allowance for effects of air compressibility and Earth's rotation) are brought together. Equations and relationships are given which are valid in different approximations accepted in dynamic meteorology: Boussinesq approximation, quasi-static approximation, and quasi-geostrophic approximation. Emphasis is placed on the analysis of helicity budget in large-scale quasi-geostrophic systems of motion; a formula for the helicity flux across the upper boundary of the nonlinear Ekman boundary layer is given, and this flux is shown to be exactly compensated for by the helicity destruction inside the Ekman boundary layer.

  10. Beta sheets with a twist: the conformation of helical polyisocyanopeptides determined by using vibrational circular dichroism.

    Science.gov (United States)

    Schwartz, Erik; Liégeois, Vincent; Koepf, Matthieu; Bodis, Pavol; Cornelissen, Jeroen J L M; Brocorens, Patrick; Beljonne, David; Nolte, Roeland J M; Rowan, Alan E; Woutersen, Sander; Champagne, Benoît

    2013-09-23

    Detailed information on the architecture of polyisocyanopeptides based on vibrational circular dichroism (VCD) spectroscopy in combination with DFT calculations is presented. It is demonstrated that the screw sense of the helical polyisocyanides can be determined directly from the C=N-stretch vibrational region of the VCD spectrum. Analysis of the VCD signals associated with the amide I and amide II modes provides detailed information on the peptide side-chain arrangement in the polymer and indicates the presence of a helical β-sheet architecture, in which the dihedral angles are slightly different to those of natural β-sheet helices. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Numerical Analysis of Helical Pile–Soil Interaction under Compressive Loads

    Science.gov (United States)

    Polishchuk, A. I.; Maksimov, F. A.

    2017-11-01

    The results of the field tests of full-scale steel helical piles in clay soils intended for prefabricated temporary buildings foundations are presented in this article. The finite element modeling was used for the evaluation of stress distribution of the clay soil around helical piles. An approach of modeling of the screw-pile geometry has been proposed through the Finite Element Analysis. Steel helical piles with a length of 2.0 m, shaft diameter of 0.108 m and a blade diameter of 0.3 m were used in the experiments. The experiments have shown the efficiency of double-bladed helical piles in the clay soils compared to single-bladed piles. It has been experimentally established that the introduction of the second blade into the pile shaft provides an increase of the bearing capacity in clay soil up to 30% compared to a single-bladed helical pile with similar geometrical dimensions. The numerical results are compared with the measurements obtained by a large scale test and the bearing capacity has been estimated. It has been found that the model results fit the field results. For a double-bladed helical pile it was revealed that shear stresses upon pile loading are formed along the lateral surface forming a cylindrical failure surface.

  12. Analysis on Energy Conversion of Screw Centrifugal Pump in Impeller Domain Based on Profile Lines

    Directory of Open Access Journals (Sweden)

    Hui Quan

    2013-01-01

    Full Text Available In order to study the power capability of impeller and energy conversion mechanism of screw centrifugal pump, the methods of theoretical analysis and numerical simulation by computational fluid dynamics theory (CFD were adopted, specifically discussing the conditions of internal flow such as velocity, pressure, and concentration. When the medium is sand-water two-phase flow and dividing the rim of the lines and wheel lines of screw centrifugal pump to segments to analyze energy conversion capabilities which along the impeller profile lines with the dynamic head and hydrostatic head changer, the results show that the energy of fluid of the screw centrifugal pump is provided by helical segment, and the helical segment of the front of the impeller has played the role of multilevel increasing energy; the sand-water two phases move at different speeds because the different force field and the impeller propeller and centrifugal effect. As liquid phase is the primary phase, the energy conversion is mainly up to the change of liquid energy, the solid phase flows under the wrapped action of liquid, and solid energy is carried out through liquid indirectly.

  13. Fatigue Performance of Cortical Bone Trajectory Screw Compared With Standard Trajectory Pedicle Screw.

    Science.gov (United States)

    Akpolat, Yusuf Tahiri; İnceoğlu, Serkan; Kinne, Nolan; Hunt, Devon; Cheng, Wayne K

    2016-03-01

    Cadaveric biomechanical study. To determine fatigue behavior of cortical bone trajectory (CBT) pedicle screws. Cortical bone trajectory screws have been becoming popular in spine surgery; however, the long-term fatigue behavior of the new CBT screws remains understudied and limitations not well defined. Twelve vertebrae from six cadaveric lumbar spines were obtained. After bone mineral density (BMD) measurements, each vertebral body was instrumented with screws from each group, that is, CBT (4.5 × 25 mm) or standard pedicle screw (6.5 × 55 mm). A load (± 4 Nm sagittal bending) was applied under displacement control at 1 Hz. Each construct was loaded for 100 cycles or until 6° of loosening was observed. After fatigue testing, the screws were pulled out axially at 5 mm/min. The standard pedicle screw showed better resistance against 100 cycle loading compared with the CBT screws (P standard pedicle screw testing usually required more than 100 cycles of loading to achieve the critical loosening (3592 ± 4564 cycles), whereas the CBT screw never exceeded 100 cycles (84 ± 24 cycles) (P = 0.002). Increased BMD was significantly associated with a higher number of cycles and less loosening. The standard pedicle screw group had a higher postfatigue pullout load than the CBT screw group (P = 0.001, 776 ± 370 N and 302 ± 232 N, respectively). The standard pedicle screw had a better fatigue performance compared with the CBT screw in vertebra with compromised bone quality. The proper insertion of the CBT screw might be prevented by the laminar anatomy depending on the screw head design. The CBT screw damaged the bone along its shaft by rotating around a fulcrum, located at either the pars, pedicle isthmus, or the junction of the pedicle and superior endplate, contingent upon the strength of the bone.

  14. Rotary Valve FY 2016 Highlights

    Energy Technology Data Exchange (ETDEWEB)

    Fitsos, P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-12-07

    The fiscal year started with the Rotary Valve (RV) being reassembled after having crashed in June of 2015. The crash occurred when the RV inner surface contacted the housing. The cause of the crash was never confirmed. No particles were found in the 2.5 thousandths of an inch gap and the filters the helium gas passed through were all clean. There were marks on the bearings that looked like electrostatic discharge as shown below in Figure 1. These marks hadn’t been seen before and there were similar discharge marks on some of the ball bearings. Examples of this were found in a literature search of bearing failures. This leads to a possible cause due to this arcing affecting the rotational accuracy of the bearings driving the RV into the housing.

  15. Rotary-wing aeroservoelastic problems

    Science.gov (United States)

    Friedmann, Peretz P.

    1992-01-01

    The state-of-the-art in the field of alleviating rotary-wing aeroservoelastic problems (by using active controls that modify the pitch of a helicopter rotor blade so as to alleviate dynamic effects) is assessed, and the more promising developments are identified. Special attention is given to the active control of aeromechanical and aeroelastic problems, such as the active control of ground resonance, active control of air resonance, and active control of blade aeroelastic instabilities; individual blade control; active control of vibration reduction using a conventional swashplate; and coupled rotor/fuselage vibration reduction using open-loop active control. Some results are presented for each of these topics, illustrating the efficiency of the techniques which have been developed.

  16. Aerodynamic seals for rotary machine

    Science.gov (United States)

    Bidkar, Rahul Anil; Cirri, Massimiliano; Thatte, Azam Mihir; Williams, John Robert

    2016-02-09

    An aerodynamic seal assembly for a rotary machine includes multiple sealing device segments disposed circumferentially intermediate to a stationary housing and a rotor. Each of the segments includes a shoe plate with a forward-shoe section and an aft-shoe section having multiple labyrinth teeth therebetween facing the rotor. The sealing device segment also includes multiple flexures connected to the shoe plate and to a top interface element, wherein the multiple flexures are configured to allow the high pressure fluid to occupy a forward cavity and the low pressure fluid to occupy an aft cavity. Further, the sealing device segments include a secondary seal attached to the top interface element at one first end and positioned about the flexures and the shoe plate at one second end.

  17. [In vivo studies of screw-bone contact of drill-free screws and conventional self-tapping screws].

    Science.gov (United States)

    Heidemann, W; Terheyden, H; Gerlach, K L

    2001-01-01

    Screw-bone contact (SBC) and bone remodeling of titanium drill-free screws or self-tapping screws should be compared. Each 10 titanium self-tapping miniscrews or microscrews, and each 10 titanium drill-free miniscrews or microscrews were inserted into the anterior wall of the frontal sinus of 5 Göttingen minipigs. Intraperitoneal injections of fluochromes (Xylenol, Calcein, Alizarincomplexon and Tetrazyklin) were performed between the 2nd and 9th postoperative week. The pigs were sacrificed after 6 months, the screw-bone blocks were resected and microradiographic, histologic and fluorescence microscopic examinations were carried out. In drill-free screws mean SBC was 88.4 (miniscrews) or 93.8% (microscrews). In self-tapping miniscrews mean SBC was 54.9, in microscrews 81%; the differences were significant in statistical analysis (t-test: p ratio of residual versus newly formed bone) was measured. Significantly more of the residual bone was found in the region of the screw threads of drill-free screws (miniscrews: mean 71.8, microscrews: mean 67.9%) than in the region of screw threads of self-tapping screws (miniscrews: mean 33.1, microscrews: mean 42.4%; t-test: p midface.

  18. Turbulent Dynamos and Magnetic Helicity

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Hantao

    1999-04-01

    It is shown that the turbulent dynamo alpha-effect converts magnetic helicity from the turbulent field to the mean field when the turbulence is electromagnetic while the magnetic helicity of the mean-field is transported across space when the turbulence is elcetrostatic or due to the elcetron diamagnetic effect. In all cases, however, the dynamo effect strictly conserves the total helicity expect for a battery effect which vanishes in the limit of magnetohydrodynamics. Implications for astrophysical situations, especially for the solar dynamo, are discussed.

  19. Conceptual Study of Rotary-Wing Microrobotics

    National Research Council Canada - National Science Library

    Chabak, Kelson D

    2008-01-01

    This thesis presents a novel rotary-wing micro-electro-mechanical systems (MEMS) robot design. Two MEMS wing designs were designed, fabricated and tested including one that possesses features conducive to insect level aerodynamics...

  20. Rotary adsorbers for continuous bulk separations

    Science.gov (United States)

    Baker, Frederick S [Oak Ridge, TN

    2011-11-08

    A rotary adsorber for continuous bulk separations is disclosed. The rotary adsorber includes an adsorption zone in fluid communication with an influent adsorption fluid stream, and a desorption zone in fluid communication with a desorption fluid stream. The fluid streams may be gas streams or liquid streams. The rotary adsorber includes one or more adsorption blocks including adsorbent structure(s). The adsorbent structure adsorbs the target species that is to be separated from the influent fluid stream. The apparatus includes a rotary wheel for moving each adsorption block through the adsorption zone and the desorption zone. A desorption circuit passes an electrical current through the adsorbent structure in the desorption zone to desorb the species from the adsorbent structure. The adsorbent structure may include porous activated carbon fibers aligned with their longitudinal axis essentially parallel to the flow direction of the desorption fluid stream. The adsorbent structure may be an inherently electrically-conductive honeycomb structure.

  1. Rotary endodontics in primary teeth - A review.

    Science.gov (United States)

    George, Sageena; Anandaraj, S; Issac, Jyoti S; John, Sheen A; Harris, Anoop

    2016-01-01

    Endodontic treatment in primary teeth can be challenging and time consuming, especially during canal preparation, which is considered one of the most important steps in root canal therapy. The conventional instrumentation technique for primary teeth remains the "gold-standard" over hand instrumentation, which makes procedures much more time consuming and adversely affects both clinicians and patients. Recently nickel-titanium (Ni-Ti) rotary files have been developed for use in pediatric endodontics. Using rotary instruments for primary tooth pulpectomies is cost effective and results in fills that are consistently uniform and predictable. This article reviews the use of nickel-titanium rotary files as root canal instrumentation in primary teeth. The pulpectomy technique is described here according to different authors and the advantages and disadvantages of using rotary files are discussed.

  2. Biomechanical Analysis of Latarjet Screw Fixation: Comparison of Screw Types and Fixation Methods.

    Science.gov (United States)

    Shin, Jason J; Hamamoto, Jason T; Leroux, Timothy S; Saccomanno, Maristella F; Jain, Akshay; Khair, Mahmoud M; Mellano, Christen R; Shewman, Elizabeth F; Nicholson, Gregory P; Romeo, Anthony A; Cole, Brian J; Verma, Nikhil N

    2017-09-01

    To compare the initial fixation stability, failure strength, and mode of failure of 5 different screw types and fixation methods commonly used for the classic Latarjet procedure. Thirty-five fresh-frozen cadaveric shoulder specimens were allocated into 5 groups. A 25% anteroinferior glenoid defect was created, and a classic Latarjet coracoid transfer procedure was performed. All grafts were fixed with 2 screws, differing by screw type and/or fixation method. The groups included partially threaded solid 4.0-mm cancellous screws with bicortical fixation, partially threaded solid 4.0-mm cancellous screws with unicortical fixation, fully threaded solid 3.5-mm cortical screws with bicortical fixation, partially threaded cannulated 4.0-mm cancellous screws with bicortical fixation, and partially threaded cannulated 4.0-mm captured screws with bicortical fixation. All screws were stainless steel. Outcomes included cyclic creep and secant stiffness during cyclic loading, as well as load and work to failure during the failure test. Intergroup comparisons were made by a 1-way analysis of variance. There were no significant differences among different screw types or fixation methods in cyclic creep or secant stiffness after cyclic loading or in load to failure or work to failure during the failure test. Post-failure radiographs showed evidence of screw bending in only 1 specimen that underwent the Latarjet procedure with partially threaded solid cancellous screws with bicortical fixation. The mode of failure for all specimens analyzed was screw cutout. In this biomechanical study, screw type and fixation method did not significantly influence biomechanical performance in a classic Latarjet procedure. When performing this procedure, surgeons may continue to select the screw type and method of fixation (unicortical or bicortical) based on preference; however, further studies are required to determine the optimal method of treatment. Surgeons may choose the screw type and

  3. Rotary Release Mechanism With Fusible Link

    Science.gov (United States)

    Sevilla, Donald R.; Blomquist, Richard S.

    1996-01-01

    Rotary release mechanism includes fusible rotary link made of alloy that melts at relatively low temperature of 60 degrees C. When solid, link couples driving shaft to driven shaft. When necessary, link melted to temporarily decouple two shafts. Upon cooling below melting temperature link hardens, so it once again couples two shafts. Release mechanism extremely compact alternative to pyrotechnic release device. Basic concept applied to such other mechanisms as pin pullers, pin pushers, electrical-disconnection mechanisms, and clutches.

  4. Magnetic Helicity and Planetary Dynamos

    Science.gov (United States)

    Shebalin, John V.

    2012-01-01

    A model planetary dynamo based on the Boussinesq approximation along with homogeneous boundary conditions is considered. A statistical theory describing a large-scale MHD dynamo is found, in which magnetic helicity is the critical parameter

  5. Helicity multiplexed broadband metasurface holograms

    Science.gov (United States)

    Wen, Dandan; Yue, Fuyong; Li, Guixin; Zheng, Guoxing; Chan, Kinlong; Chen, Shumei; Chen, Ming; Li, King Fai; Wong, Polis Wing Han; Cheah, Kok Wai; Yue Bun Pun, Edwin; Zhang, Shuang; Chen, Xianzhong

    2015-09-01

    Metasurfaces are engineered interfaces that contain a thin layer of plasmonic or dielectric nanostructures capable of manipulating light in a desirable manner. Advances in metasurfaces have led to various practical applications ranging from lensing to holography. Metasurface holograms that can be switched by the polarization state of incident light have been demonstrated for achieving polarization multiplexed functionalities. However, practical application of these devices has been limited by their capability for achieving high efficiency and high image quality. Here we experimentally demonstrate a helicity multiplexed metasurface hologram with high efficiency and good image fidelity over a broad range of frequencies. The metasurface hologram features the combination of two sets of hologram patterns operating with opposite incident helicities. Two symmetrically distributed off-axis images are interchangeable by controlling the helicity of the input light. The demonstrated helicity multiplexed metasurface hologram with its high performance opens avenues for future applications with functionality switchable optical devices.

  6. Helicity multiplexed broadband metasurface holograms.

    Science.gov (United States)

    Wen, Dandan; Yue, Fuyong; Li, Guixin; Zheng, Guoxing; Chan, Kinlong; Chen, Shumei; Chen, Ming; Li, King Fai; Wong, Polis Wing Han; Cheah, Kok Wai; Pun, Edwin Yue Bun; Zhang, Shuang; Chen, Xianzhong

    2015-09-10

    Metasurfaces are engineered interfaces that contain a thin layer of plasmonic or dielectric nanostructures capable of manipulating light in a desirable manner. Advances in metasurfaces have led to various practical applications ranging from lensing to holography. Metasurface holograms that can be switched by the polarization state of incident light have been demonstrated for achieving polarization multiplexed functionalities. However, practical application of these devices has been limited by their capability for achieving high efficiency and high image quality. Here we experimentally demonstrate a helicity multiplexed metasurface hologram with high efficiency and good image fidelity over a broad range of frequencies. The metasurface hologram features the combination of two sets of hologram patterns operating with opposite incident helicities. Two symmetrically distributed off-axis images are interchangeable by controlling the helicity of the input light. The demonstrated helicity multiplexed metasurface hologram with its high performance opens avenues for future applications with functionality switchable optical devices.

  7. Hollow Abutment Screw Design for Easy Retrieval in Case of Screw Fracture in Dental Implant System

    Directory of Open Access Journals (Sweden)

    Bo Kyun Sim

    2017-01-01

    Full Text Available The prosthetic component of dental implant is attached on the abutment which is connected to the fixture with an abutment screw. The abutment screw fracture is not frequent; however, the retrieval of the fractured screw is not easy, and it poses complications. A retrieval kit was developed which utilizes screw removal drills to make a hole on the fractured screw that provides an engaging drill to unscrew it. To minimize this process, the abutment screw is modified with a prefabricated access hole for easy retrieval. This study aimed to introduce this modified design of the abutment screw, the concept of easy retrieval, and to compare the mechanical strengths of the conventional and hollow abutment screws by finite element analysis (FEA and mechanical test. In the FEA results, both types of abutment screws showed similar stress distribution in the single artificial tooth system. A maximum load difference of about 2% occurred in the vertical load by a mechanical test. This study showed that the hollow abutment screw may be an alternative to the conventional abutment screws because this is designed for easy retrieval and that both abutment screws showed no significant difference in the mechanical tests and in the FEA.

  8. Hollow Abutment Screw Design for Easy Retrieval in Case of Screw Fracture in Dental Implant System.

    Science.gov (United States)

    Sim, Bo Kyun; Kim, Bongju; Kim, Min Jeong; Jeong, Guk Hyun; Ju, Kyung Won; Shin, Yoo Jin; Kim, Man Yong; Lee, Jong-Ho

    2017-01-01

    The prosthetic component of dental implant is attached on the abutment which is connected to the fixture with an abutment screw. The abutment screw fracture is not frequent; however, the retrieval of the fractured screw is not easy, and it poses complications. A retrieval kit was developed which utilizes screw removal drills to make a hole on the fractured screw that provides an engaging drill to unscrew it. To minimize this process, the abutment screw is modified with a prefabricated access hole for easy retrieval. This study aimed to introduce this modified design of the abutment screw, the concept of easy retrieval, and to compare the mechanical strengths of the conventional and hollow abutment screws by finite element analysis (FEA) and mechanical test. In the FEA results, both types of abutment screws showed similar stress distribution in the single artificial tooth system. A maximum load difference of about 2% occurred in the vertical load by a mechanical test. This study showed that the hollow abutment screw may be an alternative to the conventional abutment screws because this is designed for easy retrieval and that both abutment screws showed no significant difference in the mechanical tests and in the FEA.

  9. [Fracture of implant abutment screws and removal of a remaining screw piece

    NARCIS (Netherlands)

    Broeke, S.M. van den; Baat, C. de

    2008-01-01

    Fracture of the implant abutment screws is a complication which can render an implant useless. The prevalence of abutment screw fracture does not exceed 2.5% after 10 years. Causes are loosening of implant abutment screw, too few, too short or too narrow implants, implants not inserted perpendicular

  10. Optical helices and spiral interference fringes

    Science.gov (United States)

    Harris, M.; Hill, C. A.; Vaughan, J. M.

    1994-03-01

    Very pure optical helices have been generated in an argon ion laser of low Fresnel number. The beam character, with continuous cophasal surface of helical form, is clearly demonstrated by spiral interference fringes produced in a novel interferometric arrangement. In addition to single-start helices the multistart fringe patterns establish both two-start and three-start helices (of pitch two and three wavelengths, respectively), and also the state of helicity (i.e. rotational hand) of the beams.

  11. Analysis of the osseous/metal interface of drill free screws and self-tapping screws.

    Science.gov (United States)

    Heidemann, W; Terheyden, H; Gerlach, K L

    2001-04-01

    A comparison of metal/osseous interface and bone remodelling after insertion of different types of titanium bone screws in vivo. Samples of five of each of the following bone screw types were inserted into the anterior wall of the frontal sinus of five Göttingen minipigs: self-tapping micro- (1.5mm) and miniscrews (2.0 mm) or drill free micro- (1.5 mm) and miniscrews (2.0 mm) (Martin Medizintechnik, Tuttlingen, Germany). Screw length was 7mm. Sequential intraperitoneal injections of fluorochromes were performed between the second and ninth postoperative week. After 6 months the pigs were sacrificed, the screw-bone-blocks resected, and microradiographic, histological and fluorescence microscopical examinations were carried out. Using drill free screws, mean screw/bone contact was 88.4% (miniscrews), or 93.8% (microscrews). With self-tapping miniscrews it was 54.9%, but in microscrews 81%; the differences were statistically significant (t-test: pratio of residual vs. newly formed bone) was measured. Significantly more of the residual bone was found in the region of the screw threads using drill free screws (miniscrews: mean 71.8%, microscrews: mean 67.9%) than in the region of screw threads with self-tapping screws (miniscrews: mean 33.1%, microscrews: mean 42.4%). The present data support the view that screw/bone contact with drill free screws was superior to that of self-tapping screws; the greater amount of original bone in the threads of drill free screws demonstrated that the insertion of drill free screws did not cause harm to the surrounding bone. Both results are important for osteosynthesis in regions where thin cortical bone is present, such as the central midface.

  12. High Bandwidth Rotary Fast Tool Servos and a Hybrid Rotary/Linear Electromagnetic Actuator

    Energy Technology Data Exchange (ETDEWEB)

    Montesanti, Richard Clement [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

    2005-09-01

    This thesis describes the development of two high bandwidth short-stroke rotary fast tool servos and the hybrid rotary/linear electromagnetic actuator developed for one of them. Design insights, trade-o® methodologies, and analytical tools are developed for precision mechanical systems, power and signal electronic systems, control systems, normal-stress electromagnetic actuators, and the dynamics of the combined systems.

  13. Man-Made Rotary Nanomotors: A Review of Recent Development

    Science.gov (United States)

    Kim, Kwanoh; Guo, Jianhe; Liang, Z. X.; Zhu, F. Q.; Fan, D. L.

    2016-01-01

    The development rotary nanomotors is an essential step towards intelligent nanomachines and nanorobots. In this article, we review the concept, design, working mechanisms, and applications of the state-of-the-art rotary nanomotors made from synthetic nanoentities. The rotary nanomotors are categorized according to the energy sources employed to drive the rotary motion, including biochemical, optical, magnetic, and electric fields. The unique advantages and limitations for each type of rotary nanomachines are discussed. The advances of rotary nanomotors is pivotal for realizing dream nanomachines for myriad applications including microfluidics, biodiagnosis, nano-surgery, and biosubstance delivery. PMID:27152885

  14. Theoretical and Experimental Loss and Efficiency Studies of a Magnetic Lead Screw

    DEFF Research Database (Denmark)

    Berg, Nick Ilsø; Holm, Rasmus Koldborg; Rasmussen, Peter Omand

    2015-01-01

    This paper investigates mechanical and magnetic losses in a magnetic lead screw (MLS). The MLS converts a low-speed high-force linear motion of a translator into a high-speed low-torque rotational motion of a rotor through helically shaped magnets. Initial tests performed with a novel 17-k......N demonstrator and a simplified motor model showed an efficiency of only 80% at low load; however, it was expected that the efficiency should be above 95%. For understanding and future optimization, a detailed study of the loss in the MLS is presented with the aim of identifying and segregating various loss...

  15. Quasi-static and dynamic response of viscoelastic helical rods

    Science.gov (United States)

    Temel, Beytullah; Fırat Çalim, Faruk; Tütüncü, Naki

    2004-04-01

    In this study, the dynamic behaviour of cylindrical helical rods made of linear viscoelastic materials are investigated in the Laplace domain. The governing equations for naturally twisted and curved spatial rods obtained using the Timoshenko beam theory are rewritten for cylindrical helical rods. The curvature of the rod axis, effect of rotary inertia, and shear and axial deformations are considered in the formulation. The material of the rod is assumed to be homogeneous, isotropic and linear viscoelastic. In the viscoelastic material case, according to the correspondence principle, the material constants are replaced with their complex counterparts in the Laplace domain. Ordinary differential equations in scalar form obtained in the Laplace domain are solved numerically using the complementary functions method to calculate the dynamic stiffness matrix of the problem. In the solutions, the Kelvin model is employed. The solutions obtained are transformed to the real space using the Durbin's numerical inverse Laplace transform method. Numerical results for quasi-static and dynamic response of viscoelastic models are presented in the form of graphics.

  16. On Working Capacity Criteria for Screw-Roller Mechanisms

    Directory of Open Access Journals (Sweden)

    D. S. Blinov

    2015-01-01

    Full Text Available Today roller-screw mechanisms (RSM are the most prospective motion converters from rotary to linear type. RSM manufacturers have suggested their design in the way, similar to the rolling bearings, in static and dynamic load ratings. The latter means that during long operations the main criterion of the RSM working capacity is fatigue spalling. However, this approach does not permit to consider temporal changes of the most critical performance parameters of the RSM (such as the axial play, the efficiency factor, the axial stiffness, the accuracy, the starting torque force for zero lash RSMs, etc. through calculations. The abovementioned method was not perfect, because the choice of the main criterion of RSM working capacity was wrong. The article proves that wear-resistance is the main criterion of RSM working capacity. The proof is the RSM efficiency factor equal to 80-88% on the average. The power loss occurs because of overcoming a sliding friction between multiple (from 300 to 1000 interfacing turns of thread on the screw and the rollers as well as on the rollers and the nut. That is why the RSMs are the screwtype rolling mechanisms with an essential portion of sliding friction. High-accuracy measurements taken using the device called a form-tracer for threaded pieces permitted to determine the essential changes on the profiles of turns of threads on the rollers (a straight-line portion appeared on the radial profile; these changes could emerge only from wear. Besides, the length of this portion increased with the increasing RSM operation time. The JSC “Moskvich” has examined the RSMs, which have been put out of operation after completing their service life as parts of robot welding machines. There were no traces of fatigue spalling found on the threaded surfaces of the RSM parts, while the sizes of the straight-line portions on the turns of the roller threads were much bigger than they were during the measurements after the initial

  17. Simple Technique for Removing Broken Pedicular Screws

    Directory of Open Access Journals (Sweden)

    A Agrawal

    2014-03-01

    Full Text Available The procedure for removing a broken pedicle screw should ideally be technically easy and minimally invasive, as any damage to the pedicle, during removal of the broken screw, may weaken the pedicle, thus compromising on the success of re-instrumentation. We describe the case of a 32-year old man who had undergone surgery for traumatic third lumbar vertebral body fracture three years prior to current admission and had developed the complication of pedicle screw breakage within the vertebral body. The patient underwent re-exploration and removal of the distal screws. Through a paravertebral incision and muscle separation, the screws and rods were exposed and the implants were removed.

  18. Twin screw subsurface and surface multiphase pumps

    Energy Technology Data Exchange (ETDEWEB)

    Dass, P. [CAN-K GROUP OF COMPANIES, Edmonton, Alberta (Canada)

    2011-07-01

    A new subsurface twin screw multiphase pump has been developed to replace ESP and other artificial lift technologies. This technology has been under development for a few years, has been field tested and is now going for commercial applications. The subsurface twin screw technology consists of a pair of screws that do not touch and can be run with a top drive or submersible motor; and it carries a lot of benefits. This technology is easy to install and its low slippage makes it highly efficient with heavy oil. In addition twin screw multiphase pumps are capable of handling high viscosity fluids and thus their utilization can save water when used in thermal applications. It also induces savings of chemicals because asphaltenes do not break down easily as well as a reduction in SOR. The subsurface twin screw multiphase pump presented herein is an advanced technology which could be used in thermal applications.

  19. Ultrasonic/Sonic Rotary-Hammer Drills

    Science.gov (United States)

    Badescu, Mircea; Sherrit, Stewart; Bar-Cohen, Yoseph; Bao, Xiaoqi; Kassab, Steve

    2010-01-01

    Ultrasonic/sonic rotary-hammer drill (USRoHD) is a recent addition to the collection of apparatuses based on ultrasonic/sonic drill corer (USDC). As described below, the USRoHD has several features, not present in a basic USDC, that increase efficiency and provide some redundancy against partial failure. USDCs and related apparatuses were conceived for boring into, and/or acquiring samples of, rock or other hard, brittle materials of geological interest. They have been described in numerous previous NASA Tech Briefs articles. To recapitulate: A USDC can be characterized as a lightweight, lowpower, piezoelectrically driven jackhammer in which ultrasonic and sonic vibrations are generated and coupled to a tool bit. A basic USDC includes a piezoelectric stack, an ultrasonic transducer horn connected to the stack, a free mass ( free in the sense that it can bounce axially a short distance between hard stops on the horn and the bit), and a tool bit. The piezoelectric stack creates ultrasonic vibrations that are mechanically amplified by the horn. The bouncing of the free mass between the hard stops generates the sonic vibrations. The combination of ultrasonic and sonic vibrations gives rise to a hammering action (and a resulting chiseling action at the tip of the tool bit) that is more effective for drilling than is the microhammering action of ultrasonic vibrations alone. The hammering and chiseling actions are so effective that unlike in conventional twist drilling, little applied axial force is needed to make the apparatus advance into the material of interest. There are numerous potential applications for USDCs and related apparatuses in geological exploration on Earth and on remote planets. In early USDC experiments, it was observed that accumulation of cuttings in a drilled hole causes the rate of penetration of the USDC to decrease steeply with depth, and that the rate of penetration can be increased by removing the cuttings. The USRoHD concept provides for

  20. Flexible helical-axis stellarator

    Science.gov (United States)

    Harris, Jeffrey H.; Hender, Timothy C.; Carreras, Benjamin A.; Cantrell, Jack L.; Morris, Robert N.

    1988-01-01

    An 1=1 helical winding which spirals about a conventional planar, circular central conductor of a helical-axis stellarator adds a significant degree of flexibility by making it possible to control the rotational transform profile and shear of the magnetic fields confining the plasma in a helical-axis stellarator. The toroidal central conductor links a plurality of toroidal field coils which are separately disposed to follow a helical path around the central conductor in phase with the helical path of the 1=1 winding. This coil configuration produces bean-shaped magnetic flux surfaces which rotate around the central circular conductor in the same manner as the toroidal field generating coils. The additional 1=1 winding provides flexible control of the magnetic field generated by the central conductor to prevent the formation of low-order resonances in the rotational transform profile which can produce break-up of the equilibrium magnetic surfaces. Further, this additional winding can deepen the magnetic well which together with the flexible control provides increased stability.

  1. Generalized helicity and Beltrami fields

    Energy Technology Data Exchange (ETDEWEB)

    Buniy, Roman V., E-mail: roman.buniy@gmail.com [Schmid College of Science, Chapman University, Orange, CA 92866 (United States); Isaac Newton Institute, University of Cambridge, Cambridge, CB3 0EH (United Kingdom); Kephart, Thomas W., E-mail: tom.kephart@gmail.com [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Isaac Newton Institute, University of Cambridge, Cambridge, CB3 0EH (United Kingdom)

    2014-05-15

    We propose covariant and non-abelian generalizations of the magnetic helicity and Beltrami equation. The gauge invariance, variational principle, conserved current, energy–momentum tensor and choice of boundary conditions elucidate the subject. In particular, we prove that any extremal of the Yang–Mills action functional 1/4 ∫{sub Ω}trF{sub μν}F{sup μν}d{sup 4}x subject to the local constraint ε{sup μναβ}trF{sub μν}F{sub αβ}=0 satisfies the covariant non-abelian Beltrami equation. -- Highlights: •We introduce the covariant non-abelian helicity and Beltrami equation. •The Yang–Mills action and instanton term constraint lead to the Beltrami equation. •Solutions of the Beltrami equation conserve helicity.

  2. Suppression and control of leakage field in electromagnetic helical microwiggler

    Energy Technology Data Exchange (ETDEWEB)

    Ohigashi, N. [Kansai Univ., Osaka (Japan); Tsunawaki, Y. [Osaka Sangyo Univ. (Japan); Imasaki, K. [Institute for Laser Technology, Osaka (Japan)] [and others

    1995-12-31

    Shortening the period of electromagnetic wiggler introduces both the radical increase of the leakage field and the decrease of the field in the gap region. The leakage field is severer problem in planar electromagnetic wiggler than in helical wiggler. Hence, in order to develop a short period electromagnetic wiggler, we have adopted {open_quotes}three poles per period{close_quotes} type electromagnetic helical microwiggler. In this work, we inserted the permanent magnet (PM) blocks with specific magnetized directions in the space between magnetic poles, for suppressing the leakage field flowing out from a pole face to the neighboring pole face. These PM-blocks must have higher intrinsic coersive force than saturation field of pole material. The gap field due to each pole is adjustable by controlling the leakage fields, that is, controlling the position of each iron screw set in each retainer fixing the PM-blocks. At present time, a test wiggler with period 7.8mm, periodical number 10 and gap length 4.6mm has been manufactured. Because the ratio of PM-block aperture to gap length is important parameter to suppress the leakage field, the parameter has been surveyed experimentally for PM-blocks with several dimensions of aperture. The field strength of 3-5kG (K=0.2-0.4) would be expected in the wiggler.

  3. Rotary motion driven by a direct current electric field

    OpenAIRE

    Takinoue, Masahiro; Atsumi, Yu; Yoshikawa, Kenichi

    2010-01-01

    We report the rotary motion of an aqueous microdroplet in an oil phase under a stationary direct current electric field. A droplet exhibits rotary motion under a suitable geometrical arrangement of positive and negative electrodes. Rotary motion appears above a certain critical electric potential and its frequency increases with an increase in the potential. A simple theoretical model is proposed to describe the occurrence of this rotary motion, together with an argument for the future expans...

  4. A bistable electromagnetically actuated rotary gate microvalve

    Science.gov (United States)

    Luharuka, Rajesh; Hesketh, Peter J.

    2008-03-01

    Two types of rotary gate microvalves are developed for flow modulation in microfluidic systems. These microvalves have been tested for an open flow rate of up to 100 sccm and operate under a differential pressure of 6 psig with flow modulation of up to 100. The microvalve consists of a suspended gate that rotates in the plane of the chip to regulate flow through the orifice. The gate is suspended by a novel fully compliant in-plane rotary bistable micromechanism (IPRBM) that advantageously constrains the gate in all degrees of freedom except for in-plane rotational motion. Multiple inlet/outlet orifices provide flexibility of operating the microvalve in three different flow configurations. The rotary gate microvalve is switched with an external electromagnetic actuator. The suspended gate is made of a soft magnetic material and its electromagnetic actuation is based on the operating principle of a variable-reluctance stepper motor.

  5. Stability of helical Janus clusters

    Science.gov (United States)

    Eck, Connor L.; Whitmer, Jonathan K.; Chen, Qian; Granick, Steve; Luijten, Erik

    2012-02-01

    Recent experimental and computational work has elucidated the importance of kinetic pathways in the formation of helical structures by hydrophobic-charged Janus particles.ootnotetextQ. Chen, J.K. Whitmer, et al., Science 331, 199 (2011). Motivated by these findings, we perform free-energy calculations to investigate the equilibrium structure and relative stability of helical aggregates as a function of cluster size and Janus balance. These results simultaneously aid in the interpretation of experimental observations and in the design of building blocks for specific structures.

  6. 21 CFR 886.1665 - Ophthalmic rotary prism.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ophthalmic rotary prism. 886.1665 Section 886.1665...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1665 Ophthalmic rotary prism. (a) Identification. An ophthalmic rotary prism is a device with various prismatic powers intended to be handheld and...

  7. Screw-released roller brake

    Science.gov (United States)

    Vranish, John M. (Inventor)

    1999-01-01

    A screw-released roller brake including an input drive assembly, an output drive assembly, a plurality of locking sprags, a mechanical tripper nut for unlocking the sprags, and a casing therefor. The sprags consist of three dimensional (3-D) sprag members having pairs of contact surface regions which engage respective pairs of contact surface regions included in angular grooves or slots formed in the casing and the output drive assembly. The sprags operate to lock the output drive assembly to the casing to prevent rotation thereof in an idle mode of operation. In a drive mode of operation, the tripper is either self actuated or motor driven and is translated linearly up and down against a spline and at the limit of its travel rotates the sprags which unlock while coupling the input drive assembly to the output drive assembly so as to impart a turning motion thereto in either a clockwise or counterclockwise direction.

  8. Ka-band waveguide rotary joint

    KAUST Repository

    Yevdokymov, Anatoliy

    2013-04-11

    The authors present a design of a waveguide rotary joint operating in Ka-band with central frequency of 33 GHz, which also acts as an antenna mount. The main unit consists of two flanges with a clearance between them; one of the flanges has three circular choke grooves. Utilisation of three choke grooves allows larger operating clearance. Two prototypes of the rotary joint have been manufactured and experimentally studied. The observed loss is from 0.4 to 0.8 dB in 1.5 GHz band.

  9. Development of a novel rotary magnetic refrigerator

    DEFF Research Database (Denmark)

    Lozano, Jaime A.; Capovilla, Matheus S.; Trevizoli, Paulo V.

    2016-01-01

    with approximately 1.7 kg of gadolinium spheres (425-600 μm diameter) were placed in the magnetic gap. Two low-friction rotary valves were developed to synchronize the hydraulic and magnetic cycles. The valves were positioned at the hot end to avoid heat generation in the cold end. In this work, experimental results......A novel rotary magnetic refrigerator was designed and built at the Federal University of Santa Catarina (UFSC). The optimized magnetic circuit is a two-pole system in a rotor-stator configuration with high flux density regions of approximately 1 T. Eight pairs of stationary regenerator beds filled...

  10. Universal dynamic goniometer for rotary encoders

    Science.gov (United States)

    Smirnov, Nikolai V.; Latyev, Svjatoslav M.; Naumova, Anastasiia I.

    2017-06-01

    A novel dynamic goniometer for the accuracy of rotary encoders has been developed on the base of the method of comparison with the reference encoder. The set-up of the goniometer considers all constructive and informative characteristics of measured encoders. The novel goniometer construction uses the new compensating method of instrumental errors in automatic working process. The advantages of the dynamic goniometer in combination with an optical rotary encoder at the reduction of the measuring time and a simultaneous increase of the accuracy.

  11. Comparison between rotary and conventional flaring processes

    Science.gov (United States)

    Tamang, Subha; Bylya, Olga; Ward, Michael; Luo, Xichun; Halliday, Steven; Tuffs, Martin

    2017-10-01

    Rotary forming is one of the promising incremental processes. However, a wide industrial implementation of it strongly depends on the deep understanding of the mechanics of this process. This paper attempts to develop this understanding via a comparison of the rotary forming process with conventional flaring. Both the processes were simulated using commercial metal forming software QForm. The results of the simulation were validated by comparison with the experimental trials. The main focus was made on the triaxiality states taking place during forming, as it seems to be the main factor determining the success of the process.

  12. Methods and apparatus for controlling rotary machines

    Science.gov (United States)

    Bagepalli, Bharat Sampathkumaran [Niskayuna, NY; Jansen, Patrick Lee [Scotia, NY; Barnes, Gary R [Delanson, NY; Fric, Thomas Frank [Greer, SC; Lyons, James Patrick Francis [Niskayuna, NY; Pierce, Kirk Gee [Simpsonville, SC; Holley, William Edwin [Greer, SC; Barbu, Corneliu [Guilderland, NY

    2009-09-01

    A control system for a rotary machine is provided. The rotary machine has at least one rotating member and at least one substantially stationary member positioned such that a clearance gap is defined between a portion of the rotating member and a portion of the substantially stationary member. The control system includes at least one clearance gap dimension measurement apparatus and at least one clearance gap adjustment assembly. The adjustment assembly is coupled in electronic data communication with the measurement apparatus. The control system is configured to process a clearance gap dimension signal and modulate the clearance gap dimension.

  13. Applications of 2D helical vortex dynamics

    DEFF Research Database (Denmark)

    Okulov, Valery; Sørensen, Jens Nørkær

    2010-01-01

    In the paper, we show how the assumption of helical symmetry in the context of 2D helical vortices can be exploited to analyse and to model various cases of rotating flows. From theory, examples of three basic applications of 2D dynamics of helical vortices embedded in flows with helical symmetry...... of the vorticity field are addressed. These included some of the problems related to vortex breakdown, instability of far wakes behind rotors and vortex theory of ideal rotors....

  14. ICRF heating on helical devices

    Energy Technology Data Exchange (ETDEWEB)

    Rasmussen, D.A.; Lyon, J.F.; Hoffman, D.J.; Murakami, M.; England, A.C.; Wilgen, J.B.; Jaeger, E.F.; Wang, C.; Batchelor, D.B.

    1995-09-01

    Ion cyclotron range of frequency (ICRF) heating is currently in use on CHS and W7-AS and is a major element of the heating planned for steady state helical devices. In helical devices, the lack of a toroidal current eliminates both disruptions and the need for ICRF current drive, simplifying the design of antenna structures as compared to tokamak applications. However the survivability of plasma facing components and steady state cooling issues are directly applicable to tokamak devices. Results from LHD steady state experiments should be available on a time scale to strongly influence the next generation of steady state tokamak experiments. The helical plasma geometry provides challenges not faced with tokamak ICRF heating, including the potential for enhanced fast ion losses, impurity accumulation, limited access for antenna structures, and open magnetic field lines in the plasma edge. The present results and near term plans provide the basis for steady state ICRF heating of larger helical devices. An approach which includes direct electron, mode conversion, ion minority and ion Bernstein wave heating addresses these issues.

  15. ICRF heating on helical devices

    Energy Technology Data Exchange (ETDEWEB)

    Rasmussen, D.A.; Lyon, J.F.; Hoffman, D.J. [and others

    1995-09-01

    Ion cyclotron range of frequency (ICRF) heating is currently in use on CHS and W7AS and is a major element of the heating planned for steady state helical devices. In helical devices, the lack of a toroidal current eliminates both disruptions and the need for ICRF current drive, simplifying the design of antenna structures as compared to tokamak applications. However the survivability of plasma facing components and steady state cooling issues are directly applicable to tokamak devices. Results from LHD steady state experiments should be available on a time scale to strongly influence the next generation of steady state tokamak experiments. The helical plasma geometry provides challenges not faced with tokamak ICRF heating, including the potential for enhanced fast ion losses, impurity accumulation, limited access for antenna structures, and open magnetic field lines in the plasma edge. The present results and near term plans provide the basis for steady state ICRF heating of larger helical devices. An approach which includes direct electron, mode conversion, ion minority and ion Bernstein wave heating addresses these issues.

  16. Extraction of sunflower oil by twin screw extruder: screw configuration and operating condition effects

    Energy Technology Data Exchange (ETDEWEB)

    Kartika, I.A. [FATETA-IPB, Bogor (Indonesia). Department of Agroindustrial Technology; Pontalier, P.Y.; Rigal, L. [Laboratoire de Chimie Agro-Industrielle, UMR 1010 INRA/INP-ENSIACET, Toulouse (France)

    2006-12-15

    The objective of this study was to investigate the screw configuration allowing oil extraction from sunflower seeds with a twin-screw extruder. Experiments were conducted using a co-rotating twin-screw extruder. Five screw profiles were examined to define the best performance (oil extraction yield, specific mechanical energy and oil quality) by studying the influence of operating conditions, barrel temperature, screw speed and feed rate. Generally, the position and spacing between two reversed screw elements affected oil extraction yield. An increase of oil extraction yield was observed as the reversed screw elements were moved with increased spacing between two elements and with smaller pitch elements. In addition, oil extraction yield increased as barrel temperature, screw speed and feed rate were decreased. Highest oil extraction yield (85%) with best cake meal quality (residual oil content lower than 13%) was obtained under operating conditions of 120 {sup o}C, 75 rpm and 19 kg/h. Furthermore, the operating parameters influenced energy input. A decrease in barrel temperature and feed rate followed by an increase in screw speed increased energy input, particularly specific mechanical energy input. Effect of the operating parameters on oil quality was less important. In all experiments tested, the oil quality was very good. The acid value was below 2 mg of KOH/g of oil and total phosphorus content was low, below 100 mg/kg. (author)

  17. Twin Screw Mixer/Fine Grind Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The 40-mm Twin-Screw Mixer/Extruder (TSE) pilot plant is a continuous, remotely operated, flexible facility that can significantly enhance safety and environmental...

  18. Maxillary sinus perforation by orthodontic anchor screws

    National Research Council Canada - National Science Library

    Motoyoshi, Mitsuru; Sanuki-Suzuki, Rina; Uchida, Yasuki; Saiki, Akari; Shimizu, Noriyoshi

    2015-01-01

    .... The placement torque and screw mobility of each implant were determined using a torque tester and a Periotest device, and variability in these values in relation to sinus perforation was evaluated...

  19. Optical Rotary Joint For Data Transfer

    Science.gov (United States)

    Becker, Fred J.

    1988-01-01

    Proposed joint increases bandwidth and reduces errors. Scheme for transferring digital data across rotary joint uses light instead of electrical signals. Optical joint offers greater bandwidth and operates at considerably lower error rate. Concept applied to transfer of highspeed data to rotating antennas or across joints of robots and manipulators in automated manufacturing.

  20. Precision Model for Microwave Rotary Vane Attenuator

    DEFF Research Database (Denmark)

    Guldbrandsen, Tom

    1979-01-01

    A model for a rotary vane attenuator is developed to describe the attenuator reflection and transmission coefficients in detail. All the parameters of the model can be measured in situ, i.e., without diassembling any part. The tranmission errors caused by internal reflections are calculated from...

  1. REACTIVATION OF FERRIC OXIDES IN ROTARY FURNACES

    Directory of Open Access Journals (Sweden)

    S. L. Rovin

    2011-01-01

    Full Text Available The advantages of rotary furnaces, developed by specialists of GGTU named after P. O. Suhoj and UP «Tehnolit» for carrying out of ferric oxide recycling with regard to conditions of the Republic of Belarus, are described.

  2. Baryon helicity in B decay

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Mahiko [Department of Physics and Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States)

    2005-07-01

    The unexpectedly large transverse polarization measured in the decay B {yields} {phi}K* poses the question whether it is accounted for as a strong interaction effect or possibly points to a hidden nonstandard weak interaction. We extend here the perturbative argument to the helicity structure of the two-body baryonic decay and discuss qualitatively on how the baryonic B decay modes might help us in understanding the issue raised by B {yields} {phi}K*. We find among others that the helicity +1/2 amplitude dominates the leading order in the B(b-barq) decay and that unlike the B {yields} VV decay the dominant amplitude is sensitive to the right-handed b {yields} s current, if any, in the penguin interaction.

  3. An experimental superconducting helical undulator

    Energy Technology Data Exchange (ETDEWEB)

    Caspi, S.; Taylor, C. [Lawrence Berkeley Lab., CA (United States)

    1995-12-31

    Improvements in the technology of superconducting magnets for high energy physics and recent advancements in SC materials with the artificial pinning centers (APC){sup 2}, have made a bifilar helical SC device an attractive candidate for a single-pass free electron laser (FEL){sup 3}. Initial studies have suggested that a 6.5 mm inner diameter helical device, with a 27 mm period, can generate a central field of 2-2.5 Tesla. Additional studies have also suggested that with a stored energy of 300 J/m, such a device can be made self-protecting in the event of a quench. However, since the most critical area associated with high current density SC magnets is connected with quenching and training, a short experimental device will have to be built and tested. In this paper we discuss technical issues relevant to the construction of such a device, including a conceptual design, fields, and forces.

  4. A helical scintillating fiber hodoscope

    Energy Technology Data Exchange (ETDEWEB)

    Altmeier, M.; Bauer, F.; Bisplinghoff, J.; Bissel, T.; Bollmann, R.; Busch, M.; Buesser, K.; Colberg, T.; Demiroers, L.; Diehl, O.; Dohrmann, F.; Engelhardt, H.P.; Eversheim, P.D.; Felden, O.; Gebel, R.; Glende, M.; Greiff, J.; Gross, A.; Gross-Hardt, R.; Hinterberger, F.; Jahn, R.; Jeske, M.; Jonas, E.; Krause, H.; Lahr, U.; Langkau, R.; Lindemann, T.; Lindlein, J.; Maier, R.; Maschuw, R.; Mayer-Kuckuck, T.; Meinerzhagen, A.; Naehle, O.; Pfuff, M.; Prasuhn, D.; Rohdjess, H.; Rosendaal, D.; Rossen, P. von; Sanz, B.; Schirm, N.; Schulz-Rojahn, M.; Schwarz, V.; Scobel, W.; Thomas, S.; Trelle, H.J.; Weise, E.; Wellinghausen, A.; Wiedmann, W.; Woller, K.; Ziegler, R

    1999-07-21

    A novel scintillating fiber hodoscope in helically cylindric geometry has been developed for detection of low multiplicity events of fast protons and other light charged particles in the internal target experiment EDDA at the Cooler Synchrotron COSY. The hodoscope consists of 640 scintillating fibers (2.5 mm diameter), arranged in four layers surrounding the COSY beam pipe. The fibers are helically wound in opposing directions and read out individually using 16-channel photomultipliers connected to a modified commercial encoding system. The detector covers an angular range of 9 deg. {<=}{theta}{<=}72 deg. and 0 deg. {<=}phi (cursive,open) Greek{<=}360 deg. in the lab frame. The detector length is 590 mm, the inner diameter 161 mm. Geometry and granularity of the hodoscope afford a position resolution of about 1.3 mm. The detector design took into consideration a maximum of reliability and a minimum of maintenance. An LED array may be used for monitoring purposes. (author)

  5. A helical scintillating fiber hodoscope

    CERN Document Server

    Altmeier, M; Bisplinghoff, J; Bissel, T; Bollmann, R; Busch, M; Büsser, K; Colberg, T; Demiroers, L; Diehl, O; Dohrmann, F; Engelhardt, H P; Eversheim, P D; Felden, O; Gebel, R; Glende, M; Greiff, J; Gross, A; Gross-Hardt, R; Hinterberger, F; Jahn, R; Jeske, M; Jonas, E; Krause, H; Lahr, U; Langkau, R; Lindemann, T; Lindlein, J; Maier, R; Maschuw, R; Mayer-Kuckuck, T; Meinerzhagen, A; Naehle, O; Pfuff, M; Prasuhn, D; Rohdjess, H; Rosendaal, D; Von Rossen, P; Sanz, B; Schirm, N; Schulz-Rojahn, M; Schwarz, V; Scobel, W; Thomas, S; Trelle, H J; Weise, E; Wellinghausen, A; Wiedmann, W; Woller, K; Ziegler, R

    1999-01-01

    A novel scintillating fiber hodoscope in helically cylindric geometry has been developed for detection of low multiplicity events of fast protons and other light charged particles in the internal target experiment EDDA at the Cooler Synchrotron COSY. The hodoscope consists of 640 scintillating fibers (2.5 mm diameter), arranged in four layers surrounding the COSY beam pipe. The fibers are helically wound in opposing directions and read out individually using 16-channel photomultipliers connected to a modified commercial encoding system. The detector covers an angular range of 9 deg. <= THETA<=72 deg. and 0 deg. <=phi (cursive,open) Greek<=360 deg. in the lab frame. The detector length is 590 mm, the inner diameter 161 mm. Geometry and granularity of the hodoscope afford a position resolution of about 1.3 mm. The detector design took into consideration a maximum of reliability and a minimum of maintenance. An LED array may be used for monitoring purposes. (author)

  6. A helical scintillating fiber hodoscope

    Science.gov (United States)

    Altmeier, M.; Bauer, F.; Bisplinghoff, J.; Bissel, T.; Bollmann, R.; Busch, M.; Büßer, K.; Colberg, T.; Demirörs, L.; Diehl, O.; Dohrmann, F.; Engelhardt, H. P.; Eversheim, P. D.; Felden, O.; Gebel, R.; Glende, M.; Greiff, J.; Groß, A.; Groß-Hardt, R.; Hinterberger, F.; Jahn, R.; Jeske, M.; Jonas, E.; Krause, H.; Lahr, U.; Langkau, R.; Lindemann, T.; Lindlein, J.; Maier, R.; Maschuw, R.; Mayer-Kuckuck, T.; Meinerzhagen, A.; Nähle, O.; Pfuff, M.; Prasuhn, D.; Rohdjeß, H.; Rosendaal, D.; von Rossen, P.; Sanz, B.; Schirm, N.; Schulz-Rojahn, M.; Schwarz, V.; Scobel, W.; Thomas, S.; Trelle, H. J.; Weise, E.; Wellinghausen, A.; Wiedmann, W.; Woller, K.; Ziegler, R.; EDDA Collaboration

    1999-07-01

    A novel scintillating fiber hodoscope in helically cylindric geometry has been developed for detection of low multiplicity events of fast protons and other light charged particles in the internal target experiment EDDA at the Cooler Synchrotron COSY. The hodoscope consists of 640 scintillating fibers (2.5 mm diameter), arranged in four layers surrounding the COSY beam pipe. The fibers are helically wound in opposing directions and read out individually using 16-channel photomultipliers connected to a modified commercial encoding system. The detector covers an angular range of 9°⩽ Θ⩽72° and 0°⩽ ϕ⩽360° in the lab frame. The detector length is 590 mm, the inner diameter 161 mm. Geometry and granularity of the hodoscope afford a position resolution of about 1.3 mm. The detector design took into consideration a maximum of reliability and a minimum of maintenance. An LED array may be used for monitoring purposes.

  7. The rate of screw misplacement in segmental pedicle screw fixation in adolescent idiopathic scoliosis.

    Science.gov (United States)

    Abul-Kasim, Kasim; Ohlin, Acke

    2011-02-01

    There are no reports in the literature on the influence of learning on the pedicle screw insertion. We studied the effect of learning on the rate of screw misplacement in patients with adolescent idiopathic scoliosis treated with segmental pedicle screw fixation. We retrospectively evaluated low-dose spine computed tomography of 116 consecutive patients (aged 16 (12-24) years, 94 females) who were operated during 4 periods over 2005-2009 (group 1: patients operated autumn 2005-2006; group 2: 2007; group 3: 2008; and group 4: 2009). 5 types of misplacement were recorded: medial cortical perforation, lateral cortical perforation, anterior cortical perforation of the vertebral body, endplate perforation, and perforation of the neural foramen. 2,201 pedicle screws were evaluated, with an average of 19 screws per patient. The rate of screw misplacement for the whole study was 14%. The rate of lateral and medial cortical perforation was 7% and 5%. There was an inverse correlation between the occurrence of misplacement and the patient number, i.e. the date of operation (r = -0.35; p skillfulness of screw insertion improved with reduction of the rate of screw misplacement from 20% in 2005-2006 to 11% in 2009, with a breakpoint at the end of the first study period (34 patients). We found a substantial learning curve; cumulative experience may have contributed to continued reduction of misplacement rate.

  8. Minimizing Pedicle Screw Pullout Risks: A Detailed Biomechanical Analysis of Screw Design and Placement.

    Science.gov (United States)

    Bianco, Rohan-Jean; Arnoux, Pierre-Jean; Wagnac, Eric; Mac-Thiong, Jean-Marc; Aubin, Carl-Éric

    2017-04-01

    Detailed biomechanical analysis of the anchorage performance provided by different pedicle screw designs and placement strategies under pullout loading. To biomechanically characterize the specific effects of surgeon-specific pedicle screw design parameters on anchorage performance using a finite element model. Pedicle screw fixation is commonly used in the treatment of spinal pathologies. However, there is little consensus on the selection of an optimal screw type, size, and insertion trajectory depending on vertebra dimension and shape. Different screw diameters and lengths, threads, and insertion trajectories were computationally tested using a design of experiment approach. A detailed finite element model of an L3 vertebra was created including elastoplastic bone properties and contact interactions with the screws. Loads and boundary conditions were applied to the screws to simulate axial pullout tests. Force-displacement responses and internal stresses were analyzed to determine the specific effects of each parameter. The design of experiment analysis revealed significant effects (Pdesign characteristics and surgical choices, enabling to recommend strategies to improve single pedicle screw performance under axial loading.

  9. Helically twisted photonic crystal fibres

    Science.gov (United States)

    Russell, P. St. J.; Beravat, R.; Wong, G. K. L.

    2017-02-01

    Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left- and right-spinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic `space', cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of `numerical experiments' based on finite-element solutions of Maxwell's equations in a helicoidal frame. This article is part of the themed issue 'Optical orbital angular momentum'.

  10. Helically twisted photonic crystal fibres.

    Science.gov (United States)

    Russell, P St J; Beravat, R; Wong, G K L

    2017-02-28

    Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left- and right-spinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic 'space', cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of 'numerical experiments' based on finite-element solutions of Maxwell's equations in a helicoidal frame.This article is part of the themed issue 'Optical orbital angular momentum'. © 2017 The Authors.

  11. Helical Antimicrobial Sulfono- {gamma} -AApeptides

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yaqiong; Wu, Haifan; Teng, Peng; Bai, Ge; Lin, Xiaoyang; Zuo, Xiaobing; Cao, Chuanhai; Cai, Jianfeng

    2015-06-11

    Host-defense peptides (HDPs) such as magainin 2 have emerged as potential therapeutic agents combating antibiotic resistance. Inspired by their structures and mechanism of action, herein we report the fi rst example of antimicrobial helical sulfono- γ - AApeptide foldamers. The lead molecule displays broad-spectrum and potent antimicrobial activity against multi-drug-resistant Gram- positive and Gram-negative bacterial pathogens. Time-kill studies and fl uorescence microscopy suggest that sulfono- γ -AApeptides eradicate bacteria by taking a mode of action analogous to that of HDPs. Clear structure - function relationships exist in the studied sequences. Longer sequences, presumably adopting more-de fi ned helical structures, are more potent than shorter ones. Interestingly, the sequence with less helical propensity in solution could be more selective than the stronger helix-forming sequences. Moreover, this class of antimicrobial agents are resistant to proteolytic degradation. These results may lead to the development of a new class of antimicrobial foldamers combating emerging antibiotic-resistant pathogens.

  12. Standard Waste Box Lid Screw Removal Option Testing

    Energy Technology Data Exchange (ETDEWEB)

    Anast, Kurt Roy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-03-11

    This report provides results from test work conducted to resolve the removal of screws securing the standard waste box (SWB) lids that hold the remediated nitrate salt (RNS) drums. The test work evaluated equipment and process alternatives for removing the 42 screws that hold the SWB lid in place. The screws were secured with a red Loctite thread locker that makes removal very difficult because the rivets that the screw threads into would slip before the screw could be freed from the rivet, making it impossible to remove the screw and therefore the SWB lid.

  13. Transpedicular screw fixation in the thoracic and lumbar spine with a novel cannulated polyaxial screw system

    Directory of Open Access Journals (Sweden)

    Lutz Weise

    2008-10-01

    Full Text Available Lutz Weise, Olaf Suess, Thomas Picht, Theodoros KombosNeurochirurgische Klinik, Charité – Universitätsmedizin Berlin, Berlin, GermanyObjective: Transpedicular screws are commonly and successfully used for posterior fixation in spinal instability, but their insertion remains challenging. Even using navigation techniques, there is a misplacement rate of up to 11%. The aim of this study was to assess the accuracy of a novel pedicle screw system.Methods: Thoracic and lumbar fusions were performed on 67 consecutive patients for tumor, trauma, degenerative disease or infection. A total of 326 pedicular screws were placed using a novel wire-guided, cannulated, polyaxial screw system (XIA Precision®, Stryker. The accuracy of placement was assessed post operatively by CT scan, and the patients were followed-up clinically for a mean of 16 months.Results: The total medio-caudal pedicle wall perforation rate was 9.2% (30/326. In 19 of these 30 cases a cortical breakthrough of less than 2 mm occurred. The misplacement rate (defined as a perforation of 2 mm or more was 3.37% (11/326. Three of these 11 screws needed surgical revision due to neurological symptoms or CSF leakage. There have been no screw breakages or dislocations over the follow up-period.Conclusion: We conclude that the use of this cannulated screw system for the placement of pedicle screws in the thoracic and lumbar spine is accurate and safe. The advantages of this technique include easy handling without a time-consuming set up. Considering the incidence of long-term screw breakage, further investigation with a longer follow-up period is necessary.Keywords: spinal instrumentation, pedicle screws, misplacement, pedicle wall perforation

  14. Formation of macromolecules in wheat gluten/starch mixtures during twin-screw extrusion: effect of different additives.

    Science.gov (United States)

    Wang, Kaiqiang; Li, Cheng; Wang, Bingzhi; Yang, Wen; Luo, Shuizhong; Zhao, Yanyan; Jiang, Shaotong; Mu, Dongdong; Zheng, Zhi

    2017-12-01

    Wheat gluten comprises a good quality and inexpensive vegetable protein with an ideal amino acid composition. To expand the potential application of wheat gluten in the food industry, the effect of different additives on the physicochemical and structural properties of wheat gluten/starch mixtures during twin-screw extrusion was investigated. Macromolecules were observed to form in wheat gluten/starch mixtures during twin-screw extrusion, which may be attributed to the formation of new disulfide bonds and non-covalent interactions, as well as Maillard reaction products. Additionally, the water retention capacity and in vitro protein digestibility of all extruded wheat gluten/starch products significantly increased, whereas the nitrogen solubility index and free sulfhydryl group (SH) content decreased, during twin-screw extrusion. Secondary structural analysis showed that α-helices disappeared with the concomitant increase of antiparallel β-sheets, demonstrating the occurrence of protein aggregation. Microstructures suggested that the irregular wheat gluten granular structure was disrupted, with additive addition favoring transformation into a more layered or fibrous structure during twin-screw extrusion. The findings of the present study demonstrate that extrusion might affect the texture and quality of extruded wheat gluten-based foods and suggest that this process might serve as a basis for the high-value application of wheat gluten products. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  15. Rotary Mode Core Sample System availability improvement

    Energy Technology Data Exchange (ETDEWEB)

    Jenkins, W.W.; Bennett, K.L.; Potter, J.D. [Westinghouse Hanford Co., Richland, WA (United States); Cross, B.T.; Burkes, J.M.; Rogers, A.C. [Southwest Research Institute (United States)

    1995-02-28

    The Rotary Mode Core Sample System (RMCSS) is used to obtain stratified samples of the waste deposits in single-shell and double-shell waste tanks at the Hanford Site. The samples are used to characterize the waste in support of ongoing and future waste remediation efforts. Four sampling trucks have been developed to obtain these samples. Truck I was the first in operation and is currently being used to obtain samples where the push mode is appropriate (i.e., no rotation of drill). Truck 2 is similar to truck 1, except for added safety features, and is in operation to obtain samples using either a push mode or rotary drill mode. Trucks 3 and 4 are now being fabricated to be essentially identical to truck 2.

  16. Twin screw wet granulation: Binder delivery.

    Science.gov (United States)

    Saleh, Mohammed F; Dhenge, Ranjit M; Cartwright, James J; Hounslow, Michael J; Salman, Agba D

    2015-06-20

    The effects of three ways of binder delivery into the twin screw granulator (TSG) on the residence time, torque, properties of granules (size, shape, strength) and binder distribution were studied. The binder distribution was visualised through the transparent barrel using high speed imaging as well as quantified using offline technique. Furthermore, the effect of binder delivery and the change of screw configuration (conveying elements only and conveying elements with kneading elements) on the surface velocity of granules across the screw channel were investigated using particle image velocimetry (PIV). The binder was delivered in three ways; all solid binder incorporated with powder mixture, 50% of solid binder mixed with powder mixture and 50% mixed with water, all the solid binder dissolved in water. Incorporation of all solid binder with powder mixture resulted in the relatively longer residence time and higher torque, narrower granule size distribution, more spherical granules, weaker big-sized granules, stronger small-sized granules and better binder distribution compared to that in other two ways. The surface velocity of granules showed variation from one screw to another as a result of uneven liquid distribution as well as shown a reduction while introducing the kneading elements into the screw configuration. Copyright © 2015. Published by Elsevier B.V.

  17. GAS MOVEMENT IN ROTARY TILTING FURNACES

    Directory of Open Access Journals (Sweden)

    S. L. Rovin

    2016-01-01

    Full Text Available The article presents the results of studies of gas movement and heat and mass transfer processes in the rotary tilting furnace (RTF at the heat treatment of disperse materials. The study was performed through computer modeling using software packages ANSYS CFX and Solid Works Flow Simulation. The results were used to design RTF with different capacity and application and helped to improve their technical and economic characteristics.

  18. INVESTIGATIONS ON OPERATION OF ROTARY TILTING FURNACES

    Directory of Open Access Journals (Sweden)

    S. L. Rovin

    2016-01-01

    Full Text Available Rotary tilting furnace (RTF is a new type of fuel furnaces, that provide the most efficient heating and recycling of polydisperse materials. The paper describes results of the investigations on thermal processes in the RTF, movement of materials and non-isothermal gas flow during kiln rotary process. The investigations have been carried out while using physical and computer simulations and under actual operating conditions applying the pilot plant. Results of the research have served as a basis for development of recommendations on the RTF calculations and designing and they have been also used for constructional design of a rotary tilting furnace for heating and melting of cast iron chips, reduction smelting of steel mill scale, melting of aluminum scrap, melting of lead from battery scrap. These furnaces have a high thermal efficiency (~50 %, technological flexibility, high productivity and profitability. Proven technical solutions for recycling of ferrous and non-ferrous metals develop the use of RTF in the foundry and metallurgical industry as the main technological unit for creation of cost-effective small-tonnage recycling of metal waste generated at the plants. The research results open prospects for organization of its own production for high-quality charging material in Belarus in lieu of imported primary metal. The proposed technology makes it possible to solve environmental challenge pertaining to liquidation of multi-tonnage heaps of metal-containing wastes.

  19. The Wankel rotary engine a history

    CERN Document Server

    Hege, John B

    2007-01-01

    "It stands apart from the crowd as the only history of the Wankel rotary engine that brings the story into the 21st Century"--SAH Journal; "this book continues to excel...terrific...technophiles will love this"--Hemmings Motor News; "excellent"--Hemmings Sports & Exotic Car; "a complete history...guaranteed to delight"--Old Cars Weekly; "definitive…a must-read"--Choice; "informative"--SciTech Book News; "goes a long way to explaining everything"--The Automobile. This complete and well-illustrated account traces the full history of the Wankel rotary engine and its use in various cars, motorcycles, snowmobiles and other applications. It clearly explains the working of the engine and the technical challenges it presented--the difficulty of designing effective and durable seals, early emissions troubles, high fuel consumption, and others. The work done by several companies to overcome these problems is described in detail, as are the economic and political troubles that nearly killed the rotary in the 19...

  20. The dynamic stator stalk of rotary ATPases

    Science.gov (United States)

    Stewart, Alastair G.; Lee, Lawrence K.; Donohoe, Mhairi; Chaston, Jessica J.; Stock, Daniela

    2012-01-01

    Rotary ATPases couple ATP hydrolysis/synthesis with proton translocation across biological membranes and so are central components of the biological energy conversion machinery. Their peripheral stalks are essential components that counteract torque generated by rotation of the central stalk during ATP synthesis or hydrolysis. Here we present a 2.25-Å resolution crystal structure of the peripheral stalk from Thermus thermophilus A-type ATPase/synthase. We identify bending and twisting motions inherent within the structure that accommodate and complement a radial wobbling of the ATPase headgroup as it progresses through its catalytic cycles, while still retaining azimuthal stiffness necessary to counteract rotation of the central stalk. The conformational freedom of the peripheral stalk is dictated by its unusual right-handed coiled-coil architecture, which is in principle conserved across all rotary ATPases. In context of the intact enzyme, the dynamics of the peripheral stalks provides a potential mechanism for cooperativity between distant parts of rotary ATPases. PMID:22353718

  1. Does intermittence in induced rotary movement have any explanatory significance?

    Science.gov (United States)

    Reinhardt-Rutland, A H

    1991-06-01

    Induced rotary movement has been reported to start and stop repeatedly during 1 min of observation. This has been taken as evidence for the involvement either of cyclorotational optokinetic nystagmus or of roll vection. Both assertions are dubious. Regarding cyclorotational optokinetic nystagmus, available evidence shows that it is too weak to be important in induced rotary movement. Also, induced rotary movement and cyclorotational optokinetic nystagmus are affected differently by the velocity of eliciting stimulation. Regarding roll vection, the conditions for its intermittence do not match those for induced rotary movement. Also, although aftereffects for induced rotary movement are negative, those for roll vection are positive and negative. Intermittence in induced rotary movement may be parsimoniously explained as characteristic of a weak effect.

  2. Impact of screw configuration on the particle size distribution of granules produced by twin screw granulation.

    Science.gov (United States)

    Vercruysse, J; Burggraeve, A; Fonteyne, M; Cappuyns, P; Delaet, U; Van Assche, I; De Beer, T; Remon, J P; Vervaet, C

    2015-02-01

    Twin screw granulation (TSG) has been reported by different research groups as an attractive technology for continuous wet granulation. However, in contrast to fluidized bed granulation, granules produced via this technique typically have a wide and multimodal particle size distribution (PSD), resulting in suboptimal flow properties. The aim of the current study was to evaluate the impact of granulator screw configuration on the PSD of granules produced by TSG. Experiments were performed using a 25 mm co-rotating twin screw granulator, being part of the ConsiGma™-25 system (a fully continuous from-powder-to-tablet manufacturing line from GEA Pharma Systems). Besides the screw elements conventionally used for TSG (conveying and kneading elements), alternative designs of screw elements (tooth-mixing-elements (TME), screw mixing elements (SME) and cutters) were investigated using an α-lactose monohydrate formulation granulated with distilled water. Granulation with only conveying elements resulted in wide and multimodal PSD. Using kneading elements, the width of the PSD could be partially narrowed and the liquid distribution was more homogeneous. However, still a significant fraction of oversized agglomerates was obtained. Implementing additional kneading elements or cutters in the final section of the screw configuration was not beneficial. Furthermore, granulation with only TME or SME had limited impact on the width of the PSD. Promising results were obtained by combining kneading elements with SME, as for these configurations the PSD was narrower and shifted to the size fractions suitable for tableting. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Analysis of Apex Seal Friction Power Loss in Rotary Engines

    Science.gov (United States)

    Handschuh, Robert F.; Owen, A. Karl

    2010-01-01

    An analysis of the frictional losses from the apex seals in a rotary engine was developed. The modeling was initiated with a kinematic analysis of the rotary engine. Next a modern internal combustion engine analysis code was altered for use in a rotary engine to allow the calculation of the internal combustion pressure as a function of rotor rotation. Finally the forces from the spring, inertial, and combustion pressure on the seal were combined to provide the frictional horsepower assessment.

  4. Numerical Analysis on Combustion Characteristic of Leaf Spring Rotary Engine

    OpenAIRE

    Yan Zhang; Zhengxing Zuo; Jinxiang Liu

    2015-01-01

    The purpose of this paper is to investigate combustion characteristics for rotary engine via numerical studies. A 3D numerical model was developed to study the influence of several operative parameters on combustion characteristics. A novel rotary engine called, “Leaf Spring Rotary Engine”, was used to illustrate the structure and principle of the engine. The aims are to (1) improve the understanding of combustion process, and (2) quantify the influence of rotational speed, excess air ratio, ...

  5. Biomass granular screw feeding: An experimental investigation

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Jianjun; Grace, John R. [Department of Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, BC, V6 T 1Z3 (Canada)

    2011-02-15

    Successful feeding is critical to biomass utilization processes, but difficult due to the heterogeneity, physical properties and moisture content of the particles. The objectives of the present study were to find the mechanisms of blockage in screw feeding and to determine the effects of particle mean size (0.5-15 mm), size distribution, shape, moisture content (10-60%), density and compressibility on biomass particle feeding at room temperature. Wood pellets, sawdust, hog fuel and wood shavings were tested in a screw feeder/lock hopper system previously employed to feed sawdust into a pilot-scale circulating fluidized-bed gasifier. Experimental results showed that large particles, wide size distributions, large bulk densities and high moisture contents generally led to larger torque requirements for screw feeding. The ''choke section'' and seal plug play important roles in determining the torque requirements. (author)

  6. The accuracy and the safety of individualized 3D printing screws insertion templates for cervical screw insertion.

    Science.gov (United States)

    Deng, Ting; Jiang, Minghui; Lei, Qing; Cai, Lihong; Chen, Li

    2016-12-01

    Clinical trial for cervical screw insertion by using individualized 3-dimensional (3D) printing screw insertion templates device. The objective of this study is to evaluate the safety and accuracy of the individualized 3D printing screw insertion template in the cervical spine. Ten patients who underwent posterior cervical fusion surgery with cervical pedicle screws, laminar screws or lateral mass screws between December 2014 and December 2015 were involved in this study. The patients were examined by CT scan before operation. The individualized 3D printing templates were made with photosensitive resin by a 3D printing system to ensure the screw shafts entered the vertebral body without breaking the pedicle or lamina cortex. The templates were sterilized by a plasma sterilizer and used during the operation. The accuracy and the safety of the templates were evaluated by CT scans at the screw insertion levels after operation. The accuracy of this patient-specific template technique was demonstrated. Only one screw axis greatly deviated from the planned track and breached the cortex of the pedicle because the template was split by rough handling and then we inserted the screws under the fluoroscopy. The remaining screws were inserted in the track as preoperative design and the screw axis deviated by less than 2 mm. Vascular or neurologic complications or injuries did not happen. And no infection, broken nails, fracture of bone structure, or screw pullout occurred. This study verified the safety and the accuracy of the individualized 3D printing screw insertion templates in the cervical spine as a kind of intraoperative screw navigation. This individualized 3D printing screw insertion template was user-friendly, moderate cost, and enabled a radiation-free cervical screw insertion.

  7. Tallinna Rotary klubi valis aasta politseiniku ja narkokoera

    Index Scriptorium Estoniae

    2006-01-01

    Tallinna Rotary klubi autasustas parima narkopolitseiniku preemiaga Lõuna politseiprefektuuri narkokuritegude talituse vaneminspektorit Jarek Pavlihhinit ning parima narkokoera tiitliga vene spanjelit Allrighti

  8. Material Research of Rotary Sealing Device for Combined Cutting System

    OpenAIRE

    Rui Zeng; Yong Zhang; Zhenrong Lin; Lulu Wang

    2017-01-01

    In order to solve the rotary sealing problem of rotary shaft in drum shearer combined cutting system, the material and structure of combined cutting system rotary sealing device needs to be selected and designed. In the paper, the rotary sealing structure of four grades in series was designed first, and then the material of NBR-40 and PTFE 4FT-4 under the separate static and dynamic sealing tests were carried out on the combined tooth-slip-ring sealing test-bed. The tests show that the NBR-40...

  9. Helical axis stellarator with noninterlocking planar coils

    Science.gov (United States)

    Reiman, Allan; Boozer, Allen H.

    1987-01-01

    A helical axis stellarator using only noninterlocking planar, non-circular coils, generates magnetic fields having a magnetic well and large rotational transform with resultant large equilibrium beta.

  10. [Contralateral preventive screwing in proximal femoral epiphysiolysis].

    Science.gov (United States)

    Ghanem, I; Damsin, J P; Carlioz, H

    1996-01-01

    The incidence of bilaterality in slipped capital femoral epiphysis (SCFE) ranges, in the literature, from 19 per cent to 80 per cent. The role of contralateral pinning is to prevent late slipping of the femoral epiphysis and its complications. The purpose of this study is to assess the usefulness of routine preventive contralateral pinning in SCFE, and to evaluate its complications. We reviewed retrospectively 74 consecutive patients treated for unilateral SCFE by associated routine preventive contralateral pinning. The age at surgery ranged from 10 years and 6 months to 16 years and 10 months. The osteosynthesis was achieved by a single cannulated holothreaded screw with a cross grooved head, with or without the use of washers. An accidental pin penetration was noted in 4 cases. The epiphyseal position of the screw was satisfactory in 56 cases. The patient was allowed to walk the second or third day after surgery with the use of crutches. All our patients were reviewed after the end of squeletal growth. The follow-up ranged from 2 to 12 years and 8 months. The age at which the patient was last seen ranged from 15 years and 7 months to 27 years. Two major complications were noted: a femoral fracture at the level of the screw penetration in one case, and secondary slipping of the epiphysis after premature removal of the screw in two cases. The removal of the screw was considered to be very difficult in 10 cases. A relative overgrowth of the greater trochanter was noted in 8 cases, and was of no clinical significance. No infection was noted. At last follow-up, the shape of the femoral head and the function of the hip were normal in all cases except for one hip where severe coxa vara developed because of a secondary slip after premature removal of the screw. There is a lot of controversy about the real necessity of routine preventive contralateral osteosynthesis in SCFE. In our experience this surgery succeeded in reducing the incidence of secondary contralateral

  11. Drag and Torque on Locked Screw Propeller

    Directory of Open Access Journals (Sweden)

    Tomasz Tabaczek

    2014-09-01

    Full Text Available Few data on drag and torque on locked propeller towed in water are available in literature. Those data refer to propellers of specific geometry (number of blades, blade area, pitch and skew of blades. The estimation of drag and torque of an arbitrary propeller considered in analysis of ship resistance or propulsion is laborious. The authors collected and reviewed test data available in the literature. Based on collected data there were developed the empirical formulae for estimation of hydrodynamic drag and torque acting on locked screw propeller. Supplementary CFD computations were carried out in order to prove the applicability of the formulae to modern moderately skewed screw propellers.

  12. A Theoretical-Experimental Comparison of an Improved Ammonia-Water Bubble Absorber by Means of a Helical Static Mixer

    Directory of Open Access Journals (Sweden)

    Jesús Cerezo

    2017-12-01

    Full Text Available The heat transfer in double pipe heat exchangers is very poor. This complicates its application in absorption cooling systems, however, the implementation of simple passive techniques should help to increase the heat and mass transfer mainly in the absorber. This paper carried out a simulation and its experimental comparison of a NH3-H2O bubble absorption process using a double tube heat exchanger with a helical screw static mixer in both central and annular sides. The experimental results showed that the absorption heat load per area is 31.61% higher with the helical screw mixer than the smooth tube. The theoretical and experimental comparison showed that the absorption heat load difference values were 28.0 and 21.9% for smooth tube and the helical mixer, respectively. These difference values were caused by the calculation of the log mean temperature difference in equilibrium conditions to avoid the overlap of solution temperatures. Therefore, the theoretical and experimental results should be improved when the absorption heat is included in the heat transfer equation or avoiding the operation condition when output is lower than input solution temperature.

  13. Improved Riccati Transfer Matrix Method for Free Vibration of Non-Cylindrical Helical Springs Including Warping

    Directory of Open Access Journals (Sweden)

    A.M. Yu

    2012-01-01

    Full Text Available Free vibration equations for non-cylindrical (conical, barrel, and hyperboloidal types helical springs with noncircular cross-sections, which consist of 14 first-order ordinary differential equations with variable coefficients, are theoretically derived using spatially curved beam theory. In the formulation, the warping effect upon natural frequencies and vibrating mode shapes is first studied in addition to including the rotary inertia, the shear and axial deformation influences. The natural frequencies of the springs are determined by the use of improved Riccati transfer matrix method. The element transfer matrix used in the solution is calculated using the Scaling and Squaring method and Pad'e approximations. Three examples are presented for three types of springs with different cross-sectional shapes under clamped-clamped boundary condition. The accuracy of the proposed method has been compared with the FEM results using three-dimensional solid elements (Solid 45 in ANSYS code. Numerical results reveal that the warping effect is more pronounced in the case of non-cylindrical helical springs than that of cylindrical helical springs, which should be taken into consideration in the free vibration analysis of such springs.

  14. A method for removal of broken vertebral screws.

    Science.gov (United States)

    McGuire, R A

    1992-06-01

    A method for removal of a broken vertebral screw is described using an easily obtained 5/64-inch tungsten drill bit and a #1 screw extractor. It allows removal of the screw while retaining pedicle integrity and also minimizes potential nerve root compromise.

  15. Segregation of helicity in inertial wave packets

    Science.gov (United States)

    Ranjan, A.

    2017-03-01

    Inertial waves are known to exist in the Earth's rapidly rotating outer core and could be important for the dynamo generation. It is well known that a monochromatic inertial plane wave traveling parallel to the rotation axis (along positive z ) has negative helicity while the wave traveling antiparallel (negative z ) has positive helicity. Such a helicity segregation, north and south of the equator, is necessary for the α2-dynamo model based on inertial waves [Davidson, Geophys. J. Int. 198, 1832 (2014), 10.1093/gji/ggu220] to work. The core is likely to contain a myriad of inertial waves of different wave numbers and frequencies. In this study, we investigate whether this characteristic of helicity segregation also holds for an inertial wave packet comprising waves with the same sign of Cg ,z, the z component of group velocity. We first derive the polarization relations for inertial waves and subsequently derive the resultant helicity in wave packets forming as a result of superposition of two or more waves. We find that the helicity segregation does hold for an inertial wave packet unless the wave numbers of the constituent waves are widely separated. In the latter case, regions of opposite color helicity do appear, but the mean helicity retains the expected sign. An illustration of this observation is provided by (a) calculating the resultant helicity for a wave packet formed by superposition of four upward-propagating inertial waves with different wave vectors and (b) conducting the direct numerical simulation of a Gaussian eddy under rapid rotation. Last, the possible effects of other forces such as the viscous dissipation, the Lorentz force, buoyancy stratification, and nonlinearity on helicity are investigated and discussed. The helical structure of the wave packet is likely to remain unaffected by dissipation or the magnetic field, but can be modified by the presence of linearly stable stratification and nonlinearity.

  16. Clinical pedicle screw accuracy and deviation from planning in robot-guided spine surgery: robot-guided pedicle screw accuracy

    NARCIS (Netherlands)

    van Dijk, Joris David; Ende, Roy P.J.; Stramigioli, Stefano; Köchling, Matthias; Höss, Norbert

    STUDY DESIGN: A retrospective chart review was performed for 112 consecutive minimally invasive spinal surgery patients who underwent pedicular screw fixation in a community hospital setting. OBJECTIVE: To assess the clinical accuracy and deviation in screw positions in robot-assisted pedicle screw

  17. Nylon screws make inexpensive coil forms

    Science.gov (United States)

    Aucoin, G.; Rosenthal, C.

    1978-01-01

    Standard nylon screws act as coil form copper wire laid down in spiral thread. Completed coil may be bonded to printed-circuit board. However, it is impossible to tune coil by adjusting spacing between windings, technique sometimes used with air-core coils.

  18. Magnetic Helicity and the Solar Dynamo

    Science.gov (United States)

    Canfield, Richard C.

    1997-01-01

    The objective of this investigation is to open a new window into the solar dynamo, convection, and magnetic reconnection through measurement of the helicity density of magnetic fields in the photosphere and tracing of large-scale patterns of magnetic helicity in the corona.

  19. Helical Magnetic Fields in AGN Jets

    Indian Academy of Sciences (India)

    We establish a simple model to describe the helical magnetic fields in AGN jets projected on the sky plane and the line-of-sight. This kind of profile has been detected in the polarimetric VLBI observation of many blazar objects, suggesting the existence of helical magnetic fields in these sources.

  20. [Clinical application of percutaneous iliosacral screws combined with pubic ramus screws in Tile B pelvic fracture].

    Science.gov (United States)

    Xu, Qi-Fei; Lin, Kui-Ran; Zhao, Dai-Jie; Zhang, Song-Qin; Feng, Sheng-Kai; Li, Chen

    2017-03-25

    To investigate the application and effect of minimally invasive percutaneous anterior pelvic pubic ramus screw fixation in Tile B fractures. A retrospective review was conducted on 56 patients with posterior pelvic ring injury combined with fractures of anterior pubic and ischiadic ramus treated between May 2010 and August 2015, including 31 males and 25 females with an average age of 36.8 years old ranging from 35 to 65 years old. Based on the Tile classification, there were 13 cases of Tile B1 type, 28 cases of Tile B2 type and 15 cases of Tile B3 type. Among them, 26 patients were treated with sacroiliac screws combined with external fixation (external fixator group) and the other 30 patients underwent sacroiliac screw fixation combined with anterior screw fixation (pubic ramus screw group). Postoperative complications, postoperative ambulation time, fracture healing, blood loss, Majeed pelvic function score and visual analogue scale(VAS) were compared between two groups. Fifty-four patients were followed up from 3 to 24 months with a mean of 12 months. There were no significant difference in the peri-operative bleeding and operation time between two groups( P >0.05). The postoperative activity time and fracture healing time of pubic ramus screw group were shorter than those of the external fixator group, the differences were statistically significant( P safty treatment method to the Tile B pelvic fracture. It has advantages of early ambulation, relief of the pain and few complications.

  1. Evolution of heat in dry rotary swaging

    Science.gov (United States)

    Herrmann, Marius; Liu, Yang; Schenck, Christian; Kuhfuss, Bernd; Ohlsen, Inken

    2017-10-01

    In dry metal forming processes, the heat dissipation is a critical issue. The cooling by the lubricant is missing. The different heat evolution affects the machine and the process and thus the final product. For the machine the thermal expansion is affected and needs to be considered. Also the tools can bear only a maximum heat load before they get damaged. Furthermore, the heat can influence the material properties like the flow stress if it exceeds a critical value. Furthermore, the process forces and the material flow are directly affected. In addition, heat modifies in combination with plastic strain the generated microstructure of the workpiece. If the heat is high enough even positive effects of cold forming like work hardening are drastically decreased. In summary, the heat evolution during lubricated and dry forming processes need to be investigated. The evolution of heat in rotary swaging was investigated with conventional tools and machine settings. This was realized by varying the feeding velocity for the lubricated forming of aluminum tubes (3.3206) and steel tubes (1.0308). Moreover, the steel tubes are also formed with conventional tools by dry rotary swaging. A temperature measurement was integrated inside the tubes during the rotary process. Thus, the heat evolution inside the tube during the process at two different positions was examined. Also the variation between inside the tubes and the surface of the tubes was investigated by measuring the temperature at the surface directly after the forming process. Comparisons between different measured heat evolutions represent the impact of lubrication, feed rate and material. Thus, the practicability and the challenge for dry forming processes are presented.

  2. Features of rotary pump diagnostics without dismantling

    Directory of Open Access Journals (Sweden)

    Sergeev K. О.

    2017-12-01

    Full Text Available In ship power plants, rotor pumps have become very popular providing the transfer of various viscous fluids: fuels, oils, etc. Like all ship's mechanisms, pumps need proper maintenance and monitoring of technical condition. The most expedient is maintenance and repair carried out according to the results of dismantling diagnosis. The methods of vibrodiagnostics are mostly widespread for the diagnosis of pumps. Vibrodiagnosis of rotary pumps has a number of features due to the nature and condition of pumped fluids. The norms of the Russian Maritime Register of Shipping are used for setting standards of vibration and diagnostics of the rotary pumps' technical condition. To clarify the features of vibration diagnostics of rotary pumps some measurements have been made on a special bench that simulates various modes of ship's pumps' operation: different pressure in the system and temperature of the pumped medium. As a result of measurements one-third octave and narrow-band vibration spectra of pumps have been obtained at various developed pressures and temperatures of the pumped fluid. The performed analysis has shown that the RMRS norms for diagnostics of ship rotary pumps have insufficient informative value inasmuch they do not take into account the dependence of the vibrational signal spectrum on the developed pressure and temperature of the pumped fluid. The nature of the received signals shows that the levels of a third-octave spectrum of the vibration velocity depend significantly on the temperature of the pumped fluids, this fact must be taken into account when applying the RMRS norms. The fluid temperature has a great influence on the nature of the narrow-band vibration acceleration spectrum in the area of medium frequencies, less influence – on the nature of the vibration velocity spectrum. The conclusions have been drawn about the advisability of using the narrow-band vibration spectra and the envelope spectra of the high

  3. Static Model of Cement Rotary Kiln

    Directory of Open Access Journals (Sweden)

    Omar D. Hernández-Arboleda

    2013-11-01

    Full Text Available In this paper, a static model of cement rotary kilns is proposed. The system model is obtained through polynomial series. The proposed model is contrasted with data of a real plant, where optimal results are obtained. Expected results are measured with respect to the clinker production and the combustible consumption is measured in relation with the consumption calorific. The expected result of the approach is the increase of the profitability of the factory through the decrease of the consumption of the combustible.

  4. Design Robust Controller for Rotary Kiln

    Directory of Open Access Journals (Sweden)

    Omar D. Hernández-Arboleda

    2013-11-01

    Full Text Available This paper presents the design of a robust controller for a rotary kiln. The designed controller is a combination of a fractional PID and linear quadratic regulator (LQR, these are not used to control the kiln until now, in addition robustness criteria are evaluated (gain margin, phase margin, strength gain, rejecting high frequency noise and sensitivity applied to the entire model (controller-plant, obtaining good results with a frequency range of 0.020 to 90 rad/s, which contributes to the robustness of the system.

  5. Rotary Wing Deceleration Use on Titan

    Science.gov (United States)

    Young, Larry A.; Steiner, Ted J.

    2011-01-01

    Rotary wing decelerator (RWD) systems were compared against other methods of atmospheric deceleration and were determined to show significant potential for application to a system requiring controlled descent, low-velocity landing, and atmospheric research capability on Titan. Design space exploration and down-selection results in a system with a single rotor utilizing cyclic pitch control. Models were developed for selection of a RWD descent system for use on Titan and to determine the relationships between the key design parameters of such a system and the time of descent. The possibility of extracting power from the system during descent was also investigated.

  6. Rotary International and Career Education. Monographs on Career Education.

    Science.gov (United States)

    Hoyt, Kenneth B.

    Based on a series of mini-conferences, this monograph presents ideas and thoughts of members of the Rotary International organization on the concept of collaboration in career education. First, a brief description of Rotary International is provided. Next, several specific examples are given of ways in which local clubs are already involved in…

  7. Streaming current of a rotary atomizer for energy harvesting

    NARCIS (Netherlands)

    Nguyen, Trieu; de Boer, Hans L.; Tran, T.; van den Berg, Albert; Eijkel, Jan C.T.; Zengerle, R.

    2013-01-01

    We present the experimental results of an energy conversion system based on a rotary atomizer and the streaming current phenomenon. The advantage of using a rotary atomizer instead of a channel or membrane micropore as in conventional pressure-driven approached is that the centrifugal force exerted

  8. Rate acceleration of light-driven rotary molecular motors

    NARCIS (Netherlands)

    Pollard, Michael M.; Klok, Martin; Pijper, Dirk; Feringa, Ben L.

    2007-01-01

    One of the key challenges in taking light-driven unidirectional rotary motors from discovery to application is to increase the rate of rotation. Herein, we review our ongoing efforts to address this issue by meticulous improvement to the molecular design. To accelerate the rotary cycle, we have

  9. THE MOVEMENT AND MIXING OF DISPERSED MATERIALS IN ROTARY FURNACES

    Directory of Open Access Journals (Sweden)

    S. L. Rovin

    2017-01-01

    Full Text Available This article describes motion and heat and mass transfer in the layer of dispersed material in a rotary furnace. Presents the results of a comprehensive study of these processes, including pilot studies, computer modeling and simulation, which allow to optimize the design and process parameters of rotary furnaces.

  10. Mathematical modeling and design parameters of crushing machines with variable-pitch helix of the screw

    Directory of Open Access Journals (Sweden)

    Pelenko V. V.

    2017-11-01

    Full Text Available From the point of view of the effectiveness of the top cutting unit, the helix angle in the end portion of the screw is the most important and characteristic parameter, as it determines the pressure of the meat material in the zone of interaction of a knife and grate. The importance of solving the problem of mathematical modeling of geometry is due to the need to address the problem of minimizing the reverse flow of the food material when injecting into the cutting zone, as the specified effect of "locking" significantly reduces the performance of the transfer process, increases energy consumption of the equipment and entails the deterioration of the quality of the raw materials output. The problem of determining the length of the helix variable pitch for screw chopper food materials has been formulated and solved by methods of differential geometry. The task of correct description of the law of changing the angle of helix inclination along its length has been defined in this case as a key to provide the required dependence of this angle tangent on the angle of the radius-vector of the circle. It has been taken into account that the reduction in the pitch of the screw in the direction of the product delivery should occur at a decreasing rate. The parametric equation of the helix has been written in the form of three functional dependencies of the corresponding cylindrical coordinates. Based on the wide range analysis and significant number of models of tops from different manufacturers the boundaries of possible changes in the angles of inclination of the helical line of the first and last turns of the screw have been identified. The auger screw length is determined mathematically in the form of an analytical relationship and both as a function of the variable angle of its rise, and as a function of the rotation angle of the radius-vector of the circle generatrix, which makes it possible to expand the design possibilities of this node. Along

  11. Helicity Evolution at Small x

    Science.gov (United States)

    Sievert, Michael; Kovchegov, Yuri; Pitonyak, Daniel

    2017-01-01

    We construct small- x evolution equations which can be used to calculate quark and anti-quark helicity TMDs and PDFs, along with the g1 structure function. These evolution equations resum powers of ln2(1 / x) in the polarization-dependent evolution along with the powers of ln(1 / x) in the unpolarized evolution which includes saturation effects. The equations are written in an operator form in terms of polarization-dependent Wilson line-like operators. While the equations do not close in general, they become closed and self-contained systems of non-linear equations in the large-Nc and large-Nc &Nf limits. After solving the large-Nc equations numerically we obtain the following small- x asymptotics for the flavor-singlet g1 structure function along with quarks hPDFs and helicity TMDs (in absence of saturation effects): g1S(x ,Q2) ΔqS(x ,Q2) g1L S(x ,kT2) (1/x) > αh (1/x) 2.31√{αsNc/2 π. We also give an estimate of how much of the proton's spin may be at small x and what impact this has on the so-called ``spin crisis.'' Work supported by the U.S. DOE, Office of Science, Office of Nuclear Physics under Award Number DE-SC0004286 (YK), the RIKEN BNL Research Center, and TMD Collaboration (DP), and DOE Contract No. DE-SC0012704 (MS).

  12. Research and application of absorbable screw in orthopedics: a clinical review comparing PDLLA screw with metal screw in patients with simple medial malleolus fracture

    Directory of Open Access Journals (Sweden)

    TANG Jin

    2013-02-01

    Full Text Available 【Abstract】Objective: To observe the therapeutic effect of absorbable screw in medial malleolus fracture and discuss its clinical application in orthopedics. Methods: A total of 129 patients with simple medial malleolus fracture were studied. Among them, 64 patients were treated with poly-D, L-lactic acid (PDLLA absorbable screws, while the others were treated with metal screws. All the patients were followed up for 12-20 months (averaged 18.4 months and the therapeutic effect was evaluated ac-cording to the American Orthopaedic Foot and Ankle Soci-ety clinical rating systems. Results: In absorbable screw group, we obtained excel-lent and good results in 62 cases (96.88%; in steel screw group, 61 cases (93.85% achieved excellent and good results. There was no significant difference between the two groups. Conclusion: In the treatment of malleolus fracture, absorbable screw can achieve the same result compared with metal screw fixation. Absorbable screw is preferred due to its advantages of safety, cleanliness and avoiding the removal procedure associated with metallic implants. Key words: Ankle; Bone screws; Fractures, bone

  13. A thin membrane artificial muscle rotary motor

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Iain A.; Hale, Thom; Gisby, Todd; Inamura, Tokushu; McKay, Thomas; O' Brien, Benjamin; Walbran, Scott [University of Auckland, The Biomimetics Lab, Auckland Bioengineering Institute, Auckland (New Zealand); Calius, Emilio P. [Industrial Research Ltd., P.O. Box 2225, Auckland (New Zealand)

    2010-01-15

    Desirable rotary motor attributes for robotics include the ability to develop high torque in a low mass body and to generate peak power at low rotational speeds. Electro-active polymer artificial muscles offer promise as actuator elements for robotic motors. A promising artificial muscle technology for use as a driving mechanism for rotary motion is the dielectric elastomer actuator (DEA). We present a membrane DEA motor in which phased actuation of electroded sectors of the motor membrane impart orbital motion to a central drive that turns a rotor. The motor is inherently scalable, flexible, flat, silent in operation, amenable to deposition-based manufacturing approaches, and uses relatively inexpensive materials. As a membrane it can also form part of the skin of a robot. We have investigated the torque and power of stacked membrane layers. Specific power and torque ratios when calculated using active membrane mass only were 20.8 W/kg and 4.1 Nm/kg, respectively. These numbers compare favorably with a commercially available stepper motor. Multi-membrane fabrication substantially boosts torque and power and increases the active mass of membrane relative to supporting framework. Through finite element modeling, we show the mechanisms governing the maximum torque the device can generate and how the motor can be improved. (orig.)

  14. A thin membrane artificial muscle rotary motor

    Science.gov (United States)

    Anderson, Iain A.; Hale, Thom; Gisby, Todd; Inamura, Tokushu; McKay, Thomas; O'Brien, Benjamin; Walbran, Scott; Calius, Emilio P.

    2010-01-01

    Desirable rotary motor attributes for robotics include the ability to develop high torque in a low mass body and to generate peak power at low rotational speeds. Electro-active polymer artificial muscles offer promise as actuator elements for robotic motors. A promising artificial muscle technology for use as a driving mechanism for rotary motion is the dielectric elastomer actuator (DEA). We present a membrane DEA motor in which phased actuation of electroded sectors of the motor membrane impart orbital motion to a central drive that turns a rotor. The motor is inherently scalable, flexible, flat, silent in operation, amenable to deposition-based manufacturing approaches, and uses relatively inexpensive materials. As a membrane it can also form part of the skin of a robot. We have investigated the torque and power of stacked membrane layers. Specific power and torque ratios when calculated using active membrane mass only were 20.8 W/kg and 4.1 Nm/kg, respectively. These numbers compare favorably with a commercially available stepper motor. Multi-membrane fabrication substantially boosts torque and power and increases the active mass of membrane relative to supporting framework. Through finite element modeling, we show the mechanisms governing the maximum torque the device can generate and how the motor can be improved.

  15. Biomechanical analysis of an interference screw and a novel twist lock screw design for bone graft fixation.

    Science.gov (United States)

    Asnis, S; Mullen, J; Asnis, P D; Sgaglione, N; LaPorta, T; Grande, D A; Chahine, N O

    2017-12-01

    Malpositioning of an anterior cruciate ligament graft during reconstruction can occur during screw fixation. The purpose of this study is to compare the fixation biomechanics of a conventional interference screw with a novel Twist Lock Screw, a rectangular shaped locking screw that is designed to address limitations of graft positioning and tensioning. Synthetic bone (10, 15, 20lb per cubic foot) were used simulating soft, moderate, and dense cancellous bone. Screw push-out and graft push-out tests were performed using conventional and twist lock screws. Maximum load and torque of insertion were measured. Max load measured in screw push out with twist lock screw was 64%, 60%, 57% of that measured with conventional screw in soft, moderate and dense material, respectively. Twist lock max load was 78% and 82% of that with conventional screw in soft and moderate densities. In the highest bone density, max loads were comparable in the two systems. Torque of insertion with twist lock was significantly lower than with conventional interference screw. Based on geometric consideration, the twist lock screw is expected to have 35% the holding power of a cylindrical screw. Yet, results indicate that holding power was greater than theoretical consideration, possibly due to lower friction and lower preloaded force. During graft push out in the densest material, comparable max loads were achieved with both systems, suggesting that fixation of higher density bone, which is observed in young athletes that require reconstruction, can be achieved with the twist lock screw. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Dynamic Torque and Vertical Force Analysis during Nickel-titanium Rotary Root Canal Preparation with Different Modes of Reciprocal Rotation.

    Science.gov (United States)

    Tokita, Daisuke; Ebihara, Arata; Nishijo, Miki; Miyara, Kana; Okiji, Takashi

    2017-10-01

    The purpose of the present study was to compare 2 modes of reciprocal movement (torque-sensitive and time-dependent reciprocal rotation) with continuous rotation in terms of torque and apical force generation during nickel-titanium rotary root canal instrumentation. A custom-made automated root canal instrumentation and torque/force analyzing device was used to prepare simulated canals in resin blocks and monitor the torque and apical force generated in the blocks during preparation. Experimental groups (n = 7, each) consisted of (1) torque-sensitive reciprocal rotation with torque-sensitive vertical movement (group TqR), (2) time-dependent reciprocal rotation with time-dependent vertical movement (group TmR), and (3) continuous rotation with time-dependent vertical movement (group CR). The canals were instrumented with TF Adaptive SM1 and SM2 rotary files (SybronEndo, Orange, CA), and the torque and apical force were measured during instrumentation with SM2. The mean and maximum torque and apical force values were statistically analyzed using 1-way analysis of variance and the Tukey test (α = 0.05). The recordings showed intermittent increases of upward apical force and clockwise torque, indicating the generation and release of screw-in forces. The maximum upward apical force values in group TmR were significantly smaller than those in group CR (P forces when compared with continuous rotation. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  17. Thermally activated helicity reversals of skyrmions

    Science.gov (United States)

    Yu, X. Z.; Shibata, K.; Koshibae, W.; Tokunaga, Y.; Kaneko, Y.; Nagai, T.; Kimoto, K.; Taguchi, Y.; Nagaosa, N.; Tokura, Y.

    2016-04-01

    Magnetic bubbles with winding number S =1 are topologically equivalent to skyrmions. Here we report the discovery of helicity (in-plane magnetization-swirling direction) reversal of skyrmions, while keeping their hexagonal lattice form, at above room temperature in a thin hexaferrite magnet. We have observed that the frequency of helicity reversals dramatically increases with temperature in a thermally activated manner, revealing that the generation energy of a kink-soliton pair for switching helicity on a skyrmion rapidly decreases towards the magnetic transition temperature.

  18. Polymorphic transformation of helical flagella of bacteria

    Science.gov (United States)

    Lim, Sookkyung; Howard Berg Collaboration; William Ko Collaboration; Yongsam Kim Collaboration; Wanho Lee Collaboration; Charles Peskin Collaboration

    2016-11-01

    Bacteria such as E. coli swim in an aqueous environment by utilizing the rotation of flagellar motors and alternate two modes of motility, runs and tumbles. Runs are steady forward swimming driven by bundles of flagellar filaments whose motors are turning CCW; tumbles involve a reorientation of the direction of swimming triggered by motor reversals. During tumbling, the helical flagellum undergoes polymorphic transformations, which is a local change in helical pitch, helical radius, and handedness. In this work, we investigate the underlying mechanism of structural conformation and how this polymorphic transition plays a role in bacterial swimming. National Science Foundation.

  19. Investigation of backfire monofilar helical antenna

    DEFF Research Database (Denmark)

    Smith, Thomas Gunst; Larsen, Niels Vesterdal; Gothelf, Ulrich Vesterager

    2011-01-01

    This paper presents a numerical investigation of the electromagnetic properties of the backfire monofilar helical antenna. The current distribution along the helical conductor, the input impedance, and the front-to-back ratio are calculated and analyzed for the backfire operation of the antenna. ....... A parametric study of the helical geometry and the resulting antenna characteristics will be described and discussed. The currents and fields are calculated using the simulation software AWAS based on the Method of Moments with a wire representation of the ground plane....

  20. Analysis of Modeling Parameters on Threaded Screws.

    Energy Technology Data Exchange (ETDEWEB)

    Vigil, Miquela S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brake, Matthew Robert [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Vangoethem, Douglas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-06-01

    Assembled mechanical systems often contain a large number of bolted connections. These bolted connections (joints) are integral aspects of the load path for structural dynamics, and, consequently, are paramount for calculating a structure's stiffness and energy dissipation prop- erties. However, analysts have not found the optimal method to model appropriately these bolted joints. The complexity of the screw geometry cause issues when generating a mesh of the model. This paper will explore different approaches to model a screw-substrate connec- tion. Model parameters such as mesh continuity, node alignment, wedge angles, and thread to body element size ratios are examined. The results of this study will give analysts a better understanding of the influences of these parameters and will aide in finding the optimal method to model bolted connections.

  1. Screw as a Bladder Foreign Body

    Directory of Open Access Journals (Sweden)

    Seyed Reza Hosseini

    2017-02-01

    Full Text Available Foreign bodies in the bladder are among the strangest differential diagnoses in the lower urinary tract symptoms (LUTS and may be missed in initial medical evaluations. We present a 63-year-old man who was visited in the emergency department because of obstructive and irritative lower urinary tract symptoms. Two months earlier, he had a pelvic fracture due to motor vehicle accident and underwent an open reduction and internal fixation of the pubic rami and right acetabulum by an anterior ilioinguinal approach. After initial evaluation, an abdominopelvic X-ray revealed a 3 cm screw in the suprapubic area. He underwent urethrocystoscopy and a 3 cm screw was extracted by forceps.

  2. Calculating Characteristics of the Screws with Constant And Variable Step

    Directory of Open Access Journals (Sweden)

    B. N. Zotov

    2015-01-01

    Full Text Available This work is devoted to creating a technique for calculating power characteristics of the screws with constant and variable step for the centrifugal pumps. The technique feature is that the reverse currents, which are observed in screws working at low flow, are numerically taken into account. The paper presents a diagram of the stream in the screw with flow to the network Q=0, and the static pressure of the screw in this mode is computed according to reverse current parameters. Maximum flow of screw is determined from the known formulas. When calculating the power characteristics and computing the overall efficiency of the screw, for the first time a volumetric efficiency of the screw is introduced. It is defined as a ratio between the flow into the network and the sum of the reverse current flows and a flow into the network. This approach allowed us to determine the efficiency of the screw over the entire range of flows.A comparison of experimental characteristics of the constant step screw with those of calculated by the proposed technique shows their good agreement.The technique is also used in calculating characteristics of the variable step screws. The variable step screw is considered as a screw consisting of two screws with a smooth transition of the blades from the inlet to the outlet. Screws in which the step at the inlet is less than that of at the outlet as well as screws with the step at the inlet being more than that of at the outlet were investigated. It is shown that a pressure of the screw with zero step and the value of the reverse currents depend only on the parameters of the input section of the screw, and the maximum flow, if the step at the inlet is more than the step at the outlet, is determined by the parameters of the output part of the screw. Otherwise, the maximum flow is determined a little bit differently.The paper compares experimental characteristics with characteristics calculated by the technique for variable step

  3. Accurate and Simple Screw Insertion Procedure With Patient-Specific Screw Guide Templates for Posterior C1-C2 Fixation.

    Science.gov (United States)

    Sugawara, Taku; Higashiyama, Naoki; Kaneyama, Shuichi; Sumi, Masatoshi

    2017-03-15

    Prospective clinical trial of the screw insertion method for posterior C1-C2 fixation utilizing the patient-specific screw guide template technique. To evaluate the efficacy of this method for insertion of C1 lateral mass screws (LMS), C2 pedicle screws (PS), and C2 laminar screws (LS). Posterior C1LMS and C2PS fixation, also known as the Goel-Harms method, can achieve immediate rigid fixation and high fusion rate, but the screw insertion carries the risk of injury to neuronal and vascular structures. Dissection of venous plexus and C2 nerve root to confirm the insertion point of the C1LMS may also cause problems. We have developed an intraoperative screw guiding method using patient-specific laminar templates. Preoperative bone images of computed tomography (CT) were analyzed using three-dimensional (3D)/multiplanar imaging software to plan the trajectories of the screws. Plastic templates with screw guiding structures were created for each lamina using 3D design and printing technology. Three types of templates were made for precise multistep guidance, and all templates were specially designed to fit and lock on the lamina during the procedure. Surgery was performed using this patient-specific screw guide template system, and placement of the screws was postoperatively evaluated using CT. Twelve patients with C1-C2 instability were treated with a total of 48 screws (24 C1LMS, 20 C2PS, 4 C2LS). Intraoperatively, each template was found to exactly fit and lock on the lamina and screw insertion was completed successfully without dissection of the venous plexus and C2 nerve root. Postoperative CT showed no cortical violation by the screws, and mean deviation of the screws from the planned trajectories was 0.70 ± 0.42 mm. The multistep, patient-specific screw guide template system is useful for intraoperative screw navigation in posterior C1-C2 fixation. This simple and economical method can improve the accuracy of screw insertion, and reduce operation time and

  4. 2D and 3D assessment of sustentaculum tali screw fixation with or without Screw Targeting Clamp.

    Science.gov (United States)

    De Boer, A Siebe; Van Lieshout, Esther M M; Vellekoop, Leonie; Knops, Simon P; Kleinrensink, Gert-Jan; Verhofstad, Michael H J

    2017-10-26

    Precise placement of sustentaculum tali screw(s) is essential for restoring anatomy and biomechanical stability of the calcaneus. This can be challenging due to the small target area and presence of neurovascular structures on the medial side. The aim was to evaluate the precision of positioning of the subchondral posterior facet screw and processus anterior calcanei screw with or without a Screw Targeting Clamp. The secondary aim was to evaluate the added value of peroperative 3D imaging over 2D radiographs alone. Twenty Anubifix™ embalmed, human anatomic lower limb specimens were used. A subchondral posterior facet screw and a processus anterior calcanei screw were placed using an extended lateral approach. A senior orthopedic trauma surgeon experienced in calcaneal fracture surgery and a senior resident with limited experience in calcaneal surgery performed screw fixation in five specimens with and in five specimens without the clamp. 2D lateral and axial radiographs and a 3D recording were obtained postoperatively. Anatomical dissection was performed postoperatively as a diagnostic golden standard in order to obtain the factual screw positions. Blinded assessment of quality of fixation was performed by two surgeons. In 2D, eight screws were considered malpositioned when placed with the targeting device versus nine placed freehand. In 3D recordings, two additional screws were malpositioned in each group as compared to the golden standard. As opposed to the senior surgeon, the senior resident seemed to get the best results using the Screw Targeting Clamp (number of malpositioned screws using freehand was eight, and using the targeting clamp five). In nine out of 20 specimens 3D images provided additional information concerning target area and intra-articular placement. Based on the 3D assessment, five additional screws would have required repositioning. Except for one, all screw positions were rated equally after dissection when compared with 3D examinations

  5. Energy saving screw compressor technology; Energiebesparende schroefcompressortechnologie

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, A. [RefComp, Lonigo (Italy); Neus, M. [Delta Technics Engineering, Breda (Netherlands)

    2011-03-15

    Smart solutions to reduce the energy consumption are continuously part of investigation in the refrigeration technology. This article subscribed the technology on which way energy can be saved at the operation of screw compressors which are used in air conditioners and refrigerating machinery. The combination of frequency control and Vi-control (intrinsic volumetric ratio) such as researched in the laboratory of RefComp is for the user attractive because the energy efficiency during part load operation is much better. Smart uses of thermodynamics, electric technology and electronic control are the basics of these applications. According to the manufacturer's information it is possible with these new generation screw compressors to save approx. 26% energy in comparison with the standard screw compressor. [Dutch] In dit artikel wordt de technologie omschreven waarmee veel energie bespaard kan worden bij schroefcompressoren die worden gebruikt in airconditioningsystemen en koel- en vriesinstallaties. De combinatie van frequentieregeling en Vi- regeling (Vi is de intrinsieke volumetrische verhouding) zoals onderzocht in het laboratorium van RefComp biedt de gebruiker veel voordelen doordat de energie-efficintie van de compressor tijdens deellast enorm wordt verbeterd. Slim gebruik van thermodynamika, elektrotechniek en elektronica vormen de basis van deze toepassing. Volgens de fabrikant kan met deze nieuwe generatie schroefcompressoren circa 26 procent op het energiegebruik tijdens deellast worden bespaard in vergelijking met de standaard serie schroefcompressoren.

  6. FACTORS AFFECTING THE ABUTMENT SCREW LOOSENING

    Directory of Open Access Journals (Sweden)

    Dimitar Kirov

    2017-03-01

    Full Text Available Aim of the study: To establish the influence of various factors upon the loosening of abutment screw. Material and Methods: The current study has analyzed the factors leading to loosening of the abutment screws implant-supported restorations. 116 patients have been examined with 234 setting implants for a period of 2 to 9 years. Factors related to the planning of implant prostheses such as area of implantation, available bone volume have been registered, as well as those related to the functional loading of dental implants. The impact of their effect has been calculated. Results: Abutment screw loosening has been registered in 6.8% of the monitored cases. Regarding the type of connection between the implant and abutment a higher prevalence has been reported in connection with an internal octagon - 4.7% compared to the conical connection - 2.1%. It was found that the type of prosthesis, bruxism, cantilevers, non-balanced occlusion, crestal bone resorption and time of this complication setting in are factors of statistically significant influence. Conclusion: It has been concluded that the optimal choice and number of implant positions, the design of prosthesis, achieving optimal occlusion as well as reporting cases of bruxism, leading to functional overload of dental implants are of particular importance in order to avoid bio-mechanical long-term complications.

  7. In vitro evaluation of force-expansion characteristics in a newly designed orthodontic expansion screw compared to conventional screws

    Directory of Open Access Journals (Sweden)

    Oshagh Morteza

    2009-01-01

    Full Text Available Objective : Expansion screws like Hyrax, Haas and other types, produce heavy interrupted forces which are unfavorable for dental movement and could be harmful to the tooth and periodontium. The other disadvantage of these screws is the need for patient cooperation for their regular activation. The purpose of this study was to design a screw and compare its force- expansion curve with other types. Materials and Methods : A new screw was designed and fabricated in the same dimension, with conventional types, with the ability of 8 mm expansion (Free wire length: 12 mm, initial compression: 4.5 mm, spring wire diameter: 0.4 mm, spring diameter: 3 mm, number of the coils: n0 ine, material: s0 tainless steel. In this in vitro study, the new screw was placed in an acrylic orthodontic appliance, and after mounting on a stone cast, the force-expansion curve was evaluated by a compression test machine and compared to other screws. Results : Force-expansion curve of designed screw had a flatter inclination compared to other screws. Generally it produced a light continuous force (two to 3.5 pounds for every 4 mm of expansion. Conclusion : In comparison with heavy and interrupted forces of other screws, the newly designed screw created light and continuous forces.

  8. Spin versus helicity in processes involving transversity

    CERN Document Server

    Mekhfi, Mustapha

    2011-01-01

    We construct the spin formalism in order to deal in a direct and natural way with processes involving transversity which are now of increasing popularity. The helicity formalism which is more appropriate for collision processes of definite helicity has been so far used also to manage processes with transversity, but at the price of computing numerous helicity amplitudes generally involving unnecessary kinematical variables.In a second step we work out the correspondence between both formalisms and retrieve in another way all results of the helicity formalism but in simpler forms.We then compute certain processes for comparison.A special process:the quark dipole magnetic moment is shown to be exclusively treated within the spin formalism as it is directly related to the transverse spin of the quark inside the baryon.

  9. Helical magnetized wiggler for synchrotron radiation laser

    CERN Document Server

    Wang Mei; Hirshfield, J L

    1999-01-01

    A helical magnetized iron wiggler has been built for a novel infrared synchrotron radiation laser (SRL) experiment. The wiggler consists of four periods of helical iron structure immersed in a solenoid field. This wiggler is to impart transverse velocity to a prebunched 6 MeV electron beam, and thus to obtain a desired high orbit pitch ratio for the SRL. Field tapering at beam entrance is considered and tested on a similar wiggler. Analytic and simulated characteristics of wigglers of this type are discussed and the performance of the fabricated wigglers is demonstrated experimentally. A 4.7 kG peak field was measured for a 6.4 mm air gap and a 5.4 cm wiggler period at a 20 kG solenoid field. The measured helical fields compare favorably with the analytical solution. This type of helical iron wigglers has the potential to be scaled to small periods with strong field amplitude.

  10. Exact solutions for helical magnetohydrodynamic equilibria

    Energy Technology Data Exchange (ETDEWEB)

    Villata, M. (Istituto di Fisica Generale, Universita di Torino, Via Pietro Giuria 1, I-10125 Torino (Italy)); Tsinganos, K. (Department of Physics, University of Crete and Research Center of Crete, GR-71409, Heraklion, Crete (Greece))

    1993-07-01

    Three novel classes of exact solutions of the generalized Grad--Shafranov equation for helically symmetric magnetohydrodynamic (MHD) equilibria are presented. The first two classes may be applied to helical MHD equilibria for plasma confined between two coaxial cylinders, while the third one to the modeling of helicoidal magnetic fields and flows in several recently observed astrophysical jets. The same solutions can be also used for the testing of sophisticated numerical codes. It is also shown that all helically symmetric MHD equilibria can be treated by the same general method which is employed to generate exact MHD solutions for systems possessing an ignorable coordinate in a system of three orthogonal basis vectors, although in the case of helical symmetry an [ital orthogonal] ignorable coordinate does not exist, contrary to what happens in the well-known cases of axial and translational symmetries.

  11. Planetary dynamos driven by helical waves - II

    Science.gov (United States)

    Davidson, P. A.; Ranjan, A.

    2015-09-01

    In most numerical simulations of the Earth's core the dynamo resides outside the tangent cylinder and may be crudely classified as being of the α2 type. In this region the flow comprises a sea of thin columnar vortices aligned with the rotation axis, taking the form of alternating cyclones and anticyclones. The dynamo is thought to be driven by these columnar vortices within which the flow is observed to be highly helical, helicity being a crucial ingredient of planetary dynamos. As noted in Davidson, one of the mysteries of this dynamo cartoon is the origin of the helicity, which is observed to be positive in the south and negative in the north. While Ekman pumping at the mantle can induce helicity in some of the overly viscous numerical simulations, it is extremely unlikely to be a significant source within planets. In this paper we return to the suggestion of Davidson that the helicity observed in the less viscous simulations owes its existence to helical wave packets, launched in and around the equatorial plane where the buoyancy flux is observed to be strong. Here we show that such wave packets act as a potent source of planetary helicity, constituting a simple, robust mechanism that yields the correct sign for h north and south of the equator. Since such a mechanism does not rely on the presence of a mantle, it can operate within both the Earth and the gas giants. Moreover, our numerical simulations show that helical wave packets dispersing from the equator produce a random sea of thin, columnar cyclone/anticyclone pairs, very like those observed in the more strongly forced dynamo simulations. We examine the local dynamics of helical wave packets dispersing from the equatorial regions, as well as the overall nature of an α2-dynamo driven by such wave packets. Our local analysis predicts the mean emf induced by helical waves, an analysis that rests on a number of simple approximations which are consistent with our numerical experiments, while our global

  12. Intrapelvic Migration of the Lag Screw in Intramedullary Nailing

    Directory of Open Access Journals (Sweden)

    Tomoya Takasago

    2014-01-01

    Full Text Available Internal fixation with intramedullary devices has gained popularity for the treatment of intertrochanteric femoral fractures, which are common injuries in the elderly. The most common complications are lag screw cut out from the femoral head and femoral fracture at the distal tip of the nail. We report here a rare complication of postoperative lag screw migration into the pelvis with no trauma. The patient was subsequently treated with lag screw removal and revision surgery with total hip arthroplasty. This case demonstrated that optimal fracture reduction and positioning of the lag screw are the most important surgical steps for decreasing the risk of medial migration of the lag screw. Furthermore, to prevent complications, careful attention should be paid to subsequent steps such as precise insertion of the set screw.

  13. Rotary radiators for reduced space powerplant temperatures

    Science.gov (United States)

    Elliott, D. G.

    If new radiator concepts can achieve radiator weights below 3 kg/sq m, nuclear space powerplants can operate at temperatures below 900 K and use stainless steel construction. Tube-and-fin or heat-pipe radiators weigh at least 5 kg/sq m because the tube walls must be thick enough to prevent or limit meteoroid punctures. However, radiators that require no meteoroid protection can be built using low-vapor-pressure liquids that can be exposed directly to space. One possible design for such a radiator is the 'rotary radiator' that uses centrifugal force to move the liquid across a thin radiating disk and uses surface tension to retain the liquid despite meteoroid punctures.

  14. Conceptual design of rotary magnetostrictive energy harvester

    Science.gov (United States)

    Park, Young-Woo; Kang, Han-Sam; Wereley, Norman M.

    2014-05-01

    This paper presents the conceptual design of a rotary magnetostrictive energy harvester (RMEH), which consists of one coil-wound Galfenol cantilever, with two PMs adhered onto the each end, and one permanent magnet (PM) array sandwiched between two wheels. Modeling and simulation are used to validate the concept. The proof-of-concept RMEH is fabricated by using the simulation results, and subjected to the experimental characterization. The experimental setup for the simulated characterization uses the motor-driven PM array to induce a forced vibration. It can be concluded that the theoretical prediction on the induced voltage agrees well with the experimental results and that induced voltage increases with rpm and with number of PMs. Future work includes optimization of RMEH performance via PM array configuration and development of prototype.

  15. Film riding seals for rotary machines

    Science.gov (United States)

    Bidkar, Rahul Anil; Sarawate, Neelesh Nandkumar; Wolfe, Christopher Edward; Ruggiero, Eric John; Raj Mohan, Vivek Raja

    2017-03-07

    A seal assembly for a rotary machine is provided. The seal assembly includes multiple sealing device segments disposed circumferentially intermediate to a stationary housing and a rotor. Each of the segments includes a shoe plate with a forward-shoe section and an aft-shoe section having one or more labyrinth teeth therebetween facing the rotor. The sealing device includes a stator interface element having a groove or slot for allowing disposal of a spline seal for preventing segment leakages. The sealing device segment also includes multiple bellow springs or flexures connected to the shoe plate and to the stator interface element. Further, the sealing device segments include a secondary seal integrated with the stator interface element at one end and positioned about the multiple bellow springs or flexures and the shoe plate at the other end.

  16. Rotary seal with improved film distribution

    Science.gov (United States)

    Dietle, Lannie Laroy; Schroeder, John Erick

    2013-10-08

    The present invention is a generally circular rotary seal that establishes sealing between relatively rotatable machine components for lubricant retention and environmental exclusion, and incorporates seal geometry that interacts with the lubricant during relative rotation to distribute a lubricant film within the dynamic sealing interface. The features of a variable inlet size, a variable dynamic lip flank slope, and a reduction in the magnitude and circumferentially oriented portion of the lubricant side interfacial contact pressure zone at the narrowest part of the lip, individually or in combination thereof, serve to maximize interfacial lubrication in severe operating conditions, and also serve to minimize lubricant shear area, seal torque, seal volume, and wear, while ensuring retrofitability into the seal grooves of existing equipment.

  17. Kinematic dynamo induced by helical waves

    OpenAIRE

    Wei, Xing

    2014-01-01

    We investigate numerically the kinematic dynamo induced by the superposition of two helical waves in a periodic box as a simplified model to understand the dynamo action in astronomical bodies. The effects of magnetic Reynolds number, wavenumber and wave frequency on the dynamo action are studied. It is found that this helical-wave dynamo is a slow dynamo. There exists an optimal wavenumber for the dynamo growth rate. A lower wave frequency facilitates the dynamo action and the oscillations o...

  18. Multiple helical modes of vortex breakdown

    DEFF Research Database (Denmark)

    Sørensen, Jens Nørkær; Naumov, I. V.; Okulov, Valery

    2011-01-01

    Experimental observations of vortex breakdown in a rotating lid-driven cavity are presented. The results show that vortex breakdown for cavities with high aspect ratios is associated with the appearance of stable helical vortex multiplets. By using results from stability theory generalizing Kelvin......’s problem on vortex polygon stability, and systematically exploring the cavity flow, we succeeded in identifying two new stable vortex breakdown states consisting of triple and quadruple helical multiplets....

  19. A rotary motor drives Flavobacterium gliding.

    Science.gov (United States)

    Shrivastava, Abhishek; Lele, Pushkar P; Berg, Howard C

    2015-02-02

    Cells of Flavobacterium johnsoniae, a rod-shaped bacterium devoid of pili or flagella, glide over glass at speeds of 2-4 μm/s [1]. Gliding is powered by a protonmotive force [2], but the machinery required for this motion is not known. Usually, cells move along straight paths, but sometimes they exhibit a reciprocal motion, attach near one pole and flip end over end, or rotate. This behavior is similar to that of a Cytophaga species described earlier [3]. Development of genetic tools for F. johnsoniae led to discovery of proteins involved in gliding [4]. These include the surface adhesin SprB that forms filaments about 160 nm long by 6 nm in diameter, which, when labeled with a fluorescent antibody [2] or a latex bead [5], are seen to move longitudinally down the length of a cell, occasionally shifting positions to the right or the left. Evidently, interaction of these filaments with a surface produces gliding. To learn more about the gliding motor, we sheared cells to reduce the number and size of SprB filaments and tethered cells to glass by adding anti-SprB antibody. Cells spun about fixed points, mostly counterclockwise, rotating at speeds of 1 Hz or more. The torques required to sustain such speeds were large, comparable to those generated by the flagellar rotary motor. However, we found that a gliding motor runs at constant speed rather than at constant torque. Now, there are three rotary motors powered by protonmotive force: the bacterial flagellar motor, the Fo ATP synthase, and the gliding motor. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Facet violation with the placement of percutaneous pedicle screws.

    Science.gov (United States)

    Patel, Rakesh D; Graziano, Gregory P; Vanderhave, Kelly L; Patel, Alpesh A; Gerling, Michael C

    2011-12-15

    Independent review and classification of therapeutic procedures performed on cadavers by surgeons blinded to purpose of study. The objective of this study is to determine the rate of facet violation with the placement of percutaneous pedicle screws. Improvements in percutaneous instrumentation and fluoroscopic imaging have led to a resurgence of percutaneous pedicle screw insertion in lumbar spine surgery in an attempt to minimize many of the complications associated with open techniques of pedicle screw placement. Rates of pedicle breech and neurologic injury resulting from percutaneous insertion are reportedly similar to those of open techniques. Postoperative pain because of impingement and instability is believed to result from violation of the facet capsule or facet joint. To the authors' knowledge, however, the rate of facet injury associated with the placement of percutaneous pedicle screws is unreported in the literature. Percutaneous pedicle screw placement was performed on 4 cadaveric specimens by 4 certified orthopedic surgeons who had clinical experience in the procedure and who were blinded to the study's purpose. The surgeons were instructed to place pedicle screws from L1-S1 using their preferred clinical techniques and a 5.5-mm screw system with which they were all familiar. All surgeons utilized 1 OEC C-arm for fluoroscopic imaging. After insertion, 2 independent spine surgeons each reviewed and classified the placement of all facet screws. A total of 48 screws were inserted and classified. The placement of 28 screws (58%) resulted in violation of facet articulation, with 8 of these screws being intra-articular. Interobserver reliability of the classification system was 100%. Percutaneous pedicle screw placement may result in a high rate of facet violation. Facet injury can be reliability classified and therefore, perhaps, easily prevented.

  1. MHD Gauge Fields: Helicities and Casimirs

    Science.gov (United States)

    Hu, Q.; Webb, G. M.; Zank, G. P.; Anco, S.

    2016-12-01

    Clebsch potential gauge field theory for magnetohydrodynamics is developed based in part on the theory of Calkin (1963). It is shown how the polarization vector P in Calkin's approach, naturally arises from the Lagrange multiplier constraint equation for Faraday's equation for the magnetic induction B, or alternatively from the magnetic vector potential form of Faraday's equation. Gauss's equation, (divergence of Bis zero), is incorporated in the variational principle by means of a Lagrange multiplier constraint. Noether's theorem, and gauge symmetries are used to derive the conservation laws for (a) magnetic helicity (b) cross helicity, (c) fluid helicity for non-magnetized fluids, and (d) a class of conservation laws associated with curl and divergence equations, which applies to Faraday's equation and Gauss's equation. The magnetic helicity conservation law is due to a gauge symmetry in MHD and not due to a fluid relabelling symmetry. The analysis is carried out for a non-barotropic gas. The cross helicity and fluid helicity conservation are nonlocal conservation laws, that reduce to local conservation laws for the case of a barotropic gas. The connections between gauge symmetries, Clebsch potentials and Casimirs are developed. It is shown that the gauge symmetry functionals in the work of Henyey (1982) satisfy the Casimir equations.

  2. A REVIEW ON HEAT TRANSFER THROUGH HELICAL COIL HEAT EXCHANGERS

    OpenAIRE

    Surendra Vishvakarma*, Sanjay Kumbhare, K. K. Thakur

    2016-01-01

    This study presents a brief review of heat transfer through helical coil heat exchangers. Helical coils of circular cross section have been used in wide variety of applications due to simplicity in manufacturing. Enhancement in heat transfer due to helical coils has been reported by many researchers. While the heat transfer characteristics of double pipe helical heat exchangers are available in the literature, there exists no published experimental or theoretical analysis of a helically coile...

  3. A Conserved Cross Helicity for Non-Barotropic MHD

    CERN Document Server

    Yahalom, A

    2016-01-01

    Cross helicity is not conserved in non-barotropic magnetohydrodynamics (MHD) (as opposed to barotropic or incompressible MHD). Here we show that variational analysis suggests a new kind of cross helicity which is conserved in the non barotropic case. The non barotropic cross helicity reduces to the standard cross helicity under barotropic assumptions. The new cross helicity is conserved even for topologies for which the variational principle does not apply.

  4. Photoelastic Analysis of the Vertebral Fixation System Using Different Screws

    Directory of Open Access Journals (Sweden)

    A. C. Shimano

    2012-04-01

    Full Text Available The purpose of this study was to compare using photoelasticity, the internal stresses produced by two types of pedicular screws (Synthes™ with three different diameters, when submitted to different pullout strengths. The fringe orders were evaluated around the screws using the Tardy compensation method. In all the models analyzed, the shear stress was calculated. Results showed that, independently of the applied load, the screw of smaller outer diameter had larger values of shear stress. According to the analysis realized, we observed that the place of highest stress was in the last thread, close to the head of the screws.

  5. Tai Chi pedicle screw placement for severe scoliosis.

    Science.gov (United States)

    Chang, Kao-Wha; Wang, Yu-Fei; Zhang, Guo-Zhi; Cheng, Ching-Wei; Chen, Hung-Yi; Leng, Xiangyang; Chen, Yin-Yu

    2012-05-01

    Retrospective. To evaluate the clinical safety and accuracy of the Tai Chi ((Equation is included in full-text article.)) technique for placing pedicle screws, without intraoperative radiographic imaging, in severe scoliotic spines. The current techniques for pedicle screw placement have a number of drawbacks in cases of severe scoliosis, including difficulty or impossibility to use, delayed operative time, requiring the presence of trained personnel for the duration of the surgery, high cost issues, increased radiation exposure, and technical challenges. No previous report has described the application of the Tai Chi pedicle screw placement technique for severe scoliosis. Between 2006 and 2008, the cases of 39 consecutive patients with severe scoliosis (Cobb angle >100 degrees) who underwent posterior correction and stabilization (from T1 to L5) using 992 transpedicular screws were examined. The mean patient age was 25.7 (range, 11 to 63) years at the time of surgery. Pedicle screws were inserted by the Tai Chi technique using anatomic landmarks and preoperative radiographs as a guide. Tai Chi drilling fully utilizes the natural anatomic and physical characteristics of pedicles and unconstrained circular force. By nature, a drill bit driven by unconstrained circular force would migrate within the pedicle along a path of least resistance, advancing along the central cancellous bone tunnel spontaneously. Accurate drilling was achieved by following the nature and sticking to the hand sensation when the drill bit broke through the cancellous bone. The total time for inserting all pedicle screws in each case was recorded. Postoperative computed tomography scans were performed to evaluate the position of the inserted pedicle screws. The screw position was classified as "in" or "out." The distance of perforation was measured. The average Cobb angle was 127 degrees (range, 100 to 153 degrees). The number of screws inserted at each level were as follows: T1 (n=10), T2 (n

  6. Rotary endodontics in primary teeth – A review

    Directory of Open Access Journals (Sweden)

    Sageena George

    2016-01-01

    Full Text Available Endodontic treatment in primary teeth can be challenging and time consuming, especially during canal preparation, which is considered one of the most important steps in root canal therapy. The conventional instrumentation technique for primary teeth remains the “gold-standard” over hand instrumentation, which makes procedures much more time consuming and adversely affects both clinicians and patients. Recently nickel–titanium (Ni–Ti rotary files have been developed for use in pediatric endodontics. Using rotary instruments for primary tooth pulpectomies is cost effective and results in fills that are consistently uniform and predictable. This article reviews the use of nickel–titanium rotary files as root canal instrumentation in primary teeth. The pulpectomy technique is described here according to different authors and the advantages and disadvantages of using rotary files are discussed.

  7. Rotary klubi tuli rannarahvale appi / Anu Jürisson

    Index Scriptorium Estoniae

    Jürisson, Anu

    2005-01-01

    Tallinna Vanalinna Rotary klubi kinkis kolmele Rannametsa perele kümme tuhat krooni jaanuaritormi kahjustuste likvideerimiseks. Klubi presidendiks on Allan Martinson, nimekirjas ka Tõnis Palts, Toomas Hendrik Ilves, Rein Kilk, Hans H. Luik, Vahur Kraft jt.

  8. Material Research of Rotary Sealing Device for Combined Cutting System

    Directory of Open Access Journals (Sweden)

    Rui Zeng

    2017-01-01

    Full Text Available In order to solve the rotary sealing problem of rotary shaft in drum shearer combined cutting system, the material and structure of combined cutting system rotary sealing device needs to be selected and designed. In the paper, the rotary sealing structure of four grades in series was designed first, and then the material of NBR-40 and PTFE 4FT-4 under the separate static and dynamic sealing tests were carried out on the combined tooth-slip-ring sealing test-bed. The tests show that the NBR-40 O-Ring with PTFE 4FT-4 tooth-slip-ring has no low-pressure leakage problem and low leakage in the sealing progress, the sealing effect of which is the best.

  9. Precision goniometer equipped with a 22-bit absolute rotary encoder.

    Science.gov (United States)

    Xiaowei, Z; Ando, M; Jidong, W

    1998-05-01

    The calibration of a compact precision goniometer equipped with a 22-bit absolute rotary encoder is presented. The goniometer is a modified Huber 410 goniometer: the diffraction angles can be coarsely generated by a stepping-motor-driven worm gear and precisely interpolated by a piezoactuator-driven tangent arm. The angular accuracy of the precision rotary stage was evaluated with an autocollimator. It was shown that the deviation from circularity of the rolling bearing utilized in the precision rotary stage restricts the angular positioning accuracy of the goniometer, and results in an angular accuracy ten times larger than the angular resolution of 0.01 arcsec. The 22-bit encoder was calibrated by an incremental rotary encoder. It became evident that the accuracy of the absolute encoder is approximately 18 bit due to systematic errors.

  10. Axial squeeze strengthen effect on rotary magneto-rheological damper

    Science.gov (United States)

    Dong, Xiaomin; Duan, Chi; Yu, Jianqiang

    2017-05-01

    Pressure is an important factor to influence the performance of an magneto-rheological (MR) apparatus. The effect of the axial squeeze strengthen effect on rotary MR damper is investigated theoretically and experimentally in this study. First, a theoretical analysis in a microscopic view is proposed. It indicates that a concentrated increment of iron particle content in the working gap results in the effect. Then, a pressure-controlled rotary MR damper with the axial squeeze strengthen effect is designed, manufactured and tested. The results show that the axial squeeze strengthen effect on rotary MR damper is remarkable for the damper with lower particle content in MR fluids. In addition, there is an optimal pressure to obtain the maximum axial squeeze strengthen effect on the rotary MR damper.

  11. Dose Rate Calculations for Rotary Mode Core Sampling Exhauster

    CERN Document Server

    Foust, D J

    2000-01-01

    This document provides the calculated estimated dose rates for three external locations on the Rotary Mode Core Sampling (RMCS) exhauster HEPA filter housing, per the request of Characterization Field Engineering.

  12. Rotary endodontics in primary teeth – A review

    Science.gov (United States)

    George, Sageena; Anandaraj, S.; Issac, Jyoti S.; John, Sheen A.; Harris, Anoop

    2015-01-01

    Endodontic treatment in primary teeth can be challenging and time consuming, especially during canal preparation, which is considered one of the most important steps in root canal therapy. The conventional instrumentation technique for primary teeth remains the “gold-standard” over hand instrumentation, which makes procedures much more time consuming and adversely affects both clinicians and patients. Recently nickel–titanium (Ni–Ti) rotary files have been developed for use in pediatric endodontics. Using rotary instruments for primary tooth pulpectomies is cost effective and results in fills that are consistently uniform and predictable. This article reviews the use of nickel–titanium rotary files as root canal instrumentation in primary teeth. The pulpectomy technique is described here according to different authors and the advantages and disadvantages of using rotary files are discussed. PMID:26792964

  13. ROTARY FURNACES FOR THERMAL PROCESSING AND DRYING OF POLYDISPERSE MATERIALS

    Directory of Open Access Journals (Sweden)

    S. L. Rovin

    2006-01-01

    Full Text Available It is shown that rotary furnaces and drying ovens are a perspective type of furnaces, allowing to solve a number of problems in conditions of flexible production and strong resources economy

  14. Finite element analysis of osteosynthesis screw fixation in the bone stock: an appropriate method for automatic screw modelling.

    Science.gov (United States)

    Wieding, Jan; Souffrant, Robert; Fritsche, Andreas; Mittelmeier, Wolfram; Bader, Rainer

    2012-01-01

    The use of finite element analysis (FEA) has grown to a more and more important method in the field of biomedical engineering and biomechanics. Although increased computational performance allows new ways to generate more complex biomechanical models, in the area of orthopaedic surgery, solid modelling of screws and drill holes represent a limitation of their use for individual cases and an increase of computational costs. To cope with these requirements, different methods for numerical screw modelling have therefore been investigated to improve its application diversity. Exemplarily, fixation was performed for stabilization of a large segmental femoral bone defect by an osteosynthesis plate. Three different numerical modelling techniques for implant fixation were used in this study, i.e. without screw modelling, screws as solid elements as well as screws as structural elements. The latter one offers the possibility to implement automatically generated screws with variable geometry on arbitrary FE models. Structural screws were parametrically generated by a Python script for the automatic generation in the FE-software Abaqus/CAE on both a tetrahedral and a hexahedral meshed femur. Accuracy of the FE models was confirmed by experimental testing using a composite femur with a segmental defect and an identical osteosynthesis plate for primary stabilisation with titanium screws. Both deflection of the femoral head and the gap alteration were measured with an optical measuring system with an accuracy of approximately 3 µm. For both screw modelling techniques a sufficient correlation of approximately 95% between numerical and experimental analysis was found. Furthermore, using structural elements for screw modelling the computational time could be reduced by 85% using hexahedral elements instead of tetrahedral elements for femur meshing. The automatically generated screw modelling offers a realistic simulation of the osteosynthesis fixation with screws in the adjacent

  15. Finite element analysis of osteosynthesis screw fixation in the bone stock: an appropriate method for automatic screw modelling.

    Directory of Open Access Journals (Sweden)

    Jan Wieding

    Full Text Available The use of finite element analysis (FEA has grown to a more and more important method in the field of biomedical engineering and biomechanics. Although increased computational performance allows new ways to generate more complex biomechanical models, in the area of orthopaedic surgery, solid modelling of screws and drill holes represent a limitation of their use for individual cases and an increase of computational costs. To cope with these requirements, different methods for numerical screw modelling have therefore been investigated to improve its application diversity. Exemplarily, fixation was performed for stabilization of a large segmental femoral bone defect by an osteosynthesis plate. Three different numerical modelling techniques for implant fixation were used in this study, i.e. without screw modelling, screws as solid elements as well as screws as structural elements. The latter one offers the possibility to implement automatically generated screws with variable geometry on arbitrary FE models. Structural screws were parametrically generated by a Python script for the automatic generation in the FE-software Abaqus/CAE on both a tetrahedral and a hexahedral meshed femur. Accuracy of the FE models was confirmed by experimental testing using a composite femur with a segmental defect and an identical osteosynthesis plate for primary stabilisation with titanium screws. Both deflection of the femoral head and the gap alteration were measured with an optical measuring system with an accuracy of approximately 3 µm. For both screw modelling techniques a sufficient correlation of approximately 95% between numerical and experimental analysis was found. Furthermore, using structural elements for screw modelling the computational time could be reduced by 85% using hexahedral elements instead of tetrahedral elements for femur meshing. The automatically generated screw modelling offers a realistic simulation of the osteosynthesis fixation with

  16. Biomechanical efficacy of monoaxial or polyaxial pedicle screw and additional screw insertion at the level of fracture, in lumbar burst fracture: An experimental study

    Directory of Open Access Journals (Sweden)

    Hongwei Wang

    2012-01-01

    Conclusions: The addition of intermediate screws at the level of a burst fracture significantly increased the stability of short-segment pedicle screw fixation in both the MPS and PPS groups. However, in short-segment fixation group, monoaxial pedicle screw exhibited more stability in flexion and extension than the polyaxial pedicle screw.

  17. Design study of a high power rotary transformer

    Science.gov (United States)

    Weinberger, S. M.

    1982-01-01

    A design study was made on a rotary transformer for transferring electrical power across a rotating spacecraft interface. The analysis was performed for a 100 KW, 20 KHz unit having a ""pancake'' geometry. The rotary transformer had a radial (vertical) gap and consisted of 4-25 KW modules. It was assumed that the power conditioning comprised of a Schwarz resonant circuit with a 20 KHz switching frequency. The rotary transformer, mechanical and structural design, heat rejection system and drive mechanism which provide a complete power transfer device were examined. The rotary transformer losses, efficiency, weight and size were compared with an axial (axial symmetric) gap transformer having the same performance requirements and input characteristics which was designed as part of a previous program. The ""pancake'' geometry results in a heavier rotary transformer primarily because of inefficient use of the core material. It is shown that the radial gap rotary transformer is a feasible approach for the transfer of electrical power across a rotating interface and can be implemented using presently available technology.

  18. Helicity in the atmospheric boundary layer

    Science.gov (United States)

    Kurgansky, Michael; Koprov, Boris; Koprov, Victor; Chkhetiani, Otto

    2017-04-01

    An overview is presented of recent direct field measurements at the Tsimlyansk Scientific Station of A.M. Obukhov Institute of Atmospheric Physics in Moscow of turbulent helicity (and potential vorticity) using four acoustic anemometers positioned, within the atmospheric surface-adjacent boundary layer, in the vertices of a rectangular tetrahedron, with an approximate 5 m distance between the anemometers and a 5.5 m elevation of the tetrahedron base above the ground surface (Koprov, Koprov, Kurgansky and Chkhetiani. Izvestiya, Atmospheric and Oceanic Physics, 2015, Vol.51, 565-575). The same ideology was applied in a later field experiment in Tsimlyansk with the tetrahedron's size of 0.7 m and variable elevation over the ground from 3.5 to 25 m. It is illustrated with examples of the statistical distribution of instantaneous (both positive and negative) turbulent helicity values. A theory is proposed that explains the measured mean turbulent helicity sign, including the sign of contribution to helicity from the horizontal and vertical velocity & vorticity components, respectively, and the sign of helicity buoyant production term. By considering a superposition of the classic Ekman spiral solution and a jet-like wind profile that mimics a shallow breeze circulation over a non-uniformly heated Earth surface, a possible explanation is provided, why the measured mean turbulent helicity sign is negative. The pronounced breeze circulation over the Tsimlyansk polygon which is located nearby the Tsimlyansk Reservoir was, indeed, observed during the measurements period. Whereas, essentially positive helicity is injected into the boundary layer from the free atmosphere in the Northern Hemisphere.

  19. Role of helicity on the anticancer mechanism of action of cationic-helical peptides.

    Science.gov (United States)

    Huang, Yi-Bing; He, Li-Yan; Jiang, Hong-Yu; Chen, Yu-Xin

    2012-01-01

    In the present study, the 26-residue amphipathic α-helical peptide A12L/A20L (Ac-KWKSFLKTFKSLKKTVLHTLLKAISS-amide) with strong anticancer activity and specificity was used as the framework to study the effects of helicity of α-helical anticancer peptides on biological activities. Helicity was systematically modulated by introducing d-amino acids to replace the original l-amino acids on the non-polar face or the polar face of the helix. Peptide helicity was measured by circular dichroism spectroscopy and was demonstrated to correlate with peptide hydrophobicity and the number of d-amino acid substitutions. Biological studies showed that strong hemolytic activity of peptides generally correlated with high hydrophobicity and helicity. Lower helicity caused the decrease of anti-HeLa activity of peptides. By introducing d-amino acids to replace the original l-amino acids on the non-polar face or the polar face of the helix, we improved the therapeutic index of A12L/A20L against HeLa cells by 9-fold and 22-fold, respectively. These results show that the helicity of anticancer peptides plays a crucial role for biological activities. This specific rational approach of peptide design could be a powerful method to improve the specificity of anticancer peptides as promising therapeutics in clinical practices.

  20. Role of Helicity on the Anticancer Mechanism of Action of Cationic-Helical Peptides

    Directory of Open Access Journals (Sweden)

    Yu-Xin Chen

    2012-06-01

    Full Text Available In the present study, the 26-residue amphipathic α-helical peptide A12L/A20L (Ac-KWKSFLKTFKSLKKTVLHTLLKAISS-amide with strong anticancer activity and specificity was used as the framework to study the effects of helicity of α-helical anticancer peptides on biological activities. Helicity was systematically modulated by introducing D-amino acids to replace the original L-amino acids on the non-polar face or the polar face of the helix. Peptide helicity was measured by circular dichroism spectroscopy and was demonstrated to correlate with peptide hydrophobicity and the number of D-amino acid substitutions. Biological studies showed that strong hemolytic activity of peptides generally correlated with high hydrophobicity and helicity. Lower helicity caused the decrease of anti-HeLa activity of peptides. By introducing D-amino acids to replace the original L-amino acids on the non-polar face or the polar face of the helix, we improved the therapeutic index of A12L/A20L against HeLa cells by 9-fold and 22-fold, respectively. These results show that the helicity of anticancer peptides plays a crucial role for biological activities. This specific rational approach of peptide design could be a powerful method to improve the specificity of anticancer peptides as promising therapeutics in clinical practices.

  1. Wet granulation in a twin-screw extruder: implications of screw design.

    Science.gov (United States)

    Thompson, M R; Sun, J

    2010-04-01

    Wet granulation in twin-screw extrusion machinery is an attractive technology for the continuous processing of pharmaceuticals. The performance of this machinery is integrally tied to its screw design yet little fundamental knowledge exists in this emerging field for granulation to intelligently create, troubleshoot, and scale-up such processes. This study endeavored to systematically examine the influence of different commercially available screw elements on the flow behavior and granulation mechanics of lactose monohydrate saturated at low concentration (5-12%, w/w) with an aqueous polyvinyl-pyrrolidone binder. The results of the work showed that current screw elements could be successfully incorporated into designs for wet granulation, to tailor the particle size as well as particle shape of an agglomerate product. Conveying elements for cohesive granular flows were shown to perform similar to their use in polymer processing, as effective transport units with low specific mechanical energy input. The conveying zones provided little significant change to the particle size or shape, though the degree of channel fill in these sections had a significant influence on the more energy-intensive mixing elements studied. The standard mixing elements for this machine, kneading blocks and comb mixers, were found to be effective for generating coarser particles, though their mechanisms of granulation differed significantly. 2009 Wiley-Liss, Inc. and the American Pharmacists Association

  2. Magnesium alloys as a biomaterial for degradable craniofacial screws.

    Science.gov (United States)

    Henderson, Sarah E; Verdelis, Konstantinos; Maiti, Spandan; Pal, Siladitya; Chung, William L; Chou, Da-Tren; Kumta, Prashant N; Almarza, Alejandro J

    2014-05-01

    Recently, magnesium (Mg) alloys have received significant attention as potential biomaterials for degradable implants, and this study was directed at evaluating the suitability of Mg for craniofacial bone screws. The objective was to implant screws fabricated from commercially available pure Mg and alloy AZ31 in vivo in a rabbit mandible. First, Mg and AZ31 screws were compared to stainless steel screws in an in vitro pull-out test and determined to have a similar holding strength (∼40N). A finite-element model of the screw was created using the pull-out test data, and this model can be used for future Mg alloy screw design. Then, Mg and AZ31 screws were implanted for 4, 8 and 12weeks, with two controls of an osteotomy site (hole) with no implant and a stainless steel screw implanted for 12weeks. Microcomputed tomography was used to assess bone remodeling and Mg/AZ31 degradation, both visually and qualitatively through volume fraction measurements for all time points. Histological analysis was also completed for the Mg and AZ31 at 12weeks. The results showed that craniofacial bone remodeling occurred around both Mg and AZ31 screws. Pure Mg had a different degradation profile than AZ31; however, bone growth occurred around both screw types. The degradation rate of both Mg and AZ31 screws in the bone marrow space and the muscle were faster than in the cortical bone space at 12weeks. Furthermore, it was shown that by alloying Mg, the degradation profile could be changed. These results indicate the promise of using Mg alloys for craniofacial applications. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  3. Are pedicular screws and lateral hook screws more resistant against pullout than conventional spinal hooks and screws in terminal vertebral segment fixation?

    Science.gov (United States)

    Karakaşlı, Ahmet; Sekik, Eyad; Karaarslan, Ahmet; Kızmazoğlu, Ceren; Havıtçıoğlu, Hasan

    2016-01-01

    This study aims to biomechanically evaluate and compare four well-known types of terminal spinal constructs to a novel construct composed of a transpedicular screw with a lateral hook screw in terms of axial pullout strength in terminal vertebral segment fixation. Forty fresh-frozen lamb spines were divided into five groups with eight spines each. To stabilize the transverse process, a pedicular screw alone was used in group 1, a sublaminar hook alone was used in group 2, a sublaminar hook and a pedicular screw were used in group 3, claw hook alone was used in group 4, and a pedicular screw with a lateral hook screw was used in group 5. Biomechanical tests were performed using an axial compression testing machine and two noncontact camera systems. The mean pullout strength value was 927 N for group 1, 626 N for group 2, 988 N for group 3, 972 N for group 4, and 1194 N for group 5. Pullout strength values were statistically significantly higher in groups 3 and 4 compared to groups 1 and 2. There was no statistically significant difference between groups 3 and 4. Pullout strength value of group 5 was statistically significantly higher than the other groups. Pedicular screw with a lateral hook screw had the highest fixation value. Lateral hook screw may assist to prevent pullout in patients with pullout risk and hyperkyphosis and after hyperkyphosis surgery. Further prospective clinical studies are needed to show the benefit of such a construct in reducing the risk of distal instrumentation pullout.

  4. TESTING OF THE DUAL ROTARY FILTER SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Herman, D.; Fowley, M.; Stefanko, D.

    2011-08-29

    The Savannah River National Laboratory (SRNL) installed and tested two hydraulically connected SpinTek rotary microfilter (RMF) units to determine the behavior of a multiple filter system. Both units were successfully controlled by a control scheme written in DELTA-V architecture by Savannah River Remediation (SRR) Process Control Engineering personnel. The control system was tuned to provide satisfactory response to changing conditions during the operation of the multi-filter system. Stability was maintained through the startup and shutdown of one of the filter units while the second was still in operation. The installation configuration originally proposed by the Small Colum Ion Exchange (SCIX) project of independent filter and motor mountings may be susceptible to vibration. Significant stiffening of the filter and motor mounts was required to minimize the vibration. Alignment of the motor to the filter was a challenge in this test configuration. The deployment configuration must be easy to manipulate and allow for fine adjustment. An analysis of the vibration signature of the test system identified critical speeds. Whether it corresponds to the resonance frequency of a rotor radial vibration mode that was excited by rotor unbalance is uncertain based upon the measurements. A relative motion series should be completed on the filter with the final shaft configuration to determine if the resonances exist in the final filter design. The instrumentation selected for deployment, including the concentrate discharge control valve and flow meters, performed well. Automation of the valve control integrated well with the control scheme and when used in concert with the other control variables, allowed automated control of the dual RMF system. The one area of concern with the instrumentation was the condition resulting when the filtrate flow meter operated with less than three gpm. This low flow was at the lower range of performance for the flow meter. This should not be

  5. A Comparison of Apical Bacterial Extrusion in Manual, ProTaper Rotary, and One Shape Rotary Instrumentation Techniques.

    Science.gov (United States)

    Mittal, Rakesh; Singla, Meenu G; Garg, Ashima; Dhawan, Anu

    2015-12-01

    Apical extrusion of irrigants and debris is an inherent limitation associated with cleaning and shaping of root canals and has been studied extensively because of its clinical relevance as a cause of flare-ups. Many factors affect the amount of extruded intracanal materials. The purpose of this study was to assess the bacterial extrusion by using manual, multiple-file continuous rotary system (ProTaper) and single-file continuous rotary system (One Shape). Forty-two human mandibular premolars were inoculated with Enterococcus faecalis by using a bacterial extrusion model. The teeth were divided into 3 experimental groups (n = 12) and 1 control group (n = 6). The root canals of experimental groups were instrumented according to the manufacturers' instructions by using manual technique, ProTaper rotary system, or One Shape rotary system. Sterilized saline was used as an irrigant, and bacterial extrusion was quantified as colony-forming units/milliliter. The results obtained were statistically analyzed by using one-way analysis of variance for intergroup comparison and post hoc Tukey test for pair-wise comparison. The level for accepting statistical significance was set at P rotary extruded significantly more bacteria than One Shape rotary system (P < .05). The engine-driven nickel-titanium systems were associated with less apical extrusion. The instrument design may play a role in amount of extrusion. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  6. Percussive Augmenter of Rotary Drills for Operating as a Rotary-Hammer Drill

    Science.gov (United States)

    Aldrich, Jack Barron (Inventor); Bar-Cohen, Yoseph (Inventor); Sherrit, Stewart (Inventor); Badescu, Mircea (Inventor); Bao, Xiaoqi (Inventor); Scott, James Samson (Inventor)

    2014-01-01

    A percussive augmenter bit includes a connection shaft for mounting the bit onto a rotary drill. In a first modality, an actuator percussively drives the bit, and an electric slip-ring provides power to the actuator while being rotated by the drill. Hammering action from the actuator and rotation from the drill are applied directly to material being drilled. In a second modality, a percussive augmenter includes an actuator that operates as a hammering mechanism that drives a free mass into the bit creating stress pulses that fracture material that is in contact with the bit.

  7. Cadaveric study for ideal dorsal pedicle screw entry point

    Directory of Open Access Journals (Sweden)

    Sandeep Sonone

    2017-01-01

    Conclusion: We conclude that the ideal pedicle entry point described here should be considered by surgeons during thoracic pedicle screw instrumentation. The notch at the base of the superior articular process will always remain constant and therefore an important anatomical landmark in guiding the screw toward the entry of the pedicle.

  8. Determination of the of rate cross slip of screw dislocations

    DEFF Research Database (Denmark)

    Vegge, Tejs; Rasmussen, Torben; Leffers, Torben

    2000-01-01

    The rate for cross slip of screw dislocations during annihilation of screw dipoles in copper is determined by molecular dynamics simulations. The temperature dependence of the rate is seen to obey an Arrhenius behavior in the investigated temperature range: 225-375 K. The activation energy...

  9. (TAD) in Dynamic Hip Screw (DHS) Fixation of Femoral Fractures

    African Journals Online (AJOL)

    Femoral neck fractures commonly occur in elderly osteoporotic females, and include extra-capsular fractures (intertrochanteric and pertrochanteric), and usually treated with the Dynamic Hip Screw (DHS). This is based on tension band principle which allows the screw to slide within the barrel to enable compression of the ...

  10. Technical Note: Comparative Effects of Screw Press for Honey ...

    African Journals Online (AJOL)

    Honey extraction is the removal of honey from the honey bearing combs. Different local methods of honey extraction, their strengths and weaknesses were discussed. A screw press was fabricated to facilitate honey extraction. The fabricated screw honey extractor is good alternative to the existing methods of extraction.

  11. Electromagnetic Lead Screw for Potential Wave Energy Application

    DEFF Research Database (Denmark)

    Lu, Kaiyuan; Wu, Weimin

    2014-01-01

    This paper presents a new type electromagnetic lead screw (EMLS) intended for wave energy application. Similar to the mechanical lead screw, this electromagnetic version can transfer slow linear motion to high-rotational motion, offering gearing effects. Compared with the existing pure magnetic...

  12. Bone impregnated hip screw in femoral neck fracture Clinicoradiological results

    Directory of Open Access Journals (Sweden)

    P K Sundar Raj

    2015-01-01

    Full Text Available Background: Femoral neck fractures are treated either by internal fixation or arthroplasty. Usually, cannulated cancellous screws are used for osteosynthesis of fracture neck of femur. The bone impregnated hip screw (BIHS is an alternative implant, where osteosyntehsis is required in femoral neck fracture. Materials and Methods: The BIHS is a hollow screw with thread diameter 8.3 mm, shank diameter 6.5 mm and wall thickness 2.2 mm and holes in the shaft of the screw with diameter 2 mm, placed in a staggered fashion. Biomechanical and animal experimental studies were done. Clinical study was done in two phases: Phase 1 in a group of volunteers, only with BIHS was used in a pilot study and phase 2 comparative study was done in a group with AO cannulated screws and the other group treated with BIHS. Results: In the phase 1 study, out of 15 patients, only one patient had delayed union. In phase 2, there were 78 patients, 44 patients in BIHS showed early union, compared to the rest 34 cases of AO cannulated screws Out of 44 patients with BIHS, 41 patients had an excellent outcome, 2 had nonunions and one implant breakage was noted. Conclusions: Bone impregnated hip screw has shown to provide early solid union since it incorporates the biomechanical principles and also increases the osteogenic potential and hence, found superior to conventional cannulated cancellous screw.

  13. Performance of Screw Compressor for Small-Capacity Helium Refrigerators

    Science.gov (United States)

    Urashin, Masayuki; Matsubara, Katsumi; Izunaga, Yasushi

    A helium compressor is one of the important components comprising a cryogenic refrigerator. The purpous of this investigation is to develop a new small-capacity helium screw compressor. The performance of a single-stage compressor at high compression ratio and the cooling performance of the compressor are investigated. A semi-hermetic screw compressor with new profile screw rotors, with which high performance can be obtained, is utilized in this investigation. Lubricating oil is applied to cool the compressor motor and the compressed gas. As a result, an overall isentropic efficiency of 80% is obtained when helium is compressed to a compression ratio of 19.8 with a single-stage screw compressor. At the same time, the temperature of a compressor motor and discharge gas can be maintained at low levels. Therefore, it is found that a single-stage screw compressor can compress helium to high compression ratio.

  14. A four lumen screwing device for multiparametric brain monitoring.

    Science.gov (United States)

    Feuerstein, T H; Langemann, H; Gratzl, O; Mendelowitsch, A

    2000-01-01

    We describe multiparametric monitoring in severe head trauma using a new screwing device. Our aim was to create a screw which would make the implantation of the probes and thus multiparametric monitoring easier. The new screw allows us to implant 3 probes (microdialysis, Paratrend and an intracranial pressure device) through one burr hole. The screw has four channels, the fourth being for ventricular drainage. We monitored 13 patients with severe head trauma (GCS = 3-8) for up to 7 days. Brain tissue pO2, pCO2, pH, and temperature were measured on-line with the Paratrend 7 machine. The microdialytic parameters glucose, lactate, pyruvate and glutamate were determined semi on-line with a CMA 600 enzymatic analyser. There were no complications in any of the patients that could be ascribed to the screw.

  15. The Analysis of Soil Resistance During Screw Displacement Pile Installation

    Directory of Open Access Journals (Sweden)

    Krasinski Adam

    2015-02-01

    Full Text Available The application of screw displacement piles (SDP is still increasing due to their high efficiency and many advantages. However, one technological problem is a serious disadvantage of those piles. It relates to the generation of very high soil resistance during screw auger penetration, especially when piles are installed in non-cohesive soils. In many situations this problem causes difficulties in creating piles of designed length and diameter. It is necessary to find a proper method for prediction of soil resistance during screw pile installation. The analysis of screw resistances based on model and field tests is presented in the paper. The investigations were carried out as part of research project, financed by the Polish Ministry of Science and Higher Education. As a result of tests and analyses the empirical method for prediction of rotation resistance (torque during screw auger penetration in non-cohesive subsoil based on CPT is proposed.

  16. Intermaxillary Fixation Screw Morbidity in Treatment of Mandibular Fractures

    DEFF Research Database (Denmark)

    Florescu, Vlad-Andrei; Kofod, Thomas; Pinholt, E. M.

    2016-01-01

    Purpose The aim of the present retrospective study was to investigate the morbidity of screws used for intermaxillary fixation (IMF) in the treatment of mandibular fractures. A review of the published data was also performed for a comparison of outcomes. Our hypothesis was that the use of screws...... for IMF of mandibular fractures would result in minimal morbidity. Materials and Methods Patients treated for mandibular fractures from 2007 to 2013, using screws for IMF, using the international diagnosis code for mandibular fracture, DS026, were anonymously selected (Department of Oral and Maxillofacial...... retrospective study have shown that the use of screws is a valid choice for IMF in mandibular fracture treatment with minimal morbidity. The 793 screws used for IMF resulted in a negligible amount of central and peripheral tooth root trauma. © 2016 American Association of Oral and Maxillofacial Surgeons...

  17. Metallofoldamers supramolecular architectures from helicates to biomimetics

    CERN Document Server

    Maayan, Galia

    2013-01-01

    Metallofoldamers are oligomers that fold into three-dimensional structures in a controlled manner upon coordination with metal ions. Molecules in this class have shown an impressive ability to form single-handed helical structures and other three-dimensional architectures. Several metallofoldamers have been applied as sensors due to their selective folding when binding to a specific metal ion, while others show promise for applications as responsive materials on the basis of their ability to fold and unfold upon changes in the oxidation state of the coordinated metal ion, and as novel catalysts. Metallofoldamers: From Helicates to Biomimetic Architectures describes the variety of interactions between oligomers and metal species, with a focus on non-natural synthetic molecules. Topics covered include: the major classes of foldamers and their folding driving force metalloproteins and metalloenzymes helicates: self-assembly, structure and applications abiotic metallo-DNA metallo-PNA and iDNA metallopeptides inte...

  18. Trefoil knot timescales for reconnection and helicity

    Science.gov (United States)

    Kerr, Robert M.

    2018-02-01

    Three-dimensional images of evolving numerical trefoil vortex knots are used to study the growth and decay of the enstrophy and helicity. Negative helicity density (hpreserved through the first reconnection, as suggested theoretically (Laing et al 2015 Sci. Rep. 5 9224) and observed experimentally (Scheeler et al 2014a Proc. Natl Acad. Sci. 111 15350–5). Next, to maintain the growth of the enstrophy and positive helicity within the trefoil while { H } is preserved, hgood correspondence between the evolution of the simulated vortices and the reconnecting experimental trefoil of Kleckner and Irvine (2017 Nat. Phys. 9 253–8) when time is scaled by their respective nonlinear timescales t f . The timescales t f are based upon by the radii r f of the trefoils and their circulations Γ, so long as the strong camber of the experimental hydrofoil models is used to correct the published experimental circulations Γ that use only the flat-plate approximation.

  19. Lateral Movement of Screw Dislocations During Homoepitaxial Growth and Devices Yielded Therefrom Free of the Detrimental Effects of Screw Dislocations

    Science.gov (United States)

    Neudeck, Philip G. (Inventor); Powell, J. Anthony (Inventor)

    2004-01-01

    The present invention is related to a method that enables and improves wide bandgap homoepitaxial layers to be grown on axis single crystal substrates, particularly SiC. The lateral positions of the screw dislocations in epitaxial layers are predetermined instead of random, which allows devices to be reproducibly patterned to avoid performance degrading crystal defects normally created by screw dislocations.

  20. Reaction force of percussive corer, rotary-friction corer, and rotary-percussive corer

    Science.gov (United States)

    Chang, Zensheu; Sherrit, Stewart; Badescu, Mircea; Bao, Xiaoqi; Bar-Cohen, Yoseph; Backes, Paul

    2006-01-01

    Future NASA exploration missions will increasingly require sampling, in-situ analysis and possibly the return of material to Earth for laboratory analysis. To address these objective, effective and optimized drilling techniques are needed. This requires developing comprehensive tools to be able to determine analytically what takes place during the operation and what are the control parameters that can be enhanced. In this study, three types of coring techniques were studied and were identified as potential candidates for operation from a possible future Mars Sample Return (MSR) mission rover. These techniques include percussive, rotary-friction, and rotary-percussive coring. Theoretical models were developed to predict the dynamic reaction forces transmitted from these three types of corers to the robotic arms that hold them. The predicted reaction forces will then be used in a dynamic simulation environment to simulate a representative corer tool to obtain a best estimate of a tool that can be operated from a small rover. The predicted dynamic reaction forces will be presented in this paper.

  1. Biomechanical Testing of Unstable Slipped Capital Femoral Epiphysis Screw Fixation: Worth the Risk of a Second Screw?

    Science.gov (United States)

    Schmitz, Matthew R; Farnsworth, Christine L; Doan, Joshua D; Glaser, Diana A; Scannell, Brian P; Edmonds, Eric W

    2015-01-01

    In a prior biomechanical study, 2-screw fixation of anatomically reduced slipped capital femoral epiphysis (SCFE) demonstrated marginally greater stability than single-screw fixation. However, the authors judged the benefits of a second screw to be minimal compared with the additional complication risk. A similar evaluation of fixation stability in unstable moderately displaced SCFE is performed. SCFE model: Transverse periosteal incision and epiphyseal separation from the metaphysis by leveraging in 25-month-old porcine femurs. Four groups were evaluated: pinned (3.5 mm cortex screws; Synthes, Monument, CO) with no displacement (1 screw=group N1; 2 screws=group N2) or with moderate posterior-inferior displacement of 50% of the epiphyseal diameter (1 screw=group D1; 2 screws=group D2). Biomechanical testing: Cyclical shear forces (40 to 200 N, 1 Hz) were applied along the physeal plane. Maximum load increased by 100 N every 500 cycles until failure (epiphyseal translation greater than one third the epiphyseal diameter). Force cycles (the sum of the maximum cycle loads) and number of cycles to failure were reported. A sample from each D1 and D2 had fixation problems (D1, D2: n=4; N1, N2: n=5). One D1 failed through the femoral neck; all others failed through the epiphysis. The data showed nonsignificant trends of greater force cycles for nondisplaced over displaced (P=0.13) and for 2 screws over 1 (P=0.19). Number of cycles to failure showed similar trends, with no significant differences between nondisplaced and displaced (P=0.10) and screw number (P=0.13). Force cycles were significantly greater in the N2 group than in the D1 group. A trend toward higher force cycles to failure in nondisplaced and 2-screw groups was observed. Higher force cycles correspond to greater physeal stability and thus decreased risk for subsequent displacement. Within displacement groups, adding a second screw did not significantly increase stability. Reduction of displaced SCFE also did

  2. A COMPARISON OF PULLOUT STRENGTH OF PEDICULAR SCREWS BETWEEN DIFFERENT METHODS OF SCREW INSERTION IN POSTERIOR FIXATION OF THORACIC SPINE

    Directory of Open Access Journals (Sweden)

    P Habib-Allah -Zadeh

    2008-12-01

    Full Text Available "nPedicle screws provide rigid fixation for instabilities in the lumbar and lumbosacral spine. Anatomical consideration and potential risk of neurologic complications are the reasons to hesitate using pedicle screws in the thoracic spine. Twenty moulages similar to human vertebrae were instrumented with Cotrel-Dubousset (CD system pedicle screw by intratransverse process, extrapedicular and intrapedicular methods and pullout strength was measured. There was statistically significant difference between three techniques. By increasing the length of screw in any method, pullout strength increased. Average pullout strength in extrapedicular technique was less than two other techniques in dynamic state. The strongest technique for screw placement was intratransverse process technique. It seems that intratransverse process technique is safe for posterior fixation of spine.

  3. The comparison of clinical outcome of fresh type II odontoid fracture treatment between anterior cannulated screws fixation and posterior instrumentation of C1-2 without fusion: a retrospective cohort study.

    Science.gov (United States)

    Yuan, Suomao; Wei, Bin; Tian, Yonghao; Yan, Jun; Xu, Wanlong; Wang, Lianlei; Liu, Xinyu

    2018-01-08

    Recently, the excellent outcomes of temporary fixation of C1-2 without fusion in the treatment of odontoid fracture had been reported. It is still unclear if this technique could achieve the equivalent outcomes as the golden standard technique of anterior screw fixation. The objective of this study is to compare the clinical outcome of two treatments of fresh type II odontoid fracture: anterior cannulated screws fixation (ACSF) versus posterior instrumentation of C1-2 without fusion (PIWF). This is a retrospective study. This series included 28 males and 8 females, and the mean age was 41.5 years (range, 22 to 70 years). Eleven patients were treated with ACSF, and 25 patients with PIWF. For PIWF, the implants were removed after fracture union was confirmed at 0.75~1.5 years later. All patients underwent preoperative and serial postoperative clinical examinations at approximately 3 months, 6 months, and annually thereafter. The neck disability index (NDI) was used to assess the neck discomfort caused by the operation. The range of rotary motion was evaluated at each visit. All fractures were reassessed postoperatively with serial X-films and CT scans of the cervical spine at each follow-up visit, to evaluate screw position, fracture alignment, and fusion status. All patients achieved immediate spinal stabilization after surgery, and none experienced neurologic deterioration. The follow-up periods ranged from 24 to 60 months. The average range of neck rotation was dramatically lost in PIWF after fixation (46° and 89° respectively in ACSF and PIWF), and recovered to 83° after the implant was removed. The NDI in PIWF was statistically higher than that in ACSF (5 and 13% respectively in ACSF and PIWF) after the first operation and decreased to 8% 1 year after the secondary operation. The fusion rates were 90.9 and 96% respectively in ACSF and PIWF. Both groups had a case of fracture non-union. For fresh type II odontoid fractures, high rate of fracture union can be

  4. The biomechanics of pedicle screw augmentation with cement.

    Science.gov (United States)

    Elder, Benjamin D; Lo, Sheng-Fu L; Holmes, Christina; Goodwin, Courtney R; Kosztowski, Thomas A; Lina, Ioan A; Locke, John E; Witham, Timothy F

    2015-06-01

    A persistent challenge in spine surgery is improving screw fixation in patients with poor bone quality. Augmenting pedicle screw fixation with cement appears to be a promising approach. The purpose of this study was to survey the literature and assess the previous biomechanical studies on pedicle screw augmentation with cement to provide in-depth discussions of the biomechanical benefits of multiple parameters in screw augmentation. This is a systematic literature review. A search of Medline was performed, combining search terms of pedicle screw, augmentation, vertebroplasty, kyphoplasty, polymethylmethacrylate, calcium phosphate, or calcium sulfate. The retrieved articles and their references were reviewed, and articles dealing with biomechanical testing were included in this article. Polymethylmethacrylate is an effective material for enhancing pedicle screw fixation in both osteoporosis and revision spine surgery models. Several other calcium ceramics also appear promising, although further work is needed in material development. Although fenestrated screw delivery appears to have some benefits, it results in similar screw fixation to prefilling the cement with a solid screw. Some differences in screw biomechanics were noted with varying cement volume and curing time, and some benefits from a kyphoplasty approach over a vertebroplasty approach have been noted. Additionally, in cadaveric models, cemented-augmented screws were able to be removed, albeit at higher extraction torques, without catastrophic damage to the vertebral body. However, there is a risk of cement extravasation leading to potentially neurological or cardiovascular complications with cement use. A major limitation of these reviewed studies is that biomechanical tests were generally performed at screw implantation or after a limited cyclic loading cycle; thus, the results may not be entirely clinically applicable. This is particularly true in the case of the bioactive calcium ceramics, as these

  5. Sterilization of rotary NiTi instruments within endodontic sponges.

    Science.gov (United States)

    Chan, H W A; Tan, K H; Dashper, S G; Reynolds, E C; Parashos, P

    2015-08-17

    To determine whether the following can be sterilized by autoclaving - endodontic sponges, rotary nickel-titanium (NiTi) instruments within endodontic sponges, and rotary NiTi instruments with rubber stoppers. Sixty-four samples of eight different endodontic sponges (n = 512) were placed into brain heart infusion broth (BHI) for 72 h. An aliquot of this was then spread onto horse blood agar and cultured aerobically and anaerobically to test sterility at purchase. Bacterial suspensions of Enterococcus faecalis, Porphyromonas gingivalis and Geobacillus stearothermophilus in BHI were used to contaminate sterile sponges and rotary NiTi instruments (with and without rubber stoppers) inserted into sponges. The various samples were autoclaved and then cultured aerobically and anaerobically. Success of sterilization was measured qualitatively as no growth. The experiment was repeated with clinically used rotary NiTi instruments (n = 512). All experiments were conducted in quadruplicate. No sponges on purchase had microbial growth when anaerobically cultured but some did when aerobically cultured. All autoclaved sponges and instruments (within or without sponges, and with or without rubber stoppers) were associated with no microbial growth. All nonautoclaved positive control samples showed microbial growth. Autoclaving was effective in the sterilization of sponges and endodontic instruments. Endodontic sponges should be autoclaved before clinical use. For clinical efficiency and cost-effectiveness, rotary NiTi instruments can be sterilized in endodontic sponges without removal of rubber stoppers. © 2015 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  6. Planar Rotary Piezoelectric Motor Using Ultrasonic Horns

    Science.gov (United States)

    Sherrit, Stewart; Bao, Xiaoqi; Badescu, Mircea; Bar-Cohen, Yoseph; Geiyer, Daniel; Ostlund, Patrick N.; Allen, Phillip

    2011-01-01

    A motor involves a simple design that can be embedded into a plate structure by incorporating ultrasonic horn actuators into the plate. The piezoelectric material that is integrated into the horns is pre-stressed with flexures. Piezoelectric actuators are attractive for their ability to generate precision high strokes, torques, and forces while operating under relatively harsh conditions (temperatures at single-digit K to as high as 1,273 K). Electromagnetic motors (EM) typically have high rotational speed and low torque. In order to produce a useful torque, these motors are geared down to reduce the speed and increase the torque. This gearing adds mass and reduces the efficiency of the EM. Piezoelectric motors can be designed with high torques and lower speeds directly without the need for gears. Designs were developed for producing rotary motion based on the Barth concept of an ultrasonic horn driving a rotor. This idea was extended to a linear motor design by having the horns drive a slider. The unique feature of these motors is that they can be designed in a monolithic planar structure. The design is a unidirectional motor, which is driven by eight horn actuators, that rotates in the clockwise direction. There are two sets of flexures. The flexures around the piezoelectric material are pre-stress flexures and they pre-load the piezoelectric disks to maintain their being operated under compression when electric field is applied. The other set of flexures is a mounting flexure that attaches to the horn at the nodal point and can be designed to generate a normal force between the horn tip and the rotor so that to first order it operates independently and compensates for the wear between the horn and the rotor.

  7. Analysis of the dynamic characteristics of gas chamber in rotary hammer

    National Research Council Canada - National Science Library

    YAN, Shiwei; HUANG, Shangyu; ZOU, Fangli

    2016-01-01

    Rotary hammer is a high-frequency impact machine with a complicated gas chamber. The design parameters of the gas chamber are dominating to impact energy output and impact efficiency of a rotary hammer...

  8. Positioning of pedicle screws in adolescent idiopathic scoliosis using electromyography

    Directory of Open Access Journals (Sweden)

    Bruno Moreira Gavassi

    2015-06-01

    Full Text Available OBJECTIVE: To analyze the occurrence of poor positioning of pedicle screws inserted with the aid of intraoperative electromyographic stimulation in the treatment of Adolescent Idiopathic Scoliosis (AIS.METHODS: This is a prospective observational study including all patients undergoing surgical treatment for AIS, between March and December 2013 at a single institution. All procedures were monitored by electromyography of the inserted pedicle screws. The position of the screws was evaluated by assessment of postoperative CT and classified according to the specific AIS classification system.RESULTS: Sixteen patients were included in the study, totalizing 281 instrumented pedicles (17.5 per patient. No patient had any neurological deficit or complaint after surgery. In the axial plane, 195 screws were found in ideal position (69.4% while in the sagittal plane, 226 screws were found in ideal position (80.4%. Considering both the axial and the sagittal planes, it was observed that 59.1% (166/281 of the screws did not violate any cortical wall.CONCLUSION: The use of pedicle screws proved to be a safe technique without causing neurological damage in AIS surgeries, even with the occurrence of poor positioning of some implants.

  9. The Source of Helicity in Perfluorinated N-Alkanes

    OpenAIRE

    Jang, Seung Soon; Blanco, Mario; Goddard, William A.; Caldwell, Gregg; Ross, Richard B.

    2003-01-01

    The well-known helical conformations of double stranded DNA and poly(alanine) are stabilized by inter- and intramolecular hydrogen bonds, respectively. Perfluorinated n-alkanes also exhibit stable helical conformations, with ordered chiralities at low temperatures. In the absence of hydrogen bonds, one may ask what forces stabilize perfluorinated n-alkane helices. We combine ab initio and empirical data to study the likely classical source of this helical behavior. Past studies point to bad s...

  10. Review of the helicity formalism; Revision del formalismo de helicidad

    Energy Technology Data Exchange (ETDEWEB)

    Barreiro, F.; Cerrada, M.; Fernandez, E.

    1972-07-01

    Our purpose in these notes has been to present a brief and general review of the helicity formalism. We begin by discussing Lorentz invariance, spin and helicity ideas, in section 1 . In section 2 we deal with the construction of relativistic states and scattering amplitudes in the helicity basis and we study their transformation properties under discrete symmetries. Finally we present some more sophisticated topics like kinematical singularities of helicity amplitudes, kinematical constraints and crossing relations 3, 4, 5 respectively. (Author) 8 refs.

  11. Artificial, parallel, left-handed DNA helices.

    Science.gov (United States)

    Tian, Cheng; Zhang, Chuan; Li, Xiang; Li, Yingmei; Wang, Guansong; Mao, Chengde

    2012-12-19

    This communication reports an engineered DNA architecture. It contains multiple domains of half-turn-long, standard B-DNA duplexes. While each helical domain is right-handed and its two component strands are antiparallel, the global architecture is left-handed and the two component DNA strands are oriented parallel to each other.

  12. Helical chirality induction of expanded porphyrin analogues

    Indian Academy of Sciences (India)

    Helical porphyrin analogues. 1163. References. 1. (a) Jasat A and Dolphin A 1997 Chem. Rev. 97 2267;. (b) Sessler J L, Gebauer A and Weghorn S J 2000 in The porphyrin handbook, vol. 2, K M Kadish, K M Smith,. R Guilard (eds) (San Diego: Academic Press) pp55;. (c) Sessler J L and Seidel D 2003 Angew. Chem. Int.

  13. Fermion Helicity Flip Induced by Torsion Field

    OpenAIRE

    Capozziello, S.; Iovane, G.; Lambiase, G.; Stornaiolo, C.

    1999-01-01

    We show that in theories of gravitation with torsion the helicity of fermion particles is not conserved and we calculate the probability of spin flip, which is related to the anti-symmetric part of affine connection. Some cosmological consequences are discussed.

  14. Muon Beam Helical Cooling Channel Design

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Rolland; Ankenbrandt, Charles; Flanagan, G; Kazakevich, G M; Marhauser, Frank; Neubauer, Michael; Roberts, T; Yoshikawa, C; Derbenev, Yaroslav; Morozov, Vasiliy; Kashikhin, V S; Lopes, Mattlock; Tollestrup, A; Yonehara, Katsuya; Zloblin, A

    2013-06-01

    The Helical Cooling Channel (HCC) achieves effective ionization cooling of the six-dimensional (6d) phase space of a muon beam by means of a series of 21st century inventions. In the HCC, hydrogen-pressurized RF cavities enable high RF gradients in strong external magnetic fields. The theory of the HCC, which requires a magnetic field with solenoid, helical dipole, and helical quadrupole components, demonstrates that dispersion in the gaseous hydrogen energy absorber provides effective emittance exchange to enable longitudinal ionization cooling. The 10-year development of a practical implementation of a muon-beam cooling device has involved a series of technical innovations and experiments that imply that an HCC of less than 300 m length can cool the 6d emittance of a muon beam by six orders of magnitude. We describe the design and construction plans for a prototype HCC module based on oxygen-doped hydrogen-pressurized RF cavities that are loaded with dielectric, fed by magnetrons, and operate in a superconducting helical solenoid magnet.

  15. The prediction of amphiphilic alpha-helices.

    Science.gov (United States)

    Phoenix, D A; Harris, F; Daman, O A; Wallace, J

    2002-04-01

    A number of sequence-based analyses have been developed to identify protein segments, which are able to form membrane interactive amphiphilic alpha-helices. Earlier techniques attempted to detect the characteristic periodicity in hydrophobic amino acid residues shown by these structure and included the Molecular Hydrophobic Potential (MHP), which represents the hydrophobicity of amino acid residues as lines of isopotential around the alpha-helix and analyses based on Fourier transforms. These latter analyses compare the periodicity of hydrophobic residues in a putative alpha-helical sequence with that of a test mathematical function to provide a measure of amphiphilicity using either the Amphipathic Index or the Hydrophobic Moment. More recently, the introduction of computational procedures based on techniques such as hydropathy analysis, homology modelling, multiple sequence alignments and neural networks has led to the prediction of transmembrane alpha-helices with accuracies of the order of 95% and transmembrane protein topology with accuracies greater than 75%. Statistical approaches to transmembrane protein modeling such as hidden Markov models have increased these prediction levels to an even higher level. Here, we review a number of these predictive techniques and consider problems associated with their use in the prediction of structure / function relationships, using alpha-helices from G-coupled protein receptors, penicillin binding proteins, apolipoproteins, peptide hormones, lytic peptides and tilted peptides as examples.

  16. Topological characteristics of helical repeat proteins

    NARCIS (Netherlands)

    Groves, M R; Barford, D

    The recent elucidation of protein structures based upon repeating amino acid motifs, including the armadillo motif, the HEAT motif and tetratricopeptide repeats, reveals that they belong to the class of helical repeat proteins. These proteins share the common property of being assembled from tandem

  17. The effect of screw tunnels on the biomechanical stability of vertebral body after pedicle screws removal: a finite element analysis.

    Science.gov (United States)

    Liu, Jia-Ming; Zhang, Yu; Zhou, Yang; Chen, Xuan-Yin; Huang, Shan-Hu; Hua, Zi-Kai; Liu, Zhi-Li

    2017-06-01

    Posterior reduction and pedicle screw fixation is a widely used procedure for thoracic and lumbar vertebrae fractures. Usually, the pedicle screws would be removed after the fracture healing and screw tunnels would be left. The aim of this study is to evaluate the effect of screw tunnels on the biomechanical stability of the lumbar vertebral body after pedicle screws removal by finite element analysis (FEA). First, the CT values of the screw tunnels wall in the fractured vertebral bodies were measured in patients whose pedicle screws were removed, and they were then compared with the values of vertebral cortical bone. Second, an adult patient was included and the CT images of the lumbar spine were harvested. Three dimensional finite element models of the L1 vertebra with unilateral or bilateral screw tunnels were created based on the CT images. Different compressive loads were vertically acted on the models. The maximum loads which the models sustained and the distribution of the force in the different parts of the models were recorded and compared with each other. The CT values of the tunnels wall and vertebral cortical bone were 387.126±62.342 and 399.204±53.612, which were not statistically different (P=0.149). The models of three dimensional tetrahedral mesh finite element of normal lumbar 1 vertebra were established with good geometric similarity and realistic appearance. After given the compressive loads, the cortical bone was the first one to reach its ultimate stress. The maximum loads which the bilateral screw tunnels model, unilateral screw tunnel model, and normal vertebral model can sustain were 3.97 Mpa, 3.83 Mpa, and 3.78 Mpa, respectively. For the diameter of the screw tunnels, the model with a diameter of 6.5 mm could sustain the largest load. In addition, the stress distributing on the outside of the cortical bone gradually decreased as the thickness of the tunnel wall increased. Based on the FEA, pedicle screw tunnels would not decrease the

  18. Screw Compressor Characteristics for Helium Refrigeration Systems

    Science.gov (United States)

    Ganni, V.; Knudsen, P.; Creel, J.; Arenius, D.; Casagrande, F.; Howell, M.

    2008-03-01

    The oil injected screw compressors have practically replaced all other types of compressors in modern helium refrigeration systems due to their large displacement capacity, minimal vibration, reliability and capability of handling helium's high heat of compression. At the present state of compressor system designs for helium systems, typically two-thirds of the lost input power is due to the compression system. Therefore it is important to understand the isothermal and volumetric efficiencies of these machines to help properly design these compression systems to match the refrigeration process. This presentation summarizes separate tests that have been conducted on Sullair compressors at the Superconducting Super-Collider Laboratory (SSCL) in 1993, Howden compressors at Jefferson Lab (JLab) in 2006 and Howden compressors at the Spallation Neutron Source (SNS) in 2006. This work is part of an ongoing study at JLab to understand the theoretical basis for these efficiencies and their loss mechanisms, as well as to implement practical solutions.

  19. Screw pyrolysis technology for sewage sludge treatment.

    Science.gov (United States)

    Tomasi Morgano, Marco; Leibold, Hans; Richter, Frank; Stapf, Dieter; Seifert, Helmut

    2018-03-01

    Sewage sludge quantities have grown continuously since the introduction of the European Directive (UWWTD 91/271/EEC) relating to the treatment of urban wastewater. In the present, most of the sewage sludge is combusted in single fuels incineration plants or is co-fired in waste incineration or coal power plants. The combustion of sewage sludge is a proven technology. Other treatments, such as fluidized bed gasification, were successfully adopted to produce suitable syngas for power production. Besides, the number of large wastewater treatment plants is relatively small compared to the local rural ones. Moreover, alternative technologies are arising with the main target of nutrients recovery, with a special focus on phosphorus. The aforementioned issues, i.e. the small scale (below 1MW) and the nutrients recovery, suggest that pyrolysis in screw reactors may become an attractive alternative technology for sewage sludge conversion, recovery and recycling. In this work, about 100kg of dried sewage sludge from a plant in Germany were processed at the newly developed STYX Reactor, at KIT. The reactor combines the advantages of screw reactors with the high temperature filtration, in order to produce particle and ash free vapors and condensates, respectively. Experiments were carried out at temperatures between 350°C and 500°C. The yield of the char decreased from 66.7wt.% to 53.0wt.%. The same trend was obtained for the energy yield, while the maximum pyrolysis oil yield of 13.4wt.% was obtained at 500°C. Besides mercury, the metals and the other minerals were completely retained in the char. Nitrogen and sulfur migrated from the solid to the condensate and to the gas, respectively. Based on the energy balance, a new concept for the decentral production of char as well as heat and power in an externally fired micro gas turbine showed a cogeneration efficiency up to about 40%. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Numerical modelling of pullout of helical soil nail

    Directory of Open Access Journals (Sweden)

    Saurabh Rawat

    2017-08-01

    Full Text Available An investigation into the pullout response of helical soil nail using finite element subroutine Plaxis 2D is presented. The numerical modelling of actual pullout response is achieved by axisymmetric and horizontal loading condition. The effect of varying number of helical plates, helical plate spacing and helical plate diameter is studied to understand the pullout capacity behaviour. The failure surfaces for various helical soil nail configurations and their pullout mechanisms are also analysed and discussed. The pullout capacity is found to increase with increase in number of helical plates. The helical plate spacing ratio (s/Dh and diameter ratio (Dh/Ds are found to increase the pullout only up to a critical value. The response of helical soil nail using axisymmetric finite element simulation is found similar to the uplift behaviour of helical piles and helical soil anchors. In the absence of literature regarding numerical modelling of helical soil nail, simulation results are validated with uplift responses of helical piles and soil anchors. A good agreement in their comparative study for pullout response is also observed.

  1. Modeling of high gain helical antenna for improved performance ...

    African Journals Online (AJOL)

    The modeling of High Gain Helical Antenna structure is subdivided into three sections : introduction of helical structures ,Numerical analysis, modeling and simulation based on the parameters of helical antenna. The basic foundation software for the research paper is Matlab technical computing software, the modeling were ...

  2. Design of platform for removing screws from LCD display shields

    Science.gov (United States)

    Tu, Zimei; Qin, Qin; Dou, Jianfang; Zhu, Dongdong

    2017-11-01

    Removing the screws on the sides of a shield is a necessary process in disassembling a computer LCD display. To solve this issue, a platform has been designed for removing the screws on display shields. This platform uses virtual instrument technology with LabVIEW as the development environment to design the mechanical structure with the technologies of motion control, human-computer interaction and target recognition. This platform removes the screws from the sides of the shield of an LCD display mechanically thus to guarantee follow-up separation and recycle.

  3. Modelling of porous biomass pyrolysis in screw reactor

    Science.gov (United States)

    Levin, A. A.; Kozlov, A. N.

    2017-09-01

    This paper is concerned with the development of a model of wood pyrolysis in a screw reactor as the first stage of the multistage gasification process. To prevent clinkering of particles and thermal inhomogeneities, screw-type transportation is used to transport fuel. In order to describe kinetics of pyrolysis and transport of volatiles within the wood particles and their transition to the gas phase we carried out the studies using a complex of synchronous thermal analysis. A detailed numerical modeling of pyrolyzer was performed with the Comsol Multiphysics software which makes it possible to optimize the design and operating parameters of the pyrolysis process in a screw reactor.

  4. A power recirculating test rig for ball screw endurance tests

    Directory of Open Access Journals (Sweden)

    Giberti Hermes

    2016-01-01

    Full Text Available A conceptual design of an innovative test rig for endurance tests of ball screws is presented in this paper. The test rig layout is based on the power recirculating principle and it also allows to overtake the main critical issues of the ball screw endurance tests. Among these there are the high power required to make the test, the lengthy duration of the same and the high loads between the screw and the frame that holds it. The article describes the test rig designed scheme, the kinematic expedients to be adopted in order to obtain the required performance and functionality and the sizing procedure to choose the actuation system.

  5. Noninvasive method for retrieval of broken dental implant abutment screw

    Directory of Open Access Journals (Sweden)

    Jagadish Reddy Gooty

    2014-01-01

    Full Text Available Dental implants made of titanium for replacement of missing teeth are widely used because of ease of technical procedure and high success rate, but are not free of complications and may fail. Fracturing of the prosthetic screw continues to be a problem in restorative practice and great challenge to remove the fractured screw conservatively. This case report describes and demonstrates the technique of using an ultrasonic scaler in the removal of the fracture screw fragment as a noninvasive method without damaging the hex of implants.

  6. [Positions of Sustentacular Screw in Osteosynthesis of Calcaneal Fractures: Clinical and Radiographic Study].

    Science.gov (United States)

    Pazour, J; Křivohlávek, M; Lukáš, R

    2016-01-01

    PURPOSE OF THE STUDY The aim of the study was to analyse the options for sustentacular screw placement in osteosynthesis of intra-articular fractures of the heel bone and to assess the effect of various screw positions on failure to maintain the reduction in the postoperative period. In addition, problems related to screw-end protrusion over the medial cortical bone or to screw penetration into the talocalcaneal joint were assessed. MATERIAL AND METHODS The group comprised 23 patients with a total of 25 intra-articular fractures of the heel bone treated by surgery. The procedure involved insertion of a sustentacular screw under fluoroscopic guidance. Post-operatively, screw position in the sustentacular fragment was evaluated on CT scans. During follow-up, attention was focused on the effect of screw placement on maintenance of fracture reduction, and clinical symptoms potentially associated with screw malposition were recorded. RESULTS All sustentacular screws were fixed sustentacular fragments. Seven screws (28%) were inserted in the talar shelf, seven (28%) were placed under and nine (36%) over the sustentaculum tali. Two screws penetrated into the talocalcaneal joint (8%). The end of a screw projecting by 2 mm over the medial wall of the calcaneus was found in 11 cases (44%). Two patients with screws penetrating into the talocalcaneal joint had problems. On the other hand, no clinical effect of a screw extending over the medial wall of the calcaneus was recorded. No significant association of screw position with late //delayed failure of fracture reduction was detected. DISCUSSION Although the ideal trajectory for a sustentacular screw have been defined using a model of the calcaneus, it is not easy to achieve optimal screw placement due to the complex anatomy of the calcaneus and limited possibilities of intra-operative control of screw insertion. Any sustentacular screw malposition is a potential risk factor, particularly if the screw has penetrated into the

  7. Hydrophobicity and Helicity Regulate the Antifungal Activity of 14-Helical β-Peptides

    Science.gov (United States)

    2015-01-01

    Candida albicans is one of the most prevalent fungal pathogens, causing both mucosal candidiasis and invasive candidemia. Antimicrobial peptides (AMPs), part of the human innate immune system, have been shown to exhibit antifungal activity but have not been effective as pharmaceuticals because of low activity and selectivity in physiologically relevant environments. Nevertheless, studies on α-peptide AMPs have revealed key features that can be designed into more stable structures, such as the 14-helix of β-peptide-based oligomers. Here, we report on the ways in which two of those features, hydrophobicity and helicity, govern the activity and selectivity of 14-helical β-peptides against C. albicans and human red blood cells. Our results reveal both antifungal activity and hemolysis to correlate to hydrophobicity, with intermediate levels of hydrophobicity leading to high antifungal activity and high selectivity toward C. albicans. Helical structure-forming propensity further influenced this window of selective antifungal activity, with more stable helical structures eliciting specificity for C. albicans over a broader range of hydrophobicity. Our findings also reveal cooperativity between hydrophobicity and helicity in regulating antifungal activity and specificity. The results of this study provide critical insight into the ways in which hydrophobicity and helicity govern the activity and specificity of AMPs and identify criteria that may be useful for the design of potent and selective antifungal agents. PMID:24837702

  8. Long-period helical structures and twist-grain boundary phases induced by chemical substitution in the Mn1 -x(Co,Rh ) xGe chiral magnet

    Science.gov (United States)

    Martin, N.; Deutsch, M.; Chaboussant, G.; Damay, F.; Bonville, P.; Fomicheva, L. N.; Tsvyashchenko, A. V.; Rössler, U. K.; Mirebeau, I.

    2017-07-01

    We study the evolution of helical magnetism in MnGe chiral magnet upon partial substitution of Mn for 3 d -Co and 4 d -Rh ions. At high doping levels, we observe spin helices with very long periods—more than ten times larger than in the pure compound—and sizable ordered moments. This behavior calls for a change in the energy balance of interactions leading to the stabilization of the observed magnetic structures. Strikingly, neutron scattering unambiguously shows a double periodicity in the observed spectra at x =0.5 and >0.2 for Co- and Rh-doping, respectively. In analogy with observations made in smectic liquid crystals, we suggest that it may reveal the presence of magnetic "twist grain boundary" phases, involving a dense short-range correlated network of magnetic screw dislocations. The dislocation cores are here tentatively described as smooth textures, made of nonradial double-core skyrmions.

  9. 16 CFR 1205.4 - Walk-behind rotary power mower protective shields.

    Science.gov (United States)

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Walk-behind rotary power mower protective... SAFETY ACT REGULATIONS SAFETY STANDARD FOR WALK-BEHIND POWER LAWN MOWERS The Standard § 1205.4 Walk-behind rotary power mower protective shields. (a) General requirements. Walk-behind rotary power mowers...

  10. 40 CFR 63.2263 - Initial compliance demonstration for a dry rotary dryer.

    Science.gov (United States)

    2010-07-01

    ... dry rotary dryer. 63.2263 Section 63.2263 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Initial Compliance Requirements § 63.2263 Initial compliance demonstration for a dry rotary dryer. If you operate a dry rotary dryer, you must demonstrate that your dryer processes furnish with an inlet moisture...

  11. Preliminary Design on Screw Press Model of Palm Oil Extraction Machine

    Science.gov (United States)

    Firdaus, Muhammad; Salleh, S. M.; Nawi, I.; Ngali, Z.; Siswanto, W. A.; Yusup, E. M.

    2017-01-01

    The concept of the screw press is to compress the fruit bunch between the main screw and travelling cones to extract the palm oil. Visual inspection, model development and simulation of screw press by using Solidworks 2016 and calculation of design properties were performed to support the investigation. The project aims to analyse different design of screw press which improves in reducing maintenance cost and increasing lifespan. The currently existing of screw press can endure between 500 to 900 hours and requires frequent maintenance. Different configurations have been tried in determination of best design properties in screw press. The results specify that screw press with tapered inner shaft has more total lifespan (hours) compared existing screw press. The selection of the screw press with tapered inner shaft can reduce maintenance cost and increase lifespan of the screw press.

  12. Development of Laser Propelled ``Semi-Perpetual'' Rotary Machine

    Science.gov (United States)

    Gualini, M. M.; Khan, S. A.; Zulfiqar, K.

    2006-05-01

    This paper covers the initial work oriented to develop a semi-perpetual rotary machine propelled by laser ablation propulsion. The laser is equipped with a pulse repetition frequency tuned to the rotational frequency of the flying wheel. Purpose of this work is to establish the potentiality of a self-sustained closed system capable of generating kinetic rotary energy which can be exploited for traction of vehicles and production of electrical energy at very low cost. The work presented is in process of being patented.

  13. Analysis on design and performance of a solar rotary house

    Science.gov (United States)

    Fan, Xuhong; Zhang, Zhaochang; Yang, Fan; Cao, Lilin; Xu, Jing; Yuan, Mingyang

    2017-04-01

    A solar rotary house is designed, composed of rotating main structure, fixed cylinder, rotating drive system, solar photovoltaic system and so on, to achieve 360° rotation. Thus it can change the dark and humid situation of the traditional fixed house shade. Its bearing capacity, driving force and safety are analyzed. Rotary driving force and living energy are provided by solar photovoltaic system on roofs and walls. The Phonenics, Ecotect simulation analysis conclude that the rotating house indoor has better natural ventilation effect, more uniform lighting, better the sunshine time compared with traditional houses, becoming a green, energy-saving, comfortable building model.

  14. Surfzone Monitoring Using Rotary Wing Unmanned Aerial Vehicles

    OpenAIRE

    Brouwer, Ronald L.; De Schipper, Matthiew A.; Rynne, Patrick F.; Graham, Fiona J.; Reniers, J.H.M.; MacMahan, Jamie H.

    2015-01-01

    The article of record as published may be found at http://dx.doi.org/10.1175/JTECH-D-14-00122.1 This study investigates the potential of rotary wing unmanned aerial vehicles (UAVs) to monitor the surfzone. This paper shows that these UAVs are extremely flexible surveying platforms that can gather nearcontinuous moderate spatial resolution and high temporal resolution imagery from a fixed position high above a study site. The rotary wing UAVs used in this study can fly for ;12 min ...

  15. Measurement of Tip Apex Distance and Migration of Lag Screws and Novel Blade Screw Used for the Fixation of Intertrochanteric Fractures.

    Directory of Open Access Journals (Sweden)

    Jesse Chieh-Szu Yang

    Full Text Available Fixation with a dynamic hip screw (DHS is one of the most common methods for stabilizing intertrochanteric fractures, except for unstable and reverse oblique fracture types. However, failure is often observed in osteoporotic patients whereby the lag screw effectively 'cuts out' through the weak bone. Novel anti-migration blades have been developed to be used in combination with a lag screw ('Blade Screw' to improve the fixation strength in osteoporotic intertrochanteric fractures. An in-vitro biomechanical study and a retrospective clinical study were performed to evaluate lag screw migration when using the novel Blade Screw and a traditional threaded DHS. The biomechanical study showed both the Blade Screw and DHS displayed excessive migration (≥10 mm before reaching 20,000 loading cycles in mild osteoporotic bone, but overall migration of the Blade Screw was significantly less (p ≤ 0.03. Among the patients implanted with a Blade Screw in the clinical study, there was no significant variation in screw migration at 3-months follow-up (P = 0.12. However, the patient's implanted with a DHS did display significantly greater migration (P<0.001 than those implanted with the Blade Screw. In conclusion, the Blade Screw stabilizes the bone fragments during dynamic loading so as to provide significantly greater resistance to screw migration in patients with mild osteoporosis.

  16. Rotary balance data for a typical single-engine general aviation design for an angle of attack range of 8 deg to 90 deg. 1: Low wing model C. [wind tunnel tests

    Science.gov (United States)

    Mulcay, W. J.; Rose, R. A.

    1980-01-01

    Aerodynamic characteristics obtained in a helical flow environment utilizing a rotary balance located in the Langley spin tunnel are presented in plotted form for a 1/6 scale, single engine, low wing, general aviation model (model C). The configurations tested included the basic airplane and control deflections, wing leading edge and fuselage modification devices, tail designs and airplane components. Data are presented without analysis for an angle of attack range of 8 deg to 90 deg and clockwise and counter clockwise rotations covering an omega b/2v range from 0 to .9.

  17. Characteristics of immediate and fatigue strength of a dual-threaded pedicle screw in cadaveric spines.

    Science.gov (United States)

    Brasiliense, Leonardo B C; Lazaro, Bruno C R; Reyes, Phillip M; Newcomb, Anna G U S; Turner, Joseph L; Crandall, Dennis G; Crawford, Neil R

    2013-08-01

    Novel dual-threaded screws are configured with overlapping (doubled) threads only in the proximal shaft to improve proximal cortical fixation. Tests were run to determine whether dual-threaded pedicle screws improve pullout resistance and increase fatigue endurance compared with standard pedicle screws. In vitro strength and fatigue tests were performed in human cadaveric vertebrae and in polyurethane foam test blocks. Seventeen cadaveric lumbar vertebrae (14 pedicles) and 40 test sites in foam blocks were tested. Measures for comparison between standard and dual-threaded screws were bone mineral density (BMD), screw insertion torque, ultimate pullout force, peak load at cyclic failure, and pedicular side of first cyclic failure. For each vertebral sample, dual-threaded screws were inserted in one pedicle and single-threaded screws were inserted in the opposite pedicle while recording insertion torque. In seven vertebrae, axial pullout tests were performed. In 10 vertebrae, orthogonal loads were cycled at increasing peak values until toggle exceeded threshold for failure. Insertion torque and pullout force were also recorded for screws placed in foam blocks representing healthy or osteoporotic bone porosity. In bone, screw insertion torque was 183% greater with dual-threaded than with standard screws (pscrews pulled out at 93% of the force required to pull out dual-threaded screws (p=.42). Of 10 screws, five reached toggle failure first on the standard screw side, two screws failed first on the dual-threaded side, and three screws failed on both sides during the same round of cycling. In the high-porosity foam, screw insertion torque was 60% greater with the dual-threaded screw than with the standard screw (p=.005), but 14% less with the low-porosity foam (p=.07). Pullout force was 19% less with the dual-threaded screw than with the standard screw in the high-porosity foam (p=.115), but 6% greater with the dual-threaded screw in the low-porosity foam (p=.156

  18. Ion temperature gradient modes in toroidal helical systems

    Energy Technology Data Exchange (ETDEWEB)

    Kuroda, T. [Graduate University for Advanced Studies, Toki, Gifu (Japan); Sugama, H.; Kanno, R.; Okamoto, M.

    2000-04-01

    Linear properties of ion temperature gradient (ITG) modes in helical systems are studied. The real frequency, growth rate, and eigenfunction are obtained for both stable and unstable cases by solving a kinetic integral equation with proper analytic continuation performed in the complex frequency plane. Based on the model magnetic configuration for toroidal helical systems like the Large Helical Device (LHD), dependences of the ITG mode properties on various plasma equilibrium parameters are investigated. Particularly, relative effects of {nabla}B-curvature drifts driven by the toroidicity and by the helical ripples are examined in order to compare the ITG modes in helical systems with those in tokamaks. (author)

  19. Time-Mean Helicity Distribution in Turbulent Swirling Jets

    Directory of Open Access Journals (Sweden)

    V. Tesař

    2005-01-01

    Full Text Available Helicity offers an alternative approach to investigations of the structure of turbulent flows. Knowledge of the spatial distribution of the time-mean component of helicity is the starting point. Yet very little is known even about basic cases in which Helicity plays important role, such as the case of a swirling jet. This is the subject of the present investigations, based mainly on numerical flowfield computations. The region of significantly large time-mean helicity density is found only in a rather small region reaching to several nozzle diameters downstream from the exit. The most important result is the similarity of the helicity density profiles. 

  20. Odontoid screw fixation for fresh and remote fractures

    National Research Council Canada - National Science Library

    Rao, Ganesh; Apfelbaum, Ronald I

    2005-01-01

    .... If a patient requires surgical treatment of an odontoid process fracture, the timing of treatment may affect fusion rates, particularly if direct anterior odontoid screw fixation is selected as the treatment method...

  1. Kinematic analysis of parallel manipulators by algebraic screw theory

    CERN Document Server

    Gallardo-Alvarado, Jaime

    2016-01-01

    This book reviews the fundamentals of screw theory concerned with velocity analysis of rigid-bodies, confirmed with detailed and explicit proofs. The author additionally investigates acceleration, jerk, and hyper-jerk analyses of rigid-bodies following the trend of the velocity analysis. With the material provided in this book, readers can extend the theory of screws into the kinematics of optional order of rigid-bodies. Illustrative examples and exercises to reinforce learning are provided. Of particular note, the kinematics of emblematic parallel manipulators, such as the Delta robot as well as the original Gough and Stewart platforms are revisited applying, in addition to the theory of screws, new methods devoted to simplify the corresponding forward-displacement analysis, a challenging task for most parallel manipulators. Stands as the only book devoted to the acceleration, jerk and hyper-jerk (snap) analyses of rigid-body by means of screw theory; Provides new strategies to simplify the forward kinematic...

  2. Centrifuging Step-Screw Conveyor for Regolith Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A variety of ISRU operations will utilize lunar regolith as feedstock. The proposed centrifuging step-screw conveyor concept will provide a well controlled robust,...

  3. Lumbar pedicle screw placement: Using only AP plane imaging

    Directory of Open Access Journals (Sweden)

    Anil Sethi

    2012-01-01

    Conclusion: Placement of pedicle screws under fluoroscopic guidance using AP plane imaging alone with tactile guidance is safe, fast, and reliable. However, a good understanding of the radiographic landmarks is a prerequisite.

  4. Biomechanical efficacy of monoaxial or polyaxial pedicle screw and additional screw insertion at the level of fracture, in lumbar burst fracture: An experimental study

    National Research Council Canada - National Science Library

    Wang, Hongwei; Li, Changqing; Liu, Tao; Zhao, Wei-Dong; Zhou, Yue

    2012-01-01

    Use of a pedicle screw at the level of fracture, also known as an intermediate screw, has been shown to improve clinical results in managing lumbar fracture, but there is a paucity of biomechanical...

  5. Screw driver: an unusual cause of cervical spinal cord injury

    Science.gov (United States)

    Rabiu, Taopheeq Bamidele; Aremu, Abayomi Adeniran; Amao, Olusegun Adetunji; Awoleke, Jacob Olumuyiwa

    2011-01-01

    Non-missile penetrating spinal injuries are rare. Screw driver injury, more especially to the cervical spine, represents an even rarer subset. To our knowledge, this is the first reported case from West Africa of cervical spinal cord injury from a screw driver. A middle-aged man was stabbed from the back with a screw driver. He presented with right-sided C4 Brown-Sequard syndrome with the impaling object in situ. Cervical spine x-rays showed the screw driver to have gone into the spine between the spinous processes of C4 and C5, traversing the spinal canal and lodged in the anterior part of the C4/5 intervertebral disc space. C4 and C5 laminectomies were performed and the screw driver removed under vision. The object was found to have traversed the right side of the cervical spinal cord. The dural tear was repaired. He had some neurologic improvement initially, but later declined. He died from severe pulmonary complications 2 weeks postinjury. Screw driver represents an unusual cause of non-missile penetrating cervical spinal injury. Its neurological effects and complications of the cord injury lead to significant morbidity and mortality. PMID:22679187

  6. Weyl spinors and the helicity formalism

    CERN Document Server

    Diaz-Cruz, J Lorenzo; Meza-Aldama, O; Perez, Jonathan Reyes

    2015-01-01

    In this work we give a review of the original formulation of the relativistic wave equation for particles with spin one-half. Traditionally \\`a la Dirac, it's proposed that the ``square root'' of the Klein-Gordon (K-G) equation involves a 4 component (Dirac) spinor and in the non-relativistic limit it can be written as 2 equations for two 2 component spinors. On the other hand, there exists Weyl's formalism, in which one works from the beginning with 2 component Weyl spinors, which are the fundamental objects of the helicity formalism. In this work we rederive Weyl's equations directly, starting from K-G equation. We also obtain the electromagnetic interaction through minimal coupling and we get the interaction with the magnetic moment. As an example of the use of that formalism, we calculate Compton scattering using the helicity methods.

  7. Helicity of the toroidal vortex with swirl

    CERN Document Server

    Bannikova, Elena Yu; Poslavsky, Sergey A

    2016-01-01

    On the basis of solutions of the Bragg-Hawthorne equations we discuss the helicity of thin toroidal vortices with the swirl - the orbital motion along the torus diretrix. It is shown that relationship of the helicity with circulations along the small and large linked circles - directrix and generatrix of the torus - depends on distribution of the azimuthal velocity in the core of the swirling vortex ring. In the case of non-homogeneous swirl this relationship differs from the well-known Moffat relationship - the doubled product of such circulations multiplied by the number of links. The results can be applied to vortices in planetary atmospheres and to vortex movements in the vicinity of active galactic nuclei.

  8. Vacuum systems for the ILC helical undulator

    CERN Document Server

    Malyshev, O B; Clarke, J A; Bailey, I R; Dainton, J B; Malysheva, L I; Barber, D P; Cooke, P; Baynham, E; Bradshaw, T; Brummitt, A; Carr, S; Ivanyushenkov, Y; Rochford, J; Moortgat-Pick, G A

    2007-01-01

    The International Linear Collider (ILC) positron source uses a helical undulator to generate polarized photons of ∼10MeV∼10MeV at the first harmonic. Unlike many undulators used in synchrotron radiation sources, the ILC helical undulator vacuum chamber will be bombarded by photons, generated by the undulator, with energies mostly below that of the first harmonic. Achieving the vacuum specification of ∼100nTorr∼100nTorr in a narrow chamber of 4–6mm4–6mm inner diameter, with a long length of 100–200m100–200m, makes the design of the vacuum system challenging. This article describes the vacuum specifications and calculations of the flux and energy of photons irradiating the undulator vacuum chamber and considers possible vacuum system design solutions for two cases: cryogenic and room temperature.

  9. Weaving Knotted Vector Fields with Tunable Helicity

    Science.gov (United States)

    Kedia, Hridesh; Foster, David; Dennis, Mark R.; Irvine, William T. M.

    2016-12-01

    We present a general construction of divergence-free knotted vector fields from complex scalar fields, whose closed field lines encode many kinds of knots and links, including torus knots, their cables, the figure-8 knot, and its generalizations. As finite-energy physical fields, they represent initial states for fields such as the magnetic field in a plasma, or the vorticity field in a fluid. We give a systematic procedure for calculating the vector potential, starting from complex scalar functions with knotted zero filaments, thus enabling an explicit computation of the helicity of these knotted fields. The construction can be used to generate isolated knotted flux tubes, filled by knots encoded in the lines of the vector field. Lastly, we give examples of manifestly knotted vector fields with vanishing helicity. Our results provide building blocks for analytical models and simulations alike.

  10. Laser modes with helical wave fronts

    Science.gov (United States)

    Harris, M.; Hill, C. A.; Tapster, P. R.; Vaughan, J. M.

    1994-04-01

    We report the operation of an argon-ion laser in pure (single-frequency) ``doughnut'' modes of order m=1, 2, and 3. The phase discontinuity at the center of these modes leads to striking two-beam interference patterns that clearly demonstrate the existence of a helical cophasal surface (wave front). The doughnut mode with m=1 (usually called TEM*01) displays a forking interference fringe pattern characteristic of a pure single helix. The m=2 mode shows a pattern with four extra prongs, establishing that the cophasal surface is a two-start or double helix; the m=3 mode is a triple helix with a six-extra-pronged pattern. Each pure doughnut mode is shown to have two possible states corresponding to output wave fronts of opposite helicity.

  11. Weaving Knotted Vector Fields with Tunable Helicity.

    Science.gov (United States)

    Kedia, Hridesh; Foster, David; Dennis, Mark R; Irvine, William T M

    2016-12-30

    We present a general construction of divergence-free knotted vector fields from complex scalar fields, whose closed field lines encode many kinds of knots and links, including torus knots, their cables, the figure-8 knot, and its generalizations. As finite-energy physical fields, they represent initial states for fields such as the magnetic field in a plasma, or the vorticity field in a fluid. We give a systematic procedure for calculating the vector potential, starting from complex scalar functions with knotted zero filaments, thus enabling an explicit computation of the helicity of these knotted fields. The construction can be used to generate isolated knotted flux tubes, filled by knots encoded in the lines of the vector field. Lastly, we give examples of manifestly knotted vector fields with vanishing helicity. Our results provide building blocks for analytical models and simulations alike.

  12. Pullout strength of misplaced pedicle screws in the thoracic and lumbar vertebrae - A cadaveric study

    Directory of Open Access Journals (Sweden)

    Shyam K Saraf

    2013-01-01

    Full Text Available Background: The objective of this cadaveric study was to analyze the effects of iatrogenic pedicle perforations from screw misplacement on the mean pullout strength of lower thoracic and lumbar pedicle screws. We also investigated the effect of bone mineral density (BMD, diameter of pedicle screws, and the region of spine on the pullout strength of pedicle screws. Materials and Methods: Sixty fresh human cadaveric vertebrae (D10-L2 were harvested. Dual-energy X-ray absorptiometry (DEXA scan of vertebrae was done for BMD. Titanium pedicle screws of different diameters (5.2 and 6.2 mm were inserted in the thoracic and lumbar segments after dividing the specimens into three groups: a standard pedicle screw (no cortical perforation; b screw with medial cortical perforation; and c screw with lateral cortical perforation. Finally, pullout load of pedicle screws was recorded using INSTRON Universal Testing Machine. Results: Compared with standard placement, medially misplaced screws had 9.4% greater mean pullout strength and laterally misplaced screws had 47.3% lesser mean pullout strength. The pullout strength of the 6.2 mm pedicle screws was 33% greater than that of the 5.2 mm pedicle screws. The pullout load of pedicle screws in lumbar vertebra was 13.9% greater than that in the thoracic vertebra ( P = 0.105, but it was not statistically significant. There was no significant difference between pullout loads of vertebra with different BMD ( P = 0.901. Conclusion: The mean pullout strength was less with lateral misplaced pedicle screws while medial misplaced pedicle screw had more pullout strength. The pullout load of 6.2 mm screws was greater than that of 5.2 mm pedicle screws. No significant correlation was found between bone mineral densities and the pullout strength of vertebra. Similarly, the pullout load of screw placed in thoracic and lumbar vertebrae was not significantly different.

  13. Analysis of angular heat conduction in rotary heat regenerators

    Energy Technology Data Exchange (ETDEWEB)

    Reis, M.C.; Sphaier, L.A. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Programa de Pos-Graduacao em Engenharia Mecanica. Lab. de Mecanica Teorica e Aplicada], Emails: lasphaier@mec.uff.br, marcelloreis@vm.uff.br

    2010-07-01

    Heat regenerators can be found in a considerable number of engineering applications, and are either used as pair of fixed matrices or as single rotary matrix. The thermal design of these devices is usually done considering models that rely on well-established simplifying assumptions. While most of these assumptions comprise reasonable considerations, some of them could lead to noticeable errors on some occasions. One such assumption is that there is no heat transfer between adjacent channels within the regenerator matrix. While this is quite reasonable for fixed-bed exchangers, this might not be a good choice for rotary exchangers on some occasions. Since rotary matrices can operate between two process streams presenting a large temperature difference between them, a large temperature gradient may develop within the plane normal to the flow direction, especially in the angular direction. This paper proposes a new model for simulating rotary heat regenerators, taking into account this previously unconsidered matrix heat conduction effect. A numerical solution of a test case with angular heat conduction is carried-out. With this solution, a parametric analysis is performed, showing how the effects that gradually increasing the angular heat conduction can affect the temperature distributions within the matrix and regenerator outlet. (author)

  14. Evaluation of surface characteristics of rotary nickel‑titanium ...

    African Journals Online (AJOL)

    2015-05-26

    May 26, 2015 ... stainless steel instruments.[1] NiTi instruments ... and converted back to an austenite structure by heating and cooling again. .... Effect of heat treatment on cyclic fatigue resistance, thermal behavior and microstructures of K3 NiTi rotary instruments. Acta Odontol Scand 2013;71:1656‑62. 7. Kim HC, Yum J, ...

  15. Mass transfer in rolling rotary kilns: a novel approach

    NARCIS (Netherlands)

    Heydenrych, M.D.; Greeff, P.; Heesink, Albertus B.M.; Versteeg, Geert

    2002-01-01

    A novel approach to modeling mass transfer in rotary kilns or rotating cylinders is explored. The movement of gas in the interparticle voids in the bed of the kiln is considered, where particles move concentrically with the geometry of the kiln and gas is entrained by these particles. The approach

  16. Equivalent Circuit Modeling of a Rotary Piezoelectric Motor

    DEFF Research Database (Denmark)

    El, Ghouti N.; Helbo, Jan

    2000-01-01

    In this paper, an enhanced equivalent circuit model of a rotary traveling wave piezoelectric ultrasonic motor "shinsei type USR60" is derived. The modeling is performed on the basis of an empirical approach combined with the electrical network method and some simplification assumptions about...

  17. Equivalent Circuit Modeling of a Rotary Piezoelectric Motor

    DEFF Research Database (Denmark)

    El, Ghouti N.; Helbo, Jan

    2000-01-01

    In this paper, an enhanced equivalent circuit model of a rotary traveling wave piezoelectric ultrasonic motor "shinsei type USR60" is derived. The modeling is performed on the basis of an empirical approach combined with the electrical network method and some simplification assumptions about the ...

  18. Chemically Optimizing Operational Efficiency of Molecular Rotary Motors

    NARCIS (Netherlands)

    Conyard, Jamie; Cnossen, Arjen; Browne, Wesley R.; Feringa, Ben L.; Meech, Stephen R.

    2014-01-01

    Unidirectional molecular rotary motors that harness photoinduced cis-trans (E-Z) isomerization are promising tools for the conversion of light energy to mechanical motion in nanoscale molecular machines. Considerable progress has been made in optimizing the frequency of ground-state rotation, but

  19. Fixed atlantoaxial rotary deformity with bilateral facet dislocation

    Energy Technology Data Exchange (ETDEWEB)

    El-Khoury, G.Y.; Clark, C.R.; Wroble, R.R.

    1985-03-01

    A 21-year-old patient with Down syndrome who developed rotary atlantoaxial dislocation of C1 and C2 following an upper respiratory infection is presented. Techniques for detection and quantification of this potentially serious dislocation using multidirectional tomography and computerized tomography are described.

  20. Rotary ATPases: models, machine elements and technical specifications.

    Science.gov (United States)

    Stewart, Alastair G; Sobti, Meghna; Harvey, Richard P; Stock, Daniela

    2013-01-01

    Rotary ATPases are molecular rotary motors involved in biological energy conversion. They either synthesize or hydrolyze the universal biological energy carrier adenosine triphosphate. Recent work has elucidated the general architecture and subunit compositions of all three sub-types of rotary ATPases. Composite models of the intact F-, V- and A-type ATPases have been constructed by fitting high-resolution X-ray structures of individual subunits or sub-complexes into low-resolution electron densities of the intact enzymes derived from electron cryo-microscopy. Electron cryo-tomography has provided new insights into the supra-molecular arrangement of eukaryotic ATP synthases within mitochondria and mass-spectrometry has started to identify specifically bound lipids presumed to be essential for function. Taken together these molecular snapshots show that nano-scale rotary engines have much in common with basic design principles of man made machines from the function of individual "machine elements" to the requirement of the right "fuel" and "oil" for different types of motors.

  1. Lignite chemical conversion in an indirect heat rotary kiln gasifier

    Directory of Open Access Journals (Sweden)

    Hatzilyberis Kostas S.

    2006-01-01

    Full Text Available The results on the gasification of Greek lignite using two indirect heat (allothermal pilot rotary kiln gasifiers are reported in the present work. The development of this new reactor-gasifier concept intended for solid fuels chemical conversion exploits data and experience gained from the following two pilot plants. The first unit A (about 100 kg/h raw lignite demonstrated the production of a medium heating value gas (12-13 MJ/Nm3 with quite high DAF (dry ash free coal conversions, in an indirect heat rotary gasifier under mild temperature and pressure conditions. The second unit B is a small pilot size unit (about 10 kg/h raw lignite comprises an electrically heated rotary kiln, is an operation flexible and exhibits effective phase mixing and enhanced heat transfer characteristics. Greek lignite pyrolysis and gasification data were produced from experiments performed with pilot plant B and the results are compared with those of a theoretical model. The model assumes a scheme of three consecutive-partly parallel processes (i. e. drying, pyrolysis, and gasification and predicts DAF lignite conversion and gas composition in relatively good agreement with the pertinent experimental data typical of the rotary kiln gasifier performance. Pilot plant B is currently being employed in lime-enhanced gasification studies aiming at the production of hydrogen enriched synthesis gas. Presented herein are two typical gas compositions obtain from lignite gasification runs in the presence or not of lime. .

  2. Solar Alpha Rotary Joint Anomaly: The Materials and Processes Perspective

    Science.gov (United States)

    Basta, Erin A.; Dasgupta, Rijib; Figert, John; Jerman, Greg; Wright, Clara; Petrakis, Dennis; Golden, Johnny L.

    2009-01-01

    This slide presentation reviews the anomaly discovered on the Solar Alpha Rotary Joint (SARJ). This anomaly was discovered when the SARJ mechanism produced anomalous telemetry and noticeable vibrations. Metallic debris was discovered throughout the vicinity of the mechanism. Samples were taken from the SARJ, and the findings of the analysis are discussed.

  3. Rotary Drill Operator. Open Pit Mining Job Training Series.

    Science.gov (United States)

    Savilow, Bill

    This training outline for rotary drill operators, one in a series of eight outlines, is designed primarily for company training foremen or supervisors and for trainers to use as an industry-wide guideline for heavy equipment operator training in open pit mining in British Columbia. Intended as a guide for preparation of lesson plans both for…

  4. Light-Driven Rotary Molecular Motors on Gold Nanoparticles

    NARCIS (Netherlands)

    Pollard, Michael M.; ter Wiel, Matthijs K. J.; van Delden, Richard A.; Vicario, Javier; Koumura, Nagatoshi; van den Brom, Coenraad R.; Meetsma, Auke; Feringa, Ben L.

    2008-01-01

    We report the synthesis of unidirectional light-driven rotary molecular motors based oil chiral overcrowded alkenes and their immobilisation on the surface of gold nanoparticles through two anchors. Using a combination of (1)H and (13)C NMR, UV/Vis and CD spectroscopy, we show that these motors

  5. Construction and evaluation of rotary solar dryer for fish drying ...

    African Journals Online (AJOL)

    Rotary solar dryer was developed and evaluated for fish drying. People preferred dried prawns in diet in off seasons. Dried prawns are in high demand in the market and hence Prawns (Kolambi) were selected as drying material. Time required for reducing the moisture content from 75 per cent to final moisture content 16 ...

  6. Experimental results for a novel rotary active magnetic regenerator

    DEFF Research Database (Denmark)

    Engelbrecht, Kurt; Eriksen, Dan; Bahl, Christian

    2012-01-01

    in a solid refrigerant rather than the temperature change that occurs when a gas is compressed/expanded. This paper presents the general considerations for the design and construction of a high frequency rotary AMR device. Experimental results are presented at various cooling powers for a range of operating...

  7. TRANSIENT SUPPRESSION PACKAGING FOR REDUCED EMISSIONS FROM ROTARY KILN INCINERATORS

    Science.gov (United States)

    Experiments were performed on a 73 kW rotary kiln incinerator simulator to determine whether innovative waste packaging designs might reduce transient emissions of products of incomplete combustion due to batch charging of containerized liquid surrogate waste compounds bound on g...

  8. Apical extrusion of debris using reciprocating files and rotary ...

    African Journals Online (AJOL)

    Background: To compare the preparation time and amount of apically extruded debris after the preparation of root canals in extracted human teeth using the reciprocating files and rotary nickel.titanium systems. Procedure: Sixty extracted human mandibular premolars were used. The root canals were instrumented using ...

  9. Micro rotary machine and methods for using same

    Science.gov (United States)

    Stalford, Harold L [Norman, OK

    2012-04-17

    A micro rotary machine may include a micro actuator and a micro shaft coupled to the micro actuator. The micro shaft comprises a horizontal shaft and is operable to be rotated by the micro actuator. A micro tool is coupled to the micro shaft and is operable to perform work in response to motion of the micro shaft.

  10. Development of Motorized Oil Palm Fruit Rotary Digester | Asoiro ...

    African Journals Online (AJOL)

    A motorized oil palm fruit rotary digester comprising of a feed hopper, hammers, axle, screening plate, v-belt, 2hp electric motor, digesting chamber and frame was designed and developed using standard and locally sourced materials. The performance test analysis showed that its throughput capacity is 117.93kg/hr with a ...

  11. COMPUTER SIMULATION OF DISPERSED MATERIALS MOTION IN ROTARY TILTING FURNACES

    Directory of Open Access Journals (Sweden)

    S. L. Rovin

    2016-01-01

    Full Text Available The article presents the results of computer simulation of dispersed materials motion in rotary furnaces with an inclined axis of rotation. Has been received new data on the dynamic layer work that enhances understanding of heat and mass transfer processes occurring in the layer. 

  12. A reversible, unidirectional molecular rotary motor driven by chemical energy

    NARCIS (Netherlands)

    Fletcher, SP; Dumur, F; Pollard, MM; Feringa, BL

    2005-01-01

    With the long-term goal of producing nanometer-scale machines, we describe here the unidirectional rotary motion of a synthetic molecular structure fueled by chemical conversions. The basis of the rotation is the movement,of a phenyl rotor relative to a naphthyl stator about a single bond axle. The

  13. Evaluation of surface characteristics of rotary nickel‑titanium ...

    African Journals Online (AJOL)

    Background: Instrument fracture is a serious concern in endodontic practice. Objective: The aim of this study was to investigate the surface quality of new and used rotary nickel‑titanium (NiTi) instruments manufactured by the traditional grinding process and twisting methods. Materials and Methods: Total 16 instruments of ...

  14. A rotary ultrasonic motor using bending vibration transducers.

    Science.gov (United States)

    Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun

    2010-10-01

    A rotary ultrasonic motor using bending vibration transducers is proposed. In each transducer, two orthogonal bending vibrations are superimposed and an elliptical trajectory is generated at the driving foot. Typical output of the prototype is a no-load speed of 58 rpm and maximum torque of 9·5 Nm under an exciting voltage of 200 V(rms).

  15. Winding light beams along elliptical helical trajectories

    OpenAIRE

    Wen, Yuanhui; Chen, Yujie; Zhang, Yanfeng; Chen, Hui; Yu, Siyuan

    2016-01-01

    Conventional caustic methods in real or Fourier space produced accelerating optical beams only with convex trajectories. We develop a superposition caustic method capable of winding light beams along non-convex trajectories. We ascertain this method by constructing a one-dimensional (1D) accelerating beam moving along a sinusoidal trajectory, and subsequently extending to two-dimensional (2D) accelerating beams along arbitrarily elliptical helical trajectories. We experimentally implement the...

  16. Fixation strength of biocomposite wedge interference screw in ACL reconstruction: effect of screw length and tunnel/screw ratio. A controlled laboratory study

    Directory of Open Access Journals (Sweden)

    Herrera Antonio

    2010-06-01

    Full Text Available Abstract Background Primary stability of the graft is essential in anterior cruciate ligament surgery. An optimal method of fixation should be easy to insert and provide great resistance against pull-out forces. A controlled laboratory study was designed to test the primary stability of ACL tendinous grafts in the tibial tunnel. The correlation between resistance to traction forces and the cross-section and length of the screw was studied. Methods The tibial phase of ACL reconstruction was performed in forty porcine tibias using digital flexor tendons of the same animal. An 8 mm tunnel was drilled in each specimen and two looped tendons placed as graft. Specimens were divided in five groups according to the diameter and length of the screw used for fixation. Wedge interference screws were used. Longitudinal traction was applied to the graft with a Servohydraulic Fatigue System. Load and displacement were controlled and analyzed. Results The mean loads to failure for each group were 295,44 N (Group 1; 9 × 23 screw, 564,05 N (Group 2; 9 × 28, 614,95 N (Group 3; 9 × 35, 651,14 N (Group 4; 10 × 28 and 664,99 (Group 5; 10 × 35. No slippage of the graft was observed in groups 3, 4 and 5. There were significant differences in the load to failure among groups (ANOVA/P Conclusions Longer and wider interference screws provide better fixation in tibial ACL graft fixation. Short screws (23 mm do not achieve optimal fixation and should be implanted only with special requirements.

  17. Anion Recognition by Aliphatic Helical Oligoureas.

    Science.gov (United States)

    Diemer, Vincent; Fischer, Lucile; Kauffmann, Brice; Guichard, Gilles

    2016-10-24

    Anion binding properties of neutral helical foldamers consisting of urea type units in their backbone have been investigated. (1) H NMR titration studies in various organic solvents including DMSO suggest that the interaction between aliphatic oligoureas and anions (CH3 COO(-) , H2 PO4(-) , Cl(-) ) is site-specific, as it largely involves the urea NHs located at the terminal end of the helix (positive pole of the helix), which do not participate to the helical intramolecular hydrogen-bonding network. This mode of binding parallels that found in proteins in which anion-binding sites are frequently found at the N-terminus of an α-helix. (1) H NMR studies suggest that the helix of oligoureas remains largely folded upon anion binding, even in the presence of a large excess of the anion. This study points to potentially useful applications of oligourea helices for the selective recognition of small guest molecules. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Propulsion of microorganisms by a helical flagellum.

    Science.gov (United States)

    Rodenborn, Bruce; Chen, Chih-Hung; Swinney, Harry L; Liu, Bin; Zhang, H P

    2013-01-29

    The swimming of a bacterium or a biomimetic nanobot driven by a rotating helical flagellum is often interpreted using the resistive force theory developed by Gray and Hancock and by Lighthill, but this theory has not been tested for a range of physically relevant parameters. We test resistive force theory in experiments on macroscopic swimmers in a fluid that is highly viscous so the Reynolds number is small compared to unity, just as for swimming microorganisms. The measurements are made for the range of helical wavelengths λ, radii R, and lengths L relevant to bacterial flagella. The experiments determine thrust, torque, and drag, thus providing a complete description of swimming driven by a rotating helix at low Reynolds number. Complementary numerical simulations are conducted using the resistive force theories, the slender body theories of Lighthill and Johnson, and the regularized Stokeslet method. The experimental results differ qualitatively and quantitatively from the predictions of resistive force theory. The difference is especially large for and/or , parameter ranges common for bacteria. In contrast, the predictions of Stokeslet and slender body analyses agree with the laboratory measurements within the experimental uncertainty (a few percent) for all λ, R, and L. We present code implementing the slender body, regularized Stokeslet, and resistive force theories; thus readers can readily compute force, torque, and drag for any bacterium or nanobot driven by a rotating helical flagellum.

  19. Superconducting Helical Snake Magnet for the AGS

    CERN Document Server

    Willen, Erich; Escallier, John; Ganetis, George; Ghosh, Arup; Gupta, Ramesh C; Harrison, Michael; Jain, Animesh K; Luccio, Alfredo U; MacKay, William W; Marone, Andrew; Muratore, Joseph F; Okamura, Masahiro; Plate, Stephen R; Roser, Thomas; Tsoupas, Nicholaos; Wanderer, Peter

    2005-01-01

    A superconducting helical magnet has been built for polarized proton acceleration in the Brookhaven AGS. This "partial Snake" magnet will help to reduce the loss of polarization of the beam due to machine resonances. It is a 3 T magnet some 1940 mm in magnetic length in which the dipole field rotates with a pitch of 0.2053 degrees/mm for 1154 mm in the center and a pitch of 0.3920 degrees/mm for 393 mm in each end. The coil cross-section is made of two slotted cylinders containing superconductor. In order to minimize residual offsets and deflections of the beam on its orbit through the Snake, a careful balancing of the coil parameters was necessary. In addition to the main helical coils, a solenoid winding was built on the cold bore tube inside the main coils to compensate for the axial component of the field that is experienced by the beam when it is off-axis in this helical magnet. Also, two dipole corrector magnets were placed on the same tube with the solenoid. A low heat leak cryostat was built so that t...

  20. Timing of PMMA cement application for pedicle screw augmentation affects screw anchorage.

    Science.gov (United States)

    Schmoelz, Werner; Heinrichs, Christian Heinz; Schmidt, Sven; Piñera, Angel R; Tome-Bermejo, Felix; Duart, Javier M; Bauer, Marlies; Galovich, Luis Álvarez

    2017-04-03

    Cement augmentation is an established method to increase the pedicle screw (PS) anchorage in osteoporotic vertebral bodies. The ideal timing for augmentation when a reposition maneuver is necessary is controversial. While augmentation of the PS before reposition maneuver may increase the force applied it on the vertebrae, it bears the risk to impair PS anchorage, whereas augmenting the PS after the maneuver may restore this anchorage and prevent early screw loosening. The purpose of the present study was to evaluate the effect of cement application timing on PS anchorage in the osteoporotic vertebral body. Ten lumbar vertebrae (L1-L5) were used for testing. The left and right pedicles of each vertebra were instrumented with the same PS size and used for pairwise comparison of the two timing points for augmentation. For the reposition maneuver, the left PS was loaded axially under displacement control (2 × ±2 mm, 3 × ±6 mm, 3 × ±10 mm) to simulate a reposition maneuver. Subsequently, both PS were augmented with 2 ml PMMA cement. The same force as measured during the left PS maneuver was applied to the previously augmented right hand side PS [2 × F (±2 mm), 3 × F (±6 mm), 3 × F (±10 mm)]. Both PS were cyclically loaded with initial forces of +50 and -50 N, while the lower force was increased by 5 N every 100 cycles until total failure of the PS. The PS motion was measured with a 3D motion analysis system. After cyclic loading stress, X-rays were taken to identify the PS loosening mechanism. In comparison with PS augmented prior to the reposition maneuver, PS augmented after the reposition maneuver showed a significant higher number of load cycles until failure (5930 ± 1899 vs 3830 ± 1706, p = 0.015). The predominant loosening mechanism for PS augmented after the reposition maneuver was PS toggling with the attached cement cloud within the trabecular bone. While PS augmented prior to the reposition, maneuver showed a motion of

  1. NUMERICAL INVESTIGATION FOR THE HEAT TRANSFER ENHANCEMENT IN HELICAL CONE COILS OVER ORDINARY HELICAL COILS

    Directory of Open Access Journals (Sweden)

    M. M. ABO ELAZM

    2013-02-01

    Full Text Available This numerical research is introducing the concept of helical cone coils and their enhanced heat transfer characteristics compared to the ordinary helical coils. Helical and spiral coils are known to have better heat and mass transfer than straight tubes, which is attributed to the generation of a vortex at the helical coil known as Dean Vortex. The Dean number which is a dimensionless number used to describe the Dean vortex is a function of Reynolds number and the square root of the curvature ratio, so varying the curvature ratio for the same coil would vary the Dean number. Two scenarios were adopted to study the effect of changing the taper angle (curvature ratio on the heat transfer characteristics of the coil; the commercial software FLUENT was used in the investigation. It was found that Nusselt number increased with increasing the taper angle. A MATLAB code was built based on empirical correlation of Manlapaz and Churchill for ordinary helical coils to calculate the Nusselt number at each coil turn, and then calculate the average Nusselt number for the entire coil turns, the CFD simulation results were found acceptable when compared with the MATLAB results.

  2. The Effects of Spatial Smoothing on Solar Magnetic Helicity Parameters and the Hemispheric Helicity Sign Rule

    Science.gov (United States)

    Koch Ocker, Stella; Petrie, Gordon

    2016-12-01

    The hemispheric preference for negative/positive helicity to occur in the northern/southern solar hemisphere provides clues to the causes of twisted, flaring magnetic fields. Previous studies on the hemisphere rule may have been affected by seeing from atmospheric turbulence. Using Hinode/SOT-SP data spanning 2006-2013, we studied the effects of two spatial smoothing tests that imitate atmospheric seeing: noise reduction by ignoring pixel values weaker than the estimated noise threshold, and Gaussian spatial smoothing. We studied in detail the effects of atmospheric seeing on the helicity distributions across various field strengths for active regions (ARs) NOAA 11158 and NOAA 11243, in addition to studying the average helicities of 179 ARs with and without smoothing. We found that, rather than changing trends in the helicity distributions, spatial smoothing modified existing trends by reducing random noise and by regressing outliers toward the mean, or removing them altogether. Furthermore, the average helicity parameter values of the 179 ARs did not conform to the hemisphere rule: independent of smoothing, the weak-vertical-field values tended to be negative in both hemispheres, and the strong-vertical-field values tended to be positive, especially in the south. We conclude that spatial smoothing does not significantly affect the overall statistics for space-based data, and thus seeing from atmospheric turbulence seems not to have significantly affected previous studies’ ground-based results on the hemisphere rule.

  3. Investigation of an 11mm diameter twin screw granulator: Screw element performance and in-line monitoring via image analysis.

    Science.gov (United States)

    Sayin, Ridade; Martinez-Marcos, Laura; Osorio, Juan G; Cruise, Paul; Jones, Ian; Halbert, Gavin W; Lamprou, Dimitrios A; Litster, James D

    2015-12-30

    As twin screw granulation (TSG) provides one with many screw element options, characterization of each screw element is crucial in optimizing the screw configuration in order to obtain desired granule attributes. In this study, the performance of two different screw elements - distributive feed screws and kneading elements - was studied in an 11 mm TSG at different liquid-to-solid (L/S) ratios. The kneading element configuration was found to break large granules more efficiently, leading to narrower granule size distributions. While pharmaceutical industry shifts toward continuous manufacturing, inline monitoring and process control are gaining importance. Granules from an 11 mm TSG were analysed using the Eyecon™, a real-time high speed direct imaging system, which has been used to capture accurate particle size distribution and particle count. The size parameters and particle count were then assessed in terms of their ability to be a suitable control measure using the Shewhart control charts. d10 and particle count were found to be good indicators of the change in L/S ratio. However, d50 and d90 did not reflect the change, due to their inherent variability even when the process is at steady state. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Prediction of Deformity Correction by Pedicle Screw Instrumentation in Thoracolumbar Scoliosis Surgery

    Science.gov (United States)

    Kiriyama, Yoshimori; Yamazaki, Nobutoshi; Nagura, Takeo; Matsumoto, Morio; Chiba, Kazuhiro; Toyama, Yoshiaki

    In segmental pedicle screw instrumentation, the relationship between the combinations of pedicle screw placements and the degree of deformity correction was investigated with a three-dimensional rigid body and spring model. The virtual thoracolumbar scoliosis (Cobb’s angle of 47 deg.) was corrected using six different combinations of pedicle-screw placements. As a result, better correction in the axial rotation was obtained with the pedicle screws placed at or close to the apical vertebra than with the screws placed close to the end vertebrae, while the correction in the frontal plane was better with the screws close to the end vertebrae than with those close to the apical vertebra. Additionally, two screws placed in the convex side above and below the apical vertebra provided better correction than two screws placed in the concave side. Effective deformity corrections of scoliosis were obtained with the proper combinations of pedicle screw placements.

  5. Development and Testing of X-Ray Imaging-Enhanced Poly-L-Lactide Bone Screws.

    Directory of Open Access Journals (Sweden)

    Wei-Jen Chang

    Full Text Available Nanosized iron oxide particles exhibit osteogenic and radiopaque properties. Thus, iron oxide (Fe3O4 nanoparticles were incorporated into a biodegradable polymer (poly-L-lactic acid, PLLA to fabricate a composite bone screw. This multifunctional, 3D printable bone screw was detectable on X-ray examination. In this study, mechanical tests including three-point bending and ultimate tensile strength were conducted to evaluate the optimal ratio of iron oxide nanoparticles in the PLLA composite. Both injection molding and 3D printing techniques were used to fabricate the PLLA bone screws with and without the iron oxide nanoparticles. The fabricated screws were implanted into the femoral condyles of New Zealand White rabbits. Bone blocks containing the PLLA screws were resected 2 and 4 weeks after surgery. Histologic examination of the surrounding bone and the radiopacity of the iron-oxide-containing PLLA screws were evaluated. Our results indicated that addition of iron oxide nanoparticles at 30% significantly decreased the ultimate tensile stress properties of the PLLA screws. The screws with 20% iron oxide exhibited strong radiopacity compared to the screws fabricated without the iron oxide nanoparticles. Four weeks after surgery, the average bone volume of the iron oxide PLLA composite screws was significantly greater than that of PLLA screws without iron oxide. These findings suggested that biodegradable and X-ray detectable PLLA bone screws can be produced by incorporation of 20% iron oxide nanoparticles. Furthermore, these screws had significantly greater osteogenic capability than the PLLA screws without iron oxide.

  6. In-vitro comparison of biomechanical efficiency of three cannulated screws for arthrodesis of the hindfoot.

    Science.gov (United States)

    Huber, Wolfgang O; Reihsner, Roland; Trieb, Klemens; Wanivenhaus, Axel Hugo; Beer, Rudolf

    2008-02-01

    Sufficient inter-fragmentary compression is helpful to achieve successful bony fusion in hindfoot arthrodesis using internal fixation by screws. Beside bone quality, the design of a screw influences inter-fragmentary compression. Compressive force is achievable for any kind of screw system; however, the primary deformation of the bone is different for the different screw systems. The work necessary to achieve compressive force for primary stability was measured for different screw systems and compared to an AO screw with washer. The compressive force was determined as a function of screw advancement for 3 different cannulated screw types (7.3-mm AO screw with and without washer, the 6.5-mm Herbert screw and the 6.5-mm Ideal Compression Screw (I.CO.S) using different synthetic bone density (0.16, 0.24, 0.48 g/ccm). Compressive force was measured indirectly, via screw tension measurement with strain gauges. We calculated the work to reach a limit of 60 N and the corresponding ratios to the value of the golden standard: I.CO.S (35.2%), Herbert (89.0%), AO screw without washer (116%). All screw systems yielded acceptable results but the ICOS did produce greater compression. The essential differences were the primary deformation of the bone before reaching the sufficient compressive force for primary stability.

  7. Hydrodynamic studies of CNT nanofluids in helical coil heat exchanger

    Science.gov (United States)

    Babita; Sharma, S. K.; Mital Gupta, Shipra; Kumar, Arinjay

    2017-12-01

    Helical coils are extensively used in several industrial processes such as refrigeration systems, chemical reactors, recovery processes etc to accommodate a large heat transfer area within a smaller space. Nanofluids are getting great attention due to their enhanced heat transfer capability. In heat transfer equipments, pressure drop is one of the major factors of consideration for pumping power calculations. So, the present work is aimed to study hydrodynamics of CNT nanofluids in helical coils. In this study, pressure drop characteristics of CNT nanofluid flowing inside horizontal helical coils are investigated experimentally. The helical coil to tube diameter was varied from 11.71 to 27.34 keeping pitch of the helical coil constant. Double distilled water was used as basefluid. SDBS and GA surfactants were added to stablilize CNT nanofluids. The volumetric fraction of CNT nanofluid was varied from 0.003 vol% to 0.051 vol%. From the experimental data, it was analyzed that the friction factor in helical coils is greater than that of straight tubes. Concentration of CNT in nanofluids also has a significant influence on the pressure drop/friction factor of helical coils. At a constant concentration of CNT, decreasing helical coil to tube diameter from 27.24 to 11.71, fanning friction factor of helical coil; f c increases for a constant value of p/d t. This increase in the value of fanning friction factor can be attributed to the secondary flow of CNT nanofluid in helical coils.

  8. Observation of glycine zipper and unanticipated occurrence of ambidextrous helices in the crystal structure of a chiral undecapeptide

    Directory of Open Access Journals (Sweden)

    Ramagopal Udupi A

    2007-08-01

    Full Text Available Abstract Background The de novo design of peptides and proteins has recently surfaced as an approach for investigating protein structure and function. This approach vitally tests our knowledge of protein folding and function, while also laying the groundwork for the fabrication of proteins with properties not precedented in nature. The success of these studies relies heavily on the ability to design relatively short peptides that can espouse stable secondary structures. To this end, substitution with α, β-dehydroamino acids, especially α, β-dehydrophenylalanine (ΔPhe comes in use for spawning well-defined structural motifs. Introduction of ΔPhe induces β-bends in small and 310-helices in longer peptide sequences. Results The present report is an investigation of the effect of incorporating two glycines in the middle of a ΔPhe containing undecapeptide. A de novo designed undecapeptide, Ac-Gly1-Ala2-ΔPhe3-Leu4-Gly5-ΔPhe6-Leu7-Gly8-ΔPhe9-Ala10-Gly11-NH2, was synthesized and characterized using X-ray diffraction and Circular Dichroism spectroscopic methods. Crystallographic studies suggest that, despite the presence of L-amino acid (L-Ala and L-Leu residues in the middle of the sequence, the peptide adopts a 310-helical conformation of ambidextrous screw sense, one of them a left-handed (A and the other a right-handed (B 310-helix with A and B being antiparallel to each other. However, CD studies reveal that the undecapeptide exclusively adopts a right-handed 310-helical conformation. In the crystal packing, three different interhelical interfaces, Leu-Leu, Gly-Gly and ΔPhe-ΔPhe are observed between the helices A and B. A network of C-H...O hydrogen bonds are observed at ΔPhe-ΔPhe and Gly-Gly interhelical interfaces. An important feature observed is the occurrence of glycine zipper motif at Gly-Gly interface. At this interface, the geometric pattern of interhelical interactions seems to resemble those observed between helices in

  9. Biomechanical comparison of two locking plate constructs under cyclic torsional loading in a fracture gap model. Two screws versus three screws per fragment.

    Science.gov (United States)

    Bilmont, A; Palierne, S; Verset, M; Swider, P; Autefage, A

    2015-01-01

    The number of locking screws required per fragment during bridging osteosynthesis in the dog has not been determined. The purpose of this study was to assess the survival of two constructs, with either two or three screws per fragment, under cyclic torsion. Ten-hole 3.5 mm stainless steel locking compression plates (LCP) were fixed 1 mm away from bone surrogates with a fracture gap of 47 mm using two bicortical locking screws (10 constructs) or three bicortical locking screws (10 constructs) per fragment, placed at the extremities of each LCP. Constructs were tested in cyclic torsion (range: 0 to +0.218 rad) until failure. The 3-screws constructs (29.65 ± 1.89 N.m/rad) were stiffer than the 2-screws constructs (23.73 ± 0.87 N.m/rad), and therefore, were subjected to a greater torque during cycling (6.05 ± 1.33 N.m and 4.88 ± 1.14 N.m respectively). The 3-screws constructs sustained a significantly greater number of cycles (20,700 ± 5,735 cycles) than the 2-screws constructs (15,600 ± 5,272 cycles). In most constructs, failure was due to screw damage at the junction of the shaft and head. The remaining constructs failed because of screw head unlocking, sometimes due to incomplete seating of the screw head prior to testing. Omitting the third innermost locking screw during bridging osteosynthesis led to a reduction in fatigue life of 25% and construct stiffness by 20%. Fracture of the screws is believed to occur sequentially, starting with the innermost screw that initially shields the other screws.

  10. Magnetic helicity balance at Taylor relaxed states sustained by AC helicity injection

    Science.gov (United States)

    Hirota, Makoto; Morrison, Philip J.; Horton, Wendell; Hattori, Yuji

    2017-10-01

    Magnitudes of Taylor relaxed states that are sustained by AC magnetic helicity injection (also known as oscillating field current drive, OFCD) are investigated numerically in a cylindrical geometry. Compared with the amplitude of the oscillating magnetic field at the skin layer (which is normalized to 1), the strength of the axial guide field Bz 0 is shown to be an important parameter. The relaxation process seems to be active only when Bz 0 Neill et al., where the helicity injection rate is directly equated with the dissipation rate at the Taylor states. Then, the bifurcation to the helical Taylor state is predicted theoretically and the estimated magnitudes of the relaxed states reasonably agree with numerical results as far as Bz 0 < 1 . This work was supported by JSPS KAKENHI Grant Number 16K05627.

  11. Nonequilibrium transport between helical Luttinger liquids leads or helical Majorana modes

    Science.gov (United States)

    Chao, Sung Po; Silotri, Salman; Chung, Chung Hou

    2014-03-01

    We study a steady state non-equilibrium transport between (i) two interacting helical edge states of a two dimensional topological insulator, described by helical Luttinger liquids, through a quantum dot or tunneling junction. (ii) one Luttinger liquids lead and a helical Majorana modes lead connected by tunneling junction(s). We find the metal-to-insulator quantum phase transition for attractive or repulsive interactions in the leads when the magnitude of the interaction strength characterized by a charge sector Luttinger parameter goes beyond a critical value. The authors acknowledge NSC grant No.101-2628-M-009-001-MY3, the MOE-ATU program, the CTS of NCTU, the NCTS and NTHU of Taiwan, R.O.C.

  12. Coordination chemistry strategies for dynamic helicates: time-programmable chirality switching with labile and inert metal helicates.

    Science.gov (United States)

    Miyake, Hiroyuki; Tsukube, Hiroshi

    2012-11-07

    'Chirality switching' is one of the most important chemical processes controlling many biological systems. DNAs and proteins often work as time-programmed functional helices, in which specific external stimuli alter the helical direction and tune the time scale of subsequent events. Although a variety of organic foldamers and their hybrids with natural helices have been developed, we highlight coordination chemistry strategies for development of structurally and functionally defined metal helicates. These metal helicates have characteristic coordination geometries, redox reactivities and spectroscopic/magnetic properties as well as complex chiralities. Several kinds of inert metal helicates maintain rigid helical structures and their stereoisomers are separable by optical resolution techniques, while labile metal helicates offer dynamic inversion of their helical structures via non-covalent interactions with external chemical signals. The latter particularly have dynamically ordered helical structures, which are controlled by the combinations of metal centres and chiral ligands. They further function as time-programmable switches of chirality-derived dynamic rotations, translations, stretching and shape flipping, which are useful applications in nanoscience and related technology.

  13. Biomechanical comparison of the bioabsorbable RetroScrew system, BioScrew XtraLok with stress equalization tensioner, and 35-mm Delta Screws for tibialis anterior graft-tibial tunnel fixation in porcine tibiae.

    Science.gov (United States)

    Chang, Haw Chong; Nyland, John; Nawab, Akbar; Burden, Robert; Caborn, David N M

    2005-07-01

    Achieving effective soft tissue graft-tibial tunnel fixation remains problematic. No differences would exist for tibialis anterior graft-tibial tunnel fixation when comparing the RetroScrew System (20-mm retrograde screw, 17-mm antegrade screw), the 35-mm tapered Delta Screw (manual tensioning), and the 35-mm BioScrew XtraLok (applied using an instrumented tensioner). Controlled laboratory study. Porcine tibiae (apparent bone mineral density, 1.3 g/cm(2)) and human tendon allografts were divided into 3 matched groups of 6 specimens each before cyclic (500 cycles, 50-250 N, 1 Hz) and load-to-failure (20 mm/min) tests. The BioScrew XtraLok (210.9 +/- 54.9 N/mm) and the 35-mm Delta Screw (224.3 +/- 43.7 N/mm) displayed superior stiffness to the RetroScrew System (114.1 +/- 23.3 N/mm) (P = .0004) during cyclic testing. The BioScrew XtraLok (1.0 +/- 0.2 mm) and the Delta Screw (0.9 +/- 0.2 mm) also displayed less displacement during cyclic testing than the RetroScrew System (1.8 +/- 0.5 mm) (P = .001). During load-to-failure testing, the BioScrew XtraLok withstood greater loads (1436.3 +/- 331.3 N) (P = .001) and displayed greater stiffness (323.6 +/- 56.8 N/mm) (P = .002) than the 35-mm Delta Screw (load, 1042.2 +/- 214.4 N; stiffness, 257.2 +/- 22.2 N/mm) and the RetroScrew System (load, 778.7 +/- 177.5 N; stiffness, 204.4 +/- 52.9 N/mm). The BioScrew XtraLok with instrumented tensioning displayed superior fixation to the RetroScrew System and the 35-mm Delta Screw applied with manual tensioning. The BioScrew XtraLok may provide superior soft tissue graft-tibial tunnel fixation. Further in vitro studies using human tissue and in vivo clinical studies are needed.

  14. Preoperative CT planning of screw length in arthroscopic Latarjet.

    Science.gov (United States)

    Hardy, Alexandre; Gerometta, Antoine; Granger, Benjamin; Massein, Audrey; Casabianca, Laurent; Pascal-Moussellard, Hugues; Loriaut, Philippe

    2016-08-25

    The Latarjet procedure has shown its efficiency for the treatment of anterior shoulder dislocation. The success of this technique depends on the correct positioning and fusion of the bone block. The length of the screws that fix the bone block can be a problem. They can increase the risk of non-union if too short or be the cause of nerve lesion or soft tissue discomfort if too long. Suprascapular nerve injuries have been reported during shoulder stabilisation surgery up to 6 % of the case. Bone block non-union depending on the series is found around 20 % of the cases. The purpose of this study was to evaluate the efficiency of this CT preoperative planning to predict optimal screws length. The clinical importance of this study lies in the observation that it is the first study to evaluate the efficiency of CT planning to predict screw length. Inclusion criteria were patients with chronic anterior instability of the shoulder with an ISIS superior to 4. Exclusion criteria were patients with multidirectional instability or any previous surgery on this shoulder. Thirty patients were included prospectively, 11 of them went threw a CT planning, before their arthroscopic Latarjet. Optimal length of both screws was calculated, adding the size of the coracoid at 5 and 15 mm from the tip to the glenoid. Thirty-two-mm screws were used for patients without planning. On a post-operative CT scan with 3D reconstruction, the distance between the screw tip and the posterior cortex was measured. A one-sample Wilcoxon test was used to compare the distance from the tip of the screw to an acceptable positioning of ±2 mm from the posterior cortex. In the group without planning, screw 1 tended to differ from the acceptable positioning: mean 3.44 mm ± 3.13, med 2.9 mm, q1; q3 [0.6; 4.75] p = 0.1118, and screw 2 differed significantly from the acceptable position: mean 4.83 mm ± 4.11, med 3.7 mm, q1; q3 [1.7; 5.45] p = 0.0045. In the group with planning, position of

  15. The Study of Vibration Processes in Oil Flooded Screw Compressors

    Directory of Open Access Journals (Sweden)

    I. V. Filippov

    2014-01-01

    Full Text Available Vibration processes that accompany most of machines and mechanisms are of interest to the researcher, as a source of information about the technical condition and the nature of the business processes flow. Vibration-based diagnostics of oil flooded screw compressors allows us to estimate the deviation of their operation from the main mode in accordance with changing the settings of vibration processes.The oil flooded screw compressor transition from the main mode of operation to the abnormal one is accompanied by complex gas-dynamic phenomena i.e. the initial gaps and their decays. This leads to changes in the nature of vibration processes, prompting suggestions that there is a relationship to a change of vibration parameters and mode of compressor operation.Studies were conducted by combined method using an analytical calculation of the decay parameters of the initial discontinuity and an experimental one based on the measurement of acceleration on the body of the real oil flooded screw compressor. A virtually adequate reaction of the decay parameters of the initial gap and the peak values of vibration acceleration to the change of operation mode of oil flooded screw compressor has been received. The peak value of the vibration acceleration was selected by the method of Gating being time-coinciding with the beginning discharge phase of the oil flooded screw compressor, and therefore, with the decay time of the initial discontinuity.This indicates a large degree of hypothesis likelihood on an existing initial break in oil flooded screw compressor when operating in abnormal conditions. This work contains the study results of vibration processes and their relationship to the operating mode of the oil flooded screw compressor, which distinguish it from the other works studied vibration processes in reciprocating compressors. The vibration parameters control of operating oil flooded screw compressor allows us to create an automatic capacity control

  16. The effect of the screw pull-out rate on cortical screw purchase in unreamed and reamed synthetic long bones.

    Science.gov (United States)

    Zdero, R; Shah, S; Mosli, M; Bougherara, H; Schemitsch, E H

    2010-01-01

    Orthopaedic fracture fixation constructs are typically mounted on to human long bones using cortical screws. Biomechanical studies are increasingly employing commercially available synthetic bones. The aim of this investigation was to examine the effect of the screw pull-out rate and canal reaming on the cortical bone screw purchase strength in synthetic bone. Cylinders made of synthetic material were used to simulate unreamed (foam-filled) and reamed (hollow) human long bone with an outer diameter of 35 mm and a cortex wall thickness of 4 mm. The unreamed and reamed cylinders each had 56 sites along their lengths into which orthopaedic cortical bone screws (major diameter, 3.5 mm) were inserted to engage both cortices. The 16 test groups (n = 7 screw sites per group) had screws extracted at rates of 1 mm/ min, 5 mm/min, 10 mm/min, 20 mm/min, 30 mm/min, 40 mm/min, 50 mm/min, and 60 mm/ min. The failure force and failure stress increased and were highly linearly correlated with pull-out rate for reamed (R2 = 0.60 and 0.60), but not for unreamed (R2 = 0.00 and 0.00) specimens. The failure displacement and failure energy were relatively unchanged with pull-out rate, yielding low coefficients for unreamed (R2 = 0.25 and 0.00) and reamed (R2 = 0.27 and 0.00) groups. Unreamed versus reamed specimens were statistically different for failure force (p = 0.000) and stress (p = 0.000), but not for failure displacement (p = 0.297) and energy (0.054 < p < 1.000). This is the first study to perform an extensive investigation of the screw pull-out rate in unreamed and reamed synthetic long bone.

  17. In vitro assessment of cutting efficiency and durability of zirconia removal diamond rotary instruments.

    Science.gov (United States)

    Kim, Joon-Soo; Bae, Ji-Hyeon; Yun, Mi-Jung; Huh, Jung-Bo

    2017-06-01

    Recently, zirconia removal diamond rotary instruments have become commercially available for efficient cutting of zirconia. However, research of cutting efficiency and the cutting characteristics of zirconia removal diamond rotary instruments is limited. The purpose of this in vitro study was to assess and compare the cutting efficiency, durability, and diamond rotary instrument wear pattern of zirconia diamond removal rotary instruments with those of conventional diamond rotary instruments. In addition, the surface characteristics of the cut zirconia were assessed. Block specimens of 3 mol% yttrium cation-doped tetragonal zirconia polycrystal were machined 10 times for 1 minute each using a high-speed handpiece with 6 types of diamond rotary instrument from 2 manufacturers at a constant force of 2 N (n=5). An electronic scale was used to measure the lost weight after each cut in order to evaluate the cutting efficiency. Field emission scanning electron microscopy was used to evaluate diamond rotary instrument wear patterns and machined zirconia block surface characteristics. Data were statistically analyzed using the Kruskal-Wallis test, followed by the Mann-Whitney U test (α=.05). Zirconia removal fine grit diamond rotary instruments showed cutting efficiency that was reduced compared with conventional fine grit diamond rotary instruments. Diamond grit fracture was the most dominant diamond rotary instrument wear pattern in all groups. All machined zirconia surfaces were primarily subjected to plastic deformation, which is evidence of ductile cutting. Zirconia blocks machined with zirconia removal fine grit diamond rotary instruments showed the least incidence of surface flaws. Although zirconia removal diamond rotary instruments did not show improved cutting efficiency compared with conventional diamond rotary instruments, the machined zirconia surface showed smoother furrows of plastic deformation and fewer surface flaws. Copyright © 2016 Editorial Council

  18. Palliative dual iliac screw fixation for lumbosacral metastasis. Technical note.

    Science.gov (United States)

    Fujibayashi, Shunsuke; Neo, Masashi; Nakamura, Takashi

    2007-07-01

    Spinal fixation for destructive metastatic lesions at the lumbosacral junction is challenging because of the large and unique load-bearing characteristics present. In particular, caudal fixation is difficult in cases of sacral destruction because of insufficient S-1 pedicle screw anchorage. The authors describe their surgical technique for secure iliac screw placement and the clinical results obtained in five patients with metastatic spinal disease. All patients in this study underwent palliative operations with dual iliac screw fixation between April 1999 and October 2002, and the clinical and radiological findings were assessed. In all five patients, spinal metastases extended into the sacrum. The metastases were from renal cell carcinomas in two patients, lung cancer in two, and a paraganglioma in one patient. Postoperative follow-up periods ranged from 3 months to 6 years (mean 28.4 months). Preoperatively, four patients could not walk due to severe pain or neurological compromise. Postoperatively, all patients reported a reduction in pain and regained the ability to walk. Complications included one case of early wound infection. In the patients with long survival after the operation, there was one case of iliac screw loosening and one case of rod breakage. The dual iliac screw fixation technique provided sufficient immediate stability for destructive lumbosacral metastasis.

  19. Screw dislocations in GaN grown by different methods.

    Science.gov (United States)

    Liliental-Weber, Z; Zakharov, D; Jasinski, J; O'Keefe, M A; Morkoc, H

    2004-02-01

    A study of screw dislocations in hydride-vapor-phase-epitaxy (HVPE) template and molecular-beam-epitaxy (MBE) overlayers was performed using transmission electron microscopy (TEM) in plan view and in cross section. It was observed that screw dislocations in the HVPE layers were decorated by small voids arranged along the screw axis. However, no voids were observed along screw dislocations in MBE overlayers. This was true both for MBE samples grown under Ga-lean and Ga-rich conditions. Dislocation core structures have been studied in these samples in the plan-view configuration. These experiments were supported by image simulation using the most recent models. A direct reconstruction of the phase and amplitude of the scattered electron wave from a focal series of high-resolution images was applied. It was shown that the core structures of screw dislocations in the studied materials were filled. The filed dislocation cores in an MBE samples were stoichiometric. However, in HVPE materials, single atomic columns show substantial differences in intensities and might indicate the possibility of higher Ga concentration in the core than in the matrix. A much lower intensity of the atomic column at the tip of the void was observed. This might suggest presence of lighter elements, such as oxygen, responsible for their formation.

  20. Output characteristics of floating type wave power generator system using a ball screw; Fuyugata nejishiki haryoku hatsuden sochi no shutsuryoku tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Abe, T.; Omata, K. [Meiji University, Tokyo (Japan)

    1996-10-27

    A floating type wave power generator system using a ball screw is proposed. Output characteristics are simulated on the supposition of its employment aboard a navigational aid buoy. The relative linear movement produced by waves between the main body and float is transmitted via a load column to a ball nut and is converted into a rotary movement of a threaded shaft engaging the ball nut. Attached to the bottom end of the threaded shaft is a one-way clutch which connects to the generator axle when the relative velocity between the float and main body is positive. The simulation was conducted for a wave activated power generation buoy, 2.6m in outer diameter, 4.5m in length, and 6000kg in total mass. The buoy generated a mechanical output of 340kW when exposed to a sinusoidal wave 2.5 seconds in period and 40cm in wave height. A tank test was performed using a reduced scale model consisting of a ball screw, bicycle dynamo, and float, with the main body being 318mm in diameter and 833mm in length, when an average output of 4.51W was obtained at 60% efficiency. The results of the experiment agreed in some degree with the results of calculation, verifying the righteousness of the theoretical formula. 3 refs., 7 figs., 4 tabs.

  1. Freehand technique for C2 pedicle and pars screw placement: safe or not?

    Science.gov (United States)

    Punyarat, Prachya; Riew, K Daniel; Klawson, Benjamin T; Peters, Colleen; Lertudomphonwanit, Thamrong; Buchowski, Jacob M

    2017-11-16

    During placement of C2 pedicle and pars screws, intraoperative fluoroscopy is used so that neurovascular complications can be avoided, and screws can be placed in the proper position. However, this method is time consuming and increases radiation exposure. Furthermore, it does not guarantee completely safe and accurate screw placement. To evaluate the safety of the C2 pedicle and pars screw placement without fluoroscopic or other guidance methods. Retrospective comparative study. One hundred and ninety-eight patients who underwent placement of C2 pedicle or pars screws without any intraoperative radiographic guidance were included. Medical records and postoperative CT scans were evaluated. Clinical data were reviewed for intraoperative and postoperative complications. Accuracy of screw placement was evaluated with post-op CT scans using a previously published cortical-breach grading system (described by location and percentage of screw diameter over cortical edge (0 = none; grade I = pars screws were inserted by two experienced surgeons. There were no cases of CSF leakage and no neurovascular complications during screw placement. Postoperative CT scans were available for 76 patients, which included 52 pedicle and 87 pars screws. For cases with C2 pedicle screws, there were 12 breaches (23%); these included 10 screws with a grade I breach (19%), 1 screw with a grade II breach (2%), and 1 screw with a grade IV breach (2%). Lateral breaches occurred in 7 screws (13%), inferior breaches in 3 (6%), and superior breaches in 2 (4%). For cases with C2 pars screws, there were 10 breaches (11%); these included 6 screws with a grade I breach (7%), 2 screws with a grade II breach (2%), and 2 screws with a grade IV breach (2%). Medial breaches were found in 4 (5%), lateral breaches in 2 (2%), inferior breaches in 2 (2%), and superior breaches in 2 (2%). 2 of the cases with superior breaches (1 for pedicle and 1 for pars) experienced occipital neuralgia months after surgery

  2. Interferometric measurement of the helical mode of a single photon

    Energy Technology Data Exchange (ETDEWEB)

    Galvez, E J; Coyle, L E; Johnson, E; Reschovsky, B J, E-mail: egalvez@colgate.edu [Department of Physics and Astronomy, Colgate University, 13 Oak Drive, Hamilton, NY 13346 (United States)

    2011-05-15

    We present measurements of the helical mode of single photons and do so by sending heralded photons through a Mach-Zehnder interferometer that prepares the light in a helical mode with topological charge one, and interferes it with itself in the fundamental non-helical mode. Masks placed after the interferometer were used to diagnose the amplitude and phase of the mode of the light. Auxiliary measurements verified that the light was in a non-classical state. The results are in good agreement with theory. The experiments demonstrate in a direct way that single photons carry the entire spatial helical-mode information.

  3. Transmembrane helices can induce domain formation in crowded model membranes

    National Research Council Canada - National Science Library

    Domański, Jan; Marrink, Siewert J; Schäfer, Lars V

    2012-01-01

    We studied compositionally heterogeneous multi-component model membranes comprised of saturated lipids, unsaturated lipids, cholesterol, and a-helical TM protein models using coarse-grained molecular...

  4. Inhomogeneous helicity effect in the solar angular-momentum transport

    Science.gov (United States)

    Yokoi, Nobumitsu

    2017-04-01

    Coupled with mean absolute vorticity Ω∗ (rotation and mean relative vorticity), inhomogeneous turbulent helicity is expected to contribute to the generation of global flow structure against the linear and angular momentum mixing due to turbulent or eddy viscosity. This inhomogeneous helicity effect was originally derived in Yokoi & Yoshizawa (1993) [1], and recently has been validated by direct numerical simulations (DNSs) of rotating helical turbulence [2]. Turbulence effect enters the mean-vorticity equation through the turbulent vortexmotive force ⟨u'×ω'⟩ [u': velocity fluctuation, ω'(= ∇× u'): vorticity fluctuation], which is the vorticity counterpart of the electromotive force ⟨u'× b'⟩ (b': magnetic fluctuation) in the mean magnetic-field induction. The mean velocity induction δU is proportional to the vortexmotive force. According to the theoretical result [1,2], it is expressed as δU = -νT∇×Ω∗-ηT(∇2H)Ω∗, where ηT is the transport coefficient, H = ⟨u'ṡω'⟩ the turbulent helicity, and Ω∗ the mean absolute vorticity. The first term corresponds to the enhanced diffusion due to turbulent viscosity νT. The second term expresses the large-scale flow generation due to inhomogeneous helicity. Since helicity is self-generated in rotating stratified turbulence [3], an inhomogeneous helicity distribution is expected to exist in the solar convection zone. A rising flow with expansion near the surface of the Sun generates a strongly negative helicity there [4]. This spatial distribution of helicity would lead to a positive Laplacian of turbulent helicity (∇2H > 0) in the subsurface layer of the Sun. In the combination with the large-scale vorticity associated with the meridional circulation, the inhomogeneous helicity effect works for accelerating the mean velocity in the azimuthal direction. The relevance of this inhomogeneous helicity effect in the solar convection zone is discussed further. References [1] Yokoi, N. and

  5. The formation of helical mesoporous silica nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Wan Xiaobing; Pei Xianfeng; Zhao Huanyu; Chen Yuanli; Guo Yongmin; Li Baozong; Yang Yonggang [Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry and Chemical Engineering, Suzhou (Soochow) University, Suzhou 215123 (China); Hanabusa, Kenji [Department of Functional Polymer Science, Faculty of Textile Science and Technology, Shinshu University, Ueda 386-8567 (Japan)], E-mail: ygyang@suda.edu.cn

    2008-08-06

    Three chiral cationic gelators were synthesized. They can form translucent hydrogels in pure water. These hydrogels become highly viscous liquids under strong stirring. Mesoporous silica nanotubes with coiled pore channels in the walls were prepared using the self-assemblies of these gelators as templates. The mechanism of the formation of this hierarchical nanostructure was studied using transmission electron microscopy at different reaction times. The results indicated that there are some interactions between the silica source and the gelator. The morphologies of the self-assemblies of gelators changed gradually during the sol-gel transcription process. It seems that the silica source directed the organic self-assemblies into helical nanostructures.

  6. Helical CT findings in mesenteric ischemia

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seung Hoon; Lim, Hyo Keun; Lee, Won Jae; Choi, Sang Hee; Lee, Soon Jin; Cho, Jae Min; Kim, Kyung Ah; Lee, Yon Ok [Sungkyunkwan Univ. College of Medicine. Samsung Medical Center, Seoul (Korea, Republic of)

    1998-08-01

    Ischemic bowel disease is one of the common causes of acute abdomen, which results from insufficient blood flow to the small bowel and colon caused by arterial or venous occlusion or mesenteric vasoconstriction. Early diagnosis by clinical, laboratory, and radiologic findings is often difficult and delay in adequate therapy results in substantial morbidity and mortality. CT is known to be useful for the evaluation of patients with suspected bowel ischemia or infarction. This study describes the spectrum of helical CT findings in acute and chronic mesenteric ischemia due to various causes, and explains the value of CT findings for specific diagnosis.

  7. Ku Band Rotary Joint Design for SNG Vehicles

    Directory of Open Access Journals (Sweden)

    H. Torpi

    2015-12-01

    Full Text Available A wideband I-type rectangular waveguide rotary joint (RJ is designed, simulated and built. It has an excellent performance over the whole Ku Band (10.7-14.5 GHz where the return loss is less than -23 dB at its highest and the insertion loss is below 0.4 dB. The rotary joint is specifically designed for satellite news gathering (SNG vehicles providing elevation and azimuthal movement to the antenna and matching polarization when it is needed at the feed. It can also be used in other high power microwave applications,where rotation ability of the antenna is a must during the transmission such as radars.

  8. A rotary nano ion pump: a molecular dynamics study.

    Science.gov (United States)

    Lohrasebi, A; Feshanjerdi, M

    2012-09-01

    The dynamics of a rotary nano ion pump, inspired by the F (0) part of the F(0)F(1)-ATP synthase biomolecular motor, were investigated. This nanopump is composed of a rotor, which is constructed of two carbon nanotubes with benzene rings, and a stator, which is made of six graphene sheets. The molecular dynamics (MD) method was used to simulate the dynamics of the ion nanopump. When the rotor of the nanopump rotates mechanically, an ion gradient will be generated between the two sides of the nanopump. It is shown that the ion gradient generated by the nanopump is dependant on parameters such as the rotary frequency of the rotor, temperature and the amounts and locations of the positive and negative charges of the stator part of the nanopump. Also, an electrical potential difference is generated between the two sides of the pump as a result of its operation.

  9. SIMULATION ANALYSIS OF PREHEATER CHARGE TO THE ROTARY FURNACE

    Directory of Open Access Journals (Sweden)

    Jan Mikula

    2015-08-01

    Full Text Available Mathematical modeling of heat aggregates is one of the fundamental methods of the mathematical modelling research. A mathematical model based on the method of elementary balances was created for the thermal treatment of granular and lumpy materials. The adaptation of the selected aggregate model is based on prior knowledge and experiments. The paper presents an adaptation of the mathematical model for the magnesite processing rotary furnace using the mode of caustic and clinker production. A simulation of the charge preheater impact based on the thin layer principle is implemented into the model. The main advantages of using this type of preheater of rotary furnace are smaller dimensions for a large exchange surface and low pressure losses.

  10. Effect of rotational speed in rotary hammer forging process

    Directory of Open Access Journals (Sweden)

    Hamdy Muhammad M

    2015-01-01

    Full Text Available Rotary press forging (RPF has been used in the last century, but it produces many defects in the forgings. The author has invented the rotary hammer forging (RHF process to reduce such defects. RHF is a multi-axes compression process where the material is partially and incrementally deformed by the action of several repeated hammering blows, while the produced deformation region is swept through the whole area of the workpiece. The aim of the present work is to study the effects of rotational speed on the forgings produced by RPF and RHF to compare between the two processes. It has been found that as the rotational speed increases the mushroom effect is constant in RHF while it is greater and increases in RPF. As the rotational speed increases, the twist angle increases in both RHF and RPF, but it is bigger in RPF. These results demonstrate the benefits of using RHF instead of RPF.

  11. The Worringham and Beringer 'visual field' principle for rotary controls.

    Science.gov (United States)

    Hoffmann, Errol R; Chan, Alan H S

    2013-01-01

    Worringham and Beringer (1989, 1998) developed a very important principle relating compatibility of movement of horizontally moving translational controls to display movements when the operator's view of the display is in a plane different to that of the control. On the basis of past data of the current authors, it is shown that the visual field principle also applies to the operation of vertically moving translational controls and to rotary controls. These additions make the Worringham and Beringer principle the most powerful design principle available for situations where the operator is viewing a display that is not in the same plane as the control. High compatibility between control input and display output is of great importance in machine design. This paper demonstrates that, for cases where the display is not in the same plane as the control, the visual field principle is operational for vertically moving translational controls and rotary controls as well as for horizontally moving translational controls.

  12. A Diagnostic System for Speed-Varying Motor Rotary Faults

    Directory of Open Access Journals (Sweden)

    Chwan-Lu Tseng

    2014-01-01

    Full Text Available This study proposed an intelligent rotary fault diagnostic system for motors. A sensorless rotational speed detection method and an improved dynamic structural neural network are used. Moreover, to increase the convergence speed of training, a terminal attractor method and a hybrid discriminant analysis are also adopted. The proposed method can be employed to detect the rotary frequencies of motors with varying speeds and can enhance the discrimination of motor faults. To conduct the experiments, this study used wireless sensor nodes to transmit vibration data and employed MATLAB to write codes for functional modules, including the signal processing, sensorless rotational speed estimation, neural network, and stochastic process control chart. Additionally, Visual Basic software was used to create an integrated human-machine interface. The experimental results regarding the test of equipment faults indicated that the proposed novel diagnostic system can effectively estimate rotational speeds and provide superior ability of motor fault discrimination with fast training convergence.

  13. Electronic transport in single-helical protein molecules: Effects of multiple charge conduction pathways and helical symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Kundu, Sourav, E-mail: sourav.kunduphy@gmail.com; Karmakar, S.N.

    2016-07-15

    We propose a tight-binding model to investigate electronic transport properties of single helical protein molecules incorporating both the helical symmetry and the possibility of multiple charge transfer pathways. Our study reveals that due to existence of both the multiple charge transfer pathways and helical symmetry, the transport properties are quite rigid under influence of environmental fluctuations which indicates that these biomolecules can serve as better alternatives in nanoelectronic devices than its other biological counterparts e.g., single-stranded DNA.

  14. Comparison of Two Canal Preparation Techniques Using Mtwo Rotary Instruments

    OpenAIRE

    Hamze, Faeze; Honardar, Kiamars; Nazarimoghadam, Kiumars

    2011-01-01

    INTRODUCTION Root canal preparation is an important process in endodontic therapy. Nickel-titanium (NiTi) rotary file system can be used in single length technique (simultaneous technique) without early coronal enlargement, as well as in crown-down method. The purpose of this in vitro study was to compare single length with crown-down methods’ shaping ability using Mtwo NiTi files. MATERIALS AND METHODS Fifteen acrylic-resin blocks containing simulated canals were divided into two experimenta...

  15. Rotary inverted pendulum: Trajectory tracking via nonlinear control techniques

    Czech Academy of Sciences Publication Activity Database

    Ramos-Velasco, Luis Enrique; Ruiz-León, J. J.; Čelikovský, Sergej

    2002-01-01

    Roč. 38, č. 2 (2002), s. 217-232 ISSN 0023-5954 R&D Projects: GA ČR GA102/02/0709 Grant - others:CONACYT(MX) 31844-A Institutional research plan: CEZ:AV0Z1075907 Keywords : nonlinear systems * rotary inverted pendulum * output regulation * sliding modes Subject RIV: BC - Control Systems Theory Impact factor: 0.341, year: 2002

  16. Piezoelectric Versus Conventional Rotary Techniques for Impacted Third Molar Extraction

    Science.gov (United States)

    Jiang, Qian; Qiu, Yating; Yang, Chi; Yang, Jingyun; Chen, Minjie; Zhang, Zhiyuan

    2015-01-01

    Abstract Impacted third molars are frequently encountered in clinical work. Surgical removal of impacted third molars is often required to prevent clinical symptoms. Traditional rotary cutting instruments are potentially injurious, and piezosurgery, as a new osteotomy technique, has been introduced in oral and maxillofacial surgery. No consistent conclusion has been reached regarding whether this new technique is associated with fewer or less severe postoperative sequelae after third molar extraction. The aim of this study was to compare piezosurgery with rotary osteotomy techniques, with regard to surgery time and the severity of postoperative sequelae, including pain, swelling, and trismus. We conducted a systematic literature search in the Cochrane Library, PubMed, Embase, and Google Scholar. The eligibility criteria of this study included the following: the patients were clearly diagnosed as having impacted mandibular third molars; the patients underwent piezosurgery osteotomy, and in the control group rotary osteotomy techniques, for removing impacted third molars; the outcomes of interest include surgery time, trismus, swelling or pain; the studies are randomized controlled trials. We used random-effects models to calculate the difference in the outcomes, and the corresponding 95% confidence interval. We calculated the weighted mean difference if the trials used the same measurement, and a standardized mean difference if otherwise. A total of seven studies met the eligibility criteria and were included in our analysis. Compared with rotary osteotomy, patients undergoing piezosurgery experienced longer surgery time (mean difference 4.13 minutes, 95% confidence interval 2.75–5.52, P trismus in the piezosurgery groups. The number of included randomized controlled trials and the sample size of each trial were relatively small, double blinding was not possible, and cost analysis was unavailable due to a lack of data. Our meta-analysis indicates that although

  17. A rotary piezoelectric actuator using longitudinal and bending hybrid transducer

    OpenAIRE

    Yingxiang Liu; Xiaohui Yang; Weishan Chen; Junkao Liu

    2012-01-01

    A rotary piezoelectric actuator using bolt-clamped type transducer with double driving feet is proposed in this study. The first-order longitudinal and fourth-order bending vibration modes are superimposed in the actuator to produce elliptical movements on the driving tips. Longitudinal PZT and bending PZT are clamped between the exponential shape horns and the flange by bolts. The vibration shape changes of the actuator are presented to give a clear explanation of its working principle. Seve...

  18. A Review of Heavy-Fueled Rotary Engine Combustion Technologies

    Science.gov (United States)

    2011-05-01

    Engine displacement and CR are determined with these measurements. Shih et al. (63) performed a numerical analysis of the unsteady multidimensional...combustion should be performed together with turbocharging as well as fuel injector and combustion chamber designs and fuel injection strategies. These...Vol. 98. 56. Meng, P. R.; Rice, W. J.; Schock, H. J.; Pringle, D. P. Preliminary Results on Performance Testing of a Turbocharged Rotary

  19. Rotary endodontics in primary teeth – A review

    OpenAIRE

    George, Sageena; Anandaraj, S.; Issac, Jyoti S.; John, Sheen A.; Harris, Anoop

    2015-01-01

    Endodontic treatment in primary teeth can be challenging and time consuming, especially during canal preparation, which is considered one of the most important steps in root canal therapy. The conventional instrumentation technique for primary teeth remains the “gold-standard” over hand instrumentation, which makes procedures much more time consuming and adversely affects both clinicians and patients. Recently nickel–titanium (Ni–Ti) rotary files have been developed for use in pediatric endod...

  20. Development of a rotary instrumentation system, phase 2

    Science.gov (United States)

    Adler, A.; Skidmore, W.

    1982-01-01

    A rotary instrumentation system which consists of ruggedized miniature telemetry transmitters installed on the rotating shaft of a gas turbine engine to telemeter the outputs of sensors (strain gages, thermocouples, etc.) on rotating engine components was designed. A small prototype system, which demonstrates the capabilities of performing in the intended environment and demonstrates that the system is expandable to handle about 100 data channels was developed.

  1. Experimental determination of bone cortex holding power of orthopedic screw

    Directory of Open Access Journals (Sweden)

    Bolliger Neto Raul

    1999-01-01

    Full Text Available Cylindrical specimens of bone measuring 15 mm in diameter were obtained from the lateral cortical layer of 10 pairs of femurs and tibias. A central hole 3.2 mm in diameter was drilled in each specimen. The hole was tapped, and a 4.5 mm cortical bone screw was inserted from the outer surface. The montage was submitted to push-out testing up to a complete strip of the bone threads. The cortical thickness and rupture load were measured, and the shear stress was calculated. The results were grouped according to the bone segment from which the specimen was obtained. The results showed that bone cortex screw holding power is dependent on the bone site. Additionally, the diaphyseal cortical bone tissue is both quantitatively and qualitatively more resistant to screw extraction than the metaphyseal tissue.

  2. Odontoid screw fixation for fresh and remote fractures.

    Science.gov (United States)

    Rao, Ganesh; Apfelbaum, Ronald I

    2005-12-01

    Fractures of the odontoid process are common, accounting for 10% to 20% of all cervical spine fractures. Odontoid process fractures are classified into three types depending on the location of the fracture line. Various treatment options are available for each of these fracture types and include application of a cervical orthosis, direct anterior screw fixation, and posterior cervical fusion. If a patient requires surgical treatment of an odontoid process fracture, the timing of treatment may affect fusion rates, particularly if direct anterior odontoid screw fixation is selected as the treatment method. For example, type II odontoid fractures treated within the first 6 months of injury with direct anterior odontoid screw fixation have an 88% fusion rate, whereas fractures treated after 18 months have only a 25% fusion rate. In this review, we discuss the etiology, biomechanics, diagnosis, and treatment (including factors affecting fusion such as timing and fracture orientation) options available for odontoid process fractures.

  3. New concept single screw compressors and their manufacture technology

    Science.gov (United States)

    Feng, Q.; Liu, F.; Chang, L.; Feng, C.; Peng, C.; Xie, J.; van den Broek, M.

    2017-08-01

    Single screw compressors were generally acknowledged as one of the nearly perfect machines by compressor researchers and manufacturers. However the rapid wear of the star-wheel in a single screw compressor during operation is a key reason why it hasn’t previously joined the main current compressors’ market. After more than ten years of effective work, the authors of this paper have proposed a new concept single screw compressor whose mesh-couple profile is enveloped with multi-column. Also a new design method and manufacture equipment for this kind of compressor have been developed and are described in this paper. A lot of prototype tests and a long period of industrial operations under full loading conditions have shown that the mesh-couple profiles of the new concept single compressors have excellent anti-wearness.

  4. Bioabsorbable metal screws in traumatology: A promising innovation

    Directory of Open Access Journals (Sweden)

    Roland Biber

    2017-04-01

    Full Text Available MAGNEZIX® CS (Syntellix AG, Hanover, Germany is a bioabsorbable compression screw made of a magnesium alloy (MgYREZr. Currently there are only two clinical studies reporting on a limited number of elective patients who received this screw in a hallux valgus operation. We applied MAGNEZIX® CS for fixation of distal fibular fracture in a trauma patient who had sustained a bimalleolar fracture type AO 44-B2.3. Clinical course was uneventful, fracture healing occurred within three months. Follow-up X-rays showed a radiolucent area around the implant for some months, yet this radiolucent area had disappeared in the 17-months follow-up X-ray. Keywords: Magnesium, Bioabsorbable, Compression screw, Osteosynthesis, Ankle fracture

  5. Influence of bacterial colonization of the healing screws on peri-implant tissue

    Directory of Open Access Journals (Sweden)

    Simonetta D'Ercole

    2013-06-01

    Conclusion: The healing screws left in situ for a period of 90 days caused a peri-implant inflammation and the presence of periodontal pathogenic bacteria in the peri-implant sulcus, due to the plaque accumulation on screw surfaces.

  6. Correlation of bone equivalent mineral density to pull-out resistance of triangulated pedicle screw construct.

    Science.gov (United States)

    Hadjipavlou, A G; Nicodemus, C L; al-Hamdan, F A; Simmons, J W; Pope, M H

    1997-02-01

    Thirty single-pedicle and triangulated pedicle screws were subjected to pull-out tests until complete dislodgment was achieved. Peak load, displacement curves, angle of triangulation, and equivalent mineral density were recorded. Dual pedicle screw triangulation produced a 154.4% increase in peak pull-out strength compared with that of the single pedicle screw. Salvage triangulation (replacing failed screws with a triangulation construct) produced a 127.4% increase in peak strength over that of the single screw. Positive correlation was found between individual screw peak strength, bone mineral density, and displacement at peak load. Primary and salvage triangulation produced higher resistance to pull-out than a single pedicle screw, which reflects the potential, beneficial effect of using this technique. Triangulation, therefore, can be used as primary (prophylactic) technique to enhance pedicular screw pull-out during forceful vertebral manipulation.

  7. Design and multi-physics optimization of rotary MRF brakes

    Science.gov (United States)

    Topcu, Okan; Taşcıoğlu, Yiğit; Konukseven, Erhan İlhan

    2018-03-01

    Particle swarm optimization (PSO) is a popular method to solve the optimization problems. However, calculations for each particle will be excessive when the number of particles and complexity of the problem increases. As a result, the execution speed will be too slow to achieve the optimized solution. Thus, this paper proposes an automated design and optimization method for rotary MRF brakes and similar multi-physics problems. A modified PSO algorithm is developed for solving multi-physics engineering optimization problems. The difference between the proposed method and the conventional PSO is to split up the original single population into several subpopulations according to the division of labor. The distribution of tasks and the transfer of information to the next party have been inspired by behaviors of a hunting party. Simulation results show that the proposed modified PSO algorithm can overcome the problem of heavy computational burden of multi-physics problems while improving the accuracy. Wire type, MR fluid type, magnetic core material, and ideal current inputs have been determined by the optimization process. To the best of the authors' knowledge, this multi-physics approach is novel for optimizing rotary MRF brakes and the developed PSO algorithm is capable of solving other multi-physics engineering optimization problems. The proposed method has showed both better performance compared to the conventional PSO and also has provided small, lightweight, high impedance rotary MRF brake designs.

  8. Micro-assembly of three-dimensional rotary MEMS mirrors

    Science.gov (United States)

    Wang, Lidai; Mills, James K.; Cleghorn, William L.

    2009-02-01

    We present a novel approach to construct three-dimensional rotary micro-mirrors, which are fundamental components to build 1×N or N×M optical switching systems. A rotary micro-mirror consists of two microparts: a rotary micro-motor and a micro-mirror. Both of the two microparts are fabricated with PolyMUMPs, a surface micromachining process. A sequential robotic microassembly process is developed to join the two microparts together to construct a threedimensional device. In order to achieve high positioning accuracy and a strong mechanical connection, the micro-mirror is joined to the micro-motor using an adhesive mechanical fastener. The mechanical fastener has self-alignment ability and provides a temporary joint between the two microparts. The adhesive bonding can create a strong permanent connection, which does not require extra supporting plates for the micro-mirror. A hybrid manipulation strategy, which includes pick-and-place and pushing-based manipulations, is utilized to manipulation the micro-mirror. The pick-andplace manipulation has the ability to globally position the micro-mirror in six degrees of freedom. The pushing-based manipulation can achieve high positioning accuracy. This microassembly approach has great flexibility and high accuracy; furthermore, it does not require extra supporting plates, which greatly simplifies the assembly process.

  9. Fatigue behavior of lubricated Ni-Ti endodontic rotary instruments

    Directory of Open Access Journals (Sweden)

    A. Brotzu

    2014-04-01

    Full Text Available The use of Ni-Ti alloys in the practice of endodontic comes from their important properties such as shape memory and superelasticity phenomena, good corrosion resistance and high compatibility with biological tissues. In the last twenty years a great variety of nickel-titanium rotary instruments, with various sections and taper, have been developed and marketed. Although they have many advantages and despite their increasing popularity, a major concern with the use of Ni-Ti rotary instruments is the possibility of unexpected failure in use due to several reasons: novice operator handling, presence manufacturing defects, fatigue etc. Recently, the use of an aqueous gel during experimental tests showed a longer duration of the instruments. The aim of the present work is to contribute to the study of the fracture behavior of these endodontic rotary instruments particularly assessing whether the use of the aqueous lubricant gel can extend their operative life stating its reasons. A finite element model (FEM has been developed to support the experimental results. The results were rather contradictory, also because the Perspex (Poly-methyl methacrylate, PMMA cannot simulate completely the dentin mechanical behavior; however the results highlight some interesting points which are discussed in the paper.

  10. Rotation of artificial rotor axles in rotary molecular motors.

    Science.gov (United States)

    Baba, Mihori; Iwamoto, Kousuke; Iino, Ryota; Ueno, Hiroshi; Hara, Mayu; Nakanishi, Atsuko; Kishikawa, Jun-Ichi; Noji, Hiroyuki; Yokoyama, Ken

    2016-10-04

    F 1 - and V 1 -ATPase are rotary molecular motors that convert chemical energy released upon ATP hydrolysis into torque to rotate a central rotor axle against the surrounding catalytic stator cylinder with high efficiency. How conformational change occurring in the stator is coupled to the rotary motion of the axle is the key unknown in the mechanism of rotary motors. Here, we generated chimeric motor proteins by inserting an exogenous rod protein, FliJ, into the stator ring of F 1 or of V 1 and tested the rotation properties of these chimeric motors. Both motors showed unidirectional and continuous rotation, despite no obvious homology in amino acid sequence between FliJ and the intrinsic rotor subunit of F 1 or V 1 These results showed that any residue-specific interactions between the stator and rotor are not a prerequisite for unidirectional rotation of both F 1 and V 1 The torque of chimeric motors estimated from viscous friction of the rotation probe against medium revealed that whereas the F 1 -FliJ chimera generates only 10% of WT F 1 , the V 1 -FliJ chimera generates torque comparable to that of V 1 with the native axle protein that is structurally more similar to FliJ than the native rotor of F 1 This suggests that the gross structural mismatch hinders smooth rotation of FliJ accompanied with the stator ring of F 1 .

  11. Multi-Fuel Rotary Engine for General Aviation Aircraft

    Science.gov (United States)

    Jones, C.; Ellis, D. R.; Meng, P. R.

    1983-01-01

    Design studies, conducted for NASA, of Advanced Multi-fuel General Aviation and Commuter Aircraft Rotary Stratified Charge Engines are summarized. Conceptual design studies of an advanced engine sized to provide 186/250 shaft KW/HP under cruise conditions at 7620/25,000 m/ft. altitude were performed. Relevant engine development background covering both prior and recent engine test results of the direct injected unthrottled rotary engine technology, including the capability to interchangeably operate on gasoline, diesel fuel, kerosene, or aviation jet fuel, are presented and related to growth predictions. Aircraft studies, using these resultant growth engines, define anticipated system effects of the performance and power density improvements for both single engine and twin engine airplanes. The calculated results indicate superior system performance and 30 to 35% fuel economy improvement for the Rotary-engine airplanes as compared to equivalent airframe concept designs with current baseline engines. The research and technology activities required to attain the projected engine performance levels are also discussed.

  12. Numerical Investigations of an Optimized Airfoil with a Rotary Cylinder

    Science.gov (United States)

    Gada, Komal; Rahai, Hamid

    2015-11-01

    Numerical Investigations of an optimized thin airfoil with a rotary cylinder as a control device for reducing separation and improving lift to drag ratio have been performed. Our previous investigations have used geometrical optimization for development of an optimized airfoil with increased torque for applications in a vertical axis wind turbine. The improved performance was due to contributions of lift to torque at low angles of attack. The current investigations have been focused on using the optimized airfoil for micro-uav applications with an active flow control device, a rotary cylinder, to further control flow separation, especially during wind gust conditions. The airfoil has a chord length of 19.66 cm and a width of 25 cm with 0.254 cm thickness. Previous investigations have shown flow separation at approximately 85% chord length at moderate angles of attack. Thus the rotary cylinder with a 0.254 cm diameter was placed slightly downstream of the location of flow separation. The free stream mean velocity was 10 m/sec. and investigations have been performed at different cylinder's rotations with corresponding tangential velocities higher than, equal to and less than the free stream velocity. Results have shown more than 10% improvement in lift to drag ratio when the tangential velocity is near the free stream mean velocity. Graduate Assistant, Center for Energy and Environmental Research and Services (CEERS), College of Engineering, California State University, Long Beach.

  13. Design analysis of rotary turret of poucher machine

    Directory of Open Access Journals (Sweden)

    Jigar G. Patel

    2016-09-01

    Full Text Available This paper present design analysis of rotary turret plate of 5 kg capacity for food product packaging machine. The turret plate has been designed considering two different criteria, first one is inertia force approach with only self-weight of turret plate and second is with mass of pouches. A 3-dimenssional CAD model of rotary turret assembly has been prepared in using solid modelling packages CRE-O. The finite element analysis (FEA of turret plate has been carried out using analysis software ANSYS 15.0. Consideration of inertia force is one of the criteria to analyze the performance and behaviour of component in working condition. The rotational velocity is applied at the central axis of turret and friction less support is applied on inner surface, where shaft is being attached. Also, pressure is applied on the same surface to incorporate the shrink fit condition of the assembly of turret plate with shaft. The boundary conditions as fixed support have been considered at the different sixteen faces, where bolts have been attached. The obtained simulation results for induced stress, deformation and strain depict that the modified design of rotary turret plate is well within the allowable stress limits of considered material. And, further optimization can be performed for topological and strength based more efficient design of turret plate.

  14. Robustness of the rotary catalysis mechanism of F1-ATPase.

    Science.gov (United States)

    Watanabe, Rikiya; Matsukage, Yuki; Yukawa, Ayako; Tabata, Kazuhito V; Noji, Hiroyuki

    2014-07-11

    F1-ATPase (F1) is the rotary motor protein fueled by ATP hydrolysis. Previous studies have suggested that three charged residues are indispensable for catalysis of F1 as follows: the P-loop lysine in the phosphate-binding loop, GXXXXGK(T/S); a glutamic acid that activates water molecules for nucleophilic attack on the γ-phosphate of ATP (general base); and an arginine directly contacting the γ-phosphate (arginine finger). These residues are well conserved among P-loop NTPases. In this study, we investigated the role of these charged residues in catalysis and torque generation by analyzing alanine-substituted mutants in the single-molecule rotation assay. Surprisingly, all mutants continuously drove rotary motion, even though the rotational velocity was at least 100,000 times slower than that of wild type. Thus, although these charged residues contribute to highly efficient catalysis, they are not indispensable to chemo-mechanical energy coupling, and the rotary catalysis mechanism of F1 is far more robust than previously thought. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  15. Numerical Analysis on Combustion Characteristic of Leaf Spring Rotary Engine

    Directory of Open Access Journals (Sweden)

    Yan Zhang

    2015-08-01

    Full Text Available The purpose of this paper is to investigate combustion characteristics for rotary engine via numerical studies. A 3D numerical model was developed to study the influence of several operative parameters on combustion characteristics. A novel rotary engine called, “Leaf Spring Rotary Engine”, was used to illustrate the structure and principle of the engine. The aims are to (1 improve the understanding of combustion process, and (2 quantify the influence of rotational speed, excess air ratio, initial pressure and temperature on combustion characteristics. The chamber space changed with crankshaft rotation. Due to the complexity of chamber volume, an equivalent modeling method was presented to simulate the chamber space variation. The numerical simulations were performed by solving the incompressible, multiphase Unsteady Reynolds-Averaged Navier–Stokes Equations via the commercial code FLUENT using a transport equation-based combustion model; a realizable  turbulence model and finite-rate/eddy-dissipation model were used to account for the effect of local factors on the combustion characteristics.

  16. Vibration analysis of rotary cement kiln using finite element method

    Directory of Open Access Journals (Sweden)

    Basri Hasan

    2017-01-01

    Full Text Available In this research, the implementation of shell of kiln problem has been discussed. The results are analysed in detail in this research for fatigue life for the shell of a kiln. In this work, the shell of the kiln has been modelled by Solid Works. This simulation showed how the most relevant aspects of the developed work presented in this paper can contribute to the state-of-the-art of the analysis of fatigue life of rotary cement kiln technique with innovative ideas and strategies. It also reviews that the obtained results achieve the proposed objectives. Based on the FEA the transfer matrices and overall transfer equation are developed to calculate natural frequencies, and response overall motion equation is established for response analysis. Due to the dimensionality of the problem addressed, the research specification has to set limits to the applicability of the research by selecting only mechanical load problems in rotary cement kiln tasks and goal-seeking to predict the fatigue life simulation investigated. From the simulation, model and boundary conditions are defined. Crack growth behaviour in the rotary kiln was predicted.

  17. Testing and Development of a Percussive Augmenter for Rotary Drills

    Science.gov (United States)

    Donnelly, Christopher; Bar-Cohen, Yoseph; Chang, Zensheu; Badescu, Mircea; Sherrit, Stewart

    2011-01-01

    Hammering drills are effective in fracturing the drilled medium while rotary drills remove cuttings. The combination provides a highly effective penetration mechanism. Piezoelectric actuators were integrated into an adapter to produce ultrasonic percussion; augmenting rotary drilling. The drill is capable of operating at low power, low applied force and, with proper tuning, low noise. These characteristics are of great interest for future NASA missions and the construction/remodeling industry. The developed augmenter connects a commercially available drill and bit and was tested to demonstrate its capability. Input power to the drill was read using a multimeter and the augmenter received a separate input voltage. The drive frequency of the piezoelectric actuator was controlled by a hill climb algorithm that optimizes and records average power usage to operate the drill at resonating frequency. Testing the rotary drill and augmenter across a range of combinations with total power constant at 160 Watts has shown results in concrete and limestone samples that are as good as or better than the commercial drill. The drill rate was increased 1.5 to over 10 times when compared to rotation alone.

  18. Robustness of the Rotary Catalysis Mechanism of F1-ATPase*

    Science.gov (United States)

    Watanabe, Rikiya; Matsukage, Yuki; Yukawa, Ayako; Tabata, Kazuhito V.; Noji, Hiroyuki

    2014-01-01

    F1-ATPase (F1) is the rotary motor protein fueled by ATP hydrolysis. Previous studies have suggested that three charged residues are indispensable for catalysis of F1 as follows: the P-loop lysine in the phosphate-binding loop, GXXXXGK(T/S); a glutamic acid that activates water molecules for nucleophilic attack on the γ-phosphate of ATP (general base); and an arginine directly contacting the γ-phosphate (arginine finger). These residues are well conserved among P-loop NTPases. In this study, we investigated the role of these charged residues in catalysis and torque generation by analyzing alanine-substituted mutants in the single-molecule rotation assay. Surprisingly, all mutants continuously drove rotary motion, even though the rotational velocity was at least 100,000 times slower than that of wild type. Thus, although these charged residues contribute to highly efficient catalysis, they are not indispensable to chemo-mechanical energy coupling, and the rotary catalysis mechanism of F1 is far more robust than previously thought. PMID:24876384

  19. Design of an Improved Type Rotary Inductive Coupling Structure for Rotatable Contactless Power Transfer System

    Directory of Open Access Journals (Sweden)

    Lee Jia-You

    2015-01-01

    Full Text Available This paper is aimed at analyzing the rotary inductive coupling structure of contactless rotary transformer. The main feature of the proposed rotatable contactless power transfer system is which winding is coaxial-interlayered for improving the magnetic coupling capability. There is no ferrite core used in the secondary-side of the rotary inductive coupling structure, this helps to ease the exerted force that is stress by the secondary-side on spindle. In order to verify the feasibility of the proposed contactless power transfer system for rotary applications, an inductive powered rotary machinery and the control system have been integrated. The experimental results show that the maximum power transfer efficiency of the proposed rotary inductive coupling structure is about 94.8%. The maximum output power received in the load end is 1030 W with transmission efficiency of 88%.

  20. Posterior atlantoaxial transpedicle screw fixation for traumatic atlatoaxial instability

    Directory of Open Access Journals (Sweden)

    Zheng-lei WANG

    2015-10-01

    Full Text Available Objective To explore the clinical efficacy of posterior atlantoaxial pedicle screw fixation for traumatic atlantoaxial instability. Methods From September 2009 to March 2013, 17 patients with atlantoaxial instability received posterior atlantoaxial pedicle screw fixation. There were 12 males and 5 females, with a mean age of 42 years old (ranged from 19 to 63 years old. Transpedicle screw fixation was employed in 8 patients with atlantoaxial fracture and dislocation, in 2 with traumatic disruption of transverse atlantal ligament, and in 7 with odontoid fracture. The Japanese Orthopaedic Association (JOA score before operation was from 5 to 14, with a mean of 11.2. Preoperative CT, MRI and radiographs, as well as intraoperative screw placement and bone graft were administered in all the patients. Results In all the patients, complete reduction was achieved without injury to the vertebral artery, spinal cord or never root, and they started to be ambulatory on the first day after the operation. The patients were followed up for 6-36 months (mean 21 months, and clinical symptoms were seen to be improved significantly. Imaging reexamination 6 months after the surgery showed satisfactory healing of implanted bone and position of all the screws without loosening of the implant. The mean JOA scores was 15.5(11.0-17.0 twelve months after the operation. Conclusion Atlantoaxial pedicle screw fixation for traumatic atlantoaxial instability is safe and reliable with a favorable clinical result. DOI: 10.11855/j.issn.0577-7402.2015.09.14

  1. Torsional stability of interference screws derived from bovine bone - a biomechanical study

    Directory of Open Access Journals (Sweden)

    Schmitt Jan

    2010-05-01

    Full Text Available Abstract Background In the present biomechanical study, the torsional stability of different interference screws, made of bovine bone, was tested. Interference screws derived from bovine bone are a possible biological alternative to conventional metallic or bioabsorbable polymer interference screws. Methods In the first part of the study we compared the torsional stability of self-made 8 mm Interference screws (BC and a commercial 8 mm interference screw (Tutofix®. Furthermore, we compared the torsional strength of BC screws with different diameters. For screwing in, a hexagon head and an octagon head were tested. Maximum breaking torques in polymethyl methacrylate resin were recorded by means of an electronic torque screw driver. In the second part of the study the tibial part of a bone-patellar tendon-bone graft was fixed in porcine test specimens using an 8 mm BC screw and the maximum insertion torques were recorded. Each interference screw type was tested 5 times. Results There was no statistically significant difference between the different 8 mm interference screws (p = 0.121. Pairwise comparisons did not reveal statistically significant differences, either. It was demonstrated for the BC screws, that a larger screw diameter significantly leads to higher torsional stability (p = 9.779 × 10-5. Pairwise comparisons showed a significantly lower torsional stability for the 7 mm BC screw than for the 8 mm BC screw (p = 0.0079 and the 9 mm BC screw (p = 0.0079. Statistically significant differences between the 8 mm and the 9 mm BC screw could not be found (p = 0.15. During screwing into the tibial graft channel of the porcine specimens, insertion torques between 0.5 Nm and 3.2 Nm were recorded. In one case the hexagon head of a BC screw broke off during the last turn. Conclusions The BC screws show comparable torsional stability to Tutofix® interference screws. As expected the torsional strength of the screws increases significantly with the

  2. Comparison of fatigue strength of C2 pedicle screws, C2 pars screws, and a hybrid construct in C1-C2 fixation.

    Science.gov (United States)

    Su, Brian W; Shimer, Adam L; Chinthakunta, Suresh; Salloum, Kanaan; Ames, Christopher P; Vaccaro, Alexander R; Bucklen, Brandon

    2014-01-01

    A biomechanical study comparing the fatigue strength of different types of C2 fixation in a C1-C2 construct. To determine the pullout strength of a C2 pedicle screw and C2 pars screw after cyclical testing and differentiate differences in stiffness pre- and post-cyclical loading of 3 different C1-C2 fixations. Some surgeons use a short C2 pars screw in a C1-C2 construct, because it is less technically demanding and/or when the vertebral artery is high riding. Difference in construct stiffness between use of bilateral C2 pedicle screws, bilateral C2 pars screws, or a hybrid construct is unknown. Biomechanical testing was performed on 15 specimens. A bicortical C1 lateral mass screw was used in combination with 1 of 3 methods of C2 fixation: (1) bilateral long C2 pedicle screws (LL), (2) bilateral 14-mm C2 pars screws (SS), and (3) unilateral long C2 pedicle screw with a contralateral 14-mm C2 pars screw (LS). Each construct was subject to 16,000 cycles to simulate the immediate postoperative period. Changes in motion in flexion-extension, lateral bending, and axial rotation were calculated. This was followed by pullout testing. The ability to limit range of motion significantly decreased after cyclical testing in flexion-extension, lateral bending, and axial rotation for all 3 groups. After loading, the LL and LS groups had less percentage of increase in motion in flexion-extension and lateral bending than the SS group. Overall, the average pullout strength of a pedicle screw was 92% stronger than a pars screw. C2 pedicle screws have twice the pullout strength of C2 pars screws after cyclical loading. In cases in which the anatomy limits placement of bilateral C2 pedicle screws, a construct using a unilateral C2 pedicle screw with a contralateral short pars screw is a viable option and compares favorably with a bilateral C2 pedicle screw construct. N/A.

  3. Numerical analysis of helical dielectric elastomer actuator

    Science.gov (United States)

    Park, Jang Ho; Nair, Saurabh; Kim, Daewon

    2017-04-01

    Dielectric elastomer actuators (DEA) are known for its capability of experiencing extreme strains, as it can expand and contract based on specific actuation voltage applied. On contrary, helical DEA (HDEA) with its unique configuration does not only provide the contractile and extendable capabilities, but also can aid in attaining results for bending and torsion. The concept of HDEA embraces many new techniques and can be applied in multiple disciplines. Thus, this paper focuses on the simulation of HDEA with helical compliant electrodes that is a major factor prior to its application. The attributes of the material used to build the structure plays a vital role in the behavior of the system. For numerical analysis of HDEA, the material characteristics are input into a commercial grade software, and then the appropriate analysis is performed to retrieve its outcome. Applying the material characteristics into numerical analysis modeling, the functionality of HDEA for various activations can be achieved, which is used to test and comply with the fabricated final product.

  4. Quantification of a Helical Origami Fold

    Science.gov (United States)

    Dai, Eric; Han, Xiaomin; Chen, Zi

    2015-03-01

    Origami, the Japanese art of paper folding, is traditionally viewed as an amusing pastime and medium of artistic expression. However, in recent years, origami has served as a source of inspiration for innovations in science and engineering. Here, we present the geometric and mechanical properties of a twisting origami fold. The origami structure created by the fold exhibits several interesting properties, including rigid foldibility, local bistability and finely tunable helical coiling, with control over pitch, radius and handedness of the helix. In addition, the pattern generated by the fold closely mimics the twist buckling patterns shown by thin materials, for example, a mobius strip. We use six parameters of the twisting origami pattern to generate a fully tunable graphical model of the fold. Finally, we present a mathematical model of the local bistability of the twisting origami fold. Our study elucidates the mechanisms behind the helical coiling and local bistability of the twisting origami fold, with potential applications in robotics and deployable structures. Acknowledgment to Branco Weiss Fellowship for funding.

  5. Patient's perception on mini-screws used for molar distalization

    OpenAIRE

    Blaya, Micéli Guimarães; Blaya, Diego Segatto; Guimarães, Magáli Beck; Hirakata, Luciana M.; Marquezan, Marcela

    2010-01-01

    PURPOSE: The objective of this study was to evaluate and compare the perceived pain intensity, side effects and discomfort related to the moment of placement, during mechanics and removal of a mini-screw for molar distalization in orthodontic treatment. METHODS: The sample consisted of 30 adult patients with a mean age of 30 years old, with class II malocclusion subdivision right or left. A mini-screw was installed in each patient, in the maxillary arch to provide a molar distalization. The p...

  6. Role of oxygen at screw dislocations in GaN.

    Science.gov (United States)

    Arslan, I; Browning, N D

    2003-10-17

    Here we report the first direct atomic scale experimental observations of oxygen segregation to screw dislocations in GaN using correlated techniques in the scanning transmission electron microscope. The amount of oxygen present in each of the three distinct types of screw dislocation core is found to depend on the evolution and structure of the core, and thus gives rise to a varying concentration of localized states in the band gap. Contrary to previous theoretical predictions, the substitution of oxygen for nitrogen is observed to extend over many monolayers for the open core dislocation.

  7. 16 CFR 1205.6 - Warning label for reel-type and rotary power mowers.

    Science.gov (United States)

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Warning label for reel-type and rotary power... label for reel-type and rotary power mowers. (a) General. Walk-behind power lawn mowers shall be labeled... size relation to each other and to the label as shown in Fig. 7. EC03OC91.016 (b) Rotary mowers. Walk...

  8. Leaching from waste incineration bottom ashes treated in a rotary kiln

    DEFF Research Database (Denmark)

    Hyks, Jiri; Nesterov, Igor; Mogensen, Erhardt

    2011-01-01

    Leaching from municipal solid waste incineration bottom ash treated in a rotary kiln was quantified using a combination of lab-scale leaching experiments and geochemical modelling. Thermal treatment in the rotary kiln had no significant effect on the leaching of Al, Ba, Ca, Mg, Si, Sr, Zn, sulfate...... the thermal treatment. Overall, rotary kiln thermal treatment of bottom ashes can be recommended to reduce the leaching of Cu, Pb, Cl and DOC; however, increased leaching of Cr and Mo should be expected....

  9. A simple technique for on-table confirmation of locking screw ...

    African Journals Online (AJOL)

    radiographs to confirm whether or not the locking screws were correctly placed. Objective: We present a simple, inexpensive, fool-proof technique that confirms the correct placement of the locking screws on table thus allowing for revision at the time of surgery in case the locking screw missed the locking hole in the nail.

  10. The best location for proximal locking screw for femur interlocking nailing: A biomechanical study

    Directory of Open Access Journals (Sweden)

    Ahmet A Karaarslan

    2016-01-01

    Conclusion: According to our findings, there is twice as much difference in locking screw bending resistance between these two application levels. To avoid proximal locking screw deformation, locking screws should be placed in the level of the lesser trochanter in nailing of 1/3 middle and distal femur fractures.

  11. Fracture resistance of abutment screws made of titanium, polyetheretherketone, and carbon fiber-reinforced polyetheretherketone.

    Science.gov (United States)

    Neumann, Eduardo Aloisio Fleck; Villar, Cristina Cunha; França, Fabiana Mantovani Gomes

    2014-01-01

    Fractured abutment screws may be replaced; however, sometimes, the screw cannot be removed and the entire implant must be surgically removed and replaced. The aim of this study was to compare the fracture resistance of abutment retention screws made of titanium, polyetheretherketone (PEEK) and 30% carbon fiber-reinforced PEEK, using an external hexagonal implant/UCLA-type abutment interface assembly. UCLA-type abutments were fixed to implants using titanium screws (Group 1), polyetheretherketone (PEEK) screws (Group 2), and 30% carbon fiber-reinforced PEEK screws (Group 3). The assemblies were placed on a stainless steel holding apparatus to allow for loading at 45o off-axis, in a universal testing machine. A 200 N load (static load) was applied at the central point of the abutment extremity, at a crosshead speed of 5 mm/minute, until failure. Data was analyzed by ANOVA and Tukey's range test. The titanium screws had higher fracture resistance, compared with PEEK and 30% carbon fiber-reinforced PEEK screws (p carbon fiber-reinforced PEEK screws (p> 0.05). Finally, visual analysis of the fractions revealed that 100% of them occurred at the neck of the abutment screw, suggesting that this is the weakest point of this unit. PEEK abutment screws have lower fracture resistance, in comparison with titanium abutment screws.

  12. Screw angulation affects bone-screw stresses and bone graft load sharing in anterior cervical corpectomy fusion with a rigid screw-plate construct: a finite element model study.

    Science.gov (United States)

    Hussain, Mozammil; Natarajan, Raghu N; Fayyazi, Amir H; Braaksma, Brian R; Andersson, Gunnar B J; An, Howard S

    2009-12-01

    Anterior corpectomy and reconstruction with bone graft and a rigid screw-plate construct is an established procedure for treatment of cervical neural compression. Despite its reliability in relieving symptoms, there is a high rate of construct failure, especially in multilevel cases. There has been no study evaluating the biomechanical effects of screw angulation on construct stability; this study investigates the C4-C7 construct stability and load-sharing properties among varying screw angulations in a rigid plate-screw construct. A finite element model of a two-level cervical corpectomy with static anterior cervical plate. A three-dimensional finite element (FE) model of an intact C3-T1 segment was developed and validated. From this intact model, a fusion model (two-level [C5, C6] anterior corpectomy) was developed and validated. After corpectomy, allograft interbody fusion with a rigid anterior screw-plate construct was created from C4 to C7. Five additional FE models were developed from the fusion model corresponding to five different combinations of screw angulations within the vertebral bodies (C4, C7): (0 degrees, 0 degrees), (5 degrees, 5 degrees), (10 degrees, 10 degrees), (15 degrees, 15 degrees), and (15 degrees, 0 degrees). The fifth fusion model was termed as a hybrid fusion model. The stability of a two-level corpectomy reconstruction is not dependent on the position of the screws. Despite the locked screw-plate interface, some degree of load sharing is transmitted to the graft. The load seen by the graft and the shear stress at the bone-screw junction is dependent on the angle of the screws with respect to the end plate. Higher stresses are seen at more divergent angles, particularly at the lower level of the construct. This study suggests that screw divergence from the end plates not only increases load transmission to the graft but also predisposes the screws to higher shear forces after corpectomy reconstruction. In particular, the inferior screw

  13. Numerical Simulations of Helicity Condensation in the Solar Corona

    Science.gov (United States)

    Zhao, L.; DeVore, C. R.; Antiochos, S. K.; Zurbuchen, T. H.

    2015-01-01

    The helicity condensation model has been proposed by Antiochos (2013) to explain the observed smoothness of coronal loops and the observed buildup of magnetic shear at filament channels. The basic hypothesis of the model is that magnetic reconnection in the corona causes the magnetic stress injected by photospheric motions to collect only at those special locations where prominences form. In this work we present the first detailed quantitative MHD simulations of the reconnection evolution proposed by the helicity condensation model. We use the well-known ansatz of modeling the closed corona as an initially uniform field between two horizontal photospheric plates. The system is driven by applying photospheric rotational flows that inject magnetic helicity into the system. The flows are confined to a finite region on the photosphere so as to mimic the finite flux system of, for example, a bipolar active region. The calculations demonstrate that, contrary to common belief, coronal loops having opposite helicity do not reconnect, whereas loops having the same sense of helicity do reconnect. Furthermore, we find that for a given amount of helicity injected into the corona, the evolution of the magnetic shear is insensitive to whether the pattern of driving photospheric motions is fixed or quasi-random. In all cases, the shear propagates via reconnection to the boundary of the flow region while the total magnetic helicity is conserved, as predicted by the model. We discuss the implications of our results for solar observations and for future, more realistic simulations of the helicity condensation process.

  14. Energy fluxes in helical magnetohydrodynamics and dynamo action

    Indian Academy of Sciences (India)

    Renormalized viscosity, renormalized resistivity, and various energy fluxes are calculated for helical magnetohydrodynamics using perturbative field theory. The calculation is of first-order in perturbation. Kinetic and magnetic helicities do not affect the renormalized parameters, but they induce an inverse cascade of ...

  15. Interaction of 18-residue peptides derived from amphipathic helical ...

    Indian Academy of Sciences (India)

    Madhsudhan

    categories (Segrest et al. 1990; Phoenix et al. 1998; Phoenix and Harris 2002). Helices that cause membrane lysis belong to class L and those that bind to lipids but are not lytic, such as those occurring in apolipoproteins, are classified as class. A. Interest in amphipathic helices has further stemmed from the observation that ...

  16. Relative magnetic helicity as a diagnostic of solar eruptivity

    Science.gov (United States)

    Pariat, E.; Leake, J. E.; Valori, G.; Linton, M. G.; Zuccarello, F. P.; Dalmasse, K.

    2017-05-01

    Context. The discovery of clear criteria that can deterministically describe the eruptive state of a solar active region would lead to major improvements on space weather predictions. Aims: Using series of numerical simulations of the emergence of a magnetic flux rope in a magnetized coronal, leading either to eruptions or to stable configurations, we test several global scalar quantities for the ability to discriminate between the eruptive and the non-eruptive simulations. Methods: From the magnetic field generated by the three-dimensional magnetohydrodynamical simulations, we compute and analyze the evolution of the magnetic flux, of the magnetic energy and its decomposition into potential and free energies, and of the relative magnetic helicity and its decomposition. Results: Unlike the magnetic flux and magnetic energies, magnetic helicities are able to markedly distinguish the eruptive from the non-eruptive simulations. We find that the ratio of the magnetic helicity of the current-carrying magnetic field to the total relative helicity presents the highest values for the eruptive simulations, in the pre-eruptive phase only. We observe that the eruptive simulations do not possess the highest value of total magnetic helicity. Conclusions: In the framework of our numerical study, the magnetic energies and the total relative helicity do not correspond to good eruptivity proxies. Our study highlights that the ratio of magnetic helicities diagnoses very clearly the eruptive potential of our parametric simulations. Our study shows that magnetic-helicity-based quantities may be very efficient for the prediction of solar eruptions.

  17. Experimental investigation of solar powered diaphragm and helical pumps

    Science.gov (United States)

    For several years, many types of solar powered water pumping systems were evaluated, and in this paper, diaphragm and helical solar photovoltaic (PV) powered water pumping systems are discussed. Data were collected on diaphragm and helical pumps which were powered by different solar PV arrays at mul...

  18. Two new twisted helical nickel (II) and cobalt (III) octahedral ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 126; Issue 6. Two new twisted helical nickel(II) and cobalt(III) octahedral monomer complexes: Synthesis and structural characterization. Malay Dolai ... Keywords. Coordination chemistry; nickel(II); cobalt(III); Schiff base; twisted helicity; supramolecular interactions.

  19. Space vehicle electromechanical system and helical antenna winding fixture

    Energy Technology Data Exchange (ETDEWEB)

    Judd, Stephen; Dallmann, Nicholas; Guenther, David; Enemark, Donald; Seitz, Daniel; Martinez, John; Storms, Steven

    2017-12-26

    A space vehicle electromechanical system may employ an architecture that enables convenient and practical testing, reset, and retesting of solar panel and antenna deployment on the ground. A helical antenna winding fixture may facilitate winding and binding of the helical antenna.

  20. Micro helical polymeric structures produced by variable voltage direct electrospinning

    NARCIS (Netherlands)

    Shariatpanahi, S.P.; Iraji zad, A.; Abdollahzadeh, I.; Shirsavar, R.; Bonn, D.; Ejtehadi, R.

    2011-01-01

    Direct near field electrospinning is used to produce very long helical polystyrene microfibers in water. The pitch length of helices can be controlled by changing the applied voltage, allowing the production of both microsprings and microchannels. Using a novel high frequency variable voltage

  1. Coronary artery angioplasty with a helical autoperfusion balloon catheter

    NARCIS (Netherlands)

    Gurbel, PA; Anderson, RD; vanBoven, AJ; denHeijer, P

    The initial in-hospital and long-term clinical experience with a helical autoperfusion balloon catheter in the treatment of coronary artery disease is reported, This new catheter design allows blood to flow passively around the inflated balloon through a protected helical channel molded into the

  2. Helicity transport and creation in the solar convection zone

    Science.gov (United States)

    Longcope, D.; Pevtsov, A.

    Magnetic helicity provides a theoretical tool for characterizing the solar dynamo and the evolution of the coronal field. The magnetic helicity may be inferred from several types of observation including vector magnetograms of the photospehric magnetic fields. The helicty of an active region reflects, to some degree, that produced by the solar cycle dyanmo which is believed to be operating at the base of the convection zone, where the Rossby number is small. The helicty of the active region is affected by the turbulence through which it rises, and this process must be taken into account when interpreting helicity observations. The subsequent dispersal of the active region magnetic field will further affect the observed helicty of the photospheric field. This transport process suggests an observational method of identifying, through helicty measurements, the source of quiet Sun field from either a surface (non-helical) dynamo or the fragmentation of helical active region fields.

  3. Chiral Exact Relations for Helicities in Hall Magnetohydrodynamic Turbulence

    CERN Document Server

    Banerjee, Supratik

    2016-01-01

    Besides total energy, three-dimensional incompressible Hall magnetohydrodynamics (MHD) possesses two inviscid invariants which are the magnetic helicity and the generalized helicity. New exact relations are derived for homogeneous (non-isotropic) stationary Hall MHD turbulence (and also for its inertialess electron MHD limit) with non-zero helicities and in the asymptotic limit of large Reynolds numbers. The universal laws are written only in terms of mixed second-order structure functions, i.e. the scalar product of two different increments. It provides, therefore, a direct measurement of the dissipation rates for the corresponding invariant flux. This study shows that the generalized helicity cascade is strongly linked to the left polarized fluctuations while the magnetic helicity cascade is linked to the right polarized fluctuations.

  4. Broadband circularly polarizing dichroism with high efficient plasmonic helical surface.

    Science.gov (United States)

    Hu, Jingpei; Zhao, Xiaonan; Li, Ruibin; Zhu, Aijiao; Chen, Linghua; Lin, Yu; Cao, Bing; Zhu, Xiaojun; Wang, Chinhua

    2016-05-16

    We propose and experimentally demonstrate a broadband and high efficient circularly polarizing dichroism using a simple single-cycle and single-helical plasmonic surface array arranged in square lattice. Two types of helical surface structures (partially or completely covered with a gold film) are investigated. It is shown that the circular polarization dichroism in the mid-IR range (3µm - 5µm) can reach 80% (when the surface is partially covered with gold) or 65% (when the surface is completely covered with gold) with a single-cycle and single-helical surface. Experimental fabrications of the proposed helical plasmonic surface are implemented with direct 3D laser writing followed by electron beam evaporation deposition of gold. The experimental evaluations of the circular polarization dichroism are in excellent agreement with the simulation. The proposed helical surface structure is of advantages of easy-fabrication, high-dichroism and scalable to other frequencies as a high efficient broadband circular polarizer.

  5. Hierarchically arranged helical fibre actuators driven by solvents and vapours

    Science.gov (United States)

    Chen, Peining; Xu, Yifan; He, Sisi; Sun, Xuemei; Pan, Shaowu; Deng, Jue; Chen, Daoyong; Peng, Huisheng

    2015-12-01

    Mechanical responsiveness in many plants is produced by helical organizations of cellulose microfibrils. However, simple mimicry of these naturally occurring helical structures does not produce artificial materials with the desired tunable actuations. Here, we show that actuating fibres that respond to solvent and vapour stimuli can be created through the hierarchical and helical assembly of aligned carbon nanotubes. Primary fibres consisting of helical assemblies of multiwalled carbon nanotubes are twisted together to form the helical actuating fibres. The nanoscale gaps between the nanotubes and micrometre-scale gaps among the primary fibres contribute to the rapid response and large actuation stroke of the actuating fibres. The compact coils allow the actuating fibre to rotate reversibly. We show that these fibres, which are lightweight, flexible and strong, are suitable for a variety of applications such as energy-harvesting generators, deformable sensing springs and smart textiles.

  6. A molecular leverage for helicity control and helix inversion.

    Science.gov (United States)

    Akine, Shigehisa; Hotate, Sayaka; Nabeshima, Tatsuya

    2011-09-07

    The helical tetranuclear complex [LZn(3)La(OAc)(3)] having two benzocrown moieties was designed and synthesized as a novel molecular leverage for helicity control and helix inversion. Short alkanediammonium guests H(3)N(+)(CH(2))(n)NH(3)(+) (n = 4, 6, 8) preferentially stabilized the P-helical isomer of [LZn(3)La(OAc)(3)], while the longer guest H(3)N(+)(CH(2))(12)NH(3)(+) caused a helix inversion to give the M-helical isomer as the major isomer. The differences in the molecular lengths were efficiently translated into helical handedness via the novel molecular leverage mechanism using the gauche/anti conversion of the trans-1,2-disubstituted ethylenediamine unit.

  7. Helicity conservation and twisted Seifert surfaces for superfluid vortices

    Science.gov (United States)

    Salman, Hayder

    2017-04-01

    Starting from the continuum definition of helicity, we derive from first principles its different contributions for superfluid vortices. Our analysis shows that an internal twist contribution emerges naturally from the mathematical derivation. This reveals that the spanwise vector that is used to characterize the twist contribution must point in the direction of a surface of constant velocity potential. An immediate consequence of the Seifert framing is that the continuum definition of helicity for a superfluid is trivially zero at all times. It follows that the Gauss-linking number is a more appropriate definition of helicity for superfluids. Despite this, we explain how a quasi-classical limit can arise in a superfluid in which the continuum definition for helicity can be used. This provides a clear connection between a microscopic and a macroscopic description of a superfluid as provided by the Hall-Vinen-Bekarevich-Khalatnikov equations. This leads to consistency with the definition of helicity used for classical vortices.

  8. A comparison of canal preparations by Mtwo and RaCe rotary files using full sequence versus one rotary file techniques; a cone-beam computed tomography analysis

    Directory of Open Access Journals (Sweden)

    Mohsen Aminsobhani

    2014-01-01

    Full Text Available Objectives: Using one rotary file can result in a faster canal preparation. This can be done with several file systems and endodontic motors. In the present study, a newly single file technique (one rotary file technique with available rotary file systems is introduced. The aim of the present study was to evaluate centering ability and remaining dentin thickness of 2 rotary nickel-titanium systems (Mtwo versus RaCe and instrumentation techniques (conventional versus one rotary file by cone-beam computed tomography. Materials and Methods: A total of 76 mandibular molar teeth were selected and divided to 4 groups (n = 19 teeth with 57 canals. The teeth were mounted in resin and pre-instrumentation scans were prepared by Cone Beam Computed Tomography (CBCT. The canals instrumented with Mtwo and RaCe rotary files either in conventional or one rotary file technique (ORF. After cleaning and shaping of distal and mesial canals, post instrumentation scans were performed by CBCT in the same position as pre instrumentation scans. Centering ability and remaining dentin thickness were evaluated by Planmeca Romexis viewer. The data were analyzed with analysis of variance and post hoc t test (P 0.05. However, in a few cross-sections, conventional technique and/or RaCe showed higher centering ability. One rotary file technique with either RaCe or Mtwo was significantly faster than conventional technique (P = 0.02. There was no significant difference among groups regarding file fracture. Mesiolingual canals showed more transportation compared with mesiobuccal and distal canals. Conclusions: Both of the instrumentation systems and techniques produced canal preparations with adequate centering ratio. One rotary file technique prepared canal significantly faster than conventional technique.

  9. Influence of screw diameter and number on reduction loss after plating of distal radius fractures.

    Science.gov (United States)

    Drobetz, Herwig; Schueller, Michael; Tschegg, Elmar Karl; Heal, Clare; Redl, Heinz; Muller, Reinhold

    2011-01-01

    The current options for plate-screw combinations in volar locking distal radius plates used for the treatment of distal radius fractures are either plates with a single distal screw row or plates with multiple distal screw rows. Additionally, the screws themselves may have either fixed angle locking or polyaxial locking mechanisms. To date, there is no evidence or consensus regarding the optimal plate-screw combination. The aim of this study was to assess the biomechanical behaviour of different plate-screw combinations with respect to total distal screw number, number of distal screw rows and screw projection surface area of the most distal row. Biomechanical study to assess six different plating configurations in five different volar locking plate models in a Sawbone distal radius fracture model. The specimens were loaded with 800 Newton loads for 2.000 cycles at 1 Hz. After cyclic loading, load-to-failure testing was performed.   With cyclical testing, there was a significant and positive correlation between rigidity and a greater projection area of the most distal screws. Dorsal tilting was significantly more pronounced in plate models with a lesser projection area of the most distal screws and a smaller number of distal screws. With load-to-failure testing, there was a significant increase in rigidity with increasing screw projection area of the most distal row and total number of distal screws. Additional distal screw rows in volar locking distal radius plates might not add substantially to resistance against loss of reduction in the post-operative period. © 2010 The Authors. ANZ Journal of Surgery © 2010 Royal Australasian College of Surgeons.

  10. A biomechanical evaluation of three revision screw strategies for failed lateral mass fixation.

    Science.gov (United States)

    Hostin, Richard A; Wu, Chunhui; Perra, Joseph H; Polly, David W; Akesen, Burak; Wroblewski, Jill M

    2008-10-15

    This is a biomechanical study evaluating 3 revision strategies for failed cervical lateral mass screw fixation. Our primary objective was to compare, following a Magerl trajectory screw failure in the subaxial cervical spine, the pullout strength of (1) a revision screw in the same trajectory, (2) a Roy-Camille trajectory, and (3) pedicle screw fixation. We additionally analyzed the contributions of bone mineral density (BMD) and peak insertional torque to pullout strength. Biomechanical studies that have examined revision screw strategies for lateral mass fixation have found either unsatisfactory or highly variable performance. Fresh frozen cervical spinal segments were harvested and BMD testing performed. Bicortical (3.5-mm Vertex) lateral mass screws were placed in a Magerl trajectory in 57 fresh frozen human subaxial cervical vertebrae. All screws were then stripped and revision screws (4.0-mm Vertex) placed using either the same screw path or conversion to a Roy-Camille trajectory. In line pullout testing was performed on each of the revision screws (57 in Magerl revision group, 55 in Roy-Camille). Specimens that had not fractured during testing then had cervical pedicle screws (3.5-mm Vertex) placed and in-line pullout testing repeated (64 pedicles were instrumented) The pullout failure results of the Magerl revision, Roy-Camille revision, and pedicle screw revision groups were compared. No significant difference was noted in insertional torque (0.28-Nm Magerl, 0.35 Nm Roy-Camille, P > 0.05) or pullout (382-N Magerl, 351 N Roy-Camille, P > 0.05) between the Magerl and Roy-Camille revision groups. Pedicle screw revision had greater pullout strength (566 N) when compared with either the Magerl (382 N) or Roy-Camille (351 N) revision groups (P advantage over placement of an increased diameter salvage screw using the same trajectory. Pedicle screw fixation provides superior biomechanical fixation but was associated with a significant breech rate.

  11. The Writhe of Helical Structures in the Solar Corona

    Science.gov (United States)

    Toeroek, T.; Berger, M. A.; Kliem, B.

    2010-01-01

    Context. Helicity is a fundamental property of magnetic fields, conserved in ideal MHD. In flux rope topology, it consists of twist and writhe helicity. Despite the common occurrence of helical structures in the solar atmosphere, little is known about how their shape relates to the writhe, which fraction of helicity is contained in writhe, and how much helicity is exchanged between twist and writhe when they erupt. Aims. Here we perform a quantitative investigation of these questions relevant for coronal flux ropes. Methods. The decomposition of the writhe of a curve into local and nonlocal components greatly facilitates its computation. We use it to study the relation between writhe and projected S shape of helical curves and to measure writhe and twist in numerical simulations of flux rope instabilities. The results are discussed with regard to filament eruptions and coronal mass ejections (CMEs). Results. (1) We demonstrate that the relation between writhe and projected S shape is not unique in principle, but that the ambiguity does not affect low-lying structures, thus supporting the established empirical rule which associates stable forward (reverse) S shaped structures low in the corona with positive (negative) helicity. (2) Kink-unstable erupting flux ropes are found to transform a far smaller fraction of their twist helicity into writhe helicity than often assumed. (3) Confined flux rope eruptions tend to show stronger writhe at low heights than ejective eruptions (CMEs). This argues against suggestions that the writhing facilitates the rise of the rope through the overlying field. (4) Erupting filaments which are S shaped already before the eruption and keep the sign of their axis writhe (which is expected if field of one chirality dominates the source volume of the eruption), must reverse their S shape in the course of the rise. Implications for the occurrence of the helical kink instability in such events are discussed.

  12. Resorbable screws for fixation of autologous bone grafts

    NARCIS (Netherlands)

    Raghoebar, GM; Liem, RSB; Bos, RRM; van der Wal, JE; Vissink, A

    The aim of this study was to evaluate the suitability of resorbable screws made of poly (D,L-lactide) acid (PDLLA) for fixation of autologous bone grafts related to graft regeneration and osseointegration of dental implants. In eight edentulous patients suffering from insufficient retention of their

  13. Modeling The Effect Of Extruder Screw Speed On The Mechanical ...

    African Journals Online (AJOL)

    Mechanical properties of HDPE blown films produced at extruder screw speed between 15 and 40 rpm were measured experimentally. The results were modeled using LINEST function in Microsoft Excel. Two sets of multiple linear regression models were developed to predict impact failure weight and tenacity respectively.

  14. Biomechanical analysis of titanium fixation plates and screws in ...

    African Journals Online (AJOL)

    2015-08-10

    Aug 10, 2015 ... Key words: Bone plates, bone screws, finite element analysis, jaw fixation techniques, mandible, mandibular fractures. Date of Acceptance: 10-Aug- .... miniplates were based on physical specimens of W. Lorenz (Walter Lorenz .... placement via intraoral approach, the small size of the plate, and adaptability ...

  15. Biomechanical analysis of titanium fixation plates and screws in ...

    African Journals Online (AJOL)

    Biomechanical analysis of titanium fixation plates and screws in sagittal split ramus osteotomies. F Atik, MS Ataç1, A Özkan2, Y Kılınç1, M Arslan1. Department of Biomedical Engineering, Faculty of Engineering, Institute of Science, Düzce University,. 2Department of Biomedical Engineering, Faculty of Engineering, Düzce ...

  16. Sacroiliac screw fixation: A mini review of surgical technique

    Directory of Open Access Journals (Sweden)

    Hernando Raphael Alvis-Miranda

    2014-01-01

    Full Text Available The sacral percutaneous fixation has many advantages but can be associated with a significant exposure to X-ray radiation. Currently, sacroiliac screw fixation represents the only minimally invasive technique to stabilize the posterior pelvic ring. It is a technique that should be used by experienced surgeons. We present a practical review of important aspects of this technique.

  17. Residence time distribution in twin-screw extruders

    NARCIS (Netherlands)

    Jager, T.

    1992-01-01

    For the twin-screw extruders used in the food industry at short time high temperature processes the knowledge of their reactor properties is incomplete for mass- and heat flow. Therefore each process change such as: scale-up or product development requires a great number of measurements

  18. Atomistic simulations of jog migration on extended screw dislocations

    DEFF Research Database (Denmark)

    Vegge, T.; Leffers, T.; Pedersen, O.B.

    2001-01-01

    We have performed large-scale atomistic simulations of the migration of elementary jogs on dissociated screw dislocations in Cu. The local crystalline configurations, transition paths. effective masses. and migration barriers for the jogs are determined using an interatomic potential based...

  19. The harmonic oscillator in a space with a screw dislocation

    Science.gov (United States)

    Amore, Paolo; Fernández, Francisco M.

    2018-01-01

    We obtain the eigenvalues of the harmonic oscillator in a space with a screw dislocation. By means of a suitable nonorthogonal basis set with variational parameters we obtain sufficiently accurate eigenvalues for an arbitrary range of values of the space-deformation parameter. The energies exhibit a rich structure of avoided crossings in terms of such model parameter.

  20. Design of new silencers for a screw compressor

    NARCIS (Netherlands)

    Lier, L.J. van; Korst, H.J.C.; Smeulers, J.P.M.

    2014-01-01

    Two screw compressors used for the recycling of waste gas showed high vibration in the discharge piping. To mitigate the vibration problems new silencers had to be designed. A great challenge was the large variation in operating conditions, especially the variation of the molecular weight of the

  1. Cellulose and the twofold screw axis: Modeling and experimental arguments

    Science.gov (United States)

    Crystallography indicates that molecules in crystalline cellulose either have 2-fold screw-axis (21) symmetry or closely approximate it, leading to short distances between H4 and H1' across the glycosidic linkage. Therefore, modeling studies of cellobiose often show elevated energies for 21 structur...

  2. Use of locking plate and screws for triple pelvic osteotomy.

    Science.gov (United States)

    Rose, Scott A; Bruecker, Ken A; Petersen, Steve W; Uddin, Nizam

    2012-01-01

    To evaluate the efficacy and complication rate associated with use of a purpose-specific locking triple pelvic osteotomy (LTPO) plate. Prospective study. Dogs (n = 9; 15 hips). Physical examination, plain film radiography, computed tomography (CT) of the pelvis, and coxofemoral arthroscopy were performed before unilateral triple pelvic osteotomy (TPO) or staged bilateral TPO. Radiographs were taken after each procedure and 3-5, 6-8, and ≥12 weeks postoperatively. Pelvic width was measured at 3 locations to evaluate pelvic canal narrowing. No screw loosening occurred. Complications occurred in only 1 hip (7%) where pullout of the locking plate-screw construct from the caudal iliac segment occurred because of a fracture of the cis-cortex; the dog made a full recovery after a salvage procedure. There was no significant reduction in the cranial pelvic width but a small reduction at the level of the acetabuli and ischiatic tuberosities was noted 3-5 weeks after the 2nd TPO. The LTPO plate was associated with a lower complication rate than previously reported for TPOs using Slocum canine pelvic osteotomy plates (CPOP) and warrants further investigation. Pullout of the caudal plate-screw construct is a complication specific to LTPO implants. Bicortical screw purchase is recommended to prevent fracture of the cis-cortex and implant pullout. © Copyright 2011 by The American College of Veterinary Surgeons.

  3. Hollow Mill for Extraction of Stripped Titanium Screws: An Easy ...

    African Journals Online (AJOL)

    [5] However, the risk of causing a new fracture in the bone in using an osteotome for cutting the screw or plate can lead to a difficult situation especially in revision trauma surgery for non union or peri‑implant fracture. We herewith report a technique of removal of titanium plate in a case of peri‑implant fracture of the radius by.

  4. Effect of twin-screw extrusion parameters on mechanical hardness ...

    Indian Academy of Sciences (India)

    In the food industry, the following operations take place during raw-material processing by extrusion: gelation, extrusion cooking, molecular disintegration, sterilization, mixing, shaping and expansional drying. In the course of conveying the raw material through the extruder by screw-turning, mechanical energy is created ...

  5. Biomechanical analysis of titanium fixation plates and screws in ...

    African Journals Online (AJOL)

    Objective: The aim of this study was to evaluate the mechanical behavior of different rigid fixation methods in mandibular angle fractures. Materials and Methods: Three different three-dimensional finite element models of the mandible were developed to simulate the biomechanical responses of titanium plates and screws.

  6. Construction of the Helicity Injected Torus with Steady Inductive Helicity Injection (HIT-SI)

    Science.gov (United States)

    Sieck, P. E.; Gu, P.; Hamp, W. T.; Izzo, V. A.; Jarboe, T. R.; Nelson, B. A.; Rogers, J. A.

    2001-10-01

    HIT-SI is a ``bow tie'' spheromak designed to implement Steady Inductive Helicity Injection (SIHI). The engineering requirements of SIHI lead to several unique design features, including a multiply connected electrically insulating o-ring seal and a close-fitting passive flux conserver that is electrically insulated from the plasma. Prototype tests have been performed to verify the performance of the o-ring seal and the plasma sprayed zirconia insulation. An engineering test of the new HIT-SI front end will be done before it replaces the present HIT-II front end on HIT. Startup and one millisecond of sustainment will be done to test breakdown and verify power supply requirements. The power supplies and external coils are designed to provide 20 MW at 5 kHz to 50 kHz for 1 ms to the helicity injection circuits for this test. Progress in the construction and assembly of HIT-SI will be presented.

  7. Winding light beams along elliptical helical trajectories

    CERN Document Server

    Wen, Yuanhui; Zhang, Yanfeng; Chen, Hui; Yu, Siyuan

    2016-01-01

    Conventional caustic methods in real or Fourier space produced accelerating optical beams only with convex trajectories. We develop a superposition caustic method capable of winding light beams along non-convex trajectories. We ascertain this method by constructing a one-dimensional (1D) accelerating beam moving along a sinusoidal trajectory, and subsequently extending to two-dimensional (2D) accelerating beams along arbitrarily elliptical helical trajectories. We experimentally implement the method with a compact and robust integrated optics approach by fabricating micro-optical structures on quartz glass plates to perform the spatial phase and amplitude modulation to the incident light, generating beam trajectories highly consistent with prediction. The theoretical and implementation methods can in principle be extended to the construction of accelerating beams with a wide variety of non-convex trajectories, thereby opening up a new route of manipulating light beams for fundamental research and practical ap...

  8. Helical Locomotion in a Granular Medium

    Science.gov (United States)

    Darbois Texier, Baptiste; Ibarra, Alejandro; Melo, Francisco

    2017-08-01

    The physical mechanisms that bring about the propulsion of a rotating helix in a granular medium are considered. A propulsive motion along the axis of the rotating helix is induced by both symmetry breaking due to the helical shape, and the anisotropic frictional forces undergone by all segments of the helix in the medium. Helix dynamics is studied as a function of helix rotation speed and its geometrical parameters. The effect of the granular pressure and the applied external load were also investigated. A theoretical model is developed based on the anisotropic frictional force experienced by a slender body moving in a granular material, to account for the translation speed of the helix. A good agreement with experimental data is obtained, which allows for predicting the helix design to propel optimally within granular media. These results pave the way for the development of an efficient sand robot operating according to this mode of locomotion.

  9. Equilibrium Reconstruction on the Large Helical Device

    Energy Technology Data Exchange (ETDEWEB)

    Samuel A. Lazerson, D. Gates, D. Monticello, H. Neilson, N. Pomphrey, A. Reiman S. Sakakibara, and Y. Suzuki

    2012-07-27

    Equilibrium reconstruction is commonly applied to axisymmetric toroidal devices. Recent advances in computational power and equilibrium codes have allowed for reconstructions of three-dimensional fields in stellarators and heliotrons. We present the first reconstructions of finite beta discharges in the Large Helical Device (LHD). The plasma boundary and magnetic axis are constrained by the pressure profile from Thomson scattering. This results in a calculation of plasma beta without a-priori assumptions of the equipartition of energy between species. Saddle loop arrays place additional constraints on the equilibrium. These reconstruction utilize STELLOPT, which calls VMEC. The VMEC equilibrium code assumes good nested flux surfaces. Reconstructed magnetic fields are fed into the PIES code which relaxes this constraint allowing for the examination of the effect of islands and stochastic regions on the magnetic measurements.

  10. Chiral Spin Pairing in Helical Magnets

    Science.gov (United States)

    Onoda, Shigeki; Nagaosa, Naoto

    2007-07-01

    A concept of chiral spin pairing is introduced to describe a vector-chiral liquid-crystal order in frustrated spin systems. It is found that the chiral spin pairing is induced by the coupling to phonons through the Dzyaloshinskii-Moriya interaction and the four-spin exchange interaction of the Coulomb origin under the edge-sharing network of magnetic and ligand ions. This produces two successive second-order phase transitions upon cooling: an O(2) chiral spin nematic, i.e., spin cholesteric, order appears with an either parity, and then the O(2) symmetry is broken to yield a helical magnetic order. Possible candidate materials are also discussed as new multiferroic systems.

  11. Winding light beams along elliptical helical trajectories

    Science.gov (United States)

    Wen, Yuanhui; Chen, Yujie; Zhang, Yanfeng; Chen, Hui; Yu, Siyuan

    2016-07-01

    Conventional caustic methods in real or Fourier space produced accelerating optical beams only with convex trajectories. We developed a superposition caustic method capable of winding light beams along nonconvex trajectories. We ascertain this method by constructing a one-dimensional (1D) accelerating beam moving along a sinusoidal trajectory, and subsequently extending to two-dimensional (2D) accelerating beams along arbitrarily elliptical helical trajectories. We experimentally implemented the method with a compact and robust integrated optics approach by fabricating micro-optical structures on quartz glass plates to perform the spatial phase and amplitude modulation to the incident light, generating beam trajectories highly consistent with prediction. The theoretical and implementation methods can in principle be extended to the construction of accelerating beams with a wide variety of nonconvex trajectories, thereby opening up a route of manipulating light beams for fundamental research and practical applications.

  12. Pedicle screw versus hybrid posterior instrumentation for dystrophic neurofibromatosis scoliosis.

    Science.gov (United States)

    Wang, Jr-Yi; Lai, Po-Liang; Chen, Wen-Jer; Niu, Chi-Chien; Tsai, Tsung-Ting; Chen, Lih-Huei

    2017-06-01

    Surgical management of severe rigid dystrophic neurofibromatosis (NF) scoliosis is technically demanding and produces varying results. In the current study, we reviewed 9 patients who were treated with combined anterior and posterior fusion using different types of instrumentation (i.e., pedicle screw, hybrid, and all-hook constructs) at our institute.Between September 2001 and July 2010 at our institute, 9 patients received anterior release/fusion and posterior fusion with different types of instrumentation, including a pedicle screw construct (n = 5), a hybrid construct (n = 3), and an all-hook construct (n = 1). We compared the pedicle screw group with the hybrid group to analyze differences in preoperative curve angle, immediate postoperative curve reduction, and latest follow-up curve angle.The mean follow-up period was 9.5 ± 2.9 years. The average age at surgery was 10.3 ± 3.9 years. The average preoperative scoliosis curve was 61.3 ± 13.8°, and the average preoperative kyphosis curve was 39.8 ± 19.7°. The average postoperative scoliosis and kyphosis curves were 29.7 ± 10.7° and 21.0 ± 13.5°, respectively. The most recent follow-up scoliosis and kyphosis curves were 43.4 ± 17.3° and 29.4 ± 18.9°, respectively. There was no significant difference in the correction angle (either coronal or sagittal), and there was no significant difference in the loss of sagittal correction between the pedicle screw construct group and the hybrid construct group. However, the patients who received pedicle screw constructs had significantly less loss of coronal correction (P instrumentation, one with an all-hook construct and the other with a hybrid construct, required surgical revision because of progression of deformity.It is difficult to intraoperatively correct dystrophic deformity and to maintain this correction after surgery. Combined anterior release/fusion and posterior fusion using either a pedicle screw

  13. Use of computational fluid dynamics simulations for design of a pretreatment screw conveyor reactor.

    Science.gov (United States)

    Berson, R Eric; Hanley, Thomas R

    2005-01-01

    Computational fluid dynamics simulations were employed to compare performance of various designs of a pretreatment screw conveyor reactor. The reactor consisted of a vertical screw used to create cross flow between the upward conveying solids and the downward flow of acid. Simulations were performed with the original screw design and a modified design in which the upper flights of the screw were removed. Results of the simulations show visually that the modified design provided favorable plug flow behavior within the reactor. Pressure drop across the length of the reactor without the upper screws in place was predicted by the simulations to be 5 vs 40 kPa for the original design.

  14. A technique for the management of screw access opening in cement-retained implant restorations

    Directory of Open Access Journals (Sweden)

    Hamid Kermanshah

    2014-01-01

    Full Text Available Introduction: Abutment screw loosening has been considered as a common complication of implant-supported dental prostheses. This problem is more important in cement-retained implant restorations due to their invisible position of the screw access opening. Case Report: This report describes a modified retrievability method for cement-retained implant restorations in the event of abutment screw loosening. The screw access opening was marked with ceramic stain and its porcelain surface was treated using hydrofluoric acid (HF, silane, and adhesive to bond to composite resin. Discussion: The present modified technique facilitates screw access opening and improves the bond between the porcelain and composite resin.

  15. Covering the screw-access holes of implant restorations in the esthetic zone: a clinical report.

    Directory of Open Access Journals (Sweden)

    Abolfazl Saboury

    2014-12-01

    Full Text Available Screw-retained implant restorations have an advantage of predictable retention as well as retrievability, and obviate the risk of excessive sub-gingival cement commonly associated with cement retained implant restorations. Screw-retained restorations generally have screw access holes, which can compromise esthetics and weaken the porcelain around the holes. The purpose of this study is to describe the use of a separate overcasting crown design to cover the screw access hole of implant screw-retained prosthesis for improved esthetics.

  16. Direct anterior screw fixation for recent and remote odontoid fractures.

    Science.gov (United States)

    Apfelbaum, R I; Lonser, R R; Veres, R; Casey, A

    2000-10-01

    The management of odontoid fractures remains controversial. Only direct anterior screw fixation provides immediate stabilization of the spine and may preserve normal C1-2 motion. To determine the indications, optimum timing, and results for direct anterior screw fixation of odontoid fractures, the authors reviewed the surgery-related outcome of patients who underwent this procedure at two institutions. One hundred forty-seven consecutive patients (98 males and 49 females) who underwent direct anterior screw fixation for recent ( or = 18 months postinjury [18 patients]) Type II (138 cases) or III (nine cases) odontoid fractures at the University of Utah (94 patients) and National Institute of Traumatology in Budapest, Hungary (53 patients) between 1986 and 1998 are included in this study (mean follow up 18.2 months). Data obtained from clinical examination, review of hospital charts, operative findings, and imaging studies were used to analyze the surgery-related results in these patients. In patients with recent fractures there was an overall bone fusion rate of 88%. The rate of anatomical bone fusion of recent fractures was significantly (p or = 0.05) of age, sex, number of screws placed (one or two), and the degree or the direction of odontoid displacement. In patients with remote fractures there was a significantly lower rate of bone fusion (25%). Overall, complications related to hardware failure occurred in 14 patients (10%) and those unrelated to hardware in three patients (2%). There was one death (1%) related to surgery. Direct anterior screw fixation is an effective and safe method for treating recent odontoid fractures ( or = 18 months postinjury) a significantly lower rate of fusion is found when using this technique, and these patients are believed to be poor candidates for this procedure.

  17. A rationale method for evaluating unscrewing torque values of prosthetic screws in dental implants

    Science.gov (United States)

    SALIBA, Felipe Miguel; CARDOSO, Mayra; TORRES, Marcelo Ferreira; TEIXEIRA, Alexandre Carvalho; LOURENÇO, Eduardo José Veras; TELLES, Daniel de Moraes

    2011-01-01

    Objectives Previous studies that evaluated the torque needed for removing dental implant screws have not considered the manner of transfer of the occlusal loads in clinical settings. Instead, the torque used for removal was applied directly to the screw, and most of them omitted the possibility that the hexagon could limit the action of the occlusal load in the loosening of the screws. The present study proposes a method for evaluating the screw removal torque in an anti-rotational device independent way, creating an unscrewing load transfer to the entire assembly, not only to the screw. Material and methods Twenty hexagonal abutments without the hexagon in their bases were fixed with a screw to 20 dental implants. They were divided into two groups: Group 1 used titanium screws and Group 2 used titanium screws covered with a solid lubricant. A torque of 32 Ncm was applied to the screw and then a custom-made wrench was used for rotating the abutment counterclockwise, to loosen the screw. A digital torque meter recorded the torque required to loosen the abutment. Results There was a significant difference between the means of Group 1 (38.62±6.43 Ncm) and Group 2 (48.47±5.04 Ncm), with p=0.001. Conclusion This methodology was effective in comparing unscrewing torque values of the implant-abutment junction even with a limited sample size. It confirmed a previously shown significant difference between two types of screws. PMID:21437472

  18. A rationale method for evaluating unscrewing torque values of prosthetic screws in dental implants

    Directory of Open Access Journals (Sweden)

    Felipe Miguel Saliba

    2011-02-01

    Full Text Available OBJECTIVES: Previous studies that evaluated the torque needed for removing dental implant screws have not considered the manner of transfer of the occlusal loads in clinical settings. Instead, the torque used for removal was applied directly to the screw, and most of them omitted the possibility that the hexagon could limit the action of the occlusal load in the loosening of the screws. The present study proposes a method for evaluating the screw removal torque in an anti-rotational device independent way, creating an unscrewing load transfer to the entire assembly, not only to the screw. MATERIAL AND METHODS: Twenty hexagonal abutments without the hexagon in their bases were fixed with a screw to 20 dental implants. They were divided into two groups: Group 1 used titanium screws and Group 2 used titanium screws covered with a solid lubricant. A torque of 32 Ncm was applied to the screw and then a custom-made wrench was used for rotating the abutment counterclockwise, to loosen the screw. A digital torque meter recorded the torque required to loosen the abutment. RESULTS: There was a significant difference between the means of Group 1 (38.62±6.43 Ncm and Group 2 (48.47±5.04 Ncm, with p=0.001. CONCLUSION: This methodology was effective in comparing unscrewing torque values of the implant-abutment junction even with a limited sample size. It confirmed a previously shown significant difference between two types of screws.

  19. Numerical simulation of the influence factors for rotary kiln in temperature field and stress field and the structure optimization

    National Research Council Canada - National Science Library

    Li, Gongfa; Liu, Ze; Jiang, Guozhang; Liu, Honghai; Xiong, Hegen

    2015-01-01

    .... The rotary kiln is one of the most representatives of the furnace equipment; higher requirements of the rotary kiln are put forward in response to the call of the national energy saving and emission reduction...

  20. Evaluation of different screw fixation techniques and screw diameters in sagittal split ramus osteotomy: finite element analysis method.

    Science.gov (United States)

    Sindel, A; Demiralp, S; Colok, G

    2014-09-01

    Sagittal split ramus osteotomy (SSRO) is used for correction of numerous congenital or acquired deformities in facial region. Several techniques have been developed and used to maintain fixation and stabilisation following SSRO application. In this study, the effects of the insertion formations of the bicortical different sized screws to the stresses generated by forces were studied. Three-dimensional finite elements analysis (FEA) and static linear analysis methods were used to investigate difference which would occur in terms of forces effecting onto the screws and transmitted to bone between different application areas. No significant difference was found between 1·5- and 2-mm screws used in SSRO fixation. Besides, it was found that 'inverted L' application was more successful compared to the others and that was followed by 'L' and 'linear' formations which showed close rates to each other. Few studies have investigated the effect of thickness and application areas of bicortical screws. This study was performed on both advanced and regressed jaws positions. © 2014 John Wiley & Sons Ltd.

  1. Nickel-titanium rotary instrument fracture: a clinical practice assessment.

    Science.gov (United States)

    Di Fiore, P M; Genov, K A; Komaroff, E; Li, Y; Lin, L

    2006-09-01

    To prospectively determine the incidence of nickel-titanium rotary instrument fracture in an endodontic clinical practice setting. Eleven second year endodontic residents, using four nickel-titanium rotary instrument systems (ProFile, ProTaper, GTRotary and K3Endo) according to the recommendations of the manufacturers, instrumented 3181 canals in 1403 teeth of 1235 patients, in a dental school post-graduate endodontic clinic, in 1 year. The incidence of instrument fracture was determined based on the number of instruments used. When fracture occurred, data were collected concerning the type, size, taper and prior use of the fractured instruments, the length and location of the fragment within the root canal and the curvature of the canal. The overall incidence of instrument fracture was 0.39%. The incidence of fracture for ProFile, ProTaper, GTRotary and K3Endo files was 0.28%, 0.41%, 0.39% and 0.52%, respectively. There was no statistically significant difference between instrument systems. The percentage of teeth in which instruments fractured was 1.9% (0.28% for anterior teeth, 1.56% for pre-molars and 2.74% for molars). A total of 26 instruments fractured, of which 23 had tapers of 0.06 or greater. Most of the fragments were located in the apical third of the root canal, and both the median and mode amongst the fragment lengths were 2 mm. The low incidence of nickel-titanium rotary instrument fracture supports the continued use of these instruments in root canal treatment.

  2. Helical bottleneck effect in 3D homogeneous isotropic turbulence

    Science.gov (United States)

    Stepanov, Rodion; Golbraikh, Ephim; Frick, Peter; Shestakov, Alexander

    2018-02-01

    We present the results of modelling the development of homogeneous and isotropic turbulence with a large-scale source of energy and a source of helicity distributed over scales. We use the shell model for numerical simulation of the turbulence at high Reynolds number. The results show that the helicity injection leads to a significant change in the behavior of the energy and helicity spectra in scales larger and smaller than the energy injection scale. We suggest the phenomenology for direct turbulent cascades with the helicity effect, which reduces the efficiency of the spectral energy transfer. Therefore the energy is accumulated and redistributed so that non-linear interactions will be sufficient to provide a constant energy flux. It can be interpreted as the ‘helical bottleneck effect’ which, depending on the parameters of the injection helicity, reminds one of the well-known bottleneck effect at the end of inertial range. Simulations which included the infrared part of the spectrum show that the inverse cascade hardly develops under distributed helicity forcing.

  3. Theoretical model of chirality-induced helical self-propulsion

    Science.gov (United States)

    Yamamoto, Takaki; Sano, Masaki

    2018-01-01

    We recently reported the experimental realization of a chiral artificial microswimmer exhibiting helical self-propulsion [T. Yamamoto and M. Sano, Soft Matter 13, 3328 (2017), 10.1039/C7SM00337D]. In the experiment, cholesteric liquid crystal (CLC) droplets dispersed in surfactant solutions swam spontaneously, driven by the Marangoni flow, in helical paths whose handedness is determined by the chirality of the component molecules of CLC. To study the mechanism of the emergence of the helical self-propelled motion, we propose a phenomenological model of the self-propelled helical motion of the CLC droplets. Our model is constructed by symmetry argument in chiral systems, and it describes the dynamics of CLC droplets with coupled time-evolution equations in terms of a velocity, an angular velocity, and a tensor variable representing the symmetry of the helical director field of the droplet. We found that helical motions as well as other chiral motions appear in our model. By investigating bifurcation behaviors between each chiral motion, we found that the chiral coupling terms between the velocity and the angular velocity, the structural anisotropy of the CLC droplet, and the nonlinearity of model equations play a crucial role in the emergence of the helical motion of the CLC droplet.

  4. Magnetic Helicities and Dynamo Action in Magneto-rotational Turbulence

    Science.gov (United States)

    Bodo, G.; Cattaneo, F.; Mignone, A.; Rossi, P.

    2017-07-01

    We examine the relationship between magnetic flux generation, taken as an indicator of large-scale dynamo action, and magnetic helicity, computed as an integral over the dynamo volume, in a simple dynamo. We consider dynamo action driven by magneto-rotational turbulence (MRT) within the shearing-box approximation. We consider magnetically open boundary conditions that allow a flux of helicity in or out of the computational domain. We circumvent the problem of the lack of gauge invariance in open domains by choosing a particular gauge—the winding gauge—that provides a natural interpretation in terms of the average winding number of pairwise field lines. We use this gauge precisely to define and measure the helicity and the helicity flux for several realizations of dynamo action. We find in these cases that the system as a whole does not break reflectional symmetry and that the total helicity remains small even in cases when substantial magnetic flux is generated. We find no particular connection between the generation of magnetic flux and the helicity or the helicity flux through the boundaries. We suggest that this result may be due to the essentially nonlinear nature of the dynamo processes in MRT.

  5. Latarjet Fixation: A Cadaveric Biomechanical Study Evaluating Cortical and Cannulated Screw Fixation.

    Science.gov (United States)

    Alvi, Hasham M; Monroe, Emily J; Muriuki, Muturi; Verma, Rajat N; Marra, Guido; Saltzman, Matthew D

    2016-04-01

    Attritional bone loss in patients with recurrent anterior instability has successfully been treated with a bone block procedure such as the Latarjet. It has not been previously demonstrated whether cortical or cancellous screws are superior when used for this procedure. To assess the strength of stainless steel cortical screws versus stainless steel cannulated cancellous screws in the Latarjet procedure. Controlled laboratory study. Ten fresh-frozen matched-pair shoulder specimens were randomized into 2 separate fixation groups: (1) 3.5-mm stainless steel cortical screws and (2) 4.0-mm stainless steel partially threaded cannulated cancellous screws. Shoulder specimens were dissected free of all soft tissue and a 25% glenoid defect was created. The coracoid process was osteomized, placed at the site of the glenoid defect, and fixed in place with 2 parallel screws. All 10 specimens failed by screw cutout. Nine of 10 specimens failed by progressive displacement with an increased number of cycles. One specimen in the 4.0-mm screw group failed by catastrophic failure on initiation of the testing protocol. The 3.5-mm screws had a mean of 274 cycles (SD, ±171 cycles; range, 10-443 cycles) to failure. The 4.0-mm screws had a mean of 135 cycles (SD, ±141 cycles; range, 0-284 cycles) to failure. There was no statistically significant difference between the 2 types of screws for cycles required to cause failure (P = .144). There was no statistically significant difference in energy or cycles to failure when comparing the stainless steel cortical screws versus partially threaded cannulated cancellous screws. Latarjet may be performed using cortical or cancellous screws without a clear advantage of either option.

  6. SIMULATION OF OLIVE PITS PYROLYSIS IN A ROTARY KILN PLANT

    Directory of Open Access Journals (Sweden)

    Giacobbe Braccio

    2011-01-01

    Full Text Available This work deals with the simulation of an olive pits fed rotary kiln pyrolysis plant installed in Southern Italy. The pyrolysis process was simulated by commercial software CHEMCAD. The main component of the plant, the pyrolyzer, was modelled by a Plug Flow Reactor in accordance to the kinetic laws. Products distribution and the temperature profile was calculated along reactor's axis. Simulation results have been found to fit well the experimental data of pyrolysis. Moreover, sensitivity analyses were executed to investigate the effect of biomass moisture on the pyrolysis process.

  7. Rotary Percussive Auto-Gopher for Deep Drilling and Sampling

    Science.gov (United States)

    Bar-Cohen, Yoseph; Badescu, Mircea; Sherrit, Stewart

    2009-01-01

    The term "rotary percussive auto-gopher" denotes a proposed addition to a family of apparatuses, based on ultrasonic/ sonic drill corers (USDCs), that have been described in numerous previous NASA Tech Briefs articles. These apparatuses have been designed, variously, for boring into, and/or acquiring samples of, rock or other hard, brittle materials of geological interest. In the case of the rotary percussive autogopher, the emphasis would be on developing an apparatus capable of penetrating to, and acquiring samples at, depths that could otherwise be reached only by use of much longer, heavier, conventional drilling-and-sampling apparatuses. To recapitulate from the prior articles about USDCs: A USDC can be characterized as a lightweight, low-power jackhammer in which a piezoelectrically driven actuator generates ultrasonic vibrations and is coupled to a tool bit through a free mass. The bouncing of the free mass between the actuator horn and the drill bit converts the actuator ultrasonic vibrations into sonic hammering of the drill bit. The combination of ultrasonic and sonic vibrations gives rise to a hammering action (and a resulting chiseling action at the tip of the tool bit) that is more effective for drilling than is the microhammering action of ultrasonic vibrations alone. The hammering and chiseling actions are so effective that the size of the axial force needed to make the tool bit advance into soil, rock, or another material of interest is much smaller than in ordinary rotary drilling, ordinary hammering, or ordinary steady pushing. The predecessor of the rotary percussive auto-gopher is an apparatus, now denoted an ultrasonic/sonic gopher and previously denoted an ultrasonic gopher, described in "Ultrasonic/ Sonic Mechanism for Drilling and Coring" (NPO-30291), NASA Tech Briefs Vol. 27, No. 9 (September 2003), page 65. The ultrasonic/sonic gopher is intended for use mainly in acquiring cores. The name of the apparatus reflects the fact that, like a

  8. Performance analysis of a rotary active magnetic refrigerator

    DEFF Research Database (Denmark)

    Lozano, Jaime; Engelbrecht, Kurt; Bahl, Christian R.H.

    2013-01-01

    Performance results for a novel rotary active magnetic regenerator (AMR) and detailed numerical model of it are presented. The experimental device consists of 24 regenerators packed with gadolinium (Gd) spheres rotating inside a four-pole permanent magnet with magnetic field of 1.24T. A parametric......-equivalent cooling power (ExQ), and the overall second law efficiency, η2nd. Losses mapping indicated that friction and thermal leakage to the ambient are the most important contributors to the reduction of the system performance. Based on modeling results, improvements on the flow distributor design and reduction...

  9. Active magnetic regenerator refrigeration with rotary multi-bed technology

    DEFF Research Database (Denmark)

    Eriksen, Dan

    revealed a necessary trade off between the amount of magnetocaloric material and an insulating air gap in the magnetized volume provided by the Halbach-like cylindrical permanent magnet system, when designing for high efficiency rather than maximum cooling power. The central part of the magnet system...... experiments with the new prototype revealed strong impacts on COP and cooling power by minor adjustments of the individual valves controlling the flow in each bed. This effect, inherent to rotary multibed AMRs, is ad- dressed with a numerical modeling approach and confirmed experimentally with the new...

  10. A rotary electromagnetic microgenerator for energy harvesting from human motions

    Directory of Open Access Journals (Sweden)

    Mehdi Niroomand

    2016-08-01

    Full Text Available In this paper, a rotary electromagnetic microgenerator is analyzed, designed and built. This microgenerator can convert human motions to electrical energy. The small size and use of a pendulum mechanism without gear are two main characteristics of the designed microgenerator. The generator can detect small vibrations and produce electrical energy. The performance of this microgenerator is evaluated by being installed peak-to-peak during normal walking. Also, the maximum harvested electrical energy during normal walking is around 416.6 μW. This power is sufficient for many applications.

  11. Rotary Ultrasonic Machining of Poly-Crystalline Cubic Boron Nitride

    Directory of Open Access Journals (Sweden)

    Kuruc Marcel

    2014-12-01

    Full Text Available Poly-crystalline cubic boron nitride (PCBN is one of the hardest material. Generally, so hard materials could not be machined by conventional machining methods. Therefore, for this purpose, advanced machining methods have been designed. Rotary ultrasonic machining (RUM is included among them. RUM is based on abrasive removing mechanism of ultrasonic vibrating diamond particles, which are bonded on active part of rotating tool. It is suitable especially for machining hard and brittle materials (such as glass and ceramics. This contribution investigates this advanced machining method during machining of PCBN.

  12. Pengendalian Modul Rotary Handling Station Bebasis Sequential Function Chart (Sfc)

    OpenAIRE

    Budiantoro, Deli; Halim, Agus; G, Soeharsono

    2014-01-01

    The system used in this day and age has made progress in its operations. In industry itself many use automated systems that only require a small operator to run a tool because it saves time, and safety is guaranteed. In this time the tool discussed Handling Station Rotary pneumatic system uses motion to move this tool. So that the tool can be moved according to plan also required the "brains" to run this tool. Where the brain is a Program Logic Controller (PLC) to save a program that has been...

  13. ROPEC - ROtary PErcussive Coring Drill for Mars Sample Return

    Science.gov (United States)

    Chu, Philip; Spring, Justin; Zacny, Kris

    2014-01-01

    The ROtary Percussive Coring Drill is a light weight, flight-like, five-actuator drilling system prototype designed to acquire core material from rock targets for the purposes of Mars Sample Return. In addition to producing rock cores for sample caching, the ROPEC drill can be integrated with a number of end effectors to perform functions such as rock surface abrasion, dust and debris removal, powder and regolith acquisition, and viewing of potential cores prior to caching. The ROPEC drill and its suite of end effectors have been demonstrated with a five degree of freedom Robotic Arm mounted to a mobility system with a prototype sample cache and bit storage station.

  14. System and method for cooling a superconducting rotary machine

    Science.gov (United States)

    Ackermann, Robert Adolf [Schenectady, NY; Laskaris, Evangelos Trifon [Schenectady, NY; Huang, Xianrui [Clifton Park, NY; Bray, James William [Niskayuna, NY

    2011-08-09

    A system for cooling a superconducting rotary machine includes a plurality of sealed siphon tubes disposed in balanced locations around a rotor adjacent to a superconducting coil. Each of the sealed siphon tubes includes a tubular body and a heat transfer medium disposed in the tubular body that undergoes a phase change during operation of the machine to extract heat from the superconducting coil. A siphon heat exchanger is thermally coupled to the siphon tubes for extracting heat from the siphon tubes during operation of the machine.

  15. Modeling emulsification processes in rotary-disk mixers

    Science.gov (United States)

    Laponov, S. V.; Shulaev, N. S.; Ivanov, S. P.; Bondar’, K. E.; Suleimanov, D. F.

    2017-10-01

    This article presents the experimental studies results of emulsification processes in liquid-liquid systems in rotary-disk mixers, allowing regulating the distribution of dispersed particles by changing the process conditions and the ratio of the dispersed phase. It is shown that with the increase of mixer’s revolutions per minute (RPM), both the size of dispersed particles and the deviation of dispersed particles sizes from the average decrease. The increase of the dispersed particles part results in the increase of particles average sizes at the current energy consumption. Discovered relationships can be used in the design of industrial equipment and laboratory research.

  16. NASA Subsonic Rotary Wing Project - Structures and Materials Discipline

    Science.gov (United States)

    Halbig, Michael C.; Johnson, Susan M.

    2008-01-01

    The Structures & Materials Discipline within the NASA Subsonic Rotary Wing Project is focused on developing rotorcraft technologies. The technologies being developed are within the task areas of: 5.1.1 Life Prediction Methods for Engine Structures & Components 5.1.2 Erosion Resistant Coatings for Improved Turbine Blade Life 5.2.1 Crashworthiness 5.2.2 Methods for Prediction of Fatigue Damage & Self Healing 5.3.1 Propulsion High Temperature Materials 5.3.2 Lightweight Structures and Noise Integration The presentation will discuss rotorcraft specific technical challenges and needs as well as details of the work being conducted in the six task areas.

  17. 16 CFR 1205.5 - Walk-behind rotary power mower controls.

    Science.gov (United States)

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Walk-behind rotary power mower controls... ACT REGULATIONS SAFETY STANDARD FOR WALK-BEHIND POWER LAWN MOWERS The Standard § 1205.5 Walk-behind rotary power mower controls. (a) Blade control systems—(1) Requirements for blade control. A walk-behind...

  18. 33 CFR 100.914 - Trenton Rotary Roar on the River, Trenton, MI.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Trenton Rotary Roar on the River, Trenton, MI. 100.914 Section 100.914 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY REGATTAS AND MARINE PARADES SAFETY OF LIFE ON NAVIGABLE WATERS § 100.914 Trenton Rotary Roar on...

  19. Reversing the direction in a light-driven rotary molecular motor

    NARCIS (Netherlands)

    Ruangsupapichat, Nopporn; Pollard, Michael M.; Harutyunyan, Syuzanna R.; Feringa, Ben L.

    2011-01-01

    Biological rotary motors can alter their mechanical function by changing the direction of rotary motion. Achieving a similar reversal of direction of rotation in artificial molecular motors presents a fundamental stereochemical challenge: how to change from clockwise to anticlockwise motion without

  20. Design and experimental tests of a rotary active magnetic regenerator prototype

    DEFF Research Database (Denmark)

    Eriksen, Dan; Engelbrecht, Kurt; Bahl, Christian

    2015-01-01

    A rotary active magnetic regenerator (AMR) prototype with efficiency and compact design as focus points has been designed and built. The main objective is to demonstrate improved efficiency for rotary devices by reducing heat leaks from the environment and parasitic mechanical work losses while...

  1. Math modeling and computer mechanization for real time simulation of rotary-wing aircraft

    Science.gov (United States)

    Howe, R. M.

    1979-01-01

    Mathematical modeling and computer mechanization for real time simulation of rotary wing aircraft is discussed. Error analysis in the digital simulation of dynamic systems, such as rotary wing aircraft is described. The method for digital simulation of nonlinearities with discontinuities, such as exist in typical flight control systems and rotor blade hinges, is discussed.

  2. Interfragmentary compression profile of 4 headless bone screws: an analysis of the compression lost on reinsertion.

    Science.gov (United States)

    Gardner, A W; Yew, Y T; Neo, P Y; Lau, C C; Tay, S C

    2012-09-01

    To evaluate the interfragmentary compression force generated by 4 different types of headless compression screws and to examine the effects of removal and reinsertion of the screw. We chose foot bones rather than scaphoids for the model because they were larger and would enable comparison of 2 screw designs in the same bone, thereby controlling for the effect of interspecimen variability. A transverse osteotomy was made in 10 fresh-frozen cadaveric navicular bones and 10 medial cuneiforms. A load cell was used to measure compression between the 2 fragments as a screw was inserted across the fracture. Each bone was tested twice, with an Acutrak Mini (Acumed, Hillsboro, OR; n = 10) and an SBi AutoFIX screw (SBi, Morrisville, PA; n = 10) or an Extremifix (Osteomed, Addison, TX; n = 10) and a Barouk screw (Depuy, Warsaw, IN; n = 10). Compression was recorded at initial insertion and on removal and reinsertion of the screw twice to the same position. Compression was also measured after one additional full turn further than the initial position. The mean interfragmentary compression generated by the Acutrak Mini screw was greater than that of the SBi AutoFIX screw (96 N vs 22 N). There was a trend toward a greater mean compression generated by the Extremifix screw compared to the Barouk screw (85 N vs 22 N). There was a significant loss of compression upon removal and reinsertion of the screws. An additional full turn of the screw was able to re-establish a large proportion of the original compression. The compression forces achieved by headless screw systems appeared to vary according to the screw design, depth of insertion, and the quality of the bone. Substantial compression was lost if the screw was removed and replaced. Some screw designs appeared to require a greater depth of insertion to achieve effective compression, and the number of additional turns required to re-establish compression might vary according to the thread design. Surgeons should be aware of the

  3. Placement of thoracic transvertebral pedicle screws using 3D image guidance.

    Science.gov (United States)

    Nottmeier, Eric W; Pirris, Stephen M

    2013-05-01

    Transvertebral pedicle screws have successfully been used in the treatment of high-grade L5-S1 spondylolisthesis. An advantage of transvertebral pedicle screws is the purchase of multiple cortical layers across 2 vertebrae, thereby increasing the stability of the construct. At the lumbosacral junction, transvertebral pedicle screws have been shown to be biomechanically superior to pedicle screws placed in the standard fashion. The use of transvertebral pedicle screws at spinal levels other than L5-S1 has not been reported in the literature. The authors describe their technique of transvertebral pedicle screw placement in the thoracic spine using 3D image guidance. Twelve patients undergoing cervicothoracic or thoracolumbar fusion had 41 thoracic transvertebral pedicle screws placed across 26 spinal levels using this technique. Indications for placement of thoracic transvertebral pedicle screws in earlier cases included osteoporosis and pedicle screw salvage. However, in subsequent cases screws were placed in patients undergoing multilevel thoracolumbar fusion without osteoporosis, particularly near the top of the construct. Image guidance in this study was accomplished using the Medtronic StealthStation S7 image guidance system used in conjunction with the O-arm. All patients were slated to undergo postoperative CT scanning at approximately 4-6 months for fusion assessment, which also allowed for grading of the transvertebral pedicle screws. No thoracic transvertebral pedicle screw placed in this study had to be replaced or repositioned after intraoperative review of the cone beam CT scans. Review of the postoperative CT scans revealed all transvertebral screws to be across the superior disc space with the tips in the superior vertebral body. Six pedicle screws were placed using the in-out-in technique in patients with narrow pedicles, leaving 35 screws that underwent breach analysis. No pedicle breach was noted in 34 of 35 screws. A Grade 1 (image-guided placement

  4. 76 FR 62301 - Safety Zone; Rotary Club of Fort Lauderdale New River Raft Race, New River, Fort Lauderdale, FL

    Science.gov (United States)

    2011-10-07

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Rotary Club of Fort Lauderdale New River... Esplanade Park to the Henry Kinney Tunnel, in Fort Lauderdale, Florida during the Rotary Club of Fort... (NPRM) entitled Safety Zone; Rotary Club of Fort Lauderdale New River Raft Race, New River, Fort...

  5. Experimental Evidence of Helical Flow in Porous Media

    Science.gov (United States)

    Ye, Yu; Chiogna, Gabriele; Cirpka, Olaf A.; Grathwohl, Peter; Rolle, Massimo

    2015-11-01

    Helical flow leads to deformation of solute plumes and enhances transverse mixing in porous media. We present experiments in which macroscopic helical flow is created by arranging different materials to obtain an anisotropic macroscopic permeability tensor with spatially variable orientation. The resulting helical flow entails twisting streamlines which cause a significant increase in lateral mass exchange and thus a large enhancement of plume dilution (up to 235%) compared to transport in homogenous media. The setup may be used to effectively mix solutes in parallel streams similarly to static mixers, but in porous media.

  6. Experimental Evidence of Helical Flow in Porous Media

    DEFF Research Database (Denmark)

    Ye, Yu; Chiogna, Gabriele; Cirpka, Olaf A.

    2015-01-01

    . The resulting helical flow entails twisting streamlines which cause a significant increase in lateral mass exchange and thus a large enhancement of plume dilution (up to 235%) compared to transport in homogenous media. The setup may be used to effectively mix solutes in parallel streams similarly to static......Helical flow leads to deformation of solute plumes and enhances transverse mixing in porous media. We present experiments in which macroscopic helical flow is created by arranging different materials to obtain an anisotropic macroscopic permeability tensor with spatially variable orientation...

  7. Helicity-Dependent Showers and Matching with VINCIA

    CERN Document Server

    Larkoski, Andrew J.; Skands, Peter

    2013-01-01

    We present an antenna-shower formalism that includes helicity dependence for massless partons. The formalism applies to both traditional (global) showers and to sector-based variants. We combine the shower with VINCIA's multiplicative approach to matrix-element matching, generalized to operate on each helicity configuration separately. The result is a substantial gain in computational speed for high parton multiplicities. We present an implementation of both sector and global showers, with min and max variations, and helicity-dependent tree-level matching applied for vector bosons or Higgs decay to q qbar plus up to 4 gluons and for Higgs decay to up to 5 gluons.

  8. A Biomechanical Analysis of 2 Constructs for Metacarpal Spiral Fracture Fixation in a Cadaver Model: 2 Large Screws Versus 3 Small Screws.

    Science.gov (United States)

    Eu-Jin Cheah, Andre; Behn, Anthony W; Comer, Garet; Yao, Jeffrey

    2017-12-01

    Surgeons confronted with a long spiral metacarpal fracture may choose to fix it solely with lagged screws. A biomechanical analysis of a metacarpal spiral fracture model was performed to determine whether 3 1.5-mm screws or 2 2.0-mm screws provided more stability during bending and torsional loading. Second and third metacarpals were harvested from 12 matched pairs of fresh-frozen cadaveric hands and spiral fractures were created. One specimen from each matched pair was fixed with 2 2.0-mm lagged screws whereas the other was fixed with 3 1.5-mm lagged screws. Nine pairs underwent combined cyclic cantilever bending and axial compressive loading followed by loading to failure. Nine additional pairs were subjected to cyclic external rotation while under a constant axial compressive load and were subsequently externally rotated to failure under a constant axial compressive load. Paired t tests were used to compare cyclic creep, stiffness, displacement, rotation, and peak load levels. Average failure torque for all specimens was 7.2 ± 1.7 Nm. In cyclic torsional testing, the group with 2 screws exhibited significantly less rotational creep than the one with 3 screws. A single specimen in the group with 2 screws failed before cyclic bending tests were completed. No other significant differences were found between test groups during torsional or bending tests. Both constructs were biomechanically similar except that the construct with 2 screws displayed significantly less loosening during torsional cyclic loading, although the difference was small and may not be clinically meaningful. Because we found no obvious biomechanical advantage to using 3 1.5-mm lagged screws to fix long spiral metacarpal fractures, the time efficiency and decreased implant costs of using 2-2.0 mm lagged screws may be preferred. Copyright © 2017 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

  9. Choice reaction time to visual motion during prolonged rotary motion in airline pilots

    Science.gov (United States)

    Stewart, J. D.; Clark, B.

    1975-01-01

    Thirteen airline pilots were studied to determine the effect of preceding rotary accelerations on the choice reaction time to the horizontal acceleration of a vertical line on a cathode-ray tube. On each trial, one of three levels of rotary and visual acceleration was presented with the rotary stimulus preceding the visual by one of seven periods. The two accelerations were always equal and were presented in the same or opposite directions. The reaction time was found to increase with increases in the time the rotary acceleration preceded the visual acceleration, and to decrease with increased levels of visual and rotary acceleration. The reaction time was found to be shorter when the accelerations were in the same direction than when they were in opposite directions. These results suggest that these findings are a special case of a general effect that the authors have termed 'gyrovisual modulation'.

  10. The Effect of Transpedicular Screw Design on Its Performance in Vertebral Bone Under Tensile Loads: A Parametric Study.

    Science.gov (United States)

    Alkaly, Ron N; Bader, Dan L

    2016-12-01

    A biomechanical study using bovine thoracolumbar spines. To study investigated whether thread design parameters aimed at altering the state of stress at the screw-bone interface increase the screw's holding power. Internal spinal fixators utilizing transpedicular screw fixation are used to achieve early stabilization of the injured spine in a range of clinical conditions. Despite advances in the design of internal spinal fixation systems, implant loosening, and catastrophic failures at the screw-bone interface remains a serious complication in adult spine surgery. Although the performance of the screws in the vertebral bone critically depends on ability of screw thread design to provide and maintain adequate bone purchase, the effect of individual thread design parameters on screw performance and the failure process of the screw-bone interface, remains unclear. On the basis of the AO Schanz thread, this parametric study used 96 lumbar bovine vertebrae instrumented with 19 screw designs to investigate the effects of pitch, ratio of major to minor diameter, screw insertion depth, and major diameter, on screw performance under pure tensile loading. The effect of vertebral morphometry on screw performance and the extent of damage within the failed screw-bone interface were evaluated. The increase in screw insertion depth, screw pitch, and the ratio of major to minor diameter, significantly affected screw performance under tensile loads. Complex interactions existed between the major diameter and each of the design variables. Vertebral morphometry had little effect on screw performance while the damage within the failed bone-screw interface confined to the immediate region of the screw threads. Design variables, able to reduce shear stresses or modify the complex stress profile at the bone-screw interface, are more effective in preventing early failure of the interface.

  11. Influence of oscillating and rotary cutting instruments with electric and turbine handpieces on tooth preparation surfaces.

    Science.gov (United States)

    Geminiani, Alessandro; Abdel-Azim, Tamer; Ercoli, Carlo; Feng, Changyong; Meirelles, Luiz; Massironi, Domenico

    2014-07-01

    Rotary and nonrotary cutting instruments are used to produce specific characteristics on the axial and marginal surfaces of teeth being prepared for fixed restorations. Oscillating instruments have been suggested for tooth preparation, but no comparative surface roughness data are available. To compare the surface roughness of simulated tooth preparations produced by oscillating instruments versus rotary cutting instruments with turbine and electric handpieces. Different grit rotary cutting instruments were used to prepare Macor specimens (n=36) with 2 handpieces. The surface roughness obtained with rotary cutting instruments was compared with that produced by oscillating cutting instruments. The instruments used were as follows: coarse, then fine-grit rotary cutting instruments with a turbine (group CFT) or an electric handpiece (group CFE); coarse, then medium-grit rotary cutting instruments with a turbine (group CMT) or an electric handpiece (group CME); coarse-grit rotary cutting instruments with a turbine handpiece and oscillating instruments at a low-power (group CSL) or high-power setting (group CSH). A custom testing apparatus was used to test all instruments. The average roughness was measured for each specimen with a 3-dimensional optical surface profiler and compared with 1-way ANOVA and the Tukey honestly significant difference post hoc test for multiple comparisons (α=.05). Oscillating cutting instruments produced surface roughness values similar to those produced by similar grit rotary cutting instruments with a turbine handpiece. The electric handpiece produced smoother surfaces than the turbine regardless of rotary cutting instrument grit. Rotary cutting instruments with electric handpieces produced the smoothest surface, whereas the same instruments used with a turbine and oscillating instruments achieved similar surface roughness. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights

  12. Investigations of peripheral dose for helical tomotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Lissner, Steffen; Schubert, Kai; Sterzing, Florian; Herfarth, Klaus; Sroka-Perez, Gabriele; Debus, Juergen [University Hospital Heidelberg (Germany). Dept. of Radiation Oncology; Wiezorek, Tilo [University Hospital Jena (Germany). Dept. of Radiotherapy

    2013-07-01

    Purpose: Whenever treating a patient with percutaneous radiotherapy, a certain amount of dose is inevitably delivered to healthy tissue. This is mainly due to beam's entry and exit in the region of the target volume. In regions distant from the target volume, dose is delivered by leakage from the MLC and head scatter from the accelerator head and phantom scatter from the target volume (peripheral dose). Helical tomotherapy is a form of radiation therapy with a uniquely designed machine and delivery pattern which influence the peripheral dose. The goal of this work was to investigate peripheral dose in helical tomotherapy. The experiments were used to establish a complex characterization of the peripheral dose. Materials and methods: A 30*30*60cm{sup 3} slab phantom and TLD-100 (Lithium fluoride) were used for the experiments. Treatment procedures were generated with the tomotherapy planning system (TPS). Additionally, procedures were created on the Operator Station of the tomotherapy system without a calculation of the dose distribution. The peripheral dose which was produced by a typical tomotherapy treatment plan was measured. Furthermore, these procedures were used to differentiate the parts of the peripheral dose in phantom scatter dose and head scatter and leakage dose. Additionally, the relation between peripheral dose and treatment time and between peripheral dose and delivered dose was investigated. Additionally, the peripheral dose was measured in an Alderson phantom. Results: Distances of 30cm or more resulted in a decrease of the peripheral dose to less than 0.1% of the target dose. The measured doses have an offset of approximately 1cGy in comparison to the calculated doses from the TPS. The separated head scatter and leakage dose was measured in the range of 1cGy for typical treatments. Furthermore, the investigations show a linear correlation between head scatter leakage dose and treatment time and between scatter dose parts and delivered dose. A

  13. Helical CT of the urinary organs

    Energy Technology Data Exchange (ETDEWEB)

    Schreyer, H.H.; Uggowitzer, M.M.; Ruppert-Kohlmayr, A. [Graz Univ. (Austria). Dept. of Radiology

    2002-03-01

    Despite of the diagnostic potential of conventional CT (CCT), limitations being inherent in this technology reduce its diagnostic confidence and limit clinical CT applications as 3D imaging. Helical CT (HCT) has far overcome the limitations of CCT and has become the standard CT technology. After a short overview on the technique of HCT and its advantages over CCT, the impact of HCT on the detection of disorders of the urinary organs is discussed. Due to the high quality of 3D reconstructions, vessels are visualized free of artefacts resulting in a dramatic improvement and acceptance of CT angiography, which has become a clinically important examination in the evaluation of obstructive renal artery disease. Fast HCT provides a precise assessment of the three phases of the nephrogram and it is a prerequisite for an improved depiction of abnormal vascular perfusion and impaired tubule transit of contrast material. Helical CT enables an improved characterization of cystic mass lesions reducing the diagnosis of indeterminate masses and thus facilitating a better therapeutic management. The diagnosis of renal cell carcinomas (RCC) has improved due to an increased sensitivity in detecting small RCCs, and an increased specificity in the diagnosis of neoplastic lesions. Improved staging of RCCs is the result of accurate assessment of venous tumour extension. When planning nephron-sparing surgery 3D display of the renal tumour helps to determine the resectability of the mass depicting its relation to major renal vessels and the renal collecting system. In the evaluation of renal trauma HCT provides shorter scanning time and thus fewer artefacts in the examination of traumatized patients who cannot cooperate adequately. Three-dimensional postprocessing modalities allow the assessment of the renal vascular pedicel by CT angiography and improve the demonstration of complex lacerations of the renal parenchyma. In the evaluation of the upper urinary tract unenhanced HCT has

  14. Comparison of migration behavior between single and dual lag screw implants for intertrochanteric fracture fixation

    Directory of Open Access Journals (Sweden)

    Katonis Pavlos G

    2009-05-01

    Full Text Available Abstract Background Lag screw cut-out failure following fixation of unstable intertrochanteric fractures in osteoporotic bone remains an unsolved challenge. This study tested if resistance to cut-out failure can be improved by using a dual lag screw implant in place of a single lag screw implant. Migration behavior and cut-out resistance of a single and a dual lag screw implant were comparatively evaluated in surrogate specimens using an established laboratory model of hip screw cut-out failure. Methods Five dual lag screw implants (Endovis, Citieffe and five single lag screw implants (DHS, Synthes were tested in the Hip Implant Performance Simulator (HIPS of the Legacy Biomechanics Laboratory. This model simulated osteoporotic bone, an unstable fracture, and biaxial rocking motion representative of hip loading during normal gait. All constructs were loaded up to 20,000 cycles of 1.45 kN peak magnitude under biaxial rocking motion. The migration kinematics was continuously monitored with 6-degrees of freedom motion tracking system and the number of cycles to implant cut-out was recorded. Results The dual lag screw implant exhibited significantly less migration and sustained more loading cycles in comparison to the DHS single lag screw. All DHS constructs failed before 20,000 cycles, on average at 6,638 ± 2,837 cycles either by cut-out or permanent screw bending. At failure, DHS constructs exhibited 10.8 ± 2.3° varus collapse and 15.5 ± 9.5° rotation around the lag screw axis. Four out of five dual screws constructs sustained 20,000 loading cycles. One dual screw specimens sustained cut-out by medial migration of the distal screw after 10,054 cycles. At test end, varus collapse and neck rotation in dual screws implants advanced to 3.7 ± 1.7° and 1.6 ± 1.0°, respectively. Conclusion The single and double lag screw implants demonstrated a significantly different migration resistance in surrogate specimens under gait loading simulation with

  15. ROTARY DAY AT THE UNITED NATIONS OFFICE IN GENEVA

    CERN Multimedia

    Staff Association

    2017-01-01

    We have been informed about the Rotary day at the United Nations office in Geneva. Join us on November 10th & 11th, 2017 at the United Nations office Avenue de la Paix 8-14 1211 Geneva, Switzerland   PEACE: MAKING A DIFFERENCE! Conflict and violence displace millions of people each year. Half of those killed in conflict are children, and 90 percent are civilians. We, Rotarians, refuse conflict as a way of life. But how can we contribute to Peace? And what about you? Are you keen on meeting exceptional individuals and exchanging ideas to move forward? Would you like to network and collaborate with Rotarians, Government Representatives, International Civil Servants, Representatives of Nongovernmental Organizations and Liberal Professions, Businessmen/women, and Students to make a difference in Peace? In November 2017, come to Geneva, get involved, and formulate recommendations to the international community. Together, we’ll celebrate Rotary&a...

  16. A Novel Rotary Piezoelectric Motor Using First Bending Hybrid Transducers

    Directory of Open Access Journals (Sweden)

    Yingxiang Liu

    2015-08-01

    Full Text Available We report a novel rotary piezoelectric motor using bending transducers in this work. Three transducers are used to drive a disk-shaped rotor together by the elliptical movements of their driving tips; these motions are produced by the hybrid of two first bending vibration modes. The proposed piezoelectric transducer has a simple structure as it only contains an aluminum alloy beam and four pieces of PZT plates. Symmetrical structure is the only necessary condition in the design process as it will ensure the resonance frequencies of the two orthogonal first bending modes are equal. Transducers with first bending resonance frequency of about 53 kHz were fabricated and assembled into a rotary motor. The proposed motor exhibits good performance on speed and torque control. Under a working frequency of 53.2 kHz, the maximum no-load speed and the maximum torque of the prototype are tested to be 53.3 rpm and of 27 mN·m.

  17. Optimal Power Flow Control by Rotary Power Flow Controller

    Directory of Open Access Journals (Sweden)

    KAZEMI, A.

    2011-05-01

    Full Text Available This paper presents a new power flow model for rotary power flow controller (RPFC. RPFC injects a series voltage into the transmission line and provides series compensation and phase shifting simultaneously. Therefore, it is able to control the transmission line impedance and the active power flow through it. An RPFC is composed mainly of two rotary phase shifting transformers (RPST and two conventional (series and shunt transformers. Structurally, an RPST consists of two windings (stator and rotor windings. The rotor windings of the two RPSTs are connected in parallel and their stator windings are in series. The injected voltage is proportional to the vector sum of the stator voltages and so its amplitude and angle are affected by the rotor position of the two RPSTs. This paper, describes the steady state operation and single-phase equivalent circuit of the RPFC. Also in this paper, a new power flow model, based on power injection model of flexible ac transmission system (FACTS controllers, suitable for the power flow analysis is introduced. Proposed model is used to solve optimal power flow (OPF problem in IEEE standard test systems incorporating RPFC and the optimal settings and location of the RPFC is determined.

  18. Micro- and macrostructural characterization of polyvinylpirrolidone rotary-spun fibers.

    Science.gov (United States)

    Sebe, István; Kállai-Szabó, Barnabás; Kovács, Krisztián Norbert; Szabadi, Enikő; Zelkó, Romána

    2015-01-01

    The application of high-speed rotary spinning can offer a useful mean for either preparation of fibrous intermediate for conventional dosage forms or drug delivery systems. Polyvinylpyrrolidone (PVP) and poly(vinylpyrrolidone-vinylacetate) (PVP VA) micro- and nanofibers of different polymer concentrations and solvent ratios were prepared with a high-speed rotary spinning technique. In order to study the influence of parameters that enable successful fiber production from polymeric viscous solutions, a complex micro- and macrostructural screening method was implemented. The obtained fiber mats were subjected to detailed morphological analysis using scanning electron microscope (SEM), and rheological measurements while the microstructural changes of fiber samples, based on the free volume changes, was analyzed by positron annihilation lifetime spectroscopy (PALS) and compared with their mechanical characteristics. The plasticizing effect of water tracked by ortho-positronium lifetime changes in relation to the mechanical properties of fibers. A concentration range of polyvinylpyrrolidone solutions was defined for the preparation of fibers of optimum fiber morphology and mechanical properties. The method enabled fiber formulation of advantageous functionality-related properties for further formulation of solid dosage forms.

  19. Efficacy and accuracy of a novel rapid prototyping drill template for cervical pedicle screw placement.

    Science.gov (United States)

    Lu, Sheng; Xu, Yong Q; Chen, Guo P; Zhang, Yuan Z; Lu, Di; Chen, Yu B; Shi, Ji H; Xu, Xing M

    2011-01-01

    To develop and validate the efficacy and accuracy of a novel drill template for cervical pedicle instrumentation. A CT scan of the cervical vertebrae was performed, and a 3D model of the vertebrae was reconstructed using MIMICS 10.01 software. The 3D vertebral model was then exported in STL format, and opened in a workstation running UGS Imageware 12.0 software to determine the optimal pedicle screw size and orientation. A virtual navigational template was established according to the laminar anatomic trait, and physical navigational templates were manufactured using rapid prototyping. The navigational templates were used intraoperatively to assist in the placement of cervical pedicle screws. In all, 84 pedicle screws were placed, and the accuracy of screw placement was confirmed with postoperative X-rays and CT scans. Eighty-two screws were rated as Grade 0, 2 as Grade 1, and no screws as Grade 2 or 3. Hence, safer screw positioning was accomplished with the drill template technique. This study demonstrates a patient-specific template technique that is easy to use, can simplify the surgical act, and generates highly accurate cervical pedicle screw placement. The advantages of this technology over traditional techniques are that it enables planning of the screw trajectory to be completed prior to surgery, and that the screw can be sized to fit the patient's anatomy.

  20. Surgical technique: Simple technique for removing a locking recon plate with damaged screw heads.

    Science.gov (United States)

    Gopinathan, Nirmal Raj; Dhillon, Mandeep Singh; Kumar, Rajesh

    2013-05-01

    The introduction of locking plates in the treatment of periarticular fractures was a major breakthrough in orthopaedic evolution. Removal of these implants is extremely difficult as a result of cold welding and stripping of screw heads. A 31-year-old man had a schwannoma of the left C5-C6 nerve roots and upper trunk of the brachial plexus. One year before presentation he had undergone excision of the lesion through an approach using a clavicular osteotomy. The osteotomy had been fixed with a titanium locking recon plate. While surgically removing the implant, only one screw could be removed. The remaining five screws could not be turned owing to cold welding; repeated attempts at removing the screws damaged the screw heads. A large bolt cutter was used to cut the plate between the holes, and the resulting rectangular sections with the screws then were unscrewed from the bone. Limited literature is available regarding techniques for locking screw removal. These include using a carbide drill bit or diamond-tipped burr, high-speed disc, or conical extraction screw. Not all centers have specialized instruments such as carbide drill bits to remove screw heads, but a large bolt cutter usually is available when screws cannot be unscrewed owing to cold welding. The technique of cutting is easily reproducible and does not require additional soft tissue stripping.