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Sample records for impelling forces tending

  1. Rotordynamic Forces on Centrifugal Pump Impellers

    OpenAIRE

    Franz, R.; Arndt, N.; Caughey, T. K.; Brennen, C. E.; Acosta, A. J.

    1987-01-01

    The asymmetric flow around an impeller in a volute exerts a force upon the impeller. To study the rotordynamic force on an impeller which is vibrating around its machine axis of rotation, the impeller, mounted on a dynamometer, is made to whirl in a circular orbit within the volute. The measured force is expressed as the sum of a steady radial force and an unsteady force due to the eccentric motion of the impeller. These forces were measured in separate tests on a centrifugal pump with rad...

  2. Origins of hydrodynamic forces on centrifugal pump impellers

    Science.gov (United States)

    Adkins, Douglas R.; Brennen, Christopher E.

    1987-01-01

    Hydrodynamic interactions that occur between a centrifugal pump impeller and volute are experimentally and theoretically investigated. The theoretical analysis considers the inability of the blades to perfectly guide the flow through the impeller, and also includes a quasi-one dimensional treatment of the flow in the volute. The disturbance at the impeller discharge and the resulting forces are determined by the theoretical model. The model is then extended to obtain the hydrodynamic force perturbations that are caused by the impeller whirling eccentrically in the volute. Under many operating conditions, these force perturbations were found to be destablizing. Comparisons are made between the theoretical model and the experimental measurements of pressure distributions and radial forces on the impeller. The theoretical model yields fairly accurate predictions of the radial forces caused by the flow through the impeller. However, it was found that the pressure acting on the front shroud of the impeller has a substantial effect on the destablizing hydrodynamic forces.

  3. Forces on Centrifugal Pump Impellers

    OpenAIRE

    Jery, Belgacem; Brennen, Christopher E.; Caughey, Thomas K.; Acosta, Allan

    1985-01-01

    Forces are exerted on a centrifugal pump impeller, due to the asymmetry of the flow caused by the volute of diffuser, and to the motion of the center of the impeller whenever the shaft whirls. Recent work in the measurement of these forces as a function of the whirl speed to shaft speed ratio, and the influence of the volute, is reviewed. These forces may be decomposed into a steady force, a static stiffness matrix, a damping matrix and an inertia matrix. It is shown that for centrifugal p...

  4. Influence of impeller and diffuser geometries on the lateral fluid forces of whirling centrifugal impeller

    Science.gov (United States)

    Ohashi, Hideo; Sakurai, Akira; Nishihama, Jiro

    1989-01-01

    Lateral fluid forces on two-dimensional centrifugal impellers, which whirl on a circular orbit in a vaneless diffuser, were reported. Experiments were further conducted for the cases in which a three-dimensional centrifugal impeller, a model of the boiler feed pump, whirls in vaneless and vaned diffusers. The influence of the clearance configuration between the casing and front shroud of the impeller was also investigated. The result indicated that the fluid dynamic interaction between the impeller and the guide vanes induces quite strong fluctuating fluid forces to the impeller, but nevertheless its influence on radial and tangential force components averaged over a whirling orbit is relatively small.

  5. Effects of Volute Design and Number of Impeller Blades on Lateral Impeller Forces and Hydraulic Performance

    Directory of Open Access Journals (Sweden)

    Daniel O. Baun

    2003-01-01

    Full Text Available A comparison is made between the characteristics of the measured lateral impeller forces and the hydraulic performances of a four- and a five-vane impeller, each operating in a spiral volute, a concentric volute, and a double volute. The pump's rotor was supported in magnetic bearings. In addition to supporting and controlling the rotor motion, the magnetic bearings also served as active load cells and were used to measure the impeller forces acting on the pump's rotor. The lateral impeller force characteristics, as a function of a normalized flow coefficient, were virtually identical in the four- and five-vane impellers in each respective volute type. The measured impeller forces for each volute type were compared with correlations in the literature. The measured forces from the double volute configurations agreed with the forces from a correlation model over the full flow range. Single volute configurations compared well with the predictions of a published correlation at high flow rates, ϕ/ϕn>0.5. Concentric volute configurations compared well with a published correlation at low flow rates, ϕ/ϕn<0.4. The head-versus-flow characteristics of the four-vane impeller in each volute type were stable over a greater flow range than the corresponding characteristics of the five-vane impeller. At higher flow rates in the stable region of the head's characteristic curves near the best efficiency point, the five-vane impeller produced higher head than did the four-vane impeller in each volute type.

  6. Proposal of Unique Process Pump with Floating Type Centrifugal Impeller (Preliminarily Report : Axial Thrust of Impeller with Driving Shaft)

    Science.gov (United States)

    Kawashima, Ryunosuke; Kanemoto, Toshiaki; Sakamoto, Kengo; Uno, Mitsuo

    2010-06-01

    The authors have proposed the unique centrifugal pump, in which the impeller dose not have the driving shaft but is driven by the magnetic induction, namely Lorentz force, without the stay. Then, the rotating posture of the impeller is not stable, just like UFO. To make the rotating posture of the impeller stable irrespective of the operating condition, the pressure in the impeller casing was investigated experimentally while the impeller rotates at the steady state, as the preliminarily stage. The pressure, as well known, fluctuates periodically in response to the blade number. Besides, the pressure on the impeller shrouds decreases with the increase of the gap between the front shroud and the suction cover where the water leaks to the suction pipe, and is distorted in the peripheral direction. Such pressure conditions contribute directly to the hydraulic force acting on the impeller. The unstable behaviors of the impeller are induced from the above hydraulic forces, which change unsteadily in the radial and the peripheral directions in the impeller casing. The forces are affected by not only the operating condition but also the rotating posture of the impeller.

  7. Impeller radial force evolution in a large double-suction centrifugal pump during startup at the shut-off condition

    International Nuclear Information System (INIS)

    Zou, Zhichao; Wang, Fujun; Yao, Zhifeng; Tao, Ran; Xiao, Ruofu; Li, Huaicheng

    2016-01-01

    Highlights: • Conclude the characteristics of transient radial force in the startup process for a large double-suction centrifugal pump. • The overall direction of the radial force during startup process is also confirmed. • A formula used to calculate the transient radial force during startup process is proposed. • A relationship between radial force variation and axial vortex development in blade channel during the startup process is established. The mechanism of the radial force evolution is revealed. - Abstract: Double-suction centrifugal pumps play an important role in the main feedwater systems of nuclear power plant. The impeller radial force in a centrifugal pump varies dramatically during startup at the shut-off condition. In this study, the startup process of a large double-suction centrifugal pump is investigated using CFD. During testing, the impeller speed is accelerated from zero to its rated speed in 1.0 s (marked as t_0) and is then maintained at the rated speed. The results show that the radial force increase lags behind the impeller speed increase. At 0–0.4t_0, the radial force is small (approaching zero). At 0.4–1.4t_0, the radial force increases rapidly. After 1.4t_0, the average radial force stabilizes and reaches its maximum value of 55,619 N. The observed maximum radial force value during startup is approximately nine times as high as the radial force under rated condition. During startup, the overall radial force direction is proximate to the radial line located 25° from the volute tongue along circumferential direction. A transient radial force formula is proposed to evaluate the changes in radial force during startup. The streamline distribution in impeller passages and the impeller outlet pressure profile varying over time are produced. The relationship between radial force evolution and the varying axial-to-spiral vortex structure is analyzed. The radial force change mechanism is revealed. This research provides a scientific

  8. Impeller radial force evolution in a large double-suction centrifugal pump during startup at the shut-off condition

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Zhichao [College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083 (China); Wang, Fujun, E-mail: wangfj@cau.edu.cn [College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083 (China); Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System, China Agricultural University, Beijing 100083 (China); Yao, Zhifeng [College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083 (China); Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System, China Agricultural University, Beijing 100083 (China); Tao, Ran [College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083 (China); Xiao, Ruofu [College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083 (China); Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System, China Agricultural University, Beijing 100083 (China); Li, Huaicheng [Shanghai Liancheng (Group) Co., Ltd., Shanghai 201812 (China)

    2016-12-15

    Highlights: • Conclude the characteristics of transient radial force in the startup process for a large double-suction centrifugal pump. • The overall direction of the radial force during startup process is also confirmed. • A formula used to calculate the transient radial force during startup process is proposed. • A relationship between radial force variation and axial vortex development in blade channel during the startup process is established. The mechanism of the radial force evolution is revealed. - Abstract: Double-suction centrifugal pumps play an important role in the main feedwater systems of nuclear power plant. The impeller radial force in a centrifugal pump varies dramatically during startup at the shut-off condition. In this study, the startup process of a large double-suction centrifugal pump is investigated using CFD. During testing, the impeller speed is accelerated from zero to its rated speed in 1.0 s (marked as t{sub 0}) and is then maintained at the rated speed. The results show that the radial force increase lags behind the impeller speed increase. At 0–0.4t{sub 0}, the radial force is small (approaching zero). At 0.4–1.4t{sub 0}, the radial force increases rapidly. After 1.4t{sub 0}, the average radial force stabilizes and reaches its maximum value of 55,619 N. The observed maximum radial force value during startup is approximately nine times as high as the radial force under rated condition. During startup, the overall radial force direction is proximate to the radial line located 25° from the volute tongue along circumferential direction. A transient radial force formula is proposed to evaluate the changes in radial force during startup. The streamline distribution in impeller passages and the impeller outlet pressure profile varying over time are produced. The relationship between radial force evolution and the varying axial-to-spiral vortex structure is analyzed. The radial force change mechanism is revealed. This research

  9. Numerical research on the effects of impeller pump-out vanes on axial force in a solid-liquid screw centrifugal pump

    International Nuclear Information System (INIS)

    Cheng, X R; Li, R N; Gao, Y; Guo, W L

    2013-01-01

    A commercial CFD code has been used to predict the performance of a screw centrifugal pump with pump-out vanes, especially when changing regularity of impeller axial force based on the solid-liquid two-phase flow. The Unsteady Reynolds Averaged Navier-Stokes (URANS) approach has been applied to solve the unsteady, incompressible, three-dimensional turbulent. The SIMPLEC algorithm, standard wall functions and mix two-phase flow model were applied. The RNG k ε-model was used to account the turbulence effects. By changing the number of impeller pump-out vanes and width, six different screw centrifugal pump numerical simulation projects were given, and each scheme in the different solid volume fraction were calculated respectively. The change rules of axial force, velocity and pressure distribution of flow field were obtained on the different condition and different volume fraction. The results showed that the axial forces values based solid-fluid two-phase greater than based single-phase clear water, but both changing regularity of the axial force were consistent; as same condition, the same solid-phase volume concentration, with the increase of pump-out vanes number or width, the impeller axial force increased as well. Meanwhile the number of the pump-out vanes and the width of pump-out vanes in balancing the impeller axial force, there are the most optimal value

  10. Pump instability phenomena generated by fluid forces

    Science.gov (United States)

    Gopalakrishnan, S.

    1985-01-01

    Rotor dynamic behavior of high energy centrifugal pumps is significantly affected by two types of fluid forces; one due to the hydraulic interaction of the impeller with the surrounding volute or diffuser and the other due to the effect of the wear rings. The available data on these forces is first reviewed. A simple one degree-of-freedom system containing these forces is analytically solved to exhibit the rotor dynamic effects. To illustrate the relative magnitude of these phenomena, an example of a multistage boiler feed pump is worked out. It is shown that the wear ring effects tend to suppress critical speed and postpone instability onset. But the volute-impeller forces tend to lower the critical speed and the instability onset speed. However, for typical boiler feed pumps under normal running clearances, the wear ring effects are much more significant than the destabilizing hydraulic interaction effects.

  11. Gas–liquid flow in stirred reactors: Trailing vortices and gas accumulation behind impeller blades

    NARCIS (Netherlands)

    Ranade, V.; Deshpande, Vaibhav R.

    1999-01-01

    In a gas–liquid stirred reactor, gas tends to accumulate in low-pressure regions behind the impeller blades. Such gas accumulation significantly alters impeller performance characteristics. We have computationally investigated gas–liquid flow generated by a Rushton (disc) turbine. Rotating Rushton

  12. A finite element perturbation method for computing fluid-induced forces on a certrifugal impeller rotating and whirling in a volute casing

    NARCIS (Netherlands)

    Jonker, Jan B.; van Essen, T.G.; van Essen, T.G.

    1997-01-01

    A finite element based method has been developed for computing time-averaged fluid-induced radial excitation forces and rotor dynamic forces on a two-dimensional centrifugal impeller rotating and whirling in a volute casing. In this method potential flow theory is used, which implies the assumption

  13. Impeller in Precessing Motion

    Directory of Open Access Journals (Sweden)

    Yoshiki Yoshida

    2001-01-01

    destabilizing in the region of negative precessing speed ratio (-0.3<Ω/ω<0, at the design flow rate; (2 At reduced flow rate, the destabilizing fluid force moments occurred at small positive precessing speed ratio (0.2<Ω/ω<0.4; (3 From the comparison of direct measured fluid force moments with those estimated from the unsteady pressure measured on the front and back casing walls, it was found that the destabilizing moments in the backward precession are mainly caused by the fluid forces on the front surface of the present impeller, where there is large clearance between the back shroud and casing.

  14. A novel permanent maglev impeller TAH: most requirements on blood pumps have been satisfied.

    Science.gov (United States)

    Qian, K X; Zeng, P; Ru, W M; Yuan, H Y

    2003-07-01

    Based on the development of an impeller total artificial heart (TAH) (1987) and a permanent maglev (magnetic levitation) impeller pump (2002), as well as a patented magnetic bearing and magnetic spring (1996), a novel permanent maglev impeller TAH has been developed. The device consists of a rotor and a stator. The rotor is driven radially. Two impellers with different dimensions are fixed at both the ends of the rotor. The levitation of the rotor is achieved by using two permanent magnetic bearings, which have double function: radial bearing and axial spring. As the rotor rotates at a periodic changing speed, two pumps deliver the pulsatile flow synchronously. The volume balance between the two pumps is realized due to self-modulation property of the impeller pumps, without need for detection and control. Because the hemo-dynamic force acting on the left impeller is larger than that on the right impeller, and this force during systole is larger than that during diastole, the rotor reciprocates axially once a cycle. This is beneficial to prevent the thrombosis in the pump. Furthermore, a small flow via the gap between stator and rotor from left pump into right pump comes to a full washout in the motor and the pumps. Therefore, it seems neither mechanical wear nor thrombosis could occur. The previously developed prototype impeller TAH had demonstrated that it could operate in animal experiments indefinitely, if the bearing would not fail to work. Expectantly, this novel permanent magnetic levitation impeller TAH with simplicity, implantability, pulsatility, compatibility and durability has satisfied the most requirements on blood pumps and will have more extensive applications in experiments and clinics.

  15. [Improved design of permanent maglev impeller assist heart].

    Science.gov (United States)

    Qian, Kunxi; Zeng, Pei; Ru, Weimin; Yuan, Haiyu

    2002-12-01

    Magnetic bearing has no mechanical contact between the rotor and stator. And a rotary pump with magnetic bearing has therefore no mechanical wear and thrombosis due to bearing. The available magnetic bearings, however, are devised with electric magnets, need complicated control and remarkable energy consumption. Resultantly, it is difficult to apply an electric magnetic bearing to rotary pump without disturbing its simplicity, implantability and reliability. The authors have developed a levitated impeller pump merely with permanent magnets. The rotor is supported by permanent magnetic forces radially. On one side of the rotor, the impeller is fixed; and on the other side of the rotor, the driven magnets are mounted. Opposite to this driven magnets, a driving motor coil with iron corn magnets is fastened to the motor axis. Thereafter, the motor drives the rotor via a rotating magnetic field. By laboratory tests with saline, if the rotor stands still or rotates under 4,000 rpm, the rotor has one-point contact axially with the driving motor coil. The contacting point is located in the center of the rotor. As the rotating speed increases gradually to more than 4,000 rpm, the rotor will detache from the stator axially. Then the rotor will be fully levitated. Since the axial levitation is produced by hydraulic force and the driven magnets have a gyro-effect, the rotor rotates very steadly during levitation. As a left ventricular assist device, the pump works in a rotating speed range of 5,000-8,000 rpm, the levitation of the impeller hence is ensured by practical use of the pump.

  16. Effects of Impeller-Diffuser Interaction on Centrifugal Compressor Performance

    Science.gov (United States)

    Tan, Choon S.

    2003-01-01

    This research program focuses on characterizing the effect of impeller-diffuser interactions in a centrifugal compressor stage on its performance using unsteady threedimensional Reynolds-averaged Navier-Stokes simulations. The computed results show that the interaction between the downstream diffuser pressure field and the impeller tip clearance flow can account for performance changes in the impeller. The magnitude of performance change due to this interaction was examined for an impeller with varying tip clearance followed by a vaned or vaneless diffuser. The impact of unsteady impeller-diffuser interaction, primarily through the impeller tip clearance flow, is reflected through a time-averaged change in impeller loss, blockage and slip. The results show that there exists a tip clearance where the beneficial effect of the impeller-diffuser interaction on the impeller performance is at a maximum. A flow feature that consists of tip flow back leakage was shown to occur at design speed for the centrifugal compressor stage. This flow phenomenon is described as tip flow that originates in one passage, flows downstream of the impeller trailing edge and then returns to upstream of the impeller trailing edge of a neighboring passage. Such a flow feature is a source of loss in the impeller. A hypothesis is put forth to show that changing the diffuser vane count and changing impeller-diffuser gap has an analogous effect on the impeller performance. The centrifugal compressor stage was analyzed using diffusers of different vane counts, producing an impeller performance trend similar to that when the impeller-diffuser gap was varied, thus supporting the hypothesis made. This has the implication that the effect impeller performance associated with changing the impeller-diffuser gap and changing diffuser vane count can be described by the non-dimensional ratio of impeller-diffuser gap to diffuser vane pitch. A procedure is proposed and developed for isolating impeller passage

  17. Study of Pumping Capacity of Pitched Blade Impellers

    Directory of Open Access Journals (Sweden)

    I. Fořt

    2002-01-01

    Full Text Available A study was made of the pumping capacity of pitched blade impellers in a cylindrical pilot plant vessel with four standard radial baffles at the wall under a turbulent regime of flow. The pumping capacity was calculated from the radial profile of the axial flow, under the assumption of axial symmetry of the discharge flow. The mean velocity was measured using laser Doppler anemometry in a transparent vessel of diameter T = 400 mm, provided with a standard dished bottom. Three and six blade pitched blade impellers (the pitch angle varied within the interval a Îá24°; 45°ń of impeller/vessel diameter ratio D/T = 0.36, as well as a three blade pitched blade impeller with folded blades of the same diameter, were tested. The calculated results were compared with the results of experiments mentioned in the literature, above all in cylindrical vessels with a flat bottom. Both arrangements of the agitated system were described by the impeller energetic efficiency, i.e, a criterion including in dimensionless form both the impeller energy consumption (impeller power input and the impeller pumping effect (impeller pumping capacity. It follows from the results obtained with various geometrical configurations that the energetic efficiency of pitched blade impellers is significantly lower for configurations suitable for mixing solid-liquid suspensions (low impeller off bottom clearances than for blending miscible liquids in mixing (higher impeller off bottom clearances.

  18. Strength Analysis of the Carbon-Fiber Reinforced Polymer Impeller Based on Fluid Solid Coupling Method

    Directory of Open Access Journals (Sweden)

    Jinbao Lin

    2014-01-01

    Full Text Available Carbon-fiber reinforced polymer material impeller is designed for the centrifugal pump to deliver corrosive, toxic, and abrasive media in the chemical and pharmaceutical industries. The pressure-velocity coupling fields in the pump are obtained from the CFD simulation. The stress distribution of the impeller couple caused by the flow water pressure and rotation centrifugal force of the blade is analyzed using one-way fluid-solid coupling method. Results show that the strength of the impeller can meet the requirement of the centrifugal pumps, and the largest stress occurred around the blades root on a pressure side of blade surface. Due to the existence of stress concentration at the blades root, the fatigue limit of the impeller would be reduced greatly. In the further structure optimal design, the blade root should be strengthened.

  19. The performance of a centrifugal fan with enlarged impeller

    International Nuclear Information System (INIS)

    Li Chunxi; Song Lingwang; Jia Yakui

    2011-01-01

    Highlights: → The influence of impeller enlargement is evaluated numerically and experimentally. → Variation equations of the operation points for enlarged impellers are derived. → Impeller enlargement leads to louder fan noise due to reduced impeller-volute gap. - Abstract: The influence of enlarged impeller in unchanged volute on G4-73 type centrifugal fan performance is investigated in this paper. Comparisons are conducted between the fan with original impeller and two larger impellers with the increments in impeller outlet diameter of 5% and 10% respectively in the numerical and experimental investigations. The internal characteristics are obtained by the numerical simulation, which indicate there is more volute loss in the fan with larger impeller. Experiment results show that the flow rate, total pressure rise, shaft power and sound pressure level have increased, while the efficiency have decreased when the fan operates with larger impeller. Variation equations on the performance of the operation points for the fan with enlarged impellers are suggested. Comparisons between experiment results and the trimming laws show that the trimming laws for usual situation can predict the performance of the enlarged fan impeller with less error for higher flow rate, although the situation of application is not in agreement. The noise frequency analysis shows that higher noise level with the larger impeller fan is caused by the reduced impeller-volute gap.

  20. The performance of a centrifugal fan with enlarged impeller

    Energy Technology Data Exchange (ETDEWEB)

    Li Chunxi, E-mail: leechunxi@163.com [School of Energy and Power Engineering, North China Electric Power University, 071003 Baoding, Hebei (China); Song Lingwang [School of Energy and Power Engineering, North China Electric Power University, 071003 Baoding, Hebei (China); Jia Yakui [Hebei Electric Power Design and Research Institute, 050031 Shijiazhuang, Hebei (China)

    2011-08-15

    Highlights: {yields} The influence of impeller enlargement is evaluated numerically and experimentally. {yields} Variation equations of the operation points for enlarged impellers are derived. {yields} Impeller enlargement leads to louder fan noise due to reduced impeller-volute gap. - Abstract: The influence of enlarged impeller in unchanged volute on G4-73 type centrifugal fan performance is investigated in this paper. Comparisons are conducted between the fan with original impeller and two larger impellers with the increments in impeller outlet diameter of 5% and 10% respectively in the numerical and experimental investigations. The internal characteristics are obtained by the numerical simulation, which indicate there is more volute loss in the fan with larger impeller. Experiment results show that the flow rate, total pressure rise, shaft power and sound pressure level have increased, while the efficiency have decreased when the fan operates with larger impeller. Variation equations on the performance of the operation points for the fan with enlarged impellers are suggested. Comparisons between experiment results and the trimming laws show that the trimming laws for usual situation can predict the performance of the enlarged fan impeller with less error for higher flow rate, although the situation of application is not in agreement. The noise frequency analysis shows that higher noise level with the larger impeller fan is caused by the reduced impeller-volute gap.

  1. Simulation of computational fluid dynamics and comparison of cephalosporin C fermentation performance with different impeller combinations

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Shengbing; Ni, Weijia; Luo, Hongzhen; Shi, Zhongping; Liu, Fan [Jiangnan University, Wuxi (China); Yuan, Guoqiang; Zhao, Yanli [CSPC Hebei Zhongrun Pharmaceutical Co. Ltd., Shijiazhuang (China)

    2013-05-15

    Cephalosporin C (CPC) fermentation by Acremonium chrysogenum is an extremely high oxygen-consuming process and oxygen transfer rate in a bioreactor directly affects fermentation performance. In this study, fluid dynamics and oxygen transfer in a 7 L bioreactor with different impellers combinations were simulated by computational fluid dynamics (CFD) model. Based on the simulation results, two impeller combinations with higher oxygen transfer rate (K{sub L}a) were selected to conduct CPC fermentations, aiming at achieving high CPC concentration and low accumulation of major by-product, deacetoxycephalosporin (DAOC). It was found that an impeller combination with a higher K{sub L}a and moderate shear force is the prerequisite for efficient CPC production in a stirred bioreactor. The best impeller combination, which installed a six-bladed turbine and a four-pitched-blade turbine at bottom and upper layers but with a shortened impellers inter-distance, produced the highest CPC concentration of 35.77 g/L and lowest DAOC/CPC ratio of 0.5%.

  2. Simulation of computational fluid dynamics and comparison of cephalosporin C fermentation performance with different impeller combinations

    International Nuclear Information System (INIS)

    Duan, Shengbing; Ni, Weijia; Luo, Hongzhen; Shi, Zhongping; Liu, Fan; Yuan, Guoqiang; Zhao, Yanli

    2013-01-01

    Cephalosporin C (CPC) fermentation by Acremonium chrysogenum is an extremely high oxygen-consuming process and oxygen transfer rate in a bioreactor directly affects fermentation performance. In this study, fluid dynamics and oxygen transfer in a 7 L bioreactor with different impellers combinations were simulated by computational fluid dynamics (CFD) model. Based on the simulation results, two impeller combinations with higher oxygen transfer rate (K_La) were selected to conduct CPC fermentations, aiming at achieving high CPC concentration and low accumulation of major by-product, deacetoxycephalosporin (DAOC). It was found that an impeller combination with a higher K_La and moderate shear force is the prerequisite for efficient CPC production in a stirred bioreactor. The best impeller combination, which installed a six-bladed turbine and a four-pitched-blade turbine at bottom and upper layers but with a shortened impellers inter-distance, produced the highest CPC concentration of 35.77 g/L and lowest DAOC/CPC ratio of 0.5%

  3. Impeller Submergence Depth for Stirred Tanks

    Directory of Open Access Journals (Sweden)

    Thiyam T. Devi

    2011-11-01

    Full Text Available Impeller submergence governs the performance of mixing tanks employed in oxygen transfer operation. Present work experimentally investigates the effect of impeller submergence depths on oxygen transfer and corresponding power consumption. It has been found that at higher range of impeller submergence, mixing tanks consume less power and gives higher values of oxygen transfer coefficient. Optimal range of submergence depth is 0.7 to 0.9 times the impeller diameter. Copyright ©2011 BCREC UNDIP. All rights reserved.(Received: 4th March 2011; Revised: 12nd July 2011; Accepted: 14th July 2011[How to Cite: T.T. Devi, A.P. Sinha, M. Thakre, and B. Kumar. (2011. Impeller Submergence Depth for Stirred Tanks. Bulletin of Chemical Reaction Engineering & Catalysis, 6 (2: 123-128. doi:10.9767/bcrec.6.2.826.123-128][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.2.826.123-128 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/826] | View in 

  4. Retrofit of CD-6 (Smith) impeller in fermentation vessels.

    Science.gov (United States)

    Junker, B H; Mann, Z; Hunt, G

    2000-10-01

    We extended prior studies on the influence of impeller type on fermentation performance to include a novel low-power-number, high-efficiency radial flow impeller, the CD-6, possessing six curved blades on a disk turbine. Dual impeller combinations of CD-6/CD-6, CD-6/Maxflo T, and CD-6/HE-3 were compared with Rushton/Rushton and Maxflo T/Maxflo T base cases. Qualitative comparisons of unaerated and aerated power draw in both water and glycerol were conducted. These suggested minimal power drops with aeration for dual CD-6 impellers and hybrids containing the CD-6 impeller design. We also examined fermentation performance for Streptomyces and Glarea secondary metabolite fermentations. A qualitative comparison of the data suggested that dual CD-6 impellers and hybrids containing the CD-6 impeller design resulted in reasonable power draws, improved mass transfer rates with airflow increases, and acceptable peak titers. These arrangements may warrant further study under a wider range of production conditions.

  5. Preliminary design of RDE feedwater pump impeller

    International Nuclear Information System (INIS)

    Sri Sudadiyo

    2018-01-01

    Nowadays, pumps are being widely used in the thermal power generation including nuclear power plants. Reaktor Daya Experimental (RDE) is a proposed nuclear reactor concept for the type of nuclear power plant in Indonesia. This RDE has thermal power 10 MW th , and uses a feedwater pump within its steam cycle. The performance of feedwater pump depends on size and geometry of impeller model, such as the number of blades and the blade angle. The purpose of this study is to perform a preliminary design on an impeller of feedwater pump for RDE and to simulate its performance characteristics. The Fortran code is used as an aid in data calculation in order to rapidly compute the blade shape of feedwater pump impeller, particularly for a RDE case. The calculations analyses is solved by utilizing empirical correlations, which are related to size and geometry of a pump impeller model, while performance characteristics analysis is done based on velocity triangle diagram. The effect of leakage, pass through the impeller due to the required clearances between the feedwater pump impeller and the volute channel, is also considered. Comparison between the feedwater pump of HTR-10 and of RDE shows similarity in the trend line of curve shape. These characteristics curves will be very useful for the values prediction of performance of a RDE feedwater pump. Preliminary design of feedwater pump provides the size and geometry of impeller blade model with 5-blades, inlet angle 14.5 degrees, exit angle 25 degrees, inside diameter 81.3 mm, exit diameter 275.2 mm, thickness 4.7 mm, and height 14.1 mm. In addition, the optimal values of performance characteristics were obtained when flow capacity was 4.8 kg/s, fluid head was 29.1 m, shaft mechanical power was 2.64 kW, and efficiency was 52 % at rotational speed 1750 rpm. (author)

  6. Strength and dynamic characteristics analyses of wound composite axial impeller

    Science.gov (United States)

    Wang, Jifeng; Olortegui-Yume, Jorge; Müller, Norbert

    2012-03-01

    A low cost, light weight, high performance composite material turbomachinery impeller with a uniquely designed blade patterns is analyzed. Such impellers can economically enable refrigeration plants to use water as a refrigerant (R718). A strength and dynamic characteristics analyses procedure is developed to assess the maximum stresses and natural frequencies of these wound composite axial impellers under operating loading conditions. Numerical simulation using FEM for two-dimensional and three-dimensional impellers was investigated. A commercially available software ANSYS is used for the finite element calculations. Analysis is done for different blade geometries and then suggestions are made for optimum design parameters. In order to avoid operating at resonance, which can make impellers suffer a significant reduction in the design life, the designer must calculate the natural frequency and modal shape of the impeller to analyze the dynamic characteristics. The results show that using composite Kevlar fiber/epoxy matrix enables the impeller to run at high tip speed and withstand the stresses, no critical speed will be matched during start-up and shut-down, and that mass imbalances of the impeller shall not pose a critical problem.

  7. Shape Optimization of Impeller Blades for 15,000 HP Centrifugal Compressor Using Fluid Structural Interaction Analysis

    International Nuclear Information System (INIS)

    Kang, Hyun Su; Oh, Jeongsu; Han, Jeong Sam

    2014-01-01

    This paper discusses a one-way fluid structural interaction (FSI) analysis and shape optimization of the impeller blades for a 15,000 HP centrifugal compressor using the response surface method (RSM). Because both the aerodynamic performance and the structural safety of the impeller are affected by the shape of its blades, shape optimization is necessary using the FSI analysis, which includes a structural analysis for the induced fluid pressure and centrifugal force. The FSI analysis is performed in ANSYS Workbench: ANSYS CFX is used for the flow field and ANSYS Mechanical is used for the structural field. The response surfaces for the FSI results (efficiency, pressure ratio, maximum stress, etc.) generated based on the design of experiments (DOE) are used to find an optimal shape for the impeller blades, which provides the maximum aerodynamic performance subject to the structural safety constraints

  8. Shape Optimization of Impeller Blades for 15,000 HP Centrifugal Compressor Using Fluid Structural Interaction Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Hyun Su [Sungkyunkwan University, Suwon (Korea, Republic of); Oh, Jeongsu [Daejoo Machinery Co., Daegu (Korea, Republic of); Han, Jeong Sam [Andong National University, Andong (Korea, Republic of)

    2014-06-15

    This paper discusses a one-way fluid structural interaction (FSI) analysis and shape optimization of the impeller blades for a 15,000 HP centrifugal compressor using the response surface method (RSM). Because both the aerodynamic performance and the structural safety of the impeller are affected by the shape of its blades, shape optimization is necessary using the FSI analysis, which includes a structural analysis for the induced fluid pressure and centrifugal force. The FSI analysis is performed in ANSYS Workbench: ANSYS CFX is used for the flow field and ANSYS Mechanical is used for the structural field. The response surfaces for the FSI results (efficiency, pressure ratio, maximum stress, etc.) generated based on the design of experiments (DOE) are used to find an optimal shape for the impeller blades, which provides the maximum aerodynamic performance subject to the structural safety constraints.

  9. Impeller inlet geometry effect on performance improvement for centrifugal pumps

    International Nuclear Information System (INIS)

    Luo, Xianwu; Zhang, Yao; Peng, Junqi; Xu, Hongyuan; Yu, Weiping

    2008-01-01

    This research treats the effect of impeller inlet geometry on performance improvement for a boiler feed pump, who is a centrifugal pump having specific speed of 183 m.m 3 min -1 .min -1 and close type impeller with exit diameter of 450 mm. The hydraulic performance and cavitation performance of the pump have been tested experimentally. In order to improve the pump, five impellers have been considered by extending the blade leading edge or applying much larger blade angle at impeller inlet compared with the original impeller. The 3-D turbulent flow inside those pumps has been analyzed basing on RNG k-ε turbulence model and VOF cavitation model. It is noted that the numerical results are fairly good compared with the experiments. Based on the experimental test and numerical simulation, the following conclusions can be drawn: (1) Impeller inlet geometry has important influence on performance improvement in the case of centrifugal pump. Favorite effects on performance improvement have been achieved by both extending the blade leading edge and applying much larger blade angle at impeller inlet: (2) It is suspected that the extended leading edge have favorite effect for improving hydraulic performance, and the much larger blade angle at impeller inlet have favorite effect for improving cavitation performance for the test pump: (3) Uniform flow upstream of impeller inlet is helpful for improving cavitation performance of the pump

  10. Impeller inlet geometry effect on performance improvement for centrifugal pumps

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Xianwu; Zhang, Yao; Peng, Junqi; Xu, Hongyuan [Tsinghua University, Beijing (China); Yu, Weiping [Zhejiang Pump Works, Zhejiang (China)

    2008-10-15

    This research treats the effect of impeller inlet geometry on performance improvement for a boiler feed pump, who is a centrifugal pump having specific speed of 183 m.m{sup 3}min{sup -1}.min{sup -1} and close type impeller with exit diameter of 450 mm. The hydraulic performance and cavitation performance of the pump have been tested experimentally. In order to improve the pump, five impellers have been considered by extending the blade leading edge or applying much larger blade angle at impeller inlet compared with the original impeller. The 3-D turbulent flow inside those pumps has been analyzed basing on RNG k-{epsilon} turbulence model and VOF cavitation model. It is noted that the numerical results are fairly good compared with the experiments. Based on the experimental test and numerical simulation, the following conclusions can be drawn: (1) Impeller inlet geometry has important influence on performance improvement in the case of centrifugal pump. Favorite effects on performance improvement have been achieved by both extending the blade leading edge and applying much larger blade angle at impeller inlet: (2) It is suspected that the extended leading edge have favorite effect for improving hydraulic performance, and the much larger blade angle at impeller inlet have favorite effect for improving cavitation performance for the test pump: (3) Uniform flow upstream of impeller inlet is helpful for improving cavitation performance of the pump

  11. An improved design of axially driven permanent maglev centrifugal pump with streamlined impeller.

    Science.gov (United States)

    Qian, K X; Zeng, P; Ru, W M; Yuan, H Y

    2007-01-01

    In 1839, Earnshaw proved theoretically that it is impossible to achieve a stable equilibrium with a pure permanent maglev. Furthermore, in 1939, Braunbeck deduced that it is only possible to stabilize a super conductive or an electric maglev. In 2000, however, the present authors discovered that stable levitation is achievable by a combination of permanent magnetic and nonmagnetic forces, and its stability can be maintained even with mere passive magnetic forces by use of the gyro-effect. An improved design of permanent maglev impeller pump has been developed. Passive magnetic (PM) bearings support the rotor radially; on its right side, an impeller is fixed and on its left side a motor magnets-assemble is mounted. Unlike a previous prototype design, in which the rotor magnets were driven by a motor via magnetic coupling, a motor coil is installed opposite to the motor magnets disc, producing a rotating magnetic field. At standstill or if the rotating speed is lower than 4000 rpm, the rotor has one axial point contact with the motor coil. The contact point is located at the centre of the rotor. As the rotating speed increases gradually to higher than 4000 rpm, the rotor will be drawn off from the contact point by the hydrodynamic force of the fluid. Then the rotor becomes fully suspended. For radial and peripheral stabilization, a gyro-effect is important, which is realized by designing the motor magnets disc to have large diameter, short length and high rotating speed; for axial stability, an axial rehabilitating force is necessary, which is produced by PM bearings. The rotor demonstrated a full levitation by rotation over 4000 rpm. As a left ventricular assist device, the rotation of the pump has a speed range from 5000 to 8000 rpm. The relation between pressure head and flow rate indicates that there is neither mechanical friction nor hydrodynamic turbulence inside the pump; the former is due to the frictionless maglev and the latter is a result of the

  12. Interpreting Aerodynamics of a Transonic Impeller from Static Pressure Measurements

    Directory of Open Access Journals (Sweden)

    Fangyuan Lou

    2018-01-01

    Full Text Available This paper investigates the aerodynamics of a transonic impeller using static pressure measurements. The impeller is a high-speed, high-pressure-ratio wheel used in small gas turbine engines. The experiment was conducted on the single stage centrifugal compressor facility in the compressor research laboratory at Purdue University. Data were acquired from choke to near-surge at four different corrected speeds (Nc from 80% to 100% design speed, which covers both subsonic and supersonic inlet conditions. Details of the impeller flow field are discussed using data acquired from both steady and time-resolved static pressure measurements along the impeller shroud. The flow field is compared at different loading conditions, from subsonic to supersonic inlet conditions. The impeller performance was strongly dependent on the inducer, where the majority of relative diffusion occurs. The inducer diffuses flow more efficiently for inlet tip relative Mach numbers close to unity, and the performance diminishes at other Mach numbers. Shock waves emerging upstream of the impeller leading edge were observed from 90% to 100% corrected speed, and they move towards the impeller trailing edge as the inlet tip relative Mach number increases. There is no shock wave present in the inducer at 80% corrected speed. However, a high-loss region near the inducer throat was observed at 80% corrected speed resulting in a lower impeller efficiency at subsonic inlet conditions.

  13. Impeller Design of a Centrifugal Fan with Blade Optimization

    Directory of Open Access Journals (Sweden)

    Yu-Tai Lee

    2011-01-01

    Full Text Available A method is presented for redesigning a centrifugal impeller and its inlet duct. The double-discharge volute casing is a structural constraint and is maintained for its shape. The redesign effort was geared towards meeting the design volute exit pressure while reducing the power required to operate the fan. Given the high performance of the baseline impeller, the redesign adopted a high-fidelity CFD-based computational approach capable of accounting for all aerodynamic losses. The present effort utilized a numerical optimization with experiential steering techniques to redesign the fan blades, inlet duct, and shroud of the impeller. The resulting flow path modifications not only met the pressure requirement, but also reduced the fan power by 8.8% over the baseline. A refined CFD assessment of the impeller/volute coupling and the gap between the stationary duct and the rotating shroud revealed a reduction in efficiency due to the volute and the gap. The calculations verified that the new impeller matches better with the original volute. Model-fan measured data was used to validate CFD predictions and impeller design goals. The CFD results further demonstrate a Reynolds-number effect between the model- and full-scale fans.

  14. MATHEMATICAL AND EXPERIMENTAL MODELING OF CENTRIFUGAL TURBOMACHINES’ OPERATING MODES WITH A COAXIAL ARRANGEMENT OF IMPELLERS

    Directory of Open Access Journals (Sweden)

    S. V. Podbolotov

    2018-03-01

    Full Text Available The relevance of this work is conditioned by the possibility of expanding the range of efficient operation of the turbine by changing the flow pattern of the fluid flow from stage to stage. The purpose of the work is to establish rational modes of operation of turbo machines with coaxially mounted impellers. Research methodology: in this work, we used a systematic approach, which includes the analysis of the results of mathematical modeling and experimental studies. Results. We carried out the analysis of the influence of operating modes on the pressure developed by the turbine. These operating modes include directions of rotation of impellers and the value of their circumferential speeds. The study analyzed the two options of installation: the rotation of the wheels in one direction and the rotation of the wheels in the opposite direction. The theoretical studies were based on a well-known Euler theory under certain assumptions: the cross section averaged for all flow settings; the motion of impellers was made one-dimensional and axisymmetric; the impellers have an infinite number of infinitely thin blades; the flow of fluid does not have viscosity, and the influence of friction forces is absent. The experimental aerodynamic characteristics of the centrifugal turbo machine with coaxial arrangement of driving wheels were obtained on an especially designed aerodynamic stand. Pressure-flow characteristics obtained theoretically and experimentally are presented. Conclusion. The use of coaxial impellers contributes to developing pressure and allows you to extend the range of efficient operation of centrifugal turbo machines. The most rational mode of operation of coaxially mounted impellers is the counter rotation mode. The increase of pressure developed by the Turbo machinery at work in this mode is proven theoretically and confirmed experimentally. Sufficient convergence of mathematical and experimental studies suggests the reliability of the

  15. Interaction of impeller and guide vane in a series-designed axial-flow pump

    International Nuclear Information System (INIS)

    Kim, S; Choi, Y S; Lee, K Y; Kim, J H

    2012-01-01

    In this paper, the interaction of the impeller and guide vane in a series-designed axial-flow pump was examined through the implementation of a commercial CFD code. The impeller series design refers to the general design procedure of the base impeller shape which must satisfy the various flow rate and head requirements by changing the impeller setting angle and number of blades of the base impeller. An arc type meridional shape was used to keep the meridional shape of the hub and shroud with various impeller setting angles. The blade angle and the thickness distribution of the impeller were designed as an NACA airfoil type. In the design of the guide vane, it was necessary to consider the outlet flow condition of the impeller with the given setting angle. The meridional shape of the guide vane were designed taking into consideration the setting angle of the impeller, and the blade angle distribution of the guide vane was determined with a traditional design method using vane plane development. In order to achieve the optimum impeller design and guide vane, three-dimensional computational fluid dynamics and the DOE method were applied. The interaction between the impeller and guide vane with different combination set of impeller setting angles and number of impeller blades was addressed by analyzing the flow field of the computational results.

  16. Frequency and Magnitude Analysis of the Macro-instability Related Component of the Tangential Force Affecting Radial Baffles in a Stirred Vessel

    Directory of Open Access Journals (Sweden)

    P. Hasal

    2002-01-01

    Full Text Available Experimental data obtained by measuring the tangential component of force affecting radial baffles in a flat-bottomed cylindrical mixing vessel stirred with pitched blade impellers is analysed. The maximum mean tangential force is detected at the vessel bottom. The mean force value increases somewhat with decreasing impeller off-bottom clearance and is noticeably affected by the number of impeller blades. Spectral analysis of the experimental data clearly demonstrated the presence of its macro-instability (MI related low-frequency component embedded in the total force at all values of impeller Reynolds number. The dimensionless frequency of the occurrence of the MI force component is independent of stirring speed, position along the baffle, number of impeller blades and liquid viscosity. Its mean value is about 0.074. The relative magnitude (QMI of the MI-related component of the total force is evaluated by a combination of proper orthogonal decomposition (POD and spectral analysis. Relative magnitude QMI was analysed in dependence on the frequency of the impeller revolution, the axial position of the measuring point in the vessel, the number of impeller blades, the impeller off-bottom clearance, and liquid viscosity. Higher values of QMI are observed at higher impeller off-bottom clearance height and (generally QMI decreases slightly with increasing impeller speed. The QMI value decreases in the direction from vessel bottom to liquid level. No evident difference was observed between 4 blade and 6 blade impellers. Liquid viscosity has only a marginal impact on the QMI value.

  17. Mass transfer and power characteristics of stirred tank with Rushton and curved blade impeller

    Directory of Open Access Journals (Sweden)

    Thiyam Tamphasana Devi

    2017-04-01

    Full Text Available Present work compares the mass transfer coefficient (kLa and power draw capability of stirred tank employed with Rushton and curved blade impeller using computational fluid dynamics (CFD techniques in single and double impeller cases. Comparative analysis for different boundary conditions and mass transfer model has been done to assess their suitability. The predicted local kLa has been found higher in curved blade impeller than the Rushton impeller, whereas stirred tank with double impeller does not show variation due to low superficial gas velocity. The global kLa predicted has been found higher in curved blade impeller than the Rushton impeller in double and single cases. Curved blade impeller also exhibits higher power draw capability than the Rushton impeller. Overall, stirred tank with curved blade impeller gives higher efficiency in both single and double cases than the Rushton turbine

  18. Optimization of a continuous hybrid impeller mixer via computational fluid dynamics.

    Science.gov (United States)

    Othman, N; Kamarudin, S K; Takriff, M S; Rosli, M I; Engku Chik, E M F; Meor Adnan, M A K

    2014-01-01

    This paper presents the preliminary steps required for conducting experiments to obtain the optimal operating conditions of a hybrid impeller mixer and to determine the residence time distribution (RTD) using computational fluid dynamics (CFD). In this paper, impeller speed and clearance parameters are examined. The hybrid impeller mixer consists of a single Rushton turbine mounted above a single pitched blade turbine (PBT). Four impeller speeds, 50, 100, 150, and 200 rpm, and four impeller clearances, 25, 50, 75, and 100 mm, were the operation variables used in this study. CFD was utilized to initially screen the parameter ranges to reduce the number of actual experiments needed. Afterward, the residence time distribution (RTD) was determined using the respective parameters. Finally, the Fluent-predicted RTD and the experimentally measured RTD were compared. The CFD investigations revealed that an impeller speed of 50 rpm and an impeller clearance of 25 mm were not viable for experimental investigations and were thus eliminated from further analyses. The determination of RTD using a k-ε turbulence model was performed using CFD techniques. The multiple reference frame (MRF) was implemented and a steady state was initially achieved followed by a transient condition for RTD determination.

  19. The Optimal Hydraulic Design of Centrifugal Impeller Using Genetic Algorithm with BVF

    Directory of Open Access Journals (Sweden)

    Xin Zhou

    2014-01-01

    Full Text Available Derived from idea of combining the advantages of two-dimensional hydraulic design theory, genetic algorithm, and boundary vorticity flux diagnosis, an optimal hydraulic design method of centrifugal pump impeller was developed. Given design parameters, the desired optimal centrifugal impeller can be obtained after several iterations by this method. Another 5 impellers with the same parameters were also designed by using single arc, double arcs, triple arcs, logarithmic spiral, and linear-variable angle spiral as blade profiles to make comparisons. Using Reynolds averaged N-S equations with a RNG k-ε two-equation turbulence model and log-law wall function to solve 3D turbulent flow field in the flow channel between blades of 6 designed impellers by CFD code FLUENT, the investigation on velocity distributions, pressure distributions, boundary vorticity flux distributions on blade surfaces, and hydraulic performance of impellers was presented and the comparisons of impellers by different design methods were demonstrated. The results showed that the hydraulic performance of impeller designed by this method is much better than the other 5 impellers under design operation condition with almost the same head, higher efficiency, and lower rotating torque, which implied less hydraulic loss and energy consumption.

  20. Regulating Effect of Asymmetrical Impeller on the Flow Distributions of Double-sided Centrifugal Compressor

    Science.gov (United States)

    Yang, Ce; Liu, Yixiong; Yang, Dengfeng; Wang, Benjiang

    2017-11-01

    To achieve the rebalance of flow distributions of double-sided impellers, a method of improving the radius of rear impeller is presented in this paper. It is found that the flow distributions of front and rear impeller can be adjusted effectively by increasing the radius of rear impeller, thus improves the balance of flow distributions of front and rear impeller. Meanwhile, the working conversion mode process of double-sided centrifugal compressor is also changed. Further analysis shows that the flowrates of blade channels in front impeller are mainly influenced by the circumferential distributions of static pressure in the volute. But the flowrates of rear impeller blade channels are influenced by the outlet flow field of bent duct besides the effects of static pressure distributions in the volute. In the airflow interaction area downstream, the flowrate of blade channel is obviously smaller. By increasing the radius of rear impeller, the work capacity of rear impeller is enhanced, the working mode conversion process from parallel working mode of double-sided impeller to the single impeller working mode is delayed, and the stable working range of double-sided compressor is broadened.

  1. Experimental Study of Unshrouded Impeller Pump Stage Sensitivity to Tip Clearance

    Science.gov (United States)

    Williams, Robert W.; Zoladz, Thomas; Storey, Anne K.; Skelley, Stephen E.

    2002-01-01

    This viewgraph presentation provides information on an experiment. Its objective is to experimentally determine unshrouded impeller performance sensitivity to tip clearance. The experiment included: Determining impeller efficiency at scaled operating conditions in water at MSFC's Pump Test Equipment (PTE) Facility; Testing unshrouded impeller at three different tip clearances; Testing each tip clearance configuration at on- and off-design conditions, and collecting unsteady- and steady-state data in each configuration; Determining impeller efficiency directly using drive line torquemeter and pump inlet and exit total pressure measurements.

  2. Optimization of a Continuous Hybrid Impeller Mixer via Computational Fluid Dynamics

    Directory of Open Access Journals (Sweden)

    N. Othman

    2014-01-01

    Full Text Available This paper presents the preliminary steps required for conducting experiments to obtain the optimal operating conditions of a hybrid impeller mixer and to determine the residence time distribution (RTD using computational fluid dynamics (CFD. In this paper, impeller speed and clearance parameters are examined. The hybrid impeller mixer consists of a single Rushton turbine mounted above a single pitched blade turbine (PBT. Four impeller speeds, 50, 100, 150, and 200 rpm, and four impeller clearances, 25, 50, 75, and 100 mm, were the operation variables used in this study. CFD was utilized to initially screen the parameter ranges to reduce the number of actual experiments needed. Afterward, the residence time distribution (RTD was determined using the respective parameters. Finally, the Fluent-predicted RTD and the experimentally measured RTD were compared. The CFD investigations revealed that an impeller speed of 50 rpm and an impeller clearance of 25 mm were not viable for experimental investigations and were thus eliminated from further analyses. The determination of RTD using a k-ε turbulence model was performed using CFD techniques. The multiple reference frame (MRF was implemented and a steady state was initially achieved followed by a transient condition for RTD determination.

  3. Improvement of centrifugal pump performance through addition of splitter blades on impeller pump

    Science.gov (United States)

    Kurniawan, Krisna Eka; Santoso, Budi; Tjahjana, Dominicus Danardono Dwi Prija

    2018-02-01

    The workable way to improve pump performance is to redesign or modify the impellers of centrifugal pump. The purpose of impeller pump modification is to improve pump efficiency, reduce cross flow, reduce secondary incidence flows, and decrease backflow areas at impeller outlets. Number blades and splitter blades in the impeller are three. The outlet blade angle is 20°, and the rotating speed of impeller is 2400 rpm. The added splitter blades variations are 0.25, 0.375, and 0.5 of the original blade length. The splitter blade placements are on the outer side of the impeller. The addition of splitter blades on the outer side of the impeller with 0.5L increases the pump head until 22% and the pump has 38.66% hydraulic efficiency. The best efficiency point of water flow rate pump (Qbep) was 3.02 × 10-3 m3/s.

  4. High performance hydraulic design techniques of mixed-flow pump impeller and diffuser

    International Nuclear Information System (INIS)

    Kim, Sung; Lee, Kyoung Yong; Kim, Joon Hyung; Kim, Jin Hyuk; Jung, Uk Hee; Choi, Young Seok

    2015-01-01

    In this paper, we describe a numerical study about the performance improvement of a mixed-flow pump by optimizing the design of the impeller and diffuser using a commercial computational fluid dynamics (CFD) code and design-of-experiments (DOE). The design variables of impeller and diffuser in the vane plane development were defined with a fixed meridional plane. The design variables were defined by the vane plane development, which indicates the blade-angle distributions and length of the impeller and diffuser. The vane plane development was controlled using the blade-angle in a fixed meridional plane. The blade shape of the impeller and diffuser were designed using a traditional method in which the inlet and exit angles are connected smoothly. First, the impeller optimum design was performed with impeller design variables. The diffuser optimum design was performed with diffuser design variables while the optimally designed impeller shape was fixed. The importance of the impeller and diffuser design variables was analyzed using 2 k factorial designs, and the design optimization of the impeller and diffuser design variables was determined using the response surface method (RSM). The objective functions were defined as the total head (Ht) and the total efficiency (ηt) at the design flow rate. The optimally designed model was verified using numerical analysis, and the numerical analysis results for both the optimum model and the reference model were compared to determine the reasons for the improved pump performance. A pump performance test was carried out for the optimum model, and its reliability was proved by a comparative analysis of the results of the numerical analysis and an experiment using the optimum model.

  5. Disposable MagLev centrifugal blood pump utilizing a cone-shaped impeller.

    Science.gov (United States)

    Hijikata, Wataru; Sobajima, Hideo; Shinshi, Tadahiko; Nagamine, Yasuyuki; Wada, Suguru; Takatani, Setsuo; Shimokohbe, Akira

    2010-08-01

    To enhance the durability and reduce the blood trauma of a conventional blood pump with a cone-shaped impeller, a magnetically levitated (MagLev) technology has been applied to the BioPump BPX-80 (Medtronic Biomedicus, Inc., Minneapolis, MN, USA), whose impeller is supported by a mechanical bearing. The MagLev BioPump (MagLev BP), which we have developed, has a cone-shaped impeller, the same as that used in the BPX-80. The suspension and driving system, which is comprised of two degrees of freedom, radial-controlled magnetic bearing, and a simply structured magnetic coupling, eliminates any physical contact between the impeller and the housing. To reduce both oscillation of the impeller and current in the coils, the magnetic bearing system utilizes repetitive and zero-power compensators. In this article, we present the design of the MagLev mechanism, measure the levitational accuracy of the impeller and pressure-flow curves (head-quantity [HQ] characteristics), and describe in vitro experiments designed to measure hemolysis. For the flow-induced hemolysis of the initial design to be reduced, the blood damage index was estimated by using computational fluid dynamics (CFD) analysis. Stable rotation of the impeller in a prototype MagLev BP from 0 to 2750 rpm was obtained, yielding a flow rate of 5 L/min against a head pressure in excess of 250 mm Hg. Because the impeller of the prototype MagLev BP is levitated without contact, the normalized index of hemolysis was 10% less than the equivalent value with the BPX-80. The results of the CFD analysis showed that the shape of the outlet and the width of the fluid clearances have a large effect on blood damage. The prototype MagLev BP satisfied the required HQ characteristics (5 L/min, 250 mm Hg) for extracorporeal circulation support with stable levitation of the impeller and showed an acceptable level of hemolysis. The simulation results of the CFD analysis indicated the possibility of further reducing the blood damage of

  6. Modeling the Design Flow Coefficient of a Centrifugal Compressor Impeller

    Directory of Open Access Journals (Sweden)

    A. A. Drozdov

    2017-01-01

    Full Text Available In calculating gas-dynamic characteristics by the universal modeling method it is necessary to determine a non-incidence flow rate through the blades of an impeller because of its relationship with the magnitude of incidence losses. The flow area decreased by the blades of finite thickness and the blades load have impact on the critical streamline direction. The universal modeling method in primary designing uses for this a scheme of replacing the influence of the blade load by the vortex effect with identical circulation. Finally, calculating the inviscid flow around the blades allows selecting a value of the inlet blade angle. For impellers with small design flow coefficients, the condition of the non-incidence inlet for the primary design and for the calculation of the inviscid flow is significantly different. The calculating correctness of the non-incidence regime for the non-viscous flow was checked earlier by measurements of the flow in the impellers. The paper presents CFD calculations of twenty impellers in a tenfold range of design flow coefficients. To provide correct comparison, it takes into account the differences in the value of the loading factor calculated by the programs of inviscid quasi-three-dimensional calculation and CFD programs. Shows the identity of inlet conditions for both methods. To increase primary design accuracy, the calculation model was refined. The formula for calculating vortex-induced velocity involves an empirical coefficient. The analysis of data for 32 impellers with different blade profiling allowed working out formulas for calculating empirical coefficient, depending on the type of an impeller, the blade load and the width of the throat at an impeller inlet. The new scheme-based calculation with the empirical coefficient is accurate enough for the primary design.

  7. 2D and 3D impellers of centrifugal compressors - advantages, shortcomings and fields of application

    Science.gov (United States)

    Galerkin, Y.; Reksrin, A.; Drozdov, A.

    2017-08-01

    The simplified equations are presented for calculation of inlet dimensions and velocity values for impellers with three-dimensional blades located in axial and radial part of an impeller (3D impeller) and with two-dimensional blades in radial part (2D). Considerations concerning loss coefficients of 3D and 2D impellers at different design flow rate coefficients are given. The tendency of reduction of potential advantages of 3D impellers at medium and small design flow rate coefficients is shown. The data on high-efficiency compressors and stages with 2D impellers coefficients designed by the authors are presented. The reached efficiency level of 88 - 90% makes further increase of efficiency by the application of 3D impellers doubtful. CFD-analysis of stage candidates with medium flow rate coefficient with 3D and 2D impellers revealed specific problems. In some cases the constructive advantage of a 2D impeller is smaller hub ratio. It makes possible the reaching of higher efficiency. From other side, there is a positive tendency of gas turbine drive RPM increase. 3D impellers have no alternative for stages with high flow rate coefficients matching high-speed drive.

  8. Hydraulic efficiency of a Rushton turbine impeller

    Science.gov (United States)

    Chara, Z.; Kysela, B.; Fort, I.

    2017-07-01

    Based on CFD simulations hydraulic efficiency of a standard Rushton turbine impeller in a baffled tank was determined at a Reynolds number of ReM=33330. Instantaneous values of pressure and velocity components were used to draw up the macroscopic balance of the mechanical energy. It was shown that the hydraulic efficiency of the Rushton turbine impeller (energy dissipated in a bulk volume) is about 57%. Using this result we estimated a length scale in a non-dimensional equation of kinetic energy dissipation rate in the bulk volume as L=D/2.62.

  9. Characterizing the flow of stirred vessels with anchor type impellers

    Directory of Open Access Journals (Sweden)

    S.M.C. Peixoto

    2000-12-01

    Full Text Available Despite its importance in chemical industries, there are few works which studies anchor type impellers and only a fraction of the works investigate these systems under a computational approach. The great majority refers to turbine impellers, specially Rushton turbines, under turbulent flow. Anchor impellers are used specially for highly viscous flow, typical of polymer reactions. The viscosity is normally in the range 1000-10000 cp. Since this range of viscosity describe highly viscous flows, the reactions for anchor agitated systems are normally carried out under laminar flow. This work presents a detailed computational fluid dynamics (CFD approach to study the behaviour of stirred vessels using anchor impellers. The axial plane of the tank, which is being modelled, is divided into small control volumes, which collectively is referred to as the mesh, or grid. In each of these cells the momentum balance, energy and mass conservation, which describes the model, are rewritten algebraically using the finite volumes method to relate such variables as velocity, pressure and temperature to values in neighbouring cells. The equations are then solved numerically, and the results yield the flow corresponding to the model. Since the geometry of a vessel with anchor impellers strictly calls for a three dimensional method, an approximation is made to account for the effect of the blades (Kuncewics, 1992. The main objective of this work is to give a detailed description of the flow generated by this axial impeller with a view to indicate ways in which the design and operation of these systems can be improved.

  10. Pumping Capacity of Pitched Blade Impellers in a Tall Vessel with a Draught Tube

    Directory of Open Access Journals (Sweden)

    J. Brož

    2004-01-01

    Full Text Available A study was made of the pumping capacity of pitched blade impellers (two, three, four, five and six blade pitched blade impellers with pitch angles α = 35° and 45° coaxially located in a cylindrical pilot plant vessel with cylindrical draught tube provided with a standard dished bottom. The draught tube was equipped with four equally spaced radial baffles above the impeller pumping liquid upwards towards the liquid surface. In all investigated cases the liquid aspect ratio H/T = 1.2 - 1.5, the draught tube / vessel diameter ratios DT /T = 0.2 and 0.4 and the impeller / draught tube diameter ratio D/DT = 0.875. The pumping capacity of the impeller was calculated from the radial profile of the axial component of the mean velocity in the draught tube below the impeller at such an axial distance from the impeller that the rotor does not affect the vorticity of the flow. The mean velocity was measured using a laser Doppler anemometer with forward scatter mode in a transparent draught tube and a transparent vessel of diameter T = 400 mm. Two series of experiments were performed, both of them under a turbulent regime of flow of the agitated liquid. First, the optimum height of the dished bottom was sought, and then the dependences of the dimensionless flow rate criterion and the impeller power number on the number of impeller blades were determined for both pitch angles tested under conditions of optimum ratio HT /DT. It follows from the results of the experiments that the optimum ratio HT /DT = 0.25 when the cross sectional areas of the horizontal flow around the bottom and the vertical inflow to the draught tube are the same. For all the tested pitched blade impellers the impeller power number when α = 45° exceeds the value of this quantity when pitch angle α  =   35°, while the flow rate number when α = 35° exceeds this quantity when α = 45°. On the other hand, the absolute values of the impeller power number when the draught tube was

  11. Pump, sodium, inducer, intermediate size (ISIP) (impeller/inducer/diffuser retrofit)

    International Nuclear Information System (INIS)

    Paradise, D.R.

    1978-01-01

    This specification defines the requirements for the Intermediate-Size Inducer Pump (ISIP), which is to be made by replacing the impeller of the FFTF Prototype Pump with a new inducer, impeller, diffuser, seal, and necessary adapter hardware. Subsequent testing requirements of the complete pump assembly are included

  12. SSME Investment in Turbomachinery Inducer Impeller Design Tools and Methodology

    Science.gov (United States)

    Zoladz, Thomas; Mitchell, William; Lunde, Kevin

    2010-01-01

    Within the rocket engine industry, SSME turbomachines are the de facto standards of success with regard to meeting aggressive performance requirements under challenging operational environments. Over the Shuttle era, SSME has invested heavily in our national inducer impeller design infrastructure. While both low and high pressure turbopump failures/anomaly resolution efforts spurred some of these investments, the SSME program was a major benefactor of key areas of turbomachinery inducer-impeller research outside of flight manifest pressures. Over the past several decades, key turbopump internal environments have been interrogated via highly instrumented hot-fire and cold-flow testing. Likewise, SSME has sponsored the advancement of time accurate and cavitating inducer impeller computation fluid dynamics (CFD) tools. These investments together have led to a better understanding of the complex internal flow fields within aggressive high performing inducers and impellers. New design tools and methodologies have evolved which intend to provide confident blade designs which strike an appropriate balance between performance and self induced load management.

  13. Numerical Analysis for un-baffled Mixing Tank Agitated by Two Types of Impellers

    Directory of Open Access Journals (Sweden)

    Ammar Ashour Akesh

    2018-02-01

    Full Text Available The effect of impeller flow type and rotation speed on the fluid in mixing tank design under standard configurations investigated to analyses the fluid velocity, turbulent intensity and path lines. In this theoretical study, the fluid motion inside the mixing tank was investigated by solving Navier-Stokes equation and standard k-ε turbulent model in 3-dimensions, for incompressible and turbulent flow. Two types of flow with three types of impellers were investigated, axial-flow with (Lightnin200 and generic impellers and radial-flow with (Rushton turbine. All impellers evaluated under rotation velocity variation between 10 – 115 rpm. The results showed a direct proportional relationship between the impeller and turbine rotation speed with the fluid velocity in mixing vessel. Also, this case matches with the turbulent intensity and path lines.

  14. The numerical study of the rake angle of impeller blade in centrifugal compressor

    Science.gov (United States)

    Drozdov, A.; Galerkin, Y.

    2017-08-01

    Investigated impellers have blade surfaces formed by straight generatrix. Blade profiles on shroud and disc surfaces are optimized by velocity diagram control (inviscid, quasi-three dimensional calculations). The blade profiles at hub and shroud blade-to-blade surfaces must be coordinated. A designer can choose the generatrix position at a trailing edge for it. The position is defined by the rake angle that is the angle between a trailing edge generatrix and a meridional plane. Two stages with 3D impellers, vaneless diffusers and return channels were investigated. Seven candidates of impellers of these stages with rake angles in range plus-minus 30 degrees were designed and investigated by quasi-three-dimensional inviscid calculation. CFD-calculations were made for the stages with these impellers. The optimal rake angle is minus 20 degrees for the high flow rate impeller due to lesser blade surface area and favorable meridian velocity field. Zero rake angle is optimal for the medium flow rate impeller where blade surface area is not so important. The combination of inviscid and viscid calculations is the informative instrument for further studies.

  15. Mathematical modeling of fluid flow in aluminum ladles for degasification with impeller - injector

    Science.gov (United States)

    Ramos-Gómez, E.; González-Rivera, C.; Ramírez-Argáez, M. A.

    2012-09-01

    In this work a fundamental Eulerian mathematical model was developed to simulate fluid flow in a water physical model of an aluminum ladle equipped with impeller for degassing treatment. The effect of critical process parameters such as rotor speed, gas flow rate on the fluid flow and vortex formation was analyzed with this model. Commercial CFD code PHOENICS 3.4 was used to solve all conservation equations governing the process for this twophase fluid flow system. The mathematical model was successfully validated against experimentally measured liquid velocity and turbulent profiles in a physical model. From the results it was concluded that the angular speed of the impeller is the most important parameter promoting better stirred baths. Pumping effect of the impeller is increased as impeller rotation speed increases. Gas flow rate is detrimental on bath stirring and diminishes pumping effect of impeller.

  16. A Numerical Study on the Impeller Meridional Curvature of High Pressure Multistage Pump

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Deok Su; Jean, Sang Gyu; Mamatov, Sanjar [Hyosung Goodsprings, Inc., Busan (Korea, Republic of); Park, Warn Gyu [Pusan Nat’l Univ., Busan (Korea, Republic of)

    2017-07-15

    This paper presents the hydraulic design an impeller and radial diffuser of a high-pressure multistage pump for reverse osmosis. The flow distribution and hydraulic performance for the meridional design of the impeller were analyzed numerically. Optimization was conducted based on the response surface method by varying the hub and shroud meridional curvatures, while maintaining the impeller outlet diameter, outlet width, and eye diameter constant. The analysis results of the head and efficiency with the variation in the impeller meridional profile showed that angle of the front shroud near the impeller outlet (εDs) had the highest effect on head increase, while the hub inlet length (d1i) and shroud curvature (Rds) had the highest effect on efficiency. From the meridional profile variation, an approximately 0.5% increase in efficiency was observed compared with the base model (case 25).

  17. Impellers of low specific speed centrifugal pump based on the draughting technology

    International Nuclear Information System (INIS)

    Hongxun, C; Peiru, W; Weiwei, L; Wen, J

    2010-01-01

    The authors analyzed the reasons of low efficiency under different operation condition based on the performance test and CFD numerical simulation approach. And the analysis focuses on the relationship between pump efficiency and inner flow characteristics. In order to improve the internal flow and increase efficiency of the pump, some draughting methods of improving the internal flow structure have been proposed, and some new impellers were developed by these methods. The main geometric parameters of the impellers, such as diameter, width and installation of the size, were consistent with the original impeller. The experimental results show that the efficiency of new impellers was improved significantly. The authors' work has opened up a new direction for further improving the efficiency of the low specific speed centrifugal pump.

  18. Design of Stirrer Impeller with Variable Operational Speed for a Food Waste Homogenizer

    Directory of Open Access Journals (Sweden)

    Idris A. Kayode

    2016-05-01

    Full Text Available A conceptualized impeller called KIA is designed for impact agitation of food waste in a homogenizer. A comparative analysis of the performance of KIA is made with three conventional impeller types, Rushton, Anchor, and Pitched Blade. Solid–liquid mixing of a moisture-rich food waste is simulated under various operational speeds, in order to compare the dispersions and thermal distributions at homogenous slurry conditions. Using SolidWorks, the design of the impellers employs an Application Programming Interface (API which acts as the canvas for creating a graphical user interface (GUI for automation of its assembly. A parametric analysis of the homogenizer, at varying operational speeds, enables the estimation of the critical speed of the mixing shaft diameter and the deflection under numerous mixing conditions and impeller configurations. The numerical simulation of the moisture-rich food waste (approximated as a Newtonian carrot–orange soup is performed with ANSYS CFX v.15.0. The velocity and temperature field distribution of the homogenizer for various impeller rotational speeds are analyzed. It is anticipated that the developed model will help in the selection of a suitable impeller for efficient mixing of food waste in the homogenizer.

  19. Properties of made by different methods of RP impeller foundry patterns

    Directory of Open Access Journals (Sweden)

    G. Budzik

    2007-04-01

    Full Text Available This article presents the tests of properties of foundry patterns of turbocharger turbine impeller. Impellers prototypes were predestinated for casting by method losing patterns. There were carried out tests of these prototypes made by different methods of Rapid Prototyping (RP. Two impeller were made by growth methods: stereolitography (SLA and three dimensional printing (3DP. One prototype was made by the method of Vacuum Casting as a wax casting. Tests were executed in the Department of Machine Design of Rzeszow University of Technology in cooperation with WSK PZL Rzeszow and Car Technology Krakow. First impeller was carried out by method of stereolitography on SLA 250 plant. That pattern was also used to carry out silicon matrix for casting of wax pattern. Next pattern was printed by three dimensional printer Z510 from the powder ZP14. Good removability of the pattern from the mould is particularly essential for impellers of small turbines with blades of small thickness of their section. All pattern were tested on their removability from the ceramic mould. The best melting properties had the wax pattern. Patterns made from resin SL5170 (SLA and powder ZP14 (3DP were removed in the process of burning but about 1% of soot was left in the mould.

  20. Impeller Design of a Centrifugal Fan with Blade Optimization

    OpenAIRE

    Lee, Yu-Tai; Ahuja, Vineet; Hosangadi, Ashvin; Slipper, Michael E.; Mulvihill, Lawrence P.; Birkbeck, Roger; Coleman, Roderick M.

    2011-01-01

    A method is presented for redesigning a centrifugal impeller and its inlet duct. The double-discharge volute casing is a structural constraint and is maintained for its shape. The redesign effort was geared towards meeting the design volute exit pressure while reducing the power required to operate the fan. Given the high performance of the baseline impeller, the redesign adopted a high-fidelity CFD-based computational approach capable of accounting for all aerodynamic losses. The present eff...

  1. Centrifugal compressor tip clearance and impeller flow

    Energy Technology Data Exchange (ETDEWEB)

    Jaatinen-Varri, Ahti; Tiainen, Jonna; Turunen-Saaresti, Teemu; Gronman, Aki; Ameli, Alireza; Backman, Jari [Laboratory of Fluid Dynamics, LUT School of Energy Systems, Lappeenranta University of Technology, Lappeenranta (Finland); Engeda, Abraham [Turbomachinery Laboratory, Dept. of Mechanical Engineering, Michigan State University, East Lansing (United States)

    2016-11-15

    Compressors consume a considerable portion of the electricity used in the industrial sector. Hence, improvements in compressor efficiency lead to energy savings and reduce environmental impacts. The efficiency of an unshrouded centrifugal compressor suffers from leakage flow over the blade tips. The effect of tip leakage flow on the passage flow differs between the full and splitter blade passages. In this study, the differences in the flow fields between the full and splitter blade passages were studied numerically in detail. An industrial high-speed compressor with a design pressure ratio of 1.78 was modelled. Numerical studies were conducted with six different tip clearances and three different diffuser widths. The results show that increasing tip clearance considerably increases the reversed flow into the impeller with an unpinched diffuser. The reversed flow then partly mixes into the flow in the same blade passage it entered the impeller and the rest migrates over the blade, mixing with the tip clearance flow. Furthermore, as the reversed and clearance flow mix into the wake, the wake is weakened. As pinch reduces both the reversed flow and clearance flow, the passage wakes are stronger with pinches. However, the pinch is beneficial as the losses at the impeller outlet decrease.

  2. Centrifugal compressor tip clearance and impeller flow

    International Nuclear Information System (INIS)

    Jaatinen-Varri, Ahti; Tiainen, Jonna; Turunen-Saaresti, Teemu; Gronman, Aki; Ameli, Alireza; Backman, Jari; Engeda, Abraham

    2016-01-01

    Compressors consume a considerable portion of the electricity used in the industrial sector. Hence, improvements in compressor efficiency lead to energy savings and reduce environmental impacts. The efficiency of an unshrouded centrifugal compressor suffers from leakage flow over the blade tips. The effect of tip leakage flow on the passage flow differs between the full and splitter blade passages. In this study, the differences in the flow fields between the full and splitter blade passages were studied numerically in detail. An industrial high-speed compressor with a design pressure ratio of 1.78 was modelled. Numerical studies were conducted with six different tip clearances and three different diffuser widths. The results show that increasing tip clearance considerably increases the reversed flow into the impeller with an unpinched diffuser. The reversed flow then partly mixes into the flow in the same blade passage it entered the impeller and the rest migrates over the blade, mixing with the tip clearance flow. Furthermore, as the reversed and clearance flow mix into the wake, the wake is weakened. As pinch reduces both the reversed flow and clearance flow, the passage wakes are stronger with pinches. However, the pinch is beneficial as the losses at the impeller outlet decrease

  3. An Enhanced Factor Analysis of Performance Degradation Assessment on Slurry Pump Impellers

    Directory of Open Access Journals (Sweden)

    Shilong Sun

    2017-01-01

    Full Text Available Slurry pumps, such as oil sand pumps, are widely used in industry to convert electrical energy to slurry potential and kinetic energy. Because of adverse working conditions, slurry pump impellers are prone to suffer wear, which may result in slurry pump breakdowns. To prevent any unexpected breakdowns, slurry pump impeller performance degradation assessment should be immediately conducted to monitor the current health condition and to ensure the safety and reliability of slurry pumps. In this paper, to provide an alternative to the impeller health indicator, an enhanced factor analysis based impeller indicator (EFABII is proposed. Firstly, a low-pass filter is employed to improve the signal to noise ratios of slurry pump vibration signals. Secondly, redundant statistical features are extracted from the filtered vibration signals. To reduce the redundancy of the statistic features, the enhanced factor analysis is performed to generate new statistical features. Moreover, the statistic features can be automatically grouped and developed a new indicator called EFABII. Data collected from industrial oil sand pumps are used to validate the effectiveness of the proposed method. The results show that the proposed method is able to track the current health condition of slurry pump impellers.

  4. Evaluation of a respiratory assist catheter that uses an impeller within a hollow fiber membrane bundle.

    Science.gov (United States)

    Mihelc, Kevin M; Frankowski, Brian J; Lieber, Samuel C; Moore, Nathan D; Hattler, Brack G; Federspiel, William J

    2009-01-01

    Respiratory assist using an intravenous catheter may be a potential treatment for patients suffering from acute or acute-on-chronic lung failure. The objective of this study was to evaluate a novel respiratory catheter that uses an impeller within the fiber bundle to enhance gas exchange efficiency, thus requiring a smaller fiber bundle and insertional size (25 Fr) and permitting simple percutaneous insertion. Bench testing of gas exchange in deionized water was used to evaluate eight impeller designs. The three best performing impeller designs were evaluated in acute studies in four calves (122 + or - 10 kg). Gas exchange increased significantly with increasing impeller rotation rate. The degree of enhancement varied with impeller geometry. The maximum gas exchange efficiency (exchange per unit surface area) for the catheter with the best performing impeller was 529 + or - 20 ml CO(2)/min/m(2) and 513 + or - 21 ml CO(2)/min/m(2) for bench and animal studies, respectively, at a rotation rate of 20,000 rpm. Absolute CO(2) exchange was 37 and 36 ml CO(2)/min, respectively. Active mixing by rotating impellers produced 70% higher gas exchange efficiency than pulsating balloon catheters. The sensitivity of gas exchange to impeller design suggests that further improvements can be made by computational fluid dynamics-based optimization of the impeller.

  5. Performance Testing Of A Modified Centrifugal Fan With Serrated Blade Impeller

    Directory of Open Access Journals (Sweden)

    Zaimar

    2017-10-01

    Full Text Available Changes of shape dimension and component part of impeller might change of characteristic fluid flow so that pressure static in the fan housing changed. Changing some geometric characteristics of the centrifugal fan has more efficiency taking with energy crises into consideration. Several factors that can affect fan performance namely design and type size rotation speed air condition or gas through a fan operating point on the nature of the relationship between a volume of air flow and pressure. The purpose of this research was to test of fan performance of the modified centrifugal fan with the serrated blade impeller. The addition of a percentage of closing the inlet causes the air volumetric rate the airflow energy BHP and total efficiency except for the fan total and static pressure. The experimental test results there are static pressure data and the resulting total pressure is different or distorted 10-17 of deviation from calculation data based on the fan laws. This is possible because of changes in the shape of the blade with serrated on the inside of the impeller. Based on the performance curve shows that the selection of impeller speeds of 800 RPM produces a relatively high air volumetric rate is proportional to the total pressure of the fan and the flow energy so that it is more efficient than other impeller speeds.

  6. Design of Stirrer Impeller with Variable Operational Speed for a Food Waste Homogenizer

    OpenAIRE

    Idris A. Kayode; Emmanuel O. B. Ogedengbe; Marc A. Rosen

    2016-01-01

    A conceptualized impeller called KIA is designed for impact agitation of food waste in a homogenizer. A comparative analysis of the performance of KIA is made with three conventional impeller types, Rushton, Anchor, and Pitched Blade. Solid–liquid mixing of a moisture-rich food waste is simulated under various operational speeds, in order to compare the dispersions and thermal distributions at homogenous slurry conditions. Using SolidWorks, the design of the impellers employs an Application P...

  7. Design and optimization of mixed flow pump impeller blades by varying semi-cone angle

    Science.gov (United States)

    Dash, Nehal; Roy, Apurba Kumar; Kumar, Kaushik

    2018-03-01

    The mixed flow pump is a cross between the axial and radial flow pump. These pumps are used in a large number of applications in modern fields. For the designing of these mixed flow pump impeller blades, a lot number of design parameters are needed to be considered which makes this a tedious task for which fundamentals of turbo-machinery and fluid mechanics are always prerequisites. The semi-cone angle of mixed flow pump impeller blade has a specified range of variations generally between 45o to 60o. From the literature review done related to this topic researchers have considered only a particular semi-cone angle and all the calculations are based on this very same semi-cone angle. By varying this semi-cone angle in the specified range, it can be verified if that affects the designing of the impeller blades for a mixed flow pump. Although a lot of methods are available for designing of mixed flow pump impeller blades like inverse time marching method, the pseudo-stream function method, Fourier expansion singularity method, free vortex method, mean stream line theory method etc. still the optimized design of the mixed flow pump impeller blade has been a cumbersome work. As stated above since all the available research works suggest or propose the blade designs with constant semi-cone angle, here the authors have designed the impeller blades by varying the semi-cone angle in a particular range with regular intervals for a Mixed-Flow pump. Henceforth several relevant impeller blade designs are obtained and optimization is carried out to obtain the optimized design (blade with optimal geometry) of impeller blade.

  8. Optimization and Inverse Design of Pump Impeller

    International Nuclear Information System (INIS)

    Miyauchi, S; Matsumoto, H; Sano, M; Kassai, N; Zhu, B; Luo, X; Piao, B

    2012-01-01

    As for pump impellers, the meridional flow channel and blade-to-blade flow channel, which are relatively independent of each other but greatly affect performance, are designed in parallel. And the optimization design is used for the former and the inverse design is used for the latter. To verify this new design method, a mixed-flow impeller was made. Next, we use Tani's inverse design method for the blade loading of inverse design. It is useful enough to change a deceleration rate freely and greatly. And it can integrally express the rear blade loading of various methods by NACA, Zangeneh and Stratford. We controlled the deceleration rate by shape parameter m, and its value became almost same with Tani's recommended value of the laminar airfoil.

  9. Flow in a centrifugal fan impeller at off-design conditions

    Science.gov (United States)

    Wright, T.; Tzou, K. T. S.; Madhavan, S.

    1984-06-01

    A fully three-dimensional finite element analysis of inviscid, incompressible blade channel flow is the basis of the present study of both predicted and measured surface velocity and pressure distributions in the internal flow channels of a centrifugal fan impeller, for volume flow rates of 80-125 percent the design flow rate. The experimental results made extensive use of blade and sidewall surface pressure taps installed in a scale model of an airfoil-bladed centrifugal fan impeller. The results obtained illustrate the ability of both flow analyses to predict the dominant features of the impeller flow field, including peak blade surface velocities and adverse gradients at flows far from the design point. Insight is also gained into the limiting channel diffusion values for typical centrifugal cascade performance, together with the influence of viscous effects, as seen in deviations from ideal flow predictions.

  10. Development of a 3-dimensional flow analysis procedure for axial pump impellers

    International Nuclear Information System (INIS)

    Kim, Min Hwan; Kim, Jong In; Park, Jin Seok; Huh, Houng Huh; Chang, Moon Hee

    1999-06-01

    A fluid dynamic analysis procedure was developed using the three-dimensional solid model of an axial pump impeller which was theoretically designed using I-DEAS CAD/CAM/CAE software. The CFD software FLUENT was used in the flow field analysis. The steady-state flow regime in the MCP impeller and diffuser was simulated using the developed procedure. The results of calculation were analyzed to confirm whether the design requirements were properly implemented in the impeller model. The validity of the developed procedure was demonstrated by comparing the calculation results with the experimental data available. The pump performance at the design point could be effectively predicted using the developed procedure. The computed velocity distributions have shown a good agreement with the experimental data except for the regions near the wall. The computed head, however, was over-predicted than the experiment. The design period and cost required for the development of an axial pump impeller can be significantly reduced by applying the proposed methodology. (author). 7 refs., 2 tabs

  11. Estimation of changes in dynamic hydraulic force in a magnetically suspended centrifugal blood pump with transient computational fluid dynamics analysis.

    Science.gov (United States)

    Masuzawa, Toru; Ohta, Akiko; Tanaka, Nobuatu; Qian, Yi; Tsukiya, Tomonori

    2009-01-01

    The effect of the hydraulic force on magnetically levitated (maglev) pumps should be studied carefully to improve the suspension performance and the reliability of the pumps. A maglev centrifugal pump, developed at Ibaraki University, was modeled with 926 376 hexahedral elements for computational fluid dynamics (CFD) analyses. The pump has a fully open six-vane impeller with a diameter of 72.5 mm. A self-bearing motor suspends the impeller in the radial direction. The maximum pressure head and flow rate were 250 mmHg and 14 l/min, respectively. First, a steady-state analysis was performed using commercial code STAR-CD to confirm the model's suitability by comparing the results with the real pump performance. Second, transient analysis was performed to estimate the hydraulic force on the levitated impeller. The impeller was rotated in steps of 1 degrees using a sliding mesh. The force around the impeller was integrated at every step. The transient analysis revealed that the direction of the radial force changed dynamically as the vane's position changed relative to the outlet port during one circulation, and the magnitude of this force was about 1 N. The current maglev pump has sufficient performance to counteract this hydraulic force. Transient CFD analysis is not only useful for observing dynamic flow conditions in a centrifugal pump but is also effective for obtaining information about the levitation dynamics of a maglev pump.

  12. Computational Fluid Dynamics (CFD) Analysis for the Reduction of Impeller Discharge Flow Distortion

    Science.gov (United States)

    Garcia, R.; McConnaughey, P. K.; Eastland, A.

    1993-01-01

    The use of Computational Fluid Dynamics (CFD) in the design and analysis of high performance rocket engine pumps has increased in recent years. This increase has been aided by the activities of the Marshall Space Flight Center (MSFC) Pump Stage Technology Team (PSTT). The team's goals include assessing the accuracy and efficiency of several methodologies and then applying the appropriate methodology(s) to understand and improve the flow inside a pump. The PSTT's objectives, team membership, and past activities are discussed in Garcia1 and Garcia2. The PSTT is one of three teams that form the NASA/MSFC CFD Consortium for Applications in Propulsion Technology (McConnaughey3). The PSTT first applied CFD in the design of the baseline consortium impeller. This impeller was designed for the Space Transportation Main Engine's (STME) fuel turbopump. The STME fuel pump was designed with three impeller stages because a two-stage design was deemed to pose a high developmental risk. The PSTT used CFD to design an impeller whose performance allowed for a two-stage STME fuel pump design. The availability of this design would have lead to a reduction in parts, weight, and cost had the STME reached production. One sample of the baseline consortium impeller was manufactured and tested in a water rig. The test data showed that the impeller performance was as predicted and that a two-stage design for the STME fuel pump was possible with minimal risk. The test data also verified another CFD predicted characteristic of the design that was not desirable. The classical 'jet-wake' pattern at the impeller discharge was strengthened by two aspects of the design: by the high head coefficient necessary for the required pressure rise and by the relatively few impeller exit blades, 12, necessary to reduce manufacturing cost. This 'jet-wake pattern produces an unsteady loading on the diffuser vanes and has, in past rocket engine programs, lead to diffuser structural failure. In industrial

  13. Coupled Vibration of Unshrouded Centrifugal Compressor Impellers. Part II: Computation of Vibration Behavior

    Directory of Open Access Journals (Sweden)

    Dirk Hagelstein

    2000-01-01

    Full Text Available The increased use of small gas turbines and turbochargers in different technical fields has led to the development of highly-loaded centrifugal compressors with extremely thin blades. Due to high rotational speed and the correspondingly high centrifugal loads, the shape of the impeller hub must also be optimized. This has led to a reduction of the thickness of the impeller disc in the outlet region. The thin parts of the impeller are very sensitive and may be damaged by the excitation of dangerous blade vibrations.

  14. Multi-objective robust optimization method for the modified epoxy resin sheet molding compounds of the impeller

    Directory of Open Access Journals (Sweden)

    Xiaozhang Qu

    2016-07-01

    Full Text Available A kind of modified epoxy resin sheet molding compounds of the impeller has been designed. Through the test, the non-metal impeller has a better environmental aging performance, but must do the waterproof processing design. In order to improve the stability of the impeller vibration design, the influence of uncertainty factors is considered, and a multi-objective robust optimization method is proposed to reduce the weight of the impeller. Firstly, based on the fluid-structure interaction,the analysis model of the impeller vibration is constructed. Secondly, the optimal approximate model of the impeller is constructed by using the Latin hypercube and radial basis function, and the fitting and optimization accuracy of the approximate model is improved by increasing the sample points. Finally, the micro multi-objective genetic algorithm is applied to the robust optimization of approximate model, and the Monte Carlo simulation and Sobol sampling techniques are used for reliability analysis. By comparing the results of the deterministic, different sigma levels and different materials, the multi-objective optimization of the SMC molding impeller can meet the requirements of engineering stability and lightweight. And the effectiveness of the proposed multi-objective robust optimization method is verified by the error analysis. After the SMC molding and the robust optimization of the impeller, the optimized rate reached 42.5%, which greatly improved the economic benefit, and greatly reduce the vibration of the ventilation system.

  15. Microstructure and Mechanical Properties of Al-10Zn-4.5Mg-xCu Turbine Impeller Produced by Investment Casting

    Directory of Open Access Journals (Sweden)

    Muhammad Syahid

    2017-03-01

    Full Text Available Aluminium alloy can be applied for a turbine impeller of Organic Rankine Cycle power plant that operates at temperatures below 150 oC. Aluminum turbine impeller can enhance efficiency of turbine due to light weight material. Al alloys was used for impeller due to good mechanical properties. Turbine impeller commonly produced by machining but which is time-consuming and less efficient because of material removal. . It can be replace by Investment casting to produce impeller turbine due to their complex geometry and precision. This study identifies effect Cu content of Al-9Zn-4Mg-xCu on the microstructure and mechanical properties of turbine impeller produce by investment casting. The study also identifies casting defect of turbine impeller. The structures consisted of α-Al, MgZn2, CuMgAl2 and CuAl2. Higher Cu content is the higher hardness value due to CuAl2 phase. Visual examination showed that the turbine impeller was free of macro defects and misruns

  16. Optical PIV and LDV Comparisons of Internal Flow Investigations in SHF Impeller

    Directory of Open Access Journals (Sweden)

    G. Wuibaut

    2006-01-01

    Full Text Available The paper presents a comparison between two sets of experimental results in a centrifugal flow pump. The tested impeller is the so-called SHF impeller for which many experimental data have been continuously produced to built databases for CFD code validations with various levels of approximation. Measurements have been performed using optical techniques: 2D particle image velocimetry (PIV technique on an air test model and 2D laser doppler velocimetry (LDV technique on a water model, both for different flow rates. For the present study, results obtained by these optical techniques are compared together in terms of phase averaged velocity and velocity fluctuations inside the impeller flow passage for design flow rate.

  17. Performance prediction and flow field calculation for airfoil fan with impeller inlet clearance

    International Nuclear Information System (INIS)

    Kang, Shin Hyoung; Cao, Renjing; Zhang, Yangjun

    2000-01-01

    The performance prediction of an airfoil fan using a commercial code, STAR/CD, is verified by comparing the calculated results with measured performance data and velocity fields of an airfoil fan. The effects of inlet tip clearance on performance are investigated. The calculations overestimate the pressure rise performance by about 10-25 percent. However, the performance reduction due to tip clearance is well predicted by numerical simulations. Main source of performance decrease is not only the slip factor but also impeller efficiency. The reduction in performance is 12-16 percent for 1 percent gap of the diameter. The calculated reductions in impeller efficiency and slip factor are also linearly proportional to the gap size. The span-wise distributions of phase averaged velocity and pressure at the impeller exit are strongly influenced by the radial gap size. The radial component of velocity and the flow angle increase over the passage as the gap increases. The slip factor decreases and the loss increases with the gap size. The high velocity of leakage jet affects the impeller inlet and passage flows. With a larger clearance, the main stream moves to the impeller hub side and high loss region extends from the shroud to the hub

  18. Oxygen mass transfer in a stirred tank bioreactor using different impeller configurations for environmental purposes

    Science.gov (United States)

    2013-01-01

    In this study, a miniature stirred tank bioreactor was designed for treatment of waste gas containing benzene, toluene and xylene. Oxygen mass transfer characteristics for various twin and single-impeller systems were investigated for 6 configurations in a vessel with 10 cm of inner diameter and working volume of 1.77L. Three types of impellers, namely, Rushton turbine, Pitched 4blades and Pitched 2blades impellers with downward pumping have been used. Deionized water was used as a liquid phase. With respect to other independent variables such as agitation speed, aeration rate, type of sparger, number of impellers, the relative performance of these impellers was assessed by comparing the values of (KLa) as a key parameter. Based on the experimental data, empirical correlations as a function of the operational conditions have been proposed, to study the oxygen transfer rates from air bubbles generated in the bioreactor. It was shown that twin Rushton turbine configuration demonstrates superior performance (23% to 77% enhancement in KLa) compared with other impeller compositions and that sparger type has negligible effect on oxygen mass transfer rate. Agitation speeds of 400 to 800 rpm were the most efficient speeds for oxygen mass transfer in the stirred bioreactor. PMID:23369581

  19. 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. Keyword: Mixing, Helical screw agitator, Power consumption, Fluid circulation, Cylindrical tanks

  20. Effects of curvature and rotation on turbulence in the NASA low-speed centrifugal compressor impeller

    Science.gov (United States)

    Moore, Joan G.; Moore, John

    1992-01-01

    The flow in the NASA Low-Speed Impeller is affected by both curvature and rotation. The flow curves due to the following: (1) geometric curvature, e.g. the curvature of the hub and shroud profiles in the meridional plane and the curvature of the backswept impeller blades; and (2) secondary flow vortices, e.g. the tip leakage vortex. Changes in the turbulence and effective turbulent viscosity in the impeller are investigated. The effects of these changes on three-dimensional flow development are discussed. Two predictions of the flow in the impeller, one with, and one without modification to the turbulent viscosity due to rotation and curvature, are compared. Some experimental and theoretical background for the modified mixing length model of turbulent viscosity will also be presented.

  1. CFD study of leakage flows in shroud cavities of a compressor impeller

    Science.gov (United States)

    Soldatova, K.

    2017-08-01

    The flow character in a gap between shroud disc of an impeller and a stator surface (shroud cavity) influences disc friction loss, labyrinth seal loss (parasitic losses) and thrust force. Flow calculations inside the shroud cavity of a model of centrifugal compressor stage and its labyrinth seal in a range of flow rates and axial width and radial gap are presented. The results are presented in terms of non-dimensional coefficients of flow, disc friction and seal leakage losses coefficients and pressure coefficient. The distributions meridional and tangential flow velocities correspond to the continuity and equilibrium equations - flow radial circulation exists in wide cavity and is absent in narrow cavities. The radial pressure distributions as measured and calculated are not fully comparable. The possible reason is that CFD-calculated leakage coefficient is less than calculated by A.Stodola formula. The influence of a cavity width on the losses and the thrust force requires a balanced design.

  2. Estimation of the radial force using a disturbance force observer for a magnetically levitated centrifugal blood pump.

    Science.gov (United States)

    Pai, C N; Shinshi, T; Shimokohbe, A

    2010-01-01

    Evaluation of the hydraulic forces in a magnetically levitated (maglev) centrifugal blood pump is important from the point of view of the magnetic bearing design. Direct measurement is difficult due to the absence of a rotor shaft, and computational fluid dynamic analysis demands considerable computational resource and time. To solve this problem, disturbance force observers were developed, using the radial controlled magnetic bearing of a centrifugal blood pump, to estimate the radial forces on the maglev impeller. In order to design the disturbance observer, the radial dynamic characteristics of a maglev impeller were evaluated under different working conditions. It was observed that the working fluid affects the additional mass and damping, while the rotational speed affects the damping and stiffness of the maglev system. Based on these results, disturbance force observers were designed and implemented. The designed disturbance force observers present a bandwidth of 45 Hz. In non-pulsatile conditions, the magnitude of the estimated radial thrust increases in proportion to the flowrate, and the rotational speed has little effect on the force direction. At 5 l/min against 100 mmHg, the estimated radial thrust is 0.95 N. In pulsatile conditions, this method was capable of estimating the pulsatile radial thrust with good response.

  3. Centrifugal Force Based Magnetic Micro-Pump Driven by Rotating Magnetic Fields

    International Nuclear Information System (INIS)

    Kim, S H; Hashi, S; Ishiyama, K

    2011-01-01

    This paper presents a centrifugal force based magnetic micro-pump for the pumping of blood. Most blood pumps are driven by an electrical motor with wired control. To develop a wireless and battery-free blood pump, the proposed pump is controlled by external rotating magnetic fields with a synchronized impeller. Synchronization occurs because the rotor is divided into multi-stage impeller parts and NdFeB permanent magnet. Finally, liquid is discharged by the centrifugal force of multi-stage impeller. The proposed pump length is 30 mm long and 19 mm in diameter which much smaller than currently pumps; however, its pumping ability satisfies the requirement for a blood pump. The maximum pressure is 120 mmHg and the maximum flow rate is 5000ml/min at 100 Hz. The advantage of the proposed pump is that the general mechanical problems of a normal blood pump are eliminated by the proposed driving mechanism.

  4. Centrifugal Force Based Magnetic Micro-Pump Driven by Rotating Magnetic Fields

    Science.gov (United States)

    Kim, S. H.; Hashi, S.; Ishiyama, K.

    2011-01-01

    This paper presents a centrifugal force based magnetic micro-pump for the pumping of blood. Most blood pumps are driven by an electrical motor with wired control. To develop a wireless and battery-free blood pump, the proposed pump is controlled by external rotating magnetic fields with a synchronized impeller. Synchronization occurs because the rotor is divided into multi-stage impeller parts and NdFeB permanent magnet. Finally, liquid is discharged by the centrifugal force of multi-stage impeller. The proposed pump length is 30 mm long and19 mm in diameter which much smaller than currently pumps; however, its pumping ability satisfies the requirement for a blood pump. The maximum pressure is 120 mmHg and the maximum flow rate is 5000ml/min at 100 Hz. The advantage of the proposed pump is that the general mechanical problems of a normal blood pump are eliminated by the proposed driving mechanism.

  5. Numerical identification of blade exit angle effect on the performance for a multistage centrifugal pump impeller

    Directory of Open Access Journals (Sweden)

    Babayigit Osman

    2015-01-01

    Full Text Available Nowadays, single and multistage centrifugal pumps are widely used in industrial and mining enterprises. One of the most important components of a centrifugal pump is the impeller. The performance characteristics are related to the pump comprising the head and the overall efficiency rely a great deal on the impeller geometry. In this work, effects of blade exit angle change on hydraulic efficiency of a multi stage pump impeller are investigated via Ansys-Fluent computational fluid dynamics software for constant width impeller entrance and exit gates, blade numbers and blade thickness. Firstly, the flow volume of a centrifugal pump impeller is generated and then mesh structure is formed for the full impeller flow volume. Secondly, rotational periodic flow model are adopted in order to examine the effect of periodic flow assumption on the performance predictions. Corresponding to the available experimental data, inlet mass flow rate, outlet static pressure and rotation of impeller are taken as 0.02m3s-1, 450 kPa and 2950 rpm, respectively for the water fluid. No slip boundary condition is exposed to all solid of surface in the flow volume. The continuity and Navier-Stokes equations with the k-ε turbulence model and the standard wall functions are used. During the study, numerical analyses are conducted for the blade exit angle values of 18°, 20°, 25°, 30° and 35°. In consequence of the performed analyses, it is determined that hydraulic efficiency of the pump impeller value is changed between 81.0-84.6%. The most convenient blade exit angle that yields 84.6% hydraulic efficiency at is 18°. The obtained results show that the blade exit angle range has an impact on the centrifugal pump performance describing the pump head and the hydraulic efficiency.

  6. Cavitation erosion scaling: tests on a pump impeller in water and in sodium

    International Nuclear Information System (INIS)

    Dorey, J.M.; Rascalou, T.

    1992-01-01

    Tests to quantify cavitation agressivity carried out in water and in sodium (400 deg) on a model pump impeller are presented. The polished samples method has been used. It can be now applied to curved surfaces such as impeller blades with the help of new measurement devices. Results are discussed regarding scaling laws for fluid-to-fluid transposition

  7. Review on stress corrosion and corrosion fatigue failure of centrifugal compressor impeller

    Science.gov (United States)

    Sun, Jiao; Chen, Songying; Qu, Yanpeng; Li, Jianfeng

    2015-03-01

    Corrosion failure, especially stress corrosion cracking and corrosion fatigue, is the main cause of centrifugal compressor impeller failure. And it is concealed and destructive. This paper summarizes the main theories of stress corrosion cracking and corrosion fatigue and its latest developments, and it also points out that existing stress corrosion cracking theories can be reduced to the anodic dissolution (AD), the hydrogen-induced cracking (HIC), and the combined AD and HIC mechanisms. The corrosion behavior and the mechanism of corrosion fatigue in the crack propagation stage are similar to stress corrosion cracking. The effects of stress ratio, loading frequency, and corrosive medium on the corrosion fatigue crack propagation rate are analyzed and summarized. The corrosion behavior and the mechanism of stress corrosion cracking and corrosion fatigue in corrosive environments, which contain sulfide, chlorides, and carbonate, are analyzed. The working environments of the centrifugal compressor impeller show the behavior and the mechanism of stress corrosion cracking and corrosion fatigue in different corrosive environments. The current research methods for centrifugal compressor impeller corrosion failure are analyzed. Physical analysis, numerical simulation, and the fluid-structure interaction method play an increasingly important role in the research on impeller deformation and stress distribution caused by the joint action of aerodynamic load and centrifugal load.

  8. Effect of the Impeller Design on Degasification Kinetics Using the Impeller Injector Technique Assisted by Mathematical Modeling

    Directory of Open Access Journals (Sweden)

    Diego Abreu-López

    2017-04-01

    Full Text Available A mathematical model was developed to describe the hydrodynamics of a batch reactor for aluminum degassing utilizing the rotor-injector technique. The mathematical model uses the Eulerian algorithm to represent the two-phase system including the simulation of vortex formation at the free surface, and the use of the RNG k-ε model to account for the turbulence in the system. The model was employed to test the performances of three different impeller designs, two of which are available commercially, while the third one is a new design proposed in previous work. The model simulates the hydrodynamics and consequently helps to explain and connect the performances in terms of degassing kinetics and gas consumption found in physical modeling previously reported. Therefore, the model simulates a water physical model. The model reveals that the new impeller design distributes the bubbles more uniformly throughout the ladle, and exhibits a better-agitated bath, since the transfer of momentum to the fluids is better. Gas is evenly distributed with this design because both phases, gas and liquid, are dragged to the bottom of the ladle as a result of the higher pumping effect in comparison to the commercial designs.

  9. Physical aspects of liquid-impelled loop reactors

    NARCIS (Netherlands)

    Sonsbeek, van H.

    1992-01-01

    The liquid-impelled loop reactor (LLR) is a reactor that consists of two parts : the main tube and the circulation tube. Both parts are in open connection at the bottom and at the top. The reactor is filled with a liquid phase: the continuous phase. Another liquid phase is injected in the

  10. Robust design optimization method for centrifugal impellers under surface roughness uncertainties due to blade fouling

    Science.gov (United States)

    Ju, Yaping; Zhang, Chuhua

    2016-03-01

    Blade fouling has been proved to be a great threat to compressor performance in operating stage. The current researches on fouling-induced performance degradations of centrifugal compressors are based mainly on simplified roughness models without taking into account the realistic factors such as spatial non-uniformity and randomness of the fouling-induced surface roughness. Moreover, little attention has been paid to the robust design optimization of centrifugal compressor impellers with considerations of blade fouling. In this paper, a multi-objective robust design optimization method is developed for centrifugal impellers under surface roughness uncertainties due to blade fouling. A three-dimensional surface roughness map is proposed to describe the nonuniformity and randomness of realistic fouling accumulations on blades. To lower computational cost in robust design optimization, the support vector regression (SVR) metamodel is combined with the Monte Carlo simulation (MCS) method to conduct the uncertainty analysis of fouled impeller performance. The analyzed results show that the critical fouled region associated with impeller performance degradations lies at the leading edge of blade tip. The SVR metamodel has been proved to be an efficient and accurate means in the detection of impeller performance variations caused by roughness uncertainties. After design optimization, the robust optimal design is found to be more efficient and less sensitive to fouling uncertainties while maintaining good impeller performance in the clean condition. This research proposes a systematic design optimization method for centrifugal compressors with considerations of blade fouling, providing a practical guidance to the design of advanced centrifugal compressors.

  11. The effect of impeller type on silica sol formation in laboratory scale agitated tank

    Science.gov (United States)

    Nurtono, Tantular; Suprana, Yayang Ade; Latif, Abdul; Dewa, Restu Mulya; Machmudah, Siti; Widiyastuti, Winardi, Sugeng

    2016-02-01

    The multiphase polymerization reaction of the silica sol formation produced from silicic acid and potassium hydroxide solutions in laboratory scale agitated tank was studied. The reactor is equipped with four segmental baffle and top entering impeller. The inside diameter of reactor is 9 cm, the baffle width is 0.9 cm, and the impeller position is 3 cm from tank bottom. The diameter of standard six blades Rushton and three blades marine propeller impellers are 5 cm. The silicic acid solution was made from 0.2 volume fraction of water glass (sodium silicate) solution in which the sodium ion was exchanged by hydrogen ion from cation resin. The reactor initially filled with 286 ml silicic acid solution was operated in semi batch mode and the temperature was kept constant in 60 °C. The 3 ml/minute of 1 M potassium hydroxide solution was added into stirred tank and the solution was stirred. The impeller rotational speed was varied from 100 until 700 rpm. This titration was stopped if the solution in stirred tank had reached the pH of 10-The morphology of the silica particles in the silica sol product was analyzed by Scanning Electron Microscope (SEM). The size of silica particles in silica sol was measured based on the SEM image. The silica particle obtained in this research was amorphous particle and the shape was roughly cylinder. The flow field generated by different impeller gave significant effect on particle size and shape. The smallest geometric mean of length and diameter of particle (4.92 µm and 2.42 µm, respectively) was generated in reactor with marine propeller at 600 rpm. The reactor with Rushton impeller produced particle which the geometric mean of length and diameter of particle was 4.85 µm and 2.36 µm, respectively, at 150 rpm.

  12. EFFECT OF FORCED ROTATING VANELESS DIFFUSERS ON CENTRIFUGAL COMPRESSOR STAGE PERFORMANCE

    Directory of Open Access Journals (Sweden)

    S. SERALATHAN

    2011-10-01

    Full Text Available Non-uniform flow at the exit of the centrifugal impeller mixes in the vaneless space of the diffuser causing a rise in static pressure as well as significant loss of total pressure. These mixing losses are usually an important source of inefficiency. Forced rotating vaneless diffusers is one such concept which reduces the energy losses associated with diffusion. Forced rotating vaneless diffuser involves the concept of blade cutback and shroud extension. In the present computational investigations, the effects of blade cutback of 5%, 10% and 20% of vane length, shroud extension of 10%, 20%, 30% and 40% of impeller tip diameter and impeller without shroud extension on flow diffusion and performance are analyzed, while all the other dimensions remaining same. The performance characteristics of various blade cutback configurations are less in terms of efficiency, energy coefficient as well as static pressure rise. The objective of obtaining higher static pressure rise with wide operating range and reduced losses over stationary vaned diffuser is achieved by shroud extension of 30%, followed by shroud extension of 20%.

  13. Effects of impeller diameter and rotational speed on performance of pump running in turbine mode

    International Nuclear Information System (INIS)

    Jain, Sanjay V.; Swarnkar, Abhishek; Motwani, Karan H.; Patel, Rajesh N.

    2015-01-01

    Highlights: • Experiments done between 900 and 1500 rpm with original, 10% and 20% trimmed impellers. • The performance of PAT was found better in speed range of 1000–1200 rpm. • Blade rounding led to 3–4% rise in efficiency at rated speed with existing impeller. • Correlation developed has predicted η BEP within ±10% of experimental results. - Abstract: The major limitations of mini/micro hydropower schemes is the higher cost of small capacity hydro turbines. Also, it is very cumbersome, time consuming and expensive to develop the site specific turbines corresponding to local site conditions in mini/micro hydro range. In such plants, small centrifugal pumps can be used in turbine mode by running in the reverse direction. The efficiency of pump as turbines (PATs) is usually lower than the conventional hydro turbines; however, there may be substantial decrease in the capital cost of the plant. Hydropower plants usually runs at part load for several months in a year due to insufficient water availability for the power generation. The application range of PAT can be widened if its part load and/or maximum efficiency can be improved. In the present study, experimental investigations are carried out on centrifugal pump running in turbine mode to optimize its geometric and operational parameters e.g. impeller diameter and rotational speed. The experiments were performed in the wide range of rotational speeds varying from 900 to 1500 rpm with original (∅ 250 mm), 10% trimmed (∅ 225 mm) and 20% trimmed (∅ 200 mm) impellers. Impeller trimming led to improvement in efficiency at part load operating conditions. The performance of PAT was found better at the lower speeds than that at the rated speed. The effects of blade rounding were studied in all the cases and it led to 3–4% rise in efficiency at rated speed with the original impeller. The empirical correlation is also developed for prediction of efficiency in terms of impeller diameter and rotational

  14. NOVEL METHODS FOR AXIAL FAN IMPELLER GEOMETRY ANALYSIS AND EXPERIMENTAL INVESTIGATIONS OF THE GENERATED SWIRL TURBULENT FLOW

    Directory of Open Access Journals (Sweden)

    Zoran D Protić

    2010-01-01

    Full Text Available Geometry analysis of the axial fan impeller, experimentally obtained operating characteristics and experimental investigations of the turbulent swirl flow generated behind the impeller are presented in this paper. Formerly designed and manufactured, axial fan impeller blade geometry (originally designed by Prof. Dr-Ing. Z. Protić† has been digitized using a three-dimensional (3D scanner. In parallel, the same impeller has been modeled by beta version software for modeling axial turbomachines, based on modified classical calculation. These results were compared. Then, the axial fan operating characteristics were measured on the standardized test rig in the Laboratory for Hydraulic Machinery and Energy Systems, Faculty of Mechanical Engineering, University of Belgrade. Optimum blade impeller position was determined on the basis of these results. Afterwards, the impeller with optimum angle, without outlet vanes, was positioned in a circular pipe. Rotational speed has been varied in the range from 500 till 2500rpm. Reynolds numbers generated in this way, calculated for axial velocity component, were in the range from 0,8·105 till 6·105. LDA (Laser Doppler Anemometry measurements and stereo PIV (Particle Image Velocimetry measurements of the 3D velocity field in the swirl turbulent fluid flow behind the axial fan have been performed for each regime. Obtained results point out extraordinary complexity of the structure of generated 3D turbulent velocity fields.

  15. Prediction of flow- induced dynamic stress in an axial pump impeller using FEM

    International Nuclear Information System (INIS)

    Gao, J Y; Hou, Y S; Xi, S Z; Cai, Z H; Yao, P P; Shi, H L

    2013-01-01

    Axial pumps play an important role in water supply and flood control projects. Along with growing requirements for high reliability and large capacity, the dynamic stress of axial pumps has become a key problem. Unsteady flow is a significant reason which results structural dynamic stress of a pump. This paper reports on a flow-induced dynamic stress simulation in an axial pump impeller at three flow conditions by using FEM code. The pressure pulsation obtained from flow simulation using CFD code was set as the force boundary condition. The results show that the maximum stress of impeller appeared at joint between blade and root flange near trailing edge or joint between blade and root flange near leading edge. The dynamic stress of the two zones was investigated under three flow conditions (0.8Q d , 1.0Q d , 1.1Q d ) in time domain and frequency domain. The frequencies of stress at zones of maximum stress are 22.9Hz and 37.5Hz as the fundamental frequency and its harmonics. The fundamental frequencies are nearly equal to vane passing frequency (22.9 Hz) and 3 times blade passing frequency (37.5Hz). The first dominant frequency at zones of maximum stress is equal to the vane passing frequency due to rotor-stator interaction between the vane and the blade. This study would be helpful for axial pumps in reducing stress, improving structure design and fatigue life

  16. Machining the Integral Impeller and Blisk of Aero-Engines: A Review of Surface Finishing and Strengthening Technologies

    Science.gov (United States)

    Fu, Youzhi; Gao, Hang; Wang, Xuanping; Guo, Dongming

    2017-05-01

    The integral impeller and blisk of an aero-engine are high performance parts with complex structure and made of difficult-to-cut materials. The blade surfaces of the integral impeller and blisk are functional surfaces for power transmission, and their surface integrity has significant effects on the aerodynamic efficiency and service life of an aero-engine. Thus, it is indispensable to finish and strengthen the blades before use. This paper presents a comprehensive literature review of studies on finishing and strengthening technologies for the impeller and blisk of aero-engines. The review includes independent and integrated finishing and strengthening technologies and discusses advanced rotational abrasive flow machining with back-pressure used for finishing the integral impeller and blisk. A brief assessment of future research problems and directions is also presented.

  17. Fluid force predictions and experimental measurements for a magnetically levitated pediatric ventricular assist device.

    Science.gov (United States)

    Throckmorton, Amy L; Untaroiu, Alexandrina; Lim, D Scott; Wood, Houston G; Allaire, Paul E

    2007-05-01

    The latest generation of artificial blood pumps incorporates the use of magnetic bearings to levitate the rotating component of the pump, the impeller. A magnetic suspension prevents the rotating impeller from contacting the internal surfaces of the pump and reduces regions of stagnant and high shear flow that surround fluid or mechanical bearings. Applying this third-generation technology, the Virginia Artificial Heart Institute has developed a ventricular assist device (VAD) to support infants and children. In consideration of the suspension design, the axial and radial fluid forces exerted on the rotor of the pediatric VAD were estimated using computational fluid dynamics (CFD) such that fluid perturbations would be counterbalanced. In addition, a prototype was built for experimental measurements of the axial fluid forces and estimations of the radial fluid forces during operation using a blood analog mixture. The axial fluid forces for a centered impeller position were found to range from 0.5 +/- 0.01 to 1 +/- 0.02 N in magnitude for 0.5 +/- 0.095 to 3.5 +/- 0.164 Lpm over rotational speeds of 6110 +/- 0.39 to 8030 +/- 0.57% rpm. The CFD predictions for the axial forces deviated from the experimental data by approximately 8.5% with a maximum difference of 18% at higher flow rates. Similarly for the off-centered impeller conditions, the maximum radial fluid force along the y-axis was found to be -0.57 +/- 0.17 N. The maximum cross-coupling force in the x direction was found to be larger with a maximum value of 0.74 +/- 0.22 N. This resulted in a 25-35% overestimate of the radial fluid force as compared to the CFD predictions; this overestimation will lead to a far more robust magnetic suspension design. The axial and radial forces estimated from the computational results are well within a range over which a compact magnetic suspension can compensate for flow perturbations. This study also serves as an effective and novel design methodology for blood pump

  18. Multi-point optimization on meridional shape of a centrifugal pump impeller for performance improvement

    Energy Technology Data Exchange (ETDEWEB)

    Pei, Ji; Wang, Wen Jie; Yuan, Shouqi [National Research Center of Pumps, Jiangsu University, Zhenjiang (China)

    2016-11-15

    A wide operating band is important for a pump to safely perform at maximum efficiency while saving energy. To widen the operating range, a multi-point optimization process based on numerical simulations in order to improve impeller performance of a centrifugal pump used in nuclear plant applications is proposed by this research. The Reynolds average Navier Stokes equations are utilized to perform the calculations. The meridional shape of the impeller was optimized based on the following four parameters; shroud arc radius, hub arc radius, shroud angle, and hub angle as the design variables. Efficiencies calculated under 0.6Qd, 1.0Qd and 1.62Qd were selected as the three optimized objectives. The Design of experiment method was applied to generate various impellers while 35 impellers were generated by the Latin hypercube sampling method. A Response surface function based on a second order function was applied to construct a mathematical relationship between the objectives and design variables. A multi-objective genetic algorithm was utilized to solve the response surface function to obtain the best optimized objectives as well as the best combination of design parameters. The results indicated that the pump performance predicted by numerical simulation was in agreement with the experimental performance. The optimized efficiencies based on the three operating conditions were increased by 3.9 %, 6.1 % and 2.6 %, respectively. In addition, the velocity distribution, pressure distribution, streamline and turbulence kinetic energy distribution of the optimized and reference impeller were compared and analyzed to illustrate the performance improvement.

  19. Multi-point optimization on meridional shape of a centrifugal pump impeller for performance improvement

    International Nuclear Information System (INIS)

    Pei, Ji; Wang, Wen Jie; Yuan, Shouqi

    2016-01-01

    A wide operating band is important for a pump to safely perform at maximum efficiency while saving energy. To widen the operating range, a multi-point optimization process based on numerical simulations in order to improve impeller performance of a centrifugal pump used in nuclear plant applications is proposed by this research. The Reynolds average Navier Stokes equations are utilized to perform the calculations. The meridional shape of the impeller was optimized based on the following four parameters; shroud arc radius, hub arc radius, shroud angle, and hub angle as the design variables. Efficiencies calculated under 0.6Qd, 1.0Qd and 1.62Qd were selected as the three optimized objectives. The Design of experiment method was applied to generate various impellers while 35 impellers were generated by the Latin hypercube sampling method. A Response surface function based on a second order function was applied to construct a mathematical relationship between the objectives and design variables. A multi-objective genetic algorithm was utilized to solve the response surface function to obtain the best optimized objectives as well as the best combination of design parameters. The results indicated that the pump performance predicted by numerical simulation was in agreement with the experimental performance. The optimized efficiencies based on the three operating conditions were increased by 3.9 %, 6.1 % and 2.6 %, respectively. In addition, the velocity distribution, pressure distribution, streamline and turbulence kinetic energy distribution of the optimized and reference impeller were compared and analyzed to illustrate the performance improvement

  20. The effect of impeller type on silica sol formation in laboratory scale agitated tank

    Energy Technology Data Exchange (ETDEWEB)

    Nurtono, Tantular; Suprana, Yayang Ade; Latif, Abdul; Dewa, Restu Mulya; Machmudah, Siti; Widiyastuti,, E-mail: widi@chem-eng.its.ac.id; Winardi, Sugeng [Chemical Engineering Department, Institute of Technology Sepuluh Nopember, Surabaya 60111 (Indonesia)

    2016-02-08

    The multiphase polymerization reaction of the silica sol formation produced from silicic acid and potassium hydroxide solutions in laboratory scale agitated tank was studied. The reactor is equipped with four segmental baffle and top entering impeller. The inside diameter of reactor is 9 cm, the baffle width is 0.9 cm, and the impeller position is 3 cm from tank bottom. The diameter of standard six blades Rushton and three blades marine propeller impellers are 5 cm. The silicic acid solution was made from 0.2 volume fraction of water glass (sodium silicate) solution in which the sodium ion was exchanged by hydrogen ion from cation resin. The reactor initially filled with 286 ml silicic acid solution was operated in semi batch mode and the temperature was kept constant in 60 °C. The 3 ml/minute of 1 M potassium hydroxide solution was added into stirred tank and the solution was stirred. The impeller rotational speed was varied from 100 until 700 rpm. This titration was stopped if the solution in stirred tank had reached the pH of 10-The morphology of the silica particles in the silica sol product was analyzed by Scanning Electron Microscope (SEM). The size of silica particles in silica sol was measured based on the SEM image. The silica particle obtained in this research was amorphous particle and the shape was roughly cylinder. The flow field generated by different impeller gave significant effect on particle size and shape. The smallest geometric mean of length and diameter of particle (4.92 µm and 2.42 µm, respectively) was generated in reactor with marine propeller at 600 rpm. The reactor with Rushton impeller produced particle which the geometric mean of length and diameter of particle was 4.85 µm and 2.36 µm, respectively, at 150 rpm.

  1. Characterizations of the submerged fermentation of Aspergillus oryzae using a Fullzone impeller in a stirred tank bioreactor.

    Science.gov (United States)

    Ghobadi, Narges; Ogino, Chiaki; Yamabe, Kaoru; Ohmura, Naoto

    2017-01-01

    A Fullzone (FZ) impeller was used in the first study of the characteristics involved in the fermentation of Aspergillus oryzae. Both the experimental and simulation results of this study revealed novel findings into the positive relationship between the global-axial mixing patterns of a FZ impeller and fermentation efficiency. The mixing results when using the FZ impeller compared with a double Rushton turbine (DRT) impeller indicated that the culture mixed by the FZ resulted in a more homogeneous medium with higher values for oxygen mass transfer, cell growth rate, and alpha amylase activity. The simulation of fluid flow was done in a laminar regime using a two-fluid model. According to the simulation results, the maximum shear stress when using the DRT was higher than that with the FZ at the same power input (P in ). A high degree of local shear stress and the shear rate near the turbine blade of the DRT resulted in cell damage and a reduction in the enzyme activity, biomass, pellet diameter, and dissolved oxygen concentration. Calculations using the Brown equation showed that the maximum and average shear rates during mixing with the FZ impeller were lower than that when using the DRT. Therefore, the use of an FZ impeller, particularly at low P in , enhanced the cultivation of A. oryzae. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  2. Finite volume modeling of the solidification of an axial steel cast impeller

    Directory of Open Access Journals (Sweden)

    M. Copur

    2014-04-01

    Full Text Available In the foundry industry, obtaining the solidification contours in cast geometries are extremely important to know the last location(s to solidify in order to define the correct feeding path and the number of risers. This paper presents three-dimensional simulation of transient conduction heat transfer within an axial impeller, made of AISI 1016 steel, poured and solidified in chemically bonded mold and core medium, by using FVM technique and ANSYS CFX. Specific heat, density and thermal conductivity of AISI 1016 steel, mold and Core materials are considered as functions of temperatures. In this transient thermal analysis, the convection heat transfer phenomenon is also considered at the outer surfaces of the mold. In order to shorten the run-time, the nonlinear transient analysis has been made for 600/3600 segment of the impeller, core and mold. The solidification contours of the impeller as well as isothermal lines in core and mold have been obtained in 3-D. The cooling curves of diff erent points are also shown in the result section.

  3. [Computational fluid dynamics simulation of different impeller combinations in high viscosity fermentation and its application].

    Science.gov (United States)

    Dong, Shuhao; Zhu, Ping; Xu, Xiaoying; Li, Sha; Jiang, Yongxiang; Xu, Hong

    2015-07-01

    Agitator is one of the essential factors to realize high efficient fermentation for high aerobic and viscous microorganisms, and the influence of different impeller combination on the fermentation process is very important. Welan gum is a microbial exopolysaccharide produced by Alcaligenes sp. under high aerobic and high viscos conditions. Computational fluid dynamics (CFD) numerical simulation was used for analyzing the distribution of velocity, shear rate and gas holdup in the welan fermentation reactor under six different impeller combinations. The best three combinations of impellers were applied to the fermentation of welan. By analyzing the fermentation performance, the MB-4-6 combination had better effect on dissolved oxygen and velocity. The content of welan was increased by 13%. Furthermore, the viscosity of production were also increased.

  4. Evidence for forcing-dependent steady states in a turbulent swirling flow.

    Science.gov (United States)

    Saint-Michel, B; Dubrulle, B; Marié, L; Ravelet, F; Daviaud, F

    2013-12-06

    We study the influence on steady turbulent states of the forcing in a von Karman flow, at constant impeller speed, or at constant torque. We find that the different forcing conditions change the nature of the stability of the steady states and reveal dynamical regimes that bear similarities to low-dimensional systems. We suggest that this forcing dependence may be applicable to other turbulent systems.

  5. The Strength Calculation of the Pump Shaft with a Worn Impeller

    Directory of Open Access Journals (Sweden)

    Nikolay P. Ovchinnikov

    2017-12-01

    Full Text Available Introduction: This paper presents the study of the impeller wear influence on stress-strain state of a centrifugal pump shaft. In agro-industrial sector, centrifugal pumps are used for watering various agricultural crops. During pumping water, a centrifugal pump impeller is usually a subject to influence of various irreversible physical-and-mechanical and physical-and-chemical processes that can result in a certain reduction in its mass. Materials and Methods: We used a comprehensive approach including the analysis of a sufficient number domestic and foreign publications on the research topic and parametric studies conducted on a laboratory-pumping unit. We had modern vibration-based diagnostic equipment, the mathematical models of loading a pump shaft and a finite-element modeling in APM Win Machine software (Beam module. Results: The comparison of the maximum equivalent dynamic stresses obtained according to the proposed method with existing methods for carrying out the checking strength calculation of a centrifugal pump shaft showed that account of the impeller wear significantly changes picture of stress-strain state shaft. Discussion and Conclusions: The amendments proposed by the author in checking strength calculation of a centrifugal pump shaft will allow estimating its stress-strain state in certain production situations.

  6. Blade design loads on the flow exciting force in centrifugal pump

    International Nuclear Information System (INIS)

    Xu, Y; Yang, A L; Langand, D P; Dai, R

    2012-01-01

    The three-dimensional viscous flow field of two centrifugal pumps, which have the same volute, design head, design flow rate and rotational speed but the blade design load, are analyzed based on large eddy simulation. The comparisons are implemented including the hydraulic efficiencies, flow field characteristics, pressure pulsations and unsteady forces applied on the impellers to investigate the effect of the design blade load on hydraulic performance and flow exciting force. The numerical results show that the efficiency of the pump, the impeller blade of which has larger design load, is improved by 1.1%∼2.9% compared to the centrifugal pump with lower blade design load. The pressure fluctuation of the pump with high design load is more remarkable. Its maximum amplitude of coefficient of static pressure is higher by 43% than the latter. At the same time the amplitude of unsteady radial force is increased by 11.6% in the time domain. The results also imply that the blade design load is an important factor on the excitation force in centrifugal pumps.

  7. 3D Blade Hydraulic Design Method of the Rotodynamic Multiphase Pump Impeller and Performance Research

    Directory of Open Access Journals (Sweden)

    Yongxue Zhang

    2014-02-01

    Full Text Available A hydraulic design method of three-dimensional blade was presented to design the blades of the rotodynamic multiphase pump. Numerical simulations and bench test were conducted to investigate the performance of the example impeller designed by the presented method. The results obtained from the bench test were in good agreement with the simulation results, which indicated the reasonability of the simulation. The distributions of pressure and gas volume fraction were analyzed and the results showed that the designed impeller was good for the transportation of mixture composed of gas and liquid. In addition, the advantage of the impeller designed by the presented method was suitable for using in large volume rate conditions, which were reflected by the comparison of the head performance between this three-dimensional design method and another one.

  8. Investigation of CFD calculation method of a centrifugal pump with unshrouded impeller

    Science.gov (United States)

    Wu, Dazhuan; Yang, Shuai; Xu, Binjie; Liu, Qiaoling; Wu, Peng; Wang, Leqin

    2014-03-01

    Currently, relatively large errors are found in numerical results in some low-specific-speed centrifugal pumps with unshrouded impeller because the effect of clearances and holes are not accurately modeled. Establishing an accurate analytical model to improve performance prediction accuracy is therefore necessary. In this paper, a three-dimensional numerical simulation is conducted to predict the performance of a low-specific-speed centrifugal pump, and the modeling, numerical scheme, and turbulent selection methods are discussed. The pump performance is tested in a model pump test bench, and flow rate, head, power and efficiency of the pump are obtained. The effect of taking into consideration the back-out vane passage, clearance, and balance holes is analyzed by comparing it with experimental results, and the performance prediction methods are validated by experiments. The analysis results show that the pump performance can be accurately predicted by the improved method. Ignoring the back-out vane passage in the calculation model of unshrouded impeller is found to generate better numerical results. Further, the calculation model with the clearances and balance holes can obviously enhance the numerical accuracy. The application of disconnect interface can reduce meshing difficulty but increase the calculation error at the off-design operating point at the same time. Compared with the standard k-ɛ, renormalization group k-ɛ, and Spalart-Allmars models, the Realizable k-ɛ model demonstrates the fastest convergent speed and the highest precision for the unshrouded impeller flow simulation. The proposed modeling and numerical simulation methods can improve the performance prediction accuracy of the low-specific-speed centrifugal pumps, and the modeling method is especially suitable for the centrifugal pump with unshrouded impeller.

  9. Simple Impeller Systems for Maintenance of Oil Palm Culture Aggregates

    International Nuclear Information System (INIS)

    Tarmizi, A.H.; Zaiton, R.; Rosli, M.Y.

    2016-01-01

    Scaling up of liquid culture systems generally involves moving from the use of simple shake flasks to bioreactors or specialised vessels; this is costly. A new innovation called the Two-in-One MPOB Simple Impeller (2-in-1 MoSLIM) was developed using commonly available Schott bottles in the laboratory. This system provided simultaneous aeration and agitation (two-in-one) in a single device for tissue propagation in liquid culture. The 2-in-1 MoSLIM produced cell aggregates with fresh weight increments of two- to six-fold over 30-40 days. This system was a convenient alternative compared to the conventional shake flask system. Multiplication of cultures in the 2-in-1 MoSLIM did not require any shaker or a big space area. This system with a working volume of 300 - 700 ml used a simple impeller and a pump for agitation and aeration purposes. However, with the 2-in-1 MoSLIM, media replenishment remained a tedious task. To overcome this, modifications were made to the system to enable media replenishment on-site without the need of a sterile hood. The adaptation of 2-in-1 MoSLIM with an earlier innovation, Fast Transfer Technique (MoFaTT) in Liquid Culture System, resulted in the development of the Simple Impeller with Fast Transfer Technique (SLIM-FaTT) system. This new system can be applied to the liquid culture system of any crop with a potential towards automation. (author)

  10. Optimal design of impeller for centrifugal compressor under the influence of one-way fluid-structure interaction

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Hyun Soo; Kim, Youn Jae [Sungkyunkwan University, Suwon (Korea, Republic of)

    2016-09-15

    In this study, a method for optimal design of impeller for centrifugal compressor under the influence of Fluid-structure interaction (FSI) and Response surface method (RSM) was studied. Numerical simulation was conducted using ANSYS Multi-physics with various configurations of impeller geometry. Each of the design parameters was divided into 3 levels. Total 45 design points were planned by Central composite design (CCD) method, which is one of the Design of experiment (DOE) techniques. Response surfaces generated based on the DOE results were used to find the optimal shape of impeller for high aerodynamic performance. The whole process of optimization was conducted using ANSYS Design xplorer (DX). Through the optimization, structural safety and aerodynamic performance of centrifugal compressor were improved.

  11. Optimal design of impeller for centrifugal compressor under the influence of one-way fluid-structure interaction

    International Nuclear Information System (INIS)

    Kang, Hyun Soo; Kim, Youn Jae

    2016-01-01

    In this study, a method for optimal design of impeller for centrifugal compressor under the influence of Fluid-structure interaction (FSI) and Response surface method (RSM) was studied. Numerical simulation was conducted using ANSYS Multi-physics with various configurations of impeller geometry. Each of the design parameters was divided into 3 levels. Total 45 design points were planned by Central composite design (CCD) method, which is one of the Design of experiment (DOE) techniques. Response surfaces generated based on the DOE results were used to find the optimal shape of impeller for high aerodynamic performance. The whole process of optimization was conducted using ANSYS Design xplorer (DX). Through the optimization, structural safety and aerodynamic performance of centrifugal compressor were improved

  12. Study on internal flow near the impeller outlet of a winnowing fan. 2nd Report. Discussion of a impeller with forward-inclined blades by computational fluid dynamics; Karami fan no haneguruma deguchibu kinbo no nagare ni kansuru kenkyu. 2. CFD wo mochiita maemuki hane ni kansuru ichikosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Kawase, M. [Tokushima University, Tokushima (Japan); Fukutomi, J.; Nakase, Y. [Tokushima University, Tokushima (Japan). Faculty of Engineering

    2000-03-25

    Because of a strong 3-dimensional flow, it is difficult to produce a uniform flow or improve efficiency with winnowing fans. Through experiments with various types of impellers, it was found in an earlier study that a forward-inclined impeller could produce a uniform flow and improve efficiency. It was ten reported in a subsequent study aimed at identifying the mechanism behind this, in which the relationship between velocity and static pressure in an impeller of small inclination angle was examined from the perspective of flow, that flow analysis was effective towards estimating inconsistent flow characteristics. Based on these findings, this project was designed to measure and analyze flow characteristics in a forward-inclined impeller. It was found that forward-inclined impellers have many regions of circulating flow and that the mainstream which moves to the outlet is narrow in effective area. As a result, velocity increases and discharge blow rapidly expands within a short distance. Therefore, good static pressure recovery is obtained. (author)

  13. Comparing the performances of circular ponds with different impellers by CFD simulation and microalgae culture experiments.

    Science.gov (United States)

    Meng, Chen; Huang, Jianke; Ye, Chunyu; Cheng, Wenchao; Chen, Jianpei; Li, Yuanguang

    2015-07-01

    In this study, a numerical simulation using computational fluid dynamics (CFD) was used to investigate the hydrodynamic characteristics of circular ponds with three different impellers (hydrofoil, four-pitched-blade turbine, and grid plate). The reliability of the CFD model was validated by particle image velocimetry (PIV). Hydrodynamic analyses were conducted to evaluate the average velocity magnitude along the light direction (Uz), turbulence properties, average shear stress, pressure loss and the volume percentage of dead zone inside circular ponds. The simulation results showed that Uz value of hydrofoil was 58.9, 40.3, and 28.8% higher than those of grid plate with single arm, grid plate with double arms and four-pitched blade turbines in small-scale circular ponds, respectively. In addition, hydrofoil impeller with down-flow operation had outstanding mixing characteristics. Lastly, the results of Chlorella pyrenoidosa cultivation experiments indicated that the biomass concentration of hydrofoil impeller with down-flow operation was 65.2 and 88.8% higher than those of grid plate with double arms and four-pitched-blade turbine, respectively. Therefore, the optimal circular pond mixing system for microalgae cultivation involved a hydrofoil impeller with down-flow operation.

  14. Design of a centrifugal compressor impeller using multi-objective optimization algorithm

    International Nuclear Information System (INIS)

    Kim, Jin Hyuk; Husain, Afzal; Kim, Kwang Yong; Choi, Jae Ho

    2009-01-01

    This paper presents a design optimization of a centrifugal compressor impeller with hybrid multi-objective evolutionary algorithm (hybrid MOEA). Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are discretized by finite volume approximations and solved on hexahedral grids for flow analyses. Two objectives, i.e., isentropic efficiency and total pressure ratio are selected with four design variables defining impeller hub and shroud contours in meridional contours to optimize the system. Non-dominated Sorting of Genetic Algorithm (NSGA-II) with ε-constraint strategy for local search coupled with Radial Basis Neural Network model is used for multi-objective optimization. The optimization results show that isentropic efficiencies and total pressure ratios of the five cluster points at the Pareto-optimal solutions are enhanced by multi-objective optimization.

  15. Design of a centrifugal compressor impeller using multi-objective optimization algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Hyuk; Husain, Afzal; Kim, Kwang Yong [Inha University, Incheon (Korea, Republic of); Choi, Jae Ho [Samsung Techwin Co., Ltd., Changwon (Korea, Republic of)

    2009-07-01

    This paper presents a design optimization of a centrifugal compressor impeller with hybrid multi-objective evolutionary algorithm (hybrid MOEA). Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are discretized by finite volume approximations and solved on hexahedral grids for flow analyses. Two objectives, i.e., isentropic efficiency and total pressure ratio are selected with four design variables defining impeller hub and shroud contours in meridional contours to optimize the system. Non-dominated Sorting of Genetic Algorithm (NSGA-II) with {epsilon}-constraint strategy for local search coupled with Radial Basis Neural Network model is used for multi-objective optimization. The optimization results show that isentropic efficiencies and total pressure ratios of the five cluster points at the Pareto-optimal solutions are enhanced by multi-objective optimization.

  16. Evaluation of near-wall solution approaches for large-eddy simulations of flow in a centrifugal pump impeller

    Directory of Open Access Journals (Sweden)

    Zhi-Feng Yao

    2016-01-01

    Full Text Available The turbulent flow in a centrifugal pump impeller is bounded by complex surfaces, including blades, a hub and a shroud. The primary challenge of the flow simulation arises from the generation of a boundary layer between the surface of the impeller and the moving fluid. The principal objective is to evaluate the near-wall solution approaches that are typically used to deal with the flow in the boundary layer for the large-eddy simulation (LES of a centrifugal pump impeller. Three near-wall solution approaches –the wall-function approach, the wall-resolved approach and the hybrid Reynolds averaged Navier–Stoke (RANS and LES approach – are tested. The simulation results are compared with experimental results conducted through particle imaging velocimetry (PIV and laser Doppler velocimetry (LDV. It is found that the wall-function approach is more sparing of computational resources, while the other two approaches have the important advantage of providing highly accurate boundary layer flow prediction. The hybrid RANS/LES approach is suitable for predicting steady-flow features, such as time-averaged velocities and hydraulic losses. Despite the fact that the wall-resolved approach is expensive in terms of computing resources, it exhibits a strong ability to capture a small-scale vortex and predict instantaneous velocity in the near-wall region in the impeller. The wall-resolved approach is thus recommended for the transient simulation of flows in centrifugal pump impellers.

  17. Study on numerical methods for transient flow induced by speed-changing impeller of fluid machinery

    International Nuclear Information System (INIS)

    Wu, Dazhuan; Chen, Tao; Wang, Leqin; Cheng, Wentao; Sun, Youbo

    2013-01-01

    In order to establish a reliable numerical method for solving the transient rotating flow induced by a speed-changing impeller, two numerical methods based on finite volume method (FVM) were presented and analyzed in this study. Two-dimensional numerical simulations of incompressible transient unsteady flow induced by an impeller during starting process were carried out respectively by using DM and DSR methods. The accuracy and adaptability of the two methods were evaluated by comprehensively comparing the calculation results. Moreover, an intensive study on the application of DSR method was conducted subsequently. The results showed that transient flow structure evolution and transient characteristics of the starting impeller are obviously affected by the starting process. The transient flow can be captured by both two methods, and the DSR method shows a higher computational efficiency. As an application example, the starting process of a mixed-flow pump was simulated by using DSR method. The calculation results were analyzed by comparing with the experiment data.

  18. Research of fluid-induced pressure fluctuation due to impeller-volute interaction in a centrifugal pump

    International Nuclear Information System (INIS)

    Liu, Q Z; Yang, K; Li, D Y; Gong, R Z

    2013-01-01

    The fluid pressure fluctuation generated by unsteady flow is a very important factor to induce vibration of the centrifugal pump. The relative movement between impeller and volute generates an unsteady interaction which affects not only the overall pump performance, but is also responsible for pressure fluctuations. Pressure fluctuations interact with the volute casing or even with the circuit and give rise to dynamic effects over the mechanical parts, which are one of the most important sources of vibration and hydraulic noise. To investigate the flow characteristic in the centrifugal pump, the unsteady flow is simulated by CFD methods in this paper. Unsteady flow characteristic in the centrifugal pump is obtained considering the impeller-volute interaction in the whole flow field. Based on the unsteady flow simulation, amplitude-frequency characteristics of the pressure fluctuation in the centrifugal pump are obtained through setting up monitoring point at the impeller outlet. The research shows that the frequency component include the blade passing frequency as the main component, the multiplication of blade passing frequency, and the harmonic interference due to the unsteady flow

  19. A Numerical Study on the Improvement of Suction Performance and Hydraulic Efficiency for a Mixed-Flow Pump Impeller

    Directory of Open Access Journals (Sweden)

    Sung Kim

    2014-01-01

    Full Text Available This paper describes a numerical study on the improvement of suction performance and hydraulic efficiency of a mixed-flow pump by impellers. The design of these impellers was optimized using a commercial CFD (computational fluid dynamics code and DOE (design of experiments. The design variables of meridional plane and vane plane development were defined for impeller design. In DOE, variables of inlet part were selected as main design variables in meridional plane, and incidence angle was selected in vane plane development. The verification of the experiment sets that were generated by 2k factorial was done by numerical analysis. The objective functions were defined as the NPSHre (net positive suction head required, total efficiency, and total head of the impellers. The importance of the geometric design variables was analyzed using 2k factorial designs. The interaction between the NPSHre and total efficiency, according to the meridional plane and incidence angle, was discussed by analyzing the 2k factorial design results. The performance of optimally designed model was verified by experiments and numerical analysis and the reliability of the model was retained by comparison of numerical analysis and comparative analysis with the reference model.

  20. Development of advanced pump impeller fabrication technology using direct nano- ceramic dispersion casting for long time erosion durability

    International Nuclear Information System (INIS)

    Rhee, Chang Kyu; Lee, Min Ku; Park, Jin Ju

    2008-09-01

    Many components of pump impeller of nuclear power plants is generally made of stainless steel and Al-bronze with superior corrosion resistance to sea water. However, they should be replaced by one- to five-year period because of material damage by a very big cavitation impact load, even though their designed durability is twenty years. Especially, in case of Young-Gwang nuclear power plant located at the west sea, damage of components of pump impeller is so critical due to the additional damage by solid particle erosion and hence their replacement period is very short as several months compared to other nuclear power plants. In addition, it is very difficult to maintain and repair the components of pump impeller since there is no database on the exact durability and damage mechanism. Therefore, in this study, fabrication technology of new advanced materials modified by dispersion of nano-carbide and -oxide ceramics into the matrix is developed first. Secondly, technology to estimate the dynamic damage by solid particle erosion is established and hence applied to the prediction of the service life of the components of pump impeller

  1. Numerical investigation of degas performance on impeller of medium-consistency pump

    Directory of Open Access Journals (Sweden)

    Hong Li

    2015-12-01

    Full Text Available Medium-consistency technology is known as the process with high efficiency and low pollution. The gas distribution was simulated in the medium-consistency pump with different degas hole positions. Rheological behaviors of pulp suspension were obtained by experimental test. A modified Herschel–Bulkley model and the Eulerian gas–liquid two-phase flow model were utilized to approximately represent the behaviors of the medium-consistency pulp suspension. The results show that when the relative position is 0.53, the gas volume ratio is less than 0.1% at the pump outlet and 9.8% at the vacuum inlet, and the pump head is at the maximum. Because of the different numbers of the impeller blades and turbulence blades and the asymmetric volute structure, the gas is distributed unevenly in the impeller. In addition, the pump performance was tested in experiment and the results are used to validate computational fluid dynamics outcomes.

  2. Computational fluid dynamics modeling of gas dispersion in multi impeller bioreactor.

    Science.gov (United States)

    Ahmed, Syed Ubaid; Ranganathan, Panneerselvam; Pandey, Ashok; Sivaraman, Savithri

    2010-06-01

    In the present study, experiments have been carried out to identify various flow regimes in a dual Rushton turbines stirred bioreactor for different gas flow rates and impeller speeds. The hydrodynamic parameters like fractional gas hold-up, power consumption and mixing time have been measured. A two fluid model along with MUSIG model to handle polydispersed gas flow has been implemented to predict the various flow regimes and hydrodynamic parameters in the dual turbines stirred bioreactor. The computational model has been mapped on commercial solver ANSYS CFX. The flow regimes predicted by numerical simulations are validated with the experimental results. The present model has successfully captured the flow regimes as observed during experiments. The measured gross flow characteristics like fractional gas hold-up, and mixing time have been compared with numerical simulations. Also the effect of gas flow rate and impeller speed on gas hold-up and power consumption have been investigated. (c) 2009 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  3. Numerical prediction and performance experiment in a deep-well centrifugal pump with different impeller outlet width

    Science.gov (United States)

    Shi, Weidong; Zhou, Ling; Lu, Weigang; Pei, Bing; Lang, Tao

    2013-01-01

    The existing research of the deep-well centrifugal pump mainly focuses on reduce the manufacturing cost and improve the pump performance, and how to combine above two aspects together is the most difficult and important topic. In this study, the performances of the deep-well centrifugal pump with four different impeller outlet widths are studied by the numerical, theoretical and experimental methods in this paper. Two stages deep-well centrifugal pump equipped with different impellers are simulated employing the commercial CFD software to solve the Navier-Stokes equations for three-dimensional incompressible steady flow. The sensitivity analyses of the grid size and turbulence model have been performed to improve numerical accuracy. The flow field distributions are acquired and compared under the design operating conditions, including the static pressure, turbulence kinetic energy and velocity. The prototype is manufactured and tested to certify the numerical predicted performance. The numerical results of pump performance are higher than the test results, but their change trends have an acceptable agreement with each other. The performance results indicted that the oversize impeller outlet width leads to poor pump performances and increasing shaft power. Changing the performance of deep-well centrifugal pump by alter impeller outlet width is practicable and convenient, which is worth popularizing in the engineering application. The proposed research enhances the theoretical basis of pump design to improve the performance and reduce the manufacturing cost of deep-well centrifugal pump.

  4. Mathematical Modeling of Fluid Flow in a Water Physical Model of an Aluminum Degassing Ladle Equipped with an Impeller-Injector

    Science.gov (United States)

    Gómez, Eudoxio Ramos; Zenit, Roberto; Rivera, Carlos González; Trápaga, Gerardo; Ramírez-Argáez, Marco A.

    2013-04-01

    In this work, a 3D numerical simulation using a Euler-Euler-based model implemented into a commercial CFD code was used to simulate fluid flow and turbulence structure in a water physical model of an aluminum ladle equipped with an impeller for degassing treatment. The effect of critical process parameters such as rotor speed, gas flow rate, and the point of gas injection (conventional injection through the shaft vs a novel injection through the bottom of the ladle) on the fluid flow and vortex formation was analyzed with this model. The commercial CFD code PHOENICS 3.4 was used to solve all conservation equations governing the process for this two-phase fluid flow system. The mathematical model was reasonably well validated against experimentally measured liquid velocity and vortex sizes in a water physical model built specifically for this investigation. From the results, it was concluded that the angular speed of the impeller is the most important parameter in promoting better stirred baths and creating smaller and better distributed bubbles in the liquid. The pumping effect of the impeller is increased as the impeller rotation speed increases. Gas flow rate is detrimental to bath stirring and diminishes the pumping effect of the impeller. Finally, although the injection point was the least significant variable, it was found that the "novel" injection improves stirring in the ladle.

  5. Chaotic characteristics enhanced by impeller of perturbed six-bent-bladed turbine in stirred tank

    Directory of Open Access Journals (Sweden)

    Deyu Luan

    Full Text Available The fundamental way of improving the mixing efficiency is to induce the chaotic flow in a stirred vessel. The impeller form plays an important role for changing the structure of flow field and realizing chaotic mixing. Based on the velocity time series acquired by the experiment of particle image velocimetry (PIV, with the software Matlab, the macro-instability (MI, largest Lyapunov exponent (LLE, and Kolmogorov entropy in the water stirred tank is investigated respectively with the impeller of perturbed six-bent-bladed turbine (6PBT. The results show that the MI characteristics are obvious and two peak values of MI frequency are observed at the speed N = 60 rpm. With the increasing speed (more than 100 rpm, the peak characteristics of MI frequency disappear and a multi-scale wavelet structure of characterizing the chaotic flow field appears. Moreover, under the speed N = 60 rpm, the LLE is less than 0 and Kolmogorov entropy is 0, which means that the flow field is in the periodic moving state. As the speed is increased to more than 100 rpm, the LLE and Kolmogorov entropy are all more than 0, which indicates that the flow field goes into the chaotic mixing. When the speed reaches up to about 210 rpm, both of the LLE and Kolmogorov entropy achieve the optimum values, which will result in an excellent chaos with the highest mixing efficient. So it is feasible that the MI frequency, the LLE and the Kolmogorov entropy can be used to analyze the flow field characteristics in a stirred tank. The research results promote the understanding of the chaotic mixing mechanism and provide a theoretical reference for the development of new type impeller. Keywords: Macro-instability, The largest Lyapunov exponent, Kolmogorov entropy, The impeller of perturbed six-bent-bladed turbine, Chaotic mixing, PIV

  6. Effect of impeller type and stirring frequency on the behavior of an AnSBBR in the treatment of low-strength wastewater.

    Science.gov (United States)

    Cubas, Selma A; Foresti, Eugenio; Rodrigues, José Alberto D; Ratusznei, Suzana M; Zaiat, Marcelo

    2011-01-01

    The influence of impeller type and stirring frequency on the performance of a mechanically stirred anaerobic sequencing batch reactor containing immobilized biomass on an inert support (AnSBBR--Anaerobic Sequencing Batch Biofilm Reactor) was evaluated. The biomass was immobilized on polyurethane foam cubes placed in a stainless-steel basket inside a glass cylinder. Each 8-h batch run consisted of three stages: feed (10 min), reaction (460 min) and discharge (10 min) at 30 °C. Experiments were performed with four impeller types, i.e., helical, flat-blade, inclined-blade and curved-blade turbines, at stirring frequencies ranging from 100 to 1100 rpm. Synthetic wastewater was used in all experiments with an organic-matter concentration of 530±37 mg/L measured as chemical oxygen demand (COD). The reactor achieved an organic-matter removal efficiency of around 87% under all investigated conditions. Analysis of the four impeller types and the investigated stirring frequencies showed that mass transfer in the liquid phase was affected not only by the applied stirring frequency but also by the agitation mode imposed by each impeller type. The best reactor performance at all stirring frequencies was obtained when agitation was provided by the flat-blade turbine impeller. Copyright © 2010 Elsevier Ltd. All rights reserved.

  7. Laser cleaning of sulfide scale on compressor impeller blade

    International Nuclear Information System (INIS)

    Tang, Q.H.; Zhou, D.; Wang, Y.L.; Liu, G.F.

    2015-01-01

    Highlights: • The effects of sulfide layers and fluence values on the mechanism of laser cleaning were experimentally established. • The specimen surface with sulfide scale becomes slightly smoother than that before laser cleaning. • The mechanism of laser cleaning the sulfide scale of stainless steel is spallation without oxidization. • It would avoid chemical waste and dust pollution using a fiber laser instead of using nitric acids or sandblasting. - Abstract: Sulfide scale on the surface of a compressor impeller blade can considerably reduce the impeller performance and its service life. To prepare for subsequent remanufacturing, such as plasma spraying, it needs to be removed completely. In the corrosion process on an FV(520)B stainless steel, sulfide scale is divided into two layers because of different outward diffusion rates of Cr, Ni and Fe. In this paper, the cleaning threshold values of the upper and inner layers and the damage threshold value of the substrate were investigated using a pulsed fiber laser. To obtain experimental evidence, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and 3D surface profilometry were employed to investigate the two kinds of sulfide layers on specimens before, during, and after laser cleaning.

  8. Pump impeller failures - a compendium of case studies

    CSIR Research Space (South Africa)

    Van Bennekom, A

    2001-04-01

    Full Text Available surface material. It should also be noted that this stress is above the yield strengths of many materials and as such some localised plastic deformation could also be expected. The exact mechanism by which collapse of the bubbles transmits the localised... metal to cavitation damage, it appears as though the degree of degradation is related to the pitting resistance rather than the general corrosion resistance of the material [4]. The presence of pits on the surface of the impeller also causes disruption...

  9. Modal behavior of a reduced scale pump-turbine impeller. Part 1: Experiments

    International Nuclear Information System (INIS)

    Escaler, X; Huetter, J K; Egusquiza, E; Farhat, M; Avellan, F

    2010-01-01

    An experimental investigation has been carried out to quantify the effects of surrounding fluid on the modal behavior of a reduced scale pump-turbine impeller. The modal properties of the fluid-structure system have been obtained by Experimental Modal Analysis (EMA) with the impeller suspended in air and inside a water reservoir. The impeller has been excited with an instrumented hammer and the response has been measured by means of miniature accelerometers. The Frequency Response Functions (FRF's) have been obtained from a large number of impacting positions in order to ensure the identification of the main mode shapes. As a result, the main modes of vibration have been well characterized both in air and in water in terms of natural frequency, damping ratio and mode shape. The first mode is the 2 Nodal Diameter (ND), the second one is the 0ND and the following ones are the 3ND coupled with the 1ND. The visual observation of the animated mode shapes and the level of the Modal Assurance Criterion (MAC) have permitted to correlate the homologous modes of vibration of the fluid-structure system in air and in water. From this comparison the added mass effect on the natural frequencies and the fluid effect on the damping ratios have been quantified for the most significant modes. With the surrounding water, the natural frequencies decrease in average by 10%. On the other hand, the damping ratios increase in average by 0.5%. In any case, the damping ratio appears to decrease with the frequency value of the mode.

  10. Primary system hydraulic characteristics after modification of reactor coolant pumps' impeller wheels at Bohunice NPP executed in 2012 and 2013

    International Nuclear Information System (INIS)

    Hermansky, Jozef; Zavodsky, Martin

    2014-01-01

    A coolant flow through the reactor is usually determined after annual outages at Slovak NPP (VVER 440) in two distinct ways. First method is determination on the basis of the secondary system parameters - measurement of thermal balances. The value achieved by this method is used as the input parameter in the Table of allowed reactor operation modes. The second method draws from the primary system parameters - measurement of primary system hydraulic characteristics. Flow nozzles used for the measurement of feed water flow behind high pressure heaters were replaced at both Bohunice Units during outages in 2008. The feed water flow behind high pressure heaters is one of the main parameters used for the determination of coolant flow through the reactor by the first method. Compared to the measurement executed during previous fuel cycles, the calculated coolant flow through the reactor decreased considerably after the change of flow nozzles. The imaginary change of coolant flow through the reactor at Unit 3 was -1,6 %; and at Unit 4 -2,6 %. This change was not proved by the parallel measurement of primary system hydraulic characteristics. Later it was found out that the original flow nozzles used for 25 years were substantially deposited (original inner diameter of the nozzles was reduced by about 0,6-0,9 mm). Therefore feed water flow measurement was untrustworthy within the recent years. On the findings stated above, Bohunice NPP has decided to increase coolant flow through the reactor by changing the reactor coolant pumps impeller wheels. The modification of impellers wheels is planned within years 2012 to 2014. During the outages in 2013 two impeller wheels were replaced at both units. Nowadays Unit 4 is operated with all 6 new impeller wheels and Unit 3 with four new impeller wheels. Modification of last two impeller wheels at Unit 3 will be performed during the outage in 2014. On account of impeller wheels modification, non-standard measurement of PS hydraulic

  11. Semianalytical characterization of turbulence from radial impellers, with experimental and numerical validation

    Czech Academy of Sciences Publication Activity Database

    Ben-Nun, R.; Sheintuch, M.; Kysela, Bohuš; Konfršt, Jiří; Fořt, I.

    2015-01-01

    Roč. 61, č. 4 (2015), s. 1413-1426 ISSN 0001-1541 R&D Projects: GA ČR GAP101/12/2274 Institutional support: RVO:67985874 Keywords : turbulent jet * mixing * radial impeller * stirred tank * Rushton turbine Subject RIV: BK - Fluid Dynamics Impact factor: 2.980, year: 2015

  12. Analysis on the influence of the pump start transient performance with different inertia impeller

    International Nuclear Information System (INIS)

    Tang, Y; Cheng, J; Liu, E H; Tang, L D

    2012-01-01

    Centrifugal pump start-up time is very short, in the boot process, the instantaneous head and flow will have an impact role to the pipeline, and however the moment of inertia is one of the main factors affecting centrifugal pump boot acceleration. We analyzed the pump start-up transient characteristics with the different moment of inertia of the impeller corresponding to the different materials, there are three different moment of inertia of the impeller have been selected. At first, we use the 'Flowmaster' fluid system simulation software do the outer characteristics simulation to the selected-model, get the time - flow and the time - speed curve. Then, do the experiments research in the process when pump start-up, and compare with the simulation result. At last use the outer characteristics simulation result as the boundary, using the ANASYS CFX software do the transient simulation to the three groups with different inertia pump impeller, and draw the pressure distribution picture. In according to the analysis, we can confirm that the impact of inertia is one of the factors in the stability during the pump star, and we can get that the greater moment of inertia, the longer the boot stable. We also can get that combined Flowmaster with ANSYS can solved engineering practice problem in fluid system conveniently, and take it easy to solve the similar problem.

  13. Effects of Radial Gap Ratio between Impeller and Vaned Diffuser on Performance of Centrifugal Compressors

    Directory of Open Access Journals (Sweden)

    Mohammadjavad Hosseini

    2017-07-01

    Full Text Available A high-performance centrifugal compressor is needed for numerous industry applications nowadays. The radial gap ratio between the impeller and the diffuser vanes plays an important role in the improvement of the compressor performance. In this paper, the effects of the radial gap ratio on a high-pressure ratio centrifugal compressor are investigated using numerical simulations. The performance and the flow field are compared for six different radial gap ratios and five rotational speeds. The minimal radial gap ratio was 1.04 and the maximal was 1.14. Results showed that reducing the radial gap ratio decreases the choke mass flow rate. For the tip-speed Mach number (impeller inlet with Mu < 1, the pressure recovery and the loss coefficients are not sensitive to the radial gap ratio. However, for Mu ≥ 1, the best radial gap ratio is 1.08 for the pressure recovery and the loss coefficients. Furthermore, the impeller pressure ratio and efficiency are reduced by increasing the radial gap ratio. Finally, the compressor efficiency was compared for different radial gap ratios. For Mu < 1, the radial gap ratio does not have noticeable effects. In comparison, the radial gap ratio of 1.08 has the best performance for Mu ≥ 1.

  14. Swarm intelligence based on modified PSO algorithm for the optimization of axial-flow pump impeller

    International Nuclear Information System (INIS)

    Miao, Fuqing; Kim, Chol Min; Ahn, Seok Young; Park, Hong Seok

    2015-01-01

    This paper presents a multi-objective optimization of the impeller shape of an axial-flow pump based on the Modified particle swarm optimization (MPSO) algorithm. At first, an impeller shape was designed and used as a reference in the optimization process then NPSHr and η of the axial flow pump were numerically investigated by using the commercial software ANSYS with the design variables concerning hub angle β_h, chord angle β_c, cascade solidity of chord σ_c and maximum thickness of blade H. By using the Group method of data handling (GMDH) type neural networks in commercial software DTREG, the corresponding polynomial representation for NPSHr and η with respect to the design variables were obtained. A benchmark test was employed to evaluate the performance of the MPSO algorithm in comparison with other particle swarm algorithms. Later the MPSO approach was used for Pareto based optimization. Finally, the MPSO optimization result and CFD simulation result were compared in a re-evaluation process. By using swarm intelligence based on the modified PSO algorithm, better performance pump with higher efficiency and lower NPSHr could be obtained. This novel algorithm was successfully applied for the optimization of axial-flow pump impeller shape design

  15. Swarm intelligence based on modified PSO algorithm for the optimization of axial-flow pump impeller

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Fuqing; Kim, Chol Min; Ahn, Seok Young [Pusan National University, Busan (Korea, Republic of); Park, Hong Seok [Ulsan University, Ulsan (Korea, Republic of)

    2015-11-15

    This paper presents a multi-objective optimization of the impeller shape of an axial-flow pump based on the Modified particle swarm optimization (MPSO) algorithm. At first, an impeller shape was designed and used as a reference in the optimization process then NPSHr and η of the axial flow pump were numerically investigated by using the commercial software ANSYS with the design variables concerning hub angle β{sub h}, chord angle β{sub c}, cascade solidity of chord σ{sub c} and maximum thickness of blade H. By using the Group method of data handling (GMDH) type neural networks in commercial software DTREG, the corresponding polynomial representation for NPSHr and η with respect to the design variables were obtained. A benchmark test was employed to evaluate the performance of the MPSO algorithm in comparison with other particle swarm algorithms. Later the MPSO approach was used for Pareto based optimization. Finally, the MPSO optimization result and CFD simulation result were compared in a re-evaluation process. By using swarm intelligence based on the modified PSO algorithm, better performance pump with higher efficiency and lower NPSHr could be obtained. This novel algorithm was successfully applied for the optimization of axial-flow pump impeller shape design.

  16. Influence of Impeller Geometry on the Unsteady Flow in a Centrifugal Fan: Numerical and Experimental Analyses

    Directory of Open Access Journals (Sweden)

    M. Younsi

    2007-01-01

    Full Text Available The aim of this study is to evaluate the influence of design parameters on the unsteady flow in a forward-curved centrifugal fan and their impact on the aeroacoustic behavior. To do so, numerical and experimental studies have been carried out on four centrifugal impellers designed with various geometrical parameters. The same volute casing has been used to study these impellers. The effects on the unsteady flow behavior related to irregular blade spacing, blade count and radial distance between the impeller periphery and the volute tongue have been studied. The numerical simulations of the unsteady flow have been carried out using computational fluid dynamics (CFD tools based on the unsteady Reynolds averaged Navier Stokes (URANS approach. The study is focused on the unsteadiness induced by the aerodynamic interaction between the volute and the rotating impeller blades. In order to predict the acoustic pressure at far field, the unsteady flow variables provided by the CFD calculations have been used as inputs in the Ffowcs Williams-Hawkings equations (FW-H. The experimental part of this work concerns measurement of aerodynamic performance of the fans using a test bench built according to ISO 5801 (1997 standard. In addition to this, pressure microphones have been flush mounted on the volute tongue surface in order to measure the wall pressure fluctuations. The sound pressure level (SPL measurements have been carried out in an anechoic room in order to remove undesired noise reflections. Finally, the numerical results have been compared with the experimental measurements and a correlation between the wall pressure fluctuations and the far field noise signals has been found.

  17. A Comparative Assessment of Spalart-Shur Rotation/Curvature Correction in RANS Simulations in a Centrifugal Pump Impeller

    Directory of Open Access Journals (Sweden)

    Ran Tao

    2014-01-01

    Full Text Available RANS simulation is widely used in the flow prediction of centrifugal pumps. Influenced by impeller rotation and streamline curvature, the eddy viscosity models with turbulence isotropy assumption are not accurate enough. In this study, Spalart-Shur rotation/curvature correction was applied on the SST k-ω turbulence model. The comparative assessment of the correction was proceeded in the simulations of a centrifugal pump impeller. CFD results were compared with existing PIV and LDV data under the design and low flow rate off-design conditions. Results show the improvements of the simulation especially in the situation that turbulence strongly produced due to undesirable flow structures. Under the design condition, more reasonable turbulence kinetic energy contour was captured after correction. Under the low flow rate off-design condition, the prediction of turbulence kinetic energy and velocity distributions became much more accurate when using the corrected model. So, the rotation/curvature correction was proved effective in this study. And, it is also proved acceptable and recommended to use in the engineering simulations of centrifugal pump impellers.

  18. Numerical analysis of cavitating flow characteristics in impeller of residual heat removal pump

    NARCIS (Netherlands)

    Hong, Feng; Yuan, Jianping; Zhou, Banglun

    2016-01-01

    In order to investigate internal cavitating flow characteristics of the impeller in residual heat removal pumps, the three-dimensional cavitating flow in a residual heat removal model pump is numerically calculated by using the homogeneous mixture cavitation model based on the Rayleigh-Plesset

  19. Numerical and Experimental Investigation of Cavitating Characteristics in Centrifugal Pump with Gap Impeller

    Science.gov (United States)

    Zhu, Bing; Chen, Hongxun; Wei, Qun

    2014-06-01

    This paper is to study the cavitating characteristics in a low specific speed centrifugal pump with gap structure impeller experimentally and numerically. A scalable DES numerical method is proposed and developed by introducing the von Karman scale instead of the local grid scale, which can switch at the RANS and LES region interface smoothly and reasonably. The SDES method can detect and grasp unsteady scale flow structures, which were proved by the flow around a triangular prism and the cavitation flow in a centrifugal pump. Through numerical and experimental research, it's shown that the simulated results match qualitatively with tested cavitation performances and visualization patterns, and we can conclude that the gap structure impeller has a superior feature of cavitation suppression. Its mechanism may be the guiding flow feature of the small vice blade and the pressure auto-balance effect of the gap tunnel.

  20. Analyses on the Performance and Interaction Between the Impeller and Casing in a Small-Size Turbo-Compressor

    Science.gov (United States)

    Kim, Youn-Jea; Kim, Dong-Won

    The effects of casing shapes on the performance and the interaction between an impeller and a casing in a small-size turbo-compressor are investigated. Numerical analysis is conducted for the turbo-compressor with circular and single volute casings from the inlet to a discharge nozzle. The optimum design for each element is important to develop the small-size turbo-compressor using alternative refrigerant as a working fluid. Typically, the rotating speed of the compressor is in the range of 40000-45000rpm because of the small size of an impeller diameter. A blade of an impeller has backswept two-dimensional shape due to tip clearance and a vane diffuser has wedge type. In order to predict the flow pattern inside the entire impeller, the vaneless diffuser and the casing, calculations with multiple frames of reference method between the rotating and stationery parts of the domain are carried out. For compressible turbulent flow fields, the continuity and time-averaged three-dimensional Navier-Stokes equations are employed. To evaluate the performance of two types of casings, the static pressure recovery and loss coefficients are obtained with various flow rates. Also, static pressure distributions around casings are studied for different casing shapes, which are very important to predict the distribution of radial load. To prove the accuracy of numerical results, measurements of static pressure around the casing and pressure difference between the inlet and the outlet of the compressor are performed for the circular casing. The comparison of experimental and numerical results is conducted, and reasonable agreement is obtained.

  1. Flow characteristics of Newtonian and non-Newtonian fluids in a vessel stirred by a 60° pitched blade impeller

    Directory of Open Access Journals (Sweden)

    Jamshid M. Nouri

    2008-03-01

    Full Text Available Mean and rms velocity characteristics of two Newtonian flows at Reynolds numbers of 12,800 (glycerin solution and 48,000 (water and of a non-Newtonian flow (0.2% CMC solution, at a power number similar to the Newtonian glycerin flow in a mixing vessel stirred by a 60° pitched blade impeller have been measured by laser Doppler velocimetry (LDV. The velocity measurements, resolved over 360° and 1.08° of impeller rotation, showed that the mean flow of the two power number matched glycerin and CMC flows were similar to within 3% of the impeller tip velocity and the turbulence intensities generally lower in the CMC flow by up to 5% of the tip velocity. The calculated mean flow quantities showed similar discharge coefficient and pumping efficiency in all three flows and similar strain rate between the two power number matched glycerin and CMC flows; the strain rate of the higher Reynolds number Newtonian flow was found to be slightly higher. The energy balance around the impeller indicated that the CMC flow dissipated up to 9% more of the total input power and converted 7% less into the turbulence compared to the glycerin flow with the same power input which could lead to less effective mixing processes where the micro-mixing is important.

  2. Prediction of rotating stall within an impeller of a centrifugal pump based on spectral analysis of pressure and velocity data

    International Nuclear Information System (INIS)

    Ullum, Ulrik; Wright, Jennifer; Dayi, Oguz; Ecder, Ali; Soulaimani, Azzeddine; Piche, Robert; Kamath, Hemant

    2006-01-01

    Experimental data, which was acquired in two centrifugal pumps and provided by Grundfos A/S, were analysed to determine if rotating stall could be detected from the velocity and pressure time series. The pressure data, which were uniformly acquired in time at high sample rates(10 kHz), were measured simultaneously in four adjacent di.user channels just downstream of the impeller outlet. The velocity data, which were non-uniformly sampled in time at fairly low rates(100 Hz to 3.5 kHz), were acquired either in or downstream of the impeller. Two di.erent methodologies were employed for detection of stall. The first method, which involved direct analysis of raw data, yielded qualitatively useful flow reversal information from the time series for the radial velocity. The second approach, which was based on power spectrum analysis of velocity and pressure data, could detect the onset and identify the frequency of rotating stall to a satisfactory extent in one of the two pumps. Nearly identical stall frequencies were observed in both velocity and pressure power spectra and this rotating stall phenomenon, which occurred at a very low frequency relative to the impeller speed, did not reveal any noticeable degree of sensitivity to the flow rate. In the other pump, where the available data was limited to velocity time series, the power spectrum analysis was successful in detecting stationary stall for a 6 bladed impeller but did not provide conclusive results for the existence of stall in the case of the 7 bladed impeller. Recommendations on the type of experimental data required for accurate detection of stall are provided based upon the present study

  3. Study of fluid flow in baffled vessels stirred by a Rushton standard impeller

    Czech Academy of Sciences Publication Activity Database

    Chára, Zdeněk; Kysela, Bohuš; Konfršt, Jiří; Fořt, I.

    2016-01-01

    Roč. 272, č. 3 (2016), s. 614-628 ISSN 0096-3003 R&D Projects: GA ČR GAP101/12/2274 Institutional support: RVO:67985874 Keywords : trailing vortices * rushton impeller * PIV measurements * DES * numerical simulation Subject RIV: BK - Fluid Dynamics Impact factor: 1.738, year: 2016

  4. OFF-DESIGN OPERATION OF IMPELLER OF THE CENTRIFUGAL COMPRESSOR

    Directory of Open Access Journals (Sweden)

    Saim KOÇAK

    2004-02-01

    Full Text Available Inducer and discharge dimensions of impellers of centrifugal compressor are determined as a preliminary design. Blockage factor and inducer dimensionless mass flow are exercised in relation with the relative Mach number. The equation which will be based o off-design calculation, related with the discharge relative Mach number are iterated until it will equal to inducer dimensionless mass flow rate. Then discharge relative Mach number for off-design works is obtained. The results calculated in accordance with pressure, temperature and density are seen to be similar with the theoretical parameters.

  5. Studies of the impact of prerotation problem of the secondary impeller on performance of multi-stage centrifugal pumps

    International Nuclear Information System (INIS)

    Zhai, L L; Wu, P; Jiang, Q L; Wang, L Q

    2012-01-01

    In engineering practice, part of the multi-stage centrifugal pumps is designed without space guide vanes due to the size restrictions and the volute is distorted much in shape. In these pumps, tangential velocity of the fluid at the outlet of the first-stage impeller is so great that it has caused a prerotation problem which will affect the inlet flow conditions of the secondary impeller leading to serious efficiency and head decline of the secondary impeller. The head problem of the second stage in multi-stage centrifugal pumps caused by prerotation at the entrance of the second stage was analyzed and the internal hydraulic performance was optimized by setting clapboards in the volute in this paper. CFD numerical simulation method combined with experiment was applied to predict the effect of internal clapboards on the performance of the centrifugal pump. The original prototype was transformed according to the simulation result and tested to verify the optimization work. The experiment result shows that hydraulic performance is remarkably improved compared with the original one and the prerotation problem is basically solved.

  6. Numerical investigation of variable inlet guide vanes with trailing-edge dual slots to decrease the aerodynamic load on centrifugal compressor impeller

    Directory of Open Access Journals (Sweden)

    Jianchi Xin

    2016-03-01

    Full Text Available In engineering practice, most centrifugal compressors use variable inlet guide vanes which can provide pre-whirl and control volume flow rates. As the impeller of a centrifugal compressor passes through the wakes created from the guide vanes, the aerodynamic parameters change significantly. The concept of adding dual slots at the trailing-edge of the guide vanes is proposed for reducing the aerodynamic load on the compressor impeller blades. In this article, the steady and unsteady performances of the new guide vanes are analysed under two compressor operating conditions (winter and design conditions. The results show that the average amplitude of the impeller passing frequency at the leading edge has a 13% decrease under the winter condition, especially at the middle and root parts. Moreover, the dual slots structure has no effect on the overall compressor performance.

  7. CFD Analysis on the Effect of Radial Gap on Impeller-Diffuser Flow Interaction as well as on the Flow Characteristics of a Centrifugal Fan

    Directory of Open Access Journals (Sweden)

    K. Vasudeva Karanth

    2009-01-01

    Full Text Available The flow between the impeller exit and the diffuser entry (i.e., in the radial gap is generally considered to be complex. With the development of PIV and CFD tools such as moving mesh techniques, it is now possible to arrive at a prudent solution compatible with the physical nature of flow. In this work, numerical methodology involving moving mesh technique is used in predicting the real flow behavior, as exhibited when a target blade of the impeller is made to move past corresponding vane on the diffuser. Many research works have been undertaken using experimental and numerical methods on the impeller-diffuser interactive phenomenon. It is found from the literature that the effect of radial gap between impeller and diffuser on the interaction and on the performance of the fan has not been the focus of attention. Hence numerical analysis is undertaken in this work to explore and predict the flow behavior due to the radial gap. This has revealed the presence of an optimum radial gap which could provide better design characteristics or lower loss coefficient. It is found that there is a better energy conversion by the impeller and enhanced energy transformation by the diffuser, corresponding to optimum radial gap. The overall efficiency also found to increase for relatively larger gap.

  8. Preliminary Design of Compressor Impeller for innovative Sodium Cooled Fast Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jekyoung; Cho, Seongkuk; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Cha, Jae Eun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    For nuclear power plant application, applying S-CO{sub 2} Brayton cycle to Sodium cooled Fast Reactors and Small Modular Reactors are currently considered and active research is being performed by various research institutions and universities. As a part of research activities on the SCO{sub 2} Brayton cycle development for a nuclear power system, KAIST joint research team is currently working on an innovative Sodium cooled Fast Reactor (iSFR) development which utilizes S-CO{sub 2} Brayton cycle as its power conversion system. Various research subjects including reactor physics, thermo-hydraulics, material, cycle analysis and system integration are being considered as research issues currently. However, technical issues rising from dramatic change of thermodynamic property of CO{sub 2} near the critical point still remain as problems to be solved. As a result, 3D impeller model generation based on 1D mean stream line analysis results was successfully performed for non-airfoil blades. Since 3D model generation module works successfully, KAIST{sub T}MD can support 3D CFD analysis for internal flow structure in the designed impeller. Compressor loss mechanisms are complex phenomena and these are difficulties to be modeled while considering each loss mechanism separately.

  9. Dynamic stress of impeller blade of shaft extension tubular pump device based on bidirectional fluid-structure interaction

    Energy Technology Data Exchange (ETDEWEB)

    Kan, Kan; Liu, Huiwen; Yang, Chunxia [Hohai University, Nanjing (China); Zheng, Yuan [National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Nanjing (China); Fu, Shifeng; Zhang, Xin [Power China Huadong Engineering Corporation, Hangzhou (China)

    2017-04-15

    Current research on the stability of tubular pumps is mainly concerned with the transient hydrodynamic characteristics. However, the structural response under the influence of fluid-structure interaction hasn't been taken fully into consideration. The instability of the structure can cause vibration and cracks, which may threaten the safety of the unit. We used bidirectional fluid-structure interaction to comprehensively analyze the dynamic stress characteristics of the impeller blades of the shaft extension tubular pump device. Furthermore, dynamic stress of impeller blade of shaft extension tubular pump device was solved under different lift conditions of 0° blade angle. Based on Reynolds-average N-S equation and SST k-ω turbulence model, numerical simulation was carried out for three-dimensional unsteady incompressible turbulent flow field of the pump device whole flow passage. Meanwhile, the finite element method was used to calculate dynamic characteristics of the blade structure. The blade dynamic stress distribution was obtained on the basis of fourth strength theory. The research results indicate that the maximum blade dynamic stress appears at the joint between root of inlet side of the blade suction surface and the axis. Considering the influence of gravity, the fluctuation of the blade dynamic stress increases initially and decreases afterwards within a rotation period. In the meantime, the dynamic stress in the middle part of inlet edge presents larger relative fluctuation amplitude. Finally, a prediction method for dynamic stress distribution of tubular pump considering fluid-structure interaction and gravity effect was proposed. This method can be used in the design stage of tubular pump to predict dynamic stress distribution of the structure under different operating conditions, improve the reliability of pump impeller and analyze the impeller fatigue life.

  10. Pitched blade impeller - an option for mixing in continuous actinide reconversion process

    International Nuclear Information System (INIS)

    Tripathi, V.M.; Suresh Kumar, K.; Sreekumar, G.; Sugilal, G.

    2016-01-01

    In nuclear fuel cycle, current methodology for Pu reconversion involves Pu(IV)-oxalate precipitation as a semi continuous/batch process mode for a predetermined volume of Pu(NO 3 ) 4 solution in a long single column with a marine propeller type stirrer. In this process the slurry is being drained from bottom of the vessel leading to a possibility of accumulation of precipitate in the vessel which is an unfavorable condition for continuous process. As continuous reconversion process is a requirement to meet high through put of reprocessing plants, the conventional process has to be improvised with reference to its slurry exit point through overflow line. Although marine propeller type stirrer ensures an axial flow, it is not a choice for uniform solid suspension in a reactor vessel. A better alternate for complete suspension of solid in tall reactor is pitched blade turbine. Moreover pitched blade impellers are effective in low bottom clearance which ensures a thorough mixing of reactants. Present study focuses on feasibility of pitched blade impeller for mixing of reactants in a continuous actinide oxalate precipitation reactor with over flow line

  11. CFD Modelling of a Pump as Turbine (PAT with Rounded Leading Edge Impellers for Micro Hydro Systems

    Directory of Open Access Journals (Sweden)

    Ismail Mohd Azlan

    2017-01-01

    Full Text Available A Pump as Turbine (PAT is one of micro hydro system components that is used to substitute a commercially available turbine due to its wide availability and low acquisition cost. However, PAT have high hydraulic losses due to differences in pump-turbine operation and hydraulic design. The fluid flowing inside the PAT is subjected to hydraulic losses due to the longer flow passage and unmatched fluid flow within the wall boundaries. This paper presents the effect of rounding the impeller leading edges of the pump on turbine performance. A CFD model of a PAT was designed to simulate virtual performance for the analysis. The aim of this study is to observe the internal hydraulic performance resulting from the changes in the performance characteristics. Highest efficiency was recorded at 17.0 l/s, an increase of 0.18%. The simulation results reveal that there is an improvement in hydraulic performance at overflow operation. The velocity vector visualization shows that there is a reduction in wake and consequently less flow separation along impeller flow passages. However, adjusting the sensitive impeller inlet geometry will also alter the velocity inlet vector and consequently change the velocity triangles for the turbo machinery system.

  12. Development of the virtual experimental bench on the basis of modernized research centrifugal compressor stage test unit with the 3D impeller.

    Science.gov (United States)

    Aksenov, A. A.; Danilishin, A. M.; Dubenko, A. M.; Kozhukov, Y. V.

    2017-08-01

    Design modernization of the centrifugal compressor stage test bench with three dimensional impeller blades was carried out for the possibility of holding a series of experimental studies of different 3D impeller models. The studies relates to the problem of joint work of the impeller and the stationary channels of the housing when carrying out works on modernization with the aim of improving the parameters of the volumetric capacity or pressure in the presence of design constraints. The object of study is the experimental single end centrifugal compressor stage with the 3D impeller. Compressor stage consists of the 3D impeller, vaneless diffuser (VLD), outlet collector - folded side scroll and downstream pipe. The drive is a DC motor 75 kW. The increase gear (multiplier) was set between the compressor and DC motor, gear ratio is i = 9.8. To obtain the characteristics of the compressor and the flow area the following values were measured: total pressure, static pressure, direction (angles) of the stream in different cross sections. Additional pneumometric probes on the front wall of the VLD of the test bench have been installed. Total pressure probes and foster holes for the measurement of total and static pressure by the new drainage scheme. This allowed carrying out full experimental studies for two elements of centrifugal compressor stage. After the experimental tests the comprehensive information about the performance of model stage were obtained. Was measured geometric parameters and the constructed virtual model of the experimental bench flow part with the help of Creo Parametric 3.0 and ANSYS v. 16.2. Conducted CFD calculations and verification with experimental data. Identifies the steps for further experimental and virtual works.

  13. Performance Testing Of A Modified Centrifugal Fan With Serrated Blade Impeller

    OpenAIRE

    Zaimar; Mursalim; H. Abbas; Supratomo

    2017-01-01

    Changes of shape dimension and component part of impeller might change of characteristic fluid flow so that pressure static in the fan housing changed. Changing some geometric characteristics of the centrifugal fan has more efficiency taking with energy crises into consideration. Several factors that can affect fan performance namely design and type size rotation speed air condition or gas through a fan operating point on the nature of the relationship between a volume of air flow and pressur...

  14. Computer Aided Simulation Machining Programming In 5-Axis Nc Milling Of Impeller Leaf

    Science.gov (United States)

    Huran, Liu

    At present, cad/cam (computer-aided design and manufacture) have fine wider and wider application in mechanical industry. For the complex surfaces, the traditional machine tool can no longer satisfy the requirement of such complex task. Only by the help of cad/cam can fulfill the requirement. The machining of the vane surface of the impeller leaf has been considered as the hardest challenge. Because of their complex shape, the 5-axis cnc machine tool is needed for the machining of such parts. The material is hard to cut, the requirement for the surface finish and clearance is very high, so that the manufacture quality of impeller leaf represent the level of 5-axis machining. This paper opened a new field in machining the complicated surface, based on a relatively more rigid mathematical basis. The theory presented here is relatively more systematical. Since the lack of theoretical guidance, in the former research, people have to try in machining many times. Such case will be changed. The movement of the cutter determined by this method is definite, and the residual is the smallest while the times of travel is the fewest. The criterion is simple and the calculation is easy.

  15. Computer aided hydraulic design of axial flow pump impeller

    International Nuclear Information System (INIS)

    Sreedhar, B.K.; Rao, A.S.L.K.; Kumaraswamy, S.

    1994-01-01

    Pumps are the heart of any power plant and hence their design requires great attention. Computers with their potential for rapid computation can be successfully employed in the design and manufacture of these machines. The paper discusses a program developed for the hydraulic design of axial flow pump impeller. The program, written in FORTRAN 77, is interactive and performs the functions of design calculation, drafting and generation of numerical data for blade manufacture. The drafting function, which makes use of the software ACAD, is carried out automatically by means of suitable interface programs. In addition data for blade manufacture is also generated in either the x-y-z or r-θ-z system. (author). 4 refs., 3 figs

  16. Booster Pump Performance Analysis Towards Rotation Of Impeller For CSD Dredger Type

    Directory of Open Access Journals (Sweden)

    Tony Bambang Musriyadi

    2017-12-01

    Full Text Available Dredger are a vessel for lift materials from sub surface to another place above the water surface. Dredger divided into some types such Suction Dredger, Bucket Dredger, Backhoe Dredger, and Water Injection Dredger. Cutter Suction Dredger is equipped with a rotating cutter head, for cutting and fragmenting hard soils. The soil is sucked up by means of dredge pumps, and discharged through a floating pipeline and pipes on shore, to a deposit area. In some cases, the material is discharged into split hopper barges that are moored alongside the Cutter Suction Dredger. These split hopper barges unload the soil at the deposit area. The most important part of dredger are the pump unit, NPSH is needed to figure the pump performance ability and how the efficiency number of the pump. Booster pump performance analysist are needed to mantain the pump's performance and efficiency. This thesis are describe about drawing process and computerized simulation at Ansys Software for pump performance with 3 different fluid types and 5 variations of impeller rotation. The number of NPSHa are 6.8 m and 2.8 for the NPSHr. Based on the pure water state, the lowest RPM value of 300 was obtained with V = 1.1366 m / s and Q = 1227.52 m3 / h, the highest RPM value of 600 with the result v = 1.1259 m / s and Q = 1215.97 m3 / h. Then the pumps used in this final project are more efficiently used for fluid types which tend to be condensed from the liquid, and less efficient for use in the state of pure water fluid

  17. Orthogonal decomposition as a design tool: With application to a mixing impeller

    Energy Technology Data Exchange (ETDEWEB)

    Sloan, Benjamin [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    Digital manufacturing eliminates the expense and time required to develop custom products. By utilizing this technology, designers can quickly create a customized product specifically for their performance needs. But the timescale and expense from the engineering design workflows used to develop these customized products have not been adapted from the workflows used in mass production. In many cases these customized designs build upon already successful mass-produced products that were developed using conventional engineering design workflows. Many times as part of this conventional design process significant time is spent creating and validating high fidelity models that accurately predict the performance of the final design. These existing validated high fidelity models used for the mass-produced design can be reused for analysis and design of unknown products. This thesis explores the integration of reduced order modeling and detailed analysis into the engineering design workflow developing a customized design using digital manufacturing. Specifically, detailed analysis is coupled with proper orthogonal decomposition to enable the exploration of the design space while simultaneously shaping the model representing the design. This revised workflow is examined using the design of a laboratory scale overhead mixer impeller. The case study presented here is compared with the design of the Kar Dynamic Mixer impeller developed by The Dow Chemical Company. The result of which is a customized design for a refined set of operating conditions with improved performance.

  18. The Influence of Swirl Brakes and a Tip Discharge Orifice on the Rotordynamic Forces Generated by Discharge-to-Suction Leakage Flows in Shrouded Centrifugal Pumps

    Science.gov (United States)

    Sivo, Joseph M.; Acosta, A. J.; Brennen, C. E.; Caughey, T. K.

    1993-01-01

    Recent experiments conducted in the Rotor Force Test Facility at the California Institute of Technology have examined the effects of a tip leakage restriction and swirl brakes on the rotordynamic forces due to leakage flows on an impeller undergoing a prescribed circular whirl. The experiments simulate the leakage flow conditions and geometry of the Alternate Turbopump Design (ATD) of the Space Shuttle High Pressure Oxygen Turbopump and are critical to evaluating the pump's rotordynamic instability problems. Previous experimental and analytical results have shown that discharge-to-suction leakage flows in the annulus of a shrouded centrifugal pump contribute substantially to the fluid induced rotordynamic forces. Also, previous experiments have shown that leakage inlet (pump discharge) swirl can increase the cross-coupled stiffness coefficient and hence increase the range of positive whirl for which the tangential force is destabilizing. In recent experimental work, the present authors demonstrated that when the swirl velocity within the leakage path is reduced by the introduction of ribs or swirl brakes, then a substantial decrease in both the destabilizing normal and tangential forces could be achieved. Motivation for the present research is that previous experiments have shown that restrictions such as wear rings or orifices at pump inlets affect the leakage forces. Recent pump designs such as the Space Shuttle Alternate Turbopump Design (ATD) utilize tip orifices at discharge for the purpose of establishing axial thrust balance. The ATD has experienced rotordynamic instability problems and one may surmise that these tip discharge orifices may also have an important effect on the normal and tangential forces in the plane of impeller rotation. The present study determines if such tip leakage restrictions contribute to undesirable rotordynamic forces. Additional motivation for the present study is that the widening of the leakage path annular clearance and the

  19. Effectiveness of meta-models for multi-objective optimization of centrifugal impeller

    Energy Technology Data Exchange (ETDEWEB)

    Bellary, Sayed Ahmed Imran; Samad, Abdus [Indian Institute of Technology Madras, Chennai (India); Husain, Afzal [Sultan Qaboos University, Al-Khoudh (Oman)

    2014-12-15

    The major issue of multiple fidelity based analysis and optimization of fluid machinery system depends upon the proper construction of low fidelity model or meta-model. A low fidelity model uses responses obtained from a high fidelity model, and the meta-model is then used to produce population of solutions required for evolutionary algorithm for multi-objective optimization. The Pareto-optimal front which shows functional relationships among the multiple objectives can produce erroneous results if the low fidelity models are not well-constructed. In the present research, response surface approximation and Kriging meta-models were evaluated for their effectiveness for the application in the turbomachinery design and optimization. A high fidelity model such as CFD technique along with the metamodels was used to obtain Pareto-optimal front via multi-objective genetic algorithm. A centrifugal impeller has been considered as case study to find relationship between two conflicting objectives, viz., hydraulic efficiency and head. Design variables from the impeller geometry have been chosen and the responses of the objective functions were evaluated through CFD analysis. The fidelity of each metamodel has been discussed in context of their predictions in entire design space in general and near optimal region in particular. Exploitation of the multiple meta-models enhances the quality of multi-objective optimization and provides the information pertaining to fidelity of optimization model. It was observed that the Kriging meta-model was better suited for this type of problem as it involved less approximation error in the Pareto-optimal front.

  20. Effectiveness of meta-models for multi-objective optimization of centrifugal impeller

    International Nuclear Information System (INIS)

    Bellary, Sayed Ahmed Imran; Samad, Abdus; Husain, Afzal

    2014-01-01

    The major issue of multiple fidelity based analysis and optimization of fluid machinery system depends upon the proper construction of low fidelity model or meta-model. A low fidelity model uses responses obtained from a high fidelity model, and the meta-model is then used to produce population of solutions required for evolutionary algorithm for multi-objective optimization. The Pareto-optimal front which shows functional relationships among the multiple objectives can produce erroneous results if the low fidelity models are not well-constructed. In the present research, response surface approximation and Kriging meta-models were evaluated for their effectiveness for the application in the turbomachinery design and optimization. A high fidelity model such as CFD technique along with the metamodels was used to obtain Pareto-optimal front via multi-objective genetic algorithm. A centrifugal impeller has been considered as case study to find relationship between two conflicting objectives, viz., hydraulic efficiency and head. Design variables from the impeller geometry have been chosen and the responses of the objective functions were evaluated through CFD analysis. The fidelity of each metamodel has been discussed in context of their predictions in entire design space in general and near optimal region in particular. Exploitation of the multiple meta-models enhances the quality of multi-objective optimization and provides the information pertaining to fidelity of optimization model. It was observed that the Kriging meta-model was better suited for this type of problem as it involved less approximation error in the Pareto-optimal front.

  1. Influence of definition of impeller-vaneless diffuser boundary on physical validity of numerical simulations of viscid flow in the vaneless diffuser of a centrifugal compressor: A short review of case studies

    Science.gov (United States)

    Kabalyk, K.; Kryllowicz, W.

    2017-09-01

    The study aims to work out a set of recommendations for setting a proper distance between the trailing edge of impeller and the interface boundary, which on the one hand would not be too large to overpredict the impeller efficiency and not too short to introduce artificial wake-like flow structures at diffuser inlet on the other. Three individual two-element stages belonging to three different types known as medium- and low-flow coefficient stages are studied. Besides of the design flow coefficient, the focus is on the influence of impeller tip Mach number on the optimal location of the boundary.

  2. Wings as impellers: honey bees co-opt flight system to induce nest ventilation and disperse pheromones.

    Science.gov (United States)

    Peters, Jacob M; Gravish, Nick; Combes, Stacey A

    2017-06-15

    Honey bees ( Apis mellifera ) are remarkable fliers that regularly carry heavy loads of nectar and pollen, supported by a flight system - the wings, thorax and flight muscles - that one might assume is optimized for aerial locomotion. However, honey bees also use this system to perform other crucial tasks that are unrelated to flight. When ventilating the nest, bees grip the surface of the comb or nest entrance and fan their wings to drive airflow through the nest, and a similar wing-fanning behavior is used to disperse volatile pheromones from the Nasonov gland. In order to understand how the physical demands of these impeller-like behaviors differ from those of flight, we quantified the flapping kinematics and compared the frequency, amplitude and stroke plane angle during these non-flight behaviors with values reported for hovering honey bees. We also used a particle-based flow visualization technique to determine the direction and speed of airflow generated by a bee performing Nasonov scenting behavior. We found that ventilatory fanning behavior is kinematically distinct from both flight and scenting behavior. Both impeller-like behaviors drive flow parallel to the surface to which the bees are clinging, at typical speeds of just under 1 m s -1 We observed that the wings of fanning and scenting bees frequently contact the ground during the ventral stroke reversal, which may lead to wing wear. Finally, we observed that bees performing Nasonov scenting behavior sometimes display 'clap-and-fling' motions, in which the wings contact each other during the dorsal stroke reversal and fling apart at the start of the downstroke. We conclude that the wings and flight motor of honey bees comprise a multifunctional system, which may be subject to competing selective pressures because of its frequent use as both a propeller and an impeller. © 2017. Published by The Company of Biologists Ltd.

  3. Optimization of a centrifugal compressor impeller using CFD: the choice of simulation model parameters

    Science.gov (United States)

    Neverov, V. V.; Kozhukhov, Y. V.; Yablokov, A. M.; Lebedev, A. A.

    2017-08-01

    Nowadays the optimization using computational fluid dynamics (CFD) plays an important role in the design process of turbomachines. However, for the successful and productive optimization it is necessary to define a simulation model correctly and rationally. The article deals with the choice of a grid and computational domain parameters for optimization of centrifugal compressor impellers using computational fluid dynamics. Searching and applying optimal parameters of the grid model, the computational domain and solver settings allows engineers to carry out a high-accuracy modelling and to use computational capability effectively. The presented research was conducted using Numeca Fine/Turbo package with Spalart-Allmaras and Shear Stress Transport turbulence models. Two radial impellers was investigated: the high-pressure at ψT=0.71 and the low-pressure at ψT=0.43. The following parameters of the computational model were considered: the location of inlet and outlet boundaries, type of mesh topology, size of mesh and mesh parameter y+. Results of the investigation demonstrate that the choice of optimal parameters leads to the significant reduction of the computational time. Optimal parameters in comparison with non-optimal but visually similar parameters can reduce the calculation time up to 4 times. Besides, it is established that some parameters have a major impact on the result of modelling.

  4. Large eddy simulation of a pitched blade impeller mixed vessel - Comparison with LDA measurements

    Czech Academy of Sciences Publication Activity Database

    Vlček, P.; Kysela, Bohuš; Jirout, T.; Fořt, I.

    2016-01-01

    Roč. 108, April (2016), s. 42-48 ISSN 0263-8762. [15th European Conference on Mixing. St. Petersburg, 28.06.2016-03.07.2016] Institutional support: RVO:67985874 Keywords : CFD * LES * mixed vessel * pitched six-blade impeller * ensemble averaged mean velocity * flow rate Subject RIV: BK - Fluid Dynamics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.538, year: 2016 http://www.sciencedirect.com/science/article/pii/S0263876216000836

  5. Force distribution is more important than its intensity!

    Directory of Open Access Journals (Sweden)

    Alberto Consolaro

    2014-01-01

    Full Text Available A common question about root resorption is raised in orthodontic practice: What is more important, the intensity of force or its distribution along the root, periodontal and alveolar structures? Diffuse distribution of forces applied to periodontal tissues during tooth movement tends not to promote neither extensive areas of cell matrix hyalinization nor significant death of cementoblasts that lead to root resorption. However, focal distribution or concentration of forces within a restricted area - as it occurs in tipping movements, even with forces of lower intensity - tend to induce extensive areas of hyalinization and focal death of cementoblasts, which is commonly associated with root resorption. In tipping movements, the apical regions tend to concentrate more forces in addition to wounding the cementoblasts due to the smaller dimension of their root structure as well as their cone shape. For this reason, there is an increase in root resorption. In the cervical region, on the other hand, the large area resulting from a large diameter and bone crown deflection tends to reduce the effects of forces, even when they are more concentrated, thus rarely inducing death of cementoblasts and root resorption.

  6. Numerical Optimization of Impeller for Backward-Curved Centrifugal Fan by Response Surface Methodology (RSM)

    OpenAIRE

    Fannian Meng; Quanlin Dong; Yan Wang; Pengfei Wang; Chunxi Zhang

    2013-01-01

    A numerical optimum study on three-dimensional unsteady viscous flow in a centrifugal fan with backward-curved blades was performed. The influence of the inlet angle, the outlet blade angle and blade number on aerodynamic performance of the centrifugal fan was analyzed concerning the whole impeller-volute configuration. Response Surface Methodology (RSM) based on a three-level, three -variable Box-Behnken Design (BBD) was used to evaluate the interactive effects of factors such as inlet blade...

  7. Numerical Research on Hydraulically Generated Vibration and Noise of a Centrifugal Pump Volute with Impeller Outlet Width Variation

    Directory of Open Access Journals (Sweden)

    Houlin Liu

    2014-01-01

    Full Text Available The impeller outlet width of centrifugal pumps is of significant importance for numbers of effects. In the paper, these effects including the performance, pressure pulsations, hydraulically generated vibration, and noise level are investigated. For the purpose, two approaches were used to predict the vibration and sound radiation of the volute under fluid excitation force. One approach is the combined CFD/FEM analysis for structure vibration, and then the structure response obtained from the FEM analysis is treated as the boundary condition for BEM analysis for sound radiation. The other is the combined CFD/FEM/BEM coupling method. Before the numerical methods were used, the simulation results were validated by the vibration acceleration of the monitoring points on the volute. The vibration and noise were analyzed and compared at three flow conditions. The analysis of the results shows that the influences of the sound pressure of centrifugal pumps on the structure appear insignificant. The relative outlet width b2* at nq(SI = 26.7 in this paper should be less than 0.06, based on an overall consideration of the pump characteristics, pressure pulsations, vibration and noise level.

  8. Tend to Compare and Tend to Be Fair: The Relationship between Social Comparison Sensitivity and Justice Sensitivity

    OpenAIRE

    Zhen, Shanshan; Yu, Rongjun

    2016-01-01

    Social comparison is a prerequisite for processing fairness, although the two types of cognition may be associated with different emotions. Whereas social comparison may induce envy, the perception of unfairness may elicit anger. Yet, it remains unclear whether people who tend to have a strong sense of fairness also tend to compare themselves more with others. Here, Study 1 used a modified ultimatum game (UG) and a social comparison game (SCG) to examine the relationship between justice sensi...

  9. On-line PWR RHR pump performance testing following motor and impeller replacement

    International Nuclear Information System (INIS)

    DiMarzo, J.T.

    1996-01-01

    On-line maintenance and replacement of safety-related pumps requires the performance of an inservice test to determine and confirm the operational readiness of the pumps. In 1995, major maintenance was performed on two Pressurized Water Reactor (PWR) Residual Heat Removal (RHR) Pumps. A refurbished spare motor was overhauled with a new mechanical seal, new motor bearings and equipped with pump's 'B' impeller. The spare was installed into the 'B' train. The motor had never been run in the system before. A pump performance test was developed to verify it's operational readiness and determine the in-situ pump performance curve. Since the unit was operating, emphasis was placed on conducting a highly accurate pump performance test that would ensure that it satisfied the NSSS vendors accident analysis minimum acceptance curve. The design of the RHR System allowed testing of one train while the other was aligned for normal operation. A test flow path was established from the Refueling Water Storage Tank (RWST) through the pump (under test) and back to the RWST. This allowed staff to conduct a full flow range pump performance test. Each train was analyzed and an expression developed that included an error vector term for the TDH (ft), pressure (psig), and flow rate (gpm) using the variance error vector methodology. This method allowed the engineers to select a test instrumentation system that would yield accurate readings and minimal measurement errors, for data taken in the measurement of TDH (P,Q) versus Pump Flow Rate (Q). Test results for the 'B' Train showed performance well in excess of the minimum required. The motor that was originally in the 'B' train was similarly overhauled and equipped with 'A' pump's original impeller, re-installed in the 'A' train, and tested. Analysis of the 'A' train results indicate that the RHR pump's performance was also well in excess of the vendors requirements

  10. On-line PWR RHR pump performance testing following motor and impeller replacement

    Energy Technology Data Exchange (ETDEWEB)

    DiMarzo, J.T.

    1996-12-01

    On-line maintenance and replacement of safety-related pumps requires the performance of an inservice test to determine and confirm the operational readiness of the pumps. In 1995, major maintenance was performed on two Pressurized Water Reactor (PWR) Residual Heat Removal (RHR) Pumps. A refurbished spare motor was overhauled with a new mechanical seal, new motor bearings and equipped with pump`s `B` impeller. The spare was installed into the `B` train. The motor had never been run in the system before. A pump performance test was developed to verify it`s operational readiness and determine the in-situ pump performance curve. Since the unit was operating, emphasis was placed on conducting a highly accurate pump performance test that would ensure that it satisfied the NSSS vendors accident analysis minimum acceptance curve. The design of the RHR System allowed testing of one train while the other was aligned for normal operation. A test flow path was established from the Refueling Water Storage Tank (RWST) through the pump (under test) and back to the RWST. This allowed staff to conduct a full flow range pump performance test. Each train was analyzed and an expression developed that included an error vector term for the TDH (ft), pressure (psig), and flow rate (gpm) using the variance error vector methodology. This method allowed the engineers to select a test instrumentation system that would yield accurate readings and minimal measurement errors, for data taken in the measurement of TDH (P,Q) versus Pump Flow Rate (Q). Test results for the `B` Train showed performance well in excess of the minimum required. The motor that was originally in the `B` train was similarly overhauled and equipped with `A` pump`s original impeller, re-installed in the `A` train, and tested. Analysis of the `A` train results indicate that the RHR pump`s performance was also well in excess of the vendors requirements.

  11. Numerical analysis of flow in ultra micro centrifugal compressor -influence of meridional configuration

    Science.gov (United States)

    Kaneko, Masanao; Tsujita, Hoshio; Hirano, Toshiyuki

    2013-04-01

    A single stage ultra micro centrifugal compressor constituting ultra micro gas turbine is required to operate at high rotational speed in order to achieve the pressure ratio which establishes the gas turbine cycle. As a consequence, the aerodynamic losses can be increased by the interaction of a shock wave with the boundary layer on the blade surface. Moreover, the centrifugal force which exceeds the allowable stress of the impeller material can act on the root of blades. On the other hand, the restrictions of processing technology for the downsizing of impeller not only relatively enlarge the size of tip clearance but also make it difficult to shape the impeller with the three-dimensional blade. Therefore, it is important to establish the design technology for the impeller with the two-dimensional blade which possesses the sufficient aerodynamic performance and enough strength to bear the centrifugal force caused by the high rotational speed. In this study, the flow in two types of impeller with the two-dimensional blade which have different meridional configuration was analyzed numerically. The computed results clarified the influence of the meridional configuration on the loss generations in the impeller passage.

  12. Energy Performance and Radial Force of a Mixed-Flow Pump with Symmetrical and Unsymmetrical Tip Clearances

    Directory of Open Access Journals (Sweden)

    Yue Hao

    2017-01-01

    Full Text Available The energy performance and radial force of a mixed flow pump with symmetrical and unsymmetrical tip clearance are investigated in this paper. As the tip clearance increases, the pump head and efficiency both decrease. The center of the radial force on the principal axis is located at the coordinate origin when the tip clearance is symmetrical, and moves to the third quadrant when the tip clearance is unsymmetrical. Analysis results show that the total radial force on the principal axis is closely related to the fluctuation of mass flow rate in each single flow channel. Unsteady simulations show that the dominant frequencies of radial force on the hub and blade correspond to the blade number, vane number, or double blade number because of the rotor stator interaction. The radial force on the blade pressure side decreases with the tip clearance increase because of leakage flow. The unsymmetrical tip clearances in an impeller induce uneven leakage flow rate and then result in unsymmetrical work ability of each blade and flow pattern in each channel. Thus, the energy performance decreases and the total radial force increases for a mixed flow pump with unsymmetrical tip clearance.

  13. Gravity as Quantum Entanglement Force

    OpenAIRE

    Lee, Jae-Weon; Kim, Hyeong-Chan; Lee, Jungjai

    2010-01-01

    We conjecture that the total quantum entanglement of matter and vacuum in the universe tends to increase with time, like entropy, and that an effective force is associated with this tendency. We also suggest that gravity and dark energy are types of quantum entanglement forces, similar to Verlinde's entropic force, and give holographic dark energy with an equation of state comparable to current observational data. This connection between quantum entanglement and gravity could give some new in...

  14. Experimental and CFD Simulation Studies of Wall Shear Stress for Different Impeller Configurations and MBR Activated Sludge

    DEFF Research Database (Denmark)

    Ratkovich, Nicolas Rios; Chan, C.C.V.; Bentzen, Thomas Ruby

    2012-01-01

    in an MBR. Nevertheless, proper experimental validation is required to validate CFD simulation. In this work experimental measurements of shear stress induced by impellers at a membrane surface were made with an electrochemical approach and the results were used to validate CFD simulations. As good results...... appealing for full-scale applications. It has been widely demonstrated that the filtration performances in MBRs can be improved by understanding the shear stress over the membrane surface. Modern tools such as Computational Fluid Dynamics (CFD) can be used to diagnose and understand the shear stress...

  15. May the Forces Be with You!

    Science.gov (United States)

    Sirola, Christopher

    2018-01-01

    In everyday life, we usually directly note two basic forces: gravity and electromagnetism. Gravity--as in the acceleration due to Earth's gravity--tends to be a background force of sorts, something that is always present and always the same. We don't always see electricity and/or magnetism as such, but their subsidiaries are all around…

  16. New concepts and new design of permanent maglev rotary artificial heart blood pumps.

    Science.gov (United States)

    Qian, K X; Zeng, P; Ru, W M; Yuan, H Y

    2006-05-01

    According to tradition, permanent maglev cannot achieve stable equilibrium. The authors have developed, to the contrary, two stable permanent maglev impeller blood pumps. The first pump is an axially driven uni-ventricular assist pump, in which the rotor with impeller is radially supported by two passive magnetic bearings, but has one point contact with the stator axially at standstill. As the pump raises its rotating speed, the increasing hydrodynamic force of fluid acting on the impeller will make the rotor taking off from contacting point and disaffiliate from the stator. Then the rotor becomes fully suspended. The second pump is a radially driven bi-ventricular assist pump, i.e., an impeller total artificial heart. Its rotor with two impellers on both ends is supported by two passive magnetic bearings, which counteract the attractive force between rotor magnets and stator coil iron core. The rotor is affiliated to the stator radially at standstill and becomes levitated during rotation. Therefore, the rotor keeps concentric with stator during rotation but eccentric at standstill, as is confirmed by rotor position detection with Honeywell sensors. It concludes that the permanent maglev needs action of a non-magnetic force to achieve stability but a rotating magnetic levitator with high speed and large inertia can maintain its stability merely with passive magnetic bearings.

  17. Optimal Design of a Centrifugal Compressor Impeller Using Evolutionary Algorithms

    Directory of Open Access Journals (Sweden)

    Soo-Yong Cho

    2012-01-01

    Full Text Available An optimization study was conducted on a centrifugal compressor. Eight design variables were chosen from the control points for the Bezier curves which widely influenced the geometric variation; four design variables were selected to optimize the flow passage between the hub and the shroud, and other four design variables were used to improve the performance of the impeller blade. As an optimization algorithm, an artificial neural network (ANN was adopted. Initially, the design of experiments was applied to set up the initial data space of the ANN, which was improved during the optimization process using a genetic algorithm. If a result of the ANN reached a higher level, that result was re-calculated by computational fluid dynamics (CFD and was applied to develop a new ANN. The prediction difference between the ANN and CFD was consequently less than 1% after the 6th generation. Using this optimization technique, the computational time for the optimization was greatly reduced and the accuracy of the optimization algorithm was increased. The efficiency was improved by 1.4% without losing the pressure ratio, and Pareto-optimal solutions of the efficiency versus the pressure ratio were obtained through the 21st generation.

  18. Estimation of exhaust gas aerodynamic force on the variable geometry turbocharger actuator: 1D flow model approach

    International Nuclear Information System (INIS)

    Ahmed, Fayez Shakil; Laghrouche, Salah; Mehmood, Adeel; El Bagdouri, Mohammed

    2014-01-01

    Highlights: • Estimation of aerodynamic force on variable turbine geometry vanes and actuator. • Method based on exhaust gas flow modeling. • Simulation tool for integration of aerodynamic force in automotive simulation software. - Abstract: This paper provides a reliable tool for simulating the effects of exhaust gas flow through the variable turbine geometry section of a variable geometry turbocharger (VGT), on flow control mechanism. The main objective is to estimate the resistive aerodynamic force exerted by the flow upon the variable geometry vanes and the controlling actuator, in order to improve the control of vane angles. To achieve this, a 1D model of the exhaust flow is developed using Navier–Stokes equations. As the flow characteristics depend upon the volute geometry, impeller blade force and the existing viscous friction, the related source terms (losses) are also included in the model. In order to guarantee stability, an implicit numerical solver has been developed for the resolution of the Navier–Stokes problem. The resulting simulation tool has been validated through comparison with experimentally obtained values of turbine inlet pressure and the aerodynamic force as measured at the actuator shaft. The simulator shows good compliance with experimental results

  19. 29 CFR 788.7 - “Planting or tending trees.”

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 3 2010-07-01 2010-07-01 false âPlanting or tending trees.â 788.7 Section 788.7 Labor... MORE THAN EIGHT EMPLOYEES ARE EMPLOYED § 788.7 “Planting or tending trees.” Employees employed in “planting or tending trees” include those engaged in weeding, preparing firebreaks, removing “seeding...

  20. Ant tending influences soldier production in a social aphid.

    Science.gov (United States)

    Shingleton, A W; Foster, W A

    2000-09-22

    The aphid Pseudoregma sundanica (Van der Goot) (Homoptera: Aphididae) has two defence strategies. It is obligatorily tended by various species of ant and also produces sterile soldiers. We investigated how they allocate their investment in these two strategies. We measured the size, number of soldiers, number and species of tending ant, and number and species of predators in P. sundanica populations. We found that the level of ant tending correlated negatively with soldier investment in P. sundanica. The species of tending ant also influenced soldier investment. We excluded ants from aphid populations and recorded changes in population size and structure over four weeks. Ant exclusion led to population decline and extinction. At the same time, surviving populations showed a significant increase in soldier investment. The data demonstrate that social aphids can adjust their investment in soldiers in direct response to environmental change.

  1. Gas erosion of impeller housing in the operation of a high-temperature, high-pressure helium circulator

    International Nuclear Information System (INIS)

    Sanders, J.P.; Heestand, R.L.; Young, H.C.

    1987-01-01

    Three gas-bearing circulators are installed in series in a high-pressure, high-temperature loop to provide helium flow up to 0.47 m 3 /s at a total head of 78 kJ/kg. The design pressure is 10.7 MPa, and temperatures of 1000 0 C can be obtained in the test section. The inlet temperature to the circulators is limited to 450 0 C. During a routine examination of the circulator, deep V-shaped grooves were found in the stationary surface of this cavity. At the same time, a very fine, dark particulate was observed in crevices of the housing. At first it was assumed that the grooves were formed by particulate erosion; however, examination of the grooves and discussions with persons experienced with large circulator operation changed this opinion. Erosion caused by particulate is characteristically rounded on the bottom and has a greater width to depth aspect than the V-shaped grooves, which were observed. Analysis of the particulate indicated that it was essentially the material of the housing that had undergone reactions with impurities in the circulating gas. It was subsequently concluded that the impeller housing had not been heat treated in a sufficiently oxidizing atmosphere after machining to form an adherent oxide coating. This suboxide coating was eroded by the shear forces in the gas. The exposed layer of metal was then further oxidized by the impurities in the gas, and these layers of oxide were successively eroded to produce the grooves. This erosion problem was eliminated by machining a ring of the same material, heat treating it to form an adherent stable oxide, and bolting it in place in the cavity

  2. DIGITALIZACIÓN 3D DEL RODETE DE UN COMPRESOR CENTRÍFUGO: UN PROCEDIMIENTO ALTERNATIVO 3D-DIGITIZING OF A CENTRIFUGAL COMPRESSOR'S IMPELLER: AN ALTERNATIVE PROCEDURE

    Directory of Open Access Journals (Sweden)

    Jairo Andrés Acosta Rojas

    2007-12-01

    Full Text Available En la digitalización 3D del rodete del compresor centrífugo de un turbo cargador HT3B, se evaluaron numerosas metodologías que permitieran reproducir su geometría satisfactoriamente, de modo que a partir del modelo virtual obtenido se pudiera llevar a cabo una simulación computacional de flujo en el compresor centrífugo. Tras analizar dichas metodologías se decidió que la toma de tomografías axiales computarizadas era la más indicada, a pesar de que requirió previamente la construcción de un modelo en acrílico del rodete. Una vez se contó con las tomografías axiales computarizadas del rodete, se procedió a construir el modelo virtual del mismo usando un programa CAD 3D, integrando una metodología analítica para la generación de la geometría de los álabes del rodete de un compresor centrífugo, con la información metrológica adquirida a través de las tomografías. El modelo virtual del rodete presentó características aptas para el posterior trabajo de simulación, demostrando que el procedimiento planteado constituye una alternativa viable para la digitalización 3D de piezas mecánicas de alta complejidad.In the 3D digitizing of an HT3B turbocharger's centrifugal compressor's impeller, several methodologies were evaluated, reproducing its shape in such a way, that the obtained virtual model could be used to perform a computational flow simulation in the whole centrifugal compressor. After analyzing these methodologies, computerized axial tomographies were chosen as the most suitable methodology, despite requiring the previous construction of an impeller's acrylic-made model. Once the impeller's computerized axial tomographies had been taken, the generation of the virtual model was performed by software CAD 3D, by integrating an analytic methodology for the impeller's vanes' geometrical shape generation, with the metrological information extracted from the tomographies. The virtual model generated presented

  3. Sub-scale Waterflow Cavitation and Dynamic Transfer Function Testing of an Oxidizer Turbo-Pump Combined Inducer and Impeller

    Science.gov (United States)

    Karon, D. M.; Patel, S. K.; Zoladz, T. F.

    2016-01-01

    In 2009 and 2010, Concepts NREC prepared for and performed a series of tests on a 52% scale of a version of the Pratt & Whitney Rocketdyne J-2X Oxidizer Turbopump under a Phase III SBIR with NASA MSFC. The test article was a combined inducer and impeller, tested as a unit. This paper presents an overview of the test rig and facility, instrumentation, signal conditioning, data acquisition systems, testing approach, measurement developments, and lessons learned. Results from these tests were presented in the form of two papers at the previous JANNAF joint propulsion conference, in December of 2011.

  4. Comportamento mecânico de tendões calcâneo bovino sob informações clínicas Mechanical behaviour of bovine calcaneous tendon under ciclic deformations

    Directory of Open Access Journals (Sweden)

    Sergio Rocha Piedade

    2006-02-01

    Full Text Available Este trabalho teve por finalidade analisar o comportamento de tendões calcâneo bovino submetidos a ensaios mecânicos cíclicos. Para cada corpo de prova foram aplicados três ensaios de dez ciclos de tração e três níveis de deformação: 2,5%, 3% e 4%. Ao término de cada ensaio o tendão era mantido em repouso por 300 s. A velocidade de carregamento adotada foi de 10% do comprimento do corpo de prova, por segundo. Os resultados obtidos foram submetidos à análise de variância com delineamento de parcelas subdivididas no tempo e blocos casualizados nas subparcelas. Conclui-se que o pré-tensionamento de tendões realizado através da deformação relativa permanece como parâmetro mais seguro, por atuar dentro dos limites fisiológicos do tendão, evitando os efeitos nocivos do sobretensionamento.This research work reports an experimental study on the mechanical behavior of bovine calcaneous tendons. A total number of 03 cyclic relaxation tests with 10 cycles respectively at 2,5%, 3%, and 4% of deformation were performed for each specimen. The specimens were kept at rest for 300 s between tests. Deformation rates were maintained at 10% of initial length per second. Cyclic relaxation tests carried on all tendons showed that the average force correspondent to the first cycle was statistically significatively greater than the average force correspondent to the tenth cycle. This also emphasizes the occurrence of a force relaxation phenomena. It can be concluded that tendons pre-tensionning by means of specific deformations stands for a safer parameter because it acts within the tendon biological limits avoyding the overtensioning negative effects.

  5. Study of blades inclination influence of gate impeller with a non-Newtonian fluid of Bingham

    Directory of Open Access Journals (Sweden)

    Rahmani Lakhdar

    2016-01-01

    Full Text Available A large number of chemical operations, biochemical or petrochemical industry is very depending on the rheological fluids nature. In this work, we study the case of highly viscous of viscoplastic fluids in a classical system of agitation: a cylindrical tank with plate bottom without obstacles agitated by gate impeller agitator. We are interested to the laminar, incompressible and isothermal flows. We devote to a numerical approach carried out using an industrial code CFD Fluent 6.3.26 based on the method of finites volumes discretization of Navier - Stokes equations formulated in variables (U.V.P. The threshold of flow related to the viscoplastic behavior is modeled by a theoretical law of Bingham. The results obtained are used to compare between the five configurations suggested of power consumption. We study the influence of inertia by the variation of Reynolds number.

  6. Multi-condition optimization and experimental study of impeller blades in a mixed-flow pump

    Directory of Open Access Journals (Sweden)

    Houlin Liu

    2016-05-01

    Full Text Available On the basis of design of experiment and numerical simulation, a reliable optimization method for blades of a mixed-flow pump is proposed with the maximum weighted average efficiency at multi-conditions as optimum objective. First, the performance of the model pump was measured and the test results were used to validate the simulation method. To improve the simulation accuracy, the check of the grid independence and the comparison of different turbulence models were done in detail. Then, the method of design of experiment for key geometrical parameters was used to obtain the optimization scheme. The maximum weighted average efficiency of pump at three operation conditions was chosen as optimum objective. The optimum solution was gotten and confirmed by the experiment. The results demonstrate that efficiency of the mixed-flow pump with optimized impeller increases by 3.9%, and the high-efficiency zone is increased from 0.021 to 0.040.

  7. Thrombotic Depositions on Right Impeller of Double-Ended Centrifugal Total Artificial Heart In Vivo.

    Science.gov (United States)

    Karimov, Jamshid H; Horvath, David J; Okano, Shinji; Goodin, Mark; Sunagawa, Gengo; Byram, Nicole; Moazami, Nader; Golding, Leonard A R; Fukamachi, Kiyotaka

    2017-05-01

    The development of total artificial heart devices is a complex undertaking that includes chronic biocompatibility assessment of the device. It is considered particularly important to assess whether device design and features can be compatible long term in a biological environment. As part of the development program for the Cleveland Clinic continuous-flow total artificial heart (CFTAH), we evaluated the device for signs of thrombosis and biological material deposition in four animals that had achieved the intended 14-, 30-, or 90-day durations in each respective experiment. Explanted CFTAHs were analyzed for possible clot buildup at "susceptible" areas inside the pump, particularly the right pump impeller. Depositions of various consistency and shapes were observed. We here report our findings, along with macroscopic and microscopic analysis post explant, and provide computational fluid dynamics data with its potential implications for thrombus formation. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  8. Mathematical modeling of mixing phenomena in ladles of aluminium equipped with impeller and gas purging for degassing

    International Nuclear Information System (INIS)

    Ramirez-Argaez, M. A.; Conteras, F.; Gonzalez, C.

    2006-01-01

    In this work a fundamental Eulerian mathematical model was developed to study fluid flow and mixing phenomena in aluminium ladles equipped with impeller for deshidrogenization treatment. The effect of critical process parameters such as rotor speed, depth of immersion, gas flow rate, and type of rotor on the mixing behavior and vortex formation was analyzed with this model. The model simulates operation with and without gas injection and it was developed on the commercial CFD code PHOENICS 3.4 in order to solve all conservation equations governing the process, i. e. continuity, 3D turbulent Navier-Stockers and the kε turbulence model for a two-phase fluid flow problem using the Inter Phase Slip Algorithm (IPSA). (Author). 20 refs

  9. Repulsive Casimir force at zero and finite temperature

    International Nuclear Information System (INIS)

    Lim, S C; Teo, L P

    2009-01-01

    We study the zero and finite temperature Casimir force acting on a perfectly conducting piston with arbitrary cross section moving inside a closed cylinder with infinitely permeable walls. We show that at any temperature, the Casimir force always tends to move the piston away from the walls and toward its equilibrium position. In the case of a rectangular piston, exact expressions for the Casimir force are derived. In the high-temperature regime, we show that the leading term of the Casimir force is linear in temperature and therefore the Casimir force has a classical limit. Due to duality, all these results also hold for an infinitely permeable piston moving inside a closed cylinder with perfectly conducting walls.

  10. Drag force in a D-instanton background

    Science.gov (United States)

    Zhang, Zi-qiang; Luo, Zhong-jie; Hou, De-fu

    2018-06-01

    We study the drag force and diffusion coefficient with respect to a moving heavy quark in a D-instanton background, which corresponds to the Yang-Mills theory in the deconfining, high-temperature phase. It is shown that the presence of the D-instanton density tends to increase the drag force and decrease the diffusion coefficient, reverse to the effects of the velocity and the temperature. Moreover, the inclusion of the D-instanton density makes the medium less viscous.

  11. Radial loads and axial thrusts on centrifugal pumps

    International Nuclear Information System (INIS)

    Anon.

    1986-01-01

    The proceedings of a seminar organised by the Power Industries Division of the IMechE are presented in this text. Complete contents: Review of parameters influencing hydraulic forces on centrifugal impellers; The effect of fluid forces at various operation conditions on the vibrations of vertical turbine pumps; A review of the pump rotor axial equilibrium problem - some case studies; Dynamic hydraulic loading on a centrifugal pump impeller; Experimental research on axial thrust loads of double suction centrifugal pumps; A comparison of pressure distribution and radial loads on centrifugal pumps; A theoretical and experimental investigation of axial thrusts within a multi-stage centrifugal pump

  12. Development of force sensing circuit to determine the optimal force required for effective dynamic tripod grip/writing

    Science.gov (United States)

    Suraj S., S.; Kulkarni, Palash; Bokadia, Pratik; Ramanathan, Prabhu; Nageswaran, Sharmila

    2018-04-01

    Handwriting is a combination of fine motor perceptions and cognitive skills to produce words on paper. For writing, the most commonly used and recommended grip is the dynamic tripod grip. A child's handwriting starts developing during the times of pre-schooling and improves over time. While writing, children apply excessive force on the writing instrument. This force is exerted by their fingers and as per the law of reaction, the writing instruments tend to exert an equal and opposite force, that could damage the delicate soft tissue structures in their fingers and initiate cramps and pains. This condition is also prevalent in adults who tend to write for long hours under pressure. An example would be adolescence student during the exams. Clinically this condition is termed as `Writer's Cramp', which is usually characterized by muscle fatigue and pain in the fingers. By understanding and fixing the threshold of the force that should be exerted by the fingers while gripping the instrument, the pain can be controlled or avoided. This research aims in designing an electronic module which can help in understanding the threshold of pressure which is optimum enough to establish a better contact between the fingers and the instrument and should be capable of controlling or avoiding the pain. The design of FSR based electronic system is explained with its circuitry and results of initial testing is presented in this paper.

  13. Graphemes Sharing Phonetic Features Tend to Induce Similar Synesthetic Colors

    OpenAIRE

    Kang, Mi-Jeong; Kim, Yeseul; Shin, Ji-Young; Kim, Chai-Youn

    2017-01-01

    Individuals with grapheme-color synesthesia experience idiosyncratic colors when viewing achromatic letters or digits. Despite large individual differences in grapheme-color association, synesthetes tend to associate graphemes sharing a perceptual feature with similar synesthetic colors. Sound has been suggested as one such feature. In the present study, we investigated whether graphemes of which representative phonemes have similar phonetic features tend to be associated with analogous synes...

  14. Tend to Compare and Tend to Be Fair: The Relationship between Social Comparison Sensitivity and Justice Sensitivity.

    Science.gov (United States)

    Zhen, Shanshan; Yu, Rongjun

    2016-01-01

    Social comparison is a prerequisite for processing fairness, although the two types of cognition may be associated with different emotions. Whereas social comparison may induce envy, the perception of unfairness may elicit anger. Yet, it remains unclear whether people who tend to have a strong sense of fairness also tend to compare themselves more with others. Here, Study 1 used a modified ultimatum game (UG) and a social comparison game (SCG) to examine the relationship between justice sensitivity and social comparison sensitivity in 51 young adults. Study 2 examined self-reported social comparison and justice sensitivity in 142 young adults. Both studies showed a positive correlation between social comparison sensitivity and justice sensitivity. We reason that social comparison and justice sensitivity have an important positive correlation in human decision-making. The rejection of self-disadvantageous inequality offers may be due to the social comparison effect, which suggests that the tendency to compare oneself with others may contribute to having a strong sense of justice. Our findings suggest that the predictions of game theory may vary depending on the social culture context and incorporating notions of fairness and social comparison tendency may be essential to better predict the actual behavior of players in social interactive situations.

  15. Tend to Compare and Tend to Be Fair: The Relationship between Social Comparison Sensitivity and Justice Sensitivity.

    Directory of Open Access Journals (Sweden)

    Shanshan Zhen

    Full Text Available Social comparison is a prerequisite for processing fairness, although the two types of cognition may be associated with different emotions. Whereas social comparison may induce envy, the perception of unfairness may elicit anger. Yet, it remains unclear whether people who tend to have a strong sense of fairness also tend to compare themselves more with others. Here, Study 1 used a modified ultimatum game (UG and a social comparison game (SCG to examine the relationship between justice sensitivity and social comparison sensitivity in 51 young adults. Study 2 examined self-reported social comparison and justice sensitivity in 142 young adults. Both studies showed a positive correlation between social comparison sensitivity and justice sensitivity. We reason that social comparison and justice sensitivity have an important positive correlation in human decision-making. The rejection of self-disadvantageous inequality offers may be due to the social comparison effect, which suggests that the tendency to compare oneself with others may contribute to having a strong sense of justice. Our findings suggest that the predictions of game theory may vary depending on the social culture context and incorporating notions of fairness and social comparison tendency may be essential to better predict the actual behavior of players in social interactive situations.

  16. Female labor force participation in developing countries

    OpenAIRE

    Verick, Sher

    2014-01-01

    While women’s labor force participation tends to increase with economic development, the relationship is not straightforward or consistent at the country level. There is considerably more variation across developing countries in labor force participation by women than by men. This variation is driven by a wide variety of economic and social factors, which include economic growth, education, and social norms. Looking more broadly at improving women’s access to quality employment, a critica...

  17. Force sharing and other collaborative strategies in a dyadic force perception task.

    Science.gov (United States)

    Tatti, Fabio; Baud-Bovy, Gabriel

    2018-01-01

    When several persons perform a physical task jointly, such as transporting an object together, the interaction force that each person experiences is the sum of the forces applied by all other persons on the same object. Therefore, there is a fundamental ambiguity about the origin of the force that each person experiences. This study investigated the ability of a dyad (two persons) to identify the direction of a small force produced by a haptic device and applied to a jointly held object. In this particular task, the dyad might split the force produced by the haptic device (the external force) in an infinite number of ways, depending on how the two partners interacted physically. A major objective of this study was to understand how the two partners coordinated their action to perceive the direction of the third force that was applied to the jointly held object. This study included a condition where each participant responded independently and another one where the two participants had to agree upon a single negotiated response. The results showed a broad range of behaviors. In general, the external force was not split in a way that would maximize the joint performance. In fact, the external force was often split very unequally, leaving one person without information about the external force. However, the performance was better than expected in this case, which led to the discovery of an unanticipated strategy whereby the person who took all the force transmitted this information to the partner by moving the jointly held object. When the dyad could negotiate the response, we found that the participant with less force information tended to switch his or her response more often.

  18. Grave Tending: With Mom at the Cemetery

    Directory of Open Access Journals (Sweden)

    Carolyn Ellis

    2003-05-01

    Full Text Available This autoethnographic story shows the process of tending the graves of family members. In the past, the author reluctantly accompanied her mother on her visits to the family cemetery. Once there, she took on the role of distant observer as her mother took care of the family cemetery plots. When her mother becomes disabled, the author begins to arrange the flowers on the graves. Doing so leads her to examine the meaning of visiting the cemetery, feel and connect with her losses, and consider the customs she wants to be part of her own death. When her mother dies, the next generation of women in the family—the author, her sister, and sister-in-law—take on the role of tending the graves, connected in their love and respect for their mother and their feelings of family and family responsibility. This story examines the meanings of family rituals around death and how they are passed from generation to generation. URN: urn:nbn:de:0114-fqs0302285

  19. Casimir force in the presence of a medium

    International Nuclear Information System (INIS)

    Kheirandish, Fardin; Soltani, Morteza; Sarabadani, Jalal

    2010-01-01

    We investigate the Casimir effect in the presence of a medium by quantizing the electromagnetic field in the presence of a magnetodielectric medium using the path-integral technique. For a given medium with definite electric and magnetic susceptibilities, explicit expressions for the Casimir force are obtained. The Lifshitz formula is recovered and in the absence of a medium the results tend to the original Casimir force between two conducting parallel plates immersed in the quantum electromagnetic vacuum.

  20. Force sharing and other collaborative strategies in a dyadic force perception task

    Science.gov (United States)

    Tatti, Fabio

    2018-01-01

    When several persons perform a physical task jointly, such as transporting an object together, the interaction force that each person experiences is the sum of the forces applied by all other persons on the same object. Therefore, there is a fundamental ambiguity about the origin of the force that each person experiences. This study investigated the ability of a dyad (two persons) to identify the direction of a small force produced by a haptic device and applied to a jointly held object. In this particular task, the dyad might split the force produced by the haptic device (the external force) in an infinite number of ways, depending on how the two partners interacted physically. A major objective of this study was to understand how the two partners coordinated their action to perceive the direction of the third force that was applied to the jointly held object. This study included a condition where each participant responded independently and another one where the two participants had to agree upon a single negotiated response. The results showed a broad range of behaviors. In general, the external force was not split in a way that would maximize the joint performance. In fact, the external force was often split very unequally, leaving one person without information about the external force. However, the performance was better than expected in this case, which led to the discovery of an unanticipated strategy whereby the person who took all the force transmitted this information to the partner by moving the jointly held object. When the dyad could negotiate the response, we found that the participant with less force information tended to switch his or her response more often. PMID:29474433

  1. Numerical analysis of the internal flow field in screw centrifugal blood pump based on CFD

    Science.gov (United States)

    Han, W.; Han, B. X.; Y Wang, H.; Shen, Z. J.

    2013-12-01

    As to the impeller blood pump, the high speed of the impeller, the local high shear force of the flow field and the flow dead region are the main reasons for blood damage. The screw centrifugal pump can effectively alleviate the problems of the high speed and the high shear stress for the impeller. The softness and non-destructiveness during the transfer process can effectively reduce the extent of the damage. By using CFD software, the characteristics of internal flow are analyzed in the screw centrifugal pump by exploring the distribution rules of the velocity, pressure and shear deformation rate of the blood when it flows through the impeller and the destructive effects of spiral blades on blood. The results show that: the design of magnetic levitation solves the sealing problems; the design of regurgitation holes solves the problem of the flow dead zone; the magnetic levitated microcirculation screw centrifugal pump can effectively avoid the vortex, turbulence and high shear forces generated while the blood is flowing through the pump. Since the distribution rules in the velocity field, pressure field and shear deformation rate of the blood in the blood pump are comparatively uniform and the gradient change is comparatively small, the blood damage is effectively reduced.

  2. Transient flow characteristics of nuclear reactor coolant pump in recessive cavitation transition process

    International Nuclear Information System (INIS)

    Wang Xiuli; Yuan Shouqi; Zhu Rongsheng; Yu Zhijun

    2013-01-01

    The numerical simulation calculation of the transient flow characteristics of nuclear reactor coolant pump in the recessive cavitation transition process in the nuclear reactor coolant pump impeller passage is conducted by CFX, and the transient flow characteristics of nuclear reactor coolant pump in the transition process from reducing the inlet pressure at cavitation-born conditions to NPSHc condition is studied and analyzed. The flow field analysis shows that, in the recessive cavitation transition process, the speed diversification at the inlet is relative to the bubble increasing, and makes the speed near the blade entrance increase when the bubble phase region becomes larger. The bubble generation and collapse will affect the the speed fluctuation near the entrance. The vorticity close to the blade entrance gradually increasing is influenced by the bubble phase, and the collapse of bubble generated by cavitation will reduce the vorticity from the collapse to impeller outlet. Pump asymmetric structure causes the asymmetry of the flow, velocity and outlet pressure distribution within every impeller flow passage, which cause the asymmetry of the transient radial force. From the dimensionless t/T = 0.6, the bubble phase starts to have impact on the impeller transient radial force, and results in the irregular fluctuations. (authors)

  3. Liquid metal pump

    International Nuclear Information System (INIS)

    Pennell, W.E.

    1981-01-01

    A liquid metal pump comprising a shaft support structure which is isolated from the pump housing for better preservation of alignment of shaft bearings. The shaft carries an impeller and the support structure carries an impeller cage which is slidably disposed in a diffuser so as to allow complete removal of pump internals for inspection and repair. The diffuser is concentrically supported in the pump housing which also takes up all reaction forces generated by the discharge of the liquid metal from the diffuser, with floating seals arranged between impeller cage and the diffuser. The space between the diffuser and the pump housing permits the incoming liquid to essentially surround the diffuser. (author)

  4. Rapid Speed Modulation of a Rotary Total Artificial Heart Impeller.

    Science.gov (United States)

    Kleinheyer, Matthias; Timms, Daniel L; Tansley, Geoffrey D; Nestler, Frank; Greatrex, Nicholas A; Frazier, O Howard; Cohn, William E

    2016-09-01

    Unlike the earlier reciprocating volume displacement-type pumps, rotary blood pumps (RBPs) typically operate at a constant rotational speed and produce continuous outflow. When RBP technology is used in constructing a total artificial heart (TAH), the pressure waveform that the TAH produces is flat, without the rise and fall associated with a normal arterial pulse. Several studies have suggested that pulseless circulation may impair microcirculatory perfusion and the autoregulatory response and may contribute to adverse events such as gastrointestinal bleeding, arteriovenous malformations, and pump thrombosis. It may therefore be beneficial to attempt to reproduce pulsatile output, similar to that generated by the native heart, by rapidly modulating the speed of an RBP impeller. The choice of an appropriate speed profile and control strategy to generate physiologic waveforms while minimizing power consumption and blood trauma becomes a challenge. In this study, pump operation modes with six different speed profiles using the BiVACOR TAH were evaluated in vitro. These modes were compared with respect to: hemodynamic pulsatility, which was quantified as surplus hemodynamic energy (SHE); maximum rate of change of pressure (dP/dt); pulse power index; and motor power consumption as a function of pulse pressure. The results showed that the evaluated variables underwent different trends in response to changes in the speed profile shape. The findings indicated a possible trade-off between SHE levels and flow rate pulsatility related to the relative systolic duration in the speed profile. Furthermore, none of the evaluated measures was sufficient to fully characterize hemodynamic pulsatility. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  5. Mechanical Properties and Chemical Resistance of New Composites for Oil Pump Impellers

    Directory of Open Access Journals (Sweden)

    Dilyus I. Chukov

    2018-05-01

    Full Text Available In this paper, a new class of high-performance composites and a method of their production based on the carbonization of an elastomeric matrix are proposed. The use of elastomeric matrix makes it possible to manufacture products with complex shapes, while the subsequent carbonization can significantly improve their properties by changing the chemical nature of the elastomeric matrix. Such an approach can reduce the products’ machining cost, especially for composites reinforced with super hard fillers such as silicon carbide at high filling degrees. Low-temperature carbonization makes it possible to obtain composites with mechanical behavior similar to that of ceramics. In contrast to classical elastomeric materials, the nitrile butadiene rubber (NBR-based compounds were highly filled (300 parts per hundred rubber-PHR with different carbon fillers and silicon carbide; then cured and carbonized at low-temperature 360 °C with the carbonization cycle of 12 h. The feasibility of the production method was validated through the manufacturing of products with complex shapes—impellers for electric centrifugal pumps. It was found that the carbonized composites have good chemical resistance and low water absorption. The composites have high Shore D hardnesses (93–96, ultimate tensile strengths (62–85 MPa, Young’s moduli (17–24 GPa, and compressive strengths (155–181 MPa.

  6. Robotic and Human-Tended Collaborative Drilling Automation for Subsurface Exploration

    Science.gov (United States)

    Glass, Brian; Cannon, Howard; Stoker, Carol; Davis, Kiel

    2005-01-01

    Future in-situ lunar/martian resource utilization and characterization, as well as the scientific search for life on Mars, will require access to the subsurface and hence drilling. Drilling on Earth is hard - an art form more than an engineering discipline. Human operators listen and feel drill string vibrations coming from kilometers underground. Abundant mass and energy make it possible for terrestrial drilling to employ brute-force approaches to failure recovery and system performance issues. Space drilling will require intelligent and autonomous systems for robotic exploration and to support human exploration. Eventual in-situ resource utilization will require deep drilling with probable human-tended operation of large-bore drills, but initial lunar subsurface exploration and near-term ISRU will be accomplished with lightweight, rover-deployable or standalone drills capable of penetrating a few tens of meters in depth. These lightweight exploration drills have a direct counterpart in terrestrial prospecting and ore-body location, and will be designed to operate either human-tended or automated. NASA and industry now are acquiring experience in developing and building low-mass automated planetary prototype drills to design and build a pre-flight lunar prototype targeted for 2011-12 flight opportunities. A successful system will include development of drilling hardware, and automated control software to operate it safely and effectively. This includes control of the drilling hardware, state estimation of both the hardware and the lithography being drilled and state of the hole, and potentially planning and scheduling software suitable for uncertain situations such as drilling. Given that Humans on the Moon or Mars are unlikely to be able to spend protracted EVA periods at a drill site, both human-tended and robotic access to planetary subsurfaces will require some degree of standalone, autonomous drilling capability. Human-robotic coordination will be important

  7. Graphemes Sharing Phonetic Features Tend to Induce Similar Synesthetic Colors.

    Science.gov (United States)

    Kang, Mi-Jeong; Kim, Yeseul; Shin, Ji-Young; Kim, Chai-Youn

    2017-01-01

    Individuals with grapheme-color synesthesia experience idiosyncratic colors when viewing achromatic letters or digits. Despite large individual differences in grapheme-color association, synesthetes tend to associate graphemes sharing a perceptual feature with similar synesthetic colors. Sound has been suggested as one such feature. In the present study, we investigated whether graphemes of which representative phonemes have similar phonetic features tend to be associated with analogous synesthetic colors. We tested five Korean multilingual synesthetes on a color-matching task using graphemes from Korean, English, and Japanese orthography. We then compared the similarity of synesthetic colors induced by those characters sharing a phonetic feature. Results showed that graphemes associated with the same phonetic feature tend to induce synesthetic color in both within- and cross-script analyses. Moreover, this tendency was consistent for graphemes that are not transliterable into each other as well as graphemes that are. These results suggest that it is the perceptual-i.e., phonetic-properties associated with graphemes, not just conceptual associations such as transliteration, that determine synesthetic color.

  8. Graphemes Sharing Phonetic Features Tend to Induce Similar Synesthetic Colors

    Science.gov (United States)

    Kang, Mi-Jeong; Kim, Yeseul; Shin, Ji-Young; Kim, Chai-Youn

    2017-01-01

    Individuals with grapheme-color synesthesia experience idiosyncratic colors when viewing achromatic letters or digits. Despite large individual differences in grapheme-color association, synesthetes tend to associate graphemes sharing a perceptual feature with similar synesthetic colors. Sound has been suggested as one such feature. In the present study, we investigated whether graphemes of which representative phonemes have similar phonetic features tend to be associated with analogous synesthetic colors. We tested five Korean multilingual synesthetes on a color-matching task using graphemes from Korean, English, and Japanese orthography. We then compared the similarity of synesthetic colors induced by those characters sharing a phonetic feature. Results showed that graphemes associated with the same phonetic feature tend to induce synesthetic color in both within- and cross-script analyses. Moreover, this tendency was consistent for graphemes that are not transliterable into each other as well as graphemes that are. These results suggest that it is the perceptual—i.e., phonetic—properties associated with graphemes, not just conceptual associations such as transliteration, that determine synesthetic color. PMID:28348537

  9. Characterization of magnetically impelled arc butt welded T11 tubes for high pressure applications

    Directory of Open Access Journals (Sweden)

    R. Sivasankari

    2015-09-01

    Full Text Available Magnetically impelled arc butt (MIAB welding is a pressure welding process used for joining of pipes and tubes with an external magnetic field affecting arc rotation along the tube circumference. In this work, MIAB welding of low alloy steel (T11 tubes were carried out to study the microstructural changes occurring in thermo-mechanically affected zone (TMAZ. To qualify the process for the welding applications where pressure could be up to 300 bar, the MIAB welds are studied with variations of arc current and arc rotation time. It is found that TMAZ shows higher hardness than that in base metal and displays higher weld tensile strength and ductility due to bainitic transformation. The effect of arc current on the weld interface is also detailed and is found to be defect free at higher values of arc currents. The results reveal that MIAB welded samples exhibits good structural property correlation for high pressure applications with an added benefit of enhanced productivity at lower cost. The study will enable the use of MIAB welding for high pressure applications in power and defence sectors.

  10. How We Tend To Overestimate Powerlaw Tail Exponents

    OpenAIRE

    Nassim N. Taleb

    2012-01-01

    In the presence of a layer of metaprobabilities (from uncertainty concerning the parameters), the asymptotic tail exponent corresponds to the lowest possible tail exponent regardless of its probability. The problem explains "Black Swan" effects, i.e., why measurements tend to chronically underestimate tail contributions, rather than merely deliver imprecise but unbiased estimates.

  11. A qualitative model for strategic analysis of organizations. Application and alternative proposal on a study case

    Directory of Open Access Journals (Sweden)

    Santiago Ferro Moreno

    2015-12-01

    Full Text Available The strategic analysis of organizations is based on the internal and external environments, in order to identify positive and negative variables and factors. The interrelation and timing of these strategic forces are essential to create alternative solutions that tend to achieve the organizational objectives.The normative prospective has theorical and methodological foundations to create a desired future and from it, be able to identify impelling and restraining forces that have influence on the particular problematic situation (go from the current situation to a better one in a certain time.The aim of this article is to analyze on a strategic way a real case with a normative-prospective model that considers the temporal dynamics of the factors impact and variables in time allowing to suggest alternative solutions.Semi-structured interviews were performed with all the employees of this case and structured observations and workshops with the commercial and general management.In consequence, with the results, the desired, current and improved situations were built. Additionally, forces were identified classified and appreciated and lastly solutions were suggested. With the proposed prospective method, alternative solutions could be constructed in order to settle temporary organizational objectives. No constraints were found to use the current method in other cases.Keywords: Strategic forces, Normative prospective, Problematic situations, Strategies

  12. Serum carcinoembryonic antigen tends to decrease in poorly-differentiated colorectal cancer

    Directory of Open Access Journals (Sweden)

    Ester Morina Silalahi

    2015-12-01

    This was a cross-sectional study conducted on 40 CRC subjects from July 2012 until May 2013. Determination of serum CEA and CA 19-9 levels and histopathological (cellular differentiation grades in CRC biopsies was done in all subjects. RESULTS The study involved forty CRC patients, consisting of 22 males and 18 females, with mean age of 51.93 ± 11.63 years, CEA levels of 51.93 ± 84.07 ng/ml and CA 19-9 levels of 33.81 ± 62.39 U/ml. Carcino-embryonic antigen levels tended to decrease with decreasing CRC histopathological grade, while CA 19-9 levels increased in well-differentiated CRC. However, both relationships were statistically not significant (with p=0.314 and p=0.787, respectively. CONCLUSIONS Carcinoembryonic antigen (CEA levels tend to decrease with decreasing histopathological grade of CRC, and CA 19-9 levels tend to increase in well-differentiated CRC.

  13. A new model of cavern diameter based on a validated CFD study on stirring of a highly shear-thinning fluid.

    Science.gov (United States)

    Story, Anna; Jaworski, Zdzisław

    2017-01-01

    Results of numerical simulations of momentum transfer for a highly shear-thinning fluid (0.2% Carbopol) in a stirred tank equipped with a Prochem Maxflo T type impeller are presented. The simulation results were validated using LDA data and both tangential and axial force measurements in the laminar and early transitional flow range. A good agreement between the predicted and experimental results of the local fluid velocity components was found. From the predicted and experimental values of both tangential and axial forces, the power number, Po , and thrust number, Th , were also calculated. Values of the absolute relative deviations were below 4.0 and 10.5%, respectively, for Po and Th , which confirms a satisfactory agreement with experiments. An intensive mixing zone, known as cavern, was observed near the impeller. In this zone, the local values of fluid velocity, strain rate, Metzner-Otto coefficient, shear stress and intensity of energy dissipation were all characterized by strong variability. Based on the results of experimental study a new model using non-dimensional impeller force number was proposed to predict the cavern diameter. Comparative numerical simulations were also carried out for a Newtonian fluid (water) and their results were similarly well verified using LDA measurements, as well as experimental power number values.

  14. Unification of Forces: The Road to Jointness?

    Science.gov (United States)

    1991-05-15

    tend to resist large change--or innovation. Because organizations value "predictability, stability, and certainty," incremental change is the...preferred mode of behavior for organizations.29 Unification of the forces would be a large, rather than an incremental , change; thus, the services would...coordinating planning and bidgeting , providing unified direction, accounting and controlling weapons and equipment acquisition, eliminating duplication of

  15. Gas erosion of impeller housing in the operation of a high-temperature, high-pressure helium circulator

    International Nuclear Information System (INIS)

    Sanders, J.P.; Heestand, R.L.; Young, H.C.

    1988-01-01

    Three gas-bearing circulators are installed in series in a high-pressure, high-temperature loop to provide helium flow up to 0.47 m 3 /s at a total head of 78 kJ/kg. The design pressure is 10.7 MPa, and temperatures of 1000 deg. C can be obtained in the test section. The inlet temperature to the circulators is limited to 450 deg. C. The 200-kW motor for each circulator is enclosed in the pressure boundary, and the motor is cooled by circulating the gas within the cavity over a water-cooled coil. The full operating speed is 23,500 rpm. A full-flow filter, absolute for particulate above 10 μm, is installed upstream of the circulator to protect the gas bearing surfaces. The minimum clearances between these surfaces during operation are in the range of 15 to 30 μm. During a routine examination of the circulator, deep V-shaped grooves were found in the stationary surface of this cavity. At the same time, a very fine, dark particulate was observed in crevices of the housing. At first it was assumed that the grooves were formed by particulate erosion; however, examination of the grooves and discussions with persons experienced with large circulator operation changed this opinion. Erosion caused by particulate is characteristically rounded on the bottom and has a greater width to depth aspect than the V-shaped grooves, which were observed. Analysis of the particulate indicated that it was essentially the material of the housing that had undergone reactions with impurities in the circulating gas. It was subsequently concluded that the impeller housing had not been heat treated in a sufficiently oxidizing atmosphere after machining to form an adherent oxide coating. This suboxide coating was eroded by the shear forces in the gas. The exposed layer of metal was then further oxidized by the impurities in the gas, and these layers of oxide were successively eroded to produce the grooves. This erosion problem was eliminated by machining a ring of the same material, heat

  16. Numerical investigation of solid-liquid two phase flow in a non-clogging centrifugal pump at off-design conditions

    International Nuclear Information System (INIS)

    Zhao, B J; Chen, H L; Hou, D H; Huang, Z F

    2012-01-01

    The solid-liquid two-phase flow fields in the non-clogging centrifugal pump with a double-channel impeller have been investigated numerically for the design condition and also off-design conditions, in order to study the solid-liquid two-phase flow pattern and non-clogging mechanism in non-clogging centrifugal pumps. The main conclusions include: The sand volume fraction distribution is extremely inhomogeneous in the whole flow channel of the pump at off-design conditions. In the impeller, particles mainly flow along the pressure surface and hub; In the volute, particles mainly accumulate in the region near to the exit of volute, the largest sand volume fraction is observed at the tongue, and a large number of particles collide with volute wall and exit the volute after circling around the volute for several times. When the particle diameter increases, particles tend to accumulate on the pressure side of the impeller, and more particles crash with the pressure side of the blade. And larger sand volume fraction gratitude is also observed in the whole flow channel of the pump. With the decrease of the inlet sand volume fraction, particles tend to accumulate on the suction side of the blade. Compared with the particle diameter, the inlet sand volume fraction has less influence on the sand volume fraction gratitude in the whole channel of the pump. At the large flow rate, the minimum and maximum sand volume fraction in the whole flow channel of the model pump tends to be smaller than that at the small flow rate. Thus, it is concluded that the water transportation capacity increases with the flow rate. This research will strengthen people's understanding of the multiphase flow pattern in non-clogging centrifugal pumps, thus provides a theoretical basis for the optimal design of non-clogging centrifugal pumps.

  17. Classical description of dynamical many-body systems with central forces, spin-orbit forces and spin-spin forces

    International Nuclear Information System (INIS)

    Goepfert, A.

    1994-01-01

    This thesis develops a new model, and related numerical methods, to describe classical time-dependent many-body systems interacting through central forces, spin-orbit forces and spin-spin forces. The model is based on two-particle interactions. The two-body forces consist of attractive and repulsive parts. In this model the investigated multi-particle systems are self-bound. Also the total potential of the whole ensemble is derived from the two-particle potential and is not imposed 'from outside'. Each particle has the three degrees of freedom of its centre-of-mass motion and the spin degree of freedom. The model allows for the particles to be either charged or uncharged. Furthermore, each particle has an angular momentum, an intrinsic spin, and a magnetic dipole moment. Through the electromagnetic forces between these charges and moments there arise dynamical couplings between them. The internal interactions between the charges and moments are well described by electromagnetic coupling mechanisms. In fact, compared to conventional classical molecular dynamics calculations in van der Waals clusters, which have no spin degrees of freedom, or for Heisenberg spin Systems, which have no orbital degrees of freedom, the model presented here contains both types of degrees of freedom with a highly non-trivial coupling. The model allows to study the fundamental effects resulting from the dynamical coupling of the spin and the orbital-motion sub-systems. In particular, the dynamics of the particle mass points show a behaviour basically different from the one of particles in a potential with only central forces. Furthermore, a special type of quenching procedure was invented, which tends to drive the multi-particle Systems into states with highly periodic, non-ergodic behaviour. Application of the model to cluster simulations has provided evidence that the model can also be used to investigate items like solid-to-liquid phase transitions (melting), isomerism and specific heat

  18. Tendências em séries anuais de precipitação e temperaturas no Brasil

    Directory of Open Access Journals (Sweden)

    Júlio César Penereiro

    Full Text Available RESUMO Nas últimas décadas, pesquisadores científicos e acadêmicos em todo o mundo têm se preocupado com a avaliação das tendências dos climas regional e global. A avaliação das alterações no clima é uma ferramenta para o planejamento da sociedade, pois permite considerar as possíveis consequências do aumento das temperaturas do ar e de mudanças no regime de precipitação que foram observadas ao redor do mundo. Sob a hipótese da presença de alterações climáticas no Brasil, o objetivo do presente estudo foi identificar a existência de tendências climáticas em 243 séries anuais de temperaturas máxima, mínima e média do ar (T-Máx., T-Mín. e T-Méd. e precipitação pluviométrica (Prec. em cidades do Brasil. Foram empregados os testes estatísticos de Mann-Kendall (M-K. e Pettitt (Pett. para avaliação de tendências significativas. Para a visualização espacial das tendências observadas, foram elaborados mapas. Os resultados estatísticos mostram que, de todas as cidades estudadas, foram observadas tendências positivas na T-máx. em 35% das séries, negativas em 1% e ausência de tendência em 64%. Para a T-Mín., foram observadas tendências positivas em 30% dos casos, negativas em 8% e ausência de tendência em 63%. Na T-Méd., tendência positiva foi detectada em 35% das cidades analisadas, negativa em 3% e ausência de tendência em 62%. Por fim, na Prec., tendência positiva em 6% dos casos, negativa em 4% e ausência de tendência em 91%. As tendências observadas no presente estudo estão possivelmente relacionadas às atividades antrópicas em cada localidade, como o expansionismo urbano, o desenvolvimento industrial e o adensamento populacional.

  19. Determination of Pressure Fluctuations in Rotor Bundle of Centrifugal Compressor at Critical Conditions of Operation

    Science.gov (United States)

    Levashov, V. A.; Lyubchenko, K. Yu

    2017-08-01

    This article describes the physical processes that occur in the stage flow part of the compressor while it is operating and can create conditions for the occurrence of forced vibrations, which in turn can lead to the destruction of the impellers. Critical conditions of compressor operation are determined. To understand that critical condition of operation is cause of the destruction of the impellers, transient CFD analysis was carried for test stage of compressor. The obtained pressure fluctuation amplitudes allow to evaluate the critical conditions of compressor operation.

  20. The Structure of Tactical Revolution in the U.S. Army from 1968 to 1986

    National Research Council Canada - National Science Library

    Donovan, George

    1998-01-01

    .... This monograph uses ideas suggested in Thomas Kuhn's book, The Structure of Scientific Revolution, to examine the forces that impelled doctrinal change, the manner in which change occurred, and the consequences...

  1. Literature survey, numerical examples, and recommended design studies for main-coolant pumps. Final report

    International Nuclear Information System (INIS)

    Allaire, P.E.; Barrett, L.E.

    1982-06-01

    This report presents an up-to-date literature survey, examples of calculations of seal forces or other pump properties, and recommendations for future work pertaining to primary coolant pumps and primary recirculating pumps in the nuclear power industry. Five main areas are covered: pump impeller forces, fluid annuli, bearings, seals, and rotor calculations. The main conclusion is that forces in pump impellers is perhaps the least well understood area, seals have had some good design work done on them recently, fluid annuli effects are being discussed in the literature, bearing designs are fairly well known, and rotor calculations have been discussed widely in the literature. It should be noted, however, that usually the literature in a given area is not applied to pumps in nuclear power stations. The most immediate need for a combined theoretical and experimental design capability exists in mechanical face seals

  2. Plasmon-mediated binding forces on gold or silver homodimer and heterodimer

    International Nuclear Information System (INIS)

    Liaw, Jiunn-Woei; Kuo, Ting-Yu; Kuo, Mao-Kuen

    2016-01-01

    This study theoretically investigates plasmon-mediated optical binding forces, which are exerted on metal homo or heterodimers, induced by the normal illumination of a linearly polarized plane wave or Gaussian beam. Using the multiple multipole method, we analyzed the optical force in terms of Maxwell's stress tensor for various interparticle distance at some specific wavelengths. Numerical results show that for a given wavelength there are several stable equilibrium distances between two nanoparticles (NPs) of a homodimer, which are slightly shorter than some integer multiples of the wavelength in medium, such that metal dimer acts as bonded together. At these specific interparticle distances, the optical force between dimer is null and serves a restoring force, which is repulsive and attractive, respectively, as the two NPs are moving closer to and away from each other. The spring constant of the restoring force at the first stable equilibrium is always the largest, indicating that the first stable equilibrium distance is the most stable one. Moreover, the central line (orientation) of a dimer tends to be perpendicular to the polarization of light. For the cases of heterodimers, the phenomenon of stable equilibrium interparticle distance still exists, except there is an extra net photophoretic force drifting the heterodimer as one. Moreover, gradient force provided by a Gaussian beam may reduce the stability of these equilibriums, so larger NPs are preferred to stabilize a dimer under illumination of Gaussian beam. The finding may pave the way for using optical manipulation on the gold or silver colloidal self-assembly. - Highlights: • Optical binding force on Au/Ag dimer by linearly polarized light is studied. • For a wavelength several stable equilibriums for homodimer bound together exist. • The central line of a dimer tends to be perpendicular to the polarization of light. • For a heterodimer, stable equilibriums still exist with a net photophoretic

  3. Bibliotecas escolares: tendências globais

    Directory of Open Access Journals (Sweden)

    Kelley Cristine Gonçalves Dias Gasque

    2016-09-01

    Full Text Available Este artigo aborda as transformações do processo de ensinoaprendizagem e das tecnologias e o impacto dessas nas bibliotecas escolares, especificamente, na formação do acervo, na configuração do espaço e no papel dos bibliotecários. A análise da literatura mostra tendência à adoção de modelos de aprendizagem baseados na construção colaborativa do conhecimento, com ênfase na aprendizagem compreensiva e atividades de ensino em ambientes diversificados. As bibliotecas escolares podem acolher e subsidiar atividades de ensino variadas, transformando-se em locais não apenas de apropriação da informação, mas também de produção do conhecimento por meio de atividades colaborativas, conectadas e diversificadas. O bibliotecário precisa fortalecer o domínio de tecnologias para obtenção, gerenciamento, produção e compartilhamento de informações. O fomento à leitura continua a ser importante, mas precisa ser ampliado para diferentes suportes e formatos.

  4. Stimulus Control: The Sought or Unsought Influence of the Objects We Tend to

    Science.gov (United States)

    Morsella, Ezequiel; Larson, Lindsay R. L.; Zarolia, Pareezad; Bargh, John A.

    2011-01-01

    Does the mere presence of the things we have tended to influence our actions systematically, in ways that escape our awareness? For example, while entering a tool shed, does perceiving objects that we once tended to (e.g., tools, musical instruments) influence how we then execute a simple action (e.g., flicking the shed's light switch)? Ancient…

  5. [Effects of target tree tending on community structure and diversity in subtropical natural secondary shrubs].

    Science.gov (United States)

    Zhang, Hui; Zhou, Guo Mo; Bai, Shang Bin; Wang, Yi Xiang; You, Yu Jie; Zhu, Ting Ting; Zhang, Hua Feng

    2017-05-18

    The typical natural secondary shrub community was chosen in Lin'an of Zhejiang Pro-vince to discover its possibility of restoration to arbor forest with three kinds of forest management models being taken, i.e., no care as control, closed forest management and target tree tending. Over four years growth, compared with control, closed forest management significantly increased average DBH and height by 130% and 50%, respectively, while 260% and 110% for target tree tending. In target tree tending plots, larger trees had been emerging with 4.5-8.5 cm diameter class and 4.5-8.5 m height class and formed a new storey of 4 m compared with control. The species biodiversity indexes at shrub layer were significantly increased in closed management plots, and did not decrease in target tree tending plots. Closed forest management did not change the tree species composition, following its previous succession direction. However, target tree tending increased the importance value of target species with the high potential succession direction of mixed coniferous-broadleaved forest. The results revealed that the secondary shrub community with target tree tending achieved more desired goals on DBH and height growth of dominant trees and species composition improvement compared with closed management. If the secondary shrub community could be managed when the operational conditions existed, target tree tending model should be selected to accelerate the restoration of shrub toward arbor forest.

  6. Do centrioles generate a polar ejection force?

    Science.gov (United States)

    Wells, Jonathan

    2005-01-01

    A microtubule-dependent polar ejection force that pushes chromosomes away from spindle poles during prometaphase is observed in animal cells but not in the cells of higher plants. Elongating microtubules and kinesin-like motor molecules have been proposed as possible causes, but neither accounts for all the data. In the hypothesis proposed here a polar ejection force is generated by centrioles, which are found in animals but not in higher plants. Centrioles consist of nine microtubule triplets arranged like the blades of a tiny turbine. Instead of viewing centrioles through the spectacles of molecular reductionism and neo-Darwinism, this hypothesis assumes that they are holistically designed to be turbines. Orthogonally oriented centriolar turbines could generate oscillations in spindle microtubules that resemble the motion produced by a laboratory vortexer. The result would be a microtubule-mediated ejection force tending to move chromosomes away from the spindle axis and the poles. A rise in intracellular calcium at the onset of anaphase could regulate the polar ejection force by shutting down the centriolar turbines, but defective regulation could result in an excessive force that contributes to the chromosomal instability characteristic of most cancer cells.

  7. Kepler Planets Tend to Have Siblings of the Same Size

    Science.gov (United States)

    Kohler, Susanna

    2017-11-01

    After 8.5 years of observations with the Kepler space observatory, weve discovered a large number of close-in, tightly-spaced, multiple-planet systems orbiting distant stars. In the process, weve learned a lot about the properties about these systems and discovered some unexpected behavior. A new study explores one of the properties that has surprised us: planets of the same size tend to live together.Orbital architectures for 25 of the authors multiplanet systems. The dots are sized according to the planets relative radii and colored according to mass. Planets of similar sizes and masses tend to live together in the same system. [Millholland et al. 2017]Ordering of SystemsFrom Keplers observations of extrasolar multiplanet systems, we have seen that the sizes of planets in a given system arent completely random. Systems that contain a large planet, for example, are more likely to contain additional large planets rather than additional planets of random size. So though there is a large spread in the radii weve observed for transiting exoplanets, the spread within any given multiplanet system tends to be much smaller.This odd behavior has led us to ask whether this clustering occurs not just for radius, but also for mass. Since the multiplanet systems discovered by Kepler most often contain super-Earths and mini-Neptunes, which have an extremely large spread in densities, the fact that two such planets have similar radii does not guarantee that they have similar masses.If planets dont cluster in mass within a system, this would raise the question of why planets coordinate only their radii within a given system. If they do cluster in mass, it implies that planets within the same system tend to have similar densities, potentially allowing us to predict the sizes and masses of planets we might find in a given system.Insight into MassesLed by NSF graduate research fellow Sarah Millholland, a team of scientists at Yale University used recently determined masses for

  8. Knot probability of polygons subjected to a force: a Monte Carlo study

    International Nuclear Information System (INIS)

    Rensburg, E J Janse van; Orlandini, E; Tesi, M C; Whittington, S G

    2008-01-01

    We use Monte Carlo methods to study the knot probability of lattice polygons on the cubic lattice in the presence of an external force f. The force is coupled to the span of the polygons along a lattice direction, say the z-direction. If the force is negative polygons are squeezed (the compressive regime), while positive forces tend to stretch the polygons along the z-direction (the tensile regime). For sufficiently large positive forces we verify that the Pincus scaling law in the force-extension curve holds. At a fixed number of edges n the knot probability is a decreasing function of the force. For a fixed force the knot probability approaches unity as 1 - exp(-α 0 (f)n + o(n)), where α 0 (f) is positive and a decreasing function of f. We also examine the average of the absolute value of the writhe and we verify the square root growth law (known for f = 0) for all values of f

  9. A Study on the Ionosphere and Thermosphere Interaction Based on NCAR-TIEGCM: Dependence of the Interplanetary Magnetic Field (IMF on the Momentum Forcing in the High-Latitude Lower Thermosphere

    Directory of Open Access Journals (Sweden)

    Young-Sil Kwak

    2005-06-01

    Full Text Available To understand the physical processes that control the high-latitude lower thermospheric dynamics, we quantify the forces that are mainly responsible for maintaining the high-latitude lower thermospheric wind system with the aid of the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM. Momentum forcing is statistically analyzed in magnetic coordinates, and its behavior with respect to the magnitude and orientation of the interplanetary magnetic field (IMF is further examined. By subtracting the values with zero IMF from those with non-zero IMF, we obtained the difference winds and forces in the high-latitude lower thermosphere( 0.8 |bar{B}_z| or negative(B_y 0.3125 |bar{B}_y| or negative(B_z 125 km the primary forces that determine the variations of the neutral winds are the pressure gradient, Coriolis and rotational Pedersen ion drag forces; however, at various locations and times significant contributions can be made by the horizontal advection force. On the other hand, at lower altitudes(108-125 km the pressure gradient, Coriolis and non-rotational Hall ion drag forces determine the variations of the neutral winds. At lower altitudes(<108 km it tends to generate a geostrophic motion with the balance between the pressure gradient and Coriolis forces. The northward component of IMF bar{B}_y-dependent average momentum forces act more significantly on the neutral motion except for the ion drag. At lower altitudes(108-125 km for negative IMF-bar{B}_y condition the ion drag force tends to generate a warm clockwise circulation with downward vertical motion associated with the adiabatic compress heating in the polar cap region. For positive IMF-bar{B}_y condition it tends to generate a cold anticlockwise circulation with upward vertical motion associated with the adiabatic expansion cooling in the polar cap region. For negative IMF-bar{B}_z the ion drag force tends to generate a

  10. Tendências de pesquisas brasileiras sobre mulheres mastectomizadas

    OpenAIRE

    Azevedo, Elisângela Braga de; Bezerra, Pollyana Amorim Ponce de Leon; Neto, José Melquiades Ramalho; Bustorff, Leila Alcina Correia Vaz; Souto, Cláudia Maria Ramos Medeiros

    2012-01-01

    Objetivou-se analisar as tendências das pesquisas realizadas no Brasil sobre mulheres mastectomizadas. Trata-se de um estudo bibliográfico de abordagem quantitativa, realizado de 15 de junho a 31 de julho de 2009. Para coleta dos dados empíricos utilizou-se um instrumento estruturado, posteriormente os dados foram tabulados, analisados, transformados em porcentagens e agrupados em uma tabela para facilitar a visualização das informações. A amostra foi constituída por resumos adquiridos atravé...

  11. Study on flow the impeller outlet of a winnowing fan. 1st Report. Comparisons on the flow between experiments and CFD; Karami fan no haneguruma deguchibu kinbo no nagare ni kansuru kenkyu. 1. Hane shuhen no nagare ni tsuite no CFD to jikkenchitono hikaku

    Energy Technology Data Exchange (ETDEWEB)

    Kawase, M. [Tokushima University, Tokushima (Japan); Fukutomi, J.; Nakase, Y. [Tokushima University, Tokushima (Japan). Faculty of Engineering

    2000-03-25

    The winnowing fan used for head feeding type combines draw in air along the axis from the inlet of both sides, and then radially discharges it into scroll. Therefore, the internal flow of this fan shows a strong three-dimensionality and the efficiency is low. In order to improve the efficiency and make the axial distribution of discharge flow uniform, the experimental and numerical investigations were carried out. Numerical results using CFD agree well with experimental ones for the mean flow. It is found that this numerical simulation method is useful for investigation of the effect of blade and casing configurations. Moreover unsteady flow conditions in the impeller though rotations are shown. For example, in the impeller, a vortex formed around the leading edge of the blade, grows connect with another one, reduce and disappear. (author)

  12. Force estimation from ensembles of Golgi tendon organs

    Science.gov (United States)

    Mileusnic, M. P.; Loeb, G. E.

    2009-06-01

    Golgi tendon organs (GTOs) located in the skeletal muscles provide the central nervous system with information about muscle tension. The ensemble firing of all GTO receptors in the muscle has been hypothesized to represent a reliable measure of the whole muscle force but the precision and accuracy of that information are largely unknown because it is impossible to record activity simultaneously from all GTOs in a muscle. In this study, we combined a new mathematical model of force sampling and transduction in individual GTOs with various models of motor unit (MU) organization and recruitment simulating various normal, pathological and neural prosthetic conditions. Our study suggests that in the intact muscle the ensemble GTO activity accurately encodes force information according to a nonlinear, monotonic relationship that has its steepest slope for low force levels and tends to saturate at the highest force levels. The relationship between the aggregate GTO activity and whole muscle tension under some pathological conditions is similar to one seen in the intact muscle during rapidly modulated, phasic excitation of the motor pool (typical for many natural movements) but quite different when the muscle is activated slowly or held at a given force level. Substantial deviations were also observed during simulated functional electrical stimulation.

  13. Chiral forces and molecular dissymmetry

    International Nuclear Information System (INIS)

    Mohan, R.

    1992-01-01

    Chiral molecules leading to helical macromolecules seem to preserve information and extend it better. In the biological world RNA is the very paradigm for self-replication, elongation and autocatalytic editing. The nucleic acid itself is not chiral. It acquires its chirality by association with D-sugars. Although the chiral information or selectivity put in by the unit monomer is no longer of much interest to the biologists - they tend to leave it to the Darwinian selection principle to take care of it as illustrated by Frank's model - it is vital to understand the origin of chirality. There are three different approaches for the chiral origin of life: (1) Phenomenological, (2) Electromagnetic molecular and Coriolis forces and (3) Atomic or nuclear force, the neutral weak current. The phenomenological approach involves spontaneous symmetry breaking fluctuations in far for equilibrium systems or nucleation and crystallization. Chance plays a major role in the chiral molecule selected

  14. Submersible canned motor mixer pump

    International Nuclear Information System (INIS)

    Guardiani, R.F.; Pollick, R.D.

    1997-01-01

    A mixer pump is described used in a waste tank for mobilizing high-level radioactive liquid waste having a column assembly containing power cables, a motor housing with electric motor means which includes a stator can of a stator assembly and a rotor can of a rotor assembly, and an impeller assembly with an impeller connected to a shaft of the rotor assembly. The column assembly locates the motor housing with the electric motor means adjacent to the impeller which creates an hydraulic head, and which forces the liquid waste into the motor housing to cool the electric motor means and to lubricate radial and thrust bearing assemblies. Hard-on-hard bearing surfaces of the bearing assemblies and a ring assembly between the impeller and electric motor means act to grind down large particles in the liquid waste flow. These larger particles are received in slots in the static bearing members of the radial bearing assemblies. Only solid waste particles smaller than the clearances in the system can pass there through, thereby resisting damage to and the interruption of the operation of the mixer pump. 10 figs

  15. Relation of polymer properties and local temperature distribution in a stirred-type batch reactor using several types of impellers; Kakushu han`yo yokutsuki jugo hanno sonai ni okeru ondomura to jugobutsu bussei no kankei

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, K [Soken Chemical and Engineering Co. Ltd., Tokyo (Japan); Kaminoyama, M; Nishi, K; Kamiwano, M [Yokohama National University, Yokohama (Japan). Faculty of Engineering

    1996-07-10

    In polymerization involving a rapid exothermic reaction, it is necessary for the generated heat in this operation to be removed from the reactor by a cooling coil or jacket to control the reaction temperature. But, fluid in the reactor is gets stagnant as the reaction proceeds, because the viscosity is increasing due to monomer convection, therefore the reactor often has induced uneven temperature distribution. In this work, radical addition polymerization was carried out in a reactor using several types of impeller-paddle, anchor, helical screw and helical ribbon, Under these conditions, local temperature distribution was measured in detail using our prototype real-time and multi-point temperature measuring instrument which is able to measure simultaneously changing temperature at local positions via many thermocouples. As a result of these experiments the condition of changing local temperature and the obtained polymers were found to be related to the type of impellers. We found the high temperature areas in the reactor produced polymers composed of undesirably short chain length molecules. As the cooling condition of the reactor was found by measuring local temperature, we could also find a suitable position for the control sensor of temperature for lowering local higher temperature in the polymerization under the set value. 15 refs., 8 figs., 2 tabs.

  16. Tendências da desigualdade salarial para coortes de mulheres brancas e negras no Brasil

    Directory of Open Access Journals (Sweden)

    Ana Maria Hermeto Camilo de Oliveira

    2006-06-01

    Full Text Available É feita uma análise das tendências da desigualdade salarial da força de trabalho feminina no Brasil, segundo a raça, durante as décadas de 1980 e 1990. Crescentes retornos de qualificação e crescente demanda por trabalho qualificado resultam em uma divergência do crescimento salarial entre os trabalhadores com alta e baixa qualificação. Este crescente hiato resulta em um aumento da desigualdade salarial por raça. Com o propósito de interpretar as tendências, são examinadas diferenças por raça nos padrões de casamento, fecundidade, arranjos domiciliares, níveis educacionais, participação na força de trabalho, níveis de qualificação, alocação ocupacional e salários, distinguindo entre medidas de período e coorte. São usados dados provenientes das PNADs 1987-1999 para analisar a importância de mudanças inter e intracoortes para mulheres brancas e negras. Funções salariais são estimadas a partir dos dados agregados da série temporal de cross sections, usando mínimos quadrados ordinários e regressões quantílicas.We analyze trends of wage inequality of the Brazilian female labor force, by race, during the 1980s and 1990s. Increasing returns to skills and increasing demand for skilled labor result in a divergence of wages growth between high and low skilled workers. This increasing gap results in an increase of wage inequality by race. In order to interpret trends, we take into account race differences in marriage patterns, fertility, household arrangements, educational levels, labor market participation, skill levels, occupational location and earnings, distinguishing between period and cohort measures. We use 1987-1999 Brazilian Household Sample Surveys data to examine the importance of within- and between-cohort changes for black and white women. Earnings functions are estimated from the pooled time-series of these cross-section data, using OLS and quantile regressions.

  17. Soy-isoflavone supplementation tends to reduce menopausal symptoms in postmenopausal women

    Directory of Open Access Journals (Sweden)

    Raditya Wratsangka

    2013-08-01

    Full Text Available Background Menopausal symptoms in postmenopausal women tend to decrease health-related quality of life (HRQoL. The present study’s objective was to determine the effect of daily supplementation of 100 mg soy isoflavones on menopausal symptoms of healthy postmenopausal women. Isoflavones are phytoestrogens abundantly found in soy beans, and several studies have demonstrated that isoflavones are the best among the phytoestrogens. Methods The study was a community-based double blind randomized controlled trial involving 60 healthy postmenopausal women, aged between 48–60 years, in the Mampang Prapatan District, South Jakarta. Participants were block-randomized to receive either 100 mg soy-isoflavone + 500 mg calcium carbonate (intervention group or 500 mg calcium carbonate only (control group. Both supplements were taken daily for 12 weeks, from January to April 2010. Menopausal symptoms (measured by Menopause Rating Scale questionnaire were assessed at baseline and after supplementation. Chi-square test was used to examine the effect of soy isoflavone supplementation on menopausal symptoms. Results Fifty-six (93.3% of participants completed the study. There were no statistically significant differences (p>0.05 in the prevalence of menopausal symptoms between the isoflavone group and the control group. However, supplementation of soy isoflavones for 12 weeks tended to decrease the prevalence of menopausal symptoms in women with normal body mass index and adequate daily dietary isoflavone intake. Conclusion Daily supplementation of 100 mg soy isoflavones for 12 weeks tend to decrease the incidence of menopausal symptoms in postmenopausal women.

  18. Black carbon radiative forcing at TOA decreased during aging.

    Science.gov (United States)

    Wu, Yu; Cheng, Tianhai; Zheng, Lijuan; Chen, Hao

    2016-12-05

    During aging processing, black carbon (also called soot) particles may tend to be mixed with other aerosols, and highly influence their radiative forcing. In this study, freshly emitted soot particles were simulated as fractal aggregates composed of small spherical primary monomers. After aging in the atmosphere, soot monomers were coated by a thinly layer of sulfate as thinly coated soot particles. These soot particles were entirely embedded into large sulfate particle by further aging, and becoming heavily coated soot particles. In clear-sky conditions, black carbon radiative forcing with different aging states were investigated for the bottom and top of atmosphere (BOA and TOA). The simulations showed that black carbon radiative forcing increased at BOA and decreased at TOA after their aging processes. Thinly and heavily coated states increased up to ~12% and ~35% black carbon radiative forcing at BOA, and black carbon radiative forcing at TOA can reach to ~20% and ~100% smaller for thinly and heavily coated states than those of freshly emitted states, respectively. The effect of aging states of black carbon radiative forcing was varied with surface albedo, aerosol optical depth and solar zenith angles. These findings would be helpful for the assessments of climate change.

  19. Predatory behavior of Pseudodorus clavatus (Diptera, Syrphidae on aphids tended by ants

    Directory of Open Access Journals (Sweden)

    Alexandra Bächtold

    2013-12-01

    Full Text Available Predatory behavior of Pseudodorus clavatus (Diptera, Syrphidae on aphids tended by ants. In this study, we examined the interactions between myrmecophilous aphids, their ant-guards and a predatory syrphid species, Pseudodorus clavatus (F.. Larvae of this predator were found in the colonies of three aphid species: Aphis gossypii, A. spiraecola and Toxoptera sp., which were tended by eight ant species, especially Camponotus. Hoverfly larvae managed to infiltrate the aphid colonies and consume nymphs. Predator larvae exhibited inconspicuous movements and were not detected by ants which were commonly observed touching and antennating the larvae they come into contact. These results suggest that behavioral and chemical cues are involved in the infiltration and on the successful predation of syrphids upon aphids.

  20. Towards an extended Gogny force. History, state of the art and perspectives

    Energy Technology Data Exchange (ETDEWEB)

    Pillet, N.; Hilaire, S. [CEA, DAM, DIF, Arpajon (France)

    2017-10-15

    In this paper, we present a recent evolution of the analytical form of the Gogny force. The extension of the density-dependent term to a finite range is discussed and has led to the D2 Gogny force. A global refitting of the force has been done but preserving standard good properties of the Gogny force. Indeed the same fitting procedure with the same constraints and filters which have been used to obtain the D1-type parametrizations has been applied. The evolution of global properties (binding energies and nuclear radii) along the N = 8, 20, 28, 40 isotopic chains is discussed at the Hartree-Fock-Bogoliubov approximation level. Results coming from systematic calculations based on 1385 nuclei are also presented. Axial symmetry has been assumed. A comparison with the results obtained using the D1S parametrization, which tends to show that the D2 and the D1S Gogny force display very similar axial deformation properties, is done. (orig.)

  1. Study on the Performance of a Centrifugal Compressor Using Fluid-Structure Interaction Method

    Energy Technology Data Exchange (ETDEWEB)

    Lee Horim; Hwang, Yoonjei; Jeong, Jinhee [LG Electronics, Seoul (Korea, Republic of); Kim, Changhee; Yang, Jangsik; Son, Changmin [Pusan Nat’l Univ., Busan (Korea, Republic of)

    2016-06-15

    In this study, we perform a series of aero-thermo-mechanical analyses to predict the running-tip clearance and the effects of impeller deformation on the performance using a centrifugal compressor. During operation, the impeller deformation due to a combination of the centrifugal force, aerodynamic pressure and the thermal load results in a non-uniform tip clearance profile. For the prediction, we employ the one-way fluid-structure interaction (FSI) method using CFX 14.5 and ANSYS. The predicted running tip clearance shows a non-uniform profile over the entire flow passage. In particular, a significant reduction of the tip clearance height occurred at the leading and trailing edges of the impeller. Because of the reduction of the tip clearance, the tip leakage flow decreased by 19.4% In addition, the polytrophic efficiency under operating conditions increased by 0.72%. These findings confirm that the prediction of the running tip clearance and its impact on compressor performance is an important area that requires further investigation.

  2. Study on the Performance of a Centrifugal Compressor Using Fluid-Structure Interaction Method

    International Nuclear Information System (INIS)

    Lee Horim; Hwang, Yoonjei; Jeong, Jinhee; Kim, Changhee; Yang, Jangsik; Son, Changmin

    2016-01-01

    In this study, we perform a series of aero-thermo-mechanical analyses to predict the running-tip clearance and the effects of impeller deformation on the performance using a centrifugal compressor. During operation, the impeller deformation due to a combination of the centrifugal force, aerodynamic pressure and the thermal load results in a non-uniform tip clearance profile. For the prediction, we employ the one-way fluid-structure interaction (FSI) method using CFX 14.5 and ANSYS. The predicted running tip clearance shows a non-uniform profile over the entire flow passage. In particular, a significant reduction of the tip clearance height occurred at the leading and trailing edges of the impeller. Because of the reduction of the tip clearance, the tip leakage flow decreased by 19.4% In addition, the polytrophic efficiency under operating conditions increased by 0.72%. These findings confirm that the prediction of the running tip clearance and its impact on compressor performance is an important area that requires further investigation.

  3. PIV pictures of stream field predict haemolysis index of centrifugal pump with streamlined impeller.

    Science.gov (United States)

    Qian, K X; Feng, Z G; Ru, W M; Zeng, P; Yuan, H Y

    2007-01-01

    Previously it has been found by pump haemolysis testing that the flow rate has a remarkable effect on index of haemolysis (IH), while pressure head does not affect IH. Recent investigation with particle image velocimetry (PIV) technology has demonstrated that IH is directly related to the flow pattern of stream field in impeller vane channels. PIV is a visible approach showing the real flow status in the pump. The different positions of a tracer particle in two PIV pictures taken at 20 micros intervals decide the velocity value and direction. The velocity vectors of many particles draw the flow pattern of the stream field. The same pictures are taken at 2, 4 and 6 l min(-1) flow rates while the pressure head is kept unchanged at 100 mmHg; then the pictures are taken at 4 l min(-1) flow with different pressure heads of 80, 100 and 120 mmHg. Results reveal that the flow rate of 4 l min(-1) (IH = 0.030) has the best stream field, and neither turbulence nor separation can be seen. In other flow rates (IH: 0.048 - 0.082), there is obviously second flow. Meanwhile, no significant difference can be seen among the PIV pictures of different pressure heads pumped, which agrees with the results of haemolysis testing showing that pressure has no effect on pump haemolysis. It may be concluded that the haemolysis property of a centrifugal pump can be assessed approximately by PIV pictures, which are much easier to take than haemolysis tests.

  4. On transition from Alfvén resonance to forced magnetic reconnection

    International Nuclear Information System (INIS)

    Luan, Q.; Wang, X.

    2014-01-01

    We revisit the transition from Alfvén resonance to forced magnetic reconnection with a focus on the property of their singularities. As the driven frequency tends to zero, the logarithmic singularity of Alfvén resonance shifts to the power-law singularity of forced reconnection, due to merging of the two resonance layers. The transition criterion depends on either kinetic effects or dissipations that resolve the singularity. As an example, a small but finite resistivity η is introduced to investigate the transition process. The transition threshold is then obtained as the driven frequency reaches a level of ∼O((η/k) 1/3 )

  5. Correlation of changes in the employment costs and average task load with rates of accidents attributed to human error

    NARCIS (Netherlands)

    Karanikas, Nektarios

    2015-01-01

    Market competition and global financial uncertainty have been the principal drivers that impel aviation companies to proceed to budget cuts, including decreases in salary and work force levels, in order to ensure viability and sustainability. Under the concepts of Maslow and Herzberg’s motivation

  6. Investigation of Two-Phase Flow in AxialCentrifugal Impeller by Hydrodynamic Modeling Methods

    Directory of Open Access Journals (Sweden)

    V. O. Lomakin

    2014-01-01

    Full Text Available The article provides a methodology to study the flow in the wet part of the pump with fundamentally new axial-centrifugal impeller by methods of hydrodynamic modeling in the software package STAR CCM +. The objective of the study was to determine the normal and cavitation characteristics of the pump with a new type of wet part, as well as optimization of the geometrical parameters of the pump. Authors solved this problem using an example of the hot coolant pump, which should meet high requirements for cavitation quality and efficiency (hydraulic efficiency up to 87%, critical value of NPSH to 2.2 m.Also, the article focuses on the methods of numerical solution of two-phase flow simulation in a pump that are needed for a more accurate simulation of cavitation in the pump and research work in liquids with high gas content.Hydrodynamic modeling was performed on a computing cluster at the department E-10 of BMSTU for pump flow simulation in unsteady statement of problem using the computational grid size to 1.5 million cells. Simultaneously, the experimental model of the pump was made by 3D printing and tested at the stand in the BMSTU. Test results, which were compared with the calculated data are also given in the article. Inaccuracy of the calculation of pump head does not exceed 5%.The simulation results may be of interest to specialists in the field of hydrodynamic modeling, and for designers of such pumps. The authors also report production of a full-length prototype of the pump in order to conduct further testing for the verification of the data in the article, primarily in terms of cavitation characteristics.

  7. Application of a compressible flow solver and barotropic cavitation model for the evaluation of the suction head in a low specific speed centrifugal pump impeller channel

    International Nuclear Information System (INIS)

    Limbach, P; Müller, T; Skoda, R

    2015-01-01

    Commonly, for the simulation of cavitation in centrifugal pumps incompressible flow solvers with VOF kind cavitation models are applied. Since the source/sink terms of the void fraction transport equation are based on simplified bubble dynamics, empirical parameters may need to be adjusted to the particular pump operating point. In the present study a barotropic cavitation model, which is based solely on thermodynamic fluid properties and does not include any empirical parameters, is applied on a single flow channel of a pump impeller in combination with a time-explicit viscous compressible flow solver. The suction head curves (head drop) are compared to the results of an incompressible implicit standard industrial CFD tool and are predicted qualitatively correct by the barotropic model. (paper)

  8. Axial Force Analysis and Balance for Semi-open Centrifugal Pump Impeller%半开式离心泵轴向力分析及平衡

    Institute of Scientific and Technical Information of China (English)

    陶晓

    2016-01-01

    When pump working, an axial force will be generated, affecting reliability and life time of pump.Using computational fluid dynamics method, the performance parameters of the pump at different speeds were obtained.The calculation results were very close to test results.It was proved that the simulation mode and computational method are relatively reliable.On the pump, balance holes with different diameter were cut to reduce axial force.The results show that the balance hole can effectively reduce axial force, at the same time it has little effect on the other properties of pump.At last, for the balance hole the optimum diameter is 2 mm.%泵在工作过程中存在着轴向力,影响泵的可靠性及使用寿命。利用计算流体力学方法,计算泵在不同转速下的性能参数,与试验结果相近,证明该计算模型、计算方法相对可信。进而对该模型开不同直径的平衡孔以泄压平衡轴向力。结果表明:平衡孔能够有效降低轴向力,同时对其他性能的影响较小。并选取直径2 mm平衡孔作为优选方案。

  9. Estudio comparativo de cirugía percutánea del tendón de Aquiles asistida ecográficamente con la cirugía abierta convencional en roturas de tendón de Aquiles

    OpenAIRE

    Rubio Lorenzo, Mónica

    2017-01-01

    RESUMEN:El tendón de Aquiles es el tendón que con más frecuencia se rompe del cuerpo humano. Generalmente ocurre en la etapa laboral y deportiva de la vida, y conllevan complicaciones postquirúrgicas, tiempo de incapacidad laboral y restringen la calidad de vida de los pacientes, limitando su actividad deportiva y cotidiana posterior. Desarrollamos una técnica percutánea ecoguiada, y lo comparamos con la técnica convencional abierta. Encontramos que: existen diferencias significativa...

  10. Corrosion Control of Central Vehicle Wash Facility Pump Components Using Alternative Alloy Coatings

    Science.gov (United States)

    2016-07-01

    bles near the metal/solution interface that is especially prevalent in pump impellers (Fontana 1986). When the bubbles implode due to high pressure...defective in total area). The coatings were nonsacrificial protective materials of the sort that ASTM B537 is in- tended to evaluate. In addition, cavitation...be considered detrimental, but not a protec- tion defect. The new pump coatings are protective, non-sacrificial coatings of the sort that ASTM B537 is

  11. Heritability of Tpeak-Tend Interval and T-wave Amplitude: A Twin Study

    DEFF Research Database (Denmark)

    Haarmark, Christian; Kyvik, Kirsten O; Vedel-Larsen, Esben

    2011-01-01

    BACKGROUND: -Tpeak-Tend interval (TpTe) and T-wave amplitude (Tamp) carry diagnostic and prognostic information regarding cardiac morbidity and mortality. Heart rate and QT interval are known to be heritable traits. The heritability of T-wave morphology parameters such as TpTe and Tamp is unknown...... interval, QTpeak and QTend interval) were measured and averaged over three consecutive beats in lead V5. TpTe was calculated as the QTend and QTpeak interval difference. Heritability was assessed using structural equation models adjusting for age, gender and BMI. All models were reducible to a model...... of additive genetics and unique environment. All variables had considerable genetic components. Adjusted heritability estimates were: TpTe 46%, Tamp lead V1 34%, Tamp lead V5 47%, RR interval 55%, QT interval 67% and QTcB 42%. CONCLUSIONS: -RR interval, QT-interval, T-wave amplitude and Tpeak-Tend interval...

  12. Unsteady steady-states: central causes of unintentional force drift.

    Science.gov (United States)

    Ambike, Satyajit; Mattos, Daniela; Zatsiorsky, Vladimir M; Latash, Mark L

    2016-12-01

    We applied the theory of synergies to analyze the processes that lead to unintentional decline in isometric fingertip force when visual feedback of the produced force is removed. We tracked the changes in hypothetical control variables involved in single fingertip force production based on the equilibrium-point hypothesis, namely the fingertip referent coordinate (R FT ) and its apparent stiffness (C FT ). The system's state is defined by a point in the {R FT ; C FT } space. We tested the hypothesis that, after visual feedback removal, this point (1) moves along directions leading to drop in the output fingertip force, and (2) has even greater motion along directions that leaves the force unchanged. Subjects produced a prescribed fingertip force using visual feedback and attempted to maintain this force for 15 s after the feedback was removed. We used the "inverse piano" apparatus to apply small and smooth positional perturbations to fingers at various times after visual feedback removal. The time courses of R FT and C FT showed that force drop was mostly due to a drift in R FT toward the actual fingertip position. Three analysis techniques, namely hyperbolic regression, surrogate data analysis, and computation of motor-equivalent and non-motor-equivalent motions, suggested strong covariation in R FT and C FT stabilizing the force magnitude. Finally, the changes in the two hypothetical control variables {R FT ; C FT } relative to their average trends also displayed covariation. On the whole, the findings suggest that unintentional force drop is associated with (a) a slow drift of the referent coordinate that pulls the system toward a low-energy state and (b) a faster synergic motion of R FT and C FT that tends to stabilize the output fingertip force about the slowly drifting equilibrium point.

  13. Submersible canned motor transfer pump

    International Nuclear Information System (INIS)

    Guardiani, R.F.; Pollick, R.D.; Nyilas, C.P.; Denmeade, T.J.

    1997-01-01

    A transfer pump is described which is used in a waste tank for transferring high-level radioactive liquid waste from a waste tank and having a column assembly, a canned electric motor means, and an impeller assembly with an upper impeller and a lower impeller connected to a shaft of a rotor assembly. The column assembly locates a motor housing with the electric motor means adjacent to the impeller assembly which creates an hydraulic head, and which forces the liquid waste, into the motor housing to cool the electric motor means and to cool and/or lubricate the radial and thrust bearing assemblies. Hard-on-hard bearing surfaces of the bearing assemblies and a ring assembly between the upper impeller and electric motor means grind large particles in the liquid waste flow. Slots in the static bearing member of the radial bearing assemblies further grind down the solid waste particles so that only particles smaller than the clearances in the system can pass there through, thereby resisting damage to and the interruption of the operation of the transfer pump. The column assembly is modular so that sections can be easily assembled, disassembled and/or removed. A second embodiment employs a stator jacket which provides an alternate means for cooling the electric motor means and lubricating and/or cooling the bearing assemblies, and a third embodiment employs a variable level suction device which allows liquid waste to be drawn into the transfer pump from varying and discrete levels in the waste tank. 17 figs

  14. Study on solid-liquid two-phase unsteady flow characteristics with different flow rates in screw centrifugal pump

    International Nuclear Information System (INIS)

    Li, R N; Wang, H Y; Han, W; Shen, Z J; Ma, W

    2013-01-01

    The screw centrifugal pump is used as an object, and the unsteady numerical simulation of solid-liquid two-phase flow is carried out under different flow rate conditions in one circle by choosing the two-phase flow of sand and water as medium, using the software FLUENT based on the URANS equations, combining with sliding mesh method, and choosing the Mixture multiphase flow model and the SIMPLE algorithm. The results show that, with the flow rate increasing, the change trends for the pressure on volute outlet are almost constant, the fluctuation trends of the impeller axial force have a little change, the pressure and the axial force turn to decrease on the whole, the radial force gradually increases when the impeller maximum radius passes by half a cycle near the volute outlet, and the radial force gradually decreases when the maximum radius passes by the other half a cycle in a rotation cycle. The distributions of the solid particles are very uneven under a small flow rate condition on the face. The solid particles under a big flow rate condition are distributed more evenly than the ones under a small flow rate condition on the back. The theoretical basis and reference are provided for improving its working performance

  15. The evolution of vertical climbing in primates: evidence from reaction forces.

    Science.gov (United States)

    Hanna, Jandy B; Granatosky, Michael C; Rana, Pooja; Schmitt, Daniel

    2017-09-01

    Vertical climbing is an essential behavior for arboreal animals, yet limb mechanics during climbing are poorly understood and rarely compared with those observed during horizontal walking. Primates commonly engage in both arboreal walking and vertical climbing, and this makes them an ideal taxa in which to compare these locomotor forms. Additionally, primates exhibit unusual limb mechanics compared with most other quadrupeds, with weight distribution biased towards the hindlimbs, a pattern that is argued to have evolved in response to the challenges of arboreal walking. Here we test an alternative hypothesis that functional differentiation between the limbs evolved initially as a response to climbing. Eight primate species were recorded locomoting on instrumented vertical and horizontal simulated arboreal runways. Forces along the axis of, and normal to, the support were recorded. During walking, all primates displayed forelimbs that were net braking, and hindlimbs that were net propulsive. In contrast, both limbs served a propulsive role during climbing. In all species, except the lorisids, the hindlimbs produced greater propulsive forces than the forelimbs during climbing. During climbing, the hindlimbs tends to support compressive loads, while the forelimb forces tend to be primarily tensile. This functional disparity appears to be body-size dependent. The tensile loading of the forelimbs versus the compressive loading of the hindlimbs observed during climbing may have important evolutionary implications for primates, and it may be the case that hindlimb-biased weight support exhibited during quadrupedal walking in primates may be derived from their basal condition of climbing thin branches. © 2017. Published by The Company of Biologists Ltd.

  16. Enhanced Global Monsoon in Present Warm Period Due to Natural and Anthropogenic Forcings

    Directory of Open Access Journals (Sweden)

    Jing Chai

    2018-04-01

    Full Text Available In this study, we investigate global monsoon precipitation (GMP changes between the Present Warm Period (PWP, 1900–2000 and the Little Ice Age (LIA, 1250–1850 by performing millennium sensitivity simulations using the Community Earth System Model version 1.0 (CESM1. Three millennium simulations are carried out under time-varying solar, volcanic and greenhouse gas (GHG forcing, respectively, from 501 to 2000 AD. Compared to the global-mean surface temperature of the cold LIA, the global warming in the PWP caused by high GHG concentration is about 0.42 °C, by strong solar radiation is 0.14 °C, and by decreased volcanic activity is 0.07 °C. The GMP increases in these three types of global warming are comparable, being 0.12, 0.058, and 0.055 mm day−1, respectively. For one degree of global warming, the GMP increase induced by strong GHG forcing is 2.2% °C−1, by strong solar radiation is 2.8% °C−1, and by decreased volcanic forcing is 5.5% °C−1, which means that volcanic forcing is most effective in terms of changing the GMP among these three external forcing factors. Under volcanic inactivity-related global warming, both monsoon moisture and circulation are enhanced, and the enhanced circulation mainly occurs in the Northern Hemisphere (NH. The circulation, however, is weakened in the other two cases, and the GMP intensification is mainly caused by increased moisture. Due to large NH volcanic aerosol concentration in the LIA, the inter-hemispheric thermal contrast of PWP global warming tends to enhance NH monsoon circulation. Compared to the GHG forcing, solar radiation tends to warm low-latitude regions and cause a greater monsoon moisture increase, resulting in a stronger GMP increase. The finding in this study is important for predicting the GMP in future anthropogenic global warming when a change in natural solar or volcanic activity occurs.

  17. Factors That May Tend to Limit the Religious Education of Recruits

    Science.gov (United States)

    1992-05-01

    chaplains also mentioned the following as tending to limit recruit religious education : (1) a lack of adequate chapel facilities , (2) not enough chaplains...inadequate chapel facilities at Recruit Training Command for recruit worship and religious education . This is a particular concern for the Catholic and... education . Procedures Data was gathered by distributing questionnaires to members of Division Six on October 22-23, 1991. Participation was voluntary

  18. Tendências em medicina laboratorial Trends in laboratory medicine

    Directory of Open Access Journals (Sweden)

    Gustavo Aguiar Campana

    2011-08-01

    Full Text Available A patologia clínica/medicina laboratorial é uma especialidade direcionada à realização de exames complementares no auxílio ao diagnóstico, com impacto nos diferentes estágios da cadeia de saúde: prevenção, diagnóstico, prognóstico e acompanhamento terapêutico. Diversos elementos apontam para maior utilização da medicina diagnóstica no futuro. Para discutirmos as principais tendências na medicina laboratorial, descrevemos os fatores que colaboram e são fundamentais para o crescimento desse mercado denominados, neste estudo, drivers de crescimento. As principais tendências que terão forte impacto na medicina laboratorial, e que serão descritas neste artigo, são: ferramentas de gestão, inserção de novos testes no mercado e rol de procedimentos, qualidade dos serviços em medicina diagnóstica, modelos de operação, automação, consolidação e integração, tecnologia da informação, medicina personalizada e genética. Sabemos que a medicina diagnóstica demonstra sua importância ao participar de 70% das decisões clínicas, absorvendo uma pequena parte dos custos em saúde (cerca de 10%. Todas as tendências analisadas neste trabalho apontam para um crescimento na utilização dos exames laboratoriais e também para sua importância na cadeia de saúde. Esse novo posicionamento, somado às novas expectativas de alta resolubilidade, pressiona o mercado e as companhias que o compõem a buscar mudanças e novas estratégias de atuação.Clinical pathology/laboratory medicine, a specialty focused on performing complementary tests to aid diagnosis, has impact upon several stages of health care: prevention, diagnosis, prognosis, and therapeutic management. There are several factors that will foster the use of laboratory medicine in the future. In order to discuss the main trends in laboratory medicine, this article describes the major factors that have promoted growth in this market, which herein are referred to as growth

  19. Optimization of residual heat removal pump axial thrust and axial bearing

    International Nuclear Information System (INIS)

    Schubert, F.

    1996-01-01

    The residual heat removal (RHR) pumps of German 1300 megawatt pressurized-water reactor (PWR) power plants are of the single stage end suction type with volute casing or with diffuser and forged circular casing. Due to the service conditions the pumps have to cover the full capacity range as well as a big variation in suction static pressure. This results in a big difference in the axial thrust that has to be borne by the axial bearing. Because these pumps are designed to operate without auxiliary systems (things that do not exist can not fail), they are equipped with antifriction bearings and sump oil lubrication. To minimize the heat production within the bearing casing, a number of PWR plants have pumps with combined axial/radial bearings of the ball type. Due to the fact that the maximum axial thrust caused by static pressure and hydrodynamic forces on the impeller is too big to be borne by that type of axial bearing, the impellers were designed to produce a hydrodynamic axial force that counteracts the static axial force. Thus, the resulting axial thrust may change direction when the static pressure varies

  20. Optimization of residual heat removal pump axial thrust and axial bearing

    Energy Technology Data Exchange (ETDEWEB)

    Schubert, F.

    1996-12-01

    The residual heat removal (RHR) pumps of German 1300 megawatt pressurized-water reactor (PWR) power plants are of the single stage end suction type with volute casing or with diffuser and forged circular casing. Due to the service conditions the pumps have to cover the full capacity range as well as a big variation in suction static pressure. This results in a big difference in the axial thrust that has to be borne by the axial bearing. Because these pumps are designed to operate without auxiliary systems (things that do not exist can not fail), they are equipped with antifriction bearings and sump oil lubrication. To minimize the heat production within the bearing casing, a number of PWR plants have pumps with combined axial/radial bearings of the ball type. Due to the fact that the maximum axial thrust caused by static pressure and hydrodynamic forces on the impeller is too big to be borne by that type of axial bearing, the impellers were designed to produce a hydrodynamic axial force that counteracts the static axial force. Thus, the resulting axial thrust may change direction when the static pressure varies.

  1. Cloud-to-ground lightning in Portugal: patterns and dynamical forcing

    Science.gov (United States)

    Santos, J. A.; Reis, M. A.; Sousa, J.; Leite, S. M.; Correia, S.; Janeira, M.; Fragoso, M.

    2012-03-01

    An analysis of the cloud-to-ground discharges (CGD) over Portugal is carried out using data collected by a network of sensors maintained by the Portuguese Meteorological Institute for 2003-2009 (7 yr). Only cloud-to-ground flashes are considered and negative polarity CGD are largely dominant. The total number of discharges reveals a considerable interannual variability and a large irregularity in their distribution throughout the year. However, it is shown that a large number of discharges occur in the May-September period (71%), with a bimodal distribution that peaks in May and September, with most of the lightning activity recorded in the afternoon (from 16:00 to 18:00 UTC). In spring and autumn the lightning activity tends to be scattered throughout the country, whereas in summer it tends to be more concentrated over northeastern Portugal. Winter generally presents low lightning activity. Furthermore, two significant couplings between the monthly number of days with discharges and the large-scale atmospheric circulation are isolated: a regional forcing, predominantly in summer, and a remote forcing. In fact, the identification of daily lightning regimes revealed three important atmospheric conditions for triggering lightning activity: regional cut-off lows, cold troughs induced by remote low pressure systems and summertime regional low pressures at low-tropospheric levels combined with a mid-tropospheric cold trough.

  2. Tendências de temperaturas mínimas e máximas do ar no Estado de Minas Gerais

    Directory of Open Access Journals (Sweden)

    Léo Fernandes Ávila

    2014-04-01

    Full Text Available O objetivo deste trabalho foi avaliar tendências das temperaturas mínimas e máximas no Estado de Minas Gerais. Foram avaliados dados de 43 municípios, tendo-se considerado as escalas anual e sazonal - janeiro, abril, julho e outubro, que representam os meses centrais de verão, outono, inverno e primavera, respectivamente. Séries históricas de temperaturas mínimas e máximas do ar diárias, com extensão mínima de 30 anos, foram analisadas com base no teste de Mann-Kendall e no uso de regressão linear simples. As tendências foram consideradas significativas somente quando ambas as avaliações foram significativas; neste caso, determinaram-se as taxas de alteração das temperaturas. Houve boa concordância entre os testes de significância para a detecção de tendências nas séries históricas, na maioria dos municípios. Observou-se tendência de elevação das temperaturas mínimas em julho de até 1,5ºC por década, com tendências generalizadas de aumento na maior parte do estado, em outubro e janeiro, e também na escala anual. Exceções foram verificadas especialmente em municípios de maiores altitudes, em que as temperaturas mínimas diminuíram no inverno. Há predominância de municípios com tendência significativa de aumento de temperaturas, independentemente da escala de avaliação. Tendências de aumento nas temperaturas são esperadas mais comumente no sentido sul-norte do Estado de Minas Gerais.

  3. Tendência das séries temporais de precipitação da região sul do Brasil

    Directory of Open Access Journals (Sweden)

    Adilson Pinheiro

    2013-09-01

    Full Text Available O objetivo deste trabalho é avaliar a presença de tendências nas séries temporais de precipitação no Sul do Brasil. Foram analisadas séries temporais diárias, mensais e anuais de 18 estações pluviométricas. As distribuições de probabilidade normal e de extremos tipo I foram empregadas para análise dos dados. Foi, ainda, aplicado o teste de tendência de Mann-Kendall na detecção de tendências ou de variabilidades climáticas. Os resultados mostram uma tendência positiva dos máximos diários anuais ao longo do tempo, assim como significativa elevação dos totais mensais e anuais na maioria das estações. O teste de tendência de Mann-Kendal mostra mudanças estatisticamente significativas, ao nível de 95%, em 16 das 18 estações pluviométricas analisadas.

  4. Elevated atmospheric carbon dioxide concentrations promote ant tending of aphids.

    Science.gov (United States)

    Kremer, Jenni M M; Nooten, Sabine S; Cook, James M; Ryalls, James M W; Barton, Craig V M; Johnson, Scott N

    2018-04-27

    Animal mutualisms, which involve beneficial interactions between individuals of different species, are common in nature. Insect-insect mutualism, for example, is widely regarded as a keystone ecological interaction. Some mutualisms are anticipated to be modified by climate change, but the focus has largely been on plant-microbe and plant-animal mutualisms rather than those between animals. Ant-aphid mutualisms, whereby ants tend aphids to harvest their honeydew excretions and, in return, provide protection for the aphids, are widespread. The mutualism is heavily influenced by the quality and quantity of honeydew produced by aphids, which is directly affected by host plant quality. As predicted increases in concentrations of atmospheric carbon dioxide (eCO 2 ) are widely reported to affect plant nutritional chemistry, this may also alter honeydew quality and hence the nature of ant-aphid mutualisms. Using glasshouse chambers and field-based open-top chambers, we determined the effect of eCO 2 on the growth and nutritional quality (foliar amino acids) of lucerne (Medicago sativa). We determined how cowpea aphid (Aphis craccivora) populations and honeydew production were impacted when feeding on such plants and how this affected the tending behaviour of ants (Iridomyrmex sp.). eCO 2 stimulated plant growth but decreased concentrations of foliar amino acids by 29% and 14% on aphid-infested plants and aphid-free plants, respectively. Despite the deterioration in host plant quality under eCO 2 , aphids maintained performance and populations were unchanged by eCO 2 . Aphids induced higher concentrations of amino acids (glutamine, asparagine, glutamic acid and aspartic acid) important for endosymbiont-mediated synthesis of essential amino acids. Aphids feeding under eCO 2 also produced over three times more honeydew than aphids feeding under ambient CO 2 , suggesting they were imbibing more phloem sap at eCO 2 . The frequency of ant tending of aphids more than doubled in

  5. OVER CAPACITY NARAPIDANA DI LEMBAGA PEMASYARAKATAN, FAKTOR PENYEBAB, IMPLIKASI NEGATIF, SERTA SOLUSI DALAM UPAYA OPTIMALISASI PEMBINAAN NARAPIDANA

    Directory of Open Access Journals (Sweden)

    Angkasa Angkasa

    2010-09-01

    Full Text Available Overcapacity happened because growth rate dweller of ill assorted prison with dwelling medium of prison. Besides seems there are some other impeller factors to the happening of the paradigm overcapacity or law factors of itself which tend to oriented institutional crime (prison. Overcapacity tend to to have negative implication to some matters for example the lowering of security storey;level / observation and also the happening of prisonization. Solution of overcapacity convict in prison in the effort optimalization construction of convict in the effort optimalization construction of convict for example with a few actions having the character of non-institutional in the form of conditional crime, probation, suspended, compensation, restitution and also usage of restorative justice.

  6. If Not Consensus, at Least Coherence and Transparency.

    Science.gov (United States)

    Phillips, June K.

    1995-01-01

    Suggests that consensus is the result of intellectual inquiry among scholars for some common purpose. External and internal forces impel the academic community to move beyond argumentation about what students should be able to achieve as they progress. Legislatures and boards of regents are exercising increasing oversight over public and private…

  7. Novel applications of the temporal kernel method: Historical and future radiative forcing

    Science.gov (United States)

    Portmann, R. W.; Larson, E.; Solomon, S.; Murphy, D. M.

    2017-12-01

    We present a new estimate of the historical radiative forcing derived from the observed global mean surface temperature and a model derived kernel function. Current estimates of historical radiative forcing are usually derived from climate models. Despite large variability in these models, the multi-model mean tends to do a reasonable job of representing the Earth system and climate. One method of diagnosing the transient radiative forcing in these models requires model output of top of the atmosphere radiative imbalance and global mean temperature anomaly. It is difficult to apply this method to historical observations due to the lack of TOA radiative measurements before CERES. We apply the temporal kernel method (TKM) of calculating radiative forcing to the historical global mean temperature anomaly. This novel approach is compared against the current regression based methods using model outputs and shown to produce consistent forcing estimates giving confidence in the forcing derived from the historical temperature record. The derived TKM radiative forcing provides an estimate of the forcing time series that the average climate model needs to produce the observed temperature record. This forcing time series is found to be in good overall agreement with previous estimates but includes significant differences that will be discussed. The historical anthropogenic aerosol forcing is estimated as a residual from the TKM and found to be consistent with earlier moderate forcing estimates. In addition, this method is applied to future temperature projections to estimate the radiative forcing required to achieve those temperature goals, such as those set in the Paris agreement.

  8. Rotary and radial forcing effects on center-of-mass locomotion dynamics.

    Science.gov (United States)

    Shen, Z H; Larson, P L; Seipel, J E

    2014-09-01

    Rotary and radial forcing are two common actuation methods for legged robots. However, these two orthogonal methods of center-of-mass (CoM) forcing have not been compared as potentially alternative strategies of actuation. In this paper, we compare the CoM stability and energetics of running with rotary and radial actuation through the simulation of two models: the rotary-forced spring-loaded inverted pendulum (rotary-forced-SLIP), and the radially-forced-SLIP. We model both radial and rotary actuation in the simplest way, applying them as a constant force during the stance portion of the gait. A simple application of constant rotary forcing throughout stance is capable of producing fully-asymptotically stable motion; however, a similarly constant application of radial forcing throughout the stance is not capable of producing stable solutions. We then allow both the applied rotary and radial forcing functions to turn on or off based on the occurrence of the mid-stance event, which breaks the symmetry of actuation during stance towards a net forward propulsion. We find that both a rotary force applied in the first half of stance and a radial force applied in the second half of stance, are capable of stabilizing running. Interestingly, these two forcing methods improve the motion stability in different ways. Rotary forcing first reduces then greatly increases the size of the stable parameter region when gradually increased. Radial forcing expands the stable parameter region, but only in a moderate way. Also, it is found that parameter region stabilized by rotary and radial forcing are largely complementary. Overall, rotary forcing can better stabilize running for both constant and event-based forcing functions that were attempted. This indicates that rotary forcing has an inherent capability of stabilizing running, even when minimal time-or-event-or-state feedback is present. Radial forcing, however, tends to be more energy efficient when compared to rotary forcing

  9. Pump cavitation and inducer design

    International Nuclear Information System (INIS)

    Heslenfeld, M.W.; Hes, M. de

    2002-01-01

    Details of past work on sodium pump development and cavitation studies executed mainly for SNR 300 were reported earlier. Among the requirements for large sodium pumps are long life (200000 hours up to 300000 hours) and small size of impeller and pump, fully meeting the process and design criteria. These criteria are the required 'Q, H, r characteristics' in combination with a low NPSH value and the avoidance of cavitation damage to the pump. The pump designer has to develop a sound hydraulic combination consisting of suction arrangement, impeller design and diffuser. On the other hand the designer is free to choose an optimal pump speed. The pump speed in its turn influences the rotor dynamic pump design and the pump drive. The introduction of the inducer as an integral part of the pump design is based on following advantages: no tip cavitation; (possible) cavitation bubbles move to the open centre due to centrifugal forces on the fluid; the head of the inducer improves the inlet conditions of the impeller. The aim of an inducer is the increase in the suction specific speed (SA value) of a pump whereby the inducer functions as a pressure source improving the impeller inlet conditions. With inducer-impeller combinations values up to SA=15000 are realistic. With the use of an inducer the overall pump sizes can be reduced with Ca. 30%. Pumps commonly available have SA values up to a maximum of ca. 10000. A development programme was executed for SNR 300 in order to reach an increase of the suction specific speed of the impeller from SA 8200 to SA 11000. Further studies to optimize pumps design for the follow up line introduced the 'inducer acting as a pre-impeller' development. This programme was executed in the period 1979-1981. At the FDO premises a scale 1 2.8 inducer impeller combination with a suction specific speed SA=15000 was developed, constructed and tested at the water test rig. This water test rig is equipped with a perspex pipe allowing also visualisation

  10. Plasma wake and nuclear forces on fragmented H+ transport

    International Nuclear Information System (INIS)

    Barriga-Carrasco, Manuel D; Deutsch, Claude

    2006-01-01

    The objective of the present work is to study the target electronic and nuclear interactions produced when a H + ion traverses classical plasma matter. Electronic interactions are treated by means of the dielectric formalism while nuclear interactions are dealt within the classical dispersion theory through a Monte Carlo computer code. The interactions through plasma electronic medium among close ions are called wake forces. We checked that these forces screen the Coulomb explosions of the two fragmented protons from the same H + ion decreasing their relative distance in the analysed cases. These forces align the interproton vector along the motion direction. They also tend the two-proton energy loss to the value of two isolated protons when at early times it is rather larger. Nevertheless most parts of these wake effects cannot be corroborated experimentally as they are masked by the projectile collisions with target nuclei in our numerical experiment. These collisions cancel the screening produced by the wake forces, increasing the interproton distance even faster than for bare Coulomb explosion. Also they misalign the interproton vector along the motion direction and contribute moderately to increase the energy loss of the fragmented H + ion. These nuclear collisions effects are more significant in reducing projectile velocity

  11. Collective coordinates and an accompanying metric force in structural isomerization dynamics of molecules

    International Nuclear Information System (INIS)

    Yanao, Tomohiro; Takatsuka, Kazuo

    2003-01-01

    Structural isomerization dynamics of three- and four-atom clusters of vanishing total angular momentum is studied in terms of internal coordinates of n-body systems on the basis of a gauge theory. The so-called principal-axis hyperspherical coordinates are employed effectively as collective variables for the study of isomerization reactions. It turns out that the non-Euclidean metric on the internal space gives rise to a force, which works in response to internal motions called the democratic (kinematic) rotations in the internal space. This metric force generally tends to induce an asymmetry in mass balance of a system, and is coupled with the usual potential force to give rise to trapped motions in the vicinity of the transition states of the cluster. This observation provides a different perspective for the so-called recrossing problem in chemical reaction dynamics

  12. Novel Behavioral and Neural Evidences for Age-Related changes in Force complexity.

    Science.gov (United States)

    Chen, Yi-Ching; Lin, Linda L; Hwang, Ing-Shiou

    2018-02-17

    This study investigated age-related changes in behavioral and neural complexity for a polyrhythmic movement, which appeared to be an exception to the loss of complexity hypothesis. Young (n = 15; age = 24.2 years) and older (15; 68.1 years) adults performed low-level force-tracking with isometric index abduction to couple a compound sinusoidal target. Multi-scale entropy (MSE) of tracking force and inter-spike interval (ISI) of motor unit (MU) in the first dorsal interosseus muscle were assessed. The MSE area of tracking force at shorter time scales of older adults was greater (more complex) than that of young adults, whereas an opposite trend (less complex for the elders) was noted at longer time scales. The MSE area of force fluctuations (the stochastic component of the tracking force) were generally smaller (less complex) for older adults. Along with greater mean and coefficient of ISI, the MSE area of the cumulative discharge rate of elders tended to be lower (less complex) than that of young adults. In conclusion, age-related complexity changes in polyrhythmic force-tracking depended on the time scale. The adaptive behavioral consequences could be multi-factorial origins of the age-related impairment in rate coding, increased discharge noises, and lower discharge complexity of pooled MUs.

  13. Using Appreciative Inquiry to Build and Enhance a Learning Culture

    Science.gov (United States)

    Lehner, Rachelle; Ruona, Wendy

    2004-01-01

    Appreciative Inquiry (AI) has emerged as a powerful organization development philosophy that builds on past successes to impel positive change. AI is a highly participative, holistic approach to change that values the wisdom of members of the organization and amplifies positive forces. This session will introduce AI as a tool to enhance…

  14. Mediações e midiatização do consumo alimentar: #taeq e tendência da saudabilidade na rede

    Directory of Open Access Journals (Sweden)

    Lívia Silva de Souza

    2018-01-01

    Full Text Available Na perspectiva das tendências do consumo alimentar conforme Madi et al (2010, observamos os modos como as cinco tendências globais da alimentação (sensorialidade, saudabilidade, sustentabilidade, praticidade e confiabilidade comportam-se na circulação midiática nas redes. Aqui apresentamos os resultados quanto à tendência da saudabilidade, a partir da observação das interações em torno da marca Taeq, por meio da hashtag #taeq na rede social Instagram.

  15. Relationship of forces acting on implant rods and degree of scoliosis correction.

    Science.gov (United States)

    Salmingo, Remel Alingalan; Tadano, Shigeru; Fujisaki, Kazuhiro; Abe, Yuichiro; Ito, Manabu

    2013-02-01

    Adolescent idiopathic scoliosis is a complex spinal pathology characterized as a three-dimensional spine deformity combined with vertebral rotation. Various surgical techniques for correction of severe scoliotic deformity have evolved and became more advanced in applying the corrective forces. The objective of this study was to investigate the relationship between corrective forces acting on deformed rods and degree of scoliosis correction. Implant rod geometries of six adolescent idiopathic scoliosis patients were measured before and after surgery. An elasto-plastic finite element model of the implant rod before surgery was reconstructed for each patient. An inverse method based on Finite Element Analysis was used to apply forces to the implant rod model such that it was deformed the same after surgery. Relationship between the magnitude of corrective forces and degree of correction expressed as change of Cobb angle was evaluated. The effects of screw configuration on the corrective forces were also investigated. Corrective forces acting on rods and degree of correction were not correlated. Increase in number of implant screws tended to decrease the magnitude of corrective forces but did not provide higher degree of correction. Although greater correction was achieved with higher screw density, the forces increased at some level. The biomechanics of scoliosis correction is not only dependent to the corrective forces acting on implant rods but also associated with various parameters such as screw placement configuration and spine stiffness. Considering the magnitude of forces, increasing screw density is not guaranteed as the safest surgical strategy. Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. Impeller flow-meter logging of vertical cross flow between basalt aquifers through wells at the Idaho National Engineering Laboratory, Eastern Snake River Plain, Idaho

    International Nuclear Information System (INIS)

    Bennecke, W.M.; Wood, S.H.

    1992-01-01

    An impeller flowmeter was used with a COLOG digital acquisition system to determine existing borehole flows, to compare with previous logging results, and to acquire flow measurements of vertical cross-flow of water in the wells between permeable zones in the open-hole intervals. The direction of flow found was predominantly downward with velocities ranging from 0-30 ft/min. Some flow reversals were noted and attributed to nearby pumping wells. USGS wells 44 and 46 were studied in September, 1991 near the Idaho Chemical Processing Plant (ICPP). The results showed a usual overall flow direction downward with flow entering the wells at around 510 to 600 ft. below the land surface. Water exited these wells at lower levels around 550 to 580 ft. Flow velocities ranged up to 24 ft/min. Using published aquifer parameters, the rate of propagation of a pressure change in an aquifer was calculated for the well CPP-2 turning on and off, at 3100 gpm

  17. Effect of microscale protrusions on local fluid flow and mass transport in the presence of forced convection

    Energy Technology Data Exchange (ETDEWEB)

    Matzen, Gehard W. [Univ. of California, Berkeley, CA (United States)

    1997-01-01

    Three-dimensional creeping flow around single, axisymmetric protrusions is studied numerically using the boundary-integral technique. Emphasis is placed upon cylindrical protrusions on plane walls for various height-to-radius (h-to-a) aspect ratios, but cones and sections of spheres protruding from plane walls are also briefly examined. The presented items include shear-stress distributions, shear-stress contours, extents of the fluid-flow disturbance, total forces and torques on the cylinders, streamlines, and skin-friction lines. Also included is a discussion of flow topology around axisymmetric geometries. No flow reversal is observed for cylindrical protrusions with aspect ratios greater than 2.4 to 2.6. At higher aspect ratios, the fluid tends to be swept around cylindrical protrusions with little vertical motion. At lower aspect ratios, the strength of the recirculation increases, and the recirculation region becomes wider in the transverse direction and narrower in the flow direction. Also, the recirculation pattern begins to resemble the closed streamline patterns in two-dimensional flow over square ridges. However, unlike two-dimensional flow, closed streamline patterns are not observed. For arbitrary axisymmetric geometries, the extent of the fluid-flow disturbance can be estimated with the total force that is exerted on the protrusion. When the same force is exerted on protrusions with different aspect ratios, the protrusion with the higher aspect ratio tends to have a greater disturbance in the flow direction and a smaller disturbance in the transverse direction. The total force exerted on cylindrical protrusions with rounded corners is only slightly lower than the total force exerted on cylindrical protrusions with sharp corners.

  18. Impelling and Inhibitory Forces in Aggression: Sex-of-Target and Relationship Effects

    Science.gov (United States)

    Davidovic, Anna; Bell, Kurtis; Ferguson, Colin; Gorski, Elizabeth; Campbell, Anne

    2011-01-01

    The finding of symmetry in intimate partner aggression is now generally accepted, but the convergence of male and female rates in these relationships remains unexplained. From qualitative analysis of male and female focus group discussions, we identified factors believed to influence the expression of aggression toward targets differing in sex and…

  19. Torquing an upper central incisor with aligners--acting forces and biomechanical principles.

    Science.gov (United States)

    Hahn, Wolfram; Zapf, Antonia; Dathe, Henning; Fialka-Fricke, Julia; Fricke-Zech, Susanne; Gruber, Rudolf; Kubein-Meesenburg, Dietmar; Sadat-Khonsari, Reza

    2010-12-01

    The forces delivered by aligners during torquing have still not been investigated. The purpose of this study was to measure the forces delivered to an upper central incisor during torquing with three different materials of the same thickness, and to describe the biomechanical principles of torquing with aligners. Five identical appliances were manufactured from each of three materials, all with a thickness of 1.0 mm (Ideal Clear®, Erkodur®, and Biolon®). An upper central incisor, as part of the measuring device, was torqued in defined steps in the vestibular and palatal directions with the respective appliance in place. For statistical analysis, the resulting forces, Fx (forces acting in the palatal and facial directions) and Fz (intrusive force as a side-effect) at a displacement of ±0.15 and ±0.8 mm from the tooth at the gingival margin were calculated. The mean Fx forces for ±0.15 mm displacement ranged from -1.89 N [standard deviation (SD) 0.48] to 0.11 N (SD 0.1). The mean Fz forces were between -0.97 N (SD 0.57) and -0.07 N (SD 0.22). The highest intrusive forces were measured during palatal displacement of the measuring tooth. An influence of direction of displacement on the levels of force was observed, especially for Fz at the greater displacement of ±0.8 mm. In relation to the intended amount of root movement during torquing, aligners tend to 'lift up' and therefore no effective force couple can be established for further root control. The force delivery properties are also influenced by the material used and the shape of the tooth.

  20. Rotary and radial forcing effects on center-of-mass locomotion dynamics

    International Nuclear Information System (INIS)

    Shen, Z H; Larson, P L; Seipel, J E

    2014-01-01

    Rotary and radial forcing are two common actuation methods for legged robots. However, these two orthogonal methods of center-of-mass (CoM) forcing have not been compared as potentially alternative strategies of actuation. In this paper, we compare the CoM stability and energetics of running with rotary and radial actuation through the simulation of two models: the rotary-forced spring-loaded inverted pendulum (rotary-forced-SLIP), and the radially-forced-SLIP. We model both radial and rotary actuation in the simplest way, applying them as a constant force during the stance portion of the gait. A simple application of constant rotary forcing throughout stance is capable of producing fully-asymptotically stable motion; however, a similarly constant application of radial forcing throughout the stance is not capable of producing stable solutions. We then allow both the applied rotary and radial forcing functions to turn on or off based on the occurrence of the mid-stance event, which breaks the symmetry of actuation during stance towards a net forward propulsion. We find that both a rotary force applied in the first half of stance and a radial force applied in the second half of stance, are capable of stabilizing running. Interestingly, these two forcing methods improve the motion stability in different ways. Rotary forcing first reduces then greatly increases the size of the stable parameter region when gradually increased. Radial forcing expands the stable parameter region, but only in a moderate way. Also, it is found that parameter region stabilized by rotary and radial forcing are largely complementary. Overall, rotary forcing can better stabilize running for both constant and event-based forcing functions that were attempted. This indicates that rotary forcing has an inherent capability of stabilizing running, even when minimal time-or-event-or-state feedback is present. Radial forcing, however, tends to be more energy efficient when compared to rotary forcing

  1. Tendências de gerenciamento de unidades de saúde e de pessoas

    Directory of Open Access Journals (Sweden)

    Adriana Maria André

    2013-02-01

    Full Text Available OBJETIVO: Identificar que fatores produzem novas tendências no gerenciamento das unidades básicas de saúde e mudanças nos modelos de gestão. MÉTODOS: Estudo prospectivo com dez gestores de unidades de saúde e dez especialistas da área de saúde de São Paulo, SP, em 2010. Foi adotada a metodologia Delphi. Foram utilizadas quatro rodadas para a coleta de dados, três quantitativas e a quarta qualitativa. Nas três primeiras foram levantadas as tendências de mudança nos modelos de gestão; no perfil do gestor e nas competências requeridas para a função, foi utilizado o teste estatístico de Mann Whitney. A quarta rodada ocorreu por meio de um painel com os envolvidos, tendo sido escolhida a análise temática. RESULTADOS: Foram identificados os principais fatores que estão impulsionando o gerenciamento das unidades básicas de saúde, como as mudanças nos modelos de gestão. Foi consenso de que as dificuldades no gerenciamento das equipes e nas políticas influemciam nesse processo. Verificou-se que os gestores estão a par das tendências do macrocontexto com o advento das organizações sociais de saúde, mas ainda não estão se antecipando nas ações institucionais. CONCLUSÕES: A formação acadêmica deve ser revista não só quanto aos conteúdos, mas quanto ao desenvolvimento desses profissionais. O recrutamento, a seleção, o desenvolvimento e a avaliação devem ser norteados por essas competências alinhadas à missão, à visão, aos valores e aos modelos de gestão das organizações no contexto do Sistema Único de Saúde.

  2. Fabrication of high-aspect-ratio microstructures using dielectrophoresis-electrocapillary force-driven UV-imprinting

    International Nuclear Information System (INIS)

    Li, Xiangming; Shao, Jinyou; Tian, Hongmiao; Ding, Yucheng; Li, Xiangmeng

    2011-01-01

    We propose a novel method for fabricating high-aspect-ratio micro-/nano-structures by dielectrophoresis-electrocapillary force (DEP-ECF)-driven UV-imprinting. The force of DEP-ECF, acting on an air–liquid interface and an air–liquid–solid three-phase contact line, is generated by applying voltage between an electrically conductive mold and a substrate, and tends to pull the dielectric liquid (a UV-curable pre-polymer) into the mold micro-cavities. The existence of DEP-ECF is explained theoretically and demonstrated experimentally by the electrically induced reduction of the contact angle. Furthermore, DEP-ECF is proven to play a critical role in forcing the polymer to fill into the mold cavities by the real-time observation of the dynamic filling process. Using the DEP-ECF-driven UV-imprinting process, high-aspect-ratio polymer micro-/nano-structures (more than 10:1) are fabricated with high consistency. This patterning method can overcome the drawbacks of the mechanically induced mold deformation and position shift in conventional imprinting lithography and maximize the pattern uniformity which is usually poor in capillary force lithography

  3. Asymptotic forms for the energy of force-free magnetic field ion figurations of translational symmetry

    Science.gov (United States)

    Sturrock, P. A.; Antiochos, S. K.; Klinchuk, J. A.; Roumeliotis, G.

    1994-01-01

    It is known from computer calculations that if a force-free magnetic field configuration is stressed progressively by footpoint displacements, the configuration expands and approaches the open configuration with the same surface flux distribution and the energy of the field increases progressively. For configurations of translationalsymmetry, it has been found empirically that the energy tends asymptotically to a certain functional form. It is here shown that analysis of a simple model of the asymptotic form of force-free fields of translational symmetry leads to and therefore justifies this functional form. According to this model, the field evolves in a well-behaved manner with no indication of instability or loss of equilibrium.

  4. Tendências na incidência e mortalidade por acidentes de trabalho no Brasil, 1998 a 2008

    Directory of Open Access Journals (Sweden)

    Flávia Souza e Silva de Almeida

    2014-09-01

    Full Text Available O objetivo do estudo foi avaliar as tendências na incidência e mortalidade por acidentes de trabalho no Brasil, de 1998 a 2008. Trata-se de estudo ecológico de séries temporais, que incluiu, para a análise, os acidentes de trabalho registrados nas estatísticas oficiais do Governo Federal. Foram calculadas as variações percentuais anuais (APC nas taxas de incidência e de mortalidade, através da modelagem pelo método Joinpoint, usando o ano calendário como variável regressora. Observou-se tendência significativa de decréscimo na taxa de incidência de acidentes de trabalho, o mesmo ocorrendo para os acidentes de trabalho típicos. Para ambos, o número de casos aumentou nesse período. O número de casos de acidentes de trabalho de trajeto e sua incidência mostraram tendência significativa de aumento. O número de óbitos e a taxa de mortalidade registraram tendência de decréscimo. São discutidos como fatores contribuintes para o declínio das taxas de incidência de acidentes de trabalho e de mortalidade por esta causa: melhoria das condições de trabalho, maior crescimento do setor de serviços do que do setor industrial, subnotificação dos acidentes de trabalho e terceirização dos serviços. O aumento dos acidentes de trabalho de trajeto sugere a influência da violência dos centros urbanos.

  5. Motor skills under varied gravitoinertial force in parabolic flight

    Science.gov (United States)

    Ross, Helen E.

    Parabolic flight produces brief alternating periods of high and low gravitoinertial force. Subjects were tested on various paper-and-pencil aiming and tapping tasks during both normal and varied gravity in flight. It was found that changes in g level caused directional errors in the z body axis (the gravity axis), the arm aiming too high under 0g and too low under 2g. The standard deviation also increased for both vertical and lateral movements in the mid-frontal plane. Both variable and directional errors were greater under 0g than 2g. In an unpaced reciprocal tapping task subjects tended to increase their error rate rather than their movement time, but showed a non-significant trend towards slower speeds under 0g for all movement orientations. Larger variable errors or slower speeds were probably due to the difficulty of re-organising a motor skill in an unfamiliar force environment, combined with anchorage difficulties under 0g.

  6. Apparatus for pumping liquids at or below the boiling point

    Science.gov (United States)

    Bingham, Dennis N.

    2002-01-01

    A pump comprises a housing having an inlet and an outlet. An impeller assembly mounted for rotation within the housing includes a first impeller piece having a first mating surface thereon and a second impeller piece having a second mating surface therein. The second mating surface of the second impeller piece includes at least one groove therein so that at least one flow channel is defined between the groove and the first mating surface of the first impeller piece. A drive system operatively associated with the impeller assembly rotates the impeller assembly within the housing.

  7. Gastronomia Molecular: Desconstruindo 20 anos de Uma Tendência

    Directory of Open Access Journals (Sweden)

    Joana Pellerano

    2013-06-01

    Full Text Available A gastronomia molecular gera interesse e controvérsia desde que foi criada, em 1992, nos workshops de Erice, na Itália. Da curiosidade dos cientistas Nicholas Kurti e Hervé This, que desenvolveram a disciplina, à aplicação prática encontrada por chefs de todo o mundo, a gastronomia molecular é perseguida por parecer ser mais complicada do que realmente é: o estudo meticuloso dos alimentos. O objetivo desse artigo é descrever o seu surgimento e o que trouxe ao cenário contemporâneo enquanto tendência gastronômica. Para tanto, foi realizada uma revisão bibliográfica em livros e citações na imprensa estrangeira, o que permitiu descrever os motivos para que essa forma de cozinhar cause tanta polêmica.

  8. The force-free configuration of flux ropes in geomagnetotail: Cluster observations

    Science.gov (United States)

    Yang, Y. Y.; Shen, C.; Zhang, Y. C.; Rong, Z. J.; Li, X.; Dunlop, M.; Ma, Y. H.; Liu, Z. X.; Carr, C. M.; Rème, H.

    2014-08-01

    Unambiguous knowledge of magnetic field structure and the electric current distribution is critical for understanding the origin, evolution, and related dynamic properties of magnetic flux ropes (MFRs). In this paper, a survey of 13 MFRs in the Earth's magnetotail are conducted by Cluster multipoint analysis, so that their force-free feature, i.e., the kind of magnetic field structure satisfying J × B = 0, can be probed directly. It is showed that the selected flux ropes with the bipolar signature of the south-north magnetic field component generally lie near the equatorial plane, as expected, and that the magnetic field gradient is rather weak near the axis center, where the curvature radius is large. The current density (up to several tens of nA/m2) reaches their maximum values as the center is approached. It is found that the stronger the current density, the smaller the angles between the magnetic field and current in MFRs. The direct observations show that only quasi force-free structure is observed, and it tends to appear in the low plasma beta regime (in agreement with the theoretic results). The quasi force-free region is generally found to be embedded in the central portion of the MFRs, where the current is approximately field aligned and proportional to the strength of core field. It is shown that ~60% of surveyed MFRs can be globally approximated as force free. The force-free factor α is found to be nonconstantly varied through the quasi force-free MFR, suggesting that the force-free structure is nonlinear.

  9. An Altimetry-Derived Index of the Offshore Forcing on the "Pressure Point" of the West Florida Shelf: Anomalous Upwelling and Its Influence on Harmful Algal Blooms

    Science.gov (United States)

    Liu, Y.; Weisberg, R. H.; Lenes, J. M.; Zheng, L.; Hubbard, K.; Walsh, J. J.

    2017-12-01

    Gulf of Mexico Loop Current (LC) interactions with the West Florida Shelf (WFS) slope play an important role in shelf ecology through the upwelling of new inorganic nutrients across the shelf break. This is particularly the case when the LC impinges upon the shelf slope in the southwest portion of the WFS near the Dry Tortugas. By contacting shallow water isobaths at this "pressure point" the LC forcing sets the entire shelf into motion. Characteristic patterns of LC interactions with the WFS and their occurrences are identified from altimetry data using unsupervised neural network, self-organizing map. The duration of the occurrences of such LC patterns is used as an indicator of offshore forcing of anomalous upwelling. Consistency is found between the altimetry-derived offshore forcing and the occurrence and severity of WFS coastal blooms of the toxic dinoflagellate, Karenia brevis: years without major blooms tend to have prolonged LC contact at the "pressure point," whereas years with major blooms tend not to have prolonged offshore forcing. Resetting the nutrient state of the shelf by the coastal ocean circulation in response to deep-ocean forcing demonstrates the importance of physical oceanography in shelf ecology. A satellite altimetry-derived seasonal predictor for major K. brevis blooms is also proposed.

  10. Study on performance of centripetal fan, 1

    International Nuclear Information System (INIS)

    Ejiri, Eiji; Shirakura, Masaaki; Tagori, Tetsuo; Enomoto, Hisao.

    1984-01-01

    Centripetal fans are radial flow type fans which gather air from outer side into inner side. The construction is simple, and when heat exchangers are arranged around them, cooled air can be discharged upward only by connecting simple ducts, accordingly, centripetal fans are suitable to the ventilating fans for superlarge cooling towers of nuclear power plants. The static pressure rise is obtained only by the diffuser action of impellers, therefore, they are not suitable to pumps and compressors, and their use is limited only to fans. Centrifugal force exerts negative effect on static pressure rise, accordingly, the ratio of internal diameter/external diameter of impellers cannot be made very small. In this study, a small model with impeller diameter of 0.6 m was used, and its overall performance, the performance of moving blades in the range of stable operation, the rotating stall characteristics in the region of low flow rate, and the effect of side wind on the overall performance in outdoor use were examined. By changing the angle of inclination of entrance guide vanes, the range of stable operation was expanded, and the pressure coefficient and efficiency were increased. (Kako, I.)

  11. Elongamento do enxerto de tendões do músculo grácial e semitendinoso humanos: estudo realizado em cadáveres de adultos jovens Graft semitendinosus and gracilis human muscle tendons elongation: a study carried out on young adult human cadavers

    Directory of Open Access Journals (Sweden)

    Sérgio Rocha Piedade

    2005-01-01

    Full Text Available Na cirurgia de reconstrução do ligamento cruzado anterior do joelho, os enxertos de tendões autólogos são a principal opção como substitutos ligamentares. Entretanto, uma das razões da falha da reconstrução ligamentar com tecidos moles é o estiramento ou elongamento do enxerto com o tempo. Neste trabalho, foram ensaiados oito tendões do músculo grácil e oito do músculo semitendinoso humanos, obtidos de quatro cadáveres do sexo masculino, com idade média de 24,5 anos. Cada tendão foi submetido a uma deformação relativa constante de 2,5% durante 600 s, com registro contínuo do relaxamento de força. A seguir, o tendão retornava ao seu comprimento inicial e era mantido num período de repouso de 300 s. Após este intervalo, um segundo ensaio, semelhante ao primeiro, era realizado. A velocidade de carregamento empregada foi de 10% do comprimento inicial do corpo de prova por segundo. Foram obtidos valores de força inicial, com 300 s e 600 s nos dois ensaios. A análise estatística sugere um comportamento mecânico mais uniforme para o tendão do músculo semitendinoso quando comparado ao tendão do músculo grácil.In the anterior cruciate ligament knee surgery reconstruction, autologous tendons graft remains as a main option as substitutive ligaments. However time effect on graft elongation is the main reason of ligament reconstruction failure. Traction tests have been performed on eight gracilis as well as on eight semitendinosus human muscles tendons obtained from four male cadavers at an average of 24.5 years. Each tendon specimen has been submitted to a deformation of 2.5% of its initial length for a time interval of 600 s with continuous recording of the corresponding force relaxation. The tendon specimen was then kept at rest for 300 s as soon as it returned to its initial length. The same specimen was then submitted to a similar test. Deformation rate for both tests was 10% of its initial length per second. Initial

  12. Plasma wake and nuclear forces on fragmented H{sub {sup +}} transport

    Energy Technology Data Exchange (ETDEWEB)

    Barriga-Carrasco, Manuel D [E.T.S.I. Industriales, Universidad de Castilla-La Mancha, E-13071 Ciudad Real (Spain); Deutsch, Claude [Laboratoire de Physique des Gaz et des Plasmas, UMR-8578, Bat. 210, Universite Paris XI, F-91405 Orsay (France)

    2006-12-15

    The objective of the present work is to study the target electronic and nuclear interactions produced when a H{sub {sup +}} ion traverses classical plasma matter. Electronic interactions are treated by means of the dielectric formalism while nuclear interactions are dealt within the classical dispersion theory through a Monte Carlo computer code. The interactions through plasma electronic medium among close ions are called wake forces. We checked that these forces screen the Coulomb explosions of the two fragmented protons from the same H{sub {sup +}} ion decreasing their relative distance in the analysed cases. These forces align the interproton vector along the motion direction. They also tend the two-proton energy loss to the value of two isolated protons when at early times it is rather larger. Nevertheless most parts of these wake effects cannot be corroborated experimentally as they are masked by the projectile collisions with target nuclei in our numerical experiment. These collisions cancel the screening produced by the wake forces, increasing the interproton distance even faster than for bare Coulomb explosion. Also they misalign the interproton vector along the motion direction and contribute moderately to increase the energy loss of the fragmented H{sub {sup +}} ion. These nuclear collisions effects are more significant in reducing projectile velocity.

  13. Upper limb joint forces and moments during underwater cyclical movements.

    Science.gov (United States)

    Lauer, Jessy; Rouard, Annie Hélène; Vilas-Boas, João Paulo

    2016-10-03

    Sound inverse dynamics modeling is lacking in aquatic locomotion research because of the difficulty in measuring hydrodynamic forces in dynamic conditions. Here we report the successful implementation and validation of an innovative methodology crossing new computational fluid dynamics and inverse dynamics techniques to quantify upper limb joint forces and moments while moving in water. Upper limb kinematics of seven male swimmers sculling while ballasted with 4kg was recorded through underwater motion capture. Together with body scans, segment inertial properties, and hydrodynamic resistances computed from a unique dynamic mesh algorithm capable to handle large body deformations, these data were fed into an inverse dynamics model to solve for joint kinetics. Simulation validity was assessed by comparing the impulse produced by the arms, calculated by integrating vertical forces over a stroke period, to the net theoretical impulse of buoyancy and ballast forces. A resulting gap of 1.2±3.5% provided confidence in the results. Upper limb joint load was within 5% of swimmer׳s body weight, which tends to supports the use of low-load aquatic exercises to reduce joint stress. We expect this significant methodological improvement to pave the way towards deeper insights into the mechanics of aquatic movement and the establishment of practice guidelines in rehabilitation, fitness or swimming performance. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Forced sustained swimming exercise at optimal speed enhances growth of juvenile yellowtail kingfish (Seriola lalandi).

    Science.gov (United States)

    Palstra, Arjan P; Mes, Daan; Kusters, Kasper; Roques, Jonathan A C; Flik, Gert; Kloet, Kees; Blonk, Robbert J W

    2014-01-01

    Swimming exercise at optimal speed may optimize growth performance of yellowtail kingfish in a recirculating aquaculture system. Therefore, optimal swimming speeds (U opt in m s(-1) or body lengths s(-1), BL s(-1)) were assessed and then applied to determine the effects of long-term forced and sustained swimming at U opt on growth performance of juvenile yellowtail kingfish. U opt was quantified in Blazka-type swim-tunnels for 145, 206, and 311 mm juveniles resulting in values of: (1) 0.70 m s(-1) or 4.83 BL s(-1), (2) 0.82 m s(-1) or 3.25 BL s(-1), and (3) 0.85 m s(-1) or 2.73 BL s(-1). Combined with literature data from larger fish, a relation of U opt (BL s(-1)) = 234.07(BL)(-0.779) (R (2) = 0.9909) was established for this species. Yellowtail kingfish, either forced to perform sustained swimming exercise at an optimal speed of 2.46 BL s(-1) ("swimmers") or allowed to perform spontaneous activity at low water flow ("resters") in a newly designed 3600 L oval flume (with flow created by an impeller driven by an electric motor), were then compared. At the start of the experiment, ten fish were sampled representing the initial condition. After 18 days, swimmers (n = 23) showed a 92% greater increase in BL and 46% greater increase in BW as compared to resters (n = 23). As both groups were fed equal rations, feed conversion ratio (FCR) for swimmers was 1.21 vs. 1.74 for resters. Doppler ultrasound imaging showed a statistically significant higher blood flow (31%) in the ventral aorta of swimmers vs. resters (44 ± 3 vs. 34 ± 3 mL min(-1), respectively, under anesthesia). Thus, growth performance can be rapidly improved by optimal swimming, without larger feed investments.

  15. Force-free magnetic fields - The magneto-frictional method

    Science.gov (United States)

    Yang, W. H.; Sturrock, P. A.; Antiochos, S. K.

    1986-01-01

    The problem under discussion is that of calculating magnetic field configurations in which the Lorentz force j x B is everywhere zero, subject to specified boundary conditions. We choose to represent the magnetic field in terms of Clebsch variables in the form B = grad alpha x grad beta. These variables are constant on any field line so that each field line is labeled by the corresponding values of alpha and beta. When the field is described in this way, the most appropriate choice of boundary conditions is to specify the values of alpha and beta on the bounding surface. We show that such field configurations may be calculated by a magneto-frictional method. We imagine that the field lines move through a stationary medium, and that each element of magnetic field is subject to a frictional force parallel to and opposing the velocity of the field line. This concept leads to an iteration procedure for modifying the variables alpha and beta, that tends asymptotically towards the force-free state. We apply the method first to a simple problem in two rectangular dimensions, and then to a problem of cylindrical symmetry that was previously discussed by Barnes and Sturrock (1972). In one important respect, our new results differ from the earlier results of Barnes and Sturrock, and we conclude that the earlier article was in error.

  16. The development of a cavitation free sodium pump for the breeder reactor

    International Nuclear Information System (INIS)

    Baladi, J.Y.; Nyilas, C.P.

    1986-12-01

    The sodium pumps for a liquid metal fast breeder reactor must be designed for exceptionally high reliability and long life. The principal adverse factor which tends to limit the primary pump life is cavitation which becomes potentially severe under off-design flow conditions caused by the requirement of two loop operations which resulted in a large operating flow range. This problem prompted an extensive study which included experimental investigations of scaled down and full size pumps. The investigations involved visual observations, acoustic signature recordings, and physical characteristic measurements of the model and full size impellers. The blade configuration of the model was modified several times. After each modification intensive testing was conducted with feedback to established design criteria. The results obtained from the final configuration showed excellent cavitation performance. This configuration was then machined on the full scale impeller and tested. The results confirmed acceptable performance in the entire range of operating conditions. This paper describes the test facilities erected for this study, discusses the experimental techniques employed, and presents the experimental techniques employed, and presents a sample of the experimental results

  17. Effects of force fields on the conformational and dynamic properties of amyloid β(1-40) dimer explored by replica exchange molecular dynamics simulations.

    Science.gov (United States)

    Watts, Charles R; Gregory, Andrew; Frisbie, Cole; Lovas, Sándor

    2018-03-01

    The conformational space and structural ensembles of amyloid beta (Aβ) peptides and their oligomers in solution are inherently disordered and proven to be challenging to study. Optimum force field selection for molecular dynamics (MD) simulations and the biophysical relevance of results are still unknown. We compared the conformational space of the Aβ(1-40) dimers by 300 ns replica exchange MD simulations at physiological temperature (310 K) using: the AMBER-ff99sb-ILDN, AMBER-ff99sb*-ILDN, AMBER-ff99sb-NMR, and CHARMM22* force fields. Statistical comparisons of simulation results to experimental data and previously published simulations utilizing the CHARMM22* and CHARMM36 force fields were performed. All force fields yield sampled ensembles of conformations with collision cross sectional areas for the dimer that are statistically significantly larger than experimental results. All force fields, with the exception of AMBER-ff99sb-ILDN (8.8 ± 6.4%) and CHARMM36 (2.7 ± 4.2%), tend to overestimate the α-helical content compared to experimental CD (5.3 ± 5.2%). Using the AMBER-ff99sb-NMR force field resulted in the greatest degree of variance (41.3 ± 12.9%). Except for the AMBER-ff99sb-NMR force field, the others tended to under estimate the expected amount of β-sheet and over estimate the amount of turn/bend/random coil conformations. All force fields, with the exception AMBER-ff99sb-NMR, reproduce a theoretically expected β-sheet-turn-β-sheet conformational motif, however, only the CHARMM22* and CHARMM36 force fields yield results compatible with collapse of the central and C-terminal hydrophobic cores from residues 17-21 and 30-36. Although analyses of essential subspace sampling showed only minor variations between force fields, secondary structures of lowest energy conformers are different. © 2017 Wiley Periodicals, Inc.

  18. Origins of the Mexican Air Force, 1913-1915

    Directory of Open Access Journals (Sweden)

    Lawrence Douglas Taylor Hansen

    2006-07-01

    Full Text Available The study examines the efforts of the Constitutionalists to develop an aerial corps during  the period of the revolt against the usurper government headed by Victoriano Huerta (1913-1914 and the subsequent war between the revolutionary factions (1914-1915. Given that military  aviation was still in its infancy, it considers the particular circumstances and motives that impelled the revolutionaries to adopt this new arm to act in conjunction with their army groups in the northern campaigns. It assesses the overall results of the use of the airplane by the constitutionalists, especially during the factional struggle, as well as its importance for the later development of the air arm as an integral part of the national army.

  19. Forced chemical mixing in immiscible alloys during severe plastic deformation at elevated temperatures

    International Nuclear Information System (INIS)

    Vo, Nhon Q.; Odunuga, Samson; Bellon, Pascal; Averback, Robert S.

    2009-01-01

    The forced chemical mixing of atoms in model immiscible alloys during severe plastic deformation (SPD) has been investigated as a function of temperature and the heat of mixing using molecular dynamics computer simulations. At low temperatures, A 75 B 25 alloys form solid solutions during SPD for heats of mixing less than ∼20 kJ mol -1 , but tend to phase separate at larger values. At high temperatures these alloys show more extensive precipitation, with the precipitate morphology dependent on the heat of mixing. Analysis of the high-temperature mixing kinetics reveals that the precipitation process involves two separate mechanisms. The first derives from long-range diffusion mediated by shear-induced vacancies, while the second is due to local rearrangements of atoms induced by the forced mixing of atoms.

  20. Numerical simulation of hydrodynamics in a pump-turbine at off-design operating conditions in turbine mode

    International Nuclear Information System (INIS)

    Yan, J P; Seidel, U; Koutnik, J

    2012-01-01

    The hydrodynamics of a reduced-scaled model of a radial pump-turbine is investigated under off-design operating conditions, involving runaway and 'S-shape' turbine brake curve at low positive discharge. It is a low specific speed pump-turbine machine of Francis type with 9 impeller blades and 20 stay vanes as well as 20 guide vanes. The computational domain includes the entire water passage from the spiral casing inlet to the draft tube outlet. Completely structured hexahedral meshes generated by the commercial software ANSYS-ICEM are employed. The unsteady incompressible simulations are performed using the commercial code ANSYS-CFX13. For turbulence modeling the standard k-ε model is applied. The numerical results at different operating points are compared to the experimental results. The predicted pressure amplitude is in good agreement with the experimental data and the amplitude of normal force on impeller is in reasonable range. The detailed analysis reveals the onset of the flow instabilities when the machine is brought from a regular operating condition to runaway and turbine break mode. Furthermore, the rotating stall phenomena are well captured at runaway condition as well as low discharge operating condition with one stall cell rotating inside and around the impeller with about 70% of its frequency. Moreover, the rotating stall is found to be the effect of rotating flow separations developed in several consecutive impeller channels which lead to their blockage. The reliable simulation of S-curve characteristics in pump-turbines is a basic requirement for design and optimization at off-design operating conditions.

  1. Energy Performance and Pressure Fluctuation of a Multiphase Pump with Different Gas Volume Fractions

    Directory of Open Access Journals (Sweden)

    Jinsong Zhang

    2018-05-01

    Full Text Available Large petroleum resources in deep sea, and huge market demands for petroleum need advanced petroleum extraction technology. The multiphase pump, which can simultaneously transport oil and gas with considerable efficiency, has been a crucial technology in petroleum extraction. A numerical approach with mesh generation and a Navier-Stokes equation solution is employed to evaluate the effects of gas volume fraction on energy performance and pressure fluctuations of a multiphase pump. Good agreement of experimental and calculation results indicates that the numerical approach can accurately simulate the multiphase flow in pumps. The pressure rise of a pump decreases with the increasing of flow rate, and the pump efficiency decreases with the increasing of GVF (the ratio of the gas volume to the whole volume. Results show that the dominant frequencies of pressure fluctuation in the impeller and diffuser are eleven and three times those of the impeller rotational frequency, respectively. Due to the larger density of water and centrifugal forces, the water aggregates to the shroud and the gas gathers to the hub, which renders the distribution of GVF in the pump uneven. A vortex develops at the blade suction side, near the leading edge, induced by the leakage flow, and further affects the pressure fluctuation in the impeller. The obvious vortex in the diffuser indicates that the design of the divergence angle of the diffuser is not optimal, which induces flow separation due to large diffusion ratio. A uniform flow pattern in the impeller indicates good hydraulic performance of the pump.

  2. Are Sexual and Emotional Infidelity Equally Upsetting to Men and Women? Making Sense of Forced-Choice Responses

    Directory of Open Access Journals (Sweden)

    David A. Lishner

    2008-10-01

    Full Text Available Forced-choice measures that assess reactions to imagined sexual and emotional infidelity are ubiquitous in studies testing the Jealousy as a Specific Innate Module (JSIM model. One potential problem with such measures is that they fail to identify respondents who find both forms of infidelity equally upsetting. To examine this issue, an experiment was conducted in which two groups of participants imagined a romantic infidelity after which participants in the first group used a traditional forced-choice measure to indicate whether they found sexual or emotional infidelity more upsetting. Participants in the second group instead used a modified forced-choice measure that allowed them also to indicate whether they found both forms of infidelity equally upsetting. Consistent with previous research, those given the traditional forced-choice measure tended to respond in a manner that supported the JSIM model. However, the majority of participants given the modified measure indicated that both forms of infidelity were equally upsetting.

  3. Effect of the collector tube profile on Pitot pump performances

    Science.gov (United States)

    Komaki, K.; Kanemoto, T.; Sagara, K.; Umekage, T.

    2013-12-01

    The pitot pump is composed of the rotating casing with the impeller channel and the pitot tube type collector as the discharge line. The radial impeller feeds water to the rotating casing. The water rotating together with the casing is caught by the stationary pitot tube type collector, and then discharges to the outside. This type pump, as the extra high head pump, is provided mainly for boiler feed systems, and has been designed by trial and error. To optimize the pump profiles, it is desirable to investigate not only performances but also internal flow conditions. This paper discusses experimentally and numerically the relation between the pump performances and the flow conditions in the rotating casing. The moderately larger dimensions of the collector make the pump head and the discharge high with the higher hydraulic efficiency. The flow in the casing is almost the forced vortex type whose velocity is in proportion to the radius but the core velocity is affected with the drag force of the stationary collector. Based upon the above results, the profile of the pitot tube type collector was optimized with the numerical simulation.

  4. Effect of the collector tube profile on Pitot pump performances

    International Nuclear Information System (INIS)

    Komaki, K; Sagara, K; Kanemoto, T; Umekage, T

    2013-01-01

    The pitot pump is composed of the rotating casing with the impeller channel and the pitot tube type collector as the discharge line. The radial impeller feeds water to the rotating casing. The water rotating together with the casing is caught by the stationary pitot tube type collector, and then discharges to the outside. This type pump, as the extra high head pump, is provided mainly for boiler feed systems, and has been designed by trial and error. To optimize the pump profiles, it is desirable to investigate not only performances but also internal flow conditions. This paper discusses experimentally and numerically the relation between the pump performances and the flow conditions in the rotating casing. The moderately larger dimensions of the collector make the pump head and the discharge high with the higher hydraulic efficiency. The flow in the casing is almost the forced vortex type whose velocity is in proportion to the radius but the core velocity is affected with the drag force of the stationary collector. Based upon the above results, the profile of the pitot tube type collector was optimized with the numerical simulation

  5. Wall Climbing Micro Ground Vehicle (MGV)

    Science.gov (United States)

    2013-09-01

    Teheran, Iran, 2004. 4. Hill, P.; Peterson, C. The Centrifugal Compressor . In Mechanics and Thermodynamics of Propulsion, 2 nd ed.; Addison-Wesley...impeller one may choose from an axial or centrifugal impeller. Impellers are designed so that they are used for a specific application. If used for other...purposes, severe mechanical damage may be inflicted upon the impeller. In this situation, a centrifugal impeller is chosen due to its ability to

  6. Numerical Calculation for Whirling Motion of a Centrifugal Blood Pump with Conical Spiral Groove Bearings

    Science.gov (United States)

    Shigemaru, Daichi; Tsukamoto, Hiroshi

    2010-06-01

    Whirling motion of a pump impeller was calculated for the centrifugal blood pump with Conical Spiral Groove Bearings to get a criterion for the instability of impeller whirling motion. The motion of the centrifugal blood pump impeller was calculated based on a spring damping model, and unsteady flow in the pump was computed using the commercial CFD package ANSYS CFX. Also the whirling motion of rotating impeller was measured using two displacement sensors fixed to the blood pump casing. The numerical calculations were done for the blood pump impeller with conical spiral groove bearings, and impeller whirling motion was evaluated.

  7. Investigation on inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet

    Science.gov (United States)

    Yang, Ce; Wang, Yingjun; Lao, Dazhong; Tong, Ding; Wei, Longyu; Liu, Yixiong

    2016-08-01

    The inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet structures were studied in numerical method, mainly focused on three issues including the amounts and differences of the inlet recirculation in different working conditions, the circumferential non-uniform distributions of the inlet recirculation, the recirculation velocity distributions of the upstream slot of the rear impeller. The results show that there are some differences between the recirculation of the front impeller and that of the rear impeller in whole working conditions. In design speed, the recirculation flow rate of the rear impeller is larger than that of the front impeller in the large flow range, but in the small flow range, the recirculation flow rate of the rear impeller is smaller than that of the front impeller. In different working conditions, the recirculation velocity distributions of the front and rear impeller are non-uniform along the circumferential direction and their non-uniform extents are quite different. The circumferential non-uniform extent of the recirculation velocity varies with the working conditions change. The circumferential non-uniform extent of the recirculation velocity of front impeller and its distribution are determined by the static pressure distribution of the front impeller, but that of the rear impeller is decided by the coupling effects of the inlet flow distortion of the rear impeller, the circumferential unsymmetrical distribution of the upstream slot and the asymmetric structure of the volute. In the design flow and small flow conditions, the recirculation velocities at different circumferential positions of the mean line of the upstream slot cross-section of the rear impeller are quite different, and the recirculation velocities distribution forms at both sides of the mean line are different. The recirculation velocity distributions in the cross-section of the upstream slot depend on the static pressure

  8. Determination of adhesion forces between smooth and structured solids

    International Nuclear Information System (INIS)

    Fischer, Hartmut R.; Gelinck, Edwin R.M.

    2012-01-01

    Highlights: ► Extension of know data with respect to decency of adhesion from probe radius to 8 decades. ► Use of large interaction surface areas for precision measurement of adhesion forces. ► Deliberated increase of roughness as tool to tune adhesion forces and to suppress spontaneous adhesion. - Abstract: Surfaces tend to be made smoother in order to gain flatness or in order to fulfill the need for more precise and reproducible positioning of parts. Adhesion or even sticking of the surfaces is a major showstopper for these applications. There are several measures that can be taken in order to reduce spontaneous adhesion. Quantification of the effectiveness of the chosen solution is most often done using an atomic force microscope (AFM) with probes varying from 1 nm to 8 μm of contact diameter. A serious disadvantage in measuring adhesion by sharp tips is the wear of the tips. Sharp tips wear easily, resulting in undefined contact areas. When the real area of contact is not well defined, the quantification of the adhesion force is not significant. In the current study results of AFM measurements from literature with different tip diameters of colloidal probes are compared with AFM cantilevers with a plateau tip and using probes from large spheres using an alternative setup in combination with a Universal Nano-mechanical Analyzer (UNAT). Test results are shown. Another part of the study deals with a deliberately roughening of smooth surfaces to minimize (spontaneous) adhesion. Good agreement has been found with existing results.

  9. Development and test of a plastic deep-well pump

    International Nuclear Information System (INIS)

    Zhang, Q H; Gao, X F; Xu, Y; Shi, W D; Lu, W G; Liu, W

    2013-01-01

    To develop a plastic deep-well pump, three methods are proposed on structural and forming technique. First, the major hydraulic components are constructed by plastics, and the connection component is constructed by steel. Thus the pump structure is more concise and slim, greatly reducing its weight and easing its transportation, installation, and maintenance. Second, the impeller is designed by maximum diameter method. Using same pump casing, the stage head is greatly increased. Third, a sealing is formed by impeller front end face and steel end face, and two slots are designed on the impeller front end face, thus when the two end faces approach, a lubricating pair is formed, leading to an effective sealing. With above methods, the pump's axial length is greatly reduced, and its stage head is larger and more efficient. Especially, the pump's axial force is effectively balanced. To examine the above proposals, a prototype pump is constructed, and its testing results show that the pump efficiency exceeds the national standard by 6%, and the stage head is improved by 41%, meanwhile, its structure is more concise and ease of transportation. Development of this pump would provide useful experiences for further popularity of plastic deep-well pumps

  10. Noncontacting device to indicate deflection of turbopump internal rotating parts

    Science.gov (United States)

    Hamilton, D. B.; Grieser, D. R.; Plummer, A. M.; Ensminger, D.; Saccacio, E. J.

    1972-01-01

    Phase 2 (development) which was concluded for the ultrasonic Doppler device and the light-pipe-reflectance device is reported. An ultrasonic Doppler breadboard system was assembled which accurately measured runout in the J-2 LOX pump impeller during operation. The transducer was mounted on the outside of the pump volute using a C-clamp. Vibration was measured by conducting the ultrasonic wave through the volute housing and through the fluid in the volute to the impeller surface. The impeller vibration was also measured accurately using the light-pipe probe mounted in an elastomeric-gland fitting in the pump case. A special epoxy resin developed for cryogenic applications was forced into the end of the fiber-optic probe to retain the fibers. Subsequently, the probe suffered no damage after simultaneous exposure to 2150 psi and 77 F. Preliminary flash X-radiographs were taken of the turbine wheel and the shaft-bearing-seal assembly, using a 2-megavolt X-ray unit. Reasonable resolution and contrast was obtained. A fast-neutron detector was fabricated and sensitivity was measured. The results demonstrated that the technique is feasible for integrated-time measurements requiring, perhaps, 240 revolutions to obtain sufficient exposure at 35,000 rpm. The experimental verification plans are included.

  11. Effect of Buoyancy on Forced Convection Heat Transfer in Vertical Channels - a Literature Survey

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharyya, A

    1965-03-15

    This report contains a short resume of the available information from various sources on the effect of free convection flow on forced convection heat transfer in vertical channels. Both theoretical and experimental investigations are included. Nearly all of the theoretical investigations are concerned with laminar flow with or without internal heat generation. More consistent data are available for upward flow than for downward flow. Curves are presented to determine whether free convection or forced convection mode of heat transfer is predominant for a particular Reynolds number and Rayleigh number. At Re{sub b} > 10{sup 5} free convection effects are negligible. Downward flow through a heated channel at low Reynolds number is unstable. Under similar conditions the overall heat transfer coefficient for downward flow tends to be higher than that for upward flow.

  12. Use of item response curves of the Force and Motion Conceptual Evaluation to compare Japanese and American students' views on force and motion

    Science.gov (United States)

    Ishimoto, Michi; Davenport, Glen; Wittmann, Michael C.

    2017-12-01

    Student views of force and motion reflect the personal experiences and physics education of the student. With a different language, culture, and educational system, we expect that Japanese students' views on force and motion might be different from those of American students. The Force and Motion Conceptual Evaluation (FMCE) is an instrument used to probe student views on force and motion. It was designed using research on American students, and, as such, the items might function differently for Japanese students. Preliminary results from a translated version indicated that Japanese students had similar misconceptions as those of American students. In this study, we used item response curves (IRCs) to make more detailed item-by-item comparisons. IRCs show the functioning of individual items across all levels of performance by plotting the proportion of each response as a function of the total score. Most of the IRCs showed very similar patterns on both correct and incorrect responses; however, a few of the plots indicate differences between the populations. The similar patterns indicate that students tend to interact with FMCE items similarly, despite differences in culture, language, and education. We speculate about the possible causes for the differences in some of the IRCs. This report is intended to show how IRCs can be used as a part of the validation process when making comparisons across languages and nationalities. Differences in IRCs can help to pinpoint artifacts of translation, contextual effects because of differences in culture, and perhaps intrinsic differences in student understanding of Newtonian motion.

  13. Use of item response curves of the Force and Motion Conceptual Evaluation to compare Japanese and American students’ views on force and motion

    Directory of Open Access Journals (Sweden)

    Michi Ishimoto

    2017-11-01

    Full Text Available Student views of force and motion reflect the personal experiences and physics education of the student. With a different language, culture, and educational system, we expect that Japanese students’ views on force and motion might be different from those of American students. The Force and Motion Conceptual Evaluation (FMCE is an instrument used to probe student views on force and motion. It was designed using research on American students, and, as such, the items might function differently for Japanese students. Preliminary results from a translated version indicated that Japanese students had similar misconceptions as those of American students. In this study, we used item response curves (IRCs to make more detailed item-by-item comparisons. IRCs show the functioning of individual items across all levels of performance by plotting the proportion of each response as a function of the total score. Most of the IRCs showed very similar patterns on both correct and incorrect responses; however, a few of the plots indicate differences between the populations. The similar patterns indicate that students tend to interact with FMCE items similarly, despite differences in culture, language, and education. We speculate about the possible causes for the differences in some of the IRCs. This report is intended to show how IRCs can be used as a part of the validation process when making comparisons across languages and nationalities. Differences in IRCs can help to pinpoint artifacts of translation, contextual effects because of differences in culture, and perhaps intrinsic differences in student understanding of Newtonian motion.

  14. Effect of weak geometrical forcing on the stability of Taylor-vortex flow

    International Nuclear Information System (INIS)

    Pan Xiaolong; Khayat, Roger E

    2008-01-01

    Linear stability analysis of fully developed axisymmetric steady and spatially modulated Taylor-Couette flow is carried out in the narrow-gap limit. The inner cylinder is sinusoidally modulated and rotating, while the outer cylinder is straight and at rest. The modulation amplitude is assumed to be small, and the base steady flow is determined using a regular perturbation expansion of the flow field coupled to a variable-step finite-difference scheme. The disturbance flow equations are derived within the framework of Floquet theory and solved using a nonlinear two-point boundary-value approach. In contrast to unforced Taylor-Couette flow, only vortical base flow is possible in the forced case. It is found that the forcing tends to generally destabilize the base flow, especially around the critical point. Both the critical Taylor number and wavenumber are found to decrease essentially linearly with modulation amplitude.

  15. Tendências climáticas e produção de uva na região dos Vales da Uva Goethe

    Directory of Open Access Journals (Sweden)

    Álvaro José Back

    2012-04-01

    Full Text Available O objetivo deste trabalho foi avaliar tendências nas séries climáticas e nos índices agroclimáticos para o cultivo da videira na região dos Vales da Uva Goethe, em Santa Catarina. A região apresenta clima mesotérmico úmido. Foram utilizados dados de temperatura máxima e mínima do ar, do período de 1924 a 2010, e de precipitação pluvial, de 1955 a 2010. O teste de Mann‑Kendall foi utilizado para avaliar a tendência nas séries, cuja magnitude foi estimada pela declividade mediana determinada pelo teste de Theil-Sen. Foi observada tendência de aumento nas séries de temperatura mínima do ar, em escala anual, bem como nas estações do ano. Quanto à temperatura máxima, somente houve tendência de aumento na série de verão. Em relação aos índices agrometeorológicos, foi observada tendência de diminuição do número de geadas, diminuição do período entre a brotação e a colheita, aumento da soma térmica e dos índices de Huglin e de frio. Foram evidenciadas tendências de aumento da precipitação pluvial total anual e da precipitação no período de crescimento da videira, bem como aumento do número de dias, com chuva igual ou superior a 20 mm, e aumento na temperatura mínima e noturna.

  16. Análise de tendência do mercado internacional de aglomerado Analysis of international particleboard market tendency

    Directory of Open Access Journals (Sweden)

    Rommel Noce

    2008-04-01

    Full Text Available Neste estudo, analisou-se, pelo método da regressão linear, a tendência do mercado internacional de aglomerado no período de 1990 a 2004. Observou-se tendência de crescimento tanto de produção quanto de exportação, com a ressalva de que o Brasil expande sua produção em ritmo mais acelerado que a produção mundial. Conclui-se que China, Ucrânia e EUA apresentaram maior crescimento, quanto à produção, exportação e importação, entre os mercados tradicionais, respectivamente, e que os mercados não-tradicionais mudaram tendências de crescimento superiores ao grupo dos principais importadores, especialmente o leste europeu.This study analyzed international particleboard market tendency in the period from 1990 to 2004, using the linear regression method. Growth tendency was observed both for production and export, stressing that Brazil's production is expanding in a more accelerated rhythm than the world production. China, Ukraine and USA presented a greater production, export and import growth among the traditional markets, respectively, and the nontraditional markets presented greater growth tendencies, compared to the major import groups, especially East Europe.

  17. Desinserción espontánea y bilateral del tendón cuadricipital.

    Directory of Open Access Journals (Sweden)

    Jesuan Zordan

    2016-02-01

    Full Text Available La ruptura espontánea bilateral del tendón cuadricipital es una patología infrecuente (<5% de todas las rupturas cuadricipitales. El mayor número de casos reportados, se asocia a insuficiencia renal crónica,  obesidad, diabetes, lupus eritematoso sistémico, vasculitis e hiperparatiroidismo. Nuestro paciente, de 41 años de edad presenta insuficiencia renal crónica en tratamiento con hemodiálisis desde hace 8 años, asociada a hiperparatiroidismo secundario. Ingresa a nuestro servicio por incapacidad a la extensión de ambos miembros inferiores, tras incorporarse desde una silla, destacando en el examen físico una depresión palpable suprarrotuliana. Se realizan radiografías de ambas rodillas frente y perfil, ecografía de zona suprarrotuliana y resonancia magnética nuclear. Al  constatar lesión bilateral a nivel del tendón cuadricipital, se programa su reparación quirúrgica, la cual se realizó por cuestiones ajenas a nuestro servicio a los 30 días del diagnóstico. Se intervinieron de manera simultánea ambas rodillas utilizando como técnica, tunelización patelar y empleando suturas no reabsorbible. Se obtuvo un resultado excelente en ambos miembros inferiores según el Score Knee Society (S.N.S..

  18. Radiological health implications of lead-210 and polonium-210 accumulations in LPG refineries

    International Nuclear Information System (INIS)

    Summerlin, J. Jr.; Prichard, H.M.

    1985-01-01

    Radon-222, a naturally occurring radioactive noble gas, is often a contaminant in natural gas. During fractionation at processing plants, Radon tends to be concentrated in the Liquified Petroleum Gas (LPG) product stream. Radon-222 decays into a number of radioactive metallic daughters which can plate out on the interior surfaces of plant machinery. The hazards associated with gamma-emitting short-lived radon daughters have been investigated previously. The present work reports an analysis of the hazards associated with the long-lived daughters; Pb-210, Bi-210, and Po-210. These nuclides do not emit appreciable penetrating radiation, and hence do not represent a hazard as long as they remain on the inside surfaces of equipment. However, when equipment that has had prolonged exposure to an LPG stream is disassembled for repair or routine maintenance, opportunities for exposure to radioactive materials can occur. A series of measurements made on an impeller taken from a pump in an LPG facility is reported. Alpha spectroscopy revealed the presence of Po-210, and further measurements showed that the amount on the impeller surface was well above the exempt quantity. Breathing zone measurements made in the course of cleaning the impeller showed that an inhalation exposure equivalent to breathing Po-210 at the Maximum Permissible Concentration (MPC) for 60 hours could be delivered in less than half an hour. It was concluded that maintenance and repair work on LPG and derivitive product stream equipment must be carried out with the realization that a potential radiological health problem exists

  19. Assessing the quality of force feedback in soft tissue simulation.

    Science.gov (United States)

    Basafa, Ehsan; Sefati, Shahin; Okamura, Allison M

    2011-01-01

    Many types of deformable models have been proposed for simulation of soft tissue in surgical simulators, but their realism in comparison to actual tissue is rarely assessed. In this paper, a nonlinear mass-spring model is used for realtime simulation of deformable soft tissues and providing force feedback to a human operator. Force-deformation curves of real soft tissue samples were obtained experimentally, and the model was tuned accordingly. To test the realism of the model, we conducted two human-user experiments involving palpation with a rigid probe. First, in a discrimination test, users identified the correct category of real and virtual tissue better than chance, and tended to identify the tissues as real more often than virtual. Second, users identified real and virtual tissues by name, after training on only real tissues. The sorting accuracy was the same for both real and virtual tissues. These results indicate that, despite model limitations, the simulation could convey the feel of touching real tissues. This evaluation approach could be used to compare and validate various soft-tissue simulators.

  20. Aspectos de imagem do xantoma do tendão calcâneo na ultrassonografia e ressonância magnética

    Directory of Open Access Journals (Sweden)

    Eloy de Ávila Fernandes

    2015-06-01

    Full Text Available O xantoma no tendão calcâneo é uma doença rara e tem uma alta associação com hiperlipidemia primária. O diagnóstico precoce é fundamental para o início do tratamento e para alterar o curso da doença. Os exames de imagem podem auxiliar nesse diagnóstico. Este estudo relata o caso de um homem de 60 anos apresentando nódulos indolores nos cotovelos e tendões calcâneos, sem crises típicas de gota, acompanhado no ambulatório de doenças microcristalinas da Unifesp para esclarecimento diagnóstico. Os testes laboratoriais solicitados apresentavam dislipidemia. Ultrassom (US mostrou espessamento difuso dos tendões calcâneos com áreas hipoecoicas. Ressonância magnética (RM mostrou espessamento difuso dos tendões, com áreas de sinal intermediário e padrão reticulado no interior. Os exames de imagem mostraram aspectos relevantes no diagnóstico de xantoma, auxiliando no diagnóstico diferencial.

  1. Centrifugal pumps

    CERN Document Server

    Gülich, Johann Friedrich

    2014-01-01

    This book gives an unparalleled, up-to-date, in-depth treatment of all kinds of flow phenomena encountered in centrifugal pumps including the complex interactions of fluid flow with vibrations and wear of materials. The scope includes all aspects of hydraulic design, 3D-flow phenomena and partload operation, cavitation, numerical flow calculations, hydraulic forces, pressure pulsations, noise, pump vibrations (notably bearing housing vibration diagnostics and remedies), pipe vibrations, pump characteristics and pump operation, design of intake structures, the effects of highly viscous flows, pumping of gas-liquid mixtures, hydraulic transport of solids, fatigue damage to impellers or diffusers, material selection under the aspects of fatigue, corrosion, erosion-corrosion or hydro-abrasive wear, pump selection, and hydraulic quality criteria. As a novelty, the 3rd ed. brings a fully analytical design method for radial impellers, which eliminates the arbitrary choices inherent to former design procedures. The d...

  2. Atomic force microscopy measurements of bacterial adhesion and biofilm formation onto clay-sized particles

    Science.gov (United States)

    Huang, Qiaoyun; Wu, Huayong; Cai, Peng; Fein, Jeremy B.; Chen, Wenli

    2015-01-01

    Bacterial adhesion onto mineral surfaces and subsequent biofilm formation play key roles in aggregate stability, mineral weathering, and the fate of contaminants in soils. However, the mechanisms of bacteria-mineral interactions are not fully understood. Atomic force microscopy (AFM) was used to determine the adhesion forces between bacteria and goethite in water and to gain insight into the nanoscale surface morphology of the bacteria-mineral aggregates and biofilms formed on clay-sized minerals. This study yields direct evidence of a range of different association mechanisms between bacteria and minerals. All strains studied adhered predominantly to the edge surfaces of kaolinite rather than to the basal surfaces. Bacteria rarely formed aggregates with montmorillonite, but were more tightly adsorbed onto goethite surfaces. This study reports the first measured interaction force between bacteria and a clay surface, and the approach curves exhibited jump-in events with attractive forces of 97 ± 34 pN between E. coli and goethite. Bond strengthening between them occurred within 4 s to the maximum adhesion forces and energies of −3.0 ± 0.4 nN and −330 ± 43 aJ (10−18 J), respectively. Under the conditions studied, bacteria tended to form more extensive biofilms on minerals under low rather than high nutrient conditions. PMID:26585552

  3. Corrected direct force balance method for atomic force microscopy lateral force calibration

    International Nuclear Information System (INIS)

    Asay, David B.; Hsiao, Erik; Kim, Seong H.

    2009-01-01

    This paper reports corrections and improvements of the previously reported direct force balance method (DFBM) developed for lateral calibration of atomic force microscopy. The DFBM method employs the lateral force signal obtained during a force-distance measurement on a sloped surface and relates this signal to the applied load and the slope of the surface to determine the lateral calibration factor. In the original publication [Rev. Sci. Instrum. 77, 043903 (2006)], the tip-substrate contact was assumed to be pinned at the point of contact, i.e., no slip along the slope. In control experiments, the tip was found to slide along the slope during force-distance curve measurement. This paper presents the correct force balance for lateral force calibration.

  4. Numerical study of the lateral resolution in electrostatic force microscopy for dielectric samples

    International Nuclear Information System (INIS)

    Riedel, C; AlegrIa, A; Colmenero, J; Schwartz, G A; Saenz, J J

    2011-01-01

    We present a study of the lateral resolution in electrostatic force microscopy for dielectric samples in both force and gradient modes. Whereas previous studies have reported expressions for metallic surfaces having potential heterogeneities (Kelvin probe force microscopy), in this work we take into account the presence of a dielectric medium. We introduce a definition of the lateral resolution based on the force due to a test particle being either a point charge or a polarizable particle on the dielectric surface. The behaviour has been studied over a wide range of typical experimental parameters: tip-sample distance (1-20) nm, sample thickness (0-5) μm and dielectric constant (1-20), using the numerical simulation of the equivalent charge method. For potential heterogeneities on metallic surfaces expressions are in agreement with the bibliography. The lateral resolution of samples having a dielectric constant of more than 10 tends to metallic behaviour. We found a characteristic thickness of 100 nm, above which the lateral resolution measured on the dielectric surface is close to that of an infinite medium. As previously reported, the lateral resolution is better in the gradient mode than in the force mode. Finally, we showed that for the same experimental conditions, the lateral resolution is better for a polarizable particle than for a charge, i.e. dielectric heterogeneities should always look 'sharper' (better resolved) than inhomogeneous charge distributions. This fact should be taken into account when interpreting images of heterogeneous samples.

  5. Numerical study of the lateral resolution in electrostatic force microscopy for dielectric samples

    Energy Technology Data Exchange (ETDEWEB)

    Riedel, C; AlegrIa, A; Colmenero, J [Departamento de Fisica de Materiales UPV/EHU, Facultad de Quimica, Apartado 1072, 20080 San Sebastian (Spain); Schwartz, G A [Centro de Fisica de Materiales CSIC-UPV/EHU, Paseo Manuel de Lardizabal 5, 20018 San Sebastian (Spain); Saenz, J J, E-mail: riedel@ies.univ-montp2.fr [Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian (Spain)

    2011-07-15

    We present a study of the lateral resolution in electrostatic force microscopy for dielectric samples in both force and gradient modes. Whereas previous studies have reported expressions for metallic surfaces having potential heterogeneities (Kelvin probe force microscopy), in this work we take into account the presence of a dielectric medium. We introduce a definition of the lateral resolution based on the force due to a test particle being either a point charge or a polarizable particle on the dielectric surface. The behaviour has been studied over a wide range of typical experimental parameters: tip-sample distance (1-20) nm, sample thickness (0-5) {mu}m and dielectric constant (1-20), using the numerical simulation of the equivalent charge method. For potential heterogeneities on metallic surfaces expressions are in agreement with the bibliography. The lateral resolution of samples having a dielectric constant of more than 10 tends to metallic behaviour. We found a characteristic thickness of 100 nm, above which the lateral resolution measured on the dielectric surface is close to that of an infinite medium. As previously reported, the lateral resolution is better in the gradient mode than in the force mode. Finally, we showed that for the same experimental conditions, the lateral resolution is better for a polarizable particle than for a charge, i.e. dielectric heterogeneities should always look 'sharper' (better resolved) than inhomogeneous charge distributions. This fact should be taken into account when interpreting images of heterogeneous samples.

  6. Tendência da prevalência do diabetes melito autorreferido em adultos nas capitais brasileiras, 2006 a 2012

    Directory of Open Access Journals (Sweden)

    Deborah Carvalho Malta

    Full Text Available OBJETIVO: avaliar a tendência da prevalência de diabetes melito autorreferido nas capitais brasileiras, entre 2006 e 2012. MÉTODOS: estudo ecológico com dados da Vigilância de Fatores de Risco e Proteção para Doenças Crônicas por Inquérito Telefônico (Vigitel referentes a adultos (≥18 anos, analisados por meio de regressão linear simples. RESULTADOS: no período estudado, houve tendência de aumento de 5,7% para 7,4% no conjunto da população adulta das capitais (p=0,008, de 4,8% para 6,5% entre homens (p=0,002 e de 6,4% para 8,1% entre mulheres (p=0,039; a elevação entre mulheres ocorreu em 9 capitais - Belém-PA, Belo Horizonte-MG, Curitiba-PR, Macapá-AP, Maceió-AL, Palmas-TO, Recife-PE, Rio Branco-AC e Vitória-ES -; e entre homens, em 6 capitais - Boa Vista-RR, Florianópolis-SC, Fortaleza-CE, Rio Branco-AC, Rio de Janeiro-RJ e São Paulo-SP. CONCLUSÃO: houve aumento da prevalência do diabetes em diversas capitais brasileiras; o monitoramento das tendências e fatores de risco é útil ao planejamento em saúde.

  7. Quantifying immediate radiative forcing by black carbon and organic matter with the Specific Forcing Pulse

    Directory of Open Access Journals (Sweden)

    T. C. Bond

    2011-02-01

    12 additional models. We outline a framework for combining a large number of simple models with a smaller number of enhanced models that have greater complexity. Adjustments for black carbon internal mixing and for regional variability are discussed. Emitting regions with more deep convection have greater model diversity. Our best estimate of global-mean SFP is +1.03 ± 0.52 GJ g−1 for direct atmosphere forcing of black carbon, +1.15 ± 0.53 GJ g−1 for black carbon including direct and cryosphere forcing, and −0.064 (−0.02, −0.13 GJ g−1 for organic matter. These values depend on the region and timing of emission. The lowest OM:BC mass ratio required to produce a neutral effect on top-of-atmosphere direct forcing is 15:1 for any region. Any lower ratio results in positive direct forcing. However, important processes, particularly cloud changes that tend toward cooling, have not been included here.

    Global-average SFP for energy-related emissions can be converted to a 100-year GWP of about 740 ± 370 for BC without snow forcing, and 830 ± 440 with snow forcing. 100-year GWP for OM is −46 (−18, −92. Best estimates of atmospheric radiative impact (without snow forcing by black and organic matter are +0.47 ± 0.26 W m−2 and −0.17 (−0.07, −0.35 W m−2 for BC and OM, respectively, assuming total emission rates of 7.4 and 45 Tg yr−1. Anthropogenic forcing is +0.40 ± 0.18 W m−2 and −0.13 (−0.05, −0.25 W m−2 for BC and OM, respectively, assuming anthropogenic emission rates of 6.3 and 32.6 Tg yr−1. Black carbon forcing is only 18% higher than that given by the Intergovernmental Panel on Climate Change (IPCC, although the value presented here includes enhanced absorption due to internal mixing.

  8. Design Mixers to Minimize Effects of Erosion and Corrosion Erosion

    Directory of Open Access Journals (Sweden)

    Julian Fasano

    2012-01-01

    Full Text Available A thorough review of the major parameters that affect solid-liquid slurry wear on impellers and techniques for minimizing wear is presented. These major parameters include (i chemical environment, (ii hardness of solids, (iii density of solids, (iv percent solids, (v shape of solids, (vi fluid regime (turbulent, transitional, or laminar, (vii hardness of the mixer's wetted parts, (viii hydraulic efficiency of the impeller (kinetic energy dissipation rates near the impeller blades, (ix impact velocity, and (x impact frequency. Techniques for minimizing the wear on impellers cover the choice of impeller, size and speed of the impeller, alloy selection, and surface coating or coverings. An example is provided as well as an assessment of the approximate life improvement.

  9. Design and test of a high pressure centrifugal compressor

    International Nuclear Information System (INIS)

    Choi, Jae Ho; Han, Chak Heui; Paeng, Ki Seok; Chen, Seung Bae; Kim, Yong Ryun

    2005-01-01

    This paper presents an aerodynamic design, flow analysis and performance test of a pressure ratio 4:1 centrifugal compressor for gas turbine engine. The compressor is made up of a centrifugal impeller, a two-stage diffuser consisted of radial and axial types. The impeller has a 45 degree backswept angle and the design running tip clearance is 5% of impeller exit height. Three-dimensional numerical analysis is performed to analyze the flows in the impeller, diffuser and deswirler considering the impeller tip clearance. Test module and rig facilities for the compressor stage performance test are designed and fabricated. The overall compressor stage performances as well as the static pressure fields on the impeller and diffuser are measured. Two diffusers of wedge and airfoil types are tested with an impeller. The calculation and test results show that flow fields downstream the deswirler at the design and off-design points are highly nonuniform and the airfoil diffuser has the better aerodynamic characteristics than those of wedge diffuser

  10. Relationship Between Force Production During Isometric Squats and Knee Flexion Angles During Landing.

    Science.gov (United States)

    Fisher, Harry; Stephenson, Mitchell L; Graves, Kyle K; Hinshaw, Taylour J; Smith, Derek T; Zhu, Qin; Wilson, Margaret A; Dai, Boyi

    2016-06-01

    Decreased knee flexion angles during landing are associated with increased anterior cruciate ligament loading. The underlying mechanisms associated with decreased self-selected knee flexion angles during landing are still unclear. The purpose of this study was to establish the relationship between the peak force production at various knee flexion angles (35, 55, 70, and 90°) during isometric squats and the actual knee flexion angles that occur during landing in both men and women. A total of 18 men and 18 women recreational/collegiate athletes performed 4 isometric squats at various knee flexion angles while vertical ground reaction forces were recorded. Participants also performed a jump-landing-jump task while lower extremity kinematics were collected. For women, significant correlations were found between the peak force production at 55 and 70° of knee flexion during isometric squats and the knee flexion angle at initial contact of landing. There were also significant correlations between the peak force production at 55, 70, and 90° of knee flexion during isometric squats and the peak knee flexion angle during landing. These correlations tended to be stronger during isometric squats at greater knee flexion compared with smaller knee flexion. No significant correlations were found for men. Posture-specific strength may play an important role in determining self-selected knee flexion angles during landing for women.

  11. Investigation of Calibrating Force Transducer Using Sinusoidal Force

    International Nuclear Information System (INIS)

    Zhang Li; Wang Yu; Zhang Lizhe

    2010-01-01

    Sinusoidal force calibration method was studied several years before at Physikalisch-Technische Bundesanstalt (PTB). A similar dynamic force calibration system is developed at Changcheng Institute of Metrology and Measurement (CIMM). It uses electro-dynamic shakers to generate dynamic force in the range from 1 N to 20 kN, and heterodyne laser interferometers are used for acceleration measurement. The force transducer to be calibrated is mounted on the shaker, and a mass block is screwed on the top of force transducer, the sinusoidal forces realized by accelerated load masses are traceable to acceleration and mass according to the force definition. The methods of determining Spatial-dependent acceleration on mass block and measuring the end mass of force transducer in dynamic force calibration are discussed in this paper.

  12. Forced sustained swimming exercise at optimal speed enhances growth of juvenile yellowtail kingfish (Seriola lalandi

    Directory of Open Access Journals (Sweden)

    Arjan P. Palstra

    2015-01-01

    Full Text Available Swimming exercise at optimal speed may optimize growth performance of yellowtail kingfish in a recirculating aquaculture system. Therefore, optimal swimming speeds (Uopt in m s-1 or body lengths s-1, BL s-1 were assessed and then applied to determine the effects of long-term forced and sustained swimming at Uopt on growth performance of juvenile yellowtail kingfish. Uopt was quantified in Blazka-type swim-tunnels for 145 mm, 206 mm and 311 mm juveniles resulting in values of: 1 0.70 m s-1 or 4.83 BL s-1, 2 0.82 m s-1 or 3.25 BL s-1 and 3 0.85 m s-1 or 2.73 BL s-1. Combined with literature data from larger fish, a relation of Uopt (BL s-1 = 234.07(BL-0.779 (R2= 0.9909 was established for this species. Yellowtail kingfish, either forced to perform sustained swimming exercise at an optimal speed of 2.46 BL s-1 (‘swimmers’ or allowed to perform spontaneous activity at low water flow (‘resters’ in a newly designed 3,600 L oval flume (with flow created by an impeller driven by an electric motor, were then compared. At the start of the experiment, ten fish were sampled representing the initial condition. After 18 days, swimmers (n= 23 showed a 92% greater increase in BL and 46% greater increase in BW as compared to resters (n= 23. As both groups were fed equal rations, feed conversion ratio (FCR for swimmers was 1.21 vs. 1.74 for resters. Doppler ultrasound imaging showed a statistically significant higher blood flow (31% in the ventral aorta of swimmers vs. resters (44 ± 3 mL min-1 vs. 34 ± 3 mL min-1, respectively, under anesthesia. Thus growth performance can be rapidly improved by optimal swimming, without larger feed investments.

  13. Development of a Compact Maglev Centrifugal Blood Pump Enclosed in a Titanium Housing

    Science.gov (United States)

    Pai, Chi Nan; Shinshi, Tadahiko; Asama, Junichi; Takatani, Setsuo; Shimokohbe, Akira

    A compact centrifugal blood pump consisting of a controlled two-degrees-of-freedom radial magnetic bearing and a brushless DC motor enclosed in a titanium housing has been developed for use as an implantable ventricular assist device. The magnetic bearing also supports axial and angular motions of the impeller via a magnetic coupling. The top housing is made of pure titanium, while the impeller and the stator are coated with pure titanium and Ti-6Al-7Nb, respectively, to improve the biocompatibility of the pump. The combination of pure titanium and titanium alloy was chosen because of the sensitivity of eddy current type displacement sensors through the intervening conducting wall. The dimensions of the pump are 69.0 mm in diameter and 28.5 mm in height. During a pump performance test, axial shifting of the impeller due to hydraulic forces led to variations in the rotational positioning signal, causing loss of control of the rotational speed. This problem was solved by conditioning the rotational positioning signal. With a flow rate of 5 l/min against a head pressure of 100 mmHg, the power consumption and efficiency of the pump were 5.5 W and 20%, respectively. Furthermore, the hemolysis of the blood pump was 43.6% lower when compared to that of a commercially available pump.

  14. Variations of force constants, M-O distances and bond order in solid solutions between Ba/sub 2/MgUO/sub 6/ and Ba/sub 2/MgWO/sub 6/

    Energy Technology Data Exchange (ETDEWEB)

    Kemmler-Sack, S; Fadini, A [Tuebingen Univ. (Germany, F.R.). Inst. fuer Chemie

    1977-12-01

    In solid solutions between the 1:1 ordered perovskites Ba/sub 2/MgUO/sub 6/ and Ba/sub 2/MgWO/sub 6/ (system Ba/sub 2/MgUsub(1-x)Wsub(x)O/sub 6/) the force constants of the UO/sub 6/ and WO/sub 6/ octahedras are variied. The valence force constants fsub(MO) tend to adjust for each x. The bond order and the M-O distances are reported as well.

  15. Do stigma and other perceived barriers to mental health care differ across Armed Forces?

    Science.gov (United States)

    Gould, Matthew; Adler, Amy; Zamorski, Mark; Castro, Carl; Hanily, Natalie; Steele, Nicole; Kearney, Steve; Greenberg, Neil

    2010-01-01

    Summary Objectives Military organizations are keen to address barriers to mental health care yet stigma and barriers to care remain little understood, especially potential cultural differences between Armed Forces. The aim of this study was to compare data collected by the US, UK, Australian, New Zealand and Canadian militaries using Hoge et al.'s perceived stigma and barriers to care measure (Combat duty in Iraq and Afghanistan, mental health problems and barriers to care. New Engl J Med 2004;351:13–22). Design Each member country identified data sources that had enquired about Hoge et al.'s perceived stigma and perceived barriers to care items in the re-deployment or immediate post-deployment period. Five relevant statements were included in the study. Setting US, UK Australian, New Zealand and Canadian Armed Forces. Results Concerns about stigma and barriers to care tended to be more prominent among personnel who met criteria for a mental health problem. The pattern of reported stigma and barriers to care was similar across the Armed Forces of all five nations. Conclusions Barriers to care continue to be a major issue for service personnel within Western military forces. Although there are policy, procedural and cultural differences between Armed Forces, the nations studied appear to share some similarities in terms of perceived stigma and barriers to psychological care. Further research to understand patterns of reporting and subgroup differences is required. PMID:20382906

  16. Aging and low-flow degradation of auxilary feedwater pumps

    International Nuclear Information System (INIS)

    Adams, M.L.

    1992-01-01

    This paper documents the results of research done under the auspices of the Nuclear Regulatory Commission Nuclear Plant Aging Research Program. It examines the degradation imparted to safety related Auxiliary Feedwater System pumps at nuclear plants due to the low flow operation. The Auxiliary Feedwater (AFW) System is normally a stand-by system. As such it is operated most often in the test mode. Since few plants are equipped with full flow test loops, most testing is accomplished at minimum flow conditions in pump by-pass lines. It is the vibration and hydraulic forces generated at low flow conditions that have been shown to be the major causes of AFW pump aging and degradation. The wear can be manifested in a number of ways, such as impeller or diffuser breakage, thrust bearing and/or balance device failure due to excessive loading, cavitation damage on such stage impellers, increase seal leakage or failure, sear injection piping failure, shaft or coupling breakage, and rotating element seizure

  17. Aging and low-flow degradation of auxiliary feedwater pumps

    International Nuclear Information System (INIS)

    Adams, M.L.

    1991-01-01

    This paper documents the results of research done under the auspices of the Nuclear Regulatory Commission Nuclear Plant Aging Research Program. It examines the degradation imparted to safety Auxiliary Feedwater System pumps at nuclear plants due to the low flow operation. The Auxiliary Feedwater (AFW) System is normally a stand-by system. As such it is operated most often in the test mode. Since few plants are equipped with full flow test loops, most testing is accomplished at minimum flow conditions in pump by-pass lines. It is the vibration and hydraulic forces generated at low flow conditions that have been shown to be the major causes of AFW pump aging and degradation. The wear can be manifested in a number of ways, such as impeller or diffuser breakage, thrust bearing and/or balance device failure due to excessive loading, cavitation damage on such stage impellers, increase seal leakage or failure, sear injection piping failure, shaft or coupling breakage, and rotating element seizure

  18. Fluid-structure coupling effects on periodically transient flow of a single-blade sewage centrifugal pump

    International Nuclear Information System (INIS)

    Pei, Ji; Yuan, Shouqi; Yuan, Jianping

    2013-01-01

    A partitioned fluid-structure interaction (FSI) solving strategy that depends on problem characteristics is applied to quantitatively obtain the coupling effects of a fluid-structure system in a single-blade centrifugal pump on the unsteady flow. A two-way coupling method is employed to realize strong FSI effects in the calculation procedure. The successful impeller oscillation measurement using two proximity sensors validated the FSI simulation accuracy in a complicated and practical fluid-structure system having a rotating component. The results show that the hydrodynamic force deviation can be observed in the results for the coupled versus uncoupled cases. Additionally, the coupled unsteady pressure is larger than the uncoupled value for every monitoring point at every impeller rotation position. Comparison results for different monitoring points under an overload condition and partial-load condition display the same regularities. To some extent, this interaction mechanism would affect the accuracy and reliability of the unsteady flow and rotor deflection analysis.

  19. On nonlinear changes of the reflection coefficient of the fast wave at LH frequencies due to ponderomotive forces

    International Nuclear Information System (INIS)

    Petrzilka, V.

    1991-09-01

    The nonlinear changes of the reflection coefficient R of fast waves launched by waveguide arrays may be significant even for power densities S in the range of 3 or 4 kW/cm 2 . For the input parameters chosen in the computations, the effects of ponderomotive forces lead to an increase in plasma density in front of the grill , whereas for the slow wave the plasma density always decreases with growing S. For small plasma density in front of the grill, ponderomotive forces thus lead to the decrease of R, whereas for high plasma densities R grows with growing power density S. The heating of the edge plasma by the wave tends to weaken these changes. (Z.S.) 6 figs., 17 refs

  20. Membrana de PLDLA-TMC como protetor na regeneração do tendão calcâneo: Estudo in vivo em coelhos

    Directory of Open Access Journals (Sweden)

    Julia Rezende Duek

    2014-06-01

    Full Text Available Um dos maiores problemas da cirurgia restauradora dos tendões flexores é evitar a formação de aderências, pois limita seu deslizamento. Assim, é muito desejável que a cicatrização ocorra o mais rápido possível, restaurando a capacidade de deslizamento dos tendões, sem limitações dos movimentos. O objetivo deste trabalho foi analisar a resistência do Tendão calcâneo, utilizando membrana de PLDLA-TMC como protetor da aderência dos tecidos adjacentes após implantes em coelhos New Zeland. Foram utilizados 20 coelhos, divididos em dois grupos, os quais foram submetidos à secção do tendão calcâneo e posterior sutura com técnica de Kessler modificada. No grupo A, logo após sutura o animal foi sacrificado e o tendão foi enviado para ensaio mecânico. Já no grupo B, após três semanas, os animais foram sacrificados e o material foi submetido à análise histológica. Os resultados obtidos a partir do ensaio mecânico mostraram melhora nos valores da resistência à tração dos implantes com a membrana, comparados aos apenas suturados. Na cicatrização da lesão, ocorreu melhor organização das fibras colágenas quando foi utilizado o polímero PLDLA-TMC, além de uma menor aderência cicatricial. Conclui-se que a membrana de PLDLA-TMC é promissora na reparação de lesões tendíneas.

  1. A novel permanent maglev rotary LVAD with passive magnetic bearings.

    Science.gov (United States)

    Qian, K X; Yuan, H Y; Zeng, P; Ru, W M

    2005-01-01

    It has been widely acknowledged that permanent maglev cannot achieve stability; however, the authors have discovered that stable permanent maglev is possible under the effect of a combination of passive magnetic and nonmagnetic forces. In addition, a rotary left ventricular assist device (LVAD) with passive magnetic bearings has been developed. It is a radially driven impeller pump, having a rotor and a stator. The rotor consists of driven magnets and impeller; the motor coil and pump housing form the stator. Two passive magnetic bearings counteract the attractive force between motor coil iron core and rotor magnets; the rotor thereafter can be disaffiliated from the stator and become levitated under the action of passive magnetic and haemodynamic forces. Because of the pressure difference between the outlet and the inlet of the pump, there is a small flow passing through the gap of rotor and stator, and then entering the lower pressure area along the central hole of the rotor. This small flow comes to a full washout of all blood contacting surfaces in the motor. Moreover, a decreased Bernoulli force in the larger gap with faster flow produces a centring force that leads to stable levitation of the rotor. Resultantly, neither mechanical wear nor thrombosis will occur in the pump. The rotor position detection reveals that the precondition of levitation is a high rotating speed (over 3250 rpm) and a high flow rate (over 1 l min(-1)). Haemodynamic tests with porcine blood indicate that the device as a LVAD requires a rotating speed between 3500 and 4000 rpm for producing a blood flow of 4 - 6 l min(-1) against 100 mmHg mean pressure head. The egg-sized device has a weight of 200 g and an O.D. of 40 mm at its largest point.

  2. Observing how others lift light or heavy objects: time-dependent encoding of grip force in the primary motor cortex.

    Science.gov (United States)

    Alaerts, Kaat; de Beukelaar, Toon T; Swinnen, Stephan P; Wenderoth, Nicole

    2012-07-01

    During movement observation, corticomotor excitability of the observer's primary motor cortex (M1) is modulated according to the force requirements of the observed action. Here, we explored the time course of observation-induced force encoding. Force-related changes in M1-excitability were assessed by delivering transcranial magnetic stimulations at distinct temporal phases of an observed reach-grasp-lift action. Temporal changes in force-related electromyographic activity were also assessed during active movement execution. In observation conditions in which a heavy object was lifted, M1-excitability was higher compared to conditions in which a light object was lifted. Both during observation and execution, differential force encoding tended to gradually increase from the grasping phase until the late lift phase. Surprisingly, however, during observation, force encoding was already present at the early reach phase: a time point at which no visual cues on the object's weight were available to the observer. As the observer was aware that the same weight condition was presented repeatedly, this finding may indicate that prior predictions concerning the upcoming weight condition are reflected by M1 excitability. Overall, findings may provide indications that the observer's motor system represents motor predictions as well as muscular requirements to infer the observed movement goal.

  3. Tendências hidrológicas anuais e sazonais na bacia do Rio Paraibuna, Parque Estadual da Serra do Mar (SP)

    OpenAIRE

    Vilanova,Mateus Ricardo Nogueira

    2014-01-01

    O presente trabalho avalia a existência de tendências monotônicas em séries anuais e sazonais de vazão e chuva, no trecho da Bacia do Rio Paraibuna localizado entre os Núcleos Cunha e Santa Virgínia, Parque Estadual da Serra do Mar (SP). O teste de Mann-Kendall foi aplicado a séries destas variáveis, em diversos intervalos no período de 1967 a 2011. Tendências negativas estatisticamente significativas foram detectadas nas séries de c...

  4. Tendências da hanseníase no Tocantins, um estado hiperendêmico do Norte do Brasil, 2001-2012

    Directory of Open Access Journals (Sweden)

    Lorena Dias Monteiro

    2015-05-01

    Full Text Available A hanseníase é hiperendêmica no Estado do Tocantins, Brasil. O objetivo do estudo foi analisar as tendências dos indicadores da hanseníase no Tocantins em 2001-2012. Análise de dados advindos do Sistema de Informação de Agravos de Notificação (SINAN. Incluíram-se casos novos de residentes no Tocantins. Calcularam-se os indicadores da hanseníase e analisaram-se as tendências temporais por meio de regressão polinomial. Houve tendência significativa e decrescente para a detecção geral (R2 = 0,40; p 0,05, detecção de casos com grau 2 de incapacidade física (R2 = 0,37; p > 0,05 e proporção de casos com grau 2 (R2 = 0,49; p > 0,05. Houve aumento significativo para a proporção de casos com grau 1 de incapacidade (R2 = 0,82; p < 0,05 e proporção de casos multibacilares (R2 = 0,81; p < 0,05. O Tocantins apresenta regiões com alta transmissão e diagnóstico tardio da hanseníase, apontando a expansão da doença de forma heterogênea na análise temporal.

  5. Subatomic forces

    International Nuclear Information System (INIS)

    Sutton, C.

    1989-01-01

    Inside the atom, particles interact through two forces which are never felt in the everyday world. But they may hold the key to the Universe. These ideas on subatomic forces are discussed with respect to the strong force, the electromagnetic force and the electroweak force. (author)

  6. Sistemas de recuperação de informações e mecanismos de busca na web: panorama atual e tendências

    Directory of Open Access Journals (Sweden)

    Renato Rocha Souza

    Full Text Available Busca-se traçar um panorama das características básicas dos sistemas de recuperação de informações, apresentando seus modelos de recuperação mais comuns. São apresentados com ênfase especial os mecanismos de busca na web, seu estado atual de desenvolvimento e algumas tendências para o futuro. Dentre estas tendências, destacam-se notadamente aquelas introduzidas pelo Google, como o algoritmo pagerank, dentre outras inovações.

  7. Tendências de teses e dissertações sobre ensino de astronomia no Brasil

    Science.gov (United States)

    Bretones, P. S.; Megid Neto, J.

    2003-08-01

    Neste trabalho são apresentados os resultados de uma pesquisa do tipo estado da arte sobre teses e dissertações defendidas no Brasil e relativas ao ensino de Astronomia. Teve por objetivo identificar essa produção e conhecer as principais tendências da pesquisa nesse campo. O procedimento inicial consistiu de um levantamento bibliográfico junto ao Centro de Documentação em Ensino de Ciências (CEDOC) da Faculdade de Educação da UNICAMP e ao Banco de Teses da CAPES disponível na Internet. Foram localizadas 13 dissertações de mestrado e 3 teses de doutorado, as quais foram estudadas em função dos seguintes aspectos: instituição, ano de defesa, nível escolar abrangido no estudo, foco temático do estudo e gênero de trabalho acadêmico. Deste conjunto de pesquisas, 13 (81,3%) delas foram defendidas a partir da segunda metade dos anos 90, indicando uma preocupação mais recente com temas relativos ao ensino de Astronomia no conjunto da produção acadêmica em programas de pós-graduação no Brasil. Verificou-se que 43,7% dos trabalhos foram produzidas na USP e 18,8% na UNICAMP. Quanto ao nível escolar abrangido nos estudos, predominaram os estudos direcionados ao Ensino Fundamental de 5a a 8a séries (62,5%). No que diz respeito ao foco temático das pesquisas, as principais tendências voltaram-se: 56,3% para Conteúdo e Método; 43,8% para Concepções do Professor; 37,5% para Currículo e Programas; 37,5% para Recursos Didáticos. Quanto ao gênero de trabalho acadêmico, verificou-se que 43,8% são de Pesquisa Experimental e 31,3% de Pesquisa de Análise de Conteúdo. Estudos de revisão bibliográfica como este visam colaborar com a divulgação ampla da produção acadêmica em determinada área, traçando algumas de suas tendências. Ao mesmo tempo possibilita, a partir de investigações decorrentes, apontar as suas contribuições para o ensino e sinalizar com necessidades a serem supridas por futuras pesquisas.

  8. Quantitative measurements of electromechanical response with a combined optical beam and interferometric atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Labuda, Aleksander; Proksch, Roger [Asylum Research an Oxford Instruments Company, Santa Barbara, California 93117 (United States)

    2015-06-22

    An ongoing challenge in atomic force microscope (AFM) experiments is the quantitative measurement of cantilever motion. The vast majority of AFMs use the optical beam deflection (OBD) method to infer the deflection of the cantilever. The OBD method is easy to implement, has impressive noise performance, and tends to be mechanically robust. However, it represents an indirect measurement of the cantilever displacement, since it is fundamentally an angular rather than a displacement measurement. Here, we demonstrate a metrological AFM that combines an OBD sensor with a laser Doppler vibrometer (LDV) to enable accurate measurements of the cantilever velocity and displacement. The OBD/LDV AFM allows a host of quantitative measurements to be performed, including in-situ measurements of cantilever oscillation modes in piezoresponse force microscopy. As an example application, we demonstrate how this instrument can be used for accurate quantification of piezoelectric sensitivity—a longstanding goal in the electromechanical community.

  9. Development of the Floating Centrifugal Pump by Use of Non Contact Magnetic Drive and Its Performance

    Directory of Open Access Journals (Sweden)

    Mitsuo Uno

    2004-01-01

    Full Text Available This article focuses on the impeller construction, non contact driving method and performance of a newly developed shaftless floating pump with centrifugal impeller. The drive principle of the floating impeller pump used the magnet induction method similar to the levitation theory of the linear motor. In order to reduce the axial thrust by the pressure different between shroud and disk side, the balance hole and the aileron blade were installed in the floating impeller. Considering the above effect, floating of an impeller in a pump was realized. Moreover, the performance curves of a developed pump are in agreement with a general centrifugal pump, and the dimensionless characteristic curve also agrees under the different rotational speed due to no mechanical friction of the rotational part. Therefore, utility of a non contacting magnetic-drive style pump with the floating impeller was made clear.

  10. Unbalance response and stability analyses of the rotor of SMART main coolant pump

    International Nuclear Information System (INIS)

    Park, J. H.; Park, J. S.; Kim, J. I.

    2001-01-01

    SMART main coolant pump(MCP) is being designed as a vertical type and the rotor is operated immersed in hot and high pressure water. Hydraulic forces which are taken place at journal bearings, impellers and gaps between rotor and housing are inherently highly nonlinear and have unstable characteristics. Furthermore, since vertical rotor rather than horizontal type has no dominant static bearing load such as one's weight, traveling of journal center in the clearance circle of the bearing as varying of rotational speed make change in rotor characteristics greatly. In this paper, MCP rotor dynamic characteristics are estimated relating in hydraulic forces at journal bearings and gaps

  11. Phosphotyrosine signaling proteins that drive oncogenesis tend to be highly interconnected.

    Science.gov (United States)

    Koytiger, Grigoriy; Kaushansky, Alexis; Gordus, Andrew; Rush, John; Sorger, Peter K; MacBeath, Gavin

    2013-05-01

    Mutation and overexpression of receptor tyrosine kinases or the proteins they regulate serve as oncogenic drivers in diverse cancers. To better understand receptor tyrosine kinase signaling and its link to oncogenesis, we used protein microarrays to systematically and quantitatively measure interactions between virtually every SH2 or PTB domain encoded in the human genome and all known sites of tyrosine phosphorylation on 40 receptor tyrosine kinases and on most of the SH2 and PTB domain-containing adaptor proteins. We found that adaptor proteins, like RTKs, have many high affinity bindings sites for other adaptor proteins. In addition, proteins that drive cancer, including both receptors and adaptor proteins, tend to be much more highly interconnected via networks of SH2 and PTB domain-mediated interactions than nononcogenic proteins. Our results suggest that network topological properties such as connectivity can be used to prioritize new drug targets in this well-studied family of signaling proteins.

  12. Aeroacoustic characteristics and noise reduction of a centrifugal fan for a vacuum cleaner

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Wan Ho; Rew, Ho Seon; Kim, Chang Joon [LG Electronics, Seoul (Korea, Republic of)

    2004-02-01

    The aeroacoustic characteristics of a centrifugal fan for a vacuum cleaner and its noise reduction method are studied in this paper. The major noise source of a vacuum cleaner is the centrifugal fan. The impeller of the fan rotates at over 30000 rpm, and generates very high-level noise. It was revealed that the dominant noise source is the aerodynamic interaction between the rotating impeller and stationary diffuser. The directivity of acoustic pressure showed that most of the noise propagates backward direction of the fan-motor assembly. In order to reduce the high tonal sound generated from the aerodynamic interaction, unevenly pitched impeller and diffuser, and tapered impeller designs were proposed and experiments were performed. Uneven pitch design of the impeller changes the sound quality while the overall Sound Power Level (SPL) and the performance remains similar. The effect of the tapered design of impeller was evaluated. The trailing edge of the tapered fan is inclined. This reduces the flow interaction between the rotating impeller and the stationary diffuser because of some phase shifts. The static efficiency of the new impeller design is slightly lower than the previous design. However, the overall SPL is reduced by about 4 dB(A). The SPL of the fundamental Blade Passing Frequency (BPF) is reduced by about 6 dB(A) and the 2{sup nd} BPF is reduced about 20 dB(A). The vacuum cleaner with the tapered impeller design produces lower noise level than the previous one, and the strong tonal sound was dramatically reduced.

  13. Aeroacoustic characteristics and noise reduction of a centrifugal fan for a vacuum cleaner

    International Nuclear Information System (INIS)

    Jeon, Wan Ho; Rew, Ho Seon; Kim, Chang Joon

    2004-01-01

    The aeroacoustic characteristics of a centrifugal fan for a vacuum cleaner and its noise reduction method are studied in this paper. The major noise source of a vacuum cleaner is the centrifugal fan. The impeller of the fan rotates at over 30000 rpm, and generates very high-level noise. It was revealed that the dominant noise source is the aerodynamic interaction between the rotating impeller and stationary diffuser. The directivity of acoustic pressure showed that most of the noise propagates backward direction of the fan-motor assembly. In order to reduce the high tonal sound generated from the aerodynamic interaction, unevenly pitched impeller and diffuser, and tapered impeller designs were proposed and experiments were performed. Uneven pitch design of the impeller changes the sound quality while the overall Sound Power Level (SPL) and the performance remains similar. The effect of the tapered design of impeller was evaluated. The trailing edge of the tapered fan is inclined. This reduces the flow interaction between the rotating impeller and the stationary diffuser because of some phase shifts. The static efficiency of the new impeller design is slightly lower than the previous design. However, the overall SPL is reduced by about 4 dB(A). The SPL of the fundamental Blade Passing Frequency (BPF) is reduced by about 6 dB(A) and the 2 nd BPF is reduced about 20 dB(A). The vacuum cleaner with the tapered impeller design produces lower noise level than the previous one, and the strong tonal sound was dramatically reduced

  14. Karl Polanyi, la Nouvelle sociologie économique et les forces du marché

    Directory of Open Access Journals (Sweden)

    Ronan Le Velly

    2008-12-01

    Full Text Available Cet article montre en quoi plusieurs auteurs de la Nouvelle sociologie économique tendent à adopter un regard incomplet sur les forces du marché. Pour cela, l’auteur distingue deux notions d’encastrement renvoyant pour la première à un cadre méthodologique institutionnaliste et pour la seconde à l’observation du poids variable des forces du marché. Il établit qu’autant des sociologues classiques comme Weber ou Polanyi ont su coupler ces deux approches, autant plusieurs travaux majeurs de la Nouvelle sociologie économique, notamment ceux de Zelizer, de Fligstein et de Biggart, adoptent la première perspective mais ne traitent que de façon partielle de la seconde. L’auteur met particulièrement en cause les objets de recherche retenus par ces derniers auteurs, dès lors que sont systématiquement privilégiées des situations où les forces du marché sont tenues à l’écart.This article shows how many authors of the New Economic Sociology tend to adopt an incomplete view of market forces. The author distinguishes two notions of embeddedness, one related to the institutionalist theories and the second to the observation of the variable weight of market forces. It is established that classical sociologists such as Weber or Polanyi have joined these two approaches, while manyu works of the New sociological economy, for examle those of Zelizer, Fligstein or Biggart adopt the first perspective, but only treat the second partially. The author particularly questions the research objects chosen by these authors, since he considers that they generally refer to situations where market forces are held at bay.

  15. Moderate Imaging Resolution Spectroradiometer (MODIS) Aerosol Optical Depth Retrieval for Aerosol Radiative Forcing

    Science.gov (United States)

    Asmat, A.; Jalal, K. A.; Ahmad, N.

    2018-02-01

    The present study uses the Aerosol Optical Depth (AOD) retrieved from Moderate Imaging Resolution Spectroradiometer (MODIS) data for the period from January 2011 until December 2015 over an urban area in Kuching, Sarawak. The results show the minimum AOD value retrieved from MODIS is -0.06 and the maximum value is 6.0. High aerosol loading with high AOD value observed during dry seasons and low AOD monitored during wet seasons. Multi plane regression technique used to retrieve AOD from MODIS (AODMODIS) and different statistics parameter is proposed by using relative absolute error for accuracy assessment in spatial and temporal averaging approach. The AODMODIS then compared with AOD derived from Aerosol Robotic Network (AERONET) Sunphotometer (AODAERONET) and the results shows high correlation coefficient (R2) for AODMODIS and AODAERONET with 0.93. AODMODIS used as an input parameters into Santa Barbara Discrete Ordinate Radiative Transfer (SBDART) model to estimate urban radiative forcing at Kuching. The observed hourly averaged for urban radiative forcing is -0.12 Wm-2 for top of atmosphere (TOA), -2.13 Wm-2 at the surface and 2.00 Wm-2 in the atmosphere. There is a moderate relationship observed between urban radiative forcing calculated using SBDART and AERONET which are 0.75 at the surface, 0.65 at TOA and 0.56 in atmosphere. Overall, variation in AOD tends to cause large bias in the estimated urban radiative forcing.

  16. Quadriceps force and anterior tibial force occur obviously later than vertical ground reaction force: a simulation study

    OpenAIRE

    Ueno, Ryo; Ishida, Tomoya; Yamanaka, Masanori; Taniguchi, Shohei; Ikuta, Ryohei; Samukawa, Mina; Saito, Hiroshi; Tohyama, Harukazu

    2017-01-01

    Background: Although it is well known that quadriceps force generates anterior tibial force, it has been unclear whether quadriceps force causes great anterior tibial force during the early phase of a landing task. The purpose of the present study was to examine whether the quadriceps force induced great anterior tibial force during the early phase of a landing task. Methods: Fourteen young, healthy, female subjects performed a single-leg landing task. Muscle force and anterior tibial force w...

  17. Mixing quality characterization in separations process tanks

    International Nuclear Information System (INIS)

    Hassan, N.M.

    1995-01-01

    An experimental study has been performed on distribution of a dilute immiscible organic liquid dispersed in an aqueous phase contained baffled, paddle-agitated vessel, fitted with cooling coils. Acceptable total liquid levels in the vessel and minimum impeller speed were established for plant scale operation. Axial and radial distributions of the dispersed organic phase as functions of total liquid height, impeller speed, and the number of impellers were examined and some recurring trends were identified. Four stages of dispersion of organic phase in predominantly aqueous phase were identified with increasing rotational speed of impeller(s). The stages were: (1) non-dispersion stage in which the organic layer was undisturbed, (2) the organic layer was decreasing with impeller speed until complete but nonuniform dispersion was attained, (3) the non-uniformity of the completely dispersed mixture decreased with increasing rotational speed of impeller(s), and (4) a grossly uniform dispersion in which the local volume fraction of dispersed phase (organic) in mixture was the same throughout the vessel. Scale-up relations were developed for reproducing a defined mixing quality on two geometrically similar scales of operation, for the attainable condition of complete but non-uniform dispersion. The mixing quality was observed to decrease with increasing liquid depth over acceptable range, but variations in the overall concentration of organic liquid appeared to have only slight effect on the mixing quality

  18. Tendência temporal da mortalidade por homicídios na cidade de São Paulo, Brasil, 1979-1994

    Directory of Open Access Journals (Sweden)

    Rita Barradas Barata

    Full Text Available Estudou-se a tendência da mortalidade por homicídios segundo sexo e idade na cidade de São Paulo entre 1979 e 1994, utilizando modelos de ajuste de tendência temporal selecionados com base na significância de beta e valor de R², e análise de resíduos pela técnica de box and whisker plot. A mortalidade por homicídios em São Paulo passou de 12,2 óbitos por 100.000 hab. em 1979 para 34,2 em 1994, apresentando crescimento linear de 1,17 ao ano. O mesmo comportamento é observado em ambos os sexos, embora as taxas para os homens sejam cerca de 14 vezes maiores, denotando a deterioração das condições de vida urbana. Tanto os menores de dez anos como os maiores de 60 anos apresentam taxas constantes no período em valores relativamente baixos. O grupo de 10 a 19 anos apresenta crescimento das taxas segundo o modelo multiplicativo (incrementos 132,55. Os adultos jovens de 20 a 39 anos apresentam taxas crescentes durante todo o período, segundo o modelo linear, enquanto os adultos de 40 a 59 anos apresentam crescimento segundo o modelo recíproco. Observa-se, assim, que cada grupo de idade e sexo apresenta tendência temporal peculiar no período considerado.

  19. Cross flow cyclonic flotation column for coal and minerals beneficiation

    Science.gov (United States)

    Lai, Ralph W.; Patton, Robert A.

    2000-01-01

    An apparatus and process for the separation of coal from pyritic impurities using a modified froth flotation system. The froth flotation column incorporates a helical track about the inner wall of the column in a region intermediate between the top and base of the column. A standard impeller located about the central axis of the column is used to generate a centrifugal force thereby increasing the separation efficiency of coal from the pyritic particles and hydrophillic tailings.

  20. Diferentes tendências em pesquisas sobre a fala egocêntrica: análise de produções brasileiras

    Directory of Open Access Journals (Sweden)

    Alessandra de Morais

    2016-01-01

    pesquisas desenvolvidas no Brasil sobre a fala egocêntrica, de forma a identificar as principais questões teórico-metodológicas presentes em seu estudo. A busca foi feita no banco de Teses da CAPES e abarcou o período de 1987 a 2012; foram encontradas oito teses / dissertações. Os resultados demonstraram a abordagem predominante da fala egocêntrica à luz da perspectiva Histórico-Cultural, de Vigotski, com a presença, sobretudo, de duas tendências: estudos que confirmam seus postulados e os que sugerem contribuições de outros teóricos, em especial de Bakhtin. Uma terceira tendência foi também reconhecida, que, embora sinalize para os trabalhos de Piaget e Vigotski, tece críticas a ambos e não adere a nenhum deles.

  1. ENSO Modulations due to Interannual Variability of Freshwater Forcing and Ocean Biology-induced Heating in the Tropical Pacific.

    Science.gov (United States)

    Zhang, Rong-Hua; Gao, Chuan; Kang, Xianbiao; Zhi, Hai; Wang, Zhanggui; Feng, Licheng

    2015-12-18

    Recent studies have identified clear climate feedbacks associated with interannual variations in freshwater forcing (FWF) and ocean biology-induced heating (OBH) in the tropical Pacific. The interrelationships among the related anomaly fields are analyzed using hybrid coupled model (HCM) simulations to illustrate their combined roles in modulating the El Niño-Southern Oscillation (ENSO). The HCM-based supporting experiments are performed to isolate the related feedbacks, with interannually varying FWF and OBH being represented individually or collectively, which allows their effects to be examined in a clear way. It is demonstrated that the interannual freshwater forcing enhances ENSO variability and slightly prolongs the simulated ENSO period, while the interannual OBH reduces ENSO variability and slightly shortens the ENSO period, with their feedback effects tending to counteract each other.

  2. Large for Gestational Age Newborns from Mothers Without Diabetes Mellitus Tend to Become Tall and Lean Toddlers.

    Science.gov (United States)

    de Zegher, Francis; Pérez-Cruz, Miriam; Sebastiani, Giorgia; Díaz, Marta; López-Bermejo, Abel; Ibáñez, Lourdes

    2016-11-01

    A longitudinal study with dual x-ray absorptiometry disclosed that infants born large for gestational age from mothers without diabetes mellitus and without excessive gestational weight gain tend to be long with increased adipose tissue as newborns and tall and lean as toddlers. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. The prognostic value of the Tpeak-Tend interval in patients undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction

    DEFF Research Database (Denmark)

    Haarmark, Christian; Hansen, Peter R; Vedel-Larsen, Esben

    2011-01-01

    INTRODUCTION: The Tpeak-Tend interval (TpTe) has been linked to increased arrhythmic risk. TpTe was investigated before and after primary percutaneous coronary intervention (pPCI) in patients with ST-segment elevation myocardial infarction (STEMI). METHOD: Patients with first-time STEMI treated...... with pPCI were included (n = 101; mean age 62 years; range 39-89 years; 74% men). Digital electrocardiograms were taken pre- and post-PCI, respectively. Tpeak-Tend interval was measured in leads with limited ST-segment deviation. The primary end point was all-cause mortality during 22 +/- 7 months (mean...

  4. Adding Value to Force Diagrams: Representing Relative Force Magnitudes

    Science.gov (United States)

    Wendel, Paul

    2011-05-01

    Nearly all physics instructors recognize the instructional value of force diagrams, and this journal has published several collections of exercises to improve student skill in this area.1-4 Yet some instructors worry that too few students perceive the conceptual and problem-solving utility of force diagrams,4-6 and over recent years a rich variety of approaches has been proposed to add value to force diagrams. Suggestions include strategies for identifying candidate forces,6,7 emphasizing the distinction between "contact" and "noncontact" forces,5,8 and the use of computer-based tutorials.9,10 Instructors have suggested a variety of conventions for constructing force diagrams, including approaches to arrow placement and orientation2,11-13 and proposed notations for locating forces or marking action-reaction force pairs.8,11,14,15

  5. Force and Directional Force Modulation Effects on Accuracy and Variability in Low-Level Pinch Force Tracking.

    Science.gov (United States)

    Park, Sangsoo; Spirduso, Waneen; Eakin, Tim; Abraham, Lawrence

    2018-01-01

    The authors investigated how varying the required low-level forces and the direction of force change affect accuracy and variability of force production in a cyclic isometric pinch force tracking task. Eighteen healthy right-handed adult volunteers performed the tracking task over 3 different force ranges. Root mean square error and coefficient of variation were higher at lower force levels and during minimum reversals compared with maximum reversals. Overall, the thumb showed greater root mean square error and coefficient of variation scores than did the index finger during maximum reversals, but not during minimum reversals. The observed impaired performance during minimum reversals might originate from history-dependent mechanisms of force production and highly coupled 2-digit performance.

  6. Understanding environment-influenced swarm behavior from a social force perspective

    Science.gov (United States)

    Jiang, J.; Lu, D.; Jiang, Y.; Lee, Z.; Zhang, Y.; Yu, J.

    2018-02-01

    The relevant research on swarm behavior has focused on the facts that when individuals agree with other members in the system globally consistent behaviors are generated and that individual decisions are completely dominated by other members. In fact, when individuals generate their own behavior strategies, they tend to consider not only the influences of other members but also autonomically consider their current environment. For example, in the social foraging of flocks, the behavior strategy of each individual animal is influenced by the food distribution, and individual movement patterns are characterized by a highly efficient search strategy-Lévy walks. To investigate this, this paper proposes using an environment-driven social force perspective to explore the Lévy walks of individuals in a group in patchy food environments. This model adopts the concept of social force to quantify the social effects and the interactions between individuals and food. The coordination between forces is a key in the formation of individual behavior strategies. Our simulation results show a power-law frequency distribution for agent flight lengths that conforms to Lévy walks and verifies the hypothesis of a relationship between food density and the Lévy index. In our model, the flock still exhibits collective consistency and cohesion and yields a high value for the order parameter and population density when moving between food patches. In addition, our model explains the intraspecific cooperation and competition that occurs during foraging as proposed in related work. The simulation also validates the impact of two inducements for individual behaviors compared with several benchmark models.

  7. A Psicologia Social contemporânea: principais tendências e perspectivas nacionais e internacionais

    OpenAIRE

    Ferreira, Maria Cristina

    2010-01-01

    O presente trabalho faz um balanço do estado atual da Psicologia Social, no plano nacional e internacional. Para tanto, faz uma revisão inicial das principais tendências que marcaram a evolução da Psicologia Social na América do Norte, para, em seguida, apresentar as características atuais mais relevantes dessa disciplina na América do Norte, na Europa e na América Latina. Em seguida, detém-se na análise da recente produção brasileira em Psicologia Social. À guisa de conclusão, discute os des...

  8. Direct measurements of intermolecular forces by chemical force microscopy

    Science.gov (United States)

    Vezenov, Dmitri Vitalievich

    1999-12-01

    Detailed description of intermolecular forces is key to understanding a wide range of phenomena from molecular recognition to materials failure. The unique features of atomic force microscopy (AFM) to make point contact force measurements with ultra high sensitivity and to generate spatial maps of surface topography and forces have been extended to include measurements between well-defined organic molecular groups. Chemical modification of AFM probes with self-assembled monolayers (SAMs) was used to make them sensitive to specific molecular interactions. This novel chemical force microscopy (CFM) technique was used to probe forces between different molecular groups in a range of environments (vacuum, organic liquids and aqueous solutions); measure surface energetics on a nanometer scale; determine pK values of the surface acid and base groups; measure forces to stretch and unbind a short synthetic DNA duplex and map the spatial distribution of specific functional groups and their ionization state. Studies of adhesion forces demonstrated the important contribution of hydrogen bonding to interactions between simple organic functionalities. The chemical identity of the tip and substrate surfaces as well as the medium had a dramatic effect on adhesion between model monolayers. A direct correlation between surface free energy and adhesion forces was established. The adhesion between epoxy polymer and model mixed SAMs varied with the amount of hydrogen bonding component in the monolayers. A consistent interpretation of CFM measurements in polar solvents was provided by contact mechanics models and intermolecular force components theory. Forces between tips and surfaces functionalized with SAMs terminating in acid or base groups depended on their ionization state. A novel method of force titration was introduced for highly local characterization of the pK's of surface functional groups. The pH-dependent changes in friction forces were exploited to map spatially the

  9. Static forces in d=2+1 SU(N) gauge theories

    International Nuclear Information System (INIS)

    Meyer, H.B.

    2006-07-01

    Using a three-level algorithm we perform a high-precision lattice computation of the static force up to 1fm in the 2+1 dimensional SU(5) gauge theory. Discretization errors and the continuum limit are discussed in detail. By comparison with existing SU(2) and SU(3) data it is found that σr 2 0 =1.65-(π)/(24) holds at an accuracy of 1% for all N≥2, where r 0 is the Sommer reference scale. The effective central charge c(r) is obtained and an intermediate distance r s is defined via the property c(r s )=(π)/(24). It separates in a natural way the short-distance regime governed by perturbation theory from the long-distance regime described by an effective string theory. The ratio τ s /τ 0 decreases significantly from SU(2) to SU(3) to SU(5), where r s 0 . We give a preliminary estimate of its value in the large-N limit. The static force in the smallest representation of N-ality 2, which tends to the k=2 string tension as r→∞, is also computed up to 0.7 fm. The deviation from Casimir scaling is positive and grows from 0.1% to 1% in that range. (Orig.)

  10. The relationship between skull morphology, masticatory muscle force and cranial skeletal deformation during biting.

    Science.gov (United States)

    Toro-Ibacache, Viviana; Zapata Muñoz, Víctor; O'Higgins, Paul

    2016-01-01

    The human skull is gracile when compared to many Middle Pleistocene hominins. It has been argued that it is less able to generate and withstand high masticatory forces, and that the morphology of the lower portion of the modern human face correlates most strongly with dietary characteristics. This study uses geometric morphometrics and finite element analysis (FEA) to assess the relationship between skull morphology, muscle force and cranial deformations arising from biting, which is relevant in understanding how skull morphology relates to mastication. The three-dimensional skull anatomies of 20 individuals were reconstructed from medical computed tomograms. Maximal contractile muscle forces were estimated from muscular anatomical cross-sectional areas (CSAs). Fifty-nine landmarks were used to represent skull morphology. A partial least squares analysis was performed to assess the association between skull shape and muscle force, and FEA was used to compare the deformation (strains) generated during incisor and molar bites in two individuals representing extremes of morphological variation in the sample. The results showed that only the proportion of total muscle CSA accounted for by the temporalis appears associated with skull morphology, albeit weekly. However, individuals with a large temporalis tend to possess a relatively wider face, a narrower, more vertically oriented maxilla and a lower positioning of the coronoid process. The FEAs showed that, despite differences in morphology, biting results in similar modes of deformation for both crania, but with localised lower magnitudes of strains arising in the individual with the narrowest, most vertically oriented maxilla. Our results suggest that the morphology of the maxilla modulates the transmission of forces generated during mastication to the rest of the cranium by deforming less in individuals with the ability to generate proportionately larger temporalis muscle forces. Copyright © 2015 Elsevier GmbH. All

  11. Relations Between Lower Body Isometric Muscle Force Characteristics and Start Performance in Elite Male Sprint Swimmers

    Directory of Open Access Journals (Sweden)

    Igor Beretić

    2013-12-01

    Full Text Available The aim of the present study was twofold. The first aim was to examine the influence of absolute and relative lower body muscle force on kinematic component which determine the start performance. The second aim was to create multiregressional model which could use as a tool for swimming coaches with the purpose to start performance control and improvement. Twenty seven high-level trained male competitive swimmers all members of the Serbian National Youth and Senior Swimming Team (Age = 21.1 ± 4.3 yrs., Height = 1. 89 ± 0.10 m, Weight = 81.6 ± 8.4 kg, 50m freestyle - long course = 24.36 ± 0.86 s performed two trials of standing leg extensors isometric muscle force testing and three swimming start trials corresponding to 10m distance. The average start time significantly correlated with variables of leg extensors maximum voluntary force (Fmax, r = -0.559, p = 0.002, leg extensors relative muscle voluntary force (Frel, r = -0.727, p < 0.001, leg extensors specific rate of force development (RFD50%, r = -0.338, p = 0.047 and leg extensors relative value of specific rate of force development (RFD50%rel, r = -0.402, p = 0.040. Regression equation for t10m prediction was defined by following variables: maximum voluntary isometric force of leg extensors muscles at absolute and relative level (Fmax and Frel, as well as a specific rate of force development of the same muscle groups (RFD50% and RFD50%rel at absolute and relative level too with 74.4% of explained variance. Contractile abilities indicators of the leg extensors muscles included consideration: Fmax, RFD50%, Frel and RFD50%rel showed significant correlation with swimming start times on 10m. Additionally, the results suggest that swimmers, who possess greater isometric maximum force and specific rate of force development at absolute and relative levels, tend to be able to swim faster on initial 10m swim start perforamnce.

  12. StringForce

    DEFF Research Database (Denmark)

    Barendregt, Wolmet; Börjesson, Peter; Eriksson, Eva

    2017-01-01

    In this paper, we present the forced collaborative interaction game StringForce. StringForce is developed for a special education context to support training of collaboration skills, using readily available technologies and avoiding the creation of a "mobile bubble". In order to play String......Force two or four physically collocated tablets are required. These tablets are connected to form one large shared game area. The game can only be played by collaborating. StringForce extends previous work, both technologically and regarding social-emotional training. We believe String......Force to be an interesting demo for the IDC community, as it intertwines several relevant research fields, such as mobile interaction and collaborative gaming in the special education context....

  13. Dispersion Forces

    CERN Document Server

    Buhmann, Stefan Yoshi

    2012-01-01

    In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...

  14. Liquid sodium pumps

    International Nuclear Information System (INIS)

    Allen, H.G.

    1985-01-01

    The pump for use in a nuclear reactor cooling system comprises a booster stage impeller for drawing the liquid through the inlet. A diffuser is affixedly disposed within the pump housing to convert the kinetic pressure imparted to the liquid into increased static pressure. A main stage impeller is rotatively driven by a pump motor at a relatively high speed to impart a relatively high static pressure to the liquid and for discharging the liquid at a relatively high static pressure. A hydraulic coupling is disposed remotely from the liquid path for hydraulically coupling the main stage impeller and the booster stage impeller to rotate the booster stage impeller at a relatively low speed to maintain the low net positive suction pressure applied to the liquid at the inlet greater than the vapor pressure of the liquid and to ensure that the low net positive suction heat, as established by the main stage impeller exceeds the vapor pressure. The coupling comprises a grooved drum which rotates between inner and outer drag coupling members. In a modification the coupling comprises a torque converter. (author)

  15. Adolescência e Tendência Antissocial: o Rap como Expressão de uma Privação Emocional

    Directory of Open Access Journals (Sweden)

    Cláudia Yaísa Gonçalves da Silva

    Full Text Available O presente estudo objetiva refletir sobre a tendência antissocial no adolescente/jovem, por meio da análise do conteúdo descrito nas letras de músicas de rap brasileiro, as quais em geral surgem carregadas de revolta, inconformismo, denúncias sociais e esperança. A pesquisa se caracteriza como exploratória, documental e qualitativa. Para tanto, foi realizada análise de conteúdo das letras, e posterior discussão embasada na teoria de Donald Woods Winnicott, buscando nos trechos das músicas indícios referentes a privações ambientais e o sentido que as letras carregam no contexto do comportamento antissocial. Na análise de conteúdo encontraram-se três categorias: a falha ambiental como princípio para a tendência antissocial, a tendência antissocial enquanto esperança de reparação, e o rappara além da música. Nos excertos das letras de rapselecionadas, os comportamentos antissociais mostraram-se enquanto saída emocional encontrada pelos adolescentes/jovens com histórico de privação, fazendo-os adotarem uma conduta desafiadora socialmente como forma de buscar uma contenção externa para reparar a falha vivenciada antes por alguma figura referencial. Conclui-se que o rap se instaurou como solução positiva para a expressão dos sentimentos e a conquista de uma identidade e reconhecimento social frente aos pares.

  16. Reestruturação produtiva e acidentes de trabalho no Brasil: estrutura e tendências

    Directory of Open Access Journals (Sweden)

    Wünsch Filho Victor

    1999-01-01

    Full Text Available A incidência de acidentes de trabalho no Brasil apresenta tendência decrescente nas duas últimas décadas. A mortalidade também é decrescente, porém de forma menos acentuada. O subregistro tem sido o principal argumento para explanar tal fato. O estudo das séries temporais com base em dados secundários de 1970 a 1995 revela que a incidência de acidentes de trabalho é sensível às flutuações cíclicas da economia e vincula-se, em particular, ao nível de atividade industrial. Detectou-se uma correlação linear positiva (r = 0,80 entre a proporção de pessoas ocupadas na produção industrial e a incidência de acidentes em 14 estados brasileiros. A recessão econômica durante a década de 80 gerou desemprego. A queda da oferta de empregos formais no setor industrial ­ com maiores riscos de acidentes, foi acentuada pelo processo de reestruturação produtiva e a incorporação crescente da informática e da robótica em diferentes processos industriais. Como conseqüência houve o deslocamento de um maior volume de força de trabalho para o setor terciário ­ com menor risco de acidentes. Estes fatos foram determinantes na tendência dos acidentes de trabalho observada neste período de 25 anos.

  17. Reestruturação produtiva e acidentes de trabalho no Brasil: estrutura e tendências

    Directory of Open Access Journals (Sweden)

    Victor Wünsch Filho

    Full Text Available A incidência de acidentes de trabalho no Brasil apresenta tendência decrescente nas duas últimas décadas. A mortalidade também é decrescente, porém de forma menos acentuada. O subregistro tem sido o principal argumento para explanar tal fato. O estudo das séries temporais com base em dados secundários de 1970 a 1995 revela que a incidência de acidentes de trabalho é sensível às flutuações cíclicas da economia e vincula-se, em particular, ao nível de atividade industrial. Detectou-se uma correlação linear positiva (r = 0,80 entre a proporção de pessoas ocupadas na produção industrial e a incidência de acidentes em 14 estados brasileiros. A recessão econômica durante a década de 80 gerou desemprego. A queda da oferta de empregos formais no setor industrial com maiores riscos de acidentes, foi acentuada pelo processo de reestruturação produtiva e a incorporação crescente da informática e da robótica em diferentes processos industriais. Como conseqüência houve o deslocamento de um maior volume de força de trabalho para o setor terciário com menor risco de acidentes. Estes fatos foram determinantes na tendência dos acidentes de trabalho observada neste período de 25 anos.

  18. Final Environmental Assessment for the First Air Force Air Operations Center, First Air Force Headquarters/Air Force Forces Center, and Highway 98 Overpass at Tyndall Air Force Base, Florida

    Science.gov (United States)

    2004-01-01

    no comments regarding the Draft Environmental Assessment for the First Air Force Operations Center, First Air Force Headquarters/Air Force Forces...COUNCIL ] No Comment BAY - BAY COUNTY No Final Comments Received ENVIRONMENTAL POLICY UNIT - OFFICE OF POLICY AND BUDGET, ENVIRONMENTAL POLICY UNIT NO ...CONSERVATION COMMISSION [ NO COMMENT BY BRIAN BARNETT ON 4/12/04. [STATE - FLORIDA DEPARTMENT OF STATE [ No Comment [TRANSPORTATION - FLORIDA DEPARTMENT

  19. The TENDL neutron data library and the TEND1038 38-group neutron constant system

    International Nuclear Information System (INIS)

    Abramovich, S.N.; Gorelov, V.P.; Gorshikhin, A.A.; Grebennikov, A.N.; Il'in, V.N.; Krut'ko, N.A.; Farafontov, G.G.

    2002-01-01

    The library contains neutron data for 103 nuclei - i.e. for 38 actinide nuclei (from 232 Th to 249 Cm), 26 fission fragment nuclei and 39 nuclei in structural and technological materials. The 38-group constants were obtained from TENDL. The high-energy group boundary is 20 MeV. The energy range below 1.2 eV contains 11 groups. Temperature and resonance effects were taken into account. The delayed neutron parameters for 6 groups and the yields of 40 fission fragments were obtained (light and heavy, stable and non-stable). The fast neutron features of spherical critical assemblies were calculated using constants from TEND1038. (author)

  20. Dispersion forces in micromechanics: Casimir and Casimir-Polder forces affected by geometry and non-zero temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ellingsen, Simen Andreas Aadnoey

    2011-01-15

    The present thesis focuses on several topics within three separate but related branches of the overall field of dispersion forces. The three branches are: temperature corrections to the Casimir force between real materials (Part 1), explicit calculation of Casimir energy in wedge geometries (Part 2), and Casimir-Polder forces on particles out of thermal equilibrium (Part 3). Part 1 deals primarily with analysis of a previously purported thermodynamic inconsistency in the Casimir-Lifshitz free energy of the interaction of two plane mirrors - violation of the third law of thermodynamics - when the latter's dielectric response is described with dissipative models. It is shown analytically and numerically that the Casimir entropy of the interaction between two metallic mirrors described by the Drude model does tend to zero at zero temperature, provided electronic relaxation does not vanish. The leading order terms at low temperature are found. A similar calculation is carried out for the interaction of semiconductors with small but non-zero DC conductivity. In a generalisation, it is shown that a violation of the third law can only occur for permittivities whose low-frequency behaviour is temperature dependent near zero temperature. A calculation using path integral methods shows that the low temperature behaviour of the interaction of fluctuating Foucault currents in two mirrors of Drude metal is identical to that of the full Casimir-Lifshitz free energy, reasserting a previous finding by Intravaia and Henkel that such fluctuating bulk currents are the physical reason for the anomalous entropy behaviour. In a related effort, an analysis of the frequency dependence of the Casimir force by Ford is generalised to imperfectly reflecting mirrors. A paradox is pointed out, in that the effects of a perturbation of the reflecting properties of the mirrors in a finite frequency window can be calculated in two ways giving different results. It is concluded that optimistic

  1. Monsoonal Responses to External Forcings over the Past Millennium: A Model Study (Invited)

    Science.gov (United States)

    Liu, J.; Wang, B.

    2009-12-01

    understanding the latitudinal differences of the monsoonal responses to external forcings and internal feedback processes. The strength of the forced response depends on latitude. On centennial-millennial time scales, the variation of the extratropical and subtropical rainfall tends to follow the effective solar radiation forcing closely; the tropical rainfall is less sensitive to the effective solar radiation forcing but responds significantly to the modern anthropogenic CO2 forcing. The spatial patterns and structures of the forced response differ from the internal mode (i.e., interannual variability that arises primarily from the internal feedback processes within the climate system). Further, the behavior of the internal mode is effectively modulated by changes in the mean state on the centennial to millennial time scales. These findings have important ramification in understanding the differences and linkages between the forced and internal modes of variability as well as in promoting communication between scientists studying modern- and paleo-monsoon variations.

  2. Evaluation of working conditions of workers engaged in tending horses

    Directory of Open Access Journals (Sweden)

    Bożena Nowakowicz-Dębek

    2014-11-01

    Full Text Available [b]introduction[/b]. A growing interest in the horse business has resulted in the increased engagement of many people in this area, and the health problems occurring among workers create the need to search for prophylactic measures. [b]objective[/b]. The objective of the study was evaluation of the level of exposure to air pollution in a stable, and estimation of the degree of work load among workers engaged in tending horses. [b]material and methods[/b]. The study was conducted twice, during the winter season, in a stable maintaining race horses, and in a social room. In order to evaluate workers’ exposure, air samples were collected by the aspiration method. After the incubation of material, the total number of bacteria and fungi in the air was determined, as well as the number of aerobic mesophilic and thermophilic bacteria, expressed as the number of colony forming units per cubic meter of air (CFU/m[sup]3[/sup]. The measurement of total dust concentration in the air was also performed, simultaneously with the measurement of microclimatic parameters. The study of work load also covered the measurement of energy expenditure, evaluation of static physical load, and monotony of movements performed. [b]conclusions[/b]. The stable may be considered as a workplace with considerable risk of the occurrence of unfavourable health effects.

  3. Measurement of turbulent flow fields in a agitated vessel with four baffles by laser-doppler velocimetry. Analysis with periodic averaged velocity profiles; Baffle tsuki heiento kakuhan sonai nagare no LDV ni yoru keisoku. Shuki heikin sokudo bunpu ni yoru kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Suzukawa, K [Ube Industries, Ltd., Tokyo (Japan); Hashimoto, T; Osaka, H [Yamaguchi University, Yamaguchi (Japan). Faculty of Engineering

    1997-11-25

    The 3-D flow field relative to a rotating paddle blade is acquired by synchronizing LDV measurements with the output of a shaft-mounted encoder. This makes it possible to capture the impeller stream velocity field, including the details of the discharge flow region behind the blades. Mean velocities ensemble-averaged between a specific impeller blade pair (over 90deg) show the extent of periodicity and the passage and structure of the discharge flow region. Pumping capacities are determined at both sides of impeller and tip of impeller, and it is shown that the radial jet is a consequence of fluid entrainment into the discharge flow region. Mean velocities taken in a rotating frame of reference reveal a significant periodic variation near the impeller than those taken in a fixed frame. 13 refs., 12 figs., 1 tab.

  4. Rigid two-axis MEMS force plate for measuring cellular traction force

    International Nuclear Information System (INIS)

    Takahashi, Hidetoshi; Jung, Uijin G; Shimoyama, Isao; Kan, Tetsuo; Tsukagoshi, Takuya; Matsumoto, Kiyoshi

    2016-01-01

    Cellular traction force is one of the important factors for understanding cell behaviors, such as spreading, migration and differentiation. Cells are known to change their behavior according to the mechanical stiffness of the environment. However, the measurement of cell traction forces on a rigid environment has remained difficult. This paper reports a micro-electromechanical systems (MEMS) force plate that provides a cellular traction force measurement on a rigid substrate. Both the high force sensitivity and high stiffness of the substrate were obtained using piezoresistive sensing elements. The proposed force plate consists of a 70 µ m  ×  15 µ m  ×  5 µ m base as the substrate for cultivating a bovine aortic smooth muscle cell, and the supporting beams with piezoresistors on the sidewall and the surface were used to measure the forces in both the horizontal and vertical directions. The spring constant and force resolution of the fabricated force plate in the horizontal direction were 0.2 N m −1 and less than 0.05 µ N, respectively. The cell traction force was measured, and the traction force increased by approximately 1 µ N over 30 min. These results demonstrate that the proposed force plate is applicable as an effective traction force measurement. (paper)

  5. Honest People Tend to Use Less—Not More—Profanity : Comment on Feldman et al.’s Study 1

    NARCIS (Netherlands)

    de Vries, Reinout Everhard; Hilbig, Benjamin E.; Zettler, Ingo; Dunlop, Patrick D.; Holtrop, Djurre; Lee, Kibeom; Ashton, Michael C.

    2017-01-01

    This article shows that the conclusion of Feldman et al.’s (2017) Study 1 that profane individuals tend to be honest is most likely incorrect. We argue that Feldman et al.’s conclusion is based on a commonly held but erroneous assumption that higher scores on Impression Management Scales, such as

  6. Networks of conforming or nonconforming individuals tend to reach satisfactory decisions.

    Science.gov (United States)

    Ramazi, Pouria; Riehl, James; Cao, Ming

    2016-11-15

    Binary decisions of agents coupled in networks can often be classified into two types: "coordination," where an agent takes an action if enough neighbors are using that action, as in the spread of social norms, innovations, and viral epidemics, and "anticoordination," where too many neighbors taking a particular action causes an agent to take the opposite action, as in traffic congestion, crowd dispersion, and division of labor. Both of these cases can be modeled using linear-threshold-based dynamics, and a fundamental question is whether the individuals in such networks are likely to reach decisions with which they are satisfied. We show that, in the coordination case, and perhaps more surprisingly, also in the anticoordination case, the agents will indeed always tend to reach satisfactory decisions, that is, the network will almost surely reach an equilibrium state. This holds for every network topology and every distribution of thresholds, for both asynchronous and partially synchronous decision-making updates. These results reveal that irregular network topology, population heterogeneity, and partial synchrony are not sufficient to cause cycles or nonconvergence in linear-threshold dynamics; rather, other factors such as imitation or the coexistence of coordinating and anticoordinating agents must play a role.

  7. Automated force controller for amplitude modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Miyagi, Atsushi, E-mail: atsushi.miyagi@inserm.fr, E-mail: simon.scheuring@inserm.fr; Scheuring, Simon, E-mail: atsushi.miyagi@inserm.fr, E-mail: simon.scheuring@inserm.fr [U1006 INSERM, Université Aix-Marseille, Parc Scientifique et Technologique de Luminy, 163 Avenue de Luminy, 13009 Marseille (France)

    2016-05-15

    Atomic Force Microscopy (AFM) is widely used in physics, chemistry, and biology to analyze the topography of a sample at nanometer resolution. Controlling precisely the force applied by the AFM tip to the sample is a prerequisite for faithful and reproducible imaging. In amplitude modulation (oscillating) mode AFM, the applied force depends on the free and the setpoint amplitudes of the cantilever oscillation. Therefore, for keeping the applied force constant, not only the setpoint amplitude but also the free amplitude must be kept constant. While the AFM user defines the setpoint amplitude, the free amplitude is typically subject to uncontrollable drift, and hence, unfortunately, the real applied force is permanently drifting during an experiment. This is particularly harmful in biological sciences where increased force destroys the soft biological matter. Here, we have developed a strategy and an electronic circuit that analyzes permanently the free amplitude of oscillation and readjusts the excitation to maintain the free amplitude constant. As a consequence, the real applied force is permanently and automatically controlled with picoNewton precision. With this circuit associated to a high-speed AFM, we illustrate the power of the development through imaging over long-duration and at various forces. The development is applicable for all AFMs and will widen the applicability of AFM to a larger range of samples and to a larger range of (non-specialist) users. Furthermore, from controlled force imaging experiments, the interaction strength between biomolecules can be analyzed.

  8. Magnetic forces and localized resonances in electron transfer through quantum rings.

    Science.gov (United States)

    Poniedziałek, M R; Szafran, B

    2010-11-24

    We study the current flow through semiconductor quantum rings. In high magnetic fields the current is usually injected into the arm of the ring preferred by classical magnetic forces. However, for narrow magnetic field intervals that appear periodically on the magnetic field scale the current is injected into the other arm of the ring. We indicate that the appearance of the anomalous-non-classical-current circulation results from Fano interference involving localized resonant states. The identification of the Fano interference is based on the comparison of the solution of the scattering problem with the results of the stabilization method. The latter employs the bound-state type calculations and allows us to extract both the energy of metastable states localized within the ring and the width of resonances by analysis of the energy spectrum of a finite size system as a function of its length. The Fano resonances involving states of anomalous current circulation become extremely narrow on both the magnetic field and energy scales. This is consistent with the orientation of the Lorentz force that tends to keep the electron within the ring and thus increases the lifetime of the electron localization within the ring. Absence of periodic Fano resonances in electron transfer probability through a quantum ring containing an elastic scatterer is also explained.

  9. Imaging stability in force-feedback high-speed atomic force microscopy

    International Nuclear Information System (INIS)

    Kim, Byung I.; Boehm, Ryan D.

    2013-01-01

    We studied the stability of force-feedback high-speed atomic force microscopy (HSAFM) by imaging soft, hard, and biological sample surfaces at various applied forces. The HSAFM images showed sudden topographic variations of streaky fringes with a negative applied force when collected on a soft hydrocarbon film grown on a grating sample, whereas they showed stable topographic features with positive applied forces. The instability of HSAFM images with the negative applied force was explained by the transition between contact and noncontact regimes in the force–distance curve. When the grating surface was cleaned, and thus hydrophilic by removing the hydrocarbon film, enhanced imaging stability was observed at both positive and negative applied forces. The higher adhesive interaction between the tip and the surface explains the improved imaging stability. The effects of imaging rate on the imaging stability were tested on an even softer adhesive Escherichia coli biofilm deposited onto the grating structure. The biofilm and planktonic cell structures in HSAFM images were reproducible within the force deviation less than ∼0.5 nN at the imaging rate up to 0.2 s per frame, suggesting that the force-feedback HSAFM was stable for various imaging speeds in imaging softer adhesive biological samples. - Highlights: ► We investigated the imaging stability of force-feedback HSAFM. ► Stable–unstable imaging transitions rely on applied force and sample hydrophilicity. ► The stable–unstable transitions are found to be independent of imaging rate

  10. Forced response of the East Asian summer rainfall over the past millennium: results from a coupled model simulation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jian; Wang, Hongli; Ti, Ruyuan [Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, State Key Laboratory of Lake Science and Environment, Nanjing (China); Wang, Bin [University of Hawaii at Manoa, Department of Meteorology and IPRC, Honolulu, HI (United States); Kuang, Xueyuan [Nanjing University, School of Atmospheric Sciences, Nanjing (China)

    2011-01-15

    The centennial-millennial variation of the East Asian summer monsoon (EASM) precipitation over the past 1000 years was investigated through the analysis of a millennium simulation of the coupled ECHO-G model. The model results indicate that the centennial-millennial variation of the EASM is essentially a forced response to the external radiative forcing (insolation, volcanic aerosol, and green house gases). The strength of the response depends on latitude; and the spatial structure of the centennial-millennial variation differs from the interannual variability that arises primarily from the internal feedback processes within the climate system. On millennial time scale, the extratropical and subtropical precipitation was generally strong during Medieval Warm Period (MWP) and weak during Little Ice Age (LIA). The tropical rainfall is insensitive to the effective solar radiation forcing (insolation plus radiative effect of volcanic aerosols) but significantly responds to the modern anthropogenic radiative forcing. On centennial time scale, the variation of the extratropical and subtropical rainfall also tends to follow the effective solar radiation forcing closely. The forced response features in-phase rainfall variability between the extratropics and subtropics, which is in contrast to the anti-correlation on the interannual time scale. Further, the behavior of the interannual-decadal variation in the extratropics is effectively modulated by change of the mean states on the millennial time scale, suggesting that the structure of the internal mode may vary with significant changes in the external forcing. These findings imply that on the millennial time scale, (a) the proxy data in the extratropical EA may more sensitively reflect the EASM rainfall variations, and (b) the Meiyu and the northern China rainfall provide a consistent measure for the EASM strength. (orig.)

  11. Modelling of baffled stirred tanks

    Energy Technology Data Exchange (ETDEWEB)

    Ahlstedt, H.; Lahtinen, M. [Tampere Univ. of Technology (Finland). Energy and Process Engineering

    1996-12-31

    The three-dimensional flow field of a baffled stirred tank has been calculated using four different turbulence models. The tank is driven by a Rushton-type impeller. The boundary condition for the impeller region has been given as a source term or by calculating the impeller using the sliding mesh technique. Calculated values have been compared with measured data. (author)

  12. Modelling of baffled stirred tanks

    Energy Technology Data Exchange (ETDEWEB)

    Ahlstedt, H; Lahtinen, M [Tampere Univ. of Technology (Finland). Energy and Process Engineering

    1997-12-31

    The three-dimensional flow field of a baffled stirred tank has been calculated using four different turbulence models. The tank is driven by a Rushton-type impeller. The boundary condition for the impeller region has been given as a source term or by calculating the impeller using the sliding mesh technique. Calculated values have been compared with measured data. (author)

  13. Single stage high pressure centrifugal slurry pump

    Science.gov (United States)

    Meyer, John W.; Bonin, John H.; Daniel, Arnold D.

    1984-03-27

    Apparatus is shown for feeding a slurry to a pressurized housing. An impeller that includes radial passages is mounted in the loose fitting housing. The impeller hub is connected to a drive means and a slurry supply means which extends through the housing. Pressured gas is fed into the housing for substantially enveloping the impeller in a bubble of gas.

  14. Testing of Selective Laser Melting Turbomachinery Applicable to Exploration Upper Stage

    Science.gov (United States)

    Calvert, Marty; Turpin, Jason; Nettles, Mindy

    2015-01-01

    This task is to design, fabricate, and spin test to failure a Ti6-4 hydrogen turbopump impeller that was built using the selective laser melting (SLM) fabrication process (fig. 1). The impeller is sized around upper stage engine requirements. In addition to the spin burst test, material testing will be performed on coupons that are built with the impeller.

  15. Principles and applications of force spectroscopy using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young Kyu; Kim, Woong; Park, Joon Won [Dept. of Chemistry, Pohang University of Science and Technology, Pohang (Korea, Republic of)

    2016-12-15

    Single-molecule force spectroscopy is a powerful technique for addressing single molecules. Unseen structures and dynamics of molecules have been elucidated using force spectroscopy. Atomic force microscope (AFM)-based force spectroscopy studies have provided picoNewton force resolution, subnanometer spatial resolution, stiffness of substrates, elasticity of polymers, and thermodynamics and kinetics of single-molecular interactions. In addition, AFM has enabled mapping the distribution of individual molecules in situ, and the quantification of single molecules has been made possible without modification or labeling. In this review, we describe the basic principles, sample preparation, data analysis, and applications of AFM-based force spectroscopy and its future.

  16. Three-nucleon forces

    International Nuclear Information System (INIS)

    Sauer, P.U.

    2014-01-01

    In this paper, the role of three-nucleon forces in ab initio calculations of nuclear systems is investigated. The difference between genuine and induced many-nucleon forces is emphasized. Induced forces arise in the process of solving the nuclear many-body problem as technical intermediaries toward calculationally converged results. Genuine forces make up the Hamiltonian. They represent the chosen underlying dynamics. The hierarchy of contributions arising from genuine two-, three- and many-nucleon forces is discussed. Signals for the need of the inclusion of genuine three-nucleon forces are studied in nuclear systems, technically best under control, especially in three-nucleon and four-nucleon systems. Genuine three-nucleon forces are important for details in the description of some observables. Their contributions to observables are small on the scale set by two-nucleon forces. (author)

  17. Uncertainties in forces extracted from non-contact atomic force microscopy measurements by fitting of long-range background forces

    Directory of Open Access Journals (Sweden)

    Adam Sweetman

    2014-04-01

    Full Text Available In principle, non-contact atomic force microscopy (NC-AFM now readily allows for the measurement of forces with sub-nanonewton precision on the atomic scale. In practice, however, the extraction of the often desired ‘short-range’ force from the experimental observable (frequency shift is often far from trivial. In most cases there is a significant contribution to the total tip–sample force due to non-site-specific van der Waals and electrostatic forces. Typically, the contribution from these forces must be removed before the results of the experiment can be successfully interpreted, often by comparison to density functional theory calculations. In this paper we compare the ‘on-minus-off’ method for extracting site-specific forces to a commonly used extrapolation method modelling the long-range forces using a simple power law. By examining the behaviour of the fitting method in the case of two radically different interaction potentials we show that significant uncertainties in the final extracted forces may result from use of the extrapolation method.

  18. Differences in Pattern and Driving Forces between Urban and Rural Settlements in the Coastal Region of Ningbo, China

    Directory of Open Access Journals (Sweden)

    Mingxing Chen

    2014-04-01

    Full Text Available Rapid urbanization on the coast of China has attracted much attention. The objective of this study was to explore the differences in dynamics and related driving forces between urban and rural settlements. Applying the quantitative method, we demonstrate that substantial heterogeneity in settlement growth, landscape pattern metrics, change, land sources and driving forces is exhibited across the different types of urban and rural settlements. The spatial growth of urban settlements is dominated by in situ expansion, while rural settlements tend to be scattered and shrinking rapidly. The sprawl of human settlements has mainly occupied farm land, but reclamation projects are increasingly becoming important land sources for urban settlements. Local government has played a critical role in urban settlements, while the expansion of rural settlements is mainly driven by individual choice and village collective organizations. Such differences may account for differential options for the management of human settlements scientifically.

  19. Evaluation of supercritical CO2 centrifugal compressor experimental data by CFD analysis

    International Nuclear Information System (INIS)

    Takagi, Kazuhisa; Muto, Yasushi; Ishizuka, Takao; Watanabe, Noriyuki; Aritomi, Masanori

    2011-01-01

    A supercritical CO2 gas turbine of 20MPa is suitable to couple with the Na-cooled fast reactor since Na - CO2 reaction is mild at the outlet temperature of 800K, the cycle thermal efficiency is relatively high and the size of CO2 gas turbine is very compact. In this gas turbine cycle, a compressor operates near the critical point. The property of CO2 and then the behavior of compressible flow near the critical point changes very sharply. So far, such a behavior is not examined sufficiently. Then, it is important to clarify compressible flow near the critical point. In this paper, the experimental data of the centrifugal supercritical CO2 compressor have been evaluated by CFD analyses using a computer code 'CFX'. In the analyses, real gas properties of CO2 were achieved by simulating density. The test compressor consists of three kinds of impeller. First, impeller A has 16 blades and the overall diameter is 110mm. Second, impeller B has 16 blades and the overall diameter is 76mm. Third, impeller C has 12 blades and the overall diameter is 56mm. Each impeller has each diffuser. So, CFD analysis was conducted for each impeller and each diffuser. The results were compared and evaluated for the three different impeller and diffuser sets. Main output of calculation is a value of the total pressure at diffuser outlet, which agreed very well with that of the experiment. Total and static pressure distributions, relative velocity distributions and temperature distributions surrounding impeller and diffuser were obtained. Adiabatic efficiency was also evaluated. (author)

  20. Force modulation for improved conductive-mode atomic force microscopy

    NARCIS (Netherlands)

    Koelmans, W.W.; Sebastian, Abu; Despont, Michel; Pozidis, Haris

    We present an improved conductive-mode atomic force microscopy (C-AFM) method by modulating the applied loading force on the tip. Unreliable electrical contact and tip wear are the primary challenges for electrical characterization at the nanometer scale. The experiments show that force modulation

  1. Coupled thermo-fluid stress analysis of Kambara Reactor with various anchors in the stirring of molten iron at extremely high temperatures

    International Nuclear Information System (INIS)

    Huang, De-Shau; Huang, Feng-Chi

    2014-01-01

    Kambara Reactors (KR) are commonly used to reduce sulfur content in steel making, achieving efficiency levels exceeding 85% at 1300 °C. Unfortunately, the operational lifespan of the KR impeller is somewhat limited due to fracturing of the refractory material via thermal shock, resulting in the penetration of molten iron into the inner core. Few studies have investigated the coupled thermo-fluid stress of KR impellers at extremely high temperatures. This study employed CFX and FEM to simulate and analyze the molten iron and the resulting thermal stress imposed on the KR impeller. Simulation results including flow field, temperature, and thermal stress under extremely high temperatures are in strong agreement with empirical data. V-type anchors for the KR impeller outperformed Y-type anchors. - Highlights: • A thermo-fluid coupling approach is proposed to analyze the thermal stress. • The temperature and stress of the impeller are 790 °C and 744 MPa at the final stage. • The highest temperatures occur at the tip of anchors, which causes material crack. • The thermal stress in impellers with Y-type anchors is greater than V-type anchors

  2. Acesso livre à informação científica digital: dificuldades e tendências

    Directory of Open Access Journals (Sweden)

    Claudia Regina Ziliotto Bomfá

    Full Text Available O artigo discute a questão do acesso livre à informação científica digital. São discutidos aspectos conceituais do acesso livre e apresentados os principais movimentos nacionais e internacionais em favor do acesso livre. Identificam-se repositórios de pesquisas científicas baseados no movimento de acesso livre e apresentam-se dificuldades e tendências. Conclui-se sinalizando mudanças no processo de comunicação científica, com ênfase na amplitude, rapidez e transparência no acesso livre à informação científica.

  3. Numerical Calculation of Secondary Flow in Pump Volute and Circular Casings using 3D Viscous Flow Techniques

    Directory of Open Access Journals (Sweden)

    K. Majidi

    2000-01-01

    Full Text Available The flow field in volute and circular casings interacting with a centrifugal impeller is obtained by numerical analysis. In the present study, effects of the volute and circular casings on the flow pattern have been investigated by successively combining a volute casing and a circular casing with a single centrifugal impeller. The numerical calculations are carried out with a multiple frame of reference to predict the flow field inside the entire impeller and casings. The impeller flow field is solved in a rotating frame and the flow field in the casings in a stationary frame. The static pressure and velocity in the casing and impeller, and the static pressures and secondary velocity vectors at several cross-sectional planes of the casings are calculated. The calculations show that the curvature of the casings creates pressure gradients that cause vortices at cross-sectional planes of the casings.

  4. Quantum fictitious forces

    DEFF Research Database (Denmark)

    Bialynicki-Birula, I; Cirone, M.A.; Dahl, Jens Peder

    2002-01-01

    We present Heisenberg's equation of motion for the radial variable of a free non-relativistic particle in D dimensions. The resulting radial force consists of three contributions: (i) the quantum fictitious force which is either attractive or repulsive depending on the number of dimensions, (ii......) a singular quantum force located at the origin, and (iii) the centrifugal force associated with non-vanishing angular momentum. Moreover, we use Heisenberg's uncertainty relation to introduce a lower bound for the kinetic energy of an ensemble of neutral particles. This bound is quadratic in the number...... of atoms and can be traced back to the repulsive quantum fictitious potential. All three forces arise for a free particle: "Force without force"....

  5. Performance improvement of standard turbo-compressor; Han`yo turbo asshukuki no seino kaizen

    Energy Technology Data Exchange (ETDEWEB)

    Hokari, T.; Hasegawa, K.; Ozaki, S.; Majima, K. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)

    1999-05-01

    Abradable materials are soft and cause no contact damage to the impeller of the turbo-compressor. Using such materials for the inlet casing facing to the impeller allows very small clearances between the impeller and inlet casing, thus improving the compressor efficiency by 10% over conventional types. Changing the area of abradable material applied to the inlet casing identified the optimum area in which decrease of the compressor surge margin is minimized and efficiency is improved by 10%. As a result, turbo-compressors have the best performance when the abradable materials are applied from the impeller outlet to two-thirds of the forward location of the inlet casing. (author)

  6. Competência Informacional: análise evolucionária das tendências da pesquisa e produtividade científica em âmbito mundial

    OpenAIRE

    Dudziak, Elisabeth Adriana; Universidade de Sao Paulo

    2010-01-01

    Objetiva analisar a produtividade científica e identificar tendências de pesquisa em torno do tema da competência informacional (information literacy), tomando por base pesquisa reali-zada em duas das principais bases de dados internacionais multidisciplinares dedicadas à análise de citações: Web of Science (WoS) e SCOPUS. Inicia abordando o significado da análise bibliométrica e sua importância na determinação de tendências da atividade e produ-tividade científicas. Apresenta a evolução do c...

  7. The Tin Coatings Utilisation As Blood Contact Surface Modification In Implantable Rotary Left Ventricle Assist Device Religaheart Rot

    Directory of Open Access Journals (Sweden)

    Kustosz R.

    2015-09-01

    Full Text Available Constructions of the mechanical-bearingless centrifugal blood pumps utilize different types of non-contact physical bearings, which allows to balance the forces that have an impact on the pump impeller, stabilizing its position in the pump house without wall contact. The paper presents investigations of the hybrid (passive magnetic bearings and hydrodynamic bearings suspension system for the centrifugal blood pump. Numerical simulations were used to evaluate the hydrodynamic bearing lifting force and magnetic bearing forces interaction. An important aspect of rotor suspension system design was the nominal gap in hydrodynamic bearing area in order to reduce the blood damage risk in this region. The analyses results confirmed that for a small diameter centrifugal pump, the nominal operating hydrodynamic bearing gap could be established within the range from 0.033 to 0.072 mm.

  8. New gentle-wing high-shear granulator: impact of processing variables on granules and tablets characteristics of high-drug loading formulation using design of experiment approach.

    Science.gov (United States)

    Fayed, Mohamed H; Abdel-Rahman, Sayed I; Alanazi, Fars K; Ahmed, Mahrous O; Tawfeek, Hesham M; Al-Shdefat, Ramadan I

    2017-10-01

    The aim of this work was to study the application of design of experiment (DoE) approach in defining design space for granulation and tableting processes using a novel gentle-wing high-shear granulator. According to quality-by-design (QbD) prospective, critical attributes of granules, and tablets should be ensured by manufacturing process design. A face-centered central composite design has been employed in order to investigate the effect of water amount (X 1 ), impeller speed (X 2 ), wet massing time (X 3 ), and water addition rate (X 4 ) as independent process variables on granules and tablets characteristics. Acetaminophen was used as a model drug and granulation experiments were carried out using dry addition of povidone k30. The dried granules have been analyzed for their size distribution, density, and flow pattern. Additionally, the produced tablets have been investigated for; weight uniformity, breaking force, friability and percent capping, disintegration time, and drug dissolution. Results of regression analysis showed that water amount, impeller speed and wet massing time have significant (p tablets characteristics. However, the water amount had the most pronounced effect as indicated by its higher parameter estimate. On the other hand, water addition rate showed a minimal impact on granules and tablets properties. In conclusion, water amount, impeller speed, and wet massing time could be considered as critical process variables. Thus, understanding the relationship between these variables and quality attributes of granules and corresponding tablets provides the basis for adjusting granulation variables in order to optimize product performance.

  9. Tendências anuais e sazonais nos extremos de temperatura do ar e precipitação em campina grande - pb

    Directory of Open Access Journals (Sweden)

    Leydson Galvíncio Dantas

    2015-12-01

    Full Text Available RESUMO Devido à rápida expansão urbana e potencial turístico da região, o objetivo deste estudo foi a obtenção da distribuição temporal dos índices de extremos climáticos dependentes de dados diários de temperatura e precipitação, definido pela OMM, para o período de 1975 a 2011, e utilizando os testes estatísticos não paramétricos obter a magnitude das tendências dos referidos índices para a cidade de Campina Grande - PB. Os resultados mostram que as temperaturas mínimas e máxima diárias têm aumentado gradativamente ao longo das últimas décadas, apresentando tendências sazonais crescentes ao longo dos anos e que as temperaturas mínimas tiveram maior aumento. O número de dias e noites quentes por ano tem aumentado, proporcionando assim uma redução significativa dos dias e noites frias. Foi observado que as temperaturas mínimas e máximas apresentam maiores tendências de aumento nas estações do outono e primavera, respectivamente. Baseado nos índices extremos de precipitação, mesmo sem significância estatística, foi observado que as chuvas intensas tendem a aumentar, ocorrendo em um período menor de tempo.

  10. Effects of wide step walking on swing phase hip muscle forces and spatio-temporal gait parameters.

    Science.gov (United States)

    Bajelan, Soheil; Nagano, Hanatsu; Sparrow, Tony; Begg, Rezaul K

    2017-07-01

    Human walking can be viewed essentially as a continuum of anterior balance loss followed by a step that re-stabilizes balance. To secure balance an extended base of support can be assistive but healthy young adults tend to walk with relatively narrower steps compared to vulnerable populations (e.g. older adults and patients). It was, therefore, hypothesized that wide step walking may enhance dynamic balance at the cost of disturbed optimum coupling of muscle functions, leading to additional muscle work and associated reduction of gait economy. Young healthy adults may select relatively narrow steps for a more efficient gait. The current study focused on the effects of wide step walking on hip abductor and adductor muscles and spatio-temporal gait parameters. To this end, lower body kinematic data and ground reaction forces were obtained using an Optotrak motion capture system and AMTI force plates, respectively, while AnyBody software was employed for muscle force simulation. A single step of four healthy young male adults was captured during preferred walking and wide step walking. Based on preferred walking data, two parallel lines were drawn on the walkway to indicate 50% larger step width and participants targeted the lines with their heels as they walked. In addition to step width that defined walking conditions, other spatio-temporal gait parameters including step length, double support time and single support time were obtained. Average hip muscle forces during swing were modeled. Results showed that in wide step walking step length increased, Gluteus Minimus muscles were more active while Gracilis and Adductor Longus revealed considerably reduced forces. In conclusion, greater use of abductors and loss of adductor forces were found in wide step walking. Further validation is needed in future studies involving older adults and other pathological populations.

  11. Interfacial force measurements using atomic force microscopy

    NARCIS (Netherlands)

    Chu, L.

    2018-01-01

    Atomic Force Microscopy (AFM) can not only image the topography of surfaces at atomic resolution, but can also measure accurately the different interaction forces, like repulsive, adhesive and lateral existing between an AFM tip and the sample surface. Based on AFM, various extended techniques have

  12. Force Measurement with a Piezoelectric Cantilever in a Scanning Force Microscope

    OpenAIRE

    Tansock, J.; Williams, C. C.

    1992-01-01

    Detection of surface forces between a tip and sample has been demonstrated with a piezoelectric cantilever in a scanning force microscope (SFM). The use of piezoelectric force sensing is particularly advantageous in semiconductor applications where stray light from conventional optical force-sensing methods can significantly modify the local carrier density. Additionally, the piezoelectric sensors are simple, provide good sensitivity to force, and can be batch fabricated. Our piezoelectric fo...

  13. Force reconstruction from tapping mode force microscopy experiments

    International Nuclear Information System (INIS)

    Payam, Amir F; Martin-Jimenez, Daniel; Garcia, Ricardo

    2015-01-01

    Fast, accurate, and robust nanomechanical measurements are intensely studied in materials science, applied physics, and molecular biology. Amplitude modulation force microscopy (tapping mode) is the most established nanoscale characterization technique of surfaces for air and liquid environments. However, its quantitative capabilities lag behind its high spatial resolution and robustness. We develop a general method to transform the observables into quantitative force measurements. The force reconstruction algorithm has been deduced on the assumption that the observables (amplitude and phase shift) are slowly varying functions of the tip–surface separation. The accuracy and applicability of the method is validated by numerical simulations and experiments. The method is valid for liquid and air environments, small and large free amplitudes, compliant and rigid materials, and conservative and non-conservative forces. (paper)

  14. Labor Force

    Science.gov (United States)

    Occupational Outlook Quarterly, 2012

    2012-01-01

    The labor force is the number of people ages 16 or older who are either working or looking for work. It does not include active-duty military personnel or the institutionalized population, such as prison inmates. Determining the size of the labor force is a way of determining how big the economy can get. The size of the labor force depends on two…

  15. Research on energy conversion mechanism of a screw centrifugal pump under the water

    International Nuclear Information System (INIS)

    Quan, H; Li, R N; Han, W; Cheng, X R; Shen, Z J; Su, Q M

    2013-01-01

    In order to research screw centrifugal pump impeller power capability and energy conversion mechanism, we used Navier-Stokes equation and standard k-ε equation turbulence model on the basis of the Euler equations to carry out screw centrifugal pump internal flow numerical simulation. This was explored by simulating specific design conditions; the medium is water, variation of speed and pressure of flow filed under the action of the impeller, and the screw centrifugal impeller shroud line and wheel line segment take monitoring sites. The monitoring points are between dynamic head and static head change to analyze the energy conversion capability along the impeller corners of screw centrifugal pump. The results show that the energy of fluid of the screw centrifugal pump is provided by spiral segment, the spiral segment in front of the impeller has played a multi-level role, it has significant reference value to research the energy conversion mechanism of screw centrifugal pump under solid-liquid two phase

  16. Kinetics of enzymatic synthesis of liquid wax ester from oleic acid and oleyl alcohol.

    Science.gov (United States)

    Radzi, Salina Mat; Mohamad, Rosfarizan; Basri, Mahiran; Salleh, Abu Bakar; Ariff, Arbakariya; Rahman, Mohammad Basyaruddin Abdul; Rahman, Raja Noor Zaliha Raja Abdul

    2010-01-01

    The kinetics of wax ester synthesis from oleic acid and oleyl alcohol using immobilized lipase from Candida antartica as catalyst was studied with different types of impeller (Rushton turbine and AL-hydrofoil) to create different mixing conditions in 2l stirred tank reactor. The effects of catalyst concentration, reaction temperature, and impeller tip speed on the synthesis were also evaluated. Rushton turbine impeller exhibited highest conversion rate at lower impeller tip speed as compared to AL-hydrofoil impeller. A second-order reversible kinetic model from single progress curve for the prediction of fractional conversion at given reaction time was proposed and the corresponding kinetic parameter values were calculated by non-linear regression method. The results from the simulation using the proposed model showed satisfactory agreement with the experimental data. Activation energy shows a value of 21.77 Kcal/mol. The thermodynamic parameters of the process, enthalpy and entropy, were 21.15 Kcal/mol and 52.07 cal/mol.K, respectively.

  17. Modification of design methods to suit computer aided design of pumps

    International Nuclear Information System (INIS)

    Kumaraswamy, S.

    1994-01-01

    Engineering designs involve a large number of repetitive calculations to achieve optimisation. So, computers which are fast and accurate lend themselves as an aid for the design process. However, certain modifications in the steps of conventional design method become necessary for easier adaptation. In addition, it will be advantageous if the empirical coefficients of design are allowed to be chosen by the designer with prompting of ranges taken from design charts by the program itself. This paper describes two examples of modification in pump design. In the first case Anderson's area ratio method and Pfleiderer's Slip power methods are combined to achieve an integrated design of impeller and casing. The second case is the design of a Mixed flow pump impeller by considering it as an assembly of a number of radial flow pump impellers called part impellers. In addition, these modifications are useful in redesign for a different operating condition or in matching of impellers to existing casings. (author). 13 refs., 4 figs

  18. Sensitivity of Horn of Africa Rainfall to Regional Sea Surface Temperature Forcing

    Directory of Open Access Journals (Sweden)

    Zewdu T. Segele

    2015-05-01

    Full Text Available The Abdus Salam International Center for Theoretical Physics (ICTP version 4.4 Regional Climate Model (RegCM4 is used to investigate the rainfall response to cooler/warmer sea surface temperature anomaly (SSTA forcing in the Indian and Atlantic Oceans. The effect of SSTA forcing in a specific ocean basin is identified by ensemble, averaging 10 individual simulations in which a constant or linearly zonally varying SSTA is prescribed in individual basins while specifying the 1971–2000 monthly varying climatological sea surface temperature (SST across the remaining model domain. The nonlinear rainfall response to SSTA amplitude also is investigated by separately specifying +1K, +2K, and +4K SSTA forcing in the Atlantic and Indian Oceans. The simulation results show that warm SSTs over the entire Indian Ocean produce drier conditions across the larger Blue Nile catchment, whereas warming ≥ +2K generates large positive rainfall anomalies exceeding 10 mm·day−1 over drought prone regions of Northeastern Ethiopia. However, the June–September rainy season tends to be wetter (drier when the SST warming (cooling is limited to either the Northern or Southern Indian Ocean. Wet rainy seasons generally are characterized by deepening of the monsoon trough, east of 40°E, intensification of the Mascarene high, strengthening of the Somali low level jet and the tropical easterly jet, enhanced zonal and meridional vertically integrated moisture fluxes, and steeply vertically decreasing moist static energy. The opposite conditions hold for dry monsoon seasons.

  19. Inferring Interaction Force from Visual Information without Using Physical Force Sensors.

    Science.gov (United States)

    Hwang, Wonjun; Lim, Soo-Chul

    2017-10-26

    In this paper, we present an interaction force estimation method that uses visual information rather than that of a force sensor. Specifically, we propose a novel deep learning-based method utilizing only sequential images for estimating the interaction force against a target object, where the shape of the object is changed by an external force. The force applied to the target can be estimated by means of the visual shape changes. However, the shape differences in the images are not very clear. To address this problem, we formulate a recurrent neural network-based deep model with fully-connected layers, which models complex temporal dynamics from the visual representations. Extensive evaluations show that the proposed learning models successfully estimate the interaction forces using only the corresponding sequential images, in particular in the case of three objects made of different materials, a sponge, a PET bottle, a human arm, and a tube. The forces predicted by the proposed method are very similar to those measured by force sensors.

  20. Simulation of aluminium STIR casting technique

    International Nuclear Information System (INIS)

    Hafizal Yazid; Mohd Harun; Hanani Yazid; Abd Aziz Mohamed; Muhammad Rawi Muhammad Zain; Zaiton Selamat; Mohd Shariff Sattar; Muhamad Jalil; Ismail Mustapha; Razali Kasim

    2006-01-01

    In this paper, the objective is to determine the optimum impeller speed correlated with holding time to achieve homogeneous reinforcement distribution for a particular set of experimental condition. Attempts are made to simulate the flow behaviourof the liquid aluminium using FLUENT software. Stepwise impeller speed ranging from 50 to 300 rpm.with 2 impeller angle blades of 45 and 90 degree with respect to the rotational plane were used

  1. Detection and effects of pump low-flow operation

    International Nuclear Information System (INIS)

    Casada, D.A.; Greene, R.H.

    1994-01-01

    Operating experience and previous studies performed for the Nuclear Plant Aging Research Program have shown that a significant cause of pump problems and failures can result from low-flow operation. Operation at low-flow rates can create unstable flows within the pump impeller and casing. This condition can result in an increased radial and axial thrust on the rotor, which in turn causes higher shaft stresses, increased shaft deflection, and potential bearing and mechanical seal problems. Two of the more serious results of low-flow pump operation are cavitation and recirculation. Both of these conditions can be characterized by crackling sounds that accompany a substantial increase in vibration and noise level, and a reduction in total head and output capacity. Cavitation is the formation and subsequent collapse of vapor bubbles in any flow that is at an ambient pressure less than the vapor pressure of the liquid medium. It is the collapse of these vapor bubbles against the metal surfaces of the impeller or casing that causes surface pitting, erosion, and deterioration. Pump recirculation, reversal of a portion of the flow back through the impeller, can be potentially more damaging than cavitation. If located at the impeller eye, recirculation damages the inlet areas of the casing. At the impeller tips, recirculation alters the outside diameter of the impeller. If recirculation occurs around impeller shrouds, it damages thrust bearings. Recirculation also erodes impellers, diffusers, and volutes and causes failure of mechanical seals and bearings. This paper reports on a utility pump failure cause by low-flow induced phenomena. ORNL has continued to investigate the results of low-flow pump operations by evaluating the types of measurements and diagnostic techniques that are currently used by licensees to detect pump degradation

  2. Multi-objective optimization design and experimental investigation of centrifugal fan performance

    Science.gov (United States)

    Zhang, Lei; Wang, Songling; Hu, Chenxing; Zhang, Qian

    2013-11-01

    Current studies of fan performance optimization mainly focus on two aspects: one is to improve the blade profile, and another is only to consider the influence of single impeller structural parameter on fan performance. However, there are few studies on the comprehensive effect of the key parameters such as blade number, exit stagger angle of blade and the impeller outlet width on the fan performance. The G4-73 backward centrifugal fan widely used in power plants is selected as the research object. Based on orthogonal design and BP neural network, a model for predicting the centrifugal fan performance parameters is established, and the maximum relative errors of the total pressure and efficiency are 0.974% and 0.333%, respectively. Multi-objective optimization of total pressure and efficiency of the fan is conducted with genetic algorithm, and the optimum combination of impeller structural parameters is proposed. The optimized parameters of blade number, exit stagger angle of blade and the impeller outlet width are seperately 14, 43.9°, and 21 cm. The experiments on centrifugal fan performance and noise are conducted before and after the installation of the new impeller. The experimental results show that with the new impeller, the total pressure of fan increases significantly in total range of the flow rate, and the fan efficiency is improved when the relative flow is above 75%, also the high efficiency area is broadened. Additionally, in 65% -100% relative flow, the fan noise is reduced. Under the design operating condition, total pressure and efficiency of the fan are improved by 6.91% and 0.5%, respectively. This research sheds light on the considering of comprehensive effect of impeller structrual parameters on fan performance, and a new impeller can be designed to satisfy the engineering demand such as energy-saving, noise reduction or solving air pressure insufficiency for power plants.

  3. A Critical Review of Constraint-Induced Movement Therapy and Forced Use in Children With Hemiplegia

    Directory of Open Access Journals (Sweden)

    Jeanne Charles

    2005-01-01

    Full Text Available Hemiplegia is a physical impairment that can occur in childhood following head trauma, cerebral vascular accident or transient ischemic attack (stroke, brain tumor, or congenital or perinatal injury. One of the most disabling symptoms of hemiplegia is unilaterally impaired hand and arm function. Sensory and motor impairments in children with hemiplegia compromise movement efficiency. Such children often tend not to use the affected extremity, which may further exacerbate the impairments, resulting in a developmentally learned non-use of the involved upper extremity, termed ‘developmental disuse’. Recent studies suggest that children with hemiplegia benefit from intensive practice. Forced use and Constraint-lnduced Movement Therapy (CI therapy are recent therapeutic interventions involving the restraint of the non-involved upper extremity and intensive practice with the involved upper extremity. These approaches were designed for adults with hemiplegia, and increasing evidence suggests that they are efficacious in this population. Recently, forced use and constraint-induced therapy have been applied to children with hemiplegia. In this review, we provide a brief description of forced use and CI therapy and their historical basis, provide a summary of studies of these interventions in children, and discuss a number of important theoretical considerations, as well as implications for postural control. We will show that whereas the studies to date suggest that both forced use and CI therapy appear to be promising for improving hand function in children with hemiplegia, the data are limited. Substantially more work must be performed before this approach can be advocated for general clinical use.

  4. Digital force-feedback for protein unfolding experiments using atomic force microscopy

    Science.gov (United States)

    Bippes, Christian A.; Janovjak, Harald; Kedrov, Alexej; Muller, Daniel J.

    2007-01-01

    Since its invention in the 1990s single-molecule force spectroscopy has been increasingly applied to study protein (un-)folding, cell adhesion, and ligand-receptor interactions. In most force spectroscopy studies, the cantilever of an atomic force microscope (AFM) is separated from a surface at a constant velocity, thus applying an increasing force to folded bio-molecules or bio-molecular bonds. Recently, Fernandez and co-workers introduced the so-called force-clamp technique. Single proteins were subjected to a defined constant force allowing their life times and life time distributions to be directly measured. Up to now, the force-clamping was performed by analogue PID controllers, which require complex additional hardware and might make it difficult to combine the force-feedback with other modes such as constant velocity. These points may be limiting the applicability and versatility of this technique. Here we present a simple, fast, and all-digital (software-based) PID controller that yields response times of a few milliseconds in combination with a commercial AFM. We demonstrate the performance of our feedback loop by force-clamp unfolding of single Ig27 domains of titin and the membrane proteins bacteriorhodopsin (BR) and the sodium/proton antiporter NhaA.

  5. Digital force-feedback for protein unfolding experiments using atomic force microscopy

    International Nuclear Information System (INIS)

    Bippes, Christian A; Janovjak, Harald; Kedrov, Alexej; Muller, Daniel J

    2007-01-01

    Since its invention in the 1990s single-molecule force spectroscopy has been increasingly applied to study protein (un-)folding, cell adhesion, and ligand-receptor interactions. In most force spectroscopy studies, the cantilever of an atomic force microscope (AFM) is separated from a surface at a constant velocity, thus applying an increasing force to folded bio-molecules or bio-molecular bonds. Recently, Fernandez and co-workers introduced the so-called force-clamp technique. Single proteins were subjected to a defined constant force allowing their life times and life time distributions to be directly measured. Up to now, the force-clamping was performed by analogue PID controllers, which require complex additional hardware and might make it difficult to combine the force-feedback with other modes such as constant velocity. These points may be limiting the applicability and versatility of this technique. Here we present a simple, fast, and all-digital (software-based) PID controller that yields response times of a few milliseconds in combination with a commercial AFM. We demonstrate the performance of our feedback loop by force-clamp unfolding of single Ig27 domains of titin and the membrane proteins bacteriorhodopsin (BR) and the sodium/proton antiporter NhaA

  6. Quantum anticentrifugal force

    International Nuclear Information System (INIS)

    Cirone, M.A.; Schleich, W.P.; Straub, F.; Rzazewski, K.; Wheeler, J.A.

    2002-01-01

    In a two-dimensional world, a free quantum particle of vanishing angular momentum experiences an attractive force. This force originates from a modification of the classical centrifugal force due to the wave nature of the particle. For positive energies the quantum anticentrifugal force manifests itself in a bunching of the nodes of the energy wave functions towards the origin. For negative energies this force is sufficient to create a bound state in a two-dimensional δ-function potential. In a counterintuitive way, the attractive force pushes the particle away from the location of the δ-function potential. As a consequence, the particle is localized in a band-shaped domain around the origin

  7. The effect of force feedback delay on stiffness perception and grip force modulation during tool-mediated interaction with elastic force fields.

    Science.gov (United States)

    Leib, Raz; Karniel, Amir; Nisky, Ilana

    2015-05-01

    During interaction with objects, we form an internal representation of their mechanical properties. This representation is used for perception and for guiding actions, such as in precision grip, where grip force is modulated with the predicted load forces. In this study, we explored the relationship between grip force adjustment and perception of stiffness during interaction with linear elastic force fields. In a forced-choice paradigm, participants probed pairs of virtual force fields while grasping a force sensor that was attached to a haptic device. For each pair, they were asked which field had higher level of stiffness. In half of the pairs, the force feedback of one of the fields was delayed. Participants underestimated the stiffness of the delayed field relatively to the nondelayed, but their grip force characteristics were similar in both conditions. We analyzed the magnitude of the grip force and the lag between the grip force and the load force in the exploratory probing movements within each trial. Right before answering which force field had higher level of stiffness, both magnitude and lag were similar between delayed and nondelayed force fields. These results suggest that an accurate internal representation of environment stiffness and time delay was used for adjusting the grip force. However, this representation did not help in eliminating the bias in stiffness perception. We argue that during performance of a perceptual task that is based on proprioceptive feedback, separate neural mechanisms are responsible for perception and action-related computations in the brain. Copyright © 2015 the American Physiological Society.

  8. DelPhiForce web server: electrostatic forces and energy calculations and visualization.

    Science.gov (United States)

    Li, Lin; Jia, Zhe; Peng, Yunhui; Chakravorty, Arghya; Sun, Lexuan; Alexov, Emil

    2017-11-15

    Electrostatic force is an essential component of the total force acting between atoms and macromolecules. Therefore, accurate calculations of electrostatic forces are crucial for revealing the mechanisms of many biological processes. We developed a DelPhiForce web server to calculate and visualize the electrostatic forces at molecular level. DelPhiForce web server enables modeling of electrostatic forces on individual atoms, residues, domains and molecules, and generates an output that can be visualized by VMD software. Here we demonstrate the usage of the server for various biological problems including protein-cofactor, domain-domain, protein-protein, protein-DNA and protein-RNA interactions. The DelPhiForce web server is available at: http://compbio.clemson.edu/delphi-force. delphi@clemson.edu. Supplementary data are available at Bioinformatics online. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

  9. 78 FR 2996 - Meeting of the Community Preventive Services Task Force (Task Force)

    Science.gov (United States)

    2013-01-15

    ... Community Preventive Services Task Force (Task Force) AGENCY: Centers for Disease Control and Prevention... Services Task Force (Task Force). The Task Force is independent and nonfederal. Its members are nationally.... The Task Force was convened in 1996 by the Department of Health and Human Services (HHS) to assess the...

  10. 77 FR 56845 - Meeting of the Community Preventive Services Task Force (Task Force)

    Science.gov (United States)

    2012-09-14

    ... Community Preventive Services Task Force (Task Force) AGENCY: Centers for Disease Control and Prevention... Services Task Force (Task Force). The Task Force is independent and nonfederal. Its members are nationally.... The Task Force was convened in 1996 by the Department of Health and Human Services (HHS) to assess the...

  11. 78 FR 27969 - Meeting of the Community Preventive Services Task Force (Task Force)

    Science.gov (United States)

    2013-05-13

    ... Community Preventive Services Task Force (Task Force) AGENCY: Centers for Disease Control and Prevention... Services Task Force (Task Force). The Task Force is independent and nonfederal. Its members are nationally.... The Task Force was convened in 1996 by the Department of Health and Human Services (HHS) to assess the...

  12. Unsteady flow measurements in centrifugal compressors

    International Nuclear Information System (INIS)

    Bammert, K.; Mobarak, A.; Rautenberg, M.

    1976-01-01

    Centrifugal compressors and blowers are often used for recycling the coolant gas in gas-cooled reactors. To achieve the required high pressure ratios, highly loaded centrifugal compressors are built. The paper deals with unsteady flow measurements on highly loaded centrifugal impellers. Measurements of the approaching flow have been done with hot wires. The method of measurement enabled us to get the velocity distribution across the pitch ahead of the inducer. The static pressure signals along the shroud line has been discussed on the basis of some theoretical considerations. Accordingly the form of flow in the impeller and the wave flow or separation zones in the impeller can now be better interpreted. The importance of the unsteady nature of the relative flow, especially at impeller exit, is clearly demonstrated. Measurements with high responsive total pressure probes in the vicinity of impeller exit and the subsequent calculations have shown, that the instantaneous energy transfer at a certain point after the impeller may differ by more than 30% from the Euler work. Lastly, unsteady pressure measurements along the shroud line have been performed during surge and rotating stall. The surge signal have been analyzed in more detail and the mechanism of flow rupture and pressure recovery during a surge cycle is thoroughly discussed. (orig.) [de

  13. The contribution of the electrostatic proximity force to atomic force microscopy with insulators

    International Nuclear Information System (INIS)

    Stanley Czarnecki, W.; Schein, L.B.

    2005-01-01

    Measurements, using atomic force microscopy, of the force and force derivative on a charged insulating micron sized sphere as a function of gap between the sphere and a conductive plane have revealed attractive forces at finite gaps that are larger than predicted by either van der Waals or conventional electrostatic forces. We suggest that these observations may be due to an electrostatic force that we have identified theoretically and call the proximity force. This proximity force is due to the discrete charges on the surface of the sphere in close proximity to the plane

  14. The contribution of the electrostatic proximity force to atomic force microscopy with insulators

    Energy Technology Data Exchange (ETDEWEB)

    Stanley Czarnecki, W. [Aetas Technology Corporation, P.O. Box 53398, Irvine, CA 92619-3398 (United States); IBM Corporation, 5600 Cottle Rd., Building 13, San Jose, CA 95193 (United States); Schein, L.B. [Aetas Technology Corporation, P.O. Box 53398, Irvine, CA 92619-3398 (United States)]. E-mail: schein@prodigy.net

    2005-05-16

    Measurements, using atomic force microscopy, of the force and force derivative on a charged insulating micron sized sphere as a function of gap between the sphere and a conductive plane have revealed attractive forces at finite gaps that are larger than predicted by either van der Waals or conventional electrostatic forces. We suggest that these observations may be due to an electrostatic force that we have identified theoretically and call the proximity force. This proximity force is due to the discrete charges on the surface of the sphere in close proximity to the plane.

  15. Minimizing tip-sample forces in jumping mode atomic force microscopy in liquid

    Energy Technology Data Exchange (ETDEWEB)

    Ortega-Esteban, A. [Departamento de Fisica de la Materia Condensada, C-3, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Horcas, I. [Nanotec Electronica S.L., Centro Empresarial Euronova 3, Ronda de Poniente 12, 28760 Tres Cantos, Madrid (Spain); Hernando-Perez, M. [Departamento de Fisica de la Materia Condensada, C-3, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Ares, P. [Nanotec Electronica S.L., Centro Empresarial Euronova 3, Ronda de Poniente 12, 28760 Tres Cantos, Madrid (Spain); Perez-Berna, A.J.; San Martin, C.; Carrascosa, J.L. [Centro Nacional de Biotecnologia (CNB-CSIC), Darwin 3, 28049 Madrid (Spain); Pablo, P.J. de [Departamento de Fisica de la Materia Condensada, C-3, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Gomez-Herrero, J., E-mail: julio.gomez@uam.es [Departamento de Fisica de la Materia Condensada, C-3, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2012-03-15

    Control and minimization of tip-sample interaction forces are imperative tasks to maximize the performance of atomic force microscopy. In particular, when imaging soft biological matter in liquids, the cantilever dragging force prevents identification of the tip-sample mechanical contact, resulting in deleterious interaction with the specimen. In this work we present an improved jumping mode procedure that allows detecting the tip-sample contact with high accuracy, thus minimizing the scanning forces ({approx}100 pN) during the approach cycles. To illustrate this method we report images of human adenovirus and T7 bacteriophage particles which are prone to uncontrolled modifications when using conventional jumping mode. -- Highlights: Black-Right-Pointing-Pointer Improvement in atomic force microscopy in buffer solution. Black-Right-Pointing-Pointer Peak force detection. Black-Right-Pointing-Pointer Subtracting the cantilever dragging force. Black-Right-Pointing-Pointer Forces in the 100 pN range. Black-Right-Pointing-Pointer Imaging of delicate viruses with atomic force microscopy.

  16. Force-activatable biosensor enables single platelet force mapping directly by fluorescence imaging.

    Science.gov (United States)

    Wang, Yongliang; LeVine, Dana N; Gannon, Margaret; Zhao, Yuanchang; Sarkar, Anwesha; Hoch, Bailey; Wang, Xuefeng

    2018-02-15

    Integrin-transmitted cellular forces are critical for platelet adhesion, activation, aggregation and contraction during hemostasis and thrombosis. Measuring and mapping single platelet forces are desired in both research and clinical applications. Conventional force-to-strain based cell traction force microscopies have low resolution which is not ideal for cellular force mapping in small platelets. To enable platelet force mapping with submicron resolution, we developed a force-activatable biosensor named integrative tension sensor (ITS) which directly converts molecular tensions to fluorescent signals, therefore enabling cellular force mapping directly by fluorescence imaging. With ITS, we mapped cellular forces in single platelets at 0.4µm resolution. We found that platelet force distribution has strong polarization which is sensitive to treatment with the anti-platelet drug tirofiban, suggesting that the ITS force map can report anti-platelet drug efficacy. The ITS also calibrated integrin molecular tensions in platelets and revealed two distinct tension levels: 12-54 piconewton (nominal values) tensions generated during platelet adhesion and tensions above 54 piconewton generated during platelet contraction. Overall, the ITS is a powerful biosensor for the study of platelet mechanobiology, and holds great potential in antithrombotic drug development and assessing platelet activity in health and disease. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Concurrent Validity of a Portable Force Plate Using Vertical Jump Force-Time Characteristics.

    Science.gov (United States)

    Lake, Jason; Mundy, Peter; Comfort, Paul; McMahon, John J; Suchomel, Timothy J; Carden, Patrick

    2018-05-29

    This study examined concurrent validity of countermovement vertical jump (CMJ) reactive strength index modified and force-time characteristics recorded using a one dimensional portable and laboratory force plate system. Twenty-eight men performed bilateral CMJs on two portable force plates placed on top of two in-ground force plates, both recording vertical ground reaction force at 1000 Hz. Time to take-off, jump height, reactive strength index modified, braking and propulsion impulse, mean net force, and duration were calculated from the vertical force from both force plate systems. Results from both systems were highly correlated (r≥.99). There were small (dbraking impulse, braking mean net force, propulsion impulse, and propulsion mean net force (psystem (95% CL: .9% to 2.5%), indicating very good agreement across all of the dependent variables. The largest limits of agreement belonged to jump height (2.1%), time to take-off (3.4%), and reactive strength index modified (3.8%). The portable force plate system provides a valid method of obtaining reactive strength measures, and several underpinning force-time variables, from unloaded CMJ and practitioners can use both force plates interchangeably.

  18. Análise da tendência da mortalidade masculina no Rio de Janeiro: contribuição da enfermagem

    Directory of Open Access Journals (Sweden)

    Elisabete Pimenta Araújo Paz

    2014-12-01

    Full Text Available Objetivo: Analisar a tendência de mortalidade entre homens no Município do Rio de Janeiro, por grupo de causas, entre 1996 e 2011. Métodos: Estudo descritivo de série temporal, utilizando dados de óbitos masculinos de residentes no Município do Rio de Janeiro, no período de 1996 a 2011, para grandes grupos de causas. Os dados foram analisados com os softwares Excel 2010 e Statistical Package for the Social Sciences (SPSS versão 22.0. Resultados: A tendência da mortalidade por grandes grupos de causas entre homens no Município do Rio de Janeiro está decrescendo, com diferença entre os grupos de causas. Porém, estes homens seguem adoecidos com o passar dos anos. Conclusão: A Política Nacional de Atenção à Saúde do Homem deve estar mais sensível a esta realidade, ofertando uma atenção em saúde capaz de reconhecer mais integralmente as necessidades de saúde desse público.

  19. Tendências dos benefícios previdenciários por câncer bucal e de orofaringe de 2006 a 2013 no Brasil

    Directory of Open Access Journals (Sweden)

    Rafael Aiello Bomfim

    2018-02-01

    Full Text Available Resumo Objetivo: analisar as tendências de concessão de auxílios-doença previdenciários por câncer bucal e de orofaringe no período de 2006 a 2013, no Brasil. Métodos: estudo de séries temporais com dados dos trabalhadores segurados pelo Instituto Nacional de Seguridade Social (INSS; utilizaram-se regressões generalizadas lineares de Prais-Winstein para o cálculo da variação percentual anual (VPA. Resultados: os benefícios previdenciários por câncer de boca e de orofaringe mostraram tendência crescente (VPA=9,0%; IC95% 1,4;17,4; benefícios para outras partes da boca, nasofaringe, orofaringe, assoalho da boca e palato mostraram aumento significativo; comércio (5,5% e indústrias de transformação (5,2% foram as atividades mais prevalentes; evidenciaram-se altas proporções de campos ignorados nos sistemas de informações (média de 72,9%. Conclusão: as tendências dos benefícios ocupacionais por câncer de boca e de orofaringe mostraram crescimento significativo.

  20. Forces in general relativity

    International Nuclear Information System (INIS)

    Ridgely, Charles T

    2010-01-01

    Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced by an observer in general coordinates. The general force is then applied to the local co-moving coordinate system of a uniformly accelerating observer, leading to an expression of the inertial force experienced by the observer. Next, applying the general force in Schwarzschild coordinates is shown to lead to familiar expressions of the gravitational force. As a more complex demonstration, the general force is applied to an observer in Boyer-Lindquist coordinates near a rotating, Kerr black hole. It is then shown that when the angular momentum of the black hole goes to zero, the force on the observer reduces to the force on an observer held stationary in Schwarzschild coordinates. As a final consideration, the force on an observer moving in rotating coordinates is derived. Expressing the force in terms of Christoffel symbols in rotating coordinates leads to familiar expressions of the centrifugal and Coriolis forces on the observer. It is envisioned that the techniques presented herein will be most useful to graduate level students, as well as those undergraduate students having experience with general relativity and tensor analysis.

  1. Mechanized systems for early stand tending in central and eastern Canada

    Energy Technology Data Exchange (ETDEWEB)

    Ryans, M.; St-Amour, M. [Forest Engineering Research Inst. of Canada, Pointe Claire, PQ (Canada)

    1996-12-31

    Machines are currently being used for early stand tending in central and eastern Canada, but account for only 1 to 2% of the annual total for mechanical treatments (including manual and motor-manual operations). Selective and non-selective systems are used, depending on the application and stand conditions. Plantation cleaning operations and precommercial thinning (spacing) of naturally regenerated and seeded stands have been mechanized. Selective methods, primarily for plantation cleaning, use equipment with specialized prime movers, booms and controls, and cutting heads. This paper describes the Canadian experience to date based on FERIC`s studies of successful and unsuccessful operations, and lists the key features of a machine suitable for use in selective treatments. Strip precommercial thinning is used in denser natural stands, but limited improvements in crop-tree growth occur unless a motor-manual follow-up releases crop trees in the leave strips. Most off-the-shelf brushcutting equipment is not optimal for this application, primarily because it is too wide to meet local spacing prescriptions. Some applications such as the spacing of older natural stands have proven difficult to mechanize. Technical, biological, operational , regulatory, economic and social constraints prevent wider use of mechanized systems. Nonetheless, some machines are in operational use, and mechanized plantation cleaning is tested in some regions as an alternative to herbicides. 11 refs, 2 figs, 1 tab

  2. 78 FR 59939 - Meeting of the Community Preventive Services Task Force (Task Force)

    Science.gov (United States)

    2013-09-30

    ... Community Preventive Services Task Force (Task Force) AGENCY: Centers for Disease Control and Prevention... September 17, 2013, announcing the next meeting of the Community Preventive Services Task Force (Task Force... the Task Force to consider the findings of systematic reviews and issue findings and recommendations...

  3. Numerical simulation of 3-D turbulent flow through entire stage in a multistage centrifugal pump

    International Nuclear Information System (INIS)

    Huang, S.; Islam, M.F.; Liu, P.

    2005-01-01

    A three-dimensional turbulent flow through a multistage centrifugal pump is numerically simulated using a commercial CFD software package. The simulation and analysis include flow fields in rotating impeller and stationary diffuser and is completed in a multiple reference frame. The standard k-ε turbulence model is applied. The analysis of the simulation reveals that the reverse flows exist in the zone near the impeller exit and diffuser entrance, resulting in flow field asymmetric and unsteady. There is a considerable interference on velocity field at impeller exit due to the interaction between impeller blades and diffuser vanes. The hydraulic performance is connected and evaluated with the 3-D computational flow field. The current computation is verified by comparing predicted and measured head. (author)

  4. Hydrodynamic studies in a mixer of mixer settler system

    International Nuclear Information System (INIS)

    Shenoy, K.T.; Ghosh, S.K.; Keni, V.S.

    1994-01-01

    Pump-mix mixer settlers, with high throughput, are widely used in hydrometallurgical processing for recovery of uranium, copper etc. by solvent extraction. Detailed knowledge of hydrometallurgic behaviour in the mixer and settler is necessary for design. The paper presents the experimental study carried out on mixer hydrodynamics. The work was carried out on 40 litre, cubical, continuous flow mixer with bottom inlet and top discharge. The impeller was top shrouded turbine and working medium was water. Parameters such as impeller diameter, impeller clearance, inlet orifice size, impeller speed and flow rate were studied for effect on pumping head developed and power consumed by the mixer. Data are presented in the terms of dimensionless groups. Importance of the design variables is discussed. (author)

  5. Acoustic force spectroscopy

    NARCIS (Netherlands)

    Sitters, G.; Kamsma, D.; Thalhammer, G.; Ritsch-Marte, M.; Peterman, E.J.G.; Wuite, G.J.L.

    2015-01-01

    Force spectroscopy has become an indispensable tool to unravel the structural and mechanochemical properties of biomolecules. Here we extend the force spectroscopy toolbox with an acoustic manipulation device that can exert forces from subpiconewtons to hundreds of piconewtons on thousands of

  6. Handbook of force transducers

    CERN Document Server

    Stefanescu, Dan Mihai

    2011-01-01

    Part I introduces the basic ""Principles and Methods of Force Measurement"" acording to a classification into a dozen of force transducers types: resistive, inductive, capacitive, piezoelectric, electromagnetic, electrodynamic, magnetoelastic, galvanomagnetic (Hall-effect), vibrating wires, (micro)resonators, acoustic and gyroscopic. Two special chapters refer to force balance techniques and to combined methods in force measurement. Part II discusses the ""(Strain Gauge) Force Transducers Components"", evolving from the classical force transducer to the digital / intelligent one, with the inco

  7. EMC3-eIRENE simulation of impurity transport in comparison with EUV emission measurements in the stochastic layer of LHD: effects of force balance and transport coefficients

    Energy Technology Data Exchange (ETDEWEB)

    Dai, S. [National Institute for Fusion Science, Toki (Japan); Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian (China); Kobayashi, M.; Morita, S.; Oishi, T.; Suzuki, Y. [National Institute for Fusion Science, Toki (Japan); Department of Fusion Science, School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Toki (Japan); Kawamura, G. [National Institute for Fusion Science, Toki (Japan); Zhang, H.M.; Huang, X.L. [Department of Fusion Science, School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Toki (Japan); Feng, Y. [Max-Planck-Institut fuer Plasmaphysik, Greifswald (Germany); Wang, D.Z. [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian (China); Collaboration: The LHD experiment group

    2016-08-15

    The transport properties and line emissions of the intrinsic carbon in the stochastic layer of the Large Helical Device have been investigated with the three-dimensional edge transport code EMC3-EIRENE. The simulations of impurity transport and emissivity have been performed to study the dedicated experiment in which the carbon emission distributions are measured by a space-resolved EUV spectrometer system. A discrepancy of the CIV impurity emission between the measurement and simulation is obtained, which is studied with the variation of the ion thermal force, friction force and the perpendicular diffusivity in the impurity transport model. An enhanced ion thermal force or a reduced friction force in the modelling can increase the CIV impurity emission at the inboard X-point region. Furthermore, the impact of the perpendicular diffusivity Dimp is studied which shows that the CIV impurity emission pattern is very sensitive to Dimp. It is found that the simulation results with the increased Dimp tend to be closer to the experimental observation. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. 12th Air Force > Home

    Science.gov (United States)

    Force AOR Travel Info News prevnext Slide show 76,410 pounds of food delivered to Haiti 12th Air Force the French Air Force, Colombian Air Force, Pakistan Air Force, Belgian Air Force, Brazilian Air Force

  9. Development of a commercially viable piezoelectric force sensor system for static force measurement

    Science.gov (United States)

    Liu, Jun; Luo, Xinwei; Liu, Jingcheng; Li, Min; Qin, Lan

    2017-09-01

    A compensation method for measuring static force with a commercial piezoelectric force sensor is proposed to disprove the theory that piezoelectric sensors and generators can only operate under dynamic force. After studying the model of the piezoelectric force sensor measurement system, the principle of static force measurement using a piezoelectric material or piezoelectric force sensor is analyzed. Then, the distribution law of the decay time constant of the measurement system and the variation law of the measurement system’s output are studied, and a compensation method based on the time interval threshold Δ t and attenuation threshold Δ {{u}th} is proposed. By calibrating the system and considering the influences of the environment and the hardware, a suitable Δ {{u}th} value is determined, and the system’s output attenuation is compensated based on the Δ {{u}th} value to realize the measurement. Finally, a static force measurement system with a piezoelectric force sensor is developed based on the compensation method. The experimental results confirm the successful development of a simple compensation method for static force measurement with a commercial piezoelectric force sensor. In addition, it is established that, contrary to the current perception, a piezoelectric force sensor system can be used to measure static force through further calibration.

  10. Minimizing pulling geometry errors in atomic force microscope single molecule force spectroscopy.

    Science.gov (United States)

    Rivera, Monica; Lee, Whasil; Ke, Changhong; Marszalek, Piotr E; Cole, Daniel G; Clark, Robert L

    2008-10-01

    In atomic force microscopy-based single molecule force spectroscopy (AFM-SMFS), it is assumed that the pulling angle is negligible and that the force applied to the molecule is equivalent to the force measured by the instrument. Recent studies, however, have indicated that the pulling geometry errors can drastically alter the measured force-extension relationship of molecules. Here we describe a software-based alignment method that repositions the cantilever such that it is located directly above the molecule's substrate attachment site. By aligning the applied force with the measurement axis, the molecule is no longer undergoing combined loading, and the full force can be measured by the cantilever. Simulations and experimental results verify the ability of the alignment program to minimize pulling geometry errors in AFM-SMFS studies.

  11. Stable dynamics in forced systems with sufficiently high/low forcing frequency.

    Science.gov (United States)

    Bartuccelli, M; Gentile, G; Wright, J A

    2016-08-01

    We consider parametrically forced Hamiltonian systems with one-and-a-half degrees of freedom and study the stability of the dynamics when the frequency of the forcing is relatively high or low. We show that, provided the frequency is sufficiently high, Kolmogorov-Arnold-Moser (KAM) theorem may be applied even when the forcing amplitude is far away from the perturbation regime. A similar result is obtained for sufficiently low frequency, but in that case we need the amplitude of the forcing to be not too large; however, we are still able to consider amplitudes which are outside of the perturbation regime. In addition, we find numerically that the dynamics may be stable even when the forcing amplitude is very large, well beyond the range of validity of the analytical results, provided the frequency of the forcing is taken correspondingly low.

  12. High Cable Forces Deteriorate Pinch Force Control in Voluntary-Closing Body-Powered Prostheses.

    Directory of Open Access Journals (Sweden)

    Mona Hichert

    Full Text Available It is generally asserted that reliable and intuitive control of upper-limb prostheses requires adequate feedback of prosthetic finger positions and pinch forces applied to objects. Body-powered prostheses (BPPs provide the user with direct proprioceptive feedback. Currently available BPPs often require high cable operation forces, which complicates control of the forces at the terminal device. The aim of this study is to quantify the influence of high cable forces on object manipulation with voluntary-closing prostheses.Able-bodied male subjects were fitted with a bypass-prosthesis with low and high cable force settings for the prehensor. Subjects were requested to grasp and transfer a collapsible object as fast as they could without dropping or breaking it. The object had a low and a high breaking force setting.Subjects conducted significantly more successful manipulations with the low cable force setting, both for the low (33% more and high (50% object's breaking force. The time to complete the task was not different between settings during successful manipulation trials.High cable forces lead to reduced pinch force control during object manipulation. This implies that low cable operation forces should be a key design requirement for voluntary-closing BPPs.

  13. Malaysia and forced migration

    Directory of Open Access Journals (Sweden)

    Arzura Idris

    2012-06-01

    Full Text Available This paper analyzes the phenomenon of “forced migration” in Malaysia. It examines the nature of forced migration, the challenges faced by Malaysia, the policy responses and their impact on the country and upon the forced migrants. It considers forced migration as an event hosting multifaceted issues related and relevant to forced migrants and suggests that Malaysia has been preoccupied with the issue of forced migration movements. This is largely seen in various responses invoked from Malaysia due to “south-south forced migration movements.” These responses are, however, inadequate in terms of commitment to the international refugee regime. While Malaysia did respond to economic and migration challenges, the paper asserts that such efforts are futile if she ignores issues critical to forced migrants.

  14. kLa of stirred tank bioreactors revisited.

    Science.gov (United States)

    Schaepe, S; Kuprijanov, A; Sieblist, C; Jenzsch, M; Simutis, R; Lübbert, A

    2013-12-01

    By means of improved feedback control kLa measurements become possible at a precision and reproducibility that now allow a closer look at the influences of power input and aeration rate on the oxygen mass transfer. These measurements are performed online during running fermentations without a notable impact on the biochemical conversion processes. A closer inspection of the mass transfer during cultivations showed that at least the number of impellers influences mass transfer and mixing: On the laboratory scale, two hollow blade impellers clearly showed a larger kLa than the usually employed three impeller versions when operated at the same agitation power and aeration rate. Hollow blade impellers are preferable under most operational conditions because of their perfect gas handling capacity. Mixing time studies showed that these two impeller systems are also preferable with respect to mixing. Furthermore the widths of the baffle bars depict a significant influence on the kLa. All this clearly supports the fact that it is not only the integral power density that finally determines kLa. Copyright © 2013 Elsevier B.V. All rights reserved.

  15. Numerical simulation and performance prediction in multi-stage submersible centrifugal pump

    International Nuclear Information System (INIS)

    Wang, W J; Li, G D; Wang, Y; Cui, Y R; Yin, G; Peng, S

    2013-01-01

    In order to study the inner flow field of multi-stage submersible centrifugal pump, the model named QD3-60/4-1.1 was selected. Steady turbulence characteristics of impellers, diffusers and return channel were calculated by Fluent software, the SIMPLEC algorithm and RNG κ-ε turbulence model with sliding mesh technology. Then, the distributions of pressure, velocity and Turbulence kinetic energy was obtained and the distributions of velocity field of a channel were analysed. The results show that the static pressure in impeller is increasing with the increasing of radius. The circumferential component of relative velocity is in the opposite direction of impeller rotating. At the same radius, the component value of pressure surface is larger than suction surface. With the increasing of flow rate, absolute velocity and relative velocity flow angle are becoming small, in opposite of the relative velocity and absolute velocity flow angle. The high turbulent zone of impeller is located in the gap of impellers and diffusers. Flow similarity and structure similarity of the multi-stage submersible pump are confirmed

  16. Tendências católicas: perspectivas do cristianismo da libertação Catholic tendencies: perspectives of the freedom cristianism

    Directory of Open Access Journals (Sweden)

    Flávio Munhoz Sofiati

    2009-04-01

    Full Text Available O texto analisa as diferentes vertentes da Igreja Católica no Brasil, apresentando-as a partir de teóricos da própria Igreja das ciências sociais. Em seguida, discute-se a tendência ligada à Teologia da Libertação, chamada de Cristianismo da Libertação. Afirma-se que o conceito de “Tendências Internas do Catolicismo” é mais apropriado para compreender os processos internos do catolicismo e que, atualmente, a Teologia da Libertação vem perdendo espaço no cenário religioso. Isso ocorre em virtude de questões internas – como o fortalecimento do movimento carismático – e externas – como o advento do neoliberalismo. Diante dessa situação, esse segmento assume uma nova postura de atuação, que tem como idéia central a construção de mudanças “de baixo para cima” e em longo prazo. Conclui-se que houve um recuo programático dessa tendência que passa a priorizar sua ação no interior da Igreja e a valorizar temas como espiritualidade, ecologia e cultura em detrimento da dimensão política. Palavras-chaves: Sociologia da Religião. Catolicismo. Tendências católicas. Teologia da libertação. The text analyzes different aspects of the Catholic Church in Brazil, presenting them through theories of the church, from social sciences. After that there is a discussion about the tendency connected to the Theory of Freedom, so called “Freedom Cristianism”. It is said that the concept of “Inner Theories of Catholicism” is more appropriate to understand the inner processes of the Catholicism and that, nowadays, the Freedom Theory has been loosing space inside the religious scenery. This occurs due to inner reasons – such as the growing strength of the charismatic movement – and also due to external reasons – as the ascending of Neoliberalism. With that, this segment gets to a new posture of action which has as central idea the“from down to up” changes, during long terms. After all, there is the

  17. Dynamic characteristics and mechatronics model for maglev blood pump

    Science.gov (United States)

    Sun, Kun; Chen, Chen

    2017-01-01

    Magnetic bearing system(MBs) has been developed in the new-generation blood pump due to its low power consumption, low blood trauma and high durability. However, MBs for a blood pump were almost influenced by a series of factors such as hemodynamics, rotation speeds and actuator response in working fluids, compared with those applied in other industrial fields. In this study, the dynamic characteristics of MBs in fluid environments, including the influence of the pumping fluid and rotation of the impeller on the radial dynamic model were investigated by measuring the frequency response to sinusoidal excitation upon coils, and the response of radial displacement during a raise in the speed. The excitation tests were conducted under conditions in which the blood pump was levitated in air and water and with or without rotation. The experimental and simulated results indicate that rotations of the impeller affected the characteristics of MBs in water apparently, and the vibration in water was decreased, compared with that in air due to the hydraulic force. During the start-up and rotation, the actuator failed to operate fully and timely, and the voltage supplied can be chosen under the consideration of the rotor displacement and consumption.

  18. Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy

    Science.gov (United States)

    Neuman, Keir C.; Nagy, Attila

    2012-01-01

    Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. These techniques are described and illustrated with examples highlighting current capabilities and limitations. PMID:18511917

  19. Tendências observadas em indicadores de extremos climáticos de temperatura e precipitação no estado do Paraná

    Directory of Open Access Journals (Sweden)

    Wanderson Luiz Silva

    2015-06-01

    Full Text Available O presente trabalho faz uma análise das tendências de extremos climáticos baseada em indicadores calculados a partir de séries de dados observacionais diários de temperatura e de precipitação durante 35 anos em 20 estações meteorológicas do IAPAR, no Estado do Paraná. O objetivo é contribuir para estudos sobre avaliação de impactos e vulnerabilidade climática, requeridos para elaborar estratégias de adaptação às mudanças climáticas. Inicialmente as climatologias de temperatura do ar e de precipitação no Estado são revisitas. Com relação às tendências de extremos climáticos, os resultados dos indicadores associados à temperatura apontam para um padrão de aquecimento generalizado estatisticamente significativo em grande parte do Paraná. A porcentagem de dias e noites quentes no Estado aumentou consideravelmente a uma taxa de 0,1 a 0,4 %/ano entre 1976 e 2010. As médias anuais das temperaturas mínimas e máximas indicam uma elevação em quase todo o Paraná em torno de +0,02°C/ano no mesmo período. Os indicadores de temperatura mínima apresentam tendências de aumento mais significativas que os de temperatura máxima. Por outro lado, a maior parte dos indicadores de extremos climáticos associados à precipitação não apresenta significância estatística, com exceção de alguns poucos em distintas regiões do Estado. Destes, destacam-se apenas as tendências de elevação nos períodos secos (+0,25 mm/ano em Pato Branco e Planalto no sudoeste do Paraná e de redução das chuvas fortes (-0,5 mm/ano em Cambará, Ibiporã e Umuarama no norte do Estado.

  20. Tendência secular em estatura: uma revisão da literatura Secular height trend: a literature review

    Directory of Open Access Journals (Sweden)

    Gilberto Kac

    1999-09-01

    Full Text Available Esse trabalho constitui-se em uma revisão de literatura sobre tendência secular em estatura (TSE. Os principais tópicos abordados foram a definição do fenômeno, a utilização de dados históricos de estatura como estratégia alternativa no monitoramento de mudanças econômicas, as principais explicações teóricas sugeridas para a ocorrência do fenômeno, o início da antropometria militar, sua utilização no passado e no presente, e a magnitude da tendência em recrutas e na população infantil. Os principais achados revelaram que a TSE tem sido atribuída, sobretudo, a influências ambientais, em particular, a melhorias nas condições sanitárias, econômicas e sociais. As taxas médias de incremento variaram conforme a idade, o estrato sócio-econômico e o país considerado; portanto, deve-se ter cautela nas comparações interpopulacionais. A Segunda Guerra Mundial reduziu a tendência em diversos países, entre eles o Brasil, mas as taxas de incremento no pós-guerra foram ainda maiores do que as observadas no início do século. Constatou-se, por fim, que dados provenientes da antropometria militar são os mais utilizados para estimativas de TSE.This paper presents a literature review of secular height trends. The principal topics included were definition of the phenomenon, use of historical data sets on height as an alternative approach for monitoring economic changes, the main theoretical explanations of the phenomenon, the beginning of military anthropometry, and past and current use in measuring secular height trends in recruits and children. The most important results showed that the positive secular trend can be attributed to environmental influences, especially improvements in health, economic, and social conditions. The mean reported rates in height increases varied with age, socioeconomic status, and country, so one must exercise caution in drawing inferences. World War II slowed the trend in several countries

  1. Dispersal of Sediment in the Western Adriatic during Energetic Wintertime Forcing

    Science.gov (United States)

    Harris, C. K.; Sherwood, C. R.; Mullenbach, B. L.; Pullen, J. D.

    2003-12-01

    EuroSTRATAFORM aims to relate sediment delivery and reworking to seabed morphology and stratigraphy through observations and modeling of water column transport. The Po River dominates buoyancy and sediment input into the Adriatic Sea, but small Apeninne rivers (the Chienti, Pescara, etc.) may produce locally important signals. Sedimentation is influenced by fluvial supply, resuspension by waves and currents, and transport by oceanographic currents forced by winds and buoyancy. Transport is likely highest during times of energetic forcing; including Bora events with northeasterly winds and Sirocco events with southeasterly winds. It is difficult, from field measurements alone, to characterize dispersal and convergence patterns over the relevant spatial scales. We applied a three-dimensional hydrodynamic model that includes fluvial delivery, transport, resuspension, and deposition of sediment to quantify sediment dispersal with a 2-km resolution over the entire Adriatic. Circulation calculations were driven by spatially- and temporally-varying wind fields for the Fall / Winter of 2002 / 2003 and realistic Po and Apennine river discharges. Waves were hindcast with the SWAN model. Dispersion of both resuspended and river-derived sediment was estimated for periods that contained intense Bora and Sirocco winds. Predicted sediment dispersal rates and patterns are sensitive to forcing winds, buoyancy flux, and wave patterns. Higher sediment flux was predicted during Bora conditions than during Sirocco conditions. Sirocco winds weaken the Western Adriatic Coastal Current (WACC), and because they tend to concentrate over the Eastern Adriatic, they often fail to create especially energetic waves in the Western Adriatic. Bora wind conditions, on the other hand, intensify the WACC and can build high wave energies over the northwestern Adriatic. Most of the sediment transport occurs during Bora, with a net southward flux. These predictions will be compared to field observations

  2. Human Leg Model Predicts Muscle Forces, States, and Energetics during Walking.

    Science.gov (United States)

    Markowitz, Jared; Herr, Hugh

    2016-05-01

    Humans employ a high degree of redundancy in joint actuation, with different combinations of muscle and tendon action providing the same net joint torque. Both the resolution of these redundancies and the energetics of such systems depend on the dynamic properties of muscles and tendons, particularly their force-length relations. Current walking models that use stock parameters when simulating muscle-tendon dynamics tend to significantly overestimate metabolic consumption, perhaps because they do not adequately consider the role of elasticity. As an alternative, we posit that the muscle-tendon morphology of the human leg has evolved to maximize the metabolic efficiency of walking at self-selected speed. We use a data-driven approach to evaluate this hypothesis, utilizing kinematic, kinetic, electromyographic (EMG), and metabolic data taken from five participants walking at self-selected speed. The kinematic and kinetic data are used to estimate muscle-tendon lengths, muscle moment arms, and joint moments while the EMG data are used to estimate muscle activations. For each subject we perform an optimization using prescribed skeletal kinematics, varying the parameters that govern the force-length curve of each tendon as well as the strength and optimal fiber length of each muscle while seeking to simultaneously minimize metabolic cost and maximize agreement with the estimated joint moments. We find that the metabolic cost of transport (MCOT) values of our participants may be correctly matched (on average 0.36±0.02 predicted, 0.35±0.02 measured) with acceptable joint torque fidelity through application of a single constraint to the muscle metabolic budget. The associated optimal muscle-tendon parameter sets allow us to estimate the forces and states of individual muscles, resolving redundancies in joint actuation and lending insight into the potential roles and control objectives of the muscles of the leg throughout the gait cycle.

  3. Human Leg Model Predicts Muscle Forces, States, and Energetics during Walking.

    Directory of Open Access Journals (Sweden)

    Jared Markowitz

    2016-05-01

    Full Text Available Humans employ a high degree of redundancy in joint actuation, with different combinations of muscle and tendon action providing the same net joint torque. Both the resolution of these redundancies and the energetics of such systems depend on the dynamic properties of muscles and tendons, particularly their force-length relations. Current walking models that use stock parameters when simulating muscle-tendon dynamics tend to significantly overestimate metabolic consumption, perhaps because they do not adequately consider the role of elasticity. As an alternative, we posit that the muscle-tendon morphology of the human leg has evolved to maximize the metabolic efficiency of walking at self-selected speed. We use a data-driven approach to evaluate this hypothesis, utilizing kinematic, kinetic, electromyographic (EMG, and metabolic data taken from five participants walking at self-selected speed. The kinematic and kinetic data are used to estimate muscle-tendon lengths, muscle moment arms, and joint moments while the EMG data are used to estimate muscle activations. For each subject we perform an optimization using prescribed skeletal kinematics, varying the parameters that govern the force-length curve of each tendon as well as the strength and optimal fiber length of each muscle while seeking to simultaneously minimize metabolic cost and maximize agreement with the estimated joint moments. We find that the metabolic cost of transport (MCOT values of our participants may be correctly matched (on average 0.36±0.02 predicted, 0.35±0.02 measured with acceptable joint torque fidelity through application of a single constraint to the muscle metabolic budget. The associated optimal muscle-tendon parameter sets allow us to estimate the forces and states of individual muscles, resolving redundancies in joint actuation and lending insight into the potential roles and control objectives of the muscles of the leg throughout the gait cycle.

  4. Forced, Impelled and Organised Migration in the Ethno-Demographic Shaping of Croatia: The Example of Slavonia

    Directory of Open Access Journals (Sweden)

    Mario Bara

    2009-12-01

    Full Text Available Based on relevant statistical data and literature, this work analyses the demographical development of Slavonia – especially its ethnic structure - over a period of one century. It revises influences (direct and indirect that socio-political changes have had on mechanical movements of the population. The foci of attention are the First and Second World Wars, political and territorial changes, agricultural colonization (private and state, economic migrations during the post-war period, de-ruralization and urbanization, rural-urban migrations and the Homeland War. The authors devote a special chapter to the influence of the Homeland War on the development of total population, interrelations between specific ethnic groups and the disruption of population age structure in Slavonia. The analysis has shown that the disrupted age structure – partly as a consequence of previous negative movement trends and major mechanical outflow of the population during the 1990s, as well as significant war mortality among younger reproduction-capable groups – will have an affect on future demographic ageing of the observed populations. This leads the authors to the conclusion that the politically induced migrations, and in part assimilation, have had a dominant role in the ethnic homogenization of Slavonia and other parts of Croatia.

  5. Tendência Pedagógica Progressista Libertária – Uma breve apresentação

    Directory of Open Access Journals (Sweden)

    Kathlen Luana de Oliveira

    2011-10-01

    Full Text Available O presente texto versa sobre a tendência pedagógica progressista libertária. Tem como objetivo apresentar o contexto no qual surgiram os princípios libertários para, então, abordar as críticas e a proposta educacional dessa tendência. Brevemente, será exposta a Pedagogia Libertária norteada pela anarquia, pela crítica institucional, porém com propostas de práticas educativas construídas a partir da autogestão e da solidariedade. Nesse sentido, as contribuições de Lobrot, Tragtenberg serão delineadas frente aos desafios concretos e possíveis da proposta libertária.

  6. Suppression of inducer stall based on inlet recirculation in a centrifugal impeller. 1st Report. Improvement in stall limit by ring groove arrangement; Enshin haneguruma iriguchi junkanryu ni yoru inducer shissoku no yokusei. 1. kanjoko ni yoru shissoku genkai no kaizen

    Energy Technology Data Exchange (ETDEWEB)

    Ueki, H.; Ishida, M.; Sakaguchi, D.; Sun, Z. [Nagasaki University, Nagasaki (Japan). Faculty of Engineering

    2000-07-25

    A ring groove arrangement is proposed to suppress unstable flow or surge in a centrifugal blower. The ring groove arrangement connects the upstream position of impeller inlet and the inducer throat tip through a bypass. The recirculation flow 'vas formed by the pressure difference between the two positions, and the recirculation flow rate was changed by increasing the ring groove widths. The inlet recirculation results in a decrease in the flow rate of unstable flow inception, and an up to 800 improvement in stall limit was obtained by the ring groove arrangement at a small expense of the delivery pressure drop. The improvement of stall limit in the present experiment seems to be mainly due to decrease in flow incidence based on the inlet recirculation flow. Tre flow incidence decreases more as the recirculation flow rate increases, thus resulting in a larger improvement in stall limit. (author)

  7. Hydrostatic force sensor

    International Nuclear Information System (INIS)

    Evans, M.S.; Stoughton, R.S.; Kazerooni, H.

    1994-08-01

    This paper presents a theoretical and experimental investigation of a new kind of force sensor which detects forces by measuring an induced pressure change in a material of large Poisson's ratio. In this investigation we develop mathematical expressions for the sensor's sensitivity and bandwidth, and show that its sensitivity can be much larger and its bandwidth is usually smaller than those of existing strain-gage-type sensors. This force sensor is well-suited for measuring large but slowly varying forces. It can be installed in a space smaller than that required by existing sensors

  8. Crossflow force transducer

    International Nuclear Information System (INIS)

    Mulcahy, T.M.

    1982-05-01

    A force transducer for measuring lift and drag coefficients for a circular cylinder in turbulent water flow is presented. In addition to describing the actual design and construction of the strain-gauged force- ring based transducer, requirements for obtained valid fluid force test data are discussed, and pertinent flow test experience is related

  9. Hydrodynamic studies in a mixer of mixer settler system

    Energy Technology Data Exchange (ETDEWEB)

    Shenoy, K T; Ghosh, S K; Keni, V S [Chemical Engineering Division, Bhabha Atomic Research Centre, Mumbai (India)

    1994-06-01

    Pump-mix mixer settlers, with high throughput, are widely used in hydrometallurgical processing for recovery of uranium, copper etc. by solvent extraction. Detailed knowledge of hydrometallurgic behaviour in the mixer and settler is necessary for design. The paper presents the experimental study carried out on mixer hydrodynamics. The work was carried out on 40 litre, cubical, continuous flow mixer with bottom inlet and top discharge. The impeller was top shrouded turbine and working medium was water. Parameters such as impeller diameter, impeller clearance, inlet orifice size, impeller speed and flow rate were studied for effect on pumping head developed and power consumed by the mixer. Data are presented in the terms of dimensionless groups. Importance of the design variables is discussed. (author). 2 refs., 7 figs., 2 tabs.

  10. Different forces

    CERN Multimedia

    1982-01-01

    The different forces, together with a pictorial analogy of how the exchange of particles works. The table lists the relative strength of the couplings, the quanta associated with the force fields and the bodies or phenomena in which they have a dominant role.

  11. Simulation of a force on force exercise

    International Nuclear Information System (INIS)

    Terhune, R.; Van Slyke, D.; Sheppard, T.; Brandrup, M.

    1988-01-01

    The Security Exercise Evaluation System (SEES) is under development for use in planning Force on Force exercises and as an aid in post-exercise evaluation. This study is part of the development cycle where the simulation results are compared to field data to provide guidance for further development of the model. SEES is an event-driven stochastic computer program simulating individual movement and combat within an urban terrain environment. The simulator models the physics of movement, line of sight, and weapon effects. It relies on the controllers to provide all knowledge of security tactics, which are entered by the controllers during the simulation using interactive color graphic workstations. They are able to develop, modify and implement plans promptly as the simulator maintains real time. This paper reports on how SEES will be used to develop an intrusion plan, test the security response tactics and develop observer logistics. A Force on Force field exercise will then be executed to follow the plan with observations recorded. An analysis is made by first comparing the plan and events of the simulation with the field exercise, modifying the simulation plan to match the actual field exercise, and then running the simulation to develop a distribution of possible outcomes

  12. Influence of post-stroke spasticity on EMG-force coupling and force steadiness in biceps brachii.

    Science.gov (United States)

    Carlyle, Jennilee K; Mochizuki, George

    2018-02-01

    Individuals with spasticity after stroke experience a decrease in force steadiness which can impact function. Alterations in the strength of EMG-force coupling may contribute to the reduction in force steadiness observed in spasticity. The aim was to determine the extent to which force steadiness and EMG-force coupling is affected by post-stroke spasticity. This cross-sectional study involved individuals with upper limb spasticity after stroke. Participants were required to generate and maintain isometric contractions of the elbow flexors at varying force levels. Coefficient of variation of force, absolute force, EMG-force cross-correlation function peak and peak latency was measured from both limbs with surface electromyography and isometric dynamometry. Statistically significant differences were observed between the affected and less affected limbs for all outcome measures. Significant main effects of force level were also observed. Force steadiness was not statistically significantly correlated with EMG-force coupling; however, both force steadiness and absolute force were associated with the level of impairment as measured by the Chedoke McMaster Stroke Assessment Scale. Spasticity after stroke uncouples the relationship between EMG and force and is associated with reduced force steadiness during isometric contractions; however, these features of control are not associated in individuals with spasticity. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Force Reproduction Error Depends on Force Level, whereas the Position Reproduction Error Does Not

    NARCIS (Netherlands)

    Onneweer, B.; Mugge, W.; Schouten, Alfred Christiaan

    2016-01-01

    When reproducing a previously perceived force or position humans make systematic errors. This study determined the effect of force level on force and position reproduction, when both target and reproduction force are self-generated with the same hand. Subjects performed force reproduction tasks at

  14. The original Ampere force and Biot-Savart and Lorentz forces

    International Nuclear Information System (INIS)

    Pappas, P.T.

    1983-01-01

    The purpose of this paper is to present the results of a very simple experiment, which favours the original Ampere force and unambiguously disproves the Biot-Savart force of relativity, or its approximation in a covariant relativistic form, namely the Lorentz force. This experiment with its extra degree of freedom has the advantage over the many other similar ones, including Ampere's original experiment, which have been performed in the past and recently by Graneau, of giving results which are both qualitative and quantitative, as well as unambiguous. Due to the strong association of the Biot-Savart and Lorentz force to relativistic theories, the experiment can be also considered as limiting the generality of these theories

  15. Bi-Force

    DEFF Research Database (Denmark)

    Sun, Peng; Speicher, Nora K; Röttger, Richard

    2014-01-01

    of pairwise similarities. We first evaluated the power of Bi-Force to solve dedicated bicluster editing problems by comparing Bi-Force with two existing algorithms in the BiCluE software package. We then followed a biclustering evaluation protocol in a recent review paper from Eren et al. (2013) (A...... comparative analysis of biclustering algorithms for gene expressiondata. Brief. Bioinform., 14:279-292.) and compared Bi-Force against eight existing tools: FABIA, QUBIC, Cheng and Church, Plaid, BiMax, Spectral, xMOTIFs and ISA. To this end, a suite of synthetic datasets as well as nine large gene expression...

  16. 78 FR 63208 - UPDATE-Meeting of the Community Preventive Services Task Force (Task Force)

    Science.gov (United States)

    2013-10-23

    ... of the Community Preventive Services Task Force (Task Force) AGENCY: Centers for Disease Control and... Community Preventive Services Task Force (Task Force). The in-person Task Force meeting is being replaced by... CDC's ability to complete the necessary scientific and logistical support for the meeting. The Task...

  17. Interrelation between striction forces in dielectrics and optically induced forces in transparent media

    International Nuclear Information System (INIS)

    Torchigin, V P; Torchigin, A V

    2012-01-01

    Optically induced forces applied to a transparent optical medium, which is inserted in a closed plane optical resonator, are calculated by means of an analysis of the changes in the eigenfrequency and energy stored in the resonator at various positions of the medium. These forces are compared with striction forces applied to the medium considered as a dielectric placed in an alternate electrical field within the resonator. It is shown that the optically induced forces are equal to the striction forces. The results of using the classical formula for striction forces in electrostatics are considered. (paper)

  18. The Past, Present, and Future of the Air Force's Future Total Force

    National Research Council Canada - National Science Library

    Duffy, Dennis P

    2004-01-01

    This project examines the history of the Total Force policy since its inception in 1970 through its implementation today in an effort to determine a future direction for the Air Force's Future Total Force initiative...

  19. Nuclear plant components: mechanical analysis and lifetime evaluation

    International Nuclear Information System (INIS)

    Chator, T.

    1993-09-01

    This paper concerns the methodology adopted by the Research and Development Division to handle mechanical problems found in structures and machines. Usually, these often very complex studies (3-D structures, complex loadings, non linear behavior laws) call for advanced tools and calculation means. In order to do these complex studies, R and D Division is developing a software. It handles very complex thermo-mechanical analysis using the Finite Element Method. It enables us to analyse static, dynamic, elasto-plastic problems as well as contact problems or evaluating damage and lifetime of structures. This paper will be illustrated by actual industrial case examples. The major ones will be dealing with: 1. Analysis of a new impeller/shaft assembly of a primary coolant pump. The 3D meshing is submitted simultaneously to thermal load, pressure, hydraulic, centrifugal and axial forces and clamping of studs; contacts between shaft/impeller, nuts bearing side/shaft bearing side. For this study, we have developed a new method to handle the clamping of studs. The stud elongation value is given into the software which automatically computes the distorsions between both the structures in contact and then the final position of bearing areas (using an iterative non-linear algorithm of modified Newton-Raphson type). 2. Analysis of the stress intensity factor of crack. The 3D meshing (representing the crack) is submitted simultaneously to axial and radial forces. In this case, we use the Theta method to calculate the energy restitution rate in order to determine the stress intensity factors. (authors). 7 figs., 1 tab., 3 refs

  20. An Ensemble Three-Dimensional Constrained Variational Analysis Method to Derive Large-Scale Forcing Data for Single-Column Models

    Science.gov (United States)

    Tang, Shuaiqi

    Atmospheric vertical velocities and advective tendencies are essential as large-scale forcing data to drive single-column models (SCM), cloud-resolving models (CRM) and large-eddy simulations (LES). They cannot be directly measured or easily calculated with great accuracy from field measurements. In the Atmospheric Radiation Measurement (ARM) program, a constrained variational algorithm (1DCVA) has been used to derive large-scale forcing data over a sounding network domain with the aid of flux measurements at the surface and top of the atmosphere (TOA). We extend the 1DCVA algorithm into three dimensions (3DCVA) along with other improvements to calculate gridded large-scale forcing data. We also introduce an ensemble framework using different background data, error covariance matrices and constraint variables to quantify the uncertainties of the large-scale forcing data. The results of sensitivity study show that the derived forcing data and SCM simulated clouds are more sensitive to the background data than to the error covariance matrices and constraint variables, while horizontal moisture advection has relatively large sensitivities to the precipitation, the dominate constraint variable. Using a mid-latitude cyclone case study in March 3rd, 2000 at the ARM Southern Great Plains (SGP) site, we investigate the spatial distribution of diabatic heating sources (Q1) and moisture sinks (Q2), and show that they are consistent with the satellite clouds and intuitive structure of the mid-latitude cyclone. We also evaluate the Q1 and Q2 in analysis/reanalysis, finding that the regional analysis/reanalysis all tend to underestimate the sub-grid scale upward transport of moist static energy in the lower troposphere. With the uncertainties from large-scale forcing data and observation specified, we compare SCM results and observations and find that models have large biases on cloud properties which could not be fully explained by the uncertainty from the large-scale forcing

  1. Theoretical Investigation of Hydrogen Adsorption and Dissociation on Iron and Iron Carbide Surfaces Using the ReaxFF Reactive Force Field Method

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Chenyu; van Duin, Adri C.T.; Sorescu, Dan C.

    2012-06-01

    We have developed a ReaxFF reactive force field to describe hydrogen adsorption and dissociation on iron and iron carbide surfaces relevant for simulation of Fischer–Tropsch (FT) synthesis on iron catalysts. This force field enables large system (>>1000 atoms) simulations of hydrogen related reactions with iron. The ReaxFF force field parameters are trained against a substantial amount of structural and energetic data including the equations of state and heats of formation of iron and iron carbide related materials, as well as hydrogen interaction with iron surfaces and different phases of bulk iron. We have validated the accuracy and applicability of ReaxFF force field by carrying out molecular dynamics simulations of hydrogen adsorption, dissociation and recombination on iron and iron carbide surfaces. The barriers and reaction energies for molecular dissociation on these two types of surfaces have been compared and the effect of subsurface carbon on hydrogen interaction with iron surface is evaluated. We found that existence of carbon atoms at subsurface iron sites tends to increase the hydrogen dissociation energy barrier on the surface, and also makes the corresponding hydrogen dissociative state relatively more stable compared to that on bare iron. These properties of iron carbide will affect the dissociation rate of H{sub 2} and will retain more surface hydride species, thus influencing the dynamics of the FT synthesis process.

  2. Role of attractive forces in tapping tip force microscopy

    DEFF Research Database (Denmark)

    Kyhle, Anders; Sørensen, Alexis Hammer; Bohr, Jakob

    1997-01-01

    We present experimental and numerical results demonstrating the drastic influence of attractive forces on the behaviour of the atomic force microscope when operated in the resonant tapping tip mode in an ambient environment. It is often assumed that tapping is related to repulsive interaction...

  3. Surface forces studied with colloidal probe atomic force microscopy

    NARCIS (Netherlands)

    Giesbers, M.

    2001-01-01

    Forces between surfaces are a determining factor for the performance of natural as well as synthetic colloidal systems, and play a crucial role in industrial production processes. Measuring these forces is a scientific and experimental challenge and over the years several techniques have

  4. A force-sensing surgical tool with a proximally located force/torque sensor.

    Science.gov (United States)

    Schwalb, W; Shirinzadeh, B; Smith, J

    2017-03-01

    Robotic surgery has seen a rapid increase in popularity in the last few decades because advantages such as increased accuracy and dexterity can be realized. These systems still lack force-feedback, where such a capability is believed to be beneficial to the surgeon and can improve safety. In this paper a force-feedback enabled surgical robotic system is described in which the developed force-sensing surgical tool is discussed in detail. The developed surgical tool makes use of a proximally located force/torque sensor, which, in contrast to a distally located sensor, requires no miniaturization or sterilizability. Experimental results are presented, and indicate high force sensing accuracies with errors <0.09 N. It is shown that developing a force-sensing surgical tool utilizing a proximally located force/torque sensor is feasible, where a tool outer diameter of 12 mm can be achieved. For future work it is desired to decrease the current tool outer diameter to 10 mm. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  5. Probabilistic analysis of manufacturing uncertainties for an automotive turbocharger centrifugal compressor using numerical and experimental methods

    NARCIS (Netherlands)

    Javed, A.; Kamphues, E.; Hartuc, T.; Pecnik, R.; Van Buijtenen, J.P.

    2015-01-01

    The compressor impellers for mass-produced turbochargers are generally die-casted and machined to their final configuration. Manufacturing uncertainties are inherently introduced as stochastic dimensional deviations in the impeller geometry. These deviations eventually propagate into the compressor

  6. Natural resource revenues: a test of federalism. [18 papers

    Energy Technology Data Exchange (ETDEWEB)

    Scott, A [ed.

    1976-01-01

    This volume centers on the concept of an economic rent; particularly rent yielded by mineral resources. The editor, in the Introduction, divides the 18 conference papers into three groups. The first group was concerned with the taxation of the mining and energy industries and its connection with natural resource policy. The introductory chapter attempts to indicate ways of linking the choice of tax collector with the likely effects of the alternative collector's chosen system of taxation. The linkage depends on whether the taxes are on resource ''rent'' and so are ''neutral,'' or on whether they are on costs or prices and so likely to distort or affect private output and timing decisions. A second group of revenue-oriented papers started at an earlier stage: instead of assuming that certain methods of raising revenue tended to be neutral, they showed their recognition that the general literature says little or nothing that is authoritative on this subject. This recognition impelled them to make careful case studies of the effect of certain taxes and agnostic conclusions about their general tendency (that is, their tendency to distort the plans and production programs that would exist without taxation). While maintaining an interest in the neutrality distortion problem, a third group reserved their force for the problem of entitlement to resource revenues. Mr. Scott senses that the authors split their verdicts: pointing to their support for a particular compromise policy. (MCW)

  7. Female labour force participation, fertility and public policy in Sweden.

    Science.gov (United States)

    Sundstrom, M; Stafford, F P

    1992-01-01

    2nd only to Ireland in total fertility, Sweden has the highest total fertility (TFR) and female labor force participation rates (FLFPR) among European countries in the late 1980s and early 1990s. 1988 TFR and FLFPR were 1.96 and 80.1%, respectively. This paper considers the role of public policy in creating this unique trend, with particular focus on family leave policy. In 1974, Sweden became the 1st country to allow leave to both parents following childbirth. By 1990, leave duration had grown from an initial 6-month period to 15 months. In addition, subsidized day care, flexible working hours, and economic support to families with children is provided in the context of a family-supportive tax structure. While generous, benefits are related to work and income history. Labor income is replaced at 90% of gross earnings, while the unemployed receive only minimal taxable flat payments. Benefits overall are paid from general taxes. Given that benefits reflect job history and income, and income level tends to rise fastest in the initial stages of employment, women in Sweden postpone childbirth in order to realize wage increases and greater job standing over the short- to medium-terms. In sum, Sweden's policies stimulate both fertility and women's paid work by reducing the costs of having children while requiring parents to be employed to receive full benefits. This paper further reviews the development of parental leave and related policies and compares Swedish fertility, female labor force participation, and parental leave benefits to those of countries in the European Community.

  8. Method for lateral force calibration in atomic force microscope using MEMS microforce sensor.

    Science.gov (United States)

    Dziekoński, Cezary; Dera, Wojciech; Jarząbek, Dariusz M

    2017-11-01

    In this paper we present a simple and direct method for the lateral force calibration constant determination. Our procedure does not require any knowledge about material or geometrical parameters of an investigated cantilever. We apply a commercially available microforce sensor with advanced electronics for direct measurement of the friction force applied by the cantilever's tip to a flat surface of the microforce sensor measuring beam. Due to the third law of dynamics, the friction force of the equal value tilts the AFM cantilever. Therefore, torsional (lateral force) signal is compared with the signal from the microforce sensor and the lateral force calibration constant is determined. The method is easy to perform and could be widely used for the lateral force calibration constant determination in many types of atomic force microscopes. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Detection and effects of pump low-flow operation

    International Nuclear Information System (INIS)

    Casada, D.A.; Greene, R.H.

    1993-01-01

    Operating experience and previous studies have shown that a significant cause of pump problems and failures can result from low- flow operation. Operation at low-flow rates can create unstable flows within the pump impeller and casing. This condition can result in an increased radial and axial thrust on the rotor, which in turn causes higher shaft stresses, increased shaft deflection, and potential bearing and mechanical seal problems. Two of the more serious results of low-flow pump operation are cavitation and recirculation. Cavitation is the formation and subsequent collapse of vapor bubbles in any flow that is at an ambient pressure less than the vapor pressure of the liquid medium. It is the collapse of these vapor bubbles against the metal surfaces of the impeller or casing that causes surface pitting, erosion, and deterioration. Pump recirculation more damaging than cavitation. If located at the impeller eye, recirculation damages the inlet areas of the casing. At the impeller tips, recirculation alters the outside diameter of the impeller. If recirculation occurs around impeller shrouds, it damages thrust bearings. Recirculation also erodes impellers, diffusers, and volutes and causes failure of mechanical seals and bearings. This paper reports on a utility pump failure caused by low-flow induced phenomena. ORNL is investigating the results of low-flow pump operations by evaluating the types of measurements and diagnostic techniques that are currently used by licensees to detect pump degradation. A new, enhanced application of motor current and power data analysis has been developed that uses a signal comparison methodology to produce an instability ratio indicative of normal or unstable flow conditions. Examples of this type of low-flow detection technique are presented in this paper along with a brief discussion of the various types of technologies currently being used by licensees to evaluate pump operation and determine possible degradation

  10. Short-range fundamental forces

    International Nuclear Information System (INIS)

    Antoniadis, I.; Baessler, S.; Buchner, M.; Fedorov, V.V.; Hoedl, S.; Nesvizhevsky, V.V.; Pignol, G.; Protasov, K.V.; Lambrecht, A.; Reynaud, S.; Sobolev, Y.

    2010-01-01

    We consider theoretical motivations to search for extra short-range fundamental forces as well as experiments constraining their parameters. The forces could be of two types: 1) spin-independent forces; 2) spin-dependent axion-like forces. Different experimental techniques are sensitive in respective ranges of characteristic distances. The techniques include measurements of gravity at short distances, searches for extra interactions on top of the Casimir force, precision atomic and neutron experiments. We focus on neutron constraints, thus the range of characteristic distances considered here corresponds to the range accessible for neutron experiments

  11. Novel maglev pump with a combined magnetic bearing.

    Science.gov (United States)

    Onuma, Hiroyuki; Murakami, Michiko; Masuzawa, Toru

    2005-01-01

    The newly developed pump is a magnetically levitated centrifugal blood pump in which active and passive magnetic bearings are integrated to construct a durable ventricular assist device. The developed maglev centrifugal pump consists of an active magnetic bearing, a passive magnetic bearing, a levitated impeller, and a motor stator. The impeller is set between the active magnetic bearing and the motor stator. The active magnetic bearing uses four electromagnets to control the tilt and the axial position of the impeller. The radial movement of the levitated impeller is restricted with the passive stability dependent upon the top stator and the passive permanent magnetic bearing to reduce the energy consumption and the control system complexity. The top stator was designed based upon a magnetic field analysis to develop the maglev pump with sufficient passive stability in the radial direction. By implementing this analysis design, the oscillating amplitude of the impeller in the radial direction was cut in half when compared with the simple shape stator. This study concluded that the newly developed maglev centrifugal pump displayed excellent levitation performance and sufficient pump performance as a ventricular assist device.

  12. Dynamic Characteristics of Rotating Stall in Mixed Flow Pump

    Directory of Open Access Journals (Sweden)

    Xiaojun Li

    2013-01-01

    Full Text Available Rotating stall, a phenomenon that causes flow instabilities and pressure hysteresis by propagating at some fraction of the impeller rotational speed, can occur in centrifugal impellers, mixed impellers, radial diffusers, or axial diffusers. Despite considerable efforts devoted to the study of rotating stall in pumps, the mechanics of this phenomenon are not sufficiently understood. The propagation mechanism and onset of rotating stall are not only affected by inlet flow but also by outlet flow as well as the pressure gradient in the flow passage. As such, the complexity of these concepts is not covered by the classical explanation. To bridge this research gap, the current study investigated prerotation generated at the upstream of the impeller, leakage flow at the tip clearance between the casing and the impeller, and strong reserve flow at the inlet of the diffuser. Understanding these areas will clarify the origin of the positive slope of the head-flow performance curve for a mixed flow pump. Nonuniform pressure distribution and adverse pressure gradient were also introduced to evaluate the onset and development of rotating stall within the diffuser.

  13. Turbulent flow in a vessel agitated by side entering inclined blade turbine with different diameter using CFD simulation

    Science.gov (United States)

    Fathonah, N. N.; Nurtono, T.; Kusdianto; Winardi, S.

    2018-03-01

    Single phase turbulent flow in a vessel agitated by side entering inclined blade turbine has simulated using CFD. The aim of this work is to identify the hydrodynamic characteristics of a model vessel, which geometrical configuration is adopted at industrial scale. The laboratory scale model vessel is a flat bottomed cylindrical tank agitated by side entering 4-blade inclined blade turbine with impeller rotational speed N=100-400 rpm. The effect of the impeller diameter on fluid flow pattern has been investigated. The fluid flow patterns in a vessel is essentially characterized by the phenomena of macro-instabilities, i.e. the flow patterns change with large scale in space and low frequency. The intensity of fluid flow in the tank increase with the increase of impeller rotational speed from 100, 200, 300, and 400 rpm. It was accompanied by shifting the position of the core of circulation flow away from impeller discharge stream and approached the front of the tank wall. The intensity of fluid flow in the vessel increase with the increase of the impeller diameter from d=3 cm to d=4 cm.

  14. Master equation and runaway speed of the Francis turbine

    Science.gov (United States)

    Zhang, Zh.

    2018-04-01

    The master equation of the Francis turbine is derived based on the combination of the angular momentum (Euler) and the energy laws. It relates the geometrical design of the impeller and the regulation settings (guide vane angle and rotational speed) to the discharge and the power output. The master equation, thus, enables the complete characteristics of a given Francis turbine to be easily computed. While applying the energy law, both the shock loss at the impeller inlet and the swirling loss at the impeller exit are taken into account. These are main losses which occur at both the partial load and the overloads and, thus, dominantly influence the characteristics of the Francis turbine. They also totally govern the discharge of the water through the impeller when the impeller is found in the standstill. The computations have been performed for the discharge, the hydraulic torque and the hydraulic efficiency. They were also compared with the available measurements on a model turbine. Excellent agreement has been achieved. The computations also enable the runaway speed of the Francis turbine and the related discharge to be determined as a function of the setting angle of the guide vanes.

  15. Comparison of CFD and Test Techniques for Cavitation Inception

    International Nuclear Information System (INIS)

    Lee, Do Hwan; Park, Sung Keun; Lee, Sun Ki; Kim, Byung Kon

    2009-01-01

    Cavitation erosion on centrifugal pump impellers is a one of the fundamental factors that cause performance degradation and life shortening of the pumps. One approach to estimate the expected life of an impeller is to use sheet cavity length on the blade surface. While observing the cavity length is more suitable to accurately predict the impeller damage, it is not readily available in the field or on the test stand. Recently, the prediction of the cavity length by using commercial CFD codes has been tried by several authors. As an alternative to direct measure the cavity length of an impeller, a means of estimating cavity length of an impeller based on the relation of operating NPSH to that of 3% NPSH and inception NPSH was developed by Cooper. Although this method seems to be attractive, it is not easy to accurately estimate the inception NPSH without flow visualization. Some recent researchers has been paid attention to apply the high frequency Acoustic Emission(AE) technique to detect cavitation inception of pumps. As an effort to better estimate the cavity length without relying on flow visualization, CFD calculations and experiments were performed and then the results are compared in this study

  16. The force pyramid: a spatial analysis of force application during virtual reality brain tumor resection.

    Science.gov (United States)

    Azarnoush, Hamed; Siar, Samaneh; Sawaya, Robin; Zhrani, Gmaan Al; Winkler-Schwartz, Alexander; Alotaibi, Fahad Eid; Bugdadi, Abdulgadir; Bajunaid, Khalid; Marwa, Ibrahim; Sabbagh, Abdulrahman Jafar; Del Maestro, Rolando F

    2017-07-01

    OBJECTIVE Virtual reality simulators allow development of novel methods to analyze neurosurgical performance. The concept of a force pyramid is introduced as a Tier 3 metric with the ability to provide visual and spatial analysis of 3D force application by any instrument used during simulated tumor resection. This study was designed to answer 3 questions: 1) Do study groups have distinct force pyramids? 2) Do handedness and ergonomics influence force pyramid structure? 3) Are force pyramids dependent on the visual and haptic characteristics of simulated tumors? METHODS Using a virtual reality simulator, NeuroVR (formerly NeuroTouch), ultrasonic aspirator force application was continually assessed during resection of simulated brain tumors by neurosurgeons, residents, and medical students. The participants performed simulated resections of 18 simulated brain tumors with different visual and haptic characteristics. The raw data, namely, coordinates of the instrument tip as well as contact force values, were collected by the simulator. To provide a visual and qualitative spatial analysis of forces, the authors created a graph, called a force pyramid, representing force sum along the z-coordinate for different xy coordinates of the tool tip. RESULTS Sixteen neurosurgeons, 15 residents, and 84 medical students participated in the study. Neurosurgeon, resident and medical student groups displayed easily distinguishable 3D "force pyramid fingerprints." Neurosurgeons had the lowest force pyramids, indicating application of the lowest forces, followed by resident and medical student groups. Handedness, ergonomics, and visual and haptic tumor characteristics resulted in distinct well-defined 3D force pyramid patterns. CONCLUSIONS Force pyramid fingerprints provide 3D spatial assessment displays of instrument force application during simulated tumor resection. Neurosurgeon force utilization and ergonomic data form a basis for understanding and modulating resident force

  17. The erotic transference: dream or delusion?

    Science.gov (United States)

    De Masi, Franco

    2012-12-01

    The erotic transference can be seen as the Janus face of clinical work in psychoanalysis: it may either arise out of the positive emotions necessary for the building of new shared realities, or be fueled by falsified and distorted constructions. In the former case, the erotic transference expresses the capacity to anticipate, or "dream," the emotional relationship with the object-which is why Freud valued its transformative aspect as one of the "forces impelling [the patient] to . . . make changes"-whereas in the latter it is equivalent to a flight from psychic reality and may be imperceptibly transformed into an actual delusion.

  18. Study of mixing behavior of cstr using CFD

    Directory of Open Access Journals (Sweden)

    D. Rajavathsavai

    2014-03-01

    Full Text Available The continuous stirred tank reactor (CSTR is a widely used equipment in chemical related industries. The flow behaviour of fluid inside the reactor may either change from dispersion to ideal or ideal to dispersion mixing state. It is studied using the computational fluid dynamics (CFD simulation software ANSYS Fluent. The mixing behaviour is predicted in terms of age distribution function, I (θ. For the CSTR without impeller and baffles, I (θ is found by the tracer injection method. It is measured and predicted by the impeller swept volume method for the CSTR in the presence of impeller and baffles. The predicted results are found to be in good agreement with the literature experimental data. Effect of rpm of the impeller, Reynolds number and viscosity of the process fluid on the mixing characteristics has been investigated.

  19. A prediction of 3-D viscous flow and performance of the NASA Low-Speed Centrifugal Compressor

    Science.gov (United States)

    Moore, John; Moore, Joan G.

    1990-01-01

    A prediction of the three-dimensional turbulent flow in the NASA Low-Speed Centrifugal Compressor Impeller has been made. The calculation was made for the compressor design conditions with the specified uniform tip clearance gap. The predicted performance is significantly worse than that predicted in the NASA design study. This is explained by the high tip leakage flow in the present calculation and by the different model adopted for tip leakage flow mixing. The calculation gives an accumulation of high losses in the shroud/pressure-side quadrant near the exit of the impeller. It also predicts a region of meridional backflow near the shroud wall. Both of these flow features should be extensive enough in the NASA impeller to allow detailed flow measurements, leading to improved flow modeling. Recommendations are made for future flow studies in the NASA impeller.

  20. Evaluation of higher order statistics parameters for multi channel sEMG using different force levels.

    Science.gov (United States)

    Naik, Ganesh R; Kumar, Dinesh K

    2011-01-01

    The electromyograpy (EMG) signal provides information about the performance of muscles and nerves. The shape of the muscle signal and motor unit action potential (MUAP) varies due to the movement of the position of the electrode or due to changes in contraction level. This research deals with evaluating the non-Gaussianity in Surface Electromyogram signal (sEMG) using higher order statistics (HOS) parameters. To achieve this, experiments were conducted for four different finger and wrist actions at different levels of Maximum Voluntary Contractions (MVCs). Our experimental analysis shows that at constant force and for non-fatiguing contractions, probability density functions (PDF) of sEMG signals were non-Gaussian. For lesser MVCs (below 30% of MVC) PDF measures tends to be Gaussian process. The above measures were verified by computing the Kurtosis values for different MVCs.