The virtual community has become a new life style as for human,but the public's acceptance is relatively low at present.So the research about the mechanism of the influence on the cohesiveness and the collective e...The virtual community has become a new life style as for human,but the public's acceptance is relatively low at present.So the research about the mechanism of the influence on the cohesiveness and the collective efficiency in virtual community has an important theoretical value and practical value.In the paper,the key variables that affect virtual community cohesiveness are extracted from two aspects—self-perception of community members and community environment,and the influence mechanism model of virtual community cohesiveness and community collective efficiency is established based on Triadic Reciprocal Determinism.By means of the questionnaire on the community members and the empirical analysis,the key factors influencing cohesiveness of virtual community are brought up,as well as the mechanism that the four dimensions of cohesiveness work,on collective efficiency.According to the results,it is practically meaningful that the problems and insufficiency in the operation of existing virtual community are discovered,which guides the operating managers of the virtual community to formulate operation policy of the virtual community for operating managers to develop strategies.展开更多
A numerical code called RFPA-Dynamics was used to study the rockburst mechanism under dynamic load based on coupled static-dynamic analysis.The results show that dynamic disturbance has a very distinct triggering effe...A numerical code called RFPA-Dynamics was used to study the rockburst mechanism under dynamic load based on coupled static-dynamic analysis.The results show that dynamic disturbance has a very distinct triggering effect on rockburst.Under the dynamic load,rockburst is motivated by tensile stress formed by the overlapping of dynamic waves in the form of instantaneous open and cutting through of cracks in weak planes and pre-damaged areas.Meanwhile,the orientation of joint sets has an obvious leading effect on rockburst locations.Finally,a higher initial static stress state before dynamic loading can cause more pre-damaged area,thus leading to a larger rockburst scope.展开更多
The gas torque in a twin-rotor piston engine(TRPE) was modeled using adiabatic approximation with instantaneous combustion. The first prototype of TRPE was manufactured. This prototype is intended for high power densi...The gas torque in a twin-rotor piston engine(TRPE) was modeled using adiabatic approximation with instantaneous combustion. The first prototype of TRPE was manufactured. This prototype is intended for high power density engines and can produce 36 power strokes per shaft revolution. Compared with the conventional engines, the vector sum of combustion gas forces acting on each rotor piston in TRPE is a pure torque, and the combustion gas rotates the rotors while compresses the gas in the compression chamber at the same time. Mathematical modeling of gas force transmission was built. Expression for gas torque on each rotor was derived. Different variation patterns of the volume change of working chamber were introduced. The analytical and numerical results is presented to demonstrate the main characteristics of gas torque. The results show that the value of gas torque in TRPE falls to be less than zero before the combustion phase is finished; the time for one stroke is 30° in terms of the rotating angle of the output shaft; gas torque in one complete revolution of the output shaft has a period which is equal to 60° and it is necessary to put off the moment when gas torque becomes zero in order to export the maximum energy.展开更多
A new and simple microwave-assisted alkaline degradation (MAAD) method for the elimination of organoehlorine-pesticide interference on the determination of polychlorinated biphenyls (PCBs) in soil by GC is present...A new and simple microwave-assisted alkaline degradation (MAAD) method for the elimination of organoehlorine-pesticide interference on the determination of polychlorinated biphenyls (PCBs) in soil by GC is presented. Under the optimal conditions, the interference of α- HCH, β- HCH, γ -HCH,δ -HCH, o. p' - DDT, p. p' - DDD and p. p' - DDT could be eliminated completely, and p. p' - DDE, Aldrin and Dieldrin could be partially eliminated; however, Dieldrin could be completely eliminated by using concentrated sulphurie acid. The method was evaluated by analyzing the spiked-soil sample. The mean recovery obtained was 84. 1% and the Relative Standard Deviation (RSD) was 2. 7%. Experimental results also indicate that the degradation of the interference and the extraction of the target analytes, PCBs, could be carried out simuhaneously. Compared with the traditional methods, the MAAD method is a rapid, efficient and solvent-saving method,展开更多
Slope stability assessment is a geotechnical problem characterized by many sources of uncertainty. In clas- sical reliability analysis, only the randomness of uncertainties is taken into account but the fuzziness of t...Slope stability assessment is a geotechnical problem characterized by many sources of uncertainty. In clas- sical reliability analysis, only the randomness of uncertainties is taken into account but the fuzziness of them is ignored. In this paper, a fuzzy probability approach and a fuzzy JC method are presented for the reliability analysis. The two methods have been applied to stability analysis of a certain slope of permanent ship lock in the Three-Gorges Project. The results obtained from these two methods are basically the same. However, compared with the fuzzy probability means, the fuzzy JC method can reflect the real situation better because it uses a fuzzy-based analysis applied to not only limit state equation but also mechanical parameters.展开更多
Permanent magnet tubular linear motors(TLMs) arranged in multiple rows and multiple columns used for a radiotherapy machine were studied. Due to severe volumetric and thermal constraints, the TLMs were at high risk of...Permanent magnet tubular linear motors(TLMs) arranged in multiple rows and multiple columns used for a radiotherapy machine were studied. Due to severe volumetric and thermal constraints, the TLMs were at high risk of overheating. To predict the performance of the TLMs accurately, a multi-physics analysis approach was proposed. Specifically, it considered the coupling effects amongst the electromagnetic and the thermal models of the TLMs, as well as the fluid model of the surrounding air. To reduce computation cost, both the electromagnetic and the thermal models were based on lumped-parameter methods. Only a minimum set of numerical computation(computational fluid dynamics, CFD) was performed to model the complex fluid behavior. With the proposed approach, both steady state and transient state temperature distributions, thermal rating and permissible load can be predicted. The validity of this approach is verified through the experiment.展开更多
Background: Accelerometers have been suggested to provide additional information during the 6-min walk test which may be useful in evaluating changes in functional exercise capacity. The aim of the study was to ident...Background: Accelerometers have been suggested to provide additional information during the 6-min walk test which may be useful in evaluating changes in functional exercise capacity. The aim of the study was to identify whether the additional information measured by the My Wellness Key^TM(MWK) accelerometer during a treadmill 6-min walk test(t-6MWT) was related to currently used outcome measures.Methods: Fifteen participants(9 males, 6 females) performed a self-paced t-6MWT. Respiratory gas analysis and walking distance were measured whilst wearing the MWK.Results: A significant correlation was established between activity counts and 6-min walk distance(6MWD)(r=-0.847, p 〈 0.001) yet not 6-min walk work(6MWW)(r=-0.337, p=0.220). Energy expenditure estimated by the MWK was strongly correlated to 6MWW(r=0.938, p 〈 0.001)but not 6MWD(r=0.477, p=0.072). The MWK significantly underestimated energy expenditure(36.73, CI=33.9-39.7 kcal) compared to gas analysis(54.35, CI=46.2-61.4 kcal) demonstrating poor agreement between the two analyses(Bias=-17.61 kcal, Limits of agreement=-37.4,t2.2 kcal). Measurement of time spent undertaking light, moderate, and vigorous physical activity was not significantly different( p 〉 0.05)between the MWK and gas analysis.Conclusion: Estimated energy expenditure provided by the MWK was strongly correlated to 6MWW; however, MWK underestimated energy expenditure as measured by gas analysis. The MWK may provide outcome data that supplement those currently provided by the 6MWD for functional capacity assessment during the t-6MWT.展开更多
The quality of service for the aged is related to the problem of population aging in China and the quality evaluation is an important link to improve the quality and level of service for the aged. This paper mainly di...The quality of service for the aged is related to the problem of population aging in China and the quality evaluation is an important link to improve the quality and level of service for the aged. This paper mainly discusses the meaning of the third party evaluation mechanism of China' s pension service quality evaluation system, the significance on the establishment of third-party evaluation mechanism of China' s pension service quality and ways to establish third-party evaluation mechanism of China's pension service quality.展开更多
A 3-D modeling of FEA (finite element analysis) design provides for high-speed synchronous with PMs (permanent magnets) applied in aerospace application will be examined under design considerations ofn = 12,000 rp...A 3-D modeling of FEA (finite element analysis) design provides for high-speed synchronous with PMs (permanent magnets) applied in aerospace application will be examined under design considerations ofn = 12,000 rpm, short-duty operation, and etc. for an ARWM (aerospace retraction wheel motor). First, lumped-elements will be fine-tuned following numerical method results is reported steady-state and transient solutions. Besides, the equations of thermal modeling such as Re, N,,, G,. and Pr numbers in order to calculate heat-transfer coefficient of convection on the rotor and stator surfaces in the air-gap have calculated. This section illustrates the temperature distribution of each point in a clear view. By CFD (fluid dynamic analysis) analysis, the fluid dynamics were modeled, pressure and velocity streamlines of cooling-flow have analyzed. An optimization algorithm was derived in order to have optimized number of water-channels as well. Second, calculation of nodal and tangential forces which deal with mechanical stresses of the ARWM have represented. The paper discusses an accurate magnetic-field analysis that addresses equivalent stress distribution in the magnetic core through using the transient FEA to estimate motor characteristics. The whole model shear and normal mechanical stresses and total deformation oftbe ARWM has been investigated by transient FEA. The end-winding effects were included by the authors.展开更多
This paper deals with the mode analysis of the kinematic structure of human locomotion. The authors investigated synergy mechanism of human locomotion from motion-captured data and EMG signal data. The authors extract...This paper deals with the mode analysis of the kinematic structure of human locomotion. The authors investigated synergy mechanism of human locomotion from motion-captured data and EMG signal data. The authors extracted some common basic movements and residual modes, and analyzed the kinematical structures of limit cycle in joint angle space. The authors also implemented the numerical simulation analyses by using the motion captured data and EMG signal data to investigate the mechanical activities of human joints and to extract the mechanical structure of the limit cycle. The results show the joint synergy that is derived by the common basic modes, which expresses an inverted pendulum mode in support phase, and ballistic mode in swing phase with the kick-off motion in the most effective direction. This result can be guessed that the control strategy of human locomotion is simply based on the minimal control principle.展开更多
In this work, the efficiency ofa 1 kWp horizontal-axis wind turbine which is installed on the roof of the engineering building at the University of Salento has been evaluated, by means of CFD (computational fluid dyn...In this work, the efficiency ofa 1 kWp horizontal-axis wind turbine which is installed on the roof of the engineering building at the University of Salento has been evaluated, by means of CFD (computational fluid dynamic) and experimental data. Particularly, the influence of the building on the micro wind turbine performance has been studied and the numerical results (wind velocity fields and turbulence intensity above the building) have been compared with the experimental data collected over a period of three years. The results have shown that horizontal-axis wind turbines suffer from wake effect due to buildings, therefore, best sites in urban area have to be identified by a careful fluid dynamic analysis aimed at evaluating all causes that can reduce significantly the performance of the generator: in fact, building should allow to exploit increased wind intensity, but often this advantage is voided by turbulence phenomena, as in the case under investigation where the measured aerogenerator efficiency is lower than the nominal performance curve. Then, the best site can be found by crossing the contours of wind velocity with the turbulence intensity fields: in this way it is possible to localize an area (best location) where the aerogenerator can give maximum performance.展开更多
In this study, we attempt the analysis of the passage flow in the centrifugal impeller using FEM with/without the turbulence model, and compare this result with the experimental result. The turbulence model is the low...In this study, we attempt the analysis of the passage flow in the centrifugal impeller using FEM with/without the turbulence model, and compare this result with the experimental result. The turbulence model is the low Reynolds k-ε model proposed by Chien. We use the GSMAC method for the Reynolds averaged Navier-Stokes equstions, the Euler explicit method for the transport equations of the turbulent kinetic energy and the dissipation rate. All equations are discretized by the Galerkin’s method. At the midpassage of the centrifugal impeller the passagewise velocity component tends to increase in the pressure-to-suction direction, and the other component toward the pressure surface tends to be large in the region of the middle blade-to-blade to the hub side. The tip leakages appear around the region of the middle blade-to-blade near the casing together with the secondary flow toward the suction surface. These phenomena correspond with the experimental result, qualitatively.展开更多
Objective: To demonstrate the validity and reliability of volumetric quantitative computed tomography (vQCT) with multi-slice computed tomography (MSCT) and dual energy X-ray absorptiometry (DXA) for hip bone m...Objective: To demonstrate the validity and reliability of volumetric quantitative computed tomography (vQCT) with multi-slice computed tomography (MSCT) and dual energy X-ray absorptiometry (DXA) for hip bone mineral density (BMD) measurements, and to compare the differences between the two techniques in discriminating postmenopausal women with osteoporosis-related vertebral fractures from those without. Methods: Ninety subjects were enrolled and divided into three groups based on the BMD values of the lumbar spine and/or the femoral neck by DXA. Groups 1 and 2 consisted of postmenopausal women with BMD changes 〈-2SD, with and without radiographically confirmed vertebral fracture (n= 11 and 33, respectively). Group 3 comprised normal controls with BMD changes 〉-ISD (n-46). Post-MSCT (GE, LightSpeed16) scan reconstructed images of the abdominal-pelvic region, 1.25 mm thick per slice, were processed by OsteoCAD software to calculate the following parameters: volumetric BMD values of trabecular bone (TRAB), cortical bone (CORT), and integral bone (INTGL) of the left femoral neck, femoral neck axis length (NAL), and minimum cross-section area (mCSA). DXA BMD measurements of the lumbar spine (AP-SPINE) and the left femoral neck (NECK) also were performed for each subject. Results: The values of all seven parameters were significantly lower in subjects of Groups 1 and 2 than in normal postmenopausal women (P〈0.05, respectively). Comparing Groups 1 and 2, 3D-TRAB and 3D-INTGL were significantly lower in postmenopausal women with vertebral fracture(s) [(109.8±9.61) and (243.3±33.0) mg/cm^3, respectively] than in those without [(148.9±7.47) and (285.4±17.8) mg/cm^3, respectively] (P〈0.05, respectively), but no significant differences were evident in AP-SPINE or NECK BMD. Conclusion: the femoral neck-derived volumetric BMD parameters using vQCT appeared better than the DXA-derived ones in discriminating osteoporotic postmenopausal women with vertebral fractures from those without, vQCT might be useful to evaluate the effect of osteoporotic vertebral fracture status on changes in bone mass in the femoral neck.展开更多
Most of life maintains itself through turnover, namely cell proliferation, movement and elimination. Hydra's cells, for example, disappear continuously from the ends of tenta- cles, but these cells are replenished by...Most of life maintains itself through turnover, namely cell proliferation, movement and elimination. Hydra's cells, for example, disappear continuously from the ends of tenta- cles, but these cells are replenished by cell proliferation within the body. Inspired by such a biological fact, and together with various operations of polynomials, I here propose polynomial-life model toward analysis of some phenomena in multicellular organisms. Polynomial life consists of multicells that are expressed as multivariable polynomials. A cell is expressed as a term of polynomial, in which point (m, n) is described as a term zmy~ and the condition is described as its coefficient. Starting with a single term and following reductions by set of polynomials, I simulate the development from a cell to a multicell. In order to confirm uniqueness of the eventual multicell-pattern, GrSbner base can be used, which has been conventionally used to ensure uniqueness of normal form in the mathematical context. In this framework, I present various patterns through the polynomial-life model and discuss patterns maintained through turnover. Cell elimina- tion seems to play an important role in turnover, which may shed some light on cancer or regenerative medicine.展开更多
According to the mechanism of the arc plasma heating effect,and from a phenomenological perspective of view,the plasma actuation was simplified as heating energy injected into the supersonic flow field for the numeric...According to the mechanism of the arc plasma heating effect,and from a phenomenological perspective of view,the plasma actuation was simplified as heating energy injected into the supersonic flow field for the numerical research on controlling detached shock of the blunt body in non-center symmetrical positions.Besides,experimental research on the form and strength of detached shock wave control by plasma aerodynamic actuation in non-center symmetrical positions was conducted in a high-speed shock tunnel(M=2).The results showed that the detached distance of shock wave increased and the strength of normal shock wave ahead of the detached shock wave reduced when plasma actuation was applied.The control effect was greatly improved after the magnetic field was applied and the effect of upwind-direction flow was the best one.When the upwind-direction flow was applied with 1000 V voltage actuation,the distance of detached shock wave would increase from 3.4 to 7.6 mm and the time average strength of normal shock wave was weaken by 5.5%.At last,the mechanism of plasma actuation on controlling the detached shock wave was briefly analyzed.展开更多
基金This work has been supported by National Natural Science Foundation of China (No. 71271032).
文摘The virtual community has become a new life style as for human,but the public's acceptance is relatively low at present.So the research about the mechanism of the influence on the cohesiveness and the collective efficiency in virtual community has an important theoretical value and practical value.In the paper,the key variables that affect virtual community cohesiveness are extracted from two aspects—self-perception of community members and community environment,and the influence mechanism model of virtual community cohesiveness and community collective efficiency is established based on Triadic Reciprocal Determinism.By means of the questionnaire on the community members and the empirical analysis,the key factors influencing cohesiveness of virtual community are brought up,as well as the mechanism that the four dimensions of cohesiveness work,on collective efficiency.According to the results,it is practically meaningful that the problems and insufficiency in the operation of existing virtual community are discovered,which guides the operating managers of the virtual community to formulate operation policy of the virtual community for operating managers to develop strategies.
基金Project(90401004)supported by the Fundamental Research Funds for the Central Universities of ChinaProjects(20100471465,201104572)supported by China Postdoctoral Science Foundation+1 种基金Project(20091029)supported by Postdoctoral Science Foundation of Liaoning Province,ChinaProjects(50934006,51111130206)supported by the National Natural Science Foundation of China
文摘A numerical code called RFPA-Dynamics was used to study the rockburst mechanism under dynamic load based on coupled static-dynamic analysis.The results show that dynamic disturbance has a very distinct triggering effect on rockburst.Under the dynamic load,rockburst is motivated by tensile stress formed by the overlapping of dynamic waves in the form of instantaneous open and cutting through of cracks in weak planes and pre-damaged areas.Meanwhile,the orientation of joint sets has an obvious leading effect on rockburst locations.Finally,a higher initial static stress state before dynamic loading can cause more pre-damaged area,thus leading to a larger rockburst scope.
基金Project(51175500)supported by the National Natural Science Foundation of China
文摘The gas torque in a twin-rotor piston engine(TRPE) was modeled using adiabatic approximation with instantaneous combustion. The first prototype of TRPE was manufactured. This prototype is intended for high power density engines and can produce 36 power strokes per shaft revolution. Compared with the conventional engines, the vector sum of combustion gas forces acting on each rotor piston in TRPE is a pure torque, and the combustion gas rotates the rotors while compresses the gas in the compression chamber at the same time. Mathematical modeling of gas force transmission was built. Expression for gas torque on each rotor was derived. Different variation patterns of the volume change of working chamber were introduced. The analytical and numerical results is presented to demonstrate the main characteristics of gas torque. The results show that the value of gas torque in TRPE falls to be less than zero before the combustion phase is finished; the time for one stroke is 30° in terms of the rotating angle of the output shaft; gas torque in one complete revolution of the output shaft has a period which is equal to 60° and it is necessary to put off the moment when gas torque becomes zero in order to export the maximum energy.
基金Sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholar State Education Ministry (Grant No.415409) and the Scien-tific Research Foundation for Doctors, Guangdong Natural Science Foundation (Grant No.974078).
文摘A new and simple microwave-assisted alkaline degradation (MAAD) method for the elimination of organoehlorine-pesticide interference on the determination of polychlorinated biphenyls (PCBs) in soil by GC is presented. Under the optimal conditions, the interference of α- HCH, β- HCH, γ -HCH,δ -HCH, o. p' - DDT, p. p' - DDD and p. p' - DDT could be eliminated completely, and p. p' - DDE, Aldrin and Dieldrin could be partially eliminated; however, Dieldrin could be completely eliminated by using concentrated sulphurie acid. The method was evaluated by analyzing the spiked-soil sample. The mean recovery obtained was 84. 1% and the Relative Standard Deviation (RSD) was 2. 7%. Experimental results also indicate that the degradation of the interference and the extraction of the target analytes, PCBs, could be carried out simuhaneously. Compared with the traditional methods, the MAAD method is a rapid, efficient and solvent-saving method,
文摘Slope stability assessment is a geotechnical problem characterized by many sources of uncertainty. In clas- sical reliability analysis, only the randomness of uncertainties is taken into account but the fuzziness of them is ignored. In this paper, a fuzzy probability approach and a fuzzy JC method are presented for the reliability analysis. The two methods have been applied to stability analysis of a certain slope of permanent ship lock in the Three-Gorges Project. The results obtained from these two methods are basically the same. However, compared with the fuzzy probability means, the fuzzy JC method can reflect the real situation better because it uses a fuzzy-based analysis applied to not only limit state equation but also mechanical parameters.
基金Project(2015BAI03B00)supported by the National Key Technology R&D Program of ChinaProject(Z141100000514015)supported by Science and Technology Planning Program of Beijing,ChinaProject(SKLT12A03)supported by Tribology Science Fund of State Key Laboratory of Tribology,China
文摘Permanent magnet tubular linear motors(TLMs) arranged in multiple rows and multiple columns used for a radiotherapy machine were studied. Due to severe volumetric and thermal constraints, the TLMs were at high risk of overheating. To predict the performance of the TLMs accurately, a multi-physics analysis approach was proposed. Specifically, it considered the coupling effects amongst the electromagnetic and the thermal models of the TLMs, as well as the fluid model of the surrounding air. To reduce computation cost, both the electromagnetic and the thermal models were based on lumped-parameter methods. Only a minimum set of numerical computation(computational fluid dynamics, CFD) was performed to model the complex fluid behavior. With the proposed approach, both steady state and transient state temperature distributions, thermal rating and permissible load can be predicted. The validity of this approach is verified through the experiment.
文摘Background: Accelerometers have been suggested to provide additional information during the 6-min walk test which may be useful in evaluating changes in functional exercise capacity. The aim of the study was to identify whether the additional information measured by the My Wellness Key^TM(MWK) accelerometer during a treadmill 6-min walk test(t-6MWT) was related to currently used outcome measures.Methods: Fifteen participants(9 males, 6 females) performed a self-paced t-6MWT. Respiratory gas analysis and walking distance were measured whilst wearing the MWK.Results: A significant correlation was established between activity counts and 6-min walk distance(6MWD)(r=-0.847, p 〈 0.001) yet not 6-min walk work(6MWW)(r=-0.337, p=0.220). Energy expenditure estimated by the MWK was strongly correlated to 6MWW(r=0.938, p 〈 0.001)but not 6MWD(r=0.477, p=0.072). The MWK significantly underestimated energy expenditure(36.73, CI=33.9-39.7 kcal) compared to gas analysis(54.35, CI=46.2-61.4 kcal) demonstrating poor agreement between the two analyses(Bias=-17.61 kcal, Limits of agreement=-37.4,t2.2 kcal). Measurement of time spent undertaking light, moderate, and vigorous physical activity was not significantly different( p 〉 0.05)between the MWK and gas analysis.Conclusion: Estimated energy expenditure provided by the MWK was strongly correlated to 6MWW; however, MWK underestimated energy expenditure as measured by gas analysis. The MWK may provide outcome data that supplement those currently provided by the 6MWD for functional capacity assessment during the t-6MWT.
文摘The quality of service for the aged is related to the problem of population aging in China and the quality evaluation is an important link to improve the quality and level of service for the aged. This paper mainly discusses the meaning of the third party evaluation mechanism of China' s pension service quality evaluation system, the significance on the establishment of third-party evaluation mechanism of China' s pension service quality and ways to establish third-party evaluation mechanism of China's pension service quality.
文摘A 3-D modeling of FEA (finite element analysis) design provides for high-speed synchronous with PMs (permanent magnets) applied in aerospace application will be examined under design considerations ofn = 12,000 rpm, short-duty operation, and etc. for an ARWM (aerospace retraction wheel motor). First, lumped-elements will be fine-tuned following numerical method results is reported steady-state and transient solutions. Besides, the equations of thermal modeling such as Re, N,,, G,. and Pr numbers in order to calculate heat-transfer coefficient of convection on the rotor and stator surfaces in the air-gap have calculated. This section illustrates the temperature distribution of each point in a clear view. By CFD (fluid dynamic analysis) analysis, the fluid dynamics were modeled, pressure and velocity streamlines of cooling-flow have analyzed. An optimization algorithm was derived in order to have optimized number of water-channels as well. Second, calculation of nodal and tangential forces which deal with mechanical stresses of the ARWM have represented. The paper discusses an accurate magnetic-field analysis that addresses equivalent stress distribution in the magnetic core through using the transient FEA to estimate motor characteristics. The whole model shear and normal mechanical stresses and total deformation oftbe ARWM has been investigated by transient FEA. The end-winding effects were included by the authors.
文摘This paper deals with the mode analysis of the kinematic structure of human locomotion. The authors investigated synergy mechanism of human locomotion from motion-captured data and EMG signal data. The authors extracted some common basic movements and residual modes, and analyzed the kinematical structures of limit cycle in joint angle space. The authors also implemented the numerical simulation analyses by using the motion captured data and EMG signal data to investigate the mechanical activities of human joints and to extract the mechanical structure of the limit cycle. The results show the joint synergy that is derived by the common basic modes, which expresses an inverted pendulum mode in support phase, and ballistic mode in swing phase with the kick-off motion in the most effective direction. This result can be guessed that the control strategy of human locomotion is simply based on the minimal control principle.
文摘In this work, the efficiency ofa 1 kWp horizontal-axis wind turbine which is installed on the roof of the engineering building at the University of Salento has been evaluated, by means of CFD (computational fluid dynamic) and experimental data. Particularly, the influence of the building on the micro wind turbine performance has been studied and the numerical results (wind velocity fields and turbulence intensity above the building) have been compared with the experimental data collected over a period of three years. The results have shown that horizontal-axis wind turbines suffer from wake effect due to buildings, therefore, best sites in urban area have to be identified by a careful fluid dynamic analysis aimed at evaluating all causes that can reduce significantly the performance of the generator: in fact, building should allow to exploit increased wind intensity, but often this advantage is voided by turbulence phenomena, as in the case under investigation where the measured aerogenerator efficiency is lower than the nominal performance curve. Then, the best site can be found by crossing the contours of wind velocity with the turbulence intensity fields: in this way it is possible to localize an area (best location) where the aerogenerator can give maximum performance.
文摘In this study, we attempt the analysis of the passage flow in the centrifugal impeller using FEM with/without the turbulence model, and compare this result with the experimental result. The turbulence model is the low Reynolds k-ε model proposed by Chien. We use the GSMAC method for the Reynolds averaged Navier-Stokes equstions, the Euler explicit method for the transport equations of the turbulent kinetic energy and the dissipation rate. All equations are discretized by the Galerkin’s method. At the midpassage of the centrifugal impeller the passagewise velocity component tends to increase in the pressure-to-suction direction, and the other component toward the pressure surface tends to be large in the region of the middle blade-to-blade to the hub side. The tip leakages appear around the region of the middle blade-to-blade near the casing together with the secondary flow toward the suction surface. These phenomena correspond with the experimental result, qualitatively.
文摘Objective: To demonstrate the validity and reliability of volumetric quantitative computed tomography (vQCT) with multi-slice computed tomography (MSCT) and dual energy X-ray absorptiometry (DXA) for hip bone mineral density (BMD) measurements, and to compare the differences between the two techniques in discriminating postmenopausal women with osteoporosis-related vertebral fractures from those without. Methods: Ninety subjects were enrolled and divided into three groups based on the BMD values of the lumbar spine and/or the femoral neck by DXA. Groups 1 and 2 consisted of postmenopausal women with BMD changes 〈-2SD, with and without radiographically confirmed vertebral fracture (n= 11 and 33, respectively). Group 3 comprised normal controls with BMD changes 〉-ISD (n-46). Post-MSCT (GE, LightSpeed16) scan reconstructed images of the abdominal-pelvic region, 1.25 mm thick per slice, were processed by OsteoCAD software to calculate the following parameters: volumetric BMD values of trabecular bone (TRAB), cortical bone (CORT), and integral bone (INTGL) of the left femoral neck, femoral neck axis length (NAL), and minimum cross-section area (mCSA). DXA BMD measurements of the lumbar spine (AP-SPINE) and the left femoral neck (NECK) also were performed for each subject. Results: The values of all seven parameters were significantly lower in subjects of Groups 1 and 2 than in normal postmenopausal women (P〈0.05, respectively). Comparing Groups 1 and 2, 3D-TRAB and 3D-INTGL were significantly lower in postmenopausal women with vertebral fracture(s) [(109.8±9.61) and (243.3±33.0) mg/cm^3, respectively] than in those without [(148.9±7.47) and (285.4±17.8) mg/cm^3, respectively] (P〈0.05, respectively), but no significant differences were evident in AP-SPINE or NECK BMD. Conclusion: the femoral neck-derived volumetric BMD parameters using vQCT appeared better than the DXA-derived ones in discriminating osteoporotic postmenopausal women with vertebral fractures from those without, vQCT might be useful to evaluate the effect of osteoporotic vertebral fracture status on changes in bone mass in the femoral neck.
文摘Most of life maintains itself through turnover, namely cell proliferation, movement and elimination. Hydra's cells, for example, disappear continuously from the ends of tenta- cles, but these cells are replenished by cell proliferation within the body. Inspired by such a biological fact, and together with various operations of polynomials, I here propose polynomial-life model toward analysis of some phenomena in multicellular organisms. Polynomial life consists of multicells that are expressed as multivariable polynomials. A cell is expressed as a term of polynomial, in which point (m, n) is described as a term zmy~ and the condition is described as its coefficient. Starting with a single term and following reductions by set of polynomials, I simulate the development from a cell to a multicell. In order to confirm uniqueness of the eventual multicell-pattern, GrSbner base can be used, which has been conventionally used to ensure uniqueness of normal form in the mathematical context. In this framework, I present various patterns through the polynomial-life model and discuss patterns maintained through turnover. Cell elimina- tion seems to play an important role in turnover, which may shed some light on cancer or regenerative medicine.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51276197,51207169)
文摘According to the mechanism of the arc plasma heating effect,and from a phenomenological perspective of view,the plasma actuation was simplified as heating energy injected into the supersonic flow field for the numerical research on controlling detached shock of the blunt body in non-center symmetrical positions.Besides,experimental research on the form and strength of detached shock wave control by plasma aerodynamic actuation in non-center symmetrical positions was conducted in a high-speed shock tunnel(M=2).The results showed that the detached distance of shock wave increased and the strength of normal shock wave ahead of the detached shock wave reduced when plasma actuation was applied.The control effect was greatly improved after the magnetic field was applied and the effect of upwind-direction flow was the best one.When the upwind-direction flow was applied with 1000 V voltage actuation,the distance of detached shock wave would increase from 3.4 to 7.6 mm and the time average strength of normal shock wave was weaken by 5.5%.At last,the mechanism of plasma actuation on controlling the detached shock wave was briefly analyzed.