Climate change has prompted the aviation industry to reduce greenhouse gas emissions.Variable-camber leading edges,with their adaptable aerodynamic shapes,hold significant potential for laminar flow wings and contribu...Climate change has prompted the aviation industry to reduce greenhouse gas emissions.Variable-camber leading edges,with their adaptable aerodynamic shapes,hold significant potential for laminar flow wings and contribute to greener aviation.In response to this need,this paper proposes a design optimization method for a variable-camber leading edge featuring an outer variablethickness composite compliant skin and an inner open-kinematic-chain mechanism.The optimization methodology employs a fiber continuity model based on a ply-drop sequence,a guiding sequence and a thickness sequence to describe the variable-thickness composite compliant skin structure,enabling direct generation of a composite layup sequence that meets fiber continuity criteria.Additionally,the design methodology for the inner open kinematic chain considers the rigidflexible coupling effect and analyzes the number of driving ribs along the span-wise direction.Finally,a full-scale physical prototype for a large-scale civil aircraft is developed and experimented in the FL-10 wind tunnel,demonstrating that the variable-camber leading edge can smoothly and precisely achieve its target shape and hold its final profile under the corresponding aerodynamic loads,thereby validating the proposed design methodology.展开更多
A rotor CFD solver is developed for simulating the aerodynamic interaction phenomenon among rotor, wing and fuselage of a tilt rotor aircraft in its helicopter mode. The unsteady Navier-Stokes equations are discretize...A rotor CFD solver is developed for simulating the aerodynamic interaction phenomenon among rotor, wing and fuselage of a tilt rotor aircraft in its helicopter mode. The unsteady Navier-Stokes equations are discretized in inertial frame and embedded grid system is adopted for describing the relative motion among blades and nacelle/wing/fuselage. A combination of multi-layer embedded grid and 'extended hole fringe' technique is complemented in original grid system to tackle grid assembly difficulties arising from the narrow space among different aerodynamic components, and to improve the interpolation precision by decreasing the cell volume discrepancy among different grid blocks. An overall donor cell searching and automatic hole cutting technique is used for grid assembly, and the solution processes are speeded up by introduction of OpenMP parallel method. Based on this solver, flow fields and aerodynamics of a tilt rotor aircraft in hover are simulated with several rotor collective angles, and the corresponding states of an isolated rotor and rotor/wing/fuselage model are also computed to obtain reference solution. Aerodynamic interference influences among the rotor and wing/fuselage/nacelle are analyzed, and some meaningful conclusions are drawn. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd.展开更多
Damage from spinal cord injury occurs in two phases-the trauma of the initial mechanical insult and a secondary injury to nervous tissue spared by the primary insult.Apart from damage sustained as a result of direct t...Damage from spinal cord injury occurs in two phases-the trauma of the initial mechanical insult and a secondary injury to nervous tissue spared by the primary insult.Apart from damage sustained as a result of direct trauma to the spinal cord,the post-traumatic inflammatory response contributes significantly to functional motor deficits exacerbated by the secondary injury.Attenuating the detrimental aspects of the inflammatory response is a promising strategy to potentially ameliorate the secondary injury,and promote significant functional recovery.This review details how the inflammatory component of secondary injury to the spinal cord can be treated currently and in the foreseeable future.展开更多
Erythropoietin (Epo) is the regulator of red blood cell formation. Its receptor (EpoR) is now found in many cells and tissues of the body. EpoR is also shown to occur in tumor cells and Epo enhances the proliferation ...Erythropoietin (Epo) is the regulator of red blood cell formation. Its receptor (EpoR) is now found in many cells and tissues of the body. EpoR is also shown to occur in tumor cells and Epo enhances the proliferation of these cells through cell signaling. EpoR antagonist can reduce the growth of the tumor in vivo. In view of our current knowledge of Epo, its recombinant forms and receptor, use of Epo in cancer patients to enhance the recovery of hematocrit after chemotherapy treatment has to be carefully evaluated.展开更多
A method combining rotor actuator disk model and embedded grid technique is presented in this paper, aimed at predicting the flow fields and aerodynamic characteristics of tilt rotor aircraft in conversion mode more e...A method combining rotor actuator disk model and embedded grid technique is presented in this paper, aimed at predicting the flow fields and aerodynamic characteristics of tilt rotor aircraft in conversion mode more efficiently and effectively. In this method, rotor＇s influence is considered in terms of the momentum it impacts to the fluid around it; transformation matrixes among different coordinate systems are deduced to extend actuator method＇s utility to conversion mode flow fields＇ calculation. Meanwhile, an embedded grid system is designed, in which grids generated around fuselage and actuator disk are regarded as background grid and minor grid respectively, and a new method is presented for ‘donor searching＇ and ‘hole cutting＇ during grid assembling. Based on the above methods, flow fields of tilt rotor aircraft in conversion mode are simulated, with threedimensional Navier–Stokes equations discretized by a second-order upwind finite-volume scheme and an implicit lower–upper symmetric Gauss–Seidel（LU-SGS） time-stepping scheme. Numerical results demonstrate that the proposed CFD method is very effective in simulating the conversion mode flow fields of tilt rotor aircraft.展开更多
An improved model predictive control algorithm is proposed for Hammerstein-Wiener nonlinear systems.The proposed synthesis algorithm contains two parts:offline design the polytopic invariant sets,and online solve the ...An improved model predictive control algorithm is proposed for Hammerstein-Wiener nonlinear systems.The proposed synthesis algorithm contains two parts:offline design the polytopic invariant sets,and online solve the min-max optimization problem.The polytopic invariant set is adopted to replace the traditional ellipsoid invariant set.And the parameter-correlation nonlinear control law is designed to replace the traditional linear control law.Consequently,the terminal region is enlarged and the control effect is improved.Simulation and experiment are used to verify the validity of the wind tunnel flow field control algorithm.展开更多
Background:Obesity increases knee osteoarthritis(OA) risk through metabolic,inflammatory,and biomechanical factors,but how these systemic and local mediators interact to drive OA pathology is not well understood.We te...Background:Obesity increases knee osteoarthritis(OA) risk through metabolic,inflammatory,and biomechanical factors,but how these systemic and local mediators interact to drive OA pathology is not well understood.We tested the effect of voluntary running exercise after chronic diet-induced obesity on knee OA-related cartilage and bone pathology in mice.We then used a correlation-based network analysis to identify systemic and local factors associated with early-stage knee OA phenotypes among the different diet and exercise groups.Methods:Male C57 BL/6 J mice were fed a defined control(10% kcal fat) or high fat(HF)(60% kcal fat) diet from 6 to 37 weeks of age.At 25 weeks,one-half of the mice from each diet group were housed in cages with running wheels for the remainder of the study.Histology,micro computed tomography,and magnetic resonance imaging were used to evaluate changes in joint tissue structure and OA pathology.These local variables were then compared to systemic metabolic(body mass,body fat,and glucose tolerance),inflammatory(serum adipokines and inflammatory mediators),and functional(mechanical tactile sensitivity and grip strength) outcomes using a correlation-based network analysis.Diet and exercise effects were evaluated by two-way analysis of variance.Results:An HF diet increased the infrapatellar fat pad size and posterior joint osteophytes,and wheel running primarily altered the subchondral cortical and trabecular bone.Neither HF diet nor exercise altered average knee cartilage OA scores compared to control groups.However,the coefficient of variation was≥25% for many outcomes,and some mice in both diet groups developed moderate OA(>33% maximum score).This supported using correlation-based network analyses to identify systemic and local factors associated with early-stage knee OA phenotypes.In wheel-running cohorts,an HF diet reduced the network size compared to the control diet group despite similar running distances,suggesting that diet-induced obesity dampens the effects of exercise on systemic and local OA-related factors.Each of the 4 diet and activity groups showed mostly unique networks of local and systemic factors correlated with early-stage knee OA.Conclusion:Despite minimal group-level effects of chronic diet-induced obesity and voluntary wheel running on knee OA pathology under the current test durations,diet and exercise substantially altered the relationships among systemic and local variables associated with early-stage knee OA.These results suggest that distinct pre-OA phenotypes may exist prior to the development of disease.展开更多
A number of studies have indicated that plasma membrane calcium ATPases(PMCAs) are expressed in the brain and spinal cord and could play important roles not only in the maintenance of cellular calcium homeostasis but ...A number of studies have indicated that plasma membrane calcium ATPases(PMCAs) are expressed in the brain and spinal cord and could play important roles not only in the maintenance of cellular calcium homeostasis but also in the survival and function of central nervous system cells under pathological conditions.The different regional and cellular distributions of the various PMCA isoforms and splice variants in the nervous system and the diverse phenotypes of PMCA knockout mice support the notion that each isoform might play a distinct role. Especially in the spinal cord,the survival of neurons and,in particular,motor neurons could be dependent on PMCA2.This is indicated by the knockdown of PMCA2 in pure spinal cord neuronal cultures that leads to cell death via a decrease in collapsing response mediator protein 1 levels.Moreover,the progressive decline in the number of motor neurons in PMCA2-null mice andheterozygous mice further supports this notion.Therefore,the reported reduction in PMCA2 mRNA and protein levels in the inflamed spinal cord of mice affected by experimental autoimmune encephalomyelitis(EAE) ,an animal model of multiple sclerosis,and after spinal cord contusion injury,suggests that changes in PMCA2 expression could be a cause of neuronal pathology and death during inflammation and injury.Glutamate excitotoxicity mediated via kainate receptors has been implicated in the neuropathology of both EAE and spinal cord injury,and has been identified as a trigger that reduces PMCA2 levels in pure spinal cord neuronal cultures through degradation of the pump by calpain without affecting PMCA2 transcript levels.It remains to be determined which other stimuli modulate PMCA2 mRNA expression in the aforementioned pathological conditions of the spinal cord.展开更多
Different from previous temporal evolution assumption, the spatially growing mode was employed to analyze the linear stability for the channel flow of fiber suspensions. The stability equation applicable to fiber susp...Different from previous temporal evolution assumption, the spatially growing mode was employed to analyze the linear stability for the channel flow of fiber suspensions. The stability equation applicable to fiber suspensions was established and solutions for a wide range of Reynolds number and angular frequency were given numerically . The results show that, the flow instability is governed by a parameter H which represents a ratio between the axial stretching resistance of fiber and the inertial force of the fluid. An increase of H leads to a raise of the critical Reynolds number, a decrease of corresponding wave number, a slowdown of the decreasing of phase velocity , a growth of the spatial attenuation rate and a diminishment of the peak value of disturbance velocity. Although the unstable region is reduced on the whole, long wave disturbances are susceptible to fibers.展开更多
The effect of wall roughness on particle behavior in two-phase flows in a horizontal backward-facing step is studied using a phase-Doppler particle anemometer. The results show that the wall roughness widens the parti...The effect of wall roughness on particle behavior in two-phase flows in a horizontal backward-facing step is studied using a phase-Doppler particle anemometer. The results show that the wall roughness widens the particle velocity probability density distribution, enhances the redistribution of particle velocity into different directions, reduces the particle longitudinal mean velocity and increases the longitudinal and transverse fluctuation velocities and Reynolds shear stress. The effect of roughness on particle motion in the recirculation zone is weaker than that in the fully developed flow region. The effect of roughness for small particles is restricted only in the near-wall region, while that for large particles diffuses to the whole flow field.展开更多
A mixed lubrication model was established for piston skirt lubrication. The mathematical model developed in this paper incorporates governing equations of motion with average Reynolds equation. This model considers th...A mixed lubrication model was established for piston skirt lubrication. The mathematical model developed in this paper incorporates governing equations of motion with average Reynolds equation. This model considers the surfaceroughness and profile. The corresponding computer program can be used to calculate oscillatory motion of piston during the entire trajectory, which has the excellent convergence.In addition, a set of equipment, which adopt the laser induced fluorescent method, was developed to measure the oil film thickness between the piston and the bore.展开更多
An extensive database (946 measurements) for the frequency of pulsing flow in trickle beds was established by collecting the experimental results published over past 30 years. A new correlation based on artificial neu...An extensive database (946 measurements) for the frequency of pulsing flow in trickle beds was established by collecting the experimental results published over past 30 years. A new correlation based on artificial neural network (ANN) to predict the pulsation frequency was developed. Seven dimensionless numbers (groups) employed in the proposed correlation were liquid and gas Reynolds, liquid Weber, liquid Eotvos, gas Froude, and gas Stokes numbers and a bed correction factor. The comparisons of performance reported in the of literature and present correlations show that ANN correlation is a significant improvement in predicting pulsation frequency with an average absolute relative error (AARE) of 10% and a standard deviation less than 18%.展开更多
基金supported by the National Research Project“Variable CAmber wing TechNology(VCAN)”,China。
文摘Climate change has prompted the aviation industry to reduce greenhouse gas emissions.Variable-camber leading edges,with their adaptable aerodynamic shapes,hold significant potential for laminar flow wings and contribute to greener aviation.In response to this need,this paper proposes a design optimization method for a variable-camber leading edge featuring an outer variablethickness composite compliant skin and an inner open-kinematic-chain mechanism.The optimization methodology employs a fiber continuity model based on a ply-drop sequence,a guiding sequence and a thickness sequence to describe the variable-thickness composite compliant skin structure,enabling direct generation of a composite layup sequence that meets fiber continuity criteria.Additionally,the design methodology for the inner open kinematic chain considers the rigidflexible coupling effect and analyzes the number of driving ribs along the span-wise direction.Finally,a full-scale physical prototype for a large-scale civil aircraft is developed and experimented in the FL-10 wind tunnel,demonstrating that the variable-camber leading edge can smoothly and precisely achieve its target shape and hold its final profile under the corresponding aerodynamic loads,thereby validating the proposed design methodology.
文摘A rotor CFD solver is developed for simulating the aerodynamic interaction phenomenon among rotor, wing and fuselage of a tilt rotor aircraft in its helicopter mode. The unsteady Navier-Stokes equations are discretized in inertial frame and embedded grid system is adopted for describing the relative motion among blades and nacelle/wing/fuselage. A combination of multi-layer embedded grid and 'extended hole fringe' technique is complemented in original grid system to tackle grid assembly difficulties arising from the narrow space among different aerodynamic components, and to improve the interpolation precision by decreasing the cell volume discrepancy among different grid blocks. An overall donor cell searching and automatic hole cutting technique is used for grid assembly, and the solution processes are speeded up by introduction of OpenMP parallel method. Based on this solver, flow fields and aerodynamics of a tilt rotor aircraft in hover are simulated with several rotor collective angles, and the corresponding states of an isolated rotor and rotor/wing/fuselage model are also computed to obtain reference solution. Aerodynamic interference influences among the rotor and wing/fuselage/nacelle are analyzed, and some meaningful conclusions are drawn. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd.
文摘Damage from spinal cord injury occurs in two phases-the trauma of the initial mechanical insult and a secondary injury to nervous tissue spared by the primary insult.Apart from damage sustained as a result of direct trauma to the spinal cord,the post-traumatic inflammatory response contributes significantly to functional motor deficits exacerbated by the secondary injury.Attenuating the detrimental aspects of the inflammatory response is a promising strategy to potentially ameliorate the secondary injury,and promote significant functional recovery.This review details how the inflammatory component of secondary injury to the spinal cord can be treated currently and in the foreseeable future.
基金Supported in part by the funds from Central Arkansas Veterans Healthcare System
文摘Erythropoietin (Epo) is the regulator of red blood cell formation. Its receptor (EpoR) is now found in many cells and tissues of the body. EpoR is also shown to occur in tumor cells and Epo enhances the proliferation of these cells through cell signaling. EpoR antagonist can reduce the growth of the tumor in vivo. In view of our current knowledge of Epo, its recombinant forms and receptor, use of Epo in cancer patients to enhance the recovery of hematocrit after chemotherapy treatment has to be carefully evaluated.
文摘A method combining rotor actuator disk model and embedded grid technique is presented in this paper, aimed at predicting the flow fields and aerodynamic characteristics of tilt rotor aircraft in conversion mode more efficiently and effectively. In this method, rotor＇s influence is considered in terms of the momentum it impacts to the fluid around it; transformation matrixes among different coordinate systems are deduced to extend actuator method＇s utility to conversion mode flow fields＇ calculation. Meanwhile, an embedded grid system is designed, in which grids generated around fuselage and actuator disk are regarded as background grid and minor grid respectively, and a new method is presented for ‘donor searching＇ and ‘hole cutting＇ during grid assembling. Based on the above methods, flow fields of tilt rotor aircraft in conversion mode are simulated, with threedimensional Navier–Stokes equations discretized by a second-order upwind finite-volume scheme and an implicit lower–upper symmetric Gauss–Seidel（LU-SGS） time-stepping scheme. Numerical results demonstrate that the proposed CFD method is very effective in simulating the conversion mode flow fields of tilt rotor aircraft.
基金Project(61074074)supported by the National Natural Science Foundation,ChinaProject(KT2012C01J0401)supported by the Group Innovation Fund,China
文摘An improved model predictive control algorithm is proposed for Hammerstein-Wiener nonlinear systems.The proposed synthesis algorithm contains two parts:offline design the polytopic invariant sets,and online solve the min-max optimization problem.The polytopic invariant set is adopted to replace the traditional ellipsoid invariant set.And the parameter-correlation nonlinear control law is designed to replace the traditional linear control law.Consequently,the terminal region is enlarged and the control effect is improved.Simulation and experiment are used to verify the validity of the wind tunnel flow field control algorithm.
基金supported by the National Institutes of Health(P20RR018758,P20GM103441,P30GM114731,R03AR066828,and R01AG049058 to Dr.Griffin)the Arthritis Foundation(Arthritis Investigator Award to Dr.Griffin)。
文摘Background:Obesity increases knee osteoarthritis(OA) risk through metabolic,inflammatory,and biomechanical factors,but how these systemic and local mediators interact to drive OA pathology is not well understood.We tested the effect of voluntary running exercise after chronic diet-induced obesity on knee OA-related cartilage and bone pathology in mice.We then used a correlation-based network analysis to identify systemic and local factors associated with early-stage knee OA phenotypes among the different diet and exercise groups.Methods:Male C57 BL/6 J mice were fed a defined control(10% kcal fat) or high fat(HF)(60% kcal fat) diet from 6 to 37 weeks of age.At 25 weeks,one-half of the mice from each diet group were housed in cages with running wheels for the remainder of the study.Histology,micro computed tomography,and magnetic resonance imaging were used to evaluate changes in joint tissue structure and OA pathology.These local variables were then compared to systemic metabolic(body mass,body fat,and glucose tolerance),inflammatory(serum adipokines and inflammatory mediators),and functional(mechanical tactile sensitivity and grip strength) outcomes using a correlation-based network analysis.Diet and exercise effects were evaluated by two-way analysis of variance.Results:An HF diet increased the infrapatellar fat pad size and posterior joint osteophytes,and wheel running primarily altered the subchondral cortical and trabecular bone.Neither HF diet nor exercise altered average knee cartilage OA scores compared to control groups.However,the coefficient of variation was≥25% for many outcomes,and some mice in both diet groups developed moderate OA(>33% maximum score).This supported using correlation-based network analyses to identify systemic and local factors associated with early-stage knee OA phenotypes.In wheel-running cohorts,an HF diet reduced the network size compared to the control diet group despite similar running distances,suggesting that diet-induced obesity dampens the effects of exercise on systemic and local OA-related factors.Each of the 4 diet and activity groups showed mostly unique networks of local and systemic factors correlated with early-stage knee OA.Conclusion:Despite minimal group-level effects of chronic diet-induced obesity and voluntary wheel running on knee OA pathology under the current test durations,diet and exercise substantially altered the relationships among systemic and local variables associated with early-stage knee OA.These results suggest that distinct pre-OA phenotypes may exist prior to the development of disease.
基金Supported by Grants No.NS046363 from the NIHNo. 08-3073-SCR-E-0 from NJCSCR
文摘A number of studies have indicated that plasma membrane calcium ATPases(PMCAs) are expressed in the brain and spinal cord and could play important roles not only in the maintenance of cellular calcium homeostasis but also in the survival and function of central nervous system cells under pathological conditions.The different regional and cellular distributions of the various PMCA isoforms and splice variants in the nervous system and the diverse phenotypes of PMCA knockout mice support the notion that each isoform might play a distinct role. Especially in the spinal cord,the survival of neurons and,in particular,motor neurons could be dependent on PMCA2.This is indicated by the knockdown of PMCA2 in pure spinal cord neuronal cultures that leads to cell death via a decrease in collapsing response mediator protein 1 levels.Moreover,the progressive decline in the number of motor neurons in PMCA2-null mice andheterozygous mice further supports this notion.Therefore,the reported reduction in PMCA2 mRNA and protein levels in the inflamed spinal cord of mice affected by experimental autoimmune encephalomyelitis(EAE) ,an animal model of multiple sclerosis,and after spinal cord contusion injury,suggests that changes in PMCA2 expression could be a cause of neuronal pathology and death during inflammation and injury.Glutamate excitotoxicity mediated via kainate receptors has been implicated in the neuropathology of both EAE and spinal cord injury,and has been identified as a trigger that reduces PMCA2 levels in pure spinal cord neuronal cultures through degradation of the pump by calpain without affecting PMCA2 transcript levels.It remains to be determined which other stimuli modulate PMCA2 mRNA expression in the aforementioned pathological conditions of the spinal cord.
基金Foundation item: the National Natural Science Foundation of China for Outstanding Young Sci-entists (19925210)
文摘Different from previous temporal evolution assumption, the spatially growing mode was employed to analyze the linear stability for the channel flow of fiber suspensions. The stability equation applicable to fiber suspensions was established and solutions for a wide range of Reynolds number and angular frequency were given numerically . The results show that, the flow instability is governed by a parameter H which represents a ratio between the axial stretching resistance of fiber and the inertial force of the fluid. An increase of H leads to a raise of the critical Reynolds number, a decrease of corresponding wave number, a slowdown of the decreasing of phase velocity , a growth of the spatial attenuation rate and a diminishment of the peak value of disturbance velocity. Although the unstable region is reduced on the whole, long wave disturbances are susceptible to fibers.
文摘背景：以前的血管内超声（intravascular ultrasound，IVUS）试验证实，他汀治疗可减缓或阻止动脉粥样硬化的进展，但是迄今尚无应用动脉粥样斑块体积百分比（percent atheroma volume，PAV）证实粥样硬化消退的确切证据。PAV是最严格的评价病变进展和消退的IVUS测量指标。
目标：评价极高强度他汀治疗是否能逆转IVUS确定的冠状动脉粥样硬化。
设计和地点：于美国、加拿大、欧洲和澳大利亚53个社区和3级保健中心进行前瞻性开标盲法终点试验（A Study to Evaluate the Effect of Rosuvastatin on Intravascular Ultrasound-Derived Coronary Atheroma Burden，ASTEROID）。应用马达驱动回撤IVUS评价基线和治疗24个月时冠状动脉粥样斑块负荷。每对基线和随访IVUS测量结果均进行盲法分析。
病例：从2002年11月到2003年10月，507例患者有基线IVUS检查结果，并接受至少1个剂量的研究药物。在24个月后，349例患者具有可用于评估的系列IVUS检查结果。
干预：所有患者均接受瑞舒伐他汀40ms／d强化治疗。
主要观测指标：预先设定了两个一级疗效指标：PAV变化和基线最严重病变10min节段动脉粥样斑块体积变化。二级疗效指标为整个动脉标准化总斑块体积的变化。结果：平均（SD）LDL—C水平由基线时的130．4（34．3）ms／dL降至60．8（20．0）ms／扎，平均下降了53．2％（P〈0．001）。平均（SD）HDL-C水平从基线时的43．1（11．1）ms／dL升至49．0（12．6）ms／dL，平均增加了14．7％（P〈0．001）。整个血管PAV平均（SD）变化为-0．98％（3．15％），中位数为-0．79％（97．5％CI，-1．21％～-0．53％）（与基线比较，P〈0．001）。最严重病变10min节段斑块体积平均（SD）变化为-6．1（10．1）mm^3，中位数为-5．6mm^3（97．5％CI，-6．8～-4．0mm^3）（与基线比较，P〈0．001）。总斑块体积变化中位数降低了6．8％，平均减少了-14．7（25．7）mm^3，中位数为-12．5mm^3（95％CI，-15．1～-10．5mm^3）（与基线比较，P〈0．001）。不良事件少见，与其他他汀试验相似。
结论：应用瑞舒伐他汀40ms／d进行极高强度他汀治疗可使LDL-C平均水平达到60．8ms／dL，使HDL—C增加14．7％。这导致所有3个预先设定的IVUS斑块负荷指标均显示动脉粥样硬化消退。因此，将LDL-C降至低于目前指南规定的水平，同时显著提高HDL-C，可以使冠心病患者动脉粥样硬化斑块消退。这些变化对临床预后的影响尚需进一步研究确定。
基金the Special Funds for Major State Basic Research of China (No. G-1999-0222-08).
文摘The effect of wall roughness on particle behavior in two-phase flows in a horizontal backward-facing step is studied using a phase-Doppler particle anemometer. The results show that the wall roughness widens the particle velocity probability density distribution, enhances the redistribution of particle velocity into different directions, reduces the particle longitudinal mean velocity and increases the longitudinal and transverse fluctuation velocities and Reynolds shear stress. The effect of roughness on particle motion in the recirculation zone is weaker than that in the fully developed flow region. The effect of roughness for small particles is restricted only in the near-wall region, while that for large particles diffuses to the whole flow field.
文摘背景：对于非ST段抬高急性冠脉综合征（acute coronary syndromes，ACS）患者而言，与单独应用普通肝素相比，依诺肝素或者血小板糖蛋白Ⅱb／Ⅲa受体拮抗剂替罗非班与普通肝素联合应用都显示出较好的疗效。目前，尚不清楚依诺肝素和替罗非班联合应用是否像普通肝素和替罗非班标准联合方案一样安全有效。目的：在非ST段抬高的ACS患者中评价依诺肝素和替罗非班联合疗法与普通肝素和替罗非班联合方案的疗效及安全性。设计、地点及参试者：国际前瞻性、开标（open—label）、随机、非劣势（noninferiority）试验。在接受替罗非班和阿斯匹林治疗的非ST段抬高ACS患者中分别给予依诺肝素1mg／kg（n=2026）每12小时一次或经体重校正的静脉普通肝素（n=1961），然后进行比较。这项A to Z试验的A阶段试验是于1999年12月至2002年5月进行的。主要观察指标：意向治疗人群7天时死亡、再发心肌梗死和难治性缺血的发生情况，该意向治疗人群是根据优效性和非劣势原则确定的。应用“心肌梗死溶栓治疗试验”（Thrombolysis in Myocardial Infarction，TIMI）中之出血分级系统，通过监测出血发生率判定用药安全性。结果：在治疗第7天时，随机分配至依诺肝素组的2018例患者中有169例（8．4％）发生死亡、心肌梗死或者难治性缺血，而普通肝素组的1952例患者中有184例（9．4％）发生上述事件（风险比[hazard ratio，HR]为0．88，95％可信区间[confidence interval，CI]为0．71～1．08）。该结果符合预先设定的非劣势标准。除死亡外，所有一级和二级复合终点事件分析结果均提示，依诺肝素更为有益。死亡仅见于1％的患者（依诺肝素组23例，普通肝素组17例）。任何TIMI分级的出血发生率都很低（依诺肝素组为3．0％，普通肝素组为2．2％；P=0．13）。最差情况分析（合并了两种独立的出血判定策略）表明，采用依诺肝素每治疗200例患者就会发生一次TIMI严重出血。结论：对于接受替罗非班和阿斯匹林治疗的非ST段抬高ACS患者而言，依诺肝素是除普通普通肝素之外的另一种适当选择。依诺肝素可使一级终点相对减少12％，绝对减少1％，符合非劣势标准。该结果与以往未联用糖蛋白Ⅱb／Ⅲa受体拮抗剂的试验一致。
文摘A mixed lubrication model was established for piston skirt lubrication. The mathematical model developed in this paper incorporates governing equations of motion with average Reynolds equation. This model considers the surfaceroughness and profile. The corresponding computer program can be used to calculate oscillatory motion of piston during the entire trajectory, which has the excellent convergence.In addition, a set of equipment, which adopt the laser induced fluorescent method, was developed to measure the oil film thickness between the piston and the bore.
基金the State Key Development Program for Basic Research of China (No. G2000048005)the SINOPEC (X503023).
文摘An extensive database (946 measurements) for the frequency of pulsing flow in trickle beds was established by collecting the experimental results published over past 30 years. A new correlation based on artificial neural network (ANN) to predict the pulsation frequency was developed. Seven dimensionless numbers (groups) employed in the proposed correlation were liquid and gas Reynolds, liquid Weber, liquid Eotvos, gas Froude, and gas Stokes numbers and a bed correction factor. The comparisons of performance reported in the of literature and present correlations show that ANN correlation is a significant improvement in predicting pulsation frequency with an average absolute relative error (AARE) of 10% and a standard deviation less than 18%.
