In the practical slope engineering,the stability of lower sliding mass(region A)with back tensile cracks of the jointed rock slope attracts more attentions,but the upper rock mass(region B)may also be unstable.Therefo...In the practical slope engineering,the stability of lower sliding mass(region A)with back tensile cracks of the jointed rock slope attracts more attentions,but the upper rock mass(region B)may also be unstable.Therefore,in this study,based on the stepped failure mode of bedding jointed rock slopes,considering the influence of the upper rock mass on the lower stepped sliding mass,the improved failure model for analyzing the interaction force(F_(AB))between two regions is constructed,and the safety factors(F_(S))of two regions and whole region are derived.In addition,this paper proposes a method to determine the existence of F_(AB) using their respective acceleration values(a_(A) and a_(B))when regions A and B are unstable.The influences of key parameters on two regions and the whole region are analyzed.The results show that the variation of the F_(AB) and F_(S) of two regions can be obtained accurately based on the improved failure model.The accuracy of the improved failure model is verified by comparative analysis.The research results can explain the interaction mechanism of two regions and the natural phenomenon of slope failure caused by the development of cracks.展开更多
Step ladder-structured nitrocellulose(LNC)is a novel energetic binder prepared by chemically modifying nitrocellulose(NC)with the introduction of flexible polyethylene glycol(PEG-400)chain segments,with a regular stru...Step ladder-structured nitrocellulose(LNC)is a novel energetic binder prepared by chemically modifying nitrocellulose(NC)with the introduction of flexible polyethylene glycol(PEG-400)chain segments,with a regular structure and good performance of bonding.The step ladder-structured addresses critical limitations of NC-based propellants,including low-temperature brittleness and high sensitivity,while enhancing process safety.Although the structural,thermal,and other properties of LNC have been investigated in our previous research,there is a lack of systematic studies on the rheological properties during solution and gelatinization.The study of the relationship between the structural features and rheological properties of LNC is a key factor in guiding its gelatinization and improving the properties of LNC-based propellants.Steady-state rheology flow experiments revealed that LNC exhibited shear thinning in different solutions,which decreased with increasing concentration.It has desirable solu-bility and dispersion in N,N-dimethylformamide(DMF)solvent.The effect of solvents on the entan-glement or orientation of LNC molecular chains may be reduced.These results can be quantitatively demonstrated using the Herschel-Bulkley model.Dynamic viscoelastic studies identified a critical point of concentration-frequency of 2.5 rad/s.This particular frequency point is a turning point in the law of the effect of concentration on the loss factor(tanδ).For gelatinized systems,increasing the solvent content reduces the temperature sensitivity of the gelatinized materials.The viscosity-temperature correlation based on the Arrhenius equation allowed the optimization of the solvent content through the derived equilibrium relationship.These structure-rheological performance relationships establish basic guidelines for the precision gelatinization of LNC-based propellant,provide theoretical support for the replacement of conventional NC by LNC,and guide the gelatinization process to improve the performance of gun propellants.展开更多
Objectives This study aimed to evaluate the effectiveness of the stepped self-care program on the self-care,self-efficacy,and quality of life of stroke survivors.Methods This quasi-experimental study allocated 110 str...Objectives This study aimed to evaluate the effectiveness of the stepped self-care program on the self-care,self-efficacy,and quality of life of stroke survivors.Methods This quasi-experimental study allocated 110 stroke survivors from two neurology wards into an intervention group(n=55)who received the stepped self-care program and a control group(n=55)who received usual care from June to December 2023.The Self-Care of Stroke Inventory,Stroke Self-Efficacy Questionnaire,and the short version of the Stroke Specific Quality of Life Scale were administered at baseline(T0),immediately post-intervention(T_(1)),and at 1-month(T_(2))and 3-month(T_(3))follow-ups.Data were analyzed using repeated measures analyses of variance,and generalized estimating equations.Results A total of 48 participants in the intervention group and 50 participants in the control group completed the study.No statistically significant differences were observed at T0 in any of the measured indicators(all P>0.05).The study showed significant group,time,and group×time interaction effects across the assessed outcomes(all P<0.05).Follow-up between-group comparisons at T_(1),T_(2),and T_(3) indicated that the intervention group had significantly higher scores in self-care maintenance,self-care monitoring,self-care management,self-efficacy,and quality of life than the control group(all P<0.001).Conclusions The stepped self-care program significantly improved self-care behaviors,self-efficacy,and quality of life among stroke survivors.These findings support the broader implementation of this approach in post-discharge home self-care.展开更多
This study investigates the motion behavior of a slender flexible particle in a backward-facing step(BFS)flow using the direct-forcing fictitious domain method,with a particular focus on the trapping phenomena near th...This study investigates the motion behavior of a slender flexible particle in a backward-facing step(BFS)flow using the direct-forcing fictitious domain method,with a particular focus on the trapping phenomena near the separation vortex region.Three distinct motion modes are identified:periodic rotation or oscillation within the vortex(trapping),downstream transport(escape),and transition state exhibiting unstable trapping.A dynamic balance among inward migration,centrifugal effects,wall interactions,and elastic forces enables the particle to achieve stable orbital motion within two distinct limit cycles.The topology of these orbits is governed by parameters,including the aspect ratio,structural flexibility,deformation intensity,and fluid inertia,all of which are characterized by the Reynolds number(Re).Specifically,fluid inertia plays a dominant role in facilitating particle trapping.At a fixed Re,a particle with a smaller aspect ratio tends to migrate inward and become trapped,whereas one with a larger aspect ratio is more likely to escape.Structural flexibility,especially when enhanced by confinement near the wall,leads to elastic deformation that induces secondary vortices and a weak flipping motion.The deformation intensityαsignificantly influences the lateral migration of the slender particle after the initial release;a largerαcauses it to drift toward the channel centerline,increasing the probability of escape.These findings provide a theoretical foundation for optimizing the transport and capture of slender soft swimmers in complex flow environments.展开更多
In this paper,a fast step heterodyne light-induced thermoelastic spectroscopy(SH-LITES)sensor using a high-frequency quartz tuning fork(QTF)with resonant frequency of~100 kHz is reported for the first time.The theoret...In this paper,a fast step heterodyne light-induced thermoelastic spectroscopy(SH-LITES)sensor using a high-frequency quartz tuning fork(QTF)with resonant frequency of~100 kHz is reported for the first time.The theoretical principle of heterodyne LITES(H-LITES)signal generation is analyzed firstly,and an acetylene(C_(2)H_(2))H-LITES sensor is established to verify its performance.Experimental comparisons between the high-frequency QTF and a standard commercial QTF with resonant frequency of~32.768 kHz reveal that the high-frequency QTF exhibits a tenfold faster response time.Specifically,the H-LITES sensor with this QTF achieves a 33 ms measurement cycle,90%shorter than commercial counterparts.Furthermore,The SH-LITES technique is proposed to further shorten the scanning time to 15 ms,which achieves the shortest LITES measurement time known to date.To demonstrate its advantages in dynamic gas detection,an H_(2)O-LITES system integrating both QTF types is constructed for real-time monitoring of H_(2)O concentration during different respiration patterns.Comparative measurements show that the SH-LITES more accurately captures dynamic H_(2)O concentration fluctuations during respiration,outperforming the commercial QTF-based H-LITES sensor in rapid response scenarios.展开更多
In order to minimize the hot-carrier effect（HCE）and maintain on-state performance in the high voltage N-type lateral double diffused MOS（N-LDMOS）, an optimized device structure with step gate oxide is proposed. Co...In order to minimize the hot-carrier effect（HCE）and maintain on-state performance in the high voltage N-type lateral double diffused MOS（N-LDMOS）, an optimized device structure with step gate oxide is proposed. Compared with the conventional configuration, the electric field under the gate along the Si-SiO2 interface in the presented N-LDMOS can be greatly reduced, which favors reducing the hot-carrier degradation. The step gate oxide can be achieved by double gate oxide growth, which is commonly used in some smart power ICs. The differences in hot-carrier degradations between the novel structure and the conventional structure are investigated and analyzed by 2D technology computer-aided design（TCAD）numerical simulations, and the optimal length of the thick gate oxide part in the novel N-LDMOS device can also be acquired on the basis of maintaining the characteristic parameters of the conventional device. Finally, the practical degradation measurements of some characteristic parameters can also be carried out. It is found that the hot-carrier degradation of the novel N-LDMOS device can be improved greatly.展开更多
The precise time step integration method proposed for linear time-invariant homogeneous dynamic systems can provide precise numerical results that approach an exact solution at the integration points. However, difficu...The precise time step integration method proposed for linear time-invariant homogeneous dynamic systems can provide precise numerical results that approach an exact solution at the integration points. However, difficulty arises when the algorithm is used for non-homogeneous dynamic systems, due to the inverse matrix calculation and the simulation accuracy of the applied loading. By combining the Gaussian quadrature method and state space theory with the calculation technique of matrix exponential function in the precise time step integration method, a new modified precise time step integration method （e.g., an algorithm with an arbitrary order of accuracy） is proposed. In the new method, no inverse matrix calculation or simulation of the applied loading is needed, and the computing efficiency is improved. In particular, the proposed method is independent of the quality of the matrix H. If the matrix H is singular or nearly singular, the advantage of the method is remarkable. The numerical stability of the proposed algorithm is discussed and a numerical example is given to demonstrate the validity and efficiency of the algorithm.展开更多
This paper presents a new silicon-on-insulator(SOI) lateral-double-diffused metal-oxide-semiconductor transistor(LDMOST) device with alternated high-k dielectric and step doped silicon pillars(HKSD device). Due to the...This paper presents a new silicon-on-insulator(SOI) lateral-double-diffused metal-oxide-semiconductor transistor(LDMOST) device with alternated high-k dielectric and step doped silicon pillars(HKSD device). Due to the modulation of step doping technology and high-k dielectric on the electric field and doped profile of each zone, the HKSD device shows a greater performance. The analytical models of the potential, electric field, optimal breakdown voltage, and optimal doped profile are derived. The analytical results and the simulated results are basically consistent, which confirms the proposed model suitable for the HKSD device. The potential and electric field modulation mechanism are investigated based on the simulation and analytical models. Furthermore, the influence of the parameters on the breakdown voltage(BV) and specific on-resistance(R_(on,sp)) are obtained. The results indicate that the HKSD device has a higher BV and lower R_(on,sp) compared to the SD device and HK device.展开更多
The effects of journal misalignment on a journal bearing caused by an asymmetric rotor structure are presented in this study.A new model considering the asymmetric deflection is applied.Also,the thermo-hydrodynamic of...The effects of journal misalignment on a journal bearing caused by an asymmetric rotor structure are presented in this study.A new model considering the asymmetric deflection is applied.Also,the thermo-hydrodynamic of the oil film in the journal bearing and straightforward elasticity theory are considered in the analysis.Based on the structure stiffness equivalent characteristic,a simple stepped shaft can reflect the entire complex structure model.The existing lubrication model,which does not consider this angle component,is not very precise for journal bearings.Film pressure,misalignment angle,velocity field,oil leakage,and temperature field were calculated and compared in the journal bearing analysis.The results indicate that bearing performances are greatly affected by misalignment caused by the asymmetric structure.A simple stepped shaft can effectively represent a misaligned journal bearing in a rotor-bearing system.展开更多
A rigid-plastic finite element method(FEM) simulation model for a multi-wedge cross wedge rolling(MCWR) was developed to analyze an asymmetric stepped shaft. To evaluate the MCWR process and better understand its defo...A rigid-plastic finite element method(FEM) simulation model for a multi-wedge cross wedge rolling(MCWR) was developed to analyze an asymmetric stepped shaft. To evaluate the MCWR process and better understand its deformation characteristics, the material flowing mechanisms, temperature distributions, strain and rolling force were analyzed. The correctness of the finite element simulation is experimentally verified. Numerical simulations and experiments led to the following conclusions: when α=36° and β=7.5°, the quality of the work piece can be significantly improved. Finally, the development of the asymmetric stepped shaft is applied to industrial production.展开更多
AIM To define a ten-step protocol that reduced the incidence of surgical site infection in the spine surgery practice of the senior author and evaluate the support for each step based on current literature.METHODS In ...AIM To define a ten-step protocol that reduced the incidence of surgical site infection in the spine surgery practice of the senior author and evaluate the support for each step based on current literature.METHODS In response to unexplained increased infection rates at our institution following spine surgery,a ten-step protocol was implemented:(1) preoperative glycemic management based on hemoglobin A1 c(HbA1 c);(2) skin site preoperative preparation with 2% chlorhexidine gluconate disposable cloths;(3) limit operating room traffic;(4) cut the number of personnel in the room to the minimum required;(5) absolutely no flash sterilization of equipment;(6) double-gloving with frequent changing of outer gloves;(7) local application of vancomycin powder;(8) re-dosing antibiotic every 4 h for prolonged procedures and extending postoperative coverage to 72 h for high-risk patients;(9) irrigation of subcutaneous tissue with diluted povidone-iodine solution after deep fascial closure; and(10) use of Dura Prep skin preparation at the end of a case before skin closure. Through an extensive literature review,the current data available for each of the ten steps was evaluated.RESULTS Use of vancomycin powder in surgical wounds,routine irrigation of surgical site,and frequent changing of surgical gloves are strongly supported by the literature. Preoperative skin preparation with chlorhexidine wipes is similarly supported. The majority of current literature supports control of HbA1 c preoperatively to reduce risk of infection. Limiting the use of flash sterilization is supported,but has not been evaluated in spine-specific surgery. Limiting OR traffic and number of personnel in the OR are supported although without level 1 evidence. Prolonged use of antibiotics postoperativelyis not supported by the literature. Intraoperative use of Dura Prep prior to skin closure is not yet explored.CONCLUSION The ten-step protocol defined herein has significantly helped in decreasing surgical site infection rate. Several of the steps have already been shown in the literature to have significant effect on infection rates. As several measures are required to prevent infection,instituting a standard protocol for all the described steps appears beneficial.展开更多
The imaging and target detection methods for stepped frequency signal based on the wavelet transform and its power spectrum are investigated. Not only an imaging and target detection algorithm for stepped frequency si...The imaging and target detection methods for stepped frequency signal based on the wavelet transform and its power spectrum are investigated. Not only an imaging and target detection algorithm for stepped frequency signal based on the wavelet transform, but also its respective power spectrum are proposed. The multisampling property of stepped frequency signal is studied and wavelet transform is well suited for analyzing the signal. After multisampling property of stepped frequency signal being studied, it is shown that the wavelet transform is appropriate to analyze the signal. Based on the theory, the wavelet power spectrum analysis is applied to obtain the target range profile and the binary wavelet transform is used to perform target detection. To determine a suitable wavelet scaling for imaging of range profile's MMW radar, the distance resolution ΔR technique is proposed. The effectiveness of this new method is evaluated using simulated noisy radar signal. Results show that the proposed method can bring out the exactness and low computational complexity of this method.展开更多
Based on rigid-plastic finite element method, a skew rolling process of stepped part is simulated. Considering nodesaving and effective remeshing, the tetrahedron solid elements are used to discrete workpiece. The wor...Based on rigid-plastic finite element method, a skew rolling process of stepped part is simulated. Considering nodesaving and effective remeshing, the tetrahedron solid elements are used to discrete workpiece. The workpiece material adopts rigid-plastic model, where the flow stress is function of effective strain, effective strain rate and temperature.The thermomechanical coupling is considered in the simulation. To model the spinning workpiece undergoing plastic deformation, a novel solution is presented and applied in this paper. The stress state in the workpiece and forming characteristic of skew rolling are analyzed. The forming load, including roller torque and forces in three directions are predicted. The above analyses are helpful to understanding of forming mechanisms and improving of process and die design.展开更多
Shock wave/boundary layer interaction(SWBLI)is still one of the unresolved bottlenecks that restrict the development of more advanced flight vehicles.Supersonic forward-facing step(FFS),an extreme case of compression ...Shock wave/boundary layer interaction(SWBLI)is still one of the unresolved bottlenecks that restrict the development of more advanced flight vehicles.Supersonic forward-facing step(FFS),an extreme case of compression ramp,often occurs severe SWBLIs with a large separation bubble.In this paper,experimental investigations on vortical structures and density fluctuations characteristics of supersonic FFS controlled by self-sustaining dual synthetic jets(SDSJ)are carried out in a Mach number 2.95 wind tunnel.High spatial–temporal resolution flowfield images of FFS without/with active flow control are captured by adopting nano-particle-based planar laser scattering technique.The control effects of the distance between the actuator and the step are mainly compared.The paper finds that the SDSJ can effectively change the feature of flowfield,eliminate the separation shock and the reattachment shock,compel the original shock induced by the step leading edge to distort and reduce its intensity finally.Density fluctuations analysis demonstrates that the whole flows seem to move upstream with the increase of distance(dS-J).Discrete Fourier transformation spectrums results reveal that the fluctuations are mainly located in the low-frequency region at first.High-frequency components and frequency bandwidth increase slightly after the SDSJ are applied.展开更多
Model tests and numerical analyses of stepped reinforced retaining wall were performed to investigate the effects of rheology of backfill and creep of geogrids on the long-term performance of the structure.The geogrid...Model tests and numerical analyses of stepped reinforced retaining wall were performed to investigate the effects of rheology of backfill and creep of geogrids on the long-term performance of the structure.The geogrid tensions,soil pressures,wall deformations and foundation pressure were measured during model construction and loading.A visco-elasto-plastic model and an empirical nonlinear visco-elastic model were utilized to simulate the stresses and deformations of geogrid-reinforced earth-retaining wall under long-term loads.By comparing test data with numerical results,it is shown that the foundation pressure distribution is nonlinear,and the lateral constraint of geogrids for backfill can cause a redistribution of foundation pressure.The curve of soil pressure is outside convex at each step initially,and it is close to the distribution for the case of vertical wall subsequently.The variation trend of geogrid tensions at different heights is obtained.Moreover,the failure mechanism and development mode of potential slip surface in retaining wall are proposed.展开更多
To obtain intrinsic overcharge boundary and investigate overcharge mechanism,here we propose an innovative method,the step overcharge test,to reduce the thermal crossover and distinguish the overcharge thermal behavio...To obtain intrinsic overcharge boundary and investigate overcharge mechanism,here we propose an innovative method,the step overcharge test,to reduce the thermal crossover and distinguish the overcharge thermal behavior,including 5%state of charge(SOC)with small current overcharge and resting until the temperature equilibrium under adiabatic conditions.The intrinsic thermal response and the self-excitation behaviour are analysed through temperature and voltage changes during the step overcharge period.Experimental results show that the deintercalated state of the cathode is highly correlated to self-heating parasitic reactions.Before reaching the upper limit of Negative/Positive(N/P)ratio,the temperature changes little,the heat generation is significantly induced by the reversible heat(endothermic)and ohmic heat,which could balance each other.Following that the lithium metal is gradually deposited on the surface of the anode and reacts with electrolyte upon overcharge,inducing selfheating side reaction.However,this spontaneous thermal reaction could be“self-extinguished”.When the lithium in cathode is completely deintercalated,the boundary point of overcharge is about 4.7 V(~148%SOC,>40℃),and from this point,the self-heating behaviour could be continuously triggered until thermal runaway(TR)without additional overcharge.The whole static and spontaneous process lasts for 115 h and the side reaction heat is beyond 320,000 J.The continuous self-excitation behavior inside the battery is attributed to the interaction between the highly oxidized cathode and the solvent,which leads to the dissolution of metal ions.The dissolved metal ions destroy the SEI(solid electrolyte interphase)film on the surface of the deposited Li of anode,which induces the thermal reaction between lithium metal and the solvent.The interaction between cathode,the deposited Li of anode,and solvent promotes the temperature of the battery to rise slowly.When the temperature of the battery reaches more than 60℃,the reaction between lithium metal and solvent is accelerated.After the temperature rises rapidly to the melting point of the separator,it triggers the thermal runaway of the battery due to the short circuit of the battery.展开更多
基金Projects(52208369,52309138,52108320)supported by the National Natural Science Foundation of ChinaProjects(2023NSFSC0284,2025ZNSFSC0409)supported by the Sichuan Science and Technology Program,ChinaProject(U22468214)supported by the Joint Fund Project for Railway Basic Research by the National Natural Science Foundation of China and China State Railway Group Co.,Ltd.
文摘In the practical slope engineering,the stability of lower sliding mass(region A)with back tensile cracks of the jointed rock slope attracts more attentions,but the upper rock mass(region B)may also be unstable.Therefore,in this study,based on the stepped failure mode of bedding jointed rock slopes,considering the influence of the upper rock mass on the lower stepped sliding mass,the improved failure model for analyzing the interaction force(F_(AB))between two regions is constructed,and the safety factors(F_(S))of two regions and whole region are derived.In addition,this paper proposes a method to determine the existence of F_(AB) using their respective acceleration values(a_(A) and a_(B))when regions A and B are unstable.The influences of key parameters on two regions and the whole region are analyzed.The results show that the variation of the F_(AB) and F_(S) of two regions can be obtained accurately based on the improved failure model.The accuracy of the improved failure model is verified by comparative analysis.The research results can explain the interaction mechanism of two regions and the natural phenomenon of slope failure caused by the development of cracks.
基金supported by the National Natural Science Foundation of China(No.22475100 and 22075146).
文摘Step ladder-structured nitrocellulose(LNC)is a novel energetic binder prepared by chemically modifying nitrocellulose(NC)with the introduction of flexible polyethylene glycol(PEG-400)chain segments,with a regular structure and good performance of bonding.The step ladder-structured addresses critical limitations of NC-based propellants,including low-temperature brittleness and high sensitivity,while enhancing process safety.Although the structural,thermal,and other properties of LNC have been investigated in our previous research,there is a lack of systematic studies on the rheological properties during solution and gelatinization.The study of the relationship between the structural features and rheological properties of LNC is a key factor in guiding its gelatinization and improving the properties of LNC-based propellants.Steady-state rheology flow experiments revealed that LNC exhibited shear thinning in different solutions,which decreased with increasing concentration.It has desirable solu-bility and dispersion in N,N-dimethylformamide(DMF)solvent.The effect of solvents on the entan-glement or orientation of LNC molecular chains may be reduced.These results can be quantitatively demonstrated using the Herschel-Bulkley model.Dynamic viscoelastic studies identified a critical point of concentration-frequency of 2.5 rad/s.This particular frequency point is a turning point in the law of the effect of concentration on the loss factor(tanδ).For gelatinized systems,increasing the solvent content reduces the temperature sensitivity of the gelatinized materials.The viscosity-temperature correlation based on the Arrhenius equation allowed the optimization of the solvent content through the derived equilibrium relationship.These structure-rheological performance relationships establish basic guidelines for the precision gelatinization of LNC-based propellant,provide theoretical support for the replacement of conventional NC by LNC,and guide the gelatinization process to improve the performance of gun propellants.
基金The National Natural Science Foundation of China[72174184]provided policy and financialsupport for this research.
文摘Objectives This study aimed to evaluate the effectiveness of the stepped self-care program on the self-care,self-efficacy,and quality of life of stroke survivors.Methods This quasi-experimental study allocated 110 stroke survivors from two neurology wards into an intervention group(n=55)who received the stepped self-care program and a control group(n=55)who received usual care from June to December 2023.The Self-Care of Stroke Inventory,Stroke Self-Efficacy Questionnaire,and the short version of the Stroke Specific Quality of Life Scale were administered at baseline(T0),immediately post-intervention(T_(1)),and at 1-month(T_(2))and 3-month(T_(3))follow-ups.Data were analyzed using repeated measures analyses of variance,and generalized estimating equations.Results A total of 48 participants in the intervention group and 50 participants in the control group completed the study.No statistically significant differences were observed at T0 in any of the measured indicators(all P>0.05).The study showed significant group,time,and group×time interaction effects across the assessed outcomes(all P<0.05).Follow-up between-group comparisons at T_(1),T_(2),and T_(3) indicated that the intervention group had significantly higher scores in self-care maintenance,self-care monitoring,self-care management,self-efficacy,and quality of life than the control group(all P<0.001).Conclusions The stepped self-care program significantly improved self-care behaviors,self-efficacy,and quality of life among stroke survivors.These findings support the broader implementation of this approach in post-discharge home self-care.
基金Project supported by the National Natural Science Foundation of China(Nos.12132015,12332015,and 12302333)。
文摘This study investigates the motion behavior of a slender flexible particle in a backward-facing step(BFS)flow using the direct-forcing fictitious domain method,with a particular focus on the trapping phenomena near the separation vortex region.Three distinct motion modes are identified:periodic rotation or oscillation within the vortex(trapping),downstream transport(escape),and transition state exhibiting unstable trapping.A dynamic balance among inward migration,centrifugal effects,wall interactions,and elastic forces enables the particle to achieve stable orbital motion within two distinct limit cycles.The topology of these orbits is governed by parameters,including the aspect ratio,structural flexibility,deformation intensity,and fluid inertia,all of which are characterized by the Reynolds number(Re).Specifically,fluid inertia plays a dominant role in facilitating particle trapping.At a fixed Re,a particle with a smaller aspect ratio tends to migrate inward and become trapped,whereas one with a larger aspect ratio is more likely to escape.Structural flexibility,especially when enhanced by confinement near the wall,leads to elastic deformation that induces secondary vortices and a weak flipping motion.The deformation intensityαsignificantly influences the lateral migration of the slender particle after the initial release;a largerαcauses it to drift toward the channel centerline,increasing the probability of escape.These findings provide a theoretical foundation for optimizing the transport and capture of slender soft swimmers in complex flow environments.
基金financial supports from the National Natural Science Foundation of China(Grant No.62335006,62275065,624B2050,62022032,and 62405078)Open Subject of Hebei Key Laboratory of Advanced Laser Technology and Equipment(HBKL-ALTE2025001)+2 种基金Heilongjiang Postdoctoral Fund(Grant No.LBH-Z23144 and LBH-Z24155)Natural Science Foundation of Heilongjiang Province(Grant No.LH2024F031)China Postdoctoral Science Foundation(Grant No.2024M764172).
文摘In this paper,a fast step heterodyne light-induced thermoelastic spectroscopy(SH-LITES)sensor using a high-frequency quartz tuning fork(QTF)with resonant frequency of~100 kHz is reported for the first time.The theoretical principle of heterodyne LITES(H-LITES)signal generation is analyzed firstly,and an acetylene(C_(2)H_(2))H-LITES sensor is established to verify its performance.Experimental comparisons between the high-frequency QTF and a standard commercial QTF with resonant frequency of~32.768 kHz reveal that the high-frequency QTF exhibits a tenfold faster response time.Specifically,the H-LITES sensor with this QTF achieves a 33 ms measurement cycle,90%shorter than commercial counterparts.Furthermore,The SH-LITES technique is proposed to further shorten the scanning time to 15 ms,which achieves the shortest LITES measurement time known to date.To demonstrate its advantages in dynamic gas detection,an H_(2)O-LITES system integrating both QTF types is constructed for real-time monitoring of H_(2)O concentration during different respiration patterns.Comparative measurements show that the SH-LITES more accurately captures dynamic H_(2)O concentration fluctuations during respiration,outperforming the commercial QTF-based H-LITES sensor in rapid response scenarios.
基金The Natural Science Foundation of Jiangsu Province(No.BK2008287)the Preresearch Project of the National Natural Science Foundation of Southeast University(No.XJ2008312)
文摘In order to minimize the hot-carrier effect（HCE）and maintain on-state performance in the high voltage N-type lateral double diffused MOS（N-LDMOS）, an optimized device structure with step gate oxide is proposed. Compared with the conventional configuration, the electric field under the gate along the Si-SiO2 interface in the presented N-LDMOS can be greatly reduced, which favors reducing the hot-carrier degradation. The step gate oxide can be achieved by double gate oxide growth, which is commonly used in some smart power ICs. The differences in hot-carrier degradations between the novel structure and the conventional structure are investigated and analyzed by 2D technology computer-aided design（TCAD）numerical simulations, and the optimal length of the thick gate oxide part in the novel N-LDMOS device can also be acquired on the basis of maintaining the characteristic parameters of the conventional device. Finally, the practical degradation measurements of some characteristic parameters can also be carried out. It is found that the hot-carrier degradation of the novel N-LDMOS device can be improved greatly.
基金financial support from Hunan Provincial Natura1 Science Foundation of China,Grant Number:02JJY2085,for this study
文摘The precise time step integration method proposed for linear time-invariant homogeneous dynamic systems can provide precise numerical results that approach an exact solution at the integration points. However, difficulty arises when the algorithm is used for non-homogeneous dynamic systems, due to the inverse matrix calculation and the simulation accuracy of the applied loading. By combining the Gaussian quadrature method and state space theory with the calculation technique of matrix exponential function in the precise time step integration method, a new modified precise time step integration method （e.g., an algorithm with an arbitrary order of accuracy） is proposed. In the new method, no inverse matrix calculation or simulation of the applied loading is needed, and the computing efficiency is improved. In particular, the proposed method is independent of the quality of the matrix H. If the matrix H is singular or nearly singular, the advantage of the method is remarkable. The numerical stability of the proposed algorithm is discussed and a numerical example is given to demonstrate the validity and efficiency of the algorithm.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61704084 and 61874059)。
文摘This paper presents a new silicon-on-insulator(SOI) lateral-double-diffused metal-oxide-semiconductor transistor(LDMOST) device with alternated high-k dielectric and step doped silicon pillars(HKSD device). Due to the modulation of step doping technology and high-k dielectric on the electric field and doped profile of each zone, the HKSD device shows a greater performance. The analytical models of the potential, electric field, optimal breakdown voltage, and optimal doped profile are derived. The analytical results and the simulated results are basically consistent, which confirms the proposed model suitable for the HKSD device. The potential and electric field modulation mechanism are investigated based on the simulation and analytical models. Furthermore, the influence of the parameters on the breakdown voltage(BV) and specific on-resistance(R_(on,sp)) are obtained. The results indicate that the HKSD device has a higher BV and lower R_(on,sp) compared to the SD device and HK device.
基金Project supported by the National Natural Science Foundation of China (No. 60879002)the Tianjin Support Plan of China(No. 10ZCKFGX03800)
文摘The effects of journal misalignment on a journal bearing caused by an asymmetric rotor structure are presented in this study.A new model considering the asymmetric deflection is applied.Also,the thermo-hydrodynamic of the oil film in the journal bearing and straightforward elasticity theory are considered in the analysis.Based on the structure stiffness equivalent characteristic,a simple stepped shaft can reflect the entire complex structure model.The existing lubrication model,which does not consider this angle component,is not very precise for journal bearings.Film pressure,misalignment angle,velocity field,oil leakage,and temperature field were calculated and compared in the journal bearing analysis.The results indicate that bearing performances are greatly affected by misalignment caused by the asymmetric structure.A simple stepped shaft can effectively represent a misaligned journal bearing in a rotor-bearing system.
基金Projects(51375042,51505026)supported by the National Natural Science Foundation of ChinaProject(201312G02)supported by Yangfan Innovative&Entepreneurial Research Team,ChinaProject(2015M580977)supported by China Postdoctoral Science Foundation
文摘A rigid-plastic finite element method(FEM) simulation model for a multi-wedge cross wedge rolling(MCWR) was developed to analyze an asymmetric stepped shaft. To evaluate the MCWR process and better understand its deformation characteristics, the material flowing mechanisms, temperature distributions, strain and rolling force were analyzed. The correctness of the finite element simulation is experimentally verified. Numerical simulations and experiments led to the following conclusions: when α=36° and β=7.5°, the quality of the work piece can be significantly improved. Finally, the development of the asymmetric stepped shaft is applied to industrial production.
文摘AIM To define a ten-step protocol that reduced the incidence of surgical site infection in the spine surgery practice of the senior author and evaluate the support for each step based on current literature.METHODS In response to unexplained increased infection rates at our institution following spine surgery,a ten-step protocol was implemented:(1) preoperative glycemic management based on hemoglobin A1 c(HbA1 c);(2) skin site preoperative preparation with 2% chlorhexidine gluconate disposable cloths;(3) limit operating room traffic;(4) cut the number of personnel in the room to the minimum required;(5) absolutely no flash sterilization of equipment;(6) double-gloving with frequent changing of outer gloves;(7) local application of vancomycin powder;(8) re-dosing antibiotic every 4 h for prolonged procedures and extending postoperative coverage to 72 h for high-risk patients;(9) irrigation of subcutaneous tissue with diluted povidone-iodine solution after deep fascial closure; and(10) use of Dura Prep skin preparation at the end of a case before skin closure. Through an extensive literature review,the current data available for each of the ten steps was evaluated.RESULTS Use of vancomycin powder in surgical wounds,routine irrigation of surgical site,and frequent changing of surgical gloves are strongly supported by the literature. Preoperative skin preparation with chlorhexidine wipes is similarly supported. The majority of current literature supports control of HbA1 c preoperatively to reduce risk of infection. Limiting the use of flash sterilization is supported,but has not been evaluated in spine-specific surgery. Limiting OR traffic and number of personnel in the OR are supported although without level 1 evidence. Prolonged use of antibiotics postoperativelyis not supported by the literature. Intraoperative use of Dura Prep prior to skin closure is not yet explored.CONCLUSION The ten-step protocol defined herein has significantly helped in decreasing surgical site infection rate. Several of the steps have already been shown in the literature to have significant effect on infection rates. As several measures are required to prevent infection,instituting a standard protocol for all the described steps appears beneficial.
文摘The imaging and target detection methods for stepped frequency signal based on the wavelet transform and its power spectrum are investigated. Not only an imaging and target detection algorithm for stepped frequency signal based on the wavelet transform, but also its respective power spectrum are proposed. The multisampling property of stepped frequency signal is studied and wavelet transform is well suited for analyzing the signal. After multisampling property of stepped frequency signal being studied, it is shown that the wavelet transform is appropriate to analyze the signal. Based on the theory, the wavelet power spectrum analysis is applied to obtain the target range profile and the binary wavelet transform is used to perform target detection. To determine a suitable wavelet scaling for imaging of range profile's MMW radar, the distance resolution ΔR technique is proposed. The effectiveness of this new method is evaluated using simulated noisy radar signal. Results show that the proposed method can bring out the exactness and low computational complexity of this method.
基金The research is supported by the National Natural Science Foundation of China ((No. 50205013 and No. 50175060). Special thanks are expressed to the Mr. Guoji Li from Science Forming Technology Corp. (SFTC) for his assistance and advice on the simulation work of.this paper.
文摘Based on rigid-plastic finite element method, a skew rolling process of stepped part is simulated. Considering nodesaving and effective remeshing, the tetrahedron solid elements are used to discrete workpiece. The workpiece material adopts rigid-plastic model, where the flow stress is function of effective strain, effective strain rate and temperature.The thermomechanical coupling is considered in the simulation. To model the spinning workpiece undergoing plastic deformation, a novel solution is presented and applied in this paper. The stress state in the workpiece and forming characteristic of skew rolling are analyzed. The forming load, including roller torque and forces in three directions are predicted. The above analyses are helpful to understanding of forming mechanisms and improving of process and die design.
基金The present research was supported by the National Natural Science Foundation of China(Grants 11972369,51809271,11872374 and 11602299).
文摘Shock wave/boundary layer interaction(SWBLI)is still one of the unresolved bottlenecks that restrict the development of more advanced flight vehicles.Supersonic forward-facing step(FFS),an extreme case of compression ramp,often occurs severe SWBLIs with a large separation bubble.In this paper,experimental investigations on vortical structures and density fluctuations characteristics of supersonic FFS controlled by self-sustaining dual synthetic jets(SDSJ)are carried out in a Mach number 2.95 wind tunnel.High spatial–temporal resolution flowfield images of FFS without/with active flow control are captured by adopting nano-particle-based planar laser scattering technique.The control effects of the distance between the actuator and the step are mainly compared.The paper finds that the SDSJ can effectively change the feature of flowfield,eliminate the separation shock and the reattachment shock,compel the original shock induced by the step leading edge to distort and reduce its intensity finally.Density fluctuations analysis demonstrates that the whole flows seem to move upstream with the increase of distance(dS-J).Discrete Fourier transformation spectrums results reveal that the fluctuations are mainly located in the low-frequency region at first.High-frequency components and frequency bandwidth increase slightly after the SDSJ are applied.
基金Supported by National Natural Science Foundation of China (No. 50678032 and No. 90715042)Key Project of Ministry of Education of China (No. 210176)
文摘Model tests and numerical analyses of stepped reinforced retaining wall were performed to investigate the effects of rheology of backfill and creep of geogrids on the long-term performance of the structure.The geogrid tensions,soil pressures,wall deformations and foundation pressure were measured during model construction and loading.A visco-elasto-plastic model and an empirical nonlinear visco-elastic model were utilized to simulate the stresses and deformations of geogrid-reinforced earth-retaining wall under long-term loads.By comparing test data with numerical results,it is shown that the foundation pressure distribution is nonlinear,and the lateral constraint of geogrids for backfill can cause a redistribution of foundation pressure.The curve of soil pressure is outside convex at each step initially,and it is close to the distribution for the case of vertical wall subsequently.The variation trend of geogrid tensions at different heights is obtained.Moreover,the failure mechanism and development mode of potential slip surface in retaining wall are proposed.
基金funded by the National Key Research and Development Program of China(2018YFB0104400)supported by the Beijing Natural Science Foundation(2214066)。
文摘To obtain intrinsic overcharge boundary and investigate overcharge mechanism,here we propose an innovative method,the step overcharge test,to reduce the thermal crossover and distinguish the overcharge thermal behavior,including 5%state of charge(SOC)with small current overcharge and resting until the temperature equilibrium under adiabatic conditions.The intrinsic thermal response and the self-excitation behaviour are analysed through temperature and voltage changes during the step overcharge period.Experimental results show that the deintercalated state of the cathode is highly correlated to self-heating parasitic reactions.Before reaching the upper limit of Negative/Positive(N/P)ratio,the temperature changes little,the heat generation is significantly induced by the reversible heat(endothermic)and ohmic heat,which could balance each other.Following that the lithium metal is gradually deposited on the surface of the anode and reacts with electrolyte upon overcharge,inducing selfheating side reaction.However,this spontaneous thermal reaction could be“self-extinguished”.When the lithium in cathode is completely deintercalated,the boundary point of overcharge is about 4.7 V(~148%SOC,>40℃),and from this point,the self-heating behaviour could be continuously triggered until thermal runaway(TR)without additional overcharge.The whole static and spontaneous process lasts for 115 h and the side reaction heat is beyond 320,000 J.The continuous self-excitation behavior inside the battery is attributed to the interaction between the highly oxidized cathode and the solvent,which leads to the dissolution of metal ions.The dissolved metal ions destroy the SEI(solid electrolyte interphase)film on the surface of the deposited Li of anode,which induces the thermal reaction between lithium metal and the solvent.The interaction between cathode,the deposited Li of anode,and solvent promotes the temperature of the battery to rise slowly.When the temperature of the battery reaches more than 60℃,the reaction between lithium metal and solvent is accelerated.After the temperature rises rapidly to the melting point of the separator,it triggers the thermal runaway of the battery due to the short circuit of the battery.
