Along with decrease of fine particulate matter(PM_(2.5))concentration in recent years in China,secondary species become increasingly important.This work focuses on characterizing secondary components,and a few importa...Along with decrease of fine particulate matter(PM_(2.5))concentration in recent years in China,secondary species become increasingly important.This work focuses on characterizing secondary components,and a few important groups of organics including organic nitrogen(ON),organonitrates(OrgN),organosulfates(OS)and polycyclic aromatic hydrocarbons(PAHs),via online measurement of submicron aerosols(PM_(1))in Nanjing,China,during 2022 summer.The average PM_(1) concentration was 15.39μg/m^(3),dominated by secondary components(69.1%),which were even more important at higher PM_(1) levels.The primary organic aerosols(POA)were from traffic,industry and cooking;the two secondary OA factors were both closely linked with photochemistry,with one(OOA1)being relatively fresh and important in early afternoon and another(OOA2)being aged and important in late afternoon.Sulfate formation was also governed by photochemistry but resembled that of OOA2 not OOA1;nitrate formation was associated strongly with heterogeneous hydrolysis and thermodynamic equilibrium.Results also reveal a possible photochemical reaction channel from POA to OOA1,then to OOA2.Case studies show that formations of secondary components responded differently to different weather conditions and governed summer PM_(1) pollution.The average ON,OrgN,OS and PAHs concentrations were determined to be 122.8,84.4,45.6 and 3.3 ng/m^(3),respectively.ON was dominated by primary sources(53.8%).OrgN varied similarly to nitrate.OS formation was linked with aqueous-phase reactions,which were insignificant therefore its level was low.PAHs was mainly from traffic,and photochemical oxidation might be its important sink during afternoon.展开更多
The roughness of the fracture surface directly affects the strength,deformation,and permeability of the surrounding rock in deep underground engineering.Understanding the effect of high temperature and thermal cycle o...The roughness of the fracture surface directly affects the strength,deformation,and permeability of the surrounding rock in deep underground engineering.Understanding the effect of high temperature and thermal cycle on the fracture surface roughness plays an important role in estimating the damage degree and stability of deep rock mass.In this paper,the variations of fracture surface roughness of granite after different heating and thermal cycles were investigated using the joint roughness coefficient method(JRC),three-dimensional(3D)roughness parameters,and fractal dimension(D),and the mechanism of damage and deterioration of granite were revealed.The experimental results show an increase in the roughness of the granite fracture surface as temperature and cycle number were incremented.The variations of JRC,height parameter,inclination parameter and area parameter with the temperature conformed to the Boltzmann's functional distribution,while the D decreased linearly as the temperature increased.Besides,the anisotropy index(Ip)of the granite fracture surface increased as the temperature increased,and the larger parameter values of roughness characterization at different temperatures were attained mainly in directions of 20°–40°,60°–100°and 140°–160°.The fracture aperture of granite after fracture followed the Gauss distribution and the average aperture increased with increasing temperature,which increased from 0.665 mm at 25℃to 1.058 mm at 800℃.High temperature caused an uneven thermal expansion,water evaporation,and oxidation of minerals within the granite,which promoted the growth and expansion of microfractures,and reduced interparticle bonding strength.In particular,the damage was exacerbated by the expansion and cracking of the quartz phase transition after T>500℃.Thermal cycles contributed to the accumulation of this damage and further weakened the interparticle bonding forces,resulting in a significant increase in the roughness,anisotropy,and aperture of the fracture surface after five cycles.展开更多
The cognitive load plays a key role in surgical education,influencingtask performance and skill acquisition.This review explores three primary approaches to assessing cognitive load in the surgical context—paper-base...The cognitive load plays a key role in surgical education,influencingtask performance and skill acquisition.This review explores three primary approaches to assessing cognitive load in the surgical context—paper-based measures,physiological measures,and performance-based measures—and highlights their relevance and applications in surgical education.Paper-based tools,such as the NASA Task Load Index and its surgical adaptation,the Surgery Task Load Index,offer simplicity but lack realtime insight.Physiological measures,including heart rate,eye tracking,and electrodermal activity,provide objective and timely data.Neuroimaging techniques,such as electroencephalography and functional near-infrared spectroscopy,provide direct evidence of brain activity but face challenges such as cost and complexity.Performance-based metrics,such as secondary tasks,infer cognitive load from working memory capacity.Accurate assessment of cognitive load can improve training outcomes by adapting demands to cognitive capacity.Future directions include the development of more accurate,multimodal,and user-friendly tools for dynamic,timely assessment,ultimately advancing personalized surgical training and improving patient care.展开更多
The reignition of aero-engine combustors at high altitudes poses significant challenges due to the low-temperature and low-pressure environment.A novel Long Pulse-Width Plasma Ignition(LPWPI)system has been developed ...The reignition of aero-engine combustors at high altitudes poses significant challenges due to the low-temperature and low-pressure environment.A novel Long Pulse-Width Plasma Ignition(LPWPI)system has been developed to enhance ignition performance.The LPWPI system can effectively prolong the discharge duration time,improve ignition efficacy,and increase the plasma penetration depth.Experimental comparisons with the traditional Spark Ignition(SI)system demonstrate that the LPWPI increased discharge duration to 2.03 ms,which is 45 times longer than that of the SI system,while also doubling the spark penetration depth to 24.1 mm.The LPWPI system achieved a discharge efficiency of 61.1%,significantly surpassing the SI system's efficiency of23.3%.These advancements facilitated an extension of the lean ignition boundary by approximately 22.7%to 39.3%.High-speed camera recordings reveal that the spark duration of the LPWPI system was extended to 2.1 ms,compared to 0.6 ms in the SI system.Ignition progress with LPWPI shows a sustained spark kernel without the flame residence stage observed in the SI system.The impressive performance of the LPWPI system suggests that it is a promising alternative for aero-engine ignition systems.展开更多
Objective While there is consensus regarding a positive effect of video gaming on dexterity,little is known regarding how much traditional laparoscopic practice can or should be substituted with video gaming.This stud...Objective While there is consensus regarding a positive effect of video gaming on dexterity,little is known regarding how much traditional laparoscopic practice can or should be substituted with video gaming.This study was designed to assess the effects of varying the amount of traditional practice in a lap box trainer and video gaming on performance in two fundamentals of laparoscopic surgery core tasks.Methods Undergraduate and medical students were recruited and randomized into one of four groups:a control group,a lap box group,a video game group,and a combined group with 50%of the time allocated to each modality.Performance in the peg transfer and precision cutting tasks was assessed both prior to and following the 6 training sessions.Results Peg transfer performance significantly improved in the lap box group(168.4±70.6 s vs.332.9±178.2 s,p<0.001),video game group(176.7±53.3 s vs.300.0±101.2 s,p<0.001)and combined group(214.2±86.9 s vs.406.8±239.5 s,p=0.002)after training.Similar improvements were also observed in precision cutting performance in the lap box group(413.1±138.4 s vs.614.3±211.4 s,p=0.002),video game group(434.1±150.8 s vs.609.2±233.2 s,p=0.007)and combined group(469.2±185.3 s vs.663.8±296.3 s,p=0.020).When analyzing improvements in performance across three different training groups compared with the control group,we found that both the lap box group(p<0.001)and the combined group(p<0.001)showed better improvement in both tasks,and the video game group had significantly better outcomes in the precision cutting task(p=0.003).Conclusion Traditional lap box training remains the most effective method for improving the performance of simulated laparoscopic surgery.Video games can be encouraged to enhance skills retention and supplement simulated practice outside of a formal training curriculum.展开更多
Plasma-assisted combustion technology has been a hot spot in aero-engines andscramjet-engines.The electron density is a key discharge parameter related to the active-particledensity.The latter has been considered play...Plasma-assisted combustion technology has been a hot spot in aero-engines andscramjet-engines.The electron density is a key discharge parameter related to the active-particledensity.The latter has been considered playing an important role in the above applications bythe kinetic effect.In this work,an atmospheric pressure air plasma collisional-radiative model con-sidering the excited states of atomic nitrogen and oxygen is built based on previous widely kineticinvestigations of molecules and radicals,as well as their excited states.The excited states,especiallythe atomic nitrogen and oxygen states were less investigated in previous works.The emission inten-sity distributions from the model have a good agreement with those measured in the glide arcplasma with two discharge modes,as well as the microwave plasma.Based on the kinetics of molec-ular and atomic emitting states,the line-ratio method is presented to determine the electron density.The N_(2)(337 nm)/O(844 nm)and N_(2)(337 nm)/NO(γ)line ratios are used for the glide arc plasma andmicrowave plasma torch,respectively.Besides,the kinetics of the excited states involved with twoline-ratios are also investigated in the two types of discharges.Combined with the atmospheric pres-sure actinometry method,the kinetic effect of the plasma-assisted combustion can be revealed quan-titatively in the future.展开更多
To study the energy evolution and failure characteristics of saturated sandstone under unloading conditions,rock unloading tests under different stress paths were conducted.The energy evolution mechanism of the unload...To study the energy evolution and failure characteristics of saturated sandstone under unloading conditions,rock unloading tests under different stress paths were conducted.The energy evolution mechanism of the unloading failure of saturated sandstone was systematically explored from the perspectives of the stress path,the initial confining pressure,and the energy conversion rate.The results show that(1)before the peak stress,the elastic energy increases with an increase in deviatoric stress,while the dissipated energy slowly increases first.After the peak stress,the elastic energy decreases with the decrease of deviatoric stress,and the dissipated energy suddenly increases.The energy release intensity during rock failure is positively correlated with the axial stress.(2)When the initial confining pressure is below a certain threshold,the stress path is the main factor influencing the total energy difference.When the axial stress remains constant and the confining pressure is unloading,the total energy is more sensitive to changes in the confining pressure.When the axial stress remains constant,the compressive deformation ability of the rock cannot be significantly improved by the increase in the initial confining pressure.The initial confining pressure is positively correlated with the rock's energy storage limit.(3)The initial confining pressure increases the energy conversion rate of the rock;the initial confining pressure is positively correlated with the energy conversion rate;and the energy conversion rate has a high confining pressure effect.The increase in the axial stress has a much greater impact on the elastic energy than the confining pressure.(4)When the deviatoric stress is small,the confining pressure mainly plays a protective role.Compared with the case of triaxial compression paths,the rock damage is more severe under unloading paths,and compared with the case of constant axial stress,the rock damage is more severe under increasing axial stress.展开更多
背景急性胰腺炎(acute pancreatitis,AP)是常见的急腹症,不同类型预后不同.AP的免疫应答和失衡免疫与其严重程度有关,炎症因子和相关免疫细胞在AP发病机制中至关重要,因而寻找炎症细胞和新炎症免疫因子对精准治疗AP具有重要意义.目的探...背景急性胰腺炎(acute pancreatitis,AP)是常见的急腹症,不同类型预后不同.AP的免疫应答和失衡免疫与其严重程度有关,炎症因子和相关免疫细胞在AP发病机制中至关重要,因而寻找炎症细胞和新炎症免疫因子对精准治疗AP具有重要意义.目的探讨AP患者外周血CD14^+CD16^+单核细胞表达B7-H2的临床意义.方法A P患者63例[轻度A P(m i l dA P,M A P)25例、中度AP(moderately severe AP,MSAP)20例、重度AP(severe AP,SAP)18例],对照组为健康体检者20例,采用流式细胞仪检测CD14^+CD16^+细胞亚群上B7-H2表达情况,评价其与胰腺炎严重程度关联性及临床意义.结果AP患者发病24hCD14^+CD16^+细胞B7-H2出现异常高表达,显著高于健康对照组(t=11.10,P<0.001);A P各组B 7-H 2在C D 14^+C D 16^+细胞膜上表达明显高于CD14^+C D16^-细胞膜上表达(P<0.01);SAP组CD14^+C D 16^+和CD14^+C D 16^-细胞B7-H2表达(373.30±89.72和78.62±13.05)最高,M S A P组(279.55±76.95/44.92±12.44)其次,均高于M A P组(181.15±35.75/23.32±4.28),各组两两比较差异有显著性(P<0.01);MAP组、MSAP组发病24 h、48 h、72hCD14^+CD16^+和CD14^+CD16^-单核细胞膜B7-H2动态表达差异无显著性(P>0.05),然而,SAP组无论C D14^+C D16^+还是CD14^+C D16^-细胞膜B7-H2表达24h、48h、72h均呈明显上升趋势,差异有显著性(P<0.05).结论CD14^+CD16^+和CD14^+CD16^-单核细胞膜B7-H2在AP患者体内高表达,与AP严重程度密切相关,且SAP呈动态升高变化;同时B7-H2在AP患者CD14^+CD16^+单核细胞膜表达较CD14^+CD16^-单核细胞明显升高,为进一步认识AP免疫应答和失衡提供了新的线索,为AP精准靶向治疗提供参考.展开更多
We conducted experiments in a wind tunnel with Mach number 2 to explore the evolution of a transverse plasma jet and its modification effect on a shock wave induced by a ramp with an angle of 24°. The transverse ...We conducted experiments in a wind tunnel with Mach number 2 to explore the evolution of a transverse plasma jet and its modification effect on a shock wave induced by a ramp with an angle of 24°. The transverse plasma jet was created by arc discharge in a small cylindrical cavity with a 2 mm diameter orifice. Three group tests with different actuator arrangements in the spanwise or streamwise direction upstream from the ramp were respectively studied to compare their disturbances to the shock wave. As shown by a time-resolved schlieren system, an unsteady motion of the shock wave by actuation was found： the shock wave was significantly modified by the plasma jet with an upstream motion and a reduced angle. Compared to spanwise actuation, a more intensive impact was obtained with two or three streamwise actuators working together. From shock wave structures, the control effect of the plasma jet on the shock motion based on a thermal effect, a potential cause of shock modification, was discussed. Furthermore, we performed a numerical simulation by using the Improved Delayed Detached Eddy Simulation（IDDES） method to simulate the evolution of the transverse plasma jet plume produced by two streamwise actuators. The results show that flow structures are similar to those identified in schlieren images. Two streamwise vortices were recognized, which indicates that the higher jet plume is the result of the overlap of two streamwise jets.展开更多
The present study was to test the hypothesis that the plant growth retardants chlorocholine chloride(CCC) and paclobutrazol(PBZ)could improve the carbohydrate accumulation in lily bulbs by enhancing photosynthetic cap...The present study was to test the hypothesis that the plant growth retardants chlorocholine chloride(CCC) and paclobutrazol(PBZ)could improve the carbohydrate accumulation in lily bulbs by enhancing photosynthetic capacity and changing endogenous hormones.Plants of Lilium Oriental hybrids'Sorbonne'were treated with a foliar spray of CCC or PBZ(both at 300 mg/L)solution,at six weeks after planting(6 WAP).The morphological parameters,endogenous hormone contents(gibberellic acid(GA),abscisic acid(ABA),and indole-3-acetic acid(IAA)),and carbohydrate contents were measured from 6 to 18 WAP,at 2-week intervals.The results showed that CCC increased the biomass of leaves and stems which might produce more photoassimilates available for transportation and utilization.However,PBZ treatment suppressed vegetative growth and favored photoassimilate transportation into bulbs.A slight delay of bud and anthesis formation was observed in both treated plants.CCC and PBZ treatments substantially enhanced the sucrose contents in leaves probably due to the increase of chlorophyll contents.Treatment with CCC or PBZ decreased GA but increased IAA contents in lily bulbs which might stimulate starch accumulation and formation of new scales.Our experiment suggested that CCC or PBZ treatment is an effective method to promote carbohydrate accumulation in lily bulbs.展开更多
Based on the case studies and statistical analysis of earthquake-related ionospheric disturbances mainly from DEMETER satellite, ground-based GPS and ionosounding data, this paper summarizes the statisw tical characte...Based on the case studies and statistical analysis of earthquake-related ionospheric disturbances mainly from DEMETER satellite, ground-based GPS and ionosounding data, this paper summarizes the statisw tical characteristics of earthquake-related ionospheric disturbances, including electromagnetic emissions, plasma perturbations and variation of energetic particle flux. According to the main results done by Chinese scientists, fusing with the existed study from global researches, seismo-ionospheric disturbances usually occurred a few days or hours before earthquake occurrence. Paralleling to these case studies, lithosphere-atmosphere-ionosphere （LAI） coupling mechanisms are checked and optimized. A thermo-electric model was proposed to explain the seismo-electromagnetic effects before earthquakes. A propagation model was put forward to explain the electromagnetic waves into the ionosphere. According to the requirement of earthquake prediction research, China seismo-electromagnetic satellite, the first space-based platform of Chinese earthquake stereoscopic observation system, is proposed and planned to launch at about the end of 2014. It focuses on checking the LAI model and distinguishing earthquake-related ionospheric disturbance. The preliminary design for the satellite will adopt CAST-2000 platform with eight payloads onboard. It is believed that the satellite will work together with the ground monitoring network to improve the capability to capture seismo-electromagnetic information, which is beneficial for earthquake monitoring and prediction researches.展开更多
In this study,uniaxial and triaxial compression acoustic emission(AE)tests were implemented to investigate the AE effect and failure characteristics of sandstone under different confining pressures(σ3).The evolution ...In this study,uniaxial and triaxial compression acoustic emission(AE)tests were implemented to investigate the AE effect and failure characteristics of sandstone under different confining pressures(σ3).The evolution of AE parameters in the rock failure process and fracture fractal dimension characteristics after failure were analyzed.The results revealed that the activity of the AE signal is strongly related toσ3.The evolution of the Ib value can be divided into the I-fluctuation,II-stability,and III-decrease stages.In the first stage,the Ib value of the AE was relatively high,and the AE energy was low.Then,the Ib value tended to be stable;however,the fluctuation amplitude decreased,and the AE energy rapidly increased.In the stage of decrease,the AE energy sharply increased before the load approached the peak value,and the Ib value significantly decreased and dropped to the lowest point before the peak value.Asσ3 increased,the rock’s failure mode changed from tensile failure to shear failure and became more coordinated.As the confining pressure increased,the shape dimension decreased,and the order degree of rock failure increased.The confining pressure exerted a certain control effect on the rock failure.展开更多
Ice accretion on the wings seriously threatens the flight safety of an aircraft.From the perspectives of ensuring flight safety and saving power consumption,the ice shape modulation method using distributed plasma is ...Ice accretion on the wings seriously threatens the flight safety of an aircraft.From the perspectives of ensuring flight safety and saving power consumption,the ice shape modulation method using distributed plasma is proposed.Distributed plasma actuator units are designed to modulate the spanwise continuous ice at the leading edge into periodically segmented ice pieces,forming a wavy leading edge.Both airfoil and scaled aircraft model,with continuous and modulated ice,are experimentally investigated and simulated.Compared with the continuous ice,ice shape modulation can significantly improve the aerodynamic performance,flight control characteristics and flight safety.This method can save about half electric power,which is very beneficial for application.展开更多
The mechanisms for rock bursts occurrences in fold zones are complex, and the redistribution of in-situ stresses is closely related to the complexity of the structures. Analysis of the geomorphology of fold structures...The mechanisms for rock bursts occurrences in fold zones are complex, and the redistribution of in-situ stresses is closely related to the complexity of the structures. Analysis of the geomorphology of fold structures and changes of coal thickness can help identify zones prone to rock bursts to improve safety and productivity in coal mines. This study investigated the distribution characteristics of fold structures in coal seams in fold zones in four mines in northwest China. Geometrical characteristics of fold structures in coal seams and changes of coal thickness were analysed, based on comprehensive evaluation indexes,such as the length–width ratio of folds, interlimb angle, ratio P1 of projected width of fold limbs to that of the hinge zone, curvature ratio P2, the maximum curvature and amplitude. The statistical analysis of the four coal mines shows that the length–width ratio of folds changed from 0.78 to 2.03 and the maximum curvature of cross sections of folds was less than 0.04. The curvature ratio of cross section of a fold in the structure was no more than 1.4 and the interlimb angles of cross sections of 89% of folds were larger than 150°. Gentle fold structures were dominant and the specific geological morphologies were domes or basins. The isopleth of coal thickness above the coal mines showed a fluctuation trend similar to the contour line of the floor of coal seams. The coal thickness in an anticline area was smaller than that in the neighboring syncline area. Therefore, the overall variation of coal thickness in the mining areas was likely to have a relation with the direction of the regional principal stress.展开更多
基金supported by the National Natural Science Foundation of China(Nos.22361162668 and 42021004)the National Key Research and Development Program of China(No.2023YFC3706203).
文摘Along with decrease of fine particulate matter(PM_(2.5))concentration in recent years in China,secondary species become increasingly important.This work focuses on characterizing secondary components,and a few important groups of organics including organic nitrogen(ON),organonitrates(OrgN),organosulfates(OS)and polycyclic aromatic hydrocarbons(PAHs),via online measurement of submicron aerosols(PM_(1))in Nanjing,China,during 2022 summer.The average PM_(1) concentration was 15.39μg/m^(3),dominated by secondary components(69.1%),which were even more important at higher PM_(1) levels.The primary organic aerosols(POA)were from traffic,industry and cooking;the two secondary OA factors were both closely linked with photochemistry,with one(OOA1)being relatively fresh and important in early afternoon and another(OOA2)being aged and important in late afternoon.Sulfate formation was also governed by photochemistry but resembled that of OOA2 not OOA1;nitrate formation was associated strongly with heterogeneous hydrolysis and thermodynamic equilibrium.Results also reveal a possible photochemical reaction channel from POA to OOA1,then to OOA2.Case studies show that formations of secondary components responded differently to different weather conditions and governed summer PM_(1) pollution.The average ON,OrgN,OS and PAHs concentrations were determined to be 122.8,84.4,45.6 and 3.3 ng/m^(3),respectively.ON was dominated by primary sources(53.8%).OrgN varied similarly to nitrate.OS formation was linked with aqueous-phase reactions,which were insignificant therefore its level was low.PAHs was mainly from traffic,and photochemical oxidation might be its important sink during afternoon.
基金funding support from the National Natural Science Foundation of China(Grant No.52274082)the Program of Qingjiang Excellent Young Talents,Jiangxi University of Science and Technology(Grant No.JXUSTQJBJ2020003)the Innovation Fund Designated for Graduate Students of Jiangxi Province(Grant No.YC2023-B215).
文摘The roughness of the fracture surface directly affects the strength,deformation,and permeability of the surrounding rock in deep underground engineering.Understanding the effect of high temperature and thermal cycle on the fracture surface roughness plays an important role in estimating the damage degree and stability of deep rock mass.In this paper,the variations of fracture surface roughness of granite after different heating and thermal cycles were investigated using the joint roughness coefficient method(JRC),three-dimensional(3D)roughness parameters,and fractal dimension(D),and the mechanism of damage and deterioration of granite were revealed.The experimental results show an increase in the roughness of the granite fracture surface as temperature and cycle number were incremented.The variations of JRC,height parameter,inclination parameter and area parameter with the temperature conformed to the Boltzmann's functional distribution,while the D decreased linearly as the temperature increased.Besides,the anisotropy index(Ip)of the granite fracture surface increased as the temperature increased,and the larger parameter values of roughness characterization at different temperatures were attained mainly in directions of 20°–40°,60°–100°and 140°–160°.The fracture aperture of granite after fracture followed the Gauss distribution and the average aperture increased with increasing temperature,which increased from 0.665 mm at 25℃to 1.058 mm at 800℃.High temperature caused an uneven thermal expansion,water evaporation,and oxidation of minerals within the granite,which promoted the growth and expansion of microfractures,and reduced interparticle bonding strength.In particular,the damage was exacerbated by the expansion and cracking of the quartz phase transition after T>500℃.Thermal cycles contributed to the accumulation of this damage and further weakened the interparticle bonding forces,resulting in a significant increase in the roughness,anisotropy,and aperture of the fracture surface after five cycles.
基金the financialsupport from the China Scholarship Council(Grant No.202106370009)Alberta Innovate Graduate Student Scholarship.
文摘The cognitive load plays a key role in surgical education,influencingtask performance and skill acquisition.This review explores three primary approaches to assessing cognitive load in the surgical context—paper-based measures,physiological measures,and performance-based measures—and highlights their relevance and applications in surgical education.Paper-based tools,such as the NASA Task Load Index and its surgical adaptation,the Surgery Task Load Index,offer simplicity but lack realtime insight.Physiological measures,including heart rate,eye tracking,and electrodermal activity,provide objective and timely data.Neuroimaging techniques,such as electroencephalography and functional near-infrared spectroscopy,provide direct evidence of brain activity but face challenges such as cost and complexity.Performance-based metrics,such as secondary tasks,infer cognitive load from working memory capacity.Accurate assessment of cognitive load can improve training outcomes by adapting demands to cognitive capacity.Future directions include the development of more accurate,multimodal,and user-friendly tools for dynamic,timely assessment,ultimately advancing personalized surgical training and improving patient care.
基金co-supported by the National Natural Science Foundation of China(Nos.52376138 and 52025064)the Science Center for Gas Turbine Project,China(No.P2022B-Ⅱ-018-001)the Foundation Research Project,China(No.1002TJA22010)。
文摘The reignition of aero-engine combustors at high altitudes poses significant challenges due to the low-temperature and low-pressure environment.A novel Long Pulse-Width Plasma Ignition(LPWPI)system has been developed to enhance ignition performance.The LPWPI system can effectively prolong the discharge duration time,improve ignition efficacy,and increase the plasma penetration depth.Experimental comparisons with the traditional Spark Ignition(SI)system demonstrate that the LPWPI increased discharge duration to 2.03 ms,which is 45 times longer than that of the SI system,while also doubling the spark penetration depth to 24.1 mm.The LPWPI system achieved a discharge efficiency of 61.1%,significantly surpassing the SI system's efficiency of23.3%.These advancements facilitated an extension of the lean ignition boundary by approximately 22.7%to 39.3%.High-speed camera recordings reveal that the spark duration of the LPWPI system was extended to 2.1 ms,compared to 0.6 ms in the SI system.Ignition progress with LPWPI shows a sustained spark kernel without the flame residence stage observed in the SI system.The impressive performance of the LPWPI system suggests that it is a promising alternative for aero-engine ignition systems.
基金the financial support from the China Scholarship Council(Grant No.202106370009)and Alberta Innovate Graduate Student Scholarship.
文摘Objective While there is consensus regarding a positive effect of video gaming on dexterity,little is known regarding how much traditional laparoscopic practice can or should be substituted with video gaming.This study was designed to assess the effects of varying the amount of traditional practice in a lap box trainer and video gaming on performance in two fundamentals of laparoscopic surgery core tasks.Methods Undergraduate and medical students were recruited and randomized into one of four groups:a control group,a lap box group,a video game group,and a combined group with 50%of the time allocated to each modality.Performance in the peg transfer and precision cutting tasks was assessed both prior to and following the 6 training sessions.Results Peg transfer performance significantly improved in the lap box group(168.4±70.6 s vs.332.9±178.2 s,p<0.001),video game group(176.7±53.3 s vs.300.0±101.2 s,p<0.001)and combined group(214.2±86.9 s vs.406.8±239.5 s,p=0.002)after training.Similar improvements were also observed in precision cutting performance in the lap box group(413.1±138.4 s vs.614.3±211.4 s,p=0.002),video game group(434.1±150.8 s vs.609.2±233.2 s,p=0.007)and combined group(469.2±185.3 s vs.663.8±296.3 s,p=0.020).When analyzing improvements in performance across three different training groups compared with the control group,we found that both the lap box group(p<0.001)and the combined group(p<0.001)showed better improvement in both tasks,and the video game group had significantly better outcomes in the precision cutting task(p=0.003).Conclusion Traditional lap box training remains the most effective method for improving the performance of simulated laparoscopic surgery.Video games can be encouraged to enhance skills retention and supplement simulated practice outside of a formal training curriculum.
基金supported by the National Key Lab of Aerospace Power System and Plasma Technology Foundation,China(No.6142202210101)the National Science and Technology Major Project,China(No.J2019-Ⅲ-0013-0056)+2 种基金the National Natural Science Foundation of China(No.52025064)supported by the National Natural Science Foundation of China(Nos.52350072 and 52277167)the Beijing Natural Science Foundation,China(No.1242030)。
文摘Plasma-assisted combustion technology has been a hot spot in aero-engines andscramjet-engines.The electron density is a key discharge parameter related to the active-particledensity.The latter has been considered playing an important role in the above applications bythe kinetic effect.In this work,an atmospheric pressure air plasma collisional-radiative model con-sidering the excited states of atomic nitrogen and oxygen is built based on previous widely kineticinvestigations of molecules and radicals,as well as their excited states.The excited states,especiallythe atomic nitrogen and oxygen states were less investigated in previous works.The emission inten-sity distributions from the model have a good agreement with those measured in the glide arcplasma with two discharge modes,as well as the microwave plasma.Based on the kinetics of molec-ular and atomic emitting states,the line-ratio method is presented to determine the electron density.The N_(2)(337 nm)/O(844 nm)and N_(2)(337 nm)/NO(γ)line ratios are used for the glide arc plasma andmicrowave plasma torch,respectively.Besides,the kinetics of the excited states involved with twoline-ratios are also investigated in the two types of discharges.Combined with the atmospheric pres-sure actinometry method,the kinetic effect of the plasma-assisted combustion can be revealed quan-titatively in the future.
基金Anhui Natural Science Foundation Youth Program,Grant/Award Number:2208085QE142National Natural Science Foundations of China,Grant/Award Numbers:52004003,52304073Opening Foundation of Anhui Province Key Laboratory of Building Structure and Underground Engineering,Grant/Award Number:KLBSUE-2022-04。
文摘To study the energy evolution and failure characteristics of saturated sandstone under unloading conditions,rock unloading tests under different stress paths were conducted.The energy evolution mechanism of the unloading failure of saturated sandstone was systematically explored from the perspectives of the stress path,the initial confining pressure,and the energy conversion rate.The results show that(1)before the peak stress,the elastic energy increases with an increase in deviatoric stress,while the dissipated energy slowly increases first.After the peak stress,the elastic energy decreases with the decrease of deviatoric stress,and the dissipated energy suddenly increases.The energy release intensity during rock failure is positively correlated with the axial stress.(2)When the initial confining pressure is below a certain threshold,the stress path is the main factor influencing the total energy difference.When the axial stress remains constant and the confining pressure is unloading,the total energy is more sensitive to changes in the confining pressure.When the axial stress remains constant,the compressive deformation ability of the rock cannot be significantly improved by the increase in the initial confining pressure.The initial confining pressure is positively correlated with the rock's energy storage limit.(3)The initial confining pressure increases the energy conversion rate of the rock;the initial confining pressure is positively correlated with the energy conversion rate;and the energy conversion rate has a high confining pressure effect.The increase in the axial stress has a much greater impact on the elastic energy than the confining pressure.(4)When the deviatoric stress is small,the confining pressure mainly plays a protective role.Compared with the case of triaxial compression paths,the rock damage is more severe under unloading paths,and compared with the case of constant axial stress,the rock damage is more severe under increasing axial stress.
文摘背景急性胰腺炎(acute pancreatitis,AP)是常见的急腹症,不同类型预后不同.AP的免疫应答和失衡免疫与其严重程度有关,炎症因子和相关免疫细胞在AP发病机制中至关重要,因而寻找炎症细胞和新炎症免疫因子对精准治疗AP具有重要意义.目的探讨AP患者外周血CD14^+CD16^+单核细胞表达B7-H2的临床意义.方法A P患者63例[轻度A P(m i l dA P,M A P)25例、中度AP(moderately severe AP,MSAP)20例、重度AP(severe AP,SAP)18例],对照组为健康体检者20例,采用流式细胞仪检测CD14^+CD16^+细胞亚群上B7-H2表达情况,评价其与胰腺炎严重程度关联性及临床意义.结果AP患者发病24hCD14^+CD16^+细胞B7-H2出现异常高表达,显著高于健康对照组(t=11.10,P<0.001);A P各组B 7-H 2在C D 14^+C D 16^+细胞膜上表达明显高于CD14^+C D16^-细胞膜上表达(P<0.01);SAP组CD14^+C D 16^+和CD14^+C D 16^-细胞B7-H2表达(373.30±89.72和78.62±13.05)最高,M S A P组(279.55±76.95/44.92±12.44)其次,均高于M A P组(181.15±35.75/23.32±4.28),各组两两比较差异有显著性(P<0.01);MAP组、MSAP组发病24 h、48 h、72hCD14^+CD16^+和CD14^+CD16^-单核细胞膜B7-H2动态表达差异无显著性(P>0.05),然而,SAP组无论C D14^+C D16^+还是CD14^+C D16^-细胞膜B7-H2表达24h、48h、72h均呈明显上升趋势,差异有显著性(P<0.05).结论CD14^+CD16^+和CD14^+CD16^-单核细胞膜B7-H2在AP患者体内高表达,与AP严重程度密切相关,且SAP呈动态升高变化;同时B7-H2在AP患者CD14^+CD16^+单核细胞膜表达较CD14^+CD16^-单核细胞明显升高,为进一步认识AP免疫应答和失衡提供了新的线索,为AP精准靶向治疗提供参考.
基金supported by the National Natural Science Foundation of China(Nos.51522606,51507187,51276197,51407197,and 11472306)
文摘We conducted experiments in a wind tunnel with Mach number 2 to explore the evolution of a transverse plasma jet and its modification effect on a shock wave induced by a ramp with an angle of 24°. The transverse plasma jet was created by arc discharge in a small cylindrical cavity with a 2 mm diameter orifice. Three group tests with different actuator arrangements in the spanwise or streamwise direction upstream from the ramp were respectively studied to compare their disturbances to the shock wave. As shown by a time-resolved schlieren system, an unsteady motion of the shock wave by actuation was found： the shock wave was significantly modified by the plasma jet with an upstream motion and a reduced angle. Compared to spanwise actuation, a more intensive impact was obtained with two or three streamwise actuators working together. From shock wave structures, the control effect of the plasma jet on the shock motion based on a thermal effect, a potential cause of shock modification, was discussed. Furthermore, we performed a numerical simulation by using the Improved Delayed Detached Eddy Simulation（IDDES） method to simulate the evolution of the transverse plasma jet plume produced by two streamwise actuators. The results show that flow structures are similar to those identified in schlieren images. Two streamwise vortices were recognized, which indicates that the higher jet plume is the result of the overlap of two streamwise jets.
文摘The present study was to test the hypothesis that the plant growth retardants chlorocholine chloride(CCC) and paclobutrazol(PBZ)could improve the carbohydrate accumulation in lily bulbs by enhancing photosynthetic capacity and changing endogenous hormones.Plants of Lilium Oriental hybrids'Sorbonne'were treated with a foliar spray of CCC or PBZ(both at 300 mg/L)solution,at six weeks after planting(6 WAP).The morphological parameters,endogenous hormone contents(gibberellic acid(GA),abscisic acid(ABA),and indole-3-acetic acid(IAA)),and carbohydrate contents were measured from 6 to 18 WAP,at 2-week intervals.The results showed that CCC increased the biomass of leaves and stems which might produce more photoassimilates available for transportation and utilization.However,PBZ treatment suppressed vegetative growth and favored photoassimilate transportation into bulbs.A slight delay of bud and anthesis formation was observed in both treated plants.CCC and PBZ treatments substantially enhanced the sucrose contents in leaves probably due to the increase of chlorophyll contents.Treatment with CCC or PBZ decreased GA but increased IAA contents in lily bulbs which might stimulate starch accumulation and formation of new scales.Our experiment suggested that CCC or PBZ treatment is an effective method to promote carbohydrate accumulation in lily bulbs.
基金funded by National Key Technology R&D Program in the 11th Five Year Plan of China (2008BAC35B00)the international cooperation project(2009DFA21480)
文摘Based on the case studies and statistical analysis of earthquake-related ionospheric disturbances mainly from DEMETER satellite, ground-based GPS and ionosounding data, this paper summarizes the statisw tical characteristics of earthquake-related ionospheric disturbances, including electromagnetic emissions, plasma perturbations and variation of energetic particle flux. According to the main results done by Chinese scientists, fusing with the existed study from global researches, seismo-ionospheric disturbances usually occurred a few days or hours before earthquake occurrence. Paralleling to these case studies, lithosphere-atmosphere-ionosphere （LAI） coupling mechanisms are checked and optimized. A thermo-electric model was proposed to explain the seismo-electromagnetic effects before earthquakes. A propagation model was put forward to explain the electromagnetic waves into the ionosphere. According to the requirement of earthquake prediction research, China seismo-electromagnetic satellite, the first space-based platform of Chinese earthquake stereoscopic observation system, is proposed and planned to launch at about the end of 2014. It focuses on checking the LAI model and distinguishing earthquake-related ionospheric disturbance. The preliminary design for the satellite will adopt CAST-2000 platform with eight payloads onboard. It is believed that the satellite will work together with the ground monitoring network to improve the capability to capture seismo-electromagnetic information, which is beneficial for earthquake monitoring and prediction researches.
基金the financial s upport from the National Natural Science Foundation of China(No.41702326)the Jiangxi Provincial Natural Science Foundation(No.20202ACB214006)+2 种基金the Innovative Experts,Long-term Program of Jiangxi Province(jxsq2018106049)the Supported by Program of Qingjiang Excellent Young Talents,Jiangxi University of Science and Technologythe Innovation Fund Designated for Graduate Students of Jiangxi Province(YC2020-S451)。
文摘In this study,uniaxial and triaxial compression acoustic emission(AE)tests were implemented to investigate the AE effect and failure characteristics of sandstone under different confining pressures(σ3).The evolution of AE parameters in the rock failure process and fracture fractal dimension characteristics after failure were analyzed.The results revealed that the activity of the AE signal is strongly related toσ3.The evolution of the Ib value can be divided into the I-fluctuation,II-stability,and III-decrease stages.In the first stage,the Ib value of the AE was relatively high,and the AE energy was low.Then,the Ib value tended to be stable;however,the fluctuation amplitude decreased,and the AE energy rapidly increased.In the stage of decrease,the AE energy sharply increased before the load approached the peak value,and the Ib value significantly decreased and dropped to the lowest point before the peak value.Asσ3 increased,the rock’s failure mode changed from tensile failure to shear failure and became more coordinated.As the confining pressure increased,the shape dimension decreased,and the order degree of rock failure increased.The confining pressure exerted a certain control effect on the rock failure.
基金partially sponsored by the Major Program of the National Natural Science Foundation of China(No.91941105,51790511)the National Basic Research Program of China(No.2015CB/755802)。
文摘Ice accretion on the wings seriously threatens the flight safety of an aircraft.From the perspectives of ensuring flight safety and saving power consumption,the ice shape modulation method using distributed plasma is proposed.Distributed plasma actuator units are designed to modulate the spanwise continuous ice at the leading edge into periodically segmented ice pieces,forming a wavy leading edge.Both airfoil and scaled aircraft model,with continuous and modulated ice,are experimentally investigated and simulated.Compared with the continuous ice,ice shape modulation can significantly improve the aerodynamic performance,flight control characteristics and flight safety.This method can save about half electric power,which is very beneficial for application.
基金the financial support provided by the State Key Research Development Program of China (No.2016YFC0801406)the Natural Science Foundation of Jiangsu Province of China (No.BK20171191)National Natural Science Foundation of China(Nos.51674253,51734009)
文摘The mechanisms for rock bursts occurrences in fold zones are complex, and the redistribution of in-situ stresses is closely related to the complexity of the structures. Analysis of the geomorphology of fold structures and changes of coal thickness can help identify zones prone to rock bursts to improve safety and productivity in coal mines. This study investigated the distribution characteristics of fold structures in coal seams in fold zones in four mines in northwest China. Geometrical characteristics of fold structures in coal seams and changes of coal thickness were analysed, based on comprehensive evaluation indexes,such as the length–width ratio of folds, interlimb angle, ratio P1 of projected width of fold limbs to that of the hinge zone, curvature ratio P2, the maximum curvature and amplitude. The statistical analysis of the four coal mines shows that the length–width ratio of folds changed from 0.78 to 2.03 and the maximum curvature of cross sections of folds was less than 0.04. The curvature ratio of cross section of a fold in the structure was no more than 1.4 and the interlimb angles of cross sections of 89% of folds were larger than 150°. Gentle fold structures were dominant and the specific geological morphologies were domes or basins. The isopleth of coal thickness above the coal mines showed a fluctuation trend similar to the contour line of the floor of coal seams. The coal thickness in an anticline area was smaller than that in the neighboring syncline area. Therefore, the overall variation of coal thickness in the mining areas was likely to have a relation with the direction of the regional principal stress.
