函数展开计数在CLUTCH方法中的初步应用

反复裂变几率(IFP)方法广泛应用于求解k特征值对连续能量核数据的灵敏度系数,然而IFP方法存在内存占用大的问题,因此CLUTCH方法被提出以解决该问题。但对于大规模问题,如压水堆全堆问题,基于网格的CLUTCH(CLUTCH-Mesh)方法存在权重函数不易收敛的问题。本文采用函数展开计数(FET)方法对CLUTCH方法中的权重函数进行统计(CLUTCH-FET)以解决该问题,函数展开计数选取的基函数是勒让德多项式。本文在蒙特卡罗粒子输运计算程序NECP-MCX中实现了IFP、CLUTCH-Mesh和CLUTCH-FET 3种方法,以IFP方法的计算结果作为参考解,对CLUTCH-Mesh和CLUTCH-FET方法的精度和效率进行了验证。数值结果表明:对于小规模问题,如Godiva和Flattop问题,CLUTCH-Mesh和CLUTCH-FET方法具有与IFP方法相当的精度,且计算效率较IFP方法更高;对于大规模问题,如AP1000全堆问题,CLUTCH-Mesh方法的计算精度下降,而CLUTCH-FET方法可保持较高的精度和计算效率,CLUTCH-FET方法的品质因子较IFP方法和CLUTCH-Mesh方法分别最多提高了5.2和6.0倍。

Investigation of hydroxyl-terminated polybutadiene propellant breaking characteristics and mechanism impacted by submerged cavitation water jet

A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.

Fault Diagnosis for Buckling Friction Components in Wet Multi-Disc Clutches Using IHHT

The wet multi-disc clutches are extensively used in various transmission systems,withone of the most prevalent failure modes being the buckling deformation of friction components.Animproved Hilbert-Huang transform method(IHHT)is proposed to address the limitations of tradi-tional time-domain vibration analyses,such as low accuracy and mode mixing.This paper first clas-sifies the buckling degree of the friction components.Next,wavelet packet transform(WPT)isapplied to the vibration signals of different buckling plates to partition them into distinct fre-quency bands.Then,the instantaneous features are extracted by empirical mode decomposition(EMD)and Hilbert transform(HT)to discarding extraneous intrinsic mode function(IMF)com-ponents.Comparative analyses of Hilbert spectral entropy and time-domain features confirm theenhanced precision of IHHT under specific classifiers,which is better than traditional methods.

The clutch size,incubation behavior of Reeves’s Pheasant(Syrmaticus reevesii) and their responses to ambient temperature and precipitation

Weather conditions play a pivotal role in embryo development and parental incubation costs,potentially impacting the clutch size and incubation behavior of birds.Understanding these effects is crucial for bird conservation.Reeves’ s Pheasant(Syrmaticus reevesii) is a threatened species endemic to China,which is characterized by female-only incubation.However,there is a lack of information regarding the impact of weather conditions on clutch size and incubation behavior in this species.Using satellite tracking,we tracked 27 wild female Reeves’ s Pheasants from 2020 to 2023 in Hubei Province,China.We explored their clutch size and incubation behavior,as well as their responses to ambient temperature and precipitation.Clutch size averaged 7.75 ±1.36,had an association with average ambient temperature and average daily precipitation during the egglaying period,and was potentially linked to female breeding attempts.Throughout the incubation period,females took an average of 0.73 ±0.46 recesses every 24 h,with an average recess duration of 100.80 ±73.37 min and an average nest attendance of 92.98 ±5.27%.They showed a unimodal recess pattern in which nest departures peaked primarily between 13:00 and 16:00.Furthermore,females rarely left nests when daily precipitation was high.Recess duration and nest attendance were influenced by the interaction between daily mean ambient temperature and daily precipitation,as well as day of incubation.Additionally,there was a positive correlation between clutch size and recess duration.These results contribute valuable insights into the lifehistory features of this endangered species.

Determination of the flooding zone during a dam break in a channel with a bend in the presence of several obstacles by the VOF method

This paper aims to investigate a dam break in a channel with a bend in the presence of several obstacles.To accurately determine the flood zones,it is necessary to take into account many factors such as terrain,reservoir volume.Numerical modeling was used to determine the flood zone.Numerical modeling based on the Navier-Stokes equations with a turbulent k-epsilon RNG model,the Volume of Fluid(VOF)method and the PISO algorithm were used to analyze the flow in a bend channel at an angle of 10 with the obstacles.To verify the numerical model,a test on dam break in the 450 channel was conducted.The simulation results were compared with experimental data and with the numerical data of existing data.Having been convinced of the correctness of the mathematical model,the authors carried out a numerical simulation of the main problem in three versions:without barriers,with one obstacle,with two obstacles.According to the obtained numerical results,it can be noted that irregular landforms held the flow,a decrease in water level and a slower time for water emergence could be seen.Thus,the water flow without an obstacle,with one obstacle and with two obstacles showed 4.2 s,4.4 s and 4.6 s of the time of water appearance,respectively.This time shift can give a certain advantage when conducting various events to evacuate people.

Cavitation cloud impingement and scattering motion of jet in rock breaking process

The cavitation cloud impingement of the jet in the rock breaking process was experimentally investigated to reveal the jet erosion mechanism in drilling of petroleum exploitation. Serial erosion tests and flow visualization were performed, where the cavitation cloud motion in the erosion crater was obtained with the designed transparent specimen. Various erosion patterns were identified in the whole erosion process based on the eroded specimen topography. The shallow eroded crater with a shrinking erosion area is generated by the combination of impinging and scattering cavitation clouds. The increase of l_(d) promotes the development of cavitation cloud σ_(c) but reduces the impingement frequency f_(d), suggesting that the jet aggressive ability is enhanced when the balance between σ_(c) and f_(d) is reached. The cavitation cloud motion in the erosion crater was investigated with the transparent specimen. The erosion in the crater at shorter exposure periods T_(e) is generated by the combination of impingement and restricted scattering of cavitation clouds. With the continuous development of the erosion damage, the jet's aggressive ability is diminished due to the erosion expansion on sandstone, where the cavitation clouds impinge on the target and then collapse and vanish without restricted scattering.

Across two phylogeographic breaks: Quaternary evolutionary history of a mountain aspen (Populus rotundifolia) in the Hengduan Mountains

Biogeographical barriers to gene flow are central to plant phylogeography.In East Asia,plant distribution is greatly influenced by two phylogeographic breaks,the Mekong-Salween Divide and Tanaka-Kaiyong Line,however,few studies have investigated how these barriers affect the genetic diversity of species that are distributed across both.Here we used 14 microsatellite loci and four chloroplast DNA fragments to examine genetic diversity and distribution patterns of 49 populations of Populus rotundifolia,a species that spans both the Mekong-Salween Divide and the Tanaka-Kaiyong Line in southwestern China.Demographic and migration hypotheses were tested using coalescent-based approaches.Limited historical gene flow was observed between the western and eastern groups of P.rotundifolia,but substantial flow occurred across both the Mekong-Salween Divide and Tanaka-Kaiyong Line,manifesting in clear admixture and high genetic diversity in the central group.Wind-borne pollen and seeds may have facilitated the dispersal of P.rotundifolia following prevalent northwest winds in the spring.We also found that the Hengduan Mountains,where multiple genetic barriers were detected,acted on the whole as a barrier between the western and eastern groups of P.rotundifolia.Ecological niche modeling suggested that P.rotundifolia has undergone range expansion since the last glacial maximum,and demographic reconstruction indicated an earlier population expansion around 600 Ka.The phylogeographic pattern of P.rotundifolia reflects the interplay of biological traits,wind patterns,barriers,niche differentiation,and Quaternary climate history.This study emphasizes the need for multiple lines of evidence in understanding the Quaternary evolution of plants in topographically complex areas.

Generating highly active oxide-phosphide heterostructure through interfacial engineering to break the energy scaling relation toward urea-assisted natural seawater electrolysis

Urea-assisted natural seawater electrolysis is an emerging technology that is effective for grid-scale carbon-neutral hydrogen mass production yet challenging.Circumventing scaling relations is an effective strategy to break through the bottleneck of natural seawater splitting.Herein,by DFT calculation,we demonstrated that the interface boundaries between Ni_(2)P and MoO_(2) play an essential role in the selfrelaxation of the Ni-O interfacial bond,effectively modulating a coordination number of intermediates to control independently their adsorption-free energy,thus circumventing the adsorption-energy scaling relation.Following this conceptual model,a well-defined 3D F-doped Ni_(2)P-MoO_(2) heterostructure microrod array was rationally designed via an interfacial engineering strategy toward urea-assisted natural seawater electrolysis.As a result,the F-Ni_(2)P-MoO_(2) exhibits eminently active and durable bifunctional catalysts for both HER and OER in acid,alkaline,and alkaline sea water-based electrolytes.By in-situ analysis,we found that a thin amorphous layer of NiOOH,which is evolved from the Ni_(2)P during anodic reaction,is real catalytic active sites for the OER and UOR processes.Remarkable,such electrode-assembled urea-assisted natural seawater electrolyzer requires low voltages of 1.29 and 1.75 V to drive 10 and600 mA cm^(-2)and demonstrates superior durability by operating continuously for 100 h at 100 mA cm^(-2),beyond commercial Pt/C||RuO_(2) and most previous reports.

Team China’s Groundbreaking Success at Paris Olympics

China’s Olympic delegation at the Paris 2024,with 404 athletes competing in 232 events across 30 sports,clinched 40 gold,27 silver,and 24 bronze medals,marking their best performance at an Olympics held abroad.The success of these athletes across various disciplines demonstrates the country’s efforts to expand its athletic prowess while also marks a new chapter for Chinese sportsmanship on the international stage.

Enhancing textile production:Smartex exhibits groundbreaking solutions

Smartex,a trailblazing leader in textile industry innovation,was proud to announce its return to ITM 2024,showcasing unparalleled advancements in quality control and production efficiency.Building on the success of previous exhibitions at ITM 2022 and ITMA Milan 2023,Smartex emerges stronger than ever,presenting its complete Smartex System tailored to transform textile manufacturing.

Impacts of monsoon break events in the western North Pacific on the cross-equatorial flows over the Maritime Continent

本文利用ERA5逐日再分析资料,探讨了1979-2020年间西北太平洋季风中断事件对海洋性大陆越赤道气流的影响.合成结果表明,西北太平洋季风中断事件会造成高,低空越赤道气流减弱,即高层南风异常,低层北风异常,与此相关的环流异常表现为西北太平洋高层气旋,低层反气旋的斜压结构。特别的是,西北太平洋季风中断对高空越赤道气流的影响更为显著,92%的季风中断事件都导致高空越赤道气流减弱,而只有70%的事件造成低空越赤道气流减弱,这是由于低空越赤道气流同时还受到赤道中东太平洋海温异常的调控.

Numerical Simulation of Dam-Break Flows Using Radial Basis Functions: Application to Urban Flood Inundation

Dam-break flows pose significant threats to urban areas due to their potential for causing rapid and extensive flooding. Traditional numerical methods for simulating these events struggle with complex urban landscapes. This paper presents an alternative approach using Radial Basis Functions to simulate dam-break flows and their impact on urban flood inundation. The proposed method adapts a new strategy based on Particle Swarm Optimization for variable shape parameter selection on meshfree formulation to enhance the numerical stability and convergence of the simulation. The method’s accuracy and efficiency are demonstrated through numerical experiments, including well-known partial and circular dam-break problems and an idealized city with a single building, highlighting its potential as a valuable tool for urban flood risk management.

解读竞赛压力下的运动表现:一个“Clutch”视角的运动能力初探

"Clutch"是一种与"Choking"典型相反的现象,主要描述运动员在比赛关键时刻的完美表现。基于"Clutch"表现,从现象学的角度,讨论压力下运动能力的发挥,并分析"Clutch"运动员的能力表现特征,旨在为优秀运动员的训练和选拔提供理论依据。研究认为,竞赛压力下的运动表现存在极性现象,"Choking"反映的是负性运动表现,而"Clutch"反映的是正性运动表现。从特征解释上讲,"Choking"表述为情景的运动表现,而"Clutch"则是特质的运动表现。"Clutch"反映了运动员在压力下展示技术的能力,一般发生在优秀运动员身上。通过"Clutch"运动表现的案例分析,结合相关研究成果,认为"Clutch"运动员是存在的,并提出了"Clutch"运动员的能力表现解释模型。该模型主要包括"专项运动能力"、"压力认知应对能力"和"运动员人格"3个方面。

Study of Controlling Clutch Engagement for AMT Based on Fuzzy Logic

The control of the clutch engagement for an automatic mechanical transmission in the process of a tracklayer getting to start is studied. The dynamic model of power transmission and automatic clutch system is developed. Using tools of Simulink, the transient characteristics during the vehicle starting, including the jerk and the clutch slip time, are provided here. Based on the analyses of the simulation results and driver’s experiences, a fuzzy controller is designed to control the clutch engagement. Simulation results verify its value.

Dynamic Performance Simulation of Power Shift Clutch During Shift

Based on the theoretical analyses, the dynamic and mathematical models of the system were developed. The models were implemented in the ambit of the Matlab/Simulink environment, and an integrated simulation model was developed. The dynamic performance of the power shift clutch during engagement and disengagement was studied by using this assembly model. The sliding speed, torque transmitted through the clutch, and the rate at which energy is dissipated during the process were determined. Using this model, the calculation during simulation can be simplified. This lays a foundation for the dynamic performance research on the power train with the power shift clutch, and provides a powerful tool for developing an automatic, electronically controlled transmission.

Oil-Film Clutch in Soft-Start of Belt Conveyor

The oil film clutch, which is superior in speed adjustment, is capable of being used in the belt conveyor to carry out soft start operation. According to running properties of both belt conveyor and oil film clutch, equations that are used to decide the lubricating oil flow and the number of oil films (i.e. the number of rotating and stationary plates) are deduced theoretically. Also key parameters are provided for the design of the hydraulic system. All these together provide the theoretical basis for the soft start design of the belt conveyor and references for the application of the oil film clutch in similar fields.

Coffee Break和Seminar:提升大学生创新能力的有效方法——南京农业大学生物学理科基地大学生科研训练计划的实践

大学生科研训练（Student Research Training，SRT）计划是提高大学生科研能力的重要途径之一，也是培养国家理科基地创新性人才的重要举措。为了解决在实施SRT过程中出现的老师与学生交流不足的问题，南京农业大学引入了以Coffee Break和Seminar为主体的交流模式。经过近四年的实践探索，该模式有力地完善和保障了SRT的顺利实施，大大促进了创新型人才的培养。文章对此进行了详细的阐述。

“Clutch”运动员特征的概念构图

研究基于王进等(2013)的"Clutch"运动员能力特征假设模型,运用概念构图的数据分析方法,验证"Clutch"运动员的结构解释要素。被试为6名高级教练员、6名优秀运动员和6名运动训练方面的专家,通过一对一的深度访谈,收集数据作为分析素材。然后按照创建分析单元、分类、多维定标、聚类分析、完成概念构图和解释概念构图的顺序进行分析。结果支持了王进等的"Clutch"运动员的结构要素解释假设模型,并且发现解释模型的3个要素可具体分解为压力认知敏感度、压力应对能力、心智能力、身体与技战术能力、心理敢为性、态度积极性、心理坚韧性和自信8个维度。并进一步讨论了其概念的内涵。

单一界化限制与BREAK类结果句式的推导

Tenny(1994)提出的单一界化限制规定一个事件最多只能被界化一次。但是,这一论断受到了BREAK类结果句式的挑战,因为这类句式包含两个界点。本文以事件结构理论为背景,从维度的视角对这一论断进行了修订和重新解释。以此为基础,本文提出了一个基于维度和影响性并将运动事件和变化事件统于一体的事件句法模型,对英汉语BREAK类结果句式的生成过程进行了推导和分析。研究表明,这个句法模型体现出了界性、动性和影响性等事件结构特征之间的相互关系,可以较好地处理BREAK类结果句式的推导。

Analysis of the Test of ER Fan Clutch

Aim To carry out an experiment of the application of ER fluids in the clutch by reforming a fan clutch used in a truck. Methods At three different input rotating speeds,when the strength of applied electric field was changed, the output rotating speeds were recorded and analyzed. Results By comparing the results got under different experimental procedures with those measured with an electro-rheometer, it can be seen that the shearing rate has tremendous influence on the speed modulating of a fan clutch. This is because the disperse phase can't form chains (clusters)easily at high shear rate.Conclusion The result tested on the present ER fluid demonstrates that this fluid will show the properties of Newton one,i.e. its apparent viscosity is constant. as the shear rate increases.