Experimental study on age and gender differences in microscopic movement characteristics of students

Campus security has aroused many concerns from the whole society.Stampede is one of the most frequent and influential accidents in campus.Studies on pedestrian dynamics especially focusing on students are essential for campus security,which are helpful to improve facility design and emergency evacuation strategy.In this paper,primary and middle school students were recruited to participate in the single-file experiments.The microscopic movement characteristics,including walking speed,headway,gait characteristics(step length,step frequency and swaying amplitude)and their relations were investigated.Age and gender differences in the headway-speed diagram and space requirements were analyzed by statistical tests.The results indicated that the impacts of age and gender were significant.There were three stages for the influence of gender on the headway-speed diagram for both age groups.The impacts on students'space requirements were consistent for different age and gender groups.But the impacts of age and gender on free-flow speed were affected by each other.Due to the connection of walking speed and gait characteristics,the comparisons of gait characteristics between different ages and genders were performed to understand the corresponding differences in speed more deeply.The results showed that differences in step length and swaying amplitude between males and females were significant for both age groups.The effect of gender on step frequency was significant for primary students.But for middle school students,whether gender had significant impact on step frequency was not clear here because of the large P-value.Besides,the influence of age on gait characteristics changed with gender.

General Conditions for Online Estimation and Optimization of Reliability Characteristics

A novel approach to estimate reliability properties of systems or components individually during operation is presented. It is distinguished between slow and fast reliability states based on an equivalent system representation. Conditions for their observability and control are given and objectives for optimal reliability-based control are discussed in general.

Time resolved studies reveal the origin of the unparalleled high efficiency of one nanosecond laser ablation in liquids

Laser ablation in liquid is a scalable nanoparticle production method with applications in areas like catalysis and biomedicine.Due to laser-liquid interactions,different energy dissipation channels such as absorption by the liquid and scattering at the ablation plume and cavitation bubble lead to reduced laser energy available for nanoparticle production.Ultrashort pulse durations cause unwanted nonlinear effects in the liquid,and for ns pulses,intra-pulse energy deposition attenuation effects are to be expected.However,intermediate pulse durations ranging from hundreds of picoseconds up to one nanosecond have rarely been studied in particular in single-pulse settings.In this study,we explore the pico-to nanosecond pulse duration regimes to find the pulse duration with the highest ablation efficiency.We find that pulse durations around 1-2 ns enable the most efficient laser ablation in liquid since the laser beam shielding by the ablation plume and cavitation bubble sets in only at longer pulse durations.Furthermore,pump-probe microscopy imaging reveals that the plume dynamics in liquids start to differ from plume dynamics in air at about 2 ns after pulse impact.

Out of Plane Thermal Conductivity of Carbon Fiber Reinforced Composite Filled with Diamond Powder

Highly conductive fillers have a strong influence on improving the poor out of plane thermal conductivity of carbon fiber reinforced composites. The objective of this study has been to investigate the role of the diamond powder (DP) in enhancing the out-of-plane thermal conductivity of the woven composites. Samples of the standard modulus T300 carbon fiber composite with 44% and 55% fiber volume fraction and the high modulus YS90A carbon fiber composite with 50% volume fraction were fabricated with their matrices comprising of neat epoxy and different loading of diamond powder within epoxy resin. Steady state thermal conductivity measurements were carried out and it was found from the measurements that the out of plane thermal conductivity of the standard modulus composite increased by a factor of 2.3 with 14% volume fraction of diamond powder in the composite while the out of plane thermal conductivity of the high modulus composite increased by a factor of 2.8 with 12% volume fraction of diamond powder in the composite. Finite Element Modeling (FEM) with the incorporation of microstructural characteristics is presented and good consistency between the measurements and FEM results were observed.

Influence of the Heat Treatment Duration on the Critical Temperature for the Break-Down of Vertical Bloch Line Chains

For longer heat treatment duration(10 and 30 min),near and within the transi-tion region,the softening fraction p has an obvious,but not very large increase and the increment for 30min is greater than that for 10min.Ag a result,the criticad temperature To is only lowered by 2-3℃ for a typical saouple.The above results indicate the existence of a quasi-gtatic athermal instability,and the thermal activation of Bloch points is only of secondany importance.

Local thermal conductivity of polycrystalline AlN ceramics measured by scanning thermal microscopy and complementary scanning electron microscopy techniques

The local thermal conductivity of polycrystalline aluminum nitride （A1N） ceramics is measured and imaged by using a scanning thermal microscope （SThM） and complementary scanning electron microscope （SEM） based techniques at room temperature. The quantitative thermal conductivity for the A1N sample is gained by using a SThM with a spatial resolution of sub-micrometer scale through using the 3w method. A thermal conductivity of 308 W/m-K within grains corresponding to that of high-purity single crystal A1N is obtained. The slight differences in thermal conduction between the adjacent grains are found to result from crystallographic misorientations, as demonstrated in the electron backscattered diffraction. A much lower thermal conductivity at the grain boundary is due to impurities and defects enriched in these sites, as indicated by energy dispersive X-ray spectroscopy.

Confidence Intervals for Relative Intensity of Collaboration(RIC)Indicators

Purpose:We aim to extend our investigations related to the Relative Intensity of Collaboration(RIC)indicator,by constructing a confidence interval for the obtained values.Design/methodology/approach:We use Mantel-Haenszel statistics as applied recently by Smolinsky,Klingenberg,and Marx.Findings:We obtain confidence intervals for the RIC indicatorResearch limitations:It is not obvious that data obtained from the Web of Science(or any other database)can be considered a random sample.Practical implications:We explain how to calculate confidence intervals.Bibliometric indicators are more often than not presented as precise values instead of an approximation depending on the database and the time of measurement.Our approach presents a suggestion to solve this problem.Originality/value:Our approach combines the statistics of binary categorical data and bibliometric studies of collaboration.

Validation of Numerical Modeling for the Prediction of Elastic and Failure Behavior of Diamond Powder Filled Woven Composites

A numerical investigation was carried out to examine the role of micro-sized diamond powder filler on the on-axis tensile stiffness properties of the standard modulus T300 and the high modulus YS90A woven fabric composite plates by progressive damage modeling. Finite element modeling (FEM) results for the T300 composite with and without diamond powder predicted a specific case of fiber failure in all the plies showing the characteristics of brittle failure. Static tensile tests were carried out on the YS90A composite coupons containing no diamond powder (DP) and filled with 6% and 12% volume fractions of DP. A higher content of diamond powder in the coupons led to agglomeration. This induced stress concentrations and subsequently reduced the mechanical properties. FEM was carried out considering specimens with and without an induced stress concentration geometry in the YS90A coupons filled with DP. The results of the on-axis tensile tests indicated a delamination type of failure in both cases with additional fiber fracture in the Open Hole Tensile (OHT) coupons.

THE STRUGGLE OVER PRICES AND CONDITIONS OF PRICE FORMATION IN CLASSICAL ATHENS

In contemporary economic thought the up-and downward movements of prices are usually understood as resulting solely,or foremost,from the interplay of offer and demand.Conceding that these factors had a basic impact on price formation already in the monetized economy of Classical Athens,it is contended in this paper that the mechanisms of price formation cannot be explained through economic processes alone.In Classical Athens,as could be expected in an embedded economy,social and political forces as well as strictly economic ones were at work in establishing price levels.The spectrum ranges from political intervention over indirect interference to the influencing of the behavior of market participants through social pressure.Being a matter of existential importance,price formation was a subject of permanent trials of strength between various interest groups or social classes in ancient Athens.

非线性机械系统PID控制渐近稳定性分析

应用Lyapunov直接稳定性理论和LaSalle不变性原理,证明了不确定非线性机械系统常用线性PID控制的半全局渐近稳定性.同时证明了为提高系统的响应速度而发展的一种非线性PI加D(NPI—D)控制系统的全局渐近稳定性.两自由度机器人系统的数值仿真结果验证了NPI—D控制的良好性能.

默读和出声阅读的副中央凹预视效应

以往研究大多考察默读中是否存在副中央凹预视效应及存在何种类型的预视效应,很少有研究探讨出声阅读中的副中央凹预视效应以及阅读中预视信息提取的时间进程。本研究采用边界范式,通过两个眼动实验考察默读和出声阅读中的副中央凹预视效应及预视信息提取的时间进程。实验1发现在默读和出声阅读中都存在副中央凹预视效应,但是默读中副中央凹预视效应更大。实验2发现出声阅读中在注视中央凹词汇的早期不能提取副中央凹处信息。两个实验的结果表明默读和出声阅读条件下的副中央凹加工是不同的,需要用不同的眼动模型解释。

永磁直线电机驱动中低成本位置传感器的优化

本文讨论了一种定制低成本永磁直线电机位置传感器。该传感器包含两个霍尔传感元件。如果有上层控制,它可以为底层位置控制提供足够的精度,精度可达约0.2mm。文中给出了两种不同的传感器结构,并描述了开发这种传感器的优化步骤。通过传感器的优化设计省去了电磁接口。利用直线电机驱动,对该传感器与商业高精度线性传感器进行了比较。

Two New Control Signal Approaches for Obtaining the MRAS-CDM and a Real-time Application

The coefficient diagram method （CDM） is one of the most effective control design methods. It creates control systems that are very stable and robust with responses without the overshoot and small settling time. Furthermore, all control parameters of the control systems are changed by varying some adjustment parameters in CDM depending on the demands. The model reference adaptive systems （MRAS） are the systems that follow and change the control parameters according to a given model reference system. There are several methods to combine the CDM with MRAS. One of these is to use the MRAS parameters as a gain of the CDM parameters. Another is to directly use the CDM parameters as the MRAS parameters. In the industrial applications, the system parameters can be changed frequently, but if the controller, by self-tuning, recalculates and develops its own parameters continuously, the system becomes more robust. Also, if the poles of the controlled systems approach the jw axis, the response of the closed-loop MRAS becomes more and more insufficient. In order to obtain better results, CDM is combined with a self-tuning model reference adaptive system. Systems controlled by a model reference adaptive controller give responses with small or without overshoot, have small settling times, and are more robust. Thus, in this paper, a hybrid combination of MRAS and CDM is developed and two different control structures of the control signal are investigated. The two methods are compared with MRAS and applied to real-time process control systems.

Investigation on 3D fatigue crack propagation in surface-cracked specimens

In the present work the fatigue crack growth in AISI304 specimens is investigated experimentally. In 3D finite element analysis the virtual crack closure technique is applied to calculate distributions and variations of the stress intensity factor along the surface crack front. It is confirmed that the stress intensity factor along the surface crack front varies non-uniformly with crack growth. Crack growth rate is proportional to the stress intensity factor distribution in the 3D cracked specimen. The fatigue crack growth in surface cracked specimens can be described by the Forman model identified in conventional compact tension specimens. For crack growth in the free specimen surface the arc length seems more suitable to quantify crack progress. Geometry and loading configuration of the surface cracked specimen seem to not affect the fatigue crack growth substantially.

One-step preparation of a novel graphitic biochar/Cu^(0)/Fe_(3)O_(4) composite using CO_(2)-ambiance pyrolysis to activate peroxydisulfate for dye degradation

Herein,a one-step co-pyrolysis protocol was adopted for the first time to prepare a novel pyrogenic carbon-Cu^(0)/Fe_(3)O_(4)heteroatoms (FCBC) in CO_(2)ambiance to discern the roles of each component in PDS activation.During co-pyrolysis,CO_(2)catalyzed formation of reducing gases by biomass which facilitated reductive transformation of Fe^(3+)and Cu^(2+)to Cu^(0)and Fe_(3)O_(4),respectively.According to the analysis,the resulting metal (oxide) catalyzed graphitization of biocharand decomposition of volatile substances resulting in an unprecedented surface area (1240 m^(2)/g).The resulting FCBC showed greater structural defects and less electrical impedance.Batch experiments indicated that Rhodamine B (RhB) degradation by FCBC (100%) was superior to Fe_(3)O_(4)(50%) and Cu^(0)/Fe_(3)O_(4)(76.4%) in persulfate (PDS) system,which maintained reasonable efficiency (75.6%-63.6%) within three cycles.The reactive oxygen species (ROS) associated with RhB degradation was identified by an electron paramagnetic resonance and confirmed by scavenging experiments.RhB degradation invoked both(sulfate and dominantly hydroxyl) radical and non-radical (singlet oxygen,^(1)O_(2)) pathways.Regarding FCBC,Cu^(0)can continuously react with Fe^(3+)in Fe_(3)O_(4)to generate larger quantities of Fe^(2+),and both Cu^(0)and Fe^(2+)activated PDS to yield sulfate radicals which was quickly converted to hydroxyl radical.Besides,Cu^(0)/Cu^(2+)could complex with PDS to form a metastable complex,which particularly contributed to1O_(2)generation.These cascade reactions by FCBC were reinforced by carbonyl group of biochar and favorable electron transfer ability.This work highlighted a new approach to prepare a magnetic and environment-benign heterogonous catalyst to remove organic pollutants in water.

Variations of soil organic carbon fractions in response to conservative vegetation successions on the Loess Plateau of China

Land use changes profoundly affect the equilibrium of soil organic carbon(soC)sequestration and greenhouse gas emissions.With the current global climatic changes,it is vital to understand the influence of ecological restoration and conservation management on the dynamics of soC under different land uses,especially in erosion-endangered Loess soils.Therefore,we investigated changes in soc through a suit of labile fractions,namely:light fraction organic C(LFOC),heavy fraction organic C(HFOC),coarse particulate organic C(CPOC),fine particulate organic C(FPOC),and dissolved organic C(DOC),from two forests i.e.,Robinia pseudoacacia(RP)and Platycladus orientalis(PO),with different ages,in comparison with farmland(FL).The SOC and STN contents significantly increased over 42 years in the RP forest where the contents of CPOC and FPOC were significantly higher than in the FL.Moreover,total SOC and its labile fractions,in the studied land use types,significantly correlated with soil CacO3,pH,and STN contents,indicating their key roles in SoC sequestration.The results reported here from different vegetation with different ages provide a better understanding of sOC and STN alterations at different stages of vegetation restoration.Our findings suggest that long-term natural vegetation restoration could be an effective approach for SoC sequestration and soil conservation on the Loess soil.

Responses of Soil Enzyme Activities and Microbial Community Composition to Moisture Regimes in Paddy Soils Under Long-Term Fertilization Practices

The effects of fertilization on activity and composition of soil microbial community depend on nutrient and water availability;however,the combination of these factors on the response of microorganisms was seldom studied.This study investigated the responses of soil microbial community and enzyme activities to changes in moisture along a gradient of soil fertility formed within a long-term(24 years)field experiment.Soils(0–20 cm)were sampled from the plots under four fertilizer treatments:i)unfertilized control(CK),ii)organic manure(M),iii)nitrogen,phosphorus,and potassium fertilizers(NPK),and iv)NPK plus M(NPK+M).The soils were incubated at three moisture levels:constant submergence,five submerging-draining cycles(S-D cycles),and constant moisture content at 40%water-holding capacity(low moisture).Compared with CK,fertilization increased soil organic carbon(SOC) by 30.1%–36.3%,total N by 27.3%–38.4%,available N by 35.9%–56.4%,available P by 61.4%–440.9%,and total P by 28.6%–102.9%.Soil fertility buffered the negative effects of moisture on enzyme activities and microbial community composition.Enzyme activities decreased in response to submergence and S-D cycles versus low moisture.Compared with low moisture,S-D cycles increased total phospholipid fatty acids(PLFAs)and actinomycete,fungal,and bacterial PLFAs.The increased level of PLFAs in the unfertilized soil after five S-D cycles was greater than that in the fertilized soil.Variations in soil microbial properties responding to moisture separated CK from the long-term fertilization treatments.The coefficients of variation of microbial properties were negatively correlated with SOC,total P,and available N.Soils with higher fertility maintained the original microbial properties more stable in response to changes in moisture compared to low-fertility soil.

Evolution of misfit dislocation network and tensile properties in Ni-based superalloys:a molecular dynamics simulation

The structural evolution of dislocation network is closely related to ' rafting and tensile properties.In this work,the effects of strain rate and temperature on the structural evolution of interface dislocation network in Ni-based superalloys are studied by molecular dynamics simulations.The correlation between the evolution of dislocation network and tensile properties is also explored.The results indicate that the dislocation network shows different degrees of deformation and damage at various strain rates and temperatures.The ' rafting depends on the damage structure of dislocation network at various strain rates and temperatures.Moreover,the tensile properties of interface in Ni-based superalloys are closely related to the evolution of dislocation network and dislocation motion mechanisms.

Response of microbial communities to biochar-amended soils:a critical review

Application of biochar to soils changes soil physicochemical properties and stimulates the activities of soil microorganisms that influence soil quality and plant performance.Studying the response of soil microbial communities to biochar amendments is important for better understanding interactions of biochar with soil,as well as plants.However,the effect of biochar on soil microorganisms has received less attention than its influences on soil physicochemical properties.In this review,the following key questions are discussed:(i)how does biochar affect soil microbial activities,in particular soil carbon(C)mineralization,nutrient cycling,and enzyme activities?(ii)how do microorganisms respond to biochar amendment in contaminated soils?and(iii)what is the role of biochar as a growth promoter for soil microorganisms?Many studies have demonstrated that biochar-soil application enhances the soil microbial biomass with substantial changes in microbial community composition.Biochar amendment changes microbial habitats,directly or indirectly affects microbial metabolic activities,and modifies the soil microbial community in terms of their diversity and abundance.However,chemical properties of biochar,(especially pH and nutrient content),and physical properties such as pore size,pore volume,and specific surface area play significant roles in determining the efficacy of biochar on microbial performance as biochar provides suitable habitats for microorgan-isms.The mode of action of biochar leading to stimulation of microbial activities is complex and is influenced by the nature of biochar as well as soil conditions.