Activation reduction following an eccentric contraction impairs torque steadiness in the isometric steady-state

Background:The isometric steady-state following active lengthening is associated with greater torque production and lower activation,as measured by electromyographic activity(EMG),in comparison with a purely isometric contraction(ISO)at the same joint angle.This phenomenon is termed residual force enhancement(RFE).While there has been a great deal of research investigating the basic mechanisms of RFE,little work has been performed to understand the everyday relevance of RFE.The purpose of this study was to investigate whether neuromuscular control strategies differ between ISO and RFE by measuring torque steadiness of the human ankle plantar flexors.Methods:Following ISO maximal voluntary contractions in 12 males(25±4 years),an active lengthening contraction was performed at 15°/s over a 30°ankle excursion,ending at the same joint angle as ISO(5°dorsiflexion;RFE).Surface EMG of the tibialis anterior and soleus muscles was recorded during all tasks.Torque steadiness was determined as the standard deviation(SD)and coefficient of variation(CV)of the torque trace in the ISO and RFE condition during activation-matching(20%and 60%integrated EMG)and torque-matching(20%and 60%maximal voluntary contraction)experiments.Two-tailed,paired t tests were used,within subjects,to determine the presence of RFE/activation reduction(AR)and whether there was a difference in torque steadiness between ISO and RFE conditions.Results:During the maximal and submaximal conditions,there was 5%-9%RFE with a 9%-11%AR(p<0.05),respectively,with no difference in antagonist coactivation between RFE and ISO(p>0.05).There were no differences in SD and CV of the torque trace for the 20%and60%activation-matching or the 60%and maximal torque-matching trials in either the RFE or ISO condition(p>0.05).During the 20%torquematching trial,there were～37%higher values for SD and CV in the RFE as compared with the ISO condition(p<0.05).A significant moderate-to-strong negative relationship was identified between the reduction in torque steadiness following active lengthening and the accompanying AR(p<0.05).Conclusion:It appears that while the RFE-associated AR provides some improved neuromuscular economy,this comes at the cost of increased torque fluctuations in the isometric steady-state following active lengthening during submaximal contractions.

Numerical Analysis of Steady Smoldering of Biomass Rods

Understanding the steady mechanism of biomass smoldering plays a great role in the utilization of smoldering technology.In this study numerical analysis of steady smoldering of biomass rods was performed.A two-dimensional(2D)steady model taking into account both char oxidation and pyrolysis was developed on the basis of a calculated propagation velocity according to empirical correlation.The model was validated against the smoldering experiment of biomass rods under natural conditions,and the maximum error was smaller than 31%.Parameter sensitivity analysis found that propagation velocity decreases significantly while oxidation area and pyrolysis zone increase significantly with the increasing diameter of rod fuel.

Analysis of the Flow of a Molten Slag in an Open Channel Using Transient and Steady-State Solutions of the Saint-Venant Equations

In recent years, metallurgical slags have been increasingly used as materials for the manufacture of cement, pavement and filling material. The transport of the molten slag to the receiving pots is carried out through open channels. The transient and steady-state flow of a molten slag in a rectangular open channel is numerically analyzed here. For the transient flow, the Saint-Venant equations were numerically solved. For the steady-state flow, the derivatives in time and space in the Saint-Venant equations were set equal to zero and a polynomial of degree 3 is obtained whose roots are the slag height values. It was assumed that the viscosity of the slag has an Arrhenius-type behavior with temperature. Four values of temperature values, namely 1723.15, 1773.15, 1823.15, 18873.15 ˚K, and five values of the angle of inclination of the channel, namely 1, 2, 3, 4, 5 degrees, are considered. Numerical results show that the steady-state values of the height and velocity of the molten slag depend strongly on the temperature of the slag and the angle of inclination of the channel. As the slag temperature and channel angle increase, the value of the steady-state slag height decreases. The value of the steady-state slag velocity increases as the slag temperature and channel inclination angle increase.

STEADI工具包特点及其在预防老年人跌倒中的应用进展

本文综述了STEADI工具包的特点、应用现状及应用前景,为我国防范老年人跌倒提供新思路。

基于STEADI工具包筛查重庆市社区老人跌倒情况

目的:应用STEADI工具包筛查社区老人跌倒情况并分析影响因素。方法:2019年1月-4月采取多阶段整群抽样的方法,抽取重庆市某社区内符合纳入标准的老人为研究对象,运用汉化版STEADI工具包对其进行跌倒筛查。结果:共纳入1168名老人,其中跌倒低风险老人896人(76.71%),中风险老人251人(21.49%),高风险老人21人(1.80%);跌倒总发生率为14.98%,其中高风险、中风险、低风险组老人跌倒发生率分别为100.00%、18.33%、12.05%。3组老人在受教育程度、是否独居、生活照料情况、跌倒史、步态或平衡异常等项目得分差异有统计学意义(P<0.05)。结论:老人的跌倒受多种因素影响,应根据其跌倒风险等级制定分层干预策略。

STEADI跌倒风险自评量表在社区老年人中的应用研究

目的应用STEADI跌倒风险自评量表筛查社区老年人跌倒风险,并了解其对老年人远期跌倒的预测效能。方法采用多阶段整群随机抽样,选取重庆市社区老年人1 168人,运用汉化版STEADI跌倒风险自评量表筛查其跌倒风险。6个月后电话随访老年人跌倒发生情况。结果 321人(27.5%)自评有跌倒风险。6个月后有效电话随访825人,64人发生跌倒,跌倒发生率为7.8%(64/825),跌伤率为71.9%(46/64)。汉化版预测6个月后社区老年人发生跌倒的灵敏度为45.3%,特异性为75.4%,AUC为0.604,约登指数为0.208。71.6%的老年人认为跌倒风险自我评估对其有意义,69.9%的老年人评估后实施了预防跌倒的相关措施。结论大多数老年人认可跌倒风险自评的意义并采取相关措施预防跌倒,但汉化版预测社区老年人6个月后发生跌倒的效能欠佳,建议结合步态、力量和平衡的评估结果来预测老年人跌倒风险。

STEADY HEAT TRANSFER ANALYSIS AND PARAMETER OPTIMIZATION FOR MULTILAYER THERMAL INSULATIONS

The energy equilibrium equation and discrete ordinate methods are combined to establish the one-dimensional steady heat transfer mathematical model of multi-layer thermal insulations （MTIs） in metallic thermal protection systems. The inverse problem of heat transfer is solved by the genetic algorithm and data from the steady heat transfer experiment of fibrous thermal insulations. The density radiation attenuation coefficient, the albedo of fibrous thermal insulations and the surface emissivity of reflective screens are optimized. Finally, the one-dimensional steady heat transfer model of MTIs with optimized thermal physical parameters is verified by experimental data of the effective MTI conductivity.

List流上梯度Steady Solitons的位势函数

利用比较定理,研究了List流上梯度Steady Solitons的位势函数下确界的退化率,并得到了如下结论:如果位势函数是有界的,则梯度Steady Solitons一定是平凡的;梯度Steady Solitons的广义数量曲率不具有一致正下界.

STEADI工具包对我国住院患者跌倒预防的启示

该文综述了STEADI工具包的研发背景,工具包内容及目前在住院患者跌倒防范的应用研究,阐述了我国住院患者跌倒预防现状,包括国家对跌倒防范工作的重视程度,目前住院患者跌倒主要研究内容为我国跌倒防范预防主要工具及跌倒防范工作中存在的不足,同时提出了STEADI工具包对我国住院患者跌倒防范的启示,旨在为我国住院患者跌倒防范提供新工具,打开新思路。

社区老年人STEADI跌倒防范策略的实施

目的降低社区老年人跌倒发生率。方法采取多阶段整群抽样的方法,应用STEADI相关工具和自制的老年人足问题图册,筛查894名社区老年人跌倒风险和足问题,在此基础上根据STEADI跌倒风险分级干预策略,对社区老年人跌倒危险因素进行分层级、跨学科干预6个月。结果社区老年人跌倒低风险705人(78.9%),中风险175人(19.6%),高风险14人(1.6%)。老年人存在足部问题790人,其中存在与跌倒密切相关的足部疼痛和足部结构问题者333人(42.2%)。干预前发生跌倒135人(15.1%),干预后发生跌倒51人(6.2%,随访818人),跌倒发生率显著低于干预前(P<0.01)。结论STEADI跌倒防范策略有利于降低社区老年人跌倒发生率,可用于社区老年人跌倒的防范。

美国STEADI工具介绍及其对我国跌倒防范的启示

介绍美国疾病预防控制中心(CDC)2015年9月发布的预防老年人意外、死亡、伤害工具(Stopping Elderly Accidents,Deaths&Injuries Tool Kit,STEADI),旨在为我国老年人的跌倒防范提供参考和借鉴。

Numerical simulation on trapping efficiency of steady filtration process in diesel particulate filter and its experimental verification

Taking wall-flow diesel particulate filter(DPF) as the research objective and separately assuming its filtering wall to be composed of numerous spherical or cylindrical elements, two different mathematical models of steady filtration for wall-flow diesel particulate filter were developed and verified by experiments as well as numerically solved. Furthermore, the effects of the macroand micro-structural parameters of filtering wall and exhaust-flow characteristic parameters on trapping efficiency were also analyzed and researched. The results show that: 1) The two developed mathematical models are consistent with the prediction of variation of particulate size; the influence of various factors on the steady trapping efficiency is exactly the same. Compared to model 2, model 1 is more suitable for describing the steady filtration process of wall-flow diesel particulate filter; 2)The major influencing factors on steady trapping efficiency of wall-flow diesel particulate filter are the macro-and micro-structural parameters of filtering wall; and the secondary influencing factors are the exhaust-flow characteristic parameters and macro-structural parameters of filter; 3)The steady trapping efficiency will be improved by increasing filter body volume, pore density as well as wall thickness and by decreasing exhaust-flow, but effects will be weakened when particulate size exceeds a certain critical value; 4) The steady trapping efficiency will be significantly improved by increasing exhaust-flow temperature and filtering wall thickness, but effects will be also weakened when particulate size exceeds a certain critical value; 5) The steady trapping efficiency will approximately linearly increase with reducing porosity, micropore aperture and pore width.

A Calculation of Steady Pressure Drop and an Analysis of HT-7U CICC

Under the condition of steady state, the pressure drop of coolant is mainly caused by friction along the cable. In the CICC (cable-in-conduit-conductor), helium flow within the conductor consists of two parallel interconnected tubes. The velocity distribution has some differece between the central channel and conductor space. The region of Reynolds number is from 103 to 106. This paper describes the calculation of pressure drop of HT-7U CICC at various mass flows. It is assumed that the coolant flows in two parallel, rough tubes during the calculation.

Morse跌倒评估量表与STEADI跌倒风险自评量表在养老机构老年人中的应用比较

目的比较Morse跌倒评估量表与STEADI跌倒风险自评量表在评估养老机构老年人跌倒风险中的应用价值,为有效识别高跌倒风险老年人提供理论指导。方法采用便利抽样法,选取河北省8所养老机构内429名老年人为研究对象,采用一般资料调查表、Morse跌倒评估量表和STEADI跌倒风险自评量表收集资料,分析量表的接受者操作特性(ROC)曲线、最佳临界值、交叉检验准确率和阳性似然比。结果以过去1年内是否发生跌倒为参照,Morse跌倒评估量表和STEADI跌倒风险自评量表的ROC曲线下面积分别为0.889和0.832,且两者ROC曲线下面积之差为0.057(Z=2.295,P=0.022),Morse跌倒评估量表和STEADI跌倒风险自评量表的最佳临界值分别为57.500和5.500,敏感度、特异度、交叉检验准确度和阳性似然比分别为0.783、0.912、0.751、8.870和0.767、0.719、0.739、2.730。结论与STEADI跌倒风险自评量表相比,Morse跌倒评估量表更适用于评估养老机构老年人发生跌倒的风险。

Experimental study of vortex-induced vibrations of a cylinder near a rigid plane boundary in steady flow

In this study, the vortex-induced vibrations of a cylinder near a rigid plane boundary in a steady flow are studied experimentally. The phenomenon of vortex-induced vibrations of the cylinder near the rigid plane boundary is reproduced in the flume. The vortex shedding frequency and mode are also measured by the methods of hot film velocimeter and hydrogen bubbles. A parametric study is carded out to investigate the influences of reduced velocity, gap-to-diameter ratio, stability parameter and mass ratio on the amplitude and frequency responses of the cylinder. Experimental results indicate： （1） the Strouhal number （St） is around 0.2 for the stationary cylinder near a plane boundary in the sub-criti- cal flow regime; （2） with increasing gap-to-diameter ratio （eo/D）, the amplitude ratio （A/D） gets larger but frequency ratio （f/fn） has a slight variation for the case of larger values of eo/D（eo/D 〉 0.66 in this study）; （3） there is a clear difference of amplitude and frequency responses of the cylin- derbetween the larger gap-to-diameter ratios （e0/D 〉 0.66） and the smaller ones （e0/D 〈 0.3）; （4） the vibration of the cylinder is easier to occur and the range of vibration in terms of Vr number becomes more extensive with decrease of the stability parameter, but the frequency response is affected slightly by the stability parameter; （5） with decreasing mass ratio, the width of the lock-in ranges in terms of Vr and the frequency ratio （f/fn） become larger.

A new coupled map car-following model considering drivers' steady desired speed

Based on the pioneering work of Konishi et al., in consideration of the influence of drivers＇ steady desired speed ef/ect on the traffic flow, we develop a new coupled map car-following model in the real world. By use of the control theory, the stability condition of our model is derived. The validity of the present theoretical scheme is verified via numerical simulation, confirming the correctness of our theoretical analysis.

Steady motion and spiral patterns in typhoon

By using the equations describing typhoons in the atmosphere, the steady three-dimensional stream fieldand the corresponding pressure and temperature fields are obtained. The three-dimensional velocity fields construct anonlinear autonomuos system in the physical space. It is shown that the center of typhoon is a local minimum pressurewith positive vertical vorticity and horizontal convergence in lower levels and a local maximum pressure with negativevertical vorticity and horizontal divergence in the upper levels. Because there exits two saddle-focus points in the autnomous system, there exist the spiral patterns, in which the winds blow spirally in and out of the center in the lowerand upper levels in the Northern Hemisphere and cause the ascending motion near the center and dascending motionnear the edge, respectively . All these are in fair conformity with the observations. It implies that the rotation of earthand the viscosity of air play an important role in the spiral structure of typhoons.

POSITIVE STEADY STATES AND DYNAMICS FOR A DIFFUSIVE PREDATOR-PREY SYSTEM WITH A DEGENERACY

In this article, we consider positive steady state solutions and dynamics for a spatially heterogeneous predator-prey system with modified Leslie-Gower and Holling-Type II schemes. The heterogeneity here is created by the degeneracy of the intra-specific pressures for the prey. By the bifurcation method, the degree theory, and a priori estimates, we discuss the existence and multiplicity of positive steady states. Moreover, by the comparison argument, we also discuss the dynamical behavior for the diffusive predator-prey system.

A novel kind of multiple steady states characteristics in the dividing wall column

In this article, one kind of multiple steady states(MSS) phenomenon was investigated for a dividing wall column(DWC). The four-section model constructed in Aspen Plus was employed to simulate two DWC cases: mixture of n-hexane, n-heptane and n-octane;system of methanol, ethanol and n-propanol. It can be seen that there is a range of vapor split ratio in which multiple solutions of reflux ratio exist for fixed DWC configuration with the same feed and product streams. The width and the curve shapes of the MSS region, and the number of solutions change with the liquid split ratio. This MSS phenomenon was further explained using the component recovery around the prefractionator and the component recycling flow inside the DWC. This MSS phenomenon is helpful for DWC design by knowing the probable existence of multiple solutions in advance.

Realization of minute-long steady-state H-mode discharges on EAST

In the 2016 EAST experimental campaign,a steady-state long-pulse H-mode discharge with an ITER-like tungsten divertor lasting longer than one minute has been obtained using only RF heating and current drive,through an integrated control of the wall conditioning,plasma configuration,divertor heat flux,particle exhaust,impurity management,and effective coupling of multiple RF heating and current drive sources at high injected power.The plasma current（Ip - 0.45 MA） was fully-noninductively driven（Vloop 〈 0.0 V） by a combination of-2.5 MW LHW,-0.4 MW ECH and -0.8 MW ICRF.This result demonstrates the progress of physics and technology studies on EAST,and will benefit the physics basis for steady state operation of ITER and CFETR.