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.

A Study on the Transmission Dynamics of the Omicron Variant of COVID-19 Using Nonlinear Mathematical Models

This research examines the transmission dynamics of the Omicron variant of COVID-19 using SEIQIcRVW and SQIRV models,considering the delay in converting susceptible individuals into infected ones.The significant delays eventually resulted in the pandemic’s containment.To ensure the safety of the host population,this concept integrates quarantine and the COVID-19 vaccine.We investigate the stability of the proposed models.The fundamental reproduction number influences stability conditions.According to our findings,asymptomatic cases considerably impact the prevalence of Omicron infection in the community.The real data of the Omicron variant from Chennai,Tamil Nadu,India,is used to validate the outputs.

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.

A MOVING WATER EQUILIBRIA PRESERVING NONSTAGGERED CENTRAL SCHEME ACHIEVED VIA FLUX GLOBALIZATION FOR THE RIPA MODEL

In this paper,we propose a second-order moving-water equilibria preserving nonstaggered central scheme to solve the Ripa model via flux globalization.To maintain the moving-water steady states,we use the discrete source terms proposed by Britton et al.(J Sci Comput,2020,82(2):Art 30)by incorporating the expression of the source terms as a whole into the flux gradient,which directly avoids the discrete complexity of the source terms in order to maintain the well-balanced properties of the scheme.In addition,since the nonstaggered central scheme requires re-projecting the updated values of the nonstaggered cells onto the staggered cells,we modify the calculation of the global variables by constructing ghost cells and alternating the values of the global variables with the water depths obtained from the solution through the nonlinear relationship between the global flux and the water depth.In order to maintain the second-order accuracy of the scheme on the time scale,we incorporate a new Runge-Kutta type time discretization in the evolution of the numerical solution for the nonstaggered cells.Meanwhile,we introduce the"draining"time step technique to ensure that the water depth is positive and that it satisfies mass conservation.Numerical experiments verify that the scheme is well-balanced,positivity-preserving and robust.

Averaged Dynamics of Fluids near the Oscillating Interface in a Hele-Shaw Cell

The steady flow in a Hele-Shaw cell filled with fluids with a high viscosity contrast in the presence of fluid oscillations is experimentally studied.The control of oscillatory dynamics of multiphase systems with interfaces is a challenging technological problem.We consider miscible(water and glycerol)and immiscible(water and high-viscosity silicone oil PMS-1000)fluids under subsonic oscillations perpendicular to the interface.Observations show that the interface shape depends on the amplitude and frequency of oscillations.The interface is undisturbed only in the absence of oscillations.Under small amplitudes,the interface between water and glycerol widens due to mixing.When the critical amplitude is reached,the interface becomes unstable to the fingering instability:Aqueous fingers penetrate the high-viscosity glycerol and induce intensive mixing of miscible fluids and associated decay of the instability.After the disappearance of the fingers,the interface takes a U-shape in the central part of the cell.A similar effect is observed for immiscible fluids:The oscillating interface tends to bend to the side of a high-viscosity fluid.Again,when the critical amplitude is reached,the fingering instability arises at the convex interface.This paper focuses on the causes of bending of the initially undisturbed interface between miscible or immiscible fluids.For this purpose,we measure the steady flow velocity near the interface and in the bulk of a high-viscosity fluid using Particle Image Velocimetry(PIV).

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.

Numerical Study of a Three-Dimensional Laminar Flow in a Rectangular Channel with a 180-Degree Sharp Turn

This study presents a numerical analysis of three-dimensional steady laminar flow in a rectangular channel with a 180-degree sharp turn. The Navier-Stokes equations are solved by using finite difference method for Re = 900. Three-dimensional streamlines and limiting streamlines on wall surface are used to analyze the three-dimensional flow characteristics. Topological theory is applied to limiting streamlines on inner walls of the channel and two-dimensional streamlines at several cross sections. It is also shown that the flow impinges on the end wall of turn and the secondary flow is induced by the curvature in the sharp turn.

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。

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。

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.

ANALYTICAL SOLUTION OF AXIAL SYMMETRICAL WALL TEMPERATURE DISTRIBUTION FOR HOLLOW CYLINDER

Using the variable transformation method,the formulae of the axial symmetrical wall temperature distribution during steady heat conduction of a hollow cylinder are derived in this paper.The wall temperature distribution and the wall heat flux distribution in both axial and radial direction can be calculated by the temperature distribution of the liquid medium both inside and outside the cylinder with temperature changing in axial direction.The calculation results are almost consistent with the experience results.The applicative condition of the formulae in this paper consists with most of practice.They can be applied to the engineering calculation of the steady heat conduction.The calculation is simple and accurate.

Numerical prediction of the long- term soil temperature variations around shallowsections of cross-river road tunnels

Considering the coupled heat transfer effect induced by parallel cross-river road tunnels, the long-term soil temperature variations of shallow sections of cross-river tunnels under the river beach are predicted using the finite difference method for numerical simulation. The boundary conditions and the initial values are determined by in situ observations and numerical iterations.The simulation results indicate that the ultimate calculated steady heat transfer time is 68 years, and most of the heat transfer is completed in 20 years.The initial constant temperature soil surrounding the tunnels is transformed to an annually variable one.An obvious temperature-varying region of the surrounding soil is discovered within 5 m from the tunnel exterior, as well as within the entire range of soil between the two tunnels.The maximum temperature increase value reaches 7.14 ℃ and the maximum peak-to-valley value of annual temperature increase reaches 10 ℃.The temperature variation of soils surrounding tunnels below 10 m is completely controlled by the heat transfer from the tunnels.The coupled heat transfer effect is confirmed because the ultimate steady temperature of soil between the two tunnels is higher than the ones along other positions.Moreover, the regression model comprising a series of univariate functions is proposed for the annual soil temperature fluctuation estimation for the locations varied distances around the tunnel.This investigation is beneficial to gain an insight into the long-term variation tendencies of local engineering geological conditions of the river beach above shallow sections of the cross-river road tunnels.

1980年代“文化热”的知识谱系与意识形态(下)

四、"文化"的位置认为这三个核心文本提供了三种叙事,并不是要强调彼此之间的差异有多大,相反,这些叙事之所以能够成立并以"文化热"的形式产生广泛的社会影响,正因为它们分享着统一的话语逻辑和历史想象,其核心在"文化"与"现代化"及其相互关系的理解。在很长的时间当中,人们对这两个80年代的关键词一直保持着与历史当事人同样的理解方式。

S_Schema及其关系映射方法

本文根据 W3C最新提出的 XML Schema规范,提出了一种等价于 XML Schema的数据模型S-Schema,并实现了S-Schema到关系模式的生成算法和XML文档到关系数据库的加载算法。实验证明,S-Schema方法在数据转储过程中的信息保持、映射后的查询更新操作等方面的综合性能要优于文本、Xparent方法。

Research on the soft start-up performance of hydro-viscous drive

The principle and structure of hydro-viscous drive(HVD) set is introduced. Through theoretical analysis of the HVD set start-up steadiness, the conclusions were obtained that the non-linearity of the pressure performance curve and dynamic pressure instability of the pilot-operated electro-hydraulic pressure relief valve, which is used for the HVD speed regulating purpose and usually works within micro flow-rate and low oil pressure state, are the main causes of the poor start-up steadiness. So a special speed regulating valve for HVD set is developed, with which the start-up steadiness of HVD set is much improved.

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。

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.

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。