Gait speed and hospitalization among ambulatory hemodialysis patients: USRDS special study data

AIM:To assess the association of measured gait speed with hemodialysis(HD)patients’hospitalization,in conjunction with,and apart from,recent fall history.METHODS:Gait speed was measured by a standard protocol and falls during the past 12 mo were ascertained for a prevalent multi-center HD cohort(n=668)aged 20-92.Hospitalization during the past 12 mo was identified in the patient’s clinic records,and the first hospitalization after gait speed assessment(or the competing event of death)was identified in the 2013 United States Renal Data System Standard Analysis Files.RESULTS:Slow gait speed,defined as<0.8 m/s,characterized 34.7%of the patients,and 27.1%had experienced a recent fall.Patients with slow gait speed but without a history of recent falls were 1.79 times more likely to have been hospitalized during the past12 mo(OR=1.79,95%CI:1.11-2.88,P=0.02),and patients with slow gait speed and a history of recent falls were over two times more likely to have been hospitalized(OR=2.10,95%CI:1.19-3.73,P=0.01),compared with patients having faster gait speed and no recent fall history.Prospective examination of gait speed/fall history status in relation to first hospitalization(or death)incurred by the end of follow-up December 31,2011 also showed that slow gait speed was associated with these events in conjunction with a history of falls(HR=1.54,95%CI:1.04-2.30,P=0.03).CONCLUSION:The International Task Force on Nutrition and Aging reported that gait speed is a powerful predictor for older adults of adverse outcomes such as hospitalization.In our data,gait speed--apart from,as well as in conjunction with,recent fall history--was associated with HD patients’hospitalization for multiple causes.Gait speed may be a sensitive health indicator among HD patients across the age spectrum.

上跨中低速磁浮营业线的桥梁方案研究

鉴于运营过程中中低速磁浮营业线产生的电磁环境会对上跨桥梁结构以及施工设备或人员产生一定影响,同时二者交叉点附近的既有结构、构筑物、交通环境等会对上跨桥梁方案造成极大的制约。基于现有理论研究及实践结果,通过对长沙机场大道与长沙磁浮快线的交叉节点进行分析,确定了距离磁浮轨道的最小安全施工距离,制定了桥梁上跨方案并验证了该方案的科学性和可行性。通过在方案制定过程中对风险的控制和不利社会影响的规避、实施过程中的试验和监测以及运营过程中的反馈,归纳总结了上跨中低速磁浮营业线桥梁的主要影响因素以及切实可行的对策措施,以期为类似桥梁上跨方案提供参考。

The study on the shrink-fit multi-ring flywheel with fall-off function

Structural integrity of the flywheel of reactor coolant pump is important for safe operation of a nuclear power plant. A shrink-fit multi-ring flywheel is designed with a fall-off function, i.e., it will separate from the shaft at a designed fall-off rotation speed, which is determined by the assembly process and the gravity. However, the two factors are ignored in the analytical method based on the Lame's equation. In this work, we conducted fall-off experiments to analyze the two factors and used the experimental data to verify the validity of the analytical method and the finite element method(FEM). The results show that FEM performs better than the analytical method in designing the falloff function of the flywheel, though FEM cannot successfully predict the strain variation with the rotational speed.

Should gait speed be included in the clinical evaluation of Parkinson’s disease?

Background: The Unified Parkinson’s Disease Rating Scale is the most commonly used scale in the clinical study of Parkinson’s disease. However, it may fail to capture the essence of physical impairment in patients with Parkinson’s disease and thus limit responsiveness of care-givers, patients, and/or clinicians as to increasing physical disability. This study sought to compare subjective measures of physical disability in Parkinson’s disease to an objective, accurate, and proven measure of physical function-gait speed. Methods: Eighty-eight individuals with early to moderate stage Parkinson’s disease were evaluated on the Unified Parkinson’s Disease Rating Scale, the Parkinson’s disease Questionnaire 39 and during five 8 meter walking trials. Spearman correlations coefficients were used to determine the association among all variables of interest. Results: The findings demonstrate that only a fair to moderate relationship between objectively measured gait speed and physical function as measured subjectively by the clinical rating scale and as evaluated by the patients during self report. Conclusions: The results of this study suggest that commonly utilized measures of physical function in Parkinson’s disease are not highly correlated with gait speed. Because gait speed is demonstrated as a dependable proxy for physical function, the results of this study may provide a rational for the use of gait speed to provide a more accurate picture of physical function in patients with Parkinson’s disease.

In Community Dwelling Females Age 65 or Older, Gait Speed Declines as Kinesthetic Awareness of the Lower Legs Decreases

Purpose: This study investigates the existence of a correlation between the gait speed and kinesthetic sense in lower legs and to conduct further analysis of kinesthetic sense in relation to the risk of fall among community dwelling females aged 65 years or older. Materials and Methods: A non-experimental correlational, descriptive, and cohort study included 38 community dwelling females (average age of 82.5 years). The kinesthetic ruler (K-Ruler) and kinesthetic test protocol were created and used to assess lower extremity kinesthetic awareness. The GaitRite System was used to assess gait speed. Each subject was categorized into four groups: “LL” (Low K-Score and low gait speed), “LH” (Low K-Score and high gait speed), “HL” (High K-Score and low gait speed), and “HH” (High K-Score and high gait speed) according to kinesthetic awareness and gait speed measured. Voluntary fall incidence reporting over the 6-month period was followed by the initial data collection. Results: Pearson product-moment correlation (2-tailed) showed that there is a statistically significant, positive moderate-to-strong correlation between K-score and gait speed (ICC = 0.692, p Discussion: Gait speed declines as kinesthetic awareness of lower extremity decreases in community dwelling 65 or older female subjects. Additionally, the combination of kinesthetic awareness and gait speed can be served as a predictor of fall risk. The K-ruler can be used to assess lower extremity kinesthetic awareness in older people as a feasible and standard test.

旋翼驱动的微小型气动发电机

针对现有引信电源难以满足小口径、低落速弹药引信的使用需求,提出一种利用旋翼驱动的微小型气动发电机,该发电机与引信一体化集成设计,利用引信体上的旋翼作为驱动机构工作发电,具有结构紧凑,体积小等特点;经仿真分析及实验室吹风试验表明,该发电机体积不大于0.6 cm^(3),起动落速不大于25 m/s,在30 m/s落速下,输出电压大于7 V,电流大于3.5 mA,满足小体积、低落速弹药微功耗机电引信的使用需求。

A Study on Detection Method of Falling Symptoms

The purpose of this study is to prevent the occurrence of falls by defining the symptoms of falls and detecting them in advance. The focus of the study is on the specific definition of “Falling Symptoms”. In this regard, we conducted a questionnaire survey on people of different ages to obtain the state of themselves and their surroundings when they fell down. In addition, we used the elderly simulated experience kit to achieve the purpose of using young people to replace the elderly. Young people were asked to walk on different roads in different shoes with and without elderly simulated experience kit and photographed them with a high-speed camera to observe the changes of their muscles and joints. We also simulated the movement of center of gravity of the people with and without elderly simulated experience kit by a pressure distribution sensor mat.

Association between Daily Living Walking Speed and Lifestyle and Physiological Factors in Older, Female Pokémon GO Players

Background: Walking speed is a reliable barometer of adverse health outcomes, particularly among older people. Few studies evaluated factors associated with daily actual walking speed, rather than that measured in a laboratory setting or self-reported data. Methods: In a joint effort with The Pokémon Company, we recruited study participants through a women’s magazine and analyzed data from 63 Pokémon GO players. We measured the true walking speed in daily life among older women using a data-gathering mobile application. Then, using questionnaire survey data collected on these participants in 2019, we estimated the relationship between walking speed and their lifestyle and physiological factors. In the analysis, we employed a bi-directional stepwise linear regression approach, with the Akaike information criterion (AIC) for variable selection. Results: The mean age of the 63 participants was 63.03 years (standard deviation, SD 7.46);the average walking speed was 4.56 km per hour (SD 1.54);and 52 (82.5%) and 55 (87.3%) participants answered that they had excellent/good health physically and mentally, respectively. After adjusted for covariates in a stepwise regression approach, we identified a significant association between −1.33 (95% confidence intervals −2.52 to −0.15) km/hour lower walking speed and the experience of outdoor falls within a year. We also demonstrated that the walking speed was 1.07 (0.33 to 1.81) km/hour faster for those who had played Pokémon GO before the study started. Conclusions: The true walking speed in daily life among older women was measured by a data-gathering mobile application. Although all participants were women recruited on a voluntary basis with an understanding of the purpose of the study, and the surveys were conducted at a cross-sectional setting, a significant relationship with the experience of outdoor falls was demonstrated. We also present evidence suggesting a possible relationship between Pokémon GO play and faster walking speed.

高落速云雾爆轰的数值模拟

为了研究落速1000 m·s^(-1)条件下的燃料分散和爆轰过程,建立了燃料分散爆轰的计算仿真模型,以静态燃料分散及云雾爆轰实验结果作为数值方法进行了验证,分析了2 kg环氧丙烷燃料在高落速条件下分散爆轰的温度、压力随时间变化规律。结果发现:落速1000 m·s^(-1)条件下,数值模拟得到了云雾形态、浓度场随时间和空间的分布规律,云雾形态大致呈扇形,浓度随距离增加逐渐降低,最终达到稳定分布,云雾径向半径可达2.24 m,同时得到云雾爆轰过程及爆轰压力场、温度场的影响规律,起爆后形成弧形波阵面向外扩散且温度压力不断衰减。数值模拟结果与实验相吻合,为高落速云爆武器系统的安全设计提供了新途径。

低速冲击下混凝土板的能量耗散研究

针对混凝土板类构件在低速冲击作用下能量耗散的问题,采用落锤装置对6组混凝土板试件进行低速冲击试验。结合弹性力学理论计算了试件的弹性变形能,并通过能量守恒定律得出试件塑性变形能,分析了混凝土强度和落锤冲量对混凝土板破坏能量耗散的影响。结果表明:在低速冲击下混凝土板所吸收能量的98%都通过塑性变形能的方式消耗;混凝土强度不能完全决定受低速冲击混凝土板塑性变形能的耗能,混凝土板的塑性变形能随冲击能量的增大而增大,并呈现很好的线性关系。该研究可对提高混凝土板类构件在低速冲击作用下的防护能力提供参考,以供防护工程设计所需。

基于MATLAB的浅圆仓内玉米沉降运动特性分析

粮食进入浅圆仓后立即进行沉降运动,达到仓底后进行堆积运动,较高速度的粮食颗粒在堆积运动时会引起一系列的问题。从运动学角度分析了玉米颗粒在仓内的沉降运动,并使用MATLAB软件模拟了不同下落高度、初速度、粮堆组分及质量流量对颗粒沉降运动基本参数的影响。结果表明:当进粮初速度为0时,玉米颗粒历经3.45 s、沉降距离35.86 m达到最大速度即沉降速度14.51 m/s;当下落高度足够大时,玉米颗粒的下落速度增大到一定值后不再增加,开始匀速下落;玉米颗粒入仓时的初速度越大,会在更短的时间内达到沉降速度,加速段的沉降距离越小;粮堆的不同组分沉降速度不同,在相同时间内各种组分的下落距离不同;随着质量流量和下落高度的增加,颗粒群沉降时的诱导气流量不断增大,颗粒群沉降运动时的沉降速度低于单颗粒的。研究结果可为浅圆仓入仓清理工艺、辅助装置的设计、优化等提供理论依据。

不同水位下降速度对浸水土钉墙整体稳定性影响的分析

针对郑州2021年7月份突降特大暴雨,基坑几乎全部被雨水浸泡,抽排水速度对基坑的整体稳定性影响较大,速度过快会导致基坑失稳.本文通过一个实际基坑项目,计算基坑在不同水位下降速度下浸润线的位置,利用瑞典条分法计算基坑整体稳定性.研究表明:基坑内水位下降的过程中,坡体内部水渗出速度滞后于坡外水位下降的速度,会产生指向坡外的渗流力,影响基坑的稳定性.水位速度下降越快,浸润线越陡,基坑稳定性越差.

直流电机恒流制动和吊物落速动态控制方法研究

反抗性负载的快速制动与位能负载的落速控制对提高电机拖动装置的运行效率和安全具有重要意义。提出了一种由功率场效应管取代常规能耗制动电阻,通过压控方式在线调节其漏极与源极之间等效阻值实现直流电机全程恒流制动和吊物落速动态调节的方法。理论分析和实验结果表明,在无须改变硬件系统的条件下,该方法可将停车制动时间和吊物落速达到稳定的时间分别缩短为常规能耗制动方法的66.7%和33.3%,有效提高了电机拖动系统的动态工作效率以及控制系统的灵活性。

某煤粉锅炉大渣可燃物异常原因分析

某电厂300 MW亚临界机组出现了炉底烟花状落渣的现象,锅炉大渣可燃物含量达到20%以上,严重影响了锅炉运行的安全性与经济性。通过对大渣中可燃碳形态及粒径分布分析,结合中速磨煤机煤粉取样细度筛分及形态分析,认为是中速磨运行不正常导致的该现象。通过检查磨煤机内部,发现中央落煤管出现破损。修补该破损后锅炉炉底烟花状落渣现象消失,锅炉大渣可燃物含量降低到1%左右。建议电厂中速磨的日常维护中,除了要对磨辊、分离器挡板、风环部件进行检查维护,还应定期检查中央落煤管磨损情况。当电厂燃用可磨指数较低的煤种时,建议提高中速磨中央落煤管钢材耐磨等级或贴耐磨瓷片等,以避免中央落煤管的磨损。该研究结果可为国内其他锅炉同类问题解决提供参考。

水位变动速度对某库区岸坡堆积体稳定性的影响

水位变动期间库区岸坡堆积体渗流场及稳定性的变化是一个动态过程,如何评价水位变动速度对堆积体稳定性的影响是工程上一个重要课题。采用有限元计算与刚体极限平衡分析相结合的方法,探讨了水位变动速度对堆积体渗流场及稳定性的影响机理和规律,研究成果表明,水位变动速度对堆积体在水位变动期间瞬时渗流场有着较大的影响,较大水位上升速度对堆积体稳定性有利,但水位下降速度增大对堆积体稳定性不利,水位下降速度由0.5增大至5 m/d,堆积体稳定性系数可降低15%～20%,水位下降期间堆积体危险水位往往出现在堆积体坡脚以上1/3～1/5坡高处。

步进电动机升降速曲线的设计

为了保证步进电动机不丢步,必须使步进电动机的输出力矩大于负载转矩,同时要保证步进脉冲一定的宽度,因此选择合理的升降速曲线十分重要。针对这个问题,介绍了三种不同的步进电动机升降速曲线设计方法,并根据不同的设计方法对步进电动机的升降速过程进行处理。

水质变化对煤泥水絮凝沉降的影响

以高浓度难沉降煤泥水为研究对象,进行了水的pH、硬度对不同类型絮凝剂沉降澄清效果的影响研究。结果表明:非离子型聚丙烯酰胺在煤泥水pH为9,阳离子型聚丙烯酰胺和阴离子型聚丙烯酰胺在pH为5左右时絮凝沉降效果较好;非离子型聚丙烯酰胺、阳离子型聚丙烯酰胺、阴离子型聚丙烯酰胺在水质硬度分别为17.8,53.4,71.2 mmol/L时絮凝沉降效果较好。

基于非线性时间序列法研究人体步行稳定性

目的应用非线性时间序列分析方法,研究健康老年与青年志愿者的步行稳定性,为更全面评估人体的动态平衡、预测跌倒风险提供重要依据。方法应用VICON运动捕捉系统,采集肌骨系统健康志愿者(7名老年和10名青年)在不同步速(80%、100%1、20%自然步速)下的运动学数据,提取志愿者在30个连续步态周期中,第7颈椎和第10胸椎在前后和左右方向上的位移,以及下肢各关节屈曲伸展和外展内收运动角度,计算位移和运动角度变化的最大Lyapunov指数,比较分析老年与青年组之间步行稳定性差异,以及步速对人体步行稳定性影响。结果青年组步行稳定性优于老年组,并在某些运动节段呈现显著性差异(P<0.01);老年和青年的步行稳定性随步速增加而降低(P<0.05)。结论应用非线性时间序列分析方法中的最大Lyapunov指数,能有效并定量地评测人体步行中各运动节段的稳定性。

霰粒子下落速度对云系及降水发展影响的数值研究

云和降水的形成是动力过程与微物理过程相互作用的产物,云数值模式中的微物理过程参数化方案对云和降水发展过程有直接影响。在云数值模式中,粒子群体的下落速度都是用质量加权下落末速度公式来表达,而且不同的模式采用的公式存在差异,质量加权下落末速度中参数取值不同,引起的粒子下落末速度不同。为了了解粒子下落末速度变化对云系和降水发展的影响,对2004年8月12日一次冷锋降水过程,利用中尺度ARPS模式做模拟研究。在分析降水机制的基础上,对霰这一下落末速度较大的降水粒子,做下落末速度(Vg)的敏感性试验,从动力、热力、微物理的角度,通过数值模拟对比分析了霰下落末速度减小对降水分布和强度、云系的移动、云系的宏观热力和动力场的影响,并给出了影响的途径和机理。结果表明:Vg变化对云的厚度和含水量有影响,下落末速度减小对冰晶、雪、霰的含水量垂直分布及分布随时间变化影响较大,其中,霰的含水量显著减少,雪的含水量增加,并调整了云中水质粒的空间分布;Vg减小对地面累积总降水量的分布影响较小,但对降水强度的分布影响较大。Vg减小时,降水强度减小,降水时间延迟,因此,霰下落末速度变化将调整底层降水分布;对于云系的移动情况基本上没有影响,但对云中水质粒的空间分布有影响;霰下落末速度变化影响云中霰的融化和撞冻增长从而影响热力场。末速度减小时,霰和雪的融化量明显减小,导致非绝热冷却率的减小,引起下沉气流的减小。

采煤机多参数耦合匹配优化智能降尘控制研究

为实现对采煤机截割煤岩过程中粉尘质量浓度的最优控制,开发一种基于多参数耦合匹配优化的采煤机智能降尘控制方法。以最低粉尘质量浓度为目标,以牵引速度、滚筒转速以及截割深度为变量,建立采煤机最优降尘控制的多参数耦合优化匹配模型;采用迭代优化方法,结合优化终止判定条件,得到最低产尘量时的采煤机多工作参数优化结果。采用综采面3机配套模型进行截割控制与测试试验。结果表明,在采煤机多参数迭代优化过程中,粉尘质量浓度快速下降收敛,优化前后粉尘质量浓度分别为632和158 mg/m3,降尘效率达到75%。