A New Fractional Model for the Falling Body Problem

Recently, a conformable fractional derivative has been proposed to calculate the derivative of non-integer order of time functions. It has been shown that this new fractional derivative definition obeys many advantages over the preceding definitions. For mathematical models in applied sciences and to preserve the dimensionality of the physical quantities, an auxiliary parameter （~r） which has the dimension of seconds should be implemented in the fractional derivative definition. We obtain analytic solutions for the resulting conformable fractional differential equations describing the vertical velocity and the height of the falling body. It is shown that the dimensions of velocity and height are always correct without any restrictions on the auxiliary parameter cr which contradicts with the results in the literature when applying the Caputo definition to the same problem. This may open the door for many future works either to describe the role of such an auxiliary parameter or to derive a more suitable definition for the fractional derivative.

Optimal control of nonholonomic motion planning for a free-falling cat

The nonholonomic motion planning of a free-falling cat is investigated. Nonholonomicity arises in a free-falling cat subject to nonintegrable angle velocity constraints or nonintegrable conservation laws. When the total angular momentum is zero, the motion equation of a free-falling cat is established based on the model of two symmetric rigid bodies and conservation of angular momentum. The control of system can be converted to the problem of nonholonomic motion planning for a free-falling cat. Based on Ritz approximation theory, the Gauss-Newton method for motion planning by a falling cat is proposed. The effectiveness of the numerical algorithm is demonstrated through simulation on model of a free-falling cat.

Numerical Simulation of the Water Entry of a Structure in Free Fall Motion

To solve the problems concerning water entry of a structure, the RANS equations and volume of fluid （VOF） method are used. Combining the user-defined function （UDF） procedure with dynamic grids, the water impact on a structure in free fall is simulated, and the velocity, displacement and the pressure distribution on the structure are investigated. The results of the numerical simulation were compared with the experimental data, and solidly consistent results have been achieved, which validates the numerical model. Therefore, this method can be used to study the water impact problems of a structure.

Effects of Degrees of Motion Freedom on Free-Fall of A Sphere in Fluid

Free-fall of a sphere in fluid is investigated at a Galileo number of 204 by direct numerical simulations(DNS). We mainly focus on the effects of different degrees-of-freedom(DOFs) of the sphere motion during free-fall. The characteristics of free-fall are compared with those of flow past a fixed sphere. Additional numerical tests are conducted with constraints placed on the translational or rotational DOFs of the sphere motion to analyze different DOFs of sphere motion. The transverse motion contributes significantly to the characteristics of free-fall; it results in the retardation of the vortex shedding, leading to the decrease of the Strouhal number. In addition, the transversal sphere motion exhibits the tendency to promote the sphere rotation. On the contrary, the effects of the sphere rotation and vertical oscillations during free-fall are negligible.

Experiment and Numerical Simulation of Free Water Jet by a Central-body Nozzle

The recent research about cavitation jet mainly focuses on the organ-pipe nozzle and triangular nozzle. The research content mainly includes the optimized design about the structure of nozzles, the observation and flow analysis about the cavitation jet in the water, and the theory of rock attacked by the cavitation jet, while the energy characteristic of the free jet is not studied yet. In China, the research about the central-body nozzle is almost empty. For the purpose of studying the energy characteristic and the structure of free water jet discharged from central-body nozzle, an experiment with phase Doppler particle anemometry（PDPA） technology is carried out to measure the free water jet flow, which is produced by a central-body nozzle under the jet pressure of 15 MPa. While five sections with different axial distances from the nozzle outlet are selected for data process and analysis, the axial and radial velocity and the droplets of the particle size are studied. Meanwhile, numerical calculation of corresponding flow field is conducted by using volume of fluid（VOF） multiphase model, and the jet flow feature is discussed. The experimental and calculating results show that the axial velocity of high speed jet flow dissipates slowly in the air, and the core area and diffused area are discovered. The diameter of droplet in the core area is small, and jet energy is concentrated, while in the diffusion area, water is mingled with ambient air and radial velocity is relatively large. Obvious low-pressure area exists behind the central body and potential cavitation may occur in that area. The proposed research reveals the energy characteristic of free jet discharged from central-body nozzle, provides the theoretical basis for preestimating erosion feature of the central-body nozzle and also the theoretical foundation for revealing the mechanism of erosion.

AN EFFICIENT ITERATION ALGORITHM OF MIXED BOUNDARY/FINITE ELEMENT METHOD AND APPLICATION TO FREE TORSIONAL VIBRATION ANALYSIS OF BODIES OF REVOLUTION

In this paper, the general formulation of anew proposed iteration algorithm of mixed BEM/FEM for eigenvalue problems of elastodynamics is described. Approximate fundamental solutions of elastodynamics are adopted in the normal mixed BEM/FEM equations. The accuracy of solutions is progressively improved by the iteration procedure. Not only could the awkwardness of non-algebraic eigenvalue equations be avoided but also the accuracy of numerical solutions is almost independent of the interior meshing. All these give many advantages in numerical calculation. The algorithm is applied to free torsional vibration analysis of bodies of revolution. A few cases are studied. All of the numerical results are very good.

Salsa Dance Could Improve Effectively to Body Balance in Elderly with Risk of Falls

Currently the number of elderly in Indonesia tends to increase. Based on 2014 Susenas data, the number of elderly in Indonesia reaches 20.24 million people (8.03%). One of the most common physical disorders in the elderly is disruption of the body’s balance and risk to falls. The risk of falling in the elderly can be prevented by doing physical exercise in the form of Salsa dance. Salsa dance has movements that can improve stability, flexibility, mobility and body balance. This study aims to analyze the effectiveness of Salsa dance on body balance in the elderly. The research method used quasi-experimental with the pre test-post test design control group. As many as 70 elderly who experienced balance disruption in the Puskemas Sarijadi had participated in this study. The sample was taken by using consecutive sampling, then divided equally between the control group and the intervention group. The instrument used to measure elderly balance is Short Physical Performance Battery (SPPB). Data analysis is carried out in two stages, namely univariate analysis using the mean, standard deviation, maximum value and minimum value and percentage;then followed by bivariate analysis using the Wilcoxon signed rank test and independent T test. The result shows that there are differences in the balance of the elderly before and after the intervention in the treatment group, whereas in the control group there were no significant differences. Therefore, it can be concluded that Salsa dance can significantly improve elderly body balance, especially if done regularly. The increase will appear significant after the intervention carried out for 10 and 20 times. It is suggested that nurses utilize Salsa dance as an alternative in dealing with symptoms of body balance disorders in the elderly. This intervention can be implemented along with other activities of the elderly in community centre health services.

An Analysis of Milton＇s Free Will Defense From the Two Falls in Paradise Lost

Paradise Lost is a great epic written by John Milton. Deeply influenced by Christian Humanism, Milton fully shows his free will defense in Paradise Lost. Based on the text of Paradise Lost, this paper mainly analyzes the causes of Milton＇s free will defense, his pursuit for free will shown in the two falls in the work： Satan＇s fall and Adam and Eve＇s fall. This paper also discusses the practical meaning of free will defense in Paradise Lost： it reveals his grief and anger of the failure of England revolution and shows the idea that people don＇t have the freedom to interfere or destroy other people＇s free will.

Age and Gender Depending Growth of Feathers and Feather-Free Body in Modern Fast Growing Meat-Type Chickens

Two growth experiments with fast growing meat type chickens (Ross 308) were conducted to assess the growth of feathers and feather-free body dependent on age and gender (male:female ratio = 1:1). Birds were reared under uniform management and feeding conditions (floor pens;15 pens per gender;5 birds per pen) during the starter (day 1 to 22) and grower period (day 22 to 36). Diets were based on corn, wheat, soybean meal, soybean protein concentrate and balanced with feed amino acids to ensure an equal feed protein quality close to the ideal amino acid ratio by a constant mixture of the feed proteins. At start of the experiment and further on weekly up to the end of the 5th week, 15 birds per gender (each 3 pens of 5 birds) were selected and 24 h fasted before quantitative de-feathering. Both feather and feather free body fractions were significantly increased with increasing age of the birds (p < 0.001). Feather percentage as related to the empty body weight increased non-linearly from approximately 2% at the end of the first week to about 4% at the end of the experiment. Feather percentage and dry matter content of the feather-free body was significantly higher in female birds (p < 0.001) as compared to males. Further investigations will show how this varying proportions impact on nutrient deposition of modern meat-type chickens dependent on age and gender, respectively.

基于无废企业工业废料充填体强度与材料配比优化研究

为了构建无废企业,某煤电一体化企业采用连采连充式充填来循环再利用其生产的工业废弃物。结合充填工艺特点,以矸石和炉渣为骨料,粉煤灰、石膏、水泥和电厂废水配成的浆液为胶结材料,用DPS数据处理系统建立回归模型,通过方差分析与响应曲面分析法分析双因素交互作用下对充填体强度影响。研究结果表明,石膏水泥比与矸石浆液比交互作用影响最大,其次是粉煤灰水泥比与矸石浆液比的交互作用,石膏水泥比与粉煤灰水泥比交互作用影响最小。根据优化结果得到最终配比为石膏水泥比0.1,粉煤灰水泥比0.35,矸石浆液比2.9,以此参数得到充填体试验最终强度为5.21 MPa,其相对误差小于5%。研究结果可为无废企业的废弃物的循环再利用提供借鉴。

江苏省部分地区成年人脂肪质量分布特征分析

目的:探究江苏省部分地区不同性别成年人脂肪质量随年龄增长的变化情况以及不同年龄段人群体质量指数(body fat index,BMI)和脂肪质量之间的关系。方法:收集2019年9月至2021年2月江苏省南京市、淮安市以及无锡市的体检人群数据,对符合纳入标准人群进行体格检查和体成分检测,并分析其脂肪质量随年龄变化情况。结果:共收集2115名志愿者的基本信息,排除信息不全者46名,共纳入2069名进行研究分析。30岁以上成年人去脂体质量(fat free mass,FFM)随着年龄的增长呈现下降的趋势;30岁以上成年人的体脂肪量(body fat mass,BFM)、体脂百分比(percentage of body fat,PBF)、腰臀比(waist-hip ratio,WHR)和体脂指数(fat mass index,FMI)随着年龄的增长均呈现上升趋势,BFM、PBF和去脂体质量百分比(percentage of fat free mass,PFFM)在40岁出现显著上升,FFM和去脂体质量指数(fat free mass index,FFMI)在60岁开始出现显著下降。男性FMI在40岁出现显著上升,女性FMI从60岁出现显著上升。全年龄段成年人FFM随着BMI和腰围水平的升高呈上升趋势。结论:随着年龄的增长男性和女性的BFM、PBF和WHR均呈现上升趋势。各年龄段成年男性FFM显著高于女性,女性BFM、FMI、PBF和内脏脂肪面积显著高于男性。全年龄段成年人FFM随着BMI和WHR升高呈上升趋势。

明渠自由跌水水力特性及其在流量计量上的应用

【目的】明渠跌水作为衔接渠道上下游水流的有效设施,可应用于明渠流量计量,通过简单测量跌坎断面水深即可实现渠道流量的精确计量。为研究明渠自由跌水水力特性及其在流量计上的应用,【方法】采用分析对比法将国内外明渠自由跌水的研究成果进行整理,从自由跌水水力特性、跌水量水试验研究及理论研究3个方面进行了对比分析,【结果】发现明渠自由跌水水力特性的研究多集中在跌坎断面压力分布;明渠跌水量水试验研究集中在he/hc的影响因素(渠道底坡S、糙率n、渠道宽度、渠道断面形式、弗劳德数等),该值可基于能量方程、动量方程、N-S方程及其他数值模拟方法得出。【结论】结果表明:试验中he/hc值在矩形渠道中基本是一个常数,但其他断面形式的渠道中该结论未得到验证;该值与明渠底坡S和糙率n有关,底坡方面的研究主要集中在缓坡(S=0.002 6~0.097 3)渠道,陡坡研究较少而平坡研究更少,糙率n的研究范围在0.009 3~0.045 0,但实际工程中n值变化较大。因此有必要在其他形式渠道上对he/hc值做进一步验证,并在更大范围内研究he/hc值与底坡S和糙率n的关系,这样更有利于明渠跌水量水技术的推广和应用。

人体成分与脂肪细胞因子在妊娠期糖尿病患者中的关系研究

目的:探讨妊娠期女性的人体成分与脂肪细胞因子在妊娠期糖尿病(GDM)风险之间的关系。方法:选择本院常规产前检查单胎自然受孕GDM孕妇90例为GDM组,另选择同期单胎正常妊娠孕妇219例为对照组(NGT组)。在妊娠24~28周时,用生物阻抗法测定其人体成分。分析孕前体质量指数(BMI)、体脂百分比(FMP)、去脂体质量百分比(FFMP)、细胞外液/细胞内液(ECW/ICW)、体脂指数(FMI)等人体成分与GDM的关系。所有入组孕妇同期采用酶联免疫吸附法(ELISA)检测循环脂联素、脂肪酸结合蛋白4(FABP4)、瘦素以及空腹胰岛素(FINS)水平,并分析其与人体成分各指标的关系。结果:①GDM组脂联素低于NGT组,而瘦素高于NGT组(P<0.05)。②GDM组FMP、ECW/ICW、FMI显著高于NGT组(P<0.05),单因素回归分析显示孕前BMI、FMP、FMI、ECW/ICW是GDM的危险因素(OR>1,P<0.05)。而多因素分析显示仅FMP升高与GDM发病风险显著相关,是其发病的独立危险因素(OR>1,P<0.05),FFMP、MP、PP、M/F是GDM的保护因素(OR<1,P<0.05)。③GDM组,胰岛素抵抗指数(HOMA-IR)与FMI呈正相关(r>1,P<0.05),与PP呈负相关(r<1,P<0.05)。④ROC曲线显示,孕前BMI、FMP、ECW/ICW、FMI对GDM的诊断价值相似,孕前BMI、FMP和FMI相比差异无统计学意义(P>0.05),但略优于ECW/ICW(P<0.001)。结论:妊娠期的人体成分与患GDM的风险有关。FMP升高与发展为GDM的风险增加有关,FMP越高,GDM的风险越高。孕前BMI、FMP、FMI对GDM的诊断效能相似。

基于有限元柔性体理论的起落架落震仿真分析

以某飞机起落架为研究对象,研究落震动力学问题。根据前起落架的结构特性,利用多体动力学建模技术,建立前起落架多柔性体动力学(MFBD)模型,并进行落震仿真分析及非线性接触研究。采用落震试验数据对模型进行校验,仿真结果与试验数据较为吻合。通过分析缓冲器零件的变形,考虑接触因素的多柔体动力学模型能更真实反应实际情况,以最大降落速度工况进行落震仿真,同时对起落架关键零件进行强度校核,以及缓冲器内部零件进行非线性接触计算,求得不同材质的下凸轮及底托受到的垂向力与摩擦力,获得在物理试验中难以测量的数据,分析结果对起落架设计具有重要意义。

绝对重力仪落体光心质心距调校方法研究

为了最小化激光干涉式绝对重力仪中落体旋转引入的重力加速度测量误差,提出了一种基于落体悬吊的光心质心间距调校方法,结合落体的外部结构,搭建了一套简易高效的落体调校装置。该装置采用光电自准直仪测量落体悬吊状态下的俯仰角,可实现对落体质心位置的高准确度调节,进而完成对落体光心质心距的调校。对装置的测量不确定度进行了评估,得到落体光心质心距测量的合成标准不确定度为18.85μm。最后在NIM-3A型绝对重力仪上进行实验验证。结果表明,悬吊法调校落体的光心质心距优于20μm。若落体旋转角速度控制在0.02 rad/s以内,则落体引入的重力加速度的误差优于1μGal。

自落式贯入仪率相关系数标定方法

自落式贯入仪(free-falling penetrometer,FFP)作为一种新型地质勘察技术,可以高效快速地获取海底沉积物的力学性质参数。FFP贯入过程中锥尖阻力受贯入速率影响,数据处理时需借助速率因子将动贯入阻力转化为与静力触探试验(cone penetration test,CPT)等效的准静态贯入阻力,但目前速率因子中的率相关系数尚无明确测试方法。基于牛顿运动定律对率效应进行理论分析,并利用南海北部陆坡淤泥质沉积物开展室内贯入试验;并采用对数函数和幂次函数拟合锥尖阻力与贯入速率关系,提出了自落式贯入仪率相关系数的标定方法。研究结果表明,释放高度和探头质量都会影响最终贯入深度,但贯入过程中的锥尖阻力变化受探头质量影响较小,提出的率相关系数标定方法能够更准确获取FFP贯入的率相关系数。在实际应用中可采用室内试验标定的系数修正原位试验数据,为FFP实际应用提供技术支持。

全身振动训练改善脑卒中后跌倒风险的Meta分析

目的:系统评价全身振动训练对脑卒中后跌倒风险的临床疗效。方法:检索公开发表的关于全身振动训练治疗脑卒中后跌倒风险的随机对照试验文献,并用RevMan 5.4软件进行Meta分析。结果:研究共纳入21篇文献,共计1093例患者。经Meta分析发现,与传统康复组相比,全身振动训练可以改善脑卒中后“起立-行走”计时测试(TUGT)[WMD=-1.77,95%CI(-2.69,-0.86),P=0.0001]、改良Ashworth量表(MAS)[WMD=-0.33,95%CI(-0.41,-0.25),P<0.0001]情况,而对于特异性活动平衡信心量表没有影响[WMD=1.14,95%CI(-1.99,4.27),P=0.48]。亚组分析显示,全身振动训练可显著改善脑卒中后亚急性期MAS评分[WMD=-0.38,95%CI(-0.47,-0.30),P<0.00001],而对后遗症期无明显改善[WMD=-0.08,95%CI(-0.26,0.10),P=0.36]。结论:全身振动训练对脑卒中后TUGT、痉挛有积极影响,有助于降低跌倒风险,而对跌倒恐惧心理无显著作用。在亚急性期进行全身振动训练,可能会更好地改善脑卒中后患者的痉挛障碍。

低氧暴露与减控体重效果的元分析

目的:评价低氧暴露对减控体重的影响效果,提供最优的减控体重方案。方法:在数据库中检索建库至2023年10月的所有文献,使用偏倚风险评估工具评价纳入文献质量。使用Stata14.0进行异质性检验、效应量合并、敏感性分析以及发表偏倚检验。结果:共纳入49篇RCT文献,1 392名被试者;相对于常氧暴露,低氧暴露对减轻体重(SMD=-0.18,95%CI[-0.29,-0.07],P<0.01)、降低体脂肪(SMD=-0.23,95%CI[-0.35,-0.18],P<0.01)的优势明显。相对于常氧暴露,低氧暴露对去脂体重(SMD=-0.05,95%CI[-0.22,0.13],P>0.05)、肌肉质量(SMD=0.01,95%CI[-0.20,0.21],P>0.05)、身体水分(SMD=-0.12,95%CI[-0.48,0.23],P>0.05)的改善无明显效果。调节变量结果:低氧暴露对成年群体的体重减轻(SMD=-0.21,95%CI[-0.35,-0.08],P<0.01)、体脂肪降低(SMD=-0.28,95%CI[-0.42,-0.13],P<0.01)具有显著效果。低氧暴露对男性和女性的体重减轻、体脂肪降低均具有显著效果。低氧环境下,不控制饮食对体重减轻(SMD=-0.23,95%CI[-0.37,-0.09],P<0.01)、体脂肪降低(SMD=-0.33,95%CI[-0.49,-0.18],P<0.01)的效果明显;控制饮食和未控制饮食对去脂体重、肌肉质量、身体水分的影响无明显差异(P>0.05)。低氧环境下,与消极暴露相比,积极暴露时体重减轻(SMD=-0.19,95%CI[-0.31,-0.07],P <0.01)、体脂肪降低(SMD=-0.26,95%CI [-0.38,-0.14],P<0.01)的效果明显;消极暴露和积极暴露对去脂体重、肌肉质量、身体水分的影响无明显差异(P>0.05)。结论:与常氧暴露相比,低氧暴露对减体重和降体脂具有明显优势;低氧暴露对成年男性和成年女性的体重具有明显改善效果,也有效改善成年男性的体脂率;低氧暴露期间,暴露方式和饮食干预影响减控体重的效果,积极低氧暴露、自由饮食对体重和体脂肪的改善效果明显。

下肢肌力的跌倒风险预测的方法研究

分析人体行走和跌倒时下肢肌肉的作用,确定对行走稳定性有主要影响的肌肉,为跌倒预测和信号采集位置提供依据。首先建立了一个人体骨骼肌模型,并使用Vicon三维红外动作捕捉分析系统和AMTI三维测力台采集记录模拟行动不便人群的步态、向后摔倒和向前摔倒的实验数据;然后运用逆运动学分析、静态优化算法,通过OpenSim仿真软件计算出步行和跌倒时下肢冗余肌力分配;最后对数据进行分析。研究结果表明:通过仿真模型定量分析了步行和跌倒过程中下肢肌力分布,量化步行以及跌倒过程中下肢各单块肌肉力量的变化规律,得出采集肌电信号较为合适的位置为股外侧肌和比目鱼肌,并为预测跌倒以及康复指导提供了生物力学依据,为进一步揭示髋、膝、踝关节的生物力学特性和人体下肢康复机器人的设计奠定基础。

从肝“体阴而用阳”论治体位性低血压

肝“体阴而用阳”是对肝之生理功能与病理变化的高度概括。肝主藏血,其体为阴,肝主疏泄,其用为阳,知晓肝“体阴而用阳”的特性,有助于临床诊疗。体位性低血压(postural hypotension,PH)的病因多为有效循环血容量减少、体循环血管阻力降低、长期处于炎热环境、长时间站立。在肝“体阴而用阳”理论的指导下,从“体阴亏虚”“用阳不足”“肝胆火盛”“肝肾阴虚”4个方面来阐述p H。治疗上以气、血、阴、阳为纲,采取“补肝体”“调肝用”“清肝利胆”“滋养肝肾”等治法,进而为中医治疗pH提供新的临床思路。