Hamiltonian system for the inhomogeneous plane elasticity of dodecagonal quasicrystal plates and its analytical solutions

A Hamiltonian system is derived for the plane elasticity problem of two-dimensional dodecagonal quasicrystals by introducing the simple state function. By using symplectic elasticity approach, the analytic solutions of the phonon and phason displacements are obtained further for the quasicrystal plates. In addition, the effectiveness of the approach is verified by comparison with the data of the finite integral transformation method.

E-Cervix imaging displaying cervical elasticity characteristics of healthy adult nulliparous women at different age groups and different menstrual cycle stages

Objective To observe the cervical elasticity of healthy adult nulliparous women at different age groups and different stages of menstrual cycle with E-Cervix imaging technology.Methods A total of 218 healthy adult nulliparous women who underwent transvaginal ultrasound examination for routine physical examination were retrospectively enrolled,including 103 in follicular phase,78 in ovulation phase and 37 in luteal phase.Cervical canal length(CL)and E-Cervix elasticity parameters were compared among different age groups and different stages of menstrual cycle,including elasticity contrast index(ECI),hardness ratio(HR),cervical internal and external orifice strain values(IOS and EOS)and IOS/EOS ratio.Results No significant difference of CL nor cervical elasticity parameters was detected among healthy adult nulliparous women at different age groups(all P>0.05).There were significant differences of ECI,HR and IOS among different menstrual cycle stages(all P<0.05),among which women in follicular phase had higher ECI and IOS but lower HR than those in luteal phase(all P<0.05).Conclusion No significant difference of cervical elasticity existed among healthy adult nulliparous women at different age groups.Meanwhile,cervical elasticity of healthy adult nulliparous women changed during menstrual cycle,in follicular phase had higher ECI and IOS but lower HR than in luteal phase.

Monitoring the change in horizontal stress with multi-wave time-lapse seismic response based on nonlinear elasticity theory

Monitoring the change in horizontal stress from the geophysical data is a tough challenge, and it has a crucial impact on broad practical scenarios which involve reservoir exploration and development, carbon dioxide (CO_(2)) injection and storage, shallow surface prospecting and deep-earth structure description. The change in in-situ stress induced by hydrocarbon production and localized tectonic movements causes the changes in rock mechanic properties (e.g. wave velocities, density and anisotropy) and further causes the changes in seismic amplitudes, phases and travel times. In this study, the nonlinear elasticity theory that regards the rock skeleton (solid phase) and pore fluid as an effective whole is used to characterize the effect of horizontal principal stress on rock overall elastic properties and the stress-dependent anisotropy parameters are therefore formulated. Then the approximate P-wave, SV-wave and SH-wave angle-dependent reflection coefficient equations for the horizontal-stress-induced anisotropic media are proposed. It is shown that, on the different reflectors, the stress-induced relative changes in reflectivities (i.e., relative difference) of elastic parameters (i.e., P- and S-wave velocities and density) are much less than the changes in contrasts of anisotropy parameters. Therefore, the effects of stress change on the reflectivities of three elastic parameters are reasonably neglected to further propose an AVO inversion approach incorporating P-, SH- and SV-wave information to estimate the change in horizontal principal stress from the corresponding time-lapse seismic data. Compared with the existing methods, our method eliminates the need for man-made rock-physical or fitting parameters, providing more stable predictive power. 1D test illustrates that the estimated result from time-lapse P-wave reflection data shows the most reasonable agreement with the real model, while the estimated result from SH-wave reflection data shows the largest bias. 2D test illustrates the feasibility of the proposed inversion method for estimating the change in horizontal stress from P-wave time-lapse seismic data.

Ni-P-SBR composite-electroless-plating enables Si anode with high conductivity and elasticity for high performance Li-ion batteries application

Silica-based anode is widely employed for high energy density Li-ion batteries owing to their high theoretical specific capacity(4200 m A h g-1).However,it is always accompanied by a huge volume expansion(300%)and shrinks during the lithiation/delithiation process,further leading to low cycle stability.Efforts to mitigate the adverse effects caused by volume expansion such as robust binder matrix,Coreshell structure,etc.,inevitably affect the electronic conductivity within the electrode.Herein,a high conductivity and elasticity Si anode(Ni-P-SBR(styrene-butadiene rubber)@Si)was designed and fabricated via the Ni-P-SBR composite-electroless-plating process.In this design,the Si particles are surrounded by SBR polymer and Ni particles,where the SBR can adapt to the volume change and Ni particles can provide the electrode with high electronic conductivity.Therefore,the Ni-P-SBR@Si delivers a high initial capacity of 3470 m A h g-1and presents capacity retention of 49.4%within 200 cycles at 600 m A g-1.Additionally,a high capacity of 1153 m A h g-1can be achieved at 2000 m A g-1and can be cycled stably under bending conditions.This strategy provides feasible ideas to solve the key issues that limit the practical application of Si anodes.

Data envelopment analysis for scale elasticity measurement in the stochastic case:with an application to Indian banking

In the nonparametric data envelopment analysis literature,scale elasticity is evaluated in two alternative ways:using either the technical efficiency model or the cost efficiency model.This evaluation becomes problematic in several situations,for example(a)when input proportions change in the long run,(b)when inputs are heterogeneous,and(c)when firms face ex-ante price uncertainty in making their production decisions.To address these situations,a scale elasticity evaluation was performed using a value-based cost efficiency model.However,this alternative value-based scale elasticity evaluation is sensitive to the uncertainty and variability underlying input and output data.Therefore,in this study,we introduce a stochastic cost-efficiency model based on chance-constrained programming to develop a value-based measure of the scale elasticity of firms facing data uncertainty.An illustrative empirical application to the Indian banking industry comprising 71 banks for eight years(1998–2005)was made to compare inferences about their efficiency and scale properties.The key findings are as follows:First,both the deterministic model and our proposed stochastic model yield distinctly different results concerning the efficiency and scale elasticity scores at various tolerance levels of chance constraints.However,both models yield the same results at a tolerance level of 0.5,implying that the deterministic model is a special case of the stochastic model in that it reveals the same efficiency and returns to scale characterizations of banks.Second,the stochastic model generates higher efficiency scores for inefficient banks than its deterministic counterpart.Third,public banks exhibit higher efficiency than private and foreign banks.Finally,public and old private banks mostly exhibit either decreasing or constant returns to scale,whereas foreign and new private banks experience either increasing or decreasing returns to scale.Although the application of our proposed stochastic model is illustrative,it can be potentially applied to all firms in the information and distribution-intensive industry with high fixed costs,which have ample potential for reaping scale and scope benefits.

Bending and wave propagation analysis of axially functionally graded beams based on a reformulated strain gradient elasticity theory

A new size-dependent axially functionally graded(AFG) micro-beam model is established with the application of a reformulated strain gradient elasticity theory(RSGET). The new micro-beam model incorporates the strain gradient, velocity gradient,and couple stress effects, and accounts for the material variation along the axial direction of the two-component functionally graded beam. The governing equations and complete boundary conditions of the AFG beam are derived based on Hamilton's principle. The correctness of the current model is verified by comparing the static behavior results of the current model and the finite element model(FEM) at the micro-scale. The influence of material inhomogeneity and size effect on the static and dynamic responses of the AFG beam is studied. The numerical results show that the static and vibration responses predicted by the newly developed model are different from those based on the classical model at the micro-scale. The new model can be applied not only in the optimization of micro acoustic wave devices but also in the design of AFG micro-sensors and micro-actuators.

Real-time Shear Wave Elastography Assessment of Muscle Elasticity in Patients with Renal Failure

Objective:To explore the value of real-time elastic shear wave in evaluating muscle elasticity in patients with renal failure.Methods:50 patients with chronic renal failure from January 2019 to December 2022 were randomly selected as the experimental group,and 50 healthy patients aged 21-61 during the same period were selected as the control group,and the basic information of the patients,including age,gender,body mass index,etc.,were collected.Besides,the Young's modulus of the two groups of patients were observed and analyzed.Results:The Young's modulus values of left and right gastrocnemius muscles in the experimental group were significantly lower than those in the control group(P<0.05),and there was no statistical difference between the left and right sides of the experimental group and the control group(P>0.05).Conclusion:Real-time shear wave elastography provides a non-invasive,real-time and effective tool for the assessment of muscle elasticity in patients with renal failure.Through further research and optimization,real-time shear wave elastography will play a greater role in the prevention and treatment of patients with renal failure,improving the quality of life and prognosis of patients.

数据要素、新型基础设施与产业结构调整路径

数据要素和新型基础设施在各个产业发挥日益重要的作用。不同产业对数据要素和新型基础设施的应用方式和利用效率存在差异,影响产业结构调整路径。文章构建包含两个生产部门的动态一般均衡模型,用于代表不同产业或同一产业内的不同企业。每个部门将数据作为新生产要素、将新型基础设施作为数据扩展型技术,与传统生产要素结合形成新的生产函数。不同部门的数据产出弹性、数据和传统要素的替代弹性存在差异,这是影响产业结构调整路径的重要因素。通过理论模型推导和数值模拟研究,文章发现:在不同产业之间,由于产品替代弹性较低,提高数据要素和新型基础设施的数量会导致数据产出弹性较高、数据和传统要素的替代弹性较高的产业产出提高,但其产品价格和名义产出降低,促使资本和劳动力流向数据利用效率低的产业。这一过程将改变资本和劳动力的价格,影响劳动收入份额。在同一产业内部,由于不同企业间的产品替代弹性较高,数据要素和新型基础设施导致资本和劳动力流向数据利用效率高的企业,优化生产要素配置,推动整个产业的数字化转型。新型基础设施建设对产业结构调整的推动作用受到数据要素的调节,且最终的影响方向和路径与数据要素一致,可以通过调整需求结构引导更具针对性和长效的产业结构调整。最后,文章提出数据要素、新型基础设施建设的相关政策建议,并对产业结构调整可能导致的问题提出对策。

三维弹性体夹芯的夹芯板振动计算方法研究

目前夹芯结构由于其轻质、减振、隔声等优良性能,已在隔声壁板、减振结构设计等领域得到广泛的应用。夹芯板在低频振动中通常易于表现为弯曲振动模式,但夹芯板面板材料和芯材材料的性能往往差别较大,在中高频段易产生较为丰富的振动模式,因此建立一种适用于各个频段的夹芯板振动理论预报方法是十分必要的。本文发展了一种新的夹芯板振动理论计算方法,对夹芯板的芯材应用三维弹性力学理论,面板应用薄板理论。本文建立的理论方法可综合体现夹芯板弯曲变形模式和膨胀变形模式,容许夹芯板产生法向形变,可显著提高中高频夹芯板的振动预报计算精度。通过算例将本文理论方法的计算结果与其它理论计算方法和有限元计算的结果进行了对比,证明了本文理论方法的有效性和优势。

双弹性和单弹性锭子振动性能研究

为准确掌握双弹性锭子的振动性能,与传统的单弹性锭子进行试验对比研究。制备了3组仅上轴承支撑刚度不同的双弹性和单弹性锭子;通过试验对比,分析和总结了铝套管、光杆、夹纱器、锭带力等对锭子不同部位振幅的影响变化规律。结果表明:在高速时,铝套管或光杆的双弹性锭子较对应的单弹性锭子不同部位的振幅略有增加;但带夹纱器的双弹性铝套管锭子的锭端振幅明显小于对应的单弹性锭子的振幅;锭带力对不同类型锭子的锭端振幅无显著影响。认为:在高速运转时,带夹纱器的双弹性锭子的振动性能优于对应的单弹性锭子。

单双向循环荷载作用下砂砾料动模量和阻尼比试验研究

通过大型振动三轴试验,研究了单双向循环荷载作用下砂砾料动弹性模量和阻尼比的变化规律,分析围压和径向循环动应力对砂砾料动力参数的影响。研究结果表明:在双向振动三轴试验中,砂砾料的轴向动应变受径向动应力的影响较小,动应变主要与施加的轴向动应力大小有关;单双向振动下砂砾料的动弹性模量均随着动应变的增大而逐渐降低,双向振动时砂砾料动弹性模量随动应变的衰减速率基本不变,在相同动应变下双向振动的动模量均低于单向振动;砂砾料在双向振动时的阻尼比大于单向振动,双向振动时消耗的动应变能更大。通过对两种试验条件下的最大动弹性模量、动模量比进行分析,建立了表述单双向试验条件下最大动弹性模量的换算关系式和双向振动试验中动模量比和动应变的修正模型。

复合表面织构对锭子振动性能的影响研究

为提高锭子振动性能,在锭子的高速旋转表面用激光微加工出具有减阻作用的仿贝壳状、仿鲨鱼皮状、仿黄缘真龙虱状复合表面织构,对比分析了相同条件下双弹性锭子和单弹性锭子增加复合表面织构前后的振动性能。结果表明:增加仿鲨鱼皮状复合表面织构后,双弹性和单弹性锭子的振动性能略有提升;增加仿贝壳状和中尺寸仿黄缘真龙虱状复合表面织构后,双弹性锭子振幅较小且不受临界转速影响,其可在任意转速下工作;而增加大尺寸和小尺寸仿黄缘真龙虱状复合表面织构的双弹性和单弹性锭子在高速时振动性能明显提升。

闭合复位弹性髓内钉治疗股骨骨折患儿的临床效果

目的探讨闭合复位弹性髓内钉治疗股骨骨折患儿的临床效果。方法选取2019年5月至2022年5月贵州省人民医院小儿外科收治的70例股骨骨折患儿,按照随机数字表法分为对照组与观察组,每组各35例。对照组采用切开复位接骨板内固定术治疗,观察组采用闭合复位弹性髓内钉治疗。比较两组治疗效果及手术相关指标。结果两组总有效率比较,差异无统计学意义(P>0.05)。观察组术中出血量少于对照组,手术时间、骨折愈合时间、住院时间均短于对照组(P<0.05)。结论闭合复位弹性髓内钉治疗股骨骨折患儿的临床效果确切,可减少术中出血量,缩短手术时间、骨折愈合时间、住院时间,值得临床推广应用。

高温后冷却方式对玄武岩纤维混凝土力学性能的影响

高温处理后混凝土力学性能是工程建设中评价混凝土结构安全性能的重要指标之一。对不同玄武岩纤维(BF)掺量混凝土的力学性能进行了测试,将最优掺量的玄武岩纤维混凝土(BFRC)与普通混凝土(OC)进行高温处理(200、400、600、800℃),研究不同冷却方式(自然冷却和喷水冷却)对高温后BFRC性能劣化的影响,分析BFRC在不同温度和冷却方式下的力学性能变化规律。结果表明,当BF掺量为0.05%(体积分数)时,BFRC抗压强度、劈裂抗拉强度达到最大值,分别为50.2、3.5 MPa,较OC分别提高了14.87%、34.62%。BF的掺入能够有效增加混凝土的韧性以及抵抗开裂变形的能力。随着温度增加,BFRC试件的弹性模量减小但始终大于OC试件。同一冷却方式下OC的峰值应变均大于BFRC,不同冷却方式下的延性指数较常温均有所提高。

健康成年人肾脏磁共振弹性成像及其弹性值测量可行性的初步研究

目的:探讨磁共振弹性成像(MRE)评估健康成年人肾脏弹性值测定的可行性。方法:前瞻性招募22例肝肾功能正常无相关疾病的健康成年人,采用联影3.0TMRI测定双肾弹性值,由2位医师对MRE图像进行评估,分别测定双侧肾脏弹性值,测量结果行Bland-Altman分析。计算正常肾脏平均弹性值,并分析左、右肾弹性值差异及不同性别间的肾脏弹性值差异。结果:2位医师测得的肾弹性值有很好的一致性(P>0.05)。双肾实质平均弹性值为(5.37±0.26)kPa,其中左肾(5.38±0.27)kPa,右肾(5.35±0.29)kPa,差异无统计学意义(t=-0.311,P>0.05)。男性和女性双肾平均弹性值差异无统计学意义(t=-0.871,P>0.05)。结论:MRE可用于测定双肾弹性值,测量值准确且重复性好。

考虑用户比价行为的综合需求响应低碳优化策略

在我国“双碳”背景下,建立综合能源系统(integrated energy system,IES)已经成为实现“碳达峰”、“碳中和”目标,加快能源结构转型的重要举措,而综合需求响应(integrated demand response,IDR)是综合能源系统减少碳排放、缓解供需双侧不平衡的有效途径。然而,现有关于IDR的研究大多仅考虑其经济效益,未考虑其环境效益,忽略了需求侧用户对不同时段激励价格的比价行为以及不同用户的差异化响应特性。该文提出了基于碳排放因子的IDR碳排放折算模型,并将碳排放成本加入综合能源系统服务商(integrated energy system provider,IESP)的目标函数中;通过建立激励交叉弹性耦合矩阵对用户的比价行为进行了有效建模以提升模型的精确性;同时计及用户的差异化响应特性,通过制定差异化的激励策略以充分挖掘用户的响应潜力。所提模型被建立为一个IESP-用户双层优化模型,并将该模型转化为了一个单层的凸优化模型以实现高效地求解。最后通过仿真算例验证了模型的有效性,不仅减少了碳排放量,同时降低了IESP的响应成本并提升了用户的舒适度,实现了多方共赢。

基于GA-BLS方法的手势识别研究

为进一步提升人机交互领域中手势识别的精度和速度,探究肌肉疲劳对手势识别的影响规律,提出了改进的GA-BLS方法,利用遗传算法(genetic algorithms,GA)优化宽度学习(broad learning system,BLS)模型参数,并使用弹性网络回归改进传统的BLS模型。利用所提模型对8种手势下的A型超声信号和肌电信号进行手势识别分析,并与SVM、KNN、RF、LDA等方法进行对比,以验证所研究方法的有效性;将长时间段下的A型超声信号和肌电信号切分成4个数据段,发现随着肌肉疲劳程度的增加,手势识别的准确率均呈现出明显下降的趋势,而且A型超声信号相较于肌电信号具有更好的抗疲劳特性。

胶囊形气膜结构风致气弹响应及风振系数研究

针对1/3矢跨比胶囊形气膜结构进行了气弹模型风洞试验,研究了结构的风致气弹响应变化规律,并给出了可供设计参考的风振系数。研究发现:结构平均变形呈迎风面凹陷,顶部隆起,横风向向外凸出的趋势,且这种变形趋势随着内压减小和风速增大越来越明显。0°风向角时的平均变形和振幅大于45°风向角时的平均变形和振幅大于90°风向角时的平均变形和振幅,结构合位移均值的极值出现在迎风面与顶面中心点;0°和45°风向角下,顶点竖向振幅>顺风向振幅>横风向振幅,结构以1阶模态振动为主;90°风向角下,顶点横风向振幅大于其他两个方向,结构以1阶和2阶模态叠加振动为主。各工况下结构的内压均有不同程度的减小。最后给出了考虑流固耦合效应的响应风振系数。

简谐荷载作用下弹性土体中圆形隧道和轨道结构的动力响应

采用解析的方法研究了弹性土体中圆形隧道和轨道结构的动力响应。将隧道视为无限长的薄壁圆管,轨道被简化成铺设在隧道仰拱上无限长的欧拉梁,周围土体为无限空间弹性介质。通过在环向采用模态叠加法,在轴向采用傅里叶变换求解隧道与轨道之间的耦合问题,获得了在简谐荷载作用下弹性土体中圆形隧道和轨道结构的动力响应。研究结果表明:低支承刚度的结构体系会产生连续的干涉现象,这种情况在高频的情况下尤为明显;虽然轨道的弯曲刚度越大,结构的位移越小,但是整体规律保持不变;支承刚度的增加会导致轨道固有频率向高频偏移;无轨道结构中土体位移会随着荷载频率的升高而降低,在加入轨道后荷载会与轨道固有频率产生共振效应,形成特定的极大值。

黏弹性聚合物驱渗流机理研究进展

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