Influence Predictions of Contact Effects on Mesh Stiffness of Face Gear Drives with Spur Gear

Mesh stiffness is one of important base parameters of face gear dynamic studies.However,a calculation solution of mesh stiffness of face gear drives is not to be constructed due to complex geometric flakes of face gear teeth.Thus,a calculation solution of mesh stiffness of face gear drives with a spur gear,which is based on the proposed equivalent face gear teeth and Ishikawa model,is constructed,and the influence of contact effects on mesh stiffness of face gear drives is investigated.The results indicate the mesh stiffness of face gear drives is sensitive to contact effects under heavy loaded operating conditions,specially.These contributions will benefit to improve dynamic studies of face gear drives.

Distinction between critical current effects and intrinsic anomalies in the point-contact Andreev reflection spectra of unconventional superconductors

In this work,we discuss the origin of several anomalies present in the point-contact Andreev reflection spectra of（Li1-xFex）OHFeSe,LiTi2O4,and La2-xCexCuO4.While these features are similar to those stemming from intrinsic superconducting properties,such as Andreev reflection,electron-boson coupling,multigap superconductivity,d-wave and p-wave pairing symmetry,they cannot be accounted for by the modified Blonder–Tinkham–Klapwijk（BTK） model,but require to consider critical current effects arising from the junction geometry.Our results point to the importance of tracking the evolution of the dips and peaks in the differential conductance as a function of the bias voltage,in order to correctly deduce the properties of the superconducting state.

Hunting down the ohmic contact of organic field-effect transistor

We report properties of contact resistances observed on pentacene organic field-effect transistors(OFET) with four different source/drain electrodes, namely, copper(Cu), gold(Au), silver(Ag), and germanium(Ge). The metals were selected to provide a wide range of energy barriers for charge injection, from blocking contact to smooth injection. All OFETs exhibited strong voltage dependence of the contact resistance, even for devices with smooth injection, which is in strong disagreement with the definition of ohmic contacts. A comparison with current crowding, resistive network, Fowler–Nordheim tunneling, and electric field enhanced thermionic injection(Schottky emission) pointed to importance of local electric fields and/or electrostatic field charges.

Reiterated homogenization of a laminate with imperfect contact:gain-enhancement of effective properties

A family of one-dimensional(1D) elliptic boundary-value problems with periodic and rapidly-oscillating piecewise-smooth coefficients is considered. The coefficients depend on the local or fast variables corresponding to two different structural scales. A finite number of imperfect contact conditions are analyzed at each of the scales. The reiterated homogenization method(RHM) is used to construct a formal asymptotic solution. The homogenized problem, the local problems, and the corresponding effective coefficients are obtained. A variational formulation is derived to obtain an estimate to prove the proximity between the solutions of the original problem and the homogenized problem. Numerical computations are used to illustrate both the convergence of the solutions and the gain of the effective properties of a three-scale heterogeneous 1D laminate with respect to their two-scale counterparts. The theoretical and practical ideas exposed here could be used to mathematically model multidimensional problems involving multiscale composite materials with imperfect contact at the interfaces.

Effect of Metal Contact and Rapid Thermal Annealing on Electrical Characteristics of Graphene Matrix

Development of graphene field effect transistors （GFETs） faces a serious challenge of graphene interface to the dielectric material. A single layer of intrinsic graphene has an average sheet resistance of the order of 1-5 kΩ/□. The intrinsic nature of graphene leads to higher contact resistance yielding into the outstanding properties of the material. We design a graphene matrix with minimized sheet resistance of 0.185 kΩ/□ with Ag contacts. The developed matrices on silicon substrates provide a variety of transistor design options for subsequent fabrication. The graphene layer is developed over 400 nm nickel in such a way as to analyze hypersensitive electrical properties of the interface for exfoliation. This work identifies potential of the design in the applicability of few-layer GFETs with less process steps with the help of analyzing the effect of metal contact and post-process anneMing on its electrical fabrication.

Top contact organic field effect transistors fabricated using a photolithographic process

This paper proposes an effective method of fabricating top contact organic field effect transistors by using a pho- tolithographic process. The semiconductor layer is protected by a passivation layer. Through photolithographic and etching processes, parts of the passivation layer are etched off to form source/drain electrode patterns. Combined with conventional evaporation and lift-off techniques, organic field effect transistors with a top contact are fabricated suc- cessfully, whose properties are comparable to those prepared with the shadow mask method and one order of magnitude higher than the bottom contact devices fabricated by using a photolithographic process.

Experimental I-V and C-V Analysis of Schottky-Barrier Metal-Oxide-Semiconductor Field Effect Transistors with Epitaxial NiSi2 Contacts and Dopant Segregation

We present an experimental analysis of Schottky-barrier metal-oxide-semiconductor field effect transistors （SB- MOSFETs） fabricated on ultrathin body silicon-on-insulator substrates with a steep junction by the dopant implantation into the silicide process. The subthreshold swing of such SB-MOSFETs reaches 69mV/dec. Em- phasis is placed on the capacitance-voltage analysis of p-type SB-MOSFETs. According to the measurements of gate-to-source capacitance Cgs with respect to Vgs at various Vds, we find that a maximum occurs at the accumulation regime due to the most imbalanced charge distribution along the channel. At each Cgs peak, the difference between Vgs and Vds is equal to the Schottky barrier height （SBH） for NiSi2 on highly doped silicon, which indicates that the critical condition of channel pinching off is related with SBH for source/drain on chan- nel. The SBH for NiSi2 on highly doped silicon can affect the pinch-off voltage and the saturation current of SB-MOSFETs.

Study of top and bottom contact resistance in one organic field-effect transistor

This paper reports that the organic field-effect transistors with hybrid contact geometry were fabricated, in which the top electrodes and the bottom electrodes were combined in parallel resistances within one transistor. With the facility of the novel structure, the difference of contact resistance between the top contact geometry and the bottom contact geometry was studied. The hybrid contact devices showed similar characteristics with the top contact configuration devices, which provide helpful evidence on the lower contact resistance of the top contact configuration device. The origin of the different contact resistance between the top contact device and the bottom contact device was discussed.

壳聚糖抗菌成膜喷剂在鼻咽癌患者PICC所致接触性皮炎治疗中的应用效果

目的探讨壳聚糖抗菌成膜喷剂在鼻咽癌患者经外周静脉置入中心静脉导管(PICC)置管部位接触性皮炎治疗中的应用效果。方法选取2020-05至2022-04联勤保障部队第909医院因置入PICC所致接触性皮炎的94例鼻咽癌患者为研究对象,其中2020-05至2021-04的46例患者为对照组,2021-05至2022-04的48例患者为观察组。对照组采用地塞米松注射液外涂联合3M透明敷料行PICC换药,观察组采用喷涂壳聚糖抗菌成膜喷剂联合3M透明敷料行PICC换药。对比观察两组患者临床疗效、并发症的发生率、愈合时间、换药次数、患者的自付费用及满意度情况。结果观察组治疗第1周、第2周总有效率(95.83%,100%)均显著高于对照组治疗总有效率(73.91%,89.13%)(P<0.05),观察组愈合时间[(10.43±0.52)d]、换药次数[(3.30±0.69)次]显著短于或少于对照组愈合时间[(18.15±0.33)d]、换药次数[(5.67±0.96)次](P<0.05),观察组患者满意度得分(8.71±0.82)显著高于对照组患者满意度得分(5.67±0.96)(P<0.05),两组患者在导管移位率、脱管率及患者自付费用三方面无明显区别,差异无统计学意义(P>0.05)。结论壳聚糖抗菌成膜喷剂治疗鼻咽癌同步放化疗患者PICC置管部位接触性皮炎效果明显,可减少换药次数,减轻护理工作量,降低局部感染率,提高患者满意度。

非堆积型多颗粒阻尼器等效力学模型及其减振性能分析

为考虑颗粒群碰撞过程中时间效应对非堆积型多颗粒阻尼器(non-packed particle damper, NPPD)减振性能的影响,在现有考虑惯容的等效单颗粒力学模型(equivalent inertia single-particle model, EISM)研究基础上,提出了基于接触单元法的等效单颗粒力学模型(equivalent inertia single-particle model based on contact element method, EISM-CE),并基于Runge-Kutta算法建立了NPPD单自由度结构运动状态求解算法。设计进行附加NPPD单层钢框架结构振动台试验,探究不同填充率对结构顶层位移频响曲线的影响规律,提出了EISM-CE参数取值原则,进而进行力学模型试验验证及模型对比分析。在模型验证合理性基础上,基于EISM-CE依次进行了自由振动、简谐激励及记录强震动下减振性能及能量变化规律分析。研究结果表明,与现有EISM相比,提出的基于接触单元法的EISM-CE模型及参数取值原则更加合理有效。减振性能数值分析结果表明,不同激励下NPPD均具有较好的减振性能;考虑碰撞时间效应后EISM-CE与EISM对应减振性能及机理分析结果存在一定的差异。

接触自然——有潜力的物质成瘾缓解和恢复策略:理论机制及关键问题

物质成瘾对个人健康、家庭和社会都造成了严重威胁,是全球性亟待解决的公共健康问题。目前,诸多研究表明接触自然环境能多方面促进人类的健康和福祉,然而“自然-健康”议题的相关研究很少关注物质成瘾行为。那么,接触自然环境是否是一种有效缓解和恢复物质成瘾的有效策略呢?梳理了接触自然环境与物质成瘾关系的研究进程,并阐释了接触自然环境可能促进物质成瘾缓解和恢复的生理、心理和行为路径机制。基于此,提出一个研究假设:接触自然环境可能是一种有潜力的缓解和恢复物质成瘾的有效策略。指出了当前研究的局限,并从直接效应、路径机制、实践应用3个层面提出了该领域亟待解决的14个关键研究问题,以期为后续的研究和实践提供借鉴。

基于Footscan的青年女性足掌、跟区压力规律分析

目的旨在分析并总结出青年女性足掌、跟区压力的规律。方法采用Footscan足底压力步态分析系统对正常状态下行走时足底压力的分布情况进行记录。随机选取足部正常、身体状况良好的60名青年女性作为样本,分别记录样本的身高、体重、年龄以及生源地信息,利用SPSS21.0数据分析软件对系统所得的不同受试对象的足趾区、跖区、弓区、跟区的足底压力参数指标进行分析,得出方差数据表。结果通过观测分析,得出以下结论:在正常条件下,左、右足足底压力大部分区均呈现出良好的对应关系;趾区中第1趾区的峰值压强、压力有效接触面积、冲量均大于第2~5趾区,右足几乎均大于左足;跖区中压力峰值压强、冲量均在第3跖区最大,在第5跖区最小;第1跖区足底跖区压力有效接触面积最大;跟区中足跟区内侧的峰值压强、有效接触面积均大于足跟区外侧;左足的足跟区外侧冲量大于足跟区内侧,右足的足跟区内侧冲量大于足跟区外侧。结论青年女性足掌、跟区压力规律性显著,提高了对青年女性足部生物力学特征的辨识度,补充了司法鉴定的理论基础。

Potential Power of the Pyramidal Structure IV: Discovery of Entanglement Due to Pyramid Effects

Since October 2007, we have been conducting rigorous scientific research on the unexplained “power” of a pyramidal structure (PS). From our research results so far, we could classify pyramid effects by the PS into the following two types: (i) the pyramid effects due to the potential power of the PS and (ii) the pyramid effects due to the influence of the test subject meditating inside the PS. We have been using edible cucumber sections as the biosensors. The pyramid effect existence was clarified by measuring and analyzing the concentration of volatile components released from the biosensors. The biosensors were arranged as a pair: one member of the pair was placed at the PS apex and the other was placed at the calibration control point 8.0 m away from the PS. In this paper, we report a new discovery regarding the type (i) pyramid effects. We discovered a phenomenon considered to be entanglement between the biosensor pairs detecting the pyramid effects. In other words, the biosensors at the PS apex, which were affected by the potential power of the PS, affected the biosensors at the calibration control point. We also confirmed that the effects on the biosensors placed at the calibration control point were not due to the potential power of the PS. Furthermore, we showed that the magnitude of the effect of entanglement changed with the seasons. We expect that our research results will be widely accepted in the future and will become the foundation for a new research field in science, with a wide range of applications.

Potential Power of the Pyramidal Structure III: Discovery of Pyramid Effects with and without Seasonal Variation

Since October 2007, we have been conducting rigorous scientific research on the unexplained “power” of a pyramidal structure (PS). From our research results so far, we could classify the pyramid effects by the PS into the following two types. (i) The pyramid effects in which the PS converted the test subject’s unexplained energy to affect biosensors when the test subject entered the PS and meditated. (ii) The pyramid effects in which the potential power of the PS affected biosensors if the test subject had not been inside the PS for at least 20 days and the test subject’s unexplained energy was excluded. In this paper, we report new results regarding (ii). As a result of dividing a year according to the four seasons of winter, spring, summer, and autumn and analyzing the pyramid effect of each period, the following points were found. 1) There was a pyramid effect without seasonal variation. The pyramid effect on the lower and upper layers was different throughout the year for the biosensors placed at the PS apex in two layers, regardless of the season. 2) There was a pyramid effect with seasonal variation. The value of the psi index, which indicates the magnitude of the pyramid effect, changed as the seasons changed, while different pyramid effects were maintained on the lower and upper layers. Regarding the change in the pyramid effect depending on the season, the psi index in summer was larger than that in winter in both the lower and upper layers. From these results, we found that there are two types of potential power at the PS apex: seasonal potential power and non-seasonal potential power.

基于3D细观模型的混凝土动态压缩行为分析

通过建立混凝土的3D细观模型,在细观尺度上分析动态压缩荷载作用下混凝土材料内部裂缝的产生和发展、损伤演化和动态强度及其影响因素。首先,基于传统的“生成-投放”法生成粒径、形状和空间分布均随机的凸多面体粗骨料模型,并通过骨料沉降和粒径缩放实现粗骨料的大体积率(达50%)和可调控;使用四面体网格划分骨料和砂浆表征其真实物理形状;使用界面粘结接触表征界面过渡区(ITZ)提升计算效率。进一步通过对比不同粗骨料粒径混凝土的分离式霍普金森压杆(SHPB)试验数据与模拟结果,如杆上应变时程、试件动态应力-应变曲线和试件损伤破坏模式,验证了建立的混凝土3D细观有限元模型、参数确定方法和数值仿真方法的准确性。最后,分析了30~100 s^(-1)应变率范围内骨料粒径(4~8、10~14和22~26 mm)、体积率(20%、30%和40%)和类型(石灰岩、花岗岩和玄武岩)对混凝土动态压缩强度的影响。结果表明:粗骨料粒径增大,混凝土动态压缩强度先增大后减小;粗骨料体积率越高,混凝土动态压缩强度越大;混凝土动态压缩强度随粗骨料强度的增加而提高。

高心墙堆石坝接触黏土与岸坡接触特性的离心模型研究

为了提高砾石土心墙与岸坡之间的变形协调性,高心墙堆石坝通常在心墙与岸坡之间设置高塑性黏土,统称为接触黏土,接触黏土的变形特性对高心墙的应力变形性状和心墙的安全性有重大影响。开展了4组接触黏土与岸坡接触面的局部离心模型试验,通过调整施加的上覆荷载大小来探讨原型坝体不同高程处的接触面剪切位移发展规律。基于理论分析,提出了一个计算接触黏土与岸坡接触面离心模型试验中边界效应影响范围的解析表达式,以确定接触面离心试验中试验模型的相似比尺。试验结果表明:在原型坝体的不同高程处,接触黏土与岸坡之间均会产生一定的剪切位移,但不会出现分离现象;接触黏土和砾质心墙土变形主要以竖向下沉为主,并且接触黏土与砾质心墙土之间的沉降等值线变化较为连续,未出现陡变情况,这说明接触黏土起到了很好地协调变形的作用,因此在进行高心墙堆石坝的结构安全性分析过程中应考虑接触黏土与岸坡的接触效应。

喷膜防水衬砌在渗流场作用下的力学性能研究

喷膜防水衬砌结构在防水膜黏结作用和渗流场作用下的衬砌受力变形规律不明,影响了喷膜防水衬砌结构的使用与推广。为解决该问题,以某高速车行横洞为研究对象,首先,结合试验测得的界面法向、切向参数,采用FLAC3D有限差分软件内置的界面单元模拟不同防水衬砌结构的防水层形式;然后,通过内置的渗流模式赋予围岩渗流场与衬砌渗透属性;最后,对不同衬砌结构的力学性能和界面特性进行对比分析,模拟得到不同渗流场作用下的喷膜防水衬砌力学性能。研究结果表明:1)防水层对衬砌受力的影响显著,防水膜结构可以提高衬砌混凝土的协同受力能力,但也导致衬砌背后水压聚集;且在长期围岩荷载和高水压作用下,防水层对衬砌受力的影响更显著。2)高水压条件下喷膜防水衬砌与传统复合式衬砌的结构受力不同,应关注喷膜防水衬砌内力与安全系数变化。3)为了在保证隧道运营安全的条件下提高经济性,建议对可能出现高水压力的施工段采取排水设计和衬砌结构优化等措施。

基于原子层沉积IGZO场效应晶体管的接触电阻优化

氧化铟镓锌(IGZO)具有宽带隙、高迁移率、和CMOS后道工艺兼容等优势,可用于下一代高密度三维堆叠存储器。随着IGZO场效应晶体管的尺寸不断微缩,源漏接触电阻在开态时会主导器件总电阻。因此,IGZO场效应晶体管的接触电阻优化成为需要研究的一个关键问题。本文采用原子层沉积的IGZO作为沟道并制备出场效应晶体管,探究了接触金属种类及后退火工艺对IGZO场效应晶体管接触电阻的影响。结果表明,退火前镍和钛的接触电阻相当。但在Ar/O2氛围、250℃条件下退火2小时后,采用钛接触的IGZO场效应晶体管的接触电阻降低到镍接触的8.3%,实现接触电阻低至0.86 kΩ·μm,同时阈值电压正移实现了增强型器件。与此同时,制备出超短沟长(Lch=80 nm)的IGZO场效应晶体管,开态电流高达412.2μA/μm、亚阈值摆幅为88.6 mV/dec,漏致势垒降低系数低至0.02 V/V。这些结果表明,通过优化接触金属种类及后退火条件,可实现高性能IGZO场效应晶体管,并为IGZO大规模实际应用提供新思路。

重复接地与等电位联结对降低电击造成人身伤害的效果对比分析

以常见的住宅配电为例,通过计算各接地故障回路的接触电压值,以及通过人体的电流实际值,再转化为等效路径电流,并将电流对人体的生理效应作对比,总结各种电击防护措施的应用效果,从而提高从业人员对等电位联结的重视程度。

消极老化刻板印象及群际焦虑在代际接触与老年歧视间的多重中介作用

针对老年歧视问题,国内学者大多从社会政策和法律层面进行理论探讨,实证调查研究较少。对738名大学生的问卷调查数据分析结果表明,老年歧视、消极老化刻板印象、群际焦虑、代际接触得分两两之间均呈显著相关。代际接触既能够直接负向预测老年歧视,也能够通过消极老化刻板印象、群际焦虑的独立中介效应,以及消极老化刻板印象-群际焦虑的链式中介作用影响老年歧视。增加大学生与老年人的代际接触,有利于减少消极老化刻板印象和群际焦虑水平,进而减少老年歧视水平。