Dynamic and electrical responses of a curved sandwich beam with glass reinforced laminate layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact

The dynamic responses and generated voltage in a curved sandwich beam with glass reinforced laminate(GRL)layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact(LVI)are investigated.The current study aims to carry out a dynamic analysis on the sandwich beam when the impactor hits the top face sheet with an initial velocity.For the layer analysis,the high-order shear deformation theory(HSDT)and Frostig's second model for the displacement fields of the core layer are used.The classical non-adhesive elastic contact theory and Hunter's principle are used to calculate the dynamic responses in terms of time.In order to validate the analytical method,the outcomes of the current investigation are compared with those gained by the experimental tests carried out by other researchers for a rectangular composite plate subject to the LVI.Finite element(FE)simulations are conducted by means of the ABAQUS software.The effects of the parameters such as foam modulus,layer material,fiber angle,impactor mass,and its velocity on the generated voltage are reviewed.

Current advancements on charge selective contact interfacial layers and electrodes in flexible hybrid perovskite photovoltaics

Perovskite-based photovoltaic materials have been attracting attention for their strikingly improved performance at converting sunlight into electricity.The beneficial and unique optoelectronic characteristics of perovskite structures enable researchers to achieve an incredibly remarkable power conversion efficiency.Flexible hybrid perovskite photovoltaics promise emerging applications in a myriad of optoelectronic and wearable/portable device applications owing to their inherent intriguing physicochemical and photophysical properties which enabled researchers to take forward advanced research in this growing field.Flexible perovskite photovoltaics have attracted significant attention owing to their fascinating material properties with combined merits of high efficiency,light-weight,flexibility,semitransparency,compatibility towards roll-to-roll printing,and large-area mass-scale production.Flexible perovskite-based solar cells comprise of 4 key components that include a flexible substrate,semi-transparent bottom contact electrode,perovskite(light absorber layer)and charge transport(electron/hole)layers and top(usually metal)electrode.Among these components,interfacial layers and contact electrodes play a pivotal role in influencing the overall photovoltaic performance.In this comprehensive review article,we focus on the current developments and latest progress achieved in perovskite photovoltaics concerning the charge selective transport layers/electrodes toward the fabrication of highly stable,efficient flexible devices.As a concluding remark,we briefly summarize the highlights of the review article and make recommendations for future outlook and investigation with perspectives on the perovskite-based optoelectronic functional devices that can be potentially utilized in smart wearable and portable devices.

Investigation of the Relation between Rolling Contact Fatigue Property and Microstructure on the Surface Layer of D2 Wheel Steel

Through the rolling contact fatigue experiment under the condition of the lubricating oil, this article investigated the relation between contact fatigue property and microstructure on the surface layer of D2 wheel steel. The results showed that although the roughness of the original specimen induced by mechanical processing would diminish to some extent in the experiment, the 0.5 - 1.5 μm thick layer of ultrafine microstructure on the original mechanically-processed specimen surface would still become micro-cracks and small spalling pits due to spalling, and would further evolve into fatigue crack source. Additionally, even under the impact of the load that was not adequate to make the material reach fatigue limit, the ferrite in the microstructure underwent plastic deformation, which led the refinement of proeutectoid ferrite grains. During the experiment, the hardening and the refinement caused by plastic deformation consisted with the theory that dislocation gave rise to plastic deformation and grain refinement. The distribution laws of hardness and ferrite grain sizes measured could be explained by the distribution law of the shearing stress in the subsurface.

Analytical solution of axisymmetric contact problem about indentation of a circular indenter into a soft functionally graded elastic layer

The paper addresses a contact problem of the theory of elasticity,i.e.,the penetration of a circular indenter with a flat base into a soft functionally graded elastic layer.The elastic properties of a functionally graded layer arbitrarily vary with depth,and the foundation is assumed to be elastic,yet much harder than a layer.Approximated analytical solution is constructed,and it is shown that the solutions are asymptotically exact both for large and small values of characteristic dimensionless geometrical parameter of the problem.Numerical examples are analyzed for the cases of monotonic and nonmonotonic variations of elastic properties.Numerical results for the case of homogeneous layer are compared with the results for nondeformable foundation.

Distributed Contact Plan Design for Multi-Layer Satellite-Terrestrial Network

In multi-layer satellite-terrestrial network, Contact Graph Routing(CGR) uses the contact information among satellites to compute routes. However, due to the resource constraints in satellites, it is extravagant to configure lots of the potential contacts into contact plans. What's more, a huge contact plan makes the computing more complex, which further increases computing time. As a result, how to design an efficient contact plan becomes crucial for multi-layer satellite network, which usually has a large scaled topology. In this paper, we propose a distributed contact plan design scheme for multi-layer satellite network by dividing a large contact plan into several partial parts. Meanwhile, a duration based inter-layer contact selection algorithm is proposed to handle contacts disruption problem. The performance of the proposed design was evaluated on our Identifier/Locator split based satellite-terrestrial network testbed with 79 simulation nodes. Experiments showed that the proposed design is able to reduce the data delivery delay.

Low contact resistivity between Ni/Au and p-GaN through thin heavily Mg-doped p-GaN and p-InGaN compound contact layer

Thin heavily Mg-doped InGaN and GaN compound contact layer is used to form Ni/Au Ohmic contact to p-GaN. The growth conditions of the compound contact layer and its effect on the performance of Ni/Au Ohmic contact to p-GaN are investigated. It is confirmed that the specific contact resistivity can be lowered nearly two orders by optimizing the growth conditions of compound contact layer. When the flow rate ratio between Mg and Ga gas sources of p＋＋-InGaN layer is 10.6% and the thickness of p＋＋-InGaN layer is 3 nm, the lowest specific contact resistivity of 3.98× 10-5 Ω cm2 is achieved. In addition, the experimental results indicate that the specific contact resistivity can be further lowered to 1.07 × 10-7Ω.cm2 by optimizing the alloying annealing temperature to 520 ℃.

Friction contact mechanisms of layered surface

In this paper,we firstly review the carbon layered surface prepared with electron cyclotron resonance (ECR) plasma sputtering. Secondly,the friction behavior of carbon layered surface under pin-on-disk testing is described. Furthermore,the contact stress evolution processes of layered surface with and without transfer layer during wear are given for understanding the contact mechanisms. Finally,a three-dimension (3D) local yield map of layered surface is introduced,which is useful to predict the possible contact mechanisms.

Formation of the intermediate semiconductor layer for the Ohmic contact to silicon carbide using Germanium implantation

By formation of an intermediate semiconductor layer （ISL） with a narrow band gap at the metallic contact/SiC interface, this paper realises a new method to fabricate the low-resistance Ohmic contacts for SiC. An array of transfer length method （TLM） test patterns is formed on N-wells created by P＋ ion implantation into Si-faced p-type 4H- SiC epilayer. The ISL of nickel-metal Ohmic contacts to n-type 4H-SiC could be formed by using Germanium ion implantation into SiC. The specific contact resistance pc as low as 4.23×10-5Ω·cm2 is achieved after annealing in N2 at 800 ℃ for 3 min, which is much lower than that （〉 900℃） in the typical SiC metallisation process. The sheet resistance Rsh of the implanted layers is 1.5 kΩ/□. The technique for converting photoresist into nanocrystalline graphite is used to protect the SiC surface in the annealing after Ge＋ ion implantations.

Influence of Schottky drain contacts on the strained AlGaN barrier layer of AlGaN/AlN/GaN heterostructure field-effect transistors

Rectangular Schottky drain AlGaN/AlN/GaN heterostructure field-effect transistors （HFETs） with different gate contact areas and conventional AlGaN/AlN/GaN HFETs as control were both fabricated with same size. It was found there is a significant difference between Schottky drain AlGaN/AlN/GaN HFETs and the control group both in drain series resistance and in two-dimensional electron gas （2DEG） electron mobility in the gate–drain channel. We attribute this to the different influence of Ohmic drain contacts and Schottky drain contacts on the strained AlGaN barrier layer. For conventional AlGaN/AlN/GaN HFETs, annealing drain Ohmic contacts gives rise to a strain variation in the AlGaN barrier layer between the gate contacts and the drain contacts, and results in strong polarization Coulomb field scattering in this region. In Schottky drain AlGaN/AlN/GaN HFETs, the strain in the AlGaN barrier layer is distributed more regularly.

Simulation of Fragment Impact on Multi-Layer Targets Using Contact Method

Cased explosives generate highly energetic fragments as their casing breaks up. Due to the complexity of casing fragment related behavior such as embedment, perforation and ricochet, it may be insufficient to use equivalent triangular pressure loading in fragment impact simulations. This simplified method may over- or under-predict the target response. Recently, a procedure using contact techniques has been proposed to overcome such difficulties. It has been shown that the new method has the inherent capability in modeling the multi-piece and multi-hit fragment impact problems in a more realistic way. To investigate the applicability of the proposed method to simulations involving multi-layer penetration, the selected problems of fragment impact on multi-layer targets are described in this paper. It is demonstrated that this method is capable of predicting the complicated multi-layer structural response caused by fragment impact and penetration. Modeling procedures and some technical issues are also discussed.

Influence of Warm Oxide Layer on Wettability and Contact Angle for Heat Transport Devices

最近，高热密度在电子设备成为了一个问题。因此，高热转移效率在铜热 exchangers 被要求。wettability 的改进被报导改进热转移效率。在以前的研究，铜氧化物层改进 wettability。在这研究，我们集中于在温暖的条件下面生产的铜氧化物层(从 200 ～ 300 吗？？

Back contact interfacial modification mechanism in highly-efficient antimony selenide thin-film solar cells

Antimony selenide(Sb_(2)Se_(3))is a potential photovoltaic(PV)material for next-generation solar cells and has achieved great development in the last several years.The properties of Sb_(2)Se_(3)absorber and back contact influence the PV performances of Sb_(2)Se_(3)solar cells.Hence,optimization of back contact characteristics and absorber orientation are crucial steps in raising the power conversion efficiency(PCE)of Sb_(2)Se_(3)solar cells.In this work,MoO2was introduced as an intermediate layer(IL)in Sb_(2)Se_(3)solar cells,and comparative investigations were conducted.The growth of(211)-oriented Sb_(2)Se_(3)with large grains was facilitated by introducing the MoO2IL with suitable thickness.The MoO2IL substantially lowered the back contact barrier and prevented the formation of voids at the back contact,which reduced the thickness of the MoSe2interface layer,inhibited carrier recombination,and minimized bulk and interfacial defects in devices.Subsequently,significant optimization enhanced the open-circuit voltage(VOC)of solar cells from 0.481 V to 0.487 V,short-circuit current density(JSC)from 23.81 m A/cm^(2)to 29.29 m A/cm^(2),and fill factor from 50.28%to 57.10%,which boosted the PCE from 5.75%to 8.14%.

p型InGaAs薄层半导体欧姆接触特性分析

从电流在金属和半导体界面的拥堵效应出发,依据圆形传输线模型(CTLM)推导出适用于金属和薄层半导体间欧姆接触电阻率的表达式。利用四探针电阻测量法、高导电性下小电流密度测试法以及对薄膜电阻和传输线长度采用非线性拟合的方法获得薄层半导体与金属之间高精度的欧姆接触电阻和电阻率测试结果。研究了Zn掺杂浓度和合金温度对p型InGaAs薄层半导体欧姆接触特性的影响。研究发现:在相同合金温度下,掺杂浓度为1.94×10^(19)cm^(-3)时,样品的欧姆接触电阻率小于掺杂浓度为1.52×10^(19)cm^(-3)的样品,即提高p型InGaAs薄层半导体Zn掺杂浓度有利于半导体和金属Ti/Pt/Au形成良好的欧姆接触;相同Zn掺杂浓度的p型InGaAs薄层半导体,在经过光刻、等离子体去胶、湿法腐蚀等前道工艺后,合金温度为410℃的样品欧姆接触电阻率小于合金温度为380℃的样品,即可通过提高合金温度改善半导体与金属之间的欧姆接触特性。

超高速滑动电接触CuCrZr合金轨道表面磨损机制及电接触性能

电磁轨道发射具有典型超高速滑动电接触特性(出口速度大于等于2000 m/s),电磁轨道表面会发生磨损。为研究轨道表面磨损状态与接触电阻之间关系,通过开展电磁轨道发射试验,研究发射后的CuCrZr轨道表面沉积层的形成与磨损机制,揭示枢轨间静态接触电阻的演变规律,总结沉积层的形成与接触电阻的关联关系。结果表明:沿着发射方向,轨道表面沉积层覆盖面积逐渐增大,沉积层的形成机制由摩擦材料转移变为电枢表面熔化飞溅,表面磨损特征由机械磨损向电气磨损转变;由于轨道不同位置沉积层形成原因不同,导致表面粗糙度分布不一致,枢轨间静态接触电阻随接触沉积层形貌特征改变呈现上升、下降及波动3个变化阶段;并且枢轨间静态接触电阻随着接触压力的增大而减小。研究成果对电磁轨道发射装备的研究及发射动力学研究具有理论价值。

导电(Cu,Mn)_(3)O_(4)接触层在SOEC阳极侧的应用

固体氧化物电解池(SOEC)中铁素体不锈钢合金连接体和电解池阳极之间存在界面接触、连接体表面氧化以及氧电极“铬毒化”等问题,是导致电解堆性能衰减的重要影响因素之一。本工作利用反应烧结工艺在连接体与阳极之间制备了多孔的(Cu,Mn)_(3)O_(4)导电接触层,形成了粘结强度高的连接体/接触层/电解池界面结构。所得试样在750℃下表现出优异的电性能,整个500 h测试过程半电池的面比电阻(ASR)值稳定保持在20.13~20.32 mΩ·cm^(2)。通过微观结构表征技术证实,多孔(Cu,Mn)_(3)O_(4)接触层与相邻的电解堆部件具有良好的兼容性,并可以抑制连接体表面的氧化薄膜增长,同时阻止铬元素的迁移。(Cu,Mn)_(3)O_(4)接触层也降低了电解池与集流体之间的接触电阻,提高了电池电化学输出性能。

外延生长对GaN基PIN型器件的影响研究

实现了PIN型GaN外延材料的生长,并深入研究了影响器件性能的关键i-GaN外延层的生长温度和生长气流等要素。结果表明,适当的生长温度和气流条能够有效改善GaN的位错密度和背景掺杂,从而提升其晶体质量;过高或过低的生长温度和低气流则可能导致杂质原子如C、O等并入外延材料,形成高位错和缺陷。制备了GaN基PIN型器件,并探究了不同p层掺杂浓度对其电学I-V特性的影响。结果表明,较高的掺杂浓度有助于制备势垒低的欧姆接触,形成更优越的PN结特性。比较了Ni/Cr和Ni/Au两种金属接触对器件I-V特性的影响。结果表明,以Ni/Au制备P型欧姆接触能够获得更低的反向漏电流。此外,相较于Cr、Au具有更优越的稳定性和耐压性。深入探讨了PIN型GaN外延材料的生长条件对器件性能的影响,并通过制备GaN基PIN型器件深入研究了掺杂浓度和金属接触对电学特性的影响。

旧水泥混凝土路面沥青铺装层反射裂缝疲劳断裂分析

针对旧水泥混凝土路面沥青铺装层容易产生反射裂缝的特点,采用断裂力学理论,建立了5层体系平面应变模型,对各种荷载作用下不同层间结合状态和路面结构参数的应力强度因子进行了计算分析,并对常用防止反射裂缝措施进行了效果比较。结果表明:层间粘结状态对裂缝扩展的影响较大,土工格栅的防止反射裂缝效果相对较好。

富水海积砂层渗透注浆加固技术研究

富水海积砂层突水破坏是隧道建设极易诱发的地质灾害,不同的地质环境、注浆法浆液类别与海积砂层相互作用关系极为复杂。结合传统的水泥基浆液注浆施工工艺,综合运用半球形和柱形渗透扩散理论分析、模拟试验和现场监测等方法,研究富水砂层注浆扩散与加固机理,建立了注浆扩散范围与浆液对管片的压力的计算理论,并应用于特拉维夫市地铁联络隧道工程。研究结果表明:相较于冻结法,注浆法具有显著的经济效益。富水砂层扩散加固形式与砂层可注性与注浆压力相关,壁后注浆一般由渗透扩散向压密扩散的形式发展。在渗透阶段,半球形模型与柱形模型所揭示的浆液扩散规律基本一致,大小存在差异。浆液扩散半径主要取决于水泥基液中有效固体颗粒体积分数,当浆液体远离注浆口,浆液固体颗粒体积分数减小,浆液对土体孔隙的填充效果降低。浆液作用在隧道管片上的压力分布呈指数形式,沿注浆口径向急剧减小,后趋于平稳。

小车开关梅花触头电动更换装置设计与实现

针对使用螺丝刀等传统工具拆装梅花触头容易造成触头损伤、费时费力、人身伤害等问题,研制一种小车开关梅花触头电动更换装置,高效快捷拆装梅花触头,减少了停电时间,提高了保供电可靠性,避免了更换触指弹簧时损伤导电臂镀银层,最后通过应用案例验证了该技术实用、有效。

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。