Fabrication and characterization of NiCr-based films with high resistivity and low temperature coefficient of resistance

As a metal alloy,NiCr films have a relatively high resistivity and low temperature coefficient of resistance (TCR) and are widely used in electronic components and sensors.However,the resistivity of pure NiCr is insufficient for high-resistance and highly stable film resistors.In this study,a quaternary NiCrAlSi target (47:33:10:10,wt.%) was successfully used to prepare resistor films with resistivities ranging from 1000 to 10 000μΩcm and TCR within±100 ppm/K.An oxygen flow was introduced during the sputtering process.The films exhibit hightemperature stability at 450℃.The films were analyzed using Auger electron spectroscopy,x-ray diffraction,time-of-flight secondary-ion mass spectrometry,and x-ray photoelectron spectroscopy.The results show that the difference in the oxide proportion of the films caused the differences in resistivity.The near-zero TCR values were considered to be due to the competition between silicon and other metals.This study provides new insights into the electrical properties of NiCr-based films containing Si,which will drive the manufacturing of resistors with high resistivity and zero TCR.

Numerical Simulation of the Parallel Gap Resistance Welding Process of a Solar Cell and Mo/Pt/Ag Interconnector

Energy for space vehicles in low Earth orbit(LEO) is mainly generated by solar arrays, and the service time of the vehicles is controlled by the lifetime of these arrays, which depends mainly on the lifetime of the interconnects. To increase the service life of LEO satellites, molybdenum/platinum/silver(Mo/Pt/Ag) laminated metal matrix composite(LMMC) interconnectors are widely used in place of Mo/Ag LMMC and Ag interconnectors in solar arrays. A 2D thermal-electrical-mechanical coupled axisymmetric model was established to simulate the behavior of the parallel gap resistance welding(PGRW) process for solar cells and Mo/Pt/Ag composite interconnectors using the commercial software ANSYS. The direct multicoupled PLANE223 element and the contact pair elements TARGE169 and CONTA172 were employed. A transitional meshing method was applied to solve the meshing problem due to the ultrathin(1 μm) intermediate Pt layer. A comparison of the analysis results with the experimental results revealed that the best parameters were 60 W, 60 ms, and 0.0138 MPa. The voltage and current predicted by the finite element method agreed well with the experimental results. This study contributes to a further understanding of the mechanism of PGRW and provides guidance for finite element simulation of the process of welding with an ultrathin interlayer.

Corrected Formula of Bed Resistance Coefficient for Plane Numerical Simulation of Tidal Current

By means of a logarithm law for the velocity profile, a corrected formula of bed resistance coefficient, which involves many factors such as gradient of still water depth, variation of surface elevation, flow direction, and so on, is derived from the 3D governing equations of tidal current by averaging over the whole water depth. Theoretical analysis and application have shown that the 2D plane tidal current numerical model would be more reasonable and could be applied to steep bottom topography when the corrected bed resistance coefficient is used, therefore the results of reproduction simulation and engineering calculation would be more scientific and reasonable.

Study on resistance coefficient in compound channels

This paper presents a further study of the Manning and Darcy-Weisbach resistance coefficients, as they play a significant role in assessing the cross-sectional mean velocity, conveyance capacity and determining the lateral distribution of depth mean velocity and local boundary shear stress in compound channels. The relationships between the local, zonal and overall resistance coefficients, and a wide range of geometries and different roughness between the main channel and the flood plain are established by analyzing a vast amount of experimental data from a British Science and Engineering Research Council Flood Channel Facility （SERC-FCF）. And the experimental results also show that the overall Darcy-Weisbach resistance coefficient for a compound channel is the function of Reynolds number, but the function relationship is different from that for a single channel. By comparing and analyzing the conventional methods with the experimental data to predict composite roughness in compound channels, it is found that these methods are not suitable for compound channels. Moreover, the reason why the conventional methods cannot assess correctly the conveyance capacity of compound channels is also analyzed in this paper.

Thin Film Chip Resistors with High Resistance and Low Temperature Coefficient of Resistance

High resistance thin film chip resistors(0603 type) were studied,and the specifications are as follows:1 k? with tolerance about ±0.1% after laser trimming and temperature coefficient of resistance(TCR) less than ±15×10-6/℃.Cr-Si-Ta-Al films were prepared with Ar flow rate and sputtering power fixed at 20 standard-state cubic centimeter per minute(sccm) and 100 W,respectively.The experiment shows that the electrical properties of Cr-SiTa-Al deposition films can meet the specification requirements of 0603 ty...

Analysis of sliding electric contact characteristics in augmented railgun based on the combination of contact resistance and sliding friction coefficient

The contact resistance between the armature and rails is an important indicator of the contact characteristics in electromagnetic launches.As the contact resistance depends not only on the contact state but also on the contact stress and temperature,there are some limitations in analyzing the contact characteristics using only the contact resistance.In this paper,the contact characteristics of the augmented railgun are analyzed by the combination of contact resistance and sliding friction coefficient.Firstly,the theoretical calculation model of the contact resistance and friction coefficient of the augmented electromagnetic railgun is established.Then the contact resistance and friction coefficient are calculated by the measured values of the muzzle voltage,rail current and armature displacement.Finally,the contact characteristics are analyzed according to the features of the waveforms of the contact resistance and the friction coefficient,and the analysis conclusions are verified by experimental rail images.The results showed that:the aluminum melt film gradually formed on the contact surface reduces the contact resistance and the friction coefficient;the wear and erosion of the armature cause deterioration of the contact state;after the transition,the reliability of the sliding contact between the armature and rails decreases,resulting in an increase in contact resistance.

Anisotropy of Expansion Coefficient and Slag Resistance of Spinel Carbon Bricks

Effects of the pressure direction on the thermal expansion and slag corrosion resistance were investigated and anisotropic microstructures of flaky graphite in spinel carbon bricks were examined. The experimental results show that slag corrosion velocities in the direction parallel to the pressure direction display a decrease of 34% compared to those in the vertical direction. Meantime, the linear expansion coefficient in the direction parallel to the pressure direction is 2.45 times as large as that in the vertical pressure direction. Slag corrosion velocities of spinel carbon bricks soaked in the AOD melting slag display a 46%-47% decrease compared to those of magnesia carbon bricks. The microstructure observation shows that spinel carbon bricks have a high degree of preferred orientation.

Uphillshift decision strategy of an AMT off-road vehicle based on generalized road resistance coefficient

In order to improve the shift decision strategy for an off-road vehicle with automated manual transmission（AMT）,the generalized road resistance coefficient is defined based on the longitudinal dynamics analysis.Vehicle mass and generalized road resistance coefficient are estimated using the recursive least square（RLS）method with multiple forgetting factors.The improved shift schedule is designed based on the generalized road resistance coefficient under uphill road condition.The simulation and real vehicle test verify the effectiveness of improved shift strategy and the improvement of vehicle dynamic performance.

Experimental Study on Rotation Resistance Coefficient of Motor Bogie for Type A Vehicle

Rotation resistance coefficient is an important operating parameter for vehicle bogies, which influences the dynamic behavior of vehicles directly. A research on the rotation resistance coefficient of type A vehicle motor bogies was conducted by means of theoretical calculation, dynamic simulation, test certification, and so on. Result of the simulation analysis shows that the rotation resistance coefficient relates to air springs stiffness and negotiated curve radii, and it varies proportionally with the change of air springs horizontal stiffness. The greater the rotation angle is, the greater the factor becomes. The certifications made under the operating conditions(e.g., different air spring status, different rotation speeds) indicate that the rotation resistance coefficient increases with the increase of the rotation speed. The anti-yaw dampers can contribute to the rotation resistance torque acted on bogie, and the greater the rotation speeds are, the greater the torque generated by the anti-yaw dampers is. The results suggest that the theoretical analysis and dynamics simulation are in accordance with the results from the bogie bench tests, which meet the requirements in EN14363 and the indicators in vehicles safe operation.

Determination of rock mass integrity coefficient using a non-invasive geophysical approach

Determination of rock mechanical parameters is the most important step in rock mass quality evaluation and has significant impacts on geotechnical engineering practice.Rock mass integrity coefficient(KV)is one of the most efficient parameters,which is conventionally determined from boreholes.Such approaches,however,are time-consuming and expensive,offer low data coverage of point measurements,require heavy equipment,and are hardly conducted in steep topographic sites.Hence,borehole approaches cannot assess the subsurface thoroughly for rock mass quality evaluation.Alternatively,use of geophysical methods is non-invasive,rapid and economical.The proposed geophysical approach makes useful empirical correlation between geophysical and geotechnical parameters.We evaluated the rock mass quality via integration between KV measured from the limited boreholes and inverted resistivity obtained from electrical resistivity tomography(ERT).The borehole-ERT correlation provided KV along various geophysical profiles for more detailed 2D/3D(two-/three-dimensional)mapping of rock mass quality.The subsurface was thoroughly evaluated for rock masses with different engineering qualities,including highly weathered rock,semi-weathered rock,and fresh rock.Furthermore,ERT was integrated with induced polarization(IP)to resolve the uncertainty caused by water/clay content.Our results show that the proposed method,compared with the conventional approaches,can reduce the ambiguities caused by inadequate data,and give more accurate insights into the subsurface for rock mass quality evaluation.

Experimental Study on Influencing Factors of Resistance Coefficient and Residual Resistance Coefficient in Oilfield Z

In order to clarify the major influence factors of resistance coefficient and residual resistance coefficient, so as to provide the basis for optimizing the polymer flooding schemes in oilfield Z of Bohai Sea, artificial cores were made by simulated the characteristic parameters of real reservoir and the spacing of production-injection wells. The main parameters considered include reservoir permeability, polymer solution concentration and polymer injection rate. Core experiment of polymer flooding was taken by considering all the main parameters. The result showed that resistance coefficient and residual resistance coefficient decrease with the increase of core permeability. Resistance coefficient and residual resistance coefficient increase with the increase of concentration of polymer solution. The increment of displacement pressure in low permeability core is higher than in medium and high permeability core. The resistance coefficient increase with higher displacing velocity, and the increment in high permeability core is higher than in low permeability?core. The displacement velocity has little effect on the residual resistance coefficient. The experimental results can effectively guide the formulation of polymer flooding scheme in offshore oilfields, and optimize the appropriate injection rate and concentration of polymer solution for different properties of reservoirs, thus ensuring the effectiveness of polymer flooding in offshore oilfields.

Bogie's Rotational Resistance Coefficient Analysis Based on Novel Parallel Mechanism

In this paper,a novel parallel mechanism which can be used to evaluate body-to-bogie yawtorque is proposed.It can satisfy experimental testing for rotation resistance coefficient(RRC) with various types of bogies,different rotational speeds,and different states of air spring.Aiming at the problem that computing speed of Newton iterative method for solving rotational angle is incompetence to meet the real-time requirements,and also that other methods adopting physical device such as laser displacement sensor to solve rotational angle possess larger measurement error,the analytical techniques method used for solving rotational angle is presented.Finally,by using the upper-single-6-DOF motion platform as an authentic urging mean to simulate a real vehicle,the test was carried out under the speeds of 0.2 and 1.0(°)/s,with the air spring at the inflated and deflated states,respectively.The results showthat the RRC of the bogie under various conditions is less than 0.06,which meets the standard requirement EN-14363.It was also found that the speed of vehicles moving along curves and the state of air spring were key factors influencing the RRC.The feasibilities of this model and test method are verified in this study.

Experimental Determination of Local Resistance Coefficient of Sudden Expansion Tube

Theoretical derivation of local resistance coefficient of sudden expansion tube is presented. Several assumptions are analyzed in the theoretical derivation. That the head loss shall be neglected is affirmed. Experimental data proves that the pressure before and after sudden expansion section is basically the same. That the friction force on the side face of control body is neglected is denied and it is pointed out that such neglect is the main cause for error between theoretical calculation and actual measurement. Experimental device for measuring local resistance coefficient is designed in combination with theoretical derivation process. Optimal gradually varied flow section is selected after sudden expansion pipe in Bernoulli equation based on variation of piezometer tube head. It is pointed out in accordance with experimental data analysis that the value of local resistance coefficient of sudden expansion tube determined through experimental data is closer to the actual situation during pipeline design.

粗糙度对单桩竖向承载变形特性影响的试验研究

为探究桩侧粗糙度对单桩承载变形特性的影响规律,自主研发了多功能桩基静动力模型试验系统,构建了光滑、随机型及带肋规则型桩侧界面的模型单桩,通过3D形态扫描计算获得了桩侧表面粗糙度Rn,基于此开展了饱和砂土中单桩静载模型试验。试验结果表明:(1)粗糙度越大,单桩极限承载力和桩的割线刚度越大,桩顶沉降及其卸载回弹量越小,带肋桩能够有效提高桩基承载力并控制桩顶变形。(2)粗糙度越大,桩侧阻力越大,桩端附近侧阻力的强化效应越明显,桩侧阻力的分布模式随桩顶荷载增大由“单驼峰”到“锥顶柱”再至“斜坡”依次演变。(3)β值(β法中参数)随桩侧粗糙度的增大而增加,随深度增加而衰减。带肋桩的极限侧阻力及β值远大于砂纸和光滑桩,揭示了埋深和粗糙度对β值影响规律的机制。(4)桩侧粗糙度会影响砂土地基中桩端荷载传递函数类型,光滑桩、砂纸桩桩端荷载传递函数呈双曲线型,带肋桩呈直线型。上述研究结果对深刻认识桩侧粗糙度对单桩承载变形特性影响规律和机制具有重要参考价值。

金枪鱼延绳钓单丝和绳索的惯性力系数和阻力系数研究

金枪鱼延绳钓单丝和绳索的惯性力系数C_(M)和阻力系数C_(D)取值直接影响到渔具数值模拟的计算速度和精度。通过波浪水槽试验探究了7种金枪鱼延绳钓单丝和绳索材料在规则波条件下所受的波浪力,并在Morison方程的基础上,使用最小二乘法计算出相应材料的C_(M)和C_(D);分析了C_(M)和C_(D)随KC数和雷诺数Re的变化情况。结果显示:同一波高下,试验材料所受波浪力随着波浪周期增加逐渐增加;同一波浪周期下,试验材料所受波浪力随波高增加逐渐增加;相同材料随着直径增加,所受波浪力增加;3种尼龙单丝随着KC数增加C_(D)逐渐增加,C_(M)变化不明显,趋于常数,随着雷诺数Re的增加C_(M)和C_(D)有逐渐增加的趋势;3种聚丙烯绳索C_(M)随着KC数和雷诺数Re增加而增加,C_(D)在低KC数时较为平稳,其随着雷诺数Re增加逐渐下降,趋于常数;涂沥青的聚丙烯绳索的C_(M)和C_(D)较为稳定。研究表明,本试验得出的C_(D)和C_(M),可用于延绳钓渔具数值模拟。

防滑袜防滑性能检测方法的研究

文章结合防滑袜产品的实际使用场景,通过对现有的摩擦系数测试标准进行研究,确定了采用静摩擦系数来表征防滑袜防滑性能的方法。通过试验选择合适的标准平面(摩擦介质)、接触面积和滑块质量作为防滑袜防滑性能的测试参数。根据确定的试验参数,对收集的防滑袜样品进行测试,分析试验数据发现,带硅橡胶面的袜底其静摩擦系数大于织物面的袜底,本试验方法可以有效地反映出防滑袜防滑性能。

高密度电阻率法在复杂岩溶地区的应用研究

岩溶地区多存在塌陷安全隐患,严重影响工程建设及使用安全,因此准确探测岩溶的形态特征及填充性质在工程勘察中尤为重要。近年来,高密度电阻率法因其适应性强、采集效率高和显示直观的特点,已经成为岩溶探测的有效手段。本文引入反射系数K剖面法,通过分析其原理及发展,对比了与传统软件RES2DINV的处理效果。并以西南地区某机场工程为例,采用高密度电阻率法中不同装置类型、不同电极距对地下岩溶发育情况进行探测,通过对比分析得到适合该场区的探测方法和参数,同时结合钻孔资料进行综合解释,弥补由点到面的不足。通过本文的实践和验证,高密度电阻率法在复杂地形条件下探测岩溶发育有很好的反映,且斯伦贝谢装置的识别效果比温纳装置更佳,反射系数K剖面法处理后的剖面对岩溶形态特征刻画得更为清晰,为工程的后期勘察和资料处理以及防治措施提供了技术支撑,对于岩溶地区的地质勘察具有良好的应用和参考价值。

电流体喷印电磁功能微阵列结构

提出一种基于电流体喷印技术的复合材料衬底电磁功能微阵列结构制造工艺方法。通过间距补偿工艺策略,降低复合材料衬底功能结构线宽尺寸误差的47.4%,有效提高了复合材料衬底喷印精度。系统分析了电流体喷印参数对功能结构质量的影响关系,实现复合材料衬底上多尺寸、多类型电磁功能微阵列结构的按需制造。确定了电磁功能微阵列结构的最优固化条件,得到线宽60μm金属结构电阻率为9.18×10^(-8)Ω·m。所制造的带阻型电磁功能微阵列结构在中心频率23.64 GHz处能够将电磁波有效抑制,透射系数为-42.89 dB,有效验证了电流体喷印技术制造电磁功能结构的能力与实现效果。

真空筛分多孔介质床流动阻力系数预测及影响因素分析

探究真空筛分流体流动特性对于揭示真空筛分机理至关重要。然而,真空筛分过程中筛网截留的固体颗粒形成的过滤床难以采用微观结构描述,通常假设为多孔介质床。为了精确描述多孔介质床的流体流动特性,深入研究真空筛分性能,文章基于实验与机器学习方法预测真空筛分多孔介质床流动阻力系数,分析了BP神经网络,随机森林和XGBoost模型特征重要性排序结果,识别出影响多孔介质床流动阻力系数因素的敏感性顺序为气流速度>颗粒床>颗粒配比>颗粒层厚度>筛网目数。最后,采用遗传算法GA,以XGBoost预测模型作为多目标优化的适应度函数,建立真空筛分多孔介质床多目标优化模型,得到最优真空筛分工艺参数和流动阻力系数。文章为真空筛分流动阻力系数的研究提供了一种新方法,研究结果对揭示真空筛分机理具有重要意义。

冷却通道对引射器红外辐射特性影响的研究

为降低燃气轮机排气系统中的引射器排气温度,从而减少排出燃气的红外辐射强度,本文提出了一种具有冷却通道的亚音速引射器结构,并提出了评价冷却通道引射器的综合系数。在原有的引射器喷嘴内增加冷却通道,使冷气直接与主流中心位置的高温气体掺混,破坏排气包覆性分布,达到提高主流温度均匀性、降低中心温度的目的。本文运用数值模拟的方法,研究引射器内冷却通道数量、冷却通道进深和排气通道的排布对引射器内阻力特性、换热特性、出口温度分布特性的综合影响。研究结果表明:单排冷却通道排布时,通道数量与换热特性成正比,与阻力损失成反比;双排冷却通道排布时,阻力损失降低。双排12通道引射器可有效降低出流总温,均匀主流温度,综合系数最高。