加芯搅拌桩芯桩定位限垂技术的研发与应用

为控制水泥土加芯搅拌桩的芯桩贯入质量,研发了一种基于芯桩定位导向架的定位限垂挑臂装置,并通过采用不同材质、不同尺寸的方法,反复摸索、实施,分析得出了芯桩定位导向架的定位限垂挑臂装置的最优方案。同时,通过运用数据比对、图表说明的方法,有效验证了加芯搅拌桩芯桩定位限垂挑臂装置对于现场施工的重要作用。在新疆地区23450 根加芯搅拌桩工程中进行首次应用,实践表明研发的定位限垂技术可有效控制芯桩贯入的定位和垂直度,提高施工效率。该定位限垂技术经济效益良好,可为今后新疆地区特殊软基处理以及加芯搅拌桩施工提供参考价值。     

方波激励下纳米晶体铁心损耗模型建立与验证

为了实现电力机车小型化轻量化的发展要求,国内外专家考虑通过采用提高变压器的工作频率减小变压器整体的体积和质量。铁心作为高频变压器的关键部件,可以准确计算铁心损耗,对中高频变压器的设计和优化具有重要作用。针对高频变压器铁心通常是工作在方波或脉宽调制(PWM)波等非正弦激励下的特点,对传统Steinmetz损耗计算模型进行了优化改进,给出了考虑磁密的变化率及波形系数对损耗的影响的Steinmetz改进损耗模型。同时,为了提高损耗模型在不同特征频率下的通用性,进一步对损耗模型系数的非线性进行研究,给出了模型系数随频率变化的非线性函数。最后,利用有限元计算结果同实物测量结果进行比较,证明了所提损耗模型在方波激励下对纳米晶体铁心计算的准确性。     

高压输电线路在线监测设备无线供电磁耦合机构优化

对高压输电线路进行实时精准的在线监测是保障电网稳定运行的有效手段。磁耦合共振无线供电为解决在线监测设备供电困难的问题提供了一种可行方案,但传统磁耦合共振系统耦合程度弱,传输效率对传输距离变化敏感,总体性能欠佳。基于电路模型分析了耦合线圈互感对传输效率的影响,提出了考虑线圈与磁芯耦合影响关系的联合优化方案从而提升传输性能。仿真和实验结果验证了在同轴间距、水平和角度偏移变化时的系统效率提升。为提升磁耦合系统传输效率和距离提供了一种有效方案。     

Hygroresponsive Torsional Yarns and Actuators Based on Cascade Amplification of the Deformation

Fiber-based hygroresponsive torsional actuators provide desirable merits, such as light weight and shapeability, for developing smart systems to harvest energy from moisture which is a ubiquitous natural resource. A key challenge in this development is to realize moisture-triggered actuation combining large actuation and rapid responses. Here, a multiscale design strategy is explored to create high-performance hygroresponsive torsional actuators consisting of chitosan and multiwalled carbon nanotubes (MWCNTs). The superior actuation performance arises from the synergism of contributing factors at different scales, including 1) MWNCTs accelerate the water transport in primary twisted fibers (PTFs), fostering the rotation of PTFs upon moisture stimuli; 2) in situ-formed hierarchically-assembled twists realize cascade amplification of moisture-triggered actuation. Specifically, PTFs are self-twisted to generate secondary helical yarns, that are subsequently over-twisted to yield tertiary coiled yarn. The resultant yarn actuator can reach a maximum rotation speed of 11 400 rpm in 5 s, output gravitational potential energy of 2.4 J kg⁻¹ and gravitational potential power of 0.053 W kg⁻¹ during contraction. This work represents the first design of fiber-based actuators by virtue of moisture-triggered in situ formation of yarns. The established principles of multiscale design will enable high-performance fiber-based hygroresponsive actuators toward advanced intelligent textile and soft robotics.     

Stretchable,Antifreezing, Non-Drying,and Fast-Response Sensors Based on Cellulose Nanocomposite Hydrogels for Signal Detection

Conductive hydrogels have received widespread attention in the applications of biosensors, human–machine interface, and health recording electrodes. Herein, the conductive hydrogels integrated with antifreezing, water retention, reusable, and sensing performances are fabricated by introducing polyvinyl alcohol, cellulose nanofibril, MXene nanosheets, and glycerol. The as-prepared hydrogels present prominent electrical conductivity (2.58 mS cm⁻¹) and flexibility even at −18 °C. In addition, the hydrogels have favorable water retention performance and can reuse after heating and cooling. When used as sensors, the hydrogels illustrate high sensitivity (gauge factor of 2.30), fast response time (0.165 s), wide working strain range (559%), favorable linearity (R² = 0.999), and wide operating temperature range (−18 to 60 °C). The hydrogels can detect not only large strains of 10–200%, but also small strains of 1–5%, making them promising candidates for wearable sensors to monitor large and subtle movements.     

Effects of micro-sized mullite on cristobalite crystallization and properties of silica-based ceramic cores

Silica-based ceramic cores are extensively used in investment casting process, during which they must exhibit sufficient flexural strength and deformation resistance. In this study, micro-sized mullite was used as an additive to silica-based ceramic cores to optimize their high temperature properties. To investigate the effects of micro-sized mullite on cristobalite crystallization, mechanical and thermal properties of silica-based ceramic cores, ceramic cores with different amounts of micro-sized mullite were fabricated. The XRD results showed that additional micro-sized mullite diminished the crystallization of cristobalite at high temperatures, primarily caused by the mullite related compressive stresses on the surface regions of fused silica particles. Three-point bending tests and SEM results showed that micro-sized mullite had a more significant effect on the flexural strength of ceramic cores compared with conventional additives. Particularly, the fracture mechanism of silica-based ceramic cores had been changed from intergranular fracture into a mixed fracture consisting of both intergranular and transgranular fracture. The mechanical and thermal properties of ceramic cores were all reduced slightly as the mullite content exceed 4.6 wt%. Hence, to optimize the properties of silica-based ceramic cores, the micro-sized mullite content should not exceed 4.6 wt%.     

铜基薄壁热管应用现状及发展趋势

在5G通信技术及消费电子行业快速发展的背景下,铜基薄壁热管被广泛应用于大功率电子设备散热领域。通过介绍目前应用较广的几种热管,对其结构、特点及应用范围进行了对比 ;阐述热管在加工制备和使用过程中存在的一些问题和缺陷,对表面缺陷形成机理进行分析,并对热管未来的发展趋势进行了展望。     

管模工艺的优化

管模是生产离心球墨铸铁管的模具,其毛坯的锻造成型非常困难。本文介绍了管模锻造工艺的优化过程。采用优化后的工艺,解决了管模在锻造生产中出现的各种问题,使管模的成品率大幅提高。同时也为长筒型锻件的成型提供了可靠的参考依据。     

压铸模具型芯变形失效的研究分析

压铸模具的型芯变形失效很容易造成铸件的成批量报废.文中对于一失效型芯进行了分析研究,结果表明,其弯曲变形是由于受到不断循环的热作用及金属液的冲击所造成的微小变形积累造成的;同时,型芯的硬度在不同的部位均有下降,其中在冲击部位下降幅度最大.型芯在与铝液接触的表面会形成过渡层,圆形的型芯横截面会发生变形.采取有效的措施是可以避免田型芯弯曲变形所造成的铸件成批量报废的.     

气体硬化水溶性砂芯的性能研究

以电熔刚玉为骨料、氢氧化钡为粘结剂、铝粉为添加剂的型芯混合料在吹入CO_2气体后即可实现硬化。本文研究了这种型芯的硬化工艺和常温特性,并采用X射线衍射分析、失重—示差热分析等方法,结合粘结膜的扫描电镜照片,对型芯的受热物理化学变化、高温强度、水溶性等行为进行了实验研究。