基坑支护中土压力系数计算方法的探讨

为讨论不同计算方法对4类粘性土的适用性,分别用3种方法计算了各类土土压力系数和土压力强度,其结果是只考虑内摩擦角的公式法对于超固结土、正常固结土和欠固结土适用性较好,对湿陷性黄土适用性稍差;只考虑c法,对4类土均不适用;尽管等值内摩擦角法对于4类土也不适用,但考虑到等值内摩擦角法计算简便,对该法的参数选取也给出了相应的建议。     

工程机械新型全液压转向系统

本文给出一种工程机械新型全液压转向系统，能实验运输行驶，小回转半径，斜行等多种工况。     

Niobium boride coating on AISI M2 steel by boro-niobizing treatment

In this study, niobium boride coating was applied on pre-boronized AISI M2 steel by the thermo-reactive deposition technique in a powder mixture consisting of ferro-niobium, ammonium chloride and alumina at 950 °C for 1-4 h. The coated samples were characterized by X-ray diffraction, scanning electron microscope and micro-hardness tests. Niobium boride layer formed on the pre-boronized AISI M2 steel was smooth, compact and homogeneous. X-ray studies showed that the phases formed on the steel surfaces are NbB, Nb₃B₂, FeB and Fe₂B. The depth of the niobium boride layer ranged from 0.97 μm to 3.25 μm, depending on treatment time. The higher the treatment time the thicker the niobium boride layer observed. The hardness of the niobium boride layer was 2738 ± 353 HV_0.01.     

Abrasive Wear Volume Maps for PA6 and PA6 Composites Under Dry Working Condition

In this study the wear volume map is obtained and considered for evaluation of the abrasive wear performance for polyamide (PA6) and PA6 composites. Polyamide composites were tailored using 25 wt.% glass bead, 20 wt.% talc and 30 wt.% wollastonite fillers. In this work, the influence of filler materials, abrasion surface roughness and applied loading values on abrasive wear performance of PA6 and PA6 composites were evaluated. Experimental abrasive wear tests were carried out at atmospheric condition using pin-on-disc rig arrangement. Tests were performed under 4, 6, 8 and 10 N load values, traveling speed of 1 m/s and abrasion surface roughness values of 5, 20 and 45 μm. Wear volume maps were obtained and the results showed that the lowest wear volume rate for PA is reached using glass bead filler. Furthermore, the results also showed that the higher is the applied load and the roughness of the abrasion surface, the higher is the wear rate. Finally it is also concluded that abrasive wear process mechanism include ploughing mechanism and delimitation of filler tips.     

生物医用近β钛合金TLM表面官能化的研究

在新型近β钛合金Ti-3Zr-2Sn-3Mo-15Nb(TLM)表面用溶胶-凝胶法镀上一层TiO2薄膜,在500～1000℃热处理后,将薄膜分别用过硫酸钾溶液、双氧水/硫酸混合溶液、双氧水/盐酸混合溶液3种溶液处理以在薄膜表面引入活性OH.研究了3种不同溶液的处理效果以及处理时间对薄膜表面引入OH的影响.检测结果表明,3种溶液处理后均能在薄膜表面引入OH.双氧水和硫酸溶液及双氧水和盐酸溶液处理3 h后OH-密度就可达到峰值,而过硫酸钾溶液处理5 h后OH-浓度才能达到峰值,过硫酸钾溶液处理效果最好,其余两种溶液处理效果基本相同.薄膜表面引入OH-后,对蒸馏水的接触角降低,亲水性更好.     

宜昌闪长岩制备SMA及其性能研究

为了充分利用宜昌当地的矿石资源,采用宜昌闪长岩制备了沥青马蹄脂碎石(SMA)。研究结果表明:宜昌闪长岩的各项性能与京山玄武岩性能相近;采用宜昌闪长岩制备的SMA的性能指标满足施工技术规范要求。经济性分析表明:与采用外地玄武岩制备的SMA相比,其原料成本节约近50%。     

Effect of Partner Fit in International Construction Joint Ventures

Joint ventures have been an important research topic over the last few decades primarily because of their importance as a strategic alternative in global competition. Due to the inherent complexities of international joint ventures (IJVs), involving a mixture of different managerial systems, attitudes, and business strategies, such entities are very difficult to manage. In this study, the effect of strategic, organizational, and cultural fit between IJV partners and of interpartner relations on IJV performance is examined through a questionnaire survey. IJV performance is measured by means of two constructs: “project performance” and “performance of IJV management.” The results point out the significance of the quality of partner relations for a successful IJV operation. Findings of the study also suggest that the level of organizational fit between the partners has a moderate influence on IJV performance. It was observed that strategic fit between IJV partners affects interpartner relations extensively, which in turn affects IJV performance. IJV partners with compatible technical and managerial skills, financial resources, organizational size, workload, and project experiences are expected to achieve greater IJV success.     

虚拟稳态同步负阻抗的VSG功率解耦策略

伴随着分布式能源渗透率的逐渐提高,电力系统中的转动惯量相对减小,严重影响到系统安全稳定运行。其中虚拟同步发电机(Virtual Synchronous Generator, VSG)因具备同步发电机的相关特性而备受关注。针对VSG实际输出端口点到并网点的传输功率过程中存在耦合而引起VSG功率控制产生稳态误差和动态振荡,从而引起下垂特性的变化的情况,在对动静态功率耦合机理分析的基础上,提出基于虚拟稳态同步负阻抗的功率解耦策略,更好地消除了功率环间的耦合作用。通过建立基于所提出的VSG新型功率解耦策略的全局状态空间小信号模型,证明了该解耦策略的有效性。最后,搭建了基于解耦策略的VSG实验平台。通过实验结果验证了所提解耦策略的有效性,消除了功率环间的耦合作用,增强了VSG有功功率和无功功率的动静态响应性能。     

Design and Performance Study of Dynamic Fractors in Any of the Four Quadrants

A fractor is a simple fractional-order system. Its transfer function is \(1/Fs^{\alpha }\); the coefficient, F, is called the fractance, and \(\alpha \) is called the exponent of the fractor. This paper presents how a fractor can be realized, using RC ladder circuit, meeting the predefined specifications on both F and \(\alpha \). Besides, commonly reported fractors have \(\alpha \) between 0 and 1. So, their constant phase angles (CPA) are always restricted between \(0^{\circ }\) and \(-90^{\circ }\). This work has employed GIC topology to realize fractors from any of the four quadrants, which means fractors with \(\alpha \) between \(-\)2 and +2. Hence, one can achieve any desired CPA between \(+180^{\circ }\) and \(-180^{\circ }\). The paper also exhibits how these GIC parameters can be used to tune the fractance of emulated fractors in real time, thus realizing dynamic fractors. In this work, a number of fractors are developed as per proposed technique, their impedance characteristics are studied, and fractance values are tuned experimentally.     

激光干涉仪无线测控的设计和实现

针对传统激光干涉仪需要手动调节光学部件问题,设计并开发了一种激光干涉仪无线测控系统,该系统可以无线调节激光干涉仪光学部件的位置。系统采用nRF2401无线射频技术,与传统的nRF2401运用相比,该系统采用奇偶校验和CRC校验的双重校验,提高无线射频传输数据的正确率。同时系统采用闭环控制,提高了激光干涉仪的精确度和稳定性,避免了光学部件的过量调节对激光干涉仪的损伤。