Evolution of V-containing phases during preparation of Al-based Al−V master alloys

Al-based Al?V master alloys were prepared by both the stepwise heating melting experiment and stepwise melting cooling experiment with rapid solidification to investigate the transformation of V-containing phases which gave different effects on microstructures and properties of commercial Al alloys and Ti alloys, as both melting and solidification processes affect the evolution of V-containing phases largely. The results showed that the raw Al?50wt.%V alloy consisted of needle-like Al₃V phase and Al₈V₅ phase (matrix), while petal-like Al₃V, needle-like Al₇V and plate-like Al₁₀V phase were present in the Al?V master alloys. The metastable Al₇V phase was evolved from Al₃V phase and then evolved into Al₁₀V phase during melting process. The number of Al₁₀V phase increased with the decrease of temperature in the range of 800?1000 °C. Petal-like Al₃V phases could be transformed from Al₈V₅ phase, pre-precipitated from Al?V molten liquid during melting process and precipitated directly during rapid solidification, respectively.     

A novel measurement of intersegmental forces exerted on human lower limbs during forward falling and regaining balance motions

This study proposes an analysis system for evaluating the intersegmental forces exerted on human lower limbs. In existing analysis systems, the ground reaction force exerted on the feet is generally measured using force plates fixed on the motion trajectory, and the intersegmental forces are then estimated using an inverse dynamics approach. However, force plates are inconvenient and expensive. Accordingly, the present study proposes a method for evaluating the intersegmental forces without the need for force plates. In the proposed approach, the supporting and striding legs are modeled as a seven-link manipulator system, and the intersegmental forces is then derived using Newton–Euler theory. It is found that the estimated results are in good agreement with the actual measurement datum. Thus, the basic validity of the proposed analysis system is confirmed. For application, the intersegmental force would be the major reference datum to design the artificial joints.     

粉煤灰掺量对高性能自密实混凝土抗压强度发展影响分析

粉煤灰对自密实混凝土的工作性能、抗压强度和耐久性能等有着显著的影响.为了探究粉煤灰掺量对自密实混凝土抗压强度发展规律的影响,配制了粉煤灰掺量为30％、45％、60％(体积分数),水灰比为1.05、1.15、1.25(体积比)的自密实混凝土并进行立方体抗压强度试验,对其3d、7d、28d、90d抗压强度的变化规律进行了分...     

Analysis and optimization of the heat-insulating light concrete hollow brick walls design by the finite element method

Department of Public Works, owners and building proprietors are demanding high-capacity heat-insulating exterior masonry components specifically for further energy savings. For housing and industrial structures there is also a great interest in light building materials with good physical material behaviour, with respect to an energy conscious and ecological design, which fulfils all strength and serviceability requirements. The major variables influencing the thermal conductivity of masonry materials are illustrated in this work by taking blocks made from no-fine lightweight concrete and different mortar properties. The finite element method (FEM) is used for finding accurate solutions of the heat transfer equation for five different light concrete hollow brick walls. Mathematically, the non-linearity is due to the radiation boundary condition inside the inner recesses of the bricks. The conduction and convection phenomena are taking into account in this study for three different values of the mortar conductivity and three different values for the bricks. Optimization of the walls is carried out from the finite element analysis of five hollow brick geometries by means of the mass overall thermal efficiency and the equivalent thermal conductivity. Finally, conclusions of this work are exposed.     

和什托洛盖盆地北缘泥盆系海相烃源岩评价

应用地表露头样品的有机地球化学分析测试资料,从有机质丰度、类型、成熟度等方面,对和什托洛盖盆地北缘沙尔布尔山泥盆系海相烃源岩进行评价。研究表明:和布克赛尔组灰岩有机碳平均含量为0.31%、呼吉尔斯特组有机碳平均含量为0.72%,校正后分别达到中等烃源岩、好烃源岩的标准;有机显微组分以腐泥组为主,有机质类型全部为Ⅰ型;热演化程度适中,处于成熟阶段。虽然露头样品风化严重,导致各项分析测试数据存在不同程度的偏差,但沙尔布尔山地区泥盆系海相烃源岩具有一定的生烃能力是毋容置疑的。     

大凌河流域初始水权分配实践评价

结合大凌河流域初始水权分配实践,从分配范围、分配机制、分配原则、分配模型等方面,对现有研究成果进行全面梳理。在此基础上,结合大凌河流域特点,借鉴我国流域水资源配置评价指标体系,从公平性、效率性、可持续发展、政府宏观调控4个维度,设计了一套水权分配评价指标体系,进而构建了初始水权分配实践效果的耦合评价模型,并应用于大凌河流域。结果表明,在政府和大凌河流域水行政管理部门的宏观调控作用下,通过加强大凌河流域所在区域的政治民主协商,流域内各区域水权分配结果充分体现了与其社会经济发展之间的匹配性,且各区域之间的耦合协同发展效度均达到较高水平。     

堆石混凝土单轴受压应力-应变全曲线试验方法研究

为了研究堆石混凝土应力-应变全曲线,采用碟形弹簧与钢柱组合成附加刚性元件增强压力机的刚性,研究了碟形弹簧并联与串联联结装置的变形量和刚度以及实现单轴受压端部减摩措施,提出了一种堆石混凝土单轴受压应力-应变全曲线的试验方法。在混凝土压力试验机上进行了堆石混凝土立方体试件单轴受压试验,测得了堆石混凝土受压应力-应变全曲线。试件破坏形态表明,采用的端部减摩措施有效,测得的应力-应变曲线下降段验证了碟形弹簧与钢柱组合装置能够吸收试件破坏时混凝土压力试验机存储的变形能。研究结果为在混凝土压力试验机上进行堆石混凝土单轴受压应力-应变全曲线提供了可行、简便、经济的测试方法。     

Adaptive Synchronization of Complex Dynamical Networks with Time-Varying Delays

This paper addresses the problem of adaptive pinning synchronization of complex dynamical networks with nonlinear delayed intrinsic dynamics and time-varying delays. By introducing decentralized adaptive strategies to both the coupling strengths and the feedback gains, it is proved that the complex dynamical network can synchronize with the desired state for the bounded time-varying delays even when only one node is informed, without any global information of the underlying network. Finally, some numerical simulations are given to verify the main results and show the superiority of these self-designed adaptive strategies.     

新型高精度高效率LED照明驱动电路的实现

提出并设计了一种高精度、高效率LED照明驱动电路.采用平均电流控制模式代替峰值电流的控制模式;同时,采用低阶低侧的Buck拓扑结构,使输出驱动电流的精度误差控制在1％之内.整体电路的转换效率最高可达96％以上,输出驱动电流为350 mA,可驱动8个1W的HBLED灯.该设计基于CSMC 0.5μm 40 V BCD工艺,版图尺寸约为1.4 mm×1.4 mm.通过流片验证了设计的可行性.     

Network-coding based event diffusion for wireless networks using semi-broadcasting

Publish/subscribe is a well known and powerful distributed programming paradigm with many potential applications. Publish/subscribe content dissemination techniques based on opportunistic networking and network coding-based epidemic routing are key techniques for optimizing network resources, simplifying network architecture, and providing a platform for realizing innovative networking applications and service.In this paper we consider the central problem of any pub/sub implementation, namely the problem of event dissemination, in the case of a wireless mesh network. We propose a new dissemination strategy based on the notion of semi-broadcast. In a semi-broadcast based protocol the actual content is disseminated in two phases. In the first phase only a fraction of the content is broadcasted (pushed) over the network and stored inside any node, whereas in the second phase the missed part is retried (pulled) on demand from other nodes. Thanks to network coding the partial content stored in each node at the end of the first phase is a set of random linear combinations over the whole content. This allows a very efficient recovery strategy as the missed part is found in nearby nodes with a high probability.The benefit of this approach is that only the interested subscribers, which can vary in number and position over time, can engage the pulling phase.We propose several protocols based on non-trivial forwarding mechanisms that employ network coding as a central tool for supporting adaptive event dissemination while exploiting the broadcast nature of wireless transmissions and guided to the semi-broadcast principle. We show a considerable enhancement in term of total flooding costs and full decoding rates by a self parameter control deployment during the dissemination procedure.