外钓岛-册子岛水平定向钻穿越施工技术研究

外钓岛-册子岛水平定向钻穿越工程穿越曲线超长，地质条件极为复杂，施工难度前所未有。通过对穿越工程特点及施工难点的分析，考虑到实际施工中的技术要求和工程要求，采取了先进的技术措施，实现了外钓岛-册子岛长距离、复杂地层的海底管道穿越，为国内外同类条件的水平定向钻穿越施工积累了宝贵的经验。     

Evolution of elongated pores at the melt–solid interface during controlled directional solidification

The evolution of elongated gaseous pores during directional solidification has been examined through a theoretical model and compared to previous experimental findings from the literature. The model is based on the observation and interpretation of a wedge-shaped structure on the solid side that extends beyond the melt–solid interface and wraps around the bubble at its equator. At the tip of the wedge is the meeting point of the melt, solid and gas. The model takes into account the competition around the meeting point between the law of segregation of the solute at the melt–solid interface on one hand, and Henry’s law, which governs the concentration of the solute at the melt–pore interface at a given pressure, on the other. It predicts VR² = constant, where V is the processing speed and R is the pore radius, and agrees well with reported experimental data.     

An Experimental Investigation of the Effect of Strip Thickness,Metallostatic Head and Tip Setback on the Productivity of a Twin-roll Caster

Summary

An experimental study has been made of the factors affecting productivity during the twin-roll casting of AA 5182. Strip has been cast over a much wider range of thicknesses and tip setbacks than previously reported. An empirical expression is obtained which relates productivity to strip thickness, metallostatic head and tip setback. It is shown that productivities can be considerably increased over the usual commercial practice by casting thin sheet with large tip setbacks.     

Effects of spiral geometries on grain selection during casting of single crystal superalloys

Abstract

Grain texture evolution in starter block during single crystal (SX) casting with a grain selector had been investigated. Several spiral grain selectors with different spiral geometries were designed to investigate the effects of spiral geometries on grain selection in spiral passage. The results indicated that the percentage of grains with a deviation angle of <10° from the axial orientation increased simultaneously with distance from the chill plate. When the distance reached 36·1 mm, nearly 90% of the grains’ misorientations were <10°, and the minor grains deviated >12°. As the spiral angle θ and the spiral thickness T decrease, the SX structure occurred at the lower position of the grain selector. In addition, it was concluded that the SX structure cannot be selected when the spiral angle is <15°. Moreover, the effect of spiral geometries on grain selection has also been discussed.     

Tensile and fatigue behaviour of Ni–Ni3Si eutectic in situ composites

A Ni–Ni₃Si composite was fabricated via a eutectic reaction (Ni–Ni₃Si) using a rapidly cooled directional solidification technique at a solidification rate of 40?μm?s^?1. The composite consisted of approximately 62.2% Ni–Si solid solution and 37.8% Ni–Ni₃Si eutectic phase in volume. Four-point bend fatigue tests were carried out on the composite. The fatigue strength of the alloy was measured to be 520?MPa (maximum cyclic stress). It was found that the fatigue cracks were preferably initiated in the Ni–Ni₃Si eutectic phase, and that the Ni matrix was fractured in a cleavage fashion. It was probably attributed to the high level of supersaturated Si in the Ni matrix, which led to inducing the embrittlement of the Ni matrix.     

High level communication functionalities for wireless sensor networks

In this paper we show how to establish a reliable and efficient high level communication system in a randomly deployed network of sensors equipped with directional antennas. This high level communication system enables the programming of the sensor network using high level communication functionalities without the burden of taking care of their physical capacities (low range, unidirectional links, single frequency, presence of collisions, etc.). The high level communication functionalities we offer include point-to-point communication, point-to-area communication, and one-to-all communication. The basic idea to implement this system is to simulate a virtual network that emerges from the ad-hoc network using self-organization, self-discovery and collaborative methods. We also analyse the efficiency, scalability and robustness of the proposed protocols.     

太阳能电池多晶硅铸锭的凝固原理和方法浅谈

首先从定向凝固的原理讲起,其中涉及定向凝固的一些重要的工艺参数以及多晶硅铸锭的组织结构;其次,介绍了多晶硅铸锭的几种凝固方法,尤其着重讲了一下热交换法的应用;并在结尾提到了现在铸锭法中需要改进和解决的主要问题。     

70m砖烟囱定向爆破拆除及结果分析

爆破拆除一座 70m高的砖结构烟囱时 ,该烟囱没有按预期的方向倾倒。文中介绍了设计方案、实际爆破参数以及爆破效果 ,并对爆破中烟囱的实际倒塌结果与设计要求不一致的原因作了详细的分析。     

关于ICRU39号报告中的辐射量的讨论

本文介绍了 ICRU39号报告中提出的用于场所监测和个人剂量监测的四个辐射量的概念和特性,分析了它与以往的用剂量当量指数量方案的差别和改进之处,指出了它在实用中还存在的一些困难和应用中尚须注意的问题。     

A State‐Space Based New Approach To The Directional Interpolation Problem

Directional interpolation plays an important role in robust control, system realization and model reduction. Several solutions to various directional interpolation problems have been proposed. In this paper, we consider the directional interpolation problem in a general setting and present a statespace based new approach to solving the problem. The solution is simple, and its exposition is as self‐contained as possible. We describe all the (strictly) bounded real rational matrix functions that satisfy the directional interpolation requirements by means of linear fractional transformation. Moreover, we give a necessary and sufficient condition for the interpolating function to be unique and show that the unique interpolating function is an inner (a co‐inner). The main procedures used to generate the interpolating function consist of standard matrix operations consisting of easy numerical computations, so the present solution is significant from the numerical viewpoint as well as the analytical viewpoint.