高性能混凝土配合比设计的试验研究

从对HPC组成、结构的认识出发，借鉴利用拨开系数求砂率的方法，提出了一种新的HPC配制方法，并通过试验证实该方法是完全可行的．     

热电热泵换热面积最优分配

考虑实际多热电堆热泵,在总传热面积一定的条件下,研究最优供热率、供热系数时传热面积的最优分配,并分析了各种参数对最优性能的影响,所得结果对实际热电热泵性能分析与优化有一定的指导作用.     

Compaction of thick carbon/phenolic fabric composites with autoclave method

Carbon/phenolic composites are used in the nozzle parts of solid rocket motors due to their heat-resisting, ablative, and high strength characteristics, which are required to endure the high temperature and pressure of combustion gas passing through the nozzle. But the thick axi-symmetric structure of the composite nozzle induces high thermal residual stresses due to the large difference of coefficient of thermal expansion (CTE) between the in-plane and the out-of-plane. In this work, in order to reduce the through-thickness CTE and the void content, a compression in the thickness direction was applied to the composite prepreg by a compressive jig during manufacturing of composite to supplement the low autoclave pressure. The through-thickness CTE of the fabric composite was calculated by a compaction model and compared with the measured one by thermo-mechanical analysis. The through-thickness CTE changed drastically with respect to the compaction amount, and the void content of the carbon/phenolic fabric composite laminate showed different characteristics from the ordinary fabric laminates with respect to the autoclave pressure and the jig pressure.     

Single-factor coefficient bounds

In a 1993 paper Beauzamy, Trevisan and Wang derived a single-factor coefficient bound, one which limits the max norm (height) of at least one irreducible factor of any univariate integral polynomial A. Their bound is a function of the degree and the weighted norm of A. In the conclusion of their paper they ask whether the max norm of A might already be a single-factor coefficient bound. In 1998 Knuth, citing these authors, asked instead whether there is a constant c such that c times the max norm of A is a single-factor coefficient bound. We present the results of extensive calculations relating to this question. We show that c, if it exists, must be greater than 2 and accrue evidence in support of a conjecture that the answer to Knuth’s question is “no”.     

Tribological behavior of sialon ceramics sliding against steel lubricated by fluorine-containing oils

The friction and wear behavior of sialon ceramics sliding against steel and lubricated by perfluoropolyethers (PFPE), tetrakis (3-trifluoromethylphenoxy)-bis(4-fluoro-phenoxy)-cyclotriphosphazene (X-1P) and ionic liquid (1-methyl-3-octylimidazolium tetrafluoroborate, coded as L108) were investigated. It was found that the three fluorine-containing lubricants reduced friction coefficient and wear volume effectively. The effectiveness of the three lubricants in reducing wear volume could be ranked as L108>X-1P>PFPE. The antiwear films mainly consisting of organic oxyfluoride or carbonfluoride species and silicon fluoride are all observed for the three lubricants, while the degradation of PFPE during friction might account for the higher wear volume therewith. The lowest friction coefficient 0.065 was recorded for L108 under load of 0.5–400 N. This is dependent on the physically adsorbed ionic liquid on the rubbing surface and the formation of BN under the harsh conditions.     

NY-1高功率微波辐射源功率密度的简易测量

微波的生物热效应能使蛋白质变性.蛋白质变性所需要的辐照时间取决于入射的功率密度,所以高功率微波功率密度的测量是研究微波生物效应的基础.利用纸水混合介质的介电常数,计算出微波波阻抗,利用介质和空气界面上的反射系数和介质中衰减系数以及蒸发的水的质量,从而求出入射的微波功率密度.     

发电机定子线棒空心水冷导线断裂原因分析

借助扫描电子显微镜、光学显微镜和力学性能测试等分析手段对发电机定子线棒空心水冷断裂导线的断口、金相组织和力学性能进行了分析.结果表明,水冷导线是由于制造时未将水冷导线捆扎紧,造成线捆松动,在微动力的摩擦作用下,产生疲劳断裂.     

Design of μ-CNC machining centre with carbon/epoxy composite–aluminium hybrid structures containing friction layers for high damping capacity

The focus of this paper is on the design of machine tool structures, such as columns and spindle holders, for a 3-axis μ-CNC machining centre. Carbon/epoxy composite–aluminium hybrid structures with friction layers were used to increase structural damping. Two types of hybrid column structures were proposed. Finite element analyses were carried out to calculate both the static deflection of columns due to deadweight and also the first natural frequency of machine tool structures as a function of the stacking angle and thickness of the carbon/epoxy composites. To increase damping capacity, a friction layer was inserted between the aluminium-composite interface. For the design of the structures the stacking angle and the thickness ratio of the composites were considered as major design variables. And the most appropriate stacking sequence of the composite–aluminium hybrid structure employing a friction layer was determined using finite element analyses and vibration tests.     

PBX炸药在摩擦作用下的点火起爆研究

为了研究PBX炸药的摩擦感度及其在摩擦作用下的点火机理,对PBX炸药进行了摩擦感度试验,并从细观结构的角度对炸药在摩擦作用下的响应过程进行了数值模拟,分析了细观结构对炸药温度场的影响,以及压力、初速度等条件对炸药摩擦点火的影响。结果表明:摩擦作用下PBX炸药的点火点位于HMX颗粒与黏结剂交界处,点火的临界温度为1 100K;向炸药施加的压力越大,其发火可靠性越高,点火时间越早;钢柱摩擦炸药的初速度增大,能够提高其发火可靠性以及点火时间。     

Effects of Anti-Oxidant Migration on Friction and Wear of C/C Aircraft Brakes

The surfaces of carbon-carbon (C/C) aircraft brakes are usually coated with anti-oxidant to protect them from oxidation. These surfaces do not include the friction surfaces since it is known that when anti-oxidant get onto the friction surface, the friction coefficient decreases. The anti-oxidant migration (AOM), however, happens during processing, heat treatment and application. In this study, phosphorus based anti-oxidants inhibited 3-D C/C aircraft brake system was investigated. The effects of their migration on friction and wear in the 3-D C/C brakes were revealed by sub-scale dynamometer tests and microscopic analysis. Dynamometer results showed that when AOM occurred, both landing and taxi coefficients decreased in humid environment and the wear was slightly lowered. Microscopic study showed that under high humidity conditions there was no formation of the friction film.