高功率固体激光器

本文详细讨论了设计高平均功率固体激光器的有关问题,包括激光材料性质、棒状和板条状几何结构,聚光器和光学谐振腔等。分析表明,板条状几何结构固体激光器提供了达到千瓦级功率水平同时又保持良好光束质量的可能性。     

高温稀土永磁Sm2(Co,Cu,Fe,Zr)17 的制备和性能

制备了高温稀土永磁材料Sm(Coba1Fe0．26Cu0．05Zr0．026)7．0，研究了磁性能与工艺条件的关系．结果表明：提高烧结温度可使材料的Br和(BH)max增大，但是使Hci降低；适当提高真空预烧温度，可使材料在较低烧结温度下致密化，具有较高的Hci和(BH)max和温度稳定性．真空预烧温度过高使性能的急剧降低，其主要原因是Sm的析出．在最佳工艺条件下材料的磁性能参数分别为：Br1．08T3Hci2286kA／m，Hcb932kA／m，(BH)max220．8kJ／m^3；β20-200℃为-0．19％／℃．     

准连续波体制雷达最大熵方法的算法选择

准连续体制作为一种新型雷达体制以其固有的优越性给雷达界带来了巨大的冲击。其数字信号处理系统的开发是进一步完善该体制雷达的关键。本文针对数字信号处理系统中最大熵谱外推电路的算法选择进行了研究。     

便携式无线通信中的陶瓷技术

重点讨论了现代无线通信中关键元器件之一滤波器的发展进程,中、高频及微波滤波器的主要类型及性能特点。低损耗、高介电常数陶瓷在RF和IF滤波器中的应用,能够实现无线设备的微型化。对制备滤波器的介质陶瓷材料的要求是:在所使用的波段内,相对介电常数r要大,可缩小介质元件的尺寸;品质因数Q要高,可获得良好的滤波特性及通讯质量;谐振频率的温度系数f接近于零或可调节,以达到整机电子回路的要求。     

预应力锚固技术在龙滩水电站高边坡工程中的应用

龙滩水电站进水口高边坡最大坡高达420m，为保证高边坡的稳定，采用预应力锚索技术。预应力锚索的加固作用非常明显，不仅为边坡的稳定提供了经济、有效的手段，而且为按期截流创造了条件。     

高炉筑炉施工工法

从施工顺序的安排和作业设施、材料运输方面对筑炉工程的施工方法进行了介绍，并对预砌筑和试喷涂进行了阐述，探讨了高炉的砌筑方法，以保证高炉的施工质量。     

Phase Composition of Oxide Scales during Reheating in Hot Rolling of Low Carbon Steel

Low carbon steel was oxidized over the temperature range 1000‐1250°C in O₂‐CO₂‐H₂O‐N₂, O₂‐H₂O‐N₂, and O₂‐CO₂‐N₂ gas mixtures. Oxidation times were 12‐120 min. and the scales were 50‐2000 μm thick. The variations of these parameters were chosen to elucidate the phase composition of oxide scales under conditions similar to those of reheating furnaces in hot strip mills, using either thin slab casting or conventional casting and rolling technology. Two types of scales have been observed which are influenced by the furnace atmosphere, oxidation time, and temperature. The first type is a crystalline scale with an irregular outer surface, composed mostly of wustite (FeO), and a negligible amount of magnetite (Fe₃O₄). The second type is the classical three‐layer scale, composed of wustite (FeO), magnetite (Fe₃O₄), and hematite (Fe₂O₃). In general, the experiments showed that an increase in oxidation time decreased the percentage of wustite while the percentages of magnetite and hematite increased. A rise in oxygen concentration in the gas mixture increased the percentages of magnetite and hematite, confirming earlier experimental findings. In water vapour‐free atmospheres O₂‐CO₂‐N₂, the oxide scales had a low percentage of wustite, and high percentage of magnetite and hematite. Carbon dioxide showed a small influence at 1100°C, and a negligible one at 1250°C.     

Morphology development in polyethylene/polystyrene blends: the influence of processing conditions and interfacial modification

The influence of processing conditions and interfacial modification on the morphology evolution and the composition range within which fully co‐continuous high density polyethylene/polystyrene blend structures can exist during blending in a single screw extruder was studied. Blends ranging from pure A to pure B component, with and without compatibilizer, were prepared under two different shear rates. It was found that high shear rates displaced the breakdown–coalescence balance of the dispersed nodules to the side of coalescence, narrowing the percolation domain and the critical composition for full co‐continuity decreased with increasing shear rates. The addition of a tri‐block compatibilizer induced the percolation threshold of the polystyrene phase to begin at lower percentages of polyethylene but the phase inversion point did not change. The experimental results are discussed in the light of various theoretical models. Copyright © 2005 Society of Chemical Industry     

Flow stress of high density polyethylene and nylon 66 at high rates of strain

Measurement of the flow stress of high density polyethylene (HDPE) and nylon 66 at strain rates of 10³ s^?1 using a split Hopkinson pressure bar technique is discussed. The flow stress at a strain of 10% has been determined for both polymers at 20°C. The intrinsic errors involved in this technique are briefly reviewed. The results indicate that the flow stress of HDPE and nylon 66 were 50MPa and 150MPa, respectively, at strain rates of about 10³s^?1.     

瓦斯尾巷在高档普采工作面的应用

介绍了高档普采工作面利用掘送瓦斯尾巷等措施形成回风空间 ,从根本上解决高档普采工作面的瓦斯超限问题 ,其工艺有利于在其它采煤工作面内应用