Experimental Study of RF-excited Diffusion Cooled Off-axis Unstable Resonator with High Frequency Modulation in a Waveguide CO2 Laser

The experimental study of the laser beam parameters of the pulse repetitive RF-excited diffusion cooled waveguide CO2 laser are presented. The measurements are carried out for the pumping pulse duration of 100 μs and pulse repetitive rates 5 - 14 kHz. The average power density delivered to the active medium is 76 W/cm^3. Three types of the pulses, namely the square, the sine and the triangular ones have been applied at the input as pumping pulses and their effects on the output power and the delay time have been studied. The output power of the radiation versus input power, pressure of the laser gas mixture and modulation frequency has been investigated. The results indicate that the output peak power for the three types of pulses increases with increase of the pressure of the laser gas mixture and with the input power where as it decreases with the repetition frequency. The delay time of the output pulse decreases with the increase of the repetition frequency and input power, where as it increases with the increase of the pressure of the laser gas mixture. The behavior of the output power and the delay time with duty cycle for square pulse has also been investigated.     

Real-time Parallel Processing System Design and Implementation for Underwater Acoustic Communication Based on Multiple Processors

ADSP-TS101 is a high performance DSP with good properties of parallel processing and high speed. According to the real-time processing requirements of underwater acoustic communication algorithms, a real-time parallel processing system with multi-channel synchronous sample, which is composed of multiple ADSP-TS101s, is designed and carried out. For the hardware design, field programmable gate array （FPGA） logical control is adopted for the design of multi-channel synchronous sample module and cluster/data flow associated pin connection mode is adopted for multiprocessing parallel processing configuration respectively： And the software is optimized by two kinds of communication ways： broadcast writing way through shared bus and point-to-point way through link ports. Through the whole system installation, connective debugging, and experiments in a lake, the results show that the real-time parallel processing system has good stability and real-time processing capability and meets the technical design requirements of real-time processing.     

用厂坝连接解决大坝深层抗滑稳定问题

本文以万家寨水电站为背景，研究了不同厂坝连接方式对坝体和厂房的应力、变形及深层抗滑稳定性的影响。研究结果表明，考虑混凝土重力坝与坝后式厂房的相互作用后，可以提高大坝抗滑稳定性，改善坝体应力状态，并能减小由于下游尾水过高引起厂房向上游的变形。     

有软弱夹层岩体边坡稳定分析安全系数的确定

具有软弱夹层的岩体边坡稳定性分析，是水利水电工程设计和施工中经常遇到的重要问题．在我国软弱夹层引起岩体边坡失稳的情况较多，已造成巨大的损失．从岩体边坡整体滑动的几种型式出发，述及了以往稳定分析方法与安全系数的选取，以及稳定安全系数大小与边坡失稳的关系，从而根据我国抗剪强度参数的取值原则与设计经验，建议了设计应该遵循的稳定安全系数．     

南水北调调蓄工程经济性的探讨

用于调节南水北调工程来水的有两类水库，在这两类水库中，一类为已建水库，位于南水北调中线以西较高位置，叫做“高库”，例如黄壁庄水库；另一类为拟建水库，位于中线以东平原洼地，也叫“低库”，以大浪淀水库为例．技术经济指标分析表明，第一类水库的供水成本明显小于后者，故得出如下结论：利用某些已建“高库”的闲置库容调节南水北调来水可能是经济的．     

双马来酰亚胺改进硅橡胶耐热性能的研究

研究了N,N′-二对苯醚-双马来酰亚胺和N,N′-二对苯甲烷-双马来酰亚胺对硫化硅橡胶耐热性能的影响。结果表明,双马来酰亚胺中的不饱和键在过氧化物作用下,可以与硅橡胶中的乙烯基发生共交联。共交联硅橡胶性能与无双马来酰亚胺者相同。但经300℃、12h热空气老化后,未加双马来酰亚胺的硅橡胶完全变脆,而加入者仍然非常柔软,能保留原拉伸强度的45％以上。     

Imide-aryl ether benzoxazole random copolymers

Novel imide-aryl ether benzoxazole copolymers were prepared and their morphology and mechanical properties investigated. A key feature of these copolymers is the incorporation of a benzoxazole moiety by the use of 2,2′-bis[4-(3-aminophenoxy)phenyl]-6,6′-bibenzoxazole or 2,2′-bis[4-(4-aminophenoxy)-phenyl]-6,6′-bibenzoxazole as co-diamines in polyimide syntheses. The preparation of these diamines involved the nucleophilic aromatic substitution of 2,2′-bis(4-fluorophenyl)-6,6′-bibenzoxazole with either 3- or 4-aminophenol in the presence of K₂CO₃. The diamines were co-reacted with various compositions of pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) to synthesize the desired poly(amic acids). Films were cast and cured (350°C) to effect the imide formation, affording films with elongations between 40 and 110% and moduli in the 2000–2750 MPa range. The copolymers exhibited good dimensional (T_g in excess of 300°C) and thermal stability. Wide-angle X-ray diffraction measurements on the copolymers showed that the ordered morphology characteristic of PMDA/ODA polyimide was retained. Improvements in the auto-adhesion were observed, particularly in those copolymers which displayed a T_g.     

Effects of maturation and storage on solubility,emulsion stability and gelation properties of isolated soy proteins

Solubility, emulsion stability and gelation of isolated soy proteins and their 7S and 11S fractions from three stages of seed maturity were studied. The pH-solubility profile was similar irrespective of maturation and six-month storage. The 11S protein was more soluble in the acidic pH range than the 7S protein. Oil-in-water emulsion stability of isolated soy protein from mature soybeans was higher than that from the immature ones. This is due to the fact that there was more 7S fraction in the mature soybeans, and 7S protein was found to form a more stable emulsion than that formed from 11S protein. The result suggests that isolated soy protein from mature soybeans would serve as a better emulsifying agent. Heat-induced soy protein gels became weaker as the soybeans became more mature. This can be attributed to the higher content in the immature soybeans of 11S fraction which gives a stronger gel than 7S fraction in the protein from immature soybeans.     

Efficacy of tertiary butylhydroquinone on the storage and heat stability of liquid canola shortening

The sensory (odor and flavor) and physicochemical characteristics of tertiary butylhydroquinone (TBHQ) treated and butylated hydroxyanisole/toluene (BHA/BHT) treated liquid canola shortenings, subjected to accelerated storage (Schaal oven test at 65°C) and deep fat heating (at 185°C), were determined. Data for the Schaal oven test indicate that TBHQ was effective in retarding oxidative rancidity in liquid canola shortenings. However, addition of the commonly used mixture of BHA/BHT to canola shortenings resulted in only a slight decrease in oxidation during schaal oven storage. The results obtained from deep fat heating of canola liquid shortening show that neither TBHQ nor BHA/BHT was effective in enhancing oxidative and thermal stability of this product.     

Effect of randomization on oxidative stability of vegetable oils at two different temperatures

Five vegetable oils were each randomized by chemical means (with the use of a sodium potassium alloy) and by enzymatic means (using a nonspecific lipase). The success of the randomization procedure was confirmed via positional analysis. The oxidative stabilities of the native and chemically randomized oils were determined at storage temperatures of 28°C and 55°C using absorbance at 234 nm as indicative of conjugated diene content. No difference between curves occurred in oils stored at 55°C, however, at the lower temperature all chemically randomized oils had significantly steeper slopes (P<0.05), suggesting a lower stability. When both enzymatically and chemically randomized oils were compared to native oils at 28°C, no significant difference occurred between slopes of native and enzymatically randomized oils, however, the end content of conjugated dienes was significantly higher for chemically randomized canola, corn and soybean oils (P<0.05). No difference was seen between the slopes of the three different oils from either linseed or sunflower. Since both of these oils exhibited higher oxidation rates, it is possible that observation of differences between the stability of native and chemically randomized oild is dependent upon the rate of the reaction.