“BASS 300 PARACOM”: a “model” underwaterparametric communication system

Parametric transduction offers valuable advantages for underwater acoustic communications. Perhaps the most significant benefit is the fact that high directivity is achieved by means of a physically small transmit transducer. This feature may, ultimately, be employed to permit long-range, low-frequency communication using a compact source. The high directivity is desirable to combat multipath propagation and to achieve data communications in water which is shallow by comparison with range. A real-time, high data-rate “model” differential phase shift keying (DPSK) communication system has been constructed and demonstrated. This system uses parametric transduction, with a 300-kHz primary frequency and a 50-kHz secondary frequency. Experimental results show that the system can be employed to combat multipath propagation in shallow water and can achieve high data-rate text and color image transmission at 10 and 20 kb s^-1 for 2-DPSK and 4-DPSK, respectively, through a transmission bandwidth of 10 kHz. The “model” system was developed to confirm performance predictions for a future, operational long-range link employing a 50-kHz primary frequency and a 5-kHz secondary frequency     

发展地理信息系统产业

“全国地理信息系统技术与应用工作会议”今天召开了。我代表国家科委向参加会议的同志们表示热烈的欢迎,预祝会议取得圆满的成功。并向为地理信息系统技术和应用的发展做出贡献的科技、经营管理及市场营销人员致以诚挚的问候和崇高的敬意! 这次会议将对发展我国地理信息系统产业的战略、政策等问题进行研讨,同时交流产品开发和推广应用等方面的经验。希望通过这次会议,达到统一认识、推动全社会各个方面为地理信息系统产业发展多做实事的目的,加速我国地理信息系统产业的发展。     

欧盟RoHS指令与中国的对策

对欧盟RoHS指令的主要内容进行了简述,初步介绍了与RoHS指令相似或者相关的各国的环保指令,讨论了RoHS指令等对我国电子电气行业带来的巨大冲击。简要总结我国电子信息产业部、国家质量监督检验检疫总局、商务部等各管理及技术部门为了应对RoHS指令和提高我国电子电气行业竞争力而作出的相应对策。     

奎屯河流域南洼地地下水补给特征分析

独山子石油化工基地第二水源地(简称二水源)位于新疆奎屯河流域南洼地,认识和掌握南洼地地下水补给特征是研究和评价独山子石化基地用水保障程度的重要基础。通过南洼地地下水和主要河流的水化学、环境同位素特征分析,对南洼地地下水的补给得到如下认识:二水源西北缘和中部主要接受奎屯河、小巴音沟水的补给,其东南缘主要接受乌兰布拉克沟和乔路特沟地表水的补给;就整个二水源来讲,奎屯河与小巴音沟的补给是主要的。     

Refraction-Diffraction Mathematical Model for Waves With Lateral Energy Transmission Mechanism and Its Verification

To solve problems concerning wave elements and wave propagation, an effective way is the wave energy balance equation, which is widely applied in oceanography and ocean dynamics for its simple computation. The present papaer advances wave energy balance equations considering lateral energy transmission and energy loss as the governing equation for the study of wave refraction-diffraction. For the mathematical model, numerical simulation is made by means of difference method, and the result is verified with two examples.     

Selenium distribution in the Rhône delta and the Gulf of Lions

Total dissolved selenium and selenium species have been measured in the Rhône river delta and the Gulf of Lions within the framework of the EROS-2000 project. The Rhône river concentration of total selenium averages 2.30 nM with important variations related to river discharge. During estuar-ine mixing, the concentrations of total dissolved selenium, selenite and selenate (calculated as the difference between total dissolved and selenite) decrease linearly with increasing salinity, without significant interconversion between selenium species. In the open Mediterranean waters of the Gulf of Lions the total dissolved selenium increases from 0.5 nM in the surface waters to 0.9 nM in the deep waters. Organic selenium has been observed in Mediterranean deep water, an observation which is different from those from the Atlantic and the Pacific Oceans. The distributions of total inorganic selenium (Σ5e), selenite and selenate are strongly related to phosphate and silicate concentrations as observed previously for the major oceans.     

病毒膜蛋白及其表达和纯化技术的研究进展

病毒囊膜是包膜病毒除核衣壳外的另一主要成分。它主要由多种蛋白质构成，称为膜蛋白，膜蛋白以单聚体，二聚体，三聚体，甚至更多的聚合体的形式存在，具有中和抗体，与靶细胞受体结合，凝集红细胞，诱导细胞融合等多种功能，膜蛋白可采用将其基因整合入载体，并在昆虫细胞，哺乳细胞或细菌中获得体外表达，膜蛋白可在去污剂的作用下形成蛋白质－脂－去污剂的复合物而被溶解，其中去污剂的临界微团浓度，亲水物－亲脂物平衡值，荷电、紫外穿透性等是选择合适去污剂的主要参考因子，溶解后的膜蛋白多利用聚丙烯酰胺凝胶电泳、凝胶过滤层析，离子交换层析，亲和层析，高效液相层析等技术并结合梯度离心；分级沉淀等进行分离、纯化。     

地层学的发展推动油气地质理论研究的进步

自上个世纪50年代以来,地层学经历了彻底的变革,逐渐由“相模式”、“沉积体系”、“地震地层学”发展到目前的“层序地层学”,形成高分辨率层序地层学和事件地层学的理论体系和研究方法。文章围绕层序地层学、高分辨率层序地层学基本方法及理论体系,与含油气系统相关关系进行了讨论。