“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     

基于BP人工神经网络的枯水径流预报方案研究

介绍了BP人工神经网络的桔水径流预报方法,编制了锦屏一级水电站枯水径流预报方案.根据枯水径流预报方案的预报精度评定成果,总结了应用BP人工神经网络进行枯水径流预报的特点.研究表明基于BP人工神经网络的枯水径流预报方案能够满足水文情报预报规范,具有较好的实用性和可行性.     

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.     

褐藻酸降解菌侵染海带过程的超微结构观察

首次研究了褐藻酸降解菌侵入海带的途径，通过电镜观察，跟踪研究了褐藻酸降解菌染海带过程中海带表皮细胞壁的超微结构变化。结果表明，褐藻酸降解侵染海带的过程是首先引起海带表皮细胞壁藻胶层表面的破坏，然后引起藻胶层的断裂，并使藻胶层逐渐降解变突，最后褐藻酸降解菌通过海带细胞的壁藻胶层的断裂变突处进入海带细胞内。     

牙鲆肠淋巴样组织免疫细胞研究Ⅰ：颗粒细胞的超微结构*

本文探讨了电镜下牙鲆(Paralichthys olivaceus)肠淋巴样组织内颗粒细胞的形态特点及其变化过程。颗粒细胞经鉴定为嗜酸性颗粒细胞，常存在于肠黏膜层及黏膜下层靠近肌肉层的淋巴腔中，以具有大型非匀质颗粒为其主要特征。牙鲆肠淋巴样组织内嗜酸性颗粒细胞的变化可分为增长期、成熟期、分泌期和衰退期四个时期，嗜酸性颗粒细胞具有明显的外排现象说明肠淋巴样组织是鱼类免疫防御系统的重要组成部分。     

基于ArcIMS的城市小区信息发布系统的设计与实现

利用ESRI公司新一代Web GIS产品Arc IMS9.0,结合ASP及IIS6.0、SQL Serve、ArcSDE等网络、空间数据库方面技术,建立了城市小区信息发布系统。总结了ArcIMS的特点和体系结构,提出了基于ArcIMS的城市小区信息发布系统的设计思路和方案,阐述了系统的具体实现方法。     

一种基于双重距离的空间聚类方法

传统聚类方法大都是基于空间位置或非空间属性的相似性来进行聚类,分裂了空间要素固有的二重特性,从而导致了许多实际应用中空间聚类结果难以同时满足空间位置毗邻和非空间属性相近。然而,兼顾两者特性的空间聚类方法又存在算法复杂、结果不确定以及不易扩展等问题。为此,本文通过引入直接可达和相连概念,提出了一种基于双重距离的空间聚类方法,并给出了基于双重距离空间聚类的算法,分析了算法的复杂度。通过实验进一步验证了基于双重距离空间聚类算法不仅能发现任意形状的类簇,而且具有很好的抗噪性。     

HD-4002型综合测井仪

HD 4002型综合测井仪是核工业北京地质研究院于1998年开始研制的, 其目标是为铀矿地质系统提供适合砂岩型铀矿勘查的轻便型数字测井仪, 满足测井生产的需要。该仪器于2001 年3月通过部级鉴定, 2002至2003年投入海拉尔盆地铀矿勘查测井试生产。本文介绍了仪器的用途、功能及特点、性能指标, 简要说明了各部分的工作原理。     

等距等高电磁波测距三角高程测量及精度分析

介绍了等距等高电磁波测距三角高程测量的原理，详细深入地分析了这种高程测量方法的精度，通过计算和作图表示，可直观地反映在不同条件下的精度变化情况，讨论了代替国家等级水准测量的范围和条件，可供生产实际和进一步研究参考。     

蓖麻生长农业气象条件分析及栽培技术初探

根据对蓖麻发育期的观测，结合当地气象条件，分析了阿克苏种植蓖麻的适应性及栽培中应采取的趋利避害的技术措施。