基于一种特定混沌映射的跳频序列

使用一种简单的分段线性映射构造混沌跳频序列。用于跳频通信中取代传统的伪随机序列（PN序列），分析了此混沌序列的周期性。平衡性，汉明相关特性和线性间隔，最后给出了混沌序列的神经网络实现。仿真和实验结果表明，此序列具有较好的统计特性。应用于跳频多址通信中，可获得较好的抗干扰。抗截获能力。     

由乙腈一步法制备乙酸丁酯的研究

以丁醇和制备丙烯腈的副产物乙腈为原料 ,采用一步法合成了乙酸丁酯。通过正交实验得到了影响反应的 4种因素。确定了最佳的工艺条件为 :催化剂的量为样品质量的 40 % ;n(CH3CN)∶ n(C4 H9OH) =1∶ 1 .0 5 ;反应温度为 1 0 5℃ ;反应时间为 8h。在此反应条件下 ,乙酸丁酯的收率为 88.8% ,纯度可达 99.5 %。并用气相色谱及红外光谱对产品的纯度进行了表征     

低品位硼矿的富集加工技术

报道了青海大柴旦地区低品位硼矿富集加工的新工艺，该工艺使硼矿品位30％－35％，B2O3收率大于80％，该工艺路线已工业化。     

砂砾岩储集层含油性解释方法

LJ地区砂砾岩地层具有岩石结构复杂，储集层非均质性强，稠油和稀油并存的特点，利用测井资料解释含油性难度很大，以地层测试资料为依据，综合利用多种测井信息，提取反映含油性变化的测井特征参数；应用测井参数交会法和测井相分析法建立有效，快速识别稠油，油层和水层的标准，测井相分析法消除了用测井单参数和两参数交会解释含油性存在的多解性，提高子解释结果的成功率，用编制的解释软件处理了LJ地区58口井的资料，解释结果与试油资料对比吻合程度较高，为砂岩储层含油性解释提供了一种有效，快速的方法，为该区先导性试验提供了可靠的依据。     

关于长江重大问题的思考

长江流域横跨我国华东、华中、西南三大经济区,地理位置优越,水资源得天独厚,是我国最重要的经济区域之一。新中国成立后,党和政府高度重视长江治理开发工作,组建了流域机构,开展了流域综合利用规划,初步建立了长江防洪、灌溉、水力发电、航运、水土保持和水资源保护体系,在保护     

浅析嵌入式电脑及其发展趋势

主要介绍嵌入式电脑的构成特点、应用与发展前景。     

Improvement of RCA transistor using RTA annealing after theformation of interfacial oxide

A polysilicon emitter RCA transistor (an ultra-thin interfacial oxide layer exists between polysilicon and silicon emitter) is presented which can operate at 77 K for the first time. An ultra-thin (1.5 nm) interfacial oxide layer is grown deliberately between polysilicon and silicon emitter using RCA oxidation and excellent device stability is obtained after rapid thermal annealing (RTA) treatment in nitrogen atmosphere. The RCA transistor exhibits good electrical performance at very low temperature for an emitter area of 3 × 8 μm². The maximum toggle frequency of a 1:2 static divider is 1.2 GHz and 732 MHz at 300 K and 77 K, respectively     

The influence of viewing distance on subjective impairment assessment

In this paper, the influence of viewing distance on subjective assessment of the impairment in video sequences is investigated. Subjective tests using the double-stimulus impairment scale variant II (DSIS II) method have been conducted at viewing distances of 5H (where H stands for the screen height) and 3H, respectively. Several statistical measures have been used to analyze the influence, including correlations and ANOVA (analysis of variance) tests. The results reveal that there is a very high correlation between the subjective scores, the variances are similar under the two viewing distances, the means of subjective data at these two viewing distances are the same, and there is no interaction between the viewing distance and the other two factors, i.e., the codec system and the source sequence. Throughout the tests, there is no evidence that a closer viewing distance such as 3H will vary the subjective test result statistically significantly.     

An EM‐based adaptive multiple target tracking filter

Tracking targets of interest is one of the major research areas in radar surveillance systems. We formulate the problem as incomplete data estimation and apply EM to the MAP estimate. The resulting filter has a recursive structure analogous to the Kalman filter. The advantage is that the measurement‐update deals with multiple measurements in parallel and the parameter‐update estimates the system parameters on the fly. Experiments tracking separate targets in parallel show that tracking maintenance ratio of the proposed system is better than that of NNF and RMS position error is smaller than that of PDAF. Also, the system parameters are correctly obtained even from incorrect initial values. Copyright © 2001 John Wiley & Sons, Ltd.     

色用缓变光纤中交叉相位调制不稳定性分析

从非线性薛定谔方程出发得到了色散缓变光纤（DDF）中交叉相位调制（XPM）不稳定增益谱。研究了增益谱随入纤功率及光纤纵向色散参量的变化关系。结果表明：反常色散区的增益谱宽比正常色散区宽，且峰值增益高：DDF中XPM不稳定增益谱宽比常规光纤的宽，二者的比值随传输距离和光纤色散参量的乘积成指数增长；DDF的反常色散区是产生调制不稳定的较好的色散介质。