A neural network approach to ship track-keeping control

This paper presents an on-line trained neural net work controller for ship track-keeping problems. Following a brief review of the ship track-keeping control development since the 1980's, an analysis of various existing backpropagation-based neural controllers is provided. We then propose a single-input multioutput (SIMO) neural control strategy for situations where the exact mathematical dynamics of the ship are not available. The aim of this study is to build an autonomous neural controller which uses rudder to regulate both the tracking error and heading error. During the whole control process, the proposed SIMO neural controller adapts itself on-line from a direct evaluation of the control accuracy, and hence the need for a “teacher” or an off-line training process can be removed. With a relatively modest amount of quantitative knowledge of the ship behavior, the design philosophy enables real time control of a nonlinear ship model under random wind disturbances and measurement noise. Three different track-keeping tasks have been simulated to demonstrate the effectiveness of the training method and the robust performance of the proposed neural control strategy     

On penetration depth of the Shoemaker-Levy 9 fragments into the Jovian atmosphere

The actual penetration depth of the Shoemaker-Levy 9 fragments into the Jovian atmosphere is still an open question. From fundamental equations of meteoric physics with variable cross-section, a new analytic model of energy release of the fragments is presented. In use of reasonable parameters, a series of results are calculated for different initial mass of the fragments. The results show that the largest fragment explodes above pressure levels of 3 bars and does not penetrate into the H₂O cloud layer of the Jovian atmosphere, and that airburst of smaller fragments occur even above the upper cloud layer.     

A New Solar Radio Spectrometer at 1.10-2.06 GHz and First Observational Results

An improved Solar Radio Spectrometer working at 1.10-2.06 GHz with much improved spectral and temporal resolution, has been accomplished by the National Astronomical Observatories and Hebei Semiconductor Research Institute, based on an old spectrometer at 1-2 GHz. The new spectrometer has a spectral resolution of 4 MHz and a temporal resolution of 5ms, with an instantaneous detectable range from 0.02 to 10 times of the quiet Sun flux. It can measure both left and right circular polarization with an accuracy of 10% in degree of polarization. Some results of preliminary observations that could not be recorded by the old spectrometer at 1-2 GHz are presented.     

在BPL信道上增加数据广播内容的探讨

分析了现有罗兰C（包括BPL）在授时方面存在的不足，提出了在BPL信道上实现数据广播的主要目的。详细讨论了各种可能的数据信息的结构，并给出了有关参数和数据的计算方式和公式。认为发播内容的选择是由期望的系统功能决定的，广播内容的编排则与具体实现技术相关。最后给出了在不同调制方法下的传输速率，这是合理编排广播内容的基础。     

THE CHARACTERISTIC OF MARINE ENVIRONMENT IN LINGDINGYANG ESTUARY

1 HYDROLOGIC FEATURES Lingdingyang Estuary, located at the middle south of Guangdong Province, is a bell-shaped estuary with a north-south direction. Its area is about 2100km2. The north of Qi′ao Island and Inner-Lingding Island, and the south of Humen are grouped as Neilingdingyang Estuary, having an area of 1041km2. Affected by topography, runoff and tide, its dynamic condition is very complicated. Different water areas have different hydrologic features. The topography under …     

斑节对虾白斑综合症杆状病毒感染的实验模式

在建立斑节对虾实验室养殖模式的基础上，对野外采集的有白斑综合症病毒（WSSV）病典型症状的斑节对虾初步纯化其病毒，并进行WSSV的PCR检测，得到WSSV的感染用样品。对健康斑节对虾分别进行浸浴感染，投喂感染和注射感染。对感染死亡个体进行WSSA的PCR检测和细菌检测，证实WSSV感染性和致死性。浸浴感染、投喂感染和注射感染的感染量分别为4mL/L、0.2g/10g虾体、1/2稀释液0.05mL/10g虾体，死亡开始时间分别为16d、42h、28h，三种感染模式最终死亡率100%，从开始死亡到全部死亡延续时间分别为15d、82h、44h。     

On the Line Formation in Stellar Magnetized Atmospheres

1 INTRODUCTIONIn the previous paper (on et al. 1999, hereafter Paper I), we investigated the wavelength-dependence of four colltribution functions (CFs) derived from dmerent formal solutions andreferring to different emergellt quantities in the unpolarized case. Because one cannot generallyassign a single formation region to the whole line band in a real stellar atmosphere, e.g., the solaratmosphere, instead, the line formation region can be defined as the layers deviating farthestfrom t…     

富氏谱分析法模拟地壳垂直运动的地学依据及其策应力模型

应用地壳波浪与镶嵌构造学说对富氏谱分析法提取地壳垂直形变信息的科学性做了地质学意义上的阐释 ,并提出了根据多期形变资料提取特定波段上构造策应力的数学模型     

THE EFFECT OF DRAINAGE ON CHEMICALELEMENTS CONTENT OF MARSH

I INTRODUCTIONWetland has very important effect on retainingwater and against drought, regUlating climate, controlling soil erosion and so on ac. Today men often attachimportance to economic effect of wetland reclamation,but neglect and destroy other functions and effectswhich result in blind wetland development, a lot ofwetland degeneration. The area of freshwater wetland inthe 1950s was 134 x 10'ha, but in the 1970s 70% hadchanged into farmland (MITSCH, 1993). The area ofwetland in d…