四边固定载流矩形薄板的磁弹性稳定性分析

本文针对四边固定载流矩形薄板，利用Mathieu方程解的稳定性，研究其在电磁场与机械荷载共同作用下的磁弹性稳定性问题。首先在载流薄板的磁弹性非线性运动方程、物理方程、几何方程、洛仑兹力表达式及电动力学方程的基础上，导出了载流薄板在电磁场与机械荷载共同作用下的磁弹性动力稳定方程，然后应用Galerkin方法将稳定方程整理为Mathieu方程的标准形式，并将薄板的动力稳定性问题归结为对Mathieu方程的求解。利用Mathieu方程的稳定解区域与非稳定解区域的分界，即方程系数λ和η的本征值关系，得出了磁弹性问题失稳临界状态的判别方程。通过具体算例，给出了四边固定载流矩形薄板的磁弹性动力失稳临界状态与相关参量之间的关系曲线，并对计算结果及其变化规律进行了分析讨论。

四边简支载流矩形薄板的磁弹性动力屈曲分析

在载流薄板的磁弹性非线性运动方程、物理方程、几何方程、洛仑兹力表达式及电动力学方程的基础上,导出四边简支载流矩形薄板在电磁场与机械载荷共同作用下的磁弹性动力屈曲方程。应用Galerkin原理将该屈曲方程整理为Mathieu方程的标准形式,并利用Mathieu方程解的稳定区域与非稳定区域的分界,即方程系数的本征值关系,得出磁弹性问题屈曲临界状态的判别方程。通过具体算例,给出四边简支矩形板的磁弹性动力屈曲方程以及屈曲临界状态与相关参量之间的关系曲线,并对计算结果及其变化规律进行分析讨论。

Nonlinear Dynamic Responses of the Tensioned Tether under Parametric Excitations

The nonlinear dynamic responses of the tensioned tether subjected to combined surge and heave motions of floating platform are investigated using 2-D nonlinear beam model. It is shown that if the transverse-axial coupling of nonlinear beam model and the combined surge-heave motions of platform are considered, the governing equation is not Mathieu equation any more, it becomes nonlinear Hill equation. The Hill stability chart is obtained by using the Hill's infinite determinant and harmonic balance method. A parameter M, which is the function of tether length, the surge and heave amplitude of platform, is defined. The Hill stability chart is obviously different from Mathieu stability chart which is the specific case as M=0. Some case studies are performed by employing linear and nonlinear beam model respectively. It can be found that the results differences between nonlinear and linear model are apparent.

Relationship between organic carbon concentration and potential pond bottom soil respiration

There was a positive correlation between the concentration of organic carbon and potential respiration as measured by carbon dioxide evolution (R-2 = 0.923) and oxygen consumption (R-2 = 0.986) in soil samples collected from the bottoms of drained ponds. This finding supports the frequent use of organic carbon analysis as an indicator of sediment respiration rate under optimal conditions in commercial aquaculture facilities. (c) 2005 Elsevier B.V. All rights reserved.

Measurement of 5-day biochemical oxygen demand without sample dilution or bacterial and nutrient enhancement

A direct method for measuring the 5-day biochemical oxygen demand (BODS) of aquaculture samples that does not require sample dilution or bacterial and nutrient enrichment was evaluated. The regression coefficient (R-2) between the direct method and the standard method for the analyses of 32 samples from catfish ponds was 0.996. The slope of the regression line did not differ from 1.0 or the Y-intercept from 0.0 at P = 0.05. Thus, there was almost perfect agreement between the two methods. The control limits (three standard deviations of the mean) for a standard solution containing 15 mg/L each of glutamic acid and glucose were 17.4 and 20.4 mg/L. The precision of the two methods, based on eight replicate analyses of four pond water samples did not differ at P = 0.05. (c) 2005 Elsevier B.V All rights reserved.

国内外海洋热能转换概况

一、前言海洋热能转换(Ocean Thermal Energy Conversion OTEC)这一概念早在1881年法国物理学家 D~1 Arsonval 就提出来了。他设想在热带海洋表面温海水与深层冷海水之间，设置闭式朗肯循环，把海洋中所储存的太阳热能转换为电能。为实现这一设想，D~1Arsonval 的学生，法国工程师 G.Claude 于1926年在一个海水温差发电的模拟装置上使

The comparative estimation of phytoplanktonic, microphytobenthic and macrophytobenthic primary production in the oceans

The contributions of the planktonic unicellular algae [phytoplankton), the benthic unicellular algae [microphytobenthos) and the benthic multicellular algae (macrophytobenthos) to the primary production of the world ocean are evaluated, together with the respective limitations regarding data, concepts and methods. The use of “free-water” methods (e.g. in situ oxygen or CO2 budgets) is recommended in complement to the more specific measurements on enclosed organisms. For phytoplankton, a previous estimate of 30 . lo9 t C y-’ is retained as a minimal estimate. Earlier estimates of the world benthic production have been based on indirect calculations; revised estimates are suggested here which still lack precision but rely on the actual measurements available at present. Primary production of the micro- and macrobenthic algae amount to 50 and 375 g C m-? y-’ respectively as averages for the whole photic layer they can colonize, and total 2.9 . 10‘ t C y-’ for the world ocean. Thus, benthic algae contribute some 10% of the total marine primary production. On the continental shelf alone, the contributions of benthic and planktonib algae are commensurate and nearly equivalent.