Sulfonated polyaniline/vanadate composite as anode material and its electrochemical property in microbial fuel cells on ocean floor

A unique sulfonated polyaniline/vanadate composite was synthesized and utilized as a composite anode in microbial fuel cells on ocean floor (BMFCs). X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were employed to characterize its chemical composition and morphology. Wettability of the composite anodes decreases due to the addition of polytetrafluoroethylene (PTFE). The electrochemical behavior of the composite anodes was investigated by means of linear sweep voltammetry and Tafel plot measurem...     

声学Burton-Miller方程边界元法GPU并行计算

基于GPU,对声学Burton-Miller积分方程的边界元解法进行并行计算.提出并行计算格式和程序实现方法,以及Burton-Miller方程中各类奇异(包括强奇异、超奇异)积分的GPU计算和局部修正方法.典型算例结果表明,在特征频率处可获得正确的解,具有较高精度,可在普通个人计算机上快速完成自由度超过2×10⁵的声学边界元分析.为计算声学及相关工程领域的中、大规模声场分析问题提供一种快速、高效、简便的数值计算工具.     

“缓”然一新——深蓝里的金属防腐*

缓蚀剂和缓蚀涂层能够在金属表面形成一层致密保护膜,从而达到延缓金属腐蚀的目的。其具有成本低、可操作性强、缓蚀效果好、寿命长等优点,成为海洋工程防腐中一类重要的材料。围绕海洋工程中钻井平台、风力发电机、航空母舰和核潜艇等中易发生腐蚀的部位介绍化学缓蚀剂及缓蚀涂层的结构、性质,并突出其重要作用。     

海洋动力学中二维黏性原始方程组解对热源的收敛性

考虑了在一个柱形区域上的海洋动力学中二维黏性方程组解的收敛性.在此模型中存在一个关键的参数就是热源,众多周知,它的存在可能会使流体内层之间出现共振从而导致不稳定.因此,通过推导方程组的先验界,得到了方程组的解对热源自身的收敛性.     

The Acoustics of Liquid Foams

Beside other transport properties of liquid foams, like the optical or electrical ones, the acoustics of liquid foams reveals a great complexity and non-trivial features. Here we present a review of recent experimental and theoretical results on how a sound wave interacts with either a macroscopic foam sample or with its isolated building blocks (films and Plateau borders). The analysis of the literature allows us to determine what is now well understood, what could be measured in foams by acoustics, and what are the remaining issues and perspectives in this research field.     

Full-wave numerical simulation of nonlinear dissipative acoustic standing waves in wind instruments

A finite volume full-wave method is used to simulate nonlinear dissipative acoustic propagation in ducts with a circular cross-section. Thermoviscous dissipative effects, due to bulk viscosity and shear viscosity in the boundary layer adjacent to the duct walls, are also considered. The propagation is assumed to be axisymmetric, and two different geometries are considered: a straight cylindrical tube, and a cylindrical tube joined smoothly to a slowly-flaring bell. Of special interest is the study of the onset of standing waves in the nonlinear regime. The full-wave numerical scheme is particularly well-adapted for this purpose, as it is not necessary to impose boundary conditions at the open end of the duct. A simplified model of excitation is adopted, where the lips are replaced by a spring–mass system which behaves like a pressure valve with a single degree of freedom. The full system behaves as expected, with a feedback cycle established between the pressure valve and the air column. The simulation is validated successfully in the linear regime using a theoretical solution. It is shown that increasing the stiffness of the lips leads to discrete jumps in playing frequency, which is behaviour typical of brass instruments. In the nonlinear regime, shock formation is observed for sufficiently high amplitudes of oscillation, and the radiation of these shock waves by the open end of the ducts can be visualised in the time-domain, along with edge-diffraction effects. The formation and evolution of standing waves in the nonlinear regime, where the effect of these shocks is very noticeable, is also examined.     

Homogenization of high frequency nonlinear acoustics equations

High frequency nonlinear acoustics equations proposed in [1] are considered. The acoustic characteristics of the medium rapidly oscillate. This model describes the propagation of pulses of sound shocks generated by supersonic planes, blast waves in atmosphere and ocean, continuous radiation of sound sources. An asymptotic solutions of high frequency nonlinear acoustics equations is constructed (when the characteristic size of inhomogeneity is small with respect to the height of the layer where the problem is posed     

O?shore ?oating wind turbine and its dynamic problems?

Green energy sources and ocean wind power are plentiful in deep sea. More and more o?shore wind power plants are constructed in the deep water over hundred meters below the surface. While o?shore ?oating wind turbine system is working, wind turbine, ?oating foundation, and mooring system a?ect each other with wind, waves, and currents acting on them. Various o?shore ?oating wind turbine systems and the encoun-tered environmental loads are brie?y reviewed and discussed. It is di?cult and crucial to comprehensively analyze the aerodynamic-hydrodynamic-service system-structure un-der the coupling e?ect of o?shore ?oating wind turbine system. The environmental ?ow ?eld, structure scale, and rational applications of theories and approaches should be well considered in advance.     

水下多层均匀材料的声特性

本文研究水和空气中由不同厚度的两层弹性板及消声橡胶共同组成的分层介质在斜入射时的声特性,并采用数值方法求解多层结构声场的线性方程组。得到反射,透射系数,当板的厚度远小于波长时,采用弹性薄壳振动模型和弹性波模型进行计算,它们的结果基本相同,但是薄壳振动模型更便于计算和理论分析;对系统反射系数和透射系数的计算结果表明,系统增加消声橡胶层后,极大地改变后射系数和透射系数的频率响应;频率升高,反射系数减小     

Discernment of non-Newtonian behavior in liquids by acoustic means

An experiment was conducted with the use of a „sonic viscometer” to demonstrate that a change in the constitutive nature of a fluid will alter the overtones that occur from the nonlinearity of the propagation of a sine wave through the fluid. Pure sine waves ranging octave-wise from 500 to 8000Hz were introduced into distilled water, and FFT analyses of the signals received were compared with those resulting from transmission of the same set of sine waves through a 1% solution of polyethylene oxide in distilled water. Differences in the FFT spectra which occur as the result of introducing the polymeric solute indicate that the device could prove viable in indicating small changes in viscous properties. Received: 10 February 1998 Accepted: 1 June 1998