Development and simulation studies of an unsteady state biofilter model for the treatment of cyclic air emissions of an α‐pinene gas stream

This paper describes the development and simulation of an unsteady state biofilter model used to predict dynamic behaviour of cyclically‐operated biofilters and compares it with experimental results obtained from three, parallel, bench‐scale biofilters treating both periodically fluctuating concentrations and constant concentrations of an α‐pinene‐laden gas stream. The dynamic model, using kinetic parameters estimated from the constant concentration biofilter, was able to predict the performance of cyclic biofilters operating at short cycle periods (ie, in the order of minutes and hours). Steady state kinetic data from a constant concentration biofilter can be used to predict unsteady state biofilter operation. At a 24 h cycle period, the dynamic model compared well with experimental results. For long cycle periods (ie, hours and days), removal efficiency decreased after periods of non‐loading: the longer the period of non‐loading, the poorer the biofilter's performance at the re‐commencement of pollutant loading. At longer time scales the model did not effectively predict transient behaviour, as adsorption and changes in kinetic parameters were not accounted for. Modelling results showed that similar biofiltration performance for the cyclic and constant concentration biofiltration of α‐pinene is expected for biofilters operating solely in the first order kinetics regime. Poorer performance for cyclic biofilters following Monod kinetics spanning the entire kinetics range is expected as the cycle amplitude increases. The most important parameters affecting the performance of a cyclically‐operated biofilter with short cycle periods are: amplitude of cyclic fluctuations, C_{g, max}/C_g, relative value of the half‐saturation constant in the Monod expression, K_s, and effective diffusivity of α‐pinene in the biofilm, D_e. Copyright © 2005 Society of Chemical Industry     

Improvement of levitation characteristics in a magnetic bearing system using HTSC‐permanent magnet hybrid structure

Magnetic bearing using pinning force of a permanent magnet and a high‐temperature superconductor has been developed. Additional permanent magnet is introduced to increase the levitation force of the magnetic bearing. In this hybrid magnetic bearing system, levitation force is mainly given by the repulsive force of the permanent magnets, and stability for the lateral direction is given by pinning force of the superconductor. The experimental device is developed. A ring‐type superconductor and a bulk one are examined. Levitation characteristics of the hybrid magnetic bearing are measured. The bulk superconductor shows better characteristics of both levitation and lateral stability than the ring one. Levitation force of the hybrid system becomes about twice as large as that of the nonhybrid one. Although, the repulsive force of the permanent magnet decreases the lateral stability of the system, its influence becomes small by choosing an adequate position of the permanent magnets and the superconductor. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 71–77, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10350     

Performance prediction of a hybrid‐excitation synchronous machine with axially arranged excitation poles and permanent‐magnet poles

This paper presents a method of predicting the steady‐state performance of a new hybrid‐excitation synchronous machine (HESM) theoretically. The field pole of this HESM is axially divided into two parts; one is an excitation part and the other a permanent‐magnet (PM) part. A nonlinear equivalent circuit, which can include the saliency of the rotor and the magnetic saturation due to the iron core, is derived. Based on this equivalent circuit, the steady‐state performance of the HESM is calculated, and the results are confirmed through experiments. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 43–49, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20033     

Evaluation of influence of external magnetic disturbance on superconducting magnet taking conservation of linkage flux into account

External magnetic disturbance influences the quality of the image obtained with a magnetic resonance imaging (MRI) system because it causes magnetic resonance frequency drift. When a superconducting magnet in persistent current mode operation is exposed to external magnetic disturbance coil current varies to keep linkage flux constant. Conventional analysis is usually formulated with constant current and does not provide correct evaluation of drift of magnetic field in the magnet. This paper proposes a method of numerical analysis of magnetic field considering conservation of linkage flux in a superconducting magnet under a persistent current mode operation. This method is applied to evaluate drift of the magnetic field in a superconducting magnet for magnetic resonance imaging due to external magnetic disturbance. Analysis results show good agreement with the experimental results.     

Frequency response function of magnetic bearings using high-temperature superconductor

A high-temperature superconductor YBa₂Cu₃O_7-x with strong pinning force has allowed stable magnetic suspension with no control to be developed. Two types of superconducting magnetic bearings (SMB) using YBCO and permanent magnet were assembled. The two types are radial and axial. The dynamic stiffness of each SMB as it was cooled down under a magnetic field by liquid nitrogen was measured both radially and axially. As a result, it was found that the spring constants of these SMBs were almost as large as a practically desirable value; however, their damping coefficients were lower than the practical level. These findings are useful as one of the data bases for development of an optimum SMB design to support the weight of rotors in an axial direction.     

神经网络控制器用于永磁电机的伺服驱动

提出用一种遗传算法（ＧｅｎｅｔｉｃＡｌｇｏｒｉｔｈｍ，简称ＧＡ）训练的多层神经网络结构（ＮＮ），并把它用于交流直线永磁同步电动机（简称ＬＰＭＳＭ）的辩识与控制，使其运行在伺服驱动环境．ＮＮ可随时辩识被控系统的动态待性，而不需要ＬＰＭＳＭ的精确的数学模型．仿真结果令人满意     

Lennard-Jones Viscosities in Wide Ranges of Temperature and Density: Fast Calculations Using a Steady–State Periodic Perturbation Method

A method for fast calculation of viscosity from molecular dynamics simulation is revisited. The method consists of using a steady-state periodic perturbation. A methodology to choose the amplitude of the external perturbation, which is one of the major practical issues in the original technique of Gosling et al. [Mol. Phys. 26: 1475 (1973)] is proposed. The amplitude of the perturbation required for fast caculations and the viscosity values for wide ranges of temperature and density of the Lennard-Jones (LJ) model fluid are reported. The viscosity results are in agreement with recent LJ viscosity calculations. Additionally, the simulations demonstrate that the proposed approach is suitable to efficiently generate viscosity data of good quality.     

一类具高阶非线性项的发展方程的准确周期解

本文导出了具高阶非线性项的Lienard方程的准确周期解并从理论上给予了证明,然后利用这些公式得到一大批具高阶非线性项的发展方程的各种Jacobi椭圆函数型的准确周期解,由此避免了一大类非线性发展方程求周期解时求解过程的重复。     

1.5MW永磁直驱风力发电机几个问题探讨

介绍了1.5 MW低速直驱永磁风力发电机的新型整体机座结构,磁极、空心轴、轴承和润滑的结构形式,该型电机经受了风电场运行考验,安全可靠。     

介质周期结构色散特性的严格分析：一种三维边值问题的求解方法

本文以耦合模理论和Ｆｌｏｑｕｅｔ理论为基础，把本征模展开与空间谐波展开巧妙地结合起来，严格分析了斜入射情况下介质周期结构的色散特性－三维边值问题。这种新方法既避免了通常耦合模方法分析此类问题所引入的微扰近似，又比Ｆｌｏｑｕｅｔ方法简单方便。通过对斜入射情况下一些介质结构滤波特性的数值分析，证实了本文方法的有效性，精确性和实用性。