Construction of high magnetic field facilities approved

On 25 January, the National Development and Reform Commission gave the green light to a proposal to construct high magnetic field facilities for experimental use. The suggestion was jointly submitted by the Ministry of Education and CAS.     

光泵磁共振测地磁场垂直分量的改进方法

本文通过调节垂直磁场线圈电流的大小,来改变垂直方向磁场对光泵磁共振信号的影响,从而测定地球磁场的垂直分量的大小.     

海尔的创新型"文化场" --全面创新管理研究系列文章

全面创新管理（TIM：Total Innovation Management)是由浙江大学创新与发展研究中心(RCID)首次提出的创新管理新范式。其实践背景是发生在我国大多数企业里“技术创新的两难境地”,该理论认为在目前的竞争环境中,成功的技术创新应该是包含全部技术因素和所有相关的非技术因素在内的全面创新。基于对我国海尔集团的成功经验模式的案例研究,本文将进一步从理论和实践方面进行全面创新管理的研究,提出个人创新能力的发展是企业发展的关键要素,建议企业重视人本管理,推行在提高员工创新素质基础上的企业成长模式。本文将分析海尔获得成功的关键因素——每个人都是创新者!——及其管理和运作机制。并分析在此基础上形成的创新型文化是如何通过“全员创新”的运作机制将企业全面创新管理的各创新要素——战略创新、管理创新、制度创新、市场创新和技术创新——成功地融合为一的。基于“场效应”理论,本文首次提出了“文化场”概念。本研究认为正是在创新型的“文化场”和全面创新管理架构的作用下,企业才能够融合所有创新能量来推动企业绩效的整体发展。     

The control of current across a spark gap by means of an external magnetic field

An experimental study was made of the electrical discharge between parallel plates when the pressure between the plates had been reduced to a value slightly less than the critical pressure—i.e. to the condition when a tube begins to harden. Under these conditions the application of a transverse magnetic field will produce a discharge between the electrodes for potentials less than the normal potential required. It is believed that this is due to the lengthening of the path traversed by the ions in crossing the gap. The results obtained may be harmonized by means of the values found by Carr (Proc. Roy. Soc. 1903) who made a study of Paschen's Law in the region of critical pressure. In general it is found possible, under the conditions studied, to start a discharge and control the value of the current through a circuit of which the gap is a part by means of varying the magnetic field superposed on the gap and without altering either the impressed E.M.F. or the ohmic resistance of the circuit.This control is effected by altering the effective length of the spark gap in the circuit by means of the external magnetic field.     

基于HMC1023磁阻传感器的多通道宽磁场测量系统

本文针对HMC1023磁阻传感器的特点,讨论了该传感器对多通道宽磁场测量系统的设计问题。本文利用仪用放大器和采样保持器实现了多通道实时采样,利用PGA可以对传感器输出的放大倍数自动调节,从而使其满足宽磁场范围的准确测量。本文也讨论了传感器的输出在PC机上的实时显示问题。     

入世后我国企业的市场营销策略探讨

我国已经加入WTO，企业所面临的营销环境发生了深刻的变化。为此，我国企业必须不断调整营销观念、加强品牌管理、创新营销模式，同时加强营销队伍的建设，并做好市场调研工作，只有这样才能在国际市场竞争中立于不败之地。     

A test strip for the estimation of urea in serum

We have developed a biostrip for determination of urea in serum. The test strip is based on enzymatic assay where urease has been immobilized on the chromatographic paper along with chromogen, phenol red. The chromogen is easily soluble in water and does not require other components for the color change. Serum urea reacts with urease and water to liberate ammonia and carbon dioxide. The liberated ammonia changes the pH of the reaction medium, which is monitored by the chromogen phenol red. A single step working reagent strip has been developed and the reaction is completed within 50 seconds at room temperature. With this test strip urea concentration is measured in serum as low as 0.15 g/L. The speed and convenience of determining urea in serum by this strip instantly makes it well suited for individuals, physicians and emergency centres.     

磁场对液态金属粘度的影响

金属熔体的粘滞性是液态金属原子迁徙能力的一种表现,反映了原子间结合能力的大小。理论研究表明:在无磁场的条件下,随着温度的降低金属熔体的粘度增大;在磁场的条件下,金属熔体的粘度随着磁场强度的增加而增大。磁场对粘度的影响是洛伦兹力和磁化能的共同作用的结果。     

Analysis and experimental investigation into a finite time current observer based adaptive backstepping control of buck converters

In this paper, the issue of output voltage regulation in buck type dc-dc converters is addressed using a current sensorless control technique. The proposed strategy integrates a finite time current observer with an adaptive backstepping control scheme to yield a cost-effective and robust control mechanism. The overall controller stability in the sense of Lyapunov is proved. Applicability of the proposed control is verified experimentally on a buck converter in the laboratory. The control scheme is implemented on dSPACE DS1103 platform based on DSP TM320F240 processor. To examine the efficacy of the proposed method, the buck converter is subjected to a wide change in input voltage, load resistance and reference voltage. For comparison purpose, a conventional adaptive backstepping control scheme is evaluated under identical conditions of experimental study to examine the merit of the proposed control. The results obtained reveal that the proposed control is prompt in rejecting perturbations and achieves a smooth, reliable and satisfactory output voltage regulation with faithful and time bound estimation of inductor current. Thereby, this investigation demonstrates the validity of the proposed control in maintaining a stringent output voltage regulation in buck converters.     

Effects of a magnetic field on the free convective flow through a porous medium bounded by an infinite vertical porous plate with constant heat flux

This paper investigates the effects of a magnetic field on the free convective flow of a viscous, incompressible, dissipative fluid through a porous medium, occupying a semi-infinite region of the space bounded by an infinite vertical and porous plate. The plate is subjected to a normal suction velocity and the heat flux at the plate is constant. The magnetic field is of uniform strength and is applied perpendicular to the plate. An analytical solution to the problem is obtained. The influence of the magnetic parameter (M) and permeability parameter (K) is discussed for the case of air (P = 0.71) when the plate is subjected to a constant suction velocity and is being cooled by free convection currents.     

Single landmark feedback-based time optimal navigation for a differential drive robot

In this paper, we propose a feedback-based control approach to execute the time optimal motion trajectories for a differential drive robot. These trajectories are composed of straight lines and rotations in place. We show that the evolution of the position of a single landmark over time, in a local reference frame, makes it possible to track a prescribed time-optimal robot’s trajectory, based on feedback of the landmark’s position. We also show that the closed-loop system is an exponentially stable one with a nonvanishing perturbation, and that globally uniformly ultimately boundedness of the tracking errors can be achieved. The two main results of this work are: 1) Our approach leverages visual servo control type of methods with tools from optimal control for executing time-optimal trajectories in the state space based on feedback information. 2) The approach is able to work with the minimum number of landmarks–only one–this represents a necessary and sufficientcondition for landmark-based navigation. Experiments in a physical robot, a nonholonomic differential drive system equipped with an omnidirectional laser sensor, are shown, which validate the proposed theoretical modelling.