Influence of zero-loss filtering on electron optical phase contrast

Complex scattering amplitudes are used to calculate the phase contrast of colloidal gold particles. Comparison of measurements of the phase contrast intensity at the centre of the gold particle as a function of defocus for unfiltered and zero-loss filtered images demonstrates the increase in phase contrast achieved by zero-loss filtering even for a thick carbon substrate film. The granulation of amorphous germanium films is measured by the spatial rms (root mean square) values of image intensity in a defocus series.     

Cut-off Characteristics of a Cylindrical Magnetron †

The cut-off behaviour of a cylindrical magnetron is investigated experimentally, and deviation from the predictions of the Hull theory is examined as a function of the operating conditions. The anomalous anode current beyond Hull cut-off is shown to be due to cooperative space charge effects, which cause electron flow both along and at right angles to the magnetic field. The axial distribution of anode current is found to be highly non-uniform, and the anomalous current is largely incident on the anode ends. Conventional two-dimensional theories of the magnetron therefore cannot adequately describe behaviour beyond cut-off.     

The Influence of Thermionic Emission Velocities on the Cut-off Characteristic of a Cylindrical Magnetron†

It is shown that under normal operating conditions the effect of initial electron velocities is too small to account for observed deviations from the predictions of the Hull theory.     

Modification of Magnetron Cut-off Characteristics by the Introduction of Positive Ions†

Violation of the Hull cut-off criterion is due to cooperative space charge effects within the electron cloud. These cause the appearance of excess energy electrons, and at cut-off a fraction of the anode current consists of elections with abnormally high energy. The cut-off characteristic can be modified by introducing positive ions into the interaction space. These are particularly effective close to the cathode. The experiments suggest that anomalous anode current is due to a slipping stream instability which amplifies small disturbances originating near the cathode.     

汽车用铝合金开发近况

介绍了汽车车身用轻质材料铝合金的研究近况，包括材料选择和车体设计新概念等方面。为满足经济和环境保护等方面不断增长的要求，对乘用车在使用已成熟的和最新研究开发的铝合金方面的进展进行了讨论。介绍了一些改进的具有更高的强度和更好的成形性能的5系和6系铝合金，使用这些合金能减轻汽车质量和提高防撞性能。以铝合金在“多材料超轻汽车”概念中的应用到达显著的减重效果为例，介绍了多材料轻质设计方面的研究进展。     

Reply to Comments on “Cut-off Characteristics of a Cylindrical Magnetron”

A new circuit for generation of triangle/square waveform is described. The circuit uses a linear pulse amplifier, a clipper and a differentiating network, consisting of a capacitance and a FET behaving as a voltage-controlled resistor. The circuit covers a wide frequency range and the variation of frequency with the control voltage is fairly linear.     

Some urban measurements from SPOT data: urban life quality indices

Abstract

This paper reviews and illustrates the use of satellite remote sensing in urban analysis. Using the example of conventional population census data used together with SPOT imagery for Strasbourg, France, it is shown that landscape quality can be characterized and mapped with a detail that is not possible using the census alone.     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of