A new closed vessel for determining the ballistic performance of high energy solid and liquid gun propellants

Abstract

A new closed vessel, designed and build by Cranfield University under contract to the UK Defence Evaluation and Research Agency (DERA), is described. The jacketed vessel, which can be operated at high pressure (500 MPa) and has the capability of firing liquid monopropellants, is fitted with a single instrumented head and a detachable liner. The internal surface profile of the combustion chamber is shaped so as to prevent the build up of shock waves which can occur between parallel surfaces and this feature leads to improved output signal quality. Vessel venting following a firing is carried out by remote control via a proprietary air-actuated high pressure valve. The vessel can be fitted with optical windows or converted to a vented device for gas erosion studies.     

Cancer epigenetics comes of age

The discovery of numerous hypermethylated promoters of tumour-suppressor genes, along with a better understanding of gene-silencing mechanisms, has moved DNA methylation from obscurity to recognition as an alternative mechanism of tumour-suppressor inactivation in cancer. Epigenetic events can also facilitate genetic damage, as illustrated by the increased mutagenicity of 5-methylcytosine and the silencing of the MLH1 mismatch repair gene by DNA methylation in colorectal tumours. We review here current mechanistic understanding of the role of DNA methylation in malignant transformation, and suggest Knudson's two-hit hypothesis should now be expanded to include epigenetic mechanisms of gene inactivation.     

3G移动流媒体应用和技术发展方向

1移动流媒体技术 1，1移动流媒体简介 流媒体是指视频、声音等数据以实时传输协议承载，并以连续的流的形式从源端向目的端传输，在目的端接收到一定缓存数据后就可以播放出来的多媒体应用。流媒体技术应用到移动网络和终端上，称之为移动流媒体技术。     

The diverging paths of German and United States policies for renewable energy: Sources of difference

The United States and Germany started out with very similar policies for renewable energy after the energy crisis of the 1970s. By the year 2000 they were on very different policy paths and, as a result, the German renewable energy industry has moved well ahead of that in the United States, both in terms of installed capacity in the country and in terms of creating a highly successful export market. In this paper, we reject some of the conventional explanations for this difference. Instead, these differences arise from the intersection of contingent historical events with the distinctive institutional and social structures that affect policy making in each country. Our analysis of the historical path-dependent dynamics of each country suggests that those who wish to further renewable energy policy in the United States need to take into account these institutional and social factors so that they will better be able to exploit the next set of favorable historical circumstances.     

利用频域时钟抖动分析加快设计验证过程

随着数据速率的提高,时钟抖动分析的需求也在与日俱增。本文探讨参考了时钟的作用和时钟抖动对数据抖动的影响,并讨论在E5052B信号源分析仪（SSA）上运行的Agilent E5001A精确时钟抖动分析应用软件所配备的全新测量技术。     

双通带高温超导滤波器的研制

本文提出了一种双通带高温超导滤波器的设计方法,通过在非相邻谐振器间引入交叉耦合,创新实现了超导滤波器两个通带的特性,给出了双通带高温超导滤波器的拓扑结构、理论曲线、耦合矩阵、等效电路、设计过程以及模拟仿真结果.使用蒸镀于0.5mm厚度的氧化镁(MgO)基片上的DyBa2Cu3O7高温超导薄膜设计制作了一个阶数为14阶、引入3个交叉耦合的双通带高温超导滤波器.滤波器两个通带的中心频率分别为1930和1970MHz,通带宽度均为20MHz,滤波器的实际损耗小于0.2dB,其测试曲线、模拟仿真、理论计算三者有很好的吻合,每个通带内的群时延波动小于±20ns的带宽分别占到各自通带宽度的90%以上,取得了较为理想的结果.     

THE CONTROL OF GLAZE-FIT BY MEANS OF TENSILE TEST SPECIMENS1

The selection of a suitable glaze for a particular body by usual inspection of a field of glaze trials is not sufficiently precise, and gives no indication of slow crazing tendencies. A new method of selecting glazes depends on the effect of a glaze on the strength of a porcelain tensile test specimen. The best fitting glazes increase the strength while poorer ones decrease it. Glazes which craze weaken the specimens very markedly. Results obtained with various glazes on one fire porcelain are given.     

THE TENSILE STRENGTH OF PORCELAIN1

A method of accurately determining the tensile strength of porcelain has been developed. The ratio of tensile to compression strength was found to be 5.9 for the special porcelain studied. Triaxial porcelains gave an average ratio of 7.66. The tensile strength tests show in general a little more variation than compression strength tests. The tensile strength is of more significance in judging the quality of porcelain than it has been commonly considered.