Reference levels at European level for cardiac interventional procedures

In interventional cardiology, a wide variation in patient dose for the same type of procedure has been recognised by different studies. Variation is almost due to procedure complexity, equipment performance, procedure protocol and operator skill. The SENTINEL consortium has performed a survey in nine european centres collecting information on near 2000 procedures, and a new set of reference levels (RLs) for coronary angiography and angioplasty and diagnostic electrophysiology has been assessed for air kerma-area product: 45, 85 and 35 Gy cm(2), effective dose: 8, 15 and 6 mSv, cumulative dose at interventional reference point: 650 and 1500 mGy, fluoroscopy time: 6.5, 15.5 and 21 min and cine frames: 700 and 1000 images, respectively. Because equipment performance and set-up are the factors contributing to patient dose variability, entrance surface air kerma for fluoroscopy, 13 mGy min(-1), and image acquisition, 0.10 mGy per frame, have also been proposed in the set of RLs.     

一种模式关联主元分析的海流机故障检测方法

针对海流机复杂工况下发电过程数据的多模式和模式频繁变动的问题,提出一种模式关联主元分析方法。从理论上分析模式变化对传统主元分析(principal component analysis, PCA)的影响,描述了过程数据多模式下的故障检测问题。提出一种模式标准化算法,动态拟合多模式数据特征。通过构建多模式关联关系,将变化模式引起的统计量差值剔除。通过搭建海流机试验平台,对比所提方法与传统检测方法验证了所提方法的有效性。理论分析和试验结果表明:在海流机变转速同时变载荷工况下,所提方法能够快速准确的检测出故障。     

Some aspects on radiation protection in conventional and digital radiology in Romania

Since 1965, medical radiation exposure in the population of Romania has been evaluated by the Network of Radiation Hygiene Laboratories of the Ministry of Public Health, including 23 laboratories throughout the whole country; the network is co-ordinated by the Institute of Public Health Bucharest. In Romania, for a population of 22.5 million inhabitants, 465 X-ray examinations were reported during the last survey, the most frequent being chest examination. There was no specific reference to digital radiology. Digital radiology has been introduced only recently in Romania, and only some rough data on the situation can be presented. Siemens AG is now present in Romania with 23 installations, type SIEREGRAPH CF and AXIOM ICONOS. A digital image intensifier technique is used only for fluoroscopy, and radiography is performed using a conventional film/screen combination. The company Philips has nine installations for angiography, model INTEGRIS, and uses a computed radiography technique. Several direct digital radiography MULTISYSTEM SWISSRAY installations (about 40 units) are also available for adult and paediatric examinations. The Council Directive 97/43/EURATOM on health protection of individuals against dangers of ionising radiation in relation to medical exposure was fully transformed into Romanian legislation in 2002.     

Land constraints in Kenya’s densely populated rural areas: implications for food policy and institutional reform

This study analyzes the impact of increasing population density in Kenya??s rural areas on smallholder behavior and welfare indicators. We first present evidence to explain how land constraints can be emerging within an overall context of apparent land under-utilization. Using data from five panel surveys on 1,146 small-scale farms over the 1997?C2010 period, we use econometric techniques to determine how increasing rural population density is affecting farm household behavior and livelihoods. We find that farm productivity and incomes tend to rise with population density up to 600?C650 persons per km²; beyond this threshold, rising population density is associated with sharp declines in farm productivity, total household income, and asset wealth. Currently 14% of Kenya??s rural population resides in areas exceeding this population density. The study concludes by exploring the nature of institutional and policy reforms needed to address these development problems.     

基于FPGA的高精度超声波测距系统的设计

设计了一种基于FPGA的超声波测距模块。在时序和信号处理方面,采用Cyclone Ⅱ系列EP2C5T144C8芯片,通过设计时序发生器、高速计数、回波识别和可变门槛控制等逻辑电路模块可快速有序地对信号进行处理。在声速方面,加入了温度补偿模块,避免使用固定的声速值所引入的偏差,从而提高系统精度。该系统具有可靠性高、集成度高和响应速度快等特点,实验表明,在距障碍物600mm～3600mm时,相对误差在0.3%以内,测量精度得到很大提高。     

基于ANSYS Workbench的压缩机连杆优化设计

压缩机连杆是其运动机构完成活塞往复循环运动中的重要组成部件,连杆过于轻小,就不能满足在运动过程中承受拉、压交变力载荷的强度要求;连杆过于笨重,不仅浪费材料,还会给曲轴平衡带来困难。本文以某压缩机企业生产的一种型号压缩机为研究对象,利用ANSYS Workbench软件对其连杆部件进行强度校核与优化设计,节约了材料成本,缩短了产品设计周期,为企业同类产品的快速结构设计提供了一种理论方法。     

南宁城市配电网自动化建设探讨

为提高供电可靠性和配电网技术装备水平,总结南宁城市配电网自动化建设经验.通过对南宁城市配电网运行现状进行分析,指出了当前配电网故障处理存在的不足,并结合配电网运行环境特点,给出解决故障处理问题的配网自动化建设原则及目标.根据目前配网自动化实际运行效果,分析配电网自动化建设在提高故障处理效率方面的作用和效果.配网自动化的实现,可显著缩短故障停电持续时间及提升供电可靠率.     

采用混合共轭梯度迭代的频域地震数值模拟

当前频率域地震数值模拟中的时谐波动方程求解通常采用LU直接分解法或Krylov子空间迭代法。直接分解法占用内存大,耗费时间长,且难以模拟高维度、高密度地震采集;一般的Krylov子空间迭代法收敛速度较慢,在处理复杂模型时可能会出现不收敛的情况。为此,在现有共轭梯度类算法的基础上发展了一种优化的Krylov子空间法——混合共轭梯度算法,用于求解时谐波动方程。层状介质模型和标准模型的数值模拟结果表明：与LU直接法相比,新方法在保证模拟精度的前提下,可有效降低内存需要、减少计算用时;与双共轭梯度稳定迭代法相比,在处理复杂模型时具有更高的计算稳定性。     

Production potential of plateau agriculture and food sufficiency in the Kandhamal district of Orissa

The requirement for food grains in the rainfed hill plateaus of the Kandhamal district of the State of Orissa, India was calculated according to accepted nutritional standards over 14 years from 1993 to 2006 and compared with actual production during this time. Owing to the increase in population, the requirement increased from 120 × 10³ MT in 1993 to 142 × 10³ MT in 2006. Production, however, ranged from 68.5 × 10³ MT in 2002 to 134.9 × 10³ MT in 1994 and was only sufficient in 2 of the 14 years. The requirement for food grains for a projected population of 753,542 in 2011 was estimated to be 152 × 10³ MT. At present the area sown is 115 × 10³ ha and would require cultivation 1.83 times per year (cropping intensity 1.83) to produce enough foodgrains for nutritional sufficiency. This could be reduced to 1.64 if the current fallow area of 13 × 10³ ha were cultivated. Increased productivity could be achieved by greater use of irrigation and groundwater.