Comparisons of nozzle orifice processing methods using synchrotron X-ray micro-tomography

Based on the high flux synchrotron X-ray of the Shanghai Synchrotron Radiation Facility (SSRF), high precision 3D digital models of diesel nozzle tips have been established by X-ray micro-tomography technology, which reveal the internal surfaces and structures of orifices. To analyze the machining precision and characteristics of orifice processing methods, an approach is presented based on the parameters of the internal structures of nozzle orifices, including the nozzle diameter, the orifice inner surface waviness, the eccentricity distance and the angle between orifices. Using this approach, two kinds of nozzle orifice processing methods, computerized numerical control drilling and electric discharge machining, have been studied and compared. The results show that this approach enables a simple, direct, and comprehensive contrastive analysis of nozzle orifice processing methods. When processing a single orifice, the electric discharge machining method has obvious advantages. However, when there are multiple orifices, the error levels of the two methods are similar in relation to the symmetry of distribution of the orifices.     

An Arabidopsis mutant atcsr-2 exhibits high cadmium stress sensitivity involved in the restriction of H2S emission

The gene AtCSR encodes peptidyl-prolyl cis/trans isomerases (PPIases) that accelerate energetically unfavorable cis/trans isomerization of the peptide bond preceding proline production.In our studies,we found that AtCSR was associated with cadmium (Cd)-sensitive response in Arabidopsis.Our results show that AtCSR expression was triggered by Cd-stress in wild type Arabidopsis.The expression of some genes responsible for Cd2+ transportation into vacuoles was induced,and the expression of the iron-regulated transporter 1 (IRT1) related to Cd2+ absorption from the environment was not induced in wild type with Cd2+ treatment.The expression of Cd-transportation related genes was not in response to Cd-stress,whereas IRT expression increased dramatically in atcsr-2 with Cd2+ treatment.The expression of glutathione 1 (GSH1) was consistent with GSH being much lower in atcsr-2 in comparison with the wild type with Cd2+ treatment.Additionally,malondialdehyde (MDA),hydrogen peroxide,and Cd2+ contents,and activities of some antioxidative enzymes,differed between the wild type and atcsr-2.Hydrogen sulfide (H2S) has been confirmed as the third gas-transmitter over recent years.The findings revealed that the expression pattern of H2 S-releasing related genes and that of Cd-induced chelation and transportation genes matched well in the wild type and atcsr-2,and H2S could regulate the expression of the Cd-induced genes and alleviate Cd-triggered toxicity.Finally,one possible suggestion was given:down-regulation of atcsr-2,depending on H2S gas-transmitter not only weakened Cd2+ chelation,but also reduced Cd2+ transportation into vacuoles,as well as enhancing the Cd2+ assimilation,thus rendering atcsr-2 mutant sensitive to Cd-stress.     

Influence of education and working background on physicians’ knowledge of secondary prevention guidelines for coronary heart disease: results from a survey in China

Background and objective  

In clinical practice, the standard of secondary prevention for coronary heart disease (CHD) is quite disappointing in China. The physicians’ shortage of knowledge of secondary prevention guidelines is thought to be a key factor contributing to the inadequate and delayed translation of guidelines into clinical practice. The purpose of this study is to investigate the influence of physicians’ characteristics, including their education and work experience, on their knowledge of secondary prevention in China.     

“国培计划”有效途径：网络远程培训

以问题为中心,以案例为载体的“国培计划”,通过对培训机制创新,采取对骨干教师集中培训、脱产研修及大规模教师远程培训相结合方式,其中以网络远程培训为主体形式、采用远程开放教育模式是保持“国培计划”长期性、有效性的最佳路径。     

自助借还书系统图书识别模式分析

自助借还书系统的使用能有效延长图书馆的借还书时间、降低图书馆工作人员的劳动强度。传统的条形码与RFID两种图书识别模式自助借还书系统在实际使用中存在着一些问题。本文针对这些问题,在介绍ColorBit标签的基本识别原理的基础上,提出将ColorBit图书识别标签技术应用于自助借还书系统以克服传统图书识别模式自助借还系统的不足,并提出了该模式下自助借还系统的基本流程方案。     

中国《科学》月刊传播科学的编辑策略

基于科技期刊传播科学的研究视角并采用原始期刊文献分析考证法,研究创刊于1915年的中国《科学》月刊在传播科学方面的编辑策略,为近代中国以期刊为媒介的科学传播史研究提供新线索。《科学》以中国科学社为依托,清一色国外留学生的创办者与主笔者,"专述科学,归以效实",图文并茂等独特的科学传播编辑策略推进科学与科学教育传播,对近代中国科学传播与发展产生了巨大的影响,开拓了现代科技期刊传播科学的新时期。     

文物信息资源元数据建设原则、模型与方案探讨

结合文物信息资源的分类与特性,提出文物信息资源元数据标准的使用范围、编码规则,及文物信息资源元数据设计的简单性、实用性与准确性原则。在此基础上,设计了一种繁、简结合的元数据表示模型,即根据文物的最基本信息构造精简的元数据表示,而用扩展元数据模型表示文物的完整信息。该模型优缺点并存,未来文物信息资源元数据标准建设在专业词汇的选择、标准体系的构建、元数据互操作方面仍有待规范与完善。     

Material Classification-Oriented Chinese String Similarity Metric

物资分类是企业物资管理的一项基础工作,在大型企业中,物资数量巨大且类别繁多,所以需要借助计算机自动分类技术提高物资分类的效率.在自动分类的过程中,物资名称相似度是影响分类效果的关键因素之一.在分析了物资名称字符串特点和Jaro-Winkle算法的基础上,提出了一种基于动态权重的中文字符串相似度计算方法.通过在真实物资分类数据集上的实验,验证了这种相似度的计算方法可以有效提高物资分类的准确度.     

红外对管检测气液两相流型与液塞实验研究

在气液两相流实验中,流型、液塞速度是很重要的参数,需要进行检测.根据红外线可以穿透透明介质,且服从衰减定律的原理,使用红外对管以及检测电路制作了检测装置.在透明实验管路外部安装了3套检测装置,并以空气、水为介质进行实验,检测了不同流动情况下的感应电压,分析了不同流型下感应电压的特点,提出了根据感应电压特性判别流型的方法.根据液塞经过红外对管时检测电压的波动特点,检测了液塞速度,并与文献中的理论公式计算结果相对比,数据吻合较好.实验结果表明,红外对管可以用于气液流型判别与液塞检测.     

肾脏和股骨铅蓄积多元素综合指标探讨

目的:通过对血液中多元素与肾铅、股骨铅关系的分析,探讨能够准确反映肾脏、股骨铅蓄积的综合指标。方法:选取健康的4周龄雄性SD大鼠75只,随机分成25组,采取大剂量范围,小浓度间隔的染毒方法。实验开始后,于第40、80、120天分别从各组随机选取1只大鼠,经乙醚麻醉后股动脉取血,并收集肾脏、股骨,用电感耦合等离子体质谱法(ICP-MS)测定元素含量。结果:血铅、肾铅、股骨铅浓度随染毒剂量的增加而发生变化,但变化趋势各不相同;血铅浓度与肾铅、股骨铅浓度之间的相关性随染毒周期而变化;血液中其他元素的浓度或浓度比值与肾铅、股骨铅之间的相关有统计学意义,且相关系数均高于单一元素与肾铅、股骨铅间的相关系数。结论:单一血铅指标在反映脏器铅蓄积水平有一定的局限性;多元素综合指标则有可能成为估算脏器铅蓄积水平的有力工具。