A new tuning procedure for the DTL RF field pattern

The DTL tank is a multi-cell cavity.In a fabricated tank,the measured average axial field E0 for each cell may obviously deviate from the designed value.It is generally thought the deviation is due to the errors in fabrication and assembly.But it is not always true.In this paper,it is shown that the deviation may already exist before fabrication in some cases.It is partly due to the imperfection of the current design procedures.A new design method is introduced to reduce the deviation in the design stage.     

一种基于激光直写的水浊度传感结构

提出并制作了一种基于激光照射改变折射率方法的光度比浊度传感单元,综合了导波光学及检测相关知识原理.以UV光敏树脂为基底材料,采用“气体干法”除胶及分步固化的方法获得了该芯片化结构.传感器整个制作过程仅仅需要7~8 min因而使本方法具有很高的效率.由直写成型的单元组建传感系统对标准悬浊液样品进行了实验测试,所得的相关数据在SISO算法神经元网络系统中进行处理,获得了传感器浊度与对应散射系数的关系曲线.通过试剂检验的方法得知实际相对误差在5%左右.     

氢元素概念发展史与化学思想的演进

18世纪,发现氢气的卡文迪什认为该气体是水与燃素的化合物;但发现水的组成的拉瓦锡认为氢气是一种元素物质.到19世纪,原子分子论形成后,氢气被认为是由双原子分子构成的单质.20世纪30年代,氢同位素的发现使人们对氢元素概念有了新认识,并逐渐形成现代氢元素概念.氢元素概念的发展史不仅是元素概念的发展史,也是科学思想的演进史...     

离焦激光直写的线宽稳定方法

为了提高激光直写加工衍射光学元件时的线条质量,提出一种离焦激光直写的线宽稳定方法.该方法通过同时调节激光功率和离焦量,使光刻胶的曝光阈值处于线宽对曝光量的变化率较小位置,从而可以弱化线宽对实际曝光量或光刻胶阈值等变化的敏感度,提高利用离焦方法进行衍射光学元件制作时的线宽稳定性.推导了稳定线宽后的光功率控制模型和线宽模型,模型中的变量仅为离焦量,降低了光功率控制的复杂性.利用632.8 nm的He-Ne激光和NA-0.1的物镜在CCD上对采用该方法后的离焦线宽模型进行验证,实验结果与理论模型吻合较好.该方法对于线宽稳定度较高的衍射光学元件制作具有重要价值.     

How to write a research article for MRC

This nonscientific tutorial proposes best practice for authors publishing research articles in Magnetic Resonance in Chemistry (MRC). It offers authors essential insights into writing eye-catching article titles, author/co-author names and hierarchy, IMRaD and IRDaM article structures, referencing and the composition of abstracts, introductions, experimental, results and discussion, and conclusions together with the all-important covering letter. This arsenal of insights aims to provide tools for authors to maximize the chance of success for their research articles.     

拉曼光谱3D成像技术确定黑色交叉笔画顺序的研究

在文书鉴定中,经常涉及对交叉笔画的检验,进而判断文件是否存在篡改、变造,此外,交叉笔画的检验也有助于判断笔迹个性特征、笔顺特征。本文采用拉曼光谱3D成像技术对多品牌不同型号的黑色圆珠笔和国产签字笔进行实验筛选,结合现有交叉笔画检验方法中如笔画连续性、收敛现象等特征,分析该方法判断交叉笔画书写顺序适用的各种情形:经赋色的笔画3D模型大量出现明显的“峰谷”异色现象,且表现一致,则能够得出准确结论;当现象明显存在但表现不一致或现象不明显时,需结合笔画连续性在3D模型中的特征分析判断,亦能得出正确结论,但准确率受数据处理的优劣及成像效果的影响较大;无法检测的情形,即无法获得有效拉曼光谱信息或无法区分两种油墨光谱信息时,该方法失效。笔者认为采用拉曼光谱3D成像技术在一定条件下能够对交叉笔画书写顺序进行相对客观、准确的判断,受鉴定人员主观影响较小,值得更加深入全面的研究,以便推广应用。     

化学学科思想研究文献的统计分析——基于中国知网中文数据库的分析

从文献基本信息、作者所在区域、作者单位、作者合作情况、文献研究内容等5个方面对2002-2016年从中国知网检索到的104篇有关化学学科思想的研究文献进行详尽地统计和分析。结果显示：（1）研究论文数目逐年增加,但总数依然较少;（2）研究群体相对集中,但尚未形成稳定核心作者群;（3）研究内容覆盖面广,但缺乏实证性和高站位。启示如下：（1）拓展研究者的范围,加强合作研究;（2）优化研究内容,创新研究方法。     

促进分类思想形成的“硅”教学设计

以含硅材料的主要成分为分类依据,对“无机非金属材料的主角--硅”第1课时进行了教学设计。旨在以含硅材料为载体,在落实“硅及其化合物”知识与技能目标过程中,促进学生分类方法和分类思想的形成,从而促进学生对“硅为什么是无机非金属材料的主角”的理解。     

From Stochastics to Complexity in Models of Economic Instability

Sixty years ago, the leading lights of the economics profession chose to model economic fluctuations as if they were caused by stochastic disturbances to an underlying stable, heavily damped system, in the mistaken belief that a mathematically unstable system does not fluctuate; it just breaks down. A perceptive minority instead concluded that the fundamental relations in economics must be nonlinear. It is shown that a single sector model with nonlinear behavior by workers, capitalists and the government generates a chaotic explanation for the most extreme of economic fluctuations, a Great Depression. A multi-sectoral model of a stylized economy confirms the judgment that economics is fundamentally a nonlinear discipline, by establishing that the input-output nature of production generates substantive nonlinearities, even when linear behavioral functions are assumed.     

Open microfluidic gel electrophoresis: Rapid and low cost separation and analysis of DNA at the nanoliter scale

Gel electrophoresis is one of the most applied and standardized tools for separation and analysis of macromolecules and their fragments in academic research and in industry. In this work we present a novel approach for conducting on‐demand electrophoretic separations of DNA molecules in open microfluidic (OM) systems on planar polymer substrates. The approach combines advantages of slab gel, capillary‐ and chip‐based methods offering low consumable costs (<0.1$) circumventing cost‐intensive microfluidic chip fabrication, short process times (5 min per analysis) and high sensitivity (4 ng/μL dsDNA) combined with reasonable resolution (17 bases). The open microfluidic separation system comprises two opposing reservoirs of 2–4 μL in volume, a semi‐contact written gel line acting as separation channel interconnecting the reservoirs and sample injected into the line via non‐contact droplet dispensing and thus enabling the precise control of the injection plug and sample concentration. Evaporation is prevented by covering aqueous structures with PCR‐grade mineral oil while maintaining surface temperature at 15°C. The liquid gel line exhibits a semi‐circular cross section of adaptable width (∼200–600 μm) and height (∼30–80 μm) as well as a typical length of 15–55 mm. Layout of such liquid structures is adaptable on‐demand not requiring time consuming and repetitive fabrication steps. The approach was successfully demonstrated by the separation of a standard label‐free DNA ladder (100–1000 bp) at 100 V/cm via in‐line staining and laser induced fluorescent end‐point detection using an automated prototype.