Analysis of a demodulation system for Fiber Bragg Grating sensors using two fixed filters

The analysis of a demodulation system for Fiber Bragg Grating sensors based on two fixed spectral filters has been carried out both theoretically and experimentally. Different system configurations were analyzed by modifying the spectral position of the filters as well as the optical power-level of the signal reaching the two photo-detectors. Measurements with integration times that varied from 0.01 to 1 s have been compared with the low-frequency limit predicted for long-term operation. Comparisons between simulated and experimental results show good agreement, and extrapolations indicate that it should be possible to achieve an operating spectrum range of the order of 7 nm, with uncertainties equivalent to less than 2 pm in measurements of the sensor peak position.     

直线加速器驻波腔中的瞬态束流负载效应

在高能加速器中, 随着单个束团和束团串中电荷量的提高, 当粒子束穿过加速腔的时候, 感应出的瞬态束流负载电压也越来越高. 但是, 在通常分析束流负载的时候, 往往对稳态束流负载研究的比较多, 而对瞬态束流负载的研究要相对少一些. 本文首先对束流负载的瞬态特性和束团穿过加速腔时高频源所看到谐振腔谐振频率的变化方式进行了分析, 然后又对两种情况下谐振腔的最优失谐条件进行了讨论, 并给出了相应的解析公式. 在第1种情况下, 当粒子束穿过加速腔的时候, 谐振腔的自然谐振频率能够及时地得到调节, 从而使高频源的电流与谐振腔的腔压同相, 以提高高频源的效率; 在第2种情况下, 当粒子束穿过加速腔的时候, 谐振腔的自然谐振频率保持不变, 不能被调节. 最后, 还对BEPCⅡ现有预注入器的预聚束腔、BEPCⅡ未来预注入器的两个次谐波聚束腔中的瞬态束流负载效应进行了分析.     

尖晶石锂锰氧化物锂离子嵌脱过程的交流阻抗谱研究

用粉末微电极研究了尖晶石锂锰氧化物在不同嵌锂状态下嵌脱锂过程的交流阻 抗图谱，提出了新的等效电路模型。描述锂离子在固体中扩散的Warburg阻抗与累 积或消耗的嵌入电容在Lix MnO4中的x≤0．5时串联，0．5＜x≤1时并联。用提出 的等效电路模型分阶段拟合了实验所得的交流阻抗谱，拟合值与实验值相当吻合， 由拟合结果得到不同电位下锂离子在表面膜中的迁移电阻和电容，界面电荷传递电 阻，双层电容，锂离子在固体中扩散系数和累积或消耗的嵌入电容。     

Towards advanced circuit board materials: adhesion of copper foil to ultra‐high molecular weight polyethylene composite

Polyethylene based composites are attractive materials for advanced circuit board applications because of their unique combination of properties: low dielectric constant and loss factor, light weight, high flexural modulus and low thermal expansion coefficient controlled in all spatial directions. This investigation describes a process to consolidate chopped fibers of ultra‐high molecular weight polyethylene concurrently with its bonding to a copper foil. Bonding is affected by a thin sheet of low‐density polyethylene, incorporating a crosslinking agent with a concentration gradient across the sheets thickness. In this single step process, the composite material is formed and bonded to the metal foil, achieving good adhesion without the use of extraneous glue. Copyright © 2002 John Wiley & Sons, Ltd.     

废弃线路板化学分析采样、制样及检测方法

介绍废弃线路板中有回收价值元素和有害物质分析的采样、制样及检测技术。样品经过分类采样、剪切破碎和高温灰化制样,采用样品全分析或副批混合样分析。通过提高称样量、多次测定求平均值的办法,火试金富集-重量法测定贵金属金、银。湿法王水溶解样品,碘量法测定主体元素铜。电感耦合等离子体发射光谱(ICP-AES)法测定其它杂质元素,被测元素质量浓度在0~10μg/mL范围内与光谱强度呈良好线性关系,相关系数均大于0.9998。测定结果的相对标准偏差小于10%(n=5),加标回收率为97.0%~102.5%。该方法简单、快速,有效地解决了线路板样品不均匀而难采样,以及硬度、韧性强制样难,金属易包裹难分解的技术瓶颈,测定结果准确,具有代表性。该方法适用于废弃线路板化学成分分析,其它废弃电子产品检测可参考此方法。     

Novel method for bulk resistance evaluation in conductivity measurement for high-purity water

A major issue with the electrolytic conductivity measurement for pure water is the lack of standard or reference methods. A primary method traceable to SI and suitable for pure-water conductivity measurement was developed at the Physikalisch-Technische Bundesanstalt (PTB), Germany, as the base for the calibration method for the conductivity measuring devices at the low conductivity level. This paper provides a novel method to calculate the bulk resistance of pure water using impedance measured at a single frequency, which is one of the key procedures for the primary methods.     

镍电极开路电位测定微量硼氢根离子

实验采用循环伏安法，用镍电极代替铂铑等贵金属电极测定了碱性体系中不同硼氢根离子浓度下的开路电位，得出了研究电极的开路电位（-0．355～-0．280vs.SCE／V）与微量硼氢根离子浓度的对应关系，并用于监测电解偏硼酸钠制备硼氢化钠体系中微量硼氢根离子，同时计算了该方法的误差。结果表明，测量结果的相对标准偏差为2．2％；回收率为98．4％。该法简单、快速，可测定10^-5～10^-3mol／L范围的硼氢根离子浓度。     

Examination of the statistical method in the conjugated circuit theory

Summary The recently proposed statistical method for the calculation of resonance energies in the conjugated circuit theory is tested on the example of polyacenes. It is found that for the estimation of the resonance energy with a 10% average error, the method requires a sample consisting of about 20 (randomly chosen) Kekulé structures. Further increase of the sample size gives no significant gain in the accuracy of the method.

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Überprüfung der statistischen Methode in der Konjugierten-Ring-Theorie

Zusammenfassung Die unlängst vorgeschlagene statistische Methode in der Konjugierten-Ring-Theorie (conjugated circuit theory) wird am Beispiel der Polyacene getestet. Es wurde festgestellt, daß für die Abschätzung der Resonanzenergien bei einem mittleren Fehler von 10% für diese Methode ungefähr 20 (willkürlich gewählte) Kekulé-Strukturen nötig sind. Weitere Erhöhung dieser Anzahl bringt keine signifikante Verbesserung der Genauigkeit der Methode.

     

Fluorinated compounds for advanced IC interconnect applications: a survey of chemistries and processes

The semiconductor industry is now in the early stages of an unprecedented change in materials set for the integrated circuit (IC) interconnect structure. The traditional layers of aluminum conductors and silicon dioxide dielectrics are being replaced by copper thin films and a variety of low k candidates, respectively. In many cases, fluorine confers desirable properties on either the precursors or the final films. At the same time, fluorine presents some potentially adverse effects, which have led to a so-called “fear-of-fluorine” in interconnect applications. This paper will review the proposed uses of fluorinated compounds in the interconnect structures, covering both precursors and the resulting thin films. Both the status of technical studies, and the prospects for commercial implementation, will be addressed.     

压电石英晶体在电解质水溶液中的振荡性能研究(Ⅱ)——频率、频移特性

根据两面电极浸入液体中的压电晶体等效电路模型和Pierce振荡器振荡方程的解,得到晶体在电解质溶液中的振荡频率(F_1)与溶液电导率(x)的关系式:F_1=(1/2π)(1/C_1+1/C_2)(1/X_e)[(R_e~2+X_e~2)x~2+2R_ex+1]。以自行设计的Pierce晶体振荡器。研究了晶体和主振电路参数、输入电压及检测池外壳屏蔽接地对AT切9MHz石英晶体在KCl、Na_2SO_4水溶液中的频率、相对于纯水频移随溶液电导率变化的影响规律,结果与上式相符。