A comparative study of Young's modulus of single-walled carbon nanotube by CPMD, MD, and first principle simulations

Carbon nanotubes (CNTs), due to their exceptional magnetic, electrical and mechanical properties, are promising candidates for several technical applications ranging from nanoelectronic devices to composites. Young's modulus holds the special status in material properties and micro/nano-electromechanical systems (MEMS/NEMS) design. The excellently regular structures of CNTs facilitate accurate simulation of CNTs' behavior by applying a variety of theoretical methods. Here, three representative numerical methods, i.e., Car-Parrinello molecular dynamics (CPMD), density functional theory (DFT) and molecular dynamics (MD), were applied to calculate Young's modulus of single-walled carbon nanotube (SWCNT) with chirality (3,3). The comparative studies showed that the most accurate result is offered by time consuming DFT simulation. MID simulation produced a less accurate result due to neglecting electronic motions. Compared to the two preceding methods the best performance, with a balance between efficiency and precision, was deduced by CPMD

基于潮汐表数据同化的天文潮数值预报模型及其模拟预报效果

[摘要]：潮汐表是利用长期潮汐观测结果经调和分析实现的主要港湾潮汐预报结果, 具有较高的预报 精度, 而通常的天文潮数值预报目前还难以达到潮汐表的预报精度. 本研究在建立常规天文潮数值 预报模型的基础上, 建立了基于潮汐表数据同化的天文潮数值预报模型, 并分别采用这2种模型预 报福建沿岸海域的天文潮. 其结果表明同化模型的预报结果无论是在潮时还是在潮高均明显优于 常规模型; 同化模型能显著地改善所研究的沿岸海域90个水位点中至少45个水位点的潮汐预报 结果, 而其他水位点的预报结果也有不同程度地改善.国家863 计划重大资助项目( 2006AA09A302-6

EFFECT OF UNIT CELL VOLUME OF RE(Ni, Co, Mn, Ti)_5 ALLOY (RE=La, Ce, Pr, Nd) ON ITS ELECTROCHEMICAL PROPERTIES

制备了Ｌａ（Ｎｉ，Ｃｏ，Ｍｎ，Ｔｉ）５，Ｃｅ（Ｎｉ，Ｃｏ，Ｍｎ，Ｔｉ）５，Ｐｒ（Ｎｉ，Ｃｏ，Ｍｎ，Ｔｉ）５和Ｎｄ（Ｎｉ，Ｃｏ，Ｍｎ，Ｔｉ）５四种单一稀土贮氢电极合金，分别测定了它们的单胞体积、氢化物生成焓和几个主要的电化学性能指标（包括活化循环次数、最大放电容量、高倍率放电率和容量衰退速率），以分析不同稀土元素对合金电化学性能的影响.结果表明，在四种合金中，单胞体积对合金的热力学性质和电化学性能起了决定性作用，它与合金的氢化物生成焓呈简单的线性关系，对电化学性能有双重影响，使四个主要指标随单胞体积的变化均出现极大或极小值.单胞体积本身的变化与稀土元素的周期性有关．Four rare earth based AB_5 typed alloys, La(Ni, Co, Mn, Ti)5, Ce(Ni, Co, Mn, Ti)5, Pr(Ni, Co, Mn, Ti)5 and Nd(Ni, Co, Mn, Ti)5, were prepared and then their unit cell volumes (Vcell), standard enthalpies of metal hydride formation at 298 K (△H298 K), and main electrochemical characteristics, such as activation cycle number (na), maximum discharge capacity at 50 mA/g charge/discharge rate (C50,max), high-rate-dischargeability K (includes K1 and K2 ), rate of decay (-dC / dn) were measured and analyzed to reveal the effects of the rare earth elements on the electrochemical properties. The results show that the unit cell volume is the key factor in determination of the alloys' thermodynamics and electrochemical properties. The standard enthalpies of metal hydride formation at 298 K (△H298 K) are proven to vary linearly with the unit cell volume, and the four electrochemical parameters, na, C50,max, -dC/dn and K,are dualistically affected by it. The change of unit cell volume is in accord with the periodic law of the rare earth element.国家自然科学基金!59801008;; 国家863高新技术计划资助!715－004－006

钾促进钴钼耐硫CO变换催化剂的XPS和TPR表征

用 XPS和 TPR谱学表征方法 ,研究钾助剂对负载型 Co-Mo-K-O/γ-Al2 O3水煤气耐硫变换催化剂的作用 .XPS表征显示 ,硫化态催化剂随着钾添加量的增加 ,低价态钼和 S2 - 增加 ,( S-S) 2 - 受抑制 ,( Mo4+ +Mo5 + ) /Mo6 + 质量比为 0 .8～ 1和较多的 S2 - 物种有利于提高催化剂的低温活性 .TPR表征结果示出 ,硫化态及工作态催化剂皆出现α、β 2个吸氢峰 ,可分别归属 Mo6 + → Mo5 + 和 Mo5 + → Mon+ ( n=4 ,3,2 )的还原过程 ;工作态催化剂 α峰峰温较硫化态低 ,β峰为宽峰带低价钼混合峰 ;吸氢峰的大小与催化剂低温活性密切相关

Research on Fixed Abrasive Elastic Machining for Optical

目前中大口径高精度先进光学元件已经广泛应用于国家重大高技术光学工程及民用高端光电系统等领域，当前其制造工序流程“高效精密/超精密磨削成形+确定性数控抛光”已相对发展成熟，但在高效磨削和抛光之间仍存在一个效率断层和损伤控制空白区，需要在保持成形精度的前提下高效地去除数十微米的表层和亚表面缺陷，且达到光学表面。在已有抛光技术领域，由于基本都采用游离磨料抛光的加工方式，可以获得很好的表面粗糙度，但是基于压力控制的进给，游离磨料抛光较难保证工件的面形几何精度，同时加工效率相对低下。由于游离磨料的加工方式存在这些不可避免的原理性问题，已有不少研究聚焦在固结磨料研抛加工。本文提出了一种采用固结磨料弹性工具...At present, precision optical components have been widely used in the field of military project and civil photoelectric. The current manufacturing process of precision optical components usually adopts "precision grinding + deterministic polishing". However, Grinding has an advantage of high removal efficiency, but leaving lots of surface damage in the workpiece after processing. On the contrary, ...学位：工学硕士院系专业：航空航天学院_机械制造及其自动化学号：1992014115287

[[alternative]]The Research of 9th Students’ for Scientific Writing Work and Study Achievement : The Illustration from “Temperature and Heat”

[[abstract]]The purpose of this research was to use Systemic Functional Linguistics as analyzing tools for analysis of students’ scientific writing work after their viewing the video, “Temperature and Heat” (about 3 min in length), so that we may understand the correlation between the performance of students’ scientific writing work and their study achievement. Furthermore, the results of the study can also be used as references for science teachers in scientific teaching activities. Thirty five students from the 3rd grade of a Taipei municipal junior high school participated in this study. Devices including “Temperature and Heat” (video clip) and work sheets of scientific writing were designed and administered. Statistics including descriptive and Pearson’s product-moment correlation were conducted to analyze the quantity and quality of students’ scientific writing and the correlation between them and their learning achievement of Chinese and science. The study results are shown as follows: 1. The higher achievement of science and Chinese that a student has, the better performance will be on the quantity of words, content terms, small sentences, general terms, scientific terms and material process terms. 2. The students with higher achievement of science and Chinese will have better performance on the quantity of scientific explanation sentences. 3. The correlation of the highest degree of small sentences is noticeable on achievement of either science study or Chinese study. Students with higher achievement will use more small sentences to describe or explain the observations while doing scientific writing. 4. The higher achievement of science and Chinese that a student has, the better performance will be on correct scientific explanation sentences while doing scientific writing. 5. While the students are doing the second scientific writing, in addition to the difficulty of sentences, each dimension has a positive correlation with the study achievement of science and Chinese. This indicates that students with better study achievement of science or Chinese will also have better performance on explanation of phenomena.

基于离子液体的绿色催化过程

离子液体为构建绿色催化反应过程提供了新途径.本文简要评述了离子液体在几个代表性催化反应中的研究进展,如CO2羰基化、烷基化、酯交换、氧化、CO2加氢、共聚以及PET降解等;分析讨论了离子液体的特点和优势,如提高反应活性、降低废物排放以及简化分离等,并对离子液体催化反应的未来发展方向进行了展望

research of multi-channel interactive technology-oriented software systems for children

将研究一个面向少儿益智系统,该系统将多种益智娱乐开发包构建在城堡中,少儿通过多通道交互方式可以在城堡中随意漫游、体验、学习和娱乐。另外,通过该系统开发包,幼儿园和小学的教师及儿童自己都可以开发少儿益智游戏和学习素材供少儿使用

Improved Wavelet Packet Multi Threshold Denoising Method and Its Engineering Applications

针对机械振动信号提取时面临的去噪问题,在小波包多阈值准则去噪法的基础上,提出一种改进的小波包多阈值准则综合去噪方法(改进FMC去噪法)。该方法首; 先采用探测插值法对机床原始振动信号进行预处理,剔除受外界干扰产生的突变噪声信号;再以小波包分析为基础,根据有用信号的最小频率确定最大分解层数,并; 按最小代价原理确定信号分解的最佳小波包基;最后采用小波包多阈值降噪准则对振动信号进行重构,得到去噪后的机床振动信号。针对含噪blocks信号、d; oppler信号及模拟的含噪振动信号进行的仿真实验结果表明,改进后的FMC去噪法去噪效果优于传统方法。将该方法应用于气囊修整机振动信号分析中,结; 果表明,改进FMC去噪法能够有效剔除振动信号各频段的噪声,提高信号特征的可分离性。Aiming at the problems of denoising in mechine vibration signal; extrations, based on the wavelet packet multi-threshold criterion; denoising method, an improved wavelet packet denoising method to multi; threshold standards was proposed herein, referred to improved FMC; denoising method. This method was applied to pre-process original; vibration signals of machine tools by pseudo point elimination technique; to eliminate interferences of external noise signals to vibration signal; extractions. Then the method of determining decomposition level was; optimized by the method of determining maximum decomposition level with; minimum frequency components of useful signals, and optimal wavelet; packet basis was determined by minimum cost principle. Finally,; vibration signals were reconstructed by wavelet packet multi threshold; denoising criterion. Simulation experiments were implemented, and the; results show that the method has good noise reduction effect, especially; in strong noise background with a mutation of noise signal recovery.; Experimental results show that the improved FMC denoising method may; effectively eliminate band noises and improve separability of signal; characteristics. Experiments were carried out to analyze the vibration; signals of air bag dressing machine using this method, and experimental; results show that the improved FMC denoising method may effectively; eliminate the band noise and improve signal feature separability.国家自然科学基金资助项目; 深圳科技计划资助项