丙酸正丁酯绿色合成工艺中固体酸催化剂研制

针对目前酯化工艺过程中存在的环境污染问题,以丙酸正丁酯催化合成为例,对酯化过程清洁生产工艺中固体酸催化剂的制备进行了研究.制备了 SO_4~(2-)/TiO_2固体超强酸催化剂,讨论了各种制备条件对该催化剂的丙酸正丁酯合成催化活性的影响,采用 TG/DTA、FTIR、XRD 等仪器分析手段对催化剂结构进行了表征,实验结果表明,SO_4~(2-)/TiO_2固体超强酸催化剂具有很好的催化活性和选择性,且无腐蚀、反应时间短、后处理简单、重复使用性好.     

Facial motion cloning

We propose a method for automatically copying facial motion from one 3D face model to another, while preserving the compliance of the motion to the MPEG-4 Face and Body Animation (FBA) standard. Despite the enormous progress in the field of Facial Animation, producing a new animatable face from scratch is still a tremendous task for an artist. Although many methods exist to animate a face automatically based on procedural methods, these methods still need to be initialized by defining facial regions or similar, and they lack flexibility because the artist can only obtain the facial motion that a particular algorithm offers. Therefore a very common approach is interpolation between key facial expressions, usually called morph targets, containing either speech elements (visemes) or emotional expressions. Following the same approach, the MPEG-4 Facial Animation specification offers a method for interpolation of facial motion from key positions, called Facial Animation Tables, which are essentially morph targets corresponding to all possible motions specified in MPEG-4. The problem of this approach is that the artist needs to create a new set of morph targets for each new face model. In case of MPEG-4 there are 86 morph targets, which is a lot of work to create manually. Our method solves this problem by cloning the morph targets, i.e. by automatically copying the motion of vertices, as well as geometry transforms, from source face to target face while maintaining the regional correspondences and the correct scale of motion. It requires the user only to identify a subset of the MPEG-4 Feature Points in the source and target faces. The scale of the movement is normalized with respect to MPEG-4 normalization units (FAPUs), meaning that the MPEG-4 FBA compliance of the copied motion is preserved. Our method is therefore suitable not only for cloning of free facial expressions, but also of MPEG-4 compatible facial motion, in particular the Facial Animation Tables. We believe that Facial Motion Cloning offers dramatic time saving to artists producing morph targets for facial animation or MPEG-4 Facial Animation Tables.     

锂离子蓄电池正极材料LiFePO4的研究进展

锂离子蓄电池正极材料的研究正在向高比能量、长寿命、低成本、环境友好的方向发展。橄榄石型LiFePO4近年来引起注意。由于它具有170mAh/g的理论比容量和约3.5V的电压、较好的常温和高温稳定性、低廉的成本和优良的环保性能,有望作为大型移动式锂离子蓄电池的正极材料。对该材料的特性及研究情况进行了较为全面的总结,重点介绍了其结构特点与性能的关系,以及国外为改进其综合性能而进行的有关研究:(1)LiFePO4制备方法(包括高温固相合成法和低温液相合成法);(2)导电性物质的修饰以提高其在大电流密度下的比容量;(3)常温和高温贮存稳定性的实验;(4)LiFePO4的离子导电性和电子导电性。     

图像编码中的容错方法分析

随着信息社会的到来,互联网以及正在迅速发展的移动通信技术,逐渐成为人们获取信息的中心。而这些信息的传输都必须由具有较强鲁棒性的压缩数据来保证。所以,在有干扰的信道中如何保护传输的压缩数据不受干扰成为人们关注的问题。针对现代信息中的最主要的图像数据的传输问题,对一些差错控制方法,特别是在JPEG2000及MPEG-4标准中所采用的新的容错工具和方法进行了较详细地分析。     

2,4,6-三氨基嘧啶在玻碳电极上的电化学行为

用线性扫描伏安法 (LSV)、循环伏安法 (CV)和微分脉冲伏安法 (DPV)等电化学手段研究了 2 ,4,6 三氨基嘧啶 (TAP)的电化学行为。结果表明 :该化合物在玻碳电极表面存在吸附特性 ,在 0 .1 0mol·L- 1 的 pH 5 .0Britton Robinson (B R)缓冲溶液中于1 .2 0V(vs.Ag/AgCl)处有一灵敏的氧化峰。在选定的最佳条件下 ,其浓度在 8.0× 1 0 - 6～ 3.2×1 0 - 4 mol·L- 1 范围内与氧化峰电流有良好的线性关系 ,检测限为 6.5× 1 0 - 6mol·L- 1 。     

Physical and Electrochemical Properties of Doped LiFePO4 as Cathode Material for Lithium-Ion Batteries

LiFePO4 cathode material was synthesized by a solid-state reaction using doping several elements (Nb5 ,Zr4 ). The starting materials were mixed with a high-efficient sander and treated thermally under flowing N2. The samples were characterized by X-ray diffraction (XRD), field-emission gun electron microscopy (FEG), and their electrochemical performance was investigated in the term of cycling behavior. Room temperature discharge capacity about 140.6 mA·h·g-1 was obtained at C/5 rate.     

Electrical Properties and Electroluminescence of 4H-SiC p-n Junction Diodes

Homoepitaxial growth of 4H-SiC on off-oriented Si-face(0001 ) substrates was performed by using the step-controlled epitaxy technique in a newly developed low-pressure hot-wall CVD (LP-HWCVD) system with a horizontal aircooled quartz tube at around 1500 ℃and 1.33 × 104 Pa by employing SiH4 C2H4 H2. In-situ doping during growth was carried out by adding NH3 gas into the precursor gases. It was shown that the maximum Hall mobility of the undoped 4H-SiC epilayers at room temperature is about 430 cm2 ·V -1 ·s -1 with a carrier concentration of ～ 1016 cm-3 and the highest carrier concentration of the N-doped 4H-SiC epilayer obtained at NH3 flow rate of 3 sccm is about 2.7 × 1021 cm-3 with a mobility of 0.75 cm2 ·V -1 ·S -1. SiC p-n junctions were obtained by epitaxially growing N-doped 4H-SiC epilayers on Aldoped 4H-SiC substrates. The C-V characteristics of the diodes were linear in the 1/C3-V coordinates indicating that the obtained p-n junctions were graded with a built-in voltage of 2.7 eV. The room temperature electroluminescence spectra of 4H-SiC p-n junctions are studied as a function of forward current. The D-A pair recombination due to nitrogen donors and the unintentional, deep boron center is dominant at low forward bias, while the D-A pair recombination due to nitrogen donors and aluminum acceptors are dominant at higher forward biases. The p-n junctions could operate at temperature of up to 400 ℃, which provides a potential for high-temperature applications.     

Effects of lubrication and humidity on the abrasiveness of a thin boron carbide coating

Studies using thin boron carbide (B₄C) coatings have previously been performed in order to investigate their potential use as finite-life run-in coatings. Such coatings have been shown to polish the mating surface in a relatively short time. The inherent ability of these coatings to polish can potentially allow them to function as finite-life run-in coatings. Employing such coatings requires a thorough understanding of the parameters which directly influence the changes that occur in the coating abrasiveness throughout the duration of the polishing process. In past studies, changes in the coating abrasiveness during dry sliding wear under ambient conditions have been investigated. However, both lubrication and humidity can strongly influence the abrasive wear process. In this study, the influences of the operating environment, namely humidity and lubrication, on the coating abrasiveness are directly investigated. The coating abrasiveness decreases at a slower rate when a lubricant is added and when the humidity decreases.     

基于PHREEQC模拟分析Na2S2O4对退役铀矿山采区地下水生态的修复

酸法原位地浸采铀作为回收铀资源首选工艺,不可避免会存在部分铀进入地下水污染生态环境,而采用还原剂Na2S2O4将游离的铀还原固定可高效解决此类问题。为此,针对某酸法地浸采铀退役铀矿山地下水铀污染,采用PHREEQC模拟分析Na2S2O4还原固定地下水中可溶性铀的机制,讨论NaHCO3在Na2S2O4还原固定可溶性铀的影响。模拟结果表明：1）该区域地下水中铀以U(Ⅵ)为主,其中UO2SO4、UO22+和UO2(SO4)22-为优势物种,分别占63.60%、32.35%和3.89%;2）Na2S2O4还原固定可溶性铀时,会降低地下水Eh值和Fe(Ⅲ)浓度,增强地下水还原性,促进沥青铀矿和黄铁矿沉淀,但会造成地下水酸化和高SO32-浓度;3）NaHCO3+Na2S2O4在还原固定可溶性铀时,减轻了地下水酸化,增强了对U(Ⅵ)和SO32-的去除,对Na2S2O4还原固定可溶性铀的影响较小,在Na2S2O4和NaHCO3浓度比为1︰1至1︰1.5时修复效果最佳。     

高强耐热铝合金2A70-4T6棒材的研制

研究了高强耐热铝合金2A70—4T6棒材的化学成分、挤压工艺、热处理工艺对其组织性能的影响。通过大量的对比试验．确定了最佳的化学成分范围、合理的挤压工艺和热处理工艺制度。研制出多批量大规格2A70—4T6铝合金棒材，满足了用户的需要。