1,672 research outputs found
Studies on the Controlled Synthesis of Pd- and Pt-based Nanocrystals and Their Electrocatalytic Properties
Pd和Pt贵金属纳米材料是重要的催化材料,在燃料电池等中发挥着重要的作用,其催化性能好坏直接决定了燃料电池的性能等。控制合成具有高活性的Pd和Pt贵金属纳米材料,对于燃料电池等发展有着重要意义。贵金属催化剂纳米晶体的比表面积、形貌、表面结构和组成等方面对其催化性能影响很大。目前已经报道的研究中,大部分工作都是通过改善其中某一个方面,来达到提高催化剂催化活性的目的。可以预期,如果同时从两个方面、甚至三个方面对贵金属纳米材料进行调控,其催化性能会得到进一步的优化。为此,本论文面向燃料电池电催化剂,以Pd、Pt贵金属纳米晶体为主要研究对象,从纳米晶体比表面积、形貌、组成等方面对其进行调控,以改善它们...Pd- and Pt-based nanomaterials are broadly used as the key catalysts in fuel cells and etc. The performance of a fuel cell is directly determined by the activity of the catalysts. As a result, the synthesis of Pd- and Pt-based nanomaterials with high activities is significant for the development of fuel cells. Intensive studies have shown that the activity of these nanocatalysts closely depends on...学位:理学博士院系专业:化学化工学院_纳米材料化学学号:2052011015373
Research on Grinding and Using Parameters Optimization of Cemented Carbide Cutting Tool
在航空航天制造领域,航空铝合金零部件是数量最多、制造任务最重的加工对象,其高效加工使用的高端硬质合金刀具多数需要进口。由于我国航空铝合金加工专用硬质合金刀具的研究起步较晚、发展滞后,材料研发、刀具设计以及制造装备技术整体水平不高,尤其缺乏针对不同航空铝合金零件加工用硬质合金刀具从切削机理分析、几何结构设计、磨制技术、加工参数优化整个过程的全链条式研究。本文针对航空铝合金7075加工用硬质合金刀具的磨制机理、刀具铣削性能、刀具几何结构与加工参数优化等方面进行贯通性应用基础研究尝试,为航空铝合金7075加工用硬质合金刀具的合理开发与使用提供理论依据。 在硬质合金材料的磨削机理方面,采用单颗磨粒磨...In the field of aerospace manufacturing, aviation aluminum alloy is the processed object that in great demand, and most of the high performance cemented carbide tools rely on imports. Due to the research on cemented carbide tool for machining aviation aluminum alloy started late in China, the overall level of material research, tool design and equipment manufacturing technology is not that high. I...学位:工学博士院系专业:物理与机电工程学院_机械制造及其自动化学号:1992012015388
不同水生脊椎动物的血清与黏液蛋白图谱分析
因脊椎动物的血清与黏液中含有大量蛋白质及其他生物活性物质,而具有多种生理、生化与抗病防御功能。为了解水生脊椎动物血清与黏液中所含主要蛋白成分及其异同,我们分别从中华鲟(Chinese stur-geon Aclpenser sinensis grdy)、鲫鱼(Crucian carp Carassius auratus)、草鱼(Grass carp Ctenopharyngodonidellus)、赤点石斑鱼(Red-spotted grouper Epinephelus akaara)、青石斑鱼(Banded grouper Epinephelusawoara)、狗鱼(Pikes Esox reicherti)、江豚(Finless porpoise Neophocaena phocaenoides)、黄颡鱼(Yellow catfishPelteobagrus fulvidraco)、鳜鱼(Mandarin fish Siniperca chuatsi)这9种水生脊椎动物中,采集血清和皮肤黏液样本。利用考马斯亮蓝G-250法,测定了不同水生脊椎动物的血清和黏液样品中总蛋白的含量;经SDS-PAGE蛋白电泳,分别获得不同水生脊椎动物血清及黏液蛋白图谱;比较和分析了同种动物血清和黏液、不同动物之间血清与血清或黏液与黏液之间蛋白图谱的差异。结果表明:这些动物的血清蛋白组分有显著相似性,在分子量45—120 kD之间,蛋白条带大量集中分布;除青石斑鱼外,其他8种水生脊椎动物都有分子量约为28 kD和14 kD相同或相近的两条蛋白带。草鱼、鲫鱼、鳜鱼、狗鱼、黄颡鱼和江豚的黏液蛋白,除了都含有分子量大小约为45 kD的蛋白条带外,其他无显著相似性。对同种水生脊椎动物的血清与黏液蛋白比较,虽然黄颡鱼的血清与黏液中分子量相近的蛋白带最多,也仅约为38%,可见其蛋白带的种类和含量都存在显著差异
不同经济发展水平区域物流与经济增长的协整关系研究
根据协整检验和因果关系检验等计量方法,利用中国各省1991~2007年物流发展水平和国内生产总值的年度数据,将31个省(市、自治区)按经济密集度不同分成三大类地区,并对其物流和经济增长的关系分析进行了实证分析。实证结果表明:三个区域的物流与经济增长均存在协整关系,发达的一类地区两个变量存在双向Granger因果关系,而后两类地区两个变量仅存在单向的Granger原因。国家自然科学重点资助项目“中国城市化进程的资源环境基础研究”(40535026
Large-eddy simulation of flows past a flapping airfoil using immersed boundary method
The numerical simulation of flows past flapping foils at moderate Reynolds numbers presents two challenges to computational fluid dynamics: turbulent flows and moving boundaries. The direct forcing immersed boundary (IB) method has been developed to simulate laminar flows. However, its performance in simulating turbulent flows and transitional flows with moving boundaries has not been fully evaluated. In the present work, we use the IB method to simulate fully developed turbulent channel flows and transitional flows past a stationary/plunging SD7003 airfoil. To suppress the non-physical force oscillations in the plunging case, we use the smoothed discrete delta function for interpolation in the IB method. The results of the present work demonstrate that the IB method can be used to simulate turbulent flows and transitional flows with moving boundaries
The Investment Value Analysis of Goertek Inc.
价值投资是一种运用定性和定量方法计算股票的内在价值,通过对比内在价值与目前总市值孰高孰低来判断股票价格低估或高估的理念,常用于投资机构对上市公司的估值分析。中国股市以高投机性、“政策市”著称,价值投资理念备受质疑。2017年初至今,以贵州茅台、格力电器、美的电器、歌尔股份等白马股的股价走势极好,不少机构认为这是价值投资的胜利,被低估的白马股的价值重新被发现。但展望后市,多数投资机构对此依然持存疑的态度。笔者在证券投资中信奉价值投资理念,对歌尔股份这家电声行业龙头企业比较熟悉,便对该公司进行了投资价值分析,以探究该公司的内在价值到底是多少亿元,当前股价是否低估。 本文结构较为清晰:第一章为绪论...Value investment is to use qualitative and quantitative method to calculate the stock's intrinsic value, by comparison the intrinsic value with the current market capitalization, to tell if the price is undervalued and determine the concept of stock. The concept of value investment is commonly used in investment analysis of the valuation of listed companies. China's stock market is known for its h...学位:工商管理硕士院系专业:管理学院_工商管理硕士(工商管理硕士)学号:1792013115102
Investigation of Distribution of Biotoxin and Study on Poisoning of Nassarius spp. in the Coastal Area of Fujian and Zhejiang Province
织纹螺属软体动物门(Mollusca)、腹足纲(Gastroroda)、前鳃亚纲(Prosobranchia)、狭舌目(Stenoglossa)、织纹螺科(Nassariidae)。在沿海因食用水产品导致的中毒事件中,织纹螺(Nassariusspp.)导致的中毒事件非常突出。据不完全统计,仅浙江省舟山市因食用织纹螺导致的中毒人数就达300余人,死亡16人。随着中国沿海水产养殖业的迅速发展和有害赤潮的频繁爆发,人们越来越关注我国贝类的生物毒素污染问题,因为水产品安全问题直接关系到消费者的身体健康和生命安全。但到目前为止,对于造成织纹螺中毒的毒素类型、来源并没有一个非常确切的说法。以往的大部分报...Nassarius spp. is a group animal of Family Nassariidae belonging to Order Stenoglossa, Subclass Prosobrachia, Class Gastropoda, Phylum Mollusca. Poisoning incidents caused by consumption of Aquatic Products have been reported in the littoral area, especially one of the poisoning incidents caused by Nassarius spp to be extremely prominent. According to statistics incompletely, 300 people were poiso...学位:理学硕士院系专业:海洋与环境学院环境科学与工程系_环境科学学号:2122005130221
The Study of Legal Issues about the CtoC Mode of Electronic Business——With Taobao as the Example
作为一种新兴的电子商务模式,CtoC在我国刚刚起步,由于实践的不足,相关立法存在着滞后甚至空白现象,导致交易参与者的利益无法得到有力的法律保障。本文以淘宝网为例,按照淘宝网的交易程序对CtoC模式下交易主体的资格和地位、交易中存在的主要风险、ISP的法律责任和在线纠纷解决机制(ODR)等问题进行了分析,并初步提出了解决问题的思路。 文章的第一章从CtoC模式下交易主体资格入手,以淘宝网为例,在我国现行立法的基础上分析了ISP对交易主体资格的限定的不合理性,并结合学界的主要观点对非完全民事行为能力人的交易主体资格做出了重新设计。 第二章在第一部分的基础上,探讨了CtoC模式下买卖双方的法律地...As an emerging electronic business mode, CtoC is in its beginning stage in China. Due to its lack of practice and absence of relevant legislation, the interests of transaction participants are under weak protection by law. The paper, with Taobao as the example, dissects the transaction participants’ qualification and status under CtoC mode, the major risks involved in the transaction, the legal li...学位:法律硕士院系专业:法学院法律系_法律硕士(JM)学号:20040817
- …
