关于我国金融排斥状况的评价

金融排斥对于改善金融服务、促进地区均衡发展以及建设和谐社会具有重要影响,而如何衡量金融排斥程度是其中的关键一环。从地理排斥、评估排斥、条件排斥、价格排斥、营销排斥、自我排斥六个维度构建衡量金融排斥程度的指标体系,定量评价我国31个省(市、区)的金融排斥程度,可以发现我国存在地区间金融排斥明显、金融排斥与地理分布及经济发展程度联系密切的特点。当然,这种评价还存在着一些不足之处。为了有效缓解我国金融排斥问题,必须发展微观金融、加强政府规管、稳步推进利率市场化进程、依法规范民间信贷以及完善征信体系。湖南省社会科学基金项目“金融排斥视角下中部地区金融结构优化研究”(07YBB275);负责人王修

准噶尔无叶豆的地理分布、群落学特征及生物生态学特性

准噶尔无叶豆(Eremosparton songoricum(Litv.)Vass.)是国家级保护植物。对该植物地理分布、群落特征及生物生态学特性进行的研究表明:①准噶尔无叶豆分布区和生态幅狭窄,在我国仅斑块状分布于新疆古尔班通古特沙漠腹地局部地段及沙漠东南缘的部分流动沙地上;②群落中包含植物14科33属37种,可划分为7个地理区系成分,其中,温带分布型属占75.76%。依据群落组成及外貌,划分为5个群丛,主要特点为:不表现为显著的景观植被,且小面积出现;结构简单,层次单调,植物组成均系适沙和耐沙的种类;整个群落以先锋性为特征。此外,群落不稳定,有逐步被其他类型的、相对稳定的群落所替代的趋势,具有时空分布的"暂时性";③具有"花多果少"的果实产量格局,2005年结实率为(15.36±2.16)%。呈"水泡状"或"干瘪状"的种子比率达(16.2±2.31)%,虫蛀率达(16.92±2.69)%;④种子向幼苗转化率低。依靠超强的水平根茎克隆能力来扩展种群空间。经综合分析,认为准噶尔无叶豆对生境高度专一,人为干扰破坏所带来的生境丧失将使该种受胁状态加剧。对该物种进行保护首先应加强现有生境的就地保护,减少人为破坏;其次,积极开展迁地保护生物学研究,建立苗圃,营造人工种群

MOFs材料对异味气体吸附及其衍生物气敏特性研究

金属有机骨架化合物 (Metal-Organic Frameworks, MOFs) 是由金属离子或金属原子簇与有机配体连接构成的一类新型的多孔结晶性固体材料，这类材料一般具有较高的比表面积、可控的结构组成、可功能化、多活性位点等特点。被发现至今，MOFs材料在气体吸附和储存、分子分离、催化、药物载体释放和多孔模板等领域展示出重要的研究价值和应用前景。本文旨在通过制备不同MOFs材料，考察其在对室内污染气体甲硫醇 (CH3SH)和甲醛 (HCHO) 的吸附性能和吸附机理。重点研究了不同中心金属离子和形貌结构对吸附性能的影响。另外研究了以FeⅢ-IRMOF-3为模板在空气中煅烧分解生成的氧化物ZnO/ZnFe2O4异质结构的气敏性能。主要研究内容和结果如下：（1）HKUST-1结构调控及其吸附CH3SH性能以均苯三甲酸为配体，硝酸铜、醋酸铜为金属盐前驱体，通过不同方法制备不同形貌和大小的铜基MOF材料HKUST-1。考察了不同前驱体和溶剂对生成HKUST-1的影响，比较了不同形貌，大小的HKUST-1材料对CH3SH的吸附性能。结果表明：以水热法合成的大八面体HKUST-1吸附性能最好，沉淀法合成的小球形HKUST-1吸附性能次之，加入表面活性剂聚乙烯吡咯烷酮 (PVP) 合成的小八面体HKUST-1吸附性能最差。以吸附性能最好的大八面体HKUST-1为吸附剂，通过吸附前后XRD、XPS、红外等结果的变化，研究了CH3SH在HKUST-1上的吸附机制。结果表明，CH3SH在HKUST-1上发生化学吸附，CH3SH中的巯基可以和HKUST-1的金属中心离子Cu发生配位反应，导致MOFs材料结构的破坏，最终生成CuS。随着吸附过程进行，吸附剂的颜色由深蓝色变为墨绿色。以不同金属离子构成的MOF系列材料M-BTC，其中只有以Cu2+为中心离子的HKUST-1对CH3SH有明显吸附效果。而以Mn2+，Fe3+，Co2+，Ni2+，Zn2+为中心离子的M-BTC则对CH3SH没有明显的吸附效果。（2）多孔Al2O3载体生长HKUST-1膜及其吸附CH3SH性能针对HKUST-1吸附剂抗湿性较差，在造粒过程中物料损失等缺点，以商业多孔Al2O3颗粒为载体，通过二次成核法在Al2O3载体上生成均匀的HKUST-1膜 (记为HKUST-1@Al2O3)。结果表明，二次成核法可以有效的解决HKUST-1只在液相成核生长，不能生长在载体上的问题。在Al2O3载体生成的HKUST-1膜均匀没有裂缝，厚度为20&mu;m。合成的HKUST-1@ Al2O3比表面为284 m2/g，具有微孔与介孔结构，通过热重分析HKUST-1的负载量为7.5 wt%。由于HKUST-1在Al2O3载体上良好的成膜使得HKUST-1的吸附性能得到提高，吸附容量可以达到108.6 mg CH3SH/g HKUST-1。而载体Al2O3具有良好的吸水性可以减少水在HKUST-1膜上的吸附，使HKUST-1@ Al2O3具有较好的抗湿性。（3）氨基修饰MOF材料的制备及吸附甲醛性能以2氨基对苯二甲酸和对苯二甲酸为配体，分别以氯化锆、硝酸锌和氯化铁为金属前驱体，通过水热法合成了氨基修饰的MOFs材料UIO-66-NH2、IRMOF-3、MIL-53(Fe)-NH2和参照MOFs材料UIO-66、MOF-5、MIL-101(Fe)。通过吸附实验研究了合成材料对HCHO的吸附性能。结果表明，氨基修饰的MOFs材料对低浓度甲醛都具有吸附效果，而参照物MOFs材料对HCHO没有吸附效果。其中氨基修饰MOFs材料中UIO-66-NH2的吸附效果最好，吸附容量达到19.9 mg/g 吸附剂，而IRMOF-3与MIL-53(Fe)-NH2的吸附效果较差。以UIO-66-NH2为吸附剂，通过红外光谱对吸附前后的变化研究HCHO的吸附过程，证明了在氨基修饰的MOFs材料上的氨基与HCHO中的醛基发生曼尼希反应从而实现HCHO的去除。（4）FeⅢ-IRMOF-3煅烧分解制备多孔ZnO/ZnFe2O4及气敏性能以2-氨基对苯二甲酸为配体，硝酸锌为金属前驱体盐，加入乙酰丙酮铁来修饰，通过回流加热的方法合成FeⅢ-IRMOF-3。以合成的FeⅢ-IRMOF-3为模板，经过煅烧制备多孔的和较高比表面的ZnO/ZnFe2O4异质结构。结果表明，煅烧生成的ZnO/ZnFe2O4具有规则的立方体形貌，大小约为2 &mu;m，立方体颗粒内部为中空，外壁为多孔结构。通过不同温度下对ZnO/ZnFe2O4气敏性能测试得到最佳工作温度为250 oC，气敏响应值比单纯的ZnO材料要高近10倍，气敏连续响应曲线重复性良好并且ZnO/ZnFe2O4稳定性高，可以连续检测半个月而响应值基本不下降。ZnO/ZnFe2O4气敏材料在苯、甲苯、氨气、甲醛、乙醇和丙酮气体中对丙酮具有较高的响应值。ZnO/ZnFe2O4优异的气敏性能要归因于多孔的结构、高比表面积、丰富的吸附氧物种与ZnO与ZnFe2O4的异质结构。;Metal organic frameworks (MOFs) which is constructed from metal ions and organic ligands is emerging as a class of very important materials offering high levels of porosity with considerable control over pore size and composition. Such properties play a crucial role in functional applications in gas storage or separation, sensing, catalysis, drug delivery and porous template.In this thesis, various MOFs with different compositions were prepared to explore the effects of structure and conponent on the adsorptive performance of some typical indoor gaseous contaminants (CH3SH, HCHO). The physical structures and chemical properties have great influence on the adsorptive behaviour of various MOFs. Moreover, The ZnO/ZnFe2O4 hollow cube composites with heterogeneous structure were synthesized by a facile strategy through simple and direct pyrolysis of FeIII-modified Zn-based metal-organic frameworks. The research results are summarized as:(1) Copper-based metal organic frameworks (HKUST-1) with controllable size and shape was synthesized using hydrothermal and precipitation method. The as-prepared HKUST-1 materials were used to remove gaseous methyl mercaptan (CH3SH). The morphology and texture of HKUST-1 materials have great influence on the performance of the adsorption process. The HKUST-1 material synthesized by hydrothermal method exhibited the highest sulfur compound adsorptive capacity among the synthesized HKUST-1 materials. The XRD、XPS and FTIR changes of HKUST-1 during CH3SH capturing process, indicated that strong interaction between the unsaturated copper sites and &ndash;SH group which finally formed CuS and gave rise to obvious damage to the MOF structure. The color of HKUST-1 changed from blue to dark green during the adsorption process. Only HKUST-1 has effective adsorption ability toward low concentration CH3SH among the M-BTC series MOFs including Cu2+，Mn2+，Fe3+，Co2+，Ni2+，Zn2+ as central ion.(2) In order to solve the existing problems of HKUST-1 material including poor resistance to humidity and loss of material during prilling process, HKUST-1 membrane was growth on Al2O3 substrate using thermal seeding-mediated secondary growth strategy (denoted as HKUST-1@Al2O3). The synthesis method successfully avoided the nucleation of HKUST-1 crystals in the solution phase. The HKUST-1 membrane is continuous, without any cracks, pinholes and its thickness is about 20 &mu;m. The BET surface area of HKUST-1@Al2O3 is about 284 m2/g with microporous and mesoporous pores.The loading amount of HKUST-1 is 7.5 wt% of HKUST-1@Al2O3. The excellent dispersion of HKUST-1 membrane on the Al2O3 substrate enhance the use efficiency of HKUST-1 and the capacity is 108.6 mg CH3SH / g HKUST-1. The hydroscopicity of porous alumina can reduce the adsorption of water on HKUST-1 membrane leading to good water resistibility.(3) UIO-66-NH2、IRMOF-3、MIL-53(Fe)-NH2 and their counterparts UIO-66、MOF-5、MIL-101(Fe) were prepared by hydrothermal method by using ZrCl4、Zn(NO3)2、FeCl3 and NH2-BDC、BDC as raw materials. The amino modified MOFs including UIO-66-NH2、IRMOF-3 and MIL-53(Fe)-NH2 can adsorb low concentration HCHO while the MOFs without amino including UIO-66、MOF-5 and MIL-101(Fe) can hardly adsorb HCHO. Among the synthesized MOFs UIO-66-NH2 has the highest HCHO capacity which is 19.9 mg/g UIO-66-NH2 while IRMOF-3 and MIL-53(Fe)-NH2 have low HCHO capacity. Mannich reaction took place between HCHO and UIO-66-NH2 which was confirmed by FTIR investigation.(4) The ZnO/ZnFe2O4 hollow cubes composites with heterogeneous structure were synthesized by a facile strategy through simple and direct pyrolysis of FeIII-modified Zn-based metal-organic frameworks. The as-synthesized ZnO/ZnFe2O4 hollow cubes have well-defined cube morphology with ~2 &mu;m and multiple porous shell constructed by interpenetrated ZnO and ZnFe2O4 heterogeneous nanoparticles. A omparative sensing performance investigation between ZnO/ZnFe2O4 and singular ZnO demonstrate that, in contrast with ZnO, the ZnO/ZnFe2O4 showed significantly enhanced chemical sensing response low-concentration acetone. The optimum operating temperature is 250 oC of the synthesized ZnO/ZnFe2O4. Furthermore, the ZnO/ZnFe2O4 hollow cubes exhibit good reproducibility and selectivity towards gaseous acetone. The enhanced sensing performance of the MOF-derived ZnO/ZnFe2O4 hollow cubes is ascribed to the unique hierarchical structure with high specific surface area, abundant exposed active sites with surface-adsorbed oxygen species and heterojunctions formed at the interfaces between ZnO and ZnFe2O4.&nbsp;</p

基于跨层设计的AODV路由优化机制

以AODV（无线自组网按需平面距离矢量路由）协议为原型,针对WMN（无线Mesh网）中传统AODV协议路由判据单一从而导致路由性能较差的缺陷,采用跨层设计方法为WMN设计了一种新的IAODV（优化的AODV）协议。在路由计算过程中通过跨层操作机制提取节点当前负载和链路投递率这两个影响链路质量的因素,结合路由跳数设计出合理的路由判决函数。理论分析和NS2仿真结果证明,这种路由优化机制提高了吞吐量,降低了网络时延,并且能够达到负载均衡的路由效果

construction and selection scheme of seeded-key database of collisionfree cpk

组合公钥CPK(Combined Public Key)是我国拥有完全知识产权的认证技术,与PKI和IBC相比有其独特的优势。但由于密钥由种子密钥经过组合运算生成,因此可能发生碰撞,有效解决碰撞问题已成为CPK体制发展和完善的关键。介绍了CPK的发展、研究现状和存在问题;根据其构建特点,提出了两种新的种子公/私钥组合选取方法,使得在相同规模的安全需求下,所需种子公/私钥量大大减少;针对产生碰撞的两种可能因素提出了解决方案:用分组密码对用户标识进行映射、按照特定规则产生种子公/私钥库以及对椭圆曲线参数进行约束,从根本上消除了碰撞。优化后的CPK体制,无碰撞,种子库规模小,构建效率高,占用空间少,安全性高,可靠性强,便于管理。Combined Public Key(CPK)is an authentication technique which is an independent intellectual property of China.Compared with PKI and IBC,CPK has its particular advantages.However,since the secret key is generated by combining several seeded secret keys,collisions might happen.How to avoid collisions efficiently becomes the linchpin of the development of CPK.After the development and problems of CPK are introduced,two novel methods are put forward to select and combine the seeded public/private keys,which reduces the seeds space evidently with the same level of security.A solution is proposed aiming at two factors which lead to collisions:using block ciphers to map the user identity,produce seeds in accordance with specific rules and restrict the parameters of elliptic curve.The improved CPK system can provide a collision-free key space with a smaller space of seeds,high efficiency,high security,and easy management