394 research outputs found

    关联企业认定的国际比较与借鉴

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    关联企业认定,是转让定价税制的起点,虽然在实践中各个国家的具体作法可能有所不同,但大都把认定企业间是否存在关联关系作为对关联企业业务往来进行调整的前提。《联合国范本》和《经合组织范本》都把管理、控制和资本作为认定关联企业的依据,在这两个范本的基础上,..

    Analysis of Processes of Physical Distribution in E-commerce Environment

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    电子商务给物流配送带来了新变化,同时也对物流配送提出了新要求。物流配送作为电子商务的一个关键环节,承担着将虚拟活动变为现实的职能。物流配送流程可分为采购、仓储、配送作业流程和退货及后续处理作业流程等四个环节,需要在流程管理方面优化方案,提高效率。物流配送业要以目前商务模式的变革为契机,提升物流配送的专业化和现代化水平,在促进电子商务发展的同时,实现物流配送业的快速发展。Physical distribution,a key part of e-business,consists of four links,namely,purchasement,warehousing & storage,dis-tribution,return and subsequent operations,among which,distribution is the starting point for the innovation of the present business mode

    Selective hydrogenolysis of sorbitol on Ni/La202CO3 catalysts

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    采用共沉淀法制各了具有协同稳定作用的Ni/La2O2CO3催化剂,用于山梨醇选择性氢解为小分子醇的研究。采用X射线衍射、氢气程序升温还原、C02程序升温脱附和扫描电镜对催化剂进行了表征。考察了不同配比Ni、La的加氢位点和碱性调控对山梨醇氢解产物的影响。结果表明,Ni、La摩尔比为2:3时,山梨醇转化率达到98.6%,C2~c3多元醇的产率达到43.8%,催化剂经2次反应后对山梨醇的转化率仍高达90%。探究了催化剂从酸性到碱性调变过程中,山梨醇氢解的产物分布,并提出了反应路径

    Advances for the Ruthenium Complexes-Based Homogeneous Catalytic Hydrogenation of Oxalates to Ethylene Glycol

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    草酸酯加氢是重要的有机化学反应,在工业制乙二醇生产中有着重要的应用.对钌金属配合物均相催化反应的研究进行了综述.以催化反应体系为焦点,探讨了多种; 因素如温度、氢气压力、催化剂浓度、反应时间、添加剂等对底物转化率以及产物选择性的影响,并讨论了催化反应机理,其中金属-配体协同促进的H_2分子异; 裂,进而完成对底物分子中酯基依次加氢的反应机理是探讨的重点,这为新型催化剂的设计和应用提供参考.Hydrogenation of oxalates is one of the important organic reactions, which has an ultimate use for the industrial production of ethylene glycol. The studies on the ruthenium complexes-based homogeneous catalytic reaction systems are herein summarized. With the focus on the catalytic reaction systems, the important factors with significant influences on the oxalate transformation efficiency as well as the product selectivity are discussed, including temperature, H-2 pressure, catalyst concentration, reaction duration, additives, and so on. The catalytic reaction mechanisms are also discussed in detail, where the mechanism for the H-2-heterolysis promoted under the metal-ligand cooperation for the oxalate hydrogenation to ethylene glycol is enhanced. This study would be useful for designing the new catalyst applicable in industry.National Natural Science Foundation of China [21473142, 91545115,; 21473145]; Innovative Research Team of China [IRT_14R31, J1310024

    HPLC测定乳痛消Ⅱ号中橙皮苷的含量

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    甘肃省科委资助项目 (No :GS 992 A4 3 0 70

    壳聚糖絮凝法处理明黄膏提取液的研究

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    甘肃省自然科学基金暨中青年科技基金项目 (项目编号YS 0 11 A2 3 0 15

    Phytoplankton biomarkers in surface seawater from the northern South China Sea in summer 2009 and their potential as indicators of biomass/community structure

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    生物标志物已被广泛应用于重建浮游植物生产力和群落结构变化。该方法假设之一是生标的含量可以反映表层海水的浮游植物生物量,但这个假设还缺乏现场观测的充分验证。对2009年冬季南海北部表层海水颗粒物中主要生标做了分析,利用其含量及比值研究浮游植物的生物量及群落结构的分布。生标含量表明硅藻、甲藻、颗石藻的高值区位于珠江口南部及广东沿岸,在陆坡区也有高值。生标比值显示硅藻在3个类群中的相对比例最高。其中,甲藻/硅藻比值高值区位于陆坡区,这与大洋水(黑潮)的入侵,带来大量暖水性甲藻有很大关系;颗石藻/硅藻比值总体趋势与生物量的分布相反,在近岸少数站位有高值,向外海逐渐增加,主要是因为颗石藻更适于寡营养盐的环境。生标结果所指示的生物量及群落结构的空间分布与前人的调查结果类似,为利用生标重建此区域的浮游植物生产力和群落结构变化提供了依据。Biomarkers have been widely used to reconstruct phytoplankton productivity based on the assumption that biomarker contents could reflect phytoplankton productivity in the surface seawater.However,this hypothesis has not been validated with modern survey.In this study,the contents and ratios of three phytoplankton biomarkers in the surface seawater of the northern South China Sea in winter 2009 were analyzed,to indicate spatial distributions of phytoplankton biomass and community structure.The results show high values for diatoms,dinoflagellates and coccolithophorids near the Pearl River Estuary and Guangdong coastal areas.The community structure indicates diatoms are the dominant phytoplankton species in winter.High values of dinoflagellate/diatom ratio occur near the slope area owing to intrusion of the Kuroshio,which favors the growth of dinoflagellates.The coccolithophorid/diatom ratio displays an increasing trend from the Pearl River Estuary to offshore region due to the advantage of coccolithophorids in oligotrophic environment,which is opposite to the productivity pattern of all biomarkers.These results are consistent with previous studies using phytoplankton cell and pigments,which provides support for the use of biomarker to reconstruct phytoplankton productivity and community structure in the SCS.国家重点基础研究发展计划项目(2007CB815934、2009CB421201);国家自然科学基金项目(40776029

    Synthesis and characterization of cellulose acetate with high degree of substitution from miscanthus

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    以芒草为原料,用Na OH/H_2O_2溶液体系预处理制备芒草纤维,在冰醋酸环境下,以浓硫酸为催化剂与醋酸酐酯化制备芒草醋酸纤维素。优化了预处理条件:温度、时间、次数和酯化条件:催化剂量、温度、时间、醋酸酐量,最佳条件下制备出的芒草纤维的纤维素、半纤维素和木质素的质量分数分别为75.3%、17.3%、5.1%,制备出芒草醋酸纤维素的取代度DS=2.8,特性黏度[η]=1.24 d L/g,达到美国联邦贸易委员会指南认定的三醋酸纤维素标准。利用扫描电镜(SEM)和热分析(TG、DSC)对制得样品进行表征。结果表明,可以利用Na OH/H_2O_2水溶液体系预处理芒草原料制备芒草纤维,并进一步酯化制备出高取代度的醋酸纤维素。A procedure for synthesizing cellulose acetate with high degree of substitution from miscanthus biomass is developed. The miscanthus fiber is prepared by pretreatment of miscanthus biomass with Na OH / H_2O_2,which is then reacted with acetic anhydride in an acetic acid solvent to synthesize cellulose acetate by using concentrated sulfuric acid as catalyst. The effects of the pretreatment factors( such as pretreatment temperature,time and number of times) and the esterification factors( such as catalyst volume,reaction temperature,reaction time and acetic anhydride volume) are studied. Under the optimal conditions,the contents of cellulose,hemicellulose and lignin for prepared miscanthus fiber are75. 3%,17. 3% and 5. 1%,respectively. The degree of substitution( DS) and the intrinsic viscosity( [η ]) of the obtained miscanthus cellulose acetate are 2. 8 and 1. 24 d L / g,respectively. The miscanthus biomass,fiber and cellulose acetate are characterized by SEM,TG and DSC. This study shows that cellulose acetate with high degree of substitution can be prepared from miscanthus biomass pretreated with Na OH / H_2O_2.国家自然科学基金(21303142;31170067);; 福建省中青年教师教育科研项目(JA14010);; 厦门市海洋经济发展专项资金项目(14GZP59HJ29);; 福建省海洋高新产业发展专项项目(闽海洋高新[2014]25号);; 厦门大学校长基金(20720150090

    新型膦胺配体羰基钌化合物的合成及催化性能研究

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    以十二羰基三钌和o-PPh2C6H4NR2(R=H,Me)配体为原料,成功地制备出三种新型羰基钌化合物(μ-o-PPh2C6H4NH)Ru3(μ-H)(CO)9(2)、(o-PPh2C6H4NH)2Ru(CO)2(3)和(μ-o-PPh2C6H4NMe2)2Ru(CO)3(4).对这三个化合物进行了核磁共振和红外谱学、元素分析和X-射线单晶衍射分析表征,并对这三个化合物进行了催化性能研究.化合物2和4可催化苯甲醛加氢反应生成苯甲醇,但是3没有催化活性.该研究从实验角度阐述了膦胺配体钌催化剂的结构与性能关联,并进一步探讨了加氢催化反应失活的可能原因.这些结果对后续催化剂的设计提供一定的理论指导
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