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Search Results: 1 - 10 of 118548 matches for " 范海荣 "
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Solving a superstructure from two-wavelength x-ray powder diffraction data - a simulation
陈建,古元新,
中国物理 B , 2003,
Abstract: Two different kinds of phase ambiguities are intrinsic in two-wavelength x-ray powder diffraction from acentric crystal structures having pseudo-translation symmetry. In a test calculation we have solved the problem for the first time by two different phasing procedures developed originally in single-crystal structure analysis. They are the direct method of breaking enantiomorphous phase ambiguity in protein crystallography and that of breaking translational phase ambiguity for superstructures. An artificial structure was used in the test, which is based on atomic coordinates of the known structure, SHAS (C_5H_6O_5N_3K), with the atom K replaced by Rb. The arrangement of Rb atoms possesses a subperiodicity of t=(a+b+c)/2. Two-wavelength synchrotron x-ray powder diffraction data were simulated with λ_1=0.0816nm and λ_2=0.1319nm. Overlapped reflections were uniformly decomposed at the beginning and redecomposed afterward when the partial-structure information became available. The enantiomorphous phase ambiguity was resolved only for reflections with h+k+l even. Phases of reflections with h+k+l odd were derived by the direct method of solving superstructures. A fragment was then obtained, which led to the complete structure in five cycles of Fourier iteration.
秦皇岛市草坪土壤肥力数值化综合评价与对策研究
,吴素霞,常连生
草业科学 , 2013,
Abstract: ?以秦皇岛市草坪土壤为例,对土壤的理化性质进行了室内分析,并根据各肥力因子的植物效应建立了相应的隶属度函数,计算出各评价指标的隶属度值;利用主成分分析法,确定各评价指标的权重,通过模糊数学法对土壤肥力进行了综合评价。结果表明,秦皇岛市草坪土壤综合肥力水平较低,主要限制因子为容重、有机质、碱解氮、速效钾。评价结果与草坪草生长状况相一致,表明该评价方法能准确、客观地评价草坪土壤的肥力水平,具有一定的应用价值。针对评价结果得出的土壤肥力限制因子,提出了提高土壤肥力的管理措施,对秦皇岛市草坪土壤的维护和治理提供了重要的指导和参考依据。
人参皂苷的体外模拟代谢及转化研究进展
,,李晓波
中国中药杂志 , 2011,
Abstract: 人参系传统名贵中药,近年来对其代谢的研究成为热点。通过查阅国内外相关文献,作者主要从人工胃液、肠道菌代谢、酶和微生物体外转化4个方面对人参皂苷体外模拟代谢及转化进行阐述,分析人参皂苷体外代谢的主要途径,为人参皂苷代谢的系统性研究提供参考。
多面体低聚八氨基苯基硅倍半氧烷合成方法改进及其表征
,,李定华
化学学报 , 2012, DOI: 10.6023/A1110211
Abstract: 以八硝基苯基硅倍半氧烷(ONPS)为原料,5%Pd/C和FeCl3为催化剂,水合肼为还原剂,在四氢呋喃溶液中反应1h合成了八氨基苯基硅倍半氧烷(OAPS).相比文献中已有的其它合成方法,该方法合成过程简单且稳定,催化效率高、产率高、周期短.通过FTIR,1HNMR,GPC对产物进行了表征,证明了硝基已完全转化.通过催化剂的控制,分离出ONPS向OAPS转化过程中的一种含有羟胺和二羟胺基团的中间体.分析了OAPS合成机理,提出了ONPS和水合肼的反应历程.认为ONPS中的硝基先经过2电子转移转化为二羟胺化合物,然后经过脱水加氢生成羟胺化合物,最后再经过脱水加氢生成OAPS;在有ONPS存在的情况下,水合肼主要转化为氮气和氢气,待ONPS完全转化为OAPS后,水合肼转化为氮气和氨气.
多面体低聚八硝基苯基硅倍半氧烷纯度分析
,,李向梅
化学学报 , 2012, DOI: 10.6023/A12030047
Abstract: 使用高效液相色谱-电喷雾四级杆飞行时间质谱(HPLC-ESI-Q-TOFMS)联用技术对八硝基苯基硅倍半氧烷(ONPS)纯度进行分析,从而判定ONPS产物峰及杂质峰的位置,根据ONPS峰和杂质峰的面积比计算ONPS的纯度.通过改变HPLC的洗脱梯度和测试时间,将ONPS产物中的杂质峰完全分开,测得硝基苯基硅倍半氧烷(NPS)质量分数为97.55%,其中ONPS的纯度约为92.42%,产物中含有九硝基八苯基硅倍半氧烷(9-NPS)约5.13%,其它杂质含量约为2.45%.通过对ONPS高效液相色谱图峰形和同分异构体极性情况分析,进一步证明ONPS分子中硝基取代发生于对位和间位.使用超高效液相色谱(UPLC)对ONPS进行分析,以更高的分离效率验证了HPLC的结果.该方法可作为ONPS纯度的分析方法.
基于单向约束TIN的层状地质体三维建模
承达瑜,, 红东
金属矿山 , 2009,
Abstract: 在分析了三维地质建模研究现状的基础上,对前人提出的含断层信息的三维地质体建模进行了改进和简化,并根据矿山地质数据的特点和实用性需要,研究了基于单向约束TIN的三维层状矿床地质建模原理和数据模型,以及模型的可视化方法。最后,设计并开发出基于Windows平台的三维层状矿床地质建模原型系统软件,并进行了模型的验证。
累积番茄红素的大肠杆菌工程菌及其培养条件的研究
刘敏,,杜桂彩,
中国生物工程杂志 , 2006,
Abstract: 噬夏孢欧文氏菌番茄红素合成相关基因crte,crtb,crti同时克隆进表达载体pet-15b构建pet-15bcrtieb,将该重组质粒转化e.colibl21(de3)构建工程菌,iptg诱导工程菌累积红色色素,经hplc和吸收光谱分析,工程菌中合成的色素为番茄红素。研究了碳源、金属离子、培养温度、诱导剂浓度、诱导时间等参数对工程菌生长及色素累积的影响,确定了合适的培养条件:培养基为改良lb培养基(蛋白胨10g/l、酵母提取物5g/l、麦芽糖5g/l、mgcl20.1g/l,nacl10g/l);起始培养温度为37℃;培养至od600为0.6左右时加入iptg,终浓度为0.5mmol/l,诱导温度降至30℃;诱导时间为14h。发酵完成后工程菌的生物量(干重)为3.45g/l,番茄红素的最高含量可达5.8mg/gdw。
基于力的电动静液作动器阻抗控制
Force based impedance control of electro-hydrostatic actuator

周国哲,付永领,,,殿梁
- , 2017, DOI: 10.13700/j.bh.1001-5965.2016.0094
Abstract: 摘要 阻抗控制作为一种柔顺控制方式,能够实现力与位置的协同控制,在作动系统需要与外部环境发生接触的应用中具有一定优势。在集成、高效的电动静液作动器(EHA)上实现基于力的阻抗控制具有良好的应用前景,其中核心问题是EHA力伺服控制器的设计。针对阻抗控制中外部负载特性不确定,EHA部分结构参数时变等问题,采用定量反馈理论(QFT)的方法对力伺服控制器进行设计。在对EHA数学模型及参数进行分析的基础上,通过QFT方法将被控对象的不确定范围与系统性能设计指标相结合,并以定量的方式在Nichols图上形成边界,在使标称对象的开环频率特性曲线满足各边界约束条件的同时完成力伺服控制器的设计。通过不同外部负载条件下的力伺服控制实验以及静、动态阻抗控制实验对EHA的力伺服控制器与阻抗控制系统进行了验证。实验结果表明:通过QFT方法设计得到的力伺服控制器对外部环境具有较强的鲁棒性,从而确保了EHA阻抗控制的成功实现。
Abstract:As a kind of compliance control method, impedance control can realize force and position coordination control. So it has obvious advantages in the applications that the actuating systems are required to interact with the environments. Because of high energy efficiency and compact structure, electro-hydrostatic actuator (EHA) with force based impedance control has an extensive prospect. The force controller of EHA is the foundation of the impedance control. Due to the uncertain external load characteristics in impedance control and the time-invariant parameters of EHA, the quantitative feedback theory (QFT) was employed to design the force controller. The mathematical model of EHA was analyzed first. Then the uncertainty range of the controlled plant was combined with the performance specifications of the system to quantitatively plot the boundaries on the Nichols chart. The open-loop frequency characteristic curve of the nominal element was adjusted to satisfy the limitations of boundaries and the force controller was completed simultaneously. The force control and static/dynamic impedance control experiments under various load characteristics were conducted to examine the efficacy of the system. The experimental results demonstrate that the force controller designed by QFT method has sufficient robustness and the impedance control of EHA is achieved successfully.
城市草坪土壤肥力综合评价
,常连生,王洪,李晓,张立娟
草业科学 , 2010,
Abstract: ?本文以河北科技师范学院昌黎校区草坪土壤为例,测定分析了土壤容重、pH值、阳离子交换量(CEC)、全盐含量、有机质、碱解氮、速效磷、速效钾等理化性质,并对土壤各肥力因子进行了数值化处理。通过隶属度函数和偏相关分析,确定了各肥力因子的隶属度值及其权重,并利用模糊数学评价方法对土壤肥力进行了综合评价。研究结果显示,河北科技师范学院昌黎校区草坪土壤综合肥力水平低,与草坪质量状况相吻合,表明该评价方法具有可行性,有助于科学、合理、准确地评价城市草坪土壤肥力状况,提高土壤肥力,改善草坪质量。
Ab-initio determination of the incommensurate modulated structure of Bi-2212 from x-ray powder diffraction data -a simulation
陈建,古元新,郑朝德,
中国物理 B , 2003,
Abstract: A set of x-ray powder diffraction data of the high-T_c superconductor Bi_2Sr_2Ca_1Cu_2O_y (Bi-2212) was simulated based on the experimental single-crystal diffraction data by merging together reflections with diffraction angles (2θ) closer to each other than 0.04 degrees. There are three types of overlapping in the powder diffraction data, i.e. (i) overlapping of main reflections; (ii) overlapping of satellite reflections and (iii) overlapping of main and satellite reflections. The third type of overlapping was first separated into main and satellite components according to the ratio between the average intensity of that of types (i) and (ii). Then the overlapped reflections of main reflections and those of the satellites were uniformly partitioned. Heavy-atom sites in the basic/average structure were found using the uniformly decomposed main reflections by the conventional direct method. Phases of the satellites were derived by the multidimensional direct method. The resultant four-dimensional Fourier maps revealed correctly the essential feature of the modulation. No assumption on either the basic structure or the modulation is needed.
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