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Search Results: 1 - 10 of 249071 matches for " 李练培 "
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不同仪器测定化妆品中氯霉素的含量
Different Instrument for Determining the Content of Chloramphenicol in Cosmetics
 [PDF]

陈科, 刘翠红,
Advances in Analytical Chemistry (AAC) , 2016, DOI: 10.12677/AAC.2016.63009
Abstract:
目的:采用三种不同液相色谱仪,对祛痘除螨类化妆品中氯霉素含量进行测定。方法:在相同的实验条件下,以氯霉素为标准物质,C18柱(250 mm × 4.6 mm, 5 μm)为分离柱,(甲醇 + 乙腈 = 1:2):0.01 mol/L草酸(pH = 2.0) = 40:60为流动相洗脱,二极管阵列检测器,检测波长268 nm,流速:0.8 mL/min。结果:L-3000、LC-20AT、L-6000测定的线性相关系数r分别为0.9976、0.9994、0.9998,精密度的保留时间与峰面积RSD%依次分别为1.8%和2.1%、0.85%和0.91%、0.50%和0.72%,稳定性RSD%分别为2.3%、0.37%、0.16%,重复性RSD%分别为2.7%、0.86%、0.57%,回收率和RSD%依次分别为96.2%、2.2%;97.4%、1.3%;99.3%、0.7%。结论:经比较,使用超高效液相色谱仪测定氯霉素灵敏度低、精密度高、重复性好。
Objective: Using three different liquid chromatographs, to determine the chloramphenicol content in cosmetics for removing acne and acarus. Methods: Under the same experimental conditions, on the basis of chloramphenicol material, C18 column (250 mm × 4.6 mm, 5 μm) was used as the sep-aration column, (methanol + acetonitrile = 1:2):0.01 mol/L oxalic acid (pH = 2.0) = 40:60 as mobile phase elution, and diode array detector was also used with detection wavelength of 268 nm, velocity of 0.8 mL/min. Results: The linear correlation coefficient r of L-3000, LC-20AT, L-6000 was 0.9976, 0.9994, 0.9998 respectively; RSD% of precision retention time and peak area were 1.8% and 2.1%, 1.8% and 0.91%, 0.50% and 0.72%, respectively; RSD% of stability was 2.3%, 0.37% and 2.3% respectively; RSD% of repetitive peak area was 2.7%, 0.86% and 2.7% respectively; the recovery rate and RSD% were 96.2% and 96.2%, 97.4% and 1.3%, 99.3% and 0.7% respectively. Conclusion: After comparing, using ultra performance liquid chromatography to determine chloramphenicol has advantages of low sensitivity, high precision and good repeatability.
浅析农村寿险市场的开拓

天府新论 , 2002,
Abstract: 农村商业寿险市场的发展空间巨大。在当前的农村社会结构变迁过程中,农村居民风险保障需求的迫切程度不仅不亚于城市,在某些方面,甚至还有过之而无不及。农村经济发展水平远远落后城市,这是大规模拓展农村商业寿险市场最大的障碍。开拓农村寿险市场,要争取国家对农村寿险政策扶持,加强农村寿险宣传力度,提高农民的保险意识;在农村服务所推行个人代理营销机制,改变原有农村业务单一的经营模式;营销展业要有农村特色
社会保障对居民消费需求的影响

天府新论 , 2003,
Abstract: 社会保障水平过低,是我国当前消费需求增长最重要的障碍之一。通过完善社会保障体系,提高居民抵御和防范各种风险的能力,是稳定和拉动消费需求的一个重要途径。为稳定经济转型期的居民消费需求,发挥社会保障机制在经济宏观调控中的作用,需要重点解决好这样几个问题:(1)尽可能提高社会保障水平。(2)扩大社会保障覆盖面。(3)提高社会保障制度的规范化程度
基于GPS轨迹数据的地图匹配算法
清泉,
测绘学报 , 2010,
Abstract: 应用的特殊性使得GPS浮动车轨迹数据的地图匹配有别于传统的导航系统的方法,本文针对GPS浮动车轨迹数据具有整体运动趋势的特点,结合城市路网行车限制的约束,提出了一种GPS轨迹数据的全局地图匹配方法,综合考虑轨迹曲线与路网路径的曲线相似性、实际行车的路段几何拓扑和交通管制约束下的连通性,实现了较好的地图匹配效果,并通过实验进行了验证,为GPS浮动车数据的进一步分析应用打下了基础。
新型生育文化初探

人口研究 , 2001,
Abstract: ?1 新型生育文化的界定生育文化是广义文化中与人的生育行为相联系的一个文化层面。它是一种意识观念,是深层的文化心态,是人们通过历史的沉淀、积累,对嫁娶、生育、家庭等方面的认识、各种知识和区域习俗的总和。新型生育文化是一个新概念,具有丰富的内涵与外延,根据农村计生工作的实际,笔者认为,新型生育文化可以做如下界定。(1)充分认识男女性别的差异、互补和均衡。男女性别有着本质的差异,但不管怎样,在人类社会中,这种差异应该是互补和均衡的。我们不否认男性的生理和心理有优于女性的方面,他们适合于从事劳动强度大、危险等工作;但女性的生理和心理也有优于男性的方面,她们往往可以从事男性不
三峡水库提前蓄水方案的优化选择 Optimal Scheme of Early Refill Operation for the Three Gorges Reservoir  [PDF]
,郭生,天元,周研来
Journal of Water Resources Research (JWRR) , 2013, DOI: 10.12677/jwrr.2013.23023
Abstract: 应用Copula函数构建了联合分布及条件概率分布,通过随机抽样方法模拟得到三峡水库9月份随机入库流量序列。建立了提前蓄水方案优选模型,计算并分析了8月下旬不同来水情景下,三峡水库9月份提前蓄水方案的优化选择。研究结果表明:若8月下旬来水为丰水,则9月下旬起蓄,月底均匀蓄水至166 m,较原设计方案,在不增加防洪风险的前提下,多年平均发电量可增加1.57亿kW h (1.46%),弃水量减小10.72亿m3 (12.89%);若来水为平水,则9月中旬起蓄,月底均匀蓄水至166 m,较原设计方案,在不增加防洪风险的前提下,多年平均发电量可增加3.45亿kW h (3.40%),弃水量减小22.59亿m3 (34.19%);若来水为枯水,通过加强实时监测,则可进一步提前至9月上旬起蓄,月底均匀蓄水至166 m,较原设计方案,在基本不增加防洪风险的前提下,多年平均发电量可增加5.50亿kW h (6.12%),弃水量减小19.18亿m3 (51.89%)。 A joint distribution function and conditional probability distribution of this samples using copula was built and inflow series in September were obtained by stochastic simulation method. Furthermore, a refill operation optimization model of the Three Gorges Reservoir was established in this paper to derive the optimal refill scheme. The results show that the optimal refill scheme depends on the reservoir inflow in late August. In the wet year, refill begins in late September with storage level reaching 166 m on September 30 linearly. Comparing with designed scheme, the scheme can generate extra about 1.57 × 108 kW·h electrical energy (by 1.46%) and save 10.72 × 108 m3 water resources (by 12.89%) annually without increasing the flood control risk; In the normal year, refill begins in middle September with storage level reaching 166 m on September 30 linearly. Comparing with designed scheme, the scheme can generate extra about 3.45 × 108 kW·h electrical energy (by 3.40%) and save 22.59 × 108 m3 water resources (by 34.19%) annually without increasing the flood control risk; In the dry year, refill begins in early September with storage level reaching 166 m on September 30 linearly by strengthening real-time monitoring. Comparing with designed scheme, the scheme can generate extra about 5.50 × 108 kW·h electrical energy (by 6.12%) and save 19.18 × 108 m3 water resources (by 51.89%) annually without increasing the flood control risk.
多源非平稳信号频率跟踪的改进方法研究
Study of Method Improvement for Racking Frequency of Multi-Source Non-Stationary Signal
 [PDF]

赵向阳,
Smart Grid (SG) , 2012, DOI: 10.12677/sg.2012.21001
Abstract: 智能微电网的应用越来越受到重视正逐渐成为研究的热点之一,其发电系统中存在多个发电源和负载,其系统电流也是由多个频率分量而组成。由于智能微电网的组成复杂性,其发电系统更容易受到干扰和影响,因此系统电流会表现为非平稳特性。本文针对此类情况,提出了基于短时傅里叶变换,然后采用了相位建模的改进频率估计方法,对智能微电网的系统信号进行分析处理,有效实现了多分量分平稳信号的分离和频率跟踪,并且适用于能量相差悬殊的多分量信号,同时可以准确提取各频率分量的初始相位估计。
The applications of Smart MicroGrid are placed more and more attention, and it is becoming one of the hot issues. There are multiple generation sources and loads in the power generation system, and its system current consists of a number of frequency components. In addition, because of the complexity of Smart MicroGrid, the power system is vulnerable to interference and influence, and the current have characteristics of non-stationary. In such cases, this paper proposes the improved method base on short-time Fourier transform and phase modeling. It can effectively realize the separation and frequency tracking of multi-source non-stationary signal, suitable for the signal that energy of each component is very different. At the same time it can accurately extract initial phase estimationof of each frequency com- ponent of signal.
基于Copula函数的干旱特征分析
Drought Characteristics Analysis Using Copulas
 [PDF]

陈璐, 郭生, 闫宝伟, 天元
Journal of Water Resources Research (JWRR) , 2012, DOI: 10.12677/JWRR.2012.14026
Abstract: 研究干旱事件有利于水资源的规划和管理。本文以标准降水指数SPI作为干旱指标,基于Copula函数,提出了一种新的干旱分析模型。该模型首先生成M年的日降雨数据,首次采用干旱历时、干旱程度、最小SPI值和干旱间隔时间来定义干旱事件,引入四维对称和非对称型Archimedean和椭圆Copula函数构建多维联合分布;最后依据联合重现期和条件重现期的计算公式,分析了干旱事件的重现期,并以汉江上游为例进行了应用研究。结果表明,所提方法考虑了多个变量,与现有方法相比,能够更全面地反映干旱事件的真实特征;本文的分析结果将为南水北调中线工程调度决策提供科学依据和技术支持。
Droughts are of great importance in the planning and management of water resources. This study proposed a new model for analyzing the characteristics of droughts based on copula functions and Standardized Precipitation Index (SPI). First, M years of daily rainfall data were simulated for evaluating drought characteristics. Second, drought characteristics, namely, drought duration, severity, interval time and minimum SPI values, were introduced and determined in this model. Then, several copulas, including symmetric and asymmetric Archimedean and meta-elliptical copulas were applied to construct four-dimensional joint distributions. Drought probabilities and return period were calculated and analyzed based on a four-dimensional copula using the upper Han River basin,China, as a study area. The results show that compared with the current methods, the four-dimensional joint distribution considering more variables can reveal the real characteristics of droughts. The analysis results can provide technique support for the well-known South- to-North Water Diversion Project (SNWDP) inChina.
考虑水库调蓄影响的设计洪水计算方法
Design Flood Estimation at Downstream Section by Considering the Impact of Upstream Reservoir Regulation
 [PDF]

刘章君, 郭生, 天元, 徐长江
Journal of Water Resources Research (JWRR) , 2012, DOI: 10.12677/JWRR.2012.14029
Abstract: 水库的调蓄作用,改变了其下游天然洪水的水文情势,直接影响下游断面的设计洪水。以清江流域梯级水库为例,通过基于Copula函数的条件期望和最可能地区组成,结合规范采用的同频率地区组成方法,拟定了五种水布垭水库和区间流域洪水组合方案,推求受水布垭水库调蓄影响的隔河岩断面设计洪水。计算结果表明:与天然情况相比,考虑水布垭水库调蓄的不同重现期隔河岩断面设计洪水均减小。削减最大的是条件期望组合方案,最小的是条件期望组合方案。规范采用的同频率方法有一定的代表性,但它既不是最可能发生的,也不是对隔河岩断面防洪最不利的情形。研究成果可以供清江梯级水库防洪调度与运行管理参考,同时为水库下游断面设计洪水计算提供了一条新思路。
The hydrological regime of the natural flood has been changed because of the reservoir storage and regulation, which directly impact on design flood in the downstream section. The Shuibuya-Geheyan cascade reservoirs in the Qingjiang basin were chosen as the case study. Five schemes based on the conditional expectation, most likely composition and same frequency methods were used to analyse flood regional combination of the Shuibuya reservoir and interval basins. The design floods of the Geheyan section were estimated by considering the impact of the Shuibuya reservoir regulation and compared with that of natural condition. The results show that design peak discharges of five schemes are reduced; the maximum and minimum values are estimated by the conditional expectation I and the conditional expectation II schemes respectively. The same frequency methods are neither the most likely to occur, nor the most unfavorable circumstances for flood control of Geheyan section. This study not only can provide references for the Qingjiang cascade reservoirs operation and management, but also provide a new way for design flood estimation at reservoir downstream section.
巨型水库群防洪发电联合优化调度研究与应用
Joint Operation of Flood Control and Hydropower Generation for the Multi-Reservoir System
 [PDF]

郭生, , 陈炯宏
Journal of Water Resources Research (JWRR) , 2012, DOI: 10.12677/jwrr.2012.11001
Abstract: 针对三峡和清江梯级巨型水库群防洪发电补偿联合调度问题,分别建立了梯级单独和水库群联合防洪优化调度数学模型,以发电量最大为目标的水电站群联合调度模型,采用POA算法分别计算两个梯级单独运行和梯级联合运行在不同准则下的防洪标准和电力补偿效益。选取长江宜昌站1954、1981、1982和1998年为典型年推求设计洪水过程线,梯级单独和水库群联合调度分别可使荆江河段的防洪标准提高到150年168年。选择1982~1987连续水文周期年的日径流资料进行计算,与设计方案相比,三峡梯级和清江梯级联合调度后的弃水量分别减少了577.41亿m3和53.84亿m3,年平均发电量增加了59.92亿kW?h,即增加了5.37%,发电补偿效益十分显著。
Joint operation of flood control and hydropower generation for the Three Gorges cascade and Qingjiang cascade reservoirs in China was studied in this paper. The flood control and hydropower generation models were established for individual and joint operation of the cascade reservoirs. The models have considered reservoir flood prevention storage and electric compensation benefits among cascade reservoirs and were solved by the progressive optimality algorithms. Four typical years of 1954, 1981, 1982 and 1998 of the Yichang hydrological stations were selected to derive the design flood hydrographs. The results show that the average of Jingjiang River flood control standards can be raised to and 150-year and 168-year return periods respectively. The daily inflow data of consecutive hydrological years of 1982 - 1987 were used to test the models. Compared with the design operation rules, the joint operation of the multi-reservoir system can generate 5.992 billion kWh of extra power annual or an increase of 5.37% by the objective function of maximum hydropower generation. Through reservoir storage compensation, the spilled water of the Three Gorges and Qingjiang cascade reservoirs was decreased by 57.741 and 5.384 billion m3, respectively.
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