平台石墨炉原子吸收法直接测定肉类中铅——应用超低温制悬乳浊液与基体改进剂技术

本文提出了一种简便、快速测定肉类中铅的方法， 采用不经常规消化， 以液氮低温处理样品， 加基体改进剂（０－８ ％ ＮＨ４ Ｈ２ＰＯ４ － ０ ． ５ ％ 抗坏血酸———０－５％ Ｔｗｅｅｎ８０） 后制成均匀、稳定的悬乳浊液直接进样， 并在自制的石墨炉平台中进行测定。有效地提高了灰化温度和原子化效率， 消除了背景干扰。回收率在９７－３ ％ ～１０５－７ ％ 之间， 相对标准偏差≤７－４ ％ ， 与国家标准方法能很好相符。     

Gas-solid interaction force from direct numerical simulation (DNS) of binary systems with extreme diameter ratios

nding the large particles becomes less in case ofa bidisperse mixture, as compared to a monodisperse system with the same volume fraction. We further investigated this discrepancy by calculating the volume per particle by means of Voronoi tessellation.     

基于Direct3D技术的自然现象模拟

虚拟现实中自然现象的模拟一直都是研究的热点,其中雨雪天气的模拟可以增加虚拟现实的逼真程度.本文在分析粒子系统实现原理的基础上,基于Direct3D技术,实现了雨雪天气的模拟.本文采用的实现方法比较简单,实现效果具有较强的真实感.     

Cost of capital for incentives on capacity expansion investments

In this paper, the expression for the cost of capital is derived when capacity expansion investments and replacement investments exhibit differences in their effective prices. It is shown that the cost of capital derived by perturbing the optimal stock path should be constructed under an opportunity cost criterion.     

Optimal threshold analysis of segmentation methods for identifying target customers

In CRM (Customer Relationship Management), the importance of a segmentation method for identifying good customers has been increasing. For evaluation of different segmentation methods, Accuracy often plays a key role. This indicator, however, cannot distinguish two types of errors. The purpose of this paper is to overcome this pitfall by introducing two different indicators: Recall and Precision. Assuming that a promotion is addressed exclusively to the selected target customers, the financial effectiveness of the underlying segmentation method is expressed as a function of Recall and Precision. An optimization problem is then formulated so as to maximize the financial measure by finding the optimal threshold level in terms of the severeness for estimating the target set. By introducing a functional form which represents correctness and mistakes about the target set, the unique optimal solution is derived explicitly. The proposed approach is validated by using real customer purchase data.     

Rationally designed 4-phenoxy substituted prolinamide phenols organocatalyst for the direct aldol reaction in water

A rationally designed 4-phenoxy substituted prolinamide phenols as an efficient hydrophobic organocatalyst for direct asymmetric aldol reaction in water has been developed. High yield (up to 99%), diastereoselectivity (up to 99:1), and enantioselectivity (up to 97%) were obtained under optimal condition. The influence of substituent groups on the reactivity of catalysts was studied in detail.     

Determination of As,Cd, Pb,and Hg in urine using inductively coupled plasma mass spectrometry with the direct injection high efficiency nebulizer

The application of the large-bore direct injection high efficiency nebulizer (LB-DIHEN) for the determination of arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg) in urine by inductively coupled plasma mass spectrometry (ICP-MS) is described. The LB-DIHEN is compared with the standard method using a concentric pneumatic nebulizer and cyclonic spray chamber. In addition to the toxicological significance of As, Cd, Pb, and Hg, these elements represent a cross-section of analytical issues including spectral interferences (e.g., ⁴⁰Ar³⁵Cl⁺ on ⁷⁵As⁺ and ⁹⁸Mo¹⁶O⁺ on ¹¹⁴Cd⁺) and memory effects (Hg). In this study, the low sample consumption of the LB-DIHEN is used to reduce the volume of urine needed for analysis, and to reduce the volume of final diluted sample required for analysis. Eliminating the spray chamber and reducing the dead volume of the nebulizer reduces memory effects, especially for analytes such as Hg. The Dynamic Reaction Cell (DRC) is used in this study to attenuate the background level of ArCl⁺ in spite of the increase in the solvent load and, in turn, the urine matrix (chloride) delivered to the plasma by the LB-DIHEN. This is the first report on coupling the LB-DIHEN to a standard autosampler for unattended sample analysis. The robustness of direct injection nebulization for routine analysis and the issues associated with automation of the sample introduction process are discussed. Although the figures of merit (sensitivity, limit of detection, and precision) determined for both nebulizers are slightly poorer for the LB-DIHEN than for the concentric pneumatic nebulizer, there is not a clinically significant difference between the results for both sample introduction systems. The accuracy of results is assessed using archived urine materials that are circulated by several different proficiency testing (PT) programs and external quality assessment schemes (EQAS). Results obtained using the LB-DIHEN were within the acceptable range established by a consensus pool generated using different methods, none of which are likely to be using direct injection nebulization. Internal quality control sample results obtained using the LB-DIHEN were compared to those obtained using the conventional nebulizer. Reported results were similar for both nebulizers. Thus, these results show that the LB-DIHEN is certainly feasible for the analysis of urine specimens.     

紫外分光光度法测定直接耐晒翠蓝GB染色强度的方法研究

在介质水中，直接耐晒翠蓝GB在609nm处有特征吸收峰，据此建立了一种紫外分光光度法测定直接耐晒翠蓝GB染色强度的方法。     

浅析胡萝卜直播覆盖采种法

叙述了胡萝卜直播覆盖采种法比常规采种法具有种子产量高、品质好、成熟一致和节省人力的突出优点．介绍了胡萝卜直播覆盖采种法的科学施肥、小株采种、合理密植、地膜覆盖、主茎留种、加强管理等主要配套技术要点。     

A simplified version of the DEA cost efficiency model

This short paper deals with a current cost efficiency model and decreases the number of its constraints as well as its variables, which leads to a strong reduction in the computational requirements.