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91.
间甲基苯甲脒盐酸盐是农药和医药研究领域一个十分重要的原材料和中间体。间甲基苯甲脒盐酸盐的两步合成法是先以盐酸羟胺制备间甲基苯甲脒肟再通过加氢还原即可得到。在制备间甲基苯脒肟时,单因素考察了常规热反应、微波合成法、超声波合成法对间甲基苯脒肟产率的影响。并探索了一锅法合成间甲基苯甲脒盐酸盐的可行性。所得化合物由沸点、氢谱、质谱确认。实验结果表明:三种方式合成间甲基苯甲脒肟,其产率从大到小依次为:微波合成法>超声波合成法>常规热反应。本实验采用两步法合成间甲基苯甲脒盐酸盐的总产率为58.05%,采用一锅法合成间甲基苯甲脒盐酸盐的产率为78.19%。两步法和一锅法均可用于合成间甲基苯甲脒盐酸盐。 相似文献
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93.
One of the fundamental tasks of targeted marketing is to elicit associations between customers and products. Based on the results from information retrieval and utility theory, this article proposes a unified framework of targeted marketing. The customer judgments of products are formally described by preference relations and the connections of customers and products are quantitatively measured by market value functions. Two marketing strategies, known as the customer‐oriented and product‐oriented marketing strategies, are investigated. Four marketing models are introduced and examined. They represent, respectively, the relationships between a group of customers and a group of products, between a group of customers and a single product, between a single customer and a group of products, and between a single customer and a single product. Linear and bilinear market value functions are suggested and studied. The required parameters of a market value function can be estimated by exploring three types of information, namely, customer profiles, product profiles, and transaction data. Experiments on a real‐world data set are performed to demonstrate the effectiveness of the proposed framework. 相似文献
94.
In the present study, the stability condition for semi-discrete difference schemes of hyperbolic conservation laws obtained from Fourier analysis is simplified. This stability condition can be applied only to linear difference schemes with constant coefficients implemented with periodic boundary treatment. It could often give useful results for other cases, such as schemes with variable coefficients, schemes for nonperiodic problem and nonlinear problem. However, this condition usually leads to a trigonometric inequality, which makes it not convenient to use. For explicit difference schemes on uniform grids, this trigonometric inequality can be converted to polynomial form. Furthermore, if the scheme is a high-order one, the polynomial can be factorized into a simple form. Thus, it is much easier to solve than the inequality obtained directly from Fourier analysis. For compact difference schemes and conservative schemes, similar results are obtained. Some applications of this new stability criterion are shown, including judging the stability of two schemes, proving the upstream central schemes to be stable, constructing a stable upwind dissipation relation preserving (DRP) scheme and constructing an optimized weighted essentially non-oscillatory (WENO) scheme. Since WENO schemes are nonlinear schemes, the stability analysis in the present study is performed on their underlying linear schemes. According to the numerical tests, the underlying linear scheme should be stable, otherwise the corresponding WENO scheme may display instability. These applications demonstrate that this criterion is convenient and efficient for judging the linear stability of semi-discrete difference schemes and constructing stable upwind difference schemes. 相似文献
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96.
本文用反相液相色谱法,以甲醇:酸性水(75:25)作为流动相,采用ODS-C18色谱柱,成功地测定了伏草星除草颗粒剂中有效成分含量。 相似文献
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98.
Chang Yang Chengyin Liu Ning Wu Xiang Wu Yidong Li Zhiying Wang 《Neural computing & applications》2014,25(7-8):1741-1754
Collaboration representation-based classification (CRC) was proposed as an alternative approach to the sparse representation method with similar efficiency. The CRC is essentially a competition scheme for the training samples to compete with each other in representing the test sample, and the training class with the minimum representation residual from the test sample wins the competition in the classification. However, the representation error is usually calculated based on the Euclidean distance between a test sample and the weighted sum of all the same-class samples. This paper exploits alternative methods of calculating the representation error in the CRC methods to reduce the representation residual in a more optimal way, so that the sample classes compete with each other in a closer range to represent the test sample. A large number of face recognition experiments on three face image databases show that the CRC methods with optimized presentation residual achieve better performance than the original CRC, and the maximum improvement in classification accuracy is up to 12 %. 相似文献
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100.