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991.
Traditional methods based on the product of exponentials (POE) formula are parametrically continuous and complete for the calibration of the kinematic parameters of serial robots. However, these methods are not minimal due to the constraints of joint twists. This paper puts forward a new POE-based model, whose parameters are totally independent and conform to the formula of minimality. This is the first model that simultaneously satisfies the requirements of parametric continuity, completeness, and minimality with uniform and generic modeling rules. The proposed approach avoids the operations of normalization and orthogonalization which are necessary redundancy elimination steps with the traditional model. Simulations on a SCARA robot and experiments on an ABB IRB 120 robot prove that the new model outperforms in convergence, accuracy, and efficiency.  相似文献   
992.
赵海双  田鹏  马亚团 《化学试剂》2003,25(4):237-238,240
报道了以对羟基苯甲醛为原料,经过硝化、腈化和碘化反应合成牛羊抗肝片吸虫药4-羟基-3-碘-5-硝基苯甲腈的新方法,总收率为76.9%,纯度达96.8%。  相似文献   
993.
本文研究了炭黑-环氧树脂复合材料的制备工艺及炭黑填充率对材料电阻率的影响。实验结果表明,加入表面活性剂,明显改善了炭黑在环氧树脂中分布的均匀性。炭黑-环氧树脂材料具有明显的渗流效应,正温度系数效应即PTC效应,非线性伏安特性和电磁波屏蔽效应。  相似文献   
994.
Crosslinked copolymers of acrylamide (AA) and ethylacrylate and some ion exchangers derived from them containing either primary amine groups, obtained by the Hofmann degradation of the amide groups, or carboxylic groups, obtained by the alkaline hydrolysis of the ester groups, were studied. Divinylbenzene and N,N′‐methylenebisacrylamide were used as crosslinkers. The starting copolymers and the corresponding ion exchangers were characterized by IR spectroscopy, swelling behavior, and thermogravimetric analysis. The ion‐exchanger properties were correlated with the crosslinker nature and the chemical reactions performed on the AA copolymers. The average molecular weight between two crosslinks, determined from the swelling data in water, was compared with that calculated on the basis of the copolymerization stoichiometry only for the carboxylic cation exchangers. In this way, the preservation of the crosslink density after the hydrolysis was revealed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2701–2707, 2003  相似文献   
995.
对动态泡沫床处理过磷酸钙含氟尾气的有关技术及费用作了说明 ,指出该方法费用高 ;提出一种新方法 ,该方法不加任何化学助剂 ,采用水作吸收剂 ,只需改变动态泡沫床一些设计参数和选用一种特殊的喷头 (喷头周围设计 1个圆锥形死角区 ,使含氟气体不可能进入该区 )避免了硅胶堵塞。该方法已在湖南浦市化工总厂运行 1年多未发现堵塞 ,同时该法投资少、能耗低、排放尾气达标  相似文献   
996.
The surface alkaline hydrolysis of fibers made from poly(trimethylene terephthalate) (PTT) was studied after extruding the polymer at high spinning speeds from 2000 to 6000 m/min and heat setting in the range of temperatures from 100 to 180°C. Fiber weight loss increased with an increasing heat‐setting temperature but it was also dependent on the spinning speed. Some of the partially hydrolyzed fibers had a well‐developed, hydrophilic surface, and pore size in the range of 0.69 to 1.20 μm. The optimum reaction and morphological conditions for increasing porosity in PTT fibers depends on spinning speed and heat‐setting temperature. A temperature of 180°C is the upper limit for heat‐setting PTT filaments but seems to be the most effective for making porous fibers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1724–1730, 2004  相似文献   
997.
998.
R-卡尼丁的合成和改进   总被引:2,自引:2,他引:2  
胥波  程国侯 《化学世界》2000,41(9):459-461,472
以环氧氯丙烷为原料合成了 ( R,S) -卡尼丁 ,用二苯甲酰 - L-酒石酸对其进行了拆分 ,对反应和拆分条件进行了优化 ,并用氧化还原法实现了 S-卡尼丁的消旋化 ,使其可以回收利用。  相似文献   
999.
Although user experience and personal innovativeness are two important factors in new technology adoption, there has been no prior study to test these factors with the Enterprise Resource Planning (ERP) adoption. This paper investigates moderating roles of user experience on the relationship between the personal innovativeness and the ERP adoption motivations. This issue is important because if the user has more experience with the systems then the power of influence of personal innovativeness on ERP adoption motivation would be different. Thus, this paper tests these important insights of ERP systems adoption with the two different field samples with high (more than three years) and low (less than three years) user experience, based on the innovation diffusion theory, self determination theory, and different types of motivations such as intrinsic and extrinsic motivations. The findings, based on the PLS analysis of the model using 107 ERP end users, show that there are clear moderating effects of user experience—such as impacts of personal innovativeness on ERP systems adoption motivations are higher in case of low user experience samples, as expected. Academic and practical implications are discussed in the paper based on these empirical findings.  相似文献   
1000.
Web surveys are rapidly becoming standard issue in many researchers’ toolkits; however, measurement error has been shown to affect web surveys to a greater extent than paper-and-pencil surveys (Couper, 2000, Manfreda and Vehovar, 2002). Principles of aesthetic design and social presence have been applied to web surveys to reduce the prevalence of such error with promising results, which were further investigated in this research. A sample of 181 first-year psychology undergraduate students participated in this study. Participants were randomly allocated to view one of eight web survey interfaces, which varied by aesthetic quality and social presence. Exploratory structural equation modeling using the partial least squares method revealed that classical aesthetic quality and social presence were both positively related to perceived ease of use of the web survey interface and positive state affect; social presence and perceived ease of use were positively related to trust in the web survey researcher; classical aesthetic quality was negatively related to negative state affect; and, expressive aesthetic quality was negatively related to perceived ease of use and positively related to positive state affect. Interestingly, expressive aesthetic quality was also positively related to negative state affect. These relationships between aesthetic quality and social presence should inform best practice web survey design recommendations, and future empirical work should extend and test the generalizability of these findings.  相似文献   
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