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排序方式: 共有293条查询结果,搜索用时 15 毫秒
1.
Ton That Tri 《代数通讯》2013,41(11):5435-5438
Let GL n = GL(n,F p ) be the group of all n×ninvertible matrices over the field F p of p elements, p a prime number. As well known, a complete set of irreducible GL n -modules as submodules of the polynomial algebra was constructed by Stephen Doty and Grant Walker, Ton That Tri (see [1], [4]). Grant Walker has a conjecture that the occurence of these modules is the first occurence of these modules as submodules in the polynomial algebra. The aim of this paper is to give a proof of the above conjecture for p= 2. 相似文献
2.
Benny Luijsterburg Peter Jobse Daniel Hermida Merino Ton Peijs Han Goossens 《Journal of Polymer Science.Polymer Physics》2014,52(16):1071-1082
Isotactic polypropylene (i‐PP) can crystallize in different crystal modifications. In this article, the effect of sepiolite (one‐dimensional) and carbon black (three‐dimensional) fillers on the solid‐state drawability of i‐PP is discussed. The cross‐hatched structure of thermodynamically most stable α‐crystal phase in i‐PP does not allow for perfect chain alignment during solid‐state drawing. The β‐phase i‐PP, obtained by addition of specific nucleating agents, crystallizes in a non‐cross‐hatched spherulitic structure and allows more easy drawing. Depending on the filler type, β–α transformation takes place at different draw ratios, as was observed by in situ wide‐angle X‐ray diffraction measurements. It was observed that β‐nucleated i‐PP has a lower yield stress and can be drawn further than i‐PP crystallized in the α‐crystal phase. If added in the right amount, both carbon black and sepiolite have a reinforcing effect on PP tapes. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1071–1082 相似文献
3.
从系统的角度考虑电动桥式起重机起升机构工作过程中的动力学模拟问题。首先,由系统的拉格朗日函数、约束条件和电机的磁共能定义修正的拉格朗日函数;随后,应用Hamilton原理和三相感应电机瞬态模型得出起升机构工作过程中电动桥式起重机系统的运动方程。为验证模型的效果,本文还进行了转子串电阻速度控制系统控制下的32t电动桥式起重机吊运额定负载下降过程的数值模拟,分析了高速浮动轴扭转刚度以及制动过程中转子电阻的配置方案对系统动力响应的影响。模拟结果表明,制动过程中起升机构高速浮动轴所受载荷远大于起动过程中所受载荷,制动开始时在电机转子电路中增加一级较大的外串电阻有利于减小下降制动阶段系统中的动载。 相似文献
4.
建立了一种灵敏测定酸性橙Ⅱ的伏安传感器方法。以酸性橙Ⅱ为模板分子,邻苯二胺和间苯二酚为功能单体,采用电聚合法在铂电极表面制备了酸性橙Ⅱ分子印迹传感器。以K3[Fe(CN)6]为电子传递媒介,采用差分脉冲法(DPV)和循环伏安法(CV)对传感器的识别性能进行研究,以甲醇-乙酸(7∶3)洗脱模板。研究表明:该印迹传感器对酸性橙Ⅱ分子具有良好的选择性、灵敏度和稳定性。在1.0~100.0μg/L范围内,酸性橙Ⅱ的浓度与印迹传感器的响应呈良好线性关系,检出限(S/N=3)为0.10μg/L。方法应用于饮料和啤酒中酸性橙Ⅱ的测定,结果满意。 相似文献
5.
Lysine‐based functional blocked isocyanates for the preparation of polyurethanes provided with pendant side groups 下载免费PDF全文
Jie Yin Jur Wildeman Ton Loontjens 《Journal of polymer science. Part A, Polymer chemistry》2015,53(17):2036-2049
This article describes a methodology to prepare polyurethanes (PUs), decorated with pendant (bio)functional side groups, by polymerizing (bio)functionalized blocked diisocyanates with polyols. Caprolactam blocked lysine diisocyanate methyl ester (BLDI‐OMe) was prepared in high yields, by reacting the methyl ester of lysine with carbonyl biscaprolactam. In the absence of a catalyst, the polymerization of BLDI‐OMe with polycaprolactone and polytetrahydrofuran resulted in strictly linear PUs due to the high selective reactivity of the blocked isocyanates (BIs). Although the ester appeared to be less reactive, we found hydrolyzing conditions for the ester, without affecting the BIs. The free acid groups were converted into a N‐hydroxysuccinimide (NHS) activated ester, which was a versatile intermediate for further functionalization. After having demonstrated that model amines were able to substitute NHS without effecting the BIs groups, the same chemistry was used to couple biotin, giving a biotin functional caprolactam blocked lysine diisocyanate. The polymerization with polyols afforded the corresponding biotin‐functional PUs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2036–2049 相似文献
6.
Quoc Cuong Ton Ernst Egert 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(1):75-79
The antibiotic trimethoprim [5‐(3,4,5‐trimethoxybenzyl)pyrimidine‐2,4‐diamine] was cocrystallized with glutarimide (piperidine‐2,6‐dione) and its 3,3‐dimethyl derivative (4,4‐dimethylpiperidine‐2,6‐dione). The cocrystals, viz. trimethoprim–glutarimide (1/1), C14H18N4O3·C5H7NO2, (I), and trimethoprim–3,3‐dimethylglutarimide (1/1), C14H18N4O3·C7H11NO2, (II), are held together by three neighbouring hydrogen bonds (one central N—H...N and two N—H...O) between the pyrimidine ring of trimethoprim and the imide group of glutarimide, with an ADA/DAD pattern (A = acceptor and D = donor). These heterodimers resemble two known cocrystals of trimethoprim with barbituric acid and its 5,5‐diethyl derivative. Trimethoprim shows a conformation in which the planes of the pyrimidine and benzene rings are approximately perpendicular to one another. In its glutarimide coformer, five of the six ring atoms lie in a common plane; the C atom opposite the N atom deviates by about 0.6 Å. The crystal packing of each of the two cocrystals is characterized by an extended network of hydrogen bonds and contains centrosymmetrically related trimethoprim homodimers formed by a pair of N—H...N hydrogen bonds. This structural motif occurs in five of the nine published crystal structures in which neutral trimethoprim is present. 相似文献
7.
基于古斯-汉欣位移效应的波长传感研究 总被引:1,自引:0,他引:1
利用双面金属包覆波导在导模共振激发时对古斯-汉欣位移具有极大的增强效应来实现激光波长微小变化的监测.双面金属包覆波导由上层金膜、导波层和下层金膜组成.当导波层厚度为亚毫米尺度时,应用自由空间耦合技术使入射的激光以小角度入射,在满足相位匹配的条件下激发超高阶导模.理论研究表明,当波导的辐射损耗等于本征损耗时,反射光的侧向位移可达到数百微米,并且此时激发的超高阶导模对波长具有极强的色散能力.通过测量反射光的侧向位移可实现对激光波长变化的实时探测,且具有很高的灵敏度.同时,实验中探测信号只与光束位置相关,可有效避免因光源输出光强的波动带来的干扰.实验测量结果表明对激光波长在859nm附近的分辨率可达到0.2 pm. 相似文献
8.
金属-碳管复合结构的计算力学研究 总被引:1,自引:1,他引:0
系统地研究了金属-碳纳米管复合结构的力学行为,考察了单轴压缩载荷作用下填充管的临界屈曲应变对管内金属原子数目的依赖性,分析了管的几何特征,包括管径、管长及手性,对填充管变形与力学行为的影响,并与连续体力学模型的预测进+行了对比分析.本文的研究结果对金属-碳管复合结构的理论研究和工程应用都具有较好的指导意义. 相似文献
9.
10.
TM Ton F Himawan JW Chang PW Chan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(38):12020-12027
A method to prepare α,α-acyl amino acid derivatives efficiently by Cu(OTf)(2) +1,10-phenanthroline (1,10-phen)-catalyzed amination of 1,3-dicarbonyl compounds with PhI?NSO(2) Ar is described. The mechanism is thought to initially involve aziridination of the enolic form of the substrate, formed in situ through coordination to the Lewis acidic metal catalyst, by the putative copper-nitrene/imido species generated from the reaction of the metal catalyst with the iminoiodane source. Subsequent ring opening of the resultant aziridinol adduct under the Lewis acidic conditions then provided the α-aminated product. The utility of this method was exemplified by the enantioselective synthesis of a precursor of 3-styryl-2-benzoyl-L-alanine. 相似文献