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On solubility and supersolubility of some classes of finite groups

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Science China Mathematics 2009年第2期52卷 272-286页

作者： shum Kar Ping SKIBA Alexander N. Department of Mathematics University of Hong Kong Department of Mathematics Francisk Skorina Gomel State University

AbstractLet G be a finite group and H a subgroup of G. Then H is said to be S-permutable in G if HP = PH for all Sylow subgroups P of G. Let H sG be the subgroup of H generated by all those subgroups of H which are S-permutable in G. Then we say that H is S-embedded in G if G has a normal subgroup T and an S-permutable subgroup C such that T ∩ H ? H sG and HT = C.Our main result is the followingTheorem AA group G is supersoluble if and only if for every non-cyclic Sylow subgroup P of the generalized Fitting subgroup F*(G) of G, at least one of the following holds: Every maximal subgroup of P is S-embedded in G.Every cyclic subgroup H of P with prime order or order 4 (if P is a non-abelian 2-group and H ? Z ∞ (G)) is S-embedded in G.

关键词： S-permutable subgroups S-embedded subgroups saturated formations generalized Fitting subgroups supersoluble groups 20D10 20D20 20D25

Oil-mediated high-throughput generation and sorting of water-in-water droplets

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Microsystems & Nanoengineering 2020年第1期6卷 484-493页

作者： Lang Nan Yang Cao Shuai Yuan Ho Cheung shum Department of Mechanical Engineering The University of Hong KongPokfulam RoadHong KongChina Department of Electrical and Electronic Engineering The University of Hong KongPokfulam RoadHong KongChina

Aqueous two-phase system(ATPS)droplets have demonstrated superior compatibility over conventional water-in-oil droplets for various biological ***,the ultralow interfacial tension hampers efficient and stable droplet generation,limiting further development and more extensive use of such ***,we present a simple strategy to employ oil as a transient medium for ATPS droplet *** methods based on passive flow focusing and active pico-injection are demonstrated to generate water-water-oil double emulsions,achieving a high generation frequency of~2.4 *** evaporation of the oil to break the double emulsions,the aqueous core can be released to form uniform-sized water-in-water ***,this technique can be used to fabricate aqueous microgels,and the introduction of the oil medium enables integration of droplet sorting to produce single-cell-laden hydrogels with a harvest rate of over 90%.We believe that the demonstrated high-throughput generation and sorting of ATPS droplets represent an important tool to advance droplet-based tissue engineering and single-cell analyses.

关键词： limiting sized compatibility

Syntheses and Application of All-lithium Salts of Heteropolyacid as Electrolyte of Lithium-ion Battery

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Chemical Research in Chinese Universities 2004年第1期20卷 77-80页

作者： CHENYa-guang WANGCUn-guo ZHANGXi-yan XIEDe-min WANGRong-shum FacultyofChemistry NortheastNormalUniversityChangchun130024P.R.China

The all-lithium salts of heteropoly acid Li_xXM_ 12O_ 40(HPA-Li)(X=P, Si; M=Mo, W) were obtained via ion exchange and characterized by means of IR and UV spectroscopies, TG and elemental analyses. The conductivity of the electrolytic solution consisting of Li_3PW_ 12O_ 40 and PC/DME mixing solvent(1/2.5, volume ratio) is up to 7.2×10 -2 S/cm, being higher than that of LiClO_4 as the electrolyte. The all-lithium salts were used as electrolytes in secondary lithium-ion batteries. The discharge capacity of the PAS/Li batteries with Li_3PW_ 12O_ 40 electrolyte solutions reaches to 148 (mA·h)/g and the cyclic life is up to 380 times, much better than those of commercialized products with LiClO_4 and LiAsF_6 as electrolytes.

关键词： All-lithium salt Heteropoly compound Electrolyte Lithium-ion secondary battery

Design of photonic crystal fiber with elliptical air-holes to achieve simultaneous high birefringence and nonlinearity

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Chinese Physics B 2018年第1期27卷 385-389页

作者：刘敏侯静云杨虚赵昺玥 Ping shum College of Communication Engineering Chongqing University Ministry of Education Key Laboratory of Optoelectronic Technology and Systems Chongqing University School of Electrical & Electronic Engineering Nanyang Technological University

A new type of V-shaped photonic crystal fiber with elliptical air-holes is proposed to realize simultaneous high bire- fringence and nonlinearity at a wavelength of 1.55 μm. The full vector finite element method was adopted to investigate its characteristics, including birefringence, nonlinearity, and dispersion. The PCF exhibited a very high birefringence of 2.89x10-2 and very high nonlinear coefficient of 102.69 W-1 .km 1. In particular, there were two zero-dispersion wave- lengths （ZDWs） in the visible （X： 640-720 nm and Y： 730-760 nm） and near-infrared regions （X： 1050-1606 nm and Y： 850-1500 nm）. The combination of high birefringence and nonlinearity allowed the PCF to maintain the polarization state and generate a broadband super continuum, with potential applications in nonlinear optics.

关键词： photonic crystal fiber birefringence nonlinearity zero dispersion

A Hua-like Theorem in Semirings＊

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Algebra Colloquium 2015年第3期22卷 445-448页

作者： Jun Pei Yuqi Guo K.P. shum School of Mathematics and Statistics Lanzhou University Lanzhou 730000 China School of Mathematics and Statistics Southwest University Chongqing 400715 China Institute of Mathematics Yunnan University Kunming 650091 China

In this paper, we establish a Hua-Like theorem in some kind of semirings. This can be regarded as a generalized version of Hua＇s theorem from rings to semirings.

关键词： semiring Hua's theorem Hua-like theorem

Finite Groups with Character Degrees of Two Distinct Primes

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Wuhan University Journal of Natural Sciences 2006年第2期11卷 343-345页

作者： CHEN Shengan FAN Yun shum Karpin School of Mathematics trod Statistics Wuhan University Wuhan 430072 Hubei China Department of Mathematics Xianning College Xianning 437005 Hubei China Department of Mathematics Chinese University of Hong Kong Hong Kong China

It is proved that if the degree of any non-linear irreducible character of a finite group G is a product of powers of two given distinct prime integers p and q, then G has an abelian Hall {p, q} subgroup H and an Abelian normal {p, q} complement A, and the centralizer in A of the Sylow p-subgroup of G is equal to the centralizer in A of the Sylow q-subgroup of G.

关键词： degree of character Ahelian normal π-complement centralizer semi-direct product

LR-normal orthogroups

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Science China Mathematics 2006年第3期49卷 330-341页

作者： shum K. P. SEN M. K. Faculty of Science Department of Pure Mathematics

A new kind of regular orthogroups, namely, the LR-normal orthogroups is introduced and investigated. In particular, we will introduce the gearing techniques for fitting semigroup components on a semilattice in the con... 详细信息

关键词： LR-regular orthogroups, LR-normal orthogroups, gearing of semigroups.

Application of Multimedia and Internet Technology in Learning Mould Design

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厦门大学学报（自然科学版） 2002年第S1期41卷 295-296页

作者： Simon S P shum Department of Multimedia and Internet Technology

With the use of multimedia which combines the use o f text, sound, images, motion video and animation, it is more efficient for studen ts to learn mould design interactively. A program is created using several multi media software to simulate the mechanism of moulding processes in order to let s tudents understand the concept of mould design. In addition, students can even access the program through the Internet. Therefore, the software is defined as Multimedia and Internet Technology (MIT) program. The MIT program consists of four sections: (i) simulation of mould mechanisms, ( ii) cooling system, (iii) material information and (iv) games for tutorials. Sec tion One covers the basic operations of different types of moulds such as two-p late mould, three-plate mould, split mould, side-core mould and mould with und ercuts. Section Two introduces different types of cooling systems such as bubble r, baffle, cooling circuits, etc. Section Three provides some useful material in formation for mould design. Section Four contains games of matching mould compon ents, mould design problem finding and multiple choice questions to test student s how much they understand mould design concept. Multimedia is highly effective particularly in teaching and learning. It changes the nature of learning itself. It makes reading dynamic by giving words an impo rtant new dimension. It allows students to see, hear and do simultaneously, thus significantly reducing average learning time. Furthermore, through cooperative learning on Internet, students can access the program, share data or search info rmation anytime anywhere. Therefore, Multimedia and Internet Technology is one o f the vital aspects to speed up the realization of information age in society.

关键词： Application of Multimedia and Internet Technology in Learning Mould Design

A Review of physics-based and data-driven models for real-time control of polymer electrolyte membrane fuel cells

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能源与人工智能(英文) 2021年第4期6卷 97-129页

作者： Jian Zhao Xianguo Li Chris shum John McPhee Department of Mechanical and Mechatronics Engineering University of WaterlooWaterlooOntarioCanada Department of Systems Design Engineering University of WaterlooWaterlooOntarioCanada

The real-time model-based control of polymer electrolyte membrane(PEM)fuel cells requires a computationally efficient and sufficiently accurate model to predict the transient and long-term performance under various operational conditions,involving the pressure,temperature,humidity,and stoichiometry *** this article,recent progress on the development of PEM fuel cell models that can be used for real-time control is *** major operational principles of PEM fuel cells and the associated mathematical description of the transport and electrochemical phenomena are *** reduced-dimensional physics-based models(pseudo-twodimensional,one-dimensional numerical and zero dimensional analytical models)and the non-physics-based models(zero-dimensional empirical and data-driven models)have been systematically examined,and the comparison of these models has been *** is found that the current trends for the real-time control models are(i)to couple the single cell model with balance of plants to investigate the system performance,(ii)to incorporate aging effects to enable long-term performance prediction,(iii)to increase the computational speed(especially for one-dimensional numerical models),and(iv)to develop data-driven models with artificial intelligence/machine learning *** review will be beneficial for the development of physics or nonphysics based models with sufficient accuracy and computational speed to ensure the real-time control of PEM fuel cells.

关键词： Polymer electrolyte membrane fuel cell Physics-based model Real-time control Reduced dimensionality Empirical model Data-driven model Artificial intelligence