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Indexing Non-merohedrally Twinned Crystals by Bruker'sAPEX2 and Agilent's CrysAlis^(PRO), an Example of a Crystal Structure That Can Be Refined through Either the PLATONRoute or the ‘HKLF 5' Route, and, Simultaneous Data Collection of Two Crystals in a Two-in-one Run

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Chinese Journal of Structural Chemistry 2014年第2期33卷 294-303页

作者： ng Seik Weng Department of Chemistry University of Malaya 50603 Kuala Lumpur Malaysia Chemistry Department King Abdulaziz University

The first part of this report describes the data reduction of non-merohedrally twinned crystals measured on Bruker and Agilent area-detector diffractometers. The image frames of methyl-2-aminopyrazine-3-carboxylate were processed with APEX2 to furnish a set of overlapping diffraction indices that were used for solution and refinement. CrysAlisPRO was used for processing the frames of bis（diethyldicarbamato）nickel, which exists in monoclinic and tetragonal polymorphs, and in untwinned and twinned forms. In the second part, the crystal structure of [（3-formyl-4- hydroxyphenyl）methyl]triphenylphosphanium chloride was refined through the ‘HKLF 5＇（based on a combined set of diffraction indices） and PLATON（based on one set of diffraction indices） routes to give identical outcomes because the amount of overlap of the twin domains is small. For the third part, in a proof-of-concept investigation, the diffraction pattern of untwinned and twinned 4-{（E）-（4-aminophenyl）diazenyl]phenylamine was recorded simultaneously in one run; the three domains could be indexed and the crystal structure satisfactorily refined. The refinement was identical to those derived from independent measurements; the crystal structure features two independent centrosymmetric molecules, one of which is ordered and the other whole-molecule-disordered. This two-in-one run opens up the possibility that two or more crystals having different atomic compositions can be measured simultaneously if their reciprocal lattices do not overlap significantly.

关键词： merohedral non-merohedral twin APEX2 Crys Alis^PRO two-in-one data collection

A Nonstandard Lévy-Khintchine Formula and Lévy Processes

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Acta Mathematica Sinica,English Series 2008年第2期24卷 241-252页

作者： Siu Ah ng School of Mathematical Sciences University of KwaZulu-Natal Pietermaritzburg 3209 South Africa

We use methods from nonstandard analysis to obtain a short and simple derivation of the Levy-Khintchine formula via an explicit construction of certain laws of the infinitesimal increments. Consequently, any arbitrary... 详细信息

关键词： Levy processes Levy-Khintchine formula nonstandard analysis infinitesimal hyperfinite

WAVE INDUCED OSCILLATORY AND STEADY FLOWS IN THE ANNUluS OF A CATHETERIZED VISCOELASTIC TUBE

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Journal of Hydrodynamics 2010年第5期22卷 605-617页

作者： ng Chiu-On CHAng Yin-Yee Department of Mechanical Engineering The University of Hong Kong

A perturbation analysis based on equations of motion in Lagrangian form is presented for the oscillatory and time-mean viscous flows induced by a propagating wave of small amplitude in an annulus with a viscoelastic outer wall. Owing to the steady streaming effect, the existence of a catheter in a blood vessel brings in an additional steady pressure gradient, a correction to that predicted by the linear theory, and an additional steady shear stress, which may increase the possibility of hemolysis of red blood cells.

关键词： annulus flow steady streaming catheterized artery

Assessment of the kinetic–frictional model for dense granular flow

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Particuology 2008年第1期6卷 50-58页

作者： Boon Ho ng Mojtaba Ghadiri Institute of Particle Science&Engineering University of LeedsLeeds LS2 9JTUK

This paper aims to quantitatively assess the application of kinetic-frictional model to simulate the motion of dry granular materials in dense condition, in particular, the annular shearing in Couette configuration. The weight of frictional stress was varied to study the contribution of the frictional stress in dense granular flows. The results show that the pure kinetic-theory-based computational fluid dynamics （CFD） model （without frictional stress） over-predicts the dominant solids motion of dense granular flow while adding frictional stress [Schaeffer, D. G. （1987）. Instability in the evolution equations describing incompressible granular flow. Journal of Differential Equations, 66（1）, 19-50] with the solids pressure of [lun, C. NTK., Savage, S. B., Jeffrey, D. J., ＆ Chepurniy, N. （1984）. Kinetic theories for granular flow： Inelastic particles in Couette flow and slightly inelastic particles in a general flow field. Journal of Fluid Mechanics, 140, 223-256] in the CFD model improves the simulation to better conform available experimental results. The results also suggest that frictional stress transmission plays an important role in dense granular flow and should not be neglected in granular flow simulations. Compatible simulation results to the experimental data are seen by increasing the weight of frictional stress to a factor of 1.25-1.5. These improved simulation results suggest the current constitutive relations （kinetic-frictional model） need to be improved in order to better reflect the real dense granular flow.

关键词： Gas-solids flow CFD Constitutive relations Couette flow Kinetic theory Kinetic-frictional model

‘Whole-molecule Disorder’ Refinement of 4-(4-Hydroxybenzylideneiminio)phenol Hemichloride Hemihydroxide

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Chinese Journal of Structural Chemistry 2011年第9期30卷 1283-1285页

作者： ng Seik Weng Department of Chemistry University of Malaya

The two independent cations of the salt, [HO-C6H4-CH=NH-C6H4-OH]·1/2OH·1/2Cl, are both disordered about an axis connecting the two oxygen atoms at the para-positions of the aromatic rings, the disorder being in a 83：17 ratio in one cation and 91：9 in the other. The hydroxide and chloride anions are ordered. The treatment of the nearly ‘whole-molecule disorder’ by employing a small number of restraints is described. Crystal data： C13H12.5Cl0.5NO2.5, triclinic, P , a = 9.1731（4）, b = 9.2048（4）, c = 15.9144（7） , α = 104.822（1）, β = 90.077（1）, γ = 118.641（1）o and V = 1127.86（9） 3 at –173 K.

关键词： whole-molecule disorder

‘Whole-molecule Disorder’ Refinement of 4-Tricyanovinyl-N,N-diethylaniline

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Chinese Journal of Structural Chemistry 2011年第9期30卷 1286-1288页

作者： ng Seik Weng Department of Chemistry University of Malaya Chemistry Department Faculty of Science King Abdulaziz University

The molecule of 4-tricyanovinyl-N,N-diethylaniline is disordered about an axis that is close to the axis passing through the 1,4-carbon atoms. The disorder is a 1：1 type of disorder that involves only part of the molecule as the diethylamino substitutent and the three nitrogen atoms of the tricyanovinyl substituent are ordered. The treatment of the nearly ‘whole-molecule disorder’ by employing a small number of restraints is described. Crystal data： C15H14N4, triclinic, P , a = 7.1996（5）, b = 7.7232（5）, c = 12.4171（8） , α = 99.350（1）, β = 94.647（1）, γ = 103.312（1）o and V = 657.90（8） 3 at –173 K.

关键词： whole-molecule disorder

The roles of black phosphorus in performance enhancement of halide perovskite solar cells

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Journal of Energy Chemistry 2022年第4期31卷 672-683页

作者： Damir Aidarkhanov Charles Surya Annie ng Department of Electrical and Computer Engineering School of Engineering and Digital SciencesNazarbayev UniversityKabanbay Batyr Ave.53Nur-Sultan 010000Kazakhstan Innovation and Technology Commission Central Government Offices2 Tin Mei AvenueHong Kong 999077China

Hybrid organic-inorganic perovskite solar cells(PSCs) are considered to be the most promising thirdgeneration photovoltaic(PV) technology with the most rapid rate of increase in the power conversion efficiency(PCE). To date, their PCE values are comparable to the established photovoltaic technologies such as crystalline silicon. Intensive research activities associated with PSCs have been being performed,since 2009, aiming to further boost the device performance in terms of efficiency and stability via different strategies in order to accelerate the progress of commercialization. The emerging 2 D black phosphorus(BP) is a novel class of semiconducting material owing to its unique characteristics, allowing them to become attractive materials for applications in a variety of optical and electronic devices, which have been comprehensively reviewed in the literature. However, comprehensive reviews focusing on the application of BP in PSCs are scarce in the community. This review discusses the research works with the incorporation of BP as a functional material in PSCs. The methodology as well as the effects of employing BP in different regions of PSCs are summarized. Further challenges and potential research directions are also highlighted.

关键词： Perovskite solar cells Black phosphorus Power conversion efficiency Stability Low dimensional materials

NUMERICAL STUDIES OF A CLASS OF COMPOSITE PRECONDITIONERS

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Journal of Computational Mathematics 2014年第2期32卷 136-151页

作者： Qiang Niu Michael ng Mathematics and Physics Centre Xi'an Jiaotong-Liverpool University Suzhou 215123 China Department of Mathematics Hong Kong Baptist University Kowloon Tong Hong Kong

In this paper, we study a composite preconditioner that combines the modified tangential frequency filtering decomposition with the Ilu（O） factorization. Spectral property of the composite preconditioner is examined by the approach of Fourier analysis. We illustrate that condition number of the preconditioned matrix by the composite preconditioner is asymptotically bounded by O（hp -2/3） on a standard model problem. Performance of the composite preconditioner is compared with other preconditioners on several problems arising from the discretization of PDEs with discontinuous coefficients. Numerical results show that performance of the proposed composite preconditioner is superior to other relative preconditioners.

关键词： Preconditioner Ilu Tangential frequency filtering decomposition GMRES.

Lowered testosterone in male obesity： mechanisms, morbidity and management

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Asian Journal of Andrology 2014年第2期16卷 223-231,I0008页

作者： Mark ng Tang Fui Department of Medicine Austin Health University of Melbourne Melbourne Department of Endocrinology Austin Health Melbourne Victoria Australia

With increasing modernization and urbanization of Asia, much of the future focus of the obesity epidemic will be in the Asian region. Low testosterone levels are frequently encountered in obese men who do not otherwise have a recognizable hypothalamic-pituitary-testicular （HPT） axis pathology. Moderate obesity predominantly decreases total testosterone due to insulin resistance-associated reductions in sex hormone binding globulin. More severe obesity is additionally associated with reductions in free testosterone levels due to suppression of the HPT axis. Low testosterone by itself leads to increasing adiposity, creating a self-perpetuating cycle of metabolic complications. Obesity-associated hypotestosteronemia is a functional, non-permanent state, which can be reversible, but this requires substantial weight loss. While testosterone treatment can lead to moderate reductions in fat mass, obesity by itself, in the absence of symptomatic androgen deficiency, is not an established indication for testosterone therapy. Testosterone therapy may lead to a worsening of untreated sleep apnea and compromise fertility. Whether testosterone therapy augments diet- and exercise-induced weight loss requires evaluation in adequately designed randomized controlled clinical trials.

关键词： androgens hypogonadism obesity testosterone weight loss