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Broadband strong optical dichroism in topological Dirac semimetals with Fermi velocity anisotropy

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Chinese Physics B 2020年第7期29卷 128-134页

作者： j Lim k.j.a.ooi C Zhang L k Ang Yee Sin Ang Science Math and TechnologySingapore University of Technology and DesignSingapore School of Energy and Chemical Engineering Xiamen University MalaysiaSelangor Darul Ehsan 43900Malaysia College of Chemistry and Chemical Engineering Xiamen UniversityXiamen 361005China School of Physics University of WollongongNorthfields AvenueNew South Wales 2522Australia

Prototypical three-dimensional(3D)topological Dirac semimetals(DSMs),such as Cd3As2 and Na3Bi,contain electrons that obey a linear momentum-energy dispersion with different Fermi velocities along the three orthogonal momentum *** being extensively studied in recent years,the inherent Fermi velocity anisotropy has often been neglected in the theoretical and numerical studies of 3D *** this omission does not qualitatively alter the physics of light-driven massless quasiparticles in 3D DSMs,it does quantitatively change the optical coefficients which can lead to nontrivial implications in terms of nanophotonics and plasmonics *** we study the linear optical response of 3D DSMs for general Fermi velocity values along each *** the signature conductivity-frequency scaling,σ(ω)∝ω,of 3D Dirac fermion is well-protected from the Fermi velocity anisotropy,the linear optical response exhibits strong linear dichroism as captured by the universal extinction ratio scaling law,Λi j=(vi/v j)^2(where i=j denotes the three spatial coordinates x,y,z,and vi is the i-direction Fermi velocity),which is independent of frequency,temperature,doping,and carrier scattering *** Cd3As2 and Na3Bi3,an exceptionally strong extinction ratio larger than 15 and covering a broad terahertz window is *** findings shed new light on the role of Fermi velocity anisotropy in the optical response of Dirac semimetals and open up novel polarization-sensitive functionalities,such as photodetection and light modulation.

关键词： topological Dirac semimetal optical anisotropy linear dichroismn linear response theory

Long range electromagnetic field nature of nerve signal propagation in myelinated axons

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Chinese Physics B 2022年第3期31卷 619-623页

作者： Qing-Wei Zhai kelvin j A ooi Sheng-Yong Xu C k Ong School of Electrical and Computer Engineering Xiamen University MalaysiaSelangor Darul Ehsan 43900Malaysia Department of Physics Xiamen University MalaysiaSelangor Darul Ehsan 43900Malaysia Department of Electronics School of Electronics Engineering and Computer SciencePeking UniversiyBeijing 100871China Department of Physics National University of Singapore2 Science Drive 3117551 Singapore

The nature of saltatory conduction in myelinated axon described by equivalent circuit and circuit theory is still contentious. Recent experimental observations of action potentials transmitting through disjointed nerve fibers strongly suggest an electromagnetic wave propagation mechanism of the nerve signals. In this paper, we employ the electromagnetic wave model of the myelinated axon to describe action potential signal propagation. We use the experimental frequency-dependent conductivity and permittivity values of the nerve tissues in order to reliably calculate the electromagnetic modes by using electromagnetic mode solvers. We find that the electromagnetic waves above 10 kHz can be well confined in extracellular fluid–myelin sheath–intracellular fluid waveguide and propagate a distance of 7 mm without much attenuation. Our study may serve as one of the fundamental researches for the better understanding of the nervous system.

关键词： action potential propagation and axons neuronal wave propagation neuroscience electrodynamics in the nervous system

Analytical and finite-element study of optimal strain distribution in various beam shapes for energy harvesting applications

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Acta Mechanica Sinica 2016年第4期32卷 670-683页

作者： B.L.ooi j.M.Gilbert A.Rashid A.Aziz Faculty of Integrative Sciences and Technology Quest International University Perak (QIUP) Faculty of Science and Engineering School of EngineeringUniversity of Hull Center for Automotive Research and Electric Mobility(CAREM) Universiti Teknologi PETRONAS (UTP)

Owing to the increasing demand for harvesting energy from environmental vibration for use in self-powered electronic applications, cantilever-based vibration energy harvesting has attracted considerable interest from various parties and has become one of the most common approaches to converting redundant mechanical energy into electrical energy. As the output voltage produced from a piezoelectric material depends largely on the geometric shape and the size of the beam, there is a need to model and compare the performance of cantilever beams of differing *** paper presents the study of strain distribution in various shapes of cantilever beams, including a convex and concave edge profile elliptical beam that have not yet been discussed in any prior literature. Both analytical and finite-element models are derived and the resultant strain distributions in the beam are computed based on a MATLAB solver and ANSYS finite-element analysis tools. An optimum geometry for a vibration-based energy harvesting system is ***, experimental results comparing the power density for triangular and rectangular piezoelectric beams are also presented to validate the findings of the study, and the claim, as suggested in the literature, is verified.

关键词： harvesting triangular elliptical verified normalized piezoelectric cantilever redundant validate rectangular

Prediction of flow patterns during silo discharges using a finite element approach and its preliminary experimental verification

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Particuology 2015年第1期13卷 42-49页

作者： S.Ding H.Li j.Y.ooi j.M.Rotter Faculty of Science and Engineering University of AgderGrimstadand Tel-TekPorsgrunnNorway School of Material & Mineral Resources Xi'an University of Architecture & Technology Institute for Infrastructure and Environment School of EngineeringUniversity of Edinburgh

Obtaining a reliable discharge of particulate solids from a storage silo is a prerequisite to securing oper- ational adequacy in solids handling processes. If a silo is poorly designed, an unreliable interrupted discharge often occurs. In this study, an in-house finite element （FE） program was modified to predict the particulate solids flow patterns during discharges from silos, and the effect of a double-cone insert on such flow patterns. In FE modeling, a Eulerian approach was adopted with an assumption of steady-state flow-a state that greatly facilitated investigations on the effects of double-cone inserts on the flow of particulate solids. Predictions were carried out on whether the discharge was in mass flow or funnel flow, associated with the inclination angle of the silo＇s hopper. Predicted results were in agreement with the jenike Chart, and proved that an upper lateral pressure ratio value gave a better critical hopper half angle to achieve mass flow （EN 1991-4, 2006）. The shape and size of the stagnant zone were further discussed to address the flow channel boundary between the flowing and static solids if the discharge was in a funnel pattern. Results also showed the effects of a double-cone insert on the flow patterns which con- verted silos from funnel flow to mass flow up to a certain hopper inclination angle and would improve the flow pattern even for shallower angles. Experiments were carried out to verify some of the predicted results. Some qualitative comparisons were made between the predicted results and experimental mea- surements, which indicated that further efforts are needed in predicting the shape of the stagnant zone （flow channel boundary） during funnel flow discharges.

关键词： Discharge pattern Flow boundary Double-cone insert FE analysis Preliminary verification

Mucinous nonneoplastic cyst of the pancreas: A truly novel pathological entity?

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World journal of Gastroenterology 2005年第13期11卷 2045-2047页

作者： Brian k.P.Goh Yu-Meng Tan Puay-Hoon Tan London L.P.j.ooi Department of Surgery Department of Pathology

Recently, a novel and distinct pancreatic cystic tumor termed 'mudnous nonneoplastic' cyst was described in the literature. We report our experience with a 71-year-old female with a cystic tumor in the body of the pancreas demonstrating features suggestive of this diagnosis. We also review the literature regarding this 'novel' pathological entity and discuss critically its existence and its differential diagnoses.

关键词： Pancreatic cyst Mucinous nonneoplastic cyst Mucinous cysts Pancreatic cystic tumors Pancreas Cyst

Do introduced honeybees affect seed set and seed quality in a plant adapted for bird pollination?

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journal of Plant Ecology 2017年第4期10卷 721-729页

作者： Amy-Marie Gilpin justin C.Collette Andrew j.Denham Mark k.j.ooi David j.Ayre Centre for Sustainable Ecosystem Solutions School of Biological SciencesUniversity of WollongongNorthfields AvenueWollongongNSW 2522Australia NSW Department of Premier and Cabinet Office of Environment and HeritagePO Box 1967HurstvilleNSW 2220Australia Centre for Ecosystem Science School of BiologicalEarth and Environmental SciencesUniversity of New South WalesSydneyNSW 2052Australia

Aims Worldwide,evidence suggests that exotic pollinators can disrupt plant mating ***,few studies have determined if pol-lination by the honeybee Apis mellifera(the world’s most widely introduced pollinator)reduces offspring quality when compared with pollination by native *** Australian Proteaceae provides an excellent opportunity to test the impact of honeybees in pol-lination systems that are adapted to birds and non-flying *** We compared the frequency of flower visitation and foraging behav-iour of birds and insects within seven populations of Banksia *** ericifolia is hermaphroditic and has large nectar-rich,orange inflorescences typical of bird and mammal pollinated *** a subset of the study populations,we compared the qual-ity of seed produced via an exclusion treatment(that only allowed invertebrates to access flowers)with an open-pollination treatment(potentially visited by mammals,birds and invertebrates),by meas-uring seed weight,germination rates(T50),percent germination,seedling height after 14 days since the emergence of the cotyledon and time to emergence of the *** Findings Apis mellifera was the only apparent insect pollinator and the most frequent flower visitor,while the open treatment inflorescences were also frequently visited by avian pollinators,primarily hone-yeater *** foraging behaviour of honeybees and honeyeat-ers showed striking differences that potentially affect patterns of pollen *** made significantly greater proportions of within *** plant movements and only 30%(n=48)of honeybees foraged for pollen(nectar foragers carried no pollen)whilst all birds were observed to contact both stigmas and anthers when foraging for *** these fundamental differences in behaviour,there was little effect of treatment on seed set or *** data show that while honeybees appear to alter patterns of pollen transfer within *** popu

关键词： Apis mellifera Banksia ericifolia Proteaceae seedling performance seed vigour

The role of land use on the local climate and air quality during calm inter-monsoon in a tropical city

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Geoscience Frontiers 2019年第2期10卷 405-415页

作者： M.C.G.ooi A.Chan M.j.Ashfold M.Y.Oozeer k.I.Morris S.S.k.kong Department of Atmospheric Science "Central University" Department of Civil Engineering University of Nottingham Malaysia Campus School of Environmental and Geographical Sciences University of Nottingham Malaysia Campus Department of Geography and Environmental Management University of Waterloo Center of Excellence for Sustainable Innovation and Research Initiative (CESIRI) Department of Mechanical Engineering Ashesi University College

The modification of land use is known to be a major climate change driver to the local warming and air quality in cities. Despite the reduction of NOx over the years, the Selangor state has captured a higher level of O_3 in year 2011. The measurement result has shown that the surge in O_3 level was attributed to the reduction of NO_x/NMHC ratio. This paper hence attempted to identify the role of land use change from 1999 to 2011 on the ground ozone air quality in the tropical urban conurbation, Greater kuala Lumpur(GkL), Selangor, Malaysia. With the state-of-the-art chemical weather prediction tool, WRFChem, the external synoptic factors and emission inventory were controlled when comparing the chronological land use changes. The results showed that the urban-induced temperature and wind bias in the tropical region has induced stronger wind to disperse the NO_x and carries the TVOC from the suburban to the downwind urban region. The reduction of NO_x/TVOC has gradually shifted towards the optimum O_3 formation regime in 2011. The formation of highly concentrated ozone becomes more sensitive to the increment of TVOC as the NO_x level reduces in the urban. This highlights the essential involvement of TVOC in the ozone formation in lieu of the NOx reduction in the tropical city, a region with growing emitter of reactive biogenic ozone precursors.

关键词： Land use change Urban Ground ozone TVOC WRF-Chem Tropics

Superhydrophobic PVDF/TiO_2-SiO_2 Membrane with Hierarchical Roughness in Membrane Distillation for Water Recovery from Phenolic Rich Solution Containing Surfactant

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Chinese journal of Polymer Science 2019年第6期37卷 609-616页

作者： N.Hamzah C.P.Leo B.S.ooi School of Chemical Engineering Engineering Campus Universiti Sains Malaysia

Superhydrophobic poly(vinylidene fluoride)(PVDF) membrane incorporated with nanoparticles was applied in membrane distillation to recover water from phenolic rich solution containing surfactant. The membranes coated on woven support were fabricated using phase inversion with dual bath coagulation and post-modified using silane. The membranes incorporated with TiO_2, SiO_2, or a mixture of TiO_2-SiO_2 nanoparticles achieved the water contact angle higher than 160°. The addition of TiO_2-SiO_2 mixture into PVDF matrix further enhanced the hierarchical roughness of membrane. Hence, PVDF/TiO_2-SiO_2 membrane achieved the highest permeation flux and rejected 99.9% of gallic acid in the feed(100 g/L). PVDF/TiO_2-SiO_2 membrane also maintained a relative flux(j/j0) higher than0.9 after 8 h of operation. Even with the presence of surfactant in phenolic rich solution, PVDF/TiO_2-SiO_2 membrane was able to exhibit relative flux above 0.8. The significant changes on the hydrophobicity and chemical properties of PVDF/TiO_2-SiO_2 membrane due to fouling were not observed after 50 h of static adsorption test.

关键词： Superhydrophobic PVDF Nano particles Roughness Membrane distillation

Functionalization of high-moment magnetic nanodisks for cell manipulation and separation

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Nano Research 2013年第10期6卷 745-751页

作者： Mingliang Zhang Christopher M. Earhart Chinchun ooi Robert j. Wilson Mary Tang Shan X. Wang 476 Lomita Mall Department of Materials Science and Engineering Stanford University Stanford 94305 USA 350Serra Mall Department of Electrical Engineering Stanford University Stanford 94305 USA

Synthetic antiferromagnetic （SAF） nanoparticles are layer-structured particles with high single-particle magnetic moments. In order to covalently bind these nanopartides to cells, they were coated with a silica shell followed by conjugation with streptavidin. The silica coating generates both SAF@SiO2 core-shell nano- particles and silica core-free nanopartides. Using a simple magnetic separation, silica nanoparticles were removed and SAF@SiO2 nanoparticles were purified. After streptavidin conjugation, these particles were used to stain lung cancer cells, making them highly magnetically responsive. The stained cells can rotate in response to an external magnetic field and can be captured when a blood sample containing these cells flows through the sifter.

关键词： cell separation core-shell functionalization magnetic properties nanotechnology