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Dispersion of Titanium（Ⅳ） Oxide Nanoparticles in Mixed Matrix Membrane Using Octaisobutyl Polyhedral Oligomeric Silsesquioxane for Enhanced CO2/CH4 Separation Performance

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Chinese Journal of Polymer Science 2019年第7期37卷 654-663页

作者： Grace Ying En Tan Pei Ching Oh kok keong lau Siew Chun Low CO2 Research Centre (CO2RES) Institute of Contaminant ManagementChemical Engineering DepartmentUniversiti Teknologi PETRONAS32610 Seri IskandarPerakMalaysia School of Chemical Engineering Engineering CampusUniversiti Sains Malaysia14300 Nibong TebalPenangMalaysia

Titanium(IV) oxide (TiO2) nanoparticles have been incorporated into mixed matrix membranes (MMMs) to improve gas separation performance. However, TiO2 nanoparticles tend to agglomerate due to high surface energy and van der Waals forces. This leads to precipitation which causes the formation of non-homogeneous MMM morphology. In this study, the effect of octaisobutyl polyhedral oligomeric silsesquioxane (POSS) addition on TiO2/polysulfone MMM was investigated. The aims are to enhance gas separation performance whilst preventing agglomeration of TiO2 nanoparticles. The results demonstrated that inclusion of POSS as dispersant increases MMMs’ CO2/CH4 selectivity and permeance, possibly due to less void formation and more evenly distributed pore structure. For example, synergistic addition of 5 wt% TiO2 and 5 wt% POSS increased the CO2/CH4 selectivity up to 390% compared to MMM without POSS. This is supported by elemental mapping of titanium which revealed that POSS successfully dispersed TiO2 nanoparticles and prevented aggregation. TiO2-POSS/PSf MMMs also retained their favorable thermal stability.

关键词： Applications Membranes Nanoparticles Separation techniques Thermogravimetric analysis (TGA)

Kinetic Adsorption of CO2/CH4 Mixture Using 13X Zeolite： Modeling and Simulation

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Journal of Chemistry and Chemical Engineering 2010年第7期4卷 46-51页

作者： Salma Awad Nouh kok keong lau Azmi Bin Mohd Shariff Department of Chemical Engineering Universiti Teknologi PETRONAS Bandar Seri Iskandar Tronoh 31750 Perak Malaysia

In this work, the separation of carbon dioxide （CO2） from （PSA） column was modeled and simulated. The adsorption kinetics the methane （CH4） using fixed bed Pressure Swing Adsorption on the 13X zeolite adsorbent was described by Linear Driving Force （LDF） model. Simulation of adsorption phenomena inside the fixed bed was implemented using Computational Fluid Dynamic （CFD） method, based on porous media concept, and the mass transfer coefficients for gas components （COz and CH4） were developed using User Defined Scalars （UDS）. The model was validated by comparing with the experimental data, which were collected based on a varied set of laboratory conditions. The prediction of the adsorption isotherm （uptake curve） and methane recovery using the simulation results exhibited a reasonable agreement with the experimental data. Moreover, the effects of feed flow rate and bed concentration evolution were investigated. The current results suggested that CFD approach is capable to predicate the hydrodynamics and adsorption phenomena in the fixed bed adsorption column.

关键词： Computational Fluid Dynamics (CFD) LDF model PSA simulation.

Material characterization and inter/intra-particle validation for DEM simulation of urea coating process

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Particuology 2024年第5期88卷 32-48页

作者： Salma A.Nouh KuZilati KuShaari lau kok keong Shafirah Samsuri Chemical Engineering Department Universiti Teknologi PETRONAS32610 Seri IskandarPerak Darul RidzuanMalaysia

Particle coating is a common operation in the controlled-release fertilizer (CRF) industry,where a coating layer is appliedto the urea cores.A discrete element method (DEM) computer simulation was applied to model the coating process for the urea granules using measured model *** accuracy of DEM input parameters for the coating material properties and the physical and mechanical characterizations of urea granules are crucial to the study of particle coating ***,to enhance the simulation accuracy,information on the material properties (urea granules) is *** this study,the elasticity parameters,shear modulus ,coefficient of restitution (CoR),and coefficient of rolling and static friction (CoRF) and (CoSF) of urea granules are estimated experimentally in addition to the physical *** sensitivity of the angle of repose of the urea bed was investigated at different coefficients of *** to the obtained experimental value of the angle of repose,values of 0.2 and 0.3 for CoRF and CoSF,respectively,were adjusted to obtain consistent urea granules’ motion for simulation and the ***,the spray droplet sizes and velocity distributions were estimated using the video-imaging process *** on this experimental characterization,elasticity parameters and spray properties were integrated into DEM simulation software as input data to perform numerical analysis of the coating process to compare simulation and experimental results,which show uniformity at three different pan speeds with a maximum deviation of 0.033 at 5 ***,consistency between DEM and experiment results was achieved in terms of average coating thickness (μm) of the selected samples and average intra-particle thickness variation ( CoV intra ).These results revealed that the coating film thickness is proportional to the rotation speed for the experiment and *** enhance the inter-particle coating uniformity,the effects of the

关键词： Contact model Discrete element method Urea fertilizer Coating process

AI-Assisted approach for building energy and carbon footprint modeling

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Energy and AI 2021年第3期5卷 201-208页

作者： Chih-Yen Chen kok keong Chai Ethan lau School of Electronic Engineering and Computer Science Queen Mary University of LondonUnited Kingdom

This paper proposes an energy and carbon footprint modelling using artificial intelligence technique to assess the impact of occupant density for various types of office *** use EnergyPlus to simulate energy con-sumption,and then estimate the related CO₂emissions based on three years(2016–2018)of Actual Meteoro-logical Year(AMY)weather *** occupant densities were used to evaluate the annual energy consumption and CO₂*** this work,a robust deep learning technique of long short-term memory(LSTM)model was established to predict the time-series energy consumption and CO₂emissions.A power exponential curve was suggested to correlate the behaviour of annual energy and CO₂emission for occupant densities range from 10 to 100 m2/person for each office building *** results of LSTM model show high prediction performance and small variations within the three types of office building data,which can be applied to the similar building model to predict and optimise energy consumption and CO₂emission.

关键词： Building energy simulation and benchmarking Carbon footprint Occupant density Artificial intelligence Long short-term memory(LSTM) Smart city

Digitalized Mirror Array and Its Application in Large Telescope:Principle and Case Studies

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Communications in Theoretical Physics 2009年第10期52卷 750-760页

作者： CHEN Ying-Tian ZHANG Yang HU Sen Ho Tso-Hsiu Boon Ham Lim Chen Sin Lim kok keong Chong Boon kok Tan University of Science and Technology of China Department of Astronomy and Applied Physics Hefei 230026 China University of Science and Technology of China Department of Mathematics Hefei 230026 China Institute of Theoretical Physics Chinese Academy of Sciences Beijing 100190 China University of Tunku Abdul Rahman Faculty of Engineering and Science Selangor Malaysia

In this article, we report the principle and conceptual design of a fundamentally different technology in fabricating high precision aberration free optical devices. The tip-tilt of facet in a mirror array is produced by digitally controlled line-tilts of rows and columns. It has not only provided a cost-effective designing methodology in optical physics but also led to a much finer precision of 1 mili arc sec or less. As examples of the application of the proposed digitalised optics, two case studies have been given： a 10 m Schmidt telescope （off-axis） and an 8 m Cassegrain telescope （on-axis）.

关键词： tip-tilting line-tilting Schmidt telescope aberration correction cassegrain telescope

User cooperation for IRS-aided secure MIMO systems

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Intelligent and Converged Networks 2022年第1期3卷 86-102页

作者： Gui Zhou Cunhua Pan Hong Ren Kezhi Wang kok keong Chai Kai-Kit Wong School of Electronic Engineering and Computer Science Queen Mary University of LondonLondonE14NSUK. the National Mobile Communications Research Laboratory Southeast UniversityNanjing 210096China. Department of Computer and Information Sciences Northumbria UniversityNewcastle upon TyneNE18STUK. Department of Electronic and Electrical Engineering University College LondonLondonWC1E 6BTUK.

An intelligent reflecting surface(IRS)is proposed to enhance the physical layer security in the Rician fading channel wherein the angular direction of the eavesdropper(ED)is aligned with a legitimate user.A two-phase communication system under active attacks and passive eavesdropping is considered in this *** base station avoids direct transmission to the attacked user in the first phase,whereas other users cooperate in forwarding signals to the attacked user in the second phase,with the help of IRS and energy harvesting *** the occurrence of active attacks,an outage-constrained beamforming design problem is investigated under the statistical cascaded channel error model,which is solved by using the Bernstein-type *** average secrecy rate maximization problem for the passive eavesdropping is formulated,which is then addressed by a low-complexity *** numerical results of this study reveal that the negative effect of the ED’s channel error is larger than that of the legitimate user.

关键词： intelligent reflecting surface(IRS) reconfigurable intelligent surface(RIS) robust design energy harvesting physical layer security

Growth and photosynthesis of Chlorella strains from polar,temperate and tropical freshwater environments under temperature stress

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Journal of Oceanology and Limnology 2018年第4期36卷 1266-1279页

作者： kok-keong LEE Phaik-Eem LIM Sze-Wan POONG Chiew-Yen WONG Siew-Moi PHANG John BEARDALL Institute of Ocean and Earth Sciences University of Malaya Institute of Graduate Studies University of Malaya School of Health Sciences International Medical University National Antarctic Research Centre University of Malaya Institute of Biological Sciences University of Malaya School of Biological Sciences Monash University

Elevated temperatures as a consequence of global warming have significant impacts on the adaptation and survival of microalgae which are important primary producers in many ecosystems. The impact of temperature on the photosynthesis of microalgae is of great interest as the primary production of algal biomass is strongly dependent on the photosynthetic rates in a dynamic environment. Here, we examine the effects of elevated temperature on Chlorella strains originating from different latitudes, namely Antarctic, Arctic, temperate and tropical regions. Chlorophyll fluorescence was used to assess the photosynthetic responses of the microalgae. Rapid light curves(RLCs) and maximum quantum yield( F_v/F_m) were recorded. The results showed that Chlorella originating from different latitudes portrayed different growth trends and photosynthetic performance. The Chlorella genus is eurythermal, with a broad temperature tolerance range, but with strain-specific characteristics. However, there was a large overlap between the tolerance range of the four strains due to their "eurythermal adaptivity". Changes in the photosynthetic parameters indicated temperature stress. The ability of the four strains to reactivate photosynthesis after inhibition of photosynthesis under high temperatures was also studied. The Chlorella strains were shown to recover in terms of photosynthesis and growth(measured as Chl a) when they were returned to their ambient temperatures. Polar strains showed faster recovery in their optimal temperature compared to that under the ambient temperature from which they were isolated.

关键词： Antarctic Arctic Fv/Fm microalgae pigments recovery

COSMO-RS: An ionic liquid prescreening tool for gas hydrate mitigation

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Chinese Journal of Chemical Engineering 2016年第11期24卷 1619-1624页

作者： Cornelius B.Bavoh Bhajan Lal Omar Nashed Muhammad S.Khan lau K.keong Mohd.Azmi Bustam Chemical Engineering Department Universiti Teknologi PETRONAS

Recently ionic liquids(ILs) are introduced as novel dual function gas hydrate inhibitors. However, no desired gas hydrate inhibition has been reported due to poor IL selection and/or tuning method. Trial & error as well as selection based on existing literature are the methods currently employed for selecting and/or tuning ILs. These methods are probabilistic, time consuming, expensive and may not result in selecting high performance ILs for gas hydrate mitigation. In this work, COSMO-RS is considered as a prescreening tool of ILs for gas hydrate mitigation by predicting the hydrogen bonding energies(E_(HB)) of studied IL inhibitors and comparing the predicted E_(HB) to the depression temperature(?) and induction time. Results show that, predicted EHBand chain length of ILs strongly relate and significantly affect the gas hydrate inhibition depression temperature but correlate moderately(R = 0.70) with average induction time in literature. It is deduced from the results that, ? increases with increasing IL EHBand/or decreases with increasing chain length. However, the cation–anion pairing of ILs also affects IL gas hydrate inhibition performance. Furthermore, a visual and better understanding of IL/water behavior for gas hydrate inhibition in terms of hydrogen bond donor and acceptor interaction analysis is also presented by determining the sigma profile and sigma potential of studied IL cations and anions used for gas hydrate mitigation for easy IL selection.

关键词： Gas hydrates COSMO-RS Hydrogen bonding energies Ionic liquids Tuning

CFD Simulation of Particles Mixing and Segregation in a Rotary Coating Disk: Influence of Drag Models and Restitution Coefficient

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Open Journal of Applied Sciences 2022年第3期12卷 267-283页

作者： Salma Awad Nouh Ku Zilati Bt Ku Shaari lau kok keong Shafirah Bt Samsuri Tigabwa Yosef Ahmed Department of Chemical Engineering Universiti Teknologi PETRONAS Seri Iskandar Malaysia

In this paper, the dynamics of a transverse plane of a rotary coating disk of a binary mixture system comprising sand and urea particles were simulated using the two-fluid model along with the kinetic theory of granular flow in Fluent 19.1. Although some parameters relating to the material properties and size of the rotary coating disk have been researched, the effects of both drag force and restitution coefficient on the flow characteristics have yet to be examined. Thus, this paper numerically examines the effect of the inclusion of drag models and particle-particle restitution coefficients on particle dynamics in a rotary disk operating in the rolling regime of the granular bed. Three particle-particle drag models were considered: the Schiller-Naumann, Syamlal-O’Brien, and Gidaspow. The Syamlal-O’Brien and Gidaspow models were both able to successfully simulate particle segregation in a perfect rolling regime, whereas the Schiller-Naumann drag model appeared to be unable to predict the segregation of the particles and the rolling flow regime under the assumed conditions. Four different values of the restitution coefficient were also investigated: 0.7, 0.8, 0.9, and 0.95. The higher restitution values of 0.9 and 0.95 were found to substantially affect flow characteristics, ensuring suitable rolling regime behaviour for the bed during the rotational movement. The lower restitution coefficients of 0.7 and 0.8, on the other hand, indicated that irregular velocity vectors could be obtained in the active region of the granular bed.

关键词： Rolling Mode Drag Model Restitution Coefficient CFD