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Tunable passively Q-switched ytterbium-doped fiber laser with mechanically exfoliated GaSe saturable absorber

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Chinese Optics Letters 2018年第2期16卷 93-97页

作者： h.ahmad S.N.Aidit S.I.Ooi Z.C.Tiu Photonics Research Centre University of Malaya

A tunable passively Q-switched ytterbium-doped fiber laser using few-layer gallium selenide（GaSe） as a saturable absorber（SA） is *** few-layer GaSe SA,which is fabricated by the mechanical exfoliation method,is able to generate a Q-switched fiber laser that has a maximum repetition rate of 92.6 khz and a minimum pulsed width of 2.3 μ*** highest pulse energy exhibited by the generated pulse is 18.8 nJ with a signal to noise ratio of ~40 *** tunability of the proposed laser covers from 1042 to 1082 nm,giving a tuning range of 40 nm.

关键词： Tunable passively Q-switched ytterbium-doped fiber laser with mechanically exfoliated GaSe saturable absorber SA

A review of chemical absorption of carbon dioxide for biogas upgrading

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Chinese Journal of Chemical Engineering 2016年第6期24卷 693-702页

作者： Fouad R.h. Abdeen Maizirwan Mel Mohammed Saedi Jami Sany Izan Ihsan ahmad Faris Ismail Department of Biotechnology Engineering International Islamic University Malaysia Kuala Lumpur 50728 Malaysia Department of Mechanical Engineering International Islamic University Malaysia Kuala Lumpur 50728 Malaysia

Significant attention has been given to biogas production, purification and upgrading as a renewable and clean fuel supplement. Biogas is a product of an anaerobic digestion process comprising methane, carbon dioxide,and trace amounts of other gases. Biogas purification removes trace gases in biogas for safe utilisation. Biogas upgrading produces methane-rich biogas by removing bulk carbon dioxide from the gas mixture. Several carbon dioxide removal techniques can be applied for biogas upgrading. however, chemical absorption of carbon dioxide for biogas upgrading is of special significance due to its operation at ambient or near ambient temperature and pressure, thus reducing energy consumption. This paper reviews the chemical absorption of carbon dioxide using amine scrubbing, caustic solvent scrubbing, and amino acid salt solution scrubbing. Each of these techniques for biogas upgrading is discussed. The paper concludes that an optimised implementation of the chemical absorption techniques for biogas upgrading requires further research.

关键词： Biogas upgrading BiofuelCO2 captureAbsorptionAmine scrubbingCaustic scrubbing

Electronic Band Structure and Optical Parameters of Spinel SnMg_(2)O_(4) by Modified Becke–Johnson Potential

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Chinese Physics Letters 2012年第10期29卷 193-197页

作者： Masood Yousaf M.A.Saeed ahmad Radzi Mat Isa Amiruddin Shaari h.A.Rahnamaye Aliabad Physics Department Faculty of ScienceUniversiti Teknologi MalaysiaSkudai-81310JohorMalaysia Department of Physics Hakim Sabzevari UniversityIran

The electronic band structure and optical parameters of SnMg_(2)O_(4) are investigated by the first-principles technique based on a new potential approximation known as modified Becke–Johnson(mBJ).The direct band gap values by LDA,GGA and EV-GGA are underestimated significantly as compared to mBJ-GGA,which generally provides the results comparable to the experimental ***,the present band gap value(4.85 eV)using mBJ-GGA is greatly enhanced to the previous value by EV-GGA(2.823 eV).The optical parametric quantities(dielectric constant,index of refraction,reflectivity,optical conductivity and absorption coefficient)relying on the band structure are presented and *** first critical point(optical absorption's edge)in SnMg_(2)O_(4) occurs at about 4.85 eV.A strong absorption region is observed,extending between 5.4 eV to 25.0 *** SnMg_(2)O_(4),static dielectric constantε1(0),static refractive index n(0),and the magnitude of the coefficient of reflectivity at zero frequency R(0)are 2.296,1.515 and 0.0419,*** optoelectronic properties indicate that this material can be successfully used in optical devices.

关键词： absorption reflectivity dielectric

Optimal Machine Learning Enabled Intrusion Detection in Cyber-Physical System Environment

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Computers, Materials & Continua 2022年第9期72卷 4691-4707页

作者： Bassam A.Y.Alqaralleh Fahad Aldhaban Esam A.AlQarallehs ahmad h.Al-Omari MIS Department College of Business AdministrationUniversity of Business and TechnologyJeddah21448Saudi Arabia School of Engineering Princess Sumaya University for TechnologyAmman11941Jordan Faculty of Science Computer Science DepartmentNorthern Border UniversityArar91431Saudi Arabia

Cyber-attacks on cyber-physical systems(CPSs)resulted to sensing and actuation misbehavior,severe damage to physical object,and safety *** learning(ML)models have been presented to hinder cyberattacks on the CPS environment;however,the non-existence of labelled data from new attacks makes their detection quite *** Detection System(IDS)is a commonly utilized to detect and classify the existence of intrusions in the CPS environment,which acts as an important part in secure CPS *** developments in deep learning(DL)and explainable artificial intelligence(XAI)stimulate new IDSs to manage cyberattacks with minimum complexity and high *** this aspect,this paper presents an XAI based IDS using feature selection with Dirichlet Variational Autoencoder(XAIIDS-FSDVAE)model for *** proposed model encompasses the design of coyote optimization algorithm(COA)based feature selection(FS)model is derived to select an optimal subset of ***,an intelligent Dirichlet Variational Autoencoder(DVAE)technique is employed for the anomaly detection process in the CPS ***,the parameter optimization of the DVAE takes place using a manta ray foraging optimization(MRFO)model to tune the parameter of the *** order to determine the enhanced intrusion detection efficiency of the XAIIDS-FSDVAE technique,a wide range of simulations take place using the benchmark *** experimental results reported the better performance of the XAIIDSFSDVAE technique over the recent methods in terms of several evaluation parameters.

关键词： Cyber-physical systems explainable artificial intelligence deep learning security intrusion detection metaheuristics

Graphene Oxide-Based Q-Switched Erbium-Doped Fiber Laser

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Chinese Physics Letters 2013年第2期30卷 124-127页

作者： Y.K.Yap N.M.huang S.W.harun h.ahmad Photonics Research Centre Department of PhysicsFaculty of ScienceUniversity of Malaya50603 Kuala LumpurMalaysia Low Dimensional Materials Research Centre Department of PhysicsFaculty of ScienceUniversity of Malaya50603 Kuala LumpurMalaysia Department of Electrical Engineering Faculty of EngineeringUniversity of Malaya50603 Kuala LumpurMalaysia Nanotechnology Research Alliance Universiti Teknologi Malaysia81310 UTMJohore BahruJohor Darul TakzimMalaysia

We demonstrate a pulsed ring erbium-doped fiber laser based on graphene oxide(GO),employing a simplified hummer's method to synthesize the GO via chemical oxidation of graphite flakes at room *** dipping a fiber ferrule end face onto the GO suspension,GO is successfully coated onto the end face,making it a simple saturable absorption device.A stable Q-switched pulsed fiber laser is achieved with a low pump threshold of 9.5 mW at 980 *** pulse repetition rate ranges from 16.0 to 57.0 *** pulse width and the pulse energy are studied and discussed.

关键词： temperature. fiber pulse

Modeling the Dynamics of Tuberculosis with Vaccination,Treatment,and Environmental Impact:Fractional Order Modeling

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Computer Modeling in Engineering & Sciences 2024年第11期141卷 1365-1394页

作者： Muhammad Altaf Khan Mahmoud h.DarAssi Irfan ahmad Noha Mohammad Seyam Ebraheem Alzahrani Faculty of Natural and Agricultural Sciences University of the Free StateBleomfontein9300South Africa Department of Basic Sciences Princess Sumaya University for TechnologyAmman11941Jordan Department of Clinical Laboratory Sciences College of Applied Medical ScienceKing Khalid UniversityAbha62529Saudi Arabia Mathematical Sciences Department College of Applied SciencesUmm Al-Qura UniversityMakkah24381Saudi Arabia Department of Mathematics Faculty of ScienceKing Abdulaziz UniversityP.O.Box 80203Jeddah21589Saudi Arabia

A mathematical model is designed to investigate Tuberculosis(TB)disease under the vaccination,treatment,andenvironmental impact with real ***,we introduce the model formulation in non-integer order derivativeand then,extend the model into fractional order *** fractional system’s existence,uniqueness,andother relevant properties are ***,we study the stability analysis of the equilibrium *** disease-free equilibrium(DFE)D_(0)is locally asymptotically stable(LAS)when R_(v)how the globalasymptotical stability(GAS)of the endemic equilibrium(EE)D*for R_(v)>1 and D_(0)for R_(v)≤*** existenceof bifurcation analysis in the model is investigated,and it is shown the system possesses the forward *** analysis has been performed to determine the sensitive parameters that impact R_(v).Weconsider the real TB statistics from Khyber Pakhtunkhwa in Pakistan and parameterized the *** computedbasic reproduction number obtained using the real cases is R0≈*** numerical results regardingdisease elimination of the sensitive parameters are shown graphically.

关键词： Tuberculosis real data stability analysis parameter estimations discussion

Petrographical and geochemical signatures of Jurassic rocks of Chari Formation, Western India： implications for provenance and tectonic setting

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Acta Geochimica 2016年第2期35卷 184-202页

作者： Shaista Khan A. h. M. ahmad M. Masroor Alam Adnan Quasim Department of Geology Aligarh Muslim University AligarhUP. India Geology Section Civil Engineering Z.H. College of Engineering and Technology Aligarh Muslim UniversityAligarh UP India

members The sandstones of the Ridge and Athleta of Chari Formation （Callovian-Oxfordian） exposed at Jara have been analyzed for their petrographical and geochemical studies. Texturally, these sandstones are medium to coarse grained, poorly to well sorted, sub-an- gular to sub-rounded, and show low to medium sphericity. These sandstones were derived from a mixed provenance including granites, granite-gneisses, low and high-grade metamorphic, and some basic rocks of Aravalli range and Nagarparkar massif. The petrofacies analysis reveals that these sandstones belong to the continental block and recycled orogen tectonic regime. The studied sandstones are modified by paleoclimate, distance of transport, and diagenesis. Mineralogically and geochemically, sandstones are classified as quartzarenite, subarkose, arkose, sublithic arenite, and wacke, respectively. The A-CN-K ternary plot and CIA, CIW, PIA, and ICV values suggest that the similar source rocks suffered moderate to high chemical weathering under a hot-humid climate in an acidic envi- ronment with higher Pco2. Generally good to strong cor- relations between AI2O3 and other oxides in these sediments indicate clay mineral control. The K2O/Na2O versus SiO2 diagram indicates that the studied samples occupy passive margin fields but the SiO2/A12O3 versus K2O/Na20 plot suggests that the Athleta Sandstone and Ridge Sandstone fall within the passive margin field, while Ridge Shale falls within the active continental margin field.

关键词： Petrography Geochemistry Jurassic rocks Chari Formation Kachchh Gujarat

Comprehensive performance analysis and optimization of 1,3-dimethylimidazolylium dimethylphosphate-water binary mixture for a single effect absorption refrigeration system

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Frontiers in Energy 2022年第3期16卷 521-535页

作者： Gorakshnath Takalkar ahmad K.Sleiti Collage of Engineering Qatar UniversityDoha2713Qatar

The energy and exergy analyses of the absorption refrigeration system (ARS) using h2O-[mmim][DMP] mixture were investigated for a wide range of temperature. The equilibrium Dühring (P-T-XIL) and enthalpy (h-T-XIL) of mixture were assessed using the excess Gibbs free non-random two liquid (NRTL) model for a temperature range ??? of 20°C to 140°C and XIL from 0.1 to 0.9. The performance validation of the ARS cycle showed a better coefficient of performance (COP) of 0.834 for h2O-[mmim][DMP] in comparison to Nh3-h2O, h2O-LiBr, h2O-[emim][DMP], and h2O-[emim][BF4]. Further, ARS performances with various operating temperatures of the absorber (Ta), condenser (Tc), generator (Tg), and evaporator (Te) were simulated and optimized for a maximum COP and exergetic COP (ECOP). The effects of Tg from 50°C to 150°C and Ta and Tc from 30°C to 50°C on COP and ECOP, the Xa, Xg, and circulation ratio (CR) of the ARS were evaluated and optimized for Te from 5°C to 15°C. The optimization revealed that Tg needed to achieve a maximum COP which was more than that for a maximum ECOP. Therefore, this investigation provides criteria to select low grade heat source temperature. Most of the series flow of the cases of cooling water from the condenser to the absorber was found to be better than the absorber to the condenser.

关键词： ionic liquid driven absorption cycle h2O-[mmim][DMP] coefficient of performance(COP) exergy analysis thermodynamics mixture property

Numerical Study of Unsteady MhD Flow and Entropy Generation in a Rotating Permeable Channel with Slip and hall Effects

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Communications in Theoretical Physics 2018年第11期69卷 641-650页

作者： Z.h.Khan O.D.Makinde R.ahmad W.A.Khan State Key Laboratory of hydraulics and Mountain River Engineering College of Water Resource & HydropowerSichuan University Key Laboratory of Advanced Reactor Engineering and Safety Ministry of Education Tsinghua University Faculty of Military Science Stellenbosch University School of Mathematics and Physics University of Queensland Faculty of Engineering Sciences GIK Institute of Engineering Sciences and Technology Department of Mechanical Engineering College of Engineering Prince Mohammad Bin Fahd University

This article investigates an unbiased analysis for the unsteady two-dimensional laminar flow of an incompressible, electrically and thermally conducting fluid across the space separated by two infinite rotating permeable *** influence of entropy generation, hall and slip effects are considered within the flow analysis. The problem is modeled based on valid physical arguments and the unsteady system of dimensionless PDEs (partial differential equations) are solved with the help of Finite Difference Scheme. In the presence of pertinent parameters, the precise movement of the flow in terms of velocity, temperature, entropy generation rate, and Bejan numbers are presented graphically, which are parabolic in nature. Streamline profiles are also presented, which exemplify the accurate movement of the flow. The current study is one of the infrequent contributions to the existing literature as previous studies have not attempted to solve the system of high order non-linear PDEs for the unsteady flow with entropy generation and hall effects in a permeable rotating channel. It is expected that the current analysis would provide a platform for solving the system of nonlinear PDEs of the other unexplored models that are associated to the two-dimensional unsteady flow in a rotating channel.

关键词： unsteady flow rotating permeable channel MhD slip hall effects entropy analysis finite difference method