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The Effect of Non-Equilibrium Condensation on Supersonic Air Flows over Rectangular Cavities

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Journal of Thermal Science 2007年第1期16卷 33-39页

作者： Miah md. Ashraful ALAM md. mahbubul ALAM Shigeru MATSUO Kenbu TERAMOTO Toshiaki SETOGUCHI Heuy Dong KIM Shen YU Department of Mechanical Engineering Khulna University of Engineering ＆ Technology Khulna-9203 Bangladesh Department of Mechanical Engineering Saga University 1 Honjo-machi Saga-shi Saga 840-8502 Japan School of Mechanical Engineering College of Natural Science Andong National University 388 Song Cheon Dong Andong Kyung Pook Republic of Korea Institute of Engineering Thermophysics Chinese Academy of Sciences EO. Box 2706 Beijing 100080 China

Numerical simulations have been carded out for a supersonic two-dimensional flow over open, rectangular cavities （length-to-depth ratios are L/D = 1.0 and 3.0） in order to investigate the effect of non-equilibrium condensation of moist air on supersonic internal flows around the cavity for the flow Mach number 1.83 at the cavity entrance. In the present computational investigation, a condensing flow was produced by an expansion of moist air in a Laval nozzle. The computational results showed that the upstream traveling compression waves become weaker than those without the condensation. Consequently, the weaker compression waves cannot excite the shear layer strongly and amplitudes of oscillation in the cavity became smaller than those without the condensation. The occurrence of the non-equilibrium condensation in case of L/D = 1.0 affected strongly the amplitude and frequency of oscillation in the cavity compared with L/D = 3.0.

关键词： compressible flow supersonic cavity oscillation non-equilibrium condensation numerical simulation

Neural network reactive force field for C,H,N,and O systems

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npj Computational Materials 2021年第1期7卷 69-78页

作者： Pilsun Yoo Michael Sakano Saaketh Desai md.mahbubul islam Peilin Liao Alejandro Strachan School of Materials Engineering and Birck Nanotechnology Center Purdue UniversityWest LafayetteIN 47907USA Department of Mechanical Engineering Wayne State UniversityDetroitMI 48202USA

Reactive force fields have enabled an atomic level description of a wide range of phenomena,from chemistry at extreme conditions to the operation of electrochemical devices and *** significant insight and semi-quantitative understanding have been drawn from such work,the accuracy of reactive force fields limits quantitative *** developed a neural network reactive force field(NNRF)for CHNO systems to describe the decomposition and reaction of the high-energy nitramine 1,3,5-trinitroperhydro-1,3,5-triazine(RDX).NNRF was trained using energies and forces of a total of 3100 molecules(11,941 geometries)and 15 condensed matter systems(32,973 geometries)obtained from density functional theory calculations with semi-empirical corrections to dispersion *** training set is generated via a semi-automated iterative procedure that enables refinement of the NNRF until a desired accuracy is *** root mean square(RMS)error of NNRF on a testing set of configurations describing the reaction of RDX is one order of magnitude lower than current state of the art potentials.

关键词： network field reactive

Geochemical characteristics of Holocene sediments from Chuadanga district, Bangladesh: Implications for weathering, climate, redox conditions, provenance and tectonic setting

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Chinese Journal Of Geochemistry 2014年第4期33卷 336-350页

作者： Ismail Hossain Krisna Kanta Roy Pradip Kumar Biswas mahbubul Alam md. Moniruzzaman Farah Deeba Department of Geology and Mining University of Rajshahi Bangladesh Institute of Mining Mineralogy and Metallurgy (IMMM) Joypurhat Bangladesh Water Resource Planning Division Institute of Water Modelling (IWM) Dhaka Bangladesh Institute of Nuclear Science and Technology (INST) Atomic Energy Commission Dhaka Bangladesh

The present research deals with the geochemical characteristics of the Holocene sediments from Alamd.nga area, Chuadanga district, Bangladesh. Main goals of the study are to delineate source rock characteristics, degree of chemical weathering and sorting processes and behavior of redox conditions during deposition of the sediments. Geochemical characteristics of the sediments show comparatively a wide variation in accordance with stratigraphy in their major element contents(e.g. Si O2 69.46–82.13, Al2O3 2.28–8.88 in wt%), reflecting the distinctive provenance and in part an unstable period in terms of tectonic activity. Geochemical classification of the sediments shows mostly sub-arkose with few sub-litharenites. Some major and trace elements display comprehensible correlation with Al2O3 confirming their possible hydraulic fractionation. The chemical index of alteration(CIA*), W* index, index of compositional variability(ICV), plagioclase index of alteration(PIA*) values and the ratio of Si O2/Al2O3, suggest low degrees of chemical weathering in the source areas as well as immature to moderately mature the sediments. The sediments suggest semi-arid climatic trends within oxic deltaic depositional conditions during the Holocene, at 3–12 ka. Whole rock geochemistry and discrimination diagrams demonstrate the continental signature derivatives, which might have been derived from the felsic to intermediate igneous rocks(granitic plutonic rocks) as well as from quartzose sedimentary/metamorphic provenance. These typical sources are present in a vast region of the Himalayan belt and catchment areas of Ganges. The tectonic setting of the sediments demarcates typically passive margin with slightly continental arc system.

关键词：地球化学特征氧化还原条件化学风化沉积物构造背景孟加拉国气候趋势全新世

A Computational Investigation on the Control of Cavity-Induced Pressure Oscillations Using Sub-Cavity

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Journal of Thermal Science 2006年第3期15卷 213-219页

作者： md.mahbubul Alam ShigeruMatsuo KenbuTeramoto ToshiakiSetoguchi Heuy-Dong Kim Department of Mechanical Engineering Chittagong University of Engineering and TechnologyChittagong 4349Bangladesh Department of Mechanical Engineering Saga University1Honjo-machiSaga shiSaga 840-8502Japan School of Mechanical Engineering College of Natural ScienceAndong National University388Song Cheon DongAndongKyung PookRepublic of Korea

A computational investigation has been conducted to determine the effectiveness of a passive control technique of attenuating cavity-induced pressure oscillations in a confined two-dimensional supersonic flow. The passive control technique is achieved by fitting two flat plates near the front wall of a square cavity at Mach number 1.83 at the cavity entrance. The results showed that the flat plates attached near the front wall of the cavity, discouraged the formation of feedback loop which is widely believed to be the reason of cavity resonance. The resultant amount of attenuation of pressure oscillations was also dependent on the length of the flat plate used as an oscillation suppressor.

关键词： compressible flow cavity-induced pressure oscillations passive control sub-cavity

Frequency of Uveitis among Juvenile Idiopathic Arthritis Patients in a Tertiary Care Hospital of Bangladesh: A Retrospective Study

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Open Journal of Rheumatology and Autoimmune Diseases 2024年第3期14卷 144-156页

作者： md. Asif Ali Mujammel Haque Kamrul Laila Mohammad Hafiz Al-Mamun Mohammed mahbubul islam Mohammad Imnul islam Manik Kumar Talukder Pediatric Rheumatology Division Department of Pediatrics Bangabandhu Sheikh Mujib Medical University Dhaka Bangladesh

Background: Juvenile idiopathic arthritis (JIA) is the most frequently encountered pediatric rheumatologic disorder with an unknown etiology. At present there is no published data regarding the frequency of uveitis in patients with JIA in Bangladesh. This study aimed to observe the frequency of JIA-associated uveitis (JIAU) and distribution of uveitis among different sub-categories of JIA at the Pediatric Rheumatology division, both outdoor and indoor patients, Department of Pediatrics, Bangabandhu Sheikh Mujib Medical University (BSMMU) in Bangladesh. Methods: This was a retrospective study of 1784 JIA patients at the Pediatric Rheumatology division, BSMMU from July 2010 to March 2023. Results: Among the 1784 enrolled JIA patients, we observed that 0.73% of cases had uveitis. Here, 61.5% of JIAU cases were male. Most of the cases (92.3%) had bilateral uveitis and only 7.7% cases had unilateral uveitis. Among JIAU patients, the majority were Oligo JIA (53.8%), followed by ERA 30.8%, Poly JIA RF(−) 7.7% and Systemic JIA 7.7% cases respectively. This study also revealed that 15.4% of JIAU patients had ANA positivity and 23% had HLA B-27 positivity. Here we also found ocular complications associated with uveitis such as band keratopathy (23.1%), posterior synechiae (15.4%) and cataract (15.4%). Conclusions: In this study, we observed only 0.73% of patients of JIA had developed uveitis which is lower than the frequency observed in other European studies. This study also showed various ocular complications amongst JIA-associated uveitis patients which signifies the importance of adherence to periodic ophthalmological follow-up to prevent these ocular complications.

关键词： JIA Uveitis HLA-B27 ANA BSMMU

Thalidomide Is an Adjunct Therapy for the Refractory Systemic Juvenile Idiopathic Arthritis Patients in a Tertiary Hospital Study

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Open Journal of Rheumatology and Autoimmune Diseases 2023年第2期13卷 51-63页

作者： md. Taiyabur Rahman Mujammel Haque Farhana Faria Mohammed mahbubul islam Manik Kumar Talukder Mohammad Imnul islam Shahana Akhter Rahman Department of Paediatrics Bangabandhu Sheikh Mujib Medical University Dhaka Bangladesh

Background: Systemic JIA (sJIA) is one of the subtypes of JIA, which is most difficult to treat among all JIA cases. About 50% of sJIA cases did not respond to traditional disease modifying anti-rheumatic drugs (DMARDs)—metho-trexate (MTX). Thalidomide is an immunomodulating and anti-inflammatory drug that induces sustained improvement of refractory sJIA cases. Objectives: To evaluate the efficacy of thalidomide in refractory sJIA patients. Methods: This was a prospective interventional study carried out in the Paediatric Rheumatology and Immunology follow-up clinic run by the Department of Pediatrics, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka from January 2019 to July 2020. Twenty-five sJIA patients who were refractory to conventional DMARDs were included in this study. These patients were prescribed thalidomide at a dose of 3 - 5 mg/kg/day for six months and efficacy was assessed by using juvenile arthritis disease activity score (JADAS 27) at 12th and 24th weeks of treatment. Result: Active joint counts and ESR improvement were observed in 90.69%, 97.67% and 69.84%, 100% of sJIA patients respectively at 12th and 24th weeks of treatment. Improvement of physicians and parent global assessment of VAS were 77.56%, 97.43% and 70.62% and 96.04% respectively at 12th and 24th weeks of treatment. Improvement of the total score of JADAS-27 was 77.51% at 12th week and 97.52% at 24th of week follow-up which was statistically significant. Somnolence, constipation and paresthesia were found as common adverse effect in this study. Conclusion: Efficacy of thalidomide was assessed by JADAS 27 criteria showed significant improvement in refractory sJIA patients in this study. It may be concluded that Thalidomide is safe and effective as an adjunct therapy of refractory sJIA patients.

关键词： Juvenile Idiopathic Arthritis Thalidomide Refractory sJIA

GIS-Based Analysis to Identify the Distribution and Accessibility of Urban Green Space in Dhaka Metropolitan City, Bangladesh

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Journal of Geographic Information System 2023年第1期15卷 35-52页

作者： Mohammad Wahidur Khan md. Sazzad Hossain mahbubul Alam Chair of Ecosystem Services Technische Universität Dresden Dresden Germany Chair of Tropical Forestry Technische Universität Dresden Dresden Germany

Urban Green Space (UGS) plays an important role in minimizing the negative effects of urbanization on city dwellers, which is predominantly factored into the accessibility to UGS. This study elucidated the distribution and accessibility of UGS in Dhaka, Bangladesh considering the paucity of such important scientific studies in the given area. The methodological structure of this study employed a multispectral Landsat satellite image from 2020 for identifying the logically defined UGSs, as well as a minimum proxy distance being the parameter to estimate accessibility to the UGS through a primary survey scheme and literature review. Considering UGS as a public area, we adopted a hybrid (combination of supervised and unsupervised classification) method followed by post-classification for UGS distribution assessment. The unsupervised classification identified the overall distribution of green spaces, whereas the anomalies of generated classes were rectified during the post-classification. Following the study findings, UGS in Dhaka metropolitan city accounts for only 602 ha or 1.9% of the total geographical space, with Ramna thana ranked as the highest contributor of 111 ha. However, in terms of accessibility to the UGS by city residents, 19.9% of the buildings in Dhaka metropolitan city were computed to be within the determined proxy distance of 500 m around the UGS. Also, parallel to UGS distribution, green space in Ramna thana (111 ha) exhibited the highest accessibility rate (64%) to the UGS compared with other thanas in Dhaka metropolitan city. The baseline findings will contribute to the long-term sustainable urban planning and development of more accessible green spaces in the study area.

关键词： Urbanization Urban Green Space Accessibility Proxy Distance

The ReaxFF reactive force-field: development, applications and future directions

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npj Computational Materials 2016年第1期2卷 202-215页

作者： Thomas P Senftle Sungwook Hong md.mahbubul islam Sudhir B Kylasa Yuanxia Zheng Yun Kyung Shin Chad Junkermeier Roman Engel-Herbert Michael J Janik Hasan Metin Aktulga Toon Verstraelen Ananth Grama Adri CT van Duin Department of Chemical Engineering Pennsylvania State UniversityUniversity ParkPAUSA Department of Mechanical and Nuclear Engineering Pennsylvania State UniversityUniversity ParkPAUSA Department of Computer Science and Engineering PurdueWest LafayetteINUSA Department of Materials Science and Engineering Pennsylvania State UniversityUniversity ParkPAUSA Department of Computer Science and Engineering Michigan State UniversityEast LansingMIUSA Center for Molecular Modeling(CMM) Ghent UniversityZwijnaardeBelgium

The reactive force-field(ReaxFF)interatomic potential is a powerful computational tool for exploring,developing and optimizing material *** based on the principles of quantum mechanics(QM),while offering valuable theoretical guidance at the electronic level,are often too computationally intense for simulations that consider the full dynamic evolution of a ***,empirical interatomic potentials that are based on classical principles require significantly fewer computational resources,which enables simulations to better describe dynamic processes over longer timeframes and on larger *** methods,however,typically require a predefined connectivity between atoms,precluding simulations that involve reactive *** ReaxFF method was developed to help bridge this *** the gap from the classical side,ReaxFF casts the empirical interatomic potential within a bond-order formalism,thus implicitly describing chemical bonding without expensive QM *** article provides an overview of the development,application,and future directions of the ReaxFF method.

关键词： properties directions bonding

Optical and electrical properties of crystalline indium tin oxide thin film deposited by vacuum evaporation technique

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Optoelectronics Letters 2019年第5期15卷 356-359页

作者： md.Mottaleb Hosen A.K.M.Atique Ullah md.mahbubul Haque S.M.Abdur Rahim K.M.Abdus Sobahan M.N.I.Khan Department of Electrical and Electronic Engineering Islamic University Kushtia 7003 Bangladesh Nanoscience and Technology Research Laboratory Atomic Energy Centre Bangladesh Atomic Energy Commission Dhaka 1000 Bangladesh Analytical Chemistry Laboratory Chemistry Division Atomic Energy Centre Bangladesh Atomic Energy Commission Dhaka 1000 Bangladesh Department of Physics Jagannath University Dhaka 1100 Bangladesh Materials Science Division Atomic Energy Centre Bangladesh Atomic Energy Commission Dhaka 1000 Bangladesh

Indium tin oxide(ITO) thin film was deposited on glass substrate by means of vacuum evaporation technique and annealed at 200 ℃, 300℃ and 400 ℃ in air for 1 h. The characterization and properties of the deposited film samples were analyzed by X-ray diffraction(XRD), scanning electron microscopy(SEM), and UV-VIS-NIR spectroscopy techniques. From the XRD patterns, it was found that the deposited thin film was of crystalline at an annealing temperature of 400℃. The crystalline phase was indexed as cubic structure with lattice constant and crystallite size of 0.511 nm and 40 nm, respectively. The SEM images showed that the films exhibited uniform surface morphology with well-defined spherical grains. The optical transmittance of ITO thin film annealed at 400 ℃ was improved from 44% to 84% in the wavelength range from 250 nm to 2 100 nm and an optical band gap was measured as 3.86 e V. Hall effect measurement was used to measure the resistivity and conductivity of the prepared film.

关键词： Indium tin oxide(ITO) X-ray diffraction(XRD) scanning electron microscopy(SEM)