Higher-order and length-scale statistics of velocity and temperature fluctuations in turbulent boundary layer along a heated vertical flat plate

Abedin, Mohammad Zoynal,Tsuji, Toshihiro,Kim, Nae-Hyun Elsevier 2017 The International journal of heat and fluid flow Vol.65 No.-

<P><B>Abstract</B></P> <P>Time-developing direct numerical simulation (DNS) was performed to clarify the higher-order turbulent behaviors in the thermally-driven boundary layers both in air and water along a heated vertical flat plate. The predicted statistics of the heat transfer rates and the higher-order turbulent behaviors such as skewness factors, flatness factors and spatial correlation coefficients of the velocity and temperature fluctuations in the natural-convection boundary layer correspond well with those obtained from experiments for space-developing flows. The numerical results reveal that the turbulent structures of the buoyancy-driven boundary layers are mainly controlled by the fluid motions in the outer region of the boundary layer, and these large-scale structures are strongly connected with the generation of turbulence in the thermally-driven boundary layers, in accordance with the actual observations for space-developing flows. Moreover, to specify the turbulence structures of the boundary layers, the cross-correlation coefficients and the characteristic length scales are examined for the velocity and thermal fields. Consequently, it is found that with a slight increase in freestream velocity, the cross-correlation coefficient for the Reynolds shear stress and turbulent heat flux increases for opposing flow and decreases for aiding flow, and the integral scales for the velocity and temperature fields become larger for opposing flow and smaller for aiding flow compared with those for the pure natural-convection boundary layer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Temporal DNS is done for thermally-driven boundary layer along a heated vertical flat plate. </LI> <LI> Turbulent structures are mainly controlled by fluid motions in the outer boundary layer. </LI> <LI> Large-scale structures are strongly connected with the generation of turbulence in the boundary layer. </LI> <LI> Cross-correlation coefficient for velocity and temperature fluctuations increases for opposing flow and decreases for aiding flow compared with the natural-convection boundary layer. </LI> <LI> Integral scales for velocity and temperature fields become larger for opposing flow and smaller for aiding flow compared with the natural-convection boundary layer. </LI> </UL> </P>

Evaluation of Submergence Tolerance in Landrace Rice Cultivars by Various Growth and Yield Parameters

Hasanul Abedin,Abdullah -Al Mamun,Abdul Baset Mia,Abdul Karim 한국작물학회 2019 Journal of crop science and biotechnology Vol.22 No.4

Flash flood causes a serious damage to rice crops in northern and eastern parts of Bangladesh almost every year. This study was designed to identify useful agronomic parameters for evaluation of submergence tolerance and to evaluate genotypes by multiple agronomic parameters for submergence tolerance at different growth stages. Twenty-one aman rice genotypes were tested against three submergence treatments viz. (i) no submergence or control, (ii) submerge at 10 days after transplanting (DAT), and (iii) submerge at 30 DAT. The experiment was laid out in a split plot design with three replications. The plants were completely submerged in the tanks for 14 days. Dry matter production, growth, yield, and yield components of rice were significantly reduced due to interaction effect of genotypes × submergence. Submergence at the early stage of growth (10 DAT) was more detrimental to plant growth than what happened at later stages (30 DAT). Wide genotypic differences in relative submergence tolerance based on grain and tiller numbers were identified. Grains and tiller numbers contributed most of the variation to seed yield among parameters investigated. When genotypes were ranked for submergence tolerance based on the means of multiple parameters, dramatic changes of submergence tolerance at early and later stages were observed in four genotypes; BRRI dhan33, Lalchikon, Achin and Sadamota were identified with a favorable combination of submergence tolerance. Cluster group ranking of genotypes based on multiple agronomic characters can be applied in submergence tolerance breeding to evaluate submergence tolerance and may have great advantage over conventional methods.

Liquid-phase Dehydration of 1-Phenylethanol to Styrene over an Acidic Resin Catalyst

Nazmul Abedin Khan,Jin-Soo Hwang,정성화 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.4

Dehydration of 1-phenylethanol to produce styrene has been studied in liquid phase with three solid acid catalysts such as H-ZSM-5, H-Y and Amberlyst-15. Amberlyst-15 shows the highest conversion and styrene yield, suggesting the applicability of a resin catalyst in the dehydration. The good performance of the Amberlyst-15 may be due to high acid concentration and ready diffusion of reactants and products. A possible reaction scheme (such as the formation of styrene from diphenylethylether) has also been suggested.

Root Development and Anti-Oxidative Response of Rice Genotypes under Polyethylene Glycol Induced Osmotic Stress

Juthy Abedin Nupur,Afsana Hannan,Md. Abir Ul Islam,G H M Sagor,Arif Hasan Khan Robin 한국육종학회 2020 Plant Breeding and Biotechnology Vol.8 No.2

Osmotic stress is a kind of stress which is directly or indirectly related to all other abiotic stresses. Four rice varietiesnamely Binadhan-11 (with SUB1 gene), BRRI dhan52 (with SUB1 gene), Binadhan-7 and BRRI dhan71 were used to study thevariation in root development and anti-oxidative response under osmotic stress conditions. Osmotic stress was induced by applyingpolyethylene glycol (4% PEG) in hydroponic solution. Treatment was given at the panicle initiation stage and leaf samples werecollected at fourteen days after treatment to estimate antioxidant response in terms of ascorbate (APX) and peroxidase (POD) enzymaticactivity. Roots were destructively harvested at 16 days after the stress imposition. The tested varieties showed significant differences inantioxidant responses under the stress condition such as high APX and POD in Binadhan-11 and BRRI dhan52. Significant injury at the4thleaf position (the youngest leaf was the reference) was observed at 8 and 12 days after the treatment. Number of live leaves, shootdry weight, density of second order lateral roots, number of phytomer (Pr) and total roots, number of roots at Pr2, main axis diameterat Pr1, main axis length at Pr1 varied significantly among the varieties × treatment combinations. Binadhan-11 and BRRI dhan52showed comparatively higher osmotic stress tolerance compared to the other two varieties without SUB1 gene, viz., Binadhan-7 andBRRI dhan71. The varieties BRRI dhan52, and Binadhan-11 showed greater capacity to withstand osmotic stress can be further used todevelop stress tolerant variety.

Facile Syntheses of Metal-organic Framework Cu3(BTC)2(H2O)3 under Ultrasound

Nazmul Abedin Khan,정성화 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.12

Cu-BTC[Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzenetricarboxylate], one of the most well-known metal-organic framework materials (MOF), has been synthesized under atmospheric pressure and room temperature by using ultrasound. The Cu-BTC can be obtained in 1 min in the presence of DMF (N,N-dimethylformamide), suggesting the possibility of continuous production of Cu-BTC. Moreover, the surface area and pore volume show that the concentration of DMF is important for the synthesis of Cu-BTC having high porosity. The morphology and phase also depend on the concentration of DMF : Cu-BTC cannot be obtained at room temperature in the absence of DMF and aggregated Cu-BTC (with low surface area) is produced in the presence of high concentration of DMF. It seems that the deprotonation of benzenetricarboxylic acid by base (such as DMF) is inevitable for the room temperature syntheses.

A Cooperative Game based Spatial Correlation-aware Resource Allocation for Narrowband Internet of Things

Sarder Fakhrul Abedin,Anupam Kumar Bairagi,Shirajum Munir,Choong Seon Hong 한국정보과학회 2018 한국정보과학회 학술발표논문집 Vol.2018 No.6

Scandium-Triflate/Metal–Organic Frameworks: Remarkable Adsorbents for Desulfurization and Denitrogenation

Khan, Nazmul Abedin,Jhung, Sung Hwa American Chemical Society 2015 Inorganic Chemistry Vol.54 No.23

<P>Scandium-triflate (Sc(OTF)(3)) was introduced for the first time on metal organic frameworks (MOFs), to utilize acidic Sc(OTF)(3) for adsorptive desulfurization and denitrogenation of fuel containing benzothiophene (BT), dibenzothiophene (DBT), quinoline (QUI), and indole (IND). A remarkable improvement in the adsorption capacity (about 65% based on the weight of adsorbents; 90% based on the surface area of the adsorbents) was observed with the Sc(OTf)(3)/MOFs as compared to the virgin MOFs for the adsorption of BT from liquid fuel. The basic QUI was also adsorbed preferentially onto the acidic Sc(OTf)(3)/MOFs. However, nonsupported Sc(OTf)(3) showed negligible adsorption capacities. The improved adsorptive performance for BT, DBT, and QUI might be derived from acid base interactions between the acidic Sc(OTf)(3), and basic adsorbates. On the other hand, the Sc(OTf)(3), loaded on MOFs, reduced the adsorption capacity for neutral IND due to lack of interaction between the neutral adsorbate and acidic adsorbent and the reduced porosities of the modified adsorbents. The reusability of the adsorbents was found satisfactory up to the fourth run. On the basis of the result, it is suggested that metal-triflates, such as Sc(OTf)(3), can be prospective materials for adsorptive desulfurization/denitrogenation of fuels when supported on porous materials such as MOFs.</P>

A Reinforcement Learning-based Energy Efficient Trajectory and Communication Optimization for UAV-assisted 5G Network

Sarder Fakhrul Abedin,Md. Shirajum Munir,Ashis Talukder,Choong Seon Hong 한국정보과학회 2019 한국정보과학회 학술발표논문집 Vol.2019 No.12

Liquid-phase Dehydration of 1-Phenylethanol to Styrene over an Acidic Resin Catalyst

Khan, Nazmul Abedin,Hwang, Jin-Soo,Jhung, Sung-Hwa Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.4

Dehydration of 1-phenylethanol to produce styrene has been studied in liquid phase with three solid acid catalysts such as H-ZSM-5, H-Y and Amberlyst-15. Amberlyst-15 shows the highest conversion and styrene yield, suggesting the applicability of a resin catalyst in the dehydration. The good performance of the Amberlyst-15 may be due to high acid concentration and ready diffusion of reactants and products. A possible reaction scheme (such as the formation of styrene from diphenylethylether) has also been suggested.

Remarkable adsorptive performance of a metal–organic framework, vanadium-benzenedicarboxylate (MIL-47), for benzothiophene

Khan, Nazmul Abedin,Jun, Jong Won,Jeong, Jong Hwa,Jhung, Sung Hwa Royal Society of Chemistry 2011 Chemical communications Vol.47 No.4

<P>Liquid-phase adsorption of benzothiophene over isotypic MOFs such as MIL-47 and MIL-53(Al, Cr) has shown that a metal ion of a MOF-type material has a dominant role in adsorptive desulfurization and MIL-47 has a remarkable performance.</P> <P>Graphic Abstract</P><P>A MOF (V-BDC) shows remarkable performance in adsorptive desulfurization, suggesting the importance of a specific adsorption site like an acidic site. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0cc04759g'> </P>