Monitoring Mangrove Plantation along the Coastal Belts of Bangladesh (1989-2010)

Rahman, M. Mahmudur,Pramanik, Md. Abu Taleb Institute of Forest Science 2015 Journal of Forest Science Vol.31 No.3

Mangroves are important coastal ecosystems and are located at the inter-tidal zones of tropical and sub-tropical belts. The global mangrove forests are declining dramatically because of the conversion of forests to shrimp farming, over-exploitation, pollution and freshwater diversion. The Bangladesh Forest Department initiated mangrove afforestation throughout the coastal belts of Bangladesh in 1966 to provide better protection for the coastal communities. Up to 1990, 120,000 ha of mangroves had been planted and it is one of the largest coastal afforestaton programs in the world. The objective of this study is to exploit the spatial extent of mangrove plantation and their dynamics of changes over the last two decades using multispectral Landsat imagery. The study area covers the coastal areas of Bangladesh that is extended over the eastern part of Sundarbans up to Teknaf, the southern tip of mainland Bangladesh. Mangrove plantations were interpreted visually on computer screen and interactive delineation of forest boundary was done. The mangrove plantation area has been estimated as 32,725, 47,636 and 43,166 ha for the year of 1989, 2000 and 2010, respectively. Mangrove deforestation by human activity has increased almost six times in the recent decade in comparison to the previous one. The mangrove forest loss due to coastal erosion has slightly declined in the 2000s. Mangroves have been lost primarily because of agricultural expansion. The result of this investigation will be helpful to understand the dynamics of mangrove plantation and the main drivers of changes in this coastal ecosystem.

Probabilistic Strength at Serviceability Limit State for Normal and SBHS Slender Stiff ened Plates Under Uniaxial Compression

Mahmudur Rahman,Yoshiaki Okui,Muhammad Atif Anwer 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.4

Stiff ened plates with high slenderness parameters show large out-of-plane defl ections, due to elastic buckling, which may occur before the plates reach their ultimate strength. From a serviceability point of view, restriction of out-of-plane defl ections exceeding the fabrication tolerance is of primary importance. Compressive strength at the serviceability limit state (SLS) for slender stiff ened plates under uniaxial stress was investigated through nonlinear elasto-plastic fi nite element analysis, considering both geometric and material nonlinearity. Both normal and high-performance steel were considered in the study. The SLS was defi ned based on a defl ection limit and an elastic buckling strength. Probabilistic distributions of the SLS strengths were obtained through Monte Carlo simulations, in association with the response surface method. On the basis of the obtained statistical distributions, partial safety factors were proposed for SLS. Comparisons with the ultimate strength of diff erent design codes e.g. Japanese Code, AASHTO, and Canadian Code indicate that AASHTO and Canadian Code provide signifi cantly conservative design, while Japanese Code matches well with a 5% non-exceedance probability for compressive strength at SLS.

Effect of Sn Doping on the Thermoelectric Properties of P-Type Mg₃Sb₂ Synthesized by Controlled Melting, Pulverizing Followed by Vacuum Hot Pressing

Rahman, Md. Mahmudur,Kim, Il-Ho,Ur, Soon-Chul Materials Research Society of Korea 2022 한국재료학회지 Vol.32 No.3

Zintl phase Mg₃Sb₂ is a promising thermoelectric material in medium to high temperature range due to its low band gap energy and characteristic electron-crystal phonon-glass behavior. P-type Mg₃Sb₂ has conventionally exhibited lower thermoelectric properties compared to its n-type counterparts, which have poor electrical conductivity. To address these problems, a small amount of Sn doping was considered in this alloy system. P-type Mg₃Sb₂ was synthesized by controlled melting, pulverizing, and subsequent vacuum hot pressing (VHP) method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate phases and microstructure development during the process. Single phase Mg₃Sb₂ was successfully formed when 16 at.% of Mg was excessively added to the system. Nominal compositions of Mg_3.8Sb_2-xSn_x (0 ≤ x ≤ 0.008) were considered in this study. Thermoelectric properties were evaluated in terms of Seebeck coefficient, electrical conductivity, and thermal conductivity. A peak ZT value ≈ 0.32 was found for the specimen Mg_3.8Sb_1.994Sn_0.006 at 873 K, showing an improved ZT value compared to intrinsic one. Transport properties were also evaluated and discussed.

Improvement of Thermoelectric Properties in Te-Doped Zintl Phase Magnesium-Antimonide

Rahman, Md. Mahmudur,Ur, Soon-Chul Materials Research Society of Korea 2021 한국재료학회지 Vol.31 No.8

Zintl compound Mg₃Sb₂ is a promising candidate for efficient thermoelectric material due to its small band gap energy and characteristic electron-crystal phonon-glass behavior. Furthermore, this compound enables fine tuning of carrier concentration via chemical doping for optimizing thermoelectric performance. In this study, nominal compositions of Mg_3.8Sb_2-xTe_x (0 ≤ x ≤ 0.03) are synthesized through controlled melting and subsequent vacuum hot pressing method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are carried out to investigate phase development and surface morphology during the process. It should be noted that 16 at. % of excessive Mg must be added to the system to compensate for the loss of Mg during melting process. Herein, thermoelectric properties such as Seebeck coefficient, electrical conductivity, and thermal conductivity are evaluated from low to high temperature regimes. The results show that Te substitution at Sb sites effectively tunes the majority carriers from holes to electrons, resulting in a transition from p to n-type. At 873 K, a peak ZT value of 0.27 is found for the specimen Mg_3.8Sb_1.99Te_0.01, indicating an improved ZT value over the intrinsic value.

Effect of Excessive Antimony on the Thermoelectric and Transport Properties of Mg3Sb2 Synthesized by Controlled Melting, Pulverizing Followed by Vacuum Hot Pressing

Md. Mahmudur Rahman,A. K. M. Ashiquzzaman Shawon,Soon‑Chul Ur 대한금속·재료학회 2021 ELECTRONIC MATERIALS LETTERS Vol.17 No.1

Zintl compounds were recognized as very good thermoelectric candidate due to their characteristics electron-crystal phononglassproperties. Mg3Sb2is a known Group II–V Zintl semiconductor. This compound is a well-established thermoelectricmaterial and many of recent works focus on this compound due to its intrinsic low thermal conductivity. The band gap ofthis compound has been shown to be optimum, making it a promising thermoelectric material. This work introduces a newsynthetic method and analyzes the thermoelectric properties found using this method. The single phase of Mg3Sb2wassynthesized by melting elemental shots at 1173 K for 1 hour in a controlled inert Ar gas atmosphere in a tapped graphitecrucible followed by vacuum hot pressing at 873 K for 4 hours. X-ray diffraction and scanning electron microscopy werecarried out to investigate existing phases and surface morphology respectively. Thermoelectric properties in terms of Seebeckcoefficient, electrical conductivity, and thermal conductivity were evaluated and the results are discussed in comparison toanalogous studies. Transport properties were also evaluated and discussed. Single phase magnesium antimonide was foundwith a nominal formula of Mg3.8Sb2and showed a comparable ZT value which is ~ 0.24 at 873 K.

Optimized Thermoelectric Properties in Zn-doped Zintl Phase Magnesium-Antimonide

Md Mahmudur Rahman,어순철 한국재료학회 2022 한국재료학회지 Vol.32 No.6

Magnesium-antimonide is a well-known zintl phase thermoelectric material with low band gap energy, earthabundance and characteristic electron-crystal phonon-glass properties. The nominal composition Mg3.8-xZnxSb2 (0.00 ≤ x ≤ 0.02) was synthesized by controlled melting and subsequent vacuum hot pressing method. To investigate phase development and surface morphology during the process, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were carried out. It should be noted that an additional 16 at. % Mg must be added to the system to compensate for Mg loss during the melting process. This study evaluated the thermoelectric properties of the material in terms of Seebeck coefficient, electrical conductivity and thermal conductivity from the low to high temperature regime. The results demonstrated that substituting Zn at Mg sites increased electrical conductivity without significantly affecting the Seebeck coefficient. The maximal dimensionless figure of merit achieved was 0.30 for x = 0.01 at 855 K which is 30% greater than the intrinsic value. Electronic flow properties were also evaluated and discussed to explain the carrier transport mechanism involved in the thermoelectric properties of this alloy system.

Monitoring Mangrove Plantation along the Coastal Belts of Bangladesh (1989-2010)

M. Mahmudur Rahman,Md. Abu Taleb Pramanik 강원대학교 산림과학연구소 2015 Journal of Forest Science Vol.31 No.3

Mangroves are important coastal ecosystems and are located at the inter-tidal zones of tropical and sub -tropical belts. The global mangrove forests are declining dramatically because of the conversion of forests to shrimp farming, over-exploitation, pollution and freshwater diversion. The Bangladesh Forest Department initiated mangrove afforestation throughout the coastal belts of Bangladesh in 1966 to provide better protection for the coastal communities. Up to 1990, 120,000 ha of mangroves had been planted and it is one of the largest coastal afforestaton programs in the world. The objective of this study is to exploit the spatial extent of mangrove plantation and their dynamics of changes over the last two decades using multispectral Landsat imagery. The study area covers the coastal areas of Bangladesh that is extended over the eastern part of Sundarbans up to Teknaf, the southern tip of mainland Bangladesh. Mangrove plantations were interpreted visually on computer screen and interactive delineation of forest boundary was done. The mangrove plantation area has been estimated as 32,725, 47,636 and 43,166 ha for the year of 1989, 2000 and 2010, respectively. Mangrove deforestation by human activity has increased almost six times in the recent decade in comparison to the previous one. The mangrove forest loss due to coastal erosion has slightly declined in the 2000s. Mangroves have been lost primarily because of agricultural expansion. The result of this investigation will be helpful to understand the dynamics of mangrove plantation and the main drivers of changes in this coastal ecosystem.

Preliminary study on thrombolytic property of thirty six different extracts of eight Bangladeshi medicinal plants with folkloric relevance

Amina KhatunEmail author,Mahmudur Rahman,Khaza Nur Uddin,Kamrul Ahsan,Sabequn Nahar Shimu,Khadejatul Kobra,Shamme Akter Shimu,Wahidul Haque,Tobibur Rahman,Tangila Hoque Jessy,Farzana Akhter 경희대학교 융합한의과학연구소 2016 Oriental Pharmacy and Experimental Medicine Vol.31 No.4

Traditional medicinal practitioners or Kavirajes use a variety of medicinal plants for treatment of thrombus ailments-cardiovascular problems. In this study, thrombolytic activity of 36 extracts of different solvents of eight Bangladeshi medicinal plants traditionally used in cardiovascular problems were evaluated to justify their use in folklore medicinal practitice. Extraction was conceded using methanol. Five grams of the concentrated methanol extract of each crude extract were then fractionated to provide n-hexane and carbon tetrachloride fractions. Phytochemically important groups like reducing sugars, tannins, saponins, steroids, gums, flavonoids and alkaloids were tested using standard chromogenic reagents. In vitro thrombolytic potential of extracts was assayed for analyzing the clot lyses by adding the extracts to the pre-clotted blood. The results were compared with the results obtained from streptokinase as standard and water as a negative control. Thrombolytic effect of the extracts ranged from 0.73 ± 2.44 % to 45.81 ± 0.34 % clot lysis whereas the standard streptokinase showed 65.13 ± 0.96 % and the negative control water showed 2.50 ± 0.67 % clot lysis. The highest thrombolytic effect was shown by the crude extract of Melastoma malabathricum leaves and the lowest by the CCl4 fractionate of Litsea glutinosa leaves. Most of the results were found relevant to the traditional use of the plants. Plants traditionally used in thrombus ailments may be an interesting source for further drug development.

Fabrication of nano composite membrane filter from graphene oxide (GO) and banana rachis cellulose nano crystal(CNC) for industrial effluent treatment

Md. Shamim Sheikh,Md. Mahmudur Rahman,Md. Safiur Rahman,Kenan Yildirim,Mohd. Maniruzzaman 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.128 No.-

Agricultural bio-waste based cellulosic materials are highly biodegradable and naturally occurring withhigh adsorption and capable of outstanding physico-chemical properties. This study elicits neotericupliftment and impending significance of graphene oxide(GO) – cellulose nanocrystal(CNC) nano-filtercomposite membrane (NFCM) for high removal of Cr3+, Co2+, Ni2+, Pb2+, Cd2+ and Methylene blue moleculesfrom industrial wastewater. We tried to direct comparison between conventional filter andNFCM composites filter and their physical and chemical properties, production costs, use and disposalin order to show the potential of Nano structural cellulose materials as a sustainable replacement forNFCM filter for removal of heavy metals and dyes from industrial wastewater treatment technologies. The prepared GO, CNC, and NFCM were characterized by using X-ray Diffraction(XRD), FourierTransform Infrared (FTIR), Field Emission Scanning Electron Microscopy(FESEM), ThermogravimetricAnalysis(TGA) etc. The efficiency of wastewater purification of fabricated NFCM were determined byUltra Violet(UV)-vis spectrophotometer and Inductively Couple Plasma Optical Emission Spectroscopy(ICP-OES). Whereas the fabricated NFCM were highly crystalline, thermally stable, have good surfaceactivity, exhibit remarkable removal efficiency against the toxic heavy metals and soluble dye. The maximumR% was found for Cd2+ and Pb2+, around 99%. Beside this all dye molecules were removed from thewastewater simultaneously and successfully.

Comparative Analysis of Wind Power Energy Potential at Two Coastal Locations in Bangladesh

Asif Islam,Mohammad Mahmudur Rahman,Mohammad Shariful Islam,Satya Sundar Bhattacharya,김기현 한국대기환경학회 2015 Asian Journal of Atmospheric Environment (AJAE) Vol.9 No.4

In this study, wind conditions and its energy potential have been assessed by conducting a Weibull analysis of the wind speed data (over the period of 2002-2011) measured from a port city (Mongla) and an isolated island (Sandwip) in Bangladesh. The monthly mean wind speed at Mongla ranged from 1.60 m/s (December) to 2.47 m/s (April). The monthly values of Weibull shape parameter (k) were from 1.27 to 2.53. In addition, the values of the scale parameter (c) and the monthly wind power density ranged from 1.76 to 2.79 m/s and 3.95 to 17.45 W/ m2, respectively. The seasonal mean wind speed data varied from 1.72 (fall) to 2.29 m/s (spring) with the wind power density from 5.33 (fall) to 14.26 W/ m2 (spring). In the case of Sandwip, the results were comparable to those of Mongla, but moderate reductions in all the comparable variables were observed. The wind data results of these two areas have been compared with those of eight other locations in the world with respect to wind power generation scale. According to this comparison, the wind power generation scale for Mongla and Sandwip was adequate for stand-alone small/micro-scale applications such as local household consumption, solar-wind hybrid irrigation pumps, and battery charging.