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.

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.

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.

Improvement of Thermoelectric Properties of AlSb by Incorporation of Mg as p‑type Dopant

A. K. M. Ashiquzzaman Shawon,Md Mahmudur Rahman,Soon‑Chul Ur 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.6

Due to the sizably larger direct band gap of 2.26 eV of AlSb, the thermoelectric properties of intrinsic AlSb is considerablylow. Despite a promising Seebeck coefficient, the low electrical conductivity and high thermal conductivity has limited theimprovement of thermoelectric figure of merit. Replacing small amounts of Al by Mg can increase the number of holes inthe solid-state, effectively helping tune the carrier concentration. This work explores the effect of Mg doping in AlSb. Theincorporation of Mg at Al sites has increased the electrical conductivity without decreasing the Seebeck coefficient detrimentally. The thermoelectric figure of merit has shown improvement despite the large thermal conductivity observed. The work additionally explores the possibility of improving thermoelectric properties further by forming a composite with β-Zn4Sb3. The highest thermoelectric figure of merit was found to be 0.075 at 873 K, which is 6 times higher than that in intrinsic AlSb.

Eliminating concrete cover separation of NSM strengthened beams by CFRP end anchorage

Md. Akter Hosen,Mohd Zamin Jumaat,A. B. M. Saiful Islam,Mohamed Kamruzzaman,Md. Nazmul Huda,Mahmudur Rahman Soeb 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.56 No.6

Upgrading or strengthening of existing reinforced concrete (RC) infrastructure is an emerging demand nowadays. Near Surface Mounted (NSM) technique is very promising approach for flexural strengthening of RC members. However, premature failure such as concrete cover separation failure have been a main concern in utilizing this technique. In this study, U-wrap end anchorage with carbon fiber reinforced polymer (CFRP) fabrics is proposed to eliminate the concrete cover separation failure. Experimental programs were conducted to the consequence of U-wrap end anchorage on the flexurally strengthened RC beams with NSM- steel. A total of eight RC rectangular beam specimens were tested. One specimen was kept unstrengthened as a reference; three specimens were strengthened with NSM-steel bars and the remaining four specimens were strengthened with NSM-steel bars and U-wrap end anchorage using CFRP fabrics. A 3D non-linear finite element model (FEM) was developed to simulate the flexural response of the tested specimens. It is revealed that NSM-steel (with and without end-anchors) significantly improved the flexural strength; moreover decreased deflection and strains compared with reference specimen. Furthermore, NSM-steel with end anchorage strengthened specimens revealed the greater flexural strength and improve failure modes (premature to flexure) compared with the NSM-steel without end anchorage specimens. The results also ensured that the U-wrap end anchorage completely eliminate the concrete cover separation failure.