Species composition and forest structure in tropical moist deciduous forest of Bangladesh—a case study in Thakurgaon     

Sourovi Zaman  Salah Uddin Siddiquee  Masato Katoh 《Arabian Journal of Geosciences》2011,4(7-8):1315-1321

This study was conducted in the tropical moist deciduous forest in Bangladesh to describe the species composition, diversity, and the forest structure. There were three plots established in Ranishonkoil, Ruhia, and Baliadangi forest beat in Thakurgaon. A total of 126 tree species, 1,991 stems (663 ha^?1) of ≥10-cm girth were listed. Tree communities in these forest region differed in dominance, composition, diversity, and structure; and tree stand density varied from 651 to 685 ha^?1. Species diversity (H¹) ranges from 3.11 to 3.48. Meliaceae, Myrtaceae, and Rubiaceae were the most abundant families within the three plot area. Study site 2 is more diverse at spatial scale and taxonomic levels due to high rainfall and favorable edaphic condition. This study will help the foresters as baseline information for monitoring and sustaining diversity of tropical moist deciduous forests in Bangladesh.  相似文献   

Energetics and Dynamics of an Impulsive Flare on March 10, 2001     

Ramesh Chandra  Rajmal Jain  Wahab Uddin  Keiji Yoshimura  Takeo Kosugi  Taro Sakao  Anita Joshi  M. R. Deshpande 《Solar physics》2006,239(1-2):239-256

We present Hα observations from ARIES (Nainital) of a compact and impulsive solar flare that occurred on March 10, 2001 and which was associated with a CME. We have also analyzed HXT, SXT/Yohkoh observations as well as radio observations from the Nobeyama Radio Observatory to derive the energetics and dynamics of this impulsive flare. We coalign the Hα, SXR, HXR, MW, and magnetogram images within the instrumental spatial-resolution limit. We detect a single HXR source in this flare, which is found spatially associated with one of the Hα bright kernels. The unusual feature of HXR and Hα sources, observed for the first time, is the rotation during the impulsive phase in a clockwise direction. We propose that the rotation may be due to asymmetric progress of the magnetic reconnection site or may be due to the change of the peak point of the electric field. In MW emission we found two sources. The main source is at the main flare site and another is in the southwest direction. It appears that the remote source is formed by the impact of accelerated energetic electrons from the main flare site. From the spatial correlation of multiwavelength images of the different sources, we conclude that this flare has a three-legged structure.  相似文献   

Food security and dietary diversity of tea workers of two tea gardens in greater Sylhet district of Bangladesh     

Ahmed  Jasim Uddin  Mozahid  Md. Nur  Dhar  Aurup Ratan  Alamgir  Md. Shah  Jannat  Arifa  Islam  Md. Monirul 《GeoJournal》2021,86(2):1015-1027

The study analyzed the food security and dietary diversity of tea workers in Lakkatura Tea Garden and Ootterbhag Tea garden in greater Sylhet district of Bangladesh. A total of 200 respondents (100 from each tea estate) were interviewed to evaluate the food security and dietary diversity. The study found that average daily per capita calorie intake by tea workers was 2095.96 kcal. In addition, around 85.30% of the total calorie intake was received from the rice consumption. Average per capita daily intake of rice was estimated at 538.51 gm which is higher than the national average. It was also observed that 71.7 and 65.0% households were food secure in Lakkatura and Ootterbhag Tea garden, respectively. In Lakkatura Tea Garden, 61.67% tea workers have medium dietary diversity and in Ootterbhag Tea Estate 49.47% tea workers have low dietary diversity. Using the logit model analysis, this study provides food consumption patterns of tea workers and determine the factors responsible for food security. Household size, farm income and daily calorie intake were found having significant influence on households’ food security. For improving socioeconomic conditions of tea workers, educational institution should be set up to improve their educational status and government should give loans for them at a low interest rate and create alternative job opportunity in off season.

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A multi-criteria decision-making approach for quantification of accessibility to market facilities in rural areas: an application in Bangladesh     

Zafri  Niaz Mahmud  Sameen  Ishrar  Jahangir  Anurima  Tabassum  Nawshin  Hasan  Md. Musleh Uddin 《GeoJournal》2021,86(4):1863-1879

GeoJournal - The available approaches for measuring accessibility are rigid and complex in nature, and mostly impractical for decision-makers as they require a large number of data, logistics...  相似文献   

Extremely energetic 4B/X17.2 flare and associated phenomena     

Wahab Uddin  Ramesh Chandra  Syed Salman Ali 《Journal of Astrophysics and Astronomy》2006,27(2-3):267-276

We observed 4B/X17.2 flare in Hα from super-active region NOAA 10486 at ARIES, Nainital. This is one of the largest flares of current solar cycle 23, which occurred near the Sun’s center and produced extremely energetic emission almost at all wavelengths from γ-ray to radio-waves. The flare is associated with a bright/fast full-halo earth directed CME, strong type II, type III and type IV radio bursts, an intense proton event and GLE. This flare is well observed by SOHO, RHESSI and TRACE. Our Hα observations show the stretching/de-twisting and eruption of helically twisted S shaped (sigmoid) filament in the south-west direction of the active region with bright shock front followed by rapid increase in intensity and area of the gigantic flare. The flare shows almost similar evolution in Hα, EUV and UV. We measure the speed of Hα ribbon separation and the mean value is ∼ 70 km s^-1. This is used together with photospheric magnetic field to infer a magnetic reconnection rate at three HXR sources at the flare maximum. In this paper, we also discuss the energetics of active region filament, flare and associated CME.  相似文献   

Potentiality of open burnt clay as an adsorbent for the removal of Congo red from aqueous solution     

M. A. Mumin B.Sc. Eng.  M. M. R. Khan M.Sc.  Ph.D.  K. F. Akhter B.Sc. Eng.  M. J. Uddin B.Sc. Eng. 《International Journal of Environmental Science and Technology》2007,4(4):525-532

Open burnt clay was studied as a potential adsorbent for the adsorption of Congo red (a reactive dye) from aqueous solution. The effect of contact time, pH, adsorbent dosage and temperature were studied. It was observed that the amount of Congo red retained increase with decreasing pH and increasing initial concentration. Removal percentage at pH 2 and 3 are almost same. The adsorption capacity of regenerated burnt clay was showed more than 98 % recovery of the adsorption efficiency of initial virgin adsorbent. The equilibrium data were described well by both Langmuir and Freundlich isotherm model. The adsorption capacity of some natural adsorbents, namely rice husk, wood charcoal, tea waste etc. were also investigated and compared with that of open burnt clay.  相似文献   

Spatial relationship of groundwater arsenic distribution with regional topography and water-table fluctuations in the shallow aquifers in Bangladesh     

M. Shamsudduha  L. J. Marzen  A. Uddin  M.-K. Lee  J. A. Saunders 《Environmental Geology》2009,57(7):1521-1535

The present study has examined the relationship of groundwater arsenic (As) levels in alluvial aquifers with topographic elevation, slope, and groundwater level on a large basinal-scale using high-resolution (90 m × 90 m) Shuttle Radar Topography Mission (SRTM) digital elevation model and water-table data in Bangladesh. Results show that high As (>50 μg/l) tubewells are located in low-lying areas, where mean surface elevation is approximately 10 m. Similarly, high As concentrations are found within extremely low slopes (<0.7°) in the country. Groundwater elevation (weekly measured by Bangladesh Water Development Board) was mapped using water-table data from 950 shallow (depth <100 m) piezometers distributed over the entire country. The minimum, maximum and mean groundwater elevation maps for 2003 were generated using Universal Kriging interpolation method. High As tubewells are located mainly in the Ganges–Brahmaputra–Meghna delta, Sylhet Trough, and recent floodplains, where groundwater elevation in shallow aquifers is low with a mean value of 4.5 m above the Public Works Datum (PWD) level. Extremely low groundwater gradients (0.01–0.001 m/km) within the GBM delta complex hinder groundwater flow and cause slow flushing of aquifers. Low elevation and gentle slope favor accumulation of finer sediments, As-carrying iron-oxyhydroxide minerals, and abundant organic matter within floodplains and alluvial deposits. At low horizontal hydraulic gradients and under reducing conditions, As is released in groundwater by microbial activity, causing widespread contamination in the low-lying deltaic and floodplain areas, where As is being recycled with time due to complex biogeochemical processes.  相似文献   

Observation of multiple sausage oscillations in cool post-flare loop     

A. K. Srivastava  T. V. Zaqarashvili  W. Uddin  B. N. Dwivedi  Pankaj Kumar † 《Monthly notices of the Royal Astronomical Society》2008,388(4):1899-1903

Using simultaneous high spatial (1.3 arcsec) and temporal (5 and 10 s) resolution Hα observations from the 15 cm Solar Tower Telescope at Aryabhatta Research Institute of Observational Sciences (ARIES), we study the oscillations in the relative intensity to explore the possibility of sausage oscillations in the chromospheric cool post-flare loop. We use the standard wavelet tool, and find the oscillation period of ≈587 s near the loop apex, and ≈349 s near the footpoint. We suggest that the oscillations represent the fundamental and the first harmonics of the fast-sausage waves in the cool post-flare loop. Based on the period ratio   P ₁/ P ₂∼1.68  , we estimate the density scaleheight in the loop as ∼17 Mm. This value is much higher than the equilibrium scaleheight corresponding to Hα temperature, which probably indicates that the cool post-flare loop is not in hydrostatic equilibrium. Seismologically estimated Alfvén speed outside the loop is  ∼300–330  km s⁻¹  . The observation of multiple oscillations may play a crucial role in understanding the dynamics of lower solar atmosphere, complementing such oscillations already reported in the upper solar atmosphere (e.g. hot flaring loops).  相似文献   

The distribution of sunspots over the Sun     

Wahab Uddin  M. C. Pande  V. K. Verma 《Astrophysics and Space Science》1991,181(1):111-115

The distribution of the sunspots for the period 1967–1987 (solar cycles 20 and 21) is presented here. We find that the ±11–20° latitude belt is most prolific for the occurrence of various spot types irrespective of magnetic-field ranges. Furthermore, longitudinally sunspots occur most prolifically at six or more places on the Sun. Spatially 7–9 zones are present in each hemisphere (north or south) of the Sun where about 50% sunspots occur and occupy only about 4% area of the Sun. During the above cycles at least 5 flare zones were regularly present in each hemisphere. The existing models cannot explain these active zones on the Sun. Thus, the present analysis emphasizes the need for a new magnetic models of the Sun.  相似文献   

Study of calcium-K network evolution from Antarctica     

Jagdev Singh  B. S. Nagabhushana  G. S. D. Babu  Wahab Uddin 《Solar physics》1994,153(1-2):157-167

To study the evolution of large convective cells known as supergranules, a solar telescope was set up at Maitri, Indian permanent station in Antarctica region, during the local summer months (December 1989 through March 1990). A continuous sequence of calcium K-line filtergrams for 106 hours spaced at intervals of about 10 min was obtained. The analysis of the data indicates that the most probable lifetime of the calcium-K network is about 22 hours. The lifetime depends upon the size of the cell and is larger for bigger cells. The data also show that cells (of a given size) associated with remnant magnetic field regions live longer than those in the field-free region. This may mean that the magnetic field plays an important role in the confinement of these structures.  相似文献