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Search Results: 1 - 10 of 543584 matches for " M. N. Ahasan "
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Image Noise Analysis of a Large Ring PET Scanner  [PDF]
M. M. Ahasan, S. Akter, R. Khatun, M. F. Uddin, A. N. Monika, M. A. Rahman, M. N. Khanam
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2017, DOI: 10.4236/ijmpcero.2017.62019
Abstract: Image noise analysis of a large ring PET scanner “macro PET” performed using two different phantoms, namely a Jaszczak SPECT phantom and a uniform cylindrical phantom. In the present work, simple 2D filtered back projection was used to reconstruct all the images, and in almost all the cases a Hamming filter of cutoff frequency 0.4 and a 256 by 256 matrix with zoom factors from 1 to 4 were used in order to investigate the imaging capabilities of the new scanner and the influence of filter and cut-off frequency on the filtered back projected images. Results indicate that 11.1 mm cold rod in the Jaszczak phantom images can consistently be seen. The Coefficient of variation (CV) results for Hann and Hamming filters are very similar and increase approximately in linear fashion with higher cutoff frequency. The value of CV for the Parsen filter is lower than the value for Hann and Hamming filters. It concludes that all filters with low cut off-frequency (<0.6) would suppress image noise but decrease contrast.
Simulation of High Impact Rainfall Events Over Southeastern Hilly Region of Bangladesh Using MM5 Model
M. N. Ahasan,M. A. M. Chowdhury,D. A. Quadir
International Journal of Atmospheric Sciences , 2013, DOI: 10.1155/2013/657108
Abstract: Simulation of high impact rainfall events over southeastern hilly region of Bangladesh has been carried out using Fifth-Generation PSU/NCAR Mesoscale Model (MM5) conducting two historical rainfall events, namely, 21 June, 2004 and 11 July, 2004. These extraordinary rainfall events were localized over the Rangamati region and recorded 304 mm and 337?mm rainfall on 21 June, 2004 and 11 July, 2004, respectively, over Rangamati within a span of 24?h. The model performance was evaluated by examining the different predicted and derived parameters. It is found that the seasonal monsoon trough has northerly position compared to normal and pass through Bangladesh extending up to northeast India for both cases. The heat low was found to be intense (996?hPa) with strong north-south pressure gradient (12–15?hPa). The analysis of the geopotential height field at 200?hPa shows that the Tibetan high is shifted towards south by 7-8° latitudes with axis along 22–25°N for both cases. The analysis of the wind field shows that the areas of high impact rainfall exhibit strong convergence of low level monsoon circulation ( 19–58?knots). The strong southwesterlies were found to exist up to 500?hPa level in both cases. The lower troposphere (925–500?hPa) was characterized by the strong vertical wind shear ( 9–18?ms?1) and high relative vorticity ( 20–40 × 10?5?s?1). The analysis also shows that the areas of high impact rainfall events and neighbourhoods are characterized by strong low level convergence and upper level divergence. The strong southwesterly flow causes transportation of large amount of moisture from the Bay of Bengal towards Bangladesh, especially over the areas of Rangamati and neighbourhoods. The high percentage of relative humidity extends up to the upper troposphere along a narrow vertical column. Model produced details structure of the spatial patterns of rainfall over Bangladesh reasonably well though there are some biases in the rainfall pattern. The model suggests that the highly localized high impact rainfall was the result of an interaction of the mesoscale severe convective processes with the large scale active monsoon system. 1. Introduction Rangamati (22.53°N, 92.20°E), the southeastern hilly city of Bangladesh (latitudes 20°34′–26°38′N and longitudes 88°01′–92°41′E), is situated on the western slopes of Mizo Hills and Arakan Mountains. Rangamati is very different in terms of topography from the rest of Bangladesh, as the city is built on the hilly regions. On 21 June, 2004 and 11 July, 2004, Rangamati received 304?mm and 337?mm rainfall within 24
Radiation Shielding Analysis and Design of tof PET-CT Facility at Institute of Nuclear Medical Physics under Bangladesh Atomic Energy Commission, Bangladesh  [PDF]
M. F. Uddin, R. Khatun, S. Akter, H. M. Jamil, A. N. Monika, M. A. Rahaman, R. P. Das, R. A. Sharmin, M. M. Rahman, M. M. Ahasan
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2019, DOI: 10.4236/ijmpcero.2019.81001
Abstract: High resolution (4 mm) tof PET-CT (positron emission tomography-computed tomography) from Philips of model Ingenuity TF is newly installed at Institute of Nuclear Medical Physics (INMP). 128 slice CT component incorporated with PET provides comparatively lower dose than the 511 keV annihilation photons associated with positron decay from PET scan. So, for designing shielding in our PET-CT facility, only 511 keV annihilation photons energy has been considered. The main objective of this paper is to show what measures have been taken to protect patients, occupational workers as well as environment from PET-CT radiation hazard through a cost effective design that satisfy the national regulatory demand. In this paper, AAPM (American Associations of Physicists in Medicine) Task group 108 analysis for PET and PET-CT shielding requirements is followed for our PET-CT facility shielding design. From theoretical calculation as shielding requirement, 1.1 cm Pb thickness or, 13 cm concrete thicknesses are found. Practically, all walls and ceiling are of 30.48 cm (1 foot) thick made of concrete with density 2.35 gcm-3 for more safety. As x-ray from CT is not taken into account for shielding analysis, Bangladesh Atomic Energy Commission (BAEC) conducted an extensive radiation survey at controlled, supervised and public area for CT. The report that is found meets the national regulatory requirements.
Study of Image Contrast Recovery Coefficient (CRC) of a Large Ring PET Scanner  [PDF]
M. M. Ahasan, S. Akter, R. Khatun, M.F. Uddin, M. R. Islam, H. M. Jamil, A. N. Monika, M. A. Rahman, R. P. Das, M. M. Rahman, R. A. Sharmin, M. N. Khanam
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2019, DOI: 10.4236/ijmpcero.2019.81005
Abstract: Image contrast recovery coefficient (CRC) of a large ring PET scanner “macroPET” was studied with septa and without septa configuration by ac-quiring data from a laboratory made 35.7 cm square phantom filled with 18-F. Images were reconstructed with simple 2D filtered back projection using Hann, Hamming and Parsen filters with different cut-off frequencies aiming to investigate the influence of filter and cut-off frequency on image contrast with septa and without septa mode. Results indicate that the CRC, for both hot and cold lesions, is excellent for diameters ≥ 3 cm using cut-off frequencies > 0.4. For a 2 cm hot lesion CRC is around 0.8 to 0.9. CRC for 1 cm hot and cold lesions is ~0.3, as expected. There is surprisingly little difference between results with and without septa. For hot lesions, septa appear to improve CRC slightly, but for cold lesions CRC is slightly poorer using septa.
Performance Evaluation of Hybrid Green Roof System in a Subtropical Climate Using Fluent  [PDF]
S. F. Ahmed, T. Ahasan, M. G. Rasul, M. M. K. Khan, A. K. Azad
Journal of Power and Energy Engineering (JPEE) , 2014, DOI: 10.4236/jpee.2014.24017
Abstract: Energy disaster is one of the major obstacles in the progress of human society. There are some on-going researches to overcome this for a sustainable environment. Green roof system is one of them which assist to reduce energy consumption of the buildings. The green roof system for a building involves a green roof that is partially or completely covered with vegetation and plant over a waterproofing membrane. Green roofs provide shade and remove heat from the air through evapotranspiration, reducing temperatures of the roof surface and the surrounding air. This paper reports the thermal performance of hybrid green roof system for a hot and humid subtropical climatic zone in Queensland, Australia. A thermal model is developed for the green roof system using ANSYS Fluent. Data were collected from two modelled rooms, one connected with green roof system and other non-green roof system. The rooms were built from two shipping containers and?installed at Central Queensland University, Rockhampton, Australia. Impact of air temperature on room cooling performance is assessed in this study. A temperature reduction of 0.95°C was observed in the room with green roof which will save energy cost in buildings. Only 1.7% variation in temperature was found in numerical result in comparison with experimental result.
Energy Scenario: Production, Consumption and Prospect of Renewable Energy in Australia  [PDF]
A. K. Azad, M. M. K. Khan, T. Ahasan, S. F. Ahmed
Journal of Power and Energy Engineering (JPEE) , 2014, DOI: 10.4236/jpee.2014.24004
Abstract: Australia is the world’s 9th largest energy producer, 17th largest consumer of non-renewable energy resources and ranks 18th on a per person energy consumption basis.Australia’s energy consumption is primarily composed of non-renewable energy resources (coal, oil, gas and related products), which represent 96% of total energy consumption. Renewables, the majority of which is bioenergy (wood and wood waste, biomass, and biogas) combined with clear energy namely wind, solar hot water, solar electricity, hydroelectricity account for the remaining 4% consumption.Australia’s renewable energy resources are largely undeveloped which will contribute directly to the Australian economy. In this article, a review of literature on energy scenario is presented and discussed.Australia’s total energy production, consumption, storage and export (including renewable and non-renewable) data has been analyzed and discussed in this study. The main objective of the study is to analyze the prospect of renewable energy inAustralia. This study concludes that Australian economy will grow faster if its undeveloped renewable energies can be used efficiently for electricity generation and transport sector.
Initial Results from a Prototype Large (2m) Ring PET Scanner
M Monjur Ahasan,David J Parker
Lecture Notes in Engineering and Computer Science , 2008,
Abstract:
Does January Effect Exist in Bangladesh?
A. F. M. Mainul Ahsan,Ahasan Habib Sarkar
International Journal of Business and Management , 2013, DOI: 10.5539/ijbm.v8n7p82
Abstract: This paper examines existence of January effect in Dhaka Stock Exchange (DSE) in Bangladesh. Regression model combined with dummy variables and monthly DSE All Share Price Index (DSI) from January 1987 to November 2012 has been used to test January effect in the stock return in DSE. It was empirically found that, although January anomaly doesn’t exist in DSE, there is significant positive return in June which raises question against efficient market hypothesis (EMH). Thus, there is an opportunity for investors to take advantage of this June anomaly.
Anatomical study on origin, course and distribution of cranial and caudal mesenteric arteries in the White New Zealand rabbit (Orycotolagus cuniculus)
Uddin M, Rahman ML, Alim MA and Ahasan ASML
International Journal of Natural Sciences , 2012,
Abstract: The present study was carried out on fifteen healthy adult White New Zealand rabbit (Orycotolagus cuniculus) to clarify the obscure mesenteric arteries, which and their branches which are usually involved in intestinal surgery. The mesenteric artery is a high caliber vessel, 2cm in length dependent on the abdominal aorta, right below the emergence of the vessels destined for the liver and stomach. The animals were sacrificed, injecting diazepam (30 mg/kg) in jugular vein. Cannulation of the abdominal aorta, perfusion with warmed water (40oC) and stained latex injection (Neoprene 450, Capitol Scientific, Austin, U.S.A, Red carmine stain) were performed, followed by fixation. With formalin (10%) the dissection and photographic documents (Casio Cyber-shot, 12.1 mega pixels) made it possible to systemize the arteries and define the vascular patterns of the viscera. The results prone that the cranial mesenteric artery of the White New Zealand rabbit (Orycotolagus cuniculus) arose from the abdominal aorta, at the level of the second lumbar vertebra, entered the cranial mesentery forming its root, then proceeded caudoventrally in the mesojejunum and continued as the last cecal artery. The cranial mesenteric artery gave off: -Caudal pancreaticoduodenal artery to the right lobe of the pancreas and the descending and ascending parts of the duodenum. Middle colic artery, a small vessel (frequently two) arising from the left wall and passing to the transverse colon, Eighteen to twenty jejunal arteries, Ileocecocolic artery to the ileum, cecum, ascending colon, transverse colon and the cranial part of the descending colon. The caudal mesenteric artery arose from the abdominal aorta at the level of the caudal border of the root of the 6th lumbar transverse process, passed caudoventrally in the descending mesocolon, then divided into: left colic artery to the caudal two thirds of the descending colon, and cranial rectal artery to the cranial segment of the rectum. The obtained results were compared with their corresponding in the domestic animals, especially the domestic carnivores and laboratory animals.
Biochemical Analysis on Blood and Crop Contents of Household Chickens Along With Their Production and Health Status in Bangladesh
S. K. M. A. Islam, M. Alauddin1, M. M. Hassan, S. A. Khan, M. R. Alam, M. Saifuddin, S. Sultana, H. M. Tun2, A. H. Shaikat, N. C. Debnath and M. A. Hoque* B. Hossain, A. S. M. L. Ahasan, A. K. M.
Pakistan Veterinary Journal , 2012,
Abstract: This study aimed to assess the biochemical parameters of household chickens at crop and blood levels and measure the body weight. For this purpose, 350 Deshi (local) and 27 Fayoumi day old chicks were reared in 2 separate brooders within a house for 15 days. Body weight, serum total protein and calcium levels of these chicks were evaluated on day 0 and 15. After control house trial, birds were distributed among the selected households. Again, body weights and certain biochemical parameters were assessed from randomly selected birds at 60, 120 and 180 days of age. Fayoumi birds gained higher weight (P<0.001) than at control trial, whereas Deshi birds attained better weight (P<0.001) at household. Crop contents were dominated by carbohydrate. The level of crude proteins and calcium in crop contents increased along with age regardless of bird types. The average phosphorous in the crop contents was 0.3% (60 days), 2.6% (120) and 0.7% (180) regardless of bird types. Both serum total protein (P<0.05) and calcium (P<0.05) were significantly difference in between bird types at control house study. In conclusion, Deshi birds attained higher weight at household. The crude protein was below standard. Calcium and Phosphorous levels in the crop contents varied with ages, regardless of bird types.
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