Numerical Analysis of Thermal Convection in a CPU Chassis

Flow distribution and the effects of different boundary conditions are achieved for a steady-state conjugate (Conduction & Convection) heat transfer process. A plate fin heat sink with horizontal fin orientation along with a computer chassis is numerically investigated and simulated using software ANSYS CFX. Fin orientation of a heat sink changes the direction of fluid flow inside the chassis. For predicting turbulence of the flow inside the domain, a two-equation based k-ε turbulence model is chosen. The Reynolds number based on inflow velocity and geometry is found 4.2 × 103 that indicates that the flow is turbulent inside the chassis. To get proper thermal cooling, the optimum velocity ratio of inlet/outlet, dimension of inlet/outlet and different positions of outlet on the back sidewall of the chassis are predicted. Aspect velocity ratio between the inlet airflow and the outlet airflow has an effect on the steadiness of the flow. Mass flow rate depends on the dimension of the inlet/outlet. The horizontal fin orientation with 1:1.6 inlet-outlet airflow velocity ratio gives better thermal performance when outlet is located at the top corner of the chassis, near to the inner sidewall. Flow distribution and heat transfer characteristics are also analyzed to obtain the final model.

Secure Wireless Multicasting through Nakagami-m Fading Channels with Multi-Hop Relaying

The additional diversity gain provided by the relays improves the secrecy capacity of communications system significantly. The multiple hops in the relaying system is an important technique to improve this diversity gain. The development of an analytical mathematical model of ensuring security in multicasting through fading channels incorporating this benefit of multi-hop relaying is still an open problem. Motivated by this issue, this paper considers a secure wireless multicasting scenario employing multi-hop relaying technique over frequency selective Nakagami-m fading channel and develops an analytical mathematical model to ensure the security against multiple eavesdroppers. This mathematical model has been developed based on the closed-form analytical expressions of the probability of non-zero secrecy multicast capacity (PNSMC) and the secure outage probability for multicasting (SOPM) to ensure the security in the presence of multiple eavesdroppers. Moreover, the effects of the fading parameter of multicast channel, the number of hops and eavesdropper are investigated. The results show that the security in multicasting through Nakagami-m fading channel with multi-hop relaying system is more sensitive to the number of hops and eavesdroppers. The fading of multicast channel helps to improve the secrecy multicast capacity and is not the enemy of security in multicasting.

Status and Constrain for Mechanization of Rice Harvesting System in Bangladesh

To know the position, problems and suggestion of harvest mechanization of rice, the study conducted in 21 upzillas under seven regions (Dhaka, Mymensingh, Sylhet, Comilla, Bogra, Rajshahi and Rangpur) based on different agro-climatic condition and cropping intensity and 126 farmers participated in the interview. For collecting data, a structured questionnaire was used and statistical analysis of the collected data was carried out. In study area, the average cultivable area was 225 to 1239 decimal (1 decimal = 40 m2) and 97.60% farmer reaping by sickle and only 0.80% used combine harvester. Cut paddy transported by head (13.49%), shoulders (12.7%) or both of them of 11.11% farmer and 44.44% of farmers used small truck or field threshed. Threshing was mainly done using (49.21%) closed drum thresher and open drum thresher (26.20%), likewise 1 of 126 farmer use head-feed combine harvester. The study area, most farmers (37.3%) used kula for the cleaning of rice, but only 8.74% of farmers used winnower. In considerable amount, 80.95% of farmers had machinery, while the remaining (19.05%) did not have machines. Farmers agreed that harvesting was a labor-intensive method (35.71%) and time consuming (28.57%). Transporting of harvested paddy was dangerous and painful for head, shoulder, hand, waist, backbone, leg, etc. With mechanization and the introduction of machinery, 40.48% of farmers identified the main ceiling as the price of the machine and information/lack of credit system (21.43%). In survey area, most farmers (36.51%) identified the vital advantage of mechanized harvesting as lower labor requirement, while 21.43% of farmers said that a lower loss of rice. All farmers who participated in the interview expressed their need for machinery and mentioned agricultural credit with easy terms and conditions, subsidy for buying machinery and the ensuring of a fair market price for their rice.

Can picnic influence floral diversity and vitality of trees in Bhawal National Park of Bangladesh?

We examined the impact of picnic activities on forest diversity, structure, regeneration and vitality of tree species in the Bhawal National Park of Bangladesh. The study area was classified as a non-used, occasionally used and frequently used area on the basis of the intensity of the picnic activities. A total of 43 plant species were enumerated in the whole study area. The highest plant species richness （41 species） was observed in the non-used area whereas the lowest species richness （11 species） in the frequently used area. The diversity index decreased with the increase of picnic intensity whereas the concentration of dominance increased. Density of all plant groups except mature trees, and the basal area of the mature trees showed a declining trend from the non-used to frequently used area. The frequently used area exhibited very poor regeneration. Tree vitality decreased with the increase of picnic intensity. The relevance of our study as a basis for further research to determine the impact of tourism on biodiversity in Bangladesh is discussed.

Simulating Nitrogen and Irrigation Effects on Wheat Production in Bangladesh under Changing Climate

Climate change impacts are visible in Bangladesh which requires adoption of judicious crop management practices for sustainable agriculture. Crop simulation models are effective in this regard and can be used for optimizing water and nitrogen inputs for maximization of wheat yields. Two field studies were conducted at Bangladesh Agricultural Research Institute (BARI) for evaluating the effect of increased temperature on wheat production under variable water and N rates, through the use of DSSAT v4.6 model. Thirty years historic weather data and BARI Gom-26 wheat-cultivar coefficients, as generated through use of GLUE of DSSAT model, were used for evaluating the impact of temperature rise with variable rates of irrigation water and nitrogen. The effects of four levels of nitrogen (0, 40, 80 and 120 kg ha-1) and four irrigation levels [0 (no irrigation), 1, 2 and 3] on wheat yield were evaluated under 0°C, 1°C, 2°C and 3°C rise in temperature. Simulation results indicated that wheat yield increased with increase in nitrogen application rate, but decreased with the temperature rise. Crop growing duration was reduced by about five days for each degree rise in temperature, irrespective of levels of irrigation water and nitrogen-rates. In general, there was yield reduction of 8.13, 16.77 and 24.97 % with increased temperature of 1°C, 2°C and 3°C, respectively, when compared with no temperature rise treatment. For interaction of temperature rise-N dose, the magnitude of yield decline under temperature rise was higher with increased dose of N. Agronomic N use efficiency at different N rates and temperature rise level were calculated. N use efficiency decreases with the increase in temperature rise and the highest (29.95 kg grain kg-1 N) was obtained from 40 kg N ha-1 treated plot with 0°C temperature rise i.e. existing atmospheric temperature. Simulation results indicated increase in wheat yield with higher levels of irrigation water, and interaction of irrigation level with temperature rise was significant. Irrigation use efficiency decreases with the increase in temperature rise. From the present study, it was seen that the interaction of temperature rise with varying levels of N and irrigation water was significant, and there is a need to design the appropriate inputs’ management, as the adaptation strategy, to sustain the wheat yield under climate change situation.

Organic Amendments with Chemical Fertilizers Improve Soil Fertility and Microbial Biomass in Rice-Rice-Rice Triple Crops Cropping Systems

Medium-term changes in the labile nutrient pool of microbial biomass carbon (MBC) and nitrogen (MBN) resulting from organic manure application in rice (Oryza sativa L.)-based triple cropping systems have been poorly studied. Therefore, the effects of organic materials on the soil physico-chemical properties and microbial biomass in rice fields were investigated at Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh, from April 2010 to December 2012. Five treatments (control, cow dung, poultry manure, rice straw, and chemical fertilizer) were laid out in a randomized complete block design with four replications. The organic residues (2 t C ha-1) were applied 7 days before transplanting and were combined with inorganic fertilizers, following integrated plant nutrition systems. This paper presents the results from the last of the five consecutive rice growing seasons. All of the organic residues increased the pH, and organic C, N, P, and K contents of the soil. However, poultry manure was more efficient in increasing soil fertility than cow dung and rice straw, resulting in a significant increase in P from 22 mg·kg-1 to 63 mg·kg-1 at crop harvest. All of the organic residues also increased the soil water holding capacity and decreased bulk density. Furthermore, poultry manure resulted in significantly higher microbial biomass C (432 mg·kg-1;P < 0.05) and N (31.60 mg·kg-1;P < 0.05) levels in the soil at crop harvest, followed by cow dung and rice straw. These findings indicate that the regular application of organic residues and manures will help to enhance soil fertility and production sustainability.

Influence of Bleaching Powder on the Quality of Giant Freshwater Prawn (<i>Macrobrachium rosenbergii</i>)

Calcium hypochlorite commercially known as bleaching powder is used as a bleaching agent in shrimp processing industries in many countries and known to effect biochemical alteration in shrimp muscle. Studies were, therefore, undertaken to determine their effect in different concentrations viz., 10, 20, 30, 40 and 50 ppm with different time intervals on the quality of head-on, headless shell-on and peeled giant freshwater prawn (Macrobrachium rosenbergii) by determining biochemical and organoleptic aspects. Myofibrillar protein solubility of fresh head-on, headless shell-on and peeled samples were 90.5%, 90% and 88%, respectively indicating a gradual decrease in protein solubility with increasing concentration of bleaching powder. Decrease in protein solubility was also higher in samples kept at longer duration in different concentration of bleaching powder. At a given concentration of 50 ppm for 30 min treatment, the loss of myofibrillar protein was higher (26.14%) in peeled samples than those of head-on and headless shell-on samples (20.44% and 21.11%). Shelf life of bleaching powder treated prawn samples was found to be reduced to 4 - 5 days in iced condition compared to 6 - 7 days for control samples. Peeled samples were also found to be more susceptible to bleaching powder than that of head-on and headless shell-on samples.

Clinico-Demographic Characteristics of Intestinal Tuberculosis in Pre-Operative Unsuspected Laparotomy as Incidental Findings in Bangladesh

Background: Clinical presentation of intestinal tuberculosis is varied. It is also essential to know the clinical and demographic characteristics of incidentally detected intestinal tuberculosis patient. Objective: The purpose of the present study was to find out the clinic-demographic characteristics of intestinal tuberculosis in clinically and preoperatively unsuspected laparotomies. Methodology: This cross-sectional study was carried out in the Department of Surgery at Dhaka Medical College Hospital, Dhaka from March 2002 to March 2004 for a period of two (2) years. All the patients underwent laparotomy presented without any suspicion of pulmonary or intestinal tuberculosis were included as study population. Patients who were without the history of cough, haemoptysis, antitubercular drug therapy were included. Per operative suspicion was raised due to enlarged lymph nodes in mesentery, omental masses, ileocaecal masses, suspicious growth in ileum, omental thickening, perforation suspected by tuberculosis. Biopsy was taken from suspicious lesions. Histopathology was confirmed the tubercular lesion. Results: A total number of 300 patients under laparotomy were recruited for this study of which 38 positive cases were found in the study with a percentage of 12.7%. Maximum affected age group was 21 to 30 years which was 16 (42%) cases. Male was predominant to female which was 28 (73.7%) cases and 10 (26.3%) cases respectively. Low socioeconomic people are affected more (76.3%). Most common presentation in positive cases was acute and sub-acute intestinal obstruction 20 (52.6%) followed by intestinal perforation (26.31%). Conclusion: In conclusion young age male patient is the most commonly affected intestinal tuberculosis which is frequently presented with sub-acute intestinal obstruction among the preoperatively unsuspected laparotomy patients.

Performance Improvement of CIGS Solar Cell: A Simulation Approach by SCAPS-1D

Thin-film solar cells possess the distinct advantage of being cost-effective and relatively simple to manufacture. Nevertheless, it is of utmost importance to enhance their overall performance. In this research work, copper indium gallium selenide (CIGS)-based ultra-thin solar cell (SC) configuration (Ag/ZnO/ZnSe/CIGS/Si/Ni) has been designed and examined using SCAPS-1D. The numerical calculations revealed that this new design resulted in a substantial improvement in SC performance. This study explores the utilization of two absorber layers, CIGS and Si, both with a total of 2 μm thickness, to enhance device performance while reducing material costs, observing an increase in key SC parameters as the Si absorber layer thickness is increased, reaching a maximum efficiency of 29.13% when CIGS and Si thicknesses are set at 0.4 μm and 1.6 μm, respectively with doping absorber doping density of 1014 cm-3. Furthermore, we analyze the impact of variation in absorber and buffer layer thickness, as well as doping concentration, surface recombination velocity (SRV), electron affinity, series-shunt resistance, and temperature, on optimized CIGS SC parameters such as short-circuit current density (JSC), open circuit voltage (VOC), fill factor (FF), and power conversion efficiency (PCE). The findings yielded by the investigation offer significant elucidation regarding the fabrication of economically viable and highly efficient non-hazardous CIGS ultra-thin SC.

Techno-Economic Feasibility of Zoomlion Combine Harvester in Haor Areas of Bangladesh

Haor represents the food basket of Bangladesh and rice is the only crop grown once a year. Harvesting of rice is labor-intensive works and required migrated labor to complete the harvesting works. Mechanical intervention of rice harvesting is urgently needed to increase the productivity. The proper knowledge of economic valuation and operational necessities needs to use of combine harvesters. Research objective was selected to test the technical and economic analysis of Zoomlion rice combine harvester (which is originally developed in China) in Maisherkandi, Mithamain Upazila under Kishoregonj district. The above-mentioned areas are representing haor areas of Bangladesh. Based on the straight-line method, fixed cost items which are machine purchase price, shelter, tax, and insurance were calculated. During the operation of the combine harvester variable cost items such as maintenance and repair, fuel, oil, drivers and guidance were collected. The breakeven point was calculated in terms of the hectares that must be harvested yearly to cover fixed annual costs;and the payback period. Harvesting speed ranged from 1.23 - 3.20 km∙hr−1. The field capacity of harvester was obtained 0.15 ha∙hr−1 and consumed fuel of up to 32 L∙ha−1. Field sizes of less than 800 m2 should be avoided for the Zoomlion combine harvester to operate the harvester machine in an efficient manner. The combine produced grains loss ranging from 1.60% - 1.91%. At an initial cost of Tk 2,000,000, owning the combine harvester becomes profitable after 20 ha of paddy field harvested at a harvesting capacity of 0.15 ha∙hr−1. Vibration and noise were observed in tolerable limit of the operator. The operator felt comfort to operate the machine. This machine is capable to operate in the muddy field having a water height of 4 - 8 cm. Workability of the combine harvesters depended on soil, weather, crop condition, land size and shape. The combine harvester was able to develop sufficient traction in soft soil during harvesting period in haor area. Zoomlion harvester is a cost-effective and time-saving machine but the initial costs are higher.

Rice Transplanting Mechanization in Bangladesh: Way to Make It Sustainable

“Rice transplanter” has brought a radical change in the method of rice seedlings transplanting in Bangladesh. The machine is gaining popularity with the increase of labor crisis during the peak period of transplanting, reduction time of in-between crops, rapid urbanization and industrialization, and changing socio-economic status of the farmers. Alternatively, the traditional way of rice transplanting is labor-intensive and involves high drudgery. Mechanical rice transplanter is cost-effective and operation-friendly. It is suitable to plant young seedlings maintaining plant to plant and line to line distance which plays an important role in increasing yield. Moreover, it is easy to take care of the crops planted in rows. It helps in maintaining soil physical properties and is considered to be better from a crop management and productivity point of view. In malignancy of having an edge over the traditional broadcasting, the adoption rate of mechanical transplanters is low due to high primary investment, lack of knowledge in growing mat type nursery, lack of repair and maintenance facility to the end-users, and unavailability of spare parts. Imparting these, available supply, entrepreneurship development, and encouraging custom hire services may be some of the practical results for adding the rice area under mechanical transplanting. This review summarizes the problems and prospects associated with seedling rice transplanting, technological gaps in the adoption of mechanical transplanters in a sustainable manner, and future ways to make transplanters more user-friendly and cost-effective.