Browsing by Author "Khairul Islam, Md."

Now showing 1 - 3 of 3

Characterization of zinc based high temperature solder alloys with chromium and molybdenum additions
(Department of Materials and Metallurgical Engineering (MME), 2017-02) Khairul Islam, Md.; Sharif, Dr. Ahmed
Initiative of development and characterization of Pb free high temperature solders was taken. Two systems such as Zn-xMo (x= 0.4, 0.6 and 0.8 wt% Mo) and Zn-xCr (x= 0.2, 0.4 and 0.6 wt% Cr) were chosen for this study. Samples of the selected compositions were fabricated through casting in a permanent metal mold. Their microstructural, thermal, mechanical and electrical characteristics were determined using several analytical techniques such as Scanning Electron Microscope (SEM), Differential Thermal Analyzer (DTA), X-Ray Diffractometer (XRD), Thermomechanical Analyzer (TMA), Universal Testing Machine (UTM), Hardness tester, Conductivity Meter etc. Experimental findings revealed that with the addition of Mo and Cr particles grain refinement occurred in both Zn-xMo and Zn-xCr systems which was evident in the scanning electron micrographic images. Energy-dispersive X-ray spectroscopy (EDS) spots in several zones of the microstructure confirmed the presence of Mo and Cr particles throughout the respective structures. XRD analysis showed a very little or no shift in the peak pattern compared to standard Zn pattern indicating no new phase formation. However, crystallite size calculation using Scherrer equation showed that, average crystallite size decreases with increasing Mo content and it ranged from around 34.0-29.4 nm in case of Zn-xMo system, while the average crystallite size of Zn-xCr system ranged between 29.7 and 28.8 nm. Brinell hardness showed an incremental trend with increasing Mo content. Similar results were obtained in Zn-xCr system. Brinell hardness number of Zn-xCr increased from 33.98 in Zn-0.2 Cr to 42.74 in case of Zn-0.6 Cr alloy. Similarly, hardness increased from 29.71 to 41.28 in case of Zn-0.4 Mo to Zn-0.8 Mo respectively. Tensile strength of unalloyed zinc increased from 31.09 MPa to 33.04 MPa when alloyed by 0.8% Mo. In a similar manner, strength of Zn-Cr solders increased from 40.53 to 47.07 MPa due to an increase in 0.4% Cr than that of the former. Fractographic analysis of the tensile fracture surfaces with SEM indicated mixed (neither completely ductile nor completely brittle) fracture mode of both Zn-xMo and Zn-xCr systems. Coefficient of thermal expansion (CTE) of Zn-Cr system was found to vary from 4.5-5×10-5 (1/ºC) while in Zn-Mo system it was 4.14-2.64×10-5 (1/ºC). Electrical conductivity of both Zn-xMo and Zn-xCr decreased with increasing Mo and Cr contents respectively. The relative conductivity of Zn-xMo and Zn-xCr varied from 27.35 to 26.55 and 25.3 to 22.7 %IACS (International Annealed Copper Standard) respectively in the selected composition range. DTA results suggested that onset of melting started at temperature below the melting temperature of pure Zn. It was found that, the onset temperature of melting of all three compositions of the Zn-xMo system was around 416ºC whereas, the finishing temperature of melting was around 423ºC indicating a melting range of around 7ºC. On the other hand, DTA graphs exhibited that, the onset of melting of the Zn-xCr alloys started at around 412ºC and it finished near about at 418ºC showing a melting/solidification range of about 6ºC. From the experimental findings it can be said that Zn-xMo as well as Zn-xCr systems might be promising candidate for high temperature solders in replacement of Pb based solders.
Impact of accessibility on house rent in Dhaka city: a hedonic price approach
(Department of Civil Engineering, 2006-09) Khairul Islam, Md.; Jobair Bin Alam, Dr. Md.
The key aim of this research is to contribute in the understanding of the relationship between house rent and accessibility in the context of Dhaka city. Housing is a serious problem in densely populated urban areas particularly in cities like Dhaka. The imbalance of housing demand and supply is aggravated by accessibility facilitated through transportation system. It is important to understand the relative contribution of accessibility in the change of housing demand which is reflected by house rent. In the context of analyzing house rent, besides accessibility other associated variables like condition of utility services, environment and neighborhood are also incorporated in the analysis. The study is based on hedonic price model to correlate house rent with its influencing factors. Multiple Least Square Regression is used to implement hedonic price modeling concept in the analysis. The study commences with analysis of house rent pattern in Dhaka city. For this purpose a GIS based database is developed. It is observed that except north and northwestern direction, the house rent in general reduces with the distance from the eBD at Motijheel area. In the north and north western directions which include Gulshan, Banani and Dhanmondi areas, house rent is found to be high at locations farther away from the central area. It is also observed that the house rent in older Dhaka area is relatively low in general. Still there are some locations in older part of the city having a very high rent which is caused by commercial activities. In the analysis it is found that house rent is affected by the quality of utility services, which include electricity, gas and water supply, level of environmental condition, features of neighborhood, width of access road and accessibility. Based on data of household survey and network travel time among the wards obtained from Dhaka Urban Transport Model, the analytical models are calibrated. Among the three measures of accessibility investigated in the study the measure which include the population of both origin and destination as weighing factor, together with inverse ofthe travel time, is found to be the most acceptable. For analyzing policy implication house rent elasticity with respect to different variables were analyzed. It is found that house rent per unit area reduces by 0.46 percent for 1 percent increase in average floor area from 1252.36 square feet of the house. On the contrary, house rent increases by 0.19 and 0.03 percent respectively with I percent increase of average aggregate environmental index and average aggregate neighborhood index from 9.49 and 9.41. The width of the access road is found to be an important parameter determining house rent and a I percent increase in average access road width from 12.50 feet causes 0.29 percent increase in the rent. An increase of accessibility by I percent will result in augmenting house rent by about 0.1 percent as obtained from averaging the results of the three accessibility models. The results of the study can be beneficial for the city planners and municipality officials in order to analyze transportation projects and determine housing taxes.
Status of house-hold duck rearing system along with productive performance in selected area of Kaligonj, Jhenaidah
(Chattogram Veterinary and Animal Sciences University Chattogram-4225, Bangladesh, 2019-08) Khairul Islam, Md.
The study was conducted to know the present status, existing production system of duck and assess the potentiality of duck rearing in rural areas of Jhenaidah district in Bangladesh. Data were collected randomly from 20 duck rearing farmers using a pre-tested interview schedule during October to November 2019 from several villages under Kaligonj Upazila of Jhenaidah. Beside this, socio-economic conditions of the farmers, feeding system and availability of feed for raising ducks, productive performances of scavenging ducks and profitability of raising those ducks were evaluated. In the study area most of the farmers were women. The level of education of farmers varied from primary to higher secondary. Most of the duck rearers (65%) were found primary educated. The average farm size was 18 and it always remains variable with the duck’s loss attributed to different causes. About 43% of the farmers housed their ducks in bamboo made cage while the rest of the farmers kept ducks in house made of wood, tin, brick or mud. Duck reaches first laying at 6 months of age, produces average 110 eggs per year. Egg production reaches peak during winter especially after crop-harvesting season. Around 55% of the respondents fed their birds with mixture of boil rice and rice polish as it is available and cheap. Approximately 10% respondents said that they do not spend any money on supplementary feed. The mortality rate was 19% and it is highest in winter (27%). Duck were vaccinated against duck plague mainly. Around 80% households sold eggs to the local market and 20% sold to the bepari and others. Total annual expenditure and annual income per duck were on an average 443.35 and 959.20 taka, respectively. It can be concluded that duck rearing knowledge of the farmers such as breeding, feeding, housing, prevention and control of diseases are not satisfactory of this areas. Introducing of improved duck breeds/varieties, training to duck farmers, ensuring vaccination to ducks, financial and technical support to the farmers could increase the duck rearing with increased household income and employment to youth, rural women and the small-holder marginal farmers.