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  • Author: Zahid Hasan x
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Abstract

Most of the people living in developing or less developed countries have limited earning to provide somehow their basic needs and usual staff. Carrying goods is a regular task in life and several products have been invented to minimize efforts in this purpose. However, the price and features of most available products are out of the reach for the people of limited earnings. Stair climbing cart is very useful for those houses where a lift is not available. In this research, a modified mechanical design with eight wheels providing pause-rest feature has been represented with the equations of pulling force, constraints of stair dimensions and climbing mechanism. The ‘House of Quality Diagram ‘(QFD)’ has been added to accomplish the vision of further market research and customer satisfaction. The factor of safety and different types of stress have been determined for different types of loads and conditions. In addition, the details of the material with dimension, design and feasibility analysis have led this research to uniqueness.

Abstract

The aim of this study is to exploit a suitable chitosan extraction method from the chitin of indigenous shrimp shells by employing different physicochemical treatments and to improve different bioactive properties of this extracted chitosan (CS) by applying gamma radiation. Chitin was prepared from shrimp shell by pretreatment (deproteination, demineralization and oxidation). Chitosan was extracted from chitin by eight different methods varying different physicochemical parameters (reagent concentration, temperature and time) and assessed with respect to the degree of deacetylation, requirement of time and reagents. The method where chitin was repeatedly treated with 121°C for 30 min with 20 M NaOH, produced the highest degree of deacetylation (DD) value (92%) as measured by potentiometric titration, with the least consumption of time and chemicals, and thus, selected as the best suitable extraction method. For further quality improvement, chitosan with highest DD value was irradiated with different doses (i.e., 5, 10, 15, 20 and 50 kGy) of gamma radiation from cobalt-60 gamma irradiator. As the radiation dose was increased, the molecular weight of the wet irradiated chitosan, as measured by the viscosimetric method, decreased from 1.16 × 105 to 1.786 × 103, 1.518 × 103, 1.134 × 103, 1.046 × 103 and 8.23 × 102 dalton, respectively. The radiation treatment of chitosan samples increased the antimicrobial activity significantly in concentration dependent manner on both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria, as determined by the well-diffusion method. Four to five percent wet chitosan treated with a radiation dose range of 5.0–10.0 kGy rendered the highest antimicrobial activity with least energy and time consumption. Solubility, water binding capacity (WBC) and fat binding capacity (FBC) also improved due to irradiation of chitosan.

Abstract

In the present world, nuclear energy is a must need for various purposes. The main cause of nuclear energy is because of the increasing energy demand, which is not possible to provide by using convenient energy generation. Bangladesh is a lower income country and the energy sector is not so developed here though there is a very high demand for energy. Rooppur Nuclear Power Plant is the only one nuclear generation plant which can provide this kind of huge energy within a very short time. This paper mainly depicts the ins and outs of this plant and discusses it’s feasibility in Bangladesh. It also focuses on the worlds various power generation methods and comprises it with nuclear energy generation. A detailed technical brief is presented in this paper along with advantages, location selection, financial and environmental impacts. This will help researchers to do further researches about nuclear energy in Bangladesh.

Abstract

Most of the people living in developing or less developed countries have limited earning to provide somehow their basic needs & usual staff. Carrying goods is a regular task in life & several products have been invented to minimize efforts in this purpose. But the product’s price & features are not optimum for the people of fewer earnings. Stair climbing cart is very useful for those houses where a lift is not available and goods have to be carried frequently upstairs. In this research, the mechanical design has been modified so that the manufacturing cost can be minimized. Finite element analysis has been performed upon the design to find out how the manufacturing cost can be reduced by making the design optimal for manufacturing cost and process. The result shows that the structural members should not be processed further because any tooling operation will require an extra machine as well as an extra cost. Only the wheels are possible to subject under optimization by reducing material as well as weight. This article will be a valuable asset for the mass manufacturers of this type of product.