• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.559-562
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• 2006

Although flood is a very common natural disaster in Bangladesh, recently Dhaka, the capital city of Bangladesh got flooded even in moderate rainfall. Accordingly, on January 2002 the sale and use of polythene bags were banned, by identifying it as one of the main causes for such flooding. Now the question arises, whether only polythene shopping bags are alone responsible for causing water logging problem. Accordingly, the objective of this study is to detect the reason(s) for the recent prolonged water logging problem in Dhaka City, even by small amount of rainfall. Both contingent valuation method and remote sensing technique were used for comparison of the results. The results of the study indicated that, not only polythene bags, but also unplanned land filling is also liable for creating water logging problem in Dhaka City. Finally, the study suggested that, the value of wetlands lost, which is directly related to the recent water logging problem, is more higher than what actually thought by the citizens of Dhaka City.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.667-675
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• 2008

As a large construction such as highway, dam, reclaimed land etc. increase in number more and more, large amount of fill materials are required. However, it's difficult to obtain it because of environmental problems and economical efficiency. A alternative plan is to utilize a gypsum which is a by-product yielded from chemical plants and verify suitability to use gypsum as fill materials. Therefore, a characteristic of compaction for gypsum is analyzed and construction methods are given regard to this characteristic from construction of dike using gypsum. Based on the results obtained, it is found that moisture of gypsum in compaction should to be more dry side of O.M.C(optimal moisture content) because of sponge phenomenon. When gypsum is used to fill materials, standards of compaction should be decided from laboratory test.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.99-102
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• 2002

The present study describes a numerical analysis for simulation of the sloshing of flows with free-surface which contained in a rectangular tank The SOLA-VOF (Volume of fluid) method uses a fixed mesh for calculating the motion of flow and the free-surface. This Eulerian approach enables the VOF method to use only a small amount of computer memory for simulating sloshing problems with complicated free-surface contours. The VOF function, representing the volume fraction of a cell occupied by the fluid, is calculated for each cells, which gives the locating of the free-surface filling any some fraction of cells with fluid. Using SOLA-VOF method, the study describes visualization about simulation of the sloshing of flows and damping effect by baffle. Translation and pitching motion of the forms have been investigated The time-dependent changes of free-surface height are used for visualization subject to several conditions such as fluid height horizontal acceleration, sinusoidal motion, and viscosity. The free-surface heights were used for comparing wall-force, which is caused by sloshing of flows. Baffle was Installed to reduce the force on the wall by sloshing of flows. Damping effects was extensively expressed under the conditions such as baffle shape and position.

• 한국해양공학회지
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• 제19권6호통권67호
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• pp.16-21
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• 2005

In the design of super tankers or LNG carriers, which transport a large amount of liquid in the cargo tanks, the structural d11mage due to liquid sloshing is an important problem. The impact pressure from sloshing is most violent when the liquid motion of a partially filled tank is in resonance with the motion of a ship. In this study, the sloshing natural periods of a baffled tank, often installed to reduce liquid motion, is analyzed. A variational method is adopted to estimate the sloshing natural periods for a prismatic cargo tank with baffles of arbitrary filling depth of liquid; the results are compared with Lloyd's Register regulations on sloshing periods. In this study, using an effective liquid-fill-depth concept, sloshing periods for a baffled tank can be expressed by the same form as rectangular prismatic tanks without baffles. In contrast to Lloyd's Register regulations, which can be applicable only to cargo tanks with constant baffle size and distribution, the present results can be applicable to cases of variable baffle size and distribution.

• Journal of applied mathematics & informatics
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• 제19권1_2호
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• pp.397-414
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• 2005

In the existing literature, most of the purchasing models were developed only for retailers problem ignoring the constraint of storage capacity of retailers shop/showroom. In this paper, we have developed a deterministic model of wholesaler-retailers' problem of single product. The storage capacity of wholesaler's warehouse/showroom and retailers' showroom/shop are assumed to be finite. The items are transported from wholesaler's warehouse to retailers' Own Warehouse (OW) in a lot. The customer's demand is assumed to be displayed inventory level dependent. Demands are met from OW and that spaces of OW will immediately be filled by shifting the same amount from the Rented Warehouse (RW) till the RW is empty. The time duration between selling from OW and filling up its space by new ones from RW is negligible. According to relative size of the retailers' existing (own) warehouse capacity and the demand factors, different scenarios are identified. Our objectives are to optimize the cost functions of wholesaler and two retailers separately. To solve this problem, a real coded Genetic Algorithm (GA) with roulette wheel selection/reproduction, whole arithmetic crossover and non-uniform mutation is developed. Finally a numerical example is presented to illustrate the results for different scenarios. To compare the results of GA, Generalised Reduced Gradient Method has been used for the problem. Also, a sensitivity analysis has been performed to study the variations of the optimal average cost with respect to the different parameters.

• International Journal of Precision Engineering and Manufacturing
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• 제9권4호
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• pp.79-82
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• 2008

A method is described for ideally reconstructing the profile from a surface profiling measurement containing a reasonable amount of null measurement data. The proposed method can conjecture lost information and rectify irregular data that result due to bad measuring environments, signal transmission noise, or instrument-induced errors, The method adopts the concept of computer graphics and consists of several processing steps. First, a search for valid data in the neighborhood of the null data is performed. The valid data are then grouped and their contours are extracted. By analyzing these contours, a bounding box can be obtained and the general distribution of the entire area encompassing the valid and null data is determined Finally, an ideal surface model is overlaid onto the measurement results based on the bounding box, generating a complete reconstruction of the calculations, A surface-profiling task on a liquid crystal display photo spacer is used to verify the proposed method. The results are compared to those obtained through the use of a scanning electron microscope to demonstrate the accuracy of the proposed method.

• Corrosion Science and Technology
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• 제16권6호
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• pp.273-277
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• 2017

Atmospheric corrosion is clearly the most noticeable of all corrosion processes. A tremendous amount of economic losses are caused by atmospheric corrosion. Thus, it is imperative to know the level of atmosphere's aggressiveness or in other words "corrosivity", before designing or planning any corrosion prevention strategy. In Singapore, corrosivity values were not recorded earlier though the process of measurement and recording was prevalent in other countries. With an aim of filling this gap, three test sites were setup at three locations in Singapore to represent marine, industrial and urban atmospheres or their mixtures. Subsequently, corrosivity readings were measured and recorded according to ISO 9223:2012 for the first time in Singapore. Salient atmospheric constituents or parameters like time of wetness (TOW), $Cl^-$, $SO_2$, $NO_2$, $O_3$, and $HNO_3$ were measured at all sites over a period of time to categorize corrosivity of particular atmosphere. The effect of the atmosphere on corrosion of steel, Cu, Al, and Zn has also been investigated and quantified. "Estimated" and "determined" corrosivities were quantified and compared according to ISO 9223 standard. The study data along with final corrosivity measurements will be presented and discussed in the present work.

• 한국자동차공학회논문집
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• 제14권3호
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• pp.44-50
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• 2006

The mono steel forged piston was improved a mechanical strength of an aluminum piston and reduced the weight of a articulated piston. The mono steel forged piston was composed of forged crown part and forged skirt part and was completed by friction welding process of two forged parts. Forging process analysis and friction welding analysis was done by finite element simulation using numerical package DEFORM. The preform shape and the initial billet dimension were decided by maximum stress of the die, amount of the flash and filling of die. The upset length of friction welding variable was decided by the shape of the flash that was created by friction welding analysis. Through this research, we developed a forging process of the mono steel forged piston, and decided the design variables of friction welding.

• Restorative Dentistry and Endodontics
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• 제41권4호
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• pp.310-315
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• 2016

Two case reports describing a new technique of creating a repositionable piezoelectric bony window osteotomy during apicoectomy in order to preserve bone and act as an autologous graft for the surgical site are described. Endodontic microsurgery of anterior teeth with an intact cortical plate and large periapical lesion generally involves removal of a significant amount of healthy bone in order to enucleate the diseased tissue and manage root ends. In the reported cases, apicoectomy was performed on the lateral incisors of two patients. A piezoelectric device was used to create and elevate a bony window at the surgical site, instead of drilling and destroying bone while making an osteotomy with conventional burs. Routine microsurgical procedures - lesion enucleation, root-end resection, and filling - were carried out through this window preparation. The bony window was repositioned to the original site and the soft tissue sutured. The cases were re-evaluated clinically and radiographically after a period of 12 - 24 months. At follow-up, radiographic healing was observed. No additional grafting material was needed despite the extent of the lesions. The indication for this procedure is when teeth present with an intact or near-intact buccal cortical plate and a large apical lesion to preserve the bone and use it as an autologous graft.

• Korean Chemical Engineering Research
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• 제53권3호
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• pp.382-390
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• 2015

Poly(methyl methacrylate) (PMMA) supports and amine additives were investigated to adsorb $CO_2$. PMMA supports were fabricated by using different ratio of pore forming agents (porogen) to control the BET specific surface area, pore volume and distribution. Toluene and xylene are used for porogens. Supported amine sorbents were prepared by wet impregnation of tetraethylenepentamine (TEPA) on PMMA supports. So we could identify the effect of the pore structure of supports and the quantity of impregnated TEPA on the adsorption capacity. The increased amount of toluene as pore foaming agent resulted in the decreased average pore diameter and the increased BET surface area. Polymer supports with huge different pore distribution could be fabricated by controlling the ratio of porogen. After impregnation, the support with micropore structure is supposed the pore blocking and filling effect so that it has low $CO_2$ capacity and kinetics due to the difficulty of diffusing. Macropore structure indicates fast adsorption capacity and low influence of amine loading. In case of support with mesopore, it has high performance of adsorption capacity and kinetics. So high surface area and meso-/macro- pore structure is suitable for $CO_2$ capture.