• Journal of Korean Society on Water Environment
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• v.23 no.1
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• pp.46-51
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• 2007

This research work aims at treating saline wastewater generated from a fish market using four Sequencing Batch Reactors (SBR) operated under different conditions. The effect of C/N ratio (3, 6) and salt concentration (0.5~2%) on organic and nitrogen removal was studied. The synthetic wastewater prepared with glucose ($C_6H_{12}O_6$) as the primary carbon source along with ammonium chloride ($NH_4Cl$) was used in the three reactors. The fill, anoxic, aeration, settle and draw conditions were 2 hr, 4 hr, 4 hr and 2 hr respectively. The fourth reactor was operated at different conditions to investigate the practical feasibility of SBR application to handle fish market wastewater generated in Ulsan city that had fluctuating loading characteristics. Though the unacclimated sludge was initially affected by the salt concentration, the acclimated sludge removed 95% of the organics irrespective of the NaCl concentration and C/N ratio. However, the removal of nitrogen was affected more by C/N ratio than the salt concentration. While handling fish market wastewater, though the organic and nitrogen loading rate were varying between $0.009{\sim}0.259gCOD_{OH}/gVSS/day$ and 0.005~0.034 gN/gVSS/day, the effluent concentrations were far less than the effluent standard of $120mgCOD_{OH}/L$ and 60 mgN/L respectively, except when loading rates were fluctuating and 4 times higher than the average.

• Journal for History of Mathematics
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• v.23 no.4
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• pp.59-82
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• 2010

The Purpose of this study is to draw a few lessons for the effective teaching and learning throughout a comparative analysis on the results of the educational achievement on Mathematics of the primary and secondary school students. The primary sources for this research are based on the results of the six-times national level tests performed annually by all level students from 2003 to 2008. In order to achieve this goal, I, firstly, extract the lowest content area in terms of the annual average of the right answer ratio after examining the ratio of right answers to each math problem by classifying all multiple-choice questions of the educational achievement tests from 2003 to 2008 into the relevant content areas. Next, the characteristics of the content area which distinguish the lowest right answer ratio are qualitatively analyzed. Lastly, information on the content area which the school students of all classes feel very difficult to solve is provided via reckoning the average right answer ratio per each content area against all math questions at the last six-times of the national level tests.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.35 no.4
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• pp.3-14
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• 2019

The purpose of this study is to analyze the distribution characteristics of the agency-managed shared housings in Seoul and draw the possible implications from it. The needed data for the study was obtained from an on-line shared housing portal service which provides housing information from various shared housing management agencies. By mapping out the locations and other related data into a GIS(Geographic Information System) program, this study shows that shared housings in Seoul can be sorted into four large clusters. Each cluster has a different ratio of housing types and room capacities reflecting each regional circumstance and common causes. Women-only shared housing takes up 79% of the overall shared housing ratio and, while multi-family housing type has the most count, the apartment type has a noticeably high ratio in women-only housing compared to the apartment type ratio among the other gender-specific housings. Given the high crime rate against the single-person household of young adult women, the reason for the popularity of shared-apartment housing among young women can be deduced. However, the potential tenants' practical choices and their concern for safety are not the only causes that drive the current shared housing market. The young adults in their 20's and 30's choose to live in popular places where they can engage social activities. A new tier of shared housing market has also appeared in places where young adults could not have afforded if they lived alone. Choosing where we live is no longer about just meeting the requirements for a house based on what she/he needs but also about satisfying the preferences for a living based on what she/he desires. This paper indicates that although there is an undeniable premise that 'sharing a house' revolves around the realm of housing welfare and is not a typical topic for the upper-income households, the way we live and how we choose our place to live is shifting.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.399-402
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• 2009

The Clad sheet is made roll-bonding process of the one or more material with the different property. Good formability is an essential property in order to deform a clad metal sheet to a part or component. In this study, the mechanical properties and formability of a Mg-Al-SUS clad sheet are investigated. The clad sheet was deformed at elevated temperatures because of its poor formability at room temperature. Tensile tests of the each material and clad sheet were performed at various temperatures and at various strain rates. The limited draw ration (LDR) was obtained using a deep drawing test to measure the formability of the clad sheet. A finite element (FE) analysis was performed to predict formability of the cup drawing product, one_layer model and three_layer model.

• The Journal of the Acoustical Society of Korea
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• v.17 no.3E
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• pp.58-66
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• 1998

In this paper, we analyze the effects of interference canceller on the performance of multitone DS/CDMA system proposed by Vandendorpe[5]. There are various kinds of interference canceller suggested by different researchers including parallel and successive cancellers and we adopt a canceller used by Yoon et al.[9] which is a kind of parallel canceller. We consider three kinds of interferences, that is, multipath interference(MPI), interchannel interference(ICI) and multiple access interference(MAI). The ICI is the interference between multitones. The equations for variances. are derived for the inteferences and thermal noise used for signal to noise ratio calculation. We also consider RAKE reception over multipath channel which is modeled as lowpass equivalent linear filter and three stage interference canceller used for performance improvement. We show the performance results for number of canceller stage, diversity order and number of users and draw some conclusions that interference canceller is effective in multitone DS/CDMA system and the performance is further improved with the higher order of diversity and larger number of PN chips.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.04a
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• pp.23-26
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• 2003

Solid-state extrusion technique was employed for the improvement of mechanical properties of polylactic acid (PLLA) widely used as biodegradable internal fixation devices currently. Cylindrical billets were machined out from the vacuum compression-molded PLLA to have various diameters, and solid-state extrusion of the billets was performed at various drawing rates and at the extrusion temperature of $130^{\circ}C$. Throughout the whole processes the decrease in molecular weight was significantly suppressed to be about $10\%$. Flexural modulus and strength of PLLA increased up to 8.3 GPa and 221 MPa, respectively. Studies on the orientation and crystallinity of extruded PLLA could reveal the effects of billet morphology, draw ratio, and drawing rate on the flexural strengths of PLLA.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.30 no.1
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• pp.108-113
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• 2008

It would be desirable to regenerate bone vertically in a predictable way; such a technique would allow for more favorable implant - crown ratio and better esthetics for implant placement. Traditionally, several techniques has been proposed for this purpose including GBR with particulated bone and block bone graft using mandible or illium however, the efficacy of these techniques has not been firmly established because they have some week points or complications each other that it is difficult to draw firm conclusion for superiority. In recent years, We have treated 11-cases of vertical deficiency of alveolar bone using thin block and chip bone graft technique and the postoperative results showed good prognosis with few complications. So we report the results of its treatment and cases with review of literature.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.616-620
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• 2001

The wrinkling in the flange and wall of a part is a predominent failure mode in stamping of sheet metal parts. In many cases this wrinkling may be eliminated by appropriate control of the blank holding force(BHF), but BHF affects the draw depth. Although the wrinkles of flange have been made in the incipient stage of drawing, if the height of wrinkles is maintained under a prescribed limit by decrease or extinction of wrinkles in the course of drawing, small BHP can be allowed so that the depth of drawing could be increased. Authors research the variation of the wrinkles in flange in the course of square cup drawing by using aluminium A1015 and aluminium alloy A5052.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.369-374
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• 2001

Gear is general mechanical elements that used for power transmission between two shafts that interval is comparatively short. and it delivers big power as accurate ratio of speed. The profile of Spur gear which is the most basic factor is divided into Trochoidal fillet curve and Involute curve. Involute curve is used a lot of a shaped curve of machine parts such as a gear, a scroll compressor and a collar of centrifugal pump. However, it is poor to study the modeling of Trochoidal fillet curve and the three dimensions model shaped mathematical curve. This paper describes a mathematical model of profile shifted involute gear. and this model is based on Camus's theory. We draw three dimensions gear have accurate mathematical function using ADS, VisualLISP. and To check accuracy and perfection, we make a program of checking Interference. and use for this study.

• Journal for History of Mathematics
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• v.16 no.3
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• pp.69-76
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• 2003

In this article, We explained the historical origin and significance of decimal fraction, and draw some educational implications based on that. In general, it is accepted that decimal fraction was first invented by a Belgian man, Simon Stevin(1548-1620). In short, the idea of infinite decimal fraction refers to the ratio of the whole quantity to a unit. Stevin's idea of decimal fraction is significant for the history of mathematics in that it broke through the limit of Greek mathematics which separated discrete quantity from continuous quantity, and number from magnitude, and it became the origin of modern number concept. H. Eves chose the invention of decimal fraction as one of the "Great moments of mathematics."The method of teaching decimal fraction in our school mathematics tends to emphasize the computational aspect of decimal fraction too much and ignore the conceptual aspect of it. In teaching decimal fraction, like all the other areas of mathematics, the conceptual aspect should be emphasized as much as the computational aspect.al aspect.