• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.3 s.18
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• pp.29-39
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• 2005

The objective of this study is to analyze the relation of critical duration according to hydrologic characteristics in urban areas. RRL, ILLUDAS, SWMM, and SMADA urban runoff models were applied to the Seongnae and Banpo watershed and experiment area of the Dong-Eui University. Also, hydrologic characteristics such as temporal pattern of rainfall, rainfall intensity formula, antecedent moisture condition, return period, and urban runoff model were used to simulate the critical duration of the test areas. The results of this study are as follows; (1) The type of temporal pattern of rainfall which causes maximum peak discharge in urban area has resulted in Huff's 4th quartile distribution. (2) The critical duration in urban areas were not influenced by hydrological factors except urban runoff model. (3) Peak discharge and critical duration in urban areas were influenced by the urban runoff model, and the SWMM model using Huff's 4th quartile distribution shows maximum critical duration.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.3 s.22
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• pp.57-68
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• 2006

The objective of this study is to analyze the temporal pattern characteristic of short-duration rainfall defined as a rainfall durations of 6 hours or less by the Huff's 4th quartile distribution. To analyze the temporal pattern characteristic of short-duration rainfall, the rainfall data are classified by rainfall duration and rainfall type(Changma, Typhoon, Severe rain storm, Frontal storm) and change of rainfall segment. Also, the results of this study compared with result of research work of Korea Institute of Construction Technology(1989) and Ministry of Construction & Transportation(2000). The conclusions of this study are as follows; (1) Short-duration rainfall with duration of 6 hours or less is found to be most prevalent frist-quartile storms. (2) In the case of rainfall type, Changma and Severe rain storms and Frontal storm is found second-quartile storms, and Typhoon is found third-quartile storms. (3) In the result by change of sixth segment storms, the type of temporal pattern of rainfall is found to be most prevalent two sixth parts, (4) Comparative analysis of the results shows that shapes of the dimensionless cumulative curves and values are different from those of existing researches.

• Journal of Environmental Science International
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• v.23 no.4
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• pp.715-722
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• 2014

Effects of coagulation types on flocculation were investigated by using a photometric dispersion analyzer (PDA) as an on-line monitoring technique in this study. Nakdong River water were used and alum and ferric chloride were used as coagulants. The aim of this study is to compare the coagulation characteristics of alum and ferric chloride by a photometric dispersion analyzer (PDA). Floc growing rates ($R_v$) in three different water temperatures ($4^{\circ}C$, $16^{\circ}C$ and $30^{\circ}C$) and coagulants doses (0.15 mM, 0.20 mM and 0.25 mM as Al, Fe) were measured. The floc growing rate ($R_v$) by alum was 1.8~2.8 times higher than that of ferric chloride during rapid mixing period, however, for 0.15 mM~0.25 mM coagulant doses the floc growing rate ($R_v$) by ferric chloride was 1.1~2.3 times higher than that of alum in the slow mixing period at $16^{\circ}C$ water temperature. Reasonable coagulant doses of alum and ferric chloride for turbidity removal were 0.1 mM (as Al) and 0.2 mM (as Fe), respectively, and the removal efficiency of those coagulant doses showed 94% for alum and 97% for ferric chloride. The appropriate coagulant dose of alum and ferric chloride for removing dissolved organic carbon (DOC) showed about 0.3 mM (as Al, Fe) and at this dosage, DOC removal efficiencies were 36% and 44%, and ferric chloride was superior to the alum for removal of the DOC in water.

• 재활복지
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• v.22 no.2
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• pp.213-230
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• 2018

The study looked at the impact on the health of the spine caused by the increasing addiction to smart phones, and examine the moderating effect of adjusting spinal health according to cognitive strength. All subjects used the smartphone by measuring the diagnostic scale of the smartphone addiction, the angle of forward inclination of the cervical spine, and the amplitude variation of the cognitive Gamma-Peak of the brain waves. As a result, as the use of smart phones increases, the spine angle significantly increased (p<0.001), as cognitive strength increased, the spine angle decreased significantly (p<0.01). The cognitive strength also showed the effect of adjusting the spine angle through interaction with the degree of use of a smartphone (p<0.05). This results in a higher degree of smartphone use in lower and middle cognition strength groups, which results in a higher angle of forward tilt in the cervical spine.

• Korean Journal of Metals and Materials
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• v.46 no.4
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• pp.189-198
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• 2008

The changes in microstructure and mechanical properties of AZ31 alloy subjected hot-rolling process were investigated. The AZ31 plates fabricated by horizontal continuous casting process were prepared and have hot-rolled from 30 mm to 1 mm in thickness under different processing conditions. At the rolling temperature of $400^{\circ}C$, little surface and side crack was observed up to 20% reduction rate. As total reduction and reduction rate increase to more than 75% and 20% pass, respectively, Grains were more uniformly refined through overall thickness, and particularly lots of shear bands were appeared to be inclined at less than $20^{\circ}C$ along the rolling direction. Average grain size of less than $5{\mu}m$ and tensile properties of YS ${\geq}$ 250 MPa, UTS ${\geq}$ 300 MPa and El. ${\geq}$ 13% were acquired for hot-rolled AZ31 sheets without post-heat treatment. Maximum intensity of (0002) pole figure was decreased with an increase in reduction rate, indicating the improvement of texture by means of high reduction rate.

• Journal of Information Technology Services
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• v.21 no.2
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• pp.27-41
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• 2022

In a fiercely competitive environment, quality is a key factor that enables dashboard camera makers to maintain their competitive advantage. Quality affects consumer satisfaction, brand loyalty, and firm performance. Therefore, to remain competitive, it is important that manufacturers maintain product quality that meets consumer expectations. To this end, it is necessary to investigate customer preferences and product performance in terms of product quality and to properly allocate resources to improve the quality level such that the firm can maintain a competitive advantage. In this paper, we proposed the various ways in which manufacturing firms can determine which quality dimensions need improvement in order to secure competitiveness. To this end, we analyzed a case study of Urive to develop a quality improvement strategy through importance performance competitor analysis (IPCA). Urive's IPCA results showed that 14 quality dimensions, namely performance, size, price, ease of use, country of origin, manufacturer, brand, product certificate, warranty, distribution channel, market share, reliability, durability, and conformance, were not absolutely competitive compared with those of Mando, Inavi, and Finevu. In terms of color, Urive had an absolute competitive advantage over Mando, but not Inavi and Finevu. Urive's appearance was more competitive than Mando's, but not Inavi's and Finevu's. In terms of advertisement and serviceability, Urive was absolutely less competitive than Mando and Inavi, but had a competitive advantage over Finevu. Therefore, it is necessary to put resources and time as the first priority for performance, reliability, and durability, which have a large performance difference in common among the three brands. The quality dimensions in which resources and time need to be put in second place are price and ease of use, which have a large performance difference in common among the two brands.

• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.119-130
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• 2008

Uncertainties in physical and engineering parameters for the design of shallow foundations arise from various aspects such as inherent variability and measurement error. This paper aims at investigating and reducing uncertainty from deterministic method by using the reliability-based design of shallow foundations accounting for the variation of various design parameters. A probability distribution type and statistics of random variables such as unit weight, cohesion, infernal friction angle and Young's modulus in geotechnical engineering are suggested to calculate the ultimate bearing capacities and immediate settlements of foundations. Reliability index and probability of failure are estimated based on the distribution types of random variables. Widths of foundation are calculated at target reliability index and probability of failure. It is found that application and analysis of the best-fit distribution type for each random variables are more effective than adoption of the normal distribution type in optimizing the reliability-based design of shallow foundations.

• Journal of the Korean Geotechnical Society
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• v.24 no.11
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• pp.133-141
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• 2008

In this study, a new method for estimating the undrained shear strength $s_u$ of saturated clays using piezocone penetration test (CPTu) result is proposed. This is to develop more effective CPTu-based $s_u$ estimation method at lower cost with less uncertainty. For this purpose, a marine clay deposit is selected and tested through extensive experimental testing program including both in-situ and fundamental laboratory tests. The proposed method is based on a correlation between the undrained shear strength $s_u$ and the cone resistance $q_t$, without introduction of the total overburden stress into the $s_u-q_t$ correlation. As a result, no additional testing procedure for collecting undisturbed soils samples is required, which can reduce overall testing cost. To verify the proposed method, 4 test sites, which consist of a variety of soil conditions, are selected and used for comparison between measured and predicted undrained shear strength. From comparison, it is seen that predicted values of $s_u$ using the proposed method match well those from measured results.

• Journal of the Korean Geotechnical Society
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• v.23 no.8
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• pp.77-85
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• 2007

In order to estimate undrained shear strength and evaluate cone factors, various in-situ and laboratory test results at new harbor construction area near Pusan were analyzed. To evaluate Nk values and equation applicable in Korea, measured and theoretical cone factors were compared based on the test results. For comparison, various analytical solutions were adopted and used. Adopted methods include cavity expansion solutions of Baligh (1975) and Yu (1993) and steady state solutions of Teh and Houlsby (1991) and Yu et al. (2000). According to the result of comparison, cavity expansion solutions were found to be reasonable for the CPTu-based undrained shear strength evaluation.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.38-38
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• 2022

서울특별시(이하 서울시)는 기존 상습침수지역과 2010년, 2011년 집중호우로 발생한 침수피해를 바탕으로 34개의 침수취약지역을 선정하고, 이들 지역에 2011년 3월부터 2023년 12월까지 총사업비 1조 5,300억여 원을 투입하여 하수관거 정비, 펌프장 신설 및 증설, 저류조 신설 등 배수능력을 확충하는 사업을 진행해오고 있다. 하지만, 기후변화로 인해 집중형 배수시설의 설계용량을 초과하는 강우의 발생빈도가 증가하고, 극한홍수 발생위험과 기상예측 불확실성이 커짐에 따라, 배수시설의 용량을 증설하는 집중형 우수배제체계 중심의 침수관리만으로는 안전한 침수대응이 어렵게 되었다. 본 연구에서는 서울시 침수대응 다각화를 위해 유역의 자연적, 사회환경적 특성을 대표할 수 있는 52개 지표를 선정하고 서울시를 소규모 유역 단위인 163개의 배수분구로 구분하여 지표별 공간적 분포와 특성 분석을 통해 각 배수분구를 유형화하고, 유형특성에 따른 침수취약성과 잠재적 침수발생 위험성을 분석하여 침수위험성을 평가하였다. 유역의 특성을 대표하는 각종 지표의 서울시 내 공간적 분포를 분석한 결과, 지표별 공간적 분포 특성이 상이했으며, 지표별 최대/최소값의 차이가 수배에서 수백배까지 나타나는 것으로 분석되었다. 특히, 서울시 내외에 산포된 총 40개 기상청관측소의 2010년부터 2019년까지 시간강우자료를 이용하여 강우관련 지표들의 시공간적 분포를 분석한 결과, 연평균강우량, 여름철강우량, 일최대강우량 등에서 지역적으로 최대 수백 mm의 강우량 차이가 발생하는 것으로 나타났다. 유역특성에 따른 서울시 침수위험성을 평가한 결과, 침수발생 및 피해에 불리한 유역의 공간적 취약성이 높은 배수분구로는 봉천1, 송파, 길동, 미아, 상계1 등의 순으로 나타났으며, 침수발생에 대한 잠재적 위험성이 높은 배수분구는 이문, 정릉, 제기1, 장안, 전농 등의 순으로 분석되었다. 침수발생에 대한 잠재적 위험성과 침수피해에 불리한 공간적 취약성이 모두 높아 침수위험성이 큰 배수분구는 상계1, 미아, 장위, 창동1, 동선, 수유2, 방학, 길동, 월계2 등의 순으로 나타났다.