• 한국정밀공학회지
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• 제20권11호
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• pp.188-193
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• 2003

To predict changes in biomechanical parameters such as intradiscal pressure, and the shock absorbing mechanism in the spinal motion segment under different impact duration/loading rates, a three dimensional L3/L4 motion segment finite element model was modified to incorporate the poroelastic properties of the motion segment. The results were analyzed under variable impact duration for normal and degenerated discs. For short impact duration and a given maximum compressive force, relatively high cancellous pore pressure was generated as compared with a case of long impact duration, although the amount of impulse was increased. In contrast relatively constant pore pressure was generated in the nucleus. Disc degeneration increased pore pressure in the disc and decreased pore pressure in the cancellous core, which is more vulnerable to compressive fracture compared with intact case.

• 대한기계학회논문집A
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• 제22권1호
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• pp.52-63
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• 1998

The impact programmer for impact test was designed and the impact analysis was conducted. The effects of the material and geometric parameters on the impact force and pulse shape were investigated. The impact characteristics were examined by experimental and finite element method. The impact test was conducted with free drop impact tester. The ABAQUS/Explicit 5.5 version was used for finite element analysis. The geometric parameters of the conical and dome type impact programmer were analyzed. The polyurethane impact programmers were fabricated and tested. The effects of the hardness and thickness of the impact programmer were studied. The peak acceleration and time duration of impact programmer have close correlation with the hardness, impact energy and thickness of the impactor. The experiment was good agreement with analytical predictions. The impact pulse shape generated with polyurethane impact programmer was half sine shape. The maximum impact force was proportional to impact energy. The impact acceleration was decreased with thickness of impact programmer. The maximum impact time duration level was about 2 msec.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.117-120
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• 2002

In this study the occlusion of dural-sac, the outer membrane of spinal cord in the lumbar region, was quantitatively analyzed using one motion segment finite element model. Occlusion was quantified by calculating cross sectional area change of dural-sac far different compressive impact duration(loading rate) due to bony fragment at the posterior wall of the cortical shell in vertebral body. Dural-sac was occluded most highly in the range of 8∼12 msec impact duration by the bony fragment intruding into the spinal canal. t=400 msec case 4% cross sectional area change was calculated, which is the same as the cross sectional area change under 6 kN of static compressive loading.

• Steel and Composite Structures
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• 제27권6호
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• pp.691-702
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• 2018

This paper presents experimental and analytical results of fiber reinforced polymer (FRP) confined steel tubular columns under transverse impact loads. Influences of applied impact energy, thickness of FRP jacket and impact position were discussed in detail, and then the impact responses of FRP confined steel tubes were compared with bare steel tubes. The test results revealed that the FRP jacket contributes to prevent outward buckling deformation of steel at the clamped end and inward buckling of steel at the impact position. For the given applied impact energy, specimens wrapped with one layer and three layers of FRP have the lower peak impact loads than those of the bare steel tubes, whereas specimens wrapped with five layers of FRP exhibit the higher peak impact loads. All the FRP confined steel tubular specimens displayed a longer duration time than the bare steel tubes under the same magnitude of impact energy, and the specimen wrapped with one layer of FRP had the longest duration time. In addition, increasing the applied impact energy leads to the increase of peak impact load and duration time, whereas increasing the distance of impact position from the clamped end results in the decrease of peak impact load and the increase of duration time. The dynamic analysis software Abaqus Explicit was used to simulate the mechanical behavior of FRP confined steel tubular columns, and the numerical results agreed well with the test data. Analytical solution for lateral displacement of an equivalent cantilever beam model subjected to impact load was derived out. Comparison of analytical and experimental results shows that the maximum displacement can be precisely predicted by the present theoretical model.

• 동아시아식생활학회지
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• 제20권3호
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• pp.473-480
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• 2010

This study examined the different meal duration expectations and dining characteristics of customers each stage of service (order, cook, check), and investigated the impact of perceived meal duration on customers' satisfaction. The procedures consisted of four phases. During the first phase, the different meal duration expectations and dining characteristics of customers of an Italian restaurant in Seoul were examined by survey at each stage of service. The second phase investigated the impact of perceived meal duration on customer' satisfaction. The third phase compared perceived meal duration and actual meal duration. The last phase suggested appropriate meal duration for maximization of customer' satisfaction. We also examined the effects of meal time (lunch or dinner) on meal duration preferences. Customer satisfaction was decreased with longer perceived meal duration for the order and check stages and too short perceived meal duration for the cook stage. To determine appropriate meal duration for each service stage, the relationship between perceived and actual meal durations was examined. This study confirms that customers dining at restaurants preferred a longer cook time and that a shorter meal duration at dinner decreased satisfaction ratings more when compared to lunch.

• 한국식생활문화학회지
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• 제25권2호
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• pp.189-197
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• 2010

This study, which took place in an Italian restaurant in Seoul, investigated the impact of meal duration on the evaluation of satisfaction and service quality, according to the service stages (order, cook, check) of a restaurant. Research procedures included two phases: during the first phase, data on expected-perceived meal duration, and service quality and satisfaction were collected by surveys, which were distributed at the restaurant. The second phase investigated the relationships among meal duration, customers' satisfaction, and service quality. T-tests and regression analyses were used to examine relationships between these variables. Results indicate that both failing to meet customers' expected meal duration, as well as the perceived meal duration could negatively impact the satisfaction and evaluation of service quality. The study confirmed that meal duration is indeed related to the responsiveness aspect of service quality. The important aspect of meal duration management is to improve service quality and satisfaction, which can lead to a restaurant's success. Therefore, understanding the relationships among meal duration, satisfaction, and service quality is a part of a good foundation for effective meal duration management.

• 한국건축시공학회지
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• 제11권2호
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• pp.100-107
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• 2011

건설공사의 공사기간은 건설프로젝트의 성공적인 완수를 위하여 중요한 부분을 차지하기 때문에 공사기간에 영향을 미치는 요인들을 체계적으로 관리하는 것이 필요하다. 최근에는 건설 제도적 변화로 건설공사의 공사기간에 대한 관심이 증대되고 있다. 그러나 건설 프로젝트의 공사기간에 미치는 영향요인은 매우 다양하며, 각 요인들 중 어떤 요인이 어느 정도 작업의 생산성에 영향을 미치는지에 대한 데이터의 체계적인 활용이 부족하다. 또한 특정 프로젝트, 특정 작업, 특정 협력업체 등에 영향을 미치는 요인이 무엇인지 또는 전체 프로젝트에 공통적으로 영향을 미치는 요인이 무엇인지를 인식하는 것조차 어려운 경우가 많다. 그러나 데이터 웨어하우스 기술의 다차원 분석을 활용함으로써 다양한 각도에서의 공사기간 영향요인이 미치는 생산성을 파악할 수 있다. 이에 본 연구는 건설공사에서 발생하는 다양한 영향요인에 따른 작업 생산성 데이터를 다차원적으로 분석하고 의사결정에 활용할 수 있는 데이터 마이닝 기술을 적용하여 기존 생산성 데이터들을 효과적으로 활용하는 방법을 제시한다.

• 환경영향평가
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• 제21권3호
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• pp.339-352
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• 2012

Total maximum daily load have been implemented and indicated that nonpoint discharge coeffients in flow duration curve were 0.50 of Normal flow duration ($Q_{185}$) and 0.15 of low flow duration($Q_{275}$). By using SWAT, nonpoint discharge coefficients are studied with the conditions of the instream flow and the rainfall in two study areas. The nonpoint discharge coefficient average of BOD and TP for normal flows duration in 3 years are 0.32~0.36 and 0.28~0.31. For the low flow duration, the nonpoint discharge coefficient avergae of BOD and TP were 0.10~0.12 and 0.10~0.11. These are lower than the coefficients of total maximum load regulation. There are big differences between one of regulation and one of SWAT for the normal flow duration. With the consideration of rainfall condition, the nonpoint discharge coefficient of flood flow duration are influenced on the amount of rainfalls. However, the nonpoint discharge coefficients of normal flow duration and low flow duration are not effected by the rainfall condition. Since the spatial distribution and geomorphological characteristics could be considered with SWAT, the estimation of nonpoint discharge coefficient in watershed model is better method than the use of the recommended number in the regulation.

• Environmental Analysis Health and Toxicology
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• 제31권
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• pp.22.1-22.7
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• 2016

Objectives This study analyzed the associations between mobile phone call frequency and duration with non-specific symptoms. Methods This study was conducted with a population group including 532 non-patient adults established by the Korean Genome and Epidemiology Study. The pattern of phone call using a mobile phone was investigated through face-to-face interview. Structured methods applied to quantitatively assess health effects are Headache Impact Test-6 (HIT-6), Psychosocial Well-being Index-Short Form, Beck Depression Inventory, Korean-Instrumental Activities of Daily Living, Perceived Stress Scale (PSS), Pittsburgh Sleep Quality Index, and 12-item Short Form Health Survey where a higher score represents a higher greater health effect. Results The average daily phone call frequency showed a significant correlation with the PSS score in female subjects. Increases in the average duration of one phone call were significantly correlated with increases in the severity of headaches in both sexes. The mean (standard deviation) HIT-6 score in the subgroup of subjects whose average duration of one phone call was five minutes or longer was 45.98 (8.15), as compared with 42.48 (7.20) in those whose average duration of one phone call was <5 minutes. The severity of headaches was divided into three levels according to the HIT-6 score (little or no impact/moderate impact/substantial or severe impact), and a logistic regression analysis was performed to investigate the association between an increased phone call duration and the headache severity. When the average duration of one phone call was five minutes or longer, the odds ratio (ORs) and the 95% confidence intervals (CIs) for the moderate impact group were 2.22 and 1.18 to 4.19, respectively. The OR and 95% CI for the substantial or severe impact group were 4.44 and 2.11 to 8.90, respectively. Conclusions Mobile phone call duration was not significantly associated with stress, sleep, cognitive function, or depression, but was associated with the severity of headaches.

• 대한의용생체공학회:의공학회지
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• 제24권5호
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• pp.421-425
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• 2003

한 개 척추 운동 분절에 대한 유한요소 모델을 이용하여 수직 충격력이 가해질 경우 발생되는 척추 경막의 교합을 해석 하였다. 교합은 수직 충격력의 지속 시간 변화에 따른 골편의 이동으로 인한 척추 경막의 단면적 변화를 계산하여 계량화 하였다. 계산 결과 8∼12ms 의 충격 지속 시간에서 골편의 이동으로 인한 가장 큰 척추 경막의 단면적 변화가 나타났으며 $\Delta$t = 400 ms의 경우에서는 4%만의 척추 경막의 단면적 변화가 나타났다, 이와 같은 해석 결과는 6kN의 수직 정 하중이 가해질 경우에 발생되는 량이 유사한 값으로 이 정도의 충격 지속 시간은 준 정 하중 상태와 유사함을 보이고 있었다.