• 한국전문물리치료학회지
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• 제20권1호
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• pp.10-17
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• 2013

The purpose of this study was to assess the influence of the duration of smartphone usage on cervical and lumbar spine flexion angles and reposition error in the cervical spine. The study included 18 healthy smartphone users (7 males and 11 females). We measured the kinematics of the upper and lower cervical and lumbar spine flexion angles and the reposition error of the upper and lower cervical spine after 3 s and 300 s smartphone use in sitting. A paired t-test was used to compare the effects of the duration of smartphone usage on the kinematics of cervical and lumbar spine flexion angles and reposition error. The flexion angles of the lower cervical and lumbar spine and the reposition error in the upper and lower cervical spine were significantly increased after 300 s smartphone of use (p<.05). However, the flexion angle of the upper cervical spine was not significantly different between the 3 s and 300 s smartphone of use (p>.05). These findings suggest that prolonged use of smartphones can induce changes in cervical and lumbar spine posture and proprioception in the cervical spine.

• 한국국방경영분석학회지
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• 제3권1호
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• pp.123-136
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• 1977

This thesis presents a modification and extension to the Burgess and Killebrew heuristic resource leveling procedure for project networks. In contrast to previous algorithms appearing in the literature, the objective function of this algorithm. is the minimization of the sum of the squared errors in each time period (deviations around the mean usage) of all resources over the duration of the project. This objective function continues the search for an improved schedule beyond that of previous algorithms with their associated objective functions. One important feature is that the algorithm tends to reduce the number of periods that a resource is idle during its duration on the project.

• Tuberculosis and Respiratory Diseases
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• 제61권5호
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• pp.463-472
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• 2006

연구배경: 농흉을 치료하는데 VATS가 도입된 후 VATS의 유용성에 대해 많은 연구의 결과들이 보고 되고 있으며 실제로 치료 프로토콜에도 변화를 가져왔으나 아직까지는 문헌상의 보고가 양적으로 충분하지 못하며 기존의 치료방법에 비해 VATS의 장점 역시 명확하게 검증되어 있지 못한 상태이다. 방 법: 의무기록과 흉부 방사선 사진을 검토하여 기존의 치료 환자 군과 VATS 환자 군을 비교하였다. 2001년 1월부터 2003년 12월까지 한림대학교 춘천성심병원에 농흉으로 입원하여 기존의 방법으로 치료받은 환자들을 A군으로 하고 2003년 12월부터 2006년 8월까지 농흉으로 흉강경 수술을 받은 환자들을 B군으로 나누어 입원기간, 흉관 유지 기간, 백혈구증가증이 있던 기간, 발열이 있던 기간, 항생제 사용기간을 비교하였다. 그리고 흉막비후, 갈비가로막각이 각각 치료 전후 어떻게 변하였는지 비교하여 보았다. 결 과: A군은 15명으로 남자가 11명, 여자가 4명이었고, 평균 나이는 $58.2{\pm}15.7$세 이었고, B군은 11명으로 남자가 9명, 여자가 2명이었으며 평균 나이는 $51.6{\pm}9.5$세 이었다. B군에서 입원 기간($16.6{\pm}7.4$일, A군은 $33.7{\pm}22.6$일; p=0.014)과 흉관 유지 기간($10.5{\pm}5.7$일, A군은 $19.5{\pm}14.4$일; p=0.039), 백혈구증가기간($6.7{\pm}6.5$일, A군은 $18.8{\pm}13.2$일; p=0.008), 발열 기간($0.8{\pm}1.8$일, A군은 $9.4{\pm}9.2$일; p=0.004), 항생제 사용기간(B군 $14.9{\pm}6.4$일, A군 $25.4{\pm}13.9$일; p=0.018)이 A군에서보다 통계적으로 유의하게 감소하였다. 그러나 흉막비후, 갈비가로막의 둔함의 정도는 통계적으로 유의한 변화는 없었다. 결 론: 농흉에서 흉강경을 이용한 치료를 하면 기존의 방법에 비해 입원 기간, 흉관 유지기간, 백혈구증가증 기간, 발열 기간, 항생제 사용기간을 단축시킬 수 있어 환자의 증상을 더 빨리 개선시키며, 흉관을 조기에 제거할 수 있고 입원기간을 단축시킨다.

• 대기
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• 제24권3호
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• pp.391-402
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• 2014

This study investigated the performances of precipitable water vapor (PWV) retrieval from the sets of ground global positioning system (GPS) signals, each of which had different length of observing-session duration, for the purpose of obtaining as short session duration as possible that is required at the least for appropriate retrieval of the PWV for meteorological usage. The shorter duration is highly desirable to make the most use of the GPS instrument on board the mobile observation vehicle making measurements place by place. First, using Bernese 5.0 software the PWV retrieval was conducted with the data sets of GPS signals archived continuously in 30 seconds interval during 2-month period of January and February, 2012 at Bukgangneung site. Each of the PWVs produced independently using different session durations was compared to that of radio-sonde launched at the same GPS location, a Bukgangneung site. Second, the same procedure was done using the data sets obtained from the mobile observation vehicle that was operating at Boseong area in Jeonnam province during Changma observation campaign in 2013, and the results were compared to that at Bukgangneung site. The results showed that as the observing-session duration increased the retrieval errors decreased with the dramatic change happening between 3 and 4 hours of the duration. On average, the root mean square error (RMSE) of the retrieved PWV was around 1 mm for the durations of greater than 4 hours. The results at both the Bukgangneung (fixed site) and Boseong (mobile vehicle) seemed to be fairly comparable with each other. From this study it is believed that at least 4 hours of observing-session duration is needed for the retrieval of PWV from the ground GPS for meteorological usage using Bernese 5.0 software.

• 아동학회지
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• 제38권2호
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• pp.191-204
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• 2017

Objective: The purpose of this study was to explore the structural relationships among duration of media use, behavior problems, and school adjustment, while accounting for gender differences. Methods: The study used 4th-wave panel data from the Korean Children and Youth Panel Study, and 2,119 first graders in elementary school were analyzed. The data were analyzed using Structural Equation Modeling. Results: The results can be summarized as follows. First, the duration of media use had a direct effect on school adjustment. Secondly, the duration of media use had an indirect effect on school adjustment through internalizing and externalizing problems. According to multigroup analysis, gender differences were found in the structural relations among variables. Conclusion: This study emphasizes the needs for media usage education to improve children's school adjustment. Furthermore, it suggests that different intervention strategies for internalizing/externalizing behavior problems are needed depending on gender.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2004년도 제5회 정기학술발표대회 논문집
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• pp.575-578
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• 2004

건설프로젝트는 일정한 기간 동안 주어진 목표를 수행하기 위한 작업들의 모임이라 정의할 수 있으며, 이를 위해서는 필요한 자원의 효율적 계획 및 관리가 필요하고, 이때 자원배당 및 자원평준화 기법이 활용된다. 하지만 자원제약이 있는 자원배당과 공기 제한이 있는 자원평준화 방법은 하나의 프로젝트에 개별적으로 적용되고 있어 전체 프로젝트의 공기와 효율적 자원이용 측면에서 적정화하기는 어렵다. 따라서 본 연구는 자원 평준화 방법의 Minimum Moment Algorithm 개념을 확대 $\cdot$ 적용하여 적정 자원이용 및 공사기간을 산출하고자 한다. 이때 자원 활용의 상태를 나타내는 5가지 지표들 사이의 중요도는 AHP기법을 통해 파악한다.

• Earthquakes and Structures
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• 제14권6호
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• pp.577-587
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• 2018

The quantitative assessment of the seismic collapse risk of a structure requires the usage of an optimal intensity measure (IM) which can adequately characterise the severity of the ground motion. Research suggests that the average spectral acceleration ($Sa_{avg}$) may be an efficient and sufficient alternate IM as compared to the more traditional first mode spectral acceleration, $Sa(T_1)$, particularly during seismic collapse risk estimation. This study primarily presents a comparative evaluation of the sufficiency of the average spectral acceleration with respect to ground motion duration, and secondarily assesses the impact of ground motion duration on collapse risk estimation. By assembling a suite of 100 historical ground motions, incremental dynamic analysis of 60 different inelastic single-degree-of-freedom (SDF) oscillators with varying periods and ductility capacities were analysed, and collapse risk estimates obtained. Linear regression models are used to comparatively quantify the sufficiency of $Sa_{avg}$ and $Sa(T_1)$ using four significant duration metrics. Results suggests that an improved sufficiency may exist for $Sa_{avg}$ when the period of the SDF system increases, particularly beyond 0.5, as compare to $Sa(T_1)$. In reference to the ground motion duration measures, results indicated that the sufficiency of $Sa_{avg}$ is more sensitive to significant duration definitions that consider almost the full wave train of an accelerogram ($SD_{a5-95}$ and $SD_{v5-95}$). In order to obtain a reduced variability of the collapse risk estimate, the 5-95% significant duration metric defined using the Arias integral ($SD_{a5-95}$) should be used for seismic collapse risk estimation in conjunction with $Sa_{avg}$.

• Journal of Acupuncture Research
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• 제31권2호
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• pp.99-109
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• 2014

Objectives : The purpose of this study was to analysis the relationship between hours of smartphone use and neck pain in university students. Methods : A survey of 2,353 university students was conducted in Gyeonggi province and Incheon city using a self report questionnaire from April 1 to 11 2013. The questionnaire of questions regarding the hours of using smartphone, mainly used function in participant's smartphone and neck discomfort degree. Neck disability index(NDI) was used to evaluate degree of pain. The collected data were analyzed with the t-test and Kendall's tau test using the SPSS 21.0 program and R 3.1.0, respectively. Results : 1. Almost all of the survey participants(99.07 %) were smartphone users. 66.97 % of them answered that they use their smartphone daily more than 2 hours and 48.18 % of them answered that they use their smartphone 10 to 30 minutes everytime they use it. 2. The overall distribution of NDI scores was 'no disability(0~4 score, 62.92 %)', 'mild disability(5~14 score, 32.85 %)', 'moderate disability(15~24 score, 1.19 %)'. As a result of t-test, we found that the average NDI score for female students was significantly higher than the average NDI score for male students(p<0.05). 3. The Kendall's tau test revealed that total time spent daily using smartphones has a strong positive correlation with 'pain intensity', 'lifting', 'reading' 'headache', 'concentration', and 'driving'(p<0.05) in NDI. Also, time duration of one time smartphone usage has a strong positive correlation with 'pain intensity', 'lifting', 'reading', 'headache', 'concentration', 'work', and 'recreation'(p<0.05). 4. The Kendall's tau test revealed that total NDI scores have a significantly strong positive correlation with both of total time spent daily using smartphones(p<0.05) and time duration for one time smartphone usage(p<0.05). This results imply that long-time use of smartphone has a strong relationship with neck pain. Conclusions : The results of the study would be a good starting point for future studies to reduce the risks of chronic neck pain caused by smartphone usage.

• 설비공학논문집
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• 제24권8호
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• pp.599-604
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• 2012

Most air pollution and smog are a result of the burning of fossil fuels. The use of fossil fuels also causes acid rain and global warming. So the need for solar energy utilization is increased. It is essentially important to make efforts to reduce usage of fossil energy resources. In this study, we analyzed the correlation between climatic elements(Cloud cover, Duration of sunshine, Temperature) and the photovoltaic power generation. Cloud cover of the correlation coefficient was 0.87. And duration of sunshine of the correlation coefficient was 0.93. The order of the correlation coefficient was duration of sunshine, cloud cover, temperature. To accurately analyze of the degree of correlation for the photovoltaic power generation, additional research about climatic elements that show a high correlation is needed.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2007년도 정기학술발표대회 논문집
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• pp.368-372
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• 2007

최근 건설 회사들은 기능 인력의 부족현상과 고령화 현상, 그리고 선 시공 후 분양 제도의 도입 가능성 등에 대비하기 위하여 대형 시스템 거푸집의 사용을 선호하고 있다. 이러한 관심과 노력의 결과로 국내 초고층 건축의 경우는 층당 3-4일의 골조공기를 달성하고 있으나, 우리나라 건설사업의 90%이상을 차지하고 있는 공동주택, 그 중 대부분을 차지하고 있는 중층 RC조 아파트의 경우는 6-8일 정도의 층당골조공기를 형성하고 있다. 이는 북미 일반 RC조 주거건축 층당공기 대비 50%수준에 머물러 있는 실정이다. 이에 본 연구에서는 선행 연구를 통하여 도출된 공기단축의 가능성을 가진 요소기술들을 적용한 Mock-up Test를 통하여 현장적용가능성 및 개선방안을 검토하였다. 또한 기존 6day-Cycle의 단위생산성 및 T/C 가용율에 대하여 분석하고, 기존공정대비 공기단축형 공정모델의 단위생산성 및 T/C 가용율을 비교하였다.