• 한국경영과학회지
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• 제41권1호
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• pp.87-98
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• 2016

A single machine scheduling problem for jobs with stochastic processing time is considered in this study. Shortest processing time (SPT) sequencing according to the expected processing times of jobs is optimal for schedules with minimal expected mean flow time when all the jobs arrive to be scheduled and their expected processing times are known. However, SPT sequencing according to the expected processing time may not be optimal for the minimization of the mean flow time when the actual processing times of jobs are known. This study evaluates the complexity of SPT sequencing through a comparison of the mean flow times of schedules based on the expected processing times and actual processing times of randomly generated jobs. Evaluation results show that SPT sequencing according to the expected flow time exhibits chaotic variation to the optimal mean flow time. The relative deviation from the optimal mean flow time increases as the number of jobs, processing time, or coefficient of variation increases.

• Wind and Structures
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• 제20권5호
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• pp.661-682
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• 2015

This study investigates the use of time-frequency coherence analysis for detecting and evaluating coherent "structures" of surface pressures and wind turbulence components, simultaneously on the time-frequency plane. The continuous wavelet transform-based coherence is employed in this time-frequency examination since it enables multi-resolution analysis of non-stationary signals. The wavelet coherence quantity is used to identify highly coherent "events" and the "coherent structure" of both wind turbulence components and surface pressures on rectangular prisms, which are measured experimentally. The study also examines, by proposing a "modified" complex Morlet wavelet function, the influence of the time-frequency resolution and wavelet parameters (i.e., central frequency and bandwidth) on the wavelet coherence of the surface pressures. It is found that the time-frequency resolution may significantly affect the accuracy of the time-frequency coherence; the selection of the central frequency in the modified complex Morlet wavelet is the key parameter for the time-frequency resolution analysis. Furthermore, the concepts of time-averaged wavelet coherence and wavelet coherence ridge are used to better investigate the time-frequency coherence, the coherently dominant events and the time-varying coherence distribution. Experimental data derived from physical measurements of turbulent flow and surface pressures on rectangular prisms with slenderness ratios B/D=1:1 and B/D=5:1, are analyzed.

• 가족자원경영과 정책
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• 제20권3호
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• pp.25-43
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• 2016

This study focused on the time use of a dual-earner working group with preschool children on working and nonworking days using 2014 time-use survey data provided by Statistics Korea(KOSTAT). We collected the time-use data recorded in a 2,158 time diary. We divided the time use into 4 parts ; paid work, household labor work (including caring work), leisure and living essentials. For the statistical analysis, we used SPSS 18.0 packages, i.e., descriptive statistics, T-test, Anova with Duncan test and regression for the impact off the independent factors. The results verified gender differences in time use and recognized the usefulness of the time-allocation analysis for the diagnosis of Work and Life Balance(WLB). In the conclusion, we suggest increasing men's time allocation for household labor as a crucial solution to the WLB of dual-earner working groups. And the follow-up study should include the various factors that affect the time allocation of dual-earner groups, such as type of labor and job and children's ages.

• 간호행정학회지
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• 제17권3호
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• pp.293-300
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• 2011

Purpose: This study was done to explore time management behavior and self-efficacy in nursing students and to analyze the correlations between time management behavior and self-efficacy. Methods: The data were collected from May 12 to 20 2010 using self-report questionnaires about time management behavior and self-efficacy of nursing students. The data from 508 students were analyzed using descriptive analysis, K-means clustering, and one-way ANOVA. Results: The mean score for time management behavior was 3.03${\pm}$1.11 out of a possible 5, and self-efficacy was 3.65${\pm}$0.42 out of a possible 6. Four groups were identified according to time management behavior. The four groups were significantly different on self-efficacy total (p=<.05) and self-regulatory efficacy (p=.<005). The group with the highest score for time management had the highest score for self-efficacy. Conclusions: The results of the study indicate that time management behavior styles are related to self-efficacy for nursing students. Therefore, time management education programs based on the time management behavior styles are needed to increase self-efficacy in nursing students.

• 토지주택연구
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• 제2권4호
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• pp.355-365
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• 2011

Construction duration is very important as a factor which comprises three axises of construction management with quality and cost in construction project. In general project condition, construction duration is optimized while minimizing construction cost and securing required quality. However, in case of insufficient project time duration or delayed projects, project progress management is different from those of normal projects. These project areas need solutions to complete work within a given completion day. To time shortening the current duration of each typical floor of structural framework in apartment construction is investigated, and a basic time schedule planning for typical floor of structural framework in normal projects is planned. This study proposed 3 ways for time shortening of urgent project or insufficient construction duration project. Also, This study proposed detailed time shortening method and technical solution conditions while time is shortened.

• Journal of Preventive Medicine and Public Health
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• 제54권2호
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• pp.110-118
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• 2021

Objectives: A growing number of people depend on flexible employment, characterized by outsider employment status and perceived job insecurity. This study investigated whether there was a synergistic effect of employment status (full-time vs. part-time) and perceived job insecurity on major depressive disorder. Methods: Data were derived from the 2012 Canadian Community Health Survey-Mental Health of 12 640 of Canada's labor force population, aged 20 to 74. By combining employment status with perceived job insecurity, we formed four employment categories: full-time secure, full-time insecure, part-time secure, and part-time insecure. Results: Results showed no synergistic health effect between employment status and perceived job insecurity. Regardless of employment status (full-time vs. part-time), insecure employment was significantly associated with a high risk of major depressive disorder. Analysis of the interaction between gender and four flexible employment status showed a gender-contingent effect on this link in only full-time insecure category. Men workers with full-time insecure jobs were more likely to experience major depressive disorders than their women counterparts. Conclusions: This study's findings imply that perceived job insecurity may be a critical factor for developing major depressive disorder, in both men and women workers.

• 국제학술발표논문집
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• The 5th International Conference on Construction Engineering and Project Management
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• pp.479-487
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• 2013

State Highway Agencies (SHAs) have started utilizing cost-plus-time bidding (A+B bidding) since Federal Highway Agency (FHWA) declared it operational on May 4, 1995. Although this technique has successfully accelerated many projects by incorporating construction time in the bidding competition, a framework to illustrate the interactions of incentive/disincentive (I/D) rates on the competitiveness of contractors participating in the bid competition is yet to be developed. In a previous research, authors indicated that for each bid competition there is an efficient cap for I/D rates which are dictated by the capabilities of contractors in project acceleration. However, the results of previous study were based on the assumption that there is a statistically significant relationship between cost and time. In this study, the entire cost-plus-time projects implemented by the Oklahoma Department of Transportation (ODOT) were investigated. Then the significance of relationship between cost and time were analyzed for each contractor utilizing Analysis of Variance (ANOVA) technique, and the price-time function of each contractor was determined by regression analysis. The results of the analysis indicate that there is a significant relationship between cost and time for the majority of contractors. However, a quadratic relationship is not always significant and for some contractors a linear price-time relationship is significant. The results of this project can be used not only by ODOT to optimize the incentive/disincentive rates but also by contractors to determine the most competitive strategies of other bid participants.

• 산경연구논집
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• 제9권10호
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• pp.83-89
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• 2018

Purpose - The purpose of this study examines when the optimism impact on financial asset price forecasting and the boundary condition of optimism in the financial asset price forecasting. People generally tend to optimistically forecast their future. Optimism is a nature of human beings and optimistic forecasting observed in daily life. But is it always observed in financial asset price forecasting? In this study, two factors were focused on considering whether the optimism that people have applied to predicting future performance of financial investment products (e.g., mutual fund). First, this study examined whether the degree of optimism varied depending on the direction of the prior price trend. Second, this study examined whether the degree of optimism varied according to the forecast period by dividing the future forecasted by people into three time horizon based on forecast period. Research design, data, and methodology - 2 (prior price trend: rising-up trend vs falling-down trend) × 3 (forecast time horizon: short term vs medium term vs long term) experimental design was used. Prior price trend was used between subject and forecast time horizon was used within subject design. 169 undergraduate students participated in the experiment. χ² analysis was used. In this study, prior price trend divided into two types: rising-up trend versus falling-down trend. Forecast time horizon divided into three types: short term (after one month), medium term (after one year), and long term (after five years). Results - Optimistic price forecasting and boundary condition was found. Participants who were exposed to falling-down trend did not make optimistic predictions in the short term, but over time they tended to be more optimistic about the future in the medium term and long term. However, participants who were exposed to rising-up trend were over-optimistic in the short term, but over time, less optimistic in the medium and long term. Optimistic price forecasting was found when participants forecasted in the long term. Exposure to prior price trends (rising-up trend vs falling-down trend) was a boundary condition of optimistic price forecasting. Conclusions - The results indicated that individuals were more likely to be impacted by prior price tends in the short term time horizon, while being optimistic in the long term time horizon.

• 디지털융복합연구
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• 제18권11호
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• pp.539-545
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• 2020

이 연구는 코로나 바이러스 사태로 인해 국내 대학에서 실시한 온라인 실시간 수업에 대해 대학생의 수업 참여 효능감이 어떠한지 알아보고자 기획하였다. 이 연구의 참여자는 J 지역 한 대학교에 재학 중이고 실시간 온라인 수업에 참여한 경험이 있는 701명 대학생이다. 이 연구의 도구는 상호작용, 학습향상, 수업적응, 접근성 등 4 영역으로 구성하였다. 연구 결과는 다음과 같다. 첫째, 대학생의 실시간 온라인 수업 참여의 효능감은 접근성이 가장 높고 상호작용이 가장 낮았다. 둘째, 대학생의 실시간 온라인 수업 참여 효능감은 성별, 학년, 전공계열, 접근 도구에 따라 차이가 나타났다. 이 연구는 코로나 바이러스로 인한 실시간 온라인 수업의 활용성을 점검하고, 포스트(post) 코로나 시대 본격적인 원격교육의 도래를 대비하는 방법으로서 실시간 온라인 수업의 적용 가능성을 확인하였다는 데 그 의미가 있다. 마지막으로 시대의 변화를 반영한 대학 전공별 온라인 수업의 운영 방식 및 지원의 고도화를 제언하였다.

• 한국주거학회논문집
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• 제22권4호
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• pp.83-92
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• 2011

Apartment is settled down as a main housing type and massive supply has been conducted since 1990's. The government has focused on the housing supply to improve the housing number and cut its price. On the contrary, the management of the housing has been neglected to get an early deterioration. Since 1995's, various ways have been made to improve and maintain the building function and performance. Among these, the long-term repair plan has played a main role to manage the housing condition and plan the repair schedule for preparing the massive cost of repair such as a roof proof, elevator change. The long-tern repair plan provides the repair time and repair rate according to various construction types. Most of the management agent apply the repair standard into the field area. But the repair time could not reflect the present condition and bring into the wrong maintenance. Therefore, the repair time for the long-term maintenance plan would be revised and reflected from the material and technology development. |n this study, it aimed at improvement for the repair time in various construction types which are provided in the long-term repair plan. For this, the 22 management agents are surveyed directly. This study shows that the repair time of the painting are correspondent to the repair time of the long-term plan irregardless of the painting materials. Most of other areas would correspondently similar to the long-term plan. This study could not include the building location, material and other haracteristics. Therefore, the further study would be needed to reflect the building and materials attributes to get the detailed repair time.