• 한국건설관리학회논문집
• /
• 제24권6호
• /
• pp.81-90
• /
• 2023

Climate change has resulted in increased frequency and intensity of heat waves, which poses a significant threat to the health and safety of construction workers, particularly those engaged in labor-intensive and heat-stress vulnerable working environments. To address this challenge, this study aimed to propose an interpretable machine learning approach for forecasting personal heat strain by considering the cumulative effect of heat exposure as a situational variable, which has not been taken into account in the existing approach. As a result, the proposed model, which incorporated the cumulative working time along with environmental and personal variables, was found to have superior forecast performance and explanatory power. Specifically, the proposed Multi-Layer Perceptron (MLP) model achieved a Mean Absolute Error (MAE) of 0.034 (℃) and an R-squared of 99.3% (0.933). Feature importance analysis revealed that the cumulative working time, as a situational variable, had the most significant impact on personal heat strain. These findings highlight the importance of systematic management of personal heat strain at construction sites by comprehensively considering the cumulative working time as a situational variable as well as environmental and personal variables. This study provided a valuable contribution to the construction industry by offering a reliable and accurate heat strain forecasting model, enhancing the health and safety of construction workers.

• 한국지역지리학회지
• /
• 제21권1호
• /
• pp.98-113
• /
• 2015

본 연구에서는 최근 40년간(1973~2012) 우리나라 기상청 산하 61개 관측지점의 일강수량 자료를 바탕으로 1~5일 누적 최대 강수량에서 추출한 각 계절별 다중일 누적 극한강수현상의 시 공간적 발생 패턴과 변화 양상의 특징을 밝히고자 하였다. 사계절 중 다중일 누적 극한강수현상의 규모 자체는 여름철에 가장 크지만, 계절 강수량 증감에 따른 극한강수현상 규모 변화민감도는 가을철에 더 높게 나타난다. 장기간 시계열에 나타난 선형 추세 분석에 따르면, 1~5일 다중일 누적 극한강수현상의 규모는 동일하게 사계절 중 여름철에 가장 뚜렷하게 증가하는 변화 양상이 나타난다. 특히, 경기도와 강원영서, 충청도 지역을 중심으로 여름철 다중일 누적 극한강수현상의 증가 규모가 크고 뚜렷하게 나타나고, 1일에서 5일로 누적 기간이 길수록 다중일 누적 극한강수현상의 증가 경향은 이들 지역이외에 소백산맥 주변지역에서도 관찰된다. 통계적 유의성을 보이는 이러한 다중일 누적 극한강수현상 증가추세는 일부 관측지점에서는 겨울철에도 1~2일 누적 극한강수현상에 나타나는 점도 주목할 만하다. 한편, 극한강수량이 계절 강수량에서 차지하는 비율의 변화 추세를 분석해보면, 사계절 중 겨울철에 증가 경향이 가장 뚜렷하게 나타난다. 이러한 결과들은 여름철뿐만 아니라 다른 계절의 다중일 누적 극한강수현상의 시 공간적 변화에도 대비할 필요성이 있음을 가리킨다.

• 대한치과의사협회지
• /
• 제55권2호
• /
• pp.116-127
• /
• 2017

Objectives : The aim of this study was to evaluate the cumulative survival rates of the implants placed into grafted sinus and determine the effect of age, gender, smoking, and systemic disease on the implant cumulative survival rates. Materials and Methods : The retrospective study was performed on 51 implants placed in 26 patients by one dentist at the Dental Implant Center, Seoul National University Dental Hospital in the years 2000-2010. The cumulative survival rates were calculated by the Kaplan-Meier method. The differences within the factors were analyzed using log-rank test and the correlations between the factors and implant survival rates were analyzed using Cox proportional hazard model. Results : 1. Among the total of 51 implants placed in 26 patients, 7 implants failed and 44 implants remained stable. The 1-year, 5-year, and 10-year cumulative survival rates were 92%, 88%, and 85%, respectively. 2. Patients in their 50s and in their 70s showed statistically significant difference in the cumulative survival rates (P < 0.05). Gender and the existence of systemic disease did not show significant results. 3. In the implant treatment, smokers showed 7.5 times higher risk of implant failure than non-smokers (P < 0.05). Conclusion: Implants installed in combination with sinus elevation can be considered as a reliable treatment method.

• 대한통합의학회지
• /
• 제6권4호
• /
• pp.1-13
• /
• 2018

Purpose : The purpose of this study has been performed to find the relationship between seafarers' cumulative fatigue and stress by evaluating autonomic nervous functions and the results of surveys conducted using questionnaires. Methods : The subjects were seafarers working on various ships (home trade ships) of South Korea, who were healthy adults without any diseases, as confirmed through preliminary surveys were recruited through simple random sampling. A device that measures autonomic nervous functions by analyzing heart rate variability, which is also used often in clinical diagnoses and studies at universities, university hospitals, and general hospitals was used to measure the seafarers' cumulative fatigue and stress. Pearson's correlation analyses were also conducted to test the relationship between cumulative fatigue and stress measured by evaluating autonomic nervous functions and the results of surveys conducted with questionnaires. Results : There was no correlation between mean cumulative fatigue measured for each ship type and seafarers position through autonomic nervous functions evaluation and fatigue severity scale (FSS). There also was no correlation between the mean levels of stress measured for each ship type and seafarers position through autonomic nervous functions evaluation and survey scores of Korean occupational stress scale (KOSS). Conclusion : Therefore, in order to prevent man-made accidents in the sea among seafarers working with irregular port entry/departure schedules and under environments involving continued vibration, noises, and shaking, it is necessary to analyzed cumulative fatigue and stress scientifically and objectively, such as through autonomic nervous functions evaluation rather than through surveys.

• 한국산업보건학회지
• /
• 제11권1호
• /
• pp.85-91
• /
• 2001

Background : It goes without saying that cumulative trauma disorders is spreading to various types of occupation in many advanced countries including America, and it forms considerable rate of total occupational disorders already. and as the result of it, the seriousness of worker health problem and economic loss owing to production loss, recuperation expense, etc. are on the increasing trend through whole society. In case of Korea, the related measures as well as accurate fact-finding survey data on cumulative trauma disorders aren't prepared in detail, so it implies forward problem would be serious. Purpose : The purpose of this study is to draw the risk factor of cumulative trauma disorders in production factory, to forecast the rate of occurrence of cumulative trauma disorders on the basis of subjective symptoms, and to present forward realistic and effective prevention measures by showing the risk of cumulative trauma disorders, objecting the production factory of a domestic riding automobile assembly shop, by estimating in the aspect of human-engineering through the analysis of risk factor being a cause of cumulative trauma disorders. Methods : For this study, I investigated work type and on-duty hours, breathing time, and subjective symptoms of cumulative trauma disorders through questionnaire, objecting the workers in press. car body, coating, and outfit factory. Results : As a result of research, 81.2% of workers were in the physical burden due to present working, and the highest prevalence by part of body is an waist. The higher a rule score, The higher the number of workers complaind for working intensity, and the higher age work duration, tool used time, the higher prevalence of subjective symptoms by part of body. The number of workers complaind subjective symptom for treatment is the highest in drugstore.

• 한국아동복지학
• /
• 제54호
• /
• pp.79-111
• /
• 2016

본 연구는 영유아 시기에 경험하는 생애 초기 가족의 누적위험요인이 가정학습환경을 통해 유아의 언어 및 사회성 발달에 영향을 미치는 구조적 모델을 검증하는 데 그 목적이 있다. 만 3세 유아의 언어발달은 표현어휘력으로, 사회성 발달은 또래유능성으로 나타내었다. 한국아동패널(PSKC)의 2차년도와 4차년도 자료를 이용하여, 1,725가족을 대상으로 분석을 실시하였다. 상관관계 분석 및 구조방정식모델링 기법을 통하여 분석한 결과는 다음과 같다. 우선, 만 1세 누적위험요인과 만 3세 누적위험요인 간 상관관계는 높아, 누적위험요인의 종단적 지속성을 시사하였다. 만 1세 누적위험요인은 만 3세 가정학습환경의 질적 수준에 부정적인 영향을 미치고 가정학습환경은 유아의 언어 및 사회성 발달 모두를 유의하게 예측하였다. 하지만 만 1세 누적위험요인은 유아발달을 직접적으로 예측하지 않았다. 마지막으로 만3세 누적위험요인은 유아의 언어발달을 직접 예측하였으나 사회성 발달 및 가정학습환경에 유의한 영향을 미치지 않았다. 만 1세 누적위험요인${\rightarrow}$가정학습환경${\rightarrow}$유아발달의 구조적 관계에서 가정학습환경의 매개적 역할은 통계적으로 유의하였다. 종합하면, 영아기 가족 내 누적위험요인은 유아기 자녀의 발달을 돕는 가정학습환경 구성에 부정적인 영향을 미쳐 유아 발달에 간접적인 효과를 가지는 것으로 밝혀졌다. 영아기 자녀를 둔 위기가족을 대상으로 하는 조기 중재 및 지원에 대한 정책적 시사점이 논의되었다.

• 한국지진공학회논문집
• /
• 제18권1호
• /
• pp.29-36
• /
• 2014

In industrial facilities sites, the conventional method determining the earthquake magnitude (M) using earthquake ground-motion records is generally not applicable due to the poor quality of data. Therefore, a new methodology is proposed for determining the earthquake magnitude in real-time based on the amplitude measures of the ground-motion acceleration mostly from S-wave packets with the higher signal-to-ratios, given the Vs30 of the site. The amplitude measures include the bracketed cumulative parameters and peak ground acceleration (As). The cumulative parameter is either CAV (Cumulative Absolute Velocity) with 100 SPS (sampling per second) or BSPGA (Bracketed Summation of the PGAs) with 1 SPS. The arithmetic equations to determine the earthquake magnitude are derived from the CAV(BSPGA)-As-M relations. For the application to broad ranges of earthquake magnitude and distance, the multiple relations of CAV(BSPGA)-As-M are derived based on worldwide earthquake records and successfully used to determine the earthquake magnitude with a standard deviation of ${\pm}0.6M$.

• KIEAE Journal
• /
• 제15권1호
• /
• pp.69-75
• /
• 2015

Building has required the repair money to improve or maintain the decent living condition continuously after construction. It needs to grasp the building deterioration to decide the scope and contents before it is repaired. Under various conditions such as physical, social and financial constraints, the repair plan would be prepared. Among constraints, the cost is indispensible to specify the repair time, repair scope and target. The required cost would be planned to preparation over the years. In this paper, it aimed at providing the repair strategy of the public rental housing in repair time, using the cumulative cost model which is $3^{rd}$ function. In the $3^{rd}$ function, the inflection point should exist in the line. And there are two types in the cumulative model, First, if the maximum cost be shown, the repair time would be provided. Second, if the maximum cost not be shown, the cumulative function should be proportionally increased and the repair strategy is properly provided with a short cycle. In results of this study, 11 items would provide the repair time. These cumulative function would be repaired about 4 years after constructed, and after about 4 years, the cumulative function would be continuously increased.

• 대한토목학회논문집
• /
• 제7권1호
• /
• pp.43-54
• /
• 1987

본 논문에서는 압축반복하중을 받는 콘크리트의 피로누가손상 특성이 연구되었다. 압축을 받는 무근콘크리트의 원주형 공시체에 대한 기초실험을 통하여, 콘크리트의 누가손상에는 여러 인자들 중에서 반복적으로 작용되는 응력의 수준과 재하순서가 가장 크게 영향을 마친다는 것을 발견하였다. 이를 기초로 2단계 응력수준 조건하에서의 피로실험을 실시하여, 콘크리트의 누가손상특성은 Miner의 선형이론을 따르기 보다는 오히려 비선형의 상관관계를 가지며, 응력의 재하방법에 따라 누가손상의 특성과 콘크리트의 정적강도가 변화됨을 구명하였다. 또한 본 연구를 통하여 2 단계 응력수준하에서 콘크리트의 피로특성과 콘크리트구조의 잔존수명을 예측하는데 사용될 수 있는 실험공식이 도출되었다.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2007년도 추계학술대회 논문집
• /
• pp.30-34
• /
• 2007

Structural integrity of railway vehicles should last for a long period against various and continuous fatigue loadings, and the carbody structures of railway vehicle are manufactured by applying multiform welding types for each material. Since the most of cracks are occurred and proceeded at the vicinity of welding area during the lifetime of carbody structure, the fatigue strength evaluation for welding area of carbody structure should have been carried out. Rotem Company has evaluated lifetime and fatigue strength of carbody structure according to the fatigue analysis based on the international standard and/or inner-official regulation. This study introduces the fatigue analysis method that we have evaluated and calculated the damages for the welding areas of carbody structure under various fatigue loading conditions using cumulative fatigue damage rule(Miner's rule) to verify whether the cumulative damage does exceed unity. This study contains the fatigue test of specimens to derive stress-life relations(S-N curve), sub-modeling analysis and the calculation of cumulative damages under fatigue loading. The fatigue analysis verifies the welding area shall be capable of withstanding under fatigue loading, identifies how critical area shall be selected and presents the principles to be used for design verification.