• 한국주조공학회지
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• 제42권1호
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• pp.61-66
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• 2022

Hydraulic units are important components of agricultural and construction machinery, and thus require high-quality castings. However, gas defects occurring inside the sand cores of the castings due to the resin used is a problem. This study therefore aimed to develop a casting simulation method that can clarify the gas defect positions. Gas defects are thought to be caused by gas generated after the molten metal fills up the mold cavity. The gas constant is the most effective factor for simulating this gas generated from sand cores. It is calculated by gas generating temperature and analysis of composition in the inert gas atmosphere modified according to the mold filling conditions of molten metal. It is assumed that gases generated from the inside of castings remain if the following formula is established. [Time of occurrence of gas generation] + [Time of occurrence of gas floating] > [Time of occurrence of casting surface solidification] The possibility of gas defects is evaluated by the time of occurrence of gas generation and gas floating calculated using the gas constant. The residual position of generated gases is decided by the closed loops indicating the final solidification location in the casting simulation. The above procedure enables us to suggest suitable casting designs with zero gas defects, without the need to repeat casting tests.

• 한국안전학회지
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• 제31권3호
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• pp.96-101
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• 2016

Previous literature has been investigated various aspects of accident occurrence and prevention in construction field. However, those studied were limited in that they only focused on the death accident without considering the loss time accident. Based on this, the goal of current study was to investigate the nature of the loss time accident, and compare the results with the death accident. Results showed that 1) the occurrence rate of death accident was significantly higher in the form work, temporary work, and steel frame work; 2) the temporary work showed significantly higher occurrence rate of the loss time accident and the death accident as compared to others; 3) ratio of the loss time accident to the death accident in domestic construction field was 50:1; 4) fall accident showed biggest occurrence rate in both the loss time accident and the death accident; and 5) more that 80% of workers in both the loss time accident and the death accident was between 41 and 65 years old.

• 한국대기환경학회지
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• 제21권3호
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• pp.303-313
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• 2005

In this study, meteorological characteristics concerning the occurrence of fog are analyzed using 4-years $(2000\~2003)$ data at Chuncheon and the probability of prediction is investigated. From the analysis of meteorological characteristics, the fog at Chuncheon occurred before sunrise time and disappeared after that time and lasted for $2\~4$ hours. When fog occurred, on the whole, wind direction was blew the northerly and wind speed was below 2.1m/s. Especially, about $42\%$ of foggy day fell on the calm $(0\~0.2\;ms^{-1})$ conditions. The difference between air temperature and dew point temperature near the surface were mainly less than $2^{\circ}C$. For the lack of water surface temperature, the water surface temperature was calculated by using Water Quality River Reservoir System (WQRRS) and then it was used as the surface boundary condition of MM5. The numerical experiment was carried out for 2 days from 1300 LST on 14 October 2003 to 1300 LST on 16 October 2003 and fog was simulated at dawn on 15 and 16 October 2003. Simulated air temperature and dew point temperature indicate the similar tendency to observation and the simulated difference between air temperature and dew point temperature has also the similar tendency within $2^{\circ}C$. Thus, the occurrence of fog is well simulated in the terms of the difference between air temperature and dew point temperature. Horizontal distribution of the difference between air temperature and dew point temperature from the numerical experiment indicates occurrence, dissipation and lasting time of fog at Chuncheon. In Chuncheon, there is close correlation between the frequency of fog day and outflow from Soyang reservoir and high frequency of occurrence due to the difference between air and cold outlet water temperature.

• 한국도로학회논문집
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• 제15권5호
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• pp.187-193
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• 2013

PURPOSES : This research is to analyze the influence in terms of misreading rate and legibility time for drivers when condensation occurs on the road signs. METHODS : In this research, the dew occurred road signs provided to drivers to measure legibility time and misreading rate to compare with normal road sign. In order to identify the difference of legibility time between normal road sign and dew occurred road sign, the T-test and ANOVA test were used. And the vision system was used to recognize the region of dew occurrence on the road sign, then the brightness of dew occurrence region on the road sign was changed to check the misreading rate of drivers according to the change rate of brightness. RESULTS : The legibility times were measured 2.65s for normal road sign and 4.08s for dew occurrence road sign and misreading rates were measured 2.8% for normal road sign, 21.7% for dew occurrence road sign.

• 한국환경농학회지
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• 제33권1호
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• pp.52-56
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• 2014

BACKGROUND: It is known that impacts of climate change on damage occurrence by insect pests and diseases are increasing. The negative effects of climate change on production will threaten our food security. It is needed that on the basis of analysis of the impacts, proper strategies in response to climate change are developed. METHODS AND RESULTS: The objective of this paper is to estimate impacts of climate change on rice damage occurrence by insect pests and diseases, using the panal model which analyzes both cross-section data and time series data. The result of an analysis on impacts of climate change on rice damage occurrence by pest insect and disease showed that the damage occurrence by Rice leaf roller and Rice water weevil increased if temperature increased, and damage occurrence by Stripe, Sheath blight, and Leaf Blast increased if precipitation(or amount of sunshine) increased(or decreased). CONCLUSION: Adaptation strategies, supplying weather forecasting information by region, developing systematical strategies for prevention of damage occurrence by pest insect and disease, analyzing the factors of damage occurrence by unexpected pest insect and disease, enforcing international cooperation for prevention of damage occurrence are needed to minimize the impacts of damage occurrence on rice production.

• 한국컴퓨터정보학회논문지
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• 제17권4호
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• pp.163-172
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• 2012

현대 사회는 다양한 강력 범죄들이 발생하고 있다. 모든 범죄들은 발생한 후에 대처를 하는 것보다 사전에 범죄를 예방하는 것이 가장 중요하다. 이를 위해서 다양한 범죄를 예방하기 위한 연구가 진행되었다. 하지만 기존 연구 방법들은 사회학적, 심리학적인 요인들을 분석하여 범죄의 발생 확률과 발생 동기 등을 분석하여 예방하고자 하는 노력이 대부분이다. 그러므로 본 논문에서는 마코프 체인 방식을 사용하여 시간에 따른 범죄를 예측하기 위한 연구를 수행하고자 한다. 5대 강력 범죄인 강도, 살인, 강간, 절도, 폭력에 대하여 수집된 범죄 발생 건수 자료를 사용해 범죄 유형별 시간에 따른 범죄 발생 예측을 위한 모델링을 구현한다. 그리고 범죄 발생 유형별 범죄 발생 예측 값과 실제 발생 값을 비교해 본 논문에서 제안한 시간에 따른 범죄 발생 예측 모델링의 타당성을 검토하였다. 본 논문에서 제안한 범죄 발생 예측 기법이 실제로 강도, 살인, 강간 등과 같은 강력 범죄에 대해서는 최대 값을 임계값으로 적용하고, 나머지 범죄에 대해서는 평균값을 적용하는 방식을 사용함으로써 범죄 발생 예측확률을 높일 수 있을 것으로 연구되었다. 향후 범죄 유형별로 시간에 따른 범죄발생 예측율과 실제 값이 다르게 적용되는 사례들을 추가 조사하여 연구의 폭을 넓히고자 한다.

• 한국응용곤충학회지
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• 제58권3호
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• pp.239-249
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• 2019

본 연구는 북방농업지대에서 벼 해충의 지역 간 발생상황을 비교하기 위하여 곤충의 발육에 필요한 온도를 이용하여 발생 시기를 추정하는 방법으로 발생세대수나 발생 시기 등을 비교하였다. 벼 해충 6종(벼물바구미, 벼잎벌레, 흰등멸구, 벼멸구, 혹명나방, 멸강나방)에 대해 유효적산온도를 이용하여 발생 시기를 추정한 결과 월동해충은 지역에 따라 발생 시기에 차이가 있었으며, 동북방향으로 갈수록 발생시기가 늦어져, 북부고산이나 동해안북부에서는 발생시기가 가장 늦었다. 또한 해충의 발생시기가 6월부터 8월 사이에는 비래해충 1세대 성충 발생시기와 같이 지역 간 발생 시기에 차이가 적어 비슷한 시기에 발생하였으며, 기온이 낮아지는 8월부터 9월에 발생시기가 되면 지역 간 차이가 커서 벼멸구의 2세대 성충이 발생하지 못하거나, 흰등멸구, 혹명나방, 멸강나방 등의 2~3세대 성충의 발생이 안 되는 지역이 많아지고 있음을 알 수 있었다. 이러한 특징으로 보아 북방지역의 동북지역, 동해안북부, 북부내륙, 북부고산지역에서의 벼해충 발생은 적을 것으로 추정되며, 중부산간의 평강, 양덕을 제외한 동해안남부, 수양산 이남, 이북지역은 국내 경기, 강원북부지역과 비슷한 발생을 보일 것으로 추정되었다.

• 한국경영과학회지
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• 제30권4호
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• pp.99-115
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• 2005

For an analysis of the performance of a computer system, the minimum cycle time method has been widely used. The minimum cycle time method is a mathematical technique with which we can find the minimum duration time needed to fire all the transitions at least once and coming back to the Initial marking in a timed net. A timed net is a modified version of a Petri net where a transition is associated with a delay time. In the real world, an event is associated with a probability of occurrence. However, a timed net is not equipped with any facility of specifying probability of event occurrence. Therefore, the minimum cycle time method applied on a timed net can easily overlook probabilities of occurrences of events and yield a wrong result. We are proposing 'Timed Net with Probabilities of Choices' where a transition can be associated with both delay time and a probability of occurrence. We also introduce an algorithm for minimum cycle time analysis on a 'Timed Net with Probabilities of Choices'. As an example of application, we are performing an analysis of the location based service system using 'Timed Net with Probabilities of Choices'.

• 대한간호학회지
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• 제42권5호
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• pp.730-737
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• 2012

Purpose: This study was done to identify the time interval to pressure ulcer and to determine the optimal time interval for position change depending on pressure ulcer risk in patients using foam mattress in intensive care units. Methods: The Braden scale score, occurrence of pressure ulcers and position change intervals were assessed with 56 patients admitted to an intensive care unit from April to November, 2011. The time to pressure ulcer occurrence by Braden scale risk group was analyzed with Kaplan-Meier survival analysis and log rank test. Then, the optimal time interval for position change was calculated with ROC curve. Results: The median time to pressure ulcer occurrence was 5 hours at mild or moderate risk, 3.5 hours at high risk and 3 hours at very high risk on the Braden scale. The optimal time interval for position change was 3 hours at mild and moderate risk, 2 hours at high and very high risk of Braden scale. Conclusion: When foam mattresses are used a slight extension of the time interval for position change can be considered for the patients with mild or moderate pressure ulcer risk but not for patients with high or very high pressure ulcer risk by Braden scale.

• 한국농림기상학회지
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• 제6권4호
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• pp.242-249
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• 2004

This study was conducted to develop a forest fire occurrence model using meteorological characteristics for the practical purpose of forecasting forest fire danger. Forest fire in South Korea is highly influenced by humidity, wind speed, and temperature. To effectively forecast forest fire occurrence, we need to develop a forest fire danger rating model using weather factors associated with forest fire. Forest fore occurrence patterns were investigated statistically to develop a forest fire danger rating index using time series weather data sets collected from 8 meteorological observation centers. The data sets were for 5 years from 1997 through 2001. Development of the forest fire occurrence probability model used a logistic regression function with forest fire occurrence data and meteorological variables. An eight-province probability model by was developed. The meteorological variables that emerged as affective to forest fire occurrence are effective humidity, wind speed, and temperature. A forest fire occurrence danger rating index of through 10 was developed as a function of daily weather index (DWI).