• 한국안전학회지
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• 제39권2호
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• pp.38-43
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• 2024

Recently, with the expanding market for electronic devices and electric vehicles, secondary battery usage has been on the rise. Lithium-ion batteries are particularly popular due to their fast charging times and lightweight nature compared to other types of batteries. A secondary battery consists of four components: anode, cathode, electrolyte, and separator. Generally, the positive and negative electrode materials of secondary batteries are composed of an active material, a binder, and a conductive material. Acetylene Black (AB) is utilized to enhance conductivity between active material particles or metal dust collectors, preventing the binder from acting as an insulator. However, when recycling waste batteries that have been subject to high usage, there is a risk of fire and explosion accidents, as accurately identifying the characteristics of Acetylene Black dust proves to be challenging. In this study, the lower explosion limit for Acetylene Black dust with an average particle size of 0.042 ㎛ was determined to be 153.64 mg/L using a Hartmann-type dust explosion device. Notably, the dust did not explode at values below 168 mg, rendering the lower explosion limit calculation unfeasible. Analysis of explosion delay times with varying electrode gaps revealed the shortest delay time at 3 mm, with a noticeable increase in delay times for gaps of 4 mm or greater. The findings offer fundamental data for fire and explosion prevention measures in Acetylene Black waste recycling processes via a predictive model for lower explosion limits and ignition delay time.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2002년도 학술.기술논문발표회
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• pp.111-116
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• 2002

The delay of the completion of the construction project occurs frequently because the origin schedule is affected by numerous factors that contribute to the overall delay in completing the project. But in our country. the dealing with a claim is not sufficient yet by reasons of fairl relation between owner and constructor, cognitive shortage in claim, and such. especially they have make a wrong application of baseless the rule. In this study. we make a rational model ; that includes calculating of dispute costs, and suggest the solution and the prevention for claim by considerating the law followed liquidated damages.

• 한국안전학회지
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• 제21권4호
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• pp.66-72
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• 2006

An accurate knowledge of the AITs(autoignition temperatures) is important in developing appropriate prevention and control measures in industrial fire protection. The measurement of AITs are dependent upon many factors, namely initial temperature, pressure, vessel size, fuel/air stoichiometry, catalyst, concentration of vapor, ignition delay time. The values of the AITs used process safety are normally the lowest reported, to provide the greatest margin of sefety. This study measured the AITs of o-xylene+n-pentanol system from ignition delay time by using ASTM E659-78 apparatus. The experimental AITs of o-xylene and n-pentanol were $480^{\circ}C\;and\;285^{\circ}C$, respectively. The experiment AITs of o-xylene+n-pentanol system were a good agreement with the calculated AITs by the proposed equations with a few A.A.D.(average absolute deviation).

• Journal of applied mathematics & informatics
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• 제29권3_4호
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• pp.955-967
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• 2011

In this paper we have considered a nonautonomous predator-prey model with discrete time delay due to gestation, in which there are two prey habitats linked by isotropic migration. One prey habitat contains a predator and the other (a refuge) does not. Here, we have established some sufficient conditions on the permanence of the system by using in-equality analytical technique. By Lyapunov functional method, we have also obtained some sufficient conditions for global asymptotic stability of this model. We have observed that the per capita migration rate among two prey habitats and the time delay has no effect on the permanence of the system but it has an effect on the global asymptotic stability of this model. The aim of the analysis of this model is to identify the parameters of interest for further study, with a view to informing and assisting policy-maker in targeting prevention and treatment resources for maximum effectiveness.

• 대한치과의료관리학회지
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• 제10권1호
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• pp.1-8
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• 2022

This study introduces research on the quality of medical services, optimization of medical services, dental medical services, implant medical services, and time schedules, as well as the effective process of dental implant medical services, which is expensive and requires a long treatment period. For improvement, it is suggested to evaluate using a time schedule. In this method, a time schedule is prepared in which each step, starting from the patients appointment until the completion of the treatment process, is allotted a certain time. This schedule was finalized in consultation with the employees. When performing all implant operations, the starting time of each item was checked to evaluate the degree of compliance and to understand any reasons for delay in each step. After identifying the causes for delay at each step, suitable steps to rectify the drawbacks were developed, and an optimal plan for patient management was determined. Changes in waiting time and human resource utilization were shown as concrete data, suggesting that such a schedule is meaningful as a decision-making support tool.

• Child Health Nursing Research
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• 제14권1호
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• pp.44-52
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• 2008

Purpose: The purpose of this study was to evaluate and compared the growth and development of premature and full-term infants during the 2 years after birth. Method: The participants were 102 infants, 51 each for premature infants, and for healthy full-term infants. Participants in the premature group accounted for 17.5% of all premature infants who were registered at the public health center in G city. Developmental status was evaluated using the Korean Denver II. Results: The catch-up growth of the premature was 100% in weight and in height. Suspicious developmental delay according to the Korean Denver II was 3.9% in normal infants and 31.2% in premature infants. Factors related to the suspicious developmental delay in premature infants were their age and health state at birth. The rate of suspicious developmental delay was higher in infants over 6 months and infants unhealthy at birth. Conclusion: A premature follow-up program, which includes nutrition education to achieve catch-up growth and to prevention obesity, along with continuous developmental screening test for infants and children born prematurely is recommended. Provision for home visits and telephone counseling for premature infants and their families who do not to use the public health center should also be included.

• 한국화재소방학회논문지
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• 제21권3호
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• pp.33-40
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• 2007

화재 및 폭발을 방호하기 위해서 최소자연발화온도는 제시된 낮은 값을 사용하는 것이 일반적이다. 본 연구에서는 ASTM E659-78 장치를 이용하여 가연성 혼합물인 ethylbenzene+n-hexanol 계와 ethylbenzene+n-propionic acid 계의 발화지연시간과 AIT 관계를 측정하였다. 2성분계를 구성하는 순수물질인 ethylbenzene, n-hexanol, n-propionic acid의 측정된 최소자연발화온도는 각각 $475^{\circ}C,\;275^{\circ}C\;and\;511^{\circ}C$였다. 그리고 두 개의 2성분계에서 측정된 발화지연시간은 제시된 식에 의한 예측된 발화지연시간과 적은 평균절대오차에서 일치하였다.

• 한국화재소방학회논문지
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• 제18권2호
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• pp.27-33
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• 2004

화학물질의 최소자연발화온도의 정확한 지식은 산업화재를 예방하고 제어하는데 중요하다. 최소자연발화온도(AIT)는 화염이나, 스파크 없이 주위로부터 충분한 에너지를 받아서 스스로 점화할 수 있는 최저온도를 말한다. AIT는 실험 개시온도, 압력, 농도, 용기의 크기, 양론혼합비, 촉매, 증기의 농도, 발화지연시간 등 많은 인자에 영향을 받는다. 본 연구에서는 1994년에 제작된 ASTM E659-78 장치를 이용하여 산류(Acids) 발화지연시간과 AIT관계를 측정하였고, 실험에서 얻은 자료는 본 연구에서 제시한 예측 모델과 적은 오차 범위에서 일치하였다.

• Asian Pacific Journal of Cancer Prevention
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• 제17권11호
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• pp.5037-5040
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• 2016

Objectives: To determine the frequency of delayed diagnosis of oral squamous cell carcinoma in our setup; highlighting factors responsible for any delay and their possible relevance to demographic and diagnostic features. Methods: This cross sectional study of six months duration was conducted in the Oral and Maxillofacial Surgery Department of the Armed Forces Institute of Dentistry, Rawalpindi, Pakistan. A total of 246 patients, both male and female, having a biopsy proven definitive diagnosis of OSCC were included using a consecutive sampling technique. Delay in diagnosis was assessed from the stated period of time from when the patient first noticed symptoms of disease until a definitive diagnosis was made. We concluded delayed diagnosis if this was more than 40 days. Results: The ages of patients ranged from 27 to 60 years with a mean of $46.7{\pm}10.2$ years and a marked male predominance (3.7:1). Delayed diagnosis was observed in 91.5% of cases. However, statistically no significant differences were found with age, gender, marital, education status, household income and time of biopsy. Conclusion: Our primary finding of delayed diagnosis with no prior contact with any health care professional clearly reflects a need of taking urgent measures to avoid serious impacts on morbidity and mortality associated with OSCC.

• 전기학회논문지
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• 제64권1호
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• pp.182-187
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• 2015

In the three-phase power system, when any one-phase or two-phases is open-phase, the unbalanced current flows and the single-phase power supplies to three-phase loads. Specially, motor coil and transformer coil receive over-current. As a result, great damage as well as electrical fire can occur to the power system. In order to improve these problems, this paper proposes that an open-phase detection device is designed by a new algorithm using electric potential difference between the resultant voltage of neutral point and ground, and a control circuit topology of open-phase protector is composed of highly efficient semiconductor devices. It improves response speed and reliability. The control algorithm circuit also operates the cut-off of a conventional residual current protective device (RCD) which flows an enforced leakage current to ground wire at open-phase accident. Furthermore, time delay circuit is added to prevent the incapable operation of open-phase protector about instantaneous open-phase not open-phase fault. The time delay circuit improves more reliability.