• Title/Summary/Keyword: The causes of fire

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The Ion Generation Characteristics of Charge Neutralizer Applied a Pulse Voltage (펄스전압을 적용한 전하중화장치의 이온발생 특성)

  • Moon, Jae-Duk;Chung, Suk-Hwan
    • Journal of Sensor Science and Technology
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    • v.7 no.2
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    • pp.140-146
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    • 1998
  • Methods and systems to remove static electricity are requested necessarily because the static electricity causes a flammable gas explosion, a fire, reduction of production rate in manufacturing VLSI semiconductor device and so on. In this paper, abrasion and dust contaminant of needle electrode are studied experimentally. And, frequencies and pulse durations of a high frequency pulse source were controlled effectively to minimize the abrasion of needle electrode and control generated numbers of ions. As a result, it is verified experimentally that the ion generation of charge neutralizer increases by using a high frequency pulse source.

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Review of Crash Landing Load Factor (추락착륙 하중배수에 대한 고찰)

  • Bae, Hyo-gil;Kim, Do-Hyung;Park, Jea Sung
    • Journal of Aerospace System Engineering
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    • v.15 no.1
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    • pp.47-55
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    • 2021
  • When an abnormal landing occurs, aircraft structures should be designed to guarantee occupants survivability without preventing egress. To find out fire root causes at crash, lots of fixed aircraft crash tests were conducted. Appropriate crash load factors were established with the comprehension of structural behavior based on dynamic analysis and investigation of human tolerance. Cargo restraint criteria were set up considering passengers safety and operational cost while analyzing past cargo aircraft accident data using a probabilistic approach. Reviewing results of past crash tests, current crash landing load factor was appreciated physically, medically, and economically.

Reliability Analysis on Firewater Supply Facilities based on the Probability Theory with Considering Common Cause Failures (소방수 공급설비에 대한 공통원인고장을 고려한 확률론적 신뢰도 분석)

  • Ko, Jae-Sun;Kim, Hyo
    • Fire Science and Engineering
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    • v.17 no.4
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    • pp.76-85
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    • 2003
  • In this study, we write down the definitions, their causes and the techniques of analysis as a theoretical consideration of common cause failures, and investigate the limitation and the importance of the common cause failures by applying to the analysis on the fire protection as a representative safety facility. As you can know in the reliability analysis, most impressive cause is the malfunctions of pumping operations; especially the common cause failure of two pumps is dominant. In other words, it is possible to assess system-reliability as twice as actual without CCF From these, CCF is extraordinarily important and the results are highly dependent on the CCF factor. And although it would increase with multiple installations, the reliability are not defined as linear with those multiplications. In addition, the differences in results due to the models for analysis are not significant, whereas the various sources of data produce highly different results. Therefore, we conclude that the reliabilities are dependent on the quality of the usable data much better than the variety of models. As a result, the basic and engineering device for the preventions of CCF of the multiple facilities is to design it as reliably as to design the fire-water pump. That is to say, we must assess those reliabilities using PFD whether they are appropriate to SIL (Safety Integrity Level) which is required for the reliability in SIS (Safety Instrumented System). The result of the analysis on the reliability of the fire-water supply with CCF shows that PFD is 3.80E-3, so that it cannot be said to be designed as safely as in the level of SIL5. However, without CCF, PFD is 1.82E-3 which means that they are designed as unsafely as before.

A Clinical Study of Tinnitus (耳鳴에 관한 임상적 연구)

  • Choi, In-Hwa
    • The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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    • v.14 no.2
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    • pp.134-145
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    • 2001
  • Introduction: Noises in the ear, whether real or imagined, are called tinnitus. Subjective causes of tinnitus(which is heard only by the patient) are extremely common and the majority of them are treated conservatively. For certain individuals their tinnitus is a major handicap; for others a trivial concern. The most common from of subjective tinnitus is a rushing, hissing or buzzing noise; it is frequently associated with sensorineural heanng loss. The patient may be unaware of the hearing loss, especially if it is a high frequency deficit of moderate severity. The character of the tinnitus may give a clue to the etiology. But the patient often has difficulty in explaining his/her tinnitus in absolute terms, as they have no other tinnitus with which to compare it but their own Tinnitus, like pain, is a subjective state and trying to objectively assess the severity is problematic. Audiological techniques to match subjective loudness to machine-produced noise may offer some help, in that sound intensity matches can bear little correspondence to subjective complaint. In spite of many studies, most patients presently seen complaining of tinnitus are told by their doctors that there is no treatment and that they will have to learn to live with this symptom. Objectives: To perform a clinical analysis of tinnitus and estimate the efficacy of Oriental Medical treatment according to the Byeonjeung(辨證). Subject: We studied 34 patients with complaints of tinnitus who had visited Pundang Cha Oriental Medicine Hospital Department of Otorhinolaryngology from March 1998 to February 2000. All of them had been treated 2 or 3 times a week with acupuncture treatment and had taken herbs according to the Byeonjeung(辨證) method. It was therefore possible for me to know whether their symptoms improved or not. Parameters Observed and Method: We treated them with acupuncture & herb-medication. Sometimes we gave them moxibustion or negative therapy with bloodletting at the acupuncture points(耳門, 聽宮, 聽會). Parameters Observed 1) Distribution of age & sex 2) Chief complaints 3) The sites of tinnitus 4) The quality of tinnitu 5) The duration of disease 6) The problem induced tinnitus 7) Factors increasing disease severity 8) The classification of the Byeonjeung(辨證) 9) The efficacy of treatments Results: 1. Age and sex distribution: The most common occurrence was found in males in their twenties: 6 males($17.7\%$), and in females in their thirties and over sixty: 8 females($23.5\%$). Total patient numbers for men and women were 20 men($58.8\%$), 14 women ($41.2\%$). 2. The most frequent major complaints were hearing disturbances related to tinnitus; and dizziness with tinnitus; each comprising 10 cases($29.4\%$). There were also 7 patients($20.6\%$) with only tinnitus. 3. Tinnitus sites: 13($38.2\%$) said that they felt tinnitus in both ears, equally. In the right ear, 9($26.5\%$), in the left, 6($17.7\%$). 4. The most frequent descriptive symptoms of tinnitus were: humming, hissing, buzzing etc. 5. The duration of disease. 14cases($41.2\%$) had a duration of less than 1 year. 6. 15cases($44.1\%$) complained that it was hard to watch TV or make a phone call because of tinnitus. 10 cases($29.4\%$) complained about depression. 7. Factors increasing severity of tinnitus: ⅰ) fatigue: 18cases($52.9\%$) ⅱ) stress/ tension: 10 cases($29.4\%$) ⅲ) alcohol and tobacco: 5cases($l4.7\%$) 8. Classification through Byeonjeung : ⅰ) 19 cases($55.9\%$) were classified as showing Deficiency syndrome. ⅱ) 15 cases($44.l\%$) were classified as showing Excess syndrome. The deficiency of Qi was 7($20.6\%$), deficiency of Xue, 8($23.5\%$) and insufficiency of the Kidney Yin & Yang, 4($11.8\%$). The flare of Liver fire was 8($23.5\%$) and phlegm-fire, 7($20.6\%$), 9. The efficacy of treatments showed: an improvement in 17cases($50.0\%$); no real improvement or changes in 13 cases($38.2\%$); and some worsening in 4 cases($11.8\%$). In the group with deficiency in Qi, 4($57.1\%$) improved, 1($14.3\%$) showed no change and 2($28.6\%$) were aggravated. In the cases of deficiency in Xue, 6($75.0\%$) improved, 2($25.0\%$) showed no change. In the cases of insufficiency of Kidney Yin & Yang, 3($75.0\%$) showed no change and 1($25.0\%$) were aggravated. In the group of flare of Liver fire, 4($50.0\%$) improved, 3($37.5\%$) no change and 1($12.5\%$) were aggravated. In the cases of phlegm-fire, 3($42.9\%$) improved, 4($57.1\%$) showed no change. Conclusion: We would recommend that any further studies of tinnitus utilize trial treatments of longer than 2 months duration, as any positive effects observed in our study showed that improvement occurred fairly slowly. And we suggest that this study could be utilized as a reference for clinical Oriental Medical treatment of tinnitus. If we try to apply music or sound therapy treatment properly combined with ours, we expect it to provide psycological stability in addition to inducing masking effects, even though it may not directly decrease or completely remove tinnitus.

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A Comparative Study on the Theory of Lee jaema and Chang ts' ungcheng (이제마(李濟馬)와 장종정(張從正)의 학술사상(學術思想)에 대한 비교(比較) 연구(硏究))

  • Ch’ oi, yeikwen;Kim, kyungyo
    • Journal of Sasang Constitutional Medicine
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    • v.8 no.2
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    • pp.41-68
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    • 1996
  • This thesis is a try for examining the historical characteristics of Constiutional medicine. For this purpose, I have examined their theory, and made a comparison carefully. Through this study, I have obtained several results as following. Both Chang and Lee lived in the time of change, which was unstable and uncertain. Under the condition, they both rejected following the existing trends of learned circles, and developed new thoughts and clinical techniques. They rejected superstitious beliefs and fatalism, and conducted the pursuit of experimental knowledge and rationale idea. Clinical experience was the very base of their study. They both criticized the bad habits of abuse of tonifing medication and health seeking. Especially Lee regarded control of emotion and regulation of a way of life as the best way for preservation of one's health. Chang regarded pathogenic factors as the ultimate factor of diseases, and strived for eliminating pathogenic factors, but L brought to a conclusion that the final factor of diseases was what is called "heart" itself, and emotional changes were the most essential causes of disease. It can be said that the pathogenesis insisted by Chang can be called The insistence that pathologic factors are the very etiology of all the disease (邪氣致病論), or all the diseases result from pathologic factors. And his whole remedy can be summarized as following, A study on the method of eliminating pathogenic factors. But the purpose of Constitutional medicine is to correct imbalance intrinsic to one's internal organs. In this aspect, Constitutional medicine is a "regulatory medicine". Depending on the classification of six vital substances, Chang classified all disease into six categories. These were based on symptoms and sings represented. While classification of diseases made by Lee was likely to rely upon constitutional characteristics. Chang thought that the three remedies made up of perspiration, purgation, vomiting were the most efficient way of eliminating pathogenic factors. Lee, however, thought those weren't methods of eliminating pathogenic factors but the best ways restoring one's self-regulation power. Chang thought that all the febrile disease essentially has a tendency in properties to belong to "heat", but Lee pointed out that pathologic processes are variable in accordance with constitutional features. They both regarded pathogenesis of diabetes as fire. That is to say, fire is the most essential factor of diabetes. And there are many risk factors such as inappropriate foods, drugs, climate, etc., but Lee thought what is most important is heart. Putting all accounts together, medical characteristics of Chang are similar to those of T aiyinjen and Shaoyangjen, and have no relation to those of those of Shaoyinjen. Therefore we can conclude that Chang understood pathologic processes of disease of T aiyinjen and Shaoyangjen, whether he knew about constitutional features or not.

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A Case Study of Risk Assessments and Safety Measures in a PCB Manufacturing Process (인쇄회로기판 제조 공정에서 위험성평가와 안전조치 적용 사례 연구)

  • Lee, Young Man;Lee, Inseok
    • Journal of the Korean Society of Safety
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    • v.37 no.4
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    • pp.120-128
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    • 2022
  • Printed circuit boards (PCBs) are a basic component in the electronics industry and are widely used in nearly all electronic products, such as mobile phones, tablet computers, and digital cameras, as well as in electric equipment. PCB manufacturing involves the use of many chemicals and chemical processes and therefore has more risks than other manufacturing sectors. This study aims to identify the causes of possible accidents during PCB manufacturing through risk assessment, develop and implement safety measures, and evaluate the effectiveness of these measures. Note that the safety measures developed to mitigate the risks of a certain process were also implemented for other similar processes. The risk assessments conducted over seven years, from 2015 to 2021, at a PCB manufacturing company identified 361 hazardous processes. Between 2016 and 2019, 41-56 hazardous processes were identified per year; such processes decreased to fewer than 20 per year after 2020. Application of the risk assessment results to the improvement of the hazardous processes with the similar characteristics seems to be effective in decreasing the risks. Equipment-related factors such as lack of appropriate maintenance, low work standards, and defective protection devices were responsible for 59.8% of all possible accidents. Because PCB manufacturing involves many chemicals, skin contact with hazardous substances, electric shock, fire, and explosion were the most common types of possible accidents (81.7%). In total, 505 safety measures were implemented, including 157 related to purchase and improvement of equipment and devices for safety (31.1%), 147 related to the installation/modification of fire prevention facilities (29.1%), and 69 related to the use of standard electrical appliances (13.7%). Risk assessment conducted after implementing the safety measures showed that these measures significantly decreased risk; 247 processes (68.4%) had a risk level of 3, corresponding to "very low," and 114 processes (31.6%) showed a risk level of 4, corresponding to "low." In particular, risk assessment of 104 processes with risk scores of 12 and 10 other processes with risk score of 16 showed that the risk decreased to 4 after implementing the safety measures. Thus, implementing these measures in similar manufacturing sectors that involve chemical processes can mitigate risk.

Electric Circuit Analysis for PV Array on Short-Circuit Failure of Bypass Diode in PV Module (PV모듈의 바이패스 다이오드 단락 고장 시 태양광어레이 회로 특성분석)

  • Lee, Chung-Geun;Shin, Woo-Gyun;Lim, Jong Rok;Hwang, Hye-Mi;Ju, Young-Chul;Jung, Young-Seok;Kang, Gi-Hwan;Chang, Hyo-Sik;Ko, Suk-Whan
    • Journal of the Korean Solar Energy Society
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    • v.39 no.6
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    • pp.15-25
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    • 2019
  • As the installation of photovoltaic systems increases, fire accidents of PV system grow every year. Most of PV system fires have been reported to be caused by electrical components. The majority of fire accidents occurred in combiner box, which is presumed to be short-circuit accidents due to dustproof and waterproof failures or heat deterioration of blocking diode. For this reason, the blocking diode installation became optional by revised PV combiner regulation. In this paper, according to the revised regulation, reverse current that generated by voltage mismatch was measured and analyzed in PV array without a blocking diode. The factors that cause voltage mismatch in array are assumed to be shaded PV module and short circuit failure of bypass diode. As the result of experiment, there is no reverse current to flow under shading condition in module, but reverse current flows on the failure of bypass diode in module. According to the module's I-V characteristic curve analysis, open voltage was slightly reduced due to operation of bypass diode in shading. However, it showed that open circuit voltage has decreased significantly in the failure of bypass diode. This indicates that the difference in open voltage reduction of voltage mismatch factor causes reverse current to flow.

Pyrolysis and Combustion Characteristics of an Pinus densiflora for the Protection of Forest Resources (산림자원 보호를 위한 적송의 열분해 및 연소 특성 연구)

  • Park, Jin-Mo;Kim, Seung-Soo
    • Applied Chemistry for Engineering
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    • v.21 no.6
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    • pp.664-669
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    • 2010
  • The forest area of domestic is 6370304 ha, which covers 70% of the whole country, and especially Gangwon-do is remarkably larger than other Province. A thick forest of the country has the most basic component among other natural environments as well as it has invaluable worth to human being such as scientific research and educational value. However due to the breakout of forest fire since 1990s, the loss of trees, destruction of natural environment and ecology, economic damage have been occurring and its scale also has become larger. The causes of becoming larger in scale are resulted from forest components which mainly consist of needle leaf trees, wide leaf trees, fallen leaves, herbaceous plants so that it has been a direct cause for forest fire. However, few research on combustion and pyrolysis characteristics has been done in domestic and abroad. The study on the combustion and pyrolysis for Pinus densiflora which are typical needle leaf trees has been tried using TGA. Pinus desiflora started to being ignited at around $162^{\circ}C$ and pyrolysis was done at around $197^{\circ}C$. Differential method was applied to calculate activation energy and frequency factor according to the variation of conversion. Activation energy in pyrolysis was increased from 79 kJ/mol to 487 kJ/mol with increasing conversion and average activation energy was 195 kJ/mol. The activation energy in combustion was decreased from 148 kJ/mol to 133 kJ/mol.

The Evaluation of Musculoskeletal Symptom and Patient Transport Work of 119 EMTs by Ergonomics Tools (119구급대원의 근골격계 증상과 환자운반 작업의 인간공학적 평가)

  • Hong, Sung-Gi
    • Fire Science and Engineering
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    • v.28 no.4
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    • pp.81-88
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    • 2014
  • This study identified the complaint ratio of musculoskeletal symptom by 119 EMTs and investigated the work risk extent through ergonomics evaluation about the patient transport works, which cause work-related musculoskeletal disorders (WMSDs) to 119 EMTs. For this, the complaint ratio of musculoskeletal symptom utilized questionnaire tool based on KOSHA Code H-30-2008 and the risk extent about the patient transport work evaluated by using ergonomics evaluation tools such as OWAS, RULA and REBA. According to the study result, 60.9% of 119 EMTs experienced musculoskeletal symptom. Among them, the symptom on back was the most common (36.1%). The work, which mostly causes WMSDs, has been found as patient transport work (48.4%). Among the patient transport motion, loading/unloading of ambulance cot to/from ambulance and the lifting of patient by stretcher were OWAS risk-level 3 and RULA/REBA risk-level 3 to 4. Among the patient transport environment, carrying patient on stairway using emergency mini-stretcher, moving patient in vehicle using spine board and piggy-back carrying or cradle carrying patient on stairway or slope way were OWAS, RULA, REBA risk level 3 to 4. It is suggested that immediate improvement in work postures for these works should contribute to prevention against WMSDs to 119 EMTs.

An analysis of th cause of passenger ship accident -from the perspestive of policy non-compliance (여객선사고의 원인분석 -정책불응의 관점을 중심으로)

  • 배점모
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.3 no.1
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    • pp.51-71
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    • 1997
  • As passenger ship accidents so frequently have occurred, crisis consciousness is highly aroused in Korean society. Although bombastic policy guidlines were suggested in accordance with every passenger ship accident, there remains a still high possibility of such an accident reoccurring because passenger ship accidents occur from the perspective of non-compliance. The research objective of this study is to government's safety regulatory policies. Data for the analysis was collected from literature review. A Case study related to passenger ship accident is adopted for the analysis. The research methods utilized in this study consist of extensive quantitative analysis of 138 passenger ship accidents which had happened over last 10 years from 1984 to 1993 in Korea and a qualitative analysis of the passenger ship accident of the Seohae Ferry in October 1993. The results of the quantitive analysis on the 138 passenger ship accidents are as follows; Seeing the accidents yearly, the accidents which occurred by policy non-compliance are still exist, only somewhat reduced as years gone by. Seeing the accidents from the perspective of types of accident, fire accidents and death and injury accidents had more non-compliance factors than contact accidents and one-side collision accidents, etc. had. Seeing the accidents from the perspectives of types of passenger ship, large ships like car ferries and general passenger ship accidents had more non-compliance factors than any other kinds of ships had. Seeing the accidents from the perspectives of tons of passenger ships, large ships weighing more than 1, 000 tons and small ships weighing less than 50tons contained a lots of non-compliance factors. The results of the qualitative analysis of the passenger ship accident of the Seohae Ferry in Octovber 1993 are as follows; From the viewpoint of the human factor, there were non-compliance to the recruiting of required number of qualified crew members and non-compliance to the rule which prohibited them from leaving port in bad weather and high wave conditions. From the viewpoint of the ship factor, there were defects in the ship. So we might say that there was non-compliance which was aroused from the lacks of technical skills. From the viewpoint of the administrative factor, there were many non-compliance factors such as sailor education, shipping management, rescue, safety equipment. From the viewpoint of the passenger factor, there were passengers' threats which compelled the crews to leave the port under bad weather conditions. In conclusion, the principal non-compliances factors are passenger ship company did not follow safety rules such as shipping the permitted number of passengers, loading permitted tons of freight and fastening freights properly and recruiting required number of qualified crew. In order to reduce accidents, firstly we should find out the causes which play key roles in passenger ship companies' non-compliance to the government's safety regulations. Secondly we should tackle the causes.

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