• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.3
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• pp.212-221
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• 2013

Objectives: Asbestos fibers are accumulated in negative pressure unit (NPU) or vacuum cleaner in asbestos removal. Failure of operation or poor use performance of the NPU or vacuum cleaner causes asbestos fibers to spread in the air. Asbestos contractors should have an NPU fitted with a HEPA , vacuum cleaner, decontamination area, respirators, wetting equipment, and differential pressure manometer to register with the Ministry of Employment and Labor. There should be performance criteria of equipment used in asbestos removal. But there are none such criteria used in asbestos removal. This study was performed to investigate international or national performance criteria of equipment used in asbestos removal. Methods: Regulations, approved code of practice, guidance and national standards of the UK, USA and Korea were reviewed. A survey was done to investigate the requirements for equipment used in asbestos removal in Korea. Results: Air flow of NPUs used in Korea usually covers from$500m^3/h$ to over $3000m^3/h$. Some requirements for NPUs used in Korea were missing compared to the requirements of British standards for NPUs. All NPUs have different missing requirements. The UK also has separate British standard for leak tests for NPUs. Highly hazardous class vacuum cleaners should be used in asbestos removal in the UK. It has national standards on the operation of vacuum cleaners used in asbestos removal. There is only a certification system for less than 2.5kw rated voltage vacuum cleaners for home use in Korea. Powered (-assisted) respirators with mask are recommended in asbestos removal. Type 5 coveralls should be used in asbestos removal in the UK. There are international standards for requirements and leak tests of type 5 coveralls. A manometer for measuring differential pressure is needed in asbestos removal. The manometer's measuring range should cover less than ${\pm}125$ Pa and the gradation of manometer should be less than 2.5 Pa. The definition of decontamination area should be corrected. Installation of airlock and minimum area should be considered in decontamination area. Conclusions: Equipment should be used in asbestos removal proper performance and no leaks. There should be a certification system for equipment used in asbestos removal. This study can help to a certification system for equipment used in asbestos removal in Korea.

• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.128-135
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• 2012

In this paper, we proposed a system and a scenario to raise efficiency of gas safety management by developing wireless ZigBee communication modules, smart-home gas safety appliances and the system suitable for gas safety. Our designed system consists of a micom gas meter, an automatic extinguisher, sensors, and a wall-pad. A micom-gas-meter monitors gas flow, gas pressure, and earthquake. An automatic fire extinguisher checks combustible gas leaks and temperature of $100^{\circ}C$(cut off) and $130^{\circ}C$(fire). Sensors measure smoke and CO gas. In our novel system, a micom-gas meter cut off inner valve with warnings, an automatic fire extinguisher cut off middle valve and spray extinguishing materials, and sensors generate signals when detecting smoke and CO and then take a next action. Gas safety appliances and sensors automatically takes measures, and transmit those information to a wall-pad. The wall-pad again transmits real time information to server. Users can check and manage gas safety situations by connecting BcN server through web or mobile application. We hereby devised scenarios for gas safety and risk management based on the smart, and demonstrated their efficiency through test applied to filed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.197-205
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• 2015

Offshore structures for the gas production are exposed to the risk of gas leaks, and gas explosions can result in fatal damages to the primary structures as well as secondary structures. To minimize the damage from the critical accidents, the study of the dynamic response of structural members subjected to blast loads must be conducted. Furthermore, structural dynamic analysis has to be performed considering relationships between the natural frequency of structural members and time duration of the explosion loading because the explosion pressure tends to increase and dissipate within an extremely short time. In this paper, the numerical model based on time history data were proposed considering the negative phase pressure in which considerable negative phase pressures were observed in CFD analyses of gas explosions. The undamped single degree of freedom(SDOF) model was used to characterize the dynamic response under the blast loading. A blast wall of FPSO topside was considered as an essential structure in which the wall prevents explosion pressures from the process area to utility and working areas. From linear/nonlinear transient analyses using LS-DYNA, it was observed that dynamic responses of structures were influenced by significantly the negative time duration.

• Fire Science and Engineering
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• v.31 no.3
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• pp.1-10
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• 2017

This study examined the risk of accidents when handling hazardous materials in hazardous materials storage facilities without safety facilities. In the case of illegal dangerous cargo containers, the burning rate is very fast in the case of fire, which leads to explosions, that are damaging and difficult to control. In addition, accidents that occur in flammable liquid hazardous materials are caused mostly by accidents that occur in the space due to leakage. Therefore, the variables that affect these accidents were derived and the influence of these variables was investigated. Numerical and computational fluid dynamics programs were used to obtain the following final results. First, when a flammable liquid leaks into a specific space, it is influenced by temperature and relative humidity until a certain concentration (lower limit of combustion) is reached. In the case of temperature, it was found that the reaching time was shorter than the flash point In addition, the effect of variables on pool fire accidents of leakage tanks is somewhat different, but the variables that have the largest influence are the wind speed. Therefore, it is expected that the results of this study will be used as basic data for similar numerical analysis and it will provide useful numerical information about the accidental leakage of hazardous materials under various research conditions.

• Journal of Soil and Groundwater Environment
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• v.17 no.2
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• pp.15-21
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• 2012

MTBE (Methyl tertiary-butyl ether) has been commonly used as an octane enhancer to replace tetraethyl lead in gasoline, because MTBE increases the efficiency of combustion and decreases the emission of carbon monoxide. However, MTBE has been found in groundwater from the fuel spills and leaks in the UST (Underground Storage Tank). Fenton's oxidation, an advanced oxidation catalyzed with ferrous iron, is successful in removing MTBE in groundwater. However, Fenton's oxidation requires the continuous addition of dissolved $Fe^{2+}$. Zero-valent iron is available as a source of catalytic ferrous iron of MFO (Modified Fenton's Oxidation) and has been studied for use in PRBs (Permeable Reactive Barriers) as a reactive material. Therefore, this study investigated the condition of optimization in MFO-PRBs using waste zero-valent iron (ZVI) with the waste steel scrap to treat MTBE contaminated groundwater. Batch tests were examined to find optimal molar ratio of MTBE : $H_2O_2$ on extent to degradation of MTBE in groundwater at pH 7 with 10% waste ZVI. As the results, the ratio of optimization of MTBE to hydrogen peroxide for MFO was determined to be 1:300[mM]. The column experiment was conducted to know applicability of MFO-PRBs for MTBE remediation in groundwater. As the results of column test, MTBE was removed 87% of the initial concentration during 120days of operational period. Interestingly, MTBE was degraded not only within waste ZVI column but also within sand column. It means the aquifer may affect continuously the MTBE contaminated groundwater after throughout the waste ZVI barrier. The residual products showed acetone, TBF (Tert-butyl formate) and TBA (Tert-butyl acetate) during this test. The results of the present study showed that the recycled materials can be effectively used for not only a source of catalytic ferrous iron but also a reactive material of the MFO-PRBs to remove MTBE in groundwater.

• Journal of Chest Surgery
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• v.9 no.2
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• pp.298-310
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• 1976

A clinical analysis was performed on 118 cases of the benign esophageal diseases experienced at Department of Thoracic Surgery, Seoul National University Hospital during 20 year period from 1957 to 1976. Of 118 cases of the benign esophageal diseases, there were 84 patients of esophagenal stenosis, 14 of esophageal perforation, 8 of esophageal atresia, 7 of achalasia, 2 of hiatal hernia, 2 of esophageal foreign body and one of esophageal diverticulum. Fifty-one patients were male and sixty-seven were female, and ages ranged from one day to sixty-four years with peak incidence in the age group of 20 to 29 years. All but one of the esophageal stenosis were caused by corrosive esophagitis and ages ranged from three to sixty-four years with peak incidence in third decade. Main symptoms of the esophageal stenosis were dysphagia, weight loss and chest pain in order and mostly began between one month and one year after ingestion of corrosive agents. Corrosive esophageal stenosis developed most frequently in middle one-third of the esophagus and about one-forth of them were diffuse. Operations were performed on 72 patients of esophageal stenosis of whom 26 patients had esophagocologastrostomy, 21 gastrostomy, 20 esophagogastrostomy, 4 esophagojejunogastrostomy and 2 pharyngogastrostomy. There were 5 deaths in the postoperative period, an operative mortality of 6.9 percent, and 20 patients had one or two complications; eight were anastomotic leaks, 6 gangrenes of replaced loop, 4 wound abscesses and others. The causes of the esophageal perforation were traumatic in 7 cases, caustics in 4 and spontaneous in 3, and the most frequent site of the perforation was lower one-third of the esophagus. Frequent symptoms of the esophageal perforation were pain, fever, dysphagia and dyspnea, and preoperatively there were mediastinitis in 8 cases, empyema in 7, lung abscess in 3 and others. All 14 patients of the esophageal perforation underwent operation: primary closure in 7 cases, drainage in 4, esophagogastrostomy in 2 and 'esophageal diversion in one. There were 4 postoperative deaths and 11 postoperative complications occurred in 7 patients. The duration of symptoms in achalasia was between 3 months and 25 years, with an average duration of 6. 2 years. Frequent symptoms of the achlasia esophagi were dysphagia, regurgitation, pain and weight loss in order. All 7 patients of achlasia underwent modified Heller's operation where 2 patients had complications, restenosis in one and esophageal perforation in another. All 8 patients of congenital esophageal atresia had distal tracheoesophageal fistula and were admitted within 5 days of life, but there were pneumonic consolidation on chest X-ray in patients. Five patients underwent one staged operation with the result of 2 deaths and one anastomotic leak.

• Journal of the Korean Institute of Gas
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• v.9 no.4 s.29
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• pp.57-61
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• 2005

The objective of paper is to carry out a comparative Quantitative Risk Assessment (QRA) of two KOGAS tank designs using a fault tree methodology, a standard 'Full Containment' tank and a 'Membrane' tank. For the membrane tank, both the initial KOGAS design and 4 modified KOGAS designs have been assessed, giving six separate cases. In this paper, the frequencies of releases are quantified using a fault tree approach. For clarity in the analysis, and to ensure consistency, all cases have been quantified using the same fault tree. Logic within the fault tree is used to select each of the cases. Full quantification of risks is often difficult, owing to a lack of relevant failure data, but the aim of this study has been to be as quantitative as possible, with full transparency of failure information. The most significant general cause of external LNG leaks is predicted to be a seismic event, which has been quantified nominally. 4modified KOGAS desiens to Prevent damage of bottom membrane panels that was shown in preparatory estimation could quantitively confirm safety improvement. According to result, the predicted frequencies of an external LNG leak for the full containment and modified membrane tanks are very similar, failures due to dropped pumps are predicted to be significantly greater for the membrane tank with thickened plate than for the full containment tank.

• The Journal of the Petrological Society of Korea
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• v.17 no.2
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• pp.95-107
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• 2008

The Carved Buddhist Triad on Rock-cliff in Sinarnri (Treasure No. 680) consists of biotite granodiorite, which were positively carved on fore and west planes of four subvertical cliffs by two joint sets of NE-SW and NNW-SSE directions. The cliffs are $N50^{\circ}E\;85^{\circ}SE$ in fore plane, $N25^{\circ}W\;90^{\circ}$ in west plane, $N40{\sim}50^{\circ}E\; 82{\sim}85^{\circ}NW$, back plane, $N20^{\circ}W\;75^{\circ}SW$ in east plane, which are parallel to two joint sets of NE-SW and NNW-SSE directions in geology around it. The chemical index of alteration ranges 60.3 to 62.0 from the major elements in the rock that was weathered into producing kaolin minerals from alteration of feldspars and biotite. The Buddhist image has been deteriorated into joints, brown rusts, discolorations and granular disintegrations by such deterioration causes as deformation, moisture, temperature variation and microorganic living. The moisture, which leaks from groundwater in the rock, dissolve to decompose minerals.

• Journal of the Korean earth science society
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• v.34 no.6
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• pp.479-491
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• 2013

Products of the eruption of Mt. Baekdusan are identified as volcanic materials at the estuaries of the Songhuagang river to north, the Dumangang river to east and the Amnokgang river to west. More speficially, pyroclastic flows, lahars and volcanic floods can affect an area of 400km in radius, centering around Lake Cheonji caldera. However, unlike the millenium eruption, the flow situation has been changed. Because multi-purpose dams and reserviors with a combined pondage of mora than 2 billion tons of water have been built in the rivers of which sources are originated from Lake Cheonji caldera. In addition, the flow of fluids expected to take place when the volcano has erupted is thought to be affected by artificial constructions in both direct and indirect ways. This study calculates the direction of fluids flow by using numerical analyses of pyroclastic flows, lahars and volcanic floods that can occur when the volcano of Mt. Baekdusan has erupted. We also estimate the scope of damages by pyroclastic flows, lahars, volcanic flooding caused by the pondage of the dams and water storages in and around Mt. Baekdusan. Pyroclastic flows transported over the steep slopes at the early times of eruptions move over the mountain slopes, affecting airplanes, and lahars due to leaks of Lake Cheonji could reach as far as major rivers and streams near Mt. Baekdusan. Unlike historical accounts, volcanic flood is expected to be limited in its scope of influence to reservoirs bigger than Lake Cheonji in pondage.

• Journal of Korean Neurosurgical Society
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• v.29 no.2
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• pp.240-248
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• 2000

Objective : Spontaneous intracranial hypotension is a rarely reported syndrome of spontaneous postural headache associated with low CSF pressure and has rarely been demonstrated radiographically or surgically. But recently, it is being recognized with increasing frequency. The purpose of this study was to characterize clinical and imaging features, etiologic factors, and outcome in the spontaneous intracranial hypotension. Patients and Methods : We reviewed our experience with documented cases of spontaneous intracranial hypotension in 5 consecutive patients with orthostatic headaches from April 1998 to April 1999. Results : The mean age was 41 years(from 35 to 49 years). All patients had postural headaches, which were completely alleviated by recumbency position. Nausea, neck pain, horizontal diplopia, photophobia, and blurred vision were noted in some of the patients. Brain MRI showed diffuse pachymeningeal gadolinium enhancement, subdural collections of fluid, and descent of the brain. The opening pressure from lumbar puncture was $4cmH_2O$ or less in three of five patients whereas the opening pressure was within normal range in two patients. All patients underwent radioisotope cisternography and computerized tomographic myelography. On radioisotope cisternography, CSF leakage was suspected at the level of cervical area(1 patient), upper thoracic area(2 patients), mid-thoracic area(1 patient). Computed tomography myelography revealed extraarachnoid accumulation of contrast media(compatible finding with CSF leakage) at the level of cervical or thoracic area. In all patients, the symptoms resolved in response to supportive measures or epidural blood patch(1 patient). Conclusion : Spontaneous spinal CSF leakage is increasingly recognized as a cause of spinal postural headache. Most CSF leaks are located at the cervicothoracic junction or in the thoracic spine and can be demonstrated by variable diagnostic method. The condition is usually self-limiting and its prognosis is typically good.