• 한국압력기기공학회 논문집
• /
• 제17권2호
• /
• pp.90-100
• /
• 2021

Molten corium-concrete interaction (MCCI) is one of the most important phenomena that can lead to the potential hazard of late containment failure due to basemat penetration during a severe accident. In this study, MCCI analytical models of the CORQUENCH code were prepared through verification calculations of several experiments, which had been performed using concrete types similar to those of the calandria vault floor in CANDU-6 plants. The behaviors of thermal-hydraulic variables related to MCCI phenomena were analyzed under the conditions of dry floor and water flooding during the severe accident stemming from a hypothetic station blackout. Uncertainty analyses on the ablation depth were also carried out. It was estimated that the concrete ablation was not interrupted due to the continuous MCCI process under the dry condition but was terminated within 24 hours under the water flooding condition. It was confirmed that the water flooding as a mitigating action was effective to achieve the quenching and thermal stabilization of the melt discharged from the calandria vessel, showing that the present models are capable of reasonably simulating MCCI phenomena in CANDU-6 plants. This study is expected to provide the technical bases to the accident management strategy during the late-phase severe accidents.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2002년도 춘계학술대회 논문집
• /
• pp.608-613
• /
• 2002

In this paper we developed the MPC sensor for steering control and steering control of the AGVDS(Autonomous Guided Vehicle Driving System) for Durability test. Among durability tests, the accelerated durability test has been widely used to evaluate the durability of vehicle structure and chassis parts in a short period of time on the designed road that has severe surface conditions. However it increased the drivers fatigue mainly caused by the severe driving conditions. The driver's difficulty to maintain the constant speed and control the steering wheel reduces the reliability of test results. In addition to the general detecting sensor for steering control was restricted by surrounding condition. So we need to develop steering control sensor was robust in the bad driving condition. In this paper we developed steering control sensor using magnetic induction which is robust in the bad driving condition and implemented the AGVDS.

• Tribology and Lubricants
• /
• 제14권1호
• /
• pp.45-53
• /
• 1998

Friction and wear test for two kinds of Cu-based sintered metallic friction material against cast iron disk was carried out by plate-on-disk type friction and wear tester to investigate the friction and wear characteristics of brake system in severe condition. In this experimental study, the counter specimen was cast iron which is being used generally in brakes of heavy duty equipments. Test friction materials were A type which was manufactured by foreign company and B type by domestic company. Friction coefficient and wear volume were measured and compared with each other. The experiment was performed under room temperature. The worn surface of cast iron disk and friction material were observed by scanning electron microscope. The temperature of surface of disk was measured continuously by the non-contacting thermometer. It was found that A type friction material had stable friction coefficient over the wide range of sliding condition, but B type friction material had unstable friction coefficient and lower value of 0.2 under the severe sliding condition.

• 국제학술발표논문집
• /
• The 1th International Conference on Construction Engineering and Project Management
• /
• pp.655-661
• /
• 2005

For a hydro power plant project, the headrace tunnel having a finished diameter of 3.3m was constructed in volcanic rocks with well-developed vertical joint and high groundwater table. The intake facility was located 20.3 km upstream of the powerhouse and headrace tunnel of 20 km in length and penstock of 440 m in height connected the intake and the powerhouse. The typical caldera lake, Lake Toba set the geology at the site; the caving of the ground caused tension cracks in the vertical direction to be developed and initial stresses at the ground to be released. High groundwater table(the maximum head of 20 bar) in the area of well-connected vertical joints delayed the progress of tunnel excavation severely due to the excessive inflow of groundwater. The excavation of tunnel was made using open-shield type TBM and mucking cars on the rail. High volume of water inflow raised the water level inside tunnel to 70 cm, 17% of tunnel diameter (3.9 m) and hindered the mucking of spoil under water. To improve the productivity, several adjustments such as modification of TBM and mucking cars and increase in the number of submersible pumps were made for the excavation of severe water inflow zone. Since the ground condition encountered during excavation turned out to be much worse, it was decided to adopt PC segment lining instead of RC lining. Besides, depending on the conditions of the water inflow, rock mass condition and internal water pressure, one of the invert PC segment lining with in-situ RC lining, RC lining and steel lining was applied to meet the site specific condition. With the adoption of PC segment lining, modification of TBM and other improvement, the excavation of the tunnel under severe groundwater condition was successfully completed.

• 대기
• /
• 제18권3호
• /
• pp.207-224
• /
• 2008

Severe downslope windstorms observed at Gangneung, Korea in the springtime during the last 30 years are studied to understand their generation mechanisms. 92 severe wind cases are selected for which the maximum instantaneous wind speeds exceed two standard deviation of total mean plus ($18.7ms^{-1}$). They are categorized into the three mechanisms (hydraulic jump, partial reflection, and critical-level reflection) proposed in previous studies based on the flow condition, which is calculated using the wind and temperature profile observed at one upstream rawinsonde station, Osan. Among the three, partial reflection is found to be the most frequent mechanism for the last 30 years (1976 - 2005). To understand the role of inversion in generating severe downslope windstorms, horizontal velocity perturbation was calculated analytically for the atmosphere with an inversion layer. It turned out that the intensity of downslope wind was increased by inversion layer of specific heights, which are well matched with the observations. For better understanding the generation mechanisms, two-dimensional numerical simulations are conducted for the 92 severe wind cases using the ARPS model. In most simulations, surface wind speed exceeds the value of the severe-wind criterion, and each simulated case can be explained by its own generation mechanism. However, in most simulations, the simulated surface wind speed is larger than the observed, due to ignoring the flow-splitting effect in the two-dimensional framework.

• 한국안전학회지
• /
• 제27권6호
• /
• pp.192-204
• /
• 2012

For a severe accident of nuclear power plant, an approach to estimation of the radiological source term using a severe accident code(MELCOR) has been proposed. Although the MELCOR code has a capability to estimate the radiological source term, it has been hardly utilized for the radiological consequence analysis mainly due to a lack of understanding on the relevant function employed in MELCOR and severe accident phenomena. In order to estimate the severe accident source term to be linked with the radiological consequence analysis, this study proposes 4-step procedure: (1) selection of plant condition leading to a severe accident(i.e., accident sequence), (2) analysis of the relevant severe accident code, (3) investigation of the code analysis results and post-processing, and (4) generation of radiological source term information for the consequence analysis. The feasibility study of the present approach to an early containment failure sequence caused by a fast station blackout(SBO) of a reference plant (OPR-1000), showed that while the MELCOR code has an integrated capability for severe accident and source term analysis, it has a large degree of uncertainty in quantifying the radiological source term. Key insights obtained from the present study were: (1) key parameters employed in a typical code for the consequence analysis(i.e., MACCS) could be generated by MELCOR code; (2) the MELOCR code simulation for an assessment of the selected accident sequence has a large degree of uncertainty in determining the accident scenario and severe accident phenomena; and (3) the generation of source term information for the consequence analysis relies on an expert opinion in both areas of severe accident analysis and consequence analysis. Nevertheless, the MELCOR code had a great advantage in estimating the radiological source term such as reflection of the current state of art in the area of severe accident and radiological source term.

• 대한청각학회지
• /
• 제25권2호
• /
• pp.72-79
• /
• 2021

Background and Objectives: The speech-in-noise test is typically performed using an audiometer. The results of the digit-in-noise recognition (DIN) test may be influenced by the flat frequency response of free-field audiometry and frequency of the hearing aid fit based on fitting rationale. This study aims to investigate the DIN test in unaided and aided conditions. Subjects and Methods: Thirty four adults with moderate and severe sensorineural hearing loss (SNHL) participated in the study. The signal-to-noise ratio (SNR) for 50% of the DIN test was obtained in the following two conditions: 1) the unaided condition, performed using an audiometer in a free field; and 2) aided condition, performed using a hearing aid with an unvented individual earmold that was fitted based on NAL-NL2. Results: There was a statistically significant elevation in the mean SNR for the severe SNHL group in both test conditions when compared with that of the moderate SNHL group. In both groups, the SNR for the aided condition was significantly lower than that of the unaided condition. Conclusions: Speech recognition in hearing-impaired patients can be realized by fitting hearing aids based on evidence-based fitting rationale rather than by measuring it using free-field audiometry measurement that is utilized in a routine clinic setup.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
• /
• pp.565-569
• /
• 1999

In these days, the silicone insulators have been increasingly studied and applied for outdoor insulators because it has superior characteristics than porcelain and glass insulators, which have been used for outdoor insulators. First of all, The excellent performance of the silicone rubber in polluted and wet conditions is attributed to the ability of the material to maintain the hydrophobicity of the surface in the presence of severe contamination and wet conditions. This is because of the presence of low molecular weight mobile fluid in the silicone rubber which diffuses to the surface and to above the contamination layer. But, the leakage current and some surface discharge occurs on surface of the composite polymeric insulation materials when the insulator is used for a long time with severe contaminative condition and it can lead the contamination flashover. So the leakage current and the discharge current are important to estimate the condition of the silicone rubber surface. In this paper, the average leakage current, the relation of surface discharge current and phase angle were study to investigate electrical conduction of silicone rubber surface with the salt fog condition.

• Applied Biological Chemistry
• /
• 제32권3호
• /
• pp.255-264
• /
• 1989

1) 밭상태 경엽처리에서 비등점이 높은 용매일수록 더 낮은 농도에서 약해를 유발하였으며, 방향족 용매의 약해유발 최저농도가 가장 낮았다. 용매에 의한 약해에 가장 민감한 식물은 콩, 둔감한 식물은 상치였다. 2) 밭상태 발아전 토양처리에서는 비등점이 높은 용매만이 고농도에서 약해를 유발하였다. 3) 건답상례 경엽처리는 밭상태의 결과와 유사하였으나 용매의 비등점과 약해 유발최저농도간에는 고도로 유의한 부의 상관관계가 인정되었다. 발아전 처리에서는 밭상태보다 약해유발이 심하였다. 4) 논담수상태 시험에서는 발아전처리에서 약해 유발이 심하였으며 가장 약해가 심한 것은 알콜류로 ethanol은 0.001%에서도 약해를 유발하였다.

• 식물병과 농업
• /
• 제1권1호
• /
• pp.45-46
• /
• 1995

In recent years, there were considerably severe occurrences of TuMV(turnip mosaic virus) disease on radish and Chinese cabbage cultivated at alpine or sub-alpine regions, especially more severe on young Chinese cabbage sowed after late June. Started from 1991, those were very severe in 1992 and 1994, for the number of migrated aphids was increased enormously according to the weather condition of high temperature and low humidity then. This disease started at late June to early July, and continued to late August. It seemed that TuMV was transmitted easily and completely to the young chinese cabbages, but hardly and rarely the old. The regions over 1,000m of altitude had less possibility of disease-occurring, but there was severe occurrence on the second cropping of Chinese cabbage in a year. It is considered that more researches on control method of TuMV disease will be needed very urgently.