• Journal of the Korea Convergence Society
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• v.13 no.3
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• pp.33-41
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• 2022

In this article, we proposed to predict natural gas (NG) leakage levels through feature selection based on a factor analysis (FA) of the integrating the Korean Meteorological Agency data and natural gas leakage data for considering complex factors. The paper has been divided into three modules. First, we filled missing data based on the linear interpolation method on the integrated data set, and selected essential features using FA with OrdinalEncoder (OE)-based normalization. The dataset is labeled by K-means clustering. The final module uses four algorithms, K-nearest neighbors (KNN), decision tree (DT), random forest (RF), Naive Bayes (NB), to predict gas leakage levels. The proposed method is evaluated by the accuracy, area under the ROC curve (AUC), and mean standard error (MSE). The test results indicate that the OrdinalEncoder-Factor analysis (OE-F)-based classification method has improved successfully. Moreover, OE-F-based KNN (OE-F-KNN) showed the best performance by giving 95.20% accuracy, an AUC of 96.13%, and an MSE of 0.031.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.136-141
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• 2008

Due to environmental concerns $CO_2$ has been reintroduced as a potential candidate to replace HFCs in refrigeration systems since 1990s. In a refrigeration cycle, oil is utilized in lubricating a compressor. However, although oil separators are installed after a compressor oil is prone to leak to the whole system. The mixing of $CO_2$ and oil, even a small amount of oil, the heat transfer performance in heat exchanger deteriorated and the pressure drop inside tube increases. Therefore, it is needed to precisely estimate the mixture thermodynamic properties of $CO_2$-lubricant oil to correctly design a $CO_2$ refrigeration system. The commonly used method in estimating the mixture properties is the mole based weighting model. However, the accuracy of the method can not be assured. In the present study, $CO_2$-lubricant oil mixture properties including viscosity and density were estimated by using the mixture models, based on the equation of state (EOS).

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.236-245
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• 2016

In a reactor coolant system of a nuclear power plant (NPP), an overpressure protection system keeps pressure in the loop within 110% of design pressure. However if the system does not work properly, pressure in the loop could elevate hugely in a short time. It would be seriously disastrous if a weak point in the pressure boundary component bursts and releases radioactive material within the containment; and it may lead to a leak outside the containment. In this study, a gross deformation that leads to a burst of pressure boundary components was investigated. Major components in the primary pressure boundary that is structurally important were selected based on structural mechanics, then, they were used to study the burst pressure of components by finite element method (FEM) analysis and by number of closed forms of theoretical relations. The burst pressure was also used as a metric of design optimization. It revealed which component was the weakest and which component had the highest margin to bursting failure. This information is valuable in severe accident progression prediction. The burst pressures of APR-1400, AP1000 and VVER-1000 reactor coolant systems were evaluated and compared to give relative margins of safety.

• Journal of Sensor Science and Technology
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• v.24 no.5
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• pp.306-310
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• 2015

IoT(Internet of Things) based underground risk assessment system surrounding water pipeline enables an advanced monitoring and prediction for unexpected underground hazards such as abrupt road-side subsidence and urban sinkholes due to a leak in water pipeline. For the development of successful assessment technology, the PSU(Water Pipeline Safety Unit) which detects the leakage and movement of water pipes. Then, the IoT-based underground risk assessment system surrounding water pipeline will be proposed. The system consists of early detection tools for underground events and correspondence services, by analyzing leakage and movement data collected from PSU. These methods must be continuous and reliable, and cover certain block area ranging a few kilometers, for properly applying to regional water supply changes.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.159-160
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• 2020

Flat plate structures are designed in the form of long span due to the development of construction materials and the improvement of construction technology. However, a high-rise structure of a flat plate of 50 less floors is constructed without detailed review of the inequality shortening, long-term deflection of the slab, and cracks. Therefore, it is possible to examine the case of defects in the structure due to deformation and damage of non-structures such as crack and leak, deflection of the door frame, and deformation of equipment ducts. In this study, it is a high-rise structure, and the inequality shortening and long-term deflection of the slab of the flat plate structure were evaluated through finite element analysis, and it was confirmed that prior precision analysis and correction during construction is necessary.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.3
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• pp.292-296
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• 2023

Until recently, ships, automobiles, and drones using hydrogen energy are being actively researched. In addition, stations and facilities for hydrogen supply are being developed widely. Among them, a hydrogen pump is necessary for compressing it and transfer to other stations. The liquid hydrogen pump is operated at very high pressure up to 90 MPa. In our research, a reciprocating plunger pump is studied. Especially, a leakage in a liquid hydrogen pump is predicted using a finite element method. As a result, it was found that leak mass flow rates changed from 0.09 to 2.20 kg/h, when the gaps were given from 2 to 6 ㎛. Thus pump efficiencies were calculated from 99.9 to 97.9%, when the gaps changed from 2 to 6 ㎛. These results are useful for the design of the liquid hydrogen pump.

• The Journal of the Convergence on Culture Technology
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• v.10 no.2
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• pp.407-417
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• 2024

The objective of this study is to predict and reduce potential damage caused by chlorine gas leaks, a hazardous material, when vehicles transporting it overturn due to accidents or other incidents. The goal is to forecast the anticipated damages caused by chlorine toxicity levels (ppm) and to design effective response strategies for mitigating them. To predict potential damages, we conducted quantitative assessments using the ALOHA program to calculate the toxic effects (ppm) and damage distances resulting from chlorine leaks, taking into account potential negligence of drivers during transportation. The extent of damage from toxic gas leaks is influenced by various factors, including the amount of the leaked hazardous material and the meteorological conditions at the time of the leak. Therefore, a comprehensive analysis of damage distances was conducted by examining various scenarios that involved variations in the amount of leakage and weather conditions. Under intermediate conditions (leakage quantity: 5 tons, wind speed: 3 m/s, atmospheric stability: D), the estimated distance for exceeding the AEGL-2 level of 2 ppm was calculated to be 9 km. This concentration poses a high risk of respiratory disturbance and potential human casualties, comparable to the toxicity of hydrogen chloride. In particular, leaks in urban areas can lead to significant loss of life. In the event of a leakage incident, we proposed a plan to minimize damage by implementing appropriate response strategies based on the location and amount of the leak when an accident occurs.

• Food Engineering Progress
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• v.21 no.4
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• pp.312-317
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• 2017

Weight loss that influences quality and farmer incomes is affected by the storage environment of agricultural products. The interior of storage should be maintained at high humidity to prevent the weight loss of products which contain a lot of moisture. The research had constantly proceeded with change in the heat exchanger surface areas, humidity systems, and weight loss forecast to maintain high humidity within storage. Relative humidity that exerts an effect weight loss of crop is influenced by storage temperature, leak state, and volume of product. When weight loss is predicted, different conditions of these factors are derived. In case of CA storage, ways of forecasting the weight loss become easier compared to cold storage due to sealed storage with external environment during storage period. In this study, apples were stored in purge-type CA storage and weight loss has been predicted by using operating characteristics and environmental conditions. As a result, humidity variation in the storage fluctuates with the operation of the unit-cooler. Furthermore, unit-cooler operation factor is influenced by outside temperature and respiration heat. Prediction value of weight loss according to temperature and humidity has been most accurately predicted. Prediction value through defrosting water measured shows unit-cooler work quality. K-value needs verification to calculate the VPD method.

• Industry Promotion Research
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• v.9 no.2
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• pp.37-44
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• 2024

This study selected the worst-case scenario for fireball and vapor cloud explosion (VCE) of a styrene monomer storage tank installed in a petrochemical production plant and performed damage prediction and accident impact analysis. The range of influence of radiant heat and overpressure due to fireball and vapor VCE during the abnormal polymerization reaction of styrene monomer, the main component of the mixed residue oil storage tank, was quantitatively analyzed by applying the e-CA accident damage prediction program. The damage impact areas of radiant heat and explosion overpressure are analyzed to have a maximum radius of 1,150m and 626m, respectively. People within 1,150m of radiant heat of 4kW/m2 may have their skin swell when exposed to it for 20 seconds. In buildings within 626m, where an explosion overpressure of 21kPa is applied, steel structures may be damaged and separated from the foundation, and people may suffer physical injuries. In the event of a fire, explosion or leak, determine the risk standards such as the degree of risk and acceptability to workers in the work place, nearby residents, or surrounding facilities due to radiant heat or overpressure, identify the hazards and risks of the materials handled, and establish an emergency response system. It is expected that it will be helpful in establishing measures to minimize damage to workplaces through improvement and investment activities.

• Journal of Chest Surgery
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• v.50 no.6
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• pp.424-429
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• 2017

Background: The surgical treatment of secondary spontaneous pneumothorax (SSP) can be complicated by fragile lung parenchyma. The preoperative prediction of air leakage could help prevent intraoperative lung injury during manipulation of the lung. Common sites of bulla development and ruptured bullae were investigated based on computed tomography (CT) and intraoperative findings. Methods: The study enrolled 208 patients with SSP who underwent air leak control through video-assisted thoracoscopic surgery (VATS). We retrospectively reviewed the sites of bulla development on preoperative CT and the rupture sites during VATS. Results: Of the 135 cases of right-sided SSP, the most common rupture site was the apical segment (31.9%), followed by the azygoesophageal recess (27.4%). Of the 75 cases on the left side, the most common rupture site was the apical segment (24.0%), followed by the anterior basal segment (17.3%). Conclusion: The azygoesophageal recess and parenchyma along the cardiac border were common sites of bulla development and rupture. Studies of respiratory lung motion to measure the pleural pressure at the lung surface could help to determine the relationship between cardiogenic and diaphragmatic movement and bulla formation or rupture.