• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.484-492
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• 2012

The TMS(Thermal Management System) heater in a fuel cell vehicle has been developed to prevent a decline of fuel cell durability and cold start durability. Main functions of the COD(Cathode Oxygen Depletion) heater are depletion of oxygen in a cathode as heat energy and consumption of electric power for rapid warming up of a fuel cell stack. This paper covers subjects including the design specification of a heater, heater controller for detection of overheat and reliability assessment including coolant pressure cycle test of a heater. To verify the design concept, burst pressure and deformation analysis of plastic housing were carried out. Also, temperature distribution analysis of heater surface and coolant inside of housing were carried out to verify the design concept. By designing the plastic housing instead of a steel housing, the 30% weight lightening and 50% cost reduction were attained. A module-based design of a TMS system including a heater or reducing the watt density of a heater is a problem to be solved in the near future work.

• Journal of Information Processing Systems
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• 제17권5호
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• pp.972-988
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• 2021

At present, DevOps environments are getting popular in software organizations due to better collaboration and software productivity over traditional software process models. Software artefacts in DevOps environments are vulnerable to frequent changes at any phase of the software development life cycle that create a continuous integration continuous delivery pipeline. Therefore, software artefact traceability management is challenging in DevOps environments due to the continual artefact changes; often it makes the artefacts to be inconsistent. The existing software traceability related research shows limitations such as being limited to few types of artefacts, lack of automation and inability to cope with continuous integrations. This paper attempts to overcome those challenges by providing traceability support for heterogeneous artefacts in DevOps environments using a prototype named SAT-Analyser. The novel contribution of this work is the proposed traceability process model consists of artefact change detection, change impact analysis, and change propagation. Moreover, this tool provides multi-user accessibility and is integrated with a prominent DevOps tool stack to enable collaborations. The case study analysis has shown high accuracy in SAT-Analyser generated results and have obtained positive feedback from industry DevOps practitioners for its efficacy.

• 한국기계가공학회지
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• 제20권10호
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• pp.102-111
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• 2021

Maintainability is a major design parameter that includes availability as well as reliability in a RAM (reliability, availability, maintainability) analysis, and is an index that must be considered when developing a system. There is a lack of awareness of the importance of predicting and analyzing maintainability; therefore, it is dependent on past-experience data. To improve the utilization rate, maintainability must be managed as a key indicator to meet the user's requirements for failure maintenance time and to reduce life-cycle costs. To improve the maintainability-prediction accuracy in the detailed design stage, we present a maintainability-prediction method that applies Method B of the Military Standardization Handbook (MIL-HDBK-472) Procedure V, as well as a Korean maintainability-prediction software package that reflects the system complexity.

• ETRI Journal
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• 제43권3호
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• pp.459-470
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• 2021

This paper presents a low-cost prototype for monitoring online the maximum power produced by a domestic photovoltaic (PV) system using Internet of Things (IoT) technology. The most common tracking algorithms (P&O, InCond, HC, VSS InCond, and FL) were first simulated using MATLAB/Simulink and then implemented in a low-cost microcontroller (Arduino). The current, voltage, load current, load voltage, power at the maximum power point, duty cycle, module temperature, and in-plane solar irradiance are monitored. Using IoT technology, users can check in real time the change in power produced by their installation anywhere and anytime without additional effort or cost. The designed prototype is suitable for domestic PV applications, particularly at remote sites. It can also help users check online whether any abnormality has happened in their system based simply on the variation in the produced maximum power. Experimental results show that the system performs well. Moreover, the prototype is easy to implement, low in cost, saves time, and minimizes human effort. The developed monitoring system could be extended by integrating fault detection and diagnosis algorithms.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.253-257
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• 2021

This work demonstrates the use of baromembrane method based on reverse osmosis (RO) process. The method is realized on mobile complex, which allows to concentrate and determine ultra-low activity of radionuclides in water cooling ponds of Russian nuclear fuel cycle enterprises. The existence level of radionuclide background creates difficult conditions for identification the contribution of liquid discharges enterprise, as standard monitoring methods have a very high detection level for radionuclides. Traditional methods for determining the background radionuclides concentrations require the selection of at least 500 liters (l) of water, followed by their evaporation to form a dry residue. This procedure with RO membranes requires at least 5 days. It is possible to reduce the time and energy spent on evaporation of hundreds of water liters by pre-concentrating radionuclides in a smaller sample volume with baromembrane method. This approach allows preliminary concentration of water samples from 500 l volume till 20 l volume during several hours. This approach is universal for the concentration of dissolved salts of any heavy metals, other organic compounds and allows the preparation of water countable samples in much shorter time compared to the traditional evaporation method.

• 한국초전도ㆍ저온공학회논문지
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• 제24권4호
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• pp.71-77
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• 2022

Sub-Kelvin cooling has been generally demanded for the fields of low temperature physics, such as physical property measurements, astronomical detection, and quantum computing. The refrigeration system with a small size can be appropriately introduced when the measurement system does not require a high cooling capacity at sub-Kelvin temperature. The dilution refrigerator which is a common method to reach sub-Kelvin, however, must possess a large ³He circulation equipment at room temperature. As alternatives, a sorption refrigerator and a magnetic refrigerator can be adopted for sub-Kelvin cooling. This paper describes those coolers which have been developed by various research groups. Furthermore, a cold-cycle dilution refrigerator of which the size of the ³He circulation system is minimized, is also introduced. Subsequently, a new concept of dilution refrigerator is proposed by our group. The suggested cooler can achieve sub-Kelvin temperature with a small size since it does not require any recuperator and turbo-molecular vacuum pump. Its architecture allows the compact configuration to reach sub-Kelvin temperature by integrating the sorption pump and the magnetic refrigerators. Therefore, it may be suitably utilized in the low temperature experiments requiring low cooling capacity.

• 전력전자학회논문지
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• 제27권2호
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• pp.85-91
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• 2022

This study proposes a high efficiency bridgeless Power Factor Correction (PFC) converter with improved common mode noise characteristics. Conventional PFC has limitations due to low efficiency and enlarged heat sink from considerable conduction loss of bridge diode. By applying a Common Mode (CM) coupled inductor, the proposed bridgeless PFC converter generates less conduction loss as only a small magnetizing current of the CM coupled inductor flows through the input diode, thereby reducing or removing heat sink. The input diode is alternately conducted every half cycle of 60 Hz AC input voltage while a negative node of AC input voltage is always connected to the ground, thus improving common mode noise characteristics. With the aim to improve switching loss and reverse recovery of output diode, the proposed circuit employs Critical Conduction Mode (CrM) operation and it features a simple Zero Current Detection (ZCD) circuit for the CrM. In addition, the input current sensing is possible with the shunt resistor instead of the expensive current sensor. Experimental results through 480 W prototype are presented to verify the validity of the proposed circuit.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2021년도 학술발표회
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• pp.134-134
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• 2021

Precipitation is a crucial component of water cycle and play a key role in hydrological processes. Traditionally, gauge-based precipitation is the main method to achieve high accuracy of rainfall estimation, but its distribution is sparsely in mountainous areas. Recently, satellite-based precipitation products (SPPs) provide grid-based precipitation with spatio-temporal variability, but SPPs contain a lot of uncertainty in estimated precipitation, and the spatial resolution quite coarse. To overcome these limitations, this study aims to generate new grid-based daily precipitation using Automatic weather system (AWS) in Korea and multiple SPPs(i.e. CHIRPSv2, CMORPH, GSMaP, TRMMv7) during the period of 2003-2017. And this study used a machine learning based Random Forest (RF) model for generating new merging precipitation. In addition, several statistical linear merging methods are used to compare with the results of the RF model. In order to investigate the efficiency of RF, observed data from 64 observed Automated Synoptic Observation System (ASOS) were collected to evaluate the accuracy of the products through Kling-Gupta efficiency (KGE), probability of detection (POD), false alarm rate (FAR), and critical success index (CSI). As a result, the new precipitation generated through the random forest model showed higher accuracy than each satellite rainfall product and spatio-temporal variability was better reflected than other statistical merging methods. Therefore, a random forest-based ensemble satellite precipitation product can be efficiently used for hydrological simulations in ungauged basins such as the Mekong River.

• International journal of advanced smart convergence
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• 제12권4호
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• pp.378-385
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• 2023

The importance of wearing respiratory protective equipment has been highlighted even more during the COVID-19 pandemic. Even if the suitability of respiratory protection has been confirmed through testing in a laboratory environment, there remains the potential for leakage points in the respirators due to improper application by the wearer, damage to the equipment, or sudden movements in real working conditions. In this paper, we propose a method to detect the occurrence of leak holes by measuring the pressure changes inside the mask according to the wearer's breathing activity by attaching an IoT sensor to a full-face respirator. We designed 9 experimental scenarios by adjusting the degree of leak holes of the respirator and the breathing cycle time, and acquired respiratory data for the wearer of the respirator accordingly. Additionally, we analyzed the respiratory data to identify the duration and pressure change range for each breath, utilizing this data to train a neural network model for detecting leak holes in the respirator. The experimental results applying the developed neural network model showed a sensitivity of 100%, specificity of 94.29%, and accuracy of 97.53%. We conclude that the effective detection of leak holes can be achieved by incorporating affordable, small-sized IoT sensors into respiratory protective equipment.

• 한국ITS학회 논문지
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• 제13권1호
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• pp.1-14
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• 2014

국가정책 및 사회적 여건의 변화에 따라 도시부의 교통혼잡 완화를 위한 물리적 도로 확대가 한계에 다다른 지금 혼잡 완화를 위해서는 기존 도로의 효율성을 재고하는 방안이 간구되어야한다. 또한 지능형교통체계(ITS)는 과거 루프 및 영상검지기 등을 통한 도로기반 지점검지 중심의 교통정보 수집체계에서 도로, 자동차 및 보행자간의 다양한 수집 체계를 통한 실시간 구간검지 체계 중심의 차세대 지능형교통체계(C-ITS :Co-operative ITS)로 빠르게 진화하고 있으나 현재 교차로의 운영 및 제어를 위한 교통정보의 수집방법은 지점검지체계에 국한되어 있는 실정이다. 따라서 본 연구는 현재 Hi-pass에 적용된 DSRC기술을 통해 수집이 가능한 구간정보를 이용하여 접근로의 대기행렬 길이를 산정하고 이를 활용하는 독립교차로의 실시간 신호제어모형의 개발 및 평가를 목적으로 하였다. 대기행렬길이 추정을 위해 구간검지기를 통해 수집된 개별차량의 통행시간을 이용하여 시공도 상에 4개의 좌표값을 추정하였으며 한 주기동안 추정된 좌표값들을 통해 대기행렬이 생성되는 충격파의 속도 및 대기행렬길이를 추정하였다. 실시간 신호제어를 위해 각 방향별 추정된 대기행렬길이를 통해 전체 교차로의 대기행렬길이의 합이 최소가 되는 신호시간을 산정하였으며 API 기능을 제공하는 미시적 시뮬레이션 프로그램인 VISSIM을 활용하여 총 3개의 시나리오를 평가하여 알고리즘에 의해 교차로의 대기행렬 길이의 합이 최소가 되는 신호시간의 산정이 가능함을 확인하였다.