• Nuclear Engineering and Technology
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• 제49권5호
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• pp.968-978
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• 2017

Three small-break loss-of-coolant accident (SBLOCA) tests with safety injection pumps were carried out using the integral-effect test loop for SMART (System-integrated Modular Advanced ReacTor), i.e., the SMART-ITL facility. The types of break are a safety injection system line break, shutdown cooling system line break, and pressurizer safety valve line break. The thermal-hydraulic phenomena show a traditional behavior to decrease the temperature and pressure whereas the local phenomena are slightly different during the early stage of the transient after a break simulation. A safety injection using a high-pressure pump effectively cools down and recovers the inventory of a reactor coolant system. The global trends show reproducible results for an SBLOCA scenario with three different break locations. It was confirmed that the safety injection system is robustly safe enough to protect from a core uncovery.

• Fibers and Polymers
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• 제6권4호
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• pp.339-342
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• 2005

In this paper, a hand-operating method (tiled test method) of the wool-blending sample is made out, and make use of the method, the test of wool-blending bundle in different blending ratio is accomplished. According to the test data, the synthesis method of the stretch curve is worked out and the synthesis software for the typical stretch curve of wool-blending bundle is designed. Through laboratory hand-operating method, the blending fasciculus applying to fiber bundle test can be obtained in a short time. Calculation for sampling is accomplished in the article. We bring up 9 new signs to describe the characteristics of the curve behind peak for the first time: elongation behind peak (HE), elongation percentage behind peak (HEP), relative elongation rate behind peak (RHE), total break work $(W_a)$, break work behind peak (HW), break work coefficient behind peak (HWC), elongation percentage of half-load behind peak (HEL), load percentage of half-elongation behind peak (HLE), break efficiency behind peak (HEC).

• 대한기계학회논문집A
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• 제26권4호
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• pp.677-682
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• 2002

Break-in is an intentional treatment to enhance the performance life of machinery parts and to maintain static friction behavior. Most studies on break-in have concerned only about surface conditions such as roughness or film formation. But the exact mechanism of break-in has not been found yet. Friction, scuffing behavior and wear of AISI 1045 were studied in relation to break-in and residual stress. The cylinder-on-disk type tribometer was used with the line-contact geometry. Scuffing tests were carried out using a constant load of 730N. In the break-in procedure the step load was applied from 100N to 200N. In this experiment, it was found that the break-in helps compressive residual stress to be formed well enough to enhance the scuffing life during the scuffing test. Specimens that had high compressive residual stress induced by shot-peening show better wear resistance than those were not shot-peened. Results of scuffing test, break-in procedure and wear amount in relation to residual stress have been discussed.

• 복식
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• 제66권4호
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• pp.146-165
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• 2016

The aim of the study is to propose ways to improve the break line fit of women's tailored collar vests by modifying the patternmaking process. The study explored the fit effects of experimental vests with a focus on 3 different breast sizes, A, B, and C cups. Women in the ages between 20 and 24 in South Korea were targeted. In order to carry out the objective, the study implemented separate girth measurements for the front and the back of the tailored collar vests, and also allocated different dart amounts on the lapel through the break line according to the different breast cup sizes. The study adopted a 5-point rating scale to perform evaluation of the different fit effects caused by the varying dart amounts given on the experimental vests' break lines. This evaluation was carried out by apparel pattern experts. The results derived from the study were as follows: first, the implementation of separate girth measurements provided originality to the study, as the application of different measurements for the waist back length and the neck shoulder point-to-breast point-to-waist line led to the front panels of the experimental vests having varying slack amounts. Second, break line dart was applied in three different amounts, 0.5, 1.0, and 1.5cm respectively according to A, B and C breast sizes, and as the dart amount increased, extra ease on the break lines was reduced. The dart was applied on the edge lines of the lapel and it was applied from a point which was 6cm above the breast point to the end of the princess line for all the breast cup sizes.

• Safety and Health at Work
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• 제11권2호
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• pp.207-214
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• 2020

Background: Prolonged sitting at work can lead to adverse health outcomes. The health risk of office workers is an increasing concern for the society and industry, with prolonged sitting work becoming more prevalent. Objective: This study aimed to explore the variation in muscle activities during prolonged sitting work and found out when and how to take a break to mitigate the risk of muscle symptoms. Methods: A preliminary survey was conducted to find out the prevalence of muscle discomfort in sedentary work. Firstly, a 2-h sedentary computer work was designed based on the preliminary study to investigate the variation in muscle activities. Twenty-four participants took part in the electromyography (EMG) measurement study. The EMG variations in the trapezius muscle and latissimus dorsi were investigated. Then the intervention time was determined based on the EMG measurement study. Secondly, 48 participants were divided into six groups to compare the effectiveness of every break type (passive break, active break of changing their posture, and stand and stretch their body with 5 or 10 mins). Finally, data consisting of EMG amplitudes and spectra and subjective assessment of discomfort were analyzed. Results: In the EMG experiment, results from the joint analysis of the spectral and amplitude method showed muscle fatigue after about 40 mins of sedentary work. In the intervention experiment, the results showed that standing and stretching for 5 mins was the most effective break type, and this type of break could keep the muscles' state at a recovery level for about 30-45 mins. Conclusions: This study offers the possibility of being applied to office workers and provides preliminary data support and theoretical exploration for a follow-up early muscle fatigue detection system.

• 한국터널지하공간학회 논문집
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• 제14권4호
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• pp.437-451
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• 2012

최근 3차원 레이저 스캐너는 토목 분야의 적용에 관한 다수의 연구가 수행되고 있으며, 연구 분야 역시 터널 및 교량, 토공량 산정, 시공검측, 암반절리 측정 등 여러 분야에서 이루어지고 있다. 그 중 터널 시공 시 여굴량 및 미굴량을 산정함에 있어 3차원 레이저 스캐너를 활용하는 연구가 점차적으로 이루어지고 있으며, 지금까지의 연구는 스캔 데이터와 2차원 CAD 도면과의 비교를 통해 여굴량 및 미굴량을 산정하는 방식으로 이루어 졌다. 그러나 터널이 비교적 단순한 형상의 구조물이라 하더라도 3차원 형상의 구조물로 정확한 여굴량 및 미굴량을 산정하기 위해서는 3차원적인 비교가 필요하다. 본 연구에서는 3차원 레이저 스캐너로 획득한 스캔 데이터와 3차원 설계 모델링인 BIM을 활용하여 시공시 발생하는 여굴량 및 미굴량을 산정하는 시공오차 평가 프로그램을 개발하였으며, 이를 위한 효율적인 스캔 데이터의 처리 프로세스를 제안하였다. 또한 실제 현장에 3차원 레이저 스캐너를 적용하여 시공오차를 산정하였으며, 프로그램의 성능을 검증하였다.

• Nuclear Engineering and Technology
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• 제42권6호
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• pp.690-703
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• 2010

Sampling based uncertainty analysis was carried out to quantify uncertainty in predictions of best estimate code RELAP5/MOD3.2 for a thermal hydraulic test (10% hot leg break LOCA) performed in the Large Scale Test Facility (LSTF) as a part of an IAEA coordinated research project. The nodalisation of the test facility was qualified for both steady state and transient level by systematically applying the procedures led by uncertainty methodology based on accuracy extrapolation (UMAE); uncertainty analysis was carried out using the Latin hypercube sampling (LHS) method to evaluate uncertainty for ten input parameters. Sixteen output parameters were selected for uncertainty evaluation and uncertainty band between $5^{th}$ and $95^{th}$ percentile of the output parameters were evaluated. It was observed that the uncertainty band for the primary pressure during two phase blowdown is larger than that of the remaining period. Similarly, a larger uncertainty band is observed relating to accumulator injection flow during reflood phase. Importance analysis was also carried out and standard rank regression coefficients were computed to quantify the effect of each individual input parameter on output parameters. It was observed that the break discharge coefficient is the most important uncertain parameter relating to the prediction of all the primary side parameters and that the steam generator (SG) relief pressure setting is the most important parameter in predicting the SG secondary pressure.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1532-1539
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• 2019

This paper analyzes a new method for reducing boiling water reactor fuel temperature during a Loss of Coolant Accident (LOCA). The method uses a device called Reverse Flow Restriction Device (RFRD) at the inlet of fuel bundles in the core to prevent coolant loss from the bundle inlet due to the reverse flow after a large break in the recirculation loop. The device allows for flow in the forward direction which occurs during normal operation, while after the break, the RFRD device changes its status to prevent reverse flow. In this paper, a detailed simulation of LOCA has been carried out using the U.S. NRC's TRACE code to investigate the effect of RFRD on the flow rate as well as peak clad temperature of BWR fuel bundles during three different LOCA scenarios: small break LOCA (25% LOCA), large break LOCA (100% LOCA), and double-ended guillotine break (200% LOCA). The results demonstrated that the device could substantially block flow reversal in fuel bundles during LOCA, allowing for coolant to remain in the core during the coolant blowdown phase. The device can retain additional cooling water after activating the emergency systems, which maintains the peak clad temperature at lower levels. Moreover, the RFRD achieved the reflood phase (when the saturation temperature of the clad is restored) earlier than without the RFRD.

• 한국병원경영학회지
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• 제14권3호
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• pp.23-48
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• 2009

The purpose of this study was to provide criteria which help executives to make decisions through the analysis of profitability of ultrasonography conducted in each medical department. In order to achieve such purpose, the study conducted break-even analyses on three medical departments of a university hospital in which has used ultrasonography was largely conducted in diagnosing diseases and performing surgeries. The research was carried out from January to June 2008. The data necessary for calculating cost, were collected using by computerized data. The results of the study were summarized as follows. 1. The Cost structure of each medical department: The Cost of ultrasonography was divided into direct cost and indirect cost through the categorization by cost object. Labor cost accounted for the largest portion of the direct cost with 69.3% in the department of obstetrics and gynecology, 67.4% in the department of radiology and 58.2% in the cardiac ultrasonography center, which followed by the depreciation cost of ultrasonography equipment. The calculation of the average material cost of each ultrasonographic test by medical test found that the cardiac ultrasonography center took first place with 2,355 won, followed by the department of obstetrics and gynecology with 266 won and the department of radiology with 233 won. As for the power cost of ultrasonography equipment, the department of radiology took fist place with 442,000 won. The power cost, however, did not affect much the cost price, because it accounted for only a small portion of the cost. As for indirect cost, the cardiac ultrasonography center ranked first with 7,156,000 won. Building depreciation cost accounted for the largest portion of the indirect cost. 2. Break-even analysis: Under the supposition that cost price can be divided into fixed cost and variable cost, a break-even analysis was conducted using the cost price confirmed through the cost structure of each medical department. As for the average customary charge of ultrasonography test conducted in each medical department, the department of obstetrics and gynecology charged 24,627 won, the department of radiology 53,179 won and the cardiac ultrasonography center 65,174 won. According to these results, the charges of ultrasonography test imposed by the department of radiology and the cardiac ultrasonography center wre enough to surpass break-even levels, but the charge imposed by the department of obstetrics and gynecology was not enough to offset the cost price. In conclusion, labor cost accounted for the largest proportion of cost price of ultrasonography test conducted in diagnosing diseases and performing surgeries in medical departments, followed by the fixed cost of ultrasonographic equipment depreciation cost. In medical department where the current charge of ultrasonography test turned out not to offset cost price through the break-even analysis of ultrasonographic equipment, ways to reduce fixed cost which accounts for the largest proportion of the cost price should be sought. Even medical departments whose current charge of ultrasonography test is enough to surpass break-even level are required to work for efficient management and cost reduction to continuously generate profits.

• Geomechanics and Engineering
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• 제13권2호
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• pp.195-215
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• 2017

This paper proposes gob-side entry retaining by roof break and filling in thick-layer soft rock conditions based on the thick-layer soft rock roof strata migration law and the demand for non-pillar gob-side entry retaining projects. The functional expressions of main roof subsidence are derived for three break roof direction conditions: lateral deflection toward the roadway, lateral deflection toward the gob and vertically to the roof. These are derived according to the load-bearing boundary conditions of the main roadway roof stratum. It is concluded that the break roof angle is an important factor influencing the stability of gob-side entry retaining surrounding rock. This paper studies the stress distribution characteristics and plastic damage scope of gob-side entry retaining integrated coal seams, as well as the roof strata migration law and the supporting stability of caving structure filled on the break roof layer at the break roof angles of $-5^{\circ}$, $0^{\circ}$, $5^{\circ}$, $10^{\circ}$ and $15^{\circ}$ are studied. The simulation results of numerical analysis indicate that, the stress concentration and plastic damage scope to the sides of gob-side entry retaining integrated coal at the break roof angle of $5^{\circ}$ are reduced and shearing stress concentration of the caving filling body has been eliminated. The disturbance of coal mining to the roadway roof and loss of carrying capacity are mitigated. Field tests have been carried out on air-return roadway 5203 with the break roof angle of $5^{\circ}$. The monitoring indicates that the break roof filling section and compaction section are located at 0-45 m and 45-75 m behind the working face, respectively. The section from 75-100 m tends to be stable.