• Journal of Biosystems Engineering
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• 제30권5호
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• pp.274-279
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• 2005

Impact is one of the major cause of damage to fruits druing varios processes from the production on the farm to the consumer. The tissue of fruits are ruptured in a very short period time less than 10ms by impact loading. Mechanical behavior of fruits under impact loading can be analyzed better with high speed sampling data acquisition system and one of them is a digital storage oscilloscope. A impact test system was developed to test the physical properties of fruits including apple, pear, and peach which may lead to a better understanding of the physical laws. The test system consisted of a digital storage oscilloscope and simple mechanism which can apply impact force to fresh produce. Rupture force, energy, and deffrmation were measured at the five levels of drop heights from 4 to 24cm fur each internal and external tissues. Rupture forces for apple and pear were in the range of 72.9 to 87.7 N and 70.8 to 84.1 N for external and internal tissues, respectively. Rupture forces far peach external tissues were in the range of 43.4 to 65.0 N.

• 한국안전학회지
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• 제37권4호
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• pp.129-138
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• 2022

A new method for injecting cooling water into the Korean research reactor (KRR) in the event of beam tube rupture is proposed in this paper. Moreover, the research evaluates the risk to the reactor core in terms of core damage frequency (CDF). The proposed method maintains the cooling water in the chimney at a certain level in the tank to prevent nuclear fuel damage solely by gravitational coolant feeding from the emergency water supply system (EWSS). This technique does not require sump recirculation operations described in the current procedure for resolving beam tube accidents. The reduction in the risk to the core in the event of beam tube rupture that can be achieved by the proposed change in the cooling water injection design is quantified as follows. 1) The total CDF of the KRR for the proposed design change is approximately 4.17E-06/yr, which is 8.4% lower than the CDF of the current design (4.55E-06/yr). 2) The CDF for beam tube rupture is 7.10E-08/yr, which represents an 84.1% decrease compared with that of the current design (4.49E-07/yr). In addition to this quantitative reduction in risk, the modified cooling water injection design maintains a supply of pure coolant to the EWSS tank. This means that the reactor does not require decontamination after an accident. Thermal hydraulic analysis proves that the water level in the reactor pool does not cause damage to the nuclear fuel cladding after beam tube rupture. This is because the amount of water in the chimney can be regulated by the EWSS function. The EWSS supplies emergency water to the reactor core to compensate for the evaporation of coolant in the core, thus allowing water to cover the fuel assemblies in the reactor core over a sufficient amount of time.

• Nuclear Engineering and Technology
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• 제49권3호
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• pp.581-591
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• 2017

Influences of hold time and stress ratio on cyclic creep properties of Grade 91 steel were systemically investigated using a wide range of cyclic creep tests, which were performed with hold times (HTs) of 1 minute, 3 minutes, 5 minutes, 10 minutes, 20 minutes, and 30 minutes and stress ratios (R) of 0.5, 0.8, 0.85, 0.90, and 0.95 under tension loading cycles at $600^{\circ}C$. Under the influence of HT, the rupture time increased to HT = 5 minutes at R = 0.90 and R = 0.95, but there was no influence at R = 0.50, 0.80, and 0.85. The creep rate was constant regardless of an increase in the HT, except for the case of HT = 5 minutes at R = 0.90 and R = 0.95. Under the influence of stress ratio, the rupture time increased with an increase in the stress ratio, but the creep rate decreased. The cyclic creep led to a reduction in the rupture time and an acceleration in the creep rate compared with the case of monotonic creep. Cyclic creep was found to depend dominantly on the stress ratio rather than on the HT. Fracture surfaces displayed transgranular fractures resulting from microvoid coalescence, and the amount of microvoids increased with an increase in the stress ratio. Enhanced coarsening of the precipitates in the cyclic creep test specimens was found under all conditions.

• Journal of Chest Surgery
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• 제37권9호
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• pp.774-780
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• 2004

외상성 흉부대동맥 파열은 수술적 치료가 요구되는 치명적 손상이며 이외에 다른 부위에 복합손상이 동반되면 심폐 바이패스에 의한 위험도를 크게 증가시킬 수 있다. 여기서 저자들은 심한 동반손상을 먼저 치료한 후 대동맥수술을 하고 그 결과를 관찰하였다. 대상 및 방법: 1997년부터 2003년까지 외상성 흉부 대동맥질환으로 수술을 받은 24명의 환자를 대상으로 의무기록을 후향적으로 검토하여, 동반손상 여부, 수술방법, 수술 후 경과, 합병증 등을 분석하고 국내외 문헌들과 비교하였다. 수술은 초저온 심정지법하에서 심폐 바이패스를 이용한 개흉술로 하였는데 근위부 연결 후 곁가지를 통해 뇌관류를 시행하였고 요추 카테터를 통한 뇌척수액 배액으로 하반신 마비를 예방하였다. 결과： 대상환자 전원에서 83예의 동반손상이 발생하였는데, 흉부손상이 49예, 근골격계 손상 18예, 복부 손상 13예였고, 수상 후 12명의 환자에서 7.6$\pm$12.6일에 16예의 동반손상에 대한 수술이 행해졌다. 수상당시 18예에서만 대동맥 손상이 진단되었다. 중환자실에서 혈압을 약물투여로 조절하면서 안정시키고 수상 후 693 $\pm$ 1350일에 지연수술을 시행하였는데, 관찰기간 중 사망이나 대동맥 파열의 진행은 없었다. 수술 사망은 없었으며, 술 후 큰 합병증은 없었다. 결론： 외상성 흉부대동맥 파열에 있어서 다른 부위 손상이 동반되면 심한 동반손상을 먼저 치료한 후 수술하는 것이 수술 사망률이나 이병률 면에서 좋은 결과를 가져온다.

• 한국환경보건학회지
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• 제23권1호
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• pp.28-33
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• 1997

This study was carried out to investigate factors affecting anaerobic digestion enhancement of waste activated sludge(WAS). In order to this investigation, the degradability and rupture of microorganisms cell present in WAS, and mesophilic anaerobic digestion(MAD) of these compounds, were also evaluated. The micro-organisms cell in WAS were ruptured by a mechanical jet stream and smashed under pressure of 30 bar. The rupture level of micro-organisms cell in WAS were determined using phosphate, soluble protein and soluble chemical oxygen demand (SCOD)concentrations. It was found that the rupture level of micro- organisms cell within WAS increased with increasing pretreatment times, and the pretreated WAS once under pressure of 30 bar resulted in an increase in VS removal and methane production of 5%, 9% over the intact WAS of 35%, 71%, respectively, in batchwise MAD of 6-day and 14-day retention time. With the pretreatment and MAD of 6-day retention time used, mesophlic bioconvertibility as the biogasification of WAS were found to be significantly higher biogas of 1, 850 ml than 300 ml under intact WAS. In conclusion it can be stated mechanical pretreatment enhances WAS bioconvertibility, while under identical treatment conditions, resulted in a considerable decrease in the bioconvertibility of intact WAS.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.105-106
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• 2006

The creep properties have been evaluated for type 316LN stainless steel welded by the SAW method. The creep tests were conducted with different stress levels for both the base and weld metals at $550^{\circ}C\;and\;600^{\circ}C$. The results of the creep-rupture time of the weld metal did not show a large difference when compared to those of the base one, though it exhibited a little lower value at $600^{\circ}C$. The creep rate of the weld metal was lower than that of the base one at the same stress and rupture-time conditions. The creep-rupture ductility of the weld metal is found to be decreased by about 60%, compared to the base one. This is due to the decreasing of tensile elongation and the increasing of the yield stress in the weld metals.

• 한국안전학회지
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• 제17권4호
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• pp.19-24
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• 2002

User-friendly-web-based database system for searching creep property data was developed. This system includes about 38000 creep data for 270 different materials including low carbon steel, stainless steel and alloy steel. Data on creep rupture, creep deformation, creep crack growth and creeping materials can be searched through this system. Retrieved data is displayed in numeric form and also presented in graphical form for visualizing the data. Furthermore, the creep rupture data is designed to be fitted to a regression equation of logarithmic stress using time-temperature parameter(TTP). The degree of the regression equation, orthogonal polynomials, was determined using analysis of variance.

• 한국추진공학회지
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• 제25권6호
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• pp.20-28
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• 2021

극초음속 유동 시험에 활용되고 있는 충격파 터널 등은 원하는 시험 조건을 얻기 위해 격막의 파열 압력비를 맞추어 운용한다. 주로 금속 재질로 이루어진 격막은 정확한 압력비를 맞추기 위해 특정 형태로 가공하거나 강제 파열 장치를 사용하여 개방한다. 격막의 개방 과정은 수백 microsecond 동안 파열과 변형을 통해 이루어지는데, 동일한 압력비에서도 개방 정도와 개방 소요 시간에 따라 시험 조건이 달라질 수 있을 것으로 예상된다. 본 연구에서는 격막의 두께 및 재질 차이를 반영할 수 있는 파열모델을 적용하여 수치 해석을 수행하고 충격파의 형성과 정체 조건의 특성에 대해 살펴보았다. 격막 파열로 인해 생성된 충격파의 속도는 격막 개방 속도에 비례하였으며, 격막의 최종 개폐율 및 소요 시간에 따라 저압관 끝단에 형성되는 정체 압력과 시험 시간에 차이가 나타나는 것을 확인할 수 있었다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.215-218
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• 2014

High combustion efficiency of hydrogen could make it an ideal source of green energy in the future. At this time, high pressure vessel is the most reasonable method of storing hydrogen. However, such a high pressurized vessel could pose a critical threat if ruptured. For this reason, it is important to understand the mechanism of hydrogen's self-ignition when a high-pressure hydrogen released into air. This paper presents several visualization images as experimental results using high-speed camera. From the visualization images, the ignition is initiated near rupture disk immediately after failure of disk. And the initial ignition and flame is stronger as a rupture pressure increases. However, this ignition region do not affect the general self-ignition mechanism when a high-pressure hydrogen is released into air through tue after failure of disk.

• 소성∙가공
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• 제18권4호
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• pp.347-353
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• 2009

The apparent activation energy, the applied stress exponent, and rupture life have been measured from creep experiments over the range of $200^{\circ}C$ to $220^{\circ}C$ and the applied stress range of 64MPa to 94MPa. The materials were used AZ31 magnesium alloys treated by plasma electrolytic oxidation of $20{\mu}m$ and $40{\mu}m$ at surface to investigate the its influence on creep behavior, and creep tests were carried out under constant applied stress and temperature. The experimental results showed that the dipper the thickness of surface treatment the higher the activation energy and stress exponent. And the higher temperature and applied stress, the lower stress exponent and activation energy, respectively. Also the dipper the thickness of surface treatment the longer creep rupture time.