• International Journal of Fluid Machinery and Systems
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• 제10권1호
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• pp.40-46
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• 2017

Small valves including ball valves, gate valves and butterfly valves have been adopted in the fields of steam power generation, petrochemical industry, carriers, and oil tankers. Butterfly valves have normally been applied to fields where in narrow places installing the existing valves such as gate valves and ball valves have proven difficult due to the surrounding area and the heavier of these valves. Butterfly valves are used to control the mass flow of the piping system under low pressure by rotating the circular disk installed inside. The butterfly valve is benefitted by having simpler structure in which the flow is controlled by rotating the disc circular plate along the center axis, whereas the weight of the valve is light compared to the gate valve and ball valve above-mentioned, as there is no additional bracket supporting the valve body. The manufacturing company needs to acquire the performance and life test equipment, in the case of adopting the improving factors to detect leakage and damage on the seat of the valve disc. However, small companies, which are manufacturing the industrial valves, normally sell their products without the life test, which is the reliability test and environment test, because of financial and manpower problems. Furthermore, the failure mode analysis of the products failed in the field is likewise problematic as there is no system collecting the failure data on sites for analyzing the failures of valves. The analyzing and researching process is not arranged systematically because of the financial problem. Therefore this study firstly tried to obtain information about the failure data from the sites, analyzed the failure mode based on the field data collected from the customers, and then obtained field data using measuring equipment. Secondly, we designed and manufactured the performance and life test equipment which also have the real time monitoring system with the naked eye for the butterfly valves. The concept of this equipment can also be adopted by other valves, such as the ball valve, gate valve, and various others. It can be applied to variously sized valves, ranging from 25 mm to large sized valves exceeding 3000 mm. Finally, this study carries out the life test with square wave pressure, using performance and life test equipment. The performance found out that the failures from the real time monitoring system were good. The results of this study can be expanded to the other valves like ball valves, gate valves, and control valves to find out the failure mode using the real time monitoring system for durability and performance tests.

• 한국자동차공학회논문집
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• 제3권1호
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• pp.1-12
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• 1995

Isothermal and thermal-mechanical fatigue characteristics of 12Cr heat resisting steel used for high temperature applications were investigated including hold time effects. Isothermal low cycle fatigue test at $600^{\circ}C$ and in-phase, out-of-phase thermal-mechanical fatigue test at 350 to $600^{\circ}C$ were conducted using smooth cylindrical hollow specimen under strain-control with total strain ranges from 0.006 to 0.015. Regardless of thermal-mechanical and isothermal fatigue tests, cyclic softening behavior was observed and much more pronounced in the thermal-mechanical fatigue tests with hold times due to the stress relaxation during the hold time. The phase difference between temperature and strain in thermal-mechanical fatigue tests resulted in significantly shorter fatigue life for out-of-phase compared to in-phase. The differences in fatigue lives were dependent upon the magnitudes of plastic strain ranges and mean stresses. During the hold time in the strain-controlled fatigue tests, the increase in the plastic strain range and the stress relaxation were observed. It appeared that the increase in plastic strain range per cycle and the introduction of creep damage made important contributions to the reduction of thermal-mechanical fatigue life with hold time, and the life reduction tendency was more remarkable in the in-phase than in the out-of-phase thermal-mechanical fatigue. Isothermal fatigue tests performed under the combination of fast and slow strain rates at $600^{\circ}C$ showed that the fatigue life decreased as the strain rate and frequency decreased,especially for the low strain ranges.

• 국제물리치료학회지
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• 제10권1호
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• pp.1700-1705
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• 2019

Background: Mild cognitive impairment (MCI) is also called as aging related memory damage. Decreased cognitive function due to aging is known to be associated with the frontal lobe. Alpha wave is generated in the dominance in the frontal lobe or a wide range of regions in the brain, it should be doubted that the brain function might be degraded. Objective: To determine the effect of sensory stimulation type on learning and brain activity pattern of elderly persons with MCI. Design: Randomized Controlled Trial (single blind) Methods: Twenty elderly persons aged more than 65 with MCI were randonmized to simultaneous visual/auditory stimulation group (SVASG) and or auditory stimulation group (ASG). Ten peoples were assigned to each group and lectroencephalogram test was performed to individuals. In the electroencephalogram test, electroencephalography of prior to sensory stimulation, and during sensory stimulation were measured to compare brain activity pattern according to the study groups and measurement period. Results: The relative alpha power due to a sensory stimulation type showed that the SVASG significantly decreased in the left frontal lobe and the left parietal lobe statistically compared to those of the ASG while sensory stimulation was given (p<.05). The relative beta power due to a sensory stimulation type showed that the SVASG significantly increased in the left and right frontal lobes, the left and right parietal lobes, and the left temporal lobe statistically compared to those of the ASG while sensory stimulation was given (p<.05). Conclusions: Electroencephalographic analysis showed that the type of sensory stimulation can affect the brain activity pattern. However, the effects were not studied that which brain activity pattern help to improved cognitive function of elderly persons with mild cognitive impairment.

• 농업과학연구
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• 제48권1호
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• pp.141-149
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• 2021

The cultivation area for domestic cabbage increased by 26.3% from 10,968 ha in 2019 to 13,854 ha in 2020, and among leafy vegetables, the cabbage cultivation area was 62%, and production was 78.9%. Demand for field crop production of cabbage, which has a relatively high-income level compared to rice farming, is increasing, and mechanization of the field operation is urgently needed due to the insufficient development of related farming machinery. In this study, a prototype fabrication and performance test of a tractor-attached cabbage collector was carried out. The transport section was divided into two parts, one for the feeding and transportation and the other for the screening and packaging to selectively collect cabbages in bulk bags or boxes. The length of the primary collecting conveyor was designed to meet the field conditions of the Korean cabbage cultivation standards so that six cultivation rows could be worked simultaneously. Power was controlled by a hydraulic transmission line of the tractor and was easily mounted onto the 3-point hitch links behind the tractor. When the performance was evaluated, the transfer rate, loss rate, damage rate, and work performance were 100, 0, 1.2%, and 1.9 h·10 a^-1. Final improvement and commercialization of the prototype would considerably contribute to the mechanization of harvesting cabbage, the main ingredient of Kimchi.

• Composites Research
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• 제33권6호
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• pp.341-345
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• 2020

열중량분석기를 적용하여 탄소섬유/에폭시 복합재의 구성재 함유량을 평가하기 위한 측정기법을 제시하였다. 시험에 사용된 시료는 탄소섬유/에폭시 토우 프리프레그로 제작된 스트랜드 시편에서 채취하였으며 시간에 따른 시료의 무게 변화를 실시간으로 측정하였다. 또한 전자현미경을 이용하여 수지 제거 여부와 탄소섬유의 열손상 상태를 관찰하였다. 연구결과에 따르면 열중량분석기를 적용하면 기존의 머플로를 적용한 경우에 비해 소량의 시료에 대해서도 시험이 가능하며, 설정 온도와 노출 시간을 제어함으로써 구성재의 함유량을 효율적이고 정량적으로 평가할 수 있음을 알 수 있었다.

• 한국농공학회지
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• 제17권3호
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• pp.3795-3814
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• 1975

The purpoes of this thesis is to study the effect of the variation of the beginning date of the suspension of irrigation and the length of intermittent suspension period of irrigation in the paddy field on the growth and yield of rice, so as the provide a critical limit of saving irrigation water and an irrigation method to prevent drough damage in rice cultivation. In this experiment, the rice variety adopted was NONGRIM No.29. There were seven main test plot, each test plot having a different beginning date of the suspension of irrigation. A main test plot was susdivided into five small test plots, each having a different length of the suspension period of irrigation. The results obtained in this experiment are summarized as follows: 1. The number of tillers is controlled by the treatment of the suspension of irrigation, its beginning date being early of late. The reductive effects of beginning dates of suspension upon the number of tillers. investigated on July 30, are about 84% for the treatment suspended on July 8, 87% on July 12, and 92% on July 19, respectively, in comparison with the standard plot. However. the suspenion treatments after the foregoing dates does not affect the control of their numbers. On the other hand, the lengths of intermittent suspension periods influence highly on the number of tillers to be restrained considerably, the decrease ratio ranging from 91% to 80% Both treatments on dates and periods are so intermingled that the restraining effects of suspension periods become greater as the dates of its beginning are earlier. 2. The elongation of plant hieghts also restrained considerably by the longer periods and earlier dates of suspension treatments of irrigation. Especially, the effects of the lengths of suspension periods become more serious. 3. Heading dates are delayed by two to five days through the suspension treatments of irrigation. However, the heading stage ends almost on the same day without relation to the differences between the irrigation suspension treatments. In the test plot where the suspension date of irrigation comes after the young panicle forming stage, the heading stage ends one or two days later than in the standard test plot. 4. Both culm lengths and panicle lengths show significant differences in their values, i.e., their lengths are shorter, as the begining dates of irrigation suspension are earlier and the suspension periods are longer. 5. The earlier the beginning date and the longer the period of irrigation suspension, the less is the number of panicles per hill in comparison with the standard plot. 6. The earlier the beginning date and the longer the period of irrigation suspension, the higher is the significant difference in the number of kernels per panicle in comparison with that in the standard test plot, i.e., the less is the number of kernels per panicle. 7. The earlier the beginning date and the longer the period of irrigation suspension, the lighter are the weights of rough rice and straws per hill in comparison with those in the standard plot.

• 한국구조물진단유지관리공학회 논문집
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• 제24권1호
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• pp.16-23
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• 2020

우리나라의 연평균 지진발생 횟수는 꾸준히 증가하는 추세이다. 최근경주와 포항에서 규모 5를 초과하는 지진이 발생하여 상수도관의 피해가 다수 보고된 바 있다. 따라서 국내에서도 상수도관의 지진에 대한 대비가 필요 할 것으로 판단된다. 상수도관은 상수도 공급시스템 에 있어 혈관과도 같은 중요한 시설로서 다양한 규격과 재질의 배관으로 구성된다. 그러므로 지진에 의한 상수도관의 손상은 식수공급, 화재진압 등의 문제를 일으키게 되며, 인명 및 재산피해를 유발하게 된다. 하지만 국내에서는 시험 검증 및 경험에 의해 매립상수도관의 내진 성능이 평가된 예를 찾아보기 어렵다. 지진에 의한 상수도관의 손상은 액상화와 단층과 같은 지반의 변위지배적인 거동으로 인하여 발생한다. 지진에 의한 상수도관의 주된 파손은 배관 이음부에 집중되며 특히 직경 200mm 이하 배관이 위험한 것으로 조사되었다. 따라서 본 연구에서는 호칭 150mm의 클램프로 고정된 이음을 가지는 iPVC 매립 상수도관에 대하여 시험적인 접근으로 내진 성능 및 내침하 성능을 평가 하였다.

• 항공우주시스템공학회지
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• 제14권5호
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• pp.66-72
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• 2020

본 연구에서는 증기발생기 내부로 냉각수 공급 시 화염에 의한 냉각수 분사 노즐 손상이 없도록, 초반 냉각수 공급량을 늘리는 방안에 대한 연구를 진행하였다. 초기 증기발생기 시험 시 벤추리만 사용하여 유량을 제어하였는데, 초반 유량 안정화 구간 동안 연소실 내부로 냉각수 공급이 되지 않아 냉각수 노즐의 손상이 발생하였다. 이를 해결하기 위해 벤추리와 오리피스를 병렬로 구성하여, 초반 공급 유량을 늘림으로써 냉각수 매니폴드와 연소실 사이 차압을 형성시켜 냉각수를 공급하였다. 수류시험을 통해 벤추리와 오리피스 공급 시퀀스를 확립하였으며, 최종 검증을 위해 연소실험을 진행하였다. 실험 결과 연소 초반 지속적으로 냉각수를 공급하는 것을 확인하였으며, 냉각수 노즐 손상 없이 성공적으로 실험을 수행하였다.

• 콘크리트학회논문집
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• 제22권4호
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• pp.441-450
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• 2010

건식공법이 가능하도록 기존의 접합 방식과 차별화 되는 PC 보-기둥 접합부를 개발하여 실용화하기 위한 기초 연구이다. 연속된 PC 기둥 양편에 위치한 보의 접합 단부를 고강도 관통형 연결재로 긴장하여 연결하는 'PC 보-기둥 맞댐 접합(BCJ_TB : precast beam column joints connected with thru-connects)'을 고안하고 실험적 연구를 수행하여 강도저하, 초기강성, 강성저하, 에너지소산능력 등의 내진성능을 분석하였다. 실험 결과에 기둥에서는 손상이 발생하지 않고 보 단부에서 압축파괴가 발생하는데, 이는 비부착 연결재의 초기긴장과 비부착 효과에 의하여 보 단부 콘크리트에 압축응력이 증가하기 때문인 것으로 분석되었다. 보 접합 단부에 CFRP로 구속 효과를 준 접합부의 성능이 상대적으로 우수하였고 네오프렌 패드로 보 기둥 접합면을 연결한 것이 다른 것에 비하여 초기강성을 제외하고는 우수한 내진성능을 보이는 것으로 분석되었다. 비부착 연결재를 사용한 접합부의 파괴모드를 개선하기 위하여 보 단부 콘크리트의 압축 성능을 향상시키고, 연결재의 변위를 적절히 조절할 수 있는 방법이 요구된다.

• 산업기술연구
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• 제40권1호
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• pp.7-12
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• 2020

Lithium-ion cells have become the go-to energy source across all applications; however, dendritic growth remains an issue to tackle. While there have been various research conducted and possible solutions offered, there is yet to be one that efficiently rules out the problem without, however, introducing another. This paper seeks to present a fast charging method and system to which lithium-ion batteries are charged while maintaining their lifetime. In the proposed method, various lithium cells are charged under multiple profiles. The parameters of charge profiles that inflict damage to the cell's electrodes are obtained and used as thresholds. Thus, during charging, voltage, current, and temperature are actively controlled under these thresholds. In this way, dendrite formation suppressed charging is achieved, and battery life is maintained. The fast-charging system designed, comprises of a 1.5kW charger, an inbuilt 600W battery pack, and an intelligent BMS with cell balancing technology. The system was also designed to respond to the aging of the battery to provide adequate threshold values. Among other tests conducted by KCTL, the cycle test result showed a capacity drop of only 0.68% after 500 cycles, thereby proving the life maintaining capability of the proposed method and system.