• Corrosion Science and Technology
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• 제10권4호
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• pp.131-135
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• 2011

The demands of high-strength steel have been steadily increased to reduce the weight of vehicles. Although the TRIP steel has been the promising candidate material for the purpose, high strength hinders the application due to the susceptibility to hydrogen delayed fracture in the corrosive environment. Moreover, the testing method was not specified in the ISO standards. In this work, the test method to evaluate the susceptibility of hydrogen delayed fracture was studied by slow strain rate testing technique. The four test experimental parameters were studied : strain rate, hydrogen charging time, holding time after hydrogen charging, and holding time after cadmium plating. The steel was fractured by hydrogen in case the strain rate was in the range of $1{\times}10^{-4}{\sim}5{\times}10^{-7}/sec$. It was confirmed that the slow strain rate test is effective method to evaluate the susceptibility to hydrogen delayed fracture. The holding time over 24 hrs after hydrogen charging, nullified the hydrogen effect, that is, the specimen was no more susceptible to hydrogen after 24 hrs even though the specimen was fully hydrogen-charged. Moreover, cadmium electroplating could not prevent from diffusing out the hydrogen from the steel in the experiment. The effective experimental procedures were discussed.

• 한국세라믹학회지
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• 제43권9호
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• pp.582-587
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• 2006

Decomposition behavior of $ferro-Si_3N_4$was investigated with varying temperature and holding time in mud components for high temperature refractory applications. Porosities gradually increased with increasing temperature and holding time due to the carbothermal reduction of $Si_3N_4\;and\;SiO_2$. Silicon monoxide (SiO) as a intermediate resulted from evaporation of $Si_3N_4\;and\;SiO_2$ reacted with C sources to generate needle-like ${\beta}-SiC$ and Fe in $Si_3N_4$ acted as a catalyst in order to enhance growth of SiC grain with the preferred orientation. SiC generation yield increased with increasing holding time, all of the $Si_3N_4\;and\;SiO_2$ affected on SiC formation up to 2h. However, SiC generation was only dependent on residual $SiO_2$ over 2h, because the carbothermal reduction reaction of $Si_3N_4$ was no longer possible at that time.

• 기술혁신학회지
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• 제16권1호
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• pp.367-389
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• 2013

2008년부터 대학의 기술사업화 촉진을 위해 산학협력기술지주회사를 설립 운영하고 있다. 그동안 산학협력기술지수회사의 운영에 대한 필요성과 활성화 방안, 법적 제도적 요건 검토, 사례연구 등이 다양하게 수행되었다. 하지만 정책 수요자인 국가연구개발사업에 참여한 대학의 연구자들을 대상으로 산학협력기술지주회사의 전반적인 운영현황에 대한 종합적인 실태조사가 미흡하였다. 특히 현 시점은 산학협력기술지주회사 제도가 도입된 지 5년이 경과하여 이에 대한 정책적 점검이 요구되고 있다. 이에 본 연구에서는 산학협력기술지주회사의 전반적인 운영현황에 대한 설문조사와 면접조사를 실시하였다. 이 실증분석 결과에 근거해서 (1)대학의 기술사업화 기반 확충과 (2)법적 제도적 지원제도 개선, (3)조직의 우수인력 확충과 책임성 확보의 세 가지 측면에서 산학협력기술지수회사의 개선방안을 제시하였다.

• 대한물리의학회지
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• 제12권4호
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• pp.123-132
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• 2017

PURPOSE: This study aimed to examine the effects of lumbar stabilization exercise during abdominal hollowing with conscious contraction of the pelvic floor muscles on trunk muscle in healthy twenties subjects. METHODS: The participants were randomly allocated to an experimental group (n=15) and a control group (n=15). The experimental group received lumbar stabilization exercise combined with conscious contraction of the pelvic floor muscles during abdominal hollowing. The control group received lumbar stabilization exercise with abdominal hollowing. Both groups trained with the respective exercise for 30 minutes a day, 3 times a week for 6 weeks. Muscle activation of the external oblique and erector spinae muscles, thickness of the transversus abdominis and multifidus, and contraction holding time of tranversus abdominis were measured before and after exercise. RESULTS: Activations of both the external oblique muscles were significantly decreased, and thickness of both the transversus abdominis and multifidus muscles, and contraction holding time of the transversus abdominis muscle were significantly increased in the experimental group (p<.05). The thickness of the left transversus abdominis and right multifidus muscles, and the contraction holding time of the transversus abdominis muscle significantly increased in the control group (p<.05). On comparing both groups, the activations of both external oblique muscles were significantly reduced and the contraction holding time of the transversus abdominis muscle was significantly increased in the experimental group (p<.05). CONCLUSION: These results suggest that lumbar stabilization exercise by abdominal hollowing and conscious contraction of the pelvic floor muscles is suitable and efficient for healthy twenties subjects.

• Composites Research
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• 제13권5호
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• pp.31-36
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• 2000

금속/세라믹 복합체의 강화제로 사용가능한 다공성 뮬라이트 제조 시 공정변수 변화가 침상형 미세구조 형성에 미치는 영향에 대해 고찰하였다. 출발물질을 $Al_2O_3+SiO_2$와 $Al(OH)_3+SiO_2$로 달리하여 미세구조 변화를 고찰한 결과, $Al_2O_3$보다 반응성이 우수한 $Al(OH)_3$를 사용한 시편에서 더욱 발달한 침상형 구조가 나타났으며, 첨가제 $AlF_3$의 함량이 증가할수록, $SiF_4$가 발생하는 온도구간인 $900^{\circ}C$에서 유지하는 시간이 길수록 반응을 잘 일어나 시편 전체에서 침상형 뮬라이트가 형성되었다. 소결 온도의 경우 $1200^{\circ}C$에서부터 뮬라이트가 생성되었고, 소결 온도변화에 따른 미세구조는 큰 변화를 관찰할 수 없었다. 기공률은 첨가제의 양이 증가할수록, $900^{\circ}C$에서의 유지시간이 길수록 증가하였다.

• 한국가금학회지
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• 제46권1호
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• pp.1-10
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• 2019

닭의 성장과정에서 어린 병아리의 발달에 가장 결정적인 시간으로 인식되는 시점은 부화 전 수일부터 부화 후 수일간이다. 부화 전후의 충분한 영양소 공급은 배아의 최종 발달과 병아리의 초기성장에 결정적 기여를 한다고 볼 수 있다. In ovo feeding에 의한 탄수화물 또는 아미노산의 공급은 부화 전 후의 소화장기 발달에 긍정적으로 작용한다. Prebiotics과 synbiotics 등에 대한 in ovo 주입은 건강한 미생물 균총 형성 등을 제공하여 영양적, 면역적 측면에서 좋은 결과들을 볼 수 있지만, 연구 결과의 수적 제한과 in ovo 주입의 양과 주입 부위 및 주입시기 등에 대한 추가적인 연구가 요구된다. 탄수화물을 이용한 in ovo feeding은 부화시 체중 증가를 보이지만 육계의 부화 후 능력에는 크게 영향을 보이지 않으며, 탄수화물 주입에 따른 부화율 감소는 기술적 요인(최적 농도, 주입 장소, 부피 등)이 크게 작용하는 것으로 보인다. In ovo feeding에 의한 아미노산 공급은 병아리의 세포성 면역과 체액성 면역을 높여 초기 면역 향상에 도움이 되는 것으로 판단된다. In ovo feeding은 부화 전후의 최적의 영양소 공급과 면역력 증진 및 절식에 따른 병아리의 스트레스를 완화시켜주는 실용적인 기술이 될 수 있다.

• 한국실내디자인학회논문집
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• 제20권1호
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• pp.165-172
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• 2011

Visitors' behaviors within an exhibition space are a substantial means to grant spatial arrangement and validity of exhibits. Therefore, the study analyzed visitors' behaviors in the viewpoint of attraction power and holding power of exhibits on the basis of exhibition layout of real science museums. Through the analysis, the study grasped efficiency of analysis index and exhibition environment elements which might have an effect on planning the exhibition space of a large-scale museum and producing detailed ranges of exhibition. The main indicators used are: 1. Attraction power: it indicates the relative incidence of people who have stopped in front of an object/exhibit during the exhibition tour. It is calculated by dividing the number of people who stop by the total number of people who have visited the museum or gallery. 2. Holding power: it measures the average time spent in front of an information/communication element. It is calculated by dividing the average time of stay by the time "necessary" to read an element. As a result, It was expected that attraction power and holding power of exhibit would be increased when moving line of seeing was inductive. However, when the traffic movements of seeing was inductive, repetitive seeing of exhibit was almost never realized and visitors had a strong tendency which viewed on their way of moving without viewing on their way of stopping. On the other hand, it may mean that density of exhibit is low or size of exhibition space is small that most of exhibits within exhibition space have high attraction power and holding power. As Gwacheon National Science Museum, when a museum is composed of many large-scale exhibit halls, it should be formed by separating the main moving line of seeing from the optional moving line of seeing through visitors' natural choice of exhibit and proper inducement of moving line of seeing. In such structure, exhibition environment of the main moving line has an effect on attraction of exhibit and the use of optional moving line acts as a factor to increase attraction. In addition, it is thought that attribute of exhibit and proper arrangement of rest space within exhibition space will increase holding power of exhibit.

• 제어로봇시스템학회논문지
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• 제2권3호
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• pp.220-228
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• 1996

This paper presents a extended stochastic Petri net (ESPN) model for CTN(Circulated Token with No duration) service in the data link layer of IEC/ISA fieldbus. It is assumed that a station on the fieldbus has a specified minimum token holding time, a finite capacity buffer, and one transmitter queue with the highest priority. The mean transmission (or service) time at a station and the mean token rotation time for the symmetric fieldbus system atr derived using the presented SPN model and the moment generating function. These performance measures are represented in terms of the minimum token holding time, the number of stations, the arrival rate of messages, and the mean length of messages. The presented performance measure are validated by computer simulations.

• Steel and Composite Structures
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• 제18권2호
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• pp.345-355
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• 2015

In this study, the effects of weld parameters on nugget size and tensile-shear strength of welding joint in electrical resistance spot welding of galvanized DP 600 steel sheets having 1.2 mm were investigated. Taguchi design method has been employed to examine the effects of five parameters of welding current, electrode pressure, welding time, clamping time and holding time by using the $L_{27}(5^3)$ orthogonal array. Results showed that the most effective parameters on tensile shear strength and the nugget size ratio (hn/dn) were found as welding current and welding time, whereas electrode pressure, clamping time and holding time were less effective factors. Max. 545 MPa strength was obtained through proposed optimum conditions by Taguchi technique.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.202-207
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• 1993

A theoretical and experimental study is presented for the force holding control of a miniature robotic ringer which is driven by a pair of piezoelectric unimorph cells. In the theoretical analysis, one finger is modeled as a flexible cantilever with a tactile force sensor at the tip and the mate of the finger is a solid beam supposed with sufficient stiffness. Further, the force sensor is modeled by a one-degree-of-freedom, mass-spring system and the output of sensor is then described by the sensor stiffness multiplied by the relative displacement. The problem investigated in this paper is that two typical holding tasks of the human finger are picked up and applied to the robotic finger. One is the work holding a stationary object with a prescribed, time-varying force and the other one is to keep the contacted force constant even if the object is in motion. The simple PID feedback control scheme is used to control the minute gripping force of order 0.01 Newton. It is shown both experimentally and theoretically that the artificial finger with the piezoelectric actuator works well in the minute force holding of the tiny object.