• Geomechanics and Engineering
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• 제14권2호
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• pp.203-209
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• 2018

Reliable estimation of compressive as well as tensile in-situ stresses is critical in the design and analysis of underground structures and openings in rocks. Kaiser effect technique, which uses acoustic emission from rock specimens under cyclic load, is well established for the estimation of in-situ compressive stresses. This paper investigates the Kaiser effect on marble specimens under cyclic uniaxial compressive as well as cyclic uniaxial tensile conditions. The tensile behavior was studied by means of Brazilian tests. Each specimen was tested by applying the load in four loading cycles having magnitudes of 40%, 60%, 80% and 100% of the peak stress. The experimental results confirm the presence of Kaiser effect in marble specimens under both compressive and tensile loading conditions. Kaiser effect was found to be more dominant in the first two loading cycles and started disappearing as the applied stress approached the peak stress, where felicity effect became dominant instead. This behavior was observed to be consistent under both compressive and tensile loading conditions and can be applied for the estimation of in-situ rock stresses as a function of peak rock stress. At a micromechanical level, Kaiser effect is evident when the pre-existing stress is smaller than the crack damage stress and ambiguous when pre-existing stress exceeds the crack damage stress. Upon reaching the crack damage stress, the cracks begin to propagate and coalesce in an unstable manner. Hence acoustic emission observations through Kaiser effect analysis can help to estimate the crack damage stresses reliably thereby improving the efficiency of design parameters.

• Advances in concrete construction
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• 제5권5호
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• pp.539-561
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• 2017

In this study, the effects of initial damage of concrete columns on the post-repair performance of reinforced concrete (RC) columns strengthened with carbon-fiber-reinforced polymer (CFRP) composite are investigated experimentally. Four kinds of compression-damaged RC cylinders were reinforced using external CFRP composite wraps, and the stress-strain behavior of the composite/concrete system was investigated. These concrete cylinders were compressed to four pre-damaged states including low -level, medium -level, high -level and total damage states. The percentages of the stress levels of pre-damage were, respectively, 40, 60, 80, and 100% of that of the control RC cylinder. These damaged concrete cylinders simulate bridge piers or building columns subjected to different magnitudes of stress, or at various stages in long-term behavior. Experimental data, as well as a stress-strain model proposed for the behavior of damaged and undamaged concrete strengthened by external CFRP composite sheets are presented. The experimental data shows that external confinement of concrete by CFRP composite wrap significantly improves both compressive strength and ductility of concrete, though the improvement is inversely proportional to the initial degree of damage to the concrete. The failure modes of the composite/damaged concrete systems were examined to evaluate the benefit of this reinforcing methodology. Results predicted by the model showed very good agreement with those of the current experimental program.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.356-364
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• 2021

During the hydrogen fueling process, hydrogen temperature inside the compressed tank were limited below 85℃ due to the allowable pressure of tank material. The chiller system to cool compressed hydrogen used R407C, greenhouse gas with a high global warming potential (GWP), as a refrigerant. To reduce greehouse gas emission, it should be replaced by refrigerant with a low GWP. This study proposes a chiller system for fueling hydrogen with R290, consisted in propane, by applying the C3 pre-cooled system use d in the LNG liquefaction process. The proposed system consisted of hydrogen compression and cooling sections and optimized the operating pressure through exergy analysis. It was also compared to the exergy efficiency with the existing system at the optimal operating pressure. The result showed that the optimal operating pressure is 700 kPa in 2-stage, 840 kPa/490 kPa in 3-stage, and the exergy efficiency increased by 17%.

• 한국지구과학회지
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• 제44권4호
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• pp.275-290
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• 2023

Structural inversion refers to the reverse reactivation of extensional faults that influence basin shortening accommodated by contractional faults or folds. On the Korean peninsula, Miocene inversion structures have been found, but the Cretaceous rocks on Geoje Island may have undergone inversion as early as the Upper Cretaceous. To evaluate the structural inversion on Geoje Island, located on the eastern side of South Korea, and to determine the effects of preexisting weakness zones, field-based geometric and kinematic analyses of faults were performed. The lithology of Geoje Island is dominated by hornfelsified shale, siltstone, and sandstone in the Upper-Cretaceous Seongpori formation. NE and NW-oblique normal faults, conjugate strike-slip (NW-sinistral transpressional and E-W-dextral transtensional) faults, and NE-dextral transpressional faults are the most prominent structural features in Geoje Island. Structural inversion on Geoje Island was evidenced by the sinistral and dextral transpressional reactivation of the NW and NE-trending oblique normal faults respectively, under WNW-ESE/NW-SE compression, which was the orientation of the compressive stress during the Late Cretaceous to Early Cenozoic.

• 대한전자공학회논문지SP
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• 제42권5호
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• pp.29-40
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• 2005

디지털 홀로그램의 저변이 확대됨에 따라서 3차원 영상의 구성을 위한 스테레오 영상의 압축기술에 대한 국제적인 표준이 3DAV라는 형태로 진행되는 것과 같이 디지털 홀로그램의 압축 기술에 대한 논의도 활발히 이루어질 것으로 보인다. 3DAV의 경우애도 볼 수 있듯이 기존에 존재하는 여러 가지 기술들을 접목하거나 변형한 형태, 혹은 그들의 혼합된 형태로 논의될 가능성이 크다. 또한 디지털 홀로그램의 압축을 위한 전용 시스템을 구성하는 기존의 기술을 배제하고 개발하는 것은 현실적으로 어렵다. 따라서 다양한 영상압축 기술들과 디지털 홀로그램과의 상관관계에 대한 방향을 제시하고자 한다. 본 논문에서는 기존의 비디오 및 영상압축 도구들을 이용하여 디지털 홀로그램을 효율적으로 부호화하는 기술을 제안하고자 한다. Fringe 패턴의 형태로 표현되는 디지털 홀로그램의 생성 원리를 이용하여 비디오 데이터로 가공한 후에 부호화하는 방식을 이용한다. 여기에는 생성된 디지털 홀로그램을 부호화하기 위해 적절한 형태로 변형하는 전처리 과정, 객체 영상의 모든 정보를 포함하는 공간적인 분할, 디지털 홀로그램의 생성원리와 부합되는 주파수 변환기술, 비디오 데이터로 구성하기 위한 스캔방법, 부호화를 위한 주파수 계수의 분류, 그리고 하이브리드 형태의 압축기술 등이 고려되어 하나의 알고리즘을 구성한다. 압축을 위한 부호화 도구에는 정지영상 압축을 위한 JPEG2000을 비롯하여 동영상 압축을 위한 MPEG-2, MPEG-4, 및 H.264와 같은 국제 표준 압축 알고리즘들과 여러 무손실 압축 기술들이 포함된다. 실험 결과를 살펴보면 제안한 알고리즘은 기존의 기술에 비해서 4배에서 8배 이상의 높은 압축율에서 더 좋은 복원 성능을 보였다. 따라서 제안한 기술은 디지털 홀로그램의 부호화를 위한 좋은 연구 사례가 될 것으로 사료된다. 체중 부하에 의해서 생역학적인 변화를 일으키지 않고 얼마나 유지 할 수 있는지는 보다 장기적인 추시 관찰이 필요할 것으로 사료된다.이 생식소의 에너지 요구에 반응하여 변하는 것으로 추정된다.60일 후 $625{\pm}19.76{\mu}m$로 성장하였고, 생존율은 23%로 가장 높게 나타나 치패사육시 가장 적정한 수온은 $15^{\circ}C$라 판단되었다.다. 시도는 긍정적으로 평가되어야 한다. 그러므로 앞으로는 제품디자인 뿐만이 아닌 다른 다양한 분야들에게로 그 범위가 확대되어 디자인 문화적 정체성을 확립하는 연구가 뒤따라야 할 것이다.. 즉, 제품디자인의 결정요인 분석결과는 QFD의 접근방법에, 제품 디자인 파급효과 분석결과는 컨조인트 분석에 각각 보완적 기여를 할 수 있다. 이와 동시에, 실증적 분석결과는 Ettlie(1997)의 디자인 통합(DI) 이론에 대한 실증적 기반을 제공할 수 있다. 마지막으로, 성공적인 디자인 경영(DM)을 위해서는 최고 경영자의 지원뿐만 아니라 부처 간 의사소통의 장애요인을 제거하고 CFT(cross-functional team)를 운영함으로써 동시적 엔지니어링(CE) 및 제품 및 공정 디자인의 개발이 제품 개발의 속도를 가속화하고 디자인 품질을 높이며 시장 성공을 보증할 수 있도록 해야 한다.임과 채팅은 긍정적인 상호관련을 가진 것으로 나타난 반면 전자메일 서비스 이용은 성적 만족과 부정적인 상호관련을 가진 것으로 분석되었다. 이는 대학생들이 지루하게 느끼거나 외로움을 느낄 때 전자메일을 주로 이용하지만 성적 만족을 위해 전자메일을 이용하지 않고 있다는 사실을 보여주는 것이다. (3) 인터넷 이용 이후 다른 미디어와 면대면 커뮤니케이션과의 관계 인터넷을 이용한 후 응답자들의 전통적인 미디어(텔레비전, 라디오, 신문, 잡지, 편지,

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.223-223
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• 2012

Surface engineering plays a significant role in fabricating highly functionalized materials applicable to industrial and biomedical fields. Surface wrinkles and folds formed by ion beam or plasma treatment are buckling-induced patterns and controlled formation of those patterns has recently gained considerable attention as a way of creating well-defined surface topographies for a wide range of applications. Surface wrinkles and folds can be observed when a stiff thin layer attached to a compliant substrate undergoes compression and plasma treatment is one of the techniques that can form stiff thin layers on compliant polymeric substrates, such as poly (dimethylsiloxane) (PDMS). Here, we report two effective methods using plasma modification techniques for controlling the formation of surface wrinkles and folds on flat or patterned PDMS substrates. First, we show a method of creating wrinkled diamond-like carbon (DLC) film on grooved PDMS substrates. Grooved PDMS substrates fabricated by a molding method using a grooved master prepared by photolithography and a dry etching process were treated with argon plasma and subsequently coated with DLC film, which resulted in the formation of wrinkled DLC film aligning perpendicular to the steps of the pre-patterned ridges. The wavelength and the amplitude of the wrinkled DLC film exhibited variation in the submicron- to micron-scale range according to the duration of argon plasma pre-treatment. Second, we present a method for controlled formation of folds on flat PDMS substrates treated with oxygen plasma under large compressive strains. Flat PDMS substrates were strained uniaxially and then treated with oxygen plasma, resulting in the formation of surface wrinkles at smaller strain levels, which evolved into surface folds at larger strain levels. Our results demonstrate that we can control the formation and evolution of surface folds simply by controlling the pre-strain applied to the substrates and/or the duration of oxygen plasma treatment.

• 천문학회보
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• 제41권1호
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• pp.73.1-73.1
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• 2016

We present preliminary results of the submillimeter continuum observations of 14 Planck Galactic Cold Clumps (PGCCs), located in the ${\lambda}$ Orionis Complex. This region is the nearest large HII region, which is an ideal site for a study of the stellar feedback to its surroundings. We observed 14 PGCCs with JCMT/SCUBA-2 and used J=1-0 transitions of CO isotopologues from the PMO mapping observation. Several sub-clumps toward three PGCCs were detected at $850{\mu}m$. In order to examine whether these clumps can be candidates for pre-stellar cores, we compared each clump mass calculated from the $850{\mu}m$ continuum map to its Virial mass and Jeans mass calculated from the $^{12}CO$ and $C^{18}O$ (1-0) spectra, respectively. All clumps have masses smaller than their Virial and Jeans masses, indicating that none of them are gravitational bound and thus in the pre-stellar core stage. Also, the CO depletion factor, which has been derived from the dust continuum and the $C^{18}O$(1-0) line and can be an indicator of core evolution, toward the clumps is in the range of 1 to 5, suggesting that they are not very evolved dense pre-stellar cores. In addition, within individual PGCCs, we found clear gradients of velocity (${\sim}1km\;s^{-1}\;pc^{-1}$) and temperature (${\sim}10K\;pc^{-1}$) in the $^{13}CO$ (1-0) first moment map and the $^{12}CO$(1-0) excitation temperature map, respectively. This can be attributed to the compression and external heating by the HII region, which may prevent clumps from forming gravitationally bound structures and eventually disperse clumps. These results could be a hint about the negative effect of stellar feedback on core formation.

• 한국컴퓨터정보학회논문지
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• 제15권7호
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• pp.27-32
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• 2010

본 논문에서는 편집하고자 하는 위치를 포함하는 GOP(Group Of Picture) 구간만을 선택하여 복호화하고 부호화하는 과정을 수행함으로써 보다 빠르고 정확한 프레임 단위 편집 방법을 제안한다. 제안하는 방법은 편집정보 추출과정 후에 원하는 부분만을 정확하게 분할해 내는 방법과 같은 해상도를 가지는 서로 다른 MPEG 스트림을 병합시키거나 하나의 파일에서 서로 다른 시간을 가지는 부분들을 선택하여 병합시키는 방법으로 나누어 처리한다. 분할은 선택한 프레임이 존재하는 GOP를 복호화 시켜 디스플레이가 정확하게 이루어지도록 필요한 프레임을 포함하거나 제거한 후 다시 부호화한다. 또한 분할이나 병합 후에 완전한 하나의 스트림으로 구성하기 위해 시각 관리정보의 수정뿐만 아니라 시스템 표준에서 정의하는 구성에 맞도록 전체를 재구성한다. 실험 결과 본 논문이 제안하는 편집방법이 모든 프레임에 걸쳐 정확하고 빠른 분할과 병합 과정을 처리하는 것을 나타낸다.

• Journal of Korean Neurosurgical Society
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• 제30권2호
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• pp.173-179
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• 2001

Purpose : To assess therapeutic effects of percutaneous polymethylmethacrylate(PMMA) vertebroplasty on the pain caused by osteoporotic thoracic and lumbar vertebral body compression fractures in a large scale of a prospective clinical design, and to determine clinical factors influencing its therapeutic effects. Methods : A prospective clinical study was carried out in 349 vertebral levels of 159 patients between April 1998 and July 1999. The compression fractures were confirmed with bone scan and spine CT, and bone marrow density was measured. Visual analogue scale(VAS) score was used for pre- and post-operative assessments of the pain. All 159 patients were assessed immediately after surgery, and 140 patients of them were followed-up for about 6 months in average. Results : Partial and complete pain relief was sustained immediately after operation in 73%, through follow-up period in 88% of the patients. Pain relief was not proportional to the amount of PMMA or the rate of increase in the height of the compressed vertebral body. It appears that 3 to 6cc of PMMA was proper enough to sustain pain relief. Better clinical improvement was achieved in the patients treated within 6 months after occurrence of vertebral body fracture. The most frequent surgical complication was epidural leakage of PMMA, and the most serious complication was extravertebral leakage into the paravertebral muscles, which appeared to exert the worst influence on the outcome. However, surgery was not required in these patients. Conclusion : Therapeutic effects of PMMA percutaneous vertebroplasty on osteoporotic vertebral body compression fractures were confirmed in a relatively large scale of prospective clinical study. It appears that good outcome can be achieved in patients treated within 6 months after fracture, treated each level with 3 to 6cc of PMMA in amount. without serious complications.

• 마이크로전자및패키징학회지
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• 제30권4호
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• pp.98-104
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• 2023

대기 중 구리-구리 플립칩(flip-chip) 접합을 위해 제안된 효율적 공정의 실현 가능성을 평가하고자 구리(Cu) 필라(pillar) 상 다공성 구리층의 형성 및 액상 환원제 투입 후 열압착 접합을 실시하였다. 구리 필라 상 다공성 구리층은 아연(Zn) 도금-합금화 열처리-선택적 아연 에칭(etching)의 3단계 공정으로 제조되었는데, 형성된 다공성 구리층의 두께는 평균 약 2.3 ㎛였다. 본 플립칩 접합은 형성 다공성 구리층에 환원성 용제를 침투시킨 후, 반건조 과정을 거쳐 열압착 소결접합으로 진행하였다. 용제로 인한 구리 산화막의 환원 거동과 함께 추가 산화가 최대한 억제되면서 열압착 동안 다공성 구리층은 약 1.1 ㎛의 두께로 치밀해지며 결국 구리-구리 플립칩 접합이 완수되었다. 그 결과 10 MPa의 가압력 하에서 대기 중 300 ℃에서 5분간 접합 시 약 11.2 MPa의 접합부 전단강도를 확보할 수 있었는데, 이는 약 50% 이하의 필라들만이 접합된 결과로서, 공정 최적화를 통해 모든 필라들의 접합을 유도할 경우 20 MPa 이상의 강도값을 쉽게 얻을 수 있을 것으로 분석되었다.