• The Korean Journal of Physiology and Pharmacology
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• 제24권6호
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• pp.529-543
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• 2020

In contrast to ventricular myocytes, the structural and functional importance of atrial transverse tubules (T-tubules) is not fully understood. Therefore, we investigated the ultrastructure of T-tubules of living rat atrial myocytes in comparison with ventricular myocytes. Nanoscale cell surface imaging by scanning ion conductance microscopy (SICM) was accompanied by confocal imaging of intracellular T-tubule network, and the effect of removal of T-tubules on atrial excitation-contraction coupling (EC-coupling) was observed. By SICM imaging, we classified atrial cell surface into 4 subtypes. About 38% of atrial myocytes had smooth cell surface with no clear T-tubule openings and intracellular T-tubules (smooth-type). In 33% of cells, we found a novel membrane nanostructure running in the direction of cell length and named it 'longitudinal fissures' (LFs-type). Interestingly, T-tubule openings were often found inside the LFs. About 17% of atrial cells resembled ventricular myocytes, but they had smaller T-tubule openings and a lower Z-groove ratio than the ventricle (ventricular-type). The remaining 12% of cells showed a mixed structure of each subtype (mixed-type). The LFs-, ventricular-, and mixed-type had an appreciable amount of reticular form of intracellular T-tubules. Formamide-induced detubulation effectively removed atrial T-tubules, which was confirmed by both confocal images and decreased cell capacitance. However, the LFs remained intact after detubulation. Detubulation reduced action potential duration and L-type Ca²⁺ channel (LTCC) density, and prolonged relaxation time of the myocytes. Taken together, we observed heterogeneity of rat atrial T-tubules and membranous ultrastructure, and the alteration of atrial EC-coupling by disruption of T-tubules.

• 한국수자원학회논문집
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• 제45권6호
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• pp.583-596
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• 2012

호안은 제방을 보호하기 위하여 제방법면에 설치되는 구조물로써, 국내 외 설계기준에 의하여 호안을 설계할 때, 하상과 호안법면에서의 최대 소류력을 산정하여 제방 사면에 평균적인 개념으로 적용하고 있다. 제방 사면의 허용소류력을 산정하는 경우에는 비점착성 토사를 기준으로 사면의 흘러내림을 고려하지만, 본 연구에서는 0 < ${\Phi}$ < $90^{\circ}$ 의 경사를 갖는 점착성 제방 단면의 구간별 소류력 공식을 제안하였으며, 호안의 식생밀도와 공법 재료 변화에 따른 허용소류력을 산정하였다. 구간별 소류력을 산정하기 위하여 길이 20m, 폭 2m의 개수로를 설치하였고, 유량 조건을 변화하면서 수리모형실험을 수행하였다. 제방 사면의 구간별 허용소류력을 산정한 결과 호안 재료 변화에 따라서는 조도가 큰 공법의 허용소류력이 가장 크게 산정되었으며, 식생밀도에 의한 영향으로는 식생이 있는 경우 저항에 의하여 허용소류력이 증가되었지만, 밀도변화에 의하여는 큰 차이가 나타나지 않았다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.68-73
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• 2006

The present paper deals with an experimental study of boiling heat transfer characteristics of R-290, and is focused on pressure gradient and heat transfer coefficient of the refrigerant flow inside horizontal smooth minichannel with inner diameter of 3.0 mm and length of 2000 mm. The direct heating method applied for supplying heat to the refrigerant where the test tube was uniformly heated by electric current which was applied to the tube wall. The experiments were conducted with R-290 with purity of 99.99% at saturation temperature of 0 to $10^{\circ}C$. The range of mass flux is $50{\sim}250kg/m^2s$ and heat flux is $5{\sim}20kW/m^2$. The heat transfer coefficients of R-290 increases with increasing mass flux and saturation temperature, wherein the effect of mass flux is higher than that of the saturation temperature, whereas the heat flux has a low effect on increasing heat transfer coefficient. The significant effect of mass flux on heat transfer coefficient is shown at high quality, the effect of heat flux on heat transfer coefficient at low quality shows a domination of nucleate boiling contribution. The heat transfer coefficient of the experimental result was compared with six existing heat transfer coefficient correlation. Zang et al.'s correlation(2004) gave the best prediction of heat transfer coefficient.

• Steel and Composite Structures
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• 제27권5호
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• pp.537-543
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• 2018

Mechanical shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface in composite beams. Steel pipe as a new shear connector is proposed in this research and its performance to achieve composite strength is investigated. Experimental monotonic push-out tests were carried out for this connector. Then, a nonlinear finite element model of the push-out specimens is developed and verified against test results. Further, the finite element model is used to investigate the effects of pipe thickness, length and diameter on the shear strength of the connectors. The ultimate strengths of these connectors are reported and their respective failure modes are discussed. This paper comprises of the push-out tests of ten specimens on this shear connector in both the vertical and horizontal positions in different reinforced concretes. The results of experimental tests are given as load-deformation plots. It is concluded that the use of these connectors is very effective and economical in the medium shear demand range of 150-350 KN. The dominant failure modes observed were either failure of concrete block (crushing and splitting) or shear failure of pipe connector. It is shown that the horizontal pipe is not as effective as vertical pipe shear connector and is not recommended for practical use. It is shown that pipe connectors are more effective in transferring shear forces than channel and stud connectors. Moreover, based on the parametric study, a formula is presented to predict the pipe shear connectors' capacity.

• 대한기계학회논문집B
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• 제36권5호
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• pp.545-551
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• 2012

마이크로 유체구조를 기반으로 하는 약물전달장치는 마이크로 유체 채널형상의 간단한 변형만으로 약물분출량을 쉽게 조절할 수 있는 장점이 있다. 그러나 디바이스 제작에 사용된 생분해성 고분자 85/15poly(lactic-co-glycolic acid) (85/15PLGA)의 소수성 기질 때문에 약물전달 장치내부로의 release medium의 유입이 원활하게 이루어지지 않으며 그 결과, 디바이스의 임플랜트 후 초기의 약물 분출에 영향을 줄 것으로 예상된다. 따라서 surfactant인 polyethylene-glycol600 (PEG600)과 Tween80을 이용하여 micro-channel의 표면처리를 한 디바이스와 surfactant를 사용하지 않은 디바이스를 각각 제작하여 약물 전달 실험을 하였으며, 이를 바탕으로 마이크로 유체 채널의 기하학적 형상에 따른 국소 마취제의 일종인 bupivacaine HCl(BHCl)의 분출속도제어를 입증하였다.

• 한국전기전자재료학회논문지
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• 제21권9호
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• pp.835-843
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• 2008

We have fabricated the source-drain electrodes for OTFTs by screen printing method and manufactured Ag pastes as conductive paste. To obtain excellent conductivity and screen-printability of Ag pastes, the dispersion characteristics of Ag pastes prepared from two types of acryl resins with different molecular structures and Ag powder treated with caprylic acid, triethanol amine and dodecane thiol as surfactant respectively were investigated. The Ag pastes containing Ag powder treated with dodecane thiol having thiol as anchor group or AA4123 with carboxyl group(COOH) of hydrophilic group as binder resin exhibited excellent dispersity. But, Ag pastes(CA-41, TA-41, DT-41) prepared from AA4123 fabricated the insulating layer since the strong interaction between surface of Ag powder and carboxyl group(COOH) of AA4123 interfered with the formation of conduction path among Ag powders. The viscosity behavior of Ag pastes exhibited shear-thinning flow in the high shear rate range and the pastes with bad dispersion characteristic demonstrated higher shear-thinning index than those with good dispersity due to the weak flocculated network structure. The output curve of OTFT device with a channel length of 107 ${\mu}m$ using screen-printed S-D electrodes from DT-30 showed good saturation behavior and no significant contact resistance. And this device exhibited a saturation mobility of $4.0{\times}10^{-3}$ $cm^2/Vs$, on/off current ratio of about $10^5$ and a threshold voltage of about 0.7 V.

• Journal of Plant Biotechnology
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• 제7권2호
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• pp.87-95
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• 2005

The tomato ripening associated membrane protein (TRAMP) (Fray et al., 1994) is a member of the major intrinsic protein (MIP) family, defined as channels facilitating the passage of water and small solutes through membranes. During normal fruit ripening the TRAMP mRNA levels were increased whereas the expression levels of TRAMP in low ethylene ACO1-sense suppressed lines, Nr and rin fruits, were lower than at the breaker stage of wild type fruit. TRAMP mRNA is inhibited by $LaCl_3$, which is an inhibitor of $Ca^{2+}$-stimulated responses, treatment but drought condition did not affect TRAMP expression. The levels of TRAMP mRNA transcripts were substantially higher in the dark treated seedlings and fruits. These suggest that TRAMP function as a water channel may be doubted because of several reasons; no water content was changed during ripening in wild type, antisense and overexpression lines, TRAMP expression under light condition was lower than dark condition and TRAMP expression was not changed in drought condition. Co-suppression plant, 3588 was one of sense suppression lines, which contain CaMV 35S promoter and sense pNY507 cDNA, produced small antisense RNA, approximately 21-25 nucleotides in length, mediated post-transcriptional gene silencing. Therefore, TRAMP expression was inhibited by small antisense and multiple copies might induce gene silencing without any production of double strand RNA. Total seven selected volatile productions, isobutylthiazole, 6-methyl-5-hepten-2-one, hexanal, hexenal methylbutanal, hexenol, and methylbutanol, were highly reduced in sense line whereas total volatile production was increased in TRAMP antisense line. These results suggested TRAMP might change volatile related compounds.

• 한국통신학회논문지
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• 제29권7A호
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• pp.705-711
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• 2004

본 논문에서는 광 부호분할다중접속(OCDMA) 시스템 구현을 위해 각 가입자의 시간ㆍ파장영역의 2차원 부호 할당과 변경이 가능하고 다중 사용자의 암호화된 데이터의 동시 전송과 모든 수신 노드에서 복원이 가능한 배열형 가변 부호기/복호기(RAE/RAD)를 갖는 OCDMA구조를 제안하였다. 수신노드에서 부호화된 데이터의 레벨을 일정하게 제한하는 1차 하드리미터의 기능을 제한증폭기를 사용하여 구현하였고, 부호화된 데이터의 위치 검출 및 복원을 위한 2차 하드리미터의 기능을 AND 검출기를 사용하여 이중 하드리미터(Double Hard Limiter)를 최초로 구현하였다. FPGA와 4개의 서로 다른 파장을 갖는 DFB-LD를 부호다중화된 16채널의 신호중에서 특정 채널의 신호를 복원하는 실험을 성공적으로 수행하였다. 1-D OCDMA 시스템에서의 채널 증가에 따른 부호길이 증가문제를 시간과 파장 영역의 2차원 부호다중화를 사용함으로써 개선하였고, 채널 증가에 따른 MAI로 인한 기존의 문턱값 검출기의 식별력(Autocorrelation peak-to-sideloobe ratio) 저하와 비트 오류 문제를 제한증폭기와 AND 검출기를 갖는 이중 하드리미터를 적용하여 개선하였다.

• Journal of the Korean Wood Science and Technology
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• 제38권6호
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• pp.498-506
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• 2010

국산 침엽수재를 고부가가치의 구조부재로 활용하기 위해서는 국내 기준에 적합한 등급구분 체계가 갖춰져야 한다. 김 등(2009a, b)의 연구에서는 목재의 생산 및 유통규모가 작은 국내 현실에서 제재목 등급구분의 자동화 및 기계화를 목적으로 화상처리시스템을 개발하였다. 본 연구에서는 이전 연구에서 개발한 화상처리시스템의 핵심 기술 중 하나인 화상입력시스템의 성능을 향상시키기 위하여 최적 화상병합 조건을 구명하고자 하였다. 연구 결과 국산 낙엽송 $180{\time}120$ mm 부재의 화상을 병합하는 데 있어서 획득된 화상의 green채널 정보를 병합 에 이용하는 것이 가장 높은 병합정확성을 얻을 수 있었다. 입력된 화상의 전처리 과정으로 Y-derivative Sharr's kernel 필터를 적용함으로써 화상병합 성능을 향상시킬 수 있었으나, 카메라 보정에 의한 효과는 미미 하였다. 또한 화상병합을 위한 최적 템플릿 크기는 폭 30 pixel ${\time}$ 높이 150 pixel로 확인되었다. 이상의 조건을 적용하였을 때, 병합된 화상의 길이오차는 평균 3.1 mm, 연산시간은 평균 9.7초로 나타났다.

• Structural Engineering and Mechanics
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• 제47권1호
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• pp.59-73
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• 2013

The Xiaolan channel super large bridge is unique in style and with greatest span in the world with a total length of 7686.57 m. The main bridge with spans arranged as 100m+220m+100m is a combined structure composed of prestressed concrete V-shape rigid frame and concrete-filled steel tubular flexible arch. First of all, the author compiles APDL command flow program by using the unit birth-death technique and establishes simulation calculation model in the whole construction process. The creep characteristics of concrete are also taken into account. The force ratio of the suspender, arch and beam is discussed. The authors conduct studies on the three-plate webs's rule of shear stress distribution, the box girder's longitudinal bending normal stress on every construction stage, meanwhile the distribution law of longitudinal bending normal stress and transverse bending normal stress of completed bridge's box girder. Results show that, as a new combined bridge, it is featured by: Girder and arch resist forces together; Moment effects of the structure are mainly presented as compressed arch and tensioned girder; The bridge type brings the girder and arch on resisting forces into full play; Great in vertical stiffness and slender in appearance.