• 한국자기학회지
• /
• 제10권3호
• /
• pp.118-122
• /
• 2000

절연층으로 $Al_2$ $O_3$를 사용한 스핀의존성 터널링 접합에서 절연층의 두께가 자기저항특성에 미치는 효과에 대해 조사하였다. 스핀 의존성 터널링 접합은 3-gun 스퍼터링 시스템에서 4$^{\circ}$tilt-cut (111)Si 기판 위에 증착하였다. 절연층으로 사용된 $Al_2$ $O_3$는 Al을 1~3 nm로 증착한 후에 대기중에서 자연산화시켜 얻었고, 상부와 하부 강자성체 전극은 NiFe와 Co를 사용하였다. 자기저항비는 절연층의 두께가 2 nm인 터널링 접합에서 약 14 %로 최대값을 보였고 접합에 걸리는 터널링 전압이 증가함에 따라 최대 자기저항비는 급격히 감소하는 경향을 보였다.

• 한국응용과학기술학회지
• /
• 제30권3호
• /
• pp.431-443
• /
• 2013

Sulfur content of diesel fuel has been cut down to under 10 ppm ULSD (ultra low sulfur diesel) level by environmental regulation with the aim of reducing exhaust emissions. This review discusses the methods and principles of sulfur reduction in diesel and presents an overview of new approaches for ultra-deep desulfurization. The deep HDS (hydrodesulfurization) problems of diesel streams is exacerbated by the inhibiting effect of co-existing aromatics, nitrogen compounds and $H_2S$. The new approaches to deep desulfurization includes non-HDS type processing schemes such as adsorptive, extractive and oxidative desulfurization.

• Journal of Ship and Ocean Technology
• /
• 제10권3호
• /
• pp.1-16
• /
• 2006

Despite the high cost of memory and CPU time required to resolve the boundary layer, a viscous unstructured grid solver has many advantages over a structured grid solver such as the convenience in automated grid generation and vortex capturing by solution adaption. In present study, an unstructured Cartesian grid solver is developed on the basis of the existing Euler solver, NASCART-GT. Instead of cut-cell approach, immersed boundary approach is applied with ghost cell boundary condition, which can be easily applied to a moving grid solver. The standard $k-{\varepsilon}$ model by Launder and Spalding is employed for the turbulence modeling, and a new wall function approach is devised for the unstructured Cartesian grid solver. Developed approach is validated and the efficiency of the developed boundary condition is tested in 2-D flow field around a flat plate, NACA0012 airfoil, and axisymmetric hemispheroid.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2009년도 하계학술발표대회 논문집
• /
• pp.928-933
• /
• 2009

The purpose of this study is to examine the energy consumption, carbon dioxide emission & energy cost of district heating using sewage source. The annual TOE of heat pump using sewage source save 37.1 percent than city gas boiler. And annual carbon dioxide emission of heat pump cut down 41.3 percent than city gas boiler. If it charges the rate schedule for district heating to apartment resident, collected amount are 3,127,170 thousand won. As energy cost of heat pump & circulation pump are 1,378,072 thousand won. the profits are 1,749,098 thousand won. As payback period is 8.97years, applicability is low level. However, it has advantages in energy consumption, carbon dioxide emission & energy cost. Therefore, it needs to proceed through government assistance.

• 한국시스템다이내믹스연구
• /
• 제1권2호
• /
• pp.33-60
• /
• 2000

This study aims to conceptually identify the circular causal-relationship which is structured between downsizing and technological innovation in organization. First, through the literature review concerning downsizing and (technological) innovations, we have outlined the conceptual building blocks and research boundaries in this field. Second, we used system thinking method to accomplish our research purpose. The research findings are as follows. First, the promotion of financial resources by downsizing have trade-off relations that have negative of effects in short terms, but positive effects in long time. Second, workforce reduction by downsizing usually has negative influence on employees. Third, capital reduction by downsizing generates not only the climates of cost-cut but also the fact that although the climates may increase economic performance in short terms, it may interrupt technological innovations in long terms. In conclusion, this theses suggests that the relationship of downsizing and technological innovations have complex causal and feedback structures. Therefore, the results of this thesis propose that the argument or practices of downsizing with partial emphasis is very dangerous. Finally some limitations are also discussed.

• 한국지반공학회논문집
• /
• 제36권1호
• /
• pp.29-38
• /
• 2020

최근 환기구, 비상탈출용 수직구, 취수탑 가시설 등 지중 가물막이 또는 차수벽체로 원형 가물막이가 많이 적용되고 있다. 원형단면의 경우 벽체에 작용하는 토압이 원형가물막이 형상에 따라 아칭효과(arching effect)로 인하여 작용토압에 대한 구조체의 부재력이 감소하는 것으로 알려져 있다. 본 연구에서는 원형 가물막이에 대한 2D 유한요소해석(FEM)을 활용하여 원형띠장(ring beam) 강성을 산출 후 탄소성해석에 적용하여 부재의 단면력을 검토하였다. 더불어 3D 유한요소해석(FEM)을 통하여 원형단면의 가물막이가 다각형 형태의 가물막이보다 전단력, 휨모멘트, 그리고 발생변위가 최소값을 갖는 것으로 나타났으며, 이로써 원형단면 가물막이가 구조적으로 보다 효율적인 단면 형태임을 확인하였다

• 한국가축번식학회지
• /
• 제10권1호
• /
• pp.76-82
• /
• 1986

This experiment was conducted to determine the effects of trophoblastic vesicles (TV) and estradiol-17$\beta$ on the development in vitro of rabbit embryos. Thirty matured female rabbits were treated with PMSG followed by HCG injection and mating. Embryos were recovered with D-PBS (Dulbecco's Phosphate Buffered Saline) after superovulation, and normally developed to two-to four-cell embryos were used in the subsequent in vitro culture. Basal medium was Medium-199 su, pp.emented with 1.5% bovine serum albumin. Embryo on Day 5 after mating (Day 0) was cut into two or three pieces to remove the embryonic disc. Each piece of tissue was cultured for 24 hours at 37$^{\circ}C$ in 0.5 mlMedium-199 in 5% CO2. During culture, peices of trophoblastic tissue changed into spherical vesicles which were used for co-culture. These spheres were called trophoblstic vesicles. Two-to four-cell embryos were cultured for 4 days in Medium-199 in the absence or presence of trophoblastic vesicle, and two-to four-cell embryos cultured with varing concentration (0, 0.1, 1, 10ng/ml) of estradiol-17$\beta$ for 4 dyas. Culture vessels used were watch glass for coculture with trophoblastic vesicles and micortube for estradiol-17$\beta$ infusion. Compared with the Medium-199 alone as basal culture medium, more blastocysts (46.7% vs 15.1%; P<0.01) and morulae (84.4% vs 56.6%; P<0.05) were developed in the co-culture with trophoblastic vesicles. Estradiol-17$\beta$ infused in culture medium was not effective for embryo development to blastocysts (78.3% in control, 50.0% in 0.1ng/ml, 61.5% in 1ng/ml and 64.4% in 10ng/ml) and also to morulae (91.3% in control, 84.2% in 0.1ng/ml, 92.3% in 1ng/ml and 91.1% in 10ng/ml). Compared with the watch glass culture mehotd, more (P<0.01) blastocysts were developed in microtube culture (78.3% vs 56.6%) and more (P<0.01) morulae in microtube culture (91.3% vs 56.6%).

• 한국지진공학회논문집
• /
• 제28권4호
• /
• pp.183-191
• /
• 2024

Accurate seismic vulnerability assessment requires high quality and large amounts of ground motion data. Ground motion data generated from time series contains not only the seismic waves but also the background noise. Therefore, it is crucial to determine the high-pass cut-off frequency to reduce the background noise. Traditional methods for determining the high-pass filter frequency are based on human inspection, such as comparing the noise and the signal Fourier Amplitude Spectrum (FAS), f² trend line fitting, and inspection of the displacement curve after filtering. However, these methods are subject to human error and unsuitable for automating the process. This study used a deep learning approach to determine the high-pass filter frequency. We used the Mel-spectrogram for feature extraction and mixup technique to overcome the lack of data. We selected convolutional neural network (CNN) models such as ResNet, DenseNet, and EfficientNet for transfer learning. Additionally, we chose ViT and DeiT for transformer-based models. The results showed that ResNet had the highest performance with R² (the coefficient of determination) at 0.977 and the lowest mean absolute error (MAE) and RMSE (root mean square error) at 0.006 and 0.074, respectively. When applied to a seismic event and compared to the traditional methods, the determination of the high-pass filter frequency through the deep learning method showed a difference of 0.1 Hz, which demonstrates that it can be used as a replacement for traditional methods. We anticipate that this study will pave the way for automating ground motion processing, which could be applied to the system to handle large amounts of data efficiently.

• Clinical and Experimental Reproductive Medicine
• /
• 제27권1호
• /
• pp.39-46
• /
• 2000

Objective: A number of studies to improve in vitro culture conditions have been tried over past ten years by using co-culture system with helper somatic cells. However, the mechanism of coculture is poorly understood. This study was designed to understand the mechanism for the mode of actual action of co-culture using co-culture system of ICR strain's 1-cell embryos with human oviduct epithelial cells by examining the effect of conditioned medium and contactless coculture using a cell culture insert on the embryo development and by measuring the level of superoxide anion from conditioned medium after co-culture. Methods: ICR strain's zygote embryos were cultured in medium alone (control), coculture, conditioned medium, or contactless coculture system for 6 days. Conditioned media (CM) were prepared as following 5 groups. All CM were collected after culturing oviduct cells for 2 days. CM-1 was stored at $-20^{\circ}C$ until use, and CM-2 was prepared just before use as a culture medium. CM-3 was cocultured with embryos and retrieved just before use. CM-4 and CM-5 were derives from the microfilteration of CM-2 and CM-3, respectively, using Microcon-10 (10 kDa molecular weight cut-off). The percentage of the embryos developed to hatched blastocyst stage and the level of superoxide anion in supernatant from medium alone culture (control), coculture, and contactless coculture were measured. Results: The rates of embryo development to the hatched blastocyst stage were significantly higher in coculture (43%) than in control (0%) (p<0.05). The CM-1 group had no embryo development since 2-cell embryonic stage, whereas the CM-2, CM-3, CM-4 and CM-5 groups had the improved development to 4 or 8 cell embryo stage, but the similar rate of development to hatched blastocyst compared to control. The effect of coculture on embryo development was disappeared in the contactless coculture group. The level of superoxide anion was significantly reduced in coculture group compared to control. Conclusion: It is concluded that the present coculture system overcomes the 2-cell block in vitro and improves the embryo development. This beneficial effect may be due to the direct cell-cell contact between embryo and helper cells or the removal of deleterious components from medium rather than the embryotrophic factors.

• 한국환경복원기술학회지
• /
• 제10권2호
• /
• pp.1-15
• /
• 2007

A variety of revegetation methods are being utilized and developed. However, most of revegetation methods used on highway slopes in Korea are based on foreign-introduced plant varieties to stabilize road surfaces and to administer afforestation for surface covering at an earlier phase. Therefore. it results in various problems. such as failure to achieve harmony with the surrounding vegetation and 10 cause re-denudation of slopes as the foreign-in introduced plant varieties wane out from 2~3 years after hydro-seeding, etc. In addition, some of the revegetation plants seeded in the earlier phase grow excessively high, thus causes successional problems, such as to inhibit the invasion of the secondary vegetation from the surrounding areas, etc. Therefore, in this study, 160 slopes located in the nationwide express highways have been investigated and analyzed in order to produce basic data for restoration of ecological environment in slopes created on a long-term basis by investigating and analyzing locational characteristics of cut and filled slopes in express highways, status of revegetation methods, characteristics of soil and plant-ecological environment. 1. Investigation on cut and embanked slopes in express highways was carried out in the total of 160 locations, which include 108 cut slopes and 52 embanked slopes. As a whole, the most frequently used revegetation method was seed spray, which was found to be used in the total of 55 target slops investigated. 2. Planting method of Wistaria floribunda applied to some of the blasted rock zones was found to cause damages as Wistaria floribunda trailed up the surrounding vegetation and the secondary invaded trees. In order to prevent this, this method must be used only in the lowest parts of large-sized slopes. Also, it will be required to administer continuous management and maintenance in the areas already planted with this plants. 3. The areas of blasted rock and ripping rock slopes were applied with coir net (net + seeding) method. However, many of these areas failed in achieving ground covering. Most areas where revegetation was in progress, they were covered with Eragrostis curvula(Weeping lovegrass) only. In areas with soil, such as decomposition of granite, where afforestation is difficult. In this slopes, soil base must be improved by hrdroseeding with thin-layer vegetation base application methods in order to achieve success in afforestation with native plants. 4. Woody species, rather than herb species, are more helpful in stabilization of slope surfaces. Therefore, it is important to be able to grow and protect woody species on highway slopes. Growth of woody vegetation is most largely influenced by soil depth. Thus, when hydro-seeding woody plants, it is recommended to apply at the upper layer of the slopes, which is capable to sufficiently provide the fundamentals required in plant growth.