• Proceedings of the SAREK Conference
• /
• 2008.11a
• /
• pp.262-268
• /
• 2008

The present paper dealt with flow heat transfer characteristics of R-410A vaporization in horizontal smooth microchannel. The test sections were made of stainless steel tube with inner diameters of 300 mm and length of 300 mm. The refrigerant was supplied with mass flux range of 260-600 kg/$m^2s$ and applied under operating heat flux range of 5-20 kW/$m^2$ using a direct electric current heating method. The in let saturation temperature was set at $10^{\circ}C$ and vapor quality up to 1.0. The influences of mass flux, heat flux and inner tube diameter on local heat transfer coefficients were presented. Comparison with existing heat transfer coefficient correlations was performed. An improved heat transfer coefficient correlation for refrigerant vaporization in microchannel based on superposition model was developed with a mean deviation of 14.01%.

• Proceedings of the SAREK Conference
• /
• 2007.11a
• /
• pp.241-246
• /
• 2007

The present paper dealt with an experimental study of boiling heat transfer characteristics of $CO_2$. Heat transfer coefficients of the refrigerant flow inside horizontal smooth microchannel were obtained with inner tube diameter of 0.3mm and length of 300mm. The direct electric heating method was applied for supplying the heat uniformly to the refrigerant. The experiments were conducted with $CO_2$ purity of 99.99%, at saturation temperature of $10^{\circ}C$, mass flux ranges of $300{\sim}900\;kg/m^2s$, and heat flux ranges of $15{\sim}45\;kW/m^2$. While heat transfer coefficient increased with the increase of heat flux in the low quality region, the heat transfer coefficient decreased with the increase of quality in the high quality region. The heat transfer coefficients were compared with seven existing correlations with the Gungor-Winterton's(1986) correlation gave the best prediction. A new corelation to predict the two-phase flow heat transfer coefficient was developed based on the Chen(1966) correlation. The new correlation predicted the experimental data well with a mean deviation of 9.69% and average deviation of -3.03%.

• Journal of Fisheries and Marine Sciences Education
• /
• v.4 no.1
• /
• pp.47-61
• /
• 1992

An experimental study was carried out to investigate the condensation performance for the horizontal cylindrical heat transfer tube with various fin attached using R-11 vapor. The heat transfer tube used in this study was supplied by SUNG HYUNG METAL CO., LTD. Four different types of heat transfer tubes (plain tube, SH-CYR tube, thermocor tube and thermoexcel tube) were used. Each tube was surrounded by circular acrylate tube, and R-11 gas heated by boiler flows into the acrylate tube. Cooling water counter-flows in heat transfer tubes. Heat transfer coefficient of the plain tube from measured data was compared with those of three other tubes. The results are summarized as follows: 1. As the cooling water temperature decreased, the liquid film of R-11 turned to droplet drop on the top surface of the horizontal tube. 2. Heat transfer coefficient calculated theoretically was higher than that obtained from the experimental data. 3. As far as the condensation concerns the thermocor tube is the highest, the SH-CYR tube is the second, and the thermoexcel tube is the third excluding the plain tube.

• Information and Communications Magazine
• /
• v.34 no.1
• /
• pp.41-50
• /
• 2016

사물인터넷 비즈니스의 수요가 증가하면서, 다양한 사물들에 대한 식별 및 데이터 공유 체계와 서비스 디스커버리 표준을 제공하는 GS1 (Global Standard 1) 국제 표준이 글로벌 사물인터넷 표준으로써 자리잡고 있다. 유통/물류분야의 지배적 표준에서 시작한 GS1은 1999년 세계 최초로 사물인터넷(Internet of Things)이란 용어와 개념을 소개한 이후, 스마트팩토리, 헬스케어 서비스 표준에서부터 금융 서비스에 이르기까지, 다양한 산업 도메인 응용의 수평적 통합을 가능하게 하는 데이터 기반의 사물인터넷 표준으로서의 입지를 지속적으로 확장해 나가고 있다. 본 논문에서는 GS1 국제 표준에 대한 전반적인 개념 및 특징을 설명하고 현재 활발히 진행되고 있는 다양한 서비스 표준안들과 GS1 표준의 레퍼런스 구현인 Oliot(Open Language for Internet of Things) 오픈소스 프로젝트를 소개하고, 실제 글로벌 비즈니스에서의 적용 사례들을 살펴봄으로써 사물인터넷 비즈니스 플랫폼으로써의 GS1 표준의 전망을 제시한다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2020.06a
• /
• pp.103-103
• /
• 2020

Drying Stream Assessment Tool and Water Flow Tracking (DrySAT-WFT)은 하천건천화 평가 및 예측을 위해 개발된 물수지 기반의 분포형 수문모형이다. 그러나 물수지 모형의 특성상 토양층 사이를 이동하는 수직적인 물의 거동은 파악하기 용이하나, 하천 및 지표를 따라 이동하는 물의 수평적인 거동 추적에는 한계가 있다. 본 연구에서는 DrySAT-WFT 모형에 댐·보 방류량을 고려한 하도 갈수량 추적 알고리즘을 적용하여 유출 모의 성능을 개선하고, 개선된 유출 모형을 금강 유역(9,915.5 ㎢)에 적용하여 건천화 원인 추적 및 평가를 수행하였다. 하천건천화 원인 추적을 위한 영향요소로 1976년부터 2015년까지 구축한 산림높이, 도로망, 지하수 이용량, 토지이용, 토심, 기상 자료를 활용하였다. 건천화 영향요소를 적용하기 전 기상자료만을 활용해 모의한 유출결과를 기준 시나리오로 설정하고 댐·보 지점을 대상으로 검보정을 진행하였다. 이후 각 건천화 영향요소를 적용한 유출 시나리오별 유량의 감소 비율과 건천화 기여 비율을 산정하여 영향평가를 수행하였다.

• The Korean Journal of Malacology
• /
• v.19 no.2
• /
• pp.161-169
• /
• 2003

Seawater and sediment quality analysed was calculated to examinate the present environmental characteristics and pollution load was also calculated to evaluate the effect of farming area on the coastal environment. The measurements for seawater quality demonstrate the coastal environment has relatively eutrophicated with significantly decreased DO (0.2-8.5 mg/l) and elevated COD (9.6-31.2 mg/l) in summer. It was also evident that the water quality in Jindong Bay has been influenced by residues tide from Masan Bay with high metal concentration in August of 2002. Annual total pollution load (land and farm-driven) was estimated at 37,316 ton (SS) /yr: 9,809 ton/yr (26.3%) of land-driven load, 23,576 ton/yr (63.2%) of coastal sedimentation and 3,932 ton/yr (10.5%) of feces of cultural organisms. When all ark shell seedling farms are permitted species conversion to ascidian farm, the pollution load would increase by 196%, which may be another source for accelerating the eutrophication of the environment in Jindong Bay.

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.33 no.1
• /
• pp.65-75
• /
• 2015

The findings of basic study on the awareness of falls in terms of Gwanpokdo(Paintings of Viewing Falls) were drawn as follows. First, there is a difference in an esthetic sense that water brings depending on the ratio of falls, and Gwanpokdo(Fall Landscape) in which falls take up more than 20% of the canvas focuses more on falls so that it brings about the awareness of landscape through direct communication with nature. Second, the diagonal composition of the canvas has symmetry between falls and a person viewing the falls, which makes view point even clear. In addition, margins of the canvas were missing due to the effect of True-View Landscape Painting during the late Joseon Dynasty, and overall composition of using the entire canvas became popular. This overall composition is stable and disposed with lopsided composition, so this heightens sense of balance and the meaning of falls. Third, Gwanpokdo(Paintings of Viewing Falls) of Josoen Dynasty showed various types of viewing falls in distant view, but as the distance between falls and persons got closer in the latter part of Joseon Dynasty, falls were no longer utopia but it expressed a sense of beauty and aesthetic contemplation through direct communication with real nature. Fourth, Gwanpokdo(Paintings of Viewing Falls) of Joseon Dynast had many drawings of a person viewing falls and viewing behaviors such as Supyeong gyeong(level landscape), Amgang gyeong(lower landscape), Bugam Gyeong(higher landscape), and glimpse viewing. Fifth, rocks out of landscape elements make falls vivid and are so expressed as yin and yang that falls and rocks are well contrasted with each other, maximizing beautiful scenery of falls. Sixth, woody plant of Gwanpokdo(Paintings of Viewing Falls) was mostly pine trees which symbolized the literati's fidelity and integrity at that time and emphasized the firm meaning of transcending the nature, matching with symbolization of falls.

• Journal of the Korean Wood Science and Technology
• /
• v.34 no.6
• /
• pp.1-11
• /
• 2006

Grafted tissues were investigated using various microscopic techniques. Pinus thunbergii was used as stock and scion and autografted by cleft graft method. Histochemically, grafting processes can be proceeded by four stages: 1) formation of necrotic layer, 2) proliferation of callus, 3) development of neo-cambium from callus, and 4) restoration of new vascular xylem. Necrotic la yer composed of pectin and lignin was gradually degraded during grafting process and disappeared when new union was formed between stock and scion. A large number of starch and lipid bodies in the cytoplasm were also gradually degraded during grafting process and disappeared at the grafting interface. Nucleus and plasmodesmata were not changed. Bubble-like callus was generated from all living parenchyma cells and from the callus. The tracheary elements differentiated from the callus had either reticulate or pit-like thickenings in the secondary walls with bordered pits. Secondary cell wall thickening occurred toward filing to the void parts between reticulated secondary wall. Tracheids formed in the secondary xylem were short with irregular wall thickness. New secondary xylem cells with swirled shapes, which developed in graft union were oriented horizontally and obliquely to axis of the stem.

• Journal of Korea Foresty Energy
• /
• v.25 no.2
• /
• pp.9-15
• /
• 2006

The quality of wood is largely depend on the characteristics of xylem tissue and their variation. They may include tracheid length, microfibril angle, distribution and amount of resin canal, as well as specific gravity as indicator of material properties. In this study, variation of these elements between and within 30 superior families of Pinus densifloa in progeny test forest were examined and the results are as follows; In terms of elongation ratio of tracheid length which is less than 1%, the sample tree showed a transition to matured wood after 13 years particularly in Kangwon 25, 30, 90, 56 and Chungnam 4 families. The average specific gravity were from 0.35 to 0.49, and differences between the families were significant. Number of transverse resin canal per unit area were also found to be significant between the families. The microfibril angles measured at 15th ring number ranged from 0.9 degree to 28.6 degree. More studies are necessary to tell whether these variation is inherited by genetic or individual characteristic. However it would be desirable that these elements be considered as key elements in the early stage of selection process of superior tree to ensure good quality of wood production in future.

• Journal of the Korea Concrete Institute
• /
• v.27 no.6
• /
• pp.651-659
• /
• 2015

Currently, social demands for long span building structures are increasing due to architectural planning purposes and economic efficiency. As a result, lighter board-type voiding materials were suggested. With the use of board-type voiding materials, a slab is able to become light weight and convenient. This process efficiently eliminates concrete where it is not required; considerably diminishing dead weight while maintaining the flexural strength of the slab. The reduction in concrete also allows for overall cost reductions and design flexibility. Also it can be ease with fixing the voided material that is composed of one body form. Although board-type voiding materials are ideal, the top and bottom concrete plates lack integrity. Because of this, test results show horizontal cracking towards the tops and bottoms of the concrete columns, or webs, connecting the slabs. The key to correcting this problem is to increase the shear strength. In order to increase the shear strength of the structure, horizontal shear area must increase. R70(100)-D-F has the largest horizontal shear area as it also shows stronger strength. As a result, shear strength ($V_{nh}$) is dependent on the horizontal shear area (N). $V_{nh}={\alpha}{\times}0.16{\sqrt{f_{ck}}}{\frac{{\pi}D^2}{4}}{\times}N({\alpha}=1.8125)$. The web columns have a shear span to depth ratio (a/d) that is less than 2; which classifies it as a deep beam. In this case, however, the shear strength of the deep beams may be as much as 2 to 3 times greater than that predicated conventional equations developed for members of normal proportions. As a result, ${\alpha}$ is suggested as an extra coefficient in the equation for shear strength ($V_{nh}$).