• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.11
• /
• pp.1028-1034
• /
• 2004

Recently, the ice storage system using ice slurry has been used increasingly since it has been introduced where the rapid cooling load change is required. Because it overcomes a decrease of the melting performance and an increase of the thermal resistance on the ice layer in static ice thermal storage system. This study is performed to understand the effects of transporting ice slurry through horizontal, vertical and inclined tubes ($30^{\circ},\;45^{\circ}$). It used propylene glycol-water solution and ice particles (diameter of about 2 mm) in this experiment. The experiments were carried out under various conditions, with concentration of water solution ranging from 0 to $20wt\%$, and velocity of water solution at the entry ranging from 1.5 to 2.5 m/s. The results were as follows: Regarding the angle of inclined tube, the highest pressure loss was measured for vertical tube and the pressure loss for $45^{\circ},\;30^{\circ}$, horizontal straight tubes were lower successively. The lowest pressure loss in these tubes was measured at velocity of $2.0{\sim}2.5m/s$ and concentration of $10wt\%$. The outlet IPF was likewise stable in these ranges.

• Journal of Ocean Engineering and Technology
• /
• v.20 no.3 s.70
• /
• pp.61-66
• /
• 2006

The estuary has a very complex coastline and bottom topography. Before the close of floodgate, the Keum river estuary was deposited with sediment from the Keum river, created bythe construction of the Keum river estuary dike. So, a periodical dredging is necessary to assure water depth for boat entry and departure to Kunsan port. Theof this study is to find the change of tidal current of M2tide and the topography before and after construction at the Geum River estuary dike. The change of water depth is investigated by digitizing the sea map (No.305) of Kunsan port, which was edited by National Oceanographic Research Institute. The calculated co-range and co-tidal charts of M2tide before the dike construction are similar to the observed ones. Therefore, the amplitude and phase after construction at Geum River estuary dike increases compared to before construction at Geum River estuary dike. The scour occurred in the A-A' section.

• Journal of Advanced Research in Ocean Engineering
• /
• v.4 no.4
• /
• pp.146-162
• /
• 2018

The unsteady problem of a rigid body impact onto a floating plate is studied. Both the plate and the water are at rest before impact. The plate motion is caused by the impact force transmitted to the plate through an elastic layer with viscous damping on the top of the plate. The hydrodynamic force is calculated by using the second-order model of plate impact by Iafrati and Korobkin (2011). The present study is concerned with the deceleration experienced by a rigid body during its collision with a floating object. The problem is studied also by a fully-nonlinear computational-fluid-dynamics method. The elastic layer is treated with a moving body-fitted grid, the impacting body with an immersed boundary method, and a discrete-element method is used for the contact-force model. The presence of the elastic layer between the impacting bod- ies may lead to multiple bouncing of them, if the bodies are relatively light, before their interaction is settled and they continue to penetrate together into the water. The present study is motivated by ship slamming in icy waters, and by the effect of ice conditions on conventional free-fall lifeboats.

• International conference on construction engineering and project management
• /
• 2022.06a
• /
• pp.599-607
• /
• 2022

Recently, there has been a steady decrease in the proportion of the construction sector among Korean engineering firms. Thus it is essential for Korean engineering firms in the construction sector, which lack experience in overseas ventures, to identify and improve their competitiveness for successful overseas expansion. Therefore, in this study, changes in Korean engineering firms' capabilities for the last decade were analyzed to promote entry into overseas road and water resource engineering markets. Competency factors that require urgent improvement were derived based on Importance-Performance Analysis (IPA) as a tool for quantitative measurement. As a result, the factor that shows low performance compared to the importance is an overall understanding of the target country in the road and water resource areas. Knowledge of regulatory issues on design, the ability of time management software, and knowledge of the regulatory problems on construction safety are also insufficient. This study can be used as a research methodology to identify competitiveness that Korean engineering firms have to strengthen when they advance into overseas markets in roads, water resources, and other areas.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2021.06a
• /
• pp.45-45
• /
• 2021

국내 물시장은 100%에 가까운 상·하수도 서비스 수준을 달성한 지 오래다. 결과적으로 국내 물시장은 한계에 이르렀다는 평가와 함께 국내 물산업의 지속가능한 발전을 위해서는 포화된 국내 시장을 벗어나 해외 신시장을 발굴해야 한다는 견해가 보편적이다.. 이에 정부에서는 2006년 물산업 육성 전략을 수립한 이래 국내 물기업의 해외시장 진출을 위한 많은 정책과 전략을 제시하였다. 하지만 20여 년의 시간이 지난 오늘날 국내 물산업의 해외 시장 진출 성과에 대한 평가는 회의적이다. 이유는 해외 물시장 관련 국내 물기업의 레퍼런스 부족 및 영세성, 기술 부족 등 다양하다. 문헌이나 전문가 견해 등을 살펴보면 세계 물시장의 특성은 ① 첨단 기술기반의 글로벌화, ② 운영관리 시장의 확대, ③ 물기업의 토털 솔류션화(제조+건설+엔지니어링+운영관리), ④ 기후변화 대비 신규시장 형성 등으로 요약된다. 그러나 모든 시장이 이것으로 대변되지는 않는다. 즉 시장은 국가와 지역에 따라 차이가 크다. 따라서 차별성을 고려하지 시장의 진출은 실패로 종결될 수 밖에 없다. 이에 본 연구는 지역별·국가별 특성을 고려한 물시장 진출 전략의 필요성 관점에서 타겟시장으로 주목을 받고 있는 국가 우즈베키스탄의 시장성에 관하여 살펴본 후 대응 전략을 검토하고자 한다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.71-71
• /
• 2022

국내 물시장은 100%에 가까운 상·하수도 서비스 수준을 달성한 지 오래다. 결과적으로 국내 물시장은 한계에 이르렀다는 평가와 함께 국내 물산업의 지속가능한 발전을 위해서는 포화된 국내 시장을 벗어나 해외 신시장을 발굴해야 한다는 견해가 보편적이다.. 그리고 정부에서는 2006년 물산업 육성 전략을 수립하는 한편 국내 물기업의 해외시장 진출을 위해 다각적인 정책을 수립·추진하고 있다. 이에 본 연구는 지역별·국가별 특성을 고려한 물시장 진출 전략의 필요성 관점에서 타겟시장으로 주목을 받고 있는 국가 사우디아라비아의 물시장 특성을 검토함으로써 국내 기업의 현지 진입 전략을 제시하였다. 사우디아라비아 정부는 '비전 2030'에 의거 시설 및 서비스 확대, 민간참여 등 물 부문의 성과목표를 제시하였으며, 물시장 규모는 2021년 기준 116억 $ 규모로 추정된다 추정된다(GWI, 2021). 현지 물시장 관련 SWOT 분석 결과는 인프라와 담수화 분야에 대한 지속적 투자 및 시장 개방화, 그리고 다수의 레퍼런스 보유 등이 기회이자 강점인 반면 오일머니 중심의 산업구조, 정부 중심의 투자, 높은 시장경쟁 등은 약점이자 위기로 분석되었다. 그리고 본 연구는 현지 물시장 진입 전략으로 첫째, 현지 정부 및 기업과의 협력 강화를 통한 정보취득, 둘째, 향후 성장 가능성이 높은 담수화 관련 에너지 효율 제고, 막힘현상(파울링) 등에 대한 혁신 기술 및 가격경쟁력 확보, 셋째, 프로젝트 수주, 소재·부품 등의 수출을 위한 현지화(지사, 사무소, 연구소 등 개설) 등을 제시하였다.

• Journal of Convergence for Information Technology
• /
• v.9 no.6
• /
• pp.7-12
• /
• 2019

In order to shoot underwater, the photographer must be equipped with shooting equipment and enter into the water. Since the photographer directly enters the water, safety accidents occur frequently due to various obstacles or deep water in the water. The proposed underwater stereo photography technique can solve the safety accident problem caused by the entry of the photographer into the water by using the drone for underwater photographing. In addition, this technique has the advantage of obtaining underwater images at low cost. In this study, the angle of the proposed cam for stereoscopic photography was analyzed and the condition that the proper stereoscopic image can be viewed was defined as the distance from the floor of 18cm to the floor distance of 41.4cm. This provision is proposed to be used to adjust the height of the shooting area descended by the elevation chain of the water surface hovering drones.

• Journal of the Korean Society of Groundwater Environment
• /
• v.4 no.3
• /
• pp.144-152
• /
• 1997

In this study the experiment on water retention cure was conducted by using a volumetric pressure plate extractor for two different soils (SUS and KUS). When the volumetric pressure plate extractor is used, the volume of water removed from the soil sample at each increasing pressure step can be accurately measured and retained. When pressure values are subsequently reduced, the volume of water that returns to the soil can then also be accurately measured. The hysteresis effect of water retention curve was considered in the experiment. Parameters of water retention function were estimated by fitting experimental data with three proposed equations. Results of estimation showed that parameters of Gardner, Brooks-Corey and van Genuchten equations were found to be associated with air-entry value and width of size distribution. Consequently van Genuchten equation was proved to be best fined through the measured data points.

• Journal of Biosystems Engineering
• /
• v.32 no.6
• /
• pp.448-454
• /
• 2007

This study was conducted to develop a 100 kPa soil tensiometer mainly consisted of a porous ceramic cup, water-holding tube, and a digital vacuum gauge, through theoretical design analysis and experimental performance evaluation. Major findings were as follows. 1. Theoretical analysis showed that air entry value of a porous media decreased as the maximum effective size of the pore increased, and the maximum diameter of the pores was $2.9\;{\mu}m$ for measuring up a 100 kPa of soil-water tension. 2. Property analysis of tensiometer porous cups supplied in Korean domestic market indicated that main components were $SiO_2$ and $Al_2O_3$ with a porosity range of $33.8{\sim}49.3%$. 3. The porous cup selected through sample fabrication and air-permeability tests showed weight ratios of 87% and 11% for $Al_2O_3$ and $SiO_2$. The analysis of SEM (scanning electron microscope) images showed that the sample was sintered at temperatures of about $1150^{\circ}C$, which consisted of pores with sizes of up to 25% of those for commercial porous cups. 4. The prototype soil tensiometer was fabricated using the developed porous cup and a digital vacuum gauge that could measure water tension with a pressure of 85 kPa in air tests. 5. In-soil tests of the prototype conducted during a period of 25-day drying showed that soil-water tension values measured with the prototype and commercial units were not significantly different, and soil-water characteristic curves could be established for different soils, confirming accuracy and stability of the prototype.

• Journal of Fisheries and Marine Sciences Education
• /
• v.28 no.6
• /
• pp.1602-1613
• /
• 2016

Since Ballast Water Management Convention has been adopted, Ballast Water Management Convention is not effected yet. This convention will only enter into force 12 months after its ratification by 30 states, collectively representing 35% of world merchant shipping tonnnage. Morocco, Indonesia and Ghana have ratified this convention during last 29th IMO Assembly meeting which was held in November 2015. In 2016, Belgium, Fiji, Saint Lucia and Peru have become the latest countries to ratify the convention. As of now, 51 states and 34.87% combined merchant fleets are being calculated. BWM convention will be applied to not only new ships but also, existing ships after it is effected. Thus, existing vessel will be retrofitted a Ballast Water Treatment System according to D-2 Requirement until first IOPP nenewal survey after date of entry into force of the convention. Currently, about 65 BWTSs certified by Administration will be reported to IMO, even type of BWTSs is very various. Thus, a risk of each BWTS can be existed, and this existed risk can be also effected to ship's crew safety and protection of ship's own property. Therefore, we have evaluated a risk assessment for an existing vessel retrofitting an ultra violet type Ballast Water Treatment System which is mostly developed in the world. And we described the procedure of selecting a sample vessel, consequently, bulk carrier is selected because this vessel kind is mostly charged in the world. Especially, DWT 175K size is selected. Risk Assessment is using a HAZID and HAZOP method, evaluation method is referred to IMO Document "Considerated test of the Guidelines for Formal Safety Assessment (FSA) for use in the IMO rule-marking process(MSC/Circ.1203-MEPC/Circ.392)". The Risk Assessment Section is decided to 3 Nodes, Consequently, total risks have evaluated 51 items.