• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.946-953
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• 2012

When water shortage has been getting worse recently, toilet water-saving is one of the most effective way to solve the water shortage. Therefore, in this study, toilet flushing performance was investigated with VOF(Volume Of Fluid) model to obtain the basic design data for the development of high-efficiency toilets. The result showed that the shorter trapway, the longer the flushing duration time. However, the shorter trapway is found to have disadvantage in exhausting dirt due to relatively weak siphon and higher curvature. Since the remaining water in a trapway appears to help siphon, it is also an important factor in developing high-efficiency toilets. Although higher water level in the water tank shows better performance in flushing, lower water level is preferred to save water. Too low water level may cause dirt to clog the trapway due to relatively weak siphon.

• Economic and Environmental Geology
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• v.44 no.2
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• pp.153-159
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• 2011

A comprehensive mechanistic model has been used to determine the flow pattern for gas-oil two-phase flow in pipes of petroleum production system. Depending on operational parameters, geometrical variables, and physical properties of the two phases, the two phases shows a specific flow patterns. For different parameters of the system, How pattern were compared for wide range of superficial velocities of oil and gas. In a variety of parameters, the inclinational angle and superficial velocities of oil and gas are the most dominant factors in determining the flow patterns for two-phase flow in pipelines. Other parameters such as pipe diameter and fluid properties have a limited effect on the change of flow patterns except for near transition. The mechanistic model is shown to be useful to determine the flow pattern in situations where either an experimental evaluation in a laboratory or reliable correlations are not available.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.9
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• pp.589-596
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• 2016

Recently organic flash cycle (OFC) has been proposed which is a vapor power cycle where heat addition occurs with the working fluid remaining in the liquid state. This study proposes a modified OFC with regeneration and carries out thermodynamic performance analysis of the system utilizing low-temperature heat source in the form of sensible energy. Effects of working fluid and flash temperature are systemically investigated on the system performance such as net power production and thermal efficiency. Results show that the net power production has a peak value with respect to the flash temperature but the thermal efficiency increases with the flash temperature. The regenerative system shows higher thermal efficiency compared to the original OFC and improved potential for recovery of low-temperature heat sources.

• Journal of Energy Engineering
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• v.21 no.2
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• pp.144-151
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• 2012

A district heating system produces thermal energy and supplies it to a large region. District heating systems can provide higher efficiencies and better pollution control than localized boilers. The heat generated by a district heating system is distributed to the customer via a network of insulated pipes. For the optimal operation of a district heating system, it is important to predict the distributions of pressure, flow rate and temperature of heating fluid within the network of pipes at various operating conditions. In this work, a mathematical modeling was performed to predict the dynamic hydraulic-thermal behaviors of heating fluid in the network of pipes for a district heating system. The mathematical model accounts for the conservations of mass, momentum and energy. In order to verify the validity of modeling, the modeling results were compared with the monitoring data of Gang-nam Branch of District Heating.

• Journal of the korean veterinary medical association
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• v.37 no.6
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• pp.566-572
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• 2001

체세포 수는 유우유선염증의 측정에 일반적으로 수용되었다. 염증에 대단히 중요한 유방염은 미생물의 존재 또는 유선에 감염된 것이 원인이 된다. 세계의 현대 낙농생산국 들은 SCC는 사람소비가 확대되는 우유 질과 안전성 측정에 유용하다라는 것에 동의한다. 그리고 거의 모든 나라들은 상한 이상을 이룩하였고, 우유는 가공공장에 운반하지 않거나 상한 이상은 현금으로 벌을 취한다. SCC는 우유와 유제품의 국제무역에서 지레 대(leverage)의 힘으로 또한 작용한다. 현재 SCC에 관련된 국제표준은 없다. 그러나 Codex표준과 같은 국제표준은 소비자를 도와 줄 것이다. 그리고 이들에 대한 것을 우유와 유제품국제무역에 포함 시키는 것이다. 많은 것을 낙농목장 내 유방염관리와 낮은 SCC우유생산에서 배웠다. 그리고 우리 지식의 현재상태는 400,000 초과 세계표준은 적절할 수가 없다는 것을 제시하였다. 낙농생산국들은 우유에 허용될 수 있는 염증산물의 수용량에 관하여 동의 되는 것이 필요하다. 염증산물은 현실적으로 SCC에 의한 것이 가장 좋은 측정이 된다 SCC에 대한 국제표준화 이익은 소비자와 낙농산업 양자에게 줄 수 있을 것이다.

• Proceedings of the Malacological Society of Korea Conference
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• 2001.11a
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• pp.37-38
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• 2001

굴과 같은 이매패 양식장에서의 어장 환경 용량은 생물 서식환경의 질적, 양적 저하 없이 지속적으로 생산할 수 있는 생물의 양이라고 할 수 있다. 즉, 환경용량이란 환경의 악영향을 미치지 않으면서 지속적으로 최대 생산을 얻을수 있는 최대 생산을 오염부하 즉 자정 능력적 의미를 포함한다고 볼 수 있다. 연안 양식장은 대상해역에 따라 해수유동과 같은 물리적 특성, 해역이용 실태, 오염부하량 등 환경특성이 다양함으로 환경용량은 서로 다르다고 볼 수 있다. 이 연구에서는 통영시에 인접하여 도시하수의 영향으로 인하여 부영양화 되어 있다. 굴 양식이 행하여지는 북만을 대상으로 하여 양식 생물을 수용할 수 있는 환경용량을 생태유체역학 모델(藏本·中田,1991)을 이용하여 산정하고, 최적환경을 유지하기 위한 방안들을 검토하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.126-131
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• 2017

Numerical analysis using commercial CFD code was carried out to develop the drag force type vertical axis hydraulic turbine for the improvement of the production efficiency of small hydro energy at low flow velocity condition. Blade pressure changes and internal flows were analyzed according to the presence or absence of the hydraulic turbine blade holes at flow velocity of less than 1.0~3.0 m/s. According to the numerical results, the pressure and flow velocity is severly affected by the flow velocity in turbine blade with no holes, while the influence of flow velocity is comparatively decreased in turbine blade with holes. It is also found that the pressure and flow velocity on the blade surface with holes are evenly distributed with no singular location and it is believed that forming a hole in the blade may be helpful in terms of structural safety.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.4
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• pp.340-349
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• 2012

The mitigation of gap between technology and it's applicability in the oil and gas industry has led to a rapid development of deepwater resources. Historically, subsea wells have good track records. However, an ever increasing water depths and harsher environments being encountered are currently posing challenges to subsea production. Complex subsea systems are now being deployed in ways rarely encountered in previous development schemes. These increasingly complex systems present a number of technical challenges. This study presents the challenges in subsea production systems, considering the technical and safety issues in design and installation associated with current development modality.

• KSBB Journal
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• v.9 no.1
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• pp.85-90
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• 1994

The Gellan-type polysaccharide produced by Pseudomonas elodea(ATCC 31461) is one of the new heteropolysaccharides, having useful properties as gelling, suspending, stabilizing, emulsifying and binding agents in aqueous systems. Medium compositions for growth stage and production stage are improved. The problems of low cell concentration and poor productivity in highly viscous fermentation were attributed to inadequate mixing accompanied by insufficient oxygen transfer. During continuous culture, cell growth and polysaccharide production were greatly affected by the apparent viscosity, and they showed oscillation behavior, i.e. as the product concentration increases, cell concentration decreases. With improved culture conditions, the productivity of continuous culture increased up to 0.6g/$\ell$/hr(6-fold that of batch culture ) at dilution rate, D=$0.14hr^{-1}$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.1
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• pp.112-116
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• 1999

In theprevious Hizikia cultivation, holdfasts were threw into the sea after harvesting in May; the young thalli(5$\~$10cm in length) of Hizikia are annually collected from natural bed by seed collectors for the cultivation, resulting in a ruined natural populations. Therfore, the reuse method of holdfasts by regeneration capability of Hizikia fusiformis, was investigated. The effects of emergence on the growth of regenerated thalli from holdfasts over 6 months of outdoor culture from May to November, 1995. The vegetative growth from the holdfasts was good under the emergence of 3hrs/day on the air than 0, 1 and 2hr/day. The regeneration of holdfasts was determined by measuring total length, number of stipe and weight. The growth was facilitated under the exposure condition of 1$\~$3 hrs/day on the air. Outdoor cultivation for the comparsion of to artifical natural seeds were conducted from December 1995 to May 1996. There was no significant differences(0.05< P) between the two kinds of seeds. Therefore, artificial seed maybe used as a replacement for the natural seed in Hizikia cultivation. From the results, an useful method was established to obtain young fronds for the cultivation using the reuse method of holdfast, to conserve the natural population of Hizikia.