• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.109-110
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• 2016

본 논문에서는 현재 운행되고 있는 선형 유도전동기의 슬립주파수 고정 방식이 아닌 선형 유도전동기를 이용한 자기부상열차의 슬립주파수와 수직력 및 추진력과의 관계를 이용, 열차의 가감속시 운행패턴에 따라 운행 중 슬립주파수가 가변할 수 있는 슬립주파수 가변패턴을 형성, 선형유도전동기 자기부상시스템에서의 에너지 효율향상 가능성을 검증하였다. 슬립주파수와 수직력, 추진력과의 관계를 이용 슬립주파수 일정 실효치전류제어 알고리즘과 슬립주파수 일정 벡터제어 알고리즘을 사용하여 운전조건과 슬립주파수를 변경하며 운전조건에 따른 가장 효율적인 슬립주파수의 패턴을 형성하였다. 이 후 모의시험과 실차를 이용한 실험을 통해 알고리즘에 대한 정당성과 실제 효율의 증가를 통해 타당성을 검증하였다. 앞선 두 가지 알고리즘을 통해 열차부상에 영향을 미치지 않는 범위의 수직력을 가지는 범위내에서 슬립주파수를 가변 운전 조건에 따른 최적의 슬립주파수에 대한 정보를 기반으로 운행 중 가변하는 슬립주파수를 자동열차운전(ATO)시스템에 적용 모의실험을 통해 그 적용가능성과 효율을 검증하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.491-493
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• 2012

우리나라는 농업용수, 생활용수 등의 목적으로 여러 개의 호소 등을 설치하여 운영 중에 있다. 하지만 몇몇 호소들은 인구증가 및 산업발달로 인하여 매년 오염도가 증가하는 것으로 알려져 있으며, 특히 부영양화 현상으로 인하여 남조류가 과다번식 할 경우 호소 수질 및 수생태계에 악영향은 미치는 것으로 알려져 있다. 따라서 호소의 부영양화 현상을 제어하기 위한 많은 연구가 이루어지고 있으며, 부영양화 현상을 발생시킬 수 있는 여러 제한인자 중 인(P)에 대한 관심이 많아지고 있는 실정이다. 부상분리의 일종인 DAF는 침전공정의 대안으로서 25년 전부터 유럽과 미국을 중심으로 정수 및 하수처리 공정에서 이용되어 왔다. 가압부상공법에서 발생되는 기포의 크기는 $50{\sim}100{\mu}m$ 정도로 부상물질인 스컴이 파괴될 가능성이 낮고 기포의 크기가 작아 공기의 용해효율이 높으며 대전작용, 물리적 흡착효과 등의 특징을 가진다고 알려져 있다. 또한 공기와 물 뿐만 아니라 Al 성분의 응집제인 PAC를 이용하여 버블을 발생시킬 경우 인의 제거 효율이 크다고 알려져 있다. 가압부상공법의 경우 응집 침전 공정과는 달리 발생되는 처리과정에서 발생되는 부산물을 외부로 유출 시킬 수 있기 때문에 호소 수질정화에 이용될 수 있다고 판단된다. 따라서 본 연구에서는 저수지의 형태와 유사한 반응조를 설계하여 DAF를 주입하는 실내실험을 진행하였으며, 이를 통해 호소수질 정화를 위한 DAF의 타당성에 대해 평가하기 위해 이루어졌다.

• Journal of Aquaculture
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• v.18 no.4
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• pp.287-292
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• 2005

An 8-week of growth feeding trial was conducted to evaluate effects of the experimental extruded pellet (EP), commercial EP and raw fish-based moist pellet (MP) for growing flounder (Paralichthys olivaceus). Three replicate groups of the fish average weighing 43.5 g were fed four experimental diets (EP1, EP2, EP3 and EP4), four commercial diets (EP5, EP6, EP7 and EP8) and MP. Weight gain of fish fed the EP2, EP3 and EP4 was the highest among treatments, but not significantly different to that of fish fed the EPl, EP7 and MP. Feed efficiency and protein efficiency ratio of fish fed the MP were the lowest among treatments, but daily feed intake and daily protein intake of fish fed the MP were the highest among treatments. Moisture, lipid and ash contents of whole body were affected by diets, but protein content was not affected by diets. It is concluded that the dietary formulations used in the EP2, EP3 and EP4 can be applied in the practical exuded pellet feeds for growing flounder of 42-108g size.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.2
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• pp.213-220
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• 2016

This research aims to develop core technologies for passive carrier (no power in carrier itself) transfer system. The technologies are passive levitation, propulsion, and guidance, which can be great benefits for semiconductor and display manufacturing industries. Passive maglev carrier is necessary to precise position control for quiet and stable transfer operation. However, the structural characteristics of carrier and the installation errors of gap sensors cause the pitch motion. Hence, the controller design in consideration of pitch motion is required. This study deals with the reduction control of carrier pitch motion. PDA controller and PDA controller with pitch control are proposed to compare the pitch angle analysis. The pitch angle and the levitation precision are measured by experiment. Finally, the optimized design of pitch controller is presented and the effects are discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.3
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• pp.21-29
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• 1985

An effective technique of sludge separation is required for concentrated activated sludge process. The dissolved-air flotation (DAF) has been shown to be efficient process for sludge separation. The factors affecting DAF process for activated sludge separation are type and concentration of sludge, air/solid ratio, ratio of pressurized water flow, pressure, sludge detention time, temperature, sludge and hydraulic loading rate, recycle flow rate of sludge and type and quantity of chemical aid. In order to study the optimal operation condition for sludge separation, the influence factors such as type and concentration of sludge, ratio of pressurized water flow and pressure are investigated by the batch and continuous reactor experiments of DAF and sedimentation test. By the experimental investigation, the results are as follows; 1. For the bulking and concentrated sludge, DAF is more effective than sedimentation for the sludge separation. 2. In DAF, the critical ratio of pressurized water flow exist. The critical value varies with the pressure in the tank. That is, according to the pressure changes from 3 to $5kg/cm^2$, the critical value varies from 0.25 to 0.67 accordingly. 3. Pressure affects the ratio of pressurized water flow, but it does not show any influence upon the DAF efficiency directly. 4. Continuous experimental results was not better than those of batch.

• The Korean Journal of Pesticide Science
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• v.2 no.1
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• pp.32-39
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• 1998

This study was performed to develop jumbo granules floated and spreaded on the water surface after application, having low production and formulation cost, and safe to environment for paddy herbicides and to establish the formulation recipe. The jumbo granules of azimsulfuron with molinate(0.075+7.5%) was formulated by KCl as water soluble carrier and paraffin oil as solvent to impose the floating and spreading force to granules. That showed 100% of total granules to be floated on and spreaded upto the water surface within 25 minutes after application. Change in carriers, surfactants and pH did not affected to improve the time-course degradation of azimsulfuron in jumbo granules, but salt formation of azimsulfuron added by 1.15M solution of NaOH a little. Addition of N-methyl acrylate and modification of formulation process affected decrease in degradation of azimsulfuron upto 1.2, 2.1, and 7.2% after 2, 6 and 12 weeks under storage at $40{\pm}2^{\circ}C$, respectively, which showed the establishment of formulation recipe of the jumbo granules.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.203-204
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• 2009

The maglev guiderail systems, which receive directly the live load of maglev train and transfer the load to the main girder, is a important constituent in guideway system. As a process of development of maglev guideway girder adopting the precast decks, static and fatigue loading tests of the connections systems of precast deck and guiderail have been accomplished. In this stude, the structural characteristics of precast deck-guiderail connection systems are being evaluated by performing a detailed finite element analyses.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.3
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• pp.172-177
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• 2014

Low pressure air flotation (LAF) pilot plant for sludge thickening was installed in Chung Nam N.S. municipal waste water treatment plant to verify its application possibility. Effects of operating conditions such as coagulant dosages and microbubble water ratio on thickening of the mixed sludge were examined. Microbubbles which were generated in the chamber of $1.5kgf/cm^2$ by high speed collision method with foaming agent were used to float sludge. Solid loading of $30kg/m^2/hr$, solid contents in thickened sludge of 60,300 mg/L and SS removal efficiency of 99% were obtained through long period operating LAF in conditions of mixed sludge concentration of 14,400 mg/L, coagulant dosage of 27.6 mg/L, foaming agent addition of 4.0 mg/L and microbubble water injection ratio of 9.7%.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.1
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• pp.26-33
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• 1992

Physical experiments were conducted to investigate the suspension properties of silty mud in combined wave-current flow. Suspension mass when there was opposing current was much higher than that when there was following current. It is due to the fact which strong turbulent flow in the bottom is developed in the opposing current but oscillatory flow effect decreases in the following current. Critical bed shear stress for suspension of silty mud in combined wave-current flow was deduced to be $\tau$$_{c}$～0.045 N/$m^2$. Formulas expressing the relation with initial suspension rate with bed shear stress, and the relation between the former and measured significant wave height were deduced. The relationship of initial suspension rate with bed shear stress was significantly scattered, but the relationship with measured significant wave height was reasonably good. When there is wave only, vertical diffusion coefficients of sediment were calculated from the vertical concentration gradients of suspended sediment when the concentration of suspended sediment approached to nearly equilibrium state. The diffusion coefficient increased exponentially with height from the bottom in the lower half of the flow depth but were nearly constant in the upper half of the flow depth.h.

• The Korean Journal of Pesticide Science
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• v.10 no.1
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• pp.28-35
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• 2006

This study was conducted to optimize formulation factors of a self-dispersible floating granule of flucetoaulfuron that can be used at a low application volume (5 kg $ha^{-1}$). SPA and xanthan gum were selected as a binder because blending of them showed good granulation and floatation. Potassium chloride selected as a filler also showed good granulation, floatation and disintegration properties. Among wetters and dispersants, Surfynol 440 gave the best dispersibility The optimum granule size was determined to be 1.0 mm considering floating time and dispersibility. Flucetosulfuron was mixed with the blend of SPA and xanthan gum, potassium chloride, and Surfynol 440 and formulated as a floating self-dispersible granule at 1.0 mm in diameter. Indoor and outdoor field experiments showed that the floating granule of flucetosulfuron performed well, covering long range from the application spot up to 15 m in weed control. Therefore, this floating technology may be used for laborsaving herbicide formulation development and help to reduce workloads for herbicide application.