• Title/Summary/Keyword: Volume Efficiency

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CAVITATION ANALYSIS IN A CENTRIFUGAL PUMP USING VOF METHOD (VOF기법을 이용한 원심펌프 내의 공동현상에 관한 유동해석)

  • Lee, W.J.;Lee, J.H.;Hur, N.;Yoon, I.S.
    • Journal of computational fluids engineering
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    • v.20 no.4
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    • pp.1-6
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    • 2015
  • Centrifugal pumps consume considerable amount of energy in various industrial applications. Therefore, improvement of the efficiency of these machines has become a major challenge. Cavitation is a phenomenon which decreases the pump efficiency and even causes structural demage. Hence, the goal of this paper is to investigate the cavitation problem in the single-stage and double-stage centrifugal pumps. The Volume of Fraction (VOF) method has been used for the numerical simulations together with Rayliegh-Plesset model for the gas-liquid two-phase flow inside the pump. In order to capture the turbulent phenomena, the standard k-${\varepsilon}$ turbulence model has been adopted, and the simulations have been done as unsteady cases. In addition, the motion of the rotating parts has been simulated using Multi Reference Frame(MRF) method. The results are presented and compared in terms of hydraulic head and NPSH for both the single-stage and double-stage pumps. The H-Q curves show the effects of cavitation on decreasing the pumps performances.

Physical and Chemical Effects on the Sonication Treatment of Chitosan Solution

  • LEE Keun-Tai;PARK Seong-Min;PARK Chan-Kyu;KIM Sang-Moo
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.29 no.6
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    • pp.843-848
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    • 1996
  • As the first step of studies related to production of chitooligosaccharides by physical methods, chitosan solution were sonicated with 20 kHz and various treatment effects were examined to present fundamental data of sonicated chitosan solution. Intrinsic viscosity of chitosan solution sharply decreased from 3.76 dl/g to 2.90 dl/g until 5 minutes of sonication and then slowly decreased. With low volume of chitosan solution, sonication was very effective and temperature of chitosan solution slightly affected the efficiency of sonication. In case of changing the solvent, no significant differences were observed on the effect of sonication, however, acetate buffer had highest sonication effect among various solvents. The sonication effect was increased as the increasement of the value of pH, on the contrary, ionic strength and type of counterions showed no effect on sonication. With these results, we assumed that optimal sonication treatment would be as follows, solution volume was $10\~20\;ml$, temperature range was $20\~30^{\circ}C$, pH value of solution was 4.5 and type of solvent was acetate buffer.

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Runoff Hydrological Analysis in Soyanggang-dam watershed using SLURP Model (SLURP 모형을 이용한 유출수문분석 - 소양강댐 유역을 대상으로 -)

  • Lim, Hyuk Jin;Shin, Hyung Jin;Kwon, Hyung Joong;Jang, Cheol Hee;Kim, Seong Joon
    • Proceedings of the Korea Water Resources Association Conference
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    • 2004.05b
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    • pp.1142-1146
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    • 2004
  • The objective of this study is to the test applicability of SLURP on Soyanggang-dam watershed. The area of this watershed is $2,694km^2$ and mean elevation and slope is 650 m and $23^{\circ}$ respectively. Topographical parameters were derived from DEM using TOPAZ and SLURPAZ. NDVI was calculated from multi-temporal NOAA/AVHRR images. The daily meteorological data and hydrograph during $1999\~2001$ were selected for model calibration and performance tests. Weather elements (dew-point temperature, solar radiation, maximum and minimum temperature, relative humidity) were required from the S meteorological stations near the study area. The model parameters of each land cover class were optimized by sensitivity analysis and SCE-UA method. Runoff rate shows $49.33\%\~64.06\%$. Simulated results during 4 years were estimated by Nash-Sutcliffe efficiency and WMO volume error. Nash-Sutcliffe efficiency shows $0.61\~0.75$ and WMO volume error shows $6.1\%-18.8\%$.

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Effects of Rhizome Length and Node Numbers on the Proliferation of Menyanthes trifoliata Cuttings (조름나물 삽목 시 지하경의 길이와 마디 수에 따른 증식효율)

  • Lee, Gwang-Moon;Kim, Jae Geun
    • Journal of Wetlands Research
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    • v.14 no.2
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    • pp.193-198
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    • 2012
  • To enhance the proliferation efficiency of Menyanthes trifoliata L. endangered species in Korea, various rhizome cuttings were tested based on cutting length and node numbers. Growth length and increased volume of rhizomes were highest on long cuttings of 10-18cm length. But relative growth length of rhizomes were higher in short cuttings of 2-4cm and medium cutting of 4-10cm length than in long cuttings. Relative increased volume of rhizomes was highest in medium cuttings. The node numbers were not contributed to the efficiency of relative growth of rhizomes. This study suggests that medium length cutting is the best practice for the proliferation of M. trifoliata.

Combined Effects of Container Volume and Fertilizer Level on Plant Growth, Physiological Characteristics, and Nutrient Uptake of Vinca Plant (Catharanthus roseus)

  • Kang, Jong-Goo;Chon, Sang-Uk
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.55 no.3
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    • pp.268-274
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    • 2010
  • The aim of our study was to investigate the interactive effects of container size and nutrient supply on plant growth, chlorophyll synthesis, transpiration, $CO_2$ assimilation, water use efficiency (WUE), and nutrient uptake of vinca plant (Catharanthus roseus). A complete experiment utilizing four concentrations of fertilizer and three volumes of containers was conducted. As the container size was increased, the plant height, leaf area, and dry weight of vinca significantly increased regardless of fertilizer level. The leaf area and dry weight of vinca were highly sensitive to the container size. However, the chlorophyll contents of vinca 20 days after the transplant significantly increased with decreasing container sizes and increasing fertilizer concentrations. Significant differences in transpiration and $CO_2$ assimilation occurred with the use of differentfertilizer solutions, but the highest values for transpiration and $CO_2$ assimilation were in plants grown in the 15 cm-diameter containers. The highest water use efficiency was observed in the plants grown in 10 cm-containers with 4 dS/m of fertilizer, and there were no significant differences in WUE values among container sizes with fertilizer concentrations of 0, 1, or 2 dS/m. No significant difference in nutrient uptake was observed among the fertilizer levels or among the container sizes. However, at a fertilizer concentration of 4 dS/m, the uptake of several nutrients, including N, P, K, Ca, Mg, B and Fe, was higher in small containers than in larger ones.

Distance-based SAP Algorithm for Effective Collision Detection (효율적인 충돌 검출을 위한 거리 기반 SAP 알고리즘)

  • Oh, Min-Seok;Park, Sung-Jun
    • Journal of Korea Game Society
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    • v.12 no.4
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    • pp.23-31
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    • 2012
  • The collision processing is one of the essential factors to realize physical principles in the game, and it gives liveliness to the game. The collision processing requires a large amount of operations, and significantly affects the game performance. To address this problem, many studies have been conducted to reduce the operation volume, and the SAP algorithm is being widely used. However, its efficiency is low because it involves repetitive operations. In this study, a distance-based SAP algorithm was proposed to reduce the operation volume for the collision processing and address the problem of the SAP algorithm. A test was conducted to measure the FPS using the simulation program, which was developed with the proposed algorithm. The FPS was 2-33 times higher with the proposed algorithm, which indicated that the efficiency of the collision processing was improved.

Enhancement of Dye Adsorption on TiO2 Surface through Hydroxylation Process for Dye-sensitized Solar Cells

  • Jang, Inseok;Song, Kyungho;Park, Jun-Hwan;Oh, Seong-Geun
    • Bulletin of the Korean Chemical Society
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    • v.34 no.10
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    • pp.2883-2888
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    • 2013
  • To enhance the power conversion efficiency of dye-sensitized solar cell (DSSC), the surface of titanium dioxide ($TiO_2$) photoelectrode was modified by hydroxylation treatment with $NH_4OH$ solution at $70^{\circ}C$ for 6 h. The $NH_4OH$ solutions of various concentrations were used to introduce the hydroxyl groups on $TiO_2$ surface. As the concentration of $NH_4OH$ was increased, the short-circuit current density ($J_{SC}$) value and conversion efficiency of solar cells were increased because the amount of adsorbed dye molecules on $TiO_2$ surface was increased. As a result of the surface modification to introduce hydroxyl groups, the concentration of adsorbed dye on the $TiO_2$ surface could be improved up to 32.61% without the changes of morphology, surface area and pore volume of particles. The morphology, the specific surface area, the pore volume and the chemical states of $TiO_2$ surface were characterized by using FE-SEM, $N_2$ adsorption-desorption isotherms and XPS measurements. The amount of adsorbed dye and the performance of fabricated cells were analyzed by using UV-Vis absorption spectroscopy and solar simulator.

Effect of Sludge Characteristics on the Thickening of Bulking Sludge using DAF (Dissolved Air Flotation) (슬러지의 성상이 DAF(Dissolved Air Flotation)를 이용한 팽화 슬러지 농축에 미치는 영향)

  • Kim, Dong-Seog;Park, Young-Seek
    • Journal of Korean Society on Water Environment
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    • v.22 no.1
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    • pp.97-103
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    • 2006
  • Excess sludge treatment and disposal currently represent a rising challenge for domestic or wastewater treatment plants due to economic, environmental and regulation factors. Conventional gravity sedimentation process has been widely used in sludge thickening. The operation method of the process is very simple, but the process requires long detention time for sludge thickening, uses polymers, and shows low sludge thickening efficiency. To solve the problems, we studied on DAF (Dissolved Air Flotation) system. We use bulking sludge of a paper manufacturing plant. The effects of parameters such as SVI (Sludge Volume Index), storage time, initial concentration and wet density of excess sludge were examined. The results showed that the more SVI was low, the more sludge was thickened. As storage time goes by, SVI was increased and thickening performance was deteriorated. In order to improve flotation performance at high concentration, high recycling ratio and pressure did not increase the concentration due to thickening limitation. The addition of 0.8 g/L of loess was increased flotation efficiency of 1.41 times.

Enhancing photoluminescence of Au - TiO2 nanoparticles using Drude model

  • Dang, Diem Thi-Xuan;Vu, Thi Hanh Thu
    • Journal of IKEEE
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    • v.21 no.3
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    • pp.288-296
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    • 2017
  • The enhancement of photoluminescence of Au-$TiO_2$ nanoparticles by surface plasmon resonance has been studied extensively by experiment in recent years. For the purpose of optimizing the photoluminescence property of Au-$TiO_2$ nanoparticles, the manufacturing parameters related to the Au nanoparticles and $TiO_2$ nanoparticles need to be considered. In this paper, Drude model and Maier's effective volume method are used to analyze the variation of the metal nanoparticle radius, separation between metal nanoparticle and dielectric molecule, and total absorption cross-section with original radiative efficiency on the photoluminescence property of Au-$TiO_2$ nanoparticles. The results show that to obtain the optimized enhancement factor for photoluminescence process, the size of Au nanoparticle is about 13 - 20 nm, the separation between Au nanoparticle and $TiO_2$ molecule is about 5 -15 nm, the total absorption cross-section of $TiO_2$ molecules is about $1-100nm^2$ and the original radiative efficiency of $TiO_2$ molecule is weak about 0.001- 0.1. With these fabrication parameters, the photoluminescence property of Au-$TiO_2$ nanoparticles can be enhanced several thousand times compared to traditional $TiO_2$ nanoparticles.

Cooling Cycle for Energy Saving (에너지 절약용 냉방사이클)

  • Lee, Hung Joo;Kim, Yong Ku
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.1 no.2
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    • pp.116-127
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    • 1989
  • Research on reheating cooling cycle and its practical application have been made to prevent unequalized distribution of temperature and humidity of room due to lack of supply air volume and dewdrops on supply diffusers to be taken place as a result of lower temperature of supply air than that of dew point of room air in cooling cycle of constant air volume, single duct, single zone and draw-through fan type. In view of the fact that human body is insensitive to humidity, it is possible not only to construct the complete non-reheating cooling cycle by increasing the humidity point allowable with the deduction of occupant's sense of pleasantness minimizing, but also to get cooling cycle decreasing the reheating quantity if the humidity exceeds the point allowable. In addition, it is possible to save maximum 8% in electric energy for cooling in cooling system by constructing non-reheating cooling cycle instead of reheating cooling cycle and by increasing the relative humidity of room from 50% to 65% in case efficiency and air pressure of cooling system are low. It is also possible to get an optimum cooling cycle by determining the room humidity in consideration of pleasantness of occupants and conservation rate of electric energy if the cooling capacity, efficiency and total pressure of cooling equipment are fixed.

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