• Journal of Korean Society of Environmental Engineers
• /
• v.39 no.12
• /
• pp.706-713
• /
• 2017

This study compared and analyzed the water treatment efficiency and the applicability of water treatment plant using the existing Mechanical Rapid-Mixer by introducing the Non-powered Vortex Mixer to the domestic water treatment plant. For this study, fluid flow characteristics and head loss of a Non-powered Vortex Mixer are calculated by Computational Fluid Dynamics (CFD)respectively. The head loss rate inside the mixer was 11.30% when the inflow velocity was 0.5 m/sec, 16.27% at 0.6 m/sec and 21.44% at 0.7 m/sec, the head loss rapidly increased at the optimal velocity of 0.5 m/sec. For the inflow velocity of 0.5 m/sec, the turbulent intensity at the inlet was 2.37% and at the outlet was 7.83%, so there was sufficient mixing strength for the particulate matter and the coagulant. The result of the water quality of the treatment plants with the inflow velocity of 0.38 m/sec that was operated in three years after replacing all 12 units of the existing Rapid-Mixer with the Non-powered Mixer met the standards. Hence, it is possible to reduce the energy consumption of 64,143 ~ 65,306 kWh/year since the Rapid-Mixer is replaced by the Non-powered Vortex Mixer.

• Journal of Korea Water Resources Association
• /
• v.30 no.4
• /
• pp.347-355
• /
• 1997

In this study, the applicability of genetic algorithms into the parameter estimation of storage function method for flood routing model is investigated. Genetic algorithm is mathematically established theory based on the process of Darwinian natural selection and survival of fittest. It can be represented as a kind of search algorithms for optima point in solution space and make a reach on optimal solutions through performance improvement of assumed model by applying the natural selection of life as mechanical learning province. Flood events recorded in the Daechung dam are selected and used for the parameter estimation and verification of the proposed parameter estimation method by the split sample method. The results are analyzed that the performance of the model are improved including peak discharge and time to peak and shown that the parameter Rsa, and f1 are most sensitive to storage function model. Based on the analysis for estimated parameters and the comparison with the results from experimental equations, the applicability of genetic algorithm is verified and the improvements of those equations will be used for the augmentation of flood control efficiency.

• Journal of Sasang Constitutional Medicine
• /
• v.19 no.2
• /
• pp.22-29
• /
• 2007

1. Objectives Sasang Contitutional Medicine, a part of the traditional Korean medical lore, treats illness through a constitutional typing system that categorizespeople into four constitutional types. A few of the important criteria for differentiating the constitutional types are external appearances, inner state of mind, and pathological patterns. We had been developing a 3D Automatic Face Recognition Apparatus (3D-AFRA) in order to evaluate the external appearances with more objectivity. This apparatus provides a 3D image and numerical data on facial configuration, and this study aims to evaluate the mechanical accuracy of the 3D-AFRA hardware. 2. Methods Several objects of different shapes (cube, cylinder, cone, pyramid) were each scanned 10 times using the 3D Automatic Face Recognition Apparatus (3D-AFRA). The results were then compared and analyzed with data retrieved through a laser scanner known for its high accuracy. The error rates were analyzed for each grid point of facial contour scanned with Rapidform2006 (Rapidform2006 is a 3D scanning software that collects grid point data for contours of various products and products and product parts through 3D scanners and other 3D measuring devices; the grid point data thusly acquired is then used to reconstruct highly precise polygon and curvature models). 3. Results and Conclusions The average error rate was 0.22mm for the cube, 0.22mm for the cylinder, 0.125mm for the cone, and 0.172mm for the pyramid. The visual data comparing error rates for measurement figures retrieved with Rapidform2006 is shown in $Fig.3{\sim}Fig.6$. Blue tendency indicates smaller error rates, while red indicates greater error rates The protruding corners of the cube display red, indicating greater error rates. The cylinder shows greater error rates on the edges. The pyramid displays greater error rates on the base surface and around the vertex. The cone also shows greater error around the protruding edge.

• Journal of the Korean Society for Railway
• /
• v.20 no.2
• /
• pp.165-172
• /
• 2017

High frequency squeal noise can be generated when a railroad vehicle runs a sharp curved section; this noise causes environmental complaints and excessive wear on the wheel and the railroad track. In this paper, curved squeal noise experiments on a commercial railway were carried out to investigate this phenomenon. The relationship of the squeal noise pressure level, the frequency characteristics, the railway running speed, and the modal behavior of the wheel were investigated. At the same time, the lateral motion of the wheel relative to the rail was captured using a video camera; wheel movement was calculated when the noise was generated. queal noise occurred at the highest level at the inner front wheel; this phenomena is considered to be related to the lateral vibration response characteristics of the wheel. It can be seen that the magnitude of this squeal noise is not directly related to the increase in vehicle speed.

• The Journal of the Acoustical Society of Korea
• /
• v.39 no.5
• /
• pp.379-389
• /
• 2020

In this study, the flow and noise performances of high-speed fan motor unit for cordless vacuum cleaner is improved by optimizing the impeller which drives the suction air through flow passage of the cordless vacuum cleaner. Firstly, the unsteady incompressible Reynolds averaged Navier-Stokes (RANS) equations are solved to investigate the flow through the fan motor unit using the computational fluid dynamics techniques. Based on flow field results, the Ffowcs-Williams and Hawkings (FW-H) integral equation is used to predict flow noise radiated from the impeller. Predicted results are compared to the measured ones, which confirms the validity of the numerical method used. It is found that the strong vortex is formed around the mid-chord region of the main blades where the blade curvature change rapidly. Given that vortex acts as a loss for flow and a noise source for noise, impeller blade is redesigned to suppress the identified vortex. The response surface method using two factors is employed to determine the optimum inlet and outlet sweep angles for maximum flow rate and minimum noise. Further analysis of finally selected design confirms the improved flow and noise performance.

• Korean Journal of Optics and Photonics
• /
• v.8 no.6
• /
• pp.445-449
• /
• 1997

The complex refractive indices of $Ge_2Se_2Te_5$ which show reversible phase change between the crystalline phase and an amorphous one depending upon the annealing process have been determined in the spectral range of 0.7-4.5 eV. The $Ge_2Se_2Te_5$ films were DC sputter deposited on the crystalline silicon substrate. The spectro-ellipsometry data of a thick film were analyzed following the modelling procedure where the quantum mechanical dispersion relation were used for the complex refractive indices of both the cryastalline phase $Ge_2Se_2Te_5$ and and amorphous phase $Ge_2Se_2Te_5$, respectively. On the other hand, with the surface micro-roughness layer whose effective thickness was determined from AFM analysis, the spectro-ellipsometry data were numerically inverted to yield the complex refractive index of $Ge_2Se_2Te_5$ at each wavelength. With these set of complex refractive indices, the reflectance spectra were calculated and those spectra obtained from the numerical inversion showed better agreement with the experimental reflection spectra for both the cryastalline phase and an amorphous phase. Finally, the thin $Ge_2Se_2Te_5$ film which has the optimum thickness of 26 nm as the medium for optical recording was also analyzed and the quantitative result of the film thickness and the surface microroughness has been reported.

• Plant Journal
• /
• v.11 no.1
• /
• pp.39-49
• /
• 2015

The objective of this study is to improve the classification structure of commodity code for piping material management which is considered as the fundamental of commodity code and piping material management system. It enhances the efficiency of piping material management directly or indirectly affecting the engineering, procurement and construction in a petrochemical plant projects. To establish an improved code classification structure, this study identifies the problems of former code classification structure in details, as well as the characteristics of other domestic and global EPC company's code classification structures and presents the improved direction considering the recently mega-sized and specialized projects. Accordingly, to efficiently enhance piping material management, the improved code classification structures have been derived from defining suitable code classification structure for specific piping component, adding more standard attribute, expanding the number of code digits and classifying code hierarchy. The results of applying the improved classification structure of commodity code to on-going project have led to reduce the rate of rework from 4.98% to 2.48% for developing purchase description and also have saved working time for executing piping design by 3D modeling from 6 months by two persons to 4 months by a person which is decreased 67% consequently. In addition, the structures of pyramid code management have resulted to accumulation and analysis of the various piping data for other disciplines such as procurement and estimation team which require commodity code information through the company's material control system.

• Korean Journal of Agricultural Science
• /
• v.12 no.1
• /
• pp.139-152
• /
• 1985

본 NEWASA 지역의 접수관정관개 개발에 따른 정제성분석 연구는 IBRD-EDI와 INDIA RESERVE BANK의 College of Banking이 공동주최한 Trainers Trining for Rural Finance (1985. 1.19-3.1)의 일환으로 1985. 2. 14-19 까지 NEWASA BLOCK에 대한 정수정관개의 경제적 효율성을 평가하기 위하여 농가조사를 실시하였고, 그 분석결과를 정리한 것으로 농지는 넓으나 농업용수가 부족한 본 지역은 빈곤과 저생산성 농촌잠재 실업을 특징으로 하고 있다. 농촌소득의 제고와 농촌실업의 고용확대는 전 인구의 80% 이상이 농민인 본지역뿐만 아니라 선언도 경제개발의 중심과제이다. 호당 6 acres 규모의 관개가 가능한 Dug-well Irrigation Development는 연평균 강우량이 650m/m에 불과한 인도의 Plateau 지역에서는 농촌빈곤과 실업문제의 해결, 토지 이용율제고를 통한 토지생산성 향상등 농촌경제개발의 중심과제로서 인도정부가 추진하는 핵심적인 농업정책이다. 본 지역의 농가호당 평균 소유농지연적은 8.67 acres(3.5ha)로써 모두가 Rainfed farming으로 현재 본 지역의 관개율은 17.5%에 불과하다. 농작물은 Jowar라고 하는 내한성 작물이 재배되며, 관개 조건하에서는 Jowar, Wheat, Sugarcane이 재배된다. With and Without Dug-Well Irrigation 조건하에서 각 작물별 ha당 생산성을 보면 Jowar는 0.86 ton/ha에서 2.22 ton/ha으로 증산되고 Wheat는 2.96 ton/ha, Sugarcane는 98.8 ton/ha이 생산된다. 한편 Dug-well Irrigation 전후의 농가소득의 변화를 보면 시행전의 4,275Rs가 되어 4배의 농가소득이 증가된다. 이와 같은 농업소득을 획득하기 위해서는 Dug-well에 대한 Initial Investment로서 33,400Rs(2,137,600원)이 투자되어야 하는데 종류별 융자 기간을 보면 Dug-well 15년(95%융자) Pump Set 9년(95%융자), Woriking capital 1년이며 인도의 Union Bank에서 융자하고 있다. 결론적으로 이러한 Dug-well Irrigation Development에 따른 IRR는 Before Financing시에는 29%이며 After Financing 시에는 24%이고 B/C ratio는 두경우에 있어 1.89, 1.24를 각각 나타냈다. 따라서, 본 사업은 재무적인 측면 즉 농가소득증대와 농촌고용증대 및 토지이용면에서 타당성이 크며 Dug-well Irrigation은 인도의 농업성장 및 경제개발의 관건으로 생각된다. 한국의 수리개발 기술 및 농업기술(Bio-chemical, Mechanical & Hydrological Technology)이 이전된다면 보다 괄목할 만한 농업발전이 이룩될 것을 생각된다.

• Korean Journal of Materials Research
• /
• v.28 no.9
• /
• pp.528-533
• /
• 2018

In recent years, solar cells based on crystalline silicon(c-Si) have accounted for much of the photovoltaic industry. The recent studies have focused on fabricating c-Si solar modules with low cost and improved efficiency. Among many suggested methods, a photovoltaic module with a shingled structure that is connected to a small cut cell in series is a recent strong candidate for low-cost, high efficiency energy harvesting systems. The shingled structure increases the efficiency compared to the module with 6 inch full cells by minimizing optical and electrical losses. In this study, we propoese a new Conductive Paste (CP) to interconnect cells in a shingled module and compare it with the Electrical Conductive Adhesives (ECA) in the conventional module. Since the CP consists of a compound of tin and bismuth, the module is more economical than the module with ECA, which contains silver. Moreover, the melting point of CP is below $150^{\circ}C$, so the cells can be integrated with decreased thermal-mechanical stress. The output of the shingled PV module connected by CP is the same as that of the module with ECA. In addition, electroluminescence (EL) analysis indicates that the introduction of CP does not provoke additional cracks. Furthermore, the CP soldering connects cells without increasing ohmic losses. Thus, this study confirms that interconnection with CP can integrate cells with reduced cost in shingled c-Si PV modules.

• Polymer(Korea)
• /
• v.38 no.5
• /
• pp.640-644
• /
• 2014

As a process of plat panel display production, slot coating is widely used for the coating of photoresist on a wide glass substrate. A uniform coating thickness is important, and the coating uniformity is divided into nozzle and machine directions. The machine and nozzle directions coating uniformities are influenced by the operation condition of coater and flow uniformity inside the die, respectively. Non-uniform coating during steady coating process occurs according to those factors, however, non-uniform coating along the machine and nozzle directions has been observed at the beginning of coating by unsteady flow. In this study, steady and unsteady state flow simulations have been performed and compared with experiment to examine the causes of non-uniform coating. Computational results exhibited that it took a time to get a uniform pressure distribution at whole inside the die, and during this period of time edge regions showed lower exit velocity compared with center region. Subsequently edge regions had thinner coated layers than center region. However edge regions showed higher exit velocity than center region after steady state, and this made edge regions had thicker coated layer than center region.