• Journal of the Korean Solar Energy Society
• /
• v.29 no.6
• /
• pp.1-13
• /
• 2009

Photovoltaic conditioning systems normally use a maximum power point tracking (MPPT) technique to deliver the highest possible power to the load continuously when variations occur in the insolation and temperature. A unique method of tracking the maximum power points (MPPs) and forcing the boost converter system to operate close to these points is presented through deriving small-signal model and transfer function of boost converter considering input capacitor. This paper aims at modeling boost converter including fairly large equivalent series resistance(ESR) of input reservoir capacitor by state-space-averaging method and PWM switch model and compares both methods using Bode plots. In the future, properly designed controller for compensation will be constructed in 3kw real system for maximum photovoltaic power tracking control.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.57 no.1
• /
• pp.89-97
• /
• 2015

This study is to assess the effect of non-point source pollution discharge loads between tillage and no-tillage applications for upland crop areas using SWAT (Soil and Water Assessment Tool) watershed modeling. For Byulmi-cheon small rural catchment ($1.17km^2$) located in upstream of Gyeongan-cheon watershed, the rainfall, discharge and stream water quality have been monitored in the catchment outlet since 2011. The SWAT model was calibrated and validated in hourly basis using 19 rainfall events during 2011-2013. The average Nash-Sutcliffe model efficiency and $R^2$ (determination coefficient) for streamflow were 0.67 and 0.79 respectively. Using the 10 % surface runoff reduction from experiment results for no-tillage condition in field plots of 3 % and 8 % slopes under sesami cultivation, the soil saturated hydraulic conductivity for upland crop areas was adjusted from 0.001 mm/hr to 0.0025 mm/hr in average. Under the condition, the catchment sediment, T-N (total nitrogen, TN), and T-P (total phosphorus, TP) discharge loads were reduced by 6.9 %, 7.4 %, and 7.7 % respectively.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.7
• /
• pp.101-106
• /
• 2004

Measurements of linear motion accuracy for one axis of NC lathe have achieved with laser interferometer system, but measurement of plane motion accuracy for two axes on zx-plane of NC lathe have not achieved with the above system. Therefore in this study, measuring unit system is organized using two optical linear scales in order to acquire error. data during of plane motion of ATC(Automatic Tool Change.) of NC lathe by reading zx-plane coordinates. Two optical linear scales of measuring unit are fixed on zx-plane of NC lathe, and moving part of the scales are fixed to the ATC and then error motion data of z, x-coordinates of the ATC are received from the scales through the PC counter card inserted in computer at constant time intervals using tick pulses coming out from computer. And then, error motion data files acquired from measuring are saved in computer memory and the aspect of plane motion are modeled to plots, and range of the error data, means. average deviations, and standard deviations etc. are calculated by means of statistical treatments using computer programs.

• Journal of Korean Society for Quality Management
• /
• v.49 no.4
• /
• pp.527-537
• /
• 2021

Purpose: The purpose of this study was to suggest an improved version of Proof-of-Nonce (PoN) algorithm, which is a distributed consensus algorithm used for block chain system. Methods: First, we used response surface method for design of experiment that is to generate experimental points considering non-linear relationship among variables. Then, we employed overlapped contour plots for visualizing the impact of control variables to performance target. Results: First, we modified the consensus procedure of the existing PoN algorithm by diminishing the content of the exchanged message. Then, we verified the performance improvement of the new PoN algorithm by performing a numerical experiment and paired t-test. Finally, we established new regression models for consensus time and Transactions per second (TPS) and proposed a method for optimizing control variables for obtaining performance target. Conclusion: We could improve the performance of the previous version of PoN algorithm by modifying the content of the exchanged message during 4-steps of consensus procedure, which might be a stepping stone for designing an efficient and effective consensus algorithm for blockchain system with dynamic operation environment.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.688-692
• /
• 2005

Importance of substitute energy has been increasing due to environmental issues and lack of fossil fuels. In addition, heating cost that occupies from 30 to $40\%$ of the total production cost in Korean protected cultivation needs to be reduced for profitability and global competition. But, studying on substitute energy to solve these problems has not been activated for Korean protected cultivation. Therefore, this study was conducted to develop a geothermal heat pump system for cool ing and heat ing of greenhouses at a lower cost than conventional hot air heater and air conditioner. Fundamental test of heat transfer characteristics in soil was conducted by computer simulation and controlled tests for its verification. Based on the results of the theoretical and empirical investigations, an optimum heat pump system was developed and the performance was evaluated for practical use in a greenhouse at the Pusan Horticultural Experiment Station. The system was compared with a conventional hot air heating system through a cucumber growing test and economic feasibility analysis. Results of the application test of the geothermal heat pump showed that with an initial setting of $15^{\circ}C$ the inside temperature of the greenhouse could be maintained between 15 and $17^{\circ}C$. Results of the cucumber growing test showed that there were no significant differences in average height, leaf length, leaf width, number of nods, leaf area, dry weight and yield between the plots wi th the geothermal heat pump system and a conventional hot air heater. Economic feasibility analysis indicated that the variable cost of the hot air heater could be saved $81.2\%$ using the geothermal heat pump system. It was concluded that the geothermal heat pump system might be a pertinent heating and cooling system for greenhouses because of the low operating cost and the use of environment-friendly geothermal energy.

• Aerospace Engineering and Technology
• /
• v.4 no.1
• /
• pp.108-113
• /
• 2005

Strucutral and hygrothermal analysis for a composite tube is carried out in this study, that provides critical parameters for the design of a highly dimensionally stable space telescope. Carpet plots for laminate effective engineering constants are generated and used for the best tube lay-ups with high elastic modulus and highly insensitive to thermal and moisture expansion, which is essential for maintaining optical alignment of opto-mechanical system under random force applied during a launch campaign and orbital thermal load. Despace in the longitudinal direction under hygrothermal load of the tubes constructed with the selected lay-ups is calculated for the validation of lay-up designs on the dimensionalstability. Dynamic analysis is also carried out to feature the resonant behaviour. A zig-zag triangular element accurately representing through thickness stress variations for laminated structures is developed in this study and incorporated into the structural and hygrothermal analysis.

• Applied Microscopy
• /
• v.47 no.3
• /
• pp.86-94
• /
• 2017

In this study, we will describe a new design of carbon nanotubes tip. Single-walled carbon nanotubes produced using high-pressure CO over Fe particles (HiPCO) at CNI, Houston, TX used in this study. These tips were manufactured by employing a drawing technique using glass puller. Field electron microscopies with tips (cathode) to screen (Anode) separation of ~10 mm was used to characterize the electron emitters. The system was evacuated down to base pressure of (${\sim}10^{-8}$ mbar) when baked at up to (${\sim}200^{\circ}C$) over night. An electron field emission patterns, as well as current versus voltage characteristics and Fowler-Nordheim plots, are discussed.

• Korean Journal of Organic Agriculture
• /
• v.8 no.1
• /
• pp.131-137
• /
• 1999

This study was conducted to investigate the effects of microbial fertilizers on the yields of Leaf lettuce, chemical components of soil, and the microbial floras. Six micriobial fertilizers, MPK+Husk+Palma, Husk+Palma, MPK+Compost, Compost, Bio livestock cattle system(BLCS) cattle dropping, and Tomi, were used. All of the microbial fertilizers were tend to increase yields of Leaf lettuce, especially MPK+Husk+Palma treatment was most effective. In a chemical components of soil, concentrations of K, Mg were increased with Tomi treatment, however, the other concentrations of soil chemical components were not different. In a microbial floras of soil, Tomi, Husk+Palma, and MPK+Husk+Palma treated plots increased in numbers of total bacteria and bacillus. Tomi treated plot increased in numbers of actinomycetes and fungi, also. The other microbial floras of soil were not different, however. The microbial fertilizers may affect the useful microbial floras, therefore, it would be increase yield of Leaf lettuce treated with them.

• Asian Journal of Atmospheric Environment
• /
• v.3 no.1
• /
• pp.1-8
• /
• 2009

Enhancement of aerosol optical thickness (AOT) and surface aerosol mass concentration in Korea for an active forest fire episode in Northeast Asia were estimated by Community Multi-scale Air Quality (CMAQ) model. MODIS/TERRA remote detects of fires in Northeast Asia for May 2003 gave a constraint for estimation of wildfire emissions with an NDVI distribution for recent five years. The simulated wildfire plumes and enhancement of AOT were evaluated and well resolved by comparing multiple satellite observations such as MODIS, TOMS, and others. Scatter plots of observed daily mean aerosol extinction coefficient versus $PM_{10}$ concentration in ground level in Korea showed distinctively different trends based on the ambient relative humidity.

• Proceedings of the IEEK Conference
• /
• 2009.05a
• /
• pp.335-337
• /
• 2009

A scanning electron microscope(SEM) is a system that visualizes complex surface features. The resolution of SEM is affected by each of equipment components. In this study, we examined the effects of the four factors including the beam current, magnification, voltage and working distance. A statistical analysis was conducted to investigate the main and interaction effects. For a systematic characterization, a $2^4$ full factorial experiment was conducted. The $R^2$ of constructed statistical model was 88.9%. The main effect revealed that the current and working distance are dominant factors. Of the interactions, those between the current and voltage yielded the highest interaction. 3D plots generated from the model were used to explore various parameter effects.