• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11c
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• pp.613-622
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• 2000

Watering operation for oyster mushroom growing houses is regarded as drudgery and time consuming farm operation for growers. Most of mushroom growing beds in oyster mushroom growing houses are designed as two-row with four floor beds, therefore the watering and ventilation between the bed floors are much difficult for farmers because of its structural design. The study aimed to reduce the watering operation and improve the mushroom growing environment through the humidification and air supply on mushroom growing beds. Results showed that appropriate size of nozzle is between 0.8~0.5ml/s for the humidification and higher than the 2.0ml/s for the watering. The optimum water supply pressure was regarded as between 1.0~2.0MPa and the uniform distribution of droplet on the bed showed on air flow speed of 14m/s. The prototype was equipped with twin nozzle with. the humidification nozzle of 0.85ml/s and watering nozzle of 5.0ml/s, and the air blast fan with the air speed of 10m/sec in each air spout. In the field test in a practical scale mushroom growing house, it was well operated dependant on the set desire by a electric control unit. The machine can be practically used as air blast watering and air blast humidification for oyster mushroom growing farms without manual.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.1
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• pp.83-88
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• 2011

There are various environmental conditions under which ship may navigate over ocean or in harbor. Ship's torque and speed change frequently under the voyage conditions. In this case, harmonics is created in the electrical power systems. The major adverse impacts of voltage and current harmonics in the electrical power systems on generator, transformer, converter, inverter and propulsion motor lead to the increase of machine heating caused by iron and copper losses which are dependent on frequency. In this paper, an analysis of THD(total harmonic distortion) for currents and voltages in the propulsion equipment was carried out. The THD and torque ripple in the input currents of the propulsion motor have been confirmed by the simulation results.

• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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• pp.52-57
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• 1996

Mixing is most important for developing an electric washer which transforms angular momentum from rotating solid wall to laundry clothes inside it. For magnification of this mixing effect, some inventions are introduced to washing machine system, i. e., washing plate, washing rod, and even for washing cap in a model of a Korean manufacture. However, the previous efforts show dissatisfaction up till now. In this paper, a triumph to enhance mixing effects to increase washing performance is presented and verified by numerical investigation. The present model to simulate a washing tub is the simple circular cylinder with two endwall disks which is completely filled with a viscous liquid. The present improvement is to change mounting position of a bottom disk of the model cylinder. Therefore, the aim of this work just proposes a new idea, which is numerically inspected, to a producer of washing machine, In detail, this invention is alternating the mounting position of a rotating bottom disk. Actually skewed pulsator is placed in steady of a flat disk, so the two endwall disks at top and bottom are not in parallel. The angle between an inclined bottom disk and the horizontal plane is fixed as 5 degree and physical domain to consider poses a sliced cylinder. Flow fields in both a right circular cylinder and the present improved model are fully depicted by numerical integration on a body fitted nonorthogonal regular uniform grid system. Numerical data to explain flow structure are plotted for understanding of the effects of the inclined disk. Also enhanced mixing effects by the inclined rotating disk are gauged by accurate numerical data used in this work.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.32 no.9
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• pp.315-324
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• 1983

Dynamic stability problems have been experienced with a generator connected to an infinite bus through a long transmission line. Nuclear turbine-generator units #1 and #2 at the Winsconsin Electric Power Point Baech Station were found to be dynamically unstable when one unit is isolated on one of the lines to Milwaukee or when two units are isolaed on the lines to milwaukee. Power System Stabilizers(PSS) were applied to the excitation system to provide stable operation under these conditions. Suitable settings for the PSS were predetetermined analytically by computer method and root licus analysis of an equivalent single machine-infinite bus configuration. This procedure allows graphical approach to the design of power stabilizers and serves as assynthesis procedure when the design constraints are relaxed so the the speed stabilizer is required ro provide animprovement in system damping. A simplified model of the complete exciter generator system is shown to be adequate for this type of analysis.

• Journal of the Korean Magnetics Society
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• v.27 no.1
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• pp.9-17
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• 2017

A multi-phase electric machine has gained distinct interest due to its high reliability compared to a three-phase structure, and in this paper, self and mutual inductances in a five-phase permanent magnet synchronous machine (PMSM) are estimated by an analytical method. Recently, most of high-performance operations are implemented by field oriented control and/or direct torque control, and inductance for those controls is one of the key parameters in the voltage equation of phase windings. Winding function theory (WFT) is employed to calculate the inductance of phase windings, and it is verified that the result of the analytical method has a deviation of approximately 3 % compared to finite element analysis. Finally, in this paper, the way to obtain direct and quadrature inductance values are introduced from the analytical inductance calculated by WFT.

• Journal of Magnetics
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• v.6 no.2
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• pp.66-69
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• 2001

The actual magnetic induction waveform of cores in electrical machines is not sinusoidal i.e. higher harmonics are always included. Thus the core loss in actual electrical machines is different from the core loss which is measured by the standard method, because the waveform of magnetic induction should be sinusoidal in the standard testing method. Core loss analysis under higher harmonic induction is always important in electric machine design. In this works we measured the core loss when a hysteresis loop has only one period of an ac minor loop of higher harmonic frequency, depending on the position of the ac minor loop of relative to the fundamental harmonic frequency. From this experiment, the core loss P(B/sub 0/f/sub 0/, B/sub h/, nf/sub 0/)) under a higher harmonic magnetic induction B/sub h/ could be expressed by the linear combination the core loss at fundamental harmonic frequency P/sub c/(B/sub 0/, f/sub 0/), the core loss of ac minor loop at zero induction region of the major hysteresis loop P/sub cL/ (B/sub h/, nf/sub 0/), and the core loss of an ac minor loop in the high induction region of the major hysteresis loop P/sub cH/ (B/sub h/, nf/sub 0/) i.e., P/sub c/, (B/sub 0/, f/sub 0/, B/sub h/, nf/sub 0/)=P/sub c/ (B/sub 0/, f/sub 0/,)+(n-1)[k₁(B/sub 0/) P/sub cL/ (B/sub h/, nf/sub 0/)+(1-k₁(B/sub 0/)) P/sub cH/ (B/sub h/, nf/sub 0/)]. This will be useful formula for electrical machine designers and one of effective methods to predict core loss including higher harmonic induction.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.5
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• pp.357-363
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• 2021

Recently, as interest in appearance has increased, various studies on treatment method for short stature are being conducted. In this study, the effect of growth plate stimulation on the height growth of children and adolescents was studied. As a result of pre- and post-analysis of the experimental group, it was confirmed that the difference in average height according to growth plate stimulation was relatively large. In addition, in the results of analyzing the effects of demographic factors on the height growth of the experimental group and the control group, weight showed the greatest influence on height growth among the demographic factors affecting the height growth of the experimental group. The effect on the height growth of the control group was found to have an effect in the order of age, weight, and father's height. The difference in height changed post-mortem between the experimental group and the control group was 1.10 cm for 3 months, and the difference was the result of growth plate stimulation. It was confirmed that growth plate stimulation had a significant effect on the height change of children and adolescents, except for weight, which is a common factor of height change in the experimental and control groups. Therefore, it is expected that it can be used as a treatment method for short stature.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.3
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• pp.129-136
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• 2022

The most important part of the smart livestock building system is to maintain a breeding environment so that livestock can grow to high quality despite changes in the internal and external atmospheric environment. Especially, it is very important to maintain the temperature and humidity in the livestock building because various diseases occur during the summer and winter. To manage the environment suitable for livestock, a smartfarm system for livestock building is applied, but it is very expensive. In this study, we propose a hardware design and control method for low cost system based on HMI and fuzzy control. To evaluate the performance of the proposed system, we did a simulation experiment in the atmospheric conditions of summer and winter. As a result, it showed the performance of minimizing the temperature and humidity stress of livestock. And when applied to the livestock building, the proposed system showed stable control performance even in the change of the external atmospheric environment. Therefore, as with these results, if proposed system in this study is applied to the smart farm system, it will be effective in managing the environment of livestock building.

• Journal of Advanced Navigation Technology
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• v.21 no.4
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• pp.365-370
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• 2017

This study analyze correlation between weekdays data and special days data of different power demand patterns, and builds a separate data set, and suggests ways to reduce power demand prediction error by using deep learning network suitable for each data set. In addition, we propose a method to improve the prediction rate by adding the environmental elements and the separating element to the meteorological element, which is a basic power demand prediction elements. The entire data predicted power demand using LSTM which is suitable for learning time series data, and the special day data predicted power demand using DNN. The experiment result show that the prediction rate is improved by adding prediction elements other than meteorological elements. The average RMSE of the entire dataset was 0.2597 for LSTM and 0.5474 for DNN, indicating that the LSTM showed a good prediction rate. The average RMSE of the special day data set was 0.2201 for DNN, indicating that the DNN had better prediction than LSTM. The MAPE of the LSTM of the whole data set was 2.74% and the MAPE of the special day was 3.07 %.

• Journal of Energy Engineering
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• v.29 no.3
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• pp.86-90
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• 2020

This paper examines a blockchain network-based transaction system using location proofing in power direct transactions between networked energy clouds, energy communities, and prosumer machines participating in smart cities. It utilizes location-based blockchain network technology, which enables long-distance travel with recharging by power purchases during autonomous movements, autonomous electric vehicles that can purchase and sell electricity, and solar street lights that can be produced and sold in fixed form. In addition, it is possible to provide optimum power transaction matching and settlement reliability between machines without human intervention in power transactions between electric chargers. It also introduces a business-to-object business model between autonomous machines that exist in multiple and different spaces and through energy clouds that are expected to be scattered with various transaction prices, policies, and incentives.