• Journal of the Korean Institute of Intelligent Systems
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• v.8 no.6
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• pp.1-11
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• 1998

In this work, we propose a modeling method based on an artifical intelligence technique for a stem generator in a nuclear power plant. Modeling the steam generator is known to be difficult due to several facts; especially, the dynamics of the steam generator is nonminimum phase which is mainly caused by the swell and shrink phenomena from thermal effects. In order to overcome this difficulty, we adopt so-called logic processor whose structure itself has a logical meaning to be easily established and also efficiently learned. Such a manner, we could derive an useful model simulating the dynamics of the steam generator in a nuclear power plant.

• Journal of Energy Engineering
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• v.6 no.2
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• pp.170-175
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• 1997

An experimental study was carried out with the Mock-up made for the improved water level control of the steam generator in nuclear power plant and for the confirmation of swell/shrink status of the water level by opening and closing the steam dump valve. We can confirmed the possibility of using the Mock-up by introducing the PI controller and the FUZZY controller. Accordingly, we can confirmed that the practical usability of advanced controllers, which will be developed for the improved water level control of the steam generator in nuclear power plant by using the Mock-up.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.8
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• pp.34-43
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• 2007

This paper presents a methodology on the AHP(Analytic Hierarchy Process) to calculate unified power quality index which provide an overall assessment of the distribution system performance. To obtain the unified power quality index. we propose the use of the AHP model and consider contingency using Monte Carlo simulation. The proposed method is especially useful and effective for planning. We have applied the proposed method to an actual relatively large system.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.753-764
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• 1992

The steam generator water level is difficult to control at low power due to its reversed responses to the feedwater flow, which are well known as the shrink and swell phenomena. With regard to this problem a new control scheme has been studied by which the level transients could be kept within permissible ranges at low power. The relations between the various input conditions to steam generator and the level transients have been examined to be expressed in the form of process transfer functions. Analog filters have been incorporated to be expressed in the process with proper control constants. This control scheme allows the prediction of level variation together with the corresponding feedwater rate and results in mider transients with good stabilites.

• Journal of the Korean Institute of Navigation
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• v.20 no.3
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• pp.13-30
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• 1996

It is general that large ships entering or leaving a port located in the East coast of Korean peninsular are often exposed athwart to swell while maneuvering in the vicinity of breakwater at harbor enterance or to prevailing wind inside the port in winter. Particulary, Many VLCCs laden with ore coal are calling at Pohang Port, on account of which it is likely that one of those VLCCs block the port if they were to run aground in fairway due to adverse circumstance of swell, prevailing winds or improper shiphandling. This accident may result in delay of delivery of raw material for Pohang Steel Mill which will bring about shortcomings of steel products for nationwide relevant industries causing national economic shock. Therefore, This study basically aims at establishment of certain criteria for safe unberthing of VLCC in this port to prevent such unexpected disaster because any VLLC is highly affected by external forces when in ballast condition. Computer simulations are unavoidable to fulfull this study successfuly and many simulations have been carried out repeatedly to find a model of safe unberthing under various unfavourable wind conditions. The "PC-based ship maneuvering simulator for training purpose" was used to perform numerous simulations at the least economic burden and to verify its availability that it can be used not only for training but also some other purposes. purposes.

• Journal of Photoscience
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• v.4 no.1
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• pp.23-30
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• 1997

Leaf movements in nyctinastic plants are produced by changes in the turgor of extensor and flexor cells, collectively called motor cells, in opposing regions of the leaf movement organ, the pulvinus. In Samanea saman, a tropical tree of the legume family, extensor cells shrink and flexor cells swell to bend the pulvinus and fold the leaf at night, whereas extensor cells swell and flexor cells shrink to straighten the pulvinus and extend the leaf in the daytime. These changes are caused by ion fluxes primarily of potassium and chloride, across the plasma membrane of the motor cells. These ion fluxes are regulated by exogenous light signals and an endogenous biolgical clock. Inward-directed K$^+$ channels are closed in extensor and open in flexor cells in the dark period, while these channels are open in extensor and closed in flexor cells in the light period. Blue light opens the closed K$^+$ channels in extensor and closes the open them in flexor cells during darkness. Illumination of red light followed by darkness induces to open the closed K$^+$ channels in flexor and to close the open K$^+$ channels in extensor cells in the light. The dynamics of K$^+$ channels in motor cells that are controlled by light signals are consistent with the behavior of the pulvini in intact plants. Therefore, these cell types are an attractive model system to elucidate regulations of ion transports and their signal transduction pathways in plants. This review is focused on light-controlled ion movements and regulatory mechanisms involved in phosphoinositide signaling in leaf movements in nyctinastic plants.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.3
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• pp.372-378
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• 2012

This paper deals with a 3-phase voltage disturbance generator for a performance test of custom power devices such as dynamic voltage restorers (DVR), dynamic uninterruptable power supplies (UPS), etc. The operating principle of the proposed circuit is described in each mode of voltage sag, swell, outage, and unbalance. The main components of the proposed disturbance generator are silicone controlled rectifier (SCR) thyristors, variable autotransformers, and transformers. Therefore, the disturbance generator can be implemented with a considerably low cost compared to the conventional pulse width modified (PWM) inverter and converter type generators. Furthermore, it has good features of high reliability with simple structure, high efficiency caused by no PWM switching of the SCR thyristors, and easy control with a wide variation range. To verify the validity of the proposed scheme, simulations and experiments are carried out.

• Geomechanics and Engineering
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• v.8 no.2
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• pp.173-186
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• 2015

The rapid urbanization in Pakistan is creating a shortage of sustainable construction sites with good soil conditions. Attempts have been made to use rice husk ash (RHA) in concrete industry of Pakistan, however, limited literature is available on its potential to improve local soils. This paper presents an experimental study on engineering properties of low and high plastic cohesive soils blended with 0-20% RHA by dry weight of soil. The decrease in plasticity index and shrinkage ratio indicates a reduction in swell potential of RHA treated cohesive soils which is beneficial for problems related to placing pavements and footings on such soils. It is also observed that the increased formation of pozzolanic products within the pore spaces of soil from physicochemical changes transforms RHA treated soils to a compact mass which decreases both total settlement and rate of settlement. A notable increase in friction angle with increase in RHA up to 16% was also observed in direct shear tests. It is concluded that RHA treatment is a cost-effective and sustainable alternate to deal with problematic local cohesive soils in agro-based developing countries like Pakistan.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.5
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• pp.366-371
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• 2012

High swell has been known for the one of the main causes of beach erosion in the east coast of Korea. In this study, coastal topography changes due to high swells are simulated to find its effect on the backshore by using movable bed experiments and numerical experiments. Sea bottom topographical changes due to various incident waves were investigated using CSHORE model in the numerical experiments. Furthermore, the mechanism and the phenomena of beach erosion due to waves and high swells on the foreshore and backshore were analyzed and compared with movable bed hydraulic experiments.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.6
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• pp.583-588
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• 2008

Swell data observed in the East Sea in February, 2008 were analyzed using wavelet method. The wavelet analyzed results show detailed time series variation of wave group, peak frequency and spectrum. The comparison of time averaged wavelet spectrum with fourier spectrum turn out to be very similar in terms of spectrum shape and peak frequency evolution but the peak frequency wave energy and the significant wave height show discrepancies. Wavelet analysis can detect the change of spectrum in time as well as in frequency and very efficient to study transient and irregular phenomena such as freak waves and abnormal swells in the ocean. More analysis with more wave data are needed for future application.