• Journal of Korea Water Resources Association
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• v.43 no.4
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• pp.399-408
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• 2010

The sensitivity of Nash model parameters is analyzed about characteristic velocities considering geomorphological dispersion in the present study. And changing shape of IUH compared and analyzed as variation of characteristic velocities through numerical experiment. Application watersheds are selected 4 subwatersheds which are located at main stream of Bocheong basin. The mean and variance of hillslope and stream path length are estimated in each watershed with GIS. And Nash model parameters are estimated with moments of path lengths and characteristic velocities. The changing trend about IUH which is derived Nash model parameters are compared as variation of characteristic velocities. The Major results of this study are summarized as follows. The Nash model parameters sensitively present changes about hillslope characteristic velocity. And the effect of the peak discharge and shape of recession in IUH dominate with hillslope's characteristic velocity, the effect of the peak time and shape of ascension in IUH dominate with channel's characteristic velocity.

• Journal of Korea Water Resources Association
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• v.35 no.6
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• pp.693-701
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• 2002

In this study, one dimensional sediment movement numerical model(HEC-6) and semi-two dimensional sediment movement numerical model(GSTARS 2.1) were applied to solve the change of channel geometry in Bocheong stream. GSTARS 2.1 model was applied for the three selected sediment transport formulas(Ackers and White's, Engelund and Hanson, Yang formula) from 1993 to 2000 measured data on each section. The simulation results of Ackers and White formula for long -term bed changes are good when compared to the measured data. The HEC-6 model was applied for the simulation of one dimensional sediment movement for the same period. Comparison of the long-term simulations by GSTARS 2.1 and HEC-6 models with measured data shows that simulations by both models are in fair agreement with measured data in overall trend of the river bed changes. Comparisons of simulated cross sectional bed-elevations with measured data shows that GSTARS 2.1 model gives better agreement with than simulated results bed changes on the HEC-6 model.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.769-772
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• 2014

The device reliability in amorphous InGaZnO under NBS(Negative Bias Stress) and hot carrier stress with different gate overlap has been characterized. Amorphous InGaZnO thin film transistor has been measured. and is channel $width=104{\mu}m$, $length=10{\mu}m$ with gate overlap $length=0,1,2,3{\mu}m$. The device reliability has been analyzed by I-V characteristics. From the experiment results, threshold voltage variation has been increased with increasing of the gate overlap length after hot carrier stress. Also, threshold voltage variation has been decreased and Hump Effect has been observed later with increasing of the gate overlap length after NBS.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.102-115
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• 2020

In this study, the SST k - ω turbulence model and the sliding mesh technology based on RANS method have been adopted to simulate the exciting force and hydrodynamic of a pump-jet propulsor in different oblique inflow angle (0°, 10°, 20°, 30°) and different advance ratio (J = 0.95, J = 1.18, J = 1.58).The fully structured grid and full channel model have been adopted to improved computational accuracy. The classical skewed marine propeller E779A with different advance ratio was carried out to verify the accuracy of the numerical simulation method. The grid independence was verified. The time-domain data of pump-jet propulsor exciting force including bearing force and fluctuating pressure in different working conditions was monitored, and then which was converted to frequency domain data by fast Fourier transform (FFT). The variation laws of bearing force and fluctuating pressure in different advance ratio and different oblique flow angle has been presented. The influence of the peak of pulsation pressure in different oblique flow angle and different advance ratio has been presented. The results show that the exciting force increases with the increase of the advance ratio, the closer which is to the rotor domain and the closer to the blades tip, the greater the variation of the pulsating pressure. At the same time, the exciting force decrease with the oblique flow angle increases. And the vertical and transverse forces will change more obviously, which is the main cause of the exciting force. In addition, the pressure distribution and the velocity distribution of rotor blades tip in different oblique flow angles has been investigated.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.5
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• pp.137-145
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• 2008

In this study, to reduce the flood damage caused by flood discharge exceeding project flood, the primary technology was applied to determining the optimal location and size for underground sluiceway. The Jungrang Stream was selected for this study because the stream was overflowed and the embankment section of the stream was destroyed owing to localized torrential rainfall in 1998 and 2001. Considering 200-year frequency storm, the inlets of the underground discharge channel were located at Seoul City limits, the confluence of Danghyun Stream, Wolgye 1-gyo, and the confluence of Mukdong Stream. The outlets were located at the estuary of Jungrang Stream and rightbank of Banpo Bridge in Han River. The transverse discharge according to the variation of overflow depth at the inlet of underground discharge channel was estimated and the effect of inundation reduction was analyzed. To examine the appropriate scale of the underground discharge channel, the 8 operation methods for the management of outlet discharge were compared considering four rules (only storage, the constant discharge rate, the constant discharge volume, and the mixture of the constant discharge rate and discharge volume). As a result, the effect of inundation reduction was most significantly improved when the inlet was located at the confluence of Danghyun Stream. The appropriate size of underground sluiceway for 200-year frequency storm was studied, and as a result, the appropriate diameters of the underground discharge channel were 12 m in case of only storage(Rule D), 9m in 50% of discharge(Rule E), 8 m in constant discharge volume(Rule F), and 7 m in mixture method(Rule G). This investigation process can be applied to design the underground discharge channel when the inundation damage is significant in coastal area due to embankment overflow. The underground discharge channel in Jungrang Stream can also be used as an underground road to link Seoul City to Uijeongbu City during dry season.

• Magazine of the Korean Society of Agricultural Engineers
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• v.14 no.3
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• pp.2703-2715
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• 1972

1. Title of Research Research on the Loss of Irrigation Water Flowing in Earth Channel. 2. Purpose and Importance of Research The purpose of this research is to obtain the accurate loss rated of irrigation water flowing in earth channels so as to give a criterion of designing rational and effective suplpy project of irrigations water. It is the present status that the loss rates of 10 to 20% are obscurely applied without any scientific proof. Therefore, the importance of this research lies in securing loss rates, which are experimentally proves to be suitable for specific local conditions. 3. Content and Scope of Research The selected test reach of the main channel is 1,000m long. Discharges were measured at up and downstream enps by using current meter. The test reach of the lateral channel is 500m long, and parshall flumes were set at both ends to measure inflow and outflow. Finally, for the supply ditch, the test section is 200m long, and sharp-edged rectangular weirs were provided at both ends to measure inflow and outflow. In addition, various factors influence on the loss of irrigation water in channel wer examined. 4. Results of Research and Proposition Results: 1. In the main channel, which is 1,000 M long, and has a slope of 1/3,000 and was constructed by cutting earth, its loss rate is 9.64%. 2. In the lateral, which has a slope of 1/1,500, and is 500m long, and was constructed by cutting, its loss rate is 15.55%. Its average seepage rate is 2.08cm/day. 3. In the supply ditch, which has a slope of 1/300, and is 200m long, and was constructed by filling earth, its loss rate is 12.34%, its average seepage rate being 3.37cm/day. Proposition: As could be seen in the results above-mentioned, it is contradictory to apply a loss rate of 20% for every main channels and 15% for every laterals without variation, as done so for in planning irrigation project. The fact, however, is that loss rates must be different according to localities and characteristics. Due to the fact that this experiment is small in its scope and is nothing but a preliminary one, it is hardly possible to draw decisive conclusions with the results obtained in this research. Loss rates, that are secured through more extensive research, should be used, in order to establish precise irrigation project. Moreover, such researches should be carried out for a number of loclities throughout the nation.

• Journal of the Korean Geographical Society
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• v.32 no.4
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• pp.445-462
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• 1997

This study was conducted to analyze the spatial and temporal characteristics of stream water quality and to charify the management of watershed environment from the standpoint of hydrological geography. To achieve the purpose of the study, the Wangsook River was chosen. As the result of this study, the specific conclusions were drawn. 1. In general, WT(water temperature) of the downstream is higher than that of the upstream. The value of winter WT measured in densely populated area is higher than that measured under the natural conditions. The seasonal variation of WT at upstream sites is greater than that of downstream. 2. Rhe water quality of main channel is dependent on that of tributaries. Especially, the values of pH, EC, TDS in main channel depend upon those of tributaries. Among the tributaries of the Wangsook river, the Jingun-chon and Yongam-chon have mostly influence on the water quality of the main channel. 3. Generally, the values of COD measured in the Wangsook River are over the 5th Grade considering from a point of water quality standards of inland lake. However, BOD, phosphorus and nitrogen concentrations have to be measured to clear the water quality conditions of the river. 4. The regional people who live in the catchment of Wangsook river have different perception about the water pollution of the river. The regional people lacks in the understanding of the Wangsook river cause a bad influence upon the hydrological management of watershed environment.

• Journal of Korea Multimedia Society
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• v.14 no.9
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• pp.1165-1174
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• 2011

In data broadcasting systems, servers continuously disseminate data items through broadcast channels, and mobile client only needs to wait for the data of interest to present on a broadcast channel. However, because broadcast channels are shared by a large set of data items, the expected delay of receiving a desired data item may increase. This paper explores the issue of designing proper data allocation on multiple broadcast channels to minimize the average expected delay time of all data items, and proposes a new data allocation scheme named two level bin-packing(TLBP). This paper first introduces the theoretical lower-bound of the average expected delay, and determines the bin capacity based on this value. TLBP partitions all data items into a number of groups using bin-packing algorithm and allocates each group of data items on an individual channel. By employing bin-packing algorithm in two step, TLBP can reflect a variation of access probabilities among data items allocated on the same channel to the broadcast schedule, and thus enhance the performance. Simulation is performed to compare the performance of TLBP with three existing approaches. The simulation results show that TLBP outperforms others in terms of the average expected delay time at a reasonable execution overhead.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.2
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• pp.47-55
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• 2010

The power line communication channel has characteristic variation problems which are caused by load. The spread spectrum technique has been used to overcome these problems. One of that is the direct sequence spread spectrum(DS/SS) system which is not necessary to additional hardwares. The BER of DS/SS system is decreased by longer length of PN code, but data transfer rate is decreases, so data transfer rate is hard to satisfies their own specifications especially in narrowband PLC systems. Spread Spectrum system with Dual-processing Gain tries to reflect cyclic characteristics of power line noise. But that system assumes that shapes of power line channel are symmetrical with respect to the 1/4 point of main frequency(60Hz in Korea), therefore cannot achieves various shapes of real power line noise. Thus in this paper, noise adaptive DS/SS system which PN code is changed by noise levels for various channel noises is proposed and simulated. The different kinds of noises are modeled and measured for simulation, the proposed system is verified that has lower data transfer rate and lower error rate than conventional system by simulation results.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.7-13
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• 2012

The performance of blind equalization algorithm ISCA was compared with MSCA that is used for the minimization of the inter symbol interference which occurs in the time dispersive communication channel for digital transmission. Because of the non-linearities of a magnitude and phase transfer characteristics of a communication channel, the transmitting signal will be received that band limited and time dispersived. Therefore the distortion was compensated by using the self adaptive equalizer at the receiving side, then passing through the detector for the decision of "1" or "0". At this time the Constellation Dependent Constant is played an important role in the adaptive equalizer used on the receiver. In order to calculation of this constant, the ISCA and MSCA was used the second order statistics. The ISCA and MSCA which are possible to compensation of mensioned transfer function simulataneously, are improved the performance of original SCA algorithm and then was compared the performance by computer simulation. For this, the recovered constellation, residual isi and MSE was used, and a result of performance comparison, the ISCA algorithm has better than the MSCA in every performance index. But on the steady state of equalizer, the variation of performance due to the CME terms in the MSCA equalization algorithm was less than the ISCA, so MSCA has better stability.