• Journal of Korean Society of Disaster and Security
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• v.15 no.3
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• pp.15-21
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• 2022

The purpose of this study is to investigate the sedimentation area and runout distance in the downstream when debris flow occurred on a mountain slope through an experimental performance. Super typhoons and torrential rains caused by climate change cause large-scale debris flow disasters in the downstream areas of mountainous areas, mainly where sediments are deposited and flowed downstream. To analyze the characteristics of the sediment deposited downstream, the disposition area and runout distance were investigated through experiments in the case of a straight channel and channel with berm, respectively. As experimental conditions, changes in sediment volume concentration and channel slope, and channel with or without berm, reduction rates in sedimentation area and runout distance were investigated. In the straight channel, the steeper the channel slope and the lower the sedimentation concentration, the sedimentation area and runout distnace were increased. In a channel with berm, the runout distance and sediment area increased as the slope became steeper and the sediment area decreased.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.323-323
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• 2011

산지가 많은 국내의 지형적인 여건은 토지의 이용에 다양한 영향을 준다. 산지주변에서는 능선을 따르거나 가로지르는 도로가 건설되고 산지계곡 하류에 발달한 선상지에는 가옥이 들어서거나 경작지로 활용되고 있다. 이러한 환경에서 우리나라는 지난 10년간 사면재해로 인한 사망자가 전체 자연재해에 27%에 달하고 이는 집중호우가 발생하는 시기에 집중되고 있어 이에 대한 연구가 필요한 실정이다. 본 연구에서는 호우 발생 시 산지하천에서 발생하는 토석류의 흐름특성을 연구하기 위해 국내 외 토석류 실험장치에 대한 조사와 토석류 실험장치를 개발하여 토석류발생 및 도달거리 예측을 위한 실험을 수행하였다. 토석류 실험장치는 수조길이 5.5m에 10-40cm의 가동폭 그리고 상 중 하류의 3단계 경사조절이 가능하며 토석류 퇴적장치를 결합하여 도달거리 및 퇴적분포를 계측할 수 있다. 토석류를 발생시키기 위해 토사공급장치 이용방법, 하상퇴적토사를 이용한 방법 등 다양한 시도를 하였다. 토석류 실험장치를 이용하여 발생시킨 토석류의 특성과 퇴적장치 에서의 도달거리를 측정하여 유량공급과의 상관관계를 분석하였다. 이러한 연구결과는 토석류 재해지도의 작성이나 토석류 해석모형의 개발에 필요한 기초자료로 활용될 수 있다.

• Journal of Bio-Environment Control
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• v.6 no.3
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• pp.183-189
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• 1997

This study was performed to Investigate size of droplet sprinkled from mini-sprinkler. Twelve different kinds of the sprinkler having various structures and sizes of nozzle orifices were selected and tested. Diameters of the droplet reached at several distances from a sprinkler were measured by a machine vision system and the volume median diameters (VMM) were determined statistically. The size of droplet was not affected much by the size of nozzle orifice of a sprinkler but was rather more affected by structure of the sprinkler, especially by the shape of spreader of the sprinkler. Experiment of varying pressure of sprinkling water validated that the size of droplet was inversely proportional to water pressure powered by 1/3. Hence the size of droplet at any water pressure could be easily estimated from experimental data. The size of droplet increased as travel distance of the droplet increases in a relationship of and order function. The size of droplet of the tested sprinkler were in the ranges of 100-300fm within 1m of droplet travel distance, 230~470${\mu}{\textrm}{m}$ within 1~2m of droplet travel distance and 300~770${\mu}{\textrm}{m}$ within 2~3m of droplet travel distance.

• Journal of Korean Society of Disaster and Security
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• v.16 no.4
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• pp.1-7
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• 2023

The purpose of this study is an experimental research to investigate the effectiveness of debris flow reduction structures when a debris flow disaster occurs on a steep slope. The control structure for debris flow took the form of baffle, and the soil deposition area and soil runout distance due to debris flow from the downstream were investigated according to the installation number of baffle and each specification. As the slope of the channel became steeper, the sediment deposition area and runout distance increased, and as the sediment volume concentration decreased, the sediment deposition area and runout distance increased. When the sediment concentration was low, differences appeared depending on the slope of the channel because the debris flow had a high liquid content. Overall, the larger the sediment volume concentration, the greater the decrease in sediment deposition area and soil runout distance. As the number of baffles increases, the soil deposition area and runout decrease, showing that the baffles have the ability to control debris flows. The results of this research will provide good information when installing attenuation or control structures when sediment disasters occur in steep slopes.

• The Journal of the Acoustical Society of Korea
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• v.42 no.6
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• pp.511-518
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• 2023

Accurate ranging is one of the key factors in the test and evaluation process of underwater vehicles. In particular, when estimating range using Time of Arrival (ToA) values, signals such as Linear Frequency Modulation (LFM), a chirp signal, are highly applicable due to their correlated nature. However, in a Doppler shift environment with mobility, measurement errors may occur due to the range-Doppler coupling effect. In this paper, we propose a signal that compensates for the distance-Doppler coupling effect to reduce the measurement error of the arrival time value. The proposed signal is constructed by superimposing two types of LFM signals, and the range-Doppler coupling effect can be minimized. Through simulations, it is confirmed that the proposed signal is a way to compensate for the distance-Doppler coupling effect in the distance estimation of underwater mobile bodies, reducing the measurement error of the arrival time value.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.140-152
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• 1989

The study on the penetration of sprays during the initial phase of injection period, i.e. ignition delay period, in high speed small D.I. diesel engines are strongly affected by such behavior. To investigate the penetration of the sprays injected through single cylinderical orifice, a mathematical model was developed and compared with experimental results. In this model, radial heterogeneity of fuel density in the spray, transiency of injection pressure difference, and spray outrunning phenomenon were considered simultaneously. Experiments on the behaviors of sprays in the high pressure air chamber were conducted at various injection pressure differences and different levels of back air pressure. The behaviors of sprays injected into the chamber through the conventional Bosch injection pump were visualized with side stroboscopic illumination. Comparison of the experimental results with predictions from the mathematical model confirmed the validity of the model. It was also found that during the initial phase of the injection period the penetration of sprays vs. time appeared to have two transition points; one corresponded to disintegration point of liquid fuel jet, the other to the beginning of steady state injection.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.294-297
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• 2011

주어진 계획 문제로부터 휴리스틱을 이용하여 최적의 해 계획을 구하기 위해서는 허용 가능한 휴리스틱을 이용하여야 한다. 이러한 허용 가능한 휴리스틱은 실제 목표 도달거리보다 짧거나 같아야 하는데 휴리스틱 평가치가 실제 목표 도달거리에 가까울수록 계획생성을 위한 탐색 효율성이 높아진다. 하지만, 이러한 허용 가능한 휴리스틱 평가치를 구하는 과정은 매우 복잡하며 계산량이 많기 때문에 실제 계획 생성 과정에서 사용하기는 어렵다. 때문에 최대 휴리스틱과 같은 허용성을 만족하는 간단한 휴리스틱을 이용하고 있으며, 이로 인해 최적의 계획 결과를 얻을 수는 있지만, 탐색의 효율성이 떨어지는 결과를 가져오고 있다. 본 논문에서는 이러한 문제를 해결하기 위해서 기존의 계획그래프를 개선한 새로운 계획그래프인 확장된 계획그래프(EPG)를 이용한 MAX+ 휴리스틱 계산법을 소개한다. 확장된 계획그래프는 계획 문제 풀이를 위한 휴리스틱 계산에 이용되는 기존의 간략화된 계획그래프를 목표조건들 간의 상호작용을 확인 할 수 있도록 확장한 자료구조로써 목표조건들 간의 긍정적/부정적 상호작용을 찾는다. 이를 위해서 모든 목표조건들이 등장할 때까지 그래프를 전개하는 기본 전개 과정과 함께, 이 과정에서 발견된 동작과 목표 조건들과의 관계를 바탕으로 한 추가 전개 과정으로 이루어져 있다. 그리고 이 과정을 통해서 목표조건들간의 상호작용과 최단 거리를 구하게 된다. MAX+ 휴리스틱 계산에서는 이러한 목표조건들 간의 긍정적/부정적 상호작용의 존재 유무를 찾아내게 됨으로써 전체 목표 집합에 대한 보다 정확한 최소 도달거리에 대한 평가치를 찾게 된다. 따라서 MAX+ 휴리스틱은 기존의 최대 휴리스틱 보다 더 정보력 높은 휴리스틱을 구할 수 있는 장점이 있다. 본 논문에서는 MAX+ 휴리스틱의 계산 과정과 MAX+ 휴리스틱의 정확성과 이를 바탕으로 한 탐색 효율성을 확인하기 위한 실험적 분석에 대해 설명한다.

• Journal of Biosystems Engineering
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• v.7 no.2
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• pp.30-35
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• 1983

To investigate the factors affecting the transportability of spray droplets, the maximum distance, the effective distance, the ratio of even distribution, and the diameters of particles were measured in accordance with the different pressure levels of power sprayer using 3 hole swath type nozzle, and the results are summerized as follows; 1. The distance of the most dense point from the nozzle was shortened by 0.5 meter with the 100-meter-long hose. The maximum reaching distances were reduced by 1.5 and 1.0 meters for the 13m/m and the 8.5 m/m hoses respectively, and the effective distance were reduced by 0.5 meter for both cases. 2. The effective distance can not be extended beyond 14 meters even if the length of hose is minimized at the rated pump pressure 28 kg/$cm^2$, it was 1 meter longer for 13m/m hose compared to the 8.5m/m one. 3. In case of 13m/m hose, the most dense point can be extended further by 0.5 meter increasing the pump pressure by 8 kg/$cm^2$, and the maximum distance and effective distance were increased by 2.0 and 0.5 meters respectively. There was no significant effect of pressure changes on the transportability in case of 8.5m/m hose. 4. Both the reduction of hose length and the increase of pump pressure influenced in large extent to the atomization effect of droplets. It was noticed that the diameter of droplet is related to the pump pressure and inside diameter of hose. 5. The pressure drop in 100-meter-long and l3m/m hose was 5~7kg/$cm^2$ at the pump pressure range of 25~33kg/$cm^2$, and it is an equivalent of 2% per 10 meter length of hose.

• The Journal of the Acoustical Society of Korea
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• v.38 no.2
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• pp.154-159
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• 2019

When measuring the radiating noise of an underwater moving source, the range information between the acoustic source and the receiver is an important evaluation factor, and the measurement standards such as a receiver position, a moving source depth and a speed are set. Although there is a method of using the cross correlation as a method of finding the range of the underwater moving source, this method requires a time synchronization process. In this paper, we proposed the method to estimate the range by comparing the Doppler frequency difference of the theoretically calculated multipath signal with the Doppler frequency difference of the multipath signal estimated from the received signal. The proposed method does not require a separate time synchronization process. Simulations were performed to verify the performance, and the ranging error of the proposed method reduced by about 95 % than that of the conventional method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11C
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• pp.957-964
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• 2010

In this paper, we propose an indoor positioning algorithm based on 3 points near field angle-of-arrival estimation without side information. The conventional angle-of-arrival based positioning scheme requires the distance between the listener and the center of two points which is obtained by a received signal strength based range estimation. However, a received signal strength is affected by structure of room, placement of furniture, and characteristic of signal, these effects cause a large error to estimation of angle. In this paper, the proposed positioning scheme based on near field angle-of-arrival estimation can be used to estimate the position of listener without a prior distance information, just using time-difference-of-arrival information given from 3 points microphones. The performance of the proposed scheme is shown by cumulative distribution function of root mean squared error.