• Journal of Welding and Joining
• /
• 제17권5호
• /
• pp.40-46
• /
• 1999

The sensors employed in the robotic are welding system must detect the changes in weld characteristics and produce the output that is in some way related to the change being detected. Such adaptive systems, which synchronise the robot arm and eyes using a primitive brain will form the basis for the development of robotic GMA(Gas Metal Arc) welding which increasingly higher levels of artificial intelligence. The objective of this paper is to realize the mapping characteristics of bead height through learning. After learning, the neural estimation can estimate the bead height desired from the learning mapping characteristic. The design parameters of the neural network estimator(the number of hidden layers and the number of nodes in a layer) are chosen from an estimation error analysis. A series of bead of bead-on-plate GMA welding experiments was carried out in order to verify the performance of the neural network estimator. The experimental results show that the proposed neural network estimator can predict the bead height with reasonable accuracy and guarantee the uniform weld quality.

• Ocean Science Journal
• /
• 제41권4호
• /
• pp.245-254
• /
• 2006

Long term wave climate of both extreme wave and operational wave height is essential for planning and designing coastal structures. Since the field wave data for the waters around Korean peninsula is not enough to provide reliable wave statistics, the wave climate information has been generated by means of long-term wave hindcasting using available meteorological data. Basic data base of hindcasted wave parameters such as significant wave height, peak period and direction has been established continuously for the period of 25 years starting from 1979 and for major 106 typhoons for the past 53 years since 1951 for each grid point of the North East Asia Regional Seas with grid size of 18 km. Wind field reanalyzed by European Center for Midrange Weather Forecasts (ECMWF) was used for the simulation of waves for the extra-tropical storms, while wind field calculated by typhoon wind model with typhoon parameters carefully analyzed using most of the available data was used for the simulation of typhoon waves. Design wave heights for the return period of 10, 20, 30, 50 and 100 years for 16 directions at each grid point have been estimated by means of extreme wave analysis using the wave simulation data. As in conventional methodsi of design criteria estimation, it is assumed that the climate is stationary and the statistics and extreme analysis using the long-term hindcasting data are used in the statistical prediction for the future. The method of extreme statistical analysis in handling the extreme vents like typhoon Maemi in 2003 was evaluated for more stable results of design wave height estimation for the return periods of 30-50 years for the cost effective construction of coastal structures.

• Spatial Information Research
• /
• 제20권3호
• /
• pp.27-38
• /
• 2012

산림의 보존과 관리에 대한 필요성이 점차 증가하면서 항공 라이다데이터를 이용한 산림연구가 활발히 수행되고 있다. 이러한 산림연구에서 수목고도는 정량적인 산림측정을 위한 중요한 변수로 이용된다. 이에 본 연구는 항공 라이다데이터로부터 수목고도 추정을 위한 대표적인 두 종류의 방법을 적용하고 그 결과를 비교분석한다. Local maximum 필터링에 기반한 개별수목탐지 방법으로 개별수목의 수, 위치, 높이 및 평균수고를, 수목고도모델 또는 히스토그램을 이용한 평균수고 추정방법으로 개별격자 또는 전체영역에 대한 최대, 평균수고, 평균 수관고를 추정한다. 현장에서 실측한 검증데이터와 비교한 결과 개별 수목은 76.6%의 정확도로 탐지되었으며 개별수고는 전체 수종의 경우 1.91m, 침엽수종에 대해서는 0.75m의 RMSE로 추정되었다. 반면 수목고도모델을 이용하여 추정된 평균수고는 약 1~2m의 RMSE를 보였으며, 히스토그램을 이용하여 추정된 평균수고는 약 0.6m 과소 추정되었다. 정확하고 다양한 산림정보 추출을 위해 수종 및 추정인자에 따라 적합한 상호보완적인 방법을 선택하고 융합하는 것이 필요하다.

• Journal of Forest and Environmental Science
• /
• 제32권2호
• /
• pp.212-218
• /
• 2016

The research was conducted windward of an irrigated Acacia amplicips Maslin windbreak established to protect As Salam Cement Plant from winds and moving sands. Two belts with approximate optical porosities of 50% and 20% were studied in River Nile State, Sudan. The research aimed at assessing the efficiency of the two belts in wind speed reduction and sand deposition. Research methods included: (i) estimation of optical porosity, (ii) measurements of windward wind speeds at a control and at distances of 0.5 h (h stands for windbreak height), 1 h and 2 h at two vertical levels of 0.25 h and 0.5 h, (iii) estimation of relative wind speeds at the three positions (distance and height) at windward and (iv) estimation of wind erosive forces and prediction of zones of sand deposition. Results show that while the two belts reduced windward wind speeds at the two levels for the three distances, belt II was more effective. Nearest sand deposition occurred at 2 h and 1h windward of belt II and belt I, respectively, at level 0.25 h. At level 0.5 h, sand was deposited only at 2 h windward of belt II and no sand deposition occurred windward of belt I. The study concludes that less porous windbreaks are more effective in reducing wind speed and in depositing sand in windward direction at a distance of not less than twice the belt height.

• Journal of Biosystems Engineering
• /
• 제36권3호
• /
• pp.180-186
• /
• 2011

The objective of this research was to establish the estimation method of growth information on potato using Multi-Spectral Image Sensor (MSIS) and Global Positioning System (GPS). And growth estimation map for determining a prescription map over the entire field was generated. To determine the growth model, 10 ground-truth points of areas of $4m^2$ each were selected and investigated. The growth information included stem number, crop height and SPAD value. In addition, images information involving the ground-truth points were also taken by an unmanned helicopter, and reflectance value of Green, Red, and NIR bands were calculated with image processing. Then, growth status of potato was modeled by multi-regression analysis using these reflectance value of Green, Red, and NIR. As a result, potato growth information could be detected by analyzing Green, Red, and NIR images. Stem number, crop height and SPAD value could be estimated with $R^2$ values of 0.600, 0.657 and 0.747 respectively. The generated GIS map would describe variability of the potato growth in a whole field.

• 대한인간공학회:학술대회논문집
• /
• 대한인간공학회 1997년도 춘계학술대회논문집
• /
• pp.90-94
• /
• 1997

Many workers like welders are working in squat sitting postures with te object on the ground for an entire work shift. It is suspected that such prolonged squat sitting without any supporting stool would gradually cause musculoskeletal injuries to workers. This study is to quantitatively evaluate the physical stress caused by the prolonged squat sitting and to recommend a safe work/rest schedule for the task with squat sitting posture based on the lab experiment. In this study, 8 healthy student subjects participated in the experiment. They maintained a squat sitting posture for 16 minutes with 4 different stool height conditions: no stool, 10cm hight, 15cm height, 20cm height. Every 2 minutes, the discomfort was subjectively assessed using the magnitude estimation method for the whole body, lower back, upper leg and lower leg. Based on discomfort rating, we found that 10cm height stool relieved the workload most. Discomfort rating results also indicated that 20cm height stool showed the heghest workload, and that there was no difference in workload between 15cm height and no stool. We recommend to provide the workers with 10cm height stool for prolonged squat sitting tasks.

• 한국공작기계학회논문집
• /
• 제16권4호
• /
• pp.79-86
• /
• 2007

The shape of excessive penetration mainly depends on welding conditions(welding current and welding voltage), and welding process(groove gap and welding speed). These conditions are the major affecting factors to width and height of back bead. In this paper, back-bead prediction and weldability estimation using artificial neural network were investigated. Results are as follows. 1) If groove gap, welding current, welding voltage and welding speed will be previously determined as a welding condition, width and height of back bead can be predicted by artificial neural network system without experimental measurement. 2) From the result applied to three weld quality levels(ISO 5817), both experimented measurement using vision sensor and predicted mean values by artificial neural network showed good agreement. 3) The width and height of back bead are proportional to groove gap, welding current and welding voltage, but welding speed. is not.

• 한국산림과학회지
• /
• 제88권1호
• /
• pp.47-54
• /
• 1999

지위지수(地位指數) 12등급인 곰솔임분에 대한 최적(最適)의 직경(直徑) 및 수고생장함수(樹高生長函數)를 linear transformation(1), linear transformation(2) 등 2개의 선형식(線型式)과 exponential, Gompertz, Chapman-Richards, Weibull 등 4개의 비선형식(非線型式)에 의하여 도출하였다. 이들 함수에 의하여 추정된 직경 및 수고생장과 실측치인 직경 및 수고생장간의 상호관계를 분석하였다. 곰솔임분의 임령에 따른 직경과 수고생장을 추정한 결과는 선형식보다 비선형식의 적합성이 높게 나타났으며, 직경생장에는 Gompertz식, 그리고 수고생장에는 Chapman-Richards식의 적합성이 높게 나타났으나, 이들 비선형식간의 큰 차이는 없는 것으로 나타났다. 따라서 앞으로 이들 비선형식을 적용하여 현실임분(現實林分)의 직경과 수고생장을 추정하여야 할 것으로 사료된다.

• 한국산림과학회지
• /
• 제112권3호
• /
• pp.374-381
• /
• 2023

산지하천에서 발생하는 돌발홍수는 특정 지점의 점(Point) 유속보다는 전체 구간의 평균 유속에 따라 이동속도가 결정되며, 구간 평균유속은 하천경사, 하상재료, 수리적 거칠기에 많은 영향을 받는다. 이 연구에서는 하천경사 및 거칠기 높이를 이용하여 산지하천의 구간 평균유속 추정방법을 개발하였다. 염료추적자법(Dye Tracing)을 이용하여 특정 구간의 평균유속을 측정하고, LiDAR 영상으로부터 하천 지형 및 형상을 추출하였다. 거칠기 높이를 산정하기 위해 표면 거칠기 변수(R_a, R_max, R_z )와 하상재료의 크기(D₅₀, D₈₄)를 이용하였다. 현장 계측자료로부터 무차원 접근법을 이용하여 구간 평균유속과 유량과의 관계식 v = 0.5499Q^0.6165 을 도출하였으며, R² =0.77의 설명력을 나타냈다. 이 연구에 이용된 5개의 거칠기 높이 중 평균 거칠기 높이(R_a)의 RMSE가 0.45로서 다른 거칠기 높이의 범위(0.47-1.04)보다 낮게 나타나 평균 거칠기 높이(R_a)가 구간 평균유속 산정을 위한 거칠기 높이 인자로 가장 적합하다고 판단되었다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
• /
• pp.386-388
• /
• 2007

In many applications of UAVs flying in low altitude, the steady supply of accurate height measurements is very important for the UAVs to complete their mission successfully. In order to do this, a barometer or GPS height measurements are widely used. However, because these two sensors have their limitations in the application environment, a method for fusing these two measurements to produce reference heights are required. In this paper, a reference height generation filter is designed for UAV(Unmanned Air Vehicle) applications. The barometer errors originated by the change of the atmospheric environment are modeled using random walk models, and then the errors are identified and compensated through the ZSB(zero-scan-back) filter algorithm using the GPS height measurements. The performance of the proposed filter is demonstrated by realistic simulations.