• Journal of Electrical Engineering and Technology
• /
• v.3 no.3
• /
• pp.346-353
• /
• 2008

This paper defines the concept of “protectability” for the performance evaluation of distance relay considering its sensitivity and selectivity. The paper starts from the probabilistic modeling of the errors, and based on this model, a detailed explanation of protectability calculation for each zone of the distance relay is presented. An effect of the Weighting Rate and the Measurement Deviation on the protectability evaluation is also given. By considering this effect, the optimization of relay setting can be realized. The proposed method is applied to a typical model system to show its effectiveness

• Fisheries and Aquatic Sciences
• /
• v.26 no.8
• /
• pp.514-523
• /
• 2023

The visible threshold of Oreochromis niloticus responded to high light intensity under short wavelengths, whereas the response to low light intensity under long wavelengths was low, with a minimum visual threshold of 574 nm of LED lights. Movement distance of O. niloticus was dropped at 31℃ and increased abnormally at 37℃ under natural light. Comparing movement distance under red (622 nm) and green (518 nm) lights of LED, movement distance and swimming speed under red and green lights were higher than under natural light. However, the movement distance decreased rapidly at 31℃ under red light and lowest at 33℃ under green light. After that, there was a tendency to adapt to high water temperatures gradually. Consequently, red and green lights may be recommended for O. niloticus's aquaculture because the red and green lights have a positive effect on growth performance, survival rate, and metabolism, as shown in previous studies. It is necessary to control the water temperature below 32℃ because abnormal behavior above 32℃ revealed under red and green LED lights and natural light.

• Journal of Korean Ophthalmic Optics Society
• /
• v.18 no.3
• /
• pp.241-246
• /
• 2013

Purpose: The aim of this study was a comparative analysis of the effect of distance contrast sensitivity when wearing free-form progressive lens and conventional progressive lens. Methods: The 20 subjects who do not have any ocular diseases were participated in this study. Contrast sensitivities at 5 different levels of spatial frequency were conducted by using FACT (Stereo Optical, USA). Results: Contrast sensitivity was measured for free-form progressive lens and conventional progressive lens in the order of right eye, left eye and binocular. Right/left/binocular contrast sensitivity values of the free-form progressive lenses compared to the conventional progressive lenses were higher 16%/17%/11% at A(1.5 cpd) of spatial frequency, 11%/5%/5% at B(3 cpd) of spatial frequency, 6%/6%/9% at C(6 cpd) of spatial frequency, 19%/16%/13% at D(12 cpd) of spatial frequency, 4%/3%/18% at E(18 cpd) of spatial frequency. Conclusions: In all the area of spatial frequency, distance contrast sensitivity values were measured highly on free-form progressive lens than on conventional progressive lens.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2007.11a
• /
• pp.233-236
• /
• 2007

In this paper, thermal sensitivity of the solid fuel grain in the hybrid rocket motor was investigated. When the heat from the non-reacting hot flow passing the grain ports is transferred to the solid fuel grain, the temperature fields in the solid fuel was numerically analyzed. These numerical analyzes were performed under the different nine port radii, and the critical distance between the ports in which the temperature in the solid fuel is sensibly responding was determined. Thus, the critical distance between the ports would be the important consideration for the design of the fuel grain because the high temperature in the fuel can bring the structural problems.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 1996.11a
• /
• pp.53-56
• /
• 1996

In order to propose the method of the consequence analysis for fire accidents by the heavy gas release and to obtain optimum conditions of parameter selections, the consequence analysis for jet fire by the accident of xylene vapor release were performed. And the effect and the sensitivity analysis of parameters affecting the consequence were investigated. Simulation results showed that important parameters affecting results of the xylene vapor release accident were mainly hole diameter, interested distance, wind speed, and so on. For the jet fire, the accident result and the sensitivity of thermal radiation were increased with the decrease of interested distance and the increase of hole diameters, and the accidental result was increased as the increase wind speed, but the sensitivity of thermal radiation was decreased.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.2
• /
• pp.183-189
• /
• 2010

A localization system for indoor robots is an important technology for robot navigation in a building. Our localization system imports the GPS system and consists of more than 3 satellite beacons and a receiver. Each beacon emits both an ultrasonic wave and radio frequency. The receiver in the robot computes the distance from it to the beacon by measuring the flying time difference between ultrasonic wave and radio frequency. It then computes its position with the distance information from more than 3 beacons whose positions are known. However, the distance information includes errors caused from the ultrasonic sensors; we found it to be limited to within one period of a wave (${\pm}2\;cm$ tolerance). This paper presents a method for predicting the maximum position error due to distance information errors by using Taylor expansion and singular value decomposition (SVD). The paper also proposes a measuring parameter such as sensitivity to represent the accuracy of the indoor robot localization system in determining the robot's position with regards to the distance error.

• Journal of the Korean Society of Safety
• /
• v.18 no.1
• /
• pp.8-13
• /
• 2003

This study proposes integrity evaluation method of weld zone in rails using high precision distance amplitude characteristics curve(DACC) and ultrasonic signals. For these purposes, the ultrasonic signals for defects(porosity and crack) of weld zone in rails are acquired in the type of time series data and echo strength. 6 lines in the DACC indicated damage evaluation standard of weld zone in rails. The aquired ultrasonic signals agree fairly well with the mesured results of reference block and sensitivity block(defect location, beam propagation distance, echo strength, etc). The proposed high precision DACC in this study can be used for integrity evaluation of weld zone in rails.

• Journal of the Korean Society of Safety
• /
• v.23 no.4
• /
• pp.7-12
• /
• 2008

This study proposes integrity evaluation method of weld zone in titanium using titanium distance amplitude characteristics curve(TDACC) and ultrasonic signals. For these purposes, the ultrasonic signals for porosity defects of weld zone in titanium are acquired in the type of time series data and echo strength. 4 lines in the DACC indicated damage evaluation standard of weld zone in titanium. The acquired ultrasonic signals agree fairly well with the measured results of reference block and sensitivity block(defect location, bean1 propagation distance, echo strength, etc). The proposed TDACC in this study agree fairy well with the measured results of weld zone in titanium(weld defects as porosity). The proposed TDACC in this study can be used for integrity evaluation of weld zone in titanium.

• Journal of applied mathematics & informatics
• /
• v.13 no.1_2
• /
• pp.323-334
• /
• 2003

This paper presents a goal-programming (GP) model for management decision-making for sugarcane fertilizer mix problems. Sensitivity analysis on the priority structure of the goals has been performed to obtain all possible solutions. The study uses Euclidean distance function to measure distances of all possible solutions from the ideal solution. The optimum solution is determined from the minimum distance between the ideal solution and other possible solutions of the problem. The optimum solution corresponds to the appropriate priority structure of the problem in the decision-making context. furthermore, the results obtained from sensitivity analysis on the cost of combination of fertilizers confirm the priority structure.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2007.06a
• /
• pp.371-372
• /
• 2007