• 대한기계학회논문집B
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• 제30권6호
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• pp.587-593
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• 2006

A ventilated disc brake having semi-cylindrical grooves has been proposed to improve the thermal judder by way of heat transfer enhancement. The local heat transfer coefficients were measured in the flow passage of disc brake. These measured local heat transfer data were utilized to do the finite element numerical analysis which predicts the maximum temperatures on the disc brake. The results show that the maximum temperatures on the disc surface with semi-cylindrical grooves are approximately 35.2% lower than those without them.

• 로봇학회논문지
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• 제1권1호
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• pp.9-16
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• 2006

The Mobile robots are increasingly being used to perform tasks in unknown environments. The potential of robots to undertake such tasks lies in their ability to intelligently and efficiently search in an environment. An algorithm has been developed for robots which explore the environment to measure the physical properties (dust in this paper). While the robot is moving, it measures the amount of dust and registers the value in the corresponding grid cell. The robot moves from local maximum to local minimum, then to another local maximum, and repeats. To reach the local maximum or minimum, simple gradient following is used. Robust estimation of the gradient using perturbation/correlation, which is very effective when analytical solution is not available, is described. By introducing the probability of each grid cell, and considering the probability distribution, the robot doesn't have to visit all the grid cells in the environment still providing fast and efficient sensing. The extended algorithm to coordinate multiple robots is presented with simulation results.

• East Asian mathematical journal
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• 제40권2호
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• pp.127-148
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• 2024

Maximum and minimum have a historical background in mathematics and occupy an important part of the differential unit in school mathematics. As the curriculum is revised, there are changes and problems in the way definition introduced. Therefore, this study analyzes the changes in the method of introducing maximum and minimum definitions following the reorganization of the 2007 and 2009 revised mathematics curriculum, and analyzes the differences in maximum and minimum definition methods compared to the nine mathematics II textbooks in the 2015 revised mathematics curriculum and three real analysis. In addition, methods to improve the terms used in relation to the maximum and minimum values are presented.

• Water Engineering Research
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• 제1권2호
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• pp.159-168
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• 2000

In this paper, the increment of the local scour depth at piers by constructing the bridge between existing bridges is examined through the experiments in which 5 piers in the non-cohesive bed material in the experimental flume were installed. In the experiments the maximum distance of 25 times of the pier length and the maximum distortion width of 8 times of the pier width were utilized. Through the experimental studies, it was indicated that low flow, which can be characterized as the flow having low Froude numbers, the maximum bed configuration change is obtained when the piers are installed in the straight line in the flor direction without any distortion. However, In the high flow, which can be characterized as the flow having high Froude numbers, the maximum bed configuration change is obtained when the piers are installed with some distortion from the flow direction. The influence of the bed configuration by interaction between bridge piers is changed depending upon the Froude numbers, the distance between piers, and the distortion width between adjacent bridge piers. Also, because the scour patterns are affected by the bed configuration, the maximum scour should be increased by about 60% compared to that in a single pier if the interaction between bridge piers exists. It can be suggested that the maximum scour depth at bridge piers predicted by applying the existing equations should be increased if the interaction between bridge piers exist. Those cases are found when new bridges are constructed successively in the river in the urban area.

• 한국지하수토양환경학회지:지하수토양환경
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• 제26권1호
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• pp.76-87
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• 2021

Groundwater is considered to be the best water resource to solve water shortage problems during drought periods. Even though excessive pumping (overdraft) during short-period may give an unprofitable effect on groundwater hydrology, it has a primary role to solve a lack of water resources and to maintain incomes of farmers. This study evaluated maximum irrigation amounts of groundwater to each local-government and province during drought periods. Maximum irrigation amounts of groundwater were evaluated using cumulative groundwater usage data of each local-government during normal and drought years. Maximum irrigation amounts of groundwater during drought periods would be roughly identified as approximately 1.3 times more than the exploitable amounts of groundwater resources for each local-government. Drawdown-limitation depth on groundwater levels at each monitoring well was determined by transforming the maximum irrigating amounts into degree of change on levels. Universal limitation depth of drawdown on groundwater levels was evaluated to be approximately three times of annual fluctuating range on groundwater levels for each monitoring well. Systematic response on groundwater demands with abiding by drawdown-limitation depth can attain an optimal irrigation of groundwater resources during short-term drought.

• 한국산업보건학회지
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• 제32권1호
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• pp.10-20
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• 2022

Objectives: The aim of this study is to evaluate exposure levels of the extremely low frequency magnetic fields(ELF-MF) radiated from various electric facilities in Liquid Crystal Display(LCD) manufacturing processes. Methods: This study measured the exposure levels of personal and local ELF-MF for the electronic facilities installed in two LCD manufacturing companies. Samplers were installed around workers' waist during working hours to identify personal exposure levels, and direct reading equipment were located at 3 cm, 10 cm, and 30 cm away from the surface of the electronic facilities to measure local exposure levels. Average and maximum(ceiling) values were calculated for personal and local exposure levels. Results: Average and maximum of personal exposure levels for each worker were 0.56(mean) ± 0.02(SE) µT and 6.31 ± 0.75 µT, respectively. Statistical analyses of the study found that maximum of the personal exposure levels for engineers was significantly higher than that for operators since engineers spend more time near the electronic facilities for repairing. The range of maximum personal exposure levels was 0.50 ~ 43.50 µT and its highest level was equivalent to 4.35 % of ACGIH(American Conference of Governmental Industrial Hygienists) exposure limit value(1 mT). Maximum of local exposure levels was 8.18 ± 0.52 µT and the electronic facilities with higher exposure levels were roof rail and electric panel, which were not related to direct manufacturing. The range of maximum local exposure levels was 0.60 ~ 287.20 µT and its highest level was equivalent to 28.7 % of the ACGIH exposure limit value. Lastly, the local exposure levels significantly decreased as the measurement distance from the electronic facilities increased. Conclusions: Maximum of personal and local exposure levels did not exceed the exposure limit value of ACGIH. However, it is recommended to keep the workers as far as possible from the sources of ELF-MF.

• 대한전자공학회논문지TC
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• 제47권4호
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• pp.43-50
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• 2010

V2V(Vehicle-to-Vehicle)는 VANET(Vehicle Ad-hoc Network)의 한 형태로 차량 간 통신을 제공하며 차량 안전사고를 줄일 수 있는 해결책으로 알려져 있다. 이러한 V2V는 도로의 특성 및 차량 구성 장치의 특성으로 인하여 GPSR(Greedy Perimeter Stateless Routing)과 같은 지리 기반 라우팅 프로토콜이 매우 적합하지만, GPSR의 탐욕모드의 정책에 의해서 stale 노드가 local maximum에 직면하는 문제가 발생한다. 이러한 문제점은 GPSR에서의 복구모드 정책에 의하여 해결될 수 있지만 복구모드 시 전송되는 데이터의 손실이 발생할 수 있다는 단점이 있다. 따라서 본 논문에서는 V2V 환경에서의 이러한 GPSR 문제를 해결하기위해 보다 나은 데이터 신뢰성을 제공하는 GPRR(Greedy Perimeter Reliable Routing) 프로토콜을 제안한다. ns-2를 이용한 성능분석 결과 제안된 GPRR이 탐욕모드 시 local maximum에 직면할 가능성을 현저히 줄임으로써 GPSR 보다 우수함을 입증하였다.

• 한국인터넷방송통신학회논문지
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• 제19권5호
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• pp.73-78
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• 2019

본 논문은 NP-난제로 널리 알려진 최대 가중치 독립집합 문제에 대해 다항시간으로 풀 수 있는 규칙을 제시하였다. 기존에 알려진 분산형 알고리즘은 지역에서 최대 가중치 노드를 독립집합 원소로 결정하는 방법을 적용하였다. 그러나 지역에서 최대 가중치를 갖는 노드 단독이 아닌 보다 작은 가중치들을 갖는 노드들이 병합된 독립집합이 최대 가중치를 갖는 경우가 보다 빈번히 발생하여 기존에 알려진 방법으로는 최적 해를 구하지 못할 수도 있다. 이러한 문제점을 해결하기 위해, 본 논문에서는 지역에서 최대 가중치를 갖는 독립집합을 형성하는 방법을 제안하였다. 제안된 알고리즘을 다양한 망들에 적용한 결과, 기존에 알려진 알고리즘으로 구하지 못한 최적 해를 구할 수 있었다.

• Journal of Astronomy and Space Sciences
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• 제23권2호
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• pp.117-126
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• 2006

지상에서 우주선 측정기(NM, Neutron Monitor)로 관측되는 우주선 세기의 일변화는 일평균 값의 $1{\sim}2%$ 정도의 진폭을 갖는 사인곡선의 형태를 보인다. 본 연구는 NM 관측소에서 우주선 일변화의 최대 및 최소 세기가 관측되는 지방시 변화의 통계적 경향 분석을 수행하였다. 우주선 일변화 최대 및 최소 세기 시각의 분포에 영향을 주는 우주선 중성자 관측소의 위치(cut-off rigidity)와 태양활동도의 영향을 분석해 보기 위해서 저위도 지방의 Haleakala(위도: 20.72N, cut-off rigidity: 12.91Gev)와 고위도 지방의 Oulu(위도: 65.05N, cut-off rigidity: 0.81Gev) 우주선 중성자 관측소의 1996년(태양활동 극소기) 및 2000년(태양활동 극대기) 우주선 관측 자료를 분석하였다. 태양활동 극대기의 우주선 일변화 최대 및 최소 세기 시각은 태양활동 극소기에 비해 약 $2{\sim}3$시간 정도 늦은 시각에 나타난다. 우주선 중성자 관측소의 위치 즉 위도별 분포(rigidity의 크기)에 따른 영향을 살펴보면, cut-off. rigidity가 Haleakala보다 작은 Oulu에서 우주선 일변화 최대 및 최소 세기 시각이 약 $2{\sim}3$시간 정도 늦게 나타나며, 이러한 현상은 극대기에 더욱 뚜렷하게 나타났다. 태양활동에 따른 행성간 자기장 세기의 변화와 위도에 따른 cut-off rigidity의 크기에 따라 우주선 세기 일변화 위상이 결정된다고 볼 수 있다.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.180-189
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• 1999

This paper describes the collapse characteristics of the rectangular tube under eccentric compressive load. Local buckling stress and maximum crippling load are investigated. A thin-walled tube under load is controlled by local buckling or yielding of material according to the ratio of thickness to width (t/b) of the cross section, and subsequent collapse of the section. The relationship can be divided into three regions : elastic , post-buckling and crippling . the load-displacement relationship is theoretically presented in each region by introducing the stress distribution of the cross section in the loading process. And the maximum load carrying capacity is derived in the closed form as a function of normal stress on the flange and web.