• Journal of Institute of Control, Robotics and Systems
• /
• v.7 no.9
• /
• pp.723-732
• /
• 2001

In this paper, the neurofuzzy controller of optically guided AGV is proposed to improve the path-tracking performance A differential steered AGV has front-side and rear-side optical sensors, which can identify the guiding path. Due to the discontinuity of measured data in optical sensors, optically guided AGVs break away easily from the guiding path and path-tracking performance is being degraded. Whenever the On/Off signals in the optical sensors are generated discontinuously, the motion errors can be measured and updated. After sensing, the variation of motion errors can be estimated continuously by the dead reckoning method according to left/right wheel angular velocity. We define the estimated contour error as the sum of the measured contour in the sensing error and the estimated variation of contour error after sensing. The neurofuzzy system consists of incorporating fuzzy controller and neural network. The center and width of fuzzy membership functions are adaptively adjusted by back-propagation learning to minimize th estimated contour error. The proposed control system can be compared with the traditional fuzzy control and decision system in their network structure and learning ability. The proposed control strategy is experience through simulated model to check the performance.

• Journal of KIISE:Information Networking
• /
• v.35 no.4
• /
• pp.251-267
• /
• 2008

In this paper, we present a distributed topology control algorithm for constructing an optimized topology having a minimal search-time in unstructured peer-to-peer network. According to the proposed algorithm, each node selects the best nodes having higher hit-ratio than other nodes as many as the number being exponentially proportional to the hit-ratio of the node itself, and then it connects to them. The ensemble behavior of the proposed algorithm is very similar to the recrystrallizing phenomenon that is observed in nature. There is a partial order relationship among the hit-ratios of most nodes of constructed topology. Therefore once query message visits a node, it has a higher hit-ratio than the node that was visited last by the message. The query message even sent from freeloader can escape to the node having high hit-ratio by one hop forwarding, and it never revisits any freeloader again. Thus the search can be completed within a limited search time. We also propose the Chain-reactive search scheme using the constructed topology. Such a controlled multicasting reduces the query messages by 43 percent compared to that of the naive Gnutella using broadcasting, while it saves the search time by 94 percent. The search success rate of the proposed scheme is 99 percent.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.4
• /
• pp.533-541
• /
• 2022

An analysis of marine accidents that occurred in the last five years, revealed that 77.0 % of all grounding accidents and 66.1% of all marine casualties involved small vessels, which was a very high level relatively. The Mokpo Regional Maritime Safety Tribunal (Mokpo-KMST) inquired on 72 cases of marine accidents in 2021, of which 10 cases were grounding accidents. Furthermore, eight cases of grounding accidents occurred in small fishing vessels. This study analyzed eight cases of grounding accidents on small fishing vessels that inquired in the jurisdictional area of Mokpo-KMST in 2021. I found out that this grounding occurred in clear weather with good visibility (2-4 miles) and good sea conditions with a wave height of less than 1 meter. Furthermore, I found that the main causes of grounding were drowsy navigation due to fatigue, neglect of vigilance, neglect of checking ship's position, overconfidence in GPS plotter, and lack of understanding of chart symbols and tidal differences. To reduce grounding accidents of small fishing vessels, I suggested the following measures. First, crew members who have completed the able seafarer training course on bridge watchkeeping should assist to the master. Second, alarm systems to prevent drowsiness should be installed in the bridge. Third, the regulation should be prepared for the performance standards and updating GPS plotter. Finally, the skipper of small vessels should be trained periodically to be familiar with chart symbols and basic terrestrial navigation.

• Journal of Korea Water Resources Association
• /
• v.55 no.10
• /
• pp.775-784
• /
• 2022

In this study, to determine the optimal order of the full-logged I-D-F polynomial equation, which is mainly used to calculate the probable rainfall over a temporal rainfall duration, the probable rainfall was calculated and the regression coefficients of the full-logged I-D-F polynomial equation was estimated. The optimal variable of the polynomial equation for each station was selected using a stepwise selection method, and statistical significance tests were performed through ANOVA. Using these results, the statistically appropriately calculated rainfall intensity equation for each station was presented. As a result of analyzing the variable selection outputs of the full-logged I-D-F polynomial equation at 9 stations in Gyeongbuk, the 1^st to 3^rd order equations at 6 stations and the incomplete 3^rd order at 1 station were determined as the optimal equations. Since the 1^st order equation is similar to the Sherman type equation and the 2^nd order one is similar to the general type equation, it was presented as a unified form of rainfall intensity equation for convenience of use by increasing the number of independent variables. Therefore, it is judged that there is no statistical problem in considering only the 3^rd order polynomial regression equation for the full-logged I-D-F.

• Proceedings of the Korean Reliability Society Conference
• /
• 2001.06a
• /
• pp.105-111
• /
• 2001

In this study, for improvement of pneumatic valve reliability, we grasped the falling-off problem in efficiency of domestic valve and performed detailed analysis the relating International standards, and we also decided sampling method and reliability evaluation items to be evaluated valves. And, in addition, we describe the developed evaluation standard to increase the competition power and to improve the reliability of domestic pneumatic valve manufacturers through deciding of test conditions and thesis of evaluation procedures to each evaluation items.

• Animal Systematics, Evolution and Diversity
• /
• v.5 no.2
• /
• pp.89-105
• /
• 1989

농게(Ura arcuata) (달랑게과, 달랑게아과) 의 유생을 부화에서부터 첫 번째 게기까지 수온 $25^{\circ}C$ , 염분농도 33.3$\textperthousand$의 해수에서 사육하고, 각 유생기이 형태적인 특징을 기술 및 도식하였다. 이 종은 5기의 zoea와 1기의 megalopa 유생을 거쳐 첫 번째 게기로 변태하였다. 제 1 zoea 유생기는 제 1 소악의 내지에 4개의 말단강모와 제 2 악각의 기절과 내지에 각각 3개의 우상강모와 0, 0, 5 강모식을 가지고 촉각은 B형이었다. 이러한 특징들은 이미 보고된 같은 과의 유생들의 특징들과 잘 일치하고 있다.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2008.11a
• /
• pp.447-448
• /
• 2008

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2016.05a
• /
• pp.7-9
• /
• 2016

점차적으로 확대되는 ECDIS의 강제화에 따라서 반복적으로 발생되고 있는 좌초 및 충돌사고의 예방을 위해서는 효과적인 ECDIS 교육과 현장에서의 올바른 운용이 필수적이다. 이 연구에서는 ECDIS의 운용과 관련된 사고사례를 조사하여 식별된 문제점을 바탕으로 ECDIS 교육 모델의 개선 방향성을 제시하고자 한다.

• 기계와재료
• /
• v.21 no.3
• /
• pp.52-59
• /
• 2009

테이퍼롤러 베어링의 축방향 과다 예압에 의한 수명 단축 효과를 실험적으로 검증하고 그 결과에 의한 베어링의 수명 분포를 분석하여, 기존의 $L_{10}$ 수명식에 비하여 현장 작동 조건에 따른 실질적인 수명을 산출할 수 있는 축방향과 반경방향을 고려한 수명식을 도출하고 이를 프로그램화 하여 설계 및 생산 현장에서 용이하게 활용할 수 있도록 하였다.

• 기계와재료
• /
• v.21 no.3
• /
• pp.20-31
• /
• 2009

가속시험은 제품의 신뢰도가 증가할수록 늘어나는 시험시간 문제를 해결하기 위해 인위적으로 제품의 수명을 단축시키는 시험방식이다. 즉, 사용조건보다 가혹한 조건에서 시험하여 짧은 시간에 제품의 고장을 발생시켜 얻은 수명데이터를 가지고 사용조건의 신뢰성을 평가한다. 본고에서는 가속시험과 가속모형에 대해 살펴보고 기계류 부품에 적용 가능한 가속시험 방법론, 끝으로 예제를 통해 가속시험을 이용한 신뢰성평가 방법을 소개하고자 한다.