• Title/Summary/Keyword: disturbance system

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A Study on Development of Remote Crane Wire Rope Flaws Detection Systems (원격 크레인 와이어 로프 결함 탐지 시스템 개발에 관한 연구)

  • Min, Jeong-Tak;Lee, Jin-Woo;Lee, Kwon-Soon
    • Journal of Navigation and Port Research
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    • v.27 no.1
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    • pp.97-102
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    • 2003
  • Wire ropes are used in a myriad of various industrial applications such as elevator, mine hoist, construction machinery, lift, and suspension bridge. Especially, the wire rope of crane is important component to container transfer. If it happens wire rope failures during the operation, it may lead to safety accident, economic loss by productivity decline and so on. To solve this problem, we developed remote wire rope fault detecting system, and this system is consisted of 3 parts that portable fault detecting part, signal processing part and remote monitoring part. All detected signal has external noise or disturbance according to circumstances. So, we applied to discrete wavelet transform to extract a signal from noisy data. It is verified that the detecting system by de-noising has good efficiency for inspecting faults of wire ropes in service. As a result, by developing this system, container terminal could reduce expense because of extension fo wire ropes exchange period and could competitive power. Also, this system is possible to apply in several field such as elevator, lift and so on.

Comparison of the National Park Ecosystem Health Assessment and an Advanced Assessment System (국립공원 생태계 건강성 평가 시스템 개선 연구)

  • Myeong, Hyeon Ho;Kim, Jeong Eun;Kim, Hye Ri;Oh, Jang Geun
    • Ecology and Resilient Infrastructure
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    • v.8 no.2
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    • pp.112-119
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    • 2021
  • In 2012, the National Park Service conducted an ecological health assessment to efficiently preserve and manage the ecosystem. The need for improving pre-existing management indicators was recognized from the revised Natural Park Act because, while the indicators of the existing evaluation system focused on endangered species, ecosystem disturbance, diversity, water quality (BOD, DO), and habitat fragmentation, they did not reflect the lack of indicators for marine ecological assessment, policy changes, and the time demands. The evaluation results comprised a five-point grading system, which made the analysis of immediate changes, difficult. Therefore, the benthic pollution index (BPI) and habitat restoration indicators were added to improve the evaluation system. The National Park was assessed using 10 classifications, however, only four classifications were evaluated. The ratings were divided into five states, and ten classes were presented as pictograms. The assessment results showed a similar trend as the indicators were improved, increasing from level 3 to level 5. However, the results of the Wolaksan National Park after improvement in the indicators were lower than that before the improvement, whereas, for the Juwangsan National Park, it was higher. This study aims at contributing to the scientific and systematic management of the national park ecosystem by improving the ecological health assessment system.

Noncondensable gas's influence in waster vapor absorption accompanying interfacial disturbance into aqueous solution of LiBr

  • Dong-Ho RIE;Keun-Oh Lee
    • Journal of the Korean Society of Safety
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    • v.7 no.2
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    • pp.63-70
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    • 1992
  • The aim of this research is to obtain a basic quantitative understanding of the effect of a noncondensable gas on the absorption of water vapor by a $H_2O$ / LiBr combination with n-octanol as the surfactant. Nonflowing aqueous solutions of LiBr (40,45,50 mass%) were exposed to saturated water vapor following the addition of an n-octanol sufactant (0.01 and 0.6 mass%). A small amount of a noncondensable gas (air) was allowed into the absorber (0.03 volume%) and its effect was analyzed by measuring the amount of water vapor absorbed. This study will aid to predict the performance of heat pump and safety operating condition when the noncondensable gas is not allowed in the absorber The results indicate that, in the presence of small amounts of a noncondensable gas, vapor absorption enhancement ratios are less than half o( those obtained under the same experimental conditions when a noncondensable gas is not present (1). The presence of a noncondensable gas causes the partial vapor pressure of air to increase at the vapor / liquid interface, which results in an instability of vapor absorption rate nd. hence, in an inhibition of interfacial disturbance.

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Development of a battery management system(BMS) simulator for electric vehicle(EV) cars (EV용 배터리 관리시스템(BMS) 시뮬레이터 개발)

  • Park, Chan-Hee;Kim, Sang-Jung;Hwang, Ho-Suk;Lee, Hee-Gwan
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.6
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    • pp.2484-2490
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    • 2012
  • This study reports on the development and performance verification of cell simulation boards of simulator and the embedded program for board control of the battery management system (BMS) of electric vehicle (EV) cars, which manages the next-generation automotive lithium-ion battery pack. Here, we have improved the speed of the simulator by using operational (OP) amplifier and transistors that were connected in series. In addition, using a digital analog converter (DAC) in each channel, we have improved the performance by channel-to-channel isolation (isolation) as compared to the traditional methods. Furthermore, by constructing a current-limiting protection circuit, one can be protected from disturbance and, by utilizing a precision shunt resistor for the current sensor, we have increased the precision of the current control. In order to verify the performance of the developed simulator, we have performed the experiment 10 times, with values ranging from 0.5 V to 5 V, and a voltage drop step of 0.5 V. Significance analysis of experimental data, and repeatability tests were performed, showing an average standard deviation of 0.001~0.004 V, indicating high repeatability and high statistical significance of the current method and system.

Robust and Non-fragile $H_{\infty}$ Decentralized Fuzzy Model Control Method for Nonlinear Interconnected System with Time Delay (시간지연을 가지는 비선형 상호연결시스템의 견실비약성 $H_{\infty}$ 분산 퍼지모델 제어기법)

  • Kim, Joon-Ki;Yang, Seung-Hyeop;Kwon, Yeong-Sin;Bang, Kyung-Ho;Park, Hong-Bae
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.47 no.6
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    • pp.64-72
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    • 2010
  • In general, due to the interactions among subsystems, it is difficult to design an decentralized controller for nonlinear interconnected systems. In this study, the model of nonlinear interconnected systems is studied via decentralized fuzzy control method with time delay and polytopic uncertainty. First, the nonlinear interconnected system is represented by an equivalent Takagi-Sugeno type fuzzy model. And the represented model can be rewritten as Parameterized Linear Matrix Inequalities(PLMIs), that is, LMIs whose coefficients are functions of a parameter confined to a compact set. We show that the resulting fuzzy controller guarantees the asymptotic stability and disturbance attenuation of the closed-loop system in spite of controller gain variations within a resulted polytopic region by example and simulations.

Comparison of Predicted and Measured ASF (ASF 예측치와 실측치 비교)

  • Shin, Mi-Young;Hwang, Sang-Wook;Yu, Dong-Hui;Park, Chan-Sik;Lee, Chang-Bok;Lee, Sang-Jeong
    • Journal of Navigation and Port Research
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    • v.34 no.3
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    • pp.175-180
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    • 2010
  • In the almost application parts, GNSS being used the primary navigation system on world-widely. However, some of nations attempt or deliberate to enhance current Loran system, as a backup to satellite navigation system because of the vulnerability to the disturbance signal. Loran interests in supplemental navigation system by the development and enhancement, which is called eLoran, and that consists of advancement of receiver and transmitter and of differential Loran in order to increase the accuracy of current Loran-C. A significant factor limiting the ranging accuracy of the eLoran signal is the ASF in the TOAs observed by the receiver. The ASF is mostly due to the fact that the ground-wave signal is likely to propagate over paths of varying conductivity and topography. This paper presents comparison results between the predicted ASF and the measured ASF in a southern east region of Korea. For predicting ASF, the Monteath model is used. Actual ASF is measured from the legacy Loran signal transmitted Pohang station in the GRI 9930 chain. The test results showed the repeatability of the measured ASF and the consistent characteristics between the predicted and the measured ASF values.

Design of Ship-type Floating LiDAR Buoy System for Wind Resource Measurement inthe Korean West Sea and Numerical Analysis of Stability Assessment of Mooring System (서해안 해상풍력단지 풍황관측용 부유식 라이다 운영을 위한 선박형 부표식 설계 및 계류 시스템의 수치 해석적 안정성 평가)

  • Yong-Soo, Gang;Jong-Kyu, Kim;Baek-Bum, Lee;Su-In, Yang;Jong-Wook, Kim
    • Journal of Navigation and Port Research
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    • v.46 no.6
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    • pp.483-490
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    • 2022
  • Floating LiDAR is a system that provides a new paradigm for wind condition observation, which is essential when creating an offshore wind farm. As it can save time and money, minimize environmental impact, and even reduce backlash from local communities, it is emerging as the industry standard. However, the design and verification of a stable platform is very important, as disturbance factors caused by fluctuations of the buoy affect the reliability of observation data. In Korea, due to the nation's late entry into the technology, a number of foreign equipment manufacturers are dominating the domestic market. The west coast of Korea is a shallow sea environment with a very large tidal difference, so strong currents repeatedly appear depending on the region, and waves of strong energy that differ by season are formed. This paper conducted a study examining buoys suitable for LiDAR operation in the waters of Korea, which have such complex environmental characteristics. In this paper, we will introduce examples of optimized design and verification of ship-type buoys, which were applied first, and derive important concepts that will serve as the basis for the development of various platforms in the future.

Initial Responses of Quercus serrata Seedlings and Forest Understory to Experimental Gap Treatments

  • Cho, Yong-Chan;Kim, Jun-Soo;Lee, Chang-Seok;Cho, Hyun-Je;Bae, Kwan-Ho
    • Journal of Ecology and Environment
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    • v.32 no.2
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    • pp.87-96
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    • 2009
  • Pinus thunbergii plantations in Pohang-si, Gyeongsangbuk-do, Korea, are of low ecological quality, with arrested succession and a high proportion of ruderal species. To improve the quality of the habitat, we created canopy gaps ($\sim42\;m^2$) and monitored changes in abiotic (light availability, canopy openness) and biotic (survival and growth of seedlings and understory communities) variables in 2007 and 2008 in plots that had received one of five types of treatment: cutting of canopy trees and removal of the understory (CU), cutting of canopy trees only (C), girdling of canopy trees and removal of the understory (GU), girdling of canopy trees (G) or control. Each treatment was applied to three replicate plots. Abiotic variables did not significantly differ among treatments. Survival rates of target species were slightly lower in the CU, G and control conditions. Based on logistic regression analysis, the only significant growth factor affecting survival was height growth. Positive effects of seedling height and leaf area growth on survival were also detected, but did not reach statistical significance. In treatment G, gradual improvement of overstory conditions and mitigation of competition by limitation of disturbance to the understory community were likely to have promoted seedling growth. There were no significant effects of gap treatments on changes in species abundance (cover and richness) and composition of understory between the study years. This result implies that the small gaps created in our study may be below the threshold size to affect understory growth. However, the results of this study are based on a short-term investigation of only two years. Long-term research is strongly recommended to clarify the effects of gap treatment on plant communities in afforested areas.

Railbed Evaluation by using In-situ Penetration Test (원위치 관입실험기를 활용한 철도 노반 평가)

  • Kim, Ju-Han;Park, Jung-Hee;Yoon, Hyung-Koo;Koh, Tae-Hoon;Lee, Jong-Sub
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.261-267
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    • 2011
  • The test fit has commonly used for the evaluation of the railbed condition, and indirect methods by using the compressional wave are also studied. the direct evaluation method by penetration test has not been studied. For the measurement of in-situ cone tip resistance of the railbed with minimizing the disturbance of the upper railbed. the cone penetrometer with the helical type outer rod(CPH) was developed. The outer rod, which has helical screw, is penetrated through the gravel layer and provides the reaction force for cone penetration testing. the cone tip resistances are measured by the mini cone penetrometer, where diameter is 15mm. For the developing the mini cone, strain gauge installation, circuit configuration, penetration rates and calibration process are considered. For the easy penetration of the screw rod in the field, the reaction force stepping plate and guide column are arranged. The screw rod are penetrated through the gravel layer. And the mini cone was pushed into the subgrade railbed at the penetration rate of 1mm/sec. The penetration test shows that the cone tip resistance increases along the depth. In addition, the subgrade condition is evaluated. This study demonstrates that the CPH may be effectively used for the evaluation of subgrade method any damage of the gravel layer.

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Classification of Urban Forest Types and its Application Methods for Forests Creation and Management (도시숲 조성 및 관리를 위한 도시숲 유형화 및 적용방안)

  • Lee, Dong-Kun;Kim, Eun-Young;Song, Won-Kyong;Park, Chan;Choe, Hye-Young
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.12 no.5
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    • pp.101-109
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    • 2009
  • There are increasing needs about creation and sustainable management of urban forest for environmental conservation and recreational service for citizen. However, it is difficult for local governments to create or manage urban forest in recreational or conservational way. The purpose of this study is to classify the urban forest types by considering its geographical feature, biological and sociological characteristics in order to suggest a guide to local governments about effective creation or management of urban forest. In this study, we extracted common characteristics of the selected five indicators. Factors about urban forest are divided into two groups. Factors were named according to the variables as 'Urban Forest Naturalness', and 'High Accessibility and Disturbed by Human.' In addition, we classified urban forests into four types in this study. The type I of urban forest is a large forest and has high naturalness such as Mt. Bukhan and Mt. Gwanak. The type II is fragmented to large forests by developmental projects. The type III is flat and has high accessibility such as forest behind Seonjeongneung. The type IV is located near residential area such as Mt. Ansan, Mt. Inwang and Mt. Bonghwa. It is possible to set up recreational area for citizens and ecological networks for species by the research of the urban forest type. The results of the study, classification of urban forest types and its application, contribute to provide a guide for local governments to create or manage urban forests effectively.