Simultaneous out-of-plane and in-plane vibration mitigations of offshore monopile wind turbines by tuned mass dampers

Haoran Zuo,Kaiming Bi,Hong Hao 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.26 No.4

To effectively extract the vast wind resource, offshore wind turbines are designed with large rotor and slender tower, which makes them vulnerable to external vibration sources such as wind and wave loads. Substantial research efforts have been devoted to mitigate the unwanted vibrations of offshore wind turbines to ensure their serviceability and safety in the normal working condition. However, most previous studies investigated the vibration control of wind turbines in one direction only, i.e., either the out-of-plane or in-plane direction. In reality, wind turbines inevitably vibrate in both directions when they are subjected to the external excitations. The studies on both the in-plane and out-of-plane vibration control of wind turbines are, however, scarce. In the present study, the NREL 5 MW wind turbine is taken as an example, a detailed three-dimensional (3D) Finite Element (FE) model of the wind turbine is developed in ABAQUS. To simultaneously control the in-plane and out-of-plane vibrations induced by the combined wind and wave loads, another carefully designed (i.e., tuned) spring and dashpot are added to the perpendicular direction of each Tuned Mass Damper (TMD) system that is used to control the vibrations of the tower and blades in one particular direction. With this simple modification, a bi-directional TMD system is formed and the vibrations in both the out-of-plane and in-plane directions are simultaneously suppressed. To examine the control effectiveness, the responses of the wind turbine without control, with separate TMD system and the proposed bi-directional TMD system are calculated and compared. Numerical results show that the bi-directional TMD system can simultaneously control the out-of-plane and in-plane vibrations of the wind turbine without changing too much of the conventional design of the control system. The bi-directional control system therefore could be a cost-effective solution to mitigate the bi-directional vibrations of offshore wind turbines.

ANALYTIC TREATMENT FOR GENERALIZED (m + 1)-DIMENSIONAL PARTIAL DIFFERENTIAL EQUATIONS

EMAD A. AZ-ZO’BI 한국산업응용수학회 2018 Journal of the Korean Society for Industrial and A Vol.22 No.4

In this work, a recently developed semi-analytic technique, so called the residual power series method, is generalized to process higher-dimensional linear and nonlinear partial differential equations. The solutions obtained takes a form of an infinite power series which can, in turn,be expressed in a closed exact form. The results reveal that the proposed generalization is very effective,convenient and simple. This is achieved by handling the (m+1)-dimensional Burgers equation.

설명 가능한 인공지능 기반 스마트팩토리 이상 징후 탐지 및 원인 분석기술 연구

임승범(Sueng-Bum Lim),김홍비(Hong-Bi Kim),이태진(Tae-Jin Lee) 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2

스마트팩토리(ICS)는 다른 IT 환경보다도 더 높은 보안성과 가용성을 요구한다. 사이버 공격뿐만 아니라 장비의 고장 및 자연재해로 발생할 수 있는 비정상적인 변화도 감지해야 한다. 본 논문에서는 현장 분석가의 해석을 중심으로 고장진단 및 이상 징후 탐지하는 현 상황에 FFT, CDF 도입과 AI를 활용해 시각화한 분석을 통해 이상 징후 탐지 및 분석하는 방법을 제안한다. 실제 공작기계 센서를 통해 감지한 진동 값을 1차원 시계열 데이터의 의미 있는 분석을 위해 FFT를 적용해 주파수 대역으로 변환하고, 누적 분포 함수(CDF) 와 시계열 기반 이상 징후 탐지 결과에 설명 가능한 AI(XAI) SHAP 모델을 적용한 방법 두 가지를 제안한다. 누적 분포 함수(CDF)를 적용하는 방법은 정상 데이터의 평균과 표준편차를 통해 0과 1 사이의 분포 값으로 이상 징후를 탐지한다. 정상일 경우 CDF 값은 0.5 주위에 주로 분포하게 되며, 고장일 경우에 CDF 값이 0.9 이상의 비율이 크게 변화하게 된다. CDF를 통한 이상 징후 탐지 결과 정상의 경우 CDF값이 0.9 이상인 개수가 드물었고, 고장의 경우 정상에 비해 매우 많이 측정되었다. BI-LSTM 방법은 시계열 기반 이상 징후 탐지로 정상 데이터를 학습해 임계값을 설정하고 비정상 데이터를 탐지한다. 이상 징후 분석으로 SHAP 기반 XAI를 적용을 통해서 이상 점수를 산출해 이상 점수가 임계값 이상일 경우 이상으로 판단하고, Heatmap과 Plot을 통해 시각화한다. XAI를 통한 이상 징후 점수 계산 결과 정상의 평균값은 0.0025이고, 고장의 평균값은 약 0.0448로 고장이 정상과 비교하면 약 18배 정도 높게 측정이 되었다.

WTO 가입 후 한국기업의 대중국 해외직접투자 현황과 입지특성

여필순 경북대학교 사회과학대학 지리학과 2006 地理學論究 Vol.- No.25

본 연구는 중국이 WTO 가입 이후 대중국 직접투자 한국기업의 현황과 입지적 특성이 어떻게 변화하였으며, 그 잠재적 영향은 무엇인지를 밝히는 데 목적이 있다. 대중국 직접투자 한국기업 현황 자료를 분석한 결과, WTO 가입 이후 중국진출 초기 동북 · 발해만 지역으로 집중되었던 한국기업 대중투자의 지리적 패턴이 최근 東南沿海地域으로 분산화되고 있을 것이라는 예측이 현실로 나타났음이 밝혀졌다. 東南沿海地域 중에서도 특히 상해에의 집중도 증가가 뚜렷하며, 부문별로는 서비스업의 진출이 증가하고 있고 제조업에서는 전기 · 전자부문의 증가가 뚜렷하게 나타났으며 투자비율 별로는 100% 단독투자의 비중 증가가 뚜렷하다. 본 연구결과에 의하면 한국기업의 대중국 투자의 입지특성을 나타내는 주 요인은 중국의 WTO 가입에 따라 시장환경의 변화로 인한 투자동기와 업종의 변화에 의하여 결정된다고 본다. 이러한 요인을 보다 명확히 밝히고 중국진출 한국기업이 중국 현지에서 성공적으로 뿌리내리고 있는지를 알기 위해서는 향후 기업의 입지의사결정과정조사, 현지기업에 대한 심층면접조사를 통하여 해외직접투자 기업네트워크활동이 중국에서 공간적으로 어떻게 전개되는지, 특히 모기업 본사 및 해당지역기업, 환경과 이루어지는 네트워킹이 어떤 형태로 이루어지고, 국가 그리고 지방정부가 미치는 영향은 무엇인지를 밝히는 유형별 사례연구 등이 뒤따라야 한다. The purpose of this study is to make clear the change and influence of actuality and location characteristics about Korean enterprise's FDI to China after China entered into WTO. Based on data analysis of Korean enterprise's FDI to China, FDI of Korean enterprises are dispersed to Southeast littoral, which are centralized in Northeast region and Bohai bay at initial stages. These investments are especially centralized at Shanghai. Service industry, electric industry and sole ownership enterprises are increased in evidence. The main factor of these characteristics is the change of the motivation of investment and industry kind which are begot by the change of market environment. For making clear this factor and understanding the actuality of Korean enterprises, these must be studied that how the network of enterprises are composed, what kind form of network is between headquarter and filiale of the enterprise, and how the nation and local government make the influence.

경기변동의 이론 및 실증연구방법에 관한 고찰

姜起春 제주대학교 1994 논문집 Vol.38 No.-

The purpose of this study is to survey the recent developments in business cysle theory and econometic methods for it. Lots of conventional survey papers focus on the studies abroad, this paper follows that tradition but pays an equal attention to the domestic studies as well. It has three distinct objectives to deal with. First of them is to examine the historical perspective of business cycle theory affer World War Ⅱ and classifies business cycle theories according to endogenous and exogenous business cycle theory. Business cysle theory evolves through time according to the economic situation. That is, many economists did pay attention to the study of business cycle when economies go down while they regarded it as dead on the opposite situatio. In addition, it discusses the current research agenda in business cycle theory. Second objective is to examine the recent developments in econometric methods for analyzing the source and propagation of business cycles. Finally, it discusses where the developments in the business cycle theory and econometric methods, especially the widely used structural vector autoregressive(SVAR) model, would proceed and concludes that more studies should been carried out on the propagation mechanism of the business cycles to make econmic policy and forecasting easy.

전자여권 상호 호환을 위한 적합성 시험인증 규격 개발

이비나 서울여자대학교 컴퓨터과학연구소 2004 정보기술논문지 Vol.3 No.-

최근 테러로 인해 전 세계적으로 입국절차가 엄격해지면서 보다 효율적인 입출국 관리를 할 수 있도록 국제적으로 상호운용 가능한 전자여권이 발급되었다. 본 논문에서는 실제 생체인식여권과 실제 근접 연결 장치간의 상호 호환성 시험의 방법을 분석한다. 본 논문의 대상은 전자여권에 한정하며, 전자여권의 상호인증에 있어서 원활한 동작을 위한 장치 및 전자여권의 기능 부분 일부에 대한 요구사항을 포함한다. 이 논문은 산업표준국제 전자여권 상호인증을 위한 시험방법과 실제 단말기와 전자여권을 사용하여 호환성을 테스트 하는 방법을 소프트웨어 품질평가 관련 국제표준들(ISO/IEC 14598, ISO/IEC 9126)을 기반으로 연구한다. 그 결과, 적합성 시험통과기준을 좀 더 세분화하였고, 이는 한국 및 아시아 전역에서 사용되어 질 수 있다. Recently, entrance process become strict because of terror, and e-passport issued to the all over the world. This paper analyzes interoperability between actual e-passport and actual device. The target of this paper limited in e-Passport, and the contents include requirement for smoothness of working between device and e-passport. In this paper, we research test methods between actual device and actual e-passport based on ISO/IEC 14598, ISO/IEC 9126. As a result, we standardize test methods to specialized, and it can use to all the area of Asia.

전주산업단지 및 주변지역 VOCs 및 악취물질 모니터링

김용문,박비오,고영삼,심재정,송병식,양고수 전북대학교 공학연구원 ( 구 전북대학교 공업기술연구소 ) 2002 工學硏究 Vol.33 No.-

Important main odorous compounds and VOCs(volatile organic compounds) possibly emitted from the Jeon-Ju Industrial Sites were identified and measured in amount through making air sampling over Jeon-Ju Industrial Sites and analyzing them with the sate of the art analytical instrument. Sampling sites were chosen 8 points by considering the industrial characteristics for the 1,2 Industrial Sites and 2 points for the 3 Industrial. Site Sampling times were two times, the first one was March. 2002 - April. 2002, and the second was May. 2002 - July. 2002. Canister sampling units and polyester bags were used to collect 6 liters air samples during 1hour or 3minutes for VOCs and polyester bags were used to sample 10 - 50 liters of air for 3 minutes depending on analytic characteristics of odor compounds. The important main VOCs were measured as acetone, ethyl benzene, n-hexane, m,p-xylene, toluene, M.E.K.(methyl ethyl ketone), isopropanol, ethyl acetate, o-xylene, n-butyl acetate, ethanol, benzene as in order of average concentration for the Industrial Sites. The main odorous compounds were COS, H2S, CS2, MM(methyl mercaptan), form aldehyde, acetaldehyde for the 1,2 Industrial Sites and COS, H2S, form aldehyde, acetaldehyde were measured as main species for the 3 Industrial Site. NH3 was measured as below the detection limit of the instrument. The concentrations of sulfide compounds for the 1,2 Industrial Sites were relatively higher than ones for the 3 Industrial Site. Among aldehydes, form aldehyde, acetaldehyde were detected very highly as 0.1- 1ppm over all the Industrial Sites.

Synergistic effect of binanoenzyme and cryogel column on the production of formic acid from carbondioxide

Yi gitcan Sümbelli,Özlem Biçen Ünlüer,Arzu Ersöz,Rıdvan Say 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.76 No.-

In this study, binanoenzyme (BNE) was synthesized using FateDH and Cyt-C in same bionano-interface;by formation of formate dehydrogenase-co-cytochrome C by using ANADOLUCA method. Thesynthesized novel binanoenzyme was embedded into HEMA based cryogel column and the conversionof CO2 to formic acid was investigated by using this cryogel column. To maintain the conversion, CO2saturated water was passed through the cryogel column and the converted formic acid was analyzedusing HPLC. The parameters which has an effect on conversion such as pH, sample volume and CO2concentration were analyzed. The results showed that the conversion process was succeeded effectively.

광양시 생활폐기물 소각시설 건설사업 기술용역 환경성 조사 및 기본계획수립

김용문,박비오,양고수 國立 麗水大學校 環境問題硏究所 1998 環境硏究論文集 Vol.1 No.-

The physicochemical properties of Kwangyang municipal waste were analyzed in terms of bulk density, physical composition, moisture content, combustible and ashy content, chemical element, and heating value. A representative waste sample was made by collecting samples at various location in the city and considering weighting factor depending on the regional(residential, commercial, industrial sites) waste generating portion based on the last published reports regarding the waste generation on Kwangyang, Yosu, Suncheon cities by Korea Environmental Protection Agency. The Korean Waste Standard Methods were used to collect samples and analytical measurements. The estimated bulk density of total waste was 211.8㎏/㎥, the average moisture content was 40%, the average combustible content was 48%, the average ash content was 12%, The average low heat value was 1,616㎉/㎏, which was little lower than the average one of the whole country. The result of chemical elemental analysis showed that most of the hazardous heavy metals such as As. Hg were detected or negligible and the contents of sulfur and chloride were also relatively low.

공업단지 내와 인근 풍하지점의 주요 VOCs 성분별 농도측정 및 분석

김득수,양고수,박비오 7개 국립대학교 환경연구논문집 공동발행 위원회 2005 공업기술연구 Vol.5 No.-

It has been knoun that many kinds of VOC(volatile organic compound) and odorous compound's sources are in the urban and industrial areas and intensify their emissions into the atmoshere. These VOCs have adverse effects in human health and trees directly, and VOCs have an important role in production of the photochemical smog such as ozone and fine particles, so they decrease visibility and deteriorate the urban air quality as well. Specifically, in urban atmosphere, hydroxy radicals(OH) are produced largely by chemical reactions involving the VOCs emitted from vehicles. The OH promote the photochemical reactions and makes more secondary pollutants into the atmosphere. It will be necessary to make proper management plans to preserve the air quality in good level for the peoples. In order to make these plans, source information and detail emission inventory of the city and near industrial areas should be given. However, lack of the source measurements data makes us more difficult to complete the source inventory. VOC source inventory could be utilized for the feasibility study to estimate the contribution of VOC sources presenting to the receptor such as residential area. It may give policy maker and idea how to control the air quality, and improve their social environment in the area. This study shows preliminary data that measured VOC concentrations from the local industrial areas in Jeonju during from May to October 2005. The samples from the 2 receptor sites (one is at center of the industrial area and the other site is at distance residential area dounwind from the center) were collected and analyzed for the comparison to source concentration. The mass contributions of the speciated VOC from the different sources and ambient (2 receptors) were presented and discussed.