• Title/Summary/Keyword: flexible hub

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Nonlinear Behaviors of Cable Spoke Wheel Roof Systems (케이블 스포크 휠 지붕 시스템의 비선형 거동)

  • Park, Kang-Geun;Lee, Mi-Hyang;Park, Mi-Jin
    • Journal of Korean Association for Spatial Structures
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    • v.17 no.1
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    • pp.31-40
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    • 2017
  • The objective of this study is to analysis the mechanical characteristics and nonlinear behaviors on the geometric nonlinear behavior of a cable spoke wheel roof system for long span lightweight roof structures. The weight of a cable spoke wheel roof dramatically can reduce and the cable roof system can easily make the required rigidity and shape by the sag ratio and pretension forces. Determining the pretension and initial sag of cable roof system is essential in a design process and the shape of roof is changed by pretension. The nonlinear behavior of flexible cable system has greatly an affect on the sag and pretension. This paper will be carried out analyzing and comparing the tensile forces and deflection of a cable spoke wheel system for the large span retractable roof, and analyzed to deflections and tensile forces by the post height of center hub. The double arrangement of a spoke wheel system with reverse curvature works more effectively as a load bearing system, the pretension can easily increase the structural stiffness. The cable truss system can carry vertical load in up and downward direction, and act effectively as load bearing elements.

Development of RecurDyn Module for Wind Turbine Analysis Applying BEM Theory (BEM 이론을 적용한 풍력발전기 해석용 RecurDyn 모듈 개발)

  • Lim, Dae Guen;Yoo, Wan Suk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.2
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    • pp.115-120
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    • 2014
  • In this study, a module is developed for modeling and analyzing dynamic behavior of a wind turbine using RecurDyn, which is a commercial multi-body dynamics software developed by FunctionBay, Inc. The wind turbine consists of tower, nacelle, hub and blades. Tower and blades are regarded as flexible bodies for considering elastic effect using beam theory and spring force. In this paper, a constant speed wind was assumed and aerodynamic force is modeled using BEM theory. Dynamic analysis applying this aerodynamic force is carried out. To verify the validity of analysis results, these results are compared to those of GH-Bladed which is a commercial software for analyzing wind turbine system distributed by Garrad Hassan.

Vibration Reduction Simulation of UH-60A Helicopter Airframe Using Active Vibration Control System (능동 진동 제어 시스템을 이용한 UH-60A 헬리콥터 기체의 진동 감소 시뮬레이션)

  • Lee, Ye-Lin;Kim, Do-Young;Kim, Do-Hyung;Hong, Sung-Boo;Park, Jae-Sang
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.48 no.6
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    • pp.443-453
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    • 2020
  • This study using the active vibration control technique attempts to alleviate numerically the airframe vibration of a UH-60A helicopter. The AVCS(Active Vibration Control System) is applied to reduce the 4/rev vibration responses at the specified locations of the UH-60A airframe. The 4/rev hub vibratory loads of the UH-60A rotor is predicted using the nonlinear flexible dynamics analysis code, DYMORE II. Various tools such as NDARC, MSC.NASTRAN, and MATLAB Simulink are used for the AVCS simulation with five CRFGs and seven accelerometers. At a flight speed of 158knots, the predicted 4/rev hub vibratory loads of UH-60A rotor excite the airframe, and then the 4/rev vibration responses at the specified airframe positions such as the pilot seat, rotor-fuselage joint, mid-cabin, and aft-cabin are calculated without and with AVCS. The 4/rev vibration responses at all the locations and directions are reduced by from 25.14 to 96.05% when AVCS is used, as compared to the baseline results without AVCS.

Development of the Military-3PL Integrated Operation Strategy for National Defense Transportation using Simulation (시뮬레이션을 활용한 국방수송물류의 민·군 통합 운영 방안 수립)

  • Suraraksa, Juthatip;Gong, In-Taek;Kim, Jaewon;Seo, HanSeok;Shin, KwangSup
    • The Journal of Society for e-Business Studies
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    • v.24 no.3
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    • pp.111-128
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    • 2019
  • In the current procurement system in Korean military, the army, navy and air force have their own distributors, military branches and warehouses. However, especially, it has been hard to have the economy of scale because most of suppliers have shipped their order from the suppliers to each of Korean military directly. Koran military considers the transportation cost as one of the management cost factors among various kinds of cost. Furthermore they have contracted with the suppliers in annual and collectively on the transportation. Hence they have been in trouble with getting efficiency of Defense budget execution because it is hard to make a decision of Defense budget with real transportation cost. Moreover Korean army, navy and air force have their own supply chain separately, so they can not cooperate flexible and quickly when they need. Therefore, in this research, we provide a benchmarking of DTCI (Defense Transportation Coordination Initiative) which has been proved that it has improved the procurement system in US implementing the integrated transportation system with 3PL and military. In addition we propose advanced integrated shipping model using Hub & Spoke system for Korean military. In order to prove its effect, we simulate our model based on the real data of the suppliers' delivery to compare with the current system when it comes to how much we can save the cost. Our research can provide evidence that the integrated procurement system in Korean military will improve Korean military procurement system.

Aerodynamic and Aeroelastic Tool for Wind Turbine Applications

  • Viti, Valerio;Coppotelli, Giuliano;De Pompeis, Federico;Marzocca, Pier
    • International Journal of Aeronautical and Space Sciences
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    • v.14 no.1
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    • pp.30-45
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    • 2013
  • The present work focuses on the unsteady aerodynamics and aeroelastic properties of a small-medium sized wind-turbine blade operating under ideal conditions. A tapered/twisted blade representative of commercial blades used in an experiment setup at the National Renewable Energy Laboratory is considered. The aerodynamic loads are computed using Computational Fluid Dynamics (CFD) techniques. For this purpose, FLUENT$^{(R)}$, a commercial finite-volume code that solves the Navier-Stokes and the Reynolds-Averaged Navier-Stokes (RANS) equations, is used. Turbulence effects in the 2D simulations are modeled using the Wilcox k-w model for validation of the CFD approach. For the 3D aerodynamic simulations, in a first approximation, and considering that the intent is to present a methodology and workflow philosophy more than highly accurate turbulent simulations, the unsteady laminar Navier-Stokes equations were used to determine the unsteady loads acting on the blades. Five different blade pitch angles were considered and their aerodynamic performance compared. The structural dynamics of the flexible wind-turbine blade undergoing significant elastic displacements has been described by a nonlinear flap-lag-torsion slender-beam differential model. The aerodynamic quasi-steady forcing terms needed for the aeroelastic governing equations have been predicted through a strip-theory based on a simple 2D model, and the pertinent aerodynamic coefficients and the distribution over the blade span of the induced velocity derived using CFD. The resulting unsteady hub loads are achieved by a first space integration of the aeroelastic equations by applying the Galerkin's approach and by a time integration using a harmonic balance scheme. Comparison among two- and three- dimensional computations for the unsteady aerodynamic load, the flap, lag and torsional deflections, forces and moments are presented in the paper. Results, discussions and pertinent conclusions are outlined.

A Study on Calculating Relevant Length of Left Turn Storages Using UAV Spatial Images Considering Arrival Distribution Characteristics at Signalized Intersections in Urban Commercial Areas

  • Yang, Jaeho;Kim, Eungcheol;Na, Young-Woo;Choi, Byoung-Gil
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.36 no.3
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    • pp.153-164
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    • 2018
  • Calculating the relevant length of left turn storages in urban intersections is very crucial in road designs. A left turn lane consists of deceleration lanes and left turn storages. In this study, we developed methods for calculating relevant lengths of left turn storages that vary at each intersection using UAV (Unmanned Aerial Vehicle) spatial images. Problems of conventional design techniques are applying the same number of left turn vehicles (N) using Poisson distribution without considering land use types, using a vehicle length that may not be measurable when applying the length of waiting vehicles (S), and using same storage length coefficient (${\alpha}$), 1.5, for every intersections. In order to solve these problems, we estimated the number of left turn vehicles (N) using an empirical distribution, suggested to use headways of vehicles for (S) to calculate the length of waiting vehicles (S) with a help of using UAV spatial images, and defined ranges of storage length coefficient (${\alpha}$) from 1.0 to 1.5 for flexible design. For more convenient design, it is suitable to classify two cases when possible to know and impossible to know about ratio of large trucks among vehicles when planning an intersection. We developed formula for each case to calculate left turn storage lengths of a minimum and a maximum. By applying developed methods and values, more efficient signalized intersection operation can be accomplished.

A Study on the Attracting Strategy of Transshipment Cargo by Competitiveness Analysis between Busan & chinese Port (중국항만과 경쟁력분석을 통한 부산항 환적화물 유치전략 연구)

  • Rim, Il-Kyu;Kim, Myung-Jae;Ahn, Ki-Myung
    • Journal of Korea Port Economic Association
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    • v.26 no.3
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    • pp.175-197
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    • 2010
  • The purpose of this paper is to develop a new strategy from a different angle to become a preferred transshipment hub for sustainable growth. This study would derive new competitive factors through the case study on a global carrier 'A' who shows constant growth in transshipment via Busan and the questionnaire survey was conducted. As to analysis results by matrix, Busan Port needs to strengthen its competitiveness against North China ports due to less local import/export cargo volume and less government support while North China ports continue to be developed with incremental direct calling and government's flexible cabotage rule.

A Study on Analysis of the Preference of Container Ports in Northeast Asia - with the case of Busan Container Port - (동북아 경쟁항만들의 선호도 분석에 관한 연구 - 부산항을 중심으로 -)

  • Chung, Tae-Woo;Kwak, Kyo-Seok
    • Journal of Navigation and Port Research
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    • v.26 no.4
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    • pp.363-372
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    • 2002
  • Recently, mutual economy cooperation in Northeast Asia has leaded steady growth among main countries of it and rather promoted a single economy circle. In this region, Busan container port competes with min container ports in China, Taiwan and Japan in it for attracting transshipment container traffic of north-Shanghai in China and for-east Russia. Therefore, this paper aims to suggest competitive strategies for Busan container port to attract container traffic in Northeast Asia To do so, it evaluates the preference of important ports in the competitive situation and competitiveness edgy of important ports in Northeast Asia, and finally proposes the relative order of important factors. Based on the evaluation of it, first, the Busan ports hue tn strengthen port facilities to attract more traffic and in detail, reinforce the number of berth, yard areas and handling equipment Second, they also have to provide high quality of services to deliver cargos in time, not being damaged and swiftly response to shipowner and shipper's claim, Third, they need to review the strategy to adopt flexible tariff policy and to invest the profit from tariff in port service and facilities, as providing higher port tariff level by a regular rate.

A Study on the Change of Environment in East Asia and the Development Strategy of Korean Shipping and Shipbuilding Industry in Busan Port (동아시아의 환경변화와 한국해운·조선산업의 중흥과 부산항의 발전전략에 관한 연구)

  • Seo, Munsung
    • Journal of Korea Port Economic Association
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    • v.35 no.1
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    • pp.139-162
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    • 2019
  • In the case of Korea, policy support for shipping companies is limited, and the financial support should address the scale and period of support. Comprehensive measures are needed to boost the chances of reviving the industry. In order to secure competitiveness, the shipping companies need to make continuous efforts, prepare for the future by strengthening environmental regulations, and ensure that they have the ability to be flexible in their responses. The shipbuilding industry witnessed some improvement last year amid severe recession, but reforms are needed to address external and internal structural problems; further, to gain the characteristics of future leading industries, it is necessary to secure core technologies, as well as differentiated and specialized industrial competitiveness among rival countries through joint government intervention and joint R&D investment. Taking these steps will ensure that it has environment-friendly vessels and economic shipbuilding capabilities. The competitiveness of Busan Port should enable the utilization of the geopolitical characteristics of East Asia and contribute to: regional economic revitalization; development of its status as hub port; and securing the position of developed countries in East Asian logistics. For this purpose, it is necessary to establish a strategy to: expand the usability of shipowners/carriers; improve the quality of port operations; improve the portability of the smart system; expand the port of mega-ocean carriers; speed up port operations; and create low-cost ports. The establishment of a network of four countries will also require long-term global linkages. For example, there is a need to establish a logistics network between Eurasia and the European region, which will use the Russian Land Bridge System, as well as that of China.

A Folksonomy Ranking Framework: A Semantic Graph-based Approach (폭소노미 사이트를 위한 랭킹 프레임워크 설계: 시맨틱 그래프기반 접근)

  • Park, Hyun-Jung;Rho, Sang-Kyu
    • Asia pacific journal of information systems
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    • v.21 no.2
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    • pp.89-116
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    • 2011
  • In collaborative tagging systems such as Delicious.com and Flickr.com, users assign keywords or tags to their uploaded resources, such as bookmarks and pictures, for their future use or sharing purposes. The collection of resources and tags generated by a user is called a personomy, and the collection of all personomies constitutes the folksonomy. The most significant need of the folksonomy users Is to efficiently find useful resources or experts on specific topics. An excellent ranking algorithm would assign higher ranking to more useful resources or experts. What resources are considered useful In a folksonomic system? Does a standard superior to frequency or freshness exist? The resource recommended by more users with mere expertise should be worthy of attention. This ranking paradigm can be implemented through a graph-based ranking algorithm. Two well-known representatives of such a paradigm are Page Rank by Google and HITS(Hypertext Induced Topic Selection) by Kleinberg. Both Page Rank and HITS assign a higher evaluation score to pages linked to more higher-scored pages. HITS differs from PageRank in that it utilizes two kinds of scores: authority and hub scores. The ranking objects of these pages are limited to Web pages, whereas the ranking objects of a folksonomic system are somewhat heterogeneous(i.e., users, resources, and tags). Therefore, uniform application of the voting notion of PageRank and HITS based on the links to a folksonomy would be unreasonable, In a folksonomic system, each link corresponding to a property can have an opposite direction, depending on whether the property is an active or a passive voice. The current research stems from the Idea that a graph-based ranking algorithm could be applied to the folksonomic system using the concept of mutual Interactions between entitles, rather than the voting notion of PageRank or HITS. The concept of mutual interactions, proposed for ranking the Semantic Web resources, enables the calculation of importance scores of various resources unaffected by link directions. The weights of a property representing the mutual interaction between classes are assigned depending on the relative significance of the property to the resource importance of each class. This class-oriented approach is based on the fact that, in the Semantic Web, there are many heterogeneous classes; thus, applying a different appraisal standard for each class is more reasonable. This is similar to the evaluation method of humans, where different items are assigned specific weights, which are then summed up to determine the weighted average. We can check for missing properties more easily with this approach than with other predicate-oriented approaches. A user of a tagging system usually assigns more than one tags to the same resource, and there can be more than one tags with the same subjectivity and objectivity. In the case that many users assign similar tags to the same resource, grading the users differently depending on the assignment order becomes necessary. This idea comes from the studies in psychology wherein expertise involves the ability to select the most relevant information for achieving a goal. An expert should be someone who not only has a large collection of documents annotated with a particular tag, but also tends to add documents of high quality to his/her collections. Such documents are identified by the number, as well as the expertise, of users who have the same documents in their collections. In other words, there is a relationship of mutual reinforcement between the expertise of a user and the quality of a document. In addition, there is a need to rank entities related more closely to a certain entity. Considering the property of social media that ensures the popularity of a topic is temporary, recent data should have more weight than old data. We propose a comprehensive folksonomy ranking framework in which all these considerations are dealt with and that can be easily customized to each folksonomy site for ranking purposes. To examine the validity of our ranking algorithm and show the mechanism of adjusting property, time, and expertise weights, we first use a dataset designed for analyzing the effect of each ranking factor independently. We then show the ranking results of a real folksonomy site, with the ranking factors combined. Because the ground truth of a given dataset is not known when it comes to ranking, we inject simulated data whose ranking results can be predicted into the real dataset and compare the ranking results of our algorithm with that of a previous HITS-based algorithm. Our semantic ranking algorithm based on the concept of mutual interaction seems to be preferable to the HITS-based algorithm as a flexible folksonomy ranking framework. Some concrete points of difference are as follows. First, with the time concept applied to the property weights, our algorithm shows superior performance in lowering the scores of older data and raising the scores of newer data. Second, applying the time concept to the expertise weights, as well as to the property weights, our algorithm controls the conflicting influence of expertise weights and enhances overall consistency of time-valued ranking. The expertise weights of the previous study can act as an obstacle to the time-valued ranking because the number of followers increases as time goes on. Third, many new properties and classes can be included in our framework. The previous HITS-based algorithm, based on the voting notion, loses ground in the situation where the domain consists of more than two classes, or where other important properties, such as "sent through twitter" or "registered as a friend," are added to the domain. Forth, there is a big difference in the calculation time and memory use between the two kinds of algorithms. While the matrix multiplication of two matrices, has to be executed twice for the previous HITS-based algorithm, this is unnecessary with our algorithm. In our ranking framework, various folksonomy ranking policies can be expressed with the ranking factors combined and our approach can work, even if the folksonomy site is not implemented with Semantic Web languages. Above all, the time weight proposed in this paper will be applicable to various domains, including social media, where time value is considered important.