• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권11호
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• pp.2764-2783
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• 2012

Network virtualization supports future Internet environments and cloud computing. Virtualization can mitigate many hardware restrictions and provide variable network topologies to support variable cloud services. Owing to several advantages such as low cost, high flexibility, and better manageability, virtualization has been widely adopted for use in network virtualization platforms. Among the many issues related to cloud computing, to achieve a suitable cloud service quality we specifically focus on network and performance isolation schemes, which ensure the integrity and QoS of each virtual cloud network. In this study, we suggest a virtual network platform that uses Xen-based virtualization, and implement multiple virtualized networks to provide variable cloud services on a physical network. In addition, we describe the isolation of virtual networks by assigning a different virtualized network ID (VLAN ID) to each network to ensure the integrity of the service contents. We also provide a method for efficiently isolating the performance of each virtual network in terms of network bandwidth. Our performance isolation method supports multiple virtual networks with different levels of service quality.

• Journal of Power Electronics
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• 제18권1호
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• pp.195-203
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• 2018

In the variable speed Wind Turbine based on ElectroMagnetic Coupler (WT-EMC), a synchronous generator is coupled directly to the grid. Therefore, like conventional power plants, WT-EMC is able to inherently support grid frequency. However, due to the reduced inertia of the synchronous generator, WT-EMC is expected to be controlled to increase its output power in response to a grid frequency drop to support grid frequency. Similar to the grid frequency support control of Type 3 or Type 4 wind turbine, inertial control and droop control can be used to calculate the WT-EMC additional output power reference according to the synchronous generator speed. In this paper, an experimental platform is built to study the grid frequency support from WT-EMC with inertial control and droop control. Two synchronous generators, driven by two induction motors controlled by two converters, are used to emulate the synchronous generators in conventional power plants and in WT-EMCs respectively. The effectiveness of the grid frequency support from WT-EMC with inertial control and droop control responding to a grid frequency drop is validated by experimental results. The selection of the grid frequency support controller and its gain for WT-EMC is analyzed briefly.

• 한국전산구조공학회논문집
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• 제34권5호
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• pp.263-270
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• 2021

본 연구에서는 환경, 재료 물성 및 제작 등에서의 불확실성을 고려하여 130m급 고정식 해양구조물의 신뢰성 기반 최적설계를 수행하였다. 구조물의 구조건전성을 엄밀하게 반영하기 위해 작용 및 허용 응력의 비인 UC 값을 신뢰성 해석 및 신뢰성 기반 최적설계의 제약조건으로 고려하였다. 해양구조물의 제작비용을 저감하기 위해 자켓형 지지구조물의 중량을 최소화하였다. 불확실성의 통계적 특성은 문헌 등을 참고하여 관측되거나 측정된 데이터를 기반으로 정의하였다. 자켓형 해양구조물의 신뢰성 해석과 신뢰 기반 최적설계는 부재 수가 많아 계산 부담이 큼으로 문제의 차원을 축소하기 위해 응답의 중요성을 기준으로 설계변수를 선별할 수 있는 방법을 제안한다. 또한 효율적인 계산을 위해 신뢰성 기반 최적설계를 수행하기 전 결정론적 최적설계를 먼저 수행하였다. 마지막으로, 도출된 최적설계(안)을 기존 각 급 규정 기반 설계와 안전성 및 경제성 측면에서 비교 분석하였다.

• Journal of Information Technology Applications and Management
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• 제25권2호
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• pp.53-72
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• 2018

This empirical study explored characteristics that affect the usefulness of online reviews, in the China e-commerce platform, and implemented multiple regressions to find factors that significantly influence on product sales, ultimately. Till now, prior studies have continuously revealed what factor affects usefulness of online review or product sales, only in respective terms. The point of our study is that we built two-level regression models, thereby being able to comprehensively analyze these two different targets. Before plunging into running regressions, we carefully collected 192,764 online review data for 200 products extracted from the Jingdong, the second biggest e-commerce platform in China. Also, we gathered "review sentimental scores" variable from each review and used that one as a core variable in our regression model, thus we were able to implement both quantitative and qualitative research. The evidences from the two-level regression models showed that the extent to which a product is experience good positively affects both usefulness of a review and product sales, again the usefulness of a review contributes to product sales in sequence. Also, the property of experience good has interaction effect on both for two-level regression models. Our main findings highlight the importance of role of online review to business performance of e-commerce firms.

• 한국정보시스템학회지:정보시스템연구
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• 제23권1호
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• pp.29-52
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• 2014

As the advance of multi-platform and multi-channel online services, brokerages are now offering three representative online trading systems - HTS(Home Trading Systems), WTS(Web Trading Systems), MTS(Mobile Trading Systems). In this study we investigated and compared the impact of different systems on the performance of brokerages. Using the panel data of 29 brokerages of 4 periods, we empirically tested the impact of online trading systems and the commissions of trading services. We found out that there exist some differences between the impacts of online trading systems based on the platforms. HTS was identified as the main platform for online trading services. However the role of MTS was also significantly identified while WTS showed no significant impact on the brokerage performances. Commission also showed significant negative impact in case of HTS and MTS platforms. Finally, offering MTS was identified as the significant dummy variable influencing the performance of brokerages. The results provides some implication for the multi-platform strategy for online services.

• 한국정밀공학회지
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• 제26권5호
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• pp.128-134
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• 2009

This paper aims to design a variable-stiffness type economical safety joint for service robots. The safety joint was designed to have a passive shock absorbing mechanism for protecting human from a catastrophic collision under service condition of robots. A simple mechanism composed of two action disks for switching the load transfer, a spring and a screw for pre-load was proposed. In order to evaluate the performance of the safety joint a testing platform which can carry out the static and impact tests was also designed and fabricated. From the test results, the designed safety joint was proved to have a variable load-carrying capacity and about 42% impact absorption capacity with simple manipulation of the control screw.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.654-659
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• 2001

In the virtual environment, reality can be enhanced by offering the motion based on a motion simulator in harmony with visual and auditory modalities. In this research, the Stewart platform based motion simulator has been developed. This motion simulator is driven by the electric motors, and offers the slightly wider workspace compared to the commercial available simulators. In order to compensate for the limited range of the motion platform, the washout filters with fixed coefficients have been usually adopted. In this paper the new approach is proposed to tune the filter coefficients based on the fuzzy logic on the real-time basis. It is shown that performance with the variable filter coefficients is better than that with the fixed ones. The driving simulator based on the bicycle dynamics was developed by integrating the motion simulator and graphic system.

• 한국전자거래학회지
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• 제27권1호
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• pp.43-62
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• 2022

본 논문은 국내 독립 SW기업(ISV, Independent Software Vendor)이 어떤 조건을 갖추었을때 플랫폼 생태계 참여에 더 적극적인가를 분석한 연구이다. 기업은 기술혁신의 결과를 전유할 수 있을 때와 해당 기술을 가치로 전환할 수 있는 보완자산(마케팅, 제조역량 등)을 보유한 경우 기술혁신에 적극적이다. 본 연구에서는 두 조건이 플랫폼 생태계 참여에 미치는 영향을 분석하였다. 또, SW기업이 보유한 제품 포트폴리오와 플랫폼의 서비스간 경쟁관계가 플랫폼 참여에 영향을 준다고 보고, 해당 요인의 영향도 분석하였다. 디지털 플랫폼 기업들과 파트너 협약을 한 국내 독립 SW기업 그리고 이에 대응하는 비슷한 수의 플랫폼 미참여 기업으로 표본집단을 구성하여 플랫폼 참여, 특허 및 개발 후 사업화 역량, 경쟁관계 등의 데이터를 취합하고 분석하였다. 분석 결과 특허 보유 여부는 플랫폼 참여에 영향을 주지 않았다. 혁신기술과 사업모델의 노출에 따른 위험보다 플랫폼 기업과 협력으로부터 발생하는 효익이 크다고 판단한 결과로 여겨진다. 반면, 사업화 역량 보유와 경쟁 관계는 플랫폼 참여에 영향을 주었다. 협력의 결과를 가치로 전환할 수 있는 사업화 역량을 보유한 경우 플랫폼 참여 가능성이 커진다. 또, 제품 포트폴리오가 플랫폼 서비스와 경쟁보다 보완관계가 될 때 협력에 적극적이다. 본 연구는 국내 독립 SW기업과 디지털 플랫폼 기업간 협력을 다룬 실증연구로서 해외에는 유사 선행 연구가 있지만 국내에는 유사한 연구사례가 없다. 플랫폼 생태계 참여 기업과 미 참여 기업을 표본집단으로 구성하여 플랫폼 생태계 참여 결정요인을 실증분석을 통해 규명하였다는 데 의의가 있다.

• Geomechanics and Engineering
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• 제14권1호
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• pp.91-98
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• 2018

Length of a vehicle is an important variation to generate different variants of an automotive platform. This parameter is usually adjusted by embedding dimensional flexibility into different components of the Body in White (BIW) including the floor pan. Due to future uncertainties, it is not necessarily possible to define certain values of wheelbase for the future products of a platform. This work is performed to add flexibility into the design process of a length-variable floor pan. By means of this analysis, the cost and time consuming process of optimization is not necessary to be performed for designing the different variants of a product family. Stiffness and mass of the floor pan are two important functional requirements of this component which directly affect the occupant comfort, dynamic characteristics, fuel economy and environmental protection of the vehicle. A combination of Genetic algorithm, GMDH-type of artificial neural networks and TOPSIS methods is used to optimally design the floor pan associated with arbitrary length of the variant in the defined system range. The correlation between the optimal results shows that for a constant mass of the floor pan, the first natural frequency decreases by increasing the length of this component.

• 로봇학회논문지
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• 제5권3호
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• pp.270-277
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• 2010

Various robot platforms have been designed and developed to perform given tasks in a hazardous environment for the purpose of surveillance, reconnaissance, search and rescue, and etc. We have considered a terrain adaptive hybrid robot platform which is equipped with rapid navigation on flat floors and good performance on overcoming stairs or obstacles. Since our special consideration is posed to its flexibility for real application, we devised a design of a transformable robot structure which consists of an ordinary wheeled structure to navigate fast on flat floor and a variable tracked structure to climb stairs effectively. Especially, track arms installed in front side, rear side, and mid side are used for navigation mode transition between flatland navigation and stairs climbing. The mode transition is determined and implemented by adaptive driving mode control of mobile robot. The wheel and track hybrid mobile platform apparatus applied off-road driving mechanism for various professional service robots is verified through experiments for navigation performance in real and test-bed environment.