• 정보관리학회지
• /
• 제7권1호
• /
• pp.79-95
• /
• 1990

본 연구는 그동안 연구되고 개발된 여러 검색 기법을 검색된 문헌 집합의 특성과 사용된 표현에 의해서 완전 매치 검색과 부분 매치 검색으로 구분하였다. 완전 매치는 부울 논리가 그 대표적이며 현행 대부분의 정보 검색 시스템에서 사용하고 있는 검색 기법이다. 부분 매치는 부울논리가 가지고 있는 문제점과 한계점을 극복하기 위한 대한으로서 많은 연 구가 있었으나 그 본질은 부울 논리 구조안에서 검색을 향상시킨다는 점에서 한계를 가질수 밖에 없다 하겠다. 대표적인 예로 확률 검색, 벡터 공간 모델, 그리고 퍼지 집합을 대상으로 두 검색 기법을 비교하고 앞으로의 검색 기법이 나아가야 할 방향을 제시하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제10권7호
• /
• pp.2936-2951
• /
• 2016

An emerging satellite technology, Operationally Responsive Space (ORS) is expected to provide a fast and flexible solution for emergency response, such as target tracking, dense earth observation, communicate relaying and so on. To realize large distance transmission, we propose the use of available relay satellites as relay nodes. Accordingly, we apply software defined network (SDN) technology to ORS networks. We additionally propose a satellite network architecture refered to as the SDN-based ORS-Satellite (Sat) networking scheme (SDOS). To overcome the issures of node failures and dynamic topology changes of satellite networks, we combine centralized and distributed routing mechanisms and propose a fast recovery routing algorithm (FRA) for SDOS. In this routing method, we use centralized routing as the base mode.The distributed opportunistic routing starts when node failures or congestion occur. The performance of the proposed routing method was validated through extensive computer simulations.The results demonstrate that the method is effective in terms of resoving low end-to-end delay, jitter and packet drops.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권11호
• /
• pp.5223-5242
• /
• 2017

In the last decade, the 2.4 GHz band of IEEE 802.11 WLANs has become heavily congested due to the explosive increase in demand of Wi-Fi connectivity. With the current deployment of enterprise WLANs, channel switching mechanism continues to exhibit inefficiencies because it cannot adapt to real-time channel condition and the inability to support seamless channel switching. Software Defined Networking (SDN) as an emerging architecture is promising to introduce flexibility and programmability for wireless network management. Leveraging SDN to existing enterprise WLANs, channel switching method can be improved significantly. This paper presents a software-defined enterprise WLAN framework with a load aware automatic channel switching solution, which utilizes AP load and channel interference factor (CIF) to provide seamless channel switching. Two automatic channel switching algorithms named Single Switch (SS) and Double Switch (DS) are proposed to improve the overall user experience and the experience of users with highest traffic load respectively. Experiment results demonstrate that our solution can efficiently improve user experience in terms of jitter, transmission delay and network throughout when compared to the conventional channel switching mechanism.

• Journal of Information Processing Systems
• /
• 제8권1호
• /
• pp.133-144
• /
• 2012

In order to make cognitive radio systems a practical technology to be deployed in real-world scenarios, the core Software Defined Radio (SDR) systems must meet the stringent requirements of the target application, especially in terms of performance and energy consumption for mobile platforms. In this paper we present a feasibility study of hardware acceleration as an energy-efficient implementation for SDR. We identified the amplifier function from the Software Communication Architecture (SCA) for hardware acceleration since it is one of the functions called for most frequently and it requires intensive floating-point computation. Then, we used the Virtex5 Field-Programmable Gate Array (FPGA) to perform a comparison between compiler floating-point support and the on-chip floating-point support. By enabling the on-chip floating-point unit (FPU), we obtained as high as a 2X speedup and 50% of the overall energy reduction. We achieved this with an increase of the power consumption by no more than 0.68%. This demonstrates the feasibility of the proposed approach.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제13권2호
• /
• pp.514-535
• /
• 2019

Information-centric networks operate under the assumption that all network components have built-in caching capabilities. Integrating the caching strategies of information centric networking (ICN) with wireless virtualization improves the gain of virtual infrastructure content caching. In this paper, we propose a framework for software-defined information centric virtualized wireless device-to-device (D2D) networks. Enabling D2D communications in virtualized ICN increases the spectral efficiency due to reuse and proximity gains while the software-defined network (SDN) as a platform also simplifies the computational overhead. In this framework, we propose a joint virtual resource and cache allocation solution for latency-sensitive applications in the next-generation cellular networks. As the formulated problem is NP-hard, we design low-complexity heuristic algorithms which are intuitive and efficient. In our proposed framework, different services can share a pool of infrastructure items. We evaluate our proposed framework and algorithm through extensive simulations. The results demonstrate significant improvements in terms of visiting latency, end user QoE, InP resource utilization and MVNO utility gain.

• 한국항공운항학회지
• /
• 제29권4호
• /
• pp.45-51
• /
• 2021

A runway safety area (RSA) is defined as the surface surrounding the runway prepared or suitable for reducing the risk of damage to airplanes in the event of an undershoot, overshoot, or excursion from the runway. The Runway Stripe is a defined area including the runway stopway, if provided, intended firstly to reduce the risk of damage to aircraft running off a runway, and secondly, to protect aircraft flying over it during takeoff or landing operations. This study used 2 RSA analysis models; RSARA and LRSARA. The analysis utilizes historical data from the specific airport and allows to take into consideration specific operational conditions to which movements are subject, as well as the actual or planned RSA conditions in terms of dimensions, configuration, and boundaries defined by existing obstacles. This study applied the RSA and LRSA risk assessment models to a domestic airport that do not meet the criteria required by standards for aerodrome physical characteristics. The airport is considering a method to secure the runway strip standard through the displaced threshold. This study intends to confirm through quantitative risk estimation whether meeting facility standards through the runway displaced threshold leads to a positive change in risk mitigation.

• 인터넷정보학회논문지
• /
• 제22권6호
• /
• pp.1-8
• /
• 2021

With the rapid growth of intelligent devices and communication technologies, 5G network environment has become more heterogeneous and complex in terms of service management and orchestration. 5G architecture requires supportive technologies to handle the existing challenges for improving the Quality of Service (QoS) and the Quality of Experience (QoE) performances. Among many challenges, traffic steering is one of the key elements which requires critically developing an optimal solution for smart guidance, control, and reliable system. Mobile edge computing (MEC), software-defined networking (SDN), network functions virtualization (NFV), and deep learning (DL) play essential roles to complementary develop a flexible computation and extensible flow rules management in this potential aspect. In this proposed system, an accurate flow recommendation, a centralized control, and a reliable distributed connectivity based on the inspection of packet condition are provided. With the system deployment, the packet is classified separately and recommended to request from the optimal destination with matched preferences and conditions. To evaluate the proposed scheme outperformance, a network simulator software was used to conduct and capture the end-to-end QoS performance metrics. SDN flow rules installation was experimented to illustrate the post control function corresponding to DL-based output. The intelligent steering for network communication traffic is cooperatively configured in SDN controller and NFV-orchestrator to lead a variety of beneficial factors for improving massive real-time Internet of Things (IoT) performance.

• 충청수학회지
• /
• 제25권4호
• /
• pp.731-738
• /
• 2012

Let L(M) be the bundle of all linear frames over $M,\;u$ an arbitrarily given point of L(M), and ${\nabla}\;:\;\mathfrak{X}(M)\;{\times}\;\mathfrak{X}(M)\;\rightarrow\;\mathfrak{X}(M)$ a linear connection on L(M). Then the following results are well known: the horizontal subspace and the connection form at the point $u$ may be written in terms of local coordinates of $u\;{\epsilon}\;L(M)$ and Christoffel's symbols defined by $\nabla$. These results are very fundamental on the study of the theory of connections. In this paper we show that the local expressions of those at the point $u$ do not depend on the choice of a local coordinate system around the point $u\;{\epsilon}\;L(M)$, which is rarely seen. Moreover we give full explanations for the following fact: the covariant derivative on M which is defined by the parallelism on L(M), determined from the connection form above, coincides with $\nabla$.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2004년도 추계학술대회 논문집
• /
• pp.471-474
• /
• 2004

In this paper, a NURBS surface interpolator is proposed which can deal with shapes defined from CAD/CAM programs on a surface basis and can improve contour accuracy. The proposed interpolator is based on newly defined G-codes and includes online tool-path planning suitable for NURBS surface machining. The real-time interpolation algorithm, considering an effective machining method for each machining process and minimum machining time, is executed in an online manner. The proposed interpolator is implemented on a PC-based 3-axis CNC milling system and evaluated through actual machining in terms of machining time and regulation of feedrate and cutting force in comparison with the existing method.

• 대한약침학회지
• /
• 제19권2호
• /
• pp.109-113
• /
• 2016

This short review article presents a current overview of existing publications and scientific results regarding liquid (ear) acupuncture. The injection of liquids into defined acupuncture points of the ear is not a method commonly used in the Western world. The term liquid acupuncture has different definitions, which makes understanding each definition and differentiating one from the other difficult. General terms like pharmacopuncture, homeosiniatry, and liquid acupuncture, which all describe the method of injecting different kinds of drugs into a defined body acupuncture point, are used. This article presents the history of liquid acupuncture, as well as the current scientific state of the art, from the point of view of two European researchers. Some articles are discussed and a few practical examples are presented.