• Title/Summary/Keyword: Directional Relation

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Quantification of Directional Properties of Channel Network and Hill Slope (하천망과 사면의 방향성 정량화)

  • Park, Changyeol;Yoo, Chulsang
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.31 no.3B
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    • pp.233-242
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    • 2011
  • This study quantified directional properties of channel network and hill slope for a river basin by applying the von Mises distribution, also examined the relation between them. Ultimately, it was examined that whether the directional properties of channel network and hill slope have a certain relation, which might be considered to the rainfall-runoff modeling. From the results derived by analyzing the Naesung stream basin, the von Mises distribution was found well to explain the directional characteristics of directional properties of channel network. There was a clear relation between directional properties of channel network and hill slope. The higher-order streams also showed very obvious modal characteristics. The results derived in this study could be helpful to estimate more quantitatively the difference in the runoff response with respect to the directional properties of channel network and hill slope.

Analysis of MOSFET Failure Modes in Bi-directional Phase-Shift Full-Bridge Converters

  • Oh, Chang-Yeol;Sung, Won-Yong;Kim, Yun-Sung;Lee, Byoung-Kuk
    • Journal of Electrical Engineering and Technology
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    • v.10 no.4
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    • pp.1692-1699
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    • 2015
  • This paper presents an analysis of the mechanism of failure modes in bi-directional phase-shift full-bridge converters, composed of MOSFET, based on the circuit operation and parasitic parameters of MOSFET. In addition, the relation between circuit operation and parameters is suggested through an experimental comparison. From this relation, the suitable ranges of parameters for stable performance are analyzed. The design criteria of the bi-directional phase-shift full-bridge converter are presented and evaluated from the experimental verification.

A Group-aware Multicast Scheme in 60GHz WLANs

  • Park, Hyun-Hee;Kang, Chul-Hee
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.5 no.5
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    • pp.1028-1048
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    • 2011
  • The relation of multicast transmission and directional antennas is an open problem that has been debated for a long period of time. In this paper, we propose a group-aware multicast scheme of efficient multicast communication using the directional antennas for 60GHz millimeter wave wireless networks. For this purpose, we first derive the relation among beamwidth, distance between devices and most suitable data rate in the 60GHz frequency-based wireless network. In addition, for the dynamic beamforming of multicast communication, the x and y coordinates of any point with sender device at the center is generated, and a best-chosen group is deduced based on the Euclidean distance. Then the most suitable data rate for the group is obtained using the law of cosine. Using the Standard IEEE 802.11ad MAC protocol as an example, extensive simulation results demonstrate that the proposed scheme outperforms the existing multicast communication schemes with directional antennas under different situations.

Opportunistic Spectrum Access with Dynamic Users: Directional Graphical Game and Stochastic Learning

  • Zhang, Yuli;Xu, Yuhua;Wu, Qihui
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.11 no.12
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    • pp.5820-5834
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    • 2017
  • This paper investigates the channel selection problem with dynamic users and the asymmetric interference relation in distributed opportunistic spectrum access systems. Since users transmitting data are based on their traffic demands, they dynamically compete for the channel occupation. Moreover, the heterogeneous interference range leads to asymmetric interference relation. The dynamic users and asymmetric interference relation bring about new challenges such as dynamic random systems and poor fairness. In this article, we will focus on maximizing the tradeoff between the achievable utility and access cost of each user, formulate the channel selection problem as a directional graphical game and prove it as an exact potential game presenting at least one pure Nash equilibrium point. We show that the best NE point maximizes both the personal and system utility, and employ the stochastic learning approach algorithm for achieving the best NE point. Simulation results show that the algorithm converges, presents near-optimal performance and good fairness, and the directional graphical model improves the systems throughput performance in different asymmetric level systems.

Performance characteristics of a multi-directional underwater CCTV camera system to use in the artificial reef survey (인공어초 조사용 다방향 수중 CCTV 카메라 시스템의 성능 특성)

  • Lee, Dae-Jae
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.47 no.2
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    • pp.146-152
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    • 2011
  • Underwater CCTV camera systems are increasingly replaced the traditional net approach of assessing the species, numbers and aggregation patterns of marine animals distributing around the artificial reefs installed in the inshore fishing grounds, in particular, in relation to the biological investigation of behavior and distribution patterns of target fishes. In relation to these needs, we developed a multi-directional underwater CCTV camera system to use in detecting and tracking marine animals in the artificial reef ground. The marine targets to be investigated were independently tracked by using a camera module toward the bottom and four camera modules installed in the interval of $90^{\circ}$ in horizontal plane and inclination of $45^{\circ}$ in vertical plane of the CCTV system without the overlap of video frames by each camera module. From the results of several field tests at sea, we believe that the developed multi-directional underwater CCTV camera system will contribute to a better understanding in evaluating the effect of artificial reefs installed in the inshore fishing grounds.

Representation Method of Viewpoint-based Directional Relationship for 3-Dimensional Graphic Databases (3차원 그래픽 데이타베이스를 위한 시점기반의 방향관계 표현 기법)

  • 황종하;백중환;황수찬
    • Journal of KIISE:Databases
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    • v.30 no.2
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    • pp.157-167
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    • 2003
  • Spatial relations among objects we one of the most frequently used searching criteria for a query based on the contents of 3-D images. However, the existing researches have mainly focused only the absolute directional relations based on a fixed viewpoint in 2-D images. So, this paper presents a representation method of viewpoint based directional relations that enables spatial relations among objects to be retrieved based on a viewpoint of an observer. The retrieval technique based on our method is a]so described. In this paper, the notion of 3D string is defined to express the spatial relations in a 3-D space. A retrieval method based on relative directional relations among objects from a viewpoint of an observer is also presented. The proposed method simplifies the retrieval of viewpoint-based directional relations because 2D+1D scheme reduces the dimension.

A study on fabrication and characterization of directional coupling optical modulator (방향성 결합형 광 변조기 제작 및 특성연구)

  • 강기성;소대화
    • Electrical & Electronic Materials
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    • v.8 no.4
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    • pp.443-450
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    • 1995
  • A directional coupler which on the X-cut $LiNbO_3$ substrate is fabricated by using proton exchange method and self-aligned method. After proton exchange process, the waveguide is formed by annealing process. The relation ship between refractive index change of waveguide and maximum output was studied along with the annealing time. A self-aligned method was used to simplify the fabrication process of the waveguide and to maximize the efficiency of electric field. The on-off state of modulator has been observered with the switching of the directional coupler by the electric field effect and also the switching voltage of the directional coupler has been measured with 8.0 [V].

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Discrete optimal sizing of truss using adaptive directional differential evolution

  • Pham, Anh H.
    • Advances in Computational Design
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    • v.1 no.3
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    • pp.275-296
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    • 2016
  • This article presents an adaptive directional differential evolution (ADDE) algorithm and its application in solving discrete sizing truss optimization problems. The algorithm is featured by a new self-adaptation approach and a simple directional strategy. In the adaptation approach, the mutation operator is adjusted in accordance with the change of population diversity, which can well balance between global exploration and local exploitation as well as locate the promising solutions. The directional strategy is based on the order relation between two difference solutions chosen for mutation and can bias the search direction for increasing the possibility of finding improved solutions. In addition, a new scaling factor is introduced as a vector of uniform random variables to maintain the diversity without crossover operation. Numerical results show that the optimal solutions of ADDE are as good as or better than those from some modern metaheuristics in the literature, while ADDE often uses fewer structural analyses.

Effect of Multi-directional Random Waves on Characteristics of 3-D Wave Field around Permeable Submerged Breakwaters (다방향 불규칙파가 투과성 잠제 주변의 3차원 파동장에 미치는 영향)

  • Hur, Dong-Soo;Lee, Woo-Dong
    • Journal of Ocean Engineering and Technology
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    • v.26 no.2
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    • pp.68-78
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    • 2012
  • This study proposes an improved 3-D model that includes a new non-reflected wave generation system for oblique incident and multi-directional random waves, which enables us to estimate the effect of the various wave-types on 3-D wave fields in a coastal area with permeable submerged breakwaters. Then, using the numerical results,the three-dimensional wave field characteristics around permeable submerged breakwaters are examined in cases of oblique incident and multi-directional random waves. Especially, the wave height, mean surface elevation and mean flow around the submerged breakwaters are discussed in relation to the variation of incident wave condition.

CONIFER FOREST BIOMASS ESTIMATION USING MULTI ANGLE SPECTRUM OBSERVATION

  • Kajiwara, Koji;Ono, Yuhsaku;Honda, Yoshiaki
    • Proceedings of the KSRS Conference
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    • 2008.10a
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    • pp.394-397
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    • 2008
  • This research aimed at developing a technique for estimating the tree height using BRF (Bi-directional Reflectance Factor) through the clarification of the relation between shape of the tree crown and the tree height and the relations between the shape of the tree crown and BRF. This paper, reports the results of analyses of data acquired by field measurements done to clarify relation between crown shape and tree height.

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