• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.31-41
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• 2009

IEEE 802.11e proposed by IEEE 802.11 working group to guarantee QoS has contention based EDCA and contention free based HCCA. HCCA, a centralized polling based mechanism of 802.11e, needs a scheduling algorithm to allocate the network resource efficiently. The existing standard scheduler, however, is inefficient to support for QoS guarantee for real-time service having VBR traffic. To improve these limit, in this paper, we First, we propose priority polling algorithm which additionally considers the size of MSI and TXOP based on EDD algorithm to increase number of QSTAs. We also propose a dual token bucket TXOP allocation algorithm to reduce congestion caused by stations which enters network with considerable delay variance. TSPEC parameters, Maximum Burst Size (MBS) and Peak Data Rate (PR), are applied to design depth and token generation rate of two buckets. Simulation results show that the proposed algorithm has much higher performance compared with reference and SETT-EDD scheduler in terms of throughput and delay.

• Journal of KIISE:Databases
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• v.32 no.5
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• pp.536-546
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• 2005

In this paper, we focus on the filtering step of candidate objects for spatial join operations on the input tables that none of the inputs is indexed. Over the last decade, several spatial Join algorithms for the input tables with index have been extensively studied. Those algorithms show excellent performance over most spatial data, while little research on solving the performance degradation in the presence of skewed data has been attempted. Therefore, we propose a spatial hash strip join(SHSJ) algorithm that can refine the problem of skewed data in the conventional spatial hash Join(SHJ) algorithm. The basic idea is similar to the conventional SHJ algorithm, but the differences are that bucket capacities are not limited while allocating data into buckets and SSSJ algorithm is applied to bucket join operations. Finally, as a result of experiment using Tiger/line data set, the performance of the spatial hash strip join operation was improved over existing SHJ algorithm and SSSJ algorithm.

• Journal of Digital Contents Society
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• v.16 no.3
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• pp.365-371
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• 2015

In wireless network, the amount of video streaming packet information in receiver replay buffer can be varied according tothe wireless network condition. By the effect, unforeseeable delay and jitter are generated and then busty video traffics can be made. If the amount of buffer information coming in receiver replay buffer is larger than the amount of a specific buffer information, buffer overflow is generated. Such a problem makes the image skip effect and packet loss, and then causes the quality degradation and replay discontinuity of the video streaming service in destination receiver. To solve the buffer overflow problem, this paper applies the token bucket for the busty traffic to the receiver terminal and analyzes the effect of the token bucket. The simulation result using NS-2 and JSVM shows that the proposed scheme with the token bucket has significantly better performance than the conventional scheme without the token bucket in terms of overflow generation number, packet loss rate and PSNR.

• Journal of the Korea Convergence Society
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• v.10 no.5
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• pp.165-171
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• 2019

Engineering and Technology have been influencing a lot in the field of sports. Competitiveness, attributes of sports, have forced not only sports players but sports goods to enhance those performance. Particularly in the field of motorsports, the convergence of sports and technology has long been done to satisfy between performance and safety. In this study, strength analysis was carried with FEM to develop CFRP Laminate(Carbon Fiber Reinforced Plastic Laminate) bucket seat targeted to motorsports and car tuning industries and FIA($F\acute{e}d\acute{e}ration$ Internationale de l'Automobile) regulation was applied to design the racing seat and evaluate its strength. FEM modeling considered the attributes of composites was followed by strength evaluation based on Tsai-Wu failure index were done according to Lay-up sequence and layer numbers. The result showed that the lay-up sequence with stacking angle such as $[0^{\circ}/30^{\circ}/60^{\circ}/90^{\circ}/-30^{\circ}/-60^{\circ}]_4$ with 3mm form core was optimal selection in the field of weight and strength evaluation.

• Digital Contents
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• no.6 s.85
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• pp.14-17
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• 2000

인터넷 접속은 방대한 접속수를 가진 웹사이트와 콘텐츠를 쾌적하게 연결시키는 것이 목표다. 엑소더스라는 기업은 데이터 센터만으로는 콘텐츠가 어디든 연결된다는 것을 보증할 수 없다는 전제 아래 네트워크의 고객외 페이지에서 버킷을 끄집어내 그것을 마지막 사용자에게 연결하는 방법을 사용한다. 여기서도 신뢰성, 스케러비리티, 그리고 보안이 중요함은 물론이다. Yahoo!를 비롯한 방대한 접속수를 가진 닷컴기업의 웹사이트의 운용을 맡고 있는 엑소더스에 대해 알아본다.

• 월간낙농육우
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• v.34 no.8
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• pp.162-165
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• 2014

국내 낙농경영이 복합경영에서 규모화된 전업농 또는 기업농 형태의 단일경영으로 빠르게 변하고 있다는 것은 모두가 알고 있는 사실이다. 이에 따라 착유시설 또한 많은 변화가 있었으며, 사육규모 및 두당 유생산랑과 정(正)의 상관관계를 갖고 있다. 국내 낙농산업의 초창기 또는 본격적인 도입기였던 1970년대와 1980년대 초반은 가구당 착유우 두수가 10두 미만이었으며 주로 손으로 착유를 하였다. 1980년대 중반 이후, 콤프레셔와 버킷설비가 목장에 도입되었으며, 냉각기 보조금 지급 및 보냉 집유차량이 목장별로 운행하기 시작하였다. 1990년대에는 버킷식 착유기가 파이프라인식 착유기로 전환되면서 착유시스템이 일부 자동화됨에 따라 노동력을 낮추고 원유의 위생안전성을 향상시킬 수 있었다. 2000년대에는 많은 목장에서 탠덤 또는 헤링본식 착유시스템을 도입하였으며, 이후 일부 착유두수가 60두 이상인 대규모 농가에서는 자동착유시스템을 도입하여 현재에 이르고 있다. 사실 전업농, 기업농으로 전환된 단일경영에서 지동착유시스템의 도입에 많은 관심을 보이고 있으나, 고가의 자동칙유시스템에 대한 한정된 정보에서 기인하는 리스크(위험요소) 등으로 인하여 섣불리 결정을 내리지 못하고 있는 실정이다. 이에 자동착유시스템의 구성 국내 외 도입 현황 및 장 단점 사례조사 결과와 함께 현재 농가의 자동착유시스템 도입 결정에 도움을 주기 위해 진행하고 있는 연구 과제를 소개하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1332-1340
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• 2009

The front end wheel loader is widely used for the loading of materials in mining and construction fields. It has repetitive digging, loading and dumping procedures. The bucket is subjected to large resistance force from the soil during scooping. We considered the soil reaction force characteristics from scooping procedure, the protection by overload and automatic scooping mode algorithm. The main topic of this paper is the analysis of the soil reaction force characteristics. The analysis of soil mechanics is carried out and the developed soil model is verified by experimental results from the simplified experimental equipment. A simplified model of the soil shape and bucket trajectory is used to determine the scooping direction based on an estimation of the resistance force applied on the bucket during the scooping motion. In the future, this model will be used for the generation of an appropriate path for the wheel loader automation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.2
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• pp.325-332
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• 2016

Configuring excavator attachments and engine sizes is the prerequisite for appropriate excavator assignment. Existing experience based configuration practice is lack of scientific rational because many variables (e.g., equipment motion data, soil and rock type and condition, equipment's engineering dimension along with bucket properties, job and management conditions etc.) should be considered simultaneously and timely fashion. This paper presents a new excavator configuration searching method that identifies the most favorable excavator configuration (i.e., the optimal set of excavator's maximum digging height and bucket size) to complement these existing practices. The method coded by using MATLAB identifies an optimal excavator configuration by considering those variables causing the variability of productivity. A case study is presented to demonstrate and to verify the system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.175-178
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• 2007

According to recently presented QoS architecture by 3GPP, a traffic conditioner may be deployed to provide conformance of the negotiated QoS. A real-time frame-layer rate control method which can be applied to the traffic conditioner is proposed. The proposed rate control method uses a non-iterative optimization method for low computational complexity, and performs bit allocation at the frame level to minimize the average distortion over an entire sequence as well as variations in distortion between frames. The proposed algorithm does not produce time delay from encoding, and is suitable for real-time low-complexity video encoder.

• Journal of Navigation and Port Research
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• v.42 no.3
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• pp.237-244
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• 2018

When underwater rubble leveling work is carried out by a robot, real-time information on the topography around the robot is required for remote control. If the topographical information with respect to the current position of the robot is displayed as a 3D graphic image, it allows the operator to plan the working schedules and to avoid accidents like rollovers. Up until now, the topographical recognition was conducted by multi-beam sonars, which were only used to assess the quality before and after the work and could not be used to provide real-time information for remote control. This research measures the force delivered to the bucket which presses the mound to determine whether contact is made or not, and the contact position is calculated by reading the cylinder length. A variable bang-bang control algorithm is applied to control the heavy robot arms for the positioning of the bucket. The proposed method allows operators to easily recognize the terrain and intuitively plan the working schedules by showing relatively 3-D gratifications with respect to the robot body. In addition, the operating patterns of a skilled operator are programmed for raking, pushing, moving, and measuring so that they are automatically applied to the underwater rubble leveling work of the robot.