• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권6호
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• pp.575-596
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• 2009

Facing limited network resources such as bandwidth and processing capability, the Internet will have congestion from time to time. In this paper, we propose a scheme to maximize the total utility offered by the network to the end user during congested times. We believe the only way to achieve our goal is to make the scheme application-aware, that is, to take advantage of the characteristics of the application. To make our scheme scalable, it is designed to be class-based. Traffic from applications with similar characteristics is classified into the same class. We adopted the RED queue management mechanism to adaptively control the traffic belonging to the same class. To achieve the optimal utility, the traffic belonging to different classes should be controlled differently. By adjusting link bandwidth assignments of different classes, the scheme can achieve the goal and adapt to the changes of dynamical incoming traffic. We use the control theoretical approach to analyze our scheme. In this paper, we focus on optimizing the control on two types of traffic flows: TCP and Simple UDP (SUDP, modeling audio or video applications based on UDP). We derive the differential equations to model the dynamics of SUDP traffic flows and drive stability conditions for the system with both SUDP and TCP traffic flows. In our study, we also find analytical results on the TCP traffic stable point are not accurate, so we derived new formulas on the TCP traffic stable point. We verified the proposed scheme with extensive NS2 simulations.

• 한국산학기술학회논문지
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• 제7권3호
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• pp.308-313
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• 2006

포탄의 탄착점은 대포의 형상, 제작공차, 제어시스템 그리고 발사체의 제작공차 등 여러 변수의 함수이다. 본 논문에서는 포탄의 탄두를 본체와 분리, 움직임이 가능한 형태로 부착하여 탄착점의 정확도를 향상시키는 가능성에 대하여 검토하였다. 기존의 포탄이 갖는 6 개의 자유도에 탄두의 3 개의 자유도를 더한 9 자유도의 동역학 식을 유도하였고 시뮬레이션을 통하여 가변탄두를 갖는 발사체가 탄두부분의 피치(pitch)와 요(yaw) 회전운동을 통하여 발사 초기의 불확실성을 흡수할 수 있음을 확인하였다.

• Structural Engineering and Mechanics
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• 제57권6호
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• pp.989-1014
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• 2016

This paper deals with the analysis of the natural frequencies, mode shapes of an axially loaded beam system carrying ends consisting of non-concentrated tip masses and three spring-two mass sub-systems. The influence of system design and sub-system parameters on the combined system characteristics is the major part of this investigation. The effect of material properties, rotary inertia and shear deformation of the beam system is included. The end masses are elastically supported against rotation and translation at an offset point from the point of attachment. Sub-systems are attached to center of gravity eccentric points out of the beam span. The boundary conditions of the ordinary differential equation governing the lateral deflections and slope due to bending of the beam system including developed shear force frequency dependent terms, due to the sub.system suspension, have been formulated. Exact formulae for the modal frequencies and the modal shapes have been derived. Based on these formulae, detailed parametric studies are carried out. The geometrical and mechanical parameters of the system under study have been presented in non-dimensional analysis. The applied mathematical model is presented to cover wide range of mechanical, naval and structural engineering applications.

• 한국정밀공학회지
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• 제19권10호
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• pp.120-129
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• 2002

An integrated structure and controller design approach for rotating cantilever beam is presented. An optimization method is developed for improving positioning performance considering the elastic deformations during high speed rotation and adopting the beam shape and the control gains as design variables. For this end, a dynamic model is setup by the finite element method according to the shape of the beam. The mass and stiffness of the beam are distributed in such a way that the closed-loop poles of the control system should be located leftmost in the complex s-plane. For optimization method, the simulated annealing method is employed which has higher probability to find the global minimum than the gradient-based down-hill methods. Sequential design and simultaneous design methods are proposed to obtain the optimal shape and controller. Simulations are performed with new designs by the two methods to verify the effectiveness of the approach and the results show that the settling time is improved for point-to-point position controls.

• Industrial Engineering and Management Systems
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• 제12권3호
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• pp.198-206
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• 2013

The team orienteering problem (TOP) or the multiple tour maximum collection problem can be considered as a generic model that can be applied to a number of challenging applications in logistics, tourism, and other fields. This problem is generally defined as the problem of determining P paths, in which the traveling time of each path is limited by $T_{max}$ that maximizes the total collected score. In the TOP, a set of N vertices i is given, each with a score $S_i$. The starting point (vertex 1) and the end point (vertex N) of all paths are fixed. The time $t_{ij}$ needed to travel from vertex i to j is known for all vertices. Some exact and heuristics approaches had been proposed in the past for solving the TOP. This paper proposes a new solution methodology for solving the TOP using the particle swarm optimization, especially by proposing a solution representation and its decoding method. The performance of the proposed algorithm is then evaluated using several benchmark datasets for the TOP. The computational results show that the proposed algorithm using specific settings is capable of finding good solution for the corresponding TOP instance.

• Journal of Smart Tourism
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• 제3권1호
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• pp.9-21
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• 2023

This study investigated whether the Point of attachment (POA) theory can be used to measure the consumption intention on go and watch offline eSports games. The admiration for players, social interaction, and on-site consumption requirements for viewing offline eSports competitions are prioritized. In addition, eSports fans in various regions may have distinct consumption concepts and consumption patterns. Thus, this study surveyed China (n = 156) and South Korea (n = 127) eSports fans who subjectively perceive themselves to be fans of eSports player(s) and who have observed at least one offline eSports game. The results demonstrate that player attraction and socialization have positive and significant effects on offline consumption factors. There is no correlation between previous consumption behavior and satisfaction, but dining shows a significant positive effect on satisfaction. Moreover, there is a strong relationship between satisfaction and future attendance intention. In addition, effect of eSports fan attachment on future visit intentions are measured and there is no correlation between the two variables. The front end of the path in the new model's varied between Chinese and Korean supporters. Finally, theoretical and practical implications of this study are discussed.

• Advances in aircraft and spacecraft science
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• 제9권5호
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• pp.415-431
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• 2022

Secondary flows have a huge impact on losses generation in modern low pressure gas turbines (LPTs). At design point, the interaction of the blade profile with the end-wall boundary layer is responsible for up to 40% of total losses. Therefore, predicting accurately the end-wall flow field in a LPT is extremely important in the industrial design phase. Since the inlet boundary layer profile is one of the factors which most affects the evolution of secondary flows, the first main objective of the present work is to investigate the impact of two different inlet conditions on the end-wall flow field of the T106A, a well known LPT cascade. The first condition, labeled in the paper as C1, is represented by uniform conditions at the inlet plane and the second, C2, by a flow characterized by a defined inlet boundary layer profile. The code used for the simulations is based on the Discontinuous Galerkin (DG) formulation and solves the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the Spalart Allmaras turbulence model. Secondly, this work aims at estimating the influence of viscosity and turbulence on the T106A end-wall flow field. In order to do so, RANS results are compared with those obtained from an inviscid simulation with a prescribed inlet total pressure profile, which mimics a boundary layer. A comparison between C1 and C2 results highlights an influence of secondary flows on the flow field up to a significant distance from the end-wall. In particular, the C2 end-wall flow field appears to be characterized by greater over turning and under turning angles and higher total pressure losses. Furthermore, the C2 simulated flow field shows good agreement with experimental and numerical data available in literature. The C2 and inviscid Euler computed flow fields, although globally comparable, present evident differences. The cascade passage simulated with inviscid flow is mainly dominated by a single large and homogeneous vortex structure, less stretched in the spanwise direction and closer to the end-wall than vortical structures computed by compressible flow simulation. It is reasonable, then, asserting that for the chosen test case a great part of the secondary flows details is strongly dependent on viscous phenomena and turbulence.

• 정보처리학회논문지D
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• 제11D권5호
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• pp.1123-1132
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• 2004

성공적인 프로젝트 계획은 프로젝트를 개발하는데 요구되는 인력을 얼마나 정확히 추정하느냐에 달려있다. 이 정보들은 Putnam의 Rayleigh 모델이나 Phillai et al.의 Gamma 모델들로 부터 유도된다. 그러나 이들 모델들은 투입 인력이 지수적으로 계속적으로 증가하여 개발이 종료되는 시점에서 투입되는 인력이 절정에 도달하는 소프트웨어 생명주기 전체에 대한 인력분포를 대상으로 하고 있다. 그러나 실제 프로젝트에서는 대부분의 인력이 개발에 투입되고 단지 적은 규모의 인력만이 유지보수에 할당된다. 또한, 대표적인 개발 프로세스인 폭포수 모델이나 단일화된 프로세스도 개발단계만을 대상으로 하고 있다 이러한 개발환경에는 개발완료시점에서 절정에 도달하는 기존 인력분포 모델의 투입인력 분포 곡선을 적용할 수 없다 본 논문은 이러한 문제점을 해결하기 위해 개발단계에 적합한 인력분포 모델을 제시한다. 먼저, Putnam이 제시한 인력분포로부터 폭포수 모델의 개발단계 투입 인력 분포를 유도하고, 다음으로, 단일화된 프로세스에 대한 개발단계 투입인력 분포를 유도하였다. 두 프로세스 투입인력을 비교한 결과 개발 각 시점에 대한 투입인력의 양, 수행 업무 단계는 차이가 발생하지만 총 투입 인력분포는 유사한 형태를 나타내었다. 이 결과로부터 두 개발 프로세스 모두에 적용할 수 있는 단일화된 개발인력 분포 모델을 유도하였다.

• 한국인터넷방송통신학회논문지
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• 제18권6호
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• pp.251-258
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• 2018

최근 자동차 교통량의 증가로 인해 차량 추돌사고가 급증하여 이에 따른 승객의 목상해가 증가해왔으며, 이를 방지하기 위한 자동차 시트의 설계적인 주안점을 고려하여 컴퓨터 시뮬레이션 기술을 확대 이용한 자동차충돌 해석연구가 활발히 진행되고 있다 본 연구에서는 인체모형 BioRID II 더미를 이용한 차량승객거동해석을 위한 MADYMO 프로그램을 사용하여 차량속도 16 km/h 운전조건의 후방추돌시 시트의 착좌자세인 백세트의 변화에 따른 승객의 목상해를 예측하였다. 그 결과로, 백세트가 짧을수록 접촉시작시간은 단축되지만 접촉완료시간은 거의 동일함을 알 수 있었고, T1 가속도는 백세트가 넓을수록 가속도는 증가함을 나타냈다. 또한 백세트가 넓을수록 인장력은 증가하고, 머리가 머리지대에 닿는 순간의 속도가 빨라짐으로써 목상해지수(NIC)는 증가함을 보였다.

• 한국CDE학회논문집
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• 제2권4호
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• pp.253-266
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• 1997

Pencil-curve machining, which is a single-pass ball-end milling along a concave edge on adie surface, is widely employed in die-surface machining. The cutter-path used for pencil-curve machining, which is the trajectory of the “ball-center point” of a ball-endmill sliding along a concave-edge region on the die surface, is called pencil-curve. Presented in the paper is a pencil-curve tracing algorithm in which “concave-type” sharp edges are computed from a “virtually digitized” model of the tool-envelope surface. The resulting “initial” pencil-cures are then refuted by applying a series of fairing operations. illustrative examples and methods for enhancing accuracy are also presented. The proposed pencil-curve tracing algorithm has been successfully implemented in a commercial CAM system specialized in die-machining and in the CAD/CAM system CATIA.