• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.5C
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• pp.486-495
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• 2002

In this paper, we propose a delay reduction method for frame-based packet transmit scheduling algorithm. A high-speed network such as ATM network has to provide some performance guarantees such as bandwidth and delay bound. Framing strategy naturally guarantees bandwidth and enables simple rate-control while having the inherently bad delay characteristics. The proposed delay reduction method uses the same hierarchical frame structure as HRR (Hierarchical Round-Robin) but does not use the static priority scheme such as round-robin. Instead, we use a dynamic priority change scheme so that the delay unfairness between wide bandwidth connection and narrow bandwidth connection can be eliminated. That is, we use FIFO (First-In First-Out) concept to effectively reduce the occurrence of worst-case delay and to enhance delay distribution. We compare the performance for the proposed algorithm with that of HRR. The analytic and simulation results show that HFIFO inherits almost all merits of HRR with fairly better delay characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.11C
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• pp.1112-1123
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• 2002

Providing a multimedia service requires efficient network bandwidth allocation scheduling. Typically, transmission of information with bursty characteristics, such as a video data stream, utilizes some type of smoothing technique that reduces the transmission rate fluctuation. While capable of a drastic reduction in the peak transmission rate, even the optimum smoothing algorithm proposed to date, however, is rather inadequate for multi-stream applications that share network bandwidth since such an algorithm has been designed and applied toward handling each independent stream. In this paper, we proposed an efficient bandwidth allocation algorithm that addresses these shortcomings. The proposed bandwidth allocation algorithm is divided into two steps, a static bandwidth allocation and a dynamic bandwidth allocation. In the former case, the peak rate reduction is achieved by maintaining the accumulated data in the user buffer at a high level, whereas the concept of real demand factor is employed to meet the needs of multi-stream bandwidth allocation in the latter case, Finally, the proposed algorithm's performance was verified with ExSpect 6.41, a Petri net simulation tool.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.4
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• pp.485-492
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• 2009

In the mobile service environment, patterns generated by temporal synchronization are streamed with different instance values. This paper proposed a variable clustering management method, which manages multiple data streaming dynamically, to support flexible clustering. The method manages synchronization effectively and differently with conventional streaming methods in data streaming environment and manages clustering streaming after the structural presentation level and the fitness presentation level. In the structural presentation level, the stream structure is presented using level matching and accumulation matching, and clustering management is carried out by the management of dynamic segment and static segment. The performance of the proposed method is tested by using k-means method, C/S server method, CDN method, and simulation. The test results showed that the proposed method has better performance than the other methods.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.92-100
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• 2002

In this study, transonic/supersonic nonlinear flutter analysis system of a complete aircraft including forced harmonic motion pf control surfaces has been effectively developed using the modified transonic small disturbance (TSD) equation. To consider the nonlinear effects, the coupled time marching method (CTM) combining computational structural dynamics (CFD) has been directly applied for aeroelastic computations. The grid system for a complex full aircraft configuration is effectively generated by the developed inhouse code. Intransonic and supersonic flight regimes, the characteristics of static and dynamic aeroelastic effect has been investigated for a complete aircraft model. Also, nonlinear flutter flight simulations for the forced harmonic motion of control surfaces are practically presented in detail.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.10
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• pp.5260-5275
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• 2019

In the process of constructing the traditional offensive and defensive game theory model, these are some shortages for considering the dynamic change of security risk problem. By analysing the critical indicators of the incomplete information game theory model, incomplete information attack and defense game theory model and the mathematical engineering method for solving Bayes-Nash equilibrium, the risk-averse income function for information assets is summarized as the problem of maximising the return of the equilibrium point. To obtain the functional relationship between the optimal strategy combination of the offense and defense and the information asset security probability and risk probability. At the same time, the offensive and defensive examples are used to visually analyse and demonstrate the incomplete information game and the Harsanyi conversion method. First, the incomplete information game and the Harsanyi conversion problem is discussed through the attack and defense examples and using the game tree. Then the strategy expression of incomplete information static game and the engineering mathematics method of Bayes-Nash equilibrium are given. After that, it focuses on the offensive and defensive game problem of unsafe information network based on risk aversion. The problem of attack and defense is obtained by the issue of maximizing utility, and then the Bayes-Nash equilibrium of offense and defense game is carried out around the security risk of assets. Finally, the application model in network security penetration and defense is analyzed by designing a simulation example of attack and defense penetration. The analysis results show that the constructed income function model is feasible and practical.

• Journal of Digital Contents Society
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• v.15 no.6
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• pp.751-761
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• 2014

Color deficient people do not have sufficient discernment for the colors with low saturation and brightness and at the same time express their negative emotions regarding emotion distortion. The purpose of recovering the distortion of the vision which is the basis for emotion is to increase positive emotions rather than negative ones that those with color vision deficiency feel when they experience digital culture contents. Contrast increases saturation and brightness by differing the direction of their conversion and by doing so, delivers emotion distortion such as dynamic vs. static and vivid vs. somber that the original images intend to convey to those with color vision deficiency by reducing such a contrast. In this respect, this study proposes a contrast-based color conversion method to convert saturation and brightness in the zone of color conversion and identifies if this method can reduce emotion distortion by using color conversion simulation and user test.

• Current Optics and Photonics
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• v.4 no.5
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• pp.434-440
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• 2020

Based on single-mode rate equations, we present an improved equivalent-circuit model for distributed-feedback (DFB) lasers that accounts for the effects of parasitic parameters and nonradiative recombination. This equivalent-circuit model is composed of a parasitic circuit, an electrical circuit, an optical circuit, and a phase circuit, modeling the circuit equations transformed from the rate equations. The validity of the proposed circuit model is verified by comparing simulation results to measured results. The results show that the slope efficiency and threshold current of the model are 0.22 W/A and 13 mA respectively. It is also shown that increasing bias current results in the increase of the relaxation-oscillation frequency. Moreover, we show that the larger the bias current, the lower the frequency chirp, increasing the possibility of extending the transmission distance of an optical-fiber communication system. The results indicate that the proposed circuit model can accurately predict a DFB laser's static and dynamic characteristics.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.388-399
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• 2016

A motion analysis of an underwater towed cable is a complex task due to its nonlinear nature of the problem. The major source of the nonlinearity of the underwater cable analysis is that the motion of the cable involves large rigid-body motion. This large rigid-body motion makes difficult to use standard displacement-based finite element method. In this paper, the authors apply recently developed nodal position-based finite element method which can deal with the geometric nonlinearity due to the large rigid-body motion. In order to enhance the stability of the large-scale nonlinear cable motion simulation, an efficient time-integration scheme is proposed, namely predictor/multi-corrector Newmark scheme. Three different predictors are introduced, and the best predictor in terms of stability and robustness for impulsive cable motion analysis is proposed. As a result, the nonlinear motion of underwater cable is predicted in a very efficient manner compared to the classical finite element of finite difference methods. The efficacy of the method is demonstrated with several test cases, involving static and dynamic motion of a single cable element, and also under water towed cable composed of multiple cable elements.

• Journal of Power Electronics
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• v.16 no.3
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• pp.1110-1121
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• 2016

The mathematical model of a three phase PWM converter under the stationary αβ reference frame is deduced and constructed based on a Proportional-Resonant (PR) regulator, which can replace trigonometric function calculation, Park transformation, real-time detection of a Phase Locked Loop and feed-forward decoupling with the proposed accurate calculation of the inductance voltage vector. To avoid the parallel resonance of the LCL topology, the active damping method of the proportional capacitor-current feedback is employed. As to current vector error elimination, an optimized PR controller of the inner current loop is proposed with the zero-pole matching (ZPM) and cancellation method to configure the regulator. The impacts on system's characteristics and stability margin caused by the PR controller and control parameter variations in the inner-current loop are analyzed, and the correlations among active damping feedback coefficient, sampling and transport delay, and system robustness have been established. An equivalent model of the inner current loop is studied via the pole-zero locus along with the pole placement method and frequency response characteristics. Then, the parameter values of the control system are chosen according to their decisive roles and performance indicators. Finally, simulation and experimental results obtained while adopting the proposed method illustrated its feasibility and effectiveness, and the inner current loop achieved zero static error tracking with a good dynamic response and steady-state performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.2A
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• pp.55-62
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• 2003

This paper proposes an efficient and differentiated MAC scheduling algorithm for Bluetooth systems. The proposed algorithm guarantees QoS (Quality of Service) requirement of each master-slave pair or application. Conventional MAC scheduling algorithms for Bluetooth take priority of each pair into consideration and demonstrate relatively reasonable performance. However, their performances may depend on traffic characteristic, or they are limited by overheads for signaling. In this paper, we propose a new MAC scheduling algorithm superior to the conventional algorithms from the viewpoints of throughput, delay, and supporting QoS. Our proposed algorithm is evaluated via computer simulations under various environments and compared with the conventional scheduling algorithms. Simulation results indicate that the proposed algorithm shows better performance than the existing algorithms, and can support the QoS demand of each pair.