• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.2
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• pp.514-537
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• 2020

Wireless sensor network (WSN) is a distributed network composed of many sensory nodes. It is precisely due to the clustering unevenness and cluster head election randomness that the energy consumption of WSN is excessive. Therefore, a many-objective optimization WSN energy balance model is proposed for the first time in the clustering stage of LEACH protocol. The four objective is considered that the cluster distance, the sink node distance, the overall energy consumption of the network and the network energy consumption balance to select the cluster head, which to better balance the energy consumption of the WSN network and extend the network lifetime. A many-objective optimization algorithm to optimize the model (LEACH-ABF) is designed, which combines adaptive balanced function strategy with penalty-based boundary selection intersection strategy to optimize the clustering method of LEACH. The experimental results show that LEACH-ABF can balance network energy consumption effectively and extend the network lifetime when compared with other algorithms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.11
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• pp.4347-4366
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• 2015

Distinguished with traditional strategies which offload an application's computation to a single server, parallel computation offloading can promote the performance by simultaneously delivering the computation to multiple computing resources around the mobile terminal. However, due to the variability of communication and computation environments, static application component multi-partitioning algorithms are difficult to maintain the optimality of their solutions in time-varying scenarios, whereas, over-frequent algorithm executions triggered by changes of environments may bring excessive algorithm costs. To this end, an adaptive application component mapping algorithm for parallel computation offloading in variable environments is proposed in this paper, which aims at minimizing computation costs and inter-resource communication costs. It can provide the terminal a suitable solution for the current environment with a low incremental algorithm cost. We represent the application component multi-partitioning problem as a graph mapping model, then convert it into a pathfinding problem. A genetic algorithm enhanced by an elite-based immigrants mechanism is designed to obtain the solution adaptively, which can dynamically adjust the precision of the solution and boost the searching speed as transmission and processing speeds change. Simulation results demonstrate that our algorithm can promote the performance efficiently, and it is superior to the traditional approaches under variable environments to a large extent.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.2
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• pp.177-188
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• 2001

The paper presents the method to estimate the bottom shear stress driven by waves and current on rough turbulent flow. Parameter adjusting technique is suggested for the computation of bed shear stress driven by uni-directional flow, and the value ofpararneter is determined by comparing the computational results against Bijker's laboratory data. For the computation of combined flow bottom shear stress, two methods are presented; one is the modified Bijker approach (BYO Model) and the other is the modified Fredsoe approach (FY Model), both of which are refined by the present writers. BYO model is again refined in the computation of maximum shear stress, and the final version is tested against Bijkcr's laboratory data.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.1064-1081
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• 2014

This paper presents a numerical analysis of slamming and whipping using a fully coupled hydroelastic model. The coupled model uses a 3-D Rankine panel method, a 1-D or 3-D finite element method, and a 2-D Generalized Wagner Model (GWM), which are strongly coupled in time domain. First, the GWM is validated against results of a free drop test of wedges. Second, the fully coupled method is validated against model test results for a 10,000 twenty-foot equivalent unit (TEU) containership. Slamming pressures and whipping responses to regular waves are compared. A spatial distribution of local slamming forces is measured using 14 force sensors in the model test, and it is compared with the integration of the pressure distribution by the computation. Furthermore, the pressure is decomposed into the added mass, impact, and hydrostatic components, in the computational results. The validity and characteristics of the numerical model are discussed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.11
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• pp.2721-2726
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• 2014

In a MOG algorithm using the GMM to subtract background, the model parameter computation and the object classification to be performed at every pixel require a huge computation and are the chief obstacles to its uses. This paper proposes a fast MOG algorithm that partly adopts the simple model parameter computation and the object classification skip on the basis of the object prediction. The former is applied to the pixels that gives little effect on the model parameter and the latter is applied to the pixels whose object prediction is firmly trusted. In comparative experiment between the conventional and proposed algorithms using videos, the proposed algorithm carries out the simple model parameter computation and the object classification skip over 77.75% and 92.97%, respectively, nevertheless it retains more than 99.98% and 99.36% in terms of image and moving object-unit average classification accuracies, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.239-244
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• 2002

The reinforcing bar computation have to be reflected stress distribution and geometrical condition of a comer joint when the closing moment acted at comer joint. This study analyzes stress distribution of a corner joint with statically determinate truss model. Compared with FEM analysis and result of truss model suggested design method consider strengthening efficiency of main reinforcement.

• Journal of Power Electronics
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• v.19 no.2
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• pp.529-539
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• 2019

The modular multilevel converter (MMC) has become a promising topology for high-voltage direct current (HVDC) transmission systems. To control a MMC system properly, the ac-side current, circulating current and submodule (SM) capacitor voltage are taken into consideration. This paper proposes a low-computation indirect model predictive control (IMPC) strategy that takes advantages of the conventional MPC and has no weighting factors. The cost function and duty cycle are introduced to minimize the tracking error of the ac-side current and to eliminate the circulating current. An optimized merge sort (OMS) algorithm is applied to keep the SM capacitor voltages balanced. The proposed IMPC strategy effectively reduces the controller complexity and computational burden. In this paper, a discrete-time mathematical model of a MMC system is developed and the duty ratio of switching state is designed. In addition, a simulation of an eleven-level MMC system based on MATLAB/Simulink and a five-level experimental setup are built to evaluate the feasibility and performance of the proposed low-computation IMPC strategy.

• Structural Engineering and Mechanics
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• v.38 no.6
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• pp.803-823
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• 2011

In this paper, the three dimensional Parallel Realistic Failure Process Analysis ($RFPA^{3D}$-Parallel) code based on micromechanical model is employed to investigate the bonding behavior in FRP sheet bonded to concrete in single shear test. In the model, the heterogeneity of brittle disordered material at a meso-scale was taken into consideration in order to realistically demonstrate the mechanical characteristics of FRP-to-concrete. Modified Mohr-coulomb strength criterion with tension cut-off, where a stressed element can damage in shear or in tension, was adopted and a stiffness degradation approach was used to simulate the initiation, propagation and growth of microcracks in the model. In addition, a Master-Slave parallel operation control technique was adopted to implement the parallel computation of a large numerical model. Parallel computational results of debonding of FRP-concrete visually reproduce the spatial and temporal debonding failure progression of microcracks in FRP sheet bonded to concrete, which agrees well with the existing testing results in laboratory. The numerical approach in this study provides a useful tool for enhancing our understanding of cracking and debonding failure process and mechanism of FRP-concrete and our ability to predict mechanical performance and reliability of these FRP sheet bonded to concrete structures.

• Journal of the Korean Institute of Navigation
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• v.24 no.3
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• pp.123-132
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• 2000

In order to improve the ship maneuverability, It is important to estimate precisely the hydrodynamic coefficients of added mass forces acting on a ship especially in shallow waters, and simple methods for predicting such hydrodynamic forces Is also very desirable. In the previous paper using 3-Dimension potential flow theory, it has been demonstrated that potential calculation is available to estimate added mass coefficients. The present work is aimed at the suggestion of the simplified formulas for predicting the translation and lateral motion of added mass coefficients in shallow water. So, 3-D potential flow theory is also used to calculate the added mass coefficients in deep and shallow waters for Series 60 model which has 5 different kinds of block coefficients (0.6-0.8), SR196 model and T/S HANNARA. After some series computation, simplified formulas for Predicting the added mass force in shallow waters is suggested based on the computation results of Series 60 model. The formulas consist of the combination of principal dimensions and the water depth; d/B, Cb, d/H. The predicted results are compared with the Computation results for SR196 model and T/S HANNARA. The precision of predicted results by simplified formulas are good enough for the practical use. (d/B : draft-Breadth ratio, d/H draft-Water depth ratio, Cb : Block coefficients).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1182-1190
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• 2003

A parallelized FEM code based on domain decomposition method has been recently developed for large-scale computational fluid dynamics. A 4-step splitting finite element algorithm is adopted for unsteady flow computation of the incompressible Navier-Stokes equation, and Smagorinsky LES model is chosen for turbulent flow computation. Both METIS and MPI Libraries are used for domain partitioning and data communication between processors, respectively. Tiburon model of Hyundai Motor Company is chosen as the computational model at Re=7.5 $\times$ 10$^{5}$ , which is based on the car height. The calculation is carried out under both the wind tunnel condition and the road condition using IBM SP parallel architecture at KISTI Super Computing Center. Compared with the existing experimental data, both the velocity and pressure fields are predicted reasonably well and the drag coefficient is in good agreement. Furthermore, it is confirmed that the drag under the road condition is smaller than that under the wind-tunnel condition.