• ETRI Journal
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• v.36 no.4
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• pp.686-689
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• 2014

This paper studies energy-efficiency (EE) power allocation for cognitive radio MIMO-OFDM systems. Our aim is to minimize energy efficiency, measured by "Joule per bit" metric, while maintaining the minimal rate requirement of a secondary user under a total power constraint and mutual interference power constraints. However, since the formulated EE problem in this paper is non-convex, it is difficult to solve directly in general. To make it solvable, firstly we transform the original problem into an equivalent convex optimization problem via fractional programming. Then, the equivalent convex optimization problem is solved by a sequential quadratic programming algorithm. Finally, a new iterative energy-efficiency power allocation algorithm is presented. Numerical results show that the proposed method can obtain better EE performance than the maximizing capacity algorithm.

• Journal of Advanced Navigation Technology
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• v.17 no.3
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• pp.314-325
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• 2013

Smartwork is future-oriented work-environment to bring swift business transaction and convenient for users. In domestic and foreign various countries, It's already prompting introduction of smartwork. Users process work to access frequently from the outside in smartwork that's a similar client/server environment to existing Cloud Computing environment. Necessary of user authentication is increasing to be solvable to security vulnerability because there is possibility that malware flows in and leaks company's confidential information by unauthorized users especially in smartwork environment. Therefore we propose User Authentication scheme based face recognition is applicable to smartwork environment to analyze established User Authentication scheme. environment.

• Structural Engineering and Mechanics
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• v.72 no.2
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• pp.229-244
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• 2019

Weak form integral equations are developed to investigate the flapwise bending vibration of the rotating beams. Rayleigh and Eringen nonlocal elasticity theories are used to investigate the rotatory inertia and Size-dependency effects on the flapwise bending vibration of the rotating cantilever beams, respectively. Through repetitive integrations, the governing partial differential equations are converted into weak form integral equations. The novelty of the presented approach is the approximation of the mode shape function by a power series which converts the equations into solvable one. Substitution of the power series into weak form integral equations results in a system of linear algebraic equations. The natural frequencies are determined by calculation of the non-trivial solution for resulting system of equations. Accuracy of the proposed method is verified through several numerical examples, in which the influence of the geometry properties, rotatory inertia, rotational speed, taper ratio and size-dependency are investigated on the natural frequencies of the rotating beam. Application of the weak form integral equations has made the solution simpler and shorter in the mathematical process. Presented relations can be used to obtain a close-form solution for quick calculation of the first five natural frequencies of the beams with flapwise vibration and non-local effects. The analysis results are compared with those obtained from other available published references.

• Journal of the Korean Society of Safety
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• v.34 no.3
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• pp.8-14
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• 2019

Many electrical socket-outlet fire accidents take place not only in homes but in the offices each year. The causes are mostly faulty constructions, managerial problems and carelessness. Construction and managerial flaws can be resolved by regular or special inspections, but carelessness is not solvable through inspections. Such carelessness can be related to the consumption capacity of electrical socket-outlets presently, the rated current of electrical socket-outlets is based on 16A. However, even at 16A, the heat generated in the insulator of an electrical socket-outlet varies due to such factors as part damage and environmental conditions of use. To explore this situation, the study conducted an experiment to analyze thermal relationship by applying 10A, 20A, and 30A currents. To secure reliability, the study employed thermal analysis simulation and compared the thermal relationship in the same current value. The experimental and simulation values were found to be similar and therefore, diverse current values were replaced with the simulation. At 30A, the temperature was found to rise to at least $169.9^{\circ}C$ which had worked as a sufficient amount of energy to bring the insulation aging of insulator.

• Structural Engineering and Mechanics
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• v.77 no.5
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• pp.613-626
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• 2021

In this paper, an enhanced Violation-based Sensitivity analysis and Border-Line Adaptive Sliding Technique (ViS-BLAST) will be utilized for optimization of some well-known structural and mechanical engineering problems. ViS-BLAST has already been introduced by the authors for solving truss optimization problems. For those problems, this method showed a satisfactory enactment both in speed and efficiency. The Enriched ViS-BLAST or EVB is introduced to be vastly applicable to any solvable constrained optimization problem without any specific initialization. It uses one-directional step-wise searching technique and mostly limits exploration to the vicinity of FNF border and does not explore the entire design space. It first enters the feasible region very quickly and keeps the feasibility of solutions. For doing this important, EVB groups variables for specifying the desired searching directions in order to moving toward best solutions out or inside feasible domains. EVB was employed for solving seven numerical engineering design problems. Results show that for problems with tiny or even complex feasible regions with a larger number of highly non-linear constraints, EVB has a better performance compared to some records in the literature. This dominance was evaluated in terms of the feasibility of solutions, the quality of optimum objective values found and the total number of function evaluations performed.

• Journal of the Korea Society of Computer and Information
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• v.19 no.10
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• pp.169-173
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• 2014

Nobody has yet been able to determine the optimal solution conclusively whether NP-complete problems are in fact solvable in polynomial time. Gu$\acute{e}$ret et al. tries to obtain the optimal solution using linear programming with $O(m^4)$ time complexity for barge loading problem a kind of bin packing problem that is classified as nondeterministic polynomial time (NP)-complete problem. On the other hand, this paper suggests the loading rule of profit priority rank algorithm with O(m log m) time complexity. This paper decides the profit priority rank firstly. Then, we obtain the initial loading result using the rule of loading the good has profit priority order. Finally, we balance the loading and capability of barge swap the goods of unloading in previously loading in case of under loading. As a result of experiments, this algorithm reduces the $O(m^4)$ of linear programming to O(m log m) time complexity for NP-complete barge loading problem.

• Korean Journal of Community Nutrition
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• v.22 no.3
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• pp.238-247
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• 2017

Objectives: This study was conducted to investigate providers' perspectives on current challenges in implementing a program for prevention and management of childhood obesity and adoption of mobile phone as a potential solution of leveraging multimodal delivery and support in a school setting. Methods: The qualitative data were collected through face-to-face in-depth interviews with 23 elementary-school teachers, 6 pediatricians, and 6 dieticians from community health centers and analyzed using a qualitative research methodology. Results: Current challenges and potential solutions of obesity-prevention and -management program for obesity program for elementary school children were deduced as two themes each. Lack of tailored intervention due to limited recipient motivation, lack of individualized behavioral intervention, and different environmental conditions can be solvable by mobile technology-based personalized intervention which brings about interactive recipient participation, customized behavioral intervention, and ubiquitous accessibility. Lack of sustainable management due to stigmatization, limited interactions between program providers and inconsistent administrative support can be handled by multimodal support based on school setting using mobile platform providing education of health promoting behaviors toward larger scale and interactive networking between program participants, and minimizing administrative burden. Conclusions: Adoption of mobile-based health management program may overcome current limitations of child obesity program such as lack of tailored intervention and sustainable management via personalized intervention and multimodal supports although some concerns such as increased screen time need to be carefully considered in a further study.

• Journal of Korean Society of Transportation
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• v.18 no.3
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• pp.77-86
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• 2000

The shortest path problem is one of the mathematical Programming models that can be conveniently solved through the use of networks. The common shortest Path Problem is to minimize a single objective function such as distance, time or cost between two specified nodes in a transportation network. The sing1e objective model is not sufficient to reflect any Practical Problem with multiple conflicting objectives in the real world applications. In this paper, we consider the shortest Path Problem under multiple objective environment. Wile the shortest path problem with single objective is solvable in Polynomial time, the shortest Path Problem with multiple objectives is NP-complete. A genetic a1gorithm approach is developed to deal with this Problem. The results of the experimental investigation of the effectiveness of the algorithm are also Presented.

• Journal of Korean Society of Transportation
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• v.20 no.5
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• pp.67-79
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• 2002

In this paper, observed trajectories of a vehicle platoon are viewed as one realization of a finite sequence of random trajectories. In this point of view, we develop novel and mathematically rigorous concept of traffic flow variables such as local traffic density, instantaneous traffic flow, and velocity field and investigate their nature on a general probability space of a sequence of random trajectories which represent vehicle trajectories. We present a simple model of random trajectories as an illustrative example and, derive the values of traffic flow variables based on the new definitions in this model. In particular, we construct the model for the sequence of random vehicle trajectories with a system of stochastic differential equations. Each equation of the system nay represent microscopic random maneuvering behavior of each vehicle with properly designed drift coefficient functions and diffusion coefficient functions. The system of stochastic differential equations nay generate a well-defined probability space of a sequence of random vehicle trajectories. We derive the partial differential equation for the expected cumulative plot with appropriate initial conditions. By solving the equation with numerical methods, we obtain the values of expected cumulative plot, local traffic density, and instantaneous traffic flow. In addition, we derive the partial differential equation for the expected travel time to a certain location with appropriate initial and/or boundary conditions, which is solvable numerically. We apply this model to a case of single vehicle trajectory.

• Journal of the Korean Chemical Society
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• v.22 no.4
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• pp.202-220
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• 1978

Uniform semiclassical (WKB) solutions are obtained for nonseparable systems without using a close coupling formalism and are given explicitly in terms of well known analytic functions for various physically interesting and realistic cases. They do not become singular at turning points or surfaces and when taken in their asymptotic forms, they reduce to the usual WKB solutions that could be obtained if the Stokes phenomenon was properly taken care of for solutions. In obtaining such uniform solutions, the Schroedinger equations for nonseparable systems are suitably "renormalized" to solvable "normal" forms through certain transformations. Ehrenfest's adiabatic principle plays an important guiding role for obtaining such "renormalized" uniform solutions for nonseparable systems. The eigenvalues of the Hamiltonian can be calculated from the extended Bohr-Sommerfeld quantization rules when appropriate classical trajectories are obtained. An application is made to many-electron systems and for one of the simplest examples to show the utility of the method the approximate wavefunction is calculated of the ground state helium atom.