• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권6호
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• pp.2686-2708
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• 2020

This paper investigates the energy efficiency of energy harvesting (EH) bidirectional cooperative sensor networks, in which the considered system model enables the uplink information transmission from the sensor (SN) to access point (AP) and the energy supply for the amplify-and-forward (AF) relay and SN using power-splitting (PS) or time-switching (TS) protocol. Considering the minimum EH activation constraint and quality of service (QoS) requirement, energy efficiency is maximized by jointly optimizing the resource division ratio and transmission power. To cope with the non-convexity of the optimizations, we propose the low complexity iterative algorithm based on fractional programming and alternative search method (FAS). The key idea of the proposed algorithm first transforms the objective function into the parameterized polynomial subtractive form. Then we decompose the optimization into two convex sub-problems, which can be solved by conventional convex programming. Simulation results validate that the proposed schemes have better output performance and the iterative algorithm has a fast convergence rate.

• 전자공학회논문지SC
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• 제44권1호
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• pp.19-24
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• 2007

본 논문에서는 주파수 영역뿐만 아니라 시간 영역의 설계 사양을 만족할 수 있는 PID-PD 제어기 동조 방법을 제안한다. 제안한 PID-PD 제어기 동조 방법은 PID 제어기와 PI-PD 제어기를 경계로 볼록형 집합을 형성하도록 선정한다. PID-PD 제어기는 PID 제어기와 PI-PD 제어기 각각에 의한 계단 응답과 보드 선도의 이득 사이에 위치하는 응답을 제어한다. 최적 동조 방법에 의해 센서 잡음 저감도 및 안정 강인성을 변수로 하는 가격함수를 최소화하는 제어기를 설계한다. 제안된 제어기의 유용성을 사례 연구와 분석을 통해 검토한다.

• 한국실내디자인학회논문집
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• 제24권2호
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• pp.142-150
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• 2015

The purpose of this study is to analysis the change of rural house type and house plans in Bonghwa province. According to definition of rural area, the scopes of the research of rural houses limited the Bonghwa rural area(1 eup, 9 myeon). The method of study is to compare and analyze about housing situation, structure of house, housing type and construction of house space etc. through the statistical data of Bongwha statistical yearbook, space syntax(convex analysis) and other various data etc. during these 10 years. As a results of the analysis 1) According to Change of family member the supply ratio of detached house is steadily decreasing and changing from a detached house to multi-household house in Bongwha areas. 2) Most of houses structure were using lightweight steel construction because of cost-cutting of construction and easy way to construct etc.. 3) The highest Integration space is living space in rural house plans 4) The highest segregation space is bathroom space of master bed room in rural house plans. Some of bed rooms are classed as segregation space regardless of Integration space 5) Traditional front yard's function is changing from the place with the various functions to the place with the specific functions.

• Journal of Power Electronics
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• 제13권4호
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• pp.569-583
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• 2013

In this study, the simultaneous use of a multi-level converter (MLC) as a DC-motor drive and as an active battery cell balancer is investigated. MLCs allow each battery cell in a battery pack to be independently switched on and off, thereby enabling the potential non-uniform use of battery cells. By exploiting this property and the brake regeneration phases in the drive cycle, MLCs can balance both the state of charge (SoC) and temperature differences between cells, which are two known causes of battery wear, even without reciprocating the coolant flow inside the pack. The optimal control policy (OP) that considers both battery pack temperature and SoC dynamics is studied in detail based on the assumption that information on the state of each cell, the schedule of reciprocating air flow and the future driving profile are perfectly known. Results show that OP provides significant reductions in temperature and in SoC deviations compared with the uniform use of all cells even with uni-directional coolant flow. Thus, reciprocating coolant flow is a redundant function for a MLC-based cell balancer. A specific contribution of this paper is the derivation of a state-space electro-thermal model of a battery submodule for both uni-directional and reciprocating coolant flows under the switching action of MLC, resulting in OP being derived by the solution of a convex optimization problem.

• 한국주거학회논문집
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• 제22권6호
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• pp.51-60
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• 2011

The maintenance cost depends on various factors such as building volume, floor area, number of household and so on. The maintenance cost of the apartment housing is affected by the maintenance type, building physical factor, sociogeographic aspects. Among these, the maintenance characteristics is represented and made up by the total floor area and number of household which means main factor to provide the building scale roughly. In this paper, it aimed at modelling the estimation function of the maintenance cost with the total floor area and number of household and analyzing the elasticity of the two factors. Although items of maintenance cost are various in general cost, repair cost and so on, we classified these items into the 5 categories. 5 categories are a general cost, a facility maintenance cost, a utilization cost, insurance and sanitary cost. The estimation function used a power function and it has better goodness-offitness than any other estimation methods in statistics. A power function has a three curve types with concave and convex and linear style to the origin.

• 대한수학회보
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• 제37권4호
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• pp.743-753
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• 2000

In the space $C_1(X)$ of real-valued continuous functions with $L_1-norm$, every bounded set has a relative Chebyshev center in a finite-dimensional subspace S. Moreover, the set function $F\rightarrowZ_S(F)$ corresponding to F the set of its relative Chebyshev centers, in continuous on the space B[$C_1(X)$(X)] of nonempty bounded subsets of $C_1(X)$ (X) with the Hausdorff metric. In particular, every bounded set has a relative Chebyshev center in the closed convex set S(F) of S and the set function $F\rightarrowZ_S(F)$(F) is continuous on B[$C_1(X)$ (X)] with a condition that the sets S(.) are equal.

• 한국생산제조학회지
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• 제9권2호
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• pp.59-65
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• 2000

In this paper the comparison of the first order approximation schemes such as SLP(sequential linear programming) CONLIN(convex linearization) MMA(method of moving asymptotes) and the second order approximation scheme SQP(sequential quadratic programming) was accomplished for optimization of nonlinear structures. It was found that MMA and SQP are the most efficient methods for optimization. But the number of function call of SQP is much more than that of MMA. Therefore when it is considered with the expense of computation MMA is more efficient than SQP. In order to examine the efficiency of MMA for complex optimization problem it was applied to the helicopter tail boom con-sidering column buckling and local wall buckling constraints. it is concluded that MMA can be a very efficient approxima-tion scheme from simple problems to complex problems.

• 대한수학회지
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• 제52권6호
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• pp.1139-1148
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• 2015

The estimate of third Hankel determinant $$H_{3,1}(f)=\left|a_1\;a_2\;a_3\\a_2\;a_3\;a_4\\a_3\;a_4\;a_5\right|$$ of the analytic function $f(z)=z+a2z^2+a3z^3+{\cdots}$, for which ${\Re}(1+zf^{{\prime}{\prime}}(z)/f^{\prime}(z))>-1/2$ are investigated. The corrected version of a known results [2, Theorem 3.1 and Theorem 3.3] are also obtained.

• Structural Engineering and Mechanics
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• 제8권4호
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• pp.325-341
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• 1999

A procedure for the computation of the load carrying capacity of perfectly plastic plates in bending is presented. The approach, based on the kinematic theorem of limit analysis, requires the evaluation of the minimum of a convex, but non-smooth, function under linear equality constraints. A systematic solution procedure is devised, which detects and eliminates the finite elements which are predicted as rigid in the collapse mechanism, thus reducing the problem to the search for the minimum of a smooth and essentially unconstrained function of nodal velocities. Both Kirchhoff and Mindlin plate models are considered. The effectiveness of the approach is illustrated by means of some examples.

• 한국경영과학회지
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• 제21권3호
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• pp.1-10
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• 1996

In this paper, the problem of simultaneously allocating servers and loadings of stations in a class of manufacturing systems modelled as network of queues is considered. The throughput function of the closed network of queues is demonstrated as a Schur convex function of server allocation, that is, increasing the server allocation vector under majorization increases the performance in the ship in terms of the throughput. It also reduces the congestion in the open network of queues in terms of reducing the total number of jobs in the sense of likelihood ratio ordering. These are the extentions of the numerical results of Green and Guha (1995) in the service system with independent M/M/c systems to the network of queues. The results can be used to support production planning in certain manufacturing systems.