• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.3
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• pp.137-145
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• 2010

The objective of this paper is to evaluate the equilibrium price between PSTN and VoIP telephony services in the case of non-linear utility function. Currently there are two types of wired phone services we are known PSTN (Public Switched Telephone Network) and VoIP (Voice over Internet Protocol). The PSTN telephony which provide high quality service and VoIP which provides relatively low quality service form a vertically differentiated oligopoly. Therefore, the evaluation of the equilibrium price between PSTN and VoIP services is very important to wired phone service providers. The equilibrium price depends on the state of the service cost function has been proved different value. This paper was evaluated each equilibrium price for the state of the linear cost function and non-linear cost function. Subsequently, this paper analyzed the demand of both services and the equilibrium profit which can maximize the profit of both service providers.

• Structural Engineering and Mechanics
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• v.32 no.1
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• pp.179-191
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• 2009

A stochastic response spectrum method is proposed for simple evaluation of the structural response of an actively controlled aseismic structure. The response spectrum is constructed assuming a linear structure with an active mass damper (AMD) system, and an earthquake wave model given by the product of a non-stationary envelope function and a stationary Gaussian random process with Kanai-Tajimi power spectral density. The control design is executed using a linear quadratic Gaussian control strategy for an enlarged state space system, and the response amplification factor is given by the combination of the obtained statistical response values and extreme value theory. The response spectrum thus produced can be used for simple dynamical analyses. The response factors obtained by this method for a multi-degree-of-freedom structure are shown to be comparable with those determined by numerical simulations, demonstrating the validity and utility of the proposed technique as a simple design tool. This method is expected to be useful for engineers in the initial design stage for structures with active aseismic control.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.212-213
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• 2007

Grid-connected PV(Photovoltaic) power generation system has experienced increasing attention in recent years. But the growing number of non-linear equipments, such as, inverters, has been demanding the compensation for the disturbances caused by them. These non-linear loads may cause poor power factor and high degree of harmonics. Installation of an AF(active filter) can be one of the solutions to mitigate the line distortion, but it requires additional costs. On the other hand, many PV systems have been interconnected to the distribution system. So, the PV system combined with the function of the active filter system can be useful for the application in the power distribution system. In this paper, PV-AF system using DSP (Digital Signal Processing) controller confirmed that it is possible to combine the AF theory to the three phase PV system connected to the utility under various irradiation conditions.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1085-1086
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• 2008

Shunt active filter can compensate harmonic current of utility results from non-linear loads such as rectifiers, cycloconverters and arc furnaces. It has the same structure as photovoltaic(PV) generation system. So, It was proposed the system that generates PV power and also has active filter function. It is called PV-AF(Photovoltaic and Active Filter) power generation system. Islanding can be occurred in an inverter based dispersed generation system, when the system disconnected from utility and loads are entirely supplied by PV system only. Islanding may result in interference to grid protection devices, equipment damage, and even personnel safety hazards. Therefore, islanding has to be detected and protected. The conventional anti-islanding methods have NDZ(None-Detection Zone) or power quality degradation. But PV-AF power generation system has the function of not only shunt active filter but also anti-islanding method without NDZ. In this paper, a novel anti-islanding method for PV-AF system is proposed and analysed in detail.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.4
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• pp.325-332
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• 2002

In the process of designing pareto optimal insurance contract, it is necessary to assume that insurance contract conditions are endogenous to build a model. The expected utility, the non-expected utility and the state-dependent utility function can be applied as a insurance decision making principle. The insurance costs may have the linear, convex, and concave ralationship with the indemnity schedule. However, the sunk cost and fixed cost must be recognized. The deductible which decides whether an insurance contract to be a full or partial insurance contract can exist in the forms of straight deductible or diminishing deductible. Indeciding the level of deductible, the types of the insurance and the risks to be insured should be the deciding factors. Especially for recall insurance, there is relatively high chance that the recalling company being bankrupt. Therefore, the possibility of bankrupcy should be the considering factor in deciding the policy limit. The existence of the incomplete market and uninsurable background risk should be understood as restricting conditions of the pareto-optimal insurance contract.

• Korean Journal of Metals and Materials
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• v.47 no.1
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• pp.7-12
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• 2009

The detailed quantitative microstructural data on the cracking of coarse constituent particles in 7075 (T651) series wrought Al-alloys have been studied using the utility of a novel digital image processing technique, where the particle cracks are generated due to monotonic loading. The microstructural parameters such as number density, volume fraction, size distribution, first nearest neighbor distribution, and two-point correlation function have been quantitatively characterized using the developed technique and such data are very useful to verify and study the theoretical models for the damage evolution and fracture of Al-alloys. The data suggests useful relationships for damage modeling such as a linear relationship between particle cracking and strain exists for the uniaxial tensile loading condition, where the larger particles crack preferentially.

• Environmental and Resource Economics Review
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• v.24 no.2
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• pp.365-410
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• 2015

Block-rate structures are widely used in utility-pricing, including the Korean residential electricity sector. In the case of the current pricing structure, Korean citizens are highly concerned about incurring excessive electricity costs. For these reasons, there have been many discussions concerning mitigation of the strict pricing structure. Existing studies on the residential electricity demand function under block-rate structure have the following three issues - the consumer's budget constraint is non-linear, perceived price under block-rate structure is uncertain, block-rate structure has endogeneity in the price variable. In this context, this paper estimates the residential electricity demand function using micro-level household expenditure data and simulates the impact of alternative block-pricing schedules.

• Nuclear Engineering and Technology
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• v.16 no.4
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• pp.181-194
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• 1984

The in-core fuel management problem was studied by use of the calculus of variations. Two functions of interest to a public power utility, the profit function and the cost function, were subjected to the constraints of criticality, the reactor turnup equations and an inequality constraint on the maximum allowable power density. The variational solution of the initial profit rate demonstrated that there are two distinct regions of the reactor, a constant power region and a minimum inventory or flat thermal flux region. The transition point between these regions is dependent on the relative importance of the profit for generating power and the interest charges for the fuel. The fuel cycle cost function was then used to optimize a three equal volume region reactor with a constant fuel enrichment. The inequality constraint on the maximum allowable power density requires that the inequality become an equality constraint at some points in the reactor. and at all times throughout the core cycle. The finite difference equations for reactor criticality and fuel burnup in conjunction with the equality constraint on power density were solved, and the method of gradients was used to locate an optimum enrichment. The results of this calculation showed that standard non-linear optimization techniques can be used to optimize a reactor when the inequality constraints are properly applied.