• ETRI Journal
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• v.45 no.1
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• pp.45-59
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• 2023

In this paper, to optimize the average delay and power allocation (PA) for system users, we propose a resource scheduling scheme for wireless networks based on Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM) according to the first fifth-generation standards. For delay minimization, we solve a throughput maximization problem that considers CPOFDM systems with carrier aggregation (CA). Regarding PA, we consider an approach that involves maximizing goodput using an effective signal-to-noise ratio. An algorithm for jointly solving delay minimization through computation of required user rates and optimizing the power allocated to users is proposed to compose the resource allocation approach. In wireless network simulations, we consider a scenario with the following capabilities: CA, 256-Quadrature Amplitude Modulation, millimeter waves above 6 GHz, and a radio frame structure with 120 KHz spacing between the subcarriers. The performance of the proposed resource allocation algorithm is evaluated and compared with those of other algorithms from the literature using computational simulations in terms of various Quality of Service parameters, such as the throughput, delay, fairness index, and loss rate.

• Journal of Korean Society of societal Security
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• v.2 no.1
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• pp.47-55
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• 2009

Organizations and customers lose if business activities are discontinued by an incident of information systems under the current business environment because they pursue real time enterprise and on demand enterprise. The loss includes the intangible decline in brand image, customer separation, and the tangible loss such as decrease in business profits. Thus, it is necessary to have preparedness in advance and mitigation for minimization of a loss due to the business discontinuity and IT risks. This paper described a IT risk assessment case about domestic construction company.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.5
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• pp.434-441
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• 2016

This paper deals with transformer turns ratio design with the consideration of loss minimization in isolated bidirectional DC-DC converter. Generally, the rms value of current, magnitude of current at switching instance, and duty ratio of a converter vary according to the turns ratio of an isolation transformer in the converter under the same voltages and output power level. Therefore, the transformer turns ratio has an effect on the total loss in a converter. The switching and conduction losses of IGBTs and MOSFETs consisting of dual-active bridge converter are analyzed, and iron and copper losses in an isolation transformer and inductor are calculated. Total losses are calculated and measured in cases of four different transformer turns ratios through simulation and experiment with 3-kW converter, and an optimum turns ratio that provides minimum losses is found. The usefulness of the proposed transformer turns ratio design approach is verified through simulation and experimental results.

• Journal of computational fluids engineering
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• v.17 no.2
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• pp.1-10
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• 2012

This paper presents the numerical simulation results of heat transfer and friction loss for a rotating two-pass duct with the airfoil-guide vanes in the turning region. The Kriging model is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of flow field and heat transfer with shear stress transport turbulent model. To improve the heat transfer performance, angle and location of the airfoil-guide vanes have been selected as design variables. The optimization problem has been defined as a minimization of the objective function, which is defined as a linear combination of heat transfer related term and friction loss related term with a weight factor. The airfoil-guide vanes in the turning region keep the high level of heat transfer while the friction loss has a low value. By comparing the presence or absence of airfoil-guide vanes, it is shown that the airfoil-guide vanes exhibited the best heat transfer performance to improve the blade cooling except the first passage.

• Journal of the Korea Organic Resources Recycling Association
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• v.2 no.1
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• pp.87-98
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• 1994

Sludge minimization in an water treatment plant can be achieved by optimizing a main water treatment process as well as by enhancing a thickening and a dewatering facilities. In this study, dewatering and drying techniques for reducing the quantity of the water sludge generated from the conventional water treatment plant in the local states were investigated by reducing its water content. Not only the types and dosages of polymers but also the mixing intensity of the mixtures of a concentrated sludge and polymers on the different pH were evaluated for the optimum dewatering conditions of the water sludge. Weight reduction of the water sludge was also tested at a given temperature range. The dewatering efficiency of the water sludge was not affected by the types of polymer but by mixing intensity(GT value) in this study. pH effect on dewaterbility of the water sludge took a major role at the neutral pH range. The optimal polymer dose was 1.5 mg-polymer/g-TSS(about 40mg/L as polymer). Dewaterability was enhanced at a lower mixing intensity(GTbelow 10,000 sec-1). Free water in the void of sludge cake was dried around $100^{\circ}C$, chemical bound water was evaporated around $320^{\circ}C$, and organic material was burned out at the range of 300 to $600^{\circ}C$. Ignition losses of the water sludge were varied 15 to 40 % as the raw water quality. The ignition loss due to the chemical bound water was 10-20% and the loss due to the organic material was 4-20% of the total ignition loss.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.209-223
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• 2020

Executions of SCM in a chemical company of which divisions produce petrochemicals, compounds, batteries, IT material and medicine directly affect their own profit. Execution level of SCM or optimization is very important. This work presents activities of SCM and optimization of inefficient issues in several industrial divisions using mathematical optimization method. The meaning is not only academic research but also making a useful tool which active partner deals with in his work. It is explained how to do beforehand and afterward optimization problem. The benefits are mentioned in the sections. The first of examples would be cover supply plan optimization, optimal profit business plan, and scheduling of a stretching process of polarizer based on minimizing raw material loss in polarizer production. The second example would be cover the optimization of production/packaging plans to maximize productivity of Poly Olefin processes, and the third example is minimization of transition loss in the production of battery electrodes. The fourth example would be cover scheduling of vessel approaching to berth. Because transportation of large portion of raw material and products of petrochemical industry is dealt with vessel, scheduling of vessel approaching to berth is important at the shore of large difference of tide. The final example would be scheduling problem to minimization of change over time of ABS semi products.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.1
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• pp.40-49
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• 2008

Interior permanent magnet synchronous motor(IPMSM) has become a popular choice in electric vehicle applications and so of due to their excellent power to weight ratio. To obtain maximum efficiency in these applications, this paper proposes the neural network control method. The controllable electrical loss which consists of the copper loss and the iron loss can be minimized by the error back propagation algorithm(EBPA) of neural network. The minimization of loss is possible to realize eHciency optimization control for the IPMSM drive. This paper proposes high performance and robust control through a real time calculation of parameter variation such as variation of back emf constant, armature resistance and d-axis inductance about the motor operation. Proposed algorithm is applied IPMSM drive system, prove validity through analysis operating characteristics con011ed by efficiency optimization control.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.2
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• pp.72-78
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• 2021

This paper proposes a wide-band dual-polarization stacked patch array antenna for satellite SAR system applications. The array antenna was designed for loss minimization and wide-band characteristics to enhance the performance of the SAR system and optimize it for active return loss in applications to active phased arrays. The fabricated array antenna showed a performance of 19.26%/19.79% fractional bandwidth within the -10 dB reference level of the active return loss and showed loss characteristics of 0.797 dB/0.799 dB averaged within the operational frequency for both H/V-polarization cases. The pattern performance was verified by comparing the measured patterns with the calculated patterns obtained by the array factor.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.654-664
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• 2017

This paper proposed an unified dual-phase-shift (UDPS) control for dual active bridge (DAB) converters in order to improve efficiency for a wide output power range. Different operating modes of UDPS are characterized with respect to the reactive current distribution. The proposed UDPS has the same output power capability with conventional phase-shift (CPS) method. Furthermore, its implementation is simple since only the change of the leading phase-shift direction is required for different operating power range. The proposed UDPS control can minimize both the inductor rms current and the circulating reactive current for various voltage conversion ratios and load conditions. The optimal phase-shift pairs for two bridges of DAB converter are derived with respect to the comprehensive reactive power loss model, including the reactive components delivered from the load and back to the source. Simulation and experimental results are illustrated and explained with details. The effectiveness of the proposed method is verified in terms of reactive power losses minimization and efficiency improvement.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.6
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• pp.591-602
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• 2009

The Compton backscatter technique has been applied to lap-joint in aircraft structure in order to determine mass loss due to exfoliative corrosion of the aluminum alloy sheet skin. The mass loss of each layer has been estimated from Compton backscatter A-scan including the aluminum sheet, the corrosion layer, and the sealant. A Compton backscattering imaging system has been also developed to obtain a cross-sectional profile of corroded lap-splices of aging aircraft using a specially designed slit-type camera. The camera is to focus on a small scattering volume inside the material from which the backscattered photons are collected by a collimated scintillator detector for interpretation of material characteristics. The cross section of the layered structure is scanned by moving the scattering volume through the thickness direction of the specimen. The theoretical model of the Compton scattering based on Boltzmann transport theory is presented for quantitative characterization of exfoliative corrosion through deconvolution procedure using a nonlinear least-square error minimization method. It produces practical information such as location and width of planar corrosion in layered structures of aircraft, which generally cannot be detected by conventional NDE techniques such as the ultrasonic method.