• Structural Engineering and Mechanics
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• v.48 no.3
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• pp.383-394
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• 2013

Cold-formed profiles have been largely used in the building industry because they can be easily produced and because they allow for a wide range of sections and thus can be utilized to meet different project requirements. Attainment of maximum performance by structural elements with low use of material is a challenge for engineering projects. This paper presents a numerical study aimed at minimizing the weight of lipped and unlipped cold-formed channel columns, following the AISI 2007 specification. Flexural, torsional and torsional-flexural buckling of columns was considered as constraints. The simulated annealing method was used for optimization. Several numerical simulations are presented and discussed to validate the proposal, in addition to an experimental example that qualifies its implementation. The ratios between lips, web width, and flange width are analyzed. Finally, it may be concluded that the optimization process yields excellent results in terms of cross-sectional area reduction.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.3
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• pp.478-485
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• 1987

Optimization of the sub-micron N-channel MOSFET with the LDD(Lightly Doped Drain)structure has been investigated. LDD devices with various length of n-region, n-dose and n-implantation species were fabricated for this purpose. It will be shown that LDD devices have lower substrate current by an order of magnitude and higher breakdown voltage than the conventional devices with comparable channel length. Optimized LDD structure has been found when the sidewall thickness is 2500\ulcorner and n-region is phosphorus implantd with the dose of 1.0E13/cm\ulcorner It has been found that transconductance degradation is less than 20%.

• International Journal of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.44-50
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• 2023

For Wi-Fi and IoT wireless systems, high-capacity wireless communication technology is being applied using MIMO OFDM. Because of virtu0al subcarriers in the practical MIMO OFDM system, the pilot subcarriers cannot be spaced equally. Thus, it is difficult to obtain a good mean square error (MSE) performance of the channel estimate. This paper proposes applicable methods and the newly discovered locations of pilot subcarriers in four transmitted antennas resulting in a good MSE performance with proposed optimization algorithms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.1
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• pp.261-279
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• 2023

In this article, the uplink achievable rate is investigated for massive multiple-input multiple-output (MIMO) under correlated Ricean fading channel, where each base station (BS) and user are both deployed multiple antennas. Considering the availability of prior knowledge at BS, two different channel estimation approaches are adopted with and without prior knowledge. Based on these channel estimations, a two-layer decoding scheme is adopted with maximum ratio precoding as the first layer decoder and optimal second layer precoding in the second layer. Based on two aforementioned channel estimations and two-layer decoding scheme, the exact closed form expressions for uplink achievable rates are computed with and without prior knowledge, respectively. These derived expressions enable us to analyze the impacts of line-of-sight (LoS) component, two-layer decoding, data transmit power, pilot contamination, and spatially correlated Ricean fading. Then, numerical results illustrate that the system with spatially correlated Ricean fading channel is superior in terms of uplink achievable rate. Besides, it reveals that compared with the single-layer decoding, the two-layer decoding scheme can significantly improve the uplink achievable rate performance.

• Annual Conference of KIPS
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• 2013.05a
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• pp.418-420
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• 2013

Issues on design of routing scheme and routing metric for multicast in multi-channel multi-radio (MCMR) wireless mesh networks (WMNs) are discussed. Emphasis is placed on channel-diversity oriented routing metrics. From case study the conclusion to be drawn is that the key for design of channel-diversity oriented routing metrics is how to construct an optimization function to quantify interdependence between channel assignment and multicast routing throughput.

• The Journal of the Acoustical Society of Korea
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• v.21 no.7
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• pp.648-655
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• 2002

This paper describes implementation of a multi-channel G.723.1 Annex A (G.723.1A) focused on code optimization using a high performance general purpose Digital Signal Processor (DSP), To implement a multi-channel G.723.1A functional complexities of the ITU-T G.723.1A fixed-point C-code are measures an analyzed. Then we sort and optimize C functions in complexity order. In parallel with optimization, we verify the bit-exactness of the optimized code using the ITU-T test vectors. Using only internal memory, the optimized code can perform full-duplex 17 channel processing. In addition, we further increase the number of available channels per DSP into 22 using fast codebook search algorithms, referred to as bit -compatible optimization.

• The KSFM Journal of Fluid Machinery
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• v.14 no.1
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• pp.66-76
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• 2011

The heat transfer and pressure loss characteristics of a rotating two-pass channel with a guide vane in the turning region have been studied using three-dimensional Reynolds-averaged Navier-Stokes (RANS) analysis, and the shape of the guide vane has been optimized using surrogate modeling optimization technique. For the optimization, thickness, location and angle of the guide vanes have been selected as design variables. The objective function has been defined as a linear combination of the heat transfer and the friction loss related terms with a weighting factor. Latin hypercube sampling has been applied to determine the design points as design of experiments. A weighted-average surrogate model, PBA has been used as the surrogate model. The guide vane in the turning region does not influence the heat transfer in the first passage upstream of the turning region, but enhances largely the heat transfer in the turning region and the second passage. In an example of the optimization, the objective function has been increased by 13.6%.

• Journal of the Korean Operations Research and Management Science Society
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• v.28 no.3
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• pp.169-184
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• 2003

In the IS-95 packet service system, the radio channels are generally classified into the dedicated and the common traffic channels. In this paper, a common traffic channel access method is proposed for the COMA packet service system to enhance the radio resource utilization while guaranteeing QoS to the users. The proposed method is based on the permission probability for the common traffic channel user. To derive permission probability, optimization models are developed for two different QoS constraints. Approximation methods are also developed.

• Korean Management Science Review
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• v.26 no.1
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• pp.161-169
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• 2009

A traffic analysis on the Internet has an advantage for obtaining the characteristics of transferred packets. There were many studies to understand the characteristics of the Internet traffic with mathematical statistical approach. The approach of this study is different from previous studies. We first introduced a virtual network concept to present the Internet as a simplified mathematical model. It also represents each traffic flowing on the Internet as a parallel Gaussian channel on the virtual network. We suggest the optimal capacity of each parallel Gaussian channel using some related studies on the Gaussian channel model.

• Journal of IKEEE
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• v.22 no.2
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• pp.455-459
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• 2018

In this paper, proposed a multi-channel charging control strategy for electric vehicle. This control strategy can adjust the charging power according to the calculated state-of-charge (SOC). Electric vehicle (EV) charging system using Particle Swarm Optimization (PSO) algorithm is proposed. A stochastic optimization algorithm technique such as PSO in the time-of-use (TOU) price used for the energy cost minimization. Simulation results show that the energy cost can be reduced using proposed method.