• Journal of Industrial Technology
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• v.22 no.B
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• pp.71-78
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• 2002

The objective of this paper is to develop an efficient genetic algorithm (GA) to find a channel assignment method for minimum interference among the channels within reasonable time. The series of specific channel number is used as a representation of chromosome. We use minimum-channel-distance encoding scheme within the same cell to consider cosite channel interference (CSI) when chromosomes are generated. The cell base crossover is also used. This proposed method improves solution quality within limited time.

• International Journal of Fluid Machinery and Systems
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• v.9 no.3
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• pp.229-236
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• 2016

Exergetic analysis was introduced in optimization of a rotating equilateral triangular internal cooling channel with staggered square ribs to maximize the net exergy gain. The objective function was defined as the net exergy gain considering the exergy gain by heat transfer and exergy losses by friction and heat transfer process. The flow field and heat transfer in the channel were analysed using three-dimensional Reynolds-averaged Navier-Stokes equations under the uniform temperature condition. Shear stress transport turbulence model has been selected as a turbulence closure through the turbulence model test. Computational results for the area-averaged Nusselt number were validated compared to the experimental data. Three design variables, i.e., the angle of rib, the rib pitch-to-hydraulic diameter ratio and the rib width-to-hydraulic diameter ratio, were selected for the optimization. The optimization was performed at Reynolds number, 20,000. Twenty-two design points were selected by Latin hypercube sampling, and the values of the objective function were evaluated by the RANS analysis at these points. Through optimization, the objective function value was improved by 22.6% compared to that of the reference geometry. Effects of the Reynolds number, rotation number, and buoyancy parameter on the heat transfer performance of the optimum design were also discussed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.239-247
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• 2013

In network based on multi-interface, there are needed channel assignment strategy that reduce interference and improve bandwidth efficiency by assigning each interface to available channels in order to utilize effectively multiple wireless interfaces on each node. MCS protocol had been proposed, which improve capacity and throughput of network by using hybrid assignment. MCS uses as the criterion to assign channel the number of node that use the same channel in contention area. but there have an problem that this information exactly does not reflect actually offered channel load. in this paper, we proposes CAMCS protocol to assign channel by that the channel busy degree to indicate the occupancy rate of channel by nodes as well as the number of nodes that use the same channel in inference area is used as criterion for estimation channel load, and conform performance improvement effect by simulation.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.5
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• pp.205-215
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• 2006

In this paper an optical power meter using Hadamard transform, which can be used in multiple channel optical elements alignment system, is proposed. A traditional optical power meter in multiple channel optical elements alignment system is able to judge how well the elements are aligned each other by measuring optical power of the first and the last two channels with at least two detectors. It has critical drawback that the alignment accuracy per channel is dependent on the number of detectors. The proposed optical power meter can get noise reduction by the Hadamard transform based multiplexing technique. The Hadamard transform based multiplexing technique using spatial light modulators is distinguished by the best enhancement of signal-to-noise ratio (SNR) for the reconstructed signals. Moreover, the noise reduction increases with increasing the order of multiplexing, namely the number of optical element channels. The proposed system is implemented by PDLC (Polymer Dispersed Liquid Crystal) mask which is operated by electric filed and generates optimal multiplexing patterns based on the Hadamard transform and single detector. It means that we obtain not only the each channel's optical power of multiple channel elements at once but also the best enhancement of SNR with single detector. Experimental results show that the proposed optical power meter is suitable for an active optical alignment system for multiple channel optical elements.

• Journal of the Korean Society of Clothing and Textiles
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• v.38 no.2
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• pp.277-292
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• 2014

This study investigated consumers' multi-channel behavior for fashion product purchases and compared perceived risks by channel type. A survey involving male and female college students was conducted in the Daegu and Gyungbuk area in December 2013. A total of 400 responses were analyzed using descriptive statistics, chi-square analysis, independent sample t-test, paired t-test, factor analysis, and reliability analysis. An internet shopping mall was the most frequently chosen retailer type for fashion product purchases and information searches. In addition, respondents also preferred independent branded stores, department stores, and non-branded stores. The number of retailer types for clothing item purchases ranged from 1 to 6 and the average was 3.06. The number of retailer types was significantly higher in women groups according to gender variables. Perceived risk had the highest evaluation score for internet shopping malls. Department stores were recognized as a reliable retailer type. The construct of perceived risk was shown as similar in off-line stores such as department stores, independent branded stores, and non-branded stores. Instead, the construct was differentiated from the case of internet shopping malls. Some insightful suggestions were suggested for future research and industrial marketing plans based on the results.

• The Journal of the Convergence on Culture Technology
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• v.4 no.4
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• pp.419-427
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• 2018

This paper designs and develops auto-tuning temperature controller with multi-channel, which controller with multi-channel could control a number of control system simultaneously. This controller has multi-channel input and output. And a number of control algorithms run in this controller simultaneously and independently. Firstly we present design method of controller with multi-channel. Secondly we design electrical circuit of sensor input, controller output and power control for temperature control board. And finally we design data protocol for serial communication to monitor control state and present verification of temperature controller with muiti-channel through field experiment.

• ETRI Journal
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• v.45 no.6
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• pp.952-962
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• 2023

In this study, a space-time transmission scheme is proposed to tackle the limitations of channel estimation with orthogonal pilot information in colocated multiple-input multiple-output systems with several transmitting and receiving antennas. Channel information is obtained using orthogonal pilots. Channel estimation introduces pilot heads required to estimate a channel. This leads to bandwidth insufficiency. As a result, trade-offs exist between the number of pilots required to estimate a channel versus spectral efficiency. The detection of data symbols is performed using the maximum likelihood decoding method as it provides a consistent approach to parameter estimation problems. The moment-generating function of the instantaneous signal-to-noise ratio is used to drive an approximate expression of the symbol error rate for the proposed scheme. Furthermore, the order of diversity is less by one than the number of receiver antennas used in the proposed scheme. The effect of the length of a pilot sequence on the proposed scheme's performance is also investigated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3A
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• pp.362-374
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• 2000

In this paper, trellis coded 16 QAM Multi-Carrior CDMA system is proposed, Using the equivalent signal-to-noise plus interference Power ratio (SNIR) of Multi-Carrier CDMA system in the reverse link, capacity and BER performance of trellis coded 16 QAM Multi-Carrier CDMA system are analyzed taking into account the number of multi-carrier, the number of multiple access user, the number of SC/MRC diversity branch, and Rician fading parameter in multiuser interference and Rician fading channel. And the capacity and the BER performance of trellis coded 16 QAM Multi-Carrier CDMA system using selection combining (SC) and maximal ratio cabining (MRC) diversity are numerically compared. Obtained results show that the capacity of proposed system depends on the number of multi-carrier. ti is found that the trellis coded 16 QAM Multi-Carrier CDMA system with SC/MRC antenna diversity scheme is efficient to combat multipath fading and to increase the maximum number of users in high speed data communication. With the results of analysis. MRC diversity technique provides the performance fro high speed data communications. Finally, we present a numerical approach to derive the capacity and the BER performance and to find the maximum number of multiple access user for Multi-Carrier system in multiuser interference and Rician fading channel.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.1083-1090
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• 2005

Repeated ribs are used on heat exchange surfaces to promote turbulence and enhance convective heat transfer. Applications include fuel rods of gas-cooled nuclear reactors, inside cavities of turbine blades, and internal surfaces pipes used in heat exchangers. Despite the great number of literature papers, only few experimental data concern detailed distributions of friction factors and heat transfer coefficients in square channels varying the number of rough walls. This issue is tackled by investigating effects of different number of ribbed walls on heat transfer and friction characteristics in square channel. The rough wall have a 45$^{\circ}$ inclined square rib. Uniform heat flux is maintained on whole inner heat transfer channel area. The heat transfer coefficient and friction factor values increase with increasing the number of rough walls.

• Journal of Power System Engineering
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• v.9 no.1
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• pp.30-35
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• 2005

Repeated ribs are used on heat exchanger surfaces to promote turbulence and to enhance convective heat transfer. Applications include fuel rods of gas-cooled nuclear reactors, inside cavities of turbine blades, and internal surfaces pipes used in heat exchangers. Despite the great number of literature papers, only few experimental data concerns detailed distributions of friction factors and heat transfer coefficients in square channels varying the number of rough walls. This issue was tackled by investigating effects of different number of ribbed walls on heat transfer and friction characteristics in square channel. The rough wall had a $45^{\circ}$ inclined square rib. Uniform heat flux was maintained on the whole inner heat transfer channel area. The heat transfer coefficient and friction factor values increased with increasing the number of rough walls.