• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.75.1-75
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• 2002

Several model order reduction methods for large RLC circuits have been developed in the last few years. Krylop subspace based methods are extremely effective for generating the low order models of large system but there is no optimal theory for the resulting models. Alternatively, methods based truncated balanced realization have an optimality property but are too computationally expensive to use on complicated problems such as large RLC circuits. In this paper, we present a method for improving time domain response of reduced order RLC circuits. The method used here is based on combing Krylop subspace based method and truncated balanced realization method plus residualization. The metho...

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2225-2233
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• 1994

In order to improve the cutting ability of face mill, a model for optimal cutter shape was developed to minimize resultant cutting force by combing cutting force model and optimal technique. Wear test and surface roughness test for optimized and conventional cutter were performed. The new optimized cutter shows longer tool life of 2.29 times than conventional cutter in light cutting condition and 2.52 times in heavy cutting condition. The surface roughness of workpiece by optimized cutter is improved in heavy cutting condition, but deteriorated in light cutting condition in comparison with conventional cutter. The surface profiles of workpiece were analyzed by Fourier transformation. The distribution of cut lay left on workpiece by optimized cutter is more regular than that by the conventional cutter.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.19-22
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• 1997

The objective of this research is to use an analytical and experimental approach to develop optimal tool geometry for high speed machining. The tool geometry parameters and cutting process have complex relationships. Until now, numerous cutting tests were needed to acquire optimal design of endmill for the purpose of high speed machining, dut to the insufficient knowledge about process in high speed machining. In order to improve the cutting ability of endmill, a model for optimal cutter shape was developed to minimize resultant cutting force by combing cutting force and wear test and surface roughness test from optimized and conventional cutter with the same cutting condition. Using various tools with different geometry, relationships between the tool geometry parameter, rake angle, clearance angle, lengh of cutter have been stuied.

• Journal of Magnetics
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• v.16 no.3
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• pp.268-270
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• 2011

This study introduces a new topology optimization scheme combing the genetic algorithm (GA) with the on/off sensitivity method for the magnetic actuator core and the armature design. The design process intended to maximize the first eigen-frequency of the armature part and the magnetic actuating force acting on the armature simultaneously. GA based optimal design was carried out to obtain the initial structure and the modified on/off sensitivity method was succeeded to accelerate the design process. Final results show tens of percent improvement in actuating force as well as the first eigen-frequency of the armature.

• Journal of Korea Water Resources Association
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• v.51 no.3
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• pp.273-280
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• 2018

Accurate estimation of evapotranspiration is mightily important for understanding and analyzing the hydrological cycle. There are various methods for estimating evapotranspiration and each method has its own advantages and limitations. Therefore, it is necessary to develop an optimal evapotranspiration product by combing different evapotranspiration products. In this study, we developed an optimal evapotranspiration by fusing two satellite- and model-based evapotranspiration estimates, including revised remote sensing-based Penman-Monteith (RS-PM) and Modified Satellite-Based Priestley-Taylor (MS-PT) methods, Global Land Data Assimilation System (GLDAS), and Global Land Evaporation Amsterdam Model (GLEAM). The statistical analysis (i.e., correlation coefficients, index of agreement, MAE, and RMSE) of combined evapotranspiration product showed to be improved compared to the individual model results. After confirming the overall results, in future studies, advanced data fusion techniques will be used to obtained improved results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6C
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• pp.476-482
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• 2012

In this paper, we analyze and compare several co-channel interference mitigation algorithms for WBAN application in 2.4 GHz ISM frequency bands. ML (Maximum Likelihood), OC (Optimal Combining) and MMSE (Minimum Mean Square Error) has been considered for the possible techniques for interference cancellation in view of the trade off between the performance and the complexity of implementation. Based on the channel model of IEEE 802.15.6 standard, simulation results show that ML and OC attains the lower BER performance than that of MMSE if we assume the perfect channel estimation. But, ML and OC have the additional requirement of implementation for his own and other users's channel estimation process, hence, besides the BER performance, the complexity of implementation and the sensitivity to channel estimation error should be considered since it requires the simple and small sized equipment for WBAN system application. In addition, the gap of detection BER performance between ML, OC and MMSE is much decreased under the imperfect channel estimation if we adopt real channel estimation process, therefore, in order to apply to WBAN system, the trade off between the BER performance and complexity of implemetation should be seriously considered to decide the best co-channel interference cancellation for WBAN system application.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.4
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• pp.423-429
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• 2011

Cooperative spectrum sensing is proposed to overcome some problem such as multipath fading and shadowing and to improve spectrum sensing performance. There are different combining methods for cooperative spectrum sensing: hard decision method and soft decision method. In this paper, we analysis the performance of cooperative spectrum sensing with distance based weight that is kind of a soft decision rule for cognitive radio(CR) systems and CR systems sense the spectrum of the licensed user by using a energy detection method. Threshold is determined in accordance with the constant false alarm rate(CFAR) algorithm for energy detection. The signal of licensed user is OFDM signal and the wireless channel between a licensed user and CR systems is modeled as Gaussian channel. From the simulation results, the cooperative spectrum sensing with distance based weight combining(DWC) and equal gain combing(EGC) methods shows higher spectrum sensing performance than single spectrum sensing does. And the detection probability performance with the DWC is higher than that with the EGC.

• The Korean Journal of Nuclear Medicine Technology
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• v.15 no.1
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• pp.86-89
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• 2011

Purpose: The KOTRON-13 cyclotron was developed in South Korea and was introduced to regional cyclotron centers to produce short-lifetime medical radioisotopes. However, this cyclotron has limited capacity to produce carbon-11 isotope so far. We herein study how to develop and optimize an effective carbon-11 target system in the KOTRON-13 cyclotron by changing cooling system, combing with fluorine-18 target and evaluating beam currents. Materials and Method: To develop the optimal carbon-11 target and an effective cooling system, we designed the carbon-11 target system by Stopping and Range of Ions in Matter (SRIM) simulation program and considered the cavity pressure during irradiation at target grid. In this investigation, we evaluated the yield of carbon-11 production at different beam currents and the stability of the operation of the KOTRON-13 cyclotron. Results: The production of carbon-11 was enhanced from about 1.700 mCi ($50{\mu}A$) to 2,000 mCi ($60{\mu}A$) on the carbon-11 target which developed by seoul national university bundang hospital (SNUBH) and Samyoung Unitech. Additionally, the cooling condition was showed stable to produce carbon-11 under high beam current. Conclude: The carbon-11 target system of the KOTRON-13 cyclotron was successfully developed and improved carbon-11 production. Consequently, the operation of carbon-11 target system was highly effective and stable compare with other commercial cyclotrons. Our results are believed that this optimal carbon-11 target system will be helpful for the routine carbon-11 production in the KOTRON-13 cyclotron.