• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.12a
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• pp.205-208
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• 2000

In this paper, we'll show that an improved PDFF controller is obtained by substituting a feedforward compensator in the existing PDFF system with a dual-input describing function, and the controller has the ability of adjusting the bandwidth of a system as well as the phase margin simultaneously. The effectiveness of the proposed controller is confirmed by applying to the DC-motor position control system. As the results of simulation, we know that it is possible to design a controller by which the bandwidth of the closed system and its phase margin are easily adjusted.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.2
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• pp.91-99
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• 2023

Structural vibration induced by earthquake hazards is one of the most significant concerns in structure performance-based design. Structural hazards evoked from seismic events must be properly identified to make buildings resilient enough to withstand extreme earthquake loadings. To investigate the effects of combined earthquake-resistant systems, shear walls and five types of dampers are incorporated in nineteen structural models by altering their arrangements. All the building models were developed as per ACI 318-14 and ASCE 7-16. Seismic fragility curves were developed from the incremental dynamic analyses (IDA) performed by using seven sets of ground motions, and eventually, by following FEMA P695 provisions, the collapse margin ratio (CMR) was computed from the collapse curves. It is evident from the results that the seismic performance of the proposed combined shear wall-damper system is significantly better than the models equipped with shear walls only. The scrutinized dual seismic resisting system is expected to be applied practically to ensure a multi-level shield for tall structures in high seismic risk zones.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.66-70
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• 1991

A mixed $H_{2}$ / H.inf. design methodology is suggested for a single-input-single-output system. Suboptimal $H_{2 }$ controllers stabilizing the closed loop system under the additive uncertainty are obtained. An extended Nevanlinna-Pick algorithm is used to obtain the suboptimal. controllers.s.

• The Journal of Fisheries Business Administration
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• v.31 no.1
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• pp.33-54
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• 2000

This study intends to examine the distribution channel of the most popular ten species caught in Korean coastal and off-shore fisheries with the aid of interviewing fish brokers and cooperative staffs in fish landing markets. This paper finds and emphasizes the following three suggestions, in order to improve the present scheme of fish distribution system. Firstly, annual catch of 10 kinds of fishes is successively decreasing in quantity from 1994 to 1998. Moreover annual catch shows larger variations than fish price and cooperative sales quantity. Except sea eel and sole, cooperative sales accommodates more than 90% of the fish landed, accounting for the small variation in cooperative sales, which invalidates the effectiveness of the free distribution system adopted by the government. Secondly, diversified distribution channels are exposed according to the nature of the fish, the method to harvest, and the quantity caught. Large retailers such as discount stores, super chains and home shopping institutions are actively involving themselves in direct purchase in fish landing markets. Through the analysis of distribution routes, the general distribution channel of fresh fish has been found such as producers longrightarrow fish brokers in landing markets longrightarrow fish brokers in central wholesale markets longrightarrow wholesalers longrightarrow retailers longrightarrow consumers. In order to reduce distribution margin through the analysis of distribution function and distribution margin, this paper presents a new distribution channel such as producers longrightarrow fish brokers in landing markets longrightarrow wholesalers longrightarrow retailers longrightarrow consumers. Thirdly, to improve the fish landing markets, this paper suggests the M&A of uneconomical fish landing markets or renovating toward wholesalers, introduction of processing services and improvement of processing facilities, subsidizing fish brokers in landing markets, revitalization of marketing divisions in cooperatives and improvement in fish auction system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.133-142
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• 2006

This paper suggests an efficient method of protection ratio(PR) calculation and shows some results of point-to-point radio relay system for frequency coordination. The proposed PR can be expressed as a function of C/N of modulation scheme, noise-to-interference ratio(N/I), multiple interference allowance, fade margins of multi-Path and rain attenuation and net filter discrimination. And PR calculation is performed in view of fade margin, modulation scheme, distance, and interference for actual point-to-point radio relay frequency. According to results for 6.2 GHz, 64-QAM and 60 km at BER 10-6, fade margin and co-channel Protection ratio reveal 41.1dB and 74.9 dB, respectively The merit of presented method provides a systematic and easy calculation by means of PR correction factor related with various parameters and can apply the same concept to frequency coordination of millimeter wave radio relay system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.743-749
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• 2015

In this paper, we describe the dynamic tumble-stability analysis of a seabed-walking robot named Crabster (CR200) in forward-incident currents. CR200 is designed to be operated in tidal-current conditions, and its body shape is also designed to minimize hydrodynamic resistances considering hydrodynamics. To analyze its tumble stability, we adopt the dynamic stability margin of a ground-legged robot and modify the definition of the margin to consider tidal-current effects. To analyze its dynamic tumble stability, we use the estimated hydrodynamic forces that act on the robot in various tidal-current conditions, and analyze the dynamic tumble-stability margin of the robot using the estimated results obtained for the various tidal-current conditions. From the analyses, we confirm the improved tumble stability of the robot according to the movement of the tumble axis caused by the supporting points of the legs.

• Journal of Aerospace System Engineering
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• v.11 no.6
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• pp.42-49
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• 2017

A 10kw wind turbine blade aerodynamic design was carried out using the self-developed program AeroDA. The concept, basic shape, and optimization were designed and verified. A performance analysis was carried out and the key factors in each design stage are summarized. In addition, a guide for the placement of cross-section airfoils constituting the blades is presented, and the importance of the stall margin test as a method of verifying aerodynamic design is summarized. In order to verify the design program AeroDA, we compared the results of the performance analysis with a specialized program DNVGL_Bladed.

• Progress in Medical Physics
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• v.23 no.2
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• pp.81-90
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• 2012

The effect of setup uncertainties on CTV dose and the correlation between setup uncertainties and setup margin were evaluated by Monte Carlo based numerical simulation. Patient specific information of IMRT treatment plan for rectal cancer designed on the VARIAN Eclipse planning system was utilized for the Monte Carlo simulation program including the planned dose distribution and tumor volume information of a rectal cancer patient. The simulation program was developed for the purpose of the study on Linux environment using open source packages, GNU C++ and ROOT data analysis framework. All misalignments of patient setup were assumed to follow the central limit theorem. Thus systematic and random errors were generated according to the gaussian statistics with a given standard deviation as simulation input parameter. After the setup error simulations, the change of dose in CTV volume was analyzed with the simulation result. In order to verify the conventional margin recipe, the correlation between setup error and setup margin was compared with the margin formula developed on three dimensional conformal radiation therapy. The simulation was performed total 2,000 times for each simulation input of systematic and random errors independently. The size of standard deviation for generating patient setup errors was changed from 1 mm to 10 mm with 1 mm step. In case for the systematic error the minimum dose on CTV $D_{min}^{stat{\cdot}}$ was decreased from 100.4 to 72.50% and the mean dose $\bar{D}_{syst{\cdot}}$ was decreased from 100.45% to 97.88%. However the standard deviation of dose distribution in CTV volume was increased from 0.02% to 3.33%. The effect of random error gave the same result of a reduction of mean and minimum dose to CTV volume. It was found that the minimum dose on CTV volume $D_{min}^{rand{\cdot}}$ was reduced from 100.45% to 94.80% and the mean dose to CTV $\bar{D}_{rand{\cdot}}$ was decreased from 100.46% to 97.87%. Like systematic error, the standard deviation of CTV dose ${\Delta}D_{rand}$ was increased from 0.01% to 0.63%. After calculating a size of margin for each systematic and random error the "population ratio" was introduced and applied to verify margin recipe. It was found that the conventional margin formula satisfy margin object on IMRT treatment for rectal cancer. It is considered that the developed Monte-carlo based simulation program might be useful to study for patient setup error and dose coverage in CTV volume due to variations of margin size and setup error.

• Journal of Power Electronics
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• v.12 no.1
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• pp.193-200
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• 2012

Previous publications regarding the design and specifications of the interface inductor and the DC side capacitor for a STATCOM usually deal with the interface inductor and the DC side capacitor only. They seldom pay attention to the influences of the interface inductor and capacitor on the performance of a STATCOM system. In this paper a detailed analysis of influence of the interface inductor and the DC side capacitor on a STATCOM system and the corresponding design considerations is presented. Phase and amplitude control is considered as the control strategy for the STATCOM. First, a model of a STATCOM system is carried out. Second, through frequency domain methods, such as transfer functions and Bode plots, the influence of the interface inductor and the DC side capacitor on the stability and filtering characteristics of the STATCOM are extensively investigated. Third, according to this analysis, the design considerations based on the phase margin for the interface inductor and the DC side capacitor are discussed, which leads to parameters that are different from those of the traditional design.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1527-1534
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• 2016

Online voltage stability monitoring using real-time measurements is one of the most important tasks in a smart grid system to maintain the grid stability. Loading margin is a good indicator for assessing the voltage stability level. This paper presents an Extreme Learning Machine (ELM) approach for estimation of voltage stability level under credible contingencies using real-time measurements from Phasor Measurement Units (PMUs). PMUs enable a much higher data sampling rate and provide synchronized measurements of real-time phasors of voltages and currents. Depth First (DF) algorithm is used for optimally placing the PMUs. To make the ELM approach applicable for a large scale power system problem, Mutual information (MI)-based feature selection is proposed to achieve the dimensionality reduction. MI-based feature selection reduces the number of network input features which reduces the network training time and improves the generalization capability. Voltage magnitudes and phase angles received from PMUs are fed as inputs to the ELM model. IEEE 30-bus test system is considered for demonstrating the effectiveness of the proposed methodology for estimating the voltage stability level under various loading conditions considering single line contingencies. Simulation results validate the suitability of the technique for fast and accurate online voltage stability assessment using PMU data.