• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1144-1150
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• 2011

In this paper, we present methods to improve output flatness of Ultra-wideband(f1~80f1) Frequency Generator (UFG) with variable output function. That include optimal structure and output ripple calibration algorithm to realize good flatness. The UFG was manufactured by our methods, then experiments were performed. The flatness of band 1~3 and band 4 are within ${\pm}2dB$, ${\pm}4dB$ respectively. These results are very excellent in view of ultra-wideband including millimeter wave band. From this results, we can confirm the validity of our methods.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.3
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• pp.303-310
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• 2009

We processed seven years data of 142 IGS(International GNSS Service) stations were processed, which have been selected with an optimal network algorithm, to realize terrestrial reference system. To verify the result, a comparison with the ITRF2005 was given both in positions and velocities with transformation parameters estimation. The transformation parameters are within 4.3 mm in length, while the RMS(root mean square) difference of positions and velocities are 6.7 mm and 1.3 mm/yr in horizontal and 13.3 mm and 2.4 mm/yr in vertical, respectively, which represent good coincidences with ITRF2005. This research would help developing our own geodetic reference frame and may be applied for the global earth observations such as the global tectonics. A further improved TRF would be expected by applying various data processing strategies and with extension of data in number and observation period.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.20-24
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• 1997

In general, pantograph type manipulators are used for carrying heavy payloads with positional accuracy. In this paper, a double pantograph type manipulator, activated by two slider joints, is studied for applying to file handing machine in atomic power plant. In order to realize the stable horizontal movement of a heavy fuel rod whit good positional accuracy, methods for allocating slider and finding constant joint rates are proposed. In addition, the static deflection of the proposed mechanism was studied using transfer-stiffness matrix method. A neural network control algorithm which compensates static deflections is explored with computer simulations.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.346-348
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• 2001

In this paper a wind power simulator is designed and implemented. This simulator realize the torque of wind blade by DC motor. And squirrel-cage induction machine is used as generator and controlled to achieve the maximum power point tracking(MPPT) algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.78.5-78
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• 2002

We propose an evolutionary reinforcement learning (RL) system with time-varying parameters that can deal with a dynamic environment. The proposed system has three characteristics: 1) It can deal easily with a dynamic environment by using time-varying parameters; 2) The division of state space is acquired evolutionarily by genetic algorithm (GA); 3) One does not have to design the rules constructing an agent in advance. So far many RL systems have been proposed. These systems adjust constant or non time-varying parameters; by those systems it is difficult to realize appropriate behavior in complex and dynamic environment. Hence, we propose the RL system whose parameters can vary temporally. T...

• Proceedings of the Korean Society of Computer Information Conference
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• 2012.07a
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• pp.203-206
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• 2012

The System of communication with wireless devices is experiencing a huge growth. While traditional communication paradigms deal with fixed networks, mobility raises a new set of questions, techniques, and solutions. In order to realize service mobility, there is a need of protocol that can support mobility while nodes are communicating without any disruption of their connection status. This paper proposes a handover authentication protocol for mobility support. Careful considerations must be taken in priority to security issues since many unreliable public and private resources; both networks and devices are involved. The protocol is based on public key cryptography with Diffie-Hellman algorithm which provides security against both leakage-resilience of private keys on untrustworthy devices and forward secrecy.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.4
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• pp.32-39
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• 1998

Remez exchange algorithm was applied to realize an IF SAW filter for CDMA cellular phone systems. A SAW filter with withdrawal weighted transducers was simulated and then fabricated on 42.75.deg. ST-cut Quaritz wafer. Excellent agreement wasobtained between calculated andmeasured responses. Fabricated SAWfilterswere mounted on ceramic SMD package for reducing their size and volume. SAW filters were measured under matched circuit. As a result, 5 dB bandwidth of 1.32 MHz, 33dB bandwidth of 1.76 MHz, insertion loss of 13.8 dB and peak to peak ripple at passband of 0.26 dB were obtained. Linear group delay responses at passband were also obtained. These characteristics were good for practical use of IF SAW filter for CDMA system.

• Journal of Korea Multimedia Society
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• v.24 no.1
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• pp.30-39
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• 2021

Research in the field of health lighting has continued to advance to reproduce the color temperature of natural light which periodically changes. However, most of this research could only reproduce a uniform circadian color temperature of natural light, therefore failing to realize the characteristics of the circadian cycle of color temperature difference by latitude and longitude. To reproduce the color temperature of natural light on which the characteristics of a region are reflected, the collection technology of real-time characteristics of natural light is needed. If the color temperatures which are not within a periodical pattern due to climate changes, etc., are measured, it will be difficult to judge the occurrence (presence) of the anomalies and to reproduce the circadian cycle of the color temperature of natural light. Therefore, this study proposes an algorithm for judging the anomalies in real time based on the sliding window to reproduce the color temperature of natural light. First, the natural light characteristics DB collected through the on-site measurement were analyzed, the differential values at a one-minute interval were calculated and examined, and then representative color temperature circadian patterns by solar terms were drawn. The anomalies were then detected by the application of the sliding window that calculated the deviation of the color temperature for the measured color temperature data set, which was collected through RGB sensors, while moving along the time sequence. In addition, the presence of anomalies was verified through the comparison study between the detection results and the representative circadian cycle of the color temperature by solar term. The judgment method for the anomalies from the measured color temperature of natural light was proposed for the first time, confirming that the proposed method was capable of detecting the anomalies with an average accuracy of 94.6%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.4
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• pp.575-594
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• 2010

In this study, we propose a space search algorithm (SSA) and then introduce a hybrid optimization of fuzzy inference systems based on SSA and information granulation (IG). In comparison with "conventional" evolutionary algorithms (such as PSO), SSA leads no.t only to better search performance to find global optimization but is also more computationally effective when dealing with the optimization of the fuzzy models. In the hybrid optimization of fuzzy inference system, SSA is exploited to carry out the parametric optimization of the fuzzy model as well as to realize its structural optimization. IG realized with the aid of C-Means clustering helps determine the initial values of the apex parameters of the membership function of fuzzy model. The overall hybrid identification of fuzzy inference systems comes in the form of two optimization mechanisms: structure identification (such as the number of input variables to be used, a specific subset of input variables, the number of membership functions, and polyno.mial type) and parameter identification (viz. the apexes of membership function). The structure identification is developed by SSA and C-Means while the parameter estimation is realized via SSA and a standard least square method. The evaluation of the performance of the proposed model was carried out by using four representative numerical examples such as No.n-linear function, gas furnace, NO.x emission process data, and Mackey-Glass time series. A comparative study of SSA and PSO demonstrates that SSA leads to improved performance both in terms of the quality of the model and the computing time required. The proposed model is also contrasted with the quality of some "conventional" fuzzy models already encountered in the literature.

• Journal of Korea Multimedia Society
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• v.3 no.2
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• pp.201-208
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• 2000

In this paper We describe an algorithm which is devised for 4he partition o# the input space and the generation of fuzzy rules by the fuzzy entropy and tested with the time series prediction problem using Mackey-Glass chaotic time series. This method divides the input space into several fuzzy regions and assigns a degree of each of the generated rules for the partitioned subspaces from the given data using the Shannon function and fuzzy entropy function generating the optimal knowledge base without the irrelevant rules. In this scheme the basic idea of the fuzzy neural network is to realize the fuzzy rules base and the process of reasoning by neural network and to make the corresponding parameters of the fuzzy control rules be adapted by the steepest descent algorithm. The Proposed algorithm has been naturally derived by means of the synergistic combination of the approximative approach and the descriptive approach. Each output of the rule's consequences has expressed with its connection weights in order to minimize the system parameters and reduce its complexities.