• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.525-529
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• 2001

A pulse frequency control(PFM) method for single-phase SEPIC-type rectifier is described in this paper. In the SEPIC rectifier, a relationship between the output power and the respective switching frequency is investigated to establish the control scheme of PFM. The propsed control method is provided with a feed-forward control loop of the output load as well as a feed-back control loop of the output voltage. The simulation results show good dynamic responses and unity power-factor operation.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.794-797
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• 1988

G. Binnig and H. Rohrer introduced the Scanning Tunneling Microscope (STM) in 1982 and developed it into a powerful and not to be missed physical tool. Scanning tunneling Microscopy is a real space surface imaging method with the atomic or subatomic resolution in all three dimensions. The tip is scanned over the surface by two piezo translators mounted parallel (X-piezo and Y-piezo) to the surface and perpendicular to each other. The voltage applied to the third piezo (Z-piezo) translator mounted perpendicular to the surface to maintain the tunneling current through the gap at a constant level reflects then the topography of the surface. The feed back control loop for the constant gap current is designed using the automatic control technique. In the designing process of the feed back loop, the identification of the gap dynamics is very complex and has difficulty. In this research, using some suitable test signals, the system dynamics of the gap including the Z-piezo are investigated. Especially, in this paper, a system model is proposed for the gap and Z-piezo series system. Indicial response is used to find out the model. The driving voltage of the Z-piezo and the tunneling current are considered as input and output signals respectively.

• The Korean Journal of Community Living Science
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• v.17 no.1
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• pp.3-10
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• 2006

The purpose of this study was to analyze leadership competency in the rural leader roles. The data were derived from 317 leaders in 97 rural communities by questionnaire. SPSSWIN/ver10 was adopted t-test and IPA (Importance-Performance Analysis) methods employed. The major findings of this study were as follows; Rural leaders should concentrate on developing coaching/feed back, program management skills, and presentation skills. Administrative head of village should pay attention to benchmarking, brand development and conflict resolution rather than resident management, service knowledge, and making relationships. Leaders of village development council should concentrate on brand development, benchmarking, and educating residents. Head of women's organizations should concentrate on developing assessments, educating residents, and resolving conflict skills, whereas members of Samaeul organization should try to concentrate on program management, coaching/feed back and presentation skills. Rural leaders showed different leadership competency by the IPA. Therefore, this study suggested that leadership education for rural leaders should consider leadership competency.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.95-104
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• 2016

Massive multiple-input multiple-output (MIMO) is a promising approach for cellular communication due to its energy efficiency and high achievable data rate. These advantages, however, can be realized only when channel state information (CSI) is available at the transmitter. Since there are many antennas, CSI is too large to feed back without compression. To compress CSI, prior work has applied compressive sensing (CS) techniques and the fact that CSI can be sparsified. The adopted sparsifying bases fail, however, to reflect the spatial correlation and channel conditions or to be feasible in practice. In this paper, we propose a new sparsifying basis that reflects the long-term characteristics of the channel, and needs no change as long as the spatial correlation model does not change. We propose a new reconstruction algorithm for CS, and also suggest dimensionality reduction as a compression method. To feed back compressed CSI in practice, we propose a new codebook for the compressed channel quantization assuming no other-cell interference. Numerical results confirm that the proposed channel feedback mechanisms show better performance in point-to-point (single-user) and point-to-multi-point (multi-user) scenarios.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.67-69
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• 2007

PMSM (Permanent Magnet Synchronous Motor) current control is a most inner loop of electromechanical driving systems and it plays a foundation role in the hierarchy's control loop of several mechanical machine systems. In this paper, a simple RMRAC control scheme for the PMSM is proposed in the synchronous frame. In the synchronous current model, the input signal is composed of as a calculated voltage by adaptive laws and system disturbances. The gains of feed-forward and feed-back controller are estimated by the proposed e-modification methods respectively, where the disturbances are assumed as filtered current tracking errors. After the estimation of the disturbances from the tracking errors, the corresponding voltage is fed forward to control input to compensate for the disturbances. The proposed method is robust to high frequency disturbances and has a fast dynamic response to time varying reference current trajectory. It also shows a good real-time performance duo to it's simplicity of control structure. Through the simulations considering several cases of external disturbances and experimental results, efficiency of the proposed method is verified

• KSBB Journal
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• v.15 no.6
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• pp.649-657
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• 2000

The factors affecting the back-extraction efficiency of Bovine Serum Albumin (BSA, Mw. 65kDa, pl 4.9) solubilized in an AOT reverse micellar solution, prepared by the injection method, to an excess aqueous phase were investigated. In particular, the effects of pH, the types of salts, alcohols added as cosurfactants, and their concentrations in the aqueous phase were examined. Furthermore, by comparing the CD spectra of the back-extracted BSA and the feed BSA, the structural changes of BSA during the extraction process were determined. The addition of 1:1 salt such as KCl or NaCl to the aqueous phase resulted in almost a 100% extraction to the aqueous phase at a pH higher than its isoelectric point pl. This high efficiency of back-extraction might be due to the change in the interactions between the protein and micellar aggregates driven by the added salt. For 1:2 salts like $CaCl_2$ and $MgCl_2$, BSA was back-extracted with lower than 20% extraction efficiency. Maximum extraction efficiencies were attained at about pH=7 and pH=8 for monovalent and divalent salts, respectively. The addition of alcohols as cosurfactants led to an improvement in monovalent and divalent salts, respectively. From the CD spectra of BSA extracted to the aqueous phase, it was observed that denaturation of BSA was not significant. In certain back-extraction conditions, the extracted BSA showed even higher activity than the feed BSA.

• Journal of Advanced Marine Engineering and Technology
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• v.3 no.1
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• pp.19-31
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• 1979

Recently the adaptive control system, which keeps the control system always optimal by adjusting the control parameters automatically according to the variations of the plant parameters, have become very important in the field of control engineering. The adaptive control systems are usally composed of the plant identification, the decision of the optimal control parameters, and the adjustment of the control parameters. This paper deals with a method of the adaptive control system when PI or PID controller is used in the feed back control system. Its controlled object (the plant) is assumed to be described by the transfer function of $\frac{ke^{-LS}}{1+TS}$ where k, T and L are steady state gain, time constant and pure dead time respectively, and their values are variable in accordance with the change of environmental circumstance. It has been known that a pseudo-random binary signal is quite effective for the measurement of an impulse response of a plant. In adaptive control systems, however, the impulse response itself is not appropriate to determine the control parameters. In this paper, the authors propose a method to estimate directly the parameters of the plant k, T and L by means of the correlation technique using 3 level M-sequence signal as a test signal. The authors also propose a method to determine the optimal parameters of the PI or PID controller in the sense of minimizing the square integral of the control error in the feed back control system, and the values of the optimal parameters are computed numerically for various values of T and L, and the results are examined and compared with those of the conventional methods. Finally the above-mentioned two methods are combined and an algorithm to struct an adaptive control system is suggested. The experiments for the indicial responses by means of both the model of the temperature control system using SCR actuater and the analog simulations have shown good results as expected, and the effectiveness of the proposed method is verified. The M-sequence generator and the time delay circuit, which are manufactured for the experiments, are operated in quite a good condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2724-2729
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• 2010

This paper presents a method of constructing the sequential digital systems over finite fields. We assign all elements in finite fields to digit codes using mathematical properties of finite fields. Also, we discuss the operational characteristics and properties of the building block T-gate which is used to implement the sequential digital systems over finite fields. Then, we implemented sequential digital systems without feed-back. The sequential digital systems without feed-back is constructed as following steps. First, we assign the states in state-transition diagram to state digit codes, then obtain the state function and predecessor table which is explaining the relationship between present states and previous states. Next, we obtained the next-state function from state function and predecessor table. Finally we realize the circuit using T-gate and decoder. The proposed method is more efficiency and systematic than previous method.

• Journal of Practical Agriculture & Fisheries Research
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• v.10 no.1
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• pp.29-41
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• 2008

This research was conducted to develop a technology transfer and farmer's extension of newly released technology of Bokto seeding method for crop and vegetable production based on the theory of Asian and Pacific Center for Transfer of Technology(APCTT). This technology has recently transferred to not only Korea but also other countries like North Korea, China, Japan, Taiwan, Russia and Africa(Cameroon, Sudan and South Africa) since 2005. It has known as a highly reduction of production cost in terms of labors, chemical fertilizer and pesticides as well as environmental friendly due to a deep and side banded placement of chemical fertilizer at basal application. In addition this technology was proven to a precision farming on sowing depth and mechanism of chemical application method and also highly resistant against disasters like typhoon, flooding, low temperature, drought and lodging due to silicate application. It has improved a constraints such as a poor seedling establishment, weed occurrence, lodging, low yield and poor grain and eating quality in the previous direct seeding methods but still have a problem in occurrence of weedy rice and ununiformed operation of wet or flooded soil condition. Also this technology has a limit in marketing and A/S system. Based on a theory of APCTT evaluation and analysis this technology may be more concentrated on establishment of a special cooperation team among researcher and scientists, extension workers, industry sections and governmental sectors in order to rapidly transfer this technology to farmer's field. Also there will be needed to operate a web site for this newly released technology to inform and exchange an idea, experiences and newly improved information. A feed back system might be operated in this technology as well to improve a technology under way on users' operation. Also user's manual will be internationally released and provided for farmer's instruction and training at field site.

• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.191-198
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• 1994

This paper deals with a feedback system for the estimation of geotechnical parameters in underground construction works. The Ordinary Least Square (OLS) Optimization Method is utilized and combined with Finite Element Program so that optimum values of ground properties can be estimated. The preperties that can be estimated are Young's and Brown's failure criteria is proposed.