• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.5
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• pp.591-596
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• 1986

A binary continuous phase frequency shift keying (CPFSK), whose phase is a continuous function of time and instantaneous frequency is constant, is a bandwidth efficient constant envelope signalling scheme. A transmitting signal is formed by combined coding of a convolutional encoder and a binary CPFSK modulator. The signal is transmitted throuth additive white Gaussian noise(AWGN) channel. If the received signal is detected by a coherent maximum likelihood(ML) receiver, error probability can be expressed approximately in terms of minimum Euclidean distance. We propose rate 2/4 codes for the improvement of error performance without increating the data rate per bandwidth and the receiver complexity. Its minimum Euclidean distances are compared with those of rate \ulcornercodes as a function of modulation index and observation interval.

• Journal of the Korean Regional Science Association
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• v.13 no.2
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• pp.45-54
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• 1997

A regional economy is characterized as a spatial economy. However the literature shows that it has been treated as a point economy since space is little recognized in regional modeling due to mathematical complication. This leads to the fact that regional model does not sufficiently represent regional characteristic. This paper attempts to construct a regional growth model in a partial equilibrium framework specifically taking into consideration land as a primary factor. The model is formulated largely neoclassical. Labor is assumed to move in response to differences in the wage rate, while capital is perfectly mobile across regions. The paper shows that two growth equilibrium points exist, one stable equilibrium point and the other unstable equilibrium point. The unstable growth equilibrium indicates the existence of minimum threshold that a region must overcome the minimum threshold to grow constantly. Consequently, directions of regional growth are characterized by two growth paths depending on the initial condition of a region. That is to say, a region below the minimum threshold is converging toward the lower stable equilibrium point over time. When a regional economy initially lies above the minimum threshold, it will grow forever. A regional economy is not thus necessarily converging a stationary is not thus necessarily converging a stationary equilibrium point through factor movement. Finally, the impacts of the presence of agglomeration economies and diseconomies are analyzed through the phase diagram. The paper also shows that agglomeration economies result in lowering the minimum threshold and in escalating the level of stable equilibrium However, when agglomeration diseconomies prevail, the results are opposite, i.e., rising the minimum threshold of growth and lowering the growth level of stable equilibrium.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.2 s.344
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• pp.56-65
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• 2006

In this paper, we introduce modified difference type symbol timing detection method of simple structure and show the relations between S/N ratio and timing detection performance which less influenced by multipath channel delay profile and added noise level and it show very exact GI detection performance characteristics. In the computer simulations, 4 symbol time duration of short and long training of IEEE802.11a standard OFDM frame are used for symbol synchronization timing detection. The computer simulation results show the very exact symbol timing detection performance characteristic within 1 sample error of OFDM signal regardless channel delay profile from minimn phase channels of phase rotation ${\pi}/2$ to non-minimum phase channels of phase rotation ${\pi}/2$ of received OFDM signal and added noise level in channel.

• Water for future
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• v.28 no.2
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• pp.169-180
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• 1995

The cost of a looped pipe network is affected by a set of loop flows. The mathematical model for optimizing the looped pipe network is expressed in the optimal set of loop flows to apply to a stochastic optimization method. Because the feasible region of the looped pipe network problem is nonconvex with multiple local optima, the Modified Stochastic Probing Method is suggested to efficiently search the feasible region. The method consists of two phase: i) a global search phase(the stochastic probing method) and ii) a local search phase(the nearest neighbor method). While the global search sequentially improves a local minimum, the local search escapes out of a local minimum trapped in the global search phase and also refines a final solution. In order to test the method, a standard test problem from the literature is considered for the optimal design of the paralled expansion of an existing network. The optimal solutions thus found have significantly smaller costs than the ones reported previously by other researchers.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.137-139
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• 1991

This paper proposes a minimum power factor control for maximum efficiency operation of an induction motor, under low load condition. Minimum input or maximum efficiency operation is achived by properly adjusting the amplitude of the stator voltage, with the three phase AC voltage controller. Through the simulation, the relationships between the delay angle and input power under various load conditions are examined. Experimental results are also given, which show good coincidence with the simulation results.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.383-387
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• 1989

In this paper, an adaptive algorithm for processes with unmeasured deterministic disturbances is presented. This algorithm is simple to synthesize an adaptive controller with desired pole/zero assignment. The internal stability requirement is achieved so that this algorithm can easily handle any minimum or non-minimum phase system. Some simulations are given to show the applicability of this approach.

• Proceedings of the KIEE Conference
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• 1983.07a
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• pp.123-125
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• 1983

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.2
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• pp.104-110
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• 2003

This paper proposed a simple 180$^{\circ}$ MMIC phase shifter for wideband application. The phase shifter simply consists of a Lange coupler and two GaAs PIN diodes. The measured performance of the phase shifter in the 2 to 6 GHz band shows a maximum phase error of less than 13$^{\circ}$, maximum 3.2 dB insertion loss, and minimum 6.3 dB return loss.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.1
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• pp.117-120
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• 2008

This paper investigates the convergence condition of ADILC(iterative learning control with advanced output data) for nonminimum phase systems. ADILC has simple learning structure including both minimum phase and nonminimum phase systems. However, for nonminimum phase systems, the overall time horizon must be considered in input update law. This makes the dimension of convergence condition matrix large. In this paper, a new sufficient condition is proposed to satisfy the convergence condition. Also, it has been shown that this sufficient condition can be satisfied although it is not full impulse response.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.613-616
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• 2003

This paper describes the design and implementation of wideband 360$^{\circ}$ phase shifter by using I/Q vector method. One of four quadrants was selected by a switching operation and the desired phase value was obtained by varying attenuation level of attenuator located in I/Q path. The minimum phase RMS error of 3.6$^{\circ}$ and the maximum phase RMS error of 25.2$^{\circ}$ were measured over 6~180Hz frequency range. Those characteristics are good enough for the requirement of ECM radar equipment. The phase values can be adjusted by control module.