• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.4
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• pp.427-435
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• 2009

This study deals with the analytical solution for soil-lining interaction in a deep and circular tunnel. Simple closed-form analytical solutions for thrust and moment in the circular tunnel lining due to static and seismic loadings are developed by considering the relations between displacement and interaction forces at the soil-lining interface. The interaction effect at the soil-lining interface is considered with new ratios (the normal and shear stiffness ratios). The effects of the ratios on the normalized thrust and the normalized moment are investigated.

• Journal of Advanced Navigation Technology
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• v.2 no.2
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• pp.84-99
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• 1998

As a part of closed-loop guidance law studies for anti-ballistic missile defense, a mid-course guidance law is proposed to engage the target with the predetermined attitude for increased terminal effectiveness. The proposed guidance law is based on the predicted target position calculated from a simplified solution of target motion and the estimates of an extended Kalman filter utilizing noisy nonlinear radar measurements. Extension of the proposed mid-course guidance to 3 dimensional engagements are also studied. Performance of the proposed mid-course guidance law together with a terminal guidance law in the form of conventional proportional navigation guidance is evaluated by a series of simulation studies.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.167-181
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• 2008

A pavement structure analysis model plays a very important role which can correlate input variables to performance models. In this research, a standard shell element model was developed by use of the ABAQUS program so that behaviors of concrete pavements be analyzed. The model was verified in terms of its accuracy by way of comparing the results to those gathered from closed-form Solutions, the Everfe program, and the ABAQUS program with a solid model. Many input variables were analyzed in the model, and the results were stored in a database. Based on the SPSS program, stress equations with respect to temperature and curling effects were developed. All models gave over 0.90 of R2 value except the case considering top-down curling (R2=0.86)

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.10
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• pp.1084-1090
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• 2009

This paper presents a balun consisting of a T-junction, a Right/Left Handed Transmission line(RLH-TL), and a conventional Right Handed(RH) line. It is assumed that the RLH-TL consists of N unit-cells. We provide closed-form solutions and design a very compact wideband(80 %) balun using CPW lines based on the obtained solutions. Then, we propose a capacitively loaded loop antenna designed for a uniform current distribution. The antenna resistance of the proposed antenna at resonance is about 204 ohms. The length of the unit cell is about $\lambda/12$(total length: $1\;\lambda$). The magnetic field generated from the proposed antenna is stronger than that of the conventional one by as much as 20 dB. We used a coplanar strip line(CPS) to combine the loop antenna and balun. The proposed antenna may be used as a near field UHF RFID reader antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.12
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• pp.1275-1283
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• 2014

Characteristics of PCM(Pulse Code Modulation) waveform are suitable for target tracking. Especially in terms of dwell time, it is desirable to detect and track a moving target with the single PCM waveform for a MFR(Multi-Function Radar) which carries out multiple tasks. General PCM waveform processing includes Doppler filter bank caused by the characteristics of ambiguity function, to detect target and estimate Doppler frequency, which induces hardware burden and computational complexity. We propose a ML(Maximum Likelihood) based Doppler estimator for a PCM waveform, which is the closed form suboptimal solution and computationally efficient to estimate Doppler frequency and detect a moving target.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.823-832
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• 2011

In this paper, an efficient blind carrier frequency offset (CFO) estimation method in orthogonal frequency division multiplexing (OFDM) systems is proposed. In the proposed method, we obtain two time different received OFDM symbols by using both the cyclic prefix and oversampling technique, and a cost function is defined by using the two OFDM symbols. We show that the cost function can be approximately expressed as a cosine function. Using a property of the cosine function, a formular for estimating the CFO is derived. The estimator of the CFO requires three independent cost function values calculated at three different points of frequency offset. The proposed method is very efficient in computational complexity since no searching operation for the minimum cost value is required. The proposed method reduces 97% of the amount of FFT computation, compared with the ML method. Unlike the conventional methods such as the ML method and the MUSIC] method, the accuracy of the proposed method is independent of the searching resolution since the closed form solution exists. The computer simulation shows that the performance of the proposed method is superior to those of the MUSIC and the ML method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.85-95
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• 1992

The moment distribution method has been widely used for the past sixty years for determining the end moments of structural frames. However, the method trends to show more complexity of the procedures and approximation of the results as the degree of indeterminancy increases. The previous study proposed closed form formulas for the analysis of the continuous beams up to four spans. These formulars show simpler forms and provide perfectly rigorous solution in comparision with the moment distribution method. This study proposes closed form formulas for the analysis of multi-span continuous beams which are basically similar to the equations developed in the previous study. It is shown that these formulars may also produce more rigorous results and lead to simpler calculation processes. The proposed approach may be one of the new methods for the analysis of multi-span continuous beams or the rigid frames.

• Journal of Broadcast Engineering
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• v.10 no.1 s.26
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• pp.83-102
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• 2005

The problem of video scheduling is analyzed in the framework of divisible load scheduling. A divisible load can be divided into any number of fractions (parts) and can be processed/computed independently on the processors in a distributed computing system/network, as there are no precedence relationships. In the video scheduling, a frame can be split into any number of fractions (tiles) and can be processed independently on the processors in the network, and then the results are collected to recompose the single processed frame. The divisible load arrives at one of the processors in the network (root processor) and the results of the computation are collected and stored in the same processor. In this problem communication delay plays an important role. Communication delay is the time to send/distribute the load fractions to other processors in the network. and the time to collect the results of computation from other processors by the root processors. The objective in this scheduling problem is that of obtaining the load fractions assigned to each processor in the network such that the processing time of the entire load is a minimum. We derive closed-form expression for the processing time by taking Into consideration the communication delay in the load distribution process and the communication delay In the result collection process. Using this closed-form expression, we also obtain the optimal number of processors that are required to solve this scheduling problem. This scheduling problem is formulated as a linear pro-gramming problem and its solution using neural network is also presented. Numerical examples are presented for ease of understanding.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.865-875
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• 2012

In this paper, we optimize antenna locations for a distributed antenna system (DAS) with distributed antenna (DA) ports equipped with multiple antennas under per-DA port power constraint. Maximum ratio transmission and scaled zero-forcing beamforming are employed for single-user and multi-user DAS, respectively. Instead of maximizing the cell average ergodic sum rate, we focus on a lower bound of the expected signal-to-noise ratio (SNR) for the single-cell scenario and the expected signal-to-leakage ratio (SLR) for the two-cell scenario to determine antenna locations. For the single-cell case, optimization of the SNR criterion generates a closed form solution in comparison to conventional iterative algorithms. Also, a gradient ascent algorithm is proposed to solve the SLR criterion for the two-cell scenario. Simulation results show that DAS with antenna locations obtained from the proposed algorithms achieve capacity gains over traditional centralized antenna systems.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.11
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• pp.40-46
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• 2014

We introduce a parameter estimation algorithm by using pole-zero coefficients of Pade approximation for radar active cancellation. Proposed scheme is based on relation among pole-zero coefficients of Pade approximation, parameters, and samples of received signal. A closed form solution for parameter estimation is achieved with a few samples of received signal and a simple comparison. Also, stepwise estimation algorithm is proposed to suppress beat effect which is occurred by active cancellation over long time with imperfectly estimated parameters. Simulation results show that proposed scheme performs faster radar active cancellation with lower computational complexity than the conventional schemes.