• Journal of Communications and Networks
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• v.7 no.4
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• pp.450-461
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• 2005

In this paper, we derive analytical expressions for the exact pairwise error probability (PEP) of a space-time coded system operating over spatially correlated fast (constant over the duration of a symbol) and slow (constant over the length of a code word) fad­ing channels using a moment-generating function-based approach. We discuss two analytical techniques that can be used to evaluate the exact-PEPs (and therefore, approximate the average bit error probability (BEP)) in closed form. These analytical expressions are more realistic than previously published PEP expressions as they fully account for antenna spacing, antenna geometries (uniform linear array, uniform grid array, uniform circular array, etc.) and scattering models (uniform, Gaussian, Laplacian, Von-mises, etc.). Inclusion of spatial information in these expressions provides valuable insights into the physical factors determining the performance of a space-time code. Using these new PEP expressions, we investigate the effect of antenna spacing, antenna geometries and azimuth power distribution parameters (angle of arrival/departure and angular spread) on the performance of a four-state QPSK space-time trellis code proposed by Tarokh et al. for two transmit antennas.

• Structural Engineering and Mechanics
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• v.64 no.4
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• pp.437-447
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• 2017

Explicit expressions for rapid prediction of inelastic design quantities (considering cracking of concrete) from corresponding elastic quantities, are presented for multi-storey composite frames (with steel columns and steel-concrete composite beams) subjected to service load. These expressions have been developed from weights and biases of the trained neural networks considering concrete stress, relative stiffness of beams and columns including effects of cracking in the floors below and above. Large amount of data sets required for training of neural networks have been generated using an analytical-numerical procedure developed by the authors. The neural networks have been developed for moments and deflections, for first floor, intermediate floors (second floor to ante-penultimate floor), penultimate floor and topmost floor. In the case of moments, expressions have been proposed for exterior end of exterior beam, interior end of exterior beam and both interior ends of interior beams, for each type of floor with a total of twelve expressions. Similarly, in the case of deflections, expressions have been proposed for exterior beam and interior beam of each type of floor with a total of eight expressions. The proposed expressions have been verified by comparison of the results with those obtained from the analytical-numerical procedure. This methodology helps to obtain the inelastic design quantities from the elastic quantities with simple calculations and thus would be very useful in preliminary design.

• Journal of Communications and Networks
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• v.9 no.1
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• pp.67-74
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• 2007

The performance of dual diversity receivers operating over correlated Ricean fading channels is analyzed. Using a previously derived rapidly converging infinite series representation for the bivariate Ricean probability density function, analytical expressions for the statistics of dual-branch selection combining, maximal-ratio combining, and equal-gain combining output signal-to-noise ratio (SNR) are derived. These expressions are employed to obtain novel analytical formulae for the average output SNR, amount of fading, average bit error probability, and outage probability. The proposed mathematical analysis is used to study various novel performance evaluation results with parameters of interest the fading severity, average input SNRs, and the correlation coefficient. The series convergence rate is also examined verifying the fast convergence of the analytical expressions. The accuracy of most of the theoretical performance evaluation results are validated by means of computer simulations.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1694-1703
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• 2014

Lightning induced voltage is a major factor that causes interruptions on distribution lines. In this paper, analytical expressions are proposed to evaluate a lightning induced voltage on power lines directly in the time domain without the need to apply any extra conversions. The proposed expressions can consider the widely used current functions and models in contrast to the earlier analytical expressions which had a number of limitations related to the simplification of the channel base current and the current along the lightning channel. The results show that the simulated values based on the proposed method are in good agreement with the previous studies and the proposed expressions can be used for optimizing the insulation and protection level of existing and new lines being designed.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.5
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• pp.290-297
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• 2003

Analytical Expressions of temperature dependent breakdown voltage and on-resistance for silicon power MOSFETs are induced by employing the temperature dependent effective ionization coefficient extracted from temperature dependent ionization coefficients for electron and hole, and electron mobility in silicon. The analytical results for temperature dependent breakdown voltage are compared with experimental results for tile doping concentration, 4x10$^{14}$ cm$^{-3}$ , 1x10$^{15}$ cm$^{-3}$ , 6x10$^{16}$ cm$^{-3}$ respectively. The variations of temperature dependent on-resistance and breakdown voltage dependent ideal specific on-resistance are also compared with the ones reported previously. Good fits with the experimental results ate found for the breakdown voltages within 10% in error for the temperature in the range of 77~300K at each doping concentration.

• Bulletin of the Korean Chemical Society
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• v.5 no.4
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• pp.145-149
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• 1984

The entropy and heat capacity are calculated for the Morse oscillator model in order to test the quality of the partition function recently deduced by two of us. It is found that these analytical expressions are more reliable than the usually accepted one and give better results in the calculation of thermodynamic properties.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.3
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• pp.196-205
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• 2004

Although many papers about the interleaved boost converter(IBC) have been published, there are, unfortunately, no analytical and rigorous expressions for steady-state operation of the N-phase IBC. To understand the operating characteristics of the N-phase IBC, the averaged state equation and the general steady-state solutions are derived in this paper. The general expressions of the current unbalance due to the parameter mismatch, the inductor and input current ripples, and the output voltage ripple are also presented. Through the analytical expressions presented, the steady-state characteristics of the N-phase IBC are analyzed theoretically and verified experimentally.

• Geomechanics and Engineering
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• v.10 no.2
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• pp.189-205
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• 2016

Soils are subjected to additional stresses due to the loads transferred by the foundations of the buildings. The distribution of stress in soil has great importance in geotechnical engineering projects such as stress, settlement and liquefaction analyses. The purpose of this study is to examine the shear stresses on horizontal plane below the rectangular foundations subjected to biaxial bending on an elastic soil. In this study, closed-form analytical solutions for shear stresses in x and y directions were obtained from Boussinesq's stress equations. The expressions of analytical solutions were simplified by defining the shear stress influence values ($I_1$, $I_2$, $I_3$), and solution charts were presented for obtaining these values. For some special loading conditions, the expressions for shear stresses in the soil below the corners of a rectangular foundation were also given. In addition, a computer program was developed to calculate the shear stress increment at any point below the rectangular foundations. A numerical example for illustrating the use of the presented solution charts was given and, finally, shear stress isobars were obtained for the same example by a developed computer program. The shear stress expressions obtained in this work can be used to determine monotonic and cyclic behavior of soils below rectangular foundations subjected to biaxial bending.

• Transactions of The Korea Fluid Power Systems Society
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• v.3 no.3
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• pp.1-7
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• 2006

In this paper, a theoretical analysis is carried out to study the lubrication characteristics of sealless piston for hydraulic cylinders. The analytical pressure distributions are obtained solving one-dimensional Reynolds equation with partially tapered moving piston. Nearly analytical expressions for lateral forces acting on the piston and leakage flow rate through the clearance are also presented. Using the analytical expressions, the influence of design parameters on lubrication characteristics can be easily evaluated without numerical analysis. Composite-shaped piston which minimizes the leakage flow rate is the optimum in sealless piston for hydraulic cylinder.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.1
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• pp.9-14
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• 2004

In this paper, temperature dependence of effective ionization coefficient in Si is formulated as a single polynomial function of temperature, which allows analytical expressions for breakdown voltage of Si $p^+n$ junction as a function of temperature. The analytical breakdown voltages agree well with the simulation as well as the experimental ones reported within $3\%$ in error for the doping concentrations in the range of $10^{14}cm^{-3}{\~} 10^{17}cm^{-3}$ at 100K, 300K and 500K.