• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1511-1517
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• 2014

Based on the simulation model for phase noise effect, the phase noise performance of communication system using the M-ary APSK modulation method is analyzed in this paper. The phase noise effects for APSK higher order modulation method are modeled by considering the signal constellations of the modulation methods. The simulation model is verified by comparing the analytic results for lower order modulation signals with simulated results for those modulation signals. Based on the simulation model, then, the phase noise effects for M-ary APSK are analyzed. The simulated results for PSK lower order modulation signals are in agreement with the results by the analytic model in the order of 1 %. The proper phase noise effects for M-ary APSK modulation signals are deduced by the simulation model. Also, the required signal-to-noise ratios of phase noise are proposed for phase noise degradations, which are used as the design parameter that considers the phase noise effect.

• Structural Engineering and Mechanics
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• v.89 no.2
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• pp.199-211
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• 2024

The loading capacity of engineering structures/components reduces after the initiation and propagation of crack eventually leads to the final failure. Hence, it becomes essential to deal with the crack and its effects at the design and simulation stages itself, by detecting the prone area of the fracture. The phase-field (PF) method has been accepted widely in simulating fracture problems in complex geometries. However, most of the PF methods are formulated with second order continuity theoryinvolving C⁰ continuity. In the present study, PF method based on fourth-order (i.e., higher order) theory, maintaining C¹ continuity has been proposed for ductile fracture simulation. The formulation includes fourth-order derivative terms of phase field variable, varying between 0 and 1. Applications of fourth-order PF theory to ductile fracture simulation resulted in novelty in this area. The proposed formulation is numerically solved using a two-dimensional finite element (FE) framework in 3-layered manner system. The solutions thus obtained from the proposed fourth order theory for different benchmark problems portray the improvement in the accuracy of the numerical results and are well matched with experimental results available in the literature. These results are also compared with second-order PF theory and a comparison study demonstrated the robustness of the proposed model in capturing ductile behaviour close to experimental observations.

• Journal of computational fluids engineering
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• v.14 no.4
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• pp.13-22
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• 2009

A two-phase (gas and liquid) flow analysis solver, named CUPID, has been developed for a realistic simulation of transient two-phase flows in light water nuclear reactor components. In the CUPID solver, a two-fluid three-field model is adopted and the governing equations are solved on unstructured grids for flow analyses in complicated geometries. For the numerical solution scheme, the semi-implicit method of the RELAP5 code, which has been proved to be very stable and accurate for most practical applications of nuclear thermal hydraulics, was used with some modifications for an application to unstructured non-staggered grids. This paper is concerned with the effects of interpolation schemes on the simulation of two-phase flows. In order to stabilize a numerical solution and assure a high numerical accuracy, the second-order upwind scheme is implemented into the CUPID code in the present paper. Some numerical tests have been performed with the implemented scheme and the comparison results between the second-order and first-order upwind schemes are introduced in the present paper. The comparison results among the two interpolation schemes and either the exact solutions or the mesh convergence studies showed the reduced numerical diffusion with the second-order scheme.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.3
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• pp.910-932
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• 1996

A problem of determining the effective conductivity of a useful model of sphere-matrix type, disordered three-phase composite media is considered. Specifically, a three-phase media in which two-phase composite spheres, consisting of spheres of conductivity $k_2$((phase 2) and concentric shells of conductivity $k_3$(phase 3), are randomly distributed in a matrix of conductivity $k_1$( (phase 1) is considered. As for the structure models configuring three-phase composite media, three different structure models of PCS, PS-1 and PS-2 models are defined, which are analogous to well-established PCS, PS structure models of two-phase composite media. Futhermore, a generalized PS-PCS structure model is proposed to incorporate thesee three different models in one. Effective condectivity $k^{\ast}$of multiphaes composite media is greatly influenced by the phase connectivity of each disspersed phase material, as well as phase conductivities and phase volume fractions. Phase connectivity of three-phase PCS, PS-1, PS-2 composite media is quantified by the impentrability parameter $\lambda$. Mathematically rigorous first-order cluster bounds on $k^{\ast}$ are derived for these models of three-phase composite media, and as computation examples, first-order cluster bounds on $k^{\ast}$ for three-phase composites consisting of largely different phase conductivities are computed and compared as function of concnectivity parpmeter $\lambda$. Results and discussions are given.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.9
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• pp.994-1000
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• 2004

We studied the characteristics of annular phase gratings as spatial frequency filters. We first calculated the Fraunhofer diffraction patterns of annular gratings and then got the modulation transfer function (MTF) from the zeroth order Hankel transform of the intensity distribution function. Binaryphase annular grating shows higher diffraction efficiency than binary phase rectangular grating. But the MTF decreases linearly in the low-frequency region as that of rectangular grating does. The diffraction pattern of 4-phase annular grating is similar to that of 2-phase grating and hence MTFs of the two are much alike. For 8-phase annular grating, the 7th order diffracted beam is the lowest one next to the first. Consequently, the diffraction efficiency is very high and the MTF graph is curved upward. The diffracted beams except the first order are negligible and hence the MTF characteristics are more improved in the case of 16-phase grating. But the degree of improvement becomes lowered c(Impaled with 8-phase grating. We made a 16-phase annular grating and measured its MTF. The experimental result agrees well with the calculated one.

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.6-8
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• 2000

The specific heat of a partly deuterated triglycine selenage (DTGSe) crystal under $\gamma$-irradiation was measured. It was shown that $\gamma$-irradiation defects changed the thermodynamic behavior of DTGSe crystal in a small dose region. The order of the phase transition changed from the first to the second at D=0.3 MR.

• Journal of Korean Society of Transportation
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• v.14 no.2
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• pp.45-58
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• 1996

In a large signal intersection, it is the most important to set phase sequences and phase intervals of traffic signal in order to improve the efficiency of the capacity as well as safety. These setting allows to select the best sequence of signal phase among several alternatives, and thus to rearrange the starting and ending points of the individual phase using an effective interphase periods (EIP). The EIP is a gap between previous and current traffic movements at a potential collision point in an intersection. Each of traffic movements has an equality for safety and efficiency at the balanced condition of EIP. This paper presents how to set optimally the phase sequences and intervals of traffic signal in an intersection using phase based approach. And in the second part, we applied the theory developed in the first part. In particular, a numerical example of phase base signal setting is presented using a matrix computation method in order to select the best sequence among several alternatives, and thus to rearrange the starting and ending points of the individual phase using the EIP. This method also allows to apply to optimum signal setting even in five-lag or staggered-type intersection.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.450-457
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• 2003

In this paper, we studied the effect of asymmetrical 3rd order IMD of power amplifier due to changes in modulation frequency on IMD cancellation performance. The phase extraction method for determining asymmetric rate for phase distortion of IMD is proposed and the phase difference between lower and upper 3rd order IMD is measured by this method. The phase compensation circuit to decrease the phase difference is also designed and fabricated. From the measurement results using the phase compensation circuit applied to 5 W RF power amplifier fur PCS applications, the 3rd order IMD cancellation performance can be achieved up to 2-tone spacing 1.5 MHz (phase difference within 10$^{\circ}$).

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.8
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• pp.529-535
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• 2000

In this paper, a current control system of a single phase PWM AC/DC converter using a reduced-order Luenberger observer without source voltage sensors is proposed. The sinusoidal input current and unity input power factor are realised based on the estimated source voltage performed by the reduced-order Luenberger observer using actual currents and DC link voltage. The poles of the reduced-order Luenberger observer are placed in the left half plane of s-plane by the pole-placement method in order to acquire the stability of the observer. The magnitude and the phase of the estimated source voltage are used to accomplish the unity power factor. The proposed method is implemented by DSP(Digital Signal Processor). Experimental Results verify that the reduced-order observer estimates the source voltage without the estimation error and the control system accomplishes the unity power factor, and constant DC link voltage.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.8
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• pp.1145-1151
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• 1989

New method to calculate the characteristics of the dominant and higher order modes of waveguide latching phase shifters are presented. Due to the tensor permeability, E and H fields inside the ferrite are expanded in terms of the LSE and LSM eigenmodes of the dielectric-slab-loaded waveguide. The equivalent coupled transmission line equations on the transverse plane are derived to obtain the dispersion characteristics and the E and H field distributions. Numerical results at X-band are compared with those published previously. The derived field distributions can be used to suppress the higher order modes of the latching phase shifters, so that the phase shift from the dominant mode only contributes the performance of the phase shifters.