• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.349-352
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• 2002

This paper describes a design of a 1bit Carry Propagate Free Adder/Subtracter (CPFA/S) VLSI using the Adiabatic Dynamic CMOS Logic (ADCL) circuit technology. Using a PSPICE simulator, energy dissipation of the ADCL 1bit CPFA/S is compared with that of the CMOS 1bit CPFA/S. As a result, energy dissipation of the proposed ADCL circuits is about 1/23 as low as that of the CMOS circuits. The transistors count, propagation-delay tittle and energy dissipation of the ADCL 4bit CPFA/S are compared with those of the ADCL 4bit Carry Propagate Adder/Subtracter (CPA/S). The transistors count and propagation-delay tittle are found to be reduced by 7.02% and 57.1%, respectively. Also, energy dissipation is found to be reduced by 78.4%. Circuit operation and performance are evaluated using a chain of the ADCL 1bit CPFA/S fabricated in a $1.21mutextrm{m}$ CMOS process. The experimental results show that addition and subtraction are operated with clock frequencies up to about 1㎒.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.337-345
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• 2002

The present study addresses a computational result of unsteady gas flow through a critical nozzle. The axisymmetric, unsteady, compressible, Wavier-Stokes equations are solved using a finite volume method that makes use of the second order upwind scheme for spatial derivatives and the multi-stage Runge-Kutta integral scheme for time derivatives. The steady solutions of the governing equation system are validated with the previous experimental data to ensure that the present computational method is valid to predict the critical nozzle flows. In order to simulate the effects of back pressure fluctuations on the critical nozzle flows, an excited pressure oscillation with an amplitude and frequency is assumed downstream of the exit of the critical nozzle. The results obtained show that for low Reynolds numbers, the unsteady effects of the pressure fluctuations can propagate upstream of the throat of critical nozzle, and thus giving rise to the applicable fluctuations in mass flow rate through the critical nozzle, while for high Reynolds numbers, the pressure signals occurring at the exit of the critical nozzle do not propagate upstream beyond the nozzle throat. For very low Reynolds number, it is found that the sonic line near the throat of the critical nozzle remarkably fluctuateswith time, providing an important mechanism for pressure signals to propagate upstream of the nozzle throat, even in choked flow conditions. The present study is the first investigation to clarify the unsteady effects on the critical nozzle flows.

• 비파괴검사학회지
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• 제35권6호
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• pp.381-388
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• 2015

The speed and oscillation directions of elastic waves propagating in the [ab0] direction of a silicon single crystal were obtained by solving Christoffel's equation. It was found that the quasi waves propagate in the off-principal axis, and hence, the directions of the phase and group velocities are not the same. The maximum deviation of the two directions was $7.2^{\circ}$. Two modes of the pure transverse waves propagate in the [110] direction with different speeds, and hence, two peaks were observed in the pulse echo signal. The amplitude ratio of the two peaks was dependent on the initial oscillating direction of the incident wave. The pure and quasi-transverse waves propagate in the [210] direction, and the oscillation directions of these waves are perpendicular to each other. The skewing angle of the quasi wave was calculated as $7.14^{\circ}$, and it was measured as $9.76^{\circ}$. The amplitude decomposition in the [210] direction was similar to that in the [110] direction, since the oscillation directions of these waves are perpendicular to each other. These results offer useful information in measuring the crystal orientation of the silicon single crystal.

• 천문학회보
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• 제44권2호
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• pp.40.3-40.3
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• 2019

Our recent observations of the Sun through strong spectral lines have revealed several important properties of the three-minute umbral oscillations inside sunspots -- the oscillations of intensity and Doppler velocity with periods of 2 to 3 minutes. The oscillations usually occur in the form of a time series of oscillation packets each of which lasts 10 to 20 minutes, not as continuous trains. Each oscillation packet is characterized by a singly peaked power spectrum of velocity oscillation. The oscillations propagate in the vertical direction from the photosphere to the corona. In the upper chromosphere, they develop into shocks that eventually collide with the transition region. When shocks propagate along a highly inclined direction, the merging of two successive shocks can take place. Once they enter the corona, they change to linear compressional waves. In the image plane, the three-minute oscillations propagate with high speeds in the transverse direction as well, usually propagating radially outwards from a point, and sometimes accompanying spiraling patterns of Doppler velocity. These observational properties can be theoretically explained by postulating the spatio-temporally localized source of fast MHD waves at a depth of about 2000 km below the surface, the excitation of slow MHD waves via mode conversion near the photosphere, and the resonance of the slow waves in the photospheric layer below the temperature minimum, and the nonlinear development of slow waves in the chromosphere.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1835-1837
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• 2004

The UHF electromagnetic waves excited by PD pulses propagate along the GIS busbar not only TEM mode, but also TE and TM mode. Generally the waves detected by the UHF sensors are those of high order modes and such waves can only propagate the higher than cut-off frequency. In this paper, computed cut-off frequency of 362[kV] GIS by each modes and simulated electromagnetic field of each propagation modes by FEM(Finite Element Method) program. Frequency band of each TEmn/TMmn modes were determinated by simulation results and were discussed optimal position of UHF sensor from this results.

• Transactions on Electrical and Electronic Materials
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• 제7권5호
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• pp.252-256
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• 2006

When a partial discharge takes place at the stator of a generator, the electrical pulse will propagate along the stator bars and the capacitor chains formed by the end part of the stator winds. On the first path, the pulse propagates as a travel wave at slow speed. On the second path, the pulse propagates at quick speed. Based on the data of the experiments on a real 50 MW steam generator, the author has found the pulses can propagate by magnetic field of the stator winding. It was studied that how to locating the partial discharge by signals coming from the different paths, including the features of signals on the two paths at time domain and frequency domain, the measurement frequency rang of the signals, the blind area, the advantage and disadvantage of this method.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권1호
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• pp.150-153
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• 2015

An energy-efficient 64-bit prefix adder is proposed for micro-server processors based on both semidynamic and bypassing structures. Prefix adders consist of three main stages i.e. propagate-generate (PG) stage, carry merge (CM) tree, and sum generators. In this architecture, the PG and CM stages consume most of the power because these are based on domino circuits. This letter proposes a semidynamic PG stage for its energy-efficiency. In addition, we adopt the bypassing structure on the CM tree to reduce its switching activity. Experimental results show 19.1% improvement of energy efficiency from prior art.

• 대한전기학회논문지:전력기술부문A
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• 제53권11호
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• pp.624-629
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• 2004

The UHF electromagnetic waves excited by PD pulses propagate along the GIS busbar not only TEM mode, but also TE and TM mode. Generally the waves detected by the UHF sensors are those of high order modes and such waves can only propagate higher than cut-off frequency. In this paper, the cut-off frequency of 362[kV] GIS for each modes is computed and the electromagnetic field of each propagation modes is simulated by FEM(Finite Element Method) program. Frequency band of each TEmn/TMmn modes was determinated by simulation results and was discussed optimal position of UHF sensor from this results.

• 한국안전학회지
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• 제13권1호
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• pp.13-18
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• 1998

It is well known in the fracture mechanics community that the fracture toughness of brittle materials, such as ceramics, can be improved improves significantly when fibers are added into the material. This is because in presence of fibers the cracks cannot propagate as freely as it can in absence of them. Fibers bridge the gap between two adjacent surfaces of the crack and reduce the crack tip opening displacement, thus make it harder to propagate. Several investigators have experimentally studied how the length, diameter and volume fraction of fibers affect the fracture toughness of chopped strand reinforced matrix composite materials. In this paper, matrix used ALS, Arizona Lunar Simulant, types of fiber used carbon steels and stainless steels. To analyze quantitatively fiber reinforced ALS composites, experimental and analytical methods was progressed. Load-displacement curve is used to experimental method, and FEM analysis program using ABAQUS is used analytical method.

• 동력기계공학회지
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• 제10권1호
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• pp.65-70
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• 2006

A study of the possible axisymmetric modes that propagate at low frequencies in buried, water-filled iron pipes is presented. It is well known that for a vacuum-pipe-vacuum system the sole non-torsional axisymmetric mode that exists at low frequencies is the fundamental L(0,1) mode. When a pipe is filled with water and still surrounded by a vacuum it is also known that another mode then appears which at low frequencies is characterized by predominantly axial water-borne displacements. In addition to these modes, this paper explores two other, less well known axisymmetric modes whose existence depends on the acoustic properties of the outer medium that surrounds a pipe. In this paper the predicted characteristics of these modes are presented.