• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.675-678
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• 2017

In the present, various methods have been employed to obtain the lesser thrust loss. Numerical simulations have been carried out for optimizing the thrust vector control system. Thrust vector control based on coflowing shear layer is an effective method to control the primary jet direction in the absence of moving parts. Thrust vector in symmetric nozzles is acquired by secondary flow injections that result to boundary layer separation. The pressure in secondary flow inlet was varied to check the deflection angle of jet flow.

• Geotechnical Engineering
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• v.13 no.1
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• pp.111-122
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• 1997

The calculation of phase velocities in Spectral-Analysis -of-Surface -Waves (SASW) meas urements requires unwrapping phase angles. In case of layered systems with strong stiffness contrast like a pavement system, conventional phase unwrapping algorithm to add in teger multiples of 2n to the principal value of a phase angle may lead to wrong phase volocities. This is because there is difficulty in counting the number of jumps in the phase spectrum especially at the receiver spacing where the measurements are in the transition Bone of defferent modes. A new phase interpretation scheme, called "Impulse Response Fil traction ( IRF) Technique," is proposed, which is based on the separation of wave groups by the filtration of the impulse response determinded between two receivers. The separation of a wave group is based on the impulse response filtered by using information from Gabor spectrogram, which visualizes the propagation of wave groups at the frequency -time space. The filtered impulse response leads to clear interpretation of phase spectrum, which eliminates difficulty in counting number of jumps in the phase spectrum. Verification of the IRF technique was performed by theoretical simulation of the SASW measurement on a pavement system which complicates wave propagation.opagation.

• Journal of Preventive Medicine and Public Health
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• v.39 no.3
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• pp.221-228
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• 2006

Objectives: The purpose of this study was to shed further light on the effect of modifiable health behavior risk factors on dependence in activities of daily living, defined in a multidimensional fashion. Methods: The study participants were 10,278 middle aged Americans in a longitudinal health study, the Health and Retirement Survey (HRS). A multi-stage probability sampling design incorporating the effect of population sizes (Metropolitan and non-metropolitan), ethnicity (the non- Hispanic White, the Hispanic, and the Black), and age (age 51-61) was utilized. Basic Activities of Daily Living (ADL) were measured using five activities necessary for survival (impairment in dressing, eating, bathing, sleeping, and moving across indoor spaces). Explanatory variables were four health behavior risk factors included smoking, exercise, Body Mass Index (BMI), and alcohol consumption. Results: Most participants at baseline were ADL independent (1992). 97.8% of participants were independent in all ADL's at baseline and 78.2% were married. Approximately 27.5% were current smokers at baseline, and the subjects reported moderate or heavy exercise were 74.8%. All demographic characteristics and behavioral risk factors were significantly associated with the ADL status at Wave 4 except alcohol consumption. Risk behaviors such as current smoking, sedentary life style and high BMI at Wave 1 were associated with ADL status deterioration; however, moderate alcohol consumption tended to be more related to better ADL status than abstaining at Wave 4. ADL status at Wave 1 was the strongest factor and the next was exercise and smoking affecting ADL status at Wave 4. People who were in ADL dependent at Wave 1 were 15.17 times more likely to be ADL dependent at Wave 4 than people who were in ADL independent at Wave 1. Concerning smoking cigarettes, people who kept only light exercise or sedentary life style at Wave 1 were 1.70 times more likely to be died at Wave 4 than the people who did not smoke at Wave 1. Conclusions: All demographics and health behaviors at wave 1 had consistently similar OR trends for ADL status to each other except alcohol consumption. Smoking and exercise in health behaviors, and age and gender in demographics at Wave 1 were significant factors associated with ADL group separation at Wave 4.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.2
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• pp.103-111
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• 2014

The wave power, extracted from a circular array of small power buoys, is investigated under the potential theory. It is assumed that the buoy's radius, the draft, and the separation distance are much smaller than the water depth, the wave length, and the radius of a circular deployment area. The boundary value problem involving the macro-scale boundary condition on the mean surface covered by buoys is solved using the eigenfunction expansion method. The capture width, which is defined as the ratio of the extracted power to the wave power per unit length of the incident wave crest, is assessed for various combinations of packing ratio, radius of a circular array, and PTO damping coefficient. It is found that the circular array deployment is more effective in the viewpoint of efficiency than the single large buoy of the same total displaced volume.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.489-492
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• 2000

Film Bulk Acoustic Wave Resonator(FBAR) used in microwave region was analyzed with Finite Difference Time-Domain Methods(FDTD) in this paper. FBAR have been analyzed with one dimensional Mason model analysis or Finite Element methods(FEM), but the first couldn't analyze effect of area variation and spurious characteristics, the second had difficulty in element separation because of thin electrode. So in this paper FBAR was analyzed by Finite Difference Time-Domain Methods and it's results were transformed to frequency domain using Discrete Fourier Transform.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.200-205
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• 1999

In the ferromagnetic phase with electrons for La$_{1-x}$(Ca or Sr)$_x$MnO$_3$, films, a remnant resistivity of the order of 10$^{-8}$ ${\omega}$m is observed up to 100 K and increases exponentially with temperature up to T$_c$ and above one Tesla as a function of magnetic field strength (a positive magnetoresistivity). The phase below T$_c$ is regarded as a polaronic state with a polaronic tunneling conduction. Possible p-wave condensation (or superconductor) with a parabolic density of states and the phase separation are discussed on the basis of the two-fold degeneracy of ${\varrho}_{\delta}$ orbitals.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1395-1400
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• 2003

This paper introduces a novel scheme for determining the thermal diffusivity of solids using the photothermal mirage technique. The suggested scheme extends the thermal-wave coupling method, employing the solution to the heat conduction equation in close proximity to the pump beam. Therefore, determination of thermal diffusivity is possible by detecting the mirage signal with small separation between the probe and pump beams, with enhanced intensity of the mirage signal. Though the method requires information about the probe-beam height, the absolute transverse position of the probe beam need not be known as it is automatically evaluated by the iterative-computation procedure. The thermal diffusivity of Ni is measured by the proposed scheme and the result demonstrates good agreement with the literature value to within 5 %.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.475-480
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• 2001

The flowfield of transverse jet in a supersonic air stream subjected to shock wave turbulent boundary layer interactions is simulated numerically by Generalized Taylor Galerkin(GTG) finite element methods. Effects of turbulence are taken into account with a two-equation $(k-\varepsilon)$ model with a compressibility correction. Injection pressures and slot widths are varied in the present study. Pressure, separation extents, and penetration heights are compared with experimental data. Favorable comparisons with experimental measurements are demonstrated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1513-1520
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• 2000

Complex modal testing method for rotating disks with support motion is introduced which handles the pairs of two point excitation and responses of the disk as complex input and output, respectively. This method utilizes the directivity information and the separation over the rotational speed of forward and backward traveling wave modes or bending coupled modes in the directional frequency response functions(dFRFs). This method synthesizes the normal/reverse dFRFs and complex wave dFRF, which were originally applied to rotating shaft and rotating disk, respectively, and is applied to complex system with dynamically coupled rotating disks and shaft. Experiments with a commercial hard disk drive spindle system demonstrate the validity of this method.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.59.1-59.1
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• 2017

Massive Population III black hole binary systems are one of the suggested candidate sources of the recently detected gravitational wave radiation (GWR). GWR detection from a black hole binary system requires a sufficiently short orbital separation at the time of their formation, such that they would undergo coalescence within the Hubble time. This condition cannot be simply fulfilled by a short initial period, because binary interactions such as mass transfer and common envelope evolution can largely change the orbital parameters and the masses of stellar components. Here, we discuss the possibility of black hole binary mergers from massive Pop III binary systems, using a new grid of Pop III binary evolutionary models with various initial primary masses ($20M_{\odot}{\leq}M{\leq}100M_{\odot}$) and initial separations, for different initial mass ratios (q = 0.5 - 0.9).