• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.960-963
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• 2003

Sound intensity method is well known as a visualization technique of sound field and sound propagation in noise control. Sound intensity is a vector quantity that describes the magnitude and the direction of net flow of acoustic energy at a given position. The current measuring method is expensive and difficult to identify the noise source exactly. In this paper, we have studied the noise source identification and the characteristics of noise source of rotary compressor for air conditioner using complex sound intensity method. The new method for instantaneous sound intensity is also proposed and it is useful for transient state and steady state. The criteria of these state, select auto correlation coefficient. The advantage, simplicity and economic attribution of this method are verified by analyzing the characteristics of noise source with instantaneous sound intensity compared to mean sound intensity.

• Geomechanics and Engineering
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• v.22 no.2
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• pp.187-196
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• 2020

The changeable stress environment directly affect the propagation law of a stress wave. Stress wave propagation tests in sandstone with different axial stresses were carried using a modified split Hopkinson Pressure bar (SHPB) assuming the sandstone has a uniform pore distribution. Then the waveform and stress wave energy dissipation were analyzed. The results show that the stress wave exhibits the double peak phenomenon. With increasing axial stress, the intensity difference decreases exponentially and experiences first a dramatic decrease and then gentle development. The demarcation stress is σ/σ_c=30%, indicating that the closer to the incident end, the faster the intensity difference attenuates. Under the same axial stress, the intensity difference decreases linearly with propagation distance and its attenuation intensity factor displays a quadratic function with axial stress. With increasing propagation distance, the time difference decays linearly and its delay coefficient reflects the damage degree. The stress wave energy attenuates exponentially with propagation distance, and the relations between attenuation rate, attenuation coefficient and axial stress can be represented by the quadratic function.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.4
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• pp.451-455
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• 2001

The epitaxial growth of Ge on the clean and surfactant(Sn) adsorbed surface of Ge(111) was studied by the intensity oscillation of a RHEED specular spot. In the case of epitaxial growth without the adsorbed surfactant, the RHEED intensity oscillation was stable and periodic up to 24ML at the substrate temperature of $200^{\circ}C$. Therefore the optimum temperature for the epitaxial growth of Ge on clean Ge(111) seems to be $200^{\circ}C$. However, in the case of epitaxial growth with the adsorbed surfactant, the irregular oscillations are observed in the early stage of the growth. The RHEED intensity oscillation was very stable and periodic up to 38ML, and the $d2{\times}2$ structure was not charged with continued adsorption of Ge at the substrate temperature of $200^{\circ}C$. These results may be explained by the fact that the diffusion length of Ge atoms is increased by decreasing the activation energy of the Ge surface diffusion, resulted by segregation of Sn toward the growing surface. From the desorption process, the desorption energy of Sn in Ge $\sqrt{5}{\times}\sqrt{5}$ structure is observed to be 3.28eV.

• Journal of Power System Engineering
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• v.5 no.1
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• pp.21-26
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• 2001

This paper represents the turbulent intensity, the turbulent kinetic energy and Reynolds shear stress in the X-Y plane of cone type swirl gas burner measured by using X-probe from the hot-wire anemometer system. The experiment is carried out at flowrate 350 and $450{\ell}/min$ respectively in the test section of subsonic wind tunnel. The turbulent intensity and the turbulent kinetic energy show that the maximum value is formed in the narrow slits distributed radially on the edge of a cone type swirl burner, hence, the combustion reaction is anticipated to occur actively near this region. And the turbulent intensities ${\upsilon}\;and\;{\omega}$ are disappeared faster than the turbulent intensity u due to the inclined flow velocity ejecting from the swirl vanes of a cone type baffle plate of burner. Moreover, the Reynolds shear stress $u{\upsilon}$ is distributed about three times as large as the Reynolds shear stress $u{\omega}$ in the outer region of the cone type gas burner.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.417-431
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• 2020

In this study, a fundamental investigation was made on how to use LiDAR technology to determine the degree of weathering and alteration of rock mass. The purpose of the study was to identify the affecting parameters to LiDAR intensity and to quantitatively assess the relations among them through laboratory-scale experiment. A few potential affecting parameters were selected including scanning distance, incidence angle, surface roughness, surface color, mineral composition, and water saturation. In the experiment, FARO LiDAR unit was used for twelve different types of specimen. It was observed that the intensity was affected by, in the order of importance, surface color, incidence angle, scanning distance, property of rock, water condition, and surface roughness.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.56.3-56.3
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• 2019

We are currently living in the era of the wide field cosmological surveys, either spectroscopic such as Dark Energy Spectrograph Instrument or photometric such as the Dark Energy Survey or the Large Synoptic Survey Telescope. By analyzing the distribution of matter clustering, we can use the growth of structure, in combination with measurements of the expansion of the Universe, to understand dark energy or to test different models of gravity. But we also live in the era of multi-tracer or multi-messenger astrophysics. In particular, during the next decades radio surveys will map the matter distribution at higher redshifts. Like in optical surveys, there are radio imaging surveys such as continuum radio surveys such as the ongoing EMU or spectroscopic by measuring the hydrogen 21cm line. However, we can also use intensity mapping as a low resolution spectroscopic technique in which we use the intensity given by the emission from neutral hydrogen from patches of the sky, at different redshifts. By cross-correlating this maps with galaxy catalogues we can improve our constraints on cosmological parameters and to understand better how neutral hydrogen populates different types of galaxies and haloes. Creating realistic mock intensity mapping catalogues is necessary to optimize the future analysis of data. I will present the mock neutral hydrogen catalogues that we are developing, using the Horizon run 4 simulations, to cross-correlate with mock galaxy catalogues from low redshift surveys and I will show the preliminary results from the first mock catalogues.

• Journal of the Korean Solar Energy Society
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• v.33 no.6
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• pp.19-25
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• 2013

Energy generation from an instrumented Skystream 3.7 small wind turbine was used to investigate the effect of ambient turbulence levels on wind turbine power output performance. It is widely known that elevated ambient turbulence level results in decreased energy production, especially for large sized wind turbine. However, over the entire wind speed range from cut in to the rated wind speed, the measured energy generation increased as ambient turbulence levels elevated. The impact degree of turbulence levels on power generation was reduced as measured wind speed approached to the rated wind speed of 13m/s.

• Journal of the Korean Regional Science Association
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• v.33 no.1
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• pp.3-16
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• 2017

This paper analyzed 16 regional total factor energy efficiency (TFEE) of the Korean manufacturing sector using data envelopment analysis method for the period of 2005-2013. According to the empirical results, it is necessary to use TFEE as well as partial energy efficiency defined by the ratio of energy usage to output (energy intensity) when we compare energy efficiency. Secondly, TFEE in the Korean manufacturing sector is quite different across 16 regions. For example, Gangwon province should improve energy efficiency by 55% compared to Seoul, Gwangju, Ulsan, and Gyeongbuk which are located on production frontier. Furthermore, the estimation of panel tobit regression model showed that the higher non fossil fuel using, the higher production share of large-sized firms, the lower energy intensity, and the lower capital-labor ratio could have positive effect on TFEE.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11B
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• pp.1383-1388
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• 2011

Due to many recent activities on enforcement of the intensified environmental regulation such as the policies of curbing the greenhouse gas and the Restriction of Hazardous Substances (RoHS), the usage of Light emitting diode (LED) has been rapidly increased and energy efficient management of LED light system is regarded as an important technology to enhance the energy efficiency. In this paper, we propose an energy-efficient control scheme of LED light, being composed of multiple light sources. The proposed scheme controls the intensity of LED light source to minimize the total intensity while providing the quality of lighting service. The intensity of light is assumed to be proportional to power consumption, thus the objective is to minimize the total power consumption. A linear programming problem is formulated to find the optimal intensity of each light source and procedure to apply the proposed scheme in the real system is suggested. The performance evaluation results elucidate that the proposed scheme achieves over 20% improvement in power consumption of light intensity in comparison with the conventional dimming control scheme.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2019.05a
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• pp.74-75
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• 2019