• ETRI Journal
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• v.43 no.3
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• pp.377-388
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• 2021

Owing to the difficulties associated with conducting millimeter-wave (mmWave) field measurements, especially in high-speed train (HST) environments, most propagation channels for mmWave HST have been studied using methods based on simulation rather than measurement. In this study, considering a linear cell layout in which base stations are installed along a railway, measurements were performed at 28 GHz with a speed up to 170 km/h in two prevalent HST scenarios: viaduct and tunnel scenarios. By observing the channel impulse responses, we could identify single- and double-bounced multipath components (MPCs) caused by railway static structures such as overhead line equipment. These MPCs affect the delay spread and Doppler characteristics significantly. Moreover, we observed distinct path loss behaviors for the two scenarios, although both are considered line-of-sight (LoS) scenarios. In the tunnel scenario, the path loss exponent (PLE) is 1.3 owing to the waveguide effect, which indicates that the path loss is almost constant with respect to distance. However, the LoS PLE in the viaduct scenario is 2.46, which is slightly higher than the free-space loss.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.87.2-87.2
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• 2013

We studied a fine-scale half ring-like structure around a pore seen from the high spectral and the high spatial resolution data. Our observations were carried out using the Fast Imaging Solar Spectrograph (FISS) and the InfraRed Imaging Magnetograph (IRIM) installed at the 1.6 meter New Solar Telescope of Big Bear Solar Observatory (BBSO) on 2012 July 19. During the observations, we found a fine-scale half ring-like structure located very close to a pore (~0.4 arcsec apart from the pore). It was seen in the far wing images of the $H{\alpha}$ and Ca II $8542{\AA}$ lines, but it was not seen in the line center images of two lines. The length of the structure is about 4200 km and the width is about 350 km. We determined its line-of-sight velocity using the Doppler shift of the centroid of the Ti II line ($6559.6{\AA}$, close to the $H{\alpha}$ line) and determined horizontal velocity using the NAVE method. we also investigated the magnetic configurations using the Stokes I, Q, U, and V maps of the IRIM. As a results, we found that it has a high blue-shift velocity (~2km) faster than the photospheric features and has a strong horizontal component of the magnetic field. Based on our findings, we suggest that it is associated with small flux emergence, which occurs very close to the pore. Even though it is very small structure, this kind of magnetic configuration can be in chare of the upper chromosphere heating, especially above the pore.

• Korean Institute of Interior Design Journal
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• v.22 no.6
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• pp.40-48
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• 2013

Utilization of CCTV in crime prevention for public safety is accepted as the most effective measure in terms of crime prevention and control. Also, it is frequently used as a device that shows evidence of an unexpected situation or record on public social relationship. However, it is rare to find a study that qualitatively accessed the monitoring performance of a certain space depending on the choice and positioning of CCTVs. Thus, this study suggested a technology that can quantitatively compare and assess the monitoring performance of CCTVs depending on view angle and effective sight range of cameras as well as the monitoring performance depending on positioning measures. For the analysis, the concept of 3-dimensional surveillance field in the form of a frustum was suggested while deriving 3-dimensional range of sight and quantitative monitoring performance by applying Isovist theory. For the analysis technology, space of analysis subject, point of view (camera), and target point (measurement node) were installed at a 3-dimensional space and in use of ray-tracing algorithm, the line segment that was visually connected between the point of view and target point was extracted and accumulated. For such verification, analysis application was constructed and then applied to four alternative models on view angle and distance as well as four alternatives on positioning in order to verify its efficacy. Through the experiment, it was possible to compare and assess visibility depending on alternatives while quantifying the results by understanding the shadow areas beyond the monitoring range.

• Journal of Radiation Protection and Research
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• v.47 no.1
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• pp.50-57
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• 2022

Background: There are several proton therapy facilities in operation or planned in Taiwan, and these facilities are anticipated to not only treat cancer but also provide beam services to the industry or academia. The simplified approach based on the Monte Carlo-based data sets (source terms and attenuation lengths) with the point-source line-of-sight approximation is friendly in the design stage of the proton therapy facilities because it is intuitive and easy to use. The purpose of this study is to expand the Monte Carlo-based data sets to allow the simplified approach to cover the application of proton beams more widely. Materials and Methods: In this work, the MCNP6 Monte Carlo code was used in three simulations to achieve the purpose, including the neutron yield calculation, Monte Carlo-based data sets generation, and dose assessment in simple cases to demonstrate the effectiveness of the generated data sets. Results and Discussion: The consistent comparison of the simplified approach and Monte Carlo simulation results show the effectiveness and advantage of applying the data set to a quick shielding design and conservative dose assessment for proton therapy facilities. Conclusion: This study has expanded the existing Monte Carlo-based data set to allow the simplified approach method to be used for dose assessment or shielding design for beam services in proton therapy facilities. It should be noted that the default model of the MCNP6 is no longer the Bertini model but the CEM (cascade-exciton model), therefore, the results of the simplified approach will be more conservative when it was used to do the double confirmation of the final shielding design.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.8
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• pp.1-7
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• 2009

This study is intended to propose the environment friendly lighting which can be excluded the element of obtrusive light(glare, spill light) and to make the sight environment of the external and internal road more comfortable as newly approaching the lower positioned lighting from the current high pole lighting. Taking account of the current situation of putting the stress on the road sight scene. It is proposed the study focused on the aesthetic design for playing a role of scenery. For this, it is searched used situation of the low light at interior of the country and abroad and tried to find the improvement. Also it is tried find out how to raise the effectiveness. And throughout the site inspection and the data searching about the road facility of a road to be installed the low height lighting, it is suggested the standard of the lighting installation and the direction for the future on the light design and development of the low height lighting which is suitable for the domestic situation.

• Geophysics and Geophysical Exploration
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• v.13 no.1
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• pp.96-101
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• 2010

A pulse radar system has been developed recently to detect dormant underground tunnels that are deeply located at depths of hundreds of metres. To check the ability of the radar system to detect an obliquely oriented tunnel, five different borehole pairs in the tunnel test site were chosen so that the horizontal lines-of-sight cut the tunnel axis obliquely, in $15^{\circ}$ steps. The pulse radar signatures were measured over a depth range of 20 m around the centre of the air-filled tunnel. Three canonical parameters, consisting of the arrival time, attenuation, and dispersion time were extracted from the first and second peaks of the measured radar signatures. Using those parameters, the radar system can detect obliquely oriented tunnels at various angles up to 45 from the transmitter-receiver line of sight.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2B
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• pp.170-177
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• 2009

In this paper, we propose the structures of the NBTC (Narrow-Beam Trisector Cell) and the WBTC(Wide-Beam Trisector Cell) in which directional antennas both at the base station and at the relay station are used. We analyze and compare total capacity of the both systems taking the co-channel interference into consideration for two channel models. Through analysis, we find the effect of LOS (Lind of Sight) path to the total capacity of NBTC structure and that of WBTC structure. Our work may be useful as a guideline to control the interference for the next generation mobile communication and WiBro systems using multi-hop relays.

• Bulletin of the Korean Space Science Society
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• 1995.04a
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• pp.21-21
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• 1995

The structures of 17GHz microwave burst for bipolar sunspots have investigated. which included the effects of the projected shapes of radio sources as they traverse across the solar disk using a magnetic loop employing a model of solenoid coils. An ensemble of high-energy electrons confined in the loop be assumed. The projected brightnesls distributions of gyrosynchrotron emission in x- and o-modes are computed and converted into total intensity and circular polarization difference at 17GHz for various heliocentric distances using numerical integration of the transfer equation along the line of sight. The results of computations at 17GHz for optical thin case will be presented. and the effects of the orientation of the loop will be discussed in detail, as well as the effect of size, position, Structure, and polarization of the emission. Also the results of the various physical P8lrameters such as the strength of magnetic field. high and low energy cut-off of accelerated electrons. spectral index and density of electrons will be preslmted. After comparing the results of model calculation with observations. we found that the observations can be well explained in terms of a loop model and its projection effect.effect.

• Journal of the Optical Society of Korea
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• v.20 no.6
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• pp.762-769
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• 2016

The dynamic modulation transfer function (MTF) for image degradation caused by sinusoidal vibration is formulated based on a Bessel function of the first kind. The presented method makes it possible to obtain an analytical MTF expression derived for arbitrary frequency sinusoidal vibration. The error obtained by the use of finite order sum approximations instead of infinite sums is investigated in detail. Dynamic MTF exhibits a stronger random behavior for low frequency vibration than high frequency vibration. The calculated MTFs agree well with the measured MTFs with the slant edge method in imaging experiments. With the proposed formula, allowable amplitudes of any frequency vibration are easily calculated. This is practical for the analysis and design of the line-of-sight stabilization system in the remote sensing camera.

• Journal of Advanced Research in Ocean Engineering
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• v.2 no.4
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• pp.192-201
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• 2016

This study examined a PD controller and its application to automatic berthing control of an unmanned surface vehicle (USV). First, a nonlinear mathematical model was established for the maneuvering of the USV in the presence of environmental forces. A PD control algorithm was then applied to control the rudder and propeller during an automatic berthing process. The algorithm consisted of two parts, namely the forward velocity control and heading angle control. The control algorithm was designed based on longitudinal and yaw dynamic models of the USV. The desired heading angle was obtained using the "line of sight" method. Finally, computer simulations of automatic USV berthing were performed to verify the proposed controller subjected to the influence of disturbance forces. The results of the simulation revealed a good performance of the developed berthing control system.