• Tunnel and Underground Space
• /
• v.25 no.5
• /
• pp.462-469
• /
• 2015

This study carried out a topographic survey at a small-scale open-pit limestone mine in Korea (the Daesung MDI Seoggyo office) using a popular rotary-wing unmanned aerial vehicle (UAV, Drone, DJI Phantom2 Vision+). 89 sheets of aerial photos could be obtained as a result of performing an automatic flight for 30 minutes under conditions of 100m altitude and 3m/s speed. A total of 34 million cloud points with X, Y, Z-coordinates was extracted from the aerial photos after data processing for correction and matching, then an orthomosaic image and digital surface model with 5m grid spacing could be generated. A comparison of the X, Y, Z-coordinates of 5 ground control points measured by differential global positioning system and those determined by UAV photogrammetry revealed that the root mean squared errors of X, Y, Z-coordinates were around 10cm. Therefore, it is expected that the popular rotary-wing UAV photogrammetry can be effectively utilized in small-scale open-pit mines as a technology that is able to replace or supplement existing topographic surveying equipments.

• Journal of the Korea Computer Graphics Society
• /
• v.23 no.1
• /
• pp.25-32
• /
• 2017

This paper proposes a novel acceleration method for particle based large scale fluid simulation. Traditional particle-based fluid simulation has been implemented by interacting with physical quantities of neighbor particles through the Smoothed Particle Hydrodynamics(SPH) technique[1]. SPH method has the characteristic that there is no visible change compared to the computation amount in a part where the particle movement is small, such as a calm surface or inter-fluid. This becomes more prominent as the number of particles increases. Previous work has attempted to reduce the amount of spare computation by adaptively dividing each part of the fluid. In this paper, we propose a technique to calculate the motion of the entire particles by using the physical quantities of the near sampled particles by sampling the particles inside the fluid at regular intervals and using them as reference points of the fluid motion. We propose a technique to adaptively generate a triangle map based on the position of the sampled particles in order to efficiently search for nearby particles, and we have been able to interpolate the physical quantities of particles using the barycentric coordinate system. The proposed acceleration technique does not perform any additional correction for two classes of fluid particles. Our technique shows a large improvement in speed as the number of particles increases. The proposed technique also does not interfere with the fine movement of the fluid surface particles.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.05a
• /
• pp.443-446
• /
• 2003

This paper implement Remote Meter Reading System which is used Bluetooth and SMS in CDMA. This System propose system which tan detect a total amount of gas, electricity or water without a meterman, at home BlueTooth is a close range wireless communication technology which uses a wireless frequency 2.4GHz and has a high trust and self error correction technology according to a low power consumption quality and a high-speed frequency hopping. This makes get a high trust concerning a data transmission than an existing modem. In addition, though wireless modem is restricted by a minimal of a wireless terminal, it will be possible to coincide with the function of the portable with the low power consumption quality by using Bluetooth. And as the system on a chip of module progresses, the possibility of the small size is present. Nowadays, SMS Protocol in CDMA for have a network function based on PPP in CDMA Phone. The proposed Remote Meter Reading System to get more nobility, efficiency, and have good function. SMS Protocol in CDMA have profits which is low power, low cost, and low microwave output.

• Journal of Korean Ophthalmic Optics Society
• /
• v.18 no.2
• /
• pp.149-156
• /
• 2013

Purpose: The aim of this study was to determine a suitable type and size of Hangul fonts for printed materials in the presbyopic age. Methods: Based on the most common Hangul fonts used today, three types of fonts were used Hamchrombatang, Sinmoonmyungjo and Sinmyungjo at small font sizes in the range 9-11 point (pt). Subjects were 101 volunteers aged 41 through 85 years. Near visual acuity (VA) was corrected to read VA 0.5 at 40 cm after distance correction. The subjects were asked to read words containing 88 characters in 10 pt after a question about preference. Readability was assessed by reading rate that was calculated as the number of words read correctly in one minute (words per minute, wpm). Results: The most preferred font type was Simmyungjo at small font sizes. Although preferred font sizes were different in each font type, Sinmyungjo was generally preferred at 10 pt more than other fonts. Hamchrombatang and Sinmyungjo were read significantly faster than Sinmoonmyungjo. There was a weak negative relationship between readability and age in Sinmyungjo. In comparing between the top 10% and the bottom 10% group sorted by reading rate, the top group showed lower average age and addition than the bottom group, however there were no significant differences in reading rate among the fonts. Conclusions: Although increasing age tends to be low in readability for Sinmyungjo, in the light of preferred font and readability, it is recommended to use a 10 pt Sinmyungjo font in printed materials for the presbyopic age.

• Environmental and Resource Economics Review
• /
• v.17 no.4
• /
• pp.813-843
• /
• 2008

This paper investigates the presence of long-run and short-run price asymmetries in weekly gasoline prices from January 1997 to July 2008. In accordance with distribution channels, wholesale and retail stages are analyzed separately. An approach based on TAR and M-TAR cointegration tests, which entail matching asymmetric ECMs, is employed. For wholesale prices, asymmetries in the links with crude oil prices and exchange rates are found for both ECMs in the long-run and short-run. Exchange rates appear to play more significant role than crude oil prices in explaining the short-run price asymmetry. The rise in crude oil prices or exchange rates has statistically significant major impact on the increase of wholesale prices on the second week, not immediately as expected in the concept of 'rockets and feathers'. And asymmetrically, the fall does not have any statistically significant effect on the same period. The finding seems to be somewhat unusual. However, for retail prices, asymmetry m connection with wholesale prices is only revealed in the long-run. A symmetric price adjustment can be assumed in the short-run. Contrary to the long-run asymmetry found in the wholesale stage, in the retail stage, the speed of adjustment for negative deviations toward long-run equilibrium is faster than for positive ones, which is a phenomenon not favorable to consumers.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.1
• /
• pp.680-687
• /
• 2018

Borehole radar is a radar used for underground resources and geological exploration purposes. It needs a high-speed sampler to transmit electromagnetic waves with a pulse width of several ns and to receive reflected waves of several tens to several hundreds of MHz reflected from the object to be surveyed. ETS (Equivalent-Time Sampling), which can achieve sampling performance of several GHz with a sampling frequency of several tens of MHz, is suitable for use as a sampler of a borehole radar receiver. In this paper, we propose a method to control the sampling clock delay, which is the most important factor in ETS sampler design, using four clocks with phase difference of $90^{\circ}$ for one clock source. The proposed method can reduce the time required to acquire the data within the set interval by 1/25 than the conventional method using the delay generator. When the implemented sampler is applied to the receiver of existing borehole radar, it is possible to accumulate 58 additional times due to the shortened sampling time. In addition, by using one delay control logic compared with the conventional method using several sampling clock delay control logic in order to satisfy the target sampling range, it is possible to omit the correction process which was necessary in the past. As a result, the structure of the system can be simplified and a uniform sampler can be realized.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.26 no.5
• /
• pp.531-541
• /
• 2020

In this study, a computed tide of a real tide was introduced to improve the numerical solutions for tides and tidal flow simulations. The real tide was defined considering the nodal modulation amplitude, phase correction factor, astronomical argument, and tidal harmonic constants of all the constituents. The numerical simulation was performed using the real tide parameters for the west-south coastal waters of Korea, where the observation data for tides, tidal currents, waves, and winds over two seasons exist. The tidal flow simulation of the real tide was simulated successfully. The correlation coefficient between the observed and calculated values was 1.0, which indicated both accurate amplitude and phase. The U- and V-components of the tidal current obtained for the real tide had average valid correlations of 0.83 and 0.936, respectively. The speed error for the residual current was 0.006 m/s on the average, which indicated an insignificant difference, and the directional behavior of the residual current was very similar. In addition, the velocity error was attributed to various weather effects, such as high waves and wind storms. Therefore, this model is expected to improve current solutions provided that weathering forces, such as waves and winds, are considered.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.17 no.5
• /
• pp.200-209
• /
• 2018

This study proposed a method to select existing facilities as a landmark in order to reset accumulated errors of dead reckoning in a tunnel difficult to receive GNSS signals in automated driving. First, related standards and regulations were reviewed in order to survey 'variety' on shapes and installation locations as a feature of facilities. Second, 'recognition' on facilities was examined using image and Lidar sensors. Last, 'regularity' in terms of installation locations and intervals was surveyed through related references. The results of this study selected a fire fighting box / lamp (50m), an evacuation corridor lamp (300m), a lane control system (500m), a maximum / minimum speed limit sign and a jet fan as a candidate landmark to reset positioning errors. Based on those facilities, it was determined that error correction was possible. The results of this study are expected to be used in repositioning of automated driving vehicles in a tunnel.

• The Journal of the Acoustical Society of Korea
• /
• v.32 no.6
• /
• pp.494-501
• /
• 2013

The convolution code(CC) of code rate 1/2 as a forward error correction (FEC) in Quadrature Phase Shift Keying (QPSK) is applied to decrease bit error rate (BER) by background noise and multipath in shallow water acoustic channel. Ratio of transmitting signal bandwidth to channel coherence bandwidth is defined as frequency selectivity index. BER and bit energy-to-noise ratio gain of transmitted signal according to frequency selectivity index are evaluated. In the results of indoor water tank experiment, BER is well matched theoretical results at frequency selectivity index less than about 1.0. And bit energy-to-noise ratio gain is also matched theoretical value of 5 dB. BER is effectively decreased at frequency selective multipath channel with frequency selectivity index higher than 1.0. But bit energy-to-noise ratio greater than a certain size in terms of CC weaving is effective in reducing bit errors. In the results, the defined frequency selectivity index in this study could be applied to evaluate a performance of CC in multipath channel. Also it could effectively reduced BER in a low speed underwater acoustic communication system without an equalizer.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.11
• /
• pp.861-871
• /
• 2020

Raising the speed of the momentum wheel in the CMG increases the unintended force and torque caused by mass imbalance. This unintended force and torque should be minimized to get the better quality of satellite SAR image because they lead to the vibration of the output image. This paper shows the works on compensating the static imbalance and couple mass imbalance in the CMG wheel. First, the force and torque at the center of mass generated by the mass imbalance were predicted through M&S analysis. Second, the force and torque were estimated similarly through the M&S analysis when the measurement point was moved from the rotation center. Third, the measurement configuration for the force and torque by the mass imbalance was described. Fourth, the change of the force and torque by adding the specified mass to the momentum wheel was observed after comparing the measurements with the results of the M&S. And finally, the effect of the compensation was analyzed by comparing the force and torque before and after the correction while 24Nm class CMG was running in the standby mode.