• 대한원격탐사학회지
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• 제37권1호
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• pp.1-11
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• 2021

This study measures the change of ice flow velocity of David Glacier, one of the fast-moving glaciers in East Antarctica that drains through Drygalski Ice Tongue. In order to effectively observe the rapid flow velocity, we applied the offset tracking technique to Sentinel-1A SAR images obtained from 2016 to 2020 with 36-day temporal baseline. The resulting velocity maps were averaged and the two relatively fast points (A1 and A2) were selected for further time-series analysis. The flow velocity increased during the Antarctic summer (around December to March) over the four years' observation period probably due to the ice surface melting and reduced friction on the ice bottom. Bedmap2 showed that the fast flow velocities at A1 and A2 are associated with a sharp decrease in the ice surface and bottom elevation so that ice volumetric cross-section narrows down and the crevasses are being created on the ice surface. The local maxima in standard deviation of ice velocity, S1 and S2, showed random temporal fluctuation due to the rotational ice swirls causing error in offset tracking method. It is suggested that more robust offset tracking method is necessary to incorporate rotational motion.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.13-17
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• 2006

RoeM and AUSMPW+ schemes are two of the most accurate and efficient schemes which are recently developed for the analysis of single phase gas dynamics. In this paper, we developed two-phase versions of these schemes for the analysis of gas-liquid large density ratio two-phase flow. We adopt homogeneous equilibrium model (HEM) using mass fraction to describe different two phases. In the Eulerian-Eulerian framework, HEM assumes dynamic and thermal equilibrium of the two phases in the same computational mesh. From the mixture equation of state (EOS), we derived new shock-discontinuity sensing term (SDST), which is commonly used in RoeM and AUSMPW+ for the stable numerical flux calculation. The proposed two-phase versions of RoeM and AUSMPW+ schemes are applied on several air-water two-phase test problems. In spite of the large discrepancy of material properties such as density, enthalpy, and speed of sound, the numerical results show that both schemes provide very satisfactory solutions.

• 대한원격탐사학회지
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• 제11권1호
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• pp.19-29
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• 1995

The surface velocities were estimated by the Maximum Cross Correlation(MCC) method and an inverse method from AVHRR/SST. In the results of MCC, discontinuous flow fields were estimated in the case that cross correlation coefficient was above 0.5 but these flow pattern disappeared when cross correlation coefficient was above 0.9. This estimation was conspicuous near SST patterns of eddies. In the results of inverse method, flow field was continuous and eddy motion was estimated definitely but the velocity was overstimated in compared with MCC result over the area of small temperature gradient. This result may be due to temperature error included in SST calculated and spatial variation of heat flux.

• Advances in aircraft and spacecraft science
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• 제9권1호
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• pp.1-15
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• 2022

This paper presents calibration of flush air data sensing systems during ascent period of a satellite launch vehicle. Aerodynamic results are numerically computed by solving three-dimensional time dependent compressible Euler equations over a payload shroud of a satellite launch vehicle. The flush air data system consists of four pressure ports flushed on a blunt-cone section of the payload shroud and connected to on board differential pressure transducers. The inverse algorithm uses calibration charts which are based on computed and measured data. A controlled random search method coupled with neural network technique is employed to estimate pitch and yaw angles from measured transient differential pressure history. The algorithm predicts the flow direction stepwise with the function of flight Mach numbers and can be termed as an online method. Flow direction of the launch vehicle is compared with the reconstructed trajectory data. The estimated values of the flow direction are in good agreement with them.

• 대한원격탐사학회지
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• 제35권1호
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• pp.15-28
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• 2019

By applying the method of SAR interferometry to X-band synthetic aperture radar (SAR) image of COSMO-SkyMed, detailed motion patterns of five glaciers in the Parlung Zangbo River basin, Tibetan Plateau, in January 2010 have been derived. The results indicate that flow patterns are generally constrained by the valley geometry and terrain complexity. The maximum of $123.9ma^{-1}$ is observed on glacier No.1 and the minimum of $39.4ma^{-1}$ is found on glacier No.3. The mean values of five glaciers are between 22.9 and $98.2ma^{-1}$. Glaciers No.1, No.2, No.4 and No.5 exhibit high velocities in their upper sections with big slope and low velocities in the lower sections. A moraine lake accelerates the speed of mass exchange leading to a fast flow at the terminal of glacier No.3. These glaciers generally move along the direction of decreased elevation and present a macroscopic illustration of the motion from the northwest to the southeast. The accuracy of DEM and registration conditions of DEM-simulated terrain phases has certain effects on calculations of glacier flow direction and velocity. The error field is relatively fragmented in areas inconsistent with the main flow line of the glaciers, and the shape and uniformity of glacier are directly related to the continuous distribution of flow velocity errors.

• 한국수소및신에너지학회논문집
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• 제25권5호
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• pp.525-532
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• 2014

The sensing of a stack coolant deficiency is very important in that cooling performance of a fuel cell, overheating prevention of a stack or coolant heater. This paper explains the performance comparison between the coolant contact/noncontact level sensors and coolant deficiency sensing logic using the pressure sensor in a stagnant or circulating flow. Throughout the comparison, the pressure sensor is more suitable than the other sensors in terms of the precision, fast response, sensing frequency. After the experiment, the pressure sensor is equipped to an FCEV(Fuel Cell Electric Vehicle) to verify sensing definitely. There was no miss-sensing using pressure sensor while FCEV runs in the conditions of the paved road and cross country road.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권10호
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• pp.3858-3874
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• 2021

As an essential part of the urban transportation system, precise perception of the traffic flow parameters at the traffic signal intersection ensures traffic safety and fully improves the intersection's capacity. Traditional detection methods of road traffic flow parameter can be divided into the micro and the macro. The microscopic detection methods include geomagnetic induction coil technology, aerial detection technology based on the unmanned aerial vehicles (UAV) and camera video detection technology based on the fixed scene. The macroscopic detection methods include floating car data analysis technology. All the above methods have their advantages and disadvantages. Recently, indoor location methods based on wireless signals have attracted wide attention due to their applicability and low cost. This paper extends the wireless signal indoor location method to the outdoor intersection scene for traffic flow parameter estimation. In this paper, the detection scene is constructed at the intersection based on the received signal strength indication (RSSI) ranging technology extracted from the wireless signal. We extracted the RSSI data from the wireless signals sent to the road side unit (RSU) by the vehicle nodes, calibrated the RSSI ranging model, and finally obtained the traffic flow parameters of the intersection entrance road. We measured the average speed of traffic flow through multiple simulation experiments, the trajectory of traffic flow, and the spatiotemporal map at a single intersection inlet. Finally, we obtained the queue length of the inlet lane at the intersection. The simulation results of the experiment show that the RSSI ranging positioning method based on wireless signals can accurately estimate the traffic flow parameters at the intersection, which also provides a foundation for accurately estimating the traffic flow state in the future era of the Internet of Vehicles.

• 대한기계학회논문집B
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• 제27권12호
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• pp.1699-1707
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• 2003

Coriolis mass flowmeter(CMF), which can measure the mass flow directly, is getting rapid attention for the industrial and custody transfer purpose. In order to study the characteristics and the applicability of CMF, it is tested with the national flow standard system. Two types of sensing tube, U-type and straight type, are employed in the test. Water, spindle oil and viscosity Standard Reference Material whose viscosities are 1, 20 and, 67 $\textrm{mm}^2$/s, respectively, are studied. It is shown that the linearity of CMF is getting deteriorated as the fluid viscosity increases, which is due to the zero drift and the relaxation time of the fluid. To test its applicability in the case of high pressured gas, it is calibrated using compressed air, It shows 1∼l.6 % deviations compared to the calibration results using water. It concludes that the fluid velocity in CMF should be lower than the sonic velocity. In addition, the effects of the vibration from the pipeline and pump on CMF as well as the long term stability are studied.

• 센서학회지
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• 제29권3호
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• pp.194-200
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• 2020

Human detection is an important aspect in many video-based sensing and monitoring systems. Studies have been actively conducted for the automatic detection of humans in camera images, and various methods have been proposed. However, there are still problems in terms of performance and computational cost. In this paper, we describe a method for efficient human detection in the field of view of a camera, which may be static or moving, through multiple processing steps. A detection line is designated at the position where a human appears first in a sensing area, and only the one-dimensional gray pixel values of the line are monitored. If any noticeable change occurs in the detection line, corner detection and optical flow computation are performed in the vicinity of the detection line to confirm the change. When significant changes are observed in the corner numbers and optical flow vectors, the final determination of human presence in the monitoring area is performed using the Histograms of Oriented Gradients method and a Support Vector Machine. The proposed method requires processing only specific small areas of two consecutive gray images. Furthermore, this method enables operation not only in a static condition with a fixed camera, but also in a dynamic condition such as an operation using a camera attached to a moving vehicle.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.682-686
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• 2003

This paper is concerned with 'reverse difference' of marine sediments at the Camau tongue in the extreme south of Vietnam. We demonstrate the importance of remote sensing in geomorphology and marine geological application, using only visual evaluation and some data-processing techniques. In this paper, about 10,000 km$^2$ of the territorial water in the extreme south of Vietnam is being studied. We show that form and behavior of Mekong and its branch can be determined by visually interpreting remote sensing images and using ERDAS IMAGE 8.5 software. Besides, the 'reverse difference' phenomenon is explained by flows of Mekong river and its branches.