• ETRI Journal
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• v.40 no.5
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• pp.592-603
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• 2018

In order to obtain better target identification performance, an efficient waveform design method with high range resolution and low sidelobe level for orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) radar is proposed in this paper. First, the wideband CP-based OFDM signal is transmitted on each antenna to guarantee large bandwidth and high range resolution. Next, a complex orthogonal design (COD) is utilized to achieve code domain orthogonality among antennas, so that the spatial diversity can be obtained in MIMO radar, and only the range sidelobe on the first antenna needs suppressing. Furthermore, sidelobe suppression is expressed as an optimization problem. The integrated sidelobe level (ISL) is adopted to construct the objective function, which is solved using the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm. The numerical results demonstrate the superiority in performance (high resolution, strict orthogonality, and low sidelobe level) of the proposed method compared to existing algorithms.

• Journal of electromagnetic engineering and science
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• v.15 no.1
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• pp.37-43
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• 2015

We implemented a real-time radar system for an unmanned ground vehicle designed to run on unpaved or bumpy roads. The system must be able to detect slow targets in a cluttered environment and cover wide angular sections with high resolution at the same time. The system consists of array antennas, preprocessors for digital beam forming, and digital signal processors for the detection process which uses sawtooth waveforms and high-resolution estimation, and is called forward/backward spatial smoothing beamspace multiple signal classification (FBSS BS-MUSIC). We show that the sawtooth waveforms enhance the angular estimation capability of FBSS BS-MUSIC in addition to their well-known advantages of removing the ambiguity of targets and detecting slow targets with improved velocity resolution.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.630-631
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• 2021

In this paper, we propose a high-resolution fringe pattern generation technique using deep learning networks. Generating a hologram using a computer requires a very large amount of computation. Therefore, in order to replace this, it was shown that it can be replaced through deep learning, but there was a limitation in the resolution of the output fringe pattern. To improve this, we propose an algorithm for generating a high-resolution fringe pattern.

• International journal of advanced smart convergence
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• v.12 no.4
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• pp.1-7
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• 2023

Large-size, organic light-emitting device (OLED) panels based on highly reliable gate driver circuits integrated using InGaZnO thin film transistors (TFTs) were developed to achieve ultra-high resolution TVs. These large-size OLED panels were driven by using a novel gate driver circuit not only for displaying images but also for sensing TFT characteristics for external compensation. Regardless of the negative threshold voltage of the TFTs, the proposed gate driver circuit in OLED panels functioned precisely, resulting from a decrease in the leakage current. The falling time of the circuit is approximately 0.9 ㎲, which is fast enough to drive 8K resolution OLED displays at 120 Hz. 120 Hz is most commonly used as the operating voltage because images consisting of 120 frames per second can be quickly shown on the display panel without any image sticking. The reliability tests showed that the lifetime of the proposed integrated gate driver is at least 100,000 h.

• International Journal of Vascular Biomedical Engineering
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• v.2 no.2
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• pp.27-32
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• 2004

The objective of the present study is to visualize the steady and pulsatile flow fields in a branching model by using a high-resolution PIV system. A bifurcated flow system was built for the experiments in the steady and pulsatile flows. Harvard pulsatile pump was used to generate the pulsatile velocity waveforms. Conifer powder as the tracing particles was added to water to visualize the flow fields. CCD cameras($1K{\times}1K$(high resolution camera) and $640{\times}480$(low resolution camera)) captured two consecutive particle images at once for the image processing of several cross sections on the flow system. The range validation method and the area interpolation method were used to obtain the final velocity vectors with high accuracy. The results of the image processing clearly showed the recirculation zones and the formation of the paired secondary flows from the distal to the apex of the branch flow in the bifurcated model. The results also indicated that the particle velocities at the inner wall moved faster than the velocities at the outer wall due to the inertial force effects and the helical motions generated in the branch flows as the flow proceeded toward the outer wall. Even though the PIV images from the high resolution camera were closer to the simulation results than the images from the low resolution camera at some locations, both results of the PIV experiments from the two cameras generally agreed quite well with the results from the computer simulations. Therefore, instead of using the expensive stereoscopic PIV or 3D PIV system, the three-dimensional flow fields in a bifurcated model could be easily and exactly investigated by this study.

• Geophysics and Geophysical Exploration
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• v.16 no.4
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• pp.225-233
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• 2013

The accuracy of the automatic NMO velocity analysis, which is used for an effective and objective NMO velocity analysis, is highly affected by the velocity resolution of the velocity spectrum. In this study, we have developed an automatic NMO velocity algorithm, where the velocity spectra are created using high-resolution bootstrapped differential semblance (BDS), and the velocity analysis on CMP gathers is performed in parallel with MPI. We also compared the velocity models from the developed automatic NMO velocity algorithm with high-resolution BDS to those from BDS. To verify the developed automatic velocity analysis module we created synthetic seismic data from a velocity model including horizon layers. We confirmed that the developed automatic velocity analysis module estimated velocity more accurately. In addition, NMO velocity which yielded a CMP stacked section, where the coherency of the events were improved, was estimated when the developed module was applied to a marine field data set.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.8
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• pp.1222-1229
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• 2010

Compared to conventional high resolution acoustic profiling, ultra high resolution shallow acoustic profiling using parametric echo sounder is limited in penetration, yet it provides resolution suitable for detailed seabed investigation in the shallow waters. The parametric sub-bottom profiler system provides not only the exact determination of water depth, but also the detailed information about sediment layers and sub-bottom structures. Possible applications include dredging project, search of buried pipeline, ship wrecks, and other artificial objects through the detailed mapping of thickness and structure of the upper sedimentary layers. In this study, contaminated sediments were discriminated by the correlation of ultra high resolution profiles with geologic data. In addition, the burial depth of the submarine cable was measured by the interpretation of acoustic anomalies in the profiles.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.79-84
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• 2008

Compared to conventional high resolution acoustic profiling, ultra high resolution shallow acoustic profiling is limited in penetration, yet it provides resolution suitable for detailed seabed investigation in the shallow waters. Possible applications include search of buried pipeline, ship wrecks, and other artificial objects through the detailed mapping of thickness and structure of the upper sedimentary layers. In this study, contaminated sediments were discriminated by the correlation of ultra high resolution profiles with geologic data. In addition, the burial depth of submarine cable was measured by the interpretation of acoustic anomalies in the profiles.

• Investigative Magnetic Resonance Imaging
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• v.23 no.1
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• pp.38-45
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• 2019

Purpose: To demonstrate the high-resolution numerical simulation of the respiration-induced dynamic $B_0$ shift in the head using generalized susceptibility voxel convolution (gSVC). Materials and Methods: Previous dynamic $B_0$ simulation research has been limited to low-resolution numerical models due to the large computational demands of conventional Fourier-based $B_0$ calculation methods. Here, we show that a recently-proposed gSVC method can simulate dynamic $B_0$ maps from a realistic breathing human body model with high spatiotemporal resolution in a time-efficient manner. For a human body model, we used the Extended Cardiac And Torso (XCAT) phantom originally developed for computed tomography. The spatial resolution (voxel size) was kept isotropic and varied from 1 to 10 mm. We calculated $B_0$ maps in the brain of the model at 10 equally spaced points in a respiration cycle and analyzed the spatial gradients of each of them. The results were compared with experimental measurements in the literature. Results: The simulation predicted a maximum temporal variation of the $B_0$ shift in the brain of about 7 Hz at 7T. The magnitudes of the respiration-induced $B_0$ gradient in the x (right/left), y (anterior/posterior), and z (head/feet) directions determined by volumetric linear fitting, were < 0.01 Hz/cm, 0.18 Hz/cm, and 0.26 Hz/cm, respectively. These compared favorably with previous reports. We found that simulation voxel sizes greater than 5 mm can produce unreliable results. Conclusion: We have presented an efficient simulation framework for respiration-induced $B_0$ variation in the head. The method can be used to predict $B_0$ shifts with high spatiotemporal resolution under different breathing conditions and aid in the design of dynamic $B_0$ compensation strategies.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.36.1-36.1
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• 2010

OFC (Optical Frequency Comb) is an optical spectrum which consists of equidistant lines in frequency space. OFC can thus be used as an optical ruler. Since it was demonstrated in late 1990s, it is revolutionizing many fields in frequency metrology such as the measurement of absolute optical frequencies, the measure ratios of optical frequencies with extremely high precision. It is also used in high-precision spectroscopy. In astronomy, OFC can be used as a very accurate and stable wavelength standard for a high resolution spectrograph to measure the radial velocity of celestial bodies with extremely high accuracy of about several tens cm/s. In our presentation, we will introduce some basic concepts of OFC and some issues to use it in astronomical spectrograph. We will also present our plan to develop a high resolution spectrograph with OFC.