• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.60.2-60.2
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• 2011

A study of the non-linear optical properties of nanocrystal-Si embedded in SiO2 has been performed by using the z-scan method in the nanosecond and femtosecond ranges. Substoichiometric SiOx films were grown by plasma-enhanced chemical-vapor deposition(PECVD) on silica substrates for Si excesses up to 24 at/%. An annealing at $1250^{\circ}C$ for 1 hour was performed in order to precipitate nanocrystal-Si, as shown by EFTEM images. Z-scan results have shown that, by using 5-ns pulses, the non-linear process is ruled by thermal effects and only a negative contribution can be observed in the non-linear refractive index, with typical values around $-10-10cm^2/W$. On the other hand, femtosecond excitation has revealed a pure electronic contribution to the nonlinear refractive index, obtaining values in the order of 10-12 cm2/W. Simulations of heat propagation have shown that the onset of the temperature rise is delayed more than half pulse-width respect to the starting edge of the excitation. A maximum temperature increase of ${\Delta}T=123.1^{\circ}C$ has been found after 3.5ns of the laser pulse maximum. In order to minimize the thermal contribution to the z-scan transmittance and extract the electronic part, the sample response has been analyzed during the first few nanoseconds. By this method we found a reduction of 20% in the thermal effects. So that, shorter pulses have to be used obtain just pure electronic nonlinearities.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.792-799
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• 2022

Building Information Modeling (BIM) technology is a key component of modern construction engineering and project management workflows. As-is BIM models that represent the spatial reality of a project site can offer crucial information to stakeholders for construction progress monitoring, error checking, and building maintenance purposes. Geometric methods for automatically converting raw scan data into BIM models (Scan-to-BIM) often fail to make use of higher-level semantic information in the data. Whereas, semantic segmentation methods only output labels at the point level without creating object level models that is necessary for BIM. To address these issues, this research proposes a hybrid semantic-geometric approach for clutter-resistant floorplan generation from laser-scanned building point clouds. The input point clouds are first pre-processed by normalizing the coordinate system and removing outliers. Then, a semantic segmentation network based on PointNet++ is used to label each point as ceiling, floor, wall, door, stair, and clutter. The clutter points are removed whereas the wall, door, and stair points are used for 2D floorplan generation. A region-growing segmentation algorithm paired with geometric reasoning rules is applied to group the points together into individual building elements. Finally, a 2-fold Random Sample Consensus (RANSAC) algorithm is applied to parameterize the building elements into 2D lines which are used to create the output floorplan. The proposed method is evaluated using the metrics of precision, recall, Intersection-over-Union (IOU), Betti error, and warping error.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.2
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• pp.247-251
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• 2011

Botulinum toxin type A (BoNT-A) is used for treating bilateral masseter hypertrophy since 1994. Recently there have been more clinical studies in this area, with some authors reporting that BoNT-A can reduce the size of the masseter muscle, as documented by photography, ultrasonography, computed tomography, and 3D(three dimensional) laser scan. However, earlier studies were only for bilateral masseter hypertrophy cases, not for unilateral masseter hypertrophy cases. The aim of this study was to use 3D laser scanning to evaluate changes in the external facial contour induced by unilateral BoNT-A injection. BoNT-A was injected into hypertrophic masseter muscle unilaterally in 10 patients with asymmetric masseter hypertrophy. The clinical effects of unilaterally injected BoNT-A were evaluated before the injection and 4, 8, and 12weeks after the injection using 3D laser scan. And the mean values of both sides (injection and non-injection sides) were compared with. At injection side, mean values of the volume and the bulkiest height at each time point diminished significantly between pre-injection and 4, 8, and 12weeks post-injection. At non-injection side, in contrast, mean values of the volume and the bulkiest height diminished also but less than that of injected side, and there was no statistical significance. In this limited study, we concluded that the unilaterally BoNT-A injection side showed greater mean values of the reduction of muscle volume than non-injection side at 4, 8, and 12 weeks after the injection.

• The Journal of the Acoustical Society of Korea
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• v.13 no.6
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• pp.45-49
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• 1994

In this paper, photoacoustic image processing system was constructed by using 2W CW $CO_{2}$ laser of $10.6{\mu}m$ wavelength and PZT 5A acoustic transducer. Stainless steel of 5mm thickness was used as a sample in experiment. Three line cracks of $50{\mu}m$ in each width and depth were made by using plasma on the surface of the sample. Also, each gap among their lines was $200{\mu}m$ and $300{\mu}m$ in width. In the scan range of $2.2mm\times2mm$ including surface defects, a good image of $50{\mu}m$ resolution had been shown when modulation frequency of CW laser was 100Hz.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.467-475
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• 2016

Ultrasonic propagation imaging (UPI) has shown great potential for detection of impairments in complex structures and can be used in wide range of non-destructive evaluation and structural health monitoring applications. The software implementation of such algorithms showed a tendency in time-consumption with increment in scan area because the processor shares its resources with a number of programs running at the same time. This issue was addressed by using field programmable gate arrays (FPGA) that is a dedicated processing solution and used for high speed signal processing algorithms. For this purpose, we need an independent and flexible block of logic which can be used with continuously evolvable hardware based on FPGA. In this paper, we developed an FPGA-based ultrasonic propagation imaging system, where FPGA functions for both data acquisition system and real-time ultrasonic signal processing. The developed UPI system using FPGA board provides better cost-effectiveness and resolution than digitizers, and much faster signal processing time than CPU which was tested using basic ultrasonic propagation algorithms such as ultrasonic wave propagation imaging and multi-directional adjacent wave subtraction. Finally, a comparison of results for processing time between a CPU-based UPI system and the novel FPGA-based system were presented to justify the objective of this research.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.165-178
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• 2015

Physical and chemical weathering degrades rock, affecting its structural properties and thus the stability of stone buildings or other structures. Confocal laser scan microscopy (CLSM) is used here to observe temporal changes in the surface roughness of rock samples under simulated accelerated weathering. Samples were pressurized to 50, 55, or 70 MPa using a pressure frame, and subjected to freeze/thaw cycling controlled by a thermostat. The temperature was cycled from -20℃ to 40℃ and back. After each 20 cycles, CLSM was used to assess the change in surface roughness, and roughness factors were calculated to quantify the progression of the surface condition over time. Variations in cross-section line-roughness parameters and surface-roughness parameters were analyzed for specific parts of the sample surfaces at 5× and 50× magnification. The result reveals that the highest and lowest values of the roughness factors are changed according to elapsed time. Freezing/thawing at high pressure caused larger changes in the roughness factor than at low pressure.

• The Journal of Korea Robotics Society
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• v.4 no.4
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• pp.298-304
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• 2009

This paper describes an algorithm that improves 3D reconstruction result using a multi-sensor fusion disparity map. We can project LRF (Laser Range Finder) 3D points onto image pixel coordinatesusing extrinsic calibration matrixes of a camera-LRF (${\Phi}$, ${\Delta}$) and a camera calibration matrix (K). The LRF disparity map can be generated by interpolating projected LRF points. In the stereo reconstruction, we can compensate invalid points caused by repeated pattern and textureless region using the LRF disparity map. The result disparity map of compensation process is the multi-sensor fusion disparity map. We can refine the multi-sensor 3D reconstruction based on stereo vision and LRF using the multi-sensor fusion disparity map. The refinement algorithm of multi-sensor based 3D reconstruction is specified in four subsections dealing with virtual LRF stereo image generation, LRF disparity map generation, multi-sensor fusion disparity map generation, and 3D reconstruction process. It has been tested by synchronized stereo image pair and LRF 3D scan data.

• Journal of the Korean Society of Safety
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• v.33 no.3
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• pp.1-7
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• 2018

Recently, various engineering approaches have been widely used in the accident investigation field to identify the cause of the accident and to predict damage by accident. Computational analysis is the most commonly used method of accident investigation technique. This technique is mainly used to identify the mechanism of the accident generation and to determine the cause when it is difficult to reproduce the situation at the time of the accident or when it is impossible to perform a reproduction experiment. In this study, The gas explosion analysis for LPG explosion accident generated by defect of the blocking action was performed to determine the accident object, gas leakage amount and predicted the damage caused by the accident using 3D laser scanner and FLACS program. We can quantify the explosive power by LPG gas accident and predict the gas leakage amount, damage by accident and evaluate the stability of the structure through this study. In the future, This method can be widely used in the field of gas safety by improving the reliability and validity of the analysis.

• Journal of Electrochemical Science and Technology
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• v.11 no.2
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• pp.180-186
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• 2020

In this work, a metal-ligand solution (Cu-EDTA) was prepared based on the molecular precursor method and the solution was spin-coated onto 3D printed flexible photosensitive resin sheets. After being processed by microwave, a laser with a wavelength of 355 nm was utilized to scan the spin-coated sheets and then the sheets were immersed in an electroless copper plating solution to deposit copper wires. With the help of microwave processing, the adhesion between copper wires and substrate was improved which should result from the increase of roughness, decrease of contact angle and the consistent orientation of coated film according to the results of 3D profilometer and SEM. XPS results showed that copper seeds formed after laser scanning. Using the 3D printed flexible sheets as cathode and galvanized iron as anode, electrochemical machining was conducted.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.6
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• pp.389-397
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• 2015

Recently, wave propagation imaging based on laser scanning-generated elastic waves has been intensively used for nondestructive inspection. However, the proficiency of the conventional software based system reduces when the scan area is large since the processing time increases significantly due to unavoidable processor multitasking, where computing resources are shared with multiple processes. Hence, the field programmable gate array (FPGA) was introduced for a wave propagation imaging method in order to obtain extreme processing time reduction. An FPGA board was used for the design, implementing post-processing ultrasonic wave propagation imaging (UWPI). The results were compared with the conventional system and considerable improvement was observed, with at least 78% (scanning of $100{\times}100mm^2$ with 0.5 mm interval) to 87.5% (scanning of $200{\times}200mm^2$ with 0.5 mm interval) less processing time, strengthening the claim for the research. This new concept to implement FPGA technology into the UPI system will act as a break-through technology for full-scale automatic inspection.