• The Journal of Engineering Geology
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• v.27 no.3
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• pp.217-231
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• 2017

The subsidence of ground in urban area can be caused by the occurrence of the cavity and the change in ground volumetric water content. The objective of this study is the detection of abnormal area of ground in urban area where the cavity or the change in ground volumetric water content is occurred by the ground penetrating radar signal. GPR survey is carried out on the test bed with a circular buried object. From the GPR survey, the signals filtered by the bandpass filtering are measured, and the methods consisting of gain function, time zero, background removal, deconvolution and display gain are applied to the filtered signals. As a result of application of the signal processing methods, the polarity of signal corresponds with the relation of electrical impedance of the cavity and the ground in test bed. In addition, the relative permittivity calculated by GPR signal is compared with that of predicted by volumetric water content of the test bed. The relative permittivities obtained from two different methods show similar values. Therefore, the abnormal area where the change in ground volumetric water content is occurred can be detected from the results of the GPR survey in case the depth of underground utilities is known. Signal processing methods and estimation of relative permittivity performed in this study may be effectively used to detect the abnormal area of ground in urban area.

• Journal of the Optical Society of Korea
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• v.12 no.3
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• pp.131-135
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• 2008

Computational integral imaging(CII) has the advantage of generating the volumetric information of the 3D scene without optical devices. However, the reconstruction process of CII requires increasingly larger sizes of reconstructed images and then the computational cost increases as the distance between the lenslet array and the reconstructed output plane increases. In this paper, to overcome this problem, we propose a novel CII method using a depth conversion technique. The proposed method can move a far 3D object near the lenslet array and reduce the computational cost dramatically. To show the usefulness of the proposed method, we carry out the preliminary experiment and its results are presented.

• KIPS Transactions on Software and Data Engineering
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• v.10 no.10
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• pp.429-438
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• 2021

In recent, realistic content has been applied in various ways due to the development of display technology and hologram, the final realistic content technology, have been used limitedly in accordance with the growing public demand. However, most realistic content requires additional devices of HMD (head mounted device) or glasses type, and other realistic content display technologies deliver a single image plane in the experience space to the user, providing a monotonous content experience. Various realistic contents with hologram technology are introduced in this work. In addition, we propose an interaction based realistic hologram service based that combines projection mapping and floating holograms. Projection-mapped screens and multi-floating hologram device provide a three-dimensional volumetric space with extended depth orientation from the user's point of view, while allowing users' entire and partial motions to be recognizable through multiple sensors.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.1
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• pp.44-51
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• 2004

Fractal-space multiplexing using a moving window(MW) can multiplex holograms by moving a window left and right. and up and down. But, crosstalk occurs by two neighboring moving windows in the vertical direction of the holographic memory system and limits high-density information recording. Accordingly, we analyzed the crosstalk with the focal length of lens, the distance of MW, and the number of multiplexed hologram to record high-density infromation and presented the optical experimental results of fractal-space multiplexing using volumetric photorefractive crystal and disc type photopolymer.

• Journal of Korean Neurosurgical Society
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• v.51 no.2
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• pp.120-123
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• 2012

Objective : Percutaneous vertebroplasty (PVP) is usually carried out under three-dimensional (2D) fluoroscopic guidance. However, operative complications or bone cement distribution might be difficult to assess on the basis of only 2D radiographic projection images. We evaluated the feasibility of performing an intraoperative and postoperative examination in patients undergoing PVP by using three-dimensional (3D) reconstructive C-arm. Methods : Standard PVP procedures were performed on 14 consecutive patients by using a Siremobil Iso-$C^{3D}$ and a multidetector computed tomography machine. Post-processing of acquired volumetric datasets included multiplanar reconstruction (MPR) and surface shaded display (SSD). We analyzed intraoperative and immediate postoperative evaluation of the needle trajectory and bone cement distribution. Results : The male : female ratio was 2 : 12; mean age of patients, 70 (range, 77-54) years; and mean T score, -3.4. The mean operation time was 52.14 min, but the time required to perform and post-process the rotational acquisitions was 7.76 min. The detection of bone cement distribution and leakage after PVP by using MPR and SSD was possible in all patients. However, detection of the safe trajectory for needle insertion was not possible. Conclusion : 3D rotational image acquisition can enable intra- or post-procedural assessment of vertebroplasty procedures for the detection of bone cement distribution and leakage. However, it is difficult to assess the safe trajectory for needle insertion.

• Journal of the Korea Computer Graphics Society
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• v.24 no.2
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• pp.29-40
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• 2018

Direct volume rendering (DVR) is a commonly used method to visualize inner structures in 3D volumetric datasets. However, conventional volume rendering on a 2D display lacks depth perception due to dimensionality reduction caused by ray casting. In this work, we investigate how emerging Virtual Reality (VR) can improve the usability of direct volume rendering. We developed real-time high-resolution DVR system in virtual reality, and measures the usefulness of volume rendering with improved depth perception via a user study conducted by 38 participants. The result indicates that virtual reality significantly improves the usability of DVR by allowing better depth perception.

• Geomechanics and Engineering
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• v.10 no.2
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• pp.207-224
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• 2016

Granulated coal ash (GCA), a mixture of the by-product from milling processes with a small amount of cement added, has recently come to be used as a new form of geomaterial. The shear strength and deformation behaviours of GCA are greatly determined by its relative density or void ratio. A series of drained triaxial compression tests were performed on cylindrical specimens of GCA at confining pressures of between 50 kPa and 400 kPa at initial relative densities of 50%, 70% and 80%. Experimental results show that a rise in relative density increases the peak shear strength and intensifies the dilation behaviour. The initial tangent modulus and secant modulus of the stress-strain curve increase with increasing initial relative density, whereas the axial and volumetric strains at failure decrease with level of initial relative density. The stress-dilatancy relationships of GCA at different relative densities and confining pressures display similar tendency. The dilatancy behaviour of GCA is modelled by the Nova rule and the material property N in Nova rule of GCA is much larger than that of natural sand.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.154-156
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• 2002

Brachytherapy has a long history in the treatment of cancer. However, the treatment planning technique for brachytherapy has lagged somewhat behind the corresponding developments for external beam therapy as far as the imaging technique is concerned. Currently, the orthogonal-film-based treatment planning is performed at most institutions even though the CT-based planning is available. The aim of this study is to evaluate the CT-based vs. the orthogonal-film-based treatment planning in cervix cancer. The doses to point A, point B, rectum and bladder points according to ICRU 38 were calculated for the two methods above. In addition, the volumetric studies such as 3D dose computation and DVH were obtained for the CT-based planning. For the bulky tumor, the isodose lines of point A prescription were not fairly covered for the CTV. The CT -based dose planning can overestimate the maximum dose delivered to bladder and rectum by 30%. The CT-based planning has several advantages over the orthogonal-film-based such as 3D dose display, DVH, and more accurate target delineation. It is suggested that the prescription point in cervix cancer be revised especially for the bulky tumor.

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.1 s.19
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• pp.19-26
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• 2002

To provide 3D GSIS data on the internet, 3D data structures need to be researched and applied for spatial analysis for subsurface modeling. As for GSIS software R&D trend the following things have pointed out : 3-dimensional geo-processing technologies, internet-based application system development, distributed processing technologies for large volume of spatial information, real-time geo-data processing methodologies, Among them research scope within Internet-based application system or Web-based GSIS generally contains core parts of software development such as Internet application, large volume of spatial database handling, real-time spatial data processing, spatial data transfer and transformation, and volumetric display of processing results. This study shows the method of providing 3D GSIS on the internet using VRML model, which are made of DEM data, draped aerial photo, and VRML script programming. And it is also studied that offering 3D GSIS engine on the internet and precise texture mapping using satellite image and aerial photos.

• Computers and Concrete
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• v.24 no.2
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• pp.151-158
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• 2019

The sustainable development principle of replacing natural resources with renewable material is an important research topic. In this study, waste LCD (liquid crystal display) glass powder was used to replace cement (0%, 10%, 20% and 30%) through a volumetric method using three water-binder ratios (0.47, 0.59, and 0.71) to make cement mortar. The compressive strength was tested at the ages of 7, 28, 56 and 91 days. The test results show that the compressive strength increases with age but decreases as the water-binder ratio increases. The compressive strength slightly decreases with an increase in the replacement of LCD glass powder at a curing age of 7 days. However, at a curing age of 91 days, the compressive strength is slightly greater than that for the control group (glass powder is 0%). When the water-binder ratios are 0.47, 0.59 and 0.71, the compressive strength of the various replacements increases by 1.38-1.61 times, 1.56-1.80 times and 1.45-2.20 times, respectively, during the aging process from day 7 to day 91. Furthermore, a prediction model of the compressive strength of a cement mortar with waste LCD glass powder was deduced in this study. According to the comparison between the prediction analysis values and test results, the MAPE (mean absolute percentage error) values of the compressive strength are between 2.79% and 5.29%, and less than 10%. Thus, the analytical model established in this study has a good forecasting accuracy. Therefore, the proposed model can be used as a reliable tool for assessing the design strength of cement mortar from early age test results.