• Journal of KIISE:Computer Systems and Theory
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• v.31 no.12
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• pp.682-691
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• 2004

We present a novel haptic sculpting system where the user intuitively adds to and carves out material from a volumetric model using new sculpting tools in the similar way to handling real clay Haptic rendering and model deformation are implemented based on volumetric implicit surface. We enhance previous volume-based haptic sculpting systems by presenting fast and stable force computation on 3D models to be deformed. In order to bridge the gap between fast haptic process (1 KHz) and much slower visual update frequency(~30Hz), the system generates intermediate implicit surfaces between two consecutive physical models being deformed. It performs collision detection and force computation on the intermediate surface in haptic process. The volumetric model being sculpted is visualized as a geometric model which is adaptively polygonized according to the surface complexity. We also introduce various visual effects for the real-time sculpting system including mesh-based solid texturing, painting, and embossing/engraving techniques.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.10
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• pp.563-572
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• 2015

The purpose of this study was to model the effect of flushing discharge on algae removal by multi-purpose weir operation in Yeongsan River (Seungchon Weir) using a 3-dimensional (3D) model. The chlorophyceae Eudorina sp. formed bloom in May 2013. Flushing discharge was conducted in two different ways for algal bloom reduction. To elucidate the spatial variability, a high-resolution 3D model, ELCOM-CAEDYM, was used to simulate the spatial variations of water quality and chl-a over a month. The results showed that ELCOM-CAEDYM could reproduce highly spatially resolved field data at low cost, and showed very good performance in simulating the pattern of algal bloom occurrence. The effect of each flushing discharge operation was analyzed with the results of modeling. The results of case 1, flushing discharge using an open movable weir, showed that the algal bloom between the Seochang Bridge and the Hwangryong River junction is rapidly flushed after operating the movable weir, but the residual algae remained in the weir pool as the discharge decreased. However, the results of case 2, fixed weir overflow with a small hydropower stop, showed that most of the algae was removed after flushing discharge and the effect of algae removal was much bigger than that in case 1, as per modeling results and observed data.

• Journal of Life Science
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• v.34 no.7
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• pp.476-484
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• 2024

Although two-dimensional (2D) monolayer cell culture models are still widely used as the optimal models for anticancer activity research, three-dimensional (3D) multicellular tumor spheroid (3D MTS) models that can better approximate the tumor environment can offer an alternative to bridge the gap between in vitro and animal model studies. Isoalantolactone is among the sesquiterpene lactones found in medicinal plants, including the roots of Elecampane (Inula helenium L.), and is known to have various pharmacological activities, including anticancer activity. In this study, we investigated whether the anticancer activity of isoalantolactone observed in 2D models could be reproduced in a 3D MTS model derived from human hepatocellular carcinoma (HCC) Hep3B cells. According to our results, isoalantolactone inhibited the formation of MTSs in a manner dependent on the treatment concentration, which was accompanied by an increase in reactive oxygen species (ROS) generation. In particular, as isoalantolactone treatment and the culture time increased, the area of proliferating cells was replaced by cells in which apoptosis was induced. Additionally, in MTSs, isoalantolactone increased the expression of death-receptor-related proteins and the activity of caspase-3, and it decreased the expression of the Bax/Bcl-2 expression ratio and total poly(ADP-ribose) polymerase. However, when the production of ROS was artificially blocked, all these changes caused by isoalantolactone were attenuated and the cell survival rate of MTS cells was restored. Therefore, the results of this study suggest that the induction of apoptosis in Hep3B cell-derived MTSs by isoalantolactone is achieved through the activation of extrinsic and intrinsic pathways and is ROS-dependent.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.12
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• pp.1825-1836
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• 2008

Many applications in computer graphics require complex and highly detailed models. However it is often desirable to use approximations in place of excessively detailed models in order to control the processing time. Thus, we aim to develop a notion of optimal matrix to simplify surface which can rapidly obtain the high quality 2D patterns flattening 3D surface as follows. Firstly, two 3D bodies are modeled based on existing Size Korea data. Secondly, each model is divided by shell and block for its pattern draft. Thirdly, each block is flattened by grid and bridge method. Finally, we selected the optimal matrix and demonstrated the efficiency and quality of the proposed method. This proposed approach accommodates surfaces with darts, which are commonly used in the clothing industry to reduce the deformation of surface forming and flattening. The resulting optimal matrix could be an initiation of standardization for pattern flattening. It is expected that this method could facilitate much better approximation in both efficiency and precision.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.125-132
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• 2004

Statements of problem: All ceramic fixed partial denture cores can be made by the slip casting method and the advanced alumina tape method. The fracture resistance of these core connector areas is relatively low. Purpose: The purpose of this study is to standardize the appropriate volumetric figure and location of the connectors in the alumina core fabricated in alumina tape to be used in fixed partial dentures by way of topology optimization. Material and method: A maxillary anterior three-unit bridge alumina core with teeth form and surrounding periodontal apparatus model was used to ultimately design the most structurally rigid form of the connector. Loadings from a $0^{\circ}$, $45^{\circ}$ and $60^{\circ}$ to the axis of each tooth were applied and analyzed with the 3-D finite element analysis method. Using the results from these experiments, the topology optimization was applied and the optimal reinforcement layout of connector was obtained and the detail shape in the fixed partial denture core was designed. Results: The modified prosthesis with the form of a bulk in the lower lingual surface of the connector in the event, reduced the stress concentration up to 20% in the 3-D FEA. Conclusion: The formation of a bulk in the lower lingual connector area of an alumina core for a fixed partial denture decreases the stress to a clinically favorable measure but does not harm the esthetic point of view. This result illustrates the possibility of clinical application of the modified form designed by the topology optimization method.

• Geomechanics and Engineering
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• v.12 no.4
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• pp.723-738
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• 2017

Rock is a heterogeneous material, which introduces complexity in the analysis of rock slopes, since both the existing discontinuities within the rock mass and the intact rock contribute to the degradation of strength. Rock failure is often catastrophic due to the brittle nature of the material, involving the sliding along structural planes and the fracturing of rock bridge. This paper proposes an advanced discretization method of rock mass based on block theory. An in-house software, GeoSMA-3D, has been developed to generate the discrete fracture network (DFN) model, considering both measured and artificial joints. Measured joints are obtained from the photogrammetry analysis on the excavation face. Statistical tools then facilitate to derive artificial joints within the rock mass. Key blocks are searched to provide guidance on potential reinforcement measures. The discretized blocky system is subsequently implemented into a discontinuous deformation analysis (DDA) code. Strength reduction technique is employed to analyze the stability of the slope, where the factor of safety can be obtained once excessive deformation of slope profile is observed. The combined analysis approach also provides the failure mode, which can be used to guide the choice of strengthening strategy if needed. Finally, an illustrated example is presented for the analysis of a rock slope of 20 m height inclined at $60^{\circ}$ using combined GeoSMA-3D and DDA calculation.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1611-1615
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• 2006

The purpose of this study is to simulate the riverbed profile changes downstream of Daecheong re-regulation dam from 1988 to 2001, to evaluate the model's applicability and to predict a long-term riverbed-level variation between 2002 and 2017. As a result of simulation 14 sediment transport equations provided by GSTAR-1D, it was found that Acker's & White formula was the most stable relatively. The interval used to calculate its stability was 7 days for bankful discharge$(1,000m^2/s)$, 3 days for daily maximum flow$(4,273m^2/s)$, 1 day for hourly maximum flow$(7,605m^2/s)$ and minimum flow$(8.5m^2/s)$. The simulation results of river bed changes were evaluated and compared to its measure data from 1988 to 2001. It was showed that there was the degradation for a section between Daecheong re-regulation dam and Maepo water stage gage station due to bed-material, and the degradation for a reach between Maepo and Gongju water stage gage station due to massive aggregate collection. Also, as a result of simulating the river profile change for 2002 to 2017, it was predicted that the section between Daecheong re-regulation dam and Geumnam Bridge would remain as the present profile and the reach between Maepo and Gongju water stage gage station would have some degradations in several parts, which would be stable as a whole unless it was due to artificial river profile change.

• Smart Structures and Systems
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• v.29 no.1
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• pp.237-250
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• 2022

Structural health monitoring (SHM) plays an important role in ensuring the safety and functionality of critical civil infrastructure. In recent years, numerous researchers have conducted studies to develop computer vision and machine learning techniques for SHM purposes, offering the potential to reduce the laborious nature and improve the effectiveness of field inspections. However, high-quality vision data from various types of damaged structures is relatively difficult to obtain, because of the rare occurrence of damaged structures. The lack of data is particularly acute for fatigue crack in steel bridge girder. As a result, the lack of data for training purposes is one of the main issues that hinders wider application of these powerful techniques for SHM. To address this problem, the use of synthetic data is proposed in this article to augment real-world datasets used for training neural networks that can identify fatigue cracks in steel structures. First, random textures representing the surface of steel structures with fatigue cracks are created and mapped onto a 3D graphics model. Subsequently, this model is used to generate synthetic images for various lighting conditions and camera angles. A fully convolutional network is then trained for two cases: (1) using only real-word data, and (2) using both synthetic and real-word data. By employing synthetic data augmentation in the training process, the crack identification performance of the neural network for the test dataset is seen to improve from 35% to 40% and 49% to 62% for intersection over union (IoU) and precision, respectively, demonstrating the efficacy of the proposed approach.

• The Journal of Korean Academy of Prosthodontics
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• v.19 no.1
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• pp.17-27
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• 1981

This study was conducted to determine the chemical composition and the mechanical properties of four commercially available low gold-based crown and bridge alloy produced in Korea. Four dental casting gold-silver-palladium alloys, i.e., A, B, C and D (code of alloys) were selected for the evaluation of chemical composition, ultimate tensile strength, elongation. values and Vickers hardness. The chemical composition of test specimens was analyzed by both emission spectrography and wet gravitation method with a 1.5gm of low gold ingot. The tensile properties and Vickers hardness was determined with cast specimens treated in following three conditions; as-cast, softening heat treatment and hardening heat treatment. The tensile testing bars were cast in accordance with the model designed by Gettleman and Harrison (1969) which was modified from the A. D. A. Specification No. 14 for dental chromium-cobalt casting alloy. Nine tensile test specimens were made from a split silicone mold for each of the test alloys to the size of 2.5mm in diameter and a gauge length of 10mm. All four alloys were handled in accordance with conventional methods used in Type III gold alloys. Ultimate tensile strength and elongation were measured on an Instron Universal Tensile Testing Machine (Model 1125, Japan) operated at a crosshead rate of 0.1cm/min. Elongation values were measured using Digital Measuring Microscope (MS-152, FUSOH, Japan). Vickers hardness was determined with a Vickers Hardness Tester (Model VKH-l, Japan) at a 1.0kg load on a mounted tensile test specimen. The following results were obtained from this study; 1. All tested alloys were composed of Au, Ag, Pd, Cu, Zn and Fe in common. The composition rate of gold for all four alloys was found in the range of $42{\sim}47$ weight % as shown below. Alloy A; Au 45%, Ag 40.2%, Pd 5.76%, others 9.04%. Alloy B; Au 47.1%, Ag 29.03%, Pd 6.98%, others 16.92%. Alloy C; Au 45%, .Ag 26.9%, Pd 6.83%, others 21.07%. Alloy D; Au 41.8%, Ag 34.4%, Pd 6.95%, others 16.85%. 3. The ultimate tensile strength of the four alloys was in the range of $31{\sim}82kg/mm^2$. The test results were shown in the below order from the highest value; As-cast condition; D, B, C, A. Softening heat treament; B, C, D, A. Hardening heat treatment; D, B, C, A. 4. The test :results of the elongation rate for each alloy were in the range of $0.5{\sim}18%$. The test results were shown in the below order from the highest value; As-cast condition; A, D, B, C. Softening heat treatment; A, C, D, B. Hardening heat treatment; C, D, B, A. 5. Vickers hardness for each of the four alloys was in the range of $120{\sim}230$. The test results were shown in the below order from the highest value; As-cast condition; C, B, D, A Softening heat treatment; D, B, C, A. Hardening heat treatment; D, A, C, B. 6. There were no differences in the physical properties between as-cast condition and softening heat treatment.

• Korean Journal of Optics and Photonics
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• v.20 no.2
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• pp.94-101
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• 2009

A novel method for the reconstruction of 3D shape and texture from elemental images has been proposed. Using this method, we can estimate a full 3D polygonal model of objects with seamless triangulation. But in the triangulation process, all the objects are stitched. This generates phantom surfaces that bridge depth discontinuities between different objects. To solve this problem we need to connect points only within a single object. We adopt a segmentation process to this end. The entire process of the proposed method is as follows. First, the central pixel of each elemental image is computed to extract spatial position of objects by correspondence analysis. Second, the object points of central pixels from neighboring elemental images are projected onto a specific elemental image. Then, the center sub-image is segmented and each object is labeled. We used the normalized cut algorithm for segmentation of the center sub-image. To enhance the speed of segmentation we applied the watershed algorithm before the normalized cut. Using the segmentation results, the subdivision process is applied to pixels only within the same objects. The refined grid is filtered with median and Gaussian filters to improve reconstruction quality. Finally, each vertex is connected and an object-based triangular mesh is formed. We conducted experiments using real objects and verified our proposed method.