• The Journal of Korean Academy of Prosthodontics
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• v.59 no.1
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• pp.79-87
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• 2021

The digital workflow of optical impressions by the intraoral scanner and CADCAM manufacture of dental prostheses is actively developing. The complex process of traditional impression taking, definite cast fabrication, wax pattern making, and casting has been shortened, and the number of patient's visits can also be reduced. Advances in intraoral scanner technology have increased the precision and accuracy of optical impression, and its indication is progressively widened toward the long span fixed dental prosthesis. This case report describes the long span implant case, and the operator fully utilized digital workflow such as computer-guided implant surgical template and CAD-CAM produced restoration after the digital impression. The provisional restoration and customized abutments were prepared with the optical impression taken on the same day of implant surgery. Moreover, the final prosthesis was fabricated with the digital scan while utilizing the same customized abutment from the provisional restoration. During the data acquisition step, stl data of customized abutments, previously scanned at the time of provisional restoration delivery, were imported and automatically aligned with digital impression data using an 'A.I. abutment matching algorithm' the intraoral scanner software. By using this algorithm, it was possible to obtain the subgingival margin without the gingival retraction or abutment removal. Using the digital intraoral scanner's advanced functions, the operator could shorten the total treatment time. So that both the patient and the clinician could experience convenient and effective treatment, and it was possible to manufacture a prosthesis with predictability.

• Journal of Industrial Convergence
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• v.20 no.8
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• pp.1-13
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• 2022

Although the number of venture start-ups has increased significantly, it is difficult to judge the success or failure based on short-term performance alone. The survival of a company cannot be guaranteed if it does not show sustainable growth prospects. As a growth factor for venture companies, the level of technology commercialization capability and competitive strategies are considered important. Recently, the emergence of innovative business models is creating new opportunities and driving the growth of numerous venture start-ups. This study tried to investigate the mediating effect of business model innovation in the relationship between technology commercialization capability, competitive strategy and the growth prospects of venture companies. For this, empirical analysis was conducted using the original data of the Research on the Precision Status of Venture Firms 2021. As a result, production, manufacturing, marketing capability, cost leadership and product differentiation had a positive(+) effect on growth prospects. The mediating effect of business model innovation between all factors except for manufacturing capacity and growth prospects was verified. This study expanded the scope of research by shedding new light on the factors influencing the long-term growth prospects of venture companies and revealing business model innovation as a new mediating variable. In future research, it is necessary to develop an objective measurement tool and to identify differences according to industrial characteristics.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.17 no.4
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• pp.73-86
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• 2022

Interest and investment in agri-food ventures is increasing worldwide. Agri-food venture startups are also increasing in Korea, but there are constraint factors due to industrial characteristics, and infrastructure and investment for growth are insufficient. This study confirmed the effect of technology commercialization capability and competitive strategy on the growth prospects of agri-food venture companies and the mediating effect of business model innovation. And, through comparison with previous studies, the industrial characteristics were identified by confirming the difference between all venture companies and agri-food ventures. For this, only agri-food ventures data were extracted from the original data of the Research on the Precision Status of Venture Firms 2021. And empirical analysis was conducted. As a result, manufacturing capability, cost leadership and product differentiation had a positive(+) effect on growth prospects. The mediating effect of business model innovation between manufacturing capacity, product differentiation and growth prospects was verified. Through the research results, factors affecting the long-term growth prospects of agri-food ventures were identified in consideration of industrial characteristics. In addition, practical implications in connection with business model innovation of agri-food ventures were presented. In future research, it is necessary to develop an objective measurement tool and to conduct a detailed analysis according to business history and company size.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.2
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• pp.187-205
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• 2014

The global price of oil, which is both finite and limited in quantity, has been rising steadily because of the increasing requirements for energy in both developing and developed countries. Furthermore, regulations have been strengthened across all industries to address global warming. Many studies of hull resistance, propulsion and operation of ships have been performed to reduce fuel consumption and emissions. This study examined the design parameters of the propeller boss cap fin (PBCF) and hub cap for 6,000TEU container ships to improve the propulsion efficiency. The design parameters of PBCF have been selected based on the geometrical shape. Computational fluid dynamics (CFD) analysis with a propeller open water (POW) test was performed to check the validity of CFD analysis. The design of experiment (DOE) case was selected as a full factorial design, and the experiment was analyzed by POW and CFD analysis. Analysis of variance (ANOVA) was performed to determine the correlation among design parameters. Four design alternatives of PBCF were selected from the DOE. The shape of a propeller hub cap was selected as a divergent shape, and the divergent angle was determined by the DOE. Four design alternatives of PBCF were attached to the divergent hub cap, and the POW was estimated by CFD. As a result, the divergent hub cap with PBCF has a negative effect on the POW, which is induced by an increase in torque coefficient. A POW test and cavitation test were performed with a divergent hub cap with PBCF to verify the CFD result. The POW test result showed that the open water efficiency was increased approximately 2% with a divergent hub cap compared to a normal cap. The POW test result was similar to the CFD result, and the divergent hub cap with the PBCF models showed lower open water efficiency. This was attributed to an increase in the torque coefficient just like the CFD results. A cavitation test was performed using the 2 models selected. The test result showed that the hub vortex is increased downstream of the propeller.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.2
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• pp.218-222
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• 2014

In this paper, we introduce an autonomous calibration method for a 2D laser displacement sensor (e.g. laser vision sensor and laser range finder) by matching a single point on a flat structure. Many arc welding robots install a 2D laser displacement sensor to expand their application by recognizing their environment (e.g. base metal and seam). In such systems, sensing data should be transformed to the robot's coordinates, and the geometric relation (i.e. rotation and translation) between the robot's coordinates and sensor coordinates should be known for the transformation. Calibration means the inference process of geometric relation between the sensor and robot. Generally, the matching of more than 3 points is required to infer the geometric relation. However, we introduce a novel method to calibrate using only 1 point matching and use a specific flat structure (i.e. circular hole) which enables us to find the geometric relation with a single point matching. We make the rotation component of the calibration results as a constant to use only a single point by moving a robot to a specific pose. The flat structure can be installed easily in a manufacturing site, because the structure does not have a volume (i.e. almost 2D structure). The calibration process is fully autonomous and does not need any manual operation. A robot which installed the sensor moves to the specific pose by sensing features of the circular hole such as length of chord and center position of the chord. We show the precision of the proposed method by performing repetitive experiments in various situations. Furthermore, we applied the result of the proposed method to sensor based seam tracking with a robot, and report the difference of the robot's TCP (Tool Center Point) trajectory. This experiment shows that the proposed method ensures precision.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.390-397
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• 2019

A mechanical model of band sawing saw frame was established according to an analysis of a commonly used saw-frame structure diagram to overcome the problems of low service life, substandard cutting precision and efficiency, and high manufacturing cost caused by the unreasonable design of saw frame. Taking a particular type of sawing machine as an example, stress cycle analysis of the saw blade was carried out according to the mechanical model of the saw frame, and the fatigue analysis model of the most dangerous cross-section point that was most prone to fatigue failure of the saw blade was then established. The fatigue analysis result was used as the basis for the improved design of the saw frame, and the improved detailed saw-frame design parameters were obtained. The results suggested that the saw frame system is much more compact and the saw blade force met the fatigue strength requirements through the improved design. In addition, the service life of the saw blade and the cutting precision were increased. The established mechanical model of the saw frame in this paper is used widely and has high practical application values.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.241-241
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• 2012

Semiconductor industry has been taking the advantage of improvements in process technology in order to maintain reduced device geometries and stringent performance specifications. This results in semiconductor manufacturing processes became hundreds in sequence, it is continuously expected to be increased. This may in turn reduce the yield. With a large amount of investment at stake, this motivates tighter process control and fault diagnosis. The continuous improvement in semiconductor industry demands advancements in process control and monitoring to the same degree. Any fault in the process must be detected and classified with a high degree of precision, and it is desired to be diagnosed if possible. The detected abnormality in the system is then classified to locate the source of the variation. The performance of a fault detection system is directly reflected in the yield. Therefore a highly capable fault detection system is always desirable. In this research, time series modeling of the data from an etch equipment has been investigated for the ultimate purpose of fault diagnosis. The tool data consisted of number of different parameters each being recorded at fixed time points. As the data had been collected for a number of runs, it was not synchronized due to variable delays and offsets in data acquisition system and networks. The data was then synchronized using a variant of Dynamic Time Warping (DTW) algorithm. The AutoRegressive Integrated Moving Average (ARIMA) model was then applied on the synchronized data. The ARIMA model combines both the Autoregressive model and the Moving Average model to relate the present value of the time series to its past values. As the new values of parameters are received from the equipment, the model uses them and the previous ones to provide predictions of one step ahead for each parameter. The statistical comparison of these predictions with the actual values, gives us the each parameter's probability of fault, at each time point and (once a run gets finished) for each run. This work will be extended by applying a suitable probability generating function and combining the probabilities of different parameters using Dempster-Shafer Theory (DST). DST provides a way to combine evidence that is available from different sources and gives a joint degree of belief in a hypothesis. This will give us a combined belief of fault in the process with a high precision.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1438-1443
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• 2001

The significance of the casting/forging process for reducing the production cost of large components is being noted in these days. This casting/forging process is a method of forging a workpiece preformed by casting into the final shape. In this study, the casting/forging process has been applied in manufacturing a large aluminum flange in order to reduce press capacity and material cost. Firstly, a hot compression test was performed with cast cylindrical billets in order to determine the optimum forging condition of the aluminum flange. The optimum range of forging temperature of Al 5083 was from 420$\^{C}$ to 450$\^{C}$. The suitable strain rate was 1.5 sec(sup)-1. The deformation amount of a preform of a preform in a forging process is a key role in the mechanical properties of casting/forging products. In order to find the change of mechanical properties according to effective stain of cast aluminum billets, a hot upsetting test were performed with rectangular blocks and then a uniaxial tensile test was performed with specimens cut from the upsetted billets. The tensile strength and the elongation of cast/upsetted aluminum billets were increased largely until the effective strain was 0.7. FE analysis was performed to determine the configurations of case preform and die for an aluminum flange. In the FE analysis, the forging load-limit was fixed 1500ton for low equipment cost. The cast preform was designed so that the effective stain around the neck of a flange exceeded 0.7. From the result of FE analysis, optimal configurations of the cast preform and the die were designed for a large flange. The filling and solidification analysis for a sound cast-preform was carried out with MAGMA soft. In the forging experiment for an aluminum flange, it was confirmed that the optimal configuration of the cast preform predicted by FE analysis was very useful. The cast/forged products using designed preform were made perfectly without any defects.

• The Journal of the Korea Contents Association
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• v.18 no.12
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• pp.639-645
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• 2018

The objective of this research was to compare the precision of scanning the digital abutment impression and gypsum model according to 3-dimensional superimposing different skills. There were made with the abutment impression and gypsum model of a maxillary 1st premolar, blue light scanner scanned to obtain the stereolithography (STL) file. After the same process was performed 10 more times without moving them on the scanner table about the abutment impression and gypsum model, respectively (n=11, per types). By superimposing the date of scanning the abutment impression and gypsum model used with no control and best-fit-alignment skills, 10 color-difference maps and root mean square (RMS) data were obtained. The independent t-test was performed to compare RMS data between the each other groups (${\alpha}=0.05$). In the scanning abutment impressions, $RMS{\pm}SD$ of no control, best-fit-alignment showed $6.86{\pm}0.94$, $5.04{\pm}0.24$. in the scanning gypsum model, $4.98{\pm}1.16$, $3.39{\pm}0.07$, all groups showed a significant difference (P<0.001). Trough the this study's result, not only best-fit-alignment but no control is used with digital dental computer-aided design/computer-aided manufacturing (CAD/CAM) research and clinical part.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.5
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• pp.803-812
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• 2002

Reverse engineering has been widely used for the shape reconstruction of an object without CAD data and the measurement of clay or wood models for the development of new products. To generate a surface from measured points by a laser scanner, typical steps include the scanning of a clay or wood model and the generation of manufacturing data like STL file. A laser scanner has a great potential to get geometrical data of a model for its fast measuring speed and higher precision. The data from a laser scanner are composed of many line stripes of points. A new approach to remove point data with Delaunay triangulation is introduced to deal with problems during reverse engineering process. The selection of group of triangles to be triangulated based on the angle between triangles is used for robust and reliable implementation of Delaunay triangulation as preliminary steps. Developed software enables the user to specify the criteria for the selection of group of triangles either by the angle between triangles or the percentage of triangles reduced. The time and error for handling point data during modelling process can be reduced and thus RP models with accuracy will be helpful to automated process.