• Journal of Korean Society of Forest Science
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• v.88 no.2
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• pp.142-148
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• 1999

This research describes the construction of a site index equation and curves for Douglas-fir plantation (Pseudotsuga menziesii Mirb. Franco) in Nelson, New Zealand. The data sets of 146 Permanent Sample Plots (PSP) were used to build the model, and it was developed using the difference equation method. Parameter estimates were obtained using the non-linear routine of the SAS, PROC NLIN procedure. Of the models tested, a variant of the Schumacher polymorphic yield function showed the higher precision of fitting. About 95% of the observations used to fit the model could be predicted within ${\pm}1.2m$ of the actual values. Therefore, polymorphic family of site index curves, which reflect different shapes for the different site index classes, were derived from the Schumacher equation. It was found that the polymorphic site index equation was more accurate than the anamorphic equation in this study.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.39-46
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• 2018

Two surfaces that have relative motion show different characteristics according to surface roughness or surface patterns in all lubrication areas. For two rough surfaces with mixed lubrication, this paper proposes a new approach that includes the contact characteristics of the surfaces and a probabilistic method for a numerical analysis of lubrication. As the contact area of the two surfaces changes according to the loading conditions, asperity contact is very important. An average flow model developed by Patir-Cheng is central to the study of lubrication for rough surfaces. This average flow model also refers to a multi-asperity contact model for deriving a modified Reynolds equation and calculating the lubricant characteristics of a bearing surface with random roughness during fluid flow. Based on the average flow model, this paper carried out a numerical analysis of lubrication using a contact model by considering a load change made by the actual contact of asperities between two surfaces. Lubrication properties show different characteristics according to the surface patterns. This study modeled various geometric surface patterns and calculated the characteristics of lubrication.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.1
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• pp.21-27
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• 2002

Inspection and shape measurement of three-dimensional objects are widely needed in industries for quality monitoring and control. A number of visual or optical technologies have been successfully applied to measure three-dimensional surfaces. However, those conventional visual or optical methods have inherent shortcomings such as occlusion and variant surface reflection. X-ray vision system can be a good solution to these conventional problems, since we can extract the volume information including both the surface geometry and the inner structure of any objects. In the x-ray system, the surface condition of an object, whether it is lambertian or specular, does not affect the inherent characteristics of its x-ray images. In this paper, we propose a three-dimensional x-ray imaging method to reconstruct a three dimensional structure of an object out of two dimensional x-ray image sets. To achieve this by the proposed method, two or more x-ray images projected from different views are needed. Once these images are acquired, the simultaneous algebraic reconstruction technique(SART) is usually utilized. Since the existing SART algorithms have several shortcomings such as low performance in convergence and different convergence within the reconstruction volume of interest, an advanced SART algorithm named as USART(uniform SART) is proposed to avoid such shortcomings and improve the reconstruction performance. Because, each voxel within the volume is equally weighted to update instantaneous value of its internal density, it can achieve uniform convergence property of the reconstructed volume. The algorithm is simulated on various shapes of objects such as a pyramid, a hemisphere and a BGA model. Based on simulation results the performance of the proposed method is compared with that of the conventional SART method.

• Journal of Science of Art and Design
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• v.8
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• pp.267-296
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• 2005

Typography, as the median for communication, has expanded its roles according the attributes of the media where it Is used, and the change of media follwing the change of times is presenting new directions to the field of typography. The attempts of 20C experimental typography prioritize visual formativeness, free typography and language started to appear on printed matters and different kinds of prints put pep in magazines. Thus, experiments in the aspects of effective delivery of inpormation that letters have and aesthetic side of shapes of letter are continuing. Today with the appearance of multimedia, development of visual colture and rapid development of digital technology, the range of experimental typography has expanded even wider and therefore, different kinds of expressions became possible. As seen above, unlike the existing static printed media that carries linguistic information only, letters in the multimedia environment is shown in the movie titles, TV or web not only as a basic visual media such as type and image, but as a dynamic and complex factor that contains additional information of motion and sound factor. This study will attempt to find the historic context of focus of moment from the kinetic art and define the moving letters as kinetic typography. Therefore, this paper will have an understanding on kinetic typography's background, concept and characteristics following the change of communication environment in the multimedia era and tried to study the basic theories of kinetic typography and the information delivery and imagery function of letters. Also, this paper attempted to carry out a study on whether kinetic typography is delivering information smoothly from the aspect of communication through the image role as delivering information by studying major works of artists who have influenced kinetic typography. Based on this study, I would like to suggest new direction for effective delivery of information and value of use.

• Journal of Korean Society of Transportation
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• v.24 no.4 s.90
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• pp.19-29
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• 2006

As the rapid increase of highway investments from Private sector the organizations of highway operator became diversified, and thus causing various unexpected problems. Highways invested by private capitals have different fare rates and managing systems. It is desirable to reduce drivers' inconvenience using more than two sections of highways spread over different jurisdictions. The main purposes of this research are i) data survey and problem statements ii) prediction of future problems and preparing appropriate countermeasures. This research are divided into two parts. They are management system and fare collection system. Major investigations of this study are as follows, optimum toll operation models depend on charging systems and interchange shapes of two interconnecting expressways. Assuming that the current payment and the new electronic payment system aye used concurrently for a while, some alternatives for the inter-operation to collect tolls ate suggested focusing on the efficiency to tollway corporations as well as convenience to drivers. The advantages and disadvantages of the alternatives, including their characteristics, are compared.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.4
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• pp.121-126
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• 2010

The automotive weather strip has functions of isolating of water, dust, noise and vibration from outside. To achieve good sealing performance, weather strip should be designed to have the high contact force and wide contact area. However, these design causes excessive permanent deformation of weather strip. The causes of permanent deformation is generally explained to be the chemical material detrioration and physical variation and cyclic loading, etc. This paper introduces a numerical method to predict the permanent deformation using the time dependent viscoelastic model which is represented by Prony series in ABAQUS. Uniaxial tension and creep tests were conducted to obtain the material data. And the lab. test for the permanent deformation was accelerated during shorter time, 300 hours. The permanent deformation of weather strip was successfully predicted under the different loading conditions and different section shapes using the suggested numerical process.

• Journal of Adhesion and Interface
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• v.14 no.2
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• pp.75-81
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• 2013

Epoxy matrix based composites were fabricated by adding SiC nano fillers. The interfacial properties of composites were varied with different shapes of SiC nano fillers. To investigate the shape effects on the interfacial properties, beta and whisker type SiC nano fillers were used for this evaluation. The dispersion states of nano SiC-epoxy nanocomposites were evaluated by capacitance measurements. FE-SEM was used to observe the fracture surface of different structures of SiC-epoxy nanocomposites and to investigate for reinforcement effect. Interfacial properties between carbon fiber and SiC-epoxy nanocomposites were also evaluated by ILSS (interlaminar shear strength) and IFSS (interfacial shear strength) tests. The interfacial adhesion of beta type nanocomposites was better than whisker type.

• Korean Journal of Materials Research
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• v.23 no.2
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• pp.116-122
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• 2013

For fabricating silicon solar cells with high conversion efficiency, texturing is one of the most effective techniques to increase short circuit current by enhancing light trapping. In this study, four different types of textures, large V-groove, large U-groove, small V-groove, and small U-groove, were prepared by a wet etching process. Silicon substrates with V-grooves were fabricated by an anisotropic etching process using a KOH solution mixed with isopropyl alcohol (IPA), and the size of the V-grooves was controlled by varying the concentration of IPA. The isotropic etching process following anisotropic etching resulted in U-grooves and the isotropic etching time was determined to obtain U-grooves with an opening angle of approximately $60^{\circ}$. The results indicated that U-grooves had a larger diffuse reflectance than V-grooves and the reflectances of small grooves was slightly higher than those of large grooves depending on the size of the grooves. Then amorphous Si:H thin film solar cells were fabricated on textured substrates to investigate the light trapping effect of textures with different shapes and sizes. Among the textures fabricated in this work, the solar cells on the substrate with small U-grooves had the largest short circuit current, 19.20 mA/$cm^2$. External quantum efficiency data also demonstrated that the small, U-shape textures are more effective for light trapping than large, V-shape textures.

• Journal of Welding and Joining
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• v.35 no.2
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• pp.23-29
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• 2017

Mechanical properties and hardness distributions in arc brazed joints of Dual phase steel using Cu-Al insert metal were investigated. The maximum tensile shear load was 10.4kN at the highest brazing current. It was about 54% compared to tensile load of base metal. This joint efficiency is higher than that of joint of DP steel using Cu-based filler metals which are Cu-Si, Cu-Sn. Fracture positions can be divided into two types. Crack initiation commonly occurred at three point junction among upper sheet, lower sheet and the fusion zone. However crack propagations were different with increasing the brazing current. In case of the lower current, it instantaneously propagated along with the interface between fusion zone and upper base material. On the other hand, in case of higher current, a crack propagation occurred through fusion zone. When the brazing current is low (60, 70A), the interface shape is flat type. However the interface shape is rough type, when the brazing current is high (80A). It is thought that the interface shapes were the reason why the crack propagations were different with brazing current. The interface was the intermetallic compounds which consisted of $(Fe,Al)_{0.85}Cu_{0.15}$ IMC formed by crystallization at $1200^{\circ}C$during cooling. Therefore the maximum tensile shear load and the fracture behavior were determined by a interface shape and effective sheet thickness of the fracture position.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.4
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• pp.321-334
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• 2012

Purpose: In this study, the distribution and differences in refractive powers on trial case lenses were investigated. Methods: We measured refractive powers at optical center and periphery using 4 trial case lens sets. According to international standards, the distribution and uniformity in refractive powers were investigated. Results: The lens shapes were different in different kinds of trial case lenses and some of lenses were out of tolerance according international standards. In some cases, the power differences were found between front and back side as well as between optical center and peripheral regions and also the cylindrical power on spherical lens and spherical power on the cylindrical lens were measured. Conclusions: Trial case lens are used to assess the refractive error, therefore, more precise control of the manufacturing process for trial case lenses and more thorough quality control will be required to offer an accurate vision test. More careful attention in using trial case lens is also required.