• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.118-125
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• 2009

This paper reports the size classification of nanoparticles as well as electrical tuning techniques for the cut-off diameter and collection efficiency. Classifying particles < 100 nm in diameter is quite a technical challenge using a virtual impactor with the cut-off diameter being determined geometrically. However, the proposed virtual impactor can classify particles <100 nm and tune the cut-off diameter by electrically accelerating the particles. The cut-off diameter of the proposed device was tuned from 15 to 50nm.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.285-291
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• 1991

A two-stage slit type virtual impactor based on the concept of the single stage virtual impactor has been designed, fabricated, and evaluated for the purpose of concentrating the suspended particles in the air with the size range of 1.8-4.5 .mu.m and handling large flow volume. Monodisperse methylene blue particles have been generated with vibrating orifice aerosol generator (VOAG). The separation efficiency and concentration efficiency have been measured by the UV-visible absorption spectrometry. Previous study for a single stage virtual impactor were used to determine the design parameters such as 50% cut-off sizes and dimensions of the two stage virtual impactor. The separation efficiency curve and 50% cut-off Stokes number(cut-off sizes) are not sensitive to the nozzle Reynolds number, but sensitive to the ratio between the minor flow rate and the total flow rate, The measured concentration efficiency was compared with the maximum concentration efficiency determined by the separation efficiencies of the first and the second stages. The differences between the measured and the maximum concentration efficiencies result from the wall loss due to the deposited particles on the internal walls inside the impactor.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.12
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• pp.86-92
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• 2002

This paper presents a new model of NC verification in NC milling using z-map. The model can describe the motion of machine tool like a real machine effectively. The model uses x, y, and z directional feed rate as well as cutting data for modeling Z-map of workpiece. The model verifies the over-cut, the under-cut and the surface topography using NC codes and cutting conditions. To investigate the performance of the model, simulation study was carried out. As the results, the model gave the geometry accuracy of workpiece, the surface topography, and the chip loads.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.7
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• pp.63-70
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• 2019

An electro-aerodynamic lens for improving the performance of virtual impactor has been proposed in this study. ANSYS FLUENT Release 16.1 was used for numerical analysis of virtual impactor with and without the electro-aerodynamic lens, used to collimate the incoming aerosol particles into a particle beam before injecting the particles into the virtual impactor. Particles supplied to the electro-aerodynamic lens were assumed to be highly charged. By using an aerodynamic lens before the virtual impactor, without any electrostatic effect, it was found that the cut-off diameter of the virtual impactor was reduced from $4.2{\mu}m$ to $0.68{\mu}m$ and that the fine particle contamination problem became more serious. However, by employing the combined electrostatic and aerodynamic effects, that is, by applying electric voltage potential to the electro-aerodynamic lens, the cut-off diameter was found to be further reduced to $0.45{\mu}m$ and the fine particle contamination was eliminated.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.4
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• pp.173-179
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• 2003

In this paper, a real-time multibody vehicle dynamics and control model has been developed for a virtual reality intelligent vehicle simulator. The simulator consists of low PCs for a virtual reality visualization system, vehicle dynamics and control analysis system a control loading system, and a network monitoring system. Virtual environment is created by 3D Studio Max graphic tool and OpenGVS real-time rendering library. A real-time vehicle dynamics and control model consists of a control module based on the sliding mode control for adaptive cruise control and a real-time multibody vehicle dynamics module based on the subsystem synthesis method. To verify the real-time capability of the model, cut-in, cut-out simulations have been carried out.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.6
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• pp.105-111
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• 1995

The inverse dynamic equations for 5 link robot including a closed chain have been derived. The closed chain is virtually cut open, and the kinematics and dynamics of the virtual open chain robot are analyzed. The constraints are applied to the virtually cut joints by the Jacobian matrix which represents the configuration of the closed chain. The topology of tree structrued open chain robot is described by a FATHER array. The FATHER array of a link indicates the link tha tis connected in the direction of base link. Based on the inverse dynamic equations, the torque sensitivity models of the 5 link robot have been developed. The sensitivity models characterize the sensitivity of the driving torque with respect to the link parameters. All the procedures are illustrated through the 2 link robot.

• Journal of the Korean Home Economics Association
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• v.46 no.2
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• pp.73-83
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• 2008

The focus of this research was concerned with studying lower body type for Korean adult females. information from the measuring values based on research on the physical standard of the nation(2004) were summarized, in addition a factor of the need for appropriate fit in boots cut jean wear, basic lower body part applying to each item had to be taken into consideration to enhance sizing suitability. The body type are classified into three kinds by means of factor analysis and cluster analysis. Type 1 referred to the fat lower body, having thick rounding waist. compared to other body parts, and long leg according to its proportion. Type 2 represented medium stature but with a large skeleton structure of lower body. Type 3 represented a the long lower body having slender rounding waist. This study was attempted to evaluate the fitness of boots cut jeans pattern for women using 3D Clothes Modeling Software.

• Journal of the Korean Society of Clothing and Textiles
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• v.48 no.4
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• pp.744-755
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• 2024

This study analyzes the characteristics, product dimensions, and ease of haenyeo suits to inform their reproduction. Large, medium, and small haenyeo suits were collected from four manufacturers in Jeju, and their components, cut styles, product dimensions, and ease were analyzed. In the current haenyeo suit design, the upper suit has a collar and a crotch, while the lower suit has a high rise with a gusset. Additionally, there are darts behind the neck in the upper suit and behind the knees in the lower suit. Haenyeo suits have a three-dimensional shape that accommodates the postures needed for haenyeo's underwater activities. The upper suit is finished with a cuffed hem or an uncuffed side seam with a diagonal or stepped cut. The lower suit is cut and sewn with the waist and hem at right angles or with the hem diagonal to the waistline. Haenyeo suit dimensions vary between manufacturers, and the models' body dimensions show that there is little or no ease. In conclusion, haenyeo suit manufacturers currently use the same components; however, they differ in terms of cut styles, sewing methods, dimensions, and designs.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.5
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• pp.423-430
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• 2012

In this paper, the effect of wrinkling on the cut propagation direction of thin membrane was studied using geometrically nonlinear shell element post-buckling analysis. In the analysis, rectangular tensile membrane configuration with a slanted center cut was considered. The cut propagation direction was predicted by maximum energy release rate method, $K_{II}$-zero method, and maximum tangential stress method. The cut propagation angle and the $J$-integral values were calculated for the wrinkled and unwrinkled cases and the results were compared. Various initial cut orientation angles were considered and the effect on the propagation direction was studied. The cut propagation paths were also predicted by virtual cut extension approach.

• Proceedings of the Safety Management and Science Conference
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• 2000.11a
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• pp.1-5
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• 2000

With the advent of the internet era, web-based virtual training system is gaining its importance in recent years. Because of the fact that the training can take place in any place and at any time, the virtual system is now replacing many of the conventional off-line classes. Hardware environments such as communication bandwidth and computer performance gets fast enough to accommodate the virtual education. Based on the observations on current virtual training system, this paper proposes three critical design rules required when developing a new virtual training system: i) With conceptual mapping, the menu hierarchy can be organized in a clear-cut manner, ii) Extensive use of multimedia tools can help students keep their attention to the lecture materials, and iii) Provision of interaction mechanisms helps students to gain their identity and motivation.