• Journal of Korean Ophthalmic Optics Society
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• 제18권2호
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• pp.197-202
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• 2013

Purpose: This research was performed to measure and analyze scotopic pupil size in myopes and to figure out the factors that influence it. Methods: The pupil size of 191 healthy myopic subjects were measured with the pupillometer (Colvard pupillometer, OASIS medical, USA) in scotopic and analyzed with the age, corneal size, spherical equivalent refractive error, corneal curvature. In addition, it was compared with the measurements of intra-examiner and inter-examiner to verify reproducibility of pupillometer. Results: The mean (${\pm}$SD) scotopic pupil size was $6.64{\pm}0.68$ mm (range, 5.00~8.00 mm), the lower age and the larger corneal size, The bigger the pupil size. The lower spherical equivalent refractive error and steepper corneal curvature tends to be smaller. The reproducibility of intra-examiner and inter-examiner in pupillometer showed the reliability highly (Guttman splithalf point > 0.91). Conclusions: The pupil size associated with age, corneal size, spherical equivalent refractive error and corneal curvature in scotopic condition. It can refer to prevent inconvenience that may occur RGP contact lenses, cataract surgery and refractive surgery.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제24권4호
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• pp.937-945
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• 2000

The assessment of machined surface is difficult because the freeform surface must be evaluated by surface fairness as well as dimensional accuracy. In this study, the machined freeform surface is modeled by interpolating the data measured on the machine tool into the mathematical continuous surface, and then the surface model is improved with the parameterization to minimize surface fairness. The accuracy reliability of the measured data is confirmed through compensation of volumetric errors of the machine tool and of probing errors. Non-uniform B-spline surface interpolation method is adopted to guarantee the continuity of surface model. Surface fairness is evaluated with the consideration of normal curvature on the interpolated surface. The validity and usefulness of the proposed method is examined through computer simulation and experiment on the machine tool.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.60-63
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• 2004

An innovative in-core neutron flux mapping system has been developed and applied successfully for service in a commercial pressurized water reactor. With the benefit of double indexing path selector (Dip $s^{ⓡ}$) mechanism, the reliability of the detector drive system has been improved five times higher than that of conventional systems, and the problems caused by the serious friction generated between the detector cable and guide tubing has been solved completely because the Dip $s^{ⓡ}$ architecture allows the detector guide tubings to have larger curvature and shorter length in nature. The simple and fast maintenance is particularly emphasized in the detector drive system to secure minimum radiation exposure to the maintenance personnel by optimizing the number of components and providing easy access to the components. The programmable logic controller based digital controller with Window $s^{ⓡ}$ based operator s console provides fully automated and user friendly operation and maintenance support means.

• Journal of Sensor Science and Technology
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• 제18권5호
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• pp.353-358
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• 2009

Ionic polymer metal composite(IPMC) has been used as a promising material for various actuator applications. The IPMC actuator is difficult to be fabricated with complicated 3-dimensional shape. We propose a simple heat treatment process that can fabricate IPMC actuator with various shapes. Experimental results show the pre-shaped IPMC actuator by heat treatment does not show any degradation of its actuation abilities such as bending displacement, generation force and reliability in bending motion.

• Geomechanics and Engineering
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• 제38권2호
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• pp.179-189
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• 2024

This paper presents a geomechanical framework for designing and optimizing layout patterns of cutterheads for rock Tunnel Boring Machines (TBMs), aiming to enhance their engineering performance. By examining the forces and moments exerted by rock, the study addresses geometric constraints associated with cutter boxes in key regions of the cutterhead, including the center, face, and gage areas, as well as the three-dimensional effects of cutterhead curvature on the geometric constraints of the back of the cutter boxes in the gage area. Novel formulas are proposed for determining the center points of cutter boxes and calculating both the minimum angular spacing and distance spacing between consecutive cutter boxes along a spiral path. The paper outlines an optimized layout design process for four cutterhead configurations: random, random paired, radial, and double spiral designs. Examples are provided to illustrate the results of applying these designs. The findings underscore the efficacy of the proposed methods in achieving a uniform and symmetrical distribution of cutters and buckets on the cutterhead surface. This approach effectively eliminates boundary overlap and minimizes unbalanced forces and moments. From a geomechanical standpoint, this framework offers a robust strategy for enhancing the performance and reliability of TBM cutterheads in rock tunneling operations.

• Journal of the Earthquake Engineering Society of Korea
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• 제7권4호
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• pp.1-13
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• 2003

For spatial free vibration of non-symmetric thin-walled curved beams with shear deformation, an improved formulation is proposed in the present study. The elastic strain and the kinetic energies are first derived by considering constant curvature and shear deformation effects due to shear forces and restrained warping torsion. Next equilibrium equations and force-deformation relations are obtained using a stationary condition of total potential energy. And the finite element procedures are developed by using isoparametric curved beam element with arbitray thin-walled sections. Particularly not only shear deformation and thickness-curvature effects on vibration behaviors of curved beams but also mode transition and crossover phenomena with change in curvatures of beams are parametrically investigated. In order to illustrate the accuracy and the reliability of this study, various numerical solutions for spatial free vibration are compared with results by available references and ABAQUS's shell element.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.376-376
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• 2012

Semiconductor nanowires (NWs) are future building block for nano-scale devices. Especially, Ge NWs are fascinated material due to the high electrical conductivity with high carrier mobility. It is strong candidate material for post-CMOS technology. However, thermal stability of Ge NWs are poor than conventional semiconductor material such as Si. Especially, when it reduced size as small as nano-scale it will be melted around CMOS process temperature due to the melting point depression. Recently, Graphene have been intensively interested since it has high carrier mobility with single atomic thickness. In addition, it is chemically very stable due to the $sp^2$ hybridization. Graphene films shows good protecting layer for oxidation resistance and corrosion resistance of metal surface using its chemical properties. Recently, we successfully demonstrated CVD growth of monolayer graphene using Ge catalyst. Using our growth method, we synthesized Ge/graphene core/shell (Ge@G) NW and conducted it for highly thermal stability required devices. We confirm the existence of graphene shell and morphology of NWs using SEM, TEM and Raman spectra. SEM and TEM images clearly show very thin graphene shell. We annealed NWs in vacuum at high temperature. Our results indicated that surface melting phenomena of Ge NWs due to the high surface energy from curvature of NWs start around $550^{\circ}C$ which is $270^{\circ}C$ lower than bulk melting point. When we increases annealing temperature, tip of Ge NWs start to make sphere shape in order to reduce its surface energy. On the contrary, Ge@G NWs prevent surface melting of Ge NWs and no Ge spheres generated. Furthermore, we fabricated filed emission devices using pure Ge NWs and Ge@G NWs. Compare with pure Ge NWs, graphene protected Ge NWs show enhancement of reliability. This growth approach serves a thermal stability enhancement of semiconductor NWs.

• Transactions of the Korean Society of Automotive Engineers
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• 제12권4호
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• pp.101-109
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• 2004

Three models with various degree-of-freedom for a manual transmission clutch full-size tester have been developed and the models' reliability and accuracy have been verified using the measured data. A simulation study has also been conducted to understand dynamic behavior of the tester. The model for this simulation study includes clutch disk friction and damper dynamics. The developed model is very accurate in terms of maximum torque exerted on the clutch, slip duration and the vibration response except a slight difference compared to the measured data. In a history graph of the clutch torque, the maximum torque response from simulation is flat but the measured is sunken with a noticeable curvature. This phenomenon is found to be irrelevant to the dynamics of the full-size tester but is originated from the characteristics of the clutch itself. Thus, the full-size tester has been proven to be a reliable tester for clutch's power and torque transmission capability. To obtain a better understanding of clutch's characteristics and relationship between full-size tester and other testing methodologies, future research directions have been suggested.

• Physical Therapy Korea
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• 제16권1호
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• pp.42-51
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• 2009

The purpose of this study was to develop a checklist of risk factors for quantitative assessment of musculoskeletal complaints in shipbuilding workers. A key point was to develop comprehensive a checklist including the worker's physical ability, as ergonomic and workload factors. ln the first, through correlation analysis between musculoskeletal complaints and physical abilities in shipbuilding workers, risk factors related to physical abilities were selected. In the second, after the development of a checklist was composed of physical, ergonomic and workload factors, factor analysis was used to test the validity of the developed checklist. Each factors selected finally showed that physical factors were hand grip strength, spinal curvature, and flexibility (sit to reach), ergonomic factors were posture, total exposed time, duration, and force of working, and workload factors were physical and psychological workload perceived by worker. The results showed that musculoskeletal complaints was associated with physical abilities (p<.05). The developed checklist had a reliability of .761 (Cronbach=.761) and a validity and explanation of 54.9%. The criterion of management was classified in 4 stages by relative weights of each factor. It is suggested that active intervention is needed to reduce musculoskeletal complaints in workers with more than a 14.31 score.

• Smart Structures and Systems
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• 제4권6호
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• pp.741-757
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• 2008

The research field of structural control has evolved from the development of passive devices since 1970s, through the intensive investigation on active systems in 1980s, to the recent studies of semi-active control systems in 1990s. Currently semi-active control is considered most promising in civil engineering applications. However, actual implementation of semi-active devices is still limited due mainly to their system maintenance and associated long-term reliability as a result of power requirement. In this paper, the concept of functionally upgraded passive devices is introduced to streamline some of the state-of-the-art researches and guide the development of new passive devices that can mimic the function of their corresponding semi-active control devices for various applications. The general characteristics of this special group of passive devices are discussed and representative examples are summarized. Their superior performances are illustrated with cyclic and shake table tests of two example devices: mass-variable tuned liquid damper and friction-pendulum bearing with a variable sliding surface curvature.