• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.6
• /
• pp.116-125
• /
• 2008

In general, fretting is a contact damage process due to micro-slip associated with small amplitude oscillatory movement between two surfaces in contact. Previous studies in fretting fatigue have observed a contact size effect related to contact width. The volume-averaging method of theoretically predicted contact stress fields was required to emulate experimental trends and to predict the observed contact size effects. This contact size effect is captured by the mean values of stresses and strains at the element integration points of FE model and two critical plane models (SWT, FS) in the present paper. It is shown that crack nucleation and fretting fatigue life can be predicted by the FE-based critical plane models.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.488-491
• /
• 2005

Abrasive Jet Micromachining (AJM) is a process that uses high pressure air with micron-sized particles to erode a substrate. It has been considered as the most economic and appropriate technique to pattern glass surfaces for the flat panel applications. To accelerate the industrialization of AJM, it is necessary to understand the erosion mechanisms thoroughly. Thus, this paper introduces a new method to model the erosion mechanism in AJM. The model is developed by using the concept of the accumulation of the microdeformation caused by each particle. And this paper proposes the model added the effects of second impact. The developed model is used to simulate the erosion profile, and is compared with the model considered only first impact. It can be concluded that the proposed model predicts the erosion profile more accurately.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11b
• /
• pp.1280-1286
• /
• 2001

This paper presents some advanced and supplemental methods to enhance the accuracy in case of calculating geometric divergence attenuation, attenuation by multiple screening structures, ground attenuation at unflat surfaces of sound during propagation outdoors by the methods specified in ISO 9613-2. Moreover, a calculation method for considering short-term wind effect, specified in ASJ Model-1998, is also introduced. To verify the accuracy of adopted methods, we have carried out highway traffic noise prediction and measurement at the twelve locations appearing representative road shapes and structures, such as flat, retained cut, elevated, barrier-constructed roads. From the results, we have confirmed the predicted results show good correspondence with the measured at direct, diffracted and reflected sound fields within 30m from the center of near side lane.

• Proceedings of the KACD Conference
• /
• 2003.11a
• /
• pp.569-569
• /
• 2003

I. Objectives The purpose of this study was to evaluate the effort of a modified luting procedure called "dual bonding technique" by compare micro-shear bond strength to different luting procedures of ceramics to dentin. II. Materials and Methods Eighty-four freshly extracted caries-and restoration-free human third molar were embedded in epoxy resin using acrylic ring. Flat superficial occlusal dentin surfaces were obtained, initially using a Low speed diamond saw and exposed detin surface was group with ＃600-grit SiC paper.(omitted)

• Proceedings of the KACD Conference
• /
• 2003.11a
• /
• pp.609-609
• /
• 2003

I. Objectives The purpose of this study was to evaluate the effect of adhesive property on microtensile bond strength and to determine the failure mode. II. Materials and Methods Flat occlusal dentin surfaces were prepared using low-speed diamond saw. The dentin was etched with 37% phosphoric acid. The following adhesives were applied to the etched dentin according to manufacturer's directions；Scotchbond Multi-Purpose in group 1, Primer＆Bond NT in group 2, Scotchbond Multi-Purpose followed by Tetric-flow in group 3. After adhesive application, a cylinder of resin-based composite was built up the occlusal surface.(omitted)

• Korean Journal of Optics and Photonics
• /
• v.2 no.4
• /
• pp.186-192
• /
• 1991

For the micro-lithography using a excimer laser beam $(\lambda\leq0.248$\mu\textrm{m})$. a mirror system consisting of four spherical surfaces with reductlon magnification 5X is designed. Initially the aplanat, flat field and the distortion free condition of the system are analytically investigated within Seidel 3rd order aberrations. And the computer-aided optimization technique has been employed for the further improved performance of the system. The final system has N.A. of 0.15 and image field diameter 3.3 mm, and has the diffraction-limited performance for KrF eximer laser beam.

• Journal of Electrochemical Science and Technology
• /
• v.10 no.2
• /
• pp.206-213
• /
• 2019

The development of simple methods for As detection has received great attention because As is a toxic chemical element causing environmental and health-related issues. In this work, the effect of nanostructures of Au electrodes on their electroanalytical performance during As detection was investigated. Different Au nanostructures with various surface morphologies such as nanoplate Au, nanospike Au, and dendritic Au structures were prepared, and their electrochemical behaviors toward square-wave anodic stripping voltammetric As detection were examined. The difference in intrinsic efficiency for As detection between nanostructured and flat Au electrodes was explained based on the crystallographic orientations of Au surfaces, as examined by the underpotential deposition of Pb. The most efficient As detection performance was obtained with nanoplate Au electrodes, and the effects of the pre-deposition time and interference on As detection of the nanoplate Au electrodes were also investigated.

• Design & Manufacturing
• /
• v.15 no.3
• /
• pp.19-25
• /
• 2021

The bending process of a press die is to bend a flat blank to the required angle. There are V-bending, U-bending, Z-bending, O-bending etc. for bending processing, and the basic principle of calculating the unfolding length of die processing is used as the neutral plane length. Since the constant of the length value of the neutral surface is different depending on the type of bending, it is impossible to accurately calculate it. In particular, Z-bending processing is performed twice, and it is set on the upper and lower surfaces of the blank, and bending processing occurs at the same time as the upward and downward bending, and the elongation of the material occurs and the material increases. It is not possible to check with the calculated value, and it occurs in many cases where the mold is modified after start-up. This study aims to minimize die modification by developing a formula to calculate the development length of Z-bend.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.18 no.4
• /
• pp.1-11
• /
• 1981

A flow problem around a ship hull with the nonlinear free surface boundary condition has been considered within the potential flow assumption. The Green's function based on the hull boundary condition is constructed numerically and used to satisfy the free surface boundary condition. This singularity to be distributed ideally on the undulating free surface is put actually, for practical reasons, on the flat water surface with the assumption of linear variation of velocities between the two positions. The surfaces of singularity distribution are approximated by Hess and Smith type quadrilaterals. The radiation condition is only crudely satisfied and this produced one of the major difficulties arising in the present way of attacking the problem.

• Nuclear Engineering and Technology
• /
• v.55 no.1
• /
• pp.180-189
• /
• 2023

We measured the heat load to a reactor vessel with and without the in-vessel debris bed under an IVR-ERVC condition. Mass transfer methodology was adopted based on heat and mass transfer analogy to achieve high Ra'_H of order ~10¹⁵ with compact test rigs. We postulated the in-vessel debris bed has a flat top and particulate debris was simulated as an identical diameter spheres. We conducted experiments varying the height of the debris bed and the results showed that Nusselt numbers decreased in both uppermost and curved surfaces with the increasing bed height. Once the debris bed is formed, it acts as an obstacle to the natural convective flow, which reduces the buoyancy. The reduction of driving force results in the impaired heat transfer in both upward and downward heat transfers.