• Journal of Ocean Engineering and Technology
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• v.12 no.3 s.29
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• pp.49-59
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• 1998

The damage mechanism of $Cr_2O_3$ plasma coated soda-lime glass and uncoated glass by steel ball particle impact was analyzed in this study. And the shape variation of the cracks was investigated by stereo-microscope according to the impact velocity and steel ball diameter. In order to improve the damage reduction effect by $Cr_2O_3$ coating layer, crack size was measured and surface erosion state was observed for both of two kinds of specimen after impact experiment. And the results were compared with each other. The 4-point bending test was performed according to ASTM D790 testing method to evaluate the effect of coating layer for bending strength variation. As a result, it was found that the crack size of $Cr_2O_3$ coated specimen was smaller than that of uncoated one, because of the impact absorption by interior pores in the coating layer and the load dispersion by the structural characteristic of the coating layer. For the specimens subjected to the steel ball impact, the bending strength of coated specimen was higher than that of uncoated specimen.

• Journal of Biomedical Engineering Research
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• v.33 no.4
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• pp.169-176
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• 2012

Tumor cell morphology is closely related to its migratory behaviors. An active tumor cell has a highly irregular shape, whereas a spherical cell is inactive. Thus, quantitative analysis of cell features is crucial to determine tumor malignancy or to test the efficacy of anticancer treatment. We use 3D time-lapse phase-contrast microscopy to analyze single cell morphology because it enables to observe long-term activity of living cells without photobleaching and phototoxicity, which is common in other fluorescence-labeled microscopy. Despite this advantage, there are image-level drawbacks to phase-contrast microscopy, such as local light effect and contrast interference ring. Therefore, we first corrected for non-uniform illumination artifacts and then we use intensity distribution information to detect cell boundary. In phase contrast microscopy image, cell is normally appeared as dark region surrounded by bright halo ring. Due to halo artifact is minimal around the cell body and has non-symmetric diffusion pattern, we calculate cross sectional plane which intersects center of each cell and orthogonal to first principal axis. Then, we extract dark cell region by analyzing intensity profile curve considering local bright peak as halo area. Finally, we calculated the Fourier descriptor that morphological characteristics of cell to classify tumor cells into active and inactive groups. We validated classification accuracy by comparing our findings with manually obtained results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.3
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• pp.245-252
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• 2016

In this study, an alternative bend design is proposed to overcome the aging problem in piping bends. In this design, the foam pad is not included. Finite element analysis was performed based on the total pipe diameter. From this analysis, the shape of the Shear Control Ring (SCR) was determined. Temperature, stress, and other data of the proposed reinforced pipe were acquired and analyzed after the test was performed. The value of the thermal stress for the reinforced steel pipe satisfied the required standard without the foam pad based on the manufacturing of the reinforced fitting and construction site of the test. The reinforcement provided a shear strength level for the foam pad that resulted in maximum shear stress less than stress based on the original foam pad applied at the pipe bend. Additionally, an increasing factor of safety effect for the reinforced fitting application was discovered.

• Advances in concrete construction
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• v.14 no.2
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• pp.139-151
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• 2022

Filling materials poured into precast member joint are subjected to restraint stress by the precast member and joint reinforcement. The induced stress will likely cause cracks at early ages and performance degradation of the entire structure. To prevent these issues and design reasonable joints, it is very important to analyze and evaluate the restrained shrinkage cracks of filling materials at various restraint conditions. In this study, a new time zero-that defines the shrinkage development time of a filling material-is proposed to calculate the accurate amount of shrinkage. The tensile stresses and strengths at different ages were compared through the ring test (AASHTO PP34) to evaluate the crack potential of the restrained filling materials at various restraint conditions. The mixture which contained an expansive additive and a shrinkage reducing agent exhibited high resistance to shrinkage cracking owing to the high-drying shrinkage compensation effect. The high-performance, fiber-reinforced cement composite, and ultra-high-performance, fiber-reinforced cement composite yielded very high resistance to shrinkage and cracking owing to the pull-out property of steel fibers. To this end, multiple nonlinear regression analyses were conducted based on the test results. Accordingly, a modified tensile stress equation that considered both the geometric shape of the specimen and the intrinsic properties of the material is proposed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.247.1-247.1
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• 2014

The capacitive coupled plasma is used widely in the semiconductor industries. Especially, the uniformity of the industrial plasma is heavily related with defect ratio of devices. Therefore, the industries need the capacitive coupled plasma source which can generate the uniform plasma and control the plasma's uniformity. To achieving the uniformity of the large area plasma, we designed multi-powered electrodes. We controlled the uniformity by controlling the power of each electrode. After this work, we started to research another concept of the plasma device. We make the plasma chamber that has multi-ground electrodes imaginary (CST microwave studio) and simulate the electric field. The shape of the multi-ground electrodes is ring type, and it is same as the shape of the multi-power electrodes that we researched before. The diameter of the side electrode's edge is 300mm. We assumed that the plasma uniformity is related with the impedance of ground electrodes. Therefore we simulated the imaginary chamber in three cases. First, we connected L (inductor) and C (capacitor) at the center of multi-ground electrodes. Second, we changed electric conductivity of multi-ground electrode. Third, we changed the insulator's thickness between the center ground electrode and the side ground electrode. The driving frequency is 2, 13.56 and 100 MHz. We switched our multi-powered electrode system to multi-ground electrode system. After switching, we measured the plasma uniformity after installing a variable vacuum capacitor at the ground line. We investigate the effect of ground electrodes' impedance to plasma uniformity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.5
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• pp.508-514
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• 2004

A fluxgate magnetic sensor consists of a solenoid excitation coil, pick-up coil, and magnetic core. We presents the effect of magnetic core shape in a micromachined fluxgate sensor. To observe the performance of fluxgate sensor with magnetic core side width and gap, side width of 125 ${\mu}{\textrm}{m}$, 250 ${\mu}{\textrm}{m}$, and 500 ${\mu}{\textrm}{m}$ were designed in a rectangular-ring shaped core and the gaps of 0 ${\mu}{\textrm}{m}$, 50 ${\mu}{\textrm}{m}$, and 100 ${\mu}{\textrm}{m}$ were also fabricated in a racetrack shaped core. The solenoid coils and magnetic core were separated by benzocyclobutane(BCB) which had high insulation and good planarization characters. Copper coil patterns of 10 ${\mu}{\textrm}{m}$ width and 6${\mu}{\textrm}{m}$ thickness were electroplated on Ti(300 $\AA$) / Cu(1500 $\AA$) seed layers. 3 ${\mu}{\textrm}{m}$ thick N $i_{0.8}$F $e_{0.2.}$(permalloy) film for the magnetic core was also electroplated under 2000 gauss to induce the magnetic anisotropy. The magnetic core had the high DC effective permeability of ∼1,300 and coercive field of ∼0.1 Oe. Because the magnetic cores of 500 ${\mu}{\textrm}{m}$ side width and 0 gap had a low magnetic flux leakage, high sensitivity of ∼350 V/T were measured at excitation condition of 3 $V_{P-P}$ and 2 MHz square wave. The power consumption of ∼14 ㎽ was measured. The fabricated fluxgate sensor had the very small actual size of 3.0${\times}$1.7 $\textrm{mm}^2$. When two fluxgates were perpendicularly aligned in terrestrial field, their two-axis output signals were very useful to commercialize an electronic azimuth compass for the portable navigation system.m.m.m.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.3
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• pp.241-249
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• 2017

A powerlock is used to transmit torque between two shafts, to protect important equipment from overloads, and to compensate for the misalignment of assembled shafts. In this study, the effect of the shapes of the inner rings, bolt-fastening force, and friction on power transmission performance of powerlocks is investigated. Finite element analysis and experiments were conducted for two cases, and the analysis results were validated. Analyses were carried out for inner rings of various shapes and for various values of bolt-fastening force and friction coefficient. The main factors that affect the torque transmission performance were investigated based on the analysis results.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2000.11a
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• pp.1-2
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• 2000

In chip plating, several parameters must be taken into consideration. Current density, solution concentration, pH, solution temperature, components volume, chip and media ratio, barrel geometrical shape were most likely found to have an effect to the process yields. The 3 types of barrels utilized in chip plating industry are the onventional rotating barrel, vibrational barrel(vibarrel), and the centrifugal type. Conventional rotating barrel is a close type and is commonly used. The components inside the barrel are circulated by the barrel's rotation at a horizontal axis. Process yield has known to have higher thickness deviation. The vibrational barrel is an open type which offers a wide exposure to electrolyte resulting to a stable thickness deviation. It rotates in a vertical axis coupled with multi-vibration action to facilitate mixed up and easy transportation of components. The centrifugal barrel has its plated work centrifugally compacted against the cathode ring for superior electrical contact with simultaneous rotary motion. This experiment has determined the effect of barrel vibration intensity to the plating thickness distribution. The procedures carried out in the experiment involved the overall plating process., cleaning, rinse, Nickel plating, Tin-Lead plating. Plating time was adjusted to meet the required specification. All other parameters were maintained constant. Two trials were performed to confirm the consistency of the result. The thickness data of the experiment conducted showed thatbthe average mean value obtained from higher vibrational intensity is nearer to the standard mean. The distribution curve shown has a narrower specification limits and it has a reduced variation around the target value. Generally, intensity control in vi-barrel facilitates mixed up and easy transportation of components. However, it is desirable to maintain an optimum vibration intensity to prevent solution intrusion into the chips' internal electrode. A cathodic reaction can occur in the interface of the external and internal electrode. 2H20 + e $\rightarrow$M/TEX> 20H + H2.. Hydrogen can penetrate into the body and create pressure which can cause cracks. At high intensity, the chip's motion becomes stronger, its contact between each other is delayed and so plating action is being controlled. However, the strong impact created by its collision can damage the external electrode's structure there by resulting to bad plating condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.235-242
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• 2014

To investigate pressure distributions on the shaft surface of the air bearing, the commercial CFD software was employed to study three different nozzle geometries to improve the nozzle performance: general drill-shaped, matched cube-shaped and trimmed exit nozzles. Under the influence of stagnation point, the maximum pressure was observed at the center of shaft surface for all cases. Owing to the blocking effect of a fine gap between the shaft surface and the nozzle exit, the drill-shaped nozzle has the rapid local pressure increase near the nozzle exit corner, generating the ring vortex in the radial direction within pressure ratio of 6.92, and its pressure becomes negative in a certain range of downstream. In comparison, the contoured nozzle showed a local pressure increase in the measured range of pressure ratios, but a negative pressure appeared within the pressure ratio of about 10. The trimmed nozzle was seemed to extend the high pressure zone near the stagnation point in the radial direction substantially, and no negative pressure was appeared in the whole range. Based on these observations, it is found that trimming nozzle exit becomes more effective for improving the performance than modifying the nozzle inside contour.

• Polymer(Korea)
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• v.30 no.2
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• pp.146-151
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• 2006

Linear and branched copolymers consisting of poly(ethylene glycol) (PEG) and $Poly({\varepsilon}-caprolactone)$ (PCL) were prepared to compare the characterization of star-shaped copolymers with various molecular architecture. Linear and branched PEG-PCL (1-arm, 2-arm, 4-arm, and 8-arm) copolymers were synthesized by the ring-opening polymerization of ${\varepsilon}-caprolactone$ in the presence of HCl $Et_2O$ as a monomer activator at room temperature. The synthesized copolymers were characterized with $^1H-NMR$, GPC, DSC, and XRD. As a result of the DSC and XRD, each copolymers showed different thermal properties and crystallinity according to the number of ms. The micellar characterization of linear and branched copolymers in an aqueous phase was carried out by using NMR, dynamic light scattering, AM, and fluorescence techniques. The critical micelle concentration (CMC) and diameters of micelles depended on the number of arms. Most micelles exhibited a spherical shape in AFM. In this study, we characterized star-shaped PEG-PCL copolymers and investigated their molecular architecture effect on the various properties. Furthermore, we confirmed that the micelles termed with linear and branched PEG-PCL copolymers have possibility as a potential hydrophobic drug delivery vehicle.