• Nuclear Engineering and Technology
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• v.56 no.8
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• pp.3112-3122
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• 2024

Crevice corrosion is a localized attack of metal that occurs in occluded areas of materials as a result of a degradation of the oxide passivity on the metal surface in contact with stagnant environments. Materials suffer crevice corrosion when generally the crevice opening gap is so narrow that the migration or diffusion of ionic species into the crevice can be restricted and consequently results in the production of aggressive crevice solutions and differential aeration conditions over time. Among several factors affecting the crevice corrosion, differential aeration causing oxygen depletion associated with the geometry of components, acidification, and accumulation of aggressive species (e.g., Cl^-, SO₄^-2, NO₃^- ) in the crevice solution become main aspects of the mechanism of the crevice corrosion. Thus, controlling such factors is most critically necessary to either prevents or terminates the crevice corrosion. This paper covers electrochemical aspects of the crevice corrosion, roles of critical factors affecting the crevice corrosion, and electrochemical processes of impurity species in the crevice in high temperature water. A better and clear understanding of mechanisms of the crevice corrosion is important to develop the protection and mitigation technology against the crevice corrosion in order for maintaining the integrity and longevity of structural components at various industries

• Journal of Astronomy and Space Sciences
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• v.12 no.1
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• pp.21-29
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• 1995

The $\beta$ Lyrae-type eclipsing binary AW Cam was observed photoelectrically in three wavelength regions. The obtained UBV light curves of AW Cam were analyzed with two separate modes(mode 2 for detached systems and mode 5 for semi-detached ones) of the Wilson-Devinney binary mode. It is intended to resolve the discrepancy in AW Cam system that the photometrio mass ratio (q=0.21) derived by Russo and Milano (1983) is not consistent with the spectroscopic result (q=0.43) by Mammano et al.(1967). Our photomtric solutions derived with mode 2 are fitted better to the observed light curves than those of mode 5, supporting that AW Cam may be not a normal semi-detached system but a detached one. Three dimensional Roche configuration of AW Cam system calculated with the derived mass ratio (q=0.43) reveals that the less massive secondary with the confined within its inner Roche lobe, while the more massive rimary is in marginally contact. From the Roche geometry, the constancy of the orbital period and other photometric evidences of AW Cam, it is provisionally concluded that the system is an unevolved detached binary in is provisionally concluded that the system is an unevolved detached binary in the phase of case A evolution toward 'contact phase' rather than and evolved one in 'broken-contact phase' suggested by Giuricin and Mardrossian (1981).

• Journal of Applied Biological Chemistry
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• v.61 no.3
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• pp.219-226
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• 2018

The purpose of this study was to investigate the effect of thermal treatments, such as a sous-vide and a conventional hot water cooking, on the texture changes of soybean sprout. A novel method to measure texture properties of soybean sprout have been determined because of the irregular geometry of soybean sprout. The shape of cotyledon of bean spout was accurately analyzed using an image processing and a geometry model. To minimize the effect of the contact area on the texture measurement, a blade type of probe was selected for the measurement. True stress was evaluated to reflect the shape changes during deformation, and demonstrated that the measurement accurately distinguished the effect of thermal treatment on the texture. Different heating time (i.e., 0, 10, 20, and 30 min) was applied for both sous-vide and conventional cooking. Thermal processing caused hardening of textures for both cotyledon and hypocotyl of soybean sprout. The conventional cooking method showed higher stress values than those of sous-vide cooking. Sprouts cooked by sous-vide released the moisture after thermal processing while sprout cooked by a conventional water bath method could hold the moisture content during thermal processing. The soybean sprouts treated by conventional cooking method showed a higher score in sensory evaluation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.2
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• pp.101-120
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• 2023

Electrical resistivity survey have been widely conducted at diverse scales, from a few centimeters for laboratory tests to kilometers for field tests. It measures electrical resistance through relationship of electric potential difference and current between two electrodes penetrated on the surface of medium, and eventually quantifies electrical resistivity known as inherent properties of the medium. In field or full-scale test, it assumes the electrodes as equivalent half-sphere electrodes that have a same surface area with different electrodes for ease of calculation because the contact area between electrode and medium is small and sufficient distance between two electrodes. However, small-scale laboratory test is significantly affected by the electrode geometries (penetrated depth, height, radius of electrode and distance between electrodes), which change the equipotential surface and electric current flow. Indeed, the electrode geometries may eventually cause a difference of electrical resistivity value. This study reviews the theoretical electrical resistance derived with various electrode geometries (half-sphere, cylinder, cylindrical with half-spherical tip, cylindrical with conical tip) and verifies the developed numerical module by comparing results with the theoretical electrical resistance. The distributions of electrical resistance around electrodes and among electrodes are analyzed. In addition, it is discussed how the electrical characteristic of cylindrical electrode with conical tip widely used in field test has effect on the electric current flow.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.5
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• pp.345-352
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• 2014

In this paper, the CAD data for the optimal shape design obtained by isogeometric shape optimization is directly used to fabricate the specimen by using 3D printer for the experimental validation. In a conventional finite element method, the geometric approximation inherent in the mesh leads to the accuracy issue in response analysis and design sensitivity analysis. Furthermore, in the finite element based shape optimization, subsequent communication with CAD description is required in the design optimization process, which results in the loss of optimal design information during the communication. Isogeometric analysis method employs the same NURBS basis functions and control points used in CAD systems, which enables to use exact geometrical properties like normal vector and curvature information in the response analysis and design sensitivity analysis procedure. Also, it vastly simplify the design modification of complex geometries without communicating with the CAD description of geometry during design optimization process. Therefore, the information of optimal design and material volume is exactly reflected to fabricate the specimen for experimental validation. Through the design optimization examples of elasticity problem, it is experimentally shown that the optimal design has higher stiffness than the initial design. Also, the experimental results match very well with the numerical results. Using a non-contact optical 3D deformation measuring system for strain distribution, it is shown that the stress concentration is significantly alleviated in the optimal design compared with the initial design.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.344-344
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• 2014

Transparent amorphous oxide semiconductors such as a In-Ga-Zn-O (a-IGZO) have advantages for large area electronic devices; e.g., uniform deposition at a large area, optical transparency, a smooth surface, and large electron mobility >10 cm2/Vs, which is more than an order of magnitude larger than that of hydrogen amorphous silicon (a-Si;H).1) Thin film transistors (TFTs) that employ amorphous oxide semiconductors such as ZnO, In-Ga-Zn-O, or Hf-In-Zn-O (HIZO) are currently subject of intensive study owing to their high potential for application in flat panel displays. The device fabrication process involves a series of thin film deposition and photolithographic patterning steps. In order to minimize contamination, the substrates usually undergo a cleaning procedure using deionized water, before and after the growth of thin films by sputtering methods. The devices structure were fabricated top-contact gate TFTs using the a-IGZO films on the plastic substrates. The channel width and length were 80 and 20 um, respectively. The source and drain electrode regions were defined by photolithography and wet etching process. The electrodes consisting of Ti(15 nm)/Al(120 nm)/Ti(15nm) trilayers were deposited by direct current sputtering. The 30 nm thickness active IGZO layer deposited by rf magnetron sputtering at room temperature. The deposition condition is as follows: a rf power 200 W, a pressure of 5 mtorr, 10% of oxygen [O2/(O2+Ar)=0.1], and room temperature. A 9-nm-thick Al2O3 layer was formed as a first, third gate insulator by ALD deposition. A 290-nm-thick SS6908 organic dielectrics formed as second gate insulator by spin-coating. The schematic structure of the IGZO TFT is top gate contact geometry device structure for typical TFTs fabricated in this study. Drain current (IDS) versus drain-source voltage (VDS) output characteristics curve of a IGZO TFTs fabricated using the 3-layer gate insulator on a plastic substrate and log(IDS)-gate voltage (VG) characteristics for typical IGZO TFTs. The TFTs device has a channel width (W) of $80{\mu}m$ and a channel length (L) of $20{\mu}m$. The IDS-VDS curves showed well-defined transistor characteristics with saturation effects at VG>-10 V and VDS>-20 V for the inkjet printing IGZO device. The carrier charge mobility was determined to be 15.18 cm^2 V-1s-1 with FET threshold voltage of -3 V and on/off current ratio 10^9.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.433-433
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• 2012

As the requirement in patterning geometry continuously shrinks down, the termination of etch process at the exact time became crucial for the success in nano patterning technology. By virtue of real-time optical emission spectroscopy (OES), etch end point detection (EPD) technique continuously develops; however, it also faced with difficulty in low open ratio etching, typically in self aligned contact (SAC) and one cylinder contact (OCS), because of very small amount of optical emission from by-product gas species in the bulk plasma glow discharge. In developing etching process, one may observe that coupon test is being performed. It consumes costs and time for preparing the patterned sample wafers every test in priority, so the coupon wafer test instead of the whole patterned wafer is beneficial for testing and developing etch process condition. We also can observe that etch open area is varied with the number of coupons on a dummy wafer. However, this can be a misleading in OES study. If the coupon wafer test are monitored using OES, we can conjecture the endpoint by experienced method, but considering by data, the materials for residual area by being etched open area are needed to consider. In this research, we compare and analysis the OES data for coupon wafer test results for monitoring about the conditions that the areas except the patterns on the coupon wafers for real-time process monitoring. In this research, we compared two cases, first one is etching the coupon wafers attached on the carrier wafer that is covered by the photoresist, and other case is etching the coupon wafers on the chuck. For comparing the emission intensity, we chose the four chemical species (SiF2, N2, CO, CN), and for comparing the etched profile, measured by scanning electron microscope (SEM). In addition, we adopted the Dynamic Time Warping (DTW) algorithm for analyzing the chose OES data patterns, and analysis the covariance and coefficient for statistical method. After the result, coupon wafers are over-etched for without carrier wafer groups, while with carrier wafer groups are under-etched. And the CN emission intensity has significant difference compare with OES raw data. Based on these results, it necessary to reasonable analysis of the OES data to adopt the pre-data processing and algorithms, and the result will influence the reliability for relation of coupon wafer test and whole wafer test.

• Fibers and Polymers
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• v.7 no.4
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• pp.389-397
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• 2006

The beneficial effects of graduated compression stockings (GCS) in prophylaxis and treatment of venous disorders of human lower extremity have been recognized. However, their pressure functional performances are variable and unstable in practical applications, and the exact mechanisms of action remain controversial. Direct surface pressure measurements and indirect material properties testing are not enough for fully understanding the interaction between stocking and leg. A three dimensional (3D) biomechanical mathematical model for numerically simulating the interaction between leg and GCS in dynamic wear was developed based on the actual geometry of the female leg obtained from 3D reconstruction of MR images and the real size and mechanical properties of the compression stocking prototype. The biomechanical solid leg model consists of bones and soft tissues, and an orthotropic shell model is built for the stocking hose. The dynamic putting-on process is simulated by defining the contact of finite relative sliding between the two objects. The surface pressure magnitude and distribution along the different height levels of the leg and stress profiles of stockings were simulated. As well, their dynamic alterations with time processing were quantitatively analyzed. Through validation, the simulated results showed a reasonable agreement with the experimental measurements, and the simulated pressure gradient distribution from the ankle to the thigh (100:67:30) accorded with the advised criterion by the European committee for standardization. The developed model can be used to predict and visualize the dynamic pressure and stress performances exerted by compression stocking in wear, and to optimize the material mechanical properties in stocking design, thus, helping us understand mechanisms of compression action and improving medical functions of GCS.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.5
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• pp.15-20
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• 2014

The wind industry grew in the first decade of the 21st century at rates consistently above 20% a year. For wind turbine, gearbox failure can be extremely costly in terms of repair costs, replacement parts, and in lost power production due to downtime. In this paper, gear tooth micro-modification for the high speed stage was used to compensate for the deformation of the teeth due to load and to ensure a proper meshing to achieve an optimized tooth contact pattern. The gearbox was firstly modeled in a software, and then the various combined tooth modification were presented, and the prediction of transmission under the loaded torque for the helical gear pair was investigated, the normal load distribution and root stress were also obtained and compared before and after tooth modification under one torque. The simulation results showed that the transmission error and normal load distribution under the load can be minimized by the appropriate tooth modification. It is a good approach where the simulated result is used to improve the design before the prototype is available for the test.

• The Journal of the Korea Contents Association
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• v.20 no.11
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• pp.354-367
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• 2020

This study is on the consideration of the scope of application of art therapy and fractal through the review of literature at home and abroad. The complex system is the opposite of the Euclidean system, a concept suitable for understanding the contemporaries with ambiguous boundaries and decentralized phenomena. The self-similarity and inventiveness of fractal, the geometry of nature, is used as fractal art in art as well as tree trunk, cloud and plant, especially in art therapy, fractal is considered to be available in the field of mandala and neuroscience. From brain-based research to mandala, exposure to natural patterns, clinical diagnosis through fractal analysis and software development, fractal has potential elements that can be developed in art therapy. Fractal, which is easy to link with computers due to its nature, is a necessary study at this point when non-face-to-face contact with the Corona virus is recommended. Currently, research on fractal art therapy is insufficient in Korea. Therefore, this research is intended to present as a basis for scientific and objective diagnostic tools and treatment at clinical sites using art therapy using fractal.