• Journal of Welding and Joining
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• v.31 no.6
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• pp.1-7
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• 2013

In nuclear power plants, lined carbon steel pipes or PCCPs (pre-stressed concrete cylinder pipes) have been widely used for sea water transport systems. However, de-bonding of linings and oxidation of PCCP could make problems in aged NPPs (nuclear power plants). Recently at several NPPs in the United States, the PCCPs or lined carbon steel pipes of the sea water or raw water system have been replaced with HDPE (high density polyethylene) pipes, which have outstanding resistance to oxidation and seismic loading. ASME B&PV Code committee developed Code Case N-755, which describes rules for the construction of buried Safety Class 3 polyethylene pressure piping systems. Although US NRC permitted HDPE materials for Class 3 buried piping, their permission was limited to only 10-year operation because of several concerns including the quality of fusion zone of HDPE. In this study, various requirements for fusion qualification test of HDPE and some regulatory issues raised during HDPE application review in foreign NPPs are introduced.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.1079-1092
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• 2020

A parametric study of several parameters relevant to design safety on the spent nuclear fuel (SNF) rod response under a drop accident is presented. In the view of the complexity of interactions between the independent safety-related parameters, a factorial design of experiment is employed as an efficient method to investigate the main effects and the interactions between them. A detailed single full-length fuel rod is used with consideration of post-irradiated fuel conditions under horizontal and vertical free-drops onto an unyielding surface using finite-element analysis. Critical drop heights and critical g-loads that yield the threshold plastic strain in the cladding are numerically estimated to evaluate the fuel rod structural resistance to impact load. The combinatory effects of four uncertain parameters (pellet-cladding interfacial bonding, material properties, spacer grid stiffness, rod internal pressure) and the interactions between them on the fuel rod response are investigated. The principal finding of this research showed that the effects of above-mentioned parameters on the load-carrying capacity of fuel rod are significantly different. This study could help to prioritize the importance of data in managing and studying the structural integrity of the SNF.

• Journal of the Korean Wood Science and Technology
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• v.27 no.2
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• pp.38-45
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• 1999

This study was to figure out proper Formaldehyde/Urea molar ratio of UF resin with satisfactory bonding strength of plywood and properties of particleboard. The six kinds of UF resins were manufactured with F/U molar ratio 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0. The boards were made of three kinds of raw materials : Veneer, Sliver-Particle and Strand-Particle. Manufacturing condition of plywood : amount of mixing resin was 150g/$m^2$. The fourty secs/mm simple-pressing schedule in the pressure 10kgf/$m^2$ was applied for 480mm${\times}$700mm board at the temperature of $110^{\circ}C$ in a hot press. Manufacturing condition of particleboard : Target density was 0.65g/$cm^2$. The stepwise 9 minutes- multi-pressing schedule in the maximum pressure 40kgf/$cm^2$, the minimum pressure 15kgf/$cm^2$ was applied for $480mm{\times}634mm{\times}12mm$ board at the temperature of $150^{\circ}C$ in a hot press. The results are as follows : I. In bonding strength, plywood which was made by F/U molar ratio 1.2 showed the highest value. Other molar ratio resin also gave the satisfied value of KS standard, 7.5kgf/$cm^2$. 2. In internal bond strength of particleboard, Sliver-Particleboard(SLPB) and Strand-Particleboard(STPB) varied respectively from 5.9kgf/$cm^2$ to 4.8kgf/$cm^2$, from 6.7kgf/$cm^2$ to 5.4kgf/$cm^2$. SLPB with F/U=1.2 and STPB with F/U=1.6 had higher IB value. Also, both SLPB and STPB showed lower IB value in F/U molar ratio 2.0 and 1.0. 3. SLPB and STPB with six kinds of UF resin respectively satisfied bending strength of KS standard 150 Type(130kgf/$cm^2$) and 200 Type(180kgf/$cm^2$). Bending strength data for both of SLPB and STPB showed little or no loss from F/U=1.8 to F/U=1.2. Also, STPB was approximately two times higher than that of SLPB. Therefore, the raw material's shape had more effect on bending strength than the FlU molar ratio. 4. F/U=1.6 and 1.4 showed the lower thickness swelling in SLPB and STPB. All of STPBs satisfied thickness swelling of KS standard, under 12%.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.29 no.1
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• pp.73-83
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• 1997

Most of the materials used in various industrial fields and also in our daily life are multi-component materials or composite materials, and it is well known that there are many cases where adhesion between the constituents within the bonded systems plays an important role. There are various types of performance evaluation tests for the bonded materials, among which tests for evaluating the bond performance under various conditions may be regarded as the most interesting ones for those engaged in work related to adhesion. I have studied on the mechanism of adhesion form the rheological standpoint with my colleagues, including some students from Korea, and I am very happy to be able to have a talk on some of our research works. In Japan, the so-called "adhesives" are usually classified into two categories;adhesives and pressure sensitive adhesives (PSA). Adhesives are the materials which solidify after bonding and are after used as the structural adhesives because the adhesive strength is comparatively strong. On the other hand, the pressure sensitive adhesives never solidify and are used as PSA tapes, labels or decals. About the adhesives, we have examined the dependence of adhesive strength(shear, tensile, peel) upon both temperature and rate of deformation, and found out some empirical rules which are applicable to most of the adhesive systems. We have also developed a simplified theory of adhesion, which is deseribed in terms of mechanical equivalent mode1 and a few failure criteria. Although some of the common rules can be accounted for according to this theory, it must be pointed out that a fracture mechanical approach ms inevitable especially in the region where the meehanical relaxation time of the adhesive is extremely large [W. W. Lim and H. Mizumachi]. About the pressure sensitive adhesives, we have studied on the PSA performance (peel, tack, holding power) as a function of both the viscoelastic properties and surface chemical properties of the materials, and found out some rules, and again we have developed a theory which deseribes the mechanism. And in addition, we have studied on the miscibility between linear polymers and oligomers, because PSA is generally manufactured by blending gums and tackifier resins. Many phase diagrams have been found and some of them have been analyzed on thermodynamic basis, and it became evident that the miscibility is a very important factor in PSA [H. J. Kin and H. Mizumachi]. In this presentation, I want to emphasize the fact that the adhesion performance is closely related to the structure/property of the adhesives.adhesives.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.12
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• pp.8-13
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• 2001

Cerium oxide ($CeO_2$) thin film has been proposed as a buffer layer between the ferroelectric thin film and the Si substrate in Metal-Ferroelectric-Insulator-Silicon (MFIS) structures for ferroelectric random access memory (FRAM) applications. In this study, $CeO_2$ thin films were etched with $Cl_2$/Ar gas mixture in an inductively coupled plasma (ICP). Etch properties were measured for different gas mixing ratio of $Cl_2$($Cl_2$+Ar) while the other process conditions were fixed at RF power (600 W), dc bias voltage (-200 V), and chamber pressure (15 mTorr). The highest etch rate of $CeO_2$ thin film was 230 ${\AA}$/min and the selectivity of $CeO_2$ to $YMnO_3$ was 1.83 at $Cl_2$($Cl_2$+Ar gas mixing ratio of 0.2. The surface reaction of the etched $CeO_2$ thin films was investigated using x-ray photoelectron spectroscopy (XPS) analysis. There is a Ce-Cl bonding by chemical reaction between Ce and Cl. The results of secondary ion mass spectrometer (SIMS) analysis were compared with the results of XPS analysis and the Ce-Cl bonding was monitored at 176.15 (a.m.u). These results confirm that Ce atoms of $CeO_2$ thin films react with chlorine and a compound such as CeCl remains on the surface of etched $CeO_2$ thin films. These products can be removed by Ar ion bombardment.

• Journal of the Korean Wood Science and Technology
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• v.37 no.4
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• pp.388-396
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• 2009

In our study, the potential of okara as an ingredient of new bio-based adhesives was investigated for the production of fancy-veneered flooring boards. Okara was hydrolyzed by 1% sulfuric acid solution (AC) and 1% sodium hydroxide solution (AK). Phenol formaldehyde (PF) prepolymers were prepared as a cross-linker of okara hydrolyzates. Then, okara-based adhesive resins were formulated with 35% AC, 35% AK and 30% PF prepolymer on solid content basis. The adhesive resins were applied on high-density fiberboards (HDF) with the spread rate of $300g/m^2$. After that, oak fancy veneers are covered on the HDF, and then pressed with the pressure of $7kg/m^2$ at $120^{\circ}C$. The experimental variables were three mole ratios of formaldehyde to phenol (1.8, 2.1, 2.4), three assembly time (0, 10, 20 min), and two press time (90 sec, 120 sec), respectively. The fancy-veneered high-density fiberboards were tested by dry tensile strength, glueline failure by wetting and formaldehyde emission. Tensile strength of the boards exceeded the requirement of KS standard. The formaldehyde emissions were approached at the E0 level specified in KS standard. Based on these results, okara can be used as an ingredient of environmentally friendly adhesive resin systems for the production of flooring boards.

• Journal of the Mineralogical Society of Korea
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• v.30 no.2
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• pp.59-70
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• 2017

$SiO_2$ is one of the most abundant constituents of the Earth's crust and mantle. Probing its electronic structures at high pressures is essential to understand their elastic and thermodynamic properties in the Earth's interior. The in situ high-pressure x-ray Raman scattering (XRS) experiment has been effective in providing detailed bonding transitions of the low-z materials under extreme compression. However, the relationship between the local atomic structures and XRS features at high pressure has not been fully established. The ab initio calculations have been used to overcome such experimental difficulties. Here we report the partial density of states (PDOS) of O atoms and the O K-edge XRS spectra of ${\alpha}-quartz$, ${\alpha}-cristobalite$, and $CaCl_2$-type $SiO_2$ phases calculated using ab initio calculations based on the full-potential linearized augmented plane wave (FP-LAPW) method. The unoccupied O PDOSs of the $CaCl_2$-type $SiO_2$ calculated with and without applying the core-hole effects present significantly distinctive features. The unoccupied O p states of the ${\alpha}-quartz$, ${\alpha}-cristobalite$ and $CaCl_2$-type $SiO_2$ calculated with considering the core-hole effect present similar features to their calculated O K-edge XRS spectra. This confirms that characteristic features in the O K-edge XRS stem from the electronic transition from 1s to unoccupied 2p states. The current results indicate that the core-hole effects should be taken in to consideration to calculate the precise O K-edge XRS features of the $SiO_2$ polymorphs at high pressure. Furthermore, we also calculated O K-edge XRS spectrum for $CaCl_2$-type $SiO_2$ at ~63 GPa. As the experimental spectra for these high pressure phases are not currently available, the current results for the $CaCl_2$-type $SiO_2$ provide useful prospect to predict in situ high-pressure XRS spectra.

• Advances in concrete construction
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• v.3 no.4
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• pp.269-282
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• 2015

In this paper, a compression to tensile load converter device was developed to determine the anisotropic tensile strength of concrete. The samples were made from a mixture of water, fine sand and cement, respectively. Concrete samples with a hole at its center was prepared and subjected to tensile loading using the compression to tensile load converter device. A hydraulic load cell applied compressive loading to converter device with a constant pressure of 0.02 MPa per second. Compressive loading was converted to tensile stress on the sample because of the overall test design. The samples have three different configurations related to loading axis; 0, $45^{\circ}$, $-45^{\circ}$. A series of finite element analysis were done to analyze the effect of hole diameter on stress concentration of the hole side along its horizontal axis to provide a suitable criterion for determining the real tensile strength of concrete. Concurrent with indirect tensile test, Brazilian test and three point loading test were also performed to compare the results from the three methods. Results obtained by this device were quite encouraging and show that the tensile strengths of concrete were similar in different directions because of the homogeneity of bonding between the concrete materials. Also, the indirect tensile strength was clearly lower than the Brazilian test strength and three point loading test.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.217-217
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• 2016

The amorphous InGaZnO (a-IGZO) is widely accepted as a promising channel material for thin-film transistor (TFT) applications owing to their outstanding electrical properties [1, 2]. However, a-IGZO TFTs have still suffered from their bias instability with illumination [1-4]. Up to now, many researchers have studied the sub-gap density of states (DOS) as the root cause of instability. It is well known that defect states can influence on the performances and stabilities of a-IGZO TFTs. The defects states should be closely related with the deposition condition, including sputtering power, and pressure. Nevertheless, it has not been reported how these defects are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOIs) can be generated by electron attachment in oxygen atom near target surface and then accelerated up to few hundreds eV by a self-bias; at this time, the high energy bombardment of NOIs induce defects in oxide thin films. Recently, we have reported that the properties of IGZO thin films are strongly related with effects of NOIs which are generated during the sputtering process [5]. From our previous results, the electrical characteristics and the chemical bonding states of a-IGZO thin films were depended with the bombardment energy of NOIs. And also, we suggest that the deep sub-gap states in a-IGZO as well as thin film properties would be influenced by the bombardment of high energetic NOIs during the sputtering process.In this study, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process to prevent the NOIs bombardment effects and present how much to be improved the properties of a-IGZO thin film by this new deposition method. We deposited a-IGZO thin films by MFSS on SiO2/p-Si and glass substrate at various process conditions, after which we investigated the morphology, optical and electrical properties of the a-IGZO thin films.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.33-40
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• 1988

The new technique has been used to determine the soil-reinforcement interaction. The testing apparatus is essentially a triaxial cell fitted with the capability to house a hollow cylinderical sample. A hollow cylinderical sand specimen with a concentrical layer of reinfarcing material sandwitched in the middle is used in this investigation. The reinforcement is fastened at the base. The hollow specimen can be viewed as a "unit sheet" of a soil-reinforcement composite system of infinite horizontal extent. Axial load as well as inner and outer chamber pressures can be applied to perform a test. The specimen is first subjected to an isotropic stress state corresponding to the overburden pressure. Next, an extension test by reducing the axial load is carried out. The specimen is "loaded" to failure by either the breakage of reinforcing material (tensile failure) or slippage which takes place at the soil-reinforcement interface (i.e. the overcoming of the bonding capacity). Since the reinforcement is fastened at its lower end to the base, any tendency of relative movement between the reinforcement and the sand during an extension test can induce tensile force in the reinforcement thus forming a "reversed pull-out" test condition. Preliminary test results have demonstrated positively of the new approach to test the soil-reinforcement interaction. Reinforcing elements of different extensibility were used to study the deformbility of reinforced soil. Furthermore, both the breakage and the pull-out modes of failure were observed.