• Journal of Surface Science and Engineering
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• v.50 no.3
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• pp.170-176
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• 2017

EPIG (Electroless Pd/immersion Au) process was studied to replace ENIG (electroless Ni/immersion Au) and ENEPIG (electroless Ni/electroless Pd/immersion Au) processes for bump surface treatment used in high reliable flip chip packages. The palladium and gold layers formed by EPIG process were uniform with thickness of 125 nm and 34.5 nm, respectively. EPAG (Electroless Pd/autocatalytic Au) also produced even layers of palladium and gold with the thickness of 115 nm and 100 nm. TEM results exhibited that the gold layer in EPIG surface had crystalline structure while the palladium layer was amorphous one. After annealing at 250 nm, XPS analysis indicated that the palladium layer with thickness more than 22~33 nm could act as a diffusion barrier of copper interconnects. As a result of comparing the chip shear strength obtained from ENIG and EPIG surfaces, it was confirmed that the bonding strength was similar each other as 12.337 kg and 12.330 kg, respectively.

• Structural Engineering and Mechanics
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• v.32 no.4
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• pp.477-488
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• 2009

A slip critical joint has various values to adopt the proper slip coefficient in various conditions of faying surfaces in the following codes: AISC, AIJ and Eurocode 3. However, the Korean Building Code still regulates the unique slip coefficient, 0.45, regardless of the diverse faying conditions. In this study, the slip resistance test, including five kinds of surface treatments were conducted to obtain the proper slip coefficients available to steel plate KS SM490A. The faying surfaces were comprised of a clean mill, rust, red lead paint, zinc primer, and shot blast treatment. The candidates for high strength bolts were torque-shear bolts, torque-shear bolts with zinc coating, and ASTM A490 bolts. Based on the test results, the specimens with a shot blasted surface and rusted surface exhibited $k_s$, 0.61, and 0.5, respectively. It is recommended that the specimens with zinc primer exhibit $k_s{\geq}0.40$. The clean mill treated surface had prominently lower values, 0.27. For red lead painted treatment, the thickness of the coating affects the determinant of slip coefficient, so it is necessary to establish a minimum $k_s$ of 0.2, with a coating thickness of 65 ${\mu}m$. During 1,000 hours of relaxation, the uncoated surfaces exhibited the loss of clamping force behind 3%, while the coated surfaces within a certain limited thickness exhibited the loss of clamping within a range of 4.71% and 8.37%.

• Structural Engineering and Mechanics
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• v.65 no.4
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• pp.491-504
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• 2018

Because of sandwich structures with low weight and high stiffness have much usage in various industries such as civil and aerospace engineering, in this article, buckling and free vibration analyses of coupled micro composite sandwich plates are investigated based on sinusoidal shear deformation (SSDT) and most general strain gradient theories (MGSGT). It is assumed that the sandwich structure rested on an orthotropic elastic foundation and make of four composite face sheets with temperature-dependent material properties that they reinforced by carbon and boron nitride nanotubes and two flexible transversely orthotropic cores. Mathematical formulation is presented using Hamilton's principle and governing equations of motions are derived based on energy approach and applying variation method for simply supported edges under electro-magneto-thermo-mechanical, axial buckling and pre-stresses loadings. In order to predict the effects of various parameters such as material length scale parameter, length to width ratio, length to thickness ratio, thickness of face sheets to core thickness ratio, nanotubes volume fraction, pre-stress load and orthotropic elastic medium on the natural frequencies and critical buckling load of double-bonded micro composite sandwich plates. It is found that orthotropic elastic medium has a special role on the system stability and increasing Winkler and Pasternak constants lead to enhance the natural frequency and critical buckling load of micro plates, while decrease natural frequency and critical buckling load with increasing temperature changes. Also, it is showed that pre-stresses due to help the axial buckling load causes that delay the buckling phenomenon. Moreover, it is concluded that the sandwich structures with orthotropic cores have high stiffness, but because they are not economical, thus it is necessary the sandwich plates reinforce by carbon or boron nitride nanotubes specially, because these nanotubes have important thermal and mechanical properties in comparison of the other reinforcement.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.9
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• pp.1229-1238
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• 2016

This study was conducted to determine the relationships of five intragenic single nucleotide polymorphism (SNP) markers (protein kinase adenosine monophosphate-activated ${\gamma}3$ subunit [PRKAG3], fatty acid synthase [FASN], calpastatin [CAST], high mobility group AT-hook 1 [HMGA1], and melanocortin-4 receptor [MC4R]) and meat quality traits of Duroc breeding stocks in Korea. A total of 200 purebred Duroc gilts from 8 sires and 40 dams at 4 pig breeding farms from 2010 to 2011 reaching market weight (110 kg) were slaughtered and their carcasses were chilled overnight. Longissimus dorsi muscles were removed from the carcass after 24 h of slaughter and used to determine pork properties including carcass weight, backfat thickness, moisture, intramuscular fat, $pH_{24h}$, shear force, redness, texture, and fatty acid composition. The PRKAG3, FASN, CAST, and MC4R gene SNPs were significantly associated with the meat quality traits (p<0.003). The meats of PRKAG3 (A 0.024/G 0.976) AA genotype had higher pH, redness and texture than those from PRKAG3 GG genotype. Meats of FASN (C 0.301/A 0.699) AA genotype had higher backfat thickness, texture, stearic acid, oleic acid and polyunsaturated fatty acid than FASN CC genotype. While the carcasses of CAST (A 0.373/G 0.627) AA genotype had thicker backfat, and lower shear force, palmitoleic acid and oleic acid content, they had higher stearic acid content than those from the CAST GG genotype. The MC4R (G 0.208/A 0.792) AA genotype were involved in increasing backfat thickness, carcass weight, moisture and saturated fatty acid content, and decreasing unsaturated fatty acid content in Duroc meat. These results indicated that the five SNP markers tested can be a help to select Duroc breed to improve carcass and meat quality properties in crossbred pigs.

• Journal of Welding and Joining
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• v.31 no.5
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• pp.54-58
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• 2013

Joint properties of vehicle ECU (Electric Control Unit) module which was manufactured by using Sn-Cu-Cr-Ca alloy were investigated. A new solder which has a middle melting temperature about $231^{\circ}C$ was fabricated as the type of 300um solder ball and paste type. The prototype modules were made by reflow process and measured spreadability, wettability shear strength and estimated interface reaction. The spreadability of the alloy was about 84% from the measurement of contact angle of the solder ball and the wetting force was measured 2mN. The average shear strength of the module which was manufactured by using the solder paste, was 1.9 $kg/mm^2$. Also, the thickness of IMC(intermetallic compound) was evaluated with various aging temperature and time in order to understand Cr effect on Sn-0.7Cu solder. $Cu_6Sn_5$ IMC was formed between Cu pad and the solder alloy and the average thickness of the $Cu_6Sn_5$ IMC was measured about 4um and it was about 50% of thickness of $Cu_6Sn_5$ IMC in Sn-0.7Cu. It is expected to have a positive effect on reliability of the solder joint.

• Journal of the Korean Wood Science and Technology
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• v.34 no.1
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• pp.32-39
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• 2006

The acoustic properties of various coatings for stringed musical instruments made were investigated. The applied coatings were urethane topcoat, oil stain and UV-curable epoxy coating. Acoustic properties of coatings inferred from the elastic modulus and the shear modulus that ware calculated from a resonance frequency and a damping measured by FFT analyzer. The relationship between elastic modulus and density and the relationship between elastic modulus and shear modulus of coatings for stringed musical instruments ware investigated as a function of coating thickness.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5931-5937
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• 2011

The effects of coupling beam, which is generally used in high-rise building structure system as shear wall-coupling beam, on the lateral drift of high-rise buildings are studied in this paper. Six different analytical models, which are combination of two inputs, such as concrete strength and wall thickness, are selected and analyzed on lateral drifts with different stiffness of coupling beams. MIDAS GEN was used for analysis. Calculated lateral drifts were compared with allowable limits(H/400~H/500) proposed by standard CEN EC 3/1, in order to analyze the control evaluation of coupling beams. Calculated x-direction displacements were 68~87 percent of allowable limit(H/500). With increase of wall thickness(100mm) and concrete strength(5Mpa), eight to ten percent and four percent of x and y-direction displacement were decreased individually. About three percent of lateral displacement was increased with 20 percent decrease of coupling beam stiffness and additional 20 percent decrease resulted in additional five to eight percent increase.

• Structural Engineering and Mechanics
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• v.72 no.1
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• pp.113-129
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• 2019

A four-variable shear deformation refined plate theory has been proposed for dynamic characteristics of smart plates made of porous magneto-electro-elastic functionally graded (MEE-FG) materials with various boundary conditions by using an analytical method. Magneto-electro-elastic properties of FGM plate are supposed to vary through the thickness direction and are estimated through the modified power-law rule in which the porosities with even and uneven type are approximated. Pores possibly occur inside functionally graded materials (FGMs) due the result of technical problems that lead to creation of micro-voids in these materials. The variation of pores along the thickness direction influences the mechanical properties. The governing differential equations and boundary conditions of embedded porous FGM plate under magneto-electrical field are derived through Hamilton's principle based on a four-variable tangential-exponential refined theory which avoids the use of shear correction factors. An analytical solution procedure is used to achieve the natural frequencies of embedded porous FG plate supposed to magneto-electrical field with various boundary condition. A parametric study is led to carry out the effects of material graduation exponent, coefficient of porosity, magnetic potential, electric voltage, elastic foundation parameters, various boundary conditions and plate side-to-thickness ratio on natural frequencies of the porous MEE-FG plate. It is concluded that these parameters play significant roles on the dynamic behavior of porous MEE-FG plates. Presented numerical results can serve as benchmarks for future analyses of MEE-FG plates with porosity phases.

• Steel and Composite Structures
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• v.19 no.2
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• pp.277-292
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• 2015

Previous research has shown that steel plate shear walls (SPSWs) are efficient lateral force-resisting systems against both wind and seismic loads. A properly designed SPSW can have high initial stiffness, strength, and energy absorption capacity as well as superior ductility. SPSWs have been commonly designed with unstiffened and stiffened infill plates based on economical and performance considerations. Recent introduction and application of corrugated plates with advantageous structural features has motivated the researchers to consider the employment of such elements in stiffened SPSWs with the aim of lowering the high construction cost of such high-performing systems. On this basis, this paper presents results from a numerical investigation of the hysteretic performance of SPSWs with trapezoidally corrugated infill plates. Finite element cyclic analyses are conducted on a series of flat- and corrugated-web SPSWs to examine the effects of web-plate thickness, corrugation angle, and number of corrugation half-waves on the hysteretic performance of such structural systems. Results of the parametric studies are indicative of effectiveness of increasing of the three aforementioned web-plate geometrical and corrugation parameters in improving the cyclic response and energy absorption capacity of SPSWs with trapezoidally corrugated infill plates. Increasing of the web-plate thickness and number of corrugation half-waves are found to be the most and the least effective in adjusting the hysteretic performance of such promising lateral force-resisting systems, respectively. Findings of this study also show that optimal selection of the web-plate thickness, corrugation angle, and number of corrugation half-waves along with proper design of the boundary frame members can result in high stiffness, strength, and cyclic performances of such corrugated-web SPSWs.

• Advances in nano research
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• v.7 no.3
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• pp.191-208
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• 2019

In the present work the dynamic analysis of the functionally graded rectangular nanoplates is studied. The theory of nonlocal elasticity based on the quasi 3D high shear deformation theory (quasi 3D HSDT) has been employed to determine the natural frequencies of the nanosize FG plate. In HSDT a cubic function is employed in terms of thickness coordinate to introduce the influence of transverse shear deformation and stretching thickness. The theory of nonlocal elasticity is utilized to examine the impact of the small scale on the natural frequency of the FG rectangular nanoplate. The equations of motion are deduced by implementing Hamilton's principle. To demonstrate the accuracy of the proposed method, the calculated results in specific cases are compared and examined with available results in the literature and a good agreement is observed. Finally, the influence of the various parameters such as the nonlocal coefficient, the material indexes, the aspect ratio, and the thickness to length ratio on the dynamic properties of the FG nanoplates is illustrated and discussed in detail.