• Progress in Superconductivity
• /
• v.11 no.1
• /
• pp.47-51
• /
• 2009

For many large-scale applications of high-temperature superconducting materials, large critical current density ($J_c$) in high applied magnetic fields are required. A number of methods have been reported to introduce artificial pinning centers in $YBa_2Cu_3O_{7-{\delta}}$ films for enhancement of their $J_c$. We studied the microstructures and characteristic of $YBa_2Cu_3O_{7-{\delta}}$ films fabricated on $SrTiO_3$ (100) substrates with ZnO nanorods as pinning centers. Au catalyst nanoparticles were synthesized on STO substrates with self assembled monolayer to control the number of ZnO nanorods. The density of Au nanoparticles is approximately $240{\sim}260{\mu}m^{-2}$ with diameters of $41{\sim}49nm$. ZnO nanorods were grown on STO by hot-walled PLD with Au nanoparticles. Typical size of ZnO nanorod was around 179 nm in diameter and $2{\sim}6{\mu}m$ in length respectively. YBCO films deposited directly on STO substrates show the c-axis orientation, while YBCO films with ZnO nanorods exhibit any mixed phases without any typical crystal orientation.

• Journal of Korean Society of Steel Construction
• /
• v.14 no.6
• /
• pp.793-802
• /
• 2002

This study presented a finite element formulation for the dynamic analysis of horizontally curved I-girder bridges. The stiffness and mass matrices of the curved and the straight beam elements are formulated. Each node of both elements has seven degrees of freedom, including the warping degree of freedom. The curved beam element is derived from Kang and Yoo's theory of thin-walled curved beams. The computer program EQCVB has been developed to perform dynamic analyses of various horizontally curved I-girder bridges. The Gupta method is used to solve the eigenvalue problem efficiently, while the Wilson-${\theta}$ method is used for the seismic analysis. The efficiency of EQCVB is demonstrated by comparing solution time with ABAQUS. Using EQCVB, the study is applied to investigate the dynamic behavior of horizontally curved I-girder bridges under seismic loading.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.42 no.1
• /
• pp.7-12
• /
• 2010

Morphological characteristics of hemp fiber were investigated using a light microscope in order to provide fundamental data for the use of hemp as a papermaking law material. Phloem of hemp is composed of cortical parenchyma cells and bast fiber with thick walls while xylem is composed of vessel, wood fiber and ray parenchyma cells. Also there are solitary pore and radial pore multiple which exist in diffuse porous pattern. Ray cells consist of uniseriate rays and thin walled ray parenchyma cells. Wood fibers are composed of three types: a large diameter fiber with longer length; a large diameter fiber with shorter length; a small diameter fiber with medium length. Vessel elements are composed of: a medium length one; a longer length one; the one whose both end walls have ligules or tails. Parenchyma cells in xylem and pit parenchyma cells have completely different size and shape. For bast fiber, the average length is about 4.4 mm and the width is about $30.5\;{\mu}m$; for vessel element, $600.0\;{\mu}m$ in length and $493.6\;{\mu}m$ in width; for wood fiber, $1000\;{\mu}m$ and $38.9\;{\mu}m$; for parenchyma cell, $50\;{\mu}m$ and $26.4\;{\mu}m$.

• Steel and Composite Structures
• /
• v.22 no.2
• /
• pp.449-472
• /
• 2016

This paper studies the seismic behavior of reinforced concrete (RC) walls with encased cold-formed and thin-walled (CFTW) steel truss, which can be used as an alternative to the conventional RC walls or steel reinforced concrete (SRC) composite walls for high-rise buildings in high seismic regions. Seven one-fourth scaled RC wall specimens with encased CFTW steel truss were designed, manufactured and tested to failure under reversed cyclic lateral load and constant axial load. The test parameters were the axial load ratio, configuration and volumetric steel ratio of encased web brace. The behaviors of the test specimens, including damage formation, failure mode, hysteretic curves, stiffness degradation, ductility and energy dissipation, were examined. Test results indicate that the encased web braces can effectively improve the ductility and energy dissipation capacity of RC walls. The steel angles are more suitable to be used as the web brace than the latticed batten plates in enhancing the ductility and energy dissipation. Higher axial load ratio is beneficial to lateral load capacity, but can result in reduced ductility and energy dissipation capacity. A volumetric ratio about 0.25% of encased web brace is believed cost-effective in ensuring satisfactory seismic performance of RC walls. The axial load ratio should not exceed the maximum level, about 0.20 for the nominal value or about 0.50 for the design value. Numerical analyses were performed to predict the backbone curves of the specimens and calculation formula from the Chinese Code for Design of Composite Structures was used to predict the maximum lateral load capacity. The comparison shows good agreement between the test and predicted results.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.6 no.4
• /
• pp.279-290
• /
• 2004

The differential quadrature method (DQM) for a system of coupled differential equations governing the elastic stability of thin-walled curved members is presented, and is applied to computation of the eigenvalues of out-of-plane buckling of curved beams subjected to uniformly distributed radial loads including a warping contribution. Critical loads with warping, which were found to be significant, are calculated for a single-span wide-flange beam with various end conditions, opening angles, and stiffness parameters. The results are compared with the exact methods available. New results are given for the case of both ends clamped and clamped-simply supported ends without comparison since no data are available The differential quadrature method gives good accuracy and stability compared with previous theoretical results.

• Journal of Yeungnam Medical Science
• /
• v.11 no.2
• /
• pp.381-387
• /
• 1994

Plummer-Vinson syndrome is a clinical entity characterized by dysphagia, iron deficiency anemia, cheilosis, glossitis, and cervical esophageal web, especially in middle aged women. Recently, the authors experienced a case of Plummer-Vinson syndrome. A 53-year-old female was admitted due to intermittent solid food dysphagia for 18 months. She had a 2 years history of iron deficiency anemia. On admission glossitis, fissures at the angle of the mouth, spoon nails, and iron deficiency anemia were noted. Esophagogram and esophagoscopic examination revealed thin walled concentric web at upper esophagus. Esophageal web was succefully teared by endoscopic balloon dilatation with subseguant improvement of dysphagia. Skin manifestations as well as anemia were markedly improved after oral iron replacement therapy.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.42 no.2
• /
• pp.67-74
• /
• 2010

This study was carried out to investigate the pulping and papermaking characteristics of lotus (Nelumbo nucifera G.) leafstalk for the development of high performance paper. Anatomical and chemical properties of the lotus leafstalk were analyzed. The pulping and papermaking properties of the lotus leafstalk by conventional alkali and sulfomethylated pulping processes were also evaluated. The length and width of fibers were 0.06-3.32 mm (av. 1.23 mm) and 3.47-25.6 ${\mu}m$ (av. 20.7 ${\mu}m$), respectively. The length and width of vessel elements were 0.07-0.78 mm (av. 0.20 mm) and 14.1-330.0 ${\mu}m$ (av. 54.13 ${\mu}m$), respectively. The fiber length/fiber width ratio was 60.20. The extractives (cold water, hot water, 1% NaOH and ethanol-benzene) and lignin content of lotus leafstalk were higher than those of plant bast fiber. The contents of holocellulose, lignin, and ash were 73.8%, 24.3%, and 4.3%, respectively. The pulp yields based on pulping methods were sulfomethylated pulping av. 52%, and alkaline pulping av. 42%. The conventional alkaline pulping shows better pulp and sheet properties than the sulfomethylated pulping which was modified pulping processes. But the sulfomethylated pulping shows higher brightness than alkali pulping. In the consequence of FE-SEM observation, lotus leafstalk pulp consists of various kinds of thin walled fibers which have large amount of small pits.

• Journal of Korean Society of Steel Construction
• /
• v.24 no.2
• /
• pp.189-197
• /
• 2012

The cold-formed steel stud, which has been used as a load-bearing member of wall panels for steel houses, poses a significant problem in insulation due to heat bridging of the web. Therefore, some additional thermal insulating materials are required. In order to solve this problem, the cold-formed steel thermal stud with slits in the web was developed. However, estimating the structural strength of thermal studs is very difficult because of the arrangement of perforations. In this paper, an analytical and experimental research on thermal studs is described. Three types of studs with different length, pitch and arrangement of slits were tested to failure. A simple design approach was proposed based on the test results. The proposed method adopted the direct strength method, based on the elastic local and distortional buckling stress of plain studs with equivalent thickness in the web instead of thermal studs. The predictions using the proposed method were compared with test results for verification and the adequacy of the proposed method was confirmed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.5
• /
• pp.1023-1031
• /
• 1994

The closed forms of consistent mass matrix with rotational inertia matrix are developed for free vibration analysis in space sutructures containing linearly tapered members with cross section of thin-walled I-sections. The exact displacement functions are used for formulating mass matrices. The very small slopes of the tapered member are used in usual practice, such that the series expansion forms of these are also developed to avoid numerical failure in vibration analysis. Significant improvements of accuracy and efficiency of free vibation analysis are achieved by using the mass matrices developed in this study. Frequencies of free vibation of tapered members are compared with solutions based upon stepped representation of beam element in the ANSYS. The mass matrices presented in this study can be used for the free vibration analysis of tapered and prismatic members.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.41 no.5
• /
• pp.401-407
• /
• 2017

This paper describes wavenumber filtering for damage detection using single-frequency standing wave excitation and laser scanning sensing. An embedded piezoelectric sensor generates ultrasonic standing waves, and the responses are measured using a laser Doppler vibrometer and mirror tilting device. After scanning, newly developed damage detection techniques based on wavenumber filtering are applied to the full standing wave field. To demonstrate the performance of the proposed techniques, several experiments were performed on composite plates with delamination and aluminum plates with corrosion damage. The results demonstrated that the developed techniques could be applied to various structures to localize the damage, with the potential to improve the damage detection capability at a high interrogation speed.