• The KSFM Journal of Fluid Machinery
• /
• v.18 no.3
• /
• pp.26-32
• /
• 2015

The authors are developing a motion of floater body type wave energy converter of the float-counterweight system. This consists of the driving pulley, wire, float and counterweight suspended from idler pulleys and rachet mechanism. Though it has succeeded in solving the major structural strength problem in which the floats would slam against adjacent structure(s) by wave load acting horizontally. In order to overcome this problem. We propose a new system in which the wire transmitting the power is wound around the pulleys and the float receiving the wave power is pulled by the wire from both its upper and lower ends to avoid the occurrence of slackening during the wave cycle. In the paper, we developed the dynamics model for the proposed system. Energy gain has been calculated for realistic wave conditions and compared with the original float-counterweight device. The important differences from the float-counterweight system are that (1) both upward and downward motions of water surface can be utilized without problem. (2) slackening of energy gain and wire tension are effectively suppressed, and (4) for the same time averaged energy gain, the maximum wire tension is fairly lowered.

• Korean Journal of Metals and Materials
• /
• v.49 no.5
• /
• pp.380-387
• /
• 2011

Wire brushing, which is a typical surface preparation method for roll bonding, has recently been highlighted as a potentially effective method for surface nanocrystallization. In the present study, the microstructure evolution and hardness of the wire-brushed surface and roll-bonded interface of a 1050 aluminum sheet were investigated. Wire brushing formed protruded layers with a nanocrystalline structure and extremely high surface hardness. After roll bonding, the protruded layers remained as hard layers at the interface. Due to their hardness and brittleness the interface hard layers, can affect the interface bonding properties and also play an important role determining the mechanical properties of multi-layered clad sheets.

• Progress in Superconductivity and Cryogenics
• /
• v.25 no.4
• /
• pp.45-49
• /
• 2023

CORC, which is being studied as one of the conductors for large currents, is manufactured by symmetrically arranging several strands of high-temperature superconducting wires on a cylindrical former. It allows current to flow evenly between wires and has the advantage of being manufactured in a multi-layer structure to increase current capacity. In order to apply CORC to AC power devices, it is necessary to review the material of the former, which is the frame around which the superconducting wire is wound. In the case of metal formers, they are difficult to apply because eddy currents are generated in the former, and they do not have the flexibility to be manufactured into coils by winding them with CORC. In this paper, we compare and analyze the magnetization loss caused by an external alternating magnetic field of Litz wire, which is being considered as a former material for CORC, with the results from formers made of other materials. In addition, we experimentally examine the effect of reducing magnetization loss due to an external magnetic field in CORC using a split wire made by dividing a high-temperature superconducting wire into two using an etching method, and in CORC made with a non-split wire.

• Journal of the Korean Society for Heat Treatment
• /
• v.25 no.1
• /
• pp.1-5
• /
• 2012

The purpose of this study is to prepare a high strength fiberglass reinforced metal. Aluminum covering was carried out over carbon materials such as carbon fiber in order to increase their wettability to molten metals such as aluminum. A sputtering apparatus with a cylindrical target was fabricated to carry out the covering. Sputtering was caused by glow discharge between the target and the two anode plates attached to its top and bottom. As the substrate for preliminary test, a thin carbon wire was used instead of carbon fiber, and the wire was placed at the central axis of the target. Aluminium coating was formed on the whole surface of the substrate. The formation rate and structure of coating were varied by controlling the electrical potential of substrate. When the substrate was electrically isolated, coating with columnar structure was formed with a formation rate of $15{\mu}m/hr$. In case of grounded substrate, coating with amorphous structure was formed with a formation rate of $7{\mu}m/hr$.

• Korean Journal of Materials Research
• /
• v.24 no.7
• /
• pp.344-350
• /
• 2014

Metal films (i.e., Ti, Al and SUH310S) were prepared in a magnetron sputtering apparatus, and their cross-sectional structures were investigated using scanning electron microscopy. The apparatus used consisted of a cylindrical metal target which was electrically grounded, and two anode rings attached to the top and to the bottom of the target. A wire was placed along the center-line of the cylindrical target to provide a substrate. When the electrical potential of the substrate was varied, the metal-film formation rate depended on both the discharge voltage and the electrical potential of the substrate. As we made the magnetic field stronger, the plasma which appeared near the target collected on the plasma wall surface and thereby decreased the bias current. The bias current on the conducting wire was different from that for cation collection. The bias current decreased because the collection of cations decreased when we increased the magnetic-coil current. When the substrate was electrically isolated, the films deposited showed a slightly coarse columnar structure with thin voids between adjacent columns. In contrast, in the case of the grounded substrate, the deposited film did not show any clear columns but instead, showed a densely-packed granular structure. No peeling region was observed between the film and substrate, indicating good adhesion.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.7 no.3
• /
• pp.585-590
• /
• 2012

In this paper, a system using vibrating wire sensor and zigbee wireless network has been implemented to monitor and manage the structure. The implemented strain controller drives vibrating wire sensor and computes strain from measuring frequency of the output signal. Temperature sensor is included to compensate strain by temperature. Using two axis acceleration sensor of strain controller can measure the direction of strain or deformation. To measure strain more effectively, wired and wireless communication function is included in this device. As results of experiments, it is shown that the developed system can be effectively applied to measure strain of the structure.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.1
• /
• pp.96-101
• /
• 1986

The average heat transfer coefficient of 2-D impinging jet has been augmented as much as 60% on the wall with large-scale wavy roughness. The mechanism of this heat transfer augmentation is studied with emphasis on two primary flow structures in the impinging flow region by using either the surface floating method or the smoke-wire technique. They are the stream-wise vortex-like structure, which is characteristic to the impining jet, and the spanwise vortiecs associated with the flow separation around the roughness. The combined effect of these structures can effectively augment the heat transfer particularly in the downstream region where the teat transfer usually deteriorates consicerably.

• Earthquakes and Structures
• /
• v.18 no.3
• /
• pp.275-284
• /
• 2020

The scope of this study is the comparison between experimental results of tests performed on a base isolated building using helical wire rope isolators (WRs), and results of Nonlinear Response History Analyses (NRHAs) performed using SAP 2000, a commercial software for structural analysis. In the first stage of this research, WRs have been tested under shear deformation beyond their linear range of deformation, and analytical models have been derived to describe the nonlinear response of the bearings under different directions of loading. On the following stage, shaking table tests have been carried out on a 1/3 scale steel model isolated at the base by means of curved surface sliders (CSS) and WRs. The response of the structure under ground motion excitation has been compared to that obtained using numerical analyses in SAP 2000. The feasibility of modelling the nonlinear behavior of the tested isolation layer using multilinear link elements embedded in SAP 2000 is discussed in this paper, together with the advantages of using WRs as supplemental devices for CSSs base isolated structures.

• Journal of Magnetics
• /
• v.16 no.4
• /
• pp.435-439
• /
• 2011

In this work, we prepared Fe-Ni alloy nanopowders by wire electrical explosion in deionized water and ethanol. Particles size and morphology of the as-synthesized nanoparticles prepared in water and ethanol were observed by transmission electron microscopy. In both cases, the as-synthesized nanoparticles were in nearly spherical shape and their size distribution was broad. The particles prepared in the water were in core-shell structure due to the oxidation of Fe element. X-ray diffraction was used to analyze the phase of the nanopowders. It showed that the nanopowders prepared in water had ${\gamma}$-Fe-Ni solid solution and FeO phase. The samples obtained in ethanol were in two phases of Fe-Ni solid solution, ${\gamma}$-Fe-Ni and ${\alpha}$-Fe-Ni. Bulk samples were made from the as-synthesized nanopowders by spark plasma sintering at $1000^{\circ}C$ for 10 min. Structure of the bulk sample was observed by scanning electron microscope. Magnetic properties of the as-synthesized nanopowders and the bulk samples were investigated by vibrating sample magnetometer. The hysteresis loop of the assynthesized nanopowders and the sintered bulk samples revealed a ferromagnetic characteristic.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.10
• /
• pp.2008-2017
• /
• 2002

Joint structure of a transducer horn-holder assembly fur a wire bonder was examined through FEM contact analysis. A three dimensional modeling and analysis was carried out to survey the internal physics of this structure and to prove the accuracy of a computation compared to a measurement. After validation, a simple two dimensional model was built fur various parametric study considering the efficiency and speed of the computation. Several factors such as boundary conditions, a modeling boundary, mesh density and so on, were considered to obtain consistency with three dimensional analysis. An arc angle and a position of each holder boss were chosen as design parameters. A design of experiment was applied to find out an optimized design of the holder geometry. As a result, a guideline for holder boss design was suggested and main factors and their influence on stress concentration in the transducer horn were surveyed.