• Structural Engineering and Mechanics
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• v.26 no.5
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• pp.483-498
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• 2007

In case of considering the shear effect, the complete solutions are obtained for dynamic plastic response of a rigid, perfectly plastic hinged-free beam, of which one end is hinged and the other end free, subjected to a transverse strike by a travelling rigid mass at an arbitrary location along its span. Special attention is paid to new deformation mechanisms due to shear sliding on both sides of the rigid mass and the plastic energy dissipation. The dimensionless numerical results demonstrate that three parameters, i.e., mass ratio, impact position of mass, as well as the non-dimensional fully plastic shear force, have significant influence on the partitioning of dissipated energy and failure mode of the hingedfree beam. The shear effect can never be negligible when the mass ratio is comparatively small and the impact location of mass is close to the hinged end.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.3
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• pp.71-76
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• 2017

The electrical behavior and flexibility of the screen printed Ag circuits were investigated with infrared radiation sintering times and sintering temperatures. Electrical resistivity and radio frequency characteristics were evaluated by using the 4 point probe measurement and the network analyzer by using cascade's probe system, respectively. Electrical resistivity and radio frequency characteristics means that the direct current resistance and signal transmission properties of the printed Ag circuit. Flexibility of the screen printed Ag circuit was evaluated by measuring of electrical behavior during IPC sliding test. Failure mode of the Ag printed circuits was observed by using field emission scanning electron microscope and optical microscope. Electrical resistivity of the Ag circuits screen printed on Pl substrate was rapidly decreased with increasing sintering temperature and durations. The lowest electrical resistivity of Ag printed circuit was up to $3.8{\mu}{\Omega}{\cdot}cm$ at $250^{\circ}C$ for 45 min. The crack length arisen within the printed Ag circuit after $10{\times}10^4$ sliding numbers was 10 times longer than that of after $2.5{\times}10^4$ sliding numbers. Measured insertion loss and calculated insertion loss were in good agreements each other. Insertion loss of the printed Ag circuit was increased with increasing the number of sliding cycle.

• Tunnel and Underground Space
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• v.29 no.5
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• pp.332-345
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• 2019

Maximum dip vector of individual joint plane, which can be uniquely defined on the hemispherical projection plane, has been established by considering its dip and dip direction. A new stereographic projection method for the rock slope analysis which employs the maximum dip vector can intuitively predict the failure modes of rock slope. Since the maximum dip vector is uniquely projected on the maximum dip point of the great circle, the sliding direction of discontinuity plane can be recognized directly. By utilizing the maximum dip vector of discontinuity both the plane sliding and toppling directions of corresponding blocks can be discerned intuitively. Especially, by allocating the area of high dip maximum dip vector which can form the flanks of sliding block the potentiality for the formation of virtual sliding block has been estimated. Also, the potentiality of forming the triangular-sectioned sliding block has been determined by considering the dip angle of joint plane the dip direction of which is nearly opposite to that of the slope face. Safety factors of the different-shaped blocks of triangular section has been estimated and compared to the safety factor of the most hazardous block of rectangular section. For the wedge analysis the direction of crossline of two intersecting joint planes, which has same attribute of the maximum dip vector, is used so that wedge failures zone can be superimposed on the stereographic projection surface in which plane and toppling failure areas are already lineated. In addition the maximum dip vector zone of wedge top face has been delineated to extract the wedge top face-forming joint planes the orientation of which provides the vital information for the analysis of mechanical behavior of wedge block.

• Tribology and Lubricants
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• v.11 no.5
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• pp.1-9
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• 1995

The mechanism of various spherical particles formation from wide range of tribo-systerns is suggested and deduced by the action of micro-explosion on the basis of the thermally-activated wear theory, in which the flash temperature at contact could be reached clearly upto the material molten temperature due to the secondary activation energy from the exothermic reactions involving lubricant thermo-decomposition, metals oxidation, hydrogen reactions and other possible complex thermo-reactions at the contacts. Various shapes of spherical particles generated from the tribosystem can be explained by the toroidal action of micro-explosion accompanied with the complex thermo-chemical reactions at the contact surfaces or sub-surfaces.

• Plant Journal
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• v.18 no.4
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• pp.66-72
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• 2023

In order to respond to the demand for flexible operation of thermal power generation, development of natural sliding pressure operation that minimizes throttle loss by opening the turbine control valve 100% and maximize power generation efficiency in conjunction with ESS in order to quickly respond to fluctuations in the system frequency is required. The logic development of natural sliding pressure operation with ESS was developed to modify the existing logic at the power plant's top-level control logic such as the unit master, the boiler master and the turbine master. Cooperative control algorithms that complement the advantages and disadvantages of ESS operation (quick response, limited capacity) and power plant operation (slow response, continuous operation) not only improve efficiency when applied to actual power plants, but also respond quickly and flexibly to load demands to ensure system stability.

• Journal of the Korean Data and Information Science Society
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• v.27 no.2
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• pp.275-284
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• 2016

Accurate electricity demand forecasts is essential in reducing energy spend and preventing imbalance of the power supply. In forcasting electricity demand, we considered double seasonal Holt-Winters model and TBATS model with sliding window. We selected a specific time zone as the reference line of daily electric demand because it is least likely to be influenced by external factors. The forecasting performance have been evaluated in terms of RMSE and MAPE criteria. We used the observations ranging January 4, 2009 to December 31 for testing data. For validation data, the records has been used between January 1, 2012 and December 29, 2012.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1016-1021
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• 2004

The need for developing a mathematical model for pad-pivot friction in tilting pad proceeding bearings has been well-recognized, since previous experimental work about the performances of the bearings hypothesized that the friction in the bearings is closely related to their performances. Especially, the sliding friction between pad and pivot in the ball and socket type of the bearings can influence the performance of the bearing. We propose a mathematical model for pad-pivot friction in the ball and socket type, which considers the geometrics of the pad and pivot of the bearings, by assuming the sliding friction in the ball and socket bearing as Coulomb friction. By utilizing the proposed model for pad-pivot friction, we show the analysis of Reynolds equation and energy equation, which explain the thermo-hydrodynamic characteristics of tilting pad proceeding bearings, by taking into account the turbulence and inlet pressure building as well. The results of the study show that the performance of titling-pad proceeding bearings can be greatly influenced by the pad-pivot friction. In particular, we have shown that the analysis of the pad-pivot friction is useful to explain the static proceeding loci and the dynamic characteristics of the ball and socket type of the bearings. Furthermore, for a given operating condition, we can obtain various equilibrium states which satisfy the static equilibrium conditions, by considering the pad-pivot friction.

• Journal of Power System Engineering
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• v.12 no.3
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• pp.60-65
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• 2008

This study aims at investigating the wear properties of thermally sprayed $Al/Al_2O_3$ metal matrix composite(MMC) coating against different counterparts. $Al/Al_2O_3$ MMC coatings were fabricated using a flame spray system on an Al 6061 substrate. Dry sliding wear tests were performed using the sliding speeds of 0.2m/s and the applied loads of 1 and 2 N. AISI 52100, $Al_2O_3$, $Si_3N_4\;and\;ZrO_2$ balls(diameter: 8mm) were used as counterpart materials. Wear properties of $Al/Al_2O_3$ MMC coatings were analyzed using a scanning electron microscope(SEM) and energy dispersive X-ray spectroscopy (EDX). It was revealed that wear properties of $Al/Al_2O_3$ composite coatings were much influenced by counterpart materials. In the case of AISI 52100 used as counterparts, the wear rate of composites coating layer increased according to the increase of the applied load. On the contrary, in the case of ceramics used as counterparts, the wear rate of composites coating layer decreased according to the increase of the applied load.

• Journal of Advanced Research in Ocean Engineering
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• v.4 no.2
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• pp.47-52
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• 2018

The Korea Offshore Wind Power (KOWP) is planning to construct offshore wind energy farms with an overall rated power of 2.5 GW in the south-western coast of the country until 2019. Various types of support structures for offshore wind turbines have been proposed in the past. Nevertheless, in South Korea, jacket structures have in general, been applied as support structures for offshore wind turbines owing to the many accumulated experiences and know-how regarding this kind of support structure. The choice of offshore structure is mainly influenced by site conditions such as seabed soil type and sea environment during installation. In installing jacket sets on the seabed, the mudmat is necessary to maintain the equilibrium of the jacket without the aid of additional devices. Hence, this study proposes the installation of skirt plates underneath the bottom frame of jackets in order to improve the installation stability of jacket structures under rougher sea conditions. To confirm the effect of skirt plates, installation stability analyses considering overturning, sliding and bearing capacity have been performed. From the results, it is shown that jacket structures with skirt plates can contribute to improving the sliding stability of the structures of new wind power farms, while providing economic benefits.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.489-496
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• 1988

This paper is studied to know wear mechanism in variation of austempering temperature and holding time of austempered ductile cast iron against mating material SM45C hardened by heat treatment. The wear tests were carried out by rubbing the annular surface of two test pieces in dry sliding friction. The wear mechanism was investigated by scanning electron microscopy and the retained austenite volume fraction was investigated by X-ray diffractometer. The experimental results show that the wear characteristics depend largely on the oxidation of the testing materials which is influenced by the sliding velocity and distance. The retained austenite has a negative effect during frictional contact because it has increased severe wear by softened surface layer. It is shown experimentally that hard metals have lower frictional resistance and hence the resistance to adhesion is increased due to stronger interatomic linking bonds and increase in the surface energy.