• Structural Engineering and Mechanics
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• 제20권6호
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• pp.631-653
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• 2005

In this work, the mechanism of damping and its theoretical evaluation for layered aluminium cantilever structures jointed with a number of equispaced connecting bolts under an equal tightening torque have been considered. Extensive experiments have been conducted on a number of specimens for comparison with numerical results. Intensity of interface pressure, its distribution pattern, dynamic slip ratio and kinematic coefficient of friction at the interfaces, relative spacing of the connecting bolts, frequency and amplitude of excitation are found to play a major role on the damping capacity of such structures. It is established that the damping capacity of structures jointed with connecting bolts can be improved largely with an increase in number of layers maintaining uniform intensity of pressure distribution at the interfaces. Thus the above principle can be utilized in practice for construction of aircraft and aerospace structures effectively in order to improve their damping capacity which is one of the prime considerations for their design.

• Journal of electromagnetic engineering and science
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• 제3권1호
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• pp.17-21
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• 2003

In this paper, we design an optimal planar array geometry for maximum side-lobe reduction. The concept of thinned array is applied to obtain an optimal two dimensional(2-D) planar array structure. First, a 2-D rectangular array with uniform spacing is used as an initial planar array structure. Next, we modify the initial planar array geometry with the aid of thinned array theory in order to reduce the maximum side-lobe level. This is implemented by a genetic algorithm under some constraint, minimizing the maximum side-lobe level of the 2-D planar array. It is shown that the optimized planar array structure can achieve low side-lobe level without optimizing the excitations of the array antennas.

• Journal of Mechanical Science and Technology
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• 제18권10호
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• pp.1869-1879
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• 2004

The present study has numerically investigated two-dimensional flow over three circular cylinders in an equidistant side-by-side arrangement at a low Reynolds number. For the study, numerical simulations are performed, using the immersed boundary method, in the range of g* < 5 at Re= 100, where g* is the spacing between two adjacent cylinder surfaces divided by the cylinder diameter. Results show that the flow characteristics significantly depend on the gap spacing and a total of five kinds of wake patterns are observed over the range: modulation-synchronized (g* (equation omitted) 2), inphase-synchronized (g* (equation omitted) 1.5) , flip-flopping (0.3 < g* (equation omitted) 1.2) , deflected (g* (equation omitted) 0.3), and single bluff-body patterns (g* < 0.3). Moreover, the parallel and symmetric modes are also observed depending on g* in the regime of the flip-flopping pattern. The corresponding flow fields and statistics are presented to verify the observations.

• 한국의류학회지
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• 제16권2호
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• pp.169-180
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• 1992

The purpose of this study is to investigate the effects of type of clothing microclimate and exercise condition on ventilation. The experimental system employed a trace gas technique of the previous research. Clothing microclimate volume measurement was based on the substitution water technique for inter-clothing air volume. The experimental variables were tested at four levels of clothing microclimate spacing, microclimate shape of the previous research and two levels of exercise conditions. 2, 4, 6 cm ease were added to B/2+4 of basic blouse pattern for the microclimate spacing variable. Each combination of three variables were tested in triplicate. Analysis of variance of experimental variables on vetilation, such as oxygen exchange rate, half time of first order model was conducted. Oxygen exchange rate and half time of first order model are affected by the shape of microclimate air and exercise condition.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1140-1141
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• 2006

Diamond tools with several layers of diamond grits through thickness direction were tested by sawing. The saw blades with evenly distributed grits showed better cutting performance compared to the random distributed saw. At a given concentration of grits, as the spacing between layers was increased, the cutting performance was improved, and as decreased, it showed more tool life

• Steel and Composite Structures
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• 제12권2호
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• pp.149-166
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• 2012

This paper presents an experimental investigation on the performance of 2.5 m long reinforced concrete (RC) T-beams strengthened in shear using epoxy bonded glass fibre fabric. Eighteen (18) full scale, simply supported RC T-beams are tested. Nine beams are used as control beam specimens with three different stirrups spacing without glass fibre reinforced polymer (GFRP) sheet and rest nine beams are strengthened in shear with one, two, and three layers of GFRP sheet in the form of U-jacket around the web of T-beams for each type of stirrup spacing. The objective of this study is to evaluate the effectiveness, the cracking pattern and modes of failure of the GFRP strengthened RC T-beams. The test result indicates that for RC T-beams strengthened in shear with U-jacketed GFRP sheets, increase the load carrying capacity by 10-46%.

• 대한교통학회:학술대회논문집
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• 대한교통학회 2002년도 제41회 학술발표회논문집
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• pp.143-159
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• 2002

The performance of two single-barrier three-phase actuated control systems at diamond interchanges was evaluated for various traffic conditions. To emulate the actuated signal control, hardware-in-the-loop system combined with CORSIM simulation program was used. Two performance measures, average delay and total stops, were used for the evaluation process. Results showed that the two three-phase systems gave similar performance in terms of average delay, but not stops. The delay performance of each phasing system was generally dependent on the traffic pattern and ramp spacing. The total stops decreased as the spacing increased, and it was the most sensitive variable that can differentiate between the two three-phase systems. It was also shown that the hardware-in-the-loop control could provide a good method to overcome the limitations of current simulation technology.

• Elastomers and Composites
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• 제58권1호
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• pp.17-25
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• 2023

Abrasion tests of model tire tread compounds (NR and NR/BR blend compounds) were performed at different slip angles (1° and 7°) using a laboratory abrasion tester. The abrasion behavior was investigated by analyzing the worn surface and wear particles. The abrasion spacing formed on the specimen worn at the large slip angle of 7° was significantly narrower than that at the small slip angle of 1°, while the abrasion depth for the specimen worn at 7° was lower than that at 1°. The abrasion spacing and depth tended to be narrower and lower, respectively, as the BR content increased. The abrasion patterns were clearly visible on the outside of the specimen for the slip angle of 1° but not for 7°. The wear particles had a rough surface and there were numerous micro-bumps. It was found that the crosslink density affected the abrasion patterns and morphologies of the wear particles.

• 한국재료학회지
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• 제15권1호
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• pp.54-60
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• 2005

Recently a lots of problems have observed in high densified and high integrated electronic components. One of them is ion migration phenomena, which induce the electrical short of electrical circuit. ion migration phenomena has been observed in the field of exposing the specific environment and using for a long tin e. This study was evaluated the generation time of ion migration and was investigated properly test method through water drop test and high temperature high humidity test. Also we observed direct causes and confirmed generation mechanism of dendritic growth as we reproduced the ion migration phenomena. We utilized PCB(printed circuit board) having a comb pattern as follows 0.5, 1.0, 2.0 mm pattern distance. Cu, SnPb and Au were electroplated on the comb pattern. 6.5 V and 15 V were applied in the comb pattern and then we measured the electrical short time causing by ion migration. In these results, we examined a difference of ion migration time depending on pattern materials, applied voltage and pattern spacing of PCB conductor.

• Macromolecular Research
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• 제15권4호
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• pp.348-356
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• 2007

The aim of this study was to fabricate a submicro-and micro-patterned fibronectin coated wafer for a cell culture, which allows the positions and dimensions of the attached cells to be controlled. A replica molding was made into silicon via a photomask in quartz, using E-beam lithography, and then fabricated a polydimethylsiloxane stamp using the designed silicon mold. Hexadecanethiol $[HS(CH_2){_{15}}CH_3]$, adsorbed on the raised plateau of the surface of polydimethylsiloxane stamp, was contact-printed to form self-assembled monolayers (SAMs) of hexadecanethiolate on the surface of an Au-coated glass wafer. In order to form another SAM for control of the surface wafer properties, a hydrophilic hexa (ethylene glycol) terminated alkanethiol $[HS(CH_2){_{11}}(OCH_2CH_2){_6}OH]$ was also synthesized. The structural changes were confirmed using UV and $^1H-NMR$ spectroscopies. A SAM terminated in the hexa(ethylene glycol) groups was subsequently formed on the bare gold remaining on the surface of the Aucoated glass wafer. In order to aid the attachment of cells, fibronectin was adsorbed onto the resulting wafer, with the pattern formed on the gold-coated wafer confirmed using immunofluorescence staining against fibronectin. Fibronectin was adsorbed only onto the SAMs terminated in the methyl groups of the substrate. The hexa (ethylene glycol)-terminated regions resisted the adsorption of protein. Human dermal fibroblasts (P=4), obtained from newborn foreskin, only attached to the fibronectin-coated, methyl-terminated hydrophobic regions of the patterned SAMs. N-HDFs were more actively adhered, and spread in a pattern spacing below $14{\mu}m$, rather than above $17{\mu}m$, could easily migrate on the substrate containing spacing of $10{\mu}m$ or less between the strip lines.