• Polymer(Korea)
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• v.35 no.3
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• pp.272-276
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• 2011

The induction mechanisms of planar arrangements in cholesteric liquid crystals (CLC) which showed selective reflections of visible light were investigated by measuring the selective reflectivity and FTIR peak intensity of $C{\equiv}N$ stretching band. Although the planar arrangement of CLC was not as perfectly induced as the cases prepared with using alignment layers, it could be also induced by stretching polymer substrate or by applying shear forces. The planar arrangements were induced by forming CLC helical structures on top of liquid crystal molecules which were in contact with the substrate and oriented all in the same direction.

• Journal of computational fluids engineering
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• v.12 no.4
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• pp.61-67
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• 2007

Numerical simulation of laminar flow over two spheres in a side-by-side arrangement is carried out to investigate the effect of the inter-sphere spacing on the flow characteristics. The Reynolds numbers considered are 100, 250, and 300, covering the steady axisymmetric, steady planar-symmetric, and unsteady planar-symmetric flows in the case of a single sphere. Results show that the drag and lift coefficients and wake structures are significantly modified depending on both the Reynolds number and the spacing between the spheres. At Re=100, the flow is steady planar-symmetric irrespective of the spacing, but it shows some variation according to the spacing at Re=250 and 300. That is, the flow maintains planar symmetry of the single-sphere wake at large spacings, while it loses the symmetry at small spacings due to the generation of new asymmetric vortical structures. It is also shown that the drag and lift coefficients generally increase with decreasing inter-sphere spacing because the high pressure region is formed near the gap between the spheres.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.480-488
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• 2006

Numerical simulations of flow over two spheres placed in a tandem arrangement are conducted to investigate the effect of the inter-sphere spacing on the flow characteristics. The Reynolds numbers considered are 100, 250, 300 and 425, corresponding to steady axisymmetric, steady planar-symmetric, unsteady planar-symmetric, and unsteady asymmetric flows, respectively, in the case of a single sphere. For small inter-sphere spacings, the flow past two spheres is more stable than that past a single sphere. For example, with the spacing of the sphere radius, the flow is steady axisymmetric up to Re=300. However, for relatively large spacings, the flow past two spheres becomes unstable and vortex shedding takes place even at Re=250. The drag coefficient of the rear sphere decreases significantly with decreasing inter-sphere spacing due to reduction of the stagnation pressure, thus being smaller than that of the front sphere. Also, the rear sphere shows large fluctuations of the lift force as compared to the front one in the case of unsteady flow.

• Polymer(Korea)
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• v.34 no.3
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• pp.242-246
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• 2010

FTIR spectroscopy has been employed in order to quantitatively investigate the relationship between planar arrangements and selective reflectance of cholesteric liquid crystals. It was found that the selective reflection was enhanced as the amount of planar arrangements in cholesteric liquid crystals increased. Although the planar arrangements of cholesteric liquid crystals can be induced only by the shear force effect, it was more effective to use the alignment layer to obtain the perfect planar arrangements.

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.333-340
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• 1996

We have implemented a planar integrated optics for the fractional Fourier transform (FRT) which has recently been developed as a generalized form of the conventional Fourier transform. FRT optical systems provide versatile tools for analyzing signals and designing hardwares, but require high accuracy and stability in the arrangement of optical components because of their shift-variant characteristic. The planar optical FRT setup composed of free-space optical components integrated on a single glass block makes the FRT of 2-dimensional(2-D) input patterns through the 3-D glass-space. Therefore, taking advantage of the compactness, easy alignment and thermal/mechanical stability, the planar optics can provide a useful approach to realizing an optical fractional correlation system in a practical way. In the experiment, we have obtained accurate FRT results by using the planar integrated optics with 4 different fractional orders of 0.25, 0.5, 0.75, and 1.0.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.719-722
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• 2002

This paper reports the characteristics of a bidirectional antenna by using a planar array of a probe excited circular ring. The element of a bidirectional antenna is first designed to achieve the maximum directivity. The directivity can be further increased by arranging these elements to form the linear array. There are two types of linear array to be investigated i.e., on axis and off axis arrangement. On-axis linear array yields better directivity than off-axis linear array. Therefore, this orientation is further used to form the planar array. The radiation characteristics of this optimum planar array are rigorously reported. The proposed structure is very useful to extend the distance between the base station in PCT system.

• Steel and Composite Structures
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• v.47 no.1
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• pp.51-69
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• 2023

In tied-arch bridges, a properly designed connection between the arch and the deck may become crucial, since the forces in the structure may be significantly reduced. This implies substantial material savings and, consequently, cheaper constructions. The introduction of the Nielsen cable arrangement (composed of V-shaped inclined hangers) in the last century was a milestone because it was able to reduce deflections and bending moments both in the arch and in the deck. So far, the Nielsen cable arrangement has proven to be successful in traditional vertical arch bridges. However, despite its advantages, it has not been widely applied to spatial arch bridges. Thus, this article analyses the difference between the structural behavior of spatial arch bridges with Nielsen-type cable arrangements with respect to those with classical vertical hanger configurations. The main goal is to verify whether the known effectiveness of the Nielsen cable arrangement for classical arch bridges is still preserved when applied to spatial arch bridges. In order to achieve this objective, and as the first part of our study, a set of different all-steel bridges composed of vertical and inclined arches with straight decks have been compared for both cable arrangements. As a major conclusion, for planar vertical arch bridges, the Nielsen-type cable arrangement is always the most effective. In addition, it also seems that, for spatial arch bridges composed of a straight deck and an inclined arch, it still keeps most of its effectiveness as long as the arch is moderately inclined.

• Transactions of Materials Processing
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• v.30 no.2
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• pp.69-73
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• 2021

This paper addresses the product shape modification for spring-back reduction in the sheet metal forming process of the cabin sunroof which is applied to the construction equipment. Initially, the anisotropic material properties are measured in order to calculate the degree of spring-back by the numerical simulation of the sheet metal forming process. To reduce the spring-back of the stamped part, several design modifications are suggested according to the geometrical bead arrangement on the planar region. The degrees of spring-back are confirmed for various product designs with different use of the geometrical bead. Finally, the spring-back improvement was validated by manufacturing the tryout product with the modified die set for the optimized product shape.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.7
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• pp.840-843
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• 2012

In this paper, the authors present a new design for a dual-band metamaterial(MTM) absorber that utilizes resonant-magnetic inclusion of a split-ring resonator(SRR). The proposed MTM unit cell is constructed by two open complementary split-ring resonators(OCSRRs) and an SRR arrangement. To avoid the need for metallic back plate a planar array of SRRs for resonant-magnetic inclusion is placed facing toward the incident wave propagation direction. Each unit cell is printed on the two sides of a FR-4 substrate. A prototype absorber was fabricated with a planar array of $39{\times}39$ unit cells, and measured. The proposed backplane-less absorber can be used for microwave applications.

• Journal of Korea Multimedia Society
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• v.25 no.10
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• pp.1404-1415
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• 2022

The 2-dimensional arrangement method of nodes has been used in most of RF (Radio Frequency) based communication network simulations. However, this method is not useful for the an none-obstacle 3-dimensional space networks in which the propagation delay speed in communication is very slow and, moreover, the values of performance factors such as the communication speed and the error rate change on the depth of node. Such a typical example is an underwater communication network. The 2-dimensional arrangement method is also not useful for the RF based network like some WSNs (Wireless Sensor Networks), IBSs (Intelligent Building Systems), or smart homes, in which the distance between nodes is short or some of nodes can be arranged overlapping with their different heights in similar planar location. In such cases, the 2-dimensional network simulation results are highly inaccurate and unbelievable so that they lead to user's erroneous predictions and judgments. For these reasons, in this paper, we propose a method to place uniformly and randomly communication nodes in 3-dimensional network space, making the wireless link with neighbor node possible. In this method, based on the communication rage of the node, blocks are generated to construct the 3-dimensional network and a node per one block is generated and placed within a block area. In this paper, we also introduce an algorithm based on this method and we show the performance results and evaluations on the average time in a node generation and arrangement, and the arrangement time and scatter-plotted visualization time of all nodes according to the number of them. In addition, comparison with previous studies is conducted. As a result of evaluating the performance of the algorithm, it was found that the processing time of the algorithm was proportional to the number of nodes to be created, and the average generation time of one node was between 0.238 and 0.28 us. ultimately, There is no problem even if a simulation network with a large number of nodes is created, so it can be sufficiently introduced at the time of simulation.