• Journal of the Society of Naval Architects of Korea
• /
• v.55 no.4
• /
• pp.289-296
• /
• 2018

The offshore subsea platforms are connected to subsea pipelines to transport gas/oil from wells. The pipe is a multilayered structure of polymer and steel for compensating both flexibility and strength. The pipe also requires reinforcement structures to endure the extreme environmental conditions. A vertebrae structure of bend restrictors is one of the reinforcement structures installed to protect the subsea pipe from excessive bending deformations. In this study, structural behaviors of the subsea pipeline with bend restrictors are investigated by the multi-body contact analysis in Abaqus 6.14-2. Contact forces of each bend restrictor extracted from the multi-body contact analysis can be boundary conditions for topology design optimization in Altair Hyperworks 13.0 Hypermesh-Optistruct. Multiple design constraints are considered to obtain a manufacturable design with efficient material usage. Through the multi-body contact analysis with optimized bend restrictors, it is confirmed that the bending performance of the optimized design is enhanced.

• Structural Engineering and Mechanics
• /
• v.29 no.2
• /
• pp.223-235
• /
• 2008

This paper focuses on the application of artificial neural networks (ANN) for optimal design of tensegrity grid as light-weight roof structures. A tensegrity grid, 2 m ${\times}$ 2 m in size, is fabricated by integrating four single tensegrity modules based on half-cuboctahedron configuration, using galvanised iron (GI) pipes as struts and high tensile stranded cables as tensile elements. The structure is subjected to destructive load test during which continuous monitoring of the prestress levels, key deflections and strains in the struts and the cables is carried out. The monitored structure is analyzed using finite element method (FEM) and the numerical model verified and updated with the experimental observations. The paper then explores the possibility of applying ANN based on multilayered feed forward back propagation algorithm for designing the tensegrity grid structure. The network is trained using the data generated from a finite element model of the structure validated through the physical test. After training, the network output is compared with the target and reasonable agreement is found between the two. The results demonstrate the feasibility of applying the ANNs for design of the tensegrity structures.

• Proceedings of the KIEE Conference
• /
• 2005.07c
• /
• pp.2386-2388
• /
• 2005

As anti-crash and pre-crash systems in vehicles become more extensively used, the need for high performance short-range radars is playing an increasing role. This paper presents the design of a micromachined, ultra-wideband beamformer centered at 24 GHz for automotive short-range radar systems. This beamformer is a Butler matrix designed using ultra-wideband transmission-line couplers, which consist of a multilayered structure that exhibits wider bandwidth compared to conventional microstrip branch-line couplers. The circuit has been designed on a quartz substrate, and to achieve the desired coupling, lines suspended on BCB layers located at specific parts of the circuit were used, achieving a three metal layered structure in form of wide microstrips, that give low loss and a wideband response. In this paper the design and fabrication procedure of the proposed beamformer are fully described.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.235.1-235.1
• /
• 2015

Artificially-engineered materials, whose electromagnetic properties are not available in nature, such as negative reflective index, are called metamaterials (MMs). Although many scientists have investigated MMs for negative-reflective-index properties at the beginning, their interests have been extended to many other fields comprising perfect lenses. Among various kinds of MMs, metamaterial absorbers (MM-As) mimic the blackbody through minimizing transmission and reflection. In order to maximize absorption, the real and the imaginary parts of the permittivity and permeability of MM-As should be adjusted to possess the same impedance as that of free space. We propose a dual-wide-band and polarization-independent MM-A. It is basically a triple-layer structure made of metal/dielectric multilayered truncated cones. The multilayered truncated cones are periodically arranged and play a role of meta-atoms. We realize not only a wide-band absorption, which utilizes the fundamental magnetic resonances, but also another wide-band absorption in the high-frequency range based on the third-harmonic resonances, in both simulation and experiment. In simulation, the absorption bands with absorption higher than 90% are 3.93 - 6.05 GHz and 11.64 - 14.55 GHz, while the experimental absorption bands are in 3.88 - 6.08 GHz and 9.95 - 13.84 GHz. The physical origins of these absorption bands are elucidated. Additionally, it is also polarization-independent because of its circularly symmetric structures. Our design is scalable to smaller size for the infrared and the visible ranges.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.31 no.2
• /
• pp.12-27
• /
• 2003

The purpose of this study is to look for an environmental design method based on open narrative structure, and to promote various experiences and interpretations of space through user's engagements. That is to say, the designer does not lead specific events through separate Boning but using the continuous open composition users are provided with margins for their imaginations. Spatial formulation through open narrative structure gives us various thoughts and it plays an important role in making a sequential space. Like an abstract painting, it is a complex story making or arranging a montage of images containing stories that elicit the reader's engagement through diverse interpretations. Like this, open composition exists in an ambiguous state and it is possible to interpret unfinished‘evolving work’within it. Utilizing open narrative structure, this study attempts to apply the idea of sequencing and open composition in the case of designing Arirang Culture Park. Open composition should induce various engagements by users and could be a medium which organically connects nature, culture and people. The spatial strategies of‘ambiguity’ and‘transparency’are like a bundle of complex and heterogeneous factors. Finally, the study focuses on the ‘integration’of the main ideas that compose multilayered space. ‘Voidness’and‘thickening’are also used for spatial strategies in open narrative structure. As alternative plans for undecided programs of the space, the voidness can be a strategic design program with flexibility about changes of futures. Also, thickening can be a strategic design program for functional reinforcement of the space, for the dramatic effects and for the generation of incidental events. Although both voidness and thickening seem paradoxical, we can see they are similar in the way that both focus on various spatial uses and by how they do not function as one-to-one correspondence, but as multiple correspondences. Therefore, open narrative structure is possible to apply in designing space and it can be an alternative design strategy for inducing multiple interpretations of space.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.13 no.5
• /
• pp.869-874
• /
• 2010

A research for the optimal design of microwave absorbing material featuring for the broadband has been conducted to apply to warship. A multilayered structure was suggested using wave absorbing layers and resistance layer to perform high performance in broadband frequencies. For the optimization of the wave absorbing characteristics, the thickness and permittivities of the absorbing layers as well as the surface resistance of the resistant layer were determined using genetic algorithm. The data base of permittivities related to the density of the dielectric materials and loss materials was obtained by the experiments for the dielectric constants of the absorbing layers, furthermore, the results were numerically expressed and used for the optimization.

• 한국전산유체공학회:학술대회논문집
• /
• 2011.05a
• /
• pp.117-123
• /
• 2011

The low electric power and high efficiency chips are required because of the appearance of smart phones. Also, high-capacity memory chips are needed. e-MMC(embedded Multi-Media Card) for this is defined by JEDEC(Joint Electron Device Engineering Council). The e-MMC memory for research and development is a memory mulit-chip module of 64GB using 16-multilayers of 4GB NAND-flash memory. And it has simplified the chip by using SIP technique. But mulit-chip module generates high heat by higher integration. According to the result of study, whenever semiconductor chip is about 10 $^{\circ}C$ higher than the design temperature it makes the life of the chip shorten more than 50%. Therefore, it is required that we solve the problem of heating value and make the efficiency of e-MMC improved. In this study, geometry of 16-multilayered structure is compared the temperature distribution of four different geometries along the numerical analysis. As a result, it is con finned that a multilayer structure of stair type is more efficient than a multilayer structure of vertical type because a multi-layer structure of stair type is about 9 $^{\circ}C$ lower than a multilayer structure of vertical type.

• Journal of IKEEE
• /
• v.24 no.1
• /
• pp.238-242
• /
• 2020

This paper presents a technique using a multilayered dielectric coating to reduce the radar cross section (RCS) value of an integrated mast mounted in a destroyer. The proposed multilayer structure has the advantage of being easy to fabricate because the dielectric constant is defined so that a general dielectric that does not contain a magnetic component that requires high dielectric constant or is frequently used for blocking electromagnetic wave absorption can be used. After applying the proposed multi-layer dielectric structure to the integrated mast shape, the simulation results show that the RCS reduction performance is 10.9dB at 6GHz, 11.95dB at 12GHz, and 11.63dB at 18GHz compared to the structure without the multilayer structure.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.3 no.1
• /
• pp.155-163
• /
• 2000

A general characterization procedure based on the extraction of a 2n-port admittance matrix corresponding to n uniform coupled lines on the multi-layered substrate using the Finite-Difference Time-Domain (FDTD) technique is presented. The frequency-dependent normal mode parameters are obtained from the 2n-port admittance matrix, which in turn provides the frequency-dependent distributed inductance and capacitance matrices. To illustrate the technique, several practical coupled line structures on multi-layered substrate, including a three-line structure, have been simulated. It is shown that the FDTD based time domain characterization procedure is an excellent broadband simulation tool for the design of multiconductor coupled lines on multilayered PCBs as well as thick or thin hybrid structures.

• Journal of Aerospace System Engineering
• /
• v.18 no.1
• /
• pp.1-10
• /
• 2024

In a previous study, a structure of a superplastic yoke consisting of a thin FR4 layer laminated with viscoelastic tape on both sides of a shape memory alloy (SMA) was proposed to reduce residual vibration generated by a deployable solar panel during high motion of a satellite. Damping properties of viscoelastic tapes will change with temperature, which can directly affect vibration reduction performance of the yoke. To check damping performance of the yoke at different temperatures, free damping tests were performed under various temperature conditions to identify the temperature range where the damping performance was maximized. Based on above temperature test results, this paper predicts temperature of the yoke through orbital thermal analysis so that the yoke can have effective damping performance even if it is exposed to an orbital thermal environment. In addition, the thermal design method was described so that the yoke could have optimal vibration reduction performance.