• Ocean Systems Engineering
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• v.8 no.2
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• pp.167-182
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• 2018

RTI (Rayleigh-Taylor instability) is investigated by a multi-liquid MPS (Moving Particle Semi-implicit) method for both viscous and inviscid flows for various density differences, initial-disturbance amplitudes, viscosities, and surface tensions. The MPS simulation can be continued up to the late stage of high nonlinearity with complicated patterns and its initial developments agree well with the linear theoretical results. According to the relevant linear theory, the difference between inviscid and viscous fluids is the rising velocity at which upward-mushroom-like RTI flow with vortex formation is generated. However, with the developed MPS program, significant differences in both growing patters and developing speeds are observed. Also, more dispersion can be observed in the inviscid case. With larger Atwood (AT) number, stronger RTI flows are developed earlier, as expected, with higher potential-energy differences. With larger initial disturbances, quite different patterns of RTI-development are observed compared to the small-initial-disturbance case. If AT number is small, the surface tension tends to delay and suppress the RTI development when it is sufficiently large. Interestingly, at high AT number, the RTI-suppressions by increased surface tension become less effective.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.1
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• pp.11-19
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• 2010

A code is developed to simulate incompressible free surface flows using the Roe's flux-difference splitting scheme. An interface of two fluids is considered as a moving contact discontinuity. The continuities of pressure and normal velocity across the interface are enforced by the conservation law in the integral sense. The fluxes are computed using the Roe's flux-difference splitting scheme for two incompressible fluids. The interface can be identified based on the computed density distribution. However, no additional treatment is required along the interface during the whole computations. Complicated time evolution of the interface including topological change can be captured without any difficulties. The developed code is applied to simulate the Rayleigh-Taylor instability of two incompressible fluids in the density ratio of 7.2:1 and the broken dam problem of water-air. The present results are compared with other available results and good agreements are achieved for the both cases.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.198-203
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• 2008

In the present study, the deformation behavior of both of metal and polymer combination on impact was investigated. They have showed a different deformation behavior when the co-axially combined projectile was impacted on rigid target. The theory according to Taylor's simplified approach assumes an ideally rigid-plastic material model exhibiting rate-independent behavior and simple one-dimensional wave propagation concepts that neglect radial inertia. In the case of impact with polymeric materials, elastic strain in general are not negligible compared with plastic strain; and the rigid-plastic material behavior assumed by Taylor for metallic materials cannot be applied any more. Since, the sleeve and the core materials have widely different mechanical properties, they will produce a significant difference of mechanical impedance with each other. Therefore these impedance mismatch influences on the deformation behavior sleeved polymer projectile on impact. As a result, sleeved projectiles will generate a very interesting impact behavior. Therefore, the according to sleeved metal material and core polymer material can see expected. The objective of this study was to investigate the factors which influences on deformation behavior pattern of sleeve materials surface.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.97-102
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• 2003

An experimental study is conducted to investigate the effects of duct corrugation angle on heat/mass transfer characteristics in wavy ducts by using a naphthalene sublimation technique. The corrugation angles of the wavy ducts are $145^{\circ}$ , $130^{\circ}$ and $115^{\circ}$ . and the Reynolds numbers based on the duct hydraulic diameter vary from 300 to 3,000. At the low $Re(Re{\leq}1000)$, high heat/mass transfer regions are formed by the secondary vortex flows called Taylor-Gortler vortices on both pressure-side and suction-side walls. At the high $Re(Re{\geq}1000)$, the effects of these secondary flows are vanished. As corrugation angle decreases, the local peak Sh induced by Taylor-Gertler vortices are increased and average Sh also enhanced. More pumping power (pressure loss) is required with the smaller corrugation angle due to the stronger secondary vortex flows.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.3
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• pp.101-119
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• 2005

For MEMS applications, the effects of the momentum and heat loss on the stability of laminar premixed flames in a narrow channel are investigated by high-fidelity numerical simulations. A general finding is that momentum loss promotes the Saffman-Taylor (S-T) instability which is additive to the Darrieus-Landau (D-L) instabilities, while the heat loss effects result in an enhancement of the diffusive-thermal (D-T) instability. These effects are also valid in nonlinear behavior of the premixed flame. The simulations of multiple cell interactions are also conducted with heat and momentum loss effects.

• Journal of Korean Association for Spatial Structures
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• v.18 no.3
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• pp.83-91
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• 2018

In this study, we investigated the dynamic stability of the system and the semi-analytical solution of the shallow arch. The governing equation for the primary symmetric mode of the arch under external load was derived and expressed simply by using parameters. The semi-analytical solution of the equation was obtained using the Taylor series and the stability of the system for the constant load was analyzed. As a result, we can classify equilibrium points by root of equilibrium equation, and classified stable, asymptotical stable and unstable resigns of equilibrium path. We observed stable points and attractors that appeared differently depending on the shape parameter h, and we can see the points where dynamic buckling occurs. Dynamic buckling of arches with initial condition did not occur in low shape parameter, and sensitive range of critical boundary was observed in low damping constants.

• Journal of the Korean Society of Visualization
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• v.16 no.3
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• pp.40-46
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• 2018

The surface structure of the electrospun polymer fibers depends on the polymer concentration, the type of solvent used, applied voltage and so on. To make a desired surface, it is important to understand the effects of the physicochemical properties to form a stable Taylor cone and jet dispensation. We observed the formation of Taylor cone and a consequent structure of fiber by controlling the parameters of applied voltage, solution concentration, solvent and collector effectively. Once the surfaces were fabricated, the structures were analyzed using optical imaging technologies. As the solution concentration was increased, the smooth fibers were formed. In addition, different solvent ratios determined the viscosity and the surface tension of solutions. As a result, with decreased viscosity and increased surface tension, thin fibers were obtained by electrospinning. Furthermore the aligned nanofiber was successfully created by using drum collector.

• Journal of the Korean Society of Clothing and Textiles
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• v.45 no.3
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• pp.423-438
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• 2021

This study examined fashion through the lens of Charles Taylor's concept of 'Authenticity.' From the point of view of 'Authenticity,' fashion can be thought of as "a means of expressing one's inner truth" and "affirmative about everyday life." According to 'Authenticity,' fashion, in the first case ("one's inner truth") appears as 1) magnetic uniqueness, 2) inner subjectivity, and 3) poiēsis. And in the second case ("affirmative about everyday life") it is expressed as 1) naturalism, 2) positivity of self-expression, and 3) existentiality. For this study, we selected a high school 'ganzi' contest, whose participants were deemed to have a high level of interest in and understanding of fashion, compared to other teenagers living in South Korea. Among the 33 participants in 'Goganzi' Seasons 1 and 2, we analyzed the styles and looks of 30 works by the six people who made it to the final stage. As a result, we broke down the aesthetic values of authenticity that teenagers express through their fashion into three categories: plurality, originality, and creativity.

• Transactions of Materials Processing
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• v.30 no.1
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• pp.16-21
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• 2021

A new concept of ammunition without the use of explosive gunpowder has been recently studied, which achieves performance equal to or higher than that of high explosives. Frangible Armor Piercing (FAP) is one of the concepts, which utilizes a tungsten alloy penetrator specialized for fragmentation. To investigate the fracture behavior of the tungsten alloy penetrator, Taylor impact tests were conducted at various impact velocities. Additionally, finite element analysis was performed to predict the fracture behavior of the tungsten alloy. Compression tests were also carried out at six strain rates for dynamic material properties and the dynamic hardening behavior was successfully predicted with the Lim-Huh model. Finally, the Mohr-Coulomb fracture model based on the mean stress was adopted to predict impact failure in Taylor impact simulation. The analysis predicts the deformation and fracture behaviors of the tungsten alloy successfully.

• International Journal of Computer Science & Network Security
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• v.23 no.3
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• pp.31-48
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• 2023

The popularization of smart devices and subsequent optimization of their sensing capacity has resulted in a novel mobile crowdsensing (MCS) pattern, which employs smart devices as sensing nodes by recruiting users to develop a sensing network for multiple-task performance. This technique has garnered much scholarly interest in terms of sensing range, cost, and integration. The MCS is prevalent in various fields, including environmental monitoring, noise monitoring, and road monitoring. A complete MCS life cycle entails task allocation, data collection, and data aggregation. Regardless, specific drawbacks remain unresolved in this study despite extensive research on this life cycle. This article mainly summarizes single-task, multi-task allocation, and space-time multi-task allocation at the task allocation stage. Meanwhile, the quality, safety, and efficiency of data collection are discussed at the data collection stage. Edge computing, which provides a novel development idea to derive data from the MCS system, is also highlighted. Furthermore, data aggregation security and quality are summarized at the data aggregation stage. The novel development of multi-modal data aggregation is also outlined following the diversity of data obtained from MCS. Overall, this article summarizes the three aspects of the MCS life cycle, analyzes the issues underlying this study, and offers developmental directions for future scholars' reference.