• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.15-15
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• 1998

The problem of the impingement of a sonic or a supersonic jet on a flat surface has not only wide applications but has also interesting and very complex flow phenomena. The main applications of this impinging jet include prediction of solid surface erosion, design of launcher systems, stage separation of multi-stage rocket system, V/STOL operations, thermal spray system, and manufacturing technologies of materials. Much have been learned about the supersonic impinging jet flow field but many fundamental questions have not been answered satisfactorily. The problem encompasses many facets of fluid dynamics which, in combination, present the compressibility effect and the viscous-inviscid interaction, coupled with flow separation and reattachment. What is more, there are many flow parameters that have on the impinging jet flow field, for example, Mach number, Reynolds number, pressure ratio, distance between the nozzle exit and flat plate, jet shock structure, nozzle diameter and etc. Thus the existing data on the supersonic impinging jet flow present considerable disagreement in which quantitative comparison between one result and another is often impossible.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.07a
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• pp.51-55
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• 2003

Membranes made with perfluorinated polymers are of particular interest due to the unique features demonstrated by these materials. Both highly hydrophobic and hydrophilic membranes have been developed from appropriate perfluoropolymers, which were in turn obtained by copolymerization of TFE with special monomers available at the industrial scale. Highly hydrophobic membranes obtained from the glassy copolymers of TFE and 2,2,4 trifluoro-5 trifluoromethoxy-1,3 dioxole (Hyflo $n^{ }$ AD) show properties which make them particularly suited for use in the field of gas-liquid contactors and membrane distillation. Hydrophylic highly conductive proton exchange membranes obtained from the copolymer of TFE and a short-side-chain (SSC) perfluorosulfonylfluoridevinylether (Hyflo $n^{ }$ Ion) find interesting application in the field of fuel cells, especially in view of the current tendency to move to high temperature operation.n.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.50-51
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• 2017

The safety accident of construction industries occur variously in other industries, including other industries, resulting in significant losses of human and material losses. In particular, General worker represents the highest safety accident rate each year, and the various types of accidents are the ones that show the greatest interest in the field, which is the most interesting job in the field. This study aims to identify trends in safety hazards and to analyze the accident severity for major types and influence factors.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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• pp.131-136
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• 2018

Research on space development and satellites is being actively pursued. An interesting field is the study of reliable low-cost space launch vehicles. Since chemical fuel-based launching systems are expensive and take a lot of time and cost to maintain, the EML system, which is an electromagnetic force launching apparatus, is attracting attention. The EML system converts electrical energy stored in a capacitor into magnetic energy, and converts magnetic energy into mechanical kinetic energy, thereby accelerating the projectile. Although studies are actively conducted in the field, it is difficult to solve the equation because the impedance and speedance change with time and the nonlinearity is strong. Many researchers have solved this equation in a variety of methods. In this paper, the velocity analysis of the projectile was carried out by FEM (finite element method) using the commercial electromagnetic analysis program MAXWELL.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.842-847
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• 1994

This paper presents the nearfield acoustic holography (NAH) imaging system for airborne sound constructed in our own laboratory. The effects of different kinds of noise and the filter function's form in wave number space for reconstructions are analysed emphatically. Using the system we have measured the vibrating mode and the radiated field of a simulative "Chime Stone" made by metal, and gotten interesting results. These results indicate that NAH can be used to research the mechanism of sound production and evalution of musical quality for Chime Stone as an effective means.

• Kyungpook Mathematical Journal
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• v.62 no.4
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• pp.715-728
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• 2022

The aim of this article is to study the h-almost Ricci solitons and h-almost gradient Ricci solitons on generalized Sasakian-space-forms. First, we consider h-almost Ricci soliton with the potential vector field V as a contact vector field on generalized Sasakian-space-form of dimension greater than three. Next, we study h-almost gradient Ricci solitons on a three-dimensional quasi-Sasakian generalized Sasakian-space-form. In both the cases, several interesting results are obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.314-320
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• 2014

Field balancing is required in any kind of phase information for the determination location balancing mass toward a rotor unbalance mass. Phase or phase angle is a measurement of the relationship of how one vibration signal which relates to another vibration signal and is commonly used to calculate the placement of balance weight. In this paper, A right guideline shows the photo optical speed sensor as the external keyphasor is a very useful when diagnosing machinery vibration problems on considering a phase lag comparing to the laser optical speed sensor. Some experimental results generate the interesting phase errors when appling to a wrong conditions. So, Usage of photo optical speed sensor which is used primarily to measure the shaft rotating speed serves as a reference for measuring vibration phase information has effect on the placement of phase angle how it was misunderstood. This paper will help a right method to search for the position of balancing weight and serves as baseline for further measurements using low cost and much easier user convenience. It is concluded that the propose baseline is likely to be applicable to apply to the practical field balancing weight.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.2
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• pp.101-107
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• 2015

Field balancing is required in any kind of phase information for the determination location balancing mass toward a rotor unbalance mass. Phase or phase angle is a measurement of the relationship of how one vibration signal which relates to another vibration signal and is commonly used to calculate the placement of balance weight. In this paper, A right guideline shows the photo optical speed sensor as the external KeyPhasor is a very useful when diagnosing machinery vibration problems on considering a phase lag comparing to the laser optical speed sensor. Some experimental results generate the interesting phase errors when appling to a wrong conditions. So, Usage of photo optical speed sensor which is used primarily to measure the shaft rotating speed serves as a reference for measuring vibration phase information has effect on the placement of phase angle how it was misunderstood. This paper will help a right method to search for the position of balancing weight and serves as baseline for further measurements using low cost and much easier user convenience. It is concluded that the propose baseline is likely to be applicable to apply to the practical field balancing weight.

• Structural Engineering and Mechanics
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• v.39 no.5
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• pp.621-642
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• 2011

Passive tuned mass dampers (TMDs) efficiently suppress vibrations induced by quasi-stationary dynamic inputs, such as winds, sea waves or traffic loads, but may prove of little use against pulse-like excitations, such as near-field (NF) ground motions. The extent of such impairment is however controversial, partly due to the different evaluation criteria adopted within the literature, partly to the limited number of seismic records used in most investigations. In this study, three classical techniques and two new variants for designing a TMD on an SDOF structure are tested under 338 NF records from the PEER NGA database, including 156 records with forward-directivity features. Percentile response reduction spectra are introduced to statistically assess TMD performance, and TMD robustness is verified through Monte Carlo simulations. The methodology is extended to a variety of MDOF bending-type and shear-type frames, and simulated on a case study building structure recently constructed in Central Italy.Results offer an interesting insight into the performance of TMDs against NF earthquakes, ultimately showing that, if properly designed and sufficiently massive, TMDs are effective and robust even in the face of pulse-like ground motions. The two newly proposed design techniques are shown to generally outperform the classical ones.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.75.3-75.3
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• 2019

The filament is an interesting structure in the Universe because clusters form at the nodes of filaments and grow through the continuous accretion of individual galaxies and groups from the surrounding filaments. We study the chemical properties of star-forming (SF) galaxies in the five large-scale filamentary structures (Leo II A, Leo II B, Leo Minor, Canes Venatici, and Virgo III) related with the Virgo cluster, with the spectroscopic data taken with the SDSS DR12, and compare them with those of the Virgo cluster and field galaxies. In mass-metallicity relation, most of the SF galaxies in Virgo-related filaments (except Virgo III filament) show lower metallicity on average than the Virgo cluster SF galaxies, but similar to field counterparts. These chemically less evolved feature of SF galaxies in the filaments and field are more pronounced for lower mass galaxies. This is probably because low mass galaxies have low potential wells and are therefore likely to be sensitive to cluster environmental effects. Interestingly, we find that the metallicity enhancement of SF galaxies in the Virgo III filament. In chemical and morphological perspectives, SF galaxies in the Virgo III thought to be transitional objects possibly transformed from SF late-type galaxies and are on the way to red early-type galaxies in the filament environment. This is the first discovery of systematic 'chemical pre-processing' signature for filament galaxies in Local Universe before they fall into the cluster.