• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.267-274
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• 2002

Using a flexible rotating beam test bed, experimental verification of a flexible multibody dynamic simulations for a rotating beam model has been carried out. The test bed consists of a flexible arm, harmonic driver reducer, AC servo motor and DSP board with PC. The mechanical ports of the test bed has been designed using 3D CAD program. For the simulation model, mass and moment of inertia of each part of the flexible rotating beam test bed are also obtained from 3D CAD model. In the flexible multibody dynamic simulations, the substructuring model has been established to capture nonlinear effects of the flexible rotating beam. Through the experimental verification, substructuring model provides better results than those from the linear model in the high speed rotation.

• Journal of Korean Society of Water and Wastewater
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• v.10 no.1
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• pp.78-84
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• 1996

The presence of ammonia, usually in the form of ammonium ion ($NH_4{^+}$), can enhance bacterial growth m the distribution system and make the production of drinking water more costly if ammonium must be removed to ensure good disinfection. Removal of ammonia by biological oxidation could be economical which prevents excess chlorine dosage In this research, effects of hydraulic retention time (HRT) and media type on the ammonia removal efficiencies of submerged biofilm reactor were investigated. The biofilm reactors combined the characteristics of high biological solids capture efficiency and good hydraulic control. The results indicate that biofilms can remove over 77 percent of the ammonia with HRT of longer than 2 hr even at low temperature ranging from 14.6 to $16.6^{\circ}C$. The HRT has a significant effect on nitrification. The overall nitrification and efficiency of ammonia removal increase with increasing HRT. It has also been observed that when the fibrous media was used, the ammonia removal, nitrification rate and endurance to shock improved.

• Journal of computational fluids engineering
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• v.10 no.4 s.31
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• pp.32-38
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• 2005

Present study simulates oscillatory supersonic impinging jet flows using the axisymmetric Navier-Stokes code. To capture the salient features of flow oscillation and overcome the divergence during the initial transient period, several tests have been conducted for the grid and time step sizes. The results also show that the effects of the inlet flow condition at the nozzle exit and turbulence on the oscillatory behavior of supersonic impinging jets are negligible. Frequencies of the surface pressure oscillation obtained by the selected numerical method are in good accord with the measured impinging tones for various cases of nozzle-to-plate distance. Two seemingly different staging behaviors with nozzle-to-plate distance and nozzle pressure variations are found to correlate well if the frequency and distance are normalized by the length of the first shock cell.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.992-995
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• 2011

A study on the performance design schemes of the supersonic air intakes applied to the supersonic air-breathing propulsion system(Ramjet/Scramjet) was conducted and for two kinds of air intakes, the preliminary configuration designs and the performance analysis models were established. For axisymmetric conical air intake and two dimensional rectangular air intake, the performance effects were assessed according to compression angles and shock wave numbers.

• Smart Structures and Systems
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• v.21 no.1
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• pp.113-122
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• 2018

In this article, an exact analytical solution for mechanical buckling analysis of magnetoelectroelastic plate resting on pasternak foundation is investigated based on the third-order shear deformation plate theory. The in-plane electric and magnetic fields can be ignored for plates. According to Maxwell equation and magnetoelectric boundary condition, the variation of electric and magnetic potentials along the thickness direction of the plate is determined. The von Karman model is exploited to capture the effect of nonlinearity. Navier's approach has been used to solve the governing equations for all edges simply supported boundary conditions. Numerical results reveal the effects of (i) lateral load, (ii) electric load, (iii) magnetic load and (iv) higher order shear deformation theory on the critical buckling load have been investigated. These results must be the analysis of intelligent structures constructed from magnetoelectroelastic materials.

• Journal of the Korean Operations Research and Management Science Society
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• v.41 no.3
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• pp.59-74
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• 2016

Electricity sales are directly measured from individual consumers, which could minimize the time gap between data collection and public announcement. Furthermore, industrial electricity sales are highly linked with production and output. Therefore, industrial electricity consumption can be used to track production and output in real time. By using the high-frequency data of industrial electricity sales, this study develops the daily electricity business index (DEBI) to capture the daily economic status. The steps used to formulate DEBI are as follows: (1)selection of the explanatory variables and period, (2) amendment of the seasonal adjustment to eliminate daily temperature and effective day effects, (3) estimation of the weighted value via variables by using PCA, (4) calculation of DEBI and commencement of validation tests. Our empirical analysis and the Hodrick-Prescott filter analysis show that DEBI is highly related to existing economic indices.

• Proceedings of the Korea Multimedia Society Conference
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• 2012.05a
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• pp.166-167
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• 2012

High packet loss rate and impatience of messages passing through optical switches are essential characteristics in Optical Burst Switching system equipped with Optic Delay Lines buffer, which have not been solved efficiently yet by current existing models. In order to capture both effects, this paper introduces an analytical model from the viewpoint of classical queuing theory with impatient customers. We then apply it to evaluate and compare two wavelength-sharing cases, (1) all delay lines share a common wavelength resource and (2) each wavelength is associated with a number of delay lines. Our numerical results suggest to implement the first case because of lower packet loss rate for a fairly broad range of traffic load.

• Korea-Australia Rheology Journal
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• v.21 no.1
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• pp.71-79
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• 2009

The incomplete saturation and the void formation during the resin infiltration into fibrous porous media in the resin transfer molding process cause failure in the final product during its service. In order to better understand flow behavior during the filling process, a finite-element scheme for transient flow simulation across the micro-structured fibrous media is developed in the present work. A volume-of- fluid (VOF) method has been incorporated in the Eulerian frame to capture the evolution of flow front and the vertical periodic boundary condition has been combined to avoid unwanted wall effect. In the microscale simulation, we investigated the transient filling process in various fiber structures and discussed the mechanism leading to the flow fingering in the case of random fiber distribution. Effects of the filling pressure, the shear-thinning behavior of fluid and the volume fraction on the flow front have been investigated for both intra-tow and the inter-tow flows in dual-scale fiber tow models.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.2
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• pp.145-150
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• 1999

A real-time control system, composed of the controlled processor and the controller computer(s), may have a variety of task types, some of which have tight timing-constraints in generating the correct control input. The maximum period of those task failures tolerable by the system is called the hard deadline, which depends on not only fault characteristics but also task characteristics. In the paper, we extend a method deriving the hard deadline in LTI system executing single task. An algorithm to combine the deadlines of all the elementary tasks in the same operation-mode is proposed to derive the hard deadline of the entire system. For the end, we modify the state equation for the task to capture the effects of task failures (delays in producing correct values) and inter-correlation. We also classify the type of executing the tasks according to operation modes associated with relative importance of correlated levels among tasks, into series, parallel, and cascade modes. Some examples are presented to demonstrate the effectiveness of the proposed methods.

• Journal of Mechanical Science and Technology
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• v.19 no.9
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• pp.1781-1789
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• 2005

In order to realistically predict the combustion characteristics of the oxy-fuel flame, the present study employs the non-adiabatic flame let approach. In this combustion model, the detailed equilibrium chemistry is utilized to accurately account for the thermal dissociation as well as to properly include the radiative cooling effects on the detailed chemistry. Numerical results indicate that the present approach has the capability to correctly capture the essential features and precise structure of the oxy-fuel flames. In this work, the detailed discussion has been made for the characteristics of oxy-fuel flames, the capability and defect of the present approach and also uncertainties of experimental data.