• Journal of applied mathematics & informatics
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• v.23 no.1_2
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• pp.127-140
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• 2007

We present the boundary value problem (BVP) for the heave motion due to a vertical circular cylinder in water of finite depth. The BVP is presented in terms of velocity potential function. The velocity potential is obtained by considering two regions, namely, interior region and exterior region. The solutions for these two regions are obtained by the method of separation of variables. The analytical expressions for the hydrodynamic coefficients are derived. Computational results are presented for various depth to radius and draft to radius ratios.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1177-1181
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• 2009

Heat loss from a convective rectangular profile annular fin with variable inside fluid heat transfer coefficient and fin height is calculated by using both the one dimensional analytic method and two dimensional variables separation method. Heat loss from the two dimensional method and the relative error of heat loss between the one dimensional method and two dimensional method are presented as a function of the fin length, ambient convection characteristic number and fin height. One of the results shows that the relative error of heat loss between one dimensional method and two dimensional method is within 0.7% in the range of given parameters in this study.

• Resources Recycling
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• v.23 no.6
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• pp.30-39
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• 2014

The trajectories of PCB(Printed Circuit Board) particles in the corona discharge electrostatic separation was simulated. The PCB particles are prepared by crushing bare board, which disassembled from electronic components, consist mostly of copper and FR-4(Flame Retardant Level-4) Firstly, a model was established for calculating of detachment points of PCB particles from the rotating electrode in separator. The model of detachment points was derived from equilibrium of force such as gravity force, centrifugal force, electrostatic force. The trajectories of particles after detachment was calculated by acceleration derived from time-integrating method of motion equation. In this simulation, particle size, supplied voltage, rotation speed of rotating roll electrode and angle of induction electrode were adopted as variables. While the trajectories of FR-4 particles were affected by all variables, rotation speed of rotating roll electrode was dominant variables affecting trajectories of copper particles.

• Journal of the Korean institute of surface engineering
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• v.24 no.3
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• pp.125-136
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• 1991

a mathematical model is presented to describe the current distribution on a rotaing disk electrode under the galvanostatic pulse conlitions. A numerical technique by finite difference method to the transient convective diffusion equation, coordinate transformation and separation of variables to Laplace equation, and an iterative algorithm to solve the above equations simtltaneously with approximate boundary conditions were developed. An experimental investigated based on copper deposition in a copper sulfate-sulfuric acid system was performed and satisfactory agreement was obtained between expermental and theoretical current distribution. The current distribution of copper deposition is secondary current distribution within the experimental conditions. Dimensionless variables, N and J as well as Wagner number were used to determine the criteria for the uniformity of current distribution.

• Structural Engineering and Mechanics
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• v.87 no.2
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• pp.165-172
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• 2023

This paper presents a novel method for modeling elastic wave propagation in long beams. The proposed method derives a solution for the transient transverse displacement of the beam's neutral axis without assuming the separation of variables (SV). By mapping the governing equation from the space domain to the frequency domain using Fourier transformation (FT), the transverse displacement function is determined as a convolution integral of external loading functions and a combination of trigonometric and Fresnel functions. This method determines the beam's response to general loading conditions as a linear combination of the analytical response of a beam subjected to an abrupt localized loading. The proposed solution method is verified through finite element analysis (FEA) and wave propagation patterns are derived for tone burst loading with specific frequency contents. The results demonstrate that the proposed solution method accurately models wave dispersion, reduces computational cost, and yields accurate results even for high-frequency loading.

• Structural Engineering and Mechanics
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• v.31 no.6
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• pp.663-678
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• 2009

An exact solution is obtained for forced torsional vibration of a finite class 622 piezoelectric hollow cylinder with free-free ends subjected to dynamic shearing stress and time dependent electric potential at both internal and external surfaces. The solution is first expanded in axial direction with trigonometric series and the governing equations for the new variables about radial coordinate r and time t are derived with the aid of Fourier series expansion technique. By means of the superposition method and the separation of variables technique, the solution for torsional vibration is finally obtained. Natural frequencies and the transient torsional responses for finite class 622 piezoelectric hollow cylinder with free-free ends are computed and illustrated.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.1
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• pp.11-18
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• 2003

We consider a single-input-single-output nonlinear system which is represented in a normal form. The model contains the uncertainty. A high-gain observer is used to estimate the states variables to reject a modeling uncertainty We design the globally bounded output feedback controller using sliding mode control to stabilize the closed-loop system. The globally bounded output feedback controller reduce the peaking in the states variables. The proposed method give a more design freedom in the design of the globally bounded controller than that of the previous work.

• Structural Engineering and Mechanics
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• v.35 no.2
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• pp.217-240
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• 2010

A semi-analytical method is presented for accurately prediction of the free vibration behavior of generally laminated composite plates with arbitrary boundary conditions. The method employs the technique of separation of spatial variables within Hamilton's principle to obtain the equations of motion, including two systems of coupled ordinary homogeneous differential equations. Subsequently, by applying the laminate constitutive relations into the resulting equations two sets of coupled ordinary differential equations with constant coefficients, in terms of displacements, are achieved. The obtained differential equations are solved for the natural frequencies and corresponding mode shapes, with the use of the exact state-space approach. The formulation is exploited in the framework of the first-order shear deformation theory to incorporate the effects of transverse shear deformation and rotary inertia. The efficiency and accuracy of the present method are demonstrated by obtaining solutions to a wide range of problems and comparing them with finite element analysis and previously published results.

• Journal of Radiation Protection and Research
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• v.44 no.2
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• pp.53-63
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• 2019

Background: As neutron fields are always accompanied by gamma rays, it is essential to distinguish neutrons from gamma rays in the detection of neutrons. Neutrons and gamma rays can be separated by pulse shape discrimination (PSD) methods. Recently, we performed characterization of a stilbene scintillator detector and an EJ-301 liquid scintillator detector with a high-speed digitizer DT5730 and investigated optimized PSD variables for both detectors. This study is for providing a basis for developing fast neutron/gamma-ray dual-particle imager. Materials and Methods: We conducted PSD experiments using stilbene scintillator and EJ-301 liquid scintillator and evaluated neutron and gamma ray discriminability of each PSD method with a $^{137}Cs$ gamma source and a $^{252}Cf$ neutron source. We implemented digital signal processing techniques to apply two PSD methods - the charge comparison (CC) method and the constant time discrimination (CTD) method - to distinguish neutrons from gamma rays. We tried to find optimized PSD variables giving the best discriminability in a given experimental condition. Results and Discussion: For the stilbene scintillator detector, the charge comparison method and the constant time discrimination method both delivered the PSD FOM values of 1.7. For the EJ-301 liquid scintillator detector, both PSD methods delivered the PSD FOM values of 1.79. With the same PSD variables, PSD performance was excellent in $300{\pm}100keVee$, $500{\pm}100keVee$, and $700{\pm}100keVee$ energy regions. This result shows that we can achieve an effective discrimination of neutrons from gamma rays using these scintillator detector systems. Conclusion: We applied both PSD methods to a stilbene and a liquid scintillator and optimized the PSD performance represented by FOM values. We observed a good separation performance of both scintillators combined with a high-speed digitizer and digital PSD. These results will provide reference values for the dual-particle imager we are developing, which can image both fast neutrons and gamma rays simultaneously.

• Applied Chemistry for Engineering
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• v.33 no.5
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• pp.488-495
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• 2022

Activated carbon (AC) and carbon molecular sieve (CMS) have attracted attention as porous materials for recovery and separation of greenhouse gases. The carbon molecular sieve having uniform pores is used for collecting and separating gases because it may selectively adsorb a specific gas. The size and uniformity of pores determine the performance of the CMS, and chemical vapor deposition (CVD) is widely used to coat the surface with a predetermined thickness in order to control the CMS's micropores. This CVD method can be used to control the size of pores in CMS manufacturing, but it must be optimized because of its various experimental variables. Therefore, in order to produce AC and CMS for gas adsorption and separation, this review focuses on various activation processes and pore control technologies by CVD and surface treatment.