• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.12
• /
• pp.2055-2067
• /
• 1997

Values of process parameters in sheet metal forming can be estimated by various one-step inverse methods. One-step inverse methods based on deformation theory, however, cause some amount of error. The amount of error is generally increased as the deformation path becomes more complex. As a remedy, a new three dimensional multi-step inverse method is introduced for optimum design of blank shapes and strain distributions from desired final shapes. The approach extends a one-step inverse method to a multi-step inverse method in order to reduce the amount of error. The algorithm developed is applied to square cup drawing to confirm its validity by demonstrating reasonably accurate numerical results. Rapid calculation with this algorithm enables easy determination of an initial blank of sheet metal forming.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.5 s.98
• /
• pp.200-208
• /
• 1999

The statics relation of the Stewart platform has been investigated from the viewpoint of the forward and inverse force transmission analyses. Two eigenvalue problems corresponding to the forward and inverse force transmission analyses have been formulated. The forward force transmission analysis is to determine the ranges of the magnitudes of the force and moment generated at the end-effector for the given magnitude of linear actuator forces. In reverse order, the inverse force transmission analysis is to find the range of the magnitude of actuator forces for the given ranges of the magnitudes of the force and moment at the end-effector. The inverse force transmission analysis is important since it can provide a designer with a valuable information about how to choose the linear actuators. It has been proved that two eigenvalue problems have a reciprocal relation, which implies that solving either of the eigenvalue problems may complete the forward/inverse force transmission analysis. A numerical example has been also presented.

• Proceedings of the KIEE Conference
• /
• 1997.07d
• /
• pp.1633-1635
• /
• 1997

For AMLCD pixel switching device, poly-Si TFT has the advantage of high field effect mobility over a-Si TFT. However, it also has some disadvantage such as large leakage current and more masking steps. We propose a new Inverse Staggered poly-Si TFT with a-Si offset. We have fabricated the new device and verified high ON/OFF current ratio. The device has lower leakage current level than the conventional Inverse Staggered poly-Si TFT and the same number of masking steps compared with conventional a-Si TFT's.

• Structural Engineering and Mechanics
• /
• v.80 no.5
• /
• pp.539-551
• /
• 2021

With the continuous increase of computational capacity, more and more complex nonlinear elastoplastic constitutive models were developed to study the mechanical behavior of elastoplastic materials. These constitutive models generally contain a large amount of physical and phenomenological parameters, which often require a large amount of computational costs to determine. In this paper, an inverse parameter determination method is proposed to identify the constitutive parameters of elastoplastic materials, with the consideration of both strain rate effect and temperature effect. To carry out an efficient design, a hybrid optimization algorithm that combines the genetic algorithm and the Nelder-Mead simplex algorithm is proposed and developed. The proposed inverse method was employed to determine the parameters for an elasto-viscoplastic constitutive model and Johnson-cook model, which demonstrates the capability of this method in considering strain rate and temperature effect, simultaneously. This hybrid optimization algorithm shows a better accuracy and efficiency than using a single algorithm. Finally, the predictability analysis using partial experimental data is completed to further demonstrate the feasibility of the proposed method.

• Journal of the Ergonomics Society of Korea
• /
• v.6 no.1
• /
• pp.3-8
• /
• 1987

This paper develops a statistical mode which estimates mental and physical loads of light work from sinus arrhythmia (SA) scores. During experiments, various levels of mental and physical loads (respectively scored by information processing and finger tapping rates) were imposed on subjects and SA scores were measured from the subjects. Two methods were used in developing workload estimation model. One is an algebraic inverse function of a multivariate regression equation, where mental and physical loads are independent variables and SA scores are dependent variables. The other is a statistical multivariate inverse regression. Of the two methods, inverse function resulted in larger mean squqre error in predicting mental and physical loads. Hence, inverse regression model is recommended for precise workload estimation.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.12 no.3
• /
• pp.191-199
• /
• 2008

This paper proposes a new method for the inverse problem of the three-dimensional reconstruction of the electrical activity of the brain from electroencephalography (EEG). Compared to conventional direct methods using additional parameters, the proposed approach solves the EEG inverse problem iteratively without any parameter. We describe the Lagrangian corresponding to the minimization problem and suggest the numerical inverse algorithm. The restriction of influence space and the lead field matrix reduce the computational cost in this approach. The reconstructed divergence of primary current converges to a reasonable distribution for three dimensional sphere head model.

• Journal of computational fluids engineering
• /
• v.3 no.1
• /
• pp.46-53
• /
• 1998

An inverse method for the subsonic and transonic airfoil design was developed using the Euler equations. Two testcases were performed. One was a verification of the method using the supercritical airfoil of the Korean mid-sized (100 passengers class) transport aircraft. The other was the design of an airfoil showing a good cruising performance (L/D ratio) in the high subsonic flow regime. These testcases demonstrated the efficiency and the robustness of the design method in the present study.

• Journal of Mechanical Science and Technology
• /
• v.16 no.9
• /
• pp.1156-1165
• /
• 2002

The characteristics of combustion and radiation heat transfer of an oxygen-enhanced diffusion flame was experimentally analyzed. An infrared radiation heat flux gauge was used to measure the thermal radiation of various types of flames with fuel, air and pure oxygen. And the Laser Induced Incandescence (LII) technique was applied to characterize the soot concentrations which mainly contribute to the continuum radiation from flame. The results show that an oxygen-enhanced inverse diffusion flame is very effective in increasing the thermal radiation compared to normal oxygen diffusion flame. This seems to be caused by overlapped heat release rate of double flame sheets formed in inverse flame and generation of higher intermediate soot in fuel rich zone of oxygen-fuel interface, which is desirable to increase continuum radiation. And the oxygen/methane reaction at slight fuel rich condition (ø=2) in oxygen-enhanced inverse flame was found to be more effective to generate the soot with moderate oxygen availability.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.5
• /
• pp.1317-1324
• /
• 1996

An angular spectral inverse technique, applying the moment method procedure with a series expansion for the induced field in each enlarged cell, is suggested to reconstruct permittivity profiles of inhomogeneous dielectric objects and to reduce the ill-posedness inherent to inverse scattering problems. The angular spectral inverse scattering using the pulse basis function in enlarging the scatterer has the ill-posedness due to the input data of higher spectra. To reduce the number of higher spectra, enlarging the cell size and averaging over the cell with a suitable weighting function are found to play improtant roles for the reduction of ill-posedness of the angular spectral inverse scattering problems.

• Journal of computational fluids engineering
• /
• v.2 no.2
• /
• pp.35-43
• /
• 1997

An efficient inverse method for 1.he supersonic/hypersonic axisymmetric body design is developed for the parabolized Navier-Stokes equations. The developed method is examined numerically for three extreme testcases in the supersonic(M/sub ∞/=3.0) and hypersonic(M/sub ∞/=6.28) speeds. The first one is a negative pressure distribution near a vacuum pressure and the second one is a positive pressure distribution over the whole region of the body. The last one is the case of abrupt change of pressure distribution to zero in the forward region of the body. These testcases show the robustness of the method. By introducing a regular-falsi method and by using a not-fully converged inverse solution, the convergence behavior was greatly improved.