• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.10
• /
• pp.924-928
• /
• 2005

We synthesized the two types of photoalignment material of high thermal resistance with hydroxyl aromatic polyimide, and studied the liquid crystal (LC) aligning capabilities on the photopolymer layers. Also, electro-optical (EO) performances for the twisted-nematic (TN)-liquid crystal display (LCD) photoaligned with linearly polarized UV exposure were investigated. A good LC alignment with UV exposure on the two types of photopolymer surface can be obtained. The Voltage-transmittance (V-T) curve in the photoaligned TN cell with UV exposure was different from two type. The response time of photoaligned TN cell was measured about 21 ms in two alkyl chain and about 15 ms in four alkyl chain.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.1
• /
• pp.65-69
• /
• 2004

We synthesized photoalignment material of high thermal resistance with hydroxyl aromatic polyimide, and studied the liquid crystal (LC) aligning capabilities on the photopolymer layers. Also, electro-optical (EO) performances for the twisted-nematic (TN)-liquid crystal display (LCD) photoaligned with linearly polarized UV exposure were investigated. A good LC alignment with UV exposure on the photopolymer surface can be obtained. However, the low pretilt angles were obtained below 1$^{\circ}$. The Voltage-transmittance (V-T) curve without backflow bounce in the photoaligned TN cell with UV exposure was observed. The response time of photoaligned TN cell was measured about 24 ms. Finally, The photoaligned TN cell has few hysteresis, and shows the residual DC voltage that is less.

• 제어로봇시스템학회:학술대회논문집
• /
• 1994.10a
• /
• pp.742-745
• /
• 1994

In this paper we show the performance of neural Chandrasekhar filtering which is a special case for the new method of neural filtering using the artificial neural network systems developed recently for the filtering problems of linear and nonlinear, stationary and nonstationary stochastic signals. The neurofilter developed has either the finite impulse response(FIR) structure or the infinite impulse response(IIR) structure. The neurofilter differs from the conventional linear digital FIR and IIR filters because the artificial neural network system used in the neurofilter has nonlinear structure due to the sigmoid function. Numerical studies for the estimation of a second order Butterworth process are performed by changing the structures of the neurofilter in order to evaluate the performance indices under the changes of the output noises or disturbances. In the numerical studies both Chandrasekhar filtering estimates and true signals are used as the training signals for the neurofilter. The results obtained from the studies verified the capabilities which are essentially necessary for on-line filtering of various stochastic signals.

• Structural Engineering and Mechanics
• /
• v.4 no.2
• /
• pp.111-124
• /
• 1996

New active "intelligent" structural systems with integrated self-sensing, diagnosis, and control capabilities can lead to a new design dimension for the next generation high-performance structures and mechanical systems. However, temperature effects to the piezoelectric transducers are not fully understood. This paper is concerned with a mathematical modeling and analysis of a laminated piezothermoelastic cylindrical shell composite exposed to mechanical, electric, and thermal fields. Generic shell equations and solution procedures are derived. Contributions of spatial and time components in the mechanical, electric, and temperature excitations are discussed, and their analytical solutions derived. A laminated cylindrical shell composite with fully distributed piezoelectric layers is used in a case study; its multi-field step and impulse responses are investigated. Analyses suggest that the fully distributed actuators are insensitive to even modes due to load averaging and cancellation. Accordingly, these even modes are filtered from the total response and only the modes that are combinations of m = 1, 3, 5, ${\cdots}$ and n = 1, 3, 5, ${\cdots}$ participating in dynamic response of the shell.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.05a
• /
• pp.210-213
• /
• 2004

We synthesized photoalignment material of high thermal resistance with hydroxyl aromatic polyimide, and studied the liquid crystal (LC) aligning capabilities on the photopolymer layers. Also, electro-optical (EO) performances for the twisted-nematic (TN)-liquid crystal display (LCD) photoaligned with linearly polarized UV exposure were investigated. A good LC alignment with UV exposure on the photopolymer surface can be obtained. However, the low pretilt angles were obtained below $1^{\circ}$. The Voltage-transmittance (V-T) curve without backflow bounce in the photoaligned TN cell with UV exposure was observed. The response time of photoaligned TN cell was measured about 24 ms. Finally, The photoaligned TN cell has few hysteresis, and shows the residual DC voltage that is less.

• Steel and Composite Structures
• /
• v.16 no.1
• /
• pp.1-21
• /
• 2014

Knee Braced Frame (KBF) is a special form of ductile eccentrically braced frame having a diagonal brace connected to a knee element, as a hysteretic damper, instead of beam-column joint. This paper first presents an experimental investigation on cyclic performance of two knee braced single span one-story frame specimens. The general test arrangement, specimen details, and most relevant results (failure modes and hysteretic curves) are explained. Some indexes to assess the seismic performance of KBFs, including ductility; response reduction factor and energy dissipation capabilities are also subsequently discussed. Experimental results indicate that the maximum equivalent damping ratios achieved by test frames are 21.8 and 23% for the specimens, prior to failure. Finally, a simplified analytical model is derived to predict the bilinear behavior of the KBFs. Acceptable conformity between analytical and experimental results proves the accuracy of the proposed model.

• Earthquakes and Structures
• /
• v.4 no.5
• /
• pp.509-525
• /
• 2013

In this paper, learning capabilities of two types of Arterial Neural Networks, namely hierarchical neural networks and Generalized Regression Neural Network were used in a two-stage approach to develop a method for generating spatial varying accelerograms from acceleration response spectra and a distance parameter in which generated accelerogram is desired. Data collected from closely spaced arrays of seismographs in SMART-1 array were used to train neural networks. The generated accelerograms from the proposed method can be used for multiple support excitations analysis of structures that their supports undergo different motions during an earthquake.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.944-949
• /
• 2003

This paper addresses the control of free and dynamic response of composite rotating pretwisted blade modeled as non-uniform thin-walled beam fixed at the certain presetting and pretwisted angle and incorporating piezoelectric induced damping capabilities. A distributed piezoelectric actuator pair is used to suppress the vibrations caused by external disturbances. The blade model incorporates non-uniform features such as transverse shear, secondary warping and includes the centrifugal and Coriolis force field. A velocity feedback control law relating the piezoelectiriccally induced transversal bending moment at the beam tip with the appropriately selected kinematical response quantity is used and the beneficial effects upon the closed loop eigenvibration and dynamic characteristics of the blade are highlighted.

• Smart Structures and Systems
• /
• v.9 no.5
• /
• pp.441-459
• /
• 2012

Identification of vibration parameters from the analysis of the dynamic response of a structure plays a key role in current health monitoring systems. This study evaluates the capabilities of the recently developed Synchrosqueezed Wavelet Transform (SWT) to extract instant frequencies and damping values from the simulated noise-contaminated response of a structure. Two approaches to estimate the modal damping ratio from the results of the SWT are presented. The results obtained are compared to other signal processing methods based on Continuous Wavelet (CWT) and Hilbert-Huang (HHT) transforms. It was found that the time-frequency representation obtained via SWT is sharped than the obtained using just the CWT and it allows a more robust extraction of the individual modal responses than using the HHT. However, the identification of damping ratios is more stable when the CWT coefficients are employed.

• Nuclear Engineering and Technology
• /
• v.29 no.6
• /
• pp.476-487
• /
• 1997

To resolve several arguments raised for the current analysis of a structure like top hat, which is composed of flange, cylinder and plate, the dynamic response analysis is performed for the full and half models. The dynamic characteristics are investigated for full and half models and the results are compared between them. The responses such as bolt reactions and stresses due to random loading are also obtained using the analysis capabilities between commercial programs which have the routine for the random vibration analysis. Several general purpose structural analysis programs are used to get the response due to the random loadings. Also the application of the random loading and the effect of correlations such as fully correlated, partially correlated and fully uncorrelated cases are studied and the general directions for the generation of design loads due to random loading are suggested.