Taipei Chengshih University of Science and Technology

Taipei, Taiwan

Taipei Chengshih University of Science and Technology

Taipei, Taiwan
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Lee C.-N.,Taipei Chengshih University of Science and Technology
Circuits, Systems, and Signal Processing | Year: 2010

Two new multiple-mode (including voltage, current, transconductance, and transresistance modes) OTA-C universal biquad filters are proposed. The first proposed circuit uses only four operational transconductance amplifiers (OTAs) and two grounded capacitors. The second proposed circuit uses five OTAs and two grounded capacitors. Both the proposed circuits can realize voltage, current, transconductance, and transresistance mode universal filtering responses (low-pass, high-pass, band-pass, notch, and all-pass) from the same topology. The first proposed circuit uses the least number of components. This represents an attractive feature from a chip area and power consumption point of view. The second proposed circuit has no need of extra inverting and non-inverting amplifiers for special input signals. Moreover, both the proposed biquads still have (i) the employment of two grounded capacitors, (ii) cascadable connection of the former voltage-mode stage and the latter current-mode stage, and (iii) low sensitivity performance. H-SPICE simulation results confirm the theoretical analysis. © Springer Science+Business Media, LLC 2009.


Lee C.-N.,Taipei Chengshih University of Science and Technology
Journal of Circuits, Systems and Computers | Year: 2011

A fully cascadable (i.e., low/high input impedance for current/voltage input signals and high/low output impedance for current/voltage output signals) mixed-mode (input and output signals can be voltage or current) universal filter biquad by using three differential difference current conveyors (DDCCs), three grounded resistors, and two grounded capacitors is presented in this paper. The proposed biquad can realize the inverting, non-inverting, and differential types universal filtering responses (lowpass, highpass, bandpass, notch, and allpass) from the voltage and current output terminals without changing the filter topology. The proposed circuit is suitable for cascading in all the four possible modes (i.e., voltage, current, transresistance, and transconductance modes). Moreover, the proposed mixed-mode biquad still enjoys (i) using only grounded passive components, (ii) no need of extra inverting and non-inverting amplifiers for special input signals, and (iii) low active and passive sensitivities. This paper also shows how analytical synthesis can be used to produce the proposed mixed-mode filter circuit. H-Spice simulation results confirm the theory. © 2011 World Scientific Publishing Company.


Lin J.-C.,Taipei Chengshih University of Science and Technology
Composite Structures | Year: 2010

The objective of this paper is to study the vibration characteristic for a sandwich beam with silica/polymer blend as principal material, and pure polymer matrix as surface laminate. It is anticipated that high stiffness and structure damping of viscoelastic layer can be obtained by taking advantage of fascinating network of densely packed between silica and polymer matrix. Spherical particles of size 12-235 nm at various filler fraction (10-50 wt.%) and three different polymer matrices, polyacrylate, polyimide and polypropylene, were selected as the matrix materials. The mechanical damping and stiffness of the sandwich cantilever beam are recorded by using a Dynamic Mechanical Thermal Analyzer (DMTA). The silica's small particle size feature and strain difference between principal and surface layers could highly enhance the energy dissipation ability of the beam structure. A numerical model is then developed and validated for the vibration of a symmetric elastic-viscoelastic sandwich beam. Experimental results show that the structure deformation for these sandwich beams with contiguous and constraining layers are in reasonable agreement with the prediction of the model. Both higher resonant vibrations are well damped in accordance with the symmetric motion of the elastic layers and relative little motion of the constraining layer. © 2009 Elsevier Ltd. All rights reserved.


Chiu Y.-J.,Taipei Chengshih University of Science and Technology
Renewable Energy | Year: 2010

In a fuel cell of low temperature, especially a direct methanol fuel cell (DMFC), fuel crossover phenomenon plays a significant role not only in its performance evaluation and analysis, but also in the optimum control under various operating conditions. A quantitative prediction of the fuel crossover flux thus becomes essential. Generally speaking, the theoretical approaches to the issue will be dramatically complex and less practical. On the other hand, experimental schemes are time-consuming and less capable of further analysis and applications. Consequently, a semi-empirical model that incorporates dominant physical parameters and operating variables is proposed in this paper to adequately evaluate the phenomenon of fuel crossover fluxes. It is stated analytically in the form of an algebraic function, in which the fuel concentration, the current density, and the temperature of the fuel cell are considered. It is therefore more suitable for a variety of in-situ applications. In the proposed model, the methanol concentration gradient in the anode backing layer, the anode catalyst layer, and the membrane are analyzed. The transfer behavior of methanol is modeled on the basis of diffusion and electro-osmosis mechanisms. By means of the proposed model, one can obtain a better prediction and a clearer picture of the effects of operating variables and physical parameters on methanol crossover fluxes.


Hung L.-P.,Taipei Chengshih University of Science and Technology
Expert Systems with Applications | Year: 2010

This study focuses on predicting whether a credit applicant can be categorized as good, bad or borderline from information initially supplied. This is essentially a classification task for credit scoring. Given its importance, many researchers have recently worked on an ensemble of classifiers. However, to the best of our knowledge, unrepresentative samples drastically reduce the accuracy of the deployment classifier. Few have attempted to preprocess the input samples into more homogeneous cluster groups and then fit the ensemble classifier accordingly. For this reason, we introduce the concept of class-wise classification as a preprocessing step in order to obtain an efficient ensemble classifier. This strategy would work better than a direct ensemble of classifiers without the preprocessing step. The proposed ensemble classifier is constructed by incorporating several data mining techniques, mainly involving optimal associate binning to discretize continuous values; neural network, support vector machine, and Bayesian network are used to augment the ensemble classifier. In particular, the Markov blanket concept of Bayesian network allows for a natural form of feature selection, which provides a basis for mining association rules. The learned knowledge is represented in multiple forms, including causal diagram and constrained association rules. The data driven nature of the proposed system distinguishes it from existing hybrid/ensemble credit scoring systems. © 2009 Elsevier Ltd. All rights reserved.


Tao T.,Taipei Chengshih University of Science and Technology | Su S.-F.,National Taiwan University of Science and Technology
IEEE Transactions on Fuzzy Systems | Year: 2014

In this paper, a novel control scheme adopted from moment control is proposed. In the proposed approach, an adaptive fuzzy system is employed to learn the effective moment. It is easy to see that such an approach can avoid wild guessing for the effective moment, and as shown in our simulation, can have nice control performance. In traditional adaptive fuzzy control approaches, bounds of system functions are required to facilitate supervisory control so as to have the robust control property. It can be expected that when those bounds used in the supervisory controller are not proper, the output may not be able to follow the reference trajectory satisfactorily. With the proposed moment adaptive fuzzy control, the bound needed is only the supremum of the control variance between two consecutive steps. It is much easier to predict. In our study, in order to further relax this requirement, another adaptive system is employed to estimate the residue of the moment adaptive fuzzy control system. It is called residue compensation in this paper. It can be found that with residue compensation, the approach does not need a supervisory controller, but still can quickly track the reference in a satisfactory fashion. Various simulations are conducted to demonstrate the effectiveness of the proposed approaches. © 1993-2012 IEEE.


Leu D.-K.,Taipei Chengshih University of Science and Technology
Materials and Design | Year: 2015

This study describes the effect of grain size on the flow stress of sheet metal under simple tension in microforming. A simple model of the tensile flow stress of sheet metal is firstly developed based on the Hall-Petch equation. Experimental results verify the accuracy of the developed model, which is a function of T/. D (sheet thickness/grain size). A critical condition (T/. D). c that distinguishes micro-scale from macro-scale tensile flow stress is subsequently proposed based on Li's theory of dislocation with density type. The trend of the predicted (T/. D). c with varying grain size is similar to the experimental finding that the (T/. D). c decreases as the grain size increases. Therefore, the developed model can elucidate to understand the tensile flow stress of sheet metal in microforming. © 2015 Elsevier Ltd.


Tao T.,Taipei Chengshih University of Science and Technology | Su S.-F.,National Taiwan University of Science and Technology
Applied Soft Computing Journal | Year: 2011

In this paper, a novel scheme of incorporating a learning mechanism into previous step supervisory controllers for adaptive fuzzy control is proposed to relax bounds required in the control process. In traditional supervisory adaptive fuzzy control approaches, the use of fuzzy estimators for approximating system functions and a robust supervisory control law are necessary to deal with any possible uncertainties caused in the system. This kind of supervisory controller depends on the robust bounds of system functions so that it can ensure the Lyapunov stability of controlled systems. However, in those approaches, the output may not be able to follow the reference trajectory well if the robust bounds are predicted improperly. In our implementation, CMAC (Cerebellar Model Articulation Controllers) is used as the learning mechanism because of its quick learning capability. Under the Lyapunov stable criterion, the proposed CMAC learning mechanism can improve the output performance and can relax the robust bound limitation so that practical systems can easily be realized. In summary, the proposed approach not only can relax bounds for previous step supervisory controllers in adaptive fuzzy control, but also can significantly improve the control performance of the system. © 2011 Elsevier B.V. All rights reserved.


Leu D.-K.,Taipei Chengshih University of Science and Technology
International Journal of Advanced Manufacturing Technology | Year: 2013

Novel finite element analyses and a series of experiments are performed to clarify basic characteristics of high-strength steel sheet metal during fabrication by asymmetric V-die bending processes. The proposed strategy for elastic-plastic FE simulation is used to simulate asymmetric V-die bending process to test its viability for friction contact processes. Accordingly, a series of experiments is performed to verify the numerical simulation. The calculation agrees well with the experiment. The effects of process parameters such as lubrication (contact friction), material properties, and process geometries on position deviation in bending point were experimentally tested to determine the dominant parameters for minimizing position deviation in sheet metal bending processes. Moreover, springback phenomenon is also discussed to minimize bending defects and to obtain a precise asymmetric bent component. This study could be used as a process design guideline for asymmetric bending of high-strength steel sheets. © 2012 Springer-Verlag London Limited.


Leu D.-K.,Taipei Chengshih University of Science and Technology
International Journal of Advanced Manufacturing Technology | Year: 2013

Interfacial conditions such as friction and roughness tend to be the dominant process characteristics when simulating sheet metal forming processes. Therefore, accurately modeling the tool workpiece interface is essential. Additionally, the accuracy of conventional methods of modeling the interface is insufficient for microforming. This work presents a novel approach for describing friction by modeling the geometric roughness of the tool surface instead of using the conventional friction coefficient or factor in dry contact. This finite element-based model was validated in terms of loads and metal flow in two cases of micro V-die bending processes. One process modeled a conventional flat tool surface with a friction coefficient. Another process modeled a rough tool surface described as roughness geometry with zero friction. In addition to elucidating how the roughness geometry of a tool surface affects friction during microforming, this work provides fundamental information about the interfacial conditions of the contact surface as well as improved accuracy and flexibility compared to conventional friction models. Another important application of the friction calculation results in this study is in microforming applications. © 2013 Springer-Verlag London.

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