Solving infinite horizon nonlinear optimal control problems using an extended modal series method

This paper presents a new approach for solving a class of infinite horizon nonlinear optimal control problems (OCPs).In this approach,a nonlinear two-point boundary value problem (TPBVP),derived from P...     

Fuzzy cost support vector regression on the fuzzy samples

This paper presents a new version of support vector regression (SVR) named Fuzzy Cost SVR (FCSVR) with a unique property of operating on fuzzy data where fuzzy cost (fuzzy margin and fuzzy penalty) are maximized. This idea admits to have uncertainty in the penalty and margin terms jointly. Robustness against noise is shown to be superior in the experimental results as a property compared with conventional SVR.     

Investigation of styrene/1‐hexene copolymerization by homogeneous and heterogeneous bisindenyl ethane zirconium dichloride catalyst system

Homogeneous copolymerization of styrene and 1‐hexene was carried out in toluene at room temperature using bisindenyl ethane zirconium dichloride/methylaluminoxane (MAO). The supported catalyst was prepared with immobilization of Et(Ind)₂ZrCl₂/MAO on silica (calcinated at 500°C) with premixed method. Heterogeneous copolymerization of styrene/1‐hexene with different mole ratios was carried out in the presence of supported catalyst system. The copolymers obtained from homogeneous and heterogeneous catalyst system were characterized by ¹H NMR and ¹³C NMR. Composition of the resulting copolymers was determined by ¹H NMR data. Analysis of ¹³C NMR spectra of obtained copolymers by homogeneous and heterogeneous catalyst systems present isotactic olefin‐enriched copolymers. Molecular weight and thermal behavior of resulting copolymers was investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4008–4014, 2007     

Enhanced Control Algorithm in PMSMs with Machine Current Sensor FDI and Current Management for Hardware Protection

Abstract

This paper proposes an enhanced control algorithm in permanent magnet synchronous machines (PMSMs) with machine current sensor fault detection and isolation (FDI) and current management for hardware protection. Different from existing work on machine current sensor FDI, the proposed method addresses the sensor FDI problem under co-existence of PMSM current sensor and non-sensor imbalance faults, and thereby help prevent the controller performance degradation caused by a faulty machine current sensor signal. Meanwhile, hardware protection is achieved through the proposed algorithm which has a unique feature of providing online overcurrent regulation and source power management at the same time to enhance protection of power inverter and power source. Benchmark comparison of the proposed sensor FDI method to state-of-the-art techniques is carried out to validate the good performance of the proposed FDI method in terms of fault detection time, false detection rate and missed detection rate. Sensitivity analysis of the proposed current management algorithm with overcurrent regulation and source power management is performed under changing rotor flux linkage and machine stator d-axis self-inductance, as an example to demonstrate the robustness of the proposed algorithm for hardware protection against system parameter variations. The effectiveness of the proposed algorithm is confirmed by simulation results in MATLAB for a PMSM.     

A unidirectional temperature gradient stage for solidification studies in aqueous solutions

A low temperature light microscope stage has been designed and fabricated for quantitative analysis of the solidification of aqueous solutions. Thermal boundary conditions are controlled during freezing so as to enable direct comparison of data with complementary theoretical models. Evolution of the temperature distribution within the system is monitored by a one-dimensional thermocouple array, and growth of the phase interface is measured via a displacement transducer. The two-dimensional solution concentration field is assessed by computer densitometric analysis of the grey scale distribution for a light absorbing solute. Experimental and theoretical analyses of freezing processes with the stage correlate well, and the data base is shown to be internally consistent by independent thermal and mechanical measures of the interface velocity.     

Differential attitudes of international students toward seeking professional psychological help.

175 students representing 75 countries completed the Attitudes Toward Seeking Professional Help scale. Of the variance in total attitude, 23% was predicted from the variables age, sex, continent, educational level, time in US, and prior contact with mental health treatment. Prior contact and continent were the most important determinants, with Western (European?+?Latin) attitudes significantly more positive than non-Western (Asian?+?African). Three factors emerged: Confidence/Appropriateness, Stigma/Privacy, and Coping Alone. Prior contact subgroups were discriminated using the dimensions. The most highly significant factor was Confidence/Appropriateness, which suggests that Ss inexperienced with professional help perceived it as a nontrustworthy, inappropriate means for solving personal difficulties. Ss least concerned with the social stigma and invasion of privacy associated with treatment (the Stigma/Privacy dimension) were those who had received help in native countries. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of mean time to first failure and mean up time

Two unit standby redundant repairable system, parallel systems and series systems are studied. The time between failures and the repair time are assumed exponentially distributed. Expressions for mean time to first failure (MTTFF) and mean up time (MUT) have been obtained. Comparisons have been made between MTTFF and MUT and the difference illustrated by numerical examples for different systems.     

Transparent nanostructured coatings with UV-shielding and superhydrophobicity properties

Visible light transparent, UV-shielding and superhydrophobic nanostructured coatings have been successfully fabricated through a facile layer-by-layer deposition of TiO(2) and SiO(2) nanoparticles. The coatings are composed of an underlying UV-shielding TiO(2) layer and a top fully covered protective SiO(2) layer. The resulting coatings can block 100% of UVB and UVC and almost 85% of UVA. The fabricated surfaces have contact angles exceeding 165° after coating with organic PTES (1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane) molecules. The transparent superhydrophobic surfaces exhibit extremely strong UV stability. All coatings retain the initial UV-shielding and superhydrophobic properties even after exposure to 275 nm UV light with a light intensity of 75 mW cm(-2) for 12 h.     

Simultaneous Determination of Sodium Tripolyphosphate,Sodium Sulfate and Linear Alkylbenzensulfonate in Washing Powder by Attenuated Total Reflectance: Fourier Transform Infrared Spectrometry

An analytical procedure has been developed for the simultaneous quantitative determination of sodium tripolyphosphate (STPP), sodium sulfate (SS) and Linear Alkyl Benzene Sulfonate (LABS) in a single washing powder sample. The method is based on the partial least squares treatment of data obtained by the Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectrometric method in the wavenumber range of 800–1,290 cm⁻¹. Absorbance spectra were employed for measurement using 29 aqueous standard solutions of STPP, SS and LABS. The method is simple, rapid and accurate and has been applied to commercial washing powders analysis performing the STPP, SS and LABS determination with a simplified sample preparation step consisting only of powder dissolution in distilled water. The other advantage of this method is its minimal time consumption (about 15 min), in comparison with previously introduced methods based on the determination of separated analytes (more than 4 h). The relative standard deviations of the proposed method for analyzing these real samples were 0.99, 0.56 and 0.91% for STPP, SS and LABS, respectively.

Dynamic modeling and simulation of a riser-type fluid catalytic cracking unit

A dynamic model is developed for a fluid catalytic cracking (FCC) unit to describe the dynamic behavior of both the riser and the regenerator reactors and their interactions. The cracking reactions are simulated by the four-lumped kinetic model [1]. The reactions in the riser occur in a transported bed with the fluid and the solids in ideal plug flow. The two-phase nature of the regenerator-fluidized bed is considered and the kinetic model for the coke combustion on the cracking catalyst [2,3] is incorporated. The proposed model is validated using steady-state plant data from an industrial unit and the results are found to be in good agreement. One of the main advantages of the model is that it does not include any partial differential equations. This facilitates the solution of the equations and makes the model particularly suitable for control studies. Simulation studies are performed to investigate the effect of changing various process variables, such as catalyst circulation rate, gas oil feed rate, and oxygen feed concentration.