Hierarchical modeling using generalized linear models

In a complex manufacturing environment, there are hundreds of interrelated processes that form a complex hierarchy. This is especially true of semiconductor manufacturing. In such an environment, modeling and understanding the impact of critical process parameters on final performance measures such as defectivity is a challenging task. In addition, a number of modeling issues such as a small number of observations compared to process variables, difficulty in formulating a high‐dimensional design matrix, and missing data due to failures pose challenges in using empirical modeling techniques such as classical linear modeling as well as generalized linear modeling (GLM) approaches. Our approach is to utilize GLM in a hierarchical structure to understand the impact of key process and subprocess variables on the system output. A two‐level approach, comprising subprocess modeling and meta‐modeling, is presented and modeling related issues such as bias and variance estimation are considered. The hierarchical GLM approach helps not only in improving output measures, but also in identifying and improving subprocess variables attributed to poor output quality. Copyright © 2011 John Wiley & Sons, Ltd.     

Transient free convection of a second-grade fluid flowing in a vertical cylinder

The intention of the present article is to examine the transient effect on the free convection of the second-grade fluid flowing in a vertical cylinder. We have found the analytical solution of the derived governing partial differential equations in nondimensional form corresponding to the velocity as well as the temperature fields by applying the Laplace transformation method in terms of the Bessel function of the first kind. To obtain the impacts of the appropriate parameters related to the given equations, such as the second-grade fluid parameter and the Prandtl number, the numerical values of the velocity are discussed and displayed in graphs. Furthermore, the mass flow rate and the skin friction at the inner surface of the cylinder are given in a tabular form. The influence of the second-grade fluid parameter is to decelerate the velocity as well as the mass flow rate and to enhance the steady-state time.     

A novel approach for realization of primary vibration calibration standard by homodyne laser interferometer in frequency range of 0.1 Hz to 20 kHz

The paper discusses the primary vibration calibration standard of NPL, India capable of calibrating the reference accelerometers in frequency range from 0.1 Hz to 20 kHz as per ISO 16063-11. The excitation subsystem produces constant vibration at a specified amplitude and frequency, while the measurement system uses NI interface for measuring the quadrature output. The acceleration level and voltage level at the calibration frequency f is determined by applying a Discrete Fourier Transform to the voltage and displacement signals, and then examining the spectral component at frequency f. A PC-based data acquisition system acquires the accelerometer voltage signal and analog quadrature interferometer photodetector signal pair as well as a digital quadrature pair whereby the software processes the demodulated photodetector signals to reconstruct the armature displacement. The validation of the calibration results for standard reference accelerometers with manufacturer results and uncertainty in calibration in entire frequency range 0.1 Hz to 20 kHz is reported in the present work.     

Growth by SR method and characterization of bis(thiourea)zinc(II) chloride single crystals

Large size single crystals of bis(thiourea)zinc(II) chloride (BTZC), a potential nonlinear optical material, have been grown successfully by the Sankaranarayanan-Ramasamy (SR) method. Powder X-ray diffraction and Fourier transform infrared analyses confirmed the material of the grown crystal. Thermal stability was assessed by the thermogravimetric/differential thermal analysis. The high-resolution X-ray diffraction and dielectric measurements indicate that the crystal grown by the SR method has good crystalline perfection and low density of defects.     

Excess Gibbs free energy of butyl acetate with cyclohexane and aromatic hydrocarbons at 308.15K

Molar excess Gibbs free energies of mixing (C ^E ) for butyl acetate+cyclohexane or benzene or toluene or o- or m- or p-xylene were calculated by using Barker’s method from the measured vapor pressure data by static method at 308.15±0.01 K over the entire composition range. The G ^E values for the binary mixtures containing cyclohexane or benzene are positive; while these are negative for toluene, o-, m- and p-xylene system over the whole composition range. The G ^E values of an equimolar mixture for these systems vary in the order: cyclohexane>benzene>o-xylene>m-xylene>p-xylene>toluene. The G ^E values for these systems were also calculated by Sanchez and Lacome theory using the previously published excess enthalpy and excess volume data. It is found that while values of G ^E from Sanchez and Lacombe theory are in reasonably good agreement with those calculated by Barker method for m-xylene and p-xylene mixtures, agreement is very poor for other systems although they predict the sign of G ^E data except in the case of mixtures containing benzene.     

Microstrip triangular patch antenna fabricated on LiTiZn ferrite substrate and tested in the X band range

An experimental study of microstrip triangle patch antenna designed and fabricated on LiTiZn ferrite substrate is presented. This antenna geometry has been optimized with IE3D and lithographed on 2 mm thick LiTiZn ferrite substrate. LiTiZn polycrystalline substrate has been synthesized using solid state reaction technique and further characterized for microwave application. We have computed various important antenna parameters such as return-loss, bandwidth, directivity, gain, radiation power, etc. for synthesized ferrite as well as on RT-duroid substrate. A comparison of these results has also been presented.     

Silver Hexafluoroantimonate‐Catalyzed Direct α‐Alkylation of Unactivated Ketones

A practically simple and direct α‐alkylation of unactivated ketones using benzylic alcohols has been achieved. The in situ formed acetals are the key for the success of the reaction. The catalyst, silver hexafluoroantimonate(V) (AgSbF₆) provides double activation by converting the ketone into an enol ether via acetal and generation of carbocationic center at the benzylic position of the benzylic alcohol. The alcohols include benzylic propargyl alcohols, cinnamyl alcohols, and diarylmethanols.