Wavelet-based robust filtering of process data

A robust filtering methodology is proposed that reliably preserves the information encapsulated in a process signal corrupted with noise and outliers. The method is proven to be effective on benchmark examples and implemented successfully in real-time on a pilot-scale distillation column.     

An evaluation of optical profilometry techniques for CMUT characterization

Accurate characterization of thin films and geometric features including the cavities during and after the fabrication process is crucial for proper CMUT operation, reliability, consistent array operation, and improved yield. Three different optical profilometry techniques: white light interferometry, laser confocal microscopy, and structural grid illumination microscopy have been reviewed in this paper with a focus on characterization of various thin films and geometric features during different CMUT fabrication stages and post processing. The relative merits of each technique have been investigated experimentally in the context of CMUT fabrication for better characterization and process development. The surface roughness and diaphragm deformation results have also been compared with AFM data. From the review, it appears that characterization needs of CMUTs are unique and a combination of complex diversified characterization tools is necessary to generate sufficient data for design verification and functional optimization.

     

Optimum bandpass optical filter synthesis using periodic corrugatedwaveguides with π/2 phase shifts

A graphical method is proposed for the synthesis of optical bandpass filters, using π/2-phase shift sections. Bandpass filters with the desired characteristics, such as central wavelength, bandwidth, ripple factor, selectivity, minimum attenuation etc., can be synthesized by proper choice of corrugation pitch, coupling coefficient, filter length, and the location of π/2-phase shift sections. This method is relatively simple as compared to the previous works. Besides, it allows to optimize certain criteria