Modeling of pH process using wavenet based Hammerstein model

This paper outlines an approach for developing a Hammerstein model for nonlinear dynamic systems. The nonlinearity is sought to be captured through functional approximation using wavelets cast in a wavenet structure. Nonlinear block of wavenet at input side is cascaded with a linear dynamic block described by a state space model. A sequential approach is used for development of static nonlinear and linear dynamic parts of the model. Configuration and parameters of the nonlinear wavenet structure are determined from near steady state data extracted from dynamic test data while the state space model parameters of the linear dynamic part are obtained using a subspace identification approach. This approach has been applied for modeling a strongly nonlinear pH process operated over a wide range of operating conditions.     

Effects of computer self-efficacy and system reliability on user interaction with decision support systems

Computer self-efficacy (CSE) has been identified as a major determinant of computer-related ability and usage in organizational contexts. However, there has been little research on the impact of CSE on the use of high level computerized systems such as decision support systems. In order to examine this relationship, participants completed a visual search task with the assistance of an automated decision support system which varied in reliability from moderately reliable (70%) to highly reliable (90%). After completion of the task, a median split was performed on participants’ CSE scores to divide participants into high-CSE and low-CSE groups. We examined the relationship between CSE and trust and utilization of the system. High-CSE participants trusted the system more, complied with it more and generated significantly more hits than low-CSE participants, particularly on trials in which the aid was highly reliable. This indicated that high-CSE levels led to a better ability to gauge the true capabilities of the system. However, all participants uniformly underestimated the true reliability of the system at both levels of CSE. This study provides insight into the potential significance of personality factors in shaping human–technology interaction and has implications for designers of automated systems.     

Low-Cost Specification Based Testing of RF Amplifier Circuits using Oscillation Principles

In this paper, we propose a low-cost approach for testing GHz RF amplifiers. It is demonstrated for the first time that GHz RF amplifiers can be tested for their specifications using oscillation principles. In the test mode, the RF test signal is “self generated” by the amplifier with the help of additional external circuitry which forces the amplifier to oscillate (Barkhausen criterion) around its characteristic frequency. The RF sinusoidal output from the oscillating RF amplifier is down-converted to a lower frequency enabling low frequency test response analysis as well as increased sensitivity to parametric deviations. In addition to the detection of catastrophic failures, it is shown that multiple RF specifications (Gain, P1dB, and Noise Figure) can be predicted via analysis of the frequency of the down-converted response. To account for RF parasitics on the production floor, a calibration technique is proposed in the test-setup. Thus, the proposed method reduces test cost significantly by reducing the cost of test setup (by as much as 80%) and significantly reducing test time. The viability of the proposed test method is demonstrated both by simulation experiments and measurement.     

Microfabricated Silicon High-Frequency Waveguide Couplers and Antennas

A method has been developed to fabricate waveguide-to-waveguide couplers and tapered dielectric rod antennas for the millimeter-wave regime from microetched silicon. A proof-of-concept study shows that the structures can be realized using relatively simple wet etching and robotic process control. Experimental measurements of the waveguide-waveguide couplers agree in key features with simulations. The results indicate that two-stepped tapers perform nearly as well as smooth linear tapers, but are much easier to fabricate. Coupling transmissivity of better than -1 dB, and peak antenna gain of 8-10 dB are indicated at W-band frequencies. Lateral dimension etch control of 5-mum precision was realized. To solve a challenge of controlling the length of the first step, either an improved masking method or a switch to dry etching processes is required.     

EFFECT OF DISSOLVED INORGANIC SALTS ON THE VAPOR-LIQUID EQUILIBRIA AND ENTHALPY OF MIXING OF THE METHANOL-ETHYL ACETATE SYSTEM

The effect of three inorganic chloride salts, namely, sodium chloride, calcium chloride and zinc chloride on the vapor-liquid equilibria (VLE) and heat of mixing (h.o.m) of the methanol-ethyl acetate system has been investigated under the atmospheric conditions of 760 ± 3 mm Hg pressure. In the experimentation for VLE a Smith and Bonner type equilibrium still was used while in h.o.m. determination a calorimeter connected to a microprocessor-based control unit (MIPROC) which displays digitally the heat of mixing values in calories was employed. All the three salts dissolved to various concentration levels in the solvent mixture brought about a decrease in the azeotropic composition (expressed in terms of mole fraction of methanol) from 0.75 to values like 0.50, 0.37 and 0.18 depending upon the salt added and its concentration level. The salts sodium chloride and calcium chloride which are more soluble in methanol have been found to salt-in that component but with a peculiarity in that, in methanol-rich region the salting-in effect was substantial while in the methanol-lean region it is only marginal. The addition of salt zinc chloride which is more soluble in ethyl acetate results in an anomalous behaviour.

As for the salt effect on h.o.m., the addition of calcium chloride brought about a significant enhancement in the h.o.m values while the salts sodium chloride and zinc chloride (which could be added only to about 5% by weight concentration due to the experimental difficulties) entailed a decrease and lateral shift respectively in the h.o.m. values.

The VLE and h.o.m data which were found to be thermodynamically consistent have been correlated respectively by NRTL, Wilson and by a model similar to the Scatchard series type equation.     

Photocatalytic degradation of phenol over TiO2 powder: The influence of peroxomonosulphate and peroxodisulphate on the reaction rate

Advanced oxidation processes (AOPs) have been developed as an emerging technology for treating hazardous organics in wastewater and groundwater. In the present study, the effect of oxidants [peroxomonosulphate (PMS) and peroxodisulphate (PDS)] on the photocatalytic oxidation of phenol on illuminated TiO₂ surfaces has been investigated. The efficiencies of these oxidants on photocatalytic degradation of phenol are compared with that of H₂O₂. The experimental results indicate that these oxidants exhibited enhanced rates of mineralization of phenol. A reaction mechanism, involving the generation of both hydroxyl radicals and sulphate radicals, was proposed.     

Peroxomonosulphate, an efficient oxidant for the photocatalysed degradation of a textile dye, acid red 88

Visible light-assisted degradation of a mono azo textile dye acid red 88 (AR88) was carried out in presence of titanium dioxide photocatalyst. Various operational parameters such as variation of the initial dye concentration, photocatalyst and pH on the photocatalytic degradation rate were studied. Effect of the amount of oxidants such as peroxomonosulphate (PMS) and peroxodisulphate (PDS) and the ratio of concentration of oxidant to the concentration of dye (C_oxidant/C_dye) on the photocatalysed degradation rate were also investigated. Though the rate of photodegradation of the dye decreased with increase in dye concentration, the rate increased with C_oxidant/C_dye ratio. Total organic carbon (TOC) analysis revealed a rapid mineralisation of AR88 in the presence of PMS. A suitable mechanism explaining the observed enhanced decolorisation and mineralisation rate of the dye with PMS is presented.     

Improved LSB stegananalysis based on analysis of adjacent pixel pairs

We propose a simple, reliable method based on probability of transitions and distribution of adjacent pixel pairs for steganalysis on digital images in spatial domain subjected to Least Significant Bit replacement steganography. Our method is sensitive to the statistics of underlying cover image and is a variant of Sample Pair Method. We use the new method to estimate length of hidden message reliably. The novelty of our method is that it detects from the statistics of the underlying image, which is invariant with embedding, whether the results it calculate are reliable or not. To our knowledge, no steganalytic method so far predicts from the properties of the stego image, whether its results are accurate or not.     

EFFECT OF SOME MODIFICATIONS TO OXLEY'S MACHINING THEORY AND THE APPLICABILITY OF DIFFERENT MATERIAL MODELS

Oxley's machining theory has recently been extended[1] to accept material property inputs in the form of widely used constitutive models such as the Johnson-Cook and MTS material models. In the process, additional modifications have been made to the model to improve its self-consistency. For instance, the shear force is obtained from the total work of deformation, thereby eliminating the unknown parameter η, and the hydrostatic pressure at the tool-chip interface is calculated considering the gradient in temperature in addition to the gradient in strain. This study is aimed at understanding the effect of these modifications separate from the changes due to the introduction of the new material models by comparing results obtained using Oxley's original model to that obtained with the above modifications. We also compare results obtained using different constitutive models for AISI 1045 to the experimental results of the “Assessment of Machining Models” effort.     

Encapsulation of heterovalent ions of two simulated high-level nuclear wastes and crystallization into single-phase NZP-based wasteforms

Preliminary data were obtained on the immobilization of various heterovalent ions present in the two selected high-level nuclear waste compositions. The entire set of ions present in the waste compositions were immobilized into sodium zirconium phosphate (NZP) structure. The waste loading was in the range 5–25%. The two types of wasteforms loaded with the simulated high-level waste compositions were characterized by powder X-ray diffraction, FT-IR, TGA/DTA, and scanning electron microscopy. The difference in the compositions of the two simulated wastes was reflected in the waste loading percentage and the crystallization of the wasteforms into NZP structure. Up to 12% waste loading, single phase isostructural with NZP was obtained as a major product in the case of the first waste composition. An increase in the waste loading led to the segregation of ZrP₂O₇ as a secondary phase. With the second waste composition, an NZP-like phase was obtained as the major product even at 25% waste loading.