Catalytic oxidation of methanol over molybdenum oxide–tungsten oxide

The vapour phase oxidation of methanol to formaldehyde over molybdenum oxide, tungsten oxide and their mixtures has been investigated in an integral flow reactor at atmospheric pressure. The effect of several process variables on the conversion and yield were determined. A high conversion of 95.6% methanol with nearly 95% selectivity was obtained at 430°C. A rate expression has been derived from the kinetics of the reaction.     

Geomorphic diversity as a river management tool and its application to the Ganga River,India

Understanding of geomorphic processes and the determination of geomorphic diversity in catchments are prerequisites for the sustainable rehabilitation of river systems and for reach‐scale assessment of river health. The Ganga River system in India is a large, complex system consisting of several long tributaries, some >1,000 km, originating from 2 distinct hinterlands—the Himalaya to the north and the cratons to the south. Traversing through a diverse climatic regime across the Plain and through precipitation zones ranging from 600 mm/year near Delhi to 1,200 mm/year in the eastern plains, the Ganga River system has formed very diverse landform assemblages in 3 major geomorphic domains. We have recognized 10 different river classes for the trunk river from Gangotri (source) to Farakka (upstream of its confluence with the Brahmaputra) based on (a) landscape setting, (b) channel and active floodplain properties, and (c) channel planform parameters. The mountainous stretch is characterized by steep valleys and bedrock channels and is dominated by large‐scale sediment production and transport through hill slope processes. The alluvial part of the river is characterized by 8 different river classes of varying reach lengths (60–300 km) many of which show sharp transitions in landscape setting. We have highlighted the application of this approach for the assessment of habitat suitability, environmental flows, and flood risk all of which have been significantly modified during the last few decades due to large‐scale anthropogenic disturbances. We suggest that the diversity embedded in this geomorphic framework can be useful for developing a sustainable river management programme to “work with” the contemporary character and behaviour of rivers.     

2-DOF vibratory gyroscope fabricated by SU-8 based UV-LIGA process

This paper reports fabrication of 2-DOF vibratory gyroscope using SU-8 based UV-LIGA process. The device structure is designed to be symmetrical in order to match the resonance frequencies of drive and sense mode oscillators and also to minimize their relative temperature dependent drift. The overall arrangement is such that the two vibration modes do not affect each other and therefore, mechanical decoupling is achieved which helps in minimizing bias drift. The design is optimized to be compatible with the UV-LIGA process having 10 μm thick electroformed nickel as structural layer. Photolithography to create 11 μm thick SU-8 molds for electroforming sacrificial copper and structural nickel layer is optimized using multiple exposure technique that ensures near vertical side walls. Since the highly cross-linked SU-8 remaining after development is difficult to remove reliably from high aspect ratio structures without damage or alteration to the electroformed metals, a 2.45 GHz MW plasma etching process is developed with CF₄/O₂ mixes. The fabricated device is checked for off-plane misalignment between the stationary and movable comb fingers using white light interferometry and it is found to be almost negligible. Also, the prototype device is characterized for amplitude and phase spectral responses using Polytec MSA-500 Micro System Analyzer. The drive and sense mode resonance frequencies are observed at 7.3 and 7.1 kHz respectively against the mode matched designed frequency of 7.5 kHz.     

Thermal degradation of cellulose and its phosphorylated products in air and nitrogen

The thermal degradation of cellulose and its phosphorylated products (phosphates, diethylphosphate, and diphenylphosphate) were studied in air and nitrogen by differential thermal analysis and dynamic thermogravimetry from ambient temperature to 750°C. From the resulting data various thermodynamic parameters were obtained following the methods of Broido and Freeman and Carroll. The values of E_a for decomposition for phosphorylated cellulose were found to be in the range 55–138 kJ mol^?1 in air and 85–152 kJ mol^?1 in nitrogen and depended upon the percent of phosphorus contents in the samples. The mass spectrum of cellobiose phosphate indicated the absence of the molecular ion, indicating that the compound was thermally unstable. The IR spectra of the pyrolysis residues of cellulose phosphate gave indication of formation of a compound having C?O and P?O groups. A fire retardancy mechanism for the thermal degradation of cellulose phosphate has been proposed.     

Nighttime face recognition at large standoff: Cross-distance and cross-spectral matching

Face recognition in surveillance systems is important for security applications, especially in nighttime scenarios when the subject is far away from the camera. However, due to the face image quality degradation caused by large camera standoff and low illuminance, nighttime face recognition at large standoff is challenging. In this paper, we report a system that is capable of collecting face images at large standoff in both daytime and nighttime, and present an augmented heterogeneous face recognition (AHFR) approach for cross-distance (e.g., 150 m probe vs. 1 m gallery) and cross-spectral (near-infrared probe vs. visible light gallery) face matching. We recover high-quality face images from degraded probe images by proposing an image restoration method based on Locally Linear Embedding (LLE). The restored face images are matched to the gallery by using a heterogeneous face matcher. Experimental results show that the proposed AHFR approach significantly outperforms the state-of-the-art methods for cross-spectral and cross-distance face matching.     

Automatic learners with feedback queries

Automatic classes are classes of languages for which a finite automaton can decide whether a given element is in a set given by its index. The present work studies the learnability of automatic families by automatic learners which, in each round, output a hypothesis and update a long-term memory, depending on the input datum, via an automatic function. Many variants of automatic learners are investigated: where the long-term memory is restricted to be the current hypothesis whenever this exists, cannot be of length larger than the length of the longest datum seen, or has to consist of a constant number of examples seen so far. Learnability is also studied with respect to queries which reveal information about past data or past computation history; the number of queries per round is bounded by a constant.     

Humidity sensing and electrical properties of polyaniline/cobalt oxide composites

Polyaniline/cobalt oxide composites were synthesized by an in situ chemical polymerization method with ammonium persulfate as an oxidizing agent. This was a single‐step polymerization process for the direct synthesis of the emeraldine salt phase of the polymer. The polymers were characterized with X‐ray diffraction, scanning electron microscopy, and Fourier transform infrared spectral analysis. The formation of mixed phases of the polymer together with the conducting emeraldine salt phase was confirmed by spectroscopic techniques. High‐temperature conductivity measurements showed thermally activated behavior. A change in the resistance was observed with respect to the relative humidity when the pellets were exposed to a wide humidity range of 10–95%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 653–658, 2007     

Rheological characteristics of coal tar and petroleum pitches with and without additives

An extensive study of rheological characteristics of coal tar and petroleum pitches with and without additives, namely, petroleum coke, natural graphite and carbon black has been made. It is found that all pitches, pure or mixed with a carbon additive are not Newtonian as reported in the literature, but behave Theologically as Bingham plastics with certain yield stress and plastic viscosity at all temperatures of measurement between 85–180°C. The yield stress and plastic viscosity both decrease with increase in temperature of the pitch. A pure petroleum pitch having the same softening point as that of a coal tar pitch is found to have a lower viscosity compared to that of the latter at all temperatures of measurement. This suggests that the criterion of softening point as a measure of suitability of a coal tar pitch binder in the manufacture of artificial carbon is not sufficient for petroleum pitches. Addition of ten parts of carbon black by weight of pitch results in a considerable decrease in viscosity change with temperature of the coal tar pitch compared to almost insignificant change in the case of the petroleum pitch of the same softening point. However, the addition of petroleum coke or natural graphite makes the pitch more viscous but does not change the temperature dependence of viscosity of either of the two types of pitches. The implications are discussed.     

Model development and validation: Co-combustion of residual char, gases and volatile fuels in the fast fluidized combustion chamber of a dual fluidized bed biomass gasifier

A one-dimensional steady state model has been developed for the combustion reactor of a dual fluidized bed biomass steam gasification system. The combustion reactor is operated as fast fluidized bed (riser) with staged air introduction (bottom, primary and secondary air). The main fuel i.e., residual biomass char (from the gasifier), is introduced together with the circulating bed material at the bottom of the riser. The riser is divided into two zones: bottom zone (modelled according to modified two phase theory) and upper zone (modelled with core-annulus approach). The model consists of sub-model for bed hydrodynamic, conversion and conservation. Biomass char is assumed to be a homogeneous matrix of C, H and O and is modelled as partially volatile fuel. The exit gas composition and the temperature profile predicted by the model are in good agreement with the measured value.     

Estimating performance enhancement with alternate control strategies for multiloop control systems

A filter based methodology, studied earlier for SISO systems, is extended to MIMO systems. The presented approach facilitates the calculation of best achievable performance for proportional-integral (PI) controller and the optimal multiloop (ML) PI settings for stochastic disturbance rejection in ML control systems. The filter based approach is further extended to answer some of the key questions for ML control systems such as: (a) performance enhancement possible with the alternate pairing scheme, (b) benefits that will accrue through the employment of decouplers and (c) the performance achievable with the use of multivariable controller (as opposed to an ML controller). Further, the trade-off curve between output variance and control effort is generated for the various control configurations within PI controller domain.