Methanol oxidation on MoO3 promoted Pt/C electrocatalyst

MoO₃ is incorporated into Vulcan carbon XC-72R by solid-state reaction under intermittent microwave heating (IMH) method. The Pt nanoparticles are dispersed by microwave-assisted polyol process. The physicochemical characterization reveals that MoO₃ and Pt nanoparticles are evenly deposited on Vulcan carbon XC-72R. The non-conducting MoO₃ is electrochemically reduced to nonstoichiometric and electroconductive hydrogen molybdenum bronze (H_xMoO₃) in acidic solution. The peak current for methanol electrooxidation is about 128% higher on Pt-MoO₃/C electrode than Pt-Ru/C electrode. Also, there is a significant increase in the electrode response toward stability test which can be attributed to hydrogen molybdenum bronze phase and its direct role in the conversion of CO to CO₂. Intermittent microwave heating method is effective for incorporating oxide materials in Vulcan XC-72R in a short span of time which is evidenced by the formation of hydrogen molybdenum bronze phase during the CV measurements.     

Thermal analysis of dry sleeve bearings — a comparison between analytical, numerical (finite element) and experimental results

Thermal analysis of a plastic sleeve bearing in dry operation was investigated experimentally by Floquet et al. [Trans. ASME, J. Lubr. Technol. 99 (1977) 277]. For a comparison with the experimental results, Kennedy [Trans. ASME, J. Tribol. 103 (1981) 90] developed a numerical approach using the finite element method (FEM) that included the development of finite element equations for the case of a moving body heat conduction. In this investigation, both the experimental results of Floquet [Docteur-Ingenier thesis, Université Claude Bernard, Lyon, 1978] and the numerical results of Kennedy were compared with the results of the analytical method developed using the classical heat source method introduced by Jaeger [Proc. Roy. Soc. NSW 76 (1942) 203] and the heat partition principles of Blok [Proc. Inst. Mech. Engrs. 2 (1937) 222], which involves matching of the temperatures on either side of the contact interface. The non-uniform distribution of heat partition (as one body is stationary and the other moving) along the interface is addressed by matching the temperatures at the interface between the stationary and the moving bodies in relative sliding contact using the functional analysis approach originally introduced by Chao and Trigger [Trans. ASME 72 (1955) 1107]. The analytical results are found to be in excellent agreement with both the experimental and the numerical results.     

Performance of the MISR LAI and FPAR algorithm: a case study in Africa

The Multi-angle Imaging SpectroRadiometer (MISR) instrument is designed to provide global imagery at nine discrete viewing angles and four visible/near-infrared spectral bands. The MISR standard products include green leaf area index (LAI) of vegetation and fraction of photosynthetically active radiation absorbed by vegetation (FPAR). These parameters are being routinely processed from MISR data at the Langley Atmospheric Sciences Data Center (ASDC) since October 2002. This paper describes the research basis for transitioning the MISR LAI/FPAR product from beta to provisional status. The quality and spatial coverage of MISR land surface reflectances that are input to the algorithm determine the quality and spatial coverage of the LAI and FPAR products. Therefore, considerable efforts have been expended to analyze the performance of the algorithm as a function of uncertainties of MISR surface reflectances and to establish the convergence property of the MISR LAI/FPAR algorithm, namely, that the reliability and accuracy of the retrievals increase with increased input information content and accuracy. An additional objective of the MISR LAI/FPAR algorithm is classification of global vegetation into biome types—information that is usually an input to remote sensing algorithms that use single-angle observations. An upper limit of uncertainties of MISR surface reflectances that allows discrimination between biomes, minimizes the impact of biome misidentification on LAI retrievals, and maximizes the spatial coverage of retrievals was estimated. Algorithm performance evaluated on a limited set of MISR data from Africa suggests valid LAI retrievals and correct biome identification in about 20% of the pixels, on an average, given the current level of uncertainties in the MISR surface reflectance data. The other 80% of the LAI values are retrieved using incorrect information about the type of biome. However, the use of multi-angle data minimizes the impact of biome misidentification on LAI retrievals; that is, with a probability of about 70%, uncertainties in LAI retrievals due to biome misclassification do not exceed uncertainties in the observations. We also discuss in depth the parameters that characterize LAI/FPAR product quality—such as quality assessment (QA) that is available to the users along with the product. The analysis of the MISR LAI/FPAR product presented here demonstrates the physical basis of the radiative transfer algorithm used in the retrievals and, importantly, that the reliability and accuracy of the retrievals increase with increased input information content and accuracy. Further improvements in the quality of MISR surface reflectances are therefore expected to lead to LAI and FPAR retrievals of increasing quality.     

Human-vision-based real-time stereopsis

The progression in the field of stereoscopic imaging has resulted in impressive 3D videos. This technology is now used for commercial and entertainment purposes and sometimes even for medical applications. Currently, it is impossible to produce quality anaglyph video using a single camera under different moving and atmospheric conditions with the corresponding depth, local colour, and structural information. The proposed study challenges the previous researches by introducing single camera based method for anaglyph reconstruction and it mainly concentrates on human visual perception, where as the previous methods used dual camera, depth sensor, multi view, which demand not only long duration they also suffer from photometric distortion due to variation in angular alignment. This study also contributes clear individual image without any occlusion with another image. We use an approach based on human vision to determine the corresponding depth information. The source frames are shifted slightly in opposite directions as the distance between the pupils increases. We integrate the colour components of the shifted frames to generate contrasting colours for each one of the marginally shifted frames. The colour component images are then reconstructed as a cyclopean image. We show the results of our method by applying it to quickly varying video sequences and compare its performance to other existing methods.     

Functionalization of carbons for Pt electrocatalyst in PEMFC

One of the limitations of conventional carbon-supported Pt electrocatalyst in Proton Exchange Membrane Fuel cell (PEMFC) is the carbon corrosion during start-up and shut-down of a fuel cell. The present work investigates the stability of three different carbon blacks and their functionalized forms as supports for Pt electrocatalysts. Acetylene black (AB) as a low surface area carbon shows a higher degree of graphitization and effective functionalization than Vulcan carbon and Ketjan black. Electrochemical tests on corrosion studies show that the AB and its functionalized form (f-AB) as support for Pt electrocatalyst exhibits good electrochemical activity with an ECSA of 52 m²g^-1 and 78 m²g^-1 and excellent corrosion resistance with minimum ECSA loss of 6% and 16% for Pt/AB and Pt/f-AB, respectively, satisfying the DoE target (<40% ECSA loss.) This makes the Pt/f-AB a promising durable electrocatalyst for PEMFC with improved activity and durability.     

RenyiBS: Renyi entropy basis selection from wavelet packet decomposition tree for phonocardiogram classification

The Journal of Supercomputing - Wavelet packet transform (WPT) is a powerful mathematical tool for analyzing nonlinear biomedical signals, such as phonocardiogram (PCG). WPT decomposes a PCG signal...     

Performance and emission analysis of diesel engine with design modifications on piston crown

The present work aims to enhance the performance of the existing diesel engine by modifying the piston design. Swirl piston is used to induce turbulence as an active enhancement technique. The engine is run at 250 bar injection pressure and 17.5 compression ratio by varying the injection timings. A stirrer is introduced at the top of the piston so as to inculcate more turbulence to incoming charge that improves the fuel vaporisation rate. Whirling motion is created in the combustion chamber by rotating the blades on the cavity/bowl of the reciprocating piston head. A simple link mechanism is provided to convert the oscillatory motion of connecting rod into the rotary motion of the vane. The experimental result clears that the brake-specific fuel consumption is reduced by 8.7%, brake thermal efficiency is enhanced by 9.4%, 11.8% of CO emissions are controlled and NO _x emissions are controlled by 27% is observed with the modified piston compared to the normal piston at retarded injection timing.     

A Hybrid Timer Based Single Node Failure Recovery Approach for WSANs

The inter-actor connectivity is a very crucial issue to maintain network operation in the wireless sensor and actor networks. Most of the applications have been proposed for harsh environments where the backbone actor nodes are prone to failure or get damaged due to their battery power exhaustion or get physically damaged. Such failures can partition the network due to failure of the cut-vertex node and eventually decrease the network performance or even sometimes make the network useless. Currently, a few approaches have been proposed to restore the partitioned network due to failure of the cut-vertex node but without considering the recovery node capabilities. This paper proposes a localized hybrid timer based cut-vertex node failure recovery approach called distributed prioritized connectivity restoration algorithm (DPCRA) to handle such partitions and restore connectivity with the help of a small number of nodes. The main idea is to proactively identify whether the failure of an actor node causes partition or not in the network. If partition occurs the designated failure handlers (FHs) detect that partition and repair it locally using minimum information stored in each actor node. In case first designated node is unable to start the recovery process within a permissible reaction time the next designated FH could start the recovery process. The main strength of our paper is the use of multiple backup nodes for the guaranteed partitioned recovery. The experimental simulation shows that DPCRA outperforms other existing state-of-the-art approaches in terms of the number of participated repairing nodes and their total moving distance for the recovery to restore the disconnected partitions.     

On the mechanics of the grinding process, Part III—thermal analysis of the abrasive cut-off operation

This is Part III of a 3 part series on the Mechanics of the Grinding Process. Part I deals with the stochastic nature of the grinding process, Part II deals with the thermal analysis of the fine grinding process and this paper (Part III) deals with the thermal analysis of the cut-off operation. Heat generated in the abrasive cut-off operation can affect the life of resin bonded grinding wheels and cause thermal damage to the workpiece. Thermal analysis of the abrasive cut-off operation can, therefore, provide guidelines for proper selection of the grinding conditions and optimization of the process parameters for improved wheel life and minimal thermal damage to the workpiece. In this investigation, a new thermal model of the abrasive cut-off operation is presented based on statistical distribution of the abrasive grains on the surface of the wheel. Both cutting and ploughing/rubbing that take place between the abrasive grains and the work material are considered, depending on the depth of indentation of the abrasives into the work material. In contrast to the previous models, where the apparent contact area between the wheel and the workpiece was taken as the heat source, this model considers the real area of contact, namely, the cumulative area of actual contacting grains present at the interface as the heat source. It may be noted that this is only a small fraction of the total contact area as only a small percentage of the abrasive grains present on the surface of the cut-off wheel are in actual contact with the workpiece at any given time and even a smaller fraction of them are actual cutting grains taking part in the cut-off operation. Since, the Peclet number, N_Pe in the case of cut-off grinding is rather high (a few hundred), the heat flow between the work and the contacting abrasive grains can be considered to be nearly one-dimensional. In this paper, we consider the interaction between an abrasive grain and the workpiece at the contact interface. Consequently, the heat source relative to the grain is stationary and relative to the workpiece is fast moving. The interface heat source on the grain side as well as on the workpiece side is equivalent to an infinitely large plane heat source with the same heat liberation intensity as the circular disc heat source. However, it will be shown in the paper that the contacting times are different. For example, the abrasive grain contacts the heat source, as it moves over the wheel-work interface, for a longer period of time ( milliseconds) whereas the workpiece contacts the heat source for shorter period of time ( a few microseconds). The temperature in the grinding zone is taken as the sum of the background temperature due to the distributed action of the previous active grains operating in the grinding zone (global thermal analysis) and the localized temperature spikes experienced at the current abrasive grain tip-workpiece interfaces (local thermal analysis), similar to the work reported in the literature [Proc Roy Soc (London) A 453 (1997) 1083]. The equivalent thermal model developed in the present investigation is simple and represents the process more realistically, especially the heat partition. The model developed provides a better appreciation of the cut-off operation; a realistic estimation of the heat partition between the wheel, the workpiece, and the chip; thermal gradients in the workpiece due to abrasive cut-off operation, and an insight into the wear of the cut-off wheels.     

Modeling of thermomechanical shear instability in machining

The modeling of thermomechanical shear instability in the machining of some difficult-to-machine materials leading to shear localization is presented. Shear instability was observed experimentally in high-speed machining (HSM) of some of the difficult-to-machine materials, such as hardened alloy steels (e.g. AISI 4340 steel), titanium alloys (e.g. Ti-6A1-4V), and nickel-base superalloys (e.g. Inconel 718) yielding cyclic chips. Based on an analysis of cyclic chip formation in machining, possible sources of heat (including preheating effects) contributing toward the temperature rise in the shear band are identified. They include the four primary heat sources, the four preheating effects of the primary heat sources, the image heat source due to the primary shear band heat source, and the preheating effect of this heat source. The temperature rise in the shear band due to each of the heat sources is calculated using Jaeger's classical model for stationary and moving heat sources. Based on this temperature, Recht's classical model of catastrophic shear instability in metals under dynamic plastic conditions developed in 1964 is extended by predicting analytically the conditions for the onset of shear localization. This is done by comparing the strength of material in the shear band, σ′ under the combined effects of thermal softening and strain hardening with that of the material in the vicinity of the shear band, σ where the material has undergone small strains (i.e. up to yield point) and at the temperature caused by the preheating heat sources. Thus, σ is nearly the original strength of the work material. If σ′ < σ, thermal softening predominates at the shear band and shear localization will be imminent. The cutting speed for the onset of shear localization can be predicted based on thermomechanical shear instability model presented here. High-speed machining results reported in the literature for an AISI 4340 steel agree reasonably well with the analytical values developed in this investigation.