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1.
A set of runs were performed on the catalytic and thermal cracking of the tars present fn the gasifier off-gas stream; the cracking referred to here Js essentially hydrocracking, in view of the considerable amount of hydrogen being present in the gas stream. The catalyst evaluated for tar cracking was a commercial cobalt-molybdenum catalyst, suppported on γ-Al2O3(Katalco-477). It was observed that there was a decrease in the amount of tar obtained with the cracking unit on-line with the gasifier; the tars were cracked to gaseous products in the presence of catalyst. Furthermore, it appeared that higher ring structures were transformed to less heavier components; thus cracking could become beneficial in downstream processing of the gas stream coming out of a gasifier. 相似文献
2.
A single-feed dual frequency compact microstrip antenna with a shorting pin is described. This new antenna configuration gives a large variation in frequency ratio of the two operating frequencies, without increasing the overall size of the antenna 相似文献
3.
G. Babu Viswanathan Michael J. Mills Vijay K. Vasudevan 《Metallurgical and Materials Transactions A》2003,34(10):2113-2127
The effects of microstructure on the tensile properties and deformation behavior of a binary Ti-48Al gamma titanium aluminide
were studied. Tensile-mechanical properties of samples with microstructures ranging from near γ to duplex to fine grained, near- and fully-lamellar were determined at a range of temperatures, and the deformation structures
in these characterized by transmission electron microscopy (TEM). Microstructure was observed to exert a strong influence
on the tensile properties, with the grain size and lamellar volume fraction playing connected, but complex, roles. Acoustic
emission response monitored during the tensile test revealed spikes whose amplitude and frequency increased with an increase
in the volume fraction of lamellar grains in the microstructure. Analysis of failed samples suggested that microcracking was
the main factor responsible for the spikes, with twinning providing a minor contribution in the near-lamellar materials. The
most important factor that controls ductility of these alloys is grain size. The ductility, yield stress, and work-hardening
rate of the binary Ti-48Al alloy exhibit maximum values between 0.50 and 0.60 volume fraction of the lamellar constituent.
The high work-hardening rate, which is associated with the low mobility of dislocations, is the likely cause of low ductility
of these alloys. In the near-γ and duplex structures, slip by motion of 1/2<110] unit dislocations and twinning are the prevalent deformation modes at room
temperature (RT), whereas twinning is more common in the near- and fully-lamellar structures. The occurrence of twinning is
largely dictated by the Schmid factor. The 1/2<110] unit dislocations are prevalent even for grain orientations for which
the Schmid factor is higher for <101] superdislocations, though the latter are observed in favorably oriented grains. The
activity of both of these systems is responsible for the higher ductility at ambient temperatures compared with Al-rich single-phase
γ alloys. A higher twin density is observed in lamellar grains, but their propagation depends on the orientation and geometry
of the individual γ lamellae. The increase in ductility at high temperatures correlates with increased activity of 1/2<110] dislocations (including
their climb motion) and twin thickening. The role of microstructural variables on strength, ductility, and fracture are discussed.
This article is based on a presentation made in the symposium entitled “Fundamentals of Structural Intermetallics,” presented
at the 2002 TMS Annual Meeting, February 21–27, 2002, in Seattle, Washington, under the auspices of the ASM and TMS Joint
Committee on Mechanical Behavior of Materials. 相似文献
4.
The optical recording of the conditions at the tips of dynamically moving cracks is often associated with a wave pattern which arises from what we call here radial waves. This observation is prevalent for tough solids, especially when the observation tools involve surface deformations such as the caustic method. These waves can modify the caustic shape and size and thus influence the interpretation of measurements. The quantification of the sources of these waves poses a very difficult problem so that a precise evaluation of that phenomenon is not yet possible. However, in an attempt to better understand the limitation imposed on the method of caustics by this set of waves this paper analyzes primarily the change of shape in the caustic associated with the passage of radial waves over the region of the initial curve of the caustic. The analysis is approximate in that the radial waves are assumed to be insensitive to the presence of the crack surfaces, but otherwise accounts for the three dimensional character of wave propagation in a plate of finite thickness.
Résumé On associe souvent l'enregistrement optique des conditions présentes à l'extrémité de fissures en cours de propagation spectaculaire, à une disposition ondulée, due à ce que l'on dénomme ici des ondes radiales. L'observation vaut surtout pour les corps à haute ténacité, et en particulier lorsque les méthodes d'observation tiennent compte des déformations de surface, comme la méthode des caustiques. Les ondes radiales peuvent altérer la forme et la dimension d'une caustique, et, de ce fait, influencer l'interprétation des mesures. Une évaluation précise de ce phénomène n'est pas encore possible, car la quantification des sources de ces ondes pose un problème trés délicat. Néanmoins, en vue de mieux comprendre les limites qu'impose à la méthode des caustiques la formation de ces ondes, on a analysé essentiellement le changement de forme de la caustique lorsque se développent des ondes radiales sur la région couverte par la courbe originale de la caustique. On procède à une approximation dans la mesure où on suppose que les ondes radiales sont insensibles à la présence des surfaces de la fissure, mais prennent par ailleurs en considération le caractère tridimensionnel de la propagation d'une fissure dans une plaque d'épaisseur finie.相似文献
5.
A technique that is sensitive to change in texture is more reliable than mechanical property measurements for the study of
recrystallization behavior in alloys where recrystallization is coupled with precipitation. Hence, ultrasonic velocity measurements
have been employed to characterize microstructural changes during annealing of cold worked Ti-modified austenitic stainless
steel where precipitation of TiC is known to retard recrystallization. Mechanical property measurements, such as strength
and hardness, could not distinguish the recovery and recrystallization regimes, and it was difficult to determine the exact
time or temperature for onset of recrystallization. The variation of velocity with annealing time or annealing temperature
exhibited a three-stage behavior. The velocity exhibited a slight increase in the recovery region followed by a sharp and
continuous decrease in the recrystallization region and reached saturation on completion of recrystallization. Based on the
microstructural investigations, the three stages were identified to be recovery, progress of recrystallization, and completion
of recrystallization. Velocity measurements could sense the onset, progress, and completion of recrystallization more accurately
compared with that of hardness and strength measurements. 相似文献
6.
Logan Molyneux Krishnan Vasudevan Homero Gil de Zúñiga 《Journal of Computer-Mediated Communication》2015,20(4):381-399
Recent research suggests that social interactions in video games may lead to the development of community bonding and prosocial attitudes. Building on this line of research, a national survey of U.S. adults finds that gamers who develop ties with a community of fellow gamers possess gaming social capital, a new gaming‐related community construct that is shown to be a positive antecedent in predicting both face‐to‐face social capital and civic participation. 相似文献
7.
Jiayang Liu Lin Zhong Jehan Wickramasuriya Venu Vasudevan 《Pervasive and Mobile Computing》2009,5(6):657-675
The proliferation of accelerometers on consumer electronics has brought an opportunity for interaction based on gestures. We present uWave, an efficient recognition algorithm for such interaction using a single three-axis accelerometer. uWave requires a single training sample for each gesture pattern and allows users to employ personalized gestures. We evaluate uWave using a large gesture library with over 4000 samples for eight gesture patterns collected from eight users over one month. uWave achieves 98.6% accuracy, competitive with statistical methods that require significantly more training samples. We also present applications of uWave in gesture-based user authentication and interaction with 3D mobile user interfaces. In particular, we report a series of user studies that evaluates the feasibility and usability of lightweight user authentication. Our evaluation shows both the strength and limitations of gesture-based user authentication. 相似文献
8.
Wireless Personal Communications - One of the applications of Sparse Linear Wireless Sensor Networks is environmental monitoring. In these networks, sensors are deployed in sensitive and strategic... 相似文献
9.
Ravi Shanker Vidyarthy Dheerendra Kumar Dwivedi Vasudevan Muthukumaran 《Materials and Manufacturing Processes》2018,33(7):709-717
In the present work, the influence of process parameters such as welding current (I), welding speed (S), and flux coating density (F) on different aspects of weld bead geometry for example depth of penetration (DOP), bead width (BW), depth to width ratio (D/W), and weld fusion zone area (WA) were investigated by using the central composite design (CCD). 9–12% Cr ferritic stainless steel (FSS) plates were welded using A-TIG welding. It was observed that all input variables have a direct influence on the DOP, BW, and D/W. However, flux coating density has no significant effect on WA. Mathematical models were generated from the obtained responses to predict the weld bead geometry. An optimized DOP, BW, D/W, and WA of 6.95?mm, 8.76?mm, 0.80, and 41.99?mm2, respectively, were predicted at the welding current of 213.78 A, the welding speed of 96.22?mm/min, and the flux coating density of 1.99?mg/cm2. Conformity test was done to check the practicability of the developed models. The conformity test results were in good agreement with the predicted values. Arc constriction and reversal in Marangoni convection were considered as major mechanisms for the deep and narrow weld bead during A-TIG welding. 相似文献
10.
Manufacturing facilities are expected to maintain a high level of production and at the same time, employ strict safety standards to ensure the safe evacuation of the people in the event of emergencies (fire is considered in this paper). These two goals are often conflicting. This paper presents a methodology to evaluate evacuation safety versus productivity concurrently for various, widely known manufacturing layouts. While the safety performance indicators such as evacuation times are inferred from the crowd (agent based) simulation, the productivity performance indicators (e.g. throughput) are analyzed using the discrete event simulation. To this end, this research focuses on creating innovative techniques for developing accurate crowd simulations, where Belief-Desire-Intention (BDI) agent framework is employed to build each person’s individual actions and the interactions between them. The data model and rule based action algorithms for each agent are reverse-engineered from the human-in-the-loop experiments in the immersive virtual reality environments. Finally, experiments are conducted using the constructed simulations to compare safety and productivity for different layouts. To demonstrate the proposed methodology, an automotive power-train (engine and transmission) manufacturing plant was used. Initial results look quite promising. 相似文献