Scanning acoustic microscopy of SCS-6 silicon carbide fiber reveals large radial variations in acoustic reflectivity associated with the chemical composition and microstructure of a given fiber region. Rayleigh wave fringe patterns observed in each of five subregions are used to calculate the average Young modulus of that subregion. The Young modulus is found to increase monotonically from 40 GPa in the carbon core to a value of 413 GPa in the stoichiometric SiC region. The effective Young modulus of the fiber as a whole is estimated from the moduli of the individual regions and it is compared with mechanical measurements reported in the literature. 相似文献
In today’s world of connectivity there is a huge amount of data than we could imagine. The number of network users are increasing day by day and there are large number of social networks which keeps the users connected all the time. These social networks give the complete independence to the user to post the data either political, commercial or entertainment value. Some data may be sensitive and have a greater impact on the society as a result. The trustworthiness of data is important when it comes to public social networking sites like facebook and twitter. Due to the large user base and its openness there is a huge possibility to spread spam messages in this network. Spam detection is a technique to identify and mark data as a false data value. There are lot of machine learning approaches proposed to detect spam in social networks. The efficiency of any spam detection algorithm is determined by its cost factor and accuracy. Aiming to improve the detection of spam in the social networks this study proposes using statistical based features that are modelled through the supervised boosting approach called Stochastic gradient boosting to evaluate the twitter data sets in the English language. The performance of the proposed model is evaluated using simulation results.
The evolution of fretting fatigue damage was investigated in shot-peened Ti-6Al-4V samples, by measuring the changes in the
surface residual stress, using the X-ray diffraction technique. The surface residual stress was found to relax as the number
of fretting fatigue cycles increased. The relaxation behavior of the residual stress with the increasing number of fretting
fatigue cycles was observed to occur in three stages. In the first 20 pct of the fretting fatigue life, a drastic relaxation
was observed. In the second part (between 20 and 70 pct), a gradually increasing behavior was observed. During the last 20
to 30 pct of the fretting fatigue life, a dramatic relaxation of the residual stress was found to occur. A complete relaxation
of the residual stress occurred in the fracture region. A scanning electron microscope observation of the microstructure of
the damaged region was used to examine the mechanisms leading to the relaxation of the residual stress. The development of
delaminations at the early stages of the accumulation of the fretting fatigue damage was observed to be the main cause of
the initial relaxation. The generation of microcracks from the voids left behind by the delaminations is responsible for the
additional relaxation of the residual stress. The coalescence of the microcracks generated from different delaminated regions
produced yet more relaxation of residual stress and, ultimately, the final fracture of the specimen. 相似文献
Silicon - Advances in microelectronics have enabled smaller technical nodes, lower threshold voltages, and greater working frequencies. Even though VLSI circuit performance and power consumption... 相似文献
Some say that all diseases begin in the gut. Interestingly, this concept is actually quite old, since it is attributed to the Ancient Greek physician Hippocrates, who proposed the hypothesis nearly 2500 years ago. The continuous breakthroughs in modern medicine have transformed our classic understanding of the gastrointestinal tract (GIT) and human health. Although the gut microbiota (GMB) has proven to be a core component of human health under standard metabolic conditions, there is now also a strong link connecting the composition and function of the GMB to the development of numerous diseases, especially the ones of musculoskeletal nature. The symbiotic microbes that reside in the gastrointestinal tract are very sensitive to biochemical stimuli and may respond in many different ways depending on the nature of these biological signals. Certain variables such as nutrition and physical modulation can either enhance or disrupt the equilibrium between the various species of gut microbes. In fact, fat-rich diets can cause dysbiosis, which decreases the number of protective bacteria and compromises the integrity of the epithelial barrier in the GIT. Overgrowth of pathogenic microbes then release higher quantities of toxic metabolites into the circulatory system, especially the pro-inflammatory cytokines detected in osteoarthritis (OA), thereby promoting inflammation and the initiation of many disease processes throughout the body. Although many studies link OA with GMB perturbations, further research is still needed. 相似文献
Timing constraints for radar tasks are usually specified in terms of the minimum and maximum temporal distance between successive
radar dwells. We utilize the idea of feasible intervals for dealing with the temporal distance constraints. In order to increase
the freedom that the scheduler can offer a high-level resource manager, we introduce a technique for nesting and interleaving
dwells online while accounting for the energy constraint that radar systems need to satisfy. Further, in radar systems, the
task set changes frequently and we advocate the use of finite horizon scheduling in order to avoid the pessimism inherent
in schedulers that assume a task will execute forever. The combination of feasible intervals and online dwell packing allows
modular schedule updates whereby portions of a schedule can be altered without affecting the entire schedule, hence reducing
the complexity of the scheduler. Through extensive simulations we validate our claims of providing greater scheduling flexibility
without compromising on performance when compared with earlier work based on templates constructed offline. We also evaluate
the impact of two parameters in our scheduling approach: the template length (or the extent of dwell nesting and interleaving)
and the length of the finite horizon.
Sathish Gopalakrishnan is a visting scholar in the Department of Computer Science, University of Illinois at Urbana-Champaign, where he defended
his Ph.D. thesis in December 2005. He received an M.S. in Applied Mathematics from the University of Illinois in 2004 and
a B.E. in Computer Science and Engineering from the University of Madras in 1999. Sathish’s research interests concern real-time
and embedded systems, and the design of large-scale reliable systems. He received the best student paper award for his work
on radar dwell scheduling at the Real-Time Systems Symposium 2004.
Marco Caccamo graduated in computer engineering from the University of Pisa in 1997 and received the Ph.D. degree in computer engineering
from the Scuola Superiore S. Anna in 2002. He is an Assistant Professor of the Department of Computer Science at the University
of Illinois. His research interests include real-time operating systems, real-time scheduling and resource management, wireless
sensor networks, and quality of service control in next generation digital infrastructures. He is recipient of the NSF CAREER
Award (2003). He is a member of ACM and IEEE.
Chi-Sheng Shih is currently an assistant professor at the Graduate Institute of Networking and Multimedia and Department of Computer Science
and Information Engineering at National Taiwan University since February 2004. He received the B.S. in Engineering Science
and M.S. in Computer Science from National Cheng Kung University in 1993 and 1995, respectively. In 2003, he received his
Ph.D. in Computer Science from the University of Illinois at Urbana-Champaign. His main research interests are embedded systems,
hardware/software codesign, real-time systems, and database systems. Specifically, his main research interests focus on real-time
operating systems, real-time scheduling theory, embedded software, and software/hardware co-design for system-on-a-chip.
Chang-Gun Lee received the B.S., M.S. and Ph.D. degrees in computer engineering from Seoul National University, Korea, in 1991, 1993 and
1998, respectively. He is currently an Assistant Professor in the Department of Electrical Engineering, Ohio State University,
Columbus. Previously, he was a Research Scientist in the Department of Computer Science, University of Illinois at Urbana-Champaign
from March 2000 to July 2002 and a Research Engineer in the Advanced Telecomm. Research Lab., LG Information & Communications,
Ltd. from March 1998 to February 2000. His current research interests include real-time systems, complex embedded systems,
QoS management, and wireless ad-hoc networks. Chang-Gun Lee is a member of the IEEE Computer Society.
Lui Sha graduated with the Ph.D. degree from Carnegie-Mellon University in 1985. He was a Member and then a Senior Member of Technical
Staff at Software Engineering Institute (SEI) from 1986 to 1998. Since Fall 1998, he has been a Professor of Computer Science
at the University of Illinois at Urbana Champaign, and a Visiting Scientist of the SEI. He was the Chair of IEEE Real Time
Systems Technical Committee from 1999 to 2000, and has served on its Executive Committee since 2001. He was a member of National
Academy of Science’s study group on Software Dependability and Certification from 2004 to 2005, and is an IEEE Distinguished
Visitor (2005 to 2007). Lui Sha is a Fellow of the IEEE and the ACM. 相似文献
Adaptive Mesh Refinement is a method which dynamically varies the spatio-temporal resolution of localized mesh regions in numerical simulations, based on the strength of the solution features. In-situ visualization plays an important role for analyzing the time evolving characteristics of the domain structures. Continuous visualization of the output data for various timesteps results in a better study of the underlying domain and the model used for simulating the domain. In this paper, we develop strategies for continuous online visualization of time evolving data for AMR applications executed on GPUs. We reorder the meshes for computations on the GPU based on the users input related to the subdomain that he wants to visualize. This makes the data available for visualization at a faster rate. We then perform asynchronous executions of the visualization steps and fix-up operations on the CPUs while the GPU advances the solution. By performing experiments on Tesla S1070 and Fermi C2070 clusters, we found that our strategies result in 60% improvement in response time and 16% improvement in the rate of visualization of frames over the existing strategy of performing fix-ups and visualization at the end of the timesteps. 相似文献
The electron-electron scattering contribution to the ultrasonic attenuation in potassium at low temperatures is evaluated using the Landau Fermi liquid theory. The scattering function is evaluated using the approximation suggested by MacDonald and Geldart. The results are compared with theoretically evaluated electron-phonon scattering contributions. The results show that the electron-electron scattering contribution is of the same order as the electron-phonon scattering contribution in the 2–5 K range. Below 2 K the electron-electron scattering predominates. 相似文献
The extensive discomfort in the expulsion of toxic pollutants even at mild concentrations has demanded the need for prompt methods for the evacuation of dyes and heavy metals. The effective method for depuration of dye from the effluent is by sorption. Chitosan is a bio‐polymer which is gaining an increasing interest as one of the sorbents. It was obtained from the crab shells by undergoing several chemical processes and used as an adsorbent for dye, metal removal and also for pharmaceutical purposes. Cross linking it with other co polymers will increase the capacity of adsorption to a maximum level. Fish scales are considered to be a major waste in the food industry and since it takes a long time for decomposing it is considered to be one of the pollutants. Hence it is utilised by converting it into activated carbon by preliminary treatment and into a muffle furnace. The obtained activated carbon is combined with chitosan by using a cross linker and utilised for adsorption mechanism. To analyse the effect of chitosan cross linked with activated carbon obtained from fish scales in adsorption of dye Reactive Blue 9 (RB9) to evaluate the adsorption studies, kinetics, mass transfer studies, thermodynamics of the bio adsorbent.Inspec keywords: dyes, wastewater treatment, effluents, mass transfer, activated carbon, adsorption, polymer blends, water pollution control, thermodynamics, reaction kinetics, furnaces, recycling, industrial waste, waste recovery, food processing industry, pharmaceutical industry, renewable materials, nanoparticles, toxicologyOther keywords: fish scales, activated carbon, reactive dye removal, toxic pollutants, heavy metals, bio‐polymer, nanochitosan, bio adsorbent, amalgamation, RB9 dye, industrial effluent, crab shells, adsorption method, pharmaceutical purposes, copolymers, food industry waste, waste recovery, recycling process, muffle furnace, reaction kinetics, mass transfer, thermodynamic analysis, ReactiveBlue 9, wastewater treatment, water pollution control, C相似文献
We propose a simple scheme for selecting objects (either for caching or picking objects that are peers in a peer-to-peer system) to maximize the long-run reward obtained by a system. Our approach does not require a detailed record of the value specific objects add to the system. Therefore, it can be implemented using less computing and memory resources as compared to machine learning and artificial intelligent algorithms. One of the main contributions we make is to show that one can still derive optimal policies. The model that we use and the policy that we present are both applicable in a variety of contexts. 相似文献