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11.
When a jet of soluble gas is directed on to liquid surface, the kinetic energy of the jet is transferred to the liquid giving rise to circulation, which in turn enhances mass transfer. Consequently, the mass transfer coefficient is related to the characteristics of the jet. 相似文献
12.
Uma Chatterjee 《Polymer》2005,46(5):1575-1582
ATRP of several methacrylates viz. methyl methacrylate (MMA), ethyl methacrylate (EMA), n-butyl methacrylate (nBMA), t-butyl methacrylate (tBMA), benzyl methacrylate (BzMA) and (N,N-dimethylamino)ethyl methacrylate (DMAEMA) has been studied in neat as well as aqueous (up to 12 vol% water) acetone at 35 °C using CuCl/bipyridine (bpy) catalyst and ethyl 2-bromoisobutyrate as the initiator. Addition of water significantly enhances the rate of polymerization without losing control. Unlike CuCl/bpy the CuBr/bpy catalyst gives poor control which is attributed to the lower solubility and consequent heterogeneity in the latter case. Of the other ligands used with the CuCl catalyst viz. o-phenanthroline (o-phen), 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA), 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA), Me6TREN only o-phen offers reasonably good control. The CuCl/bpy catalyst system has been used also in preparing some di- and tri-block copolymers with reasonably low polydispersity index (PDI) at ambient temperature (35 °C) using aqueous acetone as the solvent. The following block copolymers have been prepared PMMA-tBMA, PMMA-b-tBMA-b-MMA, PMMA-DMAEMA, by this method. 相似文献
13.
Chatterjee Abhishek Ghaednia Hamid Bowling Alan Brake Matthew 《Multibody System Dynamics》2021,51(1):45-90
Multibody System Dynamics - Collision between hard objects causes abrupt changes in the velocities of the system, which are characterized by very large contact forces over very small time... 相似文献
14.
Machinability of a nickel aluminide intermetallic alloy 总被引:3,自引:0,他引:3
S. Chatterjee 《Journal of Materials Engineering and Performance》1993,2(1):101-105
This article reports the results of an experimental study on the machinability of a nickel aluminide intermetallic alloy.
Machining was conducted at various speeds, and results indicate low material removal rates. Chips collected for each test
run were measured for thickness for shear angle calculation and were subsequently observed microscopically. Chip segmentation
was observed microscopically, and a fluctuation in the shear angle was evidenced. A parameter characterizing the severity
of the machining process, the chip reduction coefficient (K), was calculated from chip thickness measurements. The calculated values ofK were found to be low, indicating a low severity of the metalcutting process. This, however, is in contract with the observed
low rates of metal removal and low tool life. Thus, conventional metalcutting characterization parameters require re- examination
in terms of machining high-strength materials. 相似文献
15.
The effects of silicon on the properties of tantalum 总被引:2,自引:0,他引:2
K. D. Moser B.S. T. K. Chatterjee M.S. P. Kumar Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1989,41(10):50-53
The microalloying of tantalum with silicon has been effectively used on a commercial scale. However, data on effects of microalloying on processibility, microstructure and mechanical properties are not readily available. To develop some data, tantalum powder with various levels of silicon (0–50 ppm) was processed under identical conditions. Sheet samples were then annealed at different temperatures and evaluated via microstructural, chemical and mechanical tests. The recrystallization temperature was found to increase with silicon content, most probably as a result of the presence of an intermetallic (Ta3Si) phase. The mechanical properties of unrecrystallized tantalum are, as expected, significantly different from those of recrystallized tantalum. 相似文献
16.
Wenjing Wang Shameek Bhattacharjee Mainak Chatterjee Kevin Kwiat 《Pervasive and Mobile Computing》2013,9(4):572-587
In cognitive radio networks, cognitive nodes operate on a common pool of spectrum where they opportunistically access and use parts of the spectrum not being used by others. Though cooperation among nodes is desirable for efficient network operations and performance, there might be some malicious nodes whose objective could be to hinder communications and disrupt network operations. The absence of a central authority or any policy enforcement mechanism makes these kinds of open-access network more vulnerable and susceptible to attacks.In this paper, we analyze a common form of denial-of-service attack, i.e., collaborative jamming. We consider a network in which a group of jammers tries to jam the channels being used by legitimate users who in turn try to evade the jammed channels. First, we compute the distribution of the jamming signal that a node experiences by considering a random deployment of jammers. Then, we propose different jamming and defending schemes that are employed by the jammers and legitimate users, respectively. In particular, we model and analyze the channel availability when the legitimate users randomly choose available channels and the jammers jam different channels randomly. We propose a multi-tier proxy-based cooperative defense strategy to exploit the temporal and spatial diversity for the legitimate secondary users in an infrastructure-based centralized cognitive radio network. Illustrative results on spectrum availability rates show how to improve resiliency in cognitive radio networks in the presence of jammers. 相似文献
17.
We address the issue of complexity for vector quantization (VQ) of wide-band speech LSF (line spectrum frequency) parameters. The recently proposed switched split VQ (SSVQ) method provides better rate–distortion (R/D) performance than the traditional split VQ (SVQ) method, even at the requirement of lower computational complexity, but at the expense of much higher memory. We develop the two stage SVQ (TsSVQ) method, by which we gain both the memory and computational advantages and still retain good R/D performance. The proposed TsSVQ method uses a full dimensional quantizer in its first stage for exploiting all the higher dimensional coding advantages and then, uses an SVQ method for quantizing the residual vector in the second stage so as to reduce the complexity. We also develop a transform domain residual coding method in this two stage architecture such that it further reduces the computational complexity. To design an effective residual codebook in the second stage, variance normalization of Voronoi regions is carried out which leads to the design of two new methods, referred to as normalized two stage SVQ (NTsSVQ) and normalized two stage transform domain SVQ (NTsTrSVQ). These two new methods have complimentary strengths and hence, they are combined in a switched VQ mode which leads to the further improvement in R/D performance, but retaining the low complexity requirement. We evaluate the performances of new methods for wide-band speech LSF parameter quantization and show their advantages over established SVQ and SSVQ methods. 相似文献
18.
Chakraborty A. Konar A. Chakraborty U.K. Chatterjee A. 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》2009,39(4):726-743
This paper presents a fuzzy relational approach to human emotion recognition from facial expressions and its control. The proposed scheme uses external stimulus to excite specific emotions in human subjects whose facial expressions are analyzed by segmenting and localizing the individual frames into regions of interest. Selected facial features such as eye opening, mouth opening, and the length of eyebrow constriction are extracted from the localized regions, fuzzified, and mapped onto an emotion space by employing Mamdani-type relational models. A scheme for the validation of the system parameters is also presented. This paper also provides a fuzzy scheme for controlling the transition of emotion dynamics toward a desired state. Experimental results and computer simulations indicate that the proposed scheme for emotion recognition and control is simple and robust, with good accuracy. 相似文献
19.
Sanjukta Chatterjee 《Computer Physics Communications》2008,179(8):555-561
A new class of transforms, tailored for the hypergeometric series, is proposed and tested on a number of series. From a knowledge of a given number of terms of a sequence, these transforms reproduce the functions with a better accuracy than the Levin-like transforms. Though there exists a correlation between the approximative power of a rational approximant and its ability to predict the leading terms of a series, there are exceptions to this, especially in the case of divergent series. The new transforms can, in most cases, predict a number of extra terms not used in the construction of the approximants. 相似文献
20.
The increasing penetration rate of electric kickboard vehicles has been popularized and promoted primarily because of its clean and efficient features. Electric kickboards are gradually growing in popularity in tourist and education-centric localities. In the upcoming arrival of electric kickboard vehicles, deploying a customer rental service is essential. Due to its free-floating nature, the shared electric kickboard is a common and practical means of transportation. Relocation plans for shared electric kickboards are required to increase the quality of service, and forecasting demand for their use in a specific region is crucial. Predicting demand accurately with small data is troublesome. Extensive data is necessary for training machine learning algorithms for effective prediction. Data generation is a method for expanding the amount of data that will be further accessible for training. In this work, we proposed a model that takes time-series customers’ electric kickboard demand data as input, pre-processes it, and generates synthetic data according to the original data distribution using generative adversarial networks (GAN). The electric kickboard mobility demand prediction error was reduced when we combined synthetic data with the original data. We proposed Tabular-GAN-Modified-WGAN-GP for generating synthetic data for better prediction results. We modified The Wasserstein GAN-gradient penalty (GP) with the RMSprop optimizer and then employed Spectral Normalization (SN) to improve training stability and faster convergence. Finally, we applied a regression-based blending ensemble technique that can help us to improve performance of demand prediction. We used various evaluation criteria and visual representations to compare our proposed model’s performance. Synthetic data generated by our suggested GAN model is also evaluated. The TGAN-Modified-WGAN-GP model mitigates the overfitting and mode collapse problem, and it also converges faster than previous GAN models for synthetic data creation. The presented model’s performance is compared to existing ensemble and baseline models. The experimental findings imply that combining synthetic and actual data can significantly reduce prediction error rates in the mean absolute percentage error (MAPE) of 4.476 and increase prediction accuracy. 相似文献