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111.
Wang Kay Ngai Ben Kao Reynold Cheng Michael Chau Sau Dan Lee David W. Cheung Kevin Y. Yip 《Information Systems》2011
We study the problem of clustering data objects with location uncertainty. In our model, a data object is represented by an uncertainty region over which a probability density function (pdf) is defined. One method to cluster such uncertain objects is to apply the UK-means algorithm [1], an extension of the traditional K-means algorithm, which assigns each object to the cluster whose representative has the smallest expected distance from it. For arbitrary pdf, calculating the expected distance between an object and a cluster representative requires expensive integration of the pdf. We study two pruning methods: pre-computation (PC) and cluster shift (CS) that can significantly reduce the number of integrations computed. Both pruning methods rely on good bounding techniques. We propose and evaluate two such techniques that are based on metric properties (Met) and trigonometry (Tri). Our experimental results show that Tri offers a very high pruning power. In some cases, more than 99.9% of the expected distance calculations are pruned. This results in a very efficient clustering algorithm. 1 相似文献
112.
The spatial wave-function switched field effect transistor (SWSFET) has two or three low band-gap quantum well channels inside the substrate of the semiconductor. The applied voltage at the gate region of the SWSFET, switches the charge carrier concentration in different channels from the source to the drain region. The switching of the electron wave function in different channels can be explained by the device model of the SWSFET. A circuit model of a SWSFET is developed in the Berkeley Short Channel IGFET Model (BSIM) 4.0.0. The design of a three bit analog-to-digital converter (ADC) and digital-to-analog converter (DAC) using SWSFET is explained in this work. Advanced circuit design using fewer SWSFETs will reduce the device count in future analog and digital circuit design. 相似文献
113.
A. Giaconia G. CaputoA. Ceroli M. DiamantiV. Barbarossa P. TarquiniS. Sau 《International Journal of Hydrogen Energy》2007
The Bunsen reaction for the production of hydriodic and sulfuric acids from water, iodine and sulfur dioxide, has been studied with the evaluation of the effect of some operative parameters on product phase behavior. Results show that operative temperature has a minor effect on the phase behavior. In contrast, both iodine and water loads can be adjusted to enhance the downstream operations of the sulfur–iodine thermochemical water-splitting cycle: the effect of iodine and water excess on resulting phases purity, side reaction occurrence and acid concentration was studied and, then, the most favorable operative conditions defined. 相似文献
114.
115.
Supriya Karmakar John A. Chandy Faquir C. Jain 《Journal of Signal Processing Systems》2014,75(3):209-216
This paper presents the implementation of six-bit analog to digital converters (ADCs) and digital-to-analog converters (DACs) using quantum dot gate non-volatile memory (QDNVM). The charge accumulation in the gate region varies the threshold voltage of QDNVM which can be used as a reference voltage source in a comparator circuit. A simplified comparator circuit can be implemented using the quantum dot gate non-volatile memory (QDNVM). In this work, we discuss the use of QDNVM based comparators in designing 6-bit Analog-to-Digital Converters (ADCs) and Digital-to-Analog Converters (DACs). 相似文献
116.
Supriya Karmakar Ernesto Suarez Faquir C. Jain 《Journal of Electronic Materials》2011,40(8):1749-1756
This paper presents the three-state behavior of quantum dot gate field-effect transistors (FETs). GeO
x
-cladded Ge quantum dots (QDs) are site-specifically self-assembled over lattice-matched ZnS-ZnMgS high-κ gate insulator layers grown by metalorganic chemical vapor deposition (MOCVD) on silicon substrates. A model of three-state
behavior manifested in the transfer characteristics due to the quantum dot gate is also presented. The model is based on the
transfer of carriers from the inversion channel to two layers of cladded GeO
x
-Ge quantum dots. 相似文献
117.
118.
通过等温热处理调整铸态Al-17Si-5Cu (AR)合金中Si (尤其是共晶Si)颗粒的形貌以提高合金的耐磨性能。通过销-盘式摩擦机对比研究热处理后的合金(HT合金)和AR合金的磨损行为,并采用扫描电镜观察磨损表面。结果表明,HT合金的显微组织发生显著变化,相应地,HT合金较AR合金的硬度值增大。与AR合金相比,HF合金在所有载荷下总磨损率明显降低,耐磨性能明显改善。热处理后,共晶Si颗粒由针/棒状变为球形/等轴状(长径比接近1),与基体形成良好结合,在磨损过程中保持完整且更加坚硬,为材料提供良好的耐磨性。另外,HT合金硬度的增加进一步提高合金的耐磨性。因此,完整且较硬的Si颗粒对磨损表面的作用以及材料整体硬度的提高导致HT合金在所有载荷下的磨损行为均优于AR合金。 相似文献
119.
D.C. Sau S. Mohanty K.C. Biswal 《Chemical Engineering and Processing: Process Intensification》2008,47(12):2386-2390
The tapered fluidized bed is a remedial measure for certain drawbacks of the gas–solid system, by the fact that a velocity gradient exists along the axial direction of the bed with increase in cross-sectional area. To study the dynamic characteristics of heterogeneous binary mixture of irregular particles, several experiments have been carried out with varying tapered angles and composition of the mixtures with various particles. The tapered angle of the bed has been found to affect the characteristics of the bed. Models based on dimensional analysis have been proposed to predict the critical fluidization velocity and maximum bed pressure drop for gas–solid tapered fluidized beds. Experimental values of critical fluidization velocity and maximum bed pressure drop compare well with that predicted by the proposed models and the average absolute errors are well within 15%. 相似文献
120.
G.S. Sau F. Bianco M. Lanchi R. Liberatore C.V. Mazzocchia A. Spadoni C.A. Tito P. Tarquini G. Diaz F. Pin 《International Journal of Hydrogen Energy》2010
Bioethanol steam reforming is one of the most promising route to produce hydrogen from a renewable liquid biofuel. Activity of two Cu–Zn–Al based catalysts was investigated at low temperatures, ranging from 420 to 500 °C, in view of temperature limitations associated with solar energy supply by parabolic trough technology. At 450 °C the space velocity effect was also investigated, by varying the weight hourly space velocity (WHSV) from 1.67 to 3.32 h−1. In each experimental conditions, together with the expected hydrogen and carbon dioxide, also methane, ethylene, acetaldehyde and diethylether were detect as products, so indicating the presence of several parallel reaction pathways. A good selectivity to ethanol reforming was obtained only at 500 °C (with values of the H2/CO2 mol ratio of 3.4 and 4.5) with both catalysts, while at lower temperatures alcohol dehydration into acetaldehyde seemed to be the main reaction. 相似文献