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971.
Data clustering consists of a group of procedures used to collect similar entries or data points within a set into clusters. No existing clustering technique considers entries sequentially in time. In some cases, it is desirable to generate clusters that represent a segment of a time-ordered data set. For these purposes, an order-specific clustering algorithm is proposed. The proposed algorithm employs representative load curves to describe the clusters it generates. The capabilities of the order-specific clustering algorithm are demonstrated on a case study using electricity demand data for the province of Ontario, Canada. Two different applications of the clustering algorithm on this data set are given to demonstrate the effect of error threshold values on the formation of clusters. An analysis of the error for each of these clustering applications is presented. 相似文献
972.
J. Pujara M. A. Siddiqui Z. Liu P. Bjegovic S. S. Takagaki P. Y. Li S. Ramaswamy 《Drying Technology》2008,26(3):341-348
This is part II of a study reported earlier on a method to characterize the air flow and water removal characteristics during vacuum dewatering. This article presents experimental data and analysis of results from the use of a cyclically actuated vacuum dewatering device for removing moisture from wetted porous materials such as paper with the intermittent application of vacuum and accompanying air flow though the material. Results presented include sheet moisture content as a function of residence time and hence water removal rate under a variety of process conditions. Also, experimental results on air flow through the wet porous structure and hence the role and importance of air flow during vacuum dewatering are presented. Vacuum dewatering process conditions include exit solids content between 11 and 20% solid under applied vacuum conditions of 13.5 to 67.7 kPa (4 to 20 in. Hg). Regression analysis indicated that the exit sheet moisture content exhibited a nonlinear relationship with residence time with exit solids reaching a plateau after a certain residence time. Final moisture content correlated linearly with the average overall flow rate of air through the paper sample and the basis weight of the material. 相似文献
973.
D. Ballutaud F. Jomard T. Kociniewski E. Rzepka H. Girard S. Saada 《Diamond and Related Materials》2008,17(4-5):451-456
Hot filament and microwave plasma CVD micro- nanocrystalline diamond films are analysed by visible and ultra-violet excitation source Raman spectroscopy. The sample grain size varies from 20 nm to 2 μm. The hydrogen concentration in samples is measured by SIMS and compared to the grain size, and to the ratio of sp2 carbon bonds determined by Raman spectroscopy from the 1332 cm− 1 diamond peak and the sp2 1550 cm− 1 G band. Hydrogen concentration appears to be proportional to the sp2 bonds ratio. The 3000 cm− 1 CHx stretching mode band intensity observed on the Raman spectra is decreasing with the G band intensity. Thermal annealing modifies the sp2 phase structure and concentration, as hydrogen outdiffuses. 相似文献
974.
M. Guerioune Y. Amiour W. Bounour O. Guellati A. Benaldjia A. Amara N. E. Chakri M. Ali-Rachedi D. Vrel 《International Journal of Self-Propagating High-Temperature Synthesis》2008,17(1):41-48
Aiming at preparation of shape memory alloys (SMAs), we explored the SHS of Cu1 − x
Zn1 − y
Al1 − z
alloys (0.29 < x < 0.30, 0.74 < y < 0.75, and 0.83 < z < 0.96). The most pronounced shape memory effect was exhibited by the alloys of the following compositions (wt %): (1) Cu(70.6)Zn(25.4)Al(4.0),
(2) Cu(70.1)Zn(25.9)Al(4.0), and (3) Cu(69.9)Zn(26.1)Al(4.0). The effect of process parameters on the synthesis of CuZnAl
alloys was studied by XRD, optical microscopy, and scanning electron microscopy (SEM). The grain size of CuZnAl was found
to depend on the relative amount of the primary CuZn and AlZn phases. Changes in the transformation temperature and heat of
transformation are discussed in terms of ignition intensity and compaction. Mechanism of the process depends on the level
of the temperature attained relative to the melting point of components. At the melting point of AlZn, the process is controlled
by the solid-state diffusion of AlZn into a product layer. The ignition temperature for this system depends on the temperature
of the austenite-martensite transformation in CuZnAl alloys. The composition and structure of the products was found to markedly
depend on process parameters. The SHS technique has been successfully used to prepare a variety of SMAs.
相似文献
975.
Y.M. Wong W.P. Kang J.L. Davidson J.H. Huang D.V. Kerns 《Diamond and Related Materials》2008,17(4-5):552-555
A novel integrated vacuum field emission (VFE) differential amplifier (diff-amp) utilizing carbon nanotube (CNT) emitters has been developed. A dual-mask microfabrication process was employed to achieve a VFE diff-amp by integrating identical CNT VFE transistors with built-in split gates and integrated anodes. The identical pair of triode amplifiers was well-matched in their device characteristics. The measured ac small-signal characteristics of the diff-amp showed a common-mode-rejection ratio (CMRR) of ~ 320 (~ 50 dB). The proposed analytical model of the CMRR was verified to be in good agreement with the experimental data. The successful implementation of the CNT diff-amp demonstrates a new way to achieve temperature and radiation tolerant VFE integrated microelectronics. 相似文献
976.
Song Xiao-chun Huang Song-ling Zhao Wei 《Russian Journal of Nondestructive Testing》2007,43(5):326-331
Magnetization is the key to inspection of a tank floor via the magnetic-flux-leakage (MFL) technique. In order to optimize
the magnetic circuit of the MFL detector and obtain the best detection effects, the influences of the magnet size on the floor
magnetization condition, the gap magnetic flux density, and the magnetic force were studied with the help of the finite element
method (FEM) and the effects of some other parameters, such as the magnet pole spacing and pole-piece thickness, on the signal-to-noise
ratio were analyzed. The simulation results indicate that variation of the magnet width affects the magnetization much more
than variation of the magnet thickness and that the detector can reach a trade-off between the magnetization effects and the
driving force when the magnet is about 30 mm thick and 40 mm wide. On condition that the floor has reached its magnetizing
saturation, an increase in the magnet-pole spacing and the pole-piece thickness can improve the testing sensitivity and the
signal-to-noise ratio.
The text was submitted by the authors in English. 相似文献
977.
978.
H. Möller 《Corrosion Science》2007,49(4):1992-2001
The purpose of this study was to determine how magnesium in seawater influences the corrosion behaviour of freely corroding steel. This was done by studying if Mg(OH)2 is formed and if calcite and aragonite differ in their protective properties. No Mg(OH)2 was detected after immersion of steel in a Mg2+-containing artificial seawater. Magnesium seems to influence the corrosion behaviour of freely corroding steel by causing calcium carbonate to precipitate as aragonite. Aragonite is more effective in covering the surface than calcite and is therefore more functional in preventing oxygen from reaching the steel surface, thereby lowering the corrosion rate. 相似文献
979.
980.
We present a numerical study of the packing of uniform spheres under three-dimensional vibration using the discrete element method (DEM), focusing on the effects of vibration condition (amplitude and frequency) and inter-particle frictions (sliding and rolling frictions). The results are analysed in terms of packing density, coordination number (CN), radial distribution function (RDF) and pore structure. It is shown that increasing either the vibration amplitude or frequency causes packing density to increase initially to a maximum and then decrease. Both vibration frequency and amplitude should be considered to characterize the effect of vibration process on packing structure. The sliding and rolling frictions between particles can decrease packing density since they dissipate energy, although the effect of rolling friction is less significant. In line with the change of packing density, microstructural properties such as CN, RDF and pore distribution also change: a looser packing often corresponds to smaller CN, less peaked RDF and larger but more widely distributed pores. 相似文献