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91.
Lenine Campos Miranda Fabio Cavalcanti Lopes Andre Galembeck Eduardo Padron Hemaindez 《化学与化工:英文版》2013,(12):1149-1155
This paper presents a study of the relationship between the magnetic properties and microstructure of nanocomposite Ni/MnO, Ni/CoO, Co/MnO, Co/CoO. The objective is to understand how the coupling interface FM/AFM (ferromagnetic/anti-ferromagnetic) manifests itself in magnetic response of these materials to an applied field. Sample preparation was performed using mechanochemical synthesis by means of a ball mill planetary type high power at normal atmosphere. The characterization was done by XRD (X-ray diffraction), SEM (scanning electron microscopy) and VSM (vibrating sample magnetometry). Analyzing the XRD peaks of the samples studied, there was a decrease in the average particle diameter with increasing milling time, which is important in the magnetic interactions of the atoms of the surface. In addition, the diffraction pattern showed formation of new phases by oxidation interfering with the magnetic measurements. Analyses by SEM show chipboard multiform nano- and micrometer-sized grains on the surface of the clusters being responsible for the interaction. The magnetic measurements show a strong coupling between the phases present in nanocomposites showing once again that the MS (mechanosynthesis) is a powerful technique for this kind of purpose. The effect of the decrease in crystallite size leads to large variations of magnetic properties of the material which have been specifically observed changes in HC (coercive field) in the RM (remanent magnetization) and SM (saturation magnetization). The decrease in crystallite size in the course of grinding intensifies the effects that depend on the surface-to-volume ratio of the material. M vs. T measures were taken for different values of applied field and found a jump in the moment of the sample near the N6el temperature of the antiferromagnetic. 相似文献
92.
Prof. Dr. Carsten Drebenstedt Richard Eichler Andre Simon 《BHM Berg- und Hüttenm?nnische Monatshefte》2013,158(4):155-176
The article gives ideas for the further development of planning and operation in surface mining. The key role play integrated approaches, like integrated mine planning considering the cutting resistances, integrated planning and operation, integration of exploration, extraction and processing, and integrated consideration of environmental impacts, e.g. geohydrochemical aspects in dumping. The integration approach to consolidate separate processes can contribute to discover new potentials to guarantee safety, environmental acceptability, public acceptance and economy of the system as a whole. Important bricks in these developments are efficient navigation systems, which are today widely accessible, like GPS, sensors to identify process controlling parameters, e.g. rock characteristics for selective mining and dumping, and powerful information technologies for data storage and processing. Additional topics are new developments in mining machines, mining technologies and automation, which are mentioned only in general, on the example of new cutting tool design. 相似文献
93.
Guillermo Paternina Berrocal Andre L. M. Da Silva José M. Assaf Alberto Albornoz Maria do Carmo Rangel 《Catalysis Today》2010,149(3-4):240-247
Zirconia-supported nickel catalysts with different amounts of aluminum (Al/Zr = 0.2, 1 and 2) were studied in this work in order to find alternative supports for nickel-based catalysts for the partial oxidation of methane. This reaction is a promising route for producing hydrogen and syngas for different applications. Samples were prepared by precipitation and impregnation techniques, characterized by several techniques and evaluated in the partial oxidation of methane in the range of 450–750 °C and 1 atm. It was found that aluminum affects the textural and catalytic properties of zirconia-supported nickel catalysts. The tetragonal phase of zirconia was stabilized by aluminum and gamma-alumina was also found in the aluminum-richest samples. Aluminum increased the porosity and the specific surface area of the solids. The catalytic activity also increased with the amount of aluminum in solids probably due to the stronger interaction of nickel with the support, which slowly generates active sites during the reduction step. The methane conversion and hydrogen selectivity increased with temperature, indicating no deactivation. The hydrogen to carbon monoxide molar ratio decreased due to aluminum but was not significantly affected by temperature. The coke produced was not harmful to the catalysts and aluminum affected its amount, although no simple relationship was found between these parameters. The most promising catalyst was the sample with aluminum to zirconium molar ratio of 2, which showed high activity and hydrogen selectivity and was stable under the reaction condition. 相似文献
94.
Charles F. Yamoah Andre Bationo T.J. Wyatt Barry Shapiro Saidou Koala 《Nutrient Cycling in Agroecosystems》2003,67(2):167-176
The Sudano–Sahelian agroecological zone is characterized by low and variable rainfall regimes and P deficiency. The present study complements previous research efforts and the objective was (i) to use the Newhall Simulation Model (NSM) to characterize three ICRISAT research sites, and (ii) to use output of NSM to develop an empirical model to guide efficient use of rainfall and fertilizers. The results show that length of the periods that rainfall exceeded evapotranspiration was larger in Bengou than in Gobery and Sadoré. Total positive moisture balance during the three growing seasons was 85.7 mm at Bengou and 19.7 mm at Sadoré. The model explained 52% of the variability in millet yields based on curvilinear response to P fertilizer, standardized May–June (Rmj) rainfall, and the number of wet days in the year (BW3). Yields appear more sensitive to BW3 than to Rmj. Their respective elasticity coefficients (E
c
) were 0.62 and 0.09. Assessment of the model using R2=0.76 and the D-index = 0.85 showed reasonable agreement between model estimation and actual field yields. The study demonstrates the application of simulation models as a cost-effective means in terms of time and funds to agronomic research. 相似文献
95.
96.
Teixeira A.L.J. Nogueira R.N. Andre P.S.B. Lima M.J.N. da Rocha J.R.F. 《Electronics letters》2005,41(1):30-32
A new scheme, based on Bragg gratings written in highly birefringent fibre that allows both increasing the channel density and relaxing the filter bandwidth requirements in future radio-over-fibre wavelength interleaved distribution networks, is presented and tested. 相似文献
97.
Amplifying four-wavelength combiner, based on erbium/ytterbium-doped waveguide amplifiers and integrated splitters 总被引:1,自引:0,他引:1
D. Barbier M. Rattay F. Saint Andre G. Clauss M. Trouillon A. Kevorkian J.-M.P. Delavaux E. Murphy 《Photonics Technology Letters, IEEE》1997,9(3):315-317
We report the successful system demonstration of a four-wavelength integrated-optics amplifying combiner. The arrangement consists of an all-connectorized 4/spl times/1 glass splitter followed by a 4.5-cm-long Er/Yb-doped waveguide amplifier. When injecting 120 mW of 975-nm laser diode pump, we record, in the amplifying section, 11.6 dB of net gain in the single pass configuration and 23 dB in the double pass as well as a noise figure of 4.5 dB. These results show the potentiality of ion-exchange technology for the fabrication of lossless telecommunication devices. 相似文献
98.
We have studied, by means of neutron powder diffraction, the temperature evolution of the hydrogen solid solutions ZrV2Dx in the intermediate range, 2.18≤x≤2.73, separating two hydrogen-ordered phases, ZrV2D≤2 with k=(1/2, 1/2, 1/2) and ZrV2D≥2.8 with k=(0, 0, 1−δ). Instead of ordinary phase separation, we have found an uncommon phase. This phase is a kind of a disordered one and, simultaneously, it keeps a modulation of hydrogen density with the same k as for the ordered phase, one or another. Under favourable conditions this modulation transforms into the regular ordered phase. 相似文献
99.
Chemarin A. Andre A. Botta A. Majos J. Rainard J.-L. Teyssier H. Thorel P. 《Solid-State Circuits, IEEE Journal of》1992,27(7):1116-1120
The authors describe a 0.7- mu m CMOS asynchronous transfer mode (ATM) switch circuit of 350 K transistors, the kernel of a fully autonomous 16*16 ATM switching matrix devoted to telecommunications. This matrix is able to switch ATM multiplexes with a throughput of up to 1.2 Gb/s per access line, and was implemented using 16 receiver/transmitter circuits and a control circuit. The architecture of the ATM switch circuit is based on a large embedded and shared dual-access memory. Each chip processes 4-b slices of each incoming multiplex. Seven such chips working in parallel are enough to achieve standard ATM cell switching. Up-to-date test features, such as boundary scan, built-in self-test, and redundancy were implemented in the circuit.<> 相似文献
100.
Ricardo A. Aroca C. Andre T. Salama 《Analog Integrated Circuits and Signal Processing》2006,48(3):167-174
This paper presents the design and implementation of a new wide dynamic range parallel feedback (PF) transimpedance amplifier
(TIA) for 10 Gb/s optical links. The wide dynamic range is attributed to the novel TIA architecture employing both shunt-shunt
and shunt-series feedback networks. The outstanding features of the TIA are wide dynamic range, high gain, low power consumption
and design simplicity. A prototype implemented in a 0.5 μm SiGe BiCMOS technology and operating at −3.3 V power supply features
an 18.4 dBm dynamic range with a BER less than 10−12, an optical sensitivity of −16 dBm, optical overload of +2.4 dBm, a bandwidth of 8.27 GHz, a gain of 950 Ω and a power consumption
of 189 mW. The new parallel feedback architecture offers improved overload and noise performance when compared to previously
reported, state of the art, single feedback TIA designs and meets all the 10 Gigabit Ethernet and short-reach OC-192 SONET
specifications.
Ricardo Andres Aroca received the B.S. (Hons) degree in electrical engineering from the University of Windsor, Canada, and the M.S. degree from
the University of Toronto, Canada, in 2001 and 2004, respectively. In 2000 he spent two 4 month internships with Nortel Networks
in the Microelectronics Department. Mr. Aroca received the Natural Sciences and Engineering Research Counsel of Canada (NSERC)
Postgraduate Scholarship award in 2002. He is currently working toward the Ph.D. degree at the University of Toronto where
his research interests lie in the area of high-frequency integrated circuits for wireless and wireline communication systems.
C. Andre T. Salama received the B.A.Sc. (Hons.) M.A.Sc. and Ph. D. degrees, all in Electrical Engineering, from the University of British Columbia
in 1961, 1962 and 1966 respectively. From 1962 to 1963 he served as a Research Assistant at the University of California,
Berkeley. From 1966 to 1967 he was employed at Bell Northern Research, Ottawa, as a Member of Scientific Staff working in
the area of integrated circuit design. Since 1967 he has been on the staff of the Department of Electrical and Computer Engineering,
University of Toronto where he held the J.M. Ham Chair in Microelectronics from 1987 to 1997. In 1992, he was appointed to
his present position of University Professor for scholarly achievements and preeminence in the field of microelectronics.
In 1989-90, he was awarded the ITAC/NSERC Research Fellowship in information technology. In 1994, he was awarded the Canada
Council I.W. Killam Memorial Prize in Engineering for outstanding career contributions to the field of microelectronics. In
2000, he received the IEEE Millenium Medal. In 2003, he received the Outstanding Lifetime Achievement Award from the Canadian
Semiconductor Technology Conference for seminal and outstanding contributions to semiconductor device research and promotion
of Canadian University research in microelectronics. In 2004, he received the NSERC Lifetime Achievement Award of Research
Excellence for outstanding and sustained contributions to the field of microelectronics and the Networks of Centres of Excellence
(NCE) Recognition Award for research excellence and outstanding leadership.He was associate editor of the IEEE Transactions
on Circuits and Systems in 1986–88 and a member of the International Electron Devices Meeting (IEDM) Technical Program Committeein
1980–82, 1987–89 and 1996–98. He was the chair of the Solid State Devices Subcommittee for IEDM in 1998 and was a member of
the editorial board of Solid State Electronics from 1984 to 2002. He is presently a member of the editorial board of the Analog
IC and Signal Processing Journal and the Technical Program Committee of the International Symposium on Power Semiconductor
Devices and ICs (ISPSD) and the Technical ProgramCommittee of the International Symposium on Low Power Electronics and Design
(ISLPED). He chaired the technical program committee of ISPSD in 1996 and was the general chair for the conference in 1999.Dr.
Salama is the Scientific Director of Micronet, a network of centres of excellence focussing on microelectronics research and
funded by the Canadian Government and Industry. He has published extensively in technical journals, is the holder of eleven
patents and has served as a consultant to the semiconductor industry in Canada and the U.S. His research interests include
the design and fabrication of semiconductor devices and integrated circuits with emphasis on deep submicron devices as well
as circuits and systems for high speed, low power signal processing applications. Dr. Salama is a Fellow of the Institute
of Electrical and Electronics Engineers, a Fellow of the Royal Society of Canada, a Fellow of the Canadian Academy of Engineering,
a member of the Association of Professional Engineers of Ontario, the Electrochemical Society and the Innovation Management
Association of Canada. 相似文献