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1.
This article presents a design methodology for linearizing GaN HEMT amplifiers based on splitting a large FET into multiple parallel FETs with same total gate periphery and by biasing them individually. By varying the biases, the magnitude and the phase of the IMD3 components at the output of FET changes. A detailed simulation methodology using commercial microwave CAD software is presented. Simulation results show that by biasing one device in Class AB and other(s) in deep Class AB mode, IMD3 components of parallel FETs can be made out of phase to each other leading to cancellation and improvement in linearity. Three prototype circuits were simulated using (a) a single 5 mm FET (1 × 5 mm), (b) two parallel 2.5 mm FETs (2 × 2.5 mm), and (c) four parallel 1.25 mm FETs (4 × 1.25 mm), for a total gate periphery of 5 mm, over the frequency range of 0.8 to 1.0 GHz. IMD3 improvement up to 20 dBc was achieved with the 4 × 1.25 mm circuit when the FET biases were optimized. Measurement results show improvement in linearity up to 20 dBc for 4 × 1.25 mm circuit. The proposed method improves linearity without a substantial penalty on the power consumption and is straightforward to implement. 相似文献
2.
A new debate on the potential impact of oil price changes on the value of firms was initiated in this paper. Using a stochastic frontier approach, an attempt was made to derive the optimal value Q* of firms and calculate the Q value observed. Then the shortfall (Q*–Q) which represents the inefficiency term was explained. Starting from 19 industrial Tunisian firms listed on the Tunis Stock Exchange between 2007 and 2011, the fact that variation of oil prices can largely explain distortions in the value of firms was empirically demonstrated. 相似文献
3.
Naceur Etteyeb Leila Dhouibi Mercedes Sanchez Cruz Alonso Carmen Andrade Ezzeddine Triki 《Journal of Materials Science》2007,42(13):4721-4730
The aim of this study is to investigate the viability of use of sodium phosphate (Na3PO4: SP), tetrasodium pyrophosphate (Na4P2O7: TSPP) and hydroxyethylidene-diphosphonic acid (C2H8O7P2: HEDP) as a non-toxic corrosion inhibitors of steel bars in alkaline media which simulate the electrolyte in the concrete
pores. The effectiveness of these phosphate compounds as corrosion inhibitors was investigated by measuring the corrosion
potentials, the polarization curves, the corrosion current densities, and the electrochemical impedance spectroscopy of steel
bars immersed for 30 days in saturated Ca(OH)2 solutions with and without chlorides. At the completion of the tests, the mass losses were determined in order to verify
the reliability of the electrochemical results. The results showed that phosphate compounds form a protective layer on the
steel surface when immersed in alkaline solution without chlorides. In the presence of chloride ions, the SP acts as an anodic
inhibitor and reduces the corrosion activity on steel. The HEDP shows lower efficiency, probably due to the decrease of the
pH and to the high [Cl−]/[inh] ratio used. Results obtained by electrochemical and gravimetric methods are in quite reasonable agreement. 相似文献
4.
DRYING OF CLAY. I MATERIAL CHARACTERISTICS 总被引:1,自引:0,他引:1
In this study, one got involved in the thermodynamic characterization of two types of clay to be dried. It concerns the determination of the chemical composition through X-ray diffraction, index of plasticity, volumic mass and especially the determination of the sorption isotherms of water vapor on these products at three different temperatures 30, 50 and 70°C. The isosteric enthalpy of adsorption is calculated by the Clapeyron equation it varies from 0 to 2 kJ/mol for Tunisian clay G, and from 0 to 3 kJ/mol for French clay R. Four models provided by the literature i.e., Chung-Pfost, Henderson, Halsey and Guggenheim-Anderson and de Boer (GAB) have been tested and evaluated (correlation factor, standard deviation) to determine the best possible fitting, allowing for the interpolation of experimental results. From the comparison of the results, one noticed that both the Henderson and the GAB models perfectly described the experimental measures for the two types of clay with factors of correlation situated around one and standard deviations tending towards zero. This set of characterizations will allow us at a later stage to understand the drying process of these two types of clay. 相似文献
5.
Wireless Personal Communications - This paper proposes a new energy management function intended to be integrated in the Hierarchical Smart Routing Protocol (HSRP) mainly proposed for Wireless... 相似文献
6.
Wireless Personal Communications - This paper presents a radial cluster heads selection mechanism for homogenous wireless sensor networks. It aims to ensure a good load balancing and enhance the... 相似文献
7.
Mosaicing is connecting two or more images and making a new wide area image with no visible seam-lines. Several algorithms
have been proposed to construct mosaics from image sequence where the camera motion is more or less complex. Most of these
methods are based either on the interest points matching or on theoretical corner models. This paper describes a fully automated
image-mosaicing method based on the regions and the Harris points primitives. Indeed, in order to limit the search window
of potential homologous points, for each point of interest, regions segmentation and matching steps are being performed. This
enables us to improve the reliability and the robustness of the Harris points matching process by estimating the camera motion.
The main originality of the proposed system resides in the preliminary manipulation of regions matching, thus making it possible
to estimate the rotation, the translation and the scale factor between two successive images of the input sequence. This estimation
allows an initial alignment of the images along with the framing of the interest points search window, and therefore reducing
considerably the complexity of the interest points matching algorithm. Then, the resolution of a minimization problem, altogether
considering the couples of matched-points, permits us to perform the homography. In order to improve the mosaic continuity
around junctions, radiometric corrections are applied. The validity of the herewith described method is illustrated by being
tested on several sequences of complex and challenging images captured from real-world indoor and outdoor scenes. These simulations
proved the validity of the proposed method against camera motions, illumination variations, acquirement conditions, moving
objects and image noise. To determine the importance of the regions matching stage in motion estimation, as well as for the
framing of the search window associated to a point of interest, we compared the matching points results of this described
method with those produced using the zero-mean normalized cross correlation score (without regions matching). We made this
comparison in the case of a simple motion (without the presence of a rotation around optical axis and/or a scale factor),
in the case of a rotation and in the general case of an homothety. For justifying the effectiveness of this method, we proposed
an objective assessment by defining a reconstruction error.
相似文献
Slim AmriEmail: |
8.
9.
Kerbiche Asma Jabra Saoussen Ben Zagrouba Ezzeddine Charvillat Vincent 《Multimedia Tools and Applications》2018,77(20):26769-26791
Multimedia Tools and Applications - Video watermarking technique aims at resolving insecurity problems. Recently, many approaches have been proposed in order to satisfy the new constraints of video... 相似文献
10.
ABSTRACT Processing in vibrated beds is characterized by the versatility and the easy controlability through parameters of vibration (amplitude, frequency and intensity). The main task of the control of processing is the synchronization of the residence time of particles in the processing area with the duration of drying. The drying time depends on the physical properties of the processed material, on the thermal parameters of the bed and on the operational parameters. The residence time depends on the mechanical properties of the particles, on the intensity of transport and on the eometrical parameters of the equipment. Since most of the parameters of the vibrational processing depend on the intensity of vibration, synchronization of the drying time with the residence time of particles, optimization of the process and optimal design of the vibrational equipment in general must be performed by the control of this operational parameter. Therefore a sophisticated algorithm and software for optimal control and design of vibrational processing equipment is needed. Such an algorithm based on the "Classification Scheme of Vibrated Systems" is described in this paper. The design algorithm has been tested using experimental data measured in a laboratory scale aerovibrofluidized bed dryer. 相似文献