排序方式: 共有35条查询结果,搜索用时 15 毫秒
1.
D. Ragheb C. Koumeir V. Métivier J. Gaudillot A. Guertin F. Haddad N. Michel N. Servagent 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(2):895-901
The high energy PIXE (HEPIXE) method is a multi-elemental non-destructive ion beam analysis technique. It is based on the detection of the X-ray emitted due to the interaction of high energy particle beam with a sample. This technique is fast and allows the analysis of heavy and medium elements in thin (μm), thick (mm) and multilayer samples. At the ARRONAX facility (Nantes, France), the HEPIXE method has been used to determine the composition of natural and synthetic sodalites. Photochromic properties of these samples are supposed to come from the trace elements (concentration in the ppm range) present in the samples. Taking advantage of the 70 MeV proton beam available at our facility, the HEPIXE method has been also used to study multilayer samples. It has been shown that it is possible to determine the composition of each layer, their thicknesses and their depth position by analyzing the recorded X-ray spectra. 相似文献
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3.
Ragheb M. Abu-Sarris 《Journal of Computational Analysis and Applications》2000,2(1):103-109
In this paper, we are concerned with the global behavior ofthe solutions of the difference equation
where
and
. Necessary and sufficient conditions for boundedness, persistence,and periodicity of all solutions will be established. The oscillatorybehavior will be investigated. 相似文献
4.
Tamer Ragheb Arthur Nieuwoudt Yehia Massoud 《Analog Integrated Circuits and Signal Processing》2007,51(1):11-17
In this paper, we present an analytical modeling methodology for fully integrated inductively-degenerated CMOS narrow-band
cascode Low Noise Amplifiers (LNA) that captures short channel transistor effects to enable rapid design space exploration
in current and future process technologies. The modeling methodology captures the impact of parasitics on passive components,
ESD-protection structures, and devices to accurately predict both impedance matching and noise figure. Our modeling is suitable
for numerical optimization and fully automated synthesis for LNAs. The results indicate that the methodology models ESD-protected
LNA circuits with 47.9% better accuracy in noise figure when compared with several current analytical modeling techniques
with four orders of magnitude improvement in simulation time over circuit-level simulation. Given its speed and accuracy,
the analytical modeling methodology is well-suited for design space exploration. 相似文献
5.
A cylindrical reflector is simulated byN parallel circular conducting cylinders of arbitrary radius and distribution along the trajectory of the continuous reflector surface. The resulting radiation pattern of the transmitting reflector antenna is computed as the backscattering pattern of the circular cylinders due to a line source excitation. The results for largeN are compared with published data for a cylindrical parabolic reflector by Kinzel and for a corner reflector by Tsai. It is shown that the beamwidth and first sidelobe level can be improved by using cylinders of unequal radii and spacing but that, contrary to expectation, further improvement by increasing the number of cylinders is not necessarily possible. 相似文献
6.
A modification to the Hamid-Ragheb approximation leads to a new approximate formula for the Planck's radiation law valid at all frequencies. The modified regime is useful in solving the inverse black body radiation problem in closed form. The absolute percentage errors in constructing the area-coldness distribution due to the proposed and previous approximations are presented. The results suggest that our modified approximation to Planck's law is more suitable than all other approximations at all frequencies. 相似文献
7.
Arthur Nieuwoudt Tamer Ragheb Yehia Massoud 《Analog Integrated Circuits and Signal Processing》2008,55(2):189-193
Given the increasing demand for integrated wireless systems in system-on-chip technology, narrow-band low noise amplifier (LNA) designs must be robust against variations in device parameters and passive component values to improve manufacturing yield for high volume applications. In this paper, we develop two design techniques for reducing the impact of component variations on narrow-band LNA performance. The results demonstrate that by increasing the bandwidth of the narrow-band LNA and applying more conservative design constraints, we can mitigate the reliability implications of process variations on impedance matching, gain, and power consumption. 相似文献
8.
The radiation characteristics of an axial slot on a dielectric-coated conducting circular cylinder embedded in a semi-circle in an infinite ground plane (GP) are examined. The boundary-value method is employed to obtain the solution with the aid of the partial orthogonality of the trigonometric functions. The resulting dual infinite series involved in the solution is then truncated to generate numerical results. The geometry considered here is important because it can be implemented on the body of any mobile communication system. Moreover the GP adds a new parameter to the slotted dielectric-coated conducting circular cylindrical antenna and can be used in beam shaping and to enhance the antenna performance 相似文献
9.
Peter Vorobieff C. Randall Truman Adam M. Ragheb Gregory S. Elliott Julia K. Laystrom-Woodard Darren M. King David L. Carroll Wayne C. Solomon 《Experiments in fluids》2011,51(3):711-722
We present quantitative analysis of image sequences of multi-stream injection nozzle flows with several different injection
geometries in an experiment simulating mixing in a chemical oxygen-iodine laser. To visualize mixing, image sequences were
acquired with planar laser-induced fluorescence (PLIF) in iodine that was injected into the main flow. The injection nozzle
consisted of a slot, ejector, and injector block, with rows of ejector and injector holes along the slot length. The ejector
flow exits in an underexpanded state so that upon expanding it forces the slot and injector flows together to enhance mixing.
For this study, the diameter and geometry of ejector holes were varied to assess their effect on mixing. Two configurations
of ejector holes were used, each with two different diameters for a total of four cases with data collected at downstream
stations. We carry out a quantitative mixing analysis for these configurations, using two methods to quantify the mixing.
The first method considers the statistics of the PLIF image intensity histograms, which are bimodal for poorly-mixed flows
and have a single peak in well-mixed flows. The second method quantifies the properties of the mixing interface. Our analysis
shows that two injection schemes significantly enhance mixing by stretching the mixing interface. 相似文献
10.
Pacard E Brook MA Ragheb AM Pichot C Chaix C 《Colloids and surfaces. B, Biointerfaces》2006,47(2):176-188
One way to increase the sensitivity of DNA diagnostic assays developed on microarrays is to improve the solid phase that allows the extraction of the target from a biological sample, before detection. Two parameters are influencing the performances of this capture step: (i) the specific surface area being offered for the capture and (ii) the number and the accessibility of oligonucleotide probes immobilized on the surface. In this context, we have developed an attractive approach which fulfills these two points. Our strategy was to elaborate a new material of high specific surface area, suitable to serve as support for both solid-phase oligonucleotide synthesis and in vitro diagnostic assay. This material has consisted of aggregates of colloidal amino-silica nanoparticles covalently linked by poly(ethylene oxide) (PEO) arms. The aggregation of amino-silica particles in the presence of reactive bis-isocyanate PEO was achieved in a controlled manner. The aggregate size and structure were examined by microscopy. The specific surface area of this material was measured by nitrogen adsorption technique. The composition of aggregate was studied by thermogravimetry and X-ray photoelectron spectroscopy. Then, this material has been successfully used as support for oligonucleotide synthesis of high yield and purity. The resulting system will be further evaluated in a diagnostic assay on a microarray. 相似文献