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排序方式: 共有135条查询结果,搜索用时 8 毫秒
1.
Yehia A. Ibrahim Magdy A. Abdelhameed Taher A. Al-Sahhaf Mohamed A. Fahim 《Petroleum Science and Technology》2003,21(5):825-837
Asphaltenes obtained by precipitation from crude Kuwaiti oils have been analyzed by proton magnetic resonance (1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR) and Infrared (IR) spectral techniques. The molecular weight and elemental analysis were also determined. These combined analytical data were used for the characterization of these Kuwaiti oils. The asphaltenes molecular weights range from approximately 4200-6500 with an H/C ratio of 0.91-1.1 with an average 45-71% aromatic carbons. The average side chain length was of 4-6 carbons. It can also be concluded that the asphaltenes under investigation contain 5-9 sets of condensed aromatic rings joined together by bridges of alkyl chains or other hetero atoms and the average number of each of these sets of condensed aromatic rings is nearly 7. There are a number of alicyclic rings and condensed alicyclic rings in asphaltene. The IR spectra showed main molecular groups including OH, NH, SH, C=O and aliphatic and aromatic C-H's. 相似文献
2.
Elbasuney Sherif Hamed Abdelaziz Yehia M. Ramzy Hesham Abdelgawad Ahmed Gobara Mohamed Mokhtar Mohamed 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(9):3665-3676
Journal of Inorganic and Organometallic Polymers and Materials - Surface oxygen of oxide catalyst has low coordination number; they are negatively charged. Surface oxygen can act active site for... 相似文献
3.
Arnaud Grasset Philippe Millet Philippe Bonnot Sami Yehia Wolfram Putzke-Roeming Fabio Campi Alberto Rosti Michael Huebner Nikolaos S. Voros Davide Rossi Henning Sahlbach Rolf Ernst 《International journal of parallel programming》2011,39(3):328-356
Reconfigurable computing offers a wide range of low cost and efficient solutions for embedded systems. The proper choice of the reconfigurable device, the granularity of its processing elements and its memory architecture highly depend on the type of application and their data flow. Existing solutions either offer fine grain FPGAs, which rely on a hardware synthesis flow and offer the maximum degree of flexibility, or coarser grain solutions, which are usually more suitable for a particular type of data flow and applications. In this paper, we present the MORPHEUS architecture, a versatile reconfigurable heterogeneous System-on-Chip targeting streaming applications. The presented architecture exploits different reconfigurable technologies at several computation granularities that efficiently address the different applications needs. In order to efficiently exploit the presented architecture, we implemented a complete software solution to map C applications to the reconfigurable architecture. In this paper, we describe the complete toolset and provide concrete use cases of the architecture. 相似文献
4.
M. Yehia S. M. Ismail A. Hashhash 《Journal of Superconductivity and Novel Magnetism》2014,27(3):771-774
Polycrystalline ferrites NiFe2O4 and NiFe1.99R0.01O4 (R=Sm, Gd, Eu, and La) samples were prepared by usual ceramic method. The structural and the magnetic properties of the samples were characterized by X-ray powder diffraction (XRD), Mössbauer Effect (ME) spectroscopy, and vibrating sample magnetometer (VSM). Indexed XRD patterns confirm the formation of pure cubic spinel phase. The lattice parameters (a) of the rare earth (R) doped samples were smaller than that of the pure Ni-ferrite. Mössbauer effect spectroscopy was used to study the distribution of cations in tetrahedral (A) and octahedral [B] sites of the spinel. The hysteresis loops indicated that the saturation magnetization and coercivity increased with R-substitution and appeared to be greatly affected by the nature of R ions. The obtained results are interpreted based on the rearrangement of cations between the A-site and B-site. 相似文献
5.
Solouma NH Youssef AB Badr YA Kadah YM 《IEEE transactions on bio-medical engineering》2002,49(9):1059-1067
A new system is proposed for tracking sensitive areas in the retina for computer-assisted laser treatment of choroidal neovascularization (CNV). The system consists of a fundus camera using red-free illumination mode interfaced to a computer that allows real-time capturing of video input. The first image acquired is used as the reference image and utilized by the treatment physician for treatment planning. A grid of seed contours over the whole image is initiated and allowed to deform by splitting and/or merging according to preset criteria until the whole vessel tree is demarcated. Then, the image is filtered using a one-dimensional Gaussian filter in two perpendicular directions to extract the core areas of such vessels. Faster segmentation can be obtained for subsequent images by automatic registration to compensate for eye movement and saccades. An efficient registration technique is developed whereby some landmarks are detected in the reference frame then tracked in the subsequent frames. Using the relation between these two sets of corresponding points, an optimal transformation can be obtained. The implementation details of proposed strategy are presented and the obtained results indicate that it is suitable for real-time location determination and tracking of treatment positions. 相似文献
6.
Starkey JA Mechref Y Byun CK Steinmetz R Fuqua JS Pescovitz OH Novotny MV 《Analytical chemistry》2002,74(23):5998-6005
Capillary electrochromatography using a specialty monolithic matrix was utilized in developing a rapid and highly efficient separation of isoflavones in biological materials. Without a preconcentration technique, it is relatively easy to reach ppm-ppb concentrations of these compounds in soy-based foods and verify them structurally using a photodiode array detector. With on-column preconcentration, we were able to measure low-ppb levels in human serum. Using blood samples from human volunteers, whose diet was supplemented by a soy-based product, the method has been validated for high-throughput screening of isoflavones in clinical studies. 相似文献
7.
A sample deposition device has been constructed and optimized for interfacing CEC and capillary LC columns to MALDI mass spectrometry. For CEC analysis, the device is composed of an inlet buffer reservoir and an outlet buffer reservoir connected to a matrix reservoir through a connection sleeve. The matrix reservoir is connected to a deposition capillary via another connection sleeve. CEC eluent is transported to the matrix reservoir via a capillary that is connected to the deposition capillary by the connection sleeve inside the matrix reservoir. This connection sleeve also acts as a mixing chamber, allowing the CEC eluent to be mixed with matrix prior to deposition. Complex glycan mixtures can be separated by CEC using hydrophilic-phase monolithic columns, with capillary eluent being deposited on a standard MALDI plate along with a suitable matrix solution. Thousands of discrete, highly homogeneous dots can be generated for a subsequent mass spectrometric analysis. With minor modifications, this device is also applicable to capillary LC of peptides using gradient elution. In this configuration, the outlet of the LC column is connected to a deposition capillary inside a matrix reservoir through a connection sleeve that allows mixing of the LC effluent with an appropriate matrix. The device has been evaluated with the tryptic digests of proteins. 相似文献
8.
Fat extracted from mango seed kernel (Mangifera indica) was analysed for its chemical and physical constants, triglycerides, fatty acids and phospholipids; and these were compared with those of cotton seed oil, cocoa butter and two of its substitutes, namely, Croklaan Special 555 and Wesco Special E. The effects of incorporation of mango seed kernel oil in butterscotch toffee on its organoleptic properties were also studied. It was found that mango kernel oil and cocoa butter were almost identical in several of their constants, triglycerides, fatty acids and effects on taste, odour and texture of the toffee. 相似文献
9.
For integrated spiral inductor synthesis, designers and design automation tools require efficient modeling techniques during
the initial design space exploration process. In this paper, we introduce an analytical frequency-dependent resistance model
for integrated spiral inductors. Based on our resistance formulation, we have developed a systematic technique for creating
wide-band circuit models for accurate time domain simulation. The analytical resistance model provides a fast alternative
to field solver-based approaches with typical errors of less than 2.6 percent while surpassing the accuracy of several other
analytical modeling techniques by an order of magnitude. Furthermore, the wide-band circuit generation technique captures
the frequency-dependent resistance of the inductor with typical errors of less than 3.2 percent. 相似文献
10.
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