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排序方式: 共有172条查询结果,搜索用时 15 毫秒
21.
Jagannathan B. Khater M. Pagette F. Rieh J.-S. Angell D. Chen H. Florkey J. Golan F. Greenberg D.R. Groves R. Jeng S.J. Johnson J. Mengistu E. Schonenberg K.T. Schnabel C.M. Smith P. Stricker A. Ahlgren D. Freeman G. Stein K. Subbanna S. 《Electron Device Letters, IEEE》2002,23(5):258-260
This paper reports on SiGe NPN HBTs with unity gain cutoff frequency (fT) of 207 GHz and an fMAX extrapolated from Mason's unilateral gain of 285 GHz. fMAX extrapolated from maximum available gain is 194 GHz. Transistors sized 0.12×2.5 μm2 have these characteristics at a linear current of 1.0 mA/μm (8.3 mA/μm2). Smaller transistors (0.12×0.5 μm2) have an fT of 180 GHz at 800 μA current. The devices have a pinched base sheet resistance of 2.5 kΩ/sq. and an open-base breakdown voltage BVCEO of 1.7 V. The improved performance is a result of a new self-aligned device structure that minimizes parasitic resistance and capacitance without affecting fT at small lateral dimensions 相似文献
22.
High-resolution electron energy loss spectroscopy is used to study surface phonons in the direction of
qG
on Ag(111). The gap mode (S2) at
in the surface Brillouin zone is measured for the first time. We have also measured the Rayleigh mode and the resonance mode up to the zone boundary. The results are complementary to the earlier He atom scattering measurements and are in good agreement with the first-principles calculations performed recently. 相似文献
23.
Kanniah Jagannathan Malik O. P. Hope G. S. 《Industrial Electronics, IEEE Transactions on》1984,(4):306-312
Standard single-rate sampling self-tuning regulators may not be able to effectively control fast-acting systems if the minimum computation time required is larger than the largest sampling period permissible. A dual-rate sampling self-tuning regulator that overcomes this problem by allowing a data sampling rate to be chosen consistent with the system time constants and a control output interval based on the computation time is described in this paper. This algorithm is also very suitable for implementation using fixed word-length processors as the quantization problems are minimized. The algorithm has been implemented on a microprocessor. Implementation details with emphasis on data acquisition, interrupt controlled sampling, time sufficiency test and scaling, and experimental results are also given. 相似文献
24.
It is shown that the constrained-component variation generally suggested by Rosicky and Mark is very fundamental, has consistent
variational features and reproduces, as a special case, earlier variational results for atomic systems obtained by Drake and
Goldman. Numerical merits and demerits of this method are qualitatively assessed. 相似文献
25.
It is shown that using the basis elements of the generalized Clifford algebra Cmn we can construct a group G?mn called the generalized Clifford group (G.C.G.) which is a generalization of the Dirac group of the 16 Dirac matrices and their negative counterparts. We have studied the irreducible representations of G.C.G. and we have found the connection with the group of linear transformations leaving invariant the expression for m>2. 相似文献
26.
It is emphasized that Mössbauer spectra of57Fe nuclei subjected to a combined magnetic dipole- and electric quadrupole interaction cannot give a unique solution for all parameters involved in these interactions, even if intensities are taken into account. Expressions are derived with which the full range of possible solutions can be calculated and we apply these to some recently published results in which the ambiguity was not recognized. 相似文献
27.
Quasicrystals can be considered, from the point of view of their electronic properties, as being intermediate between metals and insulators. For example, experiments show that quasicrystalline alloys such as AlCuFe or AlPdMn have conductivities far smaller than those of the metals that these alloys are composed from. Wavefunctions in a quasicrystal are typically intermediate in character between the extended states of a crystal and the exponentially localized states in the insulating phase, and this is also reflected in the energy spectrum and the density of states. In the theoretical studies we consider in this review, the quasicrystals are described by a pure hopping tight binding model on simple tilings. We focus on spectral properties, which we compare with those of other complex systems, in particular, the Anderson model of a disordered metal. We discuss ‘strong‘ and ‘weak’ quasicrystals, which are described by different universal laws. We find similarities and universal behaviour, but also significant differences between quasiperiodic models and models with disorder. Like weakly disordered metals, the quasicrystal can be described by the universal level statistics that can be derived from random matrix theory. These level statistics are only one aspect of the energy spectrum, whose very large fluctuations can also be described by a level spacing distribution that is log-normal. An analysis of spectral rigidity shows that electrons diffuse with a bigger exponent (super-diffusion) than in a disordered metal. Adding disorder attenuates the singular properties of the perfect quasicrystal, and leads to improved transport. Spectral properties are also used in computing conductances of such systems, and to attempt to resolve the experimental enigmas such as whether quasicrystals are intrinsically conductors, and if so, how conductances depend on the structure. 相似文献
28.
Kadarkarai Murugan Jagannathan Madhavan Christina Mary Samidoss Chellasamy Panneerselvam Al Thabiani Aziz Arumugam Malathi Aruliah Rajasekar Amuthavalli Pandiyan Suresh Kumar Abdullah A. Alarfaj Akon Higuchi Giovanni Benelli 《Journal of Cluster Science》2018,29(2):337-344
Anopheles stephensi is a mosquito vector of malaria, which is still considered a relevant public health problem due to increasing outdoor transmission, growing resistance to insecticides used to target vectors, and antiplasmodial drugs as well. Thus, there is a vital need to explore novel sources of effective compounds. In this study, the hydrothermal method was used for the synthesis of bismuth oxyiodide (BiOI) nanoflakes. Furthermore, the toxicity of BiOI nanoflakes was evaluated for the first time on A. stephensi, as well as in vivo against the malaria parasite Plasmodium berghei. The synthesis of BiOI nanoflakes was confirmed by various characterization techniques, including X-ray diffraction, Fourier transform-infrared spectroscopy, field emission scanning electron microscopy and transmission electron microscopy (HR-TEM). LC50 of BiOI nanoflakes on A. stephensi were 2.263 ppm (larva I), 3.414 ppm (II), 4.956 ppm (III), 6.983 ppm (IV) and 8.605 ppm (pupae). In vivo antiplasmodial experiments conducted on P. berghei infecting albino mice showed 27.2% of chemosuppression after 4 days of treatment with 300 mg/kg/day of BiOI, a lower performance if compared to chloroquine. Overall, our results suggested that hydrothermal synthesis of BiOI nanoflakes may be considered to develop newer and safer tools for malaria vector control. 相似文献
29.
Kim HM Yang PR Seo MS Yi JS Hong JH Jeon SJ Ko YG Lee KJ Cho BR 《The Journal of organic chemistry》2007,72(6):2088-2096
A novel, two-photon probe for the detection of free Mg2+ ions in living cells and live tissues has been developed. The probe can be excited by 880 nm laser photons, emits strong two-photon excited fluorescence in response to Mg2+ ions, can be easily loaded into the cell and tissue, shows high photostability, and can measure the Mg2+ ion concentration without interference by Ca2+ ions in living cells. The intracellular dissociation constant (Kdi) for Mg2+ determined by the two-photon process is 2.5 mM, which is suitable for dynamic Mg2+ concentration measurement. In addition, the probe is capable of imaging endogenous stores of free Mg2+ at a few hundred micrometers depth in live tissues using two-photon microscopy (TPM). 相似文献
30.
Baoyin Han Sai-Anand Gopalan Kwang-Don Lee Byoung-Ho Kang Sang-Won Lee Jae-Sung Lee Dae-Hyuk Kwon Seung-Ha Lee Shin-Won Kang 《Current Applied Physics》2014,14(11):1443-1450
In this study, we explored the ability of a preheated solvent (methanol) to induce characteristic changes at the organic active layer/metal interface, thereby improving the performance of fabricated organic photovoltaic (OPV) cells composed of poly(3-hexylthiopene) (P3HT) and a [6,6]-phenyl-C71-butyric acid methyl ester (PCBM) photoactive blend. Our results demonstrate that exposure to methanol (at room temperature, or preheated at 45 °C or 65 °C) improves the performance of the fabricated OPV cells. After preheated methanol exposure, the P3HT:PCBM thin films were tested for crystallinity, morphology, mobility, and photovoltaic characteristics. Our results revealed that use of the preheated solvent on the organic active layer significantly influences the micro/nano scale morphology and phase segregation of the P3HT:PCBM thin films, as well as the charge carrier mobility. It is hypothesized that the side chain ordering of P3HT and redistribution of PCBM could be results of the modified active layer. Consequently, OPV cells modified with the methanol preheated at 65 °C exhibited a power conversion efficiency (PCE) of 3.36%, with open-circuit voltage of 0.59 V, short-circuit current density of 13.83 mA/cm2, and fill-factor of 0.41. In contrast, the unmodified P3HT:PCBM thin film (without methanol exposure) showed a PCE of only 2.13%. 相似文献