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991.
Fischer B. Ghetti A. Selmi L. Bet R. Sangiorgi E. 《Electron Devices, IEEE Transactions on》1997,44(2):288-296
In this paper, new homogeneous hot-electron injection data at 300 K and 77 K is provided covering applied voltages from well below to well above the Si-SiO2 barrier height, and a wide range of oxide fields. We found that, in contrast to the MOSFET case, homogeneous injection shows two different regimes for accelerating voltages below and above the barrier height. A simple interpretation of the data is proposed, and supported by Monte Carlo (MC) simulations of the injection experiment. Essentially, the two regimes are the signature of a marked transition between an electron population mostly heated by the electric field, and a tail population created by additional but less efficient energy gain mechanisms, leading to a sharp transition in the carrier distribution function. The details of the bias and temperature dependence of injection are then interpreted as the combined effect of tunneling and carrier distribution. Furthermore, possible implications on MOSFET gate currents are briefly discussed 相似文献
992.
Uyematsu T. Okamoto E. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1997,43(3):992-996
This correspondence proposes an explicit construction of codes achieving capacity for arbitrary discrete memoryless channels. The proposed code is obtained by concatenating variable inner codes and an algebraic geometry code. Further, we clarify that the proposed code achieves the error exponent obtained by Forney for concatenated codes 相似文献
993.
An efficient method for the suppression of excitation-induced spurious modes in the symmetrical condensed node (SCN) transmission-line matrix (TLM) method is presented for the general case of dielectric, anisotropic, or lossy media in planar structures. A special mapping of the field-excitation onto the wave amplitudes of the TLM algorithm completely prevents the emanation of the spurious modes. The application of the mapping in the k-ω space can be done for waveguides with low computational effort. The method is generalized for planar structures with high spatial frequencies of the field at the discontinuities. We use precomputed field templates at the entrance of the three-dimensional (3-D) structures. The mapping is mainly done in the space domain based on the quasi-TEM propagation of the guided waves to keep the computational effort low. Instead of the four-dimensional (4-D) k-ω transformation, only independent one-dimensional (1-D) transformations to the wave coefficient of the conductors direction and ω are necessary. In the case of propagation with low dispersion, the expenditure can be further reduced to 1-D transformations with respect to ω. The efficiency of the present method is demonstrated by investigation of a coplanar waveguide and a triplate waveguide 相似文献
994.
The primary advances in speech and audio signal processing that contributed to the maturing of multimedia applications are discussed in the areas of speech and audio signal compression, speech synthesis, acoustic processing and echo control, and network echo cancellation 相似文献
995.
Chitosan microcapsules as controlled release systems for insulin 总被引:2,自引:0,他引:2
This study analyses the use of chitosan for the production of surface crosslinked microparticulate systems containing insulin. The microcapsules were prepared by an innovative technique based on interfacial crosslinkage of different amounts of chitosan solubilized in the inner phase of a water/oil emulsion by means of ascorbyl palmitate. The correlation between the main formulation parameters and the functional properties of the microcapsules were analysed. Insulin is incorporated with high efficiency. The peptide release is constant for appreciable periods of time. The content of chitosan modulates the main physico-chemical properties of the matrix. 相似文献
996.
997.
B Lembcke 《Canadian Metallurgical Quarterly》1997,86(25-26):1060-1067
Among the numerous breath tests described for gastroenterological applications, breath hydrogen (H2) tests have emerged during the past two decades as a most sensitive, reliable and feasible method for detecting carbohydrate malabsorption and maldigestion (e. g. lactose maldigestion). Hence they are regarded time honored standards of contemporary gastroenterological function tests. For the diagnosis of the small bowel bacterial overgrowth syndrome the glucose H2 breath test is a feasible tool with moderate sensitivity (approximately 65%), which, however, is not higher with alternative breath test (e. g. the 1 g 14C-D-xylose breath test). Measuring mouth-to-caecum-transit time by the breath H2 response after lactulose is more of scientific interest than clinically informative. Breath tests making use of 14C labeled substrates (usually 5 to 10 microCi) bear a rather low calculated radiation hazard and are thus in routine use in some countries, e. g. in Scandinavia, but they are abandoned in others. At least, however, radioactive 14C breath tests are (partially) dispensible, as these restrictions do not apply for the stable isotope 13C breath tests which are nonradioactive and thus devoid of any radiation hazard. For the purpose of gastroenterological function testing the 13C urea breath test for the detection of Helicobacter pylori infection, quantitative studies of gastric emptying with 13C-acetate or 13C-octanoate and quantitative liver function tests have gained diagnostic use while 13C-breath tests assessing intestinal absorption or exocrine pancreatic function have been found less effective than the respective alternatives, or too expensive. Both, H2-breath tests and 13CO2-breath tests are clinically important, diagnostic methods with well delineated indications in gastroenterology. 相似文献
998.
OBJECTIVE: To investigate the efficacy of the rectus abdominis muscle flap (RAMF) technique for the closure and augmentation of small, non-compliant bladder exstrophies. PATIENTS AND METHODS: The RAMF technique was used in two girls and two boys (mean age at operation, 31.7 months, range 3-72) with bladder exstrophy. The clinical outcome and urodynamics were assessed during a follow-up of 29 months to 6 years (mean 49.2 months) and included imaging, cystoscopy, biochemical and microbiological studies. RESULTS: There were no urinary tract infections, metabolic problems or electrolyte disturbances and kidney function remained normal in all patients. Radiography confirmed intact function and anatomy of the urinary tract and cystoscopy showed complete coverage of the inner peritoneal layer of RAMF with uroepithelium. No stone formation or mucus production were detected. Currently, three patients void using clean intermittent catheterization through the native urethra and the fourth through an appendiceal Mitrofanoff valve. However, the bladder volume was insufficient at the late follow-up and three patients required bladder augmentation. CONCLUSIONS: The RAMF technique is a good alternative for closing bladder exstrophies and achieves an increase in bladder capacity; however, although there is a mild improvement in bladder capacity and compliance. RAMF should not be used as a bladder augmentation procedure. The technique is indicated in the closure of large bladder defects, bladder exstrophies with small, inelastic, non-compliant bladder remnants and failed primary closures. 相似文献
999.
The impact of VBR video traffic characteristics on broadband network performance is analysed. In particular, the authors compare in a queue the behaviour of several models that adjust different statistical parameters of actual MPEG traces. It is proved that a good fit of the probability density function (PDF) is essential to approximate queuing behaviour while the effects of short range dependence (SRD) are of secondary importance and those of long range dependence (LRD) could be neglected for practical purposes if realistic scenarios, with strict QoS requirements, are considered 相似文献
1000.
V Kumar PM Carabateas JA Dority WG Earley JP Mallamo C Subramanyam LD Aimone B Ault DL DeHaven Hudkins MS Miller 《Canadian Metallurgical Quarterly》1995,38(10):1826-1830
Replacement of the pyridinium ring of 6,11-ethanobenzo[b]quinolizinium cations with thiazolium (4a and 4b) and N-methylimidazolium (4c and 4d) resulted in equipotent compounds in the [3H]TCP binding assay. The corresponding N-methyl-1,2,4-triazolium analogs were less potent in this assay. The thiazolium derivative 4b, with a Ki = 2.9 nM, is being evaluated as a possible neuroprotective N-methyl-D-aspartic acid (NMDA) antagonist. 相似文献