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991.
Modeling statistical dopant fluctuations in MOS transistors 总被引:1,自引:0,他引:1
Stolk P.A. Widdershoven F.P. Klaassen D.B.M. 《Electron Devices, IEEE Transactions on》1998,45(9):1960-1971
The impact of statistical dopant fluctuations on the threshold voltage VT and device performance of silicon MOSFET's is investigated by means of analytical and numerical modeling. A new analytical model describing dopant fluctuations in the active device area enables the derivation of the standard deviation, σVT , of the threshold voltage distribution for arbitrary channel doping profiles. Using the MINIMOS device simulator to extend the analytical approach, it is found that σVT, can be properly derived from two-dimensional (2-D) or three-dimensional (3-D) simulations using a relatively coarse simulation grid. Evaluating the threshold voltage shift arising from dopant fluctuations, on the other hand, calls for full 3-D simulations with a numerical grid that is sufficiently refined to represent the discrete nature of the dopant distribution. The average VT-shift is found to be positive for long, narrow devices, and negative for short, wide devices. The fast 2-D MINIMOS modeling of dopant fluctuations enables an extensive statistical analysis of the intrinsic spreading in a large set of compact model parameters for state-of-the-art CMOS technology. It is predicted that VT-variations due to dopant fluctuations become unacceptably large in CMOS generations of 0.18 μm and beyond when the present scaling scenarios are pursued. Parameter variations can be drastically reduced by using alternative device designs with ground-plane channel profiles 相似文献
992.
K Cupisti D Simon C Dotzenrath PE Goretzki HD R?her 《Canadian Metallurgical Quarterly》1997,382(6):295-301
Ileal pouch-anal anastomosis is a surgical procedure used for the treatment of people with chronic ulcerative colitis and familial adenomatous polyposis. The surgery is intended to preserve anal sphincter function, but it carries a risk for certain complications, including pouchitis and anastomotic stricture. The purpose of this article is to review the clinical manifestations, causes, and treatment of anastomotic stricture and pouchitis after ileal pouch-anal anastomosis. 相似文献
993.
Near Shannon limit performance of low density parity check codes 总被引:35,自引:0,他引:35
The authors report the empirical performance of Gallager's low density parity check codes on Gaussian channels. They show that performance substantially better than that of standard convolutional and concatenated codes can be achieved; indeed the performance is almost as close to the Shannon limit as that of turbo codes 相似文献
994.
The rare case of neurilemmoma of the larynx was presented. The difficulties in histopathologic diagnosis of such tumors were emphasized. The tumor was removed by surgery from external approach. 相似文献
995.
OBJECTIVE: To determine the validity of new subjective memory complaints (MCs) from individuals who previously, when without dementia, denied having MCs. DESIGN: Prospective cohort. SETTING: Longitudinal, community-based study of aging and dementia. PATIENTS: One hundred thirty-three community-dwelling elderly individuals who were part of a registry for the study of conditions related to aging in North Manhattan, NY. Patients were selected if they were initially without dementia and had completed at least 2 successive annual clinical and neuropsychological evaluations and provided their own medical history. MAIN OUTCOME MEASURES: Performance on memory tests--the Buschke Selective Reminding Test and a visual memory task--and global performance on a neuropsychological test battery and clinical evaluation, by which questionable dementia or dementia was diagnosed according to a well-defined paradigm. RESULTS: Fifty-three subjects with MCs at the initial evaluation performed no worse on the memory test than the 80 subjects who denied MCs initially. There was a weak association between MCs and the diagnosis of questionable dementia at baseline (P = .04), but this was nonsignificant after adjusting for age and education. At 1-year follow-up, 21 of the 80 without baseline MCs now reported MCs. At the follow-up evaluation, these 21 subjects performed significantly worse on the memory tests, were 5 times more likely to have significant cognitive impairment, and had shown significantly greater decline over the preceding year on several of the cognitive measures than the 59 who continued to deny MCs. CONCLUSION: New MCs from individuals, who when without dementia recently denied MCs, may suggest the presence of significant impairment of memory or cognition. 相似文献
996.
997.
The development and creating of new-generation full-scope simulator and new technology of simulation
N. N. Ponomarev-Stepnoi V. A. Lebedev M. M. Khudiykov S. D. Malkin V. V. Shalia I. D. Rakitin 《Nuclear Engineering and Design》1997,173(1-3)
Set out is a brief account of the two major accomplishments by the Russian Research Center ‘Kurchatov Institute’ in creating the full-scope simulators and mathematical modeling technologies. Presented are the basic specifications of one of the world's largest simulators—the full-scope simulator for the Leningrad NPP which is the new-generation one. Owing to the extended modeling scope accomplished is the possibility of training personnel to act in terms of not only the design-basis but rather beyond the design-basis accidents. To minimize the expenditures for creating the simulators, analyzers and other modeling and control means, the RRC ‘Kurchatov Institute' has created the unique technology of mathmodeling automation. Thanks to its versatility and application at its creation of the ELUD philosophy (easy to learn, use and develop) good use is made of this technology both in nuclear and thermal power engineering, as well as in gas industry. 相似文献
998.
Two experiments were conducted to explore the interaction of the two cerebral hemispheres in motor control, by examining hand, space and attentional asymmetries in goal-directed aiming. In Experiment 1, right-handed subjects moved to targets more quickly with their right hand than their left hand. In addition, each hand was faster when moving in its own hemispace. Although in a control condition, movements were initiated more quickly with the left hand, visual distractors disrupted left hand performance more than right hand performance. For contralateral aiming, ipsilateral distractors caused the greatest interference. In Experiment 2, when targets and distractors were all presented at the midline, a right hand advantage was found for movement time along with a left hand advantage for reaction time, independent of target and distractor location. Our findings are discussed in terms of a right hemisphere role in movement preparation and the allocation of attention in space, and greater left hemisphere involvement in movement execution. 相似文献
999.
1000.
We first performed autogenous bone grafting for lesions of the hallux sesamoid in 1984. During the next 9 years, 21 patients (11 men and 10 women with an average age of 34 and 32 years, respectively) underwent this surgical procedure for symptomatic tibial hallux sesamoid non-unions. Successful bony union was achieved in all but two patients. The majority of patients obtained concomitant relief of preoperative symptomatology and returned to their preinjury level of activity. We believe that this procedure serves as an alternative to hallux sesamoid excision in selected cases. 相似文献