排序方式: 共有28条查询结果,搜索用时 15 毫秒
21.
F. Comes M. Farines A. Aumelas J. Soulier 《Journal of the American Oil Chemists' Society》1992,69(12):1224-1227
Cherry seed oil, from the Rosaceae family, prunoid subfamily, is characterized by the existence of about 10% α-eleostearic
acid. The structure of the acid was proven by H and13C nuclear magnetic resonance. The triacylglycerols of this oil were identified and quantitated by highperformance liquid chromatography
by means of several types of detectors. α-Eleostearic acid was not found in the seeds of previously studied prunoids (almond,
peach, apricot and plum). The main fatty acids found in the seeds of cherry and other prunoids were linoleic (L), oleic (O)
and palmitic acids, and the major triacylglycerols were LLO, LOO and OOO. These chemical data support the botanical relationship
within the prunoid subfamily and show the proximity of cherry to the Chrysobalanaceae family. 相似文献
22.
This paper presents a buck DC-to-DC power converter using a novel lossless commutation cell for high switching frequency and high power operation. The proposed cell consists of a main and auxiliary switches, with ZVS and ZCS switching characteristics, respectively. The power converter control using this cell is realized by the PWM technique, with constant switching frequency operation. The complete operation principles, theoretical analysis, relevant equations, state-space phase, simulation and experimental results for the buck converter are presented 相似文献
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This paper presents a methodology for the restoration of the visual quality of still images affected by coding noise. This quality restoration is achieved only by considering the additive coding noise and is therefore limited to an adaptive postprocessing filtering. It is based on a model of the human visual system that considers the relationship between visual stimuli and their visibility. This phenomenon known as masking is used as a criterion for the locally adaptive filtering design. An image transformation that yields visual stimuli tuned to the frequency and orientation according to the perceptual model is proposed. It allows a local measure of the masking of each perceptual stimulus considering the contrast between signal and estimated noise. This measure is obtained by analytic filtering. Processing schemes are presented with applications to the discrete cosine transform (DCT) and subband coded images. One proposed solution considers the characteristics of DCT coding noise for the estimation of the noise. Another solution is based on a "blind" neural estimation of the noise characteristics. Experimental results of the proposed approaches show significant improvements of the visual quality, which validates our perceptual model and filtering. 相似文献
25.
The optical design of an absorption spectrometer for in situ measurements of atmospheric trace gases is reported. The light source is a rapidly tuned and power-stabilized dye-ring laser, which is frequency doubled by an intracavity BBO crystal. The second harmonic and the fundamental are used simultaneously for measurement of OH, SO(2), CH(2)O, and naphthalene in the UV and of NO(2) in the visible. The 1.2-km absorption path is folded within a 6-m White-cell-type multiple-reflection system with an open-path setup. The absorption sensitivity of the spectrometer is better than 1 part in 10(-5) under tropospheric conditions (integration time 1 min., signal-to-noise ratio 1). 相似文献
26.
Comes R. B. Terrell E. J. Higgs C. F. 《Semiconductor Manufacturing, IEEE Transactions on》2010,23(1):121-131
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Untersuchung des Verschleißverhaltens von drei verschiedenen basischen feuerfesten Steinsorten durch Ermittlung der chemischen Zusammensetzung, durch Röntgenbeugung, Auflichtmikroskopie und Elektronenstrahlmikroanalyse. Versuche unter Betriebsbedingungen in einem 20-t-Lichtbogenofen mit Edelstahlprogramm. Probenahme nach dem ?statischen? und ?dynamischen? Modell. Verhalten wesentlicher Legierungselemente auf den Verschleiß. 相似文献
28.
A Arboix L García-Eroles JB Massons M Oliveres E Comes 《Canadian Metallurgical Quarterly》1997,28(8):1590-1594
BACKGROUND AND PURPOSE: Seizures within the first 48 hours of a first stroke or transient ischemic attack (TIA) are an independent prognostic factor for in-hospital mortality. The aim of this study was to determine predictive factors of early seizures in first-ever stroke patients. METHODS: Data of 1220 first-ever stroke patients admitted consecutively to an acute stroke unit of a 450-bed teaching hospital between January 1986 and December 1993 were collected from a stroke registry. Demographic, anamnestic, clinical, neurological, and neuroimaging variables in the seizure and nonseizure group were compared using the t test and the chi 2 test. The independent predictive value of each variable on the development of early seizures was assessed with a logistic regression analysis. RESULTS: Early epileptic seizures were diagnosed in 29 patients (2.4%). Seizures were significantly more frequent in patients with hemorrhagic stroke (4.3%) than in those with ischemic stroke (2%). Patients with seizures were significantly younger and significantly more likely to have acute confusional state, cortical involvement, large stroke, and involvement of the parietal, frontal, occipital, and temporal lobes than patients without seizures. The in-hospital mortality rate was 37.9% in the seizure group and 14.4% in the nonseizure group (P < .0005). After multivariate analysis, only cortical involvement (odds ratio of 6.01) and acute agitated confusional state (odds ratio of 4.44) were independent clinical factors for developing epileptic seizures. CONCLUSIONS: Cortical involvement in the neuroimaging studies and agitated acute confusional state at the onset of stroke were independent predictive factors of early seizures in first-ever stroke patients. The efficacy of anticonvulsant drugs in the prophylactic control of seizures should be assessed in prospective, randomized, double-blind clinical trials conducted in the subgroup of patients with the highest risk of developing epileptic seizures. 相似文献