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91.
The spatial distribution of spheres in a very dilute suspension is described approximately by a Poison distribution, but much better approximations result when the volume of the spheres is taken into account. For solids fractions up to 0.32, the distribution of kth nearest neighbours calculated from the radial distribution function for a hard-sphere gas agreed closely with that determined from a computer simulation. This distribution provides insight into the concentration threshold for cluster settling and the increase in sedimentation rate with time in dilute dispersions. Two models provide rough explanations for the maintenance of cluster velocities greater than the Stokes velocity. 相似文献
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Adams Kong Author Vitae King-Hong Cheung Author Vitae Author Vitae Mohamed Kamel Author Vitae Author Vitae 《Pattern recognition》2006,39(7):1359-1368
As a result of the growing demand for accurate and reliable personal authentication, biometric recognition, a substitute for or complement to existing authentication technologies, has attracted considerable attention. It has recently been reported that, along with its variants, BioHashing, a new technique that combines biometric features and a tokenized (pseudo-) random number (TRN), has achieved perfect accuracy, having zero equal error rates (EER) for faces, fingerprints and palmprints. There are, however, anomalies in this approach. These are identified in this paper, in which we systematically analyze the details of the approach and conclude that the claim of having achieved a zero EER is based upon an impractical hidden assumption. We simulate the claimants’ experiments and find that it is not possible to achieve their reported performance without the hidden assumption and that, indeed, the results are worse than when using the biometric alone. 相似文献
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96.
S. M. Abdel-Wahaab O. Abo-El Wafa G. E. Kamel S. M. Rashwan 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1986,36(7):305-318
The corrosion behaviour of tin in stagnant mono-, di- and trichloroacetic acids solutions in the pH range 1–6 and at concentrations 4.0 to 5 × 10?4 M was investigated. The results indicate behaviour that is generally the same but there is some dependence on the acid concentration and the pH value. In 4.0 to 10?2 M solutions, the corrosion rate (W) increased with increasing acid concentration and decreasing pH value from 1 to 4 as follows: log W=a+b log C, where b=0.70, 0.42 and 0.35 for tri-, di- and mono-chloroacetic acids respectively. At high concentrations 4.0 to 10?2 M and in the pH range 1–6, the steady state corrosion potential shifted in the negative direction with increase of acid concentration accompanied by an increase in the corrosion rate, indicating that the corrosion process becomes anodically controlled by the complexing of Sn2+ ions with organic acid anions and that the order of aggressiveness is mono-<di-<trichloroacetic acids. In dilute solutions (10?2 to 5.10?4 M) in the pH range 1–6 the steady state potential shifted in the noble direction with increase of acid concentration (accompanied by a remarkable decrease in the corrosion rate). Corrosion inhibition in dilute solutions was attributed to film formation on the surface of tin which may result from the hydrolysis of tin species. 相似文献
97.
Recent studies have implicated herpesvirus 8 and Epstein-Barr virus in the development of cutaneous malignancies in immunosuppressed patients. In order to examine the strength of this association, we examined 37 malignant, pre-malignant and benign cutaneous epithelial neoplasms removed from immunosuppressed organ recipients for the presence of human herpesvirus 8 and Epstein-Barr viral genome sequences using polymerase chain reaction (PCR) and in situ hybridization. We examined 2 actinic keratoses, 1 benign keratosis, 11 invasive squamous cell carcinomas, 17 squamous cell carcinomas in situ and 6 basal cell carcinomas. We also examined 4 basal cell carcinomas, 1 invasive squamous cell carcinoma and 3 squamous cell carcinomas in immunocompetent hosts. In contrast to findings reported by other investigators, we were unable to detect viral genome sequences in any of the biopsies examined. Our findings suggest that human herpesvirus 8 and Epstein-Barr virus likely do not play an etiologic role in cutaneous epithelial oncogenesis in immunocompromised patients. 相似文献
98.
A technique for selecting a low-order system to approximate a high-order model has been suggested by Davison [2]. A critical component in this technique is the criterion used to select the most appropriate order and modes for the low-order approximation. Criteria have been discussed and analyzed by Mahapatra [5], [6], Rao, Lamba, and Rao [7], and Elrazaz and Sinha [3]. In this note we overcome deficiencies in the criteria that have been proposed and we introduce a new criterion which is rigorously justified. The criterion we suggest is also applicable when eigenvalues of the system are nonreal. 相似文献
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Fatty acids and essential oils from hydroponically cultivated Salvia officinalis leaves were analyzed by GC and GC–MS. Four different levels of NaCl (25, 50, 75 and 100 mM) were applied. The first results showed that salt treatment reduced significantly the plant growth by 61% and the total fatty acids (TFA) content by 32% at 100 mM NaCl. Alpha-linolenic, gadoleic, palmitic and oleic acids were the major fatty acids. Moreover, the polyunsaturated fatty acids decreased, while the monounsaturated ones increased with respect to increasing salinity. Regarding the essential oil composition, the main compounds were α-and β-thujone, 1,8-cineole, camphor, α-humulene, viridiflorol and manool at all salt treatments. The yield had a maximum increase at 75 mM NaCl. Hence, sage can be considered as moderately salt sensitive. 相似文献