Cu2+-doped (0–2 at%) ZnS nanoparticles stabilized by 2-mercaptoethanol (2-ME) were successfully prepared using wet precipitation route in aqueous solution. The structural and optical characteristics were studied by various techniques. XRD pattern showed zinc blende cubic structure of Cu2+-doped ZnS with grain size of 4±0.5 nm. Spherical shape and well distribution of particles is confirmed by TEM, SEM and STM microscopy. Copper doping were identified by elemental dispersive (EDS) spectrometry. UV–vis spectroscopy revealed strong confinement effect due to blue shift in absorption shoulder peak as compared to bulk ZnS. Red luminescence band at~657 nm on Cu2+ doping may be arising from recombination of electrons at sulfur vacancies (Vs) and Cu(t2) states formed at ZnS band gap. Optimum concentration of 0.25 at% (red band) of Cu2+ doping was selected by the observed enhanced PL emission. 相似文献
Gas condensate reservoirs usually exhibit complex flow behaviors due to the buildup of condensate bank around the wellbore when the bottom-hole pressure falls below the dew point. Hydraulic fracturing improves well productivity by delaying the onset of dew point pressure and also reducing the condensate saturation near the wellbore area. The authors present the results of a study that compared the near wellbore behaviors and productivities of a vertical nonfractured well and a vertical hydraulically fractured well in a low permeability lean gas condensate reservoir. Results show that there is no indication of capillary number effects in this low permeability reservoir because of low production rates. 相似文献
The Naive Bayes classifier is a popular classification technique for data mining and machine learning. It has been shown to be very effective on a variety of data classification problems. However, the strong assumption that all attributes are conditionally independent given the class is often violated in real-world applications. Numerous methods have been proposed in order to improve the performance of the Naive Bayes classifier by alleviating the attribute independence assumption. However, violation of the independence assumption can increase the expected error. Another alternative is assigning the weights for attributes. In this paper, we propose a novel attribute weighted Naive Bayes classifier by considering weights to the conditional probabilities. An objective function is modeled and taken into account, which is based on the structure of the Naive Bayes classifier and the attribute weights. The optimal weights are determined by a local optimization method using the quasisecant method. In the proposed approach, the Naive Bayes classifier is taken as a starting point. We report the results of numerical experiments on several real-world data sets in binary classification, which show the efficiency of the proposed method. 相似文献
OBJECTIVE: In order to evaluate possible artefact in interpretations of contractile behaviour in isolated heart experiments, the relative elastances of series coupled non-contractile and contractile components of the left ventricle of the isolated heart were evaluated. METHODS: Hearts were isolated from ferrets and rabbits and mounted on a servo-controlled volume regulation device. These hearts were made to beat isovolumetrically until a selected volume perturbation was introduced. Constant flow volume withdrawals at two flow values were performed over a period of < 20 ms centred around the time of peak isovolumetric pressure. Three levels of isovolumetric pressure were produced using basal, extrasystolic, and potentiated beats. Pressure responses to volume withdrawals at two flows and three isovolumetric pressures were then analysed using a mathematical model to evaluate relative values of series coupled contractile and non-contractile elastances. To validate the analysis procedure, a non-contractile series artefact with known elastance was coupled to the left ventricle; volume perturbations were then applied to the coupled left ventricle-artefact system; responses were analysed and the estimate of series coupled non-contractile elastance was compared to the known elastance of the added artefact. RESULTS: A wide range of isovolumetric pressures [208(SD 40) mmHg] was produced in the ferret with basal, extrasystolic, and potentiated beats. A lesser range of isovolumetric pressures [50(15) mmHg] was produced in the rabbit. The mathematical model fitted the data very well in both the ferret and rabbit. The elastance of the series coupled non-contractile component could be estimated only in some ferrets. When estimated in the ferret, the elastance of the series coupled non-contractile component was never less than 4x that of the contractile component. When a series artefact of sufficiently low value was coupled with the native left ventricle, the elastance of the non-contractile component could be reliably estimated in both ferrets and rabbits and the estimated value approximated that of the added artefact. This indicated that the elastance of the series coupled non-contractile component of the native left ventricle was much higher than that of the added artefact. CONCLUSIONS: The series coupled non-contractile component of the isolated heart possesses a very much higher elastance than the contractile component. In fact, the elastance of the non-contractile component is so great that it contributes very little to the dynamic behaviour of the left ventricle. Virtually all of the elastance of the left ventricle of the isolated heart is due to the contractile component. 相似文献
A unified approach is presented for calculating the resonant frequencies of all the modes in cylindrical cavities axisymmetrically loaded with dielectrics. In this method, the radial variations of the field components in the resonator are expressed in terms of first-degree finite-element polynomials, whereas the axial variations of the field components are approximated by trigonometric functions. To calculate the resonant frequencies, an H-vector variational formulation is employed and minimized with respect to the coefficients of the expanded field components. Spurious solutions which are inherent in the finite-element technique are effectively eliminated by means of a penalty term included in the variational expression, imposing a divergence-free magnetic field constraint. To show the capability of the method, resonant frequencies of several cylindrical cavities, including those loaded with dielectric rods and dielectric rings, were calculated. A mode chart is presented which can be used for designing certain multimode dielectric-loaded cavity filters. In contrast to other rigorous techniques reported in the literature, the present method is highly efficient when dielectrics are fully extended along the cavity length 相似文献
Facial feature extraction algorithms play an important role in many applications of face biometrics such as face recognition for person identification, classification of emotions by facial expression recognition and age estimation using facial images. In this paper, an integration of different type of feature extraction algorithms is applied on facial images for accurate age estimation. This integration is performed by using two-level fusion of features and scores with the help of feature-level and score-level fusion techniques. In our proposed method, the advantage of using different types of features such as biologically inspired features, texture-based features, and appearance-based features is used. Feature-level fusion of biologically inspired and texture-based methods is integrated into the proposed method and their combination is fused with an appearance-based method using score-level fusion. Experiments on the publicly available MORPH and FG-NET databases prove the effectiveness of the proposed method and the proposed method outperforms many of the state-of-the-art systems. 相似文献
In this paper, two new practical attacks on some secret sharing-based data outsourcing schemes are first introduced, and several other security and performance issues with the existing schemes are also explored. The existing and new attacks exploit the information about the share range boundaries or the correspondences between the secret values and shares. A range expansion technique is then proposed to thwart one of the attacks. It expands the ranges in every range predicate in the submitted queries in order to hide the share range boundaries from any query observer. Next, a mapping method is proposed to thwart the other attacks. It maps each secret value to a mapping value using a secret one-to-many mapping with a finite set of linear mapping rules so that the tuples of shares are generated from the mapping values rather than directly from the secret values. The proposed mapping method works as an additional layer of security and addresses any attack based on the correspondences between the secret values and shares. At the same time, it preserves the homomorphism property of secret sharing. Finally, a new secure data outsourcing scheme is elaborated on secret sharing, the proposed mapping method, and the proposed range expansion technique. The proposed scheme is resistant to various attacks and also some inferences. It supports the fully server-side or a partially server-side query execution of most types of queries. The experimental results confirm that the proposed scheme is quite practical and efficient.