Convergent optical correlator aligment based on frequency filtering

The convergent correlator is widely used but it presents the drawback of the alignment requirements: fine focusing of the input scene Fourier transform on the filter plane, filter centering, scaling the scene Fourier transform to match the filter size, and azimuth matching of the filter with the input scene. We propose a set of tests to obtain a precise alignment of the convergent correlator. These methods are based on frequency filtering properties and they are applicable either for amplitude input or for phase-encoded input. The tests we present allow us to fulfill all the alignment requirements. The theory on which these tests are based is explained. The experimental results obtained during the alignment procedure are presented. We show some additional verifications of the correct alignment of the convergent correlator.     

Blood speed imaging with an intraluminal array

In applications in which Doppler processing is not possible, such as side-looking intravascular imaging systems, decorrelation methods can be used to estimate blood speed. Here, a method is presented measuring relative blood speed using an FIR filter bank to estimate temporal decorrelation rates. It can be implemented in a modern commercially available ultrasound imaging system with no additional hardware. Both simulations and experiments using an intraluminal scanner appropriate for coronary artery applications have tested the system. In this study, the FIR filter bank is contrasted with previous methods, and its utility is further demonstrated with real-time color flow images from a pig model.     

Mode-specific strategy for controlling a single-molecule reaction

Inelastic tunnelling electrons are a proper excitation source to induce chemical transformations on a single adsorbate. When their energy is tuned to that of molecular vibrational states, the modification may follow complex internal vibrational pathways. Here, we analyse our recent results on the selective excitation of ammonium stretching or bending modes to control the outcome of a simple bond-cleavage reaction. With the help of model calculations, we provide a detailed molecular-scale picture of the competing internal pathways leading to molecular movement. A mode-selective strategy, based on local excitations of specific reaction coordinates, has an important drawback when applied to adsorbate systems due to the problem of fast energy randomization. The success of such a mode-selective strategy is determined here by the ability of the scanning tunnelling microscope to study reactivity in the limit of very low yield and very low power irradiation, in a regime where vibrational heating of the adsorbate/surface system becomes negligible.     

Modeling of zinc solubility in stabilized/solidified electric arc furnace dust

Equilibrium models which attempt for the influence of pH on the solubility of metals can improve the dynamic leaching models developed to describe the long-term behavior of waste-derived forms. In addition, such models can be used to predict the concentration of metals in equilibrium leaching tests at a given pH. The aim of this work is to model the equilibrium concentration of Zn from untreated and stabilized/solidified (S/S) electric arc furnace dust (EAFD) using experimental data obtained from a pH-dependence leaching test (acid neutralization capacity, ANC). EAFD is a hazardous waste generated in electric arc furnace steel factories; it contains significant amounts of heavy metals such as Zn, Pb, Cr or Cd. EAFD from a local factory was characterized by X-ray fluorescence (XRF), acid digestion and X-ray diffraction (XRD). Zn and Fe were the main components while the XRD analysis revealed that zincite, zinc ferrite and hematite were the main crystalline phases. Different cement/EAFD formulations ranging from 7 to 20% dry weight of cement were prepared and subjected to the ANC leaching test. An amphoteric behavior of Zn was found from the pH dependence test. To model this behavior, the geochemical model Visual MINTEQ (VMINTEQ) was used. In addition to the geochemical model, an empirical model based on the dissolution of Zn in the acidic zone and the re-dissolution of zinc compounds in the alkaline zone was considered showing a similar prediction than that obtained with VMINTEQ. This empirical model seems to be more appropriate when the metal speciation is unknown, or when if known, the theoretical solid phases included in the database of VMINTEQ do not allow to describe the experimental data.     

Tight closed-form approximation for the ergodic capacity of orthogonal STBC

In this letter we derive a simple and tight closed-form approximation for the ergodic capacity of orthogonal space-time block coding in arbitrary fading channels. The expression is an analytical function of the power covariance matrix of the channel. In the case of uncorrelated channels the expression only depends on the variances of the channel power gains. These channel statistics can be easily obtained from both analytical and physical fading channel models. Simulations results show the accuracy of the proposed expression     

Steady‐State and Dynamic Reactor Models for Hydrotreatment of Oil Fractions: A Review

The modeling of catalytic hydrotreatment reactors for petroleum fractions have been classified in several ways, for example steady‐state and dynamic, pseudohomogeneous, and heterogeneous, and so on. Depending on the system to be modeled, operating conditions and type of feedstock, these approaches could exhibit some advantages and disadvantages, wide scopes and limitations. In this review, the discussion about those modeling aspects, already published, is used to develop a generalized reactor model, which can be simplified in order to derive each single model previously reported. Some guides to estimate model parameters are also given.     

Non-linear plastic analysis of steel arches under lateral buckling

Curved graphs are proposed that relate the shape of the box cross-section of an arch to the real ultimate lateral strength for various values of length, support conditions and of height of the cross-section.The real ultimate lateral strength of a series of arches is determined and the results obtained are then compared to those provided by Sakimoto and Komatsu [1].Elastic–plastic steel material and geometric non-linearity hypotheses, residual stresses, and initial lateral deflection are all taken into consideration with respect to the real ultimate lateral strength.     

Effects of Dry Grinding on the Structural Changes of Kaolinite Powders

The present study examined the effects of dry grinding, using ball-milling, on the structure of reference well-crystallized (KGa-1) and poorly crystallized (KGa-2) kaolinite powders from Georgia. Grinding produced a strong structural alteration, mainly along the c axis, resulting in disorder and total degradation of the crystal structure of the kaolinite and the formation of an amorphous product. The surface area increased with grinding time, mainly in KGa-2 (maximum value 50.27 m²/g), a result associated with particle-size reduction. These particles became more agglomerated with grinding, and the surface area decreased after 30 min, as confirmed by scanning electron microscopy and particle-size-distribution analysis. There was a limit to particle-size reduction with grinding time. When grinding time was increased, the original endothermic differential thermal analysis (DTA) effects of dehydroxylation in both samples shifted to lower temperatures, decreased in intensity, then disappeared completely after 120 min of grinding. The temperature of the characteristic first exothermic effect shifted slightly to lower temperatures with grinding, although the DTA effects did not increase with grinding time in either kaolinite sample, at least up to 325 min. The amorphous, mechanically activated kaolinite converted into low-crystalline mullite nuclei at a lower temperature than did the unground samples, as deduced by thermal and X-ray observations. This effect was especially important for the KGa-2 sample. Grinding did not seem to influence the formation of silicon-aluminum spinel from kaolinite. The present results may explain why ground kaolinite samples prepared via different routes—e.g., with differences in grinding—behave differently during high-temperature transformations, as reported in the related literature.     

Integrating Travel Delays, Road Safety, Care, Vehicle Insurance and Cost-Benefit Analysis of Road Capacity Expansion in a Unified Framework

Assuming that both road safety and travel time are a function of traffic density and care from a driver’s standpoint, a theoretical framework is developed. First, an expected-utility framework is developed to study the optimal choice of care by a rational driver. Second, the subjective value of traffic density is derived as a measure of drivers’ willingness to pay for simultaneous road safety improvements and travel time savings. Third, the above results are revisited when car insurance is available. Fourth, a simple cost-benefit analysis rule of road capacity expansion is derived when moral hazard is present.