In this work it is presented a study on the residence time distribution (RTD) of particles in a co-current pilot-plant spray dryer operated with a rotary atomization system. A nuclear technique is applied to investigate the RTD responses of spray dryers. The methodology is based on the injection of a radioisotope tracer in the feed stream followed by the monitoring of its concentration at the outlet stream. The experiments were performed during the drying of aqueous suspensions of gadolinium oxide. The RTD responses obtained experimentally presented good reproducibility, indicating that the technique applied is well suited to investigating fluid-dynamics of spray dryers. In addition to the experimental investigation, a mathematical model was used to describe the RTD experimental curves. 相似文献
An efficient hypersingular boundary integral equation method for three-dimensional fracture mechanics was presented in a previous paper. The details of the numerical implementation of this method are further discussed herein. In particular, an algorithm for achieving the required differentiability of the crack surface displacement function is discussed. To illustrate the utility of the method, computational results for several strongly interacting multiple-crack geometries are presented. The calculated stress intensity factors are in excellent agreement with those obtained by an approximate analytical method due to Kachanov and Laures. 相似文献
Two-dimensional, unsteady flow around bodies of complex geometry (or multiple bodies) at high Reynolds number is simulated using the vortex method. This method is modified to take into account the sub-grid scale phenomena through a second order velocity structure function model adapted to the Lagrangian scheme. The dynamics of the body wake is computed using the convection-diffusion splitting algorithm; the convection process is carried out with a Lagrangian Adams-Bashforth time-marching scheme and the diffusion process is simulated using the random walk method. The pressure distribution is obtained using an integral equation derived from the pressure Poisson equation, which was first developed for a single body. Results for the numerical simulation around a linear cascade of airfoils are presented. As the flow is periodic in the y direction, the discrete vortex shedding need only be considered for a reference airfoil. The flow characteristics around the NACA 65-410 series airfoils are calculated and comparisons are made with results available in the literature. 相似文献
We compute the temperature dependent magnetic susceptibility of the single-impurity, two-channel Anderson model with an alternative multi-step numerical renormalization-group transformation, previously applied only to the two-impurity single-channel Kondo model. Compared with the traditional transformation, the new procedure requires substantially less memory and computational time, and opens therefore perspectives for the application of the numerical renormalization-group procedure to more complex Hamiltonians. 相似文献
Subalpine fir (Abies lasiocarpa Hook) lumber containing wetpockets (wetwood) was used for the measurements of gas permeability and the results were then compared to the gas permeability of normal wood, which was free of the wetpockets. The impacts of pretreatment methods were also investigated, including steaming at green condition, steaming at fiber saturation point (FSP), microwave treatment, and radio-frequency treatment. Results from this study demonstrated that both the transverse and the longitudinal gas permeability of subalpine fir wetwood are greater than that of normal wood. There is no significant change in the permeability after 4-h steaming pretreatment at green condition and at FSP. The impacts of microwave and radio-frequency pretreatments were not significant, but the findings cannot be generalized because they may depend on the power intensity applied. 相似文献
Hormone-refractory prostate cancer (HRPC) patients often have nonmeasurable disease. In such patients, predictive biomarkers other than tumor response may be required to compare therapeutic effects. We examined the predictive value for survival of various clinical and laboratory parameters, including prostate-specific antigen (PSA), in HRPC patients treated with suramin. Data from 103 HRPC patients were analyzed using various survival analyses, the likelihood ratio approach, and logistic regression analyses. When pretreatment factors, percentage decrease in PSA at 4 weeks from start of treatment (deltaPSA), and updated survival data were fit by a multivariate Cox proportional hazards model, acid phosphatase, lactate dehydrogenase, and deltaPSA were significant, with risk ratios close to 1. There was a decrease in likelihood ratio with increasing APSA. A logistic regression model was developed to predict the probability of <1 year of survival from the start of treatment. Hemoglobin and deltaPSA were found to be significant variables. However, in view of the complexities involving the relationship between PSA expression and prostate cancer growth and possible selective effect of treatment on PSA, further prospective testing is necessary. Therefore, deltaPSA cannot necessarily be used as a biomarker for survival response in individual patients during the evaluation of the therapeutic response of HRPC to new antineoplastic drugs. 相似文献
Contracts play an important role in business management where relationships among different parties are dictated by legal rules. Electronic contracts have emerged mostly due to technological advances and electronic trading between companies and customers. New challenges have then arisen to guarantee reliability among the stakeholders in electronic negotiations. In this scenario, automatic verification of electronic contracts appeared as an imperative support, specially the conflict detection task of multi-party contracts. The problem of checking contracts has been largely addressed in the literature, but there are few, if any, methods and practical tools that can deal with multi-party contracts using a contract language with deontic and dynamic aspects as well as relativizations, over the same formalism. In this work we present an automatic checker for finding conflicts on multi-party contracts modeled by an extended contract language with deontic operators and relativizations. Moreover a well-known case study of sales contract is modeled and automatically verified by our tool. Further, we performed practical experiments in order to evaluate the efficiency of our method and the practical tool.
Ethylene-propylene copolymers have been prepared by using Ziegler-Natta catalysts based on TiCl4, MgCl2, PCl3 and (n-Bu)3PO4. The catalysts TiCl4/MgCl2/PCl3 and TiCl4/MgCl2/(n-Bu)3PO4 were prepared by reacting TiCl4 with pretreated MgCl2. The support was prepared by ball milling of MgCl2 with varied amounts of PCl3 or (n-Bu)3PO4. The addition of PCl3 has remarkably increased the MgCl2 surface area in comparison with (n-Bu)3PO4. The effects of PCl3 and (n-Bu)3PO4 on ethylene homopolymerization, ethylene-propylene copolymerization and on copolymer properties were evaluated. The catalyst
system containing PCl3 permitted to synthesize propylene-ethylene copolymers with up to 75% (w/w) of propylene and provided control of copolymer
crystallinity. The reduction of the copolymer molecular weight distribution suggested that PCl3 acted as an internal donor, poisoning some active catalytic sites.
Received: 2 April 1997/Revised: 6 June 1997/Accepted: 18 June 1997 相似文献
In this work, hydrogen peroxide reactions, i.e. H2O2 decomposition and oxidation of organics in aqueous medium, were studied in the presence of activated carbon. It was observed that the carbon pre-treatment with H2 at 300, 500, 700 and 800 °C resulted in an increase in activity for both reactions. The carbons were characterized by BET nitrogen adsorption, thermogravimetric analyses (TG), temperature programmed reduction (TPR), electron paramagnetic resonance (EPR), iodometric titration and determination of the acid/basic sites. TPR experiments showed that activated carbon reacts with H2 at temperatures higher than 400 °C. The treatment produces a slight increase in the surface area. EPR analyses indicate the absence of unpaired electrons in the carbon. Iodometric titrations and TG analyses suggested that the treatment with H2 generates reduction sites in the carbon structure, with concentration of approximately 0.33, 0.53, 0.59, 0.65 and 0.60 mmol/g for carbons treated at 25, 300, 500, 700 and 800 °C, respectively. It was also observed the appearance of basic sites which might be related to the reduction sites. It is proposed that these reducing sites in the carbon can activate H2O2 to generate HO* radicals which can lead to two competitive reactions, i.e. the hydrogen peroxide decomposition or the oxidation of organics in water. 相似文献