A comparative evaluation of crumb rubber and devulcanized rubber modified binders

One of the most prominent uses of ground tire rubber (GTR) is in rubber-modified asphalt industry. Besides improving performance properties of binders, GTR induces some drawbacks like weak storage stability and inferior low temperature (LT) performance. This study sought to rectify these shortcomings through using devulcanized rubber (DVR) in place of common GTR. Binder performance grading, multiple stress creep and recovery, and storage stability tests were conducted. More resistance against traffic loads at high temperatures was observed as DVR's advantages over GTR, while its weaker LT characteristics and lower storage stability can prevent it from being a viable alternative.     

聚凝体聚合物膨胀特性实验研究

为了解决水驱窜流严重和采收率低的问题，对聚凝体聚合物的抗酸、抗碱、抗盐以及热稳定性进行了评价实验。实验结果表明，在酸性、碱性和高盐条件下，聚凝体聚合物的吸水膨胀速度变慢，但充分吸水膨胀后的体积膨胀倍数仍能达到10倍左右，具有较强的化学稳定性和热稳定性，吸水膨胀性好，能够适应恶劣的油藏条件。岩石流动实验表明，聚凝体聚合物驱可在聚合物驱的基础上再提高采收率12％。     

Phase formation and texture of nickel silicides on Si1−xCx epilayers

We investigated the phase formation and texture of nickel silicides formed during the reaction of 10 nm sputter deposited nickel with Si_1−xC_x epitaxial layers on Si(1 0 0) substrates, having a carbon content between 0 and 2.5 atomic percent. It was found that both the formation temperature as well as the texture of the metal-rich phases is influenced by the amount of carbon in the Si_1−xC_x layer. To determine the influence of the location of the carbon during the silicidation process we also investigated the reaction of 10 nm nickel on Si(1 0 0) substrates, where carbon was either alloyed in the nickel layer or deposited as an interlayer at the interface between the nickel and the substrate. Depending on the location of the carbon, a different thermal stability of the layer was found.     

A Multistage Closed-loop Sigma-Delta modulator (MSCL)

A new family of high order Sigma Delta modulators called MSCL (Multi Stage Closed-loop) is presented in this paper. They use a global feedback to lower the sensitivity to circuit imperfections. This feedback from the output of the modulator is the sum of the output of each comparator so that no digital prefiltering is required before summing up these signals. However, easy calibration will be required to compensate for the feedback imperfections.MSCL modulators present the same insensitivity to circuit imperfections as classical multi-order one-bit converters, but reach the performance of high-order MASH (MultistAge noise SHaping) modulators. They help make high-order low-pass or band-pass modulators without limit cycles so that their quantizing noise characteristics are similar to those predicted by the linear simplified model.     

Overlapping of heterogeneous and purely thermally activated solid-state processes in the combustion of a bituminous coal

Mechanistic studies of coal combustion have long highlighted the variety of reaction pathways along which gasification may take place. These involve chemisorption of reactants, formation of surface oxides, surface mobility of chemisorbed species, and product desorption. At the same time, exposure of the solid fuel to high temperatures is associated with solid-state thermally activated processes. Altogether, the course of gasification may be profoundly affected by the overlapping and interplay of heterogeneous oxidation with purely thermally activated solid-state reactions. In the present work the combustion of a South African bituminous coal is analyzed in the framework of a simplified reaction network that embodies heterogeneous oxidative and thermally activated processes (pyrolysis, thermal annealing, coal combustion, char combustion, oxygen chemisorption) active both on the raw coal and on its char. The kinetics of each process of the network is assessed by a combination of thermogravimetric and gas analysis on coal and char samples. The analysis is directed to the determination of the prevailing combustion pathway, established from the interplay of oxidative and solid-state thermally activated processes, as a function of combustion conditions (temperature, heating rate, particle size).     

Problems of hydrogen application in space power plants and power propulsion plants

Application of hydrogen is a necessary condition to achieve acceptable power and overall-dimensional characteristics of space power and propulsion plants. Some functional elements as part of the plants require protection from hydrogen, which is provided by construction and technological preparation of materials. For subsequent improvement of the plants, it is necessary to look for materials with low hydrogen penetrability in the temperature range of 800–2500 K and also for protective coatings on graphite for conditions of thermocycling in the range of 300–2100 K.     

Modeling of transient natural convection heat transfer in electric ovens

Prediction of transient natural convection heat transfer in vented enclosures has multiple applications such as understanding of cooking environment in ovens and heat sink performance in electronic packaging industry. The thermal field within an oven has significant impact on quality of cooked food and reliable predictions are important for robust design and performance evaluation of an oven. The CFD modeling of electric oven involves three-dimensional, unsteady, natural convective flow-thermal field coupled with radiative heat transfer. However, numerical solution of natural convection in enclosures with openings at top and bottom (ovens) can often lead to non-physical solutions such as reverse flow at the top vent, partly a function of initialization and sometimes dependent on boundary conditions. In this paper, development of a physics based robust CFD methodology is discussed. This model has been developed with rigorous experimental support and transient validation of this model with experiments show less than 3% discrepancy for a bake cycle. There is greater challenge in simulating a broil cycle, where the fluid inside the cavity is stably stratified and is also highlighted. A comparative analyses of bake and broil cycle thermal fields inside the oven are also presented.     

Supercooling salt hydrates: Stored enthalpy as a function of temperature

Thermal energy can be stored in supercooled liquids where the material is in thermal equilibrium with its surroundings. The stored latent heat of fusion is released by triggering the crystallization of the supercooled substance. In this study, enthalpy–temperature curves including the effect of supercooling are measured for some well known supercooling salt hydrates (disodium hydrogen phosphate dodecahydrate, sodium acetate trihydrate and STL-47). A series of properties relevant for supercooling energy storage applications are identified, including the optimal working temperature range for the materials, temperature increase during crystallization as a function of degree of supercooling, available enthalpy at different temperatures, and fraction of enthalpy lost in the initial supercooling phase. The enthalpy–temperature curves are measured by a simple and inexpensive method.     

Thermal performance of an electrochromic vacuum glazing

Using a three-dimensional finite volume model, the thermal performance of an electrochromic vacuum glazing was simulated for insolation intensities between 0 and 1200 W m⁻². The electrochromic evacuated glazing simulated consisted of three glass panes 0.5 m by 0.5 m with a 0.12 mm wide evacuated space between two 4 mm thick panes supported by 0.32 mm diameter pillars spaced on a 25 mm square grid contiguously sealed by a 6 mm wide metal edge seal. The third glass pane on which the electrochromic layer was deposited was assumed to be sealed to the evacuated glass unit. The simulations indicate that when facing the indoor environment, the temperature of the glass pane with the electrochromic layer can reach 129.5 °C for an incident insolation of 600 W m⁻². At such temperatures unacceptable occupant comfort would ensue and the durability of the electrochromic glazing would be compromised. The glass pane with the electrochromic layer must therefore face the outdoor environment.     

基于Matlab/Simulink的火电厂热力系统模块化建模方法

本文以常规热平衡法为基础,引入模块建模的思想,阐述了模块化建模的开发过程,提出了一种火电厂热力系统模块化建模的方法。通过对热力系统分解、模块化,Matlab／Simulink为开发工具建立了火电厂常用设备的模型库,并给出实例验证了所提方法的正确性和可行性。