Fe2O3/粉煤灰载氧体化学链燃烧实验与机理研究

提出了一种以粉煤灰为载体制备的新型铁基载氧体。采用同步热重分析仪、小型流化床以及DFT分别研究了新型载氧体的活性与热稳定性,发泡剂含量与反应温度以及粉煤灰主要组分之间的协同作用对新型载氧体性能的影响。研究结果表明,新型载氧体在以CO为燃料的化学链系统中具有较高的活性;新型载氧体较大的孔隙率以及粉煤灰多组分间的协同作用促使850℃下发泡剂含量为10.0%(质量)的新型铁基载氧体的最大转化率(84.9%)比Fe₂O₃/Al₂O₃的最大转化率(54.3%)高30%,且新型铁基载氧体在30个循环测试中表现出良好的热稳定性。载体制备采用的发泡剂含量以及反应温度对新型铁基载氧体性能影响很大,适当的发泡剂含量(约10%(质量))可提高新型载氧体性能。此外,高温下会造成载氧体的烧结现象。最后,采用密度泛函理论(DFT)研究了粉煤灰与载氧体之间的界面作用以及协同氧化CO的电子特性。计算结果表明,粉煤灰和Fe₂O₃之间的界面电荷转移使Fe₂O₃为电正性,促使CO在表面的相互作用,载体和活性组分之间的协同作用降低了载氧体与CO前线轨道能量差,进而促进了CO与Fe₂O₃的反应。     

Friction reduction by texturing of DLC coatings sliding against steel under oil lubrication

It has been demonstrated that tetrahedral amorphous carbon (ta-C) films provide excellent wear and friction properties in dry sliding. Recently the applications of ta-C coatings in lubricated conditions have become more important. The use of carbon coatings aims at reducing the wear and coefficient of friction under minimum lubrication and without hazardous lubricant additives. For optimum tribological performance, a modification of the ta-C coated surfaces is required. The present paper describes an innovative method of coated surface texturing, by which nanometer and micrometer size pores are processed by various methods. Particle masking was used for processing micrometer size pores and for controlling the coating growth conditions in order to produce nanometer size pores in the ta-C surface. The masking by particles yielded a pore geometry which varied from complex shaped channels to small individual pores. The texturing was performed by distributing metallic powder particles on the surface or by direct chemical deposition of metal particles on the substrate in prior to pulsed vacuum arc deposition. The tribological characterization was carried out by applying reciprocating friction tests with controlled lubricant replenishment, in order to simulate metal forming processes. The friction reducing effect, which was observed in the tribological tests, indicated a microlubrication effect of the textured coating surfaces.     

Mechanism of interactions between Hg(II) and Demeton S: an NMR study

The chemical fate of organophosphorus pesticides (OPs) has been proven to depend strongly on the chemistry of their aquatic environment. In particular, metal ions (and metal oxide surfaces) have been known to play an important role in the hydrolytic fate of OPs. Various postulates regarding the mechanism of metal-ion-promoted hydrolysis of OPs have been made over the years. However, direct spectroscopic evidence to pinpoint the hydrolytic products and the exact interaction between metal ions and organophosphorus pesticides are still lacking. We report herein the first in-situ study of the interaction between an aqueous solution of Hg(II) and Demeton S using 1H- and 31P NMR spectroscopy. It was found that the interactions between Hg(II), a soft Lewis acid, and Demeton S tend to be a strong function of the aqueous speciation of Hg(II), and the bonding between Hg2+ and Demeton S does not involve the central P=O bond but rather Hg2+ bonds with the two sulfur atoms in the Demeton S side chain and subsequently stabilizes the Demeton S molecule, a phenomenon not previously reported for any metal ion-OP systems studied. On the basis of this study, generalizations regarding the nature of metal ion binding even within a given class of OPs (i.e., phosphorodithioates, phosphorothioates, phosphorothiolates, etc.) should be avoided or only made with extreme caution.     

Non-smooth multisurface plasticity and viscoplasticity. Loading/unloading conditions and numerical algorithms

Rate-independent plasticity and viscoplasticity in which the boundary of the elastic domain is defined by an arbitrary number of yield surfaces intersecting in a non-smooth fashion are considered in detail. It is shown that the standard Kuhn-Tucker optimality conditions lead to the only computationally useful characterization of plastic loading. On the computational side, an unconditionally convergent return mapping algorithm is developed which places no restrictions (aside from convexity) on the functional forms of the yield condition, flow rule and hardening law. The proposed general purpose procedure is amenable to exact linearization leading to a closed-form expression of the so-called consistent (algorithmic) tangent moduli. For viscoplasticity, a closed-form algorithm is developed based on the rate-independent solution. The methodology is applied to structural elements in which the elastic domain possesses a non-smooth boundary. Numerical simulations are presented that illustrate the excellent performance of the algorithm.     

考虑异方差效应的风电不确定性建模及其在调度中的应用

随着风电在电力系统中渗透率的不断提升,其不确定性为电网的安全经济运行带来了重大挑战。为获得精准的风电不确定性模型,帮助运行人员实现系统的安全经济运行,文中提出了考虑异方差效应的风电预测误差条件概率分布建模方法。首先,分析了风电预测误差与各类因素的相依性水平,并基于分析结果与动态Copula理论,建立了风电波动性与风电预测误差的动态相依性模型;之后,针对边缘分布所显示出的时域特征,结合差分整合移动平均自回归(ARIMA)模型与广义自回归条件异方差(GARCH)模型,考虑异方差效应,建立了时变边缘分布模型;最后,将两模型相结合,给出了不同波动水平下的风电条件预测误差分布情况,并在不确定性机组组合模型中进行验证,证明了模型的有效性。     

Portable TL dosemeter--ESD phantom combination for chest and lumbar spine radiography

A thermoluminescence dosemeter (TLD)—entrance surfacedose (ESD) phantom combination was calibrated in terms of air-kermain IEC RQR X-ray radiation qualities between 50 and 150 kV.The ESD phantom was designed and constructed as a part of thework. With the combination, air-kermas were measured for fourradiological examinations (two chest and two lumbar spine examinationsin two hospitals), and converted to ESD_a using Monte–Carlocalculated BSF data tabulated for different tube voltages, filtrationsand beam diameters at 1 m distance. The results agreed withthe ionisation-chamber measurements within the reported overalluncertainty of the TLD method. In the calibration, the ESD phantomcan be replaced by the ISO water slab phantom unaffecting thereported overall uncertainty. Backscatter-related parametersfor the ISO water slab phantom and the newly designed ESD phantomwere determined for the IEC RQR qualities used in the secondarystandard dosimetry laboratory of STUK at 1 m distance, includingan approximate H_p(10)/H_p(0.07) ratio.     

Simulation of pressure swing adsorption in fuel ethanol production process

Fermentation derived ethanol is gaining wide popularity as a car fuel additive. A major challenge in the production of ethanol is the high energy cost associated with the separation of ethanol from the large excess of water. Distillation is usually the method of choice; however, water cannot be completely removed due to the presence of the azeotrope. The pressure swing adsorption (PSA) process is attractive for the final separation since it requires little energy input and is capable of producing a very pure product. The goal of this work was to perform a thorough analysis of the PSA process and find process improvements with the aid of mathematical modeling.

A general purpose package for the simulation of a cyclic PSA process was developed. The system of partial differential equations was solved via method of lines using a stiff equation integration package. Parameters for the model are based on the data from an operating plant as well as data from the literature. For the ethanol production technology our model provides a fundamental understanding of the dynamics of the cyclic process and effects of some operating parameters.     

POD analysis of oscillating grid turbulence in water and shear thinning polymer solution

Oscillating grids are frequently used with water and Newtonian fluids to generate controlled turbulence and mixing. Yet, their use with shear thinning fluids still requires experimental characterization. Proper orthogonal decomposition (POD) is applied to PIV measurements of the flow generated by an oscillating grid in water and a shear thinning dilute polymer solution (DPS) of xanthan gum. The aims are to investigate the ability of POD to isolate periodic flow structures, and to use it to describe the effects of the shear thinning property. A dominance of the low order POD modes is evidenced in DPS. The methods applied in blade stirred tanks to identify oscillatory motion fail here. However, a strong mode coupling in the grid swept region is observed, determined by the working fluid and by an underlying chaotic nature of the flow. Possibilities of reconstructing turbulence properties using high order modes are discussed.