Energetics of charged point defects in rutile TiO2 by density functional theory

The defect formation energies of all possible charge states of point defects in TiO₂, including titanium interstitials, titanium vacancies and oxygen vacancies, are calculated in the phase space of temperature, oxygen partial pressure and Fermi level by combining density functional theory (DFT) and thermodynamic calculations. The point defect phase diagram illustrates that fully charged defects dominate in most regimes. The calculations not only give reasonable defect formation energies compared with prior experimental measurements, but also predict n-type TiO₂ at high T and low P_O2, and p-type TiO₂ at low T and high P_O2, which agrees well with experimental data. In addition, we evaluate methods for correcting the effects of artificial electrostatic interactions caused by periodic boundary conditions in the DFT calculations, including the electrostatic potential alignment correction (ΔV correction) and the Makov–Payne correction.     

Thermochemical modeling of refractory corrosion in slagging coal gasifiers

Slagging coal gasifiers suffer corrosive attack on the refractory liner and these interactions were thermochemically simulated. The slag is observed to penetrate the refractory, which complicates modeling the phase behavior of the slag-penetrated interior of the refractory. A simple strategy was adopted such that stepwise changes in composition with decreasing slag content were assumed to account for the compositional changes as slag penetrates the refractory. The thermochemical equilibrium calculations following this strategy typically yielded three solution phases as well as the stoichiometric crystalline phases AlPO₄ and Ca₃(PO₄)₂ depending on composition/penetration. Under some conditions a slag liquid miscibility gap exists such that two slag liquids coexist.     

q(T,T_w)=α(1/T_w-1/T)传热情况下卡诺热泵的最佳供热系数与供热率间的关系

本文导出了卡诺热泵工作于非线性传热q(T,T_W)=a(1/T_W-1/T)的情况下,最佳供热系数CP_0与供热率π间的关系:π=α/(T_HT_L)((T_L-(CP_0-1)/(CP_0)T_H)/(1+δ(CP_0-1)/(CP_)))~2),式中并给出了上述关系的一些应用。     

Discussion on refrigeration cycle for regenerative cryocoolers

Based on review and analysis of thermodynamic efficiency ε of the Carnot cycle and the cycle with two isothermal and two polytropic processes, another thermodynamic cycle with two isentropic and two polytropic processes, which can achieve the Carnot value of thermodynamic efficiency, is testified theoretically. Thermodynamic efficiency expressions of a number of ideal regenerative refrigeration cycles are derived, including the ideal pulse tube refrigeration cycle. A classified branch chart and a plot of ideal thermodynamic efficiency of regenerative refrigeration cycles are given for the purpose of comparison.     

An Algorithm for Predicting RNA Secondary Structure Including Pseudoknots

A new model and corresponding dynamic programming algorithm are presented to predict RNA secondary structure including pseudoknots in this paper. This algorithm can compute arbitrary planar pseudoknots and one non-planar pseudoknots in O（n5） time and O（n4） space.     

Soret-‘shifted’ dew-point temperatures for surfaces exposed to hydrocarbon vapors dilute in compressed nitrogen

Soret-driven species transport causes concentration non-uniformities in the immediate vicinity of ‘cold’ surfaces immersed in undersaturated vapor-containing streams. These concentration non-uniformities, in turn, alter corresponding condensation onset temperatures, often by as much as 30 K (i.e., ca. 3%) in previously studied, near-atmospheric pressure combustion systems [see, e.g., Rosner, D.E. and Nagarajan, R., 1985. Chemical Engineering Science 40 (2), 177]. Because high-pressures often cause remarkable increases in the relevant binary Soret factor, α_T,12, we investigate here the importance of these vapor phase ‘transport’ effects for ‘compressed’ N₂ streams containing dilute quantities of an alkane: C₁₂H₂₆ (n-dodecane) or C₈H₁₈ (n-octane). We invoke the virial equation of state (VES) to predict gas phase non-ideality, and its appreciable effect on previously available ideal gas Soret factors. Our illustrative numerical results, valid for, say, nominally 1000 K N₂ streams up to pressures of over 100 atm, reveal that high-pressure Soret ‘shifts’ in T_dp can amount to ca. 80%, even at surface temperatures above the equilibrium freezing points of these condensates. We conclude that these high-pressure vapor phase transport phenomena will not only influence the interpretation of such hot gas/‘cold’ surface ‘dew-point’ measurements, they will significantly raise the temperatures at which containment or immersed surfaces must be maintained to avoid the ravages of corrosive or insulating inorganic condensates [Rosner, D.E., Chen, B.K., Fryburg, G.C., Kohl, F.J., 1979. Combustion Science and Technology 20, 87; Rosner, D.E., 1988a. Invited paper, Benjamin G. Levich Memorial Issue of Journal of Physico-Chemical Hydrodynamics 10 (5/6), 663]. In principle, the present theory could itself be used to study the pressure dependence of the binary Soret factor—at least for systems with well-characterized saturation vapor pressures.     

新型高强韧性冷作模具钢DM9的组织和性能

研究了新型模具钢DM9（含量范围％：0．83－0．95C，3．5－4．2Cr，1．9－2．5W，0．8－1．2Mo，0．7－1．1Si，0．35－0．55V）的组织和性能。试验结果表明，该钢DM9在840℃退火时存在M3C，M23C6，M6C，M7C3和MC5种类型碳化物，碳化物平均尺寸0．66μm；该钢950℃淬火220℃回火后，硬度HRC62，抗弯强度σbb3800MPa，冲击韧度ak72J/cm^2，其模具有高的寿命。     

整体煤气化联合循环系统两种脱硫除尘方法的比较

介绍了整体煤气化联合循环系统(IGCC)的两种净化系统——常温湿法净化系统和高温干法净化系统的结构和除尘脱硫的原理,并基于净化流程结构与热力学定律对两种净化系统进行了比较,指出在采用高温干法净化系统的IGCC整体效率要高于采用常温湿法净化系统的。