Maximum Principle for Markov Regime-Switching Forward–Backward Stochastic Control System with Jumps and Relation to Dynamic Programming

This paper presents a sufficient stochastic maximum principle for a stochastic optimal control problem of Markov regime-switching forward–backward stochastic differential equations with jumps. The relationship between the stochastic maximum principle and the dynamic programming principle in a Markovian case is also established. Finally, applications of the main results to a recursive utility portfolio optimization problem in a financial market are discussed.     

复合掺杂氧化物La0.5Sr0.5CoO2.91的性能和稳定性

采用固相反应法和柠檬酸-硝酸盐溶胶-凝胶低温自蔓延燃烧法（简称柠檬酸法）合成了La0.5Sr0.5CoO2．91（LSC）复合氧化物。借助XRD和SEM对不同制备方法合成粉体的晶体结构和晶粒形貌进行了研究。结果表明：固相反应法可制得均一钙钛矿结构的LSC氧化物，柠檬酸法除制得LSC氧化物外，还有LaSrCoO4相的生成。柠檬酸-硝酸盐溶胶-凝胶低温自蔓延燃烧法合成粉体的粒度相对较小。为研究以Ce0．9Gd0.1O1．95（GDC）为电解质的固体氧化物燃料电池阴极材料的性能，将LSC粉体与GDC粉体按6：4（质量比）制备了固体氧化物燃料电池（SOFC）的阴极片。在空气气氛下使用直流四探针法研究了烧结样品300～800℃的电导率，发现由柠檬酸法得到粉体制备的阴极片的电导率值较高。将制备的样品置于马弗炉中800℃条件下烧结800h，比较失效前后电导率的变化情况，并借助XRD，SEM等测试手段分析样品电导率变化的原因。分析发现，失效后两种样品的电导率值都有所降低，且样品中都有新相生成，晶体形貌有较大的变化。     

Relationship between surface microstructure and properties of supported catalyst Rh/Ys

The inner structure of Rh/Ys,a novel high efficiency supported catalyst,and the spreading of Rh on the Ys surface were analyzed through electron transmission microscopy and scanning tunnel microscopy.The relationship between the distribution of Rh over the support and the preparation temperature of th catalyst was determined.The formation of Rh-C bond was confirmed by XPS and far-IR spectra.The loss of Rh from the surface of the support and the catalytic activity under different preparation conditions have been compared.The internal factors for the high activity and high stability of the novel Rh/Ys catalyst have been discussed.     

Kinetic studies on vapor phase carbonylation of methanol to acetic acid over Rh/Ys catalyst

A novel catalyst Rh/Ys for the carbonylation of methanol to acetic acid with CH3I as the promoter shows excellent activity and selectivity.The reaction is kinetically controlled.The reaction rate is in proportion to the concentration of Rh and CH3I but has nothing to do with those of CH3OHH and CO.The surface active energy is Ea ~51.02 kJ/mol.A mechanism is also proposed.     

Mechanism of Formation and Consequent Evolution of Active Cellulose during Cellulose Pyrolysis

An intermediate product that was yellow, soluble, and solid was obtained in a high-radiation flash pyrolysis reactor. Under two different radiant heat fluxes, the yields tended to both increase initially until achieving a steady state, and then increase again with the progress of reaction. The compositional analysis of the yellow product was performed on high performance liquid chromatography (HPLC). It was indicated that the product mainly consisted of oligosaccharides, glucose, levoglucosan, methylglyoxal and so on. The compounds including oligosaccharides such as cellobiose and cellotriose, and monosaccharides such as glucose were regarded as active cellulose. Under the higher heat flux, the relative yield of the active cellulose increased initially, followed by a decreasing trend, and achieved a maximum mass fraction of 68% (w) in the soluble yellow product. The oligosaccharides with higher degree of polymerization (DP) were the primary components. Under the lower heat flux the yield of active cellulose was relatively lower, achieving a maximum of about 57% (w), and more saccharides with lower DP were contained. It was suggested that active cellulose was quite unstable at high temperature, and easily decomposed into saccharides with lower DP, even char, volatiles, and gaseous products. Finally an improved mechanism was proposed to describe the reaction route of formation and consequent evolution of active cellulose during cellulose pyrolysis.     

Mechanism study of wood lignin pyrolysis by using TG–FTIR analysis

In order to study the pyrolysis mechanism of lignin, Van Soest's method was performed to extract lignin from different species of biomass. Fir and birch lignins were selected as the testing samples and corresponding microstructure was studied by a Fourier transform infrared spectrometry. Several characteristic bands were observed to show the presence and species of lignin. Following experimental research on pyrolysis of lignins from fir and birch were carried out on a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometry. Wood lignin undergoes in three consecutive stages, corresponding to the evaporation of water, the formation of primary volatiles and the subsequent release of small molecular gases. The main pyrolysis sections and the maximum weight loss rates are quite different for different wood species. Phenols are the main volatile products, in addition to alcohols, aldehydes, acids, and so on. As the main gaseous products, CO, CO₂, CH₄ are released out greatly.     

CO2化学吸收剂

化学吸收法是燃后CO₂捕集的主要方法之一,本文介绍了化学吸收法脱除CO₂的系统工艺及特点,综述了CO₂吸收剂的研究现状,介绍了典型吸收剂:氨水吸收剂、氨基酸盐吸收剂、碳酸钾吸收剂的研究进展,以及新型吸收剂研究方向:混合胺吸收剂、相变吸收剂、离子液体吸收剂、纳米流体吸收剂,CO₂开关型吸收剂和新型有机胺吸收剂,并分析比较了各种吸收剂的优缺点。分析表明混合胺和相变吸收剂节能潜力较大,较其他四种新型吸收剂更为成熟,因此具有一定的工业化潜力。     

离子色谱法同时测定离子液体中六氟磷酸根及痕量杂阴离子

建立了一种同时测定离子液体中六氟磷酸根(PF~6)和痕量杂阴离子氟、氯、溴(F~,Cl~,Br~)的离子色谱方法(IC)。样品经溶解、稀释、过滤后用Dionex IonPac AS22分离柱(250 mm×4 mm)分离,淋洗液为碳酸盐-乙腈体系(体积比为70:30),流速1.0 mL/min,采用Dionex DS6电导检测器检测,外标法定量。F~,Cl~,Br~和PF~6的线性范围分别为0.5～50 μg/L、10～200 μg/L、10～200 μg/L和0.9～45 mg/L,线性相关系数分别为0.9999,0.9998,0.9999和0.9998,加标回收率为94.5%～100.5%,相对标准偏差为0.63%～1.03%,检出限(以信噪比为3计)分别为0.5 μg/L、2.0 μg/L、5.0 μg/L和0.9 mg/L。该方法用于离子液体中六氟磷酸根和痕量杂阴离子的同时测定,结果令人满意。     

Non-uniform distribution of gas–solid flow through six parallel cyclones in a CFB system: An experimental study

In large-scale circulating fluidized bed (CFB) boilers, it is common to use multiple cyclones in parallel for the capture of solids, assuming that gas–solid flow to be the same in the cyclones. This article presents a study investigating gas–solid flow through six parallel cyclones in a CFB cold test rig. The six cyclones were located asymmetrically on the left and right walls of the riser. Solid volume fraction and particle velocity profiles at the riser outlets and in the horizontal ducts were measured using a fiber optical probe. Cyclone pressure drop and solid circulating rate were measured for each individual cyclone. Measurements showed good agreement as to the non-uniform distribution of the gas–solid flow, which occurred mainly across the three cyclones on one side: the middle cyclones on both sides had higher particle velocities. Conversely, the solid volume fractions, solid fluxes and solid circulating rates of the middle cyclones were lower than those of the other four cyclones. The apparent reason for the flow non-uniformity among the cyclones is the significant flow non-uniformity at the riser outlets. Under typical operating conditions, the solid volume fractions at the riser outlets had a deviation of up to 26% whereas the solid circulating rates at the stand pipes, 7%. These results are consistent with most other studies in the literature.     

Highly active MgCl2‐supported catalysts containing novel diether donors for propene polymerization

A new generation of MgCl₂‐supported catalysts for the polymerization of propene without any external donors was prepared. Two diethers, 9,9‐bis(methoxymethyl)fluorene (for Cat‐A) and 2,2‐dipropyl‐1,3‐dimethoxypropane (for Cat‐B) differing in the bulkiness of alkyl substituents in position 2, have been used as internal donors in MgCl₂/TiCl₄/diether‐AlR₃ catalysts. The weight‐average molecular weights produced with both catalysts were over 3.5×10⁵ at low temperature in slurry polymerization (< 40°C). Cat‐A showed higher activity and produced higher isotactic polypropene than Cat‐B. The activity of both catalysts proved to be dependent on the temperature.