微通道内液-液两相流流型及传质的研究进展

微通道内液-液两相流流动在微化工系统中占有重要的地位,了解微通道内液-液两相流体流动和传质规律对推动其工业化应用有重要作用。本文以微通道内液-液两相流系统为研究对象,简述了不同工况下微通道内液-液两相流流型和混合传质效率,分析了微通道特征、流体性质和流体流动速度等对流型形成和传质效率的影响。指出目前对于微通道内液-液两相流的研究多处于定性研究,定量研究仅针对某一体系展开,所得结果具有一定的局限性。关于微通道内液-液两相流传质研究实验较多而数值模拟方法相对较少,接下来的研究工作中应该考虑建立微通道内液-液两相流基础研究的数据库,通过分析大量的数据获得有效的流型划分准则和相关经验式以此推动微通道内液-液两相流的工业化应用。同时在传质研究过程中应研究开发相应的数值模拟模型,保证实验和数值模拟相结合,提出有效的传质效率评价机制。     

Characterization of Dog Glutathione Transferase P1-1, an Enzyme Relevant to Veterinary Medicine

Glutathione transferases (GSTs) form a family of detoxication enzymes instrumental in the inactivation and elimination of electrophilic mutagenic and carcinogenic compounds. The Pi class GST P1-1 is present in most tissues and is commonly overexpressed in neoplastic cells. GST P1-1 in the dog, Canis lupus familiaris, has merits as a marker for tumors and as a target for enzyme-activated prodrugs. We produced the canine enzyme CluGST P1-1 by heterologous bacterial expression and verified its cross-reactivity with antihuman-GST P1-1 antibodies. The catalytic activity with alternative substrates of biological significance was determined, and the most active substrate found was benzyl isothiocyanate. Among established GST inhibitors, Cibacron Blue showed positive cooperativity with an IC₅₀ value of 43 nM. Dog GST P1-1 catalyzes activation of the prodrug Telcyta, but the activity is significantly lower than that of the human homolog.     

Synthesis and experimental study of novel double perovskite Ba2NixCo2−xO6 as promising oxygen carrier materials for CO2 capture application

Novel oxygen-deficient double-perovskite type oxide Ba₂Ni_xCo_2−xO₆ was applied to produce O₂/CO₂ mixed stream gas for oxyfuel combustion application. A series of different Co concentration substituted Ba₂Ni_xCo_2−xO₆ was synthesized by an EDTA-citrate sol-gel combustion method. The oxygen carriers, Ba₂Ni_0.25Co_1.75O_6, Ba₂Ni_0.45Co_1.55O₆, Ba₂Ni_0.65Co_1.35O₆ and Ba₂Ni_0.85Co_1.15O₆ were c\characterized by scanning electron microscopy and cyclic oxygen adsorption/desorption experiments. The results showed that the capacity of provided O₂ was improved by the partial substitution of Ni by Co. In addition, the synthesized perovskites exhibit good regeneration ability. The optimal degree of Co substitution was x = 0.25 for Ba₂Ni_xCo_2−xO₆ with consideration of oxygen desorption ability. Therefore, Ba₂Ni_0.25Co_1.75O₆ was selected to examine the influence of the operating parameters on the oxygen release performance. It was found that the desorption temperature and CO₂ partial pressure are the two main operating parameters for the oxygen desorption performance. Further, the proposed novel double perovskite Ba₂Ni_0.25Co_1.75O₆ provided excellent performance, the O₂ production of Ba₂Ni_0.25Co_1.75O₆ can still reach 120 mg/g after 10 cycles.     

Turbulent heat transfer characteristics of supercritical n‐decane in a vertical tube under various operating pressures

To explore the effect of the operating pressure on the flow and thermal characteristics in a vertical tube with supercritical n‐decane, the inner wall temperature along the streamwise direction, the applicability of empirical correlations and buoyancy criteria are studied firstly. The mechanisms in views of density distribution, velocity field, turbulence intensity, the thickness of the thermal boundary layer, and secondary flow are then analyzed. It is observed that the buoyancy is helpful for the phenomenon of heat transfer deterioration at lower operating pressures but higher operating pressures can diminish this tendency. According to this reason, the empirical correlation proposed by Bae and Kim is suitable for the higher operating pressures but cannot well predict the occurrence of heat transfer deterioration. However, it can be evaluated by the buoyancy criterion Gr/Re² = 0.01 qualitatively. The decrease of turbulence intensity, the thickened thermal boundary layer, and secondary flow generation make contributions to the heat transfer deterioration in particular. Similarly, this situation can be diminished and even removed by the higher operating pressures.     

A combined reflectometry and quartz crystal microbalance with dissipation setup for surface interaction studies

We have developed an instrument for surface interaction studies, which combines a newly invented four detector optical reflectometry setup with quartz crystal microbalance with dissipation (QCM-D) monitoring. The design is such that data from both techniques can be obtained simultaneously on the same sensor surface, with the same signal-to-noise ratio and time resolution, as for the individual techniques. In addition, synchronized information about structural transformations, molecular mass, and the hydration of thin films on solid surfaces can be obtained on the same specimen, as validated by monitoring the formation of supported lipid bilayers on a silica-coated QCM sensor surface. We emphasize that the optical (molecular) mass can be separated from the acoustic mass including hydrodynamically coupled solvent, which means, in turn, that the amount of solvent sensed by the QCM-D technique can be dynamically resolved during adsorption processes. In addition, the advantage/necessity to use four, compared to two, detector reflectometry is emphasized.     

Exploiting latent functional capabilities for resilience in design of engineering systems

In this paper, we address latent functional capabilities, capabilities that were neither intended nor recognized in the design process. We propose that latent capabilities can improve the resilience of engineering systems, enabling recovery of performance after disruptive events. Engineering systems are designed to meet their functional requirements, and have a limited ability to avoid critical failures. Normally, redundancies are put in place to reduce the impact of potential disruptions, adding to cost and complexity. An alternative is to uncover latent capabilities that can be used to recover from disruption by altering the function-form mapping. Existing design methods focus on intended, manifest functionality, and do not consider latent capabilities. With basis in design theory, we show that latent capabilities can enhance resilience, and demonstrate this using two illustrative cases. Further, we propose approaches to uncover latent capabilities in systems design, and discuss implications of using latent capabilities to enhance resilience.     

The influence of antioxidants on the oxidation stability of biodiesel

Oxidation stability of bodiesel is an important issue because FA derivatives are more sensitive to oxidative degradation than mineral fuel. Therefore, in the most recent European Specifications for biodiesel, a minimum value of 6 h for the induction period at 110°C, measured with a Rancimat instrument, is specified. To guarantee this value at the filling station, the use of additional antioxidants will be necessary. In this paper we show the influence of different synthetic and natural antioxidants on the oxidation stability, using the specified test method. Biodiesel produced from rapeseed oil, sunflower oil, used frying oil, and beef tallow, both undistilled and distilled, was investigated. The four synthetic antioxidants pyrogallol (PY), propylgallate (PG), TBHQ, and BHA produced the greatest enhancement of the induction period. These four compounds and the widely used BHT were selected for further studies at concentrations from 100 to 1000 mg/kg. The induction periods of methyl esters from rapeseed, oil, used frying oil, and tallow could be improved significantly with PY, PG, and TBHQ, whereas BHT was not very effective. A good correlation was found between the improvement of the oxidation stability and the FA composition.     

Bias and Imprecision in the Determination of Free Glycerin in Biodiesel: The Unexpected Role of Limitations in Solubility

Residual free glycerin (FG) is a critical marker of fatty acid methyl ester (biodiesel) fuel quality. Yet, routine determinations by standard methods display excessive imprecision, and the uncertainties undermine confidence in the data. Various degrees of agitation are used here to evaluate the possibility of heterophase formation as a contributor to imprecision and potential bias. Statistical markers from the analysis of 13 biodiesel samples reveal that seven contain unexpected heterophases, which, due to settling, cause underestimates of 15–68%. Agitation alone re‐suspends heterophases for brief periods, easing potential biases, but also increases imprecision. A promising new sample pretreatment is presented, which reduces the deleterious effects of heterophases. Solubility limitations are explored as possible contributing factors, and measurements made at 23 °C in purified soy FAME reveal an equilibrium solubility which is more than 80% below previously published estimates. Strong interactions of liquid FG with small amounts of moisture reduce solubility to below international quality limits, while interactions of initially dissolved forms of moisture and FG produce bias‐inducing heterophases at 0.02% FG. The unexpected low solubility of FG, exacerbated by interactions with impurities, is seen as an important contributor to underestimates and imprecision, and a strong influencing factor on the fate of residual FG in commercial biodiesel fuels.     

用石灰及水泥土柱稳定边坡和深开挖

本文介绍用生石灰粉或水泥与软粘土就地搅拌在地基内形成土柱以稳定沟槽,深开挖以及边坡的设计与施工方法。石灰土柱具有石灰用量低,施工振动小,挤土扰动少,透水性好的优点。文中讨论了石灰土的强度机理,石灰土柱的受力及破坏形式,给出了计算图式及应取的安全系数值。全文结合瑞典工程实例阐述。     

Early identification of reading difficulties using heterogeneous developmental trajectories.

Serious conceptual and procedural problems associated with current diagnostic methods call for alternative approaches to assessing and diagnosing students with reading problems. This study presents a new analytic model to improve the classification and prediction of children's reading development. Growth mixture modeling was used to identify the presence of 10 different heterogeneous developmental patterns. In all, 411 children in kindergarten through Grade 2 from 3 elementary schools in Texas were administered measures of phonological awareness, word recognition, and rapid naming skills 4 times a year. The mean ages were 5.8 years (SD = 0.35) for the kindergartners, 6.9 years (SD = 0.39) for Grade 1, and 8.0 years (SD = 0.43) for Grade 2; the percentage of boys was 50%. The results indicate that precursor reading skills such as phonological awareness and rapid naming are highly predictive of word reading (word recognition) and that developmental profiles formed in kindergarten are directly associated with development in Grades 1 and 2. Students identified as having reading-related difficulties in kindergarten exhibited slower development of word recognition skills in subsequent years of the study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)