水和水蒸汽热力学物性参数及导数的计算与应用

本文针对现代换热设备设计、两相流动与传热研究的需要,介绍了可供科研使用的水和水蒸汽物性计算方法,完善了计算程序。根据超临界锅炉设计中的超临界水的物性计算,两相流研究和换热设备动态特性研究中对物性导数计算的需要,提供了两个算例,并进行了定性分析。     

A 3D LIF system for turbulent buoyant jet flows

A Laser-Induced Fluorescence (LIF) system for mapping the three dimensional tracer concentration field in turbulent flows is described. The system is particularly suited to studies of single or multiple buoyant jets discharged into unstratified and stratified flowing environments for conditions typical of wastewater discharges into surface water bodies. A laser beam is scanned through the flow and LIF images are obtained in parallel planes with a high-speed synchronized CCD camera. Refractive index matching is used to minimize refractive index variations due to local density gradients. An application to vertical round buoyant jets discharging into unstratified and stratified cross flows is presented. The three-dimensional system can obtain vastly more data than is possible with probe-based techniques and can yield far more insight into the flow and mixing processes.Abbreviations a Combined attenuation coefficient, cm^-1 - a_w Attenuation coefficient for fresh water, cm^-1 - B Buoyancy flux of buoyant jet, cm⁴/s³ - c Tracer concentration, g/l - C _salt, C _eth Salt and ethanol concentrations, g/l - d Port diameter, cm - g Acceleration due to gravity, cm/s² - Modified acceleration due to gravity at source, cm/s² - Q Volume flux of buoyant jet, cm³/s - I Image gray scale level, DN - l _a,l _Q , l _M , l _s, l _t Buoyant jet length scales, cm (Eq. 8) - L _y Distance from camera to image plane, cm - M Momentum flux of buoyant jet, cm⁴/s² - M _y Image scale factor - N Buoyancy frequency, s^-1 - u _a Ambient flow velocity, cm/s - u _j Jet exit velocity, cm/s - P Laser power, W - S ₀ Lowest dilution on the vertical center-plane through the nozzle - S _m Minimum dilution: lowest dilution in a vertical plane perpendicular to the flow - x, y, z Coordinates, cm - z _m Maximum rise height of buoyant jets, cm - z _e Equilibrium rise height of buoyant jets, cm - Image calibration constant - ₀ Effluent density, g/cm³ - _a Ambient density, g/cm³     

复杂载荷作用下圆柱壳的弹塑性动力屈曲研究

对复杂载荷作用下圆柱壳的弹塑性动力屈曲问题进行了研究。基于Hamilton变分原理导出圆柱壳的运动方程 ,本构关系采用增量理论 ,借助增量数值算法求解动力方程组。结果表明 ,均匀径向外压对圆柱壳的轴向冲击的过程或冲击性态有较大的影响 ,并讨论了径向压力与轴向冲击载荷的幅值对结构临界动力屈曲载荷和临界动力失效载荷的影响。     

瀑布沟水电站库首右岸深部裂缝成因分析

水电工程常常建在高山峡谷地带,其天然岸坡通常由坡面向内有一个强卸荷带和弱卸荷带以及相应的强风化和弱风化带,内侧则为完整新鲜的岩石。对涉及的工程岸坡在正常卸荷带以内发育的一系列张性破裂或破裂带,称之为“深拉裂缝”。瀑布沟水电站库首右岸存在两个拉裂变形体,通过对其岸坡深部拉裂缝空间发育分布、变形特征的考察,综合分析造成深部裂缝发育规律与变形特征的因素。在此基础上提出,库首右岸深部拉裂缝是岸坡快速卸荷条件下浅表生改造的产物,其形成时期相当于河谷由宽谷深切为峡谷这一转换时期。     

AFM稳定性研究

“突跳”现象严重影响着原子力显微镜(AFM)的性能。根据W igner-Seitz模型微观连续介质理论,建立了AFM针尖同试样面接触力包含斥力的数学模型;由分析力学的稳定平衡条件,发现了引起AFM“突跳”的本质是不稳定平衡点的存在;通过增加AFM悬臂梁刚度,提出了一种避免AFM“突跳”现象发生的方法,并给出仿真结果。     

Heat transfer and pressure drop of a transversely finned concentric annulus with longitudinal flow

The characteristics of heat transfer and pressure drop have been experimentally studied for the fully developed concentric annular flow with transverse fins normal to the flow direction by the naphthalene sublimation technique. Correlations for calculating the heat transfer coefficient with different inner diametersD ₀ of the outer tube are presented. A characteristic Reynolds number has been proposed, by which the predominant role of the transverse fins can be evaluated. It has been indicated that the inner diameterD ₀ has much more effect on pressure drop than on heat transfer. The effect ofD ₀ on the overall performance is also compared under the same flow velocity or flow rate. It has been found that the effect of developing flow on heat transfer is significant and should be taken into account during experiment.

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Wärmeübergang und Druckverlust in einem querberippten konzentrischen Ringkanal bei Längsströmung

Zusammenfassung Mit Hilfe der Naphthalin-Sublimationstechnik werden die Wärmeübergangs- und Druckverlustcharakteristiken in quer zur voll ausgebildeten Strömung bei berippten Ringkanälen experimentell ermittelt und Korrelationen zur Berechnung des Wärmeübergangskoeffizienten bei variablen InnendurchmesserD ₀ des umschließenden Rohres angegeben. Ferner wird eine charakteristische Reynolds-Zahl vorgeschlagen, über die sich der dominierende Einfluß der Querrippen erfassen läßt. Es zeigte sich, daß der InnendurchmesserD ₀ den Druckverlust wesentlich mehr beeinflußt als den Wärmeübergang. Auch wurde die Abhängigkeit des Gesamt-Übertragungsverhaltens vonD ₀ bei gleicher Strömungsgeschwindigkeit bzw. Volumenstromdichte ermittelt. Es zeigte sich, daß die Ausbildung des Strömungsprofils bei Einlaufströmung den Wärmeübergang signifikant beeinflußt und deshalb im Experiment zu berücksichtigen ist.

     

Diaminodiacid Bridges to Improve Folding and Tune the Bioactivity of Disulfide‐Rich Peptides

Disulfide‐rich peptides containing three or more disulfide bonds are promising therapeutic and diagnostic agents, but their preparation is often limited by the tedious and low‐yielding folding process. We found that a single cystine‐to‐diaminodiacid replacement could significantly increase the folding efficiency of disulfide‐rich peptides and thus improve their production yields. The practicality of this strategy was demonstrated by the synthesis and folding of derivatives of the μ‐conotoxin SIIIA, the preclinical hormone hepcidin, and the trypsin inhibitor EETI‐II. NMR and X‐ray crystallography studies confirmed that these derivatives of disulfide‐rich peptide retained the correct three‐dimensional conformations. Moreover, the cystine‐to‐diaminodiacid replacement enabled structural tuning, thereby leading to an EETI‐II derivative with higher bioactivity than the native peptide.     

Far‐Red and Near‐IR AIE‐Active Fluorescent Organic Nanoprobes with Enhanced Tumor‐Targeting Efficacy: Shape‐Specific Effects

The rational design of high‐performance fluorescent materials for cancer targeting in vivo is still challenging. A unique molecular design strategy is presented that involves tailoring aggregation‐induced emission (AIE)‐active organic molecules to realize preferable far‐red and NIR fluorescence, well‐controlled morphology (from rod‐like to spherical), and also tumor‐targeted bioimaging. The shape‐tailored organic quinoline–malononitrile (QM) nanoprobes are biocompatible and highly desirable for cell‐tracking applications. Impressively, the spherical shape of QM‐5 nanoaggregates exhibits excellent tumor‐targeted bioimaging performance after intravenously injection into mice, but not the rod‐like aggregates of QM‐2.     

Fluorescent In Situ Targeting Probes for Rapid Imaging of Ovarian‐Cancer‐Specific γ‐Glutamyltranspeptidase

γ‐Glutamyltranspeptidase (GGT) is a tumor biomarker that selectively catalyzes the cleavage of glutamate overexpressed on the plasma membrane of tumor cells. Here, we developed two novel fluorescent in situ targeting (FIST) probes that specifically target GGT in tumor cells, which comprise 1) a GGT‐specific substrate unit (GSH), and 2) a boron–dipyrromethene (BODIPY) moiety for fluorescent signalling. In the presence of GGT, sulfur‐substituted BODIPY was converted to amino‐substituted BODIPY, resulting in dramatic fluorescence variations. By exploiting this enzyme‐triggered photophysical property, we employed these FIST probes to monitor the GGT activity in living cells, which showed remarkable differentiation between ovarian cancer cells and normal cells. These probes represent two first‐generation chemodosimeters featuring enzyme‐mediated rapid, irreversible aromatic hydrocarbon transfer between the sulfur and nitrogen atoms accompanied by switching of photophysical properties.     

A Porous Tricyclooxacalixarene Cage Based on Tetraphenylethylene

A quadrangular prismatic tricyclooxacalixarene cage 1 based on tetraphenylethylene (TPE) was efficiently synthesized by a one‐pot S_NAr condensation reaction. As a result of the porous internal structure in the solid state, cage 1 exhibited a good CO₂ uptake capacity of 12.5 wt % and a high selectivity for CO₂ over N₂ adsorption of 80 (273 K, 1 bar) with a BET surface area of 432 m² g^?1. Formation of cage 1 led to the fluorescence of TPE being switched on in solution. The system was employed as a single‐molecule platform to study the mechanism of aggregation‐induced emission (AIE) by examining the restriction of intramolecular rotation (RIR).