MATLAB并流多效蒸发过程的模拟

并流多效蒸发作为化学工业中常用的操作过程,蒸汽的消耗量、各效溶剂蒸发量、各效蒸发器的传热面积等需要计算的参数,是并流多效蒸发操作和设计的主要依据,因此对多效并流蒸发过程的模拟具有重要的意义。而已知的多效并流蒸发模拟计算的数学模型,常因模型中存在过多的近似简化或模型求解算法太复杂,造成模型的精确性低、可操作性差。联立多效蒸发系统的物料恒算方程、热量恒算方程、传热速率方程、汽液相温度平衡方程及热力学数据方程,建立了多效蒸发设计计算的数学模型,模型思路简单,推导严密,系统性强。提出了非线性方程组的MATLAB工具箱函数解法,并分析了1个三效蒸发实例,计算结果表明该方法方便快捷,收敛性好,该模型及其求解方法值得推广使用。     

Evaluation of a new preparative supercritical fluid chromatography system for compound library purification: the TharSFC SFC-MS Prep-100 system

Preparative HPLC-MS is often the method of choice for purification of small amounts (<100mg) of diverse new molecules, such as compound libraries for drug discovery. The method is robust, well proven, and widely applicable. In contrast, preparative supercritical fluid chromatography coupled with mass spectrometry (SFC-MS) has seen only slow acceptance for the same application--despite some potential scientific and economic advantages. One of the reasons for slow adoption of SFC-MS is the lack of well-proven, robust, and commercially available instrumentation. In early 2009, TharSFC (a Waters Company, Pittsburgh, PA) introduced a new fully integrated system for preparative SFC-MS: The SFC-MS Prep-100. We report herein an objective evaluation of the SFC-MS Prep-100, including tests for pump and autosampler performance, sample recovery, sample carryover, fraction triggering, detector/fraction collector synchronization, and overall robustness. Our results suggest that the SFC-MS Prep-100 represents a significant advance over previous generation instrumentation.     

Novel microstructured evaporation device

Microfluidic devices have become more and more important in the field of thermal or chemical process engineering within the last years (by Schubert et al. Microscale Thermophys Eng 5:17–39, 2001). Cooling is one point of research where microchannels and other microstructured geometries provide significant advantages compared to conventional devices as they offer much higher possible surface to volume ratios and short characteristic distances. Therefore, an intense amount of heat can be transferred by these devices, which can be significantly increased by phase transition. Thus, evaporation of a fluid flow in microchannels allows very compact, fast, and powerful cooling devices. In this research study a novel microstructured evaporator geometry consisting of curved microchannels was evaluated on its evaporation properties compared to previous studies dealing with evaporation of R134a (Tetrafluoroethane) in straight microchannels (by Wibel et al. Chem Eng J 167:705–712, 2011). This novel evaporator design takes advantage of the strong centrifugal forces acting on the (evaporating) two phase flow in the curved microchannels. Due to the feasibility of very small radii of curved microchannels, strong centrifugal forces can be obtained for the fluid flow inside the microstructures. Additionally, those forces are boosted as flow velocities within the channels become higher due to the volume increase induced by evaporation. Therefore, a phase separation could take place inside the microstructure with a higher liquid fraction of evaporating coolant near one side of the curved channels during the transition to vapor. A high liquid fraction inside the evaporator is aimed by an intended removal of the evaporated gas phase from the microstructure. Experimental results of the evaporation of water and R134a as coolants demonstrate the potential of this curved geometry in comparison to evaporation in straight channels. Optical investigations of the new micro evaporator concept by high-speed videography (by Maikowske et al. Appl Therm Eng 30:1872–1876, 2010) are carried out for further improvements of the design. Various bubble formations and movements of the evaporating fluid flow were studied for various vapor fractions by using different fluids. These investigations show how the separation and extraction of the vapor fraction of the novel microstructure concept could be improved.     

A 5.8‐in. phosphorescent color AMOLED display fabricated by ink‐jet printing on plastic substrate

Abstract— A flexible phosphorescent color active‐matrix organic light‐emitting‐diode (AMOLED) display on a plastic substrate has been fabricated. Phosphorescent polymer materials are used for the emitting layer, which is patterned using ink‐jet printing. A mixed solvent system with a high‐viscosity solvent is used for ink formulation to obtain jetting reliability. The effects of evaporation and the baking condition on the film profile and OLED performances were investigated. An organic thin‐film‐transistor (OTFT) backplane, fabricated using pentacene, is used to drive the OLEDs. The OTFT exhibited a current on/off ratio of 10⁶ and a mobility of 0.1 cm²/V‐sec. Color moving images were successfully shown on the fabricated display.     

一种自组装型SnO_2纳米线氢传感器

为了能够对低体积分数的氢气进行灵敏探测,提高氢气生产、使用、运输、存储的安全性,通过热蒸发SnO2和活性炭的混合粉末的自组装方式直接在Cr-Au梳状交叉电极上制备了一层SnO2纳米线气敏层,构成了SnO2纳米线气体传感器。经测试,发现此传感器对于体积分数范围为10×10-6~500×10-6的氢气具有良好的探测灵敏度。     

Separating the Wheat from the Chaff: High Throughput Purification of Chemical Libraries

The products of pioneering “split and mix” combinatorial synthesis techniques were multi-component mixtures of products either in solution or tethered to beads which required imaginative screening and deconvolution strategies to return information on the activity of individual components, often present in sub-microgram quantities. In recent years we have witnessed the development of a range of sophisticated synthesisers and other high throughput parallel synthesis techniques capable of delivering large numbers of compounds for screening in quantities from 10 to 50 mg. Such compounds have the potential for purification, characterisation and quantification and hence provide a high quality, long lasting screening resource. This paper will describe processes in place at SmithKline Beecham to ensure that such criteria are met, and will focus primarily on high throughput purification by preparative HPLC.     

氯霉素分子印迹聚合物预组装过程的分子动力学研究

以氯霉素(CAP)为模板分子,甲基丙烯酸(MAA)、丙烯酸(AA)、丙烯酰胺(AM)、甲基丙烯酸甲酯(MMA)为功能单体,采用分子动力学方法研究了不同预组装体系中CAP与功能单体的相互作用,考察了溶剂(氯仿、甲醇、乙腈)对预组装体系的影响,并采用试验方法验证模拟结果,最后研究了预组装体系中CAP与功能单体相互作用距离。结果表明:模拟结果与实验结果一致,在甲醇溶剂中,CAP与功能单体相互作用强弱顺序为MAA>AA>AM>MMA;乙腈溶剂中顺序为AM>MAA>AA>MMA。CAP与功能单体相互作用基团的距离在1.8~5.0,两者间可能存在较强的非共价结合作用。     

Qualification of a Zymark® Multidose® Automated Dissolution Workstation for Dissolution Testing of Fexofenadine HCI Capsules

A manual, multi-point dissolution test for powder filled capsules was transferred to an automated dissolution method utilizing a Zymark® Multidose® Automated Dissolution Workstation, a MultiFill™ station, and a Distek 2100B dissolution bath system. Both methods require a final HPLC analysis of the sample solutions.

Several MultiDose system parameters were evaluated to ensure product result integrity and equivalency. These included carryover studies, line flush studies, vessel wash studies, filter studies, and sample evaporation studies. The most critical evaluation was the statistical analyses (equivalence) of the product results from both methods.     

A basic-2 program to compute the enthalpy/mass fraction diagram of the real NH3/H2 gas mixture at 25 bar,for neutral gas absorption refrigeration units (technical note)

The thermodynamic properties of the NH₃/H₂ gas mixture, namely the enthalpy, the specific volume of the mixture and the NH₃ ‘partial pressure’ can be presented in an enthalpy/mass fraction diagram as a function of the state conditions (temperature, mass fraction, total pressure) to facilitate the calculation of the evaporation of NH₃ taking place in small absorption refrigeration units. A method and a computer program have been developed giving the desired quantities, starting from the corresponding data of the real components H₂ and NH₃ and using the method of the second virial coefficients. The relevant results are valid for a total pressure of 25 bar and temperatures between −40°C to +50°C.     

Estimation of evaporative fraction and evapotranspiration from MODIS products using a complementary based model

We present a new formulation to derive evaporative fraction (EF) and evapotranspiration (ET) maps from remotely sensed data without auxiliary relationships or site-specific relationships. This formulation is based on Granger's complementary relationship and Priestley-Taylor's equation. The proposed model eliminates the wind function and resistance parameters commonly applied to ET calculation by including a relative evaporation parameter (ET/Epot). By combining this relative evaporation parameter, Granger's complementary relationship and Priestley-Taylor equation, we obtain a simple equation to estimate ET. We tested and validated the proposed formulation over the Southern Great Plains (SGP) region of the United States for seven clear sky days during March-October 2003. MODIS Atmospheric and Land products were the only source of data used in this study. Estimates of ET show an overall root mean square error and bias of 33.89 and − 10.96 Wm^− 2, respectively. Our results suggest that the proposed approach is robust and valid for a wide range of atmospheric and surface conditions.     

SnO_2-ZnO复合膜特性研究

用真空蒸发的方法,在1.33×10-3Pa的真空中,蒸发SnO2,ZnO获得超微粒结构的SnO2-ZnO复合膜。当复合膜中ZnO质量分数为20%时,SnO2-ZnO复合膜对乙醇气体的灵敏度为40,膜的方电阻值也较低,为0.01×103Ω/□。复合膜经热处理后,其电学性能也得到改善,当温度t=600℃时,ZnO质量分数为20%的SnO2-ZnO复合膜热处理后,其膜对乙醇气体有较高的选择性,灵敏度为60。当t=400℃时,对掺有Sb2O5质量分数为450×10-6,ZnO质量分数为20%的SnO2-ZnO复合膜进行热处理,其方电阻仅为0.003×103Ω/□,具有优良的导电性能。     

Customization of a Commercially Available Prep Scale SFC System to Provide Enhanced Capabilities

Preparative Scale Supercritical Fluid Chromatography is emerging as a powerful alternative to HPLC for the purification and separation of complex chemical reaction mixtures. Advantages include greatly reduced solvent usage (and thus lower cost and environmental impact), higher throughput, and in some cases higher resolution. While there are commercially available prep SFC instruments, none currently offer all the features desired by many medicinal chemists engaged in the drug discovery process. These include: the ability to collect an unlimited number of fractions per sample with high recovery and negligible carryover, fully automated capacity to collect several hundred fractions, and the ability to collect fractions into the same disposable test tubes and racks which are already employed in HPLC. This article describes the customization of a preparatory scale SFC system purchased from Berger Instruments, Inc., Newark, DE. (a subsidiary Mettler-Toledo International, Inc., of Greifensee, Switzerland) in order to provide these capabilities.     

Electrochemical actuator based on single-layer polypyrrole film

Polypyrrole film with porous and compact zones in its vertical direction has been synthesized by direct oxidation of pyrrole in the mixed solvent of acetonitrile and dichloromethane contained a certain amount of anion surfactant of sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT). The actuator based on this single-layer film bends uniformly with the maximum bending angle much larger than 90° and has a fast response rate (∼60° s⁻¹ at 1.0 V versus SCE) and a long lifetime (>20,000 cycles). The high performance of this actuator is mainly due to that the PPy film has a high conductivity and the actuator does not have delamination problem.     

Global estimates of evapotranspiration for climate studies using multi-sensor remote sensing data: Evaluation of three process-based approaches

Three process based models are used to estimate terrestrial heat fluxes and evapotranspiration (ET) at the global scale: a single source energy budget model, a Penman-Monteith based approach, and a Priestley-Taylor based approach. All models adjust the surface resistances or provide ecophysiological constraints to account for changing environmental factors. Evaporation (or sublimation) over snow-covered regions is calculated consistently for all models using a modified Penman equation. Instantaneous fluxes of latent heat computed at the time of satellite overpass are linearly scaled to the equivalent daily evapotranspiration using the computed evaporative fraction and the day-time net radiation. A constant fraction (10% of daytime evaporation) is used to account for the night time evaporation. Interception losses are computed using a simple water budget model. We produce daily evapotranspiration and sensible heat flux for the global land surface at 5 km spatial resolution for the period 2003-2006. With the exception of wind and surface pressure, all model inputs and forcings are obtained from satellite remote sensing.Satellite-based inputs and model outputs were first carefully evaluated at the site scale on a monthly-mean basis, then as a four-year mean against a climatological estimate of ET over 26 major basins, and finally in terms of a latitudinal profile on an annual basis. Intercomparison of the monthly model estimates of latent and sensible heat fluxes with 12 eddy-covariance towers across the U.S. yielded mean correlation of 0.57 and 0.54, respectively. Satellite-based meteorological datasets of 2 m temperature (0.83), humidity (0.70), incident shortwave radiation (0.64), incident longwave radiation (0.67) were found to agree well at the tower scale, while estimates of wind speed correlated poorly (0.17). Comparisons of the four year mean annual ET for 26 global river basins and global latitudinal profiles with a climatologically estimated ET resulted in a Kendall's τ > 0.70. The seasonal cycle over the continents is well represented in the Hovmöeller plots and the suppression of ET during major droughts in Europe, Australia and the Amazon are well picked up. This study provides the first ever moderate resolution estimates of ET on a global scale using only remote sensing based inputs and forcings, and furthermore the first ever multi-model comparison of process-based remote sensing estimates using the same inputs.     

Microfluidic motion for a direct investigation of solvent interactions with PDMS microchannels

Solid surface/liquid interactions play an important role in microfluidics and particularly in manipulation of films, drops and bubbles, a basic requirement for a number of lab-on-chip applications. The behavior of solvents in coated microchannels is difficult to be predicted considering theories; therefore, experimental methods able to estimate the properties at the interface in real time and during the operational regime are amenable. Here, we propose to use an experimental setup to evaluate the effective dynamics of solvents inside PDMS microchannels. The influence of the solvent properties as well as of the channel wall’s wettability on the fluid movements was evaluated. Modification of the channel properties was achieved by introducing Teflon coatings that allow producing stable hydrophobic microchannel walls. The results were fitted according to Washburn-type power-law and compared with theoretical calculations of the parameter β that expresses the dependence of capillary dynamics on surface tension γ, liquid viscosity η, contact angles θ and the hydraulic radius R _H. A comparison between the calculated and the experimental values reveled that parameters other than the contemplated ones influenced the measurements. The main parameter that affects the flow of solvents such as water, methanol ethanol, dimethylformamide, acetonitrile and acetone was found to be the γ/η ratio. Considering these results, the investigation tool described here is believed to be promising to predict the dynamics of common organic solvents inside integrated functional fluidic devices and to accurately control solvent flow, particularly in capillary-driven pumpless systems, a basic requirement for widening the application range of PDMS lab-on-chip devices.     

Entropic-FV修正模型预测聚合物体系溶胀行为

Entropic-FV（EFV）修正模型是对原模型的自由体积分数项进行修改而获得,前者与后者具有相同的统计力学基础,且表达式简单,无需增加模型参数。将其用于聚乙二醇／甲醇二元体系中组分活度的计算,或与UNIQUAC-HB模型结合对聚乙烯醇膜／乙二醇／水和聚氨酯／正己烷／苯三元体系的溶胀平衡组成进行预测,并与EFV和原修正模型的预测结果以及文献值进行比较,结果显示该模型预测的准确度最高、稳定性较好。     

A novel porous anodic alumina based capacitive sensor towards trace detection of PCBs

To detect polychlorinated biphenyls (PCBs), a novel porous anodic alumina (PAA) based capacitive sensor working at room temperature has been developed. The parallel nanopores of PAA not only provide large surface area for PCB adsorption, but also benefit for the enhancement of capacitive response. By dropping the PCB methanol solution on the surface of PAA, it is convenient to load PCB into the nanopores by solvent evaporation. 3,3′,4,4′-tetrachlorobiphenyl (PCB77) was chosen as a typical sample of PCBs to investigate the sensing properties of the capacitive sensor. The capacitance of the PAA membrane shows remarkable enhancement after PCB77 solution was loaded while no significant change can be seen after the pure solvent was loaded. The capacitive sensor also shows good response to PCB77 even in the presence of the interferent of benzene. The sensing mechanism has been qualitatively discussed based on a parallel plate capacitor model. The detection limit is down to 8 × 10⁻⁸ M towards PCB77. The novel PAA based capacitive sensor exhibits great potential for practical application in trace detection of PCBs.     

A FORTRAN program for calculating the thermodynamic and transport properties of diesel fuel

Advanced models of the thermodynamic processes in internal combustion engines require the exact estimation of the thermodynamic and transport properties of combustion reactants and products. Although many works have been reported on the properties of air, fuel vapour and combustion products, a study on the properties of the fuel liquid phase seems to be lacking in the open literature. These properties are very important for simulating the fuel droplet evaporation process, which plays an important role on diesel engine combustion and emitted pollutant modelling. In the present work the values of the thermodynamic and transport properties of liquid diesel fuel are computed, as a function of pressure and temperature, by polynomial fitting against available experimental data. This is accomplished in a fraction of a second when using a personal computer with a very small error. N-Dodecane is treated in the present study, which forms a representative fuel of the diesel fuel in most diesel engine cycle simulations. The relevant computer program subroutines are given in an educational form, in FORTRAN-77 language.     

Electrochemical detection of TNT with in-line pre-concentration using imprinted diethylbenzene-bridged periodic mesoporous organosilicas

We examined the adsorption and release of TNT using diethylbenzene-bridged (DEB) periodic mesoporous organosilica sorbents under varying conditions. The sorbents were applied for in-line target pre-concentration in conjunction with an electrochemical flow cell containing a glassy carbon electrode. Square wave voltammetry was employed for TNT detection. TNT sample volumes between 2 and 480 mL at concentrations ranging from 0.5 to 500 ppb were passed through the DEB sorbents (imprinted or not imprinted for TNT) at pH 6 (sodium acetate) or at pH 7.4 (PBS). Release of target was accomplished using solvent mixtures of methanol/water with sodium acetate as electrolyte or acetonitrile/water with PBS components as electrolyte. Under these conditions, the TNT was released in <200 μL of the solvent mixture, and pre-concentration factors of >3000 can be achieved when using large volumes of trace TNT samples. When sample volumes of 2 mL were utilized, the sensing system gave a linear response between 20 and 500 ppb with an estimated limit of detection of 13 ppb. When pre-concentrating 480 mL of sample in either buffered solution or seawater, detection of 0.5 ppb TNT was achieved with a signal to noise ratio of 20.     

热蒸发石墨烯基SnOx-Sn传感器气敏性研究

通过化学气相沉积法制备石墨烯并采用热蒸发法在石墨烯上沉积锡(Sn)及其氧化物,得到石墨烯基SnOx-Sn气敏传感器,研究其在室温下对低体积分数甲醛和二氧化氮(NO2)气体的气敏性及SnOx-Sn膜厚和基底加热温度对传感器气敏性的影响.通过场发射扫描电镜(FESEM)、原子力显微镜(AFM)等表征手段研究了石墨烯基SnOx-Sn气敏传感器的形态结构.