Near-Infrared Spectroscopy for In Situ Monitoring of Geoenvironment

This paper demonstrates the usefulness of near-infrared optical fiber analysis for sensing moisture and liquid hydrocarbons in soil. Through experiments we have carried out sensing probes which have been developed, comprising optical fibers that use the evanescent field of the guided energy. The movement of water through dry sand was simulated in the laboratory and the sensors were used in situ to measure the variation of soil moisture in real time. A similar experiment simulated the movement of an organic liquid (mineral oil) through water-saturated sand, and the sensors were used in situ to monitor the hydrocarbon movement. We found that a hydrophobic polymer-coated waveguide can amplify the hydrocarbon signal while minimizing that of water, making it possible to detect a dissolved hydrocarbon. Tests show that the second derivative transform of the absorption spectra could be used to distinguish classes of hydrocarbons.     

Arsenic content in some Spanish wines Influence of the wine-making technique on arsenic content in musts and wines

Summary All of the essential technological means of treating grapes, must and wine were examined systematically. The main reasons for the differences in the arsenic (As) content of rosé and red wines are explained. In this study a relationship has been found between the As level and the wine-making technique. Rosé wines contain more As than red wines because they require a shorter period of contact with the skins. In order to prove this, the average values for the rosé and red wine samples from the same winery were compared.

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Arsen-Gehalt in einigen spanischen Weinen. Beeinflussung des Arsengehaltes von Most und Weinen durch kellertechnische Maßnahmen

Zusammenfassung Durch systematische Überprüfung aller wesentlichen kellertechnischen Schritte der Most- und Weinbehandlung wurden die Hauptursachen der großen Unterschiede im Arsengehalt von Weinen aufgeklärt. Dieser vermindert sich schon beim ersten Abstich nach der Gärung und weiterhin durch die Entfernung der Trübstoffe. Bei starkstreuenden Gehalten zeigte sich, daß die Rotweine geringere Werte als die Roséweine aufwiesen. Außerdem unterschieden sich vergleichbare Weine aus verschiedenen Betrieben deutlich im Arsengehalt.

     

基于电网分区的负荷恢复智能优化策略

针对电力系统大停电后的负荷快速恢复问题,提出了一种基于电网分区的负荷恢复智能优化策略.提出了一种大停电事故后系统恢复的最优分区策略,并在所建立的优化模型中考虑了为恢复发电机而引入的架空线路充电无功以及为恢复负荷所引入的线路合闸操作次数等影响因素.在完成对大规模系统优化分区后,对各分区建立了一个统一的并计及网络重构因素的负荷恢复优化模型,实现各分区负荷的并行恢复.针对上述所提出的优化模型,通过结合传统图论理论和遗传算法,实现基于电网分区的负荷恢复优化问题的求解.解算中,对遗传算法进行了改进,并针对应用遗传算法时所产生的大量不可行解问题,提出了随机甩负荷和最短路径修补策略的处理方法,进一步提高了算法的寻优效率和全局优化能力.以IEEE30节点系统为算例进行仿真分析,验证了所提模型与方法的正确性和有效性.     

Dye removal from colored textile wastewater using acrylic grafted nanomembrane

In this paper, the dye removal ability of the acrylic grafted polysulfone nanomembrane using ultraviolet radiation was studied to remove dyes from colored textile wastewater. Acrylic acid was used to modify polysulfone ultrafiltration membrane. The effect of different operating parameters such as pressure, salt concentration and chemical structure of dyes was evaluated. Data indicated that the photografted membrane has acceptable performance both in terms of flux and rejection. The dye rejection and hydraulic permeability were 86–99.9% and 7.6 L m^{− 2} h^{− 1} bar^{− 1}, respectively. It was found that the rejection of dyes decreased with salt concentration due to a decrease of the Donnan effect. Also, the low molecular weight dyes and highly charged dyes were more sensitive in the presence of salts. Addition of 80 mM Na₂SO₄ in dye solution decreased the dye rejection more than 15%. The rejection enhancement for all cases was negligible by increasing driving pressure from 1 to 4 bar. Dyes with low charger were more sensitive to operating pressure than that of dyes with higher charges. All findings supported that acrylic grafted nanomembrane is potentially capable to separate dyes from colored textile effluent.     

A new approach for determination of gel time of a glass/epoxy prepreg

Gel time of a glass/epoxy prepreg, HexPly®1454, was investigated by a parallel plate rheometer. The prepreg is based on dicyandiamide (DICY)‐cured diglycidyl ether of bisphenol A epoxy resin system. It is found that the application of the G′‐G″ crossover method for gel time determination is not suitable for this system. A new approach was proposed in which the maximum tan δ is regarded as the gel point. This can accurately define the gel point at various temperatures. The results proved that this point is independent of the applied frequency. The activation energy for the cure reaction of the system was determined via gel time determination of the prepreg at different isothermal temperatures and found to be 75.0 ± 10.2 kJ/mol. This is in good agreement with the activation energy obtained from the dynamic DSC studies. The steady‐shear rheology experiment was used to study the viscosity profile and subsequently to determine the gel point and verify the new approach for gel time determination. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Production of Wire From AA7277 Aluminum Chips via Friction-Stir Extrusion (FSE)

In this research, fully consolidated wires from aluminum alloy AA7277 machining chips were produced by the friction-stir extrusion (FSE) process. The components used in the friction-stir extrusion process consist of a stationary cartridge and a rotating plunger with a scroll-faced head. The rotating plunger was rotated at three different speeds. Optical microscopy was used to probe the microstructures formed in the wires. The hardness profile of each sample is characterized using a Vickers microhardness tester. In this work, surface quality is sufficient by using a rotation speed of 160 rpm. Cold crack and hot crack defects were shown on wires fabricated using either too low or too high plunger rotation speeds. The microstructure of extruded wire is composed of fully equiaxed, recrystallized fine grains in the center of samples. The microhardness tests show an uneven distribution, and the hardness of the center was lower than that of the parent metal. The tensile tests revealed that the mechanical properties of the extruded wires were comparable with parent material.     

Survival probability of precipitations and rain attenuation in tropical and equatorial regions

This contribution presents a stochastic model useful for the generation of a long-term tropospheric rain attenuation time series for Earth space or a terrestrial radio link in tropical and equatorial heavy rain regions based on the well-known Cox–Ingersoll–Ross model previously employed in research in the fields of finance and economics. This model assumes typical gamma distribution for rain attenuation in heavy rain climatic regions and utilises the temporal dynamic of precipitation collected in equatorial Johor, Malaysia. Different formations of survival probability are also discussed. Furthermore, the correlation between these probabilities and the Markov process is determined, and information on the variance and autocorrelation function of rain events with respect to the particular characteristics of precipitation in this area is presented. The proposed technique proved to preserve the peculiarities of precipitation for an equatorial region and reproduce fairly good statistics of the rain attenuation correlation function that could help to improve the prediction of dynamic characteristics of rain fade events.     

Separation of hydrogen from methane by asymmetric PEI membranes

Hydrogen is anticipated to play an inevitable role as one of the promising sources of energy in the future. Recovery of hydrogen from flare gases is an economical and environmental policy of Marun Petrochemical Company. The asymmetric polyetherimide (PEI) membrane was synthesized and sorption and permeation of CH₄ and H₂ were studied. The influence of pressure and temperature as operating variables were investigated. Results showed that permeance was enhanced by temperature. The pressure increase caused a decline in H₂ permeance, whereas CH₄ permeance increased due to the Flory–Huggins sorption mechanism and ideal H₂/CH₄ selectivity reduction. The effect of different non-solvents as coagulants of the phase inversion technique in membrane morphology and behavior were explained by precipitation time. Water as a non-solvent makes membrane structures denser than others, while isopropanol leads to a porous sponge-like morphology. Lower coagulation bath temperature makes the membrane denser. Finally, a selectivity of 27.8 was achieved for the separation of H₂ from CH₄.     

Role of critical concentration of PEI in NMP solutions on gas permeation characteristics of PEI gas separation membranes

In preparation of polymeric gas separation membranes by phase inversion method, polymer concentration is one of the most important variables which can change membrane morphology and behavior. In this research, critical concentration of the polyetherimide (PEI) solutions in N-methyl-2-pyrrolidone (NMP) as a solvent was determined by viscometric method. The influence of temperature on critical concentration was studied. Three asymmetric PDMS/PEI membranes with different concentrations of PEI were prepared and characterized for H₂/CH₄ separation. The results showed that the membranes with higher concentrations than critical concentration were more suitable for gas separation. In addition, the viscosity data were fitted by appropriate equations and the densities were satisfactorily correlated by a simple first-order polynomial with respect to temperature and the PEI mass fraction. The prepared membrane showed the selectivity of 26 for H₂/CH₄ separation at 1 bar and 25 °C for pure gas and 24.8 for mixed gas. The influence of the pressure on the H₂ and CH₄ permeance and the selectivity for a mixed binary gas showed that the permeance of both gases declined by pressure enhancement and the selectivity increased.     

A HistogramBased Static Error Correction Technique for Flash ADCs： Implementation

In this paper, we focus on practical issues in implementing a calibration technique for medium-resolution, high-speed flash analog-to-digital converters (ADCs). In [1], we theoretically describ the calibration technique and perform a behavioral-level simulation to test its functionality [1]. In this work, we discuss some issues in transistor-level implementation. The predominant factors that contribute to static errors such as reference generator mismatch and track-and-hold (T/H) gain error can be treated as input-referred offsets of each comparator. Using the proposed calibration technique, these errors can be calibrated with minimal detriment to the dynamic performance of the converter. We simulate a transistor-level implementation of a 5-bit, 1 GHz ADC in a 1.2 V, 65 nm CMOS process. The results show that DNL can be improved from 2.5 LSB to below 0.7 LSB after calibration, and INL can be improved from 1.6 LSB to below 0.6 LSB after calibration.