Thermodynamic interpretation of solute–polymer interactions at infinite dilution

Heats of solution at infinite dilution of solutes in poly(ethyl methacrylate) were estimated using gas–liquid chromatography over a temperature range of 417.74 K–427.55 K. The heat of solution is related to solute polarizability and dipole moment. Contributions of specific interactions such as hydrogen bonding and charge-transfer complexing to the enthalpy of solution were also determined.     

Laminar-flow non-newtonian heat transfer in flattened tubes

It is shown experimentally that flattened tubes give higher laminar-flow heat transfer coefficients than tubes of circular cross-section. Part of the increase is due to an increase in the tube-wall shear rate; the magnitude of this effect is predicted and checked by reference to the behaviour of Newtonian liquids. The other part is due to secondary flow patterns which develop in viscoelastic liquids; this effect is at a maximum when the aspect ratio of the tube cross-section is of the order 1.5:1. The first effect may increase heat transfer coefficient by over 90% and the latter by over 45%.     

Comparison of spectral fluorescent signatures-based models to characterize DOM in treated water samples

Statistical procedures enable a multivariate analysis of the measurements to identify specific characteristics of the dissolved organic matter (DOM) fractions in raw natural water, including the concentrations. In this work, three already established models were used to predict the concentrations of fractions of DOM from spectral fluorescent signatures (SFSs): a general linear regression (GLR), loadings and scores of a principal components analysis (PCA), and a partial least squares regression (PLS). Details about the method undertaken to prepare the fractions were given. Water samples from surface water treatment plants in New Jersey were used for the testing. In all cases, PLS have shown much better biases and accuracies than GLR and PCA models. Hydrophilic neutral, however, showed poor performances (bias 33%) due to the isolation technique used. Recommendations were provided in order to improve the DOM characterization through SFS, which linked to PLS make a powerful and cost-effective surrogate parameter to characterize DOM.     

Synthesis and enzymatic degradation of epichlorohydrin cross-linked pectins

The water solubility of pectin was successfully decreased by cross-linking with increasing amounts of epichlorohydrin in the reaction media. The initial molar ratios of epichlorohydrin/ galacturonic acid monomer in the reaction mixtures were 0, 0.37, 0.56, 0.74, 1.00, 1.47, and 2.44. The resulting epichlorohydrin cross-linked pectins were thus referred to as C-LP0, C-LP37, C-LP56, C-LP75, C-LP100, C-LP150, and C-LP250, respectively. Methoxylation degrees ranged from 60.5 ± 0.9% to 68.0 ± 0.6%, and the effective cross-linking degrees, determined by quantification of the hydroxyl anions consumed during the reaction, were 0, 17.8, 26.0, 38.3, 46.5, 53.5, and 58.7%, respectively. After incubating the different cross-linked pectins (0.5% w/v) in 25 mL of 0.05 M acetate-phosphate buffer (pH 4.5), containing 50 µL of Pectinex® Ultra SP-L (pectinolytic enzymes), between 60 and 80% of the pectin osidic bounds were broken in less than 1 hr. Moreover, increasing the cross-linking degree only resulted in a weak slowing on the enzymatic degradation velocity.     

Decision Analysis Applied to Tunnel Exploration Planning. II: Consideration of Uncertainty

Tunnel exploration is a classic problem of decision making under uncertainty. This paper, Part II, dealing with the exploration problem, discusses the sources of uncertainty in tunnel exploration, and provides techniques to formally incorporate uncertainties into the exploration planning. Part I described the state of uncertainty in geology and exploration reliability using assigned probabilities. These probabilities are, however, uncertain. Construction costs are also uncertain. This paper presents tools with which the decision maker is able to assess the effects of these uncertainties on exploration decisions. Decisions are therefore made based on the value of collecting new, uncertain information through “virtual” exploration prior to actually exploring.     

Noise Figure Reduction in Externally Modulated Analog Fiber-Optic Links

An octave-bandwidth microwave photonic link with a third-order limited spurious-free dynamic range of 121 dB in a 1-Hz bandwidth has been demonstrated. The link noise figure of 9 dB at a modulation frequency of 2 GHz was achieved by using a bias-shifted Mach-Zehnder modulator with an optical input power of 500 mW. This level of performance was realized without electronic or optical linearization     

Everything over IP — an overview of the strategic change in voice and data networks

This paper investigates the changes that are required in networking technology for ‘everything over IP’ to become a reality. Initially the changes that are taking place in the telecommunications industry are reviewed. This review ranges from a discussion about the companies installing massive global IP networks to the emergence of novel routeing technologies, e.g. multi-protocol label switching (MPLS) and terabit router technologies. The role of existing telecommunications operators is then discussed, along with the reasons why they are developing interworking and intelligence layers based on distributed computing principles to support all their networks — mobile, fixed, broadband and IP.     

Stabilization of gas-lift oil wells by a nonlinear model predictive control scheme based on adaptive neural network models

Producing oil from gas-lift wells are often faced with severe producing oscillatory flow regimes. A major source of the oscillations is recognized as casing–heading instability which is caused by dynamic interaction between injection gas and multiphase fluid. This phenomenon poses strict production-related challenges in terms of lower average production and strain on downstream equipment. In this paper, an effective solution is proposed based on integration of an online interpretation dynamic model and a nonlinear model predictive control (NMPC) scheme. The paper uses adaptive growing and pruning radial basis function (GAP-RBF) neural networks (NNs) to recursively capture the essential dynamics of casing–heading instability in a nonlinear model structure. Extended Kalman filter (EKF) and unscented Kalman filter (UKF) are comparatively investigated to adaptively train modified GAP-RBF NNs. NMPC methodology is developed on the basis of the identified nonlinear NN model for real-time stabilization of casing–heading instability in an oil reservoir equipped with a gas-lift production well. A set of test studies has been conducted to explore the superior performance of the proposed adaptive NMPC controller under different scenarios for an oil reservoir simulated in ECLIPSE and linked to a complementary gas-lifted oil well simulated in programming environment.     

Using bottom surface reflectance to map coastal marine areas: a new application method for Lyzenga's model

Remote sensing is widely used in coastal management. Lyzenga's model has been traditionally used to explain the relationship between bottom surface reflectance and the radiance level measured by satellite. Due to its central assumption, this model lacks accuracy compared with the other radiative transfer models. Nonetheless, it enables, with a single and simple equation, representation of the multiple optical processes taking place in coastal areas. Mapping processes associated with this model may include radiometric correction, a technique previously pointed out as a major driver of mapping accuracy. Radiometric correction is generally based on a depth-invariant index, efficient for clear waters (Jerlov water type I to II) but largely unsuitable when transparency decreases (Jerlov water type II to III). In order to overcome this problem, we developed a new index for radiometric correction, which combines bathymetry data with attenuation coefficients. The improved efficiency of our model with regard to the traditional depth invariant index was demonstrated through two case studies: Funakoshi Bay (Japan; Jerlov water type II) and the Gabes Gulf part located off Mahares (Tunisia; Jerlov water type II to III).     

High‐Performance Manganese Hexacyanoferrate with Cubic Structure as Superior Cathode Material for Sodium‐Ion Batteries

Sodium manganese hexacyanoferrate (Na_xMnFe(CN)₆) is one of the most promising cathode materials for sodium‐ion batteries (SIBs) due to the high voltage and low cost. However, its cycling performance is limited by the multiple phase transitions during Na⁺ insertion/extraction. In this work, a facile strategy is developed to synthesize cubic and monoclinic structured Na_xMnFe(CN)₆, and their structure evolutions are investigated through in situ X‐ray diffraction (XRD), ex situ Raman, and X‐ray photoelectron spectroscopy (XPS) characterizations. It is revealed that the monoclinic phase undergoes undesirable multiple two‐phase reactions (monoclinic ? cubic ? tetragonal) due to the large lattice distortions caused by the Jahn–Teller effects of Mn³⁺, resulting in poor cycling performances with 38% capacity retention. The cubic Na_xMnFe(CN)₆ with high structural symmetry maintains the structural stability during the repeated Na⁺ insertion/extraction process, demonstrating impressive electrochemical performances with specific capacity of ≈120 mAh g^?1 at 3.5 V (vs Na/Na⁺), capacity retention of ≈70% over 500 cycles at 200 mA g^?1. In addition, the TiO₂//C‐MnHCF full battery is fabricated with an energy density of 111 Wh kg^?1, suggesting the great potential of cubic Na_xMnFe(CN)₆ for practical energy storage applications.