Development of an in-line viscometer in an extrusion molding process

In this work, an in-line viscometer to measure the viscosity of polymer melts under extrusion molding processes was developed. The in-line viscometer contains a stress sensor and a shear rate sensor which were installed between the screw and the die of an extruder. In this way, the flow line after the screw cannot be changed, unlike the present in-line capillary rheometer which can change the diameter of the pipe of the flow line and hence influence the throughput. All data acquisition is done by a computer such that the melt viscosity can be calculated automatically. The shear-thinning behavior of a low-density polyethylene (LDPE) under three different temperatures is presented in all experiments. It is concluded that the melt viscosity can be effectively monitored. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 919–924, 1997     

Kinetic approach for epoxy resins cured with diaminodiphenyl sulfone under non‐isothermal conditions

The curing reactions of epoxy resin basing on diglycidyl ether bisphenol A (DGEBA) with 4,4′‐diaminodiphenyl sulfone (DDS) were investigated with a differential scanning calorimeter and gel permeation chromatography. Based on the generating function method and the Monte Carlo simulation procedure, kinetic models for both isothermal and nonisothermal curing conditions were proposed. The apparent activation energy of curing reactions was found to be 14.9 Kcal/mol by the thermal analysis. According to our kinetic models, gel points, the profiles of epoxy conversion, and the molecular weights of polymers were calculated. Good agreement is obtained between the model predictions and experimental data. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 721–728, 1999     

Modification of Nylon 6 by phenol‐containing polymers

A crystalline polymer, Nylon 6, was selectively blended with various amorphous polymers containing phenolic moieties. It was found that moisture absorption by the amide group in Nylon 6 could effectively be reduced by blending with p‐Cl‐novolac at ratios as low as 2 phr (part per hundred resin). Blends of Nylon 6 with vinylphenol homopolymer and its copolymer with styrene also showed reduced moisture uptakes, but the effect was less dramatic than that of the p‐Cl‐novolac blend at all blend ratios. Novolac content in excess of 5 phr shows little additional advantage in moisture reduction. Thermal transitions of blends of Nylon 6 with poly(vinyl phenol), its copolymer, and p‐Cl‐novolac were also investigated. At a blend ratio of 5 phr, p‐Cl‐novolac caused a larger increase in glass transition temperature than the other two blends. The melting temperatures of the blends were little influenced by low levels of the amorphous polymer incorporation, but broader melting endotherms in the differential scanning calorimetry scans were observed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 295–300, 1999     

Estimation of the ends pressure drop in an online capillary rheometer—using the neural network approach

Using an online or inline capillary rheometer as a tool of rheology measurement would come into the ends pressure drop problem. In order to derive the actual pressure drop of the capillary, another capillary with the same diameter and different length is needed (according to Bagley correction) but would result in a more complex mechanism. In this study, a neural network approach is proposed to estimate the ends pressure drops in an online capillary rheometer. The back propagation learning algorithm is used for network training. The shear rate, the die pressure, and the ratio of diameters of the reservoir to the capillary are taken as the neural network inputs, and the ends pressure drop is taken as the output. Two hundred of training sets that are made from a laboratory capillary rheometer are used for network training. The trained neural network can be consequently applied to real-time assessment of the ends pressure drops in the online capillary rheometer. It is concluded that using the proposed method for calculating the ends pressure drop is effective. Besides, the simplicity of the mechanism provides good portability for both online polymer characterization and quality control in processing. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2183–2186, 1999     

The curing reaction and physical properties of DGEBA/DETA epoxy resin blended with propyl ester phosphazene

The influences of different amounts of propyl ester phosphazene (FR) on the curing kinetics and physical properties of diglycidyl ether of bisphenol A (DGEBA) epoxy prepolymer cured with diethylenetriamine (DETA) were investigated with DSC, SEM, DMA, and tensile testing. The results revealed that FR could be a catalyst or a diluent depending on the FR content. In addition, the blending systems were partially miscible. The tensile strength and modulus of blends decreased with increasing amounts of FR, but the elongation increased with increasing FR. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 229–237, 1999     

Flame Temperature Calculations at High Temperature and Pressure

In the past, real gas effects on the flame temperature were evaluated using the virial equation of state. Usually, the virial expansion was truncated after the third term. In this work the equation of state for dense gases proposed by Haar and Shenker is considered. The implementation developed for H₂O, CO, CO₂, H₂, and N₂ by Powell, Wilmot, Haar and Klein is used. The contribution of all minor species is assumed to be approximated by a Lennard-Jones gas with ϵ/k = 100 K and σ = 3.0 Å. It is found that the more conventional approach is valid up to a loading density of 0.2 g/cm³. As density increases real gas effects cause the calculated flame temperature to decrease and the calculated pressure to increase. A computer program to perform the calculations has been devised for a personal computer.     

Multi-scaled polymersomes from self-assembly of octadecanol-modified dextrans

Lipid-conjugated polysaccharide vesicles in nano- and micro-scale were developed from amphiphilic octadecanol-modified dextrans (OMD) prepared by partial esterification of dextran with activated octadecanol-carbamate imidazole in a well-controlled manner. The critical aggregation concentration (CAC) of OMD adducts in aqueous phase varies, depending mainly on their octadecanol contents. Through supramolecular assembly of the OMD adducts comprising either 17 or 28 mol% octadecanol residues with respect to the anhydroglucopyranose units by the partial solvent displacement technique with the initial water content of DMSO/H₂O solutions beyond a critical point, stable nano-scaled OMD assemblies were developed and characterized by the vesicle-like morphology. The dimension of polymersomes can be effectively controlled by the OMD composition as well as the initial water content. On the other hand, micro-scaled OMD polymersomes can be achieved by the double emulsion technique in a water/oil/water (w₁/o/w₂) manner. Both the contents of NaCl in aqueous solution as the w₁ phase and of DMSO in DMSO/CHCl₃ co-solvents as the organic phase, in which OMD was dissolved, are of great importance in controlling the polymersome morphology and size. These micro-scaled OMD polymersome walls are characterized by size-selective permeability capable of encapsulating large water-soluble cargoes while allowing transport of small polar species across the membrane, thereby rendering these unique colloidal particles of potential applications in biomedical technologies.     

Metallic conduction and large electron-phonon-impurity interference effect in single TiSi nanowires

ABSTRACT: We report on the first electrical characterizations of single-crystalline TiSi nanowires (NWs) synthesized by chemical vapor deposition reactions. By utilizing the focused-ion-beam-induced deposition technique, we have delicately made four-probe contacts onto individual NWs. The NW resistivities have been measured between 2 and 300 K, which reveal overall metallic conduction with small residual resistivity ratios in the NWs. Surprisingly, we find that the effect due to the interference processes between the elastic electron scattering and the electron-phonon scattering largely dominates over the usual Boltzmann transport even at room temperature. Such prominent electron-phonon-impurity interference effect is ascribed to the presence of large amounts of disorder and high Debye temperatures in TiSi NWs.     

A web search-centric approach to recommender systems with URLs as minimal user contexts

In service-oriented computing, a recommender system can be wrapped as a web service with machine-readable interface. However, owing to the cross-organizational privacy issue, the internal dataset of an organization is seldom exposed to external services. In this paper, we propose a higher level recommender strategy INSERT that guides the underlying external universal recommender to suggest a set of indexes. INSERT then matches the title of each top-ranked index entry with the domain-specific keywords in the organization's internal dataset, and further directs the universal recommender to verify the popularity of such matching. INSERT finally makes recommendation based on the verification results. INSERT also employs URLs taken from a client as user contexts, which is challenging because URLs contain little content. Our experiment shows that this strategy is feasible and effective.     

Interface traps and random dopants induced characteristic fluctuations in emerging MOSFETs

In this work, we study the effect of interface traps (ITs) and random dopants (RDs) on characteristics of 16-nm MOSFETs. Totally random generated devices with 2D ITs between the interface of silicon and HfO₂ film as well as 3D RDs inside the silicon channel are simulated. Fluctuations of threshold voltage and on/off state current for devices with different EOT of insulator film are analyzed and discussed. The results of this study indicate ITs and RDs statistically correlate to each other and RDs govern device variability, compared with the influence of ITs. Notably, the position of ITs and RDs induces rather different fluctuation in spite of the same number of ITs and RDs are investigated.