Mixed modifier effect in lithium‐calcium borosilicate glasses

The mixed modifier effect (MME) in the lithium‐calcium borosilicate glasses, which have a composition of 0.4[(1?x)Li₂O–xCaO]–0.6[(1?y)B₂O₃–ySiO₂] with x in the range of 0~1 and y in the range of 0.33~0.83, is investigated. The MME manifests itself as a positive deviation from linearity in the activation energy of electrical conductivity (Ea^σ) and as a negative deviation from linearity in the fraction of four‐coordinated boron (N₄), glass transition temperature (T_g), dilatometric softening temperature (T_d), Vickers microhardness (H_v), dielectric constant (ε), and dielectric loss (tanδ). Moreover, the deviation, which exhibits a maximum at [CaO]/([CaO]+[Li₂O])=0.5, is enhanced with increasing [SiO₂]/[B₂O₃] ratio in the glass network. The observed MME in T_g, T_d, and H_v are attributed to the bond weakening in the network; however, the MME in ε, tanδ, and Ea^σ are caused by the obstruction of modifier transport in the glass network.     

High methanol oxidation activity of electrocatalysts supported by directly grown nitrogen-containing carbon nanotubes on carbon cloth

The microstructure and electrochemical activity of the Pt-Ru supported by nitrogen-containing carbon nanotubes (CN_x NTs) directly grown on the carbon cloth have been investigated. The CN_x NTs directly grown on the carbon cloth (CN_x NTs-carbon cloth composite electrode) were synthesized using microwave-plasma-enhanced chemical vapour deposition first and then use as the template to support the Pt-Ru nanoclusters subsequently sputtered on. The ferricyanide/ferrocyanide redox reaction in cyclic voltammetry (CV) measurements showed a faster electron transfer on the CN_x NTs-carbon cloth composite electrode than the one with carbon cloth alone. Comparing their methanol oxidation abilities, it is found that the Pt-Ru nanoclusters supported by the CN_x NTs-carbon cloth composite electrode have considerably higher electrocatalytic activity than the carbon cloth counterpart. This result suggests high performance of the CN_x NTs-carbon cloth composite electrode, and demonstrates its suitability for direct methanol fuel cell applications.     

Adsorption of color dyestuffs on polyurethane–chitosan blends

This study made use of poly(ethylene glycol) (PEG) samples of different molecular weights, which were reacted with a diisocyanate ester, and an anion center for the synthesis of polyurethane (PU), which was then mixed with chitosan to form a polymer adsorbent. It was tested for the determination of its adsorption toward acidic dyestuffs under various conditions. Our results showed that under all the tested conditions, the blended polymer adsorbent possessed a better adsorbing ability than chitosan by itself, and the degree of adsorption varied positively as the adsorbent concentration, ambient temperature, and contact time increased. Furthermore, the addition of PU remarkably increased the adsorption efficiency, whereas PEG with a greater molecular weight yielded a better adsorption performance. As for the dyestuffs, the red one surpassed the others in adsorption efficiency. Finally, a 5 mg/mL concentration of the adsorbent solution, a temperature of 45°C, and a contact time of 15 min gave fairly good adsorption results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3991–3998, 2004     

Dynamic modeling of the mold filling process in an injection molding machine

This paper presents the development of a nonlinear mathematical model for the study of the mold filling process in an injection molding machine. The model is formulated by the Reynolds transport theorem which is applied to describe the polymer flow dynamics. The mold filling process can be approximated by the transient phenomenon of the non-Newtonian fluids flowing through a closed conduit. The comparison between the experimental results and the theoretical simulation indicate that the nonlinear model is a reasonable representation of the mold filling dynamics when the acrylonitrile-butadiene-styrene (ABS) is injected into a disk shape mold. The actuation system dynamics of an injection molding machine are also investigated. The results indicate that the nonlinear model can also adequately predict the transient behavior of the actuation system.     

An Investigation of using statistically designed experiments and a computer model

This paper outlines the results of an experimental program aimed at established the best formation parameters for dynamic Zr (IV) — PAA membranes formed on porous ceramic supports. The membrane formation parameters investigated are the pressure, the circulation velocity, the Zr (IV) concentration, and the PAA concentration. The formation pressure was allowed to vary between 200 psig (1.4 MP_a) to 800 psig (5.4 MP_a), the circulation velocity from 6 fps (1.8 m/s) to 24 fps (7.3 m/s), the Zr (IV) concentration from 10^-4M to 9 × 10^-4M, and the PAA concentration from 50 ppm to 250 ppm.Twenty statistically designed experiments were conducted to evaluate the effect of these four parameters on the flux and rejection of the resulting membrane at the end of the formation procedure. The results were used in a multiple linear regression computer program named BMD-PIR which develops the measured values with an accuracy of +_ 2 percent. Using these models, it is possible to form a membrane with a given value of flux or rejection within their ranges.For the range of variables used in this study, the maximum membrane rejection was 91% corresponding to a flux of 10 gpd/ft²(1.7 cm/hr) for 0.05 M NaCl and 800 psi (5.4 MP_a). High rejection was obtained by increasing the membrane formation pressure and by increasing the PAA concentration. High flux can be achieved by increasing the formation pressure, by increasing the Zr (IV) concentration up to 9.0 × 10^-4M -, and by increasing the circulation velocity.     

Adsorption of o-xylene and p-xylene from water by SWCNTs

The influences of nitric acid oxidation on the surface properties and the adsorption capacity of single-walled carbon nanotubes (SWCNTs) were investigated in this work. To eliminate the size effects on the adsorption capacity, o-xylene and p-xylene were used as model adsorbates. It was found that purification of the SWCNTs by nitric acid significantly increased the internal surface area as well as the micropore volume of the SWCNTs, and introduced oxygen-containing surface groups. The adsorption capacities of the SWCNTs for o-xylene and p-xylene were mainly influenced by the positions of the methyl groups on the xylene molecules and the presence of oxygen-containing groups on the surface of the SWCNTs. Results also indicated that purification greatly changes the adsorption of o-xylene by the SWCNTs. This could be attributed to the dispersive attractions and the electrostatic repulsions between o-xylene molecules and the surface of the purified SWCNTs, which are introduced by the oxygen-containing surface groups. When compared to the as-grown and the purified SWCNTs, activated carbon had a greater adsorption capacity because of its large specific surface area and the absence of oxygen-containing surface groups. However, when the adsorption capacity was calculated based on surface area, the as-grown SWCNTs had a greater adsorption capacity than did the activated carbons because the micropore size of the activated carbon is mainly smaller than the size of a xylene molecule.     

Information technology customer aggression: The importance of an organizational climate of support

Information technology personnel are often ill prepared to react in a positive fashion to the aggressive communications from their customers, the users. Being able to regulate the emotions spiked by aggressive customer behavior is important to the long term health and retention of IT employees. Surface acting responses, the ability to display false emotions to mask strong emotions, is common, but not better for the long term health of the individual or organization. Deep acting responses, where emotional responses are modified to encourage expected behavior, are the better response and can be promoted with an organizational climate of support. A model derived from emotion response theory demonstrates these relationships hold for IT employees, who tend to be more introverted than most employees and often react differently to aggressive communication from customers. The model is verified with a sample of IT employees in Taiwan companies. Organizations should provide a climate of support for IT personnel and train them on how to respond appropriately to customer aggression through emotion regulation strategies in a direction that promotes better relationships.     

Photocatalytic Generation of H<Subscript>2</Subscript> Gas from Neat Ethanol over Pt/TiO<Subscript>2</Subscript> Nanotube Catalysts

TiO₂ nanotubes promoted with Pt metal were prepared and tested to be the photocatalytic dehydrogenation catalyst in neat ethanol for producing H₂ gas (C₂H₅OHC₃CHO +H₂). It was found that the ability to produce H₂, the liquid phase product distribution and the catlyst stability of these promoted nano catalysts all depended on the Pt loading and catalyst preparation procedure. These Pt/TiO₂ catalysts with TiO₂ nanotubes washed with diluted H₂SO₄ solution produced 1, 2-diethoxy ethane (acetal) as the major liquid phase product, while over those washed with diluted HCl solution or H₂O, acetaldehyde was the major liquid phase product.     

Mixed-Mode Fracture Toughness of Ceramic Materials

An experimental technique whereby pure mode I, mode II, and combined mode I-mode II fracture toughness values of ceramic materials can be determined using four-point bend specimens containing sharp, through-thickness precracks is discussed. In this method, notched and fatigue-precracked specimens of brittle solids are subjected to combined mode I-mode II and pure mode II fracture under asymmetric four-point bend loading and to pure mode I under symmetric bend loading. A detailed finite element analysis of the test specimen is performed to obtain stress intensity factor calibrations for a wide range of loading states. The effectiveness of this method to provide reproducible combined mode I-mode II fracture toughness values is demonstrated with experimental results obtained for a polycrystalline Al₂O₃. Multiaxial fracture mechanics of the Al₂O₃ ceramic in combined modes I, II, and III are also described in conjunction with the recent experimental study of Suresh and Tschegg (1987). While the mode II fracture toughness of the alumina ceramic is comparable to the mode I fracture toughness K _Ic, the mode III fracture initiation toughness is 2.3 times higher than K _Ic. The predictions of fracture toughness and crack path based on various mixed-mode fracture theories are critically examined in the context of experimental observations, and possible effects of fracture abrasion on the apparent mixed-mode fracture resistance are highlighted. The significance and implications of the experimental methods used in this study are evaluated in the light of available techniques for multiaxial fracture testing of brittle solids.