A case study of a stress corrosion cracking failure in an AA5083 mold material used for curing rubber compounds

Protection of Metals and Physical Chemistry of Surfaces - In this study the failure analysis of an AA5083 mold material, used for curing rubber compounds, was carried out. The problem revealed...     

Super toughened and highly ductile PLA/TPU blend systems by in situ reactive interfacial compatibilization using multifunctional epoxy-based chain extender

This study investigates the influence of using multifunctional epoxy Joncryl ADR 4468 chain extender (CE) on the properties of various polylactide (PLA)/thermoplastic polyurethane (TPU) (75 wt/25 wt) blend systems. The blends were based on two different TPU grades with ether- and ester-based soft segment as the dispersed phase (i.e., TPUether and TPUester) and an amorphous and a semicrystalline PLA grades as the matrix (i.e., aPLA and scPLA). PLA appeared to be more compatible with the TPUester, which caused the enhancement of the impact strength and strain at break values of the blends more remarkably. The dynamic rheological experiments also confirmed that the CE revealed a better reactivity with TPUester than TPUether. This further enhanced the interfacial compatibility between the PLA and TPUester and thereby dramatically improved the impact strength and ductility of the PLA/TPUester blends, specifically those with 0.5 wt% CE. Meanwhile, aPLA as the matrix reflected the TPUs toughening effect more efficiently than scPLA. This was due to the possible shrinkage caused by the crystallization of scPLA matrix, which could deteriorate the interfacial interactions between the phases in the corresponding blends.     

Poly(2‐alkyloyloxyethylacrylate) and poly(2‐alkyloyloxyethylacrylate‐co‐methylacrylate) comblike polymers as novel phase‐change materials for thermal energy storage

A series of poly(2‐alkyloyloxyethylacrylate) and poly(2‐alkyloyloxyethylacrylate‐co‐methylacrylate) polymers as novel polymeric phase‐change materials (PCMs) were synthesized starting from 2‐hydroxyethylacrylate and fatty acids. The chemical structure and crystalline morphology of the synthesized copolymers were characterized with Fourier transform infrared and ¹H‐NMR spectroscopy and polarized optical microscopy, respectively, and their thermal energy storage properties and thermal stability were investigated with differential scanning calorimetry and thermogravimetric analysis, respectively. The thermal conductivities of the PCMs were also measured with a thermal property analyzer. Moreover, thermal cycling testing showed that the copolymers had good thermal reliability and chemical stability after they were subjected to 1000 heating/cooling cycles. The synthesized poly(2‐alkyloyloxyethylacrylate) polymers and poly(2‐alkyloyloxyethylacrylate‐co‐methylacrylate) copolymers as novel PCMs have considerable potential for thermal energy storage and temperature‐control applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Rapid design space exploration using legacy design data and technology scaling trend

Rapid and effective design space exploration at all stages of a design process enables faster design convergence and shorter time-to-market. This is particularly important during the early stage of a design where design decisions can have a significant impact on design convergence. This paper describes a methodology for design space exploration using design target prediction models. These models are driven by legacy design data, technology scaling trends and, an in situ model-fitting process. Experiments on ISCAS benchmark circuits validate the feasibility of the proposed approach and yielded power centric designs that improved power by 7-32% for a corresponding 0-9% performance impact; or performance centric designs with improved performance of 10.31-17% for a corresponding 2-3.85% power penalty. Evolutionary algorithm based Pareto analysis on an industrial 65 nm design uncovered design tradeoffs which are not obvious to designers and optimize both power and performance. The high performance design option of the industrial design improved the straight-ported design's performance by 29% with a 2.5% power penalty, whereas the low power design option reduced the straight-ported design's power consumption by 40% for a 9% performance penalty.     

Combined analysis of contention window size and duty cycle for throughput and energy optimization in wireless sensor networks

The main objective in a wireless sensor network design is to minimize the energy expenditure for sustaining a long lifetime. Moreover, some recent multimedia applications require the network to satisfy specific throughput and delay constraints for large data sizes. In this paper, we analytically derive the expected throughput and the expected energy expenditure for a synchronized contention-based duty cycled MAC protocol. Our analysis explores the combined effect of contention window size, duty cycle and data size on throughput and energy expenditure for a successful transmission. We show that the performance of the network in terms of both metrics fluctuates with increased duty cycle as opposed to the general intuition that an increase in duty cycle increases the throughput and decreases the energy expenditure in the network. The results, validated by simulations, show that in order to provide an efficient MAC operation, the contention window size and the duty cycle should be optimized together for a given data size.     

The role of dislocation-induced scattering in electronic transport in GaxIn1-xN alloys

ABSTRACT: Electronic transport in unintentionally doped GaxIn1-xN alloys with various Ga concentrations (x = 0.06, 0.32 and 0.52) is studied. Hall effect measurements are performed at temperatures between 77 and 300 K. Temperature dependence of carrier mobility is analysed by an analytical formula based on two-dimensional degenerate statistics by taking into account all major scattering mechanisms for a two-dimensional electron gas confined in a triangular quantum well between GaxIn1-xN epilayer and GaN buffer. Experimental results show that as the Ga concentration increases, mobility not only decreases drastically but also becomes less temperature dependent. Carrier density is almost temperature independent and tends to increase with increasing Ga concentration. The weak temperature dependence of the mobility may be attributed to screening of polar optical phonon scattering at high temperatures by the high free carrier concentration, which is at the order of 1014 cm-2. In our analytical model, the dislocation density is used as an adjustable parameter for the best fit to the experimental results. Our results reveal that in the samples with lower Ga compositions and carrier concentrations, alloy and interface roughness scattering are the dominant scattering mechanisms at low temperatures, while at high temperatures, optical phonon scattering is the dominant mechanism. In the samples with higher Ga compositions and carrier concentrations, however, dislocation scattering becomes more significant and suppresses the effect of longitudinal optical phonon scattering at high temperatures, leading to an almost temperature-independent behaviour.     

Schistosomiasis presenting as acute appendicitis in a traveler

In the seized samples, the concentrations of diamorphine (heroin) varied from zero to more than seventy percent and the concentrations of cocaine from zero to more than ninety percent. Such variations in concentrations of active constituents constitute a major risk for those who use and abuse street drugs.     

Inhibition kinetics of polyphenol oxidase by glutamic acid

The inhibition of polyphenol oxidase (PPO) by glutamic acid was investigated. Application of different concentrations of glutamic acid to mushroom solution and Ocimum basilicum L. extract showed that glutamic acid appeared to be an effective browning inhibitor. Glutamic acid showed uncompetitive inhibition for mushroom and Ocimum basilicum L. polyphenol oxidases using 4-methylcatechol as a substrate, for mushroom PPO using catechol as a substrate and for Ocimum basilicum L. polyphenol oxidase using pyrogallol as a substrate; mixed-type inhibition for mushroom polyphenol oxidase using pyrogallol as a substrate; and non-competitive inhibition for Ocimum basilicum L. polyphenol oxidase using catechol as a substrate. Furthermore, sodium azide was used as an inhibitor for comparison with the inhibition potency of glutamic acid. It was found that glutamic acid was a more power inhibitor than sodium azide. The type of inhibition observed depended on the substrate, inhibitor and enzyme source used.     

Sulfonation degree determination of polystyrene ionomers by using adiabatic bomb calorimeter

Sulfonation degree determination of sulfonated polystyrene and the corresponding ionomers are performed by adiabatic bomb calorimeter. The theoretical calculations from the band energies for the combustion enthalpy values (calorific values) and the experimental values are compared, and a linear relation between the values is found. Sulfonation and neutralization processes are examined by elemental sulfur analysis and atomic absorption spectroscopy (AAS). It was obvious that increasing sulfonation degree yields a decrease in the combustion enthalpy values, as it is expected from the theoretical calculations. In addition, metal ion incorporation to the structure deviates the experimental combustion enthalpy values especially for the ionomers which have higher sulfonation degrees. This is due to the formation of a higher degree aggregation. © Wiley Periodicals, Inc. J Appl Polym Sci 100: 4684–4688, 2006