Thermomechanical behaviour of poly[acrylonitrile‐co‐(methyl acrylate)] fibres oxidatively treated at temperatures up to 180 °C

PAN fibres, consisting of poly[acrylonitrile‐co‐(methyl acrylate)], were oxidatively heat treated at low temperatures (up to 180 °C), during which the basic macromolecular backbone was not cyclized. The change of length of the fibres was determined under various treatment conditions (ie temperature, time, stress applied). Prolonged heat treatment resulted in lower tensile strength of the fibres. The pristine and treated fibres were characterized by Fourier‐transform infrared (FTIR), NMR and UV‐visible spectroscopy and by TGA, and the results were used for representing the different regions according to chemical aspects in a plot of temperature versus time; this is very important for the whole treatment process. A shrinkage model was proposed, having both scientific and technical importance. The change in activation volume of shrinkage of fibres with temperature, calculated from this model, is indicative of the physical transitions taking place at the molecular scale. Copyright © 2005 Society of Chemical Industry     

High intensity compounding of mica-filled thermoplastics

High-speed turbine mixers have been adapted for compounding filled thermoplastics by the partial flux method. The extreme shearing forces exerted by the mixing impellors simultaneously mixes and delaminates mica fillers to form finely dispersed compounds in a granular, partially fused state which can be directly injection molded without pelletizing. In practice, one turbine mixing unit can be employed for compounding all types of resins and fillers. The partial flux method permits compounding to be accomplished at peak sensor temperatures that are considerably below the resin softening or melting transitions, frequently 50°C less than normal compounding temperatures. The short residence times and reduced energy requirements possible with partial fluxing results in substantial cost reduction without compromising quality or performance. Examples are provided for polypropylene, nylon 66, poly(butene terephthalate), poly(ethylene terephthalate) and poly(phenylene oxide) alloys. Impact modifiers derived from carboxylated polyolefin waxes may be dispersed by the intense shearing action to form highly subdivided submicron particles, which promote crazing and shear deformation during fracture testing, thereby contributing to increased composited toughness with minor sacrifice in modulus and strength. The mechanical properties of micafilled thermoplastics have also been compared with those of short glass fiber composites. In certain applications requiring stiffness and dimensional stability at elevated temperatures, mica composites prepared by intensive mixing in a turbine mixer may be economically substituted for glass fiber counterparts.     

A Strategy for Harmonised QoS Manipulation in Heterogeneous IMS Networks

Heterogeneous networks are collections of communication platforms utilising different protocols. Heterogeneity was born by the need of operators to offer within short time many different services on the market. As a result, nowadays users communicate through collections of networks utilising different protocols, rendering service mapping from one network to another a complex issue. With the emergence of IMS and the introduction of IP and SIP protocols as a means for achieving network homogeneity, service interoperability has become even more important. With regard to this problem, the paper proposes a method for homogenising IMS networks with regard to the utilised QoS settings and charging policy. The paper explains how the method can be applied on real IMS networks for the preservation of QoS and charging records across the whole communication path and carries out a comparative analysis with performance figures obtained in real networks.

Bulk-driven class AB fully-balanced differential difference amplifier

This paper presents a new low-voltage class AB fully-balanced differential difference amplifier (FB-DDA) employing the bulk-driven technique. At the FB-DDA differential pairs the bulk terminal of the MOS transistors are used as signal inputs in order to increase the common-mode input range under low supply voltage. At the class AB output stages the bulk terminal of the MOS transistors are used as control inputs in order to adjust the quiescent currents and compensate them against the process and temperatures (P/T) variation. The voltage supply of the FB-DDA is 0.7 V and the quiescent power consumption is 8.3 µW. The open loop voltage gain is 68 dB and the gain–bandwidth product is 168 kHz for 10 pF capacitive load. The circuit performance was simulated in Cadence/Spectre environment using the TSMC 0.18 µm CMOS process.     

Differential Difference Current Conveyor Using Bulk-Driven Technique for Ultra-Low-Voltage Applications

Nowadays the necessity of having low-voltage operation and low-power consumption is essential for electronic devices, particularly for portable electronics. Therefore, this paper presents a new ultra-low-voltage CMOS topology for a differential difference current conveyor (DDCC) based on the bulk-driven (BD) principle. Due to the use of the BD technique, the proposed circuit is capable of working with a low supply voltage of ±0.3 V and consumes about 18.6 μW with a wide input common-mode range. The proposed BD-DDCC is suitable for ultra-low-voltage low-power applications. As application examples, a voltage-mode multifunction biquadratic filter based on two BD-DDCCs and four grounded passive elements, and a fourth-order band-pass filter are presented. All passive elements of both applications are grounded, which is advantageous for monolithic integration. Also, the input voltage signals are applied directly to the high input impedance terminals, which is a desirable feature for voltage-mode operation. The simulations were performed with PSPICE using the TSMC 0.18 μm n-well CMOS technology to prove the functionality and attractive results of the proposed circuit.     

Influence of electrochemical copolymerization conditions of 3‐methylthiophene and biphenyl on the morphology and nanomechanical properties of the films

The aim of this work is to synthesize novel 3‐methylthiophene (3MTh)/biphenyl (Biph) copolymer films by electropolymerization and study their mechanical properties through nanoindentation. The morphology, the chemical structure as well as the electrical conductivity of the copolymer films depended strongly on the electropolymerization conditions. It was found that the polymer deposition follow an instantaneous, two‐dimensional nucleation and growth mechanism leading to homogenous films. The copolymer films had higher Young modulus and nanohardness than poly(3‐methylthiophene) (3PMTh), indicating that the incorporation of Biph units within the P3MTh chain leads to a more densely packed structure and a more brittle polymer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42575.     

Simple models for evaluating effects of small leaks on the gas barrier properties of food packages

A detailed theoretical analysis and calculations were made for providing a simple and explicit means to evaluate the effects of small leaks on the barrier properties of food packages. Small leaks, such as pinholes and channel leaks, were approximated as cylindrical pores with diameters of 50–300 μm. The first part of the current study proposes a simple mathematical model based on Fick's law of diffusion, which accounts for both the gas leakage across small leaks and the gas permeation across package walls. The model uses an effective permeability that depends on leak dimensions, type of diffusing gas, type of packaging material and gas conditions around the leak ends. In the second part of the study, three practical cases are presented to illustrate the application of the proposed model in examining the significance of leaks. These demonstrate in a simple and explicit manner that for LDPE packages: (a) leaks affect the oxygen transfer more than the water vapour transfer; (b) leak effects are more significant at lower storage temperatures; and (c) that for high gas barrier packages, the effect of leaks is very important and should not be neglected. The model can be also used to arrive at conclusions about the significance of leaks in other packaging situations (e.g. other than LDPE packaging materials) and to correct the shelf‐life estimation of gas‐ and water vapour‐sensitive foods for errors from package leaks. Copyright © 2003 John Wiley & Sons, Ltd.     

0.8 V bulk-driven operational amplifier

A low-voltage bulk-driven CMOS operational amplifier is proposed in this paper. The inherent small transconductance of the bulk-driven devices is enlarged using a positive feedback, improving also the noise performance. The amplifier is designed using standard 0.18 μm n-well CMOS process. Although the amplifier is optimized for 0.8 V supply voltage, it is also capable to operate under supply voltage of 0.7 V. The amplifier consumes 130 μΑ, performing 56 dB open-loop gain, 154 nV/√Hz input-referred spot noise at 100 kHz, 80 dB CMRR at 100 kHz and IIP3 equal to −4.7 dBV.     

Influence of oestrus on the heat stability and other characteristics of milk from dairy goats

We examined the heat stability, somatic cell count (SCC), pH, fat, protein and lactose content of milk from goats during the oestrous period, in order to investigate evidence of possible oestrus effects on milk physical and chemical properties. Goats free from mammary infections were ranked on average SCC from three tests so that they could be stratified randomly in pairs to synchronized oestrus or left as unsynchronized non-oestrus controls. The synchronisation consisted of insertion of an intravaginal progesterone-releasing device for 17 d, and introduction of the bucks the day of the device removal (D0). The repeated measurements analysis of variance model included the fixed effects of the experimental group (oestrus or control) and day and the corresponding interaction and also the random effect of doe. Reduced milk-heat stability, increased SCC, increased protein content and reduced pH were found in the milk samples of the oestrus group on D1, 2 and 3. The fat and lactose content of the milk was not affected by oestrus. These data indicate that the milk of goats during the mating period has reduced heat stability and, therefore, that dilution into bulk tanks should be recommended to avoid clotting when milk is intended for high thermal treatment.