High third-order-intercept series-FET driver power amplifier [Application Notes]

An amplifier is called linear when the output power increases linearly with the input power. As input power increases, the amplifier transfer function becomes nonlinear, and a stage is reached where the output power does not increase with the input power. This happens because of transistor current and voltage clipping and the variations of transistor transconductance and junction capacitances with input RF power. One of the measures of nonlinearity of amplifiers is intermodulation distortion (IMD). When more than one carrier frequency is present in a nonlinear amplifier, multiple sidebands will be generated as intermodulation products due to mixing in the nonlinear device [1]-[8].     

Surface modification of lignosulfonates for reinforcement of styrene–butadiene rubber compounds

In this study, surface modification of lignosulfonates (LSs) was investigated for potential reinforcement of styrene–butadiene rubber compounds. Lignins are naturally occurring amorphous, highly branched polymers consisting of aromatic and aliphatic segments with polar functional groups such as hydroxyl, methoxy, carbonyl, and carboxyl. The polarity and hydrophilic nature render lignin incompatible with nonpolar rubber materials. In this study, cyclohexylamine (CA) modification of LS was evaluated for enhancement of compatibility with rubber via proton transfer and hydrogen bonding interactions. X‐ray photoelectron spectroscopy data confirm attachment of CA onto the surface of LS. The cure and scorch times of rubber compounds were shortened, and the crosslink density enhanced with an increase of the amount of CA in modified LS. The tensile strength at break increased by almost 45%; the 100% modulus and elongation at break also showed significant improvements. The values of storage modulus and loss tangent increased by 13% and 18%, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40123.     

Analysis of single blow effectiveness in non-uniform parallel plate regenerators

Non-uniform distributions of plate spacings in parallel plate regenerators have been found to induce loss of performance. In this paper, it has been investigated how variations of three geometric parameters (the aspect ratio, the porosity, and the standard deviation of the plate spacing) affects this loss in a single blow model of a parallel-plate regenerator. Simple analytical functions for the magnitude and the time scale of the reduction of performance are presented and compared to numerical results.     

Structural, magnetic and magnetocaloric properties of Heusler alloys Ni50Mn38Sb12 with boron addition

We report on the structural, magnetic and magnetocaloric properties of the Ni₅₀Mn₃₈Sb₁₂B_x alloys in term of boron addition with x = 1, 3 and 5. We have found that both the paramagnetic-ferromagnetic austenitic transition (T_C) and the ferromagnetic-antiferromagnetic martensitic transition (T_M) are sensitively influenced by the boron addition: T_C tends to increase, while T_M decreases with increasing boron concentration. Temperature dependent X-ray diffraction in the range of 200-500 K clearly shows an evolution of the structural transformation from orthorhombic to cubic structure phase transition on heating for the x = 1 and 3 samples. Strikingly, the addition of boron atoms into the lattice favours the ferromagnetic ordering relatively to the antiferromagnetic arrangement below T_M. This consequently affects on the magneto-structural transition as well as on the size of magnetocaloric effect.     

Finite Element Modeling of Camber Evolution During Sintering of Bilayer Structures

The need for understanding the mechanisms and optimization of shape distortions during sintering of bilayers is necessary while producing structures with functionally graded architectures. A finite element model based on the continuum theory of sintering was developed to understand the camber developments during sintering of bilayers composed of La_0.85Sr_0.15MnO₃ and Ce_0.9Gd_0.1O_1.95 tapes. Free shrinkage kinetics of both tapes were used to estimate the parameters necessary for the finite element models. Systematic investigations of the factors affecting the kinetics of distortions such as gravity and friction as well as the initial geometric parameters of the bilayers were made using optical dilatometry experiments and the model. The developed models were able to capture the observed behaviors of the bilayers’ distortions during sintering. Finally, we present the importance of understanding and hence making use of the effect of gravity and friction to minimize the shape distortions during sintering of bilayers.     

Optimization of wear and friction characteristics of Phyllanthus Emblica seed oil based lubricant using response surface methodology

The escalating prices, rapid diminution of fossil fuels, tenacious regulations of the authorities, etc. enforced towards the alternate biogenic fuel for lubrication. The present study assessed the lubricity characteristics of Phyllanthus Emblica seed oil based lubricants by using a pin on disc (POD) tester. The design of experimentations has been carried out using response surface methodology (RSM). The value of parameters such as blend ratio, load and sliding speed ranges from 0 to 20%, 50 to 100?N and 1.3 to 3.8?m/s, respectively, are used to assess the value of specific wear rate (SWR) and coefficient of friction (COF). Test results illustrate that the adhesive wear occurred during the experiments. It has been observed that AB10 shows the probable results in terms of wear and friction characteristics as compared to other lubricant variants at low load and high sliding velocity conditions and perform as an excellent lubricant additive. This contributes towards the replacement of petroleum based lubricants. Analytical ferrography and total acid number (TAN) analysis of the used oil was also done to study the wear debris in the oil.     

Doubly strainedIn0.41Al0.59As/n+-In0.65Ga0.35As HFET with high breakdown voltage

An In_0.41Al_0.59As/n⁺-In_0.65 Ga_0.35As HFET on InP was designed and fabricated, using the following methodology to enhance device breakdown: a quantum-well channel to introduce electron quantization and increase the effective channel bandgap, a strained In_0.41Al_0.59As insulator, and the elimination of parasitic mesa-sidewall gate leakage. The In_0.65Ga_0.35As channel is optimally doped to N_D=6×10¹⁸ cm^-3. The resulting device (L_g=1.9 μm, W_g =200 μm) has f_t=14.9 GHz, f_max in the range of 85 to 101 GHz, MSG=17.6 dB at 12 GHz V_B=12.8 V, and I_D(max)=302 mA/mm. This structure offers the promise of high-voltage applications at high frequencies on InP     

10W CW broadband balanced limiter/LNA fabricated using MSAG MESFET process

This article presents the design and test data for a 10W broadband balanced limiter/LNA MMIC fabricated using MSAG MESFET process. The limiter is based on Schottky diodes and the two‐stage LNA is designed using high‐performance MESFETs. The typical measured performance for the limiter/LNA circuit includes gain greater than 14 dB, NF less than 2.7 dB, and return loss better than 20 dB over the 8.5–11.5 GHz frequency range. The CW power handling for the packaged limiter/LNA circuits was greater than 10W. The packaged devices were also exposed to power levels greater than 10W, and no catastrophic failures were observed up to 18W. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 118–127, 2003.