Microstructure Design for Fast Lifetime Measurements of Magnetic Tunneling Junctions

The estimation of the reliability of magnetic field sensors against failure is a critical point concerning their application for industrial purposes. Due to the physical stochastic nature of the failure events, this can only be done by means of a statistical approach which is extremely time consuming and prevents a continuous observation of the production. Here, we present a novel microstructure design for a parallel measurement of the lifetime characteristics of a sensor population. By making use of two alternative designs and the Weibull statistical distribution function, we are able to measure the lifetime characteristics of a CoFeB/MgO/CoFeB tunneling junction population. The main parameters governing the time evolution of the failure rate are estimated and discussed and the suitability of the microstructure for highly reliable sensor application is proven.

A Method to design composite insulation structures based on reliability for pulsed power systems

A method to design the composite insulation structures in pulsed power systems is proposed in this paper. The theoretical bases for this method include the Weibull statistical distribution and the empirical insulation formula. A uniform formula to describe the reliability (R) for different insulation media such as solid, liquid, gas, vacuum, and vacuum surface is derived. The dependence curves of the normalized applied field onRare also obtained. These curves show that the normalized applied field decreases rapidly asRincreases but the declining rates corresponding to different insulation media are different. In addition, ifRis required to be higher than a given level, the normalized applied field should be smaller than a certain value. In practical design, the common range of the applied fields for different insulation media should be chosen to meet a global reliability requirement. In the end, the proposed method is demonstrated with a specific coaxial high-voltage vacuum insulator.

Characterization of Raw and Treated Curaua Fibers to be Applied as Reinforcement in Composites

Lignocellulosic fibers present several advantages over synthetic fibers, such as low cost and biodegradability. In this work the tensile mechanical behavior of as-received and surface treated curaua fibers was analyzed. Mercerization and three different enzyme surface treatments were used. The tensile stress data were analyzed using the Weibull statistical distribution, and SEM was used to characterize the surface modifications caused by the treatments. The results show that mercerization causes an increase of the deformation capacity of the fibers. This result was attributed to the removal of hemicellulose, and to an increase of mobility of the internal fibrils. The increase of NaOH concentration at the alkali solution affects both the surface characteristics and the tensile properties. Solutions with more than 5%wt NaOH degraded the fibers. The enzyme treatments increase the tensile mechanical properties, but also increase their brittleness.

Characterization of the Tensile Behavior of Pejibaye (Bactris gasipaes) Fibers

Pejibaye (Bactris gasipaes) palm is harvest in large plantations to the sustainable production of heart of palm. Residues of the cut down palms can be conveniently managed to produce short and long fibers. These fibers are now beginning to be used to produce agglomerated panels and to reinforce polymeric matrices composites, but their mechanical behavior is not yet described at the literature. In this work, the tensile mechanical behavior of pejibaye fibers is characterized and the results are described using the Weibull statistical distribution and are compared with the tensile properties of other common lignocellulosic fibers.

The determination of growth in Akkeci (White goat) female kids by various growth models

This study aimed to determine the growth of 26 Akkeci (White goat = Saanen × Kilis (Bı) crossbreed) female kids by measuring their body weight, withers height, body length, heart girth depth, heart girth width, heart girth circumference, leg circumference and volume index in two-week intervals from birth to 500 days of age and by using different growth models (Monomolecular, Gompertz, Weibull and Richards). An approximate volume index was calculated by multiplying the values of heart girth depth, body length and heart girth width. The best one among these models was determined in respect of RMS (square root of Residual Means Squares which is calculated from the Square Root of Error Mean Square in ANOVA), R²%, Adjusted R²%, Mallow’s C_pstatistic, and asymptotic correlation coefficients criteria. As a result, it was determined that Weibull growth model (which is not concerned with Weibull statistical distribution but is related to parameters of Weibull distribution) was suitable for the above-mentioned material and studied traits.