Total ionizing dose effects in shallow trench isolation oxides

The peaked evolution of leakage current with total ionizing dose observed in transistors in 130 nm generation technologies is studied with field oxide field effect transistors (FOXFETs) that use the shallow trench isolation as gate oxide. The overall radiation response of these structures is determined by the balance between positive charge trapped in the bulk of the oxide and negative charge in defect centers at its interface with the silicon substrate. That these are mostly interface traps and not border traps is demonstrated through dynamic transconductance and variable-frequency charge-pumping measurements. These interface traps, whose formation is only marginally sensitive to the bias polarity across the oxide, have been observed to anneal at temperatures as low as 80 °C. At moderate or low dose rate, the buildup of interface traps more than offsets the increase in field oxide leakage due to oxide-trap charge. Consequences of these observations for circuit reliability are discussed.     

State-of-art review of the optimization methods to design the configuration of hybrid renewable energy systems (HRESs)

The current research aims to present an inclusive review of latest research works performed with the aim of improving the efficiency of the hybrid renewable energy systems (HRESs) by employing diverse ranges of the optimization techniques, which aid the designers to achieve the minimum expected total cost, while satisfying the power demand and the reliability. For this purpose, a detailed analysis of the different classification drivers considering the design factors such as the optimization goals, utilized optimization methods, grid type as well as the investigated technology has been conducted. Initial results have indicated that among all optimization goals, load demand parameters including loss of power supply probability (LPSP) and loss of load probability (LLP), cost, sizing (configuration), energy production, and environmental emissions are the most frequent design variables which have been cited the most. Another result of this paper indicates that almost 70% of the research projects have been dedicated towards the optimization of the off-grid applications of the HRESs. Furthermore, it has been demonstrated that, integration of the PV, wind and battery is the most frequent configuration. In the next stage of the paper, a review concerning the sizing methods is also carried out to outline the most common techniques which are used to configure the components of the HRESs. In this regard, an analysis covering the optimized indicators such as the cost drivers, energy index parameters, load indicators, battery’s state of charge, PV generator area, design parameters such as the LPSP, and the wind power generation to load ratio, is also performed.     

A Very Low Voltage Bipolar Op-Amp for Sensor Applications

A new bipolar four-quadrant operational amplifier operating at a power supply voltage of 0.8 V and with a supply current of 800 A is here presented and illustrated. It features low input offset, low bias current, low noise, low crossover distortion and a rail-to-rail output swing. Control circuits ensuring minimum and maximum current limits for the output transistors have been incorporated. The biasing circuitry follows a PTAT scheme. A simple compensation topology allows the reduction of the area. The chip, whose area is about 2 mm², has been fabricated in HF2CMOS 2 /6 GHz technology. Finally, Spice simulations and experimental results, which confirm the expected overall performances of the low voltage op-amp, are reported.     

Mixed-model sequencing optimization for an automated single-station fully flexible assembly system (F-FAS)

Flexible automated assembly is an emerging need in several industries. In the case of a very wide set of models and a total medium/low derived production volume, the proper assembly system to use is a single cell with high flexibility capabilities. An innovative concept in flexible automated assembly has recently been introduced [28, 29]: the fully flexible assembly system (F-FAS). The F-FAS relies on a single-station robotized assembly system, where a unique fully flexible feeder is responsible for the delivery of the parts needed for assembly, guaranteeing a higher level of flexibility than the traditional automated FAS. The mixed-model sequencing (MMS) problem is typically related to the assembly line system. The aim of this paper is to introduce a new class of MMS problem: the single-station mixed-model sequencing problem that arises when the parts to assemble are randomly presented on the working plane, as in the F-FAS. The authors first define the MMS in such a single-station assembly system and then propose different sequencing algorithms in order to solve it. The authors first define the problem and then propose different sequencing algorithms. With the aim of finding the best sequencing approach to use in such an assembly system, the algorithms are compared through ad hoc developed benchmarking tests, using a dedicated software application that simulates the real behavior of the work cell.     

Single event effects in static and dynamic registers in a 0.25μm CMOS technology

We have studied single event effects in static and dynamic registers designed in a quarter micron CMOS process. In our design, we systematically used guardrings and enclosed (edgeless) transistor geometry to improve the total dose tolerance. This design technique improved both the SEL and SEU sensitivity of the circuits. Using SPICE simulations, the measured smooth transition of the cross-section curve between LET threshold and saturation has been traced to the presence of four different upset modes, each corresponding to a different critical charge and sensitive area. A new architecture to protect the content of storage cells has been developed, and a threshold LET around 89 MeV cm ² mg^-1 has been measured for this cell at a power supply voltage of 2 V     

Single event upset tests of an 80-Mb/s optical receiver

This paper studies the single event upset (SEU) sensitivity of a radiation-tolerant 80-Mb/s receiver developed for the CMS Tracker digital optical link. Bit error rate (BER) measurements were made while irradiating the receiver with protons and neutrons at different beam energies and incident angles and for a wide range of optical power levels in the link. Monte Carlo simulations have also been used to assist in the interpretation of the experimental results. As expected, the photodiode is the most sensitive element to SEU. The fake signal induced by direct ionization dominates the bit-error cross-section only for protons incident on the photodiode at large angles and low levels of optical power. Comparison of the neutron and proton bit-error cross-sections demonstrates that nuclear interactions contribute significantly to the proton-induced SEU errors and that they will dominate the radiation-induced error rate in the real Tracker application     

Effect of enzymatic cross-linking of β-casein on proteolysis by pepsin

Food texture has a significant influence on the sensation of satiety. The digestibility of a protein matrix can be decreased by e.g. disulfide cross-links during heating, but the structure and properties of a single protein molecule can also be modified by cross-linking enzymes. In this study the effects of cross-linking of β-casein by fungal Trichoderma reesei tyrosinase (TrTyr) and bacterial Streptoverticillium mobaraense transglutaminase (Tgase) on digestibility by proteolytic pepsin were investigated by different methods. The enzymatic reaction conditions were selected in such a way that high and low molecular mass cross-linked β-casein polymers were formed. SDS-PAGE (sodium dodecyl sulphate-polyacrylamide gel electrophoresis) was used to analyze the pH stability of the cross-linked β-casein in acidic solution mimicking gastric conditions typically present during proteolytic digestion. In order to monitor the extent of pepsin digestion, the proteolytic process was halted at specific time points and aliquots of the reaction mixtures were subjected to SDS-PAGE, size-exclusion chromatography (SEC) and matrix-assisted laser desorption ionization-time of flight mass spectrometric (MALDI-TOF MS) analyses in order to evaluate sizes and quantities of the digested protein fragments. A pH-stat method was used to determine the degree of hydrolysis (DH) of the enzymatically cross-linked β-casein. The results demonstrated that enzymatically cross-linked β-casein was stable under acidic conditions and was more resistant to pepsin digestion when compared to non cross-linked β-casein. The research results will have high impact on the development of novel food structures with improved properties such as good satiety, controlled energy intake and digestibility.     

Structural analysis of oxyfluoride borate glass and BaF2 crystallization from phase separation

Oxyfluoride glass and glass-ceramics are being studied due to the possibility of their utilization in many applications, such as thermoluminescent dosimeters, optical fibers, fluorescent concentrators, and temperature sensors. In order to improve the properties of glass, they are often crystallized. For this crystallization to be effective, knowledge and control of the structure of the starting material is required. Much work was done on silicate glass; however, a great interest exists in obtaining these kinds of materials in other matrices such as germanates, phosphates, and borates. Here, we present a structural study of some oxyfluoride borate glass with different concentrations of PbF₂ by means of Nuclear Magnetic Resonance (NMR), Raman, and Fourier Transform Infrared (FTIR) spectroscopies. We also analyzed glass-crystallization using Differential Scanning Calorimetry (DSC). The crystallization study was complemented with the use of Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED), for the purpose of identifying possible mechanisms of crystallization. Our results indicate, from the structural point of view, that the glass present groups with one or two BO₄ species, such as diborate or pentaborate. The small variation in the BO₄ fraction with the increase in PbF₂ concentration would be an indication of the formation of F⁻BO_3/2 species. Oxyfluoride borate glass containing BaO as a cation modifier and 30% PbF₂ represents a good starting point for obtaining glass-ceramics with a narrow size distribution of BaF₂ nanocrystals. We also propose that the possible mechanism for oxyfluoride borate glass crystallization started with a separation of phases.     

Molybdenum effect on the kinetic behavior of a metal hydride electrode

In the present investigation, the effect of the Mo in the LaNi_3,6Co_0,7Mn_(0.4−x)Al_0,3Mo_x AB5-type hydrogen storage alloys was studied. The alloys structural and microstructural characterizations were performed by means of X-ray diffraction phase analysis and scanning electron microscopy.