Analysis of the gate current as a suitable indicator for FET degradation under nonlinear dynamic regime

Electron device degradation, although not directly accounted for, represents a key issue in microwave circuit design. This is especially true when the particular applications involved (e.g., satellite, military, consumer) do not allow or strongly discourage any kind of maintenance. As a matter of fact, in order to account for device degradation in circuit design, a suitable electron device model is needed which is able to predict the performance degradation as a function of the actual electrical regime involved in the device operation. Such a kind of model is not available in literature. In this paper, quantitative results are provided for device degradation indicators which correlate DC and RF stress experiments. These results can be considered an important step toward the definition of a nonlinear model accounting for device degradation.     

Stereochemistry and Circular Dichroism of Chiral Internal Olefin-Platinum(II) Complexes

A series of cis- and trans-dichloro(benzylamine) (chiral olefin) platinum(II) complexes, containing (Z) and (E) isomers of the internal chiral olefins R-CH=CH-R', has been prepared by ethylene displacement from the corresponding ethylene containing complexes. The particular stereochemical features of the complexes allow one to interpret the CD on the basis of the individual contributions coming from the chiral centres already present in the free olefin and from the chiral centres formed in the complexation of the double bond. Evidence is reported showing that the aforementioned contributions are additive and that the chiral centre(s) bound to the metal dominates the CD at about 400 nm, its chirality type being reflected in the sign and its chirality prevalence in the Δϵ value.     

全有机多功能组成物用于冷却塔含高浓度总硬储水的水处理

本发明提供了一种全有机水溶性组成物,其能够提高具有高含量总硬的冷却塔水化学处理的功效,该总硬度主要由钙组成,特别用于石化行业的冷却塔水处理,并且在高浓缩倍数下运行,能够充分控制热交换设备中腐蚀、结垢和分散问题,避免工艺设备污染趋势,以及控制细菌繁殖。当在具有重金属的冷却系统中使用该配方,该组成物还可以去除重金属,如锌,通过使用本发明,可以避免排出污染物,原因是该组成物是一种多功能产品,其化学组成是全有机且能够被生物降解。     

Laterally supported sandwich panels subjected to large deflections: Part 2: FE analyses and model validation

Finite element (FE) models are used for predicting the global behavior of simply supported sandwich panels fixed by bolts on the two longitudinal edges or on all their four edges. The panels are subjected to transversal distributed loads and develop large deflections. Two finite element techniques are employed: (a) utilizing effective (equivalent) continuum solid elements for the core and plate elements for the face sheets and (b) utilizing plate elements of an equivalent three-layer laminate. In the first part of this project, discussed in a companion paper, the test set-up details were presented along with the experimental results. This second part of the work presents the procedure for estimating the panel–bolt bearing stiffness, the FE analysis procedure developed to simulate the behavior of the tested panels and the validation of the numerical models. A good correlation was observed between experimental and numerical results for the displacements of the panels and the shear loads at the attachment points. The results obtained demonstrated that the proposed two-dimensional FE approach yields a good trade off between the level of accuracy and computational efficiency.     

Photocatalytic oxidation of aliphatic and aromatic sulfides in the presence of silica adsorbed or zeolite-encapsulated 2,4,6-triphenyl(thia)pyrylium

Solid photocatalysts in which the 2,4,6-triphenylpyrylium (TP) or 2,4,6-triphenylthiapyrylium cation (TTP) are encapsulated within zeolite Y or deposited on mesoporous silica are used as photosensitizers for the oxidation of sulfides, both aromatic and aliphatic, in solvents of various polarity. Contrary to the same cations in solution, these solid sensitizers are not significantly degraded during operation. An effective oxygenation takes place leading to sulfoxides, disulfides, sulfinic and sulfenic esters as well as sulfonic acids. This large scope method shows a limited dependence on the substrate structure and on conditions and is suitable for the abatement of sulfur-containing pollutants.     

Design of a digital FM demodulator based on a 2nd-order all-digital phase-locked loop

Software-defined radio (SDR) is a revolution in radio design due to the ability to create radios that can self-adapt on the fly. In SDR devices, all of the signal processing is implemented in the digital domain, mainly on DSP blocks or by DSP software. By simply downloading a new program, a SDR device is able to interoperate with different wireless protocols, incorporate new services, and upgrade to new standards. Therefore, massively parallel signal processing at higher frequencies are needed to implement a realistic SDR. Thus, FPGAs have been used extensively for implementing essential functions in SDR architectures at lower frequencies. In this paper, we explore the design of a digital FM receiver using the approach of an All-Digital Phase Locked-Loop (ADPLL). The circuit is designed in VHDL, then synthesized and simulated using LeonardoSpectrum Level 3 and ModelSim SE 6, respectively. It operates at a frequency up to 150 MHz and occupies the area of roughly 15 K logic gates.     

Performance of curaua fibers in pullout tests

Natural lignocellulosic fibers are successfully replacing synthetic fibers as the reinforcement phase of composite materials in many engineering applications, including automobile parts. In addition to well-known conventional lignocellulosic fibers, others with promising properties, like that obtained from the leaves of the curaua plant (Ananas erectifolius) found in the Amazon region of Brazil, are now being considered. The present work investigated microstructural aspects associated with the performance of curaua fibers in pullout tests carried out to characterize the fibers interfacial strength with a polyester matrix. The results have shown that the naturally bonded filaments that constitute a curaua fiber present interspatial voids between them. These voids play an important role in providing adherence of the fiber surface to a polyester matrix, resulting in an effective reinforcement for a curaua-strengthened composite.