A simulation study of high‐order CMOS hyperbolic‐sine filters

This paper advances the field of externally linear–internally nonlinear (ELIN) filters by introducing a synthesis method that enables the design of high‐order class‐AB sinh filters by means of complementary metal–oxide semiconductor (CMOS) weak‐inversion sinh integrators comprising only one type of devices in their translinear loops. The proposed transistor‐level synthesis approach is demonstrated through the examples of (1) a biquadratic and (2) a fifth‐order filter, and their simulated performance is studied. The biquadratic filter achieves a dynamic range of 94 dB and has a tunable quality factor Q up to the value of 8, whereas its natural frequency can be tuned for four orders of magnitude. Its static power consumption amounts to 6.2 μW for Q = 1 and f_o = 2 kHz. The fifth‐order Chebyshev sinh CMOS filter with a cut‐off frequency of 100 Hz, a pass band ripple of 1 dB, and a power consumption of ~300 nW is compared head‐to‐head with its pseudo‐differential class‐AB CMOS log domain counterpart. The sinh filter achieves similar or better signal‐to‐noise ratio (SNR) and signal‐to‐noise‐plus‐distortion ratio (SNDR) performances with half the capacitor area but at the expense of higher power consumption from the same power supply level. All three presented filter topologies are novel. Cadence design framework simulations have been performed using the commercially available 0.35 µm AMS (austriamicrosystems) process parameters. Copyright © 2013 John Wiley & Sons, Ltd.     

Onset of selective laser flash sintering of AlN

Flash sintering uses a combination of heating and electric fields to rapidly densify ceramics. Previously, it has been shown that a scanning laser can be used to initiate flash sintering in localized regions on an yttria-stabilized zirconia (YSZ) sample in a process known as selective laser flash sintering (SLFS). In this work, we show using a combination of measurements of electric current flowing through the sample and observations of necks formed between powder particles that aluminum nitride (AlN) can also undergo SLFS. Scan conditions required to initiate SLFS are characterized over a range of laser powers and laser scan speeds in a dry nitrogen environment. It is shown that initiation of SLFS in AlN is governed by both the local input energy density per scan and heat dissipation and a numerical model is developed to predict temperatures during SLFS. Assuming the minimum temperature along the conductive path determines the onset of SLFS, the minimum temperature and time required is 450–670 K in 2–0.25 s for the pressed AlN pellets used in this study for laser scan speeds of 33–300 m/s, laser powers of 10–30 W, and an applied electric field of 3000 V/cm.     

The influence of the processing parameters on the reactive flash sintering of ZrO2-CeO2

Reactive flash sintering (RFS) is a method that was recently developed to produce dense single-phase bulk ceramic parts through solid-state reactions in a single-step that only takes a few minutes. The influence of the RFS parameters on the phase purity of a simple mixed oxide, (Zr_0.8,Ce_0.2)O₂, was investigated. Parameters such as furnace temperature, furnace atmosphere, electric current density, and alternating current (AC) or direct current (DC) were examined. It was found that (Zr_0.8,Ce_0.2)O₂ pellets with high densities, above 90% of its theoretical density, can be produced by RFS in a few minutes when RFS occurs under oxidizing atmospheres, AC fields with current densities of 100 mA·mm⁻², and at a furnace temperature of 1200°C. Reducing conditions such as Ar-H₂ atmosphere and DC fields, low furnace temperatures, and low current densities resulted in phase impurities and poor reactions between the ZrO₂ and the CeO₂ powders. These results show that RFS is a useful method to produce mixed oxides, but it is very sensitive to the processing parameters. This is the first time that the influence of most of the RFS processing parameters has been studied systematically. Thus, the present work aims to provide guidelines on selecting the right processing parameters when exploring RFS.     

Measured hyperbolic-sine (sinh) CMOS results: A high-order 10 Hz–1 kHz notch filter for 50/60 Hz noise

This paper presents proof-of-concept measured results from CMOS hyperbolic-sine (sinh) filters fabricated in a commercially available 0.35 µm CMOS technology. Results from two chips are reported: a practical sinh integrator and a high order (8th) notch filter dedicated to 50/60 Hz noise rejection and synthesized by means of the proposed integrator. Linearity, frequency and noise measurements are reported. The notch frequency of the 8th order filter can be tuned over almost two decades. Its attenuation exceeds 70 dB for the target frequency range of 20–60 Hz and its dynamic range (for THD<4%) amounts to 89 dB while consuming 8 µW from a 2 V power supply level. For an increased power consumption of 74 µW its dynamic range (for THD<4%) exceeds 100 dB.     

Identification of recycled water with an empirically derived symbol increases its probability of use

The experiment described in this paper compared the effects of two systems for labeling recycled water on potential consumers' intention to use this resource; the current identifying symbol used worldwide (purple color for pipes, containers, and tanks) and a new, empirically derived and validated set of symbols that provide specific information on water quality and positive comparative information. In total, 807 face-to-face surveys were carried out. Subjects were asked to rate their intentions for using different qualities of recycled water for commercial agriculture as well as for using products and facilities irrigated with recycled water, either in the presence of the established symbol or the new, empirically derived symbols. Potential consumers' self-reported intentions to use recycled water were reliably higher in the presence of empirically derived symbols with positive comparative information than in the presence of the conventional identification symbol. This program of research provides a model for the application of principles of behavioral psychology to enhance the consumer acceptance of technological advances that preserve natural resources and protect ecosystems.