New resistorless and electronically tunable realization of dual-output VM all-pass filter using VDIBA

In this paper, a new active element called voltage differencing inverting buffered amplifier (VDIBA) is presented. Using single VDIBA and a capacitor, a new resistorless voltage-mode (VM) first-order all-pass filter (APF) is proposed, which provides both inverting and non-inverting outputs at the same configuration simultaneously. The pole frequency of the filter can be electronically controlled by means of bias current of the internal transconductance. No component-matching conditions are required and it has low sensitivity. In addition, the parasitic and loading effects are also investigated. By connecting two newly introduced APFs in open loop a novel second-order APF is proposed. As another application, the proposed VM APF is connected in cascade to a lossy integrator in a closed loop to design a four-phase quadrature oscillator. The theoretical results are verified by SPICE simulations using TSMC 0.18 μm level-7 CMOS process parameters with ±0.9 V supply voltages. Moreover, the behavior of the proposed VM APF was also experimentally measured using commercially available integrated circuit OPA860 by Texas Instruments.     

Understanding the Chena Hot Springs,Alaska, geothermal system using temperature and pressure data from exploration boreholes

Chena Hot Springs is a small, moderate temperature, deep circulating geothermal system, apparently typical of those associated to hot springs of interior Alaska. Multi-stage drilling was used in some exploration boreholes and was found to be useful for understanding subsurface flow characteristics and developing a conceptual model of the system. The results illustrate how temperature profiles illuminate varying pressure versus depth characteristics and can be used alone in cases where staged drilling is not practical. The extensive exploration activities helped define optimal fluid production and injection areas, and showed that the system could provide sufficient hot fluids (∼57 °C) to run a 400-kWe binary power plant, which came on line in 2006.     

Drop-weight impact of plain-woven hybrid glass–graphite/toughened epoxy composites

The progressive damage behaviors of hybrid woven composite panels (101.6 mm × 101.6 mm) impacted by drop-weights at four different velocities were studied by a combined experimental and 3-D dynamic nonlinear finite element approach. The specimens tested were made of plain-weave hybrid S2 glass-IM7 graphite fibers/toughened epoxy (cured at 177 °C). The composite panels were damaged using a pressure-assisted Instron-Dynatup 8520 instrumented drop-weight impact tester. During these low-velocity simpact tests, the time-histories of impact-induced dynamic strains and impact forces were recorded. The damaged specimens were inspected visually and using ultrasonic C-Scan methods. The commercially available 3-D dynamic nonlinear finite element (FE) software, LS-DYNA, incorporated with a proposed user-defined damage-induced nonlinear orthotropic model, was then used to simulate the experimental results of drop-weight tests. Good agreement between experimental and FE results has been achieved when comparing dynamic force, strain histories and damage patterns from experimental measurements and FE simulations.     

Kinetic model of homogeneous thermal decomposition of methane and ethane

In this paper, the homogeneous decomposition of methane and ethane is modeled in a well stirred flow reactor. The kinetics of this process is represented by a reaction mechanism of 242 reactions and 75 species, based on a mechanism developed for hydrocarbon combustion and soot formation. It is shown that this model correctly predicts the hydrogen yield from pyrolysis in a temperature range of 600–1600 °C, and pressure range of 0.1–10 atm. Furthermore, the effect of temperature, pressure and residence time on the amount of hydrogen produced from the decomposition of methane, ethane, natural gas, and a mixture of methane and argon is studied. The model predicts that the use of ethane or its addition to methane increases the speed of hydrogen production at low temperatures and pressures. The addition of a noble gas like argon also increases the yield of hydrogen at high pressures.     

Comparison of catalytic and noncatalytic pyrolysis and product yields of some waste biomass species

The products obtained by fast pyrolysis of biomass can be used as an energy source or chemical raw material. In this study, samples of hazelnut shells, tea bush, and hazelnut knot selected as waste biomass were from the cities of Trabzon and Rize in the Eastern Black Sea Region. Firstly, the waste biomass samples were granulated into four different particle sizes by milling and sieving operations. Fast pyrolysis of the samples with specific mixing rates was carried out in a fixed bed reactor. Additionally, 2 wt% vanadium (V) oxide (V₂O₅) was used as catalyst to maximize the yield of pyrolysis liquid products. The influence of temperature, heating rate, and particle size on fast pyrolysis yields under both catalytic and noncatalytic conditions were investigated and compared. While the amount of liquid product increased with the addition of catalyst, the amount of solid products decreased. It has been found that the temperature and heating rate parameters are very effective in liquid product yield. In all experiments, the maximum liquid yield was acquired at the same heating rate of 450°C min^?1 and the temperature of 450°C with particle size of 0.5 to 1.0 mm. The maximum pyrolysis liquid (bio‐oil) was obtained with catalytic pyrolysis, and this value was 60.58 wt%.     

Time and volume-ratio effect on reusable polybenzoxazole nanofiber oil sorption capacity investigated via machine learning

Diesel oil sorption capacities (DOSCs) of polybenzoxazole/polyvinylidene fluoride nanofiber mats with four different groups (-O-, -S-S-, phenylene and diphenylene) in the main chain structures were investigated. Different experimental duration and diesel-oil/tap-water volume ratio pairs were used for diesel oil sorption. No degradation was observed in the nanofiber mat structures after diesel oil sorption. The characterizations of polybenzoxazole (PBO) nanofibers with high diesel oil selectivity were performed by scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, x-ray diffraction, thermal gravimetric analysis, differential scanning calorimetry, Brunauer–Emmett–Teller (BET), and contact angle measurement analysis. According to the result of characterizations, superoleophilic and superhydrophobic nanofiber mats show high water contact angle value in the range of 132–140^∘ and show high separation efficiency. In this study, we integrated ensemble gradient boosting model (XGBoost) to predict the DOSC of sorbent nanofiber and obtain an optimal set of conditions to maximize the DOSC. The predicted PBO-E sorbent at the 0.5 ratio of diesel-oil/tap-water measured at the end of the 3rd minute showed the most reliable and stable diesel oil sorption with at least 9.39 and at most 12.33 g/g sorbent with 95% of confidence.     

Cache recovery and spatial memory in Clark's nutcrackers (Nucifraga columbiana).

Clark's nutcrackers cache pine seeds and recover them months later. Four experiments with 5 nutcrackers tested their ability to relocate their caches when the cache sites were selected by the experimenters. During Exp I, Ss had 18 cache sites available during each of 3 caching sessions, followed 10 days later by 4 recovery sessions. Recovery performance was above chance, and there were frequent revisits to previously emptied cache sites. During Exp II, hunger level (manipulated by prefeeding) had no effect on recovery accuracy. During Exp III, Ss were released into the experimental room with no seeds present. Probing behavior was directed at the old cache sites of Exp I and especially of Exp II. During Exp IV, the number of holes available during caching sessions had no effect on the accuracy of 3 of the 4 Ss. Findings suggest that spatial memory is a primary mechanism by which nutcrackers locate their caches. (30 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Performance of four-seed caching corvid species in operant tests of nonspatial and spatial memory.

The performance of 4 seed-caching corvid species was tested using 2 different operant nonmatching tasks. These species differ in their dependence on stored food, and differences in spatial memory tests have been correlated with better performance by the more cache-dependent species. Acquisition and retention of a color non-matching-to-sample task was tested in Experiment 1. Acquisition of the color task was not correlated with cache dependence, and no differences between species in performance during memory testing were found. Acquisition and retention of an operant spatial non-matching-to-sample task was tested in Experiment 2. Species differences in the spatial task were found for acquisition and during retention testing. The influence of natural history on the evolution of memory is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)