Domino logic with variable threshold voltage keeper

A variable threshold voltage keeper circuit technique is proposed for simultaneous power reduction and speed enhancement of domino logic circuits. The threshold voltage of a keeper transistor is dynamically modified during circuit operation to reduce contention current without sacrificing noise immunity. The variable threshold voltage keeper circuit technique enhances circuit evaluation speed by up to 60% while reducing power dissipation by 35% as compared to a standard domino (SD) logic circuit. The keeper size can be increased with the proposed technique while preserving the same delay or power characteristics as compared to a SD circuit. The proposed domino logic circuit technique offers 14% higher noise immunity as compared to a SD circuit with the same evaluation delay characteristics. Forward body biasing the keeper transistor is also proposed for improved noise immunity as compared to a SD circuit with the same keeper size. It is shown that by applying forward and reverse body biased keeper circuit techniques, the noise immunity and evaluation speed of domino logic circuits are simultaneously enhanced.     

Temperature-adaptive voltage tuning for enhanced energy efficiency in ultra-low-voltage circuits

Circuits optimized for minimum energy consumption operate typically in the subthreshold regime with ultra-low power-supply voltages. Speed of a subthreshold logic circuit is enhanced with an increase in the die temperature. The excessive timing slack observed in the clock period of subthreshold logic circuits at elevated temperatures provides opportunities to lower the active-mode energy consumption. A temperature-adaptive dynamic-supply voltage-tuning technique is proposed in this paper to reduce the high-temperature energy consumption without degrading the clock frequency in ultra-low-voltage subthreshold logic circuits. Results indicate that the energy consumption can be lowered by up to 40% by dynamically scaling the supply voltage at elevated temperatures. An alternative technique based on temperature-adaptive reverse body bias to exponentially reduce the subthreshold leakage currents at elevated temperatures is also investigated. The active-mode energy consumption with two temperature-adaptive voltage-tuning techniques is compared. The impact of the process parameter and supply voltage variations on the proposed temperature-adaptive voltage scaling techniques is evaluated.     

Reversed Temperature-Dependent Propagation Delay Characteristics in Nanometer CMOS Circuits

The supply voltage to threshold voltage ratio is reduced with each new technology generation. The gate overdrive variation with temperature plays an increasingly important role in determining the speed characteristics of CMOS integrated circuits. The temperature-dependent propagation delay characteristics, as shown in this brief, will experience a complete reversal in the near future. Contrary to the older technology generations, the speed of circuits in a 45-nm CMOS technology is enhanced when the temperature is increased at the nominal supply voltage. Operating an integrated circuit at the prescribed nominal supply voltage is not preferable for reliable operation under temperature fluctuations. A design methodology based on optimizing the supply voltage for temperature-variation-insensitive circuit performance is proposed in this brief. The optimum supply voltage is 45% to 53% lower than the nominal supply voltage in a 180-nm CMOS technology. Alternatively, the optimum supply voltage is 15% to 35% higher than the nominal supply voltage in a 45-nm CMOS technology. The speed and energy tradeoffs in the supply voltage optimization technique are also presented     

Adsorption and column flotation studies on talc using anionic and cationic collectors

Adsorption properties and column flotation were studied to investigate the interaction of the anionic and cationic collectors and flotation recoveries for talc mineral. Adsorption capacity is dependent on pH, adsorption time, temperature, collector concentration, and particle size. Langmuir adsorption model was suitable for describing isotherms. Analyses were carried out using UV spectrometry. In this study, we analyzed some parameters affecting column flotation performance. It was determined that adsorption capacity, especially, had an important role in column flotation enrichment.     

Improved discrimination of soft and hard white wheat using SKCS and imaging parameters

Natural variation of hardness of wheat kernels often results in overlapping hardness indices (HI) distributions between hard and soft classes as measured with the single kernel characterization system (SKCS). This is particularly true for the case of the hard white (HW) and soft white (SW) wheat classes. To address this problem, a color camera was incorporated into the SKCS system so that color and kernel size data could be combined with SKCS measurements for classification purposes. Samples of hard red (HR), soft red (SR), HW, and SW wheat were classified using the SKCS system with and without the camera and results compared. Using the camera system, errors for separating HW from SW classes were reduced to less than 5%, as compared to 17.1% using SKCS alone. Furthermore, improved data processing applied to the low-level data currently produced by the SKCS system led to greater than 50% reduction in classification errors between SW and HR as compared to using HI data alone. Similar improvements in classification accuracies for 300-kernel sample containing mixtures of SW and HW were also achieved. The 300 kernel sample classification is usually what inspectors and grain traders use to determine sample purity rather than individual kernel results. The techniques developed should aid grain inspectors in properly identifying mixtures of these two classes. Unfortunately, for the SR and HR classes, incorporating the camera data decreased classification accuracy while increasing the complexity of the system. However, SR and HR classes can be adequately distinguished with the SKCS in its current form. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

Effects of log storage conditions and steaming process on the formaldehyde emissions of particleboard manufactured from eucalyptus (E. camaldulensis) wood

The aim of this study was to determine the changes in formaldehyde emissions of eucalyptus particleboards produced from logs stored under different conditions (indoor, outdoor, and under water) or steamed. The pH and Stiasny values of particles changed significantly according to the storage condition and log steaming process. The pH values of particles obtained from steamed logs and stored outdoors for 4 months were found to be lower than those of the particles obtained from logs stored in the other aforementioned two conditions. The peaks of acetyl groups in the IR-spectra of the four group particles were similar. There was a strong relationship among the formaldehyde emission values of the panels pressed at 150 °C and the Stiasny values of the particles from which the panels were produced. The formaldehyde emission values of the panels pressed at 190 °C were lower than those of the panels pressed at 150 °C.     

Cost-effective synthesis of polyricinoleate: Investigation of coating characteristics,in vitro degradation,and antibacterial activity

Ricinoleic acid (RA) is a component of various bio-based copolymers. However, high-molecular weight polyricinoleate homopolymers are not widely investigated due to high cost of commercial monomer and catalysts. In this work, we present low-cost approach for the synthesis of high-molecular-weight polyricinoleate by preparing large amount of pure monomer and use of lipozyme TL IM as catalyst. First, polymerization conditions were optimized and comparative studies of medium-molecular-weight polyricinoleate (PRA-M) of M_w = 30 000 gmol⁻¹ and high-molecular-weight polyricinoleate (PRA-H) of M_w = 72 000 gmol⁻¹ were conducted. Polyricinoleates were characterized by common spectroscopic, chromatographic, and thermal methods. Solvent casting of polyricinoleates resulted in thin and continuous coating with perfectly smooth surface under SEM observation. AFM analysis of PRA films showed that surface roughness decreased with increasing molecular weight of polyricinoleate (roughness PRA-M = 68.39 nm and PRA-H = 57.36 nm). Degradation studies under in vitro conditions showed that both PRA-M and PRA-H showed good stability with only ~2% of mass loss after 6 months, possibly due to its hydrophobic nature and relatively high-molecular weight. In contrast to RA, PRA-M and PRA-H do not have significant antibacterial effect on Staphylococcus aureus and Escherichia coli. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48172.     

Lumped-parameter models for low-temperature geothermal fields and their application

The behavior of low-temperature geothermal reservoirs under exploitation is simulated using analytical lumped-parameter models. These models consider the effects of fluid production and reinjection, as well as natural recharge, on the pressures (or water levels) of low-temperature, liquid-dominated geothermal systems. The computed responses for constant production/injection flow rates are given in the form of analytical expressions. Variable flow rate cases are modeled, based on the Duhamel's principle. Reservoir parameters are obtained by applying a weighted nonlinear least-squares estimation technique in which measured field data are history matched to the corresponding model response. By using history-matched models, the future performance of the reservoir can be predicted for different production/injection scenarios in order to optimize the management of a given geothermal system.We demonstrate the applicability of the models by simulating measured data from the Laugarnes geothermal field in Iceland, and the Balcova–Narlidere field in Turkey.