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     

Toxicity and Biodegradability Behavior of Xenobiotic Chemicals Before and After Ozonation: A Case Study with Commercial Textile Tannins

Ozonation of a natural tannin (NT; COD_o?=?1195 mg/L; TOC_o?=?342 mg/L; BOD_5,o?=?86 mg/L) and a synthetic tannin ST; COD_o?=?465 mg/L; TOC_o?=?55 mg/L; BOD_5,o?=?6 mg/L) being frequently applied in the polyamide dyeing process was investigated. Synthetic wastewater samples containing these tannins individually were prepared and subjected to ozonation at varying ozone doses (625– 1250 mgO₃/L wastewater), at pH?=?3.5 (the application pH of tannins) and pH?=?7.0 at an ozone dose of 1125 mgO₃/L wastewater. The collective environmental parameters COD, TOC, BOD₅, UV₂₅₄ and UV₂₈₀ (UV absorbance at 254 nm and 280 nm, representing aromatic and unsaturated moieties, respectively) were followed during ozonation. Changes in the biodegradability of the tannins were evaluated in terms of BOD₅ measurements conducted before and after ozonation. In addition, activated sludge inhibition tests employing heterotrophic biomass were run to elucidate the inhibitory effect of raw and ozonated textile tannins towards activated sludge biomass. Partial oxidation (45% COD removal at an ozone dose of 750 mg O₃/L wastewater and pH?=?3.5) of ST was sufficient to achieve elimination of its inhibitory effect towards heterotrophic biomass and acceptable biodegradability improvement, whereas the inhibitory effect and biodegradability of NT could not be reduced via ozonation under the same reaction conditions.     

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.     

Adsorption and Flotation Characteristics of the Different Types of Frothers

This article investigates the adsorption of different frothers onto talc particles. The adsorption and flotation characteristisc of tallow amine acetate (TAA) + frothers (MIBC and pine oil) was studied for talc mineral. In this study, we analyzed some parameters affecting froth flotation performance and it was determined that adsorption capacity in particular, had an important role in froth flotation enrichment. The effect of pH and adsorption time on adsorption capacity was also studied. Analyses were carried out using ultraviolet spectrometry. The results showed that MIBC had the lowest frother adsorption capacity and it improved recovery during froth flotation of on the talc. It can be said that MIBC was adsorbed on the talc surface less and provided the best conditions to generate bubbles in flotation cell.     

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.     

Characterization of a Novel Nine-Transistor SRAM Cell

Data stability of SRAM cells has become an important issue with the scaling of CMOS technology. Memory banks are also important sources of leakage since the majority of transistors are utilized for on-chip caches in today's high performance microprocessors. A new nine-transistor (9T) SRAM cell is proposed in this paper for simultaneously reducing leakage power and enhancing data stability. The proposed 9T SRAM cell completely isolates the data from the bit lines during a read operation. The read static-noise-margin of the proposed circuit is thereby enhanced by 2 X as compared to a conventional six-transistor (6T) SRAM cell. The idle 9T SRAM cells are placed into a super cutoff sleep mode, thereby reducing the leakage power consumption by 22.9% as compared to the standard 6T SRAM cells in a 65-nm CMOS technology. The leakage power reduction and read stability enhancement provided with the new circuit technique are also verified under process parameter variations.     

Characterization of Double-Junction GaAsP Two-Color LED Structure

The structural, optical, electrical and electrical–optical properties of a double-junction GaAsP light-emitting diode (LED) structure grown on a GaP (100) substrate by using a molecular beam epitaxy technique were investigated. The p–n junction layers of GaAs_1?xP_x and GaAs_1?yP_y, which form the double-junction LED structure, were grown with two different P/As ratios. High-resolution x-ray diffraction (HRXRD), photoluminescence (PL), and current–voltage (I–V) measurements were used to investigate the structural, optical and electrical properties of the sample. Alloy composition values (x, y) and some crystal structure parameters were determined using HRXRD measurements. The phosphorus compositions of the first and second junctions were found to be 63.120% and 82.040%, respectively. Using PL emission peak positions at room temperature, the band gap energies (E_g) of the first and second junctions were found to be 1.867 eV and 2.098 eV, respectively. In addition, the alloy compositions were calculated by Vegard’s law using PL measurements. The turn-on voltage (V_on) and series resistance (R_s) of the device were obtained from the I–V measurements to be 4.548 V and 119 Ω, respectively. It was observed that the LED device emitted in the red (664.020 nm) and yellow (591.325 nm) color regions.     

WiSEGATE: Wireless Sensor Network Gateway framework for internet of things

With internet of things vision, computing systems get the ubiquity of real world. Wireless Sensor Network (WSN) technology plays a critical role for the construction of this paradigm. Hence, WSN technology should be adapted to support interoperability with the commodity internet entities. Since technological background of WSN and IP networks do not fit each other, this effort is not a straightforward process. In this paper, we introduce WiSEGATE which addresses end-to-end reliable interconnection problem between multiple internet entities and sensor nodes. WiSEGATE is a prototype of a new web server which supports three tier service scheme with a data acquisition mechanism of WSN to access the physical data in particular locations in the real world. In WiSEGATE, an interconnection gateway handles operations required for the interoperability. Since this gateway maintains reliable TCP/IP connections of the interconnected entities, the resource constraint sensor nodes on WSN do not require a TCP/IP stack for handling end-to-end connections. A lightweight service layer is implemented on a sensor node for operations required by the interconnection. The strength and novelty of the model lies in the fact that this lightweight service layer relieves extra memory usage for end-to-end connection management. For determining limits of the proposed model, firstly, we examined the steps for request/response mechanism and modeled the gateway as a queueing system. By doing this, we derive a definition of the request traffic. For proof of concept, we performed comprehensive tests in simulation and real testbed environments for WLAN connection. WiSEGATE can achieve reasonable response times up to 80 simultaneous connections from remote entities to WSN when WLAN PER is less than 0.2.     

Use of Fourier transform infrared spectroscopy for rapid comparative analysis of Bacillus and Micrococcus isolates

The identification of foodborne microorganisms and their endospores in food products are important for food safety. The present work compares Bacillus (Bacillus licheniformis, Bacillus circulans and Bacillus subtilis) and Micrococcus (Micrococcus luteus) species with Fourier transform infrared (FTIR) spectroscopy. Our results show that there are several characteristic peaks belonging to both the Micrococcus and Bacillus species which can be used for the identification of these foodborne bacteria and their endospores. For Micrococcus species, a new band was observed at 1338 cm⁻¹ which may be due to acetate oxidation via the carboxylic acid cycle. The bands at 1313 cm⁻¹ and 1256 cm⁻¹ can be explained by an exopolymer formation and the other bands at 1074 cm⁻¹ and 550 cm⁻¹, may be due to the glycogen-like storage material in Micrococcus spp. There are also characteristic peaks at 993 cm⁻¹ and 801 cm⁻¹ for these bacterial species. Different Bacillus species also showed characteristic peaks at 1000–500 cm⁻¹ region. Dipicolinic acid (DPA) bands at ∼728 cm⁻¹ and ∼703 cm⁻¹ seen only in B. circulans were the marker of an endospore formation.