Power Reduction Research Articles

A FinFET Based Low-Power Write Enhanced SRAM Cell With Improved Stability

This work introduces a FinFet based low-power 11T SRAM cell with write enhanced feature, which is considered to meet modern technology requirements due to its distinctive features and performance. The proposed 11T SRAM cell is designed in such a way, so that it reduces the overall power consumption, improving access time, and static noise margin (SNM), especially during the write operation. The proposed 11T SRAM cell is compared with other SRAM cells, including conventional 6T (conv6T), dual pull-up transistor 10T (DPUT10T), dual pull-down transistor 10T (DPDT10T), dual transmission gate 9T (DTG9T), and dual transmission gate 10T (DTG10T), at an equitable standard. The results obtained at the supply voltage of 0.5 V @ 27 °C shows the reduction in leakage power during hold 1 operation by 1.61×/1.33×/1.44×/1.63×/1.46×, and reduction in power consumption during read operation by 1.02×/1.55×/ 1.01×/1.81×/1.97× in comparison with conv6T/DPUT10T/ DPDT10T/DTG9T/DTG10T, respectively. Write access time is also improved by a factor of 1.67×/1.71×/2.59×/1.45×/1.97×, respectively. Additionally, read static noise margin (RSNM) and write static noise margin (WSNM) are improved by 2.03×/1.01×/1.65×/1.54×/1.43×, and 1.42×/1.33×/1.41×/1.02×/1.62×, respectively. This demonstrates why the proposed low-power 11T SRAM cell is desirable, especially when compared to the other cells under consideration.

A numerical study on the sustainability and efficiency of deep coaxial borehole heat exchanger systems in the cold region of northeast China

Numerical simulations utilizing OpenGeoSys have been conducted on a deep coaxial borehole heat exchanger situated in the Songliao Basin. The findings reveal that the outlet temperature exhibits a downward trend as circulation flow increases, while it rises with an increase in inlet temperature. Additionally, the heat transfer power escalates with higher flow rates but diminishes as inlet temperature rises. Notably, the long-term operation results in a reduction of outlet temperature and heat transfer power. After 30 years, the decline of them is approximately 0.3 °C and 8 kW under current situation. Furthermore, long-term operation induces a decrease in formation temperature, predominantly around the vicinity of well, where the maximum temperature decline is nearly 30 °C. The reduction in formation temperature is directly proportional to the increase in flow rate and inversely proportional to inlet temperature. Within the depth range of well, the maximum influence radius expands in correlation with both the depth and duration of mining, while remaining relatively stable with variations in flow rate and inlet temperature. Following three decades of extraction, the influence radius is approximately 95m. The results provide vital scientific insights for the retrofitting of abandoned wells in Northeast China into geothermal heat exchange wells for building heating purposes.

Gaussian Kernel Approximations Require Only Bit-Shifts

An approach to approximate the 2D Gaussian filter for all possible kernel sizes based on the binary optimization technique is introduced. The approximate filter coefficients are designed as negative powers of two, allowing hardware implementation with remarkable savings in the chip area. The proposed approximate filters were evaluated and compared with competing methods using both similarity analysis and edge detection applications. The proposed method and the competing works for masks of size 3×3, 5×5, and 7×7 were implemented in a Xilinx Artix-7 FPGA. The proposed method showed up to a 60.0% reduction in DSP usage and a 75.0% increase in the maximum operating frequency when compared with state-of-art methods for the 7×7 kernel size case and a 48.8% reduction in the dynamic power normalized by the maximum operating frequency.

Delegation of environmental regulation and perceived corruption in South Africa

I study the drivers of a reduction in the discretionary power of environmental inspectors and the impact that such reduction has on firms’ perceptions. I examine the transition from the Air Pollution Protection Act of 1965 to the Air Quality Act of 2005 (AQA), a change from full to partial delegation of regulation in South Africa. By constructing a principal–agent model, I propose a theoretical explanation for why a society would restrict environmental inspectors’ discretionary power. I then use my theoretical model to discuss the air quality regulation transition in South Africa. I suggest that the transition might have occurred because of increases in inspectors’ rent-seeking motivation and capacity of appropriating rents after the end of Apartheid. Using microdata, I run difference-in-differences models in a two-period panel with 191 South African firms to show that the implementation of the AQA decreases affected firms’ perceived corruption, but does not change perceptions on obtaining licences and on the functioning of courts. My work indicates that national governments in developing countries should consider the characteristics of the agents who are implementing regulation, and the system they are embedded in, when designing environmental regulation.

Global active noise control using SIMO near-field systems - Simulation and technical implementation

The technical implementation of a single-input multiple-output (SIMO) active near-field noise control (ANC) system designed for global low-frequency noise control is presented. The SIMO control strategy is motivated by noise control simulations based on a direct boundary element method (BEM) ansatz formulated in this paper. The suitability of the chosen BEM formulation and SIMO control strategy is accompanied and confirmed by extensive experiments and comparison to analytical calculations based on isotropic sources. The influence of parameters such as the positioning of the error microphone, the membrane velocity required for optimal global reduction, the effects of phase inaccuracies and the number of actuators on global reduction are investigated. The real-time control of the SIMO system is technically implemented on field programmable gate array (FPGA) hardware using a frequency domain block FxLMS algorithm. The iterative algorithm converges in less than 0.1 s for the examined frequency range from 100 Hz to 1000 Hz. Measurements using various circular SIMO array configurations showed reductions in sound power of up to 85\%, aligning closely with the numerical results.

Noise analysis of variable-speed rotor technology on the coaxial lift-offset helicopter

The impact of variable-speed rotor technology on the aerodynamic and aeroacoustic characteristics of a coaxial lift-offset helicopter was investigated using a numerical analysis approach. The free wake vortex lattice method was utilized to predict aerodynamic performance, while the Ffowcs-Williams Hawkings acoustic analogy was employed to evaluate the noise impact. The Harrington coaxial rotor was used as the baseline configuration. Results show that reducing the rotational speed, in combination with lift-offset, leads to a decrease in overall power required during forward flight by lowering both collective and cyclic pitch. This is primarily due to a reduction in profile power across the speed range. However, excessive rotor deceleration can lead to an expanded reverse flow region, increasing induced power at high forward speeds. From an acoustics perspective, the reduced rotor speed mitigated loading noise radiated toward the ground, especially in the region 40-60 degrees below the rotor plane, achieving a maximum 2.6 dB reduction at the evaluated observer location. This study indicates that the technology can offer advantages for both performance and noise in forward flight conditions.

Experimental study of an absorption-based refrigeration driven by ocean thermal energy

Establishing an island-based cold chain is essential for ensuring food storage, vaccine preservation, and fish freezing on islands, which is indispensable for the sustainable development of island communities. The compression-absorption refrigeration system that uses ocean-thermal-energy is ideal for cold storage on islands as it efficiently utilizes local renewable energy sources and can meet refrigeration needs below 0 °C. Therefore, a refrigeration prototype has been constructed and thoroughly experimentally investigated to obtain refrigeration characterization under variations of refrigeration demand and environmental conditions. The system's energy-saving potential is evaluated by conducting comparisons with conventional refrigeration techniques. The results indicate that refrigeration temperature plays a crucial role in determining refrigeration capacity, with an increase of approximately 8.2 % observed for every 1 °C rise in refrigeration temperature. Lower cold-seawater temperatures or higher warm-seawater temperatures do not have a significant effect on the refrigeration capacity, but contribute to a reduction in compressor power due to increased thermally-driven compression force. Consequently, for every 1 °C change, the refrigeration capacity per unit compressor power increases by approximately 4 %. Additionally, the refrigeration capacity of the system is three times greater than that of a vapor-compression-refrigeration-system. The findings provide theoretical and experimental guidelines for the design and operation of refrigeration using ocean-thermal-energy.

Effects of concurrent heat and hypoxic training on cycling anaerobic capacity in men

Physical training in heat or hypoxia can improve physical performance. The purpose of this parallel group study was to investigate the concurrent effect of training performed simultaneously in heat (31 °C) and hypoxia (FIO2 = 14.4%) on anaerobic capacity in young men. For the study, 80 non-trained men were recruited and divided into 5 groups (16 participants per group): control, non-training (CTRL); training in normoxia and thermoneutral conditions (NT: 21 °C, FIO2 = 20.95%); training in normoxia and heat (H: 31 °C, FIO2 = 20.95%); training in hypoxia and thermoneutral conditions (IHT: 21 °C, FIO2 = 14.4%), and training in hypoxia and heat (IHT + H: 31 °C, FIO2 = 14.4%). Before and after physical training, the participants performed the Wingate Test, in which peak power and mean power were measured. Physical training lasted 4 weeks and the participants exercised 3 times a week for 60 min, performing interval training. Only the IHT and IHT + H groups showed significant increases in absolute peak power (p < 0.001, ES = 0.36 and p = 0.02, ES = 0.26, respectively). There were no significant changes (p = 0.18) after training in mean power. Hypoxia appeared to be an environmental factor that significantly improved peak power, but not mean power. Heat, added to hypoxia, did not increase cycling anaerobic power. Also, training only in heat did not significantly affect anaerobic power. The inclusion of heat and/or hypoxia in training did not induce negative effects, i.e., a reduction in peak and mean power as measured in the Wingate Test.

Securing the Internet of Things with Ascon-Sign

With a Cryptographically-Relevant Quantum Computer (CRQC) estimated to be viable within the next 15 years, the development of post-quantum security is imperative. Previously secure networks may soon fall victim to these CRQCs as they will likely attack the weakest link in a network. In modern networks, these weak-links are often present in the form of Internet of Things (IoT) devices, as the resource constrains imposed by these wireless nodes leads to lowered security. We offer the first Ascon-Sign implementation for resource constrained FPGAs, which allows a wireless sensor network to verify nodes. Our design runs twice as fast as similarly-area constrained devices, and shows a 33% reduction in power per operation. We demonstrate the capability of our design by integrating it with a wireless sensor network for weather detecting. We also propose an amendment to the Ascon-Sign specification that allows for shortened processing time and lower memory requirements.

Evaluating Ammonia-Diesel Blends in Engine Operations: Performance and Stability Impacts

Abstract This study investigated the effects of incorporating ammonia into diesel engine operations, focusing on its impact on performance and stability. Ammonia was introduced into the engine via the intake air. By varying ammonia ratios at different engine speeds and under full load conditions, it was found that ammonia integration could be achieved without stability issues up to an energy fraction of 54%. However, exceeding this threshold resulted in misfire occurrences during engine operation. Notably, lower energy ammonia fractions below 40% led to increased power output, while higher fractions caused power reduction. Additionally, consistent reductions in brake-specific energy consumption were observed with ammonia supplementation. Variations in in-cylinder pressure were directly correlated with power output changes. Peak pressure initially increased with ammonia but decreased beyond 40% energy sharing, with its location consistently retarded. Moreover, ammonia induction led to longer ignition delays and altered combustion phasing across all engine speeds, indicating its significant influence on engine operating parameters.

Scalable, low-power and high-performance active-RC complex band-pass/low-pass filter with automatic frequency tuning applied to the Internet of Things

This article introduces a comprehensive 3rd Chebyshev active-RC complex band-pass/low-pass filter with an automatic cut-off frequency tuning circuit. The designed filter achieves 2 dB step gain control within the range of −6 dB–24 dB and 4 different bandwidth modes including low-pass modes and complex band-pass modes. A compact fully-differential (FD) amplifier with feedforward compensation and reverse pole splitting technique is used to meet the stringent filter's performance. The novel amplifier achieves an open loop gain of 62 dB and a maximum unity-gain bandwidth (UGB) of 732 MHz with VDD = 0.9 V and 0.32 mW of power dissipation. Using the proposed amplifier, the filter achieves the lowest power consumption reported in the literature for active-RC implementations and 30 % power reduction over similar active-RC filters. By employing an optimized solution for dynamic allocation of inter-stage gain, the filter achieves a maximum in-band-IIP3 of +25.7 dBm and an improvement of 2 dB. Also, an automatic frequency tuning scheme is used to eliminate the effect of process variation. The filter is fabricated in 22 nm CMOS process occupying 0.44 mm × 0.44 mm area and consuming 1.8 mW and 1.2 mW from 0.9 V supply voltage in Wi-Fi and BLE modes, respectively. The maximum figure of merit (FoM) is 142.6 dB/J. The RC tuning circuit has a precision of 1.5 % and covers a range of 20 %.

Aerodynamic design of two-stage centrifugal compressor for vehicle hydrogen fuel cell

Abstract The on-board hydrogen fuel cell is a power generation device that converts the chemical energy of hydrogen and oxygen directly into electrical energy. The centrifugal compressor mainly provides oxygen for the cathode of the fuel cell system. With the rapid development of the hydrogen fuel cell industry, the key components of the air compressor field are also developing rapidly. In the technical route, most companies launched two-stage compression centrifugal air compressors in response to the increasing power of the product development trend. The newly developed hydrogen fuel cell system power has reached above 120kW to meet the needs of heavy trucks and other applications. Both the flow rate and pressure ratio of the air compressor are required to increase accordingly. Based on the reduction of parasitic power, the optimal efficiency at the working point of the two-stage centrifugal air compressor is taken as the design goal, from one-dimensional aerodynamic calculation to two-dimensional flow channel design. Finally, the feasibility and accuracy of the aerodynamic design are verified based on key parameters such as pressure ratio, flow rate, and efficiency of the final stage through CFD flow field simulation and test data comparison. The results show that the flow rate is consistent with the calculated flow field, and the maximum error of pressure ratio and efficiency is less than 2%, which meets the target requirements. The research results can provide a research and development basis for designing high-performance centrifugal air compressors for fuel cell vehicles.

Critical-Layered MoS2 for the Enhancement of Supercontinuum Generation in Photonic Crystal Fibre.

Supercontinuum generation (SCG) from silica-based photonic crystal fibers (PCFs) is of highly technological significance from microscopy to metrology, but has been hindered by silica's relatively low intrinsic optical nonlinearity. The prevailing approaches of filling PCF with nonlinear gases or liquids can endow fibre with enhanced optical nonlinearity and boosted SCG efficiency, yet these hybrids are easily plagued by fusion complexity, environmental incompatibility or transmission mode instability. Here this work presentsa strategy of embedding solid-state 2D MoS2 atomic layers into the air-holes of PCF to efficiently enhance SCG. This work demonstrates a 4.8 times enhancement of the nonlinear coefficient and a 70% reduction of the threshold power for SCG with one octave spanning in the MoS2-PCF hybrid. Furthermore, this work finds that the SCG enhancement is highly layer-dependent, which only manifests for a real 2D regime within the thickness of five atomic layers. Theoretical calculations reveal that the critical thickness arises from the trade-off among the layer-dependent enhancement of the nonlinear coefficient, leakage of fundamental mode and redshift of zero-dispersion wavelength. This work provides significant advances toward efficient SCG, and highlights the importance of matching an appropriate atomic layer number in the design of functional 2D material optical fibers.

Accelerating Linear Congruential Generators with Carbon Nanotube Field-Effect Transistors

Abstract In the era of technological advancements, safeguarding information privacy has become paramount across sectors like defense, finance, healthcare, and more. At the heart of these security measures lies cryptography, a field that necessitates the efficient processing and secure storage of data. Our project focuses on the optimization of Linear Congruential Generators (LCG), pivotal for cryptographic applications and pseudorandom number generation. Here it has been pioneered the implementation of LCG using Carbon Nanotube Field-Effect Transistor (CNTFET) technology, targeting the reduction of leakage power through the innovative application of sleep techniques. This advanced approach not only embodies a leap towards minimizing energy consumption but also enhances the overall performance and reliability of cryptographic systems. By integrating sleep modes into the CNTFET-based LCG design, our methodology significantly curtails leakage power without compromising the generator’s efficiency or output quality. The successful implementation and synthesis of this design, employing cutting-edge CNTFET technology, underscore the potential for substantial improvements in power efficiency while maintaining high standards of security and randomness essential for cryptographic algorithms.

Experimental study on effect of use of oxyhydrogen blends with traditional fuels in spark engines for better performance

The utilization of oxyhydrogen as a supplementary fuel in internal combustion engines has garnered significant attention due to its potential to enhance engine performance and reduce emissions. This study investigates the effects of oxyhydrogen addition on the performance, emissions, and thermodynamic efficiencies of a spark-ignition engine fueled by gasoline, propane, and methane. The engine drives a commercial stationary power generator. The results demonstrate that oxyhydrogen addition leads to a consistent reduction in CO2 and hydrocarbon emissions across all fuel types, with the most substantial reduction observed in gasoline, decreasing from 2413 g/kg to 1709 g/kg (a 29 % reduction) with 20 % oxyhydrogen addition. However, NOx emissions tend to increase, particularly pronounced in gasoline, where they escalate from 9.5 g/kg fuel with no oxyhydrogen to 24.6 g/kg fuel for the same case (a 159 % increase). The power output exhibits varying degrees of improvement depending on the fuel type and oxyhydrogen concentration. Oxyhydrogen has compensated for the power reduction when propane and methane are used as the base fuel. The energy and exergy efficiencies consistently improve with increasing oxyhydrogen addition, with the most significant improvement observed in propane, where the energy efficiency increases from 30.0 % to 37.3 % with and addition of 20 % oxyhydrogen.

Power and area efficient FIR filter using Radix- 2r multiplier for de-noise the electrooculography (EOG) signal

This article introduces a novel FIR filter using a Radix-2r multiplier combined with 4:2 and 3:2 compressors for denoising Electrooculography (EOG) signals. This approach replaces traditional ripple-carry adders with compressors to add the partial products generated by the Radix-2r multiplier, resulting in reduced delay and energy consumption. The FIR filter is implemented in gate-level Verilog HDL, verified using ModelSim and Altera DSP Builder, and synthesized with the Cadence RTL compiler. Compared to conventional designs, the proposed filter achieves a 71.48% reduction in area, 73.28% reduction in power, 51.84% reduction in delay, 86.22% reduction in the area-delay product (ADP), and 92.38% reduction in energy-per-operation (EPS), significantly outperforming the SOPOT filter.

Photodynamic activity of curcumin against Candida biofilms on toothbrushes

Oral hygiene is necessary for maintaining human health, and regular brushing is recommended to control oral microbial biofilm. Toothbrushes are manufactured free of microorganisms, but after the first use they become contaminated and can represent a potential source of cross-contamination. Regular replacement or decontamination of toothbrushes is recommended. In this context, antimicrobial photodynamic therapy (aPDT) is a technology based on the production of reactive oxygen species, when light-absorbing compounds (photosensitizers) react with light and oxygen. The products of these reactions have antimicrobial activity and are used in dentistry to control microbial biofilms. Take into account, this study evaluated the activity of curcumin photoactivated with 450nm LED light against Candida krusei Ck7 and Candida albicans ATCC 10231 biofilms adhered to toothbrushes. Curcumin without photoactivation reduced the number of viable cells by 77.5% and 91.73%, respectively. Photoactivated curcumin reduced the biofilm of C. krusei Ck7 by 97.94% and C. albicans by 98.8%. Therefore, photoactivated curcumin provided a powerful reduction in the number of viable yeasts associated with the biofilm and may represent a promising complementary technique to conventional antimicrobial agents.

Hardware optimization for effective switching power reduction during data compression in GOLOMB rice coding.

Loss-less data compression becomes the need of the hour for effective data compression and computation in VLSI test vector generation and testing in addition to hardware AI/ML computations. Golomb code is one of the effective technique for lossless data compression and it becomes valid only when the divisor can be expressed as power of two. This work aims to increase compression ratio by further encoding the unary part of the Golomb Rice (GR) code so as to decrease the amount of bits used, it mainly focuses on optimizing the hardware for encoding side. The algorithm was developed and coded in Verilog and simulated using Modelsim. This code was then synthesised in Cadence Encounter RTL Synthesiser. The modifications carried out show around 6% to 19% reduction in bits used for a linearly distributed data set. Worst-case delays have been reduced by 3% to 8%. Area reduction varies from 22% to 36% for different methods. Simulation for Power consumption shows nearly 7% reduction in switching power. This ideally suggest the usage of Golomb Rice coding technique for test vector compression and data computation for multiple data types, which should ideally have a geometrical distribution.

Zona Incerta GABAergic Neurons Facilitate Emergence from Isoflurane Anesthesia in Mice.

The zona incerta (ZI) predominantly consists of gamma-aminobutyric acid (GABAergic) neurons, located adjacent to the lateral hypothalamus. GABA, acting on GABAA receptors, serves as a crucial neuromodulator in the initiation and maintenance of general anesthesia. In this study, we aimed to investigate the involvement of ZI GABAergic neurons in the general anesthesia process. Utilizing in-vivo calcium signal optical fiber recording, we observed a decrease in the activity of ZI GABAergic neurons during isoflurane anesthesia, followed by a significant increase during the recovery phase. Subsequently, we selectively ablated ZI GABAergic neurons to explore their role in general anesthesia, revealing no impact on the induction of isoflurane anesthesia but a prolonged recovery time, accompanied by a reduction in delta-band power in mice under isoflurane anesthesia. Finally, through optogenetic activation/inhibition of ZI GABAergic neurons during isoflurane anesthesia, we discovered that activation of these neurons facilitated emergence without affecting the induction process, while inhibition delayed emergence, leading to fluctuations in delta band activity. In summary, these findings highlight the involvement of ZI GABAergic neurons in modulating the emergence of isoflurane anesthesia.

Energy-aware bio-inspired spiking reinforcement learning system architecture for real-time autonomous edge applications.

Mobile, low-cost, and energy-aware operation of Artificial Intelligence (AI) computations in smart circuits and autonomous robots will play an important role in the next industrial leap in intelligent automation and assistive devices. Neuromorphic hardware with spiking neural network (SNN) architecture utilizes insights from biological phenomena to offer encouraging solutions. Previous studies have proposed reinforcement learning (RL) models for SNN responses in the rat hippocampus to an environment where rewards depend on the context. The scale of these models matches the scope and capacity of small embedded systems in the framework of Internet-of-Bodies (IoB), autonomous sensor nodes, and other edge applications. Addressing energy-efficient artificial learning problems in such systems enables smart micro-systems with edge intelligence. A novel bio-inspired RL system architecture is presented in this work, leading to significant energy consumption benefits without foregoing real-time autonomous processing and accuracy requirements of the context-dependent task. The hardware architecture successfully models features analogous to synaptic tagging, changes in the exploration schemes, synapse saturation, and spatially localized task-based activation observed in the brain. The design has been synthesized, simulated, and tested on Intel MAX10 Field-Programmable Gate Array (FPGA). The problem-based bio-inspired approach to SNN edge architectural design results in 25X reduction in average power compared to the state-of-the-art for a test with real-time context learning and 30 trials. Furthermore, 940x lower energy consumption is achieved due to improvement in the execution time.