Low Average Power Research Articles

Scaling of ultrashort-pulsed laser structuring processes for electromobility applications using a spatial light modulator

The structuring of lithium-ion battery (LIB) electrodes and the diffusion media (DM) for polymer electrolyte membrane fuel cells (PEMFCs) with ultrashort laser pulses enables improved performance characteristics of both technologies. However, the transfer of the approaches from a laboratory scale to a commercial use has previously been hindered by the low average output power of ultrashort-pulsed (USP) laser beam sources and the limited productivity of single-beam structuring using scanning optics. Recent advancements in the development of USP laser systems have led to a steady increase in the available output power, thereby enabling new fields of applications. This study aims at accelerating the USP laser structuring of LIB electrodes and DM for PEMFCs to industrially relevant processing rates by comparing a single-beam with a multibeam structuring process regarding ablation characteristics and quality. For the multibeam strategy, the shape of the laser beam was modified by a spatial light modulator (SLM). In addition to microholes, the insertion of microchannels was investigated to demonstrate the high flexibility of state-of-the-art SLMs. The geometry of the created structures was measured with a laser scanning microscope, and the different layers were tested for their geometrical and electrochemical properties to compare both technologies. The results confirmed that applying an SLM enables high-quality microstructures with significantly higher structuring rates. Furthermore, this contribution includes a theoretical analysis of the specifications required for a laser setup to reach an industrially relevant productivity of the structuring processes.

Precise Nanoparticle Manipulation Using Femtosecond Laser Trapping.

Optical tweezers use strongly focused light for trapping, characterizing, and manipulating objects in the microscopic and nanoscopic regimes. However, fully understanding optical trapping at the nanoscale remains a significant challenge. This holds importance because the nanoscale is the frontier for numerous promising advancements, ranging from enhancing single-molecule investigations in biology to developing hybrid devices for nanoelectronics and photonics and exploring fundamental quantum phenomena in opto-mechanics. We report an experimental and theoretical study of nanoparticles of various sizes, showing the advantages of the immense peak power of ultrashort laser pulses over conventional optical tweezers. We also demonstrate highly stable trapping of nanoparticles for extended durations at low average laser power using femtosecond lasers.

Gate all around carbon nanotube field effect transistor espoused discrepancy cascode pass transistor adiabatic logic for ultra-low power application

Advances in wearable technology, IoT, and mobile applications have increased the demand for ultra-low-power electronic devices. Adiabatic Logic Circuit (ALC) is a design technique utilized in digital circuits to decrease the power consumption by decreasing the dynamic power dissipation. Current technologies face challenges in achieving both high performance and ultra-low power consumption. This research work introduces a novel approach in digital circuit design, specifically the Gate All-around Carbon Nanotube Field Effect Transistor with Discrepancy Cascode Pass Transistor Adiabatic Logic (GAA-CNTFET-DCPTAL), tailored for ultra-low power applications. This design operates efficiently with a four-phase Power Clock (PC) and demonstrates remarkable performance by achieving operation frequencies of up to 1 GHz while minimizing energy dissipation. GAA-CNTFET provides superior electrostatic control and high carrier mobility, reducing leakage currents and enhancing switching speeds. Simultaneously, Discrepancy Cascode Pass Transistor Adiabatic Logic (DCPTAL) uses adiabatic logic principles and a cascode structure to minimize energy dissipation during switching events. The technology node of proposed model is 10 nm. The software used for assessment is HSPICE is used for the simulation and validation of the proposed design. The proposed GAA-design attains 25.36 %, 14.28 %, and 16.06 % lower average power analyzed with existing techniques, such as Design with Evaluation of Clocked Differential Adiabatic Logic Families for the applications of low Power (DE-CDAL-LPA), Adiabatic logic-base strong ARM comparator for ultra-low power applications (AL-SARM-ULPA) and Analysis of 2PADCL Energy Recovery Logic for Ultra Low Power VLSI Design for SOC with Embedded Applications (2PADCL-ULP-VLSI) respectively.

Supercapacitor-Assisted Energy Harvesting Systems

Energy harvesting from energy sources is a rapidly developing cost-effective and sustainable technique for powering low-energy consumption devices such as wireless sensor networks, RFID, IoT devices, and wearable electronics. Although these devices consume very low average power, they require peak power bursts during the collection and transmission of data. These requirements are satisfied by the use of energy-storage devices such as batteries or supercapacitors (SCs). Batteries offer significantly higher energy density but are subject to regular replacement, thermal runaway risk, and environmental concerns. On the other hand, SCs provide over a million-fold increase in capacitance compared to a traditional capacitor of the same volume. They are considered as the energy-storing devices that bridge the gap between conventional capacitors and batteries. They also offer fast charging times, a long lifecycle, and low equivalent series resistance (ESR). Most importantly, they are capable of handling the high transient currents produced by energy harvesters and provide a stable power source for external loads. This study encompasses a brief exploration of the three fundamental SC types. Then, the discussion delves into the integration of SCs into energy harvesting applications. The collective knowledge presented aims to guide future research endeavors fostering the development of novel energy harvesting systems using SCs.

Experimental analysis of dust's impact on solar photovoltaic system efficiency in arid environments: a case study in Southern Algeria.

The purpose of this study is to explore the effects of accumulated dust and weather conditions on the energy generated by solar photovoltaic panels in Ouargla, Algeria, between May 3 and August 3, 2023. For this experiment, two monocrystalline panels with a power output of 390 W manufactured by Zergoune Green Energy Company, as well as data-logging equipment, were used. The first panel was perfectly cleaned before starting every test and the second panel remained uncleaned. On day 90, the cleaned panel maintained an average power of 193 W, while the dusty panel exhibited a lower average power of 139 W. The greatest average reduction in efficiency, approximately 36.32%, occurred after 3months of exposure to weather conditions. The scanning electron microscope (SEM) analysis demonstrates the existence of microscopic dust particles which prevent part of solar radiation away instead of being absorbed by the photovoltaic cells, leading to a drop in the efficiency of the PV module. The primary chemical elements found in dust are oxygen, silicon, aluminum, and magnesium.

Application of deep UV resonance Raman spectroscopy to column liquid chromatography: Development of a low-flow method for the identification of active pharmaceutical ingredients

In this study, deep UV resonance Raman spectroscopy (DUV-RRS) was coupled with high performance liquid chromatography (HPLC) to be applied in the field of pharmaceutical analysis. Naproxen, Metformin and Epirubicin were employed as active pharmaceutical ingredients (APIs) covering different areas of the pharmacological spectrum. Raman signals were successfully generated and attributed to the test substances, even in the presence of the dominant solvent bands of the mobile phase. To increase sensitivity, a low-flow method was developed to extend the exposure time of the sample. This approach enabled the use of a deep UV pulse laser with a low average power of 0.5 mW. Compared to previous studies, where energy-intensive argon ion lasers were commonly used, we were able to achieve similar detection limits with our setup. Using affordable lasers with low operating costs may facilitate the transfer of the results of this study into practical applications.

Safeguarding the Internet of Things: Elevating IoT routing security through trust management excellence

This study presents an innovative IoT routing security model that integrates trust management to bolster network reliability, improve resilience against routing attacks, and isolate malicious activities. The model, emphasizing node behavior, reputation, and past performance, offers a nuanced approach to network security. Through comprehensive comparisons between dynamic and static models in IoT routing, the impact on crucial performance parameters, including throughput, packet delivery ratio, control traffic overhead, and energy consumption, is quantified. Simulations showcase the model's effectiveness in securing IoT communication, achieving an impressive 98 % accuracy in detecting and mitigating attacks. Comparative analysis against prior studies underscores its exceptional performance, particularly in identifying and classifying attack types such as wormhole, Sybil, and rank, alongside normal traffic. This trust-based IoT routing security model represents a substantial advancement in securing dynamic IoT environments, standing out as a valuable contribution. Noteworthy is its low average power consumption, contributing to its exceptional lightweight nature.

Dynamic thresholding logarithmic companding for PAPR reduction in MIMO-OFDM systems for 5G wireless communication

In order to advance 5G wireless communication technology, this paper presents a novel method for lowering the Peak-to-Average Power Ratio (PAPR) in Multiple-Input Multiple-Output Orthogonal Frequency-Division Multiplexing (MIMO-OFDM) systems. It is called the Dynamic Thresholding-based μ-law (DT-μ-law) logarithmic companding technique, and it greatly improves the performance of the system by effectively broadcasting data streams on a single frequency across multiple channels. This technique's ability lies in compressing the amplitude of the transmitting signal beyond a specific threshold value before the parallel-to-serial conversion block in the MIMO-OFDM system. It employs the direct insertion of an offset value into the guard bits, rather than using a step function for the amplitude reduction process, which can reduce additional system complexity and data loss during signal expansion at the receiver end. This technique is more adequately suited for dynamic data rate shifting and interference within a limited threshold value. The dynamic thresholding value (α) is determined by calculating the median and standard deviation of the μ-law companding. This ensures the effective compression of higher amplitude signals at the transmitter, using μ-law log companding. To streamline the decompanding process at the receiver, an offset is introduced, facilitating a smoother transition and reducing complexity. The results demonstrate that the proposed DT- μ-law companding technique significantly improves PAPR reduction while maintaining low Bit Error Rates (BER) and high average spectral power efficiency. This efficiency is optimal when the μ value is maintained within the range of 4–4.5. Furthermore, it was observed that an increase in the μ value corresponds to a decrease in both PAPR value and BER. Specifically, at a signal-to-noise ratio of 15.2 dB, the BER stabilizes at 10−1. Compared to existing methods like the Max-Min Decomp-SLM approach, this technique offers lower Signal-to-Noise Ratio (SNR) values, thereby enhancing spectral efficiency and maximizing data capacity.

Flexible Complementary Metal‐Oxide‐Semiconductor Inverter Based on 2D p‐type WSe2 and n‐type MoS2

Transition metal dichalcogenides (TMDCs) are a promising class of two‐dimensional (2D) materials for flexible electronic applications due to their low integration temperature, good electronic properties, and excellent mechanical flexibility. Moreover, TMDCs offer the possibility of co‐integrating both n‐ and p‐type transistors on the same substrate, enabling the realization of complementary metal‐oxide‐semiconductor (CMOS) circuits. In this study, n‐type MoS2 field‐effect transistors (FETs), and p‐type WSe2‐FETs integrated on a flexible foil substrate fabricated by standard thin‐film technology are presented. These devices exhibit high stability in their electronic operation under strain and repeated bending cycles. A CMOS inverter based on these transistors is also successfully demonstrated, which shows excellent switching behaviour with high gain (up to 100), high noise margin (0.87 · VDD), and low average static power consumption (40 pW).

A Load-Adaptive Driving Method for a Quasi-Continuous-Wave Laser Diode.

A quasi-continuous-wave (QCW) laser diode (LD) driver is commonly used to drive diode bars and stacks designed specifically for QCW operations in solid-state lasers. Such drivers are optimized to deliver peak current and voltage pulses to LDs while maintaining low average power levels. As a result, they are widely used in laser processing devices and laser instruments. Traditional high-energy QCW LD drivers primarily use capacitors as energy storage components and pulsed constant-current sources with op-amps and power metal-oxide-semiconductor field-effect transistors (MOSFETs) as their core circuits for generating repeated constant-current pulses. The drawback of this type of driver is that the driver's output voltage needs to be manually adjusted according to the operating voltage of the load before use to maximize driver efficiency while providing a sufficient current. Another drawback is its inability to automatically adjust the output voltage to maintain high efficiency when the load changes during the driver operation. Drastic changes in the load can cause the driver to fail to function properly in extreme cases. Based on the above traditional circuit structure, this study designed a stability compensation circuit and realized a QCW LD driver for driving a GS20 diode stack with a maximum repetition rate of 100 Hz, a constant current of approximately 300 A, a load voltage of approximately 10 V, and a pulse width of approximately 300 μs. In particular, a high-efficiency, load-adaptive driving method was used with the MOSFETs in the critical saturation region (i.e., between the linear and saturated regions), controlling its power loss effectively while achieving maximum output current of the driver. The experiments demonstrated that the driver efficiency could be maintained at more than 80% when the load current varied from 50 to 300 A.

Spatio‐temporal integrated Bayesian species distribution models reveal lack of broad relationships between traits and range shifts

AbstractAimClimate change and habitat loss or degradation are some of the greatest threats that species face today, often resulting in range shifts. Species traits have been discussed as important predictors of range shifts, with the identification of general trends being of great interest to conservation efforts. However, studies reviewing relationships between traits and range shifts have questioned the existence of such generalized trends, due to mixed results and weak correlations, as well as analytical shortcomings. The aim of this study was to test this relationship empirically, using analytical approaches that account for common sources of bias when assessing range trends.LocationTanzania, East Africa.Time period1980–1999 and 2000–2020.Major taxa studied57 savannah specialist birds found in Tanzania, belonging to 26 families and 11 orders.MethodsWe applied recently developed integrated spatio‐temporal species distribution models in R‐INLA, combining citizen science and bird Atlas data to estimate ranges of species, quantify range shifts, and test the predictive power of traditional trait groups, as well as exposure‐related and sensitivity traits. We based our study on 40 years of bird observations in East African savannahs, a biome that has experienced increasing climatic and non‐climatic pressures over recent decades. We correlated patterns of change with species traits using linear regression models.ResultsWe find indications of relationships identified by previous research, but low average explanatory power of traits from an ecological perspective, confirming the lack of meaningful general associations. However, our analysis finds compelling species‐specific results.Main conclusionsWe highlight the importance of individual assessments while demonstrating the usefulness of our analytical approach for analyses of range shifts.

Comprehensive analysis of energy efficiency and performance of ARM and RISC-V SoCs

Over the past few years, ARM has been the dominant player in embedded systems and System-on-Chips (SoCs). With the emergence of hardware platforms based on the RISC-V architecture, a practical comparison focusing on their energy efficiency and performance is needed. In this study, our goal is to comprehensively evaluate the energy efficiency and performance of ARM and RISC-V SoCs in three different systems. We will conduct benchmark tests to measure power consumption and overall system performance. The results of our study are valuable to developers and researchers looking for the most appropriate hardware platform for energy-efficient computing applications. Our observations suggest that RISC-V Instruction Set Architecture (ISA) implementations may demonstrate lower average power consumption than ARM, but this does not automatically imply a superior performance per watt ratio for RISC-V. The primary focus of the study is to evaluate and compare these ISA implementations, aiming to identify potential areas for enhancing their energy efficiency. Furthermore, to ensure the practical applicability of our findings, we will use the Computational Fluid Dynamics software OpenFOAM. This step serves to validate the relevance of our results in real-world scenarios. It allows us to fine-tune execution parameters based on the insights gained from our initial study. By doing so, we aim not only to provide meaningful conclusions but also to investigate the transferability of our results to practical applications. Our analysis will also scrutinize the capabilities of these SoCs when handling nonsynthetic software workloads, thereby broadening the scope of our evaluation.

Experimental study of the upstream bathymetry effects on a ducted twin vertical axis turbine

Tidal turbines at sea are subject to complex flow conditions. Among that complexity, wide bathymetry obstacles can generate powerful coherent flow structures whose impact on horizontal axis tidal turbines was proved to be highly detrimental. Consequently, the present paper aims at studying the effects of such coherent flow structures on the response of another tidal turbine geometry, namely a bottom-mounted ducted twin vertical axis tidal turbine (2-VATT). We tested a 1/20 scale model of such a 2-VATT in Ifremer’s flume tank either with a flat bed or downstream of a wide bathymetry obstacle at a constant far upstream velocity and we measured the turbine response simultaneously with the flow velocity. These flow measurements make it possible to compute cross-correlations in order to analyse the influence of the velocity fluctuation on the turbine response. The results reveal a strong drop in the average power and loads coefficients of the 2-VATT combined with significantly larger fluctuation. The velocity deficit and the high level of turbulence in the obstacle wake is responsible for a 40% lower average power coefficient and more than 3 times higher standard deviation compared to the flat bed configuration. The loads standard deviations are multiplied by 2 for the drag and by 10 for the lift when the 2-VATT is downstream of the bathymetry obstacle. This behaviour strongly increases the risks of structural fatigue failure, but the turbine drifting or overturning risks under those conditions remain lower than with the flat bed. The power fluctuation increase appears to be mostly due to the flow shear in the obstacle wake whereas the load fluctuation is mostly due to the periodical passing of the coherent flow structures. Thus, a proper characterisation of the flow at each precise turbine locations prior deployment at sea is highly recommended to design their structure accordingly.

Microwave electrothermal thruster with surface wave plasma

AbstractA new microwave electrothermal thruster (MET) with small dimensions (length of 25 mm and diameter of 6 mm), utilizing surface wave (SW) plasma at low average power consumption Pav ˜ 2 W, is made. It uses microwaves at a frequency of 2.45 GHz for plasma generation within a dielectric chamber enclosed in a metal shield. The SW is excited at the plasma‐dielectric interface by a coaxial launcher and a standing wave is created due to the wave reflection from the shield. The high‐density plasma produced in this resonant chamber heats up the argon gas, which expands through the nozzle in the axial direction. The temperature of the gas decreases from 1900 K at atmospheric pressure to 1200 K at 10 Torr ambient pressure. This small‐sized MET shows stable low‐pressure operation with a thrust of 4 mN and an efficiency of 8% and is suitable for nanosatellite orbit control.

Multi-Hop and Mesh for LoRa Networks: Recent Advancements, Issues, and Recommended Applications

A comprehensive review is presented on the latest approaches to solutions focusing on multi-hop and mesh LoRa networks through the evaluation of simulations and real-world experiments, based on papers published between 2015 and 2023. The approaches are systematically classified into four (4) aspects: energy awareness, concurrent access and duty cycle regulations, routing protocols, and security. The first aspect encompasses parameter selection, distance, and clustering. The second aspect focuses on network segregation and time synchronisation. The third aspect covers proactive, reactive, and hybrid routing protocols. The aspect of security includes privacy and Denial-of-Service (DoS). Findings show a consensus that multi-hop networks and adherence to radio duty cycle are able to lower average power consumption. Concurrent access method can improve network performance, but more research is needed due to different conclusions. Reactive protocols have a slight advantage over proactive protocols in terms of node deployment scalability and lower power consumption due to less frequent routing table updates. Hybrid protocols are only beneficial in specific topology deployments. Security is still a major concern for LoRa networks, particularly on attacks such as Man-In-The-Middle (MITM), spoofing, wormholes, flooding, packet replay, and information disclosure. The upcoming trend of implementing machine learning algorithms to multi-hop and mesh LoRa networks opens up a wide range of possibilities, ranging from airspace efficiency, efficient route selection, and improving data throughput. A detailed discussion of the aspects’ issues and recommended industry applications that will benefit from multi-hop and mesh LoRa networks are also provided.

Boosting the Output of Liquid–Solid Triboelectric Nanogenerator by an External Charge‐Pumping Strategy

AbstractIn recent years, liquid–solid triboelectric nanogenerator (LSTENG) has attracted great attention. However, its low average power density and long charging time limit the practical application of this technique. Here, for the first time, a liquid–solid triboelectric nanogenerator combined with external charge‐pumping method (ECP‐LSTENG) is proposed. Compared to traditional LSTENGs, a charge storage capacitor is added in this ECP‐LSTENG to store the output charges from the pumping generator. Then, a charge extraction capacitor is formed by the spreading and shrinking processes of falling droplet, while the charging and discharging process between charge storage and extraction capacitors can generate displacement current output for external circuit. Meanwhile, it is found that a special charged droplets adhesion phenomenon happens at the liquid–solid interface, which seriously hinders the continuous output of ECP‐LSTENG. To overcome this limitation, a special coaxial deceleration commutation component is designed to ensure continuous output of the ECP‐LSTENG. Finally, the peak power density of a droplet (50 µL) reaches 231.8 W m−2, surpassing the highest research record to date by 1.43 times. This ECP‐LSTENG provides a different approach for the future development of large‐scale integrated raindrop generators for efficient raindrop energy harvesting.

Temporal power modulation in high power laser beam welding of round bars

Temporal power modulation bears an enormous potential for high power laser beam welding of round bars since all its specific challenges are faced. They can be summarised as deviating welding conditions towards the round bar‘s centre. Accordingly, a tailored amount of energy would be provided to that area. The investigations are conducted on 30 mm diameter bars of 1.4301 stainless steel with the use of a 16 kW disk laser. The modulation parameters comprise 6/12/50/100/200 Hz modulation frequency and 0.30/0.47/0.73 modulation depth or power modulation ratio. Post analysis focuses on metallographic longitudinal sections and calculations. The modulation‘s outstanding capability is creating deeper and narrower weld seams due to higher peak power and more intense evaporation of protrusions along the keyhole front wall. Therefore, more laser power is provided to the weld root and despite applying lower average power, the same weld depth is achieved. Finally, more ecological and economical welding as well as welding of more temperature sensitive materials is enabled.

Comprehensive Numerical Analysis of a Four-Way Two-Position (4/2) High-Frequency Switching Digital Hydraulic Valve Driven by a Ring Stack Actuator

This paper presents a feasibility study using a commercially available ring stack actuator to develop a four way-two position (4/2) high frequency switching digital hydraulic valve. The excellent characteristics of multilayer piezoelectric actuators, such as a simple design, reduced moving parts, high reliability, and fast response, make them ideal for constructing this type of digital hydraulic valve. High frequency switching digital hydraulic valves (HFSVs), indeed, must be able to switch from fully open to fully closed positions in less than 5 ms, while maintaining minimal pressure losses and delivering large flows. The proposed valve architecture is assessed using well-established equations implemented in a Simulink model, allowing the hydraulic, mechanical, and electrical parts of the valve to be accurately simulated. The paper first provides a detailed description of the numerical model. Next, the hysteresis model of the ring stack actuator is validated against the data provided by the manufacturers on their website. Finally, the numerical results obtained with both open-loop and closed-loop control systems are presented. The simulations show that at a switching frequency of 200 Hz with maximum amplitude and duty cycle of the input pulse digital signal, the valve exhibits high average flow rates (~60 L/min), low average power consumption (~1500 W), and maintains a pressure drop of only 15 bar. Moreover, the simulations reveal that the control system is very effective since the valve switching time is within 1 ms.

A Robust Droplet Triboelectric Nanogenerator with Self-Cleaning Ability Achieved by Femtosecond Laser

A droplet triboelectric nanogenerator (TENG) has great potential for harvesting the high entropy energy in water. Despite extensive research, it still suffers from low average power density, poor long-term stability, and insufficient flexibility. Here, a porous micronanostructured polytetrafluoroethylene (PTFE) with superhydrophobicity and self-cleaning ability, is generated by femtosecond laser direct processing. The droplet TENG with laser treated PTFE (LT-PTFE) dielectric layer (L-DTENG) can reach a higher output compared with the droplet TENG with a PTFE dielectric layer (P-DTENG). L-DTENG also demonstrated good long-term stability, self-cleaning ability, and flexibility, making it suitable for various applications, including those involving dust and sewage pollution, as well as bending and pressing conditions. Furthermore, a simulation of finite element method (FEM) and an equivalent circuit model are established to understand the working mechanism of L-DTENG. This multifunctional device and theoretical research provide a smart strategy to generate electricity in a complex environment and lay a solid foundation for droplet TENG applications on a large scale.

The winner's curse and related perils of low statistical power − spelled out and illustrated

A classical prospective power analysis estimates the chance of obtaining a statistically significant result. However, it does so with no regard to the reliability of the result. “Design analysis” is a complementary component of study planning which addresses that limitation. Monte Carlo simulations and innovative freeware were used to provide illustrations of common, potentially grave problems that make design analysis necessary. Five statements outline widely known background to those problems. (1) A regime of significance testing tends to engender publication bias. (2) Small-sample studies commonly have very low expected statistical power. (3) Many SLA (quasi-)experimental studies have used small samples. (4) A combination of publication bias and low average power seeds a research literature with findings that well-powered replication studies do not repeat. (5) Published estimates of true effects are often too high. As to the last statement, many SLA researchers may be unaware of the mathematical basis of the tendency for obtained significant estimates to be too high whenever expected power is not high, which it frequently is not. Indeed, if power is too low, a significant result can only be misleading: Any good estimate will be nonsignificant. The design analysis procedures used to illustrate the focal problems can also be used to estimate sample sizes required for adequate expected power along with good control of the risk of obtaining very misleading significant results.