Performance Power Consumption Research Articles

MAC protocol with clock synchronization correction for a practical infrastructure monitoring system

Sensor networks for infrastructure monitoring systems require battery-operated sensing nodes with a lifetime of 10 years, a standardized technology, and low engineering costs. Receiver-initiated transmission and coordinated sampled listening are promising power-saving communication methods that can be used for infrastructure monitoring. First, we compared receiver-initiated transmission and coordinated sampled listening from the viewpoint of power consumption and communication success probability. The results of the comparison showed that if we can continue coordinated sampled listening synchronous communication mode, we can satisfy the low power consumption performance required for infrastructure monitoring. However, coordinated sampled listening synchronous communication cannot be maintained for a longer period owing to performance variations of the clock crystal oscillator (CXO). We solved this problem by developing energy efficient system-media access control protocol (NES MAC), a MAC protocol with the additional function of correcting the dispersion of CXO and maintaining synchronization for a long time. NES-MAC is fully compatible with coordinated sampled listening. Furthermore, NES-MAC also has a high power-saving effect when communicating with normal coordinated sampled listening. Therefore, it is possible to expand the network easily and economically without affecting the power-saving performance. In addition, we found that through actual equipment evaluation that sensor nodes that adopt NES-MAC can operate for more than 10 years with two CR123A-type batteries.

High-Sensitivity and Low-Power Flexible Schottky Hydrogen Sensor Based on Silicon Nanomembrane.

High-performance and low-power flexible Schottky diode-based hydrogen sensor was developed. The sensor was fabricated by releasing Si nanomembrane (SiNM) and transferring onto a plastic substrate. After the transfer, palladium (Pd) and aluminum (Al) were selectively deposited as a sensing material and an electrode, respectively. The top-down fabrication process of flexible Pd/SiNM diode H2 sensor is facile compared to other existing bottom-up fabricated flexible gas sensors while showing excellent H2 sensitivity (Δ I/ I0 > 700-0.5% H2 concentrations) and fast response time (τ10-90 = 22 s) at room temperature. In addition, selectivity, humidity, and mechanical tests verify that the sensor has excellent reliability and robustness under various environments. The operating power consumption of the sensor is only in the nanowatt range, which indicates its potential applications in low-power portable and wearable electronics.

Solution-processed lanthanum-doped Al2O3 gate dielectrics for high-mobility metal-oxide thin-film transistors

Solution-processed oxide gate dielectrics play an important in thin-film transistors (TFTs), determining their operation voltage, device performance and power consumption. Up to now, various solution-processed oxide gate dielectrics such as aluminum oxide (Al2O3) have been surveyed, however, they generally exhibit relatively high leakage current, low dielectric constant, and hysteresis which are unfavorable for stable device operation. Here, we demonstrate solution-processed lanthanum (La)-doped Al2O3 (LAO) gate dielectrics which exhibit low leakage current density, high dielectric constant, and relatively small frequency-dependent capacitance variation. In order to find the optimal doping concentration of lanthanum in Al2O3 film, various electrical, morphological, and spectroscopic analyses were carried out. We found that the addition of lanthanum in Al2O3 film effectively reduced the defective metal hydroxide bonding states within the film and significantly enhanced its dielectric characteristics. At an optimal doping concentration of lanthanum (20 at.%), gate dielectrics showing leakage current density, dielectric constant, and breakdown field of ~10−8 A/cm2 (at 2 MV/cm), 10.5, and >5 MV/cm were obtained. Using the LAO film as a gate dielectric, solution-processed indium-zinc-oxide TFTs having a field-effect mobility of 11.9 cm2/V-s, subthreshold slope of 0.38 V/dec, and on/off ratio of 104–105 were demonstrated.

Design and Electrical Characterization of 2-T Thyristor RAM With Low Power Consumption

In this letter, a Si-based two-terminal (2-T) thyristor random-access memory (TRAM) device is designed and characterized, and its operation window and power consumption are closely investigated by technology computer-aided design (TCAD) simulation. The properly scaled 2-T TRAM device has higher reliability since it can rule out impact ionization. Write time ( ${T}_{\text {write}}$ ) and erase time ( ${T}_{\text {erase}}$ ) reach below 10 ns and zero energy is consumed to hold state achieving high competitiveness with the existing dynamic random-access memory (DRAM). The state current ratio reaches higher than 105. Also, ${V}_{\text {write}}$ and erase voltage ( ${V}_{\text {erase}}$ ) of the 2-T TRAM appear to be below 2 and −1.2 V, respectively, in the permissible operation window, with less energy consumption compared with the conventional ones. The 2-T TRAM is a strong candidate for capacitorless DRAM technology.

Local structural environments of Ge doped in eutectic Sb-Te film before and after crystallization

Electrical phase change device using the Ge-doped eutectic Sb-Te (e.g., Ge1Sb8Te2) film is known to exhibit improved energy efficiency thanks to lowered threshold voltage as well as decreased power consumption for the reset operation, as compared with Ge2Sb2Te5 film. Ge K-edge EXAFS analysis is employed in this study in an effort to elucidate such merits of Ge1Sb8Te2 film in connection with its local atomic arrangements. It is then verified that a Ge atom is four-fold coordinated in its nearest-neighboring shell both in the as-deposited and in the annealed films. It needs to be highlighted that approximately two Sb atoms constitute the Ge tetrahedral units in its amorphous state; however, after being crystallized, heteropolar Ge-Sb bonds hardly exist in this Ge1Sb8Te2 film. It has been known that crystallization temperature and activation energy for crystallization of this Ge1Sb8Te2 composition are greater than those of Ge2Sb2Te5 composition. In addition, these two phase change materials exhibit distinctly different crystallization mechanisms, i.e., nucleation-dominant for Ge2Sb2Te5 film but growth-dominant for Ge1Sb8Te2 film. These discrepancies in the crystallization-related properties are delineated in terms of the local structural changes verified from the present EXAFS analysis.

Electronics of a Wearable ECG With Level Crossing Sampling and Human Body Communication.

In this paper, the human body communication (HBC) and level crossing sampling (LCS) are combined to design electronics for a wearable electrocardiograph (ECG). The ECG signals acquired by capacitively coupled electrodes are sampled with LCS in place of conventional synchronous sampling. In order to transmit signals through HBC at low frequencies (100kHz, 1MHz), an electric field sensor with high input impedance is adopted as the front end of the HBC receiver. The HBC channel gain is enhanced by more than 30dB with the electric field sensor. An LCS structure based on the send-on-delta concept is implemented with discrete components to convert the ECG signals into binary impulses. The converted impulses are modulated by an on-off keying modulator and then transmitted via the human body to the receiver. A prototype ECG waist belt is developed with commercially available components and experimentally evaluated. The results indicate that the acquired ECG waveforms exhibit good agreement with regular Ag/AgCl ECG methods. The heartbeat detection using a technique based on the Kadane's algorithm and the power consumption performance of the proposed system are also discussed.

Energy saving technique for natural stone cutting machine by constant speed control in stone industry

This study presents a constant speed control technology applied to manufacturing process equipment. According to the amount of change in electrical motor (EM) load, a Silicon Controlled Rectifier element was used to modulate the phase angle so that the current drops accordingly, to meet the most appropriate output voltage of the EM, providing the machine with the best torque output. The changes in output power of the EM varied along with different process loads, so unnecessary electricity at low loads of EM can be saved; however, when the equipment undergoes a period of high-load operation, the proposed technique provides an appropriate torque, thus reducing power consumption. The present energy-saving technique by constant speed control (ESTCSC) does not affect the machine, as it only modulates the load according to the dynamic load variation of the machine. In this study, the proposed ESTCSC was practically applied to a sawing machine in the stone industry. The validation experiments were conducted w/o installing the ESTCSC, and the measured total saving rates for operating current, average operating power consumption, and 24 h long-term energy consumption were 20, 38.87, and 48.36%, respectively.

Multibit memory operation of metal-oxide bi-layer memristors

Emerging nanoionic memristive devices are considered as the memory technology of the future and have been winning a great deal of attention due to their ability to perform fast and at the expense of low-power and -space requirements. Their full potential is envisioned that can be fulfilled through their capacity to store multiple memory states per cell, which however has been constrained so far by issues affecting the long-term stability of independent states. Here, we introduce and evaluate a multitude of metal-oxide bi-layers and demonstrate the benefits from increased memory stability via multibit memory operation. We propose a programming methodology that allows for operating metal-oxide memristive devices as multibit memory elements with highly packed yet clearly discernible memory states. These states were found to correlate with the transport properties of the introduced barrier layers. We are demonstrating memory cells with up to 6.5 bits of information storage as well as excellent retention and power consumption performance. This paves the way for neuromorphic and non-volatile memory applications.

A 0.4-to-1 V Voltage Scalable $\Delta \Sigma $ ADC With Two-Step Hybrid Integrator for IoT Sensor Applications in 65-nm LP CMOS

This brief presents a two-step hybrid integrator (TSHI) that can operate at a wide supply voltage range, which is demonstrated with a third-order ${\Delta \Sigma }$ analog-to-digital converter (ADC). The proposed TSHI consists of a zero-crossing-detector (ZCD)-based integrator and an inverter-based integrator. In the coarse-integration step, the ZCD-based integrator performs a fast integration without concern for overshoot or detection delay issues. In the fine-integration step, the inverter-based integrator performs the residual integration with high accuracy. Hence, the TSHI provides fast and accurate integration process. In addition, the TSHI supports trade-off between voltage-scalable bandwidth and power consumption for an energy efficient operation of Internet-of-Things sensor nodes, owing to the scalable operation of the ZCD and inverter. The proposed ${\Delta \Sigma }$ ADC is fabricated in a 65-nm LP CMOS process, and the active area is 0.38 mm2. The fabricated ADC operates at supply voltages from 0.4 to 1 V. Depending on the supply voltage and sampling frequency, the power consumption and bandwidth of the ADC can be scaled from 12.7 to $948~{\mu }{\mathrm{W}}$ and from 7.5 to 400 kHz, respectively. The ADC maintains an SNDR higher than 60 dB within the operating supply range.

Emulsified behaviors for the formation of Methanol-Diesel oil under high gravity environment

Abstract The emulsified behaviors in the process of preparing methanol-diesel emulsified fuel are investigated by the application of an impinging stream-rotating packed bed (IS-RPB). The emulsified processes are composed of the combinations of initial emulsification of impinging stream process, intensified emulsification of IS-RPB and perfect emulsification of back-splashing and atomization to complete the entire emulsified process through the analysis of force posed on all fluid particles in IS-RPB. The existence of the three emulsified processes is proved using the computational fluid dynamics (CFD) simulations. The turbulent kinetic energy and velocity vector of the three emulsified processes using the CFD simulations were analyzed logically, which proved the existence of the three emulsified processes. Based on the analysis and CFD simulations, the properties of stabilization, dispersion, micro-mixing and power consumption performance were compared under the IS-RPB and high speed stirrer, which further prove the practicability and advancement of this technology for methanol-diesel emulsified fuel.

Energy and productivity efficient vacuum pressure swing adsorption process to separate CO2 from CO2/N2 mixture using Mg-MOF-74: A CFD simulation

Quantitatively, carbon dioxide is the main gas emitted from the burning of fossil fuels; thus, it is the primary contributor to global warming. However, climate change could be mitigated using “carbon capture and storage” (CCS) methods. CO2 separation by physical adsorption is a promising technology to achieve CO2 capture with minimum energy costs. Mg-MOF-74 is a distinguished adsorbent amongst porous materials owing to its high CO2 uptake under flue gas conditions. In this study, a vacuum pressure swing adsorption (VPSA) process composed of five steps (pressurization, feed, rinse, blowdown, and purge) for separating CO2 from a CO2/N2 mixture using Mg-MOF-74 was mathematically modeled. Two- and three-dimensional computational fluid dynamics (CFD) models were developed using a user-defined-function (UDF, written in C) linked to the ANSYS Fluent program. The models have been validated against published pressure swing adsorption experimental data. The regeneration (blowdown and purge) time has been tuned to explore the performance improvement for the VPSA process. The key optimum performance indices for VPSA in terms of CO2 purity, recovery, productivity, and process power consumption were found to be 95.3%, 94.8%, 0.50 kg_CO2 h−1 kg_MOF−1, and 68.71 kW h tonne_CO2−1, respectively. The corresponding operating carbon capture cost has been evaluated as $6.87 tonne_CO2−1 for a 500-MW post-combustion power plant. These CO2 productivity and power consumption performances represent a significant enhancement in CO2 separation using physical adsorption technology compared to those reported in the literature.

In‐DRAM bitwise processing circuit for low‐power and fast computation

In-DRAM processing circuit is able to reduce operation time and power consumption than the traditional CPU + MEMORY system in performing the complicated computation such as convolution. These benefits are gained by bitwise and parallel processing of the in-DRAM convolution circuit. To realise the in-DRAM circuit, an inter-bank processing circuit is proposed with bitwise summation/comparison circuit for performing convolution inside DRAM. Compared to the intra-bank bitwise operation, the inter-bank circuit can significantly reduce the power consumption and the number of row activation cycles to accomplish convolution. For the number of cycles, the inter-bank circuit takes only 65 cycles for calculating 16 × 16 feature map. On the contrary, the intra-bank needs as many as 192 cycles. In terms of power consumption, the inter-bank circuit consumes smaller power by 35% than the intra-bank. In the proposed in-DRAM processing circuit, no complicated multiplier and adder are needed in performing the convolution. The Modified National Institute of Standards and Technology (MNIST) recognition rate of the proposed bitwise processing circuit can be as high as 97.28%, indicating very little loss due to the ternary kernels.

A 0.1–5.0 GHz SDR transmitter with current-mode power-mixer and self-calibration scheme in 65 nm CMOS

A 0.1–5.0 GHz software-defined radio (SDR) transmitter for private network wireless communication is presented. A V-I converter with the 3rd-order nonlinearity cancellation and current-mode power-mixers are introduced to improve the CIM3 performance. The complete self-calibration scheme is proposed to alleviate the non-ideal effects, including RF resonant frequency self-tuning, LO leakage and image rejection calibration, output power control. With the self-calibration, the transmitter obtains good robustness in RF operation frequency self-tuning and achieves the average LO leakage of −61 dBc and image-rejection ratio (IRR) of 58 dBc. Moreover, the system verifications have demonstrated 24.5 dBm Pout (output power) with 0.7% EVM, 20 dBm Pout with 1.6% EVM, 6.2 dBm Pout with 2.1% EVM for 905 MHz GSM, 905 MHz EDGE and 3.5 GHz LTE signals, respectively. This SDR transmitter has achieved comparable or even better performance in linearity, CIM3 and power consumption compared with the state-of-the-art reconfigurable transmitters.

High-Performance Single-Active-Layer Memristor Based on an Ultrananocrystalline Oxygen-Deficient TiOx Film.

The theoretical and practical realization of memristive devices has been hailed as the next step for nonvolatile memories, low-power remote sensing, and adaptive intelligent prototypes for neuromorphic and biological systems. However, the active materials of currently available memristors need to undergo an often destructive high-bias electroforming process in order to activate resistive switching. This limits their device performance in switching speed, endurance/retention, and power consumption upon high-density integration, due to excessive Joule heating. By employing a nanocrystalline oxygen-deficient TiOx switching matrix to localize the electric field at discrete locations, it is possible to resolve the Joule heating problem by reducing the need for electroforming at high bias. With a Pt/TiOx/Pt stacking architecture, our device follows an electric field driven, vacancy-modulated interface-type switching that is sensitive to the junction size. By scaling down the junction size, the SET voltage and output current can be reduced, and a SET voltage as low as +0.59 V can be obtained for a 5 × 5 μm2 junction size. Along with its potentially fast switching (over 105 cycles with a 100 μs voltage pulse) and high retention (over 105 s) performance, memristors based on these disordered oxygen-deficient TiOx films promise viable building blocks for next-generation nonvolatile memories and other logic circuit systems.

Improved thermal stability of Sb materials by SiO2 doping for ultra-fast phase change memory application

SiO2-doped Sb material is proved to be a promising candidate for phase change memory (PCM) use because of its high crystallization temperature (∼239 °C), large crystallization activation energy (4.05 eV), and good data retention ability (162 °C for 10 years). The band gap is broadened and the grain size is refined by SiO2 doping. The reversible resistance transition can be achieved by an electric pulse as short as 5 ns for the PCM cell based on SiO2-doped Sb material. A lower operation power consumption (the energy for RESET operation 1.1 × 10−11 J) is obtained. In addition, SiO2-doped Sb material shows a good endurance of 2.5 × 105 cycles.

A novel analysis of delay and power consumption for polling schemes in the IoT

In the Internet of Things (IoT), various battery-powered wireless devices are connected to collect and exchange data, and typical traffic is periodic and heterogeneous. Polling with power management is a very promising technique that can be used for communication among these devices in the IoT. In this paper, we propose a novel and scalable model to study the delay and the power consumption performance for polling schemes with power management under heterogeneous settings (particularly the heterogeneous sleeping interval). In our model, by introducing the concept of virtual polling interval, we successfully convert the considered energy-efficient polling scheme into an equivalent purely-limited vacation system. Thus, we can easily evaluate the mean and variance of the delay and the power consumption by applying existing queueing formulae, without developing a new theoretical model as required in previous works. Extensive simulations show that our analytical results are very accurate for both homogeneous and heterogeneous settings.

Analog/RF performance of two tunnel FETs with symmetric structures

In this paper, the radio frequency and analog performance of two tunnel field-effect transistors with symmetric structures are analyzed. The symmetric U-shape gate tunnel field-effect transistor (SUTFET) and symmetric tunnel field-effect transistor (STFET) are investigated by Silvaco Atlas simulation. The basic electrical properties and the parameters related to frequency and analog characteristics are analyzed. Due to the lower off-state leakage current, the STFET has better power consumption performance. The SUTFET obtains larger operating current (242 μA/μm), transconductance (490 μS/μm), output conductance (494 μS/μm), gain bandwidth product (3.2 GHz) and cut-off frequency (27.7 GHz). The simulation result of these two devices can be used as a guideline for their analog/RF applications.

Energy-aware run-time task partition and allocation in dynamic partial reconfigurable systems

Abstract Dynamic partial reconfigurable systems with a processor and a field-programmable gate array are promising innovations for meeting the requirement of mobile embedded devices. These systems demonstrate low power consumption and high performance. However, with limited battery life and chip size, energy saving and area allocation are critical concerns for such systems. In this study, an energy-aware hardware/software partition is presented to minimize the system energy consumption, and a contention-aware task allocation is presented to minimize the area requirement and response time. The energy efficiency and schedulability of the proposed methodology were evaluated using a series of workloads, and impressive results were obtained.

Bifurcation analysis of an e-epidemic model in wireless sensor network

ABSTRACTIn this paper, we have formulated an e-epidemic energy efficient susceptible-infected–terminally infected-recovered (SITR) model to analyse the attacking behaviour of worms in wireless sensor network (WSN) using cyrtoid type functional response. In this model, once a sensor node has been attacked by the worms, the terminally infected node spreads the worms to its neighbouring nodes using normal communications, which further spread it to their neighbouring nodes and the process continues. To tackle this issue, we proposed an SITR model by considering the sleep mode concept of WSN in which the operational capabilities and power consumption of the motes decreases. Boundedness, existence of equilibrium points, stability and bifurcation analysis are analysed for the proposed model system. Stability and direction of Hopf-bifurcation are also obtained for endemic equilibrium point using center manifold theorem. Finally, numerical simulations are carried out that supports the analytical findings. The impact of the control parameters like transmission rate (β), inter-nodes interference coefficient () and intrinsic growth rate () on the dynamics of the model system are investigated.

High-Performance PVC Gel for Adaptive Micro-Lenses with Variable Focal Length

This paper presents a bio-inspired adaptive micro-lens with electrically tunable focus made of non-ionic high-molecular-weight polyvinyl chloride (PVC) gel. The optical device mimics the design of the crystalline lens and ciliary muscle of the human eye. It consists of a plano-convex PVC gel micro-lens on Indium Tin Oxide (ITO) glass, confined with an annular electrode operating as an artificial ciliary muscle. Upon electrical activation, the electroactive adhesive force of the PVC gel is exerted on the annular anode electrode, which reduces the sagittal height of the plano-convex PVC gel lens, resulting in focal length variation of the micro-lens. The focal length increases from 3.8 mm to 22.3 mm as the applied field is varied from 200 V/mm to 800 V/mm, comparable to that of the human lens. The device combines excellent optical characteristics with structural simplicity, fast response speed, silent operation, and low power consumption. The results show the PVC gel micro-lens is expected to open up new perspectives on practical tunable optics.