Power Dissipation Model Research Articles

Power Dissipation and Wear Modeling in Wheel–Rail Contact

This paper is concerned with the modeling of power dissipation due to friction and its relation with wear estimation in wheel–rail contact. Wear is a complex multi-scale and multi-physical phenomenon appearing in rolling contact. Wear is generated by high contact stress and the work of friction forces. This phenomenon leads to the appearing of the worn material in the form of wear debris between contacting surfaces. In contact models, wear is usually described in terms of the wear depth function. This function modifies the gap between the contacting bodies as well as the shape of the surfaces of the wheel and rail in contact. In this paper, besides the wear depth function, the dissipated energy, rather than the contact stress, is taken into account to evaluate the wear impact on rail or wheel surfaces. The dissipated energy allows us to more precisely evaluate the wear debris amount as well as the depth of wear and its distribution along the contact interface. A two-dimensional rolling contact problem with frictional heat flow is considered. The elasto-plastic deformation of the rail is considered. This contact problem is governed by a coupled system of mechanical and thermal equations in terms of generalized stresses, displacement and temperature. The finite element method is used to discretize this problem. A discretized system of equations with nonpenetration and friction conditions is transformed and formulated as a nonlinear complementarity problem. The generalized Newton method is applied to numerically solve this mechanical subproblem. The Cholesky method is used to find the solution of the heat-conductive problem. The dissipated power is evaluated based on the resultant force and slip at a reference point. Numerical results including the distribution of slip velocity, power factor and wear rate are provided and discussed.

Full-duplex cell-free mMIMO networks with coarse ADCs/DACs over Ricean fading for beyond 5G

In this article, we explore a practical full-duplex (FD) cell-free massive multiple-input multiple-output (mMIMO) network equipped with coarse analog-to-digital converters/digital-to-analog converters (ADCs/DACs) at the access points (APs) over Ricean fading channels for beyond 5G communication. First, we suppose that the minimum mean square error scheme is applied to estimate channel state information. The accurate sum achievable rate expressions for both uplink (UL) and downlink (DL) are obtained in closed-form by performing the maximum ratio combining and conjugate beamforming at the APs, respectively. Then, the expressions of energy efficiency for UL and DL can be obtained in closed-form based on the established power dissipation model. Finally, the numerical results are conducted to demonstrate our analytical results about the spectral efficiency of considered system. It is also found that when the total number of coarse ADCs/DACs precision is fixed, employing the higher-precision ADCs at the receive end of APs can notably improve the FD sum rate of proposed networks. In addition, the simulation results also show the impacts of number of antennas at each AP and resolution of coarse ADCs/DACs on the energy efficiency (EE) performance. It is revealed that the moderate quantization bits can contribute to the optimal EE.

Energy-Efficient Hybrid Symbol-Level Precoding for Large-Scale mmWave Multiuser MIMO Systems

We address the symbol-level precoding design problem for the downlink of a multiuser millimeter wave (mmWave) multiple-input multiple-output (MIMO) wireless system where the transmitter is equipped with a large-scale antenna array. The high cost and power consumption associated with the massive use of radio frequency (RF) chains prohibit fully-digital implementation of the precoder, and therefore, we consider a hybrid analog-digital architecture where a small-sized baseband precoder is followed by two successive networks of analog on-off switches and variable phase shifters according to a fully-connected structure. We jointly optimize the digital baseband precoder and the states of the switching network on a symbol-level basis, i.e., by exploiting both the channel state information (CSI) and the instantaneous data symbols, whereas the phase-shifting network is designed only based on the CSI due to practical considerations. Our approach to this joint optimization is to minimize the Euclidean distance between the optimal fully-digital and the hybrid symbol-level precoders. Remarkably, the use of a switching network allows for power-savings in the analog precoder by switching some of the phase shifters off according to the instantaneously optimized states of the switches. Our numerical results indicate that, on average, up to 50 percent of the phase shifters can be switched off. We provide an analysis of energy efficiency by adopting appropriate power dissipation models for the analog precoder, where it is shown that the energy efficiency of precoding can substantially be improved thanks to the phase shifter selection approach, compared to the fully-digital and the state-of-the-art hybrid symbol-level schemes.

Gas-Liquid Flow and Interphase Mass Transfer in LL Microreactors

This work investigates the impact of fluid (CO2(g), water) flow rates, channel geometry, and the presence of a surfactant (ethanol) on the resulting gas–liquid flow regime (bubble, slug, annular), pressure drop, and interphase mass transfer coefficient (kla) in the FlowPlateTM LL (liquid-liquid) microreactor, which was originally designed for immiscible liquid systems. The flow regime map generated by the complex mixer geometry is compared to that obtained in straight channels of a similar characteristic length, while the pressure drop is fitted to the separated flows model of Lockhart–Martinelli, and the kla in the bubble flow regime is fitted to a power dissipation model based on isotropic turbulent bubble breakup. The LL-Rhombus configuration yielded higher kla values for an equivalent pressure drop when compared to the LL-Triangle geometry. The Lockhart–Martinelli model provided good pressure drop predictions for the entire range of experimental data (AARE < 8.1%), but the fitting parameters are dependent on the mixing unit geometry and fluid phase properties. The correlation of kla with the energy dissipation rate provided a good fit for the experimental data in the bubble flow regime (AARE < 13.9%). The presented experimental data and correlations further characterize LL microreactors, which are part of a toolbox for fine chemical synthesis involving immiscible fluids for applications involving reactive gas–liquid flows.

Energy Efficiency Augmentation in Massive MIMO Systems through Linear Precoding Schemes and Power Consumption Modeling

Massive multiple-input multiple-output or massive MIMO system has great potential for 5th generation (5G) wireless communication systems as it is capable of providing game-changing enhancements in area throughput and energy efficiency (EE). This work proposes a realistic and practically implementable EE model for massive MIMO systems while a general and canonical system model is used for single-cell scenario. Linear processing schemes are used for detection and precoding, i.e., minimum mean squared error (MMSE), zero-forcing (ZF), and maximum ratio transmission (MRT/MRC). Moreover, a power dissipation model is proposed that considers overall power consumption in uplink and downlink communications. The proposed model includes the total power consumed by power amplifier and circuit components at the base station (BS) and single antenna user equipment (UE). An optimal number of BS antennas to serve total UEs and the overall transmitted power are also computed. The simulation results confirm considerable improvements in the gain of area throughput and EE, and it also shows that the optimum area throughput and EE can be realized wherein a larger number of antenna arrays at BS are installed for serving a greater number of UEs.

Analytical Modeling of D.C. Parameters of Double Gate Junctionless MOSFET in Near and Subthreshold Regime for RF Circuit Application

Aims:: In this work, a Junction-Less Double Gate MOSFET (JLDG MOSFET) based CMOS inverter circuit is proposed for ultra-low power applications in the near and sub-threshold regime operations. Background:: D.C. performances like power, delay and voltage swing of the proposed Inverter have been modeled analytically and analyzed in depth. JLDG MOSFET has promising features to reduce the short-channel effects compared to the planner MOSFET because of better gate control mechanism. So, proposed Inverter would be efficacious to offer less power dissipation and higher speed. Objective:: Impact of supply voltage, temperature, High-k gate oxide, TOX, TSI on the power, delay and voltage swing of the Inverter circuits have been detailed here. Methods: Extensive simulations using SILVACO ATLAS have been done to validate the proposed logic based digital circuits. Besides, the optimum supply voltage has been modelled and verified through simulation for low voltage operations. In depth analysis of voltage swing is added to measure the noise immunity of the proposed logic based circuits in Sub & Near-threshold operations. For ultra-low power operation, JLDG MOSFET can be an alternative compared to conventional planar MOSFET. Result:: Hence, the analytical model of delay, power dissipation and voltage swing have been proposed of the proposed logic based circuits. Besides, the ultra-low power JLDG CMOS inverter can be an alternative in saving energy, reduction of power consumption for RFID circuit design where the frequency range is a dominant factor. Conclusion:: The power consumption can be lowered in case of UHF, HF etc. RF circuits using the Double Gate Junction-less MOSFET as a device for circuit design.

Frequency Dependence of Initial Heat Generation in Granular Magnetite Nanoparticles

The frequency dependence of heat generation in granular magnetite nanoparticles was studied using vibrating sample magnetometry and the nanoTherics Magnetherm™ hyperthermia testing system. First, the particle size and its distribution were obtained by fitting the M-H curve to the classical Langevin function weight-averaged with a modified log-normal size distribution function. Next, the ac power dissipation model for monodispersed nanoparticles was extended to the polydispersed case, and the volumetric heating rate was predicted as a function of the frequency of the applied field under the assumption of the Neel relaxation mechanism. Finally, the temperature increase caused by the application of an ac magnetic field was measured experimentally at frequencies of 50, 112, 261, 335, 474 and 523 kHz, with the root-mean-squared field fixed to 250 Oe, and the results were compared with those from theoretical calculation. The frequency dependence of the initial heating rates was found to be in good agreement with the results predicted by using the polydispersed power dissipation model.

Efficiency enhancement of the high-frequency isolated grid-connected converter for the battery energy storage system

High-frequency (HF) isolated grid-connected converters for a battery energy storage system have been extensively researched in recent years. However, due to the HF isolated energy conversion link, the operation efficiency is relatively lower than that required in mass adoption. The topology of the HF isolated grid-connected converter proposed in this paper features a dual active bridge (DAB) converter containing a multi-winding HF transformer and two multi-arm converters. Through modifying the operation modes of the DAB converter, the commutation inductor in the soft switching process can be adjusted according to the load conditions. Thus, the operation efficiency of the grid-connected converter is improved under heavy load and at light load. Meanwhile, the modifying points of the operation modes are selected based on the power dissipation models. Additionally, the control system for the proposed DAB converter is designed based on the small signal model, and the parameters of the regulator are also calculated. Finally, the theoretical analyses are validated by the experimental results on a prototype circuit.

Measurement and nonlinear behavioral modeling of the dynamic bias current in an LTE‐A Chireix PA

AbstractThe measurement and modeling of the dynamic power dissipation of a dual‐input Chireix power amplifier driven by LTE modulated signals is reported to optimize its dynamic efficiency. Two memory cubic spline FIR and NARMA behavioral models are verified to accurately predict the measured instantaneous PA bias‐current and power dissipation as a function of the PA RF output power.

State diagram of a perpendicular magnetic tunnel junction driven by spin transfer torque: A power dissipation approach

The state diagram of a magnetic tunnel junction with perpendicularly magnetized electrodes in the presence of spin-transfer torques is computed in a macrospin approximation using a power dissipation model. Starting from the macrospin's energy we determine the stability of energy extremum in terms of power received and dissipated, allowing the consideration of non-conservative torques associated with spin transfer and damping. The results are shown to be in agreement with those obtained by direct integration of the Landau-Lifshitz-Gilbert-Slonczewski equation. However, the power dissipation model approach is faster and shows the reason certain magnetic states are stable, such as states that are energy maxima but are stabilized by spin transfer torque. Breaking the axial system, such as by a tilted applied field or tilted anisotropy, is shown to dramatically affect the state diagrams. Finally, the influence of a higher order uniaxial anisotropy that can stabilize a canted magnetization state is considered and the results are compared to experimental data.

Simultaneous routing and flow rate optimization in energy–aware computer networks

Abstract The issue of energy-aware traffic engineering has become prominent in telecommunications industry in the last years. This paper presents a two-criteria network optimization problem, in which routing and bandwidth allocation are determined jointly, so as to minimize the amount of energy consumed by a telecommunication infrastructure and to satisfy given demands represented by a traffic matrix. A scalarization of the criteria is proposed and the choice of model parameters is discussed in detail. The model of power dissipation as a function of carried traffic in a typical software router is introduced. Then the problem is expressed in a form suitable for the mixed integer quadratic programming (MIQP) solver. The paper is concluded with a set of small, illustrative computational examples. Computed solutions are implemented in a testbed to validate the accuracy of energy consumption models and the correctness of the proposed traffic engineering algorithm.

Standard Cell-Based Low Power Embedded Controller Design

Microcontrollers represent unavoidable parts of state-of-the-art system-on-chips (SoCs) and they are widely embedded as IP blocks. This paper describes design steps and the application of available low-power techniques, to the design of a microcontroller IP core with 8051 instruction set, based on a prescribed standard cell libraries. Choice of the technology node and the cell library supplier is a design challenge that was considered and conclusions reached. The necessary steps of microcontroller design flow are presented which enable power reduction at several abstraction levels. An optimal microcontroller was designed to be embedded in various SoCs. The goal was to get energy-efficient microcontroller operation in applications which don't require intensive data processing. The impact of technology scaling on microcontroller energy efficiency is considered by comparison of the results obtained from implementations in three standard cell technologies. Moreover, power dissipation models are created which allow for microcontroller's power estimation in low throughput sensors networks applications.

Resource Allocation for Joint Transmitter and Receiver Energy Efficiency Maximization in Downlink OFDMA Systems

This paper investigates the joint transmitter and receiver optimization for the energy efficiency (EE) in orthogonal frequency-division multiple-access (OFDMA) systems. We first establish a holistic power dissipation model for OFDMA systems, including the transmission power, signal processing power, and circuit power from both the transmitter and receiver sides, while existing works only consider the one side power consumption and also fail to capture the impact of subcarriers and users on the system EE. The EE maximization problem is formulated as a combinatorial fractional problem that is NP-hard. To make it tractable, we transform the problem of fractional form into a subtractive-form one by using the Dinkelbach transformation and then propose a joint optimization method, which leads to the asymptotically optimal solution. To reduce the computational complexity, we decompose the joint optimization into two consecutive steps, where the key idea lies in exploring the inherent fractional structure of the introduced individual EE and the system EE. In addition, we provide a sufficient condition under which our proposed two-step method is optimal. Numerical results demonstrate the effectiveness of proposed methods, and the effect of imperfect channel state information is also characterized.

Power Loss Modeling of Individual IGBT and Advanced Voltage Balancing Scheme for MMC in VSC-HVDC System

This paper presents the new power dissipation model of individual switching device in a high-level modular multilevel converter (MMC), which can be mostly used in voltage sourced converter (VSC) based high-voltage direct current (HVDC) system and flexible AC transmission system (FACTS). Also, the voltage balancing method based on sorting algorithm is newly proposed to advance the MMC functionalities by effectively adjusting switching variations of the sub-module (SM). The proposed power dissipation model does not fully calculate the average power dissipation for numerous switching devices in an arm module. Instead, it estimates the power dissipation of every switching element based on the inherent operational principle of SM in MMC. In other words, the power dissipation is computed in every single switching event by using the polynomial curve fitting model with minimum computational efforts and high accuracy, which are required to manage the large number of SMs. After estimating the value of power dissipation, the thermal condition of every switching element is considered in the case of external disturbance. Then, the arm modeling for high- level MMC and its control scheme is implemented with the electromagnetic transient simulation program. Finally, the case study for applying to the MMC based HVDC system is carried out to select the appropriate insulated-gate bipolar transistor (IGBT) module in a steady-state, as well as to estimate the proper thermal condition of every switching element in a transient state.

A novel interconnect optimal buffer insertion model considering the self-heating effect

Considering the self-heating effect, an accurate expression for the global interconnection resistance per unit length in terms of interconnection wire width and spacing is presented. Based on the proposed resistance model and according to the trade-off theory, a novel optimization analytical model of delay, power dissipation and bandwidth is derived. The proposed optimal model is verified and compared based on 90 nm, 65 nm and 40 nm CMOS technologies. It can be found that more optimum results can be easily obtained by the proposed model. This optimization model is more accurate and realistic than the conventional optimization models, and can be integrated into the global interconnection design of nano-scale integrated circuits.

Viscous Dynamics of Lyme Disease and Syphilis Spirochetes Reveal Flagellar Torque and Drag

The spirochetes that cause Lyme disease (Borrelia burgdorferi) and syphilis (Treponema pallidum) swim through viscous fluids, such as blood and interstitial fluid, by undulating their bodies as traveling, planar waves. These undulations are driven by rotation of the flagella within the periplasmic space, the narrow (∼20–40 nm in width) compartment between the inner and outer membranes. We show here that the swimming speeds of B. burgdorferi and T. pallidum decrease with increases in viscosity of the external aqueous milieu, even though the flagella are entirely intracellular. We then use mathematical modeling to show that the measured changes in speed are consistent with the exertion of constant torque by the spirochetal flagellar motors. Comparison of simulations, experiments, and a simple model for power dissipation allows us to estimate the torque and resistive drag that act on the flagella of these major spirochetal pathogens.

Multi-channel spectrum sensing in cognitive ad-hoc networks: An energy-efficient manner

Cognitive radio, which is capable of enabling dynamic spectrum access, is a promising technology in future wireless communication. The feasibility of cognitive radio network greatly depends on the energy efficiency and reliability of spectrum sensing technology. In this paper, spectrum sensing in cognitive ad-hoc network (CAN) with wide-band dynamic spectrum is considered. A cognitive cluster head (CCH) is set and responsible for dividing the wide-band spectrum into multiple sub-channels; it can either sense sub-channels in a centralized manner, or make use of sensing modules to sense sub-channels in a distributed manner. Then cognitive users (CUs) can get sensing results and access to the available sub-channel. We take the cost of control message into consideration and formulate the energy consumption of CAN in terms of sub-channel sampling rate and whole-band sensing time. We define energy efficiency intuitively and solve the energy efficiency optimization problem with sensing reliability constraints by constructing a parametric problem and obtain the optimal sampling rate and the whole-band sensing time. Power dissipation model of a practical A/D convertor (ADC) is introduced, and numerical results are given to show the energy efficiency performance of two different sensing manners.

Thermal mapping of a scanning thermal microscopy tip

Scanning thermal microscopy (SThM) is a very promising technique for local investigation of temperature and thermal properties of nanostructures with great application potential in contemporary nanoelectronics and nanotechnology. In order to increase the localization of SThM measurements, the size of probes has recently substantially decreased, which results in novel types of SThM probes manufactured with the use of modern silicon microfabrication technology. Quantitative SThM measurements with these probes need methods, which enable to assess the quality of thermal contact between the probe and the investigated surface. In this paper we propose a tip thermal mapping (TThM) procedure, which is used to estimate experimentally the distribution of power dissipated by the tip of an SThM probe. We also show that the proposed power dissipation model explains the results of active-mode SThM measurements and that the TThM procedure is reversible for a given probe and sample.

Power loss analysis of active clamp forward converter in continuous conduction mode and discontinuous conduction mode operating modes

In order to improve the light-load efficiency of active clamp forward converter with synchronous rectifier (SR), power loss analysis of the converter operating in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are presented in this study. The light-load efficiency of normal ACF converter with SR is low because the output inductor current can go negative when operating in CCM. Considering the fixed frequency control only, to shift the converter's operating mode from CCM to DCM at a critical point of output current at light-load is a solution for efficiency improvement. Based on the CCM and DCM power dissipation models proposed in this study, the power loss characteristics of the converter are analysed, and the critical shift point of output current can be derived, which has also been verified by an experimental prototype.

The effect of dust on electron heating and dc self-bias in hydrogen diluted silane discharges

In capacitive hydrogen diluted silane discharges the formation of dust affects plasma processes used, e.g. for thin film solar cell manufacturing. Thus, a basic understanding of the interaction between plasma and dust is required to optimize such processes. We investigate a highly diluted silane discharge experimentally using phase-resolved optical emission spectroscopy to study the electron dynamics, laser light scattering on the dust particles to relate the electron dynamics with the spatial distribution of dust, and current and voltage measurements to characterize the electrical symmetry of the discharge via the dc self-bias. The measurements are performed in single and dual frequency discharges. A mode transition from the α-mode to a bulk drift mode (Ω-mode) is found, if the amount of silane and, thereby, the amount of dust and negative ions is increased. By controlling the electrode temperatures, the dust can be distributed asymmetrically between the electrodes via the thermophoretic force. This affects both the electron heating and the discharge symmetry, i.e. a dc self-bias develops in a single frequency discharge. Using the Electrical Asymmetry Effect (EAE), the dc self-bias can be controlled in dual frequency discharges via the phase angle between the two applied frequencies. The Ω-mode is observed for all phase angles and is explained by a simple model of the electron power dissipation. The model shows that the mode transition is characterized by a phase shift between the applied voltage and the electron conduction current, and that the plasma density profile can be estimated using the measured phase shift. The control interval of the dc self-bias obtained using the EAE will be shifted, if an asymmetric dust distribution is present. However, the width of the interval remains unchanged, because the dust distribution is hardly affected by the phase angle.