Power Reduction Factor Research Articles

Recovery of core annular flow structure in a horizontal T-pipe using CFD approach

Previous work about CAF through a T-pipe reported that CAF stability could not be maintained after passing the intersection. The current CFD study was expected to propose a strategy to recover the stability of CAF in a horizontal T-pipe without interrupting the flow process. A recirculation zone was detected in the area near the junction. Additional water with a certain design of insertion and water velocity is introduced at the intersection to support the recovery of CAF by suppressing fouling. This numerical work covered both qualitative evaluation of CAF consistency along the T-pipe and quantitative evaluation to analyze the attainable energy savings of the proposed strategy. From some candidates for water insertion geometries and velocities of additional water, the ducting insertion with a water velocity of 2 m/s showed a consistent CAF structure starting at about 200 mm from the intersection point to the final downstream exits. This proposed design was estimated to reduce pressure drop more than 98% compared to transportation without lubrication and 4% higher than design without additional water injection. The power reduction factor was computed at a value greater than 1 (30.3), indicating that the proposed system was energetically more advantageous than the single-phase oil system.

Computational fluid dynamics approach for energy savings evaluation in core annular flow of a horizontal T-pipe

The application of core annular flow (CAF) has become an interesting solution in transporting heavy oil through pipeline because of its energy reduction and cost efficiency. At the same time, the CAF in pipe with hydraulic fittings and the problem of unstable CAF are the part of some big issues in using CAF techniques. This study intended to investigate the energy saving of CAF in horizontal T-pipe with symmetrical flow and diameter of 50 mm for oil and water system using CFD approach. Pressure reduction and power consumption were computed as the parameters to measure the energy saving of the flow system. The result of this study showed significant energy reduction of CAF with 94% of pressure drop reduction, for transporting the same amount of oil, when comparing to the traditional single phase oil flow. On the other hand, the intersection of the T-pipe was considered as critical region that promoting the change of flow direction and disturbing the existing CAF pattern. Thus, this study also proposed the strategy for returning the CAF during the process of oil transportation without stopping or restarting the flow operation. The geometry of the T-pipe was modified to facilitate the additional water injection at the intersection as a strategy to get back the CAF pattern. Consequently, the modified T-pipe with certain velocity of additional water injection was recorded to give important improvement of CAF application in terms of more stable CAF and higher pressure drop reduction (98%) compared to oil transportation without lubrication. This study also recorded the values of power reduction factor that indicating the cost of power consumption to transport the oil could be saved more than 80% than single phase oil transportation.

Analysis of a Novel Proposal Using Temperature and Efficiency to Prevent Fires in Photovoltaic Energy Systems

Fires in photovoltaic (PV) electrical systems are a real and serious problem because this phenomenon can have severe consequences for the safety of people and the environment. In some cases, fires result from a lack of maintenance or improper installation of PV modules. It is essential to consider prevention and continuous monitoring of the electrical parameters to minimize these risks, as these factors increase the temperature of the photovoltaic modules. The use of thermal analysis techniques can prevent hotspots and fires in photovoltaic systems; these techniques allow detecting and correcting problems in the installation, such as shadows, dirt, and poor-quality connections in PVs. This paper presents a case study of the implementation of thermal analysis in an installation of photovoltaic modules connected to a solar pumping system to identify the formation of hotspots through thermal images using an unmanned aerial vehicle (UAV). Here, a novel methodology is proposed based on the comparison of temperature increases concerning the values of short circuit current, open circuit voltage, and real efficiency of each PV module. In addition, an electrical safety methodology is proposed to design a photovoltaic system that prevents fires caused by hotspots, contemplating critical parameters such as photovoltaic power, number of photovoltaic modules, DC:AC conversion ratio, electrical conductor selection, control devices, and electrical protection; the performance power expected was obtained using standard power test conditions, including irradiance factor, photovoltaic module (PVM) temperature factor, and power reduction factor.

Methodology for Electromagnetic Field Exposure Assessment of 5G Massive MIMO Antennas Accounting for Spatial Variability of Radiated Power

The technology of massive Multiple Input Multiple Output (maMIMO) antennas introduces new challenges in the Radio Frequency Electromagnetic Fields (RF EMF) exposure assessment of 5G base stations due to the aleatory changes of the radiation direction. The beamforming capabilities of the antenna modify the radiation pattern both in space and in time domain in order to adapt the electromagnetic footprint to the changes of user positions, mobility, and service requests. Recently, Base Station (BS) power monitoring counters per Angular Regions (AR) were introduced in maMIMO antenna technology for monitoring the power associated to specific angular directions. By analyzing the time averaged power reported by ARs power monitoring counters the paper proposes, making use of simulations, a methodology to quantify a statistical spatial power reduction factor (0.05 to 0.5, on the base of the assumptions adopted in this paper) to be applied in the RF EMF exposure assessment process accounting for the variability of the maMIMO antenna radiation pattern. The proposed approach enhances and completes the methodology already described in normative documents for characterizing time variations of the total radiated power. The paper is completed with a sensitivity analysis for the size of each AR with respect to the antenna beam size; the analysis shows that a good spatial resolution is achieved when the AR Region has almost the same size as the beam’s half power beam width.

The influence of thermal interaction on energy harvesting efficiency of geothermal piles in a group

This paper employs coupled multiphysics modelling of pile-soil heat exchange to quantify pile thermal interaction and its influence in diminishing the power output expected from a group of geothermal piles. Three-dimensional finite element models, which account for the flow of heat carrier fluid through the circulation tubes and conductive heat transport in pile and soil, are developed for different group arrangements of geothermal piles. Finite element analyses (FEAs) of a pair of geothermal piles reveal the effects of spacing, diameter, orientation of embedded fluid circulation tubes, and thermal operation time of geothermal piles on thermal interaction between the piles. A simple analysis-based expression is proposed to calculate power reduction factor that quantifies thermal interaction between two simultaneously acting geothermal piles. The proposed factor is further employed, in conjunction with the principle of superposition, to estimate power output from a group of geothermal piles. Comparison of predictions using the proposed method with FEA results suggests that the proposed method can successfully predict total energy harvesting efficiency (i.e., power output) of a thermally interacting group of geothermal piles.

Low-Power Drone-Mountable Real-Time Artificial Intelligence Framework for Road Asset Classification

With the continuous increase in interstate highway traffic and demand for higher safety standards, there is a growing need for rapidly scalable road inspection. Currently, inspection and condition assessment of roadways involve manual operations which increase labor costs and limit the scalability and inspection coverage. Furthermore, manually inspecting highways adds additional safety risks for highway workers and road inspectors. To address these challenges, we envision a fully automated process of highway inspection. This paper presents a novel low-power drone-mountable real-time artificial intelligence (AI) framework for road asset classification through visual sensing, which is the first step toward a fully automated inspection system. We analyzed a state DOT dataset, consisting of 14 different kinds of defected road assets. To this end, we developed our baseline framework using MobileNet-V2, which is a convolutional neural network (CNN) specially developed for mobile and embedded platforms. Since our target dataset was small and CNNs networks require a huge amount of data, we leveraged transfer learning, by pretraining MobileNet-V2 using the ImageNet dataset and then fine-tuned it on our target dataset. This new framework was ported to embedded platforms Nvidia Jetson Nano with the capability to perform on-board drone processing. Overall, our results demonstrate 81.33% accuracy on the test set while processing 7.4 frames per second and occupying a total power of 1.9 W. It achieved a Power Reduction Factor (PRF) of 21.17 over Nvidia TitanV implementation, with only 8.74% impact on the projected drone flight time.

High Spatial Density 6-Mode 7-Core Fiber Amplifier for L-Band Operation

We present a high spatial density space division multiplexed fiber amplifier (i.e., 6-mode 7-core multicore fiber amplifier) supporting 42 spatial channels. A high average modal gain of 23.1 dB is obtained in the L-band with an average differential modal gain of 3.2 dB and a minimum output power of 17.5 dBm per core per mode. The total power consumption of the amplifier is improved by a power reduction factor of 0.36 and a fully fiberized optical amplifier is realized in a cladding-pumped configuration. The assembled amplifier is then tested in a few-mode multicore fiber transmission link and simultaneously amplified 42 spatial channel fiber transmission is demonstrated with the highest spatial density and energy efficiency to date.

Power Reduction Estimation of 5G Active Antenna Systems for Human Exposure Assessment in Realistic Scenarios

Maximum power extrapolation techniques from measured data are usually employed to assess the compliance with standards of average fields radiated by base stations. However, such techniques provide an upper bound, which is not reached in real scenarios. This is particularly true in 5G Communications, where Active Antenna Systems allow a decrease of the average power density according to the adopted scheduling strategy. This paper is focused on the power reduction estimation in realistic scenarios. In particular a deterministic model of a communication system is used to obtain simple formulas only requiring the knowledge of the served area angular extension and of the Envelope Radiation Pattern of the antenna. The model, developed for beam steering and grid of beams antennas, is also extended to analyze the case of Multi User massive Multiple Input Multiple Output (MU-mMIMO) antennas with single layer per user, showing that under proper hypothesis on the beams of the antenna it is possible to estimate the reduction parameter without the explicit knowledge of the number of layers of MU-mMIMO systems. In spite of the simplicity of the approach, comparison with stochastic models and results reported in recent literature show that the formulas obtained using the model proposed in this paper allow to obtain a useful approximation of the power reduction factor, making the formulas suitable for a preliminary fast estimation of the Electromagnetic Field in 5G cells for human exposure assessment.

Joint Optimization of Interference Coordination Parameters and Base-Station Density for Energy-Efficient Heterogeneous Networks.

Heterogeneous networks (HetNets), consisting of macro-cells and overlaying pico-cells, have been recognized as a promising paradigm to support the exponential growth of data traffic demands and high network energy efficiency (EE). However, for two-tier heterogeneous architecture deployment of HetNets, the inter-tier interference will be challenging. Time domain further-enhanced inter-cell interference coordination (FeICIC) proposed in 3GPP Release-11 becomes necessary to mitigate the inter-tier interference by applying low power almost blank subframe (ABS) scheme. Therefore, for HetNets deployment in reality, the pico-cell range expansion (CRE) bias, the power of ABS and the density of pico base stations (PBSs) are three important factors for the network EE improvement. Aiming to improve the network EE, the above three factors are jointly considered in this paper. In particular, we first derive the closed-form expression of the network EE as a function of pico CRE bias, power reduction factor of low power ABS and PBS density based on stochastic geometry model. Then, the approximate relationship between pico CRE bias and power reduction factor is deduced, followed by a linear search algorithm to get the near-optimal pico CRE bias and power reduction factor together at a given PBS density. Next, a linear search algorithm is further proposed to optimize PBS density based on fixed pico CRE bias and power reduction factor. Due to the fact that the above pico CRE bias and power reduction factor optimization and PBS density optimization are optimized separately, a heuristic algorithm is further proposed to optimize pico CRE bias, power reduction factor and PBS density jointly to achieve global network EE maximization. Numerical simulation results show that our proposed heuristic algorithm can significantly enhance the network EE while incurring low computational complexity.

Joint Spectral Efficiency and Energy Efficiency in FFR-Based Wireless Heterogeneous Networks

Heterogeneous cellular network is considered as an important network architecture to improve spectral efficiency and energy efficiency. Extensive research has revealed that spectral efficiency and energy efficiency could be two conflicting performance metrics under most scenarios. Toward the next generation 5G wireless systems, both spectral efficiency and energy efficiency become increasingly important. How to design a wireless system that jointly considers/optimizes these two performance metrics is critical yet challenging. This paper jointly analyzes the area spectral efficiency and area energy efficiency in a wireless heterogeneous network with inter-tier fractional frequency reuse. Proportional fairness resource allocation is used to balance the spectral efficiency and user fairness within each cell. A theoretical framework is formulated to analyze the area spectral efficiency and area energy efficiency in such a system. Fractional frequency reuse and proportional fairness resource allocation define the optimal power reduction factor and fractional bandwidth partition to maximize the joint area spectral efficiency and area energy efficiency. The system performance is evaluated by using the proposed scheme with different system parameter settings including base station densities, cell fractional bandwidth partition, power threshold, and base station power consumptions. The study shows that fractional frequency reuse with proper settings can significantly increase the area spectral efficiency and area energy efficiency in wireless heterogeneous networks.

Capacity analysis of LTE-Advanced HetNets with reduced power subframes and range expansion

Abstract The use of reduced power subframes in LTE Rel. 11 can improve the capacity of heterogeneous networks (HetNets) while also providing interference coordination to the picocell-edge users. However, in order to obtain maximum benefits from the reduced power subframes, setting the key system parameters, such as the amount of power reduction, carries critical importance. Using stochastic geometry, this paper lays down a theoretical foundation for the performance evaluation of HetNets with reduced power subframes and range expansion bias. The analytic expressions for average capacity and 5th percentile throughput are derived as a function of transmit powers, node densities, and interference coordination parameters in a two-tier HetNet scenario and are validated through Monte Carlo simulations. Joint optimization of range expansion bias, power reduction factor, scheduling thresholds, and duty cycle of reduced power subframes is performed to study the trade-offs between aggregate capacity of a cell and fairness among the users. To validate our analysis, we also compare the stochastic geometry-based theoretical results with the real macro base station (MBS) deployment (in the city of London) and the hexagonal grid model. Our analysis shows that with optimum parameter settings, the LTE Rel. 11 with reduced power subframes can provide substantially better performance than the LTE Rel. 10 with almost blank subframes, in terms of both aggregate capacity and fairness.

Analysis and modeling of effective temperature differences and electrical parameters of thermoelectric generators

We have derived an analytic model describing the interior temperature difference as a function of the load current of a thermoelectric generator (TEG); we have also proposed a method to extract the intrinsic and extrinsic Seebeck coefficients and resistances of TEG using experimental current–voltage curves. The decrement of internal temperature difference is almost linearly depending on load current of the TEG. From the experimental results, using a thermoelectric (TE) module with a thermal conductance of 3.52W/K and a parasitic thermal conductance of 50W/K, the effective internal electrical resistance was increased by approximately 5%, but the effective Seebeck coefficient was attenuated by approximately 13%, as compared to the intrinsic parameters. The relationship between the output power reduction factor and limited thermal conductance of TEG packaging was also derived. Approximately 25% of the maximum output power is lost because of the parasitic thermal resistance of the TE module used in the experiment.

Joint Power Minimization in Wireless Relay Channels

Energy-constrained multihop wireless links are considered, where the total power consumption is minimized under given requirements on the end-to-end bit error rate (BER). As multihop transmissions are known to be able to save transmission energy in a wireless environment, we study the optimal power scheduling schemes over intermediate hops when the source- relays-destination link can be modeled as cascaded binary symmetric channels. The problem is formulated with an end- to-end BER constraint, and the resulting power consumption is compared with that of the individual link requirement strategy where each hop assigns power under a per-link BER constraint. Results show that the proposed joint power scheduling strategy can achieve a maximum power reduction factor of M in an M-hop route.

On a trie partitioning algorithm for power‐efficient TCAMs

AbstractInternet routers conduct routing table (RT) lookup based on the destination IP address of the incoming packet to decide which output port to forward the packet. Ternary content‐addressible memories (TCAM) uses parallelism to achieve lookup in a single cycle. One of the major drawbacks of TCAM is its high‐power consumption. Trie‐based architecture has been proposed to reduce TCAM power consumption. The idea is to use an index TCAM to select one of many data TCAM blocks for lookup. However, power reduction is limited by the size of the index TCAM, which is always enabled for search. In this paper we develop a simple but effective trie‐partitioning algorithm to reduce the index TCAM size, which achieves better reduction in power consumption, and at the same time guarantees full TCAM space utilization. We compared our algorithm (LogSplit) with PostOrderSplit (IEEE INFOCOM, 2003). For two real‐world RTs (AADS and PAIX), the size of the index TCAM generated by LogSplit is 55–70% of that generated by PostOrderSplit; the largest power reduction factor of LogSplit is 41 for AADS and 68 for PAIX, while the largest power reduction factor of PostOrderSplit is 33 for AADS and 52 for PAIX. The improvement is even more significant in the worst case: the size of the index TCAM generated by LogSplit is 18–30% of that generated by PostOrderSplit for IPv4, and less than 1% of that generated by PostOrderSplit for IPv6; the largest power reduction factor of LogSplit is 173 for both IPv4 and IPv6, while the largest power reduction factor of PostOrderSplit is only 82 for IPv4 and 41 for IPv6. Copyright © 2007 John Wiley & Sons, Ltd.

Calibration of a stopping power model for silicon based on analysis of neutron depth profiling and secondary ion mass spectrometry measurements

We measure the boron concentration versus depth profile within a silicon sample with four delta-doped planes by secondary ion mass spectrometry. In a neutron depth profiling (NDP) experiment, we illuminate the sample with a neutron beam. Nuclear reactions between the boron nuclei and neutrons produce alpha particles. Based on the measured boron concentration profile and models for the stopping power of the silicon sample, energy straggling, multiple scattering, and the observed energy resolution of the alpha particle detector, we predict the observed energy spectrum of the detected alpha particles. We predict the stopping power of silicon using the stopping and range of ions in matter code SRIM-2000. The predicted locations of the NDP energy peaks are consistently at lower energies than the locations of the observed peaks. This discrepancy is consistent with the claim that SRIM-2000 overestimates the actual stopping power of silicon. Empirically, we estimate a stopping power reduction factor to be 5.06%±1.06%. When we reduce the SRIM-2000 prediction by this factor, we get good agreement between the observed and predicted NDP measurements.

Architectural Synthesis of Computational Engines for Subband Adaptive Filtering

Architectural synthesis of low-power computational engines (hardware accelerators) for a subband-based adaptive filtering algorithm is presented. The full-band least mean square (LMS) adaptive filtering algorithm, widely used in various applications, is confronted by two problems, viz., slow convergence when the input correlation matrix is ill-conditioned, and increased computational complexity for applications involving use of large adaptive filter orders. Both of these problems can be overcome by the use of a subband-based normalized LMS (NLMS) adaptive filtering algorithm. Since this algorithm is not amenable to pipelining, delayed coefficient adaptation in the NLMS updation is used, which provides the required delays for pipelining. However, the convergence speed of this subband-based delayed NLMS (DNLMS) algorithm degrades with increase in the adaptation delay. We first present a pipelined subband DNLMS adaptive filtering architecture with minimal adaptation delay for any given sampling rate. The architecture is synthesized by using a number of function preserving transformations on the signal flow graph (SFG) representation of the subband DNLMS algorithm. With the use of carry-save arithmetic, the pipelined architecture can support high sampling rates limited only by the delay of two full adders and a 2-to-1 multiplexer. We then extend this synthesis methodology to synthesize a pipelined subband DNLMS architecture whose power dissipation meets a specified budget. This low-power architecture exploits the parallelism in the subband DNLMS algorithm to meet the required computational throughput. The architecture exhibits a novel tradeoff between algorithmic performance (convergence speed) and power dissipation. Finally, we incorporate configurability for filter order, sample period, power reduction factor, number of subbands and decimation/interpolation factor in the low-power architecture, thus resulting in a low-power subband computational engine for adaptive filtering.

Power Loss in Propagation Through a Turbulent Medium for an Optical-Heterodyne System with Angle Tracking*

The power loss due to propagation through a turbulent medium is considered for an optical-heterodyne detection system whose axis tracks perfectly the instantaneous direction for maximum signal power. Pertinent to both fixed- and tracking-axis cases, the general expression for power reduction is found to be given correctly by neglecting the angular diffraction spread of the local-oscillator field and using the signal field evaluated on the optical axis. A plane and broad incident wave is assumed. The result for the tracking aperture is indicated to be given correctly by ray optics if L≪a2/λ, where L is the path length in the turbulent medium, a the aperture radius, and λ the signal wavelength, whereas for a fixed aperture the lateral homogeneity of the field is indicated to suffice without this condition. Refractive-index fluctuations are assumed to be described statistically by the usual Kolmogorov spectrum. For moderate aperture (a≲ae), the power reduction factor Γ is found to be given by Γ≃1-s(a/ae)5/3with s = 0.125 for a tracking axis and s = 0.955 for a fixed axis, where a. is ae certain effective radius for the fixed case. If the improvement due to tracking is extrapolated to arbitrary a/ae by conjecture of a fixed factor of increase in the effective radius, the factor of increase in maximum signal-to-noise ratio achievable by tracking is 11.5. To approach the maximum, the frequency response of the tracking system should extend beyond roughly 50 cps.