Energy Conservation Approach Research Articles

A coarse-grained model for the mechanical behavior of multi-layer graphene

Graphene is the strongest and highest weight-to-surface ratio material known, rendering it an excellent building block for nanocomposites. Multi-layer graphene (MLG) assemblies have intriguing mechanical properties distinct from the monolayer that remain poorly understood due to spatiotemporal limitations of experimental observations and atomistic modeling. To address this issue, here we establish a coarse-grained molecular dynamics (CG-MD) model of graphene using a strain energy conservation approach. The model is able to quantitatively reproduce graphene’s mechanical response in the elastic and fracture regimes. The hexagonal symmetry of graphene’s honeycomb lattice is conserved, and therefore the anisotropy in the non-linear large-deformation regime between the zigzag and armchair directions is preserved. The superlubricity effect, namely the strong orientational dependence of the shear rigidity between graphene layers, is also captured. We demonstrate the applicability of the model by reproducing recent experimental nanoindentation results in silico. Our model overcomes the limitations of current CG-MD approaches, in accurately predicting the fracture properties, the interlayer shear response, and the intrinsic anisotropy of MLG. Additionally, our fast, transferable force-field can be straightforwardly combined with existing coarse-grained models of polymers and proteins to predict the meso-scale behavior of hybrid carbon nanomaterials.

Enhancement of Energy Conservation Technologies in Wireless Sensor Network

In the last few years, wireless sensor networks (WSNs) have been widely used for many applications in both profitable and non-profitable organizations. As sensor nodes used in most of the applications are generally battery-powered devices, the challenges focus on how to increase the lifetime of each sensor node and how to reduce the energy consumption of each node, so that the network energy efficiency (EE) can be maintained to deliver the data for a reasonable time. In this paper, we analyze to enhance the energy conservation approach which reduces the energy consumption, cost and complexity. In this research, combination of routing and solar power is analyzed as enhancement of energy conservation technology (EECT) which increases the lifetime of the sensor node as well as the battery. Even though, solar power concept is not new for the WSN, EECT can be used for where some selected applications such as monitoring air condition in large organizations are directly involved with the sun light and heat.

THE MECHANISM WHY COLLIDERS COULD CREATE QUASI-STABLE BLACK HOLES

It has been postulated that black holes (BHs) could be created in particle collisions within the range of the available energies for nowadays colliders (LHC). In this paper, we analyze the evaporation of a type of BHs that are candidates for this specific behavior, namely, small BHs on a brane in a world with large extra-dimensions. We examine their evolution under the assumption that energy conservation is satisfied during the process and compare it with the standard evaporation approach. We claim that, rather than undergoing a quick total evaporation, BHs become quasi-stable. We comment on the (absence of) implications for safety of this result. We also discuss how the presence of BHs together with the correctness of the energy conservation approach might be experimentally verified.

Gravity field recovery from GOCE orbits using the energy conservation approach

Abstract: The sum of the dissipative energy and energy constant of the GOCE satellite is found by a priori gravity field model at first, and the GOCE dissipative energy is obtained by computing the adjacent epoch difference via the differential method. Then, a gravity field model GOCE-ECP01, which up to the degree and order 80, is recovered by the energy conservation approach from the 103-day precise orbital data of the GOCE satellite collected from November 1, 2009 to January 12, 2010. Finally, the model is compared with existing models EGM96, ITG-CHAMP05S, EIGEN-GRACE2010S, EIGEN-6C and GO_CONS_GCF_2_DIR_R3. The results show that at the same order and degree, the accuracy of model GOCE-EBP01 is higher than those of models EGM96 and ITG-CHAMP05S, but lower than those of models EIGEN-GRACE2010S, EIGEN-6C and GO_CONS_GCF_2_DIR_R3, which is mainly caused by the pole gap.

Experimental and theoretical studies of the spreading of bloodstains on painted surfaces

The spreading of bloodstains on matt, vinyl silk and gloss painted surfaces, following both perpendicular and non-perpendicular impact, has been studied with a view to understanding whether surface-specific properties affect the size and shape of the final stain. In all cases the dimensions of the stains on the rougher, matt paint are up to 5% less than on the other painted surfaces though this difference decreases with impact velocity. Both the diameter of circular stains and the width of elliptical stains have been successfully modelled as a function of the perpendicular component of impact velocity vn using a modification of the energy conservation approach through the inclusion of a single, empirical constant characteristic of the surface itself. By further development of this theory, the characteristic dynamical length parameter which governs the spreading has been modified to be dependent on angle thus enabling the length of elliptical stains to be predicted independently for the first time. For all these surfaces, experiment shows that the impact angles, calculated using the conventional trigonometric formula, are in deficit by around 1° at high vn increasing to around 5° at lower vn. By modelling this deficit independently using the theoretical expressions for stain width and length, this variation with vn has been successfully explained. This work has demonstrated some of the fundamental systematic sources of error in using the conventional formula for interpreting elliptical stains and established some of the basic theory on which to develop the interpretation of casework stains on surfaces, in the future.

A Survey on Distributed Topology Control Techniques for Extending the Lifetime of Battery Powered Wireless Sensor Networks

Large-scale, self-organizing wireless sensor and mesh network deployments are being driven by recent technological developments such as The Internet of Things (IoT), Smart Grids and Smart Environment applications. Efficient use of the limited energy resources of wireless sensor network (WSN) nodes is critically important to support these advances, and application of topology control methods will have a profound impact on energy efficiency and hence battery lifetime. In this survey, we focus on the energy efficiency issue and present a comprehensive study of topology control techniques for extending the lifetime of battery powered WSNs. First, we review the significant topology control algorithms to provide insights into how energy efficiency is achieved by design. Further, these algorithms are classified according to the energy conservation approach they adopt, and evaluated by the trade-offs they offer to aid designers in selecting a technique that best suits their applications. Since the concept of "network lifetime" is widely used for assessing the algorithms' performance, we highlight various definitions of the term and discuss their merits and drawbacks. Recently, there has been growing interest in algorithms for non-planar topologies such as deployments in underwater environments or multi-level buildings. For this reason, we also include a detailed discussion of topology control algorithms that work efficiently in three dimensions. Based on the outcomes of our review, we identify a number of open research issues for achieving energy efficiency through topology control.

Dissipation of ultrasonic wave propagation in bubbly liquids considering the effect of compressibility to the first order of acoustical Mach number

In this paper, the energy conservation approach presented by Louisnard (2010) [1] for bubbly liquid is modified by applying the Keller–Miksis Equation (KME) on the radial dynamics of cavitation bubbles. As the sound wave is damped through the liquid due to thermal, viscous and radiation effects, it cannot propagate over long distances. With the use of the Rayleigh–Plesset Equation (RPE) in the energy conservation approach, the part of the damping due to the acoustic radiation is neglected. However, it should be taken into account as noticed in the aforementioned reference. Here, it is shown that this damping is of importance especially above the Blake threshold. Furthermore, the thermal damping is calculated by a new formulation. The method is based on the effect of temperature gradient at the thermal boundary layer around the bubble surface on the gas pressure inside the bubble. Results show that the power dissipated by acoustic radiation has the same order of magnitude as the thermal one and cannot be neglected. Moreover, it is revealed that the rate of change of different energies which contribute in bubble oscillation, can result in damping of the wave as secondary effects. It is observed that the thermal damping has stronger effect on the pressure wave than the viscous one. Considering the compressibility of the liquid to the first order of the acoustical Mach number causes an increase in the thermal damping by a factor of about two to three for acoustic pressure amplitudes higher than the Blake threshold. Besides that, considering the compressibility has negligible effects on viscous damping.

The PowerNap Server Architecture

Data center power consumption is growing to unprecedented levels: the EPA estimates U.S. data centers will consume 100 billion kilowatt hours annually by 2011. Much of this energy is wasted in idle systems: in typical deployments, server utilization is below 30%, but idle servers still consume 60% of their peak power draw. Typical idle periods---though frequent---last seconds or less, confounding simple energy-conservation approaches. In this article, we propose PowerNap, an energy-conservation approach where the entire system transitions rapidly between a high-performance active state and a near-zero-power idle state in response to instantaneous load. Rather than requiring fine-grained power-performance states and complex load-proportional operation from individual system components, PowerNap instead calls for minimizing idle power and transition time, which are simpler optimization goals. Based on the PowerNap concept, we develop requirements and outline mechanisms to eliminate idle power waste in enterprise blade servers. Because PowerNap operates in low-efficiency regions of current blade center power supplies, we introduce the Redundant Array for Inexpensive Load Sharing (RAILS), a power provisioning approach that provides high conversion efficiency across the entire range of PowerNap’s power demands. Using utilization traces collected from enterprise-scale commercial deployments, we demonstrate that, together, PowerNap and RAILS reduce average server power consumption by 74%.

Analysis of incremental RLS adaptive networks with noisy links

In this paper, we study the effect of noisy links on the steady-state performance of incremental recursive least-squares (RLS) adaptive networks. In our analysis, using weighted spatial-temporal energy conservation approach, we arrive a variance relation which contains moments that represent the effects of noisy links. We evaluate these moments and derive closed-form expressions for the mean-square deviation (MSD) and excess mean-square error (EMSE) to explain the steady-state performance at each individual node. The derived expressions have good match with simulations.

Comment on "An Upper Bound on Rg to Lg Scattering Using Modal Energy Conservation" by Jeffry L. Stevens, Heming Xu, and G. Eli Baker

A recent short note by Stevens et al. (2009a) presents upper bound estimates of Rg -to- Lg scattering amplitudes using an energy conservation approach for plane-layered Earth models. Their results are based on calculations for two velocity models, one for low-velocity structures at the Nevada Test Site (NTS) and the other for high-velocity structures at the Semipalatinsk Test Site (STS). Stevens et al. (2009a) conclude that for low-velocity structures Rg -to- Lg scattering is a viable mechanism only for Rg waves excited by the spherical source below 0.3 Hz; direct Lg from the spherical source will dominate above 0.3 Hz; and scattering of Rg excited by the compensated linear vector dipole (CLVD) source never dominates Lg . For high-velocity structures, direct Lg from the CLVD will dominate above 1 to 3 Hz, while at lower frequencies, Rg -to- Lg scattering amplitudes from the explosion exceed amplitudes of direct Lg and dominate over scattered Rg amplitudes from the CLVD source. In this comment, we point out deficiencies in scattering estimates based on plane-layered velocity models, and we illustrate the existence of bias in the results of Stevens et al. (2009a) because their single-source spectra calculations do not account for wave-field interactions between sources and their velocity models are not representative of test site structures in the upper 2 km where Rg excitation and propagation take place. We show that, contrary to the conclusions of Stevens et al. (2009a), upper bound estimates of Rg scattering exceed amplitudes of direct Lg above 0.5 Hz for NTS velocity models with low-velocity surface layers. Also in contradiction to Stevens et al. (2009a), we find that, compared to Rg excitation by a spherical explosion source, CLVD excitation for shallow depths in low-velocity surface layers can be rich in high frequencies and an important factor in upper bound estimates of Rg -to- Lg scattering. Stevens …

Low-complexity adaptive step size constrained constant modulus SG algorithms for adaptive beamforming

In this paper, we propose two low-complexity adaptive step size mechanisms to enhance the performance of stochastic gradient (SG) algorithms for adaptive beamforming. The beamformer is designed according to the constrained constant modulus (CCM) criterion and the proposed mechanisms are employed in the SG algorithm for implementation. A complexity comparison is provided to show their advantages over existing methods, and a sufficient condition for the convergence of the mean weight vector is established. Theoretical expressions of the excess mean-squared error (EMSE), in both the steady-state and tracking cases, are derived based on the energy conservation approach. The effects of multiple access interference (MAI) and additive noise are considered. Simulation experiments are presented for both the stationary and non-stationary scenarios, illustrating that the proposed algorithms achieve superior performance compared with existing methods, and verifying the accuracy of the analyses.

PowerNap

Data center power consumption is growing to unprecedented levels: the EPA estimates U.S. data centers will consume 100 billion kilowatt hours annually by 2011. Much of this energy is wasted in idle systems: in typical deployments, server utilization is below 30%, but idle servers still consume 60% of their peak power draw. Typical idle periods though frequent--last seconds or less, confounding simple energy-conservation approaches. In this paper, we propose PowerNap, an energy-conservation approach where the entire system transitions rapidly between a high-performance active state and a near-zero-power idle state in response to instantaneous load. Rather than requiring fine-grained power-performance states and complex load-proportional operation from each system component, PowerNap instead calls for minimizing idle power and transition time, which are simpler optimization goals. Based on the PowerNap concept, we develop requirements and outline mechanisms to eliminate idle power waste in enterprise blade servers. Because PowerNap operates in low-efficiency regions of current blade center power supplies, we introduce the Redundant Array for Inexpensive Load Sharing (RAILS), a power provisioning approach that provides high conversion efficiency across the entire range of PowerNap's power demands. Using utilization traces collected from enterprise-scale commercial deployments, we demonstrate that, together, PowerNap and RAILS reduce average server power consumption by 74%.

PowerNap

Data center power consumption is growing to unprecedented levels: the EPA estimates U.S. data centers will consume 100 billion kilowatt hours annually by 2011. Much of this energy is wasted in idle systems: in typical deployments, server utilization is below 30%, but idle servers still consume 60% of their peak power draw. Typical idle periods though frequent--last seconds or less, confounding simple energy-conservation approaches. In this paper, we propose PowerNap, an energy-conservation approach where the entire system transitions rapidly between a high-performance active state and a near-zero-power idle state in response to instantaneous load. Rather than requiring fine-grained power-performance states and complex load-proportional operation from each system component, PowerNap instead calls for minimizing idle power and transition time, which are simpler optimization goals. Based on the PowerNap concept, we develop requirements and outline mechanisms to eliminate idle power waste in enterprise blade servers. Because PowerNap operates in low-efficiency regions of current blade center power supplies, we introduce the Redundant Array for Inexpensive Load Sharing (RAILS), a power provisioning approach that provides high conversion efficiency across the entire range of PowerNap's power demands. Using utilization traces collected from enterprise-scale commercial deployments, we demonstrate that, together, PowerNap and RAILS reduce average server power consumption by 74%.

An investigation on kerf characteristics in abrasive waterjet cutting of layered composites

Layered composites are “difficult-to-machine” materials as it is inhomogeneous due to the matrix properties, fibre orientation, and relative volume fraction of matrix. Abrasive waterjet cutting has proven to be a viable technique to machine such materials compared to conventional machining. This paper presents an investigation on the kerf taper angle, an important cutting performance measure, generated by abrasive waterjet (AWJ) technique to machine two types of composites: epoxy pre-impregnated graphite woven fabric and glass epoxy. Comprehensive factorial design of experiments was carried out in varying the traverse speed, abrasive flow rate, standoff distance and water pressure. Using the dimensional technique and adopting the energy conservation approach, the kerf taper angle has been related to the operating parameters in a form of a predictive model. Verification of the model for using it as a practical guideline has been found to agree with the experiments.

A study of delamination on graphite/epoxy composites in abrasive waterjet machining

Delamination is a major component defect when machining composites or layered materials. This study aims to explore the mechanism of delamination in graphite/epoxy composites under abrasive waterjet (AWJ) machining. It is found that crack tips are generated by the shock wave impact of the waterjet at the initial cutting stage, while delamination is a result of water penetration into the crack tips that promotes water-wedging and abrasive embedment. Based on an energy conservation approach, a semi-analytical model is developed to predict the maximum delamination length generated by an AWJ. The model prediction is found in good agreement with the experimental data and can be used as a practical guide for process planning to minimise or eliminate the delamination defects on the components in AWJ machining of graphite/epoxy composites.

An energy conservation approach to adsorbate-induced surface stress and the extraction ofbinding energy using nanomechanics

Surface stress induced by molecular adsorption in three different binding processes has beenstudied experimentally using a microcantilever sensor. A comprehensive free-energyanalysis based on an energy conservation approach is proposed to explain the experimentalobservations. We show that when guest molecules bind to atoms/molecules on amicrocantilever surface, the released binding energy is retained in the host surface, leadingto a metastable state where the excess energy on the surface is manifested as an increase insurface stress leading to the bending of the microcantilever. The released bindingenergy appears to be almost exclusively channeled to the surface energy, andenergy distribution to other channels, including heat, appears to be inactive forthis micromechanical system. When this excess surface energy is released, themicrocantilever relaxes back to the original state, and the relaxation time dependson the particular binding process involved. Such vapor phase experiments wereconducted for three binding processes: physisorption, hydrogen bonding, andchemisorption. Binding energies for these three processes were also estimated.

Limiting the power consumption of main memory

The peak power consumption of hardware components affects their powersupply, packaging, and cooling requirements. When the peak power consumption is high, the hardware components or the systems that use them can become expensive and bulky. Given that components and systems rarely (if ever) actually require peak power, it is highly desirable to limit power consumption to a less-than-peak power budget, based on which power supply, packaging, and cooling infrastructure scan be more intelligently provisioned. In this paper, we study dynamic approaches for limiting the powerconsumption of main memories. Specifically, we propose four techniques that limit consumption by adjusting the power states of thememory devices, as a function of the load on the memory subsystem. Our simulations of applications from three benchmarks demonstrate that our techniques can consistently limit power to a pre-established budget. Two of the techniques can limit power with very low performance degradation. Our results also show that, when using these superior techniques, limiting power is at least as effective an energy-conservation approach as state-of-the-art technique sexplicitly designed for performance-aware energy conservation. These latter results represent a departure from current energy management research and practice.

Qualitative and Quantitative Evaluation of Energy Conversation Measures (ECM) Over Baseline as Given by ASHRAE

This paper presents the state of the art of an energy conservation approach which intended to provide techniques for calculating “whole—facility” savings and individual technology savings. With a goal of enhancing the overall energy performance of new commercial buildings, a detailed summary for the Measurement and Verification (M&V) approach is given. A case study is presented in detail. The study is conducted for the Chicago Center of Green Technology Building in Chicago, IL, referred to as CCGT. The main purpose of the study is to insure compliance with the requirements of LEED v1.0 and v2.0 Energy Credit 5: Measurement and Verification. We expect that the M&V study will provide the credit points necessary to achieve the owner's desired level of certification. In this paper only the analysis portion of the verification is presented.

Fixed‐point steady‐state analysis of adaptive filters

AbstractThe steady‐state performance of adaptive filters can vary significantly when they are implemented in finite precision arithmetic, which makes it vital to analyse their performance in a quantized environment. Such analyses can become difficult for adaptive algorithms with non‐linear update equations. This paper develops a feedback and energy‐conservation approach to the steady‐state analysis of quantized adaptive algorithms that bypasses some of the difficulties encountered by traditional approaches. Copyright © 2003 John Wiley & Sons, Ltd.

Small-signal model of PWM converters for discontinuous conduction mode and its application for boost converter

A small-signal circuit model for pulsewidth-modulated DC-DC converters operated in discontinuous conduction mode is presented. The model is composed of controlled current sources, an independent voltage source and resistances. The principle of energy conservation approach is used to take into account parasitic resistances of the transistor and diode and the diode threshold voltage. The proposed model is suitable for small-signal, frequency-domain representation of the converters. This model is used to derive the expressions for a boost converter control-to-output transfer function, input-to-output voltage transfer function, input impedance and the output impedance. Bode plots are also given for these transfer functions. The predicted and experimental results were in excellent agreement.