Energy Flow Paths Research Articles

Contribution of Ballistic Electron Transport to Energy Transfer During Electron-Phonon Nonequilibrium in Thin Metal Films

AbstractWith the ever decreasing characteristic lengths of nanomaterials, nonequilibrium electron-phonon scattering can be affected by additional scattering processes at the interface of two materials. Electron-interface scattering would lead to another path of energy flow for the high-energy electrons other than electron-phonon coupling in a single material. Traditionally, electron-phonon coupling in transport is analyzed with a diffusion (Fourier) based model, such as the two temperature model (TTM). However, in thin films with thicknesses less than the electron mean free path, ballistic electron transport could lead to electron-interface scattering, which is not taken into account in the TTM. The ballistic component of electron transport, leading to electron-interface scattering during ultrashort pulsed laser heating, is studied here by a ballistic-diffusive approximation of the Boltzmann transport equation. The results for electron-phonon equilibration times are compared with calculations with TTM based approximations and experimental data on Au thin films.

Carnivory and resource‐based niche differentiation in anuran larvae: implications for food web and experimental ecology

Summary1. Food webs represent the paths of material and energy flow through organisms in an ecosystem. Anuran larvae are important components of pond food webs: they are abundant, consume large quantities of food and serve as prey for many organisms. However, there are very basic uncertainties about the feeding ecology of anuran larvae; for instance, as to which trophic level they belong and whether species differ in resource use. Because anuran larvae have been employed in model systems in experimental ecology for decades, these uncertainties could lead to misinterpretation of published experiments, or inadequate designs of experiments directed at general, conceptual issues in ecology.2. Using13C and15N stable isotope and gut content analyses of free‐ranging and enclosed tadpoles of four ranid species (Lithobates sylvaticus,L. pipiens,L. clamitans,L. catesbeianus) in the food webs of six wetlands, we tested the following null hypotheses: (i) that anuran larvae are strict primary consumers; (ii) that they are non‐selective feeders and therefore exhibit little feeding niche differentiation; (iii) that they are opportunistic consumers and (iv) that their diet remains unchanged through ontogeny.3. All four species consumed and assimilated substantial amounts of animal food; bullfrog larvae, in particular, appear to be predatory. Significant feeding niche differentiation among species occurred with respect to the sources of carbon, consumption of animal matter and nutritional quality of food ingested. We further documented opportunistic feeding habits and ontogenetic shifts in diet.4. Collectively, these studies revealed complex trophic relationships that might require a reconsideration of the role of anuran larvae in pond food webs, as well as a reinterpretation of results of previous studies employing anuran larvae in model experimental systems.

Production of marine trematode cercariae: a potentially overlooked path of energy flow in benthic systems

Parasites, in particular trematodes, are unseen but ubiquitous components of marine intertidal ecosystems. Although parasites are known to affect population dynamics and food web structure, their potential function as an unrecognized path of energy flow in these ecosystems is yet to be quantified. We use published data on rates at which trematodes produce free-swimming infec- tive larvae (cercariae) that are released from their gastropod intermediate hosts to investigate patterns in cercarial output as a function of different variables, and to calculate the annual produc- tion of cercariae in different marine benthic systems. Across 18 trematode species, cercarial output (no. cercariae shed snail -1 d -1 ) ranged over 4 orders of magnitude and was positively correlated with snail host species size. While cercarial output did not correlate with latitude, it did correlate nega- tively with the size of cercariae, and was influenced by the type of downstream host sought by cer- cariae, being highest when this host was a vertebrate. Our estimates of annual cercarial production (kJ m -2 yr -1 ), which take into account the density of infected snails in the habitat, were within the range of production values reported for free-living invertebrates inhabiting benthic ecosystems. These estimates would be much higher if they included all trematode species in an ecosystem, and not just single-species values. Overall, results suggest that trematode cercariae represent potentially important paths of energy flow in benthic systems as well as a potentially important food supply to benthic organisms.

Magnetic field transport from AGN cores to jets, lobes, and the IGM

AbstractI describe various stages of energy flow along an extragalactic jet, which subsequently evolves into an extended lobe which is visible in radio and X-rays. The sizes of the lobes vary from kpc scales to several megaparsec, so that the largest lobes are clearly injecting back hole energy into the IGM on scales comparable with a galaxy-galaxy separation. This is sometimes loosely referred to as Black hole-IGM “feedback”. My talk begins with a well-formed jet, and avoids the complex and unclarified physics at less than a few Schwarzschild radii that cause the initial launching the jet.This presentation focuses on recent thinking and supercomputer simulations that appear to clarify the fundamental nature of these remarkable jets and lobes. The energy transport process appears to be electrodynamic, rather than particle beam–driven. A new observational verification of a 1018 Ampère current in an actual jet is concordant with the predictions and simulations of poynting flux-dominated electromagnetic jets. In this model the current is tightly related to the BH mass and angular energy.The magneto-plasma properties of the lobes must obviously match to the jets which feed them. The “energy sink” phase is when BH energy is ultimately deposited on supra-galactic scales. The process from the BH to the lobe production happens with remarkable efficiency. The presence or absence of a galaxy cluster environment creates laboratory conditions that help to calibrate the energy flow paths, and the magnetic rigidity of these jet-lobe systems.I conclude by describing recent, sensitive radio observations on supra-cluster scales that test for final magnetic energy deposition - the “sink” phase - into the intergalactic medium.

Transient energy flow in ship plate and shell structures under low velocity impact

Structural members commonly employed in marine and off-shore structures are usually fabricated from plates and shells. Collision of this class of structures is usually modeled as plate and shell structures subjected to dynamic impact loading. The understanding of the dynamic response and energy transmission of the structures subjected to low velocity impact is useful for the efficient design of this type of structures. The transmissions of transient energy flow and dynamic transient response of these structures under low velocity impact are presented in the paper. The structural intensity approach is adopted to study the elastic transient dynamic characteristics of the plate structures under low velocity impact. The nine-node degenerated shell elements are adopted to model both the target and impactor in the dynamic impact response analysis. The structural intensity streamline representation is introduced to interpret energy flow paths for transient dynamic response of the structures. Numerical results, including contact force and transient energy flow vectors as well as structural intensity stream lines, demonstrate the efficiency of the present approach and attenuating impact effects on this type of structures.

SEA를 이용한 차량 진동 특성 해석

Statistical Energy Analysis(SEA) has been considered as a Possible method for predicting responses of complex structures, especially at higher frequencies. In this paper, an SEA model of a vehicle was built using 138 energy storing subsystems connected together using 1019 Junctions. SEAM software program was used to build and calculate the model. To demonstrate the accuracy of the SEA model, predicted response levels were compared with measured levels. The source Input levels were measured at the engine mounting parts. There is good agreement between the estimated and the experimental results. This paper also identifies some dominant energy flow paths from sources. It is finally presented that the SEA model can optimize the design parameters of vehicles using model parameters and energy flow paths.

Structural intensity study of plates under low-velocity impact

The transmissions of transient energy flow and dynamic transient response of plate structures under low-velocity impact are presented. The structural intensity approach is used to study the transient dynamic characteristics of plate structures under low-velocity impact. In the dynamic impact response analysis, nine-node degenerated shell elements with assumed shear and membrane strain fields are adopted to model the target and impactor. The dynamic contact-impact algorithm and the governing equations for both the target and impactor are derived based on the updated Lagrangian approach. Explicit integration algorithm has been adopted in the time integration process. The novel structural intensity streamline representation is introduced to interpret energy flow paths for transient dynamic response of plates under low-velocity impact. The effects of plates with and without structural damping on the energy flow and energy path are discussed. Numerical results, including contact force, deflection histories and transient energy flow vectors as well as structural intensity streamlines, show that the present method and representation are an efficient approach for exploring dynamic response for plate structures subjected to low-velocity impact.

Numerical study on energy transmission for rotating hard disk systems by structural intensity technique

The main purpose of this paper is to apply structural intensity technique to indicate the magnitude and direction of vibration energy flow for a rotating system, so as to modify and control the energy flow path to reduce the vibrational problems. Numerical simulations are carried out for a rotating flexible disk-spindle system supported by ball bearing and flexible shaft by the finite element method, and the vibrational energy transmission caused by an eccentric mass is analyzed by using structural intensity technique. The structural intensities in hybrid 1D, 2D and 3D elements, which are used to model different components of HDD, are obtained. Three different damping effects on the diversion and dissipation of energy flow are investigated. The calculated results show that different types of damping or dampers have different effect on energy flow path in HDD. Through numerical simulation, a more reasonable design scheme may be explored by scientifically arranging damping components for HDD to further suppress its vibration and noise problems.

The structural intensities of composite plates with a hole

The structural intensities in isotropic and orthotropic laminae and composite laminated plates with and without a hole of different rim conditions are studied using the finite element method. Patterns of superposition among structural stress fields, intensity vectors, mode shapes and streamlines of energy flow are obtained for the various cases. It is found that the hole completely changes the distributions of the stress and energy flow path in plates. Despite its nature of mode dependent the pattern of energy flow may be different from each other despite having similar structural mode shapes, moreover the position of maximum stress is not corresponding to the position of maximum structural intensity.

Self-trapped states in proteins?

We show here that the temperature dependence of the amide I band of myoglobinshows evidence for a low-lying self-trapped state at 6.15 µm.We have conducted a careful set of picosecond pump–probe experiments providingresults as a function of temperature and wavelength and show that this low-lyingstate has a 30 ps lifetime at 50 K, much longer than the relaxation time of themain amide I band at 50 K. Fits of the temperature dependence of thermaloccupation of this state yield the result that it lies 280 K below the mainamide I band. Since the gap energy of this state is approximately equal toroom temperature, this self-trapped state can act as a transient store ofvibrational energy at physiological temperatures in biomolecules and canhelp to direct the path of energy flow in a biomolecule under biologicalconditions.

349 平板における振動エネルギー流れの発生メカニズムに関する研究

This paper describes a new decomposition method for structural intensity on a plate into each intensity component at a natural frequency. This is based on an approximated description for the vibration displacement that is newly derived here and has some real parts of some natural modal displacements and an imaginary part of only one natural modal displacement exciting near the excitation frequency. The decomposed intensity components have the possibility to predict the structural energy flow path around an arbitrary frequency. The validation of this method is done using numerical simulation.

Predicted and measured structural intensity in a plate excited by a diffuse acoustic field

Structural intensity (S-I) fields indicate energy source and sink regions in structures as well as energy flow paths through structures. Various S-I-based studies have been performed for structures excited at a point or group of points. Little attention, however, has been paid to S-I fields in structures under distributed random loads, such as those due to turbulent boundary layer pressure fields and diffuse acoustic fields. Such excitations occur in common engineering problems. This study presents experimental S-I results for a thin, simply supported, rectangular plate with an attached damper excited by a diffuse acoustic field. The plates velocity response to the excitation is measured using a scanning laser Doppler vibrometer. Finite differencing techniques are applied to the measured velocity field to yield S-I vectors. The experiments results are shown to be similar to predicted S-I fields. [Work supported by ARL Penn State.]

Absorption coefficient and energy flow path identification by means of inverse local energy method

Estimation of the single absorption rate and of acoustical power input is currently made in reverberant rooms where a diffuse field is established. In this paper we aim at describing a method dedicated to absorption coefficients and energy flow path identification within all type of acoustic fields in medium and high frequencies, by means of an inverse local energy method. Making use of an energy integral equation with diffuse reflection, an estimator of the wall various absorption rates is built up, while the cavity is excited by a standard spherical acoustic source. A similar formulation is used to characterize a wall continuous excitation. Then it is possible to go through the measurements (pressure, intensity) and supply a detailed analysis of the wall input energy flow. This study also includes a numerical comparison between optimization methods used when trying to match the calculated field and the reference field. Among those methods, the spheric gradient proves to be efficient when compared with estimators based on other cost-functions. Sensitivity to discretization, robustness versus statistic measurement errors, and relevance of identified parameters are dealt with.

Application of statistical energy analysis to the design of crew rest compartments

Longer flight times for modern commercial aircraft have led to the need for crew rest compartments. Noise levels in the crew rest compartments must be conducive to proper rest and recuperation. Statistical Energy Analysis (SEA) has been used to develop a 777 crew rest compartment design that achieves appropriate noise levels at acceptable weight and cost. In this paper the design of a 777 overhead crew rest compartment is outlined using SEA design tools and methods. Noise data were gathered in flight to distinguish airplane source components and develop model inputs. Crew rest panels, the airplane fuselage, and acoustic volumes were modeled as SEA subsystems by taking into account geometry, material properties, modulus, and damping. A model was built, excited with inputs, and analyzed to determine energy flow paths and acoustic pressure at receiver locations. Prospective add-on treatments were then assessed to engineer an effective noise control package. The model development was supplemented by laboratory sound transmission loss testing of individual components. The good agreement between the laboratory tests and individual SEA models of the components increased confidence in the approach. Once the crew rest was installed on the airplane, the measured in-flight noise levels closely matched the SEA estimates.

Two structural intensity prediction methods in plates excited by turbulent boundary layers

Structural intensity (S-I) fields may be used to identify energy flow paths through a vibrating structure, as well as energy source and sink regions. Boundary layer excitation of structures occurs in numerous aerospace and underwater applications. This study describes two methods of predicting S-I fields in structures excited by turbulent boundary layers. The first prediction method combines well known multiple-input/multiple-output system theory with finite differencing techniques to obtain S-I predictions. The second method uses an analytic computation technique. This technique combines response matrices between applied pressures and response stresses and velocities to form cross spectra matrices with units of power. These cross spectra matrices are proportional to S-I. The two prediction methods are described in detail and a set of case studies incorporating these methods is presented. The case studies are based on a simply supported plate with an attached point damper. The Corcos model of the boundary layer spatial wall pressure correlation is applied to the plate due to its simplicity. The case studies include intensity fields due to flows above, at, and below aerodynamic coincidence (the frequency at which a structural wavelength equals a convective wavelength). [Work supported by The Applied Research Laboratory, Penn State.]

A topology survey of single-stage power factor corrector with a boost type input-current-shaper

A topological review of the single stage power factor corrected (PFC) rectifiers is presented in this paper. Most reported single-stage PFC rectifiers cascade a boost-type converter with a forward or a flyback DC-DC converter so that input current shaping, isolation, and fast output voltage regulation are performed in one single stage. The cost and performance of single-stage PFC converters depend greatly on how its input current shaper (ICS) and the DC-DC converter are integrated together. For the cascade connected single-stage PFC rectifiers, the energy storage capacitor is found in either series or parallel path of energy flow. The second group appears to represent the main stream. Therefore, the focus of this paper is on the second group. It is found that many of these topologies can be implemented by combining a two-terminal or three-terminal boost ICS cell with DC-DC converter along with an energy storage capacitor in between. A general rule is observed that translates a three-terminal ICS cell to a two-terminal ICS cell using an additional winding from the transformer and vice verse. According to the translation rule, many of the reported single-stage PFC topologies can be viewed as electrically equivalent to one another. Several new PFC converters were derived from some existing topologies using the translation rule.

Energy source identification using reactive structural intensity

The analysis of wave propagation phenomena in structures, especially energy flux, can be a powerful approach to noise and vibration control problems. The active mechanical intensity corresponds to the period-averaged value and is related to the propagative wave field. The reactive intensity is related to the reverberance of energy in the structure, which originates the standing waves or mode shapes. Properly separated into its wave components, reactive intensity maps agree well with operational modes, indicating the location of the nodal lines. On the other hand, active intensity is the quantity usually addressed when solving vibration and noise problems, since it provides information about the main energy flow paths, thus enabling identification of the energy sources and sinks. For highly reverberant structures, however, measuring active intensity becomes awkward, and intensity plots fail to indicate the region where the energy is injected or dissipated in the structure. A new technique to localize energy sources based on the divergence of the reactive intensity and the distribution of the potential and kinetic energy densities within the structure is presented. Numerical results are given for a beam with a point excitation using finite-element and spectral element models based on the Bernoulli–Euler beam theory.

The application of a diagnostic methodology for the identification of hydraulic design deficiencies affecting pathogen removal

An intensive diagnostic methodology designed to evaluate microbiological removal deficiencies related to design defects was applied to a two-stage waste stabilisation pond system in Colombia. This evaluation included intensive monitoring of a range of physico-chemical parameters, an integrated assessment of faecal coliform removal and simultaneous hydraulic tracing of surface flow using oranges. The dispersion/advection effects and the hydraulic regime through the facultative pond were defined using a bacteriophage. This methodology facilitated the identification of the hydraulic flow patterns and short-circuiting together with the age distribution of the pond effluent. Observed differences between surface and sub-surface flow patterns were attributed principally to the fact that wind action opposed the natural input-output energy flow path. The concentration of phage leaving the pond in 6 hours represented 1% of the original dose, confirming the finding that a 2-log reduction of pathogen indicators could not be achieved. Three stages of intervention were identified as necessary for the performance to be improved to the level at which WHO reuse targets would be met.

Highly efficient conversion technologies for energy utilization

Energy utilization systems and the related conversion technologies are evaluated from the thermodynamic view point in order to regulate the energy flow path. Involvement of thermal energy, directly as well as indirectly in any conversion process or operation is discussed, indicating that an innovative advancement of conversion technologies between heat and other forms of energy may be a breakthrough for ultimate energy utilization. Such highly efficient conversion technologies for the respective steps along the energy flow path, namely primary energy conversion, energy transportation and energy utilization including storage and recovery, are discussed.

Power flow in the equine forelimb.

A method is described for the estimation of segmental powers and power flow during the stance phase in the equine forelimb, to demonstrate the sources and paths of energy flow through the limb segments. S-VHS video and force platform data were collected for 5 walking trials in a sound Dutch Warmblood horse. Two camera views were combined using direct linear transformation and the resultant sagittal plane positional and angular data used together with the vertical and cranio-caudal ground reaction forces to calculate moments about the ends of the 4 lowermost segments of the forelimb, and the reaction forces at the segment ends. Power flows were calculated across the proximal and distal ends of each segment and total segmental power computed. During initial and terminal stance, power flowed into the cannon segment proximally, and out distally. For the rest of stance, the flow in the cannon was distal to proximal. At the pastern, power flowed in proximally during initial loading, and out distally. For most of the rest of stance, the pattern of flow was distal to proximal, except for terminal stance, when power flowed in through both ends. The largest effect at the hoof is a loss of energy in terminal stance as power flowed out proximally and into the pastern. The pastern appears to receive most of the energy during loading and pushoff and transfers this energy up the limb during midstance.