Measurement Of Energy Flow Research Articles

PCB Food Web Dynamics Quantify Nutrient and Energy Flow in Aquatic Ecosystems.

Measuring in situ nutrient and energy flows in spatially and temporally complex aquatic ecosystems represents a major ecological challenge. Food web structure, energy and nutrient budgets are difficult to measure, and it is becoming more important to quantify both energy and nutrient flow to determine how food web processes and structure are being modified by multiple stressors. We propose that polychlorinated biphenyl (PCB) congeners represent an ideal tracer to quantify in situ energy and nutrient flow between trophic levels. Here, we demonstrate how an understanding of PCB congener bioaccumulation dynamics provides multiple direct measurements of energy and nutrient flow in aquatic food webs. To demonstrate this novel approach, we quantified nitrogen (N), phosphorus (P) and caloric turnover rates for Lake Huron lake trout, and reveal how these processes are regulated by both growth rate and fish life history. Although minimal nutrient recycling was observed in young growing fish, slow growing, older lake trout (>5 yr) recycled an average of 482 Tonnes·yr(-1) of N, 45 Tonnes·yr(-1) of P and assimilated 22 TJ yr(-1) of energy. Compared to total P loading rates of 590 Tonnes·yr(-1), the recycling of primarily bioavailable nutrients by fish plays an important role regulating the nutrient states of oligotrophic lakes.

Jet Measurements in Heavy-ion Collisions with CMS

The production of a strongly interacting medium in heavy-ion collisions is identified through suppression of high transverse momentum jets leading to an effect known as jet quenching. Detailed measurements of nuclear modification factors and energy flow of the aforementioned quenched jets are performed with the CMS detector. These new results extend previous measurements to large angles with respect to the quenched jets and increase reach in the transverse momentum range. High statistics pp, pPb and PbPb data taken in 2011-13 are used in the following analysis. A new data-driven method to estimate the underlying event contribution from the forward calorimeter energy distribution is employed which takes into account possible event by event flow modulation. The flavor dependence of energy loss of jets is studied by tagging heavy flavor b-jets in these systems.

Real-time measurement and analysis of energy flow in Stirling-type pulse tube refrigerator

A stable instrument with the minimum void volume is developed for real-time measurement of physical conditions in Stirling-type pulse tube refrigerator. From the measured physical conditions, the energy flows are identified, so that we can precisely know the non-equilibrium energy conversion process in two Stirling-type pulse tube refrigerators. The results of this paper are the experimental results that are obtained from actual Stirling-type pulse tube refrigerator configurations. The proposed method can be useful for clarifying the energy conversion process and analyzing the tendency of physical conditions in cryogenic systems.

QCD and Electroweak Boson Production in the Forward Region in LHCb§

Among most recent LHCb measurements relevant in the context of low-x physics include forward energy flow, Z and W cross-section measurements. The energy flow measurements map the forward LHCb acceptance for four classes of events, namely inclusive minimum bias, non-diffractive, diffractive and hard- pT collisions. Estimates from highenergy collision generators - i.e. various PYTHIA tunes and cosmic-ray generators - were compared to the measurement values. Z→ µ+µ+ and W± → µ+µ+ ν (v-) production is measured based on data collected at 7 TeV, results are shown differentially and compared to theoretical pQCD predictions. PACS number(s): 25.75.Dw, 13.85.-t, 12.38.Bx, 12.38.Cy, 12.38.-t.

Theoretical Analysis of Open Spherical Microphone Arrays for Acoustic Intensity Measurements

Acoustic intensity is a vectorial measure of acoustic energy flow through a given region of interest. Three-dimensional measurement of acoustic intensity requires special microphone array configurations. This paper provides a theoretical analysis of open spherical microphone arrays for the 3-D measurement of acoustic intensity. The calculations of the pressure and the particle velocity components of the sound field inside a closed volume are expressed using the Kirchhoff-Helmholtz integral equation. The conditions which simplify the calculation are identified. This calculation is then constrained to a finite set of microphones positioned at prescribed points on an open sphere. Several open spherical array topologies are proposed. Their magnitude and directional errors and measurement bandwidths are investigated via numerical simulations. A comparison with conventional open-sphere 3-D intensity probes is presented.

Measurement of electromagnetic energy flow through a sparse particulate medium: A perspective

First-principle analysis of the functional design of a well-collimated radiometer (WCR) reveals that in general, this instrument does not record the instantaneous directional flow of electromagnetic energy. Only in special cases can a sequence of measurements with a WCR yield the magnitude and direction of the local time-averaged Poynting vector. Our analysis demonstrates that it is imperative to clearly formulate the physical nature of the actual measurement afforded by a directional radiometer rather than presume desirable measurement capabilities. Only then can the directional radiometer be considered a legitimate part of physically based remote sensing and radiation-budget applications. We also emphasize the need for a better understanding of the nature of measurements with panoramic radiometers.

Indirect energy flow measurement in magneto-sensitive vibration isolator systems

The indirect energy flow measurement method is extended to cover highly nonlinear, frequency, amplitude and magnetic field dependent magneto-sensitive natural rubber isolators applied in a real vibration isolation system. Energy flow is an effective measure of vibration isolation while being a single quantity that considers both force and velocity. The use of the indirect technique is of interest while requiring only accelerometers since it is usually difficult to directly measure the force in a real application. The vibration isolation system is composed of four magneto-sensitive rubber isolators that are inserted under a vibrating source consisting of a solid aluminium mass excited by an electro-dynamic shaker. Magneto-sensitive rubber isolators are more useful than conventional rubber isolators since the dynamic stiffness varies with the application of an external magnetic field, thus resulting in more effective vibration isolation. Various approximations regarding the indirect technique are investigated, concluding that average stiffness of magneto-sensitive isolators can be used and auto-spectrum of the foundation velocity ignored. In addition, various error analyses are performed. Finally, the indirect measurement of the energy flow is validated by direct measurements, showing very good agreement.

Measurement of vibrational energy flow in a plate with high energy flow boundary crossing using electronic speckle pattern interferometry

The measurement of vibrational energy flow is an important tool in understanding the vibrational behaviour of structures. In the past, because of transducer constraints, the measurement of vibrational energy flow was mostly restricted to single point measurements. However, recent developments in advanced laser measurement techniques, such as electronic speckle pattern interferometry (ESPI), have gained interest in applying two-dimensional, multi-point measurement techniques to the estimation of vibrational energy flow. This paper addresses the measurement of vibrational energy flow in a plate by using an ESPI based vibrational energy flow measurement technique. A radially symmetric bending wave plate vibration model is introduced and theoretical expressions for energy-based quantities are derived. To assess the accuracy of the measurement method, these theoretical quantities are compared to synthetic results derived from the ESPI energy flow measurement technique. The ESPI measurement technique is also applied to an experimental ‘infinite’ plate. Thus, a specially designed experimental apparatus was constructed so as to minimise undesired wave reflections in the plate and, thus, achieve a high energy flow boundary crossing at the edges of the plate. To reduce the effect of optical noise contamination on the ESPI measured out-of-plane plate displacement data, optimal filters were applied prior to the vibrational energy flow computation. To appraise the accuracy of the experimental method, measured vibrational power on the plate is compared with measured vibrational input power. A difference of less than 1dB between both quantities indicates that vibrational energy flow within a rectangular plate that contains radially symmetric wave propagation can be measured to a good degree of accuracy if appropriate filtering is applied.

Measurement of mechanical and electrical energy flows in the semiactive piezoelectric shunt damping system

The analysis of the mechanical and electric energy flows in the semiactive vibration control system, which is made of a piezoelectric actuator shunted by a negative capacitor, is presented. The vibration control system is designed to suppress the vibration transmission in a narrow frequency range. Using a proper adjustment of the electronic circuit elements, the transmissibility of vibrations has been suppressed by 35 dB at the frequency of 1.5 kHz. The results of our measurements indicate that the average apparent electrical power in the electric part of the vibration control device is about 100 times larger than the mechanical power, which is supplied to the system from the source of vibrations. The rules for designing the highly efficient and low-power electronic parts of semiactive vibration control systems are discussed.

Measurements of forward energy flow and forward jet production with CMS

We present measurements of the forward (3 < |η| < 5) energy flow in minimum bias events and in events with either hard jets or W and Z bosons produced at central rapidities, as well as measurements of the inclusive forward jet cross section and of associated production of forward and central jets. Results are compared to MC models with different parameter tunes for the description of the underlying event and to perturbative QCD calculations, the PYTHIA and HERWIG parton shower event generators, as well as to the CASCADE Monte Carlo.

Erratum: Measurement of energy flow at large pseudorapidities in pp collisions at $ \sqrt {s} = 0.9 $ and 7 TeV

Abstract The energy flow, dE/dη, is studied at large pseudorapidities in proton-proton collisions at the LHC, for centre-of-mass energies of 0.9 and 7 TeV. The measurements are made using the CMS detector in the pseudorapidity range 3.15 &lt; |η| &lt; 4.9, for both minimum-bias events and events with at least two high-momentum jets. The data are compared to various pp Monte Carlo event generators whose theoretical models and input parameter values are sensitive to the energy-flow measurements. Inclusion of multiple-parton interactions in the Monte Carlo event generators is found to improve the description of the energy-flow measurements.

Direct energy flow measurement in magneto-sensitive vibration isolator systems

The effectiveness of highly nonlinear, frequency, amplitude and magnetic field dependent magneto-sensitive natural rubber components applied in a vibration isolation system is experimentally investigated by measuring the energy flow into the foundation. The energy flow, including both force and velocity of the foundation, is a suitable measure of the effectiveness of a real vibration isolation system where the foundation is not perfectly rigid. The vibration isolation system in this study consists of a solid aluminium mass supported on four magneto-sensitive rubber components and is excited by an electro-dynamic shaker while applying various excitation signals, amplitudes and positions in the frequency range of 20–200Hz and using magneto-sensitive components at zero-field and at magnetic saturation. The energy flow through the magneto-sensitive rubber isolators is directly measured by inserting a force transducer below each isolator and an accelerometer on the foundation close to each isolator. This investigation provides novel practical insights into the potential of using magneto-sensitive material isolators in noise and vibration control, including their advantages compared to traditional vibration isolators. Finally, nonlinear features of magneto-sensitive components are experimentally verified.

Measurement of energy flow at large pseudorapidities in pp collisions at $ \sqrt {s} = 0.{9} $ and 7 TeV

The energy flow, dE/d(eta), is studied at large pseudorapidities in proton-proton collisions at the LHC, for centre-of-mass energies of 0.9 and 7 TeV. The measurements are made in the pseudorapidity range 3.15 < |eta| < 4.9, for both minimum-bias events and events with at least two high-momentum jets, using the CMS detector. The data are compared to various pp Monte Carlo event generators whose theoretical models and input parameter values are sensitive to the energy-flow measurements. Inclusion of multiple-parton interactions in the Monte Carlo event generators is found to improve the description of the energy-flow measurements.

Community Secondary Production as a Measure of Ecosystem Function: A Case Study with Aquatic Ecosystem Fragmentation

Secondary production is a composite measure of an animal population's density, biomass, and growth over time. Thus, secondary production converts animal abundance and biomass data into a functional measure of energy flow through an ecosystem. In the present study, we used community secondary production as a composite measure of ecosystem functional response to anthropogenic disturbance, and applied this approach to examine effects of fragmentation on tidal creek ecosystems in The Bahamas. Community fish production decreased from a mean of 901 g m-2 yr-1 in unfragmented creeks to 166 g m-2 yr-1 in downstream areas of fragmented creeks to 29 g m-2 yr-1 upstream of creek blockages in fragmented creeks. when compared with several univariate measures (species richness, evenness, abundance, biomass), community composition (by ordination), and community distribution (via rank-curve analysis), community secondary production appeared to be the most consistent variable for distinguishing between three creek fragmentation categories. These data suggest that small, non-significant declines in diversity or other structural metrics can yield disproportionately large declines in ecosystem function. we suggest community secondary production can be an important component of future assessments of anthropogenic impacts, especially when alterations in diversity or community structure are small, but potentially have dramatic impacts on ecosystem function.

Highlights in Forward Physics from CMS

A few CMS analyses based on data collected during 2009–2010 data taking period are reviewed, including forward jet production cross-section measurements, energy flow measurement for Minimum Bias events as well as for events with presence of hard scale, and observation of single diffraction.

Measurement of forward jets, forward energy flow and diffractive events with CMS

Abstract We report on a first measurement of forward jet production and forward energy flow in pp collisions up to highest energies of s = 7 TeV . Inclusive spectra of jets are presented with p t > 20 GeV in the region of 3 | η | 5 . The energy flow in the forward region is measured for minimum bias events and for events with a high p t dijet in the central region. In addition, the absence of energy deposition in the forward region is used to observe diffractive events. We compare our results with predictions from Monte Carlo event generators including a simulation of multi-parton scattering.

Circuit theory of crossed Andreev reflection

We consider transport in a three-terminal device attached to one superconducting and two normal-metal terminals, using the circuit theory of mesoscopic superconductivity. We compute the nonlocal conductance of the current out of the first normal-metal terminal in response to a bias voltage between the second normal-metal terminal and the superconducting terminal. The nonlocal conductance is given by competing contributions from crossed Andreev reflection and electron cotunneling, and we determine the contribution from each process. The nonlocal conductance vanishes when there is no resistance between the superconducting terminal and the device, in agreement with previous theoretical work. Electron cotunneling dominates when there is a finite resistance between the device and the superconducting reservoir. Dephasing is taken into account, and the characteristic time scale is the particle dwell time. This gives rise to an effective Thouless energy. Both the conductance due to crossed Andreev reflection and electron cotunneling depend strongly on the Thouless energy. We suggest experimental determination of the conductance due to crossed Andreev reflection and electron cotunneling in measurement of both energy and charge flow into one normal-metal terminal in response to a bias voltage between the other normal-metal terminal and the superconductor.

Energy flow measurements in acoustic waves in a duct

Where, how much and how efficiently the energy conversion takes place in a regenerator of a thermoacoustic engine are expressed using the axial distribution of acoustic work flow and heat flow. As a first step in determining the energy flows inside the regenerator, measuring methods of the work flow are briefly described and the experimental results in an acoustic resonator are shown. Applicability of these methods to the regenerator is discussed.

Numerical study of vibration damping, energy and energy flow in a beam–plate system

A full analytical model of a beam–plate system has been produced in order to study the distribution of vibration energy and energy flow in beams and rods under simple but realistic excitation conditions. Axial and flexural vibrations are only analysed. Using the developed model as well as energy formulae presented in a companion paper some characteristic features of energy distribution in thin beams/rods have been identified which can be considered as universally applicable. It has been found that axial vibrations, often neglected, may be of the same importance with respect to energy and energy flow as flexural vibrations. Moreover, axial beam vibrations may provide an efficient mechanism of energy transfer to the adjacent sub-systems. Realistic boundary conditions may result in wave conversion which in turn may reverse the flow of energy of either axial or flexural vibration toward the source. The frequency-averaged net power consumed by the beam sub-system was found to depend largely on damping, contrary to the total input power to the system which stays fairly insensitive to it. The energy sharing between the beam and the connected plate was found to depend little on the amount and distribution of damping within the system providing the coupling between the two is strong. Finally, simulation of measurements of energy flow as well as of absorption/reflection/transmission energy coefficients of incorporated joints was shown to be affected to a large degree by beam damping which is often disregarded in experimental work.

QCD AT COLLIDERS

The success of the theory of Quantum Chromodynamics (QCD) in describing processes controlled by the strong interaction is generally seen as a triumph of modern particle physics. This paper reviews recent QCD measurements using hadronic jet final states from the Fermilab Tevatron, DESY's HERA, and CERN's LEP colliders. Recent advancements in the measurements of jet production cross sections, events shapes, and energy flow, along with improved theoretical calculations, allow for new levels of precision in the study of the physics of strong interactions and point to areas in need of further refinement.