scholarly journals Factors Determining Variability Time in Active Galactic Nucleus Jets

2002 ◽  
Vol 19 (4) ◽  
pp. 486-498 ◽  
Author(s):  
R. J. Protheroe
Keyword(s):  
Energy Density ◽  
Photon Energy ◽  
Temperature Limit ◽  
High Energy ◽  
Emission Region ◽  
Intrinsic Variability ◽  
Frame Size ◽  
The Relationship ◽  
High Energy Particles ◽  
Finite Particle

AbstractThe relationship between observed variability time and emission region geometry is explored for the case of emission by relativistic jets.The approximate formula for the jet-frame size of the emission region, R′ = DcΔtobs, is shown to lead to large systematic errors when used together with observed luminosity and assumed or estimated Doppler factor D to estimate the jet-frame photon energy density. These results have implications for AGN models in which low-energy photons are targets for interaction of high energy particles and photons, e.g. synchrotron-self Compton models and hadronic blazar models, as well as models of intraday variable sources in which the photon energy density imposes a brightness temperature limit through Compton scattering.The actual relationship between emission region geometry and observed variability is discussed for a variety of geometries including cylinders, spheroids, bent, helical and conical jet structures, and intrinsic variability models including shock excitation. The effects of time delays due to finite particle acceleration and radiation timescales are also discussed.

Trends of the macroscopic behaviors of energetic compounds: insights from first-principles calculations

2019 ◽  
Vol 21 (43) ◽  
pp. 24034-24041
Author(s):  
Chuli Sun ◽  
Weijing Zhang ◽  
Yongjun Lü ◽  
Feng Wang ◽  
Wei Guo ◽  
...  
Keyword(s):  
Energy Density ◽  
First Principles ◽  
High Energy ◽  
High Energy Density ◽  
First Principles Calculations ◽  
Energetic Compounds ◽  
High Energy Density Materials ◽  
The Relationship

Studies on the relationship between the microscopic properties and macroscopic behaviors of energetic compounds may provide clues for the synthesis and assessment of novel high energy density materials.

scholarly journals On the radiation energy density in the jet of high-energy-emitting BL Lac objects and its impact on their multimessenger role

2019 ◽  
Vol 488 (3) ◽  
pp. 4023-4032 ◽  
Author(s):  
F Tavecchio ◽  
F Oikonomou ◽  
C Righi
Keyword(s):  
Energy Density ◽  
Radiation Field ◽  
Cosmic Ray ◽  
High Energy ◽  
Emission Region ◽  
Ultrahigh Energy ◽  
Radiation Energy Density ◽  
Bl Lac Objects ◽  
Bl Lac ◽  
Soft Radiation

ABSTRACT We examine the potential multimessenger role of BL Lac objects emitting at high energy (so-called HBL) focusing on the limits on the energy density of soft radiation in the jet frame, a critical parameter that regulates the proton cooling and the fragmentation of ultrahigh-energy cosmic ray nuclei possibly accelerated in the jet. We show that (under the assumption that the high-energy emission bump is dominated by inverse Compton emission) the energy density of any external soft radiation field (e.g. produced by a layer surrounding the jet or in the accretion flow) cannot be larger than few times that associated with the observed synchrotron radiation produced in the emission region. Quite interestingly, the constraint that we derive is generally stronger than the limit obtained from the condition that the source is transparent to very high-energy γ-rays. Using this constraint, we can derive a robust upper limit for the efficiency of the photopion reaction leading to the emission of PeV neutrinos, fπ ≲ 10−5, which makes HBL quite inefficient neutrino sources. For the photodisintegration of nuclei, the results are more dependent on the spectral properties of the radiation field. The photodisintegration efficiency is safely below 1 (and nuclei can escape intact) for a ‘canonical’ spectrum of the soft radiation field ∝ ν−0.5. For radiation fields characterized by a softer spectrum and extended over a large portion of the jet, the efficiency increases and for an appreciable fraction of the sources nuclei with energies above 1019 eV might suffer significant photodisintegration.

scholarly journals Deep Insight into the Influences of the Intrinsic Properties of Dielectric Elastomer on the Energy-Harvesting Performance of the Dielectric Elastomer Generator

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4202
Author(s):  
Yingjie Jiang ◽  
Yujia Li ◽  
Haibo Yang ◽  
Nanying Ning ◽  
Ming Tian ◽  
...  
Keyword(s):  
Energy Density ◽  
Energy Harvesting ◽  
Conversion Efficiency ◽  
High Energy ◽  
Dielectric Elastomer ◽  
High Energy Density ◽  
Breakdown Field ◽  
Intrinsic Properties ◽  
High Permittivity ◽  
The Relationship

The dielectric elastomer (DE) generator (DEG), which can convert mechanical energy to electrical energy, has attracted considerable attention in the last decade. Currently, the energy-harvesting performances of the DEG still require improvement. One major reason is that the mechanical and electrical properties of DE materials are not well coordinated. To provide guidance for producing high-performance DE materials for the DEG, the relationship between the intrinsic properties of DE materials and the energy-harvesting performances of the DEG must be revealed. In this study, a simplified but validated electromechanical model based on an actual circuit is developed to study the relationship between the intrinsic properties of DE materials and the energy-harvesting performance. Experimental verification of the model is performed, and the results indicate the validity of the proposed model, which can well predict the energy-harvesting performances. The influences of six intrinsic properties of DE materials on energy-harvesting performances is systematically studied. The results indicate that a high breakdown field strength, low conductivity and high elasticity of DE materials are the prerequisites for obtaining high energy density and conversion efficiency. DE materials with high elongation at break, high permittivity and moderate modulus can further improve the energy density and conversion efficiency of the DEG. The ratio of permittivity and the modulus of the DE should be tailored to be moderate to optimize conversion efficiency (η) of the DEG because using DE with high permittivity but extremely low modulus may lead to a reduction in η due to the occurrence of premature “loss of tension”.

scholarly journals Sensitization of the reinforcing value of high energy density foods is associated with increased zBMI gain in adolescents

2021 ◽  
Author(s):  
Jennifer L. Temple ◽  
Amanda M. Ziegler ◽  
Amanda K. Crandall ◽  
Tegan Mansouri ◽  
Lori Hatzinger ◽  
...  
Keyword(s):  
Energy Density ◽  
Daily Intake ◽  
High Energy ◽  
High Energy Density ◽  
Future Studies ◽  
Reinforcing Value ◽  
Prospective Longitudinal ◽  
The Relationship ◽  
Over Time

Abstract Background/Objectives Characterizing behavioral phenotypes that predict increased zBMI gain during adolescence could identify novel intervention targets and prevent the development of obesity. The purpose of this study was to determine if sensitization of the relative reinforcing value (RRV) of high (HED) or low energy density (LED) foods predicts adolescent weight gain trajectories. A secondary aim was to test the hypothesis that relationships between sensitization of the RRV of food and weight change are moderated by delay discounting (DD). Subjects/Methods We conducted a prospective, longitudinal cohort study in 201 boys and girls with an average zBMI of 0.4, who began the study between the ages of 12 and 14 years and completed the study 2 years later. Participants completed five laboratory visits where the RRV of HED and LED, and DD were assessed at a baseline (visits 1, 2, and 4) and then RRV was measured again after participants consumed a portion of the same HED and LED food for 2 weeks (visits 3 and 5; order counterbalanced). Increases (>1) in the RRV from baseline to post-daily intake were categorized as “sensitization” and decreases (≤1) were categorized as “satiation.” Participants returned to the laboratory for follow-up visits at 6, 15, and 24 months to have height and weight taken and to complete additional assessments. Results Sensitization to HED food was associated with a greater zBMI change over time (β = 0.0070; p = 0.035). There was no impact of sensitization to LED food or interaction between sensitization to HED and LED food on zBMI change and no moderation of DD on the relationship between HED sensitization and zBMI change (all p > 0.05). Conclusion Our prior work showed that sensitization to HED food is cross-sectionally associated with greater zBMI. This study extends this work by demonstrating that sensitization to HED food prospectively predicts increased zBMI gain over time in adolescents without obesity. Future studies should determine if sensitization can be modified or reduced through behavioral intervention. Trial registration Clinicaltrials.gov: NCT04027608.

scholarly journals Level Scaling and Pulse Regulating Methods to Mitigate Cycle-to-cycle Variation in Memristor Based Learning System

2020 ◽  
Author(s):  
Zhiheng Liao ◽  
Jingyan Fu ◽  
Jinhui Wang
Keyword(s):  
High Energy ◽  
Optimal Number ◽  
Learning System ◽  
Switching Behavior ◽  
Intrinsic Variability ◽  
Latency Reduction ◽  
Cycle Variation ◽  
Relationship Of ◽  
The Relationship ◽  
Great Energy

Abstract As a novel non-volatile device, the memristive crossbar array has already delivered many of its promises including low computation complexity, high energy efficiency, and high density for the neuromorphic computing. However, the intrinsic variability of switching behavior has been a major obstacle to their implementation. Here we report a model that experimentally demonstrates the natural stochasticity of cycle-to-cycle variations and quantifies it. In addition, we propose level scaling and pulse regulating methods to mitigate the adverse impact of cycle-to-cycle variations. The relationship of the level of conductance and cycle-to-cycle variation is studied, and experiment results show an optimal number of the levels to mitigate cycle-to-cycle variations in the system. Additionally, the system compresses the number of pulses when the conductance is updated by the pulse stimulus to reduce cycle-to-cycle variations, resulting in the great energy and latency reduction. This work paves the way for the adoption of memristors for more efficient applications for the era of the edge computing and Internet of Things (IoT).

Investigation on High Energy Density Materials Utilizing Biological Transport Mechanisms

Aerospace ◽  
2004 ◽  
Author(s):  
Vishnu Baba Sundaresan ◽  
Honghui Tan ◽  
Donald J. Leo ◽  
John Cuppoletti
Keyword(s):  
Energy Density ◽  
Mechanical Energy ◽  
High Energy ◽  
Chemical Energy ◽  
High Energy Density ◽  
Transport Mechanisms ◽  
Biological Transport ◽  
Element Analysis ◽  
Thin Membranes ◽  
The Relationship

Biological systems such as plants produce large deformations due to the conversion of chemical energy to mechanical energy. These chemomechanical energy conversions are controlled by the transport of charge and fluid across permeable membranes within the cellular structure of the biological system. In this paper we analyze the potential for using biological transport mechanisms to produce materials with controllable actuation properties. An energetics analysis is performed to quantify the relationship between the introduction of chemical energy in the form of ATP to the resulting osmotic pressure variation within an enclosed membrane. Our analysis demonstrates that pressure variations of between 5 and 15 MPa are achievable. The pressure variations are then coupled to a finite element analysis to determine the ability of organized arrays to produce extensional and bending actuation in thin membranes. Our analysis demonstrates that internal pressure variations on the order of 10 MPa can produce actuation materials with extensional energy density on the order of 100 kJ/m3 and bending energy density on the order of 10 kJ/m3.

scholarly journals The inverse relationship between food price and energy density: is it spurious?

2014 ◽  
Vol 18 (6) ◽  
pp. 1091-1097 ◽  
Author(s):  
George C Davis ◽  
Andrea Carlson
Keyword(s):  
Energy Density ◽  
Low Income ◽  
Inverse Relationship ◽  
Adult Population ◽  
High Energy ◽  
Food Prices ◽  
Food Price ◽  
Simple Regression Model ◽  
The Relationship ◽  
Energy Dense Food

AbstractObjectiveAn important debate in the literature is whether or not higher energy-dense foods are cheaper than less energy-dense foods. The present communication develops and applies an easy statistical test to determine if the relationship between food price and energy density is an artifact of how the data units are constructed (i.e. is it ‘spurious’ or ‘real’?).DesignAfter matching data on 4430 different foods from the National Health and Nutrition Examination Survey with corresponding prices from the Center for Nutrition Policy and Promotion’s Food Prices Database, we use a simple regression model to test if the relationship between food price and energy density is ‘real’ or ‘spurious’.SettingUSA.SubjectsTotal sample size is 4430 observations of consumed foods from 4578 participants from the non-institutionalized US adult population (aged 19 years and over).ResultsOver all 4430 foods, the null hypothesis of a spurious inverse relationship between food price per energy density and energy density is not rejected. When the analysis is broken down by twenty-five food groups, there are only two cases where the inverse relationship is not spurious. In fact, the majority of non-spurious relationships between food price and energy density are positive, not negative.ConclusionsOne of the main arguments put forth regarding the poor diet quality of low-income households is that high energy-dense food is cheaper than lower energy-dense food. We find almost no statistical support for higher energy-dense food being cheaper than low energy-dense food. While economics certainly plays a role in explaining low nutritional quality, more sophisticated economic arguments are required and discussed.

Electrodynamic processes in colliding beams of high-energy particles

1973 ◽  
Vol 110 (5) ◽  
pp. 45 ◽  
Author(s):  
V.G. Gorshkov
Keyword(s):  
High Energy ◽  
High Energy Particles ◽  
Colliding Beams
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