Gain Distribution Research Articles

Electromagnetic Waves in a Time Periodic Medium With Step-Varying Refractive Index

In this paper, we study the interactions of electromagnetic waves with a non-dispersive dynamic medium that is temporally dependent. Electromagnetic fields under material time-modulation conserve their momentum but not their energy. We assume a time-variation of the permittivity, permeability and conductivity and derive the appropriate time-domain solutions based on the causality state at a past observation time. We formulate a time-transitioning state matrix and connect the unusual energy transitions of electromagnetic fields in time-varying media with the exceptional point theory. This state-matrix approach allows us to analyze further the electromagnetic waves in terms of parity and time-reversal symmetries and signify parity-time symmetric wave-states without the presence of a spatially symmetric distribution of gain and loss, or any inhomogeneities and material periodicity. This paper provides a useful arsenal to study electromagnetic wave phenomena under time-varying media and points out novel physical insights connecting the resulting energy transitions and electromagnetic modes with exceptional point physics and operator symmetries.

Numerical Ruin Probability in the Dual Risk Model with Risk-Free Investments

In this paper, a dual risk model under constant force of interest is considered. The ruin probability in this model is shown to satisfy an integro-differential equation, which can then be written as an integral equation. Using the collocation method, the ruin probability can be well approximated for any gain distributions. Examples involving exponential, uniform, Pareto and discrete gains are considered. Finally, the same numerical method is applied to the Laplace transform of the time of ruin.

Seizure evolution can be characterized as path through synaptic gain space of a neural mass model.

Physiologically based models could facilitate better understanding of mechanisms underlying epileptic seizures. In this paper, we attempt to reveal the dynamic evolution of intracranial EEG activity during epileptic seizures based on synaptic gain identification procedure of a neural mass model. The distribution of average excitatory, slow and fast inhibitory synaptic gain in the parameter space and their temporal evolution, i.e., the path through the model parameter space, were analyzed in thirty seizures from ten temporal lobe epileptic patients. Results showed that the synaptic gain values located roughly on a plane before seizure onset, dispersed during seizure and returned to the plane when seizure terminated. Cluster analysis was performed on seizure paths and demonstrated consistency in synaptic gain evolution across different seizures from the individual patient. Furthermore, two patient groups were identified, each one corresponding to a specific synaptic gain evolution in the parameter space during a seizure. Results were validated by a bootstrapping approach based on comparison with random paths. The differences in the path revealed variations in EEG dynamics for patients despite showing identical seizure onset pattern. Our approach may have the potential to classify the epileptic patients into subgroups based on different mechanisms revealed by subtle changes in synaptic gains and further enable more robust decisions regarding treatment strategy.

Estimation of solar heat gain using illumination sensor measurements

Solar radiation is an important but unpredictable source of thermal energy in an indoor space. The incident and absorbed solar radiation, and consequently solar heat gain, is difficult to model accurately even when detailed information about the building design, orientation, and material properties is available. This article presents a novel approach to estimate radiant solar heat gain using measurements from ceiling mounted illumination sensors. This proposed approach captures the effect of directional solar radiation on solar heat gain of an indoor space that cannot be captured (or estimated) by local weather station measurements. Measured illumination data from day-long experiments for several (cloudy and sunny) days is first compared with solar heat gain to demonstrate strong correlation between them irrespective of sky condition (with average correlation coefficients of 0.84 and 0.77 for cloudy and sunny days respectively). Next, a linear model to estimate radiant heat gain from illumination sensor readings is proposed and validated against calculated solar heat gain values using the well-known Perez model. For further validation, similar experiments are performed on another testbed with different geographical location and orientation. Finally, we demonstrate that illumination sensors can also provide spatial distribution of solar heat gain inside an indoor space.

Enhanced phase-sensitive OTDR system with pulse width modulation Brillouin amplification.

A pulse width modulation (PWM) Brillouin amplification has been proposed and demonstrated to improve the signal-to-noise ratio (SNR) and sensitivity of phase-sensitive optical time domain reflectometry (Ф-OTDR) especially for the far end of a sensing fiber. In the logarithmic unit, arbitrary gain distribution can be realized with the customizable PWM function. The gain distribution is adjustable by tuning the PWM parameters. To prove the concept, three typical gain distributions including up-ramp sawtooth, sine and triangle have been achieved with the corresponding driving functions. In experiments, a linear PWM pump light has been used to amplify the backscattering Rayleigh light. The signal at the leading end has been enhanced by about 11.5 dB. Meanwhile, 9 dB transmission attenuation (along 25 km SMF) has also been compensated excellently. To verify the effectiveness of attenuation compensation, two vibrations with a frequency of 100 Hz and 300 Hz have been recovered accurately at the trailing end. Besides, preamplifier and acoustic-optic modulator (AOM) was used to suppress the ASE noise and further improve the effective ER, respectively. With that, lower relative intensity noise (RIN) has been obtained in the proposed system compared to the conventional Brillouin amplification in Ф-OTDR. So the proposed PWM Brillouin amplification not only improves the SNR but also equalizes the sensitivity along whole sensing fiber. It avoids the complex calibration and suppresses the false alarm rate in field application. Foreseeably, this scheme is universal and can be adopted by other distributed fiber optic technique to enhance the system performance.

Topological Waveguiding near an Exceptional Point: Defect-Immune, Slow-Light, and Loss-Immune Propagation.

Electromagnetic waves propagating in conventional wave-guiding structures are reflected by discontinuities and decay in lossy regions. In this Letter, we drastically modify this typical guided-wave behavior by combining concepts from non-Hermitian physics and topological photonics. To this aim, we theoretically study, for the first time, the possibility of realizing an exceptional point between coupled topological modes in a non-Hermitian nonreciprocal waveguide. Our proposed system is composed of oppositely biased gyrotropic materials (e.g., biased plasmas or graphene layers) with a balanced distribution of loss and gain. To study this complex wave-guiding problem, we put forward an exact analysis based on classical Green's function theory, and we elucidate the behavior of coupled topological modes and the nature of their non-Hermitian degeneracies. We find that, by operating near an exceptional point, we can realize anomalous topological wave propagation with, at the same time, low group velocity, inherent immunity to backscattering at discontinuities, and immunity to losses. These theoretical findings may open exciting research directions and stimulate further investigations of non-Hermitian topological waveguides to realize robust wave propagation in practical scenarios.

Modeling false alarm rate and related characteristics of laser ranging and LIDAR avalanche photodiode photoreceivers

An analysis is presented of the error introduced into estimates of avalanche photodiode (APD) laser-rangefinder performance by assuming Gaussian distribution of the APD multiplication gain. The amplitude of current pulses emitted by an APD obeys the McIntyre distribution, the tails of which diverge from the Gaussian distribution having the same mean and variance. Because extinction of false alarms requires setting a discrimination threshold far into the tail of an analog photoreceiver’s output distribution, the threshold level required to achieve a specified false alarm rate (FAR) using an APD-based photoreceiver is often not accurately predicted by the standard FAR model of Rice. Characteristics of APD-based photoreceivers are calculated using the McIntyre distribution and are compared with characteristics calculated using the Gaussian approximation.

Inverted L‐notch loaded hexa band circular patch antenna for X, ku/K band applications

AbstractA novel hexa band circular shape patch antenna with four inverted L‐shape notches is proposed. The antenna results are discussed in terms of reflection coefficient, surface current density, radiation pattern (co and cross polarization), three‐dimensional gain distribution, and voltage standing wave ratio (VSWR). Measured resonating frequencies are observed at 11.6, 13.92, 17.11, 19.47, 21.11, and 23.05 GHz. Simulated gain of 7.39 dBi (11 GHz), 2.25 dBi (13.3 GHz), 6.65 dBi (16.6 GHz), 5.83 dBi (19 GHz), 6.02 dBi (20.6 GHz), and 7.31 dBi (22.2 GHz), respectively, is observed and the antenna is suitable for X‐band, Ku‐band, and K‐band applications. The performance of the proposed antenna is validated in terms of return loss (dB), VSWR, and radiation pattern by measurement.

RNA-Seq Meta-analysis identifies genes in skeletal muscle associated with gain and intake across a multi-season study of crossbred beef steers

BackgroundFeed intake and body weight gain are economically important inputs and outputs of beef production systems. The purpose of this study was to discover differentially expressed genes that will be robust for feed intake and gain across a large segment of the cattle industry. Transcriptomic studies often suffer from issues with reproducibility and cross-validation. One way to improve reproducibility is by integrating multiple datasets via meta-analysis. RNA sequencing (RNA-Seq) was performed on longissimus dorsi muscle from 80 steers (5 cohorts, each with 16 animals) selected from the outside fringe of a bivariate gain and feed intake distribution to understand the genes and pathways involved in feed efficiency. In each cohort, 16 steers were selected from one of four gain and feed intake phenotypes (n = 4 per phenotype) in a 2 × 2 factorial arrangement with gain and feed intake as main effect variables. Each cohort was analyzed as a single experiment using a generalized linear model and results from the 5 cohort analyses were combined in a meta-analysis to identify differentially expressed genes (DEG) across the cohorts.ResultsA total of 51 genes were differentially expressed for the main effect of gain, 109 genes for the intake main effect, and 11 genes for the gain x intake interaction (Pcorrected < 0.05). A jackknife sensitivity analysis showed that, in general, the meta-analysis produced robust DEGs for the two main effects and their interaction. Pathways identified from over-represented genes included mitochondrial energy production and oxidative stress pathways for the main effect of gain due to DEG including GPD1, NDUFA6, UQCRQ, ACTC1, and MGST3. For intake, metabolic pathways including amino acid biosynthesis and degradation were identified, and for the interaction analysis the pathways identified included GADD45, pyridoxal 5’phosphate salvage, and caveolar mediated endocytosis signaling.ConclusionsVariation among DEG identified by cohort suggests that environment and breed may play large roles in the expression of genes associated with feed efficiency in the muscle of beef cattle. Meta-analyses of transcriptome data from groups of animals over multiple cohorts may be necessary to elucidate the genetics contributing these types of biological phenotypes.

Genetic gain via REML/BLUP and selection indices in snap bean

ABSTRACT The aim of this study was to compare four selection indexes and REML/BLUP methodology in the evaluation of predicted genetic gains of traits of interest in snap bean breeding program. We evaluated 17 selected lines, in a randomized complete block design, with four replicates, in four environments, Bom Jesus de Itapaboana-RJ, in 2011 and 2012 and Cambuci-RJ, in 2011 and 2013. The evaluated traits were pod and grain productivity, number of pods per plant, number of seeds per pod and weight of 100 seeds. For gain prediction, the employed selection indexes were Pesek &amp; Baker, Smith &amp; Hazel, Mulamba &amp; Mock, Williams and REML/BLUP methodology. Among the tested selection indexes, Mulamba &amp; Mock was the one which showed the best gain distribution considering the tested variables, such as the higher coincidence coefficients in comparison to REML/BLUP, resulting in 62% of grain productivity and pod productivity per plant. The REML/BLUP methodology permitted to select lines with high relative performances and obtained simultaneous gains for the evaluated traits, being superior in relation to the tested selection indexes for snap bean crop.

Nonreciprocity in synthetic photonic materials with nonlinearity

Abstract

Stability band structure for periodic states in periodic potentials

A class of periodic solutions of the nonlinear Schrödinger equation with non-Hermitian potentials are considered. The system may be implemented in planar nonlinear optical waveguides carrying an appropriate distribution of local gain and loss, in a combination with a photonic-crystal structure. The complex potential is built as a solution of the inverse problem, which predicts the potential supporting required periodic solutions. The main subject of the analysis is the spectral structure of the linear (in)stability for the stationary spatially periodic states in the periodic potentials. The stability and instability bands are calculated by means of the plane-wave-expansion method, and verified in direct simulations of the perturbed evolution. The results show that the periodic solutions may be stable against perturbations in specific Floquet–Bloch bands, even if they are unstable against small random perturbations.

On-Site Wireless Power Generation

Conventional wireless power transfer systems consist of a microwave power generator and a microwave power receiver separated by some distance. To realize efficient power transfer, the system is typically brought to resonance, and the coupled-antenna mode is optimized to reduce radiation into the surrounding space. In this scheme, any modification of the receiver position or of its electromagnetic properties results in the necessity of dynamically tuning the whole system to restore the resonant matching condition. It implies poor robustness to the receiver location and load impedance, as well as additional energy consumption in the control network. In this study, we introduce a new paradigm for wireless power delivery based on which the whole system, including transmitter and receiver and the space in between, forms a unified microwave power generator. In our proposed scenario the load itself becomes part of the generator. Microwave oscillations are created directly at the receiver location, eliminating the need for dynamical tuning of the system within the range of the self-oscillation regime. The proposed concept has relevant connections with the recent interest in parity-time symmetric systems, in which balanced loss and gain distributions enable unusual electromagnetic responses.

Infant weight gain and adolescent body mass index: comparison across two British cohorts born in 1946 and 2001

ObjectiveTo investigate how the relationship of infant weight gain with adolescent body mass index (BMI) differs for individuals born during and before the obesity epidemic era.DesignData from two British birth...

Rate-Energy Tradeoff in Simultaneous Wireless Information and Power Transfer Over Fading Channels With Uncertain Distribution

This paper investigates the tradeoff between information rate and harvested energy in a simultaneous wireless information and power transfer system under power splitting (PS) scheme and time switching (TS) scheme. A single-input-multiple-output transmitter–receiver pair is considered. For the channel from the transmitter to the receiver, only the mean and covariance matrix are known, but the instantaneous channel information or the channel gain distribution is unknown. We define robust outage capacity that applies for all possible channel distributions with the given mean and covariance matrix, and study the tradeoff between the robust outage capacity and harvested power level. By solving optimization problems, we find the PS ratio setting for PS scheme and TS ratio setting for TS scheme to achieve the outer boundary of robust outage capacity-energy region (which includes all possible pairs of achievable robust outage capacity and harvested power level). The PS and TS ratio setting are fixed over fading blocks, and thus can avoid communication overhead and computation overhead over each fading block, and facilitate a simple implementation in a practical system. We also prove that the robust outage capacity-energy regions in PS scheme and TS scheme are both convex. Further, we prove that the PS scheme outperforms the TS scheme in terms of the rate-energy tradeoff. Numerical results are also presented to verify the correctness of our theoretical results.

Direct, indirect and simultaneous selection as strategies for alfalfa breeding on forage yield and nutritive value

ABSTRACT Alfalfa breeding aimed at trait improvement for livestock feed takes longer periods of time, if compared to many other crops. Therefore, better selection methods are necessary for the success of alfalfa breeding programs. Although knowing about selection methods is quite important, there is a notable lack of information, as regards successful solutions. This study aimed to use direct, indirect and simultaneous selection methods for selecting alfalfa cultivars, based on yield traits and nutritive value. The evaluated traits were subdivided into two groups: forage yield and nutritive value. Selection gains were estimated by direct, indirect and simultaneous selection for each group, considering the selection of the 25 % best cultivars. Direct and indirect selections among genotype averages are not efficient to provide the desirable responses to the whole set of traits. The results for simultaneous selection, using the Tai index, provided a more balanced gain distribution to the set of traits in all cuts. The simultaneous selection allowed the identification of the 5681 and Verdor cultivars in the first cut, as well as ProINTA Patricia in the second cut, as superior in the two groups of evaluated traits.

Asymptotic Secrecy Analysis of Random Networks With Colluding Eavesdroppers

We perform an analysis of the secrecy outage and transmission capacity of random networks under Nakagami-m fading with colluding eavesdroppers, in the asymptotic case of large reference signal-to-noise ratios. In literature, secrecy analysis from the perspective of collusion pool has still not been well characterized. Considering a network model that accounts for uncertainties both in node locations and channel coefficients, we approximate the distribution of the aggregate path gain received by a collusion of eavesdroppers. Using this result, the asymptotic secrecy rate distribution, the secrecy outage probability, and the secrecy transmission capacity of random networks with colluding eavesdroppers are obtained, with basic factors such as density of nodes, the guarding distance, and the fading figure all accounted for by explicit parameters. Since secrecy in low-outage random networks are found to be most significant when the density of active nodes is small, the expressions derived can be seen as upper-bounds on the three aforementioned secrecy performance metrics in random networks, offering particular insight on the impact of fading, density, and guarding distances, while taking into account cooperation among eavesdroppers. Furthermore, we give a bound on colluding pool size, which is pragmatic in creating a nonprotected communication zone for the typical destination.

INFLUENCE OF THE AUDITORY SYSTEM ON PRESSURE DISTRIBUTION IN THE EAR CANAL

The pressure gain distribution along the ear canal is strongly dependent on boundary conditions, and, in normal conditions, the ear canal produces a 0–20-dB pressure gain close to the tympanic membrane in the 0.1–20[Formula: see text]kHz range. Additionally, the pressure gain distribution along the ear canal at high frequencies (over the second resonance of the ear canal at 8–9[Formula: see text]kHz) depends strongly on axis position; therefore, the middle ear transfer functions based on ear canal pressure are also strongly dependent on the measuring point.Objective: The aim of this study is to evaluate the mechanical influence of the tympanic cavity, ossicular chain and tympanic membrane connections on the pressure in the ear canal in the frequency range of 0.1–20[Formula: see text]kHz when a pressure source is applied to the ear canal entrance.Methods: We have developed numerical simulations for seven different models using the finite element method (FEM). Starting with an external ear canal finite element model, additional elements are coupled or removed to evaluate their contributions. We modeled and simulated the tympanic membrane, ossicular chain, tympanic cavity and a simplified cochlea in seven different combinations.Results: The pressure distribution along the external ear canal is obtained and represented in the 0.1–20[Formula: see text]kHz range for the seven model configurations.

Investigations of gain redshift in high peak power Ti:sapphire laser systems

Gain redshift in high peak power Ti:sapphire laser systems can result in narrowband spectral output and hence lengthen the compressed pulse duration. In order to realize broadband spectral output in 10 PW-class Ti:sapphire lasers, the influence on gain redshift induced by spectral pre-shaping, gain distribution of cascaded amplifiers and Extraction During Pumping (EDP) technique have been investigated. The theoretical and experimental results show that the redshift of output spectrum is sensitive to the spectral pre-shaping and the gain distribution of cascaded amplifiers, while insensitive to the pumping scheme with or without EDP. Moreover, the output spectrum from our future 10 PW Ti:sapphire laser is theoretically analyzed based on the investigations above, which indicates that a Fourier-transform limited (FTL) pulse duration of 21 fs can be achieved just by optimizing the spectral pre-shaping and gain distribution in 10 PW-class Ti:sapphire lasers.

Cross-eye gain distribution of multiple-element retrodirective cross-eye jamming

Cross-eye gain distribution of multiple-element retrodirective cross-eye jamming