Dependence Of Gain Research Articles

Age dependent vestibulo-ocular reflex gain in video head impulse test among normal Indians.

Determination of the normative data of Vestibulo-Ocular Reflex gain using VHIT of all three semicircular canals (anterior, posterior, horizontal) on both sides in different age groups is of interest. This is an observational study comprised of 10 healthy individuals in each decade from less than 10 years to 80 years of both sexes making a total of 80. The study was done using the equipment SYNAPSYS VHIT ULMER with Software EVOLUTION 3.0. Mean VOR gain of each decade for all the semicircular canals is calculated and they are compared using ANOVA (Analysis of variance). In our study, percentage of patients with overt saccades is nil. Hence, in our study, the occurrence of covert saccades was insignificant as compared to the above studies. Age dependent VOR gain in normal individuals did not have any significance in our study of 80 patients performed by video head impulse test. VOR gain in our study is not affected by age. Normative data for different age groups obtained compared among different age groups showing no significant difference in Mean VOR gain. The normative values of VOR gain can be compared to patients with dizziness thus helping in determining any vestibular loss.

Thermoacoustic velocity and pressure oscillations in one-dimensional combustors with spatially varying heat sources and thermal distributions

In this work, an asymptotically based framework using a naturally occurring perturbation parameter is further developed in the context of a one-dimensional tube with an open–open end point configuration without and with a spatially variable heat source. This approach is shown to produce accurate predictions of not only pressure waveforms, as previously demonstrated, but also of velocity mode shapes and frequencies for arbitrary temperature distributions that mimic a wide variety of flow heating arrangements. These include those associated with a Rijke tube as well as other thermoacoustic sound-generation devices. The underlying formulation consists of two linearly coupled partial differential equations that can be solved simultaneously while using a Green's function to capture the thermoacoustically induced velocity. The strategy leading to accurate predictions of the thermoacoustic velocity is described and then applied to several representative cases. Results pertaining to the acoustic velocity and pressure are systematically discussed and compared to other models in the literature. Overall, we find the axially dependent thermal gain to have the most significant impact on the mode shape structure, frequencies, and nodal locations. For example, higher thermal gains lead to elevated wave propagation speeds in the downstream segment of the tube. As such, they cause the velocity nodes to gradually shift upstream with successive increases in the thermal gain. Moreover, due in part to a non-homogeneous pressure–temperature pumping term that appears exclusively in the acoustic velocity formulation, the main difference between the acoustic pressure and velocity oscillation frequencies can be directly attributed to specific derivatives of the spatially varying thermal profiles.

Airy pulse dynamics in semiconductor optical amplifier with dispersive gain

We analytically as well as numerically study the Airy pulse dynamics in semiconductor optical amplifier (SOA) with dispersive gain. The frequency dependent gain of the SOA not only modifies the temporal shape of the Airy pulse but also alters the peak power of the Airy pulse. The study finds that the trajectory of the Airy pulse can be manipulated by the gain induced dispersion and the linewidth enhancement factor. Moreover, the gain dispersion introduces upchirp during the propagation that suppresses the Airy pulse acceleration in anomalous group velocity dispersion while the acceleration is pronounced when the dispersion is normal.

Polarization dependent gain in Raman fiber amplifiers with multiple pumps.

In this paper, the polarization dependent gain (PDG) in Raman fiber amplifiers (RFAs) with multiple pumps is studied thoroughly. A comprehensive model, which takes the random polarization mode dispersion, the nonlinear coupling between the pumps, and the degree of polarization (DOP) of the pumps into account, is proposed. The complex nonlinear and random coupling inside the optical fiber is described by a set of nonlinear stochastic differential equations (SDEs), which enable co-simulation of the polarized part and the depolarized part of the multiple pumps. It is revealed that the average PDG and the PDG standard deviation are linearly proportional to the DOP of the pumps, which agrees with the single mode case. More importantly, when the pump wavelength is far away from the signal amplification range (pump-signal wavelength difference larger than 100 nm), its DOP still affects the PDG of the signal. Such a phenomenon is caused by the fact that the pumps interact with each other and the pump DOP could transfer among the pumps, which could enhance the PDG of the RFA. The findings in the work will have important implications for the design of the optical transmission systems with the multi-pump RFAs.

CerS6-dependent ceramide synthesis in hypothalamic neurons promotes ER/mitochondrial stress and impairs glucose homeostasis in obese mice

Dysregulation of hypothalamic ceramides has been associated with disrupted neuronal pathways in control of energy and glucose homeostasis. However, the specific ceramide species promoting neuronal lipotoxicity in obesity have remained obscure. Here, we find increased expression of the C16:0 ceramide-producing ceramide synthase (CerS)6 in cultured hypothalamic neurons exposed to palmitate in vitro and in the hypothalamus of obese mice. Conditional deletion of CerS6 in hypothalamic neurons attenuates high-fat diet (HFD)-dependent weight gain and improves glucose metabolism. Specifically, CerS6 deficiency in neurons expressing pro-opiomelanocortin (POMC) or steroidogenic factor 1 (SF-1) alters feeding behavior and alleviates the adverse metabolic effects of HFD feeding on insulin sensitivity and glucose tolerance. POMC-expressing cell-selective deletion of CerS6 prevents the diet-induced alterations of mitochondrial morphology and improves cellular leptin sensitivity. Our experiments reveal functions of CerS6-derived ceramides in hypothalamic lipotoxicity, altered mitochondrial dynamics, and ER/mitochondrial stress in the deregulation of food intake and glucose metabolism in obesity.

Polarization Dependent Gain Stability of Raman Amplification Single-Core Feedback Structure Based on Consistency of Long-Axis Azimuths Variation

Polarization Dependent Gain Stability of Raman Amplification Single-Core Feedback Structure Based on Consistency of Long-Axis Azimuths Variation

Engineering Nonlinear Effects of Quantum-Well Semiconductor Optical Amplifiers for Applications in Optical Signal Processing

Quantum-well semiconductor optical amplifiers (QW-SOAs) have been widely used in all-optical signal processing functions because of their various nonlinear effects. For different optical signal processing functions, the requirements for performance of the QW-SOAs are different, and nonlinear effects of the QW-SOAs should be controlled selectively. Engineering nonlinear effects of QW-SOA is very important for different applications in optical signal processing. Here, a comprehensive QW-SOA model by combining the QW band structure calculation with the dynamic model is established to connect the structure parameters with the nonlinear effects of QW-SOA. Those characterized parameters of the QW-SOAs, such as gain coefficient, differential gain coefficient, refractive index change, differential refractive index change, linewidth enhancement factor, third-order susceptibility and polarization dependent gain, are used to characterize the nonlinear effects, and are calculated with different structure parameters based on this developed model. Take the wavelength conversion based on cross gain modulation effect and four wave mixing effect as examples, the structure parameters of the QW-SOAs are optimized for engineering the nonlinear effects and achieving the best output performance. This theoretical work presents a guide for choosing the optimized structure parameters while fabricating the QW-SOAs for different optical signal processing functions

Nondegenerate solitons of the (2+1)-dimensional coupled nonlinear Schrödinger equations with variable coefficients in nonlinear optical fibers

We derive the multi-hump nondegenerate solitons for the (2+1)-dimensional coupled nonlinear Schrödinger equations with propagation distance dependent diffraction, nonlinearity and gain (loss) using the developing Hirota bilinear method, and analyze the dynamical behaviors of these nondegenerate solitons. The results show that the shapes of the nondegenerate solitons are controllable by selecting different wave numbers, varying diffraction and nonlinearity parameters. In addition, when all the variable coefficients are chosen to be constant, the solutions obtained in this study reduce to the shape-preserving nondegenerate solitons. Finally, it is found that the nondegenerate two-soliton solutions can be bounded to form a double-hump two-soliton molecule after making the velocity of one double-hump soliton resonate with that of the other one.

Asynchronous Control of Fuzzy Singularly Perturbed System With a Dynamic Event-Triggered Strategy

This paper is mainly concerned with the asynchronous control problem of fuzzy singularly perturbed systems (FSPSs) by designing an effective dynamic event-triggered control (ETC) strategy. Different from the existing results, a sample-based dynamic eventtriggering condition related to the singular perturbation parameter (SPP) " is proposed. Particularly, an auxiliary variable is employed in the eventtriggered mechanism (ETM), which changes with the fluctuation of the system state. By constructing a novel parameter-dependent Lyapunov functional, some sufficient conditions are derived to stabilize FSPSs and solve the "-dependent control gain. Furthermore, the upper bound of SPP _" related with the proposed control gain is determined. The Zeno behavior can be naturally avoided by applying the sample-based dynamic ETC. Finally, two examples including a nonlinear circuit are presented to validate the effectiveness of obtained results.

Designing Distributed Impulsive Controller for Networked Singularly Perturbed Systems

This paper develops a novel synthesis approach for synchronization of a network of singularly perturbed systems (SPSs) with a small singular perturbation parameter (SPP) <inline-formula><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula> via distributed impulsive control. First, a decoupling method in the setting of directed networks is employed to decompose networked SPSs related to complex eigenvalues of the Laplacian matrix. Then, based on an improved piecewise continuous Lyapunov function, an <inline-formula><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula>-dependent synchronization criterion is established. The relationship among the impulse interval, the impulse gain matrix and <inline-formula><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula> is revealed. By employing the newly-obtained synchronization criterion, sufficient conditions on the existence of an <inline-formula><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula>-dependent impulse gain matrix are derived. Finally, an example is simulated to verify the effectiveness of the theoretical results.

Dot Off Dot Screen Printing with RGBW Reflective Inks

Recent advances in pigment production resulted in the possibility to print with RGBW primaries instead of CMYK and performing additive color mixing in printing. The RGBW pigments studied in this work have the properties of structural colors, as the primary colors are a result of interference in a thin film coating of mica pigments. In this work, we investigate the angle-dependent gamut of RGBW primaries. We have elucidated optimal angles of illumination and observation for each primary ink and found the optimal angle of observation under diffuse illumination. We investigated dot off dot halftoned screen printing with RGBW inks on black paper and in terms of angle-dependent dot gain. Based on our observations, optimal viewing condition for the given RGBW inks is in a direction of around 30&#x2218; to the surface normal. Here, the appearance of the resulting halftoned prints can be estimated well by Neugebauer formula (weighted averaging of the individual reflected spectra). Despite the negative physical dot gain during the dot off dot printing, we observe angularly dependent positive optical dot gain for halftoned prints. Application of interference RGBW pigments in 2.5D and 3D printing is not fully explored due to the technological limitations. In this work, we provide colorimetric data for efficient application of the angle-dependent properties of such pigments in practical applications.

Analytic theory of coupled-cavity traveling wave tubes

Coupled-cavity traveling wave tube (CCTWT) is a high power microwave vacuum electronic device used to amplify radio frequency signals. CCTWTs have numerous applications, including radar, radio navigation, space communication, television, radio repeaters, and charged particle accelerators. Microwave-generating interactions in CCTWTs take place mostly in coupled resonant cavities positioned periodically along the electron beam axis. Operational features of a CCTWT, particularly the amplification mechanism, are similar to those of a multicavity klystron. We advance here a Lagrangian field theory of CCTWTs with the space being represented by one-dimensional continuum. The theory integrates into it the space-charge effects, including the so-called debunching (electron-to-electron repulsion). The corresponding Euler–Lagrange field equations are ordinary differential equations with coefficients varying periodically in the space. Utilizing the system periodicity, we develop instrumental features of the Floquet theory, including the monodromy matrix and its Floquet multipliers. We use them to derive closed form expressions for a number of physically significant quantities. Those include, in particular, dispersion relations and the frequency dependent gain foundational to the RF signal amplification. Serpentine (folded, corrugated) traveling wave tubes are very similar to CCTWTs, and our theory applies to them also.

Quantitative study of birefringence effects in fiber-based orthogonal-pump FWM systems.

Optical fibers have unwanted residual birefringence due to imperfections in fabrication processes and environmental conditions. This birefringence will randomize the state of polarization of propagating signals and may harm the performance of four-wave mixing based processing devices. Here, we present a quantitative study of the effects of birefringence in orthogonal-pump four-wave mixing systems, and identify different regions of operation of the optical fiber, mainly determined by the relative magnitude between the physical length L and beat length Lb. This finding clarifies the characteristics of the complex interplay between birefringence and four-wave mixing and advises appropriate fiber length selection for minimized polarization dependent gain.

Topographic organization of eye-position dependent gain fields in human visual cortex

The ability to move has introduced animals with the problem of sensory ambiguity: the position of an external stimulus could change over time because the stimulus moved, or because the animal moved its receptors. This ambiguity can be resolved with a change in neural response gain as a function of receptor orientation. Here, we developed an encoding model to capture gain modulation of visual responses in high field (7 T) fMRI data. We characterized population eye-position dependent gain fields (pEGF). The information contained in the pEGFs allowed us to reconstruct eye positions over time across the visual hierarchy. We discovered a systematic distribution of pEGF centers: pEGF centers shift from contra- to ipsilateral following pRF eccentricity. Such a topographical organization suggests that signals beyond pure retinotopy are accessible early in the visual hierarchy, providing the potential to solve sensory ambiguity and optimize sensory processing information for functionally relevant behavior.

Generation of High Power Ultrashort Pulses in Tapered Yb-Doped PCF Through Self-Similar Compression

We present a numerical approach for analysing simultaneous amplification and compression of a chirped hyperbolic secant soliton using a tapered Yb-doped photonic crystal fiber (PCF) based self-similar compressor. Theoretical studies reveal the conservation of input soliton during the amplification process due to self-similar property, which in turn helps for high quality compression of amplified soliton. In order to satisfy the self-similar condition, we note that the Yb-doped fiber should exhibit a decreasing group velocity dispersion (GVD). Such a constraint is met using a tapered PCF in our work, which is modeled using a fully vectorial effective index method (FVEIM). Influence of spatial and spectral dependent gain, saturation energy, amplified spontaneous emission (ASE), dispersion and nonlinearity on pulse propagation are analyzed using the combined solution of dynamic rate equations (DRE) and the generalized nonlinear Schrödinger equation (GNLSE). Numerical outcomes upon solving the aforementioned equations show that a 1 ps pulse is compressed down to a pulsewidth of 55.4 fs with a peak power of 1.03 kW in a total fiber length of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L=2.5$ </tex-math></inline-formula> m and taper ratio of 2.34. Overall quality of the compression scheme is evidenced by a relatively high compression factor (F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>c</i></sub> ) = 18.12, and low percentage of pedestal energy ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$PE$ </tex-math></inline-formula> ) = 10.95 %

Millimetre Wave Kinetic Inductance Parametric Amplification using Ridge Gap Waveguide

We present the design and simulation methodology of a superconducting ridge-gap waveguide (RGWG) as a potential basis for mm-wave kinetic inductance travelling wave parametric amplifiers (KI-TWPAs). A superconducting RGWG was designed using Ansys HFSS to support a quasi-TEM mode of transmission over a bandwidth of 20–120 GHz with its internal dimensions optimised for integration with W-band rectangular waveguide. A design of an impedance loaded travelling wave structure incorporating periodic perturbations of the ridge was described. A method to simulate the nonlinear kinetic inductance via user-defined components in Keysight’s ADS was outlined, which yielded the power dependent S-parameters and parametric signal gain. A RGWG with a 30 nm NbTiN coating and 5 upmum conductor spacing, corresponding to a kinetic inductance fraction alpha sim 60% was used for the description of a KI-TWPA with 900 perturbations equivalent to a physical length 25 cm that achieved more than 10 dB of signal gain over a 75–110 GHz bandwidth via 4-wave mixing (4WM).

Comparison of electrospray and UniSpray™ ion sources with post-column hydrochloric acid infusion for 119 abuse relevant substances

Comparing the sensitivity of the Waters UniSpray™ ion source (USI) with the Waters electrospray ion source (ESI) on a Waters Xevo TQ-XS mass spectrometer with and without additional post-column infusion of low concentrated hydrochloric acid (HCl). To reduce sample volumes or increase analytical sensitivity for drugs of abuse detection in human body fluids, technological advances in mass spectrometry often target an increase in ionization efficiency. One example for this development is the USI, which claims higher ion yields and therefore higher sensitivity due to a unique geometry. Another possibility to increase sensitivity through increased ion yield is the post-column infusion of low concentrated HCl. For sensitivity comparison, we choose the, in our opinion, 119 most relevant medications and drugs of abuse. These were prepared in eleven acetonitrile solutions containing 10 analytes each and one with 9 analytes at a concentration of 1 μg/mL for each substance. For analysis, every solution was diluted 1:1000 in mobile phase A/ethylene glycol (70:30 v/v) to a concentration of 1.0 ng/mL. Solutions were analysed in triplicate on the same day interrupted by the ion source change, to decrease inter-day variations in sensitivity. Chromatographic separation was performed on a Waters 2.1 × 150 mm, 1.8 μm BEH Phenyl column kept at 60 °C on an Acquity UPLC connected to a Xevo TQ-XS detector (Waters). The standard ESI ion source or the USI ion source was mounted on the detector. Mobile phase A consisted of 20 mM ammonium formate and 0.1% formic acid (pH 3) and mobile phase B was 0.1% formic acid in methanol. Gradient elution was conducted within 6.0 min at a flow rate of 0.5 mL/min with 85% A and 15% B at the beginning and 100% B at the end. Data were acquired with the ion sources operating in the positive ionization MRM mode. Two transitions for each analyte were monitored at a constant dwell time of 10 ms over the full chromatographic run time. In an additional experiment, both ion sources were compared with additional post-column infusion of 0.0037% HCl at a flow rate of 5.0 μL/min. Injection volume was 2.0 μL in all experiments. USI provided a general gain in signal intensity (peak area): 12% ( n = 14) of the analytes showed a peak area increase up to 2-fold, 85% ( n = 101) increased between 2- and 4-fold and 3% ( n = 4) increased above 4-fold in peak area. Post-column HCl infusion with the ESI source mounted, resulted in an analyte dependent additional gain in signal intensity for 15% ( n = 18) of the analytes ranging from 2- to 21-fold. 78% ( n = 93) ranged from 0.8-fold to 2-fold. In contrast 7% ( n = 8) showed a signal decrease between 0.4-fold and 0.8-fold. The combination of USI and post-column HCl infusion resulted in an increase in peak area from 2-fold up to 62-fold compared to ESI without infusion for 91% (n = 108) of the analytes. 8% ( n = 9) where between 0.8-fold and 2-fold and 1% ( n = 2) ranged from 0.4-fold to 0.8-fold. With USI, a general improvement in analytical sensitivity under identical conditions could be achieved for all of our 119 “favorite analytes” separated in one chromatographic run. Additional post-column infusion of HCl increased sensitivity for many substances. This approach can be used very selectively when applied to certain retention time windows only. Further experiments are needed to understand how different adjustments of ESI and USI and different matrices will affect ionization. USI, especially in combination with post-column HCl infusion, is a promising tool to increase sensitivity in toxicological multi-target LC-MS/MS analysis.

Magnetic field strength dependent SNR gain at the center of a spherical phantom and up to 11.7T.

PurposeThe SNR at the center of a spherical phantom of known electrical properties was measured in quasi‐identical experimental conditions as a function of magnetic field strength between 3 T and 11.7 T.MethodsThe SNR was measured at the center of a spherical water saline phantom with a gradient‐recalled echo sequence. Measurements were performed at NeuroSpin at 3, 7, and 11.7 T. The phantom was then shipped to Maastricht University and then to the University of Minnesota for additional data points at 7, 9.4, and 10.5 T. Experiments were carried out with the exact same type of birdcage volume coil (except at 3 T, where a similar coil was used) to attempt at isolating the evolution of SNR with field strength alone. Phantom electrical properties were characterized over the corresponding frequency range.ResultsElectrical properties were found to barely vary over the frequency range. Removing the influence of the flip‐angle excitation inhomogeneity was crucial, as expected. After such correction, measurements revealed a gain of SNR growing as B0 1.94 ± 0.16 compared with B0 2.13 according to ultimate intrinsic SNR theory.ConclusionsBy using quasi‐identical experimental setups (RF volume coil, phantom, electrical properties, and protocol), this work reports experimental data between 3 T and 11.7 T, enabling the comparison with SNR theories in which conductivity and permittivity can be assumed to be constant with respect to field strength. According to ultimate SNR theory, these results can be reasonably extrapolated to the performance of receive arrays with greater than about 32 elements for central SNR in the same spherical phantom.

Multi-Instant Gain-Scheduling Stabilization of Discrete-Time Takagi–Sugeno Fuzzy Systems Based on a Time-Variant Balanced Matrix Approach

This article is devoted to the development of multi-instant gain-scheduling stabilization of discrete-time Takagi–Sugeno fuzzy systems by developing a time-variant balanced matrix approach. Many of the reported advances have provided more and more relaxed results via choosing higher order dependent gain matrices, which will be a trouble in the case of real-time implementation. Therefore, a multi-instant gain-scheduling fuzzy state-feedback controller with different working modes is given to stabilize the closed-loop systems by updating the enabled pair of lower order gain matrices in cycle. For each possible working mode, the real-time situation information of the normalized fuzzy weighting functions can be fully considered by using a set of time-variant balanced matrices in accordance to certain rules and, thus, much freedom is introduced for proposing less conservative results. More importantly, our relaxed result is obtained without requiring higher order dependent gain matrices than the existing ones, i.e., its conservatism is reduced in a more meaningful way and thus it is more conducive to real-time implementation. Finally, both the effectiveness and the superiority of the proposed results are discussed and validated in the numerical section.

Analytic theory of multicavity klystrons

Multicavity Klystron (MCK) is a high power microwave vacuum electronic device used to amplify radio frequency (RF) signals. MCKs have numerous applications, including radar, radio navigation, space communication, television, radio repeaters, and charged particle accelerators. The microwave-generating interactions in klystrons take place mostly in coupled resonant cavities positioned periodically along the electron beam axis. Importantly, there is no electromagnetic coupling between cavities. The cavities are coupled only by the flow of bunched electrons drifting from one cavity to the next. We advance here a Lagrangian field theory of MCKs with the space being represented by a one-dimensional continuum. The theory integrates into it the space-charge effects, including the so-called debunching (electron-to-electron repulsion). The corresponding Euler–Lagrange equations are ordinary differential equations with coefficients varying periodically in the space. Utilizing the system periodicity, we develop the instrumental features of the Floquet theory, including the monodromy matrix and its Floquet multipliers. We use them to derive closed form expressions for a number of physically significant quantities. Those include, in particular, the dispersion relations and the frequency dependent gain foundational to the RF signal amplification. We assume that MCKs operate in the voltage amplification mode associated with the maximal gain.