Saturation Regime Research Articles

Exceptional Points in a Spiral Ring Cavity for Enhanced Biosensing

The unique point of non-Hermitian degeneracy in an open system, known as exceptional point (EP), holds great potential in cavity quantum electrodynamics, optical signal processing, and sensing applications. For on-chip miniaturized optical cavities, auxiliary means have been employed for steering a non-Hermitian system to an EP, which typically requires either precision post-fabrication tuning or external off-chip components. Here we report a route of engineering non-Hermitian degeneracies in spiral ring microcavities without any external or temporary assistance. In such a deformed whispering gallery mode cavity which can be readily obtained through the self-rolling of pre-strained nanomembranes, the coupling strength of original non-degenerate modes can be fine tailored by spiral edge-induced backscatterings. Our theoretical results suggest that an EP can be reached by adjusting the physical scales and relative positions of inner and outer spiral edges. For EP-enhanced sensing, a functional regime upon a tiny perturbation where splitting scales as the square root of the perturbation and a saturated regime upon a sufficiently large perturbation are distinguished. For EPs in such a single-resonator system, the enhanced sensitivity towards localized perturbations and robustness towards homogenous perturbations are desirable for single-molecule detections. We expect that this work will serve as a generic guideline for realizing compact EP-empowered sensing systems and provide new insights into ultra-sensitive bioanalyses.

Diffractive Structure Function in the Dipole Picture

We calculate the contribution from the $q\bar{q}g$ component of a virtual photon state to the small-$x$ diffractive cross section in deep inelastic scattering in the saturation regime. The obtained cross section is finite by itself and a part of the full next-to-leading order result. We perform the calculation in exact kinematics in the eikonal limit, and show that the previously known high virtuality $Q^2$ and large invariant mass $M_X^2$ results for the structure functions can be extracted. We furthermore discuss the steps required to obtain the full next-to-leading order result.

Hydrological analysis of livestock water reservoir using GIS technologies

To correct this deficiency of nature, water reservoirs are built at existing water sources and water resources are managed (corrected). In order to fully and effectively use the water of rivers and streams and to prevent floods, it is necessary to correct the order of the river flow. This problem can be solved by building artificial water bodies - reservoirs. Each river is unique in terms of its source of saturation and hydrological regime. At the same time, depending on the type of management of water resources in the reservoir, and the plan for the use of collected water throughout the year, a separate plan is drawn up for each reservoir. Therefore, in studying the role of reservoirs in water resources management, attention should be paid to the characteristics of each water source and each reservoir. Water resources in our republic are extremely limited and unevenly distributed across the territory of our country. In order to correct this deficiency of nature, water reservoirs are built at existing water sources and water resources are managed. Today, geo-information systems offer their convenient capabilities in hydrological analysis. This work carried out hydrological analysis through geo-information systems. A river basin located on the base of the livestock reservoir was identified and the area was calculated. The area was found to be 392.5 km. The sequence of currents in the river basin and its total length were calculated, indicating 297.7 km. The flow density in the river basin was determined and divided into 5 categories, each category was given a separate color. The flow density was 0.76.

Continuum kinetic investigation of the impact of bias potentials in the current saturation regime on sheath formation

In this work, we examine sheath formation in the presence of bias potentials in the current saturation regime for pulsed power fusion experiments. It is important to understand how the particle and heat fluxes at the wall may impact the wall material and affect electrode degradation. Simulations are performed using the 1X-1V Boltzmann–Poisson system for a proton–electron plasma in the presence of bias potentials ranging from 0 to 10 kV. The results indicate that the sheath near the anode remains generally the same as that of a classical sheath without the presence of a bias potential. However, the sheath near the cathode becomes more prominent with a larger potential drop, a significant decrease in the electron density, and larger sheath lengths. The spatially constant current density increases to a saturation value with the increasing bias potential. For high bias potentials, the material choice needs to consider that the anode faces significantly larger particle and heat fluxes compared to the cathode. In general, the results trend with theory with differences attributed to the simplified assumptions in the theory and the kinetic effects considered in the simulations. Due to the significant computational cost of a well resolved 1X-2V simulation, only one such simulation is performed for the 5 kV case showing higher current.

Analysis of thermal noise characteristics in 10 nm metal oxide semiconductor field effect transistor

<sec>Small size metal-oxide-semiconductor field effect transistor (MOSFET), owing to their high theoretical efficiency and low production cost, have received much attention and are at the frontier of transistors. At present, their development is bottlenecked by physical limits due to equal scaling down of devices, which requires further improvement in terms of materials choice and device fabrication. As the MOSFET devices scale down to nanometer scale, on the one hand, the resulting short channel effect affects severely the thermal noise property; on the other hand, it makes the ratio of thermal noise in the gate, source, drain and substrate regions become higher and higher. However, the traditional thermal noise model mainly considers thermal noise of large-size devices, and its model does not consider the channel saturation region. In view of this, it is necessary to establish a small size MOSFET thermal noise model and analyze its characteristics.</sec><sec>At present, there are some researches on MOSFET thermal noise, but they mainly focus on the thermal noise in channel region of large size nanoscale MOSFET. In the present work, according to the device structure and inherent thermal noise characteristics, we establish a thermal noise model for MOSFETs of 10 nm feature size. The model includes contributions of substrate region, gate-source-drain region, and channel region. In the channel region is also included the thermal noise related to the device saturation regime. Using such a model, the dependence of channel thermal noise and total thermal noise on the device bias condition and device parameters are investigated, evidencing the existence of thermal noise in the device saturation regime, which are consistent with the experimental results in the literature. The thermal noise increases with the gate voltage and source-drain voltage rising as the device structure shrinks. In a temperature range of 100–400 K, the thermal noise is basically on the order of 10<sup>21</sup>, indicating that the temperature has a great influence on the thermal noise. The thermal noise model established in this work can be applied to analyzing the noise performances of small size MOSFET devices, and the conclusions drawn from the present study are beneficial to improving the efficiency, lifetime, and response speed of MOSFETs on a nanometer scale.</sec>

Exact scaling of adsorption isotherms of clay-polymer composites: Comparison to experiment

In this work, we reexamine theoretically the problem of the determination of the adsorption isotherms architecture for clay-polymer complexes using Renormalization Theory. The latter is a powerful theoretical approach giving rise to exact scaling relations near the adsorption temperature. Adsorption isotherms are expressed in terms of the evolution of the equilibrium adsorbed quantity (or simply amount adsorbed) upon the final polymer-density. First, we write exact scaling relations concerning the amount adsorbed in dilute, semi-dilute and saturation regimes, as a function of temperature, molecular-weight and final polymer-density. Second, we compare our theoretical predictions with experimental data choosing some clay–polymer composites. Finally, it is found that theory and experiment are in good agreement.

DNN-Based Physical-Layer Network Coding for Visible Light Communications

The key difference between visible light communication (VLC) and radio frequency (RF) communication is the former’s line-of-sight (LOS) transmission nature, and hence a relay node has to be adopted for VLC to extend its coverage. Physical-layer network coding (PNC) has the advantage of doubling the throughput of a two-way relay network (TWRN), where two end nodes exchange information via the help of a relay, compared with the conventional store-and-forward routing strategy. Although PNC has been studied for VLC in the literature, the state-of-the-art schemes are highly inefficient, requiring tight phase synchronization between the two end nodes, and hence difficult to realize. This paper proposes the application of a deep neural network (DNN) to a PNC VLC system, named DP-VLC, that enables misaligned phases and can deal with the light channel gains and noises in a satisfactory manner without introducing additional computation complexities. We implement DP-VLC using the universal software radio peripheral (USRP) software radio platform and a self-developed VLC optical front-end using commercial off-the-shelf (COTS) light-emitting diodes (LEDs) and photo-diodes (PDs). We find that irregular constellations generated by DP-PNC can be transmitted and recovered in a 1.5 m VLC link effectively. Experimental results show that our DP-PNC prototype performs better than conventional PNC VLC system when the signal-interference-to-noise ratio (SINR) of received optical signals is larger than 13.63 dB and can achieve a throughput of up to 77.38 Mbps in a 20 MHz channel under PNC scheme when the SINR is 22.86 dB. More importantly, we find that DP-VLC performs even better than fixed-constellation PNC system in the saturated SINR regime (e.g., 20–25 dB) where non-linear effects may happen compared with moderate SINR regimes (e.g., 10–20 dB), showing its adaptability to unpredictable impairments in optical links. Our first attempt at realizing DNN-based optical PNC in a TWRN has paved the way for future PNC-enhanced VLC systems.

On the Two-Point Function of the Potts Model in the Saturation Regime

We consider the Random-Cluster model on {mathbb {Z}}^d with interactions of infinite range of the form J_x = psi (x){mathsf {scriptstyle e}}^{-rho (x)} with rho a norm on {mathbb {Z}}^d and psi a subexponential correction. We first provide an optimal criterion ensuring the existence of a nontrivial saturation regime (that is, the existence of beta _{textrm{sat}}(s)>0 such that the inverse correlation length in the direction s is constant on [0,beta _{textrm{sat}}(s))), thus removing a regularity assumption used in our previous work (Aoun et al. in Commun Math Phys 386:433–467, 2021). Then, under suitable assumptions, we derive sharp asymptotics (which are not of Ornstein–Zernike form) for the two-point function in the whole saturation regime (0,beta _{textrm{sat}}(s)). We also obtain a number of additional results for this class of models, including sharpness of the phase transition, mixing above the critical temperature and the strict monotonicity of the inverse correlation length in beta in the regime (beta _{textrm{sat}}(s), beta _{mathrm {scriptscriptstyle c}}).

Dissipative magnetic structures and scales in small-scale dynamos

ABSTRACT Small-scale dynamos play important roles in modern astrophysics, especially on galactic and extragalactic scales. Owing to dynamo action, purely hydrodynamic Kolmogorov turbulence hardly exists and is often replaced by hydromagnetic turbulence. Understanding the size of dissipative magnetic structures is important in estimating the time-scale of galactic scintillation and other observational and theoretical aspects of interstellar and intergalactic small-scale dynamos. Here we show that, during the kinematic phase of the small-scale dynamo, the cutoff wavenumber of the magnetic energy spectra scales as expected for large magnetic Prandtl numbers, but continues in the same way also for moderately small values – contrary to what is expected. For a critical magnetic Prandtl number of about 0.3, the dissipative and resistive cutoffs are found to occur at the same wavenumber. In the non-linearly saturated regime, the critical magnetic Prandtl number becomes unity. The cutoff scale now has a shallower scaling with magnetic Prandtl number below a value of about three, and a steeper one otherwise compared to the kinematic regime.

Quantitative measurement of the charge carrier concentration using dielectric force microscopy

The charge carrier concentration profile is a critical factor that determines semiconducting material properties and device performance. Dielectric force microscopy (DFM) has been previously developed to map charge carrier concentrations with nanometer-scale spatial resolution. However, it is challenging to quantitatively obtain the charge carrier concentration, since the dielectric force is also affected by the mobility. Here, we quantitative measured the charge carrier concentration at the saturation mobility regime via the rectification effect-dependent gating ratio of DFM. By measuring a series of n-type GaAs and GaN thin films with mobility in the saturation regime, we confirmed the decreased DFM-measured gating ratio with increasing electron concentration. Combined with numerical simulation to calibrate the tip–sample geometry-induced systematic error, the quantitative correlation between the DFM-measured gating ratio and the electron concentration has been established, where the extracted electron concentration presents high accuracy in the range of 4 × 1016 – 1 × 1018 cm−3. We expect the quantitative DFM to find broad applications in characterizing the charge carrier transport properties of various semiconducting materials and devices.

Effective magnetic susceptibility in magnetoactive composites

Describing macroscopic samples made of composite material requires the development of an effective macro-continuum model where properties and microscopic arrangement of distinct phases are adequately taken into account. Here, we derive the effective magnetization behavior for compounds of magnetizable inclusions embedded in non-magnetizable medium. The homogenization is based on the dipole approximation and allows for a general formulation of the effective magnetic behavior, spanning from linear to saturation regime, for isotropic and anisotropic arrangements. For isotropic distributions presuming linear magnetization we reproduce an expression known from previous works, which proves to be very accurate in comparison to refined full-field calculations. Additionally, compelling agreement to existing experimental data is found. Consequently, we believe that our approach is of high practical relevance also in case of anisotropic distributions and beyond the linear magnetization. With a given particle arrangement and magnetization model on microscale, the expressions formulated here are obtained with low computational effort compared to homogenization based on micro-continuum approaches. The formulation can be directly implemented in a macroscopic material model for the composite of specified sample shape and solved by applying a macro-continuum approach.

Switchable Ion Current Saturation Regimes Enabled via Heterostructured Nanofluidic Devices Based on Metal-Organic Frameworks.

The use of track-etched membranes allows further fine-tuning of transport regimes and thus enables their use in (bio)sensing and energy-harvesting applications, among others. Recently, metal-organic frameworks (MOFs) have been combined with such membranes to further increase their potential. Herein, the creation of a single track-etched nanochannel modified with the UiO-66 MOF is proposed. By the interfacial growth method, UiO-66-confined synthesis fills the nanochannel completely and smoothly, yet its constructional porosity renders a heterostructure along the axial coordinate of the channel. The MOF heterostructure confers notorious changes in the transport regime of the nanofluidic device. In particular, the tortuosity provided by the micro- and mesostructure of UiO-66 added to its charged state leads to iontronic outputs characterized by an asymmetric ion current saturation for transmembrane voltages exceeding 0.3V. Remarkably, this behavior can be easily and reversibly modulated by changing the pH of the media and it can also be maintained for a wide range of KCl concentrations. In addition, it is found that the modified-nanochannel functionality cannot be explained by considering just the intrinsic microporosity of UiO-66, but rather the constructional porosity that arises during the MOF growth process plays a central and dominant role.

The Kinetics of Sorption-Desorption Phenomena: Local and Non-Local Kinetic Equations.

The kinetics of adsorption phenomena are investigated in terms of local and non-local kinetic equations of the Langmuir type. The sample is assumed in the shape of a slab, limited by two homogeneous planar-parallel surfaces, in such a manner that the problem can be considered one-dimensional. The local kinetic equations in time are analyzed when both saturation and non-saturation regimes are considered. These effects result from an extra dependence of the adsorption coefficient on the density of adsorbed particles, which implies the consideration of nonlinear balance equations. Non-local kinetic equations, arising from the existence of a time delay characterizing a type of reaction occurring between a bulk particle and the surface, are analyzed and show the existence of adsorption effects accompanied by temporal oscillations.

ZnO-based electrolyte-gated transistor (EGT) applied as multiparametric UV-sensing device

Transistors based in solution-processable semiconducting metal oxides stands out for disposable, printed and wearable electronics. Here we report a transparent and printed ZnO-based electrolyte-gated transistor (EGT), using cellulose electrolyte, which exhibited low-voltage operation, below 2 V, threshold voltage of 0.16 V, high on-state current of 0.3 mA, I on /I off ratio of 3.0×10 5 and field-effect mobility of 0.17 cm²/Vs. We have demonstrated that such EGT can be applied as an ultraviolet sensing device, showing multiparametric response with shift in its: threshold voltage (V T ), subthreshold swing (S), transconductance (g m ) and enhancement in the field-effect mobility in saturation regime ( μ s ) when exposed to different UV irradiance levels. This device achieves high I UV /I dark ratio, responsivity and EQE of 1×10 5 , 8.4×10 4 A/W and 2.7×10 6 %, respectively, presenting very stable properties when tested in ambient atmosphere, without encapsulation, and with no visible effects of ageing during the period of observation. The variation in the transistor parameters and the high values of the figures of merit for photodetectors, categorize this EGT as a multiparametric UV sensor with good performance and compatible with printed and transparent electronics. • A transparent ZnO-based electrolyte-gated transistor was successfully fabricated by a simple solution route with low-cost process; • The transistor was applied as an ultraviolet sensor that operates at low-bias; • The threshold voltage, subthreshold swing, transconductance and field-effect mobility shifted under different UV irradiance intensities, evidencing the multiparametric response characteristic of the transistor applied as sensor; • The photodetector presented high responsivity of 8.4×104 A/W and high external quantum efficiency of 2.7×106%.

Analysis of the highest energy confinement in tokamaks based on thermodynamic approach

We analyze the highest energy confinement in tokamak plasmas based on thermodynamic approach (plasma self-organization). The energy transport coefficients in the saturated confinement regimes are calculated from experiments in the T-10 tokamak. Using these coefficients, we estimate the maximal energy confinement for JET, ASDEX Upgrade, JT-60U, DIII-D and KSTAR tokamaks. Calculated energy confinement is in a good agreement with measured ones. Obtained results allow us to predict the maximal energy confinement in newly constructed machines up to a fusion reactor. The energy confinement for two basic scenarios for ITER is accessed.

Comprehensive modeling of the extrinsic transconductance for InxGa1-xAs/In0.52Al0.48As quantum-well high-electron-mobility transistors

This paper presents the comprehensive modeling of extrinsic transconductance (gm_ext) in the saturation regime for InxGa1-xAs/In0.52Al0.48As quantum-well (QW) high-electron-mobility transistors (HEMTs) with Lg from 10 μm to sub-100 nm, covering the ballistic and mobility relevant regimes. First, we fabricated and characterized two types of lattice matched (LM) channel In0.53Ga0.47As QW HEMTs on a 3-inch InP substrate. One of these was fully fabricated with an i-line stepper, yielding Lg from 10 μm to 0.5 μm, and the other was fabricated in a mix & match manner with a combination of an i-line stepper and an e-beam lithography equipment, where T-shaped gates were implemented using a tri-layer resist stack of ZEP520A-PMGI-ZEP520A in the e-beam lithography process. Using devices with a wide range of Lg values, we examined the transconductance (gm) characteristics in saturation and attempted to correlate them to analytical expressions capable of describing the carrier transport properties of the devices using only physical parameters, such as the gate capacitance (Cgi) apparent mobility (μn_app), and saturation velocity (vsat), and the series resistances (Rs and Rd). In this way, we assessed the dependences of the extrinsic transconductances of the fabricated devices on their gate lengths, with the model parameters of Cgi = 0.65 μF/cm2, μn_app = 9400 cm2/V⋅s, vsat = 4.3 × 107 cm/s and Rs = 147 Ω⋅μm. These values were observed to be well-matched with those of the physical parameters. Most importantly, we extended the proposed approach to realistically project the increase in gm_ext that could be accomplished by improving certain device parameters.

Simulation of the TAEs’ saturation phase in the Large Helical Device: MHD burst

The aim of the present study is to analyze the saturation regime of the toroidal Alfven eigenmodes (TAE) in the Large Helical Device plasma, particularly the MHD burst. The linear and nonlinear evolution of the TAEs are simulated by the FAR3d code that uses a reduced MHD model for the thermal plasma coupled with a gyrofluid model for the energetic particle (EP) species. The linear simulations indicate the overlapping of 1/2 − 1/1, 2/3–2/4 and 3/5–3/6 TAEs in the inner-middle plasma region and frequency range of 45–75 kHz, triggered by EPs with an energy of T f = 45 keV and EP β = 0.022. The nonlinear simulations show that 2/3–2/4 and 3/4–3/5 TAEs are further destabilized due to the energy transfer from the 1/1–1/2 TAE, leading to broad TAE radial overlapping and triggering of the MHD burst. The energy of the 1/1–1/2 TAE is also nonlinearly transferred to the thermal plasma destabilizing the 0/0 and 0/1 modes, inducing the generation of shear flows and zonal currents, as well as large deformations in the thermal pressure and EP density radial profiles. The nonlinear simulation reproduces the same succession of instabilities and the same frequency range with respect to the experiment. The instability propagates outward during the bursting phase, showing a large decrease of the EP density profile between the middle-outer plasma, indicating the loss of part of the EP population that explains the decrease in the plasma heating efficiency observed during the MHD burst.

Anomalous diffusion in QCD matter

We study the effects of quantum corrections on transverse momentum broadening of a fast parton passing through dense QCD matter. We show that, at leading logarithmic accuracy the broadening distribution tends at late times or equivalently for large system sizes $L$ to a universal distribution that only depends on a single scaling variable $k^2_\perp/Q^2_s$ where the typical transverse momentum scale increases with time as $\ln Q_s^2 \simeq (1+2 \beta ) \ln L - \frac{3}{2}(1+\beta )\,\ln\ln L$ up to non-universal terms, with an anomalous dimension $\beta \sim \sqrt{\alpha_s} $. This property is analogous to geometric scaling of gluon distributions in the saturation regime and traveling waves solutions to reaction-diffusion processes. We note that since $\beta >0$ the process is super-diffusive, which is also reflected at large transverse momentum where the scaling distribution exhibits a heavy tail $k_\perp^{4-2\beta }$ akin to L\'{e}vy random walks.

MGF Methods for Fixed and Gain Saturated Optically Preamplified FSO Links Impaired by Misalignments and Atmospheric Turbulence

The Gaussian approximation is commonly used to evaluate the performance of free space optical communication systems. However, other performance evaluation methods such as the saddle point approximation, Chernoff bound and the modified Chernoff bound have also been used. This paper investigates the performance of fixed and gain saturated optically preamplified communication systems limited by factors such as strong atmospheric turbulence and pointing errors using various evaluation methods. Average bit error rate results are obtained over a range of average transmitted powers for free space optical communication systems without pointing error and those with pointing error using different saturation regimes, normalised beam widths and pointing error standard deviations. Results obtained in this paper show over a propagation distance of 1500 m, a receiver diameter of 0.15 m performed better than a receiver diameter of 0.03 m when the pointing error standard deviation is 0.1. Also, a receiver diameter of 0.03 m performed better than a receiver diameter of 0.15 m when the pointing error standard deviation is 4. These results show that while larger receiving lenses performed better when pointing error effects are minimal or absent, smaller receiving lenses are better when pointing error effects are dominant. Additionally, it is shown in this paper that while fixed and gain saturated optical preamplifiers produced similar performances when the decision threshold at the receiver is adaptive, the saddle point approximation is not useful for gain saturated optically preamplified receivers. Also, results in this paper showed optimal and near-optimal adaptive decision thresholds for the modified Chernoff bound and Gaussian approximation, respectively.

High-Temperature HEMT Model

Taking into account the impact of self-heating and temperature rise effects, this work presents a physics-based analytical model for HEMTs, operating continuously from room temperature to high temperatures in linear and saturation regimes. Relying on the core École Polytechnique Fédérale de Lausanne (EPFL) HEMT model, the temperature dependence of various parameters including mobility, saturation velocity, critical electric fields, access region resistance, threshold voltage, and subthreshold slope was taken into account in the model. The accuracy of the developed model is validated by the TCAD simulation results and experimental data over a wide range of ambient temperatures from −20 °C to 500 °C.