Characteristics Of Emitter Research Articles

A bioinspired hierarchical gradient structure to maximize resilience and enhanced cooling performance in polymeric radiative cooling coatings

Despite the extensive advancements in recent years, polymeric daytime radiative cooling (PDRC) coatings face certain challenges, encompassing restricted spectral performance, susceptibility to aging, poor mechanical strength, and so forth. Herein, we proposed a facile biomimetic 500 μm thick PDRC coating, featuring a gradient distribution of pore sizes throughout the cross-section. The proposed functional structure demonstrates spectral characteristics of a near-ideal broadband emitter by attaining over 0.95 emissivity in the main atmospheric window and 0.99 reflectance in the visible spectrum. During the outdoor experiment, it achieved an 8.5 °C subambient temperature drop along with a cooling power of ∼106 W/m2 at the solar irradiance of ∼800 W/m2 and ∼650 W/m2, respectively. Experimental findings highlight that the bioinspired design results in a tensile strength of ∼9 MPa along with a tensile strain of over 200%, which is more than twice that of non-gradient porous PDRC coatings. In addition, it offers tunable surface contact angle and manifests its resilience in anti-ultraviolet and water resistance tests. Furthermore, a building energy model reveals a decrease in cooling load of between 34 and 119 kWh/(m2.year), establishing its real-world application under broader climatic regions.

Experimental studies of the characteristics of a resonant leader emitter with a single-pass amplifier

The results of experimental studies of the energy and spatial characteristics of the lidar transmitter, built according to the generator-amplifier scheme based on an organic dye with tube pumping, are presented. The choice of a single-pass traveling wave amplifier used in the experiments was determined by preserving the spectral purity of the radiation. When constructing a lidar emitter according to the generator-amplifier scheme under conditions of constant pumping density, the problem arises of choosing the ratio between the length of the active element of the generator and the length of the active medium of the traveling wave amplifier, which would ensure the maximum efficiency of the entire emitter. The main task of the work was the experimental verification of the results of theoretical studies of the narrow-band emitter of the resonant lidar in order to determine the factors affecting the choice of the ratio of the lengths of the active elements of the generator and the amplifier based on the organic dye rhodamine 6Zh with tube pumping with limited total length. The amount of effective radiated energy was used as the main criterion for evaluating the efficiency of the generator-amplifier system. The experimental results confirm the theoretical conclusions that there are optimal ratios of the lengths of the generator and the amplifier, at which the effective radiation energy is maximal. The limiting length of the amplifier and the energy of the emitter built according to the generator-amplifier circuit are limited by the increase in the intensity of the radiation amplified along the active element, as well as the increase in the intensity of the amplified noise.

Analysis of anti-clogging performance and particle transport characteristics of a stellate irrigation emitter

The service life and irrigation efficiency of drip irrigation systems are largely determined by the anti-clogging performance of the emitters. The degree and speed of clogging of the emitters are governed by the motion state of the particles in the flow channel. Computational fluid dynamics coupled discrete element method (CFD-DEM) and experiments were used to analyse anti-clogging performance and particles transport characteristics of a stellate irrigation emitter. With the angle of repose of sediment particles as the optimization objective, the key parameters of physical properties of sediment particles and container were obtained in the discrete phase model using a Plackett-Burman test, steepest climb test and Box-Behnken test. A novel evaluation method for assessing anti-clogging performance based on particles mass passing rate is proposed and its accuracy experimentally verified. Using three particles groups with different particle size distributions, the anti-clogging performance of stellate emitter was found to better than the widely used toothed emitter. In particular, the anti-clogging performance of the stellate emitter was found to be superior with the sensitive particle size of 0.03 mm. It was shown that sediment particles demonstrated retention, bonding and deposition in the inlet far away from the flow channel, the backwater area at the vertical vertex of the stellate structure and the backwater area at the joint of the stellate emitter flow channel structure units.

Plume mode instability enhanced by emitter surface poisoning in hollow cathode

The unstable plume mode of hollow cathodes should be avoided in practical applications because it severely degrades the overall cathode lifetime. In this study, we investigate the spot-plume transition and plasma stability characteristics of an unused segmented lanthanum hexaboride emitter. The expansion of the unstable plume mode region is observed during a discharge experiment. Subsequently, the segmented emitter is retrieved, the inner surface of the emitter is observed, and the work function on the surface is measured at room temperature. The emitter surface exhibits color variations with oxygen and carbon detection. The downstream edge shows the original purple color and almost no degradation in the work function. The high temperature in this region promotes the desorption of carbon and oxygen. In the spot mode, this region mainly contributes to thermionic electron emission; therefore, the discharge voltage in the spot mode does not change during the discharge experiment. Carbon or carbide is detected in the middle of the axial direction on the emitter surface, where the surface temperature is not sufficiently high to desorb carbon during discharge. Based on the surface analysis results, the dominant substance in the region where carbon is detected was lanthanum carbide. An increase in the work function is indicated in the region, which appears to increase the plasma instability. According to previous studies, an increase in the work function results in a rise in the potential in the emitter, and an increase in the electron temperature in the outside plume region induces the plasma instability. Further investigation is needed to understand the mechanism connecting the rise in the work function and the rise in the electron temperature in the plume region.

Analysis of the Physical Phenomena and Modelling Procedures of Building Heating and Cooling Emission System Energy Losses

An important research issue in assessing the energy performance of buildings concerns the modelling of the interaction between the built environment and the heating/cooling emission systems. Several methods can be used to evaluate the effect of the heating emitter characteristics, including the possible embedment in the building structure, non-uniform space temperature distribution, and the accuracy of the indoor temperature control. Generally, technical standards specify simplified, yet insufficiently validated methods, based on tabulated values. This paper outlines the main simplified procedures for assessing the efficiency of the emission subsystem, with a particular focus on the hydronic systems. It describes the essential datasets required for the analysis and highlights the interaction with phenomena related to the emitter heat loss. The simplified calculation procedures are then methodologically compared with detailed simulation tools, such as EnergyPlus, to identify differences and limitations in the models. The main discrepancies in the procedures and the required input data are highlighted, and possible strategies for improving the simplified methods are presented. A building representative of the European residential building stock is then analysed in the Italian climate using different calculation procedures. The results, in terms of thermal output of the emitter, are then analysed and compared.

Quantitative Field Emission Imaging for Studying the Doping-Dependent Emission Behavior of Silicon Field Emitter Arrays.

Field emitter arrays (FEAs) are a promising component for novel vacuum micro- and nanoelectronic devices, such as microwave power amplifiers or fast-switching X-ray sources. However, the interrelated mechanisms responsible for FEA degradation and failure are not fully understood. Therefore, we present a measurement method for quantitative observation of individual emission sites during integral operation using a low-cost, commercially available CMOS imaging sensor. The emission and degradation behavior of three differently doped FEAs is investigated in current-regulated operation. The measurements reveal that the limited current of the p-doped emitters leads to an activation of up to 55% of the individual tips in the array, while the activation of the n-type FEA stopped at around 30%. This enhanced activation results in a more continuous and uniform current distribution for the p-type FEA. An analysis of the individual emitter characteristics before and after a constant current measurement provides novel perspectives on degradation behavior. A burn-in process that trims the emitting tips to an integral current-specific ideal field enhancement factor is observed. In this process, blunt tips are sharpened while sharp tips are dulled, resulting in homogenization within the FEA. The methodology is described in detail, making it easily adaptable for other groups to apply in the further development of promising FEAs.

Dynamic open set specific emitter identification via multi‐channel reconstructive discriminant network

AbstractSpecific emitter identification (SEI) is an emerging device authentication technology, which depends on the inherent hardware characteristics of wireless devices. By analysing the received signal, the hardware characteristics of a specific emitter can be extracted at the receiver and used for device authentication and association. Most of the existing SEI schemes focus on the identification under closed sets. In view of the explosive growth of the number of IoT devices, based on generative adversarial networks, this study proposes a method that considers the identification of unknown emitters. The reconstruction network to reconstruct the signals of the known class and fully train the feature space of the signals of the known class is designed. In the discriminator, two channels are specifically designed to perform anomaly detection for unknown signals and end‐to‐end closed‐set classification for known signals. In order to better reject unknown signals and accept known signals, Receiver operating characteristic curve and Youden index are used to determine the optimal threshold for anomaly detection. Under the given optimal threshold conditions, the identified threshold points have larger True Positive Rate. In addition, the time‐frequency feature combination vector is designed to reveal the essential characteristics of emitters. The experimental results on the real‐world datasets collected from universal software radio peripherals in short‐range communication scenario show that compared with the existing open‐set recognition methods such as C2AE, Openmax and SoftMax, the average recognition accuracy of the proposed framework improved by 0.08, 0.15, and 0.2 respectively, and the Marco‐F1 score improved by 0.05, 0.1, and 0.16, respectively, which proves the superiority of the proposed framework. In addition to identifying unknown and known Universal software radio peripherals in this article, some potential and widespread applications of the proposed framework include access user security authentication in IoT, such as Hack RF and Blue tooth devices. In addition, as a relatively general signal processing framework, the model can be used for air safety management and maritime ship identity authentication in civil aspects. In the military aspect, it can be used in electronic support and various signal reconnaissance scenarios, such as automatic signal modulation recognition in open set scenarios, individual identity determination of radar emitter and unknown working state identification of transmitters, which proves reference for subsequent research on open‐set signal recognition.

Analysis of the Hydraulic Performances of a New Liquid Emitter Based on a Leaf Vein Concept

The leaf-vein drip irrigation emitter is a new type of drip emitter based on a bionic structure able to support shunting, sharp turns, and increased dissipation. In the present work, the results of twenty-five tests executed in the framework of an orthogonal design strategy are presented in order to clarify the influence of the geometrical parameters of the flow channel on the hydraulic characteristics of such emitter. The corresponding flow index and head loss coefficient are determined through numerical simulations and model testing. The results show that the flow index of the flow channel is 0.4970∼0.5461, which corresponds to good hydraulic performances. The head loss coefficient of the flow channel is 572.74∼3933.05, which in turn indicates a good energy dissipation effect. The order of influence of the leaf vein flow channel parameters on the flow index can be represented in a synthetic way as a > b > c > d > e, where (a) is the width of the inlet, (b) is the horizontal distance of the front water inlet, (c) is the vertical distance of the inner edge of the front end, (d) is the horizontal distance of the rear water outlet and (e) is the vertical distance of the outer edge of the front end. The flow index increases with d, decreases with a, first decreases, and then increases with b, and first increases and then decreases with the increase of c and e. The coefficient (R²) of the fitted model related to geometric parameters and flow index is 0.9986–0.9999. The relative errors among experimental testing, simulation calculation and predictive estimates are shown to be less than 5%.

Demultiplexed single-photon source with a quantum dot coupled to microresonator

The characteristics of a single-photon emitter based on a semiconductor quantum dot, such as their indistinguishability and brightness, depend on the stability of the recombination channel, which can switch spontaneously between exciton and trion. We show that dominant recombination through neutral exciton states can be achieved by careful control of the doping profile near an epitaxial InAs/GaAs quantum dot placed in a columnar microcavity with distributed Bragg reflectors. The Hong-Ou-Mandel experiments carried out in the fabricated device demonstrate the degree of indistinguishability of 91% of successively emitted single photons within 242 ns at an efficiency of 10% inside a single-mode optical fiber. The achieved brightness made it possible to implement spatio-temporal demultiplexing of photons in six independent spatial modes with an in-fiber generation frequency of more than 0.1 Hz.

Development of CoFe2O4 scaffolded reduced graphene oxide/carbon nanotube emitter for field emission application

The field emission (FE) characteristics of CoFe2O4/rGO/CNT (CGC) emitter is reported by comparing it with that of CoFe2O4/rGO (CG), CoFe2O4/CNT (CC), rGO/CNT (GC) and individual emitter. Among them, current density was high for CGC emitter i.e. 3.329 mA cm−2 for applied field of 5.4 V μm−1 as well as a good emission current stability. These superior FE characteristics of CGC emitter is due to the decreased bandgap as well as work function and, due to the sharp edges provided by CNTs and CoFe2O4 nanoparticles which results in easy electron liberation. A detailed mechanism for enhanced FE performance has been proposed based on obtained results.

Preclinical acoustic efficiency evaluation of bionic ear

Objective. To study the major acoustic properties of the prototype of bionic ear developed in order to confirm its functional performance.
 Materials and methods. Acoustic properties of the bionic ear were measured using Random Phase MultiSine signal in a test bench, which simulated the implant-emitter-osseous tissue-inner ear system. The resulting pulse response was converted to the target characteristics: FR and group lag. Experiments were carried out for -6dB signal level, 10 times for each of the methods used.
 Results. Microtia is a congenital auricular hypoplasia or aplasia (anotia) which often involves impairment or total loss of hearing. One way to rehabilitate this type of patients is to use bone-conducting apparatuses (bone anchored hearing aids), which allow to compensate for the functional component but not to restore facial aesthetics. This paper deals with major acoustic properties of the prototype bionic ear we have previously developed, in order to confirm its functional performance for clinical use. Our analysis of acoustic characteristics of the bionic ear system showed the frequency response was uniform enough in extended voice frequency range (100 to 10000 Hz). The experimental research demonstrated that operating time of the prototype bionic ear to battery depletion is 10 h 26 min with 25 % amplification, 10 h 05 min with 50 % amplification, 9 h 48 min with 75 % amplification.
 Thus, the acoustic characteristics of the vibratory emitter were determined, which confirmed that the bionic artificial ear was eligible for clinical testing.
 Conclusions. Major frequency response of the vibratory emitter was measured, and confirmed that preclinical studies were successful and the bionic ear was eligible for clinical testing.

Operation of a Light Emitter on Biogas

Рurpose of research. One of the ways to reduce the consumption of thermal energy for heating large-volume premises is a method based on the use of local systems, which include gas-radiant heating systems using light emitters. It is proposed to operate a light emitter on biogas. To determine the possibility of operation of a light emitter on biogas, it is necessary to calculate the optimal parameters of operation of a light emitter.Methods. The research was based on the scientific works of scientists on the theory of gorenje gas mixtures and the introduction of new design solutions of gas emitters. In the course of the study, methods of optimization and calculation of gas-burning equipment were used. In order to calculate the optimal operating parameters, it is required to conduct a study of the gorenje gorenje of biogas, and to obtain the dependence of the combustion temperature. It is necessary to make changes, confirmed by calculations, to the existing design and operating mode of the light emitter operating on natural gas for operation on biogas.Results. The features of biogas combustion are studied and the maximum gorenje gorenje temperature is determined. The possible operation of a light radiator on biogas, with a set of optimal parameters, is proved.Conclusion. The change in the design characteristics of the light emitter during operation on biogas is justified. The results obtained can be used in the pre-design development of a new design of a light emitter for biogas of various compositions.

Composite Multiferroic Terahertz Emitter: Polarization Control via an Electric Field

Electrical control of conjugate degrees of freedom in multiferroics provides the advantage of reducing energy consumption to femto- and even attojoules per switch in spintronics and memory devices. This is achieved through the development of technologies that make it possible to fabricate artificial materials with constantly improving properties. Here, we present the design, physics, and characteristics of a composite multiferroic spintronic emitter, which provides electrical control of the emitted terahertz (THz) wave polarization. The effect is due to electrical control of the magnetization in a high-quality magnetostrictive superlattice, ${\mathrm{Tb}\mathrm{Co}}_{2}/\mathrm{Fe}\text{\ensuremath{-}}\mathrm{Co},$ deposited on an anisotropic piezoelectric substrate. In our approach, several mechanisms are realized in the system simultaneously: the strain-mediated coupling of the magnetic and piezoelectric subsystems, which operate in the range of the spin-reorientation transition of the magnetic superlattice, and THz-wave generation in the superlattice by an optical femtosecond pulse. This provides flexibility and control of the set of parameters. We determine the magnetoelectric parameter, which is responsible for THz polarization control. Our results offer a significant fundamental insight into the physics of composite multiferroic systems that can be used for applications of multiferroicity, primarily for THz spintronic emitters. We believe that our findings represent a decisive step towards technologies for other types of spintronic and memory devices.

Instabilities of electrical properties of He-induced W “fuzz” within the pre-breakdown and breakdown regimes

The investigation of the He-induced W “fuzz” electrical properties was carried out. For the research, an automated experimental setup was designed. The setup was based on a vacuum chamber operated under high vacuum conditions (~ 10−7 Pa). The vacuum diode under investigation comprised of a flat W “fuzz” cathode with an area of about 1 cm2 and a 2 mm radius cylindrical copper anode with a hemisphere tip. The cathode-anode distance was about 100 μm. The voltage applied was up to 10 kV. A DAC/ADC module controlled an HV power supply and automatically registered currents and voltages in the circuit. The effect of a spontaneous change in the emissive ability of the investigated surface area was observed. These changes can vary significantly in magnitude. Large-scale changes can lead to a permanent increase in the emissive ability of a specific area or to a breakdown of the gap. Small changes, as a rule, are reversible, have a stepped nature, and make it difficult to record and interpret the current-voltage characteristics of the field emitter.

A large-area single-filament infrared emitter and its application in a spectroscopic ethanol gas sensing system

Nondispersive infrared (NDIR) spectroscopy is an important technology for highly accurate and maintenance-free sensing of gases, such as ethanol and carbon dioxide. However, NDIR spectroscopy systems are currently too expensive, e.g., for consumer and automotive applications, as the infrared (IR) emitter is a critical but costly component of these systems. Here, we report on a low-cost large-area IR emitter featuring a broadband emission spectrum suitable for small NDIR gas spectroscopy systems. The infrared emitter utilizes Joule heating of a Kanthal (FeCrAl) filament that is integrated in the base substrate using an automated high-speed wire bonding process, enabling simple and rapid formation of a long meander-shaped filament. We describe the critical infrared emitter characteristics, including the effective infrared emission spectrum, thermal frequency response, and power consumption. Finally, we integrate the emitter into a handheld breath alcohol analyzer and show its operation in both laboratory and real-world settings, thereby demonstrating the potential of the emitter for future low-cost optical gas sensor applications.

Radar Emitter Identification Based on Fully Connected Spiking Neural Network

In the face of the increasing complex electromagnetic environment and new radar system, it is difficult to extract radar emitter characteristics based on manual mode to meet requirements of modern cognitive electronic warfare. In order to improve the intelligence level of radar emitter identification, a new method based on Spiking Neuron Network (SNN) for radar emitter identification is proposed in this paper. Firstly, five kinds of common radar signals are converted into two-dimensional gray scale images by using time-frequency analysis method. Then, the images are converted into spikes by Poisson coder, which are put into a fully connected spiking neural network for training and emitter identification. Finally, the simulation results prove the validity of this method by comparing with the traditional neural network.

Characteristics of Bow-Tie Antenna Structures for Semi-Insulating GaAs and InP Photoconductive Terahertz Emitters.

This work presents a study of photoconductive (PC) terahertz (THz) emitters based upon varied bow-tie (BT) antenna structures on the semi-insulating (SI) forms of GaAs and InP. The BT antennas have electrodes in the form of a Sharp BT, a Broad BT, an Asymmetric BT, a Blunted BT, and a Doubled BT. The study explores the main features of PC THz emitters for spectroscopic studies and sensors application in terms of THz field amplitude and spectral bandwidth. The emitters’ performance levels are found to depend strongly upon the PC material and antenna structure. The SI-InP emitters display lower THz field amplitude and narrower bandwidth compared to the SI-GaAs emitters with the same structure (and dimensions). The characterized Doubled BT structure yields a higher THz field amplitude, while the characterized Asymmetric BT structure with flat edges yields a higher bandwidth in comparison to the sharp-edged structures. This knowledge on the PC THz emitter characteristics, in terms of material and structure, can play a key role in future implementations and applications of THz sensor technology.

Very Robust Spray-Synthesized CsPbI3 Quantum Emitters with Ultrahigh Room-Temperature Cavity-Free Brightness and Self-Healing Ability.

Although colloidal lead halide perovskite quantum dots (PQDs) exhibit desirable emitter characteristics with high quantum yields and narrow bandwidths, instability has limited their applications in devices. In this paper, we describe spray-synthesized CsPbI3 PQD quantum emitters displaying strong photon antibunching and high brightness at room temperature and stable performance under continuous excitation with a high-intensity laser for more than 24 h. Our PQDs provided high single-photon emission rates, exceeding 9 × 106 count/s, after excluding multiexciton emissions and strong photon antibunching, as confirmed by low values of the second-order correlation function g(2)(0) (reaching 0.021 and 0.061 for the best and average PQD performance, respectively). With such high brightness and stability, we applied our PQDs as quantum random number generators, which demonstrably passed all of the National Institute of Standards and Technology's randomness tests. Intriguingly, all of the PQDs exhibited self-healing behavior and restored their PL intensities to greater than half of their initial values after excitation at extremely high intensity. Half of the PQDs even recovered almost all of their initial PL intensity. The robust properties of these spray-synthesized PQDs resulted from high crystallinity and good ligand encapsulation. Our results suggest that spray-synthesized PQDs have great potential for use in future quantum technologies (e.g., quantum communication, quantum cryptography, and quantum computing).

Disturbance cue communication is shaped by emitter diet and receiver background risk in Trinidadian guppies.

In animal communication systems, individuals that detect a cue (i.e., “receivers”) are often influenced by characteristics of the cue emitter. For instance, in many species, receivers avoid chemical cues that are released by emitters experiencing disturbance. These chemical “disturbance cues” appear to benefit receivers by warning them about nearby danger, such as a predator’s approach. While the active ingredients in disturbance cues have been largely unexplored, by-products of metabolized protein are thought to play a role for some species. If so, the content (quality) and volume (quantity) of the emitter’s diet should affect their disturbance cues, thus altering how receivers perceive the cues and respond. Guppies Poecilia reticulata are a species known to discriminate among disturbance cues from different types of donors, but dietary variation has yet to be explored. In this study, we found evidence that diet quality and quantity can affect disturbance cues released by guppy emitters (i.e., experimental “donors”). Receivers discriminated between donor cue treatments, responding more strongly to cues from donors fed a protein-rich bloodworm diet (Experiment 1), as well as an overall larger diet (Experiment 2). We also found that receivers exposed to higher background risk were more sensitive to disturbance cue variation, with the strongest avoidance responses displayed by high-risk receivers toward disturbance cues from donors fed the high-quality diet. Therefore, diet, and perhaps protein specifically, affects either the concentration or composition of disturbance cues released by guppies. Such variation may be important in information signaling in social species like the guppy.

Characteristics of thermophotovoltaic emitter based on 2D cylindrical gear grating

A novel wavelength-selective thermophotovoltaic (TPV) emitter is proposed and analyzed with high emissivity. The suggested TPV emitter is based on cylindrical gear grating of tungsten with SiO2 spacer. The design geometry is studied to maximize its emissivity up to wavelength of 2.0 μm. The effect of oblique incidence at different polarizations on the design emissivity is also introduced. Additionally, the inductor-capacitor (LC) model is used to elucidate the behavior of magnetic resonance of the proposed grating. The reported TPV emitter exhibits high emissivity properties over large spectra range from ultraviolet to mid-infrared with spectral efficiency of 74% and 95% at 1000 and 2000 K, respectively. Further, high emissivity is achieved over a wide range of incident angles from 0 to 65° for the two polarized waves. The achieved perfect emissivity is due to the coupling between surface plasmon polariton, magnetic polariton and intrinsic loss of the tungsten material.