Emitter Parameters Research Articles

Tunable ultrabroadband hybrid terahertz emitter combining a spintronic and a GaSe source

Terahertz (THz) time-domain spectroscopy (TDS) is a sensitive approach to material characterization. It critically relies on a sufficiently large bandwidth, which is not straightforwardly available in typical THz-TDS systems that are often limited to below 3 THz. Here, we introduce a hybrid THz-source concept based on a spintronic THz emitter (STE) deposited onto a thin, free-standing GaSe nonlinear crystal. By tuning the magnetic state and the phase-matching parameters of the hybrid emitter, we generate an ultrabroadband spectrum covering the full range from 1 to 40 THz. We achieve significantly enhanced spectral amplitudes above 10 THz compared to the bare STE, resulting in ultrashort THz-pulse durations down to 32 fs. Finally, we demonstrate the straightforward tunability of the shape of the few-cycle pulse from symmetric to antisymmetric.

Theoretical Study of Quantum Efficiency and Spectral Response of Solar Cells

A theoretical study of Quantum Efficiency (QE) and Spectral Response (SR) of solar cells was done in order to suggest ways in which related parameters could be optimized for maximum conversion efficiency of solar cells. Secondary data for the base, emitter and total parameters of QE and SR were obtained. MATLAB was employed in plotting and analysing these data across different diffusion lengths. From the results obtained, it was observed that when the value of the Emitter Diffusion Length (EDL) was varied from 0.3μm to 0.5μm, the emitter and total values of QE increased by about 700% at wavelength 300nm – 400nm. In the case of SR, it was observed that when there was an increase in the Base Diffusion Length (BDL) from 20μm to 50μm, there was an increase of about 26% at wavelength 800nm – 900nm. A rise in the diffusion length was seen to increase both the QE and SR of the cell. Thus, it can be suggested that an increase in the emitter and base diffusion length of a solar cell leads to a decrease in the recombination charges in the cell, giving more time for the charge carriers to exit the cell.

Optimization of a Ge2Sb2Te5-Based Electrically Tunable Phase-Change Thermal Emitter for Dynamic Thermal Camouflage.

Controlling infrared thermal radiations can significantly improve the environmental adaptability of targets and has attracted increasing attention in the field of thermal camouflage. Thermal emitters based on Ge2Sb2Te5 (GST) can flexibly change their radiation energy by controlling the reversible phase transition of GST, which possesses fast switching speed and low power consumption. However, the feasibility of the dynamic regulation of GST emitters lacks experimental and simulation verification. In this paper, we propose an electrically tunable thermal emitter consisting of a metal-insulator-metal plasmonic metasurface based on GST. Both optical and thermal simulations are conducted to optimize the structural parameters of the GST emitter. The results indicate that this emitter possesses large emissivity tunability, wide incident angle, polarization insensitivity, phase-transition feasibility, and dynamic thermal camouflage capability. Therefore, this work proposes a reliable optimization method to design viable GST-based thermal emitters. Moreover, it provides theoretical support for the practical application of phase-change materials in dynamic infrared thermal camouflage technology.

IMPROVEMENT OF THE METHODOLOGY FOR OPTIMIZING THE PARAMETERS OF COMPLEX SYSTEMS UNDER THE INFLUENCE OF THERMAL LOAD SOURCES

The article investigates some aspects of solving the problem of constructing mathematical models for optimizing the parameters of local laser action on multilayer microbiological systems. The constraints on the desired laser parameters and on the temperature field in the material subject to laser fission are set. Verification of compliance with the restrictions on not exceeding the maximum value of the temperature field requires multiple calculations of the corresponding temperature field in the microbiological material. Control over the temperature field limits ensures the viability of its parts during the biotechnological process of laser fission. To construct adequate optimization mathematical models, the author substantiates the adequacy of the computational mathematical models describing the state of a microbiological system under the action of laser radiation sources. A multi-point boundary value problem with a system of inhomogeneous differential heat conduction equations for a multilayer microbiological medium is investigated and the correctness of this problem is substantiated for minor perturbations of the right-hand side of the differential equation. The results obtained in the article guarantee the adequacy of applied optimization mathematical models for finding rational values of technical parameters of laser emitters. In order to improve the accuracy of optimization of the technical parameters of laser emitters, the article presents a mathematical modeling of the preparatory stage of embryo defrosting. The presented mathematical models and methods of their implementation are necessary to improve the quality of embryo defrosting. Improvement of the methodology for solving applied biotechnological problems will certainly lead to the complication of mathematical models, but it will increase the accuracy of calculation and optimization of technical parameters of the biotechnological process of laser embryo division.

An Estimation of Signal Emitter Parameters from the Amplitude Measurements by an ESM Receiver

An Estimation of Signal Emitter Parameters from the Amplitude Measurements by an ESM Receiver

Screening and optimization of metal-insulator-metal selective emitter in thermophotovoltaic system

In thermophotovoltaic (TPV) systems, it is crucial that the selective emitters can tailor emission spectrum to match the bandgap of photovoltaic (PV) cells and largely enhance the system efficiency. In this work, a metamaterial emitter based on the metal-insulator-metal (MIM) structure is proposed to obtain the high energy conversion efficiencies. The geometric parameters of MIM emitter have been investigated to obtain an excellent radiation spectrum of emitter composed of W and HfO2. The excellent emission performance of MIM emitter is attributed to the excitation of surface plasmon polariton (SPP) and cavity resonance, and the structure of MIM emitter is insensitive for different polarization modes. The 21 material combinations of MIM emitters have been screened to obtain the optimal emitter matching GaSb and InGaAsSb cells. This work identifies the crucial role of structure and materials into the emitter of a TPV system. In the evaluation of MIM emitter and TPV System, when the operating temperature of emitter increases from 1400[Formula: see text]K to 2000[Formula: see text]K, the system efficiency of optimal W/HfO2/W MIM emitter increases from 20.26% to 30.41%, while the output electric power increases from 3.59[Formula: see text]kW/m2 to 42.48[Formula: see text]kW/m2. The phenomenon indicates that the MIM emitter with the optimal material combinations and geometric parameters can significantly improve the matching degree with GaSb and InGaAsSb cells. Our results will be helpful to expand the optimization scope of metamaterial emitters in TPV systems.

Elucidating The Horizontal Orientation Mechanism of Emissive Transition Dipole Moment in A Series of Stick‐Like Delayed Fluorescent Emitters for Ultra‐High‐Efficiency OLEDs

AbstractThe horizontal orientation of the emissive transition dipole moment (TDM) of emissive molecules is a crucial factor in improving the efficiency of organic light‐emitting diodes (OLEDs). However, the mechanism of this horizontal orientation remains unclear. Herein, to elucidate the horizontal orientation mechanism of the TDM of the molecules in thermally activated delayed fluorescent (TADF) emitters, the relationship between the horizontal orientation ratio (Θ) of the TDM and the key parameters of stick‐like TADF emitters dispersed in carbazole‐based host materials is systematically and quantitatively investigated. The introduction of functional groups containing weak CH/n (n = O, N) hydrogen bonds into the host material is found to significantly increase the Θ values up to 30%. The physical parameters of the dispersed emitter exhibit a strong relationship with the Θ values, with the following influence order: glass transition temperature (Tg) ≥ total surface area of the largest π‐plane and the corresponding parallel π‐plane > molecular weight > aspect ratio > permanent dipole moment. The Tg value of the host material is another key parameter determining the Θ values. By using a P=O‐based host material, namely mCP2PO, a high PLQY of 97%, a high Θ value of 88%, and a sky‐blue OLED with an EQE of 37.6% are simultaneously realized.

The Study of Structural Optimization on Hydraulic Performance and Anti-Clogging Performance of Labyrinth Drip Irrigation Emitters

The core component of a properly functioning drip irrigation system is the drip irrigation emitter. Irrigation water containing impurities and sand particles can easily lead to clogging of the drip irrigation emitter, reducing the efficiency of the drip irrigation system. In this paper, orthogonal tests were used to optimize the flow channel structure, combined with the computational fluid dynamics–discrete element method (CFD-DEM) to analyze the flow index and sand particle motion characteristics. Clear water tests and short-cycle anticlogging tests were used to validate the results of the numerical simulation, and the relationship between the hydraulic performance and anti-clogging performance was revealed via linear regression. The results showed that the structural parameters of drip irrigation emitters were important factors affecting the flow index and sand movement characteristics. The order from largest to smallest was the turning angle, amount of interdental reference, flow channel depth, flow channel width, and width of the top base. The sand passage rate and the percentage decrease in velocity can be used as important indicators of anti-clogging performance, and there was a negative correlation between the two indicators. The flow channel with a 65° turning angle had the lowest flow index, and the sand passage rate can reach up to 91.48%; the reason was that the main flow region velocity was higher, the vortex region and the sand energy loss were small, which was not easy to clog. The equation for the relationship between flow index and sand passage rate was a negative correlation for drip irrigation emitters between a 65° and 75° turning angle. The drip irrigation emitter with a 65° turning angle had better hydraulic performance and anti-clogging performance.

Tunability of a broad-band selective metamaterial emitter in thermophotovoltaic systems

In a thermophotovoltaic (TPV) system, it is crucial to realize the excellent matching between the radiation spectrum of emitter and the photovoltaic cells, which will be helpful to improve the conversion efficiency and output power. We have focused on the study of tunability of a multi-layer metamaterial (MTM) selective emitter with the dielectric-metal pyramid structure to screen and optimize the material combinations and geometric parameters for matching GaSb and InGaAsSb cells. It is found that the selective metamaterial emitter composed of various material combinations can achieve the broadband emission, which is formed by overlapping of multiple resonance peaks at the region below the cutoff wavelength. The MTM emitters composed of W/Ta/Mo−BeO, W/Ta/Mo−SiO2, W/Mo−Si3N4, and W−HfO2, respectively, are characterized by the extraordinary emission spectrum for matching GaSb cells. We have selected the material combination of Ta−SiO2 with the excellent emission spectrum to obtain an excellent emission spectrum matching the bandgap of GaSb cells by optimizing the geometric parameters. The optimal geometric parameters of emitter composed of the material combination of Ta−SiO2 have been obtained. Moreover, the efficiency and output power of TPV system reaches 17.52% and 0.025 W/cm2 at 1000 K and even approaches 36.27% and 0.79 W/cm2 at 1500 K. It is indicated that the optimized emitter can achieve the near-perfect utilization of in-band photons and well suppress the sub-band loss. It can be also found that the MTM emitter composed of W−HfO2 exhibits an excellent matching degree with InGaAsSb cells. It is also demonstrated that the MTM emitter with pyramid structure has a good scalability for matching other available PV cells. The high conversion efficiency realized by materials screening and geometric optimization provides a potential pathway for the design of TPV emitter.

Effect of nanoshell geometries, sizes, and quantum emitter parameters on the sensitivity of plasmon-exciton hybrid nanoshells for sensing application

A proposed nanosensor based on hybrid nanoshells consisting of a core of metal nanoparticles and a coating of molecules is simulated by plasmon-exciton coupling in semi classical approach. We study the interaction of electromagnetic radiation with multilevel atoms in a way that takes into account both the spatial and the temporal dependence of the local fields. Our approach has a wide range of applications, from the description of pulse propagation in two-level media to the elaborate simulation of optoelectronic devices, including sensors. We have numerically solved the corresponding system of coupled Maxwell-Liouville equations using finite difference time domain (FDTD) method for different geometries. Plasmon-exciton hybrid nanoshells with different geometries are designed and simulated, which shows more sensitive to environment refractive index (RI) than nanosensor based on localized surface plasmon. The effects of nanoshell geometries, sizes, and quantum emitter parameters on the sensitivity of nanosensors to changes in the RI of the environment were investigated. It was found that the cone-like nanoshell with a silver core and quantum emitter shell had the highest sensitivity. The tapered shape of the cone like nanoshell leads to a higher density of plasmonic excitations at the tapered end of the nanoshell. Under specific conditions, two sharp, deep LSPR peaks were evident in the scattering data. These distinguishing features are valuable as signatures in nanosensors requiring fast, noninvasive response.

Numerical investigation of the impacts on the primary cement in a new thermal approach for plug and abandonment operations

The advancement of Plug and Abandonments (P&A) procedures is pivotal for reducing the costs associated with current operations. A novel technology concept proposes a heat emitter that will produce enough energy to melt the casing steel without critically affecting the cement layer. However, recent studies concerning this proposal have not given enough attention to the potential impact on the primary cement, which is a crucial material to guarantee the plug's integrity. This study models the heat emitter as a thermite mixture with constant volumetric heat generation, and the oil well structure was approached as a 2-D axisymmetric domain. The finite volume method with a static melting/solidification model is employed to solve the governing equations numerically. A C++ code was developed and compared with the commercial software Ansys® Fluent was performed to verify the present code. The thermal parameters of the heat emitter, including density (1983.6 and 2192.4 kg m−3), specific heat (919.6 and 1016.4 J kg−1 K−1), conductivity (5 and 15 W m−1 K−1), latent heat (1267.79 and 1147.05 kJ kg−1), volumetric heat generation (104.59 and 115.6 MW m−3), and reaction time (71.25 and 78.75 s), are evaluated through a 26 factorial design. The responses analyzed are the maximum melted volume of steel and the volume of cement critically affected. The high variability associated with thermal conductivity indicated a strong dependence on this parameter. Most importantly, this study highlights that melting the casing steel could unintentionally degrade the cement layer, increasing potential leakages paths and integrity problems.

Analysis of internal flow characteristics and determination of the core structural parameters of a stellate labyrinth channel irrigation emitter

The hydraulic and anti-clogging performance of irrigation emitters are mainly governed by the internal flow characteristics in the flow channel. Computational fluid dynamics (CFD) and experiments were used to analyse internal flow characteristics and determine the key structural parameters of a stellate labyrinth channel irrigation emitter. Through experimental verification, the realisable k-ε model provided the best results for simulating the flow field. Five structural parameters of stellate labyrinth channel emitter were selected to study the influence on the flow characteristics inside the flow channel comprehensively. The velocity fields and profiles are presented along the stellate labyrinth channel. Turbulence properties and turbulent kinetic energy of flow inside the stellate labyrinth channel are analysed and discussed. The vortex zones consume energy and promote the deposition of particles. The swirling motion zone in stellate labyrinth channel emitter flow channel must be described to analyse flow characteristics. The advanced Q-criterion method was applied to identify and characterise the vortex zones in the stellate labyrinth flow channel. Through analysis results of the influence of different structural parameters on velocity fields, turbulence properties, and swirl characteristics, it was shown that a, r, h, and θ are main structural parameters that affect the flow characteristics in stellate labyrinth channel irrigation emitter. The results of this study provide references for the design theory of the new types of flow channel emitter.

Dual emission from donor-modified MR-TADF emitter: Evidence for coexistence of TICT and MR excited states

Multiresonance thermally activated delayed fluorescence (MR-TADF) materials have attracted wide attention due to their large radiation rate constant (kr) and high color purity. Attaching additional electron donor or acceptor was established as an effective strategy to optimize the optoelectronic parameters of MR-TADF emitters, such as the reverse intersystem crossing rate constant (kRISC). However, these is no report that both the MR and twisted intramolecular charge transfer (TICT) excited states can be detected simultaneously from a single molecule yet. Herein, a group of MR-TADF emitters BNCz-SAF, BNCz-DMAC and BNCz-PXZ are designed and synthesized through introducing different donor, spiroacridine (SAF), acridine (DMAC) and phenoxazine (PXZ), at the para-site of the boron atom of a famous MR core BNCz. All these three emitters maintained intrinsically excellent properties of MR-TADF molecules with high kr over 108 s−1 and high kRISC over 105 s−1. Interestingly, with gradually increasing the donor strength to PXZ, dual emissions from the MR core and the CT excited state between PXZ and BNCz moieties are detected simultaneously for BNCz-PXZ in either strong polar solvents or doped film in highly polar host, both of which are confirmed as the TADF with the lifetimes of about 4 μs. Independent of the host, the organic light-emitting diodes (OLEDs) of BNCz-SAF and BNCz-DMAC exhibited sky-blue electroluminescence with high external quantum efficiencies (EQEmax) of 25.3% and 23.8% and narrow full widths at half maximum (FWHM) of 23–25 nm. In contrast, BNCz-PXZ exhibited a single-band (482 nm) sky-blue EL in mCBP host with EQEmax of 20.9%, while exhibited dual-band EL at 484 and 548 nm from MR and CT states in higher polar host DPEPO, realizing a warm white emission with CIE (0.31, 0.48) and EQEmax of 16.4%. For the first time both the short-range CT (i.e. MR) and long-range CT (i.e. TICT) excited states are experimently detected and confirmed simultaneously from a donor-modified B,N-based polycyclic hydrocarbon skeleton, which may be a potential strategy to bulid up broad-spectra or white emission.

Ensemble Learning Simulation Method for Hydraulic Characteristic Parameters of Emitters Driven by Limited Data

The emitter is one of the most critical components in drip irrigation. The flow path geometry parameters have a significant effect on the emitter’s hydraulic performance and have a direct impact on the emitter’s irrigation uniformity and lifetime. The hydraulic characteristics of the emitter are the key indicators of its performance. However, obtaining the hydraulic characteristics of the emitter is complex. Typically, only a small number of calibrations are performed for specific equipment models, making it difficult to obtain the parameter. Therefore, limited data corresponding to the morphological parameters and the flow rate were simulated using the FLUENT software, and the influence of the characteristics was analyzeanalyzed, based on which a flow rate prediction model was constructed using the ensemble learning (CatBoost) model. The extended data set was generated by stochastic simulation and parameter fitting. The flow index and flow coefficient prediction model were built and evaluated using the CatBoost model again with the augmented data set as a benchmark. The results show that the significant correlation between the geometric structure and the flow index and flow coefficient provides the basis for the correlation model. CatBoost can fit the complex nonlinear relationships between the parameters well, achieving excellent simulation accuracy for the flow rate (R2 = 0.9987), flow index (R2 = 0.9961), and flow coefficient (R2 = 0.9946), where the path width has the highest importance score in the model construction for the flow index (score = 55.97) and flow coefficient (score = 45.2). Furthermore, the CatBoost models used in this study achieved the best prediction results compared to seven typical models (XGBoost, Bagging, Random Forest, Tree, Adaboost, and KNN).

The effects of Ar + N2 plasma power-based attachment of metal nanoparticles on the electron field emission properties of carbon nanotubes

An ideal vacuum-based electron emitter requires a low turn-on field and quick emission processes. Carbon nanotubes (CNTs) have great potential for emission applications, but have some limitations that affect their performance. Consequently, they can benefit from the alteration of their surface morphology upon decoration with plasma-based metal nanoparticles. In this work, we have attached iron nanoparticles on the CNTs surface via a radio frequency (rf) sputtering process using Ar + N2 gas with various plasma power in steps of 50 W. Field emission scanning electron microscopy (FESEM) micrographs have confirmed the attachment of the iron nanoparticles and etching of the nanotubes surface at high plasma power. The Raman spectra strongly confirm the formation of defects in the carbon sheet of the nanotubes. In the plasma treatment process, the increase in the Dband intensity enhanced the degree of disorder and may be beneficial for enhanced emission properties. The field electron emission properties are significantly enhanced after the Fe nanoparticles attached with plasma incorporated in terms of the reduction in Eto (1.64 from 2.02 V/μm) &Eth (1.98 from 2.64 V/μm), and increase in J (391.11–1179.24 μA/cm2) and β (1419–2900), respectively. The field emission parameters of the field emitters are modified due to incorporation of nitrogen species, attached Fe nanoparticles, and reduction in the nanotube density. The as-prepared field emitters also qualified the orthodox field emission hypothesis test by exhibiting fextr values in an acceptable range. Therefore, we can use the Ar + N2 plasma-based Fe nanoparticles decorated CNT field emitters in vacuum electronic device applications.

METHODOLOGICAL APPROACH TO THE MATHEMATICAL MODELS CONSTRUCTION OF BIOOBJECT PROBLEMS

This article reveals a technique for the mathematical modeling of biotechnological systems that contain sources of laser action. Calculation and optimization mathematical models for finding rational values of the technical parameters of the emitters are the basis for this. The authors researched the main aspects of the theory of analysis and synthesis of complex systems that contain concentrated, moving sources of physical fields. To ensure the viability of embryo cells, it is necessary to carefully monitor the level of embryo heating not only at the points closest to the laser dissection site but also at the end of the laser action. It should also be noted that at the end of the short-term effect of laser radiation, the flow of heat from the border of the embryo dissection passes to other parts of it. The non-stationary process of thermal distribution will occur until a stationary mode is established, which is necessary to maintain the viability of the embryo. Due to the peculiarities of the microbiological object, the authors perform mathematical modeling of a non-stationary, nonlinear, multidimensional biotechnological system, which contains a discrete, moving source of laser action. It is quite difficult to implement applied optimization mathematical models that are used to optimize the modeled system. Therefore, it is advisable to obtain approximate solutions to boundary value problems with averaged values of thermophysical parameters of laser emitters without considering the three-layer structure of the embryo. To increase the level of viability of germ cells, the authors propose to implement an applied optimization mathematical model for minimizing the deviation of the temperature of laser action from its acceptable value. This will make it possible to obtain rational technical parameters of the emitters, which are close to reality and satisfy the needs of the technical use of laser emitters.

All field emission experiments are noisy, … are any meaningful?

Representing field emission data on a Fowler–Nordheim plot is both very common and strongly not recommended. It leads to a spurious estimation of the emitter parameters despite a very good data fit. There is a lack of a reliable method of analysis and a proper estimation of the uncertainty in the extracted parameters. In this article, we show that the uncertainty in the estimation of the field enhancement factor or the emission area can be as high as ±50% even for a tungsten single emitter in good ultrahigh vacuum conditions analyzed by the Murphy–Good model. Moreover, the choice of the exact Murphy–Good method can have a noticeable impact. We found that advanced analysis methods, based on the measurement of the differential conductance of the emitter, are so demanding in terms of emitter stability that up to now its requirements are probably out of reach in any field emission laboratory.

Cooperative Electromagnetic Data Annotation via Low-Rank Matrix Completion

Electromagnetic data annotation is one of the most important steps in many signal processing applications, e.g., radar signal deinterleaving and radar mode analysis. This work considers cooperative electromagnetic data annotation from multiple reconnaissance receivers/platforms. By exploiting the inherent correlation of the electromagnetic signal, as well as the correlation of the observations from multiple receivers, a low-rank matrix recovery formulation is proposed for the cooperative annotation problem. Specifically, considering the measured parameters of the same emitter should be roughly the same at different platforms, the cooperative annotation is modeled as a low-rank matrix recovery problem, which is solved iteratively either by the rank minimization method or the maximum-rank decomposition method. A comparison of the two methods, with the traditional annotation method on both the synthetic and real data, is given. Numerical experiments show that the proposed methods can effectively recover missing annotations and correct annotation errors.

Method for remote control of radiation parameters of spacecraft based on X-ray fluorescence analysis

Existing international legal acts, instruments and procedures do not guarantee equal conditions for the exploration and use of outer space. There is a need for means of objective control of spacecraft carrying products with fissile materials. Inspection of such objects can be carried out by X-ray fluorescence methods. However, in the subject area under consideration, the use of such methods has been little studied. In this paper, a method is proposed for obtaining the spectra of X-ray fluorescence radiation of materials, the object under study based on the calculation of the spatial and energy characteristics of X-ray radiation. The X-ray fluorescence spectra of objects are obtained on the basis of the calculation of the spatial and energy characteristics of X-ray radiation according to the original geometric (mathematical) and simulation models developed by the authors. The calculations take into account the complex layered system of the object, taking into account the proportions of high-energy fluorescent radiation of the overlying layers. An original numerical experiment is proposed using a program that allows one to choose the projections of an object subjected to X-ray irradiation, the wavelength and intensity of the emitter parameters. Using the obtained spatial-energy distribution of radiation quanta and the physical properties of the radiation transmission medium, the problem of finding the coordinates and angles of intersection of tracks of quanta beams in each area of the object is solved. The result of software processing is displayed as the resulting spectrum. The obtained spectrum makes it possible to draw a conclusion about the chemical composition of the materials of the inspected object. The X-ray beam reaching the object is modeled as a spot with an area commensurate with the cross section of the device in the form of a selected geometric primitive — a square. The spot area of the incident photons is calculated from a predetermined divergence angle. On the basis of open literary sources, a physical model of an object with nuclear fissile materials W88 (USA) was chosen. The following characteristics of X-ray beams (subbeams) are accepted: a coherent beam of photons with a wavelength of 0.005 nm; beam scattering angle of 1 degree; emitter detector area of 4 m2. The resulting X-ray fluorescence spectrum was obtained which gives an idea of the chemical composition of the units and blocks of the apparatus and the object inside. The presence of specific products on the object board is confirmed by characteristic lines with normalized wavelengths indicating the presence of chemical elements belonging to the radioactive series. The results obtained can be used in the development of hardware and software for spacecraft devices that monitor the presence of fissile materials on board of the inspected vehicle.

Spatial and Temporal Characteristics of Infiltration Wetting Front of Ring-Shaped Root Emitters

Ring-shaped root emitter is a new type of emitter applicable to the roots of fruit trees in arid areas. To study the characteristics of infiltration wetting front changes in ring-shaped root emitters, the orthogonal test method was used to design nine groups of schemes for four factors: radius of irrigation ring R, burial depth H, number of orifices M, irrigation water volume V and their three levels (R = 20, 30 and 40 cm; M = 4, 6 and 8; H = 20, 30 and 40 cm, V = 40, 60 and 80 L). The infiltration process of these nine scenarios was simulated using HYDRUS-3D software. The results show that the interference infiltration time exhibited a good power function relationship with the irrigation ring radius, number of orifices and burial depth; before the interference infiltration, the wetting fronts were all in the shape of a rotating ellipsoid centered on the infiltration point and can be expressed by the equations of the upper and lower semi-elliptic curves relative to the infiltration point. With the increase in time, the wetting fronts were centered at the infiltration point and infiltrated in all directions at a different velocity. The transport rate decreased with time. The power function relationship between the wetting fronts and the influencing factors after the interference infiltration in different directions was established, and the coefficient of determination was above 0.888. The wetting front shape after infiltration stabilization can be regarded as a rotating body formed by the vertical wetting front plane around the z-axis. The wetted soil volume of deep percolation, surface and suitable infiltration scenarios was rugby-shaped, apple-shaped with a flattened top and complete apple-shaped, respectively. Burying the irrigation ring at slightly deeper than one-third of the crop root zone is recommended, and half of the horizontal range of the crop root system can be selected as the irrigation ring radius. The research results can provide a reference for selecting root emitter parameters and layout as well as developing a root irrigation system.