- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Admittance of Organic LED Structures with an Emission YAK-203 Layer
摘要： The current-voltage characteristics and admittance of multilayer structures for organic LEDs based on the PEDOT:PSS/NPD/YAK-203/BCP system have been experimentally investigated in a wide range of the measurement conditions. It is shown that at voltages corresponding to the effective radiative recombination of charge carriers, a significant decrease in the differential capacitance of the structures is observed. The frequency dependences of the normalized conductance of LED structures are in good agreement with the results of numerical simulation in the framework of the equivalent circuit method. Changes in the frequency dependences of the admittance with a change in temperature are most pronounced in the temperature range of 200–300 K and less noticeable in the temperature range of 8–200 K. From the frequency dependences of the imaginary part of impedance, the charge carrier mobilities are found at various voltages and temperatures. The mobility values obtained by this method are somewhat lower than those determined by the transient electroluminescence method. The dependence of the mobility on the electric field is well approximated by a linear function. As the temperature decreases from 300 to 220 K, the mobility decreases several times.
关键词： frequency dependence of imaginary part of impedance,LED structure,current-voltage characteristic,transient electroluminescence,organic semiconductor,charge carrier mobility,method of equivalent circuits,admittance
更新于2025-11-14 17:28:48
-
(Bi0.51 Na0.47)TiO3 based lead free ceramics with high energy density and efficiency
摘要： Dielectric ceramics with high energy storage density and energy efficiency play an important role in high power energy storage applications. In this work, lead free relaxor ferroelectric ceramics in (1-x)Bi0.51Na0.47TiO3-xBa(Zr0.3Ti0.7)O3 (BNT-BZT100x: x=0.20, 0.30, 0.40 and 0.50) system are fabricated by conventional solid-state sintering method. The BNT-BZT100x ceramics are sintered dense with minimal pores, exhibiting pseudocubic symmetry and strong relaxor characteristic. A very high energy storage density of 3.1 J/cm3 and high energy efficiency of 91% are simultaneously achieved in BNT-BZT40 ceramic with 0.1mm in thickness, at the applied electric field of 280 kV/cm. The temperature stability of the energy density is studied over temperature range of 20-160°C, showing minimal variation below 1.5%, together with the excellent cycling reliability (the variations of both energy density and efficiency are below 3% up to 106 cycles), making BNT-BZT40 ceramic promising as a candidate for high-temperature dielectric and energy storage applications.
关键词： relaxor characteristic,lead free ceramic,energy storage
更新于2025-11-14 17:28:48
-
Stability and Spectral Properties of General Tree-Shaped Wave Networks with Variable Coefficients
摘要： The stability of general tree-shaped wave networks with variable coefficients under boundary feedback controls is considered. Making full use of the tree-shaped structures, we present a detailed asymptotic spectral analysis of the networks. By proposing the from-root-to-leaf calculating technique, we deduce an explicit recursive expression for the asymptotic characteristic equation and the spectral properties are further obtained. We show that the spectrum-determined-growth (SDG) condition holds. Thus the stability analysis of the closed-loop system can be completely converted to the infimum estimation of the asymptotic characteristic equation. Especially, we further show that the infimum is positive so as to obtain the exponential stability by estimating the recursive expression in from-leaf-to-root order. Some numerical simulations are presented to illustrate and support the theoretical results.
关键词： Exponential stability,Variable coefficient,Spectrum-determined-growth (SDG) condition,Recursive characteristic equation,Feedback control,Wave network
更新于2025-09-23 15:23:52
-
Single-Photon-Emission Computed Tomography with Neutron Activation for Material Inspection
摘要： A single-photon-emission computed tomography (SPECT) system with a lanthanum-bromide (LaBr3:Ce) scintillator was proposed and simulated to detect neutron-activated prompt γ-rays from suspicious materials. The optimized parameters of the SPECT system were calculated to achieve the best performance. Under the optimized conditions, energy spectra, spatial images, and elemental ratios were obtained and employed to identify hidden materials. The carbon-to-oxygen ratios of the materials calculated through the simulations were consistent with the corresponding theoretical values while the calculated nitrogen-to-oxygen ratios were slightly different from the corresponding theoretical values. In the proposed system, not only the energy spectrum of each element but also the characteristic intensity ratios obtained using the reconstructed images were used to identify the unknown elements of hidden materials in the three-dimensional spatial domain. These results demonstrate the feasibility of using the SPECT system in field applications.
关键词： Characteristic elemental intensity ratio,Neutron-activated prompt γ-rays,Single-photon-emission computed tomography
更新于2025-09-23 15:23:52
-
Simple Design Procedure of a Broadband Circularly Polarized Slot Monopole Antenna Assisted by Characteristic Mode Analysis
摘要： In this paper, a systematic design procedure of a compact and broadband circularly polarized (CP) antenna is proposed. The antenna is first designed with a C-shaped monopole, and then a C-shaped slotted patch is utilized to produce CP radiation in the lower frequency band. Thus, the antenna's overall CP bandwidth (BW) is significantly increased. In addition, unlike the conventional method in which the operation is verified by the simulated surface current distribution, characteristic mode analysis (CMA) is carried out to give more insight into different modes on the antenna and generation of circular polarization. The CMA also helps to realize a structural optimization and identify an efficient feed location. The optimized antenna prototype with a compact size of 0.29λo × 0.29λo × 0.01λo (λo is the minimum wavelength at the minimum operation frequency) achieves a usable 10-dB reflection coefficient and 3-dB axial ratio fractional BW of 91% (2.1–5.6 GHz). The antenna realized broadside gain varies from 1.5 to 3.2 dBic within this measured overlapped BW.
关键词： UWB antenna,slot,circularly polarized (CP),monopole,characteristic mode (CM)
更新于2025-09-23 15:22:29
-
[IFIP Advances in Information and Communication Technology] Computer and Computing Technologies in Agriculture X Volume 509 (10th IFIP WG 5.14 International Conference, CCTA 2016, Dongying, China, October 19–21, 2016, Proceedings) || Modelling and Predicting of Soil Electrical Conductivity and PH from Semi-arid Grassland Using VIS-NIR Spectroscopy Technology
摘要： The electrical conductivity (EC) and pH value are key indicators for soil physical and chemical properties, which can re?ect the level of soil acid and alkali, furthermore, in?uence the vegetation growth. The spectroscopy technique can estimate and evaluate electrical conductivity and pH value rapidly and ef?ciently, which can provide useful information on the real-time soil management in the semi-arid rangeland or grassland. We picked the semi-arid grassland of northern China covering an area about 200 km2 as the target research area, given that it is highly sensitive to grazing and mining affect. Soil samples were collected from 72 sampling sites in this area, which covered grazing exclusion, over grazing and grassland restoration area. The SVC HR-1024 spectroradiometer was used to acquire soil spectrum. This study aims to indicate the spectral characteristic for soil EC and pH, and propose a predicting modeling method with optimal input spectral region and transformation by comparing the support vector machine (SVM) regression method and partial least squares (PLSR) regression modeling method. Our results showed that: (1) once EC value is larger than 0.10 ls/m, the soil spectral re?ectance decreases with increasing of EC value. The absorption depth, width and area at 1900 nm reduce with increasing of EC value as well; (2) There are positive correlation between EC, pH value and soil spectral re?ectance. The highest correlation coef?cient value of 0.7 between pH and re?ectance is recorded at visible region around 500 nm; (3) The SVM modeling method produce the higher prediction accuracy (RPD = 2.18, RMSE = 0.035, R2 = 0.78 for EC, RPD > 3, RMSE = 0.349, R2 = 0.91 for pH) rather than PLSR methods in soil EC and pH prediction. This study indicated that it was possible to use the spectroradiometer technology to predict EC and pH value for the soil from semi-arid grassland, which would provide the basis for soil acid and alkali detecting using hyper-spectral remote sensing technology.
关键词： Semi-arid grassland,Spectral modeling and predicting,Soil electrical conductivity and pH,Spectral characteristic
更新于2025-09-23 15:22:29
-
B-scan wave outline analysis in numerical modeling of ground-penetrating radar response from layered rough interfaces
摘要： Imaging of rough interfaces in a layered structure requires full understanding of the characteristics of their ground penetrating radar (GPR) echoes. In this study, a finite-difference time-domain computational model using a uniaxial perfectly matched layer boundary for GPR demining of layered rough interfaces is constructed. On the basis of this model, the numerical results of B-scan echoes from two-layered and three-layered rough interfaces with different degrees of roughness are obtained and compared with the profiles of corresponding rough surfaces. These results and comparisons highlight the relationship between the B-scan wave outlines and the profile of the layered rough interfaces. The effect of roughness of the interface on the B-scan echoes are analyzed, and the influence of the upper rough surface profile on the shape of the B-scan wave outline from the lower rough surface is discussed.
关键词： layered rough interfaces demining,finite-difference time-domain method (FDTD),ground penetrating radar (GPR),echo characteristic analysis
更新于2025-09-23 15:22:29
-
Dispersion of Love waves in size-dependent substrate containing finite piezoelectric and viscoelastic layers
摘要： The dispersion properties of Love waves are utilized for the fabrication of sensor devices in the different material environments. This study involves the propagation of Love wave in a double-layered structure consisting of two finite layers of viscoelastic and piezoelectric material lying over the semi-infinite size-dependent micropolar substrate. The bottom substrate of the structure is modeled as, the material with microstructural properties. The real and damping dispersion relations are obtained analytically in closed form expression under both the cases of electrically open and short conditions. The coupling constant and characteristic length that describe the effect of the microstructure of the micropolar substrate, are studied graphically on Love wave propagation. The effects of piezoelectric layer are shown by considering two different materials of a piezoelectric layer, i.e., PZT-5H or BaTiO3, along with the internal friction and heterogeneity parameter associated with a viscoelastic layer. The numerical computation and the graphs are given for aluminium-epoxy (substrate), viscoelastic material and PZT-5H or BaTiO3 (piezoelectric layer). Some of the particular cases are derived from the study by using different relevant conditions.
关键词： Viscoelastic,Piezoelectricity,Dispersion relations,Heterogeneity,Micropolar,Love wave,Characteristic length
更新于2025-09-23 15:22:29
-
Low-cost, Inkjet-printed UHF RFID Tag based System for Internet of Things Applications using Characteristic Modes
摘要： The radio frequency identification (RFID) has emerged Internet of things (IoT) into the identification of things. This paper presents, a low-cost smart refrigerator system for future internet of things applications. The proposed smart refrigerator is used for automatic billing and restoring of beverage metallic cans. The metallic cans can be restored by generating a product shortage alert message to a nearby retailer. To design a low-cost and low-profile tag antenna for metallic items is very challenging, especially when mass production is required for item-level tagging. Therefore, a novel ultra-high frequency (UHF) radio frequency identification (RFID) tag antenna is designed for metallic cans by exploiting the metallic structure as the main radiator. Applying Characteristics mode analysis (CMA), we observed that some characteristic modes associated with the metallic structure could be exploited to radiate more effectively by placing a suitable inductive load. Moreover, a low cost, printed (using conductive ink) small loop integrated with meandered dipole used as an inductive load, which was also connected with RFID chip. The 3-dB bandwidth of the proposed tag covers the whole UHF band ranging from 860 - 960 MHz when embedded with metal cans. The measured read range of the RFID tag is more than 2.5 meters in all directions to check the robustness of the proposed solution. To prove the concept, a case study was performed by placing the tagged metallic cans inside a refrigerator for automatic billing, 97.5 % tags are read and billed successfully. This study paves the way for tagging metallic bodies for tracking applications in domains ranging from consumer devices to infotainment solutions, which enlightens a vital aspect for the Internet of Things (IoT).
关键词： Characteristic mode theory (CMT),smart refrigerator,radio frequency identification (RFID) tag antenna,Internet of Things (IoT)
更新于2025-09-23 15:22:29
-
Coupling of Characteristic Modes on PEC and Lossy Dielectric Structures
摘要： Surface integral equation based theory of characteristic modes (TCM) is presented for structures including perfect electric conductors (PEC) and lossy dielectric bodies. The formulation is a combination of the classical TCM formulation for PEC structures and a recently developed one for penetrable bodies. The potential of the methodology for practical antenna design problems is demonstrated by studying coupling of the modes on a PEC plate (antenna ground plane) and an adjacent highly lossy dielectric block (user’s hand). This analysis reveals existence of different types of modes having weak or strong interactions between the PEC and dielectric parts.
关键词： Characteristic modes,dielectric losses,mobile handset antenna,surface integral equation structure
更新于2025-09-23 15:22:29