一种求解大型稀疏对称矩阵(极端)特征值问题的有效算法

提出一种求解大型稀疏对称矩阵几个最大(最小)特征值和相应特征向量的迭代块DL(即Davidson-Lanczos)算法并且讨论了迭代块DL算法的收敛率     

DL capacitance-emission spectroscopy of determining the electrochemical behavior of anodized aluminum in aqueous solutions

In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the double layer (DL) capacitance of aluminum samples during the initial stage of anodization processes in aqueous solution without any physical contact. In fact, because the DL capacitance values in this investigation were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the DL capacitance was called DL capacitance-emission spectroscopy. The anodization process (oxidation) of the aluminum samples was carried out chemically in different sulfuric acid concentrations (0.5-3.125% H₂SO₄) at room temperature. In the mean time, the real-time holographic interferometry was used to determine the difference of the DL capacitance of two subsequent values, dC, as a function of the elapsed time of the experiment for the aluminum samples in 0.5%, 1.0%, 1.5%, and 3.125% H₂SO₄ solutions. The DL capacitance-emission spectra of the present investigation represent a detailed picture of not only the rate change of the DL capacitance throughout the anodization processes, but also, the spectra represent the rate change of the growth of the oxide films on the aluminum samples in different solutions. Consequently, holographic interferometry is found very useful for surface-finish industries especially for monitoring the early stage of anodization processes of metals, in which the rate change of DL capacitance of the aluminum samples can be determined in situ.     

Structure and radiation properties of dislocations arising during oxygen precipitate growth in silicon

The structural and radiation properties of defects formed during oxygen precipitation in Czochralski-grown silicon (Cz-Si) has been investigated by the methods of transmission electron microscopy (TEM) and photoluminescence (PL). It has been shown that the spectral intensity of dislocation-related luminescence (DL) is considerably redistributed as precipitates grow. A comparison of the concentration of different types defects with the DL integral intensity has shown that the secondary defects, namely, dislocations punched out of precipitates, make a main contribution to DL. In this case, the spectral distribution and integral intensity of DL are related to the extension of dislocation loops. The results show the capability of optimization of the dislocation-generation process to increase the intensity of the D1 line for its use in optoelectronics.     

一种用于ICP光谱法直接分析海水样品的高盐雾化器的应用研究

制作了适用将海水样品直接进样喷入ＩＣＰ焰的高盐雾化器，连续进样喷雾１２分半钟不堵塞，测定了海水中的元素Ｓｒ，Ｂａ，Ｐ，Ｂ，Ｃａ，Ｋ，Ｌｉ的检出限（ＤＬ）和ＢＥＣ值，其结果相当于或优于ＡＲＬ－ＭＤＳＮ高盐雾化器的ＤＬ和ＢＥＣ值。     

Experimental evidence of a double layer in a large volume helicon reactor

The self-consistently generated current-free electric double layer (DL) is shown to scale up with the source tube diameter and appears not to be affected by rf driving frequency and changes in reactor geometry. This Letter presents the first simultaneous measurements of local plasma potential and beam energy as a function of axial position. The DL is shown to be no more than 5 mm thick (20 D lengths) and positioned just downstream of the maximum in the magnetic field gradient. Furthermore, its position relative to the magnetic field is observed to be invariant as the magnetic field is translated axially. Measurements of the potential drop across the DL are presented for pressures down to 0.09 mTorr and the DL strength (phiDL/T(e)) is determined to be between 5 and 7.     

X射线荧光光谱分析检出限计算公式

本文根据测量的统计误差理论,对XRFS分析中不同背景和基体校正方式下的检出限述一进行讨论并导出了相应的计算公式,所得结论可作为选择微量元素XRFS分析的背景和基体校正方法以及拟定最佳实验条件以获得最低检出限的理论依据。     

Deformation Luminescence in gamma-irradiated KCl single crystals

Abstract

Deformation Luminescence(DL) is studied on KCl crystal colored by γ-irradiation. The spectra analysis of DL and thermoluminescence reveals that F-center plays a role as electron donor through the interaction with moving dislocation and V₂-center is a probable luminescence center. A theory is presented for understanding the deformation rate and temperature dependences of DL intensity.     

Observations of ion-beam formation in a current-free double layer

With nonperturbative laser-induced fluorescence measurements of ion flow, we confirm numerical simulations of spontaneous electric double-layer (DL) formation in a current-free expanding plasma. Measurements in two different experiments confirm that the DL is localized to the region of rapidly diverging magnetic field. The measurements indicate that the trapped ion population is a single Maxwellian, that the spatial gradient of the energy of ions accelerated through the DL matches the magnetic field gradient, and that DL formation is triggered when the ion-neutral collisional mean-free path exceeds the magnetic field gradient scale length.     

Large aperture phase-coded diffractive lens for achromatic and 16° field-of-view imaging with high efficiency

Diffractive lenses (DLs) can realize high-resolution imaging with light weight and compact size. Conventional DLs suffer large chromatic and off-axis aberrations, which significantly limits their practical applications. Although many achromatic methods have been proposed, most of them are used for designing small aperture DLs, which have low diffraction efficiencies. In the designing of diffractive achromatic lenses, increasing the aperture and improving the diffraction efficiency have become two of the most important design issues. Here, a novel phase-coded diffractive lens (PCDL) for achromatic imaging with a large aperture and high efficiency is proposed and demonstrated experimentally, and it also possesses wide field-of-view (FOV) imaging at the same time. The phase distribution of the conventional phase-type diffractive lens (DL) is coded with a cubic function to expand both the working bandwidth and the FOV of conventional DL. The proposed phase-type DL is fabricated by using the laser direct writing of grey-scale patterns for a PCDL of a diameter of 10 mm, a focal length of 100 mm, and a cubic phase coding parameter of 30π. Experimental results show that the working bandwidth and the FOV of the PCDL respectively reach 50 nm and 16° with over 8% focusing efficiency, which are in significant contrast to the counterparts of conventional DL and in good agreement with the theoretical predictions. This work provides a novel way for implementing the achromatic, wide FOV, and high-efficiency imaging with large aperture DL.     

Automatic modulation classification using bimodal parallel multichannel deep learning framework for spatial multiplexing MIMO system

In recent years, automatic modulation classification (AMC) has proved its importance for the military as well as civil applications and deep learning (DL) based AMC has attracted wide attention. But existing methods neglect to consider the advantages of both multimodality and complementarities simultaneously in a single DL framework for multiple-input multiple-output (MIMO) system. To mitigate this, bimodal multichannel configurable DL-based AMC has been presented for the MIMO system under perfect channel state information with zero forcing equalizer. The proposed DL framework consists of two parallel structures of multichannel convolutional layers in which one multichannel structure is fed with in-phase/quadrature (I/Q) as first modal information while another multichannel structure accepts amplitude/phase as second modal information. Features extracted from this parallel structure then pass through long short-term memory (LSTM) layers for further extracting temporal information effectively. Finally, classification is accomplished through fully connected layers. Simulation results manifest the robustness of the proposed framework that achieves an average accuracy of about 0.6% to 12% higher compared to the state-of-the-art DL models. Simulations also illustrate the impact of antenna diversities with spatial multiplexing on the classification.     

Deep learning based physical layer security for terrestrial communications in 5G and beyond networks: A survey

The key principle of physical layer security (PLS) is to permit the secure transmission of confidential data using efficient signal-processing techniques. Also, deep learning (DL) has emerged as a viable option to address various security concerns and enhance the performance of conventional PLS techniques in wireless networks. DL is a strong data exploration technique which can be used to learn normal and abnormal behavior of 5G and beyond wireless networks in an insecure channel paradigm. Also, since DL techniques can successfully predict future new instances by learning from existing ones, they can successfully predict new attacks, which frequently involve mutations of earlier attacks. Thus, motivated by the benefits of DL and PLS, this survey provides a comprehensive review that overviews how DL-based PLS techniques can be employed for solving various security concerns in 5G and beyond networks. The survey begins with an overview of physical layer threats and security concerns in 5G and beyond networks. Then, we present a detailed analysis of various DL and deep reinforcement learning (DRL) techniques that are applicable to PLS applications. We present the specific use-cases of PLS design for each type of technique, including attack detection, physical layer authentication (PLA), and other PLS techniques. Then, we present an in-depth overview of the key areas of PLS where DL can be used to enhance the security of wireless networks, such as automatic modulation classification (AMC), secure beamforming, PLA, etc. Performance evaluation metrics for DL-based PLS design are subsequently covered. Finally, we provide insights to the readers about various challenges and future research trends in the design of DL-based PLS for terrestrial communications in 5G and beyond networks.     

Magnetic anisotropies and coupling mechanisms in Fe/Mo(110) nanostripes

Using low-temperature (5 K) spin-polarized scanning tunneling microscopy, we have studied the morphology and magnetic properties of monolayer (ML) and double layer (DL) thick Fe nanowires grown by step flow on a Mo(110) single crystal. Magnetic contrast has been obtained using tungsten tips covered by Au/Co thin films. We find that the DL Fe nanowires, similarly to ML Fe nanowires, are perpendicularly magnetized. Because of the dipolar coupling, separated DL Fe nanowires are antiferromagnetically coupled. DL wires that are touching at step edges are ferromagnetically ordered due to direct exchange coupling. We measured the widths of the magnetic domain walls in the ML and DL Fe nanowires. The domain wall width increases with the thickness of Fe.     

Light-by-light scattering in double-logarithmic approximation

In the present paper we consider the elastic \(2 \rightarrow 2\) -scattering of virtual photons at high energies in the forward kinematics at zero and non-zero values of t. Accounting for both gluon and quark double-logarithmic (DL) contributions to all orders in the QCD coupling, we obtain explicit expressions for amplitudes of this process in double-logarithmic approximation (DLA). First we keep the QCD coupling fixed and then account for running coupling effects. Applying the saddle-point method to the obtained expressions for the scattering amplitude, we calculate the high-energy asymptotics of the amplitude, which proved to be of the Regge form. The Reggeon bears the vacuum quantum numbers and therefore it is a new, DL contribution to Pomeron. Comparison of the DL Pomeron to the BFKL Pomeron shows that contribution of the DL Pomeron to the high-energy asymptotics is of the same order as contribution of the BFKL Pomeron, so the DL Pomeron should be taken into account together with the BFKL Pomeron. We estimate the applicability region for the asymptotics of the light-by-light scattering amplitude, where the the DL Pomeron can reliably represent the parent amplitude.     

Scaled and nonlinear multi-objective model for Downlink and Uplink exposure in massive MIMO

When designing wireless networks with a large number of wireless broadband devices, it is important to take into account the induced Uplink (UL) and Downlink (DL) exposure from base station broadcasting. This work focuses on the reduction of power consumption, low downlink and uplink electromagnetic exposure, and the optimization of locations and power levels of large Multiple Input–Multiple Output-Long Term Evolution base stations (MIMO-LTE). Additionally, it anticipates achieving maximum user coverage. In order to handle the power consumption and Electro Magnetic Field (EMF) exposure, a Nonlinear and Scaled Weight objective model (NLSW) is defined (DL and UL exposure). An enhanced Particle Swarm Optimization (PSO) technique is employed to resolve this optimization issue. Finally, DL exposure, UL exposure, and power performance of a NLSW are validated compared to the traditional linear model. Increased antenna leads to a 25% reduction in DL dosage. The minimum BS deployed in the area with the number of antenna elements until it reaches the ideal value is related to the UL exposure maximization.     

High quality infrared (8 μm) diode laser source design for high resolution spectroscopy with precise temperature and current control

The performance of a tunable diode laser (DL) spectrometer is directly determined by the DL qualities and its tunability control. Emission characteristics are very sensitive to current and temperature drifts. In order to obtain a high quality source for spectroscopy, we designed our own liquid nitrogen cryostat containing the DL. Moreover we compared current and temperature control and we found that temperature tuning can be more efficient. We check and demonstrate it by recording SO₂ spectra in the 1168–1169 cm^–1 spectral region.     

Contactless Spectroscopy of Deep Levels in Semiconducting Materials: Gaas

Abstract

The surface photo voltage (SPV) and photocurrent (PC) transients as a result of the excitation by the short high-intensity light pulses from semiconductor's intrinsic absorption spectral region are investigated in semi-insulating GaAs. It is shown that the mathematical convolution of SPV transients and arbitrary form double-pulse integrator (lock-in, double-boxcar) in a wide temperature range allows to receive the deep-level (DL) spectrum without the need to form electrical contacts to the crystal investigated. The use of such a procedure while scanning the crystal surface with a light spot at a temperature, corresponding to some DL maximum in the spectrum, makes possible the con tactless determination of this DL density distribution profile along the scanning direction.     

Upstream ionization instability associated with a current-free double layer

A low frequency instability has been observed using various electrostatic probes in a low-pressure expanding helicon plasma. The instability is associated with the presence of a current-free double layer (DL). The frequency of the instability increases linearly with the potential drop of the DL, and simultaneous measurements show their coexistence. A theory for an upstream ionization instability has been developed, which shows that electrons accelerated through the DL increase the ionization upstream and are responsible for the observed instability. The theory is in good agreement with the experimental results.     

On the mechanisms of thermoluminescence and deformation luminescence in gamma-irradiated KCl

Thermoluminescence (TL) and deformation luminescence (DL) studies in KC1 γ-irradiated at room temperature are reported. The roles that F-centres and their higher conglomerates on the one hand, and V₂- and V₃-centres as recombination centres on the other hand, play in these processes are specified. Two peaks at 2.5 eV and 3 eV are observed in the emission spectra of both TL and DL. The close relationship between TL and DL is confirmed.     

An in vitro thermal analysis during different light-activated hydrogen peroxide bleaching

This study measured the critical temperature reaching time and also the variation of temperature in the surface of the cervical region and within the pulp chamber of human teeth submitted to dental bleaching using 35% hydrogen peroxide gel activated by three different light sources. The samples were randomly divided into 3 groups (n = 15), according to the catalyst light source: Halogen Light (HL), High Intensity Diode Laser (DL), and Light Emmited Diode (LED). The results of temperature variation were submitted to the analysis of variance and Tukey test with p < 0.05. The temperature increase (mean value and standard deviation) inside the pulp chamber for the HL group was 6.8 ± 2.8°C; for the DL group was 15.3 ± 8.8°C; and for the LED group was 1.9 ± 1.0°C for. The temperature variation (mean value and standard deviation) on the tooth surface, for the group irradiated with HL was 9.1 ± 2.2°C; for the group irradiated with DL were 25.7 ± 18.9°C; and for the group irradiated with LED were 2.6 ± 1.4°C. The mean temperature increase values were significantly higher for the group irradiated with DL when compared with groups irradiated with HL and LED (p < 0.05). When applying the inferior limits of the interval of confidence of 95%, an application time of 38.7 s was found for HL group, and 4.4 s for DL group. The LED group did not achieve the critical temperatures for pulp or the periodontal, even when irradiated for 360 s. The HL and DL light sources may be used for dental bleaching for a short period of time. The LED source did not heat the target tissues significantly within the parameters used in this study.     

Laboratory demonstration of spotlight-mode down-looking synthetic aperture imaging ladar

We present a tabletop-scale spotlight-mode down-looking synthetic aperture imaging ladar(DL SAIL) demonstrator, which is performed by a collimator with 10 m focal length to simulate the far-field optical field.A specular-point target and a diffuse-reflection target have been used for resolution analysis and 2D imaging,respectively. The experimental result is in agreement with the theoretical design. The experiment setup is capable of simulating a real application scenario for further study. This Letter is focused on the proposition and implementation of spotlight-mode DL SAIL.