Modifications in aerosol physical, optical and radiative properties during heavy aerosol events over Dushanbe, Central Asia

The location of Central Asia,almost at the center of the global dust belt region,makes it susceptible for dust events.The studies on atmospheric impact of dust over the region are very limited despite the large area occupied by the region and its proximity to the mountain regions (Tianshan,Hindu Kush-KarakoramHimalayas,and Tibetan Plateau).In this study,we analyse and explain the modification in aerosols’physical,optical and radiative properties during various levels of aerosol loading observed over Central Asia utilizing the data collected during 2010–2018 at the AERONET station in Dushanbe,Tajikistan.Aerosol episodes were classified as strong anthropogenic,strong dust and extreme dust.The mean aerosol optical depth (AOD) during these three types of events was observed a factor of ~3,3.5 and 6.6,respectively,higher than the mean AOD for the period 2010–2018.The corresponding mean fine-mode fraction was 0.94,0.20 and 0.16,respectively,clearly indicating the dominance of fine-mode anthropogenic aerosol during the first type of events,whereas coarse-mode dust aerosol dominated during the other two types of events.This was corroborated by the relationships among various aerosol parameters (AOD vs.AE,and EAE vs.AAE,SSA and RRI).The mean aerosol radiative forcing (ARF) at the top of the atmosphere (ARF_(TOA)),the bottom of the atmosphere (ARF_(BOA)),and in the atmosphere (ARFATM) were -35±7,-73±16,and38±17 Wm^(-2)during strong anthropogenic events,-48±12,-85±24,and 37±15 Wm^(-2)during strong dust event,and -68±19,-117±38,and 49±21 Wm-2during extreme dust events.Increase in aerosol loading enhanced the aerosol-induced atmospheric heating rate to 0.5–1.6 K day^(-1)(strong anthropogenic events),0.4–1.9 K day^(-1)(strong dust events) and 0.8–2.7 K day^(-1)(extreme dust events).The source regions of air masses to Dushanbe during the onset of such events are also identified.Our study contributes to the understanding of dust and anthropogenic aerosols,in particular the extreme events and their disproportionally high radiative impacts over Central Asia.

基于RSD的脉冲发生器破碎岩混材料实验仿真

为了总结用于破碎岩混材料的脉冲发生器其设计原则和规律。通过应用一种反向晶体管开关,研制脉冲发生器进行破碎岩混材料实验,并结合CST软件对电极放电过程进行仿真,确定脉冲发生器的最佳参数。经研究发现,基于RSD脉冲发生器的输出脉冲可高效破碎岩混材料,其具有安全可控无污染的优点,有望代替炸药爆破方式。

Orange dye polyaniline composite based impedance humidity sensors

This study presents the fabrication and investigation （PANI） composite films. A blend of 3 wt.% OD with 1 of humidity sensors based on orange dye （OD） and polyaniline wt.% PANI was prepared in 1 ml water. The composite films were deposited on glass substrates between pre-deposited silver electrodes. The gap between the electrodes was 45 um. The sensing mechanism was based on the impedance and capacitance variations due to the absorption/desorption of water vapor. It was observed that with the increase in relative humidity （RH） from 30% to 90%, the impedance decreases by 5.2 × 10^4 and 8.8 × 10^3 times for the frequencies of 120 Hz and 1 kHz, respectively. The impedance-humidity relationship showed a more uniform change compared to the capacitance-humidity relationship in the RH range of 30% to 90%. The consequence of annealing, measuring frequency, response and recovery time, and absorption-desorption behavior of the humidity sensor were also discussed in detail. The annealing resulted in an increase in sensitivity of up to 2.5 times, while the measured response time and recovery time were 34 s and 450 s, respectively. The impedance-humidity relationship was simulated.

Carbon nanotube cuprous oxide composite based pressure sensors

In this paper, we present the design, the fabrication, and the experimental results of carbon nanotube （CNT） and Cu20 composite based pressure sensors. The pressed tablets of the CNT Cu20 composite are fabricated at a pressure of 353 MPa. The diameters of the multiwalled nanotubes （MWNTs） are between 10 nm and 30 nm. The sizes of the Cu20 micro particles are in the range of 3-4 μm. The average diameter and the average thickness of the pressed tablets are 10 mm and 4.0 mm, respectively. In order to make low resistance electric contacts, the two sides of the pressed tablet are covered by silver pastes. The direct current resistance of the pressure sensor decreases by 3.3 times as the pressure increases up to 37 kN/m^2. The simulation result of the resistance-pressure relationship is in good agreement with the experimental result within a variation of ±2%.

Novel pressure and displacement sensors based on carbon nanotubes

We report newly designed pressure and displacement capacitive sensors based on a flexible paper–CNT structure.The carbon nanotube（CNT） powder was deposited on a thin paper substrate and was pressed at an elevated temperature.The sheet resistance of the paper–CNT films was in the range of 2–4 kΩ/cm^2. The paper–CNT films were used to fabricate pressure and displacement sensors. The sensitivities of the pressure and the displacement sensors were found to be17.3 p F·m^2/k N and 0.93 10-3p F/μm, respectively. The experimental results were compared with the simulated data and they found good agreement with each other.

基于铁粉还原的LiFePO_4/C合成路径及其电化学性能研究

使用还原铁粉作为铁源,通过超细球磨与喷雾干燥、高温煅烧技术制备了球形微纳米LiFePO_4/C复合材料。使用DSC/TG以及XRD对LiFePO_4/C复合材料的形成过程进行了分析;使用SEM、穆斯堡谱仪等手段对复合材料进行分析;使用电化学工作站、容量测试仪对其充放电行为进行分析。研究发现,使用该合成技术路线,在500～700℃下能够合成LiFePO_4/C复合材料。获得的LiFePO_4/C复合材料具有规则的球形外貌,平均尺寸4～5μm。该微米颗粒由200 nm左右细小颗粒组成,颗粒间具有纳米尺寸微孔。穆斯堡谱仪测试结果表明,复合材料中Fe处于＋2价的价态。复合材料在1C倍率下表现出稳定的充放电行为,平均比容量在156 m Ah/g,300次循环后,容量保持率为92.8%。该技术制备的LiFePO_4/C复合材料具有潜在的应用价值。

Anomalies in Young's modulus behavior after annealing in polycrystalline SmS

In this paper,the dependencies of Young's modulus and attenuation decrement on samarium sulfide polycrystals(SmS)under various annealing temperatures are studied by the piezoelectric ultrasonic composite oscillator technique at a frequency of 100 kHz in the temperature range of 80-300 K.A decrease in Young's modulus with an increase of the annealing temperature due to the texturing of the material was revealed.At the same time,attenuation peaks were observed at temperatures about 90 and 125 K,presumably due to Niblett-Wilks and Bordoni relaxations.

Effect of displacement on resistance and capacitance of polyaniline film

This paper investigates the properties of displacement sensors based on polyaniline （PANI） films. About 1 wt% of PANI micropowder is mixed and stirred in a solution of 90 wt% water and 10 wt% alcohol at room temperature. The films of PANI axe deposited from solution by drop-casting on Ag electrodes, which are preliminary deposited on glass substrates. The thicknesses of the PANI films are in the range of 20 μm-80 μm. A displacement sensor with polyaniline film as an active material is designed and fabricated. The investigations showed that, on average, the AC resistance of the sensor decreases by 2 times and the capacitance accordingly increases by 1.6 times as the displacement changes in the range of 0 mm-0.5 mm. The polyaniline is the only active material of the displacement sensor. The resistance and capacitance of the PANI changes under the pressure of spring and elastic rubber, and this pressure is created by the downward movement of the micrometer.

Aluminium phthalocyanine chloride thin films for temperature sensing

This study presents the fabrication and temperature sensing properties of sensors based on aluminium phthalocyanine chloride （AlPcCl） thin films. To fabricate the sensors, 50-nm-thick electrodes with 50-μ gaps between them are deposited on glass substrates. AlPcCl thin films with thickness of 50–100 nm are deposited in the gap between electrodes by thermal evaporation. The resistance of the sensors decreases with increasing thickness and the annealing at 100 ℃ results in an increase in the initial resistance of sensors up to 24%. The sensing mechanism is based on the change in resistance with temperature. For temperature varying from 25 ℃ to 80 ℃, the change in resistance is up to 60%. Simulation is carried out and results obtained coincide with experimental data with an error of ±1%.

Neutrons in a nanosecond low-pressure discharge in deuterium

Stable neutron generation with a yield of ~1.2×10^(4) neutrons per pulse was obtained during d(d,n)^(3)He reaction initiated by the high-voltage nanosecond discharge in a gap with a potential tungsten cylinder(anode)and a grounded deuterated zirconium plate(cathode)filled with deuterium at a pressure of ~10^(2) Pa.Estimated duration of the neutron pulse was ~1.5 ns.Less intensive neutron emission was registered without deuterated plate.Splashing of material of the tungsten electrode was observed during the high-voltage nanosecond discharge in the deuterium,hydrogen,helium and argon at pressures of 10^(2)-10^(4) Pa.

Mathematical Modeling of the Efficiency Gadolinium Based Neutron Converters

Procedures of mathematical modeling of thin solid-state converters of neutrons are described and converters a foil from natural gadolinium and its 157 isotopes are viewed. Algorithms of calculation of absorption of neutrons in a material of converters, probabilities formation of secondary electrons, probability of an exit of electrons from a material of the converter and efficiency of converters are given. Calculation is made for various thicknesses of converters, and various wavelengths of neutrons. The optimal converter thicknesses are chosen.

The Scattering of a Cylindrical Shear-Axial Wave by a Circular Cavity in Piezoelectric Crystal

The features of a cylindrical shear-axial wave scattering by a circular cavity in piezoelectric crystal of 6(4)-class of symmetry are discussed. It is shown that the basic integral characteristics of scattering—scattering indicatrix and total cross-section scattering have large changes with approach of a linear shear-axial wave source to cavity boundary. The small-scale oscillations in spectra of scattering are caused by the interference contribution of waves circulating on a boundary as they are capable of effective capture by concave metallized boundary of a cavity.

Quantum Conductance Staircase of Edge Hole Channels in Silicon Quantum Wells

We present the findings for the quantum conductance staircase of holes that is caused by the edge channels in the ultra-shallow p-type silicon quantum well (Si-QW), 2 nm, confined by the δ-barriers heavily doped with boron on the n-type Si (100) surface. This longitudinal quantum conductance staircase, Gxx, is revealed by the voltage applied to the Hall contacts, Vxy, to a maximum of 4e2/h. In addition to the standard plateau, 2e2/h, the variations of the Vxy voltage appear to exhibit the fractional forms of the quantum conductance staircase with the plateaus and steps that bring into correlation respectively with the odd and even fractional values.

Electronic and Transport Properties of Carbon Nanotubes with Impurities and Structure Disorder

Electron relaxation time and density of states near the Fermi level were calculated for ＂dirty＂ carbon nanotubes taking into account multiple elastic electrons scattering on impurities and structural inhomogeneities of a short-range order type. A possible explanation of low-temperature behavior of density of states and electrical conductivity depending on defect structure, impurities and chirality is presented.

The Transformation of the Heterogeneous Materials under the Fatigue Deformation

The objects of our paper are aluminum alloy samples (AASs) contained the different amount of Cu, Mn, Mg, Si and Li. We are modeling the features of microstructure of potential relief of an AAS and studying its transformation under both imposed fatigue deformation and wetted by liquid metals (Ga;or Hg;Li;In). We illustrate the main ideas by using only the “time series” allied with effective internal friction Q-1eff of an AAS. AASs like B-95 or 7075 are heterogeneous materials for which the more energy can be absorbed by selected micro-regions of a tested sample. So micro-crack in the space of AAS and alarm state of AAS arises. Each micro-region will to contribute the Q-1k (the internal friction Q-1k belong to k-th micro-region) to the effective internal friction— Q-1eff accordance with fit statistic . We find a number of micro-regions—L and series gk & Qk from the experimental data like as the internal friction (Q-1)eff versus both the number of cycles—N and the deformation—е. Series gk & Qk (k=1,2,3,...,L) present the microstructures of AASs. In this paper also is presented the original technology to forecast fatigue damage of an AAS. Here the fatigue sensitive element (FSE) used. We made multiphase heterogeneous mixtures (MHMs) which contents a variable volume of initial components. It is selected MHMs are using for produce FSEs. The present paper is aimed to establish the correlation of the FSEs microstructures changes and corresponding changes of the aluminum alloy microstructures at imposing the same spectra deformation on both of them. A change of FSEs microstructure investigated by using their effective electrical resistance Reff data.

Elastic Moduli in Cadmium Selenide Doped with Chromium

Temperature dependence of elastic moduli , , and the latter for the piezo-active and non-piezo-active versions, have been measured in the interval of 4 - 180 K at 28 - 262 MHz in a CdSe: Cr2+ crystal. Anomalies below 40 K have been found for all the moduli, except . The interpretation of the results has been carried out involving the Jahn-Teller effect and relaxation between the equivalent distortions of the tetrahedral CrSe4 centers.

Multilayer GaAs-Based Heterostructures with Holographic Concentrator for Solar Cells

The present paper studies the issue of forming a diffraction concentrator in the form of relief diffraction gratings. The possibility of their application for solar energy systems based on GaAs heterostructures has been studied. It was shown that the use of diffractive and holographic concentrators proves to be very effective, since they provide for the increased radiant flux onto sensitive surface of the solar cell, whereas no automatic solar tracker is required. This will create novel approaches for a wide range application of gallium arsenide solar cells.

Polymerase-tautomeric Model for Untargeted Delayed Base Substitution Mutations Formation during Error-prone and SOS Replication of Double-stranded DNA Containing Thymine and Adenine in Some Rare Tautomeric Forms

Polymerase-tautomeric model for untargeted delayed base substitution mutations is proposed.Structural analysis of bases insertion showed that any canonical bases may be inserted opposite rare tautomeric forms of thymine T3*,adenines A2*and A4*so that between them hydrogen bonds are formed.Canonical adenine and cytosine can be incorporated opposite canonical thymine only.Canonical thymine and guanine can be incorporated opposite canonical adenine only.If in the synthesis of DNA containing rare tautomeric forms of thymine T3*,adenines A2*and A4*,involved DNA polymerases with relatively high fidelity of synthesis,mutations not appear.However,if further DNA synthesis will involve DNA polymerases having a low fidelity of synthesis,there may be base substitution mutations.It was shown that the conclusion made in the Tomasetti and Vogelstein cancer risk model that the formation of about 67%of all mutations was not caused by exposure to any mutagens is erroneous.

双腔室分子束外延复合体在Ⅲ-Ⅴ族和Ⅱ-Ⅵ族半导体异质结生长中的应用(英文)

半导体光电子学是当前科技发展最快的一个领域,光电子器件的增长需要加强新材料技术的研究与开发,Ⅲ -Ⅴ族和Ⅱ-Ⅳ族纳米结构生长的双腔室分子束外延复合体是目前工艺设备一个最好的例子,可以解决长期以来纳米光子学和纳米电子学的问题。