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We study the mechanism of van der Waals(vdW)interactions on phonon transport in atomic scale,which would boost developments in heat management and energy conversion.Commonly,the vdW interactions are regarded as a hindrance in phonon transport.Here we propose that the vdW confinement can enhance phonon transport.Through molecular dynamics simulations,it is realized that the vdW confinement is able to make more than two-fold enhancement on thermal conductivity of both polyethylene single chain and graphene nanoribbon.The quantitative analyses of morphology,local vdW potential energy and dynamical properties are carried out to reveal the underlying physical mechanism.It is found that the confined vdW potential barriers reduce the atomic thermal displacement magnitudes,leading to less phonon scattering and facilitating thermal transport.Our study offers a new strategy to modulate the phonon transport. 相似文献
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Temperature dependence of the light yield of the LAB-based and mesitylene-based liquid scintillators
We studied the temperature dependence of the light yield of linear alkyl benzene(LAB)-based and mesitylene-based liquid scintillators. The light yield increases by 23% for both liquid scintillators when the temperature is lowered from 26 to-40, correcting for the temperature response of the photomultiplier tube. The measurements help to understand the energy response of liquid scintillator detectors. Especially, the next generation reactor neutrino experiments for neutrino mass hierarchy, such as the Jiangmen Underground Neutrino Observatory(JUNO), require very high energy resolution. As no apparent degradation on the liquid scintillator transparency was observed, lowering the operation temperature of the detector to ~4 will increase the photoelectron yield of the detector by 13%, combining the light yield increase of the liquid scintillator and the quantum efficiency increase of the photomultiplier tubes. 相似文献
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Liquid scintillators are widely used as the neutrino target in neutrino experiments.The absorption and emission of different components of a ternary liquid scintillator (Linear Alkyl Benzene (LAB) as the solvent,2,5-diphenyloxazole (PPO) as the fluor and p-bis-(o-methylstyryl)-benzene (bis-MSB) as wavelength shifter) are studied.It is shown that the absorption of this liquid scintillator is dominant by LAB and PPO at wavelengths less than 349 nm,and the absorption by bis-MSB becomes prevalent at the wavelength larger than 349 nm.The fluorescence quantum yields,which are the key parameters to model the absorption and re-emission processes in large liquid scintillation detectors,are measured. 相似文献
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石墨炉原子吸收光谱法测定不同镍环境下人眼晶状体的镍量 总被引:1,自引:0,他引:1
利用高灵敏度的石墨炉原子吸收光谱仪对来自不同镍环境和不同状态的40个人眼晶状体中的镍进行了测试。在测试中,采用了方便的HNO,消解法对样品进行预处理,通过实验比较测得普通石墨管对镍的特征质量是长寿命石墨管的4.6倍,然后用长寿命石墨管对各种样品的消解后获得的测试液进行镍的测定,由此得到每个人眼晶状体中的绦量。结果表明:正常人的透明晶状体中的镍量明显低于患有白内障人眼晶状体中的镍量;而与镍矿直接接触的白内障患者的晶状体中的镍量显著高于非直接接触镍矿白内障患者和一般白内障患者晶状体中的镍量。这种关联表明人眼晶状体中的镍元素可能是白内障的致病因素之一。 相似文献
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α from natural radioactivity may interact with a nucleus and emit a neutron. The reaction introduces the background to the liquid scintillator(LS) based neutrino experiments. In the LS detector, α comes from 238 U,232Th,and 210 Po decay chains. For Gadolinium-doped LS(Gd-LS) detector, α also comes from 227 Ac. The nucleus 13 C is a natural component of Carbon which is rich in the LS. The background rate and spectrum should be subtracted carefully from the neutrino candidates. This paper describes the calculation of neutron yield and spectrum with uncertainty estimated. The results are relevant for many existing neutrino experiments and future LS or Gd-LS based experiments. 相似文献
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Hybrid-anode structure designed for a high-performance quasi-vertical GaN Schottky barrier diode 下载免费PDF全文
Qiliang Wang 《中国物理 B》2022,31(5):57702-057702
A quasi-vertical GaN Schottky barrier diode with a hybrid anode structure is proposed to trade off the on-resistance and the breakdown voltage. By inserting a SiN dielectric between the anode metal with a relatively small length, it suppresses the electric field crowding effect without presenting an obvious effect on the forward characteristics. The enhanced breakdown voltage is ascribed to the charge-coupling effect between the insulation dielectric layer and GaN. On the other hand, the current density is decreased beneath the dielectric layer with the increasing length of the SiN, resulting in a high on-resistance. Furthermore, the introduction of the field plate on the side wall forms an metal-oxide-semiconductor (MOS) channel and decreases the series resistance, but also shows an obvious electric field crowding effect at the bottom of the mesa due to the quasi-vertical structure. 相似文献
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本文结合实例,尝试从不同的视角用思维导图的方式对椭圆的弦心三角形的面积最值做一些探究,帮助学生快速识别这类模型,建立模型,再应用模型解题,最后优化模型. 相似文献
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Normally-off AlGaN/GaN heterojunction field-effect transistors with in-situ AlN gate insulator 下载免费PDF全文
AlGaN/GaN heterojunction field-effect transistors (HFETs) with p-GaN cap layer are developed for normally-off operation, in which an in-situ grown AlN layer is utilized as the gate insulator. Compared with the SiNx gate insulator, the AlN/p-GaN interface presents a more obvious energy band bending and a wider depletion region, which helps to positively shift the threshold voltage. In addition, the relatively large conduction band offset of AlN/p-GaN is beneficial to suppress the gate leakage current and enhance the gate breakdown voltage. Owing to the introduction of AlN layer, normally-off p-GaN capped AlGaN/GaN HFET with a threshold voltage of 4 V and a gate swing of 13 V is realized. Furthermore, the field-effect mobility is approximately 1500 cm2·V-1·s-1 in the 2DEG channel, implying a good device performance. 相似文献