新型功能碳材料的高压截获

高性能功能材料在诸多领域具有广泛的应用前景,是人们一直关注的研究热点。高压可以有效地改变物质的原子间距和成键方式,是获得新型功能材料的重要途径。在碳材料的高压研究中,许多有趣的功能碳材料,如光学透明碳、高强度弹性碳和超硬非晶碳等,已经通过不同的碳前驱体合成。本文简要介绍了作者近年来在低维碳基纳米复合材料高压研究中取得的进展,基于设计的不同低维碳前驱体,高压下截获了具有超硬特性、新型压致共价聚合及发光增强的碳材料。     

Instability analysis for semi-active control systems with semi-active inerters

Nonlinear Dynamics - In this paper, the instability of semi-active control systems caused by the utilization of semi-active inerters is analyzed. The purpose of this study is to demonstrate the...     

An improved evaluation of the neutron background in the PandaX-Ⅱ experiment

In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively.     

皮肤组织容积脉搏波400~1000 nm光谱特性仿真研究

根据皮肤组织解剖结构特性建立了六层层状模型,并给出了皮肤组织各层的特性参数;考虑了氧合血红蛋白和还原血红蛋白的吸收特性,依据皮肤组织各层的水、血、脂肪、血氧饱和度含量以及血管大小给出了皮肤组织各层的光谱吸收系数;对不同波长散射系数做了适当简化,给出了皮肤组织各层的光谱散射系数。利用蒙特卡罗方法仿真血管组织在收缩与舒张两种状态下, 400~1 000 nm波长光在皮肤组织多层模型中的传输过程,并通过统计大量光子的分布特性,获得了皮肤组织光谱反射系数,并利用模拟所得的两种状态下的反射系数计算得到了光谱容积脉搏波幅度。仿真结果表明,当入射光强一定时,绿光的容积脉搏波幅度优于红光和蓝光。通过计算不同波长光沿皮肤组织深度方向光能流率衰减为1/e时对应的皮肤组织深度,获得了皮肤组织光谱穿透深度。结果显示,血管舒张状态下蓝光和绿光的穿透深度较小,蓝光大部分只能达到表皮层,绿光能到达微循环层,红光可直达真皮层。考虑到光在皮肤组织中传播包含了一个从收缩到舒张的动态过程,基于此,根据穿透深度定义了脉搏波信号产生深度,利用血管舒张与收缩两种不同状态下的穿透深度计算得到了光谱产生深度。结果表明,不同波长光产生深度大于其穿透深度,蓝光产生深度较浅,且其受到的血液吸收调制较小,因而其获得的脉搏信号易受噪声干扰;红光的容积脉搏波产生深度较大,但是相比于绿光其受血液吸收调制较小,且绿光产生深度足够达到真皮血管层,因而红光容积脉搏波的幅度小于绿光。上述仿真结果明确了皮肤组织部分光谱特性,为皮肤组织多光谱容积脉搏波的精确获取及其他相关研究提供了一定的理论基础。     

运用三维离散元技术模拟落锤撞击下奥克托今颗粒的点火燃烧过程

炸药颗粒的点火燃烧过程一直是人们关注的热点问题。近年来，三维离散元技术在中尺度观测颗粒材料的动力学过程中拥有显著优势。炸药燃烧属于颗粒材料的反应动力学，运用三维离散元技术(DM3)可以有效地观测炸药燃烧传播的过程。以奥克托今(HMX)颗粒为例，本文成功模拟并观测到了HMX颗粒的燃烧反应程度，确定了颗粒开始燃烧反应的时间，以及燃烧反应传播的时间。同时，结合落锤冲击颗粒的三维图像以及其表观压强和放热功率，得到了HMX颗粒燃烧反应、燃烧传播的整个反应动力学过程，包括颗粒在冲击加载下碎化塑性变形的过程，颗粒燃烧反应放热的过程，落锤回弹颗粒喷射的过程等。同时，进一步说明了尖顶颗粒更利于颗粒点火，平顶颗粒有抑制颗粒点火的能力。     

Supercubooctahedron (Cs6Cl)2Cs5[Ga15Ge9Se48] Exhibiting Both Cation and Anion Exchange

A novel type of supertetrahedral connectivity is exhibited by the 72‐atom discrete supercubooctahedron in (Cs₆Cl)₂Cs₅[Ga₁₅Ge₉Se₄₈] ( 1 ), which undergoes both cation and anion exchange, as revealed by unambiguous single‐crystal X‐ray diffraction data. Electronic‐structure studies helped to understand the Ge/Ga distribution.     

Positive ground state solutions for Schrödinger–Poisson system with critical nonlocal term in ℝ3

This paper is dedicated to studying the following Schrödinger–Poisson system $$\left\{\begin{array}{ll}-\mathrm{\Delta }u+V(x)u-K(x)\varphi |u{|}^{3}u=a(x)f(u),& x\in {ℝ}^3,\\ -\mathrm{\Delta }\varphi =K(x)|u{|}^5,& x\in {ℝ}^3.\end{array}\right.$$ Under some different assumptions on functions V(x), K(x), a(x) and f(u), by using the variational approach, we establish the existence of positive ground state solutions.     

The High Energy X-ray telescope (HE) onboard the Insight-HXMT astronomy satellite

The Insight-Hard X-ray Modulation Telescope(Insight-HXMT) is a broadband X-ray and γ-ray(1-3000 ke V) astronomy satellite. One of its three main telescopes is the High Energy X-ray telescope(HE). The main detector plane of HE comprises 18 Na I(Tl)/Cs I(Na) phoswich detectors, where Na I(Tl) is used as the primary detector to measure ~ 20-250 ke V photons incident from the field of view(FOV) defined by collimators, and Cs I(Na) is used as the active shielding detector to Na I(Tl) by pulse shape discrimination. Additionally, Cs I(Na) is used as an omnidirectional γ-ray monitor. The HE collimators have a diverse FOV,i.e. 1.1°×5.7°(15 units), 5.7°×5.7°(2 units), and blocked(1 unit). Therefore, the combined FOV of HE is approximately5.7°×5.7°. Each HE detector has a diameter of 190 mm resulting in a total geometrical area of approximately 5100 cm2, and the energy resolution is ~15% at 60 ke V. For each recorded X-ray event by HE, the timing accuracy is less than 10 μs and the deadtime is less than 10 μs. HE is used for observing spectra and temporal variability of X-ray sources in the 20-250 ke V band either by pointing observations for known sources or scanning observations to unveil new sources. Additionally, HE is used for monitoring the γ-ray burst in 0.2-3 Me V band. This paper not only presents the design and performance of HE instruments but also reports results of the on-ground calibration experiments.     

A low-temperature electrolyte for lithium-ion batteries

In this paper, the electrochemical performance of a new low-temperature electrolyte, 0.9 mol L^?1 lithium oxalyldifluoroborate (LiODFB)/LiBF₄ (5.365:1, by mass) mixed salts in the ethylene carbonate (EC)/dimethyl sulfite (DMS)/ethyl methyl carbonate (EMC) mixed solvent (1:1:3, by volume, the same below), is studied to seek the promising candidate for advanced low-temperature lithium-ion batteries (LIBs). The results show that LIBs using this new electrolyte can be operable well at temperature below ?20 °C. This is useful to expand the application range of LIBs, especially at specific low-temperature environments, such as military and aerospace applications.