可见光条纹相机可靠性实验研究北大核心CSCD

基于“晨光号”X光机开展了可见光条纹相机在复杂的辐射/电磁环境中的可靠性实验研究。利用序列脉冲激光的成像状态表征条纹相机的扫描状态,采取了不同的辐射/电磁防护措施,研究其对扫描状态的影响。实验研究获得了该类相机在此类复杂环境中正常工作的防护方法,主要包括增强辐射屏蔽使条纹相机附近的单发次等效空气吸收剂量不超过6μGy、减少相机机壳的缝隙、采取光电隔离的触发方式等。     

Molecular dynamics simulation of TCDD adsorption on organo-montmorillonite

In this work, molecular dynamics simulation was applied to investigate the adsorption of Tetrachlorodibenzo-p-Dioxin (TCDD) on tetramethylammonium (TMA) and tetrapropylammonium (TPA) modified montmorillonite, with the aim of providing novel information for understanding the adsorptive characteristics of organo-montmorillonite toward organic contaminants. The simulation results showed that on both outer surface and interlayer space of TPA modified montmorillonite (TPA-mont), TCDD was adsorbed between the TPA cations with the molecular edge facing siloxane surface. Similar result was observed for the adsorption on the outer surface of TMA modified montmorillonite (TMA-mont). These results indicated that TCDD had stronger interaction with organic cation than with siloxane surface. While in the interlayer space of TMA-mont, TCDD showed a coplanar orientation with the siloxane surfaces, which could be ascribed to the limited gallery height within TMA-mont interlayer. Comparing with TMA-mont, TPA-mont had larger adsorption energy toward TCDD but smaller interlayer space to accommodate TCDD. Our results indicated that molecular dynamics simulation can be a powerful tool in characterizing the adsorptive characteristics of organoclays and provided additional proof that for the organo-montmorillonite synthesized with small organic cations, the available interlayer space rather than the attractive force plays the dominant role for their adsorption capacity toward HOCs.     

基于蜱虫效应的Sgn函数突变模型

通过医疗决策中由于受代表性启发方式影响误诊引起的“蜱虫效应”,建立了Sgn函数的突变模型,基于此模型发展了一种新的突变理论．论文分析了代表性启发方式引起的五种偏差,运用Sgn函数突变模型对中国用工荒这一“蜱虫效应”反映的复杂社会经济问题进行了系统研究．     

Highly efficient synthesis of a class of novel chiral-bridged atropisomeric monophosphine ligands via simple desymmetrization and their applications in asymmetric Suzuki-Miyaura coupling reaction

A series of novel chiral-bridged atropisomeric monophosphine ligands were synthesized via convenient and simple pathways. The prepared ligands, especially for ligand 7d, were found to be highly effective in the Pd-catalyzed Suzuki-Miyaura coupling reaction. The steric hindrance and electronic effect of substrates on the reactivity and enantioselectivity were explored preliminarily.     

INTERNAL SOLITARY WAVE LOADS EXPERIMENTS AND ITS THEORETICAL MODEL FOR A CYLINDRICAL STRUCTURE

在大型重力式密度分层水槽中, 对内孤立波与圆柱型结构的相互作用特性开展了系列实验. 基于两层流体中 内孤立波的KdV,eKdV和MCC理论, 建立了圆柱型结构内孤立波载荷的理论预报模型, 给出了该载荷理论预报模型中3类内孤立波理论的适用性条件.研究表明, 圆柱型结构内孤立波水平载荷包括水平Froude-Krylov力、附加质量力和拖曳力3个部分, 可以由Morison公式计算, 而内孤立波垂向载荷主要为垂向Froude-Krylov力, 可以由内孤立波诱导动压力计算.系列实验结果表明, 附加质量系数可以取为常数1.0, 拖曳力系数与内孤立波诱导速度场的雷诺数之间为指数函数关系, 而且基于理论预报模型的数值结果与系列实验结果吻合.     

Universal Scaffold for an Activatable Photosensitizer with Completely Inhibited Photosensitivity

Activatable photosensitizers (aPSs) sensitive to specific stimuli hold potential for targeting multiple disease biomarkers and are desirable for photodynamic therapy (PDT). Presented herein is the design of aPSs that can be activated and fully recover from an inhibited state in the presence of specific biomarker. A designed long‐wavelength D‐π‐A photosensitizer, PS_Se‐I , with highly efficient photosensitivity for generation of ¹O₂ was used. Caging of the phenolate donor of PS_Se‐I with a biomarker‐sensitive group provided ^ALP PS , and the drastic activation of its photosensitivity was demonstrated intracellularly. To enhance the flexibility of the design strategy, a clickable azide group was introduced into the scaffold to allow integration of more functionality. Modularly derived ^mito‐PN PS , equipped with a mitochondria‐targeting group and a specific peroxynitrite‐reactive trigger, was synthesized and demonstrated superior performance in cells. This strategy could lead to customization of aPSs applicable to a specific PDT.     

UiO-67-Sal-CuCl2在空气中催化芳香醇的选择性氧化

利用水热法一步合成了金属有机骨架(MOFs)材料UiO-67-Sal, 并将3种铜盐固定在其表面, 研究了3种铜MOFs材料催化芳香醇选择性氧化的性能. 结果表明, UiO-67-Sal-CuCl₂催化剂对芳香醇选择性氧化反应具有良好的催化活性, 且在重复使用4次后, 依然保持较好的催化效果.     

A Three-Dimensional Infinite Collapse Map with Image Encryption

Chaos is considered as a natural candidate for encryption systems owing to its sensitivity to initial values and unpredictability of its orbit. However, some encryption schemes based on low-dimensional chaotic systems exhibit various security defects due to their relatively simple dynamic characteristics. In order to enhance the dynamic behaviors of chaotic maps, a novel 3D infinite collapse map (3D-ICM) is proposed, and the performance of the chaotic system is analyzed from three aspects: a phase diagram, the Lyapunov exponent, and Sample Entropy. The results show that the chaotic system has complex chaotic behavior and high complexity. Furthermore, an image encryption scheme based on 3D-ICM is presented, whose security analysis indicates that the proposed image encryption scheme can resist violent attacks, correlation analysis, and differential attacks, so it has a higher security level.     

氦团簇及氦间隙原子在钨中的稳定性研究

首先采用分子动力学方法研究了在钨中预存氦-空位团簇（He_nV₂₂）后氦原子结合能与氦-空位比的关系。研究发现:当氦-空位比小于4.5时,氦原子结合能随氦-空位比呈线性减小趋势;当氦-空位比大于4.5时,氦原子的结合能随氦-空位比出现剧烈振荡的现象,这种现象是由于钨中预存氦-空位团簇随机挤出位错环使体系能量骤降所导致的。与此同时,氦-空位团簇周围出现了一些处于亚稳态的fcc结构和hcp结构的钨。为了研究氦团簇周围压强对钨基体相变的影响,本文利用第一性原理对钨的三种结构进行了高压相变计算,发现静水压力不能使钨的三种结构互相转变。另外,通过对bcc钨和fcc钨中四面体间隙氦原子和八面体间隙氦原子电荷密度差的计算,发现bcc钨中四面体间隙氦原子的稳定性高于八面体间隙氦原子的稳定性,而在fcc钨中四面体间隙氦原子的稳定性弱于八面体间隙氦原子的稳定性。     

丁烯在纳米H-ZSM-5催化剂上的催化裂解反应

在小型固定床反应器中考察了纳米H-ZSM-5催化剂(晶粒度为20～50nm)对丁烯催化裂解制丙烯反应的催化性能,并与两种微米H-ZSM-5催化剂样品(晶粒度分别为1～2和1～6μm)进行了比较.结果表明,在相同的反应条件下,纳米H-ZSM-5和微米H-ZSM-5催化剂上的初始丁烯转化率及丙烯收率相当,但纳米H-ZSM-5催化剂在反应中的抗积碳失活性能优于微米H-ZSM-5催化剂.在进料质量空速7h-1,常压和560℃的条件下反应,当丁烯转化率和丙烯收率下降50%时,两种微米催化剂上的反应时间仅为28h左右,而纳米催化剂上的反应时间为120h左右.积碳分析结果表明,纳米催化剂上的积碳速率明显低于微米催化剂.