聚龙一号装置上首次铝套筒Z箍缩X射线背光照相实验

在聚龙一号脉冲功率装置上首次完成了对带正弦扰动铝套筒Z箍缩的X射线背光照相实验。实验采用千焦耳激光器（1053 nm, 1 kJ, 1 ns）驱动固体靶材产生X射线, 然后利用基于球面晶体的单色背光照相技术以及直接点投影背光照相技术, 成功观测到约7.5 MA电流驱动条件下, Z箍缩铝套筒的外边界不稳定性发展情况。该实验验证了在聚龙一号装置上联合千焦耳激光器开展X射线背光照相实验的能力, 为后续精密Z箍缩物理研究奠定了基础。     

Z箍缩等离子体振荡引起的电磁脉冲辐射

从理论上研究了Z箍缩过程中单模的等离子体振荡引起的电磁脉冲辐射。当模式扰动的相速度大于真空中的光速时,电磁脉冲辐射具有类似于切伦科夫辐射的角分布特征,并且随着相速度的增大这种定向辐射特征越显著;不同波长的电磁辐射也具有不同的角分布特征,短波长的电磁脉冲具有更好的定向性。电磁辐射功率强烈依赖于电子的等离子体振荡频率和等离子体柱的半径。     

X箍缩三维数值模拟

利用FOI-PERFECT程序对X箍缩进行了3D数值模拟研究,给出了X箍缩的物理图像和动力学过程,探讨了Z箍缩中出现磁重联的可能性,并指出如果双丝Z箍缩中能够出现磁重联,那么X箍缩是更有利于磁重联出现的位形,并且,X箍缩中出现多重X射线暴的一个可能原因是z轴上多个位置出现磁重联。     

CeO2修饰Ni3S2纳米片用于高效电催化析氧

电化学水分解制氢作为重要的生产氢能的新能源技术,包括氢气析出反应(HER)和氧气析出反应(OER).然而,OER进行的是多步电子转移过程,动力学过程缓慢且过电位高,严重制约了电解水制氢的发展.因此开发低成本、高效稳定的非贵金属催化剂替代贵金属催化剂(RuO2,IrO2)来降低过电位,减少能源消耗十分必要.Ni3S2由于...     

应用理论计算研究MCM-22分子筛相邻酸性位上乙烯和苯的吸附

应用ONIOM计算方法研究了MCM-22分子筛超笼12元环上存在两个酸性位时的酸强度及其与骨架铝之间距离的关系,并研究了乙烯和苯分子吸附的规律.计算采用52T簇模型和B3LYP/6-31G**/MNDO方法.结果表明,存在两个酸性位且两个骨架铝之间间隔1个骨架硅时,酸强度比孤立的酸性位明显降低;当间隔的硅原子数增加时,酸强度呈上升趋势,间隔3个以上骨架硅时,其酸强度与孤立的酸性位几乎没有差别.对于乙烯的吸附,当两个骨架铝之间间隔1~4个骨架硅时,其吸附能几乎没有差别(31~35 kJ/mol);对于苯的吸附,当两个骨架铝之间间隔1个骨架硅时,其吸附能有所提高,因为两个桥羟基同时对苯分子产生氢键吸附作用.当两个骨架铝之间的距离增大时,苯的吸附能几乎相同(21~29 kJ/mol).若两个乙烯分子或苯分子同时吸附在双酸性位上,其吸附能与单个分子在孤立酸性位吸附时几乎没有差别.应用自然键轨道计算分析了吸附配合物的电子结构,进一步探明了乙烯和苯在分子筛酸性位上吸附的本质.     

H-ZSM-5分子筛上的乙烯二聚反应机理的理论计算研究

应用分子力学和量子力学联合的ONIOM2(B3LYP/6-31G(d,p):UFF)计算方法研究了H-ZSM-5分子筛上乙烯二聚反应的机理. 用40T簇模型模拟ZSM-5分子筛位于孔道交叉点的酸性位,对乙烯二聚过程的分步反应和协同反应两种机理进行了考察. 对于分步反应机理,乙烯分子首先通过π-氢键作用在酸性位形成稳定的吸附络合物,再进一步发生质子化并生成乙醇盐中间体,随后乙醇盐与第二个乙烯分子发生碳-碳键结合形成丁醇盐产物. 第一步质子化和第二步碳链聚合的活化能分别为152.88和119.45 kJ/mol, 表明乙烯质子化反应为速控步骤. 对于协同反应机理,乙烯质子化、碳-碳键和碳-氧键生成同时进行,生成丁醇盐,反应的活化能为162.30 kJ/mol, 略高于分步反应机理中的速控步骤. 计算结果表明这两种反应机理之间存在相互竞争.     

利用界面激基复合物发射大致估算稀土配合物LUMO能级

研究了一种利用无荧光稀土配合物与同一受体材料形成的界面激基复合物的发射来大致估算其最低未占据轨道(LUMO)能级简单方法.镥、钆、钪三种稀土配合物与星形爆炸物形成的激基复合物发射峰位分别在590,607和656 nm,与此相对应LUMO能级计算结果大致为3.0,3.06,3.21 eV.     

Interfacial Adhesion between Fatty Acid Collectors and Hydrophilic Surfaces: Implications for Low-Rank Coal Flotation

Fatty acids, which are enriched in vegetable oil, have attracted much attention in low-rank coal flotation because of their unique chemical structure. In this study, density functional theory calculations, molecular dynamics simulations, and atomic force microscopy were employed to investigate the adsorption structure and forces between collectors and hydrophilic surfaces. The results show that fatty acids can be easily adsorbed onto surfaces through hydrogen bonds, and can cover the oxygen sites. The existence of hydration film on hydrophilic surfaces prevented nonpolar molecules from being able to adsorb, while polar fatty acids could adsorb and expel water molecules. The adhesion force between the RCOOH-terminated probe and the surface appeared in the retraction process, which differed significantly from that of the RCH₃-terminated probe, indicating that polar fatty acids are more suitable as flotation collectors for low-rank coal than nonpolar hydrocarbon oil. The simulation and AFM test revealed the mechanisms of polar fatty acids, and can provide guidance for low-rank coal flotation applications.     

Adversarial Data Hiding in Digital Images

In recent studies of generative adversarial networks (GAN), researchers have attempted to combine adversarial perturbation with data hiding in order to protect the privacy and authenticity of the host image simultaneously. However, most of the studied approaches can only achieve adversarial perturbation through a visible watermark; the quality of the host image is low, and the concealment of data hiding cannot be achieved. In this work, we propose a true data hiding method with adversarial effect for generating high-quality covers. Based on GAN, the data hiding area is selected precisely by limiting the modification strength in order to preserve the fidelity of the image. We devise a genetic algorithm that can explore decision boundaries in an artificially constrained search space to improve the attack effect as well as construct aggressive covert adversarial samples by detecting “sensitive pixels” in ordinary samples to place discontinuous perturbations. The results reveal that the stego-image has good visual quality and attack effect. To the best of our knowledge, this is the first attempt to use covert data hiding to generate adversarial samples based on GAN.     

基于Arnold变换的图像逆置乱算法

针对Arnold变换的周期依赖于图像的阶数这一特性,提出了一种反变换算法.该算法通过分析加密图像任一点处两坐标分量间关系,得到原图像相应点的坐标,从而实现图像的解密.该反变换也可作为图像置乱的正变换,相应的反变换就是Arnold变换.在此基础上,把二维反变换算法推广到m维的情形.实验结果表明,对于已应用Arnold变换进行预处理的置乱图像,在无须计算原图像变换周期的前提下可快速实现图像的逆置乱,该过程具有确定性,其迭代次数与预处理置乱次数相等.