Strategy of improving the stability and detonation performance for energetic material by introducing the boron atoms

A novel stable energetic compound (E)‐1,2‐diamino‐1,2‐dinitrodiboron (DANB) was theoretically designed based on the structure of 1,1‐diamino‐2,2‐dinitroethene (FOX‐7). Atomization method in combination with Hess' law was used to predict the heat of formation. The detonation velocity (D) and detonation pressure (P) of DANB were approximatively estimated by using Kamlet–Jacobs equations. As a result, DANB has huge heat of formation (2013.5 kJ/mol) and specific enthalpy of combustion (?26.4 kJ/g). Furthermore, DANB possesses high crystal density (1.85 g/cm³) and heat of detonation (5476.0 cal/g), which lead to surprising detonation performance (D = 10.72 km/s, P = 51.9 GPa) that is greater than those of FOX‐7 (D = 8.63 km/s, P = 34.0 GPa) and CL‐20 (D = 9.62 km/s, P = 44.1 GPa). More importantly, DANB is very stable because its bond dissociation energy of the weakest bond (BDE = 357.8 kJ/mol) is larger than those of the most common explosives, such as FOX‐7 (BDE = 200.4 kJ/mol), CL‐20(BDE = 209.2 kJ/mol), HMX(BDE = 165.7 kJ/mol), and RDX (BDE = 161.4 kJ/mol). Therefore, our results show that DANB is a promising candidate for stable and powerful energetic material.     

Photochromism of new unsymmetrical diarylethenes with a quinoline moiety

Three unsymmetrical diarylethenes with a 6‐membered quinoline moiety were synthesized to investigate the effects of the substituents on their photochromism, and fluorescence, and the structure of one diarylethene was determined by single crystal X‐ray diffraction analysis. Quinoline was connected directly to the central perfluorocyclopentene ring as an aryl moiety and available to participate in photoisomerization reaction in solution, amorphous films, and crystalline phase. These diarylethenes exhibited good photochromism with excellent thermal stability and obvious fatigue resistance. The electron‐donating methoxy group could enhance the absorption maxima of closed‐ring isomers and the quantum yields of cyclization and cycloreversion, but the electron‐withdrawing trifluoromethyl had an opposite effect. In addition, they functioned as notable fluorescence switches in both solution and polymethylmethacrylate films, and the trifluoromethyl group and the methoxy group both increased the emission intensity. The results revealed that the quinoline moiety and substituents played a vital role in the process of photoisomerization reactions for these diarylethenes.     

Renal Clearable Luminescent WSe2 for Radioprotection of Nontargeted Tissues during Radiotherapy

High‐energy ionizing radiation is widely used in medical diagnosis and cancer radiation therapy. However, high‐energy radiation can also impose significant damages in healthy tissues during medical treatments via direct DNA damages and indirect damages from production of reactive oxygen species (ROS). Therefore, it is urgent to develop highly effective radioprotectants with low toxicities that can meet the increasing needs for alleviating the adverse effects from cancer radiation therapy and nuclear emergency. In this work, strongly catalytic ultrasmall (sub‐5 nm) cysteine‐protected WSe₂ dots are employed to protect healthy tissues against radiation via diminishing radiation‐induced free radicals. The WSe₂ dots with high surface activities can recover radiation‐induced DNA damages and eliminate the excessive ROS generated from radiation. In vivo experiments confirm that the survival rate of mice treated with WSe₂ dots is significantly elevated with radiation damages postponed under exposure to high‐dose ionizing radiation. Furthermore, the free radicals in major organs and hematological system can be appreciably omitted, suggesting their unique role as free radical scavengers. These WSe₂ dots in ultrasmall size show rapid renal clearance of ≈74% injection dose via urine excretion in 24 h and do not cause any apparent toxicity in vivo for up to 30 d.     

Numerical study of InGaN tandem solar cells with intermediate bands

Theoretical investigations of InGaN tandem solar cells with intermediate bands (IBs) have been conducted through calculating the diode equation taking into account the radiative and nonradiative recombination currents. The calculated maximum ef?ciencies of the double‐junction cell with one IB in each subcell are 57.85% and 68.37% under AM1.5G one‐sun and 46000‐sun illuminations, respectively. It has also been observed that the combined device with the top‐cell bandgaps of 2.9–3.4 eV (2.6–3.4 eV for full concentration) may have an opportunity to realize the application of over 50% efficiency. We suggest that the optimized width of the IB layer be designed in the range of 1–6 μm if its absorption coefficient is 10⁴–10⁵ cm^–1 in the IB region.     

基于面积灰关联相对贴近度模型的长三角制造业产业升级研究

借助“制造业高级化”产业升级理论, 从结构优度、价值链高度、环境保护程度三个维度构建制造业产业升级评价指标体系。根据TOPSIS思想, 以被评价对象数列和理想方案指标数列两相邻点间围成图形的面积来表征关联系数, 同时采用标准差修正G1组合赋权原理对指标赋权并进一步计算灰关联相对贴近度; 通过引入时间变量并赋予时间序列权重以实现对长三角制造业产业升级动态评价。研究结果显示:2010至2016年间, 上海市排名最高, 江苏省略高于浙江省, 安徽省最低; 安徽省是长三角制造业产业升级的短板。基于上述结论, 给出长三角制造业产业升级的政策建议。     

MnxGe1－x稀磁半导体薄膜的结构研究

利用X 射线衍射(XRD)和X射线吸收精细结构(XAFS)方法研究了磁控共溅射方法制备的Mn_xGe_1-x薄膜样品的结构随掺杂磁性原子Mn含量的变化规律.XRD结果表明，在Mn的含量较低(7.0%)的Mn_0.07Ge_0.93样品中，只能观察到对应于多晶Ge的XRD衍射峰，而对Mn含量较高(25.0%, 36.0%)的Mn_0.25Ge_0.75和Mn关键词： 磁控溅射 XRD XAFS xGe_1-x稀磁半导体薄膜')" href="#">Mn_xGe_1-x稀磁半导体薄膜     

High-power 880-nm diode-directly-pumped passively mode-locked Nd:YVO₄ laser at 1342 nm with a semiconductor saturable absorber mirror

A high-power 880-nm diode-directly-pumped passively mode-locked 1342 nm Nd:YVO? laser was demonstrated with a semiconductor saturable absorber mirror (SESAM). The laser mode radii in the laser crystal and on the SESAM were optimized carefully using the ABCD matrix formalism. An average output power of 2.3 W was obtained with a repetition rate of 76 MHz and a pulse width of 29.2 ps under an absorbed pump power of 12.1 W, corresponding to an optical-optical efficiency of 19.0% and a slope efficiency of 23.9%, respectively.     

基于新型MRTD模型研究扫描型红外热像仪的视距

 基于人眼视觉系统可感知的阈值信噪比,提出预测红外热像仪最小可分辨温差（MRTD）方法。该方法根据频谱理论和红外热成像系统的二维调制传递函数,并结合匹配滤波器的概念,描述4条带标准靶的空间频谱函数。利用此空间频谱函数研究了4条带标准靶经过红外热成像系统的调制传递之后人眼视觉系统的感知信噪比。基于人眼视觉系统可感知的阈值信噪比,建立一个新的MRTD模型。依据此MRTD模型和视距模型,实现红外热像仪视距的预测。仿真结果表明,该方法预测的视距与实验数据有很好的一致性。