Theoretical Study of 5,8-Dinitro-5,6,7,8-tetrahydrotetrazolo[1,5-b][1,2,4]triazine (DNTzTr)
作者：HEPiao，ZHANGJian-guo，YINXin，WUJin-ting，ZHANGTong-lai（State Key Laboratory of Explosion Science and Technology； Beijing Institute of Technology）
关键词：physical chemistry density functional theory DFT polynitro-substituted tetrazolotriazine enthalpy of formation detonation performance
摘要：The structure and properties of 5,8-Dinitro-5,6,7,8-tetrahydrotetrazolo[1,5-b][1,2,4]triazine (DNTzTr) were investigated by using quantum chemistry methods.The optimized geometry and electronic density, IR and NMR spectrum data were calculated for inspecting the electronic structure properties and nature of chemical bonds at B3LYP/6-311+G(2d) level. The critical macroscopic properties such as density, enthalpy of formation and detonation performance have been also predicted. The results show that the enthalpy of formation and density of DNTzTr are 497.64kJ/mol and 1.82g/cm3,respectively. The detonation velocity and pressure are 8.73km/s and 33.97GPa, respectively.It possesses good detonation properties and can be the potential energetic material.
作者：ZHAO Huan-juan，赵焕娟，QIAN Xin-ming，钱新明（State Key Laboratory of Explosion Science &Technology,Beijing Institute of Technology；爆炸科学与技术国家重点实验室(北京理工大学)）
关键词：民用建筑 天然气爆炸 破坏效应 仿真模拟
作者：HUANG Ping，黄平，LI Jin-jie，李晋杰，YANG Shan，杨珊（State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology；北京理工大学爆炸科学与技术国家重点实验室）
关键词：煤矿工程 生产安全 事故分析 驱动因素
作者：PANG Lei，庞磊，ZHANG Qi，张奇，MA Qiu-ju，马秋菊（Beijing Municipal Institute of Labour Protection；State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology,Beijing 100081；北京市劳动保护科学研究所；北京理工大学 爆炸科学与技术国家重点实验室；State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology,Beijing 100081；北京理工大学 爆炸科学与技术国家重点实验室）
关键词：煤矿巷道 瓦斯爆炸事故 冲击波 瓦斯浓度 数值模拟
Simplified reproducing kernel method and convergence order for linear volterra integral equations with variable coefficients
作者：Liangcai Mei;Yingzhen Lin（Zhuhai Campus, Beijing Institute of Technology, Zhuhai 519088, China）
出处：Journal of Computational and Applied Mathematics2018P
摘要：This paper proposes a simplified reproducing kernel method to solve the linear Volterra integral equations with variable coefficients. The main idea of the method is to establish a reproducing kernel direct space that can be used in Volterra integral equations. And in the first time, this paper analyzes the convergence order and stability of the approximate solution. Then the uniform convergence of the numerical solution is proved, and the time consuming Schmidt orthogonalization process is avoided. The proposed method is proved to be stable and is not less than the second order convergence. The algorithm is proved to be feasible and stable through some numerical examples.
Biocompatible semiconducting polymer nanoparticles as a robust photoacoustic and photothermal agent revealing the effects of chemical structure on high photothermal conversion efficiency
作者：Jinfeng Zhang;Jing Chen;Jingkun Ren;Weisheng Guo;Xianlei Li;Rui Chen;Jipsa Chelora;Xiao Cui;Yingpeng Wan;Xing-Jie Liang;Yuying Hao;Chun-Sing Lee（b School of Life Science, Beijing Institute of Technology, Beijing 100081, PR China a Center of Super-Diamond and Advanced Films (COSDAF) & Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, PR China d Key Lab of Advanced Transducers and Intelligent Control System, Ministry of Education and Shanxi Province, College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, PR China c Chinese Academy of Sciences (CAS) Center for Excellence in Nanoscience and Laboratory of Controllable Nanopharmaceuticals, CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, National Center for Nanoscience and Technology, Beijing 100190, PR China）
摘要：Understanding the relationship between polymer chemical structure and its performance of photoacoustic imaging (PAI) and photothermal therapy (PTT) is important for developing ideal PAI/PTT agents. In this report, four semiconducting polymer nanoparticles (SPNs) with different donor-acceptor architectures are self-assembled for highly effective PAI-guided PTT. In particular, SPN1 with the longest π-conjugation length and the highest mass extinction coefficient which are beneficial for intramolecular charge transfer as well as light harvesting, exhibits the highest photothermal conversion efficiency up to 52.6%. Moreover, the as-prepared SPN1 possess good water-dispersibility, robust size-stability and excellent photothermal properties. Furthermore, the SPN1 not only exhibits a remarkable cancer cell-killing ability but also shows a prominent tumor inhibition capacity. Finally, the as-prepared water-dispersible SPN1 displays good biocompatibility and biosafety, making it a promising candidate for future biomedical applications. Considering the plenty of near infrared absorbing semiconducting polymer available, our work provides fundamental insights for rational design and preparation of highly efficient SPN-based PAI/PTT agents for cancer theranostics.
Effect of Hartree–Fock pseudopotentials on local density functional theory calculations
作者：Hengxin Tan;Yuanchang Li;S. B. Zhang;Wenhui Duan（Corresponding authors ; a State Key Laboratory of Low-Dimensional Quantum Physics and Collaborative Innovation Center of Quantum Matter, Department of Physics, Tsinghua University, Beijing 100084, China ; b Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, Beijing 100081, China E-mail: email@example.com ; c Beijing Computational Science Research Center, No. 10 East Xibeiwang Road, Beijing 100193, China ; d Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, USA E-mail: firstname.lastname@example.org ; e Institute for Advanced Study, Tsinghua University, Beijing 100084, China E-mail: email@example.com）
出处：Physical Chemistry Chemical Physics2018P
摘要：Density functional theory (DFT) can run into serious difficulties with localized states in elements such as transition metals with occupied d states and oxygen. In contrast, including a fraction of the Hartree–Fock exchange can be a better approach for such localized states. Here, we develop Hartree–Fock pseudopotentials to be used alongside DFT for solids. The computational cost is on a par with standard DFT. Calculations for a range of II–VI, III–V and group-IV semiconductors with diverse physical properties show an observably improved band gap for systems containing d-electrons, pointing to a new direction in electronic theory.
Numerical investigation of the flow evolution of an oscillating foil with the different reduced frequency
作者：M J Zhang;Q Wu and B Huang（School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China;School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China;Department of Thermal Engineering, Tsinghua University, Beijing 100084, China;School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China）
出处：IOP Conference Series: Earth and Environmental Science2018P
摘要：The power extraction systems based on oscillating foil are played more and more attention in alternative energy extraction systems. The dynamic stall problem on oscillating foil is related to general performance of energy extraction systems, where a varying flow filed is introduced by a rapid change in the effective angle of attack. The objective of this paper is to investigate the flow evolution of an NACA0012 foil undergoing sinusoidal pitching motion with the different reduced frequency. The k-ω SST turbulence model, coupled with a two-equation γ-Reθ transition model, is used for the turbulence closure. The results showed that the numerical method can well capture the dynamic stall process. With the increasing of the reduced frequency, the dynamic stall is delayed during the development of the Leading Edge Vortex stage. During post-stall vortex shedding stage, the mechanism of post-stall vortex shedding present different style at different reduced frequency K. When K=0.1, the secondary vortex forms and covers the whole suction face again along with the shedding of LEV. Compared to the case of K=0.1, no secondary vortex was induced for K=0.05. However, When K=0.2, the secondary vortex covers the whole suction surface again because the oscillating velocity is too fast to develop the secondary vortex.
Numerical investigation of the transient cavitating flow and vortical patterns around a hydrofoil
作者：Q Wu;M J Zhang;B Huang;G Y Wang and S L Cao（Department of Thermal Engineering, Tsinghua University, Beijing 100081, China;School of Mechanical Engineering, Beijing Institute of Technology, Beijing, China;School of Mechanical Engineering, Beijing Institute of Technology, Beijing, China;School of Mechanical Engineering, Beijing Institute of Technology, Beijing, China;Department of Thermal Engineering, Tsinghua University, Beijing 100081, China）
出处：IOP Conference Series: Earth and Environmental Science2018P
摘要：The objective of this work is to investigate the cavitating flow mechanism of a specific hydrofoil, Tulin hydrofoil, and better understand the vortex-cavitation interactions in transient cavitating flows. The numerical investigations are performed using a large eddy simulation method and the Zwart cavitation model. The predicted cavity formation and evolution agree well with the experimental observation. An asymmetric vortex street has been formed, with the upper one (the trailing edge vortex street) has a regular vortex shape and a clear boundary between vortex structures, while the lower one (the leading edge vortex street) has a larger cavitation area due to the low pressure distribution on the suction side of the foil. The turbulent kinetic energy transport equation has been adopted to examine the balance and contribution of different mechanisms. The formation and evolution of the leading and trailing edge vortex structures are responsible for the generation and modification of the turbulent kinetic energy distributions. The convection term varies significantly in the cavity region during the phase change process, and the boundary of the vortex structures enhance the production term of the turbulent kinetic energy.
Numerical study of the fluid-structure interaction of composite hydrofoil with different plying angles in steady flow
作者：H Z Zhang;Q Wu;B Huang and G Y Wang（School of Mechanical Engineering, Beijing Institute of Technology, Beijing, China;Department of Thermal Engineering, Tsinghua University, Beijing, China;School of Mechanical Engineering, Beijing Institute of Technology, Beijing, China;School of Mechanical Engineering, Beijing Institute of Technology, Beijing, China）
出处：IOP Conference Series: Earth and Environmental Science2018P
摘要：The object of this paper is to numerically investigate the fluid-structure interaction of composite hydrofoil. The aim is to validate 3D numerical simulation model with fluid-structure interaction of composite materials comparing to experimental data, and study the fluid-structure interaction of composite hydrofoil. Numerical results are presented for a composite hydrofoil. The hydrofoil has unswept trapezoidal planform of aspect ratio 3.33. The numerical model has been validated and showed reasonable agreement with the experiment measurements. Then the forces and deformations of composite hydrofoil with different plying angles have been investigated at Re=1x10 6 and initial angle of attack α=6°. The results show that lift and drag coefficients and tip twist angle decrease and get minimum at about plying angle θ=35°. According to Classical Laminate Theory, the intrinsic bending-twisting coupling of composite structures leads to the variation of twist angle for different plying angles. The relation expression on elements of matrices D has been derived to estimate twist angle at tip qualitatively.
Segmented fast linear canonical transform
作者：Yan-Nan Sun and Bing-Zhao Li（1 School of Mathematics and Statistics, Beijing Institute of Technology, Beijing 100081, China 2 Beijing Key Laboratory on MCAACI, Beijing Institute of Technology, Beijing 100081, China）
出处：Journal of the Optical Society of America A2018P
摘要：Investigation of the discrete and fast linear canonical transforms is becoming one of the hottest research topics in modern signal processing and optics. How to handle and obtain the linear canonical frequency spectrum of very large input data based on equipment with limited memory space is one of the key problems. To focus on this problem, a new kind of segmented fast linear canonical transform has been proposed in this paper. First, the large data is segmented into short data. Thereby, the proposed algorithms can calculate very large input data and simultaneously keep the ideal frequency resolution. Second, the complexity of the derived algorithms has been analyzed in detail for different kinds of signals. Their performance with regard to resolution and precision are compared with the existing fast linear canonical transforms. Finally, experimental results are presented to verify the correctness of the results obtained.
Air-to-Air Path Loss Prediction Based on Machine Learning Methods in Urban Environments
作者：Yan Zhang;Jinxiao Wen;Guanshu Yang;Zunwen He;Xinran Luo（School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China）
出处：Wireless Communications and Mobile Computing2018P
摘要：Recently, unmanned aerial vehicle (UAV) plays an important role in many applications because of its high flexibility and low cost. To realize reliable UAV communications, a fundamental work is to investigate the propagation characteristics of the channels. In this paper, we propose path loss models for the UAV air-to-air (AA) scenario based on machine learning. A ray-tracing software is employed to generate samples for multiple routes in a typical urban environment, and different altitudes of Tx and Rx UAVs are taken into consideration. Two machine-learning algorithms, Random Forest and KNN, are exploited to build prediction models on the basis of the training data. The prediction performance of trained models is assessed on the test set according to the metrics including the mean absolute error (MAE) and root mean square error (RMSE). Meanwhile, two empirical models are presented for comparison. It is shown that the machine-learning-based models are able to provide high prediction accuracy and acceptable computational efficiency in the AA scenario. Moreover, Random Forest outperforms other models and has the smallest prediction errors. Further investigation is made to evaluate the impacts of five different parameters on the path loss. It is demonstrated that the path visibility is crucial for the path loss.
High-correlated residuals improved estimation in the high-dimensional SUR model
作者：Li Zhao;Liang Yan;Xingzhong Xu（School of Mathematics and Statistics, Beijing Institute of Technology, Beijing, China School of Mathematics and Statistics, Beijing Institute of Technology, Beijing, China School of Mathematics and Statistics, Beijing Institute of Technology, Beijing, China; Beijing Key Laboratory on MCAACI, Beijing, China）
出处：Communications in Statistics - Simulation and Computation2018P
摘要：This article focuses on estimating regression coefficients in the high-dimensional seemingly unrelated regression model. When the number of equations exceeds that of the observations, both the maximum likelihood estimator and Zellner’s two-stage estimator do not exist. As an alternative, we propose a two-stage conditional expectation improved estimator. The new estimator is further improved by the high-correlated residuals, and the high correlation is determined by hypothesis testings. Simulations show that the new estimator outperforms the ordinary least-squares estimator in terms of mean square errors, especially when high-correlated residuals exist between the equations.