Investigation of β-Ga_2O_3 films and β-Ga_2O_3/GaN heterostructures grown by metal organic chemical vapor deposition

In this work,(-201) β-Ga_2O_3 films are grown on GaN substrate by metal organic chemical vapor deposition(MOCVD). It is revealed that the β-Ga_2O_3 film grown on GaN possesses superior crystal quality, material homogeneity and surface morphology than the results of common heteroepitaxial β-Ga_2O_3 film based on sapphire substrate. Further, the relevance between the crystal quality of epitaxial β-Ga_2O_3 film and the β-Ga_2O_3/GaN interface behavior is investigated. Transmission electron microscopy result indicates that the interface atom refactoring phenomenon is beneficial to relieve the mismatch strain and improve the crystal quality of subsequent β-Ga_2O_3 film. Moreover, the energy band structure of β-Ga_2O_3/GaN heterostructure grown by MOCVD is investigated by X-ray photoelectron spectroscopy and a large conduction band offset of 0.89 eV is obtained. The results in this work not only convincingly demonstrate the advantages of β-Ga_2O_3 films grown on GaN substrate, but also show the great application potential of MOCVD β-Ga_2O_3/GaN heterostructures in microelectronic applications.     

Minimum-time optimal control of robotic manipulators based on Hamel’s integrators

Meccanica - In this paper, we develop a framework of time optimization path planning for robotic manipulators surrounded by static obstacles. Our approach is based on the recursive dynamics method...     

Switched-model-based compound control of hypersonic vehicles with input nonlinearities

Nonlinear Dynamics - Focusing on the large-envelope control problem of air-breathing hypersonic vehicles (AHVs), this paper employs a switched control-oriented model (SCOM) to describe vehicle...     

Deep Hierarchical Ensemble Model for Suicide Detection on Imbalanced Social Media Data

As a serious worldwide problem, suicide often causes huge and irreversible losses to families and society. Therefore, it is necessary to detect and help individuals with suicidal ideation in time. In recent years, the prosperous development of social media has provided new perspectives on suicide detection, but related research still faces some difficulties, such as data imbalance and expression implicitness. In this paper, we propose a Deep Hierarchical Ensemble model for Suicide Detection (DHE-SD) based on a hierarchical ensemble strategy, and construct a dataset based on Sina Weibo, which contains more than 550 thousand posts from 4521 users. To verify the effectiveness of the model, we also conduct experiments on a public Weibo dataset containing 7329 users’ posts. The proposed model achieves the best performance on both the constructed dataset and the public dataset. In addition, in order to make the model applicable to a wider population, we use the proposed sentence-level mask mechanism to delete user posts with strong suicidal ideation. Experiments show that the proposed model can still effectively identify social media users with suicidal ideation even when the performance of the baseline models decrease significantly.     

磁性单层膜磁学性质的Monte Carlo模拟

采用类Ising模型,利用Monte Carlo方法研究了磁性单层膜中退磁性偶极作用和铁磁性交换作用对系统磁学性质的影响.结果显示,随着偶极相互作用的增加,系统在低温下的磁化出现平台现象,此时磁化曲线可分为2个阶段,在低外场下,温度升高,系统易磁化,在高外场下则反之.这种新奇的磁化行为导致系统的磁熵变在低温低外场下出现大于零的反常行为.在模拟过程中,对长程力作用采用了比较精确的处理方法.     

Synthesis,Bioactivity Evaluation,3D-QSAR,and Molecular Docking of Novel Pyrazole-4-carbohydrazides as Potential Fungicides Targeting Succinate Dehydrogenase

To screen novel antifungal agents targeting the succinate dehydrogenase(SDH),a series of pyrazole-4-carbohydrazides were rationally designed,synthesized,and characterized under the guidance of the structures of succinate dehydrogenase inhibitors(SDHIs).Bioassay results in vitro indicated that most of the target compounds exhibited excellent activity against Rhizoctonia solani(R.solani),Fusarium graminearum(F.graminearum),Botrytis cinerea(B.cinerea)and Colletotrichum capsica(C.cinerea).Compounds 7d,7l,7t and 7x were identified as the most promoting candidates,and their anti-F.graminearum EC50 values were as low as 0.56,0.47,0.46 and 0.49μg/mL,respectively,presenting the similar antifungal activity as that of the commonly used fungicide carbendazim(0.43μg/mL).The 3D-QSAR models were built for a systematic structure-activity relationship profile to explore more potent pyrazole-4-carbohydrazides as novel fungicides.Molecular docking of 7d,7l and 7r with SDH was performed to reveal the binding modes in active pocket and analyze the interactions between the molecules and the SDH protein.     

Saturation field direction dependence of domain structures in NiFe elements

The domain structures in NiFe elements were studied by magnetic force microscopy measurement and micromagnetic modeling. The remanent states in the elements were dependent on the direction of the saturation field. The “S” and “U” states were observed at remanence by applying the saturation field at different directions. The “S” and “U” states are metastable: magnetic force microscopy tip field-induced switching from the “S” and “U” states to the flux closure configuration was observed.     

Na2GdPO4F2:Tb3+绿色荧光粉阴极射线发光研究

通过高温固相法制备Na2GdPO4F2:Tb3+绿色荧光粉,并利用X射线粉末衍射(XRD)和阴极射线光谱分别对其物相、阴极射线发光性能进行研究.结果表明,Tb3+作为绿色发光中心进入到Na2Gd2PO4F2的晶格中取代Gd3+的格位,在低电子束(0.5～5 kV)激发下主要表现出Tb3+的特征跃迁(5D3.4→7FJ,J=6～2),其中以5D4→7F5跃迁(546 nn)为主.样品Na2Gd0.95Tb0.05PO4F2在阴极射线激发下的色坐标为(0.240 3,0.438 6).随着电压、电流和掺杂量的增加,荧光粉的发光强度逐渐提高,其中,最佳的样品为Na2Gd0.9Tb0.1PO4F2.     

近红外光谱定量分析的新方法:半监督最小二乘支持向量回归机

在近红外光谱定量分析中,样品化学值测定的准确度是运用数学模型进行定量分析精确度的理论极限。但能够准确获取化学值的样品数量比较少,许多模型在建模时只考虑这部分样品数据,而不考虑大量的无化学值的样品数据。针对该问题,本文在LS-SVR的基础上,提出了可以同时利用有化学值(标签)和无化学值样品数据的半监督LS-SVR(S2LS-SVR)模型。类似于LS-SVR,该模型也只需求解一个线性方程组。最后,以烤烟样品数据集为实验材料,建立了四种样品成分(总糖、还原糖、总氮和烟碱)的定量分析模型。四种样品成分的预测值与实际值的平均误差分别为6.62%,7.56%,6.11%和8.20%,相关系数分别为0.974 1,0.973 3,0.923 0和0.948 6。经分析比较发现S2LS-SVR模型优于PLS和LS-SVR,从而验证了S2LS-SVR模型的可行性和有效性。     

冷原子系综内单集体激发态的相干操纵

原子系综内部分原子发生相干态转移后所处量子态被称为集体激发态.如果激发数目在单原子量级则被称为单激发态.在量子存储过程中,单光子以单激发态的形式在原子系综内进行存储.因此,研究单激发态的制备、演化、转化、干涉等过程是量子存储及其应用研究的关键.本文总结了近年来作者所在研究团队针对冷原子系综体系在此研究方向取得的若干成果.主要包括采用动量模式调控、三维光晶格等手段抑制单激发态的退相干,采用环形腔增强原子至光子的转化效率,发展基于拉曼光的单激发态相干转移技术,利用单量子态不同模式间干涉制备光与原子纠缠,利用里德伯阻塞机制提升纠缠制备效率等.此外,简要回顾了基于多个单激发态的量子中继及量子网络实验.