均匀聚焦磁场中束晕-混沌的孤子控制

采用粒子.束核模型,对均匀聚焦磁场中满足K-V分布的离子束进行模拟研究.观察到束晕.混沌现象,基于束晕.混沌的非线性控制策略,提出控制束晕.混沌的孤子函数控制器,并给出具体的实施方案.模拟研究表明,运用这种方法可以消除束晕及其再生现象,达到对束晕.混沌的有效控制.     

Tunable and highly sensitive temperature sensor based on graphene photonic crystal fiber

Optical fiber temperature sensors have been widely employed in enormous areas ranging from electric power industry, medical treatment, ocean dynamics to aerospace. Recently, graphene optical fiber temperature sensors attract tremendous attention for their merits of simple structure and direct power detecting ability. However, these sensors based on transfer techniques still have limitations in the relatively low sensitivity or distortion of the transmission characteristics, due to the unsuitable Fermi level of graphene and the destruction of fiber structure, respectively. Here, we propose a tunable and highly sensitive temperature sensor based on graphene photonic crystal fiber (Gr-PCF) with the non-destructive integration of graphene into the holes of PCF. This hybrid structure promises the intact fiber structure and transmission mode, which efficiently enhances the temperature detection ability of graphene. From our simulation, we find that the temperature sensitivity can be electrically tuned over four orders of magnitude and achieve up to ～ 3.34×10^-3 dB/(cm·℃) when the graphene Fermi level is ～ 35 meV higher than half the incident photon energy. Additionally, this sensitivity can be further improved by ～ 10 times through optimizing the PCF structure (such as the fiber hole diameter) to enhance the light-matter interaction. Our results provide a new way for the design of the highly sensitive temperature sensors and broaden applications in all-fiber optoelectronic devices.     

Pressure dependence of the thermal stability in LiMn2O4

Structural stability in terms of the decomposition temperature in LiMn₂O₄ was systematically investigated by a series of high-temperature and high-pressure experiments.LiMn₂O₄ was found to have structural stability up to 5 GPa at room temperature.Under ambient pressure,the compound decomposed at 1300℃.The decomposition temperature decreased with increasing pressure,yielding more complex decomposed products.Below the decomposition temperature,the crystal structure of LiMn₂O₄ varied with pressure.The presented results in this study offer new insights into the thermal and pressure stability of LiMn₂O₄ materials as a cathode for lithium-ion batteries that can operate under extreme conditions.Therefore,these findings may serve as a useful guide for future work for improving lithium-ion batteries.     

深水域近水面水下爆炸水柱形态及演变实验研究

 为研究不同起爆深度的水下爆炸水柱形态及演变特征,进行了1 kg球形RDX装药在不同起爆深度下的海上爆炸实验,通过高速摄像机记录装药起爆后水柱的形成和成长过程,获得了喷射水柱形态的演变特征以及水柱高度、直径、水柱突出水面时间等参数的变化规律,并与Cole、Hole和Swisdak等人的研究结果进行对比分析。研究结果表明：对于深水域近水面水下爆炸,水柱以垂直喷射形态为主,当气泡在膨胀阶段到达水面时水柱存在微弱的径向飞散现象;水柱最大高度随起爆深度呈脉动变化,水柱直径随起爆深度线性减小;Swisdak关于水柱最大高度的计算公式不适用深水域近水面水下爆炸情况。     

超导电力技术新进展及其未来发展的思考

近年来高温超导材料研究取得很大进展,它在电力领域的应用研究已受到广泛关注,一些示范样机,诸如高温超导输电电缆、变压器、故障电流限制器、电机和储能装置已经研制成功并投入示范性试验.超导技术是21世纪具有战略经济意义的高新技术,文章将介绍高温超导电力应用研究的新进展及其未来发展的思考。     

The pressure-induced phase transition of the solid β–HMX

The structural, vibrational and thermodynamic properties of β-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (β–HMX) crystal have been studied using the isothermal-isobaric molecular dynamics (NPT-MD) simulations. The variations of cell volume, lattice constants and molecular geometry of solid β–HMX are presented and discussed at different pressure and temperature. It was found that the N–N bond is significantly lengthened with increasing temperature, which suggests that it is relevant to the initial decomposition. An abrupt change at 27 Gpa for the volume and internal geometrical parameters was observed. This is in good accord with the experimental observation that there is a phase transition at 27 GPa, which is clearly due to conformational change, not chemical reaction. The vibrational frequencies at ambient conditions agree well with experimental results, and the pressure/temperature-induced frequency shifts of these modes are discussed. Frequency discontinuity was also observed at pressure when the phase transition occurred. The Grüneisen parameter was obtained using the vibrational frequency.     

Effects of Y incorporation in TaON gate dielectric on electrical performance of GaAs metal–oxide–semiconductor capacitor

In this study, GaAs metal–oxide–semiconductor (MOS) capacitors using Y‐incorporated TaON as gate dielectric have been investigated. Experimental results show that the sample with a Y/(Y + Ta) atomic ratio of 27.6% exhibits the best device characteristics: high k value (22.9), low interfacestate density (9.0 × 10¹¹ cm^–2 eV^–1), small flatband voltage (1.05 V), small frequency dispersion and low gate leakage current (1.3 × 10^–5A/cm² at V_fb + 1 V). These merits should be attributed to the complementary properties of Y₂O₃ and Ta₂O₅:Y can effectively passivate the large amount of oxygen vacancies in Ta₂O₅, while the positively‐charged oxygen vacancies in Ta₂O₅ are capable of neutralizing the effects of the negative oxide charges in Y₂O₃. This work demonstrates that an appropriate doping of Y content in TaON gate dielectric can effectively improve the electrical performance for GaAs MOS devices.

Capacitance–voltage characteristic of the GaAs MOS capacitor with TaYON gate dielectric (Y content = 27.6%) proposed in this work with the cross sectional structure and dielectric surface morphology as insets.     

一种大功率窄脉冲半导体激光器测试台的研制

大功率窄脉冲半导体激光器主要光电性能参数为:输出峰值光功率、阈值电流、正向电压、上升时间、峰值波长、光谱半宽、半强度角.根据激光制导系统对大功率窄脉冲激光器参数的特殊测试要求,研制一种大功率窄脉冲激光器测试平台,将小型化大功率激励器功放模块、大范围可调DC-DC模块、信号源板、激光器座、光学准直镜集成在一个平台上,与峰值功率计、光谱仪、CCD摄像机等仪器配合,可测出大功率窄脉冲激光器的峰值功率、峰值波长及波长随温度变化的漂移特性、发光芯均匀性等参数.介绍了大功率窄脉冲激光器测试台的特点,并对测试结果作了论述.     

Harmonic operation of high gain harmonic generation free electron laser

In high gain harmonic generation (HGHG) free electron laser (FEL), with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation (HO) mode. In this paper, we investigate HO of HGHG FEL.Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy.     

基于铰链式六面顶压机的二级6-8模超高压大腔体内置加热元件的设计与温度标定

 首次报道了一种新型的基于铰链式六面顶压机的二级6-8模大腔体静高压装置的内置加热元件的设计与温度标定。此加热组装结构简单,升温快,保温效果好,并有效地解决了国外基于两面顶压机构架下的二级6-8模内加热组装中热电偶在施加压力时易断的问题。以低成本的碳管为加热元件,采用直接和间接两种加热方式,用双铂铑（Pt6%Rh-Pt30%Rt）B型热电偶进行温度测量,并根据实验过程中加热功率与腔内实际温度的关系,对不同压力下腔体内的温度进行了标定。实验结果表明：此加热系统的油压达到40 MPa（腔体压力约10 GPa）时,温度可以达到1 700 ℃以上;在油压为30 MPa、样品室温度为1 000 ℃时,保温时间可达2 h,甚至更长;实验中获得样品的直径可达3 mm,高度可达7 mm,实现了在高温超高压条件下大样品的制备,满足了实验对产生高温超高压条件的需要。