600 kJ供能系统及其在轨道炮中的应用

 本文介绍了一种适合于电磁轨道炮使用的600 kJ供能系统。初级能源是电容器组。经过短路开关和电感储能线圈组成的转换电路，把能量输送给轨道炮。系统的主控开关和短路开关是金属接触型固体介质爆炸开关。本文推荐了一种爆炸开关闭合电阻随时间变化的经验模型。这套供能系统经过实验证明，它运行可靠、性能稳定。     

基于经典光学方法的物体表面微观结构的三维成像

设计了基于经典光学方法的物体表面微观结构的三维成像实验装置以及相应计算程序,从记录不同角度平行光照射下的物体表面照度出发,经图片处理后得到物体表面的三维立体结构.     

一维 Frenkel-Kontorova(FK)模型原子链的相变研究

文章基于一维Frenkel-Kontorova模型,研究了边界原子的初始速度对原子链运动状态的影响,数值模拟结果表明:当v1时,原子处于"振荡区",当v₁2时,原子处于"混沌区",当v>v₂时,原子处于 "均匀区". 同时我们发现临界速度v₁和v₂随原子数目和垫底势高度的变化而变化. 关键词： Frenkel-Kontorova(FK)模型 相变     

Switchable multiple lasing oscillations in an erbium-doped fiber ring laser using a single stage of a Sagnac loop mirror

A simple scheme for a switchable multi-wavelength erbium-doped fiber (EDF) ring laser is investigated by using a single stage of a Sagnac loop mirror. The multiple lasing outputs are obtained and switched readily by controlling the state of polarization (SOP). Since the transmission characteristics of the Sagnac loop mirror in terms of peak wavelengths and peak powers strongly depend on the SOP, the switching performance of the proposed multi-wavelength EDF laser can be effectively obtained. The proposed multi-wavelength EDF laser has versatile lasing outputs in states of a single-, dual-, triple-, and quadruple-wavelength oscillations. The multiple outputs are effectively switchable by adjusting the SOP.     

Efficient and wavelength-tunable anti-Stokes frequency conversion with good beam quality in the fundamental mode of photonic crystal fiber

Using the photonic crystal fiber (PCF) with the zero dispersion wavelength of 848 nm for the fundamental mode, the efficient anti-Stokes signal generations from 645 to 543 nm are realized by pumping in the normal dispersion region. When the pump average power increases from 200 to 500 mW, the output power of the anti-Stokes signal increases 8.46 times, the power ratio of the anti-Stokes signal at 543 nm to the residual pump is calculated as 22.6:1, and the conversion efficiency η in the experiment can be up to 46%. Moreover, good optical beam quality of the anti-Stokes signal can be achieved.     

Mn, Cr-co-doped MgAl2O4 phosphors for white LEDs

The Mn-, Cr-doped and Mn, Cr-co-doped MgAl₂O₄ powders have been synthesized via a gel-solid reaction method. Energy transfer from Mn²⁺ to Cr³⁺ has been observed for the first time in the co-doped MgAl₂O₄ phosphors. When excited with blue light with a wavelength of 450 nm at room temperature, both green emission from Mn²⁺ around 520 nm and red emission from Cr³⁺ around 675and 693 nm were generated. Moreover, the color of the emission can be modified by controlling the doping concentrations of Mn²⁺ and Cr³⁺. Therefore, MgAl₂O₄: Mn²⁺, Cr³⁺ could be used as a single-phased phosphor for white LED with a blue LED chip. The energy transfer in terms of Mn²⁺ to Cr³⁺ is determined by means of radiation and reabsorption.     

Eu2+掺杂浓度对Ca2MgSi2O7∶Eu2+荧光粉发光特性的影响

采用化学共沉淀法制备了Ca_2-xMgSi₂O₇:xEu²⁺绿色荧光粉.用X射线衍射仪、荧光分光光度计及光色综合测试系统对Ca_2-xMgSi₂O₇:xEu²⁺绿色荧光粉的相结构、发光性能进行了测试.结果表明:其激发光谱分布在300–480 nm波长范围,谱峰位于389,430 nm处,可以被InGaN管芯产生的360–480 nm辐射有效激发;在波长为430 nm蓝光激发下,其发射光谱谱峰位于531 nm处.Ca_2-xMgSi₂O₇:xEu²⁺绿色荧光粉的发光强度随Eu²⁺掺杂量的增加而增强,当Eu²⁺掺杂量x为0.04时,发光强度达到最大值,而后开始降低,发生浓度猝灭.根据Dexter能量共振理论,浓度猝灭是由电偶极-电偶极相互作用引起的. 关键词： 2MgSi₂O₇∶Eu²⁺')" href="#">Ca₂MgSi₂O₇∶Eu²⁺ 绿色荧光粉 发光特性 白光发光二极管     

A combined hybrid mixed element method for incompressible miscible displacement problem with local discontinuous Galerkin procedure

In this article, we propose a combined hybrid discontinuous mixed finite element method for miscible displacement problem with local discontinuous Galerkin method. Here, to obtain more accurate approximation and deal with the discontinuous case, we use the hybrid mixed element method to approximate the pressure and velocity, and use the local discontinuous Galerkin finite element method for the concentration. Compared with other combined methods, this method can improve the efficiency of computation, deal with the discontinuous problem well and keep local mass balance. We study the convergence of this method and give the corresponding optimal error estimates in L^∞(L²) for velocity and concentration and the super convergence in L^∞(H¹) for pressure. Finally, we also present some numerical examples to confirm our theoretical analysis.     

量子点环嵌入Aharonov-Bohm干涉器中电子的退耦合态及反共振现象

采用Anderson模型哈密顿量和非平衡态格林函数方法对量子点环以不同构型嵌入A-B干涉器中电子输运的退耦合态及反共振现象进行了理论研究. 结果表明,量子点环A-B干涉器的结构对称性以及穿过A-B干涉器的磁通量是诱发退耦合现象的两种物理机理. 耦合量子点结构的对称性越高,体系在相干电子输运过程中表现出来的退耦合及反共振现象越明显. 而且在具有高度对称性的耦合量子点结构中,通过磁场调节体系的结构参数可以分别使第奇数或第偶数分子本征态从电极上退耦合,从而使电子输运电导表现出奇偶对等振荡现象. 这为设计纳米电子开关器件提供了一个新的物理模型. 关键词： 量子点环 A-B干涉器 退耦合 反共振     

Influence of Bi underlayer on the magnetic properties of Fe<Subscript>x</Subscript>Pt<Subscript>100-x</Subscript> (<Emphasis Type="BoldItalic">x</Emphasis> =<Emphasis Type="Bold">40</Emphasis>∼<Emphasis Type="Bold">58</Emphasis>) films

We have studied the effect of a Bi underlayer on ordering and coercivity H_c of Fe_xPt_100-x thin films (atomic content of Fe x=40∼58). We found that the Bi underlayer enhances H_c remarkably. After annealing at 400 °C for 20 min, a Bi/Fe₄₉Pt₅₁ film can realize an H_c as high as 1.07×10³ kA/m and a ratio of the remnant M_r to the saturated magnetization M_s as high as 0.93. The ordering process of FePt film was promoted by the diffusion of Bi atoms. Moreover, the Bi underlayer broadens the range of x for high H_c from 49∼55 to 43∼55. Interestingly, with Bi underlayer, the high H_c is affected by x to a less extent. PACS 75.50.Ss; 75.50.Vv; 75.60.Ej