新型材料--光子晶体

半个世纪以来，对半导体技术的深入研究和广泛应用推动了电子工业和信息产业的迅速发展。目前半导体技术正向高速度、高集成化方向发展，但这也不可避免地引发了一系列问题，例如电路中能量损耗过大导致集成片发热，如何进一步将电子器件小型化等。人们由此感到半导体器件的能力已基本达到了极限，转而把目光由电子投向了光子，因为光子有着电子所不具备的优势：速度快，彼此间不存在相互作用，一旦实现用光子替代电子传递信息，     

Determination of hyperfine tensor components from nuclear frequencies at canonical orientations of the g-tensor

The analytical procedure for the determination of all components of the symmetric hyperfine tensor of the I=1/2 nucleus in the g-tensor coordinate system is described, assuming that nuclear frequencies corresponding to the principal directions of the g-tensor and exact values of the external magnetic field (or nuclear Zeeman frequencies) are experimentally available.     

Entropy Bounds in R×S Geometries

Exact calculations are given for the Casimir energy for various fields in R×S³ geometry. The Green's function method naturally gives a result in a form convenient in the high-temperature limit, while the statistical-mechanical approach gives a form convenient for low temperatures. The equivalence of these two representations is demonstrated. Some discrepancies with previous work are noted. In no case, even for N=4 SUSY, is the ratio of entropy to energy found to be bounded. This deviation, however, occurs for low temperature, where the equilibrium approach may not be relevant. The same methods are used to calculate the energy and free energy for the transverse electric modes in a half-Einstein universe bounded by a perfectly conducting 2-sphere.     

Optical phase locked-loop homodyne receiver using an eight-port 90° optical hybrid

The performance of a PSK optical phase locked-loop (PLL) homodyne system based on an eight-port 90° optical hybrid, which is used to suppress the local oscillator (LO) intensity noise in both data recovery arm (I arm) and carrier recovery arm (Q arm), is evaluated. Incomplete cancellation of LO intensity noise results from unmatched photodetectors, couplers pathlengths, and non-ideal couplers power splitting ratio. Optimum LO power can be found for the given receiver parameters.     

非晶态硒化镉薄膜瞬态光电特性

本文报道用真空热蒸发法淀积的非晶态硒化镉薄膜作光敏介质制备超快光电导探测器。用对撞脉冲锁模Nd:YAG激光器产生的超短光脉冲序列对探测器的响应时间进行检测,结果表明a-CdSe薄膜对皮秒(10^-12秒)级的超短光脉冲作用具有良好的瞬态响应光电特性,探讨a-CdSe薄膜快速弛豫过程的内在机理。     

环形装置中三维MHD平衡与稳定性的计算机模拟

一、引 言 在聚变研究中,环形等离子体的磁约束起着重要作用。目前托卡马克研究的进展令人鼓舞,其理论与实验比较符合,定标关系清楚。但是无论从聚变的最终目标来看,还是从实验的安排考虑,完全轴对称的几何形状给各方面部带来许多不便。人们希望知道如果把环形几何中加进直线段,或者把圆环改成不具有对称性的环形,会对等离子体约束产生何种影响?     

高频单线圈双调谐NMR单晶探头的研制

本文报道了一种测角单晶NMR探头。该探头采用单线圃双调谐电路,工作频率在90MHz-110 MHz连续可调,可进行交叉极化大功率去耦实验。文中提出了一种简单而有效的测角装置,可使单晶绕三个互相垂直轴转动实现单晶的NMR测量。作为典型的应用例子,本文利用该探头实现了单晶DGO(2NH₂CH₂COOH·H₂C₂O₄)屏蔽张量的测量。     

Simultaneous two-way classical communication and measurement-device-independent quantum key distribution on oceanic quantum channels

Simultaneous two-way classical and quantum (STCQ) communication combines both continuous classical coherent optical communication and continuous-variable quantum key distribution (CV-QKD), which eliminates all detection-related imperfections by being measurement-device-independent (MDI). In this paper, we propose a protocol relying on STCQ communication on the oceanic quantum channel, in which the superposition-modulation-based coherent states depend on the information bits of both the secret key and the classical communication ciphertext. We analyse the encoding combination in classical communication and consider the probability distribution transmittance under seawater turbulence with various interference factors. Our numerical simulations of various practical scenarios demonstrate that the proposed protocol can simultaneously enable two-way classical communication and CV-MDI QKD with just a slight performance degradation transmission distance compared to the original CV-MDI QKD scheme. Moreover, the asymmetric situation outperforms the symmetric case in terms of transmission distance and optical modulation variance. We further take into consideration the impact of finite-size effects to illustrate the applicability of the proposed scheme in practical scenarios. The results show the feasibility of the underwater STCQ scheme, which contributes toward developing a global quantum communication network in free space.     

An Enhanced Full-Form Model-Free Adaptive Controller for SISO Discrete-Time Nonlinear Systems

This study focuses on the full-form model-free adaptive controller (FFMFAC) for SISO discrete-time nonlinear systems, and proposes enhanced FFMFAC. The proposed technique design incorporates long short-term memory neural networks (LSTMs) and fuzzy neural networks (FNNs). To be more precise, LSTMs are utilized to adjust vital parameters of the FFMFAC online. Additionally, due to the high nonlinear approximation capabilities of FNNs, pseudo gradient (PG) values of the controller are estimated online. EFFMFAC is characterized by utilizing the measured I/O data for the online training of all introduced neural networks and does not involve offline training and specific models of the controlled system. Finally, the rationality and superiority are verified by two simulations and a supporting ablation analysis. Five individual performance indices are given, and the experimental findings show that EFFMFAC outperforms all other methods. Especially compared with the FFMFAC, EFFMFAC reduces the RMSE by 21.69% and 11.21%, respectively, proving it to be applicable for SISO discrete-time nonlinear systems.     

数字束流位置探测器通道自动增益校准方法的研究与实现

在现有硬件基础上,基于BPM测量准确度的需求,在自制的电子学FPGA芯片内,通过Verilog语言实现了一种数字BPM采样数据增益自动校准的设计。首先介绍了自动增益校准模块的系统总体设计;然后对模块的实现方法做了详细说明,设计并搭建了ADC数据自动增益校准测试平台以验证自动增益较准模块的功能;最后介绍了该设计在BPM通道标定中的应用。实验结果表明,该方法可以实现4通道增益一致,使ADC采样后的数据幅度相同,有效解决了由通道增益不一致引起的测量偏差,以及工程应用中ADC数据幅度校准工作量大且难于操作的问题,将在BPM系统通道自动标定中发挥重要作用。