New terahertz dispersive device for single-shot spectral measurements of terahertz pulse

A new terahertz dispersive device designed for single-shot spectral measurements of broadband terahertz pulses is proposed. With two-dimensional quasi-randomly distributed element design, the device exhibits approximately the dispersive property of single-order diffraction in far field. Its far-field diffraction pattern is experimentally verified employing a continuous terahertz source centered at 2.52 THz and a pyroelectric focal-plane-array camera, which is in good agreement with the numerical result. The device provides a new approach for direct single-shot spectral measurements of broadband terahertz waves.     

模拟回火马尔可夫链蒙特卡罗全波形分析方法

针对传统的全波形分析方法不能快速自动处理全波形数据的缺点,提出了一种模拟回火马尔可夫链蒙特卡罗全波形分析法,用于求解全波形数据中的波峰数和峰值位置等参量.该方法采用Metropolis更新策略求解波峰数量和噪声两个参量,以达到快速求解的目的;而峰值位置和波峰幅值则采用改进的模拟回火策略求解,通过添加的主动干预回火步骤实现对参量更新过程的有效探测,以满足对速度或运算收敛性的要求.模拟回火马尔可夫链蒙特卡罗全波形分析方法以马尔可夫算法为基础,仍保持马氏链的收敛性,从而保证本方法具有良好的鲁棒性,实现对全波形数据的自动化处理.     

基于可信基站和HASH函数的WSN密钥管理方案

针对现有的基于二元多项式或q-composite的密钥管理方案存在的被捕获率高和网络连通率低的缺点,提出了一种基于可信基站产生三元多项式密钥和HASH函数的WSN密钥管理方案;首先,采用层次型分簇路由协议将整个WSN监测区域划分为簇,然后,由可信基站产生三元多项式密钥,并将其分配给簇头,当任意两簇头之间共享的多项式密钥超过q时可以进行通信,并通过HASH函数来生成对应的通信密钥,有效地隐藏了节点的部分密钥信息;理论研究和仿真试验结果表明:文中方法能有效地实现网络的密钥管理,较其他方法相比,具有网络连通率高和抗捕获能力强的优点,具有一定的优越性。     

Dual-Color Quantum Dot–Encoded Nanoprobe for DNA Assays and Cell Imaging

In this article, a novel dual-color quantum dot–encoded fluorescent nanoprobe was prepared by the reverse microemulsion method and layer-by-layer assembly method. First, red fluorescence–emitting CdTe quantum dots were encapsulated in silica nanoparticles by the reverse microemulsion method. Yellow fluorescence–emitting quantum dots were deposited on the surface of silica nanoparticles to form a dual-color quantum dot@silica beads/quantum dot nanoprobe. Then capture DNA was linked to a QSQ nanoprobe via covalent bonding. We utilized the quantum dot@silica beads/quantum dot nanoprobe to capture and detect the mutant BRAF DNA sequence through the competitive immunoassay method. The resulting quantum dot@silica beads/quantum dot nanoprobe-capture DNA conjugates showed sequence-specific hybridization with target DNA. Furthermore, a multispectral imaging system was utilized to distinguish the quantum dot optical code in the quantum dot@silica beads/quantum dot nanoprobe. The quantum dot@silica beads/quantum dot nanoprobe was used in human osteoblast-like HepG2 cell imaging. The proposed quantum dot@silica beads/quantum dot nanoprobe and decoding analysis method could be used for targeting imaging, biological assays, and early detection of cancer.     

激光器非线性失真对SCM光波系统的影响

对于宽带副载波复用(SCM)的光波系统,研究并设法减小光源的非线性所引起的谐波失真和交调失真,是一个重要的理论课题。本文分析激光器的P—I曲线的非线性以及谐振腔里光子和电子相互耦合所引起的固有非线性及其对复用信道的影响。     

地球同步轨道二维扫描像移补偿技术建模与分析

在建立二维扫描观测模型的基础上,提出了基于椭球体地球模型的二维扫描像移补偿方案,给出了任意空间观测到的目标位置的快速迭代算法,并以真实轨道和仿真姿态数据验证了像移补偿模型的实际性能。仿真结果表明,对于长周期(大于一个东西方向扫描行周期)轨道和姿态偏差,可以通过调整仪器坐标系内的扫描轨迹来实现像移补偿;同时,在现有轨道测量和控制条件下,轨道因素引起的瞬时方位角和俯仰角补偿量在0.01°~0.1°量级,且随轨道位置不同而变化。FY-2C卫星在轨偏航轴姿态失配修正实例证实了上述模型的有效性。     

激光诱导Mg等离子体电子温度的实验研究

利用波长为1 064 nm,最大能量为500 mJ的Nd∶YAG脉冲激光器在室温,一个标准大气压下对Mg合金冲击,改变激光能量,得到相应的Mg等离子体特征谱线。分析谱线,发现谱线有不同的演化速率,同时得到了MgⅠ,MgⅡ离子谱线,证明此实验条件下,激光能量足够Mg合金靶材充分电离。选择了相对强度较大的MgⅠ 383.2 nm, MgⅠ 470.3 nm, MgⅠ 518.4 nm三条激发谱线,利用这些发射谱线的相对强度计算了等离子体的电子温度,激光能量为500 mJ时,等离子体温度为1.63×104 K。实验结果表明：在本实验条件下,Mg原子可以得到充分激发;在200～500 mJ激光能量范围内,等离子体温度随着激光能量的降低而衰减,在350～500 mJ激光能量范围内的等离子体温度随激光能量的变化速度十分明显,200～350 mJ时等离子体温度变化速度迅速减缓;激光能量为300 mJ时,谱线相对强度明显减弱,低于350和250 mJ的谱线相对强度,不符合谱线相对强度会随着激光能量提高而上升的变化趋势,证明发生了等离子体屏蔽现象,高功率激光产生的等离子体隔断了激光与材料之间的耦合。此时的等离子体温度明显升高,不符合变化趋势,这是由于在发生等离子体屏蔽现象时,激光能量被等离子体吸收,导致等离子体温度上升。     

Experimental realization of one-way quantum computing with two-photon four-qubit cluster states

We report an experimental realization of one-way quantum computing on a two-photon four-qubit cluster state. This is accomplished by developing a two-photon cluster state source entangled both in polarization and spatial modes. With this special source, we implemented a highly efficient Grover's search algorithm and high-fidelity two-qubit quantum gates. Our experiment demonstrates that such cluster states could serve as an ideal source and a building block for rapid and precise optical quantum computation.     

Observation of macroscopic quantum tunneling in a single Bi2Sr2CaCu2O8+delta surface intrinsic Josephson junction

We report on the first unambiguous observation of macroscopic quantum tunneling (MQT) in a single submicron Bi(2)Sr(2)CaCu(2)O(8+delta) surface intrinsic Josephson junction (IJJ) by measuring its temperature-dependent switching current distribution. All relevant junction parameters were determined in situ in the classical regime and were used to predict the behavior of the IJJ in the quantum regime via MQT theory. Experimental results agree quantitatively with the theoretical predictions, thus confirming the MQT picture. Furthermore, the data also indicate that the surface IJJ, where the current flows along the c axis of the crystal, has the conventional sinphi current-phase relationship.     

Existence and Stability of Compact-Like Discrete Breather in Discrete One-Dimensional Monatomic Chains

Compact-like discrete breathers in discrete one-dimensional monatomic chains are investigated by discussing a generalized discrete one-dimensional monatomic model. It is proven that compact-like discrete breathers exist not only in soft Ф^4 potential but also in hard Ф^4 potential and K4 chains. The measurements of compact-like discrete breathers＇ core in soft and hard Ф^4 potential are determined by coupling parameter K4, while the measurements of compact-like discrete breathers＇ core in K4 chains are not related to coupling parameter K4. The stabilities of compact-like discrete breathers correlate closely to coupling parameter K4 and the boundary condition of lattice.