Magnetic properties of bulk polycrystalline Pr1-x Ndx（x=0,0.8）FeB permanent magnets

For spin reorientation （SRT）, the applications of sintering NdFeB permanent magnets are limited at low temperature. The sintering PrFeB permanent magnet （PM） presents no SRT and shows excellent magnetic properties at low temperature. The magnetic properties of bulk polycrystalline sintering Prl-xNdxFeB （x = 0 and 0.8 correspond to P42H and N50M respectively） are studied in this paper. The results show that magnetic properties and stability of N50M are better than those of 42H at room temperature. With the decrease of temperature, the parameters ofBr, Hcb, and Hci of P42H present a nearly linear increasing trend; Br and Hcb of N50M first increase and then decline, Hci presents an increasing trend. At 77 K, Br, Hci, and Jr of P42H are increased by 18.7%, 308%, and 17.1% respectively over than those at 300 K; at 120 K, Br, Hci, and Jr of N50M are increased by about 16.19%, 245%, and 12.6% respectively over than those at 300 K. The magnetic properties of P42H are better than those of N50M at low temperature. The sintering PrFeB is the preferred PM in various low-temperature devices.     

Strong and broadband terahertz absorber using Si02-based metamaterial structure

We design and experimentally demonstrate a broadband metamaterial absorber in the terahertz （THz） band based on a periodic array of aluminum （A1） squares with two different sizes. A thin silicon dioxide （SiO2） film rather than a conventional polyimide （PI） layer is used as a dielectric spacer to separate A1 squares from the platinum （Pt） ground plane in our design, which significantly improves the design precision and the feasibility of the device fabrication. The combination of different sizes of AI squares gives rise to an absorption bandwidth of over 210 GHz with an absorption of over 90%. Our results also show that our device is almost polarization-insensitive. It works very well for all azimuthal angles with an absorption of beyond 80%.     

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.     

Beam dynamics studies of the photo-injector in low-charge operation mode for the ERL test facility at IHEP

The energy recovery linac test facility （ERL-TF）, which is a compact ERL-FEL （free electron laser） two-purpose machine, was proposed at the Institute of High Energy Physics, Beijing. As one important component of the ERL-TF, the photo-injector that started with a photocathode direct-current gun has been designed. In this paper, optimization of the injector beam dynamics in low-charge operation mode is performed with iterative scans using Impact-T. In addition, the dependencies between the optimized beam quality and the initial offset at cathode and element parameters are, investigated. The tolerance of alignment and rotation errors is also analyzed.     

光栅试验台的自适应模糊补偿器设计

在惯导测试设备设计过程中会经常碰到摩擦干扰问题,作提出了一种采用自适用模糊补偿器的控制系统设计方案,以克服光栅试验台隐速中影响低速平稳性的摩擦干扰。首先,采用传统方法,基于对象的简化线性模型来设计ＰＩ控制器,然后利用自适应模糊技术对摩擦干扰进行了补偿。这种方案能较好地克服摩擦干扰来的低速性能差的问题。     

美国视景系统国际公司为萄葡牙F-16提供头盔显示设备

美国视景系统国际公司(VSI)被授予合同为葡萄牙空军的F-16“猎鹰”战斗机提供联合头盔显示系统(JHMCS)。JHMCS将会为飞行员提供优越的态势感知性能,并具有离轴目标指示和显示的优势。它可为飞行员提供“首先观看、首先射击”的高离轴武器应对性能。系统能够使飞行员精确指示机载武器和传感器来对抗敌军飞机和地面目标,而不需要旋转飞机或将目标置于头顶显示器上(Head-Up Display)进行指示。瞄准指示和飞机性能参数等信息以绘图形式直接显示在飞行员的头盔上。根据合同,VSI将会交付头盔显示和相关的电子设备。交付工作预计从2007年开…     

用激光代替磁头写入数字信息

荷兰和日本的物理学家利用圆极化超短激光脉冲首次实现激光对磁比特的直接写入．通常的磁光存贮设备，激光是无法直接对磁存贮单元进行读写的，必须有磁装置的辅助．而这种用激光直接写磁比特的方式，比目前最快的磁存贮器还要快5万倍，这个进展将导致低价位超高速全激光磁硬盘的出现．     

仪器和设备

Coherent降低绿光泵浦激光器维护成本,新型钛宝石超快放大器提供更高的稳定性和更短的脉宽,新型超快可调谐OPA输出更稳定、操作更简便     

新仪器,新设备

在化工和其它一些行业中,常对各种粘滞度不同的液体进行消除气泡工艺处理.在除气过程中,又要考虑除气手段是否会引起溶液的物理或化学性质的变化,因此,以往在许多场合只能采取静止或减压来消除气泡的方法. 近年来,在感光化工中利用超声消除气泡在国外已有报道.上海超声波仪器厂与上海感光材料厂合作,研制了一套超声波消泡装置. 感光材料的彩色乳剂及保护膜——明胶都是粘滞度很大而且极易产生气泡的溶液.溶液中如有气泡存在,对质量影响很大.带有气泡的乳剂涂在底片上,底     

可重构制造系统重组过程中设备选择模型的研究

根据生产任务选择加工设备进行制造资源重组是实现可重构制造系统的关键问题之一，由于设备的选择涉及到多种因素，既有定量指标，又有定性指标，传统的依靠人工经验的方法显得力不从心。本文首先结合实际情况，提出了一套设备选择评价体系，通过对模糊判断矩阵采用最小对数二乘法确定各评价因素的权重系数，针对定性指标和定量指标采用不同的方法确定其性能指标值，通过模糊积分对评判指标进行综合评判，最后进行了实例研究。所提出的方法有效地简化了决策过程，为可重构制造系统设备选择提供了一套行之有效的方法。