一种基于防毒面具的通话系统

防毒面具的隔绝特性使得用户之间的通话较为困难,为解决其在烟雾、火灾、战场等复杂使用环境下的通信问题,基于点到多点和．董到点两项功能,构建一种基于防毒面具的无线通话系统。系统采用语音编码和跳频等技术方法,开发出防毒面具内置的小型多功能无线通话终端。经软硬件测试表明,系统通信安全可靠,保密性强,体积小,成本低。     

抗辐射加固封装国产存储器的电子辐照试验

用特种复合屏蔽材料和缝焊封接工艺进行抗辐射封装,在普通封装存储器28C256的基础上,研制了抗辐射封装加固存储器LS28C256R。设计专用试验测试电路板和测试软件,以进行存储器器件加电工作条件下电子加速器辐照试验的动态测试。辐照对比试验结果表明,加固存储器LS28C256R的抗电子源辐照能力比普通封装存储器28C256提高1～2个数量级,为商用成品（Commercial Off-The—Shelf,COTS）器件在空间领域中的应用提供了技术支撑。     

Optical fabrication of three-dimensional photonic lattices in LiNbO3:Fe crystals with a single amplitude mask

We fabricate three-dimensional nonlinear photonic lattices in iron-doped lithium niobate photorefractive crystal for the first time by a single amplitude mask. The experimental setup of this method is very simple and flexible. The period of the lattices can be dominated easily. We analyze the three-dimensional photonic lattices by plane wave guiding and far field diffraction pattern imaging. The induced photonic lattices can exist stably for a long time in the photorefractive crystal.     

Concentration and refractive index sensor for methanol using short period grating fiber

This paper reports on the spectral (response) characteristics of fiber Bragg grating sensor to various methanol concentrations. A complete experimental analysis on the use of Ge-B co-doped fiber Bragg grating sensor for a concentration and refractive index measurement is presented. The spectral changes in the grating response due to variation of concentration have been investigated in relation to new sensing configurations. The results also highlight the possibilities of using the sensor for medical and biological applications.     

高场超导MRI系统铁磁屏蔽的几何优化

磁共振成像（MRI）系统是一种重要的医学影像诊断设备,它根据核磁共振原理对处于静磁场中的人体器官进行成像,具有清晰度高和任意层面成像等优点,在医学检查和诊断方面有着重要的作用,与低场MRI相比,高场MRI系统可提高质子的磁化率,增加图像的信噪比,缩短MRI信号采集时间,从而使脑功能成像的信号变化更为明显;但是较高的背景...     

Study of radiation background at the north crossing point of the BEPCⅡ in collision mode

Understanding the radiation background at the north crossing point (NCP) in the tunnel of BEPCII is crucial for the performance safety of the High Purity Germanium (HPGe) detector, and in turn of great significance for long-term stable running of the energy measurement system. Therefore, as the first step, a NaI(Tl) detector is constructed to continuously measure the radiation level of photons as background for future experiments. Furthermore, gamma and neutron dosimeters are utilized to explore the radiation distribution in the vicinity of the NCP where the HPGe detector will be located. Synthesizing all obtained information, the shielding for neutron irradiation is studied based on model-dependent theoretical analysis.     

Preliminary shielding analysis in support of the CSNS target station shutter neutron beam stop design

The construction of China Spallation Neutron Source (CSNS) has been initiated in Dongguan, Guangdong, China. Thus a detailed radiation transport analysis of the shutter neutron beam stop is of vital importance. The analyses are performed using the coupled Monte Carlo and multi-dimensional discrete ordinates method. The target of calculations is to optimize the neutron beamline shielding design to guarantee personal safety and minimize cost. Successful elimination of the primary ray effects via the two-dimensional uncollided flux and the first collision source methodology is also illustrated. Two-dimensional dose distribution is calculated. The dose at the end of the neutron beam line is less than 2.5 μSv/h. The models have ensured that the doses received by the hall staff members are below the standard limit required.     

A fractional partial differential equation based multiscale denoising model for texture image

Traditional integer‐order partial differential equation based image denoising approach can easily lead edge and complex texture detail blur, thus its denoising effect for texture image is always not well. To solve the problem, we propose to implement a fractional partial differential equation (FPDE) based denoising model for texture image by applying a novel mathematical method—fractional calculus to image processing from the view of system evolution. Previous studies show that fractional calculus has some unique properties that it can nonlinearly enhance complex texture detail in digital image processing, which is obvious different with integer‐order differential calculus. The goal of the modeling is to overcome the problems of the existed denoising approaches by utilizing the aforementioned properties of fractional differential calculus. Using classic definition and property of fractional differential calculus, we extend integer‐order steepest descent approach to fractional field to implement fractional steepest descent approach. Then, based on the earlier fractional formulas, a FPDE based multiscale denoising model for texture image is proposed and further analyze optimal parameters value for FPDE based denoising model. The experimental results prove that the ability for preserving high‐frequency edge and complex texture information of the proposed fractional denoising model are obviously superior to traditional integral based algorithms, as for texture detail rich images. Copyright © 2013 John Wiley & Sons, Ltd.     

Stereospecificity of 1H, 13C and 15N shielding constants in the isomers of methylglyoxal bisdimethylhydrazone: problem with configurational assignment based on 1H chemical shifts

In the ¹³C NMR spectra of methylglyoxal bisdimethylhydrazone, the ¹³C‐5 signal is shifted to higher frequencies, while the ¹³C‐6 signal is shifted to lower frequencies on going from the EE to ZE isomer following the trend found previously. Surprisingly, the ¹H‐6 chemical shift and ¹J(C‐6,H‐6) coupling constant are noticeably larger in the ZE isomer than in the EE isomer, although the configuration around the –CH═N– bond does not change. This paradox can be rationalized by the C–H?N intramolecular hydrogen bond in the ZE isomer, which is found from the quantum‐chemical calculations including Bader's quantum theory of atoms in molecules analysis. This hydrogen bond results in the increase of δ(¹H‐6) and ¹J(C‐6,H‐6) parameters. The effect of the C–H?N hydrogen bond on the ¹H shielding and one‐bond ¹³C–¹H coupling complicates the configurational assignment of the considered compound because of these spectral parameters. The ¹H, ¹³C and ¹⁵N chemical shifts of the 2‐ and 8‐(CH₃)₂N groups attached to the –C(CH₃)═N– and –CH═N– moieties, respectively, reveal pronounced difference. The ab initio calculations show that the 8‐(CH₃)₂N group conjugate effectively with the π‐framework, and the 2‐(CH₃)₂N group twisted out from the plane of the backbone and loses conjugation. As a result, the degree of charge transfer from the N‐2– and N‐8– nitrogen lone pairs to the π‐framework varies, which affects the ¹H, ¹³C and ¹⁵N shieldings. Copyright © 2012 John Wiley & Sons, Ltd.     

14 kHz～18 GHz夹网电磁屏蔽视窗的研制

通过分析、比较不同制作工艺、不同目数的屏蔽玻璃的屏蔽效能测试结果，并结合电磁屏蔽原理，研制出了全新的165目屏蔽网，它完全满足GJB5729--2006中B级标准值的要求，可应用于对低频指标有高标准要求的场合。