几种认证UPT用户算法的比较

介绍了四种认证UPT用户的算法。并对这些算法进行了分析和说明,最后对它们进行了比较,指出了它们的优缺点。     

CDMA和GSM移动智能网的技术比较

介绍了移动智能网产生和发展的背景,并对WIN和CAMEL移动智能网进行了全面的比较。指出它们之间相同与不同之处,以及它们之间和它们与智能网之间的联系。     

光纤光栅传感器预拉工艺的低温效应

介绍了光纤光栅传感原理,依据传感机理制作了两种结构材料的光纤光栅传感器,对它们进行了试验,将试验后的传感数据进行了拟合分析和比对,并对它们在低温环境下产生的啁啾现象进行了分析,验证了采用预拉工艺对解决啁啾现象的可行性。     

两种密码中间件模块PKCS#11与CSP的对比分析

论文介绍了两种密码中间件模块PKCS#11与CSP,分析了它们各自的特点,并对它们进行了对比分析。     

蛋白质组分芳香族氨基酸双光子吸收选择性激发的HMO模型的理论分析

本文从色氨酸和酪氨酸的分子结构出发,运用HMO模型计算得到了它们的分子轨道能级,从而对它们的双光子吸收选择性激发的机理进行了理论分析。     

光折变空间光孤子的研究进展

对光折变空间光孤子的物理机理及研究进展进行了概括介绍,并对它们的应用前景进行了展望。     

基于DSR的路由协议综述

动态源路由协议（Dynamic Source Routing Protocol,DSR）是一种比较典型的Ad—Hoc网络路由协议。文中对目前基于DSR的路由协议进行了分析和比较,对它们进行了归纳分类,并总结了它们各自的特征及应用场合,希望在此基础上能促进将来设计出更加完善高效的Ad Hoc网络路由协议。     

LINUX进程调度算法的分析

进程调度对一个操作系统来说是至关重要的,它起着非常关键的作用.本文针对Linux操作系统中的普通进程调度算法进行了分析,对以进程为CPU时间分配单位和以用户为CPU时间分配单位的两种算法进行了分析和对比.对它们在不同环境下对进程调度效率和公平性的影响进行了探讨,并总结出它们各自适用的环境.最后为了进一步提高进程调度的效率和公平性,提出了混合算法的思想.     

MOSFET和IGBT性能的比较

介绍MOSFET和IGBT的基本原理和特性,并对它们的性能进行了比较。     

微波电路设计技术及其应用特点

阐述了微波电路设计的几种现代方法,通过对微波线性电路的S参数分析法、微波非线性电路SPICE及谐波平衡分析法较详细地讨论,分析了它们各自的技术特点,并对它们在工程应用方面的性能进行了比较,指出了它们适合应用的场合及设计者在应用中应注意的问题。     

Spatial resolution in NMR imaging

NMR imaging is used as an example of how spatial resolution can be improved in a signal-to-noise (S/N) limited situation. The NMR imaging process consists of two components-generating the NMR signal and localizing it in space. This paper will show that spatial resolution not only aids in identifying small structures, but improves the detectability of larger features by preserving their object contrast.     

双环己基酯类铁电液晶的合成与性质

以顺式结构的４－（４′－烷基－反－环己基）－环己烷羧酸为原料，合成了四种新型铁电液晶化合物，用ＩＲ、ＭＳ及ＮＭＲ仪确定了这些化合物的结构，用ＤＳＣ及偏光显微镜确定了这些化合物的相变温度和相态，讨论了化合物结构与性质的关系。     

Integrating microfabricated fluidic systems and NMR spectroscopy

The philosophy of miniature total analysis systems (mu-TAS) hinges on the integration of multiple chemical processing steps and the means of analyzing their results on the same miniaturized system. We have constructed chip-based capillary electrophoresis (CE) devices equipped with an integrated planar radio-frequency detector coil used for nuclear magnetic resonance spectroscopy (NMR). Separations were accomplished in the devices, but satisfactory NMR spectra could only be obtained from samples of high concentration. The relative sensitivity is explained and the scaling law dichotomy of CE and NMR explored.     

High resolution NMR spectroscopy using a recursive algorithm

When the DFT (discrete Fourier transform) is used as a method for obtaining NMR (nuclear magnetic resonance) spectrum, resolution of the obtained NMR spectrum depends clearly on spin-spin relaxation times of the nucleus and the sampled number of NMR signal. That is, the NMR spectrum is affected by decay of NMR signal due to the relaxation times and errors associated with discrete approximation of NMR spectrum. As a results, its resolution is degraded and the spectrum disagrees with the density distribution of the nucleus. In the present paper, we propose a new NMR spectrum estimation method for reducing their effects, demonstrating a high resolution NMR spectrum which is closer to the density distribution than that of the DFT. The proposed method is derived from applying the Kalman filter or the recursive least-square method to a NMR signal model based on Bloch equation. Under various conditions, the proposed method is compared with the DFT using a proton 1H NMR signal observed from mayonnaise in a 2 [T] static magnetic field. The results show that if spin-spin relaxation times are known previously, the proposed method can provide a higher resolution NMR spectrum than the DFT. In addition, it is shown that the method can reduce the discrete approximation errors of NMR spectrum. Finally, we demonstrate that if frequency components of sources of NMR signal are present in a limited range in frequency domain of interest, the method can magnify NMR spectrum with a sampling time and interval fixed.     

含希夫碱基团的不对称弯曲型液晶分子的合成和相变研究

以3-氨基-2-甲基苯甲酸为原料,合成了含希夫碱基团的5个不对称弯曲型液晶分子,通过1HNMR、HRMS测试手段对其结构进行了表征,采用示差扫描量热法(DSC)和偏光显微镜等方法研究了它们的液晶性和相变温度,发现不仅相变温度随着分子苯环数的下降而下降,其液晶相的稳定性也随着苯环数的下降而下降,含有5个苯环的化合物呈现多个近晶相和向列相,含4个苯环的化合物则只有一个近晶相和向列相,而3个环的化合物仅在降温的过程中呈现近晶相。     

核磁共振微陀螺的现状与发展

基于核磁共振的微型陀螺仪以其小体积、低功耗、低成本等优势成为了惯性传感器领域新的研究热点。回顾了核磁共振陀螺仪的发展历程,并跟踪了国际上基于核磁共振的微型陀螺仪的最新研究动态。从核磁共振、光抽运和自旋交换碰撞三个方面介绍了核磁共振微陀螺的理论基础和主要涉及的物理效应。针对核磁共振微陀螺的不同结构对其进行分类,并从工作原理和性能参数等方面分别进行了阐述。最后,分析了核磁共振微陀螺的应用领域,对其发展趋势和实际应用所面临的挑战进行了展望,并指出磁抑制和磁屏蔽技术将会成为制约核磁共振微陀螺实际应用的难点。     

Development of DNP-Enhanced High-Resolution Solid-State NMR System for the Characterization of the Surface Structure of Polymer Materials

A dynamic nuclear polarization (DNP)-enhanced cross-polarization/magic-angle spinning (DNP/CP/MAS) NMR system has been developed by combining a 200 MHz Chemagnetics CMX-200 spectrometer operating at 4.7 T with a high-power 131.5 GHz Gyrotron FU CW IV. The 30 W sub-THz wave generated in a long pulse TE ₄₁⁽¹⁾ _{{41}}^{{(1)}} mode with a frequency of 5 Hz was successfully transmitted to the modified Doty Scientific low-temperature CP/MAS probe through copper smooth-wall circular waveguides. Since serious RF noises on NMR signals by arcing in the electric circuit of the probe and undesired sample heating were induced by the continuous sub-THz wave pulse irradiation with higher powers, the on-off sub-THz wave pulse irradiation synchronized with the NMR detection was developed and the appropriate setting of the irradiation time and the cooling time corresponding to the non-irradiation time was found to be very effective for the suppression of the arcing and the sample heating. The attainable maximum DNP enhancement was more than 30 folds for C1 ¹³ C-enriched D-glucose dissolved in the frozen medium containing mono-radical 4-amino-TEMPO. The first DNP/CP/MAS ¹³ C NMR spectra of poly(methyl methacrylate) (PMMA) sub-micron particles were obtained at the dispersed state in the same frozen medium, indicating that DNP-enhanced ¹H spins effectively diffuse from the medium to the PMMA particles through their surface and are detected as high-resolution ¹³ C spectra in the surficial region to which the ¹H spins reach. On the basis of these results, the possibility of the DNP/CP/MAS NMR characterization of the surface structure of nanomaterials including polymer materials was discussed.     

Improvements of nuclear magnetic resonance image quality using iterations of adaptive nonlinear filtering

To improve nuclear magnetic resonance (NMR) image quality, a method using iterations of adaptive nonlinear filtering is presented. The method utilizes the properties of an NMR image's noises which are spike-like in the local region. An NMR image is iteratively filtered by a mode-change-type nonlinear filter which has two modes. The first mode reduces small amplitude noises in the NMR image, so that the S/N ratio of the image is improved, and then the residual noises become more spike-like. The second mode mainly reduces large amplitude spike-like noises of the image improved by the first mode, which cannot reduce spike-like noises. Using the proposed iterative filter, it is found by simulations that the S/N ratio of the NMR image is improved by as much as a factor of 2.7. A significant improvement in the image quality when this filter is used is demonstrated by applying it to an NMR image of a human head obtained from an actual NMR imaging apparatus.     

Development of Millimeter Wave Fabry-Pérot Resonator for Simultaneous Electron-Spin and Nuclear Magnetic Resonance Measurement

We report a Fabry-Pérot resonator with spherical and flat mirrors to allow simultaneous electron-spin resonance (ESR) and nuclear magnetic resonance (NMR) measurements that could be used for double magnetic resonance (DoMR). In order to perform simultaneous ESR and NMR measurements, the flat mirror must reflect millimeter wavelength electromagnetic waves and the resonator must have a high Q value (Q?>?3000) for ESR frequencies, while the mirror must simultaneously let NMR frequencies pass through. This requirement can be achieved by exploiting the difference of skin depth for the two frequencies, since skin depth is inversely proportional to the square root of the frequency. In consideration of the skin depth, the optimum conditions for conducting ESR and NMR using a gold thin film are explored by examining the relation between the Q value and the film thickness. A flat mirror with a gold thin film was fabricated by sputtering gold on an epoxy plate. We also installed a Helmholtz radio frequency coil for NMR and tested the system both at room and low temperatures with an optimally thick gold film. As a result, signals were obtained at 0.18 K for ESR and at 1.3 K for NMR. A flat-mirrored resonator with a thin gold film surface is an effective way to locate NMR coils closer to the sample being examined with DoMR.     

A high-resolution technique for multidimensional NMR spectroscopy

A scheme for estimating frequencies and damping factors of multidimensional nuclear magnetic resonance (NMR) data is presented-multidimensional NMR data can be modeled as the sum of several multidimensional damped sinusoids. The estimated frequencies and damping factors of multidimensional NMR data play important roles in determining protein structures. The authors present a high-resolution subspace method for estimating the parameters of NMR data, Unlike other methods, this algorithm makes full use of the rank-deficiency and Hankel properties of the prediction matrix composed of NMR data. Hence, it can estimate the signal parameters under low signal-to-noise ratio (SNR) by using a few data points. The effectiveness of the new algorithm is confirmed by computer simulations and it is tested by experimental data