不同冻藏时间对速冻草莓营养品质的影响

用非破坏快速分析方法-近红外光谱法（NIRs）分析草莓在-18℃条件下冻藏1个月、2个月、4个月和6个月时维生素C、柠檬酸、苹果酸、蔗糖、葡萄糖和果糖等6种营养成分的变化。结果表明冻藏过程中速冻草莓维生素C、柠檬酸和蔗糖含量逐渐降低；苹果酸、葡萄糖和果糖含量逐渐增加。     

Effects of erosion surface on near wall conductivity (NWC) in the Hall-type stationary plasma thrusters

The effect of erosion structure of the wall surface on near wall conductivity was studied in this paper. The electron dynamics process in the plasma was described by the test particle method where electrons were randomly injected into the wall. Monte Carlo method was used to calculate the model. The simulation results showed that the axial current density increased in the case of erosion. Furthermore, the current layers were observed and the layer thickness was approximately equal to the radical electron motion in a half of the electron Larmor period. Also, the current density increases as the erosion structure gradually growed.     

Studies on conformational transition of the maleic acid copolymer with styrene in aqueous salt solution by derivative spectroscopy

The first and second derivative spectra for the optical absorption of maleic acid copolymer with styrene were measured in aqueous 0.09 m NaCl at 25°C within a wavelength range of 240–280 nm, where contributions of groups, other than the phenyl ones, to the second derivatives seem to be negligible. The normal absorption spectra in the range were composed of seven absorption bands and the peak position of each band was determined from the derivative spectra. The peak position of the coiled form copolymer was found to shift to the shorter wavelength range compared with the compact form of the copolymer. From the extent of such blue shifts for each peak, the environment near the phenyl groups in the compact copolymer form was concluded to be similar to aqueous ethanol (40–50 vol%), by comparing with the derivative spectra for $\text{N-}\text{acetyl-}\text{l}\text{-rmphenylalanine}$ in a water-ethanol mixture. However, the first and second derivative spectra and various first derivative spectra were found to have 12 isoderivative points, and all the bands of the different spectra displayed the two-state character of the transition. The degree of transition was determined from the change in the peak height of each band and this coincided well with the pH-titration data.     

Periodic broadcasting with VBR-encoded video

We consider designing near video on demand (NVOD) systems that minimize startup latency while maintaining high image quality. Recently nonuniform segmentation has been used to develop periodic broadcasting techniques for NVOD. These techniques give significant reductions in startup latency as compared with more conventional uniform segmentation. Essentially all of these schemes assume, however, that the videos are CBR-encoded. Since a CBR-encoded video has a larger average rate than an open-loop VBR encoding with the same image quality, there is potential to obtain further performance improvements by using VBR video. In this paper we develop a series of multiplexing schemes for the periodic broadcasting of VBR-encoded video that are based on smoothing, server buffering, and client prefetching. Two key but conflicting performance measures exist when using VBR video: latency and packet loss. By introducing small additional delays in our multiplexing schemes, our trace-based numerical work shows that the schemes can achieve nearly 100% link utilization with negligible packet loss. When the ratio of the CBR rate to the VBR average rate is a modest 1.8, startup latency can be reduced by a factor of four or more for common scenarios.Martin Reisslein: Correspondence to: A shorter version of this paper appeared in Proceedings of IEEE Infocom 99, New York, March 1999, pp 464-471     

Growth and spectroscopy of Dy doped in ZnWO4 crystal

Single-crystal ZnWO₄:Dy³⁺ was grown by Czochralski technique. The XRD, absorption spectra as well as fluorescence spectrum are investigated and the Judd–Ofelt intensity parameters Ω₂, Ω₄, Ω₆ are obtained to be 7.76 × 10⁻²⁰ cm², 0.57 × 10⁻²⁰ cm², 0.31 × 10⁻²⁰ cm², respectively. Calculated radiative transition rate, branching ratios and radiative lifetime for different transition levels of ZnWO₄:Dy³⁺ crystals are presented. Fluorescence lifetime of ⁴F_9/2 level is 158 μs and quantum efficiency is 66%.The most intense fluorescence line at 575 nm correlative with transition ⁴F_9/2 → ⁶H_13/2 is potentially for application of yellow lasers.     

基于投影近似不变性的3D-2D医学图像配准

研究了同一病人的MRA和DSA图像之间的3D-2D配准问题，提出了一种基于投影近似不变性的配准算法，即在同一视角下，同一病人的三维MRA血管骨架的投影与二维DSA的骨架保持一致。通过定义二者之间的代价函数，并利用牛顿迭代法可得到视角参数的最优解。针对临床采集的MRA和DSA数据进行了实验，取得了较为满意的结果。     

氢化锆表面CO2反应层XPS分析

通过X射线光电子能谱分析了经过700℃加热前后的用CO2反应法制备的氢化锆表面反应层中一定深度(100nm、200nm和300nm)的C、O和Zr的化学态,并用相对灵敏度因子法对X射线光电子能谱分析结果进行了计算分析.结果表明:700℃加热前的膜层中含有C、O和Zr以及C-H键和-OH键;经过700℃加热以后,氢化锆表面氢渗透阻挡层中不仅有C-H键和-OH键,而且还出现了-COOH,与H结合的C、O量增大.     

Oxidation tuning in AlCrN coatings

In this work, we have studied the influence of the coating design and composition on the oxidation behavior of Al_xCr_1−xN (x = 0.70) coatings. In particular, we have studied the effect brought about by the deposition of an additional subsurface titanium nitride barrier layer as well as by the doping of the AlCrN-based coatings by tungsten, boron and silicon. The coatings studied have been deposited using the cathodic arc vacuum (CAV) technique. The multilayered AlCrN/TiN coatings with TiN sublayer were oxidized in air at 900 °C over 3 h and then analyzed by Glow Discharge Optical Emission Spectroscopy (GDOES) and X-ray photoelectron spectroscopy (XPS). Oxidation tests were performed in air at 900 and 1100 °C for the AlCrN and AlCrWN, AlCrSiN, and AlCrBN coatings. In each case weight gain was measured and the surface morphology of the oxidized samples were studied using Secondary Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The results obtained showed that the oxidation behavior of the aluminum rich AlCrN-based coatings could be improved in two ways: (1) by controlling the chromium outward diffusion rate in multi-layered coatings and (2) by alloying the AlCrN-based coatings with Si. Both improvements are related to the enhancement of the protective oxide film formation.     

激光吸收光谱技术在工业生产过程及安全预警标识性气体监测中的应用

鉴于常规的标识性气体监测方法在响应速度、测量精度、使用寿命、实时性、监测目标种类、测量范围和应用场合等方面相比激光吸收光谱技术存在不足,本文以可调谐半导体激光吸收光谱技术为依托,选取合适的无干扰激光吸收谱线,阐述了工业管道抽取式、管道原位在线对射式、扩散探头式(全量程激光监测一体机形式与多点无源传感器探头形式)、无组织排放开放光路式等多种形式的监测方法。上述系统的测量结果显示:抽取式可实现CO、CO2、O2等不同多组分气体的同时测量;管道对射式实现了O2及10μL/L以下CO的高精度在线测量;探头式则以CH4测量为例实现了响应时间T90=15s,监测极限小于150μL/L,泄漏报警准确率达100%;开放光路形式以天然气集气站场测量CH4、C2H2、C2H4三种气体为例实现了0误报的监测能力。上述分析结果表明,TDLAS技术应用于工矿安全生产及安全预警方面的标识性气体监测是完全实用、有效、准确、可靠的。     

Dissolved rare earth elements estimation of ion-absorption rare earth ores using reflectance spectroscopy in south Jiangxi province,China

Ion-absorption rare earth ores are an important mineral resource in China. Nowadays, the unauthorized mining has become a serious problem, resulting in severe water pollution and the wastage of rare earth elements (REEs). Being able to estimate the concentration of dissolved REEs in water bodies near mines is essential for tackling this environmental problem. Conventionally, quantitative analyses of the contents of dissolved REEs are performed using laboratory-based techniques, which can be time consuming and costly. Spectral reflectance is a rapid and cost-effective means of characterizing the chemical compositions of light-absorbing materials. In this study, reflectance spectroscopy was performed on dissolved REEs, and the correlation between their reflectance characteristics and REE content was determined. A total of 50 aqueous media samples collected in south Jiangxi Province and 25 laboratory-produced aqueous media samples were tested, and their reflectance spectra and REE contents were measured using reflectance spectroscopy and inductively coupled plasma mass spectrometry, respectively. Next, the reflectance, differential reflectance, and absorption depth were analysed based on the REE content. Six diagnostic absorption features related to REEs are recognised in the visible and near-infrared wavelength regions, along with several smaller peaks. It indicates that the results of the absorption depth analysis are in accordance with the absorption spectra characteristics of the REEs, with the R² value being higher than 0.97. The intensity of each of the six absorption bands exhibits a linear correlation to the total REE content. Therefore, linear regression models can be derived for estimating the total concentration of REEs in aqueous media samples. What's more, the detection limit for REEs is determined to be about 30 μg/L. Thus, it can be concluded that reflectance spectroscopy is a suitable technique for estimating the concentration of dissolved REEs.