深水域近水面水下爆炸水柱形态及演变实验研究

 为研究不同起爆深度的水下爆炸水柱形态及演变特征,进行了1 kg球形RDX装药在不同起爆深度下的海上爆炸实验,通过高速摄像机记录装药起爆后水柱的形成和成长过程,获得了喷射水柱形态的演变特征以及水柱高度、直径、水柱突出水面时间等参数的变化规律,并与Cole、Hole和Swisdak等人的研究结果进行对比分析。研究结果表明：对于深水域近水面水下爆炸,水柱以垂直喷射形态为主,当气泡在膨胀阶段到达水面时水柱存在微弱的径向飞散现象;水柱最大高度随起爆深度呈脉动变化,水柱直径随起爆深度线性减小;Swisdak关于水柱最大高度的计算公式不适用深水域近水面水下爆炸情况。     

高速传输系统CAD/CAM齿形误差最优化算法

本文提出了一种CAD/CAM齿形误差的最优化算法。本算法收敛速度快、拟合误差小,能够按照预定设计要求对齿形精度加以控制,实现最优化自动搜索,同时给出数值计算结果。     

基于FPGA的超高速线阵CCD信号采集系统的设计与实现

线阵CCD已广泛应用于在线检测、图像识别等系统,目前高帧率采集系统多在200~500Hz之间。高速线阵CCD采集系统,如1K甚至10KHz以上的采集要求,设计难度大,电路实现复杂,需要专用处理器,产品成本高,提出了一种采用并行高速FPGA驱动线阵CCD,通过常规分立元件完成模拟信号处理,实现数字信号实时传输的方案。该方案不仅简化了硬件设计上的难度,在同等性能情况下,可实现每秒万帧的高速采样,大幅度降低了成本。方案选用Altera FPGA作为控制核心,实现高速信号采集的同时,在片上实现一定的图像算法,不仅加速了图像处理速度,同时降低了计算机的处理压力。最后,本电路通过USB2.0接口,完成数据的实时传输。设计具有高帧率、高灵敏度、性能稳定,便携使用等特点,同时还有一定的通用性,已应用于一些光学系统中。     

富里叶级数的收敛速度

对正弦和余弦富立叶级数,通过合并相邻同号项,使其重排成交错级数.讨论了重排形成的交错级数的敛散性.指出根据自变量x的不同取值,该交错级数可能是单调递减或周期递减的级数.按照莱布尼茨判定法提出了不同精度要求的级数项数的计算公式.选取一到三阶收敛的富立叶级数计算了不同比值精度及差值精度要求的级数项数.计算表明,在x的取值为2π的等分点时,富立叶级数的部分和随项数的增加单调地逼近其收敛值.在x的取值为其它点时,富立叶级数的部分和随项数的增加围绕收敛值上下变动,周期地逼近其收敛值.低收敛阶富立叶级数的收敛速度较慢.要达到0.01%的精度,一收敛阶富立叶级数需要数万项,二收敛阶富立叶级数也需要数百项.在不同计算点处,要达到相同的计算精度,需要的级数项数差别较大.     

An asynchronous high‐speed synchrotron shutter

A high‐repetition‐rate mechanical shutter with asynchronous control and sub‐millisecond operation has been developed and tested for specialist X‐ray systems in the field of medical diagnostics and radiation therapy. Capacitor‐coupled linear voice coil actuators are utilized to achieve opening and closing speeds as fast as 700 µs for an aperture height of 4 mm. The design allows for asynchronous control, permitting slave operation of the shutter, a feature that is distinctly suitable for a number of applications including particle image velocimetry, where high‐frame‐rate operation must be accurately synchronized and triggered by the image acquisition sequence of the detector or timing device. The design and construction of the shutter also makes it ideal, with simple and limited modifications, for applications requiring larger apertures, in particular wide beams as found in many synchrotron beamlines.     

Green ultra‐fast high‐performance liquid chromatographic method using a short narrow‐bore column packed with fully porous sub‐2 μm particles for the simultaneous determination of selected pharmaceuticals as surface water and wastewater pollutants

Fast separations are very desirable in laboratories that analyze large numbers of samples per day or those needing short turn‐around times. Traditional HPLC methods using conventional stationary phases and standard column dimensions require significant amounts of organic solvents and generate large volumes of waste. With growing awareness about the environment, the development of green technologies has been receiving increasing attention. In this work, a very fast green analytical method based on LC‐UV using a short narrow bore column packed with fully porous sub‐2 μm particles has been developed for simultaneous determination of nine pharmaceuticals in wastewater and surface water. The chromatographic separation was optimized in order to achieve short analysis time and good resolution for all analytes in a single run. All analytes could be separated in 1 min with good resolution. Sample preparation was executed by solid phase extraction using Oasis HLB cartridges. The method developed was validated based on parameters such as linearity, precision, accuracy, detection, and quantification limits. The recovery ranged from 70.9 to 92.5% with SDs not higher than 5.4%, except for acetaminophen and sulphanilamide. LODs ranged from 0.6–2.5 μg/L, while the LOQs were in the range 2–8 μg/L.     

Application of supercritical fluid extraction coupled with counter–current chromatography for extraction and online isolation of unstable chemical components from Rosa damascena

Supercritical fluid extraction (SFE) coupled with high‐speed counter‐current chromatography (HSCCC) was successfully used for the extraction and online isolation of the unstable compounds from Rosa damascene in a single extraction and separation operation in two stages. The solvent systems of SFE/HSCCC were optimized with the help of multiexponential function model. At the first stage, the upper phase of the solvent system of n‐butanol–tert‐butyl methyl ether–acetonitrile–0.1% aqueous TFA (1.7:1.0:0.8:4.0, v/v/v/v) was used as both the SFE entrainer and the HSCCC stationary phase, and the target compounds were eluted with the corresponding lower phase to separate the hydrophobic compounds. At the second stage, the upper phase of the solvent system of n‐hexane–ethyl acetate–methanol–water (3.2:1.0:2.8:2.6, v/v/v/v) was used as both the SFE entrainer and the HSCCC stationary phase, followed by elution with the corresponding lower phase to separate the moderate hydrophobic compounds. Six compounds including formononetin, delphinidin, cyaniding, 5,6,4′‐trihydroxy‐7,8‐dimethoxy flavone, 5,3′‐dihydroxy‐7,8‐dimethoxy flavone, and 5‐hydroxy‐6,7,8,3′,4′‐pentamethoxy flavone were successfully separated in one extraction–separation operation within 300 min. The targeted compounds were identified by MS and NMR spectroscopy. This research has opened up great prospects for industrial application of SFE/HSCCC to the extraction and separation of unstable compounds.     

Solvent‐Free Reactions of Fullerenes with Diethyl Bromomalonate in the Presence of Inorganic Bases Under High‐Speed Vibration Milling Conditions

Abstract

Solvent‐free reactions of C₆₀ and C₇₀ with diethyl bromomalonate in the presence of various inorganic bases were investigated under the high‐speed vibration milling (HSVM) conditions, and are shown to give methanofullerenes 1 and 2 in good to excellent yields based on consumed fullerenes. Several weak inorganic bases were found to be quite effective in promoting the solvent‐free mechanochemical Bingel reactions of C₆₀ and C₇₀ under the HSVM conditions. Among the studied bases, sodium acetate gave the highest yield of monoadducts, while potassium carbonate afforded a considerable amount of bisadducts for both C₆₀ and C₇₀.     

Characterization of Cr‐doped Sb2Te3 films and their application to phase‐change memory

Phase‐change memory (PCM) is regarded as one of the most promising candidates for the next‐generation nonvolatile memory. Its storage medium, phase‐change material, has attracted continuous exploration. Along the traditional GeTe–Sb₂Te₃ tie line, the binary compound Sb₂Te₃ is a high‐speed phase‐change material matrix. However, the low crystallization temperature prevents its practical application in PCM. Here, Cr is doped into Sb₂Te₃, called Cr–Sb₂Te₃ (CST), to improve the thermal stability. We find that, with increase of the Cr concentration, grains are obviously refined. However, all the CST films exhibit a single hexagonal phase as Sb₂Te₃ without phase separation. Also, the Cr helps to inhibit oxidation of Sb atoms. For the selected film CST_10.5, the resistance ratio between amorphous and crystalline states is more than two orders of magnitude; the temperature for 10‐year data retention is 120.8 °C, which indicates better thermal stability than GST and pure Sb₂Te₃. PCM cells based on CST_10.5 present small threshold current/voltage (4 μA/0.67 V). In addition, the cell can be operated by a low SET/RESET voltage pulse (1.1 V/2.4 V) with 50 ns width. Thus, Cr–Sb₂Te₃ with suitable composition is a promising novel phase‐change material used for PCM with high speed and good thermal stability performances. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Comprehensive separation of iridoid glycosides and triterpenoid saponins from Dipsacus asper with salt‐containing solvent by high‐speed countercurrent chromatography coupled with recycling mode

The roots of Dipsacus asper Wall as a commonly used traditional Chinese medicine are used for tonifying liver and kidney and strengthening bones and muscles. However, an effective separation strategy for comprehensive and rapid separation of the main active compounds from the roots of D. asper is nonexistent. This investigation provided an effective separation method based on AB‐8 macroporous resin column chromatography using different ratios of ethanol in water and two different modes of high‐speed countercurrent chromatography with salt‐containing solvent system for rapid enrichment and separation from the roots of D. asper. The macroporous resin column chromatography was performed on AB‐8 resin using ethanol in water ratios of 10, 30, 40, 50, and 80% as the optimized enrichment conditions for iridoid glycosides and triterpenoid saponins with different polarities. For high‐speed countercurrent chromatography separation, the conventional and recycling modes were combined together to develop a strategy for 12 compounds ( 1 – 12 ) from the enriched parts of 30, 40, and 80% ethanol, including six high‐polarity iridoid glycosides ( 1 – 6 ) using inorganic salt‐containing solvent system and six triterpenoid saponins ( 7 – 12 ). Recycling high‐speed countercurrent chromatography separation was successfully applied to separate two isomers ( 9 and 10 ) after 11 cycles.