基于STC89C51的新型液氮低温微创冷冻控制系统设计

设计了一种新型液氮低温微创冷冻控制系统,详述了系统的控制原理及各功能模块的实现.采用热流平衡原理、PID技术与STC89C51单片机及外围控制电路对冷冻冻结面范围、液氮瓶压力及冷刀刀头温度进行实时控制和显示.应用结果表明:该系统运行稳定,可靠性高,操作简单.     

带有STC功能的接收机中频组件的设计

本文介绍了带有STC功能的接收机中频组件的设计,它动态范围宽,输出饱和电平大,选择性好,响应时间快.同时,对系统的电磁干扰加以讨论,并介绍了抗干扰的有效措施.     

基于DCT系数大小关系的自适应JPEG隐写

JPEG图像是最流行的隐写载体之一,但隐写分析的最新进展表明,如何设计安全的JPEG隐写算法仍是一个困难的问题.本文提出了一种新的JPEG自适应隐写方法.自适应隐写难点在于设计失真函数合理反应修改量化DCT系数造成的嵌入失真.由于量化DCT系数绝对值的大小能够反应JPEG图像主要统计特性,本文根据DCT系数大小关系设计失真函数,结合STC（Syndrome Trellis Codes）编码,分别给出了使用nsF5修改方式的单层嵌入方法以及使用加减一修改方式的双层嵌入方法.实验表明,本文单层嵌入方法比nsF5安全性高,双层嵌入方法比nsF5以及Filler’s Method抵抗多种检测的能力更强.     

实时主动声定位系统设计*

针对在军事演习或爆炸实验中对冲击波超压传感器位置的精确定位,设计了一种实时主动声定位系统。该系统由声信号发射系统、声信号接收处理系统和无线监控终端系统三部分组成。声信号发射系统与无线监控终端以单片机STC12C5A60S2作为核心控制器,接收处理系统以ARM9系列的S3C2440作为核心控制器。发射系统发射四种已知频率的声信号,接收处理系统接收并处理收到的四种声信号,然后把处理结果反馈到无线监控终端。通过实验表明,该系统在一定条件下,能够稳定地发射、接收并处理声信号,达到实时定位目标,并在200 m范围内将定位误差控制在厘米级内。     

Separation of phthalates by cyclodextrin modified micellar electrokinetic chromatography: Quantitation in perfumes

A new CE method has been developed for the simultaneous separation of a group of parent phthalates. Due to the neutral character of these compounds, the addition of several bile salts as surfactants (sodium cholate (SC), sodium deoxycholate (SDC), sodium taurodeoxycholate (STDC), sodium taurocholate (STC)) to the separation buffer was explored showing the high potential of SDC as pseudostationary phase. However, the resolution of all the phthalates was not achieved when employing only this bile salt as additive, being necessary the addition of neutral cyclodextrins (CD) and organic modifiers to the separation media. The optimized cyclodextrin modified micellar electrokinetic chromatography (CD-MEKC) method consisted of the employ of a background electrolyte (BGE) containing 25 mM β-CD-100 mM SDC in a 100 mM borate buffer (pH 8.5) with a 10% (v/v) of acetonitrile, employing a voltage of 30 kV and a temperature of 25 °C. This separation medium enabled the total resolution of eight compounds and the partial resolution of two of the analytes, di-n-octyl phthalate (DNOP) and diethyl hexyl phthalate (DEHP) (Rs ~ 0.8), in only 12 min. The analytical characteristics of the developed method were studied showing their suitability for the determination of these compounds in commercial perfumes. In all the analyzed perfumes the most common phthalate was diethyl phthalate (DEP) that appeared in ten of the fifteen analyzed products. Also dimethyl phthalate (DMP), diallyl phthalate (DAP), dicyclohexyl phthalate (DCP), and di-n-pentyl phthalate (DNPP) were found in some of the analyzed samples.     

精密数字式STC衰减组件的设计

主要介绍了某型号雷达接收前端中精密数字式STC衰减组件的设计。其优点是具有数字式可编程、精度高、曲线误差小。     

求解Euler方程的空间—时间守恒格式

本文在CE／SE方法的基础上，提出了空间－时间守恒（STC）格式，其特点是构造简单，物理概念清晰，守恒性好，计算速度快且精度高，容易推广到多维流动及粘性流动。通过对二维Euler方程STC格式的介绍，可以看出这一方法的主要特点。与其它格式的计算结果或精确解相比较表明，用STC格式计算的结果是令人满意的。     

基于STM32的凝结水液位监控系统的设计与实现

为降低PLC控制单容器液位控制系统的设计难度及成本,本系统选用STM32和STC89C51分别作为上位机与下位机的处理器,设计了基于Modbus-RTU协议的液位监控系统;实现了数据实时采集、显示与报警功能;采用PID算法很好的实现了凝结水液位恒值控制,满足了设计要求;最后给出了系统的实物图和测试结果。实验表明,该系统经济实用,抗干扰能力强,可以在工业控制中广泛使用。     

Ku波段高灵敏度接收模块的研制

介绍了具有噪声系数小、动态范围宽、镜频抑制高、抗烧毁能力强等优点的 Ku波段高灵敏度接收模块的设计     

Highly sensitive chiral analysis of amino acids by in-line single drop microextraction and capillary electrophoresis with laser-induced fluorescence detection

A highly sensitive method for chiral analysis of amino acids by in-line single drop microextraction (SDME) and chiral capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection was developed. In SDME, a drop of a basic aqueous acceptor phase covered with a thin organic layer was formed at the tip of a capillary by simple combination of sample-handling sequences of a CE apparatus. Then fluorescein isothiocyanate (FITC)-derivatized amino acids in an acidic donor solution were enriched into the drop through the organic layer. The enriched enantiomers were then resolved using a dual chiral selector of β-cyclodextrin (β-CD) and sodium taurodeoxycholate (STC). Here, in addition to serving as a labeling reagent providing high fluorescence signal, hydrophobic FITC was primarily used as a modifier aiding the extraction of zwitterionic amino acids by blocking the amino groups and increasing the hydrophobicity, yielding 220 times increase in extraction efficiency. Several hundred-fold enrichments were achieved with 10 min SDME, yielding LODs of 30-60 pM and enabling direct analysis of d-AAs in a 99% enantiomeric excess mixture. In view of no additional modification of the existing commercial CE instrument, this method without stirring can be easily realized using known operations. When a microstirrer was customized to the CE instrument several thousand-fold enrichments could be obtained with LODs in the low picomolar range of 1-3 pM.