CD-ROM伺服控制的设计

光驱读碟速度的快慢和稳定,很大程度上取决于伺服控制的好坏.光驱伺服控制主要分成3部分:聚焦过程、寻轨控制、轨道锁定.详细阐述了光驱伺服控制程序的设计过程.     

去皮鲜甘蔗的护色保鲜包装研究

通过不同浓度的盐、糖、酸溶液和不同的包装材料对去皮甘蔗进行保鲜处理,常温下贮藏,观察不同处理方法对去皮甘蔗腐坏变红的影响,再根据单因素实验和正交试验来确定最佳保鲜方案。实验结果表明:当盐溶液的质量分数为0.4%,糖溶液的质量分数为0.3%,酸溶液的质量分数为0.1%,包装材料为PP/PE或PVDC/PE时,对去皮鲜甘蔗进行保鲜处理的效果相对最好。     

鲜切藕片的网购产品抗氧化保鲜包装研究

为了解决鲜切藕片电商销售时,由于运输和储存条件的限制,产品本身发生的一些氧化反应,使得藕片的组织结构发生改变,导致产品的食用质量和感官品质的下降。本次研究中,分别选择合适浓度的糖、醋、盐的浸泡液,在包装保存之前对鲜切藕片进行浸泡。选择抑菌抗氧、生物气调、抗雾防霉3种不同的塑料包装袋对藕片进行包装。采用控制单一变量和正交实验的实验方法,探索并找到最为适宜的浸泡约浓度和包装袋;最后以感官评价的得分为判定基准,找出最合适的浸泡液和包装袋的组合。结果表明,在糖浓度0.5%,盐浓度1.1%,醋浓度0.5%时按照1∶1∶1比例混合的混合浸泡处理的莲藕切片,选择抑菌抗氧包装袋包装保存,对莲藕切片的保鲜效果最好。     

A near-infrared methane detection system using a 1.654 µm wavelength-modulated diode laser

By adopting a distributed feedback laser (DFBL) centered at 1.654 µm, a near-infrared (NIR) methane (CH4) detection system based on tunable diode laser absorption spectroscopy (TDLAS) is experimentally demonstrated. A laser temperature control as well as wavelength modulation module is developed to control the laser’s operation temperature. The laser’s temperature fluctuation can be limited within the range of ?0.02—0.02 °C, and the laser’s emitting wavelength varies linearly with the temperature and injection current. An open reflective gas sensing probe is realized to double the absorption optical path length from 0.2 m to 0.4 m. Within the detection range of 0—0.01, gas detection experiments were conducted to derive the relation between harmonic amplitude and gas concentration. Based on the Allan deviation at an integral time of 1 s, the limit of detection (LoD) is decided to be 2.952×10-5 with a path length of 0.4 m, indicating a minimum detectable column density of ~1.2×10-5 m. Compared with our previously reported NIR CH4 detection system, this system exhibits some improvement in both optical and electrical structures, including the analogue temperature controller with less software consumption, simple and reliable open reflective sensing probe.     

改性聚丙烯薄膜防黏性能验证及包装应用

首先测量酸奶在每种薄膜上的接触角,采用两种不同方法验证薄膜的防黏效果;再检测改性薄膜的卫生性能。结果表明:7%硅油+93%聚丙烯混合改性的薄膜和8%聚四氟乙烯+92%聚丙烯改性的薄膜性能最优,接触角分别为85.97°,98.84°;通过两种防黏连方法的验证表明,7%硅油改性的薄膜的酸奶残留量分别为28.67%,23.45%,8%聚四氟乙烯改性的薄膜的酸奶残留量分别为26.61%,23.11%;经安全性验证,改性薄膜符合国家食品包装材料的要求。     

Mid-infrared carbon monoxide detection system using differential absorption spectroscopy technique

A differential carbon monoxide (CO) concentration sensing device using a self-fabricated spherical mirror (e.g. light-collector) and a multi-pass gas-chamber is presented in this paper. Single-source dual-channel detection method is adopted to suppress the interferences from light source, optical path and environmental changes. Detection principle of the device is described, and both the optical part and the electrical part are developed. Experiments are carried out to evaluate the sensing performance on CO concentration. The results indicate that at 1.013×105 Pa and 298 K, the limit of detection (LoD) is about 11.5 mg/m3 with an absorption length of 40 cm. As the gas concentration gets larger than 115 mg/m3 (1.013×105 Pa, 298 K), the relative detection error falls into the range of ?1.7%—+1.9%. Based on 12 h long-term measurement on the 115 mg/m3 and 1 150 mg/m3 CO samples, the maximum detection errors are about 0.9% and 5.5%, respectively. Due to the low cost and competitive characteristics, the proposed device shows potential applications in CO detection in the circumstances of coal-mine production and environmental protection.     

基于虚拟锁相放大器的中红外CO检测系统

利用PC机和LabVIEW平台较强的数据处理能力, 设计并实现了一种基于虚拟锁相放大器的中红 外CO检测系统。系统采用双通道热释电探测器检测气体浓度,利用USB数据采集卡采集 探测器的传感信号,利用LabVIEW平台的乘法器、滤波器及直流幅值提取模块构建的虚拟锁 相放大器提 取传感信号幅度。为了表征虚拟锁相放大器的性能,利用幅度可调的标准正弦信号作为 待测信号,对 虚拟锁相放大器输出信号的幅度与标准正弦信号的幅度做实验测量与对比,二者呈现出良 好的线性关系, 线性拟合优度约为99.978%。对配备的20种CO气体 样品开展气体标定实验,并测量 了本文系统的精度、稳定性和检测下限等指标。实验结果显示,系统的检测下限约为50×10－6,对20种气体 样品的检测误差均小于4.2%,对浓度为3500×10－6气体样品3h测量结果的最大波动范围为±6%。 由于LabVIEW资源丰富且功能可任意扩展,因此在实验室环境中的气体检测,本文系统相 比采用嵌入式微处理器的系统更具有优势。     

相位补偿器的软件设计与实现

在控制过程中,如果控制系统是一个高阶的系统(高于1阶)．那么系统会由于相位延时造成不稳定.为了解决这一问题．就需要在控制回路中加入相位补偿器来对相位进行补偿。在本文中将介绍一种相位补偿器快速设计的方法．它通过对相位补偿系数的预估．利用MATLAB辅助快速地设计出满足实际控制需要的相位补偿器.     

聚四氟乙烯/硅油改性聚丙烯防黏包装材料的制备以及性能分析

用食品级硅油和聚四氟乙烯(PTFE)分别和同时加入到聚丙烯(PP)树脂中对其改性,共混挤出,直接流延成膜。研究了硅油和聚四氟乙烯的添加量对薄膜力学性能、微观结构、热稳定性、光学性能的影响。结果表明,添加的改性剂均能对薄膜的性能产生影响,其中硅油含量为7%和PTFE含量为8%时薄膜的接触角较大并且其不粘效果最明显,可以作为一种防粘薄膜应用于实际生活中,减少浪费。     

纳米ZnO-T树脂改性聚乙烯薄膜的制备和性能

以低密度聚乙烯为基材,将改性T树脂和改性纳米ZnO加入其中,利用双螺杆造粒机以及流延机通过熔融共混制得改性聚乙烯薄膜,并研究改性T树脂和改性纳米ZnO的含量对聚乙烯薄膜的抑菌效果、水蒸气透过量、氧气透过量、力学性能、微观结构、红外光谱及紫外透过率的影响。结果表明,当加入1.5%的改性纳米ZnO时,薄膜的抑菌性能随改性T树脂含量的不断增大而更加显著,紫外线透过率的变化趋势为先降低后上升。当改性纳米ZnO的质量分数为1.5%、改性T树脂的质量分数为1%时,水蒸气透过量和氧气透过量最小,抗拉强度和断裂伸长率最大。薄膜的阻隔性效果和抑菌性能较好,可应用于食品包装,延长食品的保质期。