工业控制网络协议MAP技术的研究与实现

计算机综合制造系统CIMS(Computer Integrated Manufacturing System)中最重要的子系统是计算机局部网络,MAP(Manufacturing Automation Protocol)则是CIMS系统中计算机局部控制网络的通信协议。本文着重研究MiniMAP网络技术,通过把目前技术比较成熟的产品(如ARCNET网络)和MiniMAP协议相结合,实现一种投资省、研制周期快的MiniMAP网络。     

Practical experiences of sensory investigations into the packaging of vegetables

The market for modified atmosphere foods continues to grow throughout Europe. This paper highlights some of the practical research studies carried out at the Campden Food and Drink Research Association during recent years. Vegetables referred to include potatoes, mushrooms, Brussels sprouts, calabrese, carrots, bean sprouts, watercress, diced onions, lettuce and mixed lettuce, and mixed vegetables. In all cases sensory evaluations of appearance were carried out on these vegetables packed in different atmospheres and in different packaging films, but only some results are included here in detail. Reference is made to a new industry guideline document for the good manufacturing and handling of modified atmosphere packed food products, and also to the use of active packaging.     

Scandinavian consumer preference for beef steaks packed with or without oxygen

Beef steaks retail-packed with (80% O₂, 20% CO₂) or without oxygen (either skin-packed or gas-packed (69.6% N₂, 30% CO₂, 0.04% CO or 70% N₂, 30% CO₂)) were compared by consumers in Denmark (n = 382), Norway (n = 316) and Sweden (n = 374). Two pairs of two steaks – one steak packed in a high oxygen atmosphere and one packed without oxygen – were given to the consumers. They were instructed to prepare the steaks at home on two consecutive days, and two persons had to taste each steak. In Denmark, the oxygen-free packing was either gas packing with CO (69.6% N₂, 30% CO₂, 0.04% CO) or without CO (70% N₂, 30% CO₂), in Norway it was either gas packing with CO (69.6% N₂, 30% CO₂, 0.04% CO) or skin packing, and in Sweden it was either skin packing or gas packing without CO (70% N₂, 30% CO₂). The meat represented animals that were between 17 and 80 months old (Denmark) and young bulls (Norway and Sweden).     

Shelf life of ready to use peeled shrimps as affected by thymol essential oil and modified atmosphere packaging

In this work the influence of different packaging strategies on the shelf life of ready to use peeled shrimps was investigated. First, the effectiveness of the coating (Coat) and the active coating loaded with different concentrations of thymol (Coat-500, Coat-1000, and Coat-1500) on the quality loss of the investigated food product packaged in air was addressed; afterwards, the thymol concentration that had shown the best performance was used in combination with MAP (5% O₂; 95% CO₂). Microbial cell load of main spoilage microorganisms, pH and sensorial quality were monitored during the refrigerated storage. Results of the first step suggested that the sole coating did not affect the microbial growth. A slight antimicrobial effect was obtained when the coating was loaded with thymol and a concentration dependence was also observed. Moreover, the active coating was effective in minimizing the sensory quality loss of the investigated product, it was particularly true at the lowest thymol concentration. In the second step, the thymol concentration (1000 ppm) that showed the strike balance between microbial and sensorial quality was chosen in combination with MAP. As expected, MAP significantly affected the growth of the mesophilic bacteria. In particular, a cell load reduction of about 2 log cycle for the samples under MAP respect to that in air was obtained. Moreover, the MAP packaging inhibited the growth of the Pseudomonas spp. and hydrogen sulphide-producing bacteria. The MAP alone was not able to improve the shelf life of the uncoated samples. In fact, no significant difference between the control samples packaged in air and MAP was observed. Whilst, the use of coating under MAP condition prolonged the shelf life of about 6 days with respect to the same samples packaged in air. Moreover, when the MAP was used in combination with thymol, a further shelf life prolongation with respect to the samples packaged in air was observed. In particular, a shelf life of about 14 days for the active coating under MAP compared to the same samples in air (5 days) was obtained.     

OFDM系统基于导频的信道估计算法分析

正交频分复用（OFDM）技术是新一代宽带无线通信最具竞争力的备选方案之一,在众多的高速数据传输领域得到广泛地应用。文章对几种典型信道估计算法的复杂度和估计性能进行了理论分析,并分析了导频位置及疏密对估计性能的影响。仿真结果有力地验证了文章的理论分析。文章的分析可以为OFDM系统信道估计算法的选择及导频的放置及其疏密度的设计提供一定的参考。     

无源毫米波图像超分辨率处理方法

超分辨率处理是一个病态问题,有效地利用已知信息和约束条件是实现最佳处理的重要因素.论文以无源毫米波成像退化模型为基础,给出点扩展函数估计;通过引入典型目标和场景毫米波辐射特性,把POCS(凸集投影)和MAP(最大后验概率)结合起来,提出一种无源毫米波图像超分辨率处理方法.实验结果表明,该方法能够加快收敛速度,在平滑噪声的同时保护图像边缘和细节.     

基于CAN总线的太阳能交通导向灯控制系统的设计

随着公路交通日趋发达,每个交通路口方向信号指示灯在夜晚都发挥重要的作用。为了节约能源,以及不可能做到在野外的每个路口都架设220伏交流电,介绍了一种采用太阳能电板和蓄电池作为电源,使用MSP430F149超低功耗单片机和独立总线控制器SJAl000实现的CAN总线的交通导向指示灯的设计。详细介绍了控制节点的硬件电路组成,给出了CAN节点初始化以及接收和发送程序流程。     

一种新的基于MAP的纹理自适应超分辨率图像复原算法

 本文论证了超分辨率图像复原计算中的两个性质,并基于此在MAP(Maximum A Posteriori)框架下提出了一种新的纹理自适应算法.算法首先根据低分辨率图像和高分辨率图像近似计算的可类比性质计算初始图像,使初始图像的质量更高,并根据超分辨率复原图像阶跃边缘的陡坡性质,将三边滤波正则化应用于迭代运算中,更好地保护了图像的陡坡和屋顶边缘.算法可根据图像的纹理自动计算初始图像融合参数以及正则化函数中的梯度阈值等参数,解决了以往超分辨率图像复原算法参数调整复杂的问题.实验结果表明,本文算法在没有人工参与的情况下,重建图像的客观评价和主观质量均有明显提高.     

NGN测试系统MAP监测模块的研究与实现

MAP监测模块是NGN网络测试仪表中针对移动网进行测试的部分。为了正确地将MAP协议运用于系统中,遵循基于ASN．1的MAP协议编码规范,采用面向对象的软件设计方法,开发出用于NGN网络测试仪的MAP监测模块。从用户需求出发,介绍了模块的设计和实现方法,并经过充分测试,效果良好,符合使用要求。     

Biobased packaging for improving preservation of fresh common mushrooms (Agaricus bisporus L.)

Freshness of common mushrooms was related to the internal atmosphere composition during modified atmosphere packaging (MAP) experiments at 20 °C and 80% RH with stretchable polyvinylchloride (PVC) film, paper, and the same paper coated with a wheat gluten solution. MAP with the stretchable film led to a detrimental deterioration of mushrooms after only one day of storage: dark brown blotches appeared and almost 30% of mushrooms exhibited open veil. This was due to the formation of condensed water at the inner surface of the material and onto mushrooms combined to a high O₂ partial pressure (16 kPa) in the headspace. Wheat gluten (WG) coated paper was the most effective to improve the shelf-life of mushrooms since it allowed the preservation of a fair colour, unbroken veils, and an acceptable texture during 3 days. This beneficial effect was attributed to the combination of a medium CO₂ (9.5 kPa) and low O₂ (2.5 kPa) partial pressure, without condensation. The main drawback of using WG-coated paper was its high water vapour permeability that led to an important weight loss (3.8 wt.% on day 3). However it did not affect the overall quality of mushrooms within the storage duration.

Industrial relevance

Even with the development of micro-perforated materials that provide the largest range of O₂ and CO₂ permeability values, several limitations are still encountered for synthetic MAP applications such as

– an insufficient perm-selectivity ratio that remains lower than 6 (value of 1 for micro-perforated material): generated atmosphere cannot reach both low O₂ and low CO₂ partial pressures and then are not adapted to CO₂-sensitive fresh produces.

– unattractive water condensation at the inner surface of the packaging that might occur due to a low water vapour permeability, favouring the development of microorganisms.

– their non biodegradability.

Previous studies reported a high selectivity ratio and a high water vapour permeability for biodegradable materials made from crops proteins (wheat gluten, for instance) that appeared well adapted for fresh fruits and vegetables preservation. However, despite low cost and such interesting functional properties, these materials exhibited poor mechanical properties and cannot be used as packaging material. Combination with other materials, such as cellulosic fibres, appeared to one way to get round this major drawback without losing its biodegradability. Indeed paper exhibits an environmental-friendliness potential (recyclability, sustainability, biodegradability, and compostability) and a high versatility in food packaging.By choosing common mushrooms, known to be sensitive to high CO₂ content, and a stretchable PVC film, commonly used to over-wrap mushrooms in tray (on European market), we demonstrate that this material was greatly less effective than a new biobased material (wheat gluten film coated onto paper) developed in collaboration with Smurfit Worldwide Research Center. This work confirms the interest in developing functionalised paper based packaging material with agro-based polymers adapted to the storage of fresh fruits and vegetable storage in ambient temperature.