Multiple objects tracking in the presence of long-term occlusions

We present a robust object tracking algorithm that handles spatially extended and temporally long object occlusions. The proposed approach is based on the concept of “object permanence” which suggests that a totally occluded object will re-emerge near its occluder. The proposed method does not require prior training to account for differences in the shape, size, color or motion of the objects to be tracked. Instead, the method automatically and dynamically builds appropriate object representations that enable robust and effective tracking and occlusion reasoning. The proposed approach has been evaluated on several image sequences showing either complex object manipulation tasks or human activity in the context of surveillance applications. Experimental results demonstrate that the developed tracker is capable of handling several challenging situations, where the labels of objects are correctly identified and maintained over time, despite the complex interactions among the tracked objects that lead to several layers of occlusions.     

Poly(lactic acid) film incorporated with marigold flower extract (Tagetes erecta) intended for fatty-food application

Bilayer functional film made of poly(lactic acid), PLA incorporated with 2 wt.% marigold flower extract containing astaxanthin (PLA2M) was fabricated by using a blown-extrusion process. The release of astaxanthin, a keto-carotenoid antioxidant, from the PLA-based film towards 95% ethanol (ETOH) was investigated at 30 and 40 °C. PLA and PLA2M that had been in contact with 95% ETOH at 30 and 40 °C were also investigated for their optical, thermal, structural, molecular weight and barrier properties. PLA2M showed approximately 21% reduction in its water vapor permeability (WVP) as compared to PLA (control bilayer functional film). No significant differences were observed between both PLA and PLA2M in terms of their thermal properties and O₂ permeability. Molecular weight of PLA2M had a slight decreased than that of PLA after processing. A significant change was observed in the IR spectra of PLA2M especially for the carbonyl stretching (1749 cm⁻¹), and –C–O–C aliphatic ester bending (1132 cm⁻¹), which due to the structure of astaxanthin that consists of polyunsaturated alkenes and carbonyl group. Diffusion of astaxanthin from PLA films into 95% ETOH at 30 and 40 °C were 12.7 and 22.8 × 10⁻¹¹ cm²/s, respectively. New crystal domains were formed for the samples exposed to 95% ETOH at 30 and 40 °C due to solvent induced crystallization, with higher temperature inducing larger crystallization. Pouches made of PLA2M were able to maintain the freshness of soybean oil at 30 °C, under light exposure to less than 5 days per guideline by the Codex Alimentarius (<10 milliequivalent/kg), and could be attributed to the slow release of astaxanthin.     

塑料包装材料化学物向食品迁移的模型研究进展

塑料包装材料内含化学物向食品的迁移会造成食品污染并最终危害消费者的健康,近年来受到国内外广泛关注.30多年来,美国食品与药品管理局(FDA)和欧盟委员会(EC)开展了大量包装材料化学物迁移相关的理论与实验研究.由于迁移实验复杂、费用昂贵、要求先进的分析测试仪器,在一般实验室很难开展,因此近年来各国开始关注迁移理论预测的研究.文中介绍了塑料包装材料化学物迁移数学解析模型的研究进展,应用无量纲化方法对比分析了模型参数对各模型的影响.     

配比与紫外老化对PLA/PBAT包装膜性能及其中增塑剂乙酰柠檬酸三丁酯迁移的影响

制备聚乳酸/聚己二酸-对苯二甲酸丁二酯(PLA/PBAT)复合食品包装薄膜,探究了配比和紫外老化时间对其性能及其中增塑剂乙酰柠檬酸三丁酯(ATBC)迁移的影响。制备了10:90、20:80、30:70三种不同配比的PLA/PBAT复合薄膜,经过72、150、300 h紫外老化时间后,对薄膜的拉伸强度、阻隔性、可见光透过率、结晶度等性能进行测试。借助GC-MS建立增塑剂ATBC的检测方法,探究不同配比及紫外老化时间对薄膜中ATBC迁移的影响。结果显示3种配比对力学性能、透光率无明显影响,30:70配比薄膜的阻隔性及结晶度最优,ATBC迁移率最低,氧气透过率和水蒸气透过率分别为894 mL/(m2·d·0.1 MPa)和520 g/(m2·day),结晶度为5.99%,ATBC的迁移率为25%;紫外老化以后会破坏薄膜内部结构,同时使表面生成致密层,降低力学性能的同时阻碍了其中ATBC的迁移。     

二苯甲酮和1-羟基环己基苯基甲酮从食品包装纸向奶粉与Tenax迁移研究

对二苯甲酮和1-羟基环己基苯基甲酮在高温条件下从食品包装纸（白卡纸和牛皮纸）向脂肪类模拟物Tenax以及全脂奶粉中的迁移规律进行研究。为避开奶粉中杂质色谱峰的干扰,气相色谱的升温条件为柱温：80 ℃保留3 min,温度以20 ℃/min 的速率升到150 ℃,保留10 min,然后再以30 ℃/min 升到290 ℃保留10 min。结果表明：温度越高,光引发剂向食品的迁移率就越高,且迁移速率也越大,达到平衡的时间也越短。纸张本身对脂肪的渗透能力是影响污染物迁移的重要影响因素,在高温下包装含脂量较高的食品时,应尽量避免选用脂肪渗透能力较强的纸张。光引发剂由同种纸质食品包装材料分别向Tenax和全脂奶粉迁移的研究表明,光引发剂向奶粉迁移的迁出率较高,奶粉作为一种真实的食品,有很好的吸附能力,因而适合用于做迁移研究,且奶粉成分复杂,更能代表真实食品的特性。     

微波条件下微波纸中邻苯二甲酸酯向食品模拟物Tenax的迁移

研究250W和600W微波加热功率条件下微波纸中5种邻苯二甲酸酯向食品模拟物Tenax迁移的规律,并与常规高温迁移实验的结果比较。结果表明:微波加热条件下的迁移受加热功率、加热时间、迁移物分子结构、相对分子质量和极性等因素影响。与常规高温迁移相比,微波加热能加速物质迁移,说明迁移过程也受加热方式影响,微波加热可作为加速纸质包装中有害物质迁移的实验方法。     

Reinforcement of polyurethane composites with an organically modified montmorillonite

A clay with reactive activity prepared by treatment of natural montmorillonite with Methylene-bis-ortho-chloroaniline (MOCA) was incorporated into polyurethane matrix and a series of PU/clay nanocomposites were obtained by in situ polymerization. The microstructure of the nanocomposites with different content of the clay was examined by atomic force microscopy (AFM). The thermal and mechanical properties of the nanocomposites with different organic clay content were characterized by dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). It was found that the moduli and thermal stability of the nanocomposites were improved with augment of clay, especially, for the PU/9 wt% MO-MMT nanocomposite, compared to pure PU, the storage modulus and the loss modulus were increased by about 300% and 667% at −45 °C, respectively.     

Dropping damage evaluation for a tangent nonlinear system with a critical component

A new concept of dropping damage boundary surface is proposed to evaluate the dropping damage of a critical component for a nonlinear packaging system, and a novel dynamical mathematical model is established to analyze the effect of three key coordinate parameters, i.e., the non-dimensional dropping shock velocity, the frequency parameter ratio and the defined system parameter, on dropping damage. An experiment was conducted to verify the theory prediction, showing good agreement.