面向冷链智能立体仓库的数字孪生系统构建

目的 当前冷链物流行业立体仓库存在货品损耗率高、失温严重、信息化水平低等问题,确保冷链智能立体仓库的食品质量安全,并实现降本增效。方法 面向冷链智能立体仓库的运行场景,设计全映射与多维仿真的数字孪生五维模型,通过对多源异构数据的融合,实现立体仓库全要素的状态实时可视化与监测预警,并提出一种支持系统联动决策的模型优化策略,对立体库负载与温控区热力分布进行智能调节,最大限度提高运行效率和降低运营成本。结果 构建了一套冷链智能立体仓库数字孪生系统,通过对优化前后仓库运行数据进行对比,同等仓储环境条件下生鲜蔬菜的食品保鲜度损耗率同比下降了25%~30%,实现了冷链智能立体仓库实时数据与动态虚拟模型的精准映射与联动运转。结论 以广东某供应链管理有限公司佛山智能冷链仓储物流中心的冷链立体仓库为实践对象,形成了冷链智能立体仓库一体化管控新模式。为冷链智能立体仓库运营管理、调度联动决策与协同作业提供了数字孪生技术的应用参考,为建立更完善的保鲜产品包装与冷链食品质量安全提供了新路径。     

我国食品冷藏链现状与发展对策

分析了我国食品冷藏链的发展现状,指出了我国食品冷藏链基础建设、技术发展、管理体制、法制规范等方面的不足。结合当今社会环境和自然环境,提出了立足绿色、低碳技术,大力发展冷藏链基础建设;长远规划,建立健全行业标准规范,完善行业管理法律法规;依靠电子信息技术,发展产品质量监控技术和溯源体系等适合我国的食品冷藏链发展对策。     

果蔬及肉类冷链食品在流通过程中的安全控制

果蔬及肉类冷链食品在贮藏、运输和销售的流通过程中要经过众多的环节,并与人手、各种工具及空气有许多接触,很容易受到微生物和尘土的污染,出现腐烂、变质等食品安全问题。针对不同食品的要求,采用合适的包装,控制好适宜的温度并保持冷链的连续性及温度的稳定性,可以最大限度地减少食品在流通过程中的腐烂变质,减少损失,确保食品的质量安全。     

Examining the interrelationships between supply chain integration scope and supply chain management efforts

In this article, we study the concept of supply chain integration scope by comparing firms that involve immediate supply chain partners in their strategic efforts (narrow supply chain scope) versus firms that involve supply chain partners beyond the immediate level, for example second tier suppliers and end customers (broad supply chain scope). By relying on Coordination Theory and expanding upon Frohlich and Westbrook's (2001 Frohlich, MT and Westbrook, R. 2001. Arcs of integration: an international study of supply chain strategies. Journal of Operations Management, 19(5): 185–200.  [Google Scholar]) ‘arcs of integration’ principle, we propose that supply chain integration scope and the type of supply chain management efforts deployed by firms are correlated. We use data from a large sample of US and European firms to explore the association between supply chain integration scope and supply chain management efforts. The results show that supply chain integration scope can be predicted by a firm's supply chain management efforts. The implications of our results for practising managers are also offered. Our results suggest that supply chain managers should consider the practices identified in this study while deciding on the appropriate level of supply chain integration scope, i.e., which extended supply chain members to include in their strategic planning efforts.     

New absorption chiller and control strategy for the solar assisted cooling system at the German federal environment agency

Typically the cooling capacity of absorption chillers is controlled by adjusting the driving hot water temperature according to the load. Meanwhile the cooling water temperature is controlled to a constant set value. In order to increase the solar cooling fraction and/or to decrease the operating costs of solar assisted cooling systems (SAC-systems) a new control strategy has been developed which controls hot and cooling water temperature simultaneously. Hereby the specific cost of cold – generated from solar or conventional heat – can be reduced. The basic concept of the strategy is explained and results are shown for the SAC-system at the Federal Environment Agency in Dessau, Germany. Here a recently developed absorption chiller is now used instead of a former adsorption chiller. With the new absorption chiller and the control strategy the seasonal energy efficiency ratio SEER is above 0.75, electric efficiency is 35% higher and water consumption is reduced by 70%.     

上下冲击式速冻机流场和换热特性研究现状

目的 为了提高食品冻结的品质,需要对冲击式速冻机的结构尺寸和内部流场进行优化,改善冲击式速冻机的冻结效率.方法 综述影响该类速冻机换热特性的4个因素,即喷嘴的形状和尺寸,射流阵列的排布,喷嘴到输送带距离和喷嘴间距的改变,速冻机进出口压差等.结果 通过回顾计算流体力学技术和实验研究在这4个方面优化速冻机换热特性的案例,总结了上下冲击式速冻机流场变化的规律.结论 该研究为新型速冻机的优化设计提供了理论支撑.     

Using ultrasonic wave reflection to monitor false set of cement paste

The standard mechanical penetration approach for monitoring cement paste stiffening (Vicat needle method, ASTM C191) does not distinguish responses associated with false set of cement paste caused by secondary gypsum formation. The objective of this research is to determine whether ultrasonic wave reflection, using a testing set up with high measurement sensitivity, could be used to monitor false set of cement paste. Penetration resistance, P-wave, and S-wave reflection coefficients were measured on cement pastes with water-to-cement ratio 0.5. The S-wave reflection coefficient showed a sharp and abrupt linear drop associated with secondary gypsum formation, thereby indicating that S-wave ultrasonic wave reflection can be used to monitor false set of cement pastes. False set could not be distinguished in penetration resistance or P-wave UWR test data.     

Aligning business process reengineering in implementing global supply chain systems by the SCOR model

As supply chains continue to replace individual companies as the management arena for value-adding from the beginning of the twenty first century, understanding the supply chain management practices in a globalisation context becomes increasingly important. The Supply Chain Operations Reference (SCOR) Model, which was developed by the experts and practitioners of the Supply Chain Council, is a major framework for supply chain planning that features supply chain management practices and business process reengineering. Despite being an integrative guide with many merits, it only provides a ‘top-down’ approach that requires the comparative analyses of post- and pro-performance indices as a basis of business process modification. This study discusses the limitations of current SCOR analysis and provides a mapping technique—Causes/Effects, the SCOR Standard, and Mutual Solution (CESM)—for gap mapping, problem prioritisation, and business process modification in a supply chain setting. As such, it is one of the early empirical studies combining BPR and SCM disciplines. The research results can facilitate the implementation processes of multinational supply chain projects by identifying the gaps and linking them to the channel entities.     

Electron microscopic and optical studies of prism faces of synthetic quartz

Spirals on quartz are very seldom seen. The centre of the spirals and screw ledges are studied in detail using electron and optical microscopic techniques. Unusual profiles of spirals have been found with overhanging kinks on one side of the centre of these spirals. It is suspected that the complicated structures might have been developed after the completion of the growth of the crystals. It is also conjuctured that such structures would arise when growth-inhibiting substances are adsorbed on the crystal faces and result in imperfect crystals.Victawet, a proprietary wetting agent, available from one or more suppliers of electron microscopy materials and accessories.     

我国食品冷藏链物流现状的分析及发展策略

冷链物流是以保持低温环境为核心要求的供应链系统,是随着科学技术的进步以及制冷技术的快速发展而发展起来的,是以冷冻工艺学为基础、以制冷技术为手段的低温物流过程。本文通过比较国内外食品冷藏链物流的现状,指出我国食品冷链物流发展中存在的问题,提出我国食品冷链物流的发展策略。     

Susceptibility of Portland cement and blended cement concretes to plastic shrinkage cracking

The market share of different types of blended cements is increasing year by year. Generally, blended cements are ground to higher fineness and exhibit a slower development of mechanical properties compared to Ordinary Portland Cement (OPC), which might affect the concrete performance in terms of shrinkage cracking at early ages.In this paper, the performance of concretes made with different cement types is compared according to the ASTM C1579-13 standard for plastic shrinkage cracking. The cracking behavior was further correlated to the deformations of both unrestrained and restrained specimens measured by a 3D image correlation system. The main factors influencing the cracking behavior were discussed based on poromechanics. It is concluded that the bulk modulus evolution has a dominant effect on controlling the plastic shrinkage cracking. Concretes made of more reactive cements, in particular with higher clinker content, are less susceptible to plastic shrinkage cracking. For cements with the same clinker content, increasing the cement fineness reduces the risk of plastic shrinkage cracking.     

Disentangling the influence of cell phone usage in the dilemma zone: An econometric approach

This paper focuses on developing an analysis framework to study the impact of cell phone treatment (cell phone type and call status) on driver behavior in the presence of a dilemma zone. Specifically, we examine how the treatment influences the driver maneuver decision at the intersection (stop or cross) and the eventual success of the maneuver. For a stop maneuver, success is defined as stopping before the stop line. Similarly, for a cross maneuver, success is defined as clearing the intersection safely before the light turns red. The eventual success or failure of the driver's decision process is dependent on the factors that affected the maneuver decision. Hence it is important to recognize the interconnectedness of the stop or cross decision with its eventual success (or failure). Toward this end, we formulate and estimate a joint framework to analyze the stop/cross decision with its eventual success (or failure) simultaneously. The study is conducted based on driving simulator data provided online for the 2014 Transportation Research Board Data Contest at http://depts.washington.edu/hfsm/upload.php. The model is estimated to analyze drivers’ behavior at the onset of yellow by employing exogenous variables from three broad categories: driver characteristics, cell phone attributes and driving attributes. We also generate probability surfaces to identify dilemma zone distribution associated with different cell phone treatment types. The plots clearly illustrate the impact of various cellphone treatments on driver dilemma zone behavior.     

Fatigue life predictions using fracture mechanics methods

In the present work, a simple engineering approach which is based on a relatively solid background and which is checked against fatigue test data for various test conditions was developed: it may provide a practical and reliable basis for the analysis of structures under in-service loading conditions, in the presence of previous corrosion attack, or in the presence of a residual stress field, by using widespread fracture mechanics software. In particular, the approach was checked against an experimental program which consists of the following fatigue tests: base and friction stir welded (FSW) material under constant amplitude loading at different loading ratios (R = 0.1, 0.5, −1); pre-corroded base and FSW material under constant amplitude loading at load ratio R = 0.1; centre hole FSW specimens under the standardised variable amplitude loading spectrum FALSTAFF. Moreover, from the literature fatigue experiments under FALSTAFF of cold expanded as well as not cold expended holes were also used to validate the approach. The predictions were performed with the last version of AFGROW and NASGRO 3.0 software.