2,504 research outputs found
Designing sustainable cold chains for long-range food distribution: Energy-effective corridors on the Silk Road Belt
Modern food production-distribution processes represent a critical stressor for the environment and for natural ecosystems. The rising flows of food across growing and consumption areas couple with the higher expectations of consumers for the quality of products and compel the intensive use of refrigerated rooms and transport means throughout the food supply chain. In order to aid the design of sustainable cold chains that incorporate such aspects, this paper proposes a mixed integer linear programming model to minimize the total energy consumption associated with the cold operations experienced by perishable products. This model is intended for food traders, logistics practitioners, retail managers, and importers collaboratively called to design and plan a cost and environmentally effective supply strategy, physical channels, and infrastructures for cold chains. The proposed model is validated with a case study inspired by the distribution of two example food products, namely fresh apples and ice cream, along the New Silk Road connecting Europe and China. The illustrated analysis investigates the effect of alternative routes and transport modes on the sustainability of the cold chain. It is found that the most energy-efficient route for ice cream is via rail over a northern route and, for apples, is via a southern maritime route, and, for these two routes, the ratios of the total energy consumed to the energy content of the food are 760 and 913, respectively. By incorporating the energy lost due to the food quality decay, the model identifies the optimal route to adopt in accordance with the shelf life and the conservation temperature of each product
Scheduling cross-docking operations under uncertainty: A stochastic genetic algorithm based on scenarios tree
A cross-docking terminal enables consolidating and sorting fast-moving products along supply chain networks and reduces warehousing costs and transportation efforts. The target efficiency of such logistic systems results from synchronizing the physical and information flows while scheduling receiving, shipping and handling operations. Within the tight time-windows imposed by fast-moving products (e.g., perishables), a deterministic schedule hardly adheres to real-world environments because of the uncertainty in trucks arrivals. In this paper, a stochastic MILP model formulates the minimization of penalty costs from exceeding the time-windows under uncertain truck arrivals. Penalty costs are affected by products' perishability or the expected customer’ service level. A validating numerical example shows how to solve (1) dock-assignment, (2) while prioritizing the unloading tasks, and (3) loaded trucks departures with a small instance. A tailored stochastic genetic algorithm able to explore the uncertain scenarios tree and optimize cross-docking operations is then introduced to solve scaled up instaces. The proposed genetic algorithm is tested on a real-world problem provided by a national delivery service network managing the truck-to-door assignment, the loading, unloading, and door-to-door handling operations of a fleet of 271 trucks within two working shifts. The obtained solution improves the deterministic schedule reducing the penalty costs of 60%. Such results underline the impact of unpredicted trucks’ delay and enable assessing the savings from increasing the number of doors at the cross-dock
ANALYSIS OF INDUSTRIAL PROCESSES BASED ON INTEGRATION OF DIFFERENT SIMULATION TOOLS
The present paper provides an example of software tools integration in order to perform simulations incomplex industry models, such as a ceramic tile manufacture. The first part of the paper presents thefeatures of the two simulation tools adopted: AutoMod\u2122 and VirtES. AutoMod\u2122 is a commercial suiteof simulation tools witch provides an environment easy to develop highly accurate models for analysis.VirtES simulation tool was developed by the Industrial Plants Research Group of the Department ofIndustrial and Civil Engineering (DIMeC) of the University of Modena and Reggion Emilia. Modelsdeveloped in VirtES are useful to investigate macro Key Performances Indicators (KPI), such aseconomic indicators. The integrated used of VirtES and AutoMod\u2122 allows to perform accuratesimulation at line production level developed by AutoMod\u2122 in multiple virtual scenarios created byVirtES
Effects of herd origin, AI stud and sire identification on genetic evaluation of Holstein Friesian bulls
The purpose of this study was to estimate the effects of herd origin of bull, AI stud and sire identification number (ID) on official estimated breeding values (EBV) for production traits of Holstein Friesian proven bulls. The data included 1,005 Italian Holstein-Friesian bulls, sons of 76 sires, born in 100 herds and progeny tested by 10 AI studs. Bulls were required to have date of first proof between September 1992 and September 1997, to be born in a herd with at least one other bull and to have sire and dam with official EBV when bull was selected for progeny testing. Records of sires with only one son were also discarded. The dependent variable analyzed was the official genetic evaluation for a “quantity and quality of milk” index (ILQ). The linear model to predict breeding values of bulls included the fixed class effects of herd origin of bull, AI testing organization, birth year of bull, and estimated breeding values of sire and dam, both as linear covariates. The R2of the model was 45% and a significant effect was found for genetic merit of sire (P < 0.001) and dam (P < 0.014), for herd origin of bull (P < 0.01) and for birth year of bull (P < 0.001). The effect of AI testing organization was not sig- nificant. The range of herd origin effect was 872 kg of ILQ. However, in this study, the causes of this result were not clear; it may be due to numerous factors, one of which may be preferential treatment on dams of bulls. Analyses of resid- uals on breeding value of proven bulls for ILQ showed a non significant effect of sire ID, after adjusting for parent aver- age, herd origin effect and birth year effect. Although the presence of bias in genetic evaluation of dairy bulls is not evi- dent, further research is recommended firstly to understand the reasons of the significant herd origin effect, secondly to monitor and guarantee the greatest accuracy and reliability of genetic evaluation procedures
A modular modelling approach to stochastic simulation of production – logistic systems
The economic scenario today is highly competitive in terms of costs and number of competitors, so it isnecessary to adopt strategies that allow the constant improvement of manufacturing processes withinthe spending constrains. Simulation models are useful to support and drive company management inimproving the performances of production and logistic systems. The costs of simulation modeldevelopment could be reduced by the reuse of some of its parts. This work presents a case studyconcerning stochastic modeling of a small manufacture operating into the wood products field. Amodular simulation model composed of reusable sub-models has been developed using AutoMod™software package. The aim of the modular architecture is to allow the use of sub-models in differentproduction systems with little changes, decreasing the costs of development in order to became moreaffordable in a SME (small medium enterprise) contest
Hybrid Design of Multiplicative Watermarking for Defense Against Malicious Parameter Identification
Watermarking is a promising active diagnosis technique for detection of
highly sophisticated attacks, but is vulnerable to malicious agents that use
eavesdropped data to identify and then remove or replicate the watermark. In
this work, we propose a hybrid multiplicative watermarking (HMWM) scheme, where
the watermark parameters are periodically updated, following the dynamics of
the unobservable states of specifically designed piecewise affine (PWA) hybrid
systems. We provide a theoretical analysis of the effects of this scheme on the
closed-loop performance, and prove that stability properties are preserved.
Additionally, we show that the proposed approach makes it difficult for an
eavesdropper to reconstruct the watermarking parameters, both in terms of the
associated computational complexity and from a systems theoretic perspective.Comment: 8 pages, first submission to the 62nd IEEE Conference on Decision and
Contro
- …