432 research outputs found
Multi-objective Models and Methods for Design and Management of Sustainable Logistic Systems
No full textLogistics is typically defined as the design and operation of the physical, managerial and informational systems needed to allow goods to overcome space and time. Traditional models and methods for logistic system design and management focus on the optimization of the techno-economic performances. However, logistic activities are distinguished by a huge environmental impact. For instance, the final energy consumption for freight transportation reached in recent years the alarming value of 13% of the total end-use energy worldwide, equal to 40 EJ per year. Thus, innovative techniques for logistic system design and management have to guarantee these system overall sustainability not only from a technical and economic perspective but also from an environmental viewpoint. To this end, multi-objective optimization is of strong help. This is a mathematical programming technique to systematically and simultaneously optimize a collection of objective functions, often conflicting among them.
Considering this scenario, aim of this Ph.D. thesis is to develop, propose and validate innovative multi-objective models and methods for design and management of sustainable logistic systems simultaneously optimizing the system technical performance, economic profitability and environmental impact.
The developed models fully manage the material flow from suppliers to assembly or manufacturing areas and from these to final customers through the distribution, storage and retrieving activities among and within the logistic actors. An original decision support system is proposed to jointly minimize the operating cost, carbon footprint and delivery time in the design of multi-modal multi-level distribution networks considering the most relevant features of the delivered products. Concerning warehousing systems, both design and operation problems are tackled. A multi-objective optimization model is developed to determine the warehouse building configuration, namely length, width and height, which simultaneously minimizes travel time, total cost and carbon footprint objective functions. These two latter are estimated through a lifecycle approach. All the activities related to warehouse building installation and operating phases are evaluated both from an economic and an environmental perspective. Warehousing system operation is analyzed by means of storage assignment strategy. A time and energy based strategy is proposed to jointly minimize the travel time and the energy required by the material handling vehicles to store and retrieve the unit loads. Proper vehicle motion configuration and unit load features are considered to accurately model the objective functions. Finally, the presented models and methods are tested and validated against case studies from the food and beverage industry. The results demonstrate that a tremendous environmental impact reduction is possible at negligible technical and economic performance worsening
A review of technologies and applications for water purification in the food & beverage industry
No full textFood & Beverage (F&B) industry is known as a water intensive sector. Thousands of litres per hour of pure water are necessary to produce the final drinks, for the line and backup process requirements of medium size production plants. Due to health restrictions and the F&B standard, the physical, chemical and biological quality of process water has to fit with high level of purity. To this purpose, all F&B plants require a dedicate water purification unit making raw water (both primary and recovered) ready-for-use. Such units are process plants based on mechanical and chemical purification technologies, mainly. This paper aims at revising the state-of-art of research and practice in this field. Starting from the process description and the expected water quality level, a matrix analysis, according to a panel of classification drivers, allows outlining the current research streams and the most popular technologies. The industrial sector, the fluid features and the adopted technology are among the investigated drivers. Results highlight a wide range of solutions, often combined in series to increase the final effect. Lacks are in applications dedicated to the wastewater purification, implementing local close-loops to decrease the overall F&B water intensity
Polypyrrole grafting onto the surface of pyrrole-modified silica nanoparticles prepared by one-step synthesis
No full textThe grafting of polypyrrole onto the surface of modified silica nanoparticles has been investigated. These silica nanoparticles were modified with pyrrole moieties prepared by the well-known Stober method in one-step starting from TEOS and a pyrrole-bearing trialkoxysilane compound. The effects of various reaction conditions, including reaction time, solvent, and molar ratio of water to alkoxy groups, have been investigated in order to obtain pyrrole-modified silica nanoparticles with the optimal coreshell structure and the smallest possible particle size. The grafting was carried out in aqueous FeCl3 solution containing the modified silica nanoparticles, with pyrrole monomers already adsorbed on the surface of the particles by soaking. Several analytical tools have been employed to characterize the particles and to assess the degree of grafting, namely TEM, SEM, TGA, FTIR, and XPS. The final polypyrrole-grafted silica nanoparticles obtained had a mean diameter of about 220 nm and 50 wt.% of grafted polypyrrole with respect to the total weight of polypyrrole formed around the surface of the cores
Kinetic Aspects of SSP of polyesters, Chapt. 3 in Solid-State Polymerization, D. Papaspyrides and S. VouyioukaEd., 2009 –
No full textThe book deals with the solid state polymerizazion of various polimeres and the chapter written by the italian authors deals in particular with the kinetic aspects of the solid state polymerization of polyesters
Data-driven prognostics: From an offline and supervised analysis to an innovative, online and unsupervised methodology
No full textAssembly line balancing with equipment requirement and parallel workers: an heuristic algorithm
No full textPurpose
Balancing assembly line means to assign assembly tasks to several stations, respecting precedence constraints so as to complete the final product with a minimum expense of resources and costs.
Aim of this paper is to suggest an heuristic algorithm to solve the balancing problem considering three important real aspects.
First, each task, or elementary assembly operation, requires specific equipments that differ from task to task involving cost and space requirements. Second, large products (e.g. cars, automatic machines or white goods), can be handled by more than one worker contemporarily processing different tasks in the same station (parallel workers). And third, parallel workers operating in the same station, can generate space or handling conflicts, considering task assembly position.
Design/methodology/approach
An heuristic algorithm is presented to design assembly lines considering a set of configuration parameters: task ordering priority rule, maximum number of parallel workers per station, maximum worker idle time allowed and maximum number of equipments per worker: varying the value of each parameter is possible to determine different assembly line configurations. A Visual Basic application is developed to evaluate such configurations with respect to four significant key performance indexes: equipment requirements, employed workers, workers saturation, number of assembly stations. The best solution can be chosen considering both plant priorities and total costs.
Originality/value
The literature proposes several models that deal with the assembly line balancing problem, nevertheless few of them investigate real world systems. This paper proposes a balancing heuristic algorithm considering the distinctive features of real assembly lines, e.g. equipment requirement. This significant characteristic is usually ignored by the literature, neglecting the equipment duplication.
Practitioners and plant managers can benefit from this algorithm exploiting its distinctive feature: the generation of several assembly line configurations. The different solutions can be compared using the key performance indexes assessed by the algorithm. The analyst can select the final configuration considering most relevant assembly line features with respect to the specific plant conditions
Motion analysis system for the ergonomic assessment of manufacturing and assembly manual activities
No full textThe environment of manufacturing and assembly manual activities radically evolved in the last decades. First, the western world workforce is alarmingly aging. In the last 15 years the percentage of European employees older than 50 years rose from 21.6% to 30.4%. Furthermore, the latest developments in legislations (EU Machinery directive, 2006/42/EC, 89/391/EEC, Occupational Safety and Health act) force the companies to assess, monitor and safeguard the health of their operators. Finally, an increasing pressure from the civil society and the stakeholders pretends safe working conditions in manufacturing and assembly processes. This paper tackles these issues proposing an original Motion Analysis System (MAS) for the ergonomic assessment of human operators involved in industrial processes. This research exploits different motion capture (MOCAP) technologies, e.g. optical, inertial and miscellaneous, to register the static postures and the dynamic movements of an operator during manufacturing or assembly activities. The information provided by the MOCAP technologies about the evolution over time of the position and orientation of the skeleton segments are processed by the MAS. This system calculates for each monitored frame the angle values of all the relevant joints of the human body accurately reproducing the operator movements. Furthermore, the MAS assesses the risk of musculoskeletal disorders of the performed manufacturing and assembly activities with the automatic evaluation of three ergonomic indices considering the features of the products and tools which the operator pick and handle. Along with the calculation of REBA and OWAS indices, an original one is developed and proposed based on the ISO 11226:2000 norm. The MAS is tested and validated with the industrial case study of a gearbox assembly process comparing the novel ergonomic index with the traditional ones. The results suggest that the proposed index accurately evaluates the ergonomic risk of specific assembly tasks compared to the classical approaches
Solvent and substrate contributions to the formation of Breath Figures Patterns in Polystyrene Films
No full textThe generation of ordered porous polymer structures by the breath figures (BFs) method has long been described as a complex phenomenon, in which several parameters combine in a fairly unknown way. Kind of polymer and solvent, degree of humidity and additives are just a few examples of the several parameters that have been described as playing a role in the generation of BFs. This work reports a detailed investigation over the role played by the solvent in the process of BFs generation from polystyrene (PS) solutions spread over different substrates, and discuss the geometrical aspects of the pores by a quantitative point of view by using a purposely developed software for image analysis. Results show that thermodynamic affinity between polymer and solvent is the key parameter for BFs formation, along with other solvent characteristics such as water miscibility, boiling point and enthalpy. According to our findings, the role played by the substrate is strictly related to the type of solvent used in the generation of BFs
Haematic pH sensor for extracorporeal circulation
No full textThe design and realization of an optical sensor for measuring haematic pH during extracorporeal circulation is presented. It consists of a chemical sensing element in contact with the blood, an interrogation optical head to externally probe the sensing element and the front-end electronics to acquire and process the information of interest. The fluorescein O-methacrylate 97% is used as the indicator. The developed system has been tested in-vitro and on an in-vivo animal model. It showed a linear behavior in the haematic range of interest with a mean error lower than 0.01 units of pH
Construction and evaluation of a disposable pH sensor based on a large core plastic optical fiber
No full textThe fabrication and characterization of a disposable optical fiber sensor for the detection of pH in the range 5-8 are described. The sensing element is a drop of sol-gel hybrid material containing phenol red and deposited onto the tip of a large core plastic optical fiber. This fiber is also exploited for the optical interrogation. This probe can be used as a disposable part of a measuring system. The dynamic range and temporal response of the sensor are here investigated
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