A Continuum Model for Metabolic Gas Exchange in Pear Fruit

Exchange of O2 and CO2 of plants with their environment is essential for metabolic processes such as photosynthesis and respiration. In some fruits such as pears, which are typically stored under a controlled atmosphere with reduced O2 and increased CO2 levels to extend their commercial storage life, anoxia may occur, eventually leading to physiological disorders. In this manuscript we have developed a mathematical model to predict the internal gas concentrations, including permeation, diffusion, and respiration and fermentation kinetics. Pear fruit has been selected as a case study. The model has been used to perform in silico experiments to evaluate the effect of, for example, fruit size or ambient gas concentration on internal O2 and CO2 levels. The model incorporates the actual shape of the fruit and was solved using fluid dynamics software. Environmental conditions such as temperature and gas composition have a large effect on the internal distribution of oxygen and carbon dioxide in fruit. Also, the fruit size has a considerable effect on local metabolic gas concentrations; hence, depending on the size, local anaerobic conditions may result, which eventually may lead to physiological disorders. The model developed in this manuscript is to our knowledge the most comprehensive model to date to simulate gas exchange in plant tissue. It can be used to evaluate the effect of environmental stresses on fruit via in silico experiments and may lead to commercial applications involving long-term storage of fruit under controlled atmospheres

Solvent Optimization Studies for a New EURO-GANEX Process with 2,2’-Oxybis( N,N -di- n -decylpropanamide) (mTDDGA) and Its Radiolysis Products

The diglycolamide 2,2’-oxybis(N,N-di-n-decylpropanamide) (mTDDGA) is being studied as an extractant for actinides and lanthanides in the European Grouped Actinide Extraction (EURO-GANEX) process. The aim is the development of a more simplified process using a single extractant instead of a mixture of extractants used in the current EURO-GANEX process. This work presents solvent optimization studies of mTDDGA, with regards to the extraction characteristics of the different diastereomers of mTDGA and of mixed diastereomer solutions. Also radiolysis behavior has been studied by irradiation of solvent extraction systems in a gamma irradiation facility using $^{60}$Co. The availability of irradiated organic solutions made it possible to gain valuable insights into the plutonium loading capacity after gamma-irradiation of the solvent up to 445 kGy and to quantify degradation compounds. Solvent extraction characteristic of the major degradation compounds themselves were determined. Like other methylated diglycolamides, we found a remarkable difference in extraction of up to two orders of magnitude between the two diastereomers. High plutonium loading (36 g L$^{−1}$) is feasible using this single extractant, even after absorbing a dose of 445 kGy. This remarkable observation is possibly promoted by the presence of the main degradation compound which extracts plutonium verywell

Cost Estimation and Integrated Production Planning for Sheet Metal Laser Cutting and Air Bending (Kostenraming en geïntegreerde productieplanning voor plaatwerk)

Door het competitieve karakter van de plaatbewerkingssector zijn de bedrijven continu op zoek naar nieuwe/betere methodologieën om kwalitatieve producten af te leveren met een korte doorlooptijd. Het onderzoek naar mogelijke verbeteringen focust niet uitsluitend op de productieprocessen maar ook op de aanverwante activiteiten zoals ontwerp, planning, enz. Deze dissertatie behandelt de ontwikkeling van methodologieën ter automatisatie en optimalisatie van een aantal belangrijke deeltaken van plaatbewerking. Wanneer een potentiële klant een prijsaanvraag indient, verwacht hij quasi onmiddellijk een respons. Indien de klant te lang moet wachten op een prijsofferte dreigt het order verloren te gaan naar de concurrentie. Aangezien kostcalculatiemethodes gebaseerd op het procesplan te veel tijd vragen, wordt een specifieke kostenramingsmethode ontwikkeld. Zowel regressie-analyse als artificiële neurale netwerken worden onderzocht op hun toepasbaarheid voor kostenraming voor de plaatbewerkingscel. Een aantal nauwkeurig geselecteerde variabelen wordt geteld van de geometrische beschrijving van het werkstuk en gecombineerd in een kostrelatie die toelaat om zeer snel en voldoende nauwkeurig de kost van een plaatwerkstuk te ramen. Nadat de orders geplaatst zijn, schiet de planningsafdeling in actie. Wetenschappelijk onderzoek focust voornamelijk op de verschillende aspecten van procesplanning. Beslissingen aangaande productieplanning zijn gebaseerd op de ervaring van de operatoren. Bij het opstellen van een productieplan merkt men daarenboven dat de individuele optimalisatie van de afzonderlijke processen er voor zorgt dat het finale productieplan suboptimaal is. Een specifieke planningsmethodologie wordt daarom ontwikkeld. Een IP-formulering laat toe om het probleem op een geïntegreerde wijze te benaderen. Dit resulteert in een productieplan met een gereduceerde maximale beëindigingstijd (makespan) en een gereduceerde omsteltijd vergeleken met de huidige manier van plannen. Om verscheidene praktische problemen aan te pakken, wordt het wiskundige model uitgebreid zodanig dat ook spoedorders, zuiver laserwerk, zuiver plooiwerk, meerdere machines, etc. geïncorporeerd kunnen worden. Specifieke VNS oplossingsheuristieken worden ontwikkeld opdat het productieplan met beperkte rekenkracht gegenereerd kan worden.Voorwoord Abstract Beknopte Samenvatting Nederlandse samenvatting Contents List of acronyms 1 Introduction 1.1 History of sheet metal working 1.2 Sheet metal processes 1.2.1 Cutting stage 1.2.2 Bending stage 1.3 Cost estimation for the sheet metal shop 1.3.1 Cost accounting 1.3.2 State of the art 1.3.3 Cost estimation: challenge 1.4 Planning for the sheet metal shop 1.4.1 State of the art 1.4.2 Production planning: challenge 1.5 Research objectives 1.5.1 Development of a dedicated cost estimation tool 1.5.2 Development of an integrated production planning model 1.5.3 Planning special cases 1.5.4 Inclusion of multiple machines 1.6 Scope of the research 1.7 Research overview 2 Production cost estimation 2.1 Introduction 2.2 Analogical cost estimation techniques 2.2.1 Regression analysis 2.2.2 Artificial neural networks 2.3 Production cost estimation for sheet metal working 2.3.1 Punching and laser cutting: 2D processes 2.3.2 Bending: 3D process 2.3.3 Case study 2.3.4 Results for both methods 2.4 Practical implementation 2.4.1 Estimating the production cost 2.4.2 Updating the module 2.4.3 Remarks 2.5 Conclusions 3 Integrated production planning for the single machine case 3.1 Introduction 3.2 IP formulation of the planning problem 3.2.1 Integer programming and branch and bound 3.2.2 Integrated approach 3.3 Data requirements and instances for testing 3.3.1 Workpiece data and sheet data 3.3.2 Laser cutting stage 3.3.3 Bending stage 3.3.4 Remarks 3.3.5 Test cases 3.4 Computational results for Appr1 3.4.1 Solving the example test case 3.4.2 Results for the different test cases 3.5 Conclusions 4 Reformulating the integrated planning problem 4.1 Introduction 4.2 The VRP: literature overview 4.3 Reformulation of the problem 4.3.1 Assigning a single production layout to the workpieces 4.3.2 IP formulation of the planning problem 4.4 Computational results for Appr2 4.4.1 Solving the example test case 4.4.2 Results for the different test cases 4.5 Heuristics for the problem 4.5.1 Neighborhood search 4.5.2 Computational results 4.6 Expanding the proposed CVRP approach 4.6.1 Individual due-dates and rush orders 4.6.2 Inclusion of pure laser-cut workpieces 4.6.3 Inclusion of pure bent workpieces 4.7 Conclusions 5 Integrated planning for multiple machines 5.1 Introduction 5.2 Flow shops with multiple machines at one or more stages 5.2.1 Literature overview 5.2.2 Current planning practices for multiple machines 5.3 Planning multiple-machine instances 5.3.1 General approach 5.3.2 Test cases and reference approach 5.4 Integrated planning for SLRP instances 5.4.1 IP formulation 5.4.2 Solving the example test case 5.4.3 Computational results 5.4.4 Heuristic procedure for SLRP instances 5.5 Integrated planning for SLUP instances 5.5.1 Computational results 5.6 Integrated planning for ULUP instances 5.6.1 Computational results 5.6.2 VNS procedure for ULUP 5.7 Predetermined routings: machine eligibility 5.8 Conclusions 6 Conclusions and recommendations 6.1 Conclusions 6.2 Recommendations Publication list Bibliographystatus: publishe

Synthese en karakterisatie van MCM's

SIGLEKULeuven Campusbibliotheek Exacte Wetenschappen / UCL - Université Catholique de LouvainBEBelgiu

Brittle to ductile fracture transition in bulk Pb-free solders

The fracture toughness of bulk Sn, Sn–Cu, Sn–Ag, and Sn–Ag–Cu lead-free solders was measured as function of the temperature by means of a pendulum impact test (Charpy test). A ductile to brittle fracture transition was found, i.e., a sharp change in the fracture toughness. No transition was found for the eutectic Sn–Pb. The transition temperature of high purity Sn, Sn–0.5%Cu and Sn–0.5%Cu(Ni) alloys is around –125 °C. The Ag-containing solders show a transition at higher temperatures: in the range of –78° to –45 °C. The increase of the Ag content shifts the transition temperature towards higher values, which is related to the higher volume fraction of SnAg₃ particles in the solder volume. At fixed volume fraction, smaller particle size shifts the transition temperature towards higher values. Therefore, a careful microstructure control is needed during the solder solidification after reflow in order to decrease the low temperature brittleness hazard.status: publishe

Infield logistics planning for crop-harvesting operations

Crop-harvesting operations are typically carried out with combine harvesters. The harvested product is transferred to one or more tractors every time the combine harvester’s storage capacity is reached. The efficiency of the process can be significantly improved by computing optimal routes and interactions for the harvest vehicles in the field. Furthermore, an automated method for generating itineraries for the harvest vehicles facilitates the planning for autonomous agricultural vehicles. The infield logistics problem is formulated as an integer linear programming vehicle routing problem with additional turn penalty constraints, but, because of the high number of decision variables, it is not possible to solve cases of realistic field size. The solution time of the infield logistics problem is considerably reduced by reformulating it as a modified minimum-cost network flowproblem. This specific structure allows the exact solution of intermediate-size planning problems in a much shorter time period. The result of solving the infield logistics problem with the proposed modelling approaches is a set of itineraries (‘tours’), covering the entire field. Each ‘tour’ is characterized by the combine harvester’s start and end points and the positions where the combine harvester needs to be unloaded. The planning models minimize non-productivity (i.e. the time when a combine harvester travels in a field without harvesting). The results indicate that coordination between combine harvesters and tractors is also improved.status: publishe

Handige tool berekent je energiewinst

status: publishe