• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 16
  • 16
  • 4
  • 4
  • 2
  • 1
  • 1
  • Tagged with
  • 54
  • 54
  • 12
  • 8
  • 8
  • 8
  • 8
  • 7
  • 6
  • 6
  • 5
  • 5
  • 4
  • 4
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A new approach to modelling process and building energy flows in manufacturing industry

Oates, Michael January 2013 (has links)
Global conservation of energy and material has become a key topic among governments, businesses, local societies and academics. A point made by many on the subject of energy begin by stating the importance of conserving the earth’s natural resources, and the need to reduce greenhouse gas emissions in a bid to reduce global warming. This research is no exception, concentrating on an energy and material intensive sector of the global economy; manufacturing industry. This research formulates a methodology for modelling energy flows between a factory building, its manufacturing process systems and the materials used. The need for such an approach arises from the gap in knowledge between the understanding of energy consumed by factory buildings and process systems in manufacturing industry. Factory buildings are purpose built environments that house manufacturing processes, manufacturing plant, materials and occupants. Modern production lines are designed to optimise the flow of materials throughout a factory; to and from storage, production, assembly and distribution. Manufacturing production systems dictate the shape and size of factory buildings. This can lead to a high proportion of the overall energy consumption to be attributed to building services. The coupling of factory energy flows assists energy managers at both the facility and process levels, in order to identify efficiency improvements and reduce energy use and associated carbon emissions. A better understanding of the overall energy balance of a factory environment will allow energy to be used in a more sustainable manner. Simulation tools are widely used in the disciplines of building design and manufacturing systems engineering. Traditional building energy flow paths are well documented and are handled within dynamic building modelling tools. Globally, manufacturing activities cover a wide field of industrial practice and use a range of simulation software packages such as flow diagramming packages, computational fluid dynamics, discrete event tools, direct coding, optimisation tools etc. The increasing use of simulation makes it difficult for a manufacturing systems analyst to choose a suitable approach for energy modelling. An important aspect of the methodology described in this thesis is the coupling of energy flows that occur internally (within a factory boundary) and externally (outside a factory boundary e.g. weather) in relation to time and location within and around a factory environment. Building modelling tools provide a structured and well defined approach to monitoring energy flows within traditional built environments. The methodology extends the framework of an existing building modelling tool; the International Building Physics Toolbox (IBPT), to include the simulation of manufacturing process systems and material flow within a factory. There is a wide range of manufacturing processes used in industry so the scope of this research is reduced to thermal and electrical processes only. A thermal process is considered to be an extension of a thermal zone (such as a room), as defined in building modelling tools. Two thermal processes are considered; processes that act on a volume of gas (i.e. air) and those that act on a volume of liquid. Material flow is represented in the model by time series. The lumped capacitance method is used to approximate the change in surface temperature of a material in relation to its stored energy, long wave radiation between the material and its surroundings, and convective heat transfer. To validate the use of the IBPT algorithms to model building physics, the results derived by using the IBPT are compared with those derived by using an industry standard trusted building modelling tool called ‘Integrated Environmental Solutions Virtual Environment’ (IES VE), in comparable areas of building modelling. Three industrial case studies have been analysed, and these represent real scenarios from the automotive and aerospace manufacturing industry sectors. Two out of the three case studies include the simulation of the building (fabric and heating system), material flow and manufacturing process systems (air and liquid based). The third case study focuses on process modelling only, with future scope to include the factory building. Data obtained from industrial practice is used to validate the results of energy modelling using the proposed method. Results from the case studies demonstrate the capabilities of the proposed method of modelling factory energy flows and associated energy consumption at both facility and process level. Opportunities to reduce energy use and associated carbon emissions are also identified. The methodology does have some limitations in the form of the number of manufacturing process types represented and the complex nature of modelling real energy flows that occur within factory buildings. However the findings of the research show that an integrated approach to modelling factory energy flows through development of a building modelling framework has real benefits for manufacturing industry. These benefits are very unlikely to be realised by modelling processes and buildings separately, as is the way current modelling methods are carried out by the separate discipline areas of building design and manufacturing systems. Factory energy managers and future factory designs are example areas in which the presented integrated tool would be most beneficial used. Future research within this area could include an extension of the framework to model moisture transfer, the inclusion of further types of manufacturing process systems and further investigation into the coupling of time-driven and event-driven hybrid modelling techniques to simulate material flow both in terms of locality and thermal behaviour.
2

Simulátor mobilních robotů v prostředí Matlab/Simulink / Simulator of mobile robots in Matlab/Simulink

Havlát, Petr January 2009 (has links)
The main goal is the programming scene MATLAB/Simulink creation of graphic user interface (GUI), which allows the simulation of mobile robots movement. The work covers two types of these robots – first one is the robot with differentially controlled truck and second one auto robot (car-like robot). As a part of this draft GUI, there are also possibilities of showing all trajectory or only actual position, selection of step after which the robot can delineate and possibility of layout between the positions by using the button back and forwards.
3

A Study On Conceptual Modeling In Simulation Systems: An Extended Methodology For Kama

Aysolmaz Bozlu, Banu E. 01 December 2007 (has links) (PDF)
Conceptual modeling is considered to be essential in simulation development activities. However, there are only a few research studies on how to develop conceptual models. One of the important and comprehensive approaches is the methodology developed under the leadership of METU Modeling and Simulation Center (MODSIMMER) for Turkish Armed Forces. The project suggests a methodology to develop mission space conceptual models (GUKAM), and provides a Conceptual Model Development Tool for C4ISR M&amp / S activities, which is named as KAMA-C4ISRMOS. KAMA methodology is developed to utilize conceptual models in requirements collection and analysis activities. Two improvement opportunities observed in KAMA approach are that, there are no methodologies defined to develop simulation space conceptual models / and although most approaches emphasize the importance of conceptual model to be used in design activities, no explanations are provided on how to do it. This thesis aims to suggest an extended KAMA methodology that, besides original KAMA properties, provides a method to develop simulation space conceptual model, and provides a guide to use conceptual model to develop design. To evaluate the suggested methodology, a case study is conducted on a synthetic environment project. In this way, implementation of the methodology on another simulation domain is depicted. Developed mission space and simulation space conceptual models and design artifacts are evaluated, and the effects of conceptual models on simulation development life cycle are discussed.
4

Advanced modelling and visualisation of liquid-liquid separations of complex sample components, with variable phase distribution and mode of operation

De Folter, Jozefus Johannes Martinus January 2013 (has links)
This research is about liquid-liquid chromatography modelling. While the main focus was on liquid-liquid chromatography, where the stationary and mobile phases are both liquid, theory of different types of chromatography, including the currently most used techniques, were considered as well. The main goal of this research was to develop a versatile liquid-liquid separation model, able to model all potential operating scenarios and modes of operation. A second goal was to create effective and usable interfaces to such a model, implying primarily information visualisation, and secondarily educative visualisation. The first model developed was a model based on Counter-Current Distribution. Next a new more elemental model was developed, the probabilistic model, which better models continuous liquid-liquid chromatography techniques. Finally, a more traditional model was developed using transport theory. These models were used and compared to experimental data taken from literature. The models were demonstrated to model all main liquid-liquid chromatography techniques, incorporated the different modes of operation, and were able to accurately model many sample components and complex sample injections. A model interface was developed, permitting functional and effective model configuration, exploration and analysis using visualisation and interactivity. Different versions of the interface were then evaluated using questionnaires, group interviews and Insight Evaluation. The visualisation and interactivity enhancements have proven to contribute understanding and insight of the underlying chromatography process. This also proved the value of the Insight Evaluation method, providing valuable qualitative evaluation results desired for this model interface evaluation. A prototype of a new graphical user interface developed, and showed great potential for combining model parameter input and exploring the liquid-liquid chromatography processes. Additionally, a new visualisation method was developed that can accurately visualise different modes of operation. This was used to create animations, which were also evaluated. The results of this evaluation show the new visualisation helps understanding of the liquid-liquid chromatography process amongst CCC novices. The model software will be a valuable tool for industry for predicting, evaluating and validating experimental separations and production processes. While effective models already existed, the use of interactive visualisation permits users to explore the relationship between parameters and performances in a simpler yet more powerful way. It will also be a valuable tool for academia for teaching & training, both staff and students, on how to use the technology. Prior to this work no such tool existed or existing tools were limited in their accessibility and educational value.
5

Simulační model populačního vývoje / The simulation model of the population growth

Urbanová, Kateřina January 2008 (has links)
In this thesis, called a simulation model of population growth, there was created the simulation model of a population growth in the Czech Republic to the year 2052. First there was constructed the projection through the component method used in demography. Deterministic values obtained by this method are then used in the simulation analysis. In the simulation analysis there was conducted an experiment with three variables which influence the population growth (the fertility, life expectancy/the coefficient of the decline of the probability of the death/ and the migration balance). With the support of the Crystal Ball, supporting program for Excel, which provides the possibility of the simulations, there was determined the stochastic character of the three variables. There are created the low, medium and high variant of the projections, as well as three other possible variants of population growth that might occur. These variations are called economic crisis, friendly migration policy and restrictive migration policy.
6

Assessment of magnetic cooling for domestic applications

Borbolla, Ivan Montenegro January 2012 (has links)
Magnetic cooling is an emerging refrigeration technology with potential to surpass the performance of vapour compression devices. It has been successfully applied in the cryogenic temperature ranges, where magnetic cooling gas liquefiers surpass the performance of conventional liquefaction systems. Magnetic refrigeration technology is based on the magnetocaloric effect, a characteristic present in all magnetic materials and alloys. In magnetic thermodynamic cycles, magnetization of a magnetocaloric material is equivalent to the compression of a gas, while demagnetization is equivalent to expansion of a gas, with a subsequent diminution of the entropy. In this thesis, the applicability of this technology to the domestic environment is reviewed. First, the thermodynamics of magnetic refrigeration are explored. Then, a comprehensive review of magnetocaloric materials suitable for use at room temperature is presented. To ascertain the state of the art, the most relevant prototypes and their performances have been described. Concluding the documentation, a survey on the existing mathematic models has been performed, that provided the foundation to create a Matlab model of a magnetic refrigeration device. To gain greater insight on the internal working of these devices, a representative room temperature cooling device has been modelled, and used to simulate a magnetic refrigerator and room air conditioner. Its performance has been analysed and compared with that of vapour compression devices. Also, the influence of parameters such as magnetic field applied, temperature span, refrigerant fluid and different regenerator configurations has been investigated.
7

Simulace provozu klientského pracoviště zdravotní pojišťovny / Simulation of the client workplace of the health insurance company

Karbusická, Martina January 2013 (has links)
Simulation is an advanced tool to capture and simplify a complex system and it allows to track the effects of changes in it to function of the entire system. The aim of the thesis was to model the current function of the system and monitor the effects of changes by experiments with the model in order to find a new and better solution. In this thesis, the running of the client workplace of Všeobecná zdravotní pojišťovna ČR was monitored and the simulation was based on real data from May 2012. The simulation was performed using the software Simul8. The results of the base case show that the system leads to accumulation of entities and long time spent in the queue. Within experimenting with the model there were created 8 scenarios that modify some parts of the system. Firstly the results of the scenarios were compared to the base case and then they were compared with each other. The scenario that was chosen as the best, was better in most of parameters compared to the base case. The parameter with the worst value in the base case - time spent queuing for a normal counter - has improved by 62 % in the new scenario. This scenario was chosen as a new and better solution for the current system.
8

Modeling of jet vane heat-transfer characteristics and simulation of thermal response

Hatzenbuehler, Mark A. 06 1900 (has links)
Approved for public release; distribution is unlimited / The development of a dynamic computational model capable of predicting, with the requisite design certainty, the transient thermal response of jet vane thrust control systems has been undertaken. The modeling and simulation procedures utilized are based on the concept that the thermal processes associated with jet vane operation can be put into a transfer function form commonly found in the discipline of automatic controls. Well established system identification methods are employed to formulate and verify the relationships between the various gains and frequencies of the transfer function model and experimental data provided by Naval Weapons Center, China Lake. / http://archive.org/details/modelingofjetvan00hatz / Lieutenant, United States Navy
9

Examining the impacts of projected precipitation changes on sugar beet yield in Eastern England

Joseph, Stanley Ob January 2018 (has links)
Projected increasing temperatures and reduced summer precipitation in the UK raises questions about the sustainability of aspects of the agriculture industry and food security. This study investigates the potential impact of precipitation changes on sugar beet yield in Eastern England. Observations of precipitation was examined for the period 1971-2000 and the expected changes in precipitation were investigated using seven CMIP5 climate models for the historical phase (1971-2000) and RCP45 and RCP85 future scenarios (2021-2050). Three out of the seven models were found to show good agreement with observations but the MOHC ensemble mean was the closest to the observed means and was used for further precipitation analyses. Statistical analysis of the future precipitation changes were performed using the Met Office Hadley Centre (MOHC) model focused on changes between the historical phase and RCP45 and RCP85. Results showed a consistent and significant reduction in annual May-October precipitation under future scenarios. The study then investigated the impact of reduced future precipitation changes on sugar beet yield by applying controlled watering regimes informed by the CMIP5 projections to sugar beet plants in a greenhouse experiment over two seasons - the use of CMIP5 projections in this way is a first. In the first experiment carried out in 2014, a climatological watering regime (i.e. where the total seasonal rainfall for the different scenarios was applied in equal and regular watering events) was applied to the plants, which meant a 16% reduction in precipitation in the "future" category relative to a "control" category. Analysis of the yields indicated a statistically significant reduction in mean tuber wet mass: mean of 360g for the control and 319g for the future (p-value 0.03). This implies a potential yield reduction of 11% by 2050. In the second experiment carried out in 2015, a "realistic distribution" watering regime (i.e. where the total seasonal rainfall is applied in a series of watering events that reflect the analysed sizes and distribution of rainfall events in the different categories), this meant a reduction in precipitation in the months of June (-15.6%), July (-7.7%) and August (-3.7%). This resulted in statistically significant reduction in mean tuber wet mass between control (153g) and RCP85 (113g) with a p-value of 0.01. This implies a reduction of 26% in future yields under RCP85 by 2050. Results in this thesis further show how changes and variation in precipitation are intertwined with changes in soil moisture and yield of sugar beet plants. The findings will enable UK sugar beet farmers to identify potential areas of challenges in order to adapt their management practices to ensure maximum crop yield in future growing seasons. Moreover, from a global perspective, the findings here are also broadly applicable to a variety of agricultural crops in different parts of the world, where changes in yield may have important consequences to food security and food prices.
10

Estimation Of Water Alternating Gas (wag) Injection Performance Of An Offshore Field (azeri Field,azerbaijan) Using A Sector Simulation Model

Babayev, Farid Nabi 01 September 2008 (has links) (PDF)
The WAG injection project feasibility of South Flank of Central Azeri field on the basis of simulation model was studied in this thesis work. The 58 sensitivity scenarios were considered to evaluate and analyze the behavior of WAG in this field. Scenarios are based on the important WAG parameters, such as half slug size volume, cycles, WAG ratio, start time, bottomhole injection pressure etc. The Base Case is set with static and dynamic characteristic close to real field. From the scenarios calculated, the Best (Scenario 53, 9.3% incremental oil) and the Worst (Scenario 52, 3.4% incremental oil) cases were analyzed to get general view of WAG in terms of profitability in comparison to the Base Case. For more profound conviction of feasibility of the WAG project, additional cases with Simultaneous WAG injection and cases with changed permeabilities have been considered. The Best case was re-evaluated under application of Carlson&rsquo / s relative permeability hysteresis model. All results eventually were analyzed in terms of economical profitability &ndash / net present value (NPV). Economical analysis of scenarios is provided at the end of the work.

Page generated in 0.1379 seconds