Thesis (M.S.)--Carnegie-Mellon University, 1981. / Includes bibliographical references (p. 44).

Global pressure to reduce greenhouse gas (GHG) emissions, energy security concerns and increasing demand for liquid fuels incentivize the search for more sustainable and secure alternative methods for producing liquid fuels with improved efficiency and reduced environmental impacts. One of the economically attractive examples of these alternate methods is the gas-to-liquid process, however, its environmental impacts are worse than traditional petroleum refining. Carbon capture and sequestration is an option to reduce greenhouse gas emissions of processes, but it decreases the efficiency of the process and often results in economic infeasibility. Instead, integrating different processes and feedstocks was demonstrated to improve the efficiency, economic and environmental performance of the processes. The focus of this thesis is to design and simulate a novel integrated biomass, gas, nuclear to liquids (BGNTL) process with negative greenhouse gas emissions. In this process, nuclear heat from a high temperature gas-cooled reactor (HTGR) is used as the heat source for a steam methane reforming (SMR) process. The integrated HTGR and SMR process requires detailed analysis and modeling to address key challenges on safety, operability, economic and environmental impacts of the integrated process. To this end, a rigorous first principle based mathematical model was developed in gPROMS modeling environment for the integrated HTGR/SMR process. The results for a large scale design of this system indicate that hydrogen rich syngas with H2/CO ratio in the range of 6.3 can be achieved. To meet the desired H2/CO ratio (around 2) required for the downstream fuel synthesis processes, the HTGR/SMR derived syngas can be blended with a hydrogen lean syngas from biomass gasification. In this thesis, the large scale design of the BGNTL process to synthesize gasoline, diesel and dimethyl ether (DME) is investigated. The results from the gPROMS model of the integrated HTGR/SMR system are used for simulating the BGNTL process in Aspen Plus. The performance of the BGNTL process was compared with a biomass, gas to liquids (BGTL) process. The efficiency, economics, and environmental impact analyses show that the BGNTL process to produce DME is the most efficient, economic and environmentally friendly process among all the considered designs. The results demonstrate that process integration exploits certain synergies that leads to significantly higher carbon and energy efficiencies and lower greenhouse gas emissions. In addition, it was found that all the studied designs yield a net negative greenhouse gas emissions when carbon capture and storage technology is implemented. As another sustainable alternative to meet the required H2/CO ratio of the syngas when biomass resources are not available, it is proposed to apply the nuclear heat to the mixed reforming of methane. This represents using steam and waste CO2 to reform methane into valuable syngas. The developed model for the integrated HTGR/SMR system is extended to the mixed reforming of methane (MRM) process and it was demonstrated that integrated HTGR/MRM process can be a promising option to achieve certain desired H2/CO ratios for the downstream energy conversion processes. / Thesis / Doctor of Philosophy (PhD)

Even though computer simulation of environmental factors and manufacturing technologies have experienced a fast development, architectural workflows that can take advantage of the possibilities created by these developments have been left behind and architectural design processes have not evolved at the same rate. This research presents design to fabrication workflows that explore data driven design to improve performance of facades, implementing for this purpose computational tools to handle environmental data complexity and proposes robotic fabrication technologies to facilitate façade components fabrication. During this research three design experiments were conducted that tested variations on the design to fabrication workflow, approaching the flow of information in top-down and bottom-up processes. Independent variables such as material, environmental conditions and structural behavior, are the framework in which workflow instances are generated based on dependent variables such as geometry, orientation and assembly logic. This research demonstrates the feasibility of a robotic based fabrication method informed by a multi-variable computational framework plus a simulation evaluator integrated into a design to fabrication workflow and put forward the discussion of a fully automated scenario. / Master of Science

Reactive ion etching has been used to obtain anisotropic silicon trenches with small sidewall angles. This work demonstrates that the sidewall angle can be controlled by the wafer temperature and there exists an Arrhenius-type relationship among isotropic polymer deposition rate, thickness of polymer, and sidewall angle.

Simulation allows the portrayal of unique environmental design concepts in order to predict the outcome prior to construction. Three (3) simulations--drawings, model and movie--were tested for their effectiveness in communicating future environmental behavior. Communication effectiveness was measured by the ability of simulation viewers to accurately predict their behavior in a built space. A comparison of, responses of on-site subjects to predicted behavioral responses of simulation viewers, found simulation viewers were accurate in their predictions in excess of sixty percent (60%). This indicated that simulations were fairly effective. An individual analysis of the three (3) groups of viewers found movie viewers having the highest rate of accurate predictions, and those viewing drawings the lowest. This general trend was consistent with other work.Testing was completed with design-oriented and non-design-oriented viewers. A significant difference in response between these two (2) groups occurred in seven (7) of the thirty-eight (38) questions. Design-oriented viewers were generally more accurate in their prediction abilities. / Department of Landscape Architecture

Rapid depletion of fossil fuel stock with a simultaneous rise in greenhouse gas emissions has led to an increase in the need for alternative energy. Cellulose based biofuels, especially bioethanol is a form of alternative energy that has the potential to replace petrol. The first step in cellulosic bioethanol production is the release of fermentable sugars via pre-treatment. Conventionally, physico-chemical and biological pre-treatment methods are energy intensive, environmentally unfavourable and expensive. This study, however reports on the use of a less energy consuming, cheap and environmental friendly alternative; photocatalysis, to produce fermentable sugars from cellulose. To achieve this, a range of photocatalysts were first screened based on their OH radical production rates using coumarin as a probe. TiO2 P25 was the photocatalyst that was found to have the highest OH radical production rate of 35.6 μM/hr, followed by Pt-C3N4 (0.88 μM/hr) and WO3 (0.28 μM/hr). LaCr-SrTiO3, Cr-SrTiO3 and yellow TiO2 did not produce any OH radicals due to their unsuitable electronic structure. P25 was further used for photocatalytic fermentable sugar production from cellulose. Photocatalytic cellulose I breakdown produced 0.04 % fermentable sugars whereas, with cellulose II feedstock the yield increased to 0.2 %. To further improve the yield, membrane bags were deployed which improved the sugar yields to 0.43 % and 0.71 % respectively from cellulose and cellulose II feedstocks. Photonic efficiencies followed the same trends as the sugar yields. Engineering design was further opted to enhance the sugar yields and hence a stacked frame photocatalytic reactor (SFPR) was designed. Various mixer configurations were designed and their mixing regime was determined using COMSOL Multiphysics 5.1 simulations. Amongst the mixers simulated, an 8-blade Rushton impeller was found to be the best configuration due its superior radial mixing profile and higher fluid velocity. The SFPR was then fabricated and operated with the impeller or a plus shaped magnetic bar as the mixer and the sugar yields were determined. Highest sugar yield and photonic efficiency was obtained from the cellulose II-impeller setup and was calculated to be 2.61 % and 9.45 % respectively. Respective lowest yields were obtained with cellulose I-stirrer bar setup and calculated to be 1.71 % and 5.64 %. Furthermore, the effect of H2O2 on fermentable sugar production was also tested. The cellulose II-stirrer bar configuration yielded 3.15 % fermentable sugars with the addition of 0.01 wt% H2O2 to the reaction mixture. The yield improved significantly to 14.1 % when the concentration of H2O2 was increased to 0.1 wt%.

University, Diss., 2005--Tübingen.

This thesis presents a tool design for production of embossments into the bottom part of the agricultural silo made of Dx51D material. The research analysis all technologies used for embossing, that is cutting and shallow drawing. This is followed by a chapter on simulation. The tool design itself is described. Its principle is based on tools for punching machines. The upper half of the tool is composed of a weldment to be clamped into pressing machine, into which are mounted functional parts in the form of inserts. The lower tool consists of several bolted plates, punches and a holding plate, which is located on the springs. In order to achieve correct design, necessary calculations were carried out and it was all confirmed by simulation in ANSYS. The two tool halfs are guided by pins attached at the edges of the lower tool. The technical - economical evaluation compares the work of the proposed tool with other possibilities of embossing.

This thesis presents an investigation of braking system characteristics, brake system performance and brake system component design parameters that influence brake pedal force / displacement characteristics as ‘felt’ by the driver in a passenger car. It includes detailed studies of individual brake system component design parameters, operation, and the linear and nonlinear characteristics of internal components through experimental study and simulation modelling. The prediction of brake pedal ‘feel’ in brake system simulation has been achieved using the simulation modelling package AMESim. Each individual brake system component was modelled individually before combining them into the whole brake system in order to identify the parameters and the internal components characteristics that influence the brake pedal ‘feel’. The simulation predictions were validated by experimentally measured data and demonstrated the accuracy of simulation modelling. Axisymmetric Finite Element Analysis (using the ABAQUS software) was used to predict the behaviour of nonlinear elastomeric internal components such as the piston seal and the booster reaction disc which was then included in the AMESim simulation model. The seal model FEA highlighted the effects of master cylinder and caliper seal deformation on the brake pedal ‘feel’. The characteristics of the brake booster reaction disc were predicted by the FEA and AMESim simulation modelling and these results highlighted the importance of the nonlinear material characteristics, and their potential contribution to brake pedal ‘feel’ improvement. A full brake system simulation model was designed, prepared, and used to predict brake system performance and to design a system with better brake pedal ‘feel’. Each of the brake system component design parameters was validated to ensure that the braking system performance was accurately predicted. The critical parameter of brake booster air valve spring stiffness was identified to improve the brake ‘pedal ‘feel’. This research has contributed to the advancement of automotive engineering by providing a method for brake system engineers to design a braking system with improved pedal ‘feel’. The simulation model can be used in the future to provide an accurate prediction of brake system performance at the design stage thereby saving time and cost.

M. Arch.