QSpace Community:http://hdl.handle.net/1974/7692015-11-26T23:17:33Z2015-11-26T23:17:33ZA New Robust Scenario Approach to Supply Chain Optimization under Bounded UncertaintyChowdhury, NIAZhttp://hdl.handle.net/1974/138362015-11-22T06:26:57Z2015-11-19T05:00:00ZTitle: A New Robust Scenario Approach to Supply Chain Optimization under Bounded Uncertainty
Authors: Chowdhury, NIAZ
Abstract: Supply Chain Optimization (SCO) problem under uncertainty can be modeled as two-stage optimization problem where first-stage decisions are associated with design and development of facilities and second-stage decisions are associated with operation of the supply chain network. Recently, a robust scenario approach combing the traditional scenario or robust approach has been developed to better address uncertainties in SCO problems, and it can ensure solution feasibility and better expected objective value. But this approach can only address uncertainties bounded with the infinity-norm.
This thesis proposes a modified robust scenario approach, which can be used to address uncertainty region bounded with the p-norm in SCO. In this case, after the normalization of the uncertainty region, the smallest box uncertainty region, that covers the normalized uncertainty region, can be partitioned into a number of box uncertainty subregions. Following some screening criteria, two subsets of the subregions that over-estimates and under-estimates the original uncertainty region can be selected. When the number of scenarios increases, the optimal objective values of the two robust scenario formulations converge to a constant, which is a good estimate of the true optimal value. This new robust scenario approach is then extended for any bounded uncertainty regions, in the context of robust optimization.
In many industrial problem, the historical realizations of uncertain parameters are known. This thesis gives a preliminary discussion on a data driven robust scenario approach, where the available data are normalized and a reference box that covers the data with a certain confidence is constructed. Then, the reference box is partitioned into box-shaped uncertainty subregions.
The benefits of the proposed robust scenario approach are demonstrated through some simple examples as well as an industrial SCO problem. The approach requires the solution of large-scale optimization problems when the number of scenarios is large, and these large-scale problems have a decomposable structure that can be exploited for efficient solution via decomposition-based optimization. A computational study demonstrates that, when the large-scale optimization problem is a second-order cone programming problem, generalized Benders decomposition is much faster than a state-of-the-art optimization solver.
Description: Thesis (Master, Chemical Engineering) -- Queen's University, 2015-11-19 16:46:06.1482015-11-19T05:00:00ZReflections on InflectionsSaengow, ChaimongkolGiacomin, A. JeffreyGilbert, Peter H.Kolitawong, Chanyuthttp://hdl.handle.net/1974/138312015-11-11T16:14:24Z2015-11-11T05:00:00ZTitle: Reflections on Inflections
Authors: Saengow, Chaimongkol; Giacomin, A. Jeffrey; Gilbert, Peter H.; Kolitawong, Chanyut
Abstract: In plastics processing, the single most important rheological property is the steady shear viscosity curve: the logarithm of the steady shear viscosity versus the logarithm of the shear rate. This curve governs the volumetric flowrate through any straight channel flow, and thus governs the production rate of extruded plastics. If the shear rate is made dimensionless with a characteristic
time for the fluid (called the Weissenberg number, Wi ), then we can readily
identify the end of the Newtonian plateau of a viscosity curve with the value
Wi ≈ 1 . Of far greater importance, however, is the slope at the point where the
viscosity curve inflects,
(n −1) , where n is called the shear power-law index. This
paper explores the physics of this point and related inflections, in the first and
second normal stress coefficients. We also discuss the first and second inflection
pairing times, λ ′B and λ ′′ B . First, we examine the generalized Newtonian fluid
(Carreau model). Then, we analyze the more versatile model, the corotational Oldroyd 8-constant model, which reduces to many simpler models, for instance, the corotational Maxwell and Jeffreys models. We also include worked examples to illustrate the procedure for calculating inflection points and power-law coefficients for all three viscometric functions, η (γ! ), Ψ1 (γ! ) and Ψ2 (γ! ).2015-11-11T05:00:00ZIndirect Co-culture of Human Adipose-Derived Stem Cells and Nucleus Pulposus Cells for Intervertebral Disc Regeneration Using Peptide-Conjugated HydrogelsGong, MINGhttp://hdl.handle.net/1974/138262015-11-06T20:30:39Z2015-11-06T05:00:00ZTitle: Indirect Co-culture of Human Adipose-Derived Stem Cells and Nucleus Pulposus Cells for Intervertebral Disc Regeneration Using Peptide-Conjugated Hydrogels
Authors: Gong, MING
Abstract: Intervertebral disc degeneration (IVDD) is a main cause of chronic low back pain, which results in significant economic loss to society and compromised life quality of patients. Traditional treatments of IVDD include surgical procedures, such as discectomy, and spinal fusion. However, these methods cannot preserve the biological or biomechanical functions of the intervertebral disc (IVD). Moreover, they decrease the mobility of the associated spinal motion segment and increase the load and stress on contiguous discs. Currently, artificial IVD replacements have gained interest. Although these implants are capable of preserving disc motion and disc height, they are unable to sustain compressive forces applied on the IVD due to their lack of elasticity. Therefore, there is a great need for an alternative therapeutic strategy for the treatment of IVDD. For mild or early stages of IVDD, regeneration by injecting pre-differentiated adipose-derived stem cells (ASCs) into the nucleus pulposus (NP) has been considered. This study aimed to investigate whether NP cells could direct human adipose-derived stem cells (hASCs) to differentiate into an NP cell phenotype. These cells could then serve as an alternative cell source for the treatment of intervertebral disc degeneration in the clinical setting. Interactions of ASCs and NP cells were studied via an indirect co-culture system using N-cadherin conjugated hyaluronic acid (HA) embedded within calcium alginate gels as scaffolds by evaluating the changing profiles of extracellular matrix (ECM) components, including glycosaminoglycans (GAGs) and type II collagen. NP cells showed the potential ability to induce hASC differentiation in terms of enhanced ECM production, such as collagen and GAG in an indirect co-culture system.
Description: Thesis (Master, Chemical Engineering) -- Queen's University, 2015-11-06 15:15:01.3252015-11-06T05:00:00ZAssessing the biocompatibility of oligomers and amine-functionalized polymers for use in two-phase partitioning bioreactorsHarris, JESSEhttp://hdl.handle.net/1974/138152015-10-29T18:37:38Z2015-10-29T04:00:00ZTitle: Assessing the biocompatibility of oligomers and amine-functionalized polymers for use in two-phase partitioning bioreactors
Authors: Harris, JESSE
Abstract: Two-phase partitioning bioreactors (TPPBs) are a bioprocessing tool that limits inhibition of cell growth by toxic compounds in bioreactors by utilizing an immiscible secondary phase to sequester compounds that inhibit microbial cell growth. Early TPPBs used organic solvents as the sequestering phase despite challenges identifying solvents that were inexpensive and biocompatible, although recent efforts have utilized polymers as the sequestering phase in TPPBs. Research on the selection of polymers for use as the sequestering phase in TPPBs has focused on predicting solute uptake by first principles in order to maximize the partitioning coefficient of a target solute. Some research has shown that low molecular weight (MW) polymers have improved partitioning coefficients, although their biocompatibility is in need of further study; this thesis investigates the effect of polymer MW on microbial biocompatibility. Trends in biocompatibility were assessed for polypropylene glycol to Saccharomyces cerevisiae and Pseudomonas putida. Given that log P has been used as an important physiochemical property for predicting biocompatibility, with higher log P values associated with improved biocompatibility, experiments were performed to determine the log P of polymers. Polymers were also water-washed to shift the log P upwards by removing low MW polymer chains. Average log P determination experiments showed that as the polymer MW increased, the measured log P also increased. Biocompatibility, as measured by the change in optical density of the cultures after 24 hours of exposure to the polymers, also improved with increasing MW and log P, and that polypropylene glycols possessing MWs of 1000 and higher were all found to be biocompatible. It was also shown that water-washing noticeably improved biocompatibility by removing low MW polymer from samples. Initial research was also undertaken to examine the use of amine-functionalized reactive polymers for extracting organic acids in TPPB in terms of their efficacy and their biocompatibility. An amine functionalized polyacrylate was synthesized which was stable under acidic conditions, and did not inhibit cell growth over 24 hour exposure. It was also shown to extract 60-85% of organic acids from aqueous solution over 2 hours with polymer concentrations of 10 g/L, and acid concentrations of 2.5 g/L.
Description: Thesis (Master, Chemical Engineering) -- Queen's University, 2015-10-29 14:13:13.4372015-10-29T04:00:00Z