Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2008. / Includes bibliographical references (leaf 74). / Many firms worldwide have adopted the process of Sales & Operations Planning (S&OP) process where internal departments within a firm collaborate with each other to generate a demand forecast. In a collaborative demand planning process buyers and sellers collaborate with each other to generate a mutually agreed upon forecast which takes into account the needs and limitations of both buyers and sellers. In this research we concentrate on finding out the value from both statistical and qualitative forecasts. We apply standard forecasting algorithms to generate a statistical forecast. We also generate a hybrid model that is a weighted technique using both a statistical and qualitative forecast. Then we evaluate the statistical, hybrid, and qualitative collaborative forecasts using an error analysis methodology. Finally we recommend an approach for forecasting a family of items based on our analysis and results. We also recommend changes to the existing process so that our recommendations on the forecasting approach can get seamlessly integrated into the overall process. / by Ratan Jha. / M.Eng.in Logistics

Thesis (Ph. D.)--Massachusetts Institute of Technology, Engineering Systems Division, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 379-385). / Processes in manufacturing, services, and healthcare are complex socio-technical systems composed of intricately sequenced activities supported by elements drawn from multiple domains. While many of these processes offer high performance, their complexity can make their design, improvement, troubleshooting, and change difficult due to the many possible and unforeseen interactions between elements. This thesis develops a design methodology and multi-domain network model for complex process design, change management, process improvement, and troubleshooting. As part of the methodology a feasibility analysis method based on solving the minimum cost flow problem for a network of process alternatives is presented to identify feasible processes subject to stakeholder requirements and constraints including performance, flexibility, modularity, and other system properties. A model based on Multi-Domain Matrix (MDM) concepts is developed specifically for process analysis called the Multi-Domain Process Matrix model (MDPM) to enumerate and analyze the interactions between process elements such that process performance under change and troubleshooting scenarios can be improved. The graph theory basis of the MDPM model enables its analysis using a proposed set of metrics derived from communications, social, and process network literature. As a demonstration of the use of the methodology, a complex DNA sequencing based surveillance process for Methicillin resistant Staphylococcus aureus (MRSA) in the US healthcare system is designed and a prototype implemented. Rapid advances in DNA-based technologies have greatly expanded the range of processes available to the clinical microbiology laboratory, however, integrating these new processes into a comprehensive surveillance system presents significant challenges. Many of these new technologies are still in early stages of development, require multidisciplinary teams to support them, and must undergo significant optimization presenting significant barriers to their rapid adoption despite the pressing need to understand and control antibiotic resistance. Data from the prototype MRSA surveillance process show significant variation at the DNA level between patient cases, providing evidence for the urgent need for a DNA sequencing based microbial surveillance process as part of clinical microbiology efforts in the US healthcare system. However, results of applying the process design methodology and MDPM model analysis indicate significant work remains to reduce complexity, further improve key technology elements, gain acceptance, develop key organizational infrastructure, and Page 3 of 385 redesign the process to efficiently absorb the rapid technology change expected in DNA sequencing. The MDPM model is used to develop a roadmap of specific multi-domain projects addressing these issues to accelerate the deployment of a national DNA sequencing based surveillance system. / by Robert Nicol. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Biological Engineering Division, September 2006. / "July 2006." / Includes bibliographical references (leaves 123-137). / Connective tissue progenitors (CTP) can act as a pluripotent source of reparative cells during injury and therefore have great potential in regenerative medicine and tissue engineering. However, the response of CTP to most growth factors and cytokines is unknown. Many envisioned applications of CTP, such as treating large defects in bone, involve in vivo implantation of CTP attached to a scaffold, a process that creates an acute inflammatory environment that may be hostile to CTP survival. This project entails the design of a two-component polymeric implant system to aid in the healing process of bony defects by influencing cell behaviors at the implant site through the covalent modification of the implant surface with selected ligands. We investigate cellular responses of CTP on a biomaterial surface covalently modified with epidermal growth factor (EGF) and find that surface-tethered EGF (tEGF) promotes both cell spreading and survival more strongly than saturating concentrations of soluble EGF. By sustaining MEK-ERK signaling, tEGF increases the contact of CTP with an otherwise moderately adhesive synthetic polymer and confers resistance to apoptosis induced by the proinflammatory cytokine, FasL. / (cont.) We confirm that these signaling, spreading, and apoptotic responses are conserved across three sources of CTP: an hTERT-immortalized human mesenchymal stem cell (MSC) line, primary porcine bone-marrow CTP, and primary human bone-marrow-derived CTP. We conclude that tEGF may offer a protective advantage to CTP in vivo during acute inflammatory reactions to tissue engineering scaffolds. The tEGF-modified polymers described here could be used together with structural materials to construct CTP scaffolds for the treatment of hard-tissue lesions, such as large bony defects. / by Vivian H. Fan. / Ph.D.

Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2007. / "June 2007." / Includes bibliographical references (leaves 69-71). / Production planning in premium fresh produce supply chains is challenging due to the uncertainty of both supply and demand. A two-stage planning algorithm using mixed integer linear programming and Monte Carlo simulation is developed for production planning in the case of a premium branded tomato. Output from the optimization model is sequentially input into the simulation to provide management with information on expected profit and customer service levels at the grocery retail distribution center. The models are formulated to incorporate uncertainty in demand, yield, and harvest failure. The outcome of the algorithm is an annual production plan that meets minimum customer service requirements, while optimizing profit. The resulting timing, location, and quantity of acres suggested by the algorithm are evaluated against the current industry heuristic of performing deterministic calculations, based on average yield and demand, and then planting double the required acreage. The suggested two-stage planning algorithm achieves 90 percent customer service with 20 percent less planted acres and almost three times as much profit than the industry heuristic of doubling the acreage. / by Joshua Matthew Merrill. / M.Eng.in Logistics

Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2006. / Includes bibliographical references (leaves 97-98). / This research examines the impact of inventory pre-positioning on humanitarian operations. The study identifies optimal locations for warehousing non-consumable inventories required for initial deployment of aid. These facility location problems are geometric optimizations using mean annual homeless resulting from hazards (atmospheric disruptions, floods, waves, landslides, seismic disruptions, volcanoes and wildfires) as an indirect estimation of demand for infrastructure inventory. Minimization of per capita distance, or the average global distance from the nearest warehouse to a forecasted homeless person, is advanced as the objective. An array of formulations, solved using mixed-integer linear programs, predict optimal facility configurations, and corresponding per capita distances, under incremental facility constraints; thereby measuring sensitivity of mean distance to facility proliferation. The problems are devised to also gather insights into maximal covering and the effects of initial conditions. / (cont.) Moreover, demand patterns, along with correlated variables such as population and hazard frequency, offer views of regional vulnerability to natural disasters. The results also exhibit the absence of re-configuration, indicating that location decisions may not be impacted by the number of facilities planned. / by Anup Roop Akkihal. / M.Eng.in Logistics

Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 91-96). / Mobile traffic has grown substantially over the last few years; a trend which is expected to continue. The chief reasons behind this phenomenon are the availability of better handsets, faster cellular networks and the variety of content available on the internet suitable for consumption on mobile devices. The nature of the traffic is also changing from pure web browsing with latency-tolerant traffic to video, which is becoming the major class of content consumed on mobile devices. This trend, combined with the trend of decreasing prices per GB of data, which constrains the amount of money an operator can spend upgrading its network and they see increasing value in alternative solutions to address this data deluge while managing costs and maintaining customer service. A variety of solutions have been tried by operators based on enhanced charging, traffic engineering and backhaul infrastructure upgrades. Wi-Fi offload is one such promising solution as it addresses the congestion problem where it is most severe because of data consumption by users using streaming video. Cellular spectrum is a scarce and expensive resource for operators, and by allowing them to offload traffic to Wi-Fi networks in unlicensed spectrum they can free cellular spectrum for more valuable applications. Wi-Fi offload has, however, suffered from the incapability to manage seamless handovers and the required interaction of the user to select a Wi-Fi network. This made the process of attaching to a Wi-Fi network very complicated. These limitations have been addressed in recent standards and make the case for Wi-Fi offload more viable and attractive than earlier. At the same time new video optimization techniques such as H.264/SVC which allow the use of multiple streams and channel will allow content providers or distributors to use multiple networks and to scale video seamlessly according to handset capabilities and network conditions. The thesis proposes a solution, based on a set of new Wi-Fi standards and the new H.264/AVC codecs, which leverages a combination of low cost Wi-Fi and high reliability cellular networks to reduce the cost of video transmission while maintaining a comparable QOE for nomadic users. The thesis also enumerates some of the basic procedures that can be supported using the proposed architecture. This new architecture opens new opportunities for existing players in the mobile content ecosystem and adds new players to the ecosystem. The thesis identifies the needs and opportunities for each of the new player and also develops a cost model for streaming video using this solution. / by Amit Limaye. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Biological Engineering Division, February 2006. / Includes bibliographical references (leaves 181-191). / Surface-based sensors take advantage of the natural high surface-to-volume ratios in microfluidic devices, low reagent consumption and high potential for integration in more complex micro total analysis systems (microTAS or pTAS). This thesis studies the fundamental limits of on-chip integrated microfluidic sensors. More specifically, it focuses on detection methods involving surface interaction in channels with thicknesses on the order of a few microns or less. Through mass transfer analysis, we demonstrate that, for thin enough channels, sample detection is limited by the convective transport of analytes, and neither by diffusion nor reaction. The results provided extend the validity of transport models to include transport in the absence of mass transfer boundary layer. All existing analytic solutions to the Graetz problem are described and compiled. The analysis, complemented by finite element simulations, successfully predicts experimental observations made for on-chip immunoassays in micron-thick fluidic channels. Subsequently, our study of on chip detection systems is carried on with emphasis on resonating cantilever sensors. In order to interpret the output signal from these devices, we develop a dynamic cantilever model to link spatially and temporally dependent mass adsorption with resonance frequency change. / (cont.) The mass adsorption is then directly related to the sensors' operating conditions via the mass transfer models previously developed. We then develop a 2D finite-element model capable of predicting the devices response and of extracting bimolecular rate constants. Finally, since hydraulic resistance severely increases as channels get shallower, we provide a structural analysis of polymer-based microsystems. Through scaling and numerical simulations we demonstrate the effect of channel deformation on the flow conditions inside the device and vice versa. Finally, channel deformation is experimentally quantified using optical methods and compared with the models developed. Throughout this thesis, the approach to physical modeling has been to use mathematical and numerical analysis as predictive tools in the design of integrated lab-on-a-chip systems. Whenever possible, scaling and analytic solutions are developed, since they provide a direct relationship between experimental observations, geometry and the multiple dependent variables in the system, and can be readily used as design criteria by the experimentalist. / by Thomas Gervais. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Biological Engineering Division, 2008. / Includes bibliographical references (p. 224-236). / Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with diagnostics and treatments that are ineffective at stopping the progression. This thesis examines new ways of both diagnosing and treating ALS, including 1) a gadolinium tetanus toxin C fragment (Gd-TTC) biomarker for axonal retrograde transport, 2) TTC-conjugated biodegradable nanoparticles, and 3) poly(glycerol-co-sebacate) acrylate (PGSA) and 3D scaffolds for human embryonic stem cell (hESC) and neuronal encapsulation.A Gd-TTC conjugate was developed and characterized that was shown to be highly visible under MRI and preserved the functionality of the native TTC protein in vitro. Live animal MRI imaging and immuno fluorescent staining of the spinal cord showed that the conjugate was transported to the central nervous system (CNS) and localized in motor neurons. H&E staining and biodistribution studies showed that GdTTC was well tolerated and bio available. Quantification of MRI and staining images showed that Gd-TTC was retrograde transported and that that this rate decreased during the disease progression of ALS in a transgenic mouse model, suggesting that Gd-TTC could be used as a biomarker for neurodegenerative diseases.TTC-conjugated nanoparticles were developed by synthesizing PLGA-PEG-biotin and using biotin binding proteins (avidin, streptavidin, and neutravidin) to specifically conjugate TTC to the nanoparticle surface. TTC nanoparticles were shown to selectively target neurons and not other cell types in vitro. / (cont.) Subsequent in vivo experiments showed that nanoparticles were well tolerated and that TTC was co-localized with neurons unilaterally, suggesting that TTC-conjugated nanoparticles may be a useful drug delivery system. Porous PGSA scaffolds were prepared and characterized by porosity, swelling, mass loss, toxicity and mechanical properties, and subsequently used to encapsulated hESC and neuroblastoma cells in vitro. Neuroblastoma cells proliferated and formed matrix fibrils, and fluorescent staining of undifferentiated hESCs showed the presence of all three germ layers. In vivo experiments showed that porous PGSA scaffolds were well-tolerated and promoted vascular ingrowths. / by Seth A. Townsend. / Ph.D.

Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2004. / Includes bibliographical references (leaves 59-60). / This research examines how an athletic footwear company should establish its new product development and launch process to eliminate wastes in the processes and improve the time to market. Currently, it typically takes an athletic footwear company twelve months to introduce new product samples. Retailers place orders after they see samples, however they will not receive and sell the shoes in their retail stores until six months later. The total process from an idea generated to the time when the final products launch takes eighteen months. While this system is set up due to historical reasons, forward looking management teams in the industry see a lot of inefficiencies in it, especially when athletic footwear becomes more and more fashion driven. Why should retailers stick to this advance buying pattern where they take big risks predicting the market six months ahead of time? What if this advance buying pattern is eliminated for whatever reasons? How companies can improve their new products launch process to make them prepared for the possible new challenges in the future? This research studies the new product development process in a large athletic footwear company (Hereinafter US-Footwear). Recommendations include adopting a systematic new products development framework to shorten the time to market. Specifically, this systematic roadmap will force companies to redefine milestones and key activities; this approach will also form a "funnel" screening and informed decision making mechanism. Consequently, companies would be able to eliminate non-value added activities and focus their valuable resources only on the most winning products. It will thus provide companies huge potential to shorten the time to market by doing fewer activities, fewer products and by greatly / (cont.) reducing iterative design changes. Lastly, the author believes that fashion business in general could benefit by adopting the similar approach. / by Xiaoqin Dong. / M.Eng.in Logistics

Thesis (M. Eng.)--Massachusetts Institute of Technology, Biological Engineering Division, 2007. / Includes bibliographical references (p. 53-57). / Alternative splicing is involved in numerous cellular functions and is often disrupted and involved in disease. Previous research has identified methods to distinguish alternative conserved exons (ACEs) in human and mouse. However, the cellular machinery, the spliceosome, does not use comparative genomics to decide when to include and when to exclude an exon. Human RefSeq exons obtained from the University of California Santa Cruz (UCSC) genome browser were analyzed for tissue-specific skipping. Expressed sequence tags (ESTs) were aligned to exons and their tissue of origin and histology were identified. ACEs were also identified as a subset of the skipped exons. About 18% of the exons were identified as tissue-specifically skipped in one of sixteen different tissues at four stringency levels. The different datasets were analyzed for both general features such as exon and intron length, splice site strength, base composition, conservation, modularity, and susceptibility to nonsense-mediated mRNA decay caused by skipping. Cis-element motifs that might bind protein factors that affect splicing were identified using overrepresentation analysis and conserved occurrence rate between human and mouse. / (cont.) Tissue-specific skipped exons were then classified with both a decision-tree based classifier (Random ForestsTM) and a support vector machine. Classification results were better for tissue-specific skipped exons vs. constitutive exons than for tissue-specific skipped exons vs. exons skipped in other tissues. / by Craig Jeremy Rothman. / M.Eng.