Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 45-46). / This thesis details the design and construction of a rig for studying surface condensation and a rig for creating anodized metal oxides (AMOs). The condensation rig characterizes condensation for different surfaces; this is done with the use of known heat transfer principles to calculate characteristic heat fluxes and heat transfer coefficient values. Preliminary results have been shown to follow predictions derived from existing heat transfer principles, and have confirmed existing literature's assertion of increased effectiveness of dropwise condensation over filmwise condensation. The AMO rig fabricates anodized metal oxide surface samples by subjecting wafers coated with thin metal layers to voltage in the presence of acidic electrolytes. Initial fabricated anodized aluminum oxide (AAO) samples have shown to display the characteristic hierarchal nanopore structure of known fabricated AAO in literature. Both the condensation rig and the AMO rig will be used in current and future condensation and superhydrophobic surface research by the Varanasi group in the MIT Department of Mechanical Engineering. / by Wei-Yang Sun. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 87-97). / 90% of cancer related deaths are due to metastatic disease and there is a need for a better understanding of cell-microenvironment interactions to identify new therapeutic targets. A key step during cancer metastasis is cancer cell intravasation (entry of cancer cells into the blood vessels) that results in tumor cell dissemination into distant organs. During this process, tumor cells navigate a complex microenvironment and interact with multiple cell types. This thesis is aimed to develop a microfluidic-based intravasation assay that allows for direct observation of tumor cell motility combined with quantitation of the endothelial barrier function. Compared with traditional in vitro assays, microfluidic assays enable "user-defined" design of the cellular and acellular microenvironment with spatio-temporal control and live high-resolution imaging. Formation of confluent endothelial layers in the device was confirmed with immunofluorescence staining for endothelial cell-cell junctions and we compared our diffusive permeability values with published in vivo and in vitro data. We employ this microfluidic assay to investigate the role of endothelial barrier function during tumor cell intravasation to address a critical question in cancer research: does tumor cell intravasation require a leaky endothelium? To induce vessel leakiness we perturb the barrier using biochemical factors, endothelial cells with low expression of basement membrane proteins and signaling with macrophages. Under all these conditions, tumor cell intravasation rates increased and we confirmed these results for multiple tumor cell types. Characterization of macrophage secreted factors and M1/M2 polarization status, identified that blocking macrophage-secreted TNF-a restored endothelial permeability and reduced tumor cell intravasation. In agreement with these results, we also found that the number and dynamics of tumor-endothelial interactions were dependent on endothelial barrier function. A novel feature of the developed assay is the ability to image in real-time the process of tumor cell intravasation, while also enabling accurate control and quantitation of the functional characteristics of the endothelial barrier. Our results not only demonstrate the important role of cell-cell paracrine signaling and biochemical factors in regulating tumor cell intravasation, but also have important implications for strategies aimed to disrupt or normalize vasculature in vivo. Keywords: 3D Microfluidics, Endothelial permeability, Cancer cell Intravasation, Macrophages. / by loannis K. Zervantonakis. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (p. 165-166). / by Robert John Ritter. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 26). / The objective of this thesis was to determine the behavior of the engine of the REMUS 600, an autonomous underwater vehicle. The first step was to evaluate the closing and opening of the choke and throttle valve and write a code that allows the user to easily control the stepper motors that attach to each valve. Then, the engine was to be started, brought up to an ideal speed, and stabilized. All these processes were done through a PIC C compiler and a microcontroller. Testing revealed that it took 10.3 +/- 0.2 and 113.6 +/- 1.7 steps to open the choke and throttle respectively and 4.5 + 0.1 and 206.4 +/- 2.2 to close the choke and throttle respectively. Code to perform the aforementioned has been preliminarily tested and successful, which should allow future users to maintain control of the engine speed and power output. / by Cindy E. Oh. / S.B.

Thesis: M. Eng. in Manufacturing, Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 83-86). / The warehouse layout and operations of a semiconductor tool manufacturer were studied with the objective of reducing the lead time for parts ordered from the warehouse to 8 hours. Current order fulfillment operations were studied and interviews with involved personnel were conducted. Additionally, data was extracted and analyzed from the company's SAP Extended Warehouse Management database to analyze the past performance of the warehouse operations. Three main areas for improvements were analyzed and recommendations were made regarding each area. First, it is recommended that a kit of parts ordered should be sent immediately the constituent parts are consolidated and the kit is completed. This saves an average of 6 hours that parts in a complete kit wait for other kits to be completed before being sent out. Second, the picking aisles of the warehouse should be cleared so that parts in storage locations are easily accessed for picking and no time is wasted on clearing a path to pick a part. This leads to an average time saving of 1.2 hours per day on the time parts are delivered. Third, the receiving and sorting areas in the warehouse should be combined together. This frees up storage space for excess bulk material which block picking aisles. These recommendations are to be combined with other material flow improvements. It was determined that the goal of 8 hours lead time is unrealistic. However, calculations suggest that lead time will be reduced to 16 hours. / by Obehi Ukpebor. / M. Eng. in Manufacturing

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001. / Includes bibliographical references (p. 111-112). / by Meow Seen Yong. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 221-226). / This thesis investigates two aspects of Vortex-Induced Vibrations (VIV) on long flexible cylinders. The work is split into a minor and major part. The minor part addresses the effect of Reynolds number on flexible cylinder VIV. The major contribution addresses the prediction of VIV under unsteady current excitation or time-varying flows. The study on the effect of Reynolds number makes extensive use of a recent set of experiments performed by MARINTEK on behalf of SHELL Exploration and Production Co. Three 38[gamma] long cylinders of different diameters were towed through the ocean basin over a wide range of Reynolds numbers in both uniform and sheared flows. The experimental data showed that the response amplitudes and dimensionless response frequency are strongly influenced by the Reynolds number. Both of these Reynolds effects should be of interest to riser designers that traditionally rely on experimental data obtained at much lower Reynolds numbers. In this thesis, I propose a dimensionless parameter, [gamma], that governs whether lock-in under unsteady flow conditions is possible and show that it is useful for determining a priori whether the response under unsteady conditions will be similar to the response under steady flows. The unsteady flow parameter, [gamma], describes the change in flow speed per cycle of cylinder vibration and is defined as: ... The experimental data necessary to support this work is taken from a set of experiments performed at the State Key Laboratory of Ocean Engineering at Shanghai Jiao Tong University (SJTU), where a 4[gamma] long flexible cylinder was towed through an ocean basin under carefully selected amounts of acceleration/deceleration. Analysis of the experimental data showed that the response can typically be divided into three regimes based on the [gamma] value: For very quickly accelerating flows ([gamma] > 0.1) the cylinder cannot react quickly enough and at most a couple of cycles of small amplitude vibration will be observed. For moderately accelerating flows (0.02 < [gamma] < 0.1), the cylinder will typically start vibrating and can build up a significant response. However, most of the time, the flow will have exited the required synchronization region before the cylinder manages to reach the large amplitudes observed in steady flows. For very slowly accelerating flows ([gamma] < 0.02), the flow is changing considerably slower than the cylinder's reaction time and thus, the cylinder has more than enough time to build up its response. Under these conditions, the observed response is qualitatively similar to the response of flexible cylinders in steady flows. The [gamma] dependence that was identified in the SJTU data is not limited to that specific situation but instead, is a general property of low mass ratio cylinders vibrating in unsteady flows. This is shown by demonstrating how the unsteady flow parameter, [gamma], can be used to analyze unsteady response data from the aforementioned SHELL tests where the riser models were considerably longer than the SJTU model. This thesis shows how a single ramp test -- where the towing speed is continuously varied in a control manner -- may be used to obtain the same information as 10 constant speed tests covering the range of speeds. This can and will significantly reduce the number of runs necessary to completely characterize the VIV response of flexible cylinders and will translate into large cost savings in the future. The thesis closes by describing the differences observed in the VIV response at high mode numbers depending on whether the time-varying flow was accelerating or decelerating. In both situations a 'hysteresis' effect is noted, where the cylinder is found to 'lag behind' preferring to vibrate in the previously excited mode as a result of cylinder lock-in. In accelerating flows, this means that the cylinder will typically be responding one mode lower than it would have in a steady flow. In decelerating flows, the same 'lag' or 'hysteresis' will cause the cylinder to respond one (or more) mode number(s) higher than it would have in a steady flow. / by Themistocles L. Resvanis. / Ph. D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 269-274). / There is a global trend towards urbanization, particularly in developing regions that are home to new and rapidly growing cities. In the center of large, dense urban areas, weak exchange between the urban canopy layer (UCL) and the urban boundary layer (UBL) above it results in insufficient removal of heat and pollutants. The magnitude of the exchange processes between the UCL and the UBL is directly related to the built environment that is devised by urban designers and influenced by policy makers. In this work, representative urban forms are defined and the vertical mixing potential is quantified for each case using computational fluid dynamics ( CFD). Insight is gained into the flow phenomena responsible for these results and the findings are presented in the context of urban design. Dense, repetitive, orthogonally-gridded neighborhood layouts are common in urban areas and are selected as the subject of analysis. Using dimensional reasoning, the relevant geometric parameters, including the dimensions of the city block as well as the spacing between blocks, are determined. These quantities are parametrically varied and the resulting flow fields are calculated using CFD for each case. Next, simulated passive scalars are released into each neighborhood from a near-ground volumetric source, and the average steady state non-dimensional concentrations are calculated in the UCL and at pedestrian height. Using these concentrations as metrics, the vertical mixing potential is quantified as a function of each of these building geometry parameters. Transient results, fluid mechanical reasoning and flow visualizations are used to develop a physical understanding of the flow phenomena responsible for these quantitative results allowing them to be interpolated and extrapolated with confidence. Analytical models are developed where applicable. The results are presented at both a neighborhood scale, of interest to policy makers and urban planners, and at a street canyon scale, of interest to urban designers and architects. In addition to the repetitive neighborhood, common urban planning elements are evaluated to determine how changes in these forms affect mixing within the UCL and between the UCL and the UBL. These include variations in building height, the introduction of parks or open areas to a gridded neighborhood and building clustering. In gridded neighborhoods with buildings of uniform height and one grid axis aligned with the wind, street canyons perpendicular to the wind have larger vertical mixing potentials than street canyons aligned with the wind. Decreasing street canyon aspect ratios significantly increases the vertical mixing potential in these gridded neighborhoods. Introducing height variation to a neighborhood with uniform height buildings increases the vertical mixing potential at a neighborhood scale and reduces the difference in vertical mixing potential between the street canyons perpendicular to and aligned with the wind. The addition of parks and open areas also increases the vertical mixing potential in gridded neighborhoods. Finally, preliminary work on building clustering suggests these urban forms have greater vertical mixing potentials than gridded neighborhoods, in general. Guidelines and quantitative methods are developed for practitioners to use in the assessment of the impact of a neighborhood scale design on the exchange processes between the UCL and the UBL, information that might otherwise be inaccessible or cost prohibitive. Examples that show how to apply these methods are presented throughout this work, and the implications of urban design choices on pedestrians are discussed. A supplemental summary of the most relevant findings for practitioners is also provided. / by Terianne Catherine Hall. / Ph. D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996. / Includes bibliographical references (leaf 45). / by Ryan Joseph Bryla. / B.S.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 111-115). / Efficient design of energy converters heavily depends on the capacity of the designer to accurately predict the device's dynamic, which ultimately leads to the power extraction. This is specially true for wave energy converters (WEC), which usually present a high cost per kWh generated. In this thesis a particular WEC which uses a rotating mass for power extraction is studied. A numerical model for the prediction of its motion and power extraction is presented. The nonlinear dynamic model consists of a time-domain three dimensional Rankine panel method coupled, in the time integration, with a MATLAB algorithm which solves for the equations of the gyroscope and Power Take-Off (PTO). The former acts as a force block, calculating the forces due to the waves on the hull, which is then sent to the latter through TCP/IP, which couples the external dynamics and performs the time-integration using a 4th order Runge-Kutta method. With the proposed code, two case studies are examined. The first consists of two gyroscopes, rotating in opposite directions, to negate undesirable yaw effects on the WEC's hull. The device's optimum PTO damping value and flywheel spin are then shown, which change for different sea states. The second is a comparison against results from experimental testing of a 1:50 model at the Davidson Laboratory during the Wave Energy Prize. / by João Seixas de Medeiros. / S.M.