Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 58-59). / The Atomic Force Microscope (AFM) is a powerful tool for the imaging of extremely small objects on the scale of nanometers, like carbon nanotubes and strands of DNA. There currently is a need for methods to actively steer the probe tip of the AFM in order to greatly reduce the time required to image certain samples. This paper proposes a tip steering method that utilizes the vertical feedback information from the AFM sensor as well as the dimensions of the sample object to determine and maintain a scanning trajectory. A comparison of similar trajectory tracking methods is also presented. The AFM system and operation is discussed in order to justify the tip steering method. Finally, the method proposed is successfully simulated with a DNA strand sample in the presence of measurement noise. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1994. / Includes bibliographical references (leaves 129-130). / by Travis Lee Hein. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997. / Includes bibliographical references (p. 111-112). / by Marcus Stewart. / M.S.

Thesis (Nav. E. and S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 53-54). / Hydrodynamic flow visualization techniques of scaled hull forms and propellers are typically limited to isolating certain operating conditions in a tow tank, circulation tunnel, or large maneuvering basin. Although cost effective, these tests provide a limited perspective on the interactions of the entire system. Full-scale testing, other the other hand, provides real world data but is costly. In between, a Froude scaled, free-running model of an existing hull form controls costs but also provides superior hydrodynamic data that can be translated more accurately to full scale. This thesis details the design and construction of a 1/ 3 0 th scale free running model of the David Taylor Model Basin 5415 hull, the precursor to the ubiquitous Arleigh Burke Guided Missile Destroyer hull. The model serves as an experimental platform for advanced maneuvering and propeller crashback studies. The propeller crashback (a core propulsion plant test for both the U.S. Navy and commercial vessels) imparts significant unsteady loads to the engineering plant and drive train. Each of these is respectively of interest to propeller designers and the Electric Ship Research and Development Consortium (ESRDC). The 1 / 3 0 th scale model provides unsteady, time-resolved, accurate 3D flow visualization and propeller loading data as well as measurements of the effects on the electrical propulsion motors. Testing conducted with the model provides the real world effects of the propeller flow interaction with the hull and appendages. The second area of research concerns the high inefficiencies of slender hull forms while maneuvering. During a turn, a significant amount of power is lost to the low pressure region developed on the inside of the turn from shedding vortices that originate along the keel. This increases the tactical diameter of the turn and reduces the turning efficiency of the vessel. Research is currently being conducted around controlling the shedding of vortices and keeping them attached to the hull thereby increasing the turning efficiency and decreasing the turning radius of the vessel. The final area of interest is in forward mounted podded propulsors for use on large vessels. / by David M. Cope. / Nav.E.and S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references. / There is urgent need to develop treatments for inducing regeneration in injured organs. Porous collagen-based scaffolds have been utilized clinically to induce regeneration in skin and peripheral nerves, however still there is no complete explanation about the underlying mechanism. This thesis utilizes advanced microscopy to study the expression of contractile cell phenotypes during wound healing, a phenotype believed to affect significantly the final outcome. The first part develops an efficient pipeline for processing challenging spectral fluorescence microscopy images. Images are segmented into regions of objects by refining the outcome of a pixel-wide model selection classifier by an efficient Markov Random Field model. The methods of this part are utilized by the following parts. The second part extends the image informatics methodology in studying signal transduction networks in cells interacting with 3D matrices. The methodology is applied in a pilot study of TGFP signal transduction by the SMAD pathway in fibroblasts seeded in porous collagen scaffolds. Preliminary analysis suggests that the differential effect of TGFP1 and TGFP3 to cells could be attributed to the "non-canonical" SMADI and SMAD5. The third part is an ex vivo imaging study of peripheral nerve regeneration, which focuses on the formation of a capsule of contractile cells around transected rat sciatic nerves grafted with collagen scaffolds, 1 or 2 weeks post-injury. It follows a recent study that highlights an inverse relationship between the quality of the newly formed nerve tissue and the size of the contractile cell capsule 9 weeks post-injury. Results suggest that "active" biomaterials result in significantly thinner capsule already 1 week post-injury. The fourth part describes a novel method for quantifying the surface chemistry of 3D matrices. The method is an in situ binding assay that utilizes fluorescently labeled recombinant proteins that emulate the receptor of , and is applied to quantify the density of ligands for integrins a113, a2p1 on the surface of porous collagen scaffolds. Results provide estimates for the density of ligands on "active" and "inactive" scaffolds and demonstrate that chemical crosslinking can affect the surface chemistry of biomaterials, therefore can affect the way cells sense and respond to the material. / by Dimitrios S. Tzeranis. / Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 87). / Micro-UAV devices can be used for a variety of purposes. This project is concerned with the design of such a device that will be used for high altitude antenna calibration. Such a UAV requires that an omni-directional antenna be integrated into the frame of the device to reduce signal interference. The device is to fold into a flare cartridge and withstand high deployment forces out of an aircraft. Design requirements include a rectangular working volume of 1.89" X 2.44" X 7.04", a minimum additional payload of 70 g, hang time requirements, and antenna operating frequencies. A standard design process was used to develop a functional prototype. Several different concepts were developed, analyzed, and tested until a discone parachute device was chosen. An umbrella-like mechanism that utilized aerodynamic forces for deployment was developed for the ground plane. A functional demonstration prototype was built and tested to ensure the device's survivability and deployment functionality. The results of the test were successful and proved that the design is viable and can be further developed and optimized to improve performance. / by My H. Vu. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 61-65). / This thesis presents the development of an entirely 3D-printed, monolithic microfluidic platform for evaluating the efficacy of immunotherapy treatments. The platform provides a dynamic microenvironment for perfusing and sustaining tumor samples extracted from a biopsy. The finely featured, non-cytotoxic, and transparent tumor trap is integrated with threaded connectors for rapid, leak-proof fluid interfacing, an in-line trap for removal of bubbles arising from oxygenated media flow or tumor loading procedures, and a network of microchannels for supplying media and immunotherapies to a retained tumor fragment. The device configuration is capable of modelling interactions between tumors and various drug treatments. Tested devices were additively manufactured in Pro3dure GR-10 -a relatively new, high-resolution stereolithographic resin with properties suitable for biomedical applications. Retention of human tumor fragments within the printed microfluidic device is confirmed through overlaid bright-field and fluorescence micrographs, which permit visualization of individual tumor cells within the biological sample. Under dynamic perfusion of media, live tumor fragments can be sustained for a period of at least 72 hours. Confocal microscopy confirmed that sustained tumors and the resident lymphocytes exhibited a response to perfused immunotherapy treatments compared to an untreated control. With further validation, the proposed platform may be capable of providing critical predictive insight into an individual's response to selected immunotherapies. / by Ashley L. Beckwith. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: leaf 150. / by David Earl DeLucia. / M.S.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002. / Includes bibliographical references (p. 209-215). / Issues of robust stability and performance have dominated the field of systems and control theory because of their practical importance. The recently developed Integral Quadratic Constraint (IQC) based analysis method provides a framework for systematically checking robustness properties of large complex dynamical systems. In IQC analysis, the system to be analyzed is represented as a nominal, Linear Time-Invariant (LTI) subsystem interconnected with a perturbation term. The perturbation is characterized in terms of IQCs. The robustness condition is expressed as a feasibility problem which can be solved using interiorpoint algorithms. Although the systems to be analyzed have nominal LTI subsystems in many applications, this is not always the case. A typical example is the problem of robustness analysis of the oscillatory behavior of nonlinear systems, where the nominal subsystem is generally Linear Periodically Time-Varying (LPTV). The objective of the first part of this thesis is to develop new techniques for robustness analysis of LPTV systems. Two different approaches are proposed. In the first approach, the harmonic terms of the LPTV nominal model are extracted, and the system is transformed into the standard setup for robustness analysis. Robustness analysis is then performed on the transformed system based on the IQC analysis method. In the second approach, we allow the nominal system to remain periodic, and we extend the IQC analysis method to include the case where the nominal system is periodically time-varying. / (cont.) The robustness condition of this new approach is posed as semi-infinite convex feasibility problems which requires a new method to solve. A computational algorithm is developed for checking the robustness condition.In the second part of the thesis, we consider the optimization problems arising from IQC analysis. The conventional way of solving these problems is to transform them into semi-definite programs which are then solved using interior-point algorithms. The disadvantage of this approach is that the transformation introduces additional decision variables. In many situations, these auxiliary decision variables become the main computational burden, and the conventional method then becomes very inefficient and time consuming. In the second part of the thesis, a number of specialized algorithms are developed to solve these problems in a more efficient fashion. The crucial advantage in this development is that it avoids the equivalent transformation. The results of numerical experiments confirm that these algorithms can solve a problem arising from IQC analysis much faster than the conventional approach does. / by Chung-Yao Kao. / Sc.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references. / This project was conducted in support of a solar concentrating technology that required the design and construction of a low cost, two axis rotational drive system with a resolution of one degree or better. The scope of this project was to design and build a two axis drive system capable of supporting a 20" square acrylic mirror. Cost, reliability, and the ability to be built by students using student resources were of primary concern. The primary design concern was the development of a low cost feedback system. Several different feedback sensors were considered, and a quadrature encoder was chosen. To reduce cost, the encoder disk was made from an overhead transparency with a slotted image printed on it. The required encoder accuracy was 1.0 degree, and a measured accuracy of 0.85 degrees was achieved. The encoder was designed with an optimum accuracy of 0.55 degrees per transition and the observed discrepancy in resolution is primarily due to high tolerances that could not be met with hand assembly. / by Rick Bryan Woodruff. / S.B.