Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996. / Includes bibliographical references (p. 109-110). / by Jean-Claude J. Saghbini. / M.S.

Thesis (S.M. in Naval Architecture and Marine Engineering)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 87-88). / Seakeeping analysis of the Zumwalt-Class destroyer was carried out in the framework of linear strip theory and potential flow. First, the problem was formulated and solved analytically. Second, a program called Ship Motions Analyzer (SMA) was written in MATLABTM to carry out the seakeeping analysis for regular waves in a discretized frequency range. SMA calculates sectional added mass and damping coefficients first. Then, it calculates excitation forces and moments acting on a ship advancing at constant forward speed with arbitrary heading for sway, heave, roll, pitch and yaw modes of motion. Finally, SMA evaluates Response Amplitude Operators (RAO's) in the same modes of motion. In addition, it also includes a subroutine which evaluates steady drift forces acting on a ship in the plane of undisturbed free surface. The added mass and damping coefficients of a fully submerged heaving circle and a semi-circle in heave and sway were calculated to validate the results of SMA. The results were compared to the results of Vugst [1] and Frank [2]. They match each other exactly. In addition, the magnitudes of heave and pitch excitation force and moment, and RAO's in the same modes of motions were calculated. The results agree with the theory. Finally, added resistance of Mariner type ship was calculated by SMA to compare the results to the ones given by Salvasen [3] and to validate the calculations. These results are also in very good agreement with the available computational and experimental results. / by Ilkay Ozer Erselcan. / S.M.in Naval Architecture and Marine Engineering

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001. / Includes bibliographical references (p. 254-268). / I built a novel prototype capillary polymerase chain reaction machine. The purpose was to perform a single reaction as fast as possible with a reaction volume - 100 nl. The PCR mix is in the form of a 1 /1 droplet that moves between three heat zones inside of a 1 mm I.D. capillary filled with mineral oil via pneumatic actuation. A laser beam waveguides down the capillary until it strikes the drop, at which point it scatters. The scatter is picked up by a series of photodiodes to provide position feedback. Due to the efficient heat transfer arrangement, the drop can transition between different temperature steps in -2 seconds, which includes both drop motion and temperature equilibration. It was extensively tested in both 10-cycle and 30-cycle PCR, including nearly 200 successful 30-cycle runs. The 30-cycle PCR was typically 74% (as high as 78%) efficient, and took only 23 minutes. This compares well with existing machines in the literature. / by Jeffrey Tsungshuan Chiou. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (p. 86-87). / A wide variety of engineering activities benefit from the use of rough estimates of the type commonly referred to as back-of-the-envelope calculations. These include evaluating the feasibility of an idea, planning experiments, sizing components, and setting up and checking detailed analyses. The overall goals of this thesis were to understand how people make rough estimates for physical quantities and to understand how that activity relates to undergraduate engineering education. The specific objectives of this thesis were to describe the nature and extent of mechanical engineering students' estimation capabilities, to develop a framework describing estimation activity and to characterize the relationship between rough estimation activities and learning activities. The intent of these objectives was to develop conceptual knowledge useful for assessing and teaching rough estimation skills as well as for guiding estimation activity in practice. Students were found to have considerable difficulty making estimates for common engineering quantities, such as force and energy. Students were also found to have difficulty applying basic engineering concepts in rough estimation situations even at the senior level. In order to identify concepts that give students difficulty, a new assessment method based on students' ability to associate correct units with common engineering quantities was developed. The mediated action framework that was developed consists of three components: effective actions people take when they make estimates, mediating characteristics and the resulting limitations imposed on these actions, and compensation methods people use to circumvent these limitations. The primary focus of this thesis was on identifying the effective actions. A set of effective actions was identified that was sufficient to describe a large number of people's solutions to a variety of estimation problems. The relationship between rough estimation and engineering curricula was examined by comparing rough estimation activities in practice and learning activities in curricula. Rough estimation activities were found to be incongruent with typical undergraduate engineering curricula. The differences between these activities suggest ways in which curricula might be changed to improve students' estimation skills. / Benjamin M. Linder. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (leaf 41). / Passive-dynamic walking robots are remarkable mechanical devices capable of maintaining dynamically stable walking gaits with no actuation or control. These systems, however, depend on ideal environmental conditions for stability. Robustness and control capabilities are increased with actuation, but so is the power consumption. Such actuated robots are designed to minimize the actuation requirement by exploiting the system natural dynamics system, but still need actuation to compensate for energy dissipated by friction and collision events, as well as for more control capabilities. A simple clutch mechanism is developed for such systems to allow intermittent control of otherwise passive joints, allowing controllers to exploit the passive or actuated control when desired. The clutch is tested on a hip actuated simple 3D walker to evaluate the performance capabilities of clutched control. Preliminary tests of several control strategies suggest the clutched actuation may provide good performance at a higher efficiency compared to fully actuated systems. This paper describes the development of the clutch device and the hip-actuated biped on with which the clutch is tested, and evaluates the performance of intermittent clutch-control for several control strategies. / by Arlis Reynolds. / S.B.

Includes bibliographical references (leaves 49-50). / Thesis (S.M. in Naval Architecture and Marine Engineering)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / (cont.) New casualty parameters were recorded and analyzed in an attempt to verify and expand on diagnostic software currently being developed for the vacuum aided sewage collection system. The analysis of the ships service compressed air system provides an example of what immediate diagnostics such software would be able to provide for the user. Additional analysis of a misaligned ventilation fan provides evidence of the NILM's ability to constantly monitor steady state systems. The expansion of testing onto the ESCANABA provides valuable verification of previous data collected onboard the SENECA during past research. / The Non-Intrusive Load Monitor (NILM) is a device that utilizes voltage and current measurements to determine the operating profile and individual loads on a system from a single aggregate measurement. The NILM can also be used to actively monitor and quickly diagnose system failures or improper operation. Current NILM research conducted at Massachusetts Institute of Technology's Laboratory for Electromagnetic and Electronic Systems (LEES) is exploring the application and expansion of NILM technology for the use of monitoring shipboard systems. This thesis presents the implementation of the NILM on a vacuum aided sewage collection system, a ship's service low pressure compressed air system, and a vane axial ventilation supply fan. The NILM's ability to the monitor the power usage profile of these systems could be used to immediately diagnose system casualties and unusual operation parameters. Measurements and experimentation were conducted onboard the USCGC ESCANABA (WMEC-907) and the USCGC SENECA (WMEC-906), 270-foot Coast Guard Cutters home ported out of Boston Harbor. / by Mark A. Piber. / S.M.in Naval Architecture and Marine Engineering / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references. / Cytoskeletal proteins function as dynamic, complex components involved in cellular structure and signaling. Characterizing the roles of such proteins would greatly benefit many research areas, including the study of cancer and protein-related diseases. There is currently no accurate, high throughput method of image analysis that clearly describes protein behavior within the cell. In addressing this problem, we chose to characterize proteins based on the colocalization parameter-the amount of overlap between two objects or signals. We aimed to create a single parameter that quantitatively defined colocalization yet complemented biological intuition about a complicated system. Cell culture techniques were used to transfect HeLa cells with four "marker" GFP-tagged protein constructs. Cells were fluorescently labeled in three channels-Hoechst for nucleus, Texas Red phalloidin for actin, and GFP for protein-and images were captured using Cellomics scanning microscopy. After collecting data and testing software applications, we analyzed our data with Definiens software and developed a flexible, comprehensible method of quantifying colocalization using minimal parameters. / by Stephanie M. Reed. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (p. 195-215). / A variety of impressive approaches to legged locomotion exist; however, the science of legged robotics is still far from demonstrating a solution which performs with a level of flexibility, reliability and careful foot placement that would enable practical locomotion on the variety of rough and intermittent terrain humans negotiate with ease on a regular basis. In this thesis, we strive toward this particular goal by developing a methodology for designing control algorithms for moving a legged robot across such terrain in a qualitatively satisfying manner, without falling down very often. We feel the definition of a meaningful metric for legged locomotion is a useful goal in and of itself. Specifically, the mean first-passage time (MFPT), also called the mean time to failure (MTTF), is an intuitively practical cost function to optimize for a legged robot, and we present the reader with a systematic, mathematical process for obtaining estimates of this MFPT metric. Of particular significance, our models of walking on stochastically rough terrain generally result in dynamics with a fast mixing time, where initial conditions are largely "forgotten" within 1 to 3 steps. Additionally, we can often find a near-optimal solution for motion planning using only a short time-horizon look-ahead. Although we openly recognize that there are important classes of optimization problems for which long-term planning is required to avoid "running into a dead end" (or off of a cliff!), we demonstrate that many classes of rough terrain can in fact be successfully negotiated with a surprisingly high level of long-term reliability by selecting the short-sighted motion with the greatest probability of success. The methods used throughout have direct relevance to machine learning, providing a physics-based approach to reduce state space dimensionality and mathematical tools to obtain a scalar metric quantifying performance of the resulting reduced-order system. / by Katie Byl. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (leaf 49). / by Kumaran Kolandaivelu. / B.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001. / Includes bibliographical references (leaf 117). / Resistance spot welding is an important part of the automotive manufacturing industry. Today's automobiles typically contain five-thousand or more welds. Spot welding is attractive to the industry for its speed and relative simplicity, however, it is not without its disadvantages. Current spot welding technology relies on volumes of empirical data to set the welding parameters. Often this data is not sufficient to ensure that a nugget of sufficient size is formed without a splash occurring. Complicating the matter further is the industry's increased use of coated steel. The chemical reaction of the coatings with the electrodes cause greater variations in the nugget size. This study seeks to characterize the nugget formation patterns of spot welding for a variety of welding materials and welding conditions. Specifically for coated steels welded over long periods with the same electrodes. The study also seeks to relate a small set of monitored parameters during welding to the accurate prediction of nugget size and splash occurrence. Welding current and voltage are identified as the key parameters of interest and are used as input to a numerical simulation to predict nugget diameter. A comparison of the simulated nugget diameters to actual diameters obtained experimentally show good agreement between the two values. The simulation, however, uses a finite difference method to obtain the nugget diameter. This method requires extensive calculations that cannot be completed in the normal welding time. Therefore, a new method of splash prediction has been investigated using the mean temperature of the workpiece. The mean temperature is obtained from a heat balance model of the workpiece. The heat balance model is advantageous to the finite difference simulation because its calculation time is short enough to be carried out during the welding process. A comparison of the maximum mean temperature and the experimental nugget diameters shows that mean temperature is capable of predicting nugget diameter. This correlation indicates that the mean temperature value can serve as a splash prediction parameter. / by Richard M. Obert. / S.M.