Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1989. / Includes bibliographical references (leaves 160-163). / by William D. Keat. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2006. / Includes bibliographical references (leaf 19). / Aerodynamic optimization was performed on Tesseract, the MIT Solar Electric Vehicle Team's 2003-2005 solar car using Wind Tunnel 8 at Jacobs/Sverdrup Drivability Test Facility in Allen Park, MI. These tests include angle of attack and ride height optimization, as well as vehicle-level details such as wheel fairing length, surface finish, sealing, and rear-view mirrors. These tests achieved a net reduction in drag, an increase in stability due to lift force reduction, and valuable knowledge of boundary layer conditions which will be used in future designs. / by Peteris K. Augenbergs. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (leaf 17). / Unmanned vehicles may provide more time- and cost-effective methods of gathering hydrographic survey data when compared to traditional, manned survey vessels. A remote-controlled unmanned surface vehicle (USV) was outfitted with a depth transducer for the purpose of conducting a depth survey of the Charles River Basin. Two windsurfer fins were added to the stem of the USV kayak for directional stability without significant drag, permitting a maximum vessel speed of 4.4 knots. A total of 1485 latitude-longitude GPS points with corresponding depth measurements were taken. Charles Basin data was plotted with ArcGIS software and used to create depth contours and three-dimensional surface plots of the river bottom. This prototype survey USV displays promise and could become readily feasible with further development and autonomy. / by Evan A. Karlik. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 51). / This project used an exoskeletal robot to increase and decrease the stiffness of the ankle joint during treadmill walking to measure the effect of ankle impedance on lower limb joint kinematics. By quantifying the effect of ankle impedance on the knee joint we sought to better understand coordination and control of the ankle and knee. Using linear regression to determine the relationship between the maximum knee flexion during stance and the imposed stiffness on the ankle, we found a measurable positive correlation in 4 out of 5 test subjects at a 95% confidence level. The knee responded to modifications in ankle stiffness as expected from a simple mechanical model. Remarkably, the response was small and variable enough to suggest the body compensates to preserve normal kinematic profiles. / by Bonnie Lucille Blackburn. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / For this thesis a small scale vacuum chamber assembly was designed and fabricated. This chamber's purpose is to provide high quality vacuum conditions for a variety of samples. Often these samples are in need of precise temperature control. An ultra-high vacuum remains the best environment to provide precise and efficient temperature (not accounting for the energy needed to evacuate the chamber). Once completed the vacuum chamber basically consists of a base plate upon which the chamber assembly is mounted. Additional accessories were designed into the assembly to aid in the disassembly of the chamber. Ideally, the user would mount their sample to a flange that possesses a sample holder. That flange can then be mounted to a rail for easy insertion into the chamber. The compact size of the chamber combined with the easy removal and installation of the sample will expedite experimentation. Moreover, the simple design will allow for easy use by a broad spectrum of users in need of precise temperature control. / by Alexander P. Clayton. / S.B.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 104-108). / A variety of improvements to the MIT Design Advisor, a whole-building energy usage modeling tool intended for use during early design stages, are investigated. These include changes to the thermal mass temperature distribution and lighting requirement calculations, the formulation of a representative day scheme to reduce the number of days that need to be simulated to find energy usage for a full year, the creation of an optimization algorithm to allow users to improve on their designs, and the addition of an algorithm to predict potential savings from retrocommissioning (RCx) using a limited set of simple inputs. Design Advisor itself is also tested for usability, speed, and accuracy using three existing buildings. The frequency of thermal mass-related calculations is reduced by finding the limits of the semi-implicit Crank-Nicolson method before it begins to return physically implausible oscillatory temperature profiles. An effort is made to speed up lighting calculations using a multivariate regression analysis in place of a multiple-reflection-based illuminance model. Representative days are formed by creating an average and two extreme weather days per month using existing climatological data, reducing the number of simulated days per year from 365 to 72 (three per month, repeated once for training). Combined, these changes lead to reductions in run time of up to 50% with roughly 10% loss of accuracy. The optimizer leverages these run time improvements to rapidly find optimal building designs given a set of input constraints. Initially, a multistep multivariate regression is used to reduce the given search space and tighten the constraints. Then, a genetic algorithm is used to find the target solution. Initial tests of this combination have led to average reductions in energy usage of 25% given 6 minutes of calculation. To extend Design Advisor's applicability to existing buildings, an algorithm for predicting potential energy savings from RCx is implemented and tested. A database of 90 buildings that have undergone an RCx process and had their resulting energy savings documented has been collected. A k-nearest neighbors algorithm is used to evaluate the potential savings of test buildings based on this data set, operating on the assumption that similar buildings (in terms of location, size, and energy usage intensity) will present similar faults or opportunities for savings. While the average savings percentage prediction error is 0.02, the root-mean-square error is 12.4, which is greater than the actual savings potential of many buildings. Model validation is performed using three existing buildings; two in the Philadelphia area and one on MIT's campus. For energy types for which no building faults or other issues were later found (as in the MIT building), final usage predictions are found to be accurate to within a mean bias error of 11.2% to 2.6%. To improve upon these accuracies, further details about key building parameters and modes of operation would be required. These studies also inform further usability improvements, including reporting site (rather than primary) energy usage and expending reported electricity usage to include loads other than lighting. / by Andrew Mandelbaum. / S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 46-47). / The Rankine cycle is at the heart of steam-electric power stations, which are responsible for generating about 90% of the world's electricity. Improving the efficiency of the cycle thus of great importance, and the greatest possible gain lies in improving the condensation process. Industrial condensers feature once-through water cooling, and the substantial amount of water they consume coupled with the increasing scarcity of freshwater supplies provides further motivation to focus on the condensation process. Condensation in these systems occurs predominantly via the filmwise mechanism, in which a thin film of water forms upon the condensing surface, adversely affecting its heat transfer abilities. However, forming a nanostructure and adding certain hydrophobic coatings on the heat exchanging surface of the condenser can render them superhydrophobic. This causes condensation to instead occur via the jumping droplet mechanism, which promises drastically improved heat exchanging performance. This thesis discusses the design and fabrication of an internal condensation loop which will allow us to test the heat transfer, fluid dynamic performance of the novel jumping droplet internal mode, and the durability and robustness of various hydrophobic coatings at the lab scale. / by Dhananjai Saranadhi. / S.B.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 53-54). / Path-planning has many applications, ranging from self-driving cars to flying drones, and to our daily commute to work. Path-planning for autonomous underwater vehicles presents an interesting problem: the ocean flow is dynamic and unsteady. Additionally, we may not have perfect knowledge of the ocean flow. Our goal is to develop a rigorous and computationally efficient methodology to perform path-planning in uncertain flow fields. We obtain new stochastic Dynamically Orthogonal (DO) Level Set equations to account for uncertainty in the flow field. We first review existing path-planning work: time-optimal path planning using the level set method, and energy-optimal path planning using stochastic DO level set equations. We build on these methods by treating the velocity field as a stochastic variable and deriving new stochastic DO level set equations. We use the new DO equations to simulate a simple canonical flow, the stochastic highway. We verify that our results are correct by comparing to corresponding Monte Carlo results. We explore novel methods of visualizing the results of the equations. Finally we apply our methodology to an idealized ocean simulation using Double-Gyre flows. / by Quantum Jichi Wei. / S.B.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / In this thesis, I designed and implemented an autonomous navigation system for a four-wheeled mobile robot with ultrasonic sonar sensors and a National Instruments myRIO real-time controller. LabVIEW code was developed to control the motors with PWM signals based on sensor feedback. A low-pass filter was used to improve the signal to noise ratio since the signals from the ultrasonic sonar sensors were quite noisy. Finally, I developed two basic algorithms to maneuver the mobile robot: the first algorithm uses proportional control to maintain a specific distance from a target in front of the mobile robot; the second also uses proportional control to keep the robot at a specified distance away from a wall to its side as it travels forward. / by Joseph Campion. / S.B.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1993. / Includes bibliographical references (leaf 24). / by Benjamin Heywood. / B.S.