Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 38). / This research attempted to assess the feasibility of using screw conveyors as a means of continuously rearing black soldier fly larvae. Farming of the black soldier fly (BSF) has gained popularity in recent years as means to supply protein for animal feed and recycle food waste. However current methods for BSF farming are labor intensive and costly. This is due partly from the batch system in which BSFs are grown. It is also a factor of space inefficiency, as BSF larvae can only live in the first 7-10 cm of the substrate they are grown in due to oxygen depletion. Screw conveyors in theory could solve both these problems by allowing for continuous production and mixing which could aerate the substrate preventing oxygen depletion. In order to test the feasibility of using screw conveyors an analysis was done to predicted energy cost. Based on the calculations done in this work energy cost would be trivial, on the order of 0.01 US dollars or less per pound of dry weight BSF larvae. Physical experiments were also done on the effectiveness of mixing in aerating the substrate and allowing BSF larvae to live deeper. This involved filling a tube with substrate and BSF larvae to various depth between 15 and 45 cm and measuring oxygen levels at the bottom depth. The tube was also flipped to simulate mixing. While there is a high level of uncertainty, the results in general indicate oxygen was depleted in the substrate on the order of 5-10 minutes for depths bellow 15 cm. This does not support the feasibility of using screw conveyors for BSF farming as the conveyor would have to be running almost constantly to prevent the development of anaerobic conditions. However many factors in this research where high conservative and the development of anaerobic zones in BSF substrate and the effects of mixing warrant further research. / by Ty Ingram. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1990. / Includes bibliographical references (leaves 186-192). / by Dragan Obradović. / Ph.D.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Lawrence D. Sobel. / Sc.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. / "September 2012." Cataloged from PDF version of thesis. / Includes bibliographical references (p. 66-68). / A droplet deposited on a rough, lyophilic surface satisfying the imbibition condition, results in spontaneous spreading and hence complete wetting. However, in this thesis, we demonstrate that this wetting behavior can be altered by superheating the substrate such that droplets can reside in a non-wetting state due to evaporation. Photolithography and deep reactive ion etching were used to fabricate well-defined silicon micropillar arrays with a square pattern with varying pillar diameter, height, and center-to-center spacing. Water droplets placed on these microstructured surfaces at room temperature demonstrated superhydrophilic behavior with liquid filling the voids between pillars resulting in very low contact angle, and hence complete wetting. However, when the microstructured surface was superheated above a critical superheat, the superhydrophilicity was lost and non-wetting droplets were formed on the top surface of the micropillar array structure. The superheat required to deposit a non-wetting droplet (> 75°C) was found to be significantly higher than that required to sustain an already deposited non-wetting droplet (< 35°C). Moreover, the superheat required to sustain a non-wetting droplet after the initial deposition was observed to decrease with the square of the droplet radius. A 1-D lubrication type model based on a force balance between the wetting and non-wetting forces is developed which explains the mechanism by which non-wetting droplets can reside on superhydrophilic surfaces at superheated conditions due to induced evaporation. Moreover, the model predicts a square relationship between the superheat required to form non-wetting droplets and the droplet radius which is in agreement with experimental observation. These observations where non-wetting droplets reside on superhydrophilic surfaces at superheated conditions have implications for phase-change based heat transfer applications where the loss of contact between the substrate and the heat transfer fluid could be detrimental to the device performance. / by Solomon Adera. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 114-132). / Although Reverse osmosis (RO) is the state-of-the-art desalination technology, it still suffers from persistent drawbacks including low permeate flux, low selectivity for non-ionic species, and lack of resistance to chlorine. This leaves ample rooms. for further improvement for RO technology by addressing these issues. In this thesis, a new approach is proposed for desalination by vapor-phase transport through hydrophobic nanopores in an isothermal condition. Hydrophobic nanopores flanked by vapor-interfaces with a submicron gap provide a complete barrier for salt while behaving as highly permeable medium for water. We first theoretically explore transport of water through a hydrophobic nanopore using a probabilistic model that incorporates rarefied gas dynamics, ballistic transport, and emission and reflection of water molecules at liquid-vapor interfaces. We then expand the model to transition regime where molecular diffusion coexists with the rarified gas transport. Effect of nanopore geometry, salinity, temperature, applied pressure, and interfacial reflection probability on the transport of water molecules through the nanopore are explored. We further realize membranes consisting of hydrophobic nanopores to experimentally study the transport with the various above-mentioned conditions. We find the existence of two mass transport regimes, i.e., diffusion-governed and interface-governed transport, determined by interplay between transmission across the nanopores and condensation at the interfaces. The condensation resistance, represented by condensation coefficient, was experimentally measured. An accurate value of the condensation coefficient was estimated accordingly, which has been debated more than a century. Based on this finding, the proposed approach is expected to produce up to ~2x higher permeate flux at 50°C and with porosity of 40% than conventional RO. This approach further decouples transport properties from membrane material properties, thereby opening the possibility of engineering membranes with appropriate materials that may lead to reverse osmosis membranes with improved flux, better selectivity, and high chlorine resistance allowing for inexpensive and simple fouling control. / by Jongho Lee. / Ph. D.

Thesis: M. Eng. in Manufacturing, Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 102-103). / The proposal for a new detector for liquid chromatography instruments that uses Ultraviolet Light Emitting Diodes (UV-LEDs) as the light source as opposed to currently used deuterium lamps required new design of the mechanical and structural components associated with it. The optics bench assembly is the heart of the detector system on which the detector optical components are mounted. The focus of this thesis is the mechanical design of the optics bench assembly of the UV-LED detector. The thesis first briefly describes the technology and operational theory of the new detector and then discusses the considerations when designing the optics bench. The thesis then presents a step by step methodology of mechanical design of the optics bench assembly. Based on functional requirements of the bench, the best suited material which minimizes vibration sensitivity, thermal gradient, distortion due to impact loading, and cost was selected. The optimal wall thickness of the optics bench was determined by analyzing the results of drop test and vibration analysis. Features to isolate the optics bench assembly from vibration, shock, dust and humidity are also discussed. Thermal analysis was carried out to find out the amount of thermal gradient produced in the optics bench assembly due to thermal heat sources. Based on the results of the thermal analysis, the design of a robust thermal management system is proposed. Guidelines for design for manufacturing, assembly and serviceability were considered at each step of the design process. On the basis of the design requirements and cost considerations, the best suited manufacturing process and surface coating was determined. In conclusion, this thesis offers a foundation and a starting point for the detailed mechanical design of optics bench assembly for UV-LED detector. / by Aditya Shankar Prasad. / M. Eng. in Manufacturing

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (leaf 16). / This research continues the work begun by Sungho Jo and Steve G. Massaquoi on modeling human walking and upright balance. The model of human neurological control of balance and gait generation put forward by Jo and Massaquoi in "A model ofcerebrocerebello-spoinomuscular interaction in the sagittal control of human walking" and executed in MATLAB Simulink/SimMechanics. This model has been used to determine the feed-forward command sequences for the generation of walking and running gaits. Furthermore, two feedback circuits controlling the center of mass relative to the swing leg and the composted leg angle of the simulated model were added. These provide a basis for a wider control of disturbances in order to implement running. This work helps forward the long-term goals of the MIT Sensorimotor Control Group--creating a control model of the neurological circuitry responsible for governing human balance and locomotion and testing that model by using it to control a bipedal robot. The results of this research help to prove the validity of the cerebrocerebello-spinomuscular control model developed by Jo and Massaquoi and point positively towards the introduction of the running of the control model on a physical robot. / by Ellen Cappo. / S.B.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 80-81). / This study was conducted at a medical device production facility where analysis was done on the reliability of Product S barrel molds for the purpose of predicting preventive maintenance (PM) schedule. Pareto Rule was utilized to filter out the defect-types that are causing 80% of the defect occurrences. Defect density was introduced, i.e. the ratio between total number of defects occurred per cavity position to the total types of defects occurring on that same position, as a performance measure to track defects over the mold cavities . Statistical distribution tests on the failure times of the molds were carried out and found that the failure times for the molds differ. Mold failure times follow the log normal or Weibull distribution. Parameter estimates obtained from probability plots of these distributions were used to obtain the mean-time-to-failure (MTTF) and reliability of the molds. Finally, this study looked into the scheduled preventive maintenance (PM) of the molds based on the current PM task list. Failure times based on individual mold PM task lists that correspond to the mitigation of the priority defect-types, were collected and assigned a statistical distribution. After which, we analyzed the expected number of annual mold failures based on the relevant parameters of the failure times distribution and the various PM scheduling policies proposed, to derive a recommendation on the optimal PM interval to be performed in a year. / by Mohammed Faizal B Mohd Fauzi. / M.Eng.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 81-84). / Tool wear is a major obstacle to realizing full automation in metal cutting operations. In this thesis, we designed and implemented a low cost Tool Condition Monitoring (TCM) system using off-the-shelf sensors and data acquisition methods . Peripheral end milling tests were done on a low carbon steel workpiece and the spindle vibration, cutting zone temperature and spindle motor current were recorded. Features from these data sources were used to train decision tree models in MATLAB with the aim of classifying the stages of tool wear. Results showed that the feature sets fusing information from all data sources performed the best, classifying the tool wear stage with up to 93% average accuracy. / by Deborah Ajilo. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 106-107. / by Nathan Graham. / M.S.