Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1991. / Includes bibliographical references (leaves 44-45). / by David H. Yoon. / B.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (leaves 37-41). / The rotator cuff is composed of the supraspinatus, infraspinatus, subcapularis, and teres minor tendons. Rotator cuff injuries are common athletic and occupational injuries that surgery cannot fully repair. Therefore tendon tissue engineering can provide alternatives to surgical solutions. Tendons are composed of parallel lines of bundles of collagen fibers and fibroblasts called fascicles and a glycoprotein, superficial zone protein (SZP), which is expressed by the gene, proteoglycan 4 (PRG4) may play a role in joint and intrafascicular lubrication. Studies have shown that a smooth muscle actin isoform (SMA), which plays a role in the contraction of smooth muscle cells, is expressed in the rotator cuff tendon cells. Previous investigations have been conducted to study PRG4 expression and distribution in different regions of the infraspinatus (ISP) tendon. The aim of this study was to investigate the behavior of adult goat ISP tendon cells and bovine bone marrow-derived mesenchymal stem cells (BMSCs) cultured in three-dimensional pellets in chondrogenic (CM), expansion (EM), and tenogenic media(TM). / (cont.) The focus was on the effects of such growth factors as TGF-[beta]1 and hormones such as dexamethasone and various culture methods, such as the use of 96-well plates and 15 ml tubes, on the ISP tendon cells' and BMSCs' cell proliferation, chondrogenesis, and expression of PRG4 and SMA. ISP tendon cells and BMSCs were obtained from five adult Spanish goats ranging. After 14 days, the pellet cultures were analyzed using Safranin-O staining and immunohistochemical staining for SZP and SMA. The biochemical contents of the cell pellet cultures were also evaluated using a DNA assay on days 0 and 14 and a GAG assay on day 14. It was found that CM, containing TGF-[beta]1 and dexamethasone, induced the most cell proliferation and chondrogenesis. SZP was expressed in all of the ISP tendon cells pellet cultures that were cultured in tubes. In comparison to the larger CM-pellets, the ISP tendon and BMSC EM- and TM- pellets cultured in tubes had higher percentages of SMA present. However SMA was also expressed in the CM-pellets cultured in the 96-well plates. / (cont.) The results of our study showed that environmental differences can change SMA expression. Further investigations on tendon cells and the effects of growth factors, bone morphogenetic proteins (BMPs), and culture methods on the cell proliferation, chondrogenesis, and SZP and SMA expression need to be conducted. / by Harmeet Gill. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (leaves 21-22). / Introduction: While there have been numerous studies demonstrating the effect of bisphosphonates in rats as either a preventative treatment or recovering treatment for osteoporosis, few have directly compared the two treatment alternatives with respect to their effects on bone microstructure and strength. This paper, then, investigates the effects of treatment timing using Zoledronate [ZOL], a potent bisphosphonate, on the lumbar and caudal vertebrae in ovariectomized [OVX], female Wistar rats. Methods: Twenty nine rats were divided into four groups according to their treatment: OVX at week 0 (n=5), OVX+earlyZOL (20 jig/kg s.c. week 0, n=8), OVX+late ZOL (20 jlg/kg s.c. week 8, n=7), and SHAM-OVX (n=9). Results: Micro-computed tomography (giCT) evaluation of six parameters characterizing bone morphology [BV/TV, ConnD, SMI, TbTh, TbNr, and TbSp] showed slightly favorable effects with early ZOL treatment in the fourth lumbar [L4] vertebrae. Compared to SHAM-OVX, OVX has a significantly (p<0.05) lower BV/TV, higher SMI, and TbSp. OVX+earlyZOL had a significantly higher BV/TV than OVX and SHAM-OVX and a lower TbSp than OVX. / (cont.) Decreasing trends but no statistically significant differences were reached in the cortical thickness with treatment, nor were there any differences in bone morphology between the groups in the sixth caudal vertebrae [CD6]. A two-way ANOVA revealed an interaction between the vertebral site and treatment group for BV/TV and TbSp. jCT and static compression tests on the L3 and L4 of rats in a secondary study revealed significant correlations in architectural parameters and biomechanical properties between the two vertebrae. L4 had a higher BV/TV, SMI, and minimum area [minA] and a lower TbNr and TbSp than L3, but L4 had lower values for stiffness, energy to failure [energy], and ultimate load. Regression analysis also showed statistically significant correlations between ultimate load [Uload] and total bone volume [BV], energy and BV, Uload and minA, stiffness and minA, and energy and minA. Conclusion: Results showed slightly favorable trends on bone microstructure for early treatment and demonstrated the potential for clinical advantages using preventative therapy. Upon further research in understanding the vertebrae's response to ZOL at different time points after OVX, treatment for osteoporosis may be better directed. / by Michal Ruchelsman. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008. / Includes bibliographical references (p. 85). / In order to better understand the effects on hydrocarbon emissions of loading, engine temperature, fuel type, and injection timing, a series of experiments was performed. The effect of loading was observed by running the engine at a higher temperature and more open throttle than would typically be observed at fast idle or low load driving. The effects of coolant temperature, the charge motion control valve, spark timing and rail pressure were tested through holding all other variables constant and sweeping through different injection timing to observe the effect on emissions and power output. A new fuel system was designed to allow for the quick testing of different ethanol blends. The system allowed for comparison testing of an 85% ethanol blend to UTG 91 as a function of coolant temperature and injection timing. Measurement of cylinder pressure and hydrocarbon emissions near the exhaust valve allowed for a better understanding of engine operation and the effect of using high ethanol content fuels. Initial testing was also done on 15% and 40% ethanol blends. The results revealed that engine emissions decrease as a function of reduced loading and higher engine temperatures. Sweeps of injection timings for all fuels demonstrated high hydrocarbon emissions for earlier injection timings which fell as injection timing was retarded. A secondary peak was observed in hydrocarbon emissions for an injection timing of approximately 150 CAD aTDC intake. Analysis of rate of fuel injection vs. indicated power revealed a steady decrease in indicated efficiency as injection timing was retarded up to 120 CAD aTDC Intake and then a slow rise in efficiency as the timing was further retarded. The exact causes of the decrease in engine efficiency are unknown; however, possible explanations involve increased heat transfer from the cylinder and piston, fuel loss, and inefficient combustion due to impingement on cold surfaces. / by Ronald Tharp. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 37). / Recent trends of green energy upgrade in commercial buildings show promise for application to residential houses as well, where there are potential energy-saving benefits of retrofitting the residential heating system from single-zone to multi-zone temperature control. The objective of this thesis is to design a physical model to simulate the thermal profile of a residential building with a conventional single-zone central heating system. A scale model of a 2-story house was designed and constructed at 1/20 of the length scale of an average lifesize house, with an external heater and five temperature sensors connected to Vernier LabPro for data acquisition. Comparison between scale model prediction and experimental result shows similarity in steady state values for temperature and characteristic heating/cooling time constants. This thesis is an important first step toward designing a model house for multi-zone heating studies. / by Alice Su-Chin Yeh. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 47-49). / Liver perfusion systems can be used as organ culture platforms for metabolic, genetic and systems engineering, tissue regeneration, pharmacokinetics, organ storage and marginal donor reconditioning for transplantation. The primary requirement of such a system is that it maintain ex vivo organ function in a stable manner for indefinite periods of time. The more physiologically relevant the perfusion system is, the lower the likelihood of incurring functional instability, and the greater the clinical relevance of the data obtained. Currently, a major limiting factor in achieving such a design is the absence of organ-specific in vivo data to standardize, evaluate and optimize the state of perfused livers. Oxygen uptake rate, the primary indicator of organ metabolism and therefore a likely important marker of organ viability, was chosen as one such parameter to be investigated. A systematic review and reproduction of numerous oxygenation conditions cited in the literature in addition to in vivo data sampling across the rat liver shows a significant paucity of oxygen uptake in perfusion compared to in vivo. The reasons stem largely from the biological and mechanical flow properties of the perfusate, but also from the altered metabolic state of the organ in perfusion. In the absence of an oxygen carrier, the liver became oxygen starved and lost functionality. The addition of erythrocytes significantly improved oxygen delivery rates while reducing the flow rate and damaging shear stress. / (cont.) However, as hematocrit approached physiological values perfusate viscosity became detrimentally high, causing severe structural and ultimately functional damage. Large strains of erythrocytes similarly impacted the liver. The addition of sodium heparin reduced erythrocyte-erythrocyte and erythrocyte-parenchyma interaction, thereby reducing sheer stress on the liver. The optimal oxygen carriers were small heparinized erythrocytes, such as goat or rat erythrocytes, at a hematocrit of 12%-20%. These conditions continued to provide adequate in vivo oxygen delivery rates and sustained organ structure and function. / by Maria-Louisa Izamis. / S.M.

Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002. / Includes bibliographical references (p. 165-166). / The feasibility of a magnetic levitation pump for oil well down-hole use is investigated. The design, development, and testing of a closed-loop magnetic levitation pump is presented. This includes the design of the maglev motor, system instrumentation, and mechanical components. The motor angular velocity and motor gap position are controlled with the use of a digital controller. The digital controller utilizes commutation laws for commanding current to the motor based on desired torque and levitation force. The design, simulation, and experimental testing of a proportional controller and a lead compensator for the control of motor velocity and motor gap, respectively, is also discussed. The experimental effort associated with the development of the maglev pump is described in detail. Major topics are the development of models for the system, implementation of control algorithms, and analysis of system response data. Testing verified that motor gap (levitation) and angular velocity are controlled effectively under various pumping conditions. These results prove the feasibility of a closed-loop maglev pump. The pump reached maximum speeds of 1432 RPM during testing, as limited by the motor drive amplifiers. Analysis shows that the pump is capable of reaching 3600 RPM and providing flow and pressure levels equal to conventional submersible pumps, if the current to the motor is increased by a factor of approximately 2.5. Such a current increase is possible without exceeding the thermal limits of the motor. Results show that designing and building magnetic levitation motors for down-hole applications, under the size constraints of current submersible pumps, is feasible. Furthermore, maintaining the levitation gap under pumping conditions and sudden pressure increases is possible through closed-loop control of the motor currents. This work serves as a first step to developing magnetic levitation techniques for down-hole submersible pumps. Suggestions for improvement of the maglev pump are given, and recommendations for future research are presented. / by Christian Daniel Garcia. / S.M.and S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 65-66). / Natural gas produced from shale formations has increased dramatically in the past decade and has altered the oil and gas industry greatly. The use of horizontal drilling and hydraulic fracturing has enabled the production of a natural gas resource that was previously unrecoverable. Estimates of the size of the resource indicate that shale gas has the potential to supply decades of domestically produced natural gas. Yet there are challenges surrounding the production of shale gas that have not yet been solved. The economic viability of the shale gas resources has recently come into question. This study uses a discounted cash flow economic model to evaluate the breakeven price of natural gas wells drilled in 7 major U.S. shale formations from 2005 to 2012. The breakeven price is the wellhead gas price that produces a 10% internal rate of return. The results of the economic analysis break down the breakeven gas price by year and shale play, along with P20 and P80 gas prices to illustrate the variability present. Derived vintage supply curves illustrate the volume of natural gas that was produced economically for a range of breakeven prices. Historic Natural Gas Futures Prices are used as a metric to determine the volumes and percentage of total yearly production that was produced at or below the Futures Price of each vintage year. From 2005 to 2008, the total production of shale gas resulted in a net profit for operators. A drop in price in 2009 resulted in a net loss for producers from 2009 to 2012. In 2012, only 26.5% of the total gas volume produced was produced at or below the 2012 Natural Gas Futures Price. / by Christopher D. Hammond. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (p. 139-140). / In product development organizations, the front end of product development is usually confined to planning within business units for product families and individual products. This can pose a problem for businesses, as individual business units and development teams do not think in terms of the big picture of the company. Business units are responsible for only their market and product strategies, and are relatively unconcerned about those of other business units. Because of this, there is the potential for product offerings across business units to overlap in the marketplace, thereby wasting development resources and confusing customers with multiple offerings of similar value propositions. There is also the potential to have gaps in the marketplace, where no business units have product offerings, which can be a prime niche for competitors to introduce products to gain a market foothold and precious market share. The purpose of this research was to "extend" the front end of the development process upward across all business units in order to understand the market relationships across the entire product-offering portfolio. This allows the company to see how its products are related across markets, and to observe the strengths and weaknesses in il'> competitive positions. The result is a better understanding of which markets and products should be prioritized when making investment decisions. This thesis develops and discusses several concepts and tools, namely those of the Core Benefit Proposition and Vector of Differentiation, that are necessary in order to identify the gaps and overlaps within a product portfolio. A basic approach was developed that combines these concepts and tools into a framework for identifying gaps and overlaps. This approach was then applied and demonstrated with a case study involving the product portfolio of the Xerox Company. / by John Andrew Hull. / S.M.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 1999. / Includes bibliographical references. / by Kuo-shen Chen. / Ph.D.