Página 7 dos resultados de 10406 itens digitais encontrados em 0.010 segundos
Resultados filtrados por Publicador: Massachusetts Institute of Technology

‣ A detailed performance comparison of distillate fuels in the Texaco stratified charge engine

Marsh, Gordon Dean
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 202 [i.e. 203] leaves; 8716546 bytes; 8738176 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
672.7397%
by Gordon D. Marsh.; Thesis (Ocean E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1976.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.; Includes bibliographical references.

‣ Actuation of shape memory polymer using magnetic fields for applications in medical devices

Buckley, Patrick Regan, 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 144 leaves; 6373979 bytes; 6373786 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
672.8755%
A novel approach to the heating and actuation of shape memory polymer using dispersed Curie temperature thermo-regulated particles is proposed. Such a material has potential applications in medical devices which are delivered via catheters. A variety of tests were performed to determine the feasibility of this new approach to shape memory polymer actuation. Calorimetry tests were performed to quantify heat generation of various Nickel Zinc Ferrite particles. Dynamic Mechanical Thermal Analysis (DMTA), tensile strain recovery tests, and Differential Scanning Calorimetry (DSC) were used to measure the mechanical effects of various particle volume contents and sizes on shape memory polymer. These tests suggest that the proposed method of actuation is very feasible, rapid heating can be achieved and the addition of particles up to 10% volume content has a minimal effect on the mechanical properties of the shape memory polymer.; by Patrick Regan Buckley.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.; "June 2004."; Includes bibliographical references (leaves 102-105).

‣ Induction heating of a metallic cylinder

Schlecht, Martin F
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 95 leaves; 4108422 bytes; 4108181 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
672.7397%
by Martin Frederick Schlecht.; Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1977.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.; Includes bibliographical references.

‣ Dynamics and statics of actin assemblies

Shin, Jennifer Hyunjong, 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 101 p.; 5409531 bytes; 5421196 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
672.8755%
The conversion of chemical energy into mechanical forces that powers cell movements is a ubiquitous theme across biology. The acrosome reaction of Limulus sperm is a simple example of such a dynamical transformation where a 60 [mu]m-long crystalline bundle of actin filaments, tightly cross-linked by actin bundling protein scruin, straightens from a coiled conformation and extends from the cell in five seconds. This spring-like mechanism represents a third type of actin-based motility that is distinctly different from the better known polymerization or myosin-driven processes. To identify the basis and mechanism for this movement, we examine the possible sources of chemical and mechanical energy and show that the stored elastic energy alone is sufficient to drive the reaction. We also provide an estimate of the maximum force generated during the uncoiling by stalling the bundle using an agarose gel. Finally, we provide a simple mathematical model that rationalizes the dynamics of uncoiling. Motivated by the very stiff cross-linking in the bundle induced by scruin, we next turn to a model system of scruin mediated cross-linked actin networks where the elastic response is dominated by the properties of actin. While the biological significance of the actin cross-linking proteins is well documented...

‣ Atomistic simulations of octacyclopentyl polyhedral oligomeric silsesquioxane polyethylene nanocomposites; Atomistic simulations of CpPOSS/PE nanocomposites

Capaldi, Franco Mario, 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 142 leaves; 7721095 bytes; 7728524 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
672.8755%
As the scientific community develops the ability to create composites which incorporate nanoscopic filler particles, the detailed atomic arrangement and atomic interactions become significant in determining the composite properties. Nanoscopic fillers such as carbon nanotubes, polyhedral oligomeric silsesquioxane (POSS), and layered silicates have already been successfully used to improve the thermal and mechanical properties of polymers. On this length scale, details describing particle organization, interaction between particles, and interactions between particle and matrix are needed to understand the behavior of the composite. In this thesis, we use atomistic simulations to investigate the detailed behavior of a blended octacyclopentyl polyhedral oligomeric silsesquioxane (CpPOSS) / polyethylene (PE) nanocomposite. The model potential employed to describe the atomic interactions in these systems is capable of reproducing the experimental vibrational and crystal structures for the POSS well. The mechanical properties of an infinite crystal were calculated. The), are anisotropic with a Reuss average isotropic elastic modulus of 11.78 GPa. Simulations of CpPOSS/PE composites revealed that the POSS had a stiffening effect on the polymer. Simulations revealed that both PE and POSS dynamics as measured by translational and rotational diffusivities decreased...

‣ Design of a biomimetic pectoral fin joint in an artificial fish

Peña, Vanessa, 1982-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 41 leaves; 2942102 bytes; 2942047 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
672.8755%
A biomimetic design of the muscle joint in a pectoral fish fin was produced based on comparisons with four design models. All four design models consisted of a mechanical joint connection and incorporated the functional operation of the pectoral fish fin rays when affected by specific actuators, such as induced contractions of conducting polymer strands. Design constraints of the joint were determined by the fundamental kinematic elements of motion determined in the Bioinstrumentation Laboratory. A mechanical pin-joint provided correct simulation of movements specialized for this phase of the development of an artificial fish fin. A compression spring with a spring coefficient of K=0.45 was used as a mechanical means to imitate the biological energy conservations produced by each stroke of the pectoral fin. The joint was designed to adhere to displacements by conducting polymer actuators that induced a 2.0% maximal strain on the fish fin ray.; by Vanessa Pena.; Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.; Includes bibliographical references (leaf 41).

‣ Stimulation of angiogenesis through collagen gel by applying shear stress and interstitial flow

Ranka, Mitun P
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 38 leaves; 1906657 bytes; 1906202 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
672.8755%
The induction of angiogenesis has been documented in many diseases such as cancer, arthritis, and diabetes. Angiogenesis can be stimulated by a variety of signals including a mechanical stress applied to the apical side of endothelial cells. To get a better understanding of this mechanical stimulus, a parallel plate flow chamber was designed and tested to elicit a constant laminar flow onto a monolayer of endothelial cells. The goal of this research was to develop a more physiologically similar in vitro system to study the effects of shear stress on endothelial cells. Unlike prior flow chamber apparatus, this chamber allows the cells to be seeded on collagen gel rather than a rigid substrate to more closely mimic in vivo environment. A shear stress of I Pa was applied to the endothelial cells for a duration of 36 hours. Results show that after flow was initiated for this duration, a change in shape of the endothelial cells can be seen when compared to the static condition. Elongation and alignment of cells plated on collagen gel can be seen in the direction of flow, though not at pronounced as the elongation typically seen from cells plated on rigid substrates. Nuclear and F-actin staining also revealed similar results.; (cont.) The nuclear staining revealed a confluent monolayer formation occurred prior to flow and was maintained throughout the experiment. A change in organization of the F-actin fibers...

‣ Constitutive modeling of the finite deformation behavior of membranes possessing a triangulated networked microstructure

Arslan, Melis
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 114 p.; 5191240 bytes; 5195975 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
672.8755%
Many biological, natural and synthetic materials possess a networked or micro-truss-like microstructure. In this thesis work, a general microstructurally-informed continuum level constitutive model of the large stretch behavior of membranes possessing a triangulated network or truss-like structure is developed. As a specific example, a constitutive model of the stress-strain behavior of the red blood cell membrane is developed. The mechanical behavior of the membrane of the red blood cell is governed by two primary microstructural features: the lipid bilayer and the underlying spectrin network. The lipid bilayer is analogous to a 2D fluid in that it resists changes to its planar area, yet poses little resistance to planar shear. A skeletal network of spectrin molecules is crosslinked to the lipid bilayer and provides the shear stiffness of the membrane. The planar triangulated structure of the spectrin network is used to identify a representative volume element (RVE) for the model. A strain energy density function in terms of an arbitrary planar deformation field is proposed using the RVE. Differentiation of the strain energy density function provides expressions for the general multiaxial stress-stretch behavior of the material.; (cont.) The stress-strain behavior of the membrane when subjected to uniaxial and simple shear loading conditions in different directions is given...

‣ High bandwidth rotary fast tool servos and a hybrid rotary/linear electromagnetic actuator; High bandwidth rotary FTS and a hybrid rotary/linear electromagnetic actuator

Montesanti, Richard Clement
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 555 p.; 37075371 bytes; 37075130 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
672.8755%
This thesis describes the development of two high bandwidth short-stroke rotary fast tool servos and the hybrid rotary/linear electromagnetic actuator developed for one of them. Design insights, trade-off methodologies, and analytical tools are developed for precision mechanical systems, power and signal electronic systems, control systems, normal-stress electromagnetic actuators, and the dynamics of the combined systems. A fast tool servo (FTS) is a high-speed auxiliary servo axis that is added to a diamond turning machine (ultra-precision lathe) to allow generating free-form non-axisymmetric or textured surfaces on a workpiece. A rotary fast tool servo produces an in-and-out motion of the tool relative to a workpiece by swinging the tool along an arc having a fixed radius. The rotary fast tool servos developed in this project were designed for diamond turning prescription textured surfaces on small spherical workpieces (diameters in the range of 10 mm or less), and are suitable for generating free-form non-axisymmetric surfaces on similar-sized workpieces. Straightforward modifications would allow them to be used on larger workpieces. These rotary fast tool servos set new benchmarks for demonstrated closed-loop bandwidth (2 kHz and 10 kHz) and tool tip acceleration (400 g).; (cont.) The first machine...

‣ Optimizing cellular attachment and function in long-term hepatocyte cultures using polyelectrolyte multilayer surface modification

Wu, Jonathan (Jonathan G.)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 38 leaves
Português
Relevância na Pesquisa
672.8755%
Hepatocyte morphology is known to be closely linked to cellular functions. As a result, morphogenesis is extremely important to attain organ-equivalent levels of tissue function from in vitro cultures. Thus, a challenge exists in designing materials suitable for supporting liver-derived cells that are not only biochemically hepatospecific but also biophysically sensitive to the mechanical nature of hepatocytes to achieve highly differentiated cell phenotype found in a natural liver. We employ a unique substrate material system of polyelectrolyte multilayers (PEM) that can be tuned to achieve mechanical compliances of several orders of magnitudes (Es = 105 to Es = 108 Pa). We have shown that PEM modification can effectively change the surface mechanical compliance, and, thus, hepatocyte morphology and attachment, by looking at varying PEM pH deposition conditions (pH 2.0, 4.0, and 6.5) and collagen concentrations (0, 3, 10 ug/cm ) on different materials (tissue-culture polystyrene, polycarbonate, and Permanox). For all materials, PAH/PAA 4.0/4.0 provided the balance of cellular attachment that appeared neither confluent nor sparse while also promoting a natural hepatocyte phenotype.; (cont.) We also observed that PEM films can effectively mask any inherent substrate material properties. Therefore...

‣ An investigation of the contribution of the multi-joint arm stiffness to the motor control defecit [sic] experienced in ataxia; Investigation of the contribution of the multi-joint arm stiffness to the motor control deficit experienced in ataxia

Oni, Olumuyiwa A. (Olumuyiwa Adetokunbo)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 20 p.
Português
Relevância na Pesquisa
672.8755%
Prior research has shown that the control response of the limbs is affected by the mechanical properties of the limb and the feedback properties of the CNS. Cerebellar ataxia describes a situation in which damage to the cerebellum results in compromised motor control. It is characterized by such things as a clumsy or disturbed gait, a lack of balance and coordination, and unsteady speech patterns; for severe cases of ataxia, gross muscle coordination can degenerate to the point where successful, coordinated movements are not possible. In order to better understand the control deficit experienced by ataxic persons, estimates of the feedback properties of the CNS and the limb-muscle mechanical properties and will be necessary. Specifically, this investigation hopes to determine to what extent ataxia is cause by abnormal effective stiffness. Because ataxic patients do not exhibit deficits in strength or postural maintenance, we hypothesize a priori that the measured stiffness of ataxic subjects will be normal. We test this by conducting postural stiffness study on an ataxic subject, and measuring stiffness for two degrees of subject co-activation - minimal subject co-activation and maximal subject co-activation - and for different equilibrium postures.; (cont.) Because the observed kinematic trajectory following neuromuscular activation...

‣ Carbon nanotube based electromechanical probes

Yaglioglu, Onnik, 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 137 p.
Português
Relevância na Pesquisa
672.8755%
Electromechanical probing applications continuously require smaller pitches, faster manufacturing and lower electrical resistance. Conventional techniques, such as MEMS based cantilever probes have their shortcomings in terms of the lowest pitch that can be achieved, cost and yield. Given their promising mechanical and electrical properties, carbon nanotubes (CNTs) are strong candidates for future probing applications. A new class of metal-CNT hybrid electromechanical probes is presented where vertically aligned carbon nanotube structures, grown with a chemical vapor deposition (CVD) technique, act as elastic springs, and a metal coating on the probes is used for increased electrical conduction. This design and architecture presents a scalable approach where thousands of probes can be fabricated in very short production times. 1.5 Ohm resistance and reliable performance for 6000 cycles at 50 [mu]m over-travel was achieved for a column of 200 [mu]m x 200[mu]m cross-section and 1plm of Au deposition. In-situ scanning electron microscope mechanical compression tests revealed a unique deformation mechanism of the CNT structures where continued compression results in successive buckle formation which later can serve as micro-bellows and elastic springs.; (cont.) A novel stiffness tuning method is presented to control the elastic properties of a given CNT probe by controlling the initial compressing amount. Further stiffness tuning is achieved by changing gas composition during CVD growth where CNT diameter and density is modified. Lateral compression and densification tests show that these CNT structures are highly anisotropic and have very different deformation mechanisms in vertical and lateral directions. Mechanical properties resulting from two main CVD growth techniques...

‣ Biomechanics of cervical function in pregnancy : case of cervical insufficiency

Paskaleva, Anastassia
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 212 p.
Português
Relevância na Pesquisa
672.8755%
The uterine cervix is a passive organ in the female body. Its normal function in pregnancy is to stay firm and closed for the duration of the gestation. At term, under the action of coordinated contractions from the myometrium the cervix dilates sufficiently to allow for the delivery of the fetus. Cervical insufficiency refers to a condition in which the cervix dilates asymptomatically and painlessly in the absence of contractions from the uterine smooth muscle and results in a spontaneous pregnancy loss between the second and third trimester of pregnancy. An elusive and often misdiagnosed condition, cervical insufficiency accounts for a significant percentage of extremely premature deliveries with high incidence of infant mortality and morbidity. Accurate diagnostic criteria and treatment guidelines for this condition are not established and remain a clinical and research challenge. In an attempt to better understand the biomechanics of cervical insufficiency, a fully three-dimensional constitutive model for the large strain, time dependent mechanical behavior of the cervical stroma is proposed. The constitutive model is implemented numerically and integrated with a three dimensional solid model of the lower pelvic region of a pregnant patient into a finite element framework. The resulting finite element model provides a tool to study the effects of different clinical features on the biomechanics of the pregnant cervix and uterus...

‣ Linear to nonlinear rheology of bread dough and its constituents

Ng, Shen Kuan (Trevor Shen Kuan)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 282 p.
Português
Relevância na Pesquisa
672.8755%
There are many practical reasons for studying the deformational behavior or rheological properties of a dough system. The mass production of bread has led to a need of machines that are able to handle and process large volumes of dough. An understanding of the deformational properties can aid in designing machines of this kind. Less obviously, the texture of the bread we eat is governed by the mechanical properties of the dough from which it is proofed and baked from. During the bread making process, large non-linear deformations feature prominently. In mixing and kneading, dough is stretched and sheared by hand or by specially designed mixing devices, while in proofing and baking, the expansion of gas cells causes significant extensional strain on the surrounding dough. Other than directly affecting the moduli of the fibers and membranes in the solid phase of bread, a link between the rheology of dough and the baked loaf volume has also been established. In this thesis, we first develop consistent and accurate techniques for measuring the rheological properties of the dough. Good experimental techniques and protocols are essential for studying the mechanical properties of such a sticky, visco-elasto-plastic, time-dependent material. We modify some of the standard rheometric hardware and protocols to accommodate this unusual material. Special attention is given to nonlinear deformations such as uniaxial extensional flows and large amplitude oscillatory shear flows (LAOS). We use the new techniques to probe the microstructure of dough and its constituents from a mechanical viewpoint. The strongly nonlinear rheological properties of dough arise from the interactions of a protein matrix and a high filler concentration consisting of hydrated starch particles.; (cont.) We demonstrate that the gluten protein that imbues the dough with its characteristic viscoelasticity should be considered as a transient network that is interconnected by finitely extensible biopolymer segments (-20nm mesh size) and held together by hydrogen bonds and/or hydrophilic interactions. Using this renewed understanding of the microstructure...

‣ Experimental methods by optical trapping for investigation of leukocyte cell rolling mechanics

Navarro, Sergio Michael
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 52 leaves
Português
Relevância na Pesquisa
672.8755%
This thesis focuses on the design and implementation of a range of experimental methods by optical trapping in order to investigate the mechanical behavior of the leukocyte cell membrane as it undergoes cell rolling. Membrane tethers extracted from the cell during rolling function to slow the cell down and to maintain contact with the endothelial wall. Understanding the dynamic behavior of the leukocyte membrane during rolling motion sheds much insight on the relationship between stages of cell immunological response and the mechanical processes occurring on the surface of the cell membrane. Traditionally, the membrane response during rolling has been probed by simulating the tethering phenomenon in vitro. However, previous work has focused on pulling tethers at a constant velocity where as during in vivo rolling the tether extension will be a function of time. The fundamental differences between constant velocity and rolling-like leukocyte tethering as well as the role of the membrane-cytoskeleton interactions during tethering were specifically focused on in this study. Research work relied on the development of biomechanical optical trapping experiments occurring in an in-vitro setting in an attempt to elucidate an accurate mechanical model accurately describing behavior of the cell during rolling. Initial results indicate that the forces necessary to pull tethers from an immortalized B cell line ranged from 40 pN to 200 pN during linear dynamic behavior...

‣ Wavelet based similarity measurement algorithm for seafloor morphology

Darilmaz, İlkay
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 73 leaves; 2975828 bytes; 2978807 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
674.1066%
The recent expansion of systematic seafloor exploration programs such as geophysical research, seafloor mapping, search and survey, resource assessment and other scientific, commercial and military applications has created a need for rapid and robust methods of processing seafloor imagery. Given the existence of a large library of seafloor images, a fast automated image classifier algorithm is needed to determine changes in seabed morphology over time. The focus of this work is the development of a robust Similarity Measurement (SM) algorithm to address the above problem. Our work uses a side-scan sonar image library for experimentation and testing. Variations of an underwater vehicle's height above the sea floor and of its pitch and roll angles cause distortion in the data obtained, such that transformations to align the data should include rotation, translation, anisotropic scaling and skew. In order to deal with these problems, we propose to use the Wavelet transform for similarity detection. Wavelets have been widely used during the last three decades in image processing. Since the Wavelet transform allows a multi-resolution decomposition, it is easier to identify the similarities between two images by examining the energy distribution at each decomposition level.; (cont.) The energy distribution in the frequency domain at the output of the high pass and low pass filter banks identifies the texture discrimination. Our approach uses a statistical framework...

‣ Modeling the deformation and failure behavior of FCC and HCP nanocrystalline materials

Wei, Yujie, Ph. D. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 188 p.
Português
Relevância na Pesquisa
672.8755%
As foreseen by Richard Feynman in his famous talk titled There's Plenty of Room at the Bottom in 1959, scientists nowadays are miniaturizing structures in materials to achieve better performance as concerned in technical applications. Reducing grain sizes in polycrystalline materials into the range of less than 100nm, for example, could achieve extraordinary high strength in these so called nanocrystalline (nc) materials. The reduced grain size gives rise to new deformation mechanisms in nc materials. It is now widely accepted that there is a strong interplay between dislocation-based deformation in the crystalline grain interiors and the inelastic deformation mechanisms operative in the grain-boundary regions. Grain-boundary regions play an increasingly significant role as the grain size decreases below the 100nm level. In this dissertation, constitutive models have been developed to investigate the deformation mechanisms of nc materials, with focus on modeling grain-boundary decohesion in nc materials. Two micromechanical models have been developed to capture the deformation in grain boundaries in nc materials.; (cont.) To the end, a phenomenological constitutive model has been developed for powder-processed nc materials, where the plastic flow could be pressure-dependent...

‣ Improving shipboard maintenance practices using non-intrusive load monitoring

Piber, Mark A. (Mark Augustin)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 50 leaves
Português
Relevância na Pesquisa
674.1066%
(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...

‣ Ultrasound : an alternative solution for removing tattoos

Teng, Jennifer
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 70 p.; 5594864 bytes; 5597541 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
673.8433%
The recent influx of tattoos has been accompanied by a rise in demand for tattoo removals. Due to the recent success of ultrasound as a noninvasive alternative for multiple medical therapies, the feasibility of ultrasound-mediated tattoo removals will be investigated in this thesis. During tattoo applications, dermal cells consume and store tattoo particles in vacuoles in the same manner fat cells store lipids. It is therefore assumed that tattooed cells adopt an "effective density" analogous to the way fat cells develop a lower density. Using this change in mechanical property, the hypothesis is that focused, high frequency ultrasound can target tattooed cells. These cells may be selectively disrupted based on differences in mechanical and acoustic properties between healthy and tattooed cells. As no previous studies have investigated the ultrasound effects or mechanical properties of particle-filled cells, a preliminary model of crudely simulated tattooed cells is designed treating each cell as a homogenous structure. Microspheres of various materials are used to represent and generate a range of density and elasticity that capture these effective properties.; (cont.) This thesis applies this preliminary model to a pilot study examining the interactions of ultrasound with glass and polystyrene microspheres. Microspheres were suspended in agar gel samples to simulate tattooed cells. Each gel sample underwent a series of ultrasound treatments. Two sets of experiments were conducted for each microsphere type testing the variables of intensity...

‣ Desktop systems for manufacturing carbon nanotube films by chemical vapor deposition; Desktop systems for manufacturing CNT films by CVD

Kuhn, David S. (David Scott)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 147 leaves
Português
Relevância na Pesquisa
672.8755%
Carbon nanotubes (CNTs) exhibit exceptional electrical, thermal, and mechanical properties that could potentially transform such diverse fields as composites, electronics, cooling, energy storage, and biological sensing. For the United States Navy, composites potentially provide a significant decrease in lifetime maintenance costs of ships by eliminating hull corrosion. A stronger composite could also improve naval ship survivability or increase combat payloads by reducing the hull weight of ships and submarines. Further, cooling requirements of ship borne electronics have grown exponentially and represent a significant weight penalty for advanced ship designs. Any improvement in thermal transport could significantly improve future naval ship designs. In order to realize these benefits, methods must be discovered to fully characterize CNT growth mechanisms, consistently produce CNTs in manufacturable quantities, and to integrate CNTs into macroscale structures which reflect the properties of individual CNTs. While growth of CNTs in laboratory scale chemical vapor deposition (CVD) tube furnaces has shown great promise, existing low cost tube furnace designs limit the researcher's ability to fully separate critical reaction parameters such as temperature and flow profiles and limit the rate of temperature change during the growth process.; (cont.) Conventional tube furnace designs also provide limited mechanical access to the growth site and prevent optical monitoring of the growth site...