Thesis (M.S.)--Rochester Institute of Technology, 2008. / Typescript. Includes bibliographical references (leaves 80-84).

With the astronomical increase in cellular traffic, there is need to cut down on the power consumption so as to reduce CO2 emissions and in the process lowering network operational expenditure (OPEX). In this thesis, one method that can be used to lower a Base Station energy consumption is proposed. Traditional cellular networks are designed to offer maximum coverage and connectivity for peak traffic. This is not energy efficient since a lot of energy will go to waste during the time cellular traffic is very low. The scheme that was developed, identifies Base Stations that have very low traffic loads and User Equipment that can all be transferred to neighbouring Base Stations and put the Base Stations to sleep for as long as necessary to save energy and to maintain Quality of Services (QoS) at an acceptable level. The Next Generation Networks (specifically 5G) will be heterogeneous networks as heterogeneous are a promising solution in increasing network performance especially in providing indoor and cell-edges coverage. The solution that was developed in this thesis was specifically designed to work with heterogeneous networks and its performance was also tested on heterogeneous networks. OMNeT++ V4.6 together with INET 2.3.0 and SimuLTE 9.1 were used for the validation of the proposed scheme. After extensive simulations were carried out, it was concluded that some Base Stations in a cellular network, can be put to sleep during the time that cellular traffic is low without compromising the Quality of Service. End-to-end delay, sum throughputs, queue length and Channel Quality Indicator were some of the performance metrics that were used to check whether the developed scheme did not reduce the QoS of a network. / Electrical and Mining Engineering / M. Tech. (Electrical Engineering)

O desenvolvimento de novos materiais a partir de elementos biodegradáveis com durabilidade considerável, versatilidade apreciável e baixo custo tem grande interesse na aplicação da bio-eletrônica. O presente trabalho objetiva a caracterização das propriedades físicas e químicas das membranas de quitosana obtidas a partir da neutralização da solução policatiônica de quitosana. O trabalho foi dividido em duas etapas: solubilização e neutralização. Na primeira etapa a quitosana foi solubilizada em três concentrações diferentes de ácido acético (1%, 0.8% e 0.5%) para avaliar se a concentração de ácido exerce diferença significativa nas propriedades físico-químicas das membranas de quitosana. Na segunda etapa o policátion de quitosana foi neutralizado com duas bases fortes (NaOH e KOH) em três concentrações molares diferentes (0.5, 1 e 5 molar) pelo método de gotejamento lento da base até atingir o pH de 6.0 no policátion e obter membranas com pH perto da neutralidade. A caracterização das membranas obtidas a partir do policátion de quitosana neutralizado mostrou que as concentrações de ácido acético não mudam de forma significativa as propriedades físico-químicas das membranas. Em contraste, o processo de neutralização afetou as propriedades físico-químicas das membranas, e em particular, diferentes comportamentos foram observados dependendo da base utilizada. Membranas mais dúcteis foram obtidas após neutralização com KOH, exibindo capacidade plastificante pela base usada, enquanto que as membranas neutralizadas com NaOH apresentam um comportamento frágil. Além disso, as membranas neutralizadas com KOH exibem uma maior condução iônica em relação às propriedades elétricas das membranas, o qual pode ser interessante no desenvolvimento de biossensores ou célula combustível. / The development of new materials from biodegradable elements with considerable durability, versatility and low cost is of great interest for applications in bioelectronics. The present work aims the characterization of the chemical and physical properties of chitosan membranes after neutralization of the polycation solution of chitosan. This work was divided into two steps: solubilization and neutralization. In the first step, the chitosan was solubilized with three different concentrations of acetic acid (1%, 0.8% and 0.5%) in order to evaluate whether the acid affects the physical-chemical properties of the chitosan films. In the second step, the polycation of chitosan was neutralized with two different strong bases (NaOH and KOH) using three different molar concentrations (0.5, 1 and 5), by the slow drip method of base until reaching a pH of 6.0 for the polycation and obtaining films with pH close to neutrality. The characterization of the membranes obtained from neutralized chitosan showed that the different concentrations of acetic acid did not affect the physical-chemical properties of the films significantly. In contrast, the neutralization process did affect the physical-chemical properties, and particularly, different behaviors were observed depending on the type of base used for neutralization. More ductile films were obtained after neutralization with KOH, exhibiting plastificant capacity by the used base, whereas the films neutralized with NaOH exhibited a more fragile behavior. Beyond this, regarding the electrical properties, the films with KOH presented a higher ionic conductivity, which could be interesting for developing biosensors or fuel cells.

Much recent research has focused on the development lead-free perovskite piezoelectrics as environmentally compatible alternatives to lead zirconate titanate (PZT). Two main categories of lead free perovskite piezoelectric ceramic systems were investigated as potential replacements to lead zirconate titanate (PZT) for actuator devices. First, solid solutions based on Li, Ta, and Sb modified (K���.���Na���.���)NbO��� (KNN) lead-free perovskite systems were created using standard solid state methods. Secondly, Bi-based materials a variety of compositions were explored for (1-x)(Bi���.���Na���.���)TiO���-xBi(Zn���.���Ti���.���)O��� (BNT-BZT) and Bi(Zn���.���Ti���.���)O������(Bi���.���K���.���)TiO������(Bi���.���Na���.���)TiO��� (BZT-BKT-BNT). It was shown that when BNT-BKT is combined with increasing concentrations of Bi(Zn[subscript 1/2]Ti[subscript 1/2])O��� (BZT), a transition from normal ferroelectric behavior to a material with large electric field induced strains was observed. The higher BZT containing compositions are characterized by large hysteretic strains (> 0.3%) with no negative strains that might indicate domain switching. This work summarizes and analyzes the fatigue behavior of the new generation of Pb-free piezoelectric materials. In piezoelectric materials, fatigue is observed as a degradation in the electromechanical properties under the application of a bipolar or unipolar cyclic electrical load. In Pb-based materials such as lead zirconate titanate (PZT), fatigue has been studied in great depth for both bulk and thin film applications. In PZT, fatigue can result from microcracking or electrode effects (especially in thin films). Ultimately, however, it is electronic and ionic point defects that are the most influential mechanism. Therefore, this work also analyzes the fatigue characteristics of bulk polycrystalline ceramics of the modified-KNN and BNT-BKT-BZT compositions developed. The defect chemistry that underpins the fatigue behavior will be examined and the results will be compared to the existing body of work on PZT. It will be demonstrated that while some Pb-free materials show severe property degradation under cyclic loading, other materials such as BNT-BKT-BZT essentially exhibit fatigue-free piezoelectric properties with chemical doping or other modifications. Based on these results, these new Pb-free materials have great potential for use in piezoelectric applications requiring a large number of drive cycles such as MEMS devices or high frequency actuators. / Graduation date: 2013

O desenvolvimento de novos materiais a partir de elementos biodegradáveis com durabilidade considerável, versatilidade apreciável e baixo custo tem grande interesse na aplicação da bio-eletrônica. O presente trabalho objetiva a caracterização das propriedades físicas e químicas das membranas de quitosana obtidas a partir da neutralização da solução policatiônica de quitosana. O trabalho foi dividido em duas etapas: solubilização e neutralização. Na primeira etapa a quitosana foi solubilizada em três concentrações diferentes de ácido acético (1%, 0.8% e 0.5%) para avaliar se a concentração de ácido exerce diferença significativa nas propriedades físico-químicas das membranas de quitosana. Na segunda etapa o policátion de quitosana foi neutralizado com duas bases fortes (NaOH e KOH) em três concentrações molares diferentes (0.5, 1 e 5 molar) pelo método de gotejamento lento da base até atingir o pH de 6.0 no policátion e obter membranas com pH perto da neutralidade. A caracterização das membranas obtidas a partir do policátion de quitosana neutralizado mostrou que as concentrações de ácido acético não mudam de forma significativa as propriedades físico-químicas das membranas. Em contraste, o processo de neutralização afetou as propriedades físico-químicas das membranas, e em particular, diferentes comportamentos foram observados dependendo da base utilizada. Membranas mais dúcteis foram obtidas após neutralização com KOH, exibindo capacidade plastificante pela base usada, enquanto que as membranas neutralizadas com NaOH apresentam um comportamento frágil. Além disso, as membranas neutralizadas com KOH exibem uma maior condução iônica em relação às propriedades elétricas das membranas, o qual pode ser interessante no desenvolvimento de biossensores ou célula combustível. / The development of new materials from biodegradable elements with considerable durability, versatility and low cost is of great interest for applications in bioelectronics. The present work aims the characterization of the chemical and physical properties of chitosan membranes after neutralization of the polycation solution of chitosan. This work was divided into two steps: solubilization and neutralization. In the first step, the chitosan was solubilized with three different concentrations of acetic acid (1%, 0.8% and 0.5%) in order to evaluate whether the acid affects the physical-chemical properties of the chitosan films. In the second step, the polycation of chitosan was neutralized with two different strong bases (NaOH and KOH) using three different molar concentrations (0.5, 1 and 5), by the slow drip method of base until reaching a pH of 6.0 for the polycation and obtaining films with pH close to neutrality. The characterization of the membranes obtained from neutralized chitosan showed that the different concentrations of acetic acid did not affect the physical-chemical properties of the films significantly. In contrast, the neutralization process did affect the physical-chemical properties, and particularly, different behaviors were observed depending on the type of base used for neutralization. More ductile films were obtained after neutralization with KOH, exhibiting plastificant capacity by the used base, whereas the films neutralized with NaOH exhibited a more fragile behavior. Beyond this, regarding the electrical properties, the films with KOH presented a higher ionic conductivity, which could be interesting for developing biosensors or fuel cells.

No description available.

[ES] El objetivo principal de esta investigación es desarrollar y determinar un proceso de fabricación de bajo coste de sensores basados en grafito para su aplicación en la captura del movimiento del cuerpo humano siendo integrados en prendas textiles y el diseño de una piel electrónica que pueda simular el sentido del tacto. Se centra de manera primordial en dos aspectos cruciales: la accesibilidad y la aplicabilidad de la tecnología. Para ello, se ha priorizado el uso de componentes de fácil adquisición y materiales biocompatibles en todas las etapas del proceso. Bajo la premisa de una fabricación de bajo coste, el proceso de fabricación consiste en una sencilla transferencia y exfoliación de una pasta de grafito, la formulación de la cual también ha sido objeto de estudio en el presente trabajo, sobre sustratos poliméricos, obteniéndose de esta forma unas láminas flexibles, con el grafito adherido y dispersado sobre ellas. Estos sensores así fabricados exhiben una alta sensibilidad al tacto, una buena respuesta en frecuencia y una alta durabilidad. Para caracterizar su respuesta, así como la estabilidad y reproducibilidad del método de fabricación, se ha desarrollado un método ad hoc que pretende recrear la interacción del sensor con un dedo humano, el cual es mostrado con detalle. Estos ensayos que conforman este método ad hoc pasan por un ensayo a compresión parametrizado de 0 N a 30 N, un análisis de la señal bajo cargas constantes, los cálculos del error de histéresis, la respuesta en frecuencia y el factor de galga, y el análisis de fatiga a flexión llegando a más de 100.000 ciclos en un recorrido de 0¿ a 100 ¿. Así mismo, se ha analizado la estructura de los sensores mediante microscopía electrónica de emisión de campo (FESEM) y microscopía óptica. Para finalizar se han realizado dos prototipos abordando cada uno de los objetivos. El resultado presentado es una lámina de grafito que no supera los 70 µm que conforma un sensor de alta sensibilidad, con el cual se llegaron a detectar presiones de 0,05 N, estable con desviaciones menores a un 5% en largos tiempos de reposo, mayor a 25 minutos, fácilmente integrable y con múltiples posibilidades de aplicación, como por ejemplo en prótesis inteligentes, en sistemas de captura del movimiento del cuerpo humano y hasta incluso para su uso como piel sintética. / [CA] L'objectiu principal d'esta investigació és desenvolupar i determinar un procés de fabricació de baix cost de sensors basats en grafit per a la seua aplicació en la captura del moviment del cos humà sent integrats en peces tèxtils i el disseny d'una pell electrònica que puga simular el sentit del tacte. Es centra de manera primordial en dos aspectes crucials: l'accessibilitat i l'aplicabilitat de la tecnologia. Per a això, s'ha prioritzat l'ús de components d'adquisició fàcil i materials biocompatibles en totes les etapes del procés. Baix la premissa d'una fabricació de baix cost, el procés de fabricació consistix en una senzilla transferència i exfoliació d'una pasta de grafit, la formulació de la qual també ha sigut objecte d'estudi en el present treball, sobre substrats polimèrics, obtenint-se d'esta forma unes làmines flexibles, amb el grafit adherit i dispersat sobre elles. Estos sensors així fabricats exhibeixen una alta sensibilitat al tacte, una bona resposta en freqüència i una alta durabilitat. Per a caracteritzar la seua resposta, així com l'estabilitat i reproducibilitat del mètode de fabricació, s'ha desenvolupat un mètode ad hoc que pretén recrear la interacció del sensor amb un dit humà, el qual és mostrat amb detall. Estos assajos que conformen este mètode ad hoc passen per un assaig a compressió parametritzat de 0 N a 30 N, una anàlisi de la senyal sota càrregues constants, els càlculs de l'error d'histèresi, la resposta en freqüència i el factor de galga, i l'anàlisi de fatiga a flexió arribant a més de 100.000 cicles en un recorregut de 0¿ a 100¿. Així mateix, s'ha analitzat l'estructura dels sensors mitjançant microscòpia electrònica d'emissió de camp (FESEM) i microscòpia òptica. Per a finalitzar s'han realitzat dos prototips abordant cadascun dels objectius. El resultat presentat és una làmina de grafit que no supera els 70 µm que conforma un sensor d'alta sensibilitat, amb el qual es van arribar a detectar pressions de 0,05 N, estables amb desviacions menors al 5% en llargs temps de repòs, majors a 25 minuts, fàcilment integrable i amb múltiples possibilitats d'aplicació, com ara en pròtesis intel·ligents, en sistemes de captura del moviment del cos humà i fins i tot per al seu ús com a pell sintètica. / [EN] The main goal of this research is to develop and determine a low-cost manufacturing process for graphite-based sensors, intended for application in capturing human body motion when integrated into textile garments, and for designing electronic skin capable of simulating the sense of touch. It primarily focuses on two crucial aspects: accessibility and applicability of the technology. To achieve this, the use of easily obtainable components and biocompatible materials has been prioritized throughout the entire process. Under the premise of low-cost manufacturing, the fabrication process involves a straightforward transfer and exfoliation of a graphite paste, the formulation of which has also been studied in this work, onto polymeric substrates. This results in flexible sheets with graphite adhered and dispersed on them. The sensors thus manufactured exhibit high touch sensitivity, a good frequency response, and high durability. To characterize their response, as well as the stability and reproducibility of the manufacturing method, a custom method has been developed to simulate the sensor's interaction with a human finger, which is detailed in the following. The tests comprising this ad hoc method include a parameterized compression test from 0 N to 30 N, signal analysis under constant loads, hysteresis error calculations, frequency response, gauge factor analysis, and fatigue analysis through bending for over 100,000 cycles in a range of 0¿ to 100¿. Additionally, the sensor structure has been analyzed using Field Emission Scanning Electron Microscopy (FESEM) and optical microscopy. To conclude, two prototypes addressing each of the objectives have been developed. The presented result is a graphite sheet not exceeding 70 µm, forming a highly sensitive sensor capable of detecting pressures as low as 0.05 N, stable with deviations of less than 5% over extended resting periods exceeding 25 minutes, easily integrable, and with multiple potential applications, such as in smart prosthetics, human body motion capture systems, and even for use as synthetic skin. / Tormo García, FJ. (2024). Diseño, fabricación y caracterización de sensores piezoresistivos basados en grafito para la captura del movimiento del cuerpo humano [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/202900