L’escalat dels transistors MOSFET convencionals ha portat a aquests dispositius a la nanoescala per incrementar tant les seves prestacions com el nombre de components per xip. En aquest process d’escalat, els coneguts “Short Channel Effects” representen una forta limitació. La forma més efectiva de suprimir aquests efectes i aixi estendre l’ús del MOSFET convencional, és la reducció del gruix de l’òxid de porta i l’augment de la concentració de dopants al canal. Quan el gruix d’òxid de porta es redueix a unes quantes capes atòmiques, apareix l’efecte túnel mecano-quàntic d’electrons, produint un gran augment en els corrents de fuita, perjudicant la normal operació dels MOSFETs. Això ha fet obligatori l’ús de materials d’alta permitivitat o materials high-κ en els dielèctrics de porta. Tot i les solucions proposades, la reducció de les dimensiones físiques del MOSFET convencional no pot ser mantinguda de forma indefinida i per mantenir la tendència tecnològica s’han suggerit noves estructures com ara MOSFETs multi-porta de cos ultra-prim. En particular, el MOSFET de doble porta és considerat com una estructura multi-porta prometedora per les seves diverses qualitats i avantatges en l’escalat. Aquesta tesi s’enfoca en la modelització de dispositius MOSFET de doble porta i, en particular, en la modelització del corrent túnel de porta que afecta críticamente al consum de potència del transistor. Primerament desenvolupem un model quàntic compacte tant per al potencial electrostàtic com per a la càrrega elèctrica en el transistor de doble-porta simètric amb cos no dopat. Després, aquest model quàntic s’utilitza per proposar un model analític compacte per al corrent túnel directe amb SiO2 com dielèctric de porta, primerament, i després amb una doble capa composta de SiO2 com a capa interfacial i un material “high-κ”. Finalment se desenvolupa un mètode precís per calcular el corrent túnel de porta. El mètode es basa en l’aplicació de condicions de frontera absorbents i, més especificament, en el mètode PML. Aquesta tesi està motivada per les recomanacions fetes pel “International Technology Roadmap of Semiconductors” (ITRS) sobre la necessitat existent de modelatge i simulació d’estructures semiconductores multi-porta. / The scaling of the conventional MOSFETs has led these devices to the nanoscale to increase both the performance and the number of components per chip. In this process, the so-called “Short Channel Effects” have arisen as a limiting factor. To extend the use of the bulk MOSFETs, the most effective ways of suppressing such effects are the reduction of the gate oxide thickness and increasing of the channel doping concentration. When the gate oxide thickness is reduced to a few atomic layers, quantum mechanical tunneling is responsible of a huge increase in the gate leakage current impairing the normal operation of MOSFETs. This has made mandatory the use of high permittivity materials or high-κ as gate dielectrics. Despite the proposed solutions, reduction of the physical dimensions of the conventional MOSFETs cannot be maintained. To keep the technological trend, new MOSFET structures have been suggested such as ultra-thin body Multi-Gate MOSFETs. In particular, the Double-Gate MOSFETs is considered as a promising MG structure for its several qualities and advantages in scaling. This thesis focuses on the modeling of Double-Gate MOSFET and, in particular, on the modeling of the gate leakage current critically affecting the power consumption. First we develop a compact quantum model for both the electrostatic potential and the electric charge in symmetric double-gate MOSFET with undoped thin body. Then, this quantum model is used to propose an analytical compact model for the direct tunnelling current with SiO2 as gate dielectric, firstly, and later assuming a dual layer consisting of a SiO2 interfacial layer and a high-κ material. Finally, an accurate method for the calculation of the gate tunnelling current is developed. It is based on Absorbing Boundary Conditions techniques and, more specifically, on the Perfectly Mached Layer (PML) method. This thesis is motivated by the recommendations given by the “International Technology Roadmap of Semiconductors” (ITRS) about the need for the modeling and simulation of multi-gate semiconductor structures.

En aquesta tesi hem desenvolupat models compactes que incorporen un model de transport hidrodinàmic adaptat a multi-gate (principalment double-gate (DG) and surrounding-gate (SRG) MOSFETs a partir de models unificats de control de càrrega I del potencial de superfície, obtinguts de l’equació de Poisson. Tots aquests dispositius es modelitzen seguint un esquema semblant. El corrent i càrregues totals s’escriuen en funció de les densitats de càrrega mòbil per unitat d’àrea als extrems drenador i font del canal. Els efectes de canal curt i quàntics també s’inclouen en el model compacte desenvolupat. El model desenvolupat mostra un bon acord amb simulacions numèriques 2D i 3D en tots els règims d’operació. El model desenvolupat s’implementa i testeja al simulador de circuits SMASH per a l’anàlisi dels comportaments DC i transitori de circuits CMOS. / En esta tesis hemos desarrollado modelos compactos que incorporan un modelo de transporte hidrodinámico adaptado a multi-gate (principalmente double-gate (DG) and surrounding-gate (SRG) MOSFETs a partir de modelos unificados de control de carga I del potencial de superficie, obtenidos de la ecuación de Poisson. Todos estos dispositivos se modelizan siguiendo un esquema similar. La corriente y cargas totales escriben en función de las densidades de carga móvil por unidad de área en los extremos drenador y fuente del canal. Los efectos de canal corto y cuánticos también se incluyen en el modelo compacto desarrollado. El modelo desarrollado muestra un buen acuerdo con simulaciones numéricas 2D y 3D en todos los regímenes de operación. El modelo desarrollado se implementa y testea el simulador de circuitos SMASH para el análisis de los comportamientos DC y transitorio de circuitos CMOS.

Jag fångades av enkelheten i inredningsarkitekten Hans Johanssons konstruktioner, flexibiliteten och den eleganta lättheten i hans möbler, de nätta dimensionerna och sättet han använder materialet trä. I mitt examensarbete undersöker jag möjligheten att vidareutveckla hans konstruktioner för att passa ett modernt liv på gränsen mellan ute och inne.Hans Johansson, som i år fyller nittio, började arbeta med sin idé om möbler konstruerade av ramar som ihopfogas utan skruv eller beslag för mer än ett halvt sekel sedan. Kanske är det först nu, i en ny sorts trångboddhet, som tiden är mogen för hans demonterbara möbler. Sparsamheten i material, flexibilitet, inhemska träslag och platta paket känns tidslöst och modernt. Jag vill lära mig att tänka om mitt hantverk i nya banor och Hans Johanssons arbete innehåller en del av det jag tror mig sakna. Mina studier av Johanssons möbler och desskonstruktioner resulterade i en demonterbar trädgårdsmöbel för fyra personer, ett bord och två bänkar som ryms i en låda bara 86 mm tjock. / I was captured by the simplicity of the interior designer Hans Johansson’s designs, theflexibility and the elegant lightness of his constructions, the petite dimensions and the way he uses wood as a material. In my thesis I investigate the possibility of developing his constructions to suit modern life on the border between outside and inside. Hans Johansson, who this year turns ninety, began working on his idea of furniture constructed by frames joined together without screws or fittings more than half a century ago. Perhaps it is only now, in a new kind of overcrowding that the time is ripe for his dismantled furniture. Frugality of materials, flexibility, native woods and flat pack feels timeless and modern. I want to learn to think about my craft in new ways and Hans Johansson’s work contains some of the aspects I wish to explore. My studies of Johansson’s furniture and its construction resulted in demountable garden furniture for four people, one table and two benches that can fit in a box only 86 mm thick.

This report is a product of Bachelor Degree Project at Mechanical Engineering department inLinnaeus University, Växjö, Sweden. The project is about a design improvement of industrialcompact mixers.This project is accomplished with Xylem, one of the main suppliers of compact mixers in theindustry, located at Emmaboda, Sweden. The company has a problem with the existing designof the two part, oil housing and entrance cover, in 4610/20 compact mixers. The 4610/20compact mixers has suffered from quality problems which affect the production and the endcustomer because of the existing design of these part. The aim of this study is to improve thequality of the product by redesigning of oil housing and entrance cover. In addition to theredesigning of these parts, another important purpose of the project is to produce these partsfrom different material than existing one.The computer aided design programs are widely used, Solid Works, during the project. Forselection of a new material a wide literature research has been accomplished.

In recent years, the miniaturization of cell phones and computers has led to a requirement for antennas to be small and lightweight. Antennas, desired to operate in the WLAN frequency range, often possess physical sizes that are too large for integration with radio-frequency (RF) devices. When integrating antennas into three-dimensional (3D) system-on-package (SOP) transceivers, the maintenance of a compact size also provides isolation from other devices, hence, surface wave propagation or high dielectric constant materials such as low temperature cofired ceramics (LTCC) does not affect nearby components of the transceiver such as filters, baluns, and other embedded passives. Therefore, the application of design methods is necessary for realizing compact antennas in the wireless community that can be integrated to RF packages. Furthermore, it is essential that these compact antennas maintain acceptable performance characteristics, such as impedance bandwidth, low cross-polarization, and high efficiency. In addition, the analysis of circuit modeling techniques that could be used to obtain a better understanding of the physical phenomena of the antenna is quite necessary as modules become more and more complex. Based on these requirements, the focus of this research is to improve the design of compact antennas for wireless communications, wireless local area networks (WLAN), and millimeter-wave applications by using time-domain electromagnetic and circuit modeling techniques and optimizations. These compact antenna designs are applied to practical wireless communications systems such as global system of mobile communications (GSM), Bluetooth Industrial-Scientific-Medical (ISM) devices, IEEE802.11a WLAN, and Local Multipoint Distribution Systems (LMDS) applications. Parametric analyses are conducted to study critical parameters that may affect the antenna designs. Moreover, optimizations are performed to optimize the structures, and measured results are presented to validate design techniques.

Let X, Y be locally compact Hausdorff spaces. A linear operator T from C0(X,E) to C0(Y,F) is called disjointness preserving if coz(Tf)¡äcoz(Tg) = whenever coz(f)¡äcoz(g) = ∅. We discuss some cases on these compact disjointness preserving operators T and prove that if £f0 is a nonzero point of £m(T), then £f0 is an eigenvalue of T and we find a projection ∏: C0(X,E) ¡÷C0(X,E), such that for Y1 = ∏C0(X;E) and Y2 = (1-∏)C0(X;E), the operator T|Y1 -£f0 is a nilpotent and £f0-T|Y2 is invertible.

In recent years, the demand for portable radio communication has been increasing which requires low profile, light weight and small size antennas. Therefore, the size of the antenna is required to be as small as possible. In this thesis, some of the compact antennas will be analyzed and simulated. The early-stage PIFA antenna will be investigated first, and then the shorting pin characteristics to design compact and dual band antenna was utilized. Because the shorting pin will lead to the decrease of bandwidth, replacement of the shorting pin by using chip-resistor could improve this characteristic. The compactness of antennas will lead to the decrease of the gain. In order to improve the gain of antennas, the combination of substrate and superstrate configuration with very high permittivity material is used. For the consideration of Bluetooth system, we use the ACPS (Asymmetrical Co-planar Striplines) structure to design the antenna. Using this structure in the design will obtain a promotion in bandwidth compared with the conventional rectangular microstrip antenna. Because the size of the antenna is small, the time to simulate this structure by the FDTD (Finite Difference Time Domain) method is too long. In order to solve this problem, this thesis mainly study a new FDTD algorithm based on the Alternating-Direction Implicit method, and use this algorithm to simulate some simple structures.

Title from PDF of title page (University of Missouri--Columbia, viewed on March 10, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis advisor: Dr. Guilherme DeSouza. Vita. Includes bibliographical references.

Thesis (Ph. D.)--York University, 2001. Graduate Programme in Mathematics and Statistics. / Typescript. Includes bibliographical references (leaves 86-87). Also available on the Internet. MODE OF ACCESS via web browser by e506ring the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ66351.

This dissertation is an observational exploration of the exciting physics that can be enabled by high-speed photometric monitoring of extremely low-mass (< 0.25 M[subscript sun symbol]) white dwarf stars, which are found in some of the most compact binaries known. It includes the cleanest indirect detection of gravitational waves at visible wavelengths, the discovery of pulsations in He-core WDs, the strongest evidence for excited p-mode pulsations in a WD, the discovery of the first tidally distorted WDs and their use to constrain the low-end of the WD mass-radius relationship, and the strongest cases of Doppler beaming observed in a binary system. It is the result of the more than 220 nights spent at McDonald Observatory doing high-speed photometry with the Argos instrument on the 2.1 m Otto Struve telescope, which has led to a number of additional exciting results, including the discovery of an intermediate timescale in the evolution of cooling DA WDs and the discovery of the most massive pulsating WD, which should have an ONe-core and should be highly crystallized. / text