Consumer demands are driving the current trend in the microelectronics industry to make electronic products that are miniature, fast, compact, high-density, reliable and low-cost. The use of surface mount devices (SMDs) has helped to decrease the size of electronic packages through the use of solder bump interconnections between the devices and the substrates/printed wiring boards (PWBs). Solder bumps act as not only mechanical, but also electrical interconnections between the device and the substrate/PWB. Common manufacturing defects ¨C such as open, cracked, missing, and misaligned solder bumps ¨C are difficult to detect because solder bumps are hidden between the device and the substrate/PWB after assembly. The reliability of packaged electronic devices in storage and usage is a major concern in the microelectronics industry. Therefore, quality inspection of solder bumps has become a critical process in the microelectronics industry to help ensure product quality and reliability. In this thesis, a methodology for quality evaluation and reliability study of solder bumps in electronic packages has been developed using the non-destructive and non-contact laser ultrasound-interferometric technique, finite element and statistical methods in this research work. This methodology includes the following aspects: 1) inspection pattern ¨C specific inspection patterns are created according to inspection purpose and package formats, 2) laser pulse energy density calibration ¨C specific laser pulse power and excitation laser spot size are selected in terms of package formats, 3) processing and analysis methods, including integrated analytical, finite element and experimental modal analyses approach, advanced signal processing methods and statistical analysis method, 4) approach combining modal analysis and advanced signal processing to improve measurement sensitivity of laser ultrasound-interferometric inspection technique, and 5) calibration curve using energy based simulation method and laser ultrasound inspection technique to predict thermomechanical reliability of solder bumps in electronic packages. Because of the successful completion of the research objectives, the system has been used to evaluate a broad range of solder bump defects in a variety of packaged electronic devices. The development of this system will help tremendously to improve the quality and reliability of electronic packages.

This study involved experimental and equivalent computational investigations into the automobile-type 3―D flow physics of a diffuser bluff body in ground-effect and novel passive flow-control methods applied to the diffuser flow to enhance the diffuser’s aerodynamic performance. The bluff body used in this study is an Ahmed-like body employed in an inverted position with the slanted section together with the addition of side plates along both sides forming the ramped diffuser section. The first part of the study confirmed reported observations from previous studies that the downforce generated by the diffuser in proximity to a ground plane is influenced by the peak suction at the diffuser inlet and subsequent static pressure-recovery towards the diffuser exit. Also, when the bluff body ride height is gradually reduced from high to low, the diffuser flow as indicated by its force curve and surface flow features undergoes four distinct flow regimes (types A to D). The types A and B regimes are reasonably symmetrical, made up of two low-pressure core longitudinal vortices travelling along both sides of the diffuser length and they increase downforce and drag with reducing ride height. However, below the ride heights of the type B regime, types C and D regimes are asymmetrical because of the breakdown of one vortex; consequently a significant loss in downforce and drag occurs. The second part of the study involved the use ― near the diffuser exit ― of a convex bump on the diffuser ramp surface and an inverted wing between the diffuser side plates as passive flow control devices. The modification of the diffuser geometry with these devices employed individually or in combination, induced a second-stage pressure-drop and recovery near the diffuser exit. This behaviour was due to the radial pressure gradient induced on the diffuser flow by the suction surface ii curvature of the passive devices. As a result of this aerodynamic phenomenon, the diffuser generated across the flow regimes additional downforce, and a marginal increase in drag due to the profile drag induced by the devices.

This thesis analyses the use of an accelerometer commonly present in a mobile device for the measuring of vibration in a vehicle. Such measurements are used to map the quality of the road surface. The signal from the accelerometer and the current travelling speed of the vehicle are evaluated according to a threshold function. This function allows for a determination of whether the signal reported by the device signifies a pot-hole or another type of defect on the road surface. If the defect is determined to pose a threat to a vehicle travelling at higher speeds, then this fact is saved into the memory of the device. The second part of this thesis deals with the design of an internet and a mobile application, which is able to collect all measured data processes using cluster analysis and then shares the results with other participating devices. Tha practical results is that a map of road surface defect is thus created, which is then displayed to road users. This thesis deals with theory of mobile device sensors, including signal processing, as well as the design creation of the internet and mobile application.

The purpose of this study is to investigate the effects of bicycle crossings and follow up on previousstudies with new data on speeds, ability to travel unhindered and accident statistics. With theintroduction of the new definition of bicycle crossing from 2014, motor vehicle drivers had to yieldfor cyclists who are traveling on, or are approaching, the bicycle crossing. The area at theintersection should also be speed-proofed to 30 km/h. The introduction meant that new behaviorswere required by both cyclists and motor vehicle drivers at these types of intersections.The report is consists of three parts; a short literature study with an international outlook, adocument analysis of accidents and bicycle crossings in Sweden as well as on site measurementsexecuted at bicycle crossings in Gävle. The literature study briefly presents some of the mostcommon speed-limiting measures to present an overview of the types of measures that can be usedto speed-proof bicycle crossings. It also presents other countries' accident statistics as well as howthey handle the problems of bicycle prioritization at crossings. The document analysis is based onthe STRADA and RDT database in order to, through a GIS software, link accidents to bicycle crossingsand thus be able to analyze how the accidents have developed over time. This analysis is made bothwith a national average and a more thorough study of the municipality of Malmö. In the on sitemeasurements executed in Gävle, the speeds of the motor vehicles on approach to bicycle crossingswere examined and the yielding behavior was studied ocularly. The measurements were carried outin two separate locations with different conditions, one with relatively high traffic flow and a plateaubump as a speed-proofing measure and one with lower flow and bus pad as a speed-proofingmeasure.It turns out that the number of accidents related to bicycle crossings has decreased in Sweden, whilethe degree of injury for these accidents has also decreased. Malmö stands out in the statistics due tothe fact that the number of accidents related to bicycle crossings has increased at the same time asthe degree of injury for the accidents has decreased. The data also shows that accidents at bicyclecrossings adjacent to roundabouts are over-represented. It is therefore proposed that bicyclecrossings adjacent to roundabouts should be avoided. The on site measurements in Gävle showedthat the speeds had decreased sharply at the site with the bus pad and that the yielding behaviorchanged after the introduction of the bicycle crossing. At the second location, with the plateaubump, the speeds have already converged and are approaching their limit values while the yieldingbehavior has improved slightly. Finally, it is concluded that bus pads have better velocity suppressioneffects than the plateau pad and that the consequential effects of a well-designed speed-proofingmeasurement can reduce the degree of injury and increased yielding.

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In this dissertation, neural networks are designed to effectively model static non-linear aeroelastic problems in adaptive structures and linear dynamic aeroelastic systems with time varying stiffness. The use of adaptive materials in aircraft wings allows for the change of the contour or the configuration of a wing (morphing) in flight. The use of smart materials, to accomplish these deformations, can imply that the stiffness of the wing with a morphing contour changes as the contour changes. For a rapidly oscillating body in a fluid field, continuously adapting structural parameters may render the wing to behave as a time variant system. Even the internal spars/ribs of the aircraft wing which define the wing stiffness can be made adaptive, that is, their stiffness can be made to vary with time. The immediate effect on the structural dynamics of the wing, is that, the wing motion is governed by a differential equation with time varying coefficients. The study of this concept of a time varying torsional stiffness, made possible by the use of active materials and adaptive spars, in the dynamic aeroelastic behavior of an adaptable airfoil is performed here. A time marching technique is developed for solving linear structural dynamic problems with time-varying parameters. This time-marching technique borrows from the concept of Time-Finite Elements in the sense that for each time interval considered in the time-marching, an analytical solution is obtained. The analytical solution for each time interval is in the form of a matrix exponential and hence this technique is termed as Matrix Exponential time marching. Using this time marching technique, Artificial Neural Networks can be trained to represent the dynamic behavior of any linearly time varying system. In order to extend this methodology to dynamic aeroelasticity, it is also necessary to model the unsteady aerodynamic loads over an airfoil. Accordingly, an unsteady aerodynamic panel method is developed using a distributed set of doublet panels over the surface of the airfoil and along its wake. When the aerodynamic loads predicted by this panel method are made available to the Matrix Exponential time marching scheme for every time interval, a dynamic aeroelastic solver for a time varying aeroelastic system is obtained. This solver is now used to train an array of neural networks to represent the response of this two dimensional aeroelastic system with a time varying torsional stiffness. These neural networks are developed into a control system for flutter suppression. Another type of aeroelastic problem of an adaptive structure that is investigated here is the shape control of an adaptive bump situated on the leading edge of an airfoil. Such a bump is useful in achieving flow separation control for lateral directional maneuverability of the aircraft. Since actuators are being used to create this bump on the wing surface, the energy required to do so needs to be minimized. The adverse pressure drag as a result of this bump needs to be controlled so that the loss in lift over the wing is made minimal. The design of such a "spoiler bump" on the surface of the airfoil is an optimization problem of maximizing pressure drag due to flow separation while minimizing the loss in lift and energy required to deform the bump. One neural network is trained using the CFD code FLUENT to represent the aerodynamic loading over the bump. A second neural network is trained for calculating the actuator loads, bump displacement and lift, drag forces over the airfoil using the finite element solver, ANSYS and the previously trained neural network. This non-linear aeroelastic model of the deforming bump on an airfoil surface using neural networks can serve as a fore-runner for other non-linear aeroelastic problems. This work enhances the traditional aeroelastic modeling by introducing time varying parameters in the differential equations of motion. It investigates the calculation of non-conservative aerodynamic loads on morphing contours and the resulting structural deformation for non-linear aeroelastic problems through the use of neural networks. Geometric modeling of morphing contours is also addressed. / Ph. D.

This thesis examines the packaging of high-temperature SiC power electronic devices. Current-voltage measurements were conducted on as-received and packaged SiC power devices. The planar structure was introduced and developed as a substitution for traditional wire-bonding vertical structure. The planar structure was applied to a high temperature (>250oC) SiC power device. Based on the current-voltage (I-V) measurements, the packaging structures were improved, materials were selected, and processes were tightly controlled. This study applies two types of planar structures, the direct bond and the bump bond, to the high-temperature packaging of high-temperature SiC diode. A drop in the reverse breakdown voltage was discovered in the packaging using a direct bond. The root cause for the drop in the breakdown voltage was identified and corrective solutions were evaluated. A few effective methods were suggested for solving the breakdown issue. The forward I-V curve of the planar packaging using direct bond showed excellent results due to the excellent electrical and thermal properties of sintered nanosilver. The packaging using a bump bond as an improved structure was processed and proved to possess desirable forward and reverse I-V behavior. The cross-sections of both planar structures were inspected. High-temperature packaging materials, including nano-silver paste, high-lead solder ball and paste, adhesive epoxy, and encapsulant, were introduced and evaluated. The processes such as stencil printing, low-temperature sintering, solder reflowing, epoxy curing, sputtering deposition, electroplating, and patterning of direct-bond copper (DBC) were tightly controlled to ensure high-quality packaging with improved performance. Finally, the planar packaging of the high temperature power device was evaluated and summarized, and the future work was recommended. / Master of Science

The present thesis is devoted to the study of various properties of Banach func- tion spaces, with a particular emphasis on applications in the theory of Sobolev spaces and in harmonic analysis. The thesis consists of four papers. In the first one we investigate higher-order embeddings of Sobolev-type spaces built upon rearrangement-invariant Banach function spaces. In particular, we show that optimal higher-order Sobolev embeddings follow from isoperimetric inequal- ities. In the second paper we focus on the question when the above-mentioned Sobolev-type space is a Banach algebra with respect to a pointwise multiplica- tion of functions. An embedding of the Sobolev space into the space of essentially bounded functions is proved to be the answer to this question in several standard as well as nonstandard situations. The third paper is devoted to the problem of validity of the Lebesgue differentiation theorem in the context of rearrangement- invariant Banach function spaces. We provide a necessary and sufficient condition for the validity of this theorem given in terms of concavity of certain functional depending on the norm in question and we find also alternative characterizations expressed in terms of properties of a maximal operator related to the norm. The object of the final paper is the boundedness of the...

This thesis deals with the concept of virtual reality, its history, present-day possibilities and available devices and technologies for virtual reality and ways of creating assets such as models, textures and animations for virtual reality applications. The practical part of this work deals with design and creation of three-dimensional models, textures, animations and environment for use in interactive application in virtual reality and also with design and creation of such application to demonstrate their use.

Human capability to recall episodic memories depends on how much time has passed since the memory was encoded. This dependency is described by a memory retrieval curve that reflects an interesting phenomenon referred to as a reminiscence bump - a tendency for older people to recall more memories formed during their young adulthood than in other periods of life. This phenomenon can be modelled with an attractor neural network, for example, the firing-rate Bayesian Confidence Propagation Neural Network (BCPNN) with incremental learning. In this work, the mechanisms underlying the reminiscence bump in the neural network model are systematically studied. The effects of synaptic plasticity, network architecture and other relevant parameters on the characteristics of the reminiscence bump are systematically investigated. The most influential factors turn out to be the magnitude of dopamine-linked plasticity at birth and the time constant of exponential plasticity decay with age that set the position of the bump. The other parameters mainly influence the general amplitude of the lifespan retrieval curve. Furthermore, the recency phenomenon, i.e. the tendency to remember the most recent memories, can also be parameterized by adding a constant to the exponentially decaying plasticity function representing the decrease in the level of dopamine neurotransmitters. / Människans förmåga att återkalla episodiska minnen beror på hur lång tid som gått sedan minnena inkodades. Detta beroende beskrivs av en sk glömskekurva vilken uppvisar ett intressant fenomen som kallas ”reminiscence bump”. Detta är en tendens hos äldre att återkalla fler minnen från ungdoms- och tidiga vuxenår än från andra perioder i livet. Detta fenomen kan modelleras med ett neuralt nätverk, sk attraktornät, t ex ett icke spikande Bayesian Confidence Propagation Neural Network (BCPNN) med inkrementell inlärning. I detta arbete studeras systematiskt mekanismerna bakom ”reminiscence bump” med hjälp av denna neuronnätsmodell. Exempelvis belyses betydelsen av synaptisk plasticitet, nätverksarkitektur och andra relavanta parameterar för uppkomsten av och karaktären hos detta fenomen. De mest inflytelserika faktorerna för bumpens position befanns var initial dopaminberoende plasticitet vid födseln samt tidskonstanten för plasticitetens avtagande med åldern. De andra parametrarna påverkade huvudsakligen den generella amplituden hos kurvan för ihågkomst under livet. Dessutom kan den s k nysseffekten (”recency effect”), dvs tendensen att bäst komma ihåg saker som hänt nyligen, också parametriseras av en konstant adderad till den annars exponentiellt avtagande plasticiteten, som kan representera densiteten av dopaminreceptorer.