Demands to handle individual particles or particle agglomerates have been emerging in the fields of biology and chemistry, and particle trapping and manipulation with mechanical waves generated from ultrasound sources, known as “acoustic tweezing”, has gained great interest by researchers and been proved useful for its unique advantages. With an analogy to optical tweezing, research has demonstrated the possibility to use modulated acoustic fields generated by ultrasound arrays for trapping individual particles and groups of particles at length scales from hundreds of µm to a few mm. This thesis explores and demonstrates particle trapping and manipulation with electronically-controlled miniaturized ultrasound arrays (element pitch around 500 µm or less), focusing on the development of dexterous electronic systems. Generally, in acoustic manipulation applications, low voltage outputs with continuous mode operation are required to create stable acoustic energy potential “landscapes” for trapping without damaging particles or cells. The research work of this thesis is oriented towards integration of control electronics with miniaturized ultrasound arrays. Test fixtures have been carefully designed and fabricated for the characterization of transducer arrays developed by collaborating researchers and array-controlled particle manipulation experiments have been demonstrated with customized fluorescence microscopy equipment. Most importantly, this thesis has established two versions of prototype Field programmable gate array (FPGA) based electronics to drive ultrasound arrays. One is a computer-controlled 16-channel system, with adjustable output frequencies, phases and amplitudes. Another is a 40-channel switching electronics for manual controlled output switching or time-shared output multiplexing. The electronic systems that have been developed are highly scalable and easily adapted for different acoustic tweezing applications. In conclusion, this thesis has proposed prototype electronic toolkits as research platforms to explore diverse possibilities for acoustic tweezing with miniaturized ultrasound arrays.

Obstructive sleep apnea is a potentially life-threatening condition characterized by repetitive episodes of upper airway obstruction that occur during sleep, usually associated with a reduction in blood oxygen saturation. In US population, 9% of women, 24% of men, and 2% of children have been diagnosed with obstructive sleep apnea, suggesting that 18 million people may suffer from the consequences of nightly episodes of apnea. One of the most significant symptoms of obstructive sleep apnea is profound and repeated hypoxia. The analysis of the interaction between cardiovascular and respiratory signals has been a widely-explored area of research due to the significance of the results in describing a functional relationship between the underlying physiologic systems; however, statistical and analytical approaches to analyze the changes in these signals before and after hypoxia are still in their early stages of evolution. A major motivation for this research has been the lack of methodologies to detect mean and/or variance shifts and identify root sources of variation in time-frequency characteristics of multichannel data. The contributions of this thesis are twofold. First, multiscale energy distributions based on wavelet transformations of the analyzed physiological signs are analyzed. This is followed by the development of an online multichannel monitoring approach based on principal curves that detects changes in the wavelet coefficients extracted from the analyzed signals.

Studien uppmärksammar det svenska företaget Jula, som vid en tidpunkt då tillväxt råder på den elektroniska marknaden, väljer att lägga ner den elektroniska försäljningskanalen, för att istället satsa på den fysiska försäljningskanalen. Forskare har de senaste decennierna fokuserat på att företag bör vara verksamma genom kombinerade försäljningskanaler, fysisk försäljning och elektronisk handel, för att nå framgång. Därmed har de inte haft fokus på att företag slutar driva kombinerade försäljningskanaler, vilket företaget Jula kan illustrera. Genom att studera företaget Jula, med hjälp av en intervju och sekundärdata, påvisas att forskare hittills inte beaktat väsentliga faktorer i praktiken, och att det idag finns företag som kan vara framgångsrika och konkurrenskraftiga utan kombinerade försäljningskanaler. Även faktorer som ligger till grund för valet av att inte bedriva elektronisk handel påvisas. Detta mynnar sedan ut i en modell som berör kombinerade försäljningskanaler, där Julas fall och agerande finns implementerat, för att illustrera företagets tillvägagångssätt. / This study shows that in a time when electronic commerce is increasing, the Swedish company Jula has decided to closure their electronic retailing channel, to instead expand their physical retailing channel. The last decades the academics have focused on multichannel retailing business to reach success on the market. They have accordingly not focused on business stops running multichannel retailing, which the example with Jula can illustrate. Through an interview with Jula and indirectly data proves that the academics have not included essential aspects in practice, and that there are business today that can reach success and have competitive advantages without multichannel retailing, plus factors that influenced Jula in the decision to closure. This discharges in a model of multichannel retailing, which includes Julas specific case and their choice, to illustrate Julas different procedure.

In this work, we consider the channel assignment problem in single radio multi-channel mobile ad-hoc networks. Specifically, we investigate the granularity of channel assignment decisions that gives the best trade-off in terms of performance and complexity. We present a new granularity for channel assignment that we refer to as component level channel assignment. The strategy is relatively simple, and is characterized by several impressive practical advantages. We also show that the theoretical performance of the component based channel assignment strategy does not lag significantly behind the optimal possible performance, and perhaps more importantly we show that when coupled with its several practical advantages, it significantly outperforms other strategies under most network conditions.

Η τεράστια τεχνολογική ανάπτυξη που χαρακτηρίζει την εποχή µας και το πλήθος των εφαρµογών που αυτή συνεπάγεται ορίζει επιτακτική την ψηφιακή µετάδοση δεδοµένων σε µεγάλες αποστάσεις και µε εγκυρότητα. Οι απαιτήσεις αυτές οδήγησαν στην ανάπτυξη της τεχνικής OFDM (Orthogonal frequency-division multiplexing), µίας από της καλύτερες τεχνικές πολυπλεξίας. Θέµα της διπλωµατικής µου εργασίας είναι η ανάπτυξη ενός πολυκαναλικού ποµπού (OFDM transmitter) για γραµµές χαµηλής τάσης εντός κτηρίου. Συγκεκριµένα στο πρώτο µέρος της εργασίας παρουσιάζεται η θεωρητική βάση στην οποία στηρίζεται η σχεδίαση και υλοποίηση του ποµπού. ∆ίνεται έµφαση στην επεξήγηση της έννοιας «πολυκαναλικό» καθώς επίσης και γιατί ένας τέτοιου είδους ποµπός θα είναι χρήσιµος ως µέρος ενός ποµποδέκτη για µεταφορά δεδοµένων εντός κτηρίου. Στη συνέχεια της εργασίας παρουσιάζεται βήµα προς βήµα η σχεδίαση και ανάπτυξη του µοντέλου προσοµοίωσης του πολυκαναλικού ποµπού µε χρήση του εργαλείου Matlab/Simulink. Αρχικά παρουσιάζονται οι διάφοροι παράµετροι του ποµπού όπως ο αριθµός των υποκαναλιών του συστήµατος, ο µέγιστος αριθµός των bit που θα µεταδίδει κάθε υποκανάλι και η διαµόρφωση που θα εφαρµόζεται σε κάθε υποκανάλι. Στη συνέχεια παρουσιάζεται σχηµατικά η διαδικασία δηµιουργίας διαµορφωµένων συµβόλων και η δειγµατοληψία αυτών µε σκοπό τη δηµιουργία δειγµάτων προς µετάδοση. Το συγκεκριµένο µοντέλο περιλαµβάνει όλες τις απαραίτητες λειτουργίες που απαιτούνται για τη δηµιουργία, κωδικοποίηση και µεταφορά δεδοµένων σύµφωνα µε την OFDM τεχνική, λαµβάνοντας υπόψην τα χρονικώς µεταβαλλόµενα χαρακτηριστικά του καναλιού µετάδοσης. Επί πλέον, δίνεται πλήρης επεξήγηση για τον σχεδιασµό κάθε υποσυστήµατος που χρησιµοποιήθηκε για την ολοκλήρωση του µοντέλου. Η παρουσίαση ολοκληρώνεται µε την παράθεση και επεξήγηση των αποτελεσµάτων των προσοµοιώσεων τα οποία επιβεβαιώνουν την ορθότητα λειτουργίας του συστήµατος που υλοποιήθηκε. / -

Some industrial applications require deterministic and bounded gathering delays. We focus on the joint time slots and channel assignment that minimizes the time of data collection and provides conflict-free schedules. This assignment allows nodes to sleep in any slot where they are not involved in transmissions. Hence, these schedules save the energy budjet of sensors. We calculate the minimum number of time slots needed to complete raw data convergecast for a sink equipped with multiple radio interfaces and heterogeneous nodes traffic. We also give optimal schedules that achieve the optimal bounds. We then propose MODESA, a centralized joint slots and channels assignment algorithm. We prove the optimality of MODESA in specific topologies. Through simulations, we show that MODESA is better than TMCP, a centralized subtree based scheduling algorithm. We improve MODESA with different strategies for channels allocation. In addition, we show that the use of a multi-path routing reduces the time of data collection .Nevertheless, the joint time slot and channels assignment must be able to adapt to changing traffic demands of the nodes ( alarms, additional requests for temporary traffic ) . We propose AMSA , an adaptive joint time slots and channel assignment based on incremental technical solution. To address the issue of scalability, we propose, WAVE, a distributed scheduling algorithm for convergecat that operates in centralized or distributed mode. We show the equivalence of schedules provided by the two modes.

No description available.

The geophysical technique known as Multichannel Analysis of Surface Waves, or MASW (Park et al., 1999) is a relatively new seismic characterisation method which utilises Rayleigh waves propagation. With MASW, the frequency dependent, planar travelling Rayleigh waves are created by a seismic source and then measured by an array of geophone receivers. The recorded data is used to image characteristics of the subsurface. This thesis explains how MASW was used as a geotechnical investigation tool on windfarms in the lower North Island, New Zealand, to determine the stiffness of the subsurface at each wind turbine site. Shear‐wave velocity (VS) profiles at each site were determined through the processing of the MASW data, which were then used to determine physical properties of the underlying, weathered greywacke. The primary research site, the Te Rere Hau Windfarm in the Tararua Ranges of the North Island, is situated within the Esk Head Belt of Torlesse greywacke (Lee & Begg, 2002). Due to the high level of tectonic activity in the area, along with the high rates of weathering, the greywacke material onsite is highly fractured and weathering grades vary significantly, both vertically and laterally. MASW was performed to characterise the physical properties at each turbine site through the weathering profile. The final dataset included 1‐dimensional MASW shear‐wave evaluations from 100 turbine sites. In addition, Poisson’s ratio and density values were characterised through the weathering profile for the weathered greywacke. During the geotechnical foundation design at the Te Rere Hau Windfarm site, a method of converting shear wave velocity profiles was utilised. MASW surveying was used to determine VS profiles with depth, which were converted to elastic modulus profiles, with the input parameters of Poisson’s ratio and density. This study focuses on refining and improving the current method used for calculating elastic modulus values from shear‐wave velocities, primarily by improving the accuracy of the input parameters used in the calculation. Through the analysis of both geotechnical and geophysical data, the significant influence of overburden pressure, or depth, on the shear wave velocity was identified. Through each of the weathering grades, there was a non‐linear increase in shear wave velocity with depth. This highlights the need for overburden pressure conditions to be considered before assigning characteristic shear wave velocity values to different lithologies. Further to the dataset analysis of geotechnical and geophysical information, a multiple variant non‐linear regression analysis was performed on the three variables of shear wave velocity, depth and weathering grade. This produced a predictive equation for determining shear wave velocity within the Esk Head belt ‘greywacke’ when depth and weathering data are known. If the insitu geological conditions are not comparable to that of the windfarm sites in this study, a set of guidelines have been developed, detailing the most efficient and cost effective method of using MASW surveying to calculate the elastic modulus through the depth profile of an investigation site.

Fast fashion retailers have faced a difficulty in translating in-store experiences to online experiences. Although online shopping is increasing, the in-store shopping is still very important for a superior shopping experience. Technology has had a major impact in making multichanneling retail more consistent, although there are gaps that technology can not fill. This study attempted to measure how consistent the customer experiences were online and in-store. Shopping experiences were measured with different concepts such as: flow, usability, interactivity, atmospherics and tactility. These concepts were measured separately in-store and online, in order to be compared. The purpose was to find out which concept is inconsistent so the authors could make recommendations for improvement to fast fashion retailers. The research approach was a mixed method approach and the chosen research design was cross sectional, using quantitative research to corroborate qualitative research findings. The results from a quantitative questionnaire of 263 experienced fast fashion consumers in Sweden show that the consistency varies between the concepts. The qualitative study was done at two occasions on a sample of six interviewees in each focus group, and gave a deeper understanding for why the shopping experience was or wasn't consistent. The qualitative results varied amongst the individuals and show that reasons for being inconsistent are intrusive salesmen, insufficient size measuring tools, long queues, lack of tactility and the most interesting of all: making better return and ordering policies. The future lies in making it easier to order online, in order for the consumer to be able to experience the product in real life, through staff-free fitting rooms and showrooms and such, rather than making the experience better online. The future seems to lie in solving the reverse of the start point of this study, namely translating online to in-store experiences.

The estimation of power spectral densities is a critical step in many speech enhancement algorithms. The demand for multi-channel speech enhancement systems is high with applications in teleconferencing, cellular phones, and hearing aids. The first objective of the thesis is to develop a general multi-channel framework to solve for the diffuse noise power spectral densities whenever the spatial correlation or coherence matrix is pre-estimated and the number of speakers is less than the number of microphones. The second objective is to develop closed-form analytical solutions. The performance of the developed algorithms is evaluated with pre-existing algorithms using prescribed performance measures.