Adaptive order-statistics multi-shell filtering for bad pixel correction within CFA demosaicking

As today's digital cameras contain millions of image sensors, it is highly probable that the image sensors will contain a few defective pixels due to errors in the fabrication process. While these bad pixels would normally be mapped out in the manufacturing process, more defective pixels, known as hot pixels, could appear over time with camera usage. Since some hot pixels can still function at normal settings, they need not be permanently mapped out because they will only appear on a long exposure and/or at high ISO settings. In this paper, we apply an adaptive order-statistics multi-shell filter within CFA demosaicking to filter out only bad pixels whilst preserving the rest of the image. The CFA image containing bad pixels is first demosaicked to produce a full colour image. The adaptive filter is then only applied to the actual sensor pixels within the colour image for bad pixel correction. Demosaicking is then re-applied at those bad pixel locations to produce the final full colour image free of defective pixels. It has been shown that our proposed method outperforms a separate process of CFA demosaicking followed by bad pixel removal

Image Asymmetry Measurement for the Study of Endangered Pygmy Bluetongue Lizard

Author version made available in accordance with the publisher's policyAbstract—There are applications for the measurement of body asymmetry as some studies have shown a correlation between asymmetry and fitness for some species. In our study of the endangered Pygmy Bluetongue Lizard, the asymmetry of its head is being investigated to see whether this has a correlation with its health and chance of survival in the wild. As there are restrictions on handling the endangered lizards, their digital photos must be taken in the field and therefore it is difficult to impose restrictions on the conditions under which the digital images are acquired. In this paper, we propose a novel automatic technique that is invariant to rotation, size, illumination and tilt, for the measurement of lizard symmetry based on its digital imagery and the resulting symmetry index is used to infer the lizard’s asymmetry. The conventional manual methods being used by biologists for fluctuating asymmetry measurement have a number of disadvantages including human errors, and their methods of measurement are based on counting the number of scales and length measurement that do not often agree well with visual assessment. Our proposed image processing technique is non-invasive, robust in a way that will give a similar symmetric index for different images of the same lizard, and more importantly based on the actual image scale pattern of the lizards. Hence our proposed method will also give a better agreement with visual assessment

Portal Imaging Using a CSI (TL) Scintillator Coupled to a Cooled CCD Camera

The purpose of this research was to design a high performance digital portal imaging system, using a transparent x-ray scintillator coupled to a cooled CCD camera. Theoretical analysis using Monte Carlo simulation was performed to calculate the QDE, SNR and DQE of the system. A prototype electronic portal imaging device (EPID) was built, using a 12.7 mm thick, 20.32 cm diameter, CsI (Tl) scintillator, coupled to an Astromed ® liquid nitrogen cooled CCD TV camera. The system geometry of the prototype EPID was optimized to achieve high spatial resolution. Experimental evaluation of the prototype EPID was performed, by determining its spatial resolution, contrast resolution, depth of focus and light scatter. Images of phantoms, animals and human subjects were acquired using the prototype EPID and were compared with those obtained using conventional and high contrast portal film and a commercial EPID. An image processing protocol was developed. The protocol was comprised of preprocessing, noise removal and image enhancement algorithms. An adaptive median filter algorithm for the removal of impulse noise was developed, analyzed and incorporated into the image processing protocol. Results from the theoretical analysis and experimental evaluation have indicated that the performance of the CsI (Tl) - CCD system is comparable or superior to that of current commercial and experimental portal imaging technologies, such as high contrast portal film, commercial TV camera based EPIDs, and amorphous silicon based flat panel EPIDs

Characterization of aerosols in an underground mine

“Diesel-powered engines are a common source of submicron carbon-rich particles. Characterizing morphological and physical attributes of diesel agglomerates is therefore of great importance to be able to identify the source and improve removal technology. Size-segregated sampling was conducted in two phases of underground experiments. Scanning transmission electron microscopy and fast mobility particle sizers were used to determine the size distribution of agglomerates based on particle mobility and projected area diameter. Controlled zone sampling test results were used to determine the morphological characteristics of agglomerates for specific types of diesel equipment both with and without removal strategies. Changes in fractal dimension, shape factor and primary particle diameter were observed for examined control strategies as well as light duty and heavy duty engines. Samples collected from uncontrolled zone showed higher fractal dimension of chain-like agglomerates. Volatile carbon particles were found on the surface of dust particles at the interaction point with diesel agglomerate. EDS measurements were used to identify chemical traces of dust related elements and identify the source of chain-like agglomerates. Controlled zone results showed the size distribution decreased for the agglomerates emitted from engines with newer technology. Three types of chain-like agglomerates were identified during image analysis: chain-like agglomerates with graphitic structure, amorphous carbon-rich agglomerates, and chain-like agglomerates with intrinsic catalyst. Size segregated sampling followed by microscopic and chemical analysis assisted to determine detailed characterization and source apportionment of aerosols in the underground atmosphere”--Abstract, page iii

Human exposure assessment of different arsenic species in household water sources in a high risk arsenic area

Understanding arsenic speciation in water is important for managing the potential health risks associated with chronic arsenic exposure. Most arsenic monitoring studies to date have only measured total arsenic, with few looking at arsenic species. This study assessed 228 ground water sources in six unstudied villages in Pakistan for total, inorganic and organic arsenic species using ion chromatography inductively coupled plasma collision reaction cell mass spectrometry. The concentration levels approached 3090 μg L−1 (95% CI, 130.31, 253.06) for total arsenic with a median of 57.55 µg L-1, 3430 μg L−1 (median=52) for arsenate (As+5) and 100 μg L−1 (median=0.37) for arsenite (As+3). Exceedance of the WHO provisional guideline value for arsenic in drinking water (10 μg L−1) occurred in 89% of water sources. Arsenic was present mainly as arsenate (As+5). Average daily intake of total arsenic for 398 residents living in the sampled houses was found up to 236.51 µg kg−1 day−1. This exposure estimate has indicated that 63% of rural residents exceeded the World Health Organization’s provisional tolerable daily intake (PTDI) of 2.1 µg kg−1 day−1 body weight. Average daily intake of As+5 was found to be 15.63 µg kg−1 day−1 (95% CI, 5.53, 25.73) for children ≤ 16 and 15.07 µg kg−1 day−1 (95% CI, 10.33, 18.02) for adults. A mean daily intake of 0.09 µg kg−1 day−1 was determined for As+3 for children and 0.26 µg kg−1 day−1 for adults. Organic arsenic species such as monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and Arsenobetaine (AsB) were found to be below their method detection limits (MDLs)

High Resolution Multi-parametric Diagnostics and Therapy of Atrial Fibrillation: Chasing Arrhythmia Vulnerabilities in the Spatial Domain

After a century of research, atrial fibrillation (AF) remains a challenging disease to study and exceptionally resilient to treatment. Unfortunately, AF is becoming a massive burden on the health care system with an increasing population of susceptible elderly patients and expensive unreliable treatment options. Pharmacological therapies continue to be disappointingly ineffective or are hampered by side effects due to the ubiquitous nature of ion channel targets throughout the body. Ablative therapy for atrial tachyarrhythmias is growing in acceptance. However, ablation procedures can be complex, leading to varying levels of recurrence, and have a number of serious risks. The high recurrence rate could be due to the difficulty of accurately predicting where to draw the ablation lines in order to target the pathophysiology that initiates and maintains the arrhythmia or an inability to distinguish sub-populations of patients who would respond well to such treatments. There are electrical cardioversion options but there is not a practical implanted deployment of this strategy. Under the current bioelectric therapy paradigm there is a trade-off between efficacy and the pain and risk of myocardial damage, all of which are positively correlated with shock strength. Contrary to ventricular fibrillation, pain becomes a significant concern for electrical defibrillation of AF due to the fact that a patient is conscious when experiencing the arrhythmia. Limiting the risk of myocardial injury is key for both forms of fibrillation. In this project we aim to address the limitations of current electrotherapy by diverging from traditional single shock protocols. We seek to further clarify the dynamics of arrhythmia drivers in space and to target therapy in both the temporal and spatial domain; ultimately culminating in the design of physiologically guided applied energy protocols. In an effort to provide further characterization of the organization of AF, we used transillumination optical mapping to evaluate the presence of three-dimensional electrical substrate variations within the transmural wall during acutely induced episodes of AF. The results of this study suggest that transmural propagation may play a role in AF maintenance mechanisms, with a demonstrated range of discordance between the epicardial and endocardial dynamic propagation patterns. After confirming the presence of epi-endo dyssynchrony in multiple animal models, we further investigated the anatomical structure to look for regional trends in transmural fiber orientation that could help explain the spectrum of observed patterns. Simultaneously, we designed and optimized a multi-stage, multi-path defibrillation paradigm that can be tailored to individual AF frequency content in the spatial and temporal domain. These studies continue to drive down the defibrillation threshold of electrotherapies in an attempt to achieve a pain-free AF defibrillation solution. Finally, we designed and characterized a novel platform of stretchable electronics that provide instrumented membranes across the epicardial surface or implanted within the transmural wall to provide physiological feedback during electrotherapy beyond just the electrical state of the tissue. By combining a spatial analysis of the arrhythmia drivers, the energy delivered and the resulting damage, we hope to enhance the biophysical understanding of AF electrical cardioversion and xiii design an ideal targeted energy delivery protocol to improve upon all limitations of current electrotherapy

Remote Sensing of Harmful Algal Blooms in the Mississippi Sound and Mobile Bay: Modelling and Algorithm Formation

The incidence and severity of harmful algal blooms have increased in recent decades, as have the economic effects of their occurrence./The diatom Pseudo-nitzschia spp. caused fisheries closures in Mobile Bay during 2005 due to elevated levels of domoic acid. In the previous 4 years Karenia brevis counts of \u3e5,000 cells L 1 have occurred in Mobile Bay and the Mississippi Sound. Population levels of this magnitude had previously been recorded only in 1996. Increases in human populations, urban sprawl, development of shoreline properties, sewage effluent and resultant changes in NP ratios of discharge waters, and decline in forest and marsh lands, will potentially increase future harmful algal bloom occurrences in the northern Gulf of Mexico. Due to this trend in occurrence of harmful algal populations, there has been an increasing awareness of the need for development of monitoring systems in this region. Traditional methods of sampling have proven costly in terms of time and resources, and increasing attention has been turned toward use of satellite data in phytoplankton monitoring and prediction. This study shows that remote sensing does have utility in monitoring and predicting locations of phytoplankton blooms in this region. It has described the composition and spatial and temporal relationships of these populations, inferring salinity, total nitrogen and total phosphorous as the primary variables driving phytoplankton populations in Mobile Bay and the Mississippi Sound. Diatoms, chlorophytes, cryptophytes, and dinoflagellates were most abundant in collections. Correlations between SeaWiFS, MODIS and in situ data have shown relationships between Rrs reflectance and phytoplankton populations. These data were used in formation of a decision tree model predicting environmental conditions conducive to the formation of phytoplankton blooms that is driven completely by satellite data. Empirical algorithms were developed for prediction of salinity, based on Rrs ratios of 510 nm/ 555 nm, creating a new data product for use in harmful algal bloom prediction. The capacity of satellite data for rapid, synoptic coverage shows great promise in supplementing future efforts to monitor and predict harmful algal bloom events in the increasingly eutrophic waters of Mobile Bay and the Mississippi Sound

Accurate sound synthesis of 3D object collisions in interactive virtual scenarios

Questa tesi affronta lo studio di algoritmi efficienti per la sintesi di suoni risultanti dalla collisione di oggetti generici, partendo da una descrizione fisica del problema. L'obiettivo della ricerca e' lo sviluppo di strumenti in grado di aumentare l'accuratezza del feedback uditivo in ambienti di realta' virtuale attraverso un approccio basato sulla fisica, senza il bisogno quindi di far riferimento a suoni pre-registrati. Data la loro versatilita' nel trattare geometrie complesse, i metodi agli elementi finiti (FEM) sono stati scelti per la discretizzazione spaziale di generici risonatori tridimensionali. Le risultanti equazioni discrete sono riarrangiate in modo da disaccoppiare i modi normali del sistema tramite l'utilizzo di tecniche di Analisi e Sintesi Modale. Queste tecniche, infatti, portano convenientemente ad algoritmi computazionalmente efficienti per la sintesi del suono. Implementazioni di esempio di tali algoritmi sono state sviluppate facendo uso solo di software open-source: questo materiale a corredo della tesi permette una migliore riproducibilita' dei risultati di questa tesi da parte di ricercatori aventi una preparazione nel campo della sintesi audio. I risultati originali presenti in questo lavoro includono: i tecniche efficienti basate sulla fisica che aiutano l'implementazione in tempo reale di algoritmi di sintesi del suono su hardware comune; ii un metodo per la gestione efficiente dei dati provenienti da analisi FEM che, assieme ad un modello espressivo per la dissipazione, permette di calcolare l'informazione caratterizzante un oggetto risonante e salvarla in una struttura dati compatta iii una trasformazione nel dominio discreto del tempo su due diverse rappresentazioni nello spazio degli stati di filtri digitali del secondo ordine, che permette il calcolo esatto di variabili derivate come la velocita' e l'energia di un risonatore anche quando semplici realizzazioni a soli poli sono impiegate i un'efficiente realizzazione multirate di un banco parallelo di risonatori, derivata usando una suddivisione con Quadrature-Mirror-Filters (QMF). Confrontata con lavori simili presenti in letteratura, questa realizzazione permette l'uso di eccitazione nonlineare in feedback per un banco di risonatori in multirate: l'idea chiave consiste nello svolgere un cambio di stato adattivo nel banco di risonatori, muovendo i risonatori dalla frequenza di campionamento elevata, usata per il processamento della fase transiente, ad un insieme di sottofrequenze ridotte usate durante l'evoluzione in stato libero del sistema.This thesis investigates efficient algorithms for the synthesis of sounds produced by colliding objects, starting from a physical description of the problem. The objective of this investigation is to provide tools capable of increasing the accuracy of the synthetic auditory feedback in virtual environments through a physics-based approach, hence without the need of pre-recorded sounds. Due to their versatility in dealing with complex geometries, Finite Element Methods (FEM) are chosen for the space-domain discretization of generic three-dimensional resonators. The resulting state-space representations are rearranged so as to decouple the normal modes in the corresponding equations, through the use of Modal Analysis/Synthesis techniques. Such techniques, in fact, conveniently lead to computationally efficient sound synthesis algorithms. The whole mathematical treatment develops until deriving such algorithms. Finally, implementation examples are provided which rely only on open-source software: this companion material guarantees the reproducibility of the results, and can be handled without much effort by most researchers having a background in sound processing. The original results presented in this work include: i efficient physics-based techniques that help implement real-time sound synthesis algorithms on common hardware; ii a method for the efficient management of FEM data which, by working together with an expressive damping model, allows to pre-compute the information characterizing a resonating object and then to store it in a compact data structure; iii a time-domain transformation of the state-space representation of second-order digital filters, allowing for the exact computation of dependent variables such as resonator velocity and energy, even when simple all-pole realizations are used; iv an efficient multirate realization of a parallel bank of resonators, which is derived using a Quadrature-Mirror-Filters (QMF) subdivision. Compared to similar works previously proposed in the literature, this realization allows for the nonlinear feedback excitation of a multirate filter bank: the key idea is to perform an adaptive state change in the resonator bank, by switching the sampling rate of the resonators from a common highest value, used while processing the initial transient of the signals at full bandwidth, to a set of lower values in ways to enable a multirate realization of the same bank during the steady state evolution of the signals