UWB system and algorithms for indoor positioning

This research work presents of study of ultra-wide band (UWB) indoor positioning considering different type of obstacles that can affect the localization accuracy. In the actual warehouse, a variety of obstacles including metal, board, worker and other obstacles will have NLOS (non-line-of-sight) impact on the positioning of the logistics package, which influence the measurement of the distance between the logistics package and the anchor , thereby affecting positioning accuracy. A new developed method attempts to improve the accuracy of UWB indoor positioning, through and improved positioning algorithm and filtering algorithm. In this project, simulate the warehouse environment in the laboratory, several simulation proves that the used Kalman filter algorithm and Markov algorithm can effectively reduce the error of NLOS. Experimental validation is carried out considering a mobile tag mounted on a robot platform.Este trabalho de pesquisa apresenta um estudo de posicionamento de banda ultra-larga (UWB) em ambientes internos considerando diferentes tipos de obstáculos que podem afetar a precisão de localização. No armazém real, uma variedade de obstáculos incluindo metal, placa, trabalhador e outros obstáculos terão impacto NLOS (não linha de visão) no posicionamento do pacote logístico, o que influencia a medição da distância entre o pacote logístico e a âncora, afetando assim a precisão do posicionamento. Um novo método desenvolvido tenta melhorar a precisão do posicionamento interno UWB, através de um algoritmo de posicionamento e algoritmo de filtragem aprimorados. Neste projeto, para simular o ambiente de warehouse em laboratório, diversas simulações comprovam que o algoritmo de filtro de Kalman e o algoritmo de Markov usados podem efetivamente reduzir o erro de NLOS. A validação experimental é realizada considerando um tag móvel montado em uma plataforma de robô

Développement des systèmes d’imagerie basés sur la tomographie par cohérence optique visant l’étude des maladies cardiovasculaires

Les maladies cardiovasculaires (CVD) sont la principale cause de décès depuis des décennies. Son taux de morbidité élevé engendre un fardeau social et économique énorme et à la société. L’imagerie biomédicale est un outil important pour étudier et évaluer les CVDs. Notamment, la tomographie par cohérence optique (OCT) a montré des avantages attrayants pour la recherche appliquée aux CVDs. Le but global de cette thèse est le développement de systèmes OCT combinés avec d’autres techniques d’imagerie optique pour étudier les CVDs. Le premier objectif est de développer un système d'imagerie intravasculaire combinant l’OCT et l'imagerie par fluorescence proche infrarouge (NIRF), qui pourrait à terme être utilisé pour la détection et l'évaluation de l'athérosclérose dans les artères coronaires. L’originalité du travail se situe dans l’utilisation d’une nouvelle technique de détection de photons, la détection de photons à déclenchement rapide, intégrée dans notre système d’imagerie, ce qui a considérablement amélioré le rapport signal sur bruit et la sensibilité en profondeur de la NIRF. Une expérience ex vivo dans des conditions réalistes a validé le mécanisme de notre système d'imagerie intravasculaire à double modalité au niveau des aspects optique, mécanique et logiciel. Les images hybrides provenant de l'OCT et de la NIRF ont fourni des informations structurelles et moléculaires sur le fantôme imitant le vaisseau sanguin, ce qui suggère un grand potentiel d’utilisation de notre système d'imagerie chez des modèles animaux. Le deuxième objectif de cette thèse était d’étudier les impacts de l’athérosclérose sur différents aspects du cerveau de souris avec l’aide de plusieurs techniques d’imagerie optique, y compris l’imagerie intrinsèque optique, l’OCT et la microscopie à deux-photon. En comparaison avec les souris athérosclérotiques jeunes, le groupe âgé a montré un changement de concentration plus faible en hémoglobine oxygénée, hémoglobine désoxygénée et hémoglobine totale dans le cortex somatosensoriel à la suite de la stimulation par vibrisse, ce qui indique que la maladie d’athérosclérose réduit la réponse hémodynamique à la stimulation sensorielle. Les résultats obtenus à partir des données Doppler OCT ont révélé que le diamètre et le débit sanguin moyen des artérioles descendantes chez les souris ATX âgées étaient significativement plus petits comparés avec ceux des souris ATX jeunes, ce qui suggère que l'athérosclérose entraîne une dégénérescence structurelle et fonctionnelle des artérioles. L’altération fonctionnelle a également été observée dans les capillaires chez les souris ATX âgées, caractérisée par une plus faible vitesse es globules rouges (RBC), un plus faible flux de RBC, un plus faible hématocrite et une plus grande hétérogénéité du temps de transit capillaire. L’oxygénation tissulaire évaluée par la microscopie à deux photons a confirmé que l’altération de la microvascularisation liée à l’athérosclérose compromettait l’apport d’oxygène au tissu cérébral, amenant une hypoxie cérébrale chez les vieilles souris ATX. Les capillaires chez les souris ATX âgées ont été trouvés dilatés, ce qui pourrait être un mécanisme de régulation servant à compenser partiellement la diminution du débit sanguin associée à l'athérosclérose. Le troisième objectif de cette thèse est d’étudier la réparation du tissu cérébral et la régénération microvasculaire suite à un accident vasculaire cérébral (AVC) ischémique chez des souris en utilisant un système OCT construit dans le laboratoire. Le modèle d'AVC ischémique a été créé par occlusion photo-thrombotique des capillaires. Sur les images de l'OCT, seuls les tissus cérébraux profonds ont été endommagés par l'AVC ischémique, alors que les tissus proches de la surface corticale étaient intacts bien qu'ils aient été exposés à une intensité de laser plus élevée pendant la photo-thrombose. Cette observation implique que les tissus cérébraux profonds sont plus vulnérables lorsque l’apport d’oxygène des capillaires est interrompu au cours d’un AVC ischémique. Au cours de la récupération post-AVC, la lésion ischémique diminuait pendant que la régénération microvasculaire progressait. De plus, le réseau capillaire nouvellement formé autour de la lésion avait une structure hautement organisée et directionnelle avec un grand pourcentage de segments capillaires s'étendant vers le centre ischémique. Plus le réseau capillaire était profond, mieux sa structure était organisée, ce qui suggère que l'oxygénation des tissus profonds est plus dépendante du réseau capillaire. Notre analyse des événements de blocage capillaire a révélé que l’AVC ischémique augmentait à la fois la densité et l’incidence de blocage capillaire. Étant donné que le blocage capillaire pourrait entraîner une réduction du débit sanguin cérébral, il pourrait être utile de le cibler pour chercher de nouveaux traitements pour l'AVC.----------ABSTRACT Cardiovascular diseases (CVD) have been the leading cause of death for decades, and their high morbidity rate has led to enormous social and economic burden to both patients and society. Biomedical imaging systems are important tools to study and assess CVDs. Optical coherence tomography (OCT) has shown appealing advantages in CVD research. The general purpose of this thesis is the development of OCT-based imaging systems coupled with other optical imaging techniques to investigate CVDs. The first objective of this thesis is to develop an intravascular imaging system combining OCT and near infrared fluorescence (NIRF) imaging, which could ultimately be used for the detection and evaluation of atherosclerosis in coronary arteries. A novel photon detection technique, fast time-gating photon detection, was integrated into our imaging system, which improved significantly the signal-to-noise ratio and the depth sensitivity of NIRF. Ex vivo experiment under realist conditions validated the mechanism of our dual modality intravascular imaging system in terms of the optical, mechanical and software aspects. The hybrid images from OCT and NIRF provided structural and molecular information on the vessel-mimicking phantom, suggesting a great potential of our imaging system to be used in animal models. The second objective of this thesis is to study the impact of atherosclerotic disease on different aspects of mouse brain by using a variety of high-resolution optical imaging techniques, including intrinsic optical signal imaging, OCT and two-photon microscopy. Compared with the young atherosclerotic (ATX) mice, the old ones displayed a smaller change in the concentration of oxygenated hemoglobin, deoxygenated hemoglobin and total hemoglobin in the barrel cortex following whisker stimulation, which indicates that atherosclerotic disease is associated with reduced hemodynamic response to sensory stimulation. Results derived from Doppler OCT data revealed that the diameter and the mean blood flow of diving arterioles in the old ATX mice were significantly smaller compared with those in the young ATX mice, suggesting that atherosclerosis leads to structural and functional degeneration in descending arterioles. Functional alteration was also observed in capillaries among the old ATX mice with lower red blood cell (RBC) speed, lower RBC flux, lower hematocrit and higher transit time heterogeneity. Tissue oxygenation assessed by two-photon microscopy confirmed that atherosclerosis-related microvasculature impairment severely compromised oxygen supply to brain tissue, causing cerebral hypoxia in the old ATX mice. Capillaries in the old ATX mice were found dilated, which could be a regulatory mechanism of partially compensating atherosclerosis-associated blood flow decrease. The third objective of this thesis is to study post-stroke tissue repair and microvasculature regeneration and function in a mouse model of stroke using a custom-made OCT imaging system. Ischemic stroke model was created by photo-thrombotic occlusion of capillaries. On OCT structural and angiographic images, only deep cerebral tissue was found damaged by the ischemic stroke, whereas tissue close to the cortical surface seemed intact although it was exposed to a high laser intensity during the photo-thrombosis. This observation implies that deep cerebral tissue is more vulnerable when oxygen supply from capillaries are interrupted during ischemic stroke. Over the course of post-stroke recovery, ischemic lesion diminished while microvasculature regeneration progressed. Furthermore, the newly formed capillary network surrounding the lesion had a highly organized and directional structure with a large percentage of capillary segments stretching towards the ischemic center. Deeper de novo microvasculature had a better organized structure than shallower one, suggesting that deeper tissue oxygenation has a higher dependence on capillary network. Our stalling event analysis revealed that ischemic stroke increased both stalling density and incidence. As stalling can lead to cerebral blood flow reduction, targeting post-stroke stalling could be useful to develop new treatment for stroke

A Comparison Study of the Transformation Behavior during Uniform Continuous Cooling and Hot Deformation Characteristics of a Wrought and Selective Laser Melting 4340 Steels

This study compares the Austenite Grain Growth Behavior and its Transformation Behavior during the uniform Continuous Cooling of a Selective Laser Melting (SLM) 4340 and conventional Wrought 4340 steels. SLM 4340 steels exhibit inferior mechanical properties then conventional Wrought 4340 steels. Hence, the effect of hot deformation on the final microstructure and mechanical properties of SLM 4340 steel were also investigated in this study. Standard dilatometry testing was used to study the Austenite decomposition behavior at different cooling rates and to develop the CCT diagrams. Hot Compression Testing was performed to investigate the effect of hot deformation on the microstructure of austenite for both systems SLM 4340 and Wrought 4340. Advanced microstructural characterization techniques, Scanning Electron Microscopy (SEM) and Orientation Imaging Microscopy (OIM) were employed to support the CCT diagrams. Electron Backscatter Diffraction (EBSD) and a special EBSD-IQ characterization technique were used to assess the percentage of the microstructural components observed. Three important observations were made: 1) the hardenability of the Wrought 4340 steel was higher than the SLM 4340 steel; 2) the presence of Granular Bainite was observed after slow cooling conditions in both steels. MTEXT, a MatLab program, was used to reconstruct the prior Austenite grains (PAG). The SLM steel exhibited finer Austenite grain size distribution than the Wrought steel in the temperature range studied; and 3) the porosity in SLM 4340 was closed during the hot compression tests improving its mechanical properties. The level of microstructural refinement of austenite after hot deformation was measured by the effective interfacial area per unit volume (Sv) parameter for the SLM 4340 and Wrought 4340 steels

Soft Phenotyping for Sepsis via EHR Time-aware Soft Clustering

Sepsis is one of the most serious hospital conditions associated with high mortality. Sepsis is the result of a dysregulated immune response to infection that can lead to multiple organ dysfunction and death. Due to the wide variability in the causes of sepsis, clinical presentation, and the recovery trajectories identifying sepsis sub-phenotypes is crucial to advance our understanding of sepsis characterization, identifying targeted treatments and optimal timing of interventions, and improving prognostication. Prior studies have described different sub-phenotypes of sepsis with organ-specific characteristics. These studies applied clustering algorithms to electronic health records (EHRs) to identify disease sub-phenotypes. However, prior approaches did not capture temporal information and made uncertain assumptions about the relationships between the sub-phenotypes for clustering procedures. We develop a time-aware soft clustering algorithm guided by clinical context to identify sepsis sub-phenotypes using data from the EHR. We identified six novel sepsis hybrid sub-phenotypes and evaluated them for medical plausibility. In addition, we built an early-warning sepsis prediction model using logistic regression. Our results suggest that these novel sepsis hybrid sub-phenotypes are promising to provide more precise information on the recovery trajectory which can be important to inform management decisions and sepsis prognosis

Internet usage and household electricity consumption

This paper investigates the impact of the popularization and usage of the Internet on household electricity consumption in China, as well as the mediating role of sleep duration. By employing data from the China Family Panel Studies (CFPS) and employing the basic ordinary least squares (OLS) model, the mediation model, and the instrumental variable (IV) approach, we derive the following conclusions. The results from the basic OLS regression indicate a positive relationship between internet usage and household electricity expenditure, implying that households that use the Internet tend to have higher electricity bills. Subsequently, by introducing sleep duration as a mediating variable, we find that internet usage leads to shorter sleep duration, indirectly resulting in increased household electricity costs. To address potential endogeneity concerns, we employ the instrumental variable approach to correct for the impact of internet usage on household electricity consumption. In addition, through heterogeneity analysis, we found that internet usage impacts households with different characteristics

Impact of atherosclerotic disease on cerebral microvasculature and tissue oxygenation in awake LDLR-/-hApoB+/+ transgenic mice

We explore cortical microvasculature changes during the progression of atherosclerosis using young and old transgenic atherosclerotic (ATX) mice with thinned-skull cranial window. In awake animals, exploiting intrinsic signal optical imaging, Doppler optical coherence tomography, and two-photon microscopy, we investigate how the progression of atherosclerotic disease affects the morphology and function of cortical microvasculature as well as baseline cerebral tissue oxygenation. Results show that aged ATX mice exhibited weaker hemodynamic response in the somatosensory cortex to whisker stimulation and that the diameter of their descending arterioles and associated mean blood flow decreased significantly compared with the young ATX group. Data from two-photon phosphorescence lifetime microscopy indicate that old ATX mice had lower and more heterogeneous partial pressure of oxygen ( PO 2 ) in cortical tissue than young ATX mice. In addition, hypoxic micropockets in cortical tissue were found in old, but not young, ATX mice. Capillary red blood cell (RBC) flux, RBC velocity, RBC velocity heterogeneity, hematocrit, and diameter were also measured using line scans with two-photon fluorescence microscopy. When compared with the young group, RBC flux, velocity, and hematocrit decreased and RBC velocity heterogeneity increased in old ATX mice, presumably due to disturbed blood supply from arterioles that were affected by atherosclerosis. Finally, dilation of capillaries in old ATX mice was observed, which suggests that capillaries play an active role in compensating for an oxygen deficit in brain tissue

Lower limb arterial calcification and its clinical relevance with peripheral arterial disease

Lower limb arterial calcification (LLAC) is associated with an increased risk of mortality and it predicts poor outcomes after endovascular interventions in patients with peripheral artery disease (PAD). Detailed histological analysis of human lower artery specimens pinpointed the presence of LLAC in two distinct layers: the intima and the media. Intimal calcification has been assumed to be an atherosclerotic pathology and it is associated with smoking and obesity. It becomes instrumental in lumen stenosis, thereby playing a crucial role in disease progression. On the contrary, medial calcification is a separate process, systematically regulated and linked with age advancement, diabetes, and chronic kidney disease. It prominently interacts with vasodilation and arterial stiffness. Given that both types of calcifications frequently co-exist in PAD patients, it is vital to understand their respective mechanisms within the context of PAD. Calcification can be easily identifiable entity on imaging scans. Considering the highly improved abilities of novel imaging technologies in differentiating intimal and medial calcification within the lower limb arteries, this review aimed to describe the distinct histological and imaging features of the two types of LLAC. Additionally, it aims to provide in-depth insight into the risk factors, the effects on hemodynamics, and the clinical implications of LLAC, either occurring in the intimal or medial layers

A simulation study investigating potential diffusion-based MRI signatures of microstrokes

ABSTRACT: Recent studies suggested that cerebrovascular micro-occlusions, i.e. microstokes, could lead to ischemic tissue infarctions and cognitive deficits. Due to their small size, identifying measurable biomarkers of these microvascular lesions remains a major challenge. This work aims to simulate potential MRI signatures combining arterial spin labeling (ASL) and multi-directional diffusion-weighted imaging (DWI). Driving our hypothesis are recent observations demonstrating a radial reorientation of microvasculature around the micro-infarction locus during recovery in mice. Synthetic capillary beds, randomly- and radially-oriented, and optical coherence tomography (OCT) angiograms, acquired in the barrel cortex of mice (n = 5) before and after inducing targeted photothrombosis, were analyzed. Computational vascular graphs combined with a 3D Monte-Carlo simulator were used to characterize the magnetic resonance (MR) response, encompassing the effects of magnetic field perturbations caused by deoxyhemoglobin, and the advection and diffusion of the nuclear spins. We quantified the minimal intravoxel signal loss ratio when applying multiple gradient directions, at varying sequence parameters with and without ASL. With ASL, our results demonstrate a significant difference (p < 0.05) between the signal-ratios computed at baseline and 3 weeks after photothrombosis. The statistical power further increased (p < 0.005) using angiograms measured at week 4. Without ASL, no reliable signal change was found. We found that higher ratios, and accordingly improved significance, were achieved at lower magnetic field strengths (e.g., B0 = 3T) and shorter echo time TE (< 16 ms). Our simulations suggest that microstrokes might be characterized through ASL-DWI sequence, providing necessary insights for posterior experimental validations, and ultimately, future translational trials

Potential impacts of pandemics on global warming, agricultural production, and biodiversity loss

The rising frequency of infectious diseases under climate change poses an emerging threat to environmental and agricultural sustainability by consuming large quantities of materials. The demand for crops to produce personal protective equipment (PPE) competes for land and fertilizers, leads to cropland expansion, and accelerates climate change, but the ecological impacts remain unclear. Here we explore the impacts of pandemics on global warming, agricultural production, and biodiversity loss in an Earth system model by developing relationships between consumption of PPE and the rate of infection during COVID-19. Meeting the demand for PPE would increase production of cotton lint, corn, and natural rubber, which accelerates global warming by 0.2°C with 1.8% additional species losses by 2100. Our results suggest that the risks of public health, food security, climate change, and ecological integrity have been connected to each other, which should be considered when predicting the impacts of future pandemics