446 research outputs found
Drought and famine relationships in Sudan: policy implications
No full textSudan is one of the few countries where famine still persists. Why? What are the determinants of famine in Sudan? What is the role of drought, especially in the context of economic policy failure and war? Who is affected by famine? What needs to be done to mitigate and prevent famine? These are some of the questions addressed in Drought and Famine Relationships in Sudan: Policy Implications, Research Report 88, by Tesfaye Teklu, Joachim von Braun, and Elsayed Zaki. The research is particularly concerned with quantitatively tracing the drought-production-consumption-nutrition linkages under famine conditions at the household level in order to identify effective means of alleviating and preventing famine.... while famine is often strongly linked to drought, this research finds that even under the severe economic constraints of Sudan, suitable government planning and action can forestall that linkage.Famines Sudan., Droughts Sudan., Food relief Government policy Sudan., Drought relief Government policy Sudan.,
HIT communication paper:Strategies and tips to increase your chances of winning an EACVI grant
No full textThe European Association of Cardiovascular Imaging (EACVI), a branch of the European Society of Cardiology (ESC), is dedicated to promoting excellence in clinical diagnosis, research, technical development, and education in cardiovascular imaging (CVI). One of the ways EACVI achieves its goals are through the grants it provides to fund the professional development of young cardiologists in the field of non-invasive CVI. In the past 12 years, EACVI awarded a total of 41 grants, 29 for research and 12 for training. The success of the EACVI grant programme and the positive impact on young professionals’ careers were published in 2009 and 2015
Intrathecal Drug Delivery Systems Survey: Trends in Utilization in Pain Practice [Corrigendum]
No full textAbd-Sayed A, Fiala K, Weisbein J, et al. J Pain Res. 2022;15:1305–1314.
The authors have advised there is an error in the author list on page 1305. The author name “Alaa Abd-Sayed” should read “Alaa Abd-Elsayed”.
The authors apologize for this error
Représentations littéraires du sacré dans le roman maghrébin de langue française
No full textThis interdisciplinary study explores how Driss Chraïbi’s L’Homme du Livre (1995), Assia Djebar’s Loin de Médine (1991), and Anissa Boumediène’s La fin d’un monde (1991) present accounts of particular historical moments in early Islam. This study explores the role of the imagination as well as freedom of invention when reconstructing historical events. It engages the novels through a study of the interplay between the literary text and the sources and traditions that impact and shape the text narrative. Gaining direct access to the original sources in Arabic serves to analyze how religious and early historical materials are considered in and reflected by the fictional texts. Because the sources tend to differ in both content and approach, this study examines their preoccupations in order to determine the criteria of selection applied by each novelist.Ph.D.Includes bibliographical referencesIncludes vitaby Hanan Elsaye
Degradation modeling of ink fading and diffusion of printed images
No full textColor printing plays an important role in the modern society. It is known that the color of printed images degrades gradually due to the fading and diffusion of the inks. Color degradation leads to a distortion or loss of the original information in printed images. Therefore, it is desirable to understand how the color of printed images changes over time. In this dissertation, we present degradation models to predict the characteristics of the ink fading and diffusion of printed images.
We begin by modeling the ink degradation from a physics-based perspective. Color images are printed by projecting small ink dots on medium, usually paper. This technique is called halftone printing. Halftone printing of color images results in a variety of ink mixtures and subsequently their potential catalytic fading. For the most commonly used Cyan-Magenta-Yellow-Black (CMYK) ink set, sixteen possible ink mixtures are generated during printing. A state transition diagram is then proposed for the ink fading in this multi-ink printing scenario. The ink area coverage is used as the performance indicator. Assuming constant fading and diffusion rates, we develop an ink fading model based on the differential equations according to the state transition diagram and an autoregressive ink diffusion model by discretizing the two-dimensional diffusion equation. The two models are then integrated into a single degradation model.
Further examination of the developed degradation models reveals that the fading or diffusion rate is equivalent to the hazard rate in reliability engineering. It is known that the hazard rate of the exponential failure time distribution is constant. Hence, the developed degradation model with constant fading and diffusion rates is equivalent to the multistate Markov process model with exponential transition time distribution. By using non-exponential transition time distributions, the fading and diffusion rates become time-varying and a more general semi-Markov process degradation model is developed accordingly.
Moreover, stochastic process models are investigated to provide stochastic area coverage prediction for the ink degradation. We first model the ink fading using the Hull-White/Vasicek (HWV) stochastic process. The HWV ink fading model considers that the variance of the ink area coverage shrinks as it approaches zero. Besides, spatial convolution is used to model ink diffusion. The two models are integrated into a spatio-temporal stochastic degradation model for the ink fading and diffusion of printed images. The cases of recurrent and non-recurrent time-varying fading and diffusion rates are investigated.
Inks on the paper degrade, so does the paper. The degradation of paper condition may in turn affect the degradation of the inks. Therefore, the investigation of the degradation modeling of ink fading and ink diffusion with ink-paper interactions is needed. Two aspects of the ink-paper interactions are considered, i.e., the effect of paper aging such as depolymerization and yellowing, and the fiber orientation of the paper.
The degradation process of printed images usually takes a very long time. An accelerated degradation model and the optimal design of accelerated degradation test planning is developed for accurate degradation prediction of printed images. The effects of three constant environmental stresses: temperature, humidity, and illumination (intensity), are investigated, and experimental data are used to validate the proposed model. The results show strong agreements between the proposed ink fading and ink diffusion prediction model and the actual experimental data.Ph.D.Includes bibliographical reference
Reliability estimation of balanced systems with multi-dimensional distributed units
No full textBalanced systems with multi-dimensional distributed units are emerging in a diverse range of industries. This includes Unmanned Aerial Vehicles (UAV) with multi-level of rotary wings, Spherical Unmanned Vehicles (SUV), Spherical Phased Array Antenna (SPAA), etc. In this dissertation, we present the reliability estimation for such systems. In particular, we consider two configurations: 1) balanced systems with units distributed circularly on multi-level and 2) balanced systems with units distributed spherically.
First, balanced systems with units distributed circularly on multi-level are generalized as (k₁, k₂)-out-of-(n, m) pairs: G balanced systems. We consider two scenarios: 1) all units perform the same function and 2) adjacent pairs perform complementary functions. For both scenarios, unbalanced system is considered as failed. When units fail and cause the system imbalance, we explore two approaches to rebalance the system: 1) forcing down units on other locations and 2) resuming units that are previously forced down (if any). When units in a system perform the same function, operational states are defined as balanced states with at least k₁ operating pairs and each operating pair has at least k₂ units on each side. The system reliability is obtained by enumerating all of the operational states and summing the probabilities of those states. For (k₁, k₂)-out-of-(n, m) pairs: G balanced systems with adjacent pairs performing complementary functions, in addition to maintaining system balance, the adjacent operating pairs are required to perform complementary functions. Thus, if a pair fails, one of the adjacent pairs is forced down. Similarly, the system reliability is obtained by enumerating all of the operational states. It becomes computational expensive when the number of units in each pair and/or the number of pairs are large. In that case, efficient algorithms are developed to obtain the reliability for such systems.
The balanced system with units distributed spherically is generalized as a spherical k-n-i: G balanced system. We consider two balancing requirements: 1) rotational balance is maintained so that the system is not rotating w.r.t. roll, yaw and pitch axes and 2) symmetrical balance is essential in improving the systems’ stability. We present mathematical approaches to determine the balance status of a system. Similarly, the unbalanced system is rebalanced by 1) forcing down units on other locations and 2) resuming previously forced-down units. The system reliability is obtained by the enumeration of operational states and calculation of operational states’ probabilities. We develop an efficient algorithm for reliability estimation when the number of units in the system is large.
Degradation models are developed for the (k₁, k₂)-out-of-(n, m) pairs: G balanced systems to further investigate the system reliability when degradation data are available. The degradation processes of units in the system are either stationary (inverse Gaussian process) or non-stationary (improved inverse Gaussian process). We propose a degradation balance mechanism in which the ‘most’ degraded units are forced down temporarily during the degradation process so that the system is less possible to fail due to imbalance. A closed-form lower bound reliability is presented when the balance mechanism is not applied. When it is applied, reliability is obtained by Monte Carlo simulation.
From the reliability study of the both configurations, it is observed that the reliability of a balanced system with multi-dimensional distributed units depends not only on the system’s total number of units and the least number of operating units, but also on the system configurations and balance requirements. Systems with more units do not necessarily provide a higher reliability since they are more likely to fail due to imbalance. Thus, optimal system design is key to maximize the system reliability which is investigated through numerical examples in this dissertation.Ph.D.Includes bibliographical reference
The Impact of Low-Power Design Methodology on Digital Libraries
No full textIn recent years, exciting new low-power design methods have been introduced, such as: multiple supply voltages, body bias techniques and power shut-off. In order to use these low power design methods, strict requirements for both libraries and tools are needed. An additional challenge is the introduction of more accurate characterization models for newer technologies (current source models like ECSM and CCS). This has made the task of library checking a serious issue that needs to be automated. The main part of this thesis presents a checker tool that is used to verify the consistency of the different library formats (views) in standard cell libraries. The layout consistency checker in our tool checks the consistency of the layout of pins between GDSII and LEF library views; we devised a new algorithm,Grid Formation and Centre Inclusion, for this checker. The tool also verifies the pin consistency and availability of cells across other library formats, such as: Verilog and Liberty. The tool was tested using different technology libraries (such as 90nm and 40nm), provided by different vendors (such as GLOBALFOUNDRIES); multiple interfacing errors were caught using our library checker tool. A second part at the end of the thesis shows experiments with some of the low-power design techniques used during the design of a digital block, using -for implementation- standard cells from one of the libraries that have been checked with the library checker tool. Benefits of using these techniques are evaluated and trade-offs are discussed. Power-Shut Off (PSO) design technique proved to be the most effective in reducing power consumption, with power savings that reached 20%.Circuits and SystemsElectrical Engineering, Mathematics and Computer Scienc
Anomaly detection and process diagnostic in three-dimensional surface topography
No full textThe recent development of optical measuring instruments has increased the use of surface topographic data for monitoring the quality of the engineered surface. Monitoring topographic variations in the surface is crucial for quality engineers since the change in the surface finish is closely related to the performance of products in use. However, several challenging issues such as the existence of spatial autocorrelation within the surface, and changes of topographic features such as position and shape of peaks and valleys across defect-free surfaces make it difficult to monitor variations in the surface. In addition, existing monitoring approaches fail to detect local changes in the surface. Moreover, surface inspection becomes more difficult when the surface contains local defects that are often concealed due to the high-dimensional data structure of the surface image.
This dissertation presents efficient anomaly detection approaches for monitoring topographic variations in the three-dimensional (3D) surface. We first propose a residual-based surface segmentation approach to effectively identify local surface changes. We obtain residuals from the surface through a fitted surface prediction model, which characterizes the generic behavior of defect-free surfaces. Then, the proposed approach binarizes the surface based on local residual properties and identifies the defective areas where residuals are spatially autocorrelated. By considering both deviated residuals and neighboring residuals, which have similar values from local regions, the approach effectively captures residual patterns in the defective areas, which are concealed due to the high-dimensional surface data structure. Then, a spatial randomness-based monitoring statistic is introduced to evaluate binarized surfaces in order to detect surface anomalies.
Second, we investigate unique surfaces that exhibit multiple in-control modes. Due to the complexities of modern industrial processes, surfaces of final products under the normal manufacturing process may have multiple modes, such that the surface consists of different topographic features from one in-control mode to another. In this case, existing monitoring approaches based on the single mode surface cannot characterize normal surfaces with multiple modes, and result in poor detection performance. To overcome this limitation, a new approach for monitoring variations in multimode surface topography is presented. We propose a multimode surface prediction model, which characterizes the generic behavior of normal surfaces with multiple in-control modes. Moreover, we present a mode-specific surface monitoring approach that identifies topographic variations on the surfaces based on the similarity between probability density function (PDF) of residuals from observed and normal surfaces obtained through the multimode surface prediction model. A novel probabilistic distance measure (PDM) is introduced to effectively measure the similarity between a single residual PDF and a set of residual PDFs under the same mode.
We then propose a novel approach for monitoring local topographic variations in the presence of multimode surface topography. We present a multimode surface binarization model that characterizes distinct topographic features of surfaces under different in-control modes and better identifies the local variations in the surface data. In order to systematically evaluate the deviations between the observed and defect-free surfaces with multiple in-control modes, we introduce a novel PDM that effectively compares spatial randomness between two binarized surfaces.
Lastly, we present a new approach for monitoring and diagnosing local topographic variations on the surface topography. Once the observed surface is considered as an anomaly, identifying the shape, location, or size of the defective area is essential for diagnosing the root cause of the abnormal surface. Thus we develop a variable selection-based fault detection and diagnostic approach that selects potentially defective areas on the surface by considering the spatial structure of the surface and residual information. Suspicious areas are then employed to detect anomalies and further utilized to identify defect size, location, and shape for fault diagnosis purposes.
The proposed surface monitoring approaches in this dissertation are efficient and effective in monitoring spatial patterns in topographic data. The proposed monitoring approach investigated in Chapter 3 is superior to existing surface monitoring approaches regardless of the defect size and the number of defects. In the presence of multimode in-control surfaces, the mode-specific surface monitoring approach developed in Chapter 4 outperforms existing single mode and multimode-based approaches in detecting global topographic variations. Moreover, local topographic variations in the presence of multimode surface topography are effectively captured by the proposed approach introduced in Chapter 5. Finally, the proposed approach presented in Chapter 6 identifies fault diagnostic information such as fault size and location, and it is sensitive to detecting local variations on the surface. The effectiveness of the proposed approaches is demonstrated through extensive numerical simulation studies and real-life applications of paper surface monitoring.Ph.D.Includes bibliographical reference
Nonsmooth impact mechanics of a free falling body
No full textIn this study, several models are developed for analyzing the oblique impact of a container dropped from a height above the impacting surface. The governing equations for impact of rigid bodies in the presence of friction are developed. A clear relationship for determining sliding behavior is presented. For both frictional regimes, the dependence of the energy loss on the initial parameters is analyzed. Several vibrational impact models are presented and analyzed. These models produce a transient description of the impact force and aid in the determination of the ratio of the cushion and cargo stiffness which produce the best impact outcome. The effect of aerodynamic drag prior to impact is also analyzed. The equations governing the aerodynamics form a set of coupled nonlinear differential equations. The numerical solution of these equations illustrates that there exists a point where the object’s velocity reaches a favorable minimum, which is substantially below the terminal velocity. An approximate solution, obtained by decoupling the aerodynamic equations, is presented and validated. Both the rigid body impact mechanics and the aerodynamics are combined in a simulation code capable of analyzing subsequent impact. The simulated tumbling distances for a container, which was designed for the U.S. Army, are compared to experimental drop test data. The results validate the use of the rigid body model for this type of container.M.S.Includes bibliographical referencesIncludes vitaby Alexey Titovic
Assessing the impacts of urban beehives on wild bees using individual, community, and population-level metrics
No full textSeveral species of wild bees are in decline globally and the presence of managed honey bees is one of many proposed stressors on wild bee populations. However, there is limited knowledge of the impacts of honey bee hives on wild bees, especially in urban landscapes. We performed a field study to assess the associations between honey bees and wild bees within the Greater Toronto Area in Ontario, Canada. We measured relative abundance of honey bees, wild bee metrics (abundance, community composition, functional diversity, and body size), and floral resources (floral density and richness); we also calculated impervious surface at 500 m and 1 km for each of our sites. Our main findings were that increasing honey bee abundance was correlated with decreases in wild bee species richness and functional diversity, as well as two wild bee species’ abundances and one wild bee species body size, out of many assessed. This research adds to the growing body of literature aiming to evaluate whether honey bees are a stressor on wild bees in urban landscapes, which will be valuable for informing conservation management practices and future research.We thank NSERC, OGS, Entomological Society of Canada, and Enbridge for funding for this research that was awarded to Sarah MacKell
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