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Mechanistic modeling of evaporating thin liquid film instability on a bwr fuel rod with parallel and cross vapor flowHu, Chih-Chieh 20 January 2009 (has links)
This work has been aimed at developing a mechanistic, transient, 3-D numerical model to predict the behavior of an evaporating thin liquid film on a non-uniformly heated cylindrical rod with simultaneous parallel and cross flow of vapor. Interest in this problem has been motivated by the fact that the liquid film on a full-length boiling water reactor fuel rod may experience significant axial and azimuthal heat flux gradients and cross flow due to variations in the thermal-hydraulic conditions in surrounding subchannels caused by proximity to inserted control blade tip and/or the top of part-length fuel rods. Such heat flux gradients coupled with localized cross flow may cause the liquid film on the fuel rod surface to rupture, thereby forming a dry hot spot. These localized dryout phenomena can not be accurately predicted by traditional subchannel analysis methods in conjunction with empirical dryout correlations. To this end, a numerical model based on the Level Contour Reconstruction Method was developed. The Standard k- turbulence model is included. A cylindrical coordinate system has been used to enhance the resolution of the Level Contour Reconstruction Model. Satisfactory agreement has been achieved between the model predictions and experimental data.
A model of this type is necessary to supplement current state-of-the-art BWR core thermal-hydraulic design methods based on subchannel analysis techniques coupled with empirical dry out correlations. In essence, such a model would provide the core designer with a "magnifying glass" by which the behavior of the liquid film at specific locations within the core (specific axial node on specific location within a specific bundle in the subchannel analysis model) can be closely examined. A tool of this type would allow the designer to examine the effectiveness of possible design changes and/or modified control strategies to prevent conditions leading to localized film instability and possible fuel failure.
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Using Availability Indicators to Enhance Context-Aware Family Communication ApplicationsNagel, Kristine Susanne 05 July 2006 (has links)
Family conversation between homes is difficult to initiate at mutually agreeable times as neither participant has exact knowledge of the other's activities or intentions. Whether calling to plan an important family gathering or simply to connect with family members, the question is: Is now a good time to call? People expect friends and family to learn their activity patterns and to minimize interruptions when calling. Can technology provide awareness cues to the caller, even prior to the initiation of the call?
This research focuses on sampling the everyday activities of home life to determine environmental factors, which may serve as an indicator for availability. These external factors may be effective for identifying household routines of availability and useful in determining when to initiate conversation across homes. Several workplace studies have shown a person's interruptibility can be reliably assessed and modeled from specific environmental cues; this work looks for similar predictive power in the home. Copresence, location, and activity in the home were investigated as correlates to availability and for their effectiveness within the social protocol of family conversation. These studies indicate there are activities that can be sensed, either in real-time or over some time span, that correlate to self-reported availability. However, the type and amount of information shared is dependent upon individual preferences, social accessibility, and patterns of activities. This research shows friends and family can improve their predictions of when to call if provided additional context, and suggests that abstract representations of either routines or explicit availability status is sufficient and may be preferred by providers. Availability prediction is feasible in the home and useful to those outside the home, but the level of detail to provide in particular situations needs further study. This work has implications for the development of groupware systems, the automatic sensing of activity to deal with interruption, and activity recognition in the home.
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Development of Novel Reconstruction Methods Based on l1--Minimization for Near Infrared Diffuse Optical TomographyShaw, Calbvin B January 2012 (has links) (PDF)
Diffuse optical tomography uses near infrared (NIR) light as the probing media to recover the distributions of tissue optical properties. It has a potential to become an adjunct imaging modality for breast and brain imaging, that is capable of providing functional information of the tissue under investigation. As NIR light propagation in the tissue is dominated by scattering, the image reconstruction problem (inverse problem) tends to be non-linear and ill-posed, requiring usage of advanced computational methods to compensate this.
Traditional image reconstruction methods in diffuse optical tomography employ l2 –norm based regularization, which is known to remove high frequency noises in the re-constructed images and make them appear smooth. The recovered contrast in the reconstructed image in these type of methods are typically dependent on the iterative nature of the method employed, in which the non-linear iterative technique is known to perform better in comparison to linear techniques. The usage of non-linear iterative techniques in the real-time, especially in dynamical imaging, becomes prohibitive due to the computational complexity associated with them.
In the rapid dynamic diffuse optical imaging, assumption of a linear dependency in the solutions between successive frames results in a linear inverse problem. This new frame work along with the l1–norm based regularization can provide better robustness to noise and results in a better contrast recovery compared to conventional l2 –based techniques. Moreover, it is shown that the proposed l1-based technique is computationally efficient compared to its counterpart(l2 –based one). The proposed framework requires a reasonably close estimate of the actual solution for the initial frame and any suboptimal estimate leads to erroneous reconstruction results for the subsequent frames.
Modern diffuse optical imaging systems are multi-modal in nature, where diffuse optical imaging is combined with traditional imaging modalities such as MRI, CT, and Ultrasound. A novel approach that can more effectively use the structural information provided by the traditional imaging modalities in these scenarios is introduced, which is based on prior image constrained- l1 minimization scheme. This method has been motivated by the recent progress in the sparse image reconstruction techniques. It is shown that the- l1 based frame work is more effective in terms of localizing the tumor region and recovering the optical property values both in numerical and gelatin phantom cases compared to the traditional methods that use structural information.
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Allocation by Association: Goal Networks and the Allocation of Resources Across Multiple DemandsDolis, Chad M. 19 August 2013 (has links)
No description available.
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Srovnání vybraných způsobů ocenění pro nemovitost typu rodinný dům v Kroměříži a okolí / Comparison of Selected Ways of Pricing of Houses Located in Kroměříž and SurroundingsŠtípalová, Hana January 2010 (has links)
The Master's thesis is engaged in analyse of methods of pricing and comparison of each other. This work is compiled from historical evolution of prising immovables, over adjustment prising in international prising standards, over defination elementary conceptions to analysis selected ways of prising of houses. The Master's thesis analyses process of prising methods and analyses sources which we need to compile a ways of prising. These are most important things to know, when we want to compare ways of prising. There are ten houses in this work from Kroměříž and surroundings. The main target of master's thesis is to ratify and to explain that location of houses and their surroundings are the most importatnt. These two points of view influenced price and salableing of houses. There is a comparison of ways of prising houses at the end of work
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Measurement of focal spots of X-ray tubes using a CT reconstruction approach on edge images of holes with a diameter larger than the focal spot and comparison to classical pinhole imagingHashemi, Seyedreza 18 July 2024 (has links)
Non-destructive testing (NDT) combines the application of the sciences of phys-ics, mathematics, chemistry, and biology to create a comprehensive process, that can be used for inspection, examination, and testing of materials or components to find flaws, defects or discontinuities at the surface, subsurface areas, or inner volume of the component under test. NDT maintains the serviceability of the component after inspection, without causing any damage to its original form or usefulness. In addition to the need for safety, NDT is used to ensure the efficiency and durability of the equipment. NDT is carried out to ascertain that the compo-nents or materials being used are not damaged or faulty and are fit to be used by any personnel. The result of testing can show whether the components need to be repaired or if they are safe for operation. The first NDT method to evolve in the industrial age was X-ray testing (RT). This innovation was discovered by German physicist Wilhelm Conrad Röntgen in 1895. His experiments involved cathode rays which led to not only the discovery of X-ray but to the first Nobel Prize. Among all NDT methods, RT is no exception, so there are still many issues for optimizations even today. One of them is the measurement of the focal spot of X-ray tubes. The size of the focal spot is critical for imaging because it deter-mines the spatial resolution in the X-ray image. The classical way to image focal spots of X-ray tubes is by pinhole imaging using a camera obscura. This is caused by the fact, that X-ray radiation cannot be imaged by lenses like optical wavelengths. This pinhole imaging has been standardized since a long time, e.g., by EN 12543:1999, ASTM E 1165:1992, IEC 336:1982, and DIN 6823:1962. But this method has a natural lower limit, which is defined by the diameter of the pin-hole (today min. 10 µm). Focal spot sizes lower than this diameter cannot be im-aged and measured correctly. Meanwhile, the development of algorithms of Computed Tomography allows a similar approach for focal spot imaging but using pinholes with a much larger diameter than the focal spot size to be imaged. In such a large hole the edge unsharpness of the hole rim by the focal spot size can be measured in different directions, and a first derivative following a CT recon-struction will deliver a nearly identical focal spot image compared to classical pin-hole imaging. There is principal no lower focal spot size limit anymore. Computa-tional problems must be analyzed and application and parameter range for practi-cal focal spot measurements have to be determined.
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