A review of quasi-coherent structures in a numerically simulated turbulent boundary layer

Preliminary results of a comprehensive study of the structural aspects of a numerically simulated number turbulent boundary layer are presented. A direct Navier-Stokes simulation of a flat-plate, zero pressure gradient boundary layer at Re0 = 670 was used. Most of the known nonrandom, coherent features of turbulent boundary layers are confirmed in the simulation, and several new aspects of their spatial character are reported. The spatial relationships between many of the various structures are described, forming the basis for a more complete kinematical picture of boundary layer physics than has been previously known. In particular, the importance of vortex structures of various forms to the generation of Reynolds shear stress is investigated

Course Journals Supporting Social Justice: Developing Equitable Scholarly Communications Through In-class Publishing Projects

How can OJS and OMP be used in classes to engage students in discussions around social justice in scholarly publishing? This presentation will discuss examples of course journals and book projects at Simon Fraser University (SFU) and Kwantlen Polytechnic University (KPU) which attempt to involve students in anti-colonial, anti-racist, and anti-oppressive forms of scholarship. These projects aim to be inclusive in a variety of ways: in terms of accessibility, language, content formats, and sustainability strategies. The presenters discuss the ways that OJS and OMP can be used in the classroom to develop students’ awareness of, and ability to address, social justice concerns in traditional publishing. Finally, they will explore how lessons learned from these case studies can be implemented in other courses

Analysis and Design of Digital Control Systems

All digital control systems contain at least one signal which is sampled in time and quantized in amplitude. Design of these systems is often based on the assumption that a very large number of levels of quantization is available leading to the approximation of the basically nonlinear system by a linear one. If the actual system is constructed so that the linear assumption is satisfied, the performance may be excellent but other design factors such as reliability, cost, weight, and power consumption may be very unsatisfactory. On the other hand, if the actual system is constructed so that only a few levels of quantization are available, the other factors may be quite satisfactory but a previously well-behaved system may now possess limit cycle oscillations, large static errors, and an objectionable transient response. Thus, an important problem in the field of digital control is the development of analysis and design procedures such that the designer has the freedom to select quantization schemes not satisfying the linear approximation but producing an overall satisfactory design. Two techniques are presented as a partial solution to the above problem. The first is based on a study of certain properties unique to quantized sampled-data system and uses Laplace transforms to carry out the analysis. It leads to closed form solutions but appears to be somewhat restricted in the class of systems to which it can be applied. The second technique is a numerical procedure based on the state transition method and uses a digital computer to carry out the numerical calculations, It is not limited by input type, order of the plant, state variables having other than zero initial conditions, or quantizer complexity. Using the first method, some closed form solutions are obtained for first and second order systems and the results favorably compared with the results obtained by the more general second method. Where possible the results of the second method are compared with the results of other workers. In other cases, typical results are checked by comparison with results from simulation on an analog computer. In all cases favorable comparisons are obtained. Design charts prepared by the numerical procedure are presented and examples given demonstrating their use to satisfy specifications on static accuracy, response time, and presence or absence of either overshoot or limit cycle oscillations. A set of rules are derived describing certain properties of the system^ e.g. a final value rule similar to the final value theorem for linear systems is obtained. These rules are found to he useful in , both analysis and design by reducing the number of computations required to solve a given problem, by providing physical insight into system operation, and by furnishing a check on certain result

A Hybrid Laser Ultrasonic Based Systemf ro Composite Molding

Conventional piezoelectric based ultrasonic systems have been extensively employed for material characterization. These systems however, have been challenged by the recent need to rapidly scan large areas of new materials such as composites having complex geometry. A promising candidate addressing this issue is laser ultrasonics. Though laser ultrasonics is not new and has generated considerable research interest in the past two decades, its industrial acceptance has been limited. Among its many benefits, laser ultrasonics promise the flexibility of a couplant free inspection system. Pulsed lasers, in particular, offer energy concentration at high repetition rates which can be readily directed at any location on the specimen for interrogation purposes. The detection of laser ultrasound is usually done through Michaelson or Fabry-Perot type interferometric systems. Though these detection systems have the advantage of couplant free detection, they constitute a major component of system cost owing to the precision required. The sensitivity of such systems are also not satisfactory

Metabolic syndrome increases risk of venous thromboembolism recurrence after acute deep vein thrombosis

An improved understanding of which patients are at higher risk of recurrent venous thromboembolism (VTE) is important to designing interventions to reduce degraded quality of life after VTE. Although metabolic syndrome (MetS), the clustering of hypertension, hyperlipidemia, diabetes mellitus, and obesity has been associated with a hypofibrinolytic state, data linking VTE recurrence with MetS remain limited. The purpose of this study was to measure the prevalence of MetS in patients with deep vein thrombosis (DVT) across a large population and determine its effect on VTE recurrence. This was a retrospective analysis of a large statewide database from 2004 to 2017. We measured the frequency with which patients with DVT carried a comorbid International Coding of Diseases diagnosis of MetS components. Association of MetS with VTE recurrence was tested with a multiple logistic regression model and VTE recurrence as the dependent variable. Risk of VTE recurrence conferred by each MetS component was assessed by Kaplan-Meier curves with the log-rank statistic. A total of 151 054 patients with DVT were included in this analysis. Recurrence of VTE occurred in 17% overall and increased stepwise with each criterion for MetS. All 4 components of MetS had significant adjusted odds ratios (OR) for VTE recurrence, with hyperlipidemia having the largest (OR, 1.8), representing the 4 largest ORs of all possible explanatory variables. All 4 MetS variables were significant on Kaplan-Meier analysis for recurrence of VTE. These data imply a role for appropriate therapies to reduce the effects of MetS as a way to reduce risk of VTE recurrence

A Discrimination Report Card

We develop an Empirical Bayes grading scheme that balances the informativeness of the assigned grades against the expected frequency of ranking errors. Applying the method to a massive correspondence experiment, we grade the racial biases of 97 U.S. employers. A four-grade ranking limits the chances that a randomly selected pair of firms is mis-ranked to 5% while explaining nearly half of the variation in firms' racial contact gaps. The grades are presented alongside measures of uncertainty about each firm's contact gap in an accessible rubric that is easily adapted to other settings where ranks and levels are of simultaneous interest

Effect of Cutting Bill Requirements on Lumber Yield in a Rip-First Rough Mill

In recent years, producers of solid wood dimension parts have emphasized improvements in lumber yield, focusing primarily on lumber grade and cutting technology rather than cutting bill design. Yet, cutting bills have a significant impact on yield. Using rip-first rough mill simulation software, a data bank of red oak lumber samples, and a cutting bill that resembles those used in industry, we determined the effect of changes in part size within an existing cutting bill and the impact of part-quantity requirements on yield. The results indicated that cutting bill requirements have a large influence on yield when the shortest part length in the bill is changed. Medium-length part sizes also affect yield except when the cutting bill requires an unlimited number of small parts; in this case, yield always will be high. When an all-blades-movable arbor is used, length changes in the bill affect yield more than changes in width. This study reveals our current lack of understanding of the complex relationship between cutting bill and lumber yield, and points out the yield gains that are possible when properly designed cutting bills are used

Science Day 2005 Abstracts

A number of different abstracts dealing with light and matter, astrophysics, simulations, biophysics, and nuclear physics

YOLO-Angio: An Algorithm for Coronary Anatomy Segmentation

Coronary angiography remains the gold standard for diagnosis of coronary artery disease, the most common cause of death worldwide. While this procedure is performed more than 2 million times annually, there remain few methods for fast and accurate automated measurement of disease and localization of coronary anatomy. Here, we present our solution to the Automatic Region-based Coronary Artery Disease diagnostics using X-ray angiography images (ARCADE) challenge held at MICCAI 2023. For the artery segmentation task, our three-stage approach combines preprocessing and feature selection by classical computer vision to enhance vessel contrast, followed by an ensemble model based on YOLOv8 to propose possible vessel candidates by generating a vessel map. A final segmentation is based on a logic-based approach to reconstruct the coronary tree in a graph-based sorting method. Our entry to the ARCADE challenge placed 3rd overall. Using the official metric for evaluation, we achieved an F1 score of 0.422 and 0.4289 on the validation and hold-out sets respectively.Comment: MICCAI Conference ARCADE Grand Challenge, YOLO, Computer Vision

Combustion of LOX with H2(sub g) under subcritical, critical, and supercritical conditions (Task 1) and experimental observation of dense spray and mixing of impinging jets (Task 2)

The objective was to achieve a better understanding of the combustion processes of liquid oxygen and gaseous hydrogen under broad range of pressure covering subcritical, critical, and supercritical conditions. The scope of the experimental work falls into the following areas: (1) design of the overall experimental setup; (2) modification of an existing windowed high pressure chamber; (3) design of the LOX feeding system; (4) provision of the safety features in the test rig design; (5) LOX cleanliness requirements; (6) cold shock testing; (7) implementation of data acquisition systems; (8) preliminary tests for system checkout; (9) modification of LOX feeding system; and (10) evaporation tests. Progress in each area is discussed