Ryerson University

About: Ryerson University is a education organization based out in Toronto, Ontario, Canada. It is known for research contribution in the topics: Computer science & Population. The organization has 7671 authors who have published 20164 publications receiving 394976 citations. The organization is also known as: Ryerson Polytechnical Institute & Ryerson Institute of Technology.

Parameters controlling the performance of AA319-type alloys: Part I. Tensile properties

Abstract: Al–Si–Cu AA319 alloy was selected for study in the present work due to its wide use in many automotive applications. In addition to the variation in the secondary dendrite arm spacing (SDAS), porosity level and the type of heat treatment applied, the presence/addition of certain alloying elements or modifiers to these alloys is known to greatly affect their mechanical properties. An extensive study was carried out to investigate the solidification and dissolution behavior of the CuAl2 phase in various AA319-type alloys (containing Sr, Fe and P element additions) and its effect on the alloy performance under two different heat treatment conditions (T5 and T6). Part I of this article reports on the tensile properties of these alloys. The tensile test samples were prepared from blanks sectioned from end-chilled castings, corresponding to dendrite arm spacings ranging from 23 to 83 μm. It was found that strontium modification leads to a fibrous eutectic Si morphology, resulting in a great increase in the ultimate tensile strength (UTS) and ductility values compared to the unmodified alloys. On the other hand, Sr addition also causes segregation of the blocky CuAl2 phase, which results in reducing the tensile properties. However, dissolution of CuAl2 particles after T6 heat treatment can minimize this kind of negative effect. Iron has a detrimental effect on the UTS and ductility values due to its precipitation in the form of the brittle β-Al5FeSi plate-like phase. The addition of phosphorus has a negative effect on the tensile properties on account of (i) its solubility in CuAl2, and (ii) the formation of (Al,P)O2 oxide particles, where the latter act as nucleation sites for the formation of the CuAl2 phase.

Simultaneous Cerebrovascular and Cardiovascular Responses During Presyncope

Abstract: BACKGROUND AND PURPOSE: Presyncope, characterized by symptoms and signs indicative of imminent syncope, can be aborted in many situations before loss of consciousness occurs. The plasticity of cerebral autoregulation in healthy humans and its behavior during this syncopal prodrome are unclear, although systemic hemodynamic instability has been suggested as a key factor in the precipitation of syncope. Using lower body negative pressure (LBNP) to simulate central hypovolemia, we previously observed falling mean flow velocities (MFVs) with maintained mean arterial blood pressure (MABP). These findings, and recent reports suggesting increased vascular tone within the cerebral vasculature at presyncope, cannot be explained by the classic static cerebral autoregulation curve; neither can they be totally explained by a recent suggestion of a rightward shift in this curve. METHODS: Four male and five female healthy volunteers were exposed to presyncopal LBNP to evaluate their cerebrovascular and cardiovascular responses by use of continuous acquisition of MFV from the right middle cerebral artery with transcranial Doppler sonography, MABP (Finapres), and heart rate (ECG). RESULTS: At presyncope, MFV dropped on average by 27.3 +/- 14% of its baseline value (P < .05), while MABP remained at 2.0 +/- 27% above its baseline level. Estimated cerebrovascular resistance increased during LBNP. The percentage change from baseline to presyncope in MFV and MABP revealed consistent decreases in MFV before MABP. CONCLUSIONS: Increased estimated cerebrovascular resistance, falling MFV, and constant MABP are evidence of an increase in cerebral vascular tone with falling flow, suggesting a downward shift in the cerebral autoregulation curve. Cerebral vessels may have a differential sensitivity to sympathetic drive or more than one type of sympathetic innervation. Future work to induce dynamic changes in MABP during LBNP may help in assessing the plasticity of the cerebral autoregulation mechanism.

A Novel Location-Penalized Maximum Likelihood Estimator for Bearing-Only Target Localization

Abstract: In this paper, we present a location-penalized maximum likelihood (LPML) estimator for bearing only target localization. We develop a new penalized maximum likelihood cost function by transforming the variables of target position and bearings. The new penalized likelihood function can also be recognized as a posterior distribution under a Bayesian framework by penalizing a prior. We give analysis of the asymptotic properties and show that both traditional bearing maximum likelihood (TBML) and LPML estimators are asymptotically efficient estimators. To compare the performances of the TBML and LPML estimators, we analyze the Cramer-Rao lower bound (CRLB) of the two estimators and show that the bound of the LPML estimator is lower than that of the TBML estimator. Extensive simulations are performed. It is observed that the new LPML algorithm consistently outperforms other well-known algorithms. Field experiments are also conducted by applying this method to localize a vehicle using real-world data acquired by an acoustic array sensor network. The new LPML algorithm demonstrates superior performance in all the field experiments.

Non plasmonic semiconductor quantum SERS probe as a pathway for in vitro cancer detection

Abstract: Surface-enhanced Raman scattering (SERS)-based cancer diagnostics is an important analytical tool in early detection of cancer. Current work in SERS focuses on plasmonic nanomaterials that suffer from coagulation, selectivity, and adverse biocompatibility when used in vitro, limiting this research to stand-alone biomolecule sensing. Here we introduce a label-free, biocompatible, ZnO-based, 3D semiconductor quantum probe as a pathway for in vitro diagnosis of cancer. By reducing size of the probes to quantum scale, we observed a unique phenomenon of exponential increase in the SERS enhancement up to ~106 at nanomolar concentration. The quantum probes are decorated on a nano-dendrite platform functionalized for cell adhesion, proliferation, and label-free application. The quantum probes demonstrate discrimination of cancerous and non-cancerous cells along with biomolecular sensing of DNA, RNA, proteins and lipids in vitro. The limit of detection is up to a single-cell-level detection. Surface enhanced Raman scattering is a bio-analytical tool and the development and optimisation of probes is an active area of investigation. Here, the authors report on the development and testing of biocompatible semiconductor zinc oxide quantum probes on a platform for cell adhesion and analysis.