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.

A Control Strategy for Enhanced Operation of Inverter-Based Microgrids Under Transient Disturbances and Network Faults

Abstract: This paper proposes an enhanced control strategy for electronically coupled distributed energy resources that improves the performance of the host microgrid under network faults and transient disturbances. The proposed control strategy does not require controller mode switchings and enables the electronically coupled distributed energy resources to ride through network faults, irrespective of whether they take place within the host microgrid or impact the upstream grid. Moreover, the proposed control ensures acceptable power quality for the duration of the faults, which is an important feature for protection against certain classes of faults, as well as for sensitive loads. Further, the paper proposes a supplementary control loop that improves the microgrid post-fault recovery. The effectiveness of the proposed control strategy is demonstrated through a comprehensive set of simulation studies, conducted in the PSCAD/EMTDC software environment.

Blurred Boundaries: Social Media Privacy and the Twenty‐First‐Century Employee

Abstract: This paper discusses the future of employee privacy in social media.Part I reviews the extant legal landscape with an emphasis on three general areas of employer activity related to employees’ online activities: (1) monitoring and surveillance of employee social media profiles, (2) evaluation of applicants’ social media profiles and online speech in making hiring decisions, and (3) limiting employees’ off-duty online activities.Part II reports the results of an empirical research project into the expectations of young employees regarding the role of social media in the workplace. We asked respondents about a wide range of topics related to social media, such as the extent of personal information they post online, the privacy-protective measures they employ on social media sites, their level of concern regarding their privacy online, and their attitudes and expectations regarding the use of social media in the workplace. Despite granting employers access to information about their private lives by participating online, respondents expect that work life and private life should be generally segregated — and that actions in one domain should not affect the other.Guided by the survey findings and legal examples from international jurisdictions, in Part III we offer workable recommendations designed to protect employees’ desire to maintain some separation between personal and professional contexts.

Stabilized soils for construction applications incorporating natural resources of Papua new Guinea

Abstract: Papua New Guinea clayey soils are stabilized with various percentages of volcanic ash (VA), finely ground natural lime (L), cement and their combinations. The influence of stabilizers and their combinations is evaluated through Atterberg limits, standard Proctor compaction, unconfined compressive strength, splitting tensile strength, modulus of elasticity and California bearing ratio (CBR) tests. The durability of 38 stabilized soil mixtures is also conducted by studying the influence of water immersion on strength, water sorptivity and drying shrinkage. Correlations between compressive strength, modulus of elasticity and CBR are also established. Theoretical analysis of pavements incorporating subgrades improved by stabilized soils under traffic loads shows technical benefits compared with conventional flexible pavements without improved subgrades. Suitable stabilized soil mixtures using VA, L, cement and their combinations are proposed which can be used for the construction of road pavements, airfields, earth dams and low-cost housing. The use of locally available soils, VA and lime in the production of stabilized soils for such applications can provide sustainability for the local construction industry.

On return stroke currents and remote electromagnetic fields associated with lightning strikes to tall structures: 2. Experiment and model validation

Abstract: [1] In this paper, simultaneous GPS time-stamped measurements of the electric and magnetic fields at three distances and of the return stroke current associated with lightning strikes to the Toronto CN Tower (553 m) during the summer of 2005 are presented. The lightning return stroke current was measured using a Rogowski coil installed at a height of 474 m above ground level (AGL). The vertical component of the electric field and the azimuthal component of the magnetic field were measured simultaneously at distances of 2.0 km, 16.8 km, and 50.9 km from the CN Tower. The propagation path from the CN Tower to the first two stations (2.0 and 16.8 km) was along the soil and through the Toronto city, whereas for the third location (50.9 km) the propagation path was nearly entirely across Lake Ontario. The waveforms of the electric and magnetic fields at 16.8 km and 50.9 km exhibit a first zero crossing about 5 μs after the onset of the return stroke. This early zero crossing is part of a narrow undershoot. For fields at 50.9 km the expected zero crossing at about 40 μs is also observed. Metallic beams and other conducting parts in buildings on which electric and magnetic field sensors were located cause an enhancement effect on the measured fields. Although an enhancement can be identified both on the electric and the magnetic fields, the degree of enhancement is actually more significant for the electric field than for the magnetic field. It is shown that the value of the wave impedance (E-field peak to H-field peak ratio) could give an estimate of the enhancement effect of the building on the electric field. Propagation effects (decrease of field amplitude and increase of its risetime) can also be observed in experimental records. It is shown that the fields at 50.9 km are less affected by such attenuation, compared to those at 16.8 km, presumably because the path of propagation is mostly across Lake Ontario. Measured waveforms are compared with theoretical predictions obtained using the five engineering return stroke models extended to include the presence of the strike object, namely, transmission line (TL), modified transmission line (MTLL and MTLE), Bruce-Golde (BG), and traveling current source (TCS) models. A reasonable agreement is found with all five engineering models for the magnetic field waveforms at the three considered distances, although the peak values of the computed fields are systematically about 25% lower than measured values. None of the models was able to reproduce the early zero crossing and the narrow undershoot. As far as the electric field is concerned, larger differences have been observed between simulations and measurements. This may be due to the fact that the enhancement effect of the building on the electric field is stronger than that on the magnetic field. The expression relating current and field peaks associated with strikes to tall structures is also tested versus obtained sets of experimental data. The overall agreement between the theoretically predicted and the experimentally observed field-to-current ratio is reasonable, although the formula of Bermudez et al. (2005) appears also to underestimate the experimentally measured ratio (by about 25%). This may be due, at least in part, to the enhancement effect of the buildings on which the field measurement antennae were installed.