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.

Study of trimming damages of CFRP structures in function of the machining processes and their impact on the mechanical behavior

Abstract: The main focus of this paper is to investigate the defects generated by different machining processes (namely burr tool machining, abrasive water jet machining ‘AWJM’ and abrasive diamond cutter ‘ADS’) and their impact on the mechanical behavior of CFRP in quasi-static (compression and inter-laminar shear) and tensile–tensile fatigue tests. The cutting conditions are selected so that different levels of degradation can be obtained. The machined surface is characterized using roughness measuring devices with and without contact and SEM observations. The results show that the defects generated during the trimming process with a cutting tool are fibers pull-out and resin degradation. These defects are mainly located in the layers with the fibers oriented at −45° and 90°. However, when using abrasive water jet and abrasive diamond processes, the defects generated have the form of streaks and are not dependent on the fiber orientation. Furthermore, the results of quasi-static tests performed on specimens machined by cutting tools show that AWJ specimens offer a better resistance in compression but the ADS samples offer higher inter-laminar-shear strengths. Moreover, the results of fatigue tests show that specimens machined with a burr tool offer higher endurance limit. Finally, it is concluded that the type and the mode of the mechanical loading (quasi-static fatigue) affect the mechanical response of CFRP and favor a given machining process.

Production system design elements influencing productivity and ergonomics - A case study of parallel and serial flow strategies

Abstract: The purpose of this paper is to investigate a strategic change from parallel cell-based assembly (old) to serial-line assembly (new) in a Swedish company with special reference to how production system design elements affect both productivity and ergonomics. Multiple methods, including records and video analysis, questionnaires, interviews, biomechanical modelling, and flow simulation were applied. The new system, unlike the old, showed the emergence of system and balance losses as well as vulnerability to disturbances and difficulty handling all product variants. Nevertheless, the new system as realised partially overcame productivity barriers in the operation and management of the old system. The new system had impaired ergonomics due to decreased physical variation and increased repetitiveness with cycle times that were 6% of previous thus increasing repetitiveness, and significantly reducing perceived influence over work. Workstations' uneven exposure to physical tasks such as nut running created a potential problem for workload management. The adoption of teamwork in the new system contributed to significantly increased co-worker support - an ergonomic benefit. Design decisions made early in the development process affect both ergonomics and productivity in the resulting system. While the time pattern of physical loading appeared to be controlled by flow and work organisation elements, the amplitude of loading was determined more by workstation layout. Psychosocial conditions appear to be affected by a combination of system elements including layout, flow, and work organisation elements. Strategic use of parallelisation elements in assembly, perhaps in hybrid forms from configurations observed here, appears to be a viable design option for improved performance by reducing the fragility and ergonomic problems of assembly lines. The interacting design elements examined here pose potential "levers" of control by which productivity and ergonomics could be jointly optimised for improved total system performance.

Aging and emotional memory: cognitive mechanisms underlying the positivity effect.

Abstract: Younger adults tend to remember negative information better than positive or neutral information (negativity bias). The negativity bias is reduced in aging, with older adults occasionally exhibiting superior memory for positive, as opposed to negative or neutral, information (positivity bias). Two experiments with younger (N 24 in Experiment 1, N 25 in Experiment 2; age range: 18 –35 years) and older adults (N 24 in both experiments; age range: 60 – 85 years) investigated the cognitive mechanisms responsible for age-related differences in recognition memory for emotional information. Results from diffusion model analyses (R. Ratcliff, 1978) indicated that the effects of valence on response bias were similar in both age groups but that Age Valence interactions emerged in memory retrieval. Specifically, older adults experienced greater overall familiarity for positive items than younger adults. We interpret this finding in terms of an age-related increase in the accessibility of positive information in long-term memory.