Shannon and Renyi Entropies to Classify Effects of Mild Traumatic Brain Injury on Postural Sway

Background: Mild Traumatic Brain Injury (mTBI) has been identified as a major public and military health concern both in the United States and worldwide. Characterizing the effects of mTBI on postural sway could be an important tool for assessing recovery from the injury. Methodology/Principal Findings: We assess postural sway by motion of the center of pressure (COP). Methods for data reduction include calculation of area of COP and fractal analysis of COP motion time courses. We found that fractal scaling appears applicable to sway power above about 0.5 Hz, thus fractal characterization is only quantifying the secondary effects (a small fraction of total power) in the sway time series, and is not effective in quantifying long-term effects of mTBI on postural sway. We also found that the area of COP sensitively depends on the length of data series over which the COP is obtained. These weaknesses motivated us to use instead Shannon and Renyi entropies to assess postural instability following mTBI. These entropy measures have a number of appealing properties, including capacity for determination of the optimal length of the time series for analysis and a new interpretation of the area of COP. Conclusions: Entropy analysis can readily detect postural instability in athletes at least 10 days post-concussion so that it appears promising as a sensitive measure of effects of mTBI on postural sway

Effect of chip breakers on the cutting force during the machining of steel C45

The paper deals with the dependence of cutting force on the breaker of an indexable cutting insert (ICI). The experiment monitored individual cutting force components for different insert breakers, cutting speeds and feed rates during machining. The cutting depth remained constant. The tool holder, material and coating of the indexable cutting insert was also identical

Modeling data envelopment analysis (DEA) efficient location/allocation decisions

Introduction The initial focus of mathematical programming models for facility location was based upon the spatial availability of a server to fulfill demand [for a review of covering models, see ReVelle (1987) and Schilling et al. (1993)]. Toregas et al. (1971) formulated the Location Set Covering Problem (LSCP) that required coverage of all demand points within some time standard. A derivative of this was the p-center problem, which minimized the maximum distance separating any demand point from its nearest facility (Hakimi 1964, ReVelle and Swain 1970). Both of these models considered demand, server capability, and service time to be homogeneous. Budgetary constraints, which might make full coverage impossible, led to the development of the Maximal Covering Location Problem (MCLP) (Church and ReVelle 1974, White and Case 1974). Non-uniform distribution of demand nodes was incorporated into these partial covering models to develop the best deployment of a given number of facilities

Psychosocial factors associated with time to recovery following concussion in adolescent ice hockey players

Objective: To investigate the association between psychosocial factors and physician clearance to return to play (RTP) in youth ice hockey players following sport-related concussion. Design: Prospective cohort study, Safe-to-Play (2013-2018). Setting: Youth hockey leagues in Alberta and British Columbia, Canada. Participants: 353 ice hockey players (aged 11-18 years) who sustained a total of 397 physician63 diagnosed concussions. Independent Variables: Psychosocial variables. Main Outcome Measures: Players and parents completed psychosocial questionnaires preinjury. Players with a suspected concussion were referred for a study physician visit, during which they completed the Sport Concussion Assessment Tool (SCAT3/SCAT5) and single question ratings of distress and expectations of recovery. Time to recovery (TTR) was measured as days between concussion and physician clearance to RTP. Accelerated failure time models estimated the association of psychosocial factors associated with TTR, summarized with time ratios (TR). Covariates included age, sex, body checking policy, days from concussion to initial physician visit, and symptom severity at initial physician visit. Results: Self-report of increased peer-related problems on the Strengths and Difficulties Questionnaire (TR, 1.10 [95% CI, 1.02-1.19]), higher ratings of distress about concussion outcomes by participants (TR, 1.06 [95% CI, 1.01-1.11]) and parents (TR, 1.05 [95% CI, 1.01- 1.09]), and higher parent ratings of distress about their child’s well-being at the time of injury (TR, 1.06 [95% CI, 1.02-1.09]), were associated with longer recovery. Conclusions: Greater pre-existing peer-related problems and acute distress about concussion outcomes and youth well-being predicted longer TTR. Treatment targeting these psychosocial factors following concussion may promote recovery.Medicine, Faculty ofOther UBCNon UBCPediatrics, Department ofReviewedFacultyResearcherPostdoctoralGraduat