The influence of helmet size and shape on peak linear decelerations when impacting crash pads

AbstractDuring training and competition in short track speed skating, skaters commonly fall on the ice and slide into crash pads that line the boards of the rink. Skaters wear helmets to protect their heads from such impacts. Nevertheless, concussion injuries are not uncommon, especially from impacts into the crash pads. Basic mechanical principles suggest that, all other things being equal, smaller sized and rounder shaped helmets should reduce peak impact forces when hitting relatively soft crash pads. This study validates these assumptions and determines the magnitude of these effects using drop tests and a 3D accelerometer. Hemispherical head forms of various radii, each weighing approx. 4.5kg, were dropped from four heights (0.3-4.0 m) onto a crash pad. Peak linear decelerations were recorded. In one set of tests, complete hemispheres were used, highlighting the effect of helmet size (radius). In a second set of tests, another set of hemispheres of various radii were sliced to produce caps each with a diameter of 8” but each with a different radius of curvature. Impact tests at four drop heights using these caps revealed the effect of helmet shape. Size was found to be more important than shape, with the greatest effects being in the 10-20cm radius range, a range which is relevant to helmets used in the sport today

Comparison of IMU Measurements of Curling Stone Dynamics with a Numerical Model

Abstract Despite almost a century of research, the question of what causes a curling stone to curl (move perpendicular to its initial direction of motion) has no complete answer. Many hypotheses have been formulated, but none has been able to account quantitatively for the full magnitude of the observed curl. The objective of this research was to equip a curling stone with an inertial measurement unit (IMU) and measure its motion, in order to verify a previously published, numerical model of curling stone dynamics. Low cost, small size, accuracy, ease of programming and operation, wireless data communication, and a data-sampling rate near 1 kHz, were selection criteria and constraints for the instrument package. We used the MicroStrain 3DM-GX4-25 system. This is a MEMS-based IMU with a tri-axial gyroscope and a tri-axial linear accelerometer. It was mounted and interfaced with a Bluetooth transmitter, on a curling stone handle. The data were streamed to a host laptop and displayed graphically in real time. Post-processing of the data included filtering and time-integration in order to obtain linear and angular velocities, and displacements. We have compared our experimental results with trajectory data calculated using a previously published numerical model, based on a thermodynamic approach to ice friction. While the observed longitudinal and angular motions are captured reasonably well by the model (errors of about 5% or less), no curl is predicted by the model

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

Memory and Electrical Properties of (100)-Oriented AlN Thin Films Prepared by Radio Frequency Magnetron Sputtering

The (100)-oriented aluminum nitride (AlN) thin films were well deposited onto p-type Si substrate by radio frequency (RF) magnetron sputtering method. The optimal deposition parameters were the RF power of 350 W, chamber pressure of 9 mTorr, and nitrogen concentration of 50%. Regarding the physical properties, the microstructure of as-deposited (002)- and (100)-oriented AlN thin films were obtained and compared by XRD patterns and TEM images. For electrical properties analysis, we found that the memory windows of (100)-oriented AlN thin films are better than those of (002)-oriented thin films. Besides, the interface and interaction between the silicon and (100)-oriented AlN thin films was serious important problem. Finally, the current transport models of the as-deposited and annealed (100)-oriented AlN thin films were also discussed. From the results, we suggested and investigated that large memory window of the annealed (100)-oriented AlN thin films was induced by many dipoles and large electric field applied

SPEEDSKATE ICE FRICTION: REVIEW AND NUMERICAL MODEL-FAST 1.0

Peer reviewed: YesNRC publication: Ye