Mathematical Model to Simulate the Trajectory Elements ofan Artillery Projectile Proof Shot

In external ballistics of a conventional spin-stabilised artillery projectile, there are a numberof trajectory models developed for computing trajectory elements having varying degrees ofcomplexity. The present study attempts to propose a single mathematical model, viz., simplifiedpoint-mass/simple particle trajectory model to simulate the trajectory elements of a typical spin-stabilised flat-head artillery projectile proof shot. Due to difficulties in the projectile shape andsize, and the complicated nature of air resistance, an accurate mathematical prediction of thetrajectory is difficult. To simplify the computations, the governing equations of motion of theprojectile have been simplified and assumed that the projectile is a particle and the only forcesacting on the projectile are drag and gravity. With this model, trajectory elements have beengenerated and compared with experimental results obtained in the field test. The measuringinstrument used in this case is a Doppler radar

High Coronary Shear Stress in Patients With Coronary Artery Disease Predicts Myocardial Infarction.

Coronary lesions with low fractional flow reserve (FFR) that are treated medically are associated with higher revascularization rates. High wall shear stress (WSS) has been linked with increased plaque vulnerability. This study investigated the prognostic value of WSS measured in the proximal segments of lesions (WSS <sub>prox</sub> ) to predict myocardial infarction (MI) in patients with stable coronary artery disease (CAD) and hemodynamically significant lesions. The authors hypothesized that in patients with low FFR and stable CAD, higher WSS <sub>prox</sub> would predict MI. Among 441 patients in the FAME II (Fractional Flow Reserve Versus Angiography for Multivessel Evaluation II) trial with FFR ≤0.80 who were randomized to medical therapy alone, 34 (8%) had subsequent MI within 3 years. Patients with vessel-related MI and adequate angiograms for 3-dimensional reconstruction (n = 29) were propensity matched to a control group with no MI (n = 29) by using demographic and clinical variables. Coronary lesions were divided into proximal, middle, and distal, along with 5-mm upstream and downstream segments. WSS was calculated for each segment. Median age was 62 years, and 46 (79%) were male. In the marginal Cox model, whereas lower FFR showed a trend (hazard ratio: 0.084; p = 0.064), higher WSS <sub>prox</sub> (hazard ratio: 1.234; p = 0.002, C-index = 0.65) predicted MI. Adding WSS <sub>prox</sub> to FFR resulted in a significant increase in global chi-square for predicting MI (p = 0.045), a net reclassification improvement of 0.69 (p = 0.005), and an integrated discrimination index of 0.11 (p = 0.010). In patients with stable CAD and hemodynamically significant lesions, higher WSS in the proximal segments of atherosclerotic lesions is predictive of MI and has incremental prognostic value over FFR