Machine learning-aided real-time detection of keyhole pore generation in laser powder bed fusion.

Porosity defects are currently a major factor that hinders the widespread adoption of laser-based metal additive manufacturing technologies. One common porosity occurs when an unstable vapor depression zone (keyhole) forms because of excess laser energy input. With simultaneous high-speed synchrotron x-ray imaging and thermal imaging, coupled with multiphysics simulations, we discovered two types of keyhole oscillation in laser powder bed fusion of Ti-6Al-4V. Amplifying this understanding with machine learning, we developed an approach for detecting the stochastic keyhole porosity generation events with submillisecond temporal resolution and near-perfect prediction rate. The highly accurate data labeling enabled by operando x-ray imaging allowed us to demonstrate a facile and practical way to adopt our approach in commercial systems.

Left ventricular stiffness in paediatric patients with end-stage kidney disease.

BACKGROUND: We tested the hypothesis that myocardial stiffness is altered in paediatric patients with end-stage kidney disease (ESKD) and explored its association with clinical parameters of chronic kidney disease (CKD). METHODS: Thirty-five patients with ESKD (16 males) aged 17.5 ± 3 years old, 18/35 of whom were receiving dialysis and 17 post kidney transplant, were studied. Left ventricular (LV) myocardial stiffness was determined by measurement of diastolic wall strain (DWS) and stiffness index (SI), while LV diastolic function was interrogated by pulsed-wave and tissue Doppler echocardiography. RESULTS: Compared with available literature data, both dialysis and transplanted patients had significantly lower DWS and greater SI, reduced transmitral early (E) to late diastolic velocity ratio and septal and lateral mitral annular early (e') diastolic velocities, and greater septal and lateral E/e' ratios (all p < 0.05). Multivariate analysis revealed that z score of diastolic blood pressure (ß = 0.43, p = 0.004) and the duration of renal replacement therapy (ß = 0.55, p < 0.001) were significant determinants of LV SI. Subgroup analysis in post-transplant patients showed z score of diastolic blood pressure (ß = 0.54, p = 0.025) remained as a significant determinant of LV SI. CONCLUSION: Increased LV myocardial stiffness is evident in paediatric dialysis and transplanted patients with ESKD, and is associated with blood pressure and duration of renal replacement therapy.