We present a new algorithm for solving large-scale security-constrained optimal power flow in polar form (AC-SCOPF). The method builds on Nonlinearly Constrained augmented Lagrangian (NCL), an augmented Lagrangian method in which the subproblems are solved using an interior-point method. NCL has two key advantages for large-scale SCOPF. First, NCL handles difficult problems such as infeasible ones or models with complementarity constraints. Second, the augmented Lagrangian term naturally regularizes the Newton linear systems within the interior-point method, enabling solution of the Newton systems with a pivoting-free factorization that can be efficiently parallelized on GPUs. We assess the performance of our implementation, called MadNCL, on large-scale corrective AC-SCOPFs, with complementarity constraints modeling the corrective actions. Numerical results show that MadNCL can solve AC-SCOPF with 500 buses and 256 contingencies fully on the GPU in less than 3 minutes, whereas Knitro takes more than 3 hours to find an equivalent solution.
Electroweak radiative corrections form a crucial ingredient in modern precision calculations for particle processes at high-energy colliders such as the Large Hadron Collider. The salient features of electroweak corrections as well as currently used techniques and concepts for their calculation are reviewed. Recent progress in this enterprise is illustrated in a discussion of electroweak multi-gauge-boson production processes: massive di-boson production, vector-boson scattering, and massive tri-boson production.
We present a variational reduced-order model for three-dimensional coplanar propagation of sharp cracks in heterogeneous perfectly brittle solids under mixed-mode I+II+III loading. The approach connects the variational fracture formulation of Francfort and Marigo (1998) and the perturbation theory of Rice (1985) by computing equilibrium crack-front configurations through minimization of the total energy defined as the sum of (i) the elastic potential energy, evaluated asymptotically from front deformations, and (ii) the dissipated energy, set by the fracture energy field. The potential energy and its derivatives are evaluated efficiently using the Fast Fourier Transform. The resulting nonconvex box-constrained minimization problem is solved with a matrix-free Newton conjugate gradient algorithm with a trust region and physics-based preconditioning, enforcing irreversibility while resolving energy barriers and long-range elastic interactions. We validate our implementation against newly derived analytical solutions. We then perform 116,000 large-scale simulations of tensile and shear crack propagation in disordered media to quantify the impact of finite-size effects, disorder intensity, and mode mixity. The simulations reproduce the transition from smooth to intermittent crack growth, and show that mode mixity has limited influence on the onset of intermittency but induces quasi-elliptic fronts in mixed II+III loading. They reveal a size-dependent crossover from disorder-induced weakening to toughening controlled by the emergence of depinning instabilities.
We present an extended study for upgrading a classical rotameter, a volume flow measuring device, by integration of wirelessly powered in-flow sensors. Therein, we used inductive power transfer operating at 13.56 MHz based on multiple transmitter coils distributed along a tube of the rotameter. The receiver coil was wound on the float being displaced along the pipe depending on the flow. A second coil on the float served for position detection, allowing, on the one hand, to identify and power just the two transmitter coils in direct vicinity of the float and, on the other hand, replace the visual readout of classical rotameters by a digital signal.We show comprehensive simulations of the transferred energy with many different coil arrangements and transmitter–receiver combinations, and normalized the results to allow for a generalized analysis. To verify our simulations, we demonstrated our approach on a 1-inch pipe, with transmitter coils of 34 mm diameter at a distance of 20 mm to each other, and a receiver coil with a diameter ranging from 11 mm to 23 mm. The system achieved a stable power transfer with less than 5% coupling factor variation regardless of the float position, delivering a steady 3.3 V output. The position detection using the second coil of the float enabled an average positioning tracking accuracy of 0.44 mm. We demonstrate the system’s functionality by powering a temperature sensor, and a Bluetooth transmitter, all embedded in the float, i.e., inside the pipe, maintaining stable operation with a standard deviation of only 381 mV in the received voltage across the entire travel range.Eventually, the system was evaluated on an industrial test rig equipped with external flow and temperature sensors showing good agreement between the embedded and external sensors.
This work investigates the fatigue damage behavior of a carbon fiber-reinforced Poly-Aryl-Ether-Ketone (CF-PAEK) laminate under monotonic, low frequency, and ultrasonic frequency three-point bending conditions. Strains and stresses are evaluated using digital image correlation (DIC) and compared with finite element analysis (FEA). The numerical results, confirmed by microscopy, successfully predict damage initiation, which occurs as localized fiber kinking in the top 0° layers due to compressive stresses and transverse cracks in off-axis layers (90° and ±45° plies) triggered by out-of-plane shear. Under low frequency cyclic loading (10 to 50 Hz), self-heating analysis revealed that fatigue life and strength are independent of testing frequency. In contrast, 20 kHz ultrasonic loading condition induces pronounced self-heating, reducing fatigue strength by approximately 12% compared to low frequency fatigue conditions. For CF-PAEK beams, overlapping stress levels between testing systems are successfully achieved, and the S-N diagram shows comparable fatigue lives up to 109 cycles. While damage initiation mechanisms remain comparable, damage accumulation is altered by the control mode. Force-controlled low frequency experiments cause multiple rapidly coalescing delamination, whereas displacement-controlled ultrasonic testing yields a single propagating delamination leading to resonance loss.
