This paper is concerned with pose and pose rate control of a rigid body. The proposed control approach contains an inner loop that tracks the desired pose rate command and an outer loop that tracks the desired pose command. The control algorithm uses the unit dual quaternion as a measure of pose errors to achieve tracking via instantaneous screw motion. The resulting tracking error equation is directly related to the screw motion parameters and can be used to determine the controller gains. The paper discusses the stability of the new algorithm and presents its performance via simulation.
In this work, we introduce Blank Space Adaptive Causal Random Linear Network Coding (BS-AC-RLNC), a novel coding scheme designed to mitigate the triplet trade-off between throughput-delay-efficiency in multi-hop networks. BS-AC-RLNC leverages the physical limitations of the network, considering the bottleneck from each node to the destination. In particular, this approach introduces a light-computational re-encoding algorithm, called Network AC-RLNC (NET), implemented independently at intermediate nodes. NET adaptively adjusts the Forward Error Correction (FEC) rates and schedules idle periods. It incorporates two distinct suspension mechanisms: 1) Blank Space Period, accounting for the forward-channels bottleneck, and 2) No-New No-FEC approach, based on data availability. We present theoretical lower and upper bounds on in-order delivery delay, goodput, and throughput; in the case of in-order delay, we further derive a mean bound. These analytical results are extended to the multicast scenario, providing a broader understanding of the algorithm's performance under diverse network conditions. The experimental results achieve significant improvements in resource efficiency, demonstrating a 20% reduction in channel usage compared to baseline RLNC solutions. Notably, these efficiency gains are achieved while maintaining competitive throughput and delay performance, ensuring improved resource utilization does not compromise network performance.
YAG-based materials, widely used as lasing media, offer only moderate thermal conductivity ( 10 W/mK), posing challenges for thermal management in solid-state lasers where pump-induced heat leads to thermal gradients that impair performance. To address this issue, MgO with high thermal conductivity (40–60 W/mK) is proposed as a heat sink material. Direct bonding of MgO to YAG is challenging due to their different thermal expansion coefficients. This study introduces a novel approach using a functionally graded material (FGM) to bond heat conductive MgO/YAG composite to YAG disc via spark plasma sintering (SPS). It was found that a YAG/MGO composite with 50 wt
This study extends a recently developed Eulerian framework for characterizing particle erosion in impinging jets to handle polydisperse systems with compressible carrier flows. The Eulerian mass and momentum conservation equations are solved using a one-way coupled sectional approach. Erosion at the eroded surface is computed using both empirical and experimentally-based erosion models. The framework allows estimating the initial erosion of polydisperse flows by first evaluating the initial erosion in the corresponding monosectional flows. Then, the erosion induced by particles from different sections is linearly added using a simplified calculator with different weights for each section. This calculator generates the initial erosion immediately, eliminating the need to run numerous expensive simulations for different polydisperse flows. Analysis of bisectional systems showed that intermediate erosion profiles are obtained when using different ratios between medium and large Stokes number particles. Finally, we demonstrate that the erosion rates calculated using our Eulerian framework are in agreement with those obtained using the commonly employed Lagrangian approach in the converging section of the BATES rocket engine.
We performed an extensive numerical study on the penetration of rigid projectiles into water. The 2D simulations were focused on evaluating the drag coefficients of projectiles with various nose shapes and on their dependence on the projectile's impact velocity. To achieve simulation convergence the mesh size was found to have at least 11 cells on a target segment with a length equal to the projectile's radius. The drag coefficients of the rigid projectiles were found to be constant up to velocity which is equal to half the sound velocity in water, and they increase for higher projectile velocities. The drag coefficients for projectiles penetrating fluid aluminum targets were found to be the same as those for projectiles penetrating water targets. We also highlight the difference between drag coefficients of conical and ogive nosed projectiles having the same sharpness and offer a possible account for this difference.
