In the early era of aviation, Frederick Lanchester was both an inventor and a theoretician driven by the need for a theory of flight that would reduce the guesswork in designing new aircraft. His ...book Aerodynamics in 1907 laid down the early foundations of such a theory. The theory with contributions from others, notably Ludwig Prandtl, was refined to become the basis for the sleek designs of WWII aircraft brought about with little guesswork. New technology changed aircraft design radically with the increased speed of jet propulsion reaching into the transonic range with nonlinear aerodynamics. In the late 1940s and early 1950s substantial guesswork returned to aircraft design. The legacy of Lanchester et al., however, lived on with the development of computational fluid dynamics (CFD) that could guide designers through nonlinear transonic effects. This article presents a historical sketch of how CFD developed, illustrated with examples explaining some of the difficulties overcome in the design of the first-generation swept-wing transonic fighters. The historical study is forensic CFD in search for the likely explanation of the designer’s choice for the wing shape that went into production a long time ago. The capability of current CFD applied to the aerodynamics of aircraft with slender wings is surveyed. The cases discussed involve flow patterns with coherent vortices over hybrid wings and wings of moderate sweep. Vortex-flow aerodynamics pertains to understanding the interaction of concentrated vortices with aircraft components. Modern Reynolds-Averaged Navier-Stokes (RANS) technology is useful to predict attached flow. But vortex interaction with other vortices and breakdown lead to unsteady, largely separated flow which has been found out of scope for RANS. Direct simulation of the Navier-Stokes equations is out of computational reach in the foreseeable future, and the need for better physical modeling is evident. Both cruise performance and stalling characteristics are influenced by strong interactions. Two important aspects of wing-flow physics are discussed: separation from a smooth surface that creates a vortex, and vortex bursting, the abrupt breakdown of a vortex with a subsequent loss of lift. Vortex aerodynamics of not-so-slender wings encounter particularly challenging problems, and it is shown how the design of early-generation operational aircraft surmounted these difficulties. Through use of forensic CFD, the article concludes with two case studies of aerodynamic design: how the Saab J29A wing maintains control authority near stall, and how the Saab J32 mitigates pitch-up instability at high incidence.
Despite additive manufacturing processes are already widely used in several industrial applications, there are few materials that are specifically designed and optimized for these technologies. ...Currently, only few Al alloys are available on the market and employed for 3D printing of structural parts. In particular, Si–Mg bearing alloys are the most common Al alloys for additive manufacturing, featuring high processability but moderate mechanical properties. By this work, we studied the effect of Si addition on the hot cracking susceptibility of a high strength Al–Zn–Mg–Cu alloy. A preliminary activity has been carried out by blending Al–Zn–Mg–Cu and Al–Si–Mg powders and analysing their microstructure and properties achieved after selective laser melting. Eventually a new Al–Zn–Si–Mg–Cu alloy has been designed, produced as powder alloy by gas atomization and tested. The microstructure and phase transformations of the new alloy has been investigated by synchrotron X-ray diffraction, differential scanning calorimetry and microscope analysis. The Al–Zn–Si–Mg–Cu alloy processed by selective laser melting featured a relative density of 99.8%, no hot cracks were noticed within the investigated microstructures. The ability of the new alloy to respond to aging starting from both as built and solution annealed conditions has been also evaluated. A good response to direct aging (directly from as built condition) was demonstrated, featuring yield strength and ultimate tensile strength of 402 and 449 MPa, respectively, and hardness of 174 HV after optimized aging at 165 °C for 2 h.
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•We proposed a novel high strength Al–Zn–Si–Mg–Cu alloy for additive manufacturing•Si has a positive effect on the SLM processability of investigated 7xxx Al alloys•We detected phases of as built Al-6.8Zn-6.5Si–2Mg-1.3Cu alloy by synchrotron XRD analysis•Cooling rates induced by SLM processing generate SSSS with full aging potential•The proposed alloy shows YS and UTS of 402 MPa and 449 MPa in horizontal direction
Running is a complex dynamic task that places strict requirements on both the physical components and software-control systems of a robot. This paper explores some of those requirements and, in ...particular, explores how a variable-compliance actuation system can satisfy many of them. We present the mechanical design and software-control system for such an actuator system. We analyze its performance through simulation and bench-top experimental validation of a prototype version. In conclusion, we demonstrate, through simulation, the application of our proof-of-concept actuator to the problem of biped running.
The transfer of photogenerated charges through interfaces
in heterojunction
photoanodes is a key process that controls the efficiency of solar
water splitting. Considering Co
3
O
4
/SiO
x
/Si ...photoanodes prepared by physical vapor deposition
as a representative case study, it is shown that defects normally
present in the native SiO
x
layer dramatically
affect the onset of the photocurrent. Electron paramagnetic resonance
indicates that the signal of defects located in dangling bonds of
trivalent Si atoms at the Si/SiO
x
interface
vanishes upon vacuum annealing at 850 °C. Correspondingly, the
photovoltage of the photoanode increases to ≈500 mV. Similar
results are obtained for NiO/SiO
x
/Si photoanodes.
Photoelectrochemical analysis and impedance spectroscopy (in solution
and in the solid state) indicate how the defect annealing modifies
the Co
3
O
4
/SiO
x
/Si
junction. This work shows that defect annealing at the solid–solid
interface in composite photoanodes strongly improves the efficiency
of charge transfer through interfaces, which is the basis for effective
solar-to-chemical energy conversion.
The important message to take from this article is that a robot is a unified dynamic system comprising electronics, software, and mechanical components, and for certain tasks such as running, a ...significant portion of the behavior is best exhibited through natural dynamics of the mechanism. Therefore, the mechanical system must be specialized for the task and designed with the same care for dynamic control as the software control system. In constructing the ECD leg, we have attempted to follow this philosophy and design the mechanical system for the specific tasks of walking and running. The prototype actuator, with dynamics verified by testing, exhibited behavior that enabled running in simulation. The ECD leg builds on design revisions from the BiMASC prototype, and the successful experiments with Thumper hopping around the laboratory have proven the ideas and engineering behind the design. Prof. Grizzle's group at the University of Michigan has already demonstrated tentative walking with MABEL, and we expect to demonstrate robust and efficient walking and running gaits in the near future.
Kinetic properties of tyrosinase immobilized on a polymeric membrane for the production of l-3,4-dihydroxyphenylalanine (l-DOPA) were investigated. A comparison with the properties shown by the free ...enzyme used in a stirred tank reactor was also carried out. The values of the Michaelis-Menten constant indicated that the immobilized tyrosinase exhibited better affinity for the substrate (Km=1.56 mM and 2.10 mM for the immobilized and free enzyme, respectively).
Background and purpose
Using an innovative chemical approach, peptide welding technology (PWT), a tetrabranched derivative of nociceptin/orphanin FQ (N/OFQ) has been generated and pharmacologically ...characterized. Both in vitro and in vivo PWT2‐N/OFQ displayed the same pharmacological profile to the natural ligand. It was more potent and produced longer‐lasting effects. The aim of the present study was to investigate the spinal effects of PWT2‐N/OFQ in nociceptive and neuropathic pain models in mice and non‐human primates.
Experimental Approach
Tail withdrawal assay in mice and monkeys was used as a nociceptive pain model and mechanical threshold in mice subjected to chronic constriction injury was used as a neuropathic pain model. The antinociceptive effects of spinally administered N/OFQ and PWT2‐N/OFQ were assessed in these models.
Key Results
PWT2‐N/OFQ mimicked the spinal antinociceptive effects of N/OFQ both in nociceptive and neuropathic pain models in mice as well as in non‐human primates displaying 40‐fold higher potency and a markedly prolonged duration of action. The effects of N/OFQ and PWT2‐N/OFQ were sensitive to the N/OFQ receptor (NOP) antagonist SB‐612111, but not to opioid receptor antagonists.
Conclusions and Implications
The present study has demonstrated that PWT2‐N/OFQ mimicked the antinociceptive effects of the natural peptide in rodents and non‐human primates acting as a potent and longer‐lasting NOP‐selective agonist. More generally, PWT derivatives of biologically active peptides can be viewed as innovative pharmacological tools for investigating those conditions and states in which selective and prolonged receptor stimulation promotes beneficial effects.
Abstract The simulation of high-energy physics collision events is a key element for data analysis at present and future particle accelerators. The comparison of simulation predictions to data allows ...looking for rare deviations that can be due to new phenomena not previously observed. We show that novel machine learning algorithms, specifically Normalizing Flows and Flow Matching, can be used to replicate accurate simulations from traditional approaches with several orders of magnitude of speed-up. The classical simulation chain starts from a physics process of interest, computes energy deposits of particles and electronics response, and finally employs the same reconstruction algorithms used for data. Eventually, the data are reduced to some high-level analysis format. Instead, we propose an end-to-end approach, simulating the final data format directly from physical generator inputs, skipping any intermediate steps. We use particle jets simulation as a benchmark for comparing both discrete and continuous Normalizing Flows models. The models are validated across a variety of metrics to identify the most accurate. We discuss the scaling of performance with the increase in training data, as well as the generalization power of these models on physical processes different from the training one. We investigate sampling multiple times from the same physical generator inputs, a procedure we name oversampling , and we show that it can effectively reduce the statistical uncertainties of a dataset. This class of ML algorithms is found to be capable of learning the expected detector response independently of the physical input process. The speed and accuracy of the models, coupled with the stability of the training procedure, make them a compelling tool for the needs of current and future experiments.
Starting from the revolutionary Retinex by Land and McCann, several further perceptually inspired color correction models have been developed with different aims, e.g. reproduction of color ...sensation, robust features recognition, enhancement of color images. Such models have a differential, spatially-variant and non-linear nature and they can coarsely be distinguished between white-patch (WP) and gray-world (GW) algorithms. In this paper we show that the combination of a pure WP algorithm (RSR: random spray Retinex) and an essentially GW one (ACE) leads to a more robust and better performing model (RACE). The choice of RSR and ACE follows from the recent identification of a unified spatially-variant approach for both algorithms. Mathematically, the originally distinct non-linear and differential mechanisms of RSR and ACE have been fused using the spray technique and local average operations. The investigation of RACE allowed us to put in evidence a common drawback of differential models: corruption of uniform image areas. To overcome this intrinsic defect, we devised a local and global contrast-based and image-driven regulation mechanism that has a general applicability to perceptually inspired color correction algorithms. Tests, comparisons and discussions are presented.
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