Single-pass finite element simulation of ECAP brass

Using DEFORM-3D with the single channel brass H63 channel Angle extrusion deformation of computer simulation, such as extrusion process for the change of load, velocity of billet, the effective stress and the distribution of strain rate, grain size billets are analyzed, and the results show that the friction force had a great influence on extrusion process of load, the change of effective stress and strain rate trend, along with the change of extrusion for grain size refinement in a certain extent, but the different location of grain size and distribution is uneven. For the ECAP (equal channel presents pressing) grain refining process of industrial production and application to provide certain theoretical basis

Ignition timing control strategy based on openECU design

Ignition system is the main important part of the engine, and has absolute influence on engine performance. OpenECU for ignition timing strategy on the basis of the design and calibration work, greatly shorten the development difficulty and cycle; machine of a LNG gas ignition timing strategy has carried on the design and optimization, and combining the calculation model for the engine (air intake, compression, power, and exhaust) feedback and verification. It can save a lot of time and resources for experiment if experiments use openECU. It also can monitor the influence of the different inputs conditions on the ignition advance angle. It has realized the map of calibration, greatly shorten the development work and has certain actual application value

Research on calibration method of electronic control parameters based on engine model

The MBC (calibration model-based) toolbox in MATLAB software and Ricardo Wave were used to optimize the power performance of a gasoline engine. In the calibration process, Firstly, the wave simulation model of the engine was established and validated; then, engine operating points were determined by using the design of experiments (DOE) method, and parameters and performance (torque, fuel consumption, power and the cylinder maximum pressure, etc.) of the engine at these operating points were calculated by the simulation model. Finally, the engine mathematical statistical model was established and calibration optimization. The engine ignition advance angle, air-fuel ratio and the torque of the engine were obtained. The results show that the method combined with the modern DoE test design theory and automatic calibration technology not only makes the engine torque from 198 Nm to 215 Nm, but also greatly reduces the test time and improve the calibration efficienc

On the Representation of Causal Background Knowledge and its Applications in Causal Inference

Causal background knowledge about the existence or the absence of causal edges and paths is frequently encountered in observational studies. The shared directed edges and links of a subclass of Markov equivalent DAGs refined due to background knowledge can be represented by a causal maximally partially directed acyclic graph (MPDAG). In this paper, we first provide a sound and complete graphical characterization of causal MPDAGs and give a minimal representation of a causal MPDAG. Then, we introduce a novel representation called direct causal clause (DCC) to represent all types of causal background knowledge in a unified form. Using DCCs, we study the consistency and equivalency of causal background knowledge and show that any causal background knowledge set can be equivalently decomposed into a causal MPDAG plus a minimal residual set of DCCs. Polynomial-time algorithms are also provided for checking the consistency, equivalency, and finding the decomposed MPDAG and residual DCCs. Finally, with causal background knowledge, we prove a sufficient and necessary condition to identify causal effects and surprisingly find that the identifiability of causal effects only depends on the decomposed MPDAG. We also develop a local IDA-type algorithm to estimate the possible values of an unidentifiable effect. Simulations suggest that causal background knowledge can significantly improve the identifiability of causal effects

Low Rank Directed Acyclic Graphs and Causal Structure Learning

Despite several important advances in recent years, learning causal structures represented by directed acyclic graphs (DAGs) remains a challenging task in high dimensional settings when the graphs to be learned are not sparse. In particular, the recent formulation of structure learning as a continuous optimization problem proved to have considerable advantages over the traditional combinatorial formulation, but the performance of the resulting algorithms is still wanting when the target graph is relatively large and dense. In this paper we propose a novel approach to mitigate this problem, by exploiting a low rank assumption regarding the (weighted) adjacency matrix of a DAG causal model. We establish several useful results relating interpretable graphical conditions to the low rank assumption, and show how to adapt existing methods for causal structure learning to take advantage of this assumption. We also provide empirical evidence for the utility of our low rank algorithms, especially on graphs that are not sparse. Not only do they outperform state-of-the-art algorithms when the low rank condition is satisfied, the performance on randomly generated scale-free graphs is also very competitive even though the true ranks may not be as low as is assumed

Research on calibration method of electronic control parameters based on engine model

The MBC (calibration model-based) toolbox in MATLAB software and Ricardo Wave were used to optimize the power performance of a gasoline engine. In the calibration process, Firstly, the wave simulation model of the engine was established and validated; then, engine operating points were determined by using the design of experiments (DOE) method, and parameters and performance (torque, fuel consumption, power and the cylinder maximum pressure, etc.) of the engine at these operating points were calculated by the simulation model. Finally, the engine mathematical statistical model was established and calibration optimization. The engine ignition advance angle, air-fuel ratio and the torque of the engine were obtained. The results show that the method combined with the modern DoE test design theory and automatic calibration technology not only makes the engine torque from 198 Nm to 215 Nm, but also greatly reduces the test time and improve the calibration efficienc

BeiDou Satellites Assistant Determination by Receiving Other GNSS Downlink Signals

GNSS’s orbit determinations always rely on ground station or intersatellite links (ISL). In the emergency of satellite-to-ground links and ISL break-off, BeiDou navigation satellite system (BDS) satellites cannot determine their orbits. In this paper, we propose to add a spaceborne annular beam antenna for receiving the global positioning system (GPS) and global navigation satellite system (GLONASS) signals; therefore, the BDS satellites may be capable of determining their orbits by GPS/GLONASS signals. Firstly, the spectrum selection, the power isolation, the range of Doppler frequency shift, and changing rate are taken into account for the feasibility. Specifically, the L2 band signals are chosen for receiving and processing in order to prevent the overlapping of the receiving and transmitting signals. Secondly, the minimum number of visible satellites (MNVS), carrier-to-noise ratio (C/N0), dilution of precision (GDOP), and geometric distance root-mean-square (gdrms) are evaluated for acquiring the effective receiving antennas’ coverage ranges. Finally, the scheme of deploying 3 receiving antennas is proved to be optimal by analysis and simulations over the middle earth orbit (MEO), geostationary earth orbit (GEO), and the inclined geosynchronous satellite orbit (IGSO). The antennas’ structures and patterns are designed to draw a conclusion that installing GPS and GLONASS receivers on BDS satellites for emergent orbits determination is cost-effective

An invisibility cloak using silver nanowires

In this paper, we use the parameter retrieval method together with an analytical effective medium approach to design a well-performed invisible cloak, which is based on an empirical revised version of the reduced cloak. The designed cloak can be implemented by silver nanowires with elliptical cross-sections embedded in a polymethyl methacrylate host. This cloak is numerically proved to be robust for both the inner hidden object as well as incoming detecting waves, and is much simpler thus easier to manufacture when compared with the earlier proposed one [Nat. Photon. 1, 224 (2007)].Comment: 7 pages, 4 figures, 2 table

Superconducting Diode Effect and Large Magnetochiral Anisotropy in Td_d-MoTe2_2 Thin Film

In the absence of time-reversal invariance, metals without inversion symmetry may exhibit nonreciprocal charge transport -- a magnetochiral anisotropy that manifests as unequal electrical resistance for opposite current flow directions. If superconductivity also sets in, the charge transmission may become dissipationless in one direction while remaining dissipative in the opposite, thereby realizing a superconducting diode. Through both direct-current and alternating-current measurements, we study the nonreciprocal effects in thin films of the noncentrosymmetric superconductor T$_d$-MoTe\textsubscript{2} with disorders. We observe nonreciprocal superconducting critical currents with a diode efficiency close to 20\%~, and a large magnetochiral anisotropy coefficient up to \SI{5.9e8}{\per\tesla\per\ampere}, under weak out-of-plane magnetic field in the millitesla range. The great enhancement of rectification efficiency under out-of-plane magnetic field is likely abscribed to the vortex ratchet effect, which naturally appears in the noncentrosymmetric superconductor with disorders. Intriguingly, unlike the finding in Rashba systems, the strongest in-plane nonreciprocal effect does not occur when the field is perpendicular to the current flow direction. We develop a phenomenological theory to demonstrate that this peculiar behavior can be attributed to the asymmetric structure of spin-orbit coupling in T$_d$-MoTe\textsubscript{2}. Our study highlights how the crystallographic symmetry critically impacts the nonreciprocal transport, and would further advance the research for designing the superconducting diode with the best performance.Comment: 7 pages, 5figure