To tackle the challenge posed by 1/f noise which significantly hinders the practical application of superconductor/tunnel magnetoresistance (TMR) composite magnetic sensors in low-frequency detection, this paper proposes a magnetic field thermal modulation method specifically tailored for the superconductor/TMR composite sensor. The method employs alternating joule heating via a resistance wire to induce partial quenching and recovery states conversion in the superconducting flux transformation amplifier (SFTA). Firstly, a thermo-electric-magnetic comprehensive finite element simulation model was developed to obtain the temperature and magnetic field distributions during the quenching and recovery state conversion process, and then to realize the size optimization of the thermal modulated structure. Final experimental tests conducted in the liquid nitrogen environment demonstrated a high modulation frequency of 5 kHz was achieved. Meanwhile, the interlayer capacitor-coupling effect was introduced to explain the phenomenon of resistance deviation from zero for the thermal modulated superconducting constriction under the higher modulation frequency. The breakthrough in this article holds promise for the low-frequency application of superconductor/TMR composite sensors.
Performing language-conditioned robotic manipulation tasks in unstructured environments is highly demanded for general intelligent robots. Conventional robotic manipulation methods usually learn semantic representation of the observation for action prediction, which ignores the scene-level spatiotemporal dynamics for human goal completion. In this paper, we propose a dynamic Gaussian Splatting method named ManiGaussian for multi-task robotic manipulation, which mines scene dynamics via future scene reconstruction. Specifically, we first formulate the dynamic Gaussian Splatting framework that infers the semantics propagation in the Gaussian embedding space, where the semantic representation is leveraged to predict the optimal robot action. Then, we build a Gaussian world model to parameterize the distribution in our dynamic Gaussian Splatting framework, which provides informative supervision in the interactive environment via future scene reconstruction. We evaluate our ManiGaussian on 10 RLBench tasks with 166 variations, and the results demonstrate our framework can outperform the state-of-the-art methods by 13.1\% in average success rate.
This article presents an exploratory study on the flexural behavior of carbon fiber–reinforced polymer–reinforced concrete beams subjected to acidic loading effect. To this end, an artificial acid rain with a pH level of 1.5 was prepared by mixing sulfate and nitric acid solutions. Eight reinforced concrete beams with/without carbon fiber–reinforced polymer applications were constructed and conditioned using the artificial acid rain. During conditioning, bending loads were applied to the top surfaces of the beams to simulate the acidic loading action. Three carbon fiber–reinforced polymer reinforcement schemes (corrosion reinforcement, reinforcement corrosion, and cracking reinforcement) were considered. After conditioning, the length and quantity of initial cracks in the beams were recorded. A combined ultrasonic–rebound method was then adopted to measure the strength and corrosion depth of the concrete and evaluate the beams’ integrity. Next, four-point bending tests were conducted to study the beams’ flexural behavior. It can be concluded that all beams deteriorated with the increase of the corrosion time. Carbon fiber–reinforced polymer–reinforced concrete beams performed better than normal reinforced concrete beams under the acidic loading effect. The initial cracks can influence the flexural behavior of carbon fiber–reinforced polymer–reinforced concrete beams.
This study employs the phase-field regularized cohesion model (PF-CZM) to simulate crack propagation and damage behavior in porous granite. The impact of the pore radius (r), initial crack–pore distance (D), and pore–crack angle (θ) on crack propagation is investigated. The simulation findings reveal that, with a fixed deflection angle and initial crack–pore distance, larger pores are more likely to induce crack extension under identical loading conditions. Moreover, with r and θ remaining constant, the crack extension can be divided into two stages: from its initiation to the lower edge of the pore and then from the lower edge to the upper boundary of the model. Multiple combinations of different D/r ratios and pore radii are derived by varying the values of D and r. These results demonstrate that with a constant r, cracks tend to deflect towards the pore closer to the initial crack. Conversely, when D remains constant, cracks will preferentially deflect toward pores with a larger r. In summary, the numerical simulation of rock pores and initial cracks, based on the PF-CZM, exhibits remarkable predictive capabilities and holds significant potential in advancing rock fracture analyses.
Adding mineral admixture is one of the leading technical ways to improve the durability of cement-based materials. Nano attapulgite clay (NAC) is a unique fiber rod crystal structure that can change the physical and mechanical properties of cement-based materials, and opens up a new idea for exploring the durability of high-performance cement-based materials. This paper studied the effects of NAC on the hydration process, pore structure, and mechanical properties of a cement substrate under different activation methods. The results show that the pH value of the pore solution of cement mixed with 5% NAC high-viscosity ore (calcined) was 8.8% higher than that of the cement without NAC. The chemically bound water contents in the 1% and 3% NAC raw (calcined) cement were 14.11% and 14.04%; when the content of calcined NAC raw ore was 1%, the improvement effect on the cement hydration process is the best. The content of calcined NAC was 1%, 3%, and 5%, and the porosity of hardened cement paste was 19%, 19.04%, and 22.27% lower than that of the cement without NAC. Calcining NAC raw ore can improve cement’s hydration process, promote cement’s hydration reaction, and increase the compactness of hardened cement paste. The fluidity of the cement mortar mixed with calcined high-viscosity ore (D and E) at a mixing amount of 5% was reduced by 32.66% and 26.13%, respectively, compared to the ordinary specimens. The flexural strength of the cement paste mixed with calcined raw ore and high-viscosity ore at a mixing amount of 1% was generally improved by 28.40% and 17.28% compared to the cement without NAC paste. After calcination, the NAC raw ore is better than the high-clay ore in improving the mechanical properties of cement.
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