| 1. |
- Dong, Yu, et al.
(author)
-
Observation of a Ubiquitous (π, π)-Type Nematic Superconducting Order in the Whole Superconducting Dome of Ultra-Thin BaFe2–xNixAs2 Single Crystals
- 2021
-
In: Chinese Physics Letters. - : Institute of Physics Publishing (IOPP). - 0256-307X .- 1741-3540. ; 38:9
-
Journal article (peer-reviewed)abstract
- In iron-based superconductors, the (0, pi) or (pi, 0) nematicity, which describes an electronic anisotropy with a four-fold symmetry breaking, is well established and believed to be important for understanding the superconducting mechanism. However, how exactly such a nematic order observed in the normal state can be related to the superconducting pairing is still elusive. Here, by performing angular-dependent in-plane magnetoresistivity using ultra-thin flakes in the steep superconducting transition region, we unveil a nematic superconducting order along the (pi, pi) direction in electron-doped BaFe2 - x Ni x As2 from under-doped to heavily overdoped regimes with x = 0.065-0.18. It shows superconducting gap maxima along the (pi, pi) direction rotated by 45 degrees from the nematicity along (0, pi) or (pi, 0) direction observed in the normal state. A similar (pi, pi)-type nematicity is also observed in the under-doped and optimally doped hole-type Ba1 - y K y Fe2As2, with y = 0.2-0.5. These results suggest that the (pi, pi) nematic superconducting order is a universal feature that needs to be taken into account in the superconducting pairing mechanism in iron-based superconductors.
|
|
| 2. |
- Li, Qiulin, et al.
(author)
-
Effect of Rotating Magnetic Field on the Thermocapillary Flow Instability in a Liquid Bridge
- 2024
-
In: Microgravity, science and technology. - : Springer Nature. - 0938-0108 .- 1875-0494. ; 36:2
-
Journal article (peer-reviewed)abstract
- The stability of thermocapillary flow in a liquid bridge under a transverse rotating magnetic field (RMF) was numerically investigated by the linear stability analysis using the spectral element method. Three commonly used RMF models, namely, the infinite model, the simplified finite model and the Φ1-Φ2 model, are employed to describe the RMF and their results are compared. Additionally, for the Φ1-Φ2 model, the uniform and non-uniform RMF were also compared. The numerical results show that with the increase of magnetic Taylor number Ta, the critical Marangoni number (Mac) for the three RMF models increases firstly, then decreases sharply to a minimum, finally increases again when the RMF is strong enough to suppress the radial and axial convection induced by thermocapillary force. Two transitions between the wavenumber k=1 and k=2 mode are observed with increasing Ta. The results obtained by the simplified finite model are in good agreement with those of the Φ1-Φ2 model, however, the infinite model has a significant deviation compared to the Φ1-Φ2 model. Besides, the results indicate that the non-uniform RMF has a relatively weak action compared with the uniform RMF.
|
|
| 3. |
- Huang, Shiliang, 1984-, et al.
(author)
-
Two Open-Framework Germanates with Nickel Complexes Incorporated into the Framework
- 2011
-
In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 50:20, s. 9921-9923
-
Journal article (peer-reviewed)abstract
- Two open-framework germanates, SUT-1 and SUT-2, have been synthesized under hydrothermal conditions using ethylenecliamine (en, H(2)NCH(2)CH(2)NH(2)) as templates and Ni(NO(3))(2)center dot 6H(2)O as the transition-metal source. Their frameworks are built with Gel() clusters and [Ni(en)(2)](2+) complexes. In both structures, Gel clusters form square nets in the a-c plane, while the [Ni(en)2]2+ complexes bridge the square nets via Ni-O-Ge bonds to form 3D networks. They present the first examples to incorporate Ni(2+) complexes into the germanate frameworks. In SUT-2, additional linkages by Ge(2)O(7) clusters between the square nets generate a new type of topology.
|
|
| 4. |
- Ma, Xuehui, et al.
(author)
-
Adaptive dual control with online outlier detection for uncertain systems
- 2022
-
In: ISA Transactions. - : Elsevier BV. - 0019-0578.
-
Journal article (peer-reviewed)abstract
- This paper proposes an adaptive dual control with outlier detection that is robust to the occurrence of outliers in uncertain systems. Outliers occasionally exist in system process noise and observation noise, which could cause poor parameter estimation and degraded control performance of uncertain systems. For this reason, we devise an online outlier detection mechanism to filter the outliers so as to enhance the parameter estimation of uncertain systems. The devised mechanism makes decisions on outlier detection via the generated predicted regions where the newly arriving data is expected to locate, and the predicted regions are updated in real-time according to the historical data. The detection mechanism is integrated into the design of adaptive dual control, which is derived based on the bicriterial method. Compared with classical dual control merely considering uncertainty in input and output data stream, we are the first to include the uncontrollable excitations into the structure of dual control to fit practical scenarios, and this inclusion also provides an extensive cover on outliers to be detected. The improved performance of the proposed approach is verified using a mathematical model through one-time simulation and Monte Carlo simulations under different conditions, and we also evaluate our method in the control of fermentation sterilization process for more convincing results.
|
|
| 5. |
- Ma, Xuehui, et al.
(author)
-
Adaptive quantile control for stochastic system
- 2022
-
In: ISA Transactions. - : Elsevier BV. - 0019-0578. ; 123, s. 110-121
-
Journal article (peer-reviewed)abstract
- Adaptive control has been successfully developed in deriving control law for stochastic systems with unknown parameters. The generation of reasonable control law depends on accurate parameter estimation. Recursive least square is widely used to estimate unknown parameters for stochastic systems; however, this approach only fits systems with Gaussian noises. In this paper, the adaptive quantile control is first proposed to cover the case where stochastic system noise follows sharp and thick tail distribution rather than Gaussian distribution. In the proposed approach, the system noise is modeled by the Asymmetric Laplace Distribution, and the unknown parameter is online estimated by our developed Bayesian quantile sum estimator, which combines recursive quantile estimations weighted by Bayesian posterior probabilities. With the real-time estimated parameter, the adaptive quantile control law is constructed based on the certainty equivalence principle. Our proposed estimator and controller are not computationally consuming and can be easily conducted in the Micro Controller Unit to fit practical applications. The comparison with some dominant controllers for the unknown stochastic system is conducted to verify the effectiveness of the adaptive quantile control.
|
|
| 6. |
- Wei, Lai, et al.
(author)
-
Multiscale identification of urban functional polycentricity for planning implications : An integrated approach using geo-big transport data and complex network modeling
- 2020
-
In: Habitat International. - : Elsevier BV. - 0197-3975. ; 97
-
Journal article (peer-reviewed)abstract
- Polycentrism has gradually become a newly emergent dimension of global urbanization. Many countries worldwide have tailored plans suited to functional polycentricity, in light of the prevalent “ghost cities” or “empty towns” as lessons from the morphologically polycentric development practices. However, the subject of defining and measuring functional polycentricity is still in an initial development phase, both in theory and in methodology. This paper first establishes a general theoretical framework for understanding functional polycentricity from the lens of interactive human mobility among spatial units. Then, a new approach is proposed to identify and measure urban functional polycentricity from a multiscale perspective and further applied to the case of Shanghai, China. More specifically, the pick-up and drop-off points from taxi GPS data are used to examine the linkages among different urban units across various scales (e.g., census tract, 3000-m grid, 5000-m grid, and community). Complex network modeling, together with the sensitivity analysis, is further employed to identify the centers according to the spatial importance of each unit. The results show that (1) the approach proposed can effectively identify functional centers within urban setting; (2) an obvious polycentric structure exists in Shanghai and is sensitive to scale effects; (3) the estimates are more accurate and precise with the shrink of analysis unit size from community level to census tract level; and (4) under the same spatial scale, the grid-based analysis produces a more elaborated polycentric pattern compared with the traditional administration-based analysis. Finally, scale-dependent differences between morphological and functional polycentricity are distinguished for providing implications for urban planning. Our study is believed to renew the knowledge of polycentricity conceptualization.
|
|
