The studies on the autonomous electric vehicle are quite attractive due to fewer human-induced errors and improved safety in recent years. Extensive research has been done on the autonomous steering ...control of the mobile robot, but study on the on-road autonomous electric vehicle is still limited. This paper proposes a potential field method to achieve the trajectory control of the autonomous electric vehicle with in-wheel motors. Instead of strictly following a desired path, this method can form a steering corridor with a desired tracking error tolerance and the vehicle can be steered smoothly with less control effort. In this paper, the innovative potential filed function is presented first to determine the desired vehicle yaw angle. Then, according to this desired yaw angle, a two-level trajectory controller is proposed to achieve the trajectory control. Simulation results are shown to prove that this suggested trajectory controller can successfully control the vehicle to move within the desired road boundary and improve the handling and stability performance of the vehicle.
Deposition of black shale of the Lower Cambrian Niutitang Formation (NTT) of the Yangtze Block, South China, in association with the Ediacaran-Cambrian (E-C) transition was accompanied by widespread ...formation of phosphate nodules. Petrological and geochemical studies of the nodules and host sedimentary rocks were carried out to elucidate hydrographic conditions of the Early Cambrian ocean. Our results reveal that NTT phosphate nodules are composed principally of concentrically banded carbonate fluorapatite (CFA) that likely reflects changing Eh and pH conditions contemporaneous with diagenetic nodule growth. Accumulation of organic-rich sediment and nodule growth may have been induced and sustained by contemporaneous volcanic and hydrothermal activities on the Yangtze Block. The introduction of voluminous nutrients with volcanic ash, including phosphate and aqueous Fe and Si, promoted the bloom of plankton, including sponges and lower algae leading to organic matter enrichment. Productivity may have been further enhanced by upwelling of phosphate-rich bottom water that resulted in widespread phosphogenesis and formation of phosphate nodules. The hyalophane-quartz association documented from phosphate nodules suggests the possible interaction of K-feldspar-rich volcanic ash and Ba-rich hydrothermal fluids at lower pH levels in association with nodule growth. The formation of phosphate nodules of the Niutitang Formation, then, reflects the complex interaction among primary productivity, volcanic and hydrothermal activity, and the accumulation of organic matter at a critical period of Earth history.
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•Phosphate nodules display a concentric structure that may be controlled by changing Eh and pH during the diagenesis.•Discovery of hyalophane-quartz associations reflects possible interaction of volcanic ash and Ba-rich hydrothermal fluids.•Volcanic and hydrothermal activities appear to be critical to the formation of phosphate nodules during the E-C transition.
The development of highly efficient electrocatalysts to reduce overpotentials is vital for accelerating the sluggish oxygen evolution reaction (OER) processes. Herein, we demonstrate ultrathin ...heterogeneous nanosheets as a promising OER electrocatalyst, which are composed of ultrafine CoFeOx nanoparticles and a monolayered CoN4-based metal–organic framework (MOF) matrix. The embedding of such inorganic nanoparticles in the MOF lattice creates metal Co sites located at the CoFeOx/MOF interfaces. Structural characterization and analysis indicated a higher valence and changed 3d electronic configuration for the interfacial Co in contrast to the CoN4 sites. Furthermore, theoretical calculations reveal the high activity of interfacial Co sites for OER. Electrochemical studies confirm that the ultrathin heterogeneous nanosheets deposited on carbon cloth can achieve an excellent electrocatalytic OER performance with a low overpotential of 232 mV at a current density of 10 mA cm–2 with good stability. This work provides insights on the development of ultrathin OER heterocatalysts with highly active interfaces of inorganic units and MOFs.
The relationship between transcription and the 3D chromatin structure is debated. Multiple studies have shown that transcription affects global Cohesin binding and 3D genome structures. However, ...several other studies have indicated that inhibited transcription does not alter chromatin conformations.
We provide the most comprehensive evidence to date to demonstrate that transcription plays a relatively modest role in organizing the local, small-scale chromatin structures in mammalian cells. We show degraded Pol I, Pol II, and Pol III proteins in mESCs cause few or no changes in large-scale 3D chromatin structures, selected RNA polymerases with a high abundance of binding sites or active promoter-associated interactions appear to be relatively more affected after the degradation, transcription inhibition alters local, small loop domains, as indicated by high-resolution chromatin interaction maps, and loops with bound Pol II but without Cohesin or CTCF are identified and found to be largely unchanged after transcription inhibition. Interestingly, Pol II depletion for a longer time significantly affects the chromatin accessibility and Cohesin occupancy, suggesting that RNA polymerases are capable of affecting the 3D genome indirectly. These direct and indirect effects explain the previous inconsistent findings on the influence of transcription inhibition on the 3D genome.
We conclude that Pol I, Pol II, and Pol III loss alters local, small-scale chromatin interactions in mammalian cells, suggesting that the 3D chromatin structures are pre-established and relatively stable.
Autonomous driving technology, especially motion planning and the trajectory tracking method, is the foundation of an intelligent interconnected vehicle, which needs to be improved urgently. ...Currently, research on path planning methods has improved, but few of the current studies consider the vehicle's nonlinear characteristics in the reference model, due to the heavy computational effort. At present, most of the algorithms are designed by a linear vehicle model in order to achieve the real-time performance at the cost of lost accuracy. To achieve a better performance, the dynamics and kinematics characteristics of the vehicle must be simulated, and real-time computing ensured at the same time. In this article, a Takagi-Sugeno fuzzy-model-based closed-loop rapidly exploring random tree algorithm with on-line re-planning process is applied to build the motion planner, which effectively improves the vehicle performance of dynamic obstacle avoidance, and plans the local obstacle avoidance path in line with the dynamic characteristics of the vehicle. A nonlinear vehicle model is integrated into the motion planner design directly. For fast local path planning mission, the Takagi-Sugeno fuzzy modelling method is applied to the modeling process in the planner design, so that the vehicle state can be directly utilized into the path planner to create a feasible path in real-time. The performance of the planner was evaluated by numerical simulation. The results demonstrate that the proposed motion planner can effectively generate a reference trajectory that guarantees driving efficiency with a lower re-planning rate.
With the development of the Internet of things (IoT), federated learning (FL) has received increasing attention as a distributed machine learning (ML) framework that does not require data exchange. ...However, current FL frameworks follow an idealized setup in which the task size is fixed and the storage space is unlimited, which is impossible in the real world. In fact, new classes of these participating clients always emerge over time, and some samples are overwritten or discarded due to storage limitations. We urgently need a new framework to adapt to the dynamic task sequences and strict storage constraints in the real world. Continuous learning or incremental learning is the ultimate goal of deep learning, and we introduce incremental learning into FL to describe a new federated learning framework. New generation federated learning (NGFL) is probably the most desirable framework for FL, in which, in addition to the basic task of training the server, each client needs to learn its private tasks, which arrive continuously independent of communication with the server. We give a rigorous mathematical representation of this framework, detail several major challenges faced under this framework, and address the main challenges of combining incremental learning with federated learning (aggregation of heterogeneous output layers and the task transformation mutual knowledge problem), and show the lower and upper baselines of the framework.
This paper presents the development of path-tracking control strategies for an over-actuated autonomous electric vehicle. The vehicle platform is equipped with four-wheel steering (4WS) as well as ...torque vectoring (TV) capabilities, which enable the control of vehicle dynamics to be enhanced. A nonlinear model predictive controller is proposed taking into account the nonlinearities in vehicle dynamics at the limits of handling as well as the crucial actuator constraints. Controllers with different actuation formulations are presented and compared to study the path-tracking performance of the vehicle with different levels of actuation. The controllers are implemented in a high-fidelity simulation environment considering scenarios of vehicle handling limits. According to the simulation results, the vehicle achieves the best overall path-tracking performance with combined 4WS and TV, which illustrates that the over-actuation topology can enhance the path-tracking performance during conditions under the limits of handling. In addition, the performance of the over-actuation controller is further assessed with different sampling times as well as prediction horizons in order to investigate the effect of such parameters on the control performance, and its capability for real-time execution. In the end, the over-actuation control strategy is implemented on a target machine for real-time validation. The control formulation proposed in this paper is proven to be compatible with different levels of actuation, and it is also demonstrated in this work that it is possible to include the particular over-actuation formulation and specific nonlinear vehicle dynamics in real-time operation, with the sampling time and prediction time providing a compromise between path-tracking performance and computational time.
The fabrication of metal–organic framework (MOF)-based macro-materials is considered as a promising strategy toward the practical applications of powdered MOF crystals. In this study, selective laser ...sintering (SLS), an advanced three-dimensional (3D) powder printing technique, has been employed to fabricate MOF–polymer mixed matrix films (MMFs) by using thermoplastic polyamide 12 (PA12) powder as the matrix material and five types of MOFs including ZIF-67, NH2-MIL-101(Al), MOF-801, HKUST-1, and ZIF-8 crystals as the fillers. A three-layer HKUST-1-PA12 complex with a grid pattern is fabricated to demonstrate the printability of 3D MOF–polymer structure. Single-layer MMFs with grid patterns are printed by using the five types of MOF fillers with different mass loadings to study their free-standing characteristic, thickness, specific surface area, hydrophilia, water permeate flux, and mechanical stability. The methylene blue (MB) adsorption tests are conducted using the NH2-MIL-101(Al)-PA12 MMFs with different grid patterns to exemplify the applications of the MMFs for water purification. It is confirmed that the MOF components retain their high maximum adsorption capacity, and the printed MMFs can be conveniently regenerated for cyclic utilization. This work provides an insight into the utilization of advanced 3D printing technology to manufacture macro-MOF–polymer materials for practical applications.
Reservoir solid bitumen is pervasive throughout the Sinian Dengying Formation dolomites of the Sichuan Basin and neighboring areas, yet its origin remains controversial. Optical and scanning electron ...microscope (SEM) studies of the Dengying Formation were carried out to elucidate the nature and origin of the solid bitumen. Solid bitumen in dissolution pores, intercrystal pores, and stylolites appears to have formed in association with regional hydrocarbon charging processes. Reservoir solid bitumen displays a variety of morphologies, each of which appears to reflect different precursor hydrocarbons. Massive/crust-like solid bitumen was probably derived from solid precursors whereas finger-like solid bitumen likely evolved from liquid precursors. Sheet-like and thin skinned globular solid bitumen appeared to have precipitated from wet gas precursors. Analyzed solid bitumen is characterized by high random reflectance (average = 3.4%) and bireflectance values (4.2–6.9%), exhibits strong optical anisotropy, and displays different coke structures, including granular mosaic, domain, and fibrous. The coke textures, which appear to reflect the nature of bitumen precursors, formed by physical coalescence of mesophase spheres and parallel arrangement of laminated aromatic sheets in association with a rapid heating event. The inferred thermal episode, which is evidenced by the presence of hydrothermal minerals, including saddle dolomite, quartz, authigenic illite, and barite, may have been associated with the Late Permian eruption of the Emeishan Traps. Thus, widespread solid bitumen in the Dengying Formation reflects the effects of hydrothermal alteration rather than the impact of normal burial-related thermal maturation. Further, the close association of sold bitumen and authigenic kaolinite indicates that natural deasphalting plays a role in the formation of reservoir solid bitumen.
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•Abnormal hydrothermal alteration was the dominant mechanism responsible for the formation of reservoir solid bitumen.•Natural deasphalting was also instrumental in the formation of reservoir solid bitumen.•The morphology of reservoir solid bitumen is a useful indicator for different precursor hydrocarbons.•A model of the formation of solid bitumen in Dengying dolomites of the Sichuan Basin was proposed.
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