Understanding Micropolar Theory in the Earth Sciences I: The Eigenfrequency $$\omega _r$$

Even though micropolar theories are widely applied for engineering applications such as the design of metamaterials, applications in the study of the Earth’s interior still remain limited and in particular in seismology. This is due to the lack of understanding of the required elastic material parameters present in the theory as well as the eigenfrequency $$\omega _r$$ ω r which is not observed in seismic data. By showing that the general dynamic equations of the Timoshenko’s beam is a particular case of the micropolar theory we are able to connect micropolar elastic parameters to physically measurable quantities. We then present an alternative micropolar model that, based on the same physical basis as the original model, circumvents the problem of the original eigenfrequency $$\omega _r$$ ω r laking in seismological data. We finally validate our model with a seismic experiment and show it is relevant to explain observed seismic dispersion curves.

Optimal Connected Cruise Control Design with Time-Varying Leader Velocity and Delays

With the development of intelligent transportation system (ITS), owing to its flexible connectivity structures and communication network topologies, connected cruise control (CCC), increasing the situation awareness of the autonomous vehicle without redesigning the other vehicles, is an advanced cruise control technology attracted extensive attention. However, due to the uncertain traffic environment and the movement of the connected vehicles, the leader speed is typically highly dynamic. In this paper, taking the uncertain time-varying leading vehicle velocity and communication delays into consideration, an optimal CCC algorithm is proposed for both near-static case and general dynamic control cases. First, the analysis for discrete-time error dynamics model of the longitudinal vehicle platoon is performed. Then, in order to minimize the error between the desired and actual states, a linear quadratic optimization problem is formulated. Subsequently, in near-static control case, an efficient algorithm is proposed to derive the solution of the optimization problem by two steps. Specifically, the online step calculates the optimal control scheme according to the current states and previous control signals, and the off-line step calculates the corresponding control gain through backward recursion. Then, the results are further extended to the general dynamic control case where the leader vehicle moves at an uncertain time-varying velocity. Finally, simulation results verify the effectiveness of the proposed CCC algorithm.

Are drivers of northern lights in the ionosphere?

Known as northern lights, auroral spirals are distinct features of substorm auroras composed of large-scale spirals (100s km Surges) mixed with smaller scale ones (10s km Folds, and 1 km Rays). Spiral patterns are generally interpreted in terms of the field line mapping of the upward field-aligned currents produced in the magnetosphere during the field line dipolarization. The field line mapping results in opposing spiral rotations of small- and large-scale auroras. Because of a rotational symmetry deformation and similarity in deformation speeds (6~8 km/s) of small- and large-scale spirals, it has been suggested that common physical processes may underlie the deforming processes. Internal processes in the polar ionosphere (ionospheric driver) will be proposed as the general dynamic for spiral auroras. The ionospheric driver rotated in the ionosphere to produce spirals that characteristically differ from the field line mapping scenario.

Design of a dynamic mock-up bench for testing robotic interventions

When a robotic intervention is required in hazardous facilities (e.g. particle accelerators or nuclear plants), it is commonly not possible to test the operation on-site in advance - a considerable challenge since robotic interventions usually require specific tasks for each location -, precluding the team from demonstrating the feasibility of the operation. It becomes mandatory to develop a particular mock-up for each operation, unsuitable for reusing it in future missions. To solve this problem, a general dynamic mock-up bench was designed, allowing to centre the testing of all remote handled tasks and to choose the best set of robots to perform them.

A Parallel Processing Approach to Dynamic Simulation of Ethylbenzene Process

Parallel computing has been developed for many years in chemical process simulation. However, existing research on parallel computing in dynamic simulation cannot take full advantage of computer performance. More and more applications of data-driven methods and increasing complexity in chemical processes need faster dynamic simulators. In this research, we discuss the upper limit of speed-up for dynamic simulation of the chemical process. Then we design a parallel program considering the process model solving sequence and rewrite the General dynamic simulation & optimization system (DSO) with two levels of parallelism, multithreading parallelism and vectorized parallelism. The dependency between subtasks and the characteristic of the hottest subroutines are analyzed. Finally, the accelerating effect of the parallel simulator is tested based on a 500 kt·a−1 ethylbenzene process simulation. A 5-hour process simulation shows that the highest speed-up ratio to the original program is 261%, and the simulation finished in 70.98 s wall clock time.

Dynamic Behavior Analysis of Tethered Satellite System Based on Floquet Theory

In this paper, an n-star general dynamic model of tethered satellite system with closed-loop configuration is provided. An analytical method for periodic solution stability of the general dynamic model is proposed based on Floquet theory, which proved that the periodic solution stability of the system depends on the maximum modulus for the eigenvalue of a matrix related to the Jacobian matrix. The periodic solution stability of a 3-star system with equilateral triangle as the initial configuration is analyzed as an example based upon the analytical method. The critical stable spin angular velocity of the 3-star system is analyzed when the system spins clockwise, and its numerical simulation is carried out to verify the results. The results show that the analytical method of periodic solution stability can solve the critical stable spin angular velocity accurately of the tethered satellite system, and the 3-star system can guarantee stable spin when the spin angular velocity is about 2.1 times of its revolution angular velocity, otherwise the disturbed system will not be able to re-converge to the initial configuration in finite time.

Retrieval of process rate parameters in the general dynamic equation for aerosols using Bayesian state estimation: BAYROSOL1.0

The uncertainty in the radiative forcing caused by aerosols and its effect on climate change calls for research to improve knowledge of the aerosol particle formation and growth processes. While experimental research has provided a large amount of high-quality data on aerosols over the last 2 decades, the inference of the process rates is still inadequate, mainly due to limitations in the analysis of data. This paper focuses on developing computational methods to infer aerosol process rates from size distribution measurements. In the proposed approach, the temporal evolution of aerosol size distributions is modeled with the general dynamic equation (GDE) equipped with stochastic terms that account for the uncertainties of the process rates. The time-dependent particle size distribution and the rates of the underlying formation and growth processes are reconstructed based on time series of particle analyzer data using Bayesian state estimation – which not only provides (point) estimates for the process rates but also enables quantification of their uncertainties. The feasibility of the proposed computational framework is demonstrated by a set of numerical simulation studies.