Adaptive Runge-Kutta algorithms for dynamic simulation

Accelerating Real-Time Coupled Cluster Methods with Single-Precision Arithmetic and Adaptive Numerical Integration

We explore the framework of a real-time coupled cluster method with a focus on improving its computational efficiency. Propagation of the wave function via the time-dependent Schrödinger equation places high demands on computing resources, particularly for high level theories such as coupled cluster with polynomial scaling. Similar to earlier investigations of coupled cluster properties, we demonstrate that the use of single-precision arithmetic reduces both the storage and multiplicative costs of the real-time simulation by approximately a factor of 2 with no significant impact on the resulting UV/vis absorption spectrum computed via the Fourier transform of the time-dependent dipole moment. Additional speedups─of up to a factor of 14 in test simulations of water clusters─are obtained via a straightforward GPU-based implementation as compared to conventional CPU calculations. We also find that further performance optimization is accessible through sagacious selection of numerical integration algorithms, and the adaptive methods, such as the Cash-Karp integrator, provide an effective balance between computing costs and numerical stability. Finally, we demonstrate that a simple mixed-step integrator based on the conventional fourth-order Runge-Kutta approach is capable of stable propagations even for strong external fields, provided the time step is appropriately adapted to the duration of the laser pulse with only minimal computational overhead.

Advances in Energy Systems Engineering and Process Systems Engineering in China—A Review Starting from Sargent’s Pioneering Work

Process systems engineering (PSE), after being proposed by Sargent and contemporary researchers, has been fast developing in various domains and research communities around the world in the last couple of decades, with energy systems engineering featuring a typical yet still fast propagating domain, and the Chinese PSE community featuring a typical community with its own unique challenges for applying PSE theory and methods. In this paper, development of energy systems engineering and process systems engineering in China is discussed, and Sargent’s impacts on these two fields are the main focus. Pioneering work conducted by Sargent is firstly discussed. Then, a venation on how his work and thoughts have motivated later researchers and led to progressive advances is reviewed and analyzed. It shows that Sargent’s idea of optimum design and his work on nonlinear programming and superstructure modelling have resulted in well-known methods that are widely adopted in energy systems engineering and PSE applications in tackling problems in China. Following Sargent’s pioneering ideas and conceptual design of the PSE mansion, future development directions of energy systems engineering are also discussed.

The Role of Social Media in Promoting Information Disclosure on Environmental Incidents: An Evolutionary Game Theory Perspective

In recent years, social media has had a crucial role in promoting governments to act more responsibly. However, few studies have investigated whether social media use actually leads to increased disclosure during environmental incidents, or how social media influences regional governments’ information disclosure, even though delayed and insufficient disclosure on relevant incidents is often widespread in China. In this article, we model information disclosure during environmental incidents as an evolutionary game process between the central government and local governments, and examine the role of social media on game participants’ strategy selections in the information disclosure game. The results indicate that social media plays an active role in promoting the regional government to proactively disclose information during environmental incidents through two mechanisms: the top–down intervention mechanism, and the bottom–up reputation mechanism. More specifically, social media can provide efficient information channels for the central government to supervise local officials’ limited disclosure during environmental incidents, essentially sharing the central government’s supervision costs, and thus improving its supervision and intervention efficiency. Social media helps focus the public’s attention on the limited disclosure of local officials in environmental incidents, and actively mobilizes citizens to protest to maintain their interests, placing considerable pressure on the reputation of local governments.