Microscopic insights into poly- and mono-crystalline methane hydrate dissociation in Na-montmorillonite pores at static and dynamic fluid conditions

Knowledge on the kinetics of gas hydrate dissociation in clay pores at static and dynamic fluid conditions is a fundamental scientific issue for improving gas production efficiency from hydrate deposits using thermal stimulation and depressurization respectively. Here, molecular dynamics simulations were used to investigate poly- and mono...

Effects of nanobubbles on methane hydrate dissociation: A molecular simulation study

Hydrate dissociation is often accompanied by the formation of nanobubbles. Knowledge of the effects of nanobubbles on hydrate dissociation is essential for understanding the dynamic behavior of the hydrate phase change and improving the gas production efficiency. Here, molecular dynamics simulations were performed to study the methane hydrate...

Numerical study of response behaviors of natural gas hydrate reservoir around wellbore induced by water jet slotting

The trial production of natural gas hydrate reservoirs remains poor. Reasonable reservoir reconstruction, which can improve formation permeability, is an important approach to increasing the efficiency and enhancing production. In this work, water jet slotting is proposed to reconstruct an natural gas hydrate reservoir near a wellbore. The...

Dual Access Control for Cloud-Based Data Storage and Sharing

Cloud-based data storage service has drawn increasing interests from both academic and industry in the recent years due to its efficient and low cost management. Since it provides services in an open network, it is urgent for service providers to make use of secure data storage and sharing mechanism to ensure data confidentiality and service...

Negative Effects of Inorganic Salt Invasion on the Dissociation Kinetics of Silica-Confined Gas Hydrate via Thermal Stimulation

Methane hydrate dissociation kinetics can be inhibited in NaCl solutions; however, this effect is reversed by promoting bubble formation that enhances dissociation. The negative and positive effects of inorganic salt injection on gas production from hydrate-bearing sediments are still controversial. Here, molecular dynamics simulations were...

Deep Deterministic Policy Gradient for High-Speed Train Trajectory Optimization

This paper proposes a novel train trajectory optimization approach for high-speed railways. We restrict our attention to single train operation scenarios with different scheduled/rescheduled running times aiming at generating optimal train recommended trajectories in real time, which can ensure punctuality and energy efficiency of train...

Letter from the Special Issue Editors: Special Issue on Enhancing Motion Comfort on Passenger and Commercial Autonomous Vehicles for Securing Their Acceptance

VAL: Volume and Access Pattern Leakage-Abuse Attack with Leaked Documents

Searchable Encryption schemes provide secure search over encrypted databases while allowing admitted information leakages. Generally, the leakages can be categorized into access and volume pattern. In most existing SE schemes, these leakages are caused by practical designs but are considered an acceptable price to achieve high search...

Mechanical Response of Nanocrystalline Ice-Contained Methane Hydrates: Key Role of Water Ice

Water ice and gas hydrates can coexist in the permafrost and polar regions on Earth and in the universe. However, the role of ice in the mechanical response of ice-contained methane hydrates is still unclear. Here, we conduct direct million-atom molecular simulations of ice-contained polycrystalline methane hydrates and identify a crossover...

The dynamic behavior of gas hydrate dissociation by heating in tight sandy reservoirs: A molecular dynamics simulation study

Knowledge on the kinetics of gas hydrate dissociation in microporous sediments is very important for developing safe and efficient approaches to gas recovery from natural gas hydrate (NGH) deposits. Herein, molecular dynamics (MD) simulations are used to study the dissociation kinetics in microporous sediments. The hydrate phase occupies a...

Mechanical properties of bi- and poly-crystalline ice

A sound knowledge of fundamental mechanical properties of water ice is of crucial importance to address a wide range of applications in earth science, engineering, as well as ice sculpture and winter sports, such as ice skating, ice fishing, ice climbing, bobsleighs, and so on. Here, we report large-scale molecular dynamics (MD) simulations...

IEA Wind Task 37 System Modeling Framework and Ontology for Wind Turbines and Plants

This presentation will provide an overview of progress to date in the development of a system modeling framework and ontology for wind turbines and plants as part of the larger IEA Wind Task 37 on wind energy systems engineering. The goals of the effort are to create a set of guidelines for a common conceptual architecture for wind turbines and...

Modeling thermodynamic properties of propane or tetrahydrofuran mixed with carbon dioxide or methane in structure-II clathrate hydrates

A sound knowledge of thermodynamic properties of sII hydrates is of great importance to understand the stability of sII gas hydrates in petroleum pipelines and in natural settings. Here, we report direct molecular dynamics (MD) simulations of the thermal expansion coefficient, the compressibility, and the specific heat capacity of C<sub>3<...

Electronic structure and site occupancy of lanthanide-doped (Sr, ca)₃(Y, lu)₂Ge₃O₁₂ garnets: A spectroscopic and first-principles study

Photoluminescence excitation (PLE) and emission spectra (PL) of undoped (Sr, Ca)₃(Y, Lu)₂Ge₃O₁₂ as well as Eu³⁺- and Ce³⁺-doped samples have been investigated. The PL spectra show that Eu³⁺ enters into both dodecahedral (Ca, Sr) and octahedral (Y, Lu) sites. Ce<sup>3...

Mechanical instability of monocrystalline and polycrystalline methane hydrates

Despite observations of massive methane release and geohazards associated with gas hydrate instability in nature, as well as ductile flow accompanying hydrate dissociation in artificial polycrystalline methane hydrates in the laboratory, the destabilising mechanisms of gas hydrates under deformation and their grain-boundary structures have not...

Free-surface evolution and wave kinematics for nonlinear uni-directional focused wave groups

A fully nonlinear numerical model for focused wave groups

Accurate and efficient modeling of global circuit behavior in VLSI layouts