The recently synthesized monolayer diamond-diamane has proved to possess excellent mechanical and electrical properties, and it holds great potential in the field of nano-mass sensors. Herein, a molecular dynamics (MD) simulation is employed to systematically investigate the vibration response of the diamane nanoribbon (DNR) for the mass inspection. The results show that under different attached masses, the natural frequency of DNR is about three times of that of the bilayer graphene nanoribbon (BGNR) with the same size. The edge flatness of the DNR can be maintained during the vibration process, while the edge of the BGNR will warp in the initial state. Increasing the pre-strain can significantly increase the natural frequency of the DNR, leading to a higher response sensitivity of the DNR. In addition, the DNR has a higher mass resolution than the BGNR, and can detect smaller attached mass. The position of the attached mass in the resonator has a significant effect on the detection response. When the attached mass is near the center of the resonator, the frequency shift reaches the maximum value, and then it rapidly decreases to zero when the attached mass is close to the edge of DNR. Finally, the attached mass has no obvious effect on the quality factor of the DNR, and its value is stable between 10 5 and 10 6 orders of magnitude. The theoretical results demonstrate the accuracy of the MD results. The MD simulations reveal that the DNR has important implications as a resonant material for nano-mass sensor in the future.
Polymer flooding has been proved to be an effective method for improving oil recovery in offshore field of Bohai area, but thief zones with high permeability could make the effect of polymer on oil production worse. To try to minimize the negative impact brought by thief zones, we apply asphalt particle to plug the high permeability regions to compel subsequent displacement fluid change flowing direction to enhance sweep efficiency.Its adaptability is studied by a series of parallel cores flooding. Besides, numerical simulations are carried out to optimize pattern of asphalt particle injection and evaluate the performances of asphalt flooding in a typical well group in Bohai area in a numerical model.In addition to performances of water cut and oil recovery for the parallel core flooding, we present dynamic features of remaining oil from micro views detected by nuclear magnetic resonance. By plugging thief zone by asphalt flooding, oil production is improved. Production in small and medium pores is increased by asphalt flowing into big pores to exert strong resistance on them. Also, with numerical simulations, optimal way of injecting asphalt has been selected to lead the operation in field. Through observation of a typical well group under asphalt injection in numerical model based on real reservoir, the water-cut and oil production are decrease 9.7% and increase 29.1m3/d respectively. We conclude that asphalt particle has good capacity to plug thief zones to improve sweep efficiency of subsequent displacement fluid in polymer flooding field.In-depth understanding such mechanisms for asphalt particle behavior may be pivotal for enhancing oil recovery in polymer flooding reservoir containing thief zones.
The parametric excited vibration of a pipe under thermal loading may occur because the fluid is often transported heatedly. The effects of thermal loading on the pipe stability and local bifurcations have rarely been studied. The stability and the local bifurcations of the lateral parametric resonance of the pipe induced by the pulsating fluid velocity and the thermal loading are studied. A mathematical model for a simply supported pipe is developed according to the Hamilton principle. Two partial differential equations describing the lateral and longitudinal vibration are obtained. The singularity theory is utilized to analyze the stability and the bifurcation of the system solutions. The transition sets and the bifurcation diagrams are obtained both in the unfolding parameter space and the physical parameter space, which can reveal the relationship between the thermal field parameter and the dynamic behaviors of the pipe. The frequency response and the relationship between the critical thermal rate and the pulsating fluid velocity are obtained. The numerical results demonstrate the accuracy of the single-mode expansion of the solution and the stability and local bifurcation analyses. It also confirms the existence of the chaos. The presented work can provide valuable information for the design of the pipeline and the controllers to prevent the structural instability.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.