Analyzing characteristics of collateral flow to parasylvian cortical arteries by three-dimensional digital subtraction angiography–magnetic resonance angiography fusion imaging in adult moyamoya disease

ObjectiveThe hemodynamic sources of recipient parasylvian cortical arteries (PSCAs) were significantly related to postoperative cerebral hyperperfusion (CHP) after bypass surgery in patients with moyamoya disease (MMD). The present study aimed to introduce a new method to investigate the characteristics of PSCAs hemodynamic sources and their relationships with clinical presentations in adult MMD and to provide preoperative evaluation for recipient vessel selection in MMD bypass surgery.MethodsThe hemodynamic sources of the PSCAs in 171 symptomatic MMD hemispheres were analyzed by three-dimensional digital subtraction angiography (3D-DSA) combined with magnetic resonance angiography (MRA) fusion imaging. The spatial and temporal characteristics of the hemodynamic sources of the PSCAs and their associations with the patient's demographics, Suzuki stage, and initial onset type were investigated.ResultsSix major types of hemodynamic sources in the PSCAs were observed. There was a significant difference between the hemodynamic sources of the PSCAs above and below the SF (P < 0.001). With advancing Suzuki stages, collateral flow to the PSCAs above the SF from the internal carotid arteries (ICAs) significantly decreased, while the non-ICAs increased (P < 0.001). Multivariate analysis revealed that hemodynamic sources of the PSCAs above the SF were significantly associated with patients' initial onset type (P = 0.026).ConclusionIn MMD hemispheres, the hemodynamic sources of the PSCAs above the SF are more varied than those below the SF and present a typical conversion trend from ICAs to non-ICAs with advancing Suzuki stages. Analyzing the hemodynamic sources of the PSCAs can help in understanding the conversion pattern of compensatory vascular systems, predicting episodes in MMD, and preoperatively evaluating suitable recipient vessel selection for bypass surgery to avoid postoperative CHP

Optimal design and performance analysis of a hybrid system combining a semi-submersible wind platform and point absorbers

Integrating point absorber wave energy converters (PAWECs) and an offshore floating wind platform provide a cost-effective way of joint wind and wave energy exploitation. However, the coupled dynamics of the complicated hybrid system and its influence on power performance are not well understood. Here, a frequency-domain-coupled hydrodynamics, considering the constraints and the power output through the relative motion between the PAWECs and the semi-submersible platform, is introduced to optimize the size, power take-off damping, and layout of the PAWECs. Results show that the annual wave power generation of a PAWEC can be improved by 30% using a 90° conical or a hemispherical bottom instead of a flat bottom. Additionally, while letting the PAWECs protrude out the sides of the triangular frame of the platform by a distance of 1.5 times the PAWEC radius, the total power generation can be improved by up to 18.2% without increasing the motion response of the platform. The PAWECs can reduce the resonant heave motion of the platform due to the power take-off damping force. This study provides a reference for the synergistic use of wave and wind energ

Optimal design and performance analysis of a hybrid system combing a floating wind platform and wave energy converters

Combined floating offshore wind platform and Wave Energy Converters (WECs) systems have the potential to provide a cost-effective solution to offshore power supply and platform protection. The objective of this paper is to optimize the size and layout of WECs within the hybrid system under a given sea state with a numerical study. The numerical model was developed based on potential flow theory with viscous correction in frequency domain to investigate the hydrodynamic performance of a hybrid system consisting of a floating platform and multiple heaving WECs. A non-dimensional method was presented to determine a series of variables, including radius, draft, and layout of the cylindrical WEC at a typical wave frequency as the initial design. WECs with larger diameter to draft ratio were found to experience relatively smaller viscous effects, and achieve more wave power, larger effective frequency range and similar wave power per unit weight compared with those with the smaller diameter to draft ratio in the same sea state. The addition of WECs reduced the maximum horizontal force and pitch moment on the platform, whereas the maximum vertical force increased due to the increasing power take-off force, especially at low frequencies. The results presented in this paper provide guidance for the optimized design of WECs and indicate the potential for synergies between wave and wind energy utilization on floating platforms

Designing a flow-controlled STA-MCA anastomosis based on the Hagen–Poiseuille law for preventing postoperative hyperperfusion in adult moyamoya disease

Background: Technical improvements for preventing postoperative symptomatic cerebral hyperperfusion (CHP) during superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis for moyamoya disease (MMD) were seldom reported. Objectives: The aim of this study was to investigate the significance of application of a novel flow-controlled concept which voluntarily reduces the hemodynamic difference between the donor and recipient arteries based on the Hagen–Poiseuille law when performing direct anastomoses of recipient parasylvian cortical arteries (PSCAs) with anterograde hemodynamic sources from the MCA (M-PSCAs) in adult MMD. Design: This was a retrospective observational study. Methods: Direct anastomoses of recipient M-PSCAs were performed on 89 symptomatic hemispheres in 82 adult MMD patients in our hospital from January 2020 to June 2021. They were divided into the flow-controlled group (patients who received direct anastomosis under designed flow-controlled principles) and non-flow-controlled group (patients who received conventional direct anastomosis to obtain maximum flow). The patients’ basic characteristics and incidence of postoperative CHP were compared between the two groups. Risk factors for occurrence of postoperative CHP were analyzed. Results: Overall, 36 hemispheres were included in the non-flow-controlled group and 53 in flow-controlled group. The incidences of postoperative focal (22.6%) and symptomatic CHP (5.7%) in the flow-controlled group were significantly lower than those (focal, 52.8%; symptomatic, 25.0%) in the non-flow-controlled group ( p  = 0.003 and 0.009, respectively). Multivariate analysis revealed that the flow-controlled concept was significantly associated with the development of focal ( p  = 0.005) and symptomatic ( p  = 0.012) CHP. Conclusion: The flow-controlled STA-MCA anastomosis can significantly decrease the incidence of postoperative CHP during direct anastomoses of recipient M-PSCAs in adult MMD

Creep Strain and Permeability Evolution in Cracked Granite Subjected to Triaxial Stress and Reactive Flow

Fluid flow and fluid-rock interaction mainly take place in fracture network, consequently resulting in deformation and permeability variation of rock and deterioration of the wellbore performance. Mechanical-reactive flow coupling creep tests are performed on cracked granite under various confining pressures and acid and alkaline solution flows. The testing results show that the confining pressure and solution pH significantly influence the creep deformation, creep strain rate, and permeability. A primary creep stage and secondary creep stage are observed in all creep tests in this study; notably, the sample under a confining pressure of 10 MPa and acid solution injection undergoes creep failure for over 2700 hours. The acid solution has a more obvious influence on the creep behavior than that of the alkaline solution. With an increase in confining pressure, the total creep strain and creep strain rate in the samples gradually decrease during the injection of either solution. The permeability of the samples injected with either solution gradually deceases during the testing process, and this deceasing rate increases with the confining pressure. The scanning electron microscopy observations on the crack surfaces after the creep tests show that the surfaces of the fractures injected with the acid solution are smooth due to the dissolution of the matrix, while those injected with the alkaline solution include voids due to the dissolution of quartz. These experimental results could improve the understanding of the long-term transport and mechanical behaviors of wellbore

Comparative Study on Beneficiation Test of a Low Grade Manganese Carbonate Ore

According to characteristics of a low-grade manganese carbonate ore, it made a respective use of high gradient magnetic separation and shaker gravity separation, as well as experimental study on flotation process of the ore．Experimental results showed that wet high-intensity magnetic separation was the reasonable way to deal with the mine. The magnetic concentrate with Mn grade of 21.04% and Mn recovery of 75.55% could be obtained by adopting high intensity process of one-stage roughing, one-stage scavenging, two-stage cleaning, and regrinding magnetic separation of cleaning tailings. The experimental study provides a basis for the development of similar manganese ores

Combining Finite Element and Analytical methods to Contact Problems of 3D Structure on Soft Foundation

The computational efficiency and nonconvergence of the iteration are two main difficulties in contact problems, especially in the creep of the foundation. This paper proposes a method to analyze the structural soft foundation system affected by time. The methodology is an explicit method, combining the finite element method with the analytical method. The creep deformation of soft foundation is obtained based on Laplace transforms. The structural deformation contains the statically determinate structural deformation and rigid body displacement, solved by the finite method. The contact forces are calculated by the deformation coordination equations and equilibrium equations. The methodology is validated through augmented Lagrangian (AL) method. The results can clearly illustrate the local disengagement phenome, greatly overcome the nonconvergence of the iteration, and significantly improve computing efficiency