GUIDANCE ON AREA OF CREATED TEARS FOR AORTIC FENESTRATION TREATMENT BASED ON COMPUTATIONAL FLUID DYNAMICS

2021 ◽  
pp. 2150037
Author(s):  
XIAOXI HOU ◽  
CHUBIN OU ◽  
KAZUHIKO HANZAWA ◽  
XILEI DAI ◽  
YI QIAN
Keyword(s):  
Fluid Dynamics ◽  
Risk Factor ◽  
Acute Aortic Dissection ◽  
Fluid Dynamic ◽  
False Lumen ◽  
Area Ratio ◽  
Dynamic Approach ◽  
Ideal Case ◽  
Blood Flows ◽  
Selection Of

Aortic fenestration (AF) uses puncture and a dilation balloon to create a tear in the intimal flap, which can directly relieve ischemia syndrome and reduce hypertension in the false lumen. The selection of a dilation balloon as well as the area of the created tear applied in reality depend on clinical experience, so we aim to provide a quantitative guidance and reference for doctors to better plan the treatment of aortic fenestration. In this study, the area of the created tear was virtually enlarged to at least 10 different values for four cases including one ideal case, and a computational fluid dynamic approach was applied to simulate blood flows in the aorta. The area ratio (AR) between the created tear and entry tear was introduced to express the enlargement of the created tear. The quantitative hemodynamic results indicate that the AR should be controlled to be larger than 7.0, but not too big to obtain the best treatment for acute aortic dissection (AD) case. Additionally, we assessed that AR might also be a risk factor for the prediction of dissection propagation.

scholarly journals Diagnosis and Treatment of Pregnancy Concurrent with Asymptomatic Aortic Dissection

2021 ◽  
Vol 24 (3) ◽  
pp. E493-E495
Author(s):  
Shao Wenchong ◽  
Tian Ailing ◽  
Fan Lufeng ◽  
Wu Han ◽  
Nianfeng Sun
Keyword(s):  
Risk Factor ◽  
Case Report ◽  
Aortic Dissection ◽  
Independent Risk Factor ◽  
Aortic Wall ◽  
False Lumen ◽  
True Lumen ◽  
Related Literature ◽  
Blood Flows ◽  
Joint Decisions

Background: Aortic dissection (AD) refers to false lumen dissected from true lumen via the internal membrane when endovascular blood flows into the aortic wall through the cleavage, which is formed after endomembrane gape of the aortic wall. Aortic dissection is a disease of extreme danger. Pregnancy is an independent risk factor for aortic dissection. Pregnancy concurrent with aortic dissection rarely is seen, not to mention pregnancy concurrent with asymptomatic aortic dissection. Case report: We present the case of a 34-year-old female patient, who was 25+ weeks pregnant, concurrent with aortic dissection. She was accepted by our hospital and successfully treated. Retrospective analysis of clinical data was carried out in this paper by combining related literature. Conclusion: This disease should be correctly straightened out to prevent misdiagnosis and save the patient’s life. Multidisciplinary joint decisions should be made to save lives of the patient and her fetus.

The DQE of an electron image recording system

1978 ◽  
Vol 36 (1) ◽  
pp. 100-101
Author(s):  
K.-H. Herrmann ◽  
D. Krahl ◽  
H.-P Rust
Keyword(s):  
Primary Electron ◽  
Ideal Case ◽  
Image Recording ◽  
Main Requirement ◽  
High Detection ◽  
Electron Image ◽  
Video Amplifier ◽  
Detection Quantum Efficiency ◽  
Selection Of ◽  
The Ideal

The high detection quantum efficiency (DQE) is the main requirement for an imagerecording system used in electron microscopy of radiation-sensitive specimens. An electronic TV system of the type shown in Fig. 1 fulfills these conditions and can be used for either analog or digital image storage and processing [1], Several sources of noise may reduce the DQE, and therefore a careful selection of various elements is imperative.The noise of target and of video amplifier can be neglected when the converter stages produce sufficient target electrons per incident primary electron. The required gain depends on the type of the tube and also on the type of the signal processing chosen. For EBS tubes, for example, it exceeds 10. The ideal case, in which all impinging electrons create uniform charge peaks at the target, is not obtainable for several reasons, and these will be discussed as they relate to a system with a scintillator, fiber-optic and photo-cathode combination as the first stage.

Cannulating a Dissecting Aorta Using Ultrasound-Epiaortic and Transesophageal Guidance

2011 ◽  
Vol 14 (6) ◽  
pp. 373 ◽  
Author(s):  
Saina Attaran ◽  
Maria Safar ◽  
Hesham Zayed Saleh ◽  
Mark Field ◽  
Manoj Kuduvalli ◽  
...  
Keyword(s):  
Cardiopulmonary Bypass ◽  
Aortic Dissection ◽  
Acute Aortic Dissection ◽  
False Lumen ◽  
Type A ◽  
Ascending Aorta ◽  
Type A Aortic Dissection ◽  
Complete Rupture

<p>Management of acute Stanford type A aortic dissection remains a major surgical challenge. Directly cannulating the ascending aorta provides a rapid establishment of cardiopulmonary bypass but consists of risks such as complete rupture of the aorta, false lumen cannulation, subsequent malperfusion and propagation of the dissection.</p><p>We describe a technique of cannulating the ascending aorta in patients with acute aortic dissection that can be performed rapidly in hemodynamically unstable patients under ultrasound-epiaortic and transesophageal (TEE) guidance.</p>

Turbulent Transport in Pin Fin Arrays: Experimental Data and Predictions

2005 ◽  
Author(s):  
F. E. Ames ◽  
L. A. Dvorak
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Boundary Layers ◽  
Fluid Dynamic ◽  
Turbulent Transport ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Velocity Profiles ◽  
Pin Fin ◽  
Pin Fin Arrays

The objective of this research has been to experimentally investigate the fluid dynamics of pin fin arrays in order to clarify the physics of heat transfer enhancement and uncover problems in conventional turbulence models. The fluid dynamics of a staggered pin fin array have been studied using hot wire anemometry with both single and x-wire probes at array Reynolds numbers of 3000; 10,000; and 30,000. Velocity distributions off the endwall and pin surface have been acquired and analyzed to investigate turbulent transport in pin fin arrays. Well resolved 3-D calculations have been performed using a commercial code with conventional two-equation turbulence models. Predictive comparisons have been made with fluid dynamic data. In early rows where turbulence is low, the strength of shedding increases dramatically with increasing in Reynolds numbers. The laminar velocity profiles off the surface of pins show evidence of unsteady separation in early rows. In row three and beyond laminar boundary layers off pins are quite similar. Velocity profiles off endwalls are strongly affected by the proximity of pins and turbulent transport. At the low Reynolds numbers, the turbulent transport and acceleration keep boundary layers thin. Endwall boundary layers at higher Reynolds numbers exhibit very high levels of skin friction enhancement. Well resolved 3-D steady calculations were made with several two-equation turbulence models and compared with experimental fluid mechanic and heat transfer data. The quality of the predictive comparison was substantially affected by the turbulence model and near wall methodology.

scholarly journals Effects of Selection of Inlet Perturbations, Multiphase and Turbulence Equations on Slug Flow Characteristics Using Altair® AcuSolve™

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2152
Author(s):  
Mohammad Sobir Abdul Basith ◽  
Nabihah Sallih ◽  
William Pao King Soon ◽  
Shinji Thomas Shibano ◽  
Ramesh Singh ◽  
...  
Keyword(s):  
Level Set ◽  
Slug Flow ◽  
Fluid Dynamic ◽  
Flow Characteristics ◽  
Convective Transport ◽  
Experimental Result ◽  
Internal Boundary ◽  
Published Data ◽  
Level Set Function ◽  
Selection Of

Selection of inlet perturbations, multiphase equations, and the turbulence equation may affect the development of slug flow using computational fluid dynamic simulation tools. The inlet perturbation, such as sinusoidal and random perturbations, play an essential role in inducing slug formation. Multiphase equations such as volume of fluid and level set methods are used to track and capture the gas-liquid immiscible interface. Similarly, turbulence equations such as Spalart Allmaras (SA), Detached Eddy Simulations (DES), k-omega, and k-epsilon can be used to predict the evolution of turbulence within the flow. At present, no direct comparison is available in the literature on the selection of (i) types of inlet perturbations, (ii) the choice of multiphase equations, and (iii) the turbulence equation on the development of slug flow using the Altair computational package. This article aims to compare the effects of the selection of inlet perturbations, multiphase models and turbulence equations on slug flow characteristics using Altair® AcuSolve™. The findings by Altair® simulation were compared to published experimental data and simulation works using ANSYS and STAR-CCM+. The slug flow characteristics of interest include slug morphology, a body length-to-diameter ratio, velocity, frequency, and pressure gradient. It was found that the slug flow could be developed for all combinations of settings. Although level set approach in Altair® can track fluid motion successfully, it has a limitation in modelling the convective transport of the multiphase mixture well, unlike ANSYS and STAR-CCM+. Compared to the standard level set method, the coupling of back-and-forth error compensation and correction with the level set function helps to capture the internal boundary more accurately by reducing errors caused by numerical diffusion in the transport of the level set. It was revealed that the Spalart Allmaras turbulence equation could mimic published experimental result better than DES as it produced the closest slug translational velocity. Since the frequency of the slugs for the developed models showed a good agreement with the published data, the models could be sufficient for the investigation of fluid-structure interaction.

scholarly journals Voltages Induced in Overhead Ground-Wire Cable as Risk Factor. Part 1

2016 ◽  
Vol 5 (1) ◽  
pp. 28-40 ◽  
Author(s):  
Токарский ◽  
A. Tokarskiy ◽  
Рубцова ◽  
Nina Rubtsova ◽  
Рябченко ◽  
...  
Keyword(s):  
Risk Factor ◽  
Single Phase ◽  
Interval Length ◽  
Maximum Permissible Level ◽  
Overhead Transmission Line ◽  
Spark Gap ◽  
Three Phase ◽  
Electric And Magnetic Fields ◽  
Short Circuits ◽  
Selection Of

To ensure the staff safety under hot-line overhead transmission line (OTL) maintenance, as well as overhead ground-wire cable (OGWC) insulation integrity maintaining, by the example of three-phase 750 kV OTL has been presented an algorithm for calculation of voltages and electromotive forces (EMF) induced in this line’s OGWC by electric and magnetic fields (EF and MF) generated by OTL phases’ voltages and currents. Algorithms for calculation of line-to-earth voltages distribution along grounded at one end OGWC’ intervals have been given. It has been shown that the voltage induced at OGWC by EF of 750 kV OTL is much less than the voltage induced by this OTL’s MF. For single-phase short circuits modes has been presented an algorithm for selection of grounded at one end OGWC’ interval length by condition of respecting of voltage’s maximum permissible level on a spark gap shunting OGWC’s insulator set.

scholarly journals Patterns and Determinants of Vietnamese Seafood Exports

2020 ◽  
Vol 55 (2) ◽  
Author(s):  
Huy Quang Nguyen ◽  
Huong Thi Lan Tran ◽  
Hoan Quang Truong ◽  
Chung Van Dong
Keyword(s):  
North America ◽  
Aquatic Invertebrates ◽  
The United States ◽  
World Market ◽  
Global Market ◽  
The European Union ◽  
Aggregate Level ◽  
Dynamic Approach ◽  
Pseudo Maximum Likelihood ◽  
Selection Of

By employing the gravity model using the Poisson pseudo-maximum-likelihood estimator, the air of this study was to investigate the determinants of Vietnam’s world seafood exports from 2000-2018 at both the aggregate and sub-sectoral level. In recent decades, Vietnam has rapidly increased its seafood exports to the global market, with a concentration on its exports to the United States, Japan, China, and South Korea. Its seafood export subsectors have been diversified among fish products (fresh, chilled, or frozen), crustaceans, mollusks, aquatic invertebrate products, aquatic fish, and invertebrates (prepared or persevered) products. The estimations show that Vietnam’s seafood exports (at both aggregate and subsector level) are determined by the size of the importing partners’ economies and income levels. At the aggregate level, Association of Southeast Asian Nations, the European Union, and North America were found to promote Vietnam’s seafood exports. At the subsector level, we found that North America had a positive link with Vietnam’s export of fish (fresh, chilled, or frozen), while there was a negative nexus between many regions with respect to the export of crustaceans, mollusks and aquatic invertebrates, as well as aquatic fish and invertebrates (prepared or persevered). To promote Vietnam’s seafood exports to the world market at the aggregate level, the country should enhance its establishment of preferential trade agreements with certain target markets, while at the subsector level, Vietnam should have a dynamic approach regarding the selection of its export destinations.

Effect of Cavities in Suddenly Expanded Flow at Supersonic Mach Number

CFD letters ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 57-71
Author(s):  
Atifatul Ismah Ismail
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Mach Number ◽  
Pressure Ratio ◽  
Area Ratio ◽  
Base Pressure ◽  
Sudden Expansion ◽  
Expansion Level ◽  
Computational Fluid Dynamics Cfd ◽  
Base Drag

The contribution from the base drag due to the sub-atmospheric pressure is significant. It can be more than two-thirds of the net drag. There is a need to increase the base pressure and hence decrease the base drag. This research examines the effect of Mach Number on base pressure. To accomplish this objective, it controls the efficacy in an enlarged duct computed by the numerical approach using Computational Fluid Dynamics (CFD) Analysis. This experiment was carried out by considering the expansion level and the aspect cavity ratio. The computational fluid dynamics method is used to model supersonic motion with the sudden expansion, and a convergent-divergent nozzle is used. The Mach number is 1.74 for the present study, and the area ratio is 2.56. The L/D ratio varied from 2, 4, 6, 8, and 10, and the simulated nozzle pressure ratio ranged from 3 to 11. The two-dimensional planar design used commercial software from ANSYS. The airflow from a Mach 1.74 convergent-divergent axi-symmetric nozzle expanded suddenly into circular ducts of diameters 17 and 24.5 mm with and without annular rectangular cavities. The diameter of the duct is taken D=17mm and D=24.5mm. The C-D nozzle was developed and modeled in the present study: K-ε standard wall function turbulence model was used with the commercial computational fluid dynamics (CFD) and validated. The result indicates that the base pressure is impacted by the expansion level, the enlarged duct size, and the passage’s area ratio.

scholarly journals Enhancing Radiation Detection by Drones through Numerical Fluid Dynamics Simulations

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1770 ◽  
Author(s):  
Fabio Marturano ◽  
Jean-François Ciparisse ◽  
Andrea Chierici ◽  
Francesco d’Errico ◽  
Daniele Di Giovanni ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Nuclear Power ◽  
Situational Awareness ◽  
Fluid Dynamic ◽  
Low Cost ◽  
Radiation Detection ◽  
First Responders ◽  
Decision Makers ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

This study addresses the optimization of the location of a radioactive-particle sensor on a drone. Based on the analysis of the physical process and of the boundary conditions introduced in the model, computational fluid dynamics simulations were performed to analyze how the turbulence caused by drone propellers may influence the response of the sensors. Our initial focus was the detection of a small amount of radioactivity, such as that associated with a release of medical waste. Drones equipped with selective low-cost sensors could be quickly sent to dangerous areas that first responders might not have access to and be able to assess the level of danger in a few seconds, providing details about the source terms to Radiological-Nuclear (RN) advisors and decision-makers. Our ultimate application is the simulation of complex scenarios where fluid-dynamic instabilities are combined with elevated levels of radioactivity, as was the case during the Chernobyl and Fukushima nuclear power plant accidents. In similar circumstances, accurate mapping of the radioactive plume would provide invaluable input-data for the mathematical models that can predict the dispersion of radioactivity in time and space. This information could be used as input for predictive models and decision support systems (DSS) to get a full situational awareness. In particular, these models may be used either to guide the safe intervention of first responders or the later need to evacuate affected regions.

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