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Modeling Blood Flow in Veins of Uniform Properties (Giraffe Jugular Vein)

Open Journal of Biophysics 2024年第2期14卷 132-153页

作者： Rogers Omboga Amenya Johanna Kibet Sigey Geoffrey Moriaso Ole Maloiy David Mwangi Theuri Department of Mathematics and Physical Sciences Dedan Kimathi University of Technology Nyeri Kenya Department of Pure and Applied Mathematics School of Mathematical Sciences Jomo Kenyatta Unversity of Agriculture and Technology Kisii Kenya Institute of Animal Physiology and Biotechnology Research University of Nairobi Nairobi Kenya

This paper models the giraffe’s jugular veins as a uniform collapsible tube from a rigid skull. The equations governing one-dimensional steady flow through such a tube for various conditions have been developed. The effects of inertial and inclination angles that have not been discussed previously have been included. It has been shown that different flows for a uniform tube (vein) are possible. However, this flow matches that of a jugular vein which is supercritical, and the steady solution has been given by the balance between the driving forces of gravity and the viscous resistance to the flow at the right atrium of the heart must be sub-critical for a fixed right-atrium pressure which means that an elastic jump is required to return the flow to sub-critical from the supercritical flow upstream this type of relationship gives rise to flow limitation at the same time given any right atrium fixed pressure there exists a maximum flow rate which when exceeded the boundary conditions of the flow do not hold boundary conditions at the right atrium are not satisfied hence making the steady flow impossible this mechanism of flow limitation is slightly different from the other one in that causes airways through forced expiration from the observation made it is clearly shown that there is an intravascular pressure difference with a change in height.

关键词： Blood Flow Jugular Vein Cross-Sectional Area Supercritical subcritical Jump

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Comparative evaluation for catalytic gasification of petroleum coke and asphaltene in subcritical and supercritical water

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Journal of Energy Chemistry 2019年第4期28卷 107-118页

作者： Rachita Rana Sonil Nanda Aimee Maclennan Yongfeng Hu Janusz A.Kozinski Ajay K.Dalai Department of Chemical and Biological Engineering University of Saskatchewan Department of Chemical and Biochemical Engineering University of Western Ontario Soft X-Ray Micro-Characterization Beamline Canadian Light Source Inc. New Model in Technology & Engineering

subcritical and supercritical water gasification of petroleum coke and asphaltene was performed at variable temperatures(350–650°C),feed concentrations(15–30 wt%)and reaction times(15–60 min).Nickel-impregnated activated carbon(Ni/AC)was synthesized as a catalyst for enhancing syngas yields at optimal gasification conditions(650°C,15 wt%and 60 min).Structural chemistry of precursors and chars developed at different gasification temperatures was studied using physicochemical and synchrotronbased approaches such as carbon–hydrogen–nitrogen–sulfur(CHNS)analysis,thermogravimetric and differential thermogravimetric analysis(TGA/DTA),scanning electron microscopy(SEM),Fourier-Transform Infrared spectroscopy(FTIR),Raman spectroscopy,X-ray diffraction(XRD)and X-ray absorption spectroscopy(XAS).Asphaltene testified to be a better precursor for catalytic hydrothermal gasification leading to 11.97 mmol/g of total gas yield compared to petroleum coke(8.04 mmol/g).In particular,supercritical water gasification using 5 wt%Ni/AC at 650°C with 15 wt%feed concentration for 60 min resulted in 4.17 and 2.98 mmol/g of H_2from asphaltene and petroleum coke,respectively.Under the same conditions,the respective CH_4yields from catalytic gasification of asphaltene and petroleum coke were 2.54and 1.07 mmol/g.Nonetheless,asphaltene also seemed to an attractive feedstock for the production of highly aromatic chars through hydrothermal gasification.

关键词： Asphaltene Petroleum coke subcritical water Supercritical water Gasification Char

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PREDICTION OF BLOCK CAVING RATE USING subcritical CRACK GROWING VELOCITY

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中国有色金属学会会刊：英文版 1995年第4期5卷 14-17页

作者： Chao Ping Pan Changliang Sun Zongqi Luo Li(Department of Resources Exploitation Engineering ,Central South University of Technology,Changsha 410083) Central South Univ of Technology Changsha China

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ＰＲＥＤＩＣＴＩＯＮＯＦＢＬＯＣＫＣＡＶＩＮＧＲＡＴＥＵＳＩＮＧＳＵＢＣＲＩＴＩＣＡＬＣＲＡＣＫＧＲＯＷＩＮＧＶＥＬＯＣＩＴＹＣｈａｏＰｉｎｇ；ＰａｎＣｈａｎｇｌｉａｎｇ；ＳｕｎＺｏｎｇｑｉ；ＬｕｏＬｉ（ＤｅｐａｒｔｍｅｎｔｏｆＲｅｓｏｕｒｃｅｓＥｘ...

关键词： subcritical crack growth double torsion testing block caving rate block caving

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Measurement of k_(eff) by delayed neutron multiplication in subcritical systems

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Nuclear Science and Techniques 2018年第2期29卷 118-124页

作者： Bin Ye Chao-Wen Yang Chun Zheng College of Physical Science and Technology Sichuan University Institute of Nuclear Physics and Chemistry China Academy of Engineering Physics

In this paper, we build on the concept of equivalent fundamental-mode source to propose using delayed neutrons as a neutron source in multiplication experiments to acquire the effective multiplication factor keffof subcritical systems, which is difficult to acquire directly from conventional neutron source multiplication method. We analyzed the difference between a fundamental-mode fission source and delayed neutron source,then adopted a factor to convert delayed neutron distribution to an equivalent fundamental-mode source distribution, and employed Monte Carlo code to acquire this factor.The delayed neutron multiplication measurement method was established for the first time, and corresponding experiments were conducted in subcritical systems. The multiplication of delayed neutrons was measured based on Chinese Fast Burst Reactor-Ⅱ(CFBR-Ⅱ) at subcritical states, and keffwas acquired from delayed neutron multiplication successfully(0.9921 and 0.9969, respectively).The relative difference between k_(eff)obtained by the new method and previous values acquired by the positive period method is less than 1% for these two studied cases.

关键词： keff Delayed neutrons Neutron source multiplication subcritical system

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Supercritical as well as subcritical Hopf bifurcation in nonlinear flutter systems

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Applied Mathematics and Mechanics(English Edition) 2008年第2期29卷 199-206页

作者：陈衍茂刘济科 Department of Mechanics Sun Yat-sen University

The Hopf bifurcations of an airfoil flutter system with a cubic nonlinearity are investigated, with the flow speed as the bifurcation parameter. The center manifold theory and complex normal form method are Used to obtain the bifurcation equation. Interestingly, for a certain linear pitching stiffness the Hopf bifurcation is both supercritical and subcritical. It is found, mathematically, this is caused by the fact that one coefficient in the bifurcation equation does not contain the first power of the bifurcation parameter. The solutions of the bifurcation equation are validated by the equivalent linearization method and incremental harmonic balance method.

关键词： nonlinear flutter Hopf bifurcation supercritical subcritical limit cycle oscillation

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Simulation of molecular dynamics of silver subcritical nuclei and crystal clusters during solidification

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Science China(Technological Sciences) 2010年第12期53卷 3203-3208页

作者： JIAN ZengYun1, CHEN Ji1, CHANG FangE1, ZENG Zhao1, HE Tan1 & JIE WanQi2 1 School of Materials Science and Engineering, Xi’an Technological University, Xi’an 710032, China 2 State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China School of Materials Science and Engineering Xi’an Technological University Xi’an China State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi’an China

Molecular dynamics simulation is carried out to investigate the effects of cooling rate on the final configurations of silver after rapid solidification. The cooling rate for the formation of a silver amorphous phase is determined by analyzing its pair distribution function, H-A bond index, and the largest crystal cluster. Further, the equilibrium structures of the subcritical nuclei and crystal clusters are studied. The results show that the solidified microstructure is composed of a mixture of crystal clusters and amorphous phases at a certain cooling rate range. The size of the largest crystal cluster decreases with the increasing cooling rate, and it completely disappears when the cooling rate exceeds a critical value. The structures of the subcritical nuclei and the largest crystal cluster are composed of lamellar structures of fcc and hcp atoms, indicating that the lamellar structure of fcc and hcp atoms in the silver crystal originates from nucleation, and not from the growth of crystals.

关键词： molecular dynamics simulation amorphous phase subcritical nuclei crystal cluster cooling rate

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Detection of subcritical crack propagation for concrete dams

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Science China(Technological Sciences) 2009年第12期52卷 3654-3660页

作者： BAO TengFei1 ,2&YU Hong 1,2 1College of Water Conservancy&Hydropower Engineering,Hohai University,Nanjing 210098,China 2National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety,Nanjing 210098,China College of Water Conservancy & Hydropower Engineering Hohai University Nanjing China National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety Nanjing China

subcritical propagation of cracks is a warning sign of fracture.If such propagation is detected at an early stage,timely maintenance measures can be taken to prevent the failure of structures.To detect the subcritical propagation of a crack,the crack needs to be monitored continuously in a long term, which is not realistic under certain conditions.However,cracks in concrete dams can be monitored continuously by dam monitoring to offer possible detection for subcritical propagation.In this paper, with measured crack openings from dam monitoring,a state equation for characterizing crack development is established based on the grey system theory.The relation between the stability of the equation and the subcritical crack propagation is investigated,then a criterion is proposed for detecting subcritical propagation.An example demonstrates the validity of the criterion and its potential for practical application.

关键词： crack subcritical propagation criterion concrete

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Application of FLUKA and OpenMC in coupled physics calculation of target and subcritical reactor for ADS

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Nuclear Science and Techniques 2019年第1期30卷 113-120页

作者： Ze-Long Zhao Yong-Wei Yang Shuang Hong Institute of Modern Physics Chinese Academy of Sciences School of Nuclear Science and Technology University of Chinese Academy of Sciences University of Science and Technology Hefei

The study of accelerator-driven subcritical reactor systems(ADSs) has been an important research topic in the field of nuclear energy for years. The main code applied in ADS research is MCNPX, which was developed by Los Alamos National Laboratory. We studied the application of the open-source Monte Carlo codes FLUKA and OpenMC to a coupled ADS calculation. The FLUKA code was used to simulate the reaction of highenergy protons with the nucleus of the target material in the ADS, which produces spallation neutrons. Information on the spallation neutrons, such as their energy, position,direction, and weight, can be recorded by a user-defined routine called FLUSCW provided by FLUKA. Then, the information was stored in an external neutron source file in HDF5 format by using a conversion code, as required by the OpenMC calculation. Finally, the fixed-source calculation function of OpenMC was applied to simulate the transport of spallation neutrons and obtain the distribution of the neutron flux in the core region. In the coupled calculation, the high-energy cross-section library JENDL4.0/HE in ACE format produced by NJOY2016 was applied in the OpenMC transport simulation. The OECD–ADS benchmark problem was calculated, and the results were compared with those obtained using MCNPX. It was found that the flux calculations performed by FLUKA–OpenMC and MCNPX were in agreement, so the coupling calculation method for ADS is reasonable and feasible.

关键词： Accelerator-driven subcritical system MCNPX FLUKA OpenMC JENDL4.0/HE N JOY2016

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Effects of Supercritical Environment on Hydrocarbon-fuel Injection

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Journal of Thermal Science 2017年第2期26卷 183-191页

作者： Bongchul Shin Dohun Kim Min Son Jaye Koo Graduate School Korea Aerospace UniversityGoyangRepublic of Korea School of Aerospace and Mechanical Engineering Korea Aerospace UniversityGoyangRepublic of Korea

In this study, the effects of environment conditions on decane were investigated. Decane was injected in subcritical and supercritical ambient conditions. The visualization chamber was pressurized to 1.68 MPa by using nitrogen gas at a temperature of 653 K for subcritical ambient conditions. For supercritical ambient conditions, the visualization chamber was pressurized to 2.52 MPa by using helium at a temperature of 653 K. The decane injection in the pressurized chamber was visualized via a shadowgraph technique and gradient images were obtained by a post processing method. A large variation in density gradient was observed at jet interface in the case of subcritical injection in subcritical ambient conditions. Conversely, for supercritical injection in supercritical ambient conditions, a small density gradient was observed at the jet interface. In a manner similar to that observed in other cases, supercritical injection in subcritical ambient conditions differed from supercritical ambient conditions such as sphere shape liquid. Additionally, there were changes in the interface, and the supercritical injection core width was thicker than that in the subcritical injection. Furthermore, in cases with the same injection conditions, the change in the supercritical ambient normalized core width was smaller than the change in the subcritical ambient normalized core width owing to high specific heat at the supercritical injection and small phase change at the interface. Therefore, the interface was affected by the changing ambient condition. Given that the effect of changing the thermodynamic properties of propellants could be essential for a variable thrust rocket engine, the effects of the ambient conditions were investigated experimentally.

关键词： Decane 喷气 subcritical Supercritical 可视化

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Simulation of an Accelerator Driven subcritical Core with Mixed Uranium-Thorium Fuel

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World Journal of Engineering and Technology 2015年第3期3卷 328-333页

作者： Ali Pazirandeh Laia Shirmohammadi Department of Nuclear Engineering Science and Research Branch Islamic Azad University Tehran Iran

During recent years, a new generation of nuclear reactors, known as “Accelerator Driven subcritical Reactors”, has been developed. One of the new application aspects for such reactors (besides transmutation of High Level Waste and burning Minor Actinides) is usage of thorium as nuclear fuel. In this work a subcritical core in experimental scale is simulated by MCNPX code. The core contains two types of fuel assemblies: (85% ThO2 + 15% UO2) and MOX (U-Pu). In the first step, only the thorium-contained fuel assemblies are loaded into the core. Criticality calculations using MCNPX show that the keff is so low that the fuel assemblies cannot run the subcritical core. This implies that MOX (U-Pu) assemblies must be loaded as well. Neutronic parameters of the thorium- fueled Accelerator Driven subcritical core are then calculated as well as some other parameters related to accelerator coupled with the core. The main objective of this simulation is to study the behavior of Accelerator Driven subcritical core with thorium assemblies.

关键词： Accelerator Driven subcritical Reactor Thorium MCNPX Neutronic Calculation

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