Sinkhole Stability in Elliptical Cavity under Collapse and Blowout Conditions

Road subsidence and sinkhole failures due to shallow cavities formed by defective water main have increased in recent decades and become one of the important research topics in geotechnical engineering. The present paper numerically studies the stability and its associated failure mechanism of ellipse-shaped cavity above defective water mains using the finite element limit analysis technique. For a wide range of geometrical parameters, the pressure ratio method is used to formulate the stability solutions in both blowout and collapse scenarios. Even though there is no published solution for elliptical cavities under blowout failure conditions, the obtained numerical results are compared with available circular solutions. Several conclusions are drawn based on the failure mechanism study of the various ellipse shape transformations in this study, whilst design charts and equations proposed for practical uses.

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МЕТОД РАСЧЕТА ТЕРМОГАЗОДИНАМИЧЕСКИХ ПАРАМЕТРОВ ТУРБОВАЛЬНОГО ГТД НА ОСНОВЕ ПОВЕНЦОВОГО ОПИСАНИЯ ЛОПАТОЧНЫХ МАШИН. ЧАСТЬ 1. ОСНОВНЫЕ УРАВНЕНИЯ

Aerospace technic and technology ◽

10.32620/aktt.2018.1.05 ◽

2018 ◽

pp. 48-58

Author(s):

Людмила Георгиевна Бойко ◽

Олег Владимирович Кислов ◽

Наталия Владимировна Пижанкова

Keyword(s):

Gas Turbine ◽

Flow Rate ◽

Pressure Ratio ◽

Turbine Engines ◽

Geometrical Parameters ◽

Gas Turbine Engines ◽

Balance Equations ◽

Wide Range ◽

In Series ◽

Multistage Compressor

Gas turbine engines processes mathematic simulations are widely used in different steps of its living cycle. All engine simulations may be divided into different difficulty levels: higher simulation level allows doing a more precise description of physical processes in main units of gas turbine engines and their elements. It gives the opportunity for getting better arrangement of calculation results and experimental data, reduce the quality of factors, which are traditionally used in determine engine operational characteristics with 1-level models.The purpose of the article is to describe the thermogasdynamic parameters and maintenance perfomances calculation method, which based on second level mathematic simulation. Its main feature is blade-to-blade turbomachines description (multistage compressor and multistage cooling gas turbine), which allows to take into account blade and flow path geometrical parameters. Their changing during the gas turbine engine design and development processes influence its performances: thrust, fuel consumption, efficiency as functions of values of flow rate, rotational speed, engine entrance conditions and so on. All these dependences could be defined by using proposed calculation method.In distinction from methods which are noted, this method allows to concede compressor or turbine incidence angles, drag values, pressure ratio, surge margin in design and off-design engine regimes. The opportunity to take into account by-passing and air bleeding from compressor blade channels and their engine parameters influence is very important also.The article includes calculation method main points, block-scheme, equations system, which gives the opportunity of alignment the engine units and their elements in wide range of state working regimes. Set of equations consists of flow rate balance equations through the stages of multistage compressor and turbine, combustion chamber and connected channels. Also system includes power balance equations, by-passing, air bleeding from compressor stages channels, its admission into the cooling turbine stages and accounts their thermodynamic parameters. Compressors and turbines maps parameters are calculated with main turbomachinery theory lows and semi-empirical dependences.This article is the first in series of articles, which considers this problem

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Characterising the kinematics of the Joffre Peak landslides using a combined numerical modeling-remote sensing approach

10.5194/egusphere-egu21-154 ◽

2021 ◽

Author(s):

Nicola Fullin ◽

Monica Ghirotti ◽

Davide Donati ◽

Doug Stead

Keyword(s):

Remote Sensing ◽

Numerical Modelling ◽

Failure Mechanism ◽

Rock Avalanche ◽

Permafrost Degradation ◽

Rock Slopes ◽

Geological Structures ◽

Runout Distance ◽

Wide Range ◽

The Stability

Geological structure and kinematics are often the most important factors controlling the stability of high rock slopes; their characterization can provide insights that are instrumental in understanding the behaviour of a slope in addition to its evolution with time. In this research, we used a combined remote sensing-numerical modelling approach to characterize the Joffre Peak landslides (British Columbia, Canada), two rock avalanche events that occurred on May, 13th and 16th 2019. The May 13th event involved a volume of 2-3million m3, and resulted in a runout distance of 6 km. The May 16th event involved a volume of 2-3 million m3, and a runout distance of 4 km. The failure was likely promoted by permafrost degradation and reduction in shear strength along geological structures (in our simulation checked in dry condition). Using a wide range of techniques, including Structure-from-Motion photogrammetry, virtual outcrop discontinuity mapping, GIS analysis, and 3D distinct element numerical modelling, we investigated the important role that structural geology and slope kinematics played prior to and during the Joffre landslide events. In particular, we demonstrate that i) a very persistent, sub-vertical geological structures formed the lateral and rear release surfaces of the rock mass volume that failed as two discrete landslide events. The landslide blocks were separated by one such sub-vertical structure, which remains visible in the fresh landslide scar; ii) the first block, failed on May 13th 2019, involving planar sliding failure mechanism, possibly promoted by progressive failure and propagation of discontinuities along the basal surface. The detachment of this block enhanced the kinematic freedom of the second landslide block, which, on May 16th, failed as wedge/toppling mechanism; iii) the first landslide block acted as a key block; its displacement and failure provided the kinematic freedom for the occurrence of the second landslide.&#160; In this paper we show that combining remote sensing mapping and 3D numerical modelling allows for the identification of the structural geological features controlling the stability and evolution of high rock slopes in alpine environments. We also show that constraining and validating the numerical modelling results using historical data is of paramount importance to ensure that the correct failure mechanism of the landslides is simulated.&#160;

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Parametric Optimization of Dental Implants

Mechanics and Mechanical Engineering ◽

10.2478/mme-2018-0084 ◽

2020 ◽

Vol 22 (4) ◽

pp. 1061-1076

Author(s):

Wafa Bensmain ◽

Mohammed Benlebna ◽

Boualem Serier ◽

Bel Abbes ◽

Bachir Bouiadjra

Keyword(s):

Dental Implants ◽

Clinical Success ◽

Equivalent Stress ◽

Radius Of Curvature ◽

Geometrical Parameters ◽

Neck Size ◽

Biomechanical Behavior ◽

Dynamic Charging ◽

The Stability ◽

Masticatory Process

AbstractOsseointegration is a fundamental phenomenon of dental implantology. It ensures the stability, the safety and the durability of dental implants and predictable clinical success in long-term. The geometric form of the implant is a defining parameter of osseointegration and implant-bone charge transfer. This is the essential constitutes of this study. In fact, we demonstrate using the finite elements method with tridimensional numerical computations, that the geometrical parameters of the implant conditionate the level and the repartition of the stresses, induced in the cortical bone and the spongy bone during the masticatory process, simulated here by dynamic charging. The effect of several parameters [size and conicity of the implant neck, size and radius of curvature of the implant apex] and the shape of the implant corps on the biomechanical behavior of the bone. The latest was analyzed in terms of variation of the equivalent stress induced in the bone. The purpose of this analysis was the developing of an implant form allowing stress relaxation, during the mastication process, in the living tissue.

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Performance of Electronic Structure Methods for the Description of Hückel-Möbius Interconversions in Extended π-Systems

10.26434/chemrxiv.10564115 ◽

2019 ◽

Author(s):

Tatiana Woller ◽

Ambar Banerjee ◽

Nitai Sylvetsky ◽

Xavier Deraet ◽

Frank De Proft ◽

...

Keyword(s):

Electronic Structure ◽

Basis Set ◽

Dft Methods ◽

Molecular Switching ◽

Wide Range ◽

Electronic Structure Methods ◽

Explicitly Correlated ◽

Relative Errors ◽

The Stability ◽

Basis Set Expansion

Expanded porphyrins provide a versatile route to molecular switching devices due to their ability to shift between several π-conjugation topologies encoding distinct properties. Taking into account its size and huge conformational flexibility, DFT remains the workhorse for modeling such extended macrocycles. Nevertheless, the stability of Hückel and Möbius conformers depends on a complex interplay of different factors, such as hydrogen bonding, p···p stacking, steric effects, ring strain and electron delocalization. As a consequence, the selection of an exchange-correlation functional for describing the energy profile of topological switches is very difficult. For these reasons, we have examined the performance of a variety of wavefunction methods and density functionals for describing the thermochemistry and kinetics of topology interconversions across a wide range of macrocycles. Especially for hexa- and heptaphyrins, the Möbius structures have a pronouncedly stronger degree of static correlation than the Hückel and figure-eight structures, and as a result the relative energies of singly-twisted structures are a challenging test for electronic structure methods. Comparison of limited orbital space full CI calculations with CCSD(T) calculations within the same active spaces shows that post-CCSD(T) correlation contributions to relative energies are very minor. At the same time, relative energies are weakly sensitive to further basis set expansion, as proven by the minor energy differences between MP2/cc-pVDZ and explicitly correlated MP2-F12/cc-pVDZ-F12 calculations. Hence, our CCSD(T) reference values are reasonably well-converged in both 1-particle and n-particle spaces. While conventional MP2 and MP3 yield very poor results, SCS-MP2 and particularly SOS-MP2 and SCS-MP3 agree to better than 1 kcal mol-1 with the CCSD(T) relative energies. Regarding DFT methods, only M06-2X provides relative errors close to chemical accuracy with a RMSD of 1.2 kcal mol-1. While the original DSD-PBEP86 double hybrid performs fairly poorly for these extended p-systems, the errors drop down to 2 kcal mol-1 for the revised revDSD-PBEP86-NL, again showing that same-spin MP2-like correlation has a detrimental impact on performance like the SOS-MP2 results.

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Insights into Potent Therapeutical Antileukemic Agent L-glutaminase Enzyme Under Solid-state Fermentation: A Review

Current Drug Metabolism ◽

10.2174/1389200221666200421122147 ◽

2020 ◽

Vol 21 (3) ◽

pp. 211-220 ◽

Cited By ~ 1

Author(s):

Chandrasai Potla Durthi ◽

Madhuri Pola ◽

Satish Babu Rajulapati ◽

Anand Kishore Kola

Keyword(s):

Solid State ◽

Solid State Fermentation ◽

Food Industry ◽

Energy Requirement ◽

Production Studies ◽

Wide Range ◽

Hybridoma Technology ◽

Bacteria And Fungi ◽

The Stability ◽

Glutaminase Activity

Aim & objective: To review the applications and production studies of reported antileukemic drug L-glutaminase under Solid-state Fermentation (SSF). Overview: An amidohydrolase that gained economic importance because of its wide range of applications in the pharmaceutical industry, as well as the food industry, is L-glutaminase. The medical applications utilized it as an anti-tumor agent as well as an antiretroviral agent. L-glutaminase is employed in the food industry as an acrylamide degradation agent, as a flavor enhancer and for the synthesis of theanine. Another application includes its use in hybridoma technology as a biosensing agent. Because of its diverse applications, scientists are now focusing on enhancing the production and optimization of L-glutaminase from various sources by both Solid-state Fermentation (SSF) and submerged fermentation studies. Of both types of fermentation processes, SSF has gained importance because of its minimal cost and energy requirement. L-glutaminase can be produced by SSF from both bacteria and fungi. Single-factor studies, as well as multi-level optimization studies, were employed to enhance L-glutaminase production. It was concluded that L-glutaminase activity achieved by SSF was 1690 U/g using wheat bran and Bengal gram husk by applying feed-forward artificial neural network and genetic algorithm. The highest L-glutaminase activity achieved under SSF was 3300 U/gds from Bacillus sp., by mixture design. Purification and kinetics studies were also reported to find the molecular weight as well as the stability of L-glutaminase. Conclusion: The current review is focused on the production of L-glutaminase by SSF from both bacteria and fungi. It was concluded from reported literature that optimization studies enhanced L-glutaminase production. Researchers have also confirmed antileukemic and anti-tumor properties of the purified L-glutaminase on various cell lines.

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Hydromechanics of low-Reynolds-number flow. Part 2. Singularity method for Stokes flows

Journal of Fluid Mechanics ◽

10.1017/s0022112075000614 ◽

1975 ◽

Vol 67 (4) ◽

pp. 787-815 ◽

Cited By ~ 300

Author(s):

Allen T. Chwang ◽

T. Yao-Tsu Wu

Keyword(s):

Exact Solutions ◽

Stokes Flow ◽

Fundamental Solutions ◽

The Body ◽

Circular Cylinders ◽

Geometrical Parameters ◽

Flow Problems ◽

Singularity Method ◽

Wide Range ◽

Body Shapes

The present study further explores the fundamental singular solutions for Stokes flow that can be useful for constructing solutions over a wide range of free-stream profiles and body shapes. The primary singularity is the Stokeslet, which is associated with a singular point force embedded in a Stokes flow. From its derivatives other fundamental singularities can be obtained, including rotlets, stresslets, potential doublets and higher-order poles derived from them. For treating interior Stokes-flow problems new fundamental solutions are introduced; they include the Stokeson and its derivatives, called the roton and stresson.These fundamental singularities are employed here to construct exact solutions to a number of exterior and interior Stokes-flow problems for several specific body shapes translating and rotating in a viscous fluid which may itself be providing a primary flow. The different primary flows considered here include the uniform stream, shear flows, parabolic profiles and extensional flows (hyper-bolic profiles), while the body shapes cover prolate spheroids, spheres and circular cylinders. The salient features of these exact solutions (all obtained in closed form) regarding the types of singularities required for the construction of a solution in each specific case, their distribution densities and the range of validity of the solution, which may depend on the characteristic Reynolds numbers and governing geometrical parameters, are discussed.

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Polymer-Drug Conjugates as Nanotheranostic Agents

Journal of Nanotheranostics ◽

10.3390/jnt2010005 ◽

2021 ◽

Vol 2 (1) ◽

pp. 63-81

Author(s):

Sajana Manandhar ◽

Erica Sjöholm ◽

Johan Bobacka ◽

Jessica M. Rosenholm ◽

Kuldeep K. Bansal

Keyword(s):

Drug Delivery ◽

Drug Release ◽

Treatment Options ◽

The Body ◽

Drug Conjugates ◽

Imaging Characteristics ◽

Wide Range ◽

Systemic Side Effects ◽

Theranostic Agents ◽

The Stability

Since the last decade, the polymer-drug conjugate (PDC) approach has emerged as one of the most promising drug-delivery technologies owing to several benefits like circumventing premature drug release, offering controlled and targeted drug delivery, improving the stability, safety, and kinetics of conjugated drugs, and so forth. In recent years, PDC technology has advanced with the objective to further enhance the treatment outcomes by integrating nanotechnology and multifunctional characteristics into these systems. One such development is the ability of PDCs to act as theranostic agents, permitting simultaneous diagnosis and treatment options. Theranostic nanocarriers offer the opportunity to track the distribution of PDCs within the body and help to localize the diseased site. This characteristic is of particular interest, especially among those therapeutic approaches where external stimuli are supposed to be applied for abrupt drug release at the target site for localized delivery to avoid systemic side effects (e.g., Visudyne®). Thus, with the help of this review article, we are presenting the most recent updates in the domain of PDCs as nanotheranostic agents. Different methodologies utilized to design PDCs along with imaging characteristics and their applicability in a wide range of diseases, have been summarized in this article.

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No-z Model for Magnetic Fields of Different Astrophysical Objects and Stability of the Solutions

Data ◽

10.3390/data6010004 ◽

2021 ◽

Vol 6 (1) ◽

pp. 4

Author(s):

Evgeny Mikhailov ◽

Daniela Boneva ◽

Maria Pashentseva

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Large Scale ◽

Point Of View ◽

Accretion Discs ◽

Wide Range ◽

Astrophysical Objects ◽

Alpha Effect ◽

The Stability ◽

The Magnetic Field

A wide range of astrophysical objects, such as the Sun, galaxies, stars, planets, accretion discs etc., have large-scale magnetic fields. Their generation is often based on the dynamo mechanism, which is connected with joint action of the alpha-effect and differential rotation. They compete with the turbulent diffusion. If the dynamo is intensive enough, the magnetic field grows, else it decays. The magnetic field evolution is described by Steenbeck—Krause—Raedler equations, which are quite difficult to be solved. So, for different objects, specific two-dimensional models are used. As for thin discs (this shape corresponds to galaxies and accretion discs), usually, no-z approximation is used. Some of the partial derivatives are changed by the algebraic expressions, and the solenoidality condition is taken into account as well. The field generation is restricted by the equipartition value and saturates if the field becomes comparable with it. From the point of view of mathematical physics, they can be characterized as stable points of the equations. The field can come to these values monotonously or have oscillations. It depends on the type of the stability of these points, whether it is a node or focus. Here, we study the stability of such points and give examples for astrophysical applications.

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Roles of vanes in diffuser on stability of centrifugal compressor

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410019844433 ◽

2019 ◽

Vol 233 (14) ◽

pp. 5380-5392

Author(s):

Wangzhi Zou ◽

Xiao He ◽

Wenchao Zhang ◽

Zitian Niu ◽

Xinqian Zheng

Keyword(s):

High Pressure ◽

Centrifugal Compressor ◽

Dynamic Pressure ◽

Pressure Ratio ◽

Pressure Rise ◽

Rotating Stall ◽

Centrifugal Compressors ◽

Compression System ◽

The Stability ◽

Rotating Instability

The stability considerations of centrifugal compressors become increasingly severe with the high pressure ratios, especially in aero-engines. Diffuser is the major subcomponent of centrifugal compressor, and its performance greatly influences the stability of compressor. This paper experimentally investigates the roles of vanes in diffuser on component instability and compression system instability. High pressure ratio centrifugal compressors with and without vanes in diffuser are tested and analyzed. Rig tests are carried out to obtain the compressor performance map. Dynamic pressure measurements and relevant Fourier analysis are performed to identify complex instability phenomena in the time domain and frequency domain, including rotating instability, stall, and surge. For component instability, vanes in diffuser are capable of suppressing the emergence of rotating stall in the diffuser at full speeds, but barely affect the characteristics of rotating instability in the impeller at low and middle speeds. For compression system instability, it is shown that the use of vanes in diffuser can effectively postpone the occurrence of compression system surge at full speeds. According to the experimental results and the one-dimensional flow theory, vanes in diffuser turn the diffuser pressure rise slope more negative and thus improve the stability of compressor stage, which means lower surge mass flow rate.

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The Effects of Ambient Conditions on Gas Turbine Emissions—Generalized Correction Factors

Journal of Engineering for Power ◽

10.1115/1.3446412 ◽

1978 ◽

Vol 100 (4) ◽

pp. 640-646 ◽

Cited By ~ 2

Author(s):

P. Donovan ◽

T. Cackette

Keyword(s):

Gas Turbine ◽

Pressure Ratio ◽

Turbine Engines ◽

Inlet Temperature ◽

Gas Turbine Engines ◽

Correction Factors ◽

Oxides Of Nitrogen ◽

Ambient Conditions ◽

Nitrogen Emission ◽

Wide Range

A set of factors which reduces the variability due to ambient conditions of the hydrocarbon, carbon monoxide, and oxides of nitrogen emission indices has been developed. These factors can be used to correct an emission index to reference day ambient conditions. The correction factors, which vary with engine rated pressure ratio for NOx and idle pressure ratio for HC and CO, can be applied to a wide range of current technology gas turbine engines. The factors are a function of only the combustor inlet temperature and ambient humidity.

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