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Articles 1 - 30 of 48
Full-Text Articles in Engineering
A Novel Membrane Distillation-Thermophilic Bioreactor System: Biological Stability And Trace Organic Compound Removal, Kaushalya Wijekoon, Faisal Hai, Jinguo Kang, William Price, Wenshan Guo, Hao Ngo, Tzahi Cath, Long Nghiem
A Novel Membrane Distillation-Thermophilic Bioreactor System: Biological Stability And Trace Organic Compound Removal, Kaushalya Wijekoon, Faisal Hai, Jinguo Kang, William Price, Wenshan Guo, Hao Ngo, Tzahi Cath, Long Nghiem
Faisal I Hai
The removal of trace organic compounds (TrOCs) by a novel membrane distillation-thermophilic bioreactor (MDBR) system was examined. Salinity build-up and the thermophilic conditions to some extent adversely impacted the performance of the bioreactor, particularly the removal of total nitrogen and recalcitrant TrOCs. While most TrOCs were well removed by the thermophilic bioreactor, compounds containing electron withdrawing functional groups in their molecular structure were recalcitrant to biological treatment and their removal efficiency by the thermophilic bioreactor was low (0-53%). However, the overall performance of the novel MDBR system with respect to the removal of total organic carbon, total nitrogen, and TrOCs …
The Use Of Initial Imperfection Approach In Design Process And Buckling Failure Evaluation Of Axially Compressed Composite Cylindrical Shells
Faculty of Engineering University of Malaya
Thin-walled cylindrical shells are susceptible to buckling failures caused by the axial compressive loading. During the design process or the buckling failure evaluation of axially-compressed cylindrical shells, initial geometric and loading imperfections are of important parameters for the analyses. Therefore, the engineers/designers are expected to well understand the physical behaviours of shell buckling to prevent unexpected serious failure in structures. In particular, it is widely reported that no efficient guidelines for modelling imperfections in composite structures are available. Knowledge obtained from the relevant works is open for updates and highly sought. In this work, we study the influence of imperfections …
Design Considerations Towards The Construction Of Hybrid Floating Brush Seal (Hfbs), S. Lattime, Minel Braun, Fred Choy
Design Considerations Towards The Construction Of Hybrid Floating Brush Seal (Hfbs), S. Lattime, Minel Braun, Fred Choy
Fred K. Choy
The hybrid floating brush seal (HFBS) represents an advance in brush seal technology by combining brush seal and film riding face seal technologies to create a hybrid seal that allows both axial and radial excursions of the sealed shaft without damage to seal integrity. At the same time, it eliminates interface surface speeds between the rotor and the brush bristles. This accomplishment is possible because the brush seal, which forms the primary seal, rotates with the shaft, while floating against a hydrodynamic face seal surface, which makes up the secondary seal. The present paper presents continuation work (Int J of …
La0.7Sr0.3Fe0.7Ga0.3O3-Δ As Electrode Material For A Symmetrical Solid Oxide Fuel Cell, Zhibin Yang, Yu Chen, Chao Jin, Guoliang Xiao, Minfang Han, Fanglin Chen
La0.7Sr0.3Fe0.7Ga0.3O3-Δ As Electrode Material For A Symmetrical Solid Oxide Fuel Cell, Zhibin Yang, Yu Chen, Chao Jin, Guoliang Xiao, Minfang Han, Fanglin Chen
Fanglin Chen
In this research, La0.7Sr0.3Fe0.7Ga0.3O3−δ (LSFG) perovskite oxide was successfully prepared using a microwave-assisted combustion method, and employed as both anode and cathode in symmetrical solid oxide fuel cells. A maximum power density of 489 mW cm−2 was achieved at 800 °C with wet H2 as the fuel and ambient air as the oxidant in a single cell with the configuration LSFG|La0.8Sr0.2Ga0.83Mg0.17O3−δ|LSFG. Furthermore, the cells demonstrated good stability in H2 and acceptable sulfur tolerance.
First Order Approximation Of The Stability Regions Of Time Delay Systems, Rifat Sipahi, Silviu-Julian Niculescu
First Order Approximation Of The Stability Regions Of Time Delay Systems, Rifat Sipahi, Silviu-Julian Niculescu
Rifat Sipahi
No abstract provided.
Kinetics Of Superoxide Ion In Dimethyl Sulfoxide Containing Ionic Liquids
Kinetics Of Superoxide Ion In Dimethyl Sulfoxide Containing Ionic Liquids
Faculty of Engineering University of Malaya
The chemical generation of superoxide ion (O-2 (aEuro cent a')) by dissolving potassium superoxide was investigated. The chemically generated O-2 (aEuro cent a') was then used to study the long-term stability of O-2 (aEuro cent a') in dimethyl sulfoxide (DMSO) containing ionic liquids (ILs) and determine the rate constants based on pseudo 1st- and 2nd-order reactions between the IL and O-2 (aEuro cent a') generated in DMSO. O-2 (aEuro cent a') was unstable in DMSO containing [S-222][TFSI], [DMIm][MS], [BDMIm][TfO], [EMIm][TFSI], [EMIm][MS], [P-14,P-666][TPTP], [P-14,P-666][TFSI], and all pyridinium-based ILs. In contrast, O-2 (aEuro cent a') was very stable in DMSO containing [MOPMPip][TFSI], …
Characterization Of Sr‐Doped Lamno3 And Lacoo3 As Cathode Materials For A Doped Lagao3 Ceramic Fuel Cell, Kevin Huang, Man Feng, John B. Goodenough, Michael Schmerling
Characterization Of Sr‐Doped Lamno3 And Lacoo3 As Cathode Materials For A Doped Lagao3 Ceramic Fuel Cell, Kevin Huang, Man Feng, John B. Goodenough, Michael Schmerling
Kevin Huang
Energy dispersive spectrometry line scan and ac impedance spectroscopy were used in this study to investigate the chemical reactions between two cathode materials, La0.84Sr0.16MnO3 (LSM), La0.5Sr0.5CoO3-δ (LSC), and the electrolyte La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM). Significant interdiffusions of Co into LSGM and Ga into LSC were found at an LSC/LSGM interface even at relatively low fabrication temperatures. In contrast, only small interdiffusions of Mn into LSGM and Ga into LSM were detected at the LSM/LSGM interface even though it was fired at 1470°C. The …
A Reversible And Stable Flake-Like Licoo2 Cathode For Lithium Ion Batteries, Tao Wei, Rui Zeng, Yongming Sun, Yunhui Huang, Kevin Huang
A Reversible And Stable Flake-Like Licoo2 Cathode For Lithium Ion Batteries, Tao Wei, Rui Zeng, Yongming Sun, Yunhui Huang, Kevin Huang
Kevin Huang
A dense and thick flake-like cathode structure was demonstrated to have a preferential crystallographic orientation for Li+ migration and a better tolerance to cracking, both of which enable a reversible and stable capacity at moderate rates from 0.1 to 2 C.
Flux Of Silver-Carbonate Membranes For Post-Combustion Co2 Capture: The Effects Of Membrane Thickness, Gas Concentration And Time, Lingling Zhang, Yunhui Gong, Kyle Brinkman, Tao Wei, Siwei Wang, Kevin Huang
Flux Of Silver-Carbonate Membranes For Post-Combustion Co2 Capture: The Effects Of Membrane Thickness, Gas Concentration And Time, Lingling Zhang, Yunhui Gong, Kyle Brinkman, Tao Wei, Siwei Wang, Kevin Huang
Kevin Huang
No abstract provided.
Surface Modified Silver-Carbonate Mixed Conducting Membranes For High Flux Co2 Separation With Enhanced Stability, Lingling Zhang, Yunhui Gong, Jacob Yaggie, Siwei Wang, Kevin Romito, Kevin Huang
Surface Modified Silver-Carbonate Mixed Conducting Membranes For High Flux Co2 Separation With Enhanced Stability, Lingling Zhang, Yunhui Gong, Jacob Yaggie, Siwei Wang, Kevin Romito, Kevin Huang
Kevin Huang
No abstract provided.
Impact Of In Situ Physical And Chemical Cleaning On Pvdf Membrane Properties And Performances
Impact Of In Situ Physical And Chemical Cleaning On Pvdf Membrane Properties And Performances
Faculty of Engineering University of Malaya
Appropriate selection of cleaning agent is an important factor to achieve a better cleaning efficiency and this topic has become an ongoing discussion. This work assesses the impacts of sodium hydroxide (NaOH) and sodium hypochlorite (NaOCl) aqueous solution towards polyvinylidene fluoride (PVDF) stability at the typical concentrations used in membrane cleaning. The cleaned membranes were characterised using held emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), pure water flux measurement, contact angle, protein retention and tensile testing. Membrane cleaned at elevated temperature and higher concentration presented a higher water flux than the virgin membrane which can be a worrying …
Impact Of In Situ Physical And Chemical Cleaning On Pvdf Membrane Properties And Performances
Impact Of In Situ Physical And Chemical Cleaning On Pvdf Membrane Properties And Performances
Faculty of Engineering University of Malaya
Appropriate selection of cleaning agent is an important factor to achieve a better cleaning efficiency and this topic has become an ongoing discussion. This work assesses the impacts of sodium hydroxide (NaOH) and sodium hypochlorite (NaOCl) aqueous solution towards polyvinylidene fluoride (PVDF) stability at the typical concentrations used in membrane cleaning. The cleaned membranes were characterised using held emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), pure water flux measurement, contact angle, protein retention and tensile testing. Membrane cleaned at elevated temperature and higher concentration presented a higher water flux than the virgin membrane which can be a worrying …
International Conference On Short And Medium Span Bridges, Calgary, July 15-18, 2014, Barry A. Palynchuk Phd, Christophe Deniaud Phd
International Conference On Short And Medium Span Bridges, Calgary, July 15-18, 2014, Barry A. Palynchuk Phd, Christophe Deniaud Phd
Barry A. Palynchuk PhD
The Jean River near Wabush, Labrador is crossed by two railways and an access road by twin 6m diameter culverts . They are heavily strutted inside their barrels to counteract some significant shape deformation, and are deemed not suitable to sustain the increased volume of rail traffic serving the development of the Bloom Lake mines. The owner requested the design and construction of a replacement scheme for an additional design life of 20 years with a time sensitive schedule for completion of the work during the 2013 construction season. This VE concept for the design of live load relief spans …
Design And Construction Of Rail And Road Live Load Relief Spans Over Existing Culverts, Barry A. Palynchuk Phd, Christophe Deniaud Phd
Design And Construction Of Rail And Road Live Load Relief Spans Over Existing Culverts, Barry A. Palynchuk Phd, Christophe Deniaud Phd
Barry A. Palynchuk PhD
DESIGN AND CONSTRUCTION OF RAIL AND ROAD LIVE LOAD RELIEF SPANS OVER EXISTING CULVERTS
Think Outside The Box: New Materials, Design Application, And Performance Of Railway Turnout Bearers, Sakdirat Kaewunruen
Think Outside The Box: New Materials, Design Application, And Performance Of Railway Turnout Bearers, Sakdirat Kaewunruen
Sakdirat Kaewunruen
Railway turnout systems are a main feature in railway tracks. There are two types of turnout support structures, which can be designed to be either a slab or a cluster of discrete bearers. The choice of turnout support system depends on asset management strategy of the rail operators or maintainers. This paper will focus on the discrete turnout bearer system where turnout alignments, settlement and deformation are comparatively more flexible and retrievable by routine ballast tamping. It embraces the consideration of new materials for use as a turnout bearer. Traditional bearer materials are timber, steel, and concrete. Recent developments have …
Reduced Graphene Oxide With Superior Cycling Stability And Rate Capability For Sodium Storage, Yunxiao Wang, Shulei Chou, Hua-Kun Liu, S X. Dou
Reduced Graphene Oxide With Superior Cycling Stability And Rate Capability For Sodium Storage, Yunxiao Wang, Shulei Chou, Hua-Kun Liu, S X. Dou
Shi Xue Dou
Sodium ion battery is a promising electrical energy storage system for sustainable energy storage applications due to the abundance of sodium resources and their low cost. In this communication, the electrochemical properties of sodium ion storage in reduced graphene oxide (RGO) were studied in an electrolyte consisting of 1 M NaClO4 in propylene carbonate (PC). The experimental results show that the RGO anode allowed significant sodium ion insertion, leading to higher capacity at high current density compared to the previously reported results for carbon materials. This is due to the fact that RGO possesses higher electrical conductivity and is a …
Performance And Stability Assessment Of Future Grid Scenarios For The Australian Nem, Hesamoddin Marzooghi Mr., David J. Hill Prof., Gregor Verbic Dr.
Performance And Stability Assessment Of Future Grid Scenarios For The Australian Nem, Hesamoddin Marzooghi Mr., David J. Hill Prof., Gregor Verbic Dr.
Hesamoddin Marzooghi
Shifting towards higher penetration of diverse renewable energy sources (RESs) in power systems is motivated mainly by reducing carbon emissions. In the long term of several decades, which we refer to in terms of the future grid (FG), balancing between supply and demand will become more challenging. Also, displacing conventional generators with RESs, especially inverter-based and intermittent RESs, could have significant effects on performance and stability of FGs. So far, FG feasibility studies have mostly considered simple balancing, but largely neglected network related issues such as line overload and stability. The main contribution of this paper is to present a …
Impact Of Wind Generation Mix On Transient Stability For An Interconnected Power System, Lasantha Meegahapola, Damian Flynn, Jason Kennedy, Tim Littler
Impact Of Wind Generation Mix On Transient Stability For An Interconnected Power System, Lasantha Meegahapola, Damian Flynn, Jason Kennedy, Tim Littler
Dr Lasantha G Meegahapola
The rapid growth of wind generation in many European countries is pushing power systems into uncharted territory. As additional wind generators are installed, the changing generation mix may impact on power system stability. This paper adopts the New England 39 bus system as a test system for transient stability analysis. Thermal generator models are based on a likely future plant mix for existing systems, while varying capacities of fixed-speed induction generators (FSIG) and doubly-fed induction generators (DFIG) are considered. The main emphasis here has been placed on the impact of wind technology mix on inter-area oscillations following transient grid disturbances. …
Impact On Transient And Frequency Stability For A Power System At Very High Wind Penetration, Lasantha Meegahapola, Damian Flynn
Impact On Transient And Frequency Stability For A Power System At Very High Wind Penetration, Lasantha Meegahapola, Damian Flynn
Dr Lasantha G Meegahapola
This paper analyzes the impact on transient and frequency stability for a power system at very high wind penetration (40% wind). Wind penetration is based on the doubly-fed induction generator (DFIG), and a systematic approach has been adopted for wind power integration. A sensitivity analysis has been carried out for each wind integration scenario and for different wind generator loading conditions. A range of fault locations has been selected for stability analysis based on the proximity to synchronous generation and wind farms. The analysis has shown that transient stability performance is subject to fault location in the network, especially when …
Transient Stability Analysis Of A Power System With High Wind Penetration, Lasantha Meegahapola, Damian Flynn, Tim Littler
Transient Stability Analysis Of A Power System With High Wind Penetration, Lasantha Meegahapola, Damian Flynn, Tim Littler
Dr Lasantha G Meegahapola
This paper presents transient stability analysis for a power system with high wind penetration. The transient stability has been evaluated based on two stability criteria: rotor angle stability and voltage stability. A modified IEEE-14 bus system has been used as the main study network and simulations have been conducted at several wind power penetration levels, defined as a fraction of total system generation. A wide range of scenarios have been presented based on the wind farm voltage at the point of connection, i.e. low voltage (LV) distribution level and high voltage (HV) transmission level, and the type of wind generator …
Active Use Of Dfig Based Wind Farms For Transient Stability Improvement During Grid Disturbances, Lasantha Meegahapola, Damian Flynn, Jason Kennedy, Tim Littler
Active Use Of Dfig Based Wind Farms For Transient Stability Improvement During Grid Disturbances, Lasantha Meegahapola, Damian Flynn, Jason Kennedy, Tim Littler
Dr Lasantha G Meegahapola
The doubly-fed induction generator (DFIG) now represents the dominant technology in wind turbine design. One consequence of this is limited damping and inertial response during transient grid disturbances. A 'decoupled' strategy is therefore proposed to operate the DFIG grid-side converter (GSC) as a static synchronous compensator (STATCOM) during a fault, supporting the local voltage, while the DFIG operates as a fixed-speed induction generator (FSIG) providing an inertial response. The modeling aspects of the decoupled control strategy, the selection of protection control settings, the significance of the fault location and operation at sub- and super-synchronous speeds are analyzed in detail. In …
Capability Curve Based Enhanced Reactive Power Control Strategy For Stability Enhancement And Network Voltage Management, Lasantha Meegahapola, Tim Littler, Sarath Perera
Capability Curve Based Enhanced Reactive Power Control Strategy For Stability Enhancement And Network Voltage Management, Lasantha Meegahapola, Tim Littler, Sarath Perera
Dr Lasantha G Meegahapola
Reactive power has become a vital resource in modern electricity networks due to increased penetration of distributed generation. This paper examines the extended reactive power capability of DFIGs to improve network stability and capability to manage network voltage profile during transient faults and dynamic operating conditions. A coordinated reactive power controller is designed by considering the reactive power capabilities of the rotor-side converter (RSC) and the grid-side converter (GSC) of the DFIG in order to maximise the reactive power support from DFIGs. The study has illustrated that, a significant reactive power contribution can be obtained from partially loaded DFIG wind …
In Situ Performance Of A Complex Urban Turnout Grillage System Using Fibre-Reinforced Foamed Urethane (Ffu) Bearers, Sakdirat Kaewunruen
In Situ Performance Of A Complex Urban Turnout Grillage System Using Fibre-Reinforced Foamed Urethane (Ffu) Bearers, Sakdirat Kaewunruen
Sakdirat Kaewunruen
A full-scale trial to investigate in-situ behaviours of a turnout grillage system using an alternative material, ‘fibre-reinforced foamed urethane (FFU)’ bearers, has been carried out at a complex turnout junction under heavy mixed traffics at Hornsby, New South Wales, Australia. The turnout junction was renewed using the FFU bearers altogether with new special track components. Influences of the FFU bearers on track geometry (recorded by track inspection vehicle ‘AK Car’ and based on survey data), track settlement, track dynamics and acoustic characteristics have been measured. Operational train pass-by measurements have been analysed to evaluate the effectiveness of the replacement methodology. …
Performance Of A Novel Osmotic Membrane Bioreactor (Ombr) System: Flux Stability And Removal Of Trace Organics, Abdulhakeem Alturki, James Mcdonald, Stuart J. Khan, Faisal I. Hai, William E. Price, Long Nghiem
Performance Of A Novel Osmotic Membrane Bioreactor (Ombr) System: Flux Stability And Removal Of Trace Organics, Abdulhakeem Alturki, James Mcdonald, Stuart J. Khan, Faisal I. Hai, William E. Price, Long Nghiem
Faisal I Hai
Results reported here highlight the potential and several challenges in the development of a novel osmotic membrane bioreactor (OMBR) process for the treatment of municipal wastewater. Following the initial gradual decline, a stable permeate flux value was obtained after approximately four days of continuous operation. There was evidence of continuous deterioration of biological activity of the OMBR system, possibly due to the build-up of salinity in the reactor. The removal of 25 out of 27 trace organic compounds with molecular weight higher than 266 g/mol was above 80% and was possibly governed by the interplay between physical separation of the …
The Stability Of Cementite Formed From Hematite And Titanomagnetite Ore Under Carburising Atmosphere, R Longbottom, D Young, J Zhang, O Ostrovski
The Stability Of Cementite Formed From Hematite And Titanomagnetite Ore Under Carburising Atmosphere, R Longbottom, D Young, J Zhang, O Ostrovski
Raymond Longbottom
The decomposition of cementite formed from hematite and pre-oxidised titanomagnetite was investigated in the temperature range from 500°C to 925°C for hematite, and from 300°C to 1100°C for titanomagnetite under a carburising atmosphere in a fixed bed reactor. For hematite, cementite was most stable at temperatures 7S0-770°C. The decomposition rate increased with decreasing temperature between 7S0°C and 600°C and with increasing temperature above 770°C. For ironsand, cementite was most stable in the temperature range 700-900°C. The rate of decomposition of cementite increased with decreasing temperature between 700°C and 400°C and with increasing temperature above 900°C. Cementite formed from ironsand was …
Performance Of A Novel Osmotic Membrane Bioreactor (Ombr) System: Flux Stability And Removal Of Trace Organics, Abdulhakeem Alturki, James Mcdonald, Stuart J. Khan, Faisal I. Hai, William E. Price, Long Nghiem
Performance Of A Novel Osmotic Membrane Bioreactor (Ombr) System: Flux Stability And Removal Of Trace Organics, Abdulhakeem Alturki, James Mcdonald, Stuart J. Khan, Faisal I. Hai, William E. Price, Long Nghiem
Long D Nghiem
Results reported here highlight the potential and several challenges in the development of a novel osmotic membrane bioreactor (OMBR) process for the treatment of municipal wastewater. Following the initial gradual decline, a stable permeate flux value was obtained after approximately four days of continuous operation. There was evidence of continuous deterioration of biological activity of the OMBR system, possibly due to the build-up of salinity in the reactor. The removal of 25 out of 27 trace organic compounds with molecular weight higher than 266 g/mol was above 80% and was possibly governed by the interplay between physical separation of the …
Stability Characteristics Of Herringbone Grooved Journal Bearings Incorporating Cavitation Effects, T.V.V.L. Rao, Jerzy Sawicki
Stability Characteristics Of Herringbone Grooved Journal Bearings Incorporating Cavitation Effects, T.V.V.L. Rao, Jerzy Sawicki
Jerzy T. Sawicki
Stabilitycharacteristics of the herringbone grooved journal bearings (HGJBs) are analyzedtaking into account cavitation of the fluid flow. The perturbedvalues of pressure and film thickness from a given equilibriumposition are substituted into the Elrod's universal equation, which considersmass conservation in the complete bearing geometry. In order toanalyze the herringbone groove configuration, the governing equations under steadyand perturbed states are transformed to a rectangular domain usingthe grid transformation techniques. It is assumed that under perturbedconditions, the cavitation extent in the bearing remains unchanged andthe pressure gradients are computed in the full film region.The linearized stiffness and damping coefficients are evaluated in thecomplete …
Linear Stability Analysis For A Hydrodynamic Journal Bearing Considering Cavitation Effects, T.V.V.L. Rao, Jerzy Sawicki
Linear Stability Analysis For A Hydrodynamic Journal Bearing Considering Cavitation Effects, T.V.V.L. Rao, Jerzy Sawicki
Jerzy T. Sawicki
The purpose of this paper is to present the two-dimensional linear stability analysis considering the fluid flow in both full film and cavitation regions for a plain cylindrical journal bearing. The Lund's infinitesimal perturbation procedure is applied to Elrod's universal equation for evaluation of unsteady pressure gradients. Based on JFO theory, the pressure distribution, film rupture, and reformation boundaries can be obtained using Elrod's universal equation, for a given operating position of the journal. In this work, it is assumed that for infinitesimal perturbation of a journal about the equilibrium position, the film rupture and film reformation boundaries are the …
Stability Analysis Of A Rough Journal Bearing Considering Cavitation Effects, T.V.V.L. Rao, Jerzy Sawicki
Stability Analysis Of A Rough Journal Bearing Considering Cavitation Effects, T.V.V.L. Rao, Jerzy Sawicki
Jerzy T. Sawicki
A modified governing equation is derived incorporating the effects of roughness and cavitation in a journal bearing. The available theories of Reynolds roughness and cavitation algorithm proposed by Elrod are utilized in this work to develop a numerical procedure for stability analysis of a liquid lubricated rough journal bearing. The Elrod generalized theory of Reynolds roughness provides a governing equation based on the surface configuration. The Elrod cavitation algorithm conserves mass throughout the bearing and automatically predicts the full film and cavitation regions using a switch function. The roughness is considered on either or both the bearing and journal surfaces. …
Thermomechanical Behavior Of Rotor With Rubbing, Jerzy T. Sawicki, Alberto Montilla-Bravo, Zdzislaw Gosiewski
Thermomechanical Behavior Of Rotor With Rubbing, Jerzy T. Sawicki, Alberto Montilla-Bravo, Zdzislaw Gosiewski
Jerzy T. Sawicki
This article presents an analytical study of the dynamics and stability of rotors subjected to rubbing due to contact with seals, taking account of associated thermal effects. The seal interaction force acting on the shaft gives rise to a friction force, which is a source of heating and can induce so-called spiral vibrations. A mathematical model that has been developed couples the heat-conduction equation with the equations for motion of the rotor. Numerical simulations have been conducted that show the thermomechanical behavior of the rotor at various operating conditions. A procedure for analyzing the stability of multibearing rotors based on …