Development of a general purpose airborne simulator

Variable stability system development for General Purpose Airborne Simulator /GPAS

Conductivity optimisation of graphene oxide-M13 bacteriophage nanocomposites:towards graphene-based gas micronano-sensors

Graphene oxide (GO) and M13 bacteriophage can self-assemble to form ultra-low density porous structures, known as GraPhage13 aerogels (GPA). Due to the insulating nature of GPA and the challenges in producing highly conductive aerogels, it is paramount to explore ways to enhance the conductivity of GPA. Herein, we have developed a method to enhance the conductivity of GPA, via the integration and optimisation of 5 nm and 20 nm diameter gold nanoparticles (AuNPs) into the aerogel structure and systematically analysed the morphology, composition and spectroscopic properties of the resulting GPA-Au nanocomposite. The fabricated GPA-Au nanocomposites exhibited remarkable increases in conductivity, with the integration of 5 nm AuNPs leading to a 53-fold increase compared to GPA, achieving a performance of up to 360 nS/cm, which is within the range suitable for miniaturised semiconductor devices. The mechanism behind the conductivity enhancement was further investigated and attributed to GO-AuNP interactions increasing the carrier density by introducing new energy levels in the GO band gap or shifting its Fermi level towards the conduction band. These findings demonstrate the potential of functionalised AuNPs to significantly improve the electrical properties of GPA, paving the way for their application in gas sensors for biological and chemical detection and a new range of advanced semiconductor devices.</p

Conductivity optimisation of graphene oxide-M13 bacteriophage nanocomposites:towards graphene-based gas micronano-sensors

Graphene oxide (GO) and M13 bacteriophage can self-assemble to form ultra-low density porous structures, known as GraPhage13 aerogels (GPA). Due to the insulating nature of GPA and the challenges in producing highly conductive aerogels, it is paramount to explore ways to enhance the conductivity of GPA. Herein, we have developed a method to enhance the conductivity of GPA, via the integration and optimisation of 5 nm and 20 nm diameter gold nanoparticles (AuNPs) into the aerogel structure and systematically analysed the morphology, composition and spectroscopic properties of the resulting GPA-Au nanocomposite. The fabricated GPA-Au nanocomposites exhibited remarkable increases in conductivity, with the integration of 5 nm AuNPs leading to a 53-fold increase compared to GPA, achieving a performance of up to 360 nS/cm, which is within the range suitable for miniaturised semiconductor devices. The mechanism behind the conductivity enhancement was further investigated and attributed to GO-AuNP interactions increasing the carrier density by introducing new energy levels in the GO band gap or shifting its Fermi level towards the conduction band. These findings demonstrate the potential of functionalised AuNPs to significantly improve the electrical properties of GPA, paving the way for their application in gas sensors for biological and chemical detection and a new range of advanced semiconductor devices.</p

A NEW GENERATION CHEMICAL FLOODING SIMULATOR Semi-annual Report for the Period

ABSTRACT 4 SUMMARY 4 Task 1: Formulation and development of Solution Scheme

Scaling laws of nanoporous gold under uniaxial compression: Effects of structural disorder on the solid fraction, elastic Poisson's ratio, Young's modulus and yield strength

AbstractIn this work the relationship between the structural disorder and the macroscopic mechanical behavior of nanoporous gold under uniaxial compression was investigated, using the finite element method. A recently proposed model based on a microstructure consisting of four-coordinated spherical nodes interconnected by cylindrical struts, whose node positions are randomly displaced from the lattice points of a diamond cubic lattice, was extended. This was done by including the increased density as result of the introduced structural disorder. Scaling equations for the elastic Poisson's ratio, the Young's modulus and the yield strength were determined as functions of the structural disorder and the solid fraction. The extended model was applied to identify the elastic–plastic behavior of the solid phase of nanoporous gold. It was found, that the elastic Poisson's ratio provides a robust basis for the calibration of the structural disorder. Based on this approach, a systematic study of the size effect on the yield strength was performed and the results were compared to experimental data provided in literature. An excellent agreement with recently published results for polymer infiltrated samples of nanoporous gold with varying ligament size was found

DESIGN OF EFFICIENT IN-NETWORK DATA PROCESSING AND DISSEMINATION FOR VANETS

By providing vehicle-to-vehicle and vehicle-to-infrastructure wireless communications, vehicular ad hoc networks (VANETs), also known as the “networks on wheels”, can greatly enhance traffic safety, traffic efficiency and driving experience for intelligent transportation system (ITS). However, the unique features of VANETs, such as high mobility and uneven distribution of vehicular nodes, impose critical challenges of high efficiency and reliability for the implementation of VANETs. This dissertation is motivated by the great application potentials of VANETs in the design of efficient in-network data processing and dissemination. Considering the significance of message aggregation, data dissemination and data collection, this dissertation research targets at enhancing the traffic safety and traffic efficiency, as well as developing novel commercial applications, based on VANETs, following four aspects: 1) accurate and efficient message aggregation to detect on-road safety relevant events, 2) reliable data dissemination to reliably notify remote vehicles, 3) efficient and reliable spatial data collection from vehicular sensors, and 4) novel promising applications to exploit the commercial potentials of VANETs. Specifically, to enable cooperative detection of safety relevant events on the roads, the structure-less message aggregation (SLMA) scheme is proposed to improve communication efficiency and message accuracy. The scheme of relative position based message dissemination (RPB-MD) is proposed to reliably and efficiently disseminate messages to all intended vehicles in the zone-of-relevance in varying traffic density. Due to numerous vehicular sensor data available based on VANETs, the scheme of compressive sampling based data collection (CS-DC) is proposed to efficiently collect the spatial relevance data in a large scale, especially in the dense traffic. In addition, with novel and efficient solutions proposed for the application specific issues of data dissemination and data collection, several appealing value-added applications for VANETs are developed to exploit the commercial potentials of VANETs, namely general purpose automatic survey (GPAS), VANET-based ambient ad dissemination (VAAD) and VANET based vehicle performance monitoring and analysis (VehicleView). Thus, by improving the efficiency and reliability in in-network data processing and dissemination, including message aggregation, data dissemination and data collection, together with the development of novel promising applications, this dissertation will help push VANETs further to the stage of massive deployment

Stress-Induced Equivalent Permeability Estimation and Iteratively-Coupled Fluid Flow and Geomechanics Simulation Using Fractal and Statistical Methods

Permeability and porosity are two of the key parameters of reservoir simulations. For naturally fractured reservoir simulations, when matrix porosity is negligible, it is important to estimate the proper fracture porosity and permeability to obtain accurate simulation results. However, it is very difficult to measure and estimate such parameters, due to factors such as the high heterogeneity of fluid and fracture properties, scale differences between the sampling window and actual reservoir domain, and so on. In order to reduce the scale discrepancy error and properly describe natural-like fracture aperture characteristics, fractal theory has been adopted, and a cumulative distribution function of the generated fracture networks was calculated after a 1,000-time Monte Carlo simulation. P50 case was then selected as the reservoir fracture map. The Discrete Fracture Network (DFN) approach can be effective when a limited numbers of fractures dominate the fluid flow in the fractured reservoir. However, if the reservoir has a very complex and large numbers of fractures, using the DFN approach to simulate a fracture flow will require significant computational effort and time. Therefore, in such cases the Equivalent Continuum (EC) approach is more suitable. I developed equivalent permeability calculation codes through a modified Oda’s algorithm; the heterogeneous nature of the fracture network was reflected by using the full tensor permeability method. I developed Stress-Induced Permeability Changing (SIPC) coupling simulation codes to better describe the anisotropic behavior and more accurately reflect the geomechanical characteristics in the coupling simulation. For that, I combined DFN and EC schemes for the SIPC coupling simulation. During the coupling simulation, generated discrete fracture network and aperture data were imported into the coupling simulator, and openings/closings of the apertures due to stress/strain changes were calculated using a kriging scheme. Permeability and porosity were directly estimated via the aperture opening/closing calculation. After a comparison of the FDM and iterative coupling simulations, it was observed that the SIPC coupling simulation successfully described the anisotropic characteristics of the directional permeability estimation, and reflected the reservoir properties in the coupling simulation. The combined DFN and EC approach was effectively applied to the stress-induced permeability changing reservoir coupling simulation

Improvements in phase behavior modeling for compositional simulation

textAccurate and reliable phase equilibrium calculations are among the most important issues in compositional reservoir simulation of enhanced oil recovery (EOR) processes especially miscible gas floods. The important challenges in equation of state (EOS)-based compositional simulators are the time-consuming nature of the phase equilibrium calculations, e.g. 30%-50% of the total computational time in the UTCOMP simulator (Chang, 1990), and accuracy as well as robustness of these calculations. Thus, increasing the computational speed and robustness of the phase equilibrium calculations is of utmost importance in IMPEC-type and fully implicit reservoir simulators. Furthermore, most current compositional reservoir simulators ignore the effect of capillary pressure in porous media on the fluid’s phase behavior. This assumption may lead to significant errors in performance prediction of tight oil and shale gas reservoirs where the small pore sizes result in very large capillary pressure values. The “tie-simplex-based (TSB) phase behavior modeling” techniques attempt to speed up phase behavior calculations by skipping stability analysis and preconditioning phase-split calculations. We implemented the compositional space adaptive tabulation (CSAT), a TSB phase behavior modeling method, in UTCOMP and compared the computational performance of CSAT when used for skipping stability analysis and generating initial estimates for flash calculations, against the standard phase behavior modeling methods in UTCOMP. The results show that the CSAT method as well as a simple heuristic technique, where stability analysis is skipped for single-phase gridblocks surrounded by single phase neighbors, can improve the total computational time by up to 30% compared to the original UTCOMP. In order to avoid the negative-flash calculations required for adaptive tie-line tabulation during the simulation, a prior set of tie-line tables can be used. We demonstrate that the tie lines from the multiple-mixing-cell (MMC) method are very close to the actual compositional simulation tie lines. Thus, the MMC tie lines were used as prior tieline tables in three tie-line-based K-value simulation methods in order to improve speed and robustness of compositional simulation. Several simulation case studies were performed to compare the computational efficiency of the three MMC-based methods, an extended CSAT method (adaptive K-value simulation) and a method based on pure heuristic techniques against the original UTCOMP formulation. The results show that the MMC-based methods and the extended CSAT method can improve the total computational time by up to 50% with acceptable accuracy for the cases studied. The MMC-based methods, the CSAT method and the heuristic methods were implemented in the natural variable formulation in the fully-implicit General Purpose Adaptive Simulator (GPAS) for speeding up the phase equilibrium calculations. The computational efficiency results for several cases that we studied show that the CSAT method and the MMC-based method improve the computational time of the phase equilibrium calculations by up to 78% in the multi-contact-miscible gas injection cases studied. Finally, we present a Gibbs free energy analysis of capillary equilibrium and demonstrate that there is a limiting maximum capillary pressure (P[subscript cmax]) where gas/oil capillary equilibrium is possible and formulate the P [subscript cmax] limit using the spinodal condition of the phase of smaller pressure in capillary equilibrium. The effect of capillary pressure on phase behavior was implemented in the UTCOMP simulator and several simulation case studies in shale gas and tight oil reservoirs were performed. The simulation results illustrate the effect of capillary pressure on production behavior in shale gas and tight oil reservoirs.Petroleum and Geosystems Engineerin

High-Pressure Structural Systematics in Neodymium to 302 GPa

Angle-dispersive x-ray powder diffraction experiments have been performed on neodymium metal to a pressure of 302 GPa. Up to 70 GPa we observe the $hP4 → cF4 → hR24 → oI16 → hP3$ transition sequence reported previously. At 71(2) GPa we find a transition to a phase which has an orthorhombic structure (oF8) with eight atoms in the unit cell, space group Fddd. This structure is the same as that recently observed in samarium above 93 GPa, and is isostructural with high-pressure structures found in the actinides Am, Cf, and Cm. We see a further phase transition at 98(1) GPa to a phase with the orthorhombic α-U (oC4) structure, which remains stable up to 302 GPa, the highest pressure reached in this study. Electronic structure calculations find the same structural sequence, with calculated transition pressures of 66 and 88 GPa, respectively, for the $hP3 → F8$ and $oF8 → oC4$ transitions. The calculations further predict that oC4-Nd loses its magnetism at 100 GPa, in agreement with previous experimental results, and it is the accompanying decrease in enthalpy and volume that results in the transition to this phase. Comparison calculations on the oF8 and oC4 phases of Sm show that they both retain their magnetism to at least 240 GPa, with the result that oC4-Sm is calculated to have the lowest enthalpy over a narrow pressure region near 200 GPa at 0 K