Investigating the changes in matrix and fracture properties and fluid flow under different stress-state conditions

The fracture aperture and fracture permeability are usually considered to remain the same during the production life of a naturally fractured reservoir, regardless of the degree of depletion; but reservoirs experience different stress state conditions, therefore understanding the fracture behavior becomes more complex. This research analyzes the effect of fracture aperture and fracture permeability on the fluid flow under different overburden pressures. This research investigates the fracture apertures under different stress-state conditions. The equations to quantify the flow through the matrix and the fracture at different overburden pressures are provided. An X-ray CT scanner was used to obtain fracture aperture distributions at various overburden pressures to verify the use of log-normal distribution, which was commonly used for distributing fracture apertures. In addition, reservoir simulations are performed to duplicate the experimental results and to provide a valid model for future stress-sensitive reservoirs. Our experimental results show that the fracture aperture and fracture permeability have significant pressure-dependent changes in response to applying variable injection rates and overburden pressures. The laboratory results show that the change in overburden pressure significantly affects the reservoir properties. The change in matrix permeability with different injection rates under variable overburden pressures is not significant in contrast with that effect on fracture aperture and fracture permeability. A calibration curve was obtained to determine fracture aperture from the X-ray CT scanner results. The aperture distribution from data obtained from X-ray CT scanner confirms lognormal distribution at various overburden pressures. This experimental research will increase the understanding of fluid flow behavior in fractured reservoirs

Investigating the changes in matrix and fracture properties and fluid flow under different stress-state conditions

The fracture aperture and fracture permeability are usually considered to remain the same during the production life of a naturally fractured reservoir, regardless of the degree of depletion; but reservoirs experience different stress state conditions, therefore understanding the fracture behavior becomes more complex. This research analyzes the effect of fracture aperture and fracture permeability on the fluid flow under different overburden pressures. This research investigates the fracture apertures under different stress-state conditions. The equations to quantify the flow through the matrix and the fracture at different overburden pressures are provided. An X-ray CT scanner was used to obtain fracture aperture distributions at various overburden pressures to verify the use of log-normal distribution, which was commonly used for distributing fracture apertures. In addition, reservoir simulations are performed to duplicate the experimental results and to provide a valid model for future stress-sensitive reservoirs. Our experimental results show that the fracture aperture and fracture permeability have significant pressure-dependent changes in response to applying variable injection rates and overburden pressures. The laboratory results show that the change in overburden pressure significantly affects the reservoir properties. The change in matrix permeability with different injection rates under variable overburden pressures is not significant in contrast with that effect on fracture aperture and fracture permeability. A calibration curve was obtained to determine fracture aperture from the X-ray CT scanner results. The aperture distribution from data obtained from X-ray CT scanner confirms lognormal distribution at various overburden pressures. This experimental research will increase the understanding of fluid flow behavior in fractured reservoirs

Stretching Directions in Cislunar Space: Stationkeeping and an Application to Transfer Trajectory Design

The orbits of interest for potential missions are stable or nearly stable to maintain long-term presence for conducting scientific studies and to reduce the possibility of rapid departure. Near Rectilinear Halo Orbits (NRHOs) offer such stable or nearly stable orbits that are defined as part of the L1 and L2 halo orbit families in the circular restricted three-body problem. Within the Earth-Moon regime, the L1 and L2 NRHOs are proposed as long-horizon trajectories for cislunar exploration missions, including NASA's upcoming Gateway mission. These stable or nearly stable orbits do not possess well-distinguished unstable and stable manifold structures. As a consequence, existing tools for stationkeeping and transfer trajectory design that exploit such underlying manifold structures are not reliable for orbits that are linearly stable. The current investigation focuses on leveraging stretching direction as an alternative for visualizing the flow of perturbations in the neighborhood of a reference trajectory. The information supplemented by the stretching directions are utilized to investigate the impact of maneuvers for two contrasting applications; the stationkeeping problem, where the goal is to maintain a spacecraft near a reference trajectory for a long period of time, and the transfer trajectory design application, where rapid departure and/or insertion is of concern. Particularly, for the stationkeeping problem, a spacecraft incurs continuous deviations due to unmodeled forces and orbit determination errors in the complex multi-body dynamical regime. The flow dynamics in the region, using stretching directions, are utilized to identify appropriate maneuver and target locations to support a long lasting presence for the spacecraft near the desired path. The investigation reflects the impact of various factors on maneuver cost and boundedness. For orbits that are particularly sensitive to epoch time and possess distinct characteristics in the higher-fidelity ephemeris model compared to their CR3BP counterpart, an additional feedback control is applied for appropriate phasing. The effect of constraining maneuvers in a particular direction is also investigated for the 9:2 synodic resonant southern L2 NRHO, the current baseline for the Gateway mission. The stationkeeping strategy is applied to a range of L1 and L2 NRHOs, and validated in the higher-fidelity ephemeris model. For missions with potential human presence, a rapid transfer between orbits of interest is a priority. The magnitude of the state variations along the maximum stretching direction is expected to grow rapidly and, therefore, offers information to depart from the orbit. Similarly, the maximum stretching in reverse time, enables arrival with a minimal maneuver magnitude. The impact of maneuvers in such sensitive directions is investigated. Further, enabling transfer design options to connect between two stable orbits. The transfer design strategy developed in this investigation is not restricted to a particular orbit but applicable to a broad range of stable and nearly stable orbits in the cislunar space, including the Distant Retrograde Orbit (DROs) and the Lunar Orbits (LO) that are considered for potential missions. Examples for transfers linking a southern and a northern NRHO, a southern NRHO to a planar DRO, and a southern NRHO to a planar LO are demonstrated

A Non-Contact System for Measuring Wrist and Carpal Kinematics

Ligamentous and bone injuries in the wrist affect tens of thousands of adults per year and leads to abnormal function. Surgical procedures as well as physical therapy intended to restorefunction have room for improvement. Measuring wrist kinematics of the small carpal bones is necessary to understand the effect of ligamentous injury during normal motion.Currently there are motion analysis systems that are used to track large scale movementfor total body kinematics such as gait analysis. The accuracy of these systems is catered toward capturing gross movement and cannot precisely measure on the order of millimeters necessary for carpal kinematics. There are some devices currently on the market that can measure the kindematics of a cadaveric wrist, however they either us expensive CT and X-Ray technology, or require physical contact with the specimen that might affect the accuracy of the data obtained. Additionally, these devices cannot measure the continuous motion and only determine the location of wrist and carpal bones at the beginning and end of movement. We propose a non-contact system for measuring wrist kinematics that can accurately and precisely measure the three dimensional movement of the scaphoid and lunate. Three designs for markers were considered; passive, active, and magnetic. Initially we decided active LED markers would be the best option for our project needs. However, after working with active LED markers we determined limitations associated with the markers like wiring that would get in the way of measurement. Thus, we decided to develop passive (not electrical) markers for our system. We created a system of color coded passive markers in order to record three dimensional movement. In addition, we began computational analysis via Matlab to identify the active markers in an image and calculate the distance between them. We have created a three dimensional matrix on Matlab in order to map the movement of each marker. Moving forward we will create an algorithm that can calculate the relative position of these two bones in a three dimensional space. The main deliverables of the product are a working prototype, consisting of a frame and passive markers, and the algorithm that can identify and measure the motion of the markers on a video recording to calculate the wrist kinematics. Thus far progress has been made toward creating the physical working prototype and the algorithm. In the end patents for the finished product and associated algorithm will be necessary.https://scholarscompass.vcu.edu/capstone/1005/thumbnail.jp

Departure and Trajectory Design Applications using Stretching Directions

Stable or nearly stable orbits do not always possess well-distinguished manifold structures that assist in departing from or arriving onto the orbit. Generally, for potential missions, the orbits of interest are nearly stable to reduce the possibility of rapid departure. The stable nature of these orbits also serves as a drawback for insertion or departure from the orbit. The Near Rectilinear Halo Orbits (NRHOs) and the Distant Retrograde Orbits (DROs) offer some potential long-horizon trajectories for exploration missions. The current investigation focuses on leveraging the stretching direction as a tool for departure and trajectory design applications. The magnitude of the state variations along the maximum stretching direction is expected to grow rapidly and, therefore, offers information for efficient departure from the orbit. Similarly, the maximum stretching in reverse time, enables arrival with a minimal maneuver magnitude

DRIFT: Deep Reinforcement Learning for Intelligent Floating Platforms Trajectories

This investigation introduces a novel deep reinforcement learning-based suite to control floating platforms in both simulated and real-world environments. Floating platforms serve as versatile test-beds to emulate microgravity environments on Earth. Our approach addresses the system and environmental uncertainties in controlling such platforms by training policies capable of precise maneuvers amid dynamic and unpredictable conditions. Leveraging state-of-the-art deep reinforcement learning techniques, our suite achieves robustness, adaptability, and good transferability from simulation to reality. Our Deep Reinforcement Learning (DRL) framework provides advantages such as fast training times, large-scale testing capabilities, rich visualization options, and ROS bindings for integration with real-world robotic systems. Beyond policy development, our suite provides a comprehensive platform for researchers, offering open-access at https://github.com/elharirymatteo/RANS/tree/ICRA24

Emulating On-Orbit Interactions Using Forward Dynamics Based Cartesian Motion

The paper presents a novel Hardware-In-the-Loop (HIL) emulation framework of on-orbit interactions using on-ground robotic manipulators. It combines Virtual Forward Dynamic Model (VFDM) for Cartesian motion control of robotic manipulators with an Orbital Dynamics Simulator (ODS) based on the Clohessy Wiltshire (CW) Model. VFDM-based Inverse Kinematics (IK) solver is known to have better motion tracking, path accuracy, and solver convergency than traditional IK solvers. Therefore it provides a stable Cartesian motion for manipulator-based HIL on-orbit emulations. The framework is tested on a ROS-based robotics testbed to emulate two scenarios: free-floating satellite motion and free-floating interaction (collision). Mock-ups of two satellites are mounted at the robots' end-effectors. Forces acting on the mock-ups are measured through an in-built F/T sensor on each robotic arm. During the tests, the relative motion of the mock-ups is expressed with respect to a moving observer rotating at a fixed angular velocity in a circular orbit rather than their motion in the inertial frame. The ODS incorporates the force and torque values on the fly and delivers the corresponding satellite motions to the virtual forward dynamics model as online trajectories. Results are comparable to other free-floating HIL emulators. Fidelity between the simulated motion and robot-mounted mock-up motion is confirmed.Comment: Submitted to ICRA2023, for associated video, see: https://www.youtube.com/watch?v=N2KYCKJ4KM

Intra-operative point-of-procedure delineation of oral cancer margins using optical coherence tomography.

ObjectivesSurgical margin status is a significant determinant of treatment outcome in oral cancer. Negative surgical margins can decrease the loco-regional recurrence by five-fold. The current standard of care of intraoperative clinical examination supplemented by histological frozen section, can result in a risk of positive margins from 5 to 17 percent. In this study, we attempted to assess the utility of intraoperative optical coherence tomography (OCT) imaging with automated diagnostic algorithm to improve on the current method of clinical evaluation of surgical margin in oral cancer.Materials and methodsWe have used a modified handheld OCT device with automated algorithm based diagnostic platform for imaging. Intraoperatively, images of 125 sites were captured from multiple zones around the tumor of oral cancer patients (n = 14) and compared with the clinical and pathologic diagnosis.ResultsOCT showed sensitivity and specificity of 100%, equivalent to histological diagnosis (kappa, ĸ = 0.922), in detection of malignancy within tumor and tumor margin areas. In comparison, for dysplastic lesions, OCT-based detection showed a sensitivity of 92.5% and specificity of 68.8% and a moderate concordance with histopathology diagnosis (ĸ = 0.59). Additionally, the OCT scores could significantly differentiate squamous cell carcinoma (SCC) from dysplastic lesions (mild/moderate/severe; p ≤ 0.005) as well as the latter from the non-dysplastic lesions (p ≤ 0.05).ConclusionThe current challenges associated with clinical examination-based margin assessment could be improved with intra-operative OCT imaging. OCT is capable of identifying microscopic tumor at the surgical margins and demonstrated the feasibility of mapping of field cancerization around the tumor

On the group theoretic structure of a class of quantum dialogue protocols

Intrinsic symmetry of the existing protocols of quantum dialogue are explored. It is shown that if we have a set of mutually orthogonal $n$-qubit states {\normalsize $\{|\phi_{0}>,|\phi_{1}>,....,|\phi_{i}\}$ and a set of $m-qubit$ ($m\leq n$) unitary operators $\{U_{0},U_{2},...,U_{2^{n}-1}\}:U_{i}|\phi_{0}>=|\phi_{i}>$ and $\{U_{0},U_{2},...,U_{2^{n}-1}\}$ forms a group under multiplication then it would be sufficient to construct a quantum dialogue protocol using this set of quantum states and this group of unitary operators}. The sufficiency condition is used to provide a generalized protocol of quantum dialogue. Further the basic concepts of group theory and quantum mechanics are used here to systematically generate several examples of possible groups of unitary operators that may be used for implementation of quantum dialogue. A large number of examples of quantum states that may be used to implement the generalized quantum dialogue protocol using these groups of unitary operators are also obtained. For example, it is shown that GHZ state, GHZ-like state, W state, 4 and 5 qubit Cluster states, Omega state, Brown state, $Q_{4}$ state and $Q_{5}$ state can be used for implementation of quantum dialogue protocol. The security and efficiency of the proposed protocol is appropriately analyzed. It is also shown that if a group of unitary operators and a set of mutually orthogonal states are found to be suitable for quantum dialogue then they can be used to provide solutions of socialist millionaire problem.Comment: 15 page