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Open Access Publications from the University of California

Scholarly Works (14 results)

  • Article
  • Peer Reviewed
Lawrence Berkeley National Laboratory (2009)
    Cover page: Modeling acid-gas generation from boiling chloride brines
    • Thesis
    • Peer Reviewed
    UC Merced Electronic Theses and Dissertations (2021)

    3D reconstruction and semantic mapping are of great importance for many tasks and applications, such as consumer robots, augmented reality, digital heritage, and autonomous vehicles. Despite the drastic advancements in solving the 3D reconstruction problem, it is still challenging to reconstruct accurate 3D models and create semantic maps. Within this dissertation, contributions are made to take steps closer towards optimal 3D reconstruction and semantic mapping.

    It is crucial to have an easy performance evaluation method for advancing 3D mapping systems. Thus, in Chapter 5, we propose dense map posterior (DMP) for 3D reconstruction and mapping performance evaluation that can work without any ground-truth data. With this metric, one can evaluate 3D mapping systems on any public or new data without worrying about the availability of ground-truth data captured by expensive and bulky equipment. We also show that the DMP can be used beyond the evaluation of final results. It can act as a supervisory figure-of-merit signal during 3D reconstruction processes.

    To improve 3D reconstruction results, we propose a novel 3D reconstruction system that corrects surface loops with sparse feature-based bundle adjustment. In the system, fast 3D surface-based loop detection is done by a GPU-accelerated random sample consensus algorithm with optimized randomness supported by fractional calculus, which is in Chapter 3. Then, to solve a low-precision problem in surface loop detection, in Chapter 4, an online method for loop sifting is proposed for real-time feedback to users. For the best 3D reconstruction performance, an offline method for loop sifting and majorization is proposed in Chapter 6. State-of-the-art performance is observed in experiments on public and our datasets.

    In Chapter 7, an exploration of semantic mapping is carried out. A simple and effective real-time 3D semantic mapping method is proposed. In addition, a benchmark suite with a dataset derived from the KITTI dataset and three novel metrics are developed for semantic mapping evaluation.

    Finally, conclusions and future works are presented in the last chapter.

      Cover page: Towards Optimal 3D Reconstruction and Semantic Mapping
      • Article
      LBL Publications (2005)
        Cover page: Use of TOUGHREACT to Simulate Effects of Fluid Chemistry on Injectivity in Fractured Geothermal Reservoirs with High Ionic Strength Fluids
        • Article
        • Peer Reviewed
        UC Merced Previously Published Works (2022)
        This article focuses on a novel three-dimensional reconstruction system that maps large archeological caves using data collected by a small unmanned aircraft system with red, green, and blue-depth cameras. Cave sites often contain the best-preserved material in the archeological record. Yet few sites are fully mapped. Large caves environment usually contains complex geometric structures and objects, which must be scanned with long overlapped camera trajectories for better coverage. Due to the error in camera tracking of such scanning, reconstruction results often contain flaws and mismatches. To solve this problem, we propose a framework for surface loop closure, where loops are detected with a compute unified device architecture accelerated point cloud registration algorithm. After a loop is detected, a novel surface loop filtering method is proposed for robust loop optimization. This loop filtering method is robust to different scan patterns and can cope with tracking failure recovery so that there is more flexibility for unmanned aerial vehicles to fly and record data. We run experiments on public data sets and our cave data set for analysis and robustness tests. Experiments show that our system produces improved results on baseline methods.
          Cover page: Smart three-dimensional processing of unconstrained cave scans using small unmanned aerial systems and red, green, and blue-depth cameras
          • Article
          LBL Publications (2003)
            Cover page: The relationship between the effective matrix diffusion coefficient and test scale
            • Article
            • Peer Reviewed
            LBL Publications (2004)
              Cover page: Modeling reactive geochemical transport of concentrated aqueous solutions in variably saturated media
              • Article
              LBL Publications (2003)
                Cover page: The active fracture model: Its relation to fractal flow patterns and a further evaluation using field observations
                • Article
                LBL Publications (2003)
                  Cover page: Coupled modeling of grounddwater flow solute transport, chemical reactions and microbial processes in the "SP" island
                  • Article
                  LBL Publications (2006)
                  TOUGHREACT (Xu, et al., 2006) is a general-purpose reactive geochemical transport numerical simulator. It deals with multiphase flow, solute transport and geochemical reactions including aqueous complexation, mineral dissolution/precipitation and cation exchange. making use of an extended Debye-Huckel ion activity model, this simulator can handle solutions concentrated to slightly above ~1 molal with caution, and only for NaCl-dominant waters at ionic strengths no greater than ~4 molal. However, brines produced under natural and artificial conditions are often more concentrated. To handle such brines, a pitzer activity model was implemented in TOUGHREACT, based on the standard Harvie-Moller-Weare (HMW) formulation that accounts for all binary and ternary combinations of interaction terms. The vapor-pressure-lowering effect caused by the low water activity in brines was also accounted for by this code. The extended version was verified and tested using published results from laboratory experiments and benchmarked against other computer codes. This new version of TOUGHREACT is being applied to the investigation of boiling and evaporation within and around proposed high-level nuclear waste emplacement tunnels at Yucca Mountain, Nevada. An example application is presented. Processes considered in the example include evaporating of porewater to near dryness, formation of highly concentrated brines, precipitation of deliquescent salts, and generation of acid gases.
                    Cover page: Implementation of a Pitzer Activity Model into TOUGHREACT for Modeling Concentrated Solutions
                    • Article
                    • Peer Reviewed
                    LBL Publications (2022)
                    TOUGHREACT-Brine implements the Pitzer ion activity model into V3.85-OMP and above, taking advantage of all code upgrades since the release of its predecessor version V1.21-Pitzer, including Open-MP parallelization of the geochemical computations, bug fixes, and upgrades to simulate the osmotic flow of water and two-dimensional Poiseuille flow for applications to membrane desalination. Contrarily to the previous standalone V1.21-Pizer version, this “Brine” version has been fully integrated into TOUGHREACT V4.00-OMP, which can be run with or without the Pitzer ion activity model option. In this report, we present: (1) The Pitzer ion-interaction theory and implemented model into TOUGREACT, (2) Input requirements for using the new Brine options, (3) Verification test cases, and (4) Sample problems.
                      Cover page: TOUGHREACT-Brine: Supplement to TOUGHREACT-V4.0-OMP User’s Guide for Modeling Concentrated Solutions and Osmosis Using the Pitzer Ion-Interaction Model
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