Development of Structurally Improved Erosion Control Dam Models for Ecosystem Connection in Mountain Streams

Non-permeable check dams (erosion control dams) have been constructed to serve specific purposes such as water storage, fire control etc. For example, the gravity check dam serves to block the passage of sediments. Numerous tons of sediments, plant material (e.g. dead leaves) etc. accumulate in these non-permeable check dams, thus rapidly degrading the upstream water. There is need to improve on the permeability of check dams by creating ecological corridors in the non-permeable check dams so as to enable upstream to downstream movement of sediments, animals such as fish, amphibians, control pollution etc. to create ecological harmony in the upstream and downstream environments. This study is therefore very important in that it highlights the challenges associated with the use of non-permeable check dams. It was thus necessary to conduct this study so as to ascertain the importance to improved check dam permeability and as well develop cost effective check dam models.   Structural improvement of the existing non-permeable check dams was carried out via demolition, drilling of dam walls to create drainage holes (Φ100 mm pipe in drainage holes replaced with Φ300mm pipes), and this has necessitated the development of improved permeable check dam models with drainage holes that as well serve as ecological corridors. Thus, there is need for improvement of the existing check dams to more ecologically-friendly structures. The required check dam shapes, construction materials and colors depends on the geographical/environmental conditions of the area. In addition, in landslide vulnerable areas with shallow landslides, especially in mountainous valley areas with constructed houses, it`s usually a big challenge to construct large check dams, thus the new model mini-type or membrane type check dams which are less costly, with narrower width and adequate height could best serve in preventing casualties and damages, and enabling harmony with the environment. Constructing these smaller size check dams in areas were landslides are characterized by smaller mass of material movement is thus best suited in such areas as it is cost effective. Keywords: Check dams, dead leaves, ecological corridors, landslide, permeability, structural improvemen

Adaptive Graduated Non-Convexity for Pose Graph Optimization

We present a novel approach to robust pose graph optimization based on Graduated Non-Convexity (GNC). Unlike traditional GNC-based methods, the proposed approach employs an adaptive shape function using B-spline to optimize the shape of the robust kernel. This aims to reduce GNC iterations, boosting computational speed without compromising accuracy. When integrated with the open-source riSAM algorithm, the method demonstrates enhanced efficiency across diverse datasets. Accompanying open-source code aims to encourage further research in this area. https://github.com/SNU-DLLAB/AGNC-PGOComment: 4 pages, 3 figures. Accepted for the workshop on Robotic Perception and Mapping(ROPEM): Frontier Vision & Learning Techniques, organized at the 2023 International Conference on Intelligent Robots and Systems (IROS

Efficient Graduated Non-Convexity for Pose Graph Optimization

We propose a novel approach to Graduated Non-Convexity (GNC) and demonstrate its efficacy through its application in robust pose graph optimization, a key component in SLAM backends. Traditional GNC methods often rely on heuristic methods for GNC schedule, updating control parameter {\mu} for escalating the non-convexity. In contrast, our approach leverages the properties of convex functions and convex optimization to identify the boundary points beyond which convexity is no longer guaranteed, thereby eliminating redundant optimization steps in existing methodologies and enhancing both speed and robustness. We show that our method outperforms the state-of-the-art method in terms of speed and accuracy when used for robust back-end pose graph optimization via GNC. Our work builds upon and enhances the open-source riSAM framework. Our implementation can be accessed from: https://github.com/SNU-DLLAB/EGNC-PGOComment: 6 pages, 6 figure

Accelerated identification of equilibrium structures of multicomponent inorganic crystals using machine learning potentials

The discovery of new multicomponent inorganic compounds can provide direct solutions to many scientific and engineering challenges, yet the vast size of the uncharted material space dwarfs current synthesis throughput. While the computational crystal structure prediction is expected to mitigate this frustration, the NP-hardness and steep costs of density functional theory (DFT) calculations prohibit material exploration at scale. Herein, we introduce SPINNER, a highly efficient and reliable structure-prediction framework based on exhaustive random searches and evolutionary algorithms, which is completely free from empiricism. Empowered by accurate neural network potentials, the program can navigate the configuration space faster than DFT by more than 10$^{2}$-fold. In blind tests on 60 ternary compositions diversely selected from the experimental database, SPINNER successfully identifies experimental (or theoretically more stable) phases for ~80% of materials within 5000 generations, entailing up to half a million structure evaluations for each composition. When benchmarked against previous data mining or DFT-based evolutionary predictions, SPINNER identifies more stable phases in the majority of cases. By developing a reliable and fast structure-prediction framework, this work opens the door to large-scale, unbounded computational exploration of undiscovered inorganic crystals.Comment: 3 figure

Heating Experiment of CNT Cementitious Composites with Single-Walled and Multiwalled Carbon Nanotubes

Carbon nanotubes (CNTs) are a primary nanomaterial that have outstanding physical and mechanical characteristics, and CNTs can be combined with cement-based materials to alter their heating characteristics. In this study, the types of CNTs used were multiwalled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs). Experiments were performed to determine the altered heating characteristics of the CNT cement mortars. The parameters of the experiment were CNT type, CNT content, curing age, and applied voltage. The results for the different CNT cement mortars indicate that mixing SWCNTs with water to produce CNT cement mortars was more effective for modifying the heating characteristics compared to mixing MWCNTs with water. In addition, field emission scanning electron microscope (FE-SEM) images supported the results found in the heating experiments

Capella: A Space-only High-frequency Radio VLBI Network Formed by a Constellation of Small Satellites

Very long baseline radio interferometry (VLBI) with ground-based observatories is limited by the size of Earth, the geographic distribution of antennas, and the transparency of the atmosphere. In this whitepaper, we present Capella, a tentative design of a space-only VLBI system. Using four small (<500 kg) satellites on two orthogonal polar low-Earth orbits, and single-band heterodyne receivers operating at frequencies around 690 GHz, the interferometer is able to achieve angular resolutions of approximately 7 microarcsec. Within a total observing time of three days, a near-complete uv plane coverage can be reached, with a 1-sigma point source sensitivity as good as about 6~mJy for an instantaneous bandwidth of 1 GHz. The required downlink data rates of >10 Gbps can be reached through near-infrared laser communication; depending on the actual downlink speed, one or multiple ground communication stations are necessary. We note that all key technologies required for the Capella system are already available, some of them off-the-shelf. Data can be correlated using dedicated versions of existing Fourier transform (FX) software correlators; dedicated routines will be needed to handle the effects of orbital motion, including relativistic corrections. With the specifications assumed in this whitepaper, Capella will be able to address a range of science cases, including: photon rings around supermassive black holes; the acceleration and collimation zones of plasma jets emitted from the vicinity of supermassive black holes; the chemical composition of accretion flows into active galactic nuclei through observations of molecular absorption lines; mapping supermassive binary black holes; the magnetic activity of stars; and nova eruptions of symbiotic binary stars - and, like any substantially new observing technique, has the potential for unexpected discoveries.Comment: 18 pages, 2 figures, 1 table. Whitepaper version 1.0. Living document, will be updated when necessar