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1. Realtime visual-inertial SLAM integrated with radar data to triangulate targets

   https://doi.org/10.1117/12.2618897  

   Girard, Joshua; Huston, Dryver; Burns, Dylan; Xia, Tian (May 2022, SPIE Virtual, Augmented, and Mixed Reality (XR) Technology for Multi-Domain Operations III)

   Dennison, Mark S.; Krum, David M.; Sanders-Reed, John; Arthur, Jarvis (Ed.)

   This paper presents research concerning the use of visual-inertial Simultaneous Localization And Mapping (SLAM) algorithms to aid in Continuous Wave (CW) radar target mapping. SLAM is an established field in which radar has been used to internally contribute to the localization algorithms. Instead, the application in this case is to use SLAM outputs to localize radar data and construct three-dimensional target maps which can be viewed live in augmented reality. These methods are transferable to other types of radar units and sensors, but this paper presents the research showing how the methods can be applied to calculate depth efficiently with CW radar through triangulation using a Boolean intersection algorithm. Localization of the radar target is achieved through quaternion algebra. Due to the compact nature of the SLAM and CW devices, the radar unit can be operated entirely handheld. Targets are scanned in a free-form manner where there is no need to have a gridded scanning layout. The main advantage to this method is eliminating many hours of usage training and expertise, thereby eliminating ambiguity in the location, size and depth of buried or hidden targets. Additionally, this method grants the user the additional power, penetration and sensitivity of CW radar without the lack of range finding. Applications include pipe and buried structure location, avalanche rescue, structural health monitoring and historical site research. 

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2. Incorporation of Digital Modulation into Vital Sign Detection and Gesture Recognition Using Multimode Radar Systems

   https://doi.org/10.3390/s23187675  

   Brown, Michael C.; Li, Changzhi (September 2023, Sensors)

   The incorporation of digital modulation into radar systems poses various challenges in the field of radar design, but it also offers a potential solution to the shrinking availability of low-noise operating environments as the number of radar applications increases. Additionally, digital systems have reached a point where available components and technology can support higher speeds than ever before. These advancements present new avenues for radar design, in which digitally controlled phase-modulated continuous wave (PMCW) radar systems can look to support multiple collocated radar systems with low radar-radar interference. This paper proposes a reconfigurable PMCW radar for use in vital sign detection and gesture recognition while utilizing digital carrier modulation and compares the radar responses of various modulation schemes. Binary sequences are used to introduce phase modulation to the carrier wave by use of a field programable gate array (FPGA), allowing for flexibility in the modulation speed and binary sequence. Experimental results from the radar demonstrate the differences between CW and PMCW modes when measuring the respiration rate of a human subject and in gesture detection. 

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3. Localization and tracking of stationary users for augmented reality

   https://doi.org/10.1007/s00371-023-02777-2  

   Baker, Lewis; Ventura, Jonathan; Langlotz, Tobias; Gul, Shazia; Mills, Steven; Zollmann, Stefanie (February 2023, The Visual Computer)

   In augmented reality applications it is essential to know the position and orientation of the user to correctly register virtual 3D content in the user’s field of view. For this purpose, visual tracking through simultaneous localization and mapping (SLAM) is often used. However, when applied to the commonly occurring situation where the users are mostly stationary, many methods presented in previous research have two key limitations. First, SLAM techniques alone do not address the problem of global localization with respect to prior models of the environment. Global localization is essential in many applications where multiple users are expected to track within a shared space, such as spectators at a sporting event. Secondly, these methods often assume significant translational movement to accurately reconstruct and track from a local model of the environment, causing challenges for many stationary applications. In this paper, we extend recent research on Spherical Localization and Tracking to support relocalization after tracking failure, as well as global localization in large shared environments, and optimize the method for operation on mobile hardware. We also evaluate various state-of-the-art localization approaches, the robustness of our visual tracking method, and demonstrate the effectiveness of our system in real-life scenarios. 

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4. Radarize: Enhancing Radar SLAM with Generalizable Doppler-Based Odometry

   https://doi.org/10.1145/3643832.3661871  

   Sie, Emerson; Wu, Xinyu; Guo, Heyu; Vasisht, Deepak (June 2024, ACM MobiSys 2024)

   Millimeter-wave (mmWave) radar is increasingly being considered as an alternative to optical sensors for robotic primitives like simultaneous localization and mapping (SLAM). While mmWave radar overcomes some limitations of optical sensors, such as occlusions, poor lighting conditions, and privacy concerns, it also faces unique challenges, such as missed obstacles due to specular reflections or fake objects due to multipath. To address these challenges, we propose Radarize, a self-contained SLAM pipeline that uses only a commodity single-chip mmWave radar. Our radar-native approach uses techniques such as Doppler shift-based odometry and multipath artifact suppression to improve performance. We evaluate our method on a large dataset of 146 trajectories spanning 4 buildings and mounted on 3 different platforms, totaling approximately 4.7 Km of travel distance. Our results show that our method outperforms state-of-the-art radar and radar inertial approaches by approximately 5x in terms of odometry and 8x in terms of end-to end SLAM, as measured by absolute trajectory error (ATE), without the need for additional sensors such as IMUs or wheel encoders. 

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5. Can early weaning calves of first-calf heifers improve long-term herd and financial performance in a vertically-integrated beef production system? A case-study application using system dynamics.

   https://doi.org/https://doi.org/10.15232/aas.2021-02235  

   Taylor, J.K. (March 2022, Applied animal science)

   Objectives: The objectives were to (a) evaluate whether marginal reproductive gains from early weaning (EW) calves of first-calf replacement heifers extend throughout the animal’s productive life and (b) compare via cost–benefit analysis EW with conventional weaning (CW) practices on a vertically integrated ranch in Florida, USA. Materials and Methods: A system dynamics model was developed to evaluate CW versus EW of calves from replacement heifers that calve in the first 21 or 42 d of the calving season. A combination of sensitivity analyses and deterministic management tests (EW vs. CW and 21- vs. 42-d calving seasons) were simulated and compared across a range of 18 production and financial metrics, including net present value, over the useful life of one generation of replacement heifers. We hypothesized that EW calves from replacement heifers would improve reproductive performance, resulting in greater total calves produced and, therefore, improved cow-calf and whole-system profitability. Results and Discussion: The 42-d calving criteria for EW created significant production and financial gains and outperformed the 21-d calving criteria. Counterintuitively, these gains did not arise in the cow-calf or feedyard segments (which saw financial declines) but in the stocker segment due to more efficient livestock gains facilitated by lower weaning weights of incoming calves. Sensitivity analyses corroborated these trade-offs. Feedyard sale price (i.e., value received for finished cattle) was the most influential factor influencing whole-system profitability. Implications and Applications: Trade-offs and incentives between enterprises may provide misleading feedback and mask changes that improve the system as a whole (e.g., EW reduced calf weaning weights and reinforced the reproductive performance pressure on management; gains at the stocker segment may mask EW benefits at the cow-calf level, making the cow-calf enterprise more reliant on short-term adjustments, a behavior known as “shifting the burden”). 

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