Performance Improvement in Automated Directional-Antenna Steering Toward Unmanned High-Altitude Balloons

The purpose of this study was to determine the conditions of the extrusion process which gave a maximum value of intrinsic viscosity response. The 2k factorial design was used to determine the effect of temperature, screw speed and pH on intrinsic viscosity and determine the accuracy of the first-order polynomial model. The temperature treatment, screw speed and pH of alginate extraction extrusion process have a significant influence on intrinsic viscosity. The maximum intrinsic alginate viscosity value of 416.16 ml/g occured under conditions of extrusion process temperature of 60oC, screw speed 75 rpm and pH 10. Quadratic first-order polynomial model, planning of research center temperature 60oC, screw speed of 75 rpm and pH 10 were appropriate.

Optimization of rhamnolipid biosurfactant production by mangrove sediment bacterium Pseudomonas aeruginosa KVD-HR42 using response surface methodology

In satellite navigation systems such as the Global Positioning System, clock error is one of the major sources of error in precise pointing. In order to remove clock error, it is modeled as a second-order polynomial and the clock-error correction parameters are sent to users. However, a random clock error cannot be modeled as a second-order polynomial. Therefore, the time discrepancies due to random clock error must be taken into consideration for precise pointing. This paper proposes an analytical computation method for estimating the random clock error in the current system which makes use of the Allan variance characteristics of random clock error without random clock realization and a lot of simulation studies. Moreover, a numerical example based on the proposed method shows that the first-order polynomial model is better for predicting a random clock error than the second-order polynomial.

Physicists seek to uncover expansion history of the universe by examining polarization patterns in the cosmic microwave background (CMB). Observatories in the South Pole are used to examine these polarization patterns, but no sucient celestial source exists to properly calibrate these observatories. A method of calibrating these observatories would be to point a tuned microwave source to the ground-based observatory from a far distance. The purpose of this paper is to outline how the McGill High-Altitude Balloon (McHAB) team intends to use a high-altitude balloon with a reaction wheel actuator to slew and point the payload at altitudes of 15km to 20km to within an accuracy of ±2°. A complementary filter with an inertial measurement unit (IMU) will be used to estimate the attitude of the payload. A proportional-derivative controller will be used to control the reaction wheel, and hence point the payload to a desired angle. The main processor will be a Raspberry Pi, a single-board computer using a single-core 700MHz ARMv6 CPU. The team has previously own a payload, McHAB-1, containing the Raspberry Pi and an IMU to test the attitude estimator and collect attitude data. The team has own a complete prototype of the system, McHAB-2, on April 28th, 2013. Data from this flight is presented showing that the reaction wheel can better point the system as the platform reaches higher altitudes.

: One of the questions most frequently asked by scientists/ experimenters who design balloon payloads concerns the magnitude of the opening forces of the parachute recovery system. Existing theory and an analytical method recently developed for horizontal deployment are adapted to balloon systems requirements. Engineering methods are used to develop expressions which allow the assessment of the parachute opening forces.

This chapter was written by Martin P. Dana, Raytheon Systems, Retired State estimation as it relates to object tracking is an important element of Level 1 fusion. While many facets of this topic were introduced in Chapter 3, here we delve further into several areas that are critical to the implementation of modern multi-sensor tracking systems that incorporate data fusion as part of the state-estimation process. These include discussions of the general design approaches and implementations for several of the fundamental elements of a radar tracking logic. Signal and data processing found in a radar tracker may need to account for the unique characteristics of measurement data, state estimates (tracks), or both depending on the output of the radar subsystems. The design must also incorporate measures of quality for tracking and tracker performance, and the ability to measure and account for sensor registration errors that exist in a multi-sensor tracking system. Other issues addressed in the chapter include the transformation of radar measurements from a local coordinate system into a system-level or master coordinate system, standard and extended Kalman filters, track initiation in clutter, state estimation using interacting multiple models, and the constraints often placed upon architectures that employ multiple radars for state estimation.

A total solar eclipse provides an opportunity to observe, quantify, and conduct experiments involving a number of unique meteorological and environmental conditions and phenomena, and the means to develop a more detailed understanding of the atmospheric variables at play during a rarely observed cosmic occurrence. High altitude ballooning is particularly suited for collecting data during an eclipse, although a number of logistical and procedural challenges are associated with launching during totality. The members of the University of Maryland, College Park Balloon Payload Program, funded by the Maryland Space Grant Consortium, traveled to South Carolina to launch a number of experimental and observational payloads during the total eclipse of August 21, 2017. This paper describes the balloon flight, launch procedures, associated challenges, and payload data, thereby providing a window into the variety of valuable engineering design expertise and hands-on skills developed through this student-run initiative.

Directional phase array antenna (PAA) has emerged as one of the most promising technologies to provide a fundamental breakthrough in mobile ad hoc network capacity. Compared to omni-directional antennas, the narrow beams of PAA provide high-gain high-rate links with longer range, low probability of detection (LPD), low probability of interception (LPI) and anti-jamming (AJ) properties. These desirable properties make directional networking technology an ideal candidate to support information superiority in future combat communication systems. However, the directionality of RF beam raises significant network protocol design challenges that rarely occur in networks with omni-directional antennas. A fundamental issue is that, in order to communicate, the sender and receiver have to point their antennas at each other at the moment of communication. This is a challenging task considering the highly dynamic battlefield environment and the absence of a global information database in practical applications. To solve this problem, we propose a mobility prediction scheme that can provide accurate node position information at the time of a directional link communication by closely tracking node movement. Specifically, we suggest a practical mobility model that is suitable for battlefield environment. Based on a node's mobility model, our mobility prediction algorithm calculates future positions using parameters specified by the mobility model. An error correction filter is further applied to the prediction results to remove system and other consistent errors. The filter is an exponentially-weighted moving average filter continuously trained by measurement update. We validated our mobility prediction algorithm via simulations and analytical calculations. The results showed that our algorithm is capable of tracking node movement in a highly dynamic battlefield environment and thus can serve as a key enabling technology in directional networking

The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) is an 8-meter baseline far-infrared interferometer designed to fly on a high altitude balloon. BETTII uses a double-Fourier Michelson interferometer to simultaneously obtain spatial and spectral information on science targets; the long baseline provides subarcsecond angular resolution, a capability unmatched by any other far-infrared facilities. BETTII had its first successful engineering flight in June 2017. The pointing loop on BETTII is based on an Extended Kalman Filter, which uses different sensors and actuators to keep the telescope pointed at the desired target star. In order to achieve high precision pointing, we use an embedded Field-programmable gate array (FPGA) that combines the gyroscope and star cameras information to generate a pointing solution every 10 milliseconds. The BETTII control system serves a critical function in making interferometric observations possible. This paper discusses the design and implementation of the BETTII control system and presents engineering data of the attitude control system from our pre-flight tests at the Columbia Scientific Balloon Facility (CSBF) and data from our first 12-hour flight from Palestine, TX. This includes pointing performance of the Kalman Filter estimator in the RA, DEC and ROLL Equatorial Coordinate System as well as the payload’s attitude behavior when switching between the different modes we implemented: Safe, Brake, Slew, Track and Acquire. These modes are part of the procedure to point the telescope to a desired target. We discuss the performance of the payload’s control system in each of these modes and present data showing how the azimuth actuators follow the position and velocity profiles calculated by the flight computers.

The NASA Radiation Dosimetry Experiment (RaD-X) stratospheric balloon flight mission, launched on 25 September 2015, provided dosimetric measurements above the Pfotzer maximum. The goal of taking these measurements is to improve aviation radiation models by providing a characterization of cosmic ray primaries, which are the source of radiation exposure at aviation altitudes. The RaD-X science payload consists of four instruments. The main science instrument is a tissue-equivalent proportional counter (TEPC). The other instruments consisted of three solid state silicon dosimeters: Liulin, Teledyne total ionizing dose (TID) and RaySure detectors. The instruments were housed in an aluminum structure protected by a foam cover. The structure partially shielded the detectors from cosmic rays but also created secondary particles, modifying the ambient radiation environment observed by the instruments. Therefore, it is necessary to account for the influence of the payload structure on the measured doses. In this paper, we present the results of modeling the effect of the balloon payload on the radiation detector measurements using a Geant-4 (GEometry ANd Tracking) application. Payload structure correction factors derived for the TEPC, Liulin, and TID instruments are provided as a function of altitude. Overall, the payload corrections are no more than a 7% effect on the radiation environment measurements.

Large stratospheric balloons are the easiest access to near space. Large long duration balloons (LDBs) can float in the stratosphere for weeks collecting measurements (e.g., astrophysical or geophysical data) or samples (e.g., contaminants, volcanic ash, micrometeorites). The recovery of data media and samples is a common problem in this type of experiment because direct radio communication becomes useless when the balloon crosses the horizon, and satellite links are too slow and expensive. For this reason, physical recovery of the payload is mandatory to obtain experimental results, which is a difficult task, especially in polar regions. The goal of HERMES (HEmera Returning MESsenger) is to allow researchers to obtain experimental data prior to payload recovery. HERMES is a system equipped with an autonomous glider capable of physically transporting data and samples from the stratosphere to a recovery point on the ground. The glider is installed on the balloon payload via a remotely controlled release system and is connected to the main computer to store a copy of the scientific data and to receive the geographic coordinates of the recovery point. This allows scientists to obtain experimental results before recovering the payload. The article describes HERMES and the first experimental flight of the entire system, which was conducted at Esrange Space Center (Kiruna, Sweden) in July 2022.

Recently a class of new in-vehicle technologies based on off-the-shelf mobile devices have been developed to improve driving safety and experience. For instance, wearables like the smartwatches are utilized to monitor the action of the driver and detect possible secondary tasks. Moreover, wearables can allow a driver to use gesture for in-vehicle controls, reducing distractions to driving. The accuracy of these systems can be significantly improved by tracking the real-time attitude of mobile devices. This paper proposes a novel system called Real-time Attitude and Motion Tracking (RAMT) that can enable a mobile device to accurately learn the coordinate system of a moving vehicle, and hence track its attitude and motion in real time. RAMT consists of a series of lightweight algorithms to sense the vehicle's movement and calculate the device's attitude. It provides a solution for trajectory-based gesture recognition. We have implemented RAMT on a smartphone and a smartwatch and evaluated the performance in 10 real driving trips. Our results show that the overall error of the coordinate system alignment is around 5° for the smartphone and 10° for the smartwatch, and over 84% of customized hand gestures can be accurately recognized with the result of RAMT. A video demo of RAMT is available at https://youtu.be/9rZp7HxyRts.

XMR systems are a new type of interventional facility in which patients can be rapidly transferred between x-ray and MR systems on a floating table. We have previously developed a technique to register MR and x-ray images obtained from such systems. We are carrying out a program of XMR guided cardiac electrophysiology study (EPS) and radio frequency ablation (RFA). The aim of our work was to apply our registration technology to XMR guided EPS/RFA in order to integrate anatomical, electrophysiological and motion information. This would assist in guidance and allow us to validate and refine electromechanical models. Registration of the imaging modalities was achieved by a combination of system calibration and real-time optical tracking. Patients were initially imaged using MR imaging. An SSFP volume scan of the heart was acquired for anatomical information, followed by tagged scans for motion information. The patients were then transferred to the x-ray system. Tracked biplane x-ray images were acquired while electrical measurements were made from catheters placed in the heart. The relationship between the MR and x-ray images was determined. The MR volume scan of the heart was segmented and the tagged scans were analysed using a non-rigid registration algorithm to compute motion. The position of catheters was reconstructed within the MR cardiac anatomy. The anatomical, electrophysiological, and motion information were displayed in the same coordinate system. Simulations of electrical depolarisation and contraction were performed using electromechanical models of the myocardium. We present results for 2 initial cases. For patient 1, a contact mapping system was used for the EPS and for patient 2, a non-contact mapping system was used. Our XMR registration technique allows the integration of anatomical, electrophysiological, and motion information for patients undergoing EPS/RFA. This integrated approach has assisted in interventional guidance and has been used to validate electromechanical models of the myocardium.

The present investigation focuses on disintegration kinetics of wet-strength tissue paper in various termo-alkaline and chemical conditions of batch low-consistency repulping process. As chlorine-free repulping aids, we applied sodium persulfate in its original state and in combination with peroxy activator (chemically activated form of sodium persulfate). Based on a first-order kinetic model, we estimated the influence of repulping conditions on the intensity of wet-strength paper defiberization process by the disintegration rate constant kd. The values of kd were found by linear least-squares curve fitting of the experimental data in the t, ln (F'/100) coordinate system, where F' is non-disintegrated or non-defibrated portion of paper, t – repulping time. The results have shown that the termo-alkaline repulping of wet-strength tissue paper (T=60 °C, pH=10.5) compared with mild conditions of repulping (T=40 °C, pH=8.5) leads to an increase of the rate constant of disintegration kd from 5.6·10-3 min-1 to 9.7·10-3 min-1. Addition of 2% persulfate at termo-alkaline repulping increases the rate constant of disintegration kd up to 14,0·10-3 min-1. Application of chemically activated persulfate under the same conditions allows to further increase the kd up to 23.4·10-3 min-1. Raising the temperature and pH of the pulp during persulfate repulping increases the disintegration rate constant kd nonlinearly. Finally, addition of persulfate along with thermo-alkaline pulp treatment lead to decline repulping time and energy by 31% and 29%. It should be noted, that more significant savings of time and energy (57% and 59% respectively) we found at the application of persulfate in a chemically activated form.

To develop a real-time automatic method for tracking implanted radiographic markers in low-contrast cine-MV patient images used in image-guided radiation therapy (IGRT). Intrafraction motion tracking using radiotherapy beam-line MV images have gained some attention recently in IGRT because no additional imaging dose is introduced. However, MV images have much lower contrast than kV images, therefore a robust and automatic algorithm for marker detection in MV images is a prerequisite. Previous marker detection methods are all based on template matching or its derivatives. Template matching needs to match object shape that changes significantly for different implantation and projection angle. While these methods require a large number of templates to cover various situations, they are often forced to use a smaller number of templates to reduce the computation load because their methods all require exhaustive search in the region of interest. The authors solve this problem by synergetic use of modern but well-tested computer vision and artificial intelligence techniques; specifically the authors detect implanted markers utilizing discriminant analysis for initialization and use mean-shift feature space analysis for sequential tracking. This novel approach avoids exhaustive search by exploiting the temporal correlation between consecutive frames and makes it possible to perform more sophisticated detection at the beginning to improve the accuracy, followed by ultrafast sequential tracking after the initialization. The method was evaluated and validated using 1149 cine-MV images from two prostate IGRT patients and compared with manual marker detection results from six researchers. The average of the manual detection results is considered as the ground truth for comparisons. The average root-mean-square errors of our real-time automatic tracking method from the ground truth are 1.9 and 2.1 pixels for the two patients (0.26 mm/pixel). The standard deviations of the results from the 6 researchers are 2.3 and 2.6 pixels. The proposed framework takes about 128 ms to detect four markers in the first MV images and about 23 ms to track these markers in each of the subsequent images. The unified framework for tracking of multiple markers presented here can achieve marker detection accuracy similar to manual detection even in low-contrast cine-MV images. It can cope with shape deformations of fiducial markers at different gantry angles. The fast processing speed reduces the image processing portion of the system latency, therefore can improve the performance of real-time motion compensation.