Development of a Numeric Predictor-Corrector Aerocapture Guidance for Direct Force Control

Direct force control, where the angle of attack and sideslip angle are modulated, has been proposed as an alternative to bank angle control for aero-assist maneuvers. This paper reimplements the current state-of-the-art aerocapture guidance for bank angle control, Fully Numeric Predictor-corrector Aerocapture Guidance (FNPAG), for direct force control. The optimal control theory underlying the structure of FNPAG is shown to not be applicable to the direct force control approach. Several solution structures for the longitudinal channel are compared by simulating dispersed three-degree-of-freedom trajectories for a reference mission consisting of a low lift-to-drag vehicle and a highly elliptical, 1-sol target orbit around Mars. The equations of motion for the lateral channel are derived, and a controller is designed to target a specified orbital plane. Finally, a Monte Carlo is used to demonstrate the performance of the new guidance

Utilizing plant genetic resources for pre-breeding of water-efficient sorghum: genetics of the limited transpiration trait

Includes bibliographical references.2022 Fall.Shifting precipitation patterns driven by the changing climate threaten productivity of dryland agricultural systems. Increasing the efficiency of water use by crops grown in dryland regions, such as sorghum (Sorghum bicolor), is a target for plant breeding to address this issue. c variants conferring efficient water use in sorghum may be found within collections of plant genetic resources (PGR). However, tropical sorghum PGR require adaptation to the target temperate environment to begin the pre-breeding trait discovery process. The landmark Sorghum Conversion Program unlocked diverse sorghum genetics for temperate breeding by adapting tropical African lines to temperate height and maturity standards. In the U.S. Sorghum Belt, spanning South Dakota to central Texas, the limited transpiration (LT) trait could provide growers a 5% yield increase in water-limited conditions with high vapor pressure deficit (VPD) according to crop modeling. To transfer the LT trait into commercial breeding programs, an elite donor line must be developed. Characterizing the genetic architecture of LT informs markers and breeding strategy for development of an elite donor. To characterize the genetic architecture of LT, two biparental recombinant inbred line (RIL) mapping families were developed from crossing putative LT parents SC979 and BTx2752 by putative non-LT parent RTx430. For this study, the families were grown together as a mapping population in three locations (continental-humid eastern Kansas, semi-arid western Kansas, and semi-arid Colorado) in one year. The families were phenotyped for the LT trait using UAS- collected thermal imaging and canopy temperature as a proxy. The families were initially designed with the goal of controlling phenotypic covariates of canopy temperature associated with height and flowering time, like neighbor-shading and artifactual temperature inflation related to panicle imaging. To test whether the family design controlled for height and flowering time covariates, the populations were phenotyped for both traits. High broad-sense heritability (H2) > 0.86 for all traits and families across locations indicates that the traits are not fixed. However, phenotypic distributions reveal that most lines are within an agronomically-relevant range that limits confounding covariates. Using DArTseq-LD genotyping data, GWAS analyses of height and flowering time reveal putatively significant marker-trait associations (MTA) with known loci underlying height and maturity in sorghum. These results collectively indicate that, while genetic variation for height and flowering exist in the LT mapping families, the resulting phenotypes are homogeneous enough to be suitable for LT genetic mapping. To test hypotheses on the monogenic, oligogenic, or polygenic architecture of the LT trait, canopy temperature data collected by the UAS-thermal imaging missions was used. Non-zero H2 of canopy temperature in most location-timepoints indicates genetic variation is present for LT in the population. Continuous phenotypic distributions imply a quantitative architecture. GWAS analyses revealed moderate marker-trait association peaks visible within timepoints and across locations, indicating oligogenic architecture of LT. Some of those peaks also colocalize with sorghum homologs of aquaporin genes in Arabidopsis thaliana, suggesting that aquaporin variation could be a molecular basis underlying the trait. These results provide a basis for marker-assisted selection in developing an LT donor line

Mid-Lift-To-Drag Ratio Rigid Vehicle 6-DOF EDL Performance Using Tunable Apollo Powered Guidance

The Mid-Lift-to-Drag ratio Rigid Vehicle (MRV) is a candidate in the NASA multi-center effort to determine the most cost effective vehicle to deliver a large-mass payload to the surface of Mars for a human mission. Products of this effort include six-degree-of-freedom (6DoF) entry-to-landing trajectory performance studies for each candidate vehicle. These high fidelity analyses help determine the best guidance and control (G&C) strategies for a feasible, robust trajectory. This paper presents an analysis of the MRV's G&C design by applying common entry and descent associated uncertainties using a Fully Numerical Predictor-corrector Entry Guidance (FNPEG) and tunable Apollo powered descent guidance

Comparison of Aerocapture Performance Using Bank Control and Direct Force Control with Two Human-Scale Vehicles at Mars

Recent studies of human-scale missions to Mars have included a wide trade space of vehicle configurations and control schemes. Some configurations fly at a low angle of attack with a low L/D,while others fly at a high angle of attack with a mid L/D. Some use bank angle control, while others use direct force control, where the angle of attack and sideslip angle are independently modulated. This paper compares the performance of three vehicle configurations: a low-L/D vehicle using direct force control, a low-L/D vehicle using bank control, and a mid-L/D vehicle using bank control. The reference mission is aerocapture at Mars into a highly elliptical, 1-sol orbit. The trajectories are integrated in three degrees of freedom. All three cases utilize numeric predictor-corrector guidances and emulate control system responses with rate and acceleration limits. The configurations are compared using a Monte Carlo analysis. The robustness of each configuration to increased dispersions is also compared

Complessità. Le organizzazioni ambidestre tra routine e cigni neri

Le organizzazioni sono come gli ossimori. Le organizzazioni si muovono tra elementi costanti ed elementi variabili, fino a trovare un giusto bilanciamento. La teoria organizzativa fornisce per lo più spunti di riflessione su come concepire le organizzazioni basate su elementi di regolarità e sulle loro ripetizioni. Compito ancora più arduo, pertanto, appare essere quello di definire e analizzare tutte le forze che interagiscono e influenzano le modalità organizzative, siano esse interne o esterne, costruttive o distruttive, espressione di regolarità o di eccezionalità. È possibile, quindi, che la strutturazione delle organizzazioni si muova, anche, tra routine organizzative e «cigni neri» (Taleb, 2007)? Gli eventi inaspettati, unici o comunque di frequenza bassissima, sono «incognite sconosciute» che, nonostante i piani e le precauzioni poste in essere, prendono le organizzazioni di sorpresa e le possono portare anche a conseguenze catastrofiche (Green, 2011). L’inatteso (Weick & Sutcliffe, 2007) impatta sulle organizzazioni minando i percorsi di conoscenza, ridefinendo le competenze necessarie e le finalità generali o specifiche. Le imprese devono tendere a sviluppare la capacità di impiegare efficacemente le risorse e le attività esistenti; al pari, devono percorrere nuove strade affinché l’impensabile non annulli le basi del proprio vantaggio competitivo. Sebbene classificato come sotto-teorizzato, poco compreso dal punto di vista operativo e sottoconcettualizzato, l’ambidestrismo organizzativo (Tushman, M. L., & O’Reilly, C. A.,1996; Birkinshaw, J., & Gibson, C., 2004; Raisch, S., & Birkinshaw, J., 2008) è – o dovrebbe essere – l’obiettivo ultimo delle organizzazioni. Ambidestrismo innato e radicato nelle competenze delle persone che animano le organizzazioni. Ambidestrismo ricercato, al tempo stesso

Ambidexterity: a possible balance to manage Complexity

The present article originates from the effort to answer the following question: is it possible for an organizational structure to steer between organizational routines and Black Swans? (Taleb, 2007). Unexpected, unique and low-frequency events are “unknown variable” that, despite the planning and precautions deployed, catch an organization off-guard, and might have catastrophic consequences. Unexpected events impact organizations, undermining the knowledge and redefining the list of competences that an organization needs in order to be competitive. The main goal of the present article is to shed light on the role and the challenges that firms undertake in their defining moments of adaptation of their organizational assets – the structure –. The rational pattern of adaptation is exemplified by the use of ambidextrous organizational structures, which focus on activities that can be defined as exploration and exploitation. Within the analysis of “the science of complexity”, parallels, paradoxes and metaphors representing a synthesis of a largely shared doctrine will be investigated: firms need to utilize known variables, or sometimes unknown ones, that are inevitably complex, in order to find the right fit, react swiftly to change, successfully compete, and obtain results

Quality changes in fresh chives (Allium Schoenoprasum L.) during refrigerated storage

This study investigates quality changes in fresh chives stored at 0 and 4C during 21 and 14 days, respectively. The product was packaged in trays and covered with polyvinyl chloride films. Weight loss, surface color, total chlorophyll, carotenoids, reducing sugars and browning potential were evaluated in order to determine shelf life at each temperature. In addition, internal atmosphere composition, total phenolics, radical scavenging activity and ascorbic acid content were measured for samples stored at 0C. Results showed that surface color change and losses of green pigments and reducing sugar content could be delayed for a week by storing fresh chives at 0C. The increase in browning potential was of lower magnitude at 0C than at 4C. High quality levels and marketability of fresh chives could be maintained for 2 weeks at 0C.Facultad de Ciencias Agrarias y ForestalesCentro de Investigación y Desarrollo en Criotecnología de Alimento

Ground state solution of Bose-Einstein condensate by directly minimizing the energy functional

In this paper, we propose a new numerical method to compute the ground state solution of trapped interacting Bose-Einstein condensation (BEC) at zero or very low temperature by directly minimizing the energy functional via finite element approximation. As preparatory steps we begin with the 3d Gross-Pitaevskii equation (GPE), scale it to get a three-parameter model and show how to reduce it to 2d and 1d GPEs. The ground state solution is formulated by minimizing the energy functional under a constraint, which is discretized by the finite element method. The finite element approximation for 1d, 2d with radial symmetry and 3d with spherical symmetry and cylindrical symmetry are presented in detail and approximate ground state solutions, which are used as initial guess in our practical numerical computation of the minimization problem, of the GPE in two extreme regimes: very weak interactions and strong repulsive interactions are provided. Numerical results in 1d, 2d with radial symmetry and 3d with spherical symmetry and cylindrical symmetry for atoms ranging up to millions in the condensation are reported to demonstrate the novel numerical method. Furthermore, comparisons between the ground state solutions and their Thomas-Fermi approximations are also reported. Extension of the numerical method to compute the excited states of GPE is also presented.Comment: 33 pages, 22 figure

Angle of Attack Modulation for Mars Entry Terminal State Optimization

From the perspective of atmospheric entry, descent, and landing (EDL), one of the most foreboding destinations in the solar system is Mars due in part to its exceedingly thin atmosphere. To benchmark best possible scenarios for evaluation of potential Mars EDL system designs, a study is conducted to optimize the entry-to-terminal-state portion of EDL for a variety of entry velocities and vehicle masses, focusing on the identification of potential benefits of enabling angle of attack modulation. The terminal state is envisioned as one appropriate for the initiation of terminal descent via parachute or other means. A particle swarm optimizer varies entry flight path angle, ten bank profile points, and ten angle of attack profile points to find maximum-final-altitude trajectories for a 10 30 m ellipsled at 180 different combinations of values for entry mass, entry velocity, terminal Mach number, and minimum allowable altitude. Parametric plots of maximum achievable altitude are shown, as are examples of optimized trajectories. It is shown that appreciable terminal state altitude gains (2.5-4.0 km) over pure bank angle control may be possible if angle of attack modulation is enabled for Mars entry vehicles. Gains of this magnitude could prove to be enabling for missions requiring high-altitude landing sites. Conclusions are also drawn regarding trends in the bank and angle of attack profiles that produce the optimal trajectories in this study, and directions for future work are identified