Linear analysis of a force reflective teleoperator

Complex force reflective teleoperation systems are often very difficult to analyze due to the large number of components and control loops involved. One mode of a force reflective teleoperator is described. An analysis of the performance of the system based on a linear analysis of the general full order model is presented. Reduced order models are derived and correlated with the full order models. Basic effects of force feedback and position feedback are examined and the effects of time delays between the master and slave are studied. The results show that with symmetrical position-position control of teleoperators, a basic trade off must be made between the intersystem stiffness of the teleoperator, and the impedance felt by the operator in free space

Isoscalar dipole strength in ^{208}_{82}Pb_{126}: the spurious mode and the strength in the continuum

Isoscalar dipole (compression) mode is studied first using schematic harmonic-oscillator model and, then, the self-consistent Hartree-Fock (HF) and random phase approximation (RPA) solved in coordinate space. Taking ^{208}Pb and the SkM* interaction as a numerical example, the spurious component and the strength in the continuum are carefully examined using the sum rules. It is pointed out that in the continuum calculation one has to use an extremely fine radial mesh in HF and RPA in order to separate, with good accuracy, the spurious component from intrinsic excitations.Comment: 19 pages, 2 figure

Attitude Control and Orbit Determination of a Crewed Spacecraft with Lunar Lander in near Rectilinear Halo Orbit

NASA's Gateway program plans to place a crew-tended spacecraft in cislunar Near Rectilinear Halo Orbit (NRHO). The craft will support arrivals of crews in Orion and the undocking and return of a crewed lunar lander. The impact to at-titude control of a Gateway with the addition of a lunar lander is investigated. Perturbations from Orion and a lander's docking and undocking from the Gate-way are considered. Deep Space Network (DSN) tracking is supplemented with optical measurements to lunar north pole craters to analyze the possible benefit in solution accuracy and/or DSN scheduling relief

Ozone depletion, greenhouse gases, and climate change

This symposium was organized to study the unusual convergence of a number of observations, both short and long term that defy an integrated explanation. Of particular importance are surface temperature observations and observations of upper atmospheric temperatures, which have declined significantly in parts of the stratosphere. There has also been a dramatic decline in ozone concentration over Antarctica that was not predicted. Significant changes in precipitation that seem to be latitude dependent have occurred. There has been a threefold increase in methane in the last 100 years; this is a problem because a source does not appear to exist for methane of the right isotopic composition to explain the increase. These and other meteorological global climate changes are examined in detail

Wavelength transduction from a 3D microwave cavity to telecom using piezoelectric optomechanical crystals

Microwave to optical transduction has received a great deal of interest from the cavity optomechanics community as a landmark application for electro-optomechanical systems. In this Letter, we demonstrate a novel transducer that combines high-frequency mechanical motion and a microwave cavity for the first time. The system consists of a 3D microwave cavity and a gallium arsenide optomechanical crystal, which has been placed in the microwave electric field maximum. This allows the microwave cavity to actuate the gigahertz-frequency mechanical breathing mode in the optomechanical crystal through the piezoelectric effect, which is then read out using a telecom optical mode. The gallium arsenide optomechanical crystal is a good candidate for low-noise microwave-to-telecom transduction, as it has been previously cooled to the mechanical ground state in a dilution refrigerator. Moreover, the 3D microwave cavity architecture can naturally be extended to couple to superconducting qubits and to create hybrid quantum systems

Earthing the Anthropos? From ‘socializing the Anthropocene’ to geologizing the social

Responding to claims of Anthropocene geoscience that humans are now geological agents, social scientists are calling for renewed attention to the social, cultural, political and historical differentiation of the Anthropos. But does this leave critical social thought’s own key concepts and categories unperturbed by the Anthropocene provocation to think through dynamic earth processes? Can we ‘socialize the Anthropocene’ without also opening ‘the social’ to climate, geology and earth system change? Revisiting the earth science behind the Anthropocene thesis and drawing on social research that is using climatology and earth systems thinking to help understand socio-historical change, this article explores some of the possibilities for ‘geologizing’ social thought. While critical social thought’s attention to justice and exclusion remains vital, it suggests that responding to Anthropocene conditions also calls for a kind of ‘geo-social’ thinking that relates human diversity and social difference to the potentiality and multiplicity of the earth itself

Stationkeeping, Orbit Determination, and Attitude Control for Spacecraft in Near Rectilinear Halo Orbits

Final document is attached. From a Near Rectilinear Halo Orbit (NRHO), NASA's Gateway at the Moon is planned to serve as a proving ground and a staging location for human missions beyond Earth. Stationkeeping, Orbit Determination (OD), and attitude control are examined for uncrewed and crewed Gateway configurations. Orbit maintenance costs are investigated using finite maneuvers, considering skipped maneuvers and perturbations. OD analysis assesses DSN tracking and identifies OD challenges associated with the NRHO and crewed operations. The Gateway attitude profile is simulated to determine an effective equilibrium attitude. Attitude control propellant use and sizing of the required passive attitude control system are assessed

By-catch species susceptibilities and potential for survival in Algarve (southern Portugal) deep-water crustacean trawl fishery

Bottom trawling for crustaceans in Portuguese coastal waters is an important fishery in terms of revenue, despite its negative impacts on deep-sea ecosystems. This fishery catches large amounts of unwanted species that were discarded for various reasons before the introduction of the Landing Obligation, which banned the discarding of regulated species. However, where it can be demonstrated that a species has an acceptably high likelihood of survival, exemptions to this ban may be granted. In this study, time-to-mortality was used to estimate immediate mortality rates and identify important biological characteristics determining the susceptibility of 14 by-catch species. most with commercial interest (Conger conger, Galeus melastomus, Helicolenus dactylopterus, Lepidorhombus boscii, Lophius budegassa, Lophius piscatorius, Merluccius merluccius. Micromesistius poutassou, Mullus surmuletus, Phycis blennoides. Scyliorhinus canicula, Trigla lyra. Trachurus trachurus and Trachurus piciuratus). Species with potential to survive after the discarding process were identified and a short-term survival assessment of conger eel (Conger conger) was performed. The results suggest that species with scales, gas bladder and high metabolic rates have higher post-discard mortality. Size was a critical factor determining survival in some species, with smaller individuals dying faster. The short-term survival rate of conger eel was determined to be 84% (95% Cl: 75.5 to 93.3%). The methodology and results from this study can help identify species that may survive the discarding process and factors influencing their survival.MINOUW project - Horizon 2020 Framework Programme of the European Union - 634495info:eu-repo/semantics/publishedVersio