Physics Information Research Articles

Knowledge-oriented task and motion planning for multiple mobile robots

ABSTRACTRobotic systems composed of several mobile robots moving in human environments pose several problems at perception, planning and control levels. In these environments, there may be obstacles obstructing the paths, which robots can remove by pushing or pulling them. At planning level, therefore, an efficient combination of task and motion planning is required. Even more if we assume a cooperative system in which robots can collaborate with each other by e.g. pushing together a heavy obstacle or by one robot clearing the way to another one. In this paper, we cope with this problem by proposing -TMP, a smart combination of an heuristic task planner based on the Fast Forward method, a physics-based motion planner, and reasoning processes over the ontologies that code the knowledge on the problem. The significance of the proposal relies on how geometric and physics information is used within the computation of the heuristics in order to guide the symbolic search, i.e. how an artificial intelligence planning method is combined with low-level motion planning to achieve a feasible sequence of actions (composed of collision-free motions plus physically-feasible push/pull actions). The proposal has been validated with several simulated scenarios (using up to five robots that need to collaborate with each other to reach the goal state), showing how the method is able to solve challenging situations and also find an efficient solution in terms of power.

Physics Evoked Cloud Method

In mesh-free methods, discrete equations are built according to physics information of micro-bodies arbitrarily spread in vicinal space. As the requirements about topology of micro-bodies are reduced, simulations with Lagrangian approach may be easier even with large distortions. Owing to the insufficiency of topological information, there is a challenge for mesh-free method to reflect physics especially as discontinuities exist. Based on the physical laws and developing trend of numerical simulation, a new mesh-free systematic method PECM (physics evoked cloud method) with excellent applicability has been developed. High fidelity to physics of the method is demonstrated through five one-dimensional challenging problems in which strong discontinuities exist.

Creation and control of multi-phonon Fock states in a bulk acoustic-wave resonator.

Quantum states of mechanical motion can be important resources for quantum information, metrology and studies of fundamental physics. Recent demonstrations of superconducting qubits coupled to acoustic resonators have opened up the possibility of performing quantum operations on macroscale motional modes1-3, which can act as long-lived quantum memories or transducers. In addition, they can potentially be used to test decoherence mechanisms in macroscale objects and other modifications to standard quantum theory4,5. Many of these applications call for the ability to create and characterize complex quantum states, such as states with a well defined phonon number, also known as phonon Fock states. Such capabilities require fast quantum operations and long coherence times of the mechanical mode. Here we demonstrate the controlled generation of multi-phonon Fock states in a macroscale bulk acoustic-wave resonator. We also perform Wigner tomography and state reconstruction to highlight the quantum nature of the prepared states6. These demonstrations are made possible by the long coherence times of our acoustic resonator and our ability to selectively couple a superconducting qubit to individual phonon modes. Our work shows that circuit quantum acoustodynamics7 enables sophisticated quantum control of macroscale mechanical objects and opens up the possibility of using acoustic modes as quantum resources.

Incorporating Uncertainties in Atomic Data into the Analysis of Solar and Stellar Observations: A Case Study in Fe xiii

Abstract Information about the physical properties of astrophysical objects cannot be measured directly but is inferred by interpreting spectroscopic observations in the context of atomic physics calculations. Ratios of emission lines, for example, can be used to infer the electron density of the emitting plasma. Similarly, the relative intensities of emission lines formed over a wide range of temperatures yield information on the temperature structure. A critical component of this analysis is understanding how uncertainties in the underlying atomic physics propagate to the uncertainties in the inferred plasma parameters. At present, however, atomic physics databases do not include uncertainties on the atomic parameters and there is no established methodology for using them even if they did. In this paper we develop simple models for uncertainties in the collision strengths and decay rates for Fe xiii and apply them to the interpretation of density-sensitive lines observed with the EUV (extreme ultraviolet) Imagining spectrometer (EIS) on Hinode. We incorporate these uncertainties in a Bayesian framework. We consider both a pragmatic Bayesian method where the atomic physics information is unaffected by the observed data, and a fully Bayesian method where the data can be used to probe the physics. The former generally increases the uncertainty in the inferred density by about a factor of 5 compared with models that incorporate only statistical uncertainties. The latter reduces the uncertainties on the inferred densities, but identifies areas of possible systematic problems with either the atomic physics or the observed intensities.

Neutron emission spectroscopy of D plasmas at JET with a compact liquid scintillating neutron spectrometer.

Neutron emission spectroscopy is a diagnostic technique that allows for energy measurements of neutrons born in nuclear reactions. The JET tokamak fusion experiment (Culham, UK) has a special role in this respect as advanced spectrometers for 2.5 MeV and 14 MeV neutrons have been developed here for the first time for measurements of the neutron emission spectrum from D and DT plasmas with unprecedented accuracy. Twin liquid scintillating neutron spectrometers were built and calibrated at the Physikalisch-Technische Bundesanstalt (PTB) (Braunschweig, Germany) and installed on JET in the recent years with tangential-equatorial (KM12) and vertical-radial (KM13) view lines, with the latter only recently operational. This article reports on the performance of KM12 and on the development of the data analysis methods in order to extract physics information upon D ions kinematics in JET auxiliary-heated D plasmas from 2.5 MeV neutron measurements. The comparison of these results with the correspondents from other JET neutron spectrometers is also presented: their agreement allows for JET unique capability of multi-lines of sight neutron spectroscopy and for benchmarking other 14 MeV neutron spectrometers installed on the same lines of sight in preparation for the DT experimental campaign at JET.

Flavor SU(3) topological diagram and irreducible representation amplitudes for heavy meson charmless hadronic decays: mismatch and equivalence**Supported by National Natural Science Foundation of China (11575110, 11575111, 11655002, 11735010), Natural Science Foundation of Shanghai (15DZ2272100) and MOST (MOST104-2112-M-002-015-MY3, 106-2112-M-002-003-MY3)

Flavor SU(3) analysis of B meson charmless hadronic two light pseudoscalar decays can be formulated in two different ways. One is to construct the SU(3) irreducible representation amplitude (IRA) according to effective Hamiltonian transformation properties, and the other is to draw the topological diagrams (TDA). We first point out that previous analyses of TDA and IRA approaches do not match in several aspects, in particular a few SU(3) independent amplitudes have been overlooked in the TDA approach. This has caused confusions in the past and sometimes resulted in incorrect interpretation of data. We then demonstrate that only if these amplitudes are included, a consistent and unified picture can be obtained. With the new TDA amplitudes, all charmless hadronic decays of heavy meson must have nonzero direct CP symmetries as already predicted by the IRA approach. In addition to their notable impact on CP asymmetry, the new amplitudes are also important to extract new physics information.

American Institute of Physics Information

American Institute of Physics Information

Experimental and Numerical Investigation of LPG-Fueled Inverse Diffusion Flame in a Coaxial Burner

An experimental and numerical investigation of unconfined liquefied petroleum gas (LPG) fuelled inverse diffusion flame (IDF) is presented. The effect of air-fuel velocity ratio on the appearance of the LPG IDF are investigated. A fixed air jet velocity of Va = 11.31 m/s is chosen for the analysis, while the fuel jet velocity is varied from 0.014 m/s to 0.083 m/s. The observations indicate that the air-fuel jet velocity ratio has significant effect on the flame appearance of LPG IDF. It is found that the flame length increases with increase in fuel jet flow. Actual flame in burner is highly complex in nature as it involves momentum, mass and energy transfer in highly turbulent flow regime. To extract detailed information of flow physics, numerical analysis of LPG IDF is performed. It is observed that temperature along the centerline of IDF increases as distance from burner exit (Z) increases. This nature of temperature distribution indicates that the central cold air in the air jet is gradually heated toward the downstream of the IDF. The highest flame temperature is noticed at Z = 30 mm. The highest flame temperature predicted numerically at axial height of 30 mm is central portion of the blue zone of the flame which is main reaction zone.

SET analysis and radiation hardening techniques for CMOS LNA topologies

This paper analyses the effects of single-event transients (SETs) on CMOS low noise amplifiers (LNA) designed for a 0.18 technology. Two well-known topologies, the common-source and common-gate cascodes, have been analysed when heavy ions strike the most sensitive nodes of these structures. In order to simulate these strikes both a physics-based technology computer aided design (TCAD) tool and an electrical circuit domain simulator have been used. This way the physics information given by the TCAD tool is combined with the fast transient simulations performed in circuit simulators. To study their SET performance, the maximum voltage peak and the recovery time of the output signal were calculated for both LNAs. Additionally, a safe operating area can be defined, setting the boundaries for acceptable SETs. Radiation hardening by design techniques have been applied at the most vulnerable nodes of both LNAs. The proposed mitigation approaches make both LNAs hardened against radiation, considerably improving their SET performance.

Erratum to: Study on the effect of ellipticity and misalignment on OAM modes in a ring fiber

In the originally published article the affiliation was incorrect and should be corrected From: Key Laboratory of Optical Communications Science and Technology in Shandong Province, School of Physics Science and Information Technology, Liaocheng 252059, China To: Key Laboratory of Optical Communications Science and Technology in Shandong Province, School of Physics Science and Information Technology, Liaocheng University, Liaocheng 252059, China Added: “Liaocheng University”

Physics and human-based information fusion for improved resident space object tracking

Maintaining a catalog of Resident Space Objects (RSOs) can be cast in a typical Bayesian multi-object estimation problem, where the various sources of uncertainty in the problem – the orbital mechanics, the kinematic states of the identified objects, the data sources, etc. – are modeled as random variables with associated probability distributions. In the context of Space Situational Awareness, however, the information available to a space analyst on many uncertain components is scarce, preventing their appropriate modeling with a random variable and thus their exploitation in a RSO tracking algorithm. A typical example are human-based data sources such as Two-Line Elements (TLEs), which are publicly available but lack any statistical description of their accuracy. In this paper, we propose the first exploitation of uncertain variables in a RSO tracking problem, allowing for a representation of the uncertain components reflecting the information available to the space analyst, however scarce, and nothing more. In particular, we show that a human-based data source and a physics-based data source can be embedded in a unified and rigorous Bayesian estimator in order to track a RSO. We illustrate this concept on a scenario where real TLEs queried from the U.S. Strategic Command are fused with realistically simulated radar observations in order to track a Low-Earth Orbit satellite.

American Institute of Physics Information

American Institute of Physics Information

Spatiotemporal video-domain high-fidelity simulation and realistic visualization of full-field dynamic responses of structures by a combination of high-spatial-resolution modal model and video motion manipulations

Structures with complex geometries, material properties, and boundary conditions exhibit spatially local dynamic behaviors. A high‐spatial‐resolution model of the structure is thus required for high‐fidelity analysis, assessment, and prediction of the dynamic phenomena of the structure. The traditional approach is to build a highly refined finite element computer model for simulating and analyzing the structural dynamic phenomena based on detailed knowledge and explicit modeling of the structural physics such as geometries, materials properties, and boundary conditions. These physics information of the structure may not be available or accurately modeled in many cases, however. In addition, the simulation on the high‐spatial‐resolution structural model, with a massive number of degrees of freedom and system parameters, is computationally demanding. This study, on a proof‐of‐principle basis, proposes a novel alternative approach for spatiotemporal video‐domain high‐fidelity simulation and realistic visualization of full‐field structural dynamics by an innovative combination of the fundamentals of structural dynamic modeling and the advanced video motion manipulation techniques. Specifically, a low‐modal‐dimensional yet high‐spatial (pixel)‐resolution (as many spatial points as the pixel number on the structure in the video frame) modal model is established in the spatiotemporal video domain with full‐field modal parameters first estimated from line‐of‐sight video measurements of the operating structure. Then in order to simulate new dynamic response of the structure subject to a new force, the force is projected onto each modal domain, and the modal response is computed by solving each individual single‐degree‐of‐freedom system in the modal domain. The simulated modal responses are then synthesized by the full‐field mode shapes using modal superposition to obtain the simulated full‐field structural dynamic response. Finally, the simulated structural dynamic response is embedded into the original video, replacing the original motion of the video, thus generating a new photo‐realistic, physically accurate video that enables a realistic, high‐fidelity visualization/animation of the simulated full‐field vibration of the structure. Laboratory experiments are conducted to validate the proposed method, and the error sources and limitations in practical implementations are also discussed. Compared with high‐fidelity finite element computer model simulations of structural dynamics, the video‐based simulation method removes the need to explicitly model the structure's physics. In addition, the photo‐realistic, physically accurate simulated video provides a realistic visualization/animation of the full‐field structural dynamic response, which was not traditionally available. These features of the proposed method should enable a new alternative to the traditional computer‐aided finite element model simulation for high‐fidelity simulating and realistically visualizing full‐field structural dynamics in a relatively efficient and user‐friendly manner.

American Institute of Physics Information

American Institute of Physics Information

Comparison of heavy-ion transport simulations: Collision integral in a box

Simulations by transport codes are indispensable to extract valuable physics information from heavy ion collisions. In order to understand the origins of discrepancies between different widely used transport codes, we compare 15 such codes under controlled conditions of a system confined to a box with periodic boundary, initialized with Fermi-Dirac distributions at saturation density and temperatures of either 0 or 5 MeV. In such calculations, one is able to check separately the different ingredients of a transport code. In this second publication of the code evaluation project, we only consider the two-body collision term, i.e. we perform cascade calculations. When the Pauli blocking is artificially suppressed, the collision rates are found to be consistent for most codes (to within $1\%$ or better) with analytical results, or completely controlled results of a basic cascade code after eliminating the correlations within the same pair of colliding particles. In calculations with active Pauli blocking, the blocking probability was found to deviate from the expected reference values. The reason is found in substantial phase-space fluctuations and smearing tied to numerical algorithms and model assumptions in the representation of phase space. This results in the reduction of the blocking probability in most transport codes, so that the simulated system gradually evolves away from the Fermi-Dirac towards a Boltzmann distribution. As a result of this investigation, we are able to make judgements about the most effective strategies in transport simulations for determining the collision probabilities and the Pauli blocking. Investigation in a similar vein of other ingredients in transport calculations, like the mean field propagation or the production of nucleon resonances and mesons, will be discussed in the future publications.

Lepton polarization asymmetries in rare semi-tauonic b rightarrow s exclusive decays at FCC-ee

We consider measurements of exclusive rare semi-tauonic b-hadron decays, mediated by the b rightarrow s tau ^+ tau ^- transition, at a future high-energy circular electron–positron collider (FCC-ee). We argue that the high boosts of b-hadrons originating from on-shell Z boson decays allow for a full reconstruction of the decay kinematics in hadronic tau decay modes (up to discrete ambiguities). This, together with the potentially large statistics of Zrightarrow bbar{b}, opens the door for the experimental determination of tau polarizations in these rare b-hadron decays. In the light of the current experimental situation on lepton flavor universality in rare semileptonic B decays, we discuss the complementary short-distance physics information carried by the tau polarizations and suggest suitable theoretically clean observables in the form of single- and double-tau polarization asymmetries.

Electromagnetic memory effect induced by axion dark matter

Memory effects of gravitational waves from astronomical events or primordial universe might have the information of new physics. It is intriguing to observe that the memory effect exists in electrodynamics as a net momentum kick, while the memory effect in gravity appears as a net relatively displacement. In particular, Winicour has shown that the B-mode memory, which characterizes parity odd global distribution of memory, does not exist. We study the memory effect in axion electrodynamics and find that the B-mode memory effect can exist provided the existence of coherently oscillating axion background field. Moreover, we examine the detectability of the axion dark matter using this effect. We also argue the existence of the B-mode gravitational memory effect in the presence of the axion dark matter.

Fast spectrum reactor fuel assembly sensitivity analysis

The Experimental Breeder Reactor-II was a sodium-cooled, metal-uranium-fueled fast-neutron reactor designed and built by Argonne National Laboratory. The reactor achieved initial criticality September 30, 1961, and continued operation until 1994. The reactor thermal power limit was 62.5MW with a corresponding electrical output of 19MW. To preserve important EBR-II reactor physics information, a benchmark evaluation is underway for proposed inclusion in the International Handbook of Evaluated Reactor Physics Benchmark Experiments. Coupled with development of the reactor physics benchmark evaluation, sensitivity analysis has been performed. Individual nuclide cross-section sensitivities for heterogeneous and homogeneous fuel assembly models were calculated using the multi-group adjoint method, the iterated fission probability (IFP) method, and the Contribution-Linked eigenvalue sensitivity/Uncertainty estimation via Track length importance Characterization (CLUTCH) method. Good agreement between the three methods was observed except for the sodium total and elastic cross-section and the uranium-235 total cross-section sensitivity coefficients where the multi-group adjoint method produced results approximately 14% and 7% lower than the IFP and CLUTCH methods, respectively.

Quantum communication with coherent states of light.

Quantum communication offers long-term security especially, but not only, relevant to government and industrial users. It is worth noting that, for the first time in the history of cryptographic encoding, we are currently in the situation that secure communication can be based on the fundamental laws of physics (information theoretical security) rather than on algorithmic security relying on the complexity of algorithms, which is periodically endangered as standard computer technology advances. On a fundamental level, the security of quantum key distribution (QKD) relies on the non-orthogonality of the quantum states used. So even coherent states are well suited for this task, the quantum states that largely describe the light generated by laser systems. Depending on whether one uses detectors resolving single or multiple photon states or detectors measuring the field quadratures, one speaks of, respectively, a discrete- or a continuous-variable description. Continuous-variable QKD with coherent states uses a technology that is very similar to the one employed in classical coherent communication systems, the backbone of today's Internet connections. Here, we review recent developments in this field in two connected regimes: (i) improving QKD equipment by implementing front-end telecom devices and (ii) research into satellite QKD for bridging long distances by building upon existing optical satellite links.This article is part of the themed issue 'Quantum technology for the 21st century'.

Experimental and Numerical Investigation of LPG-Fueled Inverse Diffusion Flame in a Coaxial Burner

An experimental and numerical investigation of unconfined liquefied petroleum gas (LPG) fuelled inverse diffusion flame (IDF) is presented. The effect of air-fuel velocity ratio on the appearance of the LPG IDF are investigated. A fixed air jet velocity of Va = 11.31 m/s is chosen for the analysis, while the fuel jet velocity is varied from 0.014 m/s to 0.083 m/s. The observations indicate that the air-fuel jet velocity ratio has significant effect on the flame appearance of LPG IDF. It is found that the flame length increases with increase in fuel jet flow. Actual flame in burner is highly complex in nature as it involves momentum, mass and energy transfer in highly turbulent flow regime. To extract detailed information of flow physics, numerical analysis of LPG IDF is performed. It is observed that temperature along the centerline of IDF increases as distance from burner exit (Z) increases. This nature of temperature distribution indicates that the central cold air in the air jet is gradually heated toward the downstream of the IDF. The highest flame temperature is noticed at Z = 30 mm. The highest flame temperature predicted numerically at axial height of 30 mm is central portion of the blue zone of the flame which is main reaction zone.