Tackling the Curse of Dimensionality in Large-scale Multi-agent LTL Task Planning via Poset Product

Linear Temporal Logic (LTL) formulas have been used to describe complex tasks for multi-agent systems, with both spatial and temporal constraints. However, since the planning complexity grows exponentially with the number of agents and the length of the task formula, existing applications are mostly limited to small artificial cases. To address this issue, a new planning algorithm is proposed for task formulas specified as sc-LTL formulas. It avoids two common bottlenecks in the model-checking-based planning methods, i.e., (i) the direct translation of the complete task formula to the associated B\"uchi automaton; and (ii) the synchronized product between the B\"uchi automaton and the transition models of all agents. In particular, each conjuncted sub-formula is first converted to the associated R-posets as an abstraction of the temporal dependencies among the subtasks. Then, an efficient algorithm is proposed to compute the product of these R-posets, which retains their dependencies and resolves potential conflicts. Furthermore, the proposed approach is applied to dynamic scenes where new tasks are generated online. It is capable of deriving the first valid plan with a polynomial time and memory complexity w.r.t. the system size and the formula length. Our method can plan for task formulas with a length of more than 60 and a system with more than 35 agents, while most existing methods fail at the formula length of 20. The proposed method is validated on large fleets of service robots in both simulation and hardware experiments.Comment: 9 pages, 9 figure

Dust Emission as a Function of Stellar Population Age in the Nearby Galaxy M33

Dust emission at 8 micron has been extensively calibrated as an indicator of current star formation rate for galaxies and ~kpc-size regions within galaxies. Yet, the exact link between the 8 micron emission and the young stellar populations in galaxies is still under question, as dust grains can be stochastically heated also by older field stars. In order to investigate this link, we have combined mid-infrared images from the Spitzer Space Telescope with a published star cluster candidates catalog for the Local Group galaxy M33. M33 is sufficiently close that the Spitzer's 8 micron images resolve individual regions of star formation. Star clusters represent almost-single-age stellar populations, which are significantly easier to model than more complex mixtures of stars. We find a decrease in the 8 micron luminosity per unit stellar mass as a function of age of the star clusters, with a large scatter that is consistent with varying fractions of stellar light absorbed by dust. The decrease and scatter both confirm findings based on more distant galaxies and are well described by simple models for the dust emission of a young stellar population. We conclude that the dust emission at 8 micron depends sensitively on the age of the stellar population, out to at least the oldest age analyzed here, ~400 Myr. This dependence complicates the use of the 8 micron emission as a star formation rate indicator, at least for small galactic regions and individual star forming regions. By leveraging the Spitzer legacy, this investigation paves the way for future explorations with the James Webb Space Telescope.Comment: Accepted for publication on ApJ. Includes 5 figure

Bringing regularized optimal transport to lightspeed: a splitting method adapted for GPUs

We present an efficient algorithm for regularized optimal transport. In contrast to previous methods, we use the Douglas-Rachford splitting technique to develop an efficient solver that can handle a broad class of regularizers. The algorithm has strong global convergence guarantees, low per-iteration cost, and can exploit GPU parallelization, making it considerably faster than the state-of-the-art for many problems. We illustrate its competitiveness in several applications, including domain adaptation and learning of generative models.Comment: 9 pages, 4 figure

Orange Organic Long-persistent Luminescence from an Electron Donor/Acceptor Binary System

Organic long-persistent luminescence (LPL) materials can overcome the disadvantages of inorganic LPL materials in terms of element sustainability, processability, and color tunability. However, all published electron donor/acceptor binary organic LPL systems show green emission. Here, we report an organic LPL system consisting of N,N,N\u27,N\u27-tetrakis(p-diisobutylaminophenyl)-p-phenylenediamine (TBAPD) as a donor dopant and 2,8-bis(diphenylphosphoryl)dibenzo[b,d]thiophene (PPT) as an acceptor host. The TBAPD/PPT film exhibits orange photoluminescence (CIEx, CIEy = 0.49, 0.49) and LPL (CIEx, CIEy = 0.51, 0.48)

Client-Server Sessions in Linear Logic

We introduce coexponentials, a new set of modalities for Classical Linear Logic. As duals to exponentials, the coexponentials codify a distributed form of the structural rules of weakening and contraction. This makes them a suitable logical device for encapsulating the pattern of a server receiving requests from an arbitrary number of clients on a single channel. Guided by this intuition we formulate a system of session types based on Classical Linear Logic with coexponentials, which is suited to modelling client-server interactions. We also present a session-typed functional programming language for server-client programming, which we translate to our system of coexponentials

Time Minimization and Online Synchronization for Multi-agent Systems under Collaborative Temporal Tasks

Multi-agent systems can be extremely efficient when solving a team-wide task in a concurrent manner. However, without proper synchronization, the correctness of the combined behavior is hard to guarantee, such as to follow a specific ordering of sub-tasks or to perform a simultaneous collaboration. This work addresses the minimum-time task planning problem for multi-agent systems under complex global tasks stated as Linear Temporal Logic (LTL) formulas. These tasks include the temporal and spatial requirements on both independent local actions and direct sub-team collaborations. The proposed solution is an anytime algorithm that combines the partial-ordering analysis of the underlying task automaton for task decomposition, and the branch and bound (BnB) search method for task assignment. Analyses of its soundness, completeness and optimality as the minimal completion time are provided. It is also shown that a feasible and near-optimal solution is quickly reached while the search continues within the time budget. Furthermore, to handle fluctuations in task duration and agent failures during online execution, an adaptation algorithm is proposed to synchronize execution status and re-assign unfinished subtasks dynamically to maintain correctness and optimality. Both algorithms are validated rigorously over large-scale systems via numerical simulations and hardware experiments, against several strong baselines.Comment: 17 pages, 14 figure

Influence of energy gap between charge-transfer and locally excited states on organic long persistence luminescence

Organic long-persistent luminescence (LPL) is an organic luminescence system that slowly releases stored exciton energy as light. Organic LPL materials have several advantages over inorganic LPL materials in terms of functionality, flexibility, transparency, and solution-processability. However, the molecular selection strategies for the organic LPL system still remain unclear. Here we report that the energy gap between the lowest localized triplet excited state and the lowest singlet charge-transfer excited state in the exciplex system significantly controls the LPL performance. Changes in the LPL duration and spectra properties are systematically investigated for three donor materials having a different energy gap. When the energy level of the lowest localized triplet excited state is much lower than that of the charge-transfer excited state, the system exhibits a short LPL duration and clear two distinct emission features originating from exciplex fluorescence and donor phosphorescence