The GRT Planning System: Backward Heuristic Construction in Forward State-Space Planning

This paper presents GRT, a domain-independent heuristic planning system for STRIPS worlds. GRT solves problems in two phases. In the pre-processing phase, it estimates the distance between each fact and the goals of the problem, in a backward direction. Then, in the search phase, these estimates are used in order to further estimate the distance between each intermediate state and the goals, guiding so the search process in a forward direction and on a best-first basis. The paper presents the benefits from the adoption of opposite directions between the preprocessing and the search phases, discusses some difficulties that arise in the pre-processing phase and introduces techniques to cope with them. Moreover, it presents several methods of improving the efficiency of the heuristic, by enriching the representation and by reducing the size of the problem. Finally, a method of overcoming local optimal states, based on domain axioms, is proposed. According to it, difficult problems are decomposed into easier sub-problems that have to be solved sequentially. The performance results from various domains, including those of the recent planning competitions, show that GRT is among the fastest planners

The Metric-FF Planning System: Translating "Ignoring Delete Lists" to Numeric State Variables

Planning with numeric state variables has been a challenge for many years, and was a part of the 3rd International Planning Competition (IPC-3). Currently one of the most popular and successful algorithmic techniques in STRIPS planning is to guide search by a heuristic function, where the heuristic is based on relaxing the planning task by ignoring the delete lists of the available actions. We present a natural extension of ``ignoring delete lists'' to numeric state variables, preserving the relevant theoretical properties of the STRIPS relaxation under the condition that the numeric task at hand is ``monotonic''. We then identify a subset of the numeric IPC-3 competition language, ``linear tasks'', where monotonicity can be achieved by pre-processing. Based on that, we extend the algorithms used in the heuristic planning system FF to linear tasks. The resulting system Metric-FF is, according to the IPC-3 results which we discuss, one of the two currently most efficient numeric planners

Sustainable Development and Complex Ecosystems. An Economist's View

The paper surveys economic aspects of sustainability and the use of complex ecological systems. In a first step, an economist's view of the concept of sustainability is presented. Then, a simple model of the economic use of a dynamic ecological system is discussed. It is shown how economically optimal trajectories look like, in which circumstances it may be optimal to destroy the ecosystem, and which problems arise if this ecosystem is a common-property resource. Extensions of the model that add complexity and uncertainty are referred to briefly. Finally, some economic concepts to determine the value of ecosystems are presented.

Automated Transit Networks (ATN): A Review of the State of the Industry and Prospects for the Future, MTI Report 12-31

The concept of Automated Transit Networks (ATN) - in which fully automated vehicles on exclusive, grade-separated guideways provide on-demand, primarily non-stop, origin-to-destination service over an area network – has been around since the 1950s. However, only a few systems are in current operation around the world. ATN does not appear “on the radar” of urban planners, transit professionals, or policy makers when it comes to designing solutions for current transit problems in urban areas. This study explains ATN technology, setting it in the larger context of Automated Guideway Transit (AGT); looks at the current status of ATN suppliers, the status of the ATN industry, and the prospects of a U.S.-based ATN industry; summarizes and organizes proceedings from the seven Podcar City conferences that have been held since 2006; documents the U.S./Sweden Memorandum of Understanding on Sustainable Transport; discusses how ATN could expand the coverage of existing transit systems; explains the opportunities and challenges in planning and funding ATN systems and approaches for procuring ATN systems; and concludes with a summary of the existing challenges and opportunities for ATN technology. The study is intended to be an informative tool for planners, urban designers, and those involved in public policy, especially for urban transit, to provide a reference for history and background on ATN, and to use for policy development and research

Information Management for Mobility-as-a-Service Based on Autonomous Vehicles

The Mobility-as-a-Service (MaaS) concept is proposed to facilitate integration of transport modes regarding personalized journey planning and payment. When conventional vehicles are replaced by autonomous road vehicles (AVs) in MaaS, the information management processes alter significantly. The research questions were: how to model, design, and operate the new mobility services based on AVs in MaaS framework, focusing on information management. System engineering (SE) principles were applied. We elaborated the system structure model, the data model and the operational model. The connections among models were also presented. A dynamic pricing method was introduced to conciliate the demand and capacity as well as to calculate the service fee in MaaS. The theoretical results are applicable during design of the new service

MimicPlay: Long-Horizon Imitation Learning by Watching Human Play

Imitation learning from human demonstrations is a promising paradigm for teaching robots manipulation skills in the real world. However, learning complex long-horizon tasks often requires an unattainable amount of demonstrations. To reduce the high data requirement, we resort to human play data - video sequences of people freely interacting with the environment using their hands. Even with different morphologies, we hypothesize that human play data contain rich and salient information about physical interactions that can readily facilitate robot policy learning. Motivated by this, we introduce a hierarchical learning framework named MimicPlay that learns latent plans from human play data to guide low-level visuomotor control trained on a small number of teleoperated demonstrations. With systematic evaluations of 14 long-horizon manipulation tasks in the real world, we show that MimicPlay outperforms state-of-the-art imitation learning methods in task success rate, generalization ability, and robustness to disturbances. Code and videos are available at https://mimic-play.github.ioComment: 7th Conference on Robot Learning (CoRL 2023 oral presentation

Carbon Sequestration, Economic Policies and Growth

The possibility of capturing and sequestering some fraction of the CO2 emissions arising from fossil fuel combustion, often labeled as carbon capture and storage (CCS), is drawing an increasing amount of attention in the business and academic communities. We present here a model of endogenous growth in which the use of a non-renewable resource in production yields flows of pollution whose accumulated stock negatively affects welfare. A CCS technology allows, via some effort, for the partial reduction of CO2 emissions in the atmosphere. We characterize the social optimum and how the availability of the CCS technology affects it, and we study the decentralized economy's trajectories. We then analyze economic policies. We first characterize the first-best policy. We derive the expression of the Pigovian carbon tax, and we give a full interpretation of its level, which is unique. We then study the impacts of three different second-best policies: a carbon tax, a subsidy to sequestered carbon, and a subsidy to labor in CCS. The first two tools foster CCS activity; so does the third, but only if it is coupled with one of the other two. While the tax postpones resource extraction, the two subsidies accelerate it's possibly yielding a rise in short-term CO2 emissions. The effects on growth are more complex. If the weight of the CCS sector in the economy is high, the tax will generally be detrimental to output growth, while the subsidies can foster it in the long-term. Finally, the carbon tax has a negative impact on the output level in the short-term, contrary to the subsidies

Investigation on the Impact of Boat Wakes to Mangrove Degradation

Mangrove ecosystem is one of the ecosystem that many people take it for granted due to lack of knowledge on the importance for having a healthier mangrove ecosystem. Several factors were identified to cause the mangrove degradation which not only because of nature activities but also factors induced by human activities. In recent days, human activities are seen the main factor leading to mangrove deterioration. Initially, boat wake was a negligible factor towards the mangrove erosion but since the increasing number of high speed craft, this issue became one of world’s concern. Previous research indicated that, boat wake could contribute to the mangrove erosion. Matang Mangrove Reserve Forest is the largest mangrove reserve in Malaysia. Unfortunately, few areas was observed facing erosion and plants gradually collapses along the mangrove fringe. This research aimed to investigate the threshold limit of the maximum wave height generated by the travelling boats that could lead to mangrove riverbank erosion