183 research outputs found
Active repositioning of storage units in Robotic Mobile Fulfillment Systems
In our work we focus on Robotic Mobile Fulfillment Systems in e-commerce
distribution centers. These systems were designed to increase pick rates by
employing mobile robots bringing movable storage units (so-called pods) to pick
and replenishment stations as needed, and back to the storage area afterwards.
One advantage of this approach is that repositioning of inventory can be done
continuously, even during pick and replenishment operations. This is primarily
accomplished by bringing a pod to a storage location different than the one it
was fetched from, a process we call passive pod repositioning. Additionally,
this can be done by explicitly bringing a pod from one storage location to
another, a process we call active pod repositioning. In this work we introduce
first mechanisms for the latter technique and conduct a simulation-based
experiment to give first insights of their effect
On the Complexity of an Unregulated Traffic Crossing
The steady development of motor vehicle technology will enable cars of the
near future to assume an ever increasing role in the decision making and
control of the vehicle itself. In the foreseeable future, cars will have the
ability to communicate with one another in order to better coordinate their
motion. This motivates a number of interesting algorithmic problems. One of the
most challenging aspects of traffic coordination involves traffic
intersections. In this paper we consider two formulations of a simple and
fundamental geometric optimization problem involving coordinating the motion of
vehicles through an intersection.
We are given a set of vehicles in the plane, each modeled as a unit
length line segment that moves monotonically, either horizontally or
vertically, subject to a maximum speed limit. Each vehicle is described by a
start and goal position and a start time and deadline. The question is whether,
subject to the speed limit, there exists a collision-free motion plan so that
each vehicle travels from its start position to its goal position prior to its
deadline.
We present three results. We begin by showing that this problem is
NP-complete with a reduction from 3-SAT. Second, we consider a constrained
version in which cars traveling horizontally can alter their speeds while cars
traveling vertically cannot. We present a simple algorithm that solves this
problem in time. Finally, we provide a solution to the discrete
version of the problem and prove its asymptotic optimality in terms of the
maximum delay of a vehicle
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Dynamic interpersonal therapy for moderate to severe depression: A pilot randomized controlled and feasibility trial
Background: Improving Access to Psychological Therapies (IAPT) services treat most patients in England who present to primary care with major depression. Psychodynamic psychotherapy is one of the psychotherapies offered. Dynamic Interpersonal Therapy (DIT) is a psychodynamic and mentalization-based treatment for depression. 16 sessions are delivered over approximately 5 months. Neither DIT's effectiveness relative to low-intensity treatment (LIT), nor the feasibility of randomizing patients to psychodynamic or cognitive-behavioural treatments (CBT) in an IAPT setting has been demonstrated.
Methods: 147 patients were randomized in a 3:2:1 ratio to DIT (n = 73), LIT (control intervention; n = 54) or CBT (n = 20) in four IAPT treatment services in a combined superiority and feasibility design. Patients meeting criteria for major depressive disorder were assessed at baseline, mid-treatment (3 months) and post-treatment (6 months) using the Hamilton Rating Scale for Depression (HRSD-17), Beck Depression Inventory-II (BDI-II) and other self-rated questionnaire measures. Patients receiving DIT were also followed up 6 months post-completion.
Results: The DIT arm showed significantly lower HRSD-17 scores at the 6-month primary end-point compared with LIT (d = 0.70). Significantly more DIT patients (51%) showed clinically significant change on the HRSD-17 compared with LIT (9%). The DIT and CBT arms showed equivalence on most outcomes. Results were similar with the BDI-II. DIT showed benefit across a range of secondary outcomes.ConclusionsDIT delivered in a primary care setting is superior to LIT and can be appropriately compared with CBT in future RCTs
Clinical management of common presentations of patients diagnosed with BPD during the COVID-19 pandemic: The contribution of the MBT framework
The coronavirus (COVID-19) pandemic has both a profound effect on mental health and affects how psychosocial interventions are delivered. In this paper, we outline particular difficulties patients with Borderline Personality Disorder (BPD) may encounter as a result of the pandemic. We also consider changes in the provision of treatment, specifically the transition from face to face encounters to remotely delivered sessions. Building on a mentalization-based developmental framework, we use clinical vignettes to chart some of these challenges for patients, clinicians and teams. We then make practical recommendations for adaptations to work during the pandemic via the phone or video-link with BPD patients and other groups characterized by a vulnerability to unstable and imbalanced mentalizing. We conclude that the response to these challenges benefits from an existing treatment context that aims at fostering mentalizing and resilience, in which practitioners address the hierarchy of patient needs and their individual responses to the experience of remote treatment during the COVID-19 pandemic
Agent-Based Markov Modeling for Improved COVID-19 Mitigation Policies
The year 2020 saw the covid-19 virus lead to one of the worst global pandemics in history. As a result, governments around the world have been faced with the challenge of protecting public health while keeping the economy running to the greatest extent possible. Epidemiological models provide insight into the spread of these types of diseases and predict the e_ects of possible intervention policies. However, to date, even the most data-driven intervention policies rely on heuristics. In this paper, we study how reinforcement learning (RL) and Bayesian inference can be used to optimize mitigation policies that minimize economic impact without overwhelming hospital capacity. Our main contributions are (1) a novel agent-based pandemic simulator which, unlike traditional models, is able to model _ne-grained interactions among people at speci_c locations in a community; (2) an RL- based methodology for optimizing _ne-grained mitigation policies within this simulator; and (3) a Hidden Markov Model for predicting infected individuals based on partial observations regarding test results, presence of symptoms, and past physical contacts
ΠΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠ΅ Π²Π»ΠΈΡΠ½ΠΈΡ ΡΠ΅Ρ Π½ΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΏΡΠΎΡΠ΅ΡΡΠ° ΠΈΠ·Π³ΠΎΡΠΎΠ²Π»Π΅Π½ΠΈΡ ΠΎΠ±ΠΌΠΎΡΠΎΠΊ Π½Π° Π΄Π΅ΡΠ΅ΠΊΡΠ½ΠΎΡΡΡ ΠΊΠΎΡΠΏΡΡΠ½ΠΎΠΉ ΠΈΠ·ΠΎΠ»ΡΡΠΈΠΈ Π°ΡΠΈΠ½Ρ ΡΠΎΠ½Π½ΡΡ Π΄Π²ΠΈΠ³Π°ΡΠ΅Π»Π΅ΠΉ
Π ΡΠ°Π±ΠΎΡΠ΅ ΠΏΡΠΎΠ²Π΅Π΄Π΅Π½ΠΎ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠ΅ Π²Π»ΠΈΡΠ½ΠΈΡ ΠΊΠΎΠ»Π΅Π±Π°Π½ΠΈΠΉ ΡΠ΅ΠΆΠΈΠΌΠΎΠ² ΡΠ°Π±ΠΎΡΡ ΡΡΠ°ΡΠΎΡΠΎΠΎΠ±ΠΌΠΎΡΠΎΡΠ½ΡΡ
ΡΡΠ°Π½ΠΊΠΎΠ² WST-660 ΠΈ ΠΏΠ°Π·ΠΎΠΈΠ·ΠΎΠ»ΠΈΡΠΎΠ²ΠΎΡΠ½ΡΡ
ΡΡΠ°Π½ΠΊΠΎΠ² ΠΠΠ‘-3 Π½Π° Π΄Π΅ΡΠ΅ΠΊΡΠ½ΠΎΡΡΡ ΠΊΠΎΡΠΏΡΡΠ½ΠΎΠΉ ΠΈΠ·ΠΎΠ»ΡΡΠΈΠΈ. ΠΠΎΠ»ΡΡΠ΅Π½Ρ ΠΌΠ°ΡΠ΅ΠΌΠ°ΡΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΌΠΎΠ΄Π΅Π»ΠΈ Π΄Π΅ΡΠ΅ΠΊΡΠΎΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΡ Π² ΠΊΠΎΡΠΏΡΡΠ½ΠΎΠΉ ΠΈΠ·ΠΎΠ»ΡΡΠΈΠΈ ΠΎΠ±ΠΌΠΎΡΠΊΠΈ Ρ ΡΡΠ΅ΡΠΎΠΌ ΡΠ΅ΠΆΠΈΠΌΠΎΠ² ΡΠ°Π±ΠΎΡΡ ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΎΠ±ΠΎΡΡΠ΄ΠΎΠ²Π°Π½ΠΈΡ ΠΈ ΠΊΠ°ΡΠ΅ΡΡΠ²Π° ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»Π° ΠΊΠΎΡΠΏΡΡΠ½ΠΎΠΉ ΠΈΠ·ΠΎΠ»ΡΡΠΈΠΈ Π² ΡΠΎΡΡΠΎΡΠ½ΠΈΠΈ ΠΏΠΎΡΡΠ°Π²ΠΊΠΈ. Π£ΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΎ, ΡΡΠΎ ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ΠΌ ΡΠ΅ΠΆΠΈΠΌΠΎΠ² ΡΠ°Π±ΠΎΡΡ ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΎΠ±ΠΎΡΡΠ΄ΠΎΠ²Π°Π½ΠΈΡ ΠΌΠΎΠΆΠ½ΠΎ Π΄ΠΎΠ±ΠΈΡΡΡΡ ΡΡΠ΅Π±ΡΠ΅ΠΌΠΎΠ³ΠΎ ΠΊΠ°ΡΠ΅ΡΡΠ²Π° ΠΊΠΎΡΠΏΡΡΠ½ΠΎΠΉ ΠΈΠ·ΠΎΠ»ΡΡΠΈΠΈ ΠΏΡΠΈ ΠΌΠ°ΠΊΡΠΈΠΌΠ°Π»ΡΠ½ΠΎΠΉ ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈΡΠ΅Π»ΡΠ½ΠΎΡΡΠΈ ΠΎΠ±ΠΎΡΡΠ΄ΠΎΠ²Π°Π½ΠΈΡ
Wind Field of a Nonmesocyclone Anticyclonic Tornado Crossing the Hong Kong International Airport
A nonmesocyclone tornado traversed the Hong Kong International Airport on September 6, 2004 directly impacting a surface weather station. This allowed for 1-second 10-meter above ground level (AGL) wind observations through the core of the tornado. Integration of these 10-meter AGL wind data with Ground-Based Velocity Track (GBVTD) wind retrievals derived from LIDAR data provided a time history of the three-dimensional wind field of the tornado. These data indicate a progressive decrease in radial inflow with time and little to no radial inflow near the time the tornado crosses the surface weather station. Anemometer observations suggest that the tangential winds approximate a modified-Rankine vortex outside the radius of maximum winds, suggesting that frictionally induced radial inflow was confined below 10βmβAGL. The radial-height distribution of angular momentum depicts an increase in low-level angular momentum just prior to the tornado reaching its maximum intensity
The Use of Software Agents for Autonomous Control of a DC Space Power System
In order to enable manned deep-space missions, the spacecraft must be controlled autonomously using on-board algorithms. A control architecture is proposed to enable this autonomous operation for an spacecraft electric power system and then implemented using a highly distributed network of software agents. These agents collaborate and compete with each other in order to implement each of the control functions. A subset of this control architecture is tested against a steadystate power system simulation and found to be able to solve a constrained optimization problem with competing objectives using only local information
Auction Protocols for Decentralized Scheduling
Scheduling is the problem of allocating resources to alternate possible uses over designated periods of time. Several have proposed (and some have tried) market-based approaches to decentralized versions of the problem, where the competing uses are represented by autonomous agents. Market mechanisms use prices derived through distributed bidding protocols to determine an allocation, and thus solve the scheduling problem. To analyze the behavior of market schemes, we formalize decentralized scheduling as a discrete resource allocation problem, and bring to bear some relevant economic concepts. Drawing on results from the literature, we discuss the existence of equilibrium prices for some general classes of scheduling problems, and the quality of equilibrium solutions. To remedy the potential nonexistence of price equilibria due to complementarity in preference, we introduce additional markets in combinations of basic goods. We present some auction mechanisms and bidding protocols corresponding to the two market structures, and analyze their computational and economic properties. Finally, we consider direct revelation mechanisms, and compare to the market-based approach.http://deepblue.lib.umich.edu/bitstream/2027.42/50443/1/gebfinal.pd
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