A data-driven and risk-based prudential approach to validate the DDMRP planning and control system

In this paper, we study the single-item dynamic lot-sizing problem in an environment characterized by stochastic demand and lead times. A recent heuristic called Demand Driven MRP, widely implemented using modern ERP systems, proposes an algorithm that is will effectively tackle this problem. Our primary goal is to propose a theoretical foundation for such a heuristic approach. To this aim, we develop an optimization model inspired by the main principles behind the heuristic algorithm. Specifically, controls are of the type (s(t), S(t)) with time varying thresholds that react to short-run real orders; in this respect, control is risk-based and data-driven. We also consider service levels derived as tail risk measures to ensure fulfillment of realized demand with a predetermined probability; in this respect, our approach is prudential. Finally, we use our model as a benchmark to theoretically validate and contextualize the aforementioned heuristic

Diseño del sistema de alcantarillado sanitario y conexiones domiciliarias en la localidad periférica El Platanar Cascas, Gran Chimu - La Libertad, usando el programa Sewercad

En el presente proyecto de tesis se formuló el DISEÑO DEL SISTEMA DE ALCANTARILLADO SANITARIO Y CONEXIONES DOMICILIARIAS, EN LA LOCALIDAD PERIFERICA EL PLATANAR EN CASCAS, GRAN CHIMÚ – LA LIBERTAD, USANDO EL PROGRAMA SEWERCAD; para el abastecimiento de redes de alcantarillado sanitario a la población del sector platanar. Para el cálculo hidráulico de alcantarillado se diseñará considerando las normas de obras de saneamiento (OS. 070) necesario para cumplir con los criterios de diseño para un óptimo proyecto a desarrollar en la zona rural del platanar. Adjuntando en el padrón la cantidad de viviendas existentes para el cálculo poblacional, asimismo se realizó un estudio de mecánica de suelos para identificar que sales solubles se encuentran y puedan afectar a la red de alcantarillado, por otro lado, se realizó un levantamiento topográfico para la definición de la red de alcantarillado; todo esto es necesario para ser usado en el diseño y cálculo hidráulico del alcantarillado en el software SEWERCAD. La zona del platanar presenta cotas altas y bajas por ser zona rural, esto me obliga a tener en cuenta la altura de buzones, en ciertos tramos de tubería se tiene que incrementar la altura de buzón del mínimo que es 1.20 m; contando con cinco buzones de arranque (Bz-01, Bz-06, Bz-08, Bz-49, Bz-45A), 64 buzones distribuidos en toda la red de alcantarillado, con 64 tramos de tubería, teniendo así una longitud total de tubería de 2965.02 metros lineales; se deberá cumplir con los criterios establecidos en la OS. 070, para una óptima proyección del sistema de redes. Se tiene como objetivo la realización del diseño y cálculo hidráulico del sistema de alcantarillado para dotar con un sistema de red de alcantarillado y evacuar las aguas residuales de esta zona a una PTAR. Con esto llegamos a la conclusión de la importancia de proporcionar un tendido de tuberías a lo largo de la zona el platanar rigiéndonos de un cálculo hidráulico de alcantarilladoIn this thesis project, the DESIGN OF THE SANITARY SEWERAGE SYSTEM AND DOMICILIARY CONNECTIONS IN THE PERIPHERAL LOCALITY OF EL PLATANAR IN CASCAS, GRAN CHIMÚ - LA LIBERTAD, USING THE SEWERCAD PROGRAM, was formulated for the supply of sanitary sewerage networks to the population of the platanar sector. For the hydraulic calculation of the sewerage system, it will be designed considering the sanitation works standards (OS. 070) necessary to comply with the design criteria for an optimal project to be developed in the rural area of El Platanar. Also, a soil mechanics study was carried out to identify the soluble salts that are found and may affect the sewerage network, on the other hand, a topographic survey was carried out to define the sewerage network; all this is necessary to be used in the design and hydraulic calculation of the sewerage system in the SEWERCAD software. The banana plantation area has high and low levels because it is a rural area, this forces me to take into account the height of mailboxes, in certain sections of pipes the height of the mailbox must be increased from the minimum, which is 1.20 m; having five starting mailboxes (Bz-01, Bz-06, Bz-08, Bz-49, Bz-45A), 64 mailboxes distributed throughout the sewerage network, with 64 pipe sections, thus having a total length of pipeline of 2965.02 linear meters; the criteria established in the OS must be met. 070, for an optimal projection of the net system. The objective is to carry out the design and hydraulic calculation of the sewage system to provide a sewage network system and evacuate wastewater from this area. With this we conclude the importance of providing a piping system along the Platanar area, based on a hydraulic sewerage calculationTesi

Ultra Low Specific Contact Resistivity in Metal-Graphene Junctions via Atomic Orbital Engineering

A systematic investigation of graphene edge contacts is provided. Intentionally patterning monolayer graphene at the contact region creates well-defined edge contacts that lead to a 67% enhancement in current injection from a gold contact. Specific contact resistivity is reduced from 1372 {\Omega}m for a device with surface contacts to 456 {\Omega}m when contacts are patterned with holes. Electrostatic doping of the graphene further reduces contact resistivity from 519 {\Omega}m to 45 {\Omega}m, a substantial decrease of 91%. The experimental results are supported and understood via a multi-scale numerical model, based on density-functional-theory calculations and transport simulations. The data is analyzed with regards to the edge perimeter and hole-to-graphene ratio, which provides insights into optimized contact geometries. The current work thus indicates a reliable and reproducible approach for fabricating low resistance contacts in graphene devices. We provide a simple guideline for contact design that can be exploited to guide graphene and 2D material contact engineering.Comment: 26 page

The role of chemistry in the oscillating combustion of hydrocarbons : an experimental and theoretical study

The stable operation of low-temperature combustion processes is an open challenge, due to the presence of undesired deviations from steady-state conditions: among them, oscillatory behaviors have been raising significant interest. In this work, the establishment of limit cycles during the combustion of hydrocarbons in a wellstirred reactor was analyzed to investigate the role of chemistry in such phenomena. An experimental investigation of methane oxidation in dilute conditions was carried out, thus creating quasi-isothermal conditions and decoupling kinetic effects from thermal ones. The transient evolution of the mole fractions of the major species was obtained for different dilution levels (0.0025 <= X-CH4 <= 0.025), inlet temperatures (1080K <= T <= 1190K) and equivalence ratios (0.75 <= Phi <= 1). Rate of production analysis and sensitivity analysis on a fundamental kinetic model allowed to identify the role of the dominating recombination reactions, first driving ignition, then causing extinction. A bifurcation analysis provided further insight in the major role of these reactions for the reactor stability. One-parameter continuation allowed to identify a temperature range where a single, unstable solution exists, and where oscillations were actually observed. Multiple unstable states were identified below the upper branch, where the stable (cold) solution is preferred. The role of recombination reactions in determining the width of the unstable region could be captured, and bifurcation analysis showed that, by decreasing their strength, the unstable range was progressively reduced, up to the full disappearance of oscillations. This affected also the oxidation of heavier hydrocarbons, like ethylene. Finally, less dilute conditions were analyzed using propane as fuel: the coupling with heat exchange resulted in multiple Hopf Bifurcations, with the consequent formation of intermediate, stable regions within the instability range in agreement with the experimental observations

DMAP: a Distributed Morphological Attention Policy for Learning to Locomote with a Changing Body

Biological and artificial agents need to deal with constant changes in the real world. We study this problem in four classical continuous control environments, augmented with morphological perturbations. Learning to locomote when the length and the thickness of different body parts vary is challenging, as the control policy is required to adapt to the morphology to successfully balance and advance the agent. We show that a control policy based on the proprioceptive state performs poorly with highly variable body configurations, while an (oracle) agent with access to a learned encoding of the perturbation performs significantly better. We introduce DMAP, a biologically-inspired, attention-based policy network architecture. DMAP combines independent proprioceptive processing, a distributed policy with individual controllers for each joint, and an attention mechanism, to dynamically gate sensory information from different body parts to different controllers. Despite not having access to the (hidden) morphology information, DMAP can be trained end-to-end in all the considered environments, overall matching or surpassing the performance of an oracle agent. Thus DMAP, implementing principles from biological motor control, provides a strong inductive bias for learning challenging sensorimotor tasks. Overall, our work corroborates the power of these principles in challenging locomotion tasks

Translocation of a polymer chain driven by a dichotomous noise

We consider the translocation of a one-dimensional polymer through a pore channel helped by a motor driven by a dichotomous noise with time exponential correlation. We are interested in the study of the translocation time, mean velocity and stall force of the system as a function of the mean driving frequency. We find a monotonous translocation time, in contrast with the mean velocity which shows a pronounced maximum at a given frequency. Interestingly, the stall force shows a nonmonotonic behavior with the presence of a minimum. The influence of the spring elastic constant to the mean translocation times and velocities is also presented.Comment: 11 pages, 7 figure

Scalable Approach to Uncertainty Quantification and Robust Design of Interconnected Dynamical Systems

Development of robust dynamical systems and networks such as autonomous aircraft systems capable of accomplishing complex missions faces challenges due to the dynamically evolving uncertainties coming from model uncertainties, necessity to operate in a hostile cluttered urban environment, and the distributed and dynamic nature of the communication and computation resources. Model-based robust design is difficult because of the complexity of the hybrid dynamic models including continuous vehicle dynamics, the discrete models of computations and communications, and the size of the problem. We will overview recent advances in methodology and tools to model, analyze, and design robust autonomous aerospace systems operating in uncertain environment, with stress on efficient uncertainty quantification and robust design using the case studies of the mission including model-based target tracking and search, and trajectory planning in uncertain urban environment. To show that the methodology is generally applicable to uncertain dynamical systems, we will also show examples of application of the new methods to efficient uncertainty quantification of energy usage in buildings, and stability assessment of interconnected power networks

Simulation of contact resistance in patterned graphene

While trying to exploit graphene in Radio Frequency applications, the reduction of the contact resistance (Rc) is probably one of the most challenging technological issues to be solved. Graphene patterning under the metal has been demonstrated to be a promising solution, leading to a reduction of Rc by up to a factor of 20, probably due to an increased conductivity at the borders of the patterns of graphene. This technology is still at the early stage and a complete understanding of the physical mechanisms at play is lacking. To this purpose we propose a multi- scale approach based on first-principle calculations, and the solution of the continuity equation to compute Rc in the considered patterned contacts

Latent Exploration for Reinforcement Learning

In Reinforcement Learning, agents learn policies by exploring and interacting with the environment. Due to the curse of dimensionality, learning policies that map high-dimensional sensory input to motor output is particularly challenging. During training, state of the art methods (SAC, PPO, etc.) explore the environment by perturbing the actuation with independent Gaussian noise. While this unstructured exploration has proven successful in numerous tasks, it ought to be suboptimal for overactuated systems. When multiple actuators, such as motors or muscles, drive behavior, uncorrelated perturbations risk diminishing each other's effect, or modifying the behavior in a task-irrelevant way. While solutions to introduce time correlation across action perturbations exist, introducing correlation across actuators has been largely ignored. Here, we propose LATent TIme-Correlated Exploration (Lattice), a method to inject temporally-correlated noise into the latent state of the policy network, which can be seamlessly integrated with on- and off-policy algorithms. We demonstrate that the noisy actions generated by perturbing the network's activations can be modeled as a multivariate Gaussian distribution with a full covariance matrix. In the PyBullet locomotion tasks, Lattice-SAC achieves state of the art results, and reaches 18% higher reward than unstructured exploration in the Humanoid environment. In the musculoskeletal control environments of MyoSuite, Lattice-PPO achieves higher reward in most reaching and object manipulation tasks, while also finding more energy-efficient policies with reductions of 20-60%. Overall, we demonstrate the effectiveness of structured action noise in time and actuator space for complex motor control tasks.Comment: Code available at https://github.com/amathislab/lattic

NanoSat MO Framework: Enabling AI Apps for Earth Observation

Following the success of the first Phi-Sat mission, in 2020, the European Space Agency (ESA) announced the opportunity to present CubeSat-based ideas for the Phi-Sat-2 mission as part of its initiative to promote the development of radically innovative technologies such as Artificial Intelligence (AI) capabilities onboard Earth Observation (EO) missions. Open Cosmos and CGI submitted a joint proposal for the Phi-Sat-2 mission idea, which takes advantage of the latest research and developments in the European ecosystem. The proposed mission idea is a game-changing EO CubeSat capable of running AI Apps that can be developed, easily deployed on the spacecraft and updated during flight operations. The AI Apps can be operated from ground using a simple user interface. This approach allows continuous improvement of the AI model parameters using the very same images acquired by the satellite. The mission takes advantage of the latest research for mission operations of CubeSats and use the NanoSat MO Framework, a framework for small satellites that allows software to be deployed in space as simple Apps, in a similar fashion to Android apps. This framework was previously demonstrated in ESA’s OPS-SAT mission, and supports the orchestration of on-board Apps. It fully decouples the App features from the underlying on-board hardware via an abstraction layer API in the form of services. Additionally, it includes a Software Development Kit with demo Apps, development tools, and tutorials to facilitate the development of Apps. By decoupling the data platform from the Apps, it is possible to distribute the development of specialized AI Apps to different partners within the Phi-Sat-2 mission consortium. The mission will include a set of default AI Apps that will be able to do vessel detection, forest monitoring, and roadmap transformation from satellite imagery. The framework allows more than just the set of default Apps and so, third-party Apps can be included on later stages of the mission lifecycle. This paper will present the NanoSat MO Framework, introduce the AI Apps that are part of the Phi-Sat-2 mission, and how the free and open-source framework enables the creation of software-defined satellite missions via on-board Apps