55 research outputs found
Man-machine interface prptotype for realtime prediction of motion of exoskeleton's users
No full textLAUREA MAGISTRALEIn the United States, over 282.000 people today are affected by Spinal Cord Injury, which is a traumatic damage to the spinal cord that leads to a partial or total body paralysis. At the UC Berkeley Human Robotics & Engineering Laboratory has been developed the Phoenix Exoskeleton which aims to reduce the impediments due to this physical damage by replacing the wheelchair in order to give to the patients the opportunity of changing their quality life, by improving overall health and mobility. This work introduces an innovative approach for replacing the current user interface, allowing to the user to have an interaction with the device totally free of active inputs, while walking, through a safe system which predicts in real time the users intentions. The software prototype is designed for providing an MMI (Man-Machine Interface) able to reduce the time gap and the balance variation between the moment when the intention of walking presents itself and the trigger of the swing really happens, according to the empiric hypothesis formulated by the author which assumes that exoskeletons users have involuntary body movements which differentiate their motion desires. The system has been developed using a machine learning model fed with post- processed data collected by two encoders and one IMU, which describe the users gait. It has been called Body Motion Triggering.
The efficiency of the prototype has been tested in laboratory by the pilot: the system turned out to be totally safe; the predicting outcomes still need to be widely improved but the achieved results are encouraging and have demonstrated the validity of the formulated hypothesis, opening a new potential field of research.
The hope behind the analysis carried out is to have been useful in order to improve the lives of people that need it
Highly concentrated H2O2 preparation, stabilization and decomposition over manganese oxide-based catalysts for space propulsion
No full textHigh concentration hydrogen peroxide (HP) promises to be an economical and green alternative for hydrazine. However, it has only limited storage life, and addition of stabilizers must be avoided to preserve the high purity required for propellants. This work has investigated the mechanical fastening of normally dissolved stabilizers on the decomposition of HP. Furthermore, there is currently no suitable ignition system for HP-ethanol rocket motors, despite extensive research. This work has investigated the viability of using a supported catalyst to decompose HP; the hence liberated heat can potentially be used to ignite ethanol. Different mechanically rigid ceramic catalyst bodies were prepared based on manganese oxide. Their reactivity was verified by repeated release of 98% HP droplets; the subsequent reaction was monitored with thermocouples and high speed imaging. This showed that γ-alumina offered the highest reactivity and thermomechanical stability. Lastly, tests showed that these catalysts may induce ignition in HP-ethanol engines. Aerospace Engineerin
General Reinforcement Learning Agents for Crop Management
No full textAgriculture plays a vital role in the global economy, providing the necessary food and resources for human survival. With the world’s population projected to surge, the demand for food is set to escalate in the coming decades. This increasing demand, coupled with the challenges posed by climate change and the detrimental effects of pollution due to fertiliz-ers, underscores the urgency for more efficient and sustainable crop management strategies. Effective crop management is a complex and time-consuming task that involves various fac-tors, including climate conditions and soil quality. Traditional crop management strategies often rely on expert knowledge to guide the decision-making process, which may be sub-optimal and prone to error. Reinforcement learning (RL) has gained significant attention in recent years as a promising approach for decision-making and control in agriculture, aiding in the management process. RL environments such as CyclesGym [51], accommodate the design of agents that oper-ate within an agricultural system, often surpassing the performance of traditional strategies. However, the optimal policy may vary heavily depending on the specific field location, due to its specific weather conditions and soil quality. In this thesis, we aim to investigate the use of RL for managing fields in multiple locations with the aim of reducing training time and data and increasing robustness compared to independent training. To this end, we plan to use multi-task learning methods and optimizers to reduce total training time, to improve RL agents’ adaptability to changing environments, and to reduce data usage required for maximum performance across multiple agricultural fields.Computer Scienc
Bitcoin-Compatible Virtual Channels
No full textCurrent permissionless cryptocurrencies such as Bitcoin suffer from a limited transaction rate and slow confirmation time, which hinders further adoption. Payment channels are one of the most promising solutions to address these problems, as they allow the parties of the channel to perform arbitrarily many payments in a peer-to-peer fashion while uploading only two transactions on the blockchain. This concept has been generalized into payment channel networks where a path of payment channels is used to settle the payment between two users that might not share a direct channel between them. However, this approach requires the active involvement of each user in the path, making the system less reliable (they might be offline), more expensive (they charge fees per payment), and slower (intermediaries need to be actively involved in the payment). To mitigate this issue, recent work has introduced the concept of virtual channels (IEEE SP'19), which involve intermediaries only in the initial creation of a bridge between payer and payee, who can later on independently perform arbitrarily many off-chain transactions. Unfortunately, existing constructions are only available for Ethereum, as they rely on its account model and Turing-complete scripting language. The realization of virtual channels in other blockchain technologies with limited scripting capabilities, like Bitcoin, was so far considered an open challenge.In this work, we present the first virtual channel protocols that are built on the UTXO-model and require a scripting language supporting only a digital signature scheme and a timelock functionality, being thus backward compatible with virtually every cryptocurrency, including Bitcoin. We formalize the security properties of virtual channels as an ideal functionality in the Universal Composability framework and prove that our protocol constitutes a secure realization thereof. We have prototyped and evaluated our protocol on the Bitcoin blockchain, demonstrating its efficiency: for n sequential payments, they require an off-chain exchange of 9+2n transactions or a total of 3524+695n bytes, with no on-chain footprint in the optimistic case. This is a substantial improvement compared to routing payments in a payment channel network, which requires 8n transactions with a total of 3026n bytes to be exchanged.Accepted author manuscriptData-Intensive System
Firm’s Intangible Assets and Multinational Activity: Joint-Venture Versus FDI
No full textThis paper provides a theoretical formalisation of the joint-venture contract, as an alternative to Foreign Direct Investment (FDI), within a Dissipation of Intangible Assets framework. In a two-period, two-country equilibrium model, we discuss how the threat of knowledge spillover shapes the boundaries of a Multinational Enterprise. Similarly to the theoretical findings on the FDI-licensing trade off, we show that Foreign Direct Investment is more likely to emerge when know-how easily spills over – i.e. when firms are endowed with more intangible assets or they belong to high tech industries. Probit estimates, from an entirely new firm-level dataset, constructed by the author, show that the experience of Italian multinationals in Asia is in line with our theoretical predictions.Intangible assets, Internalisation, FDI, Joint-venture, Asia
Standards for UAS - Acceptable Means of Compliance for Low Risk SORA Operations
No full textUnmanned aircraft systems (UAS) have been in civil use for several years. A new risk-based approach to approval was developed by the Joint Authorities for Rulemaking of Unmanned Systems (JARUS) which relies on the so-called Specific Operations Risk Assessment (SORA) for the specific category. Operational authorization is based on the assessment using the SORA process, which evaluates the safety of the operation and not solely the aircraft design. However, to comply with the resulting mitigations it is necessary to convince authorities using “Acceptable Means of Compliance” (AMC). The goal of the European research project “AW-Drones” is to identify and assess existing standards as a possible AMC for the existing and upcoming regulations. The research in “AW-Drones” is performed by an international consortium of industry and research agencies. Additional stakeholders support the project, including the European Union Aviation Safety Agency (EASA) and other groups of experts, committees, and Standard Development Organizations (SDOs). In this paper, the approach and methodology to identify possible AMC for the SORA is described, including the current state of work. The results of the data collection step and the assessment are outlined. The used criteria are shown and the impact on the SORA process is discussed. An outlook will detail on remaining tasks. The dissemination of the work in a public database is presented that offers the results on AMC assessment directly to a drone operator.Virtual/online event due to COVID-19 Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Control & Simulatio
A Tale of Three Countries: Italian, Spanish and Swiss Manufacturing Operations in China
No full textIn this paper we investigate the choice of FDI versus joint-venture, made by Italian, Spanish and Swiss multinationals in China, as shaped by the risk of Dissipation of Intangible Assets. Probit estimates, based on an entirely new firm-level dataset, constructed by the author, show that FDI is more likely to emerge when know-how easily spills over - namely for firms endowed with more Intangible Assets or belonging to high tech sectors - in line with the theoretical expectations.Intangible Assets, Internalisation, FDI, Joint-venture, China
Very-High-Resolution Airborne Synthetic Aperture Radar Imaging: Signal Processing and Applications
No full textPrognostic role of endocarditis in isolated tricuspid valve surgery. A propensity-weighted study
No full textObjectives
The role of the underlying etiology in isolated tricuspid valve surgery has not been investigated extensively in current literature. Aim of this study was to analyse outcomes of patients undergoing surgery due to endocarditis compared to other pathologies.
Methods
The SURTRI study is a multicenter study enrolling adult patients who underwent isolated tricuspid valve surgery (n = 406, 55 ± 16 y.o.; 56% female) at 13 international sites. Propensity weighted analysis was performed to compare groups (IE group n = 107 vs Not-IE group n = 299).
Results
No difference was found regarding the 30-day mortality (Group IE: 2.8% vs Group Not-IE = 6.8%; OR = 0.45) and major adverse events. Weighted cumulative incidence of cardiac death was significantly higher for patients with endocarditis (p = 0.01). The composite endpoint of cardiac death and reoperation at 6 years was reduced in the Group IE (63.2 ± 6.8% vs 78.9 ± 3.1%; p = 0.022). Repair strategy resulted in an increased late survival even in IE cases.
Conclusions
Data from SURTRI study report acceptable 30-day results but significantly reduced late survival in the setting of endocarditis of the tricuspid valve. Multi-disciplinary approach, repair strategy and earlier treatment may improve outcomes.
© 2022 The Author
- …
