Data-Driven Safety Filter: An Input-Output Perspective

Implementation of learning-based control remains challenging due to the absence of safety guarantees. Safe control methods have turned to model-based safety filters to address these challenges, but this is paradoxical when the ultimate goal is a model-free, data-driven control solution. Addressing the core question of "Can we ensure the safety of any learning-based algorithm without explicit prediction models and state estimation?" this paper proposes a Data-Driven Safety Filter (DDSF) grounded in Behavioral System Theory (BST). The proposed method needs only a single system trajectory available in an offline dataset to modify unsafe learning inputs to safe inputs. This contribution addresses safe control in the input-output framework and therefore does not require full state measurements or explicit state estimation. Since no explicit model is required, the proposed safe control solution is not affected by unmodeled dynamics and unstructured uncertainty and can provide a safe solution for systems with unknown time delays. The effectiveness of the proposed DDSF is illustrated in simulation for a high-order six-degree-of-freedom aerial robot and a time-delay adaptive cruise control system

A comprehensive study of effective parameters on the thermal performance of porous media micro combustor in thermo photovoltaic systems

Low thermal performance is one of the biggest challenges of using micro combustor in Thermo-photovoltaic (TPV) system. In this study, a novel micro-combustor with porous media was designed and installed to enhance energy and exergy performance. Furthermore, the effects of several effective parameters including different porous media materials, length, porosity coefficient, and inlet mass flow on energy efficiency, exergy, entropy generation, wall temperature and its uniformity were studied. A comprehensive CFD model for using porous media in the micro-combustor of TPV systems was proposed. Results showed utilizing porous media significantly improve the exergy efficiency and energy output of TPV system. Therefore, using a 6 mm long porous media increased the average wall temperature by 111 K compared to the case without porous media. Additionally, the uniformity coefficient of the wall temperature decreased by 80.05 %, from 4.58 % to 0.89 %. This reduction increased the temperature uniformity of the outer wall of the micro-combustor with porous media compared to the case without a media, increasing the system’s lifetime. Moreover, the 6 mm-long porous media enhanced radiation efficiency and exergy efficiency by 37 % and 79.7 %, respectively, compared to the conventional micro combustor. The total energy conversion efficiency from the fuel chemical energy to electric power increased from 8.9 % to 12.32 %.<br/

A comprehensive study of effective parameters on the thermal performance of porous media micro combustor in thermo photovoltaic systems

Low thermal performance is one of the biggest challenges of using micro combustor in Thermo-photovoltaic (TPV) system. In this study, a novel micro-combustor with porous media was designed and installed to enhance energy and exergy performance. Furthermore, the effects of several effective parameters including different porous media materials, length, porosity coefficient, and inlet mass flow on energy efficiency, exergy, entropy generation, wall temperature and its uniformity were studied. A comprehensive CFD model for using porous media in the micro-combustor of TPV systems was proposed. Results showed utilizing porous media significantly improve the exergy efficiency and energy output of TPV system. Therefore, using a 6 mm long porous media increased the average wall temperature by 111 K compared to the case without porous media. Additionally, the uniformity coefficient of the wall temperature decreased by 80.05 %, from 4.58 % to 0.89 %. This reduction increased the temperature uniformity of the outer wall of the micro-combustor with porous media compared to the case without a media, increasing the system’s lifetime. Moreover, the 6 mm-long porous media enhanced radiation efficiency and exergy efficiency by 37 % and 79.7 %, respectively, compared to the conventional micro combustor. The total energy conversion efficiency from the fuel chemical energy to electric power increased from 8.9 % to 12.32 %.<br/

Digital Subtraction Phonocardiography (DSP) applied to the detection and characterization of heart murmurs

<p>Abstract</p> <p>Background</p> <p>During the cardiac cycle, the heart normally produces repeatable physiological sounds. However, under pathologic conditions, such as with heart valve stenosis or a ventricular septal defect, blood flow turbulence leads to the production of additional sounds, called murmurs. Murmurs are random in nature, while the underlying heart sounds are not (being deterministic).</p> <p>Innovation</p> <p>We show that a new analytical technique, which we call Digital Subtraction Phonocardiography (DSP), can be used to separate the random murmur component of the phonocardiogram from the underlying deterministic heart sounds.</p> <p>Methods</p> <p>We digitally recorded the phonocardiogram from the anterior chest wall in 60 infants and adults using a high-speed USB interface and the program Gold Wave <url>http://www.goldwave.com</url>. The recordings included individuals with cardiac structural disease as well as recordings from normal individuals and from individuals with innocent heart murmurs. Digital Subtraction Analysis of the signal was performed using a custom computer program called <b>Murmurgram</b>. In essence, this program subtracts the recorded sound from two adjacent cardiac cycles to produce a difference signal, herein called a "murmurgram". Other software used included Spectrogram (Version 16), GoldWave (Version 5.55) as well as custom MATLAB code.</p> <p>Results</p> <p>Our preliminary data is presented as a series of eight cases. These cases show how advanced signal processing techniques can be used to separate heart sounds from murmurs. Note that these results are preliminary in that normal ranges for obtained test results have not yet been established.</p> <p>Conclusions</p> <p>Cardiac murmurs can be separated from underlying deterministic heart sounds using DSP. DSP has the potential to become a reliable and economical new diagnostic approach to screening for structural heart disease. However, DSP must be further evaluated in a large series of patients with well-characterized pathology to determine its clinical potential.</p

Effect of Amount of 3-Methacryloxy Propyl Thrimethoxysilane Coupling Agent and Nano Filling Structure on Physic-Mechanical Properties of Dental Resin Composite

Many researchers in the field of dental polymeric base nano composite investigated the effect filling morphology and filling material content on mechanical and physical properties of construction after setting reaction. Our present study concentrated on the effect of ϒ metacryloxy propyloxt tri metoxy silane (ϒ MPS) content as coupling agent (orgnic material) on physical and mechanical performance of nano composite material. It was shown that despite of contraction after setting reaction, all this properties improved and efficient silanization can efficiently affect structural integrity of dental filling nano composite</p

Electrospun Poly Caprolactone-Carbon Nanotube Scaffold for Nerve Regeneration in Dental Tissue Engineering

Regeneration and engineering of functional new tissues containing the neural network have great importance. Progression of neural network into the dental tissue has a crucial role in dental tissue regeneration. In the present study polymer-ceramic blended scaffolds containing different weight percentages of carbon nanotube in poly caprolactone nanofiber matrix were fabricated. Morphological, mechanical and electrical properties of the prepared scaffolds have been characterized. Results showed that the sample containing 5 weight % of carbon nanotube had the smallest mean fiber diameter (50 - 300 nm) and the highest mechanical behavior. Also, its electrical conductivity was suitable to be used in nerve tissue scaffolds. The static culture of the Schwann cells on the prepared scaffolds indicated that increasing weight percentage of carbon nanotube into the polycaprolactone matrix up to the 5 wt. % enhanced cell viability