Robust Estimator-Based Safety Verification: A Vector Norm Approach

In this paper, we consider the problem of verifying safety constraint satisfaction for single-input single-output systems with uncertain transfer function coefficients. We propose a new type of barrier function based on a vector norm. This type of barrier function has a measurable upper bound without full state availability. An identifier-based estimator allows an exact bound for the uncertainty-based component of the barrier function estimate. Assuming that the system is safe initially allows an exponentially decreasing bound on the error due to the estimator transient. Barrier function and estimator synthesis is proposed as two convex sub-problems, exploiting linear matrix inequalities. The barrier function controller combination is then used to construct a safety backup controller. And we demonstrate the system in a simulation of a 1 degree-of-freedom human-exoskeleton interaction.Comment: 6 pages, 5 figures. Accepted for publication at the 2020 American Control Conference. Copyright IEEE 202

Adaptive Compliance Shaping with Human Impedance Estimation

Human impedance parameters play an integral role in the dynamics of strength amplification exoskeletons. Many methods are used to estimate the stiffness of human muscles, but few are used to improve the performance of strength amplification controllers for these devices. We propose a compliance shaping amplification controller incorporating an accurate online human stiffness estimation from surface electromyography (sEMG) sensors and stretch sensors connected to the forearm and upper arm of the human. These sensor values along with exoskeleton position and velocity are used to train a random forest regression model that accurately predicts a person's stiffness despite varying movement, relaxation, and muscle co-contraction. Our model's accuracy is verified using experimental test data and the model is implemented into the compliance shaping controller. Ultimately we show that the online estimation of stiffness can improve the bandwidth and amplification of the controller while remaining robustly stable.Comment: 8 pages, 9 figures, Accepted for publication at the 2020 American Control Conference. Copyright IEEE 202

The interaction between warming and enrichment accelerates food‐web simplification in freshwater systems

Nutrient enrichment and climate warming threaten freshwater systems. Metabolic theory and the paradox of enrichment predict that both stressors independently can lead to simpler food-webs having fewer nodes, shorter food-chains and lower connectance, but cancel each other's effects when simultaneously present. Yet, these theoretical predictions remain untested in complex natural systems. We inferred the food-web structure of 256 lakes and 373 streams from standardized fish community samplings in France. Contrary to theoretical predictions, we found that warming shortens fish food-chain length and that this effect was magnified in enriched streams and lakes. Additionally, lakes experiencing enrichment exhibit lower connectance in their fish food-webs. Our study suggests that warming and enrichment interact to magnify food-web simplification in nature, raising further concerns about the fate of freshwater systems as climate change effects will dramatically increase in the coming decades

Update On the Status of the FLUKA Monte Carlo Transport Code*

The FLUKA Monte Carlo transport code is a well-known simulation tool in High Energy Physics. FLUKA is a dynamic tool in the sense that it is being continually updated and improved by the authors. We review the progress achieved since the last CHEP Conference on the physics models, some technical improvements to the code and some recent applications. From the point of view of the physics, improvements have been made with the extension of PEANUT to higher energies for p, n, pi, pbar/nbar and for nbars down to the lowest energies, the addition of the online capability to evolve radioactive products and get subsequent dose rates, upgrading of the treatment of EM interactions with the elimination of the need to separately prepare preprocessed files. A new coherent photon scattering model, an updated treatment of the photo-electric effect, an improved pair production model, new photon cross sections from the LLNL Cullen database have been implemented. In the field of nucleus-- nucleus interactions the electromagnetic dissociation of heavy ions has been added along with the extension of the interaction models for some nuclide pairs to energies below 100 MeV/A using the BME approach, as well as the development of an improved QMD model for intermediate energies. Both DPMJET 2.53 and 3 remain available along with rQMD 2.4 for heavy ion interactions above 100 MeV/A. Technical improvements include the ability to use parentheses in setting up the combinatorial geometry, the introduction of pre-processor directives in the input stream. a new random number generator with full 64 bit randomness, new routines for mathematical special functions (adapted from SLATEC). Finally, work is progressing on the deployment of a user-friendly GUI input interface as well as a CAD-like geometry creation and visualization tool. On the application front, FLUKA has been used to extensively evaluate the potential space radiation effects on astronauts for future deep space missions, the activation dose for beam target areas, dose calculations for radiation therapy as well as being adapted for use in the simulation of events in the ALICE detector at the LHC

Guidelines for automated manual infusion: a practical way of prescribing post dilution on-line haemodiafiltration

La hemodiafiltración on-line (HDF-OL) posdilucional es la modalidad más eficaz para obtener la máxima depuración de toxinas urémicas, con un flujo de infusión (Qi) recomendable del 25% del flujo sanguíneo y con el principal inconveniente de provocar alarmas por hemoconcentración a lo largo de la sesión. Recientes avances técnicos permiten la prescripción automática del Qi si se especifican los valores del hematocrito y de las proteínas totales. Como no es posible disponer en cada sesión de estos valores, una forma práctica de pautar la HDF-OL posdilucional es realizar una prescripción automática ajustando el hematocrito y las proteínas totales para obtener al inicio de la sesión la prescripción manual prescrita, a la que llamaremos prescripción manual automatizada. El objetivo del estudio fue comparar la pauta convencional de Qi manual respecto a la manual automatizada. Se incluyeron 30 pacientes (16 varones y 14 mujeres), de 59,9 ± 15 años de edad, en programa de hemodiálisis durante 50,1 ± 67 meses. Cada paciente recibió cuatro sesiones de HDF-OL, dos con Qi manual (monitores 4008-S y 5008) y dos con Qi manual automatizada (M-A), una con Qi igual a la manual y otra incrementando el Qi 20 ml/min (M-A+20). El resto de parámetros de diálisis no variaron: filtro de helixona, tiempo de diálisis 266 ± 39 minutos, flujo de sangre 420 ± 36 ml/min. En cada sesión se recogieron el Kt, la recirculación y las alarmas. No se observaron diferencias significativas en el índice de recirculación ni en la dosis de diálisis medida con el Kt. El volumen total de infusión fue de 24,9 ± 4 l (4008S), 23,4 ± 4 l (5008) con Qi manual, 23,6 ± 4 l (M-A) y 25,8 ± 5 l (M-A+20). En sólo el 14% de los pacientes no hubo incidencias. El número de alarmas fue significativamente superior con la prescripción manual, 55 alarmas con 4008 y 40 con 5008, respecto a la M-A (11, p <0,01) y M-A+20 (16 alarmas). Concluimos que la prescripción del Qi manual automatizada es una forma práctica de prescribir la HDF-OL posdilucional consiguiendo el mismo volumen convectivo y la misma eficacia, con una importante reducción de las alarmas intradiálisis, lo que permite un incremento del Qi un 20% sin aumento del número de alarmas.Post-dilution on-line hemodiafiltration (OL-HDF) is the most efficient infusion mode to obtain maximum clearances of uremic toxins, with a recommended manual infusion flow (Qi) of 25% of the blood flow with the main limitation that causes alarms by hemoconcentration throughout the session. Recent technical advances allow automatic prescription of Qi if hematocrit and total protein (TP) values are specified. As these analytical results are not possible to obtain in each dialysis session, a practical way to prescribe Qi is to make an automatic prescription adjusting the hematocrit and total protein values at the beginning of the session to obtain the manual prescription required and we will call it automatic-manual prescription. The aim of this study was to compare manual Qi with automatic-manual Qi in postdilution OL-HDF. 30 patients (16 men and 14 women), 59.9 +/- 15 years old, in hemodialysis program for 50.1 +/- 67 months were included. Every patient underwent four OL-HDF sessions, two with manual Qi (4008-S and 5008 monitors) and two with automatic-manual Qi (A-M), one with the same Qi and one with manual Qi +20 (A-M+20). The same usual dialysis parameters were maintained: helixone dialyzer, dialysis time of 266 +/- 39 minutes, blood flow of 420 +/- 36. Recirculation, Kt and intradialysis alarms were measured at each session. No significant differences in the fistula recirculation or dialysis dose measured using Kt. Total infusion volume was 24.9 +/- 4 (4008 S), 23.4 +/- 4 L (5008) with manual Qi, 23.6 +/- 4 L (A-M) Qi (NS) and 25.8 +/- 5 L (A-M+20). Only 14% of patients had no incidents. The number of alarms was significantly higher with manual prescription 55 alarms with 4008 and 40 with 5008 vs. AM (11) p < 0.01) and A-M+20 (16 alarms) We concluded that automatic-manual Qi is a practical way for post-dilutional OL-HDF prescription where the same efficiency and total reinfusion volume with an important reduction of intradialysis alarms are obtained, allowing to rise Qi by 20% without increasing intradialysis alarms