Distributed Delay-Tolerant Strategies for Equality-Constraint Sum-Preserving Resource Allocation

This paper proposes two nonlinear dynamics to solve constrained distributed optimization problem for resource allocation over a multi-agent network. In this setup, coupling constraint refers to resource-demand balance which is preserved at all-times. The proposed solutions can address various model nonlinearities, for example, due to quantization and/or saturation. Further, it allows to reach faster convergence or to robustify the solution against impulsive noise or uncertainties. We prove convergence over weakly connected networks using convex analysis and Lyapunov theory. Our findings show that convergence can be reached for general sign-preserving odd nonlinearity. We further propose delay-tolerant mechanisms to handle general bounded heterogeneous time-varying delays over the communication network of agents while preserving all-time feasibility. This work finds application in CPU scheduling and coverage control among others. This paper advances the state-of-the-art by addressing (i) possible nonlinearity on the agents/links, meanwhile handling (ii) resource-demand feasibility at all times, (iii) uniform-connectivity instead of all-time connectivity, and (iv) possible heterogeneous and time-varying delays. To our best knowledge, no existing work addresses contributions (i)-(iv) altogether. Simulations and comparative analysis are provided to corroborate our contributions

Risk-based optimal power flow with probabilistic guarantees

ISSN:1879-3517ISSN:0142-061

Mitigation of cascading failures by real-time controlled islanding and graceful load shedding

This paper presents an emergency control strategy, which serves to counteract a cascading disturbance in a large power system that would eventually lead to a blackout. The strategy is composed of two parts: after a disturbance, a real-time controlled islanding algorithm based on slow coherency of synchronous generators and k-means clustering splits the system into autonomously operating parts. The imbalances between load and generation are then accounted for by generator tripping in the generation-rich islands and a novel type of under-frequency load shedding in the load-rich islands, if the available primary control reserves are insufficient or too slow to stabilize the frequency. As opposed to the under-frequency relays in substations which are often used nowadays, the system considered here utilizes a ”smart home ” communication and control infrastructure for assigning frequency thresholds to individual appliances owned by consumers. Pervasive availability of this infrastructure is assumed. The strategy is evaluated in time-domain simulations using the IEEE 118-bus system. I. I

Tailored One Anastomosis Gastric Bypass: 3-Year Outcomes of 94 Patients

Background: One anastomosis gastric bypass (OAGB) claims its place among bariatric operations, proving itself a safe and effective procedure. Methods: This is a retrospective analysis of prospectively collected data regarding 94 patients who underwent surgery in a single surgical unit. Tailoring of the biliopancreatic limb length decided upon preoperative BMI was applied. Patients’ excess weight loss and resolution of comorbidities were evaluated. Data on patients’ nutritional status is also presented. Results: Mean BMI reduction at 36 months postoperatively was 21.7 ± 6.3 kg/m 2 . Mean excess weight loss (%EWL) was 83.6%, 91.8%, and 92.5% at 12, 24, and 36 months postoperatively, respectively. When controlling for preoperative BMI, a 36-month %EWL of 89.1% for the 2-m subgroup, a 95.3% for the 2.5-m subgroup, and a 104.7% for the 3-m subgroup were found. Operation’s success, defined as %EWL greater than 50%, was 97.9% 36 months postoperatively. All patients suffering from hypertension, diabetes, and dyslipidemia achieved full remission. Furthermore, the percentage of patients with obstructive sleep apnea and gastroesophageal reflux disease, achieving full remission was 91.7% and 86.7%, respectively. An incidence of 5.3% new onset regurgitation was noted. Iron deficiency presented in 26 (27.7%) patients postoperatively, vitamin B 12 deficiency in 13 (13.8%), folic acid deficiency in 18 (19.1%), and mild hypoalbuminemia in 7 (7.4%). Major early postoperative complications (Clavien-Dindo grade ≥ 3) were reported in 1.7% of our patients. One (1.1%) patient developed marginal ulcer and two (2.2) patients had late dumping. Conclusions: OAGB is a safe and efficient technique; however, careful selection of patients and postoperative surveillance with respect to weight regain and nutritional deficiencies are mandatory for optimal results. © 2018, Springer Science+Business Media, LLC, part of Springer Nature

30-Day Morbidity and Mortality of Bariatric Surgery During the COVID-19 Pandemic: a Multinational Cohort Study of 7704 Patients from 42 Countries.

BACKGROUND There are data on the safety of cancer surgery and the efficacy of preventive strategies on the prevention of postoperative symptomatic COVID-19 in these patients. But there is little such data for any elective surgery. The main objectives of this study were to examine the safety of bariatric surgery (BS) during the coronavirus disease 2019 (COVID-19) pandemic and to determine the efficacy of perioperative COVID-19 protective strategies on postoperative symptomatic COVID-19 rates. METHODS We conducted an international cohort study to determine all-cause and COVID-19-specific 30-day morbidity and mortality of BS performed between 01/05/2020 and 31/10/2020. RESULTS Four hundred ninety-nine surgeons from 185 centres in 42 countries provided data on 7704 patients. Elective primary BS (n = 7084) was associated with a 30-day morbidity of 6.76% (n = 479) and a 30-day mortality of 0.14% (n = 10). Emergency BS, revisional BS, insulin-treated type 2 diabetes, and untreated obstructive sleep apnoea were associated with increased complications on multivariable analysis. Forty-three patients developed symptomatic COVID-19 postoperatively, with a higher risk in non-whites. Preoperative self-isolation, preoperative testing for SARS-CoV-2, and surgery in institutions not concurrently treating COVID-19 patients did not reduce the incidence of postoperative COVID-19. Postoperative symptomatic COVID-19 was more likely if the surgery was performed during a COVID-19 peak in that country. CONCLUSIONS BS can be performed safely during the COVID-19 pandemic with appropriate perioperative protocols. There was no relationship between preoperative testing for COVID-19 and self-isolation with symptomatic postoperative COVID-19. The risk of postoperative COVID-19 risk was greater in non-whites or if BS was performed during a local peak