Search

Event-triggered control, as networked systems are popular, is increasingly appreciated. Such control could arouse essential saving of communication/computation and would lay the groundwork for networked (control) systems. However, due to the discontinuity and hybrid nature of event-triggered control, the exclusion of Zeno phenomenon is the premise of its workability. Aiming to circumvent the Zeno behaviour more explicitly, we attach a dynamic dwell time to triggering mechanism and propose a new adaptive event-triggered control scheme for uncertain nonlinear systems. Specifically, a set of dynamic gains are first introduced to compensate for large uncertainties and nonlinearities, and the indispensability of a set of gains rather than a gain is elaborated on. Then, from a dynamic-gain-dependent monitoring rule, the positive dwell time is generated so that the Zeno phenomenon can be excluded automatically. In particular, the rule enables system behaviour to be always monitored by evaluating the sampling errors of gains. Based on this, we construct an adaptive controller with linear structure, which allows the execution error can be estimated explicitly, and in turn suppressed by the gains. It is shown that, with the proposed event-triggered control, all the closed-loop system signals are bounded and the system state ultimately converges to zero. Notably, the designed triggering mechanism could save more resources in theory since the event detection and gains monitoring are performed alternately. The effectiveness and superiority of the proposed scheme is illustrated by two simulation examples. [ABSTRACT FROM AUTHOR]

The aim of this retrospective study was to assess the value of using an enema alone for mechanical bowel preparation (MBP) before transvaginal pelvic floor reconstruction (TPFR) in patients ≥65 years old. In total, 190 patients were included [81 in the enema group vs. 109 in the enema + polyethylene glycol (PEG) group]. The levels of serum potassium (p =.004) and calcium (p =.005) were higher in the enema group after surgery. The decrease in serum calcium was more significant in the enema + PEG group (p =.027). More patients in the enema + PEG group developed hypokalaemia (p =.035) or hypocalcaemia (p =.008) after surgery. The incidence of thrombus and surgical site infection was similar and earlier bowel movement was evident in the enema group (p =.000). Overall, the enema group used more laxatives (p =.026). Using enema alone before TPFR reduces the incidence of electrolyte disturbances with no increase in surgical complications in elderly patients. What is already known on this subject? TPFR is an effective treatment for pelvic organ prolapse (POP) in elderly women. Bowel preparation performed before gynecological surgery can reduce surgical site infection, but increase discomfort and electrolyte disturbance. What do the results of this study add? The levels of serum potassium and calcium were lower in the enema + PEG group than in the enema group after surgery and more patients developed hypokalaemia or hypocalcaemia in the enema + PEG group. The incidence of thrombus and surgical site infection was similar between the two groups. Bowel movement was earlier in the enema group. What are the implications of these findings for clinical practice and/or future research? Using enema alone before TPFR reduces the incidence of electrolyte disturbance and does not increase surgical complications. This conclusion needs to be confirmed by random controlled trial studies in the future. [ABSTRACT FROM AUTHOR]

In this paper, an observer-based adaptive neural tracking control approach is proposed for a class of stochastic nonlinear systems with immeasurable states. The radial basis function neural networks (RBFNNs) are used to approximate the unknown nonlinear functions, and a linear reduced-order state observer is designed for estimating the unmeasured states. Based on the designed the state observer, an adaptive neural output feedback control approach is developed via backstepping control design. It is shown that the proposed controller ensures that all signals of the closed-loop system remain bounded in probability, and the tracking error converges to an arbitrarily small neighbourhood around the origin in the sense of mean quartic value. Finally, two examples are given to illustrate the effectiveness of the proposed design approach. [ABSTRACT FROM AUTHOR]

This paper is concerned with the problem of multi-dimensional Taylor network (MTN) tracking control for a class of nonlinear systems with unknown control direction. By combining MTN' universal approximation ability and adaptive control method in the backstepping recursive design, a new adaptive MTN control approach is presented for the nonlinear system. The computation complexity of the designed controller has significantly reduced thanks to the simple structure of MTN. It is shown that the designed controller can guarantee all the signals in the closed-loop system remain bounded and the tracking error finally converges to a small neighbourhood of the origin. Finally, simulation results demonstrate the effectiveness of the proposed design approach. [ABSTRACT FROM AUTHOR]

Background: The optimal PECD surgical approach for cervical intervertebral disc herniation (CIVDH) remains controversial. The conventional posterior K-hole approach for PECD leads to damage of facet joint. Objectives: This article is to first describe a novel posterior lamina–hole approach of percutaneous endoscopic cervical discectomy (PECD) for CIVDH. The objective of this study is to evaluate the feasibility and short-term clinical effect of this approach. Methods: Single-center retrospective observational study of all patients managed with posterior percutaneous endoscopic cervical discectomy (PPECD) using the lamina–hole approach for symptomatic single-level CIVDH between January 2015 and January 2016. The clinical outcomes were evaluated with the visual analog scale, modified MacNab criteria and radiographical results. Results: Twelve patients (seven women, five men) were enrolled in the study. Positive clinical response for pain relief was achieved in these patients receiving PPECD through lamina–hole approach for CIVDH. Postoperative MRI showed complete removal of the disc material in all the patients, no failure due to residual fragment was observed. Conclusion: As an alternative surgical approach of PPECD, PPECD through lamina–hole approach is a novel access for CIVDH and may be considered a valid and safe therapeutic option for CIVDH. The advantages of this approach are not only providing a valid and secure access to herniated cervical intervertebral fragment but also avoiding the iatrogenic damage to the facet joint and relevant functional spinal unit (FSU). Theoretically, the potential of secondary degeneration of FSU is low. [ABSTRACT FROM AUTHOR]