Vibration control by means of piezoelectric actuators shunted with LR impedances: Performance and robustness analysis

This paper deals with passive monomodal vibration control by shunting piezoelectric actuators to electric impedances constituting the series of a resistance and an inductance. Although this kind of vibration attenuation strategy has long been employed, there are still unsolved problems; particularly, this kind of control does suffer from issues relative to robustness because the features of the electric impedance cannot be adapted to changes of the system. This work investigates different algorithms that can be employed to optimise the values of the electric components of the shunt impedance. Some of these algorithms derive from the theory of the tuned mass dampers. First a performance analysis is provided, comparing the attenuation achievable with these algorithms. Then, an analysis and comparison of the same algorithms in terms of robustness are carried out. The approach adopted herein allows identifying the algorithm capable of providing the highest degree of robustness and explains the solutions that can be employed to resolve some of the issues concerning the practical implementation of this control technique. The analytical and numerical results presented in the paper have been validated experimentally by means of a proper test setup

Vibration Control by Means of Piezoelectric Actuators Shunted with LR

This paper deals with passive monomodal vibration control by shunting piezoelectric actuators to electric impedances constituting the series of a resistance and an inductance. Although this kind of vibration attenuation strategy has long been employed, there are still unsolved problems; particularly, this kind of control does suffer from issues relative to robustness because the features of the electric impedance cannot be adapted to changes of the system. This work investigates different algorithms that can be employed to optimise the values of the electric components of the shunt impedance. Some of these algorithms derive from the theory of the tuned mass dampers. First a performance analysis is provided, comparing the attenuation achievable with these algorithms. Then, an analysis and comparison of the same algorithms in terms of robustness are carried out. The approach adopted herein allows identifying the algorithm capable of providing the highest degree of robustness and explains the solutions that can be employed to resolve some of the issues concerning the practical implementation of this control technique. The analytical and numerical results presented in the paper have been validated experimentally by means of a proper test setup

Damage detection based on strain transmissibility for beam structure by using distributed fiber optics

Structural damage identification is a coral and challenging research topic. Research mainly focuses on identification and detection of linear damage in structures by using modal parameters such as change of natural frequency, frequency response function, mode shape, etc. Transmissibility is conventionally defined as the spectra ratio of two measurement points, which has been utilized for damage identification as a powerful damage indicator. In this paper, strain transmissibility, defined as ratio of strain response spectra, is proposed as a new damage indicator. In order to achieve more precise sensing information, distributed fiber optics has been applied to damage detection on a beam structure, which adds new capability of sensing with its combination of high spatial density sensing and dynamic acquisition over a single optical fiber sensor. A numerical simulation has been conducted to investigate the feasibility of strain transmissibility for damage detection which has revealed a better performance compared to traditional transmissibility. The applicability of the proposed method has been confirmed by applying distributed fiber optics on a clamped-clamped beam. Both simulation and experiment validate the effectiveness of damage detection approach based on strain transmissibility by using distributed fiber optics

Three-Dimensional-Printed Sensing Samples Embedding Fiber Bragg Gratings: Metrological Evaluation of Different Sample Materials and Fiber Coatings

Embedding optical fibers with fiber Bragg grating (FBG) sensors in 3-D-printed samples can effectively facilitate the systematic use of smart materials in many fields, such as civil, biomedical, and soft robotics applications. The aim of this study is to analyze different combinations of filament materials and FBG coatings and to assess their metrological characteristics. Eighteen samples are fabricated and tested under different mechanical and thermal conditions. The repeated tests allow to perform an evaluation of the measurement repeatability for each sample, along with an analysis of the sample's sensitivity. The filaments employed are acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), and thermoplastic polyurethane (TPU). The fiber coatings are acrylate, Ormocer,Registered trademark. and polyimide. Results indicate that the fiber coating has no sigificative influence on the performance of the sensors. The tests for temperature sensitivity highlight a good performance of ABS (116 pm/°C) and TPU samples (32 pm/°C) up to 60 °C, whereas the fabricated PLA samples (139 pm/°C for polyimide, 55 pm/°C for acrylate, and 14 pm/°C for Ormocer1) cannot be used above 40 °C. The tests for strain sensitivity in axial elongation show an average sensitivity of 3.049 nm/mm for ABS, 1.991 nm/mm for PLA, and 3.726 nm/mm for TPU. The bending tests show that all specimen materials have different sensitivities to elongation (2.994 nm/mm for ABS, 0.668 nm/mm for PLA, and 0.149 nm/mm for TPU). Only for acrylate in PLA samples, an effective difference for bending sensitivity resulted (1.241 nm/mm for the acrylate coating versus 2.366 nm/mm for the other coatings)

Boussignac continuous positive airway pressure for the management of acute cardiogenic pulmonary edema: prospective study with a retrospective control group

<p>Abstract</p> <p>Background</p> <p>Continuous positive airway pressure (CPAP) treatment for acute cardiogenic pulmonary edema can have important benefits in acute cardiac care. However, coronary care units are usually not equipped and their personnel not adequately trained for applying CPAP with mechanical ventilators. Therefore we investigated in the coronary care unit setting the feasibility and outcome of the simple Boussignac mask-CPAP (BCPAP) system that does not need a mechanical ventilator.</p> <p>Methods</p> <p>BCPAP was introduced in a coronary care unit where staff had no CPAP experience. All consecutive patients transported to our hospital with acute cardiogenic pulmonary edema, a respiratory rate > 25 breaths/min and a peripheral arterial oxygen saturation of < 95% while receiving oxygen, were included in a prospective BCPAP group that was compared with a historical control group that received conventional treatment with oxygen alone.</p> <p>Results</p> <p>During the 2-year prospective BCPAP study period 108 patients were admitted with acute cardiogenic pulmonary edema. Eighty-four of these patients (78%) were treated at the coronary care unit of which 66 (61%) were treated with BCPAP. During the control period 66 patients were admitted over a 1-year period of whom 31 (47%) needed respiratory support in the intensive care unit. BCPAP treatment was associated with a reduced hospital length of stay and fewer transfers to the intensive care unit for intubation and mechanical ventilation. Overall estimated savings of approximately € 3,800 per patient were achieved with the BCPAP strategy compared to conventional treatment.</p> <p>Conclusion</p> <p>At the coronary care unit, BCPAP was feasible, medically effective, and cost-effective in the treatment of acute cardiogenic pulmonary edema. Endpoints included mortality, coronary care unit and hospital length of stay, need of ventilatory support, and cost (savings).</p

Neurological assessment with validated tools in general ICU : multicenter, randomized, before and after, pragmatic study to evaluate the effectiveness of an e-learning platform for continuous medical education

BACKGROUND: International guidelines recommend systematic assessment of pain, agitation/sedation and delirium with validated scales for all ICU patients. However, these evaluations are often not done. We have created an e-learning training platform for the continuous medical education, and assessed its efficacy in increasing the use of validated tools by all medical and nursing staff of the participating ICUs during their daily practice. METHODS: Multicenter, randomized, before and after study. The eight participating centers were randomized in two groups, and received training at different times. The use of validated tools (Verbal Numeric Rating or Behavioral Pain Scale for pain; Richmond Agitation-Sedation Scale for agitation; Confusion Assessment Method for the ICU for delirium) was evaluated from clinical data recorded in medical charts during a week, with follow-up up to six months after the training. All the operators were invited to complete a questionnaire, at baseline and after the training. RESULTS : Among the 374 nurses and physicians involved, 140 (37.4%) completed at least one of the three courses. The assessment of pain (38.1 vs. 92.9%, P<0.01) and delirium (0 vs. 78.6%, P<0.01) using validated tools significantly increased after training. Observation in the follow-up showed further improvement in delirium monitoring, with no signs of extinction for pain and sedation/agitation measurements. CONCLUSIONS: This e-learning program shows encouraging effectiveness, and the increase in the use of validated tools for neurological monitoring in critically ill patients lasts over time.BACKGROUND: International guidelines recommend systematic assessment of pain, agitation/sedation and delirium with validated scales for all ICU patients. However, these evaluations are often not done. We have created an e-learning training platform for the continuous medical education, and assessed its efficacy in increasing the use of validated tools by all medical and nursing staff of the participating ICUs during their daily practice. METHODS: Multicenter, randomized, before and after study. The eight participating centers were randomized in two groups, and received training at different times. The use of validated tools (Verbal Numeric Rating or Behavioral Pain Scale for pain; Richmond Agitation-Sedation Scale for agitation; Confusion Assessment Method for the ICU for delirium) was evaluated from clinical data recorded in medical charts during a week, with follow-up up to six months after the training. All the operators were invited to complete a questionnaire, at baseline and after the training. RESULTS : Among the 374 nurses and physicians involved, 140 (37.4%) completed at least one of the three courses. The assessment of pain (38.1 vs. 92.9%, P<0.01) and delirium (0 vs. 78.6%, P<0.01) using validated tools significantly increased after training. Observation in the follow-up showed further improvement in delirium monitoring, with no signs of extinction for pain and sedation/agitation measurements. CONCLUSIONS: This e-learning program shows encouraging effectiveness, and the increase in the use of validated tools for neurological monitoring in critically ill patients lasts over time

Prospective observational cohort study of cerebrovascular CO2 reactivity in patients with inflammatory CNS diseases

The purpose of this study was to evaluate the significance of cerebrovascular CO(2) reactivity (CO(2) R) in the course and outcome of inflammatory central nervous system (CNS) diseases. Sixty-eight patients with inflammatory CNS diseases and 30 healthy volunteers were included in this prospective observational cohort study. The observational period was between January 2005 and May 2009. The CO(2) R was measured by transcranial Doppler (TCD) ultrasound using the breath-holding method. We compared patients with normal CO(2) R (breath-holding index [BHI(m)] ≥ 1.18 = BHI(N) group) with patients who showed impaired CO(2) R (BHI(m) < 1.18 = BHI(R) group). We also analyzed the association of impaired CO(2) R with the etiology, severity, and outcome of disease. When compared to the BHI(N) group, the patients from the BHI(R) group were older, had a heavier consciousness disturbance, experienced more frequent respiratory failure, and, subsequently, had worse outcomes. There were no fatalities among the 28 patients in the BHI(N) group. The comparison of subjects with bacterial and non-bacterial meningitis revealed no significant differences. The unfavorable outcome of disease (Glasgow Outcome Scale [GOS] score 1-3) was significantly more common in subjects with impaired CO(2) R (62.5% vs. 10.7%). Logistic regression analysis was performed in order to establish the prognostic value of BHI(m). The outcome variable was unfavorable outcome (GOS 1-3), while the independent variables were age, Glasgow Coma Scale (GCS) score, and BHI(m). The age and BHI(m) showed the strongest influence on disease outcome. A decrease of BHI(m) for each 0.1 unit increased the risk of unfavorable outcome by 17%. Our study emphasizes the importance of CO(2) R assessment in patients with inflammatory CNS diseases