Computational and experimental characterization of a low-cost piezoelectric valveless diaphragm pump

Flow pumps act as important devices in areas such as Bioengineering, Medicine, and Pharmacy, among other areas of Engineering, mainly for delivering liquids or gases at small-scale and precision flow rate quantities. Principles for pumping fluids based on piezoelectric actuators have been widely studied, since they allow the construction of pump systems for displacement of small fluid volumes with low power consumption. This work studies valveless piezoelectric diaphragm pumps for flow generation, which uses a piezoelectric ceramic (PZT) as actuator to move a membrane (diaphragm) up and down as a piston. The direction of the flow is guaranteed by valveless configuration based on a nozzle-diffuser system that privileges the flow in just one pumping direction. Most research efforts on development of valveless flow pump deal either with computational simulations based on simplified models or with simplified physical approaches based on analytical models. The main objective of this work is the study of a methodology to develop a low-cost valveless piezoelectric diaphragm flow pump using computational simulations, parametric study, prototype manufacturing, and experimental characterization. The parametric study has shown that the eccentricity of PZT layer and metal layer plays a key role in the performance of the pump.

Integrating on-line process control and imperfect corrective maintenance: An economical design

Existing studies of on-line process control are concerned with economic aspects, and the parameters of the processes are optimized with respect to the average cost per item produced. However, an equally important dimension is the adoption of an efficient maintenance policy. In most cases, only the frequency of the corrective adjustment is evaluated because it is assumed that the equipment becomes "as good as new" after corrective maintenance. For this condition to be met, a sophisticated and detailed corrective adjustment system needs to be employed. The aim of this paper is to propose an integrated economic model incorporating the following two dimensions: on-line process control and a corrective maintenance program. Both performances are objects of an average cost per item minimization. Adjustments are based on the location of the measurement of a quality characteristic of interest in a three decision zone. Numerical examples are illustrated in the proposal. (c) 2012 Elsevier B.V. All rights reserved.

Lumpiness, capital adjustment costs and investment dynamics

Aggregate investment in the US economy displays a hump-shaped pattern in response to shocks, and the autocorrelation of aggregate investment growth is positive for the first few quarters, turning negative for the later quarters. This paper shows that this feature of the data is the natural outcome of a two-sector consumption/investment model designed and calibrated to reproduce plant-level evidence on capita: accumulation. (C) 2012 Elsevier B.V. All rights reserved.

Cost-Effectiveness Analysis for Surgical, Angioplasty, or Medical Therapeutics for Coronary Artery Disease 5-Year Follow-Up of Medicine, Angioplasty, or Surgery Study (MASS) II Trial

Background-The Second Medicine, Angioplasty, or Surgery Study (MASS II) included patients with multivessel coronary artery disease and normal systolic ventricular function. Patients underwent coronary artery bypass graft surgery (CABG, n = 203), percutaneous coronary intervention (PCI, n = 205), or medical treatment alone (MT, n = 203). This investigation compares the economic outcome at 5-year follow-up of the 3 therapeutic strategies. Methods and Results-We analyzed cumulative costs during a 5-year follow-up period. To analyze the cost-effectiveness, adjustment was made on the cumulative costs for average event-free time and angina-free proportion. Respectively, for event-free survival and event plus angina-free survival, MT presented 3.79 quality-adjusted life-years and 2.07 quality-adjusted life-years; PCI presented 3.59 and 2.77 quality-adjusted life-years; and CABG demonstrated 4.4 and 2.81 quality-adjusted life-years. The event-free costs were $9071.00 for MT; $19 967.00 for PCI; and $18 263.00 for CABG. The paired comparison of the event-free costs showed that there was a significant difference favoring MT versus PCI (P<0.01) and versus CABG (P<0.01) and CABG versus PCI (P<0.01). The event-free plus angina-free costs were $16 553.00, $25 831.00, and $24 614.00, respectively. The paired comparison of the event-free plus angina-free costs showed that there was a significant difference favoring MT versus PCI (P=0.04), and versus CABG (P<0.001); there was no difference between CABG and PCI (P>0.05). Conclusions-In the long-term economic analysis, for the prevention of a composite primary end point, MT was more cost effective than CABG, and CABG was more cost-effective than PCI.

Clinical correlates of social adjustment in patients with obsessive-compulsive disorder

Background: Patients with obsessive-compulsive disorder (OCD) frequently show poor social adjustment, which has been associated with OCD severity. Little is known about the effects that age at symptom onset, specific OCD symptoms, and psychiatric comorbidities have on social adjustment. The objective of this study was to investigate the clinical correlates of social functioning in OCD patients. Methods: Cross-sectional study involving 815 adults with a primary DSM-IV diagnosis of OCD participating in the Brazilian Research Consortium on Obsessive-Compulsive Spectrum Disorders. Patients were assessed with the Social Adjustment Scale, the Medical Outcomes Study 36-item Short-Form Health Survey, the Yale-Brown Obsessive-Compulsive Scale, the Dimensional Yale-Brown Obsessive-Compulsive Scale, and the Structured Clinical Interview for DSM-IV Axis I Disorders. Clinical correlates of social adjustment were assessed with generalized linear models with gamma distribution. Results: Poor overall social functioning was associated with greater OCD severity (p = 0.02); hoarding symptoms (p = 0.004); sexual/religious obsessions (p = 0.005); current major depressive disorder (p = 0.004); current post-traumatic stress disorder (p = 0.002); and current eating disorders (p = 0.02). Poor social adjustment was also associated with impaired quality of life. Conclusions: Patients with OCD have poor social functioning in domains related to personal relationships and professional performance. Hoarding symptoms and sexual/religious obsessions seem to have the strongest negative effects on social functioning. Early age at OCD symptom onset seems to be associated with professional and academic underachievement and impairment within the family unit, whereas current psychiatric comorbidity worsen overall social functioning. In comparison with quality of life, social adjustment measures seem to provide a more comprehensive overview of the OCD-related burden. (C) 2012 Elsevier Ltd. All rights reserved.

Comparison between the complete Bayesian method and empirical Bayesian method for ARCH models using Brazilian financial time series

In this work we compared the estimates of the parameters of ARCH models using a complete Bayesian method and an empirical Bayesian method in which we adopted a non-informative prior distribution and informative prior distribution, respectively. We also considered a reparameterization of those models in order to map the space of the parameters into real space. This procedure permits choosing prior normal distributions for the transformed parameters. The posterior summaries were obtained using Monte Carlo Markov chain methods (MCMC). The methodology was evaluated by considering the Telebras series from the Brazilian financial market. The results show that the two methods are able to adjust ARCH models with different numbers of parameters. The empirical Bayesian method provided a more parsimonious model to the data and better adjustment than the complete Bayesian method.