Effect of process parameters in nanosecond pulsed laser micromachining of PMMA-based microchannels at near-infrared and ultraviolet wavelengths

This paper presents investigations on the effects of nanosecond laser processing parameters on depth and width of microchannels fabricated from polymethylmethacrylate (PMMA) polymer. A neodymium-doped yttrium aluminium garnet pulsed laser with a fundamental wavelength of 1,064 nm and a third harmonic wavelength of 355 nm with pulse duration of 5 ns is utilized. Hence, experiments are conducted at near-infrared (NIR) and ultraviolet (UV) wavelengths. The laser processing parameters of pulse energy (402–415 mJ at NIR and 35–73 mJ at UV wavelengths), pulse frequency (8–11 Hz), focal spot size (140–190 μm at NIR and 75 μm at UV wavelengths) and scanning rate (400–800 pulse/mm at NIR and 101–263 pulse/mm at UV wavelengths) are varied to obtain a wide range of fluence and processing rate. Microchannel width and depth profile are measured, and main effects plots are obtained to identify the effects of process parameters on channel geometry (width and depth) and material removal rate. The relationship between process variables (width and depth of laser-ablated microchannels) and process parameters is investigated. It is observed that channel width (140–430 μm at NIR and 100–150 μm at UV wavelengths) and depth (30–120 μm at NIR and 35–75 μm at UV wavelengths) decreased linearly with increasing fluence and increased non-linearly with increasing scanning rate. It is also observed that laser processing at UV wavelength provided more consistent channel profiles at lower fluences due to higher laser absorption of PMMA at this wavelength. Mathematical modeling for predicting microchannel profile was developed and validated with experimental results obtained with pulsed laser micromachining at NIR and UV wavelengths.     

Acceptance and commitment therapy for smoking cessation: A preliminary study of its effectiveness in comparison with cognitive behavioral therapy.

This controlled preliminary trial determined the feasibility and initial effectiveness of a promising behavioral intervention for smoking: Acceptance and Commitment Therapy (ACT). In a quasi-experimental design, the ACT intervention condition used metaphors and experiential exercises focused on personal values to motivate quitting smoking and enhancing the willingness to experience internal cues to smoke (e.g., urges) and abstinence-related internal distress. The comparison condition was cognitive behavioral therapy (CBT)—the current standard in behavioral intervention for smoking cessation. Each treatment was delivered in seven weekly 90-min sessions in a group format to 81 (43 in ACT; 38 in CBT) adult smokers. Results show that the ACT treatment was as feasible as the CBT treatment. They also demonstrate promising evidence of ACT’s effectiveness: 30.2% intent-to-treat biochemically-supported 30-day point prevalence at twelve month follow-up, compared with 13.2% in the CBT condition (odds ratio = 5.13; p = .02). Replication in a well-powered, randomized, controlled trial is now needed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Resistance.

This article reviews extant literature on how patient resistance has been defined and its effects on psychotherapy. Resistance has been considered as both a patient-in-treatment state and as an enduring trait. In either form, patient resistance seems to interfere with treatment outcome. Resistance also functions as a moderating variable in determining the effectiveness of different levels of therapist directiveness. The evidence that patients who enter treatment with high levels of trait like resistance will benefit most from nondirective interventions is moderately strong. Conversely, those who enter treatment with low levels of trait like resistance benefit most from therapist directed interventions. Therapeutic practices associated with the research evidence are advanced. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Orienting Fibers by Extrusion in Reinforced Reactive Powder Concrete

This paper deals with the problem of orienting short metal fibers (12 mm length, aspect ratio 60) in a reactive powder concrete during an extrusion process to manufacture reinforced tubes. By choosing an appropriate geometry for the die it is possible to orient the fibers in an orthoradial direction, which is the most efficient if one wishes to reinforce the tube for an internal pressure loading. This result is obtained with both a theoretical and an experimental approach. In a theoretical framework the authors carried out numerical modeling with a constitutive behavior deduced from the anisotropic suspensions theory. This calculus enabled the authors to design the shape of the die. Tubes have then been extruded and the fibers' orientation has been measured with optical microscopy.     

Estimation of hourly direct normal from measured global solar irradiance in Spain

The availability of a good data set, registered in six Spanish locations, including several radiometric variables, has been used to test different approaches for estimating hourly direct normal irradiance by decomposition models. Models proposed by different authors have been tested. Following this preliminary study, to improve the k_b–k_t correlations, another geometric variable has been used as a predictor of hourly beam transmittance, k_b, by means of piecewise correlations. The new beam transmittance correlations, which include additional geometric information, reduce the root mean square deviation. In addition, they show a better performance in terms of the determination coefficient of the regression analysis of measured vs calculated values, providing an improved capture of the real world effects than models that are function of the clearness index only. A new model that uses only two ranges of clearness index is proposed. The proposed model shows seasonal dependence and thus we have developed a seasonal version of it. However, the performance of the seasonal version has proved to be similar to the corresponding annual model.     

Control mechanisms to improve the robustness of mpeg-2 based communications over ATM networks

Audio-visual and other multimedia services are seen as an important source of traffic for ATM networks. Due to the statistical multiplexing schemes used by ATM networks, cells are exposed to delays, jitters and losses. These phenomena affect the quality of the service provided to the video-based applications. In this paper, we introduce a set of control mechanisms at different levels of the protocol architecture. These mechanisms have been particularly tailored to better support MPEG-2-based video communications applications using ATM networks as their underlying transmission mechanism. We show that the use of errorconcealment mechanisms prove more effective when supplemented by a structured set of protocol mechanisms. We study the impact of cell losses on the quality of MPEG-2 video sequences and provide an evaluation of the quality of the decoded video as perceived by the end user. Our results demonstrate the effectiveness of the proposed protocol architecture in improving the quality of service provided to the video application.     

Science and technology policies: A tale of political use,misuse and abuse of traditional R&;D indicators

Future political priorities for science and technology (S&T) policy formulation usually rest on a rather simplistic interpretation of past events. This can lead to serious errors and distortions and can negatively affect the innovation system. In this article we try to highlight the riskiness involved in policy making based on traditional R&D indicators and trends. We would emphasise that this approach does not take account of structural aspects crucial for the analysis of the innovation system. We examine the implications for science, technical and human resources policies of the political challenge of R&D convergence in a peripheral EU region. Three scenarios are developed based on application of the same criteria to the trends observed in traditional R&D input indicators.     

Beta autoregressive moving average models

We build upon the class of beta regressions introduced by Ferrari and Cribari-Neto (J. Appl. Stat. 31:799–815, 2004) to propose a dynamic model for continuous random variates that assume values in the standard unit interval (0,1). The proposed βARMA model includes both autoregressive and moving average dynamics, and also includes a set of regressors. We discuss parameter estimation, hypothesis testing, goodness-of-fit assessment and forecasting. In particular, we give closed-form expressions for the score function and for Fisher’s information matrix. An application that uses real data is presented and discussed.