This paper deals with the nonlinear system identification of structures exhibiting distributed nonlinearities, which has become of great interest recently, due to the continuous interest to improve ...the performance of structures. This brings the need for designing lighter and more flexible structural elements, which are usually characterized by moderate and large deformation, resulting in a distributed nonlinear behavior. In this framework, system identification remains a particularly challenging problem, especially when experimental measurements are considered. This work proposes a method to perform such a task, based on a convenient model order reduction of the considered structure, followed by a nonlinear system identification algorithm. The methodology is validated on a very thin beam undergoing large-amplitude oscillations, firstly using numerical data and then considering an experimental test bench. On the experimental side, the nonlinearity is first characterized using just the measured data, in order to acquire information that would help the identification process. Eventually, nonlinear system identification is performed in the reduced-order domain. An ad-hoc version of the nonlinear subspace identification (NSI) algorithm is used, but the presented methodology can also be applied with other nonlinear identification tools. Results confirm the goodness of the identification strategy in obtaining a reliable model which takes into account the distributed nonlinear behavior.
Epidemiological research has linked exposure to atmospheric particulate matter (PM) to several adverse health effects, including cardiovascular and pulmonary morbidity and mortality. Despite these ...links, the mechanisms by which PM causes adverse health effects are poorly understood. The generation of hydroxyl radical (OH) and other reactive oxygen species (ROS) through transition-metal-mediated pathways is one of the main hypotheses for PM toxicity. In order to better understand the ability of particulate transition metals to produce ROS, we have quantified the amounts of OH produced from dissolved iron and copper in a cell-free, surrogate lung fluid (SLF). We also examined how two important biological molecules, citrate and ascorbate, affect the generation of OH by these metals. We have found that Fe(II) and Fe(III) produce little OH in the absence of ascorbate and citrate, but that they efficiently make OH in the presence of ascorbate and this is further enhanced when citrate is also added. In the presence of ascorbate, with or without citrate, the oxidation state of iron makes little difference on the amount of OH formed after 24h. In the case of Cu(II), the production of OH is greatly enhanced in the presence of ascorbate, but is inhibited by the addition of citrate. The mechanism for this effect is unclear, but appears to involve formation of a citrate–copper complex that is apparently less reactive than free, aquated copper in either the generation of hydrogen peroxide (HOOH) or in the Fenton-like reaction of copper with HOOH to make OH. By quantifying the amount of OH that Fe and Cu can produce in surrogate lung fluid, we have provided a first step into being able to predict the amounts of OH that can be produced in the human lung from exposure to PM containing known amounts of transition metals.
Feature Indented Assertions for Analog and Mixed-Signal Validation Ain, Antara; Bruto da Costa, Antonio Anastasio; Dasgupta, Pallab
IEEE transactions on computer-aided design of integrated circuits and systems,
2016-Nov., 2016-11-00, 20161101, Letnik:
35, Številka:
11
Journal Article
Recenzirano
The acceptance criteria for analog designs are traditionally defined in terms of real-valued features defined over behavioral responses. For example, rise time, peak overshoot, and settling time are ...features of the response of a second-order system under a step input. Designers of analog and mixed-signal (AMS) designs typically like to see whether the relevant features lie within their specified ranges, and if so, by what margin. Assertions are capable of capturing the acceptance criteria, but they do not help in evaluating how well (or by what margin) the design satisfies the specification. We introduce the notion of Feature Indented Assertions (FIAs) for overlaying the definition of real-valued features over the syntactic fabric of AMS assertions. In this paper, we present the formal syntax and semantics of our language, FIA, and demonstrate its ability to capture a wide variety of AMS features. We present our dynamic feature evaluation tool that plugs into standard AMS simulators through Verilog Procedural Interfaces and evaluates features over simulation. At the heart of this tool, we have our interval arithmetic-based algorithm for monitoring features over continuous time and value domains. This algorithm is presented with corresponding proofs of correctness and with results over industrial testcases.
Extends Gaertner et al's (1993) work on the mediating role of cognitive representations in intergroup interactions by examining how affective responses predict overall attitudinal favorability of ...intergroup responses, considering the role of dual identity & examining the role of students' majority & minority group status on features pertaining to the common in-group identity model. Highlighted is the contact hypothesis, which suggests that intergroup contact promotes greater intergroup harmony under certain conditions. Survey data from 1,357 students attending a multicultural high school in the northeastern US generally supported the hypothesis. The more favorably students perceived the conditions of contact, the lower their intergroup bias in affective reactions & overall attitudinal favorability. Conditions of contact are demonstrated to achieve their influence through a variety of direct & indirect pathways. It is concluded that future research must set the common in-group identity model in a more unified explanatory framework that captures the interaction of these pathways. 1 Table, 3 Figures. D. M. Smith
Like other neurodegenerative diseases, Alzheimer Disease (AD) has a prominent inflammatory component mediated by brain microglia. Reducing microglial inflammation could potentially halt or at least ...slow the neurodegenerative process. A major challenge in the development of treatments targeting brain inflammation is the sheer complexity of the molecular mechanisms that determine whether microglia become inflammatory or take on a more neuroprotective phenotype. The process is highly multifactorial, raising the possibility that a multi-target/multi-drug strategy could be more effective than conventional monotherapy. This study takes a computational approach in finding combinations of approved drugs that are potentially more effective than single drugs in reducing microglial inflammation in AD. This novel approach exploits the distinct advantages of two different computer programming languages, one imperative and the other declarative. Existing programs written in both languages implement the same model of microglial behavior, and the input/output relationships of both programs agree with each other and with data on microglia over an extensive test battery. Here the imperative program is used efficiently to screen the model for the most efficacious combinations of 10 drugs, while the declarative program is used to analyze in detail the mechanisms of action of the most efficacious combinations. Of the 1024 possible drug combinations, the simulated screen identifies only 7 that are able to move simulated microglia at least 50% of the way from a neurotoxic to a neuroprotective phenotype. Subsequent analysis shows that of the 7 most efficacious combinations, 2 stand out as superior both in strength and reliability. The model offers many experimentally testable and therapeutically relevant predictions concerning effective drug combinations and their mechanisms of action.
Enhancing river passability is considered a central part of the efforts to maintain fish population and achieving good ecological status, according to the EU Water Framework Directive (WFD). One ...commonly proposed approach to achieving this aim involves the creation of fishways. However, recent studies have shown that many of these fish passes are often lacking an optimal design with far reaching consequences for fish migration. Several promising new designs such as nature-like rock ramps, with uphill flow, have been recently developed. Such studies attempt to address these drawbacks by adapting several structure-related features (i.e., boulder size and shape and friction walls). In this study, we used a 2D computational fluid dynamic model to assess how the key hydraulic variables (water depth, velocity and turbulent kinetic energy) were impacted by different design elements of uphill flow fishways with different configurations. With regard to the standard boulder shapes and sizes, our results reveal that: (1) doubling the boulder sizes results in a decrease of turbulent kinetic energy in resting corridors of up to 33%; (2) the inclusion of small friction-walls in the ramp design increases uphill velocity in the intermediate corridors by up to 49%; (3) the trapezoidal shape of the boulder leads to the largest decreases in maximum velocity in the gaps (16%) and the largest increases in the uphill velocity in the resting corridors (180%). These results may allow us to optimise the uphill flow rock-ramp design to improve the passability of this type of fishways.
Railway overhead contact lines are very low-damped structures with a high modal density in the low-frequency region. This has a significant impact on the interaction with the pantograph, especially ...in the high-speed case and in multiple pantographs operations. This paper studies the optimal spatial damping distribution in overhead contact lines obtained by introducing localised damping connections, resulting in a non-proportional damping distribution. To this end, the simulation software Cateway is presented and adopted in conjunction with evolutionary multi-objective optimisers to seek for the most efficient spatial damping distribution. The study is conducted on a high-speed reference model considering two different train speeds. The final goal of this optimisation is to obtain useful hints about the most and least sensitive regions to damping modifications. A dedicated study on the locus of the poles of the system is also proposed to corroborate the findings of the analysis. Results show that significant improvements on the current collection quality can be achieved by carefully designing the spatial damping distribution, especially for the rear (trailing) pantograph. On the other hand, wrong design choices can lead to a degradation of the contact forces.
The provision of public goods by agriculture and forestry has taken increasing importance in the policy debate. The objective of this editorial is to set the scene for the special issue, to provide a ...summary of the main messages from the papers therein, highlight the most relevant lessons learnt for policy and generate insights for future research. The results highlight that there is a need to investigate further both the micro-mechanisms of decision-making, value creation and coordination among actors, including the micro-level issues in policy design, and to address the topic of public goods, taking a holistic view of how agriculture and forestry systems work. In order to meet these real-world requirements, different research approaches need to be better integrated, promoting cross-fertilisation and synergies among different methodological perspectives, able to complement one another in meeting policy challenges.
•Predictors of at-risk older drivers were evaluated in an on-road pilot study.•Useful field of view (UFOV) subtest 2 was the best single predictor.•An optimal 4-test combination had 95% specificity ...and 80% sensitivity.•It included: visual acuity, contrast sensitivity, UFOV-2 and Mini-Mental State Exam.
To conduct a pilot study to evaluate the predictive value of the Montreal Cognitive Assessment test (MoCA) and a brief test of multiple object tracking (MOT) relative to other tests of cognition and attention in identifying at-risk older drivers, and to determine which combination of tests provided the best overall prediction.
Forty-seven currently licensed drivers (58–95 years), primarily from a clinical driving evaluation program, participated. Their performance was measured on: (1) a screening test battery, comprising MoCA, MOT, Mini-Mental State Examination (MMSE), Trail-Making Test, visual acuity, contrast sensitivity, and Useful Field of View (UFOV) and (2) a standardized road test.
Eighteen participants were rated at-risk on the road test. UFOV subtest 2 was the best single predictor with an area under the curve (AUC) of .84. Neither MoCA nor MOT was a better predictor of the at-risk outcome than either MMSE or UFOV, respectively. The best four-test combination (MMSE, UFOV subtest 2, visual acuity and contrast sensitivity) was able to identify at-risk drivers with 95% specificity and 80% sensitivity (.91 AUC).
Although the best four-test combination was much better than a single test in identifying at-risk drivers, there is still much work to do in this field to establish test batteries that have both high sensitivity and specificity.
PDF
