It is still a challenge to select "good" test inputs for concurrent programs within limited testing resources. We present in this paper a test case diversity metric for multi-threaded programs, which evaluates a test input with its effect in exposing concurrent thread interactions. We then propose an input-driven active testing approach with two test input selection strategies based on our test case diversity metric. We implement our testing approach based on Maple, an interleaving coverage-driven active testing tool. The effectiveness and efficiency of our testing approach are compared closely with Maple, which on its own is supplied with random test inputs. Experimental results show that our testing approach can outperform the original active testing approach in the number of test inputs executed and the time usage for fulfilling the interleaving coverage criterion of Maple. The selected test inputs based on our test case diversity metric are very cost-effective in exposing concurrent thread interactions and hence can help detect concurrency bugs with less cost and effort.
The state-of-the-art model-checkers for probabilistic timed automata (PTAs) use separate representations for the dense-time and discrete parts of PTA states. In the literature, integrated state-space representations based on decision diagrams, e.g., RED diagrams (the underlying symbolic representation in the model checker RED), have shown considerable performance enhancement in model-checking timed automata (TAs) and linear hybrid automata (LHAs). A RED diagram for a TA can represent the dense-time and discrete parts of TA states in a single and integrated decision diagram. In this work, we experiment to investigate whether such performance enhancement can be duplicated with PTA model-checking. Specifically, we propose a lightweight extension to RED diagrams to represent quantitative states of PTAs in an integrated manner, yet preserving the structure-sharing capacity of RED diagrams. We then develop and implement a symbolic reachability analysis algorithm for PTAs based on the extended RED diagrams. We further carry out experiments with the PTA benchmarks from a popular probabilistic model checker PRISM to evaluate the performance of such integrated decision diagrams and the reachability analysis algorithm. Experimental results show that our approach can indeed help to improve the time-efficiency and scalability of PTA model-checking.
Fluorescent nanoparticles (NPs) for Al3+ sensing with high selectivity were developed from a type of carbazole-based conjugated polymer with a two-dimensional donor–π bridge–acceptor (D–π–A) structure. These NPs are characterized by their small particle diameter (∼18 nm), far-red fluorescence emission (centered ∼710 nm), and Al3+-induced fluorescence enhancement with high selectivity owing to an Al3+-triggered inhibition on the intramolecular charge transfer (ICT) processes between the conjugated backbone and the pendant acceptors. This type of nanoparticle is easily suspended in aqueous solutions, indicating their practical applicability in physiological media, and their ability for intracellular Al3+ sensing was confirmed. As compared to other types of conjugated polymer based probes showing metal ion mediated fluorescence quenching, these as-prepared NPs possess analyte-enhanced fluorescence emission, which is analytically favored in terms of sensitivity and selectivity. Fluorescence emission with wavelengths in the biological window of maximum optical transparency (∼700 to 1000 nm) is expected to impart a salient advantage for biological detection applications to these as-prepared probes. The superior features of merit of this new type of fluorescent probe, together with the validation of practicability for intracellular Al3+ ion sensing, are indicative of their potential for application in fluorescence-based imaging and sensing, such as investigations on Al3+-related physiological and pathological processes.
In this paper, we propose a bipolar charge plasma spectrometer based on the double-channel electrostatic analyzer for simultaneously measuring thermal ions and electrons with a 2π hemispherical field-of-view. Both ions and electrons within the wide field-of-view enter the spectrometer, pass through the variable geometric factor channel, and are then separated by the double-channel electric fields. Two microchannel plates are accommodated at the exit of the analyzer for ion and electron detection. The main performance of the spectrometer has been obtained from on-ground calibration. With the electrostatic deflectors and the cylindrically symmetric structure, the spectrometer provides simultaneous measurements of thermal ion and electron velocity distributions with a shared field-of-view of 360° (azimuth angle) by 90° (elevation angle) and a broad energy range for both ions and electrons. The ion analyzer constant and the electron analyzer constant are 11.1 and 9.7, respectively. The detecting energy range of 33.3-44.4 keV for ions and 29.1-38.8 keV for electrons can be obtained by using the sweeping electrostatic analyzer voltage range of 3-4000 V. The ion and electron energy resolutions are 9.6% and 6.1%, respectively. The variable geometric factor function provides a large geometric factor adjusting range for both ion and electron measurements by two orders of magnitude, which fulfills the requirements of a large dynamic flux range for simultaneous measurements of space thermal plasma in the solar wind and magnetosphere.
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