5,343 research outputs found
Code coverage of adaptive random testing
Random testing is a basic software testing technique that can be used to assess the software reliability as well as to detect software failures. Adaptive random testing has been proposed to enhance the failure-detection capability of random testing. Previous studies have shown that adaptive random testing can use fewer test cases than random testing to detect the first software failure. In this paper, we evaluate and compare the performance of adaptive random testing and random testing from another perspective, that of code coverage. As shown in various investigations, a higher code coverage not only brings a higher failure-detection capability, but also improves the effectiveness of software reliability estimation. We conduct a series of experiments based on two categories of code coverage criteria: structure-based coverage, and fault-based coverage. Adaptive random testing can achieve higher code coverage than random testing with the same number of test cases. Our experimental results imply that, in addition to having a better failure-detection capability than random testing, adaptive random testing also delivers a higher effectiveness in assessing software reliability, and a higher confidence in the reliability of the software under test even when no failure is detected
Effects of Biofloc on Plankton Abundance in the Water
This study was conducted to evaluate the effects of biofloc on the species and quantity of plankton in pond water. There were four treatments in the experiment: the control, no supplementation; treatment I, pond water supplemented with glucose; treatment II, pond water supplemented with both glucose and Bacillus subtilis; and treatment III, pond water supplemented with Bacillus subtilis only. Water quality, plankton, and biofloc formation were monitored every five days. Results showed that biofloc formation was enhanced by adding glucose to the pond water. The addition of glucose together with Bacillus subtilis shortened the formation time of mature bioflocs by about five days than the supplementation with glucose only. In ponds supplemented with glucose and those supplemented with glucose + bacillus, the ammonia nitrogen, and nitrite nitrogen content in the water column decreased, and the number of cyanobacteria and green algae were significantly inhibited, while the number of zooplankton such as Rotatoria increased during the experimental period
Characterization of high exopolysaccharide-producing Lactobacillus strains isolated from mustard pickles for potential probiotic applications
The aim of this study was to characterize high exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) isolated from mustard pickles in Taiwan for potential probiotic applications. Among 39 collected LAB strains, four most productive EPS-producing strains were selected for further analysis. Comparative analyses of 16S rDNA genes rpoA and pheS sequences demonstrated that these strains were members of Lactobacillus plantarum-group (LPG). NCD 2, NLD 4, SLC 13, and NLD 16 showed survival rates of 95.83% ± 0.49%, 95.07% ± 0.64%, 105.84% ± 0.82%, and 99.65% ± 0.31% under simulated gastrointestinal conditions, respectively. No cytotoxic effects on macrophage RAW 264.7 cells were observed when they were treated with a low dose (1 μg/ml) of stimulants extracted from the tested LAB strains. The production of nitric oxide in RAW 264.7 cells incubated with various LAB stimulants showed a dose-dependent increase. Among the four strains, SLC 13 showed higher inhibitory activity on growth of Enterococcus faecalis (BCRC 12302) and Yersinia enterocolitica (BCRC 10807). NLD 4 showed strong inhibitory activity against Escherichia coli O157:H7 (ATCC 43894) as compared with the other three strains. In summary, our results suggest that Lactobacillus pentosus SLC 13 may be a good candidate for probiotic applications and for development of antibacterial compounds. [Int Microbiol 20(2):75-84 (2017)]Keywords: Lactobacillus spp. · exopolysaccharide · probiotic
Heuristics in permutation GOMEA for solving the permutation flowshop scheduling problem
The recently introduced permutation Gene-pool Optimal Mixing Evolutionary Algorithm (GOMEA) has shown to be an effective Model Based Evolutionary Algorithm (MBEA) for permutation problems. So far, permutation GOMEA has only been used in the context of Black-Box Optimization (BBO). This paper first shows that permutation GOMEA can be improved by incorporating a constructive heuristic to seed the initial population. Secondly, the paper shows that hybridizing with job swapping neighborhood search does not lead to consistent improvement. The seeded permutation GOMEA is compared to a state-of-the-art algorithm (VNS4) for solving the Permutation Flowshop Scheduling Problem (PFSP). Both unstructured and structured instances are used in the benchmarks. The results show that permutation GOMEA often outperforms the VNS4 algorithm for the PFSP with the total flowtime criterion
Means and covariance functions for geostatistical compositional data: an axiomatic approach
This work focuses on the characterization of the central tendency of a sample
of compositional data. It provides new results about theoretical properties of
means and covariance functions for compositional data, with an axiomatic
perspective. Original results that shed new light on the geostatistical
modeling of compositional data are presented. As a first result, it is shown
that the weighted arithmetic mean is the only central tendency characteristic
satisfying a small set of axioms, namely continuity, reflexivity and marginal
stability. Moreover, this set of axioms also implies that the weights must be
identical for all parts of the composition. This result has deep consequences
on the spatial multivariate covariance modeling of compositional data. In a
geostatistical setting, it is shown as a second result that the proportional
model of covariance functions (i.e., the product of a covariance matrix and a
single correlation function) is the only model that provides identical kriging
weights for all components of the compositional data. As a consequence of these
two results, the proportional model of covariance function is the only
covariance model compatible with reflexivity and marginal stability
Quasiparticle Lifetime of the Repulsive Fermi Polaron
We investigate the metastable repulsive branch of a mobile impurity coupled to a degenerate Fermi gas via short-range interactions. We show that the quasiparticle lifetime of this repulsive Fermi polaron can be experimentally probed by driving Rabi oscillations between weakly and strongly interacting impurity states. Using a time-dependent variational approach, we find that we can accurately model the impurity Rabi oscillations that were recently measured for repulsive Fermi polarons in both two and three dimensions. Crucially, our theoretical description does not include relaxation processes to the lower-lying attractive branch. Thus, the theory-experiment agreement demonstrates that the quasiparticle lifetime is dominated by many-body dephasing within the upper repulsive branch rather than by relaxation from the upper branch itself. Our findings shed light on recent experimental observations of persistent repulsive correlations, and have important consequences for the nature and stability of the strongly repulsive Fermi gas
Nanoantenna-enhanced ultrafast nonlinear spectroscopy of a single gold nanoparticle
Optical nanoantennas are a novel tool to investigate previously unattainable
dimensions in the nanocosmos. Just like their radio-frequency equivalents,
nanoantennas enhance the light-matter interaction in their feed gap. Antenna
enhancement of small signals promises to open a new regime in linear and
nonlinear spectroscopy on the nanoscale. Without antennas especially the
nonlinear spectroscopy of single nanoobjects is very demanding. Here, we
present for the first time antenna-enhanced ultrafast nonlinear optical
spectroscopy. In particular, we utilize the antenna to determine the nonlinear
transient absorption signal of a single gold nanoparticle caused by mechanical
breathing oscillations. We increase the signal amplitude by an order of
magnitude which is in good agreement with our analytical and numerical models.
Our method will find applications in linear and nonlinear spectroscopy of
nanoobjects, ranging from single protein binding events via nonlinear tensor
elements to the limits of continuum mechanics
Effect of Pulsed or Continuous Delivery of Salt on Sensory Perception Over Short Time Intervals
Salt in the human diet is a major risk factor for hypertension and many countries have set targets to reduce
salt consumption. Technological solutions are being sought
to lower the salt content of processed foods without altering their taste. In this study, the approach was to deliver salt solutions in pulses of different concentrations to determine whether a pulsed delivery profile affected sensory perception of salt. Nine different salt profiles were delivered by a Dynataste device and a trained panel assessed their saltiness using time–intensity and single-score sensory techniques. The profile duration (15 s) was designed to match eating conditions and the effects of intensity and duration of the pulses on sensory perception were investigated. Sensory results from the profiles delivered in either water or in a bouillon base were not statistically different. Maximum perceived salt intensities and the area under the time–
intensity curves correlated well with the overall perceived
saltiness intensity despite the stimulus being delivered as
several pulses. The overall saltiness scores for profiles
delivering the same overall amount of sodium were statistically not different from one another suggesting that, in this system, pulsed delivery did not enhance salt
perception but the overall amount of salt delivered in each
profile did affect sensory perception
Optical detection of single non-absorbing molecules using the surface plasmon of a gold nanorod
Current optical detection schemes for single molecules require light
absorption, either to produce fluorescence or direct absorption signals. This
severely limits the range of molecules that can be detected, because most
molecules are purely refractive. Metal nanoparticles or dielectric resonators
detect non-absorbing molecules by a resonance shift in response to a local
perturbation of the refractive index, but neither has reached single-protein
sensitivity. The most sensitive plasmon sensors to date detect single molecules
only when the plasmon shift is amplified by a highly polarizable label or by a
localized precipitation reaction on the particle's surface. Without
amplification, the sensitivity only allows for the statistical detection of
single molecules. Here we demonstrate plasmonic detection of single molecules
in realtime, without the need for labeling or amplification. We monitor the
plasmon resonance of a single gold nanorod with a sensitive photothermal assay
and achieve a ~ 700-fold increase in sensitivity compared to state-of-the-art
plasmon sensors. We find that the sensitivity of the sensor is intrinsically
limited due to spectral diffusion of the SPR. We believe this is the first
optical technique that detects single molecules purely by their refractive
index, without any need for photon absorption by the molecule. The small size,
bio-compatibility and straightforward surface chemistry of gold nanorods may
open the way to the selective and local detection of purely refractive proteins
in live cells
Microstructure and Wear Resistance of an Arc-Sprayed Fe-Based Coating after Surface Kemelting Treatment
The aim of the study was to improve the
lamellar structure and wear resistance of
arc-sprayed coatings. FeNiCrAl arc-sprayed
coatings were remelted by the tungsten inert gas
welding method. The as-sprayed and remelted
specimens were subjected to comparative structural
phase composition examination using optical
microscopy, scanning electron microscopy
and X-ray diffraction. Additionally, the effect
of the remelting treatment on the wear mechanism
of the arc sprayed coatings was also studied.
It was found from the experiments that the
tungsten inert gas surface process has the potential
to form pore- and crack-free coatings. Further
investigations showed that the dominant
mechanism of wear for the as-sprayed coatings
was oxide delamination and for the tungsten
inert gas remelted coatings was cutting and
ploughingУсовершенствованы пластинчатая структура и износостойкость покрытий, полученных
электродуговой металлизацией. С помощью дуговой сварки вольфрамовым электродом в
среде инертного газа проведена переплавка покрытий на основе FeNiCrAl, полученных электро-дуговой металлизацией. С использованием методов оптической микроскопии, растровой
электронной микроскопии и дифракции рентгеновских лучей осуществлено сравнительное
исследование структуры и фазового состава напыленных и переплавленных покрытий. Изучено влияние обработки путем переплавки на механизм износа покрытий, полученных электро-дуговой металлизацией. Установлено, что реализация дуговой сварки вольфрамовым электродом в среде инертного газа позволяет разрабатывать покрытия без пор и трещин. Даль-
нейшие исследования показали, что основной признак износа покрытий, полученных электро-дуговой металлизацией, – расщепление оксида, в то время как покрытий, переплавленных с
помощью дуговой сварки вольфрамовым электродом в среде инертного газа, – резание и
пропахивание.Удосконалено пластинчасту структуру та зносостійкість покриттів, отриманих електро-дуговою металізацією. За допомогою дугового зварювання вольфрамовим електро-дом у середовищі інертного газу проведено переплавку покриттів на основі FeNiCrAl,
отриманих електродуговою металізацією. Із використанням методів оптичної мікроскопії, растрової електронної мікроскопії та дифракції рентгенівських променів проведено порівняльне дослідження структури і фазового складу напилених і переплавлених покриттів. Вивчено вплив обробки шляхом переплавки на механізм зношення
покриттів, отриманих електродуговою металізацією. Установлено, що реалізація дугового зварювання вольфрамовим електродом у середовищі інертного газу дозволяє розробляти покриття без пор і тріщин. Подальші дослідження показали, що основними
ознаками зношення покриттів, отриманих електродуговою металізацією, є розщеплення оксиду, в той час як покриттів, переплавлених за допомогою дугового зварювання
вольфрамовим електродом у середовищі інертного газу, – різання і проорюванн
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