5,456 research outputs found
Target Directed Event Sequence Generation for Android Applications
Testing is a commonly used approach to ensure the quality of software, of
which model-based testing is a hot topic to test GUI programs such as Android
applications (apps). Existing approaches mainly either dynamically construct a
model that only contains the GUI information, or build a model in the view of
code that may fail to describe the changes of GUI widgets during runtime.
Besides, most of these models do not support back stack that is a particular
mechanism of Android. Therefore, this paper proposes a model LATTE that is
constructed dynamically with consideration of the view information in the
widgets as well as the back stack, to describe the transition between GUI
widgets. We also propose a label set to link the elements of the LATTE model to
program snippets. The user can define a subset of the label set as a target for
the testing requirements that need to cover some specific parts of the code. To
avoid the state explosion problem during model construction, we introduce a
definition "state similarity" to balance the model accuracy and analysis cost.
Based on this model, a target directed test generation method is presented to
generate event sequences to effectively cover the target. The experiments on
several real-world apps indicate that the generated test cases based on LATTE
can reach a high coverage, and with the model we can generate the event
sequences to cover a given target with short event sequences
Effects of Finite Deformed Length in Carbon Nanotubes
The effect of finite deformed length is demonstrated by squashing an armchair
(10,10) single-walled carbon nanotube with two finite tips. Only when the
deformed length is long enough, an effectual metal-semiconductor-metal
heterojunction can be formed in the metallic tube. The effect of finite
deformed length is explained by the quantum tunnelling effect. Furthermore,
some conceptual designs of nanoscale devices are proposed from the
metal-semiconductor-metal heterojunction.Comment: 4 pages, 4 figure
Converting normal insulators into topological insulators via tuning orbital levels
Tuning the spin-orbit coupling strength via foreign element doping and/or
modifying bonding strength via strain engineering are the major routes to
convert normal insulators to topological insulators. We here propose an
alternative strategy to realize topological phase transition by tuning the
orbital level. Following this strategy, our first-principles calculations
demonstrate that a topological phase transition in some cubic perovskite-type
compounds CsGeBr and CsSnBr could be facilitated by carbon
substitutional doping. Such unique topological phase transition predominantly
results from the lower orbital energy of the carbon dopant, which can pull down
the conduction bands and even induce band inversion. Beyond conventional
approaches, our finding of tuning the orbital level may greatly expand the
range of topologically nontrivial materials
Reconsideration of the QCD corrections to the decays into light hadrons using the principle of maximum conformality
In the paper, we analyze the decays into light hadrons at the
next-to-leading order QCD corrections by applying the principle of maximum
conformality (PMC). The relativistic correction at the -order level has been included in the discussion, which gives about
contribution to the ratio . The PMC, which satisfies the renormalization
group invariance, is designed to obtain a scale-fixed and scheme-independent
prediction at any fixed order. To avoid the confusion of treating -terms,
we transform the usual pQCD series into the one under the
minimal momentum space subtraction scheme. To compare with the prediction under
conventional scale setting, , after applying the PMC, we obtain
, where the
errors are squared averages of the ones caused by and . The PMC prediction agrees with the recent PDG value within errors, i.e.
. Thus we think the mismatching
of the prediction under conventional scale-setting with the data is due to
improper choice of scale, which however can be solved by using the PMC.Comment: 5 pages, 2 figure
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