751 research outputs found
Intra-Class Testing of Abstract Class Features
One of the characteristics of the increasingly widespread
use of object-oriented libraries and the resulting intensive
use of inheritance is the proliferation of dependencies on
abstract classes. Such classes defer the implementation of
some features, and are typically used as a specification or
design tool. However, since their features are not fully implemented,abstract classes cannot be instantiated, and thus pose challenges for execution-based testing strategies.
This paper presents a structured approach that supports
the testing of features in abstract classes. Core to the approach is a series of static analysis steps that build a comprehensive view of the inter-class dependencies in the system under test. We then leveraged this information to define a test order for the methods in an abstract class that minimizes the number of stubs required during testing, and clearly identifies the required functionality of these stubs.
Our approach is based on a comprehensive taxonomy of
object-oriented classes that provides a framework for our
analysis. First we describe the algorithms to calculate the
inter-class dependencies and the test-order that minimizes
stub creation. Then we give an overview of our tool, AbstractTestJ that implements our approach by generating a
test order for the methods in an abstract Java class. Finally, we harness this tool to provide an analysis of 12 substantial Java applications that demonstrates both the feasibility of our approach and the importance of this technique
Theory of Andreev reflection in a junction with a strongly disordered semiconductor
We study the conduction of a {\sl N~-~Sm~-~S} junction, where {\sl Sm} is a
strongly disordered semiconductor. The differential conductance of this
{\sl N~-~Sm~-~S} structure is predicted to have a sharp peak at . Unlike
the case of a weakly disordered system, this feature persists even in the
absence of an additional (Schottky) barrier on the boundary. The zero-bias
conductance of such a junction is smaller only by a numerical factor
than the conductance in the normal state . Implications for experiments on
gated heterostructures with superconducting leads are discussed.Comment: 4 pages, 2 figures, to appear in Rapid Communication section of Phys.
Rev.
Triplet-charge annihilation in a small molecule donor: acceptor blend as a major loss mechanism in organic photovoltaics
Organic photovoltaics (OPV) are close to reaching a landmark 20% device efficiency. One of the proposed reasons that OPVs have yet to attain this milestone is their propensity toward triplet formation. Herein, a small molecule donor, DRCN5T, is studied using a variety of morphology and spectroscopy techniques, and blended with both fullerene and non-fullerene acceptors. Specifically, grazing incidence wide-angle X-ray scattering and transient absorption, Raman, and electron paramagnetic resonance spectroscopies are focused on. It is shown that despite DRCN5T's ability to achieve OPV efficiencies of over 10%, it generates an unusually high population of triplets. These triplets are primarily formed in amorphous regions via back recombination from a charge transfer state, and also undergo triplet-charge annihilation. As such, triplets have a dual role in DRCN5T device efficiency suppression: they both hinder free charge carrier formation and annihilate those free charges that do form. Using microsecond transient absorption spectroscopy under oxygen conditions, this triplet-charge annihilation (TCA) is directly observed as a general phenomenon in a variety of DRCN5T: fullerene and non-fullerene blends. Since TCA is usually inferred rather than directly observed, it is demonstrated that this technique is a reliable method to establish the presence of TCA
A new determination of the orbit and masses of the Be binary system delta Scorpii
The binary star delta Sco (HD143275) underwent remarkable brightening in the
visible in 2000, and continues to be irregularly variable. The system was
observed with the Sydney University Stellar Interferometer (SUSI) in 1999,
2000, 2001, 2006 and 2007. The 1999 observations were consistent with
predictions based on the previously published orbital elements. The subsequent
observations can only be explained by assuming that an optically bright
emission region with an angular size of > 2 +/- 1 mas formed around the primary
in 2000. By 2006/2007 the size of this region grew to an estimated > 4 mas.
We have determined a consistent set of orbital elements by simultaneously
fitting all the published interferometric and spectroscopic data as well as the
SUSI data reported here. The resulting elements and the brightness ratio for
the system measured prior to the outburst in 2000 have been used to estimate
the masses of the components. We find Ma = 15 +/- 7 Msun and Mb = 8.0 +/- 3.6
Msun. The dynamical parallax is estimated to be 7.03 +/- 0.15 mas, which is in
good agreement with the revised HIPPARCOS parallax.Comment: 8 pages, 4 figs. Accepted for publication in MNRA
Impact of health warning labels and calorie labels on selection and purchasing of alcoholic and nonâalcoholic drinks: a randomized controlled trial
Aims: To estimate the impact on selection and actual purchasing of (a) health warning labels (textâonly and imageâandâtext) on alcoholic drinks and (b) calorie labels on alcoholic and nonâalcoholic drinks. Design: Parallelâgroups randomised controlled trial. Setting: Drinks were selected in a simulated online supermarket, before being purchased in an actual online supermarket. Participants: Adults in England and Wales who regularly consumed and purchased beer or wine online (n = 651). Six hundred and eight participants completed the study and were included in the primary analysis. Interventions: Participants were randomized to one of six groups in a betweenâsubjects three [health warning labels (HWLs) (i): imageâandâtext HWL; (ii) textâonly HWL; (iii) no HWL] Ă 2 (calorie labels: present versus absent) factorial design (n per group 103â113). Measurements: The primary outcome measure was the number of alcohol units selected (with intention to purchase); secondary outcomes included alcohol units purchased and calories selected and purchased. There was no time limit for selection. For purchasing, participants were directed to purchase their drinks immediately (although they were allowed up to 2 weeks to do so). Findings: There was no evidence of main effects for either (a) HWLs or (b) calorie labels on the number of alcohol units selected (HWLs: F(2,599) = 0.406, P = 0.666; calorie labels: F(1,599) = 0.002, P = 0.961). There was also no evidence of an interaction between HWLs and calorie labels, and no evidence of an overall difference on any secondary outcomes. In preâspecified subgroup analyses comparing the âcalorie label onlyâ group (n = 101) with the âno labelâ group (n = 104) there was no evidence that calorie labels reduced the number of calories selected (unadjusted means: 1913 calories versus 2203, P = 0.643). Among the 75% of participants who went on to purchase drinks, those in the âcalorie label onlyâ group (n = 74) purchased fewer calories than those in the âno labelâ group (n = 79) (unadjusted means: 1532 versus 2090, P = 0.028). Conclusions: There was no evidence that health warning labels reduced the number of alcohol units selected or purchased in an online retail context. There was some evidence suggesting that calorie labels on alcoholic and nonâalcoholic drinks may reduce calories purchased from both types of drinks
Numerical analysis of the radio-frequency single-electron transistor operation
We have analyzed numerically the response and noise-limited charge
sensitivity of a radio-frequency single-electron transistor (RF-SET) in a
non-superconducting state using the orthodox theory. In particular, we have
studied the performance dependence on the quality factor Q of the tank circuit
for Q both below and above the value corresponding to the impedance matching
between the coaxial cable and SET.Comment: 14 page
Anomalous c-axis charge dynamics in copper oxide materials
Within the t-J model, the c-axis charge dynamics of the copper oxide
materials in the underdoped and optimally doped regimes is studied by
considering the incoherent interlayer hopping. It is shown that the c-axis
charge dynamics is mainly governed by the scattering from the in-plane
fluctuation. In the optimally doped regime, the c-axis resistivity is a linear
in temperatures, and shows the metallic-like behavior for all temperatures,
while the c-axis resistivity in the underdoped regime is characterized by a
crossover from the high temperature metallic-like behavior to the low
temperature semiconducting-like behavior, which are consistent with experiments
and numerical simulations.Comment: 6 pages, Latex, Three figures are adde
Tyrian purple : an ancient natural dye for cross-conjugated n-type charge transport
Herein, we present two novel organic semiconducting polymers synthesised from an ancient dye. By employing cross-conjugation within the polymer backbone as a synthetic strategy, we are able to engineer optical gaps such that the novel materials absorb over the entire visible spectrum. The cross-conjugated polymers exhibited relatively high n-type charge transport performance in organic field-effect transistors, a rare characteristic for this type of polymer. Quantum chemical calculations provide insight into this behaviour, suggesting that, whilst conjugation along the HOMO is indeed inhibited via molecular design, these materials possess highly delocalized LUMOs, facilitating high n-type charge transport
Multi-layered Ruthenium-modified Bond Coats for Thermal Barrier Coatings
Diffusional approaches for fabrication of multi-layered Ru-modified bond coats for thermal
barrier coatings have been developed via low activity chemical vapor deposition and high activity
pack aluminization. Both processes yield bond coats comprising two distinct B2 layers, based on
NiAl and RuAl, however, the position of these layers relative to the bond coat surface is reversed
when switching processes. The structural evolution of each coating at various stages of the
fabrication process has been and subsequent cyclic oxidation is presented, and the relevant
interdiffusion and phase equilibria issues in are discussed. Evaluation of the oxidation behavior of
these Ru-modified bond coat structures reveals that each B2 interlayer arrangement leads to the
formation of α-Al 2 O 3 TGO at 1100°C, but the durability of the TGO is somewhat different and in
need of further improvement in both cases
Labour after Land Reform: The Precarious Livelihoods of Former Farmworkers in Zimbabwe
What happens to labour when major redistributive land reform restructures a system of settler colonial agriculture? This article examines the livelihoods of former farmworkers on largeâscale commercial farms who still live in farm compounds after Zimbabwe's land reform. Through a mix of surveys and inâdepth biographical interviews, four different types of livelihood are identified, centred on differences in land access. These show how diverse, but often precarious, livelihoods are being carved out, representing the âfragmented classes of labourâ in a restructured agrarian economy. The analysis highlights the tensions between gaining new freedoms, notably through access to land, and being subject to new livelihood vulnerabilities. The findings are discussed in relation to wider questions about the informalization of the economy and the role of labour and employment in a postâsettler agrarian economy, where the old âfarmworkerâ label no longer applies
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