Studying the needed effort for identifying duplicate issues

Many recent software engineering papers have examined duplicate issue reports. Thus far, duplicate reports have been considered a hindrance to developers and a drain on their resources. As a result, prior research in this area focuses on proposing automated approaches to accurately identify duplicate reports. However, there exists no studies that attempt to quantify the actual effort that is spent on identifying duplicate issue reports. In this paper, we empirically examine the effort that is needed for manually identifying duplicate reports in four open source projects, i.e., Firefox, SeaMonkey, Bugzilla and Eclipse-Platform. Our results show that: (i) More than 50 % of the duplicate reports are identified within half a day. Most of the duplicate reports are identified without any discussion and with the involvement of very few people; (ii) A classification model built using a set of factors that are extracted from duplicate issue reports classifies duplicates according to the effort that is needed to identify them with a precision of 0.60 to 0.77, a recall of 0.23 to 0.96, and an ROC area of 0.68 to 0.80; and (iii) Factors that capture the developer awareness of the duplicate issue’s peers (i.e., other duplicates of that issue) and textual similarity of a new report to prior reports are the most influential factors in our models. Our findings highlight the need for effort-aware evaluation of approaches that identify duplicate issue reports, since the identification of a considerable amount of duplicate reports (over 50 %) appear to be a relatively trivial task for developers. To better assist developers, research on identifying duplicate issue reports should put greater emphasis on assisting developers in identifying effort-consuming duplicate issues.     

Experimentally validated analytical modeling of diesel engine power and in-cylinder gas speed dynamics

Supercharged diesel engines are a key element in diesel powertrains that have been extensively modelled yet often without explainable mathematical trends. The present paper demonstrates the analytical modelling of in-cylinder gas speed dynamics and engine brake power. These analytical models provide explainable mathematical trends. In addition, they provide gear-shifting-based modeling because the model parameters can be adjusted to reflect different driving conditions without the need for gathering field data. An unprecedented sensitivity analysis was conducted on these developed models for simplifying them. They were validated using experimental data and the relative error of the developed model of the in-cylinder gas speed dynamics was 9.8%. The study demonstrates with 73% coefficient of determination that the average percentage of deviation of the simulated results from the corresponding field data on the engine brake power is 6.9%. The relative error of the developed model of the engine brake power is 7%. These values of relative error are an order of magnitude of deviation that is less than that of widely recognized models in the field of vehicle powertrain modeling such as the CMEM and GT-Power. These analytically developed models serve as widely valid models. Having addressed and corrected flaws in the corresponding models, such as the model of the in-cylinder gas speed dynamics presented in a key reference in this research area, these developed models can help in better analyzing and assessing the performance of diesel engines.

     

Structural Characterization of Oat Bran (1→3), (1→4)-β-D-Glucans by Lichenase Hydrolysis Through High-Performance Anion Exchange Chromatography with Pulsed Amperometric Detection

Cereal mixed linkages (1 → 3) (1 → 4)-β-D-glucan is a linear polysaccharide composed of glucose units. Oat β-glucan is a natural polymer. The main products of β-glucanase are oligosaccharides with DP3 and DP4, i.e., 3-Ob-cellobiosyl-D-glucose and 3-Ob-cellotriosyl-D-glucose, which represent over 90% of the molecule. Keeping in mind all the benefits of oat bran, the present study was planned to investigate the structural properties of oat bran, high-performance anion exchange chromatography with pulsed amperometric detection was used to examine these oligosaccharides. The structural analysis of oat bran of two oat varieties revealed that the ratio of soluble and insoluble triose to tetraose in β-glucan fraction was 1.44 and 1.78, respectively, for Avon variety; while the ratio of soluble and insoluble triose to tetraose in β-glucan fraction for Sargodha-81 was 1.49 and 1.77. The major units determined were cellotriose and cellotetraose. Other units cellopentaose and hexaoses were also existed but in minor fractions. Lichenase hydrolysis high-performance anion exchange chromatography with pulsed amperometric detection appeared to be the best choice for structural analysis of purified samples of mixed-linkage β-glucan.     

Influence of pH of phenol-formaldehyde resin and thermal treatment on the properties of hardboard

Hydrogen ion concentration greatly affects the properties of finished hardboard products, since it serves the dual purpose of imporoving both strength and hydrophobic properties of the board. Improvement in the physical and mechanical properties was greater with increasing hydrogen ion concentration up to a certain pH (which is about 3.3 and 5 for boards pressed with resin and with pH adjusted by means of acid and alum respectively). However, higher hydrogen ion concentrations caused damage of cellulose fibers, thereby deteriorating the strength properties. In most cases the rate of improvement was much higher with alum adjustment of pH, especially when the boards were subsequently subjected to thermal treatment. With thermal treatment a greater improvement is attained at lower hydrogen ion concentrations than without it.     

Reinforcement effect of nanodiamond on properties of epoxy matrix

Epoxy/nanocrystalline diamond nanocomposites composites were prepared by dispersing ultrasonically, 0.4, 0.7, 1.0, and 4.0 wt% acid‐treated nanocrystalline diamond (NCD) powder in epoxy matrix. Fourier infrared spectroscopy was utilized to study the moieties attached to the nanodiamond particles. The trace elements present in NCD powder before and after acid treatment were analyzed by ion beam techniques. Thermomechanical properties of the nanocomposites showed that incorporation of low content (0.4 wt%) of nanodiamond powder into epoxy matrix enhanced the storage modulus, loss modulus, and hardness by ∼68, ∼55, and ∼86%, respectively, over neat epoxy. By increasing the concentration of modified NCD to 0.7 wt% resulted in lower values of hardness and thermomechanical properties but still remain higher than neat epoxy. An increasing trend in properties was again observed at 4 wt% concentration of modified nanofiller. The glass transition temperature was up shifted to ∼110°C over neat epoxy. The mechanisms responsible for enhanced properties of epoxy matrix are also discussed in detail. POLYM. COMPOS., 34:811–818, 2013. © 2013 Society of Plastics Engineers     

Revisiting the performance of automated approaches for the retrieval of duplicate reports in issue tracking systems that perform just-in-time duplicate retrieval

Issue tracking systems (ITSs) allow software end-users and developers to file issue reports and change requests. Reports are frequently duplicately filed for the same software issue. The retrieval of these duplicate issue reports is a tedious manual task. Prior research proposed several automated approaches for the retrieval of duplicate issue reports. Recent versions of ITSs added a feature that does basic retrieval of duplicate issue reports at the filing time of an issue report in an effort to avoid the filing of duplicates as early as possible. This paper investigates the impact of this just-in-time duplicate retrieval on the duplicate reports that end up in the ITS of an open source project. In particular, we study the differences between duplicate reports for open source projects before and after the activation of this new feature. We show how the experimental results of prior research would vary given the new data after the activation of the just-in-time duplicate retrieval feature. We study duplicate issue reports from the Mozilla-Firefox, Mozilla-Core and Eclipse-Platform projects. In addition, we compare the performance of the state of the art of the automated retrieval of duplicate reports using two popular approaches (i.e., BM25F and REP). We find that duplicate issue reports after the activation of the just-in-time duplicate retrieval feature are less textually similar, have a greater identification delay and require more discussion to be retrieved as duplicate reports than duplicates before the activation of the feature. Prior work showed that REP outperforms BM25F in terms of Recall rate and Mean average precision. We observe that the performance gap between BM25F and REP becomes even larger after the activation of the just-in-time duplicate retrieval feature. We recommend that future studies focus on duplicates that were reported after the activation of the just-in-time duplicate retrieval feature as these duplicates are more representative of future incoming issue reports and therefore, give a better representation of the future performance of proposed approaches.     

Incorporation of hydrogen in diamond thin films

In this investigation, diamond thin films with grain size ranging from 50 nm to 1 µm deposited using hot filament chemical vapor deposition (HFCVD) have been analyzed by elastic recoil detection analysis (ERDA) for determining hydrogen concentration. Hydrogen concentration in diamond thin films increases with decreasing grain size. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) results showed that part of this hydrogen is bonded to carbon forming C–H bonding. Raman spectra also indicated the increase of non diamond phase with the decrease in crystallite size. Incorporation of hydrogen in the samples and increase of hydrogen content in nanocrystalline sample are discussed. Large separation between filament and substrate used for the synthesis of nanocrystalline film helped to understand the large incorporation of hydrogen in nanocrystalline diamond films during growth. The study addresses the hydrogen trapping in different samples and higher hydrogen concentration in nanocrystallites by considering the synthesis conditions, growth mechanisms for different grain sized diamond films and from the quality of CVD diamond films.