Is It Safe to Uplift This Patch? An Empirical Study on Mozilla Firefox

In rapid release development processes, patches that fix critical issues, or implement high-value features are often promoted directly from the development channel to a stabilization channel, potentially skipping one or more stabilization channels. This practice is called patch uplift. Patch uplift is risky, because patches that are rushed through the stabilization phase can end up introducing regressions in the code. This paper examines patch uplift operations at Mozilla, with the aim to identify the characteristics of uplifted patches that introduce regressions. Through statistical and manual analyses, we quantitatively and qualitatively investigate the reasons behind patch uplift decisions and the characteristics of uplifted patches that introduced regressions. Additionally, we interviewed three Mozilla release managers to understand organizational factors that affect patch uplift decisions and outcomes. Results show that most patches are uplifted because of a wrong functionality or a crash. Uplifted patches that lead to faults tend to have larger patch size, and most of the faults are due to semantic or memory errors in the patches. Also, release managers are more inclined to accept patch uplift requests that concern certain specific components, and-or that are submitted by certain specific developers.Comment: In proceedings of the 33rd International Conference on Software Maintenance and Evolution (ICSME 2017

Improving software engineering processes using machine learning and data mining techniques

The availability of large amounts of data from software development has created an area of research called mining software repositories. Researchers mine data from software repositories both to improve understanding of software development and evolution, and to empirically validate novel ideas and techniques. The large amount of data collected from software processes can then be leveraged for machine learning applications. Indeed, machine learning can have a large impact in software engineering, just like it has had in other fields, supporting developers, and other actors involved in the software development process, in automating or improving parts of their work. The automation can not only make some phases of the development process less tedious or cheaper, but also more efficient and less prone to errors. Moreover, employing machine learning can reduce the complexity of difficult problems, enabling engineers to focus on more interesting problems rather than the basics of development. The aim of this dissertation is to show how the development and the use of machine learning and data mining techniques can support several software engineering phases, ranging from crash handling, to code review, to patch uplifting, to software ecosystem management. To validate our thesis we conducted several studies tackling different problems in an industrial open-source context, focusing on the case of Mozilla

Real-time setup to measure radon emission during rock deformation. Implications for geochemical surveillance

Laboratory experiments can represent a valid approach to unravel the complex interplay between the geochemical behaviour of radon and rock deformation mechanisms. In light of this, we present a new real-time experimental setup for analysing in continuum the alpha-emitting 222Rn and 220Rn daughters over variable stress–strain regimes. The most innovative segment of this setup consists of the radon accumulation chamber obtained from a tough and durable material that can host large cylindrical rock samples. The accumulation chamber is connected, in a closed-loop configuration, to a gas-drying unit and to a RAD7 radon monitor. A recirculating pump moves the gas from the rock sample to a solid-state detector for alpha counting of radon and thoron progeny. The measured radon signal is enhanced by surrounding the accumulation chamber with a digitally controlled heating belt. As the temperature is increased, the number of effective collisions of radon atoms increases favouring the diffusion of radon through the material and reducing the analytical uncertainty. The accumulation chamber containing the sample is then placed into a uniaxial testing apparatus where the axial deformation is measured throughout a linear variable displacement transducer. A dedicated software allows obtaining a variety of stress–strain regimes from fast deformation rates to long-term creep tests. Experiments conducted with this new real-time setup have important ramifications for the interpretation of geochemical anomalies recorded prior to volcanic eruptions or earthquakes

Microstructure-sensitive estimation of small fatigue crack growth in bridge steel welds

A probabilistic finite element model is implemented to estimate microstructurally small fatigue crack growth in bridge steel welds. Simulations are based on a microstructure-sensitive crystal plasticity model to quantify fatigue indicator parameters (FIPs) at the slip system level and a fatigue model that relates FIPs to fatigue lives of individual grains. Microstructures from three weld zones, namely, fusion zone (FZ), heat affected zone (HAZ), and base metal (BM), are constructed based on their microstructural attributes such as grain morphology, size, and orientation. Statistical volume elements (SVEs) are generated and meshed independently for the three welding zones. Each grain within the SVEs is divided into several slip bands parallel to crystallographic planes. During the loading process, cracks nucleate at the slip bands (SBs) with the largest FIP next to the free surface. The crack extension path is assumed to be transgranular along SBs and the number of cycles required to crack the neighbor grain is calculated by the corresponding FIP-based crack growth rate equation. The simulation process is carried out using ABAQUS with a user defined subroutine UMAT for crystal plasticity. After the calibration of the constitutive model and irreversibility parameters, numerical simulations for small crack growth in three zones are presented. The crack length vs. the predicted fatigue resistance shows significant differences in the mean values and variability among the three weld zones

Assessment of Microplastics Distribution in a Biological Wastewater Treatment

Full-scale wastewater treatment facilities are not able to prevent microplastics (MPs) from discharging into natural waters and they are also associated with the land application of the sludge. This study evaluates the distribution of microfibers (MFs) in a lab-scale sequencing batch reactor (SBR) fed by synthetic wastewater (SW) for 93 days. The MFs were analyzed through optical microscopy in the mixed liquor (ML) and the effluent, and sulfuric acid digestion was applied to discriminate between natural and synthetic MFs (i.e., MPs). The results of the optical microscopy analyses were further validated through FTIR spectroscopy. A model describing the evolution over time of the MF concentration in the ML was created, accounting for the MFs entering the system through the SW and atmospheric deposition. The ratio between the MF concentration in the ML and the effluent was 1409   781, demonstrating that MFs settle with the sludge. Consistently, in the ML, 64.9% of the recovered MFs were smaller than 1000 μm (average size 968 μm), while in the effluent, 76.1% of MFs were smaller than 1000 μm (average size 772 μm). Overall, 72% of MFs recovered from the ML were natural fibers and sulfuric acid digestion was successful in eliminating the natural MFs

Adjusting for Non-Ignorable Verification Bias in Clinical Studies for Alzheimer’s Disease

A common problem for comparing the relative accuracy of two screening tests for Alzheimer’s disease (D) in a two-stage design study is verification bias. If the verification bias can be assumed to be ignorable, Zhou and Higgs (2000) have proposed a maximum likelihood approach to compare the relative accuracy of screening tests in a two-stage design study. However, if the verification mechanism also depends on the unobserved disease status, the ignorable assumption does not hold. In this paper, we discuss how to use a profile likelihood approach to compare the relative accuracy of two screening tests for AD without assuming the ignorable verification bias mechanism

Helicopter operations: the environmental impact and ground facilities. Procedures and operational standards for the system’s acceptance.

The link between the heliports, environmental quality and safety is an important challenge in the field of helicopter transport. This challenge is especially crucial when the helicopter operations are carried out on densely urbanized areas. Often these areas have significant constraints and obstacles, particularly in terms of noise pollution. These constraints make the approach/takeoff maneuvers very complicated. The theme of the environmental sustainability of the rotorcraft is strongly felt in many countries. The production of noise is subjected to numerous rules and procedures, which tend to improve the acceptability of the helicopter by residents in neighboring areas to verti/heliports. The attention of manufacturers towards the problems of noise compatibility has produced technological innovations to reduce emissions, such as the shape of the tip of rotor blades, a speed reduction of rotation of the rotors, etc. Environmental concerns are becoming increasingly important when siting all aviation facilities. In particular, heliport facilities generate both positive and negative impacts on the surrounding environment. Negative impacts are mainly related to soil quality, water resources, safety issues, air environment (especially during the construction phase), noise (during operations) and biological environment. Positive ones could occur by the increase of emergency services, revenue generation, and the provision of a better connectivity with the neighborhoods located nearby the facility, the raise of employment opportunities and the general improvement of air transport facilities. The current international regulatory framework on heliport facilities seems to be lacking with regards to the evaluation of the environmental impacts of the heliport facilities. Moreover, the national rules on this topic are often undefined or vague. For this reason, it seems necessary to define guidelines to improve the awareness of the consequences which spontaneously arise from the planning and designing phase of heliports. Already from the site selection stage, heliport planners have to take into account all potential environmental issues. Noise is always the primary concern in these cases. A candidate site must be compatible with its surroundings. Compatibility must include any increase in activity resulting from IFR capability. Additional issues that citizens and municipalities are concerned about include air pollution, water pollution, ground access, and safety flight operations. Air pollution by helicopters is negligible although this issue may be brought up by concerned citizens and communities. Water pollution caused by fueling or maintenance facilities at a verti/heliport is coming under greater scrutiny. The ability to deal with all these public issues must be addressed during final site selection and community standards must be upheld. Ground access to a new transportation mode may increase traffic at and en route to that location and create a potential increase in noise and air pollution. These concerns must be dealt with in the design of ground access to the facility and by incorporating the individual community's standards, regulations, and goals. The receptivity of community leaders to work with the vertical landing facility to solve these problems should be measured in the final site selection process. Beyond the direct benefit of affecting the environment as little as possible, addressing environmental issues is an additional, albeit indirect tool, in obtaining and keeping good relations with the local government and its citizens. A heliport that has been developed into an IFR facility must be viable for a sufficient length of time to realize a return on investment (ROI) and to also achieve a contribution to the transportation system. In order to select a potentially viable heliport it is vital to consider the compatibility of surrounding land uses, both existing and future. A heliport that, at the present time, is considered by its neighbors as a nuisance cannot be counted on to remain in operation for an acceptable amount of time. Plans for future land use in the area must be determined through an investigation of planning documents at the appropriate levels (city, county, regional, etc.). Issues that instead will be addressed are related to the identification of the flight phases producing noise, by analyzing the different type of noise emission regarding the flight phase. Moreover, the role of helicopter’s pilot into the restraint of helicopter’s noise with particular regards to the driving behavior and its impact on noisiness’ reduction will be treated. In general, it can be stated that pilots have to do everything for reducing helicopter’s noise while remaining within the safety range’s parameters of the rotorcraft. Here comes the need of developing a worldwide analysis of the regulatory constraints for restricting helicopters’ impact on the populations residing nearby ground facilities. These constraints dictate operational rules for departure and approach phases of rotorcraft. Others factors affecting noise emissions are, for instance, temperature, humidity, wind, rotor blades. Standard procedures for noise abatement are: to fly at the highest altitude possible among those compatible with the airspace and safety rules; to enhance the awareness of the different noise perception that can be induced depending on the overflown environment (e.g. urban areas or country); The proposed study is articulated as follow: identification of measures to be implemented for reducing the environmental impact; analysis of current standard rules in several countries with regards to environmental constraints; proposals for initiatives aiming to the rules’ standardization regarding operations on heliports and helipads; samples of operational actions to be implemented for departure and approach phases; review of international experiences in the flight procedures applied for noise abatement