Evolution of statistical analysis in empirical software engineering research: Current state and steps forward

Software engineering research is evolving and papers are increasingly based on empirical data from a multitude of sources, using statistical tests to determine if and to what degree empirical evidence supports their hypotheses. To investigate the practices and trends of statistical analysis in empirical software engineering (ESE), this paper presents a review of a large pool of papers from top-ranked software engineering journals. First, we manually reviewed 161 papers and in the second phase of our method, we conducted a more extensive semi-automatic classification of papers spanning the years 2001--2015 and 5,196 papers. Results from both review steps was used to: i) identify and analyze the predominant practices in ESE (e.g., using t-test or ANOVA), as well as relevant trends in usage of specific statistical methods (e.g., nonparametric tests and effect size measures) and, ii) develop a conceptual model for a statistical analysis workflow with suggestions on how to apply different statistical methods as well as guidelines to avoid pitfalls. Lastly, we confirm existing claims that current ESE practices lack a standard to report practical significance of results. We illustrate how practical significance can be discussed in terms of both the statistical analysis and in the practitioner's context.Comment: journal submission, 34 pages, 8 figure

Limits on non-minimal Lorentz violating parameters through FCNC and LFV processes

In this work we analyse a non-minimal Lorentz-violating extension of the electroweak theory in the fermionic sector. Firstly we analyse the relation between the CKM rotation in the quark sector and possible contributions of this new coupling to flavour changing neutral currents (FCNC) processes. In sequel we look for non-diagonal terms through possible leptonic flavour violation (LFV) decays. Strong bounds are presented to the Lorentz violating parameters of both the quark and the leptonic sectors.Comment: Published versio

Theoretical study of the competition between folding and contact interactions on the properties of polymers using self-avoid random walk algorithm

The self-avoid random walk algorithm has been extensively used in the study of polymers. In this work we study the basic properties of the trajectories generated with this algorithm when two interactions are added to it: contact and folding interaction. These interactions represent the internal forces of the polymer as well as the effect of the solvent. When independently added to the algorithm, the contact interaction creates the compact phase while the folding one creates the extended phase. These are the consequences of the typical event of each interaction. On the other hand, when this typical event is avoided there is no established phase on the system. When simultaneously added, there is a competition between the interactions and the folding one is dominant over the contact one. The resulting phase is always the extended one with and without the contact interaction.Comment: 8 pages, 7 figure

A new methodology to predict damage tolerance based on compliance via global-local analysis

Over the years several design philosophies to fatigue developed in order to combine structural safety and economy to manufacturing and operating aircraft process. The safe-life approach, which consists of designing and manufacturing a safe aeronautical structure throughout its useful life, results in factors that oversize the structural elements, preventing the possibility of failure and evidently leading to high design costs. On the other hand, the approach based on the damage tolerance concept, in which it is assumed that the structure, even whether damaged, is able to withstand the actions for which it was designed until the detection of a crack due to fatigue or other defects during its operation. Here, we propose a new methodology to the damage tolerance problem in which two-dimensional global-local analysis at different levels of external requests will be made by means of compliance, aimed at finding a relationship between fatigue life and the Paris constant. Moreover, the BemCracker2D program for simulating two-dimensional crack growth is used. This methodology has been proved to be an efficient and applied alternative in the damage tolerance analysis

Efeito de modificadores químicos sobre o comportamento eletrotérmico de selênio em digerido de material vegetal.

A demanda crescente por alimentação balanceada tem despertado interesse em dietas diferenciadas baseadas em alimentos funcionais, os quais possuem propriedades ou substancias bioativas capazes de modular alguma função no organismo. As crucíferas, vegetais com capacidade de absorver altos teores de Se, compõem um grupo de uma série de alimentos desse tipo. A determinação de Se nesses vegetais é de interesse em função tanto de sua importância no metabolismo humano e animal como do ponto de vista de sua toxicidade. Com relação a determinação de Se por espectrometria de absorção atômica com atomização eletrotérmica em forno de grafite (GFAAS), os modificadores químicos convencionais mais citados são: Pd(NO3)2, Mg(NO3)2, Ni(NO3)2, Pd(NO3)2 + Mg(NO3)2,- Pd(NO3)2 + Cd(NO3)2, Pd(NO3)2+ acido ascórbico; Pd (pré-reduzido). Neste trabalho foi avaliada a influência de modificadores químicos sobre o comportamento eletrotérmico de Se em um vegetal da classe das cruciferas (nabo) empregando curvas de pirólise e atomização em presença de Pd(II), Ni(II), Mg(II), Pd pré-reduzido e das misturas Pd(II)/Mg(II) e Pd(II)/Cd(II). Foram preparadas soluções analíticas contendo 20 pg Se L-1 em meio 0,014 mol L-1 HNO3 e 30 pg Se L -1 em digerido do material vegetal