An Empirical Study of Goto in C Code from GitHub Repositories

ABSTRACT It is nearly 50 years since Dijkstra argued that goto obscures the flow of control in program execution and urged programmers to abandon the goto statement. While past research has shown that goto is still in use, little is known about whether goto is used in the unrestricted manner that Dijkstra feared, and if it is 'harmful' enough to be a part of a post-release bug. We, therefore, conduct a two part empirical study -(1) qualitatively analyze a statistically representative sample of 384 files from a population of almost 250K C programming language files collected from over 11K GitHub repositories and find that developers use goto in C files for error handling (80.21±5%) and cleaning up resources at the end of a procedure (40.36 ± 5%); an

VADA: A transformation-based system for variable dependence analysis

Variable dependence is an analysis problem in which the aim is to determine the set of input variables that can affect the values stored in a chosen set of intermediate program variables. This paper shows the relationship between the variable dependence analysis problem and slicing and describes VADA, a system that implements variable dependence analysis. In order to cover the full range of C constructs and features, a transformation to a core language is employed Thus, the full analysis is required only for the core language, which is relatively simple. This reduces the overall effort required for dependency analysis. The transformations used need preserve only the variable dependence relation, and therefore need not be meaning preserving in the traditional sense. The paper describes how this relaxed meaning further simplifies the transformation phase of the approach. Finally, the results of an empirical study into the performance of the system are presented

Development, Validation, and Application of a Refrigerator Simulation Model

This report describes the further development and validation of the Refrigerator/Freezer Simulation (RFSIM) model. The reports also describes the first major application of the model as an analysis tool for new refrigerator designs; several aspects of multi-speed compressor operation were examined with the model. Several improvements were made to the model that facilitated the validation process and the examination of multi-speed compressors: the model was made more general so that it could operate in numerous configurations in addition to the original design and simulation modes; many improvements were made in the modeling logic and robustness of the capillary tube-suction line heat exchanger model; and the equation-of-statebased property routines that calculated the thermodynamic properties were replaced with interpolation routines that were much faster. The RFSIM model, in design and simulation mode, was validated with data from two refrigerators. In both modes, the average model errors were less than ??5% for several important variables such as evaporator capacity and coefficient of performance. The errors of the simulation mode were reduced from the previous model validation primarily by using a different void fraction correlation in the refrigerant charge equations. The results from the validated RFSIM model indicate that a two-speed compressor could yield energy savings of 4% to 14% due to the increased steady-state efficiency at the low speed and an additional 0.5 to 4% savings due to the decreased cycling frequency. The results also showed that the capillary tube-suction line heat exchanger, when designed for the low speed, did not adversely affect the pull-down capacity when the compressor operated at the high speed. Lastly, it was found that a refrigerator operating at low ambient temperatures could actually benefit from a decrease in the condenser fan speed. This change in fan speed increased the evaporator capacity by reallocating charge to the evaporator and subsequently reducing the superheat at the evaporator exit.Air Conditioning and Refrigeration Project 6

NASA/DOD Aerospace Knowledge Diffusion Research Project. Report 14: Engineering work and information use in aerospace: Results of a telephone survey

A telephone survey of U.S. aerospace engineers and scientists who were on the Society of Automotive Engineers (SAE) mailing list was conducted between August 14-26, 1991. The survey was undertaken to obtain information on the daily work activities of aerospace engineers and scientists, to measure various practices used by aerospace engineers and scientists to obtain STI, and to ask aerospace engineers and scientists about their use of electronic networks. Co-workers were found important sources of information. Co-workers are used to obtain technical information because the information they have is relevant, not because co-workers are accessible. As technical uncertainty increases, so does the need for information internal and external to the organization. Electronic networks enjoy widespread use within the aerospace community. These networks are accessible and they are used to contact people at remote sites. About 80 percent of the respondents used electronic mail, file transfer, and information or data retrieval to commercial or in-house data bases

A mass and solute balance model for tear volume & osmolarity in the normal and the dry eye

Tear hyperosmolarity is thought to play a key role in the mechanism of dry eye, a common symptomatic condition accompanied by visual disturbance, tear film instability, inflammation and damage to the ocular surface. We have constructed a model for the mass and solute balance of the tears, with parameter estimation based on extensive data from the literature which permits the influence of tear evaporation, lacrimal flux and blink rate on tear osmolarity to be explored. In particular the nature of compensatory events has been estimated in aqueous-deficient (ADDE) and evaporative (EDE) dry eye.\ud \ud The model reproduces observed osmolarities of the tear meniscus for the healthy eye and predicts a higher concentration in the tear film than meniscus in normal and dry eye states. The differential is small in the normal eye, but is significantly increased in dry eye, especially for the simultaneous presence of high meniscus concentration and low meniscus radius. This may influence the interpretation of osmolarity values obtained from meniscus samples since they need not fully reflect potential damage to the ocular surface caused by tear film hyperosmolarity.\ud \ud Interrogation of the model suggests that increases in blink rate may play a limited role in compensating for a rise in tear osmolarity in ADDE but that an increase in lacrimal flux, together with an increase in blink rate, may delay the development of hyperosmolarity in EDE. Nonetheless, it is predicted that tear osmolarity may rise to much higher levels in EDE than ADDE before the onset of tear film breakup, in the absence of events at the ocular surface which would independently compromise tear film stability. Differences in the predicted responses of the pre-ocular tears in ADDE compared to EDE or hybrid disease to defined conditions suggest that no single, empirically-accessible variable can act as a surrogate for tear film concentration and the potential for ocular surface damage. This emphasises the need to measure and integrate multiple diagnostic indicators to determine outcomes and prognosis. Modelling predictions in addition show that further studies concerning the possibility of a high lacrimal flux phenotype in EDE are likely to be profitable

Returns on R&D investment: A comprehensive survey on the magnitude and evaluation methodologies

As technology and innovation seem to be contingent upon each other a great deal of attention has been given to the importance of assessing the contribution of R&D investment to firm and industry performance and, ultimately, to the economic performance of countries and regions. In industrialised societies not only private but also public agents have allocated increasing amounts of their resources to R&D activities, often considered the key path to innovativeness. At the same time, due to advances in empirical research, increasingly more focused on the micro (firms) rather than on the macro (country) level, old myths about the relationship between R&D, innovation and success began to fall down. Firstly, the idea that innovation is much broader than R&D has gained large support and has made it possible to identify other sources of innovation, beyond excellence in R&D, which had been largely hidden or neglected. As result, perceptions about small firms - or the so-called low-tech industries, which either do not carry out any significant R&D activities or are likely to perform them outside formal classifications - started to change. Secondly, the idea that more R&D investment is always automatically bond to success - whatever criteria one may choose to define success – has become nothing more than a utopia. In this paper we carry out an analysis of the literature on the magnitude and evaluation of R&D, and, possibly, of innovation. We identify the methodologies used and analyse to what extent the magnitude of (eventual) R&D returns is dependent on the methodology pursued and the level of analysis - firms (micro), industry (meso), and regions/countries (macro) - considered. We conclude that methodological approaches and levels of analysis determine, to a certain extent, the type of results obtained and, thus, variances between them.Innovations and R&D indicators; Methodologies; Macro, meso and micro levels; R&D payoff