The Meaning of Memory Safety

We give a rigorous characterization of what it means for a programming language to be memory safe, capturing the intuition that memory safety supports local reasoning about state. We formalize this principle in two ways. First, we show how a small memory-safe language validates a noninterference property: a program can neither affect nor be affected by unreachable parts of the state. Second, we extend separation logic, a proof system for heap-manipulating programs, with a memory-safe variant of its frame rule. The new rule is stronger because it applies even when parts of the program are buggy or malicious, but also weaker because it demands a stricter form of separation between parts of the program state. We also consider a number of pragmatically motivated variations on memory safety and the reasoning principles they support. As an application of our characterization, we evaluate the security of a previously proposed dynamic monitor for memory safety of heap-allocated data.Comment: POST'18 final versio

Space Station based options for orbiter docking/berthing

Conceptual efforts to develop a Space Station based system for docking and/or berthing the NSTS Orbiter are described. Past docking and berthing systems are reviewed, the general requirements and options for mating the Orbiter and Space Station are discussed, and the rationale for locating the system on the Station is established. One class of Station-based system is developed in several variations and evaluated with respect to weight distribution, loads, safety, reliability, viewing, and maintainability. An evolutionary presentation of the variations provides insight into the development process and the problems encountered. An overall evaluation of the Station-based variations compared to an optimized Orbiter-based system demonstrates the potential benefits of this approach as well as the issues that must be resolved to realize the benefits

Comparison of Alternative Safety Net Programs for the 2000 Farm Bill

As Congress begins its debate for the 2002 farm bill, there have been calls for a counter cyclical safety net that will provide a better basis for targeting longer term planning than exists with ad hoc emergency assistance. Further subsidization of the multi-peril crop insurance (MPCI) program has been proposed, as well as reliance on a farm and ranch risk management (FARRM) account to help farmers. A whole farm revenue income support program and several variations of national income supplement programs have been put forward. A comprehensive analysis of different safety net alternatives using a common methodology is needed so farmers and policy makers can make objective comparisons. The objective of this paper is to quantitatively analyze the economic effects of alternative safety net/insurance programs on farmers in the Southern United States. The objective is accomplished by simulating representative crop farms in the South over the 2001-2005 planning horizon for alternative safety net options. The simulated net present value distributions for the farms are compared using certainty equivalents to determine the value of alternative safety net options to feed grain, cotton and rice farms in the South.Agricultural and Food Policy,

Children’s travel as pedestrians: an international survey of policy and practice

A survey of OECD member countries was carried out to provide high level data on a consistent basis to identify and account for current patterns of child road safety . This paper reports the findings relating to children, aged 0-14 years, as pedestrians. Key survey elements included analyses of fatality data, relationships between socio-economic, demographic factors and fatality rates, and a questionnaire based survey. League tables based on average child pedestrian fatality rates were constructed for each OECD member country participating in our questionnaire enabling identification of the top five countries with the lowest pedestrian fatality rate as Sweden, The Netherlands, Finland, Germany, and Denmark. Few countries had quantitative information about children’s travel and its absence means that assessments are difficult about children’s safety and the relative risks they face, especially as pedestrians. There are large variations in the amount of walking between countries and growing car use is becoming an issue in one third of OECD countries. The main findings from the questionnaire survey were that the majority of countries did not have information on high risk groups but of those that did, the cross cutting themes of socio-economic and ethnic minority groups, young children and urban areas were identified. Three characteristics distinguish top countries in the League table from those doing less well: a strong approach to the introduction of infrastructure measures for pedestrian safety, including low speed limits in residential areas; conducting road safety campaigns at least once a year; and having legislation which assumes driver responsibility in an accident involving a child pedestrian. Having compulsory road safety education for children aged 6-9 years was a characteristic shared by most countries, as was the promotion of child pedestrian education and training initiatives and the commissioning of research. However there is lower research activity in less well performing countries

Some myths about industrial safety

MINES ParisTech - CRC Technical Report.There are many definitions of safety, but most of them are variations on the theme that safety can be measured by the number of adverse outcomes. This vision has consequences for how industry thinks safety can be achieved. This paper looks at six safety-related assumptions, or safety myths, which impact industry practices. We argue that these practices are littered with fragile beliefs, which in many cases make the safety management flawed and ineffectual. The open acknowledgement of these myths is a necessary first step to genuinely improve industrial safety

Anisotropy effects on the undrained stability of cuts in clays

It has long been recognised that soils are generally anisotropic with some of their properties varying depending on the direction of measurement. In particular, strength anisotropy should be a main concern in relation with the stability assessment of geotechnical cases. Nevertheless, the incorporation of this feature is rarely considered in routine slope stability analyses in spite of the fact that its absence may lead, in some cases, to an overestimation of the factor of safety. In the paper, the effects of strength anisotropy on the undrained stability of cuts in clays are examined. A literature review reveals that clays have different patterns of undrained strength anisotropy depending on their overconsolidation ratio. A constitutive model is introduced, able to account for the different observed variations of undrained strength with loading direction. A series of numerical stability analyses have been performed to explore the effects of the type of undrained strength anisotropy on the stability of cuts. The effects of slope inclination, bedding orientation, and pattern of undrained strength anisotropy on factors of safety and failure mechanisms are examined and discussed. In addition, a real case study of the failure of an underwater cut is analysed showing that undrained strength anisotropy is able to explain satisfactorily the collapse observed.Postprint (published version

Parents’ perceived neighborhood safety and children’s cognitive performance:Complexities by race, ethnicity, and cognitive domain

Background:Aim: To examine racial/ethnic variations in the effect of parents’ subjective neighborhood safety on children’s cognitive performance. Methods: This cross-sectional study included 10,027 children from the Adolescent Brain Cognitive Development (ABCD) study. The exposure variable was parents’ subjective neighborhood safety. The outcomes were three domains of children’s cognitive performance: general cognitive performance, executive functioning, and learning/memory. We used mixed-effects regression models for data analysis. Results: Overall, parents’ subjective neighborhood safety was positively associated with children’s executive functioning, but not general cognitive performance or learning/memory. Higher parents’ subjective neighborhood safety had a more positive influence on the executive functioning of non-Hispanic White than Asian American children. Higher parents’ subjective neighborhood safety was associated with higher general cognitive performance and learning/memory for non-White children relative to non-Hispanic White children. Conclusion: The race/ethnicity of children moderates the association between neighborhood safety and cognitive performance. This becomes more complicated, as the patterns seem to differ across ethnicity and cognitive domains. It is unknown whether the observed racial/ethnic variations in the effect of neighborhood safety on cognitive performance are neighborhood characteristics such as residential segregation. Addressing neighborhood inequalities is needed if we wish to reduce racial/ethnic inequities in the cognitive development of children

A Geo-Statistical Analysis of Road Mortality in the Enlarged EU

This paper aims at showing and understanding the spatial regional disparities hidden behind average national statistics on road fatalities in Europe; special attention is given on the EU last enlargement. The work is not limited on differences descriptions, but unveils what is hidden behind the observed infra-national heterogeneity in terms of road risk. It is indeed common practice to compare countries in terms of road safety performance and to rank them in terms of a risk indicator such as the mortality rate, which is often expressed by the number of fatalities due to road accidents per 100,000 inhabitants. Some countries are known for their very bad risk records and are often pointed out by national or international authorities, without any understanding of the regional differences hidden behind a national mean value. The data analysis shows that changes in the level of spatial aggregation of the data produce significant differences in the variables describing the level of road safety, and hence in operational recommendation and conclusions. Beside the differences in national conditions and polices, the regional differences in road environment characteristics, traffic performance, road user mix, travel speeds, seat-belt use, and availability of emergency care have been major contributors to these variations. Road safety professionals and decision makers should be aware of the differences existing when trying to reduce road toll of the country in sustainable and cost-effective way.