A Formalization of Polytime Functions

We present a deep embedding of Bellantoni and Cook's syntactic characterization of polytime functions. We prove formally that it is correct and complete with respect to the original characterization by Cobham that required a bound to be proved manually. Compared to the paper proof by Bellantoni and Cook, we have been careful in making our proof fully contructive so that we obtain more precise bounding polynomials and more efficient translations between the two characterizations. Another difference is that we consider functions on bitstrings instead of functions on positive integers. This latter change is motivated by the application of our formalization in the context of formal security proofs in cryptography. Based on our core formalization, we have started developing a library of polytime functions that can be reused to build more complex ones.Comment: 13 page

Neighboring suboptimal control for vehicle guidance

The neighboring optimal feedback control law is developed for systems with a piecewise linear control for the case where the optimal control is obtained by nonlinear programming techniques. To develop the control perturbation for a given deviation from the nominal path, the second variation is minimized subject to the constraint that the final conditions be satisfied (neighboring suboptimal control). This process leads to a feedback relationship between the control perturbation and the measured deviation from the nominal state. Neighboring suboptimal control is applied to the lunar launch problem. Two approaches, single optimization and multiple optimization for calculating the gains are used, and the gains are tested in a guidance simulation with a mismatch in the acceleration of gravity. Both approaches give acceptable results, but multiple optimization keeps the perturbed path closer to the nominal path

Policies and Programs Affecting the Employment of People with Disabilities - Policy Brief

The purpose of this brief is to summarize the wide range of federal programs and government policies that influence the employment and program participation decisions of people with disabilities and current research initiatives related to these programs and policies. The brief is organized by the following types of programs, policies, and initiatives: • federal programs that provide cash assistance, in-kind transfers (e.g., health insurance) and education, training, and rehabilitation support based on disability status and/or other characteristics (e.g., family structure); • federal tax policies that provide credits either directly to individuals with disabilities or to employers as an incentive to hire a person with a disability; • other employment-related programs and public policies that provide accommodation support and work incentives for people with disabilities; • recent policy changes that affect people with disabilities; and • some of the current research initiatives related to federal programs, tax policies, other employment programs and policies, and recent policy changes. We conclude with a summary of our program, policy, and research scan. This publication is based on The Economics of Policies and Programs Affecting the Employment of People with Disabilities, which provides a more comprehensive review of the policies and programs discussed here (as well as others) and analyzes the employment effects of these policies and programs within an economic framework

Chronic cough due to occupational factors

Within the large variety of subtypes of chronic cough, either defined by their clinical or pathogenetic causes, occupational chronic cough may be regarded as one of the most preventable forms of the disease. Next to obstructive airway diseases such as asthma or chronic obstructive pulmonary disease, which are sometimes concomitant with chronic cough, this chronic airway disease gains importance in the field of occupational medicine since classic fiber-related occupational airway diseases will decrease in the future. Apart from acute accidents and incidental exposures which may lead to an acute form of cough, there are numerous sources for the development of chronic cough within the workplace. Over the last years, a large number of studies has focused on occupational causes of respiratory diseases and it has emerged that chronic cough is one of the most prevalent work-related airway diseases. Best-known examples of occupations related to the development of cough are coal miners, hard-rock miners, tunnel workers, or concrete manufacturing workers. As chronic cough is often based on a variety of non-occupational factors such as tobacco smoke, a distinct separation into either occupational or personally -evoked can be difficult. However, revealing the occupational contribution to chronic cough and to the symptom cough in general, which is the commonest cause for the consultation of a physician, can significantly lead to a reduction of the socioeconomic burden of the disease

The Economics of Policies and Programs Affecting the Employment of People with Disabilities

Over the last several decades, there has been a movement toward the inclusion of people with disabilities in mainstream social institutions. The 1990 Americans with Disabilities Act (ADA), which supports the full participation of people with disabilities in society and mainstream institutions, illustrates the shift in attitudes toward people with disabilities. Rather than being perceived as having a social or medical problem, individuals with disabilities are increasingly viewed as people with challenges that can be solved if appropriate policies and supports are available for addressing them

Investigation of Surface Roughness and Lay on Metal Flow in Hot Forging

A study was conducted to explore the possibility of using machining marks (i.e. surface roughness and lay) as a parameter for die design. The study was performed using 6061-T6 aluminum 1.25 diameter rounds and 0.25 square bar stock to investigate the effects of temperature, surface roughness, and lay on metal flow and friction factor. Metal flow was assessed using component true strains and spread ratio. Compression testing was performed using an instrumented die set that was mounted on a 10 ton hydraulic pres. Cigar tests were performed where the axis of the specimen were oriented at angles of 0o, 45o and 90o with respect to the surface lay on the compression platens. Ring tests were completed to quantify friction factor at different die temperatures and surface roughness values. Results indicate that die temperature has a strong effect on bulge radius and friction factor. Lay and surface roughness were found to exhibit an effect on metal flow but surface lay of the dies was not discernible on friction factor. The study was repeated under limited conditions using graphite lubricant in order to discover if the trend was repeatable using conditions observed in industry. This was found to be the case

Formal security proofs with minimal fuss: Implicit computational complexity at work

International audienceWe show how implicit computational complexity can be used in order to increase confidence in game-based security proofs in cryptography. For this purpose we extend CSLR, a probabilistic lambda-calculus with a type system that guarantees the existence of a probabilistic polynomial-time bound on computations. This allows us to define cryptographic constructions, feasible adversaries, security notions, computational assumptions, game transformations, and game-based security proofs in a unified framework. We also show that the standard practice of cryptographers, ignoring that polynomial-time Turing machines cannot generate all uniform distributions, is actually sound. We illustrate our calculus on cryptographic constructions for public-key encryption and pseudorandom bit generation

Extending Equational Monadic Reasoning with Monad Transformers

There is a recent interest for the verification of monadic programs using proof assistants. This line of research raises the question of the integration of monad transformers, a standard technique to combine monads. In this paper, we extend Monae, a Coq library for monadic equational reasoning, with monad transformers and we explain the benefits of this extension. Our starting point is the existing theory of modular monad transformers, which provides a uniform treatment of operations. Using this theory, we simplify the formalization of models in Monae and we propose an approach to support monadic equational reasoning in the presence of monad transformers. We also use Monae to revisit the lifting theorems of modular monad transformers by providing equational proofs and explaining how to patch a known bug using a non-standard use of Coq that combines impredicative polymorphism and parametricity