First-order logic (FOL) is undecidable — that is, no algorithm exists that can decide whether a formula of FOL is valid or not. However, there are various fragments of FOL that are known to be decidable. FO, the two-variable fragment of FOL, is one of such languages [1,2]. FO is a first-order language where formulas have maximally two variables, no function symbols, but possibly do have equalit...

Several models have been proposed for scheduling the preventive maintenance (PM) of complex repairable systems in industry. These are often application-speci"c and some make unrealistic assumptions about stationarity of the process and quality of repairs. We investigate two principal types of general model, which have wider applicability. The "rst considers "xed PM intervals and is based on the...

PURPOSE Various antibiotics are available to treat soft-tissue infections. However, it is unclear if the empirical antibiotic is always appropriate or the most economical. OBJECTIVE To determine the percentage of empirically treated wounds susceptible to the antibiotic therapy prescribed, and to determine the percentage of wounds treated with the most economical antibiotic therapy. METHODS ...

Introduction The tremendous growth of activity in the composites industry continues to create a need for materials that meet the tough demands for environmental compliance and high performance at an economical cost. Much of this activity has been focused on composite systems based on unsaturated polyester resins (UPRs) and vinyl esters (VEs) utilized in laminating, gel coat and free-flowing mol...

Determinant factors of dengue global epidemiology trends include, but are not limited to: 1) demographic changes including population growth, economical trends in tropical countries and land use patterns; 2) increased urban population size and density due to rural to urban migration 3) modern transportation with increased movement of people, commodities, animals, vectors and pathogens; and 4) c...

Since the work of André Martinet back in the 60’s [7], the notion of ‘economy’ has been accepted as one of the main principles underlying the organization of phonological inventories (hereafter PI). This principle, also named MUAF (‘Maximal Use of Available Features’) by John Ohala [8], states that PI are organized along a few phonetic dimensions that they tend to maximize in terms of number of...

the object of the regional planning is optimum use of resource for the development of regions. one of the most important items in regional development is the recognition of spatial and economical structure of the region. middle sized cities, have the secondary role in the study of economical structure of the regions. global experiments demonstrate that lack of attention to the role of secondary...