Sharif Digital Repository

Rules are used as a way of managing and configuring firewalls to fulfill security requirements in most cases. Managers have to specify their organizational security policies using low level and order-dependent rules. Furthermore, dependency of firewalls to the network topology, frequent changes in network topology (specially in dynamic networks), and lack of a method for analysis and verification of specified security policy may reduce to inconsistencies and security holes. Existence of a higher level environment for security policy specification can rectify part of the problems. In this paper we present a language for high level and formal specification of security policy in firewalls.... 

In this paper we present a formal definition of the basic concepts and notations of Object Role Modeling (ORM) using the Z formal specification language. Most of ORM concepts such as object and relationship types, value types, objectification, reference schemes, sub-types, roles and constraints such as uniqueness, mandatory, cardinality, subset, equality, exclusive and ring constraints are specified formally. Population is specified as objects, relationships and roles instances. These are specified using Z axioms and diagram instances are specified using Z schemas. This would enable validation and reasoning on the formal properties of ORM diagrams such as detecting constraint contradictions... 

The abstraction inherent in most specifications and the need to specify nondeterministic programs are two well-known sources of nondeterminism in formal specifications. In this paper, we present a Z-based formalism by which one can specify bounded, unbounded, erratic, angelic, demonic, loose, strict, singular, and plural nondeterminism. To interpret our specifications, we use a constructive set theory, called CZ set theory, instead of the classical set theory Z. We have chosen CZ since it allows us to investigate the notion of nondeterminism from the formal program development point of view. In this way, we formally construct functional programs from Z specifications and then probe the... 

The aim of this study is to investigate the effect of the rock brittleness indexes on the specific ampere draw of the circular diamond saws. In this study, twelve rock types belonging to granite and carbonate rock were cut with two different types of circular diamond saws on a fully instrumented laboratory-sawing rig at different feed rate and depths of cut. Rock samples were collected from factories from Iran for laboratory tests and uniaxial compressive strength and tensile strength were determined. The brittleness of B 1 (the ratio of compressive strength to tensile strength), B 2 (the ratio of compressive strength minus tensile strength to compressive strength plus tensile strength), and... 

Automatic translation of a high-level specification language to an executable implementation would be highly useful in maximizing the benefits of formal methods. We will introduce a set of translation functions to fill the specification-implementation gap in the domain of database applications. Because the mathematical foundation of Z has many properties in common with SQL, a direct mapping from Z to SQL structures can be found. We derive a set of translation functions from Z to SQL for the generation of a database. The proposed methodology results in reducing the expenses and duration of the software development, and also, prevents the errors originated from the manual translation of... 

This work employs two membrane bioreactors (with and without carrier) to evaluate the influence of carrier and hydraulic retention time (HRT) on the sludge specifications when removing organic volatile compounds (e.g. styrene and ethylbenzene) from petrochemical wastewater. This study is conducted during three various HRTs. The results indicate that the optimum HRT (e.g. 15 h.) was achieved in the reactor with carrier during biological removal and membrane fouling minimization. During the optimum HRT, the biological removal efficiency for styrene, ethylbenzene, and COD is 99.8 ± 0.1%, 99.8 ± 0.1%, and 99 ± 0.8%, respectively, and the concentration of styrene and ethylbenzene in the exit air... 

Corrosion behaviour of copper metal in acid solutions (HCl, H 2SO4 and H3PO4) containing 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) was investigated experimentally and theoretically via gravimetric, potentio-dynamic and quantum electrochemical approaches. Similar behavior was observed for H2SO4 and H3PO4 media, and related to the nature of anions at metal/solution interface. With regard to HCl, however, the rate of corrosion was determined to be low at initial stages, but high later on using an auto-catalyzing mechanism. In the presence of AMT, the experimental studies revealed that this molecule was a good anodic-type inhibitor causing substantial changes in corrosion potential. Moreover,... 

This work employs two membrane bioreactors (with and without carrier) to evaluate the influence of carrier and hydraulic retention time (HRT) on the sludge specifications when removing organic volatile compounds (e.g. styrene and ethylbenzene) from petrochemical wastewater. This study is conducted during three various HRTs. The results indicate that the optimum HRT (e.g. 15 h.) was achieved in the reactor with carrier during biological removal and membrane fouling minimization. During the optimum HRT, the biological removal efficiency for styrene, ethylbenzene, and COD is 99.8 ± 0.1%, 99.8 ± 0.1%, and 99 ± 0.8%, respectively, and the concentration of styrene and ethylbenzene in the exit air... 

In this study, a thermal method was used to synthesize spinel NiCo2O4 and carbon nanotubes (CNTs)@NiCo2O4 with an average size 50 nm and 20 nm, respectively. Addition of CNTs into NiCo2O4 noticeably increases the active surface area compared to pure spinel NiCo2O4. SEM analyses showed that the morphologies are spherical in both pure and composite samples. Uniform CNTs@NiCo2O4 nanoparticles exhibit high specific capacitance of 210 F g−1 at 2 A g−1 and a good retention capacity of 92.70% after 2500 cycles, which shows a considerable improvement compared to NiCo2O4. Additionally, an exceptional rate capability of about 73.2% was obtained at 50 A g−1. Such remarkable electrochemical performance... 

Epidemiological studies have identified obesity asa possible risk factor for low back disorders. Biomechanical models can help test such hypothesis and shed light on the mechanism involved. A novel subject-specific musculoskeletal-modelling approach is introduced to estimate spinal loads during static activities in five healthy obese (BMI>30kg/m2) and five normal-weight (20