A cooperative agent-based model for active security systems

This paper presents a multi-agent model for implementing active security concepts. In this model, a group of agents can carry out their tasks cooperatively in order to achieve an ultimate security goal. Thus a low-level module of the proposed model reads the values of interesting data items of the relevant current network events and passes them to a relational database. Comparing these measurements against predefined values in an intruder signature database may point to a particular attack.The proposed model consists of two parts. (1) A multiagent Intrusion Detection System (MIDS) for detecting attacks. (2) An Active Security Mechanism (ASM) for taking active, network-wide, response against attackers. The proposed approach provides a customizable host environment built from various systems software components to allow an optimal match between the intrusion circumstances and the underlying security architecture. Thus, different frameworks can support alternative responses of existing security services. In addition, the ASM can take rapid response against attacks by making use of sensible sharing of attack intelligence. System agents communicate with each other on different hosts using an agent communication language through a message router.     

A novel synthesis of high-area alumina via H2O2-precipitated boehmite from sodium aluminate solutions

A novel procedure was devised, whereby crystalline boehmite, γ-AlO(OH), was efficiently precipitated from sodium aluminate solutions, NaAlO₂(aq), following controlled addition of H₂O₂ aqueous solution. The effects of the aluminate solution variables (viz. concentration, volume, caustic ratio, pH and temperature), as well as the H₂O₂/Al₂O₃ molar ratio, on the amount and composition of the yield, were examined. Accordingly, optimal conditions for 98% recovery of the aluminium content of the parent aluminate solution were realized. The remaining NaOH can be recycled and used to extract further amounts of aluminium from bauxite (Bayer process). Thermal stability of the resulting boehmite was explored by thermogravimetry and differential thermal analysis. Accordingly, various calcination products of the boehmite were obtained at some selected temperatures in the range 400–1100°C and characterized by chemical analysis, X-ray powder diffractometry, and surface charge and specific area measurements. The results obtained indicated the synthesis of relatively high surface area transitional aluminas of industrial and catalytic merits. © 1998 SCI     

LIQUEFACTION OF CELLULOSIC WASTE V. WATER FORMATION AND EVALUATION OF PYROLYTIC CHAR AS A BY —PRODUCT OF PYROLYSIS REACTION

Liquid hydrocarbon oil and water have been produced from the liquefaction of cellulosic matter present in municipal solid wastes (MSW). Gases and residual char have also been produced as by-products resulting from the pyrolysis reaction of cellulose. Quantities of water and pyrolytic char were estimated at different conditions of the process (temperature pressure of hydrogen, carrier oil medium and concentration of boric acid). From the results obtained, it was suggested that the formation of water seems to be sensitive to the operational conditions which enhance a water-gas shift reaction (in which water molecules are consumed to produce carbon dioxide and hydrogen). Decreasing of the undesired chary by-product could be achieved by increasing the concentration of boric acid that catalyzes the liquefaction reaction. Two petroleum distillates, namely gas oil and residual fuel oil, were used as carrier media of a solid refuse. It was found that fuel oil is more efficient as a buffering medium that prevents cellulose macromolecules from a rapid and complete charing during the liquefaction process. The pyrolytic char was characterized and evaluated by means of different analytical procedures and solvent extraction using petroleum ether 40-60°C and methanol. Calorific value of the pyrolytic char was found to be 4.6 Kcal g^-1 which is quite close to that of a brown coal. Dropping point test of the extracted material by petroleum ether indicated that the extract can be utilized for producing lubricating greases via saponificattion with a salt of sodium or calcium.     

Modeling of cylindrical dielectric resonators in rectangularwaveguides and cavities

The mode matching method is used to accurately model a generalized cylindrical dielectric resonator structure in a rectangular waveguide or cavity. The field distributions of different modes in cavities are given. The resonant frequencies of the cavities are calculated and compared to the measured data, showing very good agreement. The resonator structure can be a dielectric disk resonator, a ring resonator, a dielectric resonator with support, etc. This structure can be used in filter design as the basic element, providing very good mechanical stability. The slot coupling between cavities is also analyzed, showing some interesting results     

Mining residue contacts in proteins using local structure predictions

In this paper we develop data mining techniques to predict 3D contact potentials among protein residues (or amino acids) based on the hierarchical nucleation-propagation model of protein folding. We apply a hybrid approach, using a hidden Markov model to extract folding initiation sites, and then apply association mining to discover contact potentials. The new hybrid approach achieves accuracy results better than those reported previously.     

Construction Workspace Planning: Assignment and Analysis Utilizing 4D Visualization Technologies

Abstract:   This article describes a construction activity execution space analysis approach and a decision support tool for resolving execution space interference and conflict between work-face construction activities. Lack of execution pace planning interrupt and badly affect the progress of construction activities. Also, in real situations, spatial congestion can severely reduce the productivity of workers sharing the same workspace, and may cause health and safety hazard issues. The aim of this article is to present a critical space-time analysis (CSA) approach that was developed to model and quantify workspace congestion and was encapsulated in a computerized tool dubbed PECASO (patterns execution and critical analysis of site-space organization) that was developed to assist site managers in the assignment and identification of workspace conflicts. A new concept of "visualizing workspace competition" between the construction activities is presented based on a unique representation of the dynamic nature of activities within the execution workspace, in 3D space and time. PECASO embraces 4D visualization and highlights the critical space control aspect to formulate an innovative 4D space planning and visualization tool. The CSA methodology and PECASO were validated using a real case study and the article concludes that the PECASO system has the potential to reduce the number of competing workspaces, as well as the conflicting volume/space between occupied workspaces. This in turn produces better assessment of the execution strategy for a given project schedule. Additionally, the PECASO system has introduced a new way of communicating the program of work in a high level of detail for space planning purposes.     

Spectrophotometric determination of nickel in steels

New, simple and sensitive spectrophotometric methods for the determination of nickel with hematoxylin in the presence and absence of a cationic surfactant are described. The sensitivity of the color reaction of nickel and hematoxylin is greatly increased by the sensitizing action of cetyltrimethylammonium bromide (CTAB). The optimum pH range for the formation of nickel-hematoxylin and nickel-hematoxylin-CTAB systems is 7.8–8.3 and 7.4–8.1, respectively. The molar absorptivities are 4.1 × 10⁴ and 8.3 × 10⁴ mol^?1 cm^?1 at 595 and 608 nm, respectively. The corresponding values of Sandell's sensitivity index are 0.0014 and 0.0007 μg cm^?2 of nickel. The methods adhere to Beer's law up to 0.52 and 0.60 ppm nickel, respectively. The mole ratio of nickel-hematoxylin in both complexes is 1:2. Preliminary separation of nickel by extraction as dimethylglyoxime chelate into chloroform makes it possible to determine nickel in steel samples.     

Effect of γ-irradiation on the sheet resistance of two-dimensional island platinum films

Four sets (A, B, C, and D) of two-dimensional island platinum films were prepared via the thermal evaporation technique. The mass thicknesses of the films of the different sets are 1, 5, 10, and 20 Å, respectively. The sheet resistance of these films was found experimentally from knowing the d.c. resistance of the films. Before exposing the films to γ-rays, we monitored the increase in the sheet resistance in air with time (aging) till short-term stability for the films was achieved. The stabilized films were exposed to γ-rays such that the different doses are 100, 200, 300, 500, and 700 Gy using ¹³⁷Cs (0.662 MeV) radiation source with dose rate 0.5 Gy/min. It was found that; (i) the sheet resistance of the investigated films decreases with the increase in the dose, (ii) for any particular mass thickness, the value of the fractional change in sheet resistance increases with the increase in dose, (iii) for any particular dose the increase in the fractional change in sheet resistance becomes more pronounced with the increase in mass thickness. Qualitative interpretation for our results was given on the ground that γ-rays changed the shape of islands from spherical to prolate.     

Effect of suspended solids on the flow-induced corrosion of a modified Al-2.5Mg alloy in arabian gulf water

Suspended solids increase the rate of corrosion and decrease the resistance of a modified Al-2.5Mg alloy to pitting in Arabian Gulf water. It has been shown by electrochemical studies that the pitting potential of the alloy shifts to more negative values in the presence of suspended solids. The rate of mass transfer and the limiting current is significantly increased by suspended particles.     

Effect of amyl acetate sorption on mechanical and thermal properties of polypropylene packaging

Sorption kinetics of amyl acetate in polypropylene is studied at 23, 40 and 55°C. Diffusion (D) and partition (Kp) coefficients were determined by fitting the sorption curves with a theoretical curve calculated from Fick's diffusion equation. The role of temperature and concentration of amyl acetate was investigated. The results show that D is not affected and Kp decreases with increasing concentration of amyl acetate in the solution. The sorption rate or total amount absorbed increased considerably with temperature. Concentration profiles were calculated by using a numerical algorithm based on a finite element method. The effect of amyl acetate concentration on the mechanical and thermal properties of the polymer was investigated. Copyright © 2007 John Wiley & Sons, Ltd.