Photochemically assisted solar energy storage using eriochrome black-T in solar flat collector

The criteria for cis-trans photoisomerization of eriochrome black-T (EBT) in the flat-plate collector system, which consists of endoergic photochemical reaction, has been investigated. The efficiencies of this collector in both summer and winter have been compared with blank (distilled water only) and colored liquid (non-isomer-dye-absorbing in the same wavelength range). The photochemical storage efficiency was found to be higher in winter than in summer. The optimum efficiency for this photoisomerization-thermal reversion cycle was found by varying with the pumping rate of the liquid to match the value of rate constant of cis to trans reaction. The stability of (EBT) has been studied under different environmental conditions.     

The theory of functional and template dependencies

Template dependencies were introduced by Sadri and Ullman [17] to generalize existing forms of data dependencies. It was hoped that by studying a large and natural class of dependencies, we could solve the inference problem for these dependencies, while that problem was elusive for restricted subsets of the template dependencies, such as embedded multivalued dependencies. At about the same time, other generalizations of known dependency forms were developed, such as the implicational dependencies of Fagin [11] and the algebraic dependencies of Yannakakis and Papadimitriou [20]. Unlike the template dependencies, the latter forms include the functional dependencies as special cases. In this paper we show that no nontrivial functional dependency follows from template dependencies, and we characterize those template dependencies that follow from functional dependencies. We then give a complete set of axioms for reasoning about combinations of functional and template dependencies. As a result, template dependencies augmented by functional dependencies can serve as a substitute for the more general implicational or algebraic dependencies, providing the same ability to represent those dependencies that appear ‘in nature’, while providing a somewhat simpler notation and set of axioms than the more general classes.     

Electromagnetic unbalance in power systems with untransposed transmission lines

Transposition of power transmission lines represents high costs due to the required transposition towers and also results in low mechanical and electrical strengths. These disadvantages make it desirable not to transpose lines if the resulting unbalances are not adverse. This paper proposes a method to predict the electromagnetic (combination of inductive and capacitive) unbalance of untransposed lines. The method is validated by its application to typical lines under various load conditions and various geometric mean radii.     

LAMINAR FREE CONVECTION IN VERTICAL AIR-FILLED CAVITIES WITH MIXED BOUNDARY CONDITIONS

A numerical investigation was conducted on the two-dimensional laminar free convection within rectangular cavities having mixed boundary conditions on the vertical surfaces and adiabatic top and bottom walls. The time-dependent governing energy, vorticity and stream function equations were solved using a modified ADI method and Gauss-Seidel SOR. Steady state solutions for air (Pr ≈ 0.7) were obtained for cavity aspect ratios of 0.5 to 15 over a modified Rayleigh number range of 690 to 1.3 × 10₅. For a given heat flux, it was found that the average Nusselt number peaked at an aspect ratio of about 1.5. The boundary between the asymptotic and laminar boundary layer regimes also showed a reversing behaviour in this region. In general, the reported results are compatible with and form an extension to the limited numerical and experimental results of previous investigators.     

Desulphurization of petroleum coke by butagas

The work described concerns the desulphurization of Egyptian petroleum coke by butagas in a fixed-bed reactor. Optimum values for reaction temperature and coke particle size were observed; but increased gas flow rate, prolonged reaction time, and decreased coke bed depth all favoured increased sulphur removal throughout the ranges studied. The effects of the different factors could be interpreted satisfactorily in terms of the thermodynamic potential of the desulphurization reaction and the diffusion of gases into and out of the coke particles. While gas/coke ratio governs the former, the latter is mainly influenced by sintering of the coke particles. For comparison, some desulphurization runs were carried out using hydrogen in place of butagas, and Syrian petroleum coke instead of the Egyptian coke. The Syrian coke proved difficult to desulphurize.     

Thermal desulphurization of ultra-high-sulphur petroleum coke

A study has been made of the desulphurization of Syrian petroleum coke, containing 8.83% sulphur, by calcination in a Tamman furnace at high temperatures (1000–1600 °C) using heating times up to 4 h. Sulphur elimination (up to 96% in 30 min at 1600 °C) was found to increase with calcination temperature and heating time and to decrease with increase in ash. Reactivity of petroleum coke increases with the extent of sulphur elimination, but this is counteracted to some extent by the annealing effect of the higher temperature.     

Adequacy of decompositions of relational databases

We consider conditions that have appeared in the literature with the purpose of defining a “good” decomposition of a relation scheme. We show that these notions are equivalent in the case that all constraints in the database are functional dependencies. This result solves an open problem of Rissanen. However, for arbitrary constraints the notions are shown to differ.     

Instruction-Level Fault Tolerance Configurability

Due to modern technology trends such as decreasing feature sizes and lower voltage levels, fault tolerance (FT) is becoming increasingly important in computing systems. Several schemes have been proposed to enable a user to configure the FT at the application level, thereby enabling the user to trade stronger FT for performance or vice versa. In this paper, we propose supporting instruction-level rather than application-level configurability of FT, since different parts of some applications (e.g., multimedia) can have different reliability requirements. Weak or no FT will be applied to less critical parts, resulting in time and/or resource gains. These gains can be used to apply stronger FT techniques to the more critical parts; hence increasing the overall reliability. The paper shows how some existing FT techniques can be adapted to support instruction-level FT configurability, how a programmer can specify the desired FT level of the instructions, and how the compiler can manage it automatically. A comparison between the existing FT scheme EDDI (which duplicates all instructions) and the proposed approach is performed both at the kernel and at full application levels. The simulation results show that both the performance and the energy consumption are significantly improved (up to 50% at the kernel and up to 16% at full application level), while the fault coverage depends on the application. For the full application (JPEG encoder), our approach is only applied to one kernel in order to avoid increasing the programming effort significantly.