Analysis of double-diffusive hydrothermal flow in a domestic stack: The effect of side walls patterns

Domestic stack is considered to investigate the double-diffusive laminar natural convection. The working fluid is a gaseous mixture that has similar physical properties to carbon dioxide. Knowing the patterns of gaseous mixture distribution and determining the carbon deposit regions can help in carbon capture problems. The present study uses the finite element method to numerically examine the double ratio-diffusive physical phenomena in a rectangular-trapezoidal enclosure and to simulate the stack under a wide range of dimensionless parameters, such as buoyancy ratio $1\le N_{\mathit{BR}}\le 7$, Lewis number $2\le \mathit{Le}\le 8$, and Rayleigh number ${10}^3\le \mathit{Le}\le {10}^5$ for different aspect ratios. Nine different cases of the geometrical ratio are selected to cover most possible design configurations. The results indicate that increasing the Lewis number leads to augmented solutal transport but reduces heat transfer. However, both heat and mass transfer are observed by increasing the buoyancy ratio. It is worth mentioning that increasing the ratio of upper side length to base length $\left(\frac{d}{D}\right)$ from $\left(\frac{1}{4}\right)$ to $\left(\frac{3}{8}\right)$ leads to a significant increase in mass transfer by 75% and heat transfer enhancement ratio by around 50%.     

Thermodynamic Consistent Formulations of Viscoplastic Deformations in FCC Metals

A general consistent thermodynamic framework for small strain thermoviscoplastic deformations of face-centered cubic (FCC) metals is presented in this study. An appropriate and consistent Helmholtz free energy definition is incorporated, after considering the strain rate effect imbedded through the hardening definition, in deriving the proposed three-dimensional kinematical model. Microstructural physically based thermal and athermal yield function definitions (von Mises type) are utilized in this work for dynamic and static deformations of FCC metals. A length scale parameter introduced implicitly through the viscosity parameter is related to the waiting time of dislocations at an obstacle. The role of material dependence in setting the character of the governing equations is illustrated in the context of a simple uniaxial tensile problem in order to check the effectiveness and the performance of the proposed framework and its finite-element implementation. Results obtained for OFHC copper at low and high strain rates and temperatures show, generally, good comparisons with experimental results.     

Supramolecular association of acid terminated polydimethylsiloxanes

Summary. Benzoic acid terminated polydimethylsiloxanes (PDMS) have been synthesized by hydrosilylation of allyloxybenzylbenzoate with SiH terminated precursors followed by deprotection. These oligomers have been characterized by ¹H, ¹³C and ²⁹Si NMR, by FTIR and by SEC in tetrahydrofurane. Because of the flexibility and low polarity of the siloxane backbone, they are ideally suited to study the effect of hydrogen bonding on macromolecular properties. Received: 17 July 1997/Revised: 22 July 1997/Accepted: 6 August 1997     

Acute intestinal obstruction and pregnancy. Apropos of 3 cases

The axillary artery has been successfully cannulated in critically ill adult and paediatric patients. There is little information about experience with this technique in neonates. We report the use of axillary cannulation in 62 mechanically ventilated neonates with birth weight from 750 to 3800 g (mean 1950 g). The axillary artery was catheterized with 24 or 22 gauge teflon catheters by means of the catheter-over-a-needle technique. Arterial access was used for blood pressure monitoring, blood sampling and in seven cases for blood removal during exchange transfusions. Cannulae were removed when the fraction of inspired oxygen (FIO2) was less than 0.3. During cannulation capillary refill, radial artery pulse and neurological status of the arm were checked daily. The mean period of cannulation was 4.1 days (1-10 days). During cannulation and after catheter removal there were no complications related to the chosen vessel e.g. no change in the skin colour, skin warmth, capillary refill and the quality of the radial pulse. No changes in the motor activity of the limb on the cannulated side were observed. CONCLUSION: Axillary artery cannulation is a useful alternative for establishing an arterial access in ventilated neonates. Further studies are needed to evaluate the long-term consequences of this technique.     

A human-centred methodology applied to decision support system design and evaluation in a railway network context

This article describes a methodological process for the design and evaluation of an interactive system in an industrial context. The process is called the U-model, and has been used in many projects since the early 1990s. The article describes a recent case study in which the U-model was adapted and used during a project involving the design of a decision support system intended for a railway investment context.

PETROGRAPHY AND GEOCHEMISTRY OF SOME JORDANIAN OIL SHALES FROM NORTH JORDAN

Twenty-two "oil shale" samples from north Jordan have been investigated. They are in fact all bituminous limestones, of ages ranging from Uppermost Cretaceous to Paleocene. Major elements, organic matter and trace elements, were determined, together with aspects of mineralogy and petrography. Although macrofossils are rare, trace fossils were encountered. These rocks are postulated to be normal limestones deposited in an oxygenated shallow marine environment. The H₂S/O₂ interface coincided or lay just below the water/sediment interface. The organic matter is indigenous and not related to migrating oil.     

Guardian maps and the generalized stability of parametrized families of matrices and polynomials

The generalized stability of families of real matrices and polynomials is considered. (Generalized stability is meant in the usual sense of confinement of matrix eigenvalues or polynomial zeros to a prescribed domain in the complex plane, and includes Hurwitz and Schur stability as special cases.) Guardian maps and semiguardian maps are introduced as a unifying tool for the study of this problem. These are scalar maps which vanish when their matrix or polynomial argument loses stability. Such maps are exhibited for a wide variety of cases of interest corresponding to generalized stability with respect to domains of the complex plane. In the case of one- and two-parameter families of matrices or polynomials, concise necessary and sufficient conditions for generalized stability are derived. For the general multiparameter case, the problem is transformed into one of checking that a given map is nonzero for the allowed parameter values. This research was supported in part by the National Science Foundation’s Engineering Research Centers Program, NSFD CDR 8803012, and was also supported by the NSF under Grants ECS-86-57561, DMC-84-51515, and by the Air Force Office of Scientific Research under Grant AFOSR-87-0073.     

Defensive secretion of Therea petiveriana: chemical identification and evidence of an alarm function

The volatile constituents of the supposed defensive secretions of the glandular pouches of the adults of both sexes of the cockroach Therea petiveriana have been shown to contain N-3-methylbutylacetamide (MBA) and N-3-methylbutylpropanamide (MBP), which represented 60% of the volatile fraction. The other 40% included acidic, aromatic, and aldehydic compounds. Behavioral experiments demonstrated that the secretion acts as an alarm pheromone for adults.     

Annealing and oxidation mechanism of evaporated zinc thin films from zinc oxide powder

Zinc oxide (ZnO) thin films were deposited by thermal evaporation of a high quality ZnO powder; the obtained films were then oxidized in the air. We have systematically investigated the influence of annealing temperature ranged from 100 to 400 °C on the films composition and structural and optical properties by using Rutherford Back Scattering (RBS) analysis, X-ray Diffraction (XRD) and UV-Visible transmission respectively. The as grown films exhibit a hexagonal single phase of Zn with no preferential orientation and contain 28% oxygen. With an increase in the annealing temperature the oxygen content is enhanced to the detriment of Zn; samples were totally oxidized at 300 °C and the films are converted to stoichiometric ZnO material. However, in situ XRD pattern analysis shows that the oxidation starts at 250 °C. From the XRD results of annealed Zn samples under an electrical field we inferred that the oxidation mechanism is achieved by the ionization of oxygen atom at the film surface and subsequently followed by the diffusion of the produced ions in the film network.     

SAT‐based and CP‐based declarative approaches for Top‐Rank‐K closed frequent itemset mining

Top‐Rank‐K Frequent Itemset (or Pattern) Mining (FPM) is an important data mining task, where user decides on the number of top frequency ranks of patterns (itemsets) they want to mine from a transactional dataset. This problem does not require the minimum support threshold parameter that is typically used in FPM problems. Rather, the algorithms solving the Top‐Rank‐K FPM problem are fed with $K$, the number of frequency ranks of itemsets required, to compute the threshold internally. This paper presents two declarative approaches to tackle the Top‐Rank‐K Closed FPM problem. The first approach is Boolean Satisfiability‐based (SAT‐based) where we propose an effective encoding for the problem along with an efficient algorithm employing this encoding. The second approach is CP‐based, that is, utilizes Constraint Programming technique, where a simple CP model is exploited in an innovative manner to mine the Top‐Rank‐K Closed FPM itemsets from transactional datasets. Both approaches are evaluated experimentally against other declarative and imperative algorithms. The proposed SAT‐based approach significantly outperforms IM, another SAT‐based approach, and outperforms the proposed CP‐approach for sparse and moderate datasets, whereas the latter excels on dense datasets. An extensive study has been conducted to assess the proposed approaches in terms of their feasibility, performance factors, and practicality of use.