Optimization of flow in additively manufactured porous columns with graded permeability

Chemical engineering systems often involve a functional porous medium, such as in catalyzed reactive flows, fluid purifiers, and chromatographic separations. Ideally, the flow rates throughout the porous medium are uniform, and all portions of the medium contribute efficiently to its function. The permeability is a property of a porous medium that depends on pore geometry and relates flow rate to pressure drop. Additive manufacturing techniques raise the possibilities that permeability can be arbitrarily specified in three dimensions, and that a broader range of permeabilities can be achieved than by traditional manufacturing methods. Using numerical optimization methods, we show that designs with spatially varying permeability can achieve greater flow uniformity than designs with uniform permeability. We consider geometries involving hemispherical regions that distribute flow, as in many glass chromatography columns. By several measures, significant improvements in flow uniformity can be obtained by modifying permeability only near the inlet and outlet.     

LPNN-based approach for LASSO problem via a sequence of regularized minimizations

In compressive sampling theory, the least absolute shrinkage and selection operator (LASSO) is a representative problem. Nevertheless, the non-differentiable constraint impedes the use of Lagrange programming neural networks (LPNNs). We present in this article the -LPNN model, a novel algorithm that tackles the LASSO minimization together with the underlying theory support. First, we design a sequence of smooth constrained optimization problems, by introducing a convenient differentiable approximation to the non-differentiable -norm constraint. Next, we prove that the optimal solutions of the regularized intermediate problems converge to the optimal sparse signal for the LASSO. Then, for every regularized problem from the sequence, the -LPNN dynamic model is derived, and the asymptotic stability of its equilibrium state is established as well. Finally, numerical simulations are carried out to compare the performance of the proposed -LPNN algorithm with both the LASSO-LPNN model and a standard digital method.     

A survey and taxonomy on virtual data center embedding

The Journal of Supercomputing - Data center network virtualization is being considered as a promising technology to provide a performance guarantee for cloud computing applications. One important...     

Synthesis of heterocyclic metal complexes and their evaluation as marine antifoulants

4-Amino-3-thio-1,24-triazolidine (L₁) and 4-amino-5-thio-1,3,4-thiadiazole (L_II) as well as their metal complexes of the general formulae ML_I·2H₂O and ML_IICl (M; Pb(II), Cd(II) and Zn(II)) were prepared. With Sn(II), we obtained Sn(L_I)₂·2H₂O and SnL_IICl, respectively. The structures of the compounds were identified through elemental analysis, and IR and UV spectra measurements, in addition to thermal analysis in case of the metal complexes. The antifouling properties of the compounds were tested by their incorporation into paint formulations which were applied to PVC substrates and tested in water from Alexandria western harbour. When the compounds were added at 17·5% by volume, the coated panels were fouled after 3 months of immersion. The addition of 6·7% by volume of tributyltin oxide to 15·8% of the prepared compounds in one formulation elevated the paint efficiency and prevented fouling for 11 months. Paint containing solely tributyltin oxide at the same concentration was inactive against algae.     

Formation of titanium and cobalt germanides on Si (100) using rapid thermal processing

Titanium and cobalt germanides have been formed on Si (100) substrates using rapid thermal processing. Germanium was deposited by rapid thermal chemical vapor deposition prior to metal evaporation. Solid phase reactions were then performed using rapid thermal annealing in either Ar or N₂ ambients. Germanide formation has been found to occur in a manner similar to the formation of corresponding silicides. The sheet resistance was found to be dependent on annealing ambient (Ar or N₂) for titanium germanide formation, but not for cobalt germanide formation. The resistivities of titanium and cobalt germanides were found to be 20 μΩ-cm and 35.3μΩ-cm, corresponding to TiGe₂ and Co₂Ge, respectively. During solid phase reactions of Ti with Ge, we have found that the Ti₆Ge₅ phase forms prior to TiGe₂. The TiGe₂ phase was found to form approximately at 800° C. Cobalt germanide formation was found to occur at relatively low temperatures (425° C); however, the stability of the material is poor at elevated temperatures.     

Regulation of distal esophageal mucosal blood flow: the roles of nitric oxide and substance P

BACKGROUND: An increase in esophageal mucosal blood flow (MBF) may be an important protective mechanism against mucosal injury from noxious agents that are ingested or refluxed. This study investigated the changes in MBF and the regulation thereof after intraluminal application of noxious chemical stimuli. The role, if any, of substance P (SP) and nitric oxide (NO), two potent vasodilatory substances, and the vascular distribution of SP in the distal esophagus were evaluated. METHODS: Esophageal MBF was measured in anesthetized dogs with a laser Doppler flow probe attached to manometry and pH probes. MBF was measured before and after topical application of HCl (2 ml; 1N) or capsaicin (2 ml; 0.5%) in the distal esophagus. The effects on MBF of intraarterial SP and bradykinin were also determined. Pharmacologic antagonists and denervation procedures were used to delineate the mechanisms that regulate MBF. RESULTS: Sequential luminal applications of hydrochloric acid (HCl) or a single application of capsaicin increased MBF (p < 0.01). Topical intraluminal lidocaine blocked the response to capsaicin (p > 0.2) but not to HCl (p < 0.05). Abrupt increases in MBF occurred with intraarterial SP or bradykinin (p < 0.01). Neither atropine nor truncal vagotomy blocked the increase in MBF from these peptides or noxious stimuli. The NO synthesis antagonist NG-nitro-L-arginine methyl ester (L-NAME) blocked the response to bradykinin and attenuated the response to HCl (p < 0.05). NG-nitro-L-arginine methyl ester did not affect the response to SP or capsaicin. A substance P antagonist blocked the effects of both capsaicin (p > 0.6) and SP (p > 0.1) but not that of HCl (p < 0.01) or bradykinin (p > 0.01). CONCLUSIONS: Intraluminal applications of HCl or capsaicin appear to stimulate increases in esophageal MBF by different mechanisms. HCl produces an adaptive response that appears dependent on the paracrine effect of NO. Capsaicin-sensitive neurons mediate vasodilation through SP neurotransmission, independent of extrinsic vagal or cholinergic innervation.     

Synthesis of some new 3-(2′-heterocyclicethyl)-2-methyl-3,4-dihydroquinazolin-4-one derivatives as antimicrobial agents

3-(2′-Chloroethyl)-2-methyl-3,4-dihydroquinazolin-4-one was reacted with acetylacetone, ethyl acetoacetate and diethylmalonate in the presence of sodium ethoxide to afford the alkylation products IV, V and VI , Compounds IV, V and VI were reacted with hydrazine hydrate, phenylhydrazine, hydroxylamine hydrochloride, urea and thiourea to yield 3-(2′-heterocyclicethyl)-2-methyl-3,4-dihydroquinazolin-4-one derivatives VII-XV . The structures of the synthesized compounds were elucidated by elemental analyses and spectroscopic (IR and XH-NMR) analyses. The prepared compounds were tested for their antimicrobial activities in comparison with tetracycline as a reference compound.     

Co-evolution as a computational and cognitive model of design

Co-evolutionary design has been developed as a computational model that assumes two parallel search spaces: the problem space and the solution space. The design process iteratively searches each space using the other space as the basis for a fitness function when evaluating the alternatives. Co-evolutionary design can also be developed as a cognitive model of design by characterizing the way in which designers iteratively search for a design solution, making revisions to the problem specification. This paper presents the computational model of co-evolutionary design and then describes a protocol study of human designers looking for evidence of co-evolution of problem specifications and design solutions. The study shows that co-evolutionary design is a good cognitive model of design and highlights the similarities and differences between the computational model and the cognitive model. The results show that the two kinds of co-evolutionary design complement each other, having strengths in different aspects of the design process. Electronic Publication