Thermally loaded thick-walled cylindrically curved aluminum/steel-FGM-panel

Subject of the investigation is a thick-walled cylindrically curved shell guided at the ends which is heated at its inner or outer surface. The material is presupposed to be functionally graded obeying a power law. Both the elastic limits according to von Mises and the stress distributions for different grading exponents are discussed. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Heat Transfer Characteristics for Condensation of R134a in a Vertical Smooth Tube

In this study, condensation of pure refrigerant R134a vapor inside a smooth vertical tube was experimentally investigated. The test section was made of a copper tube with inside diameter of 7.52 mm and length of 1 m. Experimental tests were conducted for mass fluxes in the range of 20–175 kg/m²s with saturation pressure ranging between 5.8 and 7 bar. The effects of mass flux, saturation pressure, and temperature difference between the refrigerant and tube inner wall (ΔT) on the heat transfer performance were analyzed through experimental data. Obtained results showed that average condensation heat transfer coefficient decreases with increasing saturation pressure or temperature difference (ΔT). In addition, for the same temperature difference (ΔT), heat can be removed from the refrigerant at a higher rate at relatively low pressure values. Under the same operating conditions, it was shown that average condensation heat transfer coefficient increases as mass flux increases. Finally, the most widely used heat transfer coefficient correlations for condensation inside smooth tubes were analyzed through the experimental data. The best fit was obtained with Akers et al.'s (1959) correlation with an absolute mean deviation of 22.6%.     

Experimental Investigation of Laminar Heat Transfer Inside Trapezoidal Duct Having Different Corner Angles

In this study, steady-state laminar forced flow and heat transfer in a horizontal smooth trapezoidal duct having different corner angles were experimentally investigated in the Reynolds number range from 10² to 10³. Flow is hydrodynamically fully developed and thermally developing under a uniform surface temperature condition. Based on the present experimental data of laminar flow in the thermal entrance region, new engineering correlations were presented for the heat transfer and friction coefficients for each corner angle. The results have shown that as the Reynolds number increases heat transfer coefficient increases but Darcy friction factor decreases. Also, it is observed that average Nusselt number increases while average Darcy friction factor decreases with increasing corner angle of the duct.     

New Heterocyclic Phosphorus Ylides: Synthesis,Crystal Structure,and Theoretical Calculation of Alkyl Substituted 3-(4-Benzoyl-1,5-diphenyl-2,3-dihydro-1H-pyrazol-3-yl)-3-oxo-2-(triphenylphosphoranylidene) Propanoates

Novel alkyl substituted 3-(4-benzoyl-1,5-diphenyl-2,3-dihydro-1H-pyrazol-3-yl)-3-oxo-2-(triphenylphosphoranylidene) propanoates (3) were synthesized from 4-benzoyl-1,5-diphenyl-1H-pyrazole-3-carbonylchloride (1) and alkyl (triphenylphosphoranylidene) acetates (2a–b). The synthesized compounds were characterized by elemental analysis, spectroscopic studies (3a–b), and single crystal X-ray diffraction (3a). The mechanism of the reaction between (1) and (2a) was studied by AM1, and the geometrical parameters of the studied molecules were also carried out in B3LYP methods with the standard 6–31G (d,p) basis set. NBO analysis were studied for 1 and 2a B3LYP methods with the standard 6–31G (d,p) basis set.     

Preparation and Spectral and Biological Investigation of vic-Dioxime Ligands Containing Piperazine Moiety and Their Mononuclear Transition-Metal Complexes

Two vic-dioxime ligands, N-(4-benzylpiperazine-1-yl) p-tolylglyoxime (L¹H₂) and N,N′-bis(4-benzylpiperazine-1-yl) glyoxime (L²H₂), containing piperazine moieties were synthesized, and their Ni(II), Cu(II), Co(II) and Zn(II) complexes were obtained. The ligands were characterized by elemental analysis, Fourier transform–infrared (FT-IR), ultraviolet–visible NMR (¹H, ¹³C, and heteronuclear multiple-bond correlation), and electrospray ionization (ESI) mass spectrometry. The isolated complexes were characterized by a combination of elemental analysis, IR, UV-vis, and ESI mass spectrometry and in the case of Ni(II) and Zn(II) complexes by ¹H and ¹³C NMR spectroscopy. The electrochemical behaviors of the ligands and their complexes were studied by cyclic voltammetry (CV) in dimethylsulfoxide solution containing tetrabutylammoniumtetrafluoroborate (TBATFB). The antibacterial activity was also studied against S. aureus ATCC 25923, S. aureus ATCC 29213, S. mutans RSHM 676, E. faecalis ATCC 29212, E. coli ATCC 25922, and P. aeruginosa ATCC 27853. The antimicrobial test results indicated that all the compounds have good antibacterial activity against P. auriginosa ATCC 27853 bacteria and were as effective as ampicilin.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resources: Full experimental and spectral details.]     

Synthesis,characterization, and fluorescence phenomena of 1‐naphthoxy and 1‐naphthylamino substituted cyclotriphosphazenes

The reactions of hexachlorocyclotriphosphazene N₃P₃Cl₆ ( 1 ) with 1‐naphthol and 1‐naphthylamine have been examined. The reaction of 1 with sodium 1‐naphthoxy gave the hexakis(1‐naphthoxy)cyclotriphosphazene ( 2 ) in high yield. Geminal 2,2‐di(1‐naphthylamino)‐4,4,6,6‐tetrachlorocyclotriphosphazene ( 3 ) was obtained from the reaction of 1 with 1‐naphthylamine. The structures of phosphazene derivatives were defined by elemental analysis, FTIR, UV‐‐visible, and ¹H, ¹³C, ³¹P NMR spectroscopy. The fluorescence intensity of the compounds was measured in THF and CH₂Cl₂. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:158–162, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20400     

Anionic cobalt-platinum-ethynyl (CoPt–C<Subscript>2</Subscript>H) metal-organic subnanoparticles: a DFT modeling study

Anionic CoPt-ethynyl metal-organic clusters have been investigated comprehensively. The lowest energetic of anionic Co _n Pt _m (ethynyl) clusters have been generally found as 3D structure but with low symmetrical point groups. Our results indicate that the most preferred dissociation channel of the studied clusters is Co atom ejection and the favorable dissociation channel is independent of cluster size. The anionic Pt₅C₂H cluster shows the highest chemical stability according to the HOMO-LUMO Gap analysis. The C₂H generally prefers to bind on a bridge site with a few exceptions. The Co_4?5 nanoparticles have a lengthening effect on the C≡C bond of the ethynyl molecule, which may be valuable for C≡C bond activation. In addition, the lowest and the highest vibrational frequencies are reported to guide further experimental studies.     

A Lightweight Image Encryption Algorithm Based on Chaotic Map and Random Substitution

Chaotic-maps-based image encryption methods have been a topic of research interest for a decade. However, most of the proposed methods suffer from slow encryption time or compromise on the security of the encryption to achieve faster encryption. This paper proposes a lightweight, secure, and efficient image encryption algorithm based on logistic map, permutations, and AES S-box. In the proposed algorithm, SHA-2 based on the plaintext image, a pre-shared key, and an initialization vector (IV) are used to generate the initial parameters for the logistic map. The logistic map chaotically generates random numbers, which are then used for the permutations and substitutions. The security, quality, and efficiency of the proposed algorithm are tested and analyzed using a number of metrics, such as correlation coefficient, chi-square, entropy, mean square error, mean absolute error, peak signal-to-noise ratio, maximum deviation, irregular deviation, deviation from uniform histogram, number of pixel change rate, unified average changing intensity, resistance to noise and data loss attacks, homogeneity, contrast, energy, and key space and key sensitivity analysis. Experimental results reveal that the proposed algorithm is up to 15.33× faster compared to other contemporary encryption methods.