Optical, Energetic and Exergetic Analyses of Parabolic Trough Collectors

Parabolic trough collectors generate thermal energy from solar energy. Especially, they are very convenient for applications in high temperature solar power systems. To determine the design parameters, parabolic trough collectors must be analysed with optical analysis. In addition, thermodynamics （energy and exergy） analysis in the development of an energy efficient system must be achieved. Solar radiation passes through Earth＇s atmosphere until it reaches on Earth＇s surface and is focused from the parabolic trough collector to the tube receiver with a transparent insulated envelope. A11 of them constitute a complex mechanism. We investigate the geometry of parabolic trough reflector and characteristics of solar radiation to the reflecting surface through Earth＇s atmosphere, and calculate the collecting totM energy in the receiver. The parabolic trough collector, of which design parameters are given, is analysed in regard to the energy and exergy analysis considering the meteorological specification in May, June, July and August in 1sparta/TUrkey, and the results are presented.     

Synthesis and characterization of novel flavonoid-substituted phthalocyanines using (±)naringenin

In this study, novel unsymmetrical mono- and di-substituted metal free and metallo phthalocyanines containing peripheral naringeninoxy moieties have been prepared. The naringenin-substituted phthalonitrile was synthesized from 4-nitrophthalonitrile and (±)naringenin in dimethylsulfoxide. Preparation of unsymmetrical mono- and di-substituted phthalocyanines, 2-naringenin-7-O-phthalocyaninatozinc, 2,9-bis-naringenin-7-O-phthalocyaninatozinc, 2,9-bis-naringenin-7-O-phthalocyaninatocobalt and 2,9-bis-naringenin-7-O-phthalocyanine was performed at 120-140 °C using the corresponding phthalonitrile in the presence of N,N-dimethylethanolamine (DMAE), ZnCl₂, CoCl₂ and LiCl, respectively. Synthesized new phthalocyanine compounds have been characterized by elemental analysis and ¹H NMR, ¹³C NMR, FT-IR, MS and UV-vis spectroscopy. These are the first known examples of flavonoid-substituted phthalocyanines.     

The neural network and multivariate linear regression approach for observing phase transitions of polymers with the differential thermal analysis method

The aim of this study was to correlate the results of experimental data using DTA method and predictions of artificial neural network (ANN) and multivariate linear regression (MLR). Thermal decomposition of polymers was analyzed by simultaneous DTA method, and kinetic parameters (critical points, the change of enthalpy and entropy) of polymers were investigated. A computer model based on multilayer feed forwarding back propagation and multilayer linear regression model were used for the prediction of critical points, phase transitions of low-density polyethylene (LDPE) and mid-density polyethylene. As a result of our study, we concluded that ANN model is more suitable than MLR about prediction of experimental data.     

Structured replacement policies for a Markov-modulated shock model

We establish the optimality of structured replacement policies for a periodically inspected system that fails silently whenever the cumulative number of shocks, or the magnitude of a single shock it has received, exceeds a corresponding threshold. Shocks arrive according to a Markov-modulated Poisson process which represents the (controllable or uncontrollable) environment.     

Supplier diversification under binomial yield

We consider supplier diversification in an EOQ type inventory setting with multiple suppliers and binomial yields. We characterize the optimal policy for the model and show that, in this case, it does not pay to diversify, in contrast to previous results in the random yield literature.     

Pressure-induced phase transition of zinc-blende AlN: An ab initio molecular dynamics study

An ab initio constant pressure technique is carried out to study the pressure-induced phase transition of the zinc blende AlN (aluminum nitride). A first order phase transformation into a rock salt structure is observed in the constant pressure simulations. The transformation is accompanied by an initial tetragonal distortion and a subsequent shearing, similar to that found in the other zinc blende structured materials. This phase transition should occur around 6.2 GPa based upon the enthalpy calculations.     

Synthesis of water-soluble Mo(0) tetracarbonyl complexes containing nitrogen donor ligands and polymerization of methyl methacrylate

Water-soluble Mo(0) tetracarbonyl complexes containing a α-diimine ligand have been prepared. All the complexes were characterized by elemental, LC-MS (APCI), FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy. The pH dependent phase transfer of these complexes was investigated. This pH dependent phase transfer was accomplished over 10 times with no evidence of complex decomposition. Their catalytic activities on methyl methacrylate polymerization were determined.     

ChemInform Abstract: Structure,Ionization, and Fragmentation of Hydrogenated Aluminoboron Clusters: Al2B2H2n (n = 0—6).

Energetic and structural stability of Al₂B₂H_2n (n = 0—6) clusters is investigated by DFT calculations and a stochastic search algorithm.