A new direction in design and manufacture of co-sensitized dye solar cells: Toward concurrent optimization of power conversion efficiency and durability

A novel methodology was implemented in the present study to concurrently control power conversion efficiency (η) and durability (D) of co-sensitized dye solar cells. Applying response surface methodology (RSM) and Desirability Function (DF), the main influential assembling (dye volume ratio and anti-aggregation agent concentration) and operational (performance temperature) parameters were systematically changed to probe their main and interactive effects on the η and D responses. Individual optimization based on RSM elucidated that D can be solely controlled by changing the ratio of vat-based organic photosensitizers, whereas η takes both effects of dye volume ratio and anti-aggregation concentration into account. Among the studied factors, the performance temperature played the most vital role in η and D regulation. In particular, however, multi-objective optimization by DF explored the degree to which one should be careful about manipulation of assembling and operational parameters in the way maximization of performance of a co-sensitized dye solar cell.     

SOLVENT-FREE CONVERSION OF OXIRANES TO THIIRANES WITH THIOUREA

A simple and efficient method for the conversion of various oxiranes to the corresponding thiiranes using thiourea under solvent free conditions is described.     

Low Temperature Preparation of 3D Solid and Hollow ZnS Nanosphere Self-Assembled from Nanoparticles by Varying Sulfur Source

In this work, we report a facile hydrothermal method for the preparation of three dimensional hollow ZnS nanostructures, using Zinc bis(salicyle aldehitato), Zn(Sal)₂, thioacetamide (TAA) and thioglycolic acid (TGA) as Zn²⁺, sulfur source and capping agent, respectively. The ZnS solid and hollow sphere was produced from the self-assembly of nanoparticles with diameters of 11 ± 2 nm with TGA and TGA, TAA, respectively. Furthermore, with changing zinc precursor from Zn(Sal)₂ to zinc acetate [Zn(OAC)₂], ZnS nanorods were obtained. The products were characterized by XRD, SEM, TEM, selected area electron diffraction, and FT-IR spectra. The influence of surfactant (Polyethylene glycol) on the morphology of the products was also investigated. Possible formation mechanism and optical properties of these architectures were also reported.     

Solvothermal Synthesis and Characterization of PbSe Nanostructures with the Aid of Schiff-base Ligand

In this work, Pb(II)N,N-bis(salicylidene)-ethylenediamine; [Pb(salen)]; was applied as lead precursor to synthesis PbSe nanostructures. Besides [Pb(salen)], SeCl₄ and reducing agents like N₂H₄·H₂O have been employed for the production of PbSe nanostructures via a solvothermal route at 180 °C for 3 h in propylene glycol. The effect of preparation factors such as temperature, reaction time, and surfactant on the morphology of PbSe nanostructures was investigated. The experimental results indicated that PbSe synthesized at 150 and 210 °C was composed of agglomerated particles. On the other hand, the use of KBH₄ as reducing agent led to produce PbSe with higher particle size and agglomeration. The as-prepared PbSe nanostructures were characterized by XRD, SEM, TEM, EDS, and FT-IR.     

Sonochemical Synthesis and Photocatalytic Properties of Metal Hydroxide and Carbonate (M:Mg, Ca, Sr or Ba) Nanoparticles

In this work Mg(OH)₂, Ca(OH)₂, CaCO₃, SrCO₃ and BaCO₃ nanoparticles were synthesized via a simple sonochemical reaction at room temperature. Nanoparticles were synthesized via a surfactant-free reaction solvent water. Nanostructures materials were characterized by scanning electron microscopy, X-ray diffraction and fourier transform infrared spectroscopy. The photocatalytic behavior of nanoparticles was evaluated using the degradation of a methyl orange aqueous solution under ultraviolet light irradiation. The results show that metal hydroxide and metal carbonate nanoparticles are promising materials with excellent performance in photocatalytic applications.     

A Facile One-Pot Synthesis of Highly-Functionalized Stable Heterocyclic Phosphorus Ylides in Aqueous Media

Phthalimide or succinimide undergo a reaction with dialkyl acetylenedicarboxylates and triphenylphosphine to produce highly-functionalized stable heterocyclic phosphorus ylides in good yields in water-tetrahydrofuran (6:1). This methodology is of interest because of the use of water as solvent, thus minimizing the cost, operational hazards, and environmental pollution.     

A quantile-based Time at Risk: A new approach for assessing risk in financial markets

In this paper, we provide a new measure for evaluation of risk in financial markets. This measure is based on the return interval of critical events in financial markets or other investment situations. Our main goal was to devise a model like Value at Risk (VaR). As VaR, for a given financial asset, probability level and time horizon, gives a critical value such that the likelihood of loss on the asset over the time horizon exceeds this value is equal to the given probability level, our concept of Time at Risk (TaR), using a probability distribution function of return intervals, provides a critical time such that the probability that the return interval of a critical event exceeds this time equals the given probability level. As an empirical application, we applied our model to data from the Tehran Stock Exchange Price Index (TEPIX) as a financial asset (market portfolio) and reported the results.     

Design study and heat transfer analysis of a neutron converter target for medical radioisotope production

A worldwide challenge in the near future will be to find a way of producing radioisotopes in sufficient quantity without relying on research reactors. The motivation for this innovative work on targets lies in the accelerator-based production of radioisotopes using a neutron converter target as in the transmutation by adiabatic resonance crossing concept. Thermal analysis of a multi-channel helium cooled device is performed with the computational fluid dynamics code CFX. Different boundary conditions are taken into account in the simulation process and many important parameters such as maximum allowable solid target temperature as well as uniform inlet velocity and outlet pressure changes in the channels are investigated. The results confirm that the cooling configuration works well; hence such a solid target could be operated safely and may be considered for a prototype target.