Low‐cost dye‐sensitized solar cells with ball‐milled tellurium‐doped graphene as counter electrodes and a natural sensitizer dye

This paper presents a facile and economic development of dye‐sensitized solar cells using a nonprecious counter electrode made from ball‐milled tellurium‐doped graphene (Te‐Gr) and a natural sensitizer extracted from Calotropis gigantea leaves. The prepared materials were characterized using various techniques, such as Raman spectroscopy, X‐ray diffraction (XRD), atomic force microscopy (AFM), impedance spectroscopy, and scanning electron microscopy with built‐in energy‐dispersive X‐ray spectroscopy (SEM with EDS). The electrochemical activity of the produced counter electrodes and the impedance of the fabricated cells were examined and discussed to devise plans for future enhancement of cell performance. A clear pattern of improvement was found when using cost‐effective Te‐Gr relative to the costly platinum counter electrodes, especially when compared with cells employing another natural sensitizer. The results show approximately 51% enhancement over chlorophyll‐based cells made from spinach, where the added advantage in our approach is the utilization of an abundant plant extract with little nutritional appeal.     

Assessment of temperature gradient effects on moisture transfer through thermogradient coefficient

The objective of this paper is to describe moisture transfer through porous material due to temperature gradient. For that purpose, an experimental device was set up to assess moisture flux under isothermal and non-isothermal conditions. This involves placing samples between two compartments with controlled air conditions and monitoring relative humidity and temperature profiles inside the samples over the time. To interpret these results, we proposed to express the mass flux in terms of two driving potentials: water vapor content gradient and temperature gradient. Accordingly, thermogradient coefficient was calculated and discussed. It represents the difference between the moisture fluxes under isothermal and non-isothermal conditions. The impact of temperature gradient on the moisture buffer value (MBV) was also considered through a numerical experiment taking into account thermogradient coefficient. Results show that temperature gradient implies a relative variation of the MBV for about 14%. Thus, it would be better to consider non-isothermal conditions for its assessment.     

Evaluation of bleaching capacity of acid-leached egyptian bentonites

The acid activation of Egyptian bentonites was tested by their bleaching capacity for cottonseed oil and was compared with that of a standard bleaching compound Tonsil AC. The bleaching ability of two samples representing two Egyptian deposits was relatively high, while the third sample could not be used for bleaching purposes. There is parallelism between the bleaching ability and the surface area of acid activated bentonites. Bleaching ability is greatly dependent on the montmorillonite content in the bentonite sample and on the method of acid activation.     

Contribution to analytical and numerical study of combined heat and moisture transfers in porous building materials

In this paper, one-dimensional model for evaluating coupled heat and moisture transfer in porous building materials was proposed. The transient partial differential equations system was solved analytically for Dirichlet boundary conditions. It consists first to introduce the Laplace transformation and then to use the potential function technique. This approach allows simplifying the initial mathematical problem to a fourth order ordinary differential equation which can be easily solved. This solution was used to assess the transient temperature and moisture distribution across materials. A comparison with numerical models from Luikov [2] and Vafai et al. [12] was performed, a good agreement was obtained.     

Periodic homogenization for heat,air, and moisture transfer of porous building materials

ABSTRACT

In this work, a macroscopic model of hygrothermal transfers in porous building materials was developed, using periodic homogenization, where the air infiltration was added to the classical mass and energy balance equations written at the microscopic scale. The corresponding infiltration, hygric, and thermal input parameters were carefully identified. Numerical calculations of thermal and diffusion tensors were performed on a representative concrete elementary cell. Further, the diffusion tensor was compared to the equivalent experimental results available in the literature, and its sensitivity to the water content variations and porosity has been evaluated on the concerned elementary cell.     

Sensitivity analyses of convective and diffusive driving potentials on combined heat air and mass transfer in hygroscopic materials

ABSTRACT

The focus of this paper was to examine the contribution of two key mechanisms—moisture convection and diffusion–on heated air and moisture transfer in porous building envelopes and to define the validity of the sub-models. A numerical simulation was performed and is focused on the one-dimensional problem for drying test boundary conditions. Thereafter, a detailed parametric analysis was carried out in order to investigate the influence of typical nondimensional parameters. Results show that convection is a prominent driving potential with respect to the diffusion process when the hygric state is stable between the environment and the envelope.     

A multi to wideband frequency reconfigurable antenna

A frequency reconfigurable antenna with a simple design structure and biasing circuit is presented. The antenna is able to configure its frequencies to operate either in multiband or wideband modes. The antenna is fed by a coplanar waveguide transmission line. The reconfiguration characteristics of the antenna is achieved by using PIN diode switches. The operating frequencies of the multiband mode are designed within the wideband mode operating range, from 2 to 6 GHz. Both simulated and measured results of S₁₁, radiation pattern and realized gains are verified. The antenna allows a degree of freedom in providing the frequency reconfiguration from multiband to wideband mode and vice versa.     

An explicit and novel structure,lattice dynamics,and photoemission of La-doped nanocrystalline SrZrO3 perovskite

As no complete and comprehensive studies have been previously reported for La-doped nanocrystalline SrZrO3(SZO),we researched herein a detailed investiga-tion f...     

Reply on the comments regarding the paper “Assessment of temperature gradient effects on moisture transfer through thermogradient coefficient”

This paper is a reply on the paper “A comment to’ Assessment of temperature gradient effects on moisture transfer through thermogradient coefficient’ ” (DOI: 10.1007/s12273-012-0099-y).