Papers by Keyword: EC

Abstract: We investigated the structure transition and the electrocaloric effect in PbZr_1-xTi_xO₃ (PZT) with x=0.7, 0.8 and 0.9. The results show that 50 MV/m can make the structural transition be a continuous one. When x=0.7, 0.8 and 0.9 at the zero field, the first order structural transition occurs at T₀=685, 687, and 698 K, respectively. Upon a strong electric field, the first order structural transition comes to the second one, which leads to lower the change of specific heat. The structural transition temperature is shifted at high temperature with increasing electric field. The maximum electrocaloric effect is present occurs at about 200 K above the corresponding Curie temperature. With increasing composition of Ti, the electrocaloric effect is enlarged, together with increasing structure transition temperatures.

Abstract: In order to investigate the carbon components of atmospheric particles, TSP, PM₁₀ and PM_2.5 were collected and analyzed in July 2008 to June 2010. The results shows that the OC variation of three particles presents of the lower concentration in the middle and the higher on both sides with the highest point in January which is 5 to 7 times of July. The monthly change of concentration was very obvious in PM_2.5 and OC was mainly from fuel combustion. The monthly variation of EC is not very clear in TSP, PM₁₀ and PM_2.5 with the range of 3.06 ± 1.23 μg/m³, 2.44 ± 1.18 μg/m³, 1.55 ± 0.50 μg/m³. EC mainly came from the direct emissions of combustion sources. The concentration of EC was stable in the year. OC / EC is more than 2 in major months, which indicates that secondary chemical reaction has occurred and it is strongest in January and December.

Abstract: The aim of this research work was to develop the controlled release of two model drugs i.e. water insoluble drug - resveratrol and water soluble drug - lignan by matrix tableting with an eccentric tablet machine. For this purpose different kinds of polymers i.e. Metolose 90 SH-4000^® (HMPC), Fetocel RT-N-100^® (EC) and Eudragit RLPO^® (polymethacrylate) were used. The matrix tablets containing 2 %wt of a model drug which were mixed with 5, 10, 20, 30 and 50 %wt of the polymers mentioned above. In addition, a glidant composed of 1 %wt talc and 1 %wt magnesium stearate as well as a filler Ludipress^® were processed. Different physical properties of the powder mixtures (e.g. flowability) and of the tablets (e.g. hardness, uniformity of mass or drug content, drug release, etc.) were determined. Most of the tablets met the physical requirements. If the polymer content got higher the release was slower, which can be confirmed by the lower values of k. The release kinetics were described by three typical mathematic models i.e. biphasic, Noyes-Whitney and KorsmeyerPeppas. The best fitting results were ordered as follows: biphasic > Noyes-Witney > KorsmeyerPeppas.

Abstract: Subsurface drainage was known as an effective method to solve salinity problems, in this paper, two different subsurface drainage systems were designed to study how the system affect the surface soil EC(electric conductivity), besides, the economic benefits of the system were evaluated. Results showed that: under the drainage system, the surface soil EC was in a trend of fluctuant reduction, the desalination ratio of T1.1, T1.2, T2.1, T2.2 and CK was 13.5%, 11.2%, 14.8%, 12.6%, and 6.0% respectively; the surface soil EC would present an rising trend in an irrigation cycle on account of the evaporation and the groundwater level, compared with CK, the drainage treatments could better suppress the soil resalination; the calculation results of economic indexes proved that both T1 and T2 could gain favorable economic benefits, and T2 was preferable with higher EIRR (16.4%), ENPV (4536$/hm2) and EBCR (1.48). The results also suggest that the subsurface drainage system was practicable from ecological and economic angle.

Abstract: Poly (vinyl) chloride (PVC)-based proton conducting polymer electrolytes have been prepared by solution cast technique. The effect of addition of ethylene carbonate (EC) as the plasticizer on the structural property of the prepared proton conducting polymer electrolyte system was investigated by X-Ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) while its effect on electrical property was investigated by Impedance Spectroscopy (IS). With addition of plasticizer, the crystalline nature of the polymer was found to be disrupted as revealed by X-Ray diffraction. FTIR showed interactions between Cl^- and H⁺ which was accounted by shifts in the bands of Cl^-. Ionic conductivity was found to be 3.06 x 10 ^-5 S cm^-1 at room temperature (300 K) for the films containing 95 wt. % (PVC -NH₄CF₃SO₃) –5 wt. % EC.

Abstract: Hexanoyl chitosan that exhibited solubility in THF was prepared by acyl modification of chitosan. Films of hexanoyl chitosan-based polymer electrolyte were prepared by the technique of solution casting. The effect of plasticizers on the electrical properties of hexanoyl chitosan: LiCF3SO3 electrolytes have been investigated. The plasticizers used were EC, PC and a mixture of EC and PC. The highest room temperature conductivity of about 1.1 x 10-4 S cm-1 was achieved for electrolyte with composition of 50:50 (wt.%) mixture of PC: EC. The variations in conductivity have been explained using the Rice and Roth model from which the numbers of free ions per unit volume, mobility and diffusion coefficient of free ions were obtained. Electrochemical cells based on LiCoO2/MCMB couple were assembled using the electrolyte that exhibited the highest ionic conductivity. The performance of the cells have been studied and discussed in this paper.