Search

The temperature effect on photovoltaic modules is usually quantified by means of some coefficients relating the variations of the open‐circuit voltage, of the short‐circuit current, and of the maximum power to temperature changes. In this paper, comprehensive experimental guidelines to estimate the temperature coefficients when measurements are performed outdoors are given. In addition, a correction procedure is applied to the short‐circuit current to cancel out the influence of the fluctuations in the irradiance level. The experimental results shown in this paper refer to several single‐crystalline silicon modules that have been operating for 21 years. Consequently, the estimated values of the temperature coefficients also account for module ageing processes. The coefficients of determination achieved in the case of the temperature coefficients of the open‐circuit voltage and the maximum power are very close to one. Results concerning the temperature coefficients of the short‐circuit current are also suitable if they are previously corrected. A comprehensive experiment guideline is to estimate the temperature coefficients outdoors. A novel correction procedure is applied to the short‐circuit current to cancel out the influence of the fluctuation in the irradiance level. The experiment result refers to several single‐crystalline silicon modules that have been operating for 21 years; hence, the estimated values account for module ageing processes. [ABSTRACT FROM AUTHOR]

Aim To evaluate the effects of repeated autoclave sterilization cycles on surface topography of conventional nickel-titanium ( NiTi) and titanium nitride ( TiN)-coated rotary instruments. Methodology A total of 60 NiTi rotary instruments, 30 Pro Taper ( Dentsply Maillefer) and 30 TiN-coated Alpha Kite ( Komet/ Gebr. Brasseler), were analysed. Instruments were evaluated in the as-received condition and after 1, 5 and 10 sterilization cycles. After sterilization, the samples were observed using scanning electron microscope ( SEM), and surface chemical analysis was performed on each instrument with energy dispersive X-ray spectroscopy ( EDS). Moreover, the samples were analysed by atomic force microscopy ( AFM), and roughness average (Ra) and the root mean square value (RMS) of the scanned surface profiles were recorded. Data were analysed by means of anova followed by Tukey's test. Result Scanning electron microscope observations revealed the presence of pitting and deep milling marks in all instruments. EDS analysis confirmed that both types of instruments were composed mainly of nickel and titanium, whilst Alpha Kite had additional nitride. After multiple autoclave sterilization cycles, SEM examinations revealed an increase in surface alterations, and EDS values indicated changes in chemical surface composition in all instruments. Ra and RMS values of Pro Taper significantly increased after 5 ( P = 0.006) and 10 cycles ( P = 0.002) with respect to the as-received instruments, whilst Alpha Kite showed significant differences compared with the controls after 10 cycles ( P = 0.03). Conclusions Multiple autoclave sterilization cycles modified the surface topography and chemical composition of conventional and TiN-coated NiTi rotary instruments. [ABSTRACT FROM AUTHOR]

Aim To use atomic force microscopy (AFM) to evaluate the effects of sodium hypochlorite (NaOCl) and ethylene-diaminetetraacetic acid (EDTA) on the surface characteristics of ProTaper rotary nickel-titanium instruments. Methodology A total of twenty ProTaper (Dentsply Maillefer, Ballaigues, Switzerland) instruments (S1, S2, F1, F2) were divided into five groups: no immersion, immersion in 5.25% NaOCl for 5 or 10 min and immersion in 17% EDTA for 5 or 10 min. Twenty surface areas along 3- mm sections at the tip of the files (perfect squares of 1 × 1 lm) were analysed by AFM operating in contact mode under ambient conditions. Three-dimensional images (400 × 400 lines) were processed using Gwyddion software, and the roughness average (Ra) and the root mean square value (RMS) of the scanned surface profiles were recorded. Data were analysed by means of anova and paired samples t-test. Results Three-dimensional AFM images of the surface of ProTaper instruments, including new and those immersed in NaOCl and EDTA solutions, revealed topographic irregularities at the nanometric scale. RMS and Ra values of instruments treated with NaOCl and EDTA solutions were statistically higher than that of the new ones (P < 0.05). Conclusions Atomic force microscopy threedimensional images and roughness values indicated that short-term contact between NaOCl and EDTA endodontic irrigants and ProTaper instruments caused alterations in the surface of instruments. [ABSTRACT FROM AUTHOR]