Search results for "Maxim"
showing 10 items of 1236 documents
Charge carrier concentration optimization of thermoelectric p-type half-Heusler compounds
2015
The carrier concentration in the p-type half-Heusler compound Ti0.3Zr0.35Hf0.35CoSb1−xSnx was optimized, which is a fundamental approach to enhance the performance of thermoelectric materials. The optimum carrier concentration is reached with a substitution level x = 0.15 of Sn, which yields the maximum power factor, 2.69 × 10−3 W m−1 K−2, and the maximum ZT = 0.8. This is an enhancement of about 40% in the power factor and the figure of merit compared to samples with x = 0.2. To achieve low thermal conductivities in half-Heusler compounds, intrinsic phase separation is an important key point. The present work addresses the influence of different preparation procedures on the quality and re…
A Monte Carlo study of intersource effects in dome-type applicators loaded with LDR Cs-137 sources
2005
In this study, the dose rate distributions produced by low dose rate Cs-137 sources loaded in afterloadable dome applicators are studied using the Monte Carlo method. Dose differences between Monte Carlo results and calculations done using the superposition principle are within 1-3% in front of the applicator and between 3 and 10% near and along the longitudinal source axis. Consequently, the real doses to lateral vaginal wall, rectum and bladder are very close to the doses estimated applying the superposition principle, while the dose to the vaginal cuff has been overestimated by up to 10%.
Modeling and parameter identification of crystalline silicon photovoltaic devices
2011
This paper tests the standard single-exponential model of the electrical characteristics of crystalline-Si photovoltaic devices, focusing on the (apparent) shunt current. Measured characteristics of illuminated polycrystalline-Si photovoltaic modules are modeled, and the apparent shunt current is analyzed. It is shown that an Ohmic-like behavior only takes place at voltages well below the maximum-power point. At higher voltages, the apparent shunt current quickly drops to negligible values. Modeling a crystalline-Si PV device with a fixed shunt resistance may therefore lead to underestimation of the maximum power exceeding 10% at certain irradiance levels.
Optical absorption and electron paramagnetic resonance of theEα′center in amorphous silicon dioxide
2008
We report a combined study by optical absorption (OA) and electron paramagnetic resonance (EPR) spectroscopy on the E{sub {alpha}}{sup '} point defect in amorphous silicon dioxide (a-SiO{sub 2}). This defect has been studied in {beta}-ray irradiated and thermally treated oxygen-deficient a-SiO{sub 2} materials. Our results have pointed out that the E{sub {alpha}}{sup '} center is responsible for an OA Gaussian band peaked at {approx}5.8 eV and having a full width at half maximum of {approx}0.6 eV. The estimated oscillator strength of the related electronic transition is {approx}0.14. Furthermore, we have found that this OA band is quite similar to that of the E{sub {gamma}}{sup '} center in…
The controlled growth of GaN microrods on Si(111) substrates by MOCVD
2015
Abstract In this paper, a selective area growth (SAG) approach for growing GaN microrods on patterned SiN x /Si(111) substrates by metal-organic chemical vapor deposition (MOCVD) is studied. The surface morphology, optical and structural properties of vertical GaN microrods terminated by pyramidal shaped facets (six { 10 1 ¯ 1 } planes) were characterized using scanning electron microscopy (SEM), room temperature photoluminescence (PL) and Raman spectroscopy, respectively. Measurements revealed high-quality GaN microcolumns grown with silane support. Characterized structures were grown nearly strain-free (central frequency of Raman peak of 567±1 cm −1 ) with crystal quality comparable to bu…
Optical, structural, and morphological characterisation of epitaxial ZnO films grown by pulsed-laser deposition
2013
We report on ZnO epitaxial growth by pulsed-laser deposition (PLD) on different substrates, such as quartz, sapphire, and GaN template. Approximately 1 mu m-thick films were grown under different substrate temperatures and background oxygen conditions. X-ray diffraction analysis indicated preferential growth along the c-axis direction with a full-width at half maximum(FWHM) of the rocking curve as narrow as 230 arcs in the case of the GaN template. Low-temperature photoluminescence showed A-excitonic emission near 3.36 eV and a FWHM of (DXA)-X-0 emission as small as 2.89 meV at 9 K. Atomic force microscope measurements showed that roughness as low as 18 nm could be obtained. These results p…
Vacuum ultraviolet excitation of the 1.9-eV emission band related to nonbridging oxygen hole centers in silica
2004
Physical review / B 69, 153201 (2004). doi:10.1103/PhysRevB.69.153201
Nd:KGW Laser under Flashlamp-pumping at Repetition Rate up to 50 Hz and Average Power of 70 W (free-lasing and Q-switched mode)
1997
The laser performance of Nd:KGd(WO4)2 crystal or Nd:KGW has been studied under flashlamp-pumping in the free-running and Q-switched mode (with active or passive Q-switching) at repetition rate up to 50 Hz. Maximum output powers respectively of 70 and 30 W were achieved at 1.06 pm with a maximum efficiency of 6%. Free-running emission was also obtained at 1.35 pm with a maximum average power of 24 W and a total efficiency of 2.9% at this wavelength. A comparison with a similar Nd:YAG crystal is given showing a noticeable advantage for Nd:KGW.
Electrical measurements in µ-EDM
2008
The phenomena occurring between the electrodes in electric discharge machining when manufacturing features on the micro-metre scale (µ-EDM) is not fully understood. Poor quantitative knowledge of the sources of variability affecting this process hinders the identification of its natural tolerance limits. Moreover, improvements in measuring systems contribute to the acquisition of new information that often conflicts with existent theoretical models of this process. The prime objective of this paper is to advance the experimental knowledge of µ-EDM by providing a measurement framework for the electrical discharges. The effects of the electrodes metallic materials (Ag, Ni, Ti, W) on the elect…
Assessment of a New Analytical Expression for the Maximum-Power Point Voltage with Series Resistance
2021
This work compares a recently developed analytical expression for the maximum-power point voltage with experimental data, to test its usability for crystalline silicon solar cells. The experimental data covers measurements from 18 multicrystalline silicon solar cells with different bulk resistivities and cell architectures. We show that the expression is able to predict the maximum power obtainable by the measured cells with relative discrepancies below 1%. Additionally, we compare the accuracy of this new expression with two already existing models.