Characteristics of the motions, turbulence intensity, diffusivity, flux of momentum and sensible heat in the upper atmosphere

Analyses of the meteorological rocket data obtained from an experiment conducted at 3-hour intervals at 8 western meridional rocket stations are presented. Large variations in the meridional wind contribute substantially to overall turbulence in the tropical stratosphere. The solar semidiurnal component of wind oscillations in the tropics was observed to be much higher than predicted by theory, often exceeding the magnitude of the diurnal amplitude throughout the stratosphere. The observed value of the solar diurnal amplitude in the stratosphere was in line with theoretical prediction. The solar terdiurnal amplitudes for temperature, meridional and zonal winds were non-negligible and must be considered in any harmonic analysis. Phase angle variation with height was rapid for all harmonics; however, there was general agreement between predicted and observed phase angles. Because of large changes in the mean winds in the mesosphere with season, harmonic determinations are difficult. There appear to be large zonal wind changes even within the same season as mentioned previously. Turbulence diffusivity in the upper stratosphere is greater near the equator than in the mid-latitudes

Powder Compaction: Compression Properties of Cellulose Ethers

Effective development of matrix tablets requires a comprehensive understanding of different raw material attributes and their impact on process parameters. Cellulose ethers (CE) are the most commonly used pharmaceutical excipients in the fabrication of hydrophilic matrices. The innate good compression and binding properties of CE enable matrices to be prepared using economical direct compression (DC) techniques. However, DC is sensitive to raw material attributes, thus, impacting the compaction process. This article critically reviews prior knowledge on the mechanism of powder compaction and the compression properties of cellulose ethers, giving timely insight into new developments in this field

Intermixing and Formation of Cu-Rich Secondary Phases at Sputtered CdS/CuInGaSe2 Heterojunctions

The Cu migration behavior in PVD-CdS/PVD-Cu(In,Ga)Se2 (CIGS) heterojunctions is investigated by high-resolution electron microscopy (HREM) and energy dispersive X-ray spectroscopy (EDS). Incorporation of Cu into the CdS forms Cu-rich domains but has no effect on epitaxy of the CdS. Epitaxy is commonly observed in the CdS studied. Secondary ion mass spectroscopy depth profiles confirm the presence of Cu in the CdS. In some cases, Cd is completely replaced by Cu, resulting in a Cu-S binary compound epitaxially grown on the CIGS and fully coherent with the surrounding CdS. This is most likely to be cubic Cu2S, based on lattice spacing measurements from HREM images and EDS elemental quantification. In addition, we find that the buffer layer crystal structure influences the extent of Ga depletion at the CIGS surface, which is more pronounced adjacent to zinc-blende CdS than wurtzite CdS. Density functional theory calculations reveal that Cu clustering and different Ga depletion widths can be attributed to the inherent anisotropy of wurtzite CdS and differences in CIGS point-defect migration barriers. Understanding the influence of these effects on device properties is a critical step in developing more efficient CdS/CIGS-based photovoltaics

The role of oxygen doping on elemental intermixing at the PVD-CdS/Cu (InGa)Se 2 heterojunction

Elemental intermixing at the CdS/CuIn Ga Se (CIGS) heterojunction in thin-film photovoltaic devices plays a crucial role in carrier separation and thus device efficiency. Using scanning transmission electron microcopy in combination with energy dispersive X-ray mapping, we find that by controlling the oxygen in the sputtering gas during physical vapor deposition (PVD) of the CdS, we can tailor the degree of elemental intermixing. More oxygen suppresses Cu migration from the CIGS into the CdS, while facilitating Zn doping in the CdS from the ZnO transparent contact. Very high oxygen levels induce nanocrystallinity in the CdS, while moderate or no oxygen content can promote complete CdS epitaxy on the CIGS grains. Regions of cubic Cu S phase were observed in the Cu-rich CdCuS when no oxygen is included in the CdS deposition process. In the process-of-record sample (moderate O ) that exhibits the highest solar conversion efficiency, we observe a ~26-nm-thick Cu-deficient CIGS surface counter-doped with the highest Cd concentration among all of the samples. Cd movement into the CIGS was found to be less than 10 nm deep for samples with either high or zero O . The results are consistent with the expectation that Cd doping of the CIGS surface and lack of Zn diffusion into the buffer both enhance device performance. 1−x x 2 2 2

The role of oxygen doping on elemental intermixing at the PVD-CdS/Cu (InGa)Se 2 heterojunction

Elemental intermixing at the CdS/CuIn 1−x Ga x Se 2 (CIGS) heterojunction in thin-film photovoltaic devices plays a crucial role in carrier separation and thus device efficiency. Using scanning transmission electron microcopy in combination with energy dispersive X-ray mapping, we find that by controlling the oxygen in the sputtering gas during physical vapor deposition (PVD) of the CdS, we can tailor the degree of elemental intermixing. More oxygen suppresses Cu migration from the CIGS into the CdS, while facilitating Zn doping in the CdS from the ZnO transparent contact. Very high oxygen levels induce nanocrystallinity in the CdS, while moderate or no oxygen content can promote complete CdS epitaxy on the CIGS grains. Regions of cubic Cu 2 S phase were observed in the Cu-rich CdCuS when no oxygen is included in the CdS deposition process. In the process-of-record sample (moderate O 2 ) that exhibits the highest solar conversion efficiency, we observe a ~26-nm-thick Cu-deficient CIGS surface counter-doped with the highest Cd concentration among all of the samples. Cd movement into the CIGS was found to be less than 10 nm deep for samples with either high or zero O 2 . The results are consistent with the expectation that Cd doping of the CIGS surface and lack of Zn diffusion into the buffer both enhance device performance