Pb1−xSnxSe-on-Si LWIR sensor arrays and thermal imaging with JFET/CMOS read-out

Long wavelength infrared (LWIR) sensor arrays were fabricated in Pb_1−xSn_xSe layers grown epitaxially on Si-substrates by MBE. A CaF2 intermediate buffer layer ≈30dgA thick was employed for compatibility reasons. The photovoltaic sensors are based on the blocking Pb-contact technique on p-type material. They were fabricated using simple wet-etching process steps only. Cut-off wave-lengths were about 10.5 μm, quantum efficiencies >60%, and resistance-aera products above 3 Ω-cm² at 90K. A demonstrational LWIR thermal imaging camera was assembled with a 256 element line array with 50 μm pitch. Low-noise signal processing was achieved with sensors with differential resistances in the 10 kOhm range by using JFET/CMOS technology. For each channel, an integrator, correlated multiple sampling and sample/hold amplifier was used before multiplexing to a common output.     

Photoelectron spectroscopy characterization of diamond-like carbon films

The electronic states of diamond-like hydrogenated carbon (DLC) films were studied by synchrotron radiation photoelectron spectroscopy. The valence band spectra measured at different excitation energies show the gradual emergence of the p-pi band in relation to the sample annealing and ion bombardment amorphization. The p-pi band of the annealed DLC was characterized by localized p(z) states, while the formation of the amorphous carbon surface was accompanied by appearance of the delocalized p(z) states, which reduce the optical gap. A simple approach permitting the extraction of the 2p band shape from the photoelectron spectra is proposed.     

Technical note: A spectral-angle methodology for mapping net forest cover change in northeastern China

As part of the Global Observations of Forest Cover/Land Cover Dynamics (GOFC-GOLD) project, forest-cover change in northeastern China is being mapped using Landsat-5 and Landsat-7 imagery. This technical note details some of the challenges associated with mapping net forest-cover conversion in the region, and presents a new algorithm that overcomes some of these challenges. The mapping approach uses the concept of spectral angle to establish change between images, and implements spectral thresholds to determine the type of change. Validation results give an overall accuracy of 84-96% and a detection accuracy of 72-83%.     

An enhanced spatial and temporal adaptive reflectance fusion model for complex heterogeneous regions

Due to technical and budget limitations, remote sensing instruments trade spatial resolution and swath width. As a result not one sensor provides both high spatial resolution and high temporal resolution. However, the ability to monitor seasonal landscape changes at fine resolution is urgently needed for global change science. One approach is to “blend” the radiometry from daily, global data (e.g. MODIS, MERIS, SPOT-Vegetation) with data from high-resolution sensors with less frequent coverage (e.g. Landsat, CBERS, ResourceSat). Unfortunately, existing algorithms for blending multi-source data have some shortcomings, particularly in accurately predicting the surface reflectance of heterogeneous landscapes. This study has developed an enhanced spatial and temporal adaptive reflectance fusion model (ESTARFM) based on the existing STARFM algorithm, and has tested it with both simulated and actual satellite data. Results show that ESTARFM improves the accuracy of predicted fine-resolution reflectance, especially for heterogeneous landscapes, and preserves spatial details. Taking the NIR band as an example, for homogeneous regions the prediction of the ESTARFM is slightly better than the STARFM (average absolute difference [AAD] 0.0106 vs. 0.0129 reflectance units). But for a complex, heterogeneous landscape, the prediction accuracy of ESTARFM is improved even more compared with STARFM (AAD 0.0135 vs. 0.0194). This improved fusion algorithm will support new investigations into how global landscapes are changing across both seasonal and interannual timescales.     

Automated masking of cloud and cloud shadow for forest change analysis using Landsat images

Accurate masking of cloud and cloud shadow is a prerequisite for reliable mapping of land surface attributes. Cloud contamination is particularly a problem for land cover change analysis, because unflagged clouds may be mapped as false changes, and the level of such false changes can be comparable to or many times more than that of actual changes, even for images with small percentages of cloud cover. Here we develop an algorithm for automatically flagging clouds and their shadows in Landsat images. This algorithm uses clear view forest pixels as a reference to define cloud boundaries for separating cloud from clear view surfaces in a spectral-temperature space. Shadow locations are predicted according to cloud height estimates and sun illumination geometry, and actual shadow pixels are identified by searching the darkest pixels surrounding the predicted shadow locations. This algorithm produced omission errors of around 1% for the cloud class, although the errors were higher for an image that had very low cloud cover and one acquired in a semiarid environment. While higher values were reported for other error measures, most of the errors were found around the edges of detected clouds and shadows, and many were due to difficulties in flagging thin clouds and the shadow cast by them, both by the developed algorithm and by the image analyst in deriving the reference data. We concluded that this algorithm is especially suitable for forest change analysis, because the commission and omission errors of the derived masks are not likely to significantly bias change analysis results.     

Improvement of Mechanical Properties of Automotive Components Using Hot Stamping With Integrated Q-P Process

Cold forming of high strength materials is accompanied by an undesirable spring-back effect and therefore the automotive industry prefers to produce components from high strength steels by hot stamping.Hot deformation and cooling in a die are applied to obtain shaped components with martensitic microstructure and high yield strength and ultimate tensile strength.This article presents new applications of this forming technology by incorporating another innovative heat treatment by the Q-P process,which improves both strength and ductility of obtained structures at the same time.Ultimate strengths over 2000 MPa with ductility above 10% can be achieved by this processing.To test microstructure development,thin sheet was hot formed and a corresponding FEM simulation was created.This processing was applied to low alloyed AHS steel with 0.42% of carbon and with an alloying strategy based on Mn,Si and Cr.Martensitic microstructure with retained austenite was obtained by this processing with a strength of around 2000 MPa and ductility of 10%.     

Reading psychoanalytic developments contextually: A reply to Bocknek on Kohut.

Replies to comments by Gene Bocknek (see record 2009-05605-008) on the author's original article (1986) on self psychology and Heinz Kohut. Masek believes that three problems separate his reading of Kohut's contributions from Bocknek's reading of Kohut and Masek's paper. All three problems converge on the issue of how Bocknek's response understands the issues raised in Masek's paper. These problems are as follows: (1) Precedents are not paradigms; (2) trends ≠ sameness of contributions; and (3) the relations between ego, the self, and Ego Psychology and Self Psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infrared sensor arrays with 3-12 μm cutoff wavelengths inheteroepitaxial narrow-gap semiconductors on silicon substrates

The authors describe heteroepitaxy of IV-VI lead chalcogenide narrow-gap semiconductor (NGS) as well as II-VI materials (CdTe) on Si substrates. Epitaxy is achieved by using stacked intermediate CaF₂ -BaF₂ bilayers to overcome the large lattice and thermal expansion mismatch. The authors use lead chalcogenides (PbS, PbTe, Pb_1-xEu_xSe, and Pb_1-xSn_x Se) rather than Hg_1-xCd_xTe (MCT) as IR-sensitive NGS material because growth and fabrication techniques are much easier and compositional homogeneity much less critical with lead salts, while maximum sensitivities are comparable to those of MCT. The high permittivity of lead salts yields much more fault-tolerant devices due to the effective shielding of charges resulting from defects. The authors have fabricated linear sensor arrays on Si substrates with cutoff wavelengths ranging from 3 to above 12 μm. The sensitivities of the best PbTe on Si sensors (cutoff 5.5 μm) are already comparable to those of MCT with the same cutoff wavelengths, while those of the first Pb_1-xSn_xSe devices are a factor of 2-5 below. Although many fabrication steps are rather crude and far from being optimized, this considerable improvement is easily possible