Due to the inherently high trap density at the SiC/SiO 2 interface, SiC-MOSFETs are subject to a hysteresis effect depending on the previous bias of the gate. Applying a negative bias to the gate ...leads to trapping of holes that influence the threshold voltage. We present the application-relevant phenomenon caused by the Vth-hysteresis under different operating and measurement conditions. Furthermore, we introduce a measurement technique to determine the transient threshold-voltage shift Vth(t) in different operating points. A simple power-law approach can be used to describe the trap-induced Vth-shift. In addition, we show that positive biasing leads to electron trapping which temporarily weakens the conductivity of the channel.
SiC-MOSFETs can reach very high temperatures during short circuit events. Under these conditions, significant drain leakage currents eventually cause the destruction of the device. In some operating ...points with low V DS , another failure mechanism affecting the gate insulation can be observed. Theses two defects manifest themselves either as drain-source breakdown or as degradation of the gate-source insulation. In this work, we investigate the conditions that lead to the different failure types via various measurements and numerical simulations. Furthermore, we evaluate the feasibility of a temperature estimation via measurements of the gate current.
Dense pixel matching is important for many computer vision tasks such as disparity and flow estimation. We present a robust, unified descriptor network that considers a large context region with high ...spatial variance. Our network has a very large receptive field and avoids striding layers to maintain spatial resolution. These properties are achieved by creating a novel neural network layer that consists of multiple, parallel, stacked dilated convolutions (SDC). Several of these layers are combined to form our SDC descriptor network. In our experiments, we show that our SDC features outperform state-of-the-art feature descriptors in terms of accuracy and robustness. In addition, we demonstrate the superior performance of SDC in state-of-the-art stereo matching, optical flow and scene flow algorithms on several famous public benchmarks.
In this work we investigate the effect of negative off-state gate-source voltages on SiC MOSFETs. With increasingly negative V GS, Off voltages, a more pronounced drain current over-shoot immediately ...after turn-on is observed. This effect is most noticeable in saturation, where the drain current is determined primarily by the channel. The phenomenon is attributed to positively charged oxide- and interface-traps that temporarily enhance the inversion charge in the channel before they are gradually neutralized. The amount of charged traps depends on the position of the valence band edge in accumulation, hence the V GS, Off dependence. Two distinct components with very different time constants are observed.
The in vitro culture system presented here provides an inexpensive and simple method for investigating cell attachment, growth, and differentiation on an acellular biological active substrate. It ...offers a significant reduction in feeder cell contamination and provides a substantially “cleaner” platform for further cultivation and downstream analyses of differentiated cells.
Pluripotent cells such as human embryonic stem cells and human induced pluripotent stem cells are useful in the field of regenerative medicine because they can proliferate indefinitely and differentiate into all cell types. However, a limiting factor for maintaining and propagating stem cells is the need for inactivated fibroblasts as a growth matrix, since these may potentially cause cross‐contamination. In this study, we aimed to maintain stem cells on the extracellular matrix (ECM) of either nonirradiated or γ‐irradiated fibroblasts. It has been demonstrated that the ECM contains factors and proteins vital for the adhesion, proliferation, and differentiation of pluripotent cells. In order to preserve the ECM, the cell layers of the fibroblasts were decellularized by treatment with 0.05% sodium dodecyl sulfate (SDS), which resulted in an absence of DNA as compared with conventional feeder culture. However, SDS treatment did not cause a detectable change in the ECM architecture and integrity. Furthermore, immunohistochemistry demonstrated that expressions of major ECM proteins, such as fibronectin, collagen, and laminin, remained unaltered. The human pluripotent cells cultured on this decellularized matrix maintained gene expression of the pluripotency markers NANOG and OCT4 and had the potency to differentiate to three germ layers. The in vitro culture system shown here has an excellent potential since the main allogeneic components (i.e., DNA of the feeder cells) are removed. It is also a technically easy, fast, safe, and cheap method for maintaining a refined feeder‐free stem cell culture for further cell differentiation studies.
The method for the simultaneous determination of neomycin and bacitracin in human or rabbit serum was developed by using ion pairing reversed phase chromatography and tandem mass spectrometry (MS/MS) ...detection with electrospray (ESI) in positive mode. Both substances elute under these conditions at the same time and also kanamycin as internal standard elutes almost at the same time. The sample preparation was simple—only using 0.1
mL serum by protein precipitation with acetonitrile. Neomycin and bacitracin were detected as two-fold charged ions as well as the internal standard. The calibration range of these quite difficult detectable substances was 0.2–50
μg/mL of serum. The method was validated for both human or rabbit serum. The inter batch precision of quality control samples in human serum for neomycin ranged from 4.46% to 8.99% and for bacitracin from 6.85% to 11.17%. The inter batch accuracy for neomycin ranged from 98.7% to 100.7% and for bacitracin from 99.2% to 103.0%. At lower limit of quantitation (LLOQ) level of 0.2
μg/mL inter batch precision in human serum for neomycin was 12.05% and for bacitracin 11.91%, whereas accuracies were 99.9% for neomycin and 102.7% for bacitracin. Bench top stability in human or rabbit serum was given over three freeze thaw cycles and 4
h at room temperature.
The method can be considered to be specific and recoveries for sample preparation were high.
State-of-the-art scene flow algorithms pursue the conflicting targets of accuracy, run time, and robustness. With the successful concept of pixel-wise matching and sparse-to-dense interpolation, we ...shift the operating point in this field of conflicts towards universality and speed. Avoiding strong assumptions on the domain or the problem yields a more robust algorithm. This algorithm is fast because we avoid explicit regularization during matching, which allows an efficient computation. Using image information from multiple time steps and explicit visibility prediction based on previous results, we achieve competitive performances on different data sets. Our contributions and results are evaluated in comparative experiments. Overall, we present an accurate scene flow algorithm that is faster and more generic than any individual benchmark leader.
Energy capability of SiC MOSFETs Unger, Christian; Pfost, Martin
2016 28th International Symposium on Power Semiconductor Devices and ICs (ISPSD),
06/2016
Conference Proceeding, Journal Article
Odprti dostop
The superior electrical and thermal properties of silicon carbide (SiC) allow further shrinking of the active area of future power semiconductor devices. A lower boundary of the die size can be ...obtained from the thermal impedance required to withstand the high power dissipation during a short-circuit event. However, this implies that the power distribution is homogeneous and that no current filamentation has to be considered. Therefore, this work investigates this assumption by evaluating the stability of a SiC-MOSFET over a wide range of operation conditions by measurements up to destruction, thermal simulations, and high-temperature characterization.
Human embryonic stem cell (hESC) lines, after directed differentiation, hold the greatest potential for cell transplantation treatment in many severe diseases. Good manufacturing practice (GMP) ...quality, defined by both the European Medicines Agency and the Food and Drug Administration, is a requirement for clinical-grade cells, offering optimal defined quality and safety in cell transplantation. Using animal substance-free culture media, feeder cells or feeder-free matrix in derivation, passaging, expansion and cryopreservation procedures, immune reactions against animal proteins in the cells, and infection risk caused by animal microbes can be avoided. It is also possible to apply GMP to animal components if no better options are available. In recent production of GMP-quality hESC lines, feeder cells had been cultured in fetal bovine serum, and the medium supplemented with an animal protein containing a serum replacement component. Using embryos cultured in a GMP laboratory, isolating the inner cell mass mechanically, deriving lines on human feeder cells originally cultured in xeno-free medium in a GMP laboratory, and using xeno-free media for derivation and culture of hESC lines themselves, GMP-quality xeno-free hESC lines could be established today. Human serum is a xeno-free component available today, but many chemically defined media are under development.
Motion estimation is one of the core challenges in computer vision. With traditional dual-frame approaches, occlusions and out-of-view motions are a limiting factor, especially in the context of ...environmental perception for vehicles due to the large (ego-) motion of objects. Our work pro-poses a novel data-driven approach for temporal fusion of scene flow estimates in a multi-frame setup to overcome the issue of occlusion. Contrary to most previous methods, we do not rely on a constant motion model, but instead learn a generic temporal relation of motion from data. In a second step, a neural network combines bi-directional scene flow estimates from a common reference frame, yielding a refined estimate and a natural byproduct of occlusion masks. This way, our approach provides a fast multi-frame extension for a variety of scene flow estimators, which outperforms the underlying dual-frame approaches.
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