237,889 research outputs found
Thermal stability of chemical vapor deposition grown W and WNx thin films in low-k integration structure
No full textThe Cu/barrier/low-k SiCOH/Si structures were fabricated and their thermal stability was investigated. SiCOH films were deposited by plasma-enhanced chemical vapor deposition using divinyldimethylsilane (DVDMS) and O-2. As barrier materials, tungsten and tungsten nitride films were deposited by chemical vapor deposition using W(CO)(6) and NH3 sources at 450 degrees C. Variations of scanning electron microscopy and x-ray diffraction results of Cu/barrier/low-k SiCOH/Si were examined depending on the annealing temperature. Both results showed that W and W2N film were stable up to 500 and above 600 degrees C, WO3 nanorods were grown from the sample surface. It is thought that the thermal stability of the Cu/barrier/SiCOH/Si structure is closely related with the thermal destruction of the W and WNx films. (c) 2006 American Vacuum Society.X113sciescopu
Joshua Davis: Author of Spare Parts
No full textCitation: K-State First (2016). Joshua Davis: Author of Spare Parts [Flier]. Manhattan, Kansas: K-State First.Flyer advertising Joshua Davis's author talk at Kansas State University
K-theory for group C*-algebras
No full textThese notes are based on a lecture course given by the first author in the Sedano Winter School on K-theory held in Sedano, Spain, on January 22-27th of 2007. They aim at introducing K-theory of C*-algebras, equivariant K-homology and KK-theory in the context of the Baum-Connes conjectur
Modeling of high speed erosion with a morphological updating routine
No full textErosion is a phenomenon present in several industrial processes. In dredging, the jetting of sand in drag heads erodes the sand bed. In construction of offshore infrastructure such as wind turbines, oil and gas production units, marine pipelines, erosion of material near the foundations can put the stability of structures at stake. Furthermore, rivers or even tsunamis are some of the natural phenomena that can be the cause of erosion. C. van Rhee, 2007 and Bisschop et al., 2015, distinguished two regimes for the erosion of sand dependent on the fluid velocity. On one hand, for low flow velocities, 0.5-1m/s, the erosion process is dependent on the size and the density of the sand grains. On the other, for flow velocities >1.5 m/s, the upper layers of sand are sheared. Densely packed sand has a dilatant behaviour to shearing (see image). This dilatant behaviour leads to a drop of pressure in the interior of the sand-bed, creating a hydraulic gradient and forcing water to flow towards the interior of the sand-bed to fill the voids. The hydraulic gradient caused by the drop in pressure acts against the eroding forces adding resistance to the erosion process. This regime is defined as hindered erosion. The improvements in computing power have led to a spread in the use of numerical modelling for industrial purposes. The aim of this thesis is to develop a numerical solver able to model the behaviour of sand-water mixtures with an emphasis on the erosive process. The numerical model was developed in C++ using the Foam-extend 3.2 framework. The sand is modelled using 2 different approaches. It is modelled as a continuum when in suspension and, through the morphological updating routine when settled in a sand-bed. The fluid motion is modelled by a transient incompressible fluid solver (P.I.S.O) using a collocated arrangement of the unknowns. The momentum exchange between suspended sand grains and the fluid is approached by the Boussinesq approximation of the density. The transport of suspended sand is modelled by an advection-diffusion relation, including the hindered settlement effect. The turbulence model is a standard k-ε model. The erosion process is here modelled using the pick-up flux approach (van Rijn, 1984), with a modified stability criterion (θ_cr). X. Lui, 2008 and N. Jacobsen, 2011, corrected the stability criterion calculated from the sand grain properties (θ_(cr,0)) to include the slope effect (θ_slope). For this work, and following the formulation proposed by van Rhee, 2007, the stability criterion will be corrected to include the resistance due to the dilatant behaviour presented previously in this abstract (θ_vR). θ_cr=θ_(cr,0) (θ_slope+θ_vR ) The solver developed was used in two test cases. First, a settling test, with an initial concentration of sand of c=0.3. For this model, the solver shows a good behavior modeling the settling of sediment, nevertheless, the settling velocity is slightly higher than the one seen in the test. In the high speed erosion test, the velocity above the bed varies from 0-6 m/s. The fitting parameter of this model is the bed roughness; which for this test is 1.05 cm. The bed roughness (ks) was fitted to have the same erosion time. The calculated sand-bed height has values similar to the experimental results. The conservation of sediment presents satisfactory results as the error is lower than 1%, for the settling and the erosion test case. The automatic mesh motion presents certain limitations in this specific application. In the settling case an important shrinking of the mesh will lead to instabilities in the calculations of other fields. In the erosion test, the upper row of cells is greatly deformed sacrificing accuracy near the upper boundary. The mesh deformation should be explored more in depth in further studies.Mechanical, Maritime and Materials EngineeringMarine and Transport TechnologyOffshore and Dredging Engineerin
Steven Johnson Author Talk Poster
No full textK-State Book NetworkA poster advertising an author talk by Steven Johnson at Kansas State University on September 3, 2014. Steven Johnson's book "The Ghost Map" was the 2014-2015 common book
Photoelectrochemical Hydrogen Generation Using C-dot/ZnO Hierarchical Nanostructure as an Efficient Photoanode
No full textIn this study, we have developed a stable and environmental-friendly photoelectrode of carbon nanodots (C-dots) coupled with a 3 dimensional ZnO structure. Our C-dots are synthesized hydrothermally with a high yield of 40%, and they are successfully anchored onto the ZnO backbone via a facile solution procedure. The as-prepared C-dot/ZnO photoelectrodes have exhibited reasonable photocurrent density and remarkable photostability under the 1 sun irradiation condition without any sacrificial reagent. We have studied the chemistry beneath the C-dot/ZnO interface through various spectroscopic and electrochemical techniques. This work could shed light on future application of C-dots in efficient and toxin-free solar water-splitting systems. (C) 2015 The Electrochemical Society. All rights reserved.X1165sciescopu
Enhancement of heat transfer in turbulent separated and reattaching flow by local forcing
No full textA numerical study was made of heat transfer in locally forced turbulent separated and reattaching flow over a backward-facing step. The local forcing was given to the flow by means of a sinusoidally oscillating jet from a separation line. The Rhee and Sung version of the unsteady k - epsilon --f(mu) model and the diffusivity tensor heat transfer model were employed. The Reynolds number was fixed at Re-H = 33,000 and the forcing frequency was varied in the range 0 less than or equal to fH / U-infinity less than or equal to 2. The condition of constant heat flux was imposed at the bottom wall. The predicted results were compared and validated with the experimental data of Chun and Sung and Vogel and Eaton. The enhancement of heat transfer in turbulent separated and reattaching flow by local forcing was evaluated and analyzed
Organic field-effect transistors with cross-linked high-k cyanoethylated pullulan polymer as a gate insulator
No full textLow-voltage operable organic field-effect transistors (OFETs) were fabricated with a high-k polymer gate insulator, consisting of cyanoethylated pullulan (CEP) and poly(methylated melamine-co-formaldehyde) (PMMF) as a cross-linker. Effect of the cross-linker amount on the dielectric properties of the film was studied and transistor performance was evaluated. At the optimum PMMF contents, field-effect mobility as high as 2.16 cm(2)/V s, on/off current ratio of similar to 3 x 10(5), low hysteresis (Delta V-th similar to 0.01 V) and a steep inverse subthreshold slope of 0.066 V/dec were obtained. A utilization of stainless steel as a gate metal and substrate markedly improved the device performance under a low-voltage operation (similar to 1 V) due to the positively shifted threshold voltage from the work function change. The devices showed very little degradation in electrical properties with bending. (C) 2010 Elsevier B.V. All rights reserved.X113029sciescopu
High Performance Organic Field-Effect Transistors Using cyanoethyl Pullulan (CEP) High- k Polymer Cross-linked with Trimethylolpropane Triglycidyl Ether (TTE) at Low Temperatures
No full textLow-voltage operable organic field-effect transistors (OFETs) were fabricated using a low-temperature curable high-k polymer cyanoethyl pullulan (CEP) as a gate insulator with trimethylolpropane triglycidyl ether (TTE) as a crosslinking agent. With this crosslinking agent, the gate insulators showed low leakage current and a high dielectric constant of 14.8-16, and most importantly, could be cured at low temperatures around 100 degrees C, which is compatible with most plastic substrates for future plastic electronics. The favorable semiconductor-dielectric interface was obtained due to the surface alignment of well-packed pentacene domains, which enabled excellent transistor performance, with one of the highest mobilities around 6 cm(2) V-1 s(-1), an on/off current ratio (I-on/I-off) similar to 10(5), and a steep subthreshold (SS) similar to 0.095 V dec(-1). The high mobility was found to be closely correlated with the surface C equivalent to N dipole density rather than other possibilities, such as dielectric roughness and surface energy. The initial growth of the semiconductors was also studied and correlated with the affecting variables.open112322sciescopu
Low-Voltage Bendable Pentacene Thin-Film Transistor with Stainless Steel Substrate and Polystyrene-Coated Hafnium Silicate Dielectric
No full textThe hafnium silicate and aluminum oxide high-k dielectrics were deposited on stainless steel substrate using atomic layer deposition process and octadecyltrichlorosilane (OTS) and polystyrene (PS) were treated improve crystallinity of pentacene grown on them. Besides, the effects of the pentacene deposition condition on the morphologies, crystallinities and electrical properties of pentacene were characterized. Therefore, the surface treatment condition on dielectric and pentacene deposition conditions were optimized. The pentacene grown on polystyrene coated high-k dielectric at low deposition rate and temperature (0.2-0.3 angstrom/s and R.T.) showed the largest grain size (0.8-1.0 mu m) and highest crystallinity among pentacenes deposited various deposition conditions, and the pentacene TFT with polystyrene coated high-k dielectric showed excellent device-performance. To decrease threshold voltage of pentacene TFT, the polystyrene-thickness on high-k dielectric was controlled using different concentration of polystyrene solution. As the polystyrene-thickness on hafnium silicate decreases, the dielectric constant of polystyrene/hafnium silicate increases, while the crystallinity of pentacene grown on polystyrene/hafnium silicate did not change. Using low-thickness polystyrene coated hafnium silicate dielectric, the high-performance and low voltage operating ( 1 X 10(4)) and complementary inverter (DC gains, similar to 20) could be fabricated.X111212sciescopu
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