We present a novel mechanism of particle manipulation in alternating-current (ac)-driven electro-osmotic micropumps, utilizing the tunable ratio of viscous drag, inertial and dielectrophoretic forces. The latter are induced by three-dimensional (3D) stepped electrode arrays in the channel, which are driven by ac voltages enabling so-called 3D-ac-electro-osmotic pumping, as has been proposed recently. Due to size-and density-dependent differences in polarizability, targeted particles in the fluid stream can be slowed down or even pinned above the electrode structures solely by adjusting the operation parameters of the pump. Hence the presented device, fabricated in SU-8/glass technology, enables simultaneous pumping and manipulation of particles in suspension.
One of the biggest challenges of communication networks is the video transmission in real time. It requires high demands on the available network capacity and transport mechanisms. Availability of smart mobile devices with batteries, which keep the terminal working for several hours, caused an increased interest in the research of the deployment of video transmission in wireless transmission systems. The presented paper deals with the transmission of video encoded with H.264/AVC (Advanced Video Coding) video coding standard through wireless local area network (WLAN) using the programming environment OPNET Modeller (OM). The test network studied in this work was prepared by combining real and simulated networks, which allows interesting possibilities when working with the OM tools. Such an approach to working with OM allows a detailed video streaming analysis, because the video output was noticeably not only in the form of statistics, but we can see the real impact of transmission failures. Using the OM simulation environment allows to design the transmission systems, which would be difficult to establish in laboratory conditions.
The formation of two-dimensional carrier gases in gated GaN/AlGaN/GaN heterostructures is investigated theoretically. It is shown that under certain conditions a two-dimensional hole gas at the upper GaN/AlGaN interface can be formed in addition to the two-dimensional electron gas at the lower AlGaN/GaN interface. For the calculations, a Schrdinger-Poisson solver and a simple analytical model developed in the present work are used. Conditions for the formation of a two-dimensional hole gas are elaborated. It is shown that once a two-dimensional hole gas is created, it shields the coexisting two-dimensional electron gas which will result in a diminishing effect of the gate voltage on the two-dimensional electron gas
We report on the properties of metal–insulator–semiconductor
(MIS) photoanodes for water oxidation employing a thin RuO2–(IrO2) film as a top catalytic layer. In this
study, MIS photoanodes with the configurations RuO2/SiO2/n-Si and IrO2–RuO2/SiO2/n-Si were prepared and their
photoelectrochemical (PEC) oxygen evolution under solar irradiation
has been discussed. The thin SiO2 layers were prepared
by the atomic layer deposition method and the RuO2–(IrO2) thin layers were deposited by the metal–organic chemical
vapor deposition method. The photocurrent and photovoltage of these
MIS photoanodes were studied in 1 M aq. H2SO4 (pH = 0), 0.5 M aq. Na2SO4 (pH = 6), and 1
M aq. KOH (pH = 14) electrolytes showing the trend acidic > alkaline
> near-neutral pH conditions for both RuO2- and IrO2–RuO2-based structures. The RuO2/SiO2/n-Si photoanode exhibited a photovoltage
of 0.49 V and was able to generate a photocurrent of ∼10 mA/cm2 at a thermodynamic water oxidation potential (1.23 V vs the normal hydrogen electrode, NHE) in 1 M aq. H2SO4 solution under 1 Sun intensity with AM 1.5
spectrum. A photovoltage of 0.42 V and a photocurrent of ∼4
mA/cm2 were achieved for the IrO2–RuO2/SiO2/n-Si photoanode under acidic
conditions. The stability of the photoanodes was examined in 1 M aq.
H2SO4 and 1 M aq. KOH solutions. Chronoamperometry
measurements on the RuO2/SiO2/n-Si photoanode in acidic solution under an applied voltage of 1.23
V versus NHE showed the deterioration of the photoanode
after 2 h of operation. Similarly, stability measurements were performed
on IrO2–RuO2/SiO2/n-Si photoanodes in 1 M aq. H2SO4 solution.
Under acidic conditions, at an applied bias of 1.23 V versus NHE, a photocurrent of ∼2 mA/cm2 was observed,
which was stable for 24 h for the IrO2–RuO2-based photoanodes. The preparation, PEC activity, stability, and
characterization of the RuO2/SiO2/n-Si and IrO2–RuO2/SiO2/n-Si have been discussed in our study.
Ga2O3, a wide-bandgap semiconductor material, offers a great potential for power and high-voltage electronic devices. We report on the growth of undoped α- and β-phase Ga2O3 using liquid-injection metal-organic chemical vapor deposition (LI-MOCVD) on sapphire substrates. Using the same precursor (gallium acetylacetonate) and deposition temperature of 700 °C, the phase selection was controlled by the sapphire substrate orientation, where the growth of α- and β-phase Ga2O3 was achieved on m- and c-plane surface, respectively. As deduced from x-ray diffraction, α-Ga2O3 films show epitaxial character, while β- Ga2O3 films exhibit highly textured structure. Oxygen flow was also found to have a strong impact on the phase purity of α-Ga2O3 for the flow rates examined. Optical and electrical properties of the layers grown at different oxygen flow rates were also studied systematically. LI-MOCVD growth of α-phase Ga2O3 layers at relatively high deposition temperature widens the high-temperature processing of the Ga2O3-based electronic and optoelectronic devices.
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