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University of Twente Publications (60.939 recursos)

University of Twente Repository provides publications of UT scientific staff, in many cases full text and publicly available.

Group = KEUR

Mostrando recursos 1 - 20 de 7.326

  1. Desalination by Electrodialysis Using a Stack of Patterned Ion-Selective Hydrogels on a Microfluidic Device

    Gumuscu, Burcu; Haase, A. Sander; Benneker, Anne M.; Hempenius, Mark A.; Berg, Albert van den; Lammertink, Rob G.H.; Eijkel, Jan C.T.
    This study reports a novel approach for separation of charged species using anion-exchange hydrogel (AEH) and cation-exchange hydrogel (CEH) in a microfluidic device. The capillary line pinning technique, which is applied in this study, enables in situ fabrication of alternating AEH and CEH that are placed in confined compartments. Adjacent enriched and depleted streams are obtained in continuous flow when a potential difference is applied over the hydrogel stack. The desalination performance of the microchip is demonstrated at different salt concentrations (0.01 × 10−3–1× 10−3m sodium chloride), potentials (10–100 V), current densities (12–28 A m−2), and liquid flow rates (0–5...

  2. Synchrotron SAXS and Impedance Spectroscopy Unveil Nanostructure Variations in Redox-Responsive Porous Membranes from Poly(ferrocenylsilane) Poly(ionic liquid)s

    Folkertsma, Laura; Zhang, Kaihuan; Czakkel, Orsolya; Boer, Hans L. de; Hempenius, Mark A.; Berg, Albert van den; Odijk, Mathieu; Vancso, G. Julius
    Nanostructured cellular polymeric materials with controlled cell sizes, dispersity, architectures, and functional groups provide opportunities in separation technology, smart catalysts, and controlled drug delivery and release. This paper discusses porous membranes formed in a simple electrostatic complexation process using a NH3 base treatment from redox responsive poly(ferrocenysilane) (PFS)-based poly(ionic liquid)s and poly(acrylic acid) (PAA). These porous membranes exhibit reversible switching between more open and more closed structures upon oxidation and reduction. The porous structure and redox behavior that originate from the PFS matrix are investigated by small-angle X-ray scattering (SAXS) using synchrotron radiation combined with electrochemical impedance spectroscopy. In order...

  3. Reasoning about semantic conflicts between aspects

    Durr, Pascal; Staijen, Tom; Bergmans, Lodewijk; Aksit, Mehmet
    The AOP community has successfully promoted and illustrated the power and elegance of aspect-oriented programming. One of the main problems of Aspect-oriented programming is, however, the aspect interference problem. When multiple aspects are superimposed on the same join point, undesired or incorrect behavior may emerge due to the side effects of behavior of the aspects at the join point. In this paper we present a technique and a tool to detect and correct the semantic conflicts among aspects that are superimposed on the same join point.

  4. Integrated dual-channel X-band offset-transmitter for phase steering and DDMA arrays

    Withagen, Johan C.J.G.; Annema, A.J.; Nauta, B.; Vliet, F.E. van
    Multiple-Input and Multiple-Output (MIMO) arrays provide more degrees of freedom than conventional phased arrays. They require that every transmitting element of the array can be identified when received. One way to achieve this is to give every element its own unique frequency. Offset-Transmitters may be used to introduce MIMO or Doppler Division Multiple Access (DDMA) into phased-arrays without an excessive increase in waveform-generating hardware. Our dual-channel demonstrator IC can obtain a phase accuracy better than 1 degree and an spurious level of better than -65dBc for a single on-chip channel. This work investigates at X-band the effects of the limited...

  5. Electrically controllable oscillator circuit, and electrically controllable filter arrangement comprising said circuits

    Nauta, Bram
    An electrically controllable oscillator circuit (30) comprises two balanced transconductance circuits (G1, G2), each including transistor pairs arranged as inverters (Inv14) and as resistors (Inv5-6). The oscillation frequency (f) and the quality factor (Q) of the oscillator circuit (30) are controlled by means of a single control signal provided by a combined control circuit (Inv7, Dif, IM1, IM2). The current mirror circuit (IM1, IM2) and a differential pair (Dif) derived the control signal for adjusting the quality factor (Q) from a resistor-connected further transistor pair (Inv7) connected to the control signal for adjusting the frequency (f). The quality factor of...

  6. Single-to-differential converter

    Nauta, Bram
    A single-to-differential converter for generating two balanced output signals from one single-ended input signal includes first (3) and second (6) output terminals for providing the balanced output signal, a first transistor (M1) having a control electrode coupled to an input terminal (4) for receiving the input signal, a first main electrode coupled to a supply voltage terminal (1) for receiving a supply voltage and a second main electrode coupled to the first output terminal (3). A second transistor (M2) is provided having a control electrode coupled to a bias voltage terminal (5), a first main electrode coupled to the control...

  7. Frequency divider

    Acar, Mustafa; Leenaerts, Dominicus Martinus Wilhelmus; Nauta, Bram
    A frequency divider includes a first latch and a second latch. The first latch is configured to receive a clock signal. The first latch is cross-coupled to the second latch. The second latch includes a circuit configured as a low-pass filter. The second latch further includes a differential pair of transistors. Each of the transistors include a drain, a source and a gate. The gates of the least two transistors configured to receive a signal generated by the first latch. Additionally, the gates of the at least two other transistors are coupled to a control signal for determining a low-pass...

  8. Folding stage and folding analog-to-digital converter

    Nauta, Bram; Venes, Arnoldus G.W.
    A folding stage for a folding analog-to-digital converter includes a plurality of consecutive reference terminals providing ascending different reference voltages, a first summing node, a second summing node and a first output node. A plurality of differentially coupled transistor pairs wherein each of the pairs has a first transistor having a main current path and a control electrode which is coupled to an input terminal (IT) for receiving an input voltage to be folded and a second transistor having a main current path and a control electrode which is coupled to a respective one of the consecutive reference terminals. The...

  9. Folding stage for a folding analog-to-digital converter

    Venes, Arnoldus G.W.; Nauta, Bram
    A folding stage for a folding analog-to-digital converter comprising a plurality of consecutive reference terminals for providing ascending different reference voltages; a first summing node, a second summing node and a first output node. A plurality of differentially coupled transistor pairs with each one of the pairs comprising a first transistor having a main current path and a control electrode which is coupled to an input terminal for receiving an input voltage to be folded and a second transistor having a main current path and a control electrode which is coupled to a respective one of the consecutive reference terminals....

  10. Degenerated differential pair with controllable transconductance

    Mensink, Clemens H.J.; Nauta, Bram
    A differential pair with input transistors and provided with a variable degeneration resistor. The degeneration resistor comprises a series arrangement of two branches of coupled resistors which are shunted in mutually corresponding points by respective control transistors whose gates are interconnected. The differential pair further comprises a control loop comprising two current mirrors a bias resistor and a current source for providing a control signal to the gates of the control transistors. The control loop does not influence the DC bias of the differential pair

  11. Line driver with adaptive output impedance

    Nauta, Bram

  12. Line driver with adaptive output impedance

    Nauta, Bram
    A line driver comprising: an input terminal for receiving an input signal, an output terminal for connecting a load, a first and a second transconductance-controlled transconductor having substantially equal transconductances, each transconductor having a non-inverting input, an inverting input, an output and a common control input for controlling the transconductance, the non-inverting inputs of the first and second transconductors being coupled to the input terminal, the outputs of the first and second transconductors being coupled to the output terminal, the inverting input of the first transconductor being coupled to a point of reference potential, the inverting input of the second...

  13. Phase-Locked-loop with reduced clock jitter

    Nauta, Bram; Beek, Remco Cornelis Herman van de; Vaucher, Cicero Silveira
    The present invention relates to a phase-locked-loop (PLL) circuit and a method for controlling such a PLL circuit, wherein the frequency of an input reference signal and the frequency of a feedback signal derived from an output oscillation signal are divided by a predetermined rate to thereby reduce the frequency at a phase detection means (1) of the PLL circuit. The dividing step is inhibited in response to a detection of a phase-locked-state of the PLL circuit. Thus, after phase-lock has been achieved, extra reference dividers (6) added to decrease the comparison frequency are removed from the loop to thereby...

  14. 3D capillary valves for versatile capillary patterning of channel walls

    Papadimitriou, V.A.; Berg, A. van den; Eijkel, J.C.T.
    We demonstrate passive capillary patterning of channel walls with a liquid in situ. Patterning is performed using a novel 3D capillary valve system combining three standard capillary stop valves. A range of different patterns is demonstrated in three channel walls. Capillary patterning was designed for precise in situ patterning of phase-change materials (e.g. UV curable hydrogels, gels, resins), but may find further applications such as local surface functionalization

  15. Optimization theory for ballistic conversion

    Xie, Yanbo; Versluis, Michel; Berg, Albert van den; Eijkel, Jan C.T.
    The growing demand of renewable energy stimulates the exploration of new materials and methods for clean energy. We recently demonstrated a high efficiency and power density energy conversion mechanism by using jetted charged microdroplets, termed as ballistic energy conversion. Hereby, we model and experimentally characterize the physical properties of the ballistic energy conversion system.

  16. Large-area fabrication of sub-30 NM periodic nanostructures

    Le-The, H.; Berenschot, E.; Tiggelaar, R.M.; Tas, N.R.; Berg, A. van den; Eijkel, J.C.T.
    We demonstrate a robust and high-yield fabrication method without deep-UV laser source by combining displacement Talbot lithography (DTL) using a monochromatic UV beam with dryetching techniques to pattern sub-30 nm periodic nanostructures over large-areas. Using this fabrication method, we fabricated 30-100 nm nanocolumns arrays of photoresist and sub-30 nm gold (Au) nanoparticle arrays.

  17. Desalination by electrodialysis using a stack of charged hydrogels in a microfluidic platform

    Gumuscu, Burcu; Haase, A. Sander; Benneker, Anne M.; Berg, Albert van den; Lammertink, Rob G.H.; Eijkel, Jan C.T.
    We show a new approach for desalinating water, using a stack of periodic hydrogel structures in a microfluidic platform. This technique utilizes alternating anion- (AEH) and cation-exchange hydrogels (CEH) locally fabricated in confined compartments by capillary line pinning. Parallel streams of concentrated and ion-depleted water are formed in continuous flow when applying a potential difference across the microchip. Different electric fields (10-100 V/cm) and fluid flow rates (0-5 μl/min) are investigated.

  18. Microfluidic fabrication of plasmonic microcapsules

    Wang, J.; Jin, M.L.; Eijkel, J.C.T.; Berg, A. van den; Zhou, G.F.; Shui, L.L.
    This paper presents the plasmonic microcapsules with well-ordered nanoparticles embedded in polymer network fabricated by using a microfluidic device. The well-ordered nanoparticle arrays on the microcapsule form high-density uniform “hot-spots” with a deposited metal film, on which the localized surface plasmon resonance effect is obtained. These plasmonic microcapsules can be engineered and modified by nanoparticle size and the metal film thickness. Repeatable Surfaced-Enhanced Raman Scattering (SERS) effect has been obtained with the highest analytical enhancement factor of 107 being achieved.

  19. A 915 MHz 175 uW receiver using transmitted-reference and shifted limiters for 50 dB in-band interference tolerance

    Ye, Dawei; Zee, Ronan van der; Nauta, Bram
    Improving interference robustness in ultralow power (ULP) receivers (RXs) is a big challenge due to their low power budget. This paper presents an envelope detector based 915 MHz 10 kb/s ULP RX, which is fabricated in 65 nm CMOS process for wireless sensor networks and Internet of Things. Two power-efficient techniques, transmitted-reference and shifted limiter, are proposed to improve the nterference robustness. The RX sensitivity is between −61 and −76 dBm. The maximum in-band signal-to-interference ratio at ±1 MHz offset is up to −50 dB while just consuming 175 μW power from a 1 V supply.

  20. Two-Wire interface for digital microphones

    Groothedde, Wouter; Klumperink, Eric Antonius Maria; Nauta, Bram; Eschauzier, Rudolphe Gustave Hubertus; Rijn, Nico van
    A two-wire interface for a digital microphone circuit includes a power line and a ground line. The interface utilizes the ground line as a "voltage active line" to transmit both clock and data signals between the digital microphone circuit and a receiving circuit. The digital microphone circuit detects the clock signal on the voltage active line and uses the detected clock signal to operate an ADC to provide digital data. The digital data is used to selectively drive current back to the receiving circuit over the voltage active line. The receiving circuit detects the transmitted data by monitoring the voltage...

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