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University of Twente Publications (47,497 recursos)
University of Twente Repository provides publications of UT scientific staff, in many cases full text and publicly available.

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Mostrando recursos 1 - 20 de 6,710

1. Software defined radio receivers exploiting noise cancelling: a tutorial review - Klumperink, Eric; Nauta, Bram
Traditional radio receivers were narrowband and dedicated to a single frequency band exploiting LC tanks, whereas software defined radios target a flexibly programmable frequency. The broadband noise cancelling circuit technique has proven useful to achieve this target, as it breaks the traditional trade-off between low noise and broadband impedance matching. Different variants exist, with noise cancellation in the voltage or current domain, either at RF or after frequency translation to baseband. This article reviews the development of the noise cancelling technique and its role in inductorless interference robust software defined radio receivers.

2. A 110mW, 0.04mm2, 11GS/s 9-bit interleaved DAC in 28nm FDSOI with >50dB SFDR across Nyquist - Olieman, Erik; Annema, Anne-Johan; Nauta, Bram
A 9-bit 11GS/s current-steering (CS) digital-to-analog converter (DAC) is designed in 28nm FDSOI. The DAC uses two-times interleaving to suppress the effects of the main error mechanisms of CS DACs while its clock timing can be tuned by the back gates bias voltage of the multiplexer transistors. The DAC achieves higher than 50dB SFDR and less than -50dBc IM3 over Nyquist at a sampling rate of 11GS/s, occupying only 0.04mm2 and consuming 110mW from a single 1V supply.

3. An ultra low energy FSK receiver with in-band interference robustness exploiting a 3-Phase chirped LO - Dutta, Ramen; Zee, Ronan van der; Kokkeler, André B.J.; Bentum, Mark J.; Klumperink, Eric; Nauta, Bram
An ultra-low-energy Binary Frequency Shift Keying (BFSK) receiver is proposed. It features improved in-band interference tolerance by chirping the transmission frequency. To reduce the receiver power consumption, a novel three-phase passive mixer along with a three stage digitally controlled ring oscillator is proposed, while still allowing quadrature detection. A mixer-first direct conversion receiver architecture moves the required gain to lowest frequency and lowest bandwidth to reduce power consumption. A low power flip-flop based BFSK demodulator is proposed that reduces the baseband power further. The receiver is designed and fabricated in a 65 nm complementary metal-oxide-semiconductor process. It consumes 219 μW...

4. Effective coastal boundary conditions for tsunami wave run-up over sloping bathymetry - Kristina, W.; Bokhove, O.; Groesen, E.W.C. van
An effective boundary condition (EBC) is introduced as a novel technique for predicting tsunami wave run-up along the coast, and offshore wave reflections. Numerical modeling of tsunami propagation in the coastal zone has been a daunting task, since high accuracy is needed to capture aspects of wave propagation in the shallower areas. For example, there are complicated interactions between incoming and reflected waves due to the bathymetry and intrinsically nonlinear phenomena of wave propagation. If a fixed wall boundary condition is used at a certain shallow depth contour, the reflection properties can be unrealistic. To alleviate this, we explore a...

5. Turbulent sediment fluxes along migrating sand dunes - Naqshband, S.; Ribberink, J.S.; Hurther, D.; Hulscher, S.J.M.H.

6. River dune predictions: Comparison between a parameterized dune model and a cellular automation dune model - Seuren, J.M.; Duin, O.J.M. van; Warmink, J.J.; Knaapen, M.A.F.; Hulscher, S.J.M.H.

7. Challenges in the design of the Virtual River serious game - Haan, R.J. den; Voort, M.C. van der; Hulscher, S.J.M.H.

8. Correlation impact in piping erosion for safety assessment of multi-functional flood defences - Aguilar Lopez, J.P.; Warmink, J.J.; Schielen, R.M.J.; Hulscher, S.J.M.H.

9. RiverCare: towards self-sustaining multifunctional rivers - Hulscher, S.J.M.H.; Schielen, R.M.J.; Augustijn, D.C.M.; Warmink, J.J.; Voort, M.C. van der; Middelkoop, H.; Kleinhans, M.G.; Leuven, R.S.E.W.; Lenders, H.J.R.; Smits, A.J.M.; Fliervoet, J.M.; Uijttewaal, W.S.J.; Blom, A.; Wallinga, J.; Hoitink, A.J.F.; Buijsse, A.D.; Geerling, G.W.; Makaske, B.

10. De wankele democratie: heeft de democratie haar beste tijd gehad? - Thomassen, Jacques; Ham, Carolien van; Andeweg, Rudy
Wankelt de Nederlandse democratie? Er gaat geen dag voorbij of er wordt wel ergens in de media verwezen naar het dalende vertrouwen van burgers in politici, politieke partijen en regering. De economische crisis en de steeds meer onder druk staande Europese samenwerking hebben de problemen alleen nog maar verergerd. Weinigen vertrouwen erop dat de politiek in staat is de juiste oplossingen te bieden. Men zou denken dat de democratie haar beste tijd gehad heeft. Maar klopt dit beeld wel? Wenden burgers zich inderdaad af van de representatieve democratie, of is dit slechts een mythe? Aan de hand van onderzoek vanaf de...

11. How social learning influences further collaboration: experiences from an international collaborative water project - Vinke-de Kruijf, Joanne; Bressers, Hans; Augustijn, Denie C.M.
Social learning in collaborative settings can play an important role in reducing water management problems. In this paper we analyze the nature and effects of these learning processes in an international collaborative setting. We assert that social interactions contribute to substantive and relational learning, which involves changes in the motivations, cognitions and resources of individual actors. In addition, interactions may contribute to social learning, which is the case when actors develop collective outcomes on which further collaboration can be based. We use these theoretical insights to examine a water project in which Dutch and Romanian actors collaborate. Their interactions changed...

12. Bed load and suspended load contributions to migrating sand dunes in equilibrium - Naqshband, S.; Ribberink, J.S.; Hurther, D.; Hulscher, S.J.M.H.
Dunes dominate the bed of sand rivers and are of central importance in predicting flow roughness and water levels. The present study has focused on the details of flow and sediment dynamics along migrating sand dunes in equilibrium. Using a recently developed acoustic system (Acoustic Concentration and Velocity Profiler), new insights are obtained in the behavior of the bed and the suspended load transport along mobile dunes. Our data have illustrated that, due to the presence of a dense sediment layer close to the bed and migrating secondary bedforms over the stoss side of the dune toward the dune crest,...

13. The role of suspended load transport in the occurrence of tidal sand waves - Borsje, B.W.; Kranenburg, W.M.; Roos, P.C.; Matthieu, J.; Hulscher, S.J.M.H.
Tidal sand waves are dynamic bed patterns which are formed by the complex interaction between hydrodynamics, sediment transport, and geomorphology. Field data from the southern North Sea reveal that sand waves are absent where suspended load transport is the dominant transport mode. In order to understand the mechanisms responsible for the absence of sand waves, we study the influence of suspended load transport on the formation of tidal sand waves with a numerical process-based geomorphological model (Delft3D). Model simulations are presented in which the vertical eddy viscosity and sediment diffusivity are both spatially and temporally variable (k-ε turbulence model). First,...

14. Using both free surface effect and sediment transport mode parameters in defining the morphology of river dunes and their evolution to upper stage plane beds, doi: 10.1061/(ASCE)HY.1943-7900.0000873 - Naqshband, S.; Ribberink, J.S.; Hulscher, S.J.M.H.
Dunes are common bed forms in sand bed rivers and are of central interest in water management purposes. Due to flow separation and associated energy dissipation, dunes form the main source of hydraulic roughness. A large number of dune dimension data sets was compiled and analyzed in this study—414 experiments from flumes and the field—showing a significantly different evolution of dune height and length in flows with low Froude numbers (negligible free surface effects) and flows with high Froude numbers (large free surface effects). For high Froude numbers (0.32–0.84 ), relative dune heights are observed to grow only in the...

15. A Shift Toward Building with Nature in the Dredging and Port Development Industries: Managerial Implications for Projects in or Near Natura 2000 Areas - Vikolainen, Vera; Bressers, Hans; Lulofs, Kris
Building with Nature is a new approach to designing water infrastructure, one that seeks to realize socioeconomic project goals in harmony with the environment. The Dutch dredging industry is promoting its application in the Netherlands, but similar concepts are emerging internationally. The Working with Nature concept has been developed under the auspices of the World Association for Waterborne Transport Infrastructure, Engineering with Nature by the US Army Corps of Engineers, and Flanders Bays 2100 by a group of Belgian dredging companies and international consultants. The research discussed in this article focuses on the feasibility of implementing the Building with Nature...

16. Formation and erosion of biogeomorphological structures: A model study on the tube-building polychaete Lanice conchilega - Borsje, B.W.; Bouma, T.J.; Rabaut, M.; Herman, P.M.J.; Hulscher, S.J.M.H.
We study how organism traits and population densities of ecosystem engineering species, in combination with environmental factors, affect the formation and erosion rates of biogeomorphological structures, and focus on the widely distributed marine tube-building polychaete Lanice conchilega, which lives in patches that form mounds up to 80 cm high in soft-bottom sediments. We modeled the tube-building worms as thin solid piles that affect drag and turbulence, and thereby the local sediment dynamics and thus mound dynamics. Hydrodynamic model predictions showed good agreement with flume experiments for flow-velocity adaptations both within and in front of a patch of tube-building worms. The...

17. The challenge of addressing Grand Challenges: a think piece on how innovation can be driven towards the "Grand Challenges" as defined under the prospective European Union Framework Programme Horizon 2020 - Kuhlmann, Stefan; Rip, Arie

18. Understanding river dune splitting through flume experiments and analysis of a dune evolution model - Warmink, J.J.; Dohmen-Janssen, C.M.; Lansink, J.; Naqshband, S.; Duin, O.J.M. van; Paarlberg, A.J.; Termes, A.P.P.; Hulscher, S.J.M.H.
Forecasts of water level during river floods require accurate predictions of the evolution of river dune dimensions, because the hydraulic roughness of the main channel is largely determined by the bed morphology. River dune dimensions are controlled by processes like merging and splitting of dunes. Particularly the process of dune splitting is still poorly understood and – as a result – not yet included in operational dune evolution models. In the current paper, the process of dune splitting is investigated by carrying out laboratory experiments and by means of a sensitivity analysis using a numerical dune evolution model. In the...

19. Situative Prävention von Cybercrime: ein chancenreicher Bekämpfungsansatz - Hartel, P.H.

20. Situative Prävention von Cybercrime: ein chancenreicher Bekämpfungsansatz - Hartel, P.H.

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