Delft University of Technology

About: Delft University of Technology is a education organization based out in Delft, Zuid-Holland, Netherlands. It is known for research contribution in the topics: Population & Catalysis. The organization has 37681 authors who have published 94404 publications receiving 2741710 citations. The organization is also known as: TU-Delft & Technische Hogeschool Delft.

A Low Dark Count p-i-n Diode Based SPAD in CMOS Technology

Abstract: In this paper, a novel CMOS single-photon avalanche diode (SPAD) is presented, and the device is designed using a vertical p-i-n diode construction. The p-i-n diode with a wide depletion region enables a low-noise operation. The proposed design achieves dark count rates of 1.5 cps/ $\mu \text{m}^{2}$ at 11 V excess bias, while the photon detection probability (PDP) is greater than 40% from 460 to 600 nm. Through the operation at very high excess bias voltages, it is possible to reach the PDP compression point where sensitivity to the breakdown voltage is low, thus ensuring high PDP uniformity; this feature makes it, especially, suitable for multimegapixel SPAD arrays.

Low-stress PECVD SiC thin films for IC-compatible microstructures

Abstract: A low-temperature, IC-compatible, deposition process for SiC thin films with low mechanical stress and good passivating properties has been developed. SiC films with excellent etch resistance to various electrolytes have been deposited using a commercial-type PECVD reactor and patterned by dry etching in a fluorine-based chemistry. Deposition rates up to 100 nm min−1 and good uniformity have been measured. A low compressive stress (350 MPa) has been obtained for as-deposited films by adjusting the deposition parameters. The stress can be further reduced (20 MPa) and even shifted into the low tensile region by a post-deposition anneal at 600 °C. Due to their excellent properties, these SiC thin films can be used as masking layers in various etch processes, particularly for deep etching of glass or silicon, and to realize IC-compatible SiC membranes.

TempLab: a testbed infrastructure to study the impact of temperature on wireless sensor networks

Abstract: Temperature has a strong impact on the operations of all electrical and electronic components. In wireless sensor nodes, temperature variations can lead to loss of synchronization, degradation of the link quality, or early battery depletion, and can therefore affect key network metrics such as throughput, delay, and lifetime. Considering that most outdoor deployments are exposed to strong temperature variations across time and space, a deep understanding of how temperature affects network protocols is fundamental to comprehend flaws in their design and to improve their performance. Existing testbed infrastructures, however, do not allow to systematically study the impact of temperature on wireless sensor networks.In this paper we present TempLab, an extension for wireless sensor network testbeds that allows to control the on-board temperature of sensor nodes and to study the effects of temperature variations on the network performance in a precise and repeatable fashion. TempLab can accurately reproduce traces recorded in outdoor environments with fine granularity, while minimizing the hardware costs and configuration overhead. We use TempLab to analyse the detrimental effects of temperature variations (i) on processing performance, (ii) on a tree routing protocol, and (iii) on CSMA-based MAC protocols, deriving insights that would have not been revealed using existing testbed installations.

Computational Fluid Dynamics of a Radial Compressor Operating With Supercritical CO2

Abstract: The merit of using supercritical CO2 (scCO2) as the working fluid of a closed Brayton cycle gas turbine is now widely recognized, and the development of this technology is now actively pursued. scCO2 gas turbine power plants are an attractive option for solar, geothermal and nuclear energy conversion. Among the challenges which must be overcome in order to successfully bring the technology to the market, the efficiency of the compressor and turbine operating with the supercritical fluid should be increased as much as possible. High efficiency can be reached by means of sophisticated aerodynamic design, which, compared to other overall efficiency improvements, like cycle maximum pressure and temperature increase, or increase of recuperator effectiveness, does not require an increase in equipment cost, but only an additional effort in research and development.This paper reports a three-dimensional CFD study of a high-speed centrifugal compressor operating with CO2 in the thermodynamic region slightly above the vapor-liquid critical point. The investigated geometry is the compressor impeller tested in the Sandia scCO2 compression loop facility [1]. The fluid dynamic simulations are performed with a fully implicit parallel Reynolds-averaged Navier-Stokes code based on a finite volume formulation on arbitrary polyhedral mesh elements. The CFD code has been validated on test cases which are relevant for this study, see Ref. [2,3]. In order to account for the strongly nonlinear variation of the thermophysical properties of supercritical CO2, the CFD code is coupled with an extensive library for the computation of properties of fluids and mixtures [4]. Among the available models, the one based on reference equations of state for CO2 [5,6] has been selected, as implemented in one of the sub-libraries [7]. A specialized look-up table approach and a meshing technique suited for turbomachinery geometries are also among the novelties introduced in the developed methodology.A detailed evaluation of the CFD results highlights the challenges of numerical studies aimed at the simulation of technically relevant compressible flows occurring close to the liquid-vapor critical point. The data of the obtained flow field are used for a comparison with experiments performed at the Sandia scCO2 compression-loop facility.© 2012 ASME