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- De Jong, Roelof S., et al.
(author)
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4MOST : The 4-metre Multi-Object Spectroscopic Telescope project at preliminary design review
- 2016
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In: Ground-Based and Airborne Instrumentation for Astronomy VI. - : SPIE. - 0277-786X .- 1996-756X. - 9781510601956 ; 9908
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Conference paper (peer-reviewed)abstract
- We present an overview of the 4MOST project at the Preliminary Design Review. 4MOST is a major new wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of ESO. 4MOST has a broad range of science goals ranging from Galactic Archaeology and stellar physics to the high-energy physics, galaxy evolution, and cosmology. Starting in 2021, 4MOST will deploy 2436 fibres in a 4.1 square degree field-of-view using a positioner based on the tilting spine principle. The fibres will feed one high-resolution (R∼20,000) and two medium resolution (R∼5000) spectrographs with fixed 3-channel designs and identical 6k x 6k CCD detectors. 4MOST will have a unique operations concept in which 5-year public surveys from both the consortium and the ESO community will be combined and observed in parallel during each exposure. The 4MOST Facility Simulator (4FS) was developed to demonstrate the feasibility of this observing concept, showing that we can expect to observe more than 25 million objects in each 5-year survey period and will eventually be used to plan and conduct the actual survey.
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- Giannone, Domenico, et al.
(author)
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High Performance Multichannel Photonic Biochip Sensors for Future Point of Care Diagnostics : an Overview on Two EU-Sponsored Projects
- 2010
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In: SPIE Proc. 7715 BIOPHOTONICS - PHOTONIC SOLUTIONS FOR BETTER HEALTH CARE II. - : SPIE. - 9780819481887 ; , s. 77150U-1-77150U-12
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Conference paper (peer-reviewed)abstract
- We present here research work on two optical biosensors which have been developed within two separate European projects (6(th) and 7(th) EU Framework Programmes). The biosensors are based on the idea of a disposable biochip, integrating photonics and microfluidics, optically interrogated by a multichannel interrogation platform. The objective is to develop versatile tools, suitable for performing screening tests at Point of Care or for example, at schools or in the field. The two projects explore different options in terms of optical design and different materials. While SABIO used Si(3)N(4)/SiO(2) ring resonators structures, P3SENS aims at the use of photonic crystal devices based on polymers, potentially a much more economical option. We discuss both approaches to show how they enable high sensitivity and multiple channel detection. The medium term objective is to develop a new detection system that has low cost and is portable but at the same time offering high sensitivity, selectivity and multiparametric detection from a sample containing various components (e. g. blood, serum, saliva, etc.). Most biological sensing devices already present on the market suffer from limitations in multichannel operation capability (either the detection of multiple analytes indicating a given pathology or the simultaneous detection of multiple pathologies). In other words, the number of different analytes that can be detected on a single chip is very limited. This limitation is a main issue addressed by the two projects. The excessive cost per test of conventional bio sensing devices is a second issue that is addressed.
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| 4. |
- Gustafsson, Oskar, 1990-
(author)
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Some Contributions to Heteroscedastic Time Series Analysis and Computational Aspects of Bayesian VARs
- 2020
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Doctoral thesis (other academic/artistic)abstract
- Time-dependent volatility clustering (or heteroscedasticity) in macroeconomic and financial time series has been analyzed for more than half a century. The inefficiencies it causes in various inference procedures are well known and understood. Despite this, heteroscedasticity is surprisingly often neglected in practical work. The correct way is to model the variance jointly with the other properties of the time series by using some of the many methods available in the literature. In the first two papers of this thesis, we explore a third option, that is rarely used in the literature, in which we first remove the heteroscedasticity and only then fit a simpler model to the homogenized data.In the first paper, we introduce a filter that removes heteroscedasticity from simulated data without affecting other time series properties. We show that filtering the data leads to efficiency gains when estimating parameters in ARMA models, and in some cases to higher forecast precision for US GDP growth.The work of the first paper is extended to the case of multivariate time series in Paper II. In this paper, the stochastic volatility model is used for tracking the latent evolution of the time series variances. Also in this scenario variance stabilization offers efficiency gains when estimating model parameters.During the last decade, there has been an increasing interest in using large-scale VARs together with Bayesian shrinkage methods. The rich parameterization together with the need for simulations methods results in a computational bottleneck that either force concessions regarding the flexibility of the model or the size of the data set. In the last two papers, we address these issues with methods from the machine learning literature. In Paper III, we develop a new Bayesian optimization strategy for finding optimal hyperparameters for econometric models via maximization of the marginal likelihood. We illustrate that the algorithm finds optimal values fast compared to conventional methods. Finally, in Paper IV we present a fast variational inference (VI) algorithm for approximating the parameter posterior and predictive distribution of the steady-state BVAR. We show that VI produces results that are very close to those of the conventional Gibbs sampler but are obtained at a much lower computational cost. This is illustrated in both a simulation study and on US macroeconomic data.
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| 7. |
- Kazmierczak, Andrzej, et al.
(author)
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High quality optical microring resonators in Si3N 4/SiO2
- 2008
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In: Proceedings of the 14th European Conference on Integrated Optics - ECIO'08 Eindhoven. - 9789038613178 ; , s. 313-316
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Conference paper (peer-reviewed)abstract
- We have experimentally demonstrated high Q-factors strip waveguide resonators using the Si3N4/SiO2 material platform at the wavelength of 1.31μm. The analyzed filters demonstrate high quality factors reaching 133,000. The dependence on resonator radii and coupling gap is also discussed.
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| 8. |
- Kazmierczak, Andrzej, et al.
(author)
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Light coupling and distribution for Si3N4/SiO2 integrated multichannel single-mode sensing system
- 2009
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In: Optical Engineering. - : SPIE-Intl Soc Optical Eng. - 0091-3286 .- 1560-2303. ; 48:1
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Journal article (peer-reviewed)abstract
- We present an efficient and highly alignment-tolerant light coupling and distribution system for a multichannel Si3N4/SiO2 single-mode photonics sensing chip. The design of the input and output couplers and the distribution splitters is discussed. Examples of multichannel data obtained with the system are given.
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| 9. |
- Maire, Guillaume, et al.
(author)
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High efficiency silicon nitride surface grating couplers
- 2008
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In: Optics Express. - 1094-4087. ; 16:1, s. 328-333
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Journal article (peer-reviewed)abstract
- High efficiency surface grating couplers for silicon nitride waveguides have been designed, fabricated, and characterized. Coupling efficiencies exceeding 60 % are reported at a wavelength of 1.31 mu m, as well as angular and wavelength -3 dB tolerances of 4 and 50 nm, respectively. When the wavelength is increased from 1310 nm to 1450 nm the coupling efficiency progressively decreases but remains above 20 % at 1450 nm. The influence of the duty ratio of the grating has also been investigated: maximum coupling efficiency was obtained at 50 % duty ratio.
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