Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Pattern Recognition and Machine Learning

Context. We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on astrophysical parameters and variability, for sources brighter than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. Aims: A summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. Methods: The raw data collected with the Gaia instruments during the first 22 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to Gaia DR1 in terms of completeness, performance, and richness of the data products. Results: Gaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0.5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the GBP (330-680 nm) and GRP (630-1050 nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14 000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent. Conclusions: Gaia DR2 represents a major achievement for the Gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the Gaia survey which covers a very substantial fraction of the volume of our galaxy.

/pdf/gaia-data-release-2-summary-of-the-contents-and-survey-539viwt72y.pdf

Gaia Data Release 2. Summary of the contents and survey properties

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim$1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg$^2$ at a luminosity distance of $40^{+8}_{-8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Msun. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim$40 Mpc) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over $\sim$10 days. Following early non-detections, X-ray and radio emission were discovered at the transient's position $\sim$9 and $\sim$16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. (Abridged)

Multi-messenger Observations of a Binary Neutron Star Merger

This paper describes the ATLAS experiment as installed in i ts experimental cavern at point 1 at CERN. It also presents a brief overview of the expec ted performance of the detector.

http://absimage.aps.org/image/SES08/MWS_SES08-2008-020010.pdf

The ATLAS Experiment at the CERN Large Hadron Collider

基礎講座 電気泳動(Electrophoresis)

3D sensing devices are becoming increasingly prevalent in robotics, self-driving cars, human-computer interfaces, as well as consumer electronics. Recent years have seen single-photon avalanche diodes (SPADs) emerging as one of the key technologies underlying 3D time-of-flight sensors, with the capability to capture accurate 3D depth maps in a range of environmental conditions, and with low computational overhead. In particular, direct ToF SPADs (dToF), which measure the return time of back-scattered laser pulses, form the backbone of many automotive LIDAR systems. We here consider an advanced direct ToF SPAD imager with a 3D-stacked structure, integrating significant photon processing. The device generates photon timing histograms in-pixel, resulting in a maximum throughput of 100's of giga photons per second. This advance enables 3D frames to be captured at rates in excess of 1000 frames per second, even under high ambient light levels. By exploiting the re-configurable nature of the sensor, higher resolution intensity (photon counting) data may be obtained in alternate frames, and depth upscaled accordingly. We present a compact SPAD camera based on the sensor, enabling high-speed object detection and classification in both indoor and outdoor environments. The results suggest a significant potential in applications requiring fast situational awareness.

High-speed vision with a 3D-stacked SPAD image sensor

An NMOS only Class-D output driver which uses charge pump techniques in a low voltage CMOS technology is presented. Compared to conventional Class-D output stages, the given implementation shows a gate area reduction of 45%, resulting in efficiency improvements. The circuit has been simulated in a 0.13µm process and is implemented using 3.3V I/O devices. The structure does not violate any gate-oxide reliability rules.

NMOS-only Class-D output stages based on charge pump architectures

In this paper, an analytical approach for the nonlinear distorted bit error rate performance of optical orthogonal frequency division multiplexing (O-OFDM) with single photon avalanche diode (SPAD) receivers is presented. Major distortion effects of passive quenching (PQ) and active quenching (AQ) SPAD receivers are analysed in this study. The performance analysis of DC-biased O-OFDM and asymmetrically clipped O-OFDM with PQ and AQ SPAD are derived. The comparison results show the maximum optical irradiance caused by the nonlinear distortion, which limits the transmission power and bit rate. The theoretical maximum bit rate of SPAD-based OFDM is found which is up to 1~Gbits/s. This approach supplies a closed-form analytical solution for designing an optimal SPAD-based system.

Performance Analysis of SPAD-based OFDM.

An image sensor has pixels of four-transistor,
pinned-photodiode type. In each pixel, the charge
on a photodiode (22) is transferred by transfer gate
(14) to a sensing node (Vpix). Readout of reset and
read voltages is via an amplifier (36). A gain
capacitor (Ch) is connected in feedback across the
amplifier (36) and the read and reset gates are
controlled such that the pixel is reset to a virtual
ground voltage controlled by Ch and independent of
the pixel parasitic capacitance (Cp).

Improved image sensor

A new architecture for Positron Emission Tomography visible-light detectors is presented. The architecture is based on mini-SiPMs (arrays of 32 SPADs), which are locally digitized. With this architecture we expect to achieve a high fill factor while still performing an early enough analog-to-digital conversion so as to avoid interconnect parasitics common of standard SiPMs. The detector is implemented as a 14 × 10 pixel array where each pixel contains a mini-SiPM, a digital counter and individual SPAD SRAMs for disabling high DCR devices. The achieved fill factor is 29% and the expected maximum event rate is 16 kcps.

Robert Henderson

Papers

High-speed vision with a 3D-stacked SPAD image sensor

NMOS-only Class-D output stages based on charge pump architectures

Performance Analysis of SPAD-based OFDM.

Improved image sensor

A mini-SiPM array for PET detectors implemented in 0.35-µm HV CMOS technology