There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

/pdf/the-observation-of-gravitational-waves-from-a-binary-black-58srpupgg9.pdf

The Observation of Gravitational Waves from a Binary Black Hole Merger

Microwave photonics, which brings together the worlds of radiofrequency engineering and optoelectronics, has attracted great interest from both the research community and the commercial sector over the past 30 years and is set to have a bright future. The technology makes it possible to have functions in microwave systems that are complex or even not directly possible in the radiofrequency domain and also creates new opportunities for telecommunication networks. Here we introduce the technology to the photonics community and summarize recent research and important applications.

Microwave photonics combines two worlds

An overview of analog microwave photonics will be presented. The performance requirements for externally-modulated analog microwave photonic links will be reviewed with specific emphasis placed on modulator efficiency, laser noise, detected photocurrent, and link linearity.

http://ieeexplore.ieee.org/iel5/6387506/6403300/06403360.pdf

Microwave photonics

We propose and demonstrate transmission of MIMO radio signals over optical fibre using a novel phase quadrature double sideband frequency translation technique which employs fewer LO sources than SCM and does not require WDM.

Transmission of MIMO radio signals over fibre using a novel phase quadrature double sideband frequency translation technique

Impact of sub-wavelength-size dielectric particles on Zenneck surface waves on planar metallic antennas is investigated at terahertz (THz) frequencies with THz near-field probe microscopy Perturbations of the surface waves show the particle presence, despite its sub-wavelength size The experimental configuration, which utilizes excitation of surface waves at metallic edges, is suitable for THz imaging of dielectric sub-wavelength size objects As a proof of concept, the effects of a small strontium titanate rectangular particle and a titanium dioxide sphere on the surface field of a bow-tie antenna are experimentally detected and verified using full-wave simulations

/pdf/terahertz-imaging-of-sub-wavelength-particles-with-zenneck-14zq2flgco.pdf

Terahertz imaging of sub-wavelength particles with Zenneck surface waves

The paper describes the use of an avalanche diode to provide the combined functions of optical detection and harmonic electrical mixing. A simple analytic theory of avalanche optoelectronic mixer operation is presented and used to evaluate the conversion loss and noise performance of the mixer. The theoretical predictions are compared with experimental measurements of harmonic optoelectronic mixing up to the fifth harmonic. Measured conversion losses relative to direct optical detection ranged from 3 dB for fundamental mixing to IS dB for fifth-harmonic mixing. Frequency response limitations are briefly discussed.

Avalanche diode harmonic optoelectronic mixer

A theory of large-signal Impatt oscillator operation, including the effects of both constant and modulated optical carrier generation, is developed. This theory is related to easily measurable parameters of the particular device and predicts useful oscillator locking ranges for modest modulated optical-power levels. Computer simulations of practical device structures, under optical control, supplement the analytical work. The paper concludes with some recent results from an experiment in which optical subharmonic locking of an X-band Impatt oscillator has been achieved.

Analysis of the optically controlled Impatt (Opcad) oscillator

A comparison between the performance of modified first-order and second-order optical phase-lock loops (OPLL's) is made, revealing that the modified first-order loop offers better performance when long loop delay time is present and a wide bandwidth loop filter is used. The introduction of a 10 dB gain margin from the critical gain can be used to keep the damping close to that expected when the delay time is negligible. If OPLL design is optimized for this gain margin and 5 MHz linewidth lasers are used, the increase in the phase-error variance with delay time is 54 rad/sup 2///spl mu/s for a modified first-order and 80 rad/sup 2///spl mu/s for a second-order loop, confirming that modified first-order loops are less sensitive to loop delay. >

Alwyn J. Seeds

Papers

Transmission of MIMO radio signals over fibre using a novel phase quadrature double sideband frequency translation technique

Terahertz imaging of sub-wavelength particles with Zenneck surface waves

Avalanche diode harmonic optoelectronic mixer

Analysis of the optically controlled Impatt (Opcad) oscillator

Comparison between first-order and second-order optical phase-lock loops