London : An evolving city
C The drawbacks of big cities This photo must have been taken quite a few years ago as the clothes of the policeman are old-fashioned and the photo is in black and white The photo may have been taken in London as we can see an urban area and there is a “bobby”: a British policeman
Big Data: Uses and Limitations
3 Definitions of Big Data (or lack thereof) • Wikipedia: “Big data is the term for a collection of data sets so large and complex that it becomes difficult to process using on-
Too Big To Fail: The Pros and Cons of Breaking Up Big Banks
re the nation’s biggest banks too big? Many people think so Some econo - mists and policymakers have called for breaking up the largest banks and strictly limiting how large banks can become 1 U S banks, on average, have grown increasingly larger over time, while the total number of banks has declined As the chart
THE PROS AND CONS OF USING BIG DATA IN AUDITING: A SYNTHESIS
THE PROS AND CONS OF USING BIG DATA IN AUDITING: A SYNTHESIS OF THE LITERATURE Abstract With corporate investment in Big Data of $34 billion in 2013 growing to $232 billion through 2016 (Gartner 2012), the Big 4 professional service firms are aiming to be at the forefront of Big Data implementations
YouTube TV has some nifty features - and some big drawbacks
some big drawbacks 5 April 2017, by Anick Jesdanun In this Tuesday, Feb 28, 2017, file photo, YouTube CEO Susan Wojicki speaks during the introduction of YouTube TV at YouTube Space LA in Los
Multicenter assessment of the Brain Injury Guidelines and a
The BIG do have some drawbacks The guidelines have only been validated at the institution at which they were developed Although both prospective and retrospective analyses have been completed, further independent validation is required before the guidelines can be widely implemented 12 13 The BIG are often vague in defining specific aspects of
The Impact of the Railroad - California State University
annals of California history as the Big Four Judah also was instrumental in securing government aid for the construction of the railroad Building the railroad was a monumental undertaking The greatest challenge was laying rails through the heart of the Sierra Nevada After six years of toil, the railroad was completed with
Using Workplace Assessments: Pros and Cons
Many personality tests, for example, are based on the ˝The Big Five ˛ theory of personality that was developed almost 100 years ago, originally for use in the armed forces ˝Personality ˛ (at least in the assessment world) can be thought of as an individual ˇs typical or preferred way of behaving, thinking and feeling Big 5 measures
VLF & ULF Signals, Receivers & Antennas - thenackcom
• 50Hz interference is a big problem (audible) • Filter out broadcast station (overload & detection) – easy to achieve – Can use filters in a purpose-designed receiver, get about 40dB attenuation at 50Hz and 20kHz, or – Record signals and process on a PC with Spectrum Lab , Spectran , or
[PDF] london global city pdf
[PDF] global cities spaces and exchanges
[PDF] la performance globale de l'entreprise pdf
[PDF] performance globale définition
[PDF] mesure de la performance globale des entreprises
[PDF] reynaud 2003 la performance globale
[PDF] qu'est-ce que la performance globale
[PDF] bourguignon 1995
[PDF] concept de performance globale
[PDF] performance globale de l'entreprise définition
[PDF] repérage sur une sphère
[PDF] couple diaphragme vitesse et sensibilité iso
[PDF] ouverture vitesse et iso le triangle d'exposition
[PDF] tableau ouverture vitesse a imprimer
Spectrum of interest - 300Hz to 3kHz (ULF)
- 3kHz to 15kHz (part VLF) - There are Schumann resonances around 5-50Hz, but not as easy to receive.Sounds to listen for - Atmospherics
- Tweeks - Whistlers - Dawn ChorusHistory of atmospheric "sounds"
•First noticed by early telegraphists, and then by rural telephone customers with long telephone lines (up to 22km long - copper was cheaper then!).
•Some studies done in early 20thcentury (Barkhausen, 1919). •Became a serious subject for study post WW2. •Storey (UK, 1953) showed they are caused by lightning strikes.What sounds can you hear?
•Atmospherics ('spherics", or 'sferics") •Tweeks •Whistlers •Dawn chorusAtmospherics
•The sounds of nearby lightning strikes •Approximately 100 strikes per second world-wide •A typical cloud-to-ground stroke might be 10kA for 100μs!Tweeks
•At night when the Earth-ionosphere waveguide (slide 9) is highly conducting, the energy from an atmospheric travels with little attenuation and therefore many different ray paths can exist between the source and receiver.
•This causes group delay to increase and the effect is the arrival at the receiver of a train of pulses with a musical sound, called a "tweek".
-Dispersion causes higher frequencies to arrive just before lower frequencies, hence the sharply descending notes.
Whistlers
•Energy from lightning near the earth"s surface may travel along the Earth-ionosphere waveguide, but also enter the ionosphere and then travel along magnetic lines of force to re-enter the Earth-ionosphere waveguide in the opposite hemisphere.
•Whistlers are most evident at mid latitudes, peaking at about 50 degrees latitude. There is almost no activity at the equator and none at the poles.
•Whistlers generally originate from very powerful lightning strikes. Simplified diagram of Earth"s magnetosphere, ignoring the solar wind.Dawn Chorus
•Occurs mostly around dawn.•Believed to be generated by the interaction of high-energy electrons with VLF noise, injected into the Earth"s magnetosphere.
•Occurs more frequently during magnetic storms •Also occurs during aurorae and is then referred to as an auroral chorus.When to listen (See [5] and others)
•Over the long term, the period from two hours before sunrise until an hour after sunrise is the optimum time to listen for natural VLF
phenomena of all sorts as the amount of spherics (lightning stroke pops and crackling) is lower.•Statistically, the time between local midnight and an hour after sunrise is when the greatest number of whistlers are heard, although dusk to midnight may also have substantial activity.
•Tweeks are best heard after local sunset up to midnight.•Listen to the dawn chorus 2 hours before sunrise, for a few hours, and during magnetic storm events.
2. Receivers [1, 2, 3]
•Field strength ranges from about 5μV/m to 4mV/m [6] •Basic receiver is an audio amplifier-With a 1m whip antenna, needs front-end gain of about 30dB to achieve a good SNR for recording purposes.
-Ideal bandpass response from about 300Hz to 10kHz. •50Hz interference is a big problem (audible). •Filter out broadcast station (overload & detection) - easy to achieve.-Can use filters in a purpose-designed receiver, get about 40dB attenuation at 50Hz and 20kHz, or ...
-Record signals and process on a PC with Spectrum Lab, Spectran, or similar DSP filter programs with "brick-wall" filters.•Can use a simple (active) antenna impedance converter into a PC sound-card input, then DSP as above.
3. Antennas
•Simplest antenna is a short 1m vertical whip (E-field).-A 1m vertical whip looks like a 15pF (approx) capacitor between the signal and the input of the amplifier. Therefore the input impedance of the amplifier needs to be about 22 Megohm (or more) to lower the high-pass filter corner-frequency and reduce LF attenuation.
•To receive lower frequencies (down to 10Hz), a 10-15m long wire can be used in place of the whip. Increases SNR.
•Magnetic loop (B-field) antenna is balanced and can eliminate some interference, but requires a more complex pre-amplifier.