Petroleum Exploration History. Petroleum exploration in the Philippines dates back to 1896 with the drilling of Toledo-1 well in Cebu Island by Smith & Bell. Widespread exploration activities were carried out from the 1950s to 1970s. This video was mainly focused on education and how students brought change to the education system. The changed was made from all ages from 4 young 1st graders, to 9 high schoolers, to a college student trying to go to ole miss.

U.S. Geological Survey
Open-File Report 99-430 Online version 1.0

Public Review Draft – Digital Cartographic Standard for Geologic Map Symbolization (PostScript Implementation)

Prepared in cooperation with the Geologic Data Subcommittee of the Federal Geographic Data Committee

By the

U.S. Geological Survey

To assist in the review of the 'Public Review Draft – Digital Cartographic Standard for Geologic Map Symbolization,' a PostScript implementation of the proposed standard has been prepared. The symbols are included in EPS files that can be downloaded here.

To review this standard, please go to the Geologic Data Subcommittee's Web site, which contains all necessary instructions and materials for your review. Your comments and suggestions will be used to improve the draft standard. Please visit the site and give us your feedback.

In order to help you locate the symbols in which you are interested, we have prepared a PDF version of each EPS file. To view a PDF file of the appendix section containing a particular group of symbols, click on the appropriate section title shown below.

For help in locating a particular symbol, please see the detailed index of symbols included in the introductory text. General guidelines on symbol usage, as well as on color design and map labeling, are also found there.

The EPS files can be downloaded by following the links in the PDF document that makes up each section. The name of the EPS file that contains the geologic map symbols is shown in red in the upper right-hand corner of each page of every PDF document. These names are links to the EPS files containing the symbols.

Download a free copy of Adobe Reader(required to view the PDF documents that lead to the EPS files).

APPENDIX A

Unit 4: Exploration Of The Universemr. Mac's Page -

PLATES

For questions about the content of this report, contact Taryn Lindquist

This report will also be available from

USGS Information Services, Box 25286,
Federal Center, Denver, CO 80225
telephone: 303-202-4210; e-mail: infoservices@usgs.gov

URL of this page: https://pubs.usgs.gov/of/1999/of99-430/
Maintained by: Michael Diggles
Created: May 11, 2000
Last modified: February 24, 2009(mfd)

In signal processing, the Nyquist frequency (or folding frequency), named after Harry Nyquist, is a characteristic of a sampler, which converts a continuous function or signal into a discrete sequence. In units of cycles per second (Hz), its value is one-half of the sampling rate (samples per second).^[1][2][A] When the highest frequency (bandwidth) of a signal is less than the Nyquist frequency of the sampler, the resulting discrete-time sequence is said to be free of the distortion known as aliasing, and the corresponding sample-rate is said to be above the Nyquist rate for that particular signal.^[3][4]

In a typical application of sampling, one first chooses the highest frequency to be preserved and recreated, based on the expected content (voice, music, etc.) and desired fidelity. Then one inserts an anti-aliasing filter ahead of the sampler. Its job is to attenuate the frequencies above that limit. Finally, based on the characteristics of the filter, one chooses a sample-rate (and corresponding Nyquist frequency) that will provide an acceptably small amount of aliasing.

In applications where the sample-rate is pre-determined, the filter is chosen based on the Nyquist frequency, rather than vice versa. For example, audio CDs have a sampling rate of 44100 samples/sec. The Nyquist frequency is therefore 22050 Hz. The anti-aliasing filter must adequately suppress any higher frequencies but negligibly affect the frequencies within the human hearing range; a filter that preserves 0–20 kHz is more than adequate for this.

Folding frequency[edit]

In this example, f_s is the sampling rate, and 0.5 f_s is the corresponding Nyquist frequency. The black dot plotted at 0.6 f_s represents the amplitude and frequency of a sinusoidal function whose frequency is 60% of the sample-rate. The other three dots indicate the frequencies and amplitudes of three other sinusoids that would produce the same set of samples as the actual sinusoid that was sampled. Undersampling of the sinusoid at 0.6 f_s is what allows there to be a lower-frequency alias. If the true frequency were 0.4 f_s, there would still be aliases at 0.6, 1.4, 1.6, etc.

The red lines depict the paths (loci) of the 4 dots if we were to adjust the frequency and amplitude of the sinusoid along the solid red segment (between f_s/2 and f_s). No matter what function we choose to change the amplitude vs frequency, the graph will exhibit symmetry between 0 and f_s. This symmetry is commonly referred to as folding, and another name for f_s/2 (the Nyquist frequency) is folding frequency.^[5]

Other meanings[edit]

Early uses of the term Nyquist frequency, such as those cited above, are all consistent with the definition presented in this article. Some later publications, including some respectable textbooks, call twice the signal bandwidth the Nyquist frequency;^[6][7] this is a distinctly minority usage, and the frequency at twice the signal bandwidth is otherwise commonly referred to as the Nyquist rate.

Notes[edit]

1. ^When the function domain is distance, as in an image sampling system, the sample rate might be dots per inch and the corresponding Nyquist frequency would be in cycles per inch.

References[edit]

1. ^Grenander, Ulf (1959). Probability and Statistics: The Harald Cramér Volume. Wiley. The Nyquist frequency is that frequency whose period is two sampling intervals.
2. ^Harry L. Stiltz (1961). Aerospace Telemetry. Prentice-Hall. the existence of power in the continuous signal spectrum at frequencies higher than the Nyquist frequency is the cause of aliasing error
3. ^James J. Condon & Scott M. Ransom (2016). Essential Radio Astronomy. Princeton University Press. pp. 280–281. ISBN9781400881161.
4. ^John W. Leis (2011). Digital Signal Processing Using MATLAB for Students and Researchers. John Wiley & Sons. p. 82. ISBN9781118033807. The Nyquist rate is twice the bandwidth of the signal ... The Nyquist frequency or folding frequency is half the sampling rate and corresponds to the highest frequency which a sampled data system can reproduce without error.
5. ^Thomas Zawistowski; Paras Shah. 'An Introduction to Sampling Theory'. Retrieved 17 April 2010. Frequencies 'fold' around half the sampling frequency - which is why the [Nyquist] frequency is often referred to as the folding frequency.
6. ^Jonathan M. Blackledge (2003). Digital Signal Processing: Mathematical and Computational Methods, Software Development and Applications. Horwood Publishing. ISBN1-898563-48-9.
7. ^Paulo Sergio Ramirez Diniz, Eduardo A. B. Da Silva, Sergio L. Netto (2002). Digital Signal Processing: System Analysis and Design. Cambridge University Press. ISBN0-521-78175-2.CS1 maint: multiple names: authors list (link)

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