Searching Online Databases
Online searching is generally provided by and accessed through database vendors. Two
examples of such vendors are STN and
DIALOG. STN is operated cooperatively by
Fachinformationszentrum (FIZ) Karlsruhe, Chemical Abstracts Service (CAS) of the American
Chemical Society (ACS), and The Japan Science and Technology Corporation (JST),
Information Center for Science and Technology (JICST).
For the purposes of this course DIALOG lets us search some of their databases at the vaery
reasonable rate of $15 per hour and so most of the following discussion will focus on
DIALOG as a vendor. DIALOG services provide access to millions of documents in more than
450 databases which are compiled from the world's most respected and authoritative
information sources. The Complete Database Catalogue, which is available at the reference
desk, is a selection tool that helps pinpoint the right database(s) for your search.
Database descriptions are summarized in the Catalogue in the form of Bluesheets. They
contain detailed instructions on search techniques for the special features of each
database, including file description, subject coverage, date range, update frequency,
sources of the data, and the origin of the information. On each Bluesheet you will also
find a sample record that shows what you can expect to obtain when you perform a search in
the database
The most important part of the Bluesheet, however, is the Search Options section. Here you
will find the field labels that you can use to focus or narrow your search, as well as
examples of how to use them online. Bluesheets on the Web are updated regularly and
reflect the most current database information available. They also contain up-to-date
information on the cost of accessing these databases.
A broad range of disciplines are covered:
| Worldwide company information | both directory listings and full financials. |
| Industry information | trends, overviews, market research, and specialized industry newsletters and reports, U.S. and international news - an extensive collection of newspapers and newswires from North America and Asia, U.S. government news - including public affairs, law, and regulatory information. |
| Patents and trademarks | a worldwide collection for research and competitive intelligence tracking. |
| Chemistry, environment, science and technology |
technical literature and reference material to support your research needs. |
| Social Science and Humanities | including education, information science, psychology, sociology, and political science, from public opinion, news, and leading scholarly and popular publications. |
| General reference information | people, books, consumer news, and travel. |
Here is an example of a sample record from a DIALOG search:
DIALOG(R)File 6:NTIS
Comp&distr 1998 NTIS, Intl Copyright All Rights Re. All rts. reserv.
AA=,RN=1998527 NTIS Accession Number: AD-D018 520/7/XAB
TI=Sigma-Delta Modulator for Wide Bandwidth Applications (Patent Application)
AU=Fischer, G. ; Davis, A. J.
CS=Department of the Navy, Washington, DC.
CS=Corp. Source Codes: 001840000; 110050
RN=Report No.: PAT-APPL-8-854 511
PY=Filed 12 May 97 21p
LA=Languages: English Document Type: Patent
JA=Journal Announcement:
NT= This Government-owned invention available for U.S. licensing and,
possibly, for foreign licensing. Copy of application available NTIS.
Order this product from NTIS by: phone at 1-800-553-NTIS (U.S.
customers); (703)605-6000 (other countries); fax at (703)321-8547; and
email at orders ntis.fedworld.gov. NTIS is located at 5285 Port Royal
Road, Springfield, VA, 22161, USA.
PR=NTIS Prices: PC N03/MF A04
CP=Country of Publication: United States
AB= A wide-band sigma-delta modulator is disclosed having a cascade of two modulators or
stages, the first stage being of third or greater order and the second being of second or
greater order. Both stages utilize simple ternary quantizers to avoid linearity problems
associated with the digital to analog converters in the feedback paths of the modulators
and to maintain stable operation. Additional zeros are placed in the noise transfer
functions of third or higher order stages by means of additional feed back loops between
the output of the third integrator and the second summing junction to maximize the dynamic
range. The new topology significantly enhances the dynamic range of the system while
hardly affecting the circuit's sensitivity with regard to some non-idealities such as
finite amplifier open-loop gains or capacitor ratio mismatches. The excess dynamic range
gained by these additional zeros is substantial and independent of OSR, hence, the present
invention is particularly useful in wide-band applications where the OSR is inherently
low. By employing only two cascaded stages, amplifier gain and capacitor ratio matching
requirements are kept reasonably low.
/DE,/DE, Descriptors: *Patent applications; *Analog to digital converters
Assignment Notes:
1. You need to make an appointment with the Reference Librarian to carry out this search.
2. Prior to meeting with the reference librarian you should:
a. identify the databases in which you plan to search, by consulting the catalog of
databases available through DIALOG
b. construct a heirarchical list of the keywords and combinations of keywords that you
plan to use in the search.