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52-516: The Science Citation Index (SCI) was officially launched in 1964, and later was distributed via CD / DVD . Then in 1997, Science Citation Index Expanded (SCIE) superseded SCI, and becomes available online. SCIE is now owned by Clarivate (previously the Intellectual Property and Science business of Thomson Reuters ). The indexing database covers more than 9,200 notable and significant journals , across 178 disciplines, from 1900 to

104-452: A 12×/10×/32× CD drive can write to CD-R discs at 12× speed (1.76 MB/s), write to CD-RW discs at 10× speed (1.46 MB/s), and read from CDs at 32× speed (4.69 MB/s), if the CPU and media player software permit speeds that high. Software distributors, and in particular distributors of computer games, often make use of various copy protection schemes to prevent software running from any media besides

156-416: A CD-ROM, each track can have its sectors in a different mode from the rest of the tracks. They can also coexist with audio CD tracks, which is the case of mixed mode CDs . Both Mode 1 and 2 sectors use the first 16 bytes for header information, but differ in the remaining 2,336 bytes due to the use of error correction bytes. Unlike an audio CD, a CD-ROM cannot rely on error concealment by interpolation ;

208-414: A block). Disc image formats that store raw CD-ROM sectors include CCD/IMG , CUE/BIN , and MDS/MDF . The size of a disc image created from the data in the sectors will depend on the type of sectors it is using. For example, if a CD-ROM mode 1 image is created by extracting only each sector's data, its size will be a multiple of 2,048; this is usually the case for ISO disc images . On a 74-minute CD-R, it

260-423: A chemist". In 1992, an electronic and print form of the index was derived from a core of 330 chemistry journals, within which all areas were covered. Additional information was provided from articles selected from 4,000 other journals. All chemistry subdisciplines were covered: organic, inorganic, analytical, physical chemistry, polymer, computational, organometallic, materials chemistry, and electrochemistry. By 2002,

312-466: A higher reliability of the retrieved data is required. To achieve improved error correction and detection, Mode 1, used mostly for digital data, adds a 32-bit cyclic redundancy check (CRC) code for error detection, and a third layer of Reed–Solomon error correction using a Reed-Solomon Product-like Code (RSPC). Mode 1 therefore contains 288 bytes per sector for error detection and correction, leaving 2,048 bytes per sector available for data. Mode 2, which

364-483: A proprietary interface, such as the Panasonic CD interface , LMSI/Philips, Sony and Mitsumi standards. Virtually all modern CD-ROM drives can also play audio CDs (as well as Video CDs and other data standards) when used with the right software. CD-ROM drives employ a near- infrared 780 nm laser diode . The laser beam is directed onto the disc via an opto-electronic tracking module, which then detects whether

416-489: A very similar manner (only differing from audio CDs in the standards used to store the data). Discs are made from a 1.2 mm thick disc of polycarbonate plastic , with a thin layer of aluminium to make a reflective surface. The most common size of CD-ROM is 120 mm in diameter, though the smaller Mini CD standard with an 80 mm diameter, as well as shaped compact discs in numerous non-standard sizes and molds (e.g., business card-sized media ), also exist. Data

468-468: Is a maximum. 20× was thought to be the maximum speed due to mechanical constraints until Samsung Electronics introduced the SCR-3230, a 32× CD-ROM drive which uses a ball bearing system to balance the spinning disc in the drive to reduce vibration and noise. As of 2004, the fastest transfer rate commonly available is about 52× or 10,400 rpm and 7.62 MB/s. Higher spin speeds are limited by the strength of

520-633: Is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data computers can read, but not write or erase. Some CDs, called enhanced CDs , hold both computer data and audio with the latter capable of being played on a CD player , while data (such as software or digital video) is only usable on a computer (such as ISO 9660 format PC CD-ROMs). During the 1990s and early 2000s, CD-ROMs were popularly used to distribute software and data for computers and fifth generation video game consoles . DVDs as well as downloading started to replace CD-ROMs in these roles starting in

572-584: Is defined as "1× speed". Therefore, for Mode 1 CD-ROMs, a 1× CD-ROM drive reads 150/2 = 75 consecutive sectors per second. The playing time of a standard CD is 74 minutes, or 4,440 seconds, contained in 333,000 blocks or sectors . Therefore, the net capacity of a Mode-1 CD-ROM is 650 MB (650 × 2 ). For 80 minute CDs, the capacity is 703 MB. CD-ROM XA is an extension of the Yellow Book standard for CD-ROMs that combines compressed audio, video and computer data, allowing all to be accessed simultaneously. It

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624-464: Is equal to one gigabyte (1 GB), where 1 GB is one billion bytes. Randomly addressable semiconductor memory doubles in size for each address lane added to an integrated circuit package, which favors counts that are powers of two. The capacity of a disk drive is the product of the sector size, number of sectors per track, number of tracks per side, and the number of disk platters in the drive. Changes in any of these factors would not usually double

676-418: Is more appropriate for image or video data (where perfect reliability may be a little bit less important), contains no additional error detection or correction bytes, having therefore 2,336 available data bytes per sector. Both modes, like audio CDs, still benefit from the lower layers of error correction at the frame level. Before being stored on a disc with the techniques described above, each CD-ROM sector

728-428: Is possible to fit larger disc images using raw mode, up to 333,000 × 2,352 = 783,216,000 bytes (~747 MB). This is the upper limit for raw images created on a 74 min or ≈650 MB Red Book CD. The 14.8% increase is due to the discarding of error correction data. CD-ROM capacities are normally expressed with binary prefixes , subtracting the space used for error correction data. The capacity of a CD-ROM depends on how close

780-548: Is present in the computer's CD-ROM drive. Manufacturers of CD writers ( CD-R or CD-RW ) are encouraged by the music industry to ensure that every drive they produce has a unique identifier, which will be encoded by the drive on every disc that it records: the RID or Recorder Identification Code. This is a counterpart to the Source Identification Code (SID), an eight character code beginning with " IFPI " that

832-602: Is scrambled to prevent some problematic patterns from showing up. These scrambled sectors then follow the same encoding process described in the Red Book in order to be finally stored on a CD. The following table shows a comparison of the structure of sectors in CD-DA and CD-ROMs: The net byte rate of a Mode-1 CD-ROM, based on comparison to CD-DA audio standards, is 44,100 Hz × 16 bits/sample × 2 channels × 2,048 / 2,352 / 8 = 150 KB/s (150 × 2 ) . This value, 150 Kbyte/s,

884-421: Is stored on the disc as a series of microscopic indentations called "pits", with the non-indented spaces between them called "lands". A laser is shone onto the reflective surface of the disc to read the pattern of pits and lands. Because the depth of the pits is approximately one-quarter to one-sixth of the wavelength of the laser light used to read the disc, the reflected beam 's phase is shifted in relation to

936-402: Is used for data. XA Mode 2 Form 2 has 2,324 bytes of user data, and is similar to the standard Mode 2 but with error detection bytes added (though no error correction). It can interleave with XA Mode 2 Form 1 sectors, and it is used for audio/video data. Video CDs , Super Video CDs , Photo CDs , Enhanced Music CDs and CD-i use these sector modes. The following table shows a comparison of

988-477: Is usually stamped on discs produced by CD recording plants. Megabyte The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB . The unit prefix mega is a multiplier of 1 000 000 (10 ) in the International System of Units (SI). Therefore, one megabyte is one million bytes of information. This definition has been incorporated into

1040-727: The ISO 9660 standard in 1988. One of the first products to be made available to the public on CD-ROM was the Grolier Academic Encyclopedia , presented at the Microsoft CD-ROM Conference in March 1986. CD-ROMs began being used in home video game consoles starting with the PC Engine CD-ROM (TurboGrafx-CD) in 1988, while CD-ROM drives had also become available for home computers by

1092-404: The International System of Quantities . In the computer and information technology fields, other definitions have been used that arose for historical reasons of convenience. A common usage has been to designate one megabyte as 1 048 576 bytes (2 B), a quantity that conveniently expresses the binary architecture of digital computer memory. Standards bodies have deprecated this binary usage of

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1144-432: The 1990s were called " multimedia " computers because they incorporated a CD-ROM drive, which allowed for the delivery of several hundred megabytes of video, picture, and audio data. The first laptop to have an integrated CD-ROM drive as an option was 1993's CF-V21P by Panasonic ; however, the drive only supported mini CDs up to 3.5 inches in diameter. The first notebook to support standard 4.7-inch-diameter discs

1196-775: The SI prefix kilo- , it was a convenient term to denote the binary multiple. In 1999, the International Electrotechnical Commission (IEC) published standards for binary prefixes requiring the use of megabyte to denote 1000 bytes, and mebibyte to denote 1024 bytes. By the end of 2009, the IEC Standard had been adopted by the IEEE , EU , ISO and NIST . Nevertheless, the term megabyte continues to be widely used with different meanings. In this convention, one thousand megabytes (1000 MB)

1248-406: The beam has been reflected or scattered. CD-ROM drives are rated with a speed factor relative to music CDs. If a CD-ROM is read at the same rotational speed as an audio CD , the data transfer rate is 150 Kbyte/s, commonly called "1×" (with constant linear velocity, short "CLV" ). At this data rate, the track moves along under the laser spot at about 1.2 m/s. To maintain this linear velocity as

1300-521: The company he founded, Gauss Electrophysics. The LaserDisc was the immediate precursor to the CD, with the primary difference being that the LaserDisc encoded information through an analog process whereas the CD used digital encoding. Key work to digitize the optical disc was performed by Toshi Doi and Kees Schouhamer Immink during 1979–1980, who worked on a taskforce for Sony and Philips . The result

1352-458: The core journal coverage increased to 500 and related article coverage increased to 8,000 other journals. One 1980 study reported the overall citation indexing benefits for chemistry, examining the use of citations as a tool for the study of the sociology of chemistry and illustrating the use of citation data to "observe" chemistry subfields over time. CD-ROM A CD-ROM ( / ˌ s iː d iː ˈ r ɒ m / , compact disc read-only memory )

1404-423: The data are recorded on them by a laser changing the properties of a dye or phase transition material in a process that is often referred to as " burning ". Data stored on CD-ROMs follows the standard CD data encoding techniques described in the Red Book specification (originally defined for audio CD only). This includes cross-interleaved Reed–Solomon coding (CIRC), eight-to-fourteen modulation (EFM), and

1456-504: The data stored in these sectors corresponds to any type of digital data, not audio samples encoded according to the audio CD specification. To structure, address and protect this data, the CD-ROM standard further defines two sector modes, Mode 1 and Mode 2, which describe two different layouts for the data inside a sector. A track (a group of sectors) inside a CD-ROM only contains sectors in the same mode, but if multiple tracks are present in

1508-401: The disc at 1600 to 4000 rpm, giving a linear velocity of 9.6 m/s and a transfer rate of 1200 Kbyte/s. Above 12× speed most drives read at Constant angular velocity (CAV, constant rpm) so that the motor is not made to change from one speed to another as the head seeks from place to place on the disc. In CAV mode the "×" number denotes the transfer rate at the outer edge of the disc, where it

1560-565: The early 2000s, and the use of CD-ROMs for commercial software is now uncommon. The earliest theoretical work on optical disc storage was done by independent researchers in the United States including David Paul Gregg (1958) and James Russel (1965–1975). In particular, Gregg's patents were used as the basis of the LaserDisc specification that was co-developed between MCA and Philips after MCA purchased Gregg's patents, as well as

1612-453: The end of the 1980s. In 1990, Data East demonstrated an arcade system board that supported CD-ROMs, similar to 1980s LaserDisc video games but with digital data, allowing more flexibility than older LaserDisc games. By early 1990, about 300,000 CD-ROM drives were sold in Japan, while 125,000 CD-ROM discs were being produced monthly in the United States. Some computers that were marketed in

Science Citation Index Expanded - Misplaced Pages Continue

1664-525: The first Japanese COMDEX computer show in 1985. In November 1985, several computer industry participants, including Microsoft , Philips , Sony , Apple and Digital Equipment Corporation, met to create a specification to define a file system format for CD-ROMs. The resulting specification, called the High Sierra format, was published in May 1986. It was eventually standardized, with a few changes, as

1716-549: The incoming beam, causing destructive interference and reducing the reflected beam's intensity. This is converted into binary data. Several formats are used for data stored on compact discs, known as the Rainbow Books . The Yellow Book , created in 1983, defines the specifications for CD-ROMs, standardized in 1988 as the ISO / IEC 10149 standard and in 1989 as the ECMA -130 standard. The CD-ROM standard builds on top of

1768-673: The late 1990s. Over 10 years later, commonly available drives vary between 24× (slimline and portable units, 10× spin speed) and 52× (typically CD- and read-only units, 21× spin speed), all using CAV to achieve their claimed "max" speeds, with 32× through 48× most common. Even so, these speeds can cause poor reading (drive error correction having become very sophisticated in response) and even shattering of poorly made or physically damaged media, with small cracks rapidly growing into catastrophic breakages when centripetally stressed at 10,000–13,000 rpm (i.e. 40–52× CAV). High rotational speeds also produce undesirable noise from disc vibration, rushing air and

1820-448: The mega- prefix in favor of a new set of binary prefixes , by means of which the quantity 2 B is named mebibyte (symbol MiB). The unit megabyte is commonly used for 1000 (one million) bytes or 1024 bytes. The interpretation of using base 1024 originated as technical jargon for the byte multiples that needed to be expressed by the powers of 2 but lacked a convenient name. As 1024 (2 ) approximates 1000 (10 ), roughly corresponding to

1872-412: The optical head moves to different positions, the angular velocity is varied from about 500 rpm at the inner edge to 200 rpm at the outer edge. The 1× speed rating for CD-ROM (150 Kbyte/s) is different from the 1× speed rating for DVDs (1.32 MB/s). When the speed at which the disc is spun is increased, data can be transferred at greater rates. For example, a CD-ROM drive that can read at 8× speed spins

1924-479: The original Red Book CD-DA standard for CD audio. Other standards, such as the White Book for Video CDs , further define formats based on the CD-ROM specifications. The Yellow Book itself is not freely available, but the standards with the corresponding content can be downloaded for free from ISO or ECMA. There are several standards that define how to structure data files on a CD-ROM. ISO 9660 defines

1976-432: The original CD-ROMs. This differs somewhat from audio CD protection in that it is usually implemented in both the media and the software itself. The CD-ROM itself may contain "weak" sectors to make copying the disc more difficult, and additional data that may be difficult or impossible to copy to a CD-R or disc image, but which the software checks for each time it is run to ensure an original disc and not an unauthorized copy

2028-576: The outer edge of the disc with the same rotational speed as a standard ( constant linear velocity , CLV) 12×, or 32× with a slight increase. However, due to the nature of CAV (linear speed at the inner edge is still only 12×, increasing smoothly in-between) the actual throughput increase is less than 30/12; in fact, roughly 20× average for a completely full disc, and even less for a partially filled one. Problems with vibration, owing to limits on achievable symmetry and strength in mass-produced media, mean that CD-ROM drive speeds have not massively increased since

2080-463: The outward data track is extended to the disc's outer rim. A standard 120 mm, 700 MB CD-ROM can actually hold about 703 MB of data with error correction (or 847 MB total). In comparison, a single-layer DVD-ROM can hold 4.7 GB (4.7 × 10 bytes) of error-protected data, more than 6 CD-ROMs. CD-ROM discs are read using CD-ROM drives. A CD-ROM drive may be connected to the computer via an IDE ( ATA ), SCSI , SATA , FireWire , or USB interface or

2132-536: The polycarbonate plastic of which the discs are made. At 52×, the linear velocity of the outermost part of the disc is around 65 m/s. However, improvements can still be obtained using multiple laser pickups as demonstrated by the Kenwood TrueX 72× which uses seven laser beams and a rotation speed of approximately 10×. The first 12× drive was released in late 1996. Above 12× speed, there are problems with vibration and heat. CAV drives give speeds up to 30× at

Science Citation Index Expanded - Misplaced Pages Continue

2184-523: The present. These are alternatively described as the world's leading journals of science and technology , because of a rigorous selection process. The index is available online within Web of Science , as part of its Core Collection (there are also CD and printed editions, covering a smaller number of journals). The database allows researchers to search through over 53 million records from thousands of academic journals that were published by publishers from around

2236-575: The spindle motor itself. Most 21st-century drives allow forced low speed modes (by use of small utility programs) for the sake of safety, accurate reading or silence, and will automatically fall back if numerous sequential read errors and retries are encountered. Other methods of improving read speed were trialled such as using multiple optical beams, increasing throughput up to 72× with a 10× spin speed, but along with other technologies like 90~99 minute recordable media, GigaRec and double-density compact disc ( Purple Book standard) recorders, their utility

2288-485: The standard file system for a CD-ROM. ISO 13490 is an improvement on this standard which adds support for non-sequential write-once and re-writeable discs such as CD-R and CD-RW , as well as multiple sessions . The ISO 13346 standard was designed to address most of the shortcomings of ISO 9660, and a subset of it evolved into the UDF format, which was adopted for DVDs . A bootable CD specification, called El Torito ,

2340-467: The structure of sectors in CD-ROM XA modes: When a disc image of a CD-ROM is created, this can be done in either "raw" mode (extracting 2,352 bytes per sector, independent of the internal structure), or obtaining only the sector's useful data (2,048/2,336/2,352/2,324 bytes depending on the CD-ROM mode). The file size of a disc image created in raw mode is always a multiple of 2,352 bytes (the size of

2392-407: The use of pits and lands for coding the bits into the physical surface of the CD. The structures used to group data on a CD-ROM are also derived from the Red Book . Like audio CDs (CD-DA), a CD-ROM sector contains 2,352 bytes of user data, composed of 98 frames, each consisting of 33 bytes (24 bytes for the user data, 8 bytes for error correction, and 1 byte for the sub code). Unlike audio CDs,

2444-565: The world. Clarivate previously marketed several subsets of this database, termed "Specialty Citation Indexes", such as the Neuroscience Citation Index and the Chemistry Citation Index , however these databases are no longer actively maintained. The Chemistry Citation Index was first introduced by Eugene Garfield, a chemist by training. His original "search examples were based on [his] experience as

2496-466: Was IBM 's ThinkPad 755CD in 1994. On early audio CD players that were released prior to the advent of the CD-ROM, the raw binary data of CD-ROM was played back as noise. To address this problem, the subcode channel Q has a "data" flag in areas of the disc that contain computer data rather than playable audio. The data flag instructs CD players to mute the audio. CD-ROMs are identical in appearance to audio CDs , and data are stored and retrieved in

2548-581: Was intended as a bridge between CD-ROM and CD-i ( Green Book ) and was published by Sony and Philips , and backed by Microsoft , in 1991, first announced in September 1988. "XA" stands for eXtended Architecture. CD-ROM XA defines two new sector layouts, called Mode 2 Form 1 and Mode 2 Form 2 (which are different from the original Mode 2). XA Mode 2 Form 1 is similar to the Mode 1 structure described above, and can interleave with XA Mode 2 Form 2 sectors; it

2600-468: Was issued in January 1995, to make a CD emulate a hard disk or floppy disk . Pre-pressed CD-ROMs are mass-produced by a process of stamping where a glass master disc is created and used to make "stampers", which are in turn used to manufacture multiple copies of the final disc with the pits already present. Recordable ( CD-R ) and rewritable ( CD-RW ) discs are manufactured by a different method, whereby

2652-1085: Was nullified by the introduction of consumer DVD-ROM drives capable of consistent 36× equivalent CD-ROM speeds (4× DVD) or higher. Additionally, with a 700 MB CD-ROM fully readable in under 2.5 minutes at 52× CAV, increases in actual data transfer rate are decreasingly influential on overall effective drive speed when taken into consideration with other factors such as loading/unloading, media recognition, spin up/down and random seek times, making for much decreased returns on development investment. A similar stratification effect has since been seen in DVD development where maximum speed has stabilised at 16× CAV (with exceptional cases between 18× and 22×) and capacity at 4.3 and 8.5 GB (single and dual layer), with higher speed and capacity needs instead being catered to by Blu-ray drives. CD-Recordable drives are often sold with three different speed ratings: one speed for write-once operations, one for re-write operations, and one for read-only operations. The speeds are typically listed in that order; i.e.

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2704-521: Was the Compact Disc Digital Audio (CD-DA), defined in 1980. The CD-ROM was later designed as an extension of the CD-DA, and adapted this format to hold any form of digital data, with an initial storage capacity of 553 MB . Sony and Philips created the technical standard that defines the format of a CD-ROM in 1983, in what came to be called the Yellow Book . The CD-ROM was announced in 1984 and introduced by Denon and Sony at

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