click links in text for more info
SUMMARY / RELATED TOPICS

Carrier-sense multiple access with collision detection

Carrier-sense multiple access with collision detection is a media access control method used most notably in early Ethernet technology for local area networking. It uses carrier-sensing to defer transmissions; this is used in combination with collision detection in which a transmitting station detects collisions by sensing transmissions from other stations while it is transmitting a frame. When this collision condition is detected, the station stops transmitting that frame, transmits a jam signal, waits for a random time interval before trying to resend the frame. CSMA/CD is a modification of pure carrier-sense multiple access. CSMA/CD is used to improve CSMA performance by terminating transmission as soon as a collision is detected, thus shortening the time required before a retry can be attempted. With the growing popularity of Ethernet switches in the 1990s, IEEE 802.3 deprecated Ethernet repeaters in 2011, making CSMA/CD and half-duplex operation less common and less important. The following procedure is used to initiate a transmission.

The procedure is complete when the frame is transmitted or a collision is detected during transmission. Is a frame ready for transmission? If not, wait for a frame. Is medium idle? If not, wait until it becomes ready. Start monitor for collision during transmission. Did a collision occur? If so, go to collision detected procedure. Reset retransmission counters and complete frame transmission; the following procedure is used to resolve a detected collision. The procedure is complete when retransmission is initiated or the retransmission is aborted due to numerous collisions. Continue transmission until minimum packet time is reached to ensure that all receivers detect the collision. Increment retransmission counter. Was the maximum number of transmission attempts reached? If so, abort transmission. Calculate and wait the random backoff period based on number of collisions. Re-enter main procedure at stage 1. Methods for collision detection are media dependent. On a shared, electrical bus such as 10BASE5 or 10BASE2, collisions can be detected by comparing transmitted data with received data or by recognizing a higher than normal signal amplitude on the bus.

On all other media, a carrier sensed on the receive channel while transmitting triggers a collision event. Repeaters or hubs detect collisions on their propagate jam signals; the collision recovery procedure can be likened to what happens at a dinner party, where all the guests talk to each other through a common medium. Before speaking, each guest politely waits for the current speaker to finish. If two guests start speaking at the same time, both wait for short, random periods of time; the hope is that by each choosing a random period of time, both guests will not choose the same time to try to speak again, thus avoiding another collision. The jam signal or jamming signal is a signal that carries a 32-bit binary pattern sent by a data station to inform the other stations of the collision and that they must not transmit; the maximum jam-time is calculated as follows: The maximum allowed diameter of an Ethernet installation is limited to 232 bits. This makes a round-trip-time of 464 bits; as the slot time in Ethernet is 512 bits, the difference between slot time and round-trip-time is 48 bits, the maximum "jam-time".

This in turn means: A station noting a collision has occurred is sending a 4 to 6 byte long pattern composed of 16 1-0 bit combinations. Note: The size of this jam signal is above the minimum allowed frame-size of 64 bytes; the purpose of this is to ensure that any other node which may be receiving a frame will receive the jam signal in place of the correct 32-bit MAC CRC, this causes the other receivers to discard the frame due to a CRC error. A late collision is a type of collision that happens further into the packet than is allowed for by the protocol standard in question. In 10 megabit shared medium Ethernet, if a collision error occurs after the first 512 bits of data are transmitted by the transmitting station, a late collision is said to have occurred. Late collisions are not re-sent by the NIC unlike collisions occurring before the first 64 octets; as a set up CSMA/CD network link should not have late collisions, the usual possible causes are full-duplex/half-duplex mismatch, exceeded Ethernet cable length limits, or defective hardware such as incorrect cabling, non-compliant number of hubs in the network, or a bad NIC.

A local collision is a collision. A NIC cannot detect a local collisions without attempting to send information. On UTP cable, a local collision is detected on the local segment only when a station detects a signal on the RX pair at the same time it is sending on the TX pair. Since the two signals are on different pairs there is no characteristic change in the signal. Collisions are only recognized on UTP; the only functional difference between half and full-duplex operation in this regard is whether or not the transmit and receive pairs are permitted to be used simultaneously. The channel capture effect is a phenomenon where one user of a shared medium "captures" the medium for a significant time. During this period, other users are denied use of the medium; this effect was first seen in networks using CSMA/CD on Ethernet. Because of this effect, the most data-intense connection dominates the multiple-access wireless channel; this happens in Ethernet links because of th

Ognjen Ožegović

Ognjen Ožegović is a Serbian professional footballer who plays as a striker for SV Darmstadt 98. Born in Gradiška, Ožegović made his first football steps with the local club Kozara and he moved to Borac Banja Luka. Subsequently, Ožegović went through the youth setup at Red Star Belgrade, where captained a team for a period, he was sent out on loan to Banat Zrenjanin, to Voždovac, in order to gain experience. In early 2014, Ožegović terminated his contract with Red Star, he subsequently signed a six-month deal with Rad, helping them avoid relegation from the top flight in the 2013–14 campaign. In the 2014 -- 15 season, Ožegović played for Borac Čačak, he scored six times for the latter side, including a long-range volley in a 3–1 win over his former club Jagodina, securing him the Goal of the Season award. In July 2015, Ožegović signed a three-year contract with Vojvodina, he netted seven league goals for the side, including a bicycle kick in a 2–0 win against Javor Ivanjica that earned him the Goal of the Season award for the second time in a row.

He scored a twice in the first leg of the third qualifying round for UEFA Europa League, in 4–0 away vicory over Sampdoria. In early 2016, Ožegović joined Super League club Changchun Yatai, he failed to score before returning to Serbia. On 31 August 2016, Ožegović signed a one-year contract with Čukarički, he scored a total of 16 goals in 25 league appearances over the course of the 2016-17 season. In addition to the regular season, Ožegović was prolific in Čukarički's 2016–17 Serbian Cup campaign, scoring in the second round against Javor and in the second leg of the semi-final against Red Star Belgrade. On 31 August 2017, Ožegović joined Partizan, he was given the number 51 shirt. He made his debut for the club on 9 September 2017, against Mladost Lučani, he scored his first goal for Partizan on 17 September 2017 against Radnički Niš in a 3–1 home league victory. On 28 September 2017, he recorded his first European goals after found the back of the net in a 2–3 home loss to Dynamo Kyiv in 2017–18 UEFA Europa League group stage second match.

He scored goal in 2–1 home victory over Young Boys, on 26 November, as Partizan advanced to the knockout stage after 13 years. On 14 April 2018, Ožegović scored his first goal in Eternal Derby, converting a penalty kick in a 2–1 defeat. On 4 September 2018, he joined Russian Premier League club FC Arsenal Tula on loan. Ožegović returned to Partizan for the 2019–20 season, he scored his first Super Liga goal on 4 August 2019, in a 4–0 win over Mačva. On 2 September 2019, Ožegović joined Darmstadt 98 on a two-year deal. Ožegović made his official debut for the Serbia U17s at the 2011 UEFA European Under-17 Championship, he subsequently represented Serbia at the 2013 UEFA European Under-19 Championship, as the team won the tournament. Four years Ožegović was named in the final 23-man squad for the 2017 UEFA European Under-21 Championship. In September 2016, Ožegović appeared in Serbia's friendly match against Qatar. In an interview for mondo.rs in summer 2017, he said that his dream was to win a title with Red Star and celebrate it in front of the north stand with Delije.

He said that his dream did not come truth because of club policy at time, which, in his words, favoured "players from Ghana and Uganda over Red Star children." When he became a potential transfer target of Partizan in late August that summer, many Partizan supporters were against their club signing him. Ožegović signed with Partizan on last day of the summer transfer window. During the official promotion at new club, sports director Ivica Iliev revealed that Ožegović started playing football with Partizan. Several days in interview for Sportski žurnal, Ožegović explained that he spent three months training with the club at the age of 13; as of 25 July 2018 As of 29 September 2016 Red Star BelgradeSerbian Cup: 2011–12PartizanSerbian Cup: 2017–18SerbiaUEFA Under-19 Championship: 2013 Ožegović is religious Orthodox Christian. He was born as the only child in family. Ognjen's father, Marinko, is a retired football goalkeeper, who played with Borac Banja Luka and Rudar Velenje. Ognjen Ožegović at FootballDatabase.eu Ognjen Ožegović at WorldFootball.net Ognjen Ožegović at Soccerbase Ognjen Ožegović – UEFA competition record

Liangzhu culture

The Liangzhu culture was the last Neolithic jade culture in the Yangtze River Delta of China. The culture was stratified, as jade, silk and lacquer artifacts were found in elite burials, while pottery was more found in the burial plots of poorer individuals; this division of class indicates that the Liangzhu period was an early state, symbolized by the clear distinction drawn between social classes in funeral structures. A pan-regional urban center had emerged at the Liangzhu city-site and elite groups from this site presided over the local centers; the Liangzhu culture was influential and its sphere of influence reached as far north as Shanxi and as far south as Guangdong. The type site at Liangzhu was discovered in Yuhang County and excavated by Shi Xingeng in 1936. A 2007 analysis of the DNA recovered from human remains shows high frequencies of Haplogroup O1 in Liangzhu culture linking this culture to modern Austronesian and Tai-Kadai populations, it is believed that the Liangzhu culture or other associated subtraditions are the ancestral homeland of Austronesian speakers.

On 6 July 2019, Liangzhu was inscribed as a UNESCO World Heritage Site. The Liangzhu Culture entered its prime about 4000 ~ 5000 years ago, but disappeared from the Taihu Lake area about 4200 years ago when it reached the peak. There are no traces in the following years in this area. Recent research has shown that the development of human settlements was interrupted several times by rising waters; this led researchers to conclude the demise of the Liangzhu culture was brought about by extreme environmental changes such as floods, as the cultural layers are interrupted by muddy or marshy and sandy–gravelly layers with buried paleo trees. Some evidence suggests that the Taihu lake was formed as an impact crater only 4500 years ago, which could help explain the disappearance of the Liangzhu culture. However, other work does not shocked minerals at Taihu Lake; the culture possessed advanced agriculture, including irrigation, paddy rice cultivation and aquaculture. Houses were constructed on stilts, on rivers or shorelines.

A new discovery of ancient city wall base relics was announced by the Zhejiang provincial government on November 29, 2007. It was concluded. A new Liangzhu Culture Museum was opened late in the year; the Liangzhu Ancient City is located in a wetland environment on the plain of river networks between Daxiong Mountain and Dazhe Mountain of the Tianmu Mountain Range. This ancient city is said to be the largest city during this time period, its interior area is 290 hectares, surrounded by clay walls. Two gates were located in the north and south walls. At its center was a palace site that spanned 30 hectares and there was evidence of an artificial flood protection design implemented within the city. Both of these constructions are said to be indicators of the social complexity developing in Liangzhu at the time. A granary may have been in place containing up to 15,000 kg of rice grain. There are numerous waterway entrances both inside and outside of the city, linking it to the river networks. Inside the city were artificial earth mounds and natural hills.

Outside of the walled area, remains are found for 700 hectares, the residences are said to be built in an urban planning system. 8 kilometers to the north various dam-like sites were found and are speculated to be an ancient flood protection system. Discovered inside and outside the city are a large number of utensils for production, living and ritual purposes represented by numerous delicate Liangzhu jade wares of cultural profoundness; the Liangzhu city-site is said to have been settled and developed with a specific purpose in mind since this area has few remains that can be traced back to earlier periods. A typical Liangzhu community, of which there are over 300 found so far, chose to live near rivers. There have been oars recovered which indicate proficiency with boats and watercraft. A Liangzhu site has provided the remains of a wooden pier and an embankment thought to have been used for protection against floods. Houses were raised on wood to help against flooding, although houses on higher ground included semi-subterranean houses with thatched roofs.

Well technology at the Miaoqian site during this period was similar to that of the earlier Hemudu period. The Liangzhu culture is said to have been more developed and complex than northern contemporaries in the Han Valley; the inhabitants of Liangzhu sites used artifact designs of "bent knee" shaped adze handles, stone untangled adzes, art styles emphasizing the use of spirals and circles, cord-marking of pottery, pottery pedestals with cut-out decorations, baked clay spindle whorls, slate reaping knives and spear points. Pottery was decorated with a red slip; these artifacts are common in neolithic Southeast Asia and the technological and economic toolkits of these societies developed in the neolithic Yangtze River area. Some of the Liangzhu pottery is reminiscent of the Shandong Longshan black "eggshell" style, however most differed and were a soft-fired gray with a black or red slip. There has been evidence of tremolite particles being used as an ingredient for crafting some of the black "eggshell" pottery.

It was determined that the black color of the pottery resulted from similar advancements in carburization and firing processes. Similarities between Liangchengzhen, the largest Dawenkou site, pottery making process and that of the Liangzhu we

Huntley, Nebraska

Huntley is a village in Harlan County, United States. The population was 44 at the 2010 census. Huntley is located at 40°12′35″N 99°17′31″W. According to the United States Census Bureau, the village has a total area of 0.35 square miles, all of it land. As of the census of 2010, there were 44 people, 19 households, 12 families living in the village; the population density was 125.7 inhabitants per square mile. There were 24 housing units at an average density of 68.6 per square mile. The racial makeup of the village was 100.0% White. Hispanic or Latino of any race were 11.4% of the population. There were 19 households of which 21.1% had children under the age of 18 living with them, 63.2% were married couples living together, 36.8% were non-families. 36.8% of all households were made up of individuals. The average household size was 2.32 and the average family size was 3.08. The median age in the village was 47 years. 25% of residents were under the age of 18. The gender makeup of the village was 52.3 % female.

As of the census of 2000, there were 67 people, 25 households, 18 families living in the village. The population density was 190.3 people per square mile. There were 28 housing units at an average density of 79.5 per square mile. The racial makeup of the village was 100.00% White. Hispanic or Latino of any race were 1.49% of the population. There were 25 households out of which 36.0% had children under the age of 18 living with them, 68.0% were married couples living together, 4.0% had a female householder with no husband present, 28.0% were non-families. 24.0% of all households were made up of individuals and 8.0% had someone living alone, 65 years of age or older. The average household size was 2.68 and the average family size was 3.28. In the village, the population was spread out with 29.9% under the age of 18, 4.5% from 18 to 24, 38.8% from 25 to 44, 17.9% from 45 to 64, 9.0% who were 65 years of age or older. The median age was 38 years. For every 100 females, there were 139.3 males. For every 100 females age 18 and over, there were 123.8 males.

As of 2000 the median income for a household in the village was $41,250, the median income for a family was $42,917. Males had a median income of $25,000 versus $18,750 for females; the per capita income for the village was $16,375. There were 4.3% of families and 5.3% of the population living below the poverty line, including no under eighteens and 20.0% of those over 64

Beloostrov

Beloostrov, from 1922 to World War II—Krasnoostrov, is a municipal settlement in Kurortny District of the federal city of St. Petersburg, located on the Sestra River, Karelian Isthmus. Population: 2,080 . Beloostrov consists of two parts: Novy Beloostrov along the railway and Stary Beloostrov several kilometers to the north belonging to Vsevolozhsky District of Leningrad Oblast under the name Sadovodstva; until the Winter War Beloostrov was the last railway station before the Russia–Finland border. Beloostrov has been a key station of the Saint Petersburg-Vyborg railroad since 1870 at the junction of Saint Petersburg–Zelenogorsk and Saint Petersburg–Sestroretsk–Beloostrov sections, being the final destination of many suburban passenger electric trains from the Finland Railroad Station

Pam Kelly

Pamela Kelly-Flowers, a native of Columbia, Louisiana is a former American women's basketball player at Louisiana Tech University. She won two national championships for the Lady Techsters, she was named to the All-American team in 1980, 1981, 1982, her school's only three-time All-American. Kelly won the 1982 Wade Trophy and the 1982 Honda Sports Award for basketball, awards presented annually to the best women's basketball player in the National Collegiate Athletic Association, she was enshrined as a charter member into the Louisiana Tech Athletic Hall of Fame in 1984, her #41 jersey was retired. She was inducted in 1992 into the Louisiana Sports Hall of Fame, she was inducted into the Women's Basketball Hall of Fame in 2007. Kelly is married to Nathan Flowers, Sr. and the couple has two sons. Her son John Flowers is a professional basketball player. Source 1982—Winner of the Honda Sports Award for basketball 1982—Wade Trophy