romikgosai/squad_modified huggingface dataset:
In quantum mechanics and quantum field theory, the vacuum is defined as the state (that is, the solution to the equations of the theory) with the lowest possible energy (the ground state of the Hilbert space). In quantum electrodynamics this vacuum is referred to as 'QED vacuum' to distinguish it from the vacuum of quantum chromodynamics, denoted as QCD vacuum. QED vacuum is a state with no matter particles (hence the name), and also no photons. As described above, this state is impossible to achieve experimentally. (Even if every matter particle could somehow be removed from a volume, it would be impossible to eliminate all the blackbody photons.) Nonetheless, it provides a good model for realizable vacuum, and agrees with a number of experimental observations as described next.

Questions and answers:
['
Q: The state with the lowest possible energy in quantum mechanics defines what ?
A: vacuum', '
Q: A vacuum state with no matter particles or photons is called what?
A: QED', '
Q: why is a QED vacuum impossible to achieve ?
A: impossible to eliminate all the blackbody photons', '
Q: What is a QCD?
A: vacuum of quantum chromodynamics,']
QED vacuum has interesting and complex properties. In QED vacuum, the electric and magnetic fields have zero average values, but their variances are not zero. As a result, QED vacuum contains vacuum fluctuations (virtual particles that hop into and out of existence), and a finite energy called vacuum energy. Vacuum fluctuations are an essential and ubiquitous part of quantum field theory. Some experimentally verified effects of vacuum fluctuations include spontaneous emission and the Lamb shift. Coulomb's law and the electric potential in vacuum near an electric charge are modified.

Questions and answers:
['
Q: When are electric and magnetic fields with zero average values, but their variances are not at zero?
A: In QED vacuum', '
Q: What is a verified effect of vacuum fluctuation?
A: spontaneous emission', '
Q: what is  vacuum fluctuation?
A: virtual particles that hop into and out of existence', '
Q: Finite energy in a QED is called what?
A: vacuum energy', "
Q: What modifies can Coulomb's Law in a vacuum?
A: vacuum near an electric charge"]
Stars, planets, and moons keep their atmospheres by gravitational attraction, and as such, atmospheres have no clearly delineated boundary: the density of atmospheric gas simply decreases with distance from the object. The Earth's atmospheric pressure drops to about 6998320000000000000♠3.2×10−2 Pa at 100 kilometres (62 mi) of altitude, the Kármán line, which is a common definition of the boundary with outer space. Beyond this line, isotropic gas pressure rapidly becomes insignificant when compared to radiation pressure from the Sun and the dynamic pressure of the solar winds, so the definition of pressure becomes difficult to interpret. The thermosphere in this range has large gradients of pressure, temperature and composition, and varies greatly due to space weather. Astrophysicists prefer to use number density to describe these environments, in units of particles per cubic centimetre.

Questions and answers:
['
Q: `Why does thermosphere past the Karman line vary so greatly?
A: due to space weather', '
Q: What is commonly known as the boundary of outer space?
A: the Kármán line', '
Q: What do Astrophysicists use to describe outer space beyond the karman line?
A: number density', '
Q: What is more significant than isotropic gas pressure past the Karman line?
A: radiation pressure from the Sun and the dynamic pressure of the solar winds']
Vacuum is useful in a variety of processes and devices. Its first widespread use was in the incandescent light bulb to protect the filament from chemical degradation. The chemical inertness produced by a vacuum is also useful for electron beam welding, cold welding, vacuum packing and vacuum frying. Ultra-high vacuum is used in the study of atomically clean substrates, as only a very good vacuum preserves atomic-scale clean surfaces for a reasonably long time (on the order of minutes to days). High to ultra-high vacuum removes the obstruction of air, allowing particle beams to deposit or remove materials without contamination. This is the principle behind chemical vapor deposition, physical vapor deposition, and dry etching which are essential to the fabrication of semiconductors and optical coatings, and to surface science. The reduction of convection provides the thermal insulation of thermos bottles. Deep vacuum lowers the boiling point of liquids and promotes low temperature outgassing which is used in freeze drying, adhesive preparation, distillation, metallurgy, and process purging. The electrical properties of vacuum make electron microscopes and vacuum tubes possible, including cathode ray tubes. The elimination of air friction is useful for flywheel energy storage and ultracentrifuges.

Questions and answers:
['
Q: What was the object to use first in widespread manner process of vacuum?
A: incandescent light bulb', '
Q: What is produced by a vacuum and used in electron beam welding and vacuum frying?
A: chemical inertness', '
Q: Hight to ultra-high vacuums removes what obstruction?
A: obstruction of air,', '
Q: How does freeze drying, distillation and metallurgy benefit from a deep vacuum?
A: Deep vacuum lowers the boiling point of liquids and promotes low temperature outgassing', '
Q: What are two things made possible by the electrical properties of vacuum?
A: electron microscopes and vacuum tubes']
Manifold vacuum can be used to drive accessories on automobiles. The best-known application is the vacuum servo, used to provide power assistance for the brakes. Obsolete applications include vacuum-driven windscreen wipers and Autovac fuel pumps. Some aircraft instruments (Attitude Indicator (AI) and the Heading Indicator (HI)) are typically vacuum-powered, as protection against loss of all (electrically powered) instruments, since early aircraft often did not have electrical systems, and since there are two readily available sources of vacuum on a moving aircraft—the engine and an external venturi. Vacuum induction melting uses electromagnetic induction within a vacuum.

Questions and answers:
['
Q: What provides power assistance for auto brakes?
A: vacuum servo', '
Q: What are two available sources of vacuum on a moving airplane?
A: engine and an external venturi', '
Q: Why are the Attitude indicator and heading indicator vacuum-powered?
A: protection against loss of all (electrically powered) instruments,', '
Q: What does a manifold vacuum do on a car?
A: drive accessories', '
Q: What no longer used accessories were powered by vacuum?
A: vacuum-driven windscreen wipers and Autovac fuel pumps']
Evaporation and sublimation into a vacuum is called outgassing. All materials, solid or liquid, have a small vapour pressure, and their outgassing becomes important when the vacuum pressure falls below this vapour pressure. In man-made systems, outgassing has the same effect as a leak and can limit the achievable vacuum. Outgassing products may condense on nearby colder surfaces, which can be troublesome if they obscure optical instruments or react with other materials. This is of great concern to space missions, where an obscured telescope or solar cell can ruin an expensive mission.

Questions and answers:
['
Q: what is evaporation and sublimation in a vacuum?
A: outgassing', '
Q: Why can outgassing products ruin a space mission?
A: obscure optical instruments', '
Q: When does outgassing become important in all solid or liquid materials?
A: vacuum pressure falls below this vapour pressure']
To continue evacuating a chamber indefinitely without requiring infinite growth, a compartment of the vacuum can be repeatedly closed off, exhausted, and expanded again. This is the principle behind positive displacement pumps, like the manual water pump for example. Inside the pump, a mechanism expands a small sealed cavity to create a vacuum. Because of the pressure differential, some fluid from the chamber (or the well, in our example) is pushed into the pump's small cavity. The pump's cavity is then sealed from the chamber, opened to the atmosphere, and squeezed back to a minute size.

Questions and answers:
['
Q: Repeatedly closing off a compartment of a vacuum allows what?
A: continue evacuating a chamber indefinitely without requiring infinite growth', '
Q: How is a vacuum created inside of a manual water pump?
A: a mechanism expands a small sealed cavity', '
Q: Why is fluid in a manual pump pushed into the pumps cavity when a small sealed cavity is expanded?
A: Because of the pressure differential', '
Q: What are pumps based off principle of sealed compartment pulling,pushing and expanding called?
A: displacement pumps']
The above explanation is merely a simple introduction to vacuum pumping, and is not representative of the entire range of pumps in use. Many variations of the positive displacement pump have been developed, and many other pump designs rely on fundamentally different principles. Momentum transfer pumps, which bear some similarities to dynamic pumps used at higher pressures, can achieve much higher quality vacuums than positive displacement pumps. Entrapment pumps can capture gases in a solid or absorbed state, often with no moving parts, no seals and no vibration. None of these pumps are universal; each type has important performance limitations. They all share a difficulty in pumping low molecular weight gases, especially hydrogen, helium, and neon.

Questions and answers:
['
Q: What pump can capture gases in a solid or absorbed state?
A: Entrapment pumps', '
Q: Entrapment pumps often work without seals, moving parts and what else?
A: no vibration.', '
Q: What pump has a higher quality vacuum than a positive displacement pump?
A: Momentum transfer pumps']
The lowest pressure that can be attained in a system is also dependent on many things other than the nature of the pumps. Multiple pumps may be connected in series, called stages, to achieve higher vacuums. The choice of seals, chamber geometry, materials, and pump-down procedures will all have an impact. Collectively, these are called vacuum technique. And sometimes, the final pressure is not the only relevant characteristic. Pumping systems differ in oil contamination, vibration, preferential pumping of certain gases, pump-down speeds, intermittent duty cycle, reliability, or tolerance to high leakage rates.

Questions and answers:
['
Q: When multiple pumps are connected in series to produce higher vacuum it is called what?
A: stages', '
Q: The choice of seals, or chamber geometry ,for example impact a pump. Together these are options are called what?
A: vacuum technique', '
Q: What are two other relevant characteristics of a pumping system along with final pressure?
A: oil contamination, vibration']
The Han dynasty (Chinese: 漢朝; pinyin: Hàn cháo) was the second imperial dynasty of China, preceded by the Qin dynasty (221–207 BC) and succeeded by the Three Kingdoms period (220–280 AD). Spanning over four centuries, the Han period is considered a golden age in Chinese history. To this day, China's majority ethnic group refers to itself as the "Han people" and the Chinese script is referred to as "Han characters". It was founded by the rebel leader Liu Bang, known posthumously as Emperor Gaozu of Han, and briefly interrupted by the Xin dynasty (9–23 AD) of the former regent Wang Mang. This interregnum separates the Han dynasty into two periods: the Western Han or Former Han (206 BC – 9 AD) and the Eastern Han or Later Han (25–220 AD).

Questions and answers:
['
Q: What period followed the Han dynasty?
A: Three Kingdoms', '
Q: What dynasty came before the Han dynasty?
A: Qin', '
Q: Who founded the Han dynasty?
A: Liu Bang', '
Q: When did the Former Han period begin?
A: 206 BC', '
Q: When did the Later Han period end?
A: 220 AD']
The emperor was at the pinnacle of Han society. He presided over the Han government but shared power with both the nobility and appointed ministers who came largely from the scholarly gentry class. The Han Empire was divided into areas directly controlled by the central government using an innovation inherited from the Qin known as commanderies, and a number of semi-autonomous kingdoms. These kingdoms gradually lost all vestiges of their independence, particularly following the Rebellion of the Seven States. From the reign of Emperor Wu onward, the Chinese court officially sponsored Confucianism in education and court politics, synthesized with the cosmology of later scholars such as Dong Zhongshu. This policy endured until the fall of the Qing dynasty in AD 1911.

Questions and answers:
['
Q: When did the Qing dynasty fall?
A: AD 1911', '
Q: What innovation was acquired from the Qin?
A: commanderies', '
Q: What philosphy in education was sanctioned by the Chinese court?
A: Confucianism', '
Q: What was an attributing factor that caused kingdoms to lose their Independence during the Han dynasty?
A: the Rebellion of the Seven States', '
Q: What class did a majority of appointed ministers come from during the Han dynasty?
A: scholarly gentry']
The Han dynasty was an age of economic prosperity and saw a significant growth of the money economy first established during the Zhou dynasty (c. 1050–256 BC). The coinage issued by the central government mint in 119 BC remained the standard coinage of China until the Tang dynasty (618–907 AD). The period saw a number of limited institutional innovations. To pay for its military campaigns and the settlement of newly conquered frontier territories, the government nationalized the private salt and iron industries in 117 BC, but these government monopolies were repealed during the Eastern Han period. Science and technology during the Han period saw significant advances, including papermaking, the nautical steering rudder, the use of negative numbers in mathematics, the raised-relief map, the hydraulic-powered armillary sphere for astronomy, and a seismometer employing an inverted pendulum.

Questions and answers:
['
Q: In what year did the central government issue coins?
A: 119 BC', '
Q: What industry did the government use to help pay for its military campaigns?
A: iron', '
Q: In what period did several government monopolies become repealed?
A: Eastern Han', '
Q: A money based economy was first entrenched in what dynasty?
A: Zhou', '
Q: A seismometer during the Han dynasty used what type of pendulum?
A: inverted']
The Xiongnu, a nomadic steppe confederation, defeated the Han in 200 BC and forced the Han to submit as a de facto inferior partner, but continued their raids on the Han borders. Emperor Wu of Han (r. 141–87 BC) launched several military campaigns against them. The ultimate Han victory in these wars eventually forced the Xiongnu to accept vassal status as Han tributaries. These campaigns expanded Han sovereignty into the Tarim Basin of Central Asia, divided the Xiongnu into two separate confederations, and helped establish the vast trade network known as the Silk Road, which reached as far as the Mediterranean world. The territories north of Han's borders were quickly overrun by the nomadic Xianbei confederation. Emperor Wu also launched successful military expeditions in the south, annexing Nanyue in 111 BC and Dian in 109 BC, and in the Korean Peninsula where the Xuantu and Lelang Commanderies were established in 108 BC.

Questions and answers:
['
Q: Which confederation defeated the Han in 200 BC?
A: The Xiongnu', '
Q: What type of campaign helped establish the Silk Road?
A: military', '
Q: In what year was Nanyue annexed?
A: 111 BC', "
Q: Which confederation conquered the territories north of the Han's border?
A: Xianbei", "
Q: In what year did Emperor Wu of Han's reign end?
A: 87 BC"]
After 92 AD, the palace eunuchs increasingly involved themselves in court politics, engaging in violent power struggles between the various consort clans of the empresses and empress dowagers, causing the Han's ultimate downfall. Imperial authority was also seriously challenged by large Daoist religious societies which instigated the Yellow Turban Rebellion and the Five Pecks of Rice Rebellion. Following the death of Emperor Ling (r. 168–189 AD), the palace eunuchs suffered wholesale massacre by military officers, allowing members of the aristocracy and military governors to become warlords and divide the empire. When Cao Pi, King of Wei, usurped the throne from Emperor Xian, the Han dynasty ceased to exist.

Questions and answers:
['
Q: Which religious societies instigated the Yellow Turban Rebellion?
A: Daoist', '
Q: Who killed the palace eunichs after the death of Emperor Ling?
A: military officers', '
Q: Who was the last Emperor of the Han dynasty?
A: Xian', '
Q: Which King took the seat of power from Emperor Xian?
A: Cao Pi', '
Q: In what year did Emperor Ling die?
A: 189 AD']
China's first imperial dynasty was the Qin dynasty (221–206 BC). The Qin unified the Chinese Warring States by conquest, but their empire became unstable after the death of the first emperor Qin Shi Huangdi. Within four years, the dynasty's authority had collapsed in the face of rebellion. Two former rebel leaders, Xiang Yu (d. 202 BC) of Chu and Liu Bang (d. 195 BC) of Han, engaged in a war to decide who would become hegemon of China, which had fissured into 18 kingdoms, each claiming allegiance to either Xiang Yu or Liu Bang. Although Xiang Yu proved to be a capable commander, Liu Bang defeated him at Battle of Gaixia (202 BC), in modern-day Anhui. Liu Bang assumed the title "emperor" (huangdi) at the urging of his followers and is known posthumously as Emperor Gaozu (r. 202–195 BC). Chang'an was chosen as the new capital of the reunified empire under Han.

Questions and answers:
['
Q: With what action did the Qin bring together the Chinese Warring States?
A: conquest', '
Q: Which commander did Liu Bang defeat in the Battle of Gaixia?
A: Xiang Yu', '
Q: Who was the first emperor during the Qin dynasty?
A: Qin Shi Huangdi', "
Q: What ultimately caused the Qin dynasty's authority to be dissolved?
A: rebellion", '
Q: Who urged Liu Bang to become emperor?
A: his followers']
At the beginning of the Western Han dynasty, thirteen centrally controlled commanderies—including the capital region—existed in the western third of the empire, while the eastern two-thirds were divided into ten semi-autonomous kingdoms. To placate his prominent commanders from the war with Chu, Emperor Gaozu enfeoffed some of them as kings. By 157 BC, the Han court had replaced all of these kings with royal Liu family members, since the loyalty of non-relatives to the throne was questioned. After several insurrections by Han kings—the largest being the Rebellion of the Seven States in 154 BC—the imperial court enacted a series of reforms beginning in 145 BC limiting the size and power of these kingdoms and dividing their former territories into new centrally controlled commanderies. Kings were no longer able to appoint their own staff; this duty was assumed by the imperial court. Kings became nominal heads of their fiefs and collected a portion of tax revenues as their personal incomes. The kingdoms were never entirely abolished and existed throughout the remainder of Western and Eastern Han.

Questions and answers:
['
Q: How many commanderies were in the western third of the empire?
A: thirteen', '
Q: Who could appoint staff to the kings?
A: imperial court', '
Q: When was the Rebellion of the Seven States?
A: 154 BC', '
Q: From what source did kings derive their personal income from?
A: tax revenues', '
Q: The Han court replaced several kings with members of what royal family?
A: Liu']
To the north of China proper, the nomadic Xiongnu chieftain Modu Chanyu (r. 209–174 BC) conquered various tribes inhabiting the eastern portion of the Eurasian Steppe. By the end of his reign, he controlled Manchuria, Mongolia, and the Tarim Basin, subjugating over twenty states east of Samarkand. Emperor Gaozu was troubled about the abundant Han-manufactured iron weapons traded to the Xiongnu along the northern borders, and he established a trade embargo against the group. Although the embargo was in place, the Xiongnu found traders willing to supply their needs. Chinese forces also mounted surprise attacks against Xiongnu who traded at the border markets. In retaliation, the Xiongnu invaded what is now Shanxi province, where they defeated the Han forces at Baideng in 200 BC. After negotiations, the heqin agreement in 198 BC nominally held the leaders of the Xiongnu and the Han as equal partners in a royal marriage alliance, but the Han were forced to send large amounts of tribute items such as silk clothes, food, and wine to the Xiongnu.

Questions and answers:
['
Q: Who was the chieftain of the Xiongnu?
A: Modu Chanyu', '
Q: What group had a trade embargo created against them?
A: the Xiongnu', '
Q: In what year were Han forces defeated in Baideng?
A: 200 BC', '
Q: What agreement established equality between the Xiongnu and the Han?
A: heqin', '
Q: What type of clothing were sent as a tribute to the Xiongnu?
A: silk clothes']
Despite the tribute and a negotiation between Laoshang Chanyu (r. 174–160 BC) and Emperor Wen (r. 180–157 BC) to reopen border markets, many of the Chanyu's Xiongnu subordinates chose not to obey the treaty and periodically raided Han territories south of the Great Wall for additional goods. In a court conference assembled by Emperor Wu (r. 141–87 BC) in 135 BC, the majority consensus of the ministers was to retain the heqin agreement. Emperor Wu accepted this, despite continuing Xiongnu raids. However, a court conference the following year convinced the majority that a limited engagement at Mayi involving the assassination of the Chanyu would throw the Xiongnu realm into chaos and benefit the Han. When this plot failed in 133 BC, Emperor Wu launched a series of massive military invasions into Xiongnu territory. Chinese armies captured one stronghold after another and established agricultural colonies to strengthen their hold. The assault culminated in 119 BC at the Battle of Mobei, where the Han commanders Huo Qubing (d. 117 BC) and Wei Qing (d. 106 BC) forced the Xiongnu court to flee north of the Gobi Desert.

Questions and answers:
['
Q: The heqin agreement was reaffirmed by a court conference in what year?
A: 135 BC', '
Q: In what year did Emperor Wu begin a series of attacks in Xiongnu territories?
A: 133 BC', '
Q: What type of colony did Chinese armies use to help firm their hold on the strongholds that they had taken over?
A: agricultural', '
Q: In what year did the Battle of Mobei take place?
A: 119 BC', '
Q: Which Han commander died in the year 106 BC?
A: Wei Qing']
In 121 BC, Han forces expelled the Xiongnu from a vast territory spanning the Hexi Corridor to Lop Nur. They repelled a joint Xiongnu-Qiang invasion of this northwestern territory in 111 BC. In that year, the Han court established four new frontier commanderies in this region: Jiuquan, Zhangyi, Dunhuang, and Wuwei. The majority of people on the frontier were soldiers. On occasion, the court forcibly moved peasant farmers to new frontier settlements, along with government-owned slaves and convicts who performed hard labor. The court also encouraged commoners, such as farmers, merchants, landowners, and hired laborers, to voluntarily migrate to the frontier.

Questions and answers:
['
Q: Who made up a majority of the people on the frontier?
A: soldiers', '
Q: Who forced peasant farmers to move to new settlements?
A: the court', '
Q: In what year did Han forces stop a joint Xiongnu-Qiang invasion?
A: 111 BC', '
Q: Where were landowners encouraged to migrate willingly to?
A: the frontier', '
Q: How many commanderies in the new frontier were created by the Han court in the year 111 BC?
A: four']