Building
A building, or edifice, is a structure with a roof and walls standing more or less permanently in one place, such as a house or factory. Buildings come in a variety of sizes and functions, have been adapted throughout history for a wide number of factors, from building materials available, to weather conditions, land prices, ground conditions, specific uses, aesthetic reasons. To better understand the term building compare the list of nonbuilding structures. Buildings serve several societal needs – as shelter from weather, living space, privacy, to store belongings, to comfortably live and work. A building as a shelter represents a physical division of the outside. Since the first cave paintings, buildings have become objects or canvasses of much artistic expression. In recent years, interest in sustainable planning and building practices has become an intentional part of the design process of many new buildings; the word building is the act of making it. As a noun, a building is'a structure that has a roof and walls and stands more or less permanently in one place'.
In the broadest interpretation a fence or wall is a building. However, the word structure is used more broadly than building including natural and man-made formations and does not have walls. Structure is more to be used for a fence. Sturgis' Dictionary included that " differs from architecture in excluding all idea of artistic treatment; as a verb, building is the act of construction. Structural height in technical usage is the height to the highest architectural detail on building from street-level. Depending on how they are classified and masts may or may not be included in this height. Spires and masts used as antennas are not included; the definition of a low-rise vs. a high-rise building is a matter of debate, but three storeys or less is considered low-rise. A report by Shinichi Fujimura of a shelter built 500 000 years ago is doubtful since Fujimura was found to have faked many of his findings. Supposed remains of huts found at the Terra Amata site in Nice purportedly dating from 200 000 to 400 000 years ago have been called into question.
There is clear evidence of homebuilding from around 18 000 BC. Buildings became common during the Neolithic. Single-family residential buildings are most called houses or homes. Multi-family residential buildings containing more than one dwelling unit are called a duplex or an apartment building. A condominium is an apartment rather than rents. Houses may be built in pairs, in terraces where all but two of the houses have others either side. Houses which were built as a single dwelling may be divided into apartments or bedsitters. Building types may range from huts to multimillion-dollar high-rise apartment blocks able to house thousands of people. Increasing settlement density in buildings is a response to high ground prices resulting from many people wanting to live close to work or similar attractors. Other common building materials are concrete or combinations of either of these with stone. Residential buildings have different names for their use depending if they are seasonal include holiday cottage or timeshare.
If the residents are in need of special care such as a nursing home, orphanage or prison. Many people lived in communal buildings called longhouses, smaller dwellings called pit-houses and houses combined with barns sometimes called housebarns. Buildings are defined to be substantial, permanent structures so other dwelling forms such as houseboats and motorhomes are dwellings but not buildings. Sometimes a group of inter-related builds are referred to as a complex – for example a housing complex, educational complex, hospital complex, etc; the practice of designing and operating buildings is most a collective effort of different groups of professionals and trades. Depending on the size and purpose of a particular building project, the project team may include: A real estate developer who secures funding for the project. Other possible design Engineer specialists may be involved such as Fire, facade engineers, building physics, Telecomms, AV (Audio V
Spacecraft thermal control
In spacecraft design, the function of the thermal control system is to keep all the spacecraft's component systems within acceptable temperature ranges during all mission phases. It must cope with the external environment, which can vary in a wide range as the spacecraft is exposed to deep space or to solar or planetary flux, with ejecting to space the internal heat generated by the operation of the spacecraft itself. Thermal control is essential to guarantee the optimum performance and success of the mission because if a component is subjected to temperatures which are too high or too low, it could be damaged or its performance could be affected. Thermal control is necessary to keep specific components within a specified temperature stability requirement, to ensure that they perform as efficiently as possible; the thermal control subsystem can be composed both of passive and of active items and works in two ways: protects the equipment from overheating, either by thermal insulation from external heat fluxes, or by proper heat removal from internal sources.
Protects the equipment from temperatures that are too cold, by thermal insulation from external sinks, by enhanced heat absorption from external sources, or by heat release from internal sources. Passive Thermal Control System components include: Multi-layer insulation, which protects the spacecraft from excessive solar or planetary heating as well as from excessive cooling when exposed to deep space coatings that change the thermo-optical properties of external surfaces thermal fillers to improve the thermal coupling at selected interfaces thermal washers to reduce the thermal coupling at selected interfaces thermal doublers to spread on the radiator surface the heat dissipated by equipment mirrors to improve the heat rejection capability of the external radiators and at the same time to reduce the absorption of external solar fluxes radioisotope heater units, used by some planetary and exploratory missions to produce heat for TCS purposesActive Thermal Control System components include: thermostatically controlled resistive electric heaters to keep the equipment temperature above its lower limit during the mission's cold phases fluid loops to transfer the heat emitted by equipment to the radiators.
They can be: single-phase loops, controlled by a pump two-phase loops, composed of heat pipes, loop heat pipes or capillary pumped loops louvers thermoelectric coolers Environment interaction Includes the interaction of the external surfaces of the spacecraft to the environment. Either the surfaces need to be protected from the environment or there has to be improved interaction. Two main goals of environment interaction are the reduction or increase of absorbed environmental fluxes and reduction or increase of heat losses to the environment. Heat collection Includes the removal of dissipated heat from the equipment in which it is created to avoid unwanted increases in the spacecraft’s temperature. Heat transport Is taking the heat from. Heat rejection The heat collected and transported has to be rejected at an appropriate temperature to a heat sink, the surrounding space environment; the rejection temperature depends on the amount of heat involved, the temperature to be controlled and the temperature of the environment into which the device radiates the heat.
Heat provision and storage. Is to maintain a desired temperature level where heat has to be provided and suitable heat storage capability has to be foreseen. For a spacecraft the main environmental interactions are the energy coming from the sun and the heat radiated to deep space. Other parameters influence the thermal control system design such as the spacecraft’s altitude, attitude stabilization, spacecraft shape. Different types of orbit, such as low earth orbit and geostationary orbit affect the design of the thermal control system. Low Earth Orbit This orbit is used by spacecraft that monitor or measure the characteristics of the Earth and its surrounding environment and by unmanned and manned space laboratories, such as EURECA and the International Space Station; the orbit's proximity to the Earth has a great influence on the thermal control system needs, with the Earth's infrared emission and albedo playing a important role, as well as the short orbital period, less than 2 hours, long eclipse duration.
Small instruments or spacecraft appendages such as solar panels that have low thermal inertia can be affected by this continuously changing environment and may require specific thermal design solutions. Geostationary orbit In this 24-hour orbit, the Earth's influence is negligible except for the shadowing during eclipses, which can vary in duration from zero at solstice to a maximum of 1.2 hours at equinox. Long eclipses influence the design of heating systems; the seasonal variations in the direction and intensity of the solar input have a great impact on the design, complicating the heat transport by the need to convey most of the dissipated heat to the radiator in shadow, the heat-rejection systems via the increased radiator area needed. All telecommunications and many meteorological satellites are in this type of orbit. Eccentric Orbits These orbits can have a wide range of apogee and perigee altitudes, dependi
Aluminium
Aluminium or aluminum is a chemical element with symbol Al and atomic number 13. It is a silvery-white, soft and ductile metal in the boron group. By mass, aluminium makes up about 8% of the Earth's crust; the chief ore of aluminium is bauxite. Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals. Aluminium is remarkable for its low density and its ability to resist corrosion through the phenomenon of passivation. Aluminium and its alloys are vital to the aerospace industry and important in transportation and building industries, such as building facades and window frames; the oxides and sulfates are the most useful compounds of aluminium. Despite its prevalence in the environment, no known form of life uses aluminium salts metabolically, but aluminium is well tolerated by plants and animals; because of these salts' abundance, the potential for a biological role for them is of continuing interest, studies continue.
Of aluminium isotopes, only 27Al is stable. This is consistent with aluminium having an odd atomic number, it is the only aluminium isotope that has existed on Earth in its current form since the creation of the planet. Nearly all the element on Earth is present as this isotope, which makes aluminium a mononuclidic element and means that its standard atomic weight equates to that of the isotope; the standard atomic weight of aluminium is low in comparison with many other metals, which has consequences for the element's properties. All other isotopes of aluminium are radioactive; the most stable of these is 26Al and therefore could not have survived since the formation of the planet. However, 26Al is produced from argon in the atmosphere by spallation caused by cosmic ray protons; the ratio of 26Al to 10Be has been used for radiodating of geological processes over 105 to 106 year time scales, in particular transport, sediment storage, burial times, erosion. Most meteorite scientists believe that the energy released by the decay of 26Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago.
The remaining isotopes of aluminium, with mass numbers ranging from 21 to 43, all have half-lives well under an hour. Three metastable states are known, all with half-lives under a minute. An aluminium atom has 13 electrons, arranged in an electron configuration of 3s23p1, with three electrons beyond a stable noble gas configuration. Accordingly, the combined first three ionization energies of aluminium are far lower than the fourth ionization energy alone. Aluminium can easily surrender its three outermost electrons in many chemical reactions; the electronegativity of aluminium is 1.61. A free aluminium atom has a radius of 143 pm. With the three outermost electrons removed, the radius shrinks to 39 pm for a 4-coordinated atom or 53.5 pm for a 6-coordinated atom. At standard temperature and pressure, aluminium atoms form a face-centered cubic crystal system bound by metallic bonding provided by atoms' outermost electrons; this crystal system is shared by some other metals, such as copper. Aluminium metal, when in quantity, is shiny and resembles silver because it preferentially absorbs far ultraviolet radiation while reflecting all visible light so it does not impart any color to reflected light, unlike the reflectance spectra of copper and gold.
Another important characteristic of aluminium is its low density, 2.70 g/cm3. Aluminium is a soft, lightweight and malleable with appearance ranging from silvery to dull gray, depending on the surface roughness, it is nonmagnetic and does not ignite. A fresh film of aluminium serves as a good reflector of visible light and an excellent reflector of medium and far infrared radiation; the yield strength of pure aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa. Aluminium has stiffness of steel, it is machined, cast and extruded. Aluminium atoms are arranged in a face-centered cubic structure. Aluminium has a stacking-fault energy of 200 mJ/m2. Aluminium is a good thermal and electrical conductor, having 59% the conductivity of copper, both thermal and electrical, while having only 30% of copper's density. Aluminium is capable of superconductivity, with a superconducting critical temperature of 1.2 kelvin and a critical magnetic field of about 100 gauss.
Aluminium is the most common material for the fabrication of superconducting qubits. Aluminium's corrosion resistance can be excellent due to a thin surface layer of aluminium oxide that forms when the bare metal is exposed to air preventing further oxidation, in a process termed passivation; the strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper. This corrosion resistance is reduced by aqueous salts in the presence of dissimilar metals. In acidic solutions, aluminium reacts with water to form hydrogen, in alkaline ones to form aluminates—protective passivation under these conditions is negligible; because it is corroded by dissolved chlorides, such as common sodium chloride, household plumbing is never made from aluminium. However, because
Cavitation
Cavitation is a phenomenon in which rapid changes of pressure in a liquid lead to the formation of small vapor-filled cavities, in places where the pressure is low. When subjected to higher pressure, these cavities, called "bubbles" or "voids", collapse and can generate an intense shock wave. Cavitation is a significant cause of wear in some engineering contexts. Collapsing voids that implode near to a metal surface cause cyclic stress through repeated implosion; this results in surface fatigue of the metal causing a type of wear called "cavitation". The most common examples of this kind of wear are to pump impellers, bends where a sudden change in the direction of liquid occurs. Cavitation is divided into two classes of behavior: inertial cavitation and non-inertial cavitation; the process in which a void or bubble in a liquid collapses, producing a shock wave, is called inertial cavitation. Inertial cavitation occurs in nature in the strikes of mantis shrimps and pistol shrimps, as well as in the vascular tissues of plants.
In man-made objects, it can occur in control valves, pumps and impellers. Non-inertial cavitation is the process in which a bubble in a fluid is forced to oscillate in size or shape due to some form of energy input, such as an acoustic field; such cavitation is employed in ultrasonic cleaning baths and can be observed in pumps, etc. Since the shock waves formed by collapse of the voids are strong enough to cause significant damage to moving parts, cavitation is an undesirable phenomenon, it is often avoided in the design of machines such as turbines or propellers, eliminating cavitation is a major field in the study of fluid dynamics. However, it is sometimes useful and does not cause damage when the bubbles collapse away from machinery, such as in supercavitation. Inertial cavitation was first observed in the late 19th century, considering the collapse of a spherical void within a liquid; when a volume of liquid is subjected to a sufficiently low pressure, it may rupture and form a cavity. This phenomenon is coined cavitation inception and may occur behind the blade of a rotating propeller or on any surface vibrating in the liquid with sufficient amplitude and acceleration.
A fast-flowing river can cause cavitation on rock surfaces when there is a drop-off, such as on a waterfall. Other ways of generating cavitation voids involve the local deposition of energy, such as an intense focused laser pulse or with an electrical discharge through a spark. Vapor gases evaporate into the cavity from the surrounding medium; such a low-pressure bubble in a liquid begins to collapse due to the higher pressure of the surrounding medium. As the bubble collapses, the pressure and temperature of the vapor within increases; the bubble collapses to a minute fraction of its original size, at which point the gas within dissipates into the surrounding liquid via a rather violent mechanism which releases a significant amount of energy in the form of an acoustic shock wave and as visible light. At the point of total collapse, the temperature of the vapor within the bubble may be several thousand kelvin, the pressure several hundred atmospheres. Inertial cavitation can occur in the presence of an acoustic field.
Microscopic gas bubbles that are present in a liquid will be forced to oscillate due to an applied acoustic field. If the acoustic intensity is sufficiently high, the bubbles will first grow in size and rapidly collapse. Hence, inertial cavitation can occur if the rarefaction in the liquid is insufficient for a Rayleigh-like void to occur. High-power ultrasonics utilize the inertial cavitation of microscopic vacuum bubbles for treatment of surfaces and slurries; the physical process of cavitation inception is similar to boiling. The major difference between the two is the thermodynamic paths that precede the formation of the vapor. Boiling occurs when the local temperature of the liquid reaches the saturation temperature, further heat is supplied to allow the liquid to sufficiently phase change into a gas. Cavitation inception occurs when the local pressure falls sufficiently far below the saturated vapor pressure, a value given by the tensile strength of the liquid at a certain temperature. In order for cavitation inception to occur, the cavitation "bubbles" need a surface on which they can nucleate.
This surface can be provided by the sides of a container, by impurities in the liquid, or by small undissolved microbubbles within the liquid. It is accepted that hydrophobic surfaces stabilize small bubbles; these pre-existing bubbles start to grow unbounded when they are exposed to a pressure below the threshold pressure, termed Blake's threshold. The vapor pressure here differs from the meteorological definition of vapor pressure, which describes the partial pressure of water in the atmosphere at some value less than 100% saturation. Vapor pressure as relating to cavitation refers to the vapor pressure in equilibrium conditions and can therefore be more defined as the equilibrium vapor pressure. Non-inertial cavitation is the process in which small bubbles in a liquid are forced to oscillate in the presence of an acoustic field, when the intensity of the acoustic field is insufficient to cause total bubble collapse; this form of cavitation causes less erosion than inertial cavitation, is used for the cleaning of delicate materials, such as silicon wafers.
Hydrodynamic cavitation describes the process of vaporisation, bubble generation and bubble implosion which occurs in a flowing liquid as a result of a decrease and su
Density
The density, or more the volumetric mass density, of a substance is its mass per unit volume. The symbol most used for density is ρ, although the Latin letter D can be used. Mathematically, density is defined as mass divided by volume: ρ = m V where ρ is the density, m is the mass, V is the volume. In some cases, density is loosely defined as its weight per unit volume, although this is scientifically inaccurate – this quantity is more called specific weight. For a pure substance the density has the same numerical value as its mass concentration. Different materials have different densities, density may be relevant to buoyancy and packaging. Osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. To simplify comparisons of density across different systems of units, it is sometimes replaced by the dimensionless quantity "relative density" or "specific gravity", i.e. the ratio of the density of the material to that of a standard material water.
Thus a relative density less than one means. The density of a material varies with pressure; this variation is small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object and thus increases its density. Increasing the temperature of a substance decreases its density by increasing its volume. In most materials, heating the bottom of a fluid results in convection of the heat from the bottom to the top, due to the decrease in the density of the heated fluid; this causes it to rise relative to more dense unheated material. The reciprocal of the density of a substance is called its specific volume, a term sometimes used in thermodynamics. Density is an intensive property in that increasing the amount of a substance does not increase its density. In a well-known but apocryphal tale, Archimedes was given the task of determining whether King Hiero's goldsmith was embezzling gold during the manufacture of a golden wreath dedicated to the gods and replacing it with another, cheaper alloy.
Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated and compared with the mass. Baffled, Archimedes is said to have taken an immersion bath and observed from the rise of the water upon entering that he could calculate the volume of the gold wreath through the displacement of the water. Upon this discovery, he leapt from his bath and ran naked through the streets shouting, "Eureka! Eureka!". As a result, the term "eureka" entered common parlance and is used today to indicate a moment of enlightenment; the story first appeared in written form in Vitruvius' books of architecture, two centuries after it took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time. From the equation for density, mass density has units of mass divided by volume; as there are many units of mass and volume covering many different magnitudes there are a large number of units for mass density in use.
The SI unit of kilogram per cubic metre and the cgs unit of gram per cubic centimetre are the most used units for density. One g/cm3 is equal to one thousand kg/m3. One cubic centimetre is equal to one millilitre. In industry, other larger or smaller units of mass and or volume are more practical and US customary units may be used. See below for a list of some of the most common units of density. A number of techniques as well as standards exist for the measurement of density of materials; such techniques include the use of a hydrometer, Hydrostatic balance, immersed body method, air comparison pycnometer, oscillating densitometer, as well as pour and tap. However, each individual method or technique measures different types of density, therefore it is necessary to have an understanding of the type of density being measured as well as the type of material in question; the density at all points of a homogeneous object equals its total mass divided by its total volume. The mass is measured with a scale or balance.
To determine the density of a liquid or a gas, a hydrometer, a dasymeter or a Coriolis flow meter may be used, respectively. Hydrostatic weighing uses the displacement of water due to a submerged object to determine the density of the object. If the body is not homogeneous its density varies between different regions of the object. In that case the density around any given location is determined by calculating the density of a small volume around that location. In the limit of an infinitesimal volume the density of an inhomogeneous object at a point becomes: ρ = d m / d V, where d V is an elementary volume at position r; the mass of the body t
Fossil fuel power station
A fossil fuel power station is a thermal power station which burns a fossil fuel such as coal, natural gas, or petroleum to produce electricity. Central station fossil fuel power plants are designed on a large scale for continuous operation. In many countries, such plants provide most of the electrical energy used. Fossil fuel power stations have machinery to convert the heat energy of combustion into mechanical energy, which operates an electrical generator; the prime mover may be a steam turbine, a gas turbine or, in small plants, a reciprocating internal combustion engine. All plants use the energy extracted from expanding either steam or combustion gases. Although different energy conversion methods exist, all thermal power station conversion methods have efficiency limited by the Carnot efficiency and therefore produce waste heat. By-products of fossil fuel power plant operation must be considered in their operation; the flue gas from combustion of the fossil fuels is discharged to the air.
This gas contains carbon dioxide and water vapor, as well as other substances such as nitrogen oxides, sulfur oxides, traces of other metals, for coal-fired plants, fly ash. Solid waste ash from coal-fired boilers must be removed; some coal ash can be recycled for building materials. Fossil fueled power stations are major emitters of carbon dioxide, a greenhouse gas, a major contributor to global warming; the results of a recent study show that the net income available to shareholders of large companies could see a significant reduction from the greenhouse gas emissions liability related to only natural disasters in the United States from a single coal-fired power plant. However, as of 2015, no such cases have awarded damages in the United States. Per unit of electric energy, brown coal emits nearly two times as much CO2 as natural gas, black coal emits somewhat less than brown. Carbon capture and storage of emissions has been proposed to limit the environmental impact of fossil fuel power stations, but it is still at a demonstration stage.
In a fossil fuel power plant the chemical energy stored in fossil fuels such as coal, fuel oil, natural gas or oil shale and oxygen of the air is converted successively into thermal energy, mechanical energy and electrical energy. Each fossil fuel power plant is a custom-designed system. Construction costs, as of 2004, run to $650 million for a 500 MWe unit. Multiple generating units may be built at a single site for more efficient use of land, natural resources and labor. Most thermal power stations in the world use fossil fuel, outnumbering nuclear, biomass, or solar thermal plants; the second law of thermodynamics states that any closed-loop cycle can only convert a fraction of the heat produced during combustion into mechanical work. The rest of the heat, called waste heat, must be released into a cooler environment during the return portion of the cycle; the fraction of heat released into a cooler medium must be equal or larger than the ratio of absolute temperatures of the cooling system and the heat source.
Raising the furnace temperature improves the efficiency but complicates the design by the selection of alloys used for construction, making the furnace more expensive. The waste heat cannot be converted into mechanical energy without an cooler cooling system. However, it may be used in cogeneration plants to heat buildings, produce hot water, or to heat materials on an industrial scale, such as in some oil refineries and chemical synthesis plants. Typical thermal efficiency for utility-scale electrical generators is around 37% for coal and oil-fired plants, 56 – 60% for combined-cycle gas-fired plants. Plants designed to achieve peak efficiency while operating at capacity will be less efficient when operating off-design Practical fossil fuels stations operating as heat engines cannot exceed the Carnot cycle limit for conversion of heat energy into useful work. Fuel cells do not have the same thermodynamic limits; the efficiency of a fossil fuel plant may be expressed as its heat rate, expressed in BTU/kilowatthour or megajoules/kilowatthour.
In a steam turbine power plant, fuel is burned in a furnace and the hot gasses flow through a boiler. Water is converted to steam in the boiler; the hot steam is sent through controlling valves to a turbine. As the steam expands and cools, its energy is transferred to the turbine blades which turn a generator; the spent steam has low pressure and energy content. The condensed water is pumped into the boiler to repeat the cycle. Emissions from the boiler include carbon dioxide, oxides of sulfur, fly ash from non-combustible substances in the fuel. Waste heat from the condenser is transferred either to the air, or sometimes to a cooling pond, lake or river. One type of fossil fuel power plant uses a gas turbine in conjunction with a heat recovery steam generator, it is referred to as a combined cycle power plant because it combines the Brayton cycle of the gas turbine with the Rankine cycle of the HRSG. The thermal efficiency of these plants has reached a record heat rate of 5690 Btu/, or just under 60%, at a facility in Baglan Bay, Wales.
The turbines are fueled either with natural gas, syngas or fuel oil. While more efficient and faster to construct, the economics of such plants is influenced by the volatile cost of fuel natural gas; the combined cycle plants are designed in a vari
Saint Petersburg
Saint Petersburg is Russia's second-largest city after Moscow, with 5 million inhabitants in 2012, part of the Saint Petersburg agglomeration with a population of 6.2 million. An important Russian port on the Baltic Sea, it has a status of a federal subject. Situated on the Neva River, at the head of the Gulf of Finland on the Baltic Sea, it was founded by Tsar Peter the Great on 27 May 1703. During the periods 1713–1728 and 1732–1918, Saint Petersburg was the capital of Imperial Russia. In 1918, the central government bodies moved to Moscow, about 625 km to the south-east. Saint Petersburg is one of the most modern cities of Russia, as well as its cultural capital; the Historic Centre of Saint Petersburg and Related Groups of Monuments constitute a UNESCO World Heritage Site. Saint Petersburg is home to the Hermitage, one of the largest art museums in the world. Many foreign consulates, international corporations and businesses have offices in Saint Petersburg. An admirer of everything German, Peter the Great named the city, Sankt-Peterburg.
On 1 September 1914, after the outbreak of World War I, the Imperial government renamed the city Petrograd, meaning "Peter's city", in order to expunge the German name Sankt and Burg. On 26 January 1924, shortly after the death of Vladimir Lenin, it was renamed to Leningrad, meaning "Lenin's City". On 6 September 1991, Sankt-Peterburg, was returned. Today, in English the city is known as "Saint Petersburg". Local residents refer to the city by its shortened nickname, Piter; the city's traditional nicknames among Russians are the Window to Europe. Swedish colonists built Nyenskans, a fortress at the mouth of the Neva River in 1611, in what was called Ingermanland, inhabited by Finnic tribe of Ingrians; the small town of Nyen grew up around it. At the end of the 17th century, Peter the Great, interested in seafaring and maritime affairs, wanted Russia to gain a seaport in order to trade with the rest of Europe, he needed a better seaport than the country's main one at the time, on the White Sea in the far north and closed to shipping during the winter.
On 12 May 1703, during the Great Northern War, Peter the Great captured Nyenskans and soon replaced the fortress. On 27 May 1703, closer to the estuary 5 km inland from the gulf), on Zayachy Island, he laid down the Peter and Paul Fortress, which became the first brick and stone building of the new city; the city was built by conscripted peasants from all over Russia. Tens of thousands of serfs died building the city; the city became the centre of the Saint Petersburg Governorate. Peter moved the capital from Moscow to Saint Petersburg in 1712, 9 years before the Treaty of Nystad of 1721 ended the war. During its first few years, the city developed around Trinity Square on the right bank of the Neva, near the Peter and Paul Fortress. However, Saint Petersburg soon started to be built out according to a plan. By 1716 the Swiss Italian Domenico Trezzini had elaborated a project whereby the city centre would be located on Vasilyevsky Island and shaped by a rectangular grid of canals; the project is evident in the layout of the streets.
In 1716, Peter the Great appointed Frenchman Jean-Baptiste Alexandre Le Blond as the chief architect of Saint Petersburg. The style of Petrine Baroque, developed by Trezzini and other architects and exemplified by such buildings as the Menshikov Palace, Kunstkamera and Paul Cathedral, Twelve Collegia, became prominent in the city architecture of the early 18th century. In 1724 the Academy of Sciences and Academic Gymnasium were established in Saint Petersburg by Peter the Great. In 1725, Peter died at the age of fifty-two, his endeavours to modernize Russia had met with opposition from the Russian nobility—resulting in several attempts on his life and a treason case involving his son. In 1728, Peter II of Russia moved his seat back to Moscow, but four years in 1732, under Empress Anna of Russia, Saint Petersburg was again designated as the capital of the Russian Empire. It remained the seat of the Romanov dynasty and the Imperial Court of the Russian Tsars, as well as the seat of the Russian government, for another 186 years until the communist revolution of 1917.
In 1736–1737 the city suffered from catastrophic fires. To rebuild the damaged boroughs, a committee under Burkhard Christoph von Münnich commissioned a new plan in 1737; the city was divided into five boroughs, the city centre was moved to the Admiralty borough, situated on the east bank between the Neva and Fontanka. It developed along three radial streets, which meet at the Admiralty building and are now one street known as Nevsky Prospekt, Gorokhovaya Street and Voznesensky Prospekt. Baroque architecture became dominant in the city during the first sixty years, culminating in the Elizabethan Baroque, represented most notably by Italian Bartolomeo Rastrelli with such buildings as the Winter Palace. In the 1760s, Baroque architecture was succeeded by neoclassical architecture. Established in 1762, the Commission of Stone Buildings of Moscow and Saint Petersburg ruled that no structure in the
