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PERSONAL TRANSPORT: GROUND, WATER, AIR
Transport of the future. Personal transport
Directory / Personal transport: land, water, air Scientists dealing with the problems of the future - futurologists - are already trying today to determine what the world around us will become, say, by the end of the second millennium or even 100 years from now. At the same time, something is viewed relatively easily, something with difficulty. But we can firmly say that in 50, 100 and more years transport will exist. And not only to exist, but also to develop steadily. Science fiction writers sometimes express the idea that in the future the bulk of information will be transmitted mainly by means of communication - from video phones to laser channels. The role of transport as a carrier of not only goods, but also information is not taken into account. But this is far from true. The advantage of transport lies precisely in the fact that it ensures the movement of not only goods, but also people - the most capacious carriers of information. Prof. V. N. Ivanov, a well-known Soviet transport scientist, emphasizes: "People need direct communication, and neither the telephone, nor the TV set, nor anything else can replace it." It is no coincidence that, despite the significant progress in communications, transport continues to rapidly improve today. How will it develop in the future? Basically, the problems can be reduced to the following: vehicles, or rather their engines, must become environmentally friendly, or, as they say, "ecologically friendly." In order to stretch as far as possible the "expenditure of the fuel and energy resources of our planet, the engines must become as economical as possible. Much attention is paid to the safety of machines, as well as to such traditional problems as a further increase in speed, maneuverability, and comfort. New, specialized modes of transport will be created and developed for the national economy However, what will it be like, the transport of the future, its engines? Are there any prototypes of them already now, in our days? The proposed materials are devoted to all these issues. 1. Thermal - "for" and "against" Grateful humanity accuses. This is how one can formulate the current attitude towards the most massive engine - the thermal one, and in particular towards the internal combustion engine (ICE). There are basically two articles of "guilty" of heat engines before mankind. The first one is uneconomical, barbarous spending of irreplaceable natural fuel resources. The second is environmental pollution with toxic exhaust gases and other wastes of the energy received, including excess heat, noise and smell. There is a lot of talk about all this right now. As well as about the inexorable conclusion that follows from this: if heat engines are not improved (or not completely abandoned), then the planet in the foreseeable future, measured in only tens of years, is threatened, firstly, by fuel starvation due to the complete depletion of reserves natural fuel; secondly, the mass poisoning of mankind by the products of burning this fuel, and possibly excessive (worse than in the hottest steam room!) warming of the atmosphere. So, improvement or complete failure. If we remember that heat engines are installed on hundreds of millions of cars, motorcycles, tractors, combines, aircraft, ships, motor boats and other machines, it becomes clear that a person cannot completely abandon them yet. However, it is necessary to make sure that, while extending their age, not significantly reduce the age of your own! How to "reconcile" the heat engine and man?
The answer is simple and complex: it is necessary to eliminate the toxicity of the exhaust gases of thermal engines and increase their efficiency. The main harm is caused by carbon monoxide, nitrogen oxides and hydrocarbons (aldehydes) contained in the exhaust gases, as well as carcinogens. But surely they can be captured? Yes, such traps-neutralizers have already been created: liquid, plasma, catalytic and combined. They are usually installed at the gas outlet behind the engine exhaust pipe. However, all these devices provide only a partial solution to the problem: even with their presence, the engine itself remains the same voracious mechanical monster. For centuries, the dream of engine specialists has been to build one where the piston would not reciprocate, but only rotate. This promised a significant reduction in the size and weight of the engine, a reduction in fuel consumption and the emission of toxic combustion products. Closer to solving this problem than anyone else, Professor F. Wankel. Many experts believe that the rotary engine he created can become the main internal combustion engine in an automobile. Recall how the wankel is arranged and works. In its body there is a cavity of a complex configuration, in which a triangular-shaped rotor-piston rotates, connected to the shaft by means of gears. It sits freely on the eccentric of the shaft, the center of which coincides with the center of the fixed gear. Running around it along a complex curve, the rotor-piston constantly touches the tops of the inner walls of the housing. For sealing, movable plates are installed at the tops. At the same time, the volumes of the chambers formed by the surfaces of the rotor-piston and the walls of the housing change sequentially. Here the processes of intake, compression and ignition of the fuel, expansion and release of exhaust gases take place. The opening and closing of the intake and exhaust channels is carried out by the rotor-piston itself. Thus, for one complete revolution in the Wankel engine, all the processes of a conventional four-stroke engine take place, and simultaneously in different working chambers: with flashes of fuel ignited by one candle, three power strokes, three exhaust gases, three fresh mixture inlets. The Wankel engine turned out to be not only the most compact and lightest (one of its first prototypes with a power of about 30 hp weighed only 10 kg), but also with the highest speed. Add to that that it can run on cheap diesel fuel. It would seem that this is the solution to the problem. But ... no matter how "wise" the designers, so far it has not been possible to achieve the reliability of the seals of the rotating rotor. This defect, which mainly prevents the further improvement of the motor, is a real scourge of engines of this type. Another line of research is the development of engines currently used in aviation - gas turbine engines (GTEs). They are obtained much less than the same power internal combustion engines, simpler and more reliable in operation. Despite a slightly increased fuel consumption, less toxic products are emitted, especially nitrogen dioxide. This is explained by the fact that in the gas turbine engine the combustion of fuel goes on continuously, at lower pressures and temperatures than in piston engines. A gas turbine engine is also an internal combustion engine. Only in it the combustible mixture is compressed by a compressor (usually centrifugal). Outside air, entering the compressor, rotates along with its blades, is compressed under the action of centrifugal force, and then heated in the heat exchanger and enters the combustion chamber. As a result of combustion of the mixture, hot gases press on the turbine blades, on the axis of which the compressor is located. Once further on the blades of the turbine impeller, they spend the main part of their energy to perform useful work. This is the principle diagram of the operation of the so-called twin-shaft gas turbine. It differs in that both turbines, high (compressor) and low (working) pressure, are kinematically completely independent. Single-shaft and three-shaft turbines are being developed for motor vehicles. It is still unknown which of these schemes will prove to be the most promising. Most likely, depending on the required power and specialization of the car, each of them will receive the right to further development. In all the engines discussed above, the fuel is burned in the combustion chamber - inside the cavity where the rotor, piston or turbine is located. It is very difficult to control combustion there, so often the fuel is not completely burned, a lot of toxic products are released. Next, consider such engines, where the fuel is oxidized outside the working cavity (cylinders). By analogy with internal combustion engines, they can be called external combustion engines. The main ones are steam engines and Stirling engines. The second era of steam engines began only a few years ago, when the largest research centers took up their design on a modern basis. These motors have many attractive features: a large initial torque, the absence of a complicated gearbox, the complete harmlessness of the exhaust. And the dynamism of the steam engine is one of the important advantages. With the improvement of old schemes, it was possible to overcome such problems of the classic steam engine as the explosion hazard of the boiler, prohibitive weight, the difficulty of starting and the difficulty of using water as a vapor-generating liquid in winter. Bulky and dangerous hot water boilers have been replaced by compact tubular steam generators. It was possible to successfully fit all the units into the dimensions of the car. Another promising branch of research is related to the motor, invented back in 1816 by the Scot R. Stirling. This external combustion engine was a pipe muffled at both ends, in which the piston went. The cavity on one side of the piston was continuously heated, on the other side it was cooled. The cold gas was liquefied and pumped into the hot cavity. Here, when the piston was stationary, its temperature and pressure rose due to heating. After the gas reached its maximum parameters, the piston began to move, making a working stroke. Then the expanded gas was pumped into a cold cavity, where, continuously cooled, it was compressed by a moving piston. The cycle was repeated.
Since less mechanical work is expended on compressing a cold gas than is released when expanding a hot gas, the Stirling engine generated excess mechanical energy. It is clear that such engine operation could not be particularly economical. However, if the compressed cold gas is heated before being fed into the hot cavity with the heat that was removed when the hot gas was cooled, the stirling can become a very economical engine, exceeding the efficiency of both carburetor and diesel engines. A device for heating gas - a container called a regenerator - was proposed at one time by the author of the invention himself. Today, the efficiency of such a heater has been increased to 98%. And the engine cavities began to be filled with hydrogen or helium compressed to 100 - 200 atm. The drive of the Stirling pistons was also improved, making it similar to the drive of an axial piston pump - with an oblique washer. As a result, modernized stirling is suitable for most machines using heat engines. Its toxicity is hundreds of times less than carburetor, and it works almost silently. But while stirlings are complex and expensive, and even heavier than carburetor ones. And yet, the engines discussed above are overwhelmingly active consumers of natural fuel. And its reserves are not unlimited. Therefore, attempts to use artificially produced hydrogen as a fuel are of great interest. It can be extracted from water, decomposing it with electric current, sunlight, high temperature with catalysts. The main advantage of such fuel is much lower toxicity of combustion products than gasoline. Nitrogen oxides are formed, for example, 200 times less, and carbon monoxide and hydrocarbons are not present in the exhaust at all. However, other problems arise - for example, the storage of gas in cylinders. However, scientists propose to saturate the hydrides of certain metals with hydrogen, absorbing it like a sponge. Interestingly, tanks filled with hydride hold 40 times more hydrogen than hollow tanks. Engines are also being created that use the most unexpected natural factors - solar radiation, evaporation, osmosis. It is no coincidence that they are called exotic: so far they have a very small distribution. But the growing interest in environmentally friendly energy sources will certainly lead to an increase in their role. They will also be useful in space transport - planetary rovers, systems for servicing orbital stations. An example of exotic motors is the so-called light absorption motor. The working cylinder in it has a transparent window through which the sun's rays or a laser beam are passed, heating the gas in the cylinder. Due to this heating, the working stroke is performed. An experimental sample of the laser motor produces up to 600 rpm at a machine power of 30 watts. The efficiency of this engine, however, did not exceed 2%. Motors powered by solar radiation are known. It is converted by photocells into electric current.
And absolutely unusual are the models of motors that operate thanks to the "memory" discovered in the nitinol alloy. Welded from nickel and titanium, it has an unusual property: it remembers the shape that is given to it when heated. It is possible, for example, to twist a strip of this alloy into a spiral - alternately heated and cooled, it will either become a strip again, then twist back, and so on countless times. American engineers managed to build an engine using this property. Its base is a wheel with curved spokes that were straight when hot. When such a spoke is immersed in a bath of warm water, it straightens up and pushes the wheel. Immediately, the needle falls into the cold water and bends, and in its place a new curved needle comes into the warm bath. To operate the engine, a temperature difference of only 23 ° is sufficient. The inventors believe that this strange engine will help, for example, to use the heat carried away by the cooling water of nuclear power plants. Motors are also possible, where solar (or any other) heat is used to change the magnetic properties of metals. Thanks to this, mechanical work can also be obtained. An illustration of this is the engine proposed by the inventor and journalist A. G. Presnyakov. It is extremely simple, consists of a rim with spokes - and nothing more. The rim is made of a ferromagnetic alloy, which loses its magnetic properties at +65 °C. (Today, alloys are already known where this loss occurs at lower temperatures.) Install a strong permanent magnet close enough to the rim and not even heat, but only illuminate any section of the rim until it loses its magnetic properties, as the magnet will attract neighboring sections of the rim , causing it to rotate. It should not be thought that such an engine is very weak. The solar water lift built by Presnyakov pumped up to 800 liters of water per hour in the desert. Presnyakov also made a cart that rolls into the light of a strong electric lamp. In principle, any young designer can build such a model.
Some inventors are trying to use the phenomenon of osmosis to obtain mechanical work. It is known that it consists in the diffusion of a substance through a semi-permeable septum, due to which an excess osmotic pressure is created. In the UK, patent No. 1343391 was issued for an osmotic engine, which is rather complicated, but suitable, according to the inventors, for use in cars. The Soviet engineer P. Rogovik from Makeevka proposes a very simple low-speed low-power osmotic engine based on the swelling of materials when moistened. So swells, for example, gelatin. The inventor squeezed a ring of this material between two rolls immersed in water to the levels of the axes. The parts of the ring, which are below the level, expand from swelling and put pressure on the rolls, causing them to rotate. Together with the rolls, the ring also rotates slowly. Its swollen parts gradually rise up, and the dry parts sink, absorb water, swell and put pressure on the rolls, continuing to rotate them. The parts of the ring that come out of the water dry up and the cycle continues. Young designers can also make another model of an exotic motor. It works from the light energy of an electric lamp or the sun, focused through a lens. For its construction, several bimetallic plates are required, which are used in various thermal relays. It is known that a bimetallic plate, assembled from two strips of metal with different coefficients of thermal expansion, bends rather strongly when heated. The working cylinder, made, for example, of plastic, is sheathed around the perimeter with bimetallic plates attached to the cylinder at one end. At the other end are weights. The cylinder is mounted on a spoke fixed in two bushings on the edges of a vessel. In the normal state, the plates are curved around the circumference of the cylinder. When heated, the plate straightens and moves away from the wall, the balance of the forces of the weights is disturbed, and the cylinder scrolls. The place of this plate is occupied by a new one, E, straightened, cools and again presses against the wall of the cylinder. To speed up cooling, cold water can be poured into the vessel. 2. Bank of horsepower We talked about the fact that heat engines are constantly being improved: fuel consumption and exhaust toxicity are reduced. But a fair question arises: is it possible to do without these negative qualities at all? This question can be answered positively: it is possible to obtain energy for vehicles that do not require fuel combustion, and then "entrust" this energy to the consumer, accumulating it in batteries. Now most of the energy in the world is produced by thermal power plants - thermal power plants. If we imagine them in the form of special engines of colossal dimensions, we will see that they are as economical as possible, and the atmosphere suffers less from them, on stationary devices of greater power it is much easier to regulate the correct combustion of fuel than on thousands of small engines, the operating conditions of which are moreover they change every minute. But... Thermal power plants do not pass the test for environmental friendliness, that is, for the absence of a harmful effect on natural processes occurring in the field of application of a particular technique. Mankind, however, puts at its service and environmentally friendly sources of energy, and the sources are practically inexhaustible. This is the energy of the sun, rivers, tides, wind, internal heat of the earth, ocean heat and currents. Relatively harmless nuclear (future and thermonuclear) stations. The energy received from these sources can be brought to the consumer in various ways. If the latter is stationary or tied to a specific route (electric train, tram, trolley bus), let the electric wires work. If the consumer is mobile, those energy will have to be accumulated beforehand, so that the buttocks, black with such a sawn-off "energy canned food", can be used when moving. By the way, such energy has been used since ancient times. The first batteries were, of course, the simplest mechanical devices in which a person stores potential energy. Lifted loads, stretched bunch, catapult - these types of batteries have been used since time immemorial. There are similar batteries today. They are used very widely in the form of clockwork springs: in watches, appliances, children's toys. Previously, they were also used in vehicles: for example, huge clockwork chariots were built, on which emperors made parade trips. The springs were constantly wound up by the slaves hidden inside the wagon. However, spring-loaded batteries have a low energy density, that is, its amount contained in a unit mass. It is much more in rubber elastic accumulators. Every modeller knows that motors made of elastic bands lift models of airplanes and helicopters into the air. Of course, there are also disadvantages here: low CPV, fragility.
For transport vehicles, another battery is more suitable, which can accumulate so much energy that it will be able to provide movement for tens and even hundreds of kilometers. It's a compressed gas. The accumulation of energy occurs when gas is pumped into a cylinder under pressure; release - when gas is released from the cylinder. A pneumatic motor works here, similar to those used, for example, in pneumatic hand tools - wrenches, drills. As early as 1876, a compressed air tram was built in the French city of Nantes. He overcame a six-kilometer route from one gas station. Compressed to 30 atm. ten cylinders with a total volume of 2800 liters were filled with air. The consumption was 8 kg of air per kilometer. The total supply was enough for 10-12 km. This idea is not forgotten today. Pneumoaccumulators appeared on cars operating in urban conditions: the Sorgato company in Italy is experimenting with a car equipped with nine steel cylinders of compressed air. It is enough to cover about 100 km at a speed of 50 km/h. The weight of the "pneumomobile" is about half a ton. The pneumatic accumulator is "charged" with other gases, most often with liquid nitrogen, 50 liters of which is enough for a 230-km car run. But the gas accumulator also has drawbacks, and significant ones. Thus, when injected, the gas heats up, and when released, it cools. And this is an unproductive loss of thermal energy. More promising is another energy accumulator - the flywheel. When rotating, it accumulates mechanical energy in the form of kinetic energy, and it is present in the flywheel as long as it rotates. One of the most ancient flywheels, more than 55 thousand years old, was discovered by archaeologist Leonard Woolley during excavations in Iraq: a massive wheel that served as a potter's wheel for an ancient master. Over time, the flywheel has undergone significant changes, turned into a steel disk, the shape of which is dictated by the requirement of "equal strength": after all, the speed of spinup has also increased. Today it is placed in a vacuum chamber - to reduce very significant losses due to friction against air. For the same purpose, instead of bearings, magnetic bearings are used, friction losses on them are practically excluded. Skeptics brought their position for a long time, pointing to the main drawback of the flywheel as a battery - low energy density. With what it was connected! It would seem that everything is simple: by raising the rotation speed, say, twice, we, as is known from physics, quadruple the kinetic energy of the flywheel. But at the same time, the mechanical loads on the flywheel body also increase fourfold, leading to its rupture with the formation of fragments that pose a great danger to others. And then the search for scientists and designers led to the creation of the so-called super-flywheels made from thin fibers or tapes by winding. The fact is that modern filament- and tape-like materials have tremendous strength - several times stronger than a monolith made of the same material. A superflywheel rupture is also safer: thin fibers or tapes do not form fragments that can cause serious destruction. The author of these lines had to test a tape super-flywheel for a break: it could not even break through a casing of two millimeters in thickness, while monolithic flywheels did not care about meter walls. The main thing is that the energy density of a super flywheel is much higher than that of monolithic ones. Theoretically, it is even much higher than that of electric batteries, but practically does not concede to them. However, batteries are characterized not only by energy density, but also by power density: that is, the power that each kilogram of mass develops. And according to this indicator, the flywheel has no equal. Thus, the super flywheel is a promising battery (and engine) for the transport of the future. It provides fast acceleration of the car and no less effective braking, has great durability - in a word, all the qualities that a battery car needs and which it lacks so much now. The super flywheel is especially promising for driving buses, metro trains, taxis and other means of urban transport operating on a cyclic, busy schedule, with frequent acceleration and deceleration. Modern super flywheels in a vacuum chamber of rotation store energy even for weeks, and special samples of poppy batteries can rule it for years. In terms of energy conservation, they have only one worthy rival - electric, or, more correctly, electromechanical, batteries. They were created relatively recently, although the date of their appearance can be considered 1799, when Alexander Volta, placing copper and zinc electrodes in dilute sulfuric acid, received the first galvanic cell. After all, almost any galvanic cell, in principle, can become a battery if a current is passed through it in the opposite direction, charging it. Even ordinary dry batteries, used for flashlights and transistor receivers, can be charged 8-10 times like a battery. Another thing is that such "charging" is not particularly economically profitable: the efficiency is very low. But, you see, it is still much higher than that of a discarded battery. Real batteries, although more expensive than conventional galvanic batteries, can withstand not 8-10 recharging cycles, but more than a hundred times more. Therefore, storing energy in electric batteries is not very expensive. Of the electric batteries, lead-acid batteries are the most common; they are installed on every car as a starter battery. These are modest hard workers, they do not shine with energy and power indicators, but they are quite economical - they have a high efficiency. True, they do not tolerate frost, high currents, and strong discharge. Unlike them, the battery is unpretentious, but has a low efficiency: up to 0,4-0,5 compared to 0,75-0,8 for lead-acid. You can't expect much from these two batteries. Their energy and power density is low, and a car with such a load will mainly carry itself - they are so heavy. Special hopes are currently placed by scientists on superaccumulators - sodium sulphur, lithium chloride, etc. They maintain a high (300 - 600 °) temperature, the electrolyte is melted. Of course, the destruction of such a battery in a car accident does not bode well, and their efficiency is low, especially considering the need to warm up the contents. However, the energy density is very high - ten times more than that of lead-acid, and the power density is twice as high - up to 150 W per kilogram of mass. It should be noted that such "superaccumulators" have not yet left the walls of laboratories and they have to work and work on them. Finally, one cannot fail to mention the so-called fuel cells, which make it possible to directly convert the energy of the fuel into electric current. The most interesting of these are oxygen-hydrogen elements, which use the process of water decomposition directly in the element itself; it also has containers for storing the produced gases. Hydrogen and oxygen are again combined into water, for example, with the help of catalysts, high temperature, etc. In this case, electrical energy is released, which was spent during the decomposition of water, and battery energy is released in hydrogen and oxygen. Fuel cells are very promising for electric vehicles, but are still very heavy and expensive.
Thermal energy accumulators stand apart. By themselves, they cannot make the car move, but in combination with a heat engine, for example, Stirling, they can provide good results. We have already mentioned a motor scooter operating for about five hours from a bucket of molten lithium fluoride - a heat accumulator. A thermos with hot water, a warm stone in the sun, a hot iron, in a word, any heated body is an energy accumulator. However, there are compounds that can accumulate it ten times more than just a body heated to the same temperature. It is known from physics that during the melting of a crystalline substance, its temperature will not rise by a single degree until a certain, usually quite large amount of heat is expended, the so-called latent heat of fusion. During solidification, this heat is released, and also without changing the temperature of the substance. It is on this phenomenon that the so-called heat accumulators of melting are built. If the required temperature is low, below 100°C, then various crystalline hydrates are used as accumulator substances. For temperatures of 600-800°, fluorides and lithium hybrids are best suited; above - silicides and borides of some metals: Thermal accumulators store enormous amounts of energy - more than any of the most promising types of accumulators. The only trouble is that when trying to use this energy in the form of mechanical, electrical and other "high-quality" types of it, the main amount of energy is lost, leaving for heating the environment. In addition, the mass of a device that converts heat into a "high-quality" type of energy (for example, a Stirling engine, thermoelements, etc.) significantly reduces such an indicator as the energy density of the entire device, bringing it closer to the most ordinary types of energy storage devices. However, today thermal the battery can be of good use, for example, for heating a transport vehicle, driven from another energy accumulator: electric, poppy. Talk about batteries, we always refer to their main indicator - energy density. For their various types, if expressed in kilojoules per kilogram of mass, it is as follows: for potential energy accumulators: steel springs - 0,32; rubber - 32; gas and hydro-gas - 28. Heat accumulator with Stirling engine - 9. Electrochemical batteries: lead-acid - 64; nickel-cadmium (alkaline) - 110; sulfuric sodium - 800; fuel cell at different times of decoupling - 15-150. Flywheel batteries: steel disk with a hole - 30; solid disk of equal strength - 120; tape super flywheel - 150; super flywheel made of special fiber - 650 (model). However, one should not forget that flywheel batteries have very large energy storage reserves. So, for example, if you make a super flywheel from quartz fiber, which so far exists only in laboratories, you will be able to increase the energy density to 5000 kilojoules per kilogram. And if we use "super scarce" carbon fiber with a diamond structure, we will get a completely fantastic figure - 15 kJ / kg! Recently, Japanese scientists have come to such conclusions. In conclusion, I want to propose to build an interesting model of a "perpetual" engine running on accumulated energy obtained from a heat accumulator that is simple in design. To do this, we will make a cylindrical cap by gluing it from wax paper or other thin and strong paper with a top made of whatman paper or rigid aluminum foil. This cover will have the form of an impeller formed by cutouts with bent edges; the optimal angle of bending can be determined empirically. In the center of the impeller, a light metal nest is attached to the glue: a spore with a conical notch into which the tip of the needle is inserted. The blunt end of the needle enters a cork, mounted on a heavy fireproof stand with a tripod made of thick wire. The cap does not warp on the needle and easily rotates from a slight push or breath from below. To set such a "perpetual mobile" in motion, you need to put a metal blank heated to 300-400 ° on a stand and cover it with a cap. The heat accumulator blank will cause air to move inside the hood from the bottom up. Passing through the turbine, the air will rotate it the faster, the more the heat accumulator is heated. Even better results can be achieved if the blank is replaced by a can of molten lead or zinc. Then we get a real melting battery. It is best, of course, to use lithium fluoride or lithium hydride. Here you need to be very careful not to burn yourself and not start a fire, but the experiment should be carried out in a specially equipped physical laboratory or workshop. Someone, perhaps, will say that it is easier to cover an electric lamp with this cap. Then the lampshade cap (which can be painted at the same time) will rotate as long as the lamp is on. But at the same time, we will make a conventional heat engine work without energy storage. We have only talked about some types of heat engines being developed for the machines of the future. Of course, these are not even all the main types of motors of tomorrow. Of course, young designers and modellers can also try their hand at their development. However, we must remember that the creation of new engines is a complex and time-consuming matter, which requires serious and specialized knowledge; One "invention" will not achieve much. And the first test for the performance of your idea can be a self-built operating model. Author: N. Gulia
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