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The high number of people, who lived in the cities composed of cave-houses, made necessary adjustments to make the places healthy: the underground dwellings, therefore, were equipped with ventilation systems, cisterns, warehouses, wells and small openings not visible to the outdoor but that allowed the exchange air.
In the case of windmills the driving force is the wind: this moves the large blades, made of wood, placed at the top of the structure; a system of gears is connected to these, which move the millstones that grind the grain or operate the mechanisms being used to pump the water.
Over the centuries the system has been applied on several occasions and it is certainly easy to associate the shape of the water mill with the millstones for the grain and, therefore, the production of flour.

The wear resistance of Al-Si alloys depends on a number of material related parameters, i.e., size, shape, composition and distribution of micro-constituents, in addition to service conditions [2,3].
However, the primary Si particles formed in the hypereutectic Al-Si alloys produced by casting methods, even though modified to refine them, are larger, and the Si particles themselves are hard and brittle, which causes the serious disseverance to the matrix and stress concentration at the tips or edges of the primary Si particles, leading to the cracking at the grain boundary or in primary silicon particles oneself, thereby, the mechanical properties, especially the elongation are significantly reduced [4].
It is important that the CDS method accomplishes the same task efficiently without the additional cost of grain refiners.

Experimental procedures The ingots of Al7SiMg alloy (chemical composition: Si 6.69; Mg 0.37; Fe 0.29; Zn <0.01; Ti<0.01; balance Al; numbers as quoted by the producer in mass %) were melted in resistance furnace at 750 °C.
Mg3Sb2 will be crystallized at grain boundary prior to eutectic phases because of the high melting point.
As modifier for Al7SiMg alloy equal or over 0.20 wt. % Sb, some surplus Sb will precipitate at grain boundary in the form of compound Mg3Sb2.

In case of aggregates it depends on mineralogy and size of grain and can by specified by coefficient of thermal expansion or coefficient of thermal conductivity.
Even though the content of fine particles under 0.063 was 7.2%, the grains are very sharp and don’t contribute to improving the workability.
Volume 15/Number 1, March 1994

Initial time 196 [min] Setting time 267 [min] Specific surface 377 [m2/kg] Average grain size 20 [µm] Density 3110 [kg/m3] Bulk density 980 [kg/m3] Table 2.
Density 2120 [kg/m3] Specific surface 225 [m2/kg] Average grain size 87 [µm] Before adding to concrete mix, nanosilica had to be treated in the ultrasonic bath Bandelin Sonorex Super RK 106.
Similar results were shown by a number of authors, e.g.

The size, the number and the distribution of these second phase particles have a great influence on the quality of aluminum foil.
A small amount of Mn can improve the corrosion resistance and weldability of the aluminum, Mg can improve its tensile strength, Ti and B are mainly added as grain refiner [6].
New combination of polishing and etching technique for revealing grain structure of an annealed aluminum (AA1235) alloy[J].

For example, egg shell membrane, plant leaves, insect wings, bacterial, DNA, and flower pollen grains have been selected as template to produce various advanced biomimetic inorganic oxide[9-15].
The BJH (Barret-Joyner-Halenda) calculation revealed a narrow distribution for the sample centered at 1-4 nm, proving that biomorphic TiO2 contains large numbers of mesopores, which agrees with TEM test.
Mann, Morphosynthesis of complex inorganic forms using pollen grain templates, Chem.

The specimens were etched to show the grain boundaries in the microstructure using the (NH4OH+H2O2+H2O) etchant [16].
Nearly equiaxed grain morphologies are generated, and Be addition modifies the Cu-Zn-Al alloys' structural characteristics. 4.
[18] J L Olajide F J Zannu, O O Daramola, A S Ogunbadejo, E A Okotete, E R Sadiku and K K Alaneme, Morphological characterization, in vitro biomedical corrosion and corrosion behaviour of As-Cast Cu-Zn-Al-FeMn alloys in selected intravenous and industrial fluids, Materials Research Express, Volume 6, Number 9, 2019.

The latter method allows to obtain nanocrystalline/amorphous, amorphous or polycrystalline materials and to control the grain size of the obtained Ni-Mo coatings from several to hundreds of nanometers.
It should be stressed that independently on the type of the plating bath used, with the increase in the Mo content in electrolyte, the grain size of the electrodeposited Ni-Mo coatings decreases.
Number of these micro-spheres is dependent on the electrochemical conditions of deposition.

The degree of their impact depends on the wood density as well as on the orientation of the wood grain [7].
Altogether sixteen sets of specimens were prepared for the experiment, all of them consisting of seven veneer layers while the grain of veneer in alternate plies was at right angles.
Mechanical properties were determined using a set consisting of an equal number of convex and concave specimens and the properties were determined through statical bend using testing device in accordace with the standard [13].