1,504 research outputs found
The effect of heat on the resistance of varnish.
Varnish and its use has been known since ancient times. Altho the knowledge of varnish has been attributed to the Japanese as early as 500-600 B.C., Tschirsch and A.D. Stevens say that the Japs did not possess this art originally, but that they probably acquired it from the continent during the third century. Nevertheless, varnish did not come into general use until the middle ages. In the 12th century, a monk by the name of Theophilus published the first directions for making an oil varnish, but it was not until 1790 in England, and between 1820 and 1830 in France and Germany, that a factory was established for the commercial production of varnish. In general, a varnish may be defied as a homogeneous, sticky, viscous solution of resins, of a colloidal nature, which when applied to a surface in a thin coat, dries to a hard, smooth, glossy surface. The color of varnish varies considerably, depending on the grade and on its use. Pale varnishes are generally sought, yet there are many dark varnishes of excellent quality. The following scale gives an idea of the degree of color of varnish. A solution of 0.25g K2Cr2O7 in 100g pure concentrated H2SO4 is equivalent to a very light varnish. A solution of 2.00g K2Cr2O7 in 100g pure concentrated H2SO4 is equivalent to a medium varnish. A solution of 4.00g K2Cr2O7 in 100g pure concentrated H2SO4 is equivalent to a dark varnish. Varnishes may be divided into two main classes, according to the manner in which the film dries. The varnishes of the first class, which is the largest and most important, are known as oil varnishes. These varnishes dry mainly by the oxidation of the oil, which forms a tough, elastic film. The secondary drying in these oil varnishes is caused by the evaporation of the volatile vehicle, and by the polymerization of the constituents. On the whole, the drying of an oil varnish is of a chemical nature. The varnishes of the second class are called spirit varnishes. These dry merely by the evaporation of the solvent, and there is practically no chemical action. The gum is transferred from a lump form into a thin sheet by means of the solvent. The most important example of this class is shellac, which is the hardened secretion of the lac insect, dissolved in alcohol
ΠΠ»Π³ΠΎΡΠΈΡΠΌ ΠΏΠΎΡΡΡΠΎΠ΅Π½ΠΈΡ ΠΏΡΠΎΠ³Π½ΠΎΠ·ΠΈΡΡΠ΅ΠΌΠΎΠΉ ΠΏΠ»ΠΎΡΠ°Π΄ΠΈ ΠΏΠΎΠΆΠ°ΡΠ° Π² ΡΠ°ΠΊΡΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΌΠΎΠ΄Π΅Π»ΠΈ
The miniaturization of components in the field of life science, consumer electronics and micro-electro-mechanical systems (MEMS) is becoming a part of our everyday life. As the manufacturing of these components demands in many cases the machining by micromilling with cutting tools down to 100 Β΅m diameter, highly dynamic machine tools are needed to machine the more and more complex freeform surfaces at optimal process parameters. The paper describes the development of a highly dynamic milling machine which is equipped with linear direct drives in all axes with integrated impulse decoupling units to allow high dynamics and especially high jerks at low impact on the machine structure. Additionally the development of a metrology frame is detailed which can be used to characterize the dyna mic tool path of machine tools to optimize its dynamic setup and to increase the work piece precision at minimized machining time
ΠΠ΅ΡΠΎΠ΄ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΠΊΠ°Π·Π°Π½ΠΈΡ ΠΊ ΡΠ°ΠΌΠΎΡΡΠΎΡΡΠ΅Π»ΡΠ½ΠΎΠΌΡ ΠΈΠ·ΡΡΠ΅Π½ΠΈΡ ΠΊΡΡΡΠ° "Π£Π½ΠΈΠ²Π΅ΡΡΠΈΡΠ΅ΡΡΠΊΠΎΠ΅ ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΠ΅" ΡΡΡΠ΄Π΅Π½ΡΠ°ΠΌΠΈ-ΠΈΠ½ΠΎΡΡΡΠ°Π½ΡΠ°ΠΌΠΈ
ΠΠ΅ΡΠΎΠ΄ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΠΊΠ°Π·Π°Π½ΠΈΡ ΡΠ°Π·ΡΠ°Π±ΠΎΡΠ°Π½Ρ Π² ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΠΈΠΈ Ρ ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠΎΠΉ ΡΡΠ΅Π±Π½ΠΎΠ³ΠΎ ΠΊΡΡΡΠ° "Π£Π½ΠΈΠ²Π΅ΡΡΠΈΡΠ΅ΡΡΠΊΠΎΠ΅ ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΠ΅" ΠΈ ΡΠΎΡΡΠ°Π²Π»Π΅Π½Π° Π² ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΠΈΠΈ Ρ ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°ΡΠ΅Π»ΡΠ½ΠΎΠΉ ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠΎΠΉ ΠΏΠΎΠ΄Π³ΠΎΡΠΎΠ²ΠΈΡΠ΅Π»ΡΠ½ΠΎΠ³ΠΎ ΠΎΡΠ΄Π΅Π»Π΅Π½ΠΈΡ ΡΠ°ΠΊΡΠ»ΡΡΠ΅ΡΠ° ΠΌΠ΅ΠΆΠ΄ΡΠ½Π°ΡΠΎΠ΄Π½ΠΎΠ³ΠΎ ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΡ, ΠΊΠΎΡΠΎΡΠ°Ρ Π·Π°Π½ΠΈΠΌΠ°Π΅Ρ Π²Π°ΠΆΠ½ΠΎΠ΅ ΠΌΠ΅ΡΡΠΎ Π² ΡΠΈΡΡΠ΅ΠΌΠ΅ ΠΏΠΎΠ΄Π³ΠΎΡΠΎΠ²ΠΊΠΈ ΠΊΠ°Π΄ΡΠΎΠ² Π²ΡΡΡΠΈΡ
ΡΡΠ΅Π±Π½ΡΡ
Π·Π°Π²Π΅Π΄Π΅Π½ΠΈΠΉ Π£ΠΊΡΠ°ΠΈΠ½Ρ. ΠΠ΅ΡΠΎΠ΄ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΠΊΠ°Π·Π°Π½ΠΈΡ ΡΠ°ΡΡΡΠΈΡΠ°Π½Ρ Π½Π° ΠΈΠ½ΠΎΡΡΡΠ°Π½Π½ΡΡ
ΡΡΡΠ΄Π΅Π½ΡΠΎΠ² ΠΏΠΎΠ΄Π³ΠΎΡΠΎΠ²ΠΈΡΠ΅Π»ΡΠ½ΠΎΠ³ΠΎ ΠΎΡΠ΄Π΅Π»Π΅Π½ΠΈΡ ΠΠΠ III-IV ΡΡΠΎΠ²Π½Π΅ΠΉ Π°ΠΊΠΊΡΠ΅Π΄ΠΈΡΠ°ΡΠΈΠΈ ΠΈ ΡΠΎΠ΄Π΅ΡΠΆΠ°Ρ ΠΎΠ±ΡΠΈΠ΅ ΡΠ²Π΅Π΄Π΅Π½ΠΈΡ ΠΎΠ± ΡΡΠ΅Π±Π½ΠΎΠΌ ΠΊΡΡΡΠ΅, ΡΠ΅ΠΌΠ°ΡΠΈΡΠ΅ΡΠΊΠΈΠΉ ΠΏΠ»Π°Π½ ΠΈ ΡΡΡΡΠΊΡΡΡΡ ΠΊΡΡΡΠ°, ΡΡΠ΅Π±ΠΎΠ²Π°Π½ΠΈΡ ΠΊ ΡΡΠΎΠ²Π½Ρ ΠΊΠΎΠΌΠΏΠ΅ΡΠ΅Π½ΡΠ½ΠΎΡΡΠΈ ΡΡΡΠ΄Π΅Π½ΡΠΎΠ², ΡΠ΅ΠΊΠΎΠΌΠ΅Π½Π΄ΠΎΠ²Π°Π½Π½ΡΡ Π»ΠΈΡΠ΅ΡΠ°ΡΡΡΡ ΠΏΠΎ ΡΠ΅ΠΌΠ°ΠΌ ΠΊΡΡΡΠ°, ΡΠ΅ΠΌΡ ΠΏΡΠ°ΠΊΡΠΈΡΠ΅ΡΠΊΠΈΡ
Π·Π°Π½ΡΡΠΈΠΉ, ΠΎΠ±ΡΠ°Π·ΡΡ Π²ΠΎΠΏΡΠΎΡΠΎΠ² ΠΊ ΡΠ΅ΡΡΠΎΠ²ΠΎΠΌΡ ΠΈ ΠΈΡΠΎΠ³ΠΎΠ²ΠΎΠΌΡ ΠΊΠΎΠ½ΡΡΠΎΠ»ΡΠΌ, ΡΠΈΡΡΠ΅ΠΌΡ ΠΎΡΠ΅Π½ΠΈΠ²Π°Π½ΠΈΡ ΡΡΠ΅Π±Π½ΡΡ
Π΄ΠΎΡΡΠΈΠΆΠ΅Π½ΠΈΠΉ ΡΡΡΠ΄Π΅Π½ΡΠΎΠ²
ΠΠΠΠ‘ΠΠ ΠΠ ΠΠΠΠΠΠΠ¦Π― Π.Π. ΠΠΠΠΠΠΠΠ§Π Π£ ΠΠΠ‘ΠΠΠΠΠΠΠΠ― ΠΠ Π₯ΠΠΠΠΠΠΠ§ΠΠΠ₯ ΠΠΠβΠ―Π’ΠΠ ΠΠΠΠΠΠ ΠΠΠΠ―
Π ΠΎΠ·Π³Π»ΡΠ½ΡΡΠΎ ΡΠ²ΠΎΡΡΠΈΠΉ ΡΠ»ΡΡ
Π²ΠΈΠ·Π½Π°ΡΠ½ΠΎΠ³ΠΎ Π΄Π½ΡΠΏΡΠΎΠΏΠ΅ΡΡΠΎΠ²ΡΡΠΊΠΎΠ³ΠΎ ΠΊΡΠ°ΡΠ·Π½Π°Π²ΡΡ ΠΠΎΠ»ΠΎΠ΄ΠΈΠΌΠΈΡΠ° ΠΠ°ΡΠΈΠ»ΡΠΎΠ²ΠΈΡΠ° ΠΡΠ½ΠΊΠ΅Π²ΠΈΡΠ°.The author considers creative way of the famous dnipropetrovsk student of local lore Volodimir Vasilβovich Binkevich
What did the students expect from TPU and what they have got: comparative study
Backlight units are the most relevant element in display with respect to the energy consumption. In addition, the quality of backlight units in terms of brightness, homogenous light distribution, and the angle of light radiation, dramatically influence the overall quality of a display. Within this paper a new approach for the production of complex micro optics on large surfaces is presented. The technology is being optimised within the FlexPAET project for the production of next generation backlight units which allow for more efficient display illumination
Self-study guide to developing English linguistic competences for students of Computer Sciences
ΠΠ΅ΡΠΎΠ΄ΠΈΡΠ½Ρ Π²ΠΊΠ°Π·ΡΠ²ΠΊΠΈ ΠΏΡΠΈΠ·Π½Π°ΡΠ΅Π½Ρ Π΄Π»Ρ ΡΠ°ΠΌΠΎΡΡΡΠΉΠ½ΠΎΡ ΡΠΎΠ±ΠΎΡΠΈ ΡΡΡΠ΄Π΅Π½ΡΡΠ² ΠΠ’ ΡΠΏΠ΅ΡΡΠ°Π»ΡΠ½ΠΎΡΡΠ΅ΠΉ Π½Π°Π΄ ΠΎΠΏΠ°Π½ΡΠ²Π°Π½Π½ΡΠΌ ΡΠ°Ρ
ΠΎΠ²ΠΎΡ ΡΠ΅ΡΠΌΡΠ½ΠΎΠ»ΠΎΠ³ΡΡ ΡΠ° ΠΌΠ°ΡΡΡ Π½Π° ΠΌΠ΅ΡΡ Π΄ΠΎΠΏΠΎΠΌΠΎΠ³ΡΠΈ ΡΡΡΠ΄Π΅Π½ΡΠ°ΠΌ Π ΡΠ° ΠΠ ΠΊΡΡΡΡΠ² ΡΠ°ΠΌΠΎΡΡΡΠΉΠ½ΠΎ ΠΏΡΠ°ΡΡΠ²Π°ΡΠΈ Π½Π°Π΄ ΡΠΎΠ·ΡΠΈΡΠ΅Π½Π½ΡΠΌ ΡΠ»ΠΎΠ²Π½ΠΈΠΊΠΎΠ²ΠΎΠ³ΠΎ Π·Π°ΠΏΠ°ΡΡ, ΡΠΎΠ·Π²ΠΈΡΠΊΠΎΠΌ Π²ΠΌΡΠ½Ρ Π·Π΄ΠΎΠ±ΡΠ²Π°Π½Π½Ρ ΡΠ½ΡΠΎΡΠΌΠ°ΡΡΡ Π· Π°Π½Π³Π»ΠΎΠΌΠΎΠ²Π½ΠΈΡ
ΡΠ΅ΠΊΡΡΠΎΠ²ΠΈΡ
Π΄ΠΆΠ΅ΡΠ΅Π»
ΠΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠ΅ ΠΏΠ»Π°ΡΡΠΈΡΠΈΡΠΈΡΡΡΡΠΈΡ ΡΠ²ΠΎΠΉΡΡΠ² Π½Π΅ΠΊΠΎΡΠΎΡΡΡ ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄Π½ΡΡ ΠΊΠ°ΡΠ±Π°Π·ΠΎΠ»Π°
During the assembly of customized miniaturized solid-state lasers, robot based operations can significantly reduce cycle times and improve performance and quality. Automation of the resistance soldering technique for optical components based on planar technology described in the previous work of Dolkemeyer et. al can be self-optimized to compensate component and process tolerances, cope with different element geometries and therefore reduce planning efforts and facilitate the operator's work.solder pads. Planar adjustment of an optical element and exemplary resistance measurement during soldering process For the automation of the soldering process itself the modification of the system's electrical resistance is measured since this value can be calculated by evaluating the process parameters without supplementary equipment. In addition, it can be used as a documented quality control. The increase of the resistance at the solder's melting point is related to the length of the molten zone and is always continuous even if current and voltage are discontinuous. Presented are the technique for planar adjustment and current results of the automation and self-optimization process
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