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

Алгоритм построения прогнозируемой площади пожара в тактической модели

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 µm 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

Методические указания к самостоятельному изучению курса "Университетское образование" студентами-иностранцами

Методические указания разработаны в соответствии с программой учебного курса "Университетское образование" и составлена в соответствии с образовательной программой подготовительного отделения факультета международного образования, которая занимает важное место в системе подготовки кадров высших учебных заведений Украины. Методические указания рассчитаны на иностранных студентов подготовительного отделения ЗВО III-IV уровней аккредитации и содержат общие сведения об учебном курсе, тематический план и структуру курса, требования к уровню компетентности студентов, рекомендованную литературу по темам курса, темы практических занятий, образцы вопросов к тестовому и итоговому контролям, систему оценивания учебных достижений студентов

ВНЕСОК КРАЄЗНАВЦЯ В.В. БІНКЕВИЧА У ДОСЛІДЖЕННЯ АРХЕОЛОГІЧНИХ ПАМ’ЯТОК НАДПОРІЖЖЯ

Розглянуто творчий шлях визначного дніпропетровського краєзнавця Володимира Васильовича Бінкевича.The author considers creative way of the famous dnipropetrovsk student of local lore Volodimir Vasil’ovich 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

Методичні вказівки призначені для самостійної роботи студентів ІТ спеціальностей над опануванням фахової термінології та мають на меті допомогти студентам І та ІІ курсів самостійно працювати над розширенням словникового запасу, розвитком вмінь здобування інформації з англомовних текстових джерел

Исследование пластифицирующих свойств некоторых производных карбазола

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