New cationic surfactants were synthesized by the quaternization of a number of straight-chain amide derivatives with triethylamine or pyridine. The corrosion inhibition tests of the surface-active compounds were performed at room temperature for 24 h on carbon steel coupons in acidic media using the gravimetric method. The acidic media used were 1.5 M HCl and 1.5 M H2SO4. Almost all of the synthesized cationic surfactants showed efficient inhibition of corrosion in the test. To establish the inhibition efficiencies of the inhibitors, surface characterization studies (contact angle measurements, SEM analysis and optical profilometer images) of the metal coupons used were performed. 相似文献
The Impedance Group Laboratories of National Metrology Institute of Turkey previously developed a new method for the characterization of Agilent 16380A-type four-terminal-pair air dielectric capacitance standards ranged from 1 to 1,000 pF up to 30 MHz. This method is based on obtaining all resonance frequencies of standard capacitors using a vector network analyzer in order to calculate inductive residual parameters of the standards. As a continuation of the study, this paper gives a detailed uncertainty analysis for the method. 相似文献
Bulletin of Engineering Geology and the Environment - Single- and double-shield tunnel boring machines are being increasingly considered for use in rock tunneling projects. However, one of the main... 相似文献
Lefke stone is a sandstone that has been widely used in mosques, madrasas, churches, and houses as building stone. The geological features and engineering properties of Lefke stone outcropped in the southern part of Osmaneli/Bilecik were investigated in field and laboratory studies. Samples acquired during the fieldwork were tested to determine the physical, mechanical, durability, and hygrothermal properties in the laboratory. The mean physico-mechanical properties of Lefke stone yielded apparent density of 2.38 g/cm3, specific gravity of 2.68 g/cm3, total porosity of 11.26%, 2.93% water absorption by weight, uniaxial compressive strength of 94 MPa, flexure strength of 11.45 MPa, a 3.90 MPa point load strength, 4.5–5 Mohs hardness, and field Schmidt hammer rebound value of 36. According to durability tests, Lefke stone is resistant to CaCl2 salt mist but has low resistance to SO2 aging. Salt crystals placed in the discontinuities of the rock caused slight crack growth. The stone’s resistance to crystallization of sodium sulphate salt is low, and an increase in the volume of salts crystallized in the rock results in low corner strengths. A capillary water-absorption value of 0.0016 kg/m2.h places Lefke stone into the category of very low water absorption capacity and permeability. The water vapor diffusion resistance factor (μ) less than 1 indicates that the sandstone has high breathability. Its performance in historical buildings, field observations, and values obtained through laboratory tests confirm that Lefke sandstone can be used as a building stone.
The aim of the study was to determine the effect of a temperature of 29°C on performance in tasks involving different cognitive demands and to assess the effect on perceived performance, subjective workload, thermal comfort, perceived working conditions, cognitive fatigue, and somatic symptoms in a laboratory with realistic office environment. A comparison was made with a temperature of 23°C. Performance was measured on the basis of six different tasks that reflect different stages of cognitive performance. Thirty‐three students participated in the experiment. The exposure time was 3.5 h in both thermal conditions. Performance was negatively affected by slightly warm temperature in the N‐back working memory task. Temperature had no effect on performance in other tasks focusing on psychomotor, working memory, attention, or long‐term memory capabilities. Temperature had no effect on perceived performance. However, slightly warm temperature caused concentration difficulties. Throat symptoms were found to increase over time at 29°C, but no temporal change was seen at 23°C. No effect of temperature on other symptoms was found. As expected, the differences in thermal comfort were significant. Women perceived a temperature of 23°C colder than men. 相似文献