PLANNING OF A RATIONAL SEQUENCE OF A COMPLEX OF CONSTRUCTION WORKS TAKING INTO ACCOUNT RESOURCE CONSTRAINTS

The duration of a separate construction process depends on many factors: the number of workers, machines and mechanisms, weather conditions and others. Quantitative characteristics of some of them can be established and accepted from among the possible ones. Such factors are called capacity-type resources (renewable). The need for renewable resources at a certain point in time is characterized by the intensity of their consumption and is expressed by the number of resource units used simultaneously (workers, machines and mechanisms, etc.). The intensity of resource consumption is the main organizational and technological parameter of the construction of buildings, which determines the development of construction processes over time and the duration of the construction of the object as a whole.

Comparative study of frequency converters of three-phase electric motors in automatic control of technological parameter

Frequency converters of asynchronous three-phase AC motors are widely used in industry, including food production. A thorough understanding of the technical capabilities of frequency converters contributes to their efficient use. This article discusses a technical comparison of two frequency converters of three-phase electric motors of the Russian company "OWEN" and the Danish company "DANFOSS" according to the criterion of the quality of regulation of the technological parameter. For comparison, a test bench was created, in which the devices were tested in turn, under the same conditions. During the preparation and implementation of testing, it turned out that the hardware capabilities of frequency converters for their use in regulating technological parameters are the same, and the parametric capabilities are different. The frequency converter of the "OWEN" company is equipped with a PI controller, and the frequency converter from "DANFOSS" is equipped with a PID controller. As the results of testing the devices show, despite

ENZYMATIC SACHARIFICATION OF ALKALINE PRETREATED RICE STRAW BY CELLULASE FROM CELLULOSIMICROBIUM SP. MP1

The effects of different physical and technological parameter such as time, substrate to liquid ratio, enzyme concentration, temperature, and pH on enzymatic saccharification of alkaline pretreated straw cellulose were studied. For alkaline pretreatment, the straw was incubated with 10 % NaOH at ratio 1:20 (w/v) at 90 °C for 1 hour. After the alkaline pretreatment the cellulose content increased from 50.2 % (w/w) to 67.3 % (w/w). Enzyme used for saccharification of treated and untreated straw was produced from Cellulosimicrobium sp MP1 which was isolated from termite gut. Results from research showed that the highest percentage of saccharification of alkaline pretreated straw was 69.91 %, corresponding to 10.58 mg/mL of reducing sugar. The hydrolysis conditions for reaching this highest saccharification yield were: temperature of 55 ºC, substrate to liquid ratio of 2 g/100 mL, enzyme concentration of 37.5 U/g, pH of 5.5 and hydrolysis time of 48 hours.

Influence of transverse ultrasonic vibrations on the efficiency of threaded joint assembly

The disadvantages arising during assembly of threaded joints are considered. The existing methods of improving the quality of a threaded joint are analyzed and the most promising one is identified - the use of ultrasound at the assembly stage. Dependence of the unscrewing moment on the main technological parameter, which is vibration amplitude is obtained.

THE INFLUENCE OF FRICTION STIR WELDED PROCESS PARAMETERS OF AA2519-T62 ON JOINT QUALITY DEFINED BY NON-DESTRUCTIVE LASER AMPLIFIED ULTRASONIC METHOD AND BY MICROSTRUCTURE ANALYSIS

The presented research contains a description of a non-destructive laser ultrasound internal structure analysis of aluminium joints made by friction stir welding. In the research, four selected technological parameter groups were taken into account. Modifications used in different parameter groups included changing tool traverse speeds and also its rotation speeds. The most important goal of this research was to determine the joint quality using a non-destructive laser amplified ultrasound method To verify obtained test results, an additional microstructural analysis was also conducted.

Assurance of microgeometric state of parts surface made of plastic materials by ultrasonic machining

The possibility for using of surface plastic deformation when applying ultrasonic vibrations to the instrument to form microgeometric state of the parts surface made of copper M1 and aluminum alloy D16 are studied. Two ultrasonic machining schemes are compared: when the direction of vibration is normal to the surface of the part and tangent to this surface. It is shown that the use of tangent scheme changes the interaction nature of the tool with the surface of the part and the trajectory of the tool motion. It is established that the angle β between the direction of the rotation speed vector of the part and the vibration speed vector of the tool significantly affects on the microgeometry being formed. Therefore, angle β together with the main motion speed, feed, static load, frequency and amplitude of the tool’s vibrations, is technological parameter that extend the capabilities of tangential scheme in surface roughness forming. It is revealed that processing according to this scheme allows escaping the intensive flow of material in the deformation zone and the formation of waves on the surface of the part.

Improving in mandrelling efficiency of spline holes under infl uence of ultrasonic field

The analysis of the technological parameters of the finishing and strengthening of spline holes by shaped mandrels is performed. It is shown that the main technological parameter determining the processing efficiency is pull. Technological scheme for the mandrelling of spline holes of gear wheels is proposed, which ensures its reduction by applying ultrasonic field to the workpiece.