Vol 30, No 1 (2020)

Introduction. The development of the agro-industrial complex is impossible without creating innovative techniques and technologies. The key role in technical support of agricultural production processes is played by machine-tractor aggregates. One of their most important operational characteristics is reliability, i.e. the ability to perform specified functions, keeping over time the values of the operational indicators within the required limits.
Materials and Methods. The object of the study is the reliability of machine-tractor aggregates. The methods of mathematical modeling were used for the study. The general patterns were used for special cases, taking into account the prediction of changes in parameters over time. The analytical description of machine-tractor aggregate operation reliability was based on stationary random and correlation functions. Generalized patterns were used to construct mathematical reliability models using the results of predecessor (analogue) tests. Optimal reliability of the machine-tractor aggregate operation was determined on the basis of the mathematical model of object resource.
Results. There are obtained analytical dependences for the prediction of changes in reliability parameters of machine-tractor aggregate operation over time. The methods for creating reliability mathematical models are developed. Conditions affecting the functioning of the research object are determined.
Discussion and Conclusion. The analysis and synthesis of research in this science field and the obtained mathematical models show that to achieve high results it is necessary to decrease the variance of factors affecting the reliability of machine-tractor aggregates.

Introduction. The relevance of the study is determined by the need to estimate the influence of mixed fuel, including diesel and biofuel (rapeseed oil), on ecological parameters of an agricultural tractor diesel in working in agricultural fields and transporting. The objective of the study is forecasting, obtaining and comparing the calculated and experimental environmental performance indicators of the Belarus-922 tractor diesel engine using mixed fuel for farming operations.
Materials and Methods. To achieve the objective of the study, the quantitative indicators of component structure of rapeseed oil samples of various origins have been defined, a theoretical estimation and the comparison of calculated and experimental environmental performance indicators of tractor diesel engine have been made with the use of the necessary equipment.
Results. For the first time, quantitative values of indexes of the component composition of rapeseed oils of various origins have been obtained. The analysis has shown that the most recommended to be used as fuel is the sample with the maximum content of unsaturated acids that will allow providing the maximum speed and combustion efficiency. The calculations show a decrease in working temperature by 200 K as a result of added rapeseed oils that should lead to a reduction of the constant of the reaction speed and concentration of nitrogen oxides approximately by a factor of 2.7. The endogenous origin of nitrogen compounds influences essentially on the concentration of nitrogen oxides in worked-out gases.
Discussion and Conclusions. Based on the analysis of nitrogen oxide mechanisms on combustion of rapeseed oils, the calculation of the semi-quantitative reaction rate is theoretically proved and experimentally confirmed.

Introduction. The article describes an algorithm for determining the system of tolerances for ensuring reliable operation of parts on the section. The block diagram of the program for determining the variable tolerances is demonstrated. There determined blocks of initial information − broken and smooth curves of the controlled parameter, histogram and graph of resource distribution and definition of active area of control, and blocks of building graphs of “marginal fan curves of wear” and systems of admissions for objects of study of two types: for universal fuel pump (UTN-5) and four-section small-sized fuel pump with mechanical regulator. Two ways of determining the system of tolerances are suggested. Variant 1 is a graphical way through constructing “limit fan curves of wear” and determining tolerances by the value of ordinates in the control points. Variant 2 is an analytical way. There is created a formula to replace the graphical method for determining system tolerances.
Materials and Methods. Two models of high-pressure pump were selected as objects of the study. Nominal and limit values of parameters were known for the pumps. Schedules for checking and equation of wear curves are determined. Dependencies describing the pump plunger pair wear curves are determined. A histogram and graph for determining pump life cycles are drawn. The active area of control is determined with a given failure probability coefficient.
Results. As a result of the study the values for the tolerances system of two types of high pressure fuel pumps are obtained. Reliability values for one pump type are determined. Graphic and analytical algorithms for determining the system of tolerances by the formula are developed.
Discussion and Conclusion. The study approves the possibility of using the variable tolerance as a basis for determining the system of tolerances and reliability indicators of the diagnostic object.

Introduction. The current problem is the high level of grain injuries during the threshing process. Therefore it is necessary to develop the gentle methods for separating grains from ears. These methods shall exclude direct shock influence of operative parts of the threshing devices on cereal grains. The objective of research is to study the process of the wheatear threshing in the pneumatic device and to estimate the influence of device settings on cereal grain separation and damage.
Materials and Methods. The experimental apparatus is a pneumatic threshing device. The threshing is carried out in case of the interaction of an ear and concave under the influence of the alternating high and low pressure of the airflow generating by the rotor’s blades. Separation is carried out by means of deriving light-load tailings into the reduced pressure chamber.
Results. The grain damage decreases in reducing the speed of rotor blades motion and consequently the speed of ears motion in the threshing unit. Germ damage and grain breakage decrease almost to zero at a minimum blade motion speed of 13.5 mps. The range of blade speed between 13.5 and 20 mps is the most favorable for the pneumatic grain threshing in terms of the germ damage. The pneumatic threshing on the experimental device results in effective assorting of grains and light-load tailings of ears.
Discussion and Conclusion. Process of the wheat ears pneumatic threshing has satisfactory results. The pneumatic threshing reduces grain endosperm damage by 10…12%. Grain germ damage decreases by 5%, practically to zero. Comparison of shares of the damaged and crushed grains when using the pneumatic threshing with shares of the damaged grains when using the traditional combine threshing has showed that the offered method of the threshing provides a reduction in grain damage.

Introduction. The article presents an analysis of the various applications of crystals, describes the historical and cultural foundations of using mineral raw materials for various purposes, including medical ones. It is shown that a special place in this list is occupied by jade (nephrite), which is one of the most common minerals used in therapeutic equipment. Therefore, the task is to conduct a study of jade of different colors by physical methods.
Materials and Methods. For the study samples of yellow jade, green jade, black jade, and white jade were made; samples of different colors of jades were made according to the “thin section” type and had a flat surface. The phase analysis of jades was carried out on the DRON-1 diffractometer. The diffraction pattern was recorded using a scintillation counter with amplitude discrimination. The diffraction pattern was recorded sequentially as the sample and counter, which were located on the GUR-5 goniometer, rotated. 
Results. The article presents the results of studying the chemical analysis of jades of different colors and a diffractogram of yellow, green, black and white jades. The authors also provide a table for deciphering the interplanar distances and the intensities of the main lines of the studied jade samples.
Discussion and Conclusion. The studies have shown that the studied samples are tremolites by chemical composition. The chemical analysis of black jade showed that because of an increase in ferrous iron and a decrease in the proportion of magnesium, a transition to actinolite is noted. A decrease in fluorine content by an order of magnitude is also observed in the black jade sample.The conducted studies offer new possibilities for expanding the general concepts of creating a healthy environment, where all events are connected in a single logical chain.