Time series research in the non-ferrous scrap recycling sector with identification of trend-seasonal components by Chetverikov method

The article is devoted to identifying of trend-seasonal components using iterative methods of the non-ferrous scrap metal collection filtering. According to the study objectives and the results of the time series characteristics analysis, the Chetverikov method implementation as a method for data filtering is described stepwise. Calculations and construction of diagrams were carried out in MS Excel. The study result is a visualized stepwise filtering of the trend-seasonal time series of the non-ferrous scrap mass in two positions - copper and brass, as well as the values of the seasonal component and specific seasonality indices calculated using the Chetverikov method, which makes it possible to study further the use and predicting of the non-ferrous metal scrap collection rate in the region, to select effective forecasting methods and models.


Introduction
The growth of the metallurgical industry determines the successful development of a significant number of other economic sectors. The metallurgical complex plays an important role in the industry of any country, thus it is the basic economic industry. Russian metallurgy is a major player in the global metals market; it is one of the Russia's specialization branches within the international labor division. The metallurgical industry includes two main directions: ferrous and non-ferrous metallurgy. Ferrous metallurgy works with iron-based alloys and products. The second direction includes work on the alloys smelting and the products manufacture from non-ferrous metals (all metals except iron). Non-ferrous metals are corrosion and wear resistant, have good electrical conduction properties. These properties determine a wide range of non-ferrous metal applications in the national economy.
The achievement of effective economic indicators in this sector of the economy is associated, among other things, with the usage expansion of waste from metal and scrap metal. The non-ferrous scrap recycling is a promising direction in the development of the metallurgical industry and business organization in our country for the following reasons, which are revealed in these industry specifics [1,2].
1. Materials intensify. For the majority of non-ferrous metals, Russian deposits are characterized by the poverty of mined ores. For example, in copper ore, the copper content ranges from 1% to 5%.
2. Energy intensity, resource consumption. The raw materials extraction, their processing and metal smelting is accompanied by the need for a large amount of fuel, electricity and water.
3. Labour effort. 4. The inaccessibility of ores, the problem of the transport infrastructure provision. 5. Impressive costs for the construction, technical and technological equipment of the full cycle metallurgical complex plants.
6. Environmental impact etc. The relevance of non-ferrous metal processing is primarily due to the fact that industrial and manufacturing enterprises, taking into account modern trends in the development of the metallurgical industry, are looking for real opportunities to reduce costs. The processing of non-ferrous scrap metal contributes to natural resources saving, the raw materials supply problem solving, reducing of production costs, as well as the costs of erecting, creating and maintaining of a full-cycle metallurgical plants complex infrastructure, time expenditures, labor inputs, is energetically more efficient in comparison with mining from ore material, helps to reduce the level of environmental pollution. The metals recycling leads to a reduction in a vast list of expenditure items, which in sum, will affect the metal products cost and lead to the price decrease of finished products for the end consumer. At the same time, recyclable materials are endowed with practically the same properties as primary ones and, unlike plastic and other recyclable materials, metal can be recycled and involved in economic circulation many times.
The prospect of economic research in the field of non-ferrous metals recycling is also determined by the state interest in the development of opportunities related to the organization of collection and processing of secondary metal. These trends are reflected in the draft Strategy for the development of the metallurgical industry in Russia for the period up to 2030 and in the order of the President of the Russian Federation dated February 23, 2019 draft number 277, 1b item-on improving the rules for handling scrap and waste of ferrous and non-ferrous metals, mechanisms for involving these scrap and waste into recycling, as well as the introduction of a procedure for their alienation by selling at public auctions, including digital platforms using. In the long term, in order to increase the use of secondary metal raw materials, it is planned to organize the construction of small plants for the scrap metal processing. In the medium term, measures are being developed and implemented to increase scrap collection in the country. Thus, economic research at all stages of the scrap metal recycling, including at its primary stage -the scrap metal collection, becomes relevant, since the identification of its economic indicators, in particular seasonal fluctuations, contributes to an increase in scrap collection.

Research methodology
By seasonal fluctuations we mean regular, periodic onset of intra-annual ups and downs in production, cargo and commodities turnover associated with the seasons change. Seasonality is a stable, timerepeating periodicity in the development of economic phenomena. It means any economic processes that are caused by calendar and (or) climatic reasons. To be able to use and influence seasonality purposefully, you need to be able to isolate, measure, analyze, and make forecasts regarding processes subjected to seasonal fluctuations, as well as carry out long-term, medium-term and current planning.
A time-ordered sequence of economic process observations is called a time series, and if the process is subject to periodic fluctuations with a definite and constant period equal to an annual interval, then this is a trend-seasonal time series [2].
At the beginning of the last century, Chetverikov developed an iterative method that makes it possible to exclude the influence of seasonal waves of variable structure. Using this method, we investigate the monthly time series of the non-ferrous scrap (copper, brass) metals mass handed over to scrap metal collection stations in Krasnodar. Copper and brass as the most frequently donated nonferrous metals with daily weight values other than zero were selected for the study. The period of time series research is from 01/01/2016 to 01/01/2019.

Research stages 1.
A visual assessment of the initial data diagram was made (monthly indicators of the copper and brass scrap mass for 2016-2019 with a discreteness of 1 year), which allowed us to assume the presence of seasonality in these time series (Fig. 1).     Figure  3: (1) (3)

Results discussion and conclusion
Currently, one of the most promising and used forms of forecasting is forecasting based on a time series, which allows you to carry out all types of planning, calculate the amount of required resources, minimize risks and losses in economic activity. The author of the work plans to conduct further research of the time series presented in the work to predict the development dynamics of processes using nonlinear dynamics methods, for the effective usage of which it is necessary to perform a comprehensive analysis of time series, taking into account the seasonal component [3].