BIBLIOMETRIC ANALYSIS OF THE DEVELOPMENT OF THE DIRECTION "DREDGING" IN WORLD PRACTICE

Objective. The study is aimed at obtaining new up-to-date knowledge and analysis of already existing one about the development of the "Dredging" direction in the world scientific space using the products and services of the Scopus scientometric database. Therefore, the chronological framework of the scientific articles under study is limited only by their availability in the Scopus database. Methods. In order to obtain relevant empirical data, the authors of the study reviewed the world scientific literature on the topic "Dredging" using the resources of the international reference and scientometric database of peer-reviewed literature Scopus. The algorithm of "step by step" actions in the Scopus database is considered: 1. Forming the circle of the most cited publications; 2. Defining the most relevant topics; 3. Identifying the most productive authors; 4. Determining the level of representation in the Scopus database of publications of Ukrainian scientists by the research topic. Results. During the study the authors have proved: 1. The main topics of the “Dredging” direction are: the impact of dredging on the ecology of the aquatic environment and marine life; models and algorithms for assessing and minimizing the risks associated with dredging; application of bottom sediments after dredging and their disposal in open waters; dredging fleet maintenance; 2. Scientists of our country are very slowly joining the world processes of exchange of scientific information in the "Dredging" direction; 3. The most intellectually productive authors of scientific articles in this field are scientists from the USA, Spain, Great Britain and Australia. Conclusions. For the first time in Ukraine, the authors conducted a bibliometric study in the field of water transport (subject area "Dredging") on the basis of products and services of the Scopus scientometric database. The results obtained can be used for further scientific research on this and related topics, as well as applied in the dredging discipline teaching process.


Introduction
Ukrainian ports are an essential element of the country's logistics infrastructure. In the World Economic Forum's Port Quality Rating, from 2014 to 2017, Ukraine improved its position slightly, rising from 107th to 93rd position (among 137 countries) (Hryhorenko, 2018). Dredging works are of great economic importance for increasing freight traffic and expanding ports, as the development of world trade is forcing ports to increase their capacity. This leads to the deepening of the water areas of the ports and the existing access channels, which makes it possible to accept larger merchant vessels (Dnouglubitelnyie i morskie rabotyi, 2018).
For Mykolayiv, these works are very important, because the Mykolayiv seaport will have all the conditions for servicing Panamax heavy-duty vessels, which will increase the port fees and payments to the state budget of Ukraine and will allow to develop business for Ukrainian companies operating in the water area of the port. For a long time no one has addressed the dredging issue in Ukraine properly. There is almost no research on the dredging problems in modern Ukrainian scientific literature. International experience confirms the necessity and prospect of this direction. Numerous world studies in recent years indicate the continued interest of scientists in various aspects of the development of water transport and the provision of uninterrupted and safe navigation through the regular production of track works, one of the main types of which is dredging.
Recently, the results of scientific studies in librarianship and scientometrics in various directions are increasingly appearing in the domestic scientific literature. However, the authors conducted the bibliometric research in the field of water transport ("Dredging" subject area) on the basis of products and services of Scopus scientometric database (DB) for the first time in Ukraine.

Methods
The practical part of the study is based on the Scopus DB -a bibliographic and abstract database and a tool for tracking the citation of articles published in scientific publications. This database is the most comprehensive resource for the search of scientific literature.
Step by step search activity in Scopus DB. 1. We start working with the Scopus database from the main page at https://www.scopus.com. In the Advanced Search tab, we list the keywords "dredging" and "ships" and select the "AND" operator. The system search result consists of 2,593 documents. 2. Then we specify the request. In the "Knowledge area" select "Engineering". In the field "Document type" select "Article". In the "Keywords" field, we choose, among the ones provided by the system, those that are directly related to dredging and ships, ports and terminals, environmental and ecosystem protection, sediment contamination, etc. ("Dredging", "Ships", "Dredges", "Sediments", "Ports And Harbors", "Dredger", "Geologic Sediments", "Marine Environment", "Shipbuilding", "Ecosystem", "Water Pollution", "Sediment Pollution", "Waterway Transportation", "Environmental Protection", "Land Reclamation", "Climate Change", "Suction Dredger", "Coastal Engineering", "Ecosystems", "Environmental Impact Assessment", "Hydraulic Structures", "Marine Engineering", "Dredging Operations", "Port Terminals", "Cutter Suction Dredger", "Marine Sediment", "Oceans And Seas", "Coastal Zone", "Port Development", "Navigation Channels", "Conservation Of Natural Resources"). As a result, we get 1,441 documents. 3. Further work is the analysis of selected documents using the service "Analyze search results". The analysis results is the number of published documents for each year ( 5. The leader in international recognition of publications is determined by the citation of works. Therefore, the next step is to identify the most cited articles that will constitute the so-called "core" and to compile a citation report (Table 1). To do this, go to the tab "View Citation Overview" and sort the selected documents by the number of citations in order of reduction. The number of citations during the last 15 years is presented in Figure 2.

Figure 2. Number of citations during the last 15 years according to Scopus database
The total number of citations of 1 411 documents selected for analysis is 11 134. Among the selected articles, 676 have non-zero citations. Of these, 557 articles have been cited more than 1 time and 20 cited more than 100 times. The most citations were received by articles in 2018 (1689), 2017 (1414) and 2016 (1205). In 2019, the articles received 1,316 citations.
Of the 1 411 articles, 97 are presented in Open Access, thereof 76 have more than 1 citation. 3 articles have more than 100 citations. The main topics of the most cited works are, first of all, devoted to the impact of dredging on the ecology of the aquatic environment and marine life. The addressed issues also include: dredging risk assessment and minimization; environmental impact of deepening of the bottom and widening of the reservoir bed by extraction of underwater soil; application of bottom sediments after dredging and their disposal in open waters; dredging fleet maintenance.
The distribution of the most cited articles by country is as follows, %: United Kingdom -20 Australia -40 Belgium -20 Spain -20 The distribution of the most intellectually productive authors of scientific articles by the Hirsch index is presented in Table 2.

Results and Discussion
The content analysis of publications in the field of dredging proves that dredging problems are relevant in many countries of the world. They are considered and researched from numerous aspects. Scientists study and analyse: projects for deepening rivers, lakes and ponds; environmental issues related to the clarification of reservoirs after dredging; the impact of hydrotechnical structures on the environmental situation in water bodies and adjacent territories; problems of design and application of dredging equipment; solving port infrastructure problems. During the study the following results were obtained: in Scopus database 1 411 documents correspond to the given parameters. Most articles (70)  Ukrainian scientists are represented in the Scopus database by two papers which discuss the problems of dredging. They were published in the journal Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu (2014) and in the proceedings of the US/EU-Baltic International Symposium: Ocean Observations, Ecosystem-Based Management and Forecasting -Provisional Symposium Proceedings, BALTIC (2008). Such a number of documents confirms the fact that for a long time nobody has properly dealt with the dredging issue in Ukraine.

Conclusions
During the study the authors proved that the main topics of the "Dredging" direction are: the impact of dredging on the ecology of the aquatic environment and marine life; models and algorithms for assessing and minimizing the risks associated with dredging; application of bottom sediments after dredging and their disposal in open waters; dredging fleet maintenance; scientists of our country are very slowly joining the world processes of exchange of scientific information in the "Dredging" direction; the most intellectually productive authors of scientific articles in this field are scientists from the USA, Spain, Great Britain and Australia.
Subsequently, the study materials can be used to create an information base and to train dredging specialists.