Since the second half of the 20th century many cities in Poland lose population and the rate is more than likely to increase in future. The determinants that have the greatest impact on the process of shrinking cities are those related to economic transformation and restructuring of the so called traditional industry and consequences of the second demographic transition. In general, it can be distinguished a few main drivers for shrinkage of cities: transformation, suburbanization, demographic change (e.g. falling birth rates, outmigration in rural depopulation areas), environmental pollution. Shrinkage is a varied phenomenon because of its multidimensional, multiscalar and multitemporal character. But the multifacted character of these processes renders their recognition and estimation difficult. The purpose of the article is to identify the sorts of shrinking cities and to presents method of measuring this process. This paper presents the differentiation of shrinking cities process in Poland on the basic of selected empirical indicators. A detailed analysis was conducted in cities with more than 100 thousand inhabitants in the period of 2000–2017.
At thermal junctions of aluminium alloy castings and at points where risering proves to be difficult there appear internal or external shrinkages, which are both functionally and aesthetically inadmissible. Applying the Probat Fluss Mikro 100 agent, which is based on nano-oxides of aluminium, results in the appearance of a large amount of fine microscopic pores, which compensate for the shrinking of metal. Experimental tests with gravity die casting of AlSi8Cu3 and AlSi10Mg alloys have confirmed that the effect of the agent can be of advantage in foundry practice, leading to the production of castings without local concentrations of defects and without the appearance of shrinkages and macroscopic gas pores. Also, beneficial effect on the mechanical properties of the metal has been observed.