Article presents the results of the effect of humidity on early shrinkage of normal concrete with variable W/C ratio. As known for a long time, shrinkage is dependent of many factors. One of them is the W/C ratio and the quantity of water which is located in the concrete mix. In article there were discussed changes taking place in the concrete mix, the methods of research and the partial results obtained by the authors of the paper. Shrinkage is a phenomenon well known and studied by various research centers. The total amount of shrinkage may depend on various factors such as humidity, temperature, composition of the concrete mix, the W/C ratio, the size of the item. The study was conducted to determine the amount of shrinkage in its early stages. It is very important for concrete floors contractors, precast manufacturers to start at the right time finishing work and prevent the formation of shrinkage cracks.

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.

Metal casting process involves processes such as pattern making, moulding and melting etc. Casting defects occur due to combination of

various processes even though efforts are taken to control them. The first step in the defect analysis is to identify the major casting defect

among the many casting defects. Then the analysis is to be made to find the root cause of the particular defect. Moreover, it is especially

difficult to identify the root causes of the defect. Therefore, a systematic method is required to identify the root cause of the defect among

possible causes, consequently specific remedial measures have to be implemented to control them. This paper presents a systematic

procedure to identify the root cause of shrinkage defect in an automobile body casting (SG 500/7) and control it by the application of

Pareto chart and Ishikawa diagram. with quantitative Weightage. It was found that the root causes were larger volume section in the cope,

insufficient feeding of riser and insufficient poured metal in the riser. The necessary remedial measures were taken and castings were

reproduced. The shrinkage defect in the castings was completely eliminated.

In modern times, there are increasing requirements for products quality in every part of manufacturing industry and in foundry industry it

is not different. That is why a lot of foundries are researching, how to effectively produce castings with high quality. This article is dealing

with search of the influence of using different types of risers or chills on shrinkage cavity production in ductile iron castings. Differently

shaped risers were designed using the Wlodawer´s modulus method and test castings were poured with and without combination of chills.

Efficiency of used risers and chills was established by the area of created shrinkage cavity using the ultrasound nondestructive method.

There are introduced the production process of test castings and results of ultrasound nondestructive reflective method. The object of this

work is to determine an optimal type of riser or chill for given test casting in order to not use overrated risers and thus increase the cost

effectiveness of the ductile iron castings production.

This paper presents a new stand for studying the linear shrinkage kinetics of foundry alloys. The stand is equipped with a laser displacement sensor. Thanks to this arrangement, the measurement is of a contactless nature. This solution allows for the elimination of errors which occur in measurements made using intermediary elements (steel rods). The supposition of the expansion (shrinkage) of the sample and the expansion of the heated rod lead to the distortion of the image of the actual dimensional changes of the studied sample. A series of studies of foundry alloys conducted using the new stand allowed a new image of shrinkage kinetics to be obtained, in particular regarding cast iron. The authors introduce in the study methodology a real-time measurement of two linked quantities; shrinkage (the displacement of the free end of the sample) and temperature in the surface layer of the sample casting. This generates not only a classic image of shrinkage (S) understood as S = f (t), but also the view S = f (T). The latter correlation, developed based on results obtained using the contactless method, provide a new, so far poorly known image of the course of shrinkage in foundry alloys, especially cast iron with graphite in the structure. The study made use of hypo- and hypereutectic cast iron in order to generate an image of the differences which occur in the kinetics of shrinkage (as well as in pre-shrinkage expansion - expansion occurs during solidification).

The article is an attempt to compare the impact of the use of various types of limestone as the main constituent of cement on selected mortar properties. Four different limestones were added in amount of 15, 30, 40% to CEM I 42.5 R to obtain limestone cemens. Rheological properties (yield stress, plastic viscosity) of fresh mortar, tensile and compressive mortar strength, early shrinkage, and drying shrinkage were tested. Obtained results indicate that both tensile and compressive strength decreases with the increase of the limestone content in cement. Limestone can worsen or improve workability, depending on distribution of limestone grains. The addition of limestone increases the early shrinkage, but reduces the shrinkage after 28 days. Studies show that the granulation of limestone plays an important role in determining the influence of limestone on mortar properties.

Bayesian VAR (BVAR) models offer a practical solution to the parameter proliferation concerns as they allow to introduce a priori information on seasonality and persistence of inflation in a multivariate framework. We investigate alternative prior specifications in the case of time series with a clear seasonal pattern. In the empirical part we forecast the monthly headline inflation in the Polish economy over the period 2011‒2014 employing two popular BVAR frameworks: a steady-state reduced-form BVAR and just-identified structural BVAR model. To evaluate the forecast performance we use the pseudo real-time vintages of timely information from consumer and financial markets. We compare different models in terms of both point and density forecasts. Using formal testing procedure for density-based scores we provide the empirical evidence of superiority of the steady-state BVAR specifications with tight seasonal priors.

Bartlett’s paradox has been taken to imply that using improper priors results in Bayes factors that are not well defined, preventing model comparison in this case. We use well understood principles underlying what is already common practice, to demonstrate that this implication is not true for some improper priors, such as the Shrinkage prior due to Stein (1956). While this result would appear to expand the class of priors that may be used for computing posterior odds, we warn against the straightforward use of these priors. Highlighting the role of the prior measure in the behaviour of Bayes factors, we demonstrate pathologies in the prior measures for these improper priors. Using this discussion, we then propose a method of employing such priors by setting rules on the rate of diffusion of prior certainty.

The demand for castings of high quality and sound work is nowadays very high. The production of sound castings without foundry errors is the big issue in modern foundries. Foundry simulation software can do a lot to help improve the disposition of castings, gating system and feeder system, and assure good filling and solidification conditions, and also produce sound casting without the need of the old method of "try and error". One can easily change a lot of parameters for filling and solidification, and create the best proposal for production. Connor inlets have two functions. One is that it serves as an ingate, through which molten metal passes and comes into the mould cavity. The second function is that it serves as a feeder and substitutes the metal contracted during solidification and cooling of the castings. It can also save quite a lot of metal in comparison to classic feeders.

The paper presents the results of experimental-simulation tests of expansion-shrinkage phenomena occurring in cast iron castings. The

tests were based on the standard test for inspecting the tendency of steel-carbon alloys to create compacted discontinuities of the pipe

shrinkage type. The cast alloy was a high-silicone ductile iron of GJS - 600 - 10 grade. The validation regarding correctness of prognoses

of the shrinkage defects was applied mostly to the simulation code (system) NovaFlow & Solid CV (NFS CV). The obtained results were

referred to the results obtained using the Procast system (macro- and micromodel). The analysis of sensitivity of the modules responsible

for predicting the shrinkage discontinuities on selected pre-processing parameters was performed, focusing mostly on critical fractions

concerning the feeding flows (mass and capillary) and variation of initial temperature of the alloy in the mould and heat transfer

coefficient (HTC) on the casting - chill interface.

Design of gating system is an important factor in obtaining defect-free casting. One of the casting defects is a porosity caused by internal

shrinkage in solidification process. Prediction of the internal shrinkage porosity in the femoral stem of commercially pure titanium (CP-Ti)

is investigated based on the gating system design. The objective of this research is to get the best gating system between three gating

system designs. Three gating system designs of the femoral stem were simulated in an investment casting method. The internal shrinkage

porosity occurs on the largest part and near the ingate of the femoral stem. The gating system design that has ingates cross section area:

78.5; 157; and 128.5 mm2

has the least of the internal shrinkage porosity. This design has the most uniform solidification in the entire of

the femoral stem. An experiment is conducted to validate the simulation data. The results of internal shrinkage porosity in the three gating

system designs in the simulation were compared with the experiment. Based on the comparison, the trend of internal shrinkage porosity at

the three gating system designs in the simulation agrees with the experiment. The results of this study will aid in the elimination of casting

defect.

The volume changes caused by coupled temperature and moisture variations in early-age concrete elements lead to formation of stresses. If a restraint exists along the contact surface of mature concrete against which a new concrete element has been cast, generated stresses are mostly of a restraint origin. In engineering practice a wide range of externally restrained concrete elements can be distinguished such as tank walls or bridge abutments cast against an old set foundation, in which early-age cracking may endanger their durability or functionality. Therefore, for years methods were being developed to predict early-age stresses and cracking risk of externally restrained concrete elements subjected to early-age thermal-moisture effects. The paper presents the comparative study of the most recognised analytical approaches: the method proposed in EC2, the method proposed by ACI Committee 207 and the method developed at the Luleå University of Technology.

This paper presents the results of measurements of liquid metal fluidity and linear shrinkage of nickel alloy IN-713C in vacuum induction

melting furnace Balzers VSG-2. Because of limited volume of the furnace chamber special models for technological trials were designed

and constructed to fit in the mould of dimensions 170x95x100mm. Two different designs of test models were proposed: horizontal round

rods and modified spiral. Preliminary studies were carried out for alloys Al-Si. Horizontal round rods test was useful for evaluation of

fluidity of hypoeutectic silumin, however in case of nickel superalloy the mould cavity was completely filled in each test because of high

required pouring temperature. Positive results were obtained from the modified spiral test for all alloys used in the research. Relationship

between the linear shrinkage for the test rod and a specific indicator of contraction defined on a spiral was observed.

In order to predict the distribution of shrinkage porosity in steel ingot efficiently and accurately, a criterion R√L and a method to obtain its

threshold value were proposed. The criterion R√L was derived based on the solidification characteristics of steel ingot and pressure

gradient in the mushy zone, in which the physical properties, the thermal parameters, the structure of the mushy zone and the secondary

dendrite arm spacing were all taken into consideration. The threshold value of the criterion R√L was obtained with combination of

numerical simulation of ingot solidification and total solidification shrinkage rate. Prediction of the shrinkage porosity in a 5.5 ton ingot of

2Cr13 steel with criterion R√L>0.21 m･℃1/2･s

-3/2 agreed well with the results of experimental sectioning. Based on this criterion,

optimization of the ingot was carried out by decreasing the height-to-diameter ratio and increasing the taper, which successfully eliminated

the centreline porosity and further proved the applicability of this criterion.

This work presents a scheme for the manufacture of spherical grinding bodies used in grinding and crushing machinery as a grinding medium from abrasion-resistant cast iron CHKH16 (according to GOST 7769-82) free of shrinkage defects produced by casting into single sand molds with a vertical joint and by usingcoolers. The grinding efficiency in terms of material destruction and energy consumption has been studied according to a wide range of operating parameters and new scheme for calculating the sprue and supply system has been developed by the authors of the article. Its functionality has been substantiated, particularly the use of a central riser acting as a head and the use of coolers. The conducted numerical simulation has shown the dependence of a solid phase formation over time, which characterizes the direction of the system crystallization and determines the locations of the shrinkage defects concentration. The manufacture of the grinding body with a 100 mm diameter using the considered technology is presented in this paper.

US A356 and US 413 cast aluminium alloys shrinkage characteristic have been discussed in the present study. Specific volume reduction

leads to shrinkage in castings and it can be envisaged as a casting defect. Finite difference based casting process simulation software has

been used to study the shrinkage characteristic and it is quantified using mathematical formulae. The three dimensional model of the

shrinkage defect has been constructed using CAD application software. Shrinkage characteristic has also been quantified through

experimental validation studies and compared well with casting process simulation. Shrinkage characteristic study and control is essential

for producing defect free castings. Influence of casting shape on the shrinkage characteristic has been studied in this paper.