Influencing of foundry bentonite mixtures by binder activation

Although new moulding processes for manufacture of high quality castings have been developed and introduced into foundry practice in recent years, the green-sand moulding in bentonite mixture still remains the most widely used technology. Higher utility properties of bentonite binders are achieved through their activation. This contribution is aimed at finding a suitable activating agent. A number of sodium salts and MgO based agents has been chosen. In the framework of the experiment the swelling volume of chosen agents was tested and technological parameters of a bentonite mixture with a binder activated with the studied agents were determined

Motion study in interactive remote experiments with data collection and transfer across internet

Within the strategy of Integrated e-Learning (INTe-L) we set up several remote interactive mechanics experiments across the Internet studying the linear and curvilinear motion For the purpose, we use the measuring hardware and software -Intelligent School Experimental System (ISES) with sensing units for data collection, recording and evaluation and the software ISES WEB CONTROL kit for establishing the server-client connection. As the first experiment we devised and constructed a new and sophisticated experiment free fall, based on the motion of the permanent magnet in a glass tube with induction pick up coils for position measurement (http://remotelab4.truni.sk) To transform the hands-on experiment into a remote one, we have had to move the magnets to their starting position by the magnetic vessel, surrounding the tube. Second experiment, the mathematical pendulum remote experiment (http://remotelab5.truni.sk) was created with a unique reconstruction of its instantaneous angle of deflection using two force-sensing elements and an on-line exploited algorithm (ISES supported) for the angle of deflection on line display

Comparison of surgical treatment results of critical limb ischemia and analysis off actors influencing the outcome of surgical treatment

Objective. To evaluate the results of surgical treatment of critical limb ischemia in two specialized vascular centers. Materials and methods. The results of surgical treatment of 202 patients with critical lower limb ischemia, which were operated in two specialized vascular centers: I Group (76 patients) -ClinicofVascularSurgery at the Military Hospital, Ruzomberok,Slovak Republic; II Group (126 patients) -ClinicofVascularSurgery, EastSlovakInstituteofCardiovascularDiseases, Kosice, Slovak Republic. Results.The patency of arterial reconstructions in I Group was: the femoro-supragenicular segment: 1 year -83%, 3 years - 73%;the infragenicular segment: 1 year - 68%, 3 years - 52%. In II Group -the femoro-supragenicular segment: 1 year - 91%, 3 years - 82%;the infragenicular segment: 1 year - 72%, 3 years - 64%. Conclusion.The patency of arterial reconstructions during the first year in both vascular centers was without statistical difference. The femoro-supragenicular reconstructions had the best patency over three years (> 70%). The following factors influenced the duration of arterial reconstructions: the type of graft used, diabetesmellitus, smoking

Influence of ecologically friendly cores on surface quality of castings based on magnesium alloys

Constructional materials as Al - alloys can be replaced by other materials with high strength to low mass density ratio, e.g. Mg-alloys. In order to pre-casting of holes and cavities cores based on pure inorganic salt can be applied due to easy cleaning of even geometrically complex pre-cast holes. This technology is applied mainly for gravity and low-pressure casting technology. This contribution is aimed at studying of mutual interaction of the Mg-alloy and the salt core. Experiments were focused on surface quality; macro- and microstructure of testing casting samples determination. Metallographic analysis and scanning electron microscope (SEM) with X-ray energy-dispersion superficial and spot microanalysis (EDAX) were employed

Upalni i hematotoksični potencijal metabolita plijesni Stachybotrys chartarum (Ehrenb.) Hughes u zatvorenim prostorijama

Mould Stachybotrys chartarum (Ehrenb.) Hughes is known to pose a health risk in indoor environments. Most of its strains can produce several intra- and extracellular trichothecene mycotoxins. Complex secondary metabolites of stachybotrys isolates from mouldy dwellings/public buildings in Slovakia were intratracheally instilled in Wistar male rats (4 μg in 0.2 mL of 0.2 % dimethylsulphoxide; diacetoxyscirpenol as the positive control). After three days, haematological parameters were measured in peripheral blood and infl ammatory response biomarkers in bronchoalveolar lavage fl uid (BALF), and the results were statistically analysed. Exometabolites proved to suppress red blood cell (RBC), decreasing the total RBC count, haemoglobin, and haematocrit. The exposed rats showed signifi cantly higher total BALF cell count, indicating infl ammation, lower alveolar macrophage counts, and increased granulocyte count related to the BALF cells. Due to haematotoxic and infl ammation-inducing properties, metabolites of S. chartarum can cause damage to the airways and haematological disorders in occupants of mouldy buildings.Plijesan Stachybotrys chartarum (Ehrenb.) Hughes poznata je kao rizični mikroorganizam u zatvorenim prostorijama. Većina njezinih sojeva može proizvesti nekoliko unutarstaničnih i izvanstaničnih trikotecenskih mikotoksina. Muškim Wistar štakorima instilirani su intratrahealno kompleksni sekundarni metaboliti stahibotrisa izolirani iz stambenih i javnih zgrada u Slovačkoj zahvaćenima plijesni (4 μg na 0,2 mL 0,2 %-tnog dimetilsulfoksida; dok se diacetoksiscirpenol rabio kao pozitivna kontrola). Tri dana kasnije izmjereni su hematološki parametri u perifernoj krvi te biopokazatelji upalnoga odgovora u bronhoalveolarnome ispirku te su rezultati obrađeni statistički. Pokazalo se da egzometaboliti suprimiraju eritrocite, smanjujući njihov ukupni broj, hemoglobin i hematokrit. Izloženi štakori imali su značajno veći broj stanica u bronhoalveolarnome ispirku, što upućuje na upalu, dok im je broj alveolarnih makrofaga bio manji, a broj granulocita povezanih sa stanicama u ispirku veći. Zbog svojih hematotoksičnih i upalnih svojstava S. chartarum može dovesti do oštećenja dišnih putova i poremećaja u krvotvornome sustavu osoba koje žive i/ili rade u zgradama zahvaćenima tom plijesni

The optimal tribotechnical factors in the design of machines – environmental element in the production systems

The article deals with the experimental detection of the tribotechnical parameters for two different types of sliding bearings which are intended for operation without an additional lubrication due to the increasing requirements in ecology and environment. The dominant tribotechnical parameters of the self-lubricating bearing are the coefficient of friction and temperature. To determine these parameters, an experimental method was applied in this paper. The introductory part deals with materials of self-lubricating sliding bearings, their properties and usage. The experimental part consists of the evaluation of friction characteristics and geometric change of a surface after sliding pairs were being worn. Experimental examined sliding pairs comprise a sliding bearing and the shaft. The aim of this research was to determine the effect of radial force on tribotechnical parameters in order to predict the behavior of examined sliding bearings in real operating conditions

Reclamation of self-setting mixtures with olivine bound with alkaline resols

For the reasons of environmental problems connected with the use of furan binders the attention is increasingly paid to self-setting mixtures with alkali resols. A resol binder stabilized with KOH, NaOH is hardened by liquid esters with the formation of alkaline salts. The increase of their concentration affects the shortening of the mixture bench life, it decreases strength, abrasive wear of moulds and cores is growing, and it results in uneconomical dilution of the reclaim with expensive new base sand. Length of life (bench life) of mixtures plays an important role just in manufacture of huge and voluminous moulds and cores in self-setting mixtures. This contribution aims at analyzing the function of reactive alkaline salts in the reclaim, it monitors consequences of its thermal exposure on properties of self-setting mixtures, and it deals with development of methods evaluating its qualities

Reclamation of Self-Setting Mixtures with Olivine Bound with Alkaline Resols

For the reasons of environmental problems connected with the use of furan binders the attention is increasingly paid to self-setting mixtures with alkali resols. A resol binder stabilized with KOH, NaOH is hardened by liquid esters with the formation of alkaline salts. The increase of their concentration affects the shortening of the mixture bench life, it decreases strength, abrasive wear of moulds and cores is growing, and it results in uneconomical dilution of the reclaim with expensive new base sand. Length of life (bench life) of mixtures plays an important role just in manufacture of huge and voluminous moulds and cores in self-setting mixtures. This contribution aims at analyzing the function of reactive alkaline salts in the reclaim, it monitors consequences of its thermal exposure on properties of self-setting mixtures, and it deals with development of methods evaluating its qualities

Alternatywna ocena jakosci piasków kwarcowych

For the evaluation of silica sands, which belongs to the most employed sands of foundry molding mixtures, there are a number of methods and techniques to characterize their quality. This implies good knowledge of their strengths and weaknesses. However, a small proportion of published results are dedicated to the impact of transport on transport routes in the foundry and the processes of dry reclamation on the properties of the silica sands, in particular on changes to the granulometry and the formation of undesirable dust sands shares, which significantly affect the properties of the sand mixture. The aim of this contribution is the evaluation of inclination of the silica sand to crush (the formation of dust, change the granulometry) according to the newly developed methodology with regard to its nature of sand (genesis, the shape of the grains, the character of the surface).Piaski kwarcowe stanowią podstawowe tworzywo na osnowę mas formierskich i rdzeniowych. Stąd istnieje bardzo wiele metod charakteryzujących ich jakość, co umożliwia poznanie ich zalet i wad. Mało jest jednak prac opisujących wpływ systemów transportowych odlewni oraz systemów suchej regeneracji mas na zmianę ich składu granulometrycznego oraz zawartości frakcji pylastych na właściwości mas. Celem niniejszej pracy jest ocena skłonności piasku kwarcowego do rozkruszania, (tworzenia frakcji pyłowych i zmianie granulometrii) według nowo opracowanej metodyki uwzględniającej charakterystyczne cechy piasku wynikające z jego pochodzenia, kształty ziaren i charakteru powierzchni