A metamaterial absorber (MA) based sensor is designed and analysed for various important applications including pressure, temperature, density, and humidity sensing. Material parameters, as well as equivalent circuit model have been extracted and explained. After obtaining a perfect absorption (PA) at around 6.46 GHz and 7.68 GHz, surface current distributions at resonance points have been explained. Since bandwidth and applicability to different sensor applications are important for metamaterial sensor applications, we have realized distinctive sensor demonstrations for pressure, temperature, moisture content and density and the obtained results have been compared with the current literature. The proposed structure uses the changes on the overall system resonance frequency which is caused by the sensor layer’s dielectric constant that varies depending on the electromagnetic behaviour of the sample placed in. This model can be adapted to be used in sensor applications including industrial, medical and agricultural products.

Presented are results of a research on usability of an innovative reclamation process of microwave-hardened moulding sands containing

water-glass, combined with activation of binder. After each subsequent stage of reclamation, quality of the reclaimed material was

determined on the grounds of measurements of permeability and results of screen analysis. The reclaimed material was next used again to

prepare new moulding sand. The sandmix based on high-silica sand prepared with water-glass grade 145, was subject to the following

cyclical treatment operations: mixing components, consolidation, microwave hardening, cooling, heating the mould up to 800 °C, cooling

to ambient temperature, mechanical reclamation dry and wet. It was found that the used-up and reclaimed sandmix containing water-glass

is susceptible to the applied activation process of thermally reacted film of binder and, in addition, it maintains good quality and

technological properties of high-silica base. Observations of surfaces of reclaimed high-silica grains with activated film of reacted

inorganic binder were carried-out using a scanning microscope. Thanks to properly selected reclamation parameters, the high-silica base

can be reused even five times, thus reducing demand for fresh aggregate and inorganic binder.

In the paper, an attempt was made to evaluate the effect of preliminary wetting of high-silica base during preparation of moulding sands

containing a selected grade of sodium water-glass, designed for hardening by traditional drying or by electromagnetic microwaves at 2.45

GHz. In the research, some water was dosed during stirring the sandmix before adding 1.5 wt% of the binder that was unmodified sodium

water-glass grade 137, characterised by high molar module within 3.2 to 3.4. Scope of the examinations included determining the effect of

wetting the base on mechanical parameters like compression, bending and tensile strength, as well as on technological parameters like

permeability, abrasion resistance and apparent density. The research revealed a significant positive effect of adding water to wet surfaces

of high-silica base grains on mechanical properties and quality of moulding sands hardened by physical methods, in particular by

microwave heating

In this study, laboratory-scale experiments were carried out to investigate the effects of microwave-assisted alkaline leaching on the treatment of electric arc furnace dusts to recover zinc and lead. Microwave treatment is a new innovative technology in waste treatment and now is an attractive advanced inter-disciplinary field and also environmental friendly. The highest zinc extraction, 50.3% in 60 minutes using 5 M NaOH at 750 W and L:S ratio 20, and lead extraction up to 92.84% was achieved in these same conditions but in 30 minutes. Compared with conventional leaching, the top extraction rate using MW-assisted leaching was higher by 16% (Zn) and 26% (Pb). Zinc presents in the flue dust in the form of franklinite (ZnFe2O4), its leaching in sodium hydroxide does not occur under the examined conditions, because it is enclosed in a matrix of iron.

This original paper deals with a new approach for the study of behavior in nonlinear regime of a new three-phase high voltage power supply for magnetrons, used for the microwave generators in industrial applications. The design of this system is composed of a new three-phase leakage flux transformer supplying by phase a cell, composed of a capacitor and a diode, which multiplies the voltage and stabilizes the current. Each cell. in turn, supplies a single magnetron. An equivalent model of this transformer is developed taking into account the saturation phenomenon and the stabilization process of each magnetron. Each inductance of the model is characterized by a non linear relation between flux and current. This model was tested by EMTP software near the nominal state. The theoretical results were compared to experimental measurements with a good agreement. Relative to the current device, the new systemprovides gains of size, volume, cost of implementation and maintenance which make it more economical.

In the paper, an attempt is made to explain the previously observed increased effectiveness of utilising hydrated sodium water-glass grade

137 after hardening moulding sands with selected physical methods. In the modified process of preparing sandmixes, during stirring

components, water as a wetting additive was introduced to the sand-binder system. Presented are examination results of influence of faster

microwave heating and slower traditional drying of the so-prepared moulding sands on their tensile and bending strength, calculated per

weight fraction of the binder. The measurement results were confronted with SEM observations of linking bridges and with chemical

analyses of grain surfaces of high-silica base. On the grounds of comprehensive evaluation of hardened moulding sands, positive effects

were found of the applied physical process of binder dehydration and presence of the wetting additive. It was observed that introduction of

this additive during stirring, before adding the binder, improves flowing the binder to the places where durable linking bridges are created.

It was also found that the applied methods of hardening by dehydration enable creation of very durable linking bridges, strongly connected

with the sand base, which results in damages of high-silica grain surfaces, when the bridges are destroyed.

Within the research, selected multilayer technological systems created as combinations of water-glass containing moulding sand with

foundry tooling, were characterised on the grounds of their electrical properties. By measuring resonance frequency and quality factor of a

waveguide resonance cavity, real component of permittivity εr′ and loss tangent tgδ were determined for multilayer foundry systems with

various qualitative and quantitative compositions. It was demonstrated that combination of a sandmix and foundry tooling with known

dielectric properties results in a system with different physico-chemical properties, whose relation to the parameters of individual

components of the system is undefined at this research stage. On the grounds of measurement results, theoretical value of microwave

heating power, dissipated in unit volume of the selected multilayer foundry system, was determined. Knowledge of theoretical heating

power and evaluation of physical, chemical and structural changes occurring in moulding sands exposed to microwaves in such a

technological system makes a ground for empirical modelling of the process of microwave heating of foundry moulds and cores.

In the paper presented are results of a research on influence of electrical and physico-chemical properties of materials being parts of

multicomponent and multimaterial systems used in foundry practice on efficiency and effectiveness of microwave heating. Effectiveness

of the process was evaluated on the grounds of analysis of interaction between selected parameters of permittivity and loss factor, as well

as collective index of energy absorbed, reflected and transmitted by these materials. In the examinations used was a stand of waveguide

resonance cavity for determining electrical properties and a stand of microwave slot line for determining balance of microwave power

emitted into selected materials. The examinations have brought closer the possibility of forecasting the behaviour of multimaterial systems

like e.g. model, moulding sand or moulding box in microwave field on the grounds of various electrical and physico-chemical properties.

On the grounds of analysis of the results, possible was selecting a group of materials designed for building foundry instrumentation to be

effectively used in electromagnetic field.

Moulding sands containing sodium silicate (water-glass) belong to the group of porous mixture with low resistance to increased humidity.

Thanks to hydrophilic properties of hardened or even overheated binder, possible is application of effective methods of hydrous

reclamation consisting in its secondary hydration. For the same reason (hydrophilia of the binder), moulds and foundry cores made of

high-silica moulding sands with sodium silicate are susceptible to the action of components of atmospheric air, including the contained

steam. This paper presents results of a research on the effect of (relative) humidity on mechanical and technological properties of

microwave-hardened moulding mixtures. Specimens of the moulding sand containing 1.5 wt% of sodium water-glass with module 2.5

were subjected, in a laboratory climatic chamber, to long-term action of steam contained in the chamber atmosphere. Concentration of

water in atmospheric air was stabilized for 28 days (672 h) according to the relative humidity parameter that was ca. 40%, 60% and 80% at

constant temperature 20 °C. In three cycles of the examinations, the specimens were taken out from the chamber every 7 days (168 h) and

their mechanical and technological parameters were determined. It was found on the grounds of laboratory measurements that moulds and

cores hardened with microwaves are susceptible to action of atmospheric air and presence of water (as steam) intensifies action of the air

components on glassy film of sodium silicate. Microwave-hardened moulding sands containing sodium silicate may be stored on a longterm

basis in strictly determined atmospheric conditions only, at reduced humidity. In spite of a negative effect of steam contained in the

air, the examined moulding mixtures maintain a part of their mechanical and technological properties, so the moulds and foundry cores

stored in specified, controlled conditions could be still used in manufacture.

In the paper, presented is a research on effectiveness of absorbing electromagnetic waves at frequency 2.45 GHz by unhardened moulding

sands prepared of three kinds of high-silica base and a selected grade of sodium silicate. Measurements of power loss of microwave

radiation (Pin) expressed by a total of absorbed power (Pabs), output power (Pout) and reflected power (Pref) were carried-out on a stand of

semiautomatic microwave slot line. Values of microwave power loss in the rectangular waveguide filled with unhardened moulding sands

served for determining effectiveness of microwave heating. Balance of microwave power loss is of technological and economical

importance for manufacture of high-quality casting moulds and cores of various shapes and sizes. It was found that relative density

influences parameters of power output and power reflected from samples of moulding sand placed in a waveguide. Absorption expressed

by the parameter Pabs is not related to granularity of high-silica base: fine, medium and coarse. It was found that the semiautomatic

microwave slot line supports evaluation of effectiveness of microwave absorption on the grounds of power loss measurements and enables

statistic description of influence of relative density of the sandmix on penetration of electromagnetic waves in unhardened moulding sands.

Presented are results of a preliminary research on determining a possibility to use microwave radiation for drying casting protective

coatings applied on patterns used in the lost foam technology. Taken were measurements of permittivity εr and loss factor tgδ at 2.45 GHz,

as well as attempts were made of microwave drying of a protective coating based on aluminium silicates, applied on shapes of foamed

polystyrene and rigid polymeric foam. Time and results of microwave drying were compared with the results obtained by drying at 50 °C

by the traditional method commonly used for removing water from protective coatings. Analysis of the obtained drying kinetics curves

demonstrated that selection of proper operation parameters of microwave equipment permits the drying time to be significantly shortened.

Depending on kind of the pattern material, drying process of a protective coating runs in a different way, resulting in obtaining different

quality of the dried coating.

This paper analyses the influence of the applied microwave power output on the intensification of drying in the context of process kinetics and product quality. The study involved testing samples of beech wood (Fagus sylvatica L.). Wood samples were dried in the microwave chamber at: 168 W, 210 W, 273 W, 336 W and 378 W power output level. For comparison, wood was dried convectively at 40 ◦C and 87% air relative humidity. The analysis of drying process kinetics involved nonlinear regression employing the Gompertz model. Dried samples were subjected to static bending tests in order to specify the influence of the applied microwave power on modulus of elasticity (MOE) and modulus of rapture (MOR). The obtained correlations of results were verified statistically. Analysis of drying kinetics, strength test results and Tukey’s test showed that the applied microwaves of a relatively low level significantly shortened the drying time, but did not cause a reduction in the final quality of dried wood, compared with conventional drying.