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.

W pracy przedstawiono wyniki badań nad wpływem promieniowania mikrofalowego na proces oczyszczania ścieków w reaktorze z błoną biologiczną. Do reaktorów umieszczonych we wnętrzu komory mikrofalowej dostarczano promieniowanie mikrofalowe o częstotliwości 2,45 GI-Iz. Jako źródło mikrofal wykorzystano pracujący ze stalą moc magnetron, natomiast sterowania ilością dostarczanego promieniowania odbywało si, poprzez zmienne czasy trwania następujących kolejno faz napromieniowania i oczyszczania. Badania przeprowadzono w trzech układach następujących cyklicznie faz: 7 s napromieniowanie 10 min oczyszczanie, 7 s napromieniowanie 5 min oczyszczanie oraz 25 s napromieniowanie I O min. oczyszczanie. W ten sposób dostarczanego do reaktora promieniowania, odpowiednio w ilości 1,2 W·s. 2,5 W· s oraz 4,3 W· s. Uzyskane wyniki badań wskazują, że promieniowanie mikrofalowe wpływa na proces biologicznego oczyszczania ścieków nie tylko w wyniku klasycznego ogrzewania. ale i poprzez swoje właściwości atcrrnicznc. Szczególnie w przypadku przemian prowadzących do usunięcia azotu obserwowane było istotne zwiększenie ich sprawności w wyniku oddziaływania mikrofal.

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

The paper presents results of preliminary examinations on possibility of determining binder content in traditional moulding sands with the microwave method. The presented measurements were carried-out using a special stand, the so-called slot line. Binder content in thesandmix was determined by measurements of absorption damping Ad and insertion losses IL of electromagnetic wave. One of main advantages of the suggested new method of binder content measurement is short measuring time.

The paper presents measurement results of standing wave ratio to be used as an efficiency indicator of microwave absorption by used moulding and core sands chosen for the microwave utilization process. The absorption measurements were made using a prototype stand of microwave slot line. Examined were five used moulding and core sands. It was demonstrated that the microwave absorption measurements can make grounds for actual microwave utilization of moulding and core sands.

This study looks at determining the main trends in the application of microwaves on plants in agricultural production in the processing of grain material, it provides examples of their effectiveness and an overview of the use of microwaves on plants available on the Russian market. Additionally, the research studied the experience and developments of leading scien-tists in the field of microwave radiation. Analysis of the available sources provided information on the positive effect of microwave radiation in the processing of crops. The use of microwaves on plants during drying destroys pathogens and bacteria, in particular, microwave processing of red lentils reduces grey mould damage by up to 30%. Positive results are also noted in the microwave processing of other crops, providing an increase in germination capacity of up to 7% and yield growth of up to 6%. The microwave plant market in Russia is represented mainly by dryers, and the use of microwaves on plants combining several functions of drying, disinfection, and pre-sowing stimulation.

Rape is an important oil crop with a wide range of uses. Harvested rapeseed must be cleaned and dried before processing. The process of drying rapeseed as a small-seeded crop has its own specifics. One of the new drying methods is the use of microwave radiation, the disadvantage of which is uneven heating of the product. The purpose of this work was to study the modes of drying rapeseed by electromagnetic radiation in the ultra-high frequency range in combination with filtration. The indicators of the intensity of oilseed drying by infrared irradiation on the experimental stand were determined. The analysis of the conducted studies showed that the temperature of seeds at the maximum microwave power rises in general 1.5 to 1.8 times faster than at half the power. The higher the seed moisture content is, the higher the rate of temperature increase. After each blowing cycle, which lasted for five seconds, the temperature of the rapeseeds was set higher than the previous temperature, and after increasing the blowing time up to fifteen seconds, the temperature decreased by 8–12°C and cyclically stabilized. The applications of microwave drying represented in the paper are environmentally friendly, since the seeds do not come into direct contact with the products of gas combustion, which deteriorate its quality due to the possible penetration of carcinogenic components into the products. Experimental data was taken into account when developing the design of a small-sized grain dryer for farms, in which the drying process takes place without heating the air as a heat carrier.

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.

In this work, a real-time label-free microwave sensing mechanism for glucose concentration monitoring using a planar biosensor configured with an inset fed microstrip patch antenna has been demonstrated. A microstrip patch antenna with the resonating frequency of 1.45 GHz has been designed and is fabricated on the Flame Retardant (FR-4) substrate. Due to the intense electromagnetic field at the edges of the patch antenna, edge length has been used as the detecting area where the sample under test (SUT) interacts with the electromagnetic field. The Poly-Dimethyl-Siloxane (PDMS) with the trench in the centre has been employed as the sample holder. Here, the SUT is the glucose dissolved in DI (de-ionized) water with the concentration range of 0.2 to 0.6 g/mL. The dielectric constant dependency on the glucose concentration has been used as the distinguishing factor which results in a shift in the S-parameter. The experimentally measured RF parameters were observed closely which showed the shift in S11 magnitude from –40 to –15 dB and resonant frequency from 1.27 to 1.3 GHz w.r.t the SUT solution of 0.2 to 0.6 g/mL with linear regression coefficient of 0.881, and 0.983 respectively.

Due to urbanization, the population in the major cities in Malaysia is approximately 72.8% of its total population. The increase of population density has directly increased the amount of sewerage sludge waste that poses threat to the environment. In line with the green initiatives, alternative method to develop good quality concrete material from sewerage sludge waste can be further explored. Traditionally, sewerage sludge waste is processed using incinerator that require high energy and it is time consuming. In this study, microwave heating which require less energy consumption and less time consuming is used for sewerage sludge preparation. Prior to heating process, sewerage sludge waste is over dried at 105°C for 24 hours. Three types of microwave heating namely medium heating, medium high heating and high heating has been used. The chemical and physical properties microwaved sewerage sludge ash (MSSA) was tested using X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Based on the result, the recommended temperature for the MSSA production for the concrete is High Mode Temperature. This is due to the result of MSSA for X-Ray Fluorescent test as its shows the highest in the content for pozzolanic element which are SiO2 and Fe2O3 that produce after the microwave burning process. The mineralogical composition and the crystalline phase of the High temperature MSSA due to X-Ray Diffraction test also shows high content of SiO2 as the major component as it is good for pozzolanic reaction in concrete. From the Scanning Electron Microscope test, it is observed that particle of High heated MSSAare slightly smaller than other temperature. Also, the densification occurs at High temperature MSSA. Hence, the optimal burning temperature mode for MSSA is High Mode temperature.

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.

Presently, finding effective, simple, inexpensive, hygienic and safe pest control agents are the biggest challenges in management of stored product insects, where those features are available in most physical factors. The insecticidal efficiency of four diversified physical control agents (ultraviolet and microwave irradiations, thermal remediation and silica nanoparticles) were assayed against the most common coleopteran insect species ( Sitophilus oryzae L. and Tribolium castaneum Herbst) on stored wheat. Exposing tested insects to microwave irradiations (2450 MHz) for 25 sec gave preventive efficiency for stored material, which reached 97.68 and 99.02%, respectively. Sufficient exposure periods to kill 50% of the coleopteran adults (LT50%) were 13 and 14 sec, respectively. For effective control with UV radiations, S. oryzae should be exposed for 12 h and T. castaneum for 24 h. An exposure period of 24 h caused progeny reduction 95.24 and 89.72% and gave preventive efficiency of 94.25 and 93.37%, respectively. Values of LT50% were 56.76 and 74.04 h, respectively. Exposing infested samples of the tested species to 70oC for 10 min killed 100% of adults and caused complete cessation of egg laying. Furthermore, 65°C or 70°C caused full progeny reduction. The lowest level of stored product weight loss (1.15 and 1.35%, respectively) occurred at 70°C, where sufficient exposure temperatures to kill 50% of the coleopteran adults (LTD50%) were 60.95°C and 61.63°C, respectively. Synthetic silica nanoparticles (SSiNPs) were more toxic against the tested populations than bio-silica nanoparticles (BSiNPs) after 48–72 h. A concentration of 1.00 g kg–1 of tested silica nanoparticles caused significant reduction in adult populations, saved wheat grain vitality and gave least lost weights of flour (3.35–6.85%).

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.

In the paper presented are results of a research on effectiveness of absorbing electromagnetic waves at frequency 2.45 GHz by unhardened sodium silicate base sands (SSBS) prepared of high-silica base sand and a PLA (Polylactide) 3D-prited (3DP) mould walls. Measurements of power loss of microwave radiation (P _in) expressed by a total of absorbed power (P _abs), output power (P _out) and reflected power (P _ref) were carried-out on a stand of semiautomatic microwave slot line for determining balance of microwave power emitted into selected multimaterial systems. Values of microwave power loss in the rectangular waveguide filled with unhardened moulding sands and prepared by fused deposition modelling (FDM) 5 mm polylactide (PLA) walls with grid infill density from 25% to c.a. 100% served for determining effectiveness of microwave heating. Balance of microwave power loss is of technological importance for microwave manufacture of high-quality casting sand moulds and cores in possibility of use 3D-printed mould tools and core boxes. It was found that apparent density of SSBS placed in a waveguide with PLA walls influences parameters of power output (P _out) and power reflected (P _ref). The PLA wall position and grid infill density were identified to have a limited effect on effectiveness of absorbing microwaves (P _abs).

In this study, Hydroxyapatite (HAp) is extracted from the Rihu fish scales which are generally dumped as garbage. The aluminium composite was fabricated through the powder metallurgy technique by reinforcing HAp (0, 5, 10 and 15 wt%) as a reinforcement. The fabricated samples were sintered through microwave sintering at 530℃ for 15 min under an argon gas environment. The fabricated composites were subjected to X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analysis to confirm the constituting elements and to describe the reinforcement dispersion in the matrix. Uniform reinforcement dispersion was observed for the composite reinforces with 5%HAp, 10%HAp particles. The mechanical characterization results reveal that the Al-10% HAp composite exhibits a microhardness value of 123 ± 3 Hv and maximum ultimate tensile strength of 263 ± 10 MPa and 299 ± 9 MPa compression strength was obtained due to the presence of a strong bond among the aluminium and HAp particles.

The present research addresses the low-temperature sintering of 4% kaolin clay reinforced aluminium composite using susceptor-aided microwave sintering at 2.45 GHz frequency. Kaoline clay the naturally available mineral in the north-eastern regions of india. The study aims to convert this kaoline clay into the value added product with enhanced mechanical properties. The Al-x% Kaolin (x = 2, 4, 6, 8, 10) composite was fabricated through the powder metallurgy process by the application of 600 MPa compaction pressure. The composite corresponding to optimum ultimate tensile strength (U.T.S) was subjected to single-mode cavity microwave-assisted sintering by varying the sintering temperatures as 500°C, 550°C and 600°C. The effect of incorporating kaolin clay on the dielectric characteristics of composite powders, as well as the effect of sintering temperature on the microstructural changes and mechanical characteristics of Al-4%Kaolin composites were also examined. Results concluded that the addition of 4 wt% kaolin powder improves the dielectric characteristics of the composite powder. The maximum Hardness. Compression strength and U.T.S of 97 Hv, 202 MPa and 152 MPa respectively achieved for the Al-4% Kaolin composite sintered at 550°C. The higher fracture toughness of 9.56 Ma. m1/2 reveals the ductile fracture for the composite sintered at 550°C.