RESEARCH OF THE ULTRASONIC DRYING PROCESS OF VARIOUS MATERIALS

В статье рассматривается процесс конвективной сушки тканых материалов и продуктов растительного происхождения. Показано, что длительность процесса может быть уменьшена за счет дополнительного воздействия ультразвуковыми колебаниями высокой интенсивности. Для определения ускорения процесса сушки ультразвуковыми колебаниями были разработаны лабораторные установки, позволяющие организовать комбинированное воздействие потока теплого воздуха и ультразвуковых колебаний. Комбинированная сушка ткани проводилась при трех различных температурах сушильного агента. Было установлено, что сокращение времени процесса по сравнению с конвективной сушкой зависит от температуры сушильного агента и составляет от 10% при температуре 40 0C до 20% при температуре 60 0C. В свою очередь, сушка овощей проводилась на резонансных промежутках от излучающего диска, при этом овощи нарезались толщиной 5 мм и располагались тонкими слоями. Комбинированная сушка моркови и картофеля позволила достичь сокращения времени сушки на 45-47%. При этом затраты на электроэнергию для ультразвукового аппарата составляют не более 30% от затрат на конвективную сушку. В результате проведенной работы была показана эффективность применения комбинированной ультразвуковой и конвективной сушки прежде всего для обезвоживания овощей, тогда как для ткани эффект не столь очевиден. Лабораторные исследования проводились при малом объеме высушиваемого материала, из-за слабого проникновения ультразвуковых колебаний на большую глубину, поэтому дальнейшие исследования необходимо направить на разработку полупромышленных и промышленных сушильных аппаратов для ультразвуковой сушки овощей и других термолабильных материалов. The article deals with the process of convective drying of fabrics and vegetables. The duration of the process can be reduced by additional exposure to high-intensity ultrasonic vibrations. To carry out drying, laboratory installations were developed that allow organizing the combined effect of a stream of warm air and ultrasonic vibrations. The combined drying of the fabric was carried out at three different temperatures of the drying agent and it was noted that the greatest reduction in drying time compared to convective drying was achieved at a temperature of 60 ° C. Although the overall reduction in drying time ranged from 10% to 20% depending on the temperature of the air flow. Drying of vegetables was carried out at resonance intervals from the emitting disk, while vegetables were cut 5 mm thick and placed in thin layers. Combined drying of carrots and potatoes made it possible to achieve a reduction in drying time of 45-47%. In this case, the cost of electricity for the ultrasonic apparatus is a small part of the cost of convective drying. As a result of the work carried out, it is possible to draw conclusions about the effectiveness of the use of combined ultrasonic and convective drying for dehydration of vegetables, while the effect is not so obvious for tissue. Laboratory studies were carried out with a small volume of dried material, due to the weak penetration of ultrasonic vibrations to a great depth, therefore, further research should be directed to the development of semi-industrial and industrial dryers for ultrasonic drying of vegetables and other heat-sensitive materials.

Evaluation of Antibacterial and Antifungal Properties of ZnO and Silver Nanoparticles against Candida Albicans and Streptococcus Mutans in Acrylic Resin

Introduction: This study aimed to evaluate the antibacterial and antifungal effect of Ag and zinc oxide nanoparticles to complete denture acrylic resin. Materials & Methods: In this experimental laboratory study, 144 samples were evaluated. The powder of acrylic resin (PMMA Ivoclar Vivadent, Lichenstein SR Triplex Hot) was mixed homogeneously in the ultrasonic apparatus with Ag (purity: 99.99%, size: 20nm, spherical) and ZnO (purity: 99%, size: 10-30 nm, nearly spherical) particles with mass fraction 0.5, 1 ,2 and 5. The microorganisms of this study were Candida albicans and Streptococcus mutans. The growth rate of microorganisms was measured by spectrophotometer based on turbidity and readings at 600 nm. Data were analyzed by ANOVA and Tukey post hoc tests. The significance level was set at 0.05. Results: Increasing Ag and ZnO nanoparticles to acrylic resin reduced the growth of Candida Albicans and Streptococcus Mutans. Even the concentration of 0.5% significantly reduced the growth of microorganisms. Complete growth inhibition was in the concentration of 5% after 24 and 48 hours. Conclusion: Increasing the Ag and ZnO nanoparticles to acrylic resin reduced the growth of microorganisms.

Cavitation erosion behavior of microwave-processed Ni–40Cr3C2 composite clads: A parametric investigation using ultrasonic apparatus

Cavitation erosion is the primary cause of material failure of the hydroelectric power plant components. The rapid development in the advanced surface engineering techniques has provided an effective treatment solution for cavitation erosion. One such novel method is microwave cladding. Hence, the Ni–40Cr3C2 composite clad was deposited on austenitic stainless steel (SS-316) using a microwave cladding process in the present study. The processing was carried out in a domestic microwave oven of 2.45 GHz frequency and 900 W power. The developed clad was thoroughly characterized for the metallurgical and mechanical properties related to its behavior as a successful cavitation erosion resistance material, like microstructure, crystal structure, porosity, microhardness, flexural strength, and fracture toughness. The results showed that the stripe-type and agglomerated carbides were present in the Ni–40Cr3C2 clad. The developed composite clad consists of various carbides (SiC, Ni3C, Cr3Ni2SiC, Cr7C3, and NiC) and intermetallic phases (Ni3Fe, Ni2Si, and Cr3Si). Microhardness, flexural strength, and fracture toughness of the microwave-processed clad were observed to be 605 ± 80 HV0.3, 813.23 ± 16.2 MPa, and 7.44 ± 0.2 MPa√m, respectively. The microwave-processed composite clad performance in terms of cavitation erosion resistance was determined using the ultrasonic apparatus (ASTM-G32-17). The cavitation experiments were carried out according to Taguchi L9 orthogonal array, taking into account three parameters: standoff distance, amplitude, and immersion depth. The developed composite clad exhibited significant resistance (mass loss 7.6 times lesser as compared to SS-316) to cavitation erosion. ANOVA results showed the standoff distance as the most important factor followed by amplitude and immersion depth. Least cavitation resistance was observed at a smaller standoff distance, higher amplitude, and lower immersion depth. Linear regression equations were obtained to establish the correlation between parameters and cumulative mass loss. The microwave clad specimens tested at optimized test parameters were damaged in the form of fractured intermetallic, extruded lips, pits, and craters.

Application of carbon nanotubes as additives improving the environmental performance of diesel engine

The actuality of the article is due to the need to improve the toxicity indicators of dieselengines exhaust gases. One of the modern ways to achieve the required indicators of exhaustgas toxicity is to add eco-friendly additives to the fuel. An opportunity of using carbonnanotubes as eco-friendly additives to petroleum diesel fuel is considered. Experimentalstudies of the D-243 diesel engine running on petroleum diesel fuel with the addition of 125,250 and 500 mg/l nanotubes were carried out. Mixing of petroleum diesel fuel with nanotubeswas performed with the usage of an ultrasonic apparatus. A possibility of improving theenvironmental performance of a diesel engine when adding nanotubes to the fuel is shown. Ina full-load mode, the addition of 500 mg/l carbon nanotubes to the fuel reduced the exhaustsmoke from 26.0 % to 11.2 % according to the Hartridge scale. Keywords diesel engine; petroleum diesel fuel; carbon nanotubes; exhaust gas toxicity indicators; exhaust gas smokiness

An Innovative Ultrasonic Apparatus and Technology for Diagnosis of Freeze-Drying Process

The freeze-drying process removes water from a product through freezing, sublimation and desorption procedures. However, the extreme conditions of the freeze-drying environment, such as the limited space, vacuum and freezing temperatures of as much as −50 °C, may block the ability to use certain diagnostic sensors. In this paper, an ultrasonic transducer (UT) is integrated onto the bottom of a specially designed frozen bottle for the purpose of observing the freeze-drying process of water at varying amounts. The temperatures and visual observations made with a camera are then compared with the corresponding ultrasonic signatures. Among all of the diagnostic tools and technologies available, only ultrasonic and visual records are able to analyze the entire progression of the freeze-drying process of water. Compared with typical experiment settings, the indication of drying point for water by the amplitude variations of ultrasonic L3 echo could reduce the process period and energy consumption. This study demonstrates how an innovative frozen bottle, an integrated ultrasonic sensor and diagnostic methods used to measure and optimize the freeze-drying process of water can save energy.

Synthesis of Cotton Fibers Impregnated with Bactericidal Hydrotalcites to be used in Medical Textile Supplies

ABSTRACTHydrotalcites or layered double hydroxides are solids having laminar structures with remarkable basic properties. They can be synthesized with bactericidal metal ions incorporated into the structure. Both, basic species and metals can provide a high activity against microorganisms. Regarding this, it should be interesting to obtain a novel composite material consisting of cotton fibers impregnated with antimicrobial hydrotalcites to be used, for example, in medical textile supplies. In the present study, the retention of antimicrobial hydrotalcites in cotton fibers using mechanical mixing procedures was evaluated. The impregnation was carried out by three procedures, consisting in stirring the hydrotalcite with the cotton fibers in a rotatory or orbital system or in an ultrasonic apparatus. Composites were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The retention of hydrotalcites in the fibers depended on the impregnation method. The composite obtained by the ultrasound procedure showed better retention.

Effect of Light Illumination on Leaves Movement of Mimosa pudica

A study on the effect of light illumination introduced to the leaves of Mimosa pudica was carried out using different light intensities. The leaves will open gradually from the closed condition after the light was illuminated. Plant of M. pudica was placed in the dark box during measurement meanwhile the Petiole (part of the stem) of the plant was at normal position (hanging up). The camera was fixed to the box to monitor the leaves’ movement continuous and real time. By using this method the change of the top view area of the leaves could be observed. A crossed line was drawn on the image recorded and was measured its length. The calculation of the length gives the percentage of leaves at open during the observation time. Ultrasonic apparatus was also used to monitor the change of leaves. From the results, at an illumination intensity of 200 Lux, the percentage of leaves to open completely with respects to the observation time was found to increase nonlinearly by taking the time of 25 minutes. For intensities of 400 Lux, the trend of curve was also similar but increase rapidly. The ultrasonic signals show much stable at 200 Lux comparing to 400 Lux that was fluctuating. That may be due to the relatively faster movement of the leaves to open. This natural phenomenon is interesting and may introduce any change of natural indication that could be explored for further applications.

Cavitation-jet deinking: A new technology for deinking of recovered paper

A new method and in-house device for treating secondary fiber were developed. The method is based on the fluid-jet cavitation technique. In this apparatus, pulp suspension was injected into the reacting vessel by using a high-speed jet that produced cavitation bubbles around the jet. The impact of the collapse of cavitation bubbles detached ink, binder, and other contaminants from fiber surfaces. The effects of the cavitating jet (CV-jet) treatment on deinking of the pulp from mixed office waste (MOW) and old newsprint/old magazines (ONP/OMG) mixture were studied. The basic experiments on cavitation control showed that the intensity and region of cavitation were controlled by the jet velocity and the pressure difference in the reacting vessel. The CV-jet generated broad ultrasound waves; the conventional ultrasonic apparatus generated an intrinsic frequency. The MOW test results showed that CV-jet, even without chemicals and high temperature, decreased dirt speckles and reached almost the same dirt reduction level as the mill kneader. Moreover, the CV-jet minimized fiber damage during the process. This yielded pulp handsheets giving much higher paper strength compared with pulp from the kneader. The ONP/OMG test revealed that CV-jet was superior to mill disperser in terms of ink detachment and stickies dispersion.