SOUTHERN JOURNAL OF SCIENCES

Background: Antioxidant compounds are widely used in medicine to protect the organism from the impact of various stresses and strengthen the immune system. The primary source of natural antioxidants is considered plant-based products. That is precisely why scientists are interested in extracting active compounds out of plant materials and use them. However, diverse resources of medicinal plants of Georgia is poorly studied and used as a source of antioxidants. Aim: The research aimed to study the antioxidant composition and total antioxidant activity of some dried medicinal plants sold in the pharmacy network in Tbilisi, Georgia. Methods: Several types of medicinal plants (3 berry plants and 3 herbaceous plants) sold in the pharmacy chain were chosen as the research object. These are Crataegus sp., Sorbus sp., Viburnum sp., Helichrysum sp., Leonurus quinquelobatus Gilib, Origanum vulgare L. Results: As a result, it has been found that the content of ascorbic acid and carotene in the studied plants is not so high to fill the daily intake of a man with an infusion prepared from one tablespoon. As for proline and the number of total antioxidants, all the plants we have chosen are high in content, considerably increasing their medicinal value. Discussion: The low amount of ascorbic acid and carotine found in studied plant, this increases their medicinal value, and in combination with other antioxidants/plants, the healing effect of the raw materials has been used. Conclusions: The studied plants are characterized by high levels of proline and antioxidant activity, so their infusions can be safely used as a source of antioxidants both in folk medicine and for the preparation of biologically active preparations.

Sand casting is a viable waste as an alternative raw material, regarding a good solution in the production of concrete blocks. The use of sand casting to produce concrete blocks is performed by about 80% of the productive capacity of the company considered in this study. Thus, this work aims to make an improvement by applying fuzzy logic. The methodology was applied from the formulation of ranking criteria, which improved the production process. Therefore, after the implementation of the established criteria, was achieved an improvement of about 10%. Thus, the results achieved can help companies, generating alternatives with more excellent reliability and assertiveness. Moreover, Fuzzy is a methodology that provides strong support for decision making, supporting subjective and intuitive criteria.

Background: MQ-series gas sensors belong to the metal oxide semiconductor (MOS) family of sensors that can sense the presence of many gases. These sensors find their application in gas alarm systems as key components. While necessary sensor circuit output voltage value for alarm point in a stand-alone gas alarm system is desirable, but what exact combination of the sensor circuit parameters is required? Hitherto, the determination of these circuit parameters has not been given much attention in the research community. Aim: the purpose of this work is to explore a structured graphical approach of determination of MQ series gas sensor circuit parameters for a stand-alone gas alarm system that yields desired sensor circuit output voltage value for the alarm point; the main objective of the study was to develop mathematical model equations that relate the: (i) sensor resistance (RS) with the gas concentration (x) and the sensor resistance at standard calibration concentration of the sensor base gas in the clean air (Ro) and (ii) sensor circuit output voltage (VRL), load resistance (RL) and sensor resistance (RS). It is expected from the model equations developed that graphical correlations of the sensor circuits parameters will be generated. Using these graphs for a particular case of an MQ-4 gas sensor under the influence of LPG, the parameters that yield desired sensor circuit output voltage of 2V for 1000 ppm of LPG alarm point will be determined. Methods: Model equations were developed for the sensor dynamics, and based on these model equations, graphs for the determination of required sensor parameters were plotted for a case of MQ-4 gas sensor response to LPG. Results and Discussion: The results yielded optimal values for R_O,R_S and R_L of 20 kΩ, 30 kΩ and 20 kΩ respectively, for alarm settings of 1000 ppm and a desired sensor circuit output voltage of 2 V. Based on determined parameters, the calibration equation for determination of best concentration value for a given value of emulated LPG concentration was developed. Using the method proposed in this study makes the process of determining the MQ-series gas sensor circuit parameters less cumbersome as their value can easily be obtained from the resulting graphs. Conclusions: a structured graphical approach for determination of MQ-series gas sensor circuit parameters for alarm points in a stand-alone gas alarm system showed that using MQ-4 gas sensor and LPG as the target gas, and for a sensor circuit output voltage of 2 V for alarm point at 1000 ppm of LPG, the corresponding value of R_O, R_S and R_L obtained were 20 kΩ, 30 kΩ, and 20 kΩ respectively. Hence, a structured graphical approach is suitable for determining MQ series gas sensor circuit parameters for a stand-alone gas alarm system under the influence of its associated gases.