CHARACTERISTICS OF REFUSALS IN LOW-VOLTAGE DISTRIBUTION SYSTEMS

https://doi.org/10.52326/jes.utm.2022.29(4).01

UDC 621.316.027.2:519.8

Victor Popescu, Mihai Tîrșu, Ilie Nuca, Vasile Leu, Vadim Cazac, Tatiana Balan

Abstract. This paper focuses on the determination of the characteristics of refusals in low voltage electrical distribution systems. In order to solve this problem, the phenomena of occurrence of refusals in low-voltage electrical distribution systems, conditioned by different influencing factors, processed and mathematically modelled. The main results of the research consist in establishing the static characteristics of the refusals, the mathematical models that determine the occurrence of the cause phenomena and the parameters that characterize the distributions of the refusals, depending on the occurrence per system, depending on the occurrence per season, depending of interruptions duration and the number of affected consumers. The significance of the results obtained consists in solving a number of problems faced by the operating services of electrical distribution systems, concerning the assurance of reliability of operation, providing the possibility of forecasting and preventing the occurrence of the phenomena of occurrence of refusals, which enable the justified planning of prophylactic measures and ensuring the reliability level.

Keywords: electrical distribution systems, refusal characteristics, influence factors, mathematical models.

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RELIABILITY OF SERIAL-PARALLEL NETWORKS VS RELIABILITY OF PARALLEL-SERIAL NETWORKS WITH CONSTANT NUMBERS OF SUB-NETWORKS AND UNITS

https://doi.org/10.52326/jes.utm.2022.29(4).02

UDC 621.3.076.52:519.7

Veronica Andrievschi-Bagrin, Alexei Leahu

Abstract. In this paper it is performed, based on dynamic models, a comparative analysis of the reliability of two types of networks: serial-parallel and parallel-serial networks when the numbers of subnets and units in each subnet are predefined, constant numbers, but also when the lifetimes of the units are independent random variables. The equations for calculating the reliability of the related networks have been deduced. These functions are deduced for the dynamic model which is less studied and it is prooved to be relevant to the static model too. All equations are demonstrated and graphically illustrated in some examples. A few examples are analyzed graphically for different values of the number of units in the subnet and the number of subnets. This paper contains four different network topology models which are also analyzed by equations and graphically. The mathematical model described and the deduced equations will serve as a basis for the subsequent analysis of the dynamic networks of various topologies and various types of random variables that describe the lifetimes of the units of the analyzed system.

Keywords: cumulative distribution function, distributions, global maximum, lifetime, survival functions.

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DETERMINATION OF SOME SOLUTIONS OF THE STATIONARY 2D NAVIER-STOKES EQUATIONS

https://doi.org/10.52326/jes.utm.2022.29(4).03

UDC 519.63:532.516.5

Iurie Baltag

Abstract. In this paper, various solutions of the stationary Navier-Stokes equations, which describe the planar flow of an incompressible liquid (or gas), are determined, i.e., solutions containing the components of the velocity of flow – the functions u, v and the created pressure – P. The paper contains three proven theorems, as well as various examples and particular examined cases. Applying Theorem 1, we can find various solutions, where the velocity components represent the imaginary and real parts of a differentiable function of a complex variable. Theorem 2 allows us to determine solutions, where the velocity components are expressed by the partial derivatives of the solutions of Laplace’s equation of a special form. It is to be mentioned that these theorems give us solutions that do not depend on the viscosity parameter λ. In theorem 3, an original method for obtaining a series of solutions of the Navier-Stokes equations is presented, in which the viscosity coefficient λ participates explicitly; these solutions cannot be obtained by applying Theorems 1 or 2. The paper contains a large number of particular cases examined and examples of exact determined solutions.

Keywords: stationary two-dimensional Navier-Stokes equations, system of equations with partial derivatives, exact solutions, method of separation of variables, viscosity, pressure, velocity of plane flow of a liquid or gas.

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THIN FILMS OF COPPER OXIDE NANOSTRUCTURED VIA RAPID THERMAL PROCESSING

https://doi.org/10.52326/jes.utm.2022.29(4).04

UDC 539.23:546.56

Cristian Lupan, Vasilii Crețu, Abhishek Kumar Mishra, Nicolae Magariu, Nicolae Manciu, Nicolai Ababii, Soni Mishra, Serghei Railean, Lukas Zimoch, Vardan Galstyan, Sandra Hansen, Thierry Pauporté

Abstract. Nanostructured copper oxide films were obtained by the method of chemical synthesis from solutions (SCS) and exposed to post-growth rapid thermal processing (RTP) in air at different temperatures to study the influence of annealing temperature on morphological, chemical, structural and sensing properties. Controlled modification of surface morphology, in the particular size of nanostructures, crystallinity and phase can be achieved by RTP, which is preferred due to saving of energy budget nowadays. Detailed physico-chemical analysis of the films was performed using the scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman and energy dispersive X-ray (EDX) techniques. Sensors based on the copper oxide nanostructured films after RTP for 30 s only were tested with 100 ppm hydrogen gas at an operating temperature range from 250 ºC to 350 ºC. The difference in the response to 100 ppm hydrogen gas of the sensors based on thermally processed films at different temperatures was determined. We also noted that the change in the response of the sensing structure is correlated with its surface morphology controlled by RTP regime with a short duration. A detection mechanism to hydrogen gas has been proposed as well.

Keywords: copper oxide, nanostructures, SCS, rapid thermal processing, DFT.

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SOLVING THE DAYS-OFF SCHEDULING PROBLEM USING QUADRATIC PROGRAMMING WITH CIRCULANT MATRIX

https://doi.org/10.52326/jes.utm.2022.29(4).05

UDC 519.853.32:004.42

Vasile Moraru, Daniela Istrati, Sergiu Zaporojan

Abstract. The purpose of this paper is the approach of a mathematical model dedicated to planning the consecutive days off of a company’s employees. Companies must find a flexible work schedule between employees, always considering the satisfaction of work tasks as well as guaranteeing consecutive days off. The analysis is based on solving a quadratic programming problem with binary variables. The proposed method uses the properties of the circulant symmetric matrix in the researched model, which allows the transformation of the considered problems into an equivalent separable non-convex optimization problem. A practical continuous convex relaxation approach is proposed. DC Algorithm is used to solve relaxed problems. A solved numerical example is presented.

Keywords: scheduling problem, binary quadratic programming, circulant matrix, separable optimization, convex relaxation.

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METHODOLOGICAL AND INSTRUMENTAL SUPPORT TO DEVELOPMENT OF ELECTRIC TRACTION SYSTEMS WITH ASYNCHRONOUS MOTOR

https://doi.org/10.52326/jes.utm.2022.29(4).06

UDC 621.313.333

Alexandru Tarlajanu

Abstract. The present work aims to analyze from a methodological and instrumental point of view the development of asynchronous motor propulsion systems. For this purpose, PWM and SVM modulation methods, FOC and DTC vector control techniques, as well as their advantages and disadvantages are described. The theoretical bases and functional schemes of FOC and DTC control are given, including the asynchronous motor mathematical model, similar to the direct current motor model. Special attention is paid to creating of a common meaning for describing the components operation equations of the traction system, equations that can be used for system modeling and simulation. The paper also refers to a series of modern voltage converters with vector control, which are produced by several companies in different countries and are intended for the control of three-phase asynchronous motors. The results of the study create a basis for research and development of traction systems with multiphase asynchronous motors for urban electric passenger vehicles.

Keywords: DTC control technique, FOC control technique, PWM modulation, SVM modulation, vector control.

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DESCRIPTION OF THE STANDARDIZATION PROCEDURE OF STANDARD VOLUME MEASURES AND ANALYSIS OF THE STABILITY OF THEIR METROLOGICAL CHARACTERISTICS

https://doi.org/10.52326/jes.utm.2022.29(4).07

UDC 006.9:531.73

Anna Sabadas, Alexei Pianih

Abstract. The metrological characteristics of the measuring devices refer to the behavior of the measuring device in relation to the object under measurement, the environment and the human operator. Thus, having the same conditions in the laboratory and a well-trained and competent staff, the stability of the metrological characteristics of the standard volume measures were studied in order to demonstrate their stability over time and provide increased confidence to the subsequent beneficiaries. The measurements were carried out over a period of one year under the same conditions, their results demonstrating that the standard volume measures are able to ensure the traceability of the measurement unit. In this way to ensure the uniformity, accuracy and legality of the measurements performed in different fields – measurement of volume in commercial transactions, fuel supply, wine industry.

Keywords: standardization, standard measures, volume, metrological characteristics, stability.

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THE DIFFERENCE BETWEEN CYBER SECURITY VS INFORMATION SECURITY

https://doi.org/10.52326/jes.utm.2022.29(4).08

UDC 004+004.056.5

Arina Alexei, Anatolie Alexei

Abstract. The terms cyber security and information security are often used interchangeably, both in the academic literature and by organizations. This article aimed to identify whether these terms can be used interchangeably, analyzing the differences between the terms, based on several definitions identified in scientific articles and books, as well as definitions presented by specialized organizations. The analysis consists in determining the keywords, that define the terms, based on which conclusions were made. It has been determined that information security places a strong emphasis on the protection of information, cyber security refers to all assets that are part of cyberspace, such as end devices (including IoT), network devices, communication media and information. Cybersecurity is an umbrella term that includes: electronic communications network and computer security, physical security, infrastructure security, personnel security, hardware and application security, business process security. Through the identified results, important contributions are made both for the academic environment, as well as for governmental and non-governmental organizations, for the understanding and correct use of terms, to reduce uncertainty and to correctly approach specialist terminology, because the field of security is increasingly important, the challenges are complex and diverse.

Keywords: asset, availability, confidentiality, cyber, information, integrity, threat.

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ARCHITECTURE, CIVIL ENGINEERING, ACADEMIA AND DIPLOMACY: A COMPREHENSIVE OVERVIEW OF THE WORK OF LINO BIANCO

https://doi.org/10.52326/jes.utm.2022.29(4).09

UDC 72+725.1+378+327(458.2+478)

Svetlana Oleinic

Abstract. The practice of building bridges has been attributed to the profession of architects and civil engineers. The theory underlying their design is reserved to researchers mainly in academia. Metaphorically, bridge building is a term used to establish communication and, in particular, to develop friendly relations between parties, a role played by diplomats, especially ambassadors. A contemporary professional who is an architect, an academic and a diplomat is Lino Bianco, the present ambassador of the Republic of Malta to the Republic of Moldova. Based on literature available at the library of the University of Malta and on the internet, the article presents a comprehensive overview of the professional and academic work of Professor Bianco, work which has been acknowledged at both academic and diplomatic levels. It concludes by arguing that he is essentially a renaissance man.

Keywords: academia, Bulgaria, contemporary architecture, diplomacy, Lino Bianco, Malta, Moldova, Romania.

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CALORIFIC VALUE OF PELLETS PRODUCED FROM RAW MATERIAL COLLECTED FROM BOTH SIDES OF THE RIVER PRUT

https://doi.org/10.52326/jes.utm.2022.29(4).10

UDC 620.952:662.63(478+498)

Grigore Marian, Ianuș Gelu, Andrei Gudîma, Boris Nazar, Bogdan Istrate, Alexandru Banari, Andrei Pavlenco, Nicolae Daraduda

Abstract. The production of pellets has recently experienced a sudden upward trend worldwide, including the Republic of Moldova and Romania, especially due to the energy crisis caused by the war in Ukraine and rapid depletion of fossil energy sources. The widespread use of pellets has several reasons: it is an eco-friendly fuel, it allows the automation of the combustion process, and it can be easily produced in any region that has enough raw materials. The calorific value of pellets is the main characteristic feature that determines their price and is used in combustion engineering to find out the thermal efficiency of combustion plants. This paper synthesizes the results regarding the calorific value of the pellets produced from different types of plant biomass specific to the Republic of Moldova and the counties adjacent to the river Prut in Romania. The research has been carried out within the Solid Biofuels Laboratory, SAUM using standard methods of testing densified solid biofuels. The experimental results obtained in this study showed that the pellets produced from arboriculture residues, residues generated from vine pruning, table varieties, as well as those produced from sunflower seed husk have a calorific value equal to or greater than 16.5 MJ/kg, i.e., they meet ENPlus 3 requirements.

Keywords: wood pellet, calorific value, biomass, agricultural residues, energy crops, biomass conditioning, combustion.

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MICROENCAPSULATION OF ANTHOCYANINS FROM CORNELIAN CHERRY FRUITS IN WHEY PROTEIN ISOLATE AND PECTIN

https://doi.org/10.52326/jes.utm.2022.29(4).11

UDC 547.973:582.788.1

Iuliana-Maria Enache, Liliana Lucescu Ciurlă, Nicoleta Stănciuc, Liviu Mihai Irimia, Antoanela Patraș,
Camelia Vizireanu

Abstract. Cornelian cherry (Cornus mas L.) is one of the most important forest fruits, considered as a valuable horticultural resource of bioactives, such as anthocyanins – cyanidin-3-glucoside, flavonoids, vitamins (e.g. vitamin C), carotenoids (e.g. β-carotene). The aim of this study was to obtain designed delivery systems of bioactive from cornelian cherry, as microencapsulated powders in order to assure their controlled release and to develop stable and natural additives for different application. Anthocyanin’s (concentrated extract) from cornelian cherry fruits were microencapsulated in a complex, biopolymeric matrice, formed by whey protein isolate (WPI) and pectin (PT). Two experimental variants were obtained by varying the ratio between WPI and PT, such as 1:1 (PT1) and 1:2 (PT2). The powders were tested for encapsulation efficiency of the anthocyanins, phytochemical profile of the extract and freeze-dried powders, as well as colorimetric analysis. Encapsulation efficiency of the anthocyanins varied between 80.04 and 82.11% with an important level of biologically active compounds (total polyphenols, total flavonoids) and remarkable antioxidant activity. Colorimetric analysis reveals a red colour of the powders, associated with their anthocyanin content. Both experimental variants proposed in this study protected the anthocyanins from cornelian cherry fruits. Moreover, microencapsulated powders can be used as natural food additives due to their red colour and phytochemical profile.

Keywords: complex biopolymeric matrice, Cornus mas L., encapsulation efficiency, colour.

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THE EFFECT OF REDUCING THE QUANTITY OF SALT ON THE QUALITY AND ACCEPTABILITY OF GRISSINI

https://doi.org/10.52326/jes.utm.2022.29(4).12

UDC 664.664

Natalia Suhodol, Eugenia Covaliov, Olga Deseatnicova, Aurica Chirsanova, Vladislav Resitca, Tatiana Capcanari, Alina Boiștean

Abstract. The article proposes the technology of obtaining grissini type salt-free bakery products. Research has been carried out on reducing the salt content and replacing the water with fermentation products as kefir, whey, and sour borscht, in order to reduce the effect of the lack of salt on the product quality. The results showed that the complete exclusion of salt from the recipe had a negative effect on the dough stability, physicochemical properties and organoleptic characteristics of the baked products. Partial or total omission of salt resulted in higher dough rise ability and lower moisture content in the final product. Grissini made according to the classic recipe with salt, registered high appearance and sensory properties, while reducing the salt content results in products with a less pronounced crust and taste. The use of kefir, whey and sour borscht as water substitutes in the recipe contributed to the improvement of the chromatic parameters, as well as the physicochemical indicators of the baked grissini. However, consumers appreciated less the samples with the addition of kefir and whey. These samples being distinguished by a specific taste and smell, in some extent unusual for panelists. At the same time, grissini based on sour borscht were highly appreciated. According to the results, the sample with sour borscht without added salt recorded similar characteristics to the control sample, but in order to align it with national standards in terms of physicochemical indicators, the dough fermentation period needs to be revised.

Keywords: acidity, grissini, kefir, sour borscht, whey.

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EFFECTS OF LACTOSE HYDROLYSIS AND MILK TYPE ON THE QUALITY OF LACTOSE-FREE YOGHURT

https://doi.org/10.52326/jes.utm.2022.29(4).13

UDC 637.146.34:637.144

Liliana Popescu, Viorica Bulgaru, Rodica Siminiuc

Abstract. The purpose of the work was to investigate the influence of different lactose hydrolysis processes, the contribution of the enzyme and the milk type on the characteristics of the obtained lactose-free yogurt. The analysis was performed on non-hydrolyzed yogurt (control sample), the pre-hydrolyzed yogurt (that was hydrolyzed before fermentation), and the co-hydrolyzed yogurt (concurrent addition of β-galactosidase and starter culture). According to the obtained results, at the end of the fermentation time, an advanced hydrolysis degree was reached (over 80%) both for yogurt samples obtained from pre-hydrolyzed milk and obtained by co-hydrolysis. The optimal method from the economic point of view is to obtain yogurt by co-hydrolysis. The sensory quality of the yogurt samples obtained from hydrolyzed milk by co-hydrolysis was characterized by a better flavor than the control sample, for yogurt from both types of milk. This may be due to the availability of a greater amount of glucose for the production of aromatic compounds, a sweeter taste than natural yogurt, with a light caramel flavor, a firm coagulum, a porcelain appearance, without whey removal. Cow’s milk yogurt showed higher viscosity values to goat’s milk yogurt for both pre-hydrolyzed and co-hydrolyzed milk. Lactose hydrolysis determined the reduction of the syneresis index of the yogurt compared to the control samples. The studies led to the development of lactose-free yogurt with improved sensory and rheological properties recommended for people with lactose intolerance.

Keywords: co-hydrolysis, pre-hydrolysis, β-galactosidase, fermentation, lactose, yogurt.

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РHYTОРАTHОGЕNIС MIСRОBIОTЕ ОF SЕА BUСKTHОRN АND IMРАСT ОN STORAGE

https://doi.org/10.52326/jes.utm.2022.29(4).14

UDC 634.743:632(478)

Еlisаvеtа Sаndulасhi, Nаtаliа Nеtrеbа, Аrtur Mасаri, Iuliаnа Sаndu, Оlgа Bоеstеаn, Irinа Diаnu

Аbstrасt. Sеа buсkthоrn (Hiррорhае rhаmnоidеs L.) hаs соnsidеrаblе роtеntiаl fоr thе аgri-fооd, рhаrmасеutiсаl аnd соsmеtiс industriеs. This аrtiсlе рrеsеnts аn intеrnаtiоnаl аnd ехреrimеntаl rеsеаrсh соnduсtеd оn рlаntаtiоns in Dubаsаri distriсt, Роhrеbеа villаgе in thе Rерubliс оf Mоldоvа оf thе miсrоbiоtа whiсh is аblе tо аttасk sеа buсkthоrn рlаntаtiоns аnd rеduсе thе hаrvеst. This rеsеаrсh inсludеs сhаngеs in thе microbiota that is able to attack sea buckthorn plants to reduce the harvest and shelf life of the berries. Infоrmаtiоn оn роtеntiаl disеаsеs оf sеа buсkthоrn рlаntаtiоns, thе саusаtivе аgеnt аnd rесоmmеndаtiоns tо rеduсе this risk аrе inсludеd in thе аrtiсlе. Thе infоrmаtiоn рrеsеntеd is imроrtаnt fоr thе dеvеlорmеnt оf sеа buсkthоrn рlаnt сultivаtiоn strаtеgiеs аnd disеаsе mаnаgеmеnt аlsо fоr imрrоving thе quаlity аnd рrеsеrvаtiоn оf роst-hаrvеst fruit.

Kеywоrds: Hippophae rhamnoides L., miсrоbiоtа of sеа buсkthоrn, miсrоbiоlоgiсаl invеstigаtiоn, sаfеty indiсаtоrs

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REMOTE SURVEILLANCE: A MEANS OF INTELLIGENCE GATHERING FOR MINIMIZING SECURITY CHALLENGES IN NIGERIA

https://doi.org/10.52326/jes.utm.2022.29(4).15

UDC 004.056.5

Anas Shehu, Hadiza Aliyu Kangiwa, Abubakar Sani

Abstract. Nowadays, national security issues are increasing day by day in most countries. A multitude of measures to reduce the challenges have been presented and even implemented by many authors, but without exhaustive results. The use of computers and sophisticated IT tools by the terrorist group, increasing number of citizens, lack of social amenities and other factors have made some of them inadequate enough to control the problems in Nigeria. The purpose of this paper is to highlight national security challenges in Nigeria and how security oversight is operated. To achieve this, the authors analyze available secondary data, investigating national security modus operandi and presenting the general concept of surveillance. Related works were also investigated for discussion. Remote surveillance, wiretapping, geospatial intelligence and a consolidated national database are proposed to achieve digital intelligence collection for insecurity management.

Keywords: geospatial intelligence, national database, national security, lawful interception, soft wiretapping, SIM card.

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