bluuebunny/crossref_metadata_2025 huggingface dataset:
SARS-Cov-2 and COVID-19, Basic and Clinical Aspects of the Human Pandemic: A Review
Authors: Zavva Mahdi , Emadi Kochak Hamid , Abdolmohammadi Kamal , Rashidi Nesa , Mokhtari Majid , Noorbakhsh Farshid , Azadmanesh Kayahan , Shamsi Gooshki Ehsan , Fatahi Yousef , Mokhtari Azad Talat , Jahangirifard Alireza , Mousavi Mohammad Javad , Masoumi Elham , Mirzaei Hamid Reza , Gouya Mohammad Mahdi , Rezaei Farshid , Nicknam Mohammad Hossein
Published: April 2021

In the last two decades, we have witnessed three major epidemics of the coronavirus human disease namely, severe acute respiratory syndrome (SARS), Middle Eastern respiratory syndrome, and more recently an ongoing global pandemic of coronavirus disease 2019 (COVID-19). Iran, a country of nearly 84 million, in the Middle East, severely involved with the COVID-19 disease. A documented multidimensional approach to COVID-19 disease is therefore mandatory to provide a well-balanced platform for the concerned medical community in our county and beyond. In this review, we highlight the disease status in Iran and attempt to provide a multilateral view of the fundamental and clinical aspects of the disease including the clinical features of the confirmed cases, virology, pathogenesis, epidemiology, and laboratory methods needed for diagnosis.
The Prevalence of Musculoskeletal Disorders among Miners around the World: A Systematic Review and Meta-Analysis
Authors: Rabiei Hadiseh , Malakoutikhah Mahdi , Vaziri Mohammad Hossein , Salehi Sahlabadi Ali
Published: April 2021

Background: Musculoskeletal disorders are responsible for significant problem for workers' health. The present study aimed to investigate the prevalence of musculoskeletal disorders among mining workers.
Methods: This systematic review and meta-analysis study were designed in 2020 (from Jan to Mar). The researchers searched five international databases Medline/PubMed, ProQuest, Scopus, Embase and Web of Science. All analyzes were performed using STATA statistical software.
Results: The search results were 447 articles and after screening stage finally 50 studies were included in review. The highest number of studies (26 studies) reported the prevalence of musculoskeletal disorders of upper back and 4 studies reported the prevalence of musculoskeletal disorders of the arms and ankles & feet. The results of meta-analysis based on prevalence in different organs showed that the highest prevalence of musculoskeletal disorders was in the upper back and the lowest in the knees with a prevalence of 50.39% (CI 95%: 31.23- 54.73%) and 16.03% (CI 95%: 11.78-20.28%), respectively.
Conclusion: The prevalence of musculoskeletal disorders among miners is relatively high. Therefore, supervisors and mine managers should pay more attention to reducing musculoskeletal disorders and increasing the ergonomic level of mines in order to increase workers' health.
The Effect of Chronic Diseases, Age and Gender on Morbidity and Mortality of COVID-19 Infection
Authors: Aslaner Hümeyra , Aslaner Hacı Ahmet , Gökçek Mebrure Beyza , Benli Ali Ramazan , Yıldız Orhan
Published: April 2021

Background: We aimed to reveal how chronic diseases, age and gender affected morbidity and mortality in patients with Coronavirus disease of 2019 (COVID-19).
Methods: Medical records of all reverse transcription polymerase chain reaction (RT-PCR) positive COVID-19 patients followed up in hospital and home isolation between 13th of Mar 2020 and 12th of May 2020 were retrospectively reviewed. The patients were from Kayseri Province, Turkey. Patients’ demographic and clinical characteristics and the factors associated with morbidity and mortality were analyzed.
Results: Of all the patients, 773 (95.8%) were alive and 34 (4.24%) died. The fatality rate was 4.2%. There were differences between the age groups in terms of fatality rate (P<0.001). The fatality rate in patients above the age of 65 yr was significantly higher. The fatality rate in the male gender was 2.44 times higher (P<0.05). It was 1.104 times higher in advanced age (P<0.001) and 10.893 times higher in patients with at least one comorbid disease (P<0.05). Hypertension increased mortality by 3.635 times (P<0.05) and chronic pulmonary diseases by 2.926 times (P<0.05).
Conclusion: Advanced age, male gender and accompanying chronic diseases have adverse effects on the course and severity of the disease and hospitalization. They also increased the rate and risk of mortality.
Self-Assessment of Health among the Citizens of Serbia in the Transition Period
Authors: Mihailovic Natasa , Simic-Vukomanovic Ivana , Luketina Sunjka Marina , Zivanovic Sandra , Milicic Biljana , Milicic Vesna
Published: April 2021

Background: The aim of the research was to compare the differences between the self-assessment of the health in the latest National Health Surveys research and in the one before that.
Methods: We used the database of the latest National Health Survey in the Republic of Serbia (2013) and of the one before that (2006), as cross-sectional studies (n=29485). Logistic regression was used to predict the relationship between self-assessment of health and independent predictors.
Results: Health condition of the interviewees improved according to their self-assessment. With aging respondents who poorly assessed their health; women assessed their health 1.7 and 1.6 times poorer in the latest research and in the one before that respectively. The odds ratio in patients diagnosed with some disease in the previous 12 months ranged from 2.15 (1.85 – 2.51) to 4.03 (3.22 – 5.05) in the latest research. The strongest predictor was sick leave in the past 12 months with 95% CI = 3.19 (1.87-5.44) in the latest research and 95% CI = 2.27 (1.67-3.08) in the one before that.
Conclusion: There was an improvement of the health condition of individuals. Female interviewees, less educated, unemployed, the ones who have some disease and who were on a sick leave rated their health as bad.
The Effects of Initial Rehabilitation Exercise on Range of Motion, Muscular Strength, and Muscle Pain after Surgery for Osteochondritis Dissecans of the Humeral Capitellum in Middle and High School Baseball Players
Authors: Seo Jung-Shik , Yoon Jin-Ho
Published: April 2021

Background: This study evaluated the effects of a 4-week initial rehabilitation program in middle and high school baseball players who underwent removal of a loose body from osteochondritis dissecans of the capitellum humerus.
Methods: Middle and high school baseball players with osteochondritis dissecans of the capitellum humerus were enrolled in this study. Each had more than 3 yr of experience and had undergone arthroscopic removal of loose bodies from the same expert at Kim's Orthop Special Clinic in Seoul. The initial exercise rehabilitation program was based on a two-stage program. Body composition, range of motion of flexion and extension in the elbow and wrist joints, grip strength, and subjective pain scale were measured before and after rehabilitation. To assess the differences between groups, we used a two-way analysis of variance.
Results: The range of motion for flexion and extension of the elbow and wrist joints, grip strength, and score on the visual analog scale each were significantly improved following the 4-week program (P<0.001), had an interactive effect in time × group (P<0.001), and had significance between groups (P<0.05).
Conclusion: The 4-week initial rehabilitation exercise program might improve the overall range of motion of the elbow joint and has a positive therapeutic effect on grip strength and visual analog scores. However, future welldesigned studies with more subjects and multicentric research groups are necessary for verification.
Comparison of Clinical Effects of Ankle Rehabilitation Exercise Bare Foot or Wearing Shoes
Authors: Yoon Tae Hoon , Ju Sung Bum
Published: April 2021

The article's abstract is not available.
Emerging New Challenge for Providing Health Education in Iranian Rural Primary Health Care
Authors: Heshmati Hashem , Mortaz Hejri Sara , Shakibazadeh Elham , Sadeghi Roya
Published: April 2021

The article's abstract is not available.
Detection of genetically modified food products in indian market using PCR based GMO detection kit: a pilot study
Authors: Dayal Navami , Murugan Vaishnavi , Shah Meghal , Deepak Suparna
Published: April 2021

The Food Safety and Standards Authority of India (FSSAI) have not approved any genetically modified (GM) food products to be manufactured, distributed, sold/or imported in the country. Many countries across the globe are legally approved to cultivate GM crops like soybean, maize, canola, cotton seeds, etc. Many people living in urban India nowadays prefer to purchase imported food products. As a result, an increasing number of food items (without GM labels) are being imported in India. Nevertheless, these products are also easily available for buyers online. Thus, it is important to understand whether these imported food items available in the Indian market are GMO-free. The objective of this study is to check the availability of GM food products in raw and processed forms in the Indian local market through the use of conventional Polymerase Chain Reaction (PCR). The study is designed to screen for the presence of regulatory genes (35S promoter and NOS terminator) which are the most common sequences found in transgenic food products. Using the cetyl trimethyl ammonium bromide (CTAB) method, DNA was extracted from 12 food samples commercially available in the Indian market (locally and online) followed by PCR to detect the presence of GM DNA using HIMEDIA’S MBPCR055 GMO detection kit. Overall, 16.66% of the total samples were tested positive for GM DNA. Of the imported food items, 33.33% were tested positive. Products that were manufactured in the US and Netherlands were tested positive for GMOs. Their main ingredients were also soy and corn. Samples manufactured in India were GMO negative.
Detection and antibiogram of Edwardsiella tarda from Oreochromis niloticus (Tilapia fish) obtained from selected farms in Ibadan, Nigeria
Authors: Charles Ogunleye Seto , Olabisi Ishola Olayinka , Olufemi Olatoye Isaac , Bolarinwa Adedeji Olufemi
Published: April 2021

Edwardsiellosis caused by Edwardsiella tarda is a septicemic bacterial disease responsible for 5- 70% mortalities and prevalence up-to 70% in freshwater fishes. Although rarely associated with human infections, Edwardsiella tarda have been found to cause gastroenteritis, soft tissue infection, liver abscess, tubo-ovarian abscess, and mycotic aneurysm mostly in immunocompromised humans. This study investigated prevalence and antibiogram of E. tarda isolated from Oreochromis niloticus obtained from selected farms in Ibadan, Nigeria. A total of 156 samples consisting: gills, intestines and skins were collected from 52 O. niloticus from Egbeda-(A), Ido-(B), Ibadan: NorthEast-(C) and North-West-(D) for bacteriological analysis. E. tarda Isolation, identification, and antibiogram were performed using standard methods. Data were analyzed using Chi-Square. An overall prevalence of 62.5% was observed for E. tarda with 87.5%, 62.5% and 50.0% for gills, intestine and skin samples, respectively, whilst overall location prevalence were observed as: 100.0%-(A), 50.0%-(B), 66.6%-(C) and 50.0%-(D). Isolates exhibited resistance patterns comprising; 100.0%-(Ceftazidime-(CPZ), Cefuroxime-(CRX) and Meropenem-(MEM)), 91.7%- Cefotaxime-(CTX), 83.3%-(Tetracyclin-(TET)), 50.0%-(Cotrimoxazole-(COT)), 33.3% (Ceftriaxone-(CTR) and Gentamicin-(GEN)), 25.0%-(Chloramphenicol-(CHL)), 16.7%-Amikacin- (AMK) and 8.3%-(Ciprofloxacin-(CIP)). Multi-drug resistance pattern: CRX-CFZ-MEM-(100%), CRX-CTR-CTX-CFZ-MEM-(83.3%), CRX-CTR-CTX-CFZ-MEM-TET-(66.7%), CRX-CTRCTX-CFZ-MEM-TET-COT-(58.3%) and CRX-CTR-CTX-CFZ-MEM-TET-COT-GEN-(8.3%) was observed. Isolation and identification of E. tarda from O. niloticus confirm its presence in Ibadan and affirms that O. niloticus harbors, and could serve as a source of infection to humans. The antimicrobial resistance patterns of isolates to antibiotics indicate misuse in aquaculture and indiscriminate disposal of antibiotics into aquatic environments. This suggests risks of transmission of infectious agents to human and probable spread of resistant pathogens to humans from the environment.
Total viable microbial count of the selected street foods obtained from Palampur, India
Authors: Sharma Diksha , Modgil Rajni , Sandal Anupama
Published: April 2021

The present study was undertaken to evaluate the total viable microbial count of selected street foods i.e Samosa, Pakoda, Tikki, Momo, Spring rolls and Veggie burger in Palampur city of Himachal Pradesh, India. Samples of each street food were collected from 3 different locations and named as street vended samples. The samples prepared in the food laboratory by using traditional recipes were named as control samples and the samples prepared by using locally available healthy and more nutritious ingredients were named as value added samples. The samples were prepared for microbial analysis as per standard protocol. During the comparison, a significant (p≤0.05) difference existed in the viable count of street vended samples when compared to control and value-added samples. Poor hygienic conditions during processing and handling might be responsible for the higher microbial load. Common Indian street foods namely Samosa, Pakoda and Tikki had less colony count in comparison to the Moms, Spring rolls and burgers.
Utilizing Formative Assessment to Encourage Study Strategy Modifications by Osteopathic Medical Students: An Observational Study
Authors: JOSHİ Vivek , YOUNGER Michael , JOSHİ Bhargavi , KHAN Safeer
Published: April 2021

Aim: The standardized mode of delivering curriculum across the globe is didactic lectures. Formative and summative assessment methods are routine practices used to assess the students understanding and mastery in content and concepts which is delivered. The formative assessment methods are extremely popular in medical educational training but the data supporting such claims is largely lacking. The aim of this observational study was to determine if frequently provided formative assessment methods like practice quizzes, take home assignments can have any positive impact on student learning strategies and assessment outcomes in examination.
Material and Methods: A total of 145 students were included in this study. This study explored the relationship between student performance in various low stakes formative quizzes and high stakes summative examination. Based on the student performances across various formative assessment methods, the students were encouraged to modify or retain the study strategies and the effect of such recommendations were observed over the course of the semester.
Results: The data analysis showed positive relationship between the student performance on formative assessments and summative assessment before and after the intervention to study methods and strategies. Students in top, second, third and bottom quartile gained a cumulative average of 72.4%, 61.0%, 56.6% and 48.3% in the formative assessment and an average of 89.3%, 79.8%, 75.0%, and 65.7% on their summative examination which were used as tools for early intervention.
Conclusion: Following the early intervention and modifications in study strategies, there was a steady increase in student performance on high stakes examination.
A Brief Analysis and Suggestions on the Current Situation of New Energy Vehicles in China
Authors: Guan Tianzuo
Published: April 2021

With continuous development of China’s economy in the past two decades, people’s living conditions have been greatly improved. The improved living quality boosts the prosperity of the automobile industry in China. However, whilst the popularity of automobiles promotes the rapid development of social economy and modern civilization, it also brings severe energy and environmental problems.

The government pays great attention to these problems, and promotes the development of new energy vehicle industry by issuing various policies and encouraging consumers to actively buy new energy vehicles. However, under these policy incentives and economic incentives, the domestic new energy vehicle industry did not present the expected market response.

This paper briefly describes the development status and existing problems of domestic new energy vehicle industry, and puts forward some feasible suggestions.
Research on Optimal Allocation Strategy of Bank Credit Funds Based on KMV Model and Logit Model
Authors: Liu Chao , Zhang Xiaofan , Wang Yuerong
Published: April 2021

Using KMV model, normal Copula function, K-means cluster analysis and logit model, this paper constructs the enterprise credit risk assessment model, bank credit fund optimal allocation model, banking risk index system, and synthetically uses software such as MATLAB、SPSS to solve the problem of credit fund distribution strategy for small and medium-sized enterprises, and draws the conclusion that the loan interest rate classification of enterprise credit risk assessment, the weight of bank to credit fund distribution, and the change of bank risk index weight in sudden situation.Finally, the above model provides the strategy for bank credit fund allocation and gives the test and evaluation.

The outstanding features of this paper are: using the KMV model and the normal Copula function, combining the enterprise credit rating and default times to establish a linear model to quantify the enterprise credit risk, will not beeasy to calculate the industry violation probability quantitative analysis, also get the bank credit annual interest rate fordifferent industries and levels of enterprises, and through the representative industries of the optimal loan weight calculation, so that the bank decision has the characteristics of the least unit risk. This paper also establishes a banking risk index system with emergency factors, which is of practical significance to make decision analysis of emergency events.
Information Security Management in Financial Sector Based on Security Baseline
Authors: Xi Yanli
Published: April 2021

On the whole, the structure of information security in financial sector will become more complex and diverse, for its system’s expansion will, to a certain extent, promote such situation. Thus, such situation will increase the number of key and server applications. If staff makes mistakes in operation, it will inevitably cause adverse obstacles to the normal turnover of the system. In view of the above drawbacks, it is necessary to set up baselines of information security management to cater the needs of the financial sector, and to ensure the safe and effective operation of information systems to the greatest extent. This article studies the above issue and aims to provide some theoretical reference for information security management under the financial environment.
Communicating CSR in the online environment: evidence from the Romanian tourism distribution sector
Authors: Moisescu Ovidiu I.
Published: April 2021

Purpose – The purpose of this paper is to investigate the extent to which the largest Romanian travel agencies communicate their CSR practices and policies in the online environment, as reflected by the contents of their websites and social media pages, outlining the manner of this online disclosure within specific CSR domains. Design & methodology – The websites and social media pages of the largest Romanian travel agencies, in terms of net turnover, were analyzed considering several variables related to CSR communication/disclosure: having a CSR dedicated section, including CSR reports, emphasizing legal and economic responsibilities, and disclosing workforce, society, market, and environment oriented CSR actions or policies. Findings – The research reveals significant deficiencies and superficiality in communicating CSR in the online environment by the investigated organizations. Only 10% dedicate a section on their website to CSR, none of them include any form of CSR reports, while the most frequent CSR aspects comprised in their online domains can be categorized as market-oriented, service quality being the most emphasized facet, fair pricing and honest/transparent communication being also consistently outlined. Originality of the research – Research on how the members of the tourism distribution sector communicate CSR in the online environment with focus on Central and Eastern Europe has been extremely scarce. This paper’s contribution consists in reducing this literature gap, bringing insights into CSR communication practices from the Central and Eastern European tourism distribution sector. Moreover, the proposed methodology for analyzing travel agencies’ websites and social media pages can be further used in order to research the issue of online CSR communication in other regions or tourism sectors.
Investigating the Approach of Socialization and Strengthening Social Interactions for Designing Residential Town of Engineers
Authors: Pir Mohammadi Sahar
Published: April 2021

The quality of the environment affects human behavior, the micro-communities of human beings need creative thinking and ideas. Social environments have a significant impact on collective behaviors and social interactions. Nowadays achieving social indicators in housing with a sustainable approach is one of the goals that have been considered. The most important issue in the field of research is recognizing and examining the value of spaces in residential environments to achieve social life, in which it leads human to be social in public residential spaces. Paying attention to social relations with neighbors and people to create Social relationships are proportionate to the presence of individuals in their realm of life. The concept of neighborhood is being responsible for creating social relationships, influencing people living in the complex and community-based life. In this research, by satisfying the human need to communicate and interact with others, creating collective spaces in different scales such as commercial and recreational spaces in residential complexes, the presence of people in these spaces leads to the socialization of collective space and the factor in which the space achieves success. By explaining and identifying the components of socialization in the collective spaces of residential complexes, such spaces can be prepared for the presence of people in the space.
Internet of Things pada Dashboard Informasi Kandang Jangkrik
Authors: Yoga Putra Qurnia Dwi , Cahyo Puji Winar
Published: April 2021

Abstrak :

Kondisi lingkungan sering berubah-ubah membuat kondisi hewan ternak menjadi kurang produktif, terutama pada hewan ternak jangkrik. Selain dipengaruhi kondisi lingkungan yang berubah-ubah dan tidak menentu, penurunan hasil ternak jangkrik dipengaruhi oleh suhu dan kelembaban. Suhu yang ideal untuk ternak jangkrik ini berada pada kisaran 20°C-32°C. Sedangkan untuk kelembaban kandang berada pada kisaran 65%-80%. Untuk itu perlu alat untuk mengukur suhu dan kelembaban kandang jangkrik yang dapat mengawasi keadaan serta mengetahui kondisi kandang jangkrik itu sendiri sehingga dapat meningkatkan kualitas produksi jangkrik.

Berdasarkan permasalahan tersebut dibuat sistem monitoring ternak jangkrik. Dimana sistem ini dapat melakukan penyiraman secara otomatis jika suhu kandang jangkrik terlalu panas dan kandang terlalu lembab.

Hasil dari penelitian ini adalah dashboard informasi kondisi kandang jangkrik dengan sensor suhu dan kelembaban. Sistem ini pada menggunakan sensor suhu, kelembaban dan perangkat water pump yang didirakit pada mikrokontroler NodeMCU. Sedangkan Informasi ditampilkan secara dashboard monitoring dengan menggunakan framework Codeigniter.

_____________________________

Abstract :

Environmental conditions often change, making conditions for livestock to be less productive, especially for crickets. Apart from being influenced by changing and erratic environmental conditions, the decline in cricket production is influenced by temperature and humidity. The ideal temperature for crickets is in the range of 20 ° C-32 ° C. Meanwhile, the humidity of the cage is in the range of 65% -80%. For that, we need a tool to measure the cricket cage's temperature and humidity that can monitor the situation and know the condition of the cricket cage itself so that it can improve the quality of cricket production.

Based on these problems, a monitoring system for crickets was created. This system can do watering automatically if the cricket cage's temperature is too hot and the cage is too humid.

This research made a dashboard of information on the crickets cage's condition with temperature and humidity sensors. This system uses temperature, humidity sensors, and water pump devices, which are assembled on the NodeMCU microcontroller. Meanwhile, information is displayed in a monitoring dashboard using a Codeigniter framework.
Analisis POM QM V5.2 For Windows pada Penerapan Metode ABC dan EOQ Dalam Pengendaliaan Persediaan Bahan Baku PVC Compound (Studi Kasus PT.SMI)
Authors: Widodo Amin Widodo
Published: April 2021

Abstrak : 

PT. SMI Perusahaan konsisten  dalam menerapkan  ISO  9001: 2015 dalam upaya tersebut yang dilakukan perusahaan yaitu menginginkan pengendalian persediaan lebih terpola. Tujuan penelitian untuk mengetahui bahan baku yang membutuhkan monitoring sangat ketat dengan Metode ABC dan EOQ. Metode penelitian yang digunakan kuantitatif, diskriptif dengan cara observasi dan wawancara, metode untuk penyeselesaian Riset Operasi menggunakan perangkat lunak berbasis POM QM V5.2 For Windows. Hasil observasi data kebutuhan bahan baku, biaya persediaan akan di lakukan proses pengolahan data dengan menggunakan metode inventory ABC dan EOQ dengan bantuan Tools teknologi informasi POM QM V5.2 For Windows, Hasil penelitian ABC Analisys menujukan bahan baku yang membutuhkan monitoring sangat ketat yaitu PVC 66, Stabilizer, dan PVC 71, Lubricant 16A, dan Lubricant 15 . Hasil penelitian Metode EOQ berpengaruh positif, keuntungan perusahaan akan meningkat karena terjadi efisiensi biaya pembelian bahan baku yaitu PVC 66  menghemat biaya rata-rata Rp 96.321.440,00 atau 44%, Stabilizer  menghemat biaya rata-rata Rp 4.634.959,00 atau 57%, PVC 71  menghemat biaya rata-rata Rp 49.304.566.00 atau 38%, Lubricant 16A menghemat biaya rata-rata Rp 869.640,7  atau 38%, Lubricant 15  menghemat biaya rata-rata Rp 1.663.651,38 atau 60%.

_________________________________

Abstract :

PT. The SMI of the Company is consistent in the application of ISO 9001: 2015, in this effort the company does, namely wanting a more patterned inventory control. The research objective is to find out the raw materials that require very strict monitoring with the ABC and EOQ methods. The research method used is quantitative, descriptive by means of observation and interviews, the method for completing Operations Research using software based on POM QM V5.2 For Windows. The results of the observation of data on raw material requirements, inventory costs will be processed using the ABC and EOQ inventory methods with the help of information technology tools POM QM V5.2 For Windows, the results of ABC Analisys research show that raw materials that require very strict monitoring are PVC 66. , Stabilizer, and PVC 71, Lubricant 16A, and Lubricant 15 . The results of the EOQ method research have a positive effect, company profits will increase due to the efficiency of the cost of purchasing raw materials, namely PVC 66 which saves an average of Rp. 96,321,440.00 or 44%, Stabilizer saves an average of IDR 4,634,959.00 or 57%, PVC 71 saves an average of IDR 49,304,566.00 or 38%, Lubricant 16A saves an average of IDR 869,640.7 or 38%, Lubricant 15  saves costs an average of IDR 1,663,651.38 or 60%.
Features of excitation of a linear electromechanical converter of induction type from an AC source
Authors: Bolyukh V.F. , Kashansky Yu.V. , Schukin I.S.
Published: April 2021

Purpose. The purpose of the article is to establish the basic laws of operation of induction-type linear electromechanical converter (LEMС) during operation in high-speed and shock-power modes and excitation from an AC source of increased frequency. Methodology. With the help of a mathematical model, the regularities of the course of processes in a LEMС, excited from an AC source, were established when working with shock-power and high-speed modes. The solutions of the equations of the mathematical model, which describe interrelated electrical, magnetic, mechanical and thermal processes, are presented in a recurrent form. Results. It was found that when the LEMC operates in the shock-power mode, the maximum value of the current in the inductor winding occurs in the first half-period, and in the inhibited armature winding in the second half-period. The electrodynamic force changes at twice the frequency, taking on both positive and negative values. Since the positive values exceed the negative ones, the magnitude of the impulse of the electrodynamic force increases with each period of the force. Depending on the initial voltage phase, the relative change in the magnitude of the force impulse is 1.5 %. It was found that when the LEMC operates in high-speed mode, the current in the inductor winding in the first half-period has the greatest value, but after several periods it takes on a steady state. The temperature rise of the inductor winding increases with the time of connection to the AC source, and the temperature rise of the armature winding has the nature of saturation. The electrodynamic force has an oscillatory character with strong damping and a significant predominance of the positive component. Depending on the initial phase of the voltage, the relative change in the maximum speed of the armature winding is 2.5 %. Originality. For the first time, a mathematical model of the LEMC, excited from an AC source, was developed, the solutions of the equations of which describe the interrelated electrical, magnetic, mechanical and thermal processes. For the first time, the regularities of the course of processes in LEMC were established when working with shock-power and high-speed modes. Practical value. The characteristics of LEMC are obtained, which determine the efficiency of work in shock-power and high-speed modes. It is shown that the initial voltage phase has no significant effect on the power, high-speed thermal performance of the converter excited from an alternating current source.
Analysis of the payback period of a modernized pump unit with induction electric motors of advanced energy efficiency classes
Authors: Goman V.V. , Prakht V.A. , Kazakbaev V.M. , Dmitrievskii V.A. , Valeev E.A. , Paramonov A.S.
Published: April 2021

Aim. The comparative analysis of energy consumption, electricity costs during lifetime cycle and payback period of a pump unit with 90 kW 2-pole induction motors, belonging to various energy efficiency classes, feeding directly from power grid. Methods. The examined operating modes aligned with a typical operating cycle of a pump unit with approximately constant flow rate of 75-110 % of the rated flow. The calculations were based on the pump and induction motors nameplate data, which, in their turn, were based on the manufacturers’ experimental data. Results. The calculations of energy consumption, electricity costs and payback periods of a pump unit with 90 kW 2-pole induction motors, feeding directly from power grid have been performed in the article. The application of induction motors belonging to IE2, IE3 and IE4 energy efficiency classes has been discussed. Practical value. It has been demonstrated, than in case of replacement of an induction motor of energy efficiency class IE2 due to planned retrofit, payback period for an IE4 induction motor is 2.18 years, energy savings within a calculated 20-year operating period are 268MW·h, which makes €41110 in money terms. Under the same conditions, the replacement of an induction motor of energy efficiency class IE2 with an induction motor of energy efficiency class IE3 will allow to save 88 MW·h within a calculated operating period, which, expressed in monetary terms, is €13500 and the payback period is 5.11 years. Thus, the article proves that despite a higher initial price, the choice of an induction motor of energy efficiency class IE4 tends to be more economically advantageous.
Numerical simulation of gap length influence on energy deposition in spark discharge
Authors: Korytchenko K.V. , Shypul O.V. , Samoilenko D. , Varshamova I.S. , Lisniak А.A. , Harbuz S.V. , Ostapov K.M.
Published: April 2021

The aim of the work is to study the influence of the length of the spark gap on energy input into the discharge channel during its gas-dynamic expansion. Methodology. The research is carried out by numerical modeling of the process of spark discharge development at variable values of the discharge gap length and at invariable other discharge conditions. The length of the gap was set in the range from 1 mm to 20 mm. The study was conducted using a numerical model of spark development, which takes into account the processes of nonstationary gas-dynamic expansion of the spark channel, the transient process in the electric circuit, nonequilibrium chemical processes, gas ionization, heat transfer and electrons thermal conductivity. The simulation was performed in atmospheric pressure nitrogen. The calculation was performed for various parameters of the RLC circuit, such as capacitance, inductance, resistance and voltage across the capacitor. Results. The study evaluates the influence of the spark length on the discharge current, the resistance of the spark channel, the energy deposited in the spark channel, and the distribution of thermodynamic parameters of the gas during the development of the spark discharge. It is confirmed that increasing the length of the gap increases the resistance of the spark. The deviation from the linear relationship between the deposited energy or the radiated energy and the length of the spark gap is estimated. Scientific novelty. A linear relationship between the gap length and the deposited energy is revealed when the total energy is above tens of Joules. Deviations from the linear dependence were detected in the discharge circuit when the total energy is below one of Joules. Practical value. The research results allow predicting the effect of the spark gap length on the energy input into the discharge channel under conditions of a slight change in the discharge current. In the conditions of essential change of amplitude of discharge current it is expedient to apply numerical researches for specification of changes in the energy deposited into a spark discharge.
Multi-objective optimal power flow considering the multi-terminal direct current
Authors: Ayachi B. , Boukra T. , Mezhoud N.
Published: April 2021

Introduction. In recent years, transmission systems comprise more direct current structures; their effects on alternating current power system may become significant and important. Also, multi-terminal direct current is favorable to the integration of large wind and solar power plants with a very beneficial ecological effect. The novelty of the proposed work consists in the effects of the aforementioned modern devices on transient stability, thus turn out to be an interesting research issue. In our view, they constitute a new challenge and an additional complexity for studying the dynamic behavior of modern electrical systems. Purpose. We sought a resolution to the problem of the transient stability constrained optimal power flow in the alternating current / direct current meshed networks. Convergence to security optimal power flow has been globally achieved. Methods. The solution of the problem was carried out in MATLAB environment, by an iterative combinatorial approach between optimized power flow computation and dynamic simulation. Results. A new transient stability constrained optimal power flow approach considering multi-terminal direct current systems can improve the transient stability after a contingency occurrence and operate the system economically within the system physical bounds. Practical value. The effectiveness and robustness of the proposed method is tested on the modified IEEE 14-bus test system with multi-objective optimization problem that reflect active power generation cost minimization and stability of the networks. It should be mentioned that active power losses are small in meshed networks relative to the standard network. The meshed networks led to a gain up to 46,214 % from the base case.
Estimation of the main dimensions of the traction permanent magnet-assisted synchronous reluctance motor
Authors: Liubarskyi B. G. , Overianova L. V. , Riabov Ie. S. , Iakunin D. I. , Ostroverkh O. O. , Voronin Y. V.
Published: April 2021

Goal. The goal of the research is to develop an algorithm for selecting the main dimensions of a traction permanent magnet-assisted synchronous reluctance motor. Methodology. A method for determining the main dimensions of the motor, which combines the analytical selection of stator parameters and numerical field calculations for the selection of rotor parameters. The need to check the mechanical strength of a rotor with permanent NdFeB magnets in flux barriers is shown. Results. The article proposes an algorithm for selecting the main dimensions of a traction permanent magnet-assisted synchronous reluctance motor, which combines analytical expressions for selecting stator parameters and numerical field calculations for selecting rotor parameters. It is determined that analytical methods for calculating the magnetic circuit need to be developed in order to reduce the time to select the main dimensions of the motor. Originality. For the first time the sizes of active parts of the permanent magnet-assisted synchronous reluctance motor with power of 180 kW for the drive of wheels of the trolleybus are defined. Practical significance. As a result of research the sizes of active parts, stator winding data and a design of a rotor of the electric motor are defined. The obtained results can be applied when creating an electric motor for a trolleybus.
Mathematical modelling of starting modes of induction motors with squirrel-cage rotor
Authors: Malyar V. S. , Hamola O. Ye. , Maday V. S. , Vasylchyshyn I. I.
Published: April 2021

Purpose. Development of methods and algorithms for calculation of starting modes of the induction motors with the squirrel-cage rotor. Methodology. Mathematical modelling of starting modes of asynchronous electric drives in various coordinate systems with the use of numerical methods for solving boundary problems for systems of differential equations and nonlinear systems of final equations and calculation with their use of static characteristics. Results. Methods and algorithms for numerical analysis of the starting modes of asynchronous electric drive have been developed, which make it possible to calculate the static characteristics and transients in fixed three-phase and orthogonal two-phase coordinate systems. Academic novelty. Known in the literature methods of calculation of starting modes have in their basis classical equivalent circuits with different approximate methods of calculating the parameters taking into account the saturation of a magnetic core and current displacement in a rotor winding. This approach requires a special solution of the adequacy problem for each problem. The methods described in the article for the saturation accounting use real magnetization characteristics of the main magnetic flux and leakage fluxes separately, and the skin effect phenomenon is taken into account by representing the squirrel-cage rotor winding as multilayer. Such mathematical model of the motor is universal and makes it possible to take into account the saturation and current displacement in any dynamic mode, including the start-up process. Mathematical models developed on the basis of the proposed methods provide the adequacy of results with a minimum amount of calculations and make it possible to perform optimization calculations. Practical value. Created on the basis of developed algorithms calculation programs allow to carry out with high reliability calculation of starting modes both in three-phase and two-phase axes of coordinates that gives the chance to analyze not only symmetric, but also asymmetric modes and to predict special features of functioning of system of the electric drive in the set technological conditions of operation and to form requirements to development and adjustment of starting systems with the purpose of maintenance of power effective and reliable operation of system of asynchronous electric drives.
Overhead power lines magnetic field reducing in multi-story building by active shielding means
Authors: Kuznetsov B. I. , Nikitina T. B. , Bovdui I. V. , Kolomiets V. V. , Kobylianskiy B. B.
Published: April 2021

Aim. Reducing of magnetic flux density of magnetic field in multi-storey building, generated by overhead power lines to the sanitary standards level by active shielding means. The tasks of the work are the synthesis, computer simulation and experimental research of three-circuits system of active shielding, which includes three shielding coils. Methodology. When synthesizing the system of active shielding of magnetic field, are determined their number, configuration, spatial arrangement and of shielding coils as well as the shielding coils currents and resulting magnetic flux density value in the shielding space. The synthesis is based on the multi-criteria game decision, in which the payoff vector is calculated on the basis on quasi-stationary approximation solutions of the Maxwell equations. The game decision is based on the stochastic particles multiswarm optimization algorithms. Results. Computer simulation and experimental research of three-circuit system of active shielding of magnetic field, generated by overhead power lines with phase conductors triangle arrangements in multi-storey building are given. The possibility of initial magnetic flux density level reducing in multi-storey building to the sanitary standards level is shown. Originality. For the first time to reducing of magnetic flux density of magnetic field in multi-storey building the synthesis, computer simulation and experimental research of three-circuit system of active shielding of magnetic field generated by single-circuit overhead power line with phase conductors triangular arrangements carried out. Practical value. Practical recommendations from the point of view of the practical implementation on reasonable choice of the spatial arrangement of three shielding coils of three-circuit system of active shielding of the magnetic field generated by single-circuit overhead power line with phase conductors triangular arrangements in multi-storey building are given.
The efficiency of the active controlled rectifier operation in the mains voltage distortion mode
Authors: Krylov D. S. , Kholod O. I.
Published: April 2021

Goal. Checking the efficiency of the active rectifier with differences types of control systems in conditions of deep voltage distortions of a three-phase three-wire supply network. Methodology. The authors have used the Matlab/Simulink software environment to create a model of an active rectifier with various types of control systems as part of a frequency electric drive. We performed a series of simulations of the operating modes of an active rectifier with various control systems when the supply voltage is distorted. Results. When the active rectifier is operating in an unregulated mode, the distortions of the current and mains voltage exceed the maximum permissible values. The quality indicators of the mains current and mains voltage are significantly higher than the normally permissible values. In the absence of voltage distortions in the supply network, the operation of the active rectifier can effectively eliminate the distortions of the mains current, regardless of the type of control system of the active rectifier. In conditions of deep distortions of the supply network voltage, the operation of an active rectifier with a vector control system is more efficient than with a parametric control system. Originality. Criteria for determining the quality of consumed electricity at the connection point of the circuit are proposed. Practical significance. Recommendations have been developed for the use of active rectifier control systems when working with a distorted power supply voltage.
Ability to Use DFIT to Replace the Minifrac in Sandstone Formations for Reservoir Characterizations
Authors: A. Gabry Mohamed , A. Thabet Samuel , Abdelhaliem Emad , Algarhy Ahmed , Palanivel Maharaja
Published: April 2021

One of essential parts of hydraulic fracture job design optimization in deep sandstone formations is to conduct a minifrac test using fracture fluid to identify the closure pressure for calibration of the stress profile and to calibrate the leak-off coefficient of the fracturing fluid, but the test could not provide good understanding for reservoir properties of permeability, reservoir pressure, and intensity of natural fractures.

By conducting the actual DFIT (Diagnostic Fracture Injection Test) and minifrac in more than thirty wells in different formations from different fields, several leak-off behaviors are observed and several conclusions can be reached by integrating minifrac, DFIT, geologic settings information, and production data.

With the experience of conducting high rate and low rate DFIT before minifrac jobs, we can conclude that there are several benefits for the DFIT by replacing the minifrac, which conventionallyusesg a polymer fracturing fluid, with a non-wall-building fluid consisting mainly of water from the operations and job design perspective, and from the post frac production perspective. DFIT with water can introduce the best methodology to detect the induced complexity that may cause hydraulic fracture job cancellation in cases of detecting high complexity value early before rig movement. Implementing DFIT in a complete hydraulic fracturing design, execution and evaluation workflow can provide a deep understanding of the fracture geometry propagation and reservoir characterization. The main disadvantages of the DFIT is that it requires a long leak-off observation period but that can be minimized in the mD range of sandstone permeability.

This paper introduces DFIT in sandstone formations as a good method for integration between the geology, reservoir management, and fracture operations. The paper provides the operational and integral benefits of replacing minifrac and fracturing fluid with DFIT and water in deep sandstone formations, which provides more accurate data analysis because testing is done with same fluid. In addition, it can reduce fracture operations cost by 10%.