correct selection
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2022 ◽  
Vol 5 (4) ◽  
Muhammad Ilyas ◽  
Shaheen Abbas ◽  
Afzal Ali

In this study, we present a univariate probability distribution through application of the three Sub and Super Exponential heavier-longer and lighter-shorter tails fitting. This univariate family includes the Lognormal, Gamma and Weibull distribution, the adequacy of the distribution tails is obtained by adequate Fitting Tests and descriptive Criterion. It emphasizes on tail values and is independent of the number of intervals. In this regards the time series analysis for the last three centuries of the logarithm population data sets over to Karachi region (from1729 to1946 and from 1951 to 2018) is used, which contains irregular and regular length and peaks, That peaks /tails fitting is attained by methods for validation and normality tests and defined by stochastic depiction. In other hand, Weibull and Lognormal distribution tails are found as heavier distribution by two validation tests (Maximum Likelihood Estimation and probability of correct selection), In the final section, the univariate probability distributions are used to Monte Carlo simulation for generating the actual population data, it indicates that the heavy-tailed Lognormal and Weibull distributions are also fitted contract than the more commonly seen lighter tailed Gamma distribution. So, the Monte Carlo Simulation performs the appropriate Lognormal and Weibull distributions for irregular and regular data and generate data values (298 and 69) from duration of 1729 to 2020 and 1951 to 2020. Copyright(c) The Author

2022 ◽  
Vol 15 ◽  
Chengcheng Han ◽  
Guanghua Xu ◽  
Xiaowei Zheng ◽  
Peiyuan Tian ◽  
Kai Zhang ◽  

The refresh rate is one of the important parameters of visual presentation devices, and assessing the effect of the refresh rate of a device on motion perception has always been an important direction in the field of visual research. This study examined the effect of the refresh rate of a device on the motion perception response at different stimulation frequencies and provided an objective visual electrophysiological assessment method for the correct selection of display parameters in a visual perception experiment. In this study, a flicker-free steady-state motion visual stimulation with continuous scanning frequency and different forms (sinusoidal or triangular) was presented on a low-latency LCD monitor at different refresh rates. Seventeen participants were asked to observe the visual stimulation without head movement or eye movement, and the effect of the refresh rate was assessed by analyzing the changes in the intensity of their visual evoked potentials. The results demonstrated that an increased refresh rate significantly improved the intensity of motion visual evoked potentials at stimulation frequency ranges of 7–28 Hz, and there was a significant interaction between the refresh rate and motion frequency. Furthermore, the increased refresh rate also had the potential to enhance the ability to perceive similar motion. Therefore, we recommended using a refresh rate of at least 120 Hz in motion visual perception experiments to ensure a better stimulation effect. If the motion frequency or velocity is high, a refresh rate of≥240 Hz is also recommended.

2022 ◽  
Vol 354 ◽  
pp. 00043
Lucian Moldovan ◽  
Mihai Magyari ◽  
Dragoș Fotău ◽  
Clementina Sabina Moldovan

When using electrical equipment in installations operating in hazardous areas endangered by potentially explosive atmospheres, care shall be taken also to the selection of such equipment. The correct selection of equipment for use in potentially explosive atmospheres must be considered in the design phase of an installation and verified in the mounting phase. Equipment intended for use in potentially explosive atmospheres must be designed, manufactured and placed on the EU market considering the provisions of the ATEX Directive 2014/34/EU. In order to adequately select the electrical equipment, the provisions of the regulations in force must be considered together with the provisions of applicable standards.

Volodymir Martynenko

The work is devoted to the development and calculation of the strength of a new composite fan blade of the main ventilation of the mine, including the static and modal analyzes, as well as the stability analysis. The studies took into account the pre-determined aerodynamic loads on the lateral surface of the blade airfoil. The research was carried out by means of the finite element analysis of the thin-walled airfoil structure using the theory of thick multilayer shells. Estimation of the static strength was performed using the Hashin strength criterion. Analysis of the airfoil shell buckling resistance under the action of bending aerodynamic loads was performed using the methods of the linear stability theory. The modal analysis was performed taking into account the prestressed state from the action of static loads. The analysis of the research results testifies to the sufficient static and dynamic strength of the composite airfoil and the possibility of its implementation in a real rotary machine with the correct design of the fastening between the metal part of the blade root and the composite airfoil. The method of designing and analyzing the strength of the fan blade composite airfoil can be used to create new composite elements of turbomachines: the correct selection of thicknesses of different parts of the airfoil allows obtaining a uniform design with rational use of material; the optimal location of the stiffeners inside the airfoil shell avoids its excessive displacement and stress and the buckling effects, as well as achieving the maximal detuning level from the bending natural frequencies of vibrations; the proposed integrated approach to the strength assessment, which takes into account the effect of aerodynamic loads on the blade airfoil in the static analysis and the prestressed state during the modal analysis can significantly improve the accuracy and correctness of calculations. The approach described in the paper is new for low-speed rotary machines, as at present there are no comprehensive methods for designing composite blades of fans and compressors, and there is no mention of specific examples of their implementation in the projects implemented by manufacturers.

Paliva ◽  
2021 ◽  
pp. 123-130
Karel Ciahotný

Adsorption technologies used for gas desulfurization are a widespread technique which, due to its relative simplicity, are widely used to the purification smaller volumes of gas. However, for their trouble-free and economical use, it is necessary to respect several basic requirements for the selection of suitable types of adsorbents with respect to the specific composition of the purified gas. The article provides a brief overview of the history of the development of adsorption technologies and also provides several different examples of the operational use of this technology for the purification of gases containing high concentrations of sulfur substances. Furthermore, the principles of correct selection of a suitable adsorbent for specific application cases are also specified here. Iron oxide adsorbents were used in the early times of the operation of the technology, which were inexpensive but had a relatively low sorption capacity for sulfur compounds. Therefore, sorbents based on iron oxides have been gradually replaced by more powerful, but also more expensive sorbents based on activated carbon. Initially, activated carbon without impregnation was used, the production of which took place in the Czech Republic on an industrial scale. By the further development of impregnated types of activated carbon and their introduction into industrial production, these adsorbents have been also used in adsorption technologies intended for gas desulfurization. Their sorption capacity is much higher in comparison with non-impregnated types of activated carbon, because the impregnants used convert sulfur compounds from gas into non-volatile substances (elemental sulfur, sulfides, polysulfides). This ensures a long service life of the adsorbent and high efficiency of gas purification from sul-fur substances.

Jazmín Balderrabano-Briones ◽  
Gloria Pérez-Garmendia ◽  
Montserrat Acosta-Cadenas ◽  
David Antonio García-Reyes

Management control tools are of great importance for any organization, therefore, in this research work, the study of management control tools will be carried out in the operational areas of a logistics facility in the state of Veracruz. , to later develop a measuring instrument. The study proposes to design a measurement instrument based on a Likert scale, converting qualitative information into quantitative data by the researcher, which allows visualization and clarity in determining the ideal tools for the control management of the studied area. The instrument will be applied to the company's experts, since they provide reliable information and provide a reliable scenario. The information is analyzed by the researcher, to later design and define a proposal, a proposal that allows the correct selection of control management tools and comprehensively improve the organization.

Forecasting ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 36-50
Le Quyen Nguyen ◽  
Paula Odete Fernandes ◽  
João Paulo Teixeira

Vietnam has experienced a tourism expansion over the last decade, proving itself as one of the top tourist destinations in Southeast Asia. The country received more than 18 million international tourists in 2019, compared to only 1.5 million twenty-five years ago. Tourist spending has translated into rising employment and incomes for Vietnam’s tourism sector, making it the key driver to the socio-economic development of the country. Following the COVID-19 pandemic, only 3.8 million international tourists visited Vietnam in 2020, plummeting by 78.7% year-on-year. The latest outbreak in early summer 2021 made the sector continue to hit bottom. Although Vietnam’s tourism has suffered extreme losses, once the contagion is under control worldwide, the number of international tourists to Vietnam is expected to rise again to reach pre-pandemic levels in the next few years. First, the paper aims to provide a summary of Vietnam’s tourism characteristics with a special focus on international tourists. Next, the predictive capability of artificial neural network (ANN) methodology is examined with the datasets of international tourists to Vietnam from 2008 to 2020. Some ANN architectures are experimented with to predict the monthly number of international tourists to the country, including some lockdown periods due to the COVID-19 pandemic. The results show that, with the correct selection of ANN architectures and data from the previous 12 months, the best ANN models can be forecast for next month with a MAPE between 7.9% and 9.2%. As the method proves its forecasting accuracy, it would serve as a valuable tool for Vietnam’s policymakers and firm managers to make better investment and strategic decisions.

Land ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 15
Qiang He ◽  
Xin Deng ◽  
Chuan Li ◽  
Fangxia Kong ◽  
Yanbin Qi

The topic of quality of life has long been a focus of global research and the public. The land transfer policy implemented by the Chinese government affects farmers’ quality of life (FQOL); however, the extent of this effect remains unclear. As land transfer may be a self-selection behaviour, it may be subject to selection bias such that traditional measurement methods are unable to effectively estimate its quantitative impact. This study used data from a questionnaire given to 5668 rural households in 25 provinces of mainland China. It sought to quantify the impact of land transfer on FQOL by using endogenous switching regression (ESR) models to correct selection bias. The results show: (1) for farmers who choose to transfer land, if they choose not to transfer land, FQOL may decrease by 64.11%; (2) for farmers who choose not to transfer their land, if they go on to choose to transfer their land, FQOL may increase by 0.75%; (3) land transfer can improve the quality of life of the older generation of farmers but will reduce the quality of life of the newer generation. The results of this study provide research support for China and other countries seeking to effectively implement land policies and improve the FQOL, helping to provide practical strategies for the sustainable development of rural areas.

Inventions ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 3
Pavel Ilushin ◽  
Kirill Vyatkin ◽  
Anton Kozlov

The formation of wax deposits is a common phenomenon in the production and transportation of formation fluids. On the territory of the Perm Krai, this problem occurs in half of the mining funds. One of the most common and promising methods of dealing with these deposits is the use of inhibitor regents. The most popular technique for assessing the effectiveness of a wax inhibitor is the «Cold Finger», which has a number of significant drawbacks. This work presents a number of methods for assessing the effectiveness of inhibition of paraffin formation on the laboratory installation «WaxFlowLoop». A number of laboratory studies have been carried out to determine the effectiveness of a paraffin deposition inhibitor for inhibiting the paraffin formation process of four target fluids. Verification of the obtained values was carried out by comparing them with the field data. As a result of laboratory studies, it was found that the value of the inhibitor efficiency, determined by the «Cold Finger» method, differs from the field data by an average of 2 times. At the same time, the average deviation of the results determined at the «WaxFlowLoop» installation from the field data is 8.1%. The correct selection of a paraffin deposition inhibitor and its dosage can significantly increase the inter-treatment period of the well, thereby reducing its maintenance costs and increasing the efficiency of well operation.

2021 ◽  
Vol 7 (12) ◽  
pp. 1087
Alberto Pedrero-Méndez ◽  
H. Camilo Insuasti ◽  
Theodora Neagu ◽  
María Illescas ◽  
M. Belén Rubio ◽  

The search for endophytic fungi in the roots of healthy wheat plants from a non-irrigation field trial allowed us to select 4 out of a total of 54 cultivable isolates belonging to the genus Trichoderma, identified as T. harzianum T136 and T139, T. simmonsii T137, and T. afroharzianum T138. In vitro assays against the phytopathogenic fungus Fusarium graminearum showed that the T. harzianum strains had the highest biocontrol potential and that T136 exhibited the highest cellulase and chitinase activities. Production patterns of eight phytohormones varied among the Trichoderma strains. All four, when applied alone or in combination, colonized roots of other wheat cultivars and promoted seed germination, tillering, and plant growth under optimal irrigation conditions in the greenhouse. Apart from T136, the endophytic Trichoderma strains showed plant protection capacity against drought as they activated the antioxidant enzyme machinery of the wheat plants. However, T. simmonsii T137 gave the best plant size and spike weight performance in water-stressed plants at the end of the crop. This trait correlated with significantly increased production of indole acetic acid and abscisic acid and increased 1-aminocyclopropane-1-carboxylic acid deaminase activity by T137. This study shows the potential of Trichoderma endophytes and that their success in agricultural systems requires careful selection of suitable strains.

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