Journal articles on the topic 'Leveling Mathematical models'
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1
Cui, Li, Xian Lei Hu, and Xiang Hua Liu. "Research on Mathematical Model of Leveling Process for Plate Mill." Advanced Materials Research 148-149 (October 2010): 368–71. http://dx.doi.org/10.4028/www.scientific.net/amr.148-149.368.
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In order to calculate the parameters of roller leveling process, the 3D mathematical models of plate leveling based on the curvature integral by elastic-plastic differences were set up. The calculation results by the models showed a good correlation with the measured data from a plate mill which adopts the advanced control system by SMS. The analytic models can be developed which analyzed the leveling process so efficiently that it can be used for process controlling. Additionally, the plastic deformation ratio was analyzed which can account for the leveling phenomenon, and the model was regressed which can be used easily for engineering calculation.
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Maksimov, E. A. "Elaboration of a mathematical model of parameters calculation for section bars leveling at a roller leveling machine." Ferrous Metallurgy. Bulletin of Scientific , Technical and Economic Information 76, no. 7 (August 11, 2020): 721–27. http://dx.doi.org/10.32339/0135-5910-2020-7-721-727.
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During rolling and cooling at cooling beds, section bars get general and local curvatures, to correct which, leveling at roller leveling machines (RLM) is used. Calculation of leveling parameters of section bars at RLM is based on hypothesis of isotropy and homogeneity of the deformed metal. Besides the calculation is based also on assumptions of a linear distribution of penetration coefficient of plastic deformation along the rolled product thickness at alternating bending, point character of roller and rolled product surface contact, vertical direction of leveling force for all rollers of RLM. Application of those hypothesizes considerably deteriorates the accuracy of technological parameters calculation for rolling and leveling operations. A mathematical model presented for leveling parameters of section bars at RLM calculation. The novelty of the model is an accurate determination of the border between elastic and plastic zone Z0, which is accomplished by an iterative method. The information about exact value of Z0 is necessary for calculation of stress distribution along the piece section, as well as sag and curvature calculation after the leveling. In traditional models the Z0 value is determined approximately and does not meet the today’s requirements. Stress distribution diagrams along the rolled product section at bending under RLM rollers presented for rectangular, square, channel, Z-section profiles of rolled products, as well as for I-beam and rail, necessary for calculation of residual stresses. The comparison was done of P65 rail sag in the plane of maximum rigidity at the six-roller RLM of Kuznetsk steel-works and their value, obtained by the mathematical model application. The discrepancy between actual and calculated data is only 4.5%, which speaks about conformity of the elaborated mathematical model.
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Hu, Jinpeng, Jiahui Pan, Buwang Dai, Xiaoyu Chai, Yixin Sun, and Lizhang Xu. "Development of an Attitude Adjustment Crawler Chassis for Combine Harvester and Experiment of Adaptive Leveling System." Agronomy 12, no. 3 (March 16, 2022): 717. http://dx.doi.org/10.3390/agronomy12030717.
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Body tilt is typically unavoidable for agricultural vehicles or platforms when operated over tough terrain in agricultural production, and, therefore, it is not possible to guarantee the operation performance. Current leveling methods mainly focus on wheeled vehicles or adjustment for single working parts rather than the vehicle body, and few of them could be applied to crawler vehicles. The objective of this research was to put forward an adaptive leveling system for combine harvesters based on the development of a new four-point lifting adjustable crawler chassis. The working principle of the proposed adjustable mechanism was studied on the basis of the analysis of adjustment characteristics under multiple posture adjustment conditions in a RecurDyn environment. The design relies on the combination of the attitude detection of the leveling system and adjustment calculation of driving hydraulic cylinders according to the established mathematical models. Within the designed adjustable extent (including adjustment range of vehicle height 0–87.8 mm, lateral inclination ±3.98° and longitudinal inclination −2.9–5.2°), the leveling performance of lateral and longitudinal inclination was then tested separately. The experiment showed that the leveling system could achieve automatic leveling with an accuracy of ±0.4° and could provide technical support for the development of crawler vehicles.
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Liu, Jin Hui, W. J. Xie, C. Zhao, L. Zhang, and Z. L. Lu. "Mechanics Study on Leveling Process by a Roller during Selective Laser Forming." Advanced Materials Research 670 (March 2013): 101–5. http://dx.doi.org/10.4028/www.scientific.net/amr.670.101.
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Generally, pressures resulted from roller during leveling process in selective laser sintering has the effect of densification of powder materials. But extra frictions due to them become the forces which always deteriorate the surface of the part and mark it with several lines trace. Sometimes, the manufacturing can even not continue if these forces accumulate to a large extent to move the whole part. Therefore, the whole forming process will be obliged to stop owing to the displacement of part from above mentioned damage. In this work, the emerging reason and related variation factors of these forces were studied mathematically, the mathematical and physical model of friction force was also built to describe the connections between the leveling process parameters and them. How to control the influence factor of friction to abate their damages to surfaces and promote the forming quality were also discussed based on these models. This will provide a common reference for the application of selective laser sintering technology.
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Soycan, Metin. "Improving EGM2008 by GPS and leveling data at local scale." Boletim de Ciências Geodésicas 20, no. 1 (March 2014): 3–18. http://dx.doi.org/10.1590/s1982-21702014000100001.
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The development of the Earth Gravitational Model 2008 (EGM2008) model is a significant contribution for modeling the Earth's gravity and geoid. Recently, it can be confidently used versus geometric models following a simple refinement procedure. Several studies show that, EGM2008 can reach the accuracy of regional or local geoid models after modeling the differences between the GPS-leveling geoid heights and EGM2008 derived geoid heights at identified control points. The study focuses on a corrector surface fitting (CSF) approach based on radial basis functions (RBF) as improvement procedure for EGM2008. A detailed mathematical model and solution algorithm of the proposed model is given, and it has been applied in different test areas covering the city borders of Bursa, Konya, Denizli and Gaziantep in Turkey. Accuracy of the improved model was evaluated in scattered check points within test regions. The geoid heights of all check points obtained by GPS-leveling measurements were compared with the geoid heights obtained from improved model. The discrepancies between the calculated and measured geoid heights were analyzed and discussed.
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FEDORCHUK, A. "Analysis of modern models of counterfeiting surfaces for determination of heights by GNSS-leveling method." Modern achievements of geodesic science and industry 2, no. 44 (September 1, 2022): 31–41. http://dx.doi.org/10.33841/1819-1339-2-44-31-41.
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This paper discusses various sources of information related to the issue of determining heights by GNSS-leveling. Implementation of the GNSS leveling method requires the presence of geoid or quasi-geoid heights, which today can be obtained from the corresponding models. In recent decades, scientists from around the world have developed many global, regional and local models of geoid and quasigeoid. This has contributed to the emergence of numerous publications on GNSS leveling. The purpose of the work is to perform the analysis of modern models of reference surfaces on the basis of materials of scientific publications according to the criteria that have a significant impact on research in the field of determining the height by GNSS-leveling. Method. The paper considers 44 publications published in the period 2001–2021. Among the research in this direction, there are three types of work: 1) 13 publications on methods of constructing the models themselves; 2) 12 works on their accuracy analysis and 3) 19 works on “adjustment” of model heights. At the first stage of the research the analysis was performed according to criteria related to geoid and quasi-geoid surface modeling, including Stokes and Molodensky theory, mathematical methods of data analysis and processing, tidal systems, zero-order geoid undulation and scale levels of geoid and quasi-geoid models. In the second stage, the frequency of publications by years was analyzed and the activity of publications of existing geoid and quasigeoid models on the sample of countries, which was made on the basis of all selected works in this study, was established. At the third stage, a quantitative analysis of official published models of geoid and quasi-geoid on the frequency of publications for the study period. The ratio of the accuracy of the heights of global geoid models in relation to the magnitude of the degree and order of their calculation is established. Results. In 58 % of the analyzed works, the authors use Stokes’ theory in their research, and in 42 % – Molodensky’s theory. Among the mathematical methods of data analysis and processing, 27 % use the method of mean square collocation, 20 % use the least squares method, the “delete-restore” method and the method of modifying Stokes’ formula with least squares (or KTH-method). The Fast Fourier transform method was used in 13 % of the works. Publications on the creation of global models of the Earth mostly use the parameters of the tide free tidal system in their calculations – a total of 40 % works. No less important criterion (33 % of works) should be taken into account the parameter of undulation of the geoid of zero order (“zero degree term”). In total, 41 % of research is aimed at creating and analyzing quasi-geoid models on a regional scale. During the study period, most works were published in 2012 and 2018. Leading countries in the development of quasi-geoid models are Canada, Poland, Sweden and the United States, and global geoid models are Germany, the United States and China. For the period 2001–2021, 99 global geoid models of various degree and order were officially presented, among which GOCO, EIGEN and EGM series models are most often used for research. Also during this period, 177 quasi-geoid models were presented, the most of which were published in 2019. Based on these data, the relationship with the frequency of publications in 2008–2021 can be traced. The accuracy of global geoid models in relation to the degree and order of their calculation is systematic in the range of 0.52–1.92 m, 0.38–0.50 m, 0.23–0.38 m and 0.12–0,14 m for models 60-220, 220-260, 260-720 and 720-2190 degree and order respectively. Scientific novelty. It is shown that the analysis of modern models of reference surfaces on the basis of materials of scientific publications in the field of GNSS-leveling method allows establishing the existing advantages and disadvantages of research in this field. Practical significance. The data of such analysis can be used to solve key problems in determining the height of the GNSS-leveling method, which require further research and to find modernized solutions.
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Esina, Ekaterina N., and Vladislava V. Likhodeevskaya. "Development of methods for equalizing level networks." RUDN Journal of Engineering Researches 21, no. 1 (December 15, 2020): 58–65. http://dx.doi.org/10.22363/2312-8143-2020-21-1-58-65.
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The article is devoted to comparison of methods of calculating the approximate elevations of nodal points when adjusting leveling networks by strict and non-strict methods. Ensuring geomechanical monitoring of the mutual influence of constructed and operated objects is important in the intensive development of underground space of megacities, the construction of unique objects and structures. In the course of the research, mathematical models of level networks were developed and presented in the form of a closed loop and a set of open polygons. Analysis of modeling allows to determine the feasibility of applying the knot method by Professor V.V. Popov instead of the parametric method of adjustment. It is established that the quality of the results of strict equalization depends entirely on the quality of measurements, since deviations from the true values do not exceed the measurement error. The research has shown that it is possible to simplify the processing of monitoring data and evaluation of various configuration options for leveling networks, using algorithms for calculating approximate marks of nodal points. This makes it easier to process monitoring results and evaluate various network configuration options while ensuring the required level of measurement accuracy.
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Xing, Chen, Yuan, and Shi. "An Improved Time-Series Model Considering Rheological Parameters for Surface Deformation Monitoring of Soft Clay Subgrade." Sensors 19, no. 14 (July 11, 2019): 3073. http://dx.doi.org/10.3390/s19143073.
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Building deformation models consistent with reality is a crucial step for time-series deformation monitoring. Most deformation models are empirical mathematical models, lacking consideration of the physical mechanisms of observed objects. In this study, we propose an improved time-series deformation model considering rheological parameters (viscosity and elasticity) based on the Kelvin model. The functional relationships between the rheological parameters and deformation along the Synthetic Aperture Radar ( SAR) line of sight are constructed, and a method for rheological parameter estimation is provided. To assess the feasibility and accuracy of the presented model, both simulated and real deformation data over a stretch of the Lungui highway (built on soft clay subgrade in Guangdong province, China) are investigated with TerraSAR-X satellite imagery. With the proposed deformation model, the unknown rheological parameters over all the high coherence points are obtained and the deformation time-series are generated. The high-pass (HP) deformation component and external leveling ground measurements are utilized to assess the modeling accuracy. The results show that the root mean square of the residual deformation is ±1.6 mm, whereas that of the ground leveling measurements is ±5.0 mm, indicating an improvement in the proposed model by 53%, and 34% compared to the pure linear velocity model. The results indicate the reliability of the presented model for the application of deformation monitoring of soft clay highways. The estimated rheological parameters can be provided as a reference index for the interpretation of long-term highway deformation and the stability control of subgrade construction engineering.
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Celkevicius, Roberto, and Rosaria F. S. M. Russo. "An integrated model for allocation and leveling of human resources in IT projects." International Journal of Managing Projects in Business 11, no. 2 (May 8, 2018): 234–56. http://dx.doi.org/10.1108/ijmpb-09-2016-0074.
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Purpose The purpose of this paper is to propose an integrated model for allocation and leveling of human resources in IT projects. Design/methodology/approach A single case study was conducted in a large company of IT outsourcing services, which were assessed the management of 14 projects. The survey was conducted through interviews with project managers, and digital files and internal documents of the organization related to these projects. Findings In the analysis, it was identified that the critical path is not identified in all projects, and even when this happens, resources are not allocated in the first tasks in that path. A committee controls the allocation of resources with the assessment of skills, but there is no control of all resource constraints. Research limitations/implications The main limiting factors for this study are: use of data of one company in the IT industry, making it difficult to generalize the model for other sectors companies; it was noted during interviews that the project managers interviewed do not always know in detail all the company’s processes for allocation and resource leveling, due to the large number of processes and different management activities of these professionals. Practical implications A model and actions for this implementation was proposed, such as training for the use of the technique of critical path; allocation and leveling done simultaneously; decisions of the management committee based on information of availability, key skills, holidays, days off of human resources; development of a software tool that integrates this information, generating graphical interfaces that are not provided by project management software with the use of an allocation factor. Social implications The characteristics of the proposed model, as well as the use of the allocation factor, can help managers to validate their allocation models and leveling of human resources in an integrated manner. Originality/value The study explains that the granularity of analysis of resource allocation increases by decomposition of the duration of each activity in fixed time segments. It is suggested to use the mathematical concept of the allocation factor (Fa).
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Rustamov, Kamoliddin, Samandar Komilov, Mavlon Kudaybergenov, Shamshir Shermatov, and Shahzod Xudoyqulov. "Experimental study of hydraulic equipment operation process." E3S Web of Conferences 264 (2021): 02026. http://dx.doi.org/10.1051/e3sconf/202126402026.
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Relevance. When the hydraulic fluid is operated for several cycles, the impact on hydraulic performance and longevity is greatly increased. So, there are several ways to fix this problem. To increase the efficiency of the hydraulic system, it is necessary to study the working processes, the hydraulic systems of the quick-change equipment of the machine with a lawn of the kshp are made as a whole, and the equipment of the machine is attached to the suspension device. The complexity of these processes lies in the fact that they allow experimental research and verification of results using mathematical models. Aim. The purpose of the experimental study in this dissertation is to study the effect of forces acting on the hydraulic system when excavating the hydraulic system of a multipurpose machine and substantiate the parameters by assessing power use efficiency. Methods. Checking the suitability of the working fluid during earthworks, as well as the mathematical model. In this case, we studied the hydraulic system of a single-bucket excavator, the device of quick-change equipment for a universal machine. Results. The theoretical work performed has been verified and the confirmation of the operation of a multipurpose machine designed with earth and dozer equipment. The installation of equipment based on TTZ-80 made it possible to carry out experimental research with the most energy-intensive workflow, determining energy efficiency indicators for excavation and leveling. Conclusion. Comprehensive tests made it possible to conclude that the characteristics of the developed design and the characteristics of the engine of the base machine - the TTZ-80.10 - KM-1 tractor, overcome the resistance encountered during technological operations of a multipurpose machine.
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Li, Zhiwen, Zhongxia Yang, and Youzhi Li. "Effects of Fruit Sizes of Two Camellia Trees on the Larval Sizes of Curculio styracis (Roelofs, 1875): Testing the Endoparasitoid Body Size Hypothesis." Insects 13, no. 3 (February 28, 2022): 246. http://dx.doi.org/10.3390/insects13030246.
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The endoparasitoid body size hypothesis suggests that the size of larvae that develop in a single host should be subject to a trade-off: larger size could lead to increase overall fitness but could simultaneously increase the risk of resource depletion and starvation, resulting in a body size just below the host holding capacity. However, this hypothesis has not been rigorously tested using mathematical models thus far. The camellia weevil, C.styracis (Coleoptera: Curculionidae), is a notorious pest attacking fruits of Camellia oleifera Abel. and C. meiocarpa Hu., in which the larvae develop within a single fruit and larval development is limited by the available food resources. We developed a feasible method to test this hypothesis. First, five models were used to describe the relationship between larval mass and host size. Then, the minimum fruit threshold that had to be met for ad libitum larval development and the corresponding larval size (Wa) of this threshold were calculated based on the characteristics of the optimal model. Finally, the difference between the measured larval size and the predicted larval size (Wa) was determined. The results showed that (1) the data were better described by a logistic function than any other equation; (2) larval size in both host plants increased with increasing fruit size until leveling off when the fruits were large enough to allow unconstrained larval development; (3) larval size remained just below the host-fruit holding capacity, as there was no difference between the measured and predicted larval sizes (Wa); and (4) larvae developed in host plant with larger fruits had a larger size. These results confirmed the endoparasitoid body size hypothesis.
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Xing, Xuemin, Lingjie Zhu, Bin Liu, Wei Peng, Rui Zhang, and Xiaojun Ma. "Measuring Land Surface Deformation over Soft Clay Area Based on an FIPR SAR Interferometry Algorithm—A Case Study of Beijing Capital International Airport (China)." Remote Sensing 14, no. 17 (August 29, 2022): 4253. http://dx.doi.org/10.3390/rs14174253.
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Long-term settlement monitoring of infrastructure built in soft clay areas is of great importance. When using InSAR technology for soft clay settlement monitoring, deformation modeling is a key process. In most InSAR deformation modeling, each component of the total deformation is expressed directly with a fixed functional model in phase functions and assumed to occupy an equal weight. This causes equal weight assumption uncertainty and ignores the actual certain contribution of each phase component related to certain deformational factors. Moreover, the commonly used mathematical empirical models in traditional InSAR are not suitable for describing the nonlinear characteristics of the temporal settlement evolution for soft clay. To address these limitations, we propose an SAR interferometry algorithm, namely, FIPR (FastICA Poisson-curve reciprocal accumulation method), which separates the original InSAR signal based on FastICA to extract each deformation component, and then the models can each extract deformation components and estimate the unknown parameters based on a reciprocal accumulation method. Each independent component and the obtained deformation parameters are used to generate the final deformation time series. Both simulated and real data experiments were designed. The simulated experimental results indicated that the sICA (spatial independent component analysis) separated results were much closer to the original signals than those of the tICA (temporal independent component analysis), with their RMSE lower than 2 mm, and the sICA is thus more highly recommended. Beijing Capital International Airport in China was selected as the study area in the real data experiment. Using 24 high-resolution TerraSAR-X radar satellite images from January 2012 to February 2015, the time-series deformation was obtained, with the maximum cumulative subsidence of 126 mm. The modeling accuracy for the proposed model was estimated as ±2.6 mm, with an improvement of 36.6% compared to the EWA-LM (linear model with equal weight accumulation) algorithm and 16.1% compared to the EWA-PC (Poisson curve with equal weight accumulation) algorithm. The RMSE with external leveling measurements was estimated as ±1.0 mm, with 69.7% improvement compared to EWA-LM and 50% to EWA-PC. This indicated that FIPR can reduce the uncertainty of artificial assumptions in deformation modeling and improve the accuracy of deformation analysis for highways in soft clay areas, providing a reference for road maintenance and management.
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Makienko, Marina A. "SMART AS A PARADIGM OF MODERN CULTURE." Vestnik Tomskogo gosudarstvennogo universiteta. Kul'turologiya i iskusstvovedenie, no. 39 (2020): 52–65. http://dx.doi.org/10.17223/22220836/39/6.
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The article problematizes the characteristic of modern society as a Smart Society. As the evalua-tion criteria, the motives of human activity are suggested, which find their embodiment in the form of cultural objects. The consequence of the transformation of motives is presented by a change in cultural paradigm. The application of the term “paradigm” in relation to the phenomenon of culture allows focusing the attention on its components: axiological system to which the subjects of a particular cul-ture are oriented; algorithms of human behavior within the framework of culture and, accordingly, the prediction of his behavior; the formation of social mechanisms for typical problems solution. These elements of cultural paradigm present the criteria for the analysis of smart society. The analysis of various approaches to understanding the smart society allows concluding that the smart society pre-supposes continuous creation and development of new technologies, which accordingly requires continuous development and creation of knowledge, environment and infrastructure for its production and transmission. Thus, the author draws the conclusion that a smart-person is necessary for the functioning of the smart society. The comparison of philosophical concept of an intelligent person, formulated by Plato and modern social trends, makes it possible to distinguish the following characteristics of a smart per-son: a smart person makes smart decisions based on mathematical models and accurate calculations and competently uses smart devices. The formation of a smart-person is possible through an appropri-ate educational system which forms the appropriate characteristics and a cultural paradigm that trans-mits the corresponding axiological system. The contradictions within the smart paradigm are revealed: 1. Smart education aimed at the formation of open and responsible person finally creates only the skills of task performance, rather than problem statement of software products usage, without under-standing of the principles of their work; interaction with educational content, but not with a single person. 2. Absolute reliance on figures and statistical data leads to the leveling of the significance of hu-man being as imperfect against the background of the possibilities of accurate and rapid calculations and the error-free operations of artificial intelligence. The indicated contradictions are possible within axiological system formed by the smart para-digm: openness to perception of new components, continuous change, and elimination of emotional aspect. The condition for the existence of the presented values is the leveling of the transcendental component. In this context, the limitations of human existence are interpreted in a new perspective: a person is limited by his needs, which is an obstacle to economic growth; a person is limited to every-day life, as a result of which the process of self-determination is carried out only through the things and events that surround a person. This reduces the process of the formation of meanings to the pro-cess of continuous minor changes in material reality. A person does not become a goal for the world of smart technologies; he becomes a means of its existence. As a result, the conclusion is made that the actualization of human being within the framework of the smart paradigm requires the modification of some cultural landmarks, first of all, in the system of education, gender identity and religious affiliation.
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Sjöberg, Lars E. "Geoid model validation and topographic bias." Journal of Geodetic Science 12, no. 1 (January 1, 2022): 38–41. http://dx.doi.org/10.1515/jogs-2022-0133.
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Abstract Recently a number of geoid campaigns were performed to verify different types of geoid and quasigeoid modeling techniques. Typically, GNSS-leveling was employed as an independent method, but in some cases zenith camera astronomic deflection data were also used in astrogeodetic determinations of the geoid and/or quasigeoid. However, due to the uncertainty in the topographic density distribution data (and thereby in orthometric heights), we conclude that neither GNSS-leveling nor astrogeodetic techniques can reliably verify differences between gravimetric geoid models at several centimeter levels in rough mountainous regions. This is because much the same topographic data are used both in the gravimetric geoid models and in their verifications by geometric and/or astrogeodetic geoid models. On the contrary, this is not a problem in verifying gravimetric quasigeoid models, as they are independent of the topographic density distribution, and so is the related normal height used in GNSS-leveling.
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Puziene, Ruta, Asta Anikeniene, and Gitana Karsokiene. "INQUIRY INTO VERTICAL MOVEMENTS OF THE EARTH‘S CRUST BASED ON SAMPLES FROM EASTERN LITHUANIA." Geodesy and cartography 40, no. 2 (June 24, 2014): 58–67. http://dx.doi.org/10.3846/20296991.2014.890308.
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In the research of vertical movements of the earth’s crust, examination of statistical correlations between the measured vertical movements of the earth’s crust and territorial geo-indexes is accomplished with the help of mathematical statistical analysis. Availability of the precise repeated levelling measuring data coupled with the preferred research methodology offer a chance to determine and predict recent vertical movements of the earth’s crust. For the inquiry into recent vertical movements of the earth’s crust, a Lithuanian class I vertical network levelling polygon was used. Drawing on measurements made in the polygon, vertical velocities of earth’s crust movements were calculated along the following levelling lines. For determining the relations shared by vertical movements of the earth’s crust and territorial geo-parameters, the following territory-defining parameters are accepted. Examination of the special qualities of relations shared by vertical movements of the earth’s crust and geo-parameters in the territory under research contributed to the computation of correlation matrices. Regression models are worked out taking into consideration only particular territory-defining geo-parameters, i.e. only those parameters which exhibit the following correlation coefficient value of the vertical earth’s crust movement velocity: r ≥ 0.50. A forecast of the velocities pertaining to vertical movements of the earth’s crust in the territory under examination was made with the application of regression models. Further in the process of this research, a map was compiled specifying the velocities of vertical movements of the earth’s crust in the territory. In the eastern part of this territory, the earth’s crust rises at a rate of up to 3 mm/year; while in the western part of it, the earth crust lowers at a rate of up to –1.5 mm/year. In order to pinpoint territories characterised by temperate and regular rising/lowering or intensive rising/lowering, a map of horizontal gradients of recent vertical earth crust movements in the territory enclosed by levelling polygon was compiled.
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Elshambaky, Hossam Talaat. "Application of neural network technique to determine a corrector surface for global geopotential model using GPS/levelling measurements in Egypt." Journal of Applied Geodesy 12, no. 1 (January 26, 2018): 29–43. http://dx.doi.org/10.1515/jag-2017-0017.
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AbstractOwing to the appearance of many global geopotential models, it is necessary to determine the most appropriate model for use in Egyptian territory. In this study, we aim to investigate three global models, namely EGM2008, EIGEN-6c4, and GECO. We use five mathematical transformation techniques, i.e., polynomial expression, exponential regression, least-squares collocation, multilayer feed forward neural network, and radial basis neural networks to make the conversion from regional geometrical geoid to global geoid models and vice versa. From a statistical comparison study based on quality indexes between previous transformation techniques, we confirm that the multilayer feed forward neural network with two neurons is the most accurate of the examined transformation technique, and based on the mean tide condition, EGM2008 represents the most suitable global geopotential model for use in Egyptian territory to date. The final product gained from this study was the corrector surface that was used to facilitate the transformation process between regional geometrical geoid model and the global geoid model.
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Sushchenko, Olha. "Features of Designing High-precision Systems for Stabilization and Determination of Attitude and Heading." Electronics and Control Systems 4, no. 70 (January 4, 2022): 58–63. http://dx.doi.org/10.18372/1990-5548.70.16771.
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The paper deals with features of designing high-precision systems for stabilization and determination of attitude and heading reference systems. Features of the parametrical optimization are considered. The necessity to use the robust control laws is grounded. The mathematical model of the studied system in the preliminary levelling mode is represented. Simulink model of the navigation loop is shown. The necessity and features of the model’s linearization are explained, Basic concepts of creating models directed for solution of the studied problem are represented. The design process is considered on the example of the precision gimballed navigation system assigned for operation on marine vehicles. The proposed approach to problem solution is accompanied with simulation. The simulation results prove efficiency of the described design procedure. The obtained results can be useful for creating stabilization and motion control systems of the wide class.
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Elshambaky, Hossam Talaat. "Using direct transformation approach as an alternative technique to fuse global digital elevation models with GPS/levelling measurements in Egypt." Journal of Applied Geodesy 13, no. 3 (July 26, 2019): 159–77. http://dx.doi.org/10.1515/jag-2018-0050.
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Abstract Open global digital elevation models (GDEMs) represent a free and important source of information that is available to any country. Fusion processing between global and national digital elevation models is neither easy nor inexpensive. Hence, an alternative solution to fuse a GDEM (GTOPO30 or SRTM 1) with national GPS/levelling measurements is adopted. Herein, a transformation process between the GDEMs and national GPS/levelling measurements is applied using parametric and non-parametric equations. Two solutions are implemented before and after the filtration of raw data from outliers to assess the ability of the generated corrector surface model to absorb the effect of the outliers’ existence. In addition, a reliability analysis is conducted to select the most suitable transformation technique. We found that when both the fitting and prediction properties have equal priority, least-squares collocation integrated with a least-squares support vector machine inherited with a linear or polynomial kernel function exhibits the most accurate behavior. For the GTOPO30 model, before filtration of the raw data, there is an improvement in the mean and root mean square of errors by 39.31 % and 68.67 %, respectively. For the SRTM 1 model, the improvement in mean and root mean square values reached 86.88 % and 75.55 %, respectively. Subsequently, after the filtration process, these values became 3.48 % and 36.53 % for GTOPO30 and 85.18 % and 47.90 % for SRTM 1. Furthermore, it is found that using a suitable mathematical transformation technique can help increase the precision of classic GDEMs, such as GTOPO30, making them to be equal or more accurate than newer models, such as SRTM 1, which are supported by more advanced technologies. This can help overcome the limitation of shortage of technology or restricted data, particularly in developed countries. Henceforth, the proposed direct transformation technique represents an alternative faster and more economical way to utilize unfiltered measurements of GDEMs to estimate national digital elevations in areas with limited data.
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Sergeev, Alexander, Daria Ryabchuk, Vladimir Zhamoida, Igor Leont’yev, Alexander Kolesov, Olga Kovaleva, and Kaarel Orviku. "Coastal dynamics of the eastern Gulf of Finland, the Baltic Sea: toward a quantitative assessment." Baltica 31, no. 1 (June 15, 2018): 49–62. http://dx.doi.org/10.5200/baltica.2018.31.05.
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The easternmost part of the Gulf of Finland is characterized by intense coastal processes dominated by wave erosion. Reliable prediction of the coastal zone development, as well as effective strategy for coastal protection, demands a quantitative assessment of beach transformation and volume of sediment loss as a result of extreme storms. The main goal of this study based on results of terrestrial laser scanning was to establish volumes of eroded, transported, and redeposited sand during storm surge events that occurred between 2012 and 2017, and to verify a mathematical model of beach profile changes within key areas located in the Kurortny District of St. Petersburg (Gulf of Finland, Baltic Sea), where the longest set of levelling and terrestrial laser scanning was conducted. The resulting detailed 3D GIS models of coastal relief, based on high-resolution geodesic surveys, produced a highly reliable database of beachface transformation under the extreme storm impact and quantitative assessment of erosion volumes and sediment loss.
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Consejo, Alejandra, Arwa Fathy, Bernardo T. Lopes, Renato Ambrósio, and Ahmed Abass. "Effect of Corneal Tilt on the Determination of Asphericity." Sensors 21, no. 22 (November 17, 2021): 7636. http://dx.doi.org/10.3390/s21227636.
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Purpose: To quantify the effect of levelling the corneal surface around the optical axis on the calculated values of corneal asphericity when conic and biconic models are used to fit the anterior corneal surface. Methods: This cross-sectional study starts with a mathematical simulation proving the concept of the effect that the eye’s tilt has on the corneal asphericity calculation. Spherical, conic and biconic models are considered and compared. Further, corneal asphericity is analysed in the eyes of 177 healthy participants aged 35.4 ± 15.2. The optical axis was determined using an optimization procedure via the Levenberg–Marquardt nonlinear least-squares algorithm, before fitting the corneal surface to spherical, conic and biconic models. The influence of pupil size (aperture radii of 1.5, 3.0, 4.0 and 5.0 mm) on corneal radius and asphericity was also analysed. Results: In computer simulations, eye tilt caused an increase in the apical radii of the surface with the increase of the tilt angle in both positive and negative directions and aperture radii in all models. Fitting the cornea to spherical models did not show a significant difference between the raw-measured corneal surfaces and the levelled surfaces for right and left eyes. When the conic models were fitted to the cornea, changes in the radii of the cornea among the raw-measured corneal surfaces’ data and levelled data were not significant; however, significant differences were recorded in the asphericity of the anterior surfaces at radii of aperture 1.5 mm (p < 0.01). With the biconic model, the posterior surfaces recorded significant asphericity differences at aperture radii of 1.5 mm, 3 mm, 4 mm and 5 mm (p = 0.01, p < 0.01, p < 0.01 & p < 0.01, respectively) in the nasal temporal direction of right eyes and left eyes (p < 0.01, p < 0.01, p < 0.01 & p < 0.01, respectively). In the superior–inferior direction, significant changes were only noticed at aperture radii of 1.5 mm for both right and left eyes (p = 0.05, p < 0.01). Conclusions: Estimation of human corneal asphericity from topography or tomography data using conic and biconic models of corneas are affected by eyes’ natural tilt. In contrast, the apical radii of the cornea are less affected. Using corneal asphericity in certain applications such as fitting contact lenses, corneal implant design, planning for refractive surgery and mathematical modelling when a geometrical centre of the eye is needed should be implemented with caution.
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STEWART, D. W., and L. M. DWYER. "YIELDS AND PROTEIN TRENDS OF SPRING WHEAT (Triticum aestivum L.) ON THE CANADIAN PRAIRIES, 1961–1982." Canadian Journal of Plant Science 70, no. 1 (January 1, 1990): 33–44. http://dx.doi.org/10.4141/cjps90-004.
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Mathematical models of hard red spring wheat (Triticum aestivum L.) were used to account for effects of weather on annual variations in yield and protein content on the Canadian prairies. When weather effects were calculated, other relatively slow-changing trends became much clearer. Results indicate that yields in the three major soil zones have increased an average of 806 kg ha−1, while protein contents have decreased (1.0% from 1961 to 1982). Both trends show the largest change at the beginning of the period (1961) with a levelling off at the end (1982). There seems to be an inverse relationship between yield and protein, with technology contributing to yield increases and at the same time decreasing protein content by dilution although this was not conclusively proved. Decreases in soil organic matter or other soil factors may be contributing to the protein decline but these factors were not required to explain the observed patterns in yield and percent protein. The results indicated that the potential to produce high protein wheats has decreased during the period 1961–1982.Key words: Nonlinear fitting, physical model, technology effects, protein dilution
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HNAIDI, HOUSSAM, ERIC GUÉRIN, and SAMIR AKKOUCHE. "MULTIRESOLUTION CONTROL OF CURVES AND SURFACES WITH A SELF-SIMILAR MODEL." Fractals 18, no. 03 (September 2010): 271–86. http://dx.doi.org/10.1142/s0218348x1000497x.
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This paper presents two self-similar models that allow the control of curves and surfaces. The first model is based on IFS (Iterated Function Systems) theory and the second on subdivision curve and surface theory. Both of these methods employ the detail concept as in the wavelet transform, and allow the multiresolution control of objects with control points at any resolution level.In the first model, the detail is inserted independently of control points, requiring it to be rotated when applying deformations. In contrast, the second method describes details relative to control points, allowing free control point deformations.Modeling examples of curves and surfaces are presented, showing manipulation facilities of the models.
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Mrówczyńska, Maria, and Jacek Sztubecki. "Approximation of the process of changes in deformation of land surface using artificial neural networks." E3S Web of Conferences 55 (2018): 00009. http://dx.doi.org/10.1051/e3sconf/20185500009.
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Artificial neural networks are an interesting method for modelling phenomena, including spatial phenomena, which are difficult to describe with known mathematical models. The properties of neural networks enable their practical application for solving such problems as: approximation, interpolation, identification and classification of patterns, compression, prediction, etc. The article presents the use of multilayer feedforward artificial neural networks for describing the process of changes in land surface deformation in the area of the Legnica-Głogów Copper Mining Centre, located in the southern part of the Fore Sudetic Monocline. Results provided by geodesic monitoring, which consists of land surveying and interpreting data obtained in this way, are undoubtedly significant in terms of identifying the impact of mining on the land surface the results of measurements carried out by precise levelling in the years 19672014 were used to determine changes in land deformation in the Legnica-Głogów Copper Mining Centre. The concept of a flexible reference system was used to assess the stability of points in the measurement and control network stabilized in order to determine vertical displacements. However, the reference system itself was identified on the basis of the critical value of the increment of the square of the norm of corrections to the observations.
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Pochukalin, A. Ye. "COMPARING THE VALUES OF CONSOLIDATION AND DISCRETION BY SELECTIVE OBSERVATIONS AND THEIR COMPLEXES IN RIGIONAL FAMILIES OF VOLINIAN BEEF." Animal Breeding and Genetics 54 (November 29, 2017): 91–97. http://dx.doi.org/10.31073/abg.54.11.
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Factory families today have not lost their influence on the formation of the desired genotype of offspring with high performance. This is contributed to the forgotten but active biological role of the maternal effect. The reduced attention in the breeding process with the work of factory families is reduced to two factors, namely the reduction of the length of productive use of cows and a small number of offspring. But in scientific publications, especially in dairy cattle breeding, there are constantly reported on the number, characteristics of breeding grounds or the evaluation of plant families in mathematical models based on population genetic parameters. In meat cattle, the importance of families has not become widespread, although the duration of productive use of cows of meat production has advantages over diary. The aim of the research was to evaluate the factory families of Volinian meat breed for using different coefficients of consolidation of the main breeding grounds. Materials and methods of research. The research was carried out in the conditions of the breeding farm of LLC "Zorya" of Kovel district of Volyn region. The object of research was the cows of the Volinian meat breed. According to the breeding records, 18 regional families were formed, which belong to six lines with a total population of 160 heads. In order to assess the stability (restriction of phenotypic variability) of plant families in practical selection, we have tested the methods of determining the degree of consolidation by certain characteristics of Yu. P. Polupan and the degree of discreteness of families V. V. Seromolot, S. I. Svyatchenko. The average level of consolidation by Yu. P. Polupan was calculated from the mean-square values. The methodical suitability of these methods was evaluated in two (dairy animals after the first calving and live weight in 210 days) and four (live weight at the age of 210 days, 12, 15 months and breast milk) by the studied characteristics. In the long-term selection process in families, the process of consolidation with a constant level of quantitative attributes, which are consistently inherited in generations while simultaneously narrowing genotype and phenotypic variability, is achieved. The mentioned process in the studied factory families has a significant variability according to the selection criteria. In studying the consolidation of live weight in different age periods, there are variables in ten families. The families of Akula 102, Arpha 599 and Wisla 1016 for live weight were unconsolidated at all ages, and their average rate was -0.148. Among the five, the consolidated families have an average value of 210 days, 0.244, in the 12 and 15 months, respectively, 0.375 and 0.268. The greatest value are the families of Verbi 1536, Galky 37 and Veselky 444 and Bistroi 1124, whose consolidation coefficient ranges from 0.260 to 0.430. These families, in our opinion, should be considered valuable, since, in addition to the reduced group volatility, they have high actual mean values for live weight, and therefore extensions of these families should have an advantage over the selection of repair young animals. The lowest level of consolidation is with the families of Arpha 599, Bulana 943 and Wisla 1016. Selection work with them should be aimed at selecting the breeding stock of prey bulls of high tribal value. The significant difference (1,136) between the threshold levels of the coefficient of family consolidation for the milk yield of cows after the first calving indicates a high variability. The average of nine consolidated families is 0.175, which is only 0.088 above the average for the general group. The highest coefficient values were obtained in the families of Garna 536, Galka 421 and Rosetka 1313. With a decrease in the number of economic indicators considered useful in both methods, there is a decrease in unconsolidated families to six. The average values in discrete families are 0.336, consolidated at 0.178. The most consolidated were the families of Galka 421, Rosetka 1313 and Garna 536, and the discrete families of Galka 421, Corona 2382 and Rosetka 1313, the average value of which is respectively 0.630 and 0.367. The use of the coefficients of phenotypic consolidation and discreteness in the complex of breeding grounds in the factory families showed the advantage of consolidation by the leveling of the results obtained and the lower the dependence on the number of accounted signs. The index of discreteness for an increase of two to four characteristics taken into account on a modulus increases on average by 1.54 times.
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Lo, Weicheng, Sanidhya Nika Purnomo, Bondan Galih Dewanto, Dwi Sarah, and Sumiyanto. "Integration of Numerical Models and InSAR Techniques to Assess Land Subsidence Due to Excessive Groundwater Abstraction in the Coastal and Lowland Regions of Semarang City." Water 14, no. 2 (January 11, 2022): 201. http://dx.doi.org/10.3390/w14020201.
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This study was carried out to assess land subsidence due to excessive groundwater abstraction in the northern region of Semarang City by integrating the application of both numerical models and geodetic measurements, particularly those based on the synthetic aperture radar interferometry (InSAR) technique. Since 1695, alluvial deposits caused by sedimentations have accumulated in the northern part of Semarang City, in turn resulting in changes in the coastline and land use up to the present. Commencing in 1900, excessive groundwater withdrawal from deep wells in the northern section of Semarang City has exacerbated natural compaction and aggravated the problem of land subsidence. In the current study, a groundwater model equivalent to the hydrogeological system in this area was developed using MODFLOW to simulate the hydromechanical coupling of groundwater flow and land subsidence. The numerical computation was performed starting with the steady-state flow model from the period of 1970 to 1990, followed by the model of transient flow and land subsidence from the period of 1990 to 2010. Our models were calibrated with deformation data from field measurements collected from various sources (e.g., leveling, GPS, and InSAR) for simulation of land subsidence, as well as with the hydraulic heads from observation wells for simulation of groundwater flow. Comparison of the results of our numerical calculations with recorded observations led to low RMSEs, yet high R2 values, mathematically indicating that the simulation outcomes are in good agreement with monitoring data. The findings in the present study also revealed that land subsidence arising from groundwater pumping poses a serious threat to the northern part of Semarang City. Two groundwater management measures are proposed and the future development of land subsidence is accordingly projected until 2050. Our study shows quantitatively that the greatest land subsidence occurs in Genuk District, with a magnitude of 36.8 mm/year. However, if the suggested groundwater management can be implemented, the rate and affected area of land subsidence can be reduced by up to 59% and 76%, respectively.
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Shaw, L. M., and M. R. Tranter. "Levelling the playing field in assessment: an analysis of attainment gaps for widening participation, black and minority ethnic mathematics undergraduates before and after the COVID-19 lockdown." Teaching Mathematics and its Applications: An International Journal of the IMA 40, no. 4 (October 29, 2021): 497–505. http://dx.doi.org/10.1093/teamat/hrab024.
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Abstract The 2019/20 Level 4 mathematics cohort at the Nottingham Trent University sat a full set of mid-year assessments in January 2020 under completely normal circumstances. However, the Covid-19 lockdown meant that their end of year assessments, along with all of their teaching and learning from March 2020 onwards, moved fully online. This has given us a unique opportunity to understand how the same cohort perform in contrasting situations. In this study we consider the issue of attainment gaps and find that the attainment gap closed in this cohort for black and minority ethnic students but that students from a lower socio-economic background may have been put at a disadvantage by the move to online teaching, learning and assessment. We use a linear mixed effect models approach to present statistical evidence to support these two claims as well as investigating the specific aspects of the move online, which may have caused these results.
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Li, Xiang, Zhencai Zhu, Gang Shen, and Yu Tang. "Wire Tension Coordination Control of Electro-Hydraulic Servo Driven Double-Rope Winding Hoisting Systems Using a Hybrid Controller Combining the Flatness-Based Control and a Disturbance Observer." Symmetry 13, no. 4 (April 19, 2021): 716. http://dx.doi.org/10.3390/sym13040716.
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When the double-rope winding hoisting system (DWHS) is in operation, tensions of two wire ropes of the DWHS will not be symmetrical because of some factors such as different manufacturing deviation between the twin winding drum and two wire ropes, different winding groove depths, the winding asynchronism of two wire ropes, and elastic modulus difference of two wire ropes and so on. Therefore, an electro-hydraulic servo system (EHSS) is employed to actively control two wire ropes tensions to guarantee operation security of the DWHS. Dynamic models of the hoisting system and the EHSS are introduced, of which dynamic model of the DWHS is expressed with state representation. The flatness-based controller (FBC) is designed for the hoisting system. A disturbance observer is utilized to deal with the external disturbance and unmodeled characteristics of the EHSS. Hence, a disturbance observer based integral backstepping controller (DO-BIBC) is designed for the EHSS. The stability of the overall control system is proved by de-fining an overall Lyapunov function. To investigate the property of the proposed controller, an experimental setup of the DWHS is established. As well, comparative experimental results indicate that the proposed controller exhibits a better performance on leveling control of the conveyance and tension coordination control on the two wire ropes than a conventional PI controller.
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Li, Duo, and Yajing Liu. "Cascadia megathrust earthquake rupture model constrained by geodetic fault locking." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 379, no. 2196 (March 15, 2021): 20200135. http://dx.doi.org/10.1098/rsta.2020.0135.
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Paleo-earthquakes along the Cascadia subduction zone inferred from offshore sediments and Japan coastal tsunami deposits approximated to M9+ and ruptured the entire margin. However, due to the lack of modern megathrust earthquake records and general quiescence of subduction fault seismicity, the potential megathrust rupture scenario and influence of downdip limit of the seismogenic zone are still obscure. In this study, we present a numerical simulation of Cascadia subduction zone earthquake sequences in the laboratory-derived rate-and-state friction framework to investigate the potential influence of the geodetic fault locking on the megathrust sequences. We consider the rate-state friction stability parameter constrained by geodetic fault locking models derived from decadal GPS records, tidal gauge and levelling-derived uplift rate data along the Cascadia margin. We incorporate historical coseismic subsidence inferred from coastal marine sediments to validate our coseismic rupture scenarios. Earthquake rupture pattern is strongly controlled by the downdip width of the seismogenic, velocity-weakening zone and by the earthquake nucleation zone size. In our model, along-strike heterogeneous characteristic slip distance is required to generate margin-wide ruptures that result in reasonable agreement between the synthetic and observed coastal subsidence for the AD 1700 Cascadia Mw∼9.0 megathrust rupture. Our results suggest the geodetically inferred fault locking model can provide a useful constraint on earthquake rupture scenarios in subduction zones. This article is part of the theme issue ‘Fracture dynamics of solid materials: from particles to the globe’.
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Jacobsen, K. "SYSTEMATIC GEOMETRIC IMAGE ERRORS OF VERY HIGH RESOLUTION OPTICAL SATELLITES." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-1 (September 26, 2018): 233–38. http://dx.doi.org/10.5194/isprs-archives-xlii-1-233-2018.
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<p><strong>Abstract.</strong> Very high resolution optical satellites are imaging the object space by a combination of CCD-lines in one direction and by time, speed and satellite rotation in the other direction. The combination of the CCD-lines usually is known by pre-calibration. Remaining errors of the pre-calibration, also slightly depending upon the satellite movement and rotation, with few exceptions are usually small up to negligible. This may not be the case for the image component in the scan direction and the alignment of the line combinations - they are controlled by giros and stellar cameras. Stellar cameras are compensating giro drifts, but their recording frequency is limited as well as in general the accuracy of the satellite view direction. In addition the satellites may show a jitter caused by the fast rotation from one pointed area to another. Not all giros are able to record the jitter frequency. A limited accuracy of the view direction is causing systematic image errors in relation to the used mathematical model of geometric reconstruction.</p><p> The systematic image errors can be determined theoretically by image orientation based on ground control points (GCPs), but usually not a satisfying number and distribution of GCPs is available. Another possibility is the analysis of the intersection of corresponding rays in a stereo model and an analysis of generated height models against reference height models. Here also free of charge available height models as the SRTM Digital Surface Model (DSM) or AW3D30 can be used. Several very high resolution satellite cameras have been analyzed; this includes images from WorldView-2, WorldView-4, Kompsat-3, Kompsat-1, Pleiades, Cartosat-1, ZY3, OrbView-3, QuickBird, IKONOS, ASTER, IRS-1C, SPOT, SPOT-5 HRS, EROS-B, IKONOS, QuickBird, OrbView and GeoEye but only results of the today more important satellites are shown in detail. For few satellites the systematic image errors can be ignored, but others require a correction which may be just a levelling of the DSM but also a higher degree of deformation up to a compensation of the satellite jitter effect.</p><p> The used method cannot be named as calibration due to variation from image to image, only the character and size of deformation is typical for the used special optical satellite, but it depends also upon the operating conditions as fast satellite rotation. Due to the very high number of reference points in a DSM the determination of systematic image errors is independent upon random errors and also high frequent jitter can be determined with a standard deviation down to 0.1 ground sampling distance (GSD) or even better.</p>
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Uvarov, A. I., N. A. Parkhomenko, and A. S. Garagul. "Mathematical models of water surface for geodetic support of construction in agro-industrial complex." Zemleustrojstvo, kadastr i monitoring zemel' (Land management, cadastre and land monitoring), no. 8 (August 1, 2021). http://dx.doi.org/10.33920/sel-04-2108-12.
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The purpose of the study was to analyze the possibilities of using mathematical models of the water (level) surface of rivers and reservoirs for the transfer of elevations. The use of an empirical mathematical model obtained for the Irtysh River near the city of Omsk makes it possible to determine the heights in the investigated area with an accuracy of about 0.1 m. To determine the level of the water edge at the selected area, it is necessary to obtain: the mark of the water edge at the gauging station; the distance along the river from the gauging station to the work site. It is advisable to fix the water level at the gauging station and the work site simultaneously. For the elevation transfer from one river bank to another by the III class leveling program, the authors propose the technology of laying temporary benchmarks on the banks, fixing the level using special devices, and transferring the elevations of the fixed water level to temporary benchmarks. The technology contains the devices of simple design for accurate level fixing. The factors influencing the accuracy of the height transmission are: fixing the water level, the centrifugal forces of the flow, the Coreolis force caused by the rotation of the Earth, and the wind surge. The authors calculated the expected values of errors determining the accuracy: for fixing the level it was about 1 mm according to the proposed method; the height difference at the banks due to the forces of Coreolis was 0.007 m; the influence of centrifugal forces at a turning radius of 500 m causes a difference in heights at opposite banks of 0.1 m. In the result, the authors proposed the recommendations developed for transferring heights from one river bank to another using a class III leveling program, which ensure the specified accuracy.
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Schwartz, Ashley V., Karilyn E. Sant, Julian Navarrete, and Uduak Z. George. "Mathematical modeling of the interaction between yolk utilization and fish growth in zebrafish, Danio rerio." Development 148, no. 9 (May 1, 2021). http://dx.doi.org/10.1242/dev.193508.
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ABSTRACT Optimal embryonic development plays a major role in the health of an individual beyond the developmental stage. Nutritional perturbation during development is associated with cardiovascular and metabolic disease later in life. With both nutritional uptake and overall growth being risk factors for eventual health, it is necessary to understand not only the behavior of the processes during development but also their interactions. In this study, we used differential equations, image analyses, curve fittings, parameter estimation and laboratory experiments to quantify the rate of yolk absorption and its effect on early development of a vertebrate model (Danio rerio). Findings from this study establish a nonlinear functional relationship between nutrient absorption and early fish growth. We found that the rate of change in fish length and yolk utilization is logistic, that is the yolk decays rapidly for a period of time before leveling out. An interesting finding from this study is that yolk utilization reaches its maximum at 84 h post-fertilization. We validated our mathematical models against experimental observations, making them powerful tools for replication and future simulations.
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Novak, Mark, and Daniel B. Stouffer. "Geometric Complexity and the Information-Theoretic Comparison of Functional-Response Models." Frontiers in Ecology and Evolution 9 (November 11, 2021). http://dx.doi.org/10.3389/fevo.2021.740362.
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The assessment of relative model performance using information criteria like AIC and BIC has become routine among functional-response studies, reflecting trends in the broader ecological literature. Such information criteria allow comparison across diverse models because they penalize each model's fit by its parametric complexity—in terms of their number of free parameters—which allows simpler models to outperform similarly fitting models of higher parametric complexity. However, criteria like AIC and BIC do not consider an additional form of model complexity, referred to as geometric complexity, which relates specifically to the mathematical form of the model. Models of equivalent parametric complexity can differ in their geometric complexity and thereby in their ability to flexibly fit data. Here we use the Fisher Information Approximation to compare, explain, and contextualize how geometric complexity varies across a large compilation of single-prey functional-response models—including prey-, ratio-, and predator-dependent formulations—reflecting varying apparent degrees and forms of non-linearity. Because a model's geometric complexity varies with the data's underlying experimental design, we also sought to determine which designs are best at leveling the playing field among functional-response models. Our analyses illustrate (1) the large differences in geometric complexity that exist among functional-response models, (2) there is no experimental design that can minimize these differences across all models, and (3) even the qualitative nature by which some models are more or less flexible than others is reversed by changes in experimental design. Failure to appreciate model flexibility in the empirical evaluation of functional-response models may therefore lead to biased inferences for predator–prey ecology, particularly at low experimental sample sizes where its impact is strongest. We conclude by discussing the statistical and epistemological challenges that model flexibility poses for the study of functional responses as it relates to the attainment of biological truth and predictive ability.
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Lysenko, Olena. "MODELING THE FINANCIAL PROVISION’S ADEQUACY OF ONGOING OPERATIONAL PERIODS FOR RESORT BUSINESSES." Economic scope, 2021. http://dx.doi.org/10.32782/2224-6282/171-21.
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The article dwells upon investigation into the issue of providing the adequate financing level of firms’ operational period attained by creation and employment of the suggested economic mathematical toolkit. Its nucleus is the firm’s special stabilizing surplus fund operated with the set of the following models: model for the fund’s elaboration, its adaptive mathematical model and algorithmic model for the fund’s management (implemented via designed computer program). The mathematical model of special stabilizing surplus fund, as well as calculation of its amount for every next industrial period is being set forward in the paper. Both indispensable and sufficient condition of special stabilizing surplus fund’s organization is being enunciated. In order to estimate the volume of special stabilizing surplus fund, an analytical approach of «temporary money cost» is applied to expenditure function analysis. Thereby, we suggest the following approach to handling the issue of cash flow leveling within each step of calculation. Furthermore, the author suggests an approach brought forward in order to estimate the effect of resorting to special stabilizing surplus fund in the course of either one or several industrial periods. Purpose of the article is implementation of such a short-term prognostication technique as proportional predictive method. The methods applied include: proportional predictive method, dialectical method, observation method, critical and contrastive analysis and synthesis method. The decision was made to repudiate the approach implying creation of econometric models of time series dynamics for the present research due to the lack of statistical data. This article also aims at improving evaluation methods of financial state of a certain company at a definite period of time. The research held is based on the statistical data on business activities over the year of 2020 provided by the hotel «Dnister» (Ukraine).