Reference Model Research Articles

Complex modeling of complicated processes: analytical model parameters adaptation in solving qualimetric problems

The relevance of the study is due to the fact that despite the sustainable development of methods and technologies for creating models of various classes and purposes, the tasks of managing their quality (the so-called inverse problems of theoretical qualimetry) are often neglected. For example, in the field of information technology, much more attention is paid to assessing the quality of software products, which is reflected in the corresponding standards. These tasks become especially relevant when models reflect a complex process (CP), and such processes may be unique, and obtaining complete objective data on such CPs prior to modeling is difficult or impossible (accidents and disasters models, military operations, natural disasters, and others like that). The article’s main purpose is to consider the issues of solving the inverse qualimetric problem by parametric adaptation of analytical models to unpredictable possible changes in the complex processes’ nature. The solution to this problem is based on the combined (analytical and simulation) modeling of unique processes. Theoretical qualimetry involves a quantitative assessment of any product's qualitative properties; to ensure the adequacy level of analytical models (based on the results of their parametric adaptation), it is planned to evaluate with the use of well-known metrology principles regarding relative measurement deviations. In this case, detailed simulation modelling results are used as a reference for combined modelling. The complexity of the processes conditiond by the expediency of their polymodel description in order to mutually compensate for the objective deficiencies of heterogeneous models, as well as the use of simulation capabilities to adjust the parameters of analytical models in cases where the use of the latter is due to strict time constraints on obtaining calculation results and developing control actions based onthem. A variant of the formalized statement of the problem of parametric adaptation of analytical models is presented. A presented example that considers the adaptation of parameters of the Lanchestertype analytical model conducted on simulation data. The adaptation of parameters could be carried out in different ways, and the expediency of choosing a certain one is determined by the assessment of mutual deviations of the results of heterogeneous modeling. The results of the calculations witnesses that parametric adaptation can be an effective element in solving one of the key tasks of model qualimetry, namely, ensuring their required qualitative properties. The prospect of further research is to consider the issues of structural adaptation of simulation models to the given conditions for displaying complex processes.

Sensorless control of permanent magnet synchronous motor for exhaust energy recovery of internal combustion engine: a comparison between Kalman filter and MRAS observer

This paper deals with the sensorless control of a Permanent Magnet Synchronous Motor (PMSM) to be employed on a turbo-generator to recover the exhaust gas energy of an Internal Combustion Engine (ICE). The main problem with this application is the high rotational speed required by the exhaust gas turbo-generator. Indeed, this implies the difficulty of installing an encoder for speed measurement and control. For this reason, sensorless control is highly recommendable, but, on the other hand, the main sensorless techniques could fail in this peculiar situation because of the high computational effort required compared with the other sensorless applications. Moreover, a good knowledge of the model parameters is necessary. Therefore, the main goal of this paper is to compare two main sensorless techniques for rotational speed measurement, both in the deterministic framework (Model Reference Adaptive System (MRAS) observer) and stochastic framework (Extended Kalman Filter (EKF)), to verify their effectiveness, their computational load, their sensitivity against parameter variation and noisy measurements, and, finally, to present the best solution for the exhaust gas energy recovery from the internal combustion engine.

Evaluation of Implant Impression Accuracy Using Different Trays and Techniques With a 3D Superimposition Method.

The purpose of this study was to evaluate the dimensional accuracy of implant impressions obtained using different tray types and techniques. A partially dentate maxillary Kennedy Class II model was created as a reference model through three-dimensional (3D) printing. Then, 4.3-mm diameter implant analogs were placed at the first premolar, first molar, and second molar regions. Five types of trays-metal and plastic stock trays and custom trays fabricated using liquid crystal display (LCD), fused deposition modeling (FDM), and urethane dimethacrylate (UDMA) resin-were used to create impressions. Open- and closed-tray techniques were also compared. In total, 150 impressions were obtained. The reference model and impressions were scanned using a laboratory scanner. The positional and angular deviations of implants with different tray types and techniques were evaluated using the superimposition method. There was no statistically significant difference (P>0.05) between the impression accuracy with the different tray types and impression techniques. The angular deviations with plastic and UDMA trays were greater than those with metal, FDM, and LCD trays. Angular deviation at the second molar by using closed trays was greater than that using open plastic trays. The highest and lowest positional deviation were observed at the first molar implant with an open plastic tray impression (mean: 62.46 ± standard deviation: 28.54 μm) and a closed LCD tray impression (36.59 ± 29.93 μm). The greatest angular deviation was observed with an open FDM tray impression at the first premolar implant (0.067 ± 0.024°), and the lowest angular deviation was observed with a closed metal stock tray impression at the second molar implant (0.039 ± 0.025°). Statistical differences were detected using Mann-Whitney U tests for pair groups and the Kruskal- Wallis test for groups with more than three comparisons (P>0.05). Plastic and metal stock trays or conventional and 3D-printed custom trays can be used to obtain implant impressions for maxillary partially edentulous arches with similar dimensional accuracy. The five tray types and two techniques may be safely used to obtain impressions of partially edentulous maxillary arches with three implants.

UAV trajectory tracking under wind disturbance based on novel antidisturbance sliding mode control

With the widespread application of unmanned aerial vehicles, harsh environments require higher control performance. Numerous existing works offer solutions for handling external disturbances during flight; however, the timeliness of the disturbance compensation is rarely discussed. This study focuses on trajectory tracking under external wind disturbances, specifically under two types of interference: average wind and wind shear. After compensating for the disturbance, a novel antidisturbance sliding mode control is designed based on reference model, to realize accurate, robust, and chatterless trajectory tracking under wind disturbance. Firstly, we addressed the limitations of conventional extended state observers, nonderived forms, and inadequate use of information by introducing state compensation function observers to enhance estimation accuracy for states and disturbances that are challenging to measure directly. Moreover, the disturbance variation is estimated using tracking differentiator and then compensated in the controller to enhance antidisturbance sensitivity. In addition, the effectiveness and stability of the proposed observer and controller are analyzed. Finally, a two-step verification is presented, including simulation with input disturbances and actual flight under two wind field types; multiple industrial fans are used to generate the average wind and wind shear during the experiment. Two robust control methods, state-of-the-art active disturbance rejection control and sliding mode control, are also implemented for comparison, and the results indicate that more than 61.2% accuracy improvement over comparison methods is achieved in simulation and actual experiments.

Convection‐Permitting Climate Models Can Support Observations to Generate Rainfall Return Levels

AbstractInformation about the frequency and intensity of extreme precipitation is generally derived from fitting extreme value models using point‐observations, but the regionalization of these models is challenging. Here we propose using high‐resolution convection‐permitting climate model output as covariates for the estimation of observation‐based spatial rainfall return levels. We apply the Weather and Forecasting Research (WRF) model at a 1.5 km resolution driven by ERA5 reanalysis data over southern Germany, where 1,132 rain gauges provide observations of daily rainfall. For this complex topography, we build three different smooth spatial Generalized Extreme Value (GEV) models: (a) a reference model using latitude, longitude and elevation as covariates; (b) a model adding mean annual precipitation from the WRF; (c) a model adding extreme value statistical model estimates using WRF output. We show that the additional information provided by the WRF model can improve the representation of 10‐year and 100‐year return levels of daily rainfall by lowering the percentage bias, mean absolute error, and root‐mean‐square error. Furthermore, we conduct an extensive cross‐validation, where only 5%, 10%, 20%, 50%, 80%, 90%, and 95% of all rain gauges are considered when building spatial GEV models. Again, the additional information provided by the WRF model can improve results here. This cross‐validation study also highlights the robustness of our approach, showing great potential for use in data‐scarce regions.

Accuracy of 3D Printed Model Acquired from Different Types of Intra Oral Scanners and 3D Printers

ABSTRACT Objective: The aim of this study was to verify the influence of different types of intraoral scanners and 3D printers on the accuracy of printed models in comparison to plaster models obtained from conventional impressions. Material and Methods: A dental study model was used as the reference model and was molded with polyvinyl siloxane to produce the plaster models which were scanned by a reference scanner. Two types of intraoral scanners and digital files were printed by two types of 3D printers. To measure the accuracy (trueness and precision) amongst the groups, the datasets were superimposed via a best-fit alignment method utilizing a 3D analysis program (Geomagic Verify; 3D Systems). The trueness of the complete arch was evaluated by superimposing the STL file data of the reference model with STL file data obtained from other scanners. The precision of the complete arch was evaluated by superimposing the scan data within each group. The quantitative values were automatically calculated by the 3D analysis program based on the root mean square (RMS). Results: It was observed that all the tested combinations of the scanner and 3D printer showed variation from reference which was nonsignificant. However, Trios 4 intraoral scanner and Formlabs 3D printer was the combination that showed the best trueness and precision values. Conclusions: It was concluded that the accuracy of printed and plaster models was impaired due to the trueness of the models. The type of printer influenced the accuracy of the printed models, while the type of scanner did not. The standardization of the method of obtaining printed models must be carried out to provide the production of quality models. However, there will be differences between the technologies.

DuKA: A Dual-Keyless-Attention Model for Multi-Modality EHR Data Fusion and Organ Failure Prediction.

Organ failure is a leading cause of mortality in hospitals, particularly in intensive care units. Predicting organ failure is crucial for clinical and social reasons. This study proposes a dual-keyless-attention (DuKA) model that enables interpretable predictions of organ failure using electronic health record (EHR) data. Three modalities of medical data from EHR, namely diagnosis, procedure, and medications, are selected to predict three types of vital organ failures: heart failure, respiratory failure, and kidney failure. DuKA utilizes pre-trained embeddings of medical codes and combines them using a modality-wise attention module and a medical concept-wise attention module to enhance interpretation. Three organ failure tasks are addressed using two datasets to verify the effectiveness of DuKA. The proposed multi-modality DuKA model outperforms all reference and baseline models. The diagnosis history, particularly the presence of cachexia and previous organ failure, emerges as the most influential feature in organ failure prediction. DuKA offers competitive performance, straightforward model interpretations and flexibility in terms of input sources, as the input embeddings can be trained using different datasets and methods. DuKA is a lightweight model that innovatively uses dual attention in a hierarchical way to fuse diagnosis, procedure and medication information for organ failure predictions. It also enhances disease comprehension and supports personalized treatment.

Digital twins for smart building at the facility management stage: a systematic review of enablers, applications and challenges

PurposeDespite the opportunities of digital twins (DTs) for smart buildings, limited research has been conducted regarding the facility management stage, and this is explained by the high complexity of accurately representing and modelling the physics behind the DTs process. This study thus organises and consolidates the fragmented literature on DTs implementation for smart buildings at the facility management stage by exploring the enablers, applications and challenges and examining the interrelationships amongst them.Design/methodology/approachA systematic literature review approach is adopted to analyse and synthesise the existing literature relating to the subject topic.FindingsThe study revealed six main categories of enablers of DTs for smart building at the facility management stage, namely perception technologies, network technologies, storage technologies, application technologies, knowledge-building and design processes. Three substantial categories of DTs application for smart buildings were revealed at the facility management stage: efficient operation and service monitoring, efficient building energy management and effective smart building maintenance. Subsequently, the top four major challenges were identified as being “lack of a systematic and comprehensive reference model”, “real-time data integration”, “the complexity and uncertainty nature of real-time data” and “real-time data visualisation”. An integrative framework is finally proposed by examining the interactive relationship amongst the enablers, the applications and the challenges.Practical implicationsThe findings could guide facility managers/engineers to fairly understand the enablers, applications and challenges when DTs are being implemented to improve smart building performance and achieve user satisfaction at the facility management stage.Originality/valueThis study contributes to the knowledge body on DTs by extending the scope of the existing studies to identify the enablers and applications of DTs for smart buildings at the facility management stage and the specific challenges.

Improved Position Sensorless Resonant Frequency Tracking Control Method for Linear Oscillatory Machine

To improve the reliability of control system and obtain the maximum output efficiency, it is very necessary to carry out the position sensorless piston stroke control and the resonance frequency tracking control for linear oscillatory machine (LOM) at the same time. The conventional resonant frequency tracking control method based on model reference adaptive system (MRAS) has the problem of low estimation accuracy caused by inaccurate model parameters. In order to obtain more accurate resonant frequency, an improved position sensorless resonant frequency tracking control method is proposed in this article. In this method, the adjustable model is constructed based on the mechanical dynamics equation of LOM to track the system resonant frequency. A hybrid terminal sliding-mode observer (HTSMO) is designed to replace the conventional reference model, which can obtain more accurate velocity reference signal for adjustable model by introducing the current error feedback link, thereby further improving the resonant frequency tracking accuracy. Moreover, a second-order generalized integrator (SOGI) is introduced to filter the estimated velocity signal of HTSMO. The filtered velocity signal is not only used for the adjustable model to track the resonant frequency, but also used to obtain the smooth piston stroke signal for the stroke closed-loop control. Comprehensive simulation and experimental results have proved the effectiveness and the superiority of the proposed method.

Daily ranging and den usage patterns structure the spatiotemporal properties of social encounters in spotted hyenas

Fission–fusion dynamics describe the tendency for members of some animal societies to associate in subgroups that change size and structure fluidly over time. These dynamics shape social complexity and social structure, but are difficult to study because they unfold simultaneously over large spatial scales. Here we use simultaneous, fine-scale GPS data from spotted hyenas to examine fission–fusion dynamics through a dyadic analysis of merge-split events between pairs of individuals. We introduce a species-agnostic framework for identifying merge-split events and discretizing them into three phases (merging, together, and splitting), enabling analysis of each phase as well as the connections among phases. Applying this framework to the hyena data, we examine the temporal and spatial properties of merges and splits between dyads and test the extent to which social encounters are driven by key locations. Specifically, we focus on communal dens—shelters for juvenile hyenas where classical observational studies often report large aggregations of adults. We find that overall, 62% of merges occurred at communal dens, supporting the idea that dens facilitate meet-ups and subsequent social behavior. Social encounters most commonly involved close approaches within a few meters between hyenas, while co-travel together occurred in only 11% of events. Comparison to permutation-based reference models suggests that independent movement decisions structure broad-scale patterns of social encounters but do not explain the fine-scale dynamics of interactions that unfold during these encounters. We reflect on how physical features such as dens can become social hotspots, causing social and spatial processes to become fundamentally intertwined.

Xenotransplantation of Human Hematopoietic Stem Cells into NBSGW Mice: A Basic Model for Preclinical Development of Gene Therapy Approaches

Background. The gene therapy based on hematopoietic cell xenotransplantation is becoming a powerful and universally applied therapeutic strategy in an ever-expanding range of human diseases. One of the current issues in implementing the techniques of genome modification in hematopoietic stem cells (HSCs) into clinical practice is to assure the quality and safety of gene and cell therapy products for human use. This is achieved by animal model testing at the stage of preclinical studies. With this purpose in view, NBSGW mice seem to be a unique and promising model for human HSC engraftment without pre-conditioning.
 Aim. To test the NBSGW mouse model for human HSC engraftment, to optimize the methods of assessing the state of the animals and monitoring the chimerism level for translational preclinical development of HSC-based products for gene and cell therapy.
 Materials & Methods. The xenograft models of NBSGW mice were generated using the samples of the selected peripheral blood CD34+ HSCs from a healthy donor. Serial transplantation was performed by intravenous injection of bone marrow cells from primary recipients with a high chimerism level. Engraftment efficiency was evaluated by flow cytofluorometry (FCF) and droplet digital PCR (ddPCR). Subpopulation pattern of human cell engraftment was assessed by FCF.
 Results. The tested HSC transplantation regimen is characterized by favorable toxicity profile. In the entire study sample of mice, the FCF analysis showed a long-term engraftment of human cells with a high chimerism level (23.5–93.6 %) in the bone marrow of the animals, also after serial transplantation, which was confirmed by ddPCR. The B-lineage differentiation cells predominated in all tested samples (of peripheral blood, bone marrow, and spleen) from mice after primary and serial transplantation. The ddPCR assay can be used as an additional tool for validating the level of human cell engraftment determined by FCF.
 Conclusion. NBSGW mice present a promising reference model for preclinical development of gene and cell therapy products based on human primary HSCs with a modified genome.

A new output feedback adaptive control method for fractional order systems with inaccessible state

In this paper, the output tracking control problem for fractional-order (FO) systems with inaccessible state is investigated, and a new fractional-order model reference adaptive control (FOMRAC) method is proposed. The designed FO adaptive update law is able to adjust the controller parameters online in real time according to the system output information. Compared with the classical output feedback FOMRAC method, the proposed FOMRAC strategy only needs the online updating of a scalar function, which significantly reduces the complexity of the controller design and the online computational burden, and can achieve better control effect. Furthermore, the scheme ensures the boundedness of the closed-loop signals and that the mean value of the squared norm of the output error converges to zero. Finally, simulation results are carried out to verify the effectiveness of the established approach.

Hydrocarbon-conversion reaction and new paraffin-kinetic model during straight-run gas oil (SRGO) hydrotreating

A series of related experiments were carried out based on prepared hydrocracking catalyst, Catalyst-HC. Ni & W and USY molecular sieve were selected as the hydrogenation active component and the cracking component of Catalyst-HC, respectively. Meanwhile, a kinetic model for paraffin conversion was constructed based on paraffin conversion law. Results obtained through this work indicate that the impact of H2-pressure is relatively complex. As the H2-pressure changes, the degree of hydrocracking reaction may be influenced by both hydrogen supply capacity and hydrogen proton concentration. Obtained conversion priority for three types of hydrocarbons on USY molecular sieve is as follows, aromatic ≫ cycloalkane > paraffin. Aromatic content in SRGO can affect its paraffin-retention in Hydro-D. Compared with the hydrotreating of SRGO with low aromatic content, when SRGO with relatively higher aromatic content is hydrotreated, its paraffin-retention is higher and its paraffin loss is also relatively smaller. Base on constructed model, the calculated values of SRGO-BJ conversion rate and paraffin-retention in Hydro-D are within ±10 % and ±5 % error lines, respectively. Thus, model schematic diagram is reasonable and can provide modeling reference for relevant model research.

Effects of using UHSS material for weight reduction of Cukurova 885 model backhoe loader boom element

Construction machines have played an important role in building and sustaining civilizations in all walks of human life by making human life easier for centuries. These heavy machines consume a lot of fuel due to their high energy consumption and cause severe damage to the environment. Studies are being conducted to avoid harmful gas emissions due to fuel consumption of vehicles. One of the methods used in these studies is weight reduction. In this study, the fuel saving achieved by weight reduction with the material change in the boom element of a backhoe loader was investigated. The 3D model of the boom element of the backhoe loader model Cukurova885 was used for the study. The Ansys Workbench Software was used for the study. The weight of the reference model was reduced by reducing the dimensions of the reference model by using Ansys Spaceclaim in the software. Ultra-High Strength Steel with the same density but higher strength was used instead of the ST52 material currently used. The structural analyzes were carried out using the finite element method by applying exactly the same loads to the ST52 reference model and the weight-reduced UHSS model. In the study, thickness reductions on the model were made in Ansys Space Claim, a component of Ansys Workbench Software. In the Space Claim component, changes can be made to the geometry of a model imported into Ansys. For static structural analysis, Ansys Mechanical, a component of Ansys Software, was used. The model, whose thickness and therefore its weight is reduced in Space Claim, is opened in Mechanical, the necessary parameters are entered and it is prepared for analysis. Afterwards, analysis is performed via Ansys Mechanical. Comparing the results obtained, it was found that the weight of the model decreased by 23.16% and a fuel saving of 16.49% was achieved by using UHSS. Higher deformation and stress values were obtained for the model with UHSS. The safety factor was found to be 1.22 for the ST52 model and 2.14 for the UHSS model.

生鲜农产品冷链集货车辆路径与货物配载联合优化研究

As a bridge connecting agricultural production and consumption, the circulation of agricultural products has the function of connecting supply and demand, guiding production and promoting consumption. However, the development of rural logistics in China is slow, and most logistics centers still rely on experience to plan the pick-up vehicle routings, resulting in long transport time and high cost. In order to improve the efficiency of pick-up and reduce transportation costs, a joint optimization model of cold-chain pick-up vehicle routing and cargo allocation for fresh agricultural products was proposed in this study. Soft time window constraint and three-dimensional loading constraints were considered, and the lowest pick-up cost was used as optimization goals in this model. In addition, adaptive large neighborhood search algorithm (ALNS) and heuristic depth-first search algorithm (HDFS) were combined to solve the model. A case study of Kunming International Flower Auction Center was conducted to compare the schemes of pick-up vehicle routing before and after optimization. Results demonstrate that the pick-up cost after optimization decreases by 9.6 %, the number of vehicles decreases by one, the total volume utilization rate of vehicles increases by 23 %, and the total load utilization rate of vehicles increases by 15 %. This study provides a model reference and solution method for enterprise operators to formulate schemes of pick-up vehicle routing quickly and reasonably.

THE IMPACT OF LIGHTNING STRIKE ON HYBRID HIGH VOLTAGE OVERHEAD TRANSMISSION LINE – INSULATED GAS LINE

The electrical network is the set of elements where loads are connected to the generation plants by transmission lines. They can be either overhead or underground cables. A new technology has been introduced to replace these transmission lines with underground cables gas insulated line “GIL”. The latest has many advantages over underground cables and overhead transmission lines, such as low transmission losses, less capacitive load, reliability, personal safety, same operation as overhead lines and negligible electrical aging. GIL can handle much more power than overhead lines due to its large conductive area. GIL is the best for high voltage. In this paper, the simulation of lightning strike effects on a 400 kV hybrid transmission line located in the Wilaya of Setif in northern Algeria is presented in the absence and presence of line arresters and GIL arresters. The results of this paper can provide a rich and valuable theoretical reference for GIL simulation modeling and evaluation of lightning strike impact on hybrid overhead – GIL lines.

Positive psychotic symptoms as a marker of clinical severity in a transdiagnostic sample of help-seeking adolescents.

The present study aimed to examine the association between the presence, number, and type of positive psychotic symptoms (PPS) and clinical severity in adolescent patients. Five hundred-six patients aged 11-17years were assigned to either the noPPS (n = 341), the delusional beliefs only (del; n = 32), the hallucinations only (hall; n = 80), or the delusional beliefs and hallucinations (del&hall; n = 53) group. Generalized Structural Equation Modeling was applied to identify the best-fitting model representing clinical severity indicated by psychiatric diagnoses, depressivity, personality pathology, non-suicidal self-injury, suicide attempts, perceived stress, and psychosocial impairments, assessed by interviews and questionnaires. The groups were compared concerning the final model's factors. The final model consisted of three factors representing psychopathology and functional impairments, self-harming behavior, and perceived stress (BIC difference to reference model: 103.99). Participants with any PPS scored higher on all factors than the noPPS group (differences in SD: 0.49-1.48). Additionally, the del&hall group scored 1.31 SD higher on psychopathology and functional impairments than the hall group, and 1.16 SD higher on self-harming behavior compared to the del group. Finally, the hall group scored 0.84 SD higher on self-harming behavior than the del group, with no group differences in the other factors. In adolescent patients, the presence of PPS may represent a marker for a more severe form of mental disorder, with hallucinations being indicative of self-harming behavior. Early transdiagnostic assessment of PPS seems indicated as it may inform treatment in the context of clinical staging.

3D Galileo Reference Antenna Pattern for Space Service Volume Applications.

There is an increasing demand for navigation capability for space vehicles. The exploitation of the so-called Space Service Volume (SSV), and hence the extension of the Global Navigation Satellite System (GNSS) from terrestrial to space users, is currently considered a fundamental step. Knowledge of the constellation antenna pattern, including the side lobe signals, is the main input for assessing the expected GNSS signal availability and navigation performance, especially for high orbits. The best way to define and share this information with the final GNSS user is still an open question. This paper proposes a novel methodology for the definition of a high-fidelity and easy-to-use statistical model to represent GNSS constellation antenna patterns. The reconstruction procedure, based on antenna characterization techniques and statistical learning, is presented here through its successful implementation for the "Galileo Reference Antenna Pattern (GRAP)" model, which has been proposed as the reference model for the Galileo programme. The GRAP represents the expected Equivalent Isotropic Radiated Power (EIRP) variation for the Galileo FOC satellites, and it is obtained by processing the measurements retrieved during the characterization campaign performed on the Galileo FOC antennas. The mathematical background of the model is analyzed in depth in order to better assess the GRAP with respect to different objectives such as improved resolution, smoothness and proper representation of the antenna pattern statistical distribution. The analysis confirms the enhanced GRAP properties and envisages the possibility of extending the approach to other GNSSs. The discussion is complemented by a preliminary use case characterization of the Galileo performance in SSV. The accessibility, a novel indicator, is defined in order to represent in a quick and compact manner, the expected Galileo SSV quality for different altitudes and target mission requirements. The SSV characterization is performed to demonstrate how simply and effectively the GRAP model can be inserted into user analysis. The work creates the basis for an improved capability for assessing Galileo-based navigation in SSV according to the current knowledge of the antenna pattern.

Stability analysis of heavy machinery moving on weak subsoil. 3D FEM model vs. analytical models

In this paper, the authors present an extension of the scope of the previously conducted research to the full three-dimensional computer simulation (using the finite element method), which takes into account the interaction between: heavy caterpillar tracks system – working platform – weak subsoil. The article presents a computer model considering two caterpillars, resting on elastic-plastic sub-soil, with standard Mohr-Coulomb yield conditions, allowing for computer simulation of the behavior of the system up to achievement of ultimate limit state. The results of the above model are treated as the reference for a simplified Analytical Models of estimating the limit state, which might be used in design procedures. In turn, these Analytical Models are enhancements of previously presented one. The most important results concluding form the Analytical Model are simple interaction formulas, in the space of moments acting on the machine-subsoil system, limiting a domain of safety in given soil conditions.

Evaluation of the accuracy of full-arch impressions between three different intraoral scanners and conventional impressions: A prospective in vivo study.

This in-vivo study evaluated the accuracy of full-arch digital impressions obtained through different intraoral scanning technologies regarding trueness and efficiency against the standard alginate impressions. Alginate impressions were taken from 50 subjects, and the resulting stone casts were scanned using the Trios 3Shape desktop scanner. In-vivo scans were conducted on each participant using three intraoral scanners: Medit, CEREC Primescan, and 3Shape Trios. The scanned files were superimposed onto two software platforms: the 3Shape Orthoanalyser and Geomagic software. This superimposition was performed against the reference model to calculate 3D and 2D deviations, enabling efficiency comparisons between digital and traditional workflows based on work time in minutes. Measurements and comparisons were made in three planes: transverse, sagittal, and vertical dimensions for all the models and stone casts. Statistical analysis employed SPSS 23, with the significance level set at P<0.05. Significant deviations were observed between the three intraoral scanners and the alginate impression, with molar and premolar areas showing greater imprecision across dental arches. Compared to the alginate technique, Medit i500 tended to reduce the transverse dimension in the areas mentioned above, while CEREC exhibited higher precision. Molar and premolar areas emerged as the regions with the greatest discrepancies, both in excess and deficiency, compared to the alginate impression. This difference in dimensions was, however, statistically insignificant overall. 3Shape Trios exhibited the shortest scan times, indicating higher efficiency. Among the intraoral scanners, Medit recorded the longest scanning duration. Accepting the null hypothesis, the scans obtained using all three scanners were comparable with statistically insignificant differences in the measurements. The three scanners differed in the total scan time taken, with the Medit scanner requiring the longest scan time and the 3Shape TRIOS 3 scanner demonstrating the shortest scan duration.