Internal Homogeneity Research Articles

Investigating the Internal Deterioration of the Auriga Statue of Mozia Island, Sicily, through Ultrasonic and Ground-Penetrating Radar Studies

The Greek marble statue of the Auriga of Mozia Island, in Sicily, is the most important artwork displayed at the Whitaker Foundation Archaeological Museum. It underwent geophysical investigations twice, in 2012 and 2021, to assess the marble’s degradation. The 2012 investigation prepared the statue for transfer to the Paul Getty Museum in New York and repositioning on an anti-seismic pedestal. The 2021 investigation evaluated potential new damage before another transfer. Both investigations utilized 3D ultrasonic tomography (UST) to detect degraded marble areas and ground-penetrating radar (GPR) to identify internal discontinuities, such as fractures or lesions, and locate metal pins that were previously inserted to reassemble the statue and its pedestal. Results from the UST indicate an average marble velocity of approximately 4700 m/s, suggesting good mechanical strength, with some areas showing lower velocities (~3000 m/s) within the material’s variability range. The GPR profiles demonstrated internal signal homogeneity, excluding internal fracture surfaces or lesions, and confirmed the presence of metallic pins. This study highlights the effectiveness of integrating UST and GPR for non-invasive diagnostics of marble sculptures, providing detailed insights into the marble’s condition and identifying hidden defects or damage.

Response of PLA material to 3D printing speeds: A comprehensive examination on mechanical properties and production quality

This study investigates the impact of printing speed on the mechanical properties of parts produced through the fused deposition modeling (FDM) method using a three-dimensional (3D) printer. Tensile test specimens, fabricated with Polylactic Acid (PLA) material on an Ender 3 S1 3D printer, were subjected to varying printing speeds from 15 mm/s to 105 mm/s in 15 mm/s increments, maintaining a 100% infill rate. Detailed measurements of sample masses, hardness values, and surface roughness were conducted to assess the potential effects of printing speed on PLA’s mechanical properties. Porosity values were also calculated to evaluate internal structure homogeneity and void ratios. The results indicate that an increase in printing speed leads to a substantial reduction in production time. For instance, at a speed of 15 mm/s, the printing time was 119 minutes, decreasing to 15 minutes at 105 mm/s. As speed increased, there was a tendency for a decrease in sample masses, with a notable 12% reduction from 8.21 grams at 15 mm/s to 7.21 grams at 105 mm/s. While lower speeds (15 and 30 mm/s) exhibited higher Shore D hardness values, an overall decrease in hardness was observed with increasing speed. Surface roughness showed a proportional increase with printing speed; for example, at 0° angle, the roughness value increased from 0.8 at 15 mm/s to 1.9 at 105 mm/s. Moreover, tensile strength values decreased with higher printing speeds. For samples printed at 15 mm/s, the tensile strength was 60 MPa, decreasing to 44 MPa at 105 mm/s, representing a 27% reduction. These numerical findings underscore the significant influence of 3D printing speed on both production efficiency and the mechanical properties of the printed material.

Virtual item trade scams: A typology of young victims

This study examined behavioral differences across groups of children and young people who have been victims of virtual item trade scams to explore the potential for grouping this type of victims into meaningful clusters. Using data from a representative survey among Danish children and young people (n = 1,026), three clusters of trade scam victims that showed significant internal homogeneity as well as cross-cluster differences were identified. Based on their modal behavior, these clusters were labeled Moderately Engaged Gamers, Diverse Active Gamers, and Highly Engaged Gamers. The typology represents a first step toward a better understanding of different types of virtual item trade scam victims and their behavioral patterns. Implications for policy and preventive measures on game design, personal, and parental levels are discussed.

Study on the synergistic effect of electromagnetic stirring and mechanical reduction on the improvement of the internal homogeneity of high-carbon steel billet

The synergistic effect of electromagnetic stirring (EMS) and mechanical reduction on the improvement of the internal homogeneity has been studied during the continuous casting of high-carbon steel billet. Plant trials were conducted with different parameters both for mold electromagnetic stirring (M-EMS) and final electromagnetic stirring (F-EMS), at the same casting condition and with a unified mechanical reduction process. As the stirring intensity of EMS increases, both the initiation and termination of columnar to equiaxed transition occur at an earlier timing. The results also indicate that, EMS could result in a decline trend for the compactness of the casting billet to a certain extent, especially in the pure equiaxed crystal zone at the core part of the billet. Under the proper intensity setting of M-EMS and F-EMS, the crack susceptibility of the high-carbon steel billet was markedly decreased by enlarging the mixed crystal zone, which is not arrayed with distinct directionality while featured with a relatively high compactness. The effect of EMS on the solidification behavior, and therefore on the crack susceptibility of the high-carbon steel billet was further explained with the numerical simulation. Consequently, a superior inner quality of high-carbon steel billet was successfully achieved with the effective synergy of EMS and mechanical reduction.

Development of aGerman short version of the Nijmegen Cochlear Implant Questionnaire

The Nijmegen Cochlear Implant Questionnaire (NCIQ) is aquestionnaire for assessing hearing-specific quality of life in the context of cochlear implantation. Its length (60items) makes it difficult to use in clinical practice, so ashort version is desirable. The question arises as to which items should be selected for the short version. The items were selected statistically using uncorrected item-total score correlation. Item selection was made based on datasets from three measurement points: before implantation and 3and 12months after processor activation. The items were selected according to the criterion that they were among the 40items with the highest item-total score correlation at each of the three measurement points. Of the 60items in the NCIQ, 25met the criterion and were hence included in the short version. The short version yields similar scores as the long version at the postoperative timepoints; however, at the preoperative timepoint, the agreement of the scores is suboptimal. Split-half reliability and internal homogeneity of the short version are very good. The present study constitutes an initial positive evaluation of ashort form of the NCIQ in terms of standard psychometric criteria. Application of the short form is associated with significantly reduced resources in terms of processing and evaluating.

Identifying latent subgroups in the older population seeking primary health care for a new episode of back pain – findings from the BACE-N cohort

BackgroundBack pain is the number one condition contributing to years lived with disability worldwide, and one of the most common reasons for seeking primary care. Research on this condition in the ageing population is sparse. Further, the heterogeneity of patients with back pain complicates the management in clinical care. It is possible that subgrouping people with similar characteristics would improve management. This paper aimed to identify latent classes based on demographics, pain characteristics, psychosocial behavior, and beliefs and attitudes about back pain, among older patients seeking primary care with a new episode of back pain, and to examine if there were differences regarding the classes’ first point-of-contact.MethodsThe study was part of the international BACE (Back complaints in elders) consortium and included 435 patients aged ≥ 55 years seeking primary care (general practitioners, physiotherapists, and chiropractors) in Norway from April 2015 to March 2020. A latent class analysis was performed to identify latent classes. The classes were described in terms of baseline characteristics and first point-of-contact in primary care.ResultsFour latent classes were identified. The mean age was similar across groups, as were high expectations towards improvement. Class 1 (n = 169, 39%), the “positive” class, had more positive attitudes and beliefs, less pain catastrophizing and shorter duration of current pain episode. Class 2 (n = 31, 7%), the “fearful” class, exhibited the most fear avoidance behavior, and had higher mean pain intensity. Class 3 (n = 33, 8%), the “distressed” class, had the highest scores on depression, disability, and catastrophizing. Finally, class 4 (n = 202, 46%), the “hopeful” class, showed the highest expectations for recovery, although having high pain intensity. The identified four classes showed high internal homogeneity, sufficient between-group heterogeneity and were considered clinically meaningful. The distribution of first point-of-contact was similar across classes, except for the positive class where significantly more patients visited chiropractors compared to general practitioners and physiotherapists.ConclusionsThe identified classes may contribute to targeting clinical management of these patients. Longitudinal research on these latent classes is needed to explore whether the latent classes have prognostic value. Validation studies are needed to evaluate external validity.Trial registrationClinicaltrials.gov NCT04261309.

Slope unit-based genetic landform mapping on Tibetan plateau- a terrain unit-based framework for large spatial scale landform classification

Genetic landform classification and mapping provide crucial information concerning the formation and evolution of the earth surface, aiding in understanding geological processes, climate variation, and driving mechanisms of earth dynamics. Conventional pix and object unit-based research paradigms poss challenges in classifying and mapping the genetic landform on a large spatial scale, while the terrain unit-based method offers an inspiring opportunity for this typical landform task. In this context, we herein developed a slope unit (SU)-based landform classification framework, involving improving the mean curvature method for SU segmentation, developing the spectra method to determine the minimal area size of SU, introducing a specific quantitative indicator system for describing SU, and a universal classification model based on XGBoost. Using the entire Tibetan Plateau as the study area, we first implemented the genetic landform map and divided it into nine genetic landform types including aeolian, arid, loess, karst, periglacial, fluvial, glacial, volcanic-lava, and lacustrine. Classification results achieved an encouraging performance with overall accuracy, kappa coefficient, and mean accuracy of up to 90.2%, 84.71%, and 88.65%, respectively. Experimental results suggested that delineated genetic landform regions and their boundaries are generally closely correlated with regional climatic conditions, geological factors, or surface processes. Compared to pix or object-unit-based methods, the SU delineation results possess internal homogeneity and clear terrain boundaries with geo-meaning. Compared to the watershed-unit-based method, our method is better suited for large-scale landform classification. In the end, we confirmed that the proposed framework can be extended to large-scale planetary genetic landform mapping via two case studies on Mars and Moon, which is transferable yet straightforward. In brief, we argued that the proposed framework offered a powerful and effective method in large-scale genetic landform classification, somewhat effectively circumventing the limitations of existing landform classification methods.

Study on the effect of dynamic chemical polishing treatment on porous titanium alloy scaffolds fabricated using laser powder bed fusion

This study addresses the issue of a significant amount of unmelted powder adhering to the surface of Laser Powder Bed Fusion (LPBF) porous titanium alloy scaffolds, and the current inability of existing technologies to effectively handle such surface defects. Porous titanium alloy scaffolds with a triple periodical minimal surface (TPMS) Gyroid structure were prepared using powder bed fusion technology for dynamic chemical polishing. The spatial and surface morphology, as well as the mechanical properties of the scaffolds, were evaluated before and after treatment. Concurrently, fluid finite element simulation was employed to analyze the flow state of the solution inside the porous scaffold during dynamic chemical polishing. Cell culture samples were prepared and subjected to dynamic chemical polishing to study the specific effects of scaffold surface morphology on cell activity. The results indicate that the surface treatment effect, internal and external homogeneity, and dynamic and static mechanical properties of the porous scaffolds with a Gyroid structure are significantly improved after dynamic chemical polishing. Additionally, it was found that dynamic chemical polishing could effectively reduce the micrometer roughness and increase the nanometer roughness of the sample surface, thereby enhancing the adhesion, proliferation, and differentiation activities of Human Bone Mesenchymal Stem cells.

Psychometric of the Persian Version of Shift Work Disorder Questionnaire in Employee Women

Introduction: Shift work disorder (SWD) is a sleep disorder that affects the circadian rhythm and is characterized by symptoms such as excessive daytime sleepiness and insomnia. This condition can significantly increase the risk of accidents and diminish the overall quality of life for individuals affected by it. Therefore, using the four-question of shift work disorder questionnaire (SWDQ) can be useful for identifying people at risk of SWD. In this research, we evaluated the accuracy and consistency of the Persian adaptation of the SWDQ among female employees.
 Methods: In this descriptive cross-sectional investigation, a sampling available method was employed to select employed women who were referred to Royan Institute, Arash Hospital, and Gynecological Office in Tehran. It was used translated and reverse translation methods for the questionnaire of SWDQ. Statistical analysis was performed by using the Statistical Package for the Social Sciences (SPSS version 16, Inc. Chicago, IL, USA).The tests used in this study were Cronbach's alpha, internal correlation, and confirmatory factor analysis.
 Results: In terms of content validity rate (CVR) with an average of 70% (questions 80%, 80%, 60% and 60%, respectively) and content validity index (CVI) with an average of 87.5% (questions 100%, 90%, 80% and 80%, respectively) was acceptable. The internal homogeneity of the SWD questionnaire with Cronbach's alpha was 63.4% and deleting each of the four items of the questionnaire reduced it. Moreover, the range of total correlated changes for the questionnaire was from 0.339 to 0.488, which was more than the minimum of 0.3.
 Conclusion: Overall, the validity and reliability of the Persian version of SWDQ (the four-item) have acceptable.

Construction of rating systems using global sensitivity analysis: A numerical investigation

AbstractThe ratemaking process is a key issue in insurance pricing. It consists in pooling together policyholders with similar risk profiles into rating classes and assigning the same premium for policyholders in the same class. In actuarial practice, rating systems are typically not based on all risk factors but rather only some of factors are selected to construct the rating classes. The objective of this study is to investigate the selection of risk factors in order to construct rating classes that exhibit maximum internal homogeneity. For this selection, we adopt the Shapley effects from global sensitivity analysis. While these sensitivity indices are used for model interpretability, we apply them to construct rating classes. We provide a new strategy to estimate them, and we connect them to the intra-class variability and heterogeneity of the rating classes. To verify the appropriateness of our procedure, we introduce a measure of heterogeneity specifically designed to compare rating systems with a different number of classes. Using a well-known car insurance dataset, we show that the rating system constructed with the Shapley effects is the one minimizing this heterogeneity measure.

Development and psychometric evaluation of a questionnaire for assessment of exposure to chemical hazards in operating room nurses

BackgroundOccupational hazards are a significant cause of death in the world. Healthcare workers are highly exposed to a variety of physical, chemical, biological, ergonomic and psychological risks. Chemical hazards are one of the threatening factors for operating room nurses and cause many complications for their health. ObjectivesThe present study aimed at developing the psychometric properties of a questionnaire for evaluation of exposure to chemical hazards in operating room nurses. MethodsThe present methodological study was performed in two stages: first, the items of the questionnaire were developed based on the findings of a qualitative study and a literature review; and second, the psychometric properties of the questionnaire were measured using the methods to evaluate face, content, and construct validities. To assess construct validity of the questionnaire, the researchers measured divergent validity. The reliability was measured through an assessment of the internal homogeneity and consistency of the questionnaire. ResultsIn the first stage of the study, 35 items were developed according to the results of a qualitative study, review of relevant literature and several meetings with experts. The content validity ratio (CVR) of all the items was greater than 0.49. The content validity index (CVI) of all the items was over 0.79. The average CVI (S-CVI/Ave) of the questionnaire with 13 items was 0.98. Kuder-Richardson coefficient for the internal homogeneity of the instrument was found to be 0.70 and the results of the test–retest showed its consistency to be 0.88. ConclusionsThe results of the current study showed that the present questionnaire is sufficiently valid and reliable to evaluate the exposure to chemical hazards in operating room nurses.

Methodology for assessing the efficiency of public financing of national projects on the basis of cluster analysis

Subject. Increased external challenges and threats slow down the growth rate of gross domestic product as a basic source of financial resources for the development of the State. The key to improving the living standards is to enhance the mechanism of capital redistribution within national projects implementation, given the need for balance and existing imbalances in the development of Russian regions. Objectives. The aim of the study is to develop methodological tools for assessing the effectiveness of State financing of national projects, based on cluster analysis as a modern tool to identifying groups of regions according to specified variables, which include targets and financial indicators for national projects implementation. Methods. We applied methods of cluster analysis and mathematical statistics, to form groups of Russian regions with different levels of socio-economic efficiency and financial risks of national projects execution. To divide regions into clusters, considering their internal homogeneity and external heterogeneity, we developed indices of centralization of financing and achievement of targets of national projects, which were used as variables. Results. The offered methodology contributes to the development of scientific approaches to financial analysis and forecasting in the field of socio-economic development of Russian regions and the country as a whole. Its practical implementation enables to assess the likelihood of successful implementation of national projects in Russian regions and shape a flexible State policy for financing national projects. Conclusions. The study confirmed prospects for using cluster analysis to assess the effectiveness of State financing of national projects and established that the amount of financing of national projects is not a determining factor in the effectiveness of their implementation.

THE PSYCHOMETRIC FEATURES OF THE QUIET EGO SCALE AND THE CONSTRUCT VALIDITY OF THE QUIET EGO

The concept of quiet ego is conceived as a personal identity that transcends selfishness without ignoring personal interest at the same time. It is measured through a scale consisting of 14 items. The limited scope of research on this concept in psychological literature, as well as the absence of research for the Macedonian population, is the main motive for this research. This research aims to examine the psychometric properties of the Quiet Ego Scale and the validity of the construct of Quiet Ego (Quiet Ego Scale, Waymet, Bauer & Slaskia, 2014). Two studies were conducted for the purposes of the study. The first study is a correlational one, in which, in addition to the Quiet Ego Measurement Scale, instruments for measuring of narcissism (Narcissism Measurement Inventory, Raskin & Terry, 1988) and of empathy (Toronto Empathy Questionnaire, Spreng et al, 2009) are been set. In this study the analysis of the main components also take part. The results have shown that the Quiet Ego Scale has satisfactory internal homogeneity and a factor structure that confirms the theoretical solution of the construct, as well as a significant correlation with concepts similar and contrary to the researched concept. Using an experimental design, in the second study the levels of narcissism and empathy were manipulated (increased narcissism vs. reduced narcissism and increased empathy versus reduced empathy), in order to investigate the impact of different levels of narcissism and empathy on the level of quiet ego. The results of the second study confirmed the relationship between quiet ego, narcissism and empathy and justification for using the construct of the quiet ego.

Psychometric properties of the fear of missing out (FOMO) Scale in iranian students: Reliability, validity, factor structure, and measurement invariance

Fear of Missing Out (FOMO) is described as negative affect resulting from thoughts that one is left out of the rewarding experiences of others. The development of a popular FOMO scale (Przybylski et al., 2013) has generated a wealth of research studies on FOMO. The present study aimed to examine the reliability, factor structure, measurement invariance, and construct validity of the FOMO scale using a cross-sectional online survey administered to a convenience sample of 400 Iranian students. The results showed that the construct validity (loadings > 0.40), model goodness-of-fit (CMIN/DF = 1.56, RMSEA = 0.038, CFI = 0.99, GFI=0.97 and NFI=0.97), internal homogeneity reliability (Cronbach's alpha = 0.91), and composite reliability (0.84) of the scale were good. Results indicate that the 10-item Persian version of the FOMO scale is a reliable and valid tool in an Iranian student sample. The current findings serve as a confirmation of the utility of the FOMO scale and allow for the advancement of research on mental health implications of social media use in Persian-speaking populations.

Educommunication 2.0 in food and physical activity. Study of mobile applications in the fast food sector

ABSTRACT This research article analyzes the educommunicative dimension of the mobile apps developed by the main franchise companies in the fast food sector from the perspective of CSR. The study follows an exploratory and descriptive research design that combines quantitative and qualitative methods, namely a descriptive analysis of a sample of apps belonging to eight leading fast-food companies and focus groups, respectively. For the focus groups, 25 students agreed to participate (n = 25). They were selected based on structural criteria established to guarantee internal homogeneity and heterogeneity. The results reveal an underutilization of the educommunicative potential of mobile applications and confirm millennials’ interest in the acquisition and practice of healthy habits and the use of mobile applications for this purpose. The study concludes that fast food companies must encourage and educate their publics about good eating habits and physical activity. Organizations, especially those that operate in sectors of social interest, must undertake mCSR actions to prevent and counteract social ills and meet the expectations of stakeholders. Mobile applications are excellent tools to support this endeavor. To overcome the main limitation of the study, it is necessary to complement it with quantitative research.

Potential of Precise Fertilization through Adoption of Management Zones Strategy to Enhance Wheat Production

The variability in soil properties and crop yield can be overcome by adoption of smart farming practices through interpolation and mapping of spatial variability patterns. Geospatial technologies can be utilized to determine the cause of spatial variability in fields for site-specific application of fertilizer. This study was designed to quantify and identify the spatial variation in soil properties and wheat (Triticum aestivum L.) yield and to delineate prescription maps for precise application of fertilizer in a semi-arid subtropical region of Pakistan. To examine the variability in soil properties on the production of the considered crop, this study comprised two different fields and each field was divided into (20 × 20 m) grids. The samples of soil were collected at 15 cm and 30 cm soil depths before the fertilization to analyze the different soil characteristics i.e., nitrogen (N), electrical conductivity (EC), potassium (K), soil organic matter (SOM), phosphorus (P), and pH. The boundaries of selected fields and grid points were established with a real-time kinematics-global positioning system (RTK-GPS). The soil data were acquired with a soil proximal sensor at a depth of 7 cm after fertilization. The statistical analysis coefficient of variation (CV), geostatistical-analysis-nugget-to-sill ratio (N:S), and the interpolated maps (ArcGIS pro 2.3) were used to characterize the least to moderate variability of soil parameters and yield, demanding site-specific management of fertilizer application. Cluster analysis was conducted using Minitab 21, which classified soil and yield characteristics into five categories: “very good”, “very low”, “good”, “poor”, and “medium”, with an external heterogeneity and internal homogeneity both more than 60%. Significant relationships (p < 0.05) between soil and crop properties were used to develop the management zones (MZs) for the precise application of fertilizer in wheat fields. Significant differences (p < 0.05) in soil nutrients were found in the very high and very low productivity zones at both sampling times, which suggest delineating the MZs for precise application of fertilizer according to the need of crop and soil properties. The results revealed that the optimum number of MZs for the wheat fields was five and there was heterogeneity in the soil nutrients in five MZs. The findings of this study also highlight the necessity of predicting the crop and soil factors by using precision technologies to develop the prescription maps, because sampling and analysis of soil are expensive and time-consuming. Based on the demand of the soil and crops, site-specific fertilization can increase economic and environmental efficiency.

Translation and psychometric assessment of a Persian version of medication safety competence scale (MSCS) for clinical nurses

Nurses play a key role in medication safety and, by extension, patient safety. Evaluation of medication safety competence in nurses requires valid, specific, and comprehensive instruments. The present study was conducted to translate and psychometric assessment a Persian version of medication safety competence scale (MSCS) for clinical nurses in Iran. This is a cross-sectional and multi-centric work of research with a methodological design. A total of 1080 clinical nurses were selected from 5 cities located in Iran. The original version of the MSCS was translated into Persian and the psychometric properties of MSCS were assessed using COSMIN criteria. The exploratory factor analysis (EFA) showed that the factor loading of the 36 items was between 0.72–0.87, all of which were significant. The confirmatory factor analysis (CFA) fitted the data well (χ2/df = 7, RMSEA = 0.01, CFI = 0.96, NFI = 0.95, and TLI = 0.97). The reliability of the instrument was assessed in terms of its internal homogeneity where the Cronbach's alpha of the whole instrument was found to be 0.96. The Persian version of MSCS for nurses possesses satisfactory validity and reliability. Thus, nurse managers can use this instrument to measure medication safety competence in nurses.

Verification of Uniformity of Dosimetric Characteristics of Couch Tops in Proton Radiation Therapy

In proton therapy the couches used for patient positioning and alignment can affect the uncertainty in the dose distribution from the applied proton beam. In order to limit the additional uncertainty of the proton range, it is necessary to know the determined water equivalent thickness (WET) of the couch top and carefully reflect it in the calculations of the dosimetry planning system. The method presented in this article is based on the difference in the measured depth of the proton beam detected by the multilayer ionization chamber with the beam passing through the couch top and without passing through it.
 A range shifter (proton beam modifier) installed in the nozzle with the known WET for evaluating couch tops before commissioning was used in this research work. A nozzle is a proton beam delivery system consisting of quadrupole magnets, ionization chambers and an X-ray tube. CT scans were also acquired to evaluate the internal homogeneity of the test couch tops.
 Several kVue couch inserts Proton one (Qfix Systems, Avondale, PA) were evaluated in this study. The results show that the inserts are largely interchangeable for this type of design and the use of the range shifter during treatment, using gantry angles with the proton beam passing through the couch top, does not affect its WET, adding a deflection of approximately 0.1 mm. It was also determined that the reproducibility of the WET determination method has a deviation less than ±0.03 mm. In conclusion, the described above method of couch top testing before commissioning in proton therapy can also be applied to other patient immobilization systems.

PDBI: A partitioning Davies-Bouldin index for clustering evaluation

Clustering validation and identifying the optimal number of clusters are crucial in expert and intelligent systems. However, the commonly used cluster validity indices (CVI) are not relevant enough to measure data structures. They do not embed the necessary mechanisms to be as effective as that of the clustering algorithm used to give the clustering results. This paper proposes a novel CVI called PDBI (Partitioning Davies-Bouldin Index) initially inspired from the native idea of the Davies-Bouldin Index (DBI). PDBI is based on a strategy that consists in dividing each cluster into sub-clusters that redefine the concepts of internal homogeneity and cluster separation via the integration of sophisticated mechanisms. This strategy makes it possible to process a relevant CVI even in the case of complex data structures and in presence of clusters with noisy patterns. PDBI is deterministic, runs independently of a given clustering algorithm and generates a normalized score between 0 and 1. Numerous tests were carried out using 2-dimensional benchmark data sets and data generated in higher dimensions with consistent ground truths. The experimental comparisons with the state-of-the-art validity indices demonstrate the efficiency of the proposal in discovering the true number of clusters and dealing with various sorts of data sets. The PDBI demonstration as well as illustrations can be found on the author’s website11A demonstration is available at: http://r-riad.net/

CO2 adsorption-deformation-percolation characteristics of coals with different degrees of metamorphism and improvement of dynamic prediction model

The deformation and permeability changes occurring during CO2 adsorption in the coal body are important factors affecting CO2 injectability. In order to reveal the characteristic laws of adsorption, deformation and permeability of coal in the process of CO2 adsorption by different coal rank coals, the test experiments of adsorption, deformation and permeability of different coal rank coals under the condition of constant external force were carried out. The adsorption capacity of different coal samples for CO2 was obtained as anthracite > coking coal > long flame coal; The radial deformation ɛ2 and axial deformation ɛ1 of coal after CO2 gas adsorption by anthracite are the closest (ɛ2/ɛ1 is about 1.37), coking coal is the second (ɛ2/ɛ1 is about 1.73), long-flame coal is the largest (ɛ2/ɛ1 is about 2.72), In other words, the higher the coal rank, the more significant the degree of internal homogeneity and isotropy of the coal body, and the mean value of the volume deformation of CO2 adsorbed by long-flame coal is 1.07 and 1.17 times higher than that of coking coal and anthracite. The permeability curves of CO2 adsorption in all three coal samples decreased first and then increased, and the permeability of CO2 in coking coal was the largest, and the sensitivity coefficient of CO2 permeability in coal to adsorption pressure showed a trend of rapid decrease and then small increase. Based on the CO2 adsorption-deformation-percolation variation law of coal, an improved dynamic prediction model of adsorption (fitting accuracy 0.9850 ∼ 0.9963), an improved dynamic prediction model of coal body deformation (fitting accuracy 0.9889 ∼ 0.9921) and an improved dynamic prediction model of permeability (fitting accuracy 0.9848 ∼ 0.9914).