Regionalisierung der Durchlässigkeitsbeiwerte mit unscharfen (fuzzy) Zahlen: Der Natur näher?

This article demonstrates an application of fuzzy geostatistics in spatial regionalization of imprecise hydrogeological data. The regionalization was carried out for hydraulic condictivity values of a major aquifer in northwestern Germany. The original data set consists of 557 borehole points with known (crisp) hydraulic conductivities. This data set was supplemented by 30 additional data points, placed in areas with lowest borehole density. At these points, hydraulic conductivities were estimated based on subjective expert knowledge of regional geology, and entered the regionalization procedure as fuzzy (imprecise) numbers. By utilizing the expert knowledge, which cannot be implemented in conventional geostatistics, the reliability of regionalization has been improved. The imprecision of fuzzy-regionalization is fully quantifiable, so that it can be easily accounted for when evaluating the results.     

Quadrotor Flight Controller Design Using Classical Tools

International Journal of Control, Automation and Systems - A principal aspect of quadrocopter in-flight operation is to maintain the required attitude of the craft’s frame, which is done...     

Experience-Driven Model of Decision-Making Processes in Project Teams

This article presents a model of decision-making processes in project teams. Project teams constitute a specific type of organization appointed to implement a project. Decisions made by project teams result from the methods of project management and best management practices. The authors have undertaken the task of formalizing these processes using the classical method of constructing decision trees. It has been established that this method cannot be fully exploited because the decision-making paths need changing (the decision tree must be dynamically generated after every decision). Therefore, the authors applied a method for collecting experiences, the Set of Experience Knowledge Structure (SOEKS), to support the structure of a decision tree. This method was used to support decision-making processes regarding the selection of methods and technologies of project management and to classify the location decisions resulting from exceeding levels of particulate matter.     

Irregularly shaped DSC exotherms in the analysis of polymer crystallization

Summary This article details a study of irregularly shaped DSC exotherms of poly(3-hydroxybutyrate) (PHB) developed during isothermal and non-isothermal crystallization. Due to the extreme purity of the polymer, PHB crystallization is mainly initiated by homogeneous nucleation, with the formation of very large spherulites, especially under slow nucleation conditions. When the number of growing spherulites is low, the evolution of latent heat is very sensitive to every act of nucleation as well as to the space limitations in the process of growth, resulting in non-monotonous development of latent heat, with sudden increases and decreases in crystallization rates. This results in non conventional DSC exotherms, under given crystallization conditions, characterized by spikes or shoulders associated to nucleation of new spherulites.     

Maxwell’s reciprocal diagrams and discrete Michell frames

This paper unites two major legacies of James Clerk Maxwell’s ground-breaking paper, “On Reciprocal Figures, Frames, and Diagrams of Forces” (Maxwell, Philos Mag 26:250-261, 1864; Edinb Roy Soc Proc 7:160–208, 1870): (i) the fundamental theorem used by Michell (Philos Mag 8(47):589–597, 1904) to derive trusses of least weight and (ii) reciprocal frames. This paper presents some remarkable relationships between discrete Michell frames and their corresponding reciprocal force polygons using Graphic Statics. Several examples are given to illustrate the notions of duality and self-reciprocity in these diagrams, with particular emphasis placed on discrete optimal benchmark structures. For a given connectivity of nodes, Graphic Statics provides all of the information needed to determine the total load path of the structure in the form and force diagrams. Because the form and force diagrams are reciprocal, in the course of finding one minimum load path structure, a second minimum load path structure is also found. These observations between the corresponding form and force diagrams are generalized for discrete cantilever Michell frames, and several comments on the extensions of this work are included.     

Tribocorrosion modeling of stainless steel in a sliding pair of pin-on-plate type

In this paper, the results of research into tribocorrosion wear of three types of stainless steel: AISI 430, 304 and 420 are presented. The research was carried out on a pin-on-plate stand in a 0.5 M solution of H₂SO₄. The aim of the research was to define relations between original properties of steel (resistance to abrasion and corrosion) and the intensity of tribocorrosion wear.Moreover, the authors present their own computational model allowing to forecast the effects of tribocorrosion in pin-on-plate type combination. As concerns forecasting the intensity of tribocorrosion, the authors state that maximum differences did not exceed 15%.     

Modulations in Chlorophyll a Fluorescence Based on Intensity and Spectral Variations of Light

Photosynthetic efficiency is significantly affected by both qualitative and quantitative changes during light exposure. The properties of light have a profound effect on electron transport and energy absorption in photochemical reactions. In addition, fluctuations in light intensity and variations in the spectrum can lead to a decrease in photosystem II efficiency. These features necessitate the use of a simple and suitable tool called chlorophyll a fluorescence to study photosynthetic reactions as a function of the aforementioned variables. This research implies that chlorophyll a fluorescence data can be used to determine precise light conditions that help photoautotrophic organisms optimally function.     

Is Periodontitis Associated with Age-Related Cognitive Impairment? The Systematic Review,Confounders Assessment and Meta-Analysis of Clinical Studies

It has been suggested that molecular pathological mechanisms responsible for periodontitis can be linked with biochemical alterations in neurodegenerative disorders. Hypothetically, chronic systemic inflammation as a response to periodontitis plays a role in the etiology of cognitive impairment. This study aimed to determine whether periodontitis (PDS) is a risk factor for age-related cognitive impairment (ACI) based on evidence of clinical studies. A comprehensive, structured systematic review of existing data adhering to the Preferred Reporting Items for Systematic Review and Meta Analyses (PRISMA) guidelines was carried out. Five electronic databases, PubMed, Embase, Scopus, Web of Science, and Cochrane, were searched for key terms published in peer-reviewed journals until January 2021. The Newcastle–Ottawa scale was used to assess the quality of studies and risk of bias. The primary and residual confounders were explored and evaluated. A meta-analysis synthesizing quantitative data was carried out using a random-effects model. Seventeen clinical studies were identified, including 14 cohort, one cross-sectional, and two case-control studies. Study samples ranged from 85 to 262,349 subjects, with follow-up between 2 and 32 years, and age above 45 years, except for two studies. The findings of studies suggesting the PDS-ACI relationship revealed substantial differences in design and methods. A noticeable variation related to the treatment of confounders was observed. Quality assessment unveiled a moderate quality of evidence and risk of bias. The subgroups meta-analysis and pooled sensitivity analysis of results from seven eligible studies demonstrated overall that the presence of PDS is associated with an increased risk of incidence of cognitive impairment (OR = 1.36, 95% CI 1.03–1.79), particularly dementia (OR = 1.39, 95% CI 1.02–1.88) and Alzheimer’s disease (OR = 1.03 95% CI 0.98–1.07)). However, a considerable heterogeneity of synthesized data (I² = 96%) and potential publication bias might affect obtained results. While there is a moderate statistical association between periodontitis and dementia, as well as Alzheimer’s disease, the risk of bias in the evidence prevents conclusions being drawn about the role of periodontitis as a risk factor for age-related cognitive impairment.     

Dynamical changes during composite milling: recurrence and multiscale entropy analysis

Fluctuations describing chatter in the milling process of a composite material were analyzed using statistical, recurrence, and multiscaled entropy analyses. Through changing the rotational speed, we observed the appearance of chatter vibrations and signatures of intermittency. The corresponding characteristic change of recurrences could be used to invent a new efficient control procedure of milling. The workpiece was prepared from nonuniform material based on epoxy-polymer matrix composite reinforced by carbon fibers.