Die kinematische Geometrie der allgemeinräumlichen Relativbewegung von drei Gliedern

Zusammenfassung In einer vorangehenden Arbeit wurde der von Aronhold-Kennedy angegebene wichtige Dreipolsatz der ebenen Kinematik (Getriebelehre) eingehend untersucht. Dieser Satz lautet: Bei der relativen Bewegung dreier Ebenen liegen die relativen Momentanpole auf einer Geraden, d.h. diese sind kollinear. Bei eben beweglichen starren K?rpern treten anstelle der Momentanpole die parallelen Momentanpolachsen auf. Insbesondere werden s?mtliche Entartungsf?lle dieses Satzes als Folge der speziellen Lagen der Momentandrehachsen angegeben. In der vorliegenden Arbeit werden diese Untersuchungen auf die r?umlichen relativen Bewegungen dreier K?rper ausgedehnt. Hier steht der folgende bekannte Satz im Vordergund: Bei den allgemein r?umlichen Relativbewegungen von drei K?rpern haben die drei Schraubachsen stets eine gemeinsame Normale. In der Arbeit sind die folgenden Kombinationen dieser Achsen in Betracht gezogen worden: Schraubenpaar-Schraubenpaar, Schraubenpaar-Drehpaar, Schraubenpaar-Schiebepaar, Drehpaar-Drehpaar, Drehpaar-Schiebepaar und Schiebepaar-Schibepaar. Au?erdem werden deren Beziehungen zum sogenannten Zylindroid (einer Regelfl?che dritter Ordnung) eingehend untersucht. Die Entatungsf?lle dieses Zylindroids werden für spezielle Lagen und Parameter dieser Achsen angegeben. Schlie?lich werden die Ergebnisse in Form von Tabellen zusmmengefa?t.     

Artificial neural network-based prediction technique for wear loss quantities in Mo coatings

Mo coated materials are used in automotive, aerospace, pulp and paper industries in order to protect machine parts against wear and corrosion. In this study, the wear amounts of Mo coatings deposited on ductile iron substrates using an atmospheric plasma-spray system were investigated for different loads and environment conditions. The Mo coatings were subjected to sliding wear against AISI 303 counter bodies under dry and acid environments. In a theoretical study, cross-sectional microhardness from the surface of the coatings, loads, environment and friction test durations were chosen as variable parameters in order to determine the amount of wear loss. The numerical results obtained via a neural network model were compared with the experimental results. Agreement between the experimental and numerical results is reasonably good.     

Domain-Size-Dependent Residual Stress Governs the Phase-Transition and Photoluminescence Behavior of Methylammonium Lead Iodide

Methylammonium lead iodide (MAPbI₃) perovskite has garnered significant interest as a versatile material for optoelectronic applications. The temperature-dependent photoluminescence (TDPL) and phase-transition behaviors revealed in previous studies have become standard indicators of defects, stability, charge carrier dynamics, and device performance. However, published reports abound with examples of irregular photoluminescence and phase-transition phenomena that are difficult to reconcile, posing major challenges in the correlation of those properties with the actual material state or with the subsequent device performance. In this paper, a unifying explanation for the seemingly inconsistent TDPL and phase-transition (orthorhombic-to-tetragonal) characteristics observed for MAPbI₃ is presented. By investigating MAPbI₃ perovskites with varying crystalline states, ranging from polycrystal to highly oriented crystal as well as single-crystals, key features in the TDPL and phase-transition behaviors are identified that are related to the extent of crystal domain-size-dependent residual stress and stem from the considerable volume difference (ΔV ≈ 4.5%) between the primitive unit cells of the orthorhombic (at 80 K) and tetragonal phases (at 300 K) of MAPbI₃. This fundamental connection is essential for understanding the photophysics and material processing of soft perovskites.     

The Underlying Reasons of the Navigation Control Effect on Performance in a Virtual Reality Endoscopic Surgery Training Simulator

Navigation control skills of surgeons become very critical for surgical procedures. Strategies improving these skills are important for developing higher-quality surgical training programs. In this study, the underlying reasons of the navigation control effect on performance in a virtual reality-based navigation environment are evaluated. The participants’ performance is measured in conditions: navigation control display and paper-map display. Performance measures were collected from 45 beginners and experienced residents. The results suggest that navigation display significantly improved performance of the participants. Also, navigation was more beneficial for beginners than experienced participants. The underlying reason of the better performance in the navigation condition was due to lower number of looks to the map, which causes attention shifts between information sources. Accordingly, specific training scenarios and user interfaces can be developed to improve the navigation skills of the beginners considering some strategies to lower their number of references to the information sources.     

Fabrication,characterization, and performance of YbDSB ternary compounds for IT‐SOFC applications

(Yb₂O₃)_x(Dy₂O₃)_y(Bi₂O₃)_1?x?y (0.04≤x+y≤0.20) powders (xYbyDSB) were synthesized by modified sol‐gel Pecchini method. The powders were characterized for structural, surface morphological, thermal, and electrical properties and power density measurements by means of X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis/thermal gravimetry (DTA/TG), and impedance spectroscopy, respectively. Lattice parameters and crystalline size of δ‐phase of Yb₂O₃‐ and Dy₂O₃‐doped Bi₂O₃ samples were calculated from the X‐ray diffraction data. Surface and grain properties of the related phases were determined by SEM analysis. In the investigated system, the maximum electrical conductivity was observed as σ=0.954 S cm^?1 for 6% mol Yb₂O₃ and 6% mol Dy₂O₃ at 800°C among all δ‐YbDSB systems. Cathode supported electrochemical cell was fabricated and 6Yb6DSB was used as the electrolyte. Maximum power density of single cell with an active area of 1.5 cm² is 72.50 mW/cm² at 700°C.     

Artificial neural networks–based backcalculation of the structural properties of a typical flexible pavement

Pavement evaluation is one of the foremost phases in all pavement engineering activities. In the backcalculation process, the researcher or the engineer varies the structural properties of the layers until the theoretical (calculated) deflections and the obtained (measured) deflections from FWD tests are closely matched to each other within a tolerable limit. However, this process is substantially time-consuming and poses some difficulties due to inherent inaccuracies in the results. In this study, synthetically derived deflections from a typical flexible pavement are used to estimate asphaltic concrete layer’s elastic modulus, Poisson’s ratio and thickness. Furthermore, artificial neural network (ANN) is utilized to determine the structural parameters, and it can be clearly seen that satisfactory results are obtained. ANN estimation of the three pavement layer characteristic parameters, that is, layer elastic modulus, Poisson’s ratio and layer thickness, was carried out for the first time in the study.     

Effects of different cooling conditions on twist drill temperature

In the past, many researchers have studied wear developed on drilling tools mainly due to the high temperatures generated which accelerate thermally related wear mechanisms and thereby reducing tool life. This paper deals with an experimental investigation on the effect of an internal coolant approach (for different air pressure) on drill bit temperature, comparing it with an external coolant approach and dry cutting. Drill temperatures were measured by inserting standard thermocouples through the coolant (oil) hole of TiN/TiAlN-coated carbide drills. Experimental studies have been conducted using Al 2014 alloy materials. In the drilling tests, cutting conditions had different spindle speeds, coolant approaches and feed rate values. The settings of drilling parameters were determined by using the Taguchi experimental design method. An orthogonal array, the signal-to-noise (S/N) ratio, and the analysis of variance (ANOVA) were employed to analyse the effect of coolant approaches and drilling parameters. The objective was to establish a model using multiple regression analysis between spindle speed, coolant (air) pressure and feed rate with the drill bit temperature. Mathematical models for drill bit temperature are proposed that agree well with the experiments.     

Evolution of connected health: a network perspective

In this study, the evolution of the connected health concept is analysed and visualized to investigate the ever-tightening relationship between health and technology as well as emerging possibilities regarding delivery of healthcare services. A scientometric analysis was undertaken to investigate the trends and evolutionary relations between health and information systems through the queries in the Web of Science database using terms related to health and information systems. To understand the evolutionary relation between different concepts, scientometric analyses were conducted within five-year intervals using the VantagePoint, SciMAT, and CiteSpace II software. Consequently, the main stream of publications related to the connected health concept matching telemedicine cluster was determined. All other developments in health and technologies were discussed around this main stream across years. The trends obtained through the analysis provide insights about the future of healthcare and technology relationship particularly with rising importance of privacy, personalized care along with mobile networks and mobile infrastructure.     

Fatty acid profile and proximate composition of Pacific mullet (Mugil so‐iuy) caught in the Black Sea

This study demonstrates proximate composition and fatty acid profile of Pacific mullet caught in Turkey. The highest moisture and protein contents were observed with muscle tissues as 83.74 and 10.52%, while the highest fat and ash contents were attributed to female gonads as 11.80 and 0.94%, respectively, with a significant variation amongst months (P < 0.05). Significant variation (P < 0.05) usually occurred amongst months within the same sex for total saturated fatty acids ( ∑ SFA), monosaturated fatty acids ( ∑ MUFA), polyunsaturated fatty acids ( ∑ PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in muscle, although overall mean values between sexes were not found significant. Except for EPA, no variation observed for gonads while significant changes occurred (P < 0.05) with liver samples amongst months. Overall total values of ∑ SFA, ∑ MUFA, ∑ PUFA, DHA and EPA in muscle samples were 29.59, 29.26, 18.06 and 4.48%, respectively, while in gonads ranged as 30.26–33.23%, 35.17–37.47%, 11.87–14.88%, 4.38–5.34% and 3.02–5.02%. These FAs were 21.57–33.11%, 32.89–50.96%, 14.78–20.08%, 0.89–9.94% and 5.85–9.54% for liver, respectively. The results of this study showed that muscle and gonads of Pacific mullet were rich in n‐3 PUFA, especially, EPA, DHA, increasing the value of this species for human consumption.     

The Effect of Different Polishing Sequences on the Adhesion of Streptococcus mutans to Feldspathic Porcelain

The aim of this research was to determine whether extra-oral surface treatments on feldspathic porcelain surfaces influence initial adhesion of Streptococcus mutans. Ninety-six porcelain specimen discs were fabricated and divided into six equal groups according to surface treatment: fine-grit diamond polishing (Group 1); self-glazing (Group 2); overglazing (Group 3); overglazing followed by a finishing procedure and then overglazing (Group 4); Pearl Surface polishing (Group 5); and Diamond Twist SCL^TM polishing (Group 6). Surface roughness and hydrophobicity were assessed. An S. mutans suspension was incubated on each specimen group and evaluated. A one-way analysis of variance, post-hoc Tukey honestly significantly different test, Friedman test, and t-test were used for statistical analysis. Group 1 showed the highest surface roughness (p < 0.001) and bacterial adhesion (p < 0.05). Groups 5 and 6 specimen surfaces presented significantly higher contact angles (p < 0.05). Group 1 had the highest S. mutans adhesion, followed by Groups 3, 5, 6, 2, and 4 (p < 0.05). Reglazing after grinding may therefore decrease bacterial adhesion beneficially.