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In recent years, hybrid towers have become increasingly established, especially for tall wind turbines. The concrete part of these towers, commonly constructed using segmental construction methods, consists of several circular ring segments stacked on top of each other. To reduce the amount of fabrication and erection effort, the joints between the segments are typically designed as dry ground joints. This paper deals with experimental investigations to determine the torsional load‐bearing capacity of such dry ground concrete joints subjected to combined loading of prestressing, bending, and torsion. Based on the experience of previous investigations, a test set‐up consisting of three reinforced concrete segments with circular ring cross‐sections was developed. The herein newly developed evaluation concept enabled precise identification of the failure point for each test run utilizing the measured tangential displacements of the joint. The test results clarify the weaknesses of the current design model regarding the insufficient interaction with the bending moment and show very good accordance with the new calculation model, the so‐called fiber model. [ABSTRACT FROM AUTHOR]

This study delves into the dynamic behavior of ultra-high-speed rotor systems underpinned by helium hydrostatic gas bearings, with a focus on the impact of rotational velocity on system performance. We have formulated an integrative dynamic model that harmonizes the rotor motion equation with the transient Reynolds equation. This model has been meticulously resolved via the Finite Difference Method (FDM) and the Wilson-Θ technique. Our findings unveil intricate nonlinear dynamics, including 2T-periodic and multi-periodic oscillations, and underscore the pivotal role of first-order temporal fluctuations, which account for over 20% of the transient pressure at rotational speeds exceeding 95.0 krpm. Further, we have executed empirical studies to evaluate the system's performance in practical settings. It is observed that when the ratio of low-frequency to fundamental frequency approaches 0.3 and the amplitude ratio exceeds 3, the vigilant monitoring of system stability and reliability is imperative. Collective insights from both computational simulations and experimental studies have enriched our understanding of the dynamic attributes of ultra-high-speed rotor systems. These revelations are crucial for the advancement of more efficacious and resilient rotor systems designed for high-speed applications. [ABSTRACT FROM AUTHOR]

In turbomachinery, geometric variances of the blades, due to manufacturing tolerances, deterioration over a lifetime, or blade repair, can influence overall aerodynamic performance as well as aeroelastic behaviour. In cooled turbine blades, such deviations may lead to streaks of high or low temperature. It has already been shown that hot streaks from the combustors lead to inhomogeneity in the flow path, resulting in increased blade dynamic stress. However, not only hot streaks but also cold streaks occur in modern aircraft engines due to deterioration-induced widening of cooling holes. This work investigates this effect in an experimental setup of a five-stage axial turbine. Cooling air is injected through the vane row of the fourth stage at midspan, and the vibration amplitudes of the blades in rotor stage five are measured with a tip-timing system. The highest injected mass flow rate is 2% of the total mass flow rate for a low-load operating point. The global turbine parameters change between the reference case without cooling air and the cold streak case. This change in operating conditions is compensated such that the corrected operating point is held constant throughout the measurements. It is shown that the cold streak is deflected in the direction of the hub and detected at 40% channel height behind the stator vane of the fifth stage. The averaged vibration amplitude over all blades increases by 20% for the cold streak case compared to the reference during low-load operating of the axial turbine. For operating points with higher loads, however, no increase in averaged vibration amplitude exceeding the measurement uncertainties is observed because the relative cooling mass flow rate is too low. It is shown that the cold streak only influences the pressure side and leads to a widening of the wake deficit. This is identified as the reason for the increased forcing on the blade. The conclusion is that an accurate prediction of the blade's lifetime requires consideration of the cooling air within the design process and estimation of changes in cooling air mass flow rate throughout the blade's lifetime. [ABSTRACT FROM AUTHOR]

The current work aims to develop a new composite-based epoxy doped with calcinated clay for low and intermediate gamma-ray energy applications. The increased calcinated clay material concentration between 0 and 60 wt% enhances the constructed composites by 21.07%, from 1.139 ± 0.011 to 1.379 ± 0.013 g·cm−3. Moreover, new bonds have appeared in Fourier transform infrared analyses of fabricated composites, which confirm the diffusion and interactions between the calcinated clay material and epoxy resin. Furthermore, the impacts of the calcinated clay on the gamma-ray shielding properties were examined experimentally using the NaI (Tl) detector over an energy interval changing from 33 to 1,408 keV. The experimental examinations depict that the addition of calcinated clay with concentrations between 0 and 60 wt% enhances the developed composites’ linear attenuation coefficient by 67.9%, 24.5%, 35.9%, and 46.0% at gamma-ray energies of 81, 662, 1,275, and 1,408 keV, respectively. The improvement in the linear attenuation coefficient leads to a decrease in the required half-value layer for each composite, where it decreased between 4.82–3.87 cm (at 662 keV) and 7.63–5.22 cm (at 1,408 keV).

Detonation combustion represents a significant advancement in efficiency over traditional deflagration methods. This paper presents a Pulsed Detonation Combustor (PDC) model that is designed with an aerodynamic mixing chamber featuring Hartmann–Sprenger resonators and crossflow injection. This design enhances operational cycle frequency and enables sustained detonation over short distances (below 200 mm). The PDC's performance was evaluated through a comprehensive full-factorial experimental campaign, incorporating four factors with four discrete levels each. Testing was conducted using both hydrogen/air and hydrogen/oxygen mixtures, highlighting the PDC's potential as a carbon-free combustion chamber suitable for both air-breathing and space-based propulsion systems. One advantage is the versatility of our PDC breadboard, which lies in its applicability to both terrestrial and in-space applications, such as interplanetary travel or trajectory corrections. Thrust measurements were recorded using a load cell and time-averaged thrust levels were determined over the detonation cycle and are reported herein, together with the specific impulse. The results underscore the PDC's promise as an efficient propulsion technology for future aerospace applications. [ABSTRACT FROM AUTHOR]

Structural stability tests on two‐span channel members in bending, axial compression and torsion The use of slender steel members promotes the competitiveness of steel structures in structural engineering. However, these members often necessitate stability verifications. Global research activities in this field have so far mainly focussed on single‐span members with doubly symmetric cross‐sections. For mono‐symmetric sections such as channels, only a few design models exist based on experimental evidence. Moreover, the potential of structural systems such as multi‐span members is yet not entirely exploited in the normative verification models. Therefore, this paper presents a comprehensive experimental study on the stability behaviour of two‐span members with steel channels under combined loading. Five‐point bending tests were conducted to determine the load‐bearing capacities and to experimentally analyse the influence of the constructional detail of the central support, the axial load, the slenderness ratio and other parameters on the load‐bearing behaviour. The article provides the scientific basis for extending the scope of the stability verification for members subjected to bending, axial compression and torsion in Annex C.2 of the novel EN 1993‐1‐1:2022 to two‐span channel members. [ABSTRACT FROM AUTHOR]

Steel‐free wedge connection made of prestressed carbon concrete – Kappa QX and Kappa QXL In November 2021, the CPC concrete panels (carbon prestressed concrete) received national technical approval from the DiBt in Germany. The area of application has so far been limited to simple load‐bearing structures mainly subject to bending stress, such as balcony slabs, stair treads or plank decks for bridges and landing stages. In order to enable complex load‐bearing structures that do not require steel or adhesive connections, the high‐load‐bearing plug‐in connection system called Kappa was developed at the ZHAW in collaboration with CPC. The connection system consists solely of CPC concrete slabs and hydraulic mortar. The load‐bearing method and the surprisingly high mechanical values are recorded below. [ABSTRACT FROM AUTHOR]

Belled piles are increasingly being employed for transmission tower foundations in the mountainous regions of Western China, but their uplift behavior is not fully understood. This paper presents experimental investigations of the pull-out behavior of belled piles in horizontal and inclined ground (overlying soil and underlying soft rock). 3D non-linear finite element analyses related to the model tests were also conducted using ABAQUS software, and the influence of slope effect on the ultimate uplift capacity of rock-socketed belled piles was evaluated. The results demonstrated that the inclined ground led to deterioration in its uplift performance, thus increasing both the displacement of the pile cap and ground surface. When the slope angle changes between 0° and 30°, the weakening effect of the slope on the ultimate uplift capacity increases linearly. When the slope angle is increased to 45°, the weakening effect of the slope on the ultimate uplift capacity is greatly enhanced, and the relationship between the ultimate uplift capacity of belled piles in the inclined ground and the slope angle is proposed. Moreover, the failure mode of the horizontal bedrock is an inverted cone with a failure angle between 0.8 and 1.0φr (φr is the internal friction angle of bedrock). In contrast, the bedrock failure of inclined ground is bulb-shaped, and it mainly occurs within 4d (d represents pile diameter) of the downslope side. It was also discovered that the downslope side of the belled pile in the sloped ground generated cracks that directed to the pile axis if the pile top load reached 82.3% of the ultimate uplift capacity. These findings are valuable for practicing engineers in the rational design of belled piles, taking account of the weakening effect of inclined ground. Highlights: Reveal the adverse effect of inclined ground on the uplift bearing deformation characteristics of the belled pile. It is clarified that the failure mode of rock-socketed belled piles in inclined ground varies with the slope angle through model test and 3D numerical method. Propose an empirical relationship to quantify the ultimate uplift capacity of rock-socketed belled piles in inclined ground and the slope angle. [ABSTRACT FROM AUTHOR]

Despite the proven effectiveness of rehabilitation robots (RR) in the literature, they are still little used in clinical rehabilitation. The aim of this study was to analyse the factors influencing the use of RR and the perception of therapists who used RR. In order to characterize the factors influencing the use of RR by therapists, a semi-structured interview was conducted with 18 therapists. These interviews are based on an interview guide inspired by the Unified Theory of Acceptance and Use of Technology model. The interviews were recorded and then transcribed, summarized and finally synthesized cross-sectionally. In addition and in parallel, the System Usability Scale (SUS) was also proposed to clinicians in order to collect quantitative data. The interviews highlight the facilitators perceived by the therapists, such as the intensity of the movement, the complementarity with conventional rehabilitation. The results also showed the possible barriers perceived, these can be sometimes inconclusive (e.g., bugs). The SUS results show no effect, either on the gender of the users, their therapists, or the duration of use of the tool. Better communication on the functionality of the robot and the construction of achievable goals would lead to more results that are conclusive but also better patient care. To date, and despite the evidence for the effectiveness of RRs, therapists believe that there are still many barriers to their use. They agree, however, that if changes are made, RRs will become an integral part of therapy. The study idenfied and highlighted the factors influencing the use of the rehabilitation robot in the clinics through metric and ergonomic evaluations. The study allowed to quantify the level of acceptance of the Lokomat among therapists. This study allowed to identify negative factors that could be resolved through the implementation of a structured and generalized protocol for patients and thus improve their care. [ABSTRACT FROM AUTHOR]

This paper is dedicated to the memory of Dr. Miklós Iványi, who instilled in the authors an appreciation for experimental investigations, which are foundational to understanding material and structural behavior. Timber-concrete composite structures are increasingly adopted for new buildings due to their favorable sustainability parameters and the increased availability of cross laminated timber. For larger spans, however, solid timber floors lead to higher timber volumes and the use of glulam beams may become necessary for a more efficient use of wood. This paper presents laboratory tests of glulam-concrete composite beams and is the first in a series of two papers on investigating the associated failure mechanisms. Three full-scale glulam-concrete beam specimens were studied. The glulam and concrete are monolithically interconnected using a continuous layer of adhesive. Shear reinforcement was added to the glulam beams to allow for failure mode control. Static load tests to failure were conducted along with acoustic emission monitoring to track the progression of the failure. The results indicate that the shear reinforcement of the glulam layer affects the load capacity of the composite beam through shifting the failure from a shear to a tension failure mode. Similar glulam-concrete beams can enable larger span applications for buildings and bridges while maintaining an attractive sustainability performance. [ABSTRACT FROM AUTHOR]

This study provides a detailed analysis of the aerodynamic performance of various airfoil configurations, focusing on lift coefficient, stall characteristics, and maximum lift-to-drag ratio. The investigation includes the NACA23012C profile and configurations with different step geometries, ranging from one-step to five-step designs. Experimental measurements were conducted using a well-equipped aerodynamic laboratory, Institute of Aviation Engineering and Technology (IAET), Giza, Egypt. The lab features a wind tunnel, propeller test rig, and data acquisition system. The experiments were conducted meticulously to ensure accuracy and reproducibility, with a standardized method employed for uncertainty analysis. The results reveal distinct aerodynamic behaviors among the different configurations, highlighting the significant impact of design variations on aerodynamic performance. Notably, the three-step configuration consistently exhibited high performance, with a competitive or superior lift coefficient across a range of Reynolds numbers, showing an improvement of up to 35.1 %. Similarly, the four-step configuration demonstrated substantial increases in lift-to-drag ratios, reaching up to 53.2 %, while the five-step configuration exhibited varying trends with a minimum drag coefficient. The study also investigated stall characteristics and sensitivity to Reynolds numbers, revealing the complex trade-offs inherent in airfoil design. The findings provide valuable insights into optimizing airfoil performance under different operational conditions. Additionally, the adoption of two and three stepped airfoils resulted in significant reductions in blade material and associated costs for turbine blades.

Load bearing behaviour of beam‐series structures – Recommendations and remarks on the computational evaluation of beam series structures on the basis of experimental inverstigations The verification formats from the german guideline „Nachrechnungsrichtlinie" and its supplement are applicable for numerous bridge systems in the Western states of Germany (Republik of Germany until 1990). The transferability to a large part of the older bridge structures in the new German states (former German Democratic Republic) is problematic. The structures have special specifications or designs, as they were only executed in the former GDR. In particular, the so‐called beam‐row structures are still widespread, both in the stock of the state building authorities and of municipalities. Due to their frequency and their special design, adapted calculation approaches would greatly facilitate the evaluation of these structures. In the GDR, prestressing steel from Hennigsdorf was used almost exclusively, which is considered to be susceptible to stress corrosion cracking. Nevertheless, it is generally assumed that this type of structure is not affected by prefabricated structures today. The following article describes the background and calculation recommendations for this particular bridge type. The findings are based on experience gained from the dismantling of a beam‐row structure in the course of the A 19. Here, the unique opportunity arose to carry out investigations on a bridge superstructure that was designed as a beam‐row structure. The following article summarizes the elementary results and gives recommendations for the computational evaluation. [ABSTRACT FROM AUTHOR]

Recently, there has been a growing interest in the use of sandwich panels that, beyond handling well-known bending stress, can withstand torsional stresses. This is particularly relevant for wall applications when the panels are equipped with photovoltaic or supplemental curtain wall modules. This research article presents a detailed exploration of the structural behavior of eccentrically loaded sandwich panels, with a specific focus on warping torsion. Experimental and numerical studies were conducted on polyisocyanurate (PU) core sandwich panels, commonly employed in building envelopes. These studies involved various dimensions and material properties, while omitting longitudinal joints. The experimental study provided essential insights and validated the numerical model in ANSYS. Enabling parametric variation, the numerical analysis extends the analysis beyond the experimental scope. Results revealed a high degree of correlation between experimental, numerical, and analytical solutions, regarding the rotation, as well as the normal and shear stress of the panel. Confirming the general applicability of warping torsion in sandwich panels with certain limitations, the study contributes valuable data for applications and design of eccentrically loaded sandwich panels, laying the foundation for potential engineering calculation methods. [ABSTRACT FROM AUTHOR]

In the modern theory of compressed concrete elements, the most attention is paid to longitudinal deformations, whereas transverse ones are rarely considered and just within Poisson's coefficient limits (i.e., elastic concrete behavior in the transverse direction). However, transverse deformations significantly develop beyond the limits corresponding to Poisson's coefficient, where they lead to longitudinal crack initiation and development. In-depth experimental and numerical investigations of transverse deformations in the inelastic stage showed that it is necessary to consider crack propagation. The present study proposes simultaneous consideration of longitudinal and transverse deformations, as well as the appearance of cracks and their widths and depths. This allowed us to obtain a complete compressed concrete element behavior pattern at all performance stages in two types of limit states (based on longitudinal and transverse deformations). Consequently, new ultimate limit states by the depth and width of cracks caused by transverse deformations are proposed to be included in modern design practices and codes. [ABSTRACT FROM AUTHOR]

The experimental investigations performed in this work and practice have shown that the main defects significantly reducing the service life of enamel-coated pipes are the roughness of the inner surface of a pipe and the presence of small bubbles and layers of macro- and microcracks. The problem of the occurrence of defects in the enamel coating that destroy the integrity of the enamel is considered in this article. The causes of these defects are associated with an incorrect choice of the technological regime when applying an enamel coating to the inner surface of the pipes. The choice of the technological regime on application of a coating depends on the geometric dimensions and technological parameters of the pipes. It is known that imprecise implementation of the technology for applying enamel coatings to the inner surface of pipes effects the formation of microcracks. Taking this into account, the main objectives of this work are to automatically adjust the parameters of the technological regime of the device and to adjust the control system so as to prevent the formation of microcracks during coating application and to improve the automatic regulation of the process. [ABSTRACT FROM AUTHOR]

Experiments have been performed to investigate the efficiency of the process of thermostabilization of a high-temperature surface with dispersed flow of a heat transfer agent at a pressure of 0.2–0.6 MPa in it and at a mass rate of flow of heat transfer agent of (3.3–6.15)·10–3 kg/s and a surface sprinkler density of 1.67–3.11 kg/(m2·s). Assessments have been made of the amount of heat transfer agent evaporating in all investigated heat transfer regimes. An equation describing various heat transfer regimes has been obtained for heat transfer from a high-temperature surface to a dispersed flow of a heat transfer agent in a criterial form. Criterial equations qualitatively describe experimental data within a small error, which indicates their satisfactory reproducibility in the said range of regime parameters of the process. [ABSTRACT FROM AUTHOR]

An existing hydroelectric facility affected by alkali–aggregate reaction (AAR) is considered in this study through numerical and experimental investigations. A new developed phenomenological hygro–chemo–mechanical approach for AAR is presented and is shown to be practical and effective in damage assessing of large-scale hydraulic concrete structures. Experimental investigations were conducted to characterize the AAR kinetics of mass concrete mixture with very large aggregates, used in the construction of the facility. By combining experimental, numerical, and monitoring investigations, it was possible to assess size effects related to the free AAR expansion of mass concrete. Numerical simulations allowed to obtain a damage pattern similar to the cracking profile of the existing facility, to provide mechanical interpretation of the jumps observed in the instrumentation data, and most importantly, to predict the remaining time before reaching the asymptotic expansion of the facility: a very important result for owners of hydroelectric facilities affected by AAR. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive dataset comprising experimental test data and numerical simulations of hole bearing tests involving 32 single-bolt, 20 two-bolt, and 20 four-bolt specimens. The dataset encompasses load-deformation curves obtained from experimental tests and displacement data acquired via the Digital Image Correlation (DIC) system, which covers specific regions of the specimens. Additionally, the dataset incorporates force-deformation curves derived from corresponding numerical simulations.The numerical simulation procedure is outlined, involving a simplified model employing solid elements for the specimen and rigid shell elements for the bolts. A “hard-contact” is employed to define the normal behavior of surface-to-surface contact between the specimen and the bolts. Material behavior modeling utilizes true stress–strain curves obtained from experimental tensile tests, encompassing both material properties extracted from these tests and the ensuing input parameters for numerical simulations.Furthermore, the DIC-system measurements provide data on displacements and strain distributions across various regions of the specimens. These strain measurements are meticulously evaluated and presented.The validation of the numerical simulations against experimental results substantiates the robustness of the numerical methodology, instilling confidence in its application for simulating bearing-type connections. Moreover, this dataset serves as a valuable resource for comparative analysis, enhancing the comprehension of these connections, and providing reference points for further numerical simulations.

This study delves into the dynamic behavior of ultra-high-speed rotor systems underpinned by helium hydrostatic gas bearings, with a focus on the impact of rotational velocity on system performance. We have formulated an integrative dynamic model that harmonizes the rotor motion equation with the transient Reynolds equation. This model has been meticulously resolved via the Finite Difference Method (FDM) and the Wilson-Θ technique. Our findings unveil intricate nonlinear dynamics, including 2T-periodic and multi-periodic oscillations, and underscore the pivotal role of first-order temporal fluctuations, which account for over 20% of the transient pressure at rotational speeds exceeding 95.0 krpm. Further, we have executed empirical studies to evaluate the system’s performance in practical settings. It is observed that when the ratio of low-frequency to fundamental frequency approaches 0.3 and the amplitude ratio exceeds 3, the vigilant monitoring of system stability and reliability is imperative. Collective insights from both computational simulations and experimental studies have enriched our understanding of the dynamic attributes of ultra-high-speed rotor systems. These revelations are crucial for the advancement of more efficacious and resilient rotor systems designed for high-speed applications.

In turbomachinery, geometric variances of the blades, due to manufacturing tolerances, deterioration over a lifetime, or blade repair, can influence overall aerodynamic performance as well as aeroelastic behaviour. In cooled turbine blades, such deviations may lead to streaks of high or low temperature. It has already been shown that hot streaks from the combustors lead to inhomogeneity in the flow path, resulting in increased blade dynamic stress. However, not only hot streaks but also cold streaks occur in modern aircraft engines due to deterioration-induced widening of cooling holes. This work investigates this effect in an experimental setup of a five-stage axial turbine. Cooling air is injected through the vane row of the fourth stage at midspan, and the vibration amplitudes of the blades in rotor stage five are measured with a tip-timing system. The highest injected mass flow rate is 2% of the total mass flow rate for a low-load operating point. The global turbine parameters change between the reference case without cooling air and the cold streak case. This change in operating conditions is compensated such that the corrected operating point is held constant throughout the measurements. It is shown that the cold streak is deflected in the direction of the hub and detected at 40% channel height behind the stator vane of the fifth stage. The averaged vibration amplitude over all blades increases by 20% for the cold streak case compared to the reference during low-load operating of the axial turbine. For operating points with higher loads, however, no increase in averaged vibration amplitude exceeding the measurement uncertainties is observed because the relative cooling mass flow rate is too low. It is shown that the cold streak only influences the pressure side and leads to a widening of the wake deficit. This is identified as the reason for the increased forcing on the blade. The conclusion is that an accurate prediction of the blade’s lifetime requires consideration of the cooling air within the design process and estimation of changes in cooling air mass flow rate throughout the blade’s lifetime.

Detonation combustion represents a significant advancement in efficiency over traditional deflagration methods. This paper presents a Pulsed Detonation Combustor (PDC) model that is designed with an aerodynamic mixing chamber featuring Hartmann–Sprenger resonators and crossflow injection. This design enhances operational cycle frequency and enables sustained detonation over short distances (below 200 mm). The PDC’s performance was evaluated through a comprehensive full-factorial experimental campaign, incorporating four factors with four discrete levels each. Testing was conducted using both hydrogen/air and hydrogen/oxygen mixtures, highlighting the PDC’s potential as a carbon-free combustion chamber suitable for both air-breathing and space-based propulsion systems. One advantage is the versatility of our PDC breadboard, which lies in its applicability to both terrestrial and in-space applications, such as interplanetary travel or trajectory corrections. Thrust measurements were recorded using a load cell and time-averaged thrust levels were determined over the detonation cycle and are reported herein, together with the specific impulse. The results underscore the PDC’s promise as an efficient propulsion technology for future aerospace applications.

PurposeTo evaluate the feasibility and accuracy of simulated postcontrast T1-weighted brain MR images generated by using precontrast MR images in patients with brain glioma.Materials and methodsIn this retrospective study, a three-dimensional deep convolutional neural network was developed to simulate T1-weighted postcontrast images from eight precontrast sequences in 400 patients (mean age, 57 years; 239 men; from 2015 to 2020), including 332 with glioblastoma and 68 with lower-grade gliomas. Performance was evaluated by using quantitative image similarity and error metrics and enhancing tumor overlap analysis. Performance was also assessed on a multicenter external dataset (n = 286 from the 2019 Multimodal Brain Tumor Segmentation Challenge; mean age, 60 years; ratio of men to women unknown) by using transfer learning. A subset of cases was reviewed by neuroradiologist readers to assess whether simulated images affected the ability to determine the tumor grade.ResultsSimulated whole-brain postcontrast images were both qualitatively and quantitatively similar to the real postcontrast images in terms of quantitative image similarity (structural similarity index of 0.84 ± 0.05), pixelwise error (symmetric mean absolute percent error of 3.65%), and enhancing tumor compartment overlap (Dice coefficient, 0.65 ± 0.25). Similar results were achieved with the external dataset (Dice coefficient, 0.62 ± 0.27). There was no difference in the ability of the neuroradiologist readers to determine the tumor grade in real versus simulated images (accuracy, 87.7% vs 90.6%; P = .87).ConclusionThe developed model was capable of producing simulated postcontrast T1-weighted MR images that were similar to real acquired images as determined by both quantitative analysis and radiologist assessment.Keywords: MR-Contrast Agent, MR-Imaging, CNS, Brain/Brain Stem, Contrast Agents-Intravenous, Neoplasms-Primary, Experimental Investigations, Technology Assessment, Supervised Learning, Transfer Learning, Convolutional Neural Network, Deep Learning Algorithms, Machine Learning Algorithms Supplemental material is available for this article. © RSNA, 2021.

Rutting is the most common and most dangerous defect of asphalt pavements. One of the problems of northern countries such as the Russian Federation is abrasive rut due to studded tire loading. Precise prediction of the asphalt concrete abrasion and wear resistance allows improving the durability and reliability of asphalt pavements. Several laboratory tests are used for the prediction of asphalt concrete abrasion resistance. An abrasive wear model of asphalt concrete is needed to predict wear resistance changes under different conditions. The aim of this article is to evaluate compaction quality effect and air voids value on the abrasion resistance of asphalt concrete. To estimate the influence of the percentage of connected voids on abrasive wear of asphalt concrete, an asphalt wear model was presented. This model is based on G.Y. Lee’s approach. This approach divides the abrasive processes into normal abrasion and particle loss. Air voids lead to the aggregate loss and affect the abrasion resistance of the asphalt pavements. Calculation of these effects is possible using G.Y. Lee’s approach. Calculations of the lost particles include the empirical coefficient (1/mm) characterizing the influence of the pores on the lack of adhesion to the aggregate particle surface and the influence of the lack of adhesion on the fraction of lost particles. The Prall test was used for the abrasion resistance estimation. The saturation degree method was used for the estimation of compaction quality and air voids content. For the coefficient estimation, 63 samples of different mixes were tested. The mixes were used for the construction of the Republic of Tatarstan road network. The used asphalt concretes correspond to requirements of Russian standards GOST 9128-2013 and GOST 31015-2002. The experiments show good reliability of the presented model. This model predicts abrasion resistance of asphalt concretes under uncompaction and provides insight into the abrasive wear processes in the asphalt concretes. Furthermore, the study results allow us to improve the laboratory tests precision by 2.3 % by excluding the uncompaction effect during the comparison of the results.

Nails in wood construction – fundamental research and continuous standardisation The nail as a load‐bearing timber fastener is well known today. But 100 years ago, it was different: its structural use was not allowed. This changed with the beginning of systematical research at the end of the 1920s. Since 1933, the nail has been part of the German regulations and has been widely used ever since. For much of the 20th century, it served as the highly efficient fastener of choice especially in roof structures such as board and plank trusses. These material‐saving load‐bearing structural elements were always in demand due to the periodically recurring scarcity of material resources and are an important part in construction history. The following article deals with the research of the load‐bearing behaviour of nails and the standardisation that has constantly accompanied it. The achievements of individual research projects are presented. A timeline shows the connections between research and standardisation. Tables and graphics illustrate the changes within the standards from the first DIN 1052 in 1933 to the first independent timber construction standard in the DDR, TGL 112‐0730, from 1963 to DIN 1052‐1988. Reference is always made to the Eurocode 5 valid today. In general, it can be seen that a large part of today's knowledge still goes back to the basic research of the 1930s. [ABSTRACT FROM AUTHOR]

A large number of structures in various fields are repeatedly subjected to dynamic loading during their lifetime. To avoid or reduce vibration amplitudes possibly occuring, the use of vibration damping measures is necessary. Due to their inherent material damping, viscoelastic adhesives show a potential to reduce the dynamic effects of structures. This has not yet been comprehensively investigated for adhesively bonded joints. This paper reports on experimental and numerical investigations of damping properties of adhesively bonded tubular steel joints in a scale relevant for construction industry and thus represents a fundamental data set. Different adhesive joint geometries and test parameters were investigated experimentally and their influence on the damping properties of adhesively bonded specimens is discussed and evaluated. The test results show that the damping properties of adhesively bonded joints can be enhanced by increasing the adhesive layer thickness and reducing the overlap length. In addition, the damping properties of the test specimens increase with a rise in the stress on the adhesive layer. The influence of the test frequency on the loss factor is of secondary importance. Furthermore, material models of the adhesives used were developed and validated successfully on the basis of the experimental test result presented. [ABSTRACT FROM AUTHOR]

Results are presented of an experimental investigation into the structure of a steady-state air flow in a cylinder of reciprocating internal combustion engines with intake systems of various designs when it is filled through a poppet valve on the basis of the method of thermal visualization imaging. It has been established that cross profiling of cylinder inlet pipes has a substantial effect on the structure of the flow in it. It is shown that the use of square and triangular pipes makes it possible to obtain a more uniform flow distribution through the cylinder volume compared to pipes of other configurations, which ensures a more complete combustion of the fuel–air mixture and, accordingly, an improvement of technical-economic and environmental performance of a piston engine. [ABSTRACT FROM AUTHOR]

As part of the experiments, 4-point-bending tests to investigate the shear capacity of strengthened T-beams were carried out. Thereby, 5 reference beams and 25 T-beams with carbon reinforced concrete strengthening were tested. Two different impregnated carbon grids in various strengthening configurations at the beams' webs were checked. The number of strengthening layers was varied as well as the orientation of the grid in the strengthening layer. Furthermore, the influence of pre-damage of the RC beam before strengthening and two different shear slendernesses were investigated. A load increase of 25% to 42% compared to the unstrengthened reference specimens demonstrates the capability of carbon concrete for shear strengthening. In addition to the presentation of tested large-scale specimens, a test analysis will also be conducted, along with the derivation of a limit value for the maximum possible strengthening ratio using carbon-reinforced concrete based on the observed failure modes. [ABSTRACT FROM AUTHOR]

State‐of‐the‐art stability design methods of the current and future Eurocode 3 are based on idealized, simply supported members with fork restraints. However, in real‐world structural engineering applications, continuous members or frame structures are more common. The verification of these members often requires complex geometrically nonlinear computations. This paper addresses the extension of simplified methods to structural systems. The basis is laid with experimental, numerical and analytical studies on the stability behavior of two‐span members with doubly symmetric I‐sections in bending, axial compression and torsion. Five‐point bending tests were conducted to analyze the buckling behavior of two‐span members. The experimental results validate a numerical model subsequently used to extend the data basis. A comparison of the numerical load capacities with the results of the simplified method for the buckling resistance according to Annex C.2 of EN 1993‐1‐1:2022 reveals the method's applicability. The sensitivity analysis of the method to various parameters identifies potential for improvement concerning the capture of the influence of bending moments about the weak axis and warping moments, as well as the influence of lateral‐torsional buckling for stocky members. [ABSTRACT FROM AUTHOR]

As recent research findings evidenced a significant potential of the steel‐concrete hybrid coupled wall (HCW) systems, further research activities are still needed for addressing particular issues and for developing advancements in the analysis, design, and detailing. These aspects are currently being addressed within the ongoing European research project "HYCAD", which also represents the research framework of the current study. This paper investigates through a set of nonlinear static and dynamic analyses the behavior and the seismic performance of a newly introduced steel‐concrete HCW system. In particular, a case‐study was carried out on a 3D multi‐story building structure with perimeter lateral load resisting frames, each composed of: (i) a HCW, i.e. a steel‐concrete composite wall coupled to steel columns through a set of replaceable steel shear links; (ii) a moment resisting frame (MRF). Beside a brief state of the art, a description of the research framework and the case‐study structural system, the current paper makes an overview of the following: (i) experimental program on components; (ii) proposed technical solution for connecting the replaceable dissipative shear links to the composite wall; (iii) experimental test set‐up; (iv) response of the shear links based on pretest FE investigations; (v) seismic demand in terms of rotation for the shear links. [ABSTRACT FROM AUTHOR]

Strong earthquake loads can cause significant damage to buildings, but even moderate earthquakes with higher return periods are socially relevant as they may cause both infrastructure and economic failures. In an ongoing German nationally funded research project, the behavior of facade elements in lightweight metal construction under in‐plane deformation is currently being investigated with the aim to assess the response and the energy dissipation capacity in the case of seismic events. As past research results indicate the contribution of wall and roof elements to the stiffening of buildings, with the possible consequence of increased earthquake loads due to the natural frequency change, a novel approach for increased resilience of structures with building envelopes in lightweight metal construction may be developed. On the basis of a series of experimental tests, under monotonic and cyclic loading, the effects of in‐plane deformation were studied separately from external influences such as wind and thermal loads. This paper presents: (i) a brief state of the art; (ii) a description of the research framework; (iii) the experimental program; (iv) the specimen configuration, test set‐up, loading protocol and instrumentation; (v) the response under monotonic and cyclic loading; (vi) the main conclusions, as well as the ongoing and future research activities. [ABSTRACT FROM AUTHOR]

Steel rolled I shape beam‐columns, especially of narrow flange sections unrestrained between the end supports are sensitive to flexural‐torsional buckling. In order to increase their resistance, in‐span lateral‐torsional restraints are applied. Experimental investigations into the behaviour of steel rolled I‐section beam‐columns under moment gradient are presented in this paper. The beam‐column tested is restrained laterally and torsionally in a mid‐length. The experimental setup and testing procedures are described. A total number of 5 specimens (used for 9 tests with different proportions between the dimensionless maximum bending moment and compressive force) were designed. Test measurements and observations are reported. Finally, the experimental resistance results are compared with those of the preliminary finite element model made available in ABAQUS. [ABSTRACT FROM AUTHOR]

Vibratory technological machines are widely implemented in various branches of industrial, manufacturing, and mechanical engineering. Particularly, such equipment can be effectively used while conducting finishing technological operations, e.g., lapping and polishing of different machine parts. The present paper is focused on developing the control system for the novel design of a vibratory lapping-polishing machine driven by six solenoids. The main purpose consists in providing the circular trajectory of the working member and ensuring the machining uniformity at each point of the surface being treated. In such a case, it is proposed to actuate the solenoids with the specified time shift depending on the forced frequency needed to be provided. The duration of the signal actuating the solenoid is equal to one-sixth of the total duration of a cycle (period) of the working body oscillation. The corresponding control approach is developed and simulated in the Tinkercad application, while the control system is designed based on the Arduino software and hardware. In addition, the laboratory prototype of the vibratory lapping-polishing machine and the corresponding control system are implemented in practice. The performed experimental investigations substantiate the possibilities of generating the circular oscillations of the working member of the vibratory lapping-polishing machine. The obtained results may be useful for engineers and technologists dealing with control systems of various vibratory technological equipment based on electromagnetic and solenoid-type drives. [ABSTRACT FROM AUTHOR]

Homogenized micro-crack crushing can fully retain the bearing capacity of concrete pavement, but local weak road base needs to be reinforced before being directly overlaid with hot-mixed asphalt. Therefore, indoor tests were conducted to study the mechanical properties of slag-based geopolymer as a grouting material for weak road base, and the morphology and influence of polymerization reactants were observed. Concurrently, on-site grouting tests were conducted to study the grouting effect. The results show that the compressive strength, flexural strength and bonding strength of slag-based geopolymer all increase with age. The maximum compressive strength and flexural strength of the geopolymer at 28 d were 18.88 MPa and 6.50 MPa, respectively. The maximum flexural bonding strength at 14 d was 4.58 MPa. As the ratio between water and slag powder increased, the compressive strength and flexural strength gradually decreased, while the bonding strength first increased and then decreased. In the range of ratios of water to slag powder from 0.26 to 0.28, the above three strengths were relatively high, and the compressive shear bonding strength was the highest when the ratio of water to slag powder was 0.28. The shrinkage of the slag-based geopolymer increases with the increase in ratio of water to slag powder, and the porosity also increases, resulting in a decrease in compactness after consolidation. When the ratio of water to slag powder was 0.28, the reactant was mainly a gel-phase material, and the shrinkage crack of the consolidated geopolymer was relatively small. After grouting the weak road base of the concrete pavement, the voids at the bottom of the concrete pavement slab were effectively filled, and the deflection of the pavement slab was significantly reduced. The average deflections of monitoring line I, monitoring line II and monitoring line III decreased by 49%, 41% and 54%, respectively, after grouting. After solidification, the slag-based geopolymer was distributed in layers, which further compacted the road structure layer and improved the bearing capacity. [ABSTRACT FROM AUTHOR]

The results of theoretical and experimental investigations of the influence of scale deposits on heat-transfer processes in glass-lined pipes laved by sea water are presented. Experimental investigations have shown that on long-term operation of heat exchangers, very insubstantial deposits of scale with layer thickness reaching 0.4 mm are observed on the surface of the glass coatings of the pipes, while a firm layer of scale up to 2 mm thick is formed on the inner surfaces of metal pipes. The virtual absence of deposits in glass-lined vitrified pipes is due to the heightened purity of the glass surface and its resistance to the aggressiveness of substances dissolved in sea water. This excludes the formation of large foci of scale on the glass surface, and the flow of sea water washes away the resulting scale. [ABSTRACT FROM AUTHOR]

Various methods have been developed to produce deck slabs for steel–concrete composite bridges. Usually, the deck slabs are cast with in situ concrete using a formwork carriage, resulting in construction progress of 15 to 25 m of deck slab per week. A new construction method was developed at the Institute of Structural Engineering (TU Wien), which enables the swift erection of the concrete deck slab. This method employs precast deck slab elements with reinforced concrete cross-beams which span in the transverse direction. With this new construction method, producing up to two deck slab sections of 15–25 m per day becomes possible. Further, the performance of novel reinforcement detailing required for the precast deck slab elements is investigated by structural testing. The experiments consist of eight load-bearing tests on four specimens which represent sections of the element during casting and after completion. The investigated parameters in series 1 are the length and spacing of loops, used for protruding longitudinal bars enclosure. In series 2, the enclosure of the shear reinforcement and the height of the cross beams are varied. The results show that the targeted bending capacity could be reached in all tests with no signs of premature failure due to detailing reasons. Based on the experimental results, the feasibility of the new approach is shown and recommendations for detailing are given. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a new approach for the modelling of post-tensioned beams with calibration of the FE model to experimental results until the load capacity and post-critical state are reached. Two post-tensioned beams with different nonlinear tendon layouts were analysed. Material testing for concrete, reinforcing steel and prestressing steel was performed prior to the experimental testing of the beams. The Hypermesh program was used to define the geometry of the spatial arrangement of the finite elements of the beams. The Abaqus/Explicit solver was used for numerical analysis. The concrete damage plasticity model was used to describe the behaviour of concrete with different laws of elastic–plastic stress–strain evolution for compression and tension. Elastic-hardening plastic constitutive models were used to describe the behaviour of steel components. An effective approach to modelling the load was developed, supported by the use of Rayleigh mass damping in an explicit procedure. The presented model approach ensures good agreement between numerical and experimental results. The crack patterns obtained in concrete reflect the actual behaviour of structural elements at every loading stage. Random imperfections found during experimental studies on the results of numerical analyses were also discussed. [ABSTRACT FROM AUTHOR]

Although the blast furnace process is the dominant ironmaking route to supply the feedstocks for steelmaking, a number of alternative ironmaking technologies such as the direct reduction process have grown rapidly in recent decades. This development is largely in response to the increasingly stringent emission control policies, rising costs of energy, and the increasing costs and environmental effects of coke usage. In direct reduction processes, iron oxides are reduced to iron at a temperature below its melting point. More than 79% of direct reduced iron is produced by Midrex and Energiron, both of which use gas‐based shaft furnaces. A proper understanding of these processes is required to improve the performance and operation of the plants based on them. Therefore, herein, it is aimed to provide a comprehensive review of research that is carried out over the last several decades to examine the effects of the important phenomena on the performance of the gas‐based shaft furnaces. The review is divided into experimental and mathematical investigations. The main features, limitations, and shortcomings of each study are discussed. Finally, the review concludes with current knowledge gaps and suggestions for further research in this thriving sector of the steel industry. [ABSTRACT FROM AUTHOR]

It is widely recognized that the quality of fruits and vegetables can be altered during transportation and storage. Firmness and loss of weight are the crucial attributes used to evaluate the quality of various fruits, as many other quality attributes are related to these two attributes. These properties are influenced by the surrounding environment and preservation conditions. Limited research has been conducted to accurately predict the quality attributes during transport and storage as a function of storage conditions. In this research, extensive experimental investigations have been conducted on the changes in quality attributes of four fresh apple cultivars (Granny Smith, Royal Gala, Pink Lady, and Red Delicious) during transportation and storage. The study evaluated the weight loss and change in firmness of these apples varieties at different cooling temperatures ranging from 2 °C to 8 °C to assess the impact of storing at these temperatures on the quality attributes. The results indicate that the firmness of each cultivar continuously decreased over time, with the R2 values ranging from 0.9489–0.8691 for red delicious, 0.9871–0.9129 for royal gala, 0.9972–0.9647 for pink lady, and 0.9964–0.9484 for granny smith. The rate of weight loss followed an increasing trend with time, and the high R2 values indicate a strong correlation. The degradation of quality was evident in all four cultivars, with temperature having a significant impact on firmness. The decline in firmness was found to be minimal at 2 °C, but increased as the storage temperature increased. The loss of firmness also varied among the four cultivars. For instance, when stored at 2 °C, the firmness of pink lady decreased from an initial value of 8.69 kg·cm2 to 7.89 kg·cm2 in 48 h, while the firmness of the same cultivar decreased from 7.86 kg·cm2 to 6.81 kg·cm2 after the same duration of storage. Based on the experimental results, a multiple regression quality prediction model was developed as a function of temperature and time. The proposed models were validated using a new set of experimental data. The correlation between the predicted and experimental values was found to be excellent. The linear regression equation yielded an R2 value of 0.9544, indicating a high degree of accuracy. The model can assist stakeholders in the fruit and fresh produce industry in anticipating quality changes at different storage stages based on the storage conditions. [ABSTRACT FROM AUTHOR]