Model Calculations Research Articles

First-principles study and mesoscopic modeling of two-dimensional spin and orbital fluctuations in FeSe

We calculated the structural, electronic, and magnetic properties of FeSe within density-functional theory at the generalized gradient approximation level. First, we studied how the bandwidth of the d-bands at the Fermi energy is renormalized by adding simple corrections: Hubbard U, Hund's J, and by introducing long-range magnetic orders. We found that introducing either a striped or a staggered dimer antiferromagnetic order brings the bandwidths—which are starkly overestimated at the generalized gradient approximation level—closer to those experimentally observed. Second, for the ferromagnetic, the striped, checkerboard, and staggered dimer antiferromagnetic order, we investigate the change in magnetic formation energy with local magnetic moment of Fe at a pressure up to 6 GPa. The bilinear and biquadratic exchange energies are derived from the Heisenberg model and noncollinear first-principles calculations, respectively. We found a nontrivial behavior of the spin-exchange parameters on the magnetization, and we put forward a field-theory model that rationalizes these results in terms of two-dimensional spin and orbital fluctuations. The character of these fluctuations can be either that of a standard density wave or a topological vortex. Topological vortices can result in mesoscopic magnetization structures. Published by the American Physical Society 2024

Analysis of Water Film Distribution and Aerodynamic Performances of High-Speed Train Under Rainfall Environment

AbstractThe current research on the aerodynamic performance of the train running in rainy weather is primarily concerned with the trajectory of the raindrops and the aerodynamic variation of trains caused by raindrops. In fact, water film will generate on the train body when raindrops hit the train, which interacts with the flow field around the train, and would probably affect the aerodynamic performance of the train. In this paper, based on shear stress transport (SST) k-w turbulence model and Euler-Lagrange discrete phase model, the aerodynamic calculation model of a high-speed train under rainfall environment is established. The LWF (Lagrangian wall film) is used to simulate the water film distribution of the high-speed train under different rainfall intensities, and the aerodynamic performance of the train are studied. The calculation results show that raindrops will gather on the train surface and form water film under rainfall environment. With the extension of rainfall time, the thickness and coverage range of water film expand, and the maximum thickness of water film can reach 4.95 mm under the working conditions in this paper. The average thickness of water film on the train body increases with the rainfall intensity. When the rainfall intensity increases from 100 mm/h to 500 mm/h, the average water film thickness will increase by 3.26 times. The velocity of water film in the streamlined area of head car is larger than that in other areas, and the maximum velocity is 22.14 m/s. Compared with the rainless environment condition, the skin friction coefficient of the high-speed train increases and the average value will increase by 10.74% for a rainfall intensity of 500 mm/h. The positive pressure and resistance coefficient of the head car increase with the rainfall intensity. This research proposes a methodology to systematically analyze the generation of water film on the train surface and its influence on the train aerodynamic performance; the analysis can provide more practical results and can serve as a reference basis for the design and development of high-speed trains.

A Model of Microwave Emission from Mouth Regions of Arctic Rivers Providing for Radiometer Pixel Land Contamination

The paper presents a model of microwave emission from mouth regions of Arctic rivers taking into account radiometer pixel contamination by land. Modeling of seasonal and interannual dynamics of brightness temperature of different regions of the Yenisei Bay is performed on the example of MIRAS radiometer data from the SMOS satellite. The necessity of considering the coastal zone in brightness temperature modeling in the studied regions is shown. Comparison of the model calculations with SMOS L1C data has shown a good agreement. Analysis of model calculations and satellite data has allowed us to determine the location of the fresh and salt water mixing zone in the Yenisei Bay during the ice period, provided that the model takes into account the coastal zone captured by the radiometer pixel.

DFT and Model Hamiltonian Study of Optoelectronic Properties of Some Low-Symmetry Graphene Quantum Dots.

We have studied the electronic and optical properties of three low-symmetry graphene quantum dots (GQDs), with point-group symmetries C2v and C2h. For the calculations of linear optical absorption spectra, we employed both first-principles time-dependent density-functional theory (TDDFT) and the electron-correlated Pariser-Parr-Pople (PPP) model coupled with the configuration-interaction (CI) approach. In the PPP-CI approach, calculations were performed using both screened and standard parameters, along with efficiently incorporating electron correlation effects using multireference singles-doubles CI for both ground and excited states. We assume that the GQDs are saturated by hydrogen atoms at the edges, making them effectively polycyclic aromatic hydrocarbons (PAHs) dibenzo[bc,ef]coronene (also known as benzo(1,14)bisanthene, C30H14) and two isomeric compounds, dinaphtho[8,1,2abc;2',1',8'klm]coronene and dinaphtho[8,1,2abc;2',1',8'jkl]coronene with the chemical formula C36H16. The two isomers have different point group symmetries; therefore, this study will also help us understand the influence of symmetry on the optical properties. A common feature of the absorption spectra of the three GQDs is that the first peak representing the optical gap is of low to moderate intensity, while the intense peaks appear at higher energies. For each GQD, PPP model calculations performed with the screened parameters agree well with the experimental results of the corresponding PAH and also with the TDDFT calculations. To further quantify the influence of electron-correlation effects, we also computed the singlet-triplet gap (spin gap) of the three GQDs, and we found them to be significant.

Optimization of working parameters of high-pressure roller mill based on entropy weight method and response surface method.

In order to improve the crushing efficiency of high-pressure roller mill and reduce energy consumption, the optimal parameter combination of high-pressure roller mill is sought, GM160-140 high-pressure roller mill is taken as the research object, and the discrete element simulation calculation model of high-pressure roller mill is established to simulate the crushing process. Taking the roll surface pressure, productivity, and the proportion of discharge particle diameter as the performance evaluation indexes, the simulation data are used to analyze the influence of each working condition parameter of the high-pressure roller mill on its performance law. Through the entropy weighting method to determine the weights of high-pressure roller mill productivity, roll surface pressure, the proportion of discharge particle diameter, and through the extreme difference analysis to get the optimal parameter combination. Minitab software is used to carry out the response surface method (RSM) experimental design, the optimal parameter combinations are derived from the optimization using the response surface apparatus, the optimal parameter combinations derived from the two optimization methods are compared and analyzed, and ultimately it is concluded that the optimization of the response surface is the global optimal, and the optimal parameter combinations are as follows: the roller speed is 2.50rad/s, the roller gap is 28.87mm, and the feed size is 31.97mm, Under the above optimal parameters, the roll surface pressure is 150450.00N, the productivity is 1268.00t/h, the percentage of the material less than 6mm is 58.14%, so as to achieve the purpose of optimizing the parameters of the high-pressure roller mill, It is of significance to save resources and respond to the national green development and intelligent development.

Study the Dynamics of the Transformation Processes for Nitrogen and Phosphorus Compounds in the Ecosystem of the Vistula Lagoon of the Baltic Sea using the Methods of Mathematical Modeling

By using mathematical modeling methods, a systematic study of the interaction of hydrobiological, hydrochemical, hydrological and hydrophysical processes that occur in the ecosystem of the Vistula Lagoon (VL) of the Baltic Sea was carried out, taking into account the processes in the active layer of bottom sediments (BS). The features of the dynamics of nitrogen and phosphorus compounds, the turnover time and the components of the balance of compounds of biogenic elements in the VL ecosystem, as well as the degree of their temporal variability have been analyzed. It is shown that the variability of nitrogen and phosphorus compounds in the aquatic environment increases in spring and autumn periods. This is due to an increase in river flow into the lagoon and an increase in the level of external biogenic load on the water area of the VL. Model calculations of matter fluxes allow us to state that the inputs of dissolved organic and suspended matter into the lagoon from external sources and the removal to the Baltic Sea are important processes that significantly affect their content in the VL ecosystem. It has been established that under strong winds the process of sedimentation of suspensions can be largely blocked, and the intensity of BS resuspension can increase significantly. An analysis of the main qualitative and quantitative features of the nature of the temporal dynamics of the DON and DOP turnover times, as well as the mineral compounds of nitrogen and phosphorus, indicates a close conjugation of the processes of transformation of dissolved organic and inorganic substances in the water of the VL. A quantitative assessment of the processes of consumption and excretion of compounds of biogenic elements by different groups of aquatic organisms has been performed, and the important role of heterotrophic bacterioplankton and protozoa in the processes of transformation of compounds of nutrients in the VL ecosystem has been shown. The model can be used to perform scenario modeling and analysis of possible changes in the VL ecosystem under changing climatic and anthropogenic conditions.

Risk for nitrogen leaching after application of solid manure in autumn differs between manure types

Manure application performed in autumn requires regulation due to the risk of nitrogen (N) leaching during winter. On the other hand, application of manure in spring can pose some practical problems depending on the risk for N immobilization and the difficulty in ploughing heavy clay soils during this time of year. The risk for leaching is likely to differ between different soil texture and manure characteristics. In this study, we sought to estimate the risk for nitrogen leaching depending on the carbon/nitrogen ratio (C/N) of the manure, time for manure application, and soil type. We combined 3-year lysimeter experiments with 2-year field plot experiments and laboratory soil incubations and compared results with those from an empirical model. We compared effects of manure application on two soils (silty clay and loamy sand) and solid manures with different representing C/N ratios. In incubations, only manure with a C/N-ratio below 14 contributed with significant amounts of leachable N during the first months after application. In the lysimeter study, N leaching was unaffected by the timing of the application of the manure with C/N-ratio 18. However, regarding manure with C/N-ratio 10, N leaching was elevated with 10–15 kg N per ha after manure application in October compared to November and March on both soil types. The mineral N analyses from soil profiles in the field experiments showed a similar pattern, however, the increase was higher on the loamy sand compared to the silty clay. The ammonia emissions did not differ between manure types, but were on average 24% of applied NH4-N after application in October when air temperature was on average 12°C compared to only 3% of applied NH4-N in November and March when air temperature was on average 5°C. Similar to lysimeter results, the modelled N leaching was higher the earlier the manure application occurred in autumn. However, the model also predicted increased leaching for the manure with a high C/N-ratio, and a smaller effect on leaching on clay soil. Considering this, the model calculations overestimated the leaching effects from manure with a high C/N-ratio and underestimated the leaching effects on clay soil.

Influence of Compressive Strength and Steel-Tube Thickness on Axial Compression Performance of Ultra-High-Performance Concrete-Filled Stainless-Steel Tube Columns Containing Coarse Aggregates

With the increasing use of concrete-filled steel tubular (CFST) structures, exposed steel tubes are highly susceptible to corrosion, posing potential safety hazards. This study innovatively proposes the use of stainless-steel tubes instead of traditional carbon-steel ones and introduces coarse aggregates into ultra-high-performance concrete (UHPC), forming a coarse aggregate-incorporated ultra-high-performance concrete-filled stainless-steel tube (CA-UFSST). The inclusion of coarse aggregates not only compensates for the shortcomings of UHPC but also enhances the overall mechanical performance of the composite structure. Twenty sets of specimens were designed to analyze the influence of four parameters, including the coarse aggregate content, compressive strength, stainless-steel-tube thickness, and stainless-steel type on the axial compression performance of UHPC. The experimental results indicate that the failure mode of UHPC is related to the confinement ratio. As the confinement ratio increases, the failure mode transitions from shear failure to bulging failure. The addition of coarse aggregates enhances the stiffness of the specimens. Furthermore, this paper discusses the applicability of six current codes in predicting the bearing capacity of CA-UFSST and finds that the European code exhibits the best prediction performance. However, as the confinement ratio increases, the prediction accuracy becomes notably insufficient. Therefore, it is necessary to establish a more accurate calculation model for the axial compression bearing capacity.

Investigation of geometric structure on energy performance and flow characteristics in underwater hydraulic machinery

PurposeFor underwater hydraulic machinery, the unique structure significantly enhances the three-dimensional non-uniformity of turbulence within the flow domain and high Reynolds number turbulence introduces complex effects on the machinery. Therefore, studying the turbulent flow characteristics in underwater hydraulic machinery is crucial for system stability.Design/methodology/approachThis paper conducts a numerical analysis on a specific type of underwater hydraulic machinery. A numerical calculation model is established under stable inflow conditions to analyze the flow trends and pressure changes at different flow speeds. Subsequently, structural modifications are made to the underwater hydraulic machinery, and the characteristics of the velocity field, pressure field and vorticity distribution under different model parameters are analyzed.FindingsThe results indicate that changes in internal structure have a certain impact on flow characteristics. When the structural changes are significant, the fluid flow becomes more complex and pressure fluctuations become more intense. The research findings provide a scientific basis and theoretical guidance for the structural design of underwater hydraulic machinery and have significant research implications for controlling fluid-induced noise.Originality/valueAffected by the inherent structural characteristics of the flow channel structure, the flow direction of the high-speed water flow changes drastically in the flow channel, so it is of great significance to study its flow characteristics for the stability of the system.

Carbon Footprint of Electric Vehicles—Review of Methodologies and Determinants

The carbon footprint of a product and organization is one of the most important environmental indicators in many sectors, including transport. Consequently, electric vehicles (EV) are being introduced as an alternative to achieve decarbonization targets. This article presents an overview of methodologies for assessing the carbon footprint of electric vehicles, including a review of concepts, methods, standards, and calculation models based on the life cycle of the carbon footprint. The article also includes a systematic review of the results of EV carbon footprint analyses. The analysis of current knowledge on the carbon footprint focuses on road transport vehicles: Battery Electric Vehicles (BEV), Fuel Cell Electric Vehicles (FCEV), Hybrid Electric Vehicles (HEV), and Plug-in Hybrid Electric Vehicles (PHEV). Additionally, a review of factors determining the carbon footprint assessment of electric vehicles, considering their entire life cycle, has been conducted.

Design of judicial public opinion supervision and intelligent decision-making model based on Bi-LSTM

Fuzzy preference modeling in intelligent decision support systems aims to improve the efficiency and accuracy of decision-making processes by incorporating fuzzy logic and preference modeling techniques. While network public opinion (NPO) has the potential to drive judicial reform and progress, it also poses challenges to the independence of the judiciary due to the negative impact of malicious public opinion. To tackle this issue within the context of intelligent decision support systems, this study provides an insightful overview of current NPO monitoring technologies. Recognizing the complexities associated with handling large-scale NPO data and mitigating significant interference, a novel judicial domain NPO monitoring model is proposed, which centers around semantic feature analysis. This model takes into account time series characteristics, binary semantic fitting, and public sentiment intensity. Notably, it leverages a bidirectional long short-term memory (Bi-LSTM) network (S-Bi-LSTM) to construct a judicial domain semantic similarity calculation model. The semantic similarity values between sentences are obtained through the utilization of a fully connected layer. Empirical evaluations demonstrate the remarkable performance of the proposed model, achieving an accuracy rate of 85.9% and an F1 value of 87.1 on the test set, surpassing existing sentence semantic similarity models. Ultimately, the proposed model significantly enhances the monitoring capabilities of judicial authorities over NPO, thereby alleviating the burden on public relations faced by judicial institutions and fostering a more equitable execution of judicial power.

Metal heteroatoms significantly enhance efficacy of TiO2 nanomaterials in promoting hydrolysis of organophosphates: Implications for mitigating pollution of plastic additives.

Organophosphate esters (OPEs) are prevalent pollutants in the aquatic environment. OPEs are released from many sources, particularly, from the breakdown and weathering of plastic wastes, as OPEs are commonly used plastic additives. Metal oxide mineral nanoparticles play critical roles in the hydrolytic transformation of OPEs. While natural minerals often contain metal impurities, it is unclear how metal heteroatoms affect the efficiency of mineral nanoparticles in mediating hydrolysis reactions. Herein, we show that transition metal-doped anatase titanium dioxide (TiO2) nanomaterials are more effective in catalyzing the hydrolysis of 4-nitrophenyl phosphate (pNPP), a model OPE compound, with the relative effects of the heteroatoms following the order of Fe > Cr > Mn ≈ Ni > Co > Cu. With multiple lines of evidence based on spectroscopic analysis, kinetics modeling, and theoretical calculations, we show that metal doping increases the Lewis acidity of the TiO2 nanomaterials by increasing the oxidation state of surface Ti atoms, inducing oxygen vacancies, and creating additional Lewis acid sites with stronger acidities. Moreover, the increased amounts of surface hydroxyl groups due to metal-doping enhance inner-sphere complexation of pNPP through ligand exchange. The interesting observation that Fe-doped TiO2 exhibited the highest catalytic efficiency may have important implications for reducing the risks of organophosphate plastic additives, as iron is the most common heteroatom of naturally occurring TiO2 (nano)materials.

The effect of different mission profiles and ambient temperature on the lifetime of boost converter IGBT with a robust controller in a hybrid electric vehicle

AbstractThe reliability of power electronic converters is one of the essential issues in designing of electric vehicles. This paper estimates the lifetime of the boost converter switch by Semikron and Coffin‐Manson models for two common failure mechanisms of Bond wire and Base plate solder, respectively. Four mission profiles based on the Artemis standard are applied to hybrid electrical vehicle model to determine unidirectional output power. Kharitonov's theory is used to design a robust controller to handle the uncertainty raised by different power cycles of the electric vehicle and the parameters of the converter during simulation. Stability of converter is achieved during simulation by identifying simple proportional integral controller coefficients with Kharitonov's theorem. A prototype 230 W boost converter is designed and utilized to validate average model and switch loss calculation relationships. The lifetime results indicate that the number of cycles, and the average and the maximum junction temperature have a more impact than the duration of the drive cycle on the lifetime of the converter. A mixed mission profile is considered to investigate the effect of sudden change in driving modes and speed on total consumed life and lifetime to enhance the study's applicability. Lifetime of switch is decreased significantly in mixed mode in comparison with other mission profiles in the same driving time. Furthermore, the motorway mission profile has 53%, 39.6%, and 160% less total consumed life in comparison with the urban, rural and mixed mission profiles, respectively. In addition, the effect of ambient temperature changes on IGBT lifetime has been investigated for four mission profiles. While motorway had the least total consumed life in 25°C, the urban had better performance in comparison with other mission profiles from 25 to 55°C.

Resistance standards with very small calculable AC-DC difference at frequencies up to 2 MHz for the calibration of precision LCR meters

Abstract We have developed novel impedance standards based on thin-film surface mount device (SMD) resistors. Due to the small dimensions of such resistors, the frequency dependence is very small and can be calculated from quantities that can be either measured or numerically calculated. For nominal resistance values in the 10 kΩ range, as for our application, the DC and AC properties of a single thin-film SMD resistor are not sufficient but can be greatly improved by connecting several thin-film SMD resistors in series. Then the calculated frequency dependence at frequencies up to 2 MHz amounts to only a few parts per million of the DC value, which is about four orders of magnitude smaller than for all conventional calculable AC-DC resistors with a similar nominal DC value. A precision inductance-capacitance-resistance (LCR) meter for frequencies up to 2 MHz, which has a resolution and a reproducibility of a few parts per million but a systematic uncertainty of up to 3000 parts per million, is used to measure two very different SMD-based resistance standards. This enables the verification of the model calculation as well as the calibration of the LCR meter and the correction of its systematic effects, both with a relative uncertainty of a few parts per million in the whole frequency range. This boost in precision enables new applications in this frequency range such as the verification of conventional calculable resistance standards, the calibration of impedance standards, and future measurements of the quantum Hall resistance.We have developed novel impedance standards based on thin-film surface mount device

Kinetics of γ-LiAlO2 Formation out of Li2O-Al2O3 Melt—A Molecular Dynamics-Informed Non-Equilibrium Thermodynamic Study

Slags generated from pyrometallurgical processing of spent Li-ion batteries are reservoirs of Li compounds that, on recycling, can reintegrate Li into the material stream. In this context, γ-LiAlO2 is a promising candidate that potentially increases recycling efficiency due to its high Li content and favorable morphology for separation. However, its solidification kinetics depends on melt compositions and cooling strategies. The Engineered Artificial Minerals approach aims to optimize process conditions that maximize the desired solid phases. To realize this goal, understanding the coupled influence of external cooling kinetics and internal kinetics of solid/liquid interface migration and mass and thermal diffusion on solidification is critical. In this work, the solidification of γ-LiAlO2 from a Li2O-Al2O3 melt is computationally investigated by applying a non-equilibrium thermodynamic model to understand the influence of varying processing conditions on crystallization kinetics. A strategy is illustrated that allows the effective utilization of thermodynamic information obtained by the CALPHAD approach and molecular dynamics-generated diffusion coefficients to simulate kinetic-dependent solidification. Model calculations revealed that melts with compositions close to γ-LiAlO2 remain comparatively unaffected by the external heat extraction strategies due to rapid internal kinetic processes. Kinetic limitations, especially diffusion, become significant for high cooling rates as the melt composition deviates from the stoichiometric compound.

Electrical and Financial Impacts of Inverter Clipping on Oversized Bifacial Photovoltaic Systems

This paper studies the impacts of inverter clipping on bifacial PV modules under different weather and ground reflectivity. A 5 kW bifacial array was connected to a 3.8 kW grid-tied inverter, a 10 kWh Li-ion battery, and an EV charger. A PV output calculation model was developed to compare the estimated output of the modules with the actual measurements to evaluate the relation between ground reflectivity and clipping loss. The results showed that clipping potentially occurs on sunny days in summer from 10:00 to 15:00 during the period with the highest solar irradiance. Three colors of ground cover were also examined to compare the performance of bifacial modules under different albedo reflective properties. The results indicated that the white ground in winter leads to the highest bifacial gain (13.1%) and daily DC efficiency (22.2%) due to the combination of high reflectivity with low solar angle giving maximum upward reflection of direct sunlight. This same combination shows a minimal advantage in summer due to the clipping. The proposed model is evaluated, demonstrating 98.2% agreement between modeled and actual data for all conditions. Furthermore, simulation models based on the actual system with different system sizes and ground reflectivities have been studied to evaluate the impacts of the clipping in terms of technical losses and financial returns. The analysis shows that a high reflective ground condition can provide the best financial benefit, and the clipping loss does not have a great effect on the finance of the project since the loss is less than 4% of the annual production even in an extreme case.

Photoelectric sensor array-based measurement method for the key motion parameters of the small flying object considering non-uniform curve trajectory

Purpose The paper aims to accurately measure the key motion parameters, such as velocity, azimuth and pitch angle, of the small flying object with a non-uniform curve trajectory. It proposes a measurement method and its calculation model of non-uniform curve trajectory using a photoelectric sensor array. Design/methodology/approach First, the basic composition of the measurement system and mechanism of photoelectric sensor array are described, respectively. Second, a non-uniform curve mathematical measurement model is constructed differently from the traditional linear trajectory, taking into account the influence of gravity and air resistance. Third, the measurement error of the system is analyzed through numerical simulation. Finally, the accuracy and feasibility of the approach are verified by live-ammunition experiments. Findings The results show that the systematic error of the hitting point coordinates can be reduced by 9% compared to the traditional linear measurement model. Consequently, this method can meet the higher measurement requirement for the key motion parameters of the small flying object under the non-uniform curve trajectory. Research limitations/implications (if applicable)- although the approach itself is generalizable, the method is unable to detect the motion parameters of multiple small flying objects. Research limitations/implications Although the approach itself is generalizable, the method is unable to detect the motion parameters of the multiple small flying objects. Practical implications It is evident that the proposed non-uniform curve measurement model is more precise in quantifying the essential characteristics of the small flying object, particularly in consideration of the environmental conditions. Social implications The precise measurement of the key motion parameters of the small flying object can facilitate the enhancement of the protective performance of protective materials. Originality/value A novel approach to measurement is proposed, which differs from the conventional uniform trajectory model. To this end, the space construction of the photoelectric sensor array is optimized. The number of the sensors is revised.

Pore-Scale Visualized Transport and Retention of Fibrous and Fragmental Microplastics in Porous Media under Various Surfactant Conditions.

For advancing current knowledge on the transport of microplastics (MPs) in the environment, this study used a real-time pore-scale visualization and quantitative system to examine the motions and mobility of fibrous and fragmental MPs under various surfactant (AEO, CTAC, and AES) and electrolyte conditions. The videos showed that fibrous MPs formed tangles through entanglement, which moved in an axial direction aligned with the flow streamline. Both fibrous and fragmental MPs showed suspended movement as well as surface movement (e.g., sliding, rolling, and saltating) in the porous media. Some deposited fibrous MPs showed flexible deformation due to shear flow. Compared to fragmental MPs, fibrous MPs showed lower mobility due to the tendency to deposit and clog the porous media. The mobility of fragmental MPs was enhanced in the presence of AEO but remained relatively unchanged with AES. In the presence of CTAC, the mobility of fragmental MPs was slightly inhibited under low ionic strength (IS) conditions but remarkably enhanced under high IS conditions. However, the mobility of fibrous MPs was largely unaffected by the surfactants. Both the numerical model and FDLVO calculations effectively described the transport and deposition of MPs in porous media.

Influence of rope fastening on the spectrum of its natural transverse vibrations

According to the previously developed method, which takes into account the bending stiffness of steel ropes during their transverse oscillation, the ropes of the pedestrian bridge ‘Lovers’ in the city of Tyumen were investigated. The obtained values of tension forces and bending stiffness were within the expected range. The high variation of bending stiffness values forced to pay attention to the accuracy of the initial values of rope lengths, which were obtained from the photograph. To measure the rope lengths, a method of nodal harmonic registration was proposed, but the results obtained by this method were higher than the values obtained from the photograph. The evaluation of measurement errors did not explain this overestimation, which led to the necessity to revise the solution of the differential equation of transverse oscillations. It turned out that previously only its partial solution was considered, assuming a hinged rope attachment, whereas it is cantilevered and has a bending reaction. Taking this feature into account by introducing an additional boundary condition allowed to improve the calculation model and explain the overestimation of the rope length in the method of nodal harmonics.Taking into account the nature of the rope attachment allowed us to introduce a generalised parameter s, which takes zero value for rigid cantilever attachment, and is equal to one for articulated attachment. Then the stiffness weakening inside the anchorage will be manifested by the growth of the parameter s and can be detected by the results of the oscillation spectrum registration.

Probabilistic analysis of crack widths associated with quality control procedures

AbstractExisting concrete specifications limit the crack width in order to fulfill the limits of serviceability and durability. The crack width calculation results differ depending on the influences of the variability of the used materials, the geometry, the actions and the uncertainty of the used calculation model itself. In this contribution, the influence of the variability of the input parameters on the calculated crack width is investigated using probabilistic methods in a real case study of a highly loaded tunnel lining cross‐section. The primary objective of this study is a sensitivity analysis to identify the geometric and material‐related input parameters with the most significant influence, which must be particularly controlled during execution for quality control purposes. The study in this article is based on the Eurocode deterministic model for calculating crack width for a stabilized cracking stage in late concrete age.