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Evaluation of wind-induced effect on seismically isolated super high-rise building based on integrated seismic isolation design method: A case study

In recent years, an increasing number of seismically isolated high-rise buildings have been constructed in coastal and inland areas exposed to strong winds. However, the effect of wind on seismically isolated high-rise buildings has not been sufficiently investigated, especially from the perspective of wind-resistance design. Accordingly, in this study, the wind-induced effect is comprehensively investigated using a seismically base-isolated super high-rise engineering building in China as a case study. According to China’s recently released “Standard for Seismic Isolation Design of Building” (GB/T51408-2021), the integrated seismic isolation design method (ISIM) based on the theory of complex mode superposition response spectrum and complex complete quadratic combination is adopted for seismic isolation design. The ISIM and traditional seismic isolation design methods are compared from the perspectives of economy and safety. An analysis approach for evaluating the wind-induced effect on seismically isolated high-rise buildings is proposed based on current national codes. The wind-resistance stability of the seismic isolation interface is examined when the return periods of wind loads exceed the 50-year fortification value. The research results show that the ISIM improves the seismic safety of seismically isolated buildings significantly; moreover, the method is economical. The wind vibration comfort problem is observed at the top of a seismically isolated high-rise building, where it is more difficult to meet the comfort requirement under the wind load with a 1-year return period compared with those under wind loads with 5-year and 10-year return periods. The current wind-resistance design method, which is an intrinsically equivalent static calculation method, underestimates the wind-induced effect on seismically isolated high-rise buildings. The wind vibration comfort and wind-resistance stability of seismically isolated high-rise buildings require further evaluation. The possible adverse effects of wind-induced cumulative residual deformation on the seismic isolation interface must be sufficiently considered in the wind-resistance design of seismically isolated high-rise buildings in the future.

Experimental study on cyclic-bend-over-sheave (CBOS) characteristics of an HMPE fibre rope under dynamic loading

Cyclic bending over sheave (CBOS) is one of the most typical usage scenarios of marine handling ropes, where the rope will be subjected to both tensile deformation and bending deflection. In this paper, the CBOS characteristics of a 24 mm high module polyethylene (HMPE) marine handling rope subjected to dynamic tension are investigated by a series of full-scale experimental tests at the diameter ratio of D/d=400/24, where D=400mm is the sheave diameter. The variations in useful life, strain, stiffness and surface temperature have been measured at different loading conditions. Two stages of temperature variation at the bending section of the rope are found, and those stages are associated with the variation in the area of hysteresis loop from the tension-strain figure. On the other hand, the CBOS lifetime is found to decrease with the increasing average, amplitude and period of the dynamic loading, while the nominal stiffness increases with the average magnitude and period of loading but decreases with increasing amplitude. On this basis, two empirical equations taking into account the loading conditions are proposed through regression analysis. The obtained coefficients have good agreement with the present experimental results.

Prediction of nature of hysteresis and hysteresis based extraction of viscoelastic material model parameters

As almost all materials exhibit viscoelastic behaviour, it is important to understand the material behaviour which would help in its application in different fields. The current research work firstly focuses on understanding the dissipating behaviour of any viscoelastic material through operator-based multi-element model from the experimental hysteresis subject to cyclic or periodic displacement loading. Genetic algorithm-based constrained optimization technique is used as an extraction technique by curve fitting. Further, the technique is used to predict the model parameters of a pig’s lumbar spinal motion segment subjected to periodic displacement loading. Following the derived model parameters, the effect of varying periodic loading on the calculated hysteresis is also compared.

ONE CASE OF VIBRATION DIAGNOSTICS OF RVM-45 VIBRATION MILLS AT A SINTEZ-PKZH LLC PLANT

The article describes the course of vibration measurements at a particular metallurgical plant, one of the workshops of which is equipped with vibration mills, from the formulation of the problem to the analysis of the results. The problem lies in the low quality of the floor on which four RVM-45 vibratory mills of the RVM-45/131.01 design are located, causing periodic loads and vibrations. The paper presents the results of vibration tests obtained through measurements at various points in the room during the startup, operation and shutdown of mills. The studies were carried out using a measuring device “Vibran-2.1”. The reason for the occurrence of progressive vibration caused by the intearactive operation of vibration mills RVM-45 is revealed. Ways to reduce the overall level of vibration in the room with the simultaneous operation of all mechanisms are proposed.

Experimental investigation of perforated nanocomposites under thermal cycles for use in the shell of sports buildings

One of the most important applications of composites is their use in structures with periodic thermal loading. Sports buildings are one of the most appropriate options for using these composites due to the need for a balanced temperature. In this research, composite samples of polymeric base reinforced with nanoparticles, structure, and effects of thermal cycling and circular holes on it have been investigated. The nanoparticles used were multi-walled carbon nanotubes and the weight percentage was 0.1%. In this research, the behavior of perforated nanocomposite samples with a diameter of 2 and 4 mm holes under thermal cycles was investigated. By performing a tensile test on the samples, the fracture toughness and modulus of elasticity due to the number of different heating cycles and the ratio of the hole diameter to the width for different samples were checked and compared. According to the results, as the ratio of diameter to width increases, the coefficient of stress concentration also increases. Also, the results show that the fracture strength increases during the thermal cycle. Fracture strength increases between 9% and 25% after 360 thermal cycles. It seems that one reason for this increase in tensile strength is the sintering of glass/epoxy nanocomposite during the thermal cycle.

Fixed-/Preassigned-Time Stability Control of Chaotic Power Systems

A power system shows chaotic oscillation when it is subjected to periodic load disturbance, which makes it a challenging and interesting problem for stability control of chaotic power system. In this paper, a unified controller is designed to solve the fixed-time and preassigned-time stability problems of fourth-order chaotic power systems. In addition, based on Lyapunov stability theory, sufficient conditions are established for the fixed-time and preassigned-time stability of the underlying chaotic power systems, and a more accurate estimation of the settling time is also derived. Finally, according to numerical simulations, we validate the theoretical results.

Heat pump water heater enhanced with phase change materials thermal energy storage: Modeling study

A promising solution to improve the first hour rating (FHR) of a heat pump water heater (HPWH) involves employing a secondary tank which contains phase change material (PCM) capsules. To better understand the influence of PCM thermal storage on the HPWH operational performance, a dynamic model was developed to simulate and analyze the behavior of a newly developed HPWH technology that incorporates PCM storage into a standard HPWH to optimize key parameters such as the uniform energy factor and FHR. Mathematical models of several key components of the proposed HPWH-PCM integrated thermal energy storage (TES) system, e.g., water heater tank, PCM TES tank, evaporator, compressor, and expansion valve, have been elaborated. Also, a model-based control co-simulation platform was developed to integrate a embed PCM storage HPWH dynamic model with a control model for better supporting control design, analysis, verification, and validation. The model accuracy has been validated through comparing simulation results with lab test results, with a mean average percentage error of <5.5% for most of the selected performance variables. In addition, using the developed co-simulation platform, the demand response control strategy was studied to evaluate the load flexibility of the combined HPWH-PCM storage system by shifting system power usage to outside of the 3.5 h peak load period.

Fatigue damage quantitative evaluation of carbon fiber composites at different stress ratios based on nonlinear ultrasonic

In order to investigate the fatigue behavior of carbon fiber composites and the influence of different stress levels on their fatigue damage characteristics, the fatigue experiments of carbon fiber composites under different stress ratios are carried out. The nonlinear ultrasonic technique is used to online detect the fatigue damage process of carbon fiber composites, the relative nonlinear coefficient β under different stress ratios and different measuring positions is analyzed with the fatigue loading period. The experimental results indicate the relative nonlinear coefficient increases significantly and the rising trend accelerates when the fatigue life of specimen reaches 50%, it is the most sensitive to the change of material microstructure by comparing other parameters and can be used as the characteristic parameter to evaluate the fatigue damage of materials. In addition, the fatigue damage factor D is proposed by analyzing the relationship between the relative nonlinear coefficient and the damage degree of materials, the nonlinear ultrasonic quantitative analysis is carried out and the fatigue damage prediction model based on the relative nonlinear coefficient is established to characterize the severity of fatigue damage of materials. Therefore, the nonlinear ultrasonic quantitative evaluation method for carbon fiber composites is established, it provides a new method and data support for quantitative evaluation of fatigue damage degree of materials by nonlinear ultrasonic method.

Multistep Forecasting of Power Flow Based on LSTM Autoencoder: A Study Case in Regional Grid Cluster Proposal

A regional grid cluster proposal is required to tackle power grid complexities and evaluate the impact of decentralized renewable energy generation. However, implementing regional grid clusters poses challenges in power flow forecasting owing to the inherent variability of renewable power generation and diverse power load behavior. Accurate forecasting is vital for monitoring the imported power during peak regional load periods and surplus power generation exported from the studied region. This study addressed the challenge of multistep bidirectional power flow forecasting by proposing an LSTM autoencoder model. During the training stage, the proposed model and baseline models were developed using autotune hyperparameters to fine-tune the models and maximize their performance. The model utilized the last 6 h leading up to the current time (24 steps of 15 min intervals) to predict the power flow 1 h ahead (4 steps of 15 min intervals) from the current time. In the model evaluation stage, the proposed model achieved the lowest RMSE and MAE scores with values of 32.243 MW and 24.154 MW, respectively. In addition, it achieved a good R2 score of 0.93. The evaluation metrics demonstrated that the LSTM autoencoder outperformed the other models for multistep forecasting task in a regional grid cluster proposal.

Influence of stiffness parameters on vibro-impact damper dynamics

The article studies the dynamic behavior of a low-mass vibro-impact damper, considered as a device for passive vibration control. Its design scheme corresponds to the scheme of single-sided vibro-impact nonlinear energy sink (SSVI NES), which is supposed to be used for effective vibrations attenuation under different transient loads, namely, impulsive, broadband, wind. Its dynamics and effectiveness strongly depend both on the damper own parameters and the external load parameters. We consider the response regimes and the damper efficiency for two options of its optimized parameters under periodic loading. The influence of the elasticity characteristics of the colliding surfaces on the damper effectiveness is also analyzed. We show that the modes with rich complex dynamics are implemented in a system with a heavier damper with low stiffness. Despite this, it is more effective, especially with a softer impact.

Dynamic Stability of Tensegrity Structures-Part II: The Periodic External Load.

The paper contains a parametric analysis of tensegrity structures subjected to periodic loads. The analysis focuses on determining the main region of dynamic instability. When load parameters fall within this region, the resulting vibration amplitudes increase, posing a risk to the durability of structures. The study considers structures built using commonly used modules. The influence of the initial prestress on the distribution of the instability regions is examined. Additional prestress can significantly reduce the extent of instability regions, potentially narrowing them by up to 99%. A nondimensional parameter is introduced to accurately assess changes in the extent of the instability region. A geometrically non-linear model is employed to evaluate the behavior of the analyzed structures.

Взаимосвязь креативности личности и эмоциональной сферы в период взрослости в условиях пандемии COVID-19

The relevance: The COVID-19 pandemic became an unprecedentedly serious test for many Russian people. This negatively affected their psycho-emotional state. Therefore, the search for protective factors that can minimize the negative effects of the pandemic has become an urgent psychological task. The objective is to study the correlation between the individual’s creativity and the indicators of the emotional sphere of an adult in conditions of the COVID-19 pandemic. The study hypothesizes that personality creativity is connected with the manifestation degree of the stress experienced, of depression and anxiety manifestation in mentally healthy adult respondents in conditions of the COVID-19 pandemic. Participants: 200 respondents aged 19 to 55 (M = 35.83, SD = ±13.16), 55% are men, 45% are women. The study methods (tools). To study the intensity and specific features of the respondents’ experiences during the COVID-19 pandemic, the questionnaire “Psychological Experiences in a Pandemic” (by O. V. Rychkova, A. Y. Shmiganovskaya) was used; to determine the level characteristics of anxiety, depression and stress, the “DASS-21” questionnaire (by S. Lovibond and P. Lovibond) was used; to measure the creativity level of the respondents’ personality, the “Creativity Questionnaire” (by D. Johnson) was used. The results. The study allowed us to discover, statistically prove and describe the correlation between the personality creativity and emotional maladjustment indicators (expressed as the symptoms of depression, anxiety, and stress experienced) which were observed in the conditions of the negative impact of the COVID-19 pandemic on mentally healthy individuals: adults with a higher level of personality creativity are less susceptible to the negative psychological impact of such a crisis situation as a pandemic. The conclusions. The results obtained made it possible to substantiate the correlation between the personality creativity and the adults’ emotional sphere indicators. More creative people have lower levels of worries, stress, anxiety and depression in the context of the COVID-19 pandemic. It proves the necessity and relevance to search for and test psychological practices that contribute to the development of the personal creativity during a crisis and periods of high psycho-emotional load. In particular, it is recommended to conduct art therapy in a distance format when working with adults.

Pharmacodynamics Monitoring of Emicizumab in Patients with Hemophilia A.

Emicizumab is a bispecific antibody mimicking coagulation factor VIII (FVIII) employed to treat patients with hemophilia A (PwHA) regardless of FVIII inhibitor status. The identification of biological markers reflecting the hemostatic competence of patients under emicizumab therapy would have a great clinical value. Unfortunately, emicizumab over-corrects standard coagulation assays, precluding their use for evaluating the hemostatic correction achieved in vivo. Here, we investigated whether global coagulation assays (GCA) would allow monitoring the biological response to non-factor replacement therapy with emicizumab. Six adults PwHA received a weekly dose of emicizumab of 3 mg/kg during weeks (W) 1 4 and 1.5 mg/kg from W5 onwards. Response to treatment was monitored weekly by emicizumab plasma concentration, thrombin generation (TG), and fibrin clot formation (FCF) and structure. TG and FCF results were compared to patient baseline, FVIII replacement, and healthy donors. TG and FCF significantly increased in PwHA after the loading period, reaching a plateau that lasted until the end of monitoring. Similarly, fibrin clot network became denser with thinner fibrin fibers. However, TG contrary to FCF remained at the lower limits of reference values. Remarkably, despite having similar plateau concentrations of emicizumab some patients showed markedly different degrees of TG and FCF improvement. Our study enriches the knowledge on the use of GCA to monitor non-factor replacement therapy, indicating that TG and FCF could act as direct markers of emicizumab biological activity. GCA allow to capture and visualize the individually variable response to emicizumab, leading a step forward to the personalization of patient treatment.

ДИНАМИКА СЕГЕТАЛЬНОЙ ФЛОРЫ ЮГА НЕЧЕРНОЗЕМНОЙ ЗОНЫ РФ ПРИ ИЗМЕНЕНИИ УРОВНЯ АНТРОПОГЕННОГО ВОЗДЕЙСТВИЯ

The article presents a comparative analysis of the taxonomic structure of the segetal flora of the south of the Non-Chernozem zone of the Russian Federation over a 90-year period of time. The segetal flora is represented by weeds of agrophytocenoses of the main cereals, leguminous and row crops, perennial and annual grasses. The maximum species richness of the segetal flora was established for the period of the minimum anthropogenic load of the 1930s - 166 species. The minimum number of species was noted for the segetal flora of the 1980s, a period characterized by maximum anthropogenic loading. The core of weed species in all periods were representatives of the Asteraceae, Poaceae, Brassicaceae, Fabaceae, Lamiaceae, Caryophyllaceae, Scrophulariaceae families. When comparing the species composition of agrophytocenoses of individual crops, it was found that the increase in anthropogenic load contributes to an increase in the coefficient of similarity between them. The coefficient of similarity in all periods of research was quite high between cultures similar in biology and cultivation technology. A pool of segetal species was identified that maintained a high population density during all periods of research. They are treated as perennial (Elytrigia repens (L.) Nevski Convolvulus arvensis L., Cirsium setosum (Willd.) Besser., Equisetum arvense L) so are juvenile (Chenopodium album L., Amaranthus retroflexus L.) weed species. At the present stage of the phlorogenesis of segetal vegetation, there is an increase in the proportion of adventitious species of its components. Stable populations for the region were noted in such adventitious species as Galinsoga parviflores Cav., Erigeron annuus L., Heracleum sosnowskyi Manden.

Optimization method of power supply mode and connected to external power grid of CZ railway traction station

Aiming at the problem of long slopes and weak power grids along the railway in high altitude mountainous areas, an optimization method of power supply mode and access to external power grid of CZ railway traction station is proposed. First, combined with the terrain and altitude along the railway and the characteristics of the regional power grid, a sample library of the power supply mode and access to external power grid of CZ railway traction station is designed. Secondly, combined with the train operation diagram and line ramp parameters, the full-day periodic load of each power supply arm is simulated. Then, according to the sample library, a “source-net-load” integrated simulation model is constructed in Simulink. Then, the three-phase voltage unbalance evaluation model of the power system is constructed in combination with relevant standards. Finally, the optimal wiring scheme is selected by using the evaluation model and the simulated voltage unbalance index.

Reinforcement of Hydrogels with a 3D-Printed Polycaprolactone (PCL) Structure Enhances Cell Numbers and Cartilage ECM Production under Compression

Hydrogels show promise in cartilage tissue engineering (CTE) by supporting chondrocytes and maintaining their phenotype and extracellular matrix (ECM) production. Under prolonged mechanical forces, however, hydrogels can be structurally unstable, leading to cell and ECM loss. Furthermore, long periods of mechanical loading might alter the production of cartilage ECM molecules, including glycosaminoglycans (GAGs) and collagen type 2 (Col2), specifically with the negative effect of stimulating fibrocartilage, typified by collagen type 1 (Col1) secretion. Reinforcing hydrogels with 3D-printed Polycaprolactone (PCL) structures offer a solution to enhance the structural integrity and mechanical response of impregnated chondrocytes. This study aimed to assess the impact of compression duration and PCL reinforcement on the performance of chondrocytes impregnated with hydrogel. Results showed that shorter loading periods did not significantly affect cell numbers and ECM production in 3D-bioprinted hydrogels, but longer periods tended to reduce cell numbers and ECM compared to unloaded conditions. PCL reinforcement enhanced cell numbers under mechanical compression compared to unreinforced hydrogels. However, the reinforced constructs seemed to produce more fibrocartilage-like, Col1-positive ECM. These findings suggest that reinforced hydrogel constructs hold potential for in vivo cartilage regeneration and defect treatment by retaining higher cell numbers and ECM content. To further enhance hyaline cartilage ECM formation, future studies should focus on adjusting the mechanical properties of reinforced constructs and exploring mechanotransduction pathways.

Survival probability determination of nonlinear oscillators subject to combined deterministic periodic and non-stationary stochastic loads

This paper presents a technique based on Wiener path integrals (WPI) for computing the survival probability of nonlinear oscillators under combined nonstationary stochastic and periodic excitation. Specifically, the equation of motion is equivalently decomposed into a correlated combination of a nonlinear stochastic differential equation (SDE) and a nonlinear deterministic differential equation. The nonstationary response probability density function (PDF) of the stochastic component is obtained using the Wiener path integral concept in conjunction with stochastic averaging/linearization. The approach involves utilizing stochastic averaging/linearization techniques to transform the nonlinear SDE into a linear one with varying equivalent stiffness and damping. Afterwards, using the WPI method and the concept of the most probable path, a closed-form approximate analytical expression of the joint transition probability density function (PDF) is obtained for small intervals corresponding to the equivalent linear SDE. Additionally, the survival probability of the original nonlinear oscillator subject to combined excitation with fixed barriers can be approximated equivalently by using the survival probability with time-varying barriers of the equivalent linear system with time-varying stiffness and damping subject only to the nonstationary stochastic excitation. Finally, by using the analytical expression of the transition PDF of the equivalent linear system and a discrete version of the Chapman–Kolmogorov (C–K) equation, it is possible to determine the response and survival probability of the original oscillator under combined excitation step by step. Examples involving a Duffing oscillator and a vibro-impact oscillator are analyzed to showcase the precision and efficacy of the suggested technique in contrast to relevant Monte Carlo simulations.

Major Depressive Disorder and Chronic Fatigue Syndrome Show Characteristic Heart Rate Variability Profiles Reflecting Autonomic Dysregulations: Differentiation by Linear Discriminant Analysis.

Major depressive disorder (MDD) and chronic fatigue syndrome (CFS) have overlapping symptoms, and differentiation is important to administer the proper treatment. The present study aimed to assess the usefulness of heart rate variability (HRV) indices. Frequency-domain HRV indices, including high-frequency (HF) and low-frequency (LF) components, their sum (LF+HF), and their ratio (LF/HF), were measured in a three-behavioral-state paradigm composed of initial rest (Rest), task load (Task), and post-task rest (After) periods to examine autonomic regulation. It was found that HF was low at Rest in both disorders, but was lower in MDD than in CFS. LF and LF+HF at Rest were low only in MDD. Attenuated responses of LF, HF, LF+HF, and LF/HF to task load and an excessive increase in HF at After were found in both disorders. The results indicate that an overall HRV reduction at Rest may support a diagnosis of MDD. HF reduction was found in CFS, but with a lesser severity. Response disturbances of HRV to Task were observed in both disorders, and would suggest the presence of CFS when the baseline HRV has not been reduced. Linear discriminant analysis using HRV indices was able to differentiate MDD from CFS, with a sensitivity and specificity of 91.8% and 100%, respectively. HRV indices in MDD and CFS show both common and different profiles, and can be useful for the differential diagnosis.

Efficiency Optimization of Asynchronous Motor with Particle Swarm Algorithm Incorporating Parameter Identification

Asynchronous motors are commonly utilized in industrial and agricultural production due to their inexpensive manufacturing cost and reliable structure. However, due to the demands of production and everyday usage, these motors may be operated at no or light load for long periods of time, resulting in a decrease in the efficiency of the motor system. A model-referenced adaptive parameter identification in combination with a particle swarm algorithm is proposed in this paper to enhance the operating efficiency of asynchronous motors. This control strategy can reduce motor power loss and improve efficiency. Simulation model is established and simulation results are provided to verify the feasibility of the proposed control strategy for optimizing the efficiency of asynchronous motors.

Evaluation of the contact endurance of machine parts based on the mechanical characteristics of fatigue strength

The condition of contact endurance of machine parts is proposed, in which the maximum equivalent stress in the contact zone of the parts is used as a criterion, and the material endurance limit is used as a critical value. The use of this condition would allow to avoid time-consuming experiments on determination of the contact endurance limit and quickly assess the working ability of parts exposed to periodic contact load. Keywords: contact endurance, strength, fatigue strength, fatigue contact tests. alexmed@bmstu.ru