Search Results (715)

Propagation properties represent a critical aspect of laser beams utilized in free space optical (FSO) communications. We examined the evolution characteristics of the electric field associated with partially coherent flat-topped beam rectangular arrays propagating bidirectionally through the turbulent atmosphere and plasma links. Utilizing the optical transmission matrix, alongside the second moment theory and Wigner distribution functions, we derived analytical expressions for both the intensity distribution and propagation factors of the partially coherent flat-topped beam rectangular arrays affected by the atmospheric turbulence and plasma disturbances. The numerical results indicate that appropriately selecting parameters such as beam order, transverse spatial coherence width, and beam width can effectively mitigate the adverse effects on propagation properties caused by the turbulent atmosphere and plasma. Our results have significant implications for FSO communications within specific environmental contexts. Full article

The increasing use of cable-stayed bridges with steel box girders necessitates more sophisticated design approaches, as the diverse environments of bridge locations place higher demands on the design process. Determining a reasonable finished state is a critical aspect of bridge design, yet the current methods are significantly constrained. A new approach to optimizing the finished state is proposed. This method’s practicality and efficiency are verified through a case study, analyzing how constraints on vertical girder deflection, horizontal pylon displacement, cable forces, and cable force uniformity affect the optimization outcome. The results show that convergence of the mixed-constraint quadratic programming model is achieved within 30 iterations, yielding an optimized finished state that meets the design criteria. The chosen constraint ranges are deemed appropriate, and the optimization method for the construction stage is thus demonstrably feasible and efficient. The multiplier path following optimization algorithm is computationally efficient, exhibiting good convergence and insensitivity to the problem size. Being easy to program, it avoids the arbitrariness of manual cable adjustment, enabling straightforward determination of a reasonable finished state for the cable-stayed bridge with a steel box girder. The vertical displacement of the main girder, the positive and negative bending moments, and the normal stresses at the top and bottom edges, as well as the positive and negative bending moments in the towers, are significantly influenced by the constraint ranges. The horizontal displacement of the pylon roof is significantly affected by the constraint ranges of both the main girder’s vertical displacement and the pylon’s horizontal displacement, while the remaining constraint ranges have a limited impact. Full article

Ride comfort is an important requirement that passenger rail vehicles must meet. Carbody–anti-bending system is a relatively new passive method to enhance the ride comfort in passenger rail vehicles with long and light carbody. The resonance frequency of the first bending mode (FBM) of such vehicle is within the most sensitive frequency range that affects ride comfort. Anti-bending bars consist of two bars that are mounted under the longitudinal beams of the carbody chassis using vertical supports. When the carbody bends, the anti-bending bars develop moments in the neutral axis of the carbody opposing the bending of the carbody. In this way, the carbody structure becomes stiffer and the resonance frequency of the FBM can be increased beyond the upper limit of the discomfort range of frequency, improving the ride comfort. The theoretical principle of this method has been demonstrated employing a passenger rail vehicle model that includes the carbody as a free–free Euler–Bernoulli beam and the anti-bending bars as longitudinal springs jointed to the vertical supports. Also, the method feasibility has been verified in the past using an experimental scale demonstrator system. In this paper, a new model of the carbody–anti-bending bar system is proposed by including three-directional elastic elements (vertical and longitudinal direction and rotation in the vertical–longitudinal plane) to model the fastening of the anti-bending bars to the supports and the vertical motion of the anti-bending bars modelled as free–free Euler–Bernoulli beams connected to the elastic elements of the fastening. In the longitudinal direction, the anti-bending bars work as springs connected to the longitudinal elastic elements of the fastening. The modal analysis method is applied to point out the basic properties of the frequency response functions (FRFs) of the carbody–anti-bending bars system, considering the bounce and FBMs of both the carbody and the anti-bending bars. A parametric study of the FRF of the carbody shows that the vertical stiffness of the fastening should be sufficiently high enough to eliminate the influence of the modes of the anti-bending bars upon the carbody response and to reduce the anti-bending bars vibration in the frequency range of interest. Longitudinal stiffness of the elastic elements of the fastening is critical to increase the bending resonance frequency of the carbody out of the sensitive range. Longer anti-bending bars can improve the capability of the anti-bending bars to increase the bending resonance without the risk of interference effects caused by the bounce and bending modes of the anti-bending bars. Full article

The numerical modelling procedures and damage criteria of both existing and retrofitted reinforced concrete (RC) elements are crucial for reliable seismic assessment and the retrofitting of existing RC buildings. A widely used retrofitting technique involves the application of fiber-reinforced polymers (FRPs) to vulnerable RC elements, enhancing their flexural and shear capacities. However, the current version of EC8-3 does not explicitly provide guidelines for numerical modelling, nor does it offer specific information on the assessment of retrofitting elements. This study focuses on developing a concentrated plasticity modelling approach and defining the damage state criteria for retrofitted RC columns with FRPs, based on experimental data from the literature. A database comprising 99 FRP-retrofitted RC columns was compiled, and regression analysis procedures were used to calibrate the peak load rotation, ultimate rotation, and post-capping rotation capacities. The modelling approach was validated through comparison with existing formulations using OpenSees, and the results indicate its adequacy for the seismic assessment of retrofitted buildings. This research advances the seismic assessment of FRP-retrofitted RC elements by introducing a novel trilinear moment–rotation model and refined damage criteria, which provide higher predictive accuracy in comparison to existing proposals. It also addresses critical gaps in seismic assessment practices by proposing the peak load rotation as a more reliable SD limit state threshold for retrofitted columns. Full article

Construction sites are among the most hazardous workplaces, making safety a critical concern in the sector. This study investigates the interplay between safety leadership, employee morale, harmonious safety passion, and safety performance through the lens of the social exchange theory. This research aims to assess how safety leadership impacts safety performance directly and indirectly, with employee morale acting as a mediator while harmonious safety passion moderates these relationships. A quantitative approach was employed, with data collected through structured questionnaires administered to construction workers in Istanbul and Ankara, Turkey. A total of 438 valid responses were analyzed using the Statistical Package for the Social Sciences (version 25) and Analysis of Moment Structures (version 24) for reliability, validity, and hypothesis testing. The findings confirm that safety leadership positively influences both safety performance and employee morale. Employees with high morale directly contribute to improved safety performance and act as a mediator between safety leadership and safety performance. Additionally, harmonious safety passion moderates the relationship between employee morale and safety performance, strengthening the link for workers with higher levels of passion. However, its moderating effect on the relationship between safety leadership and safety performance was not significant. These insights offer practical implications for designing safety training programs, leadership development initiatives, and policies aimed at improving safety outcomes in construction. Future research should explore longitudinal designs and diverse contexts to further validate these findings. Full article

In recent seismic events that occurred worldwide and in Peru, it has been observed that irregular structures in plan present greater structural damage compared to regular structures. Investigations carried out after seismic events indicate that irregular plan structures collapse due to erroneous structural conception and poor seismic analysis. Likewise, the Peruvian earthquake-resistant standard does not establish a permissible limit for the degree of irregularity under analysis, instead qualitatively assessing the structural irregularity. The objective of this article was to study the effect of plan irregularities using innovative methodologies on the structural response of tall 10-story reinforced concrete buildings. In this sense, seventeen (17) structural models are proposed that reflect different irregular configurations in plan: 06 structures Type L, 05 structures Type I, 05 structures Type I, and one regular building. These buildings are numerically modeled using ETABS software V.18.0 through modal analysis, Modal Spectral and Linear Time History (MSLTH), and Multi-Mode Pushover (MPA). For the MSLTH, seven (07) pairs of representative Peruvian earthquakes were analyzed. The results of the modal analysis evaluated in the first two vibration modes demonstrated that Type L irregular structures change their behavior from translational to torsional when the structures present an irregularity greater than 57%. Type I and O structures present translational behavior. Furthermore, the results of the Modal Spectral and MSLTH analysis demonstrate that Type L structures present greater displacements and drifts in both directions. The shear force and the overturning moment for Types L, I, and O decrease as the irregularity in plan increases. Finally, the results of the MPA for irregular Type L structures demonstrated that the lateral stiffness of the structures decreases as the irregularity in plan is critical, increasing the possibility of the formation of plastic mechanisms in the structural elements. Full article

With advancements in bipedal locomotion for humanoid robots, a critical challenge lies in generating gaits that are bounded to ensure stable operation in complex environments. Traditional Model Predictive Control (MPC) methods based on Linear Inverted Pendulum (LIP) or Cart–Table (C-T) methods are straightforward and linear but inadequate for robots with flexible joints and linkages. To overcome this limitation, we propose a Flexible MPC (FMPC) framework that incorporates joint dynamics modeling and emphasizes bounded gait control to enable humanoid robots to achieve stable motion in various conditions. The FMPC is based on an enhanced flexible C-T model as the motion model, featuring an elastic layer and an auxiliary second center of mass (CoM) to simulate joint systems. The flexible C-T model’s inversion derivation allows it to be effectively transformed into the predictive equation for the FMPC, therefore enriching its flexible dynamic behavior representation. We further use the Zero Moment Point (ZMP) velocity as a control variable and integrate multiple constraints that emphasize CoM constraint, embed explicit bounded constraint, and integrate ZMP constraint, therefore enabling the control of model flexibility and enhancement of stability. Since all the above constraints are shown to be linear in the control variables, a quadratic programming (QP) problem is established that guarantees that the CoM trajectory is bounded. Lastly, simulations validate the effectiveness of the proposed method, emphasizing its capacity to generate bounded CoM/ZMP trajectories across diverse conditions, underscoring its potential to enhance gait control. In addition, the validation of the simulation of real robot motion on the robots CASBOT and Openloong, in turn, demonstrates the effectiveness and robustness of our approach. Full article

The death of Russian dissident Alexey Navalny in a far-northern colony after three years of imprisonment was declared a martyrdom by the Russian opposition, reflecting the sentiments of a part of Russian society. This unexpected reference to martyr narrative by a largely secular and anti-clerical opposition has set a significant precedent when religious discourse is instrumentalized not only by official propaganda but also by its critics. The authors posit that the construction of a martyr narrative is deeply political, being a part of contemporary ideological war. This article argues that Alexey Navalny’s death and its subsequent sacralization by opposition figures represent a significant moment in contemporary Russian politics. By adopting religious narratives and symbols, the opposition not only mobilizes support but also challenges the regime’s monopoly on ideological and religious discourse. However, this strategic use of martyrdom carries inherent contradictions, reflecting the opposition’s ambivalent relationship with religion and the Russian Orthodox Church. Full article

The limits of plastic deformation without failure are considered to be a measure of formability and can be estimated by the standard tests. However, the mechanical states observed during commonly used compression tests are similar to those observed in many bulk deformation processes, with an additional advantage of those tests having the possibility of applying large deformations without the risk of the appearance of necking (in tension) or material reorientation (in torsion). Thus, this study presents the results of modified compression tests under conditions of a real forging process, since knowledge of the geometrical parameters of the tools and samples makes it possible to determine the areas of stress concentration which contribute to the formation of controlled cracks. The digital image correlation system (DIC) was used to analyze the deformation parameters that lead to achieving the critical values of fracture criterion; simulations were additionally performed to confirm the reliability of predicting the location and the critical moment just before failure in the forging process under consideration. After the accuracy of the model was verified, this approach was applied to a case of backward extrusion, also correctly predicting the locations with high probability of fracture. Full article

Sustainable development, a key global priority, is increasingly shaped by factors such as the sharing economy, environmental patents, and energy efficiency, which have significant social, economic, and environmental implications. With rising public concern about the environment, volatile energy prices, and growing market pressure, more businesses are seeking ways to optimize energy usage. The purpose of this study is to explore the impact of green technologies, the sharing economy, and energy efficiency on environmental sustainability in the G7 countries. By utilizing quarterly data from 2014Q1 to 2020Q4, this study measures ecological sustainability using the load capacity factor. The research employs the Moments Quantile Regression (MMQR) approach to assess the relationships between variables, while the Cross-Sectionally Augmented IPS (CIPS) test is used to examine unit roots in the data. The objective of this study is to evaluate how these factors contribute to environmental sustainability and to provide policy recommendations for enhancing sustainability practices across the G7 countries. The scientific novelty of this work lies in its application of MMQR to understand the varying effects of energy efficiency, the sharing economy, and green technologies on sustainability and its incorporation of short-term quarterly data, offering fresh insights into the dynamics of these relationships. The findings reveal that an increasing number of sharing economy users and population growth positively impact environmental sustainability. Moreover, policies promoting efficient resource utilization and the sharing economy can significantly enhance sustainability. However, urbanization and industrialization pose challenges, necessitating more stringent industrial regulations and careful urban planning. The results indicate that while energy efficiency and the sharing economy hold theoretical potential for sustainability, their practical impacts can vary. To ensure long-term sustainability, the adoption of environmental patents and green technologies is critical, with initial investments yielding substantial returns as these technologies become more widely adopted. This study proposes policy recommendations including greater international collaboration, comprehensive energy policies, advanced urban planning, expanded support for green innovation, and stricter industrial regulations. The research also underscores the role of the United States in leading global sustainable development initiatives. Finally, this study suggests that future research should consider longer timeframes, advanced analytical methods, and a broader range of variables to further understand the complexities of sustainable development. Full article

Various industries see digital transformation (DT) as the pillar to coping with intensified competition, energy crises, and climate change. As a critical sector for DT, the construction industry’s project-oriented paradigm and immature industrialized production method limit the research on emerging digital technology and ignore the theoretical mechanism. Through the lens of system adaptability, this study proposes a multifaceted model to examine the DT effectiveness and unveil the driving mechanism. (1) An extensive literature review, action research, and the nominal group technique identified 21 determinants, which were categorized into a technological–organizational–environmental (TOE) framework to analyze the construction industry’s DT determinants from multiple dimensions. (2) This research utilizes data from 272 respondents collected through field research, with a survey designed to measure the relationships among variables. (3) Structural equation modeling (SEM) through Analysis of Moment Structures (AMOSs) has been used to analyze the hypotheses and analyze the impact of determinants from various dimensions on DT and examine their influence pathways. The results indicate that determinants in the technological, organizational, and environmental dimensions positively affect DT’s success in the construction industry. The influence of the technological dimension is the strongest, and the organizational dimension is the weakest. The research findings offer valuable recommendations and insights for stakeholders in the construction industry, highlighting the importance of considering these three dimensions to enhance the overall effectiveness of DT when driving industry transformation and upgrading. Additionally, this study uses the TOE framework to reveal determinants from multiple dimensions. It combines SEM to explore the pathways of their effects, offering key theoretical insights for the body of knowledge. Full article

The visual perception of interior architecture plays a crucial role in real estate marketing, influencing the decisions of buyers, interior architects, and real estate agents. These professionals rely on personal assessments of space, often drawing from their experience of using décor to influence how interiors are perceived. While intuition may validate some approaches, this study explores an under-examined aspect of interior design using a mobile eye-tracking device. It investigates how decorative elements affect spatial perception and offers insights into how individuals visually engage with interior environments. By integrating décor into the analysis of interior architecture, this study broadens the traditional scope of the field, demonstrating how décor composition can modulate spatial perception using eye-tracking technology. Results show that effective styling can redirect attention from key architectural elements, sometimes causing them to be overlooked during the critical first moments of observation commonly known as the “first impression”. These findings have important implications for interior design practice and architectural education. Full article

This study investigates the combustion characteristics and critical thermodynamic conditions for the ignition of TC4 and TC17 alloys under high-speed friction conditions. The results indicate that, under identical rubbing conditions, both the critical pressure and the ignition temperature of the TC17 alloy are higher than those of the TC4 alloy. The critical ignition conditions for both alloys increase with thickness, while they decrease with increasing rotational speed, oxygen concentration, and oxygen pressure. The primary characteristics in the initial stage of friction ignition are abrasive and adhesive wear. As the duration of friction increases, material from the friction surface begins to peel away, creating favorable conditions for ignition. At the moment of ignition, significant peeling occurs, along with visible cracks and molten structures, resulting in the production of a substantial amount of titanium oxide on the friction surface. Based on the ignition theory proposed by Frank-Kamenetskii, the reaction order, adsorption coefficient, pre-exponential factor, and activation energy of the ignition criterion under high-speed friction conditions were determined by fitting and analyzing the experimental results. The ignition temperatures of the TC4 and TC17 alloys at different speeds were predicted with a relative error of less than 2.06%. This demonstrates that the Frank-Kamenetskii model can be utilized to explain the critical ignition conditions of titanium alloys under high-speed rubbing conditions. Full article

This study introduces the critical individual contribution coefficient (CR-ICC), a novel metric that evaluates player effectiveness in critical moments of the game. We analyzed 16,631 technical actions from the top eight teams across 77 sets of the 2019 FIVB Women’s Club World Championship, ensuring data quality through inter- and intra-observer reliability. Traditional variables such as points scored, attack and reception efficiency, and balance were examined. Python programming was utilized to calculate the values of CR-ICC, which consider the contextual variables of set period, score difference, competitive load, and opponent’s level. Akaike’s and Bayesian information criteria, along with Nagelkerke’s coefficient of determination, were employed. Binomial logistic regression and receiver operating characteristic curves estimated the probability of victory associated with each variable. Interactive dashboards were developed, enabling dynamic analysis and data visualization. Statistically significant differences were observed in all variables (p < 0.05), except for reception efficiency (p < 0.05), at both the team and individual player levels. At the team level, points scored, attack efficiency, and balance exhibited the highest predictive abilities, with CR-ICC also demonstrating a strong predicting ability. The proposed CR-ICC has remarkable potential as a strategic asset for coaches, enabling the identification of players who excel in critical moments of the game. Full article

The diagnosis of residuals of independence is critical in association analysis and loglinear modeling of two-way contingency tables. Most residual diagnostics depend on large-sample methods, and diagnostic results become dubious when sample sizes are small or data are sparse. In such cases, statistical inference based on non-asymptotic theory or exact inference is desirable. This paper explicitly derives the first four moments of the residuals of independence in a two-way contingency table under a multinomial model. These exact moments are necessary tools for studying the analytical features of the distribution of residuals of independence, such as skewness and kurtosis. Higher-order moments can be found similarly, but the results are more complicated. Full article