Complex Path Research Articles

A Path Model for Subjective Well-Being during the Second Wave of the COVID-19 Pandemic: A Comparative Study among Polish and Ukrainian University Students.

Background: Previous studies showed several associations between physical and mental health dimensions and well-being. This study aims to examine a complex path model explaining the life satisfaction of university students from Poland and Ukraine during the second wave of the COVID-19 pandemic. Methods: The cross-sectional web-based study was performed in November 2020 using Google Forms. The conventional sample of 3230 university students from Poland (n = 1581) and Ukraine (n = 1649), aged 18–59 (M = 21.40, SD = 3.46), with 59% women, participated in the study. We used standardized questionnaires to measure life satisfaction (SWLS), self-reported physical health (GSRH), perceived stress (PSS-10), coronavirus-related PTSD (PCL-S), anxiety (GAD-7), and depression (PHQ-9). We also developed some questions to assess the exposure to the COVID-19 pandemic, positive effects of the pandemic, religiosity, and physical activity (PA). Results: We found a high prevalence of stress, coronavirus-related PTSD, anxiety, and depression and a low level of life satisfaction and physical health. Polish students, women, and those with insufficient PA levels reported worse physical and mental health than Ukrainians, men, and those who exercised sufficiently during the pandemic. Low perceived stress can directly predict life satisfaction, anxiety, and depression. Low stress also leads to better physical health, sufficient PA levels, high religiosity, and more perceived positive effects of the pandemic. Several indirect effects between particular variables and life satisfaction were also found in the path model. Conclusions: The target group for campus prevention programs is Polish university students, women, and people with insufficient PA levels. Intervention and prevention programs should focus on coping strategies and techniques for improving mental and physical health.

Multi-array analysis of volcano-seismic signals at Fogo and Brava, Cape Verde

Abstract. Seismic arrays provide tools for the localization of events without clear phases or events outside the network, where the station coverage prohibits classical localization techniques. Beam forming allows the determination of the direction (back azimuth) and horizontal (apparent) velocity of an incoming wavefront. Here we combine multiple arrays to retrieve event epicentres from the area of intersecting beams without the need to specify a velocity model. The analysis is performed in the time domain, which allows selecting a relatively narrow time window around the phase of interest while preserving frequency bandwidth. This technique is applied to earthquakes and hybrid events in the region of Fogo and Brava, two islands of the southern chain of the Cape Verde archipelago. The results show that the earthquakes mainly originate near Brava, whereas the hybrid events are located on Fogo. By multiple-event beam stacking we are able to further constrain the epicentral locations of the hybrid events in the northwestern part of the collapse scar of Fogo. In previous studies, these events were attributed to shallow hydrothermal processes. However, we obtain relatively high apparent velocities at the arrays, pointing to either deeper sources or complex ray paths. For a better understanding of possible errors of the multi-array analysis, we also compare slowness values obtained from the array analysis with those derived from earthquake locations from classical (local network) localizations. In general, the results agree well. Nevertheless, some systematic deviations of the array-derived back-azimuth and slowness values occur that can be quantified for certain event locations.

Three-dimensional stress rotation and control mechanism of deep tunneling incorporating generalized Zhang–Zhu strength-based forward analysis

Deep rock tunneling exhibits a significant three-dimensional (3D) space effect. The complex stress path and extrusion deformation during excavation are the most significant and decisive factors in the stability and construction safety of a deep tunnel. 3D and forward numerical analyses based on generalized Zhang–Zhu (GZZ) strength criterion are performed to investigate the principal stress rotation behavior and active control mechanism during deep tunneling. The surrounding rock element experiences significant stress rotations because of the sharply increased shear stress (τry) near the tunnel face. A dimensionless stress index (τry/I1) is proposed to quantitatively evaluate the principal stress rotation during excavation. τry/I1 increases with increasing buried depth, and the deep tunnel presents significant principal stress rotation that reaches a large τry/I1 value. The mechanical behavior of the advanced core rock is primarily affected by the strengthening parameter, geological strength index (GSI). Strengthening of the core rock can greatly improve the stress conditions and mechanical behavior, increase the strength of the rock mass, and reduce the stress rotation. The pre-extrusion deformation of the core rock and pre-convergence of the surrounding rock are discovered to follow a consistency law, which suggests that the pre-convergence deformation and surrounding rock stability near the tunnel face depend on the extrusion deformation of the tunnel face. The GZZ strength-based 3D forward analysis and stress control method proposed in this study can enhance the design and construction of deep and ultra-deep tunnels by weakening the 3D space effect (e.g., tunnel face extrusion and stress rotation) and exerting the strength potential (self-bearing capacity) of a rock mass.

Open Innovation, Open Wallets? Innovation Strategy Congruence in Crowdfunding

New ventures using an external open innovation strategy face a more complex path to resource acquisition. On the one hand, openness removes the barriers for both collaboration and widespread adoption; on the other, openness offers little to no intellectual property protection, thus creating a scenario where virtually anyone can appropriate value from property as they without necessarily providing a benefit to the creator. As such, open innovation can be a disadvantage in early-stage resource acquisition because the strategy is incongruent with professional investor expectations, which typically seek to maximize returns. Despite these concerns, the rapid rise of crowdfunding has created a more communal and democratic method for innovators to access capital markets and have created opportunities for open innovation strategies. In this paper, we take a multi-methodological approach to test whether an open innovation strategy provides unique advantages in the crowdfunding context. We theorize that openness yields greater trust, which in turn leads to superior financing outcomes. Our results from an archival study using Kickstarter data and through a randomized experiment provide consistent support that an open innovation strategy is indeed advantageous in the crowdfunding context. These results are also mediated by perceptions of trust.

Numerical study on tri-fuel combustion: Ignition properties of the mixture of methane-hydrogen-diesel fuel

The research on the multi-fuel combustion is of great significance for power machinery especially rocket engines. In this study, the ignition characteristics of tri-fuel (TF) are studied in the aspects of chemical dynamics through sensitivity analysis, rate of production (ROP) analysis and pathway analysis. The role of trace diesel in different CH4/H2 mixtures was researched, especially three components of diesel alternative fuels (NC16H34, IC16H34, A2CH3 (1-methylnaphthalene)) were studied in detail. In addition, the “stop changing” effect of trace diesel was investigated in the ignition process of TF. The results showed that the increase of pressure reduces the ignition delay times (IDTs) of TF, and it makes the linear relationship between IDTs and temperature stronger at the equivalence ratio of 0.5. Among the diesel alternative fuels in this study, NC16H34 has the greatest influence on ignition through sensitivity analysis, and A2CH3 is the component that has the most complex reaction paths through pathway analysis. In the process of TF ignition, the “stop changing” effect of trace diesel still exists, and the temperature at which the “stop changing” occurs rises gradually with the increase of εCH4 and the effect is closely related to reaction NC16H34+O2=NC16H33+HO2.

Unsupervised Tool Wear Monitoring in the Corner Milling of a Titanium Alloy Based on a Cutting Condition-Independent Method

Real-time tool condition monitoring (TCM) for corner milling often poses significant challenges. On one hand, corner milling requires configuring complex milling paths, leading to the failure of conventional feature extraction methods to characterize tool conditions. On the other hand, it is costly to obtain sufficient test data on corner milling for most of the current pattern recognition methods, which are based on the supervised method. In this work, we propose a time-frequency intrinsic feature extraction strategy of acoustic emission signal (AEs) to construct a cutting condition-independent method for tool wear monitoring. The proposed new feature-extraction strategy is used to obtain the tool wear conditions through the intrinsic information of the time-frequency image of AEs. In addition, an unsupervised tool condition recognition framework, including the unsupervised feature selection, the clustering based on adjacent grids searching (CAGS) and the density factor based on CAGS, is proposed to determine the relationship between tool wear values and AE features. To test the effectiveness of the monitoring system, the experiment is conducted through the corner milling of a titanium alloy workpiece. Five metrics, PUR, CSM, NMI, CluCE and ClaCE, are used to evaluate the effectiveness of the recognition results. Compared with the state-of-the-art supervised methods, our method provides commensurate monitoring effectiveness but requires much fewer test data to build the model, which greatly reduces the operating cost of the TCM system.

Fractional-order nonsingular terminal sliding mode controller for a quadrotor with disturbances

This paper proposes a finite-time controller for an unmanned aerial vehicle in the presence of Figures/uncertainties using fractional-order terminal sliding mode. First, contrary to existing fractional-order backstepping sliding mode controllers, this paper introduces a new control approach for quadrotor position control, which is based on fractional-order fast terminal backstepping sliding mode control. Using an appropriate sliding surface, the position tracking error converges to zero in finite time while providing good robustness properties in different complex path scenarios under unknown disturbances. Then, a novel fractional-order fast terminal sliding mode control scheme is developed for quadrotor attitude control, which provides good properties in terms of robustness against unknown disturbances, and in terms of convergence time, etc. Finally, simulation results are presented to discuss the advantages of the hybrid control approach proposed in this work for quadrotors under unknown disturbances compared to other existing controllers.

Research on Architectural Planning and Landscape Design of Smart City Based on Computational Intelligence.

City brain is a complex system, including online center, server network, and system with given algorithm. The core of the city brain is the intelligent system. After putting the urban brain into the intelligent nerve center, on the basis of not changing its original data structure, combining its own characteristics for design and then integrating into application, it can intelligently change the urban management mode. Urban planning leads the development of smart cities on a certain meaning, and smart city planning must have scientific and rational urban planning. The intelligent model is used to make urban planning form a more modern, convenient, and reasonable urban architectural planning. Some influential books on classical architectural theory are the theoretical basis of intelligent urban planning and even the trend and implementation blueprint of how smart cities will develop in the future. In this paper, four algorithms, ant colony algorithm, particle swarm optimization algorithm, genetic algorithm, and improved ant colony algorithm, are proposed to optimize the characteristics of urban architectural planning and landscape design; especially the security research of architecture and landscape characteristics is very important. The improved ant colony algorithm has the shortcoming of insufficient optimization ability in the face of complex path selection. By improving the influencing factors, a new ant colony algorithm is created. The improved ant colony algorithm achieves the best in security features, so it is advocated to use this algorithm for planning and design. The urban form in smart city aims to create a beautiful and comfortable urban environment, improve the competitiveness of cities in the rapid urbanization process, improve the living standards of the public, and shape the image of this beautiful city.

Study of the Polishing Characteristics by Abrasive Flow Machining with a Rotating Device

Since only uni-direction motion is produced by traditional abrasive flow machining (AFM), so the polishing effects of the inner hole is not easy to achieve uniform roughness of the whole surface after polishing. Therefore, in this study, a rotating device with a DC servo motor was set up in the AFM to increase the tangential forces on the machining surface, and therefore, improve the uniform surface roughness and polishing efficiency. The rotating device was designed by a group of transmission gear set and a DC servo motor to create a rotational finishing path for the abrasive medium. The rotational motion of an abrasive can create different tangential forces on the working surface, inducing a more complex polishing path than that of traditional AFM. In addition to rotational speed, a servo motor can also change rotation directions in one working process, causing an abrasive medium to create many irregular finishing paths in the AFM. The experimental results showed that the surface roughness of the workpiece was significantly decreased with an increase in the rotational speed. Additionally, the results also showed that the surface roughness (SR) of the inner hole decreased from 0.61 μm Ra to 0.082 μm Ra after 20 machining cycles, the surface roughness improvement rate reached 87% at 15 rpm rotational speed, by applying a 1.5:1 silicone gel/abrasive concentration ratio and #60 abrasive mesh in the experiments. This study created excellent polishing efficiency by using a servo rotational device with AFM to produce good surface quality.

Flight Test of the Novel Fixed-Wing Multireference Multiscale LN Guidance Logic for Complex Path Following

Flight Test of the Novel Fixed-Wing Multireference Multiscale LN Guidance Logic for Complex Path Following

Synchro-Drive-Based Underwater Climbing Adsorption Robot

This article proposes an underwater climbing adsorption robot. The robot avoids coming into contact with adsorbates by using a mechanism of negative pressure adsorption based on Bernoulli's theorem, which allows it to generate a maneuverable force. A synchro-drive locomotion mechanism is developed to boost the maneuverability of the robot such that it can carry out omnidirectional motion using the least mechanical parts. Discrete and continuous modes of locomotion are proposed and verified to enable the robot to follow a complex path, and a switch strategy to balance its adsorption and locomotion is developed. In stationary operation mode, the adsorption force can be increased by reducing the gap to maintain the stability of the robot when carrying loads. In the motion mode, the size of the gap is increased to lend the robot a powerful obstacle-surmounting capacity when it moves on rough and curved surfaces. The results show that the proposed robot has the advantages of being non-contact, and having high adsorption and mobility that are suitable for challenging operations on a variety of underwater structural surfaces.

Impending doom or unnecessary panic? The struggle for discursive hegemony in South Africa’s acid mine drainage policy problem

ABSTRACT This article contributes to the literature on environmental policy controversies. We utilize an Argumentative Discourse Analysis (ADA)-based approachto analyze the struggle for discursive hegemony that took place between competing story-lines in the context of the acid mine drainage (AMD) environmental policy problem, located in the gold mining areas of greater Johannesburg, South Africa. With this article we make a theoretical contribution by presenting and applying an adapted ADA framework strongly focused on the operationalization of key ADA concepts. Our empirical contribution lies in providing a rich and deep analysis of an environmental policy controversy that has not yet been studied from an ADA perspective. In particular, we demonstrate and discuss the complex path to discourse institutionalization followed by the dominant emergent AMD story-line. In conclusion , we recommend steps for updating the ADA approach and developing an accompanying set of guidelines to further enable the operationalization of its concepts.

Fatty acid composition of macroinvertebrate scrapers in relation to environmental conditions in subtropical mountain streams.

Biochemical fatty acids (FAs) in vivo are essential to the growth and reproduction of animals including macroinvertebrates in streams and are subject to ambient abiotic variables. However, the main abiotic drivers of FA composition in macroinvertebrate scrapers are varying and uncertain. The aim of this research was to quantify the contributions of abiotic variables, including stream physical, chemical, and climatic variables, to the variation of FAs of macroinvertebrate functional feeding group-scrapers (e.g., Bellamya aeruginosa, Radix swinhoe, Heptagenia sp., and Stenelmis sp.). Stream physical, chemical, and climatic variables and the FAs of scrapers were measured in six subtropical streams during spring. The principal component analysis (PCA) indicated the parameters responsible for FA variation were mainly related to polyunsaturated fatty acids (PUFAs), saturated fatty acids (SAFAs), ω3 PUFA, and ω6 PUFA. Multiple factor analysis (MFA) showed that the FA profiles of scrapers strongly correlated with the physical variables. Specifically, the correlation analysis showed that PUFA and terrestrial FA were significantly positively associated with canopy cover, and in contrast that SAFA was negatively correlated with canopy cover. Although water quality and climate variables did not have a good relationship with FAs, they had a strong correlation with physical variables. This research suggested that the influence of environmental variables (e.g., stream physical, chemical, and climatic variables) on FAs of macroinvertebrate scrapers has complex paths. This study provides a theoretical basis for stream management and an empirical framework for the construction of an interactive network beyond food webs that includes environmental variables.

Analysis of damage characteristics of fine and medium‐fine cracked sandstones under a complex stress path

AbstractIn underground engineering such as mining and tunnel excavation, the rock mass is often subjected to repeated loading and unloading stress environments. Herein, true triaxial cyclic loading and unloading tests are carried out on fine sandstone and medium‐fine sandstone specimens with cracks of different angles. The test results show that the mechanical properties of fine sandstone and medium‐fine sandstone samples show obvious differences, and the crack angle has a significant effect on the mechanical properties of the sandstone specimen. During the experimentation, the expansion phenomenon of medium‐fine sandstone is more obvious than that of fine sandstone, and its brittleness is also weaker. The damage law of the sample has nothing to do with the type of sandstone. The damage caused by the stress in the σ1 direction varies linearly with the cumulative damage of the specimen, however, the damage caused by the directions of σ2 and σ3 grow nonlinearly in terms of the cumulative damage of the specimen. The hysteretic loop dissipated energy of the same type of sandstone specimens at different angles are dissimilar, and the dissipated energy increases with the increase of the crack angle. Based on the equivalent irreversible strain and the hysteretic loop dissipated energy, the damage law of the rock strength is analyzed. The obtained results reveal that the index based on the equivalent irreversible strain is helpful in exploring the damage degree of rock in the initial stage of cyclic loading and unloading. Furthermore, the damage index established based on the energy dissipation concept is beneficial to predicting the damage and failure law of rock in the advanced stage of loading.

Improved Analytic Expansions in Hybrid A-Star Path Planning for Non-Holonomic Robots

In this study, we concisely investigate two phases in the hybrid A-star algorithm for non-holonomic robots: the forward search phase and analytic expansion phase. The forward search phase considers the kinematics of the robot model in order to plan continuous motion of the robot in discrete grid maps. Reeds-Shepp (RS) curve in the analytic expansion phase augments the accuracy and the speed of the algorithm. However, RS curves are often produced close to obstacles, especially at corners. Consequently, the robot may collide with obstacles through the process of movement at these corners because of the measurement errors or errors of motor controllers. Therefore, we propose an improved RS method to eventually improve the hybrid A-star algorithm’s performance in terms of safety for robots to move in indoor environments. The advantage of the proposed method is that the non-holonomic robot has multiple options of curvature or turning radius to move safer on pathways. To select a safer route among multiple routes to a goal configuration, we introduce a cost function to evaluate the cost of risk of robot collision, and the cost of movement of the robot along the route. In addition, generated paths by the forward search phase always consist of unnecessary turning points. To overcome this issue, we present a fine-tuning of motion primitive in the forward search phase to make the route smoother without using complex path smoothing techniques. In the end, the effectiveness of the improved method is verified via its performance in simulations using benchmark maps where cost of risk of collision and number of turning points are reduced by up to around 20%.

A phase field model for electromechanical fracture in flexoelectric solids

Flexoelectricity describes the electromechanical coupling between the stain gradient and the electric polarization, which can play an important role in the fracture behavior of piezoelectrics since large strain gradients exist near the crack tip. In this paper, in order to investigate this effect, a phase field (PF) model is developed for electromechanical fracture in brittle flexoelectric solids, where the crack surfaces are assumed to be either electrically impermeable or electrically permeable. The damage driving force of the PF model is derived from the non-negative energy dissipation rate for both kinds of crack surface conditions, where the mechanical part is regarded as the driving force for the crack evolution. A decomposition method of the mechanical driving force is proposed to characterize the asymmetric fracture behavior under tension and compression. The governing equations are solved numerically with finite element method. The finite element formulation is implemented in Abaqus through the user defined subroutine UEL. The PF model and its numerical implementation are validated by studying benchmark problems. The simulation results indicate that the proposed PF model can well characterize the flexoelectric effect and predict complex crack propagation paths in flexoelectric solids. In addition, the numerical results show that whether a negative applied electric field promotes the crack propagation or retard the crack propagation is closely related to the electric field strength and the flexoelectric coefficients, which can reconcile the contradictory phenomena observed in previous experimental studies. The influences of the applied electric field and the length scale parameters on the electromechanical fracture behavior of flexoelectric solids as well as the size effect are discussed in detail in the paper.

Visibility, impact and relevance in international law

How does international law have influence and impact in and on the world? Daniel Joyce’s new book asks this question from a viewpoint that has received surprisingly limited scholarly attention: the role of the media and an engaged public. A wide-ranging and original work, the book raises pivotal questions about power and legitimacy, patterns of influence, and agency. My reading rests on my disciplinary specialisation at the intersection of anthropology—in particular the study of international organisations, documents, bureaucracy, and expertise1—and international law, complemented by research on the history of human rights and human rights education.2 Joyce’s book is loosely divided into two distinct areas of inquiry. The first of these regards the long, complex, and still-evolving path of media regulation under international law. My attention is drawn to the book’s second part, particularly Chapters 4–6, in which he discusses the role of an informed public and informed media in the sustained legitimacy and influence of international law. In this essay, I will bring Joyce’s book into conversation with my ethnography of the UN Human Rights Committee, the treaty body that monitors state compliance with the International Covenant on Civil and Political Rights (ICCPR).3 Specifically, I will connect the book with previously untheorised fieldnotes of an NGO coalition meeting at the Palais Wilson, the headquarters of the UN Office of the High Commissioner for Human Rights (UN OHCHR) in Geneva.4 In the meeting, NGO delegates—who, in the sessions of the Human Rights Committee, very much occupy the role of an ‘enlightened public’—discussed the issuing of a press release following the Constructive Dialogue between a state party and the Human Rights Committee in which the periodic report submitted by the state is discussed.

The development of EASI-based multi-path analysis code for nuclear security system with variability extension

The Physical Protection System (PPS) plays an important role and must effectively deal with various adversary attacks in nuclear security. In specific single adversary path scenarios, we can calculate the PPS effectiveness by EASI (Estimated Adversary Sequence Interruption) through Probability of Interruption (PI) calculation. EASI uses a single value of the probability of detection (PD) and the probability of alarm communications (PC) in the PPS. In this study, we develop a multi-path analysis code based on EASI to evaluate the effectiveness of PPS. Our quantification method for PI considers the variability and uncertainty of PD and PC value by Monte Carlo simulation. We converted the 2-D scheme of the nuclear facility into an Adversary Sequence Diagram (ASD). We used ASD to find the adversary path with the lowest probability of interruption as the most vulnerable paths (MVP). We examined a hypothetical facility (Hypothetical National Nuclear Research Facility - HNNRF) to confirm our code compared with EASI. The results show that implementing the variability extension can estimate the PI value and its associated uncertainty. The multi-path analysis code allows the analyst to make it easier to assess PPS with more extensive facilities with more complex adversary paths. However, the variability of the PD value in each protection element allows a significant decrease in the PI value. The possibility of this decrease needs to be an important concern for PPS designers to determine the PD value correctly or set a higher standard for PPS performance that remains reliable.

In-situ 4-point flexural testing and synchrotron micro X-ray computed tomography of 3D printed hierarchical-porous ultra-high temperature ceramic

3D printed ceramics have received much attention of late due to the ability to manufacture complex near net shapes with a range of structures across multiple length scales. The introduction of hierarchical features offers a wider array of properties, yet with this comes additional unknowns as to their limits including the mechanisms behind failures. The present work applies in-situ Synchrotron micro X-ray computed tomography (μXCT) with 4-point flexural testing to study and further understand the failure pattern of 3D printed hierarchical porous ultra-high temperature ceramics. Samples were imaged at incremental load steps to observe the propagation of defects until final failure, where in the case of the strain tolerant logpile structure a full crack spanning the height and width of the sample was captured and reconstructed revealing a complex tortuous fracture path. The relative strength and density of the structures are related to the sintered microstructure and the printed logpile or honeycomb geometry, which are described using Gibson’s and Ashby’s theory for brittle foams. In addition, tomographic data was used to extract detailed information on porosity and material density distribution within honeycomb and logpile 3D printed lattice structures that was related to the tool path planning of each layer. • First capture and tomographic reconstruction of complex fracture path in 3D printed UHTC logpile lattice structure. • Synchrotron μXCT of honeycomb and logpile lattice structures provided detailed density information. • Relative strength and density were related to microstructure and the 3D printed logpile/honeycomb internal lattice structure. • Logpile structures exhibited tortuous fracture path and resulted in greater strain tolerance compared to honeycomb.

Experimental investigation of failure process and characteristics in circular tunnels under different stress states and internal unloading conditions

In this study, we investigated the failure process and evolution mechanisms in circular tunnels under a complex stress path of deep in-situ stress + excavation unloading + stress adjustment using a simulation test based on loading first and then drilling (LFTD) mode. This test was performed on cubic sandstone specimens using a true-triaxial testing system combined with a self-developed drilling unloading test device. For comparison, another set of sandstone specimens, similar to the original specimens but with Φ 25 mm circular through-holes, were processed to perform another set of simulation tests based on drilling first and then loading (DFTL) mode. Under constant lateral stress , compared with the DFTL test, the initial failure vertical stress was lower, and the surrounding rock was more prone to failure in the LFTD test, indicating that drilling unloading causes damage to the surrounding rock, thereby inducing a strength-weakening effect. Under constant lateral and vertical stresses, sidewall failure in the LFTD test was more severe. The sidewall's initial failure vertical stress difference between the LFTD and DFTL tests increases with increasing lateral stress or initial hydrostatic pressure . The effect of drilling unloading becomes more apparent under a higher initial stress state. Comparing the same types of simulation tests under different stress states, the initial failure vertical stress increases with the lateral stress or initial hydrostatic pressure, inducing a strength-strengthening effect in the surrounding rock. Comparing the strength-strengthening effect caused by increasing the lateral pressure or initial hydrostatic pressure and the strength-weakening effect caused by drilling unloading shows that the strength-strengthening effect is more evident.