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In this paper, a novel Doppler shift estimation method for frequency diverse array (FDA) radar based on graph signal processing (GSP) theory is proposed and investigated. First, a well-designed graph signal model for a monostatic linear FDA is formulated. Subsequently, spectral decomposition is conducted on the constructed signal model utilizing graph Fourier transform (GFT) techniques, enabling the extraction of the target’s Doppler shift parameter through spectral peak search. A comprehensive series of simulation experiments demonstrates that the proposed method can achieve the accurate estimation of target parameters even under low signal-to-noise ratio (SNR) conditions. Furthermore, the proposed method exhibits superior performance compared to the MUSIC algorithm, offering enhanced resolution and estimation accuracy. Additionally, the method is highly amenable to parallel processing, significantly reducing the computational burden associated with traditional procedures. Full article

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6 pages, 242 KiB

Open AccessEditorial

Water Treatment Technology for Emerging Contaminants

by Wenjie Zhang

Water 2025, 17(5), 644; https://doi.org/10.3390/w17050644 (registering DOI) - 22 Feb 2025

Abstract

The rapid advancement of industrialization and urbanization has brought about significant challenges to water quality and environmental health [...] Full article

(This article belongs to the Special Issue Water Treatment Technology for Emerging Contaminants)

20 pages, 6751 KiB

Open AccessArticle

Altered Directed-Connectivity Network in Temporal Lobe Epilepsy: A MEG Study

by Chen Zhang, Wenhan Hu, Yutong Wu, Guangfei Li, Chunlan Yang and Ting Wu

Sensors 2025, 25(5), 1356; https://doi.org/10.3390/s25051356 (registering DOI) - 22 Feb 2025

Abstract

Temporal lobe epilepsy (TLE) is considered a network disorder rather than a localized lesion, making it essential to study the network mechanisms underlying TLE. In this study, we constructed directed brain networks based on clinical MEG data using the Granger Causality Analysis (GCA) method, aiming to provide new insights into the network mechanisms of TLE. MEG data from 13 lTLE and 21 rTLE patients and 14 healthy controls (HCs) were analyzed. The preprocessed MEG data were used to construct directed brain networks using the GCA method and undirected brain networks using the Pearson Correlation Coefficient (PCC) method. Graph theoretical analysis extracted global and local topologies from the binary matrix, and SVM classified topologies with significant differences (p < 0.05). Comparative studies were performed on connectivity strengths, graph theory metrics, and SVM classifications between GCA and PCC, with an additional analysis of GCA-weighted network connectivity. The results show that TLE patients showed significantly increased functional connectivity based on GCA compared to the control group; similarities of the hub brain regions between lTLE and rTLE patients and the cortical–limbic–thalamic–cortical loop were identified; TLE patients exhibited a significant increase in GCA-based Global Clustering Coefficient (GCC) and Global Local Efficiency (GLE); most brain regions with abnormal local topological properties in TLE patients overlapped with their hub regions. The directionality of brain connectivity has played a significantly more pivotal role in research on TLE. GCA may be a potential tool in MEG analysis to distinguish TLE patients and HC effectively. Full article

(This article belongs to the Section Biomedical Sensors)

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Figure 1
Overview of the experimental workflow. (A) Data Preprocessing: This phase includes the preprocessing of MEG data, the construction of head and source models using T1-weighted MRI, and source reconstruction with the beamformer algorithm to derive regional brain signals. Brain regions are then parcellated according to the AAL116 atlas, and representative signals are extracted based on the maximum power values. (B) Brain Network Construction and Analysis: This section includes brain network construction, brain network binarization, and weighted network analysis. Directed brain networks are established through Granger Causality Analysis (GCA), while undirected networks are formed using the Pearson Correlation Coefficient (PCC). Both networks are binarized using a Global Cost Efficiency (GCE) approach. Weighted network analysis includes comparing connection strengths, evaluating directed connectivity and out-degree metrics, and identifying hub regions. (C) Graph Theoretical Analysis: The analysis focuses on extracting four global topologies: Global Clustering Coefficient (GCC), Global Characteristic Path Length (GCLP), Global Efficiency (GE), and Global Local Efficiency (GLE); and four local topologies: Node Clustering Coefficient (NCC), Node Efficiency (NE), Node Local Efficiency (NLE), and Node Degree Centrality (NDC) from the binarized brain networks. (D) Machine Learning Application: Support Vector Machine (SVM) is utilized to classify topologies with differences of p < 0.05, highlighting differences between the two methodologies. Full article ">Figure 2
Average connection strengths based on PCC and GCA methods. Blue boxplots represent average connection strengths using the Pearson Correlation Coefficient (PCC) method for healthy controls (HCs), left temporal lobe epilepsy (lTLE) patients, and right TLE (rTLE) patients. Red boxplots represent average connection strengths using the Granger Causality Analysis (GCA) method for HC, lTLE, and rTLE. Abbreviations: PCC HC, PCC lTLE, and PCC rTLE denote HC, lTLE, and rTLE using the PCC method, respectively. Similarly, GCA HC, GCA lTLE, and GCA rTLE denote HC, lTLE, and rTLE using the GCA method. (*) indicates statistical significance between HC and lTLE, as well as between HC and rTLE, assessed using a t-test. * p < 0.05, ** p < 0.01, *** p < 0.001. Full article ">Figure 3
Different connectivity analysis based on GCA. This figure presents a comparative analysis of brain network connectivity between left temporal lobe epilepsy (lTLE), right temporal lobe epilepsy (rTLE), and healthy controls (HCs). The four sections (A–D) represent different network connectivity features. (A) Top 20 LCS: The top 20 strongest connections in each group, ranked by connection strength. (B) Top 20 GDC: The top 20 connections with the greatest dissimilarity for lTLE and rTLE compared to HC. (C) Top 5 HODR: The top 5 brain regions with the highest out-degree in each group. (D) Top 5 GDR: The top 5 brain regions with the greatest dissimilarity for lTLE and rTLE compared to HC. The color legend indicates the brain regions involved, with each color corresponding to a specific brain region. Full article ">Figure 4
Hub regions in TLE. This figure illustrates the hub regions of brain networks in patients with lTLE and rTLE. The hubs are identified based on their frequency of appearance in different analyses. (A) lTLE hub regions: hub regions in patients with lTLE. (B) rTLE hub regions: hub regions in patients with rTLE. Arrows indicate the increasing frequency of hub regions from bottom to top in each section. Each brain slice shows the anatomical location of these regions and is visualized using axial, sagittal, and coronal brain slices. Full article ">Figure 5
Global topological parameters of brain functional networks in lTLE patients, rTLE patients, and HC. In the bar graph, black lines indicate data ranges and bars depict means. (*) indicates: p < 0.05, as determined by the Mann–Whitney U non-parametric test. Full article ">Figure 6
AUC of SVM classification of TLE and HC based on PCC and GCA methods. Full article ">Figure 7
Classification effect of GCA under different model orders. Full article ">

20 pages, 278 KiB

Open AccessArticle

Extending the Transhuman Person: Religious Practices as Cognitive Technological Enhancements

by Tobias Tanton

Religions 2025, 16(3), 272; https://doi.org/10.3390/rel16030272 (registering DOI) - 22 Feb 2025

Viewed by 82

Abstract

Transhumanism embraces the use of technology to enhance human capabilities. In keeping with traditional theories of cognition, transhumanists typically assume that mental capacities are organism-bound (or brain-bound), and enhancement is thus achieved exclusively by modifying the human organism. However, 4E cognition challenges this assumption. Instead, understanding the mind as extended or scaffolded highlights how cognitive processes recruit environmental resources to perform their tasks. Therefore, as Andy Clark argues, cognitive enhancement is no longer restricted to modifications of the biological organism but is also achieved by using cognitive tools or niches that allow brain–body–world coalitions to perform more efficient or more sophisticated cognitive functions. Hence, humans are ‘natural-born cyborgs’ who have long been using environmental resources to enhance cognitive abilities. In this article, I extend this analysis to religion. Drawing on recent work on 4E cognition in religious practices, I argue that religious practices can themselves be understood as ‘cognitive technologies’ that count as enhancements. These insights from cognitive science serve to reframe the dialog between Christian theology and transhumanism: (1) enhancements are reframed as belonging to a long history of self-modification, rather than being the sole purview of the future, (2) humans should be understood as intrinsically technological, and (3) theologians are already in the enhancement game and, conversely, transhumanists should consider religious practices. Full article

(This article belongs to the Special Issue Situating Religious Cognition)

15 pages, 3543 KiB

Open AccessArticle

Study on Vacuum Breakdown Properties of Surface-Modified 304 Stainless Steel Electrodes Based on Fractal Theory

by Shiqing Wang, Shenming Zhao, Bo Liu, Weihong Shan, Hao Wei, Dayan Ma and Hongbo Wang

Nanomaterials 2025, 15(5), 340; https://doi.org/10.3390/nano15050340 (registering DOI) - 22 Feb 2025

Viewed by 101

Abstract

This paper reports on the effect of the micro-morphological characteristics of stainless steel electrodes on vacuum breakdown properties under the action of a strong electric field generated by high-power electric pulses. Using chemical passivation modification and atomic layer deposition (ALD) technology, alumina composite films were prepared on the surface of the stainless steel electrodes to reshape the surface microstructure of the electrodes. The surface morphology features of the electrodes were characterized in detail. Based on fractal theory, a fractal model based on the box dimensional method was proposed to quantitatively describe the morphological and structural characteristics of the film, and its relationship with the vacuum breakdown properties was established. The results indicated that the fractal dimension effectively reflected the complexity of the electrode morphology and could serve as a key parameter to evaluate the vacuum breakdown performance of the electrodes, which showed a negative correlation with the change tendency of the electrode breakdown threshold. Full article

(This article belongs to the Special Issue Nano Surface Engineering: 2nd Edition)

14 pages, 7661 KiB

Open AccessArticle

Single Scattering Dynamics of Vector Bessel–Gaussian Beams in Winter Haze Conditions

by Yixiang Yang, Yuancong Cao, Wenjie Jiang, Lixin Guo and Mingjian Cheng

Photonics 2025, 12(3), 182; https://doi.org/10.3390/photonics12030182 (registering DOI) - 22 Feb 2025

Viewed by 93

Abstract

This study investigates the scattering dynamics of vector Bessel–Gaussian (BG) beams in winter haze environments, with a particular emphasis on the influence of ice-coated haze particles on light propagation. Employing the Generalized Lorenz–Mie Theory (GLMT), we analyze the scattering coefficients of particles transitioning from water to ice coatings under varying atmospheric conditions. Our results demonstrate that the presence of ice coatings significantly alters the scattering and extinction efficiencies of BG beams, revealing distinct differences compared to particles coated with water. Furthermore, the study examines the role of Orbital Angular Momentum (OAM) modes in shaping scattering behavior. We show that higher OAM modes, characterized by broader energy distributions and larger beam spot sizes, induce weaker localized interactions with individual particles, leading to diminished scattering and attenuation. In contrast, lower OAM modes, with energy concentrated in smaller regions, exhibit stronger interactions with particles, thereby enhancing scattering and attenuation. These findings align with the Beer–Lambert law in the single scattering regime, where beam intensity attenuation is influenced by the spatial distribution of radiation, while overall power attenuation follows the standard exponential decay with respect to propagation distance. The transmission attenuation of BG beams through haze-laden atmospheres is further explored, emphasizing the critical roles of particle concentration and humidity. This study provides valuable insights into the interactions between vector BG beams and atmospheric haze, advancing the understanding of optical communication and environmental monitoring in hazy conditions. Full article

(This article belongs to the Special Issue Advances in Structured Light: Propagation, Scattering, and Applications)

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(a) Transmission schematic of BG beams in haze environment. (b) Ice-coated haze particles corrected model and schematic of BG beam particle scattering. Full article ">Figure 2
RCS of various haze particles with ice and water coatings under X-polarized BG beam irradiation: (a) meteoric-type particles, (b) dust-like particles, (c) soot particles, and (d) sulfate particles. Full article ">Figure 3
RCS of soot-type haze particles with ice and water coatings under linearly polarized BG beam irradiation featuring OAM modes s = 1 and s = 3: (a) λ = 0.86 μm, (b) λ = 1.06 μm, (c) λ = 2.0 μm, (d) λ = 5 μm. Full article ">Figure 4
RCS of soot-type haze particles with ice and water coatings for various inner-to-outer diameter ratios (a/b = 0.7 and a/b = 0.9) under vector BG beam irradiation with different polarization states: (a) X-polarized, (b) Y-polarized, (c) left circularly polarized, (d) right circularly polarized, (e) azimuthally polarized, and (f) radially polarized. Full article ">Figure 5
Efficiency factors of soot-type haze particles with ice and water coatings under X-polarized BG beam irradiation at wavelengths λ = 0.86 μm and λ = 5.0 μm: (a) absorption efficiency factor, (b) scattering efficiency factor, and (c) extinction efficiency factor. Full article ">Figure 6
Transmittance of X-polarized BG beam at wavelengths λ = 0.86 μm (a), λ = 1.06 μm (b), λ = 2.0 μm (c), and λ = 5.0 μm (d) in soot-type haze environments with varying concentrations N = 5000, 10,000, 15,000, 20,000 cm−3. Full article ">Figure 7
Transmittance of X-polarized BG beam with OAM modes m = 0 (a), m = 1 (b), m = 2 (c), and m = 3 (d) in haze environments containing varying components: meteoric, dust-type, soot, and sulfate particles. Full article ">

15 pages, 246 KiB

Open AccessArticle

Some New Fibonacci Matrices and Error Detecting-Correcting Codes

by Ferhat Kürüz

Symmetry 2025, 17(3), 333; https://doi.org/10.3390/sym17030333 (registering DOI) - 22 Feb 2025

Viewed by 119

Abstract

The rapid and accurate transfer of information is essential in today’s digital world, where error detecting and correcting codes play a crucial role. In this context, Fibonacci numbers have been extensively applied in coding theory, particularly in coding structures based on Fibonacci polynomials and symmetric matrices. This study proposes a novel coding framework by defining and using some new Fibonacci matrices with their determinants. The properties of these matrices are analyzed to construct efficient coding and error correction mechanisms. The proposed structure enables the transmission of larger data volumes in a single iteration without compromising the error correction performance, demonstrating the potential of Fibonacci matrices for reliable and efficient information transfer. Full article

(This article belongs to the Special Issue Fibonacci and Lucas Numbers and the Golden Ratio in Physics and Biology)

29 pages, 4209 KiB

Open AccessArticle

Profit-Efficient Elastic Allocation of Cloud Resources Using Two-Stage Adaptive Workload Prediction

by Lei Li and Xue Gao

Appl. Sci. 2025, 15(5), 2347; https://doi.org/10.3390/app15052347 (registering DOI) - 22 Feb 2025

Viewed by 105

Abstract

Internet services are increasingly being deployed using cloud computing. However, the workload of an Internet service is not constant; therefore, the required cloud computing resources need to be allocated elastically to minimize the associated costs. Thus, this study proposes a proactive cloud resource scheduling framework. First, we propose a new workload prediction method—named the adaptive two-stage multi-neural network based on long short-term memory (LSTM)—which can adaptively route prediction tasks to the corresponding LSTM sub-model according to the workload change trend (i.e., uphill and downhill categories), in order to improve the predictive accuracy. To avoid the cost associated with manual labeling of the training data, the first-order gradient feature is used with the k-means algorithm to cluster and label the original training data set automatically into uphill and downhill training data sets. Then, based on stochastic queueing theory and the proposed prediction method, a maximum cloud service profit resource search algorithm based on the network workload prediction algorithm is proposed to identify a suitable number of virtual machines (VMs) in order to avoid delays in resource adjustment and increase the service profit. The experimental results demonstrate that the proposed proactive adaptive elastic resource scheduling framework can improve the workload prediction accuracy (MAPE: 0.0276, RMSE: 3.7085, : 0.9522) and effectively allocate cloud resources. Full article

16 pages, 652 KiB

Open AccessArticle

Alcohol and Cannabis Perceived Descriptive and Injunctive Norms, Personal Use, and Consequences Among 2-Year College Students

by Jennifer C. Duckworth, Kristi M. Morrison and Christine M. Lee

Behav. Sci. 2025, 15(3), 251; https://doi.org/10.3390/bs15030251 (registering DOI) - 22 Feb 2025

Viewed by 35

Abstract

Two-year college students represent 35% of U.S. undergraduates, yet substance use among them is understudied. Grounded in Social Norms Theory, the present study examined alcohol and cannabis use prevalence and associations between perceived peer use (descriptive norms), approval of use (injunctive norms), and personal use among 2-year students. We also explored whether identification with the reference group or age moderated associations. Data were collected from May through August of 2020 from 1037 2-year college students in Washington State (screening sample) aged 18–29. Of these, 246 participants who reported recent, moderate alcohol and/or cannabis use completed a follow-up survey. Screening survey participants reported past-month alcohol and cannabis use and demographics, while follow-up participants provided data on perceived peer descriptive and injunctive norms and group identification. Screening participants reported drinking an average of 3.32 (SD = 7.76) drinks weekly and being high for 8.18 h (SD = 20.95). Follow-up participants overestimated peer alcohol and cannabis use. Regression analyses showed perceived descriptive alcohol and cannabis norms were positively associated with personal use, and perceived injunctive alcohol norms were positively related to alcohol-related consequences. Differences by student age were also observed. Findings suggest perceived peer norms are risk factors for substance use behaviors among 2-year college students. Tailored normative feedback interventions may reduce high-risk use in this underserved population. Full article

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Differences in alcohol and cannabis use among 2-year college students and perceived peer alcohol and cannabis use among 2-year college students who reported recent use. Full article ">Figure 2
Differences in percent of 2-year college students who engaged in HED and perceived percent of peer HED among 2-year college students with recent use. Full article ">

28 pages, 638 KiB

Open AccessReview

Public Sector Entrepreneurship: Present State and Research Avenues for the Future

by Bojan Moric Milovanovic, Matea Cvjetkovic and Jasmina Masovic

Adm. Sci. 2025, 15(3), 71; https://doi.org/10.3390/admsci15030071 (registering DOI) - 22 Feb 2025

Viewed by 112

Abstract

Public sector entrepreneurship (PSE) is a growing area of knowledge that studies the application of innovative activities and processes to enhance public service quality. This can ultimately affect the public organization’s performance and the country’s economic success and growth. Even though PSE has been studied through the lenses of several academic disciplines, its assumptions are often based on the insights derived from research on entrepreneurship in the private sector. The theories of public entrepreneurship are scattered throughout the literature, while empirical research is still scarce. There exists a need to build a conceptual characterization that distinguishes its unique indicative dimensions. This paper aims to collect and summarize some of the definitions, theories, dimensions, and determinants of public sector entrepreneurship and propose avenues for future empirical research. It is a literature review using the PRISMA methodology to examine public sector entrepreneurship, systematically collecting and synthesizing previous research. This approach yielded 55 publications, which were used as sources for developing a comprehensive conceptualization of PSE. The paper’s contribution is reflected in this review and analysis, as well as its suggestions for future research topics and empirical methods in this developing area of knowledge. Full article

(This article belongs to the Special Issue Catalyzing Growth: Nurturing Innovation and Entrepreneurship for Sustainable Business Development)

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PRISMA flowchart. Source: authors, based on <a href="#B24-admsci-15-00071" class="html-bibr">Criado et al.</a> (<a href="#B24-admsci-15-00071" class="html-bibr">2023</a>). Full article ">

14 pages, 490 KiB

Open AccessArticle

Exploring the Responsibilities, Boundaries, and Well-Being of Teachers in the Philippines

by Lucas Dominic C. Tan and Tim Urdan

Psychol. Int. 2025, 7(1), 14; https://doi.org/10.3390/psycholint7010014 (registering DOI) - 22 Feb 2025

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Abstract

Teacher identity is a multidimensional construct that includes elements such as teachers’ perceptions of their responsibilities and the boundaries they place on those responsibilities. The purpose of this study was to examine how elements of teacher identity, specifically their perceived responsibilities and the boundaries they place on their responsibilities, are related to teacher well-being. Individual, semi-structured interviews were conducted with 23 teachers in the Philippines. Teachers were asked about their perceptions of their responsibilities, where they draw the boundaries on what they are responsible for, and their feelings of stress and burnout. A grounded theory approach was used to develop a coding scheme and code the interview transcripts. The results revealed that most of the teachers in the sample felt responsible for promoting both academic and social–moral development in their students but created boundaries that prevented them from prying into students’ personal lives and helped them maintain professional boundaries. Unlike many teachers in the U.S., few of the teachers in the Filipino sample expressed high levels of burnout or a desire to leave the profession. We argue that cultural differences in the way teachers define their roles and responsibilities may explain the differences in the burnout levels of teachers in the U.S. compared to those of teachers in the Philippines. Lessons learned from how teachers with low levels of burnout define their roles and responsibilities can be used to help teachers at risk of burning out reframe their role identities. Full article

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Percentage of teachers who said their responsibilities changed in specific ways. Full article ">

14 pages, 4626 KiB

Open AccessTechnical Note

Long-Term Stability Evaluation Method of Coastal Rocky Slope Considering Wave Loading

by Miaojun Sun, Zhigang Shan, Haiyuan Wu, Qingbing Liu and Jinge Wang

Water 2025, 17(5), 637; https://doi.org/10.3390/w17050637 (registering DOI) - 22 Feb 2025

Viewed by 159

Abstract

Under the influence of long-term external and internal dynamic conditions such as waves, tides, and earthquakes, coastal rock masses may slide along unfavorable structural planes, leading to landslide disasters. These events pose threats to offshore engineering facilities, coastal tourism, and economic production safety. To elucidate the impact of wave loading on the stability of coastal rocky slopes, this paper first establishes a generalized geological model and a computational mechanics model of coastal rocky slopes. Using computational fluid dynamics programs, the study analyzes the magnitude and distribution characteristics of wave pressure on coastal slopes with different inclinations under varying wave heights. The results indicate that the maximum wave pressure and resultant wave forces acting on the slope surface decrease with increasing slope angle and decreasing wave height. The relationship between the maximum wave pressure or resultant wave force with the wave height and slope angle conforms to an exponential mathematical model. By decomposing the wave force along the potential sliding surface, the variation in shear stress caused by wave pressure can be calculated. Considering the effects of wave, tide, and seismic loads, the study further analyzes the long-term weakening patterns of shear strength due to the variation in shear stress on the sliding surface induced by wave action. Based on the limit equilibrium theory and the constitutive model of strain-softening in rock and soil material, this paper proposes a method to calculate the current and long-term factor of safety (FOS) of coastal rocky slopes under wave loading. Full article

(This article belongs to the Special Issue Slope Stability Analyses and Landslide Risk Assessment Under Hydrodynamic Action)

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Typical photo (a) and generalized geological model (b) of coastal rocky slope. Full article ">Figure 2
Mechanical model of coastal rocky slopes. Full article ">Figure 3
Numerical model (a) and materials (b) of wave pressure on coastal rocky slope. Full article ">Figure 4
Schematic diagram of wave generation simulation. Full article ">Figure 5
Formation process of wave pressure on coastal rocky slopes. Full article ">Figure 6
Numerical simulation results of wave pressure distribution on slopes under different slope angles and wave heights. Full article ">Figure 7
Maximum wave pressure (a) and resultant wave force (b) on slope surface for different slope angles and wave heights and their 3D fitted surfaces (c,d). Full article ">Figure 8
Schematic diagram of shear stress on potential sliding surface due to wave pressure on slope surface. Full article ">

15 pages, 564 KiB

Open AccessArticle

Understanding Stigma in Mental Illness: A Novel Literature-Based Model of Development

by Jorge Magalhães Rodrigues, Ana Sofia Cruz and Cristina Queirós

Psychiatry Int. 2025, 6(1), 21; https://doi.org/10.3390/psychiatryint6010021 (registering DOI) - 22 Feb 2025

Viewed by 144

Abstract

The concept of stigma has evolved, initially denoting a mark of shame and now encompassing a broader range of negative societal perceptions. Cognitive-social models describe stigma as containing stereotypes, discrimination, and prejudice, with each dimension significantly impacting individuals’ health, social interactions, and willingness to seek help. This study has the objective of exploring the main theories about stigma to propose a novel model that integrates these dimensions, illustrating their interactions and cumulative impact on individuals and their families. The model aims for a comprehensive understanding of stigma development in mental illness and provides valuable insights for developing targeted anti-stigma interventions, ultimately improving the lives of individuals with mental illness and their families. Full article

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Proposal for the development of stigma in its dimensions related to the individual with mental illness and their family members. Full article ">

19 pages, 774 KiB

Open AccessArticle

Analysis of Flutter Characteristics for Composite Laminates in Hypersonic Yawed Flow

by Shuang Cao, Tongqing Guo, Jiangpeng Wu, Di Zhou and Ennan Shen

Aerospace 2025, 12(3), 174; https://doi.org/10.3390/aerospace12030174 - 21 Feb 2025

Viewed by 219

Abstract

This paper investigates the flutter characteristics of composite laminates in hypersonic yawed flow using numerical simulations. The governing equations are derived based on Hamilton’s principle and were discretized using the assumed mode method. The unsteady aerodynamic force is calculated by using the piston theory, including the influence of the yaw angle. Several laminate models are designed to study the effects of the stacking sequence, thickness ratio, and fiber orientation on the critical dynamic pressure and the amplitude of the limit cycle oscillation. Numerical results show that positioning the material with higher stiffness on the upper layer can lead to a higher critical dynamic pressure and a smaller amplitude of the limit cycle oscillation. In the case of large yaw angles, increasing the thickness of the material with larger stiffness can clearly suppress the amplitude of the limit cycle oscillation. Fiber orientation symmetry to the x-axis can improve the flight stability with the change in the yaw angle. Full article

(This article belongs to the Special Issue Advanced Aircraft Structural Design and Applications)

13 pages, 537 KiB

Open AccessArticle

Dipolar Copper(I) Complexes: A Novel Appealing Class of Highly Active Second-Order NLO-Phores

by Alessia Colombo, Claudia Dragonetti, Francesco Fagnani, Dominique Roberto and Simona Fantacci

Molecules 2025, 30(5), 1009; https://doi.org/10.3390/molecules30051009 - 21 Feb 2025

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Abstract

The second-order nonlinear optical (NLO) properties of the known heteroleptic complex [Cu(1,10-phenanthroline)xantphos][PF₆] (complex 1) and the related new complexes [Cu(5-NO₂-1,10-phenanthroline)xantphos][PF₆] and [Cu(5-NO₂-1,10-phenanthroline)(dppe)][PF₆] (dppe = 1,2-bis(diphenylphosphino)ethane) (complexes 2 and 3) were investigated in solution by the EFISH (Electric Field-Induced Second Harmonic generation) technique, working at a non-resonant wavelength of 1907 nm. It turned out that they are characterized by large μβ values (957–1100 × 10⁻⁴⁸ esu), much higher than that of the Disperse Red One benchmark. Unexpectedly, the homoleptic complex [Cu(2-mesityl-1,10-phenanthroline)₂][PF₆] (complex 4) shows a similar high second-order NLO response. Quantum chemical calculations based on Density Functional Theory (DFT) methods have been carried out to give insight into the electronic structure of the investigated complexes in relation to NLO properties. This investigation, which represents the first EFISH study on copper(I) complexes, opens a convenient route for the development of low-cost dipolar NLO-active heteroleptic [Cu(P^P)(N^N)][PF₆] and homoleptic [Cu(N^N)₂][PF₆] complexes. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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