Search Results (4,357)

Tuned liquid dampers (TLDs) are widely used in structural vibration mitigation, but they are limited by their damping frequency to use as passive damping equipment. To enhance the damping performance of the conventional TLD, a unique layered tuned liquid damper (LTLD) filled with water and diesel is proposed. The interfacial wave coupling mechanism for broadband energy dissipation has not been previously explored in sloshing-type dampers. A series of frequency-sweeping tests were carried out in the laboratory to compare the vibration suppression performance of the proposed LTLD against conventional TLD. The dampers were installed on an elastic supporting structural platform (SSP) with a height of one meter, and the bottom was horizontally excited with different amplitudes and frequencies using a hexapod motion simulator. The results indicate that the LTLD showed a better damping performance than the TLD under small-amplitude excitation and achieved optimization at two peaks. The separation surface movement dissipated the liquid motion’s energy and enhanced the hydrodynamic force in the horizontal direction. However, the damping effect of the LTLD weakened when the two liquids were no longer immiscible under large-amplitude excitation. Therefore, we recommend utilizing the LTLD to improve structural damping performance when $d_{max}/L$< 0.04984. In addition, the LTLD reduced the maximum wall pressure by about 25% in the transient state under large-amplitude excitation. This study presents experimental evidence that a water–diesel LTLD achieves broadband damping through interfacial wave coupling. The stable interfacial waves enhance energy dissipation and excite new vibration mitigation frequencies, offering a novel approach to overcoming the narrow-band limitation of conventional TLD. Full article

Damage to tunnel structures under seismic action severely affects engineering safety and post-earthquake rescue, making it crucial to enhance the seismic capacity of tunnels. Current seismic approaches for tunnel engineering mainly include seismic isolation (shock absorption layer technology), damping, and anti-seismic, among which shock absorption layer technology has attracted considerable attention due to its economic efficiency and effectiveness. However, existing research has primarily focused on single shock absorption layer materials, lacking systematic classification frameworks and multi-dimensional comparative analyses, making it difficult to provide comprehensive guidance for material selection and engineering applications. This paper systematically reviews the research status of tunnel shock absorption layers. First, it elucidates three core mechanisms through which shock absorption layers function: wave-impedance mismatch and energy reflection, material damping and energy dissipation, and system stiffness reduction with natural period elongation. This study proposes categorizing the existing materials for tunnel shock absorption layers into five main types: foam concrete, other types of concrete, polymer materials, asphalt materials, and porous metallic materials. A detailed introduction is provided for each material category, covering their physical properties, shock absorption performance, advantages and disadvantages, as well as relevant optimization studies conducted to address material limitations. By comprehensively comparing the mechanical properties, shock absorption performance, durability, constructability, recyclability, and economy of these five types of materials, revealing their unique advantages and applicable limitations in tunnel shock absorption. Finally, the limitations of existing research are summarized, development directions for tunnel shock absorption layer materials are proposed, and the future research trend of tunnel damping layer technology is envisioned. This paper provides a reference for the research, selection, and standard formulation of tunnel shock absorption layer materials. Full article

The rapid, field-ready detection of methamphetamine (MET) directly in sewage under flow remains a bottleneck for public health and law enforcement surveillance. We engineered a low-cost, 3D-printed flow-through electrochemical cell that houses a commercial screen-printed carbon electrode and operates in both non-flow and flow regimes. The platform was validated using the [Ru(NH₃)₆]^3+/2+ couple, confirming negligible kinetic hindrance and suitability for voltammetric sensing under convective transport. Using square wave voltammetry and chronoamperometry, MET was quantified in filtered wastewater, with limits of detection of 15.9 µg L⁻¹ in non-flow and 211.2 µg L⁻¹ in flow conditions. Specificity tests yielded well-separated faradaic responses for the pre precursor α-phenylacetoacetonitrile (APAAN) and for MET, while amphetamine produced only a weak signal, enabling side-by-side discrimination in a single run. To our knowledge, this is the first demonstration of direct electrochemical sensing of MET in flowing wastewater using a 3D-printed flow-through platform. The simple, disposable design provides an actionable foundation for portable, near-real-time sewer surveillance and motivates antifouling/auto-cleaning strategies for long-term deployment. Full article

Many of the film thickness measurements that have been reported in the literature tend to focus on small pipe diameters, which may not be practical for a variety of industrial applications. Additionally, single-point measurements are unable to provide the necessary film thickness data around the circumference of the pipe as well as in the axial direction. This paper aims to experimentally study the behaviour of wavy liquid films, including wave frequency, wave velocity, wave width, and wave spacing. A Multi-Pin Film Sensor (MPFS) was used to extract the thickness of a free-falling liquid film in axial, circumferential, and temporal coordinates. The range of liquid Reynolds number Re_L used was 618–1670. It was found that the power spectral density of the disturbance waves showed a pronounced peak at the modal frequency of 6–8 Hz. The number of disturbance waves was found to be almost independent of Re_L. The axial interfacial wave seemed to travel at a constant velocity while the mean velocity in circumferential direction was negligible. The mean width of the disturbance waves was approximately 17.7% of the pipe diameter. Full article

Fiber Bragg Gratings (FBGs) are essential components in fiber-optic sensing systems owing to their high sensitivity, compact structure, and immunity to electromagnetic interference, and have been widely applied in structural health monitoring, aerospace, energy, and biomedical fields. Conventional FBG fabrication methods, including standing-wave, two-beam interference and phase mask methods, rely heavily on the photosensitivity of optical fibers and are limited in terms of fabrication flexibility and grating structural diversity. Femtosecond Laser Direct Writing (FLDW) has emerged as a prospective approach for FBG fabrication due to its nonlinear absorption mechanism, low thermal damage, three-dimensional processing capability and broad material compatibility. This review summarizes recent progress in FLDW-FBGs, with particular emphasis on the characteristics of point-by-point (PbP), line-by-line (LbL) and plane-by-plane (Pl-by-Pl) methods. The implementation of these methods in various fiber, including standard single-mode fibers, sapphire fibers, and polymer optical fibers, is discussed in detail. In addition, recent advances in FBG-based sensing applications under extreme environments, as well as in biomedical sensing and optical fiber communication, are reviewed. Key challenges related to fabrication efficiency, process stability, and microstructural characterization are further analyzed. Finally, potential development directions toward improved controllability, structural design flexibility, and engineering applicability of FLDW-FBGs are outlined. Full article

Older adults with disabilities face compounded vulnerabilities due to both functional limitations and socioeconomic disadvantage. In South Korea, where public welfare systems remain fragmented and cultural values emphasize independence and productivity, understanding the mechanisms linking socioeconomic status (SES) to health outcomes is critical. This study investigates whether reserve capacity mediates the relationship between SES and self-rated health (SRH) in older adults with disabilities. Data were drawn from the supplementary survey on people with disabilities in the 18th wave (2023) of the Korea Welfare Panel Study (KWePS). The analytic sample included older adults aged 65 and above with registered disabilities. A multiple mediation analysis was conducted using Model 4 of the PROCESS macro in SPSS to examine whether three dimensions of reserve capacity—intrapsychic resources (self-esteem), interpersonal resources (social support satisfaction), and tangible resources (use of public disability services)—mediated the relationship between SES and SRH. Demographic and health-related covariates were statistically controlled. The results are as follows: The direct effect of SES on SRH was not significant; however, significant indirect effects were found through all three mediators. Higher SES was positively associated with intrapsychic and interpersonal resources and negatively associated with tangible resource use. Among the mediators, interpersonal resources had the strongest positive effect on SRH, while tangible resources showed a negative association—possibly due to compensatory activation or increased disease awareness among service users. The findings highlight the importance of psychosocial and relational resources in shaping perceived health among disabled older adults in Korea. Policy interventions should move beyond material assistance and focus on strengthening social networks and psychological resilience to reduce health disparities in this population. Full article

Background/Objectives: Olfactory dysfunction and dysgeusia are common neurosensory manifestations of Coronavirus Disease 2019 (COVID-19), affecting approximately 60% of patients. These symptoms have been mechanistically linked to receptors involved in Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) cell entry, including angiotensin-converting enzyme 2 (ACE2), transmembrane protease serine 2 (TMPRSS2), furin, and neuropilin-1 (NRP1), which are highly expressed in the olfactory epithelium. Nevertheless, clinical evidence supporting a direct association between receptor expression and sensory impairment remains inconsistent. Methods: We conducted a multicenter, observational, cross-sectional study including 104 adults with polymerase chain reaction–confirmed SARS-CoV-2 infection during the first and second pandemic waves. Approximately 75 days after diagnosis, nasal and/or pharyngeal samples were obtained to quantify gene expression levels of ACE2, TMPRSS2, furin, and NRP1 using quantitative polymerase chain reaction. Olfactory dysfunction and dysgeusia were recorded as dichotomous variables. Logistic regression analyses were performed with adjustment for age, sex, and race, considering receptor expression as continuous variables and as tertiles. Missing data were addressed using multiple imputation methods. Results: Olfactory dysfunction was reported by 37.5% of participants, and dysgeusia by 36.5%. No statistically significant associations were observed between baseline expression levels of ACE2, TMPRSS2, furin, or NRP1 and the presence of olfactory dysfunction or dysgeusia in either adjusted continuous or categorical models. Although these associations did not reach statistical significance, higher ACE2 and furin expression showed a nonsignificant trend toward an increased probability of sensory alterations, whereas intermediate NRP1 levels were associated with lower disease severity. Conclusions: COVID-19-related olfactory dysfunction and dysgeusia do not appear to be directly determined by isolated baseline expression of SARS-CoV-2 entry receptors. These findings support a multifactorial and dynamic pathophysiological model involving temporal receptor regulation, inflammatory processes, and host-related factors, highlighting the need for longitudinal and interventional studies. Full article

This study examines how sustainability orientation shapes sustainability behavior among entrepreneurial small and medium-sized enterprises (SMEs) in Turkey. Grounded in self-determination theory (SDT) and the theory of planned behavior (TPB), this study develops and empirically tests a conditional process model in which perceived social support functions as a mediating mechanism and sustainable entrepreneurship operates as a boundary condition. Data were collected from 519 senior managers of ISO 14001-certified SMEs using a two-wave survey design to mitigate common method variance (CMV). Using Hayes’ PROCESS macro, the results indicate that sustainability orientation is positively associated with sustainability behavior and that perceived social support partially mediates this relationship by facilitating the translation of sustainability values into action. Furthermore, sustainable entrepreneurship strengthens both the direct association between sustainability orientation and sustainability behavior and the indirect pathway operating through perceived social support. SMEs with higher sustainable entrepreneurship capabilities are better positioned to leverage internal values and external social reinforcement to enact proactive sustainability practices. Overall, the findings highlight the joint role of motivational orientations, social reinforcement, and entrepreneurial capability in shaping sustainability outcomes. The study contributes to sustainability and entrepreneurship research by clarifying how value-based orientations are converted into sustainable behavior and offers practical implications for policymakers and SME leaders seeking to accelerate sustainability transitions in emerging economies. Full article

The Laser Interferometer Space Antenna (LISA) is an ESA mission designed to detect gravitational waves from space. To initiate the science phase, six test masses (TMs) are precisely handled and released into near-perfect free fall by dedicated mechanisms known as the Grabbing, Positioning, and Release Mechanisms (GPRMs). The stringent requirements on the noise level affecting the TMs’ release acceleration are extremely ambitious, motivating the need to experimentally verify the feasibility of achieving such performance. To this end, a dedicated precursor mission, LISA Pathfinder (LPF), flew from 2015 to 2017 to test key technologies. However, during the LPF mission, most release tests exhibited anomalous release velocities, often exceeding the requirements. In addition, the TM repositioning tests also revealed a bi-stable behavior in the TM rotations, which depend on the repositioning direction. This effect is produced by an unexpected non-rectilinear motion of the GPRM end effector, characterized by a micrometric side motion at the reversal of its axial motion. The bi-stable behavior also contributes to a TM-GPRM end effector misalignment, producing unwanted contacts and increasing the probability of a non-compliant TM release. Previous analyses identified asymmetric friction forces in the side-guiding system of the GPRM end effector as the primary cause of this behavior. Starting from the LPF flight experience, the GPRM delta development project in view of LISA led to a redesign of the mechanism architecture, supported by numerical analyses and multi-body models. Since the rectilinearity of the end-effector motion has been identified as critical for flight operation, alternative side-guiding concepts are developed, analyzed, and tested experimentally to evaluate their impact on the overall mechanism performance. The correlation of the models with ground and flight experimental data strengthens the understanding of the guiding system behavior, providing pivotal insights for selecting the GPRM design baseline for LISA. Full article

This study addresses a critical gap in sustainable human resource management research by examining the psychological mechanisms through which Green Human Resource Management (GHRM) influences Sustainable Employee Performance in hospitality organizations. Data were collected through a two-wave time-lagged design from 392 hotel employees in Egypt’s hospitality sector. Partial Least Squares Structural Equation Modeling (PLS-SEM) was employed to test direct effects, parallel mediation, and sequential mediation pathways. The results reveal that GHRM significantly shapes both Moral Self and Moral Integrity, which in turn drive Sustainable Employee Performance. The sequential mediation pathway through which GHRM influences Moral Self, subsequently cultivating Moral Integrity and ultimately enhancing performance, was strongly supported, with approximately 81% of GHRM’s total effect operating through these moral identity mechanisms. Sustainable performance was found to be explained by over 61% of variance in the model, illustrating substantial predictive validity, thus confirming that moral identity is the central psychological conduit for the direct effect of the organizational sustainability system on employee behavior. Full article

In response to the high stiffness and hardness levels of alumina ceramic materials, the traditional SHPB (split Hopkinson pressure bar) experimental setup has been modified. This study analyzes the propagation patterns of stress waves in the SHPB system after adding cushion blocks. Experiments demonstrated that the modified SHPB apparatus can effectively perform dynamic mechanical property tests on alumina ceramics. The JH-2 constitutive damage model parameters for alumina ceramics were determined based on theoretical analysis and static/dynamic experimental data. An LS-DYNA numerical model for the impact compression simulation of alumina ceramics was established to investigate the effects of stress waves with three wavelengths (300 mm, 400 mm, and 600 mm) at the same impact velocity, along with the dynamic fragmentation process. The results indicate that alumina ceramics exhibit strain rate hardening effects in compressive strength, failure strain, and elastic modulus under high strain rates; compressive strength and failure strain show positive correlations with stress wave wavelength under high strain rates; and microcracks initially nucleate preferentially along grain boundaries on the end surfaces, forming annular damage zones symmetrically about the central axis. This study presents a modified SHPB setup that improves test capability for high-hardness ceramics, rather than overturning classical methodologies. The absence of a direct comparison with unmodified setups stems from the known limitations of conventional systems in handling small-diameter alumina specimens without bar damage—a challenge addressed proactively in this work through impedance-matched cushion blocks and refined data processing. Full article

Terahertz waves are located in the “transition zone” between millimeter waves and infrared light. Terahertz video synthetic aperture radar (THz-ViSAR) utilizes the high operating frequency, strong radar cross-section intensity, and high azimuth repetition frequency of terahertz waves to detect and track ground moving targets. The conventional methods for detecting moving targets do not take into account the imaging characteristics of moving targets in THz-ViSAR. The constant false alarm rate (CFAR) detection method is used together with other methods to detect moving targets, resulting in unsatisfactory detection performance. This article proposes a new detection method for single channel slow-moving targets in THz-ViSAR based on shadows and light spots, which extracts the features of the shadow and spot areas of the moving target, and determines the position and direction of the moving target through the identification of the shadow and spot areas. The progressiveness of this method is verified by simulation and experimental tests. Full article

Cylindrical charges are widely used in engineering blasting, yet the three-dimensional propagation mechanism of the associated stress waves remains inadequately understood. This study aims to investigate the effects of key wave source parameters on stress wave propagation and rock damage in cylindrical charge blasting. A semi-analytical solution for spherical stress wave propagation in a full elastic space is developed to theoretically describe the stress field, and a computational model for cylindrical charges is established based on the superposition principle of equivalent spherical charges. Numerical simulations using the RHT constitutive model are then performed to verify the theoretical predictions and further investigate stress wave propagation and rock damage. The results show that the attenuation index of radial stress decreases from 1.5 to 1 as the loading rate increases. Higher loading rates produce more but shorter cracks, whereas lower rates result in fewer but longer cracks. The blast-induced damage region shifts from the detonation direction toward the horizontal plane with increasing detonation velocity, and the resulting rock damage exhibits a conical distribution controlled by the initiation point. These findings provide practical guidance for optimizing cylindrical charge blasting and controlling crack patterns in engineering applications. Full article

Aboveground storage tanks are used to store various fluids and chemicals for many industrial purposes. According to API standard 653, the structural integrity of these tanks must be regularly assessed. The U.S. EPA requires each operator to have a Spill Prevention, Control and Countermeasure Plan (SPCC) for aboveground storage containers. The accepted practice for inspection of these tanks, particularly the tank bottoms, requires removing the tank from service, emptying the tank, and interior entry for direct inspection of the structure. The required inspection operations are hazardous due to the chemicals themselves as well as the requirement to operate within confined spaces. An inspection from outside the tank would have significant cost and time benefits and would provide a large reduction in the risks faced by inspection personnel. Guided wave (GW) testing is a promising candidate for screening of storage tank walls and bottoms from the tank exterior due to the ability of GWs to propagate over long distances from a fixed probe location. The lowest-order transverse-motion guided wave modes (e.g., torsional vibrations in pipes) are a good choice for long-range inspection because this mode is not dispersive; therefore, the wave packets do not spread out in time. A common weakness of guided wave inspection is the complexity of report generation in the presence of multiple geometry features in the structure, such as welds, welded plate corners, attachments and so on. In some cases, these features cause generation of non-relevant indications caused by mode conversion. Another significant challenge in applying GW testing is development of probes with high-enough signal amplitudes and relatively small footprints to allow them to be mounted on short tank bottom extensions. In this paper, a new generation of magnetostrictive transducers will be presented. The transducers are based on the reversed Wiedemann effect and can generate shear horizontal mode guided waves over a wide frequency range (20–150 kHz) with SNRs in excess of 50 dB. The recently developed SwRI MST 8 × 8 probe contains an array of eight pairs of individual magnetostrictive transducers (MsTs). The data acquisition hardware allows acquisition using Full Matrix Capture (FMC) and analysis software reporting of anomalies based on Total Focusing Method (TFM) image reconstruction. This novel inspection package allows generation of reports that map out corrosion locations and provide estimates of defect widths. Case studies of this technology on actual storage tank walls and bottoms will be presented together with validation of processing methods on mockups with known anomalies and geometry features. Full article

This paper presents a cover lens concept for camera modules based on surface acoustic waves (SAW) to mitigate the degradation of physical AI optical sensor field-of-view performance caused by surface contamination. The proposed approach utilizes a single-phase unidirectional transducer (SPUDT) that intentionally breaks left–right symmetry through a geometrically asymmetric electrode array to generate SAW, thereby removing droplet contamination. First, the acoustic streaming induced inside a single sessile droplet by the SAW was visualized, and the dynamic behavior of the droplet upon SAW actuation was observed using a high-speed camera. The internal flow developed into a recirculating vortex structure with directional deflection relative to the SAW propagation direction, indicating a symmetry-broken streaming pattern rather than a purely symmetric circulation. Upon the application of the SAW, the droplet was confirmed to move a total of 7.2 mm along the SAW propagation direction, accompanied by interfacial deformation and oscillation. Next, an analysis of transport trajectories for five sessile droplets dispensed at different y-coordinates ($y_1$–$y_5$) revealed that all droplets were transported along the x-axis regardless of their initial positions. Furthermore, the analysis of transport velocity as a function of droplet viscosity (1 $\mathrm{c}\mathrm{P}$ and 10 $\mathrm{c}\mathrm{P}$) and volume (2$\mathrm{\mu }\mathrm{L}$, 4$\mathrm{\mu }\mathrm{L}$, and 6 $\mathrm{\mu }\mathrm{L}$) demonstrated that the transport velocity gradually increased with driving voltage but decreased as viscosity increased under identical actuation conditions. Finally, the proposed cover lens was applied to an automotive front camera module to verify its effectiveness in improving object recognition performance by removing surface contamination. Based on its simple structure and driving principle, the proposed technology is deemed to be expandable as a surface contamination cleaning technology for various physical AI perception systems, including intelligent security cameras and drone camera lenses. Full article