Search Results (135)

This study proposes a novel anti-resonant fiber sensing structure based on a composite “egg-shaped” configuration with surface plasmon resonance (SPR) effect. By designing a novel anti-resonant structure consisting of a semicircle and a semi-ellipse and coating its inner surface with a gold film, the optimal structural parameters are determined through three sets of simulation experiments using temperature sensitivity as the criterion. The optimal sensing structure was applied to the simulated detection and analysis of cancer cells, aiming to provide value and reference for the application of high-sensitivity optical fiber sensor in the field of cancer cell detection. Simulation results show that the proposed sensing structure achieves a maximum temperature sensitivity (TS) of 3.86 nm/°C. For the detection of six different types of cancer cells, the maximum wavelength sensitivity (WS), optimal resolution (R), maximum figure of merit (FOM), maximum signal-to-noise ratio (SNR), and best limit of detection (LOD) reach 12,142.86 nm/RIU, 8.24 × 10⁻⁶, 3035.72 RIU⁻¹, 65.50, and 0.94 nm, respectively. Owing to its unique detection mechanism, the proposed sensing structure exhibits label-free characteristics and demonstrates balanced and excellent performance across all metrics for both temperature and cancer cell detection, showing broad application prospects and great potential in the fields of environmental monitoring and medical prevention and treatment. Full article

Fabrication of auxetic structures has always been a limiting factor in their availability. Their complex shape, a requirement originating from the deformation mechanism that leads to a negative Poisson’s ratio, has also limited their manufacturability. In the case of auxetic systems that deform through the rotating semi-rigid mechanism—which allows for the concurrent deformation and rotation of their constituent element—the situation is even more complicated. Relatively few examples of these types of structures are known, with most work on them being largely theoretical. This includes their use in explaining the auxetic mechanism in certain molecules. Nevertheless, these systems can, in principle, offer added functionalities, as they undergo a shape change while still exhibiting a negative Poisson’s ratio. To this end, this work presents a practical scheme for the manufacturing of 3D rotating semi-rigid units, whereby these are produced through perforations of corrugated sheets. For the purpose of this investigation, diamond-shaped perforations were chosen, and the side profile of the corrugated sheet consisted of successive semicircles that alternate in orientation. Analysis of the system indicated that a 3D negative Poisson’s ratio can be obtained while allowing the distance between the hinges to change during deformation. Full article

This paper presents two analytic mappings defined on probability measures that extend and unify the $(a,b)$- and $(s,t)$-deformations arising in free probability for s, $b>0$ and a, $t\in \mathbb{R}$. These unified operators, denoted ${\mathbf{U}}_{(a,b,s,t)}^{\prime }$ and ${\mathbf{U}}_{(a,b,s,t)}^{″}$, are characterized by a functional equation involving the Cauchy–Stieltjes transform, providing a transform-based formulation of measure deformation. They reduce to the $(a,b)$-transformation when $s=t=1$ and to the $(s,t)$-transformation when $a=b=1$. Working in the framework of Cauchy–Stieltjes kernel families, we study the induced effect of these transformations on the associated variance functions and obtain explicit transformation formulas. These results yield a stability theorem showing that the free Meixner class is stable under both operators. In addition, we derive two properties of the semicircle law via the restricted deformations ${\mathbf{U}}_{(a,b,1/b,t)}^{\prime }$ and ${\mathbf{U}}_{(a,b,1/b,t)}^{″}$, thereby emphasizing the structural role of symmetry in measure transformations and in the preservation of canonical measures. Full article

The study addresses the challenge of accurately simulating and visualising the kinematics of agricultural machinery during field operations. The research is motivated by the current lack of comprehensive guidelines for selecting optimal movement and turning modes under varying forward speeds, working widths, and field geometries. A spreadsheet-based environment was utilised to perform simultaneous kinematic simulation and trajectory visualisation. Turning manoeuvres were modelled using smooth composite curves, consisting of straight segments, clothoids, and circular arcs, with trajectories represented in a Cartesian coordinate system through geometric transformations including translation, rotation, and mirror symmetry. Continuity between curve elements was ensured by dimensional chains linking abscissas, ordinates, and direction angles at their start and end points. The influence of key operational factors—forward speed, angular turning velocity, working direction, and field boundaries—was evaluated for a range of turn types, including semicircle, pear-shaped, figure-eight, side exit, U-turn, and P-turn manoeuvres. Field experiments conducted on selected patterns confirmed that the proposed approach can reproduce actual trajectories with sufficient practical accuracy. These results demonstrate that spreadsheet-based kinematic modelling is a robust and accessible tool for optimising tractor–implement movement, enhancing operational planning, and providing a reliable framework for further research into machinery performance under complex field conditions. Full article

Background: This study investigates the impact of initial head position prior to stimulus presentation on sound localization accuracy in children. The quadratic angular root mean square error (RMSE) and the linear mean-absolute-error (MAE) have been considered for this study. Material and Methods: A total of 28 normal-hearing children (ages 6–10) participated in sound localization. The participants localized sounds presented from five speakers at the frontal semicircle. Head positions at stimulus onset were tracked using glasses with a built-in webcam. The localization results were analyzed with and without correcting for the offset from the frontal direction of the initial head position prior to stimulus presentation. Results: The initial head position prior to stimulus presentation significantly affected the RMSE but had no influence on the MAE. This effect was stronger in younger children. The MAE showed fewer changes in head position due to its linear nature, which reduces the effect of large errors. An analysis of the children’s initial head positions revealed a tendency to deviate from the frontal direction. Therefore, the initial head position prior to stimulus presentation should be considered when calculating localization measures. Conclusions: The initial head position prior to a stimulus can distort the RMSE in directional hearing tests for children, while the MAE remains robust against such deviations. Full article

In this paper, we introduce two analytic deformations of probability measures that unify and extend two classical deformations from free probability theory, namely the $\mathbb{T}=(s,t)$-deformation $U^{\mathbb{T}}$ and the $T_a$-deformation, where $a,t\in \mathbb{R}$ and $s>0$. The corresponding operators, denoted by ${\mathbb{Y}}_{(a,s,t)}^{\prime }$ and ${\mathbb{Y}}_{(a,s,t)}^{\prime \prime }$, are defined via a functional equation involving the Cauchy–Stieltjes transform (CST). This framework recovers the classical cases as particular instances, specifically ${\mathbb{Y}}_{(0,s,t)}^{\prime }={\mathbb{Y}}_{(0,s,t)}^{\prime \prime }=U^{\mathbb{T}}$ and ${\mathbb{Y}}_{(a,1,1)}^{\prime }={\mathbb{Y}}_{(a,1,1)}^{\prime \prime }=T_a$. We analyze the analytic and structural properties of the operators ${\mathbb{Y}}_{(a,s,t)}^{\prime }$ and ${\mathbb{Y}}_{(a,s,t)}^{\prime \prime }$ within the concept of Cauchy–Stieltjes kernel (CSK) families, with particular emphasis on their action on variance functions (VFs). In particular, we derive explicit formulas for the VFs associated with measures deformed by ${\mathbb{Y}}_{(a,s,t)}^{\prime }$ and ${\mathbb{Y}}_{(a,s,t)}^{\prime \prime }$. As an application, we establish an invariance property showing that the class of free Meixner family (FMF) is stable under both deformations. Furthermore, by restricting the parameters to ${\mathbb{Y}}_{(a,1,t)}^{\prime }$ and ${\mathbb{Y}}_{(a,1,t)}^{\prime \prime }$, we obtain two new characterizations of the semicircle law. These results highlight the role of symmetry in the analytic deformation and in the stability properties of fundamental distributions in free probability. Full article

This article proposes a single-deformation scheme for probability measures that simultaneously encompasses two classical deformations from free probability: the $V_a$ deformation ($a\in \mathbb{R}$) and the $T_c$ deformation ($c\in \mathbb{R}$). The associated operator, written as ${\mathcal{W}}_{(a,c)}$, is introduced via a functional relation involving the Cauchy–Stieltjes transform and is constructed so as to recover the initial deformations as special cases, namely ${\mathcal{W}}_{(0,c)}=T_c$ and ${\mathcal{W}}_{(a,0)}=V_a$. Working within the concept of Cauchy–Stieltjes kernel families, we analyze the action of ${\mathcal{W}}_{(a,c)}$ on variance functions and establish an explicit expression for the variance function induced by this deformation. This approach leads to a structural invariance property demonstrating that the free Meixner class is preserved under the action of ${\mathcal{W}}_{(a,c)}$. In addition, the operator provides a new perspective on the semicircle distribution, yielding a characterization that reflects the symmetric nature of the deformation and its compatibility with fundamental distributions in free probability. Full article

This paper will present a constant-force vibration isolator (CFVI), in which the isolated load is supported by two pulley-roller mechanisms, while the dynamic stiffness is modified by a cam mechanism with the piecewise profile redefined by the user. As a result, this model can generate the constant force-displacement response within the working region, thereby obtaining quasi-zero stiffness in this range. Because of the piecewise configuration of the cam, the system motion governed by the piecewise dynamic equation under base motion excitation will be analyzed and established. The approximate solution of the piecewise dynamic equation is derived by using the average method, from which the relative amplitude–frequency relation and the absolute amplitude transmissibility of the CFVI will be obtained. The effects of the key working parameters involving the damping coefficient, critical position, and excited amplitude on the dynamic behavior and isolation effectiveness of the CFVI are considered through numerical simulations. The simulation result reveals that the dynamic response of the CFVI offers two branches: resonance and isolation. The former is significantly affected by the working parameters, whereas the latter is weakly influenced. Furthermore, the isolation effectiveness of the CFVI will be compared with that of its linear counterpart and the quasi-zero stiffness vibration isolation model using a semicircle cam (QZSI). The results demonstrate that the CFVI outperforms the other models for base motion excitations. Full article

In this paper, we propose an analytic deformation acting on probability measures, designed to encompass and extend two fundamental operators in free probability: the $(a,b)$- and the $T_c$-deformations. This unified operator, indicated by ${\mathcal{X}}_{(a,b,c)}$, is introduced through a functional relation for the Cauchy–Stieltjes transform. We have ${\mathcal{X}}_{(a,b,0)}={\tilde{U}}^{(a,b)}$ and ${\mathcal{X}}_{(1,1,c)}=T_c$. We examine the structural properties of this transformation within the setting of Cauchy–Stieltjes kernel (CSK) families, with special emphasis on the behavior of the associated variance functions (VFs). An explicit formula for the VF corresponding to measure deformed by ${\mathcal{X}}_{(a,b,c)}$ is established. This result allows us to demonstrate a key invariance property: the free Meixner class of probability measures remains stable under the ${\mathcal{X}}_{(a,b,c)}$-transformation. Furthermore, a novel characterization of the semicircle law is obtained through the action of ${\mathcal{X}}_{(a,1,c)}$, highlighting the role of symmetry in the deformation and preservation of free-probabilistic distributions. Full article

Infertility treatment often requires patients to self-administer hormonal injections, creating significant physical, logistical, and psychological burdens. While medical technologies have improved pharmacological efficacy and safety, design aspects addressing usability, portability, and emotional distress remain underexplored. This study presents Blloom, a compact self-injection device that integrates ergonomic, thermal, and emotional considerations designed through an interdisciplinary design-thinking framework. This study identified critical user needs related to self-injection anxiety, medication refrigeration, and treatment-related stigma through in-depth, multi-method qualitative design research. The resulting prototype is characterized by one-handed operation, concealed needle delivery, and built-in passive cooling (2–8 °C for up to 8 h). Formative evaluations with patients and clinicians confirmed its improved usability, emotional comfort, and contextual compatibility. At this prototypical stage, medication- and container-specific compatibility, as well as long-term reliability, require further bench testing and clinical validation. Process analysis further revealed how designer–engineer collaboration evolved from empathic exploration to implementation-driven convergence. The findings demonstrate how human-centered design can mitigate the multidimensional burdens of infertility treatment and provide a replicable framework for interdisciplinary innovation in self-managed healthcare devices. Full article

In this paper, the Distribution of Relaxation Times (DRT) method is introduced for analyzing aging and failure conditions in lithium-ion (Li-ion) batteries, addressing challenges associated with its implementation. While Electrochemical Impedance Spectroscopy (EIS) and Equivalent Circuit Models (ECMs) are commonly used to monitor battery performance, their interpretation is often complicated by overlapping semicircles in impedance spectra. The DRT technique resolves this issue by deconvolving relaxation times, enabling the separation of individual electrochemical processes and providing a clearer understanding of aging and failure conditions. The peaks of lower frequency components in DRT plots, specifically the charge transfer and diffusion processes, are key indicators of the battery failure point. When these two processes merge, it signals that the battery can no longer function, marking a critical failure point in Li-ion batteries. Identifying failure conditions and aging in Li-ion batteries using DRT offers a more advanced approach compared to ECM, as it delivers greater detail in the electrochemical processes that contribute to performance degradation. The analysis of two kinds of different Lithium-Ion battery cells based on the DRT reveals the specific aging and failure patterns, particularly in later battery life stages. The findings demonstrate the potential of DRT as a real-time indicator to monitor the status and the lifecycle of the battery. Full article

To address the critical issue of low cold storage rate of phase-change materials in commercial phase-change modules, this study designed and constructed four heat-conducting-fin-enhanced cold storage blocks featuring different heat-conducting fin configurations: semi-equilateral triangles, semi-squares, semi-regular pentagons, and semi-circles. It systematically investigates the influence of the fin shape and thickness parameters of heat-conducting fins on the cooling charging process of cold storage blocks and clarifies the correlation between heat transfer enhancement and the cooling storage and release performance of refrigerators. The results show that laying copper high-thermal-conductivity fins on the surface of cold storage blocks can significantly accelerate the phase change cold storage rate. Among these structures, the semi-square fin configuration exhibits the optimal enhancement effect: compared with the baseline model without fins, its solidification time is shortened by 35 min. The results indicate that with the increase in fin thickness, the cooling charging time decreases continuously, and there exists a nonlinear positive correlation between cooling charging efficiency and fin thickness. Specifically, the cooling charging time reaches the minimum value when the fin thickness increases to 2.5 mm, while the rate of reduction in cooling charging time slows down significantly after the thickness exceeds 1.5 mm. In addition, the phase-change cold storage block can notably prolong the cooling release duration of the refrigerator. However, although the introduction of heat-conducting fins can improve the cooling charging rate, it will shorten the continuous cooling release time, thus presenting a trade-off between cooling charging efficiency and cooling release duration. The conclusions of this study provide theoretical support and practical guidance for the structural design and performance optimization of efficient commercial phase-change thermal storage and release systems. Full article

A sequenced ultrasonic atomization coupled with a pyrolysis process is developed to synthesize a series of cross-scale (Co/Cu)-NC catalysts. The catalysts demonstrate high metal utilization efficiency with a metal loading of 22.45 ± 0.07 wt%. Electrochemical evaluations for the oxygen reduction reaction (ORR) suggest that the best (Co/Cu)-NC catalysts are prepared with a Co/Cu ratio of 1/1 and a calcination temperature of 800 °C, which achieve a half-wave potential of 0.87 V and an electrochemical impedance spectroscopy semicircle radius as low as 30 ohms. Linear sweep voltammetry measurements indicate that (Co/Cu)-NC catalysts exhibit the highest current density. Under a potential of −0.73 V versus the reversible hydrogen electrode, (Co/Cu)-NC catalysts demonstrate long-term stability with the CO Faradaic efficiency of about 70% for catalyzing carbon dioxide reduction reaction (CO₂RR). Overall, the above metrics identify CoCu-800 as the optimal bifunctional catalyst among the tested samples for ORR and CO₂RR under the investigated conditions. Full article

Two-dimensional graphitic carbon nitride 2D g-C₃N₄ has the potential for gas sensing as a metal-free semiconductor with a layered structure, high surface area, and tunability of electronic properties. In this context, 2D g-C₃N₄ nanosheets were prepared by the thermal polycondensation of urea followed by ultrasonic exfoliation. X-ray diffraction revealed diffraction peaks corresponding to the (110) and (002) crystallographic planes of g-C₃N₄. Scanning electron microscopy showed a nanosheet structure with a 10-nm crystallite size, while energy-dispersive X-ray spectroscopy demonstrated a uniform distribution of carbon and nitrogen. Ultraviolet–visible absorption spectroscopy revealed a band gap of 2.8 eV. Gas sensing measurements exhibited an increase in response to isopropanol and ethanol as the operating temperature and gas concentration increased. Impedance spectroscopy provided additional insight into the sensing mechanism. Observed depressed semicircles in Nyquist plots were fitted with a charge transfer resistance R_ct in parallel with a constant phase element model. The charge transfer resistance R_ct fell systematically with isopropanol exposure, confirming the crucial role of adsorption-induced electron transfer in the gas sensing response. Full article

In electric vehicle (EV) drivetrains, lubricant films must not only mitigate friction and wear but also manage stray currents to safely dissipate stray charge and avoid micro-arcing. This study directly compares how a conventional antiwear additive (ZDDP) and a long-chain, ashless, sulfur-free phosphite ester (Duraphos AP240L) manage this balance under current-carrying boundary lubrication conditions. Reciprocating steel-on-steel tests were conducted at fixed load and speed with applied current densities of 0, 0.02, and 42.4 A/cm². Friction and four-probe electrical contact resistance (ECR) were measured in situ, and impedance of tribofilms was measured over a 1–10⁵ Hz range after friction test. In the presence of ZDDP, ECR initially increased and then decreased to a value that was as low as the initial direct contact of two solid surfaces or even lower sometimes. During the initial stage with high ECR, a well-defined impedance semicircle was observed in the Nyquist plot; after forming the tribofilm with low ECR, frequency dependence of impedance could not be measured due to the very low resistance. The decrease in ECR suggested a structural evolution of the anti-wear film on the substrate. However, post-test wear analysis indicated that the formation of this film was accompanied by tribochemical polishing of the countersurface and sometimes pitting of the substrate, which may have been due to localized electrical discharge producing trenches deeper than ~0.5 µm; in additive-free base oil, wear was dominated by ploughing with micro-cutting of the substrate. In contrast, AP240L performed better in terms of friction and wear, showing a remarkable ~30% lower coefficient of friction, while the overall cycle dependence of ECR was similar to the ZDDP case. AP240L showed negligible boundary film controlled wear producing a shallow, smooth track (depth < 0.2 µm) during the friction test, and there was no sign of electrical arc damage. These findings support long-chain, ashless, sulfur-free phosphite esters as promising candidates for EV boundary lubrication where both mechanical and electrical protection are required. Full article