Sqrt Research Articles

Probabilistic Approach for Electromechanical Impedance-Based SHM Models

Applying structural health monitoring techniques has become very important in engineering and aeronautics. The technique based on electromechanical impedance is one of them. In this work, the electromechanical impedance-based SHM technique is applied to determine the existence of damage in an aluminum beam using the Root Square Deviation (RMSD) damage metric. Furthermore, this contribution aims to apply the concept of stochastic evaluation in the context of the electromechanical impedance-based SHM technique by using the Monte Carlo method to generate random numbers. The development of the work is to validate two models, one with the impedance signals and the other stochastically, and thus build the linear regression model for both. In the end, the results are compared to test the representation of the failure identification in the beam.

Broadband dual‐podal multilayer Vivaldi antenna array for remote sensing applications

AbstractA novel wideband multilayer dual‐podal Vivaldi antenna with broadband characteristics from 5.5 to 20.82 GHz, is presented. Contrary to traditional Vivaldi antennas that are antipodal‐based, this design is realised by placing a pair of podal Vivaldi antennas with corrugated slots on the top and bottom of a substrate stack (consisting of two dielectric layers) using a Bondply. The pair is fed in‐phase with the help of a Strip‐Line (SL) transmission section that is terminated on a radial stub to couple capacitively to the antenna elements. With this technique of electrically coupling a podal Vivaldi pair, improved performance parameters are achieved, specifically: a measured maximum gain of 9.33 dBi, Half Power Beam Width of 126.5° in the H‐plane, and a maximum Front‐to‐Back (F/B) ratio of 14.36 dB with an overall antenna size of 29 × 21 × 1.63 mm. The in‐depth understanding of the working mechanism is supported by a detailed parametric analysis, current distribution, and a clear physical insight into the operating principles. Moreover, a 1 × 4 Vivaldi antenna array is also designed and analysed. A measured maximum gain of the 13 dBi at 15 GHz in the array is achieved along with the wide bandwidth of 6.3 GHz from 10.78 to 17.07 GHz. The array is fed through an SL corporate feed network that ensures in‐phase excitation of all four Vivaldi pairs. A Grounded Co‐planar Waveguide to SL transition is adopted for connecting the 2.92 mm Radio Frequency launcher on the top layer. The very compact geometry of the proposed structure enables its integration into the systems for remote sensing applications.

A novel numerical method for estimation the photovoltaic cells/modules parameters based on dichotomy method

The demand for photovoltaic (PV) energy has been growing in recent years, parallel to an increase in scientific research about the PV cells, such as the electrical modelling and extraction of unknown PV model parameters. This paper introduces a highly efficient and straightforward numerical method to determine the unknown parameters for the single-diode model. The proposed approach utilizes Dichotomy (Bisection) to estimate the series resistance Rs and an iterative process to determine the diode ideality factor a and the parameters that achieve the minimum Root Square Error (RMSE). The proposed approach has been tested on five cells/modules from different technologies. The results show that the proposed approach outperforms various analytical, numerical, and meta-heuristic approaches in terms of accuracy. The RMSE produced by the proposed method is in order of 7.8514e-04 A and 2.2256e-03 A for the RTC France cell and the PWP201 module, respectively.

Effects of Lens-Induced Astigmatism at Near and Far Distances.

To investigate and compare the degradation of visual acuity (VA) in myopic presbyopes due to lens-induced astigmatism at near and at far distance. Fourteen corrected myopic presbyopes were recruited. VA (logarithm of the minimum angle of resolution) was measured binocularly for different conditions of lens-induced astigmatism: cylindrical powers of -0.25, -0.50, -0.75, -1.00, -1.50, and -2.00 diopters (and positive spherical power of half the cylindrical power) with two axis orientations (with-the-rule WTR and against-the-rule ATR) were added to their optical correction. Measurements were carried out at far and near distance both in photopic and mesopic conditions, and for high and low contrast (HC/LC) stimuli. The paired Wilcoxon signed-rank statistics test was used to evaluate difference between conditions. The measured VA as a function of the lens-induced astigmatism was described by regression lines in all investigated experimental conditions. The angular coefficients (slopes) of these lines represent the VA degradation, ie, the variation in logMAR corresponding to the addition of 1.00 diopters of cylindrical power. In photopic HC conditions, the VA degradation is significantly more pronounced at far distance than at near distance (0.22±0.06 diopters-1 vs 0.15±0.05 diopters-1, p = 0.0061 in WTR conditions; 0.18±0.06 diopters-1 vs 0.12±0.05 diopters-1, p = 0.0017 in ATR conditions), although VAs at near and at far with zero cylinder were similar (-0.14±0.10 vs -0.14±0.08, p = 0.824). The better tolerance to lens-induced astigmatism blur at near than at far distance in photopic conditions with HC stimuli is tentatively attributed to a possible experience-mediated neural compensation associated to the tendency of the eye toward an inherent astigmatism at near.

Improvement in Blood Pressure After Intermittent Fasting in Hipertension: Could Renin-Angiotensin System and Autonomic Nervous System Have a Role?

Although it has been reported that the intermittent fasting (IF) diet has positive effects on heart health and improvement in blood pressure, it has not been sufficiently clarified how it could have these positive effects yet. We aimed to evaluate the effects of IF on the autonomic nervous system (ANS) and renin-angiotensin system (RAS), which are closely related to blood pressure. Seventy-two hypertensive patients were included in the study, and the data of 58 patients were used. All the participants fasted for about 15-16 hours for 30 days. Participants were evaluated with 24-hour ambulatory blood pressure monitoring and Holter electrocardiography before and after IF; also, 5 ml venous blood samples were taken for assessment of Serum angiotensin I (Ang-I) and angiotensin II (Ang-II) levels and angiotensin-converting enzyme (ACE) activity. For data analysis, the p-value <0.05 was accepted as significant. Compared to pre-IF, a significant decrease was observed in the patients' blood pressures in post-IF. An increase in high-frequency (HF) power and the mean root square of the sum of squares of differences between adjacent NN intervals (RMSSD) were observed after the IF protocol (p=0.039, p=0.043). Ang-II and ACE activity were lower in patients after IF (p=0.034, p=0.004), and decreasing Ang-II levels were determined as predictive factors for improvement of the blood pressure, like the increase in HF power and RMSSD. The present findings of our study demonstrated an improvement in blood pressure and the relationship of blood pressure with positive outcomes, including HRV, ACE activity, and Ang-II levels after the IF protocol.

Experimental and Numerical Analysis of the Performance of Various Damper Materials

The vibration in ships causes structural fatigue, damage to electrical and mechanical devices, excessive level of noise and discomfort to the passengers and crews. Sometimes the increase in ship vibration leads to unsafe operating conditions and thereby discarding it. Thus, the research on vibration reduction is essential in the maritime field and this paper deals with the reduction of vibrations in marine machinery using elastomeric bearings. The numerical analysis of the performance of passive vibration isolators with different damping materials was conducted using ANSYS and the results are validated experimentally. With the help of a vibration exciter, vibration transmissibility at different frequencies is plotted and the hysteresis curve was generated numerically by applying a cyclic load to the bearing. Then, the best damping material was deducted by comparing the calculated loss factor of different elastomeric materials such as natural rubber, styrene-butadiene rubber and polybutadiene Rubber (PBR) and their combinations. The natural rubber blended with styrene-butadiene rubber (SBR) and polybutadiene rubber (PBR) shows an increase in the damping property of the elastomer and can be used for high-frequency damping applications. HIGHLIGHTS Study of damping property of various elastomers. Experimental as well as numerical analysis were done to find the loss factor of elastomers The transmissibility curve of the elastomers was plotted at different frequencies ranging from 10 - 4000 Hz using a vibration exciter and the loss factor was calculated using half power band width method Hysteresis curve of elastomers were generated numerically using ANSYS software and the loss factor of the elastomers was calculated theoretically GRAPHICAL ABSTRACT

Adjustment-Free Long-Distributed-Cavity Laser Using Small Glass Ball Cat-Eye Retroreflector

We report an adjustment-free long-distributed-cavity laser using a small high-index glass ball cat-eye retroreflector as the receiver. When the glass ball cat-eye was rotated or off-axis moved, its working characteristics were studied via the single cat-eye structure and the double cat-eyes structure. With the single cat-eye structure and an incident pump power of 4.22 W, the end-pumped Nd: YVO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {4}}$ </tex-math></inline-formula> laser delivered 985 mW continuous-wave output at a working distance of 2.85 m, whose full rotation angle at half power was ±27°. In addition, with the double cat-eyes structure and the same incident pump power, the laser delivered 385 mW output at a working distance of 1.20 m, which had a full rotation angle of ±19° and a transverse displacement tolerance of ±21 mm. As far as we know, this is the first time that a ball-shaped cat-eye retroreflector is used to establish an adjustment-free long-distributed-cavity laser.

Full 360° beam steering millimetre‐wave leaky‐wave antennas coupled with bespoke 3D‐printed dielectric lenses for 5G base stations

AbstractA fast beam‐steering capability has been demonstrated using an array of high‐gain corrugated substrate integrated waveguide (CSIW) slot antennas coupled with a bespoke dielectric lens. The proposed system prototype has been simulated, fabricated, and measured. The proposed system is shown to have a full 360° beam‐steer in azimuth plane with an angular sensitivity of 9°, half power beamwidth (HPBW) of 18° and a gain of &lt; 20.5 dBi at n257 frequency band of 26 to 29 GHz. Further, the antenna is shown to have a fixed frequency beam steer of ±15° along with a frequency‐controlled beam‐scanning of ±45° in the elevation plane. The antenna setup is shown to be suitable for applications for 5G base‐stations.

Antenna Setup for Future Joint Radar-Communications – Characteristics and Mounting Positions

Abstract. The development of millimeter wave systems is driven by the strong trend toward new communications generations and especially by the emerging joint radar and communications design approach. Safety-critical applications like platooning or intersection assistance will significantly benefit from the combination of sensing and communications. While radar performs a channel measurement and thus, needs a wide field of view (especially in city/intersection scenarios), communications aims to minimize the interference for other not addressed receivers (e. g. in a platoon) by a focused antenna design. The proposed work extends the analysis of the influence of various antenna positioning for a typical automotive scene by taking also different characteristics (antenna gain, half power beamwidth, and sidelobe level) into account. Hereby, it is mandatory to investigate the communications and sensing performance simultaneously. The positions at the front bumper – typical for radar sensors – and especially at the left mirror convinced regarding the vehicular communications as well as the sensing behaviour. Applying focused antennas is promising, however, has also limits if the signals are not received out of the main beam but out of the sidelobes, resulting in a critical communications performance. Thus, beam steering is recommended to be applied in the future.

The Development of Copper Clad Laminate Horn Antennas for Drone Interferometric Synthetic Aperture Radar

Interferometric synthetic aperture radar (InSAR) is an active remote sensing technique that typically utilises satellite data to quantify Earth surface and structural deformation. Drone InSAR should provide improved spatial-temporal data resolutions and operational flexibility. This necessitates the development of custom radar hardware for drone deployment, including antennas for the transmission and reception of microwave electromagnetic signals. We present the design, simulation, fabrication, and testing of two lightweight and inexpensive copper clad laminate (CCL)/printed circuit board (PCB) horn antennas for C-band radar deployed on the DJI Matrice 600 Pro drone. This is the first demonstration of horn antennas fabricated from CCL, and the first complete overview of antenna development for drone radar applications. The dimensions are optimised for the desired gain and centre frequency of 19 dBi and 5.4 GHz, respectively. The S11, directivity/gain, and half power beam widths (HPBW) are simulated in MATLAB, with the antennas tested in a radio frequency (RF) electromagnetic anechoic chamber using a calibrated vector network analyser (VNA) for comparison. The antennas are highly directive with gains of 15.80 and 16.25 dBi, respectively. The reduction in gain compared to the simulated value is attributed to a resonant frequency shift caused by the brass input feed increasing the electrical dimensions. The measured S11 and azimuth HPBW either meet or exceed the simulated results. A slight performance disparity between the two antennas is attributed to minor artefacts of the manufacturing and testing processes. The incorporation of the antennas into the drone payload is presented. Overall, both antennas satisfy our performance criteria and highlight the potential for CCL/PCB/FR-4 as a lightweight and inexpensive material for custom antenna production in drone radar and other antenna applications.

Planar metasurface sub-reflector based dual-reflector antenna for multi-directional beaming

This paper presents a novel planar metasurface subreflector (MSSR) array-based dual-reflector antenna inspired by Cassegrain arrangement for simultaneous beaming in far-field microwave wireless power transfer at f0=2.45 GHz for the first time. The MSSR unit cell exhibits 94.8% reflection and 0.0065λ0 thin geometry where λ0=122.45mm is the operating wavelength. The antenna exhibits optimum gain at focus F=0.93λ0, and with variation in F, required beamwidth and sidelobe levels can be easily achieved. The experimental studies show 15.8 dBi gain and 13.4°, 25.2° half power beamwidths in E- and H-plane, respectively in the main direction. When the MSSR array is placed at F, the measured electric field shows a nearly equal concentration in three directions. This is to be used to power small IoT devices at different angles simultaneously. This work may serve as a design guide for designing the planar MSSR-based dual-reflector antenna in the microwave domain.

Examination of the Relationship Between Severity of Addiction and Personality: The Mediating Effect of Social Alienation and Emotional, Cognitive Regulation

Background: The current research investigated the mediating roles of social alienation and emotional and cognitive regulation in the relation between personality and severity of substance abuse in students. This study is a descriptive-correlational research design. Objectives: This study, used a structural equation modeling (SEM) approach to evaluate the correlates of the severity of the addiction. This path analytical strategy allowed for the simultaneous examination of the mentioned variables. Methods: The sample of this study included all students in Tehran province (the academic year of 2022). Five hundred fifty students took part in the current research. NEO-PI-R, social alienation, and the Severity of Dependence Scale (SDS) were used. Data analysis was done using descriptive statistics, correlation analysis, and structural equation modeling. Results: Considering that the model fit indices represent a good fit of the model and the mean root square of the estimation error (RMSEA) was equal to 0.029, which shows a very good fit, and according to the presented indicators, the research model is confirmed. The results indicate that the relationship between variables is significant (P value 0.05). The direct effect of personality on the severity of addiction and social isolation is equal to -0.68 and -0.73, respectively, and in terms of cognitive emotion regulation is estimated to be 0.85. The indirect effect of personality on addiction severity was calculated at 0.86 by social alienation and -0.79 by emotional cognition. Conclusions: Our results suggest that personality features mediated by social alienation and emotional and cognitive regulation can be used to predict the severity of the addiction. Therefore, the proposed model was cleared to be an appropriate model for predicting substance abuse in students.

Analysis of Milk Production and Failure Data: Using Unit Exponentiated Half Logistic Power Series Class of Distributions

The unit exponentiated half logistic power series (UEHLPS), a family of compound distributions with bounded support, is introduced in this study. This family is produced by compounding the unit exponentiated half logistic and power series distributions. In the UEHLPS class, some interesting compound distributions can be found. We find formulas for the moments, density and distribution functions, limiting behavior, and other UEHLPS properties. Five well-known estimating approaches are used to estimate the parameters of one sub-model, and a simulation study is created. The simulated results show that the maximum product of spacing estimates had lower accuracy measure values than the other estimates. Ultimately, three real data sets from various scientific areas are used to analyze the performance of the new class.

Assessing Leadership Behavior in Health Care: Introducing the Local Leadership Scale of the SCORE Survey.

Engaged and accessible leadership is a key component of care excellence. However, the field lacks brief, reliable, and actionable measures of feedback and coaching-related behaviors of local leaders (for example, provides frequent feedback). The current study introduces a five-item Local Leadership (LL) scale by examining its psychometric properties, providing benchmarking across demographic factors and work settings, assessing its association with psychological safety, and testing whether LL predicts reports of restricted activities and absenteeism. In this cross-sectional study, 23,853 questionnaires were distributed across 31 Midwestern US hospitals. The survey included the LL scale, as well as safety culture and well-being scales. Psychometric analyses (Cronbach's α, confirmatory factor analysis [CFA] fit: root square mean error of the approximation [RMSEA], comparative fit index [CFI], Tucker-Lewis index [TLI]), Spearman correlations, t-tests, and analyses of variance (ANOVAs) were used to test the properties of the LL scale and differences by health care worker and work setting characteristics. A total of 16,797 surveys were returned (70.4% response rate). The LL scale exhibited strong psychometric properties (Cronbach's α = 0.94; RMSEA = 0.079; CFI = 0.99; TLI = 0.98). LL scores differed by role, shift, shift length, and years in specialty. Of all roles, leaders (for example, managers) rated leaders most favorably. Nonclinical (vs. clinical) and nonsurgical (vs. surgical) work settings reported higher LL. LL scores correlated positively with psychological safety, absenteeism, and activities restricted due to illness. The LL scale exhibits strong psychometric properties, convergent validity with psychological safety, and variation by work setting, work setting type, role, shift, shift length, and specialty. The study indicates that assessing leadership behaviors with the LL scale is useful and offers actionable behaviors for leaders to improve safety culture within teams.

다문화 청소년의 삶의 만족도 구조모형

The purpose of this study was to construct a hypothetical model based on the life satisfaction of multicultural youths and ecological system theory. In this study, the data of 1,197 high school students who participated in the 8th year of the Multicultural Youth Panel Survey (2018) conducted by the Korea Youth Policy Institute were used for the final analysis. The measurement variables consisted of bi-cultural acceptance attitude, achievement motivation, and family support as exogenous variables, self-esteem and school adaptation as endogenous variables, and life satisfaction as outcome variables. The collected data were analyzed using the SPSS/WIN 23.0 and Amos 21.0 programs. The hypothetical model calculated chi verification, basic fit index, adjusted fit index, double root of approximate error mean square, comparative fit index, standard fit index, and average difference between elements, and the model was found to be suitable. Factors that directly affect life satisfaction of multicultural adolescents were self-esteem, family support, and school adaptation, In addition, self-esteem and school adaptation were found to be important mediating factors between bi-cultural acceptance attitude, achievement motivation, and family support. Therefore various programs should be prepared to improve the life satisfaction of multicultural youths.

Evaluating the dynamic characteristics of microwave-casted metal matrix composite material by using experimental modal analysis

This paper proposes an experimental modal analysis technique to measure the dynamic characteristics of microwave-casted metal matrix composite (MMC). To fabricate MMC, silicon carbide (SiC) is reinforced into the SS202 matrix. The damping capacities of MMC at different reinforcements of SiC powder such as 0.05%, 0.1% and 0.2% are measured through experimental modal analysis. The main objective is to study the effect of reinforcement on the damping capacity of SS202. The domestic microwave oven with the specification of 2.45 GHz and 900 W power is used to cast the MMC material. The graphite split mold is used for in-situ microwave casting. The mechanical characterization in terms of micro-hardness and scanning electron microscopy (SEM) of MMC is also examined. From SEM imagining, complete diffusion of the SiC in SS matrix is observed for 0.05% of SiC reinforcement; however, incomplete diffusion is observed for 0.1% and 0.2% of SiC reinforcement. It is observed that the hardness of the SS202 is increasing with the decrease in the percentage of SiC powder. The experimental modal analysis is carried out by using SO Analyzer. The response model in terms of the frequency response function (FRF) curve is measured when the specimen is excited at impact excitations. The half power bandwidth method is used to calculate the damping factor of the material from the measured FRFs. It is observed that the damping capacity increases with the increase in percentage of SiC in SS202. SS202 with 0.05%, 0.1% and 0.2% SiC have the hardness value of 155.33 HV, 107.33 HV and 58.33 HV, respectively.

Broadband dual‐polarized dipole antenna array for 2G/3G/4G/5G base station

AbstractA broadband dual‐polarized antenna array with excellent impedance matching and stable radiation performance is proposed. The array comprises four folded‐dipole antenna elements. Two trapezoidal baluns are used to excite the folded‐dipole antenna to obtain good impedance matching and generate a ±45°‐polarized radiation pattern. To improve the impedance matching and achieve steady radiation performance, a square parasitic director is used and placed above the folded dipoles. The antenna element realizes a broad bandwidth of 76.9% (voltage standing wave ratio [VSWR] &lt; 1.5 from 1.69 to 3.8 GHz) and high isolation of 28 dB. Then an antenna array comprised of four elements is designed. It is fed by two miniaturized 1‐to‐4 power divides. Several metal baffles are added between adjacent elements to reduce the mutual coupling. The array achieves a broad bandwidth of 78.4% (VSWR &lt; 1.5 from 1.66 to 3.8 GHz), high isolation of 25 dB, stable half power beamwidth in the E‐plane within 65° ± 5°, and high gain within 12–15 dBi.

Recommendations and requirements for the wavelengths in Rayleigh equation anomaloscopes.

DIN 6160:2019 is a technical standard that sets requirements for Rayleigh equation anomaloscopes. Table 1 of the standard contains the limits for centroid wavelengths and spectral half power bandwidths (SHBW). The centroid limits are more restrictive than dominant wavelength recommendations. The SHBW limits have no known evidence base and are inconsistent between colors. The spectral characteristics of three commercial anomaloscopes brands were measured using a telespectroradiometer. Only the oculus instruments complied with DIN 6160 Table1, but all the anomaloscopes complied with published recommendations. All complied with the DIN 6160 bandwidth requirements. This highlights the need to provide an evidence base for such requirements.

A fast BDF2 Galerkin finite element method for the one-dimensional time-dependent Schrödinger equation with artificial boundary conditions

In this paper, we propose an efficient numerical scheme with linear complexity for the one-dimensional time-dependent Schrödinger equation on unbounded domains. The artificial boundary method is used to address the unboundedness of the domain. By applying the two-step backward difference formula for time discretization and performing the Z-transform, we derive an exact semi-discrete artificial boundary condition of the Dirichlet-to-Neumann type. To expedite the discrete temporal convolution involved in the exact semi-discrete artificial boundary conditions, we design a fast algorithm based on the best relative Chebyshev approximation of the square-root function. The Galerkin finite element method is used for spatial discretization. By introducing a constant damping term to the original Schrödinger equation, we present a complete error estimate for the fully discrete problem. Several numerical examples are provided to demonstrate the accuracy and efficiency of the proposed numerical scheme.

Electrochemical study of agarose hydrogels for natural convection on macroelectrodes and ultramicroelectrodes

Electrochemical measurements using an agarose hydrogel as a solid electrolyte and ferrocyanide as a redox probe were conducted to analyze transport properties and natural convection effects. The mass transport properties and diffusion coefficients of ferrocyanide were studied using various macroelectrodes and ultramicroelectrodes via cyclic voltammetry. The experimental results confirmed that the mass transfer behavior in agarose was similar to that in solution. The good linearity of the square root of the scan-rate-dependent peak current demonstrated that diffusion is dominant during mass transfer in agarose hydrogel owing to a reduction in other mass transport effects (i.e., migration and convection). Furthermore, chronoamperometry (CA) was performed to estimate the effects of natural convection in the solution and agarose hydrogel. CA curves and plots of current as a function of the inverse square root of time yielded irregular and irreproducible responses in the solution for relatively long-term electrochemistry. However, in the agarose hydrogel, the CA response was more regular and reproducible for > 300 s because of reduced natural convection, based on the Cottrell’s theory.