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This work examines the utilization of negative mass and negative stiffness principles to enhance the effectiveness of Dynamic Vibration Absorbers (DVAs) for vibration attenuation developed in structures. The proposed idealized model aims to reduce the amplitude of resonance and expand the frequency stopband range to achieve vibration reduction by attaching two parallel dynamic vibration absorbers to the primary system. By incorporating stiffness, mass, and damping ratio for each one of the absorbers and in the presence of harmonic excitation, it is possible to expand the frequency range in which vibration may be suppressed, leading to a substantial decrease in the maximum vibration amplitude of the primary system and the stroke length of the absorbers. The Nelder-Mead method is successfully used as an optimization tool to obtain the best selection of the absorbers' design parameters that assure the best vibration attenuation and frequency stopband. The results indicate a strong association between the change in frequency and the decrease in vibration. In the instance of frequency response, the vibration amplitude decreased by an average of 91.46% across all three modes of the whole system. Another optimal selection exhibited the most significant enhancement, achieving an average reduction in vibration amplitude of 97.06% across all three modes. Finally, the results indicate that the suggested lumped parallel architecture of the absorbers with precisely adjusted negative mass and negative stiffness characteristics along with the presented optimization method, can greatly improve the effectiveness of reducing vibrations in various applications. The results illustrate a direct relationship between shifts in frequency and vibration. If the value of the shift is greater than 1 the vibration is decreased, while less than 1 means the worst form of reducing such magnitude. The most notable drop off in amplitude occurred when averaging a simple drop off of up to 91.46% for all three patterns where frequency shifts by Y=2.008. [ABSTRACT FROM AUTHOR]

Soil plays a crucial role in human health through its impact on food and habitation. However, it often contains toxic heavy metals, with mercury being particularly hazardous when methylated. Currently, high-sensitivity, rapid detection of mercury is achievable only through electrochemical measurements. These measurements require pretreatment of the soil sample and the preparation of a calibration curve tailored to the sample's condition. In this study, we developed a method to determine the environmental standard value of mercury content in soil by significantly reducing the pretreatment process. Our approach involves analyzing current peaks from electrodeposition times using specific electrodes and solvent settings. This method demonstrates low error rates under low concentration conditions and can detect mercury levels as low as 0.5 ppb in soil leachate and reagent dilution series. This research facilitates the determination of low mercury concentrations in solutions containing various soil micro-compounds without the need for calibration curves. [ABSTRACT FROM AUTHOR]

The damping of spruce wood is analysed at different moisture content levels for the first three vibration modes of tangentially and radially vibrating samples. Two methods were used to determine the damping. The first was the vibration envelope fitting as an improved version of the well-known logarithmic decrement, and the second was the newer and recently increasingly used wavelet transform. Both methods showed that the damping of spruce wood first decreases and then increases with moisture content, with the damping in the first vibration mode being about 9% higher in the radial direction than in the tangential direction. In the second and third vibration modes, the damping in the tangential direction was higher than in the radial direction by about 10% and 8.8%, respectively. The measured damping factors from the envelope fitting had, on average, 15.9% higher values than those from the wavelet transform. It can be concluded from the results that the wavelet transform is more accurate for determining the damping factor, as it enables the decoupling of multi-degree of freedom systems if mode coupling is present. [ABSTRACT FROM AUTHOR]

Soil plays a crucial role in human health through its impact on food and habitation. However, it often contains toxic heavy metals, with mercury being particularly hazardous when methylated. Currently, high-sensitivity, rapid detection of mercury is achievable only through electrochemical measurements. These measurements require pretreatment of the soil sample and the preparation of a calibration curve tailored to the sample’s condition. In this study, we developed a method to determine the environmental standard value of mercury content in soil by significantly reducing the pretreatment process. Our approach involves analyzing current peaks from electrodeposition times using specific electrodes and solvent settings. This method demonstrates low error rates under low concentration conditions and can detect mercury levels as low as 0.5 ppb in soil leachate and reagent dilution series. This research facilitates the determination of low mercury concentrations in solutions containing various soil micro-compounds without the need for calibration curves.

The article presents the results of a study of a modal filter (MF) based on a microstrip line (MSL) with two side conductors grounded at both ends. For the first time, the quasi-static simulation and measurements of the filter are conducted with two devices, and the results are compared. Frequency dependences of |S11| and |S21| are measured and calculated in the range from 0 to 10 GHz. At the MF output, the time response to an ultrashort pulse (USP) was analyzed. It was experimentally proved that the performed quasi-static simulation was correct. The simulation and measurement results showed remarkable consistency. The proposed MF provides the protection of electrical circuits from USP by decomposing it into two pulses with the amplitudes that are more than three times smaller. This confirms that such MF obtained simply by adding to a MSL two passive conductors grounded at both ends can be used to create simple and cheap protection, for example, of critical radioelectronics against powerful intentional USP created by electromagnetic weapons. [ABSTRACT FROM AUTHOR]

Purpose: The feasibility of harvesting electrical energy from mechanical vibration is demonstrated in the thesis. In the technique, energy is harvested from simply supported beam vibration under a moving mass using a thin piezoelectric material. Design/methodology/approach: The structure is represented by a basic beam of length L that is supported at both ends and traversed by a moving mass M travelling at a constant velocity v. The Euler-Bernoulli differential equation describes its behaviour. The dynamic analysis of a beam is performed by using three moving masses of (35.61, 65.81, and 79.41) gr each travelling three uniform speeds of (1.6, 2 and 2.4) m/s. A differential equation of the electromechanical system is obtained by transforming the piezoelectric constitutive equation and solved numerically by MATLAB. Findings: The results indicate that the numerical and experimental values for the midpoint deflection of the beam and the piezoelectric voltage are very close. Research limitations/implications: Using the COMSOL programme, the proposed approach is checked by comparing results with data obtained by the finite element method (FEM). An experimental setup was also built and constructed to determine the voltage created by the piezoelectric patch and the beam response as a result of the mass travelling along the beam. Practical implications: The results show that the dynamic deflection, piezoelectric voltage, and piezoelectric energy harvesting all increase as the speed and magnitude of the moving mass increase. The harvesting power vs. load resistance curve begins at zero, increases to a maximum value, and then remains almost constant as the resistance is increased further. The optimal length of the piezoelectric patch was obtained to be 0.63 m. When the length of the beam increases, the resonant frequency decreases, and at the same time the harvested energy increases. However, increasing the beam thickness has the opposite effect; whereas raising the beam width does not affect the resonant frequency but decreases energy harvesting. Originality/value: The most essential point here is the need to have correctly built scale models. They can provide a substantial amount of information at a low cost, accommodate a variety of test settings, and aid in the selection and verification of the most effective analytical model to resolve the actual issue. [ABSTRACT FROM AUTHOR]

The damping of spruce wood is analysed at different moisture content levels for the first three vibration modes of tangentially and radially vibrating samples. Two methods were used to determine the damping. The first was the vibration envelope fitting as an improved version of the well-known logarithmic decrement, and the second was the newer and recently increasingly used wavelet transform. Both methods showed that the damping of spruce wood first decreases and then increases with moisture content, with the damping in the first vibration mode being about 9% higher in the radial direction than in the tangential direction. In the second and third vibration modes, the damping in the tangential direction was higher than in the radial direction by about 10% and 8.8%, respectively. The measured damping factors from the envelope fitting had, on average, 15.9% higher values than those from the wavelet transform. It can be concluded from the results that the wavelet transform is more accurate for determining the damping factor, as it enables the decoupling of multi-degree of freedom systems if mode coupling is present.

GNSS tomography is a method for the three-dimensional reconstruction of wet refractivity ( N w ) in a set of voxels, each covering a specific part of the troposphere. The substantial assumption is the homogeneity of atmosphere in each voxel in given time intervals, known as the time response of model. Determining the optimal time resolution is one of the existing challenges in the tomography of the Earth's atmosphere. We apply Empirical Orthogonal Functions (EOFs) to find an optimal time response for our tomographic model. To investigate our method, we compute the EOFs using the numerical atmospheric model that is available in our test area as the reference field on an already designed tomographic model. Using time resolutions of 30, 45, 60, 75, 90, 105 and 120 min, our EOF based method suggests the time periods of 60 to 75 and 75 to 90 min as the time response in the two days (a dry and a wet day) of our experiments, respectively According to our analysis, because of the quality of our reference field, it is not possible to expect similarities better than 85% for wet day and 93% for dry days in the scattering of the N w field between the reconstructed images and our reference model. [ABSTRACT FROM AUTHOR]

Spatial and temporal characteristics of a degenerate four-wave converter in a multimode waveguide with resonant nonlinearity in a scheme with counter-pumping waves are analyzed using the time response function and the point spread function. For single-mode pump waves with equal mode numbers, the dependences of the time response width on the waveguide length, the intensity of the first pump waves, and the mode number in the mode expansion of the object wave amplitude are obtained for the four-wave converter. The greatest contribution to the object wave amplitude is shown to be from the waveguide mode whose number coincides with the mode number of single-mode pump waves. For the stationary model, taking into account the spatial structure of the Gaussian pump wave leads to a monotonous decrease with a decrease in the pump beam width, followed by a constant value of the PSF module width. With single-mode pump waves with equal mode numbers, An increase in the mode number of the pump waves leads to a redistribution of energy concentrated in the side maxima of the point signal image and improvement in the quality of the wavefront reversal for a model with single-mode pump waves with equal mode numbers.

For the first time, the effect of temperature on the time response of a new modal filter (MF) based on a microstrip line with two side conductors grounded at both ends is estimated. The estimation was performed based on the results of quasi-static modeling, taking into account the temperature model and measuring the manufactured MF layout using the heat-cold chamber. The time responses to the ultrashort pulse at the MF output were analyzed. The results of modeling without taking into account losses, with taking into account losses, and measurements at temperatures of –50, 25, and +150°C are presented. Deviations of the delay and voltage amplitude are estimated. The consistency of the simulation and measurement results is shown. A small effect of temperature on the delay (about 1%) and a significant effect on the amplitude (up to 36%) of the first pulse were revealed. [ABSTRACT FROM AUTHOR]

The present study aimed to examine the validity of a novel method to assess cerebrovascular carbon dioxide (CO2) reactivity (CVR) that does not require a CO2 inhalation challenge, e.g., for use in patients with respiratory disease or the elderly, etc. In twenty-one healthy participants, CVR responses to orthostatic stress (50° head-up tilt, HUT) were assessed using two methods: (1) the traditional CO2 inhalation method, and (2) transfer function analysis (TFA) between middle cerebral artery blood velocity (MCA V) and predicted arterial partial pressure of CO2 (PaCO2) during spontaneous respiration. During HUT, MCA V steady-state (i.e., magnitude) and MCA V onset (i.e., time constant) responses to CO2 inhalation were decreased (p < 0.001) and increased (p = 0.001), respectively, indicative of attenuated CVR. In contrast, TFA gain in the very low-frequency range (VLF, 0.005–0.024 Hz) was unchanged, while the TFA phase in the VLF approached zero during HUT (−0.38 ± 0.59 vs. 0.31 ± 0.78 radians, supine vs. HUT; p = 0.003), indicative of a shorter time (i.e., improved) response of CVR. These findings indicate that CVR metrics determined by TFA without a CO2 inhalation do not track HUT-evoked reductions in CVR identified using CO2 inhalation, suggesting that enhanced cerebral blood flow response to a change in CO2 using CO2 inhalation is necessary to assess CVR adequately. [ABSTRACT FROM AUTHOR]

We tested the impact of heart rate variability biofeedback (HRV-BF) on police performance in order to reduce protocol gaps and response time in scenarios that simulate life-threatening situations. The sample gathered fifty-one frontline police officers from the city of Barueri in Brazil who were distributed into two groups: (i) the experimental group (26 officers) which attended a 5-days protocol of HRV-BF training; and (ii) the control group (25 officers) which did not train. The performance of both groups was assessed before and after the HRV-BF training, and the results were compared. The findings show that HRV-BF positively impacted the experimental group's performance by decreasing procedural gaps and timing. In contrast, the performance of the control group remained stable. Based on this evidence, the Secretariat of Urban Security and Social Defense of Barueri decided to make HRV-BF into public policy. [ABSTRACT FROM AUTHOR]

A frequency-domain model is developed to analyze isolated interconnects of multilayer graphene-nanoribbon (MLGNR) and mixed carbon-nanotube bundle (MCB) driven by CMOS gates. The model derived is founded on an equivalent-single-conductor model of MLGNR and MCB that takes thermal considerations into account (i.e. TD-ESC). The model includes the derivation of transfer function of interconnect to estimate its delay and bandwidth performance. The attained results, reveals that among the neutral MLGNR (N-MLGNR), intercalation doped MLGNR (ID-MLGNR) intercalated with FeCl 3 , MCB and Cu interconnects, FeCl 3 ID-MLGNR achieves the best bandwidth efficiency. At a global interconnect length of 1 mm, FeCl 3 ID-MLGNR outperforms N-MLGNR, MCB, and Cu in terms of bandwidth with an improved bandwidth value of 12.2 GHz, 7 GHz, and 61.4 GHz, respectively. Further, employing the proposed CMOS-gate-driven model, for FeCl 3 ID-MLGNR, bandwidth is improved by nearly 7.52 × at global length (∼1 mm) in relation to the linear resistance model. Additionally, TD-ESC dependency of the proposed model reveals that FeCl 3 ID-MLGNR becomes more stable as interconnect resistance increases. • CMOS-driven interconnects of multilayer graphene-nanoribbon(MLGNR) and mixed CNT bundle(MCB) analysed in frequency-domain. • A temperature-dependent equivalent-single-conductor (TD-ESC) approach estimates interconnect performance accurately. • The derived transfer function for interconnects allows for the estimation of delay and bandwidth performance. • At global interconnect domain, FeCl3 intercalation-doped MLGNR (ID-MLGNR) outperforms neutral-MLGNR (N-MLGNR), MCB and Cu. [ABSTRACT FROM AUTHOR]

This work presents geometrically nonlinear transient analyses of various rotating blades. The structures are discretized through refined beams or multi-dimensional finite element models, which are generated using the Carrera Unified Formulation (CUF). The CUF offers a procedure to develop low- and high-fidelity one-dimensional, two-dimensional, and three-dimensional finite element models hierarchically and automatically. Various beam models were developed using different kinematics models based on Taylor or Lagrange expansion functions. Multi-dimensional models were obtained by merging beam and solid elements, exploiting the unique feature of Lagrange polynomials to have only pure displacements as unknowns. This property allows beam and solid elements to be coupled at the node level without requiring complicated mathematical formulations. By utilizing the Finite Element Method in conjunction with the CUF, the governing equations are written by including all rotation effects, namely the Coriolis term, spin-softening, and geometrical stiffening. In a total Lagrangian scenario, the Hilbert-Hughes-Taylor-α method and the iterative Newton-Raphson scheme are employed to solve the equations of motion. The proposed methodology has been applied to evaluate different blade configurations, comparing the solution obtained using linear, linearized, and nonlinear approaches. The results have been verified and validated by comparing them with existing solutions present in the literature. [ABSTRACT FROM AUTHOR]

Carbon Nanotube (CNT) is a material consisting of carbon atoms arranged in a series of condensed benzene rings that are coiled into a tubular structure. CNTs are used in various fields, such as reinforcing materials, coatings and films, biotechnology and biomedicine, and nano electromechanic systems (NEMS). The application of CNT in the biotechnology and biomedical fields as a nanopipe for carrying fluids is due to its high elastic modulus, good thermal and electrical conductivity, and other superior mechanical properties. One of the phenomena that can reduce CNT performance is flutter, so fluid-structure interaction is one of the important considerations in the design and application of CNTs. This study analyzes the effect of mass ratio on flutter instability due to flow in the CNT cantilever using the finite element method. Meanwhile, the system's responses are calculated using the Newmark method time scheme. The structural characteristics of the CNT were modeled as the EulerBernoulli beam. In this case, the fluid flowing in it is characterized in terms of two parameters, namely the average flow velocity (U) and the fluid mass density (per unit length). The results showed that the analysis of the response in the time domain is very sensitive to changes in flow velocity, the critical speed will decrease with an increase in the aspect ratio. and the mass ratio affects the flutter stability limit, where the larger the mass ratio for a given fluid density, the higher the flutter stability limit. The findings also revealed that the higher the density of the fluid flowing through the CNT, the lower its ultimate stability limit. [ABSTRACT FROM AUTHOR]

This paper presents a novel design technique of H-infinity based temperature and molar concentration controller for the highly non-linear system, namely continuous stirred tank reactor (CSTR). Model uncertainties and perturbation in CSTR parameters are considered in the proposed design. The stability, robustness, disturbance rejection capability, sensitivity to the parameter variations, and speed of the proposed controller are investigated through time and frequency response, complementary, and worst-case sensitivity analysis. Further, performances of the proposed controller are compared with the other existing controllers to reveal its effectiveness and accuracy. It is shown that, the proposed controller provides better time- and frequency-responses characteristics along with high disturbance rejection capability than the other existing controllers. The rise time, peak overshoot, and settling time of the proposed controller are found smallest among the conventional and AI based controllers and are 0.14 s, 0, and 0.6 s, respectively. Further, performance indices of the proposed controller are also found smaller than the other existing controllers. Also, the magnitude of sensitivity and complementary sensitivity functions is found in the desired limit under worst condition. Proposed control is found proficient to control the other parameter, such as molar concentration control, also. [ABSTRACT FROM AUTHOR]

The article presents the results of calculating time responses of a meander line (ML) turn to pulse excitation. The responses were calculated at the ML nodes analytically and numerically, and demonstrated coincidence. Besides, the created prototype of the ML turn was measured and showed good qualitative and acceptable quantitative agreement with the simulation results. Analytical models were found to be promising since they may significantly accelerate the design of such MLs in contrast to numerical methods which provide costly multivariate simulation of the time response during optimization. [ABSTRACT FROM AUTHOR]

Pressure-sensitive paint (PSP) is an optical sensor that can measure global pressure distribution by using the oxygen quenching of dye molecules. In particular, anodized aluminum pressure-sensitive paint (AA-PSP) exhibits a fast time response. AA-PSP has been used in unsteady measurements at supersonic and transonic speeds, such as on the surface of a transonic free-flying sphere or the wall of a shock tube when the shock wave passes. To capture such ultrafast phenomena, the frame rate of the camera must be sufficiently fast, and the exposure time must be sufficiently short. Therefore, it is desirable that the AA-PSP exhibits bright luminescence, high-pressure sensitivity, and fast response time. This study focused on pyrene-based AA-PSPs and investigated their characteristics, such as luminescence intensity and pressure sensitivity, at different anodization times, dipping solvents, and dipping concentrations. Furthermore, a time-response test using a shock tube was conducted on the brightest AA-PSP. Consequently, the time for a 90% rise in pressure was 2.2 μs. [ABSTRACT FROM AUTHOR]

This work presents a detailed, comprehensive study of a new structural design of protective devices with a circular cross-section (CS) (protective cables) for protecting equipment against ultra-wideband (UWB) pulses. Multiconductor structures with 2–5 conductors with and without a protective shield are considered. The disadvantages of using symmetric configurations of protective cables are shown. Their simulation, multivariate analysis, and optimization through heuristic search, as well as evolutionary strategies, were carried out. Optimization was carried out according to the amplitude (to minimize the maximum voltage level at the output of the structures) and time (to maximize the duration of the exciting signal) criteria. The optimization results allowed for increasing the duration and overall attenuation of the exciting UWB pulse. The article shows the possibility of improving the characteristics of such structures through their cascade connection, both among themselves and with strip protective structures. The results of parametric optimization of such structures are presented in the range of real (used in practice) geometric and electrophysical parameters in terms of amplitude and time criteria, as well as the matching criterion. The article also presents the developed prototypes of protective structures with a circular CS of three types: circular 3-conductor cable, flat 3-conductor cable, and circular 4-conductor cable. The experimental results describe how these prototypes were developed and created and confirm the feasibility of these protective structures to decompose the exciting pulse signal, which was previously shown only in simulation. Finally, it is shown that the use of asymmetry in the proposed cable structures can improve their protective characteristics. [ABSTRACT FROM AUTHOR]

The aim of almost any electromagnetic actuator development is to increase the electromagnetic force with which an actuator acts on a plunger with as fast a time response as possible while maintaining the dimensions as small as possible. This paper presents research on the impact of the lower core angle on the force and time response of a DC solenoid electromagnetic actuator. The research method is based on the analytical analysis of the magnetic path of the DC solenoid electromagnetic actuator and a comparison with the numerical simulation results. A transient numerical simulation was performed on a 2D axial-symmetric model of the electromagnetic actuator and included simultaneously solving time-dependent partial differential equations of the electromagnetic actuator’s magnetic, electrical, and mechanical subsystems. The magnetic subsystem was analyzed by the finite element method (FEM) using the ANSYS Electronics software package. The three prototype models with different lower core angles were produced and tested in the accredited Laboratory Center of KONČAR Electrical Engineering Institute. The obtained measurements are compared with the analytical results and numerical simulation results.

در این مقاله ، یک دیود تونل زنی تشدید با ساختار سد مضاعف AlAs / GaAs با استفاده از عملکرد سبز غیر تعادلی شبیه سازی شده است. یک لایه جذب InGaAs منطبق شده برای تشخیص نور در طول موج λ = 600 نانومتر به دستگاه اضافه می شود . میدان الکتریکی از طریق دستگاه و مشخصات نمودار باند انرژی ارائه شده است. جریان عکس دستگاه و منحنی های جریان جریان منبع در مقابل شدت نور مقایسه می شوند . در دمای اتاق ، بازده کوانتومی 95/0 برای دستگاه بدست آمد . پاسخ زمان گذرا دستگاه به دست آمد و وابستگی آن به پارامترهای ساختاری (ضخامت لایه جذب ، ضخامت کلکتور و انتشار دهنده ودوپینگ مخاطبین) ، شدت نور ، زاویه نور ساطع شده و سوگیری ولتاژ شبیه سازی شده و تأثیر آنها بر عملکرد دستگاه مورد تجزیه و تحلیل قرار گرفت. پهنای باند دستگاه به دست آمد. نتایج شبیه سازی نشان می دهد که وقتی بایاس ولتاژ افزایش یابد ، زمان افتادن کاهش می یابد و پاسخ دستگاه سریعتر است. با تغییر ضخامت لایه جذب و مخاطب ، پاسخ زمان RTD-PD تغییر می کند. تغییرات دوپینگ در لایه های تماس بر روی پهنای باند تأثیر می گذارد. نتیجه نشان می دهد که تغییرات شدت نور و زاویه نور ساطع شده ، پاسخ زمان گذرا را تغییر می دهند.

Micro-electro-mechanical-systems scale robots are prone to impulsive disturbances during operation. Such disturbance leads to adverse oscillations of the robot manipulator. So, it is essential to mitigate and control such unwanted oscillations. On the other hand, to capture size dependencies of such robot elements, it is required to adopt nonclassical models. To address these cases, robot manipulator is modeled as a mechanical rod, comprehensive rod models are utilized, proportional integral derivative (PID) controller is designed, and the time-domain response of the system is simulated in MATLAB. Results show that adopting proper gain values of the PID controller leads to total rejection of the pulsive disturbances. However, findings conceal the importance of the nonclassical rod model such that strain gradient (SG) model shows less oscillatory amplitude than the classical theory (CT) model. While considering the nonlocal model effects (NL), such undesired vibrations are bigger than CT model. In other words, meanwhile, a simple PID controller can reject the disturbance for SG models; a stronger controller should be adopted to reject such pulsive disturbances with NL models. Eventually, it is valuable to note that to suppress unwanted oscillations in small-sized robots, PID closed-loop feedback controller is a decent choice because of the simplicity and less costs. Application of successful control design alongside the proper nonclassical theory leads to neutralizing the disturbances and increases the robot manipulator precision. [ABSTRACT FROM AUTHOR]

Residuální kmitání způsobené poddajnostmi v soustavě lineárního pohonu a zátěže ovlivňuje přesnost výsledné polohy pracovního členu. Článek se zabývá modelováním dynamického chování zátěže tvořené seismickou hmotou uloženou na dvou plochých pružinách. Uvedeny jsou dva lineární modely – spojitý model odvozený na základě teorie ohybových kmitů prizmatického nosníku s odpovídajícími okrajovými podmínkami a diskrétní model se soustředěnými prvky o jednom stupni volnosti. Oba modely byly použity k simulaci pohybu připojené soustavy pro různé průběhy zdvihových funkcí motoru a porovnány s průběhy naměřenými na reálné soustavě.

This paper deals with the evaluations of lower and upper bounds of dynamic responses and natural frequencies for structures with uncertain interval parameters. The structural physical parameters, geometric dimensions and initial conditions can be considered as interval parameters. The modified Chebyshev interval method (MCIM) is presented to handle the uncertainties. In comparison with the Chebyshev interval method (CIM), MICM provides with tighter bounds of the time responses and natural frequencies without a significant increase in computation time. Monte Carlo method is also used to provide with exact bounds. MICM, CIM and Monte Carlo method are applied for structures with interval parameters, and the efficiency and accuracy of CIM and MCIM are verified.

Target flowmeter is commonly used for measuring flow rates, but there are some shortcomings of the conventional target flowmeter, such as complex structure, low sensitivity, non-linearity. Here, a Surface Acoustic Wave (SAW) sensor-based target flowmeter has been proposed where a SAW sensor is placed on the target rod of the flowmeter. When liquid flows through the pipe in contact with the target rod, the force is produced. This force then acts on the target rod and deflects the target rod from its original position, which results strain in it. SAW sensor senses the strain level at different flow rates, and the output is in terms of delayed time response of the order of a nanosecond. The output is non-linear with respect to the flow rate and it is linearized with the help of a neural network technique. This minimizes the non-linearity error up to 0.27% of full-scale output (FSO). The modification in the target type flowmeter is done with the help of the SAW sensor in such a way that the flow transmitter can transmit sensed information through the wireless channel. Simulation and mathematical approaches are reported in this paper for the range of 0 to 1200 LPH. [ABSTRACT FROM AUTHOR]

Pressure-sensitive paint (PSP) is an optical sensor that can measure global pressure distribution by using the oxygen quenching of dye molecules. In particular, anodized aluminum pressure-sensitive paint (AA-PSP) exhibits a fast time response. AA-PSP has been used in unsteady measurements at supersonic and transonic speeds, such as on the surface of a transonic free-flying sphere or the wall of a shock tube when the shock wave passes. To capture such ultrafast phenomena, the frame rate of the camera must be sufficiently fast, and the exposure time must be sufficiently short. Therefore, it is desirable that the AA-PSP exhibits bright luminescence, high-pressure sensitivity, and fast response time. This study focused on pyrene-based AA-PSPs and investigated their characteristics, such as luminescence intensity and pressure sensitivity, at different anodization times, dipping solvents, and dipping concentrations. Furthermore, a time-response test using a shock tube was conducted on the brightest AA-PSP. Consequently, the time for a 90% rise in pressure was 2.2 μs.

Principal Component Analysis is used for damage detection in structures excited by harmonic forces. Time responses are directly analysed by Singular Value Decomposition to deduct two dominant Proper Orthogonal Values corresponding to two Proper Orthogonal Modes. Damage index is defined by the concept of subspace angle that a subspace is built from the two Proper Orthogonal Modes. A subspace angle reflects the coherence between two different structural health states. An example is given through the application on a part of a real prestressed concrete bridge in Luxembourg where different damage states were created by cutting a number of prestressed tendons in four scenarios with increasing levels. Results are better by using excitation frequency close to an eigenfrequency of the structure. The technique is convenient for practical application in operational bridge structures.

The aim of almost any electromagnetic actuator development is to increase the electromagnetic force with which an actuator acts on a plunger with as fast a time response as possible while maintaining the dimensions as small as possible. This paper presents research on the impact of the lower core angle on the force and time response of a DC solenoid electromagnetic actuator. The research method is based on the analytical analysis of the magnetic path of the DC solenoid electromagnetic actuator and a comparison with the numerical simulation results. A transient numerical simulation was performed on a 2D axial-symmetric model of the electromagnetic actuator and included simultaneously solving time-dependent partial differential equations of the electromagnetic actuator's magnetic, electrical, and mechanical subsystems. The magnetic subsystem was analyzed by the finite element method (FEM) using the ANSYS Electronics software package. The three prototype models with different lower core angles were produced and tested in the accredited Laboratory Center of KONČAR Electrical Engineering Institute. The obtained measurements are compared with the analytical results and numerical simulation results. [ABSTRACT FROM AUTHOR]

Breakdown of stackers and excavators in opencast mines is possible because of operating, manufacturing and structural causes, and it produces high financial losses. These can be prevented by using various measures, including analyses and strength tests, with computerized modeling and simulation using FEA or other techniques being implemented in the recent years. In this paper a fatigue study is conducted on the boom of a BWE. Based on a computer model of the boom previously developed in SOLIDWORKS by our author team, first the modal analysis is conducted for three positions of the boom by studying the frequency response during the excavation process. This is followed by the time response determination corresponding to the maximum displacement frequency, in order to assess the stress during the excavation process, which causes the material fatigue in the boom structure. It was found that the maximum displacements appear when the BWE boom operates in a horizontal position. The aim was to estimate the period of time to failure in order to prevent unwanted accidents, and to develop a method that is applicable to any surface mining or industrial machine with similar structure.

An investigation into the dynamic response and frequency split behavior of a cylindrical fused silica resonator is performed via simulations and experiments. For this purpose, a structure for the cylindrical resonators with appropriate dimensions has been designed and fabricated. A laser Doppler vibrometer is utilized for the experimental quantification of the physical characteristics of the resonator. Natural frequencies of n = 2 modes, frequency split and quality factor have been extracted from the measured frequency sweep. Then the influence of mass change on the frequency split is investigated by chemical trimming. Time response predictions utilizing a ring model is employed to predict the resonant amplitudes as well as the influence of driving force and input angular velocity variations. The numerical predictions of the relationship between the mass mismatch and the frequency split are found to be consistent with the exper imental results. Predictions of frequency split of resonators via the simulation model are envisaged to greatly increase the efficacy of the chemical trimming process. [ABSTRACT FROM AUTHOR]

Fig. Response of perovskite thin films electrical conductivity to light variation. (a) In function of time (b) in function of light intensity • Time response of the electrical resistivity of perovskite thin films at light exposure. • Temperature dependencies of the electrical resistivity of CH 3 NH 3 PbI 3. • Analysis of optical properties and band gap model. Structural and morphological properties of CH 3 NH 3 PbI 3 thin films deposited by spin coating, with different spin speeds on glass and ITO patterned substrates were investigated. It results that long length acicular crystals, growth parallel to substrates (>200 μm for spin speeds of 800RPM/min). For low deposition spin speed these crystals are interconnected and deposited films present a high electrical conductivity. The XRD investigations indicate the formation generally of the cubic phase, or a mixture between cubic and tetragonal phase. For compact films the absorption is high over a large range of spectral domain (from 200 nm to 2100 nm), the transmission being lower than 20% in IR and less than 15% in the visible domain. From electrical properties point of view, films are highly sensitive to light. An increase of the electrical conductivity with three order of magnitude is noticed when films are exposed to a white light of a solar simulator with an intensity of 1000 W/m2, but also an important increase is observed when films are exposed to a continuous low intensity ambient light, at least one order of magnitude in less than six seconds. This behavior is identical no matter the films thickness. The variation of the electrical conductivity at exposure to light in function of time and light intensity and the variation of the electrical conductivity in function of temperature were investigated and interpreted. The experimental results, since now, comforting the assumption of a multiband model. [ABSTRACT FROM AUTHOR]

Utilizing ball-type auto-balancer in rotating systems is a popular method in industry in order to eliminate the rotational vibration. Recently, by using numerical methods, it is shown that a ball-type auto-balancer equipped with both the radial and peripheral springs, ball-spring automatic balancer (AB), is an improved model. In this paper, due to the advantages of analytical methods over the numerical ones, the complete system dynamics, i.e., the stability analysis and the time response, of the rotor equipped with ball-spring AB is analyzed by the multiple scales method as a unified technique. Therefore, with no need for implementing any other stability theories, the stability analysis is a definite advantage of this method due to the less computation cost. Moreover, the time responses show a good agreement with those obtained through the numerical method. Finally, for the first time, the influence of the peripheral springs on the time responses and the stable equilibrium points of the rotor with ball-spring AB is studied in details. The results show that the peripheral springs decrease the vibration amplitude at the transient and leave some residual imbalance at the steady state and accordingly, there is a compromise between the system working performance at the transient and the steady state. [ABSTRACT FROM AUTHOR]

To acquire the direct time response of ZnO crystals to high energy particles, a dual-channels single photon correlation (DCSPC) system based on the measurement of the autocorrelation function of the fluoresce temporal profile was employed. The measuring resolution of the DCSPC system calibrated by Cerenkov luminescence is 46 ps. With this DCSPC system, the fast decay time constants of ZnO:Ga, ZnO:In and ZnO:Sc under charged particle alpha and beta excitation were successfully measured, which are 1.56 ns, 0.48 ns, 0.12 ns, and 1.11 ns, 0.40 ns, 0.10 ns, respectively. For all the three samples, it is found that the decay time constants under beta excitation are faster than those under alpha excitation, indicating that ZnO crystal is a fast scintillation material with pulse shape discrimination (PSD) ability. This would be applied in selective detection of mixed radiation field, particularly where high counting rate is required. [ABSTRACT FROM AUTHOR]

Abstract Analysis of vibration signal plays a fundamental role in fault diagnosis and monitoring of rotating machines. Diagnosis, identification and evaluation of bearing faults are critical aspects for a healthy operating system. Among bearing failures, wear is one of the most common, directly affecting the bearing clearance, resulting in changes of the rotating system characteristics. Therefore, time response of a rotor-bearing system, under different worn bearing condition, is analyzed in order to define a general vibration behavior that characterizes the presence of bearing wear. Spectrum response is used to compare healthy and worn bearings. Experimental tests were performed to validate the numerical findings. Results show a standard tendency in dynamic behavior related to the backward component of the shaft whirling movement. Highlights • Numerical and experimental analysis of wear in hydrodynamic bearings. • Time response of a rotor-bearing system, under worn bearings condition. • Identification of the presence and severity of wear in hydrodynamic bearings. • Prediction of machine operating state, fault condition and its progression. [ABSTRACT FROM AUTHOR]

This paper proposes a new sensor architecture inspired on the classical accelerometer and the fractional calculus. The fractional sensor (FS) adopts a modular construction with N∈ℕ stages, where each stage consists of an association of mass–spring–damper elements. A proper selection of the elements in the global mechanical structure yields fractional-order characteristics. The frequency and time responses of the proposed apparatus are studied and compared with those exhibited by an ideal fractional order device. The FS can be implemented by means of modern fabrication techniques used with micro electro-mechanical systems. [ABSTRACT FROM AUTHOR]

• Time responses of engineering structures with interval and/or random parameters are investigated systematically. • Polynomial-chaos-Legendre-metamodel method is presented for structure with hybrid interval and random parameters. • Legendre metamodel method is presented for structure with interval parameters. • Polynomial chaos theory is applied for structure with random parameters. Abstract Practical structures often operate with some degree of uncertainties, and the uncertainties are often modelled as random parameters or interval parameters. For realistic predictions of the structures behaviour and performance, structure models should account for these uncertainties. This paper deals with time responses of engineering structures in the presence of random and/or interval uncertainties. Three uncertain structure models are introduced. The first one is random uncertain structure model with only random variables. The generalized polynomial chaos (PC) theory is applied to solve the random uncertain structure model. The second one is interval uncertain structure model with only interval variables. The Legendre metamodel (LM) method is presented to solve the interval uncertain structure model. The LM is based on Legendre polynomial expansion. The third one is hybrid uncertain structure model with both random and interval variables. The polynomial-chaos-Legendre-metamodel (PCLM) method is presented to solve the hybrid uncertain structure model. The PCLM is a combination of PC and LM. Three engineering examples are employed to demonstrate the effectiveness of the proposed methods. The uncertainties resulting from geometrical size, material properties or external loads are studied. [ABSTRACT FROM AUTHOR]

This paper proposes a comparative assessment of NN based current controllers followed by hardware validation towards power quality improvement in grid-interactive VSI controlled solar system. The steady state errors, transient disturbances and high current harmonic effects encountered in conventional linear PI and PR controllers are nullified by employing intelligent adaptive current controller. Three adaptive current control strategies viz. ADALINE-LMS, ALLMS, and VLAS-LMS are identified by using artificial neural network topology having been controlled by different weight-regulating algorithms which helps in minimizing current harmonics generated by the widespread use of VSI, non-linear loads, faults and uncertain polluted grid. A comprehensive comparative study is driven from the proposed adaptive controller's stability and convergence criterion, current magnitudes calculated at different power zones, % overshoot, settling time and power quality and analyzed under numerous operating conditions. From the comparative assessment performed in between conventional and intelligent current controllers, it is confirmed that the intelligent control technique performs best under the non-linear loads and transient conditions whereas all the controllers perform equally good under the linear loads. Proposed methods are simulated in MATLAB/Simulink and their effectiveness is compared in terms of time responses, stability and low-order current harmonics compensation capability. The robustness of the intelligent current controller is established through the experimental performances using dSPACE RTI 1202. [ABSTRACT FROM AUTHOR]

In this paper, we employed optical waveguides in a silicon rod base structure to realize AND, OR logical operation simultaneously based on two-dimensional photonic crystals. All of the structure is composed of silicon rods. Employing silicon rods of different radii as defect rods in optical waveguide filtered the desired wavelength. We utilized two similar waveguides as our input bits and two waveguides as AND and OR outputs. The overall footprint of the proposed device is 60 μm2 and hence is very compact. The time responses of device are about 0.5 ps and hence in conjunction with the mentioned characteristics suggest the use of the device for computational applications. The electric field distribution is obtained by the finite-difference time-domain method. In this paper, the logic state of ‘1’ and ‘0’ at output port is defined as the transmission is around ‘1’ and less than 0.25, respectively. The compact size of the proposed structure and the materials used make the proposed device suitable for optical integrated circuits. [ABSTRACT FROM AUTHOR]

A two-dimensional steady laminar natural convection in rectangular enclosure filled with CuO-water nanofluid is numerically investigated. The horizontal walls are thermally insulated and the left vertical side one is heated by a temporal sinusoidal temperature variation, whereas the right wall is kept at cold temperature. Mass Conservation, momentum, and energy equations are numerically solved by the finite volume element method using the SIMPLER algorithm for pressure-velocity coupling. This study has been carried out for four parameters: the volumetric fraction of nanoparticles  (0%≤≤4%), aspect ratio Ar (0.25≤Ar≤1), amplitude of temperature a (0.2≤a≤0.8) and its period (0.2≤Θ≤0.8). These simulations are performed at constant Rayleigh and Prandtl numbers (Ra=105and Pr=7.02). Numerical results show that the addition of nanoparticules into the basic fluid has a double role, increasing heat transfer and reducing the response time of the system. The decreasing of aspect ratio shows an increasing trend of the heat transfer and increases the amplitude of Nusselt number. We also see that after a time period the system does not return to its initial state (hysteresis phenomenon) because of the system inertia.

The analysis of the mechanical behavior of ancient structures is an essential engineering task concerning the preservation of architectural heritage. As many monuments of classical antiquity are located in regions of earthquake activity, the safety assessment of these structures, as well as the selection of possible restoration interventions, requires numerical models capable of correctly representing their seismic response. The work presented herein was part of a research project in which a better understanding of the dynamics of classical column-architrave structures was sought by means of numerical techniques. In this paper, the seismic behavior of ancient monumental structures with multi-drum classical columns is investigated. In particular, the column-architrave classical structure under strong ground excitations was represented by a finite element method. This approach simulates the individual rock blocks as distinct rigid blocks interconnected with slidelines and incorporates seismic isolation dampers under the basement of the structure. Sliding and rocking motions of individual stone blocks and drums are modeled utilizing non-linear frictional contact conditions. The seismic isolation is modeled through the application of pad bearings under the basement of the structure. These pads are interpreted by appropriate rubber and steel layers. Time domain analyses were performed, considering the geometric and material non-linear behavior at the joints and the characteristics of pad bearings. The deformation and failure modes of drum columns subject to seismic excitations of various types and intensities were analyzed. The adverse influence of drum imperfections on structural safety was also examined.

Abstract Preparing organometal halide perovskite array thin films from solution is a big challenge due to its soluble nature. In this work, we provide a fast chemical vapor-solid reaction (FCVR) for fabricating perovskite array thin films. An elemental Pb array thin film was firstly prepared by magnetron sputtering using a shadow mask, which then converted to CH 3 NH 3 PbI 3 arrays by reacting with CH 3 NH 3 I. The related photoelectric characteristics were investigated by Uv–Vis spectroscopy, photoluminescence spectroscopy, and transient photovoltage analysis. The photodetector devices were assembled using these resultant perovskite thin films, which showed a fast response with 3 ms rise time and 3 ms decay time both under 405 nm and 660 nm light illumination. The response was faster than the commercial photodetector. This FCVR method not only provides a high quality perovskite array thin film, but also a novel synthesis strategy for new organic-inorganic hybrid perovskite photoelectric materials. Graphical abstract Image 1 Highlights • Fast chemical vapor-solid reaction (FCVR) was used for perovskite fabrication. • Perovskite array thin films can be easily fabricated by FCVR method. • Fast time response photodetectors were assembled. [ABSTRACT FROM AUTHOR]

Abstract A dynamic lumped-parameters model has been developed in order to analyse the performance of a combined cooling, heating and power (CCHP) plant during transient load variations. The plant allows the waste heat recovery from four Internal Combustion Engines (ICEs) to produce simultaneously refrigeration power for an absorption chiller, hot water for thermal user and electrical power. The heat recovery is realized through the exhaust gases, the jacket cooling water and the lubricant. The plant includes an auxiliary boiler, which maintains the water temperature levels to the values required by the absorption chiller, and a dry-cooler, which refrigerates the plant water before entering the internal combustion engines. Moreover, a three-way valve, which controls the water flow rate in order to satisfy both the refrigeration and the thermal loads, is considered. The simulations are carried out under thermal-drive and electric-drive strategy and the evaluation of the performance and time response of the CCHP apparatus are presented. [ABSTRACT FROM AUTHOR]

Lithium batteries are currently used as the main energy storage for electronic devices. Progress in the field of portable electronic devices is significantly determined by the improvement of their weight/dimensional characteristics and specific capacity. In addition to the high reliability required of lithium batteries, in some critical applications proper diagnostics are required. Corresponding techniques allow prediction and prevention of operation interruption and avoidance of expensive battery replacement, and also provide additional benefits. Many effective diagnostic methods have been suggested; however, most of them require expensive experimental equipment, as well as interruption or strong perturbation of the operating mode. In the framework of this investigation, a simple diagnostic method based on analysis of transient processes is proposed. The transient response is considered as a reaction to an applied load variation that typically corresponds to normal operating conditions for most real applications. The transient response contains the same information as the impedance characteristic for the system operating in linear mode. Taking into account the large number of publications describing the impedance response associated with diagnostic methods, it can be assumed that the transient response contains a sufficient amount of information for creation of effective diagnostic systems. The proposed experimental installation is based on a controlled load, providing current variation, measuring equipment, and data processing electronics. It is proposed to use the second exponent parameters U2 and β to estimate the state of charge for secondary lithium batteries. The proposed method improves the accuracy and reliability of a set of quantitative parameters associated with electrochemical energy sources. [ABSTRACT FROM AUTHOR]

A new shaft element is proposed for viscoelastic rotors in a spinning frame considering the shear deformation in addition to bending deformation. The Maxwell–Wiechert model is considered here to replicate linear viscoelastic behavior. This model considers additional internal damping displacement variables between elastic and viscous elements and the stress depends not only on the elastic strain and elastic strain rate, but also on additional strains and their rates corresponding to the damping variables. The present work assumes that these additional strains can be derived from continuous fictitious displacement variables, which in turn are interpolated from their nodal values using the Timoshenko beam shape functions. Therefore, in addition to the standard degrees of freedom for a three-dimensional shaft, extra degrees of freedom are defined at the nodes. The finite element matrices are assembled in state space. The time domain equations are then used for stability analysis and computation of response to a unit step load and an unbalance. [ABSTRACT FROM AUTHOR]

There has been recent progress in the understanding of the evolution of Quaternary climate. Simultaneously, there have been improvements in the understanding of glacial erosion processes, with better parameter constraints. Despite this, there remains much debate about whether or not the observed cooling over the Quaternary has driven an increase in glacial erosion rates. Most studies agree that the erosional response to climate change must be transient; therefore, the time scale of the climatic change and the response time of glacial erosion must be accounted for. Here we analyze the equations governing glacial erosion in a steadily uplifting landscape with variable climatic forcing and derive expressions for two fundamental response time scales. The first time scale describes the response of the glacier and the second one the glacial erosion response. We find that glaciers have characteristic time scales of the order of 10 to 10,000 years, while the characteristic time scale for glacial erosion is of the order of a few tens of thousands to a few million years. We then use a numerical model to validate the approximations made to derive the analytical solutions. The solutions show that short period forcing is dampened by the glacier response time, and long period forcing (>1 Myr) may be dampened by erosional response of glaciers when the rock uplift rates are high. In most tectonic and climatic conditions, we expect to see the strongest response of glacial erosion to periodic climatic forcing corresponding to Plio‐Pleistocene climatic cycles. Finally, we use the numerical model to predict the response of glacial systems to the observed climatic forcing of the Quaternary, including, but not limited to, the Milankovich periods and the long‐term secular cooling trend. We conclude that an increase of glacial erosion in response to Quaternary cooling is physically plausible, and we show that the magnitude of the increase depends on rock uplift and ice accumulation rates. [ABSTRACT FROM AUTHOR]

Hundreds of concurrent collisions per bunch crossing are expected at future hadron colliders. Precision timing calorimetry has been advocated as a way to mitigate the pileup effects and, thanks to their excellent time resolution, microchannel plates (MCPs) are good candidate detectors for this goal. We report on the response of MCPs, used as secondary emission detectors, to single relativistic particles and to electromagnetic showers. Several prototypes, with different geometries and characteristics, were exposed to particle beams at the INFN-LNF Beam Test Facility and at CERN. Their time resolution and efficiency are measured for single particles and as a function of the multiplicity of particles. Efficiencies between 50% and 90% to single relativistic particles are reached, and up to 100% in presence of a large number of particles. Time resolutions between 20 ps and 30 ps are obtained. [ABSTRACT FROM AUTHOR]

The paper considers the protection of critical radio-electronic equipment (REE) from ultrashort pulses (USP) by means of modal filters (MFs). A new approach to improve modal filtration by using reflection symmetry is analyzed. The results of a sophisticated research into protective devices based on reflection symmetric MFs are presented: improving the characteristics of four MFs through optimization both by one and simultaneously by several criteria; calculating the per-unit-length time delays matrix of a reflection symmetric MF using the obtained analytical expressions; calculating the time and frequency responses of an MF with and without losses in conductors and dielectric; developing the laboratory evaluation board; analyzing the effect of moisture protection on the characteristics; analyzing the features of reflection symmetry structures; comparing microstrip and reflection symmetric four-conductor MFs. The obtained results allow us to argue that the reflection symmetric MF protects REE from a USP due to its decomposition into a sequence of pulses with pairwise equalized voltage amplitudes and close time intervals between decomposition pulses with an attenuation coefficient of four times with a controlled bandwidth of a useful signal. This research helps take advantage of the possibilities of using the symmetry to improve modal filtering and opens the ways to create a large number of new MF designs, applying only the principles of the symmetry described in the work.