Mean Output Power Research Articles

Microwave Ablation after VATS in Patients with Multiple Pulmonary Nodules.

The management of residual nodules after video-assisted thoracoscopic surgery (VATS) for multiple pulmonary nodules (MPNs) is challenging. Microwave ablation (MWA), which is highly repeatable and minimally invasive, has garnered widespread attention in the treatment of MPNs. Ninety-one patients with MPNs who underwent VATS for resection of high-risk nodules followed by MWA for residual nodules were examined. Clinical efficacy and complications were assessed. The primary end points were MWA success rate and complete ablation rate. Secondary end points were local progression-free survival (LPFS), overall survival (OS), and complications. MWA was successfully completed in all patients. Mean tumor diameter, ablation time, and ablation output power were 0.81 cm, 3.4 minutes, and 39 W, respectively. LPFS was 100% at 3, 6, 12, and 24 months, respectively. OS was 100% at 12 and 24 months, respectively. No intraoperative or postoperative deaths occurred. Complications with MWA were infrequent. Pneumothorax was most common, occurring in 31 patients (34.07%); among these, seven (7.69%) required closed thoracic drainage. Pleural effusion occurred in six patients (6.59%), hydropneumothorax in five (5.49%), and pneumonia in three (3.30%). The pain level after MWA was moderate-to-severe in 29 patients (31.87%). MWA is safe and feasible for treating residual nodules in patients with MPNs who have undergone VATS. The incidence of complications was low, and most complications were mild.

Diode-end-pumped self-Q-switched Tm:YAlO3 laser at 2362 nm

A diode-end-pumped self-Q-switched Tm:YAlO3 laser at 2362 nm based on 3H4→3H5 transition is proposed for the first time according to the references. The max mean output power of 0.41 W with a slope efficiency of 14.1% was obtained under the absorbed pump power of 6.7 W, corresponding pulse width and pulse repetition frequency were 7.82 μs and 45.09 kHz respectively. By analyzing the laser beam spatial distribution, the self-Q-switched Tm:YAlO3 laser at 2362 nm was originated from the time-dependent lens mechanism. The present research provides an approach for generating Q-switched lasers in the 2.3 μm spectral region.

A viscoelastic nonlinear energy sink with an electromagnetic energy harvester: Narrow-band random response

Abstract Nonlinear energy sink is a passive energy absorption device that surpasses linear dampers, and has gained significant attention in various fields of vibration suppression. This is owing to its capacity to offer high vibration attenuation and robustness across a wide frequency spectrum. Energy harvester is a device employed to convert kinetic energy into usable electric energy. In this paper, we propose an electromagnetic energy harvester enhanced viscoelastic nonlinear energy sink (VNES) to achieve passive vibration suppression and energy harvesting simultaneously. A critical departure from prior studies is the investigation of the stochastic P-bifurcation of the electromechanically coupled VNES system under narrow-band random excitation. Initially, approximate analytical solutions are derived using a combination of a multiple-scale method and a perturbation approach. The substantial agreement between theoretical analysis solutions and numerical solutions obtained from Monte Carlo simulation underscores the method’s high degree of validity. Furthermore, the effects of system parameters on system responses are carefully examined. Additionally, we demonstrate that stochastic P-bifurcation can be induced by system parameters, which is further verified by the steady-state density functions of displacement. Lastly, we analyze the impacts of various parameters on the mean square current and the mean output power, which are crucial for selecting suitable parameters to enhance the energy harvesting performance.

Assessing the potential efficacy of 830-nanometer low-level laser therapy in cats: Extraoral applications.

Low-level laser therapy (LLLT) has shown benefits as an alternative treatment of feline chronic gingivostomatitis by reducing pain and inflammation within the oral cavity. Extraoral application technique in cats provides more comfort compared to intraoral application. However, the efficacy of LLLT through buccal tissue is still controversial. This study aimed to investigate the penetration efficacy of LLLT using 830 nm continuous waves with various settings and different application techniques. Twenty-four healthy cats were included in this study. The wavelength of LLLT was 830 nm with an output power of 200 mW through extraoral application, using fluences of 2 and 6 J/cm2 in continuous-wave mode. This study compared different distances (contact and non-contact) and three different transmission media (absent media, alcohol, and normal saline solution). Measurement of the laser power within the oral cavity is represented as the mean output power (MOP). Penetration efficacy was detectable for all fluences, distances, and transmission media, with an average buccal thickness of 2.68 mm. MOP did not differ between fluences of 2 and 6 J/cm2 (p = 0.19). In the absence of media, MOP was significantly higher compared with alcohol (p < 0.05) but was not significantly different from normal saline solution (p = 0.26). Extraoral application of LLLT demonstrated penetration efficacy through the buccal tissue with both contact and non-contact skin (<10 mm). This is a potential alternative treatment for oral diseases in clinical practice. However, there is a need for further study on the efficacy of treatment in clinical practice.

Standard log-capture differentials as performance metrics for deepwater wave power generation

As a support to performance assessment of deepwater wave energy converters, this work quantifies susceptibility of output power to short duration variations, independent of source wave statistics. Introduced as ς-metrics, the quantified measures may be a basis for technology comparisons, with possible convergence to a choice for implementation. The metrics further allow comparison between different versions of a specific converter technology, thereby helping in design revision and refinement.With power conversion represented in terms of a technology specific capture width function, the log-capture differential is defined relative to a hypothetical benchmark characterised by negligible power variability. Root-mean-square aggregation of the differential further leads to standard log-capture differentials as site independent ς-metrics for a capture-and-conversion mechanism.Study results are included in three phases. First, three established wave energy conversion technologies are analysed at respective power maximums, so as to illustrate applicability of log-capture differential and ς-metrics. Next, the metrics are analysed at fractional output power to realise converter performance at reduced variability. Finally for a given marine environment, ς-metrics are shown to be useful in projection of output power variability across technologies, together with the mean output power as fraction of rated maximum.

Design and analysis of a galloping energy harvester with V-shape spring structure under Gaussian white noise

This paper presents the design of an innovative galloping energy harvester (GEH) that incorporates an elastic structure to reconstructed the traditional GEH. The mathematical model of the GEH is derived based on the Euler–Bernoulli beam theory and Kirchhoff’s law. Due to the nonlinear properties of the model, the partial linearization technique and Fokker–Planck–Kolmogorov equation are used to further explore the joint probability density function (PDF) and the stationary PDF of displacement and velocity. Subsequently, Monte Carlo simulation is used to illustrate the behavior of the theoretical results. The simulation results show that, under different conditions, the stationary PDF exhibits double-peak or single-peak shape, which is caused by the compression or elongation state. Meanwhile, higher wind speeds correspond to larger displacement amplitudes. Then, the stationary PDF of displacement amplitude is obtained using the stochastic average method, and the expressions for mean square voltage and mean output power are derived. Numerical results indicate that when the wind speed is below the critical wind speed for galloping phenomenon, the vibration of the GEH is mainly driven by noise. When the wind speed exceeds the critical wind speed, the GEH is mainly affected by the wind speed. Higher wind speeds correspond to higher mean output power. An optimal electromechanical coupling coefficient and the ratio of the mechanical and electrical can be derived based on the GEH parameters when galloping occurs.

Moment analysis of galloping energy harvesters with a parallel circuit under stochastic excitation

In this paper, the stochastic response performance of a galloping energy harvester with a parallel circuit under Gaussian white noise excitation is analyzed. To overcome the complexity of the distributed parameter model and the two-degree-of-freedom characteristics of the harvester, firstly, the exact closed expressions for the mean square displacement, mean square voltage and mean output power are derived by the equivalent linearization method. The results obtained by the direct Monte Carlo simulations verify the accuracy of the theoretical analysis. Then, the conditions for the occurrence of the galloping phenomenon can be identified. The influences of dimensionless parameters and noise intensity on the statistical moments are discussed. The results show that most of the parameters have the same tendency to affect the mean square displacement and the mean square voltage. However, the electromechanical coupling term has the opposite effect on both of them. It is also shown that the mean output power decreases as the coefficients of the electromechanical coupling term and mechanical damping ratio increase, however, it increases dramatically with increasing the wind speed and the linear galloping force coefficient. In addition, utilizing the stationary probability density of the stochastic harvester, the influences of important parameters and noise intensity on the harvester’s performance are studied. It is observed that a larger level of noise intensity results in the greater peak value of the stationary probability density.

Higher-order averaging procedure for performance analysis of a mono-stable Duffing piezoelectric energy harvesting system under white noise excitation

This work is concerned with the energy harvesting of mono-stable Duffing oscillators with piezoelectric coupling under white noise excitation. This is the first time that the higher-order averaging procedure is extended to find the first-, second- and third-order approximate stationary joint probability density functions of amplitude and full phase by solving the corresponding Fokker-Planck-Kolmogorov (FPK) equation. Then the mean-square electric voltage and mean output power are derived through the approximate relation between the electric voltage and the mechanical states. The analytical results are verified by Monte Carlo simulation. The effects of system parameters, such as excitation intensity, mechanical damping term, nonlinear stiffness coefficients, and the resistance ratio of the resistive–capacitive circuit on the mean-square displacement and mean output power are discussed in detail. It has been shown that the averaging procedure of the averaging method of coefficients in FPK equation can be considered as a particular case of the proposed higher-order averaging procedure and the higher-order approximate solutions are much more accurate than the one obtained by the averaging method of coefficients in FPK equation.© 2022 The Authors. Published by Elsevier Ltd.

SOA-MZI Differential Transformation Approach Applied on Simultaneous Electro-Optical Mixing

We experimentally incubate a ground-breaking design, for the first time, of concurrent electro-optical semiconductor optical amplifier Mach–Zehnder interferometer mixing (SOA-MZI) based on a differential transformation methodology. Projecting the simultaneous electro-optical mixing system and improving its efficiency and quality achievement in optical and electrical features is a crucial task due to the characteristics of an optical pulse source (OPS) operating with a repetition rate of f= 58.5 GHz and a pulse width duration of 1 picosecond (ps). The resultant of the contemporaneous electro-optical mixing exhibits exceptional passive power stability, reaching 0.8% RMS over a two-hour period. Furthermore, when the optical bandpass filter is controlled at the data wavelength of 1540 nm, we achieve up to 30 dBm of the overall mean output power with an optical conversion gain of 46 dB and an exceptionally high optical signal-to-noise ratio reaching 80 dB. Using orthogonal frequency division multiplexing (OFDM) signals, each data subcarrier is modulated using 128 quadratic amplitude modulation (128-QAM) at carrier frequencies fk and simultaneously up-mixed to high aim frequencies nf±fk at the SOA-MZI output. Additionally, the resulting OFDM_128-QAM up-mixed signal is examined using the specifications for the error vector magnitudes (EVMs) and the electrical conversion gains (ECGs). The SOA-MZI mixing experiment can handle high frequencies up to 120 GHz. Positive ECGs are followed by a sharp reduction over the entire band of the aim frequencies. The highest frequency range achieved during the realistic investigation is shown at 2f+f4= 120 GHz, where the EVM reaches 8% with a symbol rate of 15 GSymb/s. Furthermore, the concurrent OFDM_128-QAM up-mixed signal achieves an absolute maximum bit rate of 80.4 Gbit/s. The investigation into the simultaneous electro-optical mixing regime is finally supported by unmatched characterization improvements.

Dynamic responses of an energy harvesting system based on piezoelectric and electromagnetic mechanisms under colored noise

Because of the increasing demand for electrical energy, vibration energy harvesters (VEHs) that convert vibratory energy into electrical energy are a promising technology. In order to improve the efficiency of harvesting energy from environmental vibration, here we investigate a hybrid VEH. Unlike previous studies, this article analyzes the stochastic responses of the hybrid piezoelectric and electromagnetic energy harvesting system with viscoelastic material under narrow-band (colored) noise. Firstly, a mass-spring-damping system model coupled with piezoelectric and electromagnetic circuits under fundamental acceleration excitation is established, and analytical solutions to the dimensionless equations are derived. Then, the formula of the amplitude-frequency responses in the deterministic case and the first-order and second-order steady-state moments of the amplitude in the stochastic case are obtained by using the multi-scales method. The amplitude-frequency analytical solutions are in good agreement with the numerical solutions obtained by the Monte Carlo method. Furthermore, the stochastic bifurcation diagram is plotted for the first-order steady-state moment of the amplitude with respect to the detuning frequency and viscoelastic parameter. Eventually, the influence of system parameters on mean-square electric voltage, mean-square electric current and mean output power is discussed. Results show that the electromechanical coupling coefficients, random excitation and viscoelastic parameter have a positive effect on the output power of the system.

Using a hyperbolic structure to enhance thse dynamic performance of a thermoelectric generator

• The transient behaviors of a hyperbolic TEG are simulated using SIMULINK. • Hyperbolic TEG is better than constant cross-section under a periodic thermal source. • Increasing the shape factor can improve the performance of the hyperbolic TEG. • TEG performance improves as the period of the thermal source is decreased. A TEG typically operates in a dynamic environment and efforts invested on furthering TEG should focus on the dynamic performance. A hyperbolically-shaped variable cross-section design is proposed to improve a TEG’s performance under a sinusoidal thermal load. To this end, a transient TEG model was established in SIMULINK in which the TEG heat transfer process is simulated as an electrical circuit. Because of the mathematical equivalence, the transient thermal behavior can be solved and recognized by a circuit simulator in SIMULINK. The simulations indicate that when the source temperature and ambient temperature are given, the hyperbolic shape, with a shape factor β in a range of -2.5 to 1.5, provides a higher power output and a better overall efficiency compared to the non-tapered TEG ( β =0). Additionally, it was found that in decreasing the period of the oscillating source temperature from 60 mins to 10 mins, there are obvious improvements in both the mean output power and overall efficiency of the hyperbolic TEG.

Response Analysis of Nonlinear Viscoelastic Energy Harvester with Bounded Noise Excitation

Energy harvesting has become a popular topic in recent years. A number of studies have been conducted in the field of vibration energy harvesting system (VEHS). However, few studies have concentrated on viscoelastic energy harvesters driven by bounded noise excitation. In this paper, the stochastic response of a viscoelastic energy harvester subjected to bounded noise is discussed. Approximate solutions of the system were derived by utilizing the method of multiple scales, and the expressions of the mean square voltage (MSV) and mean output power (MOP) were obtained. The relation between the detuning frequency and first-order steady moment was first revealed. The effectiveness of the approach was verified by a good agreement between theoretical results and numerical results. Furthermore, the variations in the detuning frequency can result in the stochastic jump phenomenon, and stochastic bifurcation is induced with the changes in the viscoelastic parameter and detuning frequency. Finally, the impacts of system parameters on the MSV and the MOP were also analyzed.

Dynamics of a tri-stable hybrid energy harvester under narrow-band random excitation

This paper aims to reveal the stochastic dynamics of a tri-stable piezoelectric–electromagnetic hybrid vibration energy harvester (HVEH) driven by narrow-band random excitation for purpose of enhancing the energy harvesting performance. The steady-state solutions of the electromechanical coupling tri-stable HVEH in the symmetric case are derived by the method of multiple scales, which are verified by Monte Carlo simulations. Results show that the stochastic jump phenomenon exists and the operational bandwidth of HVEH can be extended. The effects of narrow-band random excitation, critical system parameters and asymmetric potential function on stochastic dynamics are discussed. It is found that the miniaturization design of the HVEH can be optimized and the mean output power can be improved by selecting appropriate system parameters. Moreover, compared with the symmetric structure, in the case of the same highest potential-well depth, the asymmetric structure with a smaller potential-well distance is beneficial for HVEH to achieve high-energy inter-well oscillation under low-level excitation. Meanwhile, the power conversion efficiency reaches the maximum in the high-energy inter-well oscillations triggered at the critical excitation amplitude.

Stochastic analysis of a hybrid energy harvester with viscoelastic material

The hybrid energy conversion mechanism can improve the performance of the energy harvester compared to the single energy conversion mechanism. Meanwhile, the use of viscoelastic materials can also improve the energy harvesting efficiency, but there is not much research on hybrid energy harvesting systems with viscoelastic material. Different from existing research, this manuscript investigates the probabilistic response and stochastic bifurcation of a hybrid piezoelectric and electromagnetic energy harvester(HPEEH) with viscoelastic term under random excitation. Firstly, the viscoelastic element is approximately equivalent to the linear combination of damping term and stiffness term through variable transformation. Secondly, the accuracy of the proposed method is verified by comparing the numerical solution with the analytical solution using the stochastic averaging technique to solve the equivalent system. Furthermore, the bifurcation conditions for amplitude steady-state probability density are given according to the singularity theory and the definition of the extreme point. It is found that changes in viscoelastic parameters, damping coefficients and electromagnetic coupling coefficients can induce stochastic P-bifurcation. Finally, the effects of system parameters on mean square current, mean square voltage and mean output power are explored.

Stochastic analysis of a time-delayed viscoelastic energy harvester subjected to narrow-band noise

Vibration energy harvester (VEH) has proven to be a favorable potential device to supply continuous energy for electric components. Researchers have done a lot of investigations on VEH in recent years. However, there are few studies on delayed VEH with viscoelastic property under random excitation. A new viscoelastic energy harvester with time delay subjected to narrow-band random excitation is investigated in this paper. Firstly, we utilize the multiple scales method to obtain the analytical approximations of the steady-state amplitude close to the primary resonance. Secondly, Monte Carlo simulations are applied to verify the correctness of the proposed method. Results demonstrate the satisfactory accuracy of the method presented in this paper. Then, the phenomena of stochastic jump, stochastic bifurcation, and the extension of the effective bandwidth of VEH can be found. Finally, the influence of system parameters on the mean square voltage and mean output power are discussed. It is shown that a negative feedback gain is profitable to the enhancement of the performance of VEH, and we find that the piezoelectric coupling term has a positive effect on the mean square voltage and mean output power. The mean square voltage and mean output power can reach the maximum at an appropriate time delay and feedback gain. These results indicate that the narrow-band random excitation has an important effect on the dynamics of the delayed vibration energy harvester with viscoelastic property, namely a large dose of noise intensity can decline the responses in the energy harvester.

Research on an internal combustion engine with an injected pre-chamber to operate with low methane number fuels for future gas flaring reduction

Flaring gas is the action of burning waste crude natural gas that is not possible to process or sell during the extraction and processing of oil and gas extraction. However, the surge of the oil and gas (O&G) fields caused an augmentation of flared gas; making society aware of its impact on the planet. To solve this problem, internal combustion engines showed clear advantages. However, there is a lack of information about how to utilize this associated petroleum gas (APG) as fuel for these engines due to its reduced methane number (MN). A methodical investigation about the optimal combustion and design needs for low MN fuels is proposed based on tests conducted in a natural gas engine with an injected pre-chamber ignition technology and a future technology that could replace flaring is proposed. Experiments conducted when using low MN gases showed different misfire limits and knocking margins. A 15% efficiency drop was obtained, however, this could be considered as a good performance as the Brake Mean Effective Pressure (BMEP) or output power reduction was 53.3%. In consequence, different engine design modifications are proposed to improve the former situation.

Power Output of Two Semiconductor Lasers: An Observational Study

The objective of this study was to evaluate the power output of two dental devices. The study examined two semiconductor lasers, namely, SIROLaser Blue (445 nm, 970 nm) and Picasso (810 nm). The power output performance was studied at the maximum output power of the devices. The study compared the preset power output measured by a power meter in a continuous-wave mode and in pulsed mode at 50% duty cycles. Ten 60 s measurements were performed for each setting. The largest difference between the stipulated and the actual output power at continuous-wave (D-cw) and pulsed (D-p) modes was calculated. Moreover, the percentage variations in the mean output power at continuous-wave (%D-cw) and pulsed (%D-p) modes were calculated. The D-cw values for 445 nm, 970 nm, and 810 nm lasers were 0.7 W, 0.5 W, and −0.3 W, respectively, and %D-cw values were 21%, 23%, and −8%, respectively. The D-p values for 445 nm, 970 nm, and 810 nm lasers were 1.1 W, 0.5 W, and −0.1 W, respectively, whereas the %D-p values were 37%, 26%, and −3%, respectively. This study found that the actual power is not necessarily lower but can be higher than the displayed power output. Clinicians are recommended to calibrate the laser output by using a power meter before use.

Dynamic performance of the energy harvester with a fractional-order derivative circuit

Vibration energy harvesters are expected to replace chemical batteries and achieve self-power for low-power electronic devices, and their design has attracted significant attention. In previous studies, circuits consistent with the constitutive relationship with integer derivatives were frequently used, but fractional-order derivative circuits have received less attention. Because of the dissipation effects, such as internal friction and thermal memory, the fractional-order derivative is an effective mathematical approach for determining such nonconservative behaviors. In this study, the dynamic performance of a vibration energy harvester with a fractional-order derivative circuit in a random environment was investigated. Both linear and nonlinear vibration energy harvesters were evaluated using the linear random vibration theory and the equivalent linearization technique. The effects of the system parameters on the mean output power were analyzed, and the optimal system parameters, such as the oscillation frequency of the circuit and the coupling coefficient, were determined. Furthermore, the relationships between the optimal parameters and the order of the fractional derivative were established. Our study will potentially guide future designs of vibration energy harvesters.

Dynamic response mechanism of the galloping energy harvester under fluctuating wind conditions

The galloping energy harvesting technique has been extensively applied to harvest fluid energy and utilize the aeroelastic instability of mechanical systems in a flow field for low-powered electronic devices. However, the flow field is random in the real world. In previous studies, fluid motion was regarded as a deterministic process (i.e., with a constant wind speed). However, to determine the actual dynamic characteristics of the galloping energy harvester (GEH), fluctuations in wind speeds should be fully considered. In this study, the wind speed is separated into a mean component and a fluctuating component with the latter being considered Gaussian white noise. The mechanical and electrical dynamical statuses of the GEH are described by electromechanical coupled equations. The output voltage is decoupled by applying a generalized harmonic transformation and is approximated by the mechanical subsystem status. The mean output power is derived by applying stochastic averaging. The critical wind speed and optimal parameters of the harvester were determined in detail. The presented analytical procedure was verified by Monte Carlo simulation.

The analysis of parameter uncertainty on performance and reliability of photovoltaic cells

In engineering practice, the parameters affecting the output of a photovoltaic cell such as its irradiation intensity, surface temperature, current temperature coefficient, series resistance, parallel resistance, and ideality factor each inevitably possess a degree of uncertainty. Based on a photovoltaic cell model, this study uses the quasi-Monte Carlo method to model the randomness of these parameters, then discusses the influence of the uncertainty of each parameter on the output power performance, stability, and reliability. The results show that a high current temperature coefficient is beneficial to the average output power and fill factor. The smaller the series resistance and the greater the parallel resistance, the greater the mean and standard deviation of the output power and fill factor. In a normal working environment, the lower the average surface temperature, the higher the mean output power and fill factor, and the smaller the standard deviation of the output power. Finally, optimal values of the ideality factor and radiation intensity are found to exist for the mean output power. The research in this paper expands the performance evaluation standards of photovoltaic cells and provides a theoretical and technical basis for the optimization of photovoltaic cell designs that accounts for parameter randomness. • The influence of the randomness of parameters on the output performance is studied. • The influence of each variable on the performance of PV cell model is quantified. • The results can be used to extend the criteria used to evaluate PV cell. • The results can provide a theoretical basis for the optimization of PV cell.