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Copyright of Journal of Test & Measurement Technology is the property of Publishing Center of North University of China and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To improve the quality of protection for mains and electric motors, it is expedient to additionally control the electromagnetic time constant. The necessary information is obtained from analyzing the sum of squared instant phase currents or the sum of instant phase powers. The determination of the time constant makes it possible to control the temperature of windings of electric motors, preventing them from overheating at direct frequent starts, and block network protection when starting electric motors, which allows implementing long-range redundancy protection and protection from remote short circuits. [ABSTRACT FROM AUTHOR]

The use of integrated heaters is widespread in silicon photonics for waveguide temperature control. The dynamical behavior of the heaters is important for determining their usefulness for certain applications. There exists ambiguity in the literature when it comes to reporting the thermo-optic time constants of Si photonic devices. Many studies report devices with different heating and cooling times without providing an explanation to this phenomenon. In this paper, a comprehensive theoretical framework is developed for interpreting experimental results. This framework is developed for interferometric devices (Mach–Zehnder-based) and resonant devices (rings). With this framework, the impact of measurement conditions on the obtained thermo-optic time constant can be simulated, and we provide an explanation to the observed difference between heating and cooling time constants. We also provide guidelines on how to disentangle optical non-linearities from the pure thermal response, which should be useful in for future reporting of thermo-optic time constants. [ABSTRACT FROM AUTHOR]

Abstract Background Lung volume optimization maneuvers (LVOM) are necessary to make physiologic use of high-frequency oscillatory ventilation (HFOV), but lung behavior during such maneuvers has not been studied to determine lung volume changes after initiation of HFOV, to quantify recruitment versus derecruitment during the LVOM and to calculate the time to stabilization after a pressure change. Methods We performed a secondary analysis of prospectively collected data in subjects

Background: Lung volume optimization maneuvers (LVOM) are necessary to make physiologic use of high-frequency oscillatory ventilation (HFOV), but lung behavior during such maneuvers has not been studied to determine lung volume changes after initiation of HFOV, to quantify recruitment versus derecruitment during the LVOM and to calculate the time to stabilization after a pressure change. Methods: We performed a secondary analysis of prospectively collected data in subjects < 18 years on HFOV. Uncalibrated respiratory inductance plethysmography (RIP) tracings were used to quantify lung recruitment and derecruitment during the LVOM inflation and deflation. The time constant was calculated according to the Niemann model. Results: RIP data of 51 subjects (median age 3.5 [1.7–13.3] months) with moderate-to-severe pediatric acute respiratory distress syndrome (PARDS) in 85.4% were analyzed. Lung recruitment and derecruitment occurred during the LVOM inflation phase upon start of HFOV and between and within pressure changes. At 90% of maximum inflation pressure, lung derecruitment already started during the deflation phase. Time to stable lung volume (time constant) could only be calculated in 26.2% of all pressure changes during the inflation and in 21.4% during the deflation phase, independent of continuous distending pressure (CDP). Inability to calculate the time constant was due to lack of stabilization of the RIP signal or no change in any direction. Conclusions: Significant heterogeneity in lung behavior during a staircase incremental–decremental LVOM occurred, underscoring the need for higher initial inflation pressures when transitioning from conventional mechanical ventilation (CMV) and a longer time between pressure changes to allow for equilibration. [ABSTRACT FROM AUTHOR]

The chemically synthesized poly (aniline-co-o-aminobenzoic acid) copolymer was functionalized electrochemically by cationic and anionic doping and tailored its property for suitable redox behavior. The mechanism during this process has been proposed using cyclic voltammetry studies, and the doping was confirmed in FTIR and UV studies. In the electrochemical impedance spectroscopy, undoped and doped behavior revealed the possibility of fine-tuning of conditions that are required for redox supercapacitor. A symmetrical supercapacitor was fabricated with an optimized doped co-polymer-based electrode and the specific capacitance values were 107 Fg−1 for n-doped polymer and 140 Fg−1 for p-doped polymer. The electrochemical characterization of n/p 1 cm2 cells in terms of specific power, specific energy, specific capacitance, columbic efficiency, IR drop, and ESR was calculated from charge/discharge studies. Data were analyzed in terms of complex power versus complex capacitance, and hence, active region of n/p supercapacitor was obtained. This concept paves way for future tailoring of dopants during the synthesis of conducting polymer and its copolymers. [ABSTRACT FROM AUTHOR]

This paper presents a response time/time constant of III-V material-based interband long wavelength multistage infrared detector optimized for a wavelength of 10.6 µm at 200 K. The device is based on the InAs/InAsSb type-II superlattice with highly doped p+/n+ tunneling junctions among the stages. The detector exhibits a response time of 9.87 ns under zero voltage condition, while for 0.15 V reverse bias, that time decreases to approximately 350 ps. The presented device shows a significant increase in response time, especially for low bias, and for a voltage of −0.2 V, the decrease in the detector's response time by an order of magnitude was estimated. Higher voltage slightly affects the time constant, and between −0.3 V and −1 V, it varies between 300 and 400 ps. The significant change in the detector's response time between −0.1 V and −0.2 V probably results from electric field drop over entire absorber region. The optimal operating condition can be reached for −0.15 V, where the time constant reaches approximately 350 ns with peak detectivity at a level of ~3 × 109 Jones. [ABSTRACT FROM AUTHOR]

This paper focuses on the design, analysis and implementation of Integer-order (IO) and Fractional-order (FO) controllers for systems characterized by lag-dominant time delays. The existing literature has been examined to analyze the methodology employed in tuning IO and FO controllers for first-order time delay system for perturbations in process parameters. It is observed that there is scope to investigate better controllers for lag-dominant time delay systems. The five different structures of controllers are chosen. The paper proposes IO and FO controllers tailored for a test group comprising 16 first-order systems with time delays. These IO and FO controllers are designed to fulfil design specifications: phase margin, peak overshoot, IAE, ITAE and ISE using Modified Bode's Ideal Loop Transfer Function with delay method. For comparison conventional IO tuning method, Gain-Phase Margin Tester(GPMT) and Fractional Ms Constrained Integral Gain Optimization Method (F-MIGO) is used. The simulation results and performance evaluation for both IO and FO controllers are obtained for a range of values of relative dead time of the system represented by . The value is obtained by varying conditions of delay (L) and time constant (T). Two scenarios are taken into account: the first involves varying L while keeping T constant, and the second involves keeping L constant while varying T. The main objective of the paper is to analyze IO and FO controllers based on time and frequency domain parameters, performance error indices, disturbance rejection, gain variations, Total Variation (TV) and control efforts for perturbations in process parameters. The simulation results indicate that FO controllers show superior tolerance to perturbations in L and T when compared to IO counterparts. This observation was noted during the analysis of the control system by varying values of L and T to obtain a consistent value of . Thus, the extensive simulation studies demonstrate that the FO controller tailored for lag-dominant time delay systems outperforms its IO counterpart in terms of robustness, closed-loop stability and error performance metrics. [ABSTRACT FROM AUTHOR]

Phase-locking motor drive based on phase-lock principal provides high accuracy and wide shaft speed range. А low-pass filter is used for PWM-signal demodulation in phase-lock loop. This type of demodulator limits loop bandwidth and working range of motor drive. The main purpose of this article is to analyze low-pass filter influence on motor drive dynamic characteristics in low shaft speed area. The authors developed Matlab Simulink model to researcher phase-locking motor drive working in synchronous mode. As a result the dependence of angular velocity ripple versus rotational speed is obtained. The choosing condition of low-pass filter time constant is defined for different shaft speed area by using the obtained dependence. The received results can be applicable for design precision phaselock motor drive.

The induced polarization (IP) response in media containing clay and/or metallic minerals has been modeled in different research. Increasing the IP applications and measurements has revealed these models’ limitations. For instance, no model has described IP response in the media with metallic minerals higher than 22 percent. So, our goal in this contribution is to explain the IP response of clay-rich samples containing low- to high-grade pyrite, galena, and sphalerite from the Zn-Pb sedimentary-exhalative mine Koushk, central Iran. The samples’ background consists of clayey/micaceous minerals, including illite, muscovite, and chlorite, that, along with the metallic minerals, make the consecutive layers in some samples, while others have a different formation. The samples also contain some insulating grains such as quartz and gypsum. Therefore, there are different conduction and polarization mechanisms in them. These properties make our samples unique and substantial to study the IP response. To do this, we measured the samples’ complex conductivity, density, porosity, cation exchange capacity (CEC), and metallic/non-metallic minerals. Then, we investigated the relationship between electrical and petrophysical properties. The results showed that the chargeability has no relationship with CEC and is a complete representation of the metallic minerals’ polarization. The normalized chargeability depends linearly on the quadrature conductivity and is affected by the metallic minerals besides CEC. The content and type of clay/mica minerals control the CEC. Hence, the normalized chargeability is influenced by the metallic and non-metallic polarizable components. The conductivity linearly relates to metallic minerals’ content and, in vein mineralizations, has higher values than disseminated ones. Ultimately, comparing our samples’ IP response with Revil et al.’s and Pelton et al.’s models for chargeability, metallic minerals volume content, and time constant determined that increasing the metallic minerals makes the chargeability decrease and the time constant increase. So, in high-grade porous media or non-dispersive formations, chargeability is a function of the metallic minerals’ volume content and the time constant. Complex media like our samples are expected in geological environments. Hence, recognizing the parameters affecting IP response in these media helps to better understand their properties and, in general, IP response characteristics.

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The use of integrated heaters is widespread in silicon photonics for waveguide temperature control. The dynamical behavior of the heaters is important for determining their usefulness for certain applications. There exists ambiguity in the literature when it comes to reporting the thermo-optic time constants of Si photonic devices. Many studies report devices with different heating and cooling times without providing an explanation to this phenomenon. In this paper, a comprehensive theoretical framework is developed for interpreting experimental results. This framework is developed for interferometric devices (Mach–Zehnder-based) and resonant devices (rings). With this framework, the impact of measurement conditions on the obtained thermo-optic time constant can be simulated, and we provide an explanation to the observed difference between heating and cooling time constants. We also provide guidelines on how to disentangle optical non-linearities from the pure thermal response, which should be useful in for future reporting of thermo-optic time constants.

Abstract Intracranial pressure (ICP) is an important parameter in clinical management and diagnosis of several neurological diseases which is indirectly measured via lumbar puncture (LP). In routine measurements of cerebrospinal fluid pressure (P CSF ) from lumbar region, a spinal needle and a spinal manometer are used. P CSF measurement via LP with the use of a spinal manometer may not yield correct P CSF results due to prolonged times required to obtain an accurate pressure value. Equilibrium pressure may be underestimated in circumstances where spinal manometry procedure is terminated prematurely, with the wrong assumption that equilibrium pressure is reached. Elevated P CSF levels can lead to visual loss and brain damage when go undiagnosed. In this study, the spinal needle-spinal manometer combination was modelled with a first-order differential equation and a time constant (τ) was defined as the product of the resistance to flow of the needle with the bore area of the manometer divided by the dynamic viscosity of CSF, i.e. τ= RA/ρ CSF . Each needle/manometer combination had a unique constant as a predictor of the equilibrium pressure. The fluid pressure in the manometer rose in an exponential manner which was tested in a simulated environment using 22G spinal needles namely Braun-Spinocan, Pajunk-Sprotte and M.Schilling. Curve fitting of the manometer readings were obtained with regression coefficients of R2 ≥ 0.99 to determine measurement time constants. The residual differences between predicted and true values were less than 1.18 cmH2O. For a given needle/manometer combination, time required to reach equilibrium pressure was identical for all pressure levels. P CSF measured at reduced times can easily be interpolated to their equilibrium level allowing clinicians to obtain P CSF values with high accuracy within seconds. This method can be used as an indirect estimation of ICP in routine clinical practice.

A novel diagnostic method has been developed for microvascular lesions using time constants obtained from the peripheral Windkessel model (WK model). Since the time constant of the WK model reflects changes in resistance and vascular elasticity due to a decrease in the internal vessel diameter, an increase in surface roughness of intima, andan increase in bloodviscosity, it was proposedto use it as an indicator for vascular evaluation. For noninvasive andeasy measurement of the time constant, it is necessary to calculate from the frequency components of the arterial pressure pulse andphalangeal volume pulse. Therefore, it is necessary to establish each pulse wave measurement methodandto consider the optimal combination. The fingertip photoplethysmograph was usedbecause it is saidto be proportional to the volume pulse of the fingertip. Owing to the difficulty of using the conventional air-conduction method for measuring the arterial pressure pulse, reflection photo and cuff pressure methods were considered. The probability of obtaining time constants and the fluctuation rate were compared across the three methods. The results demonstrated the superiority of the air-conduction methodover the other two. The air-conduction methodwas consideredto produce a waveform proportional to the arterial bloodpressure pulse wave. The best pulse wave measurement methodfor measuring peripheral time constants were the air-conduction methodfor arterial pressure pulse andthe transmission photo methodfor fingertip volume pulse. [ABSTRACT FROM AUTHOR]

High-frequency temperature measurements were carefully conducted for a 15 kW buoyant turbulent ethylene diffusion flame over a 15.2 cm diameter gas burner with air co-flow. A dual-thermocouple probe, consisting of two fine-wire thermocouples with 25 μm and 50 μm wire diameters, was used to determine a compensated turbulent gas temperature. A sensitivity analysis shows that temperatures resolved using this dual-thermocouple technique are less sensitive to changes in thermocouple bead size, therefore, uncertainty is greatly reduced even when soot deposition on the thermocouple bead occurs in sooty flames. Mean and root-mean square (rms) fluctuations of gas temperature were recorded in a two-dimensional plane across the flame centerline. The mean gas temperature monotonically decreases away from the flame centerline at most flame heights, except for 1 diameter above the burner, where a temperature dip is observed. The rms temperature peaks shift from the edge of the flame to the center as the height increases. This is due to the enhanced mixing between fuel and air, which is further shown using probability density functions of the local gas temperature. A systematic temperature dataset with high spatial resolution is established for sooty flames, which is valuable for future soot and radiation model validation.

High-frequency temperature measurements were carefully conducted for a 15 kW buoyant turbulent ethylene diffusion flame over a 15.2 cm diameter gas burner with air co-flow. A dual-thermocouple probe, consisting of two fine-wire thermocouples with 25 μm and 50 μm wire diameters, was used to determine a compensated turbulent gas temperature. A sensitivity analysis shows that temperatures resolved using this dual-thermocouple technique are less sensitive to changes in thermocouple bead size, therefore, uncertainty is greatly reduced even when soot deposition on the thermocouple bead occurs in sooty flames. Mean and root-mean square (rms) fluctuations of gas temperature were recorded in a two-dimensional plane across the flame centerline. The mean gas temperature monotonically decreases away from the flame centerline at most flame heights, except for 1 diameter above the burner, where a temperature dip is observed. The rms temperature peaks shift from the edge of the flame to the center as the height increases. This is due to the enhanced mixing between fuel and air, which is further shown using probability density functions of the local gas temperature. A systematic temperature dataset with high spatial resolution is established for sooty flames, which is valuable for future soot and radiation model validation.

The paper further developed the methodological approach in obtaining mathematical models that describe the running-in of tribosystems under boundary lubrication conditions.The structural and parametric identification of the tribosystem as an object of simulation of running-in under conditions of extreme lubrication was carried out. It has been established that the processes of running-in of tribosystems are described by a second-order differential equation and, unlike the known ones, take into account the limit of loss of stability (robustness reserve) of tribosystems. It is shown that the nature of tribosystems running-in conditions of extreme lubrication depends on the gain coefficients and time constants, which are included in the right-hand side of the differential equation. It is shown that the processes of running-in of tribosystems depend on the type of the magnitude of the input influence on the tribosystem, the first and second derivatives. The input influence is represented as a product of coefficients and a time constant К0·К2·Т3. This allows us to state that the processes of the tribosystem running-in will effectively take place when the input action (load and sliding speed), will change in time and have fluctuations with positive and negative acceleration of these values from the set (program) value. This requirement corresponds to the running-in program "at the border of seizing".The left part of the equation is the response of the tribosystem to the input signal. Tribosystem time constants Т2 and Т3 have the dimension of time and characterize the inertia of the processes occurring in the tribosystem during running-in. Increasing the time constants makes the process less sensitive to changes in the input signal, the warm-up process increases in time, and the tribosystem becomes insensitive to small changes in load and sliding speed. Conversely, the reduction of time constants makes the tribosystem sensitive to any external changes

This study uses a serial information transmission scheme to discuss the issues faced in transmitting unit average power of laser radiation from a reference converter of the corresponding standard to a control measuring converter. A large difference in the time constants of these converters leads to increased measurement error. To reduce this error, herein, an algorithm is proposed based on averaging the results of multiple measurements while determining the main transmission parameter of unit average power (calibration coefficient). The statistical characteristics of the estimation of the calibration coefficient are analyzed herein. In the model based on measuring transducers having lumped parameters of the first order, relationships that characterize the influence of a correlated stationary-fluctuation component related to the instability in laser radiation power are obtained to determine the calibration coefficient while averaging the results of multiple measurements. In this case, the median of the distribution of its estimate should be used as the calibration coefficient because the median is unbiased and consistent. Equations are obtained to determine the error in estimating the calibration coefficient, and dependencies are presented that enable setting the required measurement averaging time and number of readings of the measured signals. Using the proposed algorithm improves the metrological characteristics of GET 28-2016, the state primary standard of the unit of average laser radiation. [ABSTRACT FROM AUTHOR]

Electric field initiated chemical reactions result in surface modifications which have potential applications in the field of micro- and nano-scale patterning and the same is demonstrated through the electrolithography (ELG) technique. In ELG, electrochemical reaction backed modifications on chromium (Cr) thin films have resulted in patterns having a width in the nanometer range. The chemical reaction on the Cr surface results in the formation of a liquid compound. The reaction equation has a similar anatomy to that of a local anodic oxidation reaction. The liquid material formation process takes place under the influence of both unidirectional and alternating electric fields. However, the true nature of the formed liquid region, specifically its electronic characteristic, remains unknown. In this study, we explore the electrical properties of the said liquid domain by employing impedance spectroscopy. Frequency sweeps are carried out in a range spanning five orders of magnitude, from 10 Hz to 1 MHz, on the liquid region formed on electrical stressing of Cr films of thickness 100 nm. Based on the studies, a simple equivalent electrical circuit is proposed. The circuit model is justified with fundamental physics. The impedance spectroscopy results also help us to estimate a time constant for the liquid material formation process. The results of this study will help us better regulate the material formation process on Cr thin films and thereby control the ELG process better. [ABSTRACT FROM AUTHOR]

The paper analyzes the modern methods of storing spent nuclear fuel and its processing, taking into account the finding of fuel in spent fuel assemblies. Currently, the most common methods involve storage in containers for fuel assemblies filled with a substance that has a high thermal conductivity. Therefore, experimental methods of researching the storage properties of spent fuel assemblies in containers are promising. In the work, research was carried out in the indicated directions with the help of the created experimental stand. A description of the stand itself and the sequence of conducting the experiment are given, as a result of which the necessary experimental data should be obtained. Namely, the heating regimes in the experimental heater were determined, which are close to the real processes of heating spent fuel assemblies loaded into the container. For this purpose, a laboratory autotransformer with a capacity of 4.6 kW was used. The next task was to determine the time required for the heater to go into constant operation. For this purpose, the concept of constant time of the heating process was introduced. FLIR ONE thermal imager was used to determine this parameter, as well as devices that allowed to determine the voltage on the laboratory autotransformer. This made it possible to determine the dependence of the change in the temperature of the heater on time and voltage, as well as the voltage of the heater, which simulates real heating modes. The paper presents the thermographic results of thermal imager measurement of the main areas of the stand. Taking into account that the power of the heater should be about 1.5 kW, the stand was made airtight with pressure control and taking into account the real conditions of storage of spent fuel assemblies, where there may be damage and cracks in the container. As a result of the conducted experimental studies, the optimal heating modes of the heater were determined. [ABSTRACT FROM AUTHOR]

Intracranial pressure (ICP) is an important parameter in clinical management and diagnosis of several neurological diseases which is indirectly measured via lumbar puncture (LP). In routine measurements of cerebrospinal fluid pressure (PCSF) from lumbar region, a spinal needle and a spinal manometer are used. PCSF measurement via LP with the use of a spinal manometer may not yield correct PCSF results due to prolonged times required to obtain an accurate pressure value. Equilibrium pressure may be underestimated in circumstances where spinal manometry procedure is terminated prematurely, with the wrong assumption that equilibrium pressure is reached. Elevated PCSF levels can lead to visual loss and brain damage when go undiagnosed. In this study, the spinal needle-spinal manometer combination was modelled with a first-order differential equation and a time constant (τ) was defined as the product of the resistance to flow of the needle with the bore area of the manometer divided by the dynamic viscosity of CSF, i.e. τ= RA/ρCSF. Each needle/manometer combination had a unique constant as a predictor of the equilibrium pressure. The fluid pressure in the manometer rose in an exponential manner which was tested in a simulated environment using 22G spinal needles namely Braun-Spinocan, Pajunk-Sprotte and M.Schilling. Curve fitting of the manometer readings were obtained with regression coefficients of R2 ≥ 0.99 to determine measurement time constants. The residual differences between predicted and true values were less than 1.18 cmH2O. For a given needle/manometer combination, time required to reach equilibrium pressure was identical for all pressure levels. PCSF measured at reduced times can easily be interpolated to their equilibrium level allowing clinicians to obtain PCSF values with high accuracy within seconds. This method can be used as an indirect estimation of ICP in routine clinical practice. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study introduces a novel methodology to evaluate the behaviour of biomass material by examining the ratio of aeration and deaeration time constants. To this end, a series of tests were conducted on four different materials, namely, cottonseed, wood chips, wood pellets, and wheat straw, in order to investigate their aeration and deaeration behaviours. The study derives the aeration and deaeration pressure drop equations, and discusses the corresponding time constant expression. Subsequently, the four materials were conveyed in 12 m long batch-fed and continuous pneumatic conveying pipelines to examine their behaviour in longer pipelines. The results indicate that the aeration and deaeration time constants increased with an increase in air superficial velocity. However, the ratio of the aeration and deaeration time constants was identified as a unique number, where a value close to 1 indicates a higher likelihood of plug flow. On the basis of the results, cottonseed, with the lowest ratio of time constant, was more likely to form a stable plug flow in both batch-fed and continuous pneumatic conveying. Given the unique properties of biomass and the limited research on the pneumatic conveyance of biomass, this methodology represents a novel approach for predicting modes of flow in materials with complex properties. [ABSTRACT FROM AUTHOR]

In the process of plunge cylindrical grinding, it is difficult to directly measure the contact stiffness between the grinding wheel and the workpiece. In order to solve this problem, a simplified method for qualitatively determining the contact stiffness between the grinding wheel and the workpiece is proposed, and the grinding parameters are optimized. Based on the dynamic model of plunge cylindrical grinding process, the transfer function of grinding process is deduced, and the mathematical model of the time constant and contact stiffness is established. A simplified method for qualitative determination of grinding contact stiffness is proposed. Further, multiple tests are conducted by controlling the wheel feed speed and the workpiece speed. According to the experimental results, the variation of the system time constant and the grinding force with the grinding parameters are analyzed. The relationship model between the contact stiffness and the grinding parameters is established by regression analysis, and the optimal values of the wheel feed speed and the workpiece speed in the specific grinding process are determined under the condition of meeting the machining requirements.

Limited information is available regarding the role of anaerobic metabolism capacity on GOLD 1 and 2 COPD patients during upper limb exercise. We aimed to compare the upper limb anaerobic power capacity, blood lactate concentration, cardiovascular and respiratory responses, in male COPD patients versus healthy subjects during the 30-s Wingate anaerobic test (WAnT). The rate of fatigue and time constant of the power output decay (τ, tau) were also calculated and a regression analysis model was built to assess the predictors of τ in these patients. Twenty-four male COPD patients (post-bronchodilator FEV1 73.2 ± 15.3% of predicted) and 17 healthy subjects (FEV1 103.5 ± 10.1% of predicted) underwent the WAnT. Measurements were performed at rest, at the end of the WAnT, and during 3′ and 5′ of recovery time. Peak power (p = 0.04), low power (p = 0.002), and mean power output (p = 0.008) were significantly lower in COPD patients than in healthy subjects. Power output decreased exponentially in both groups, but at a significantly faster rate (p = 0.007) in COPD patients. The time constant of power decay was associated with resistance (in ohms) and fat-free mass (r2 = 0.604, adjusted r2 = 0.555, and p = 0.002). Blood lactate concentration was significantly higher in healthy subjects at the end of the test, as well as during 3′ and 5′ of recovery time (p

The capacitance-resistance model (CRM) has been widely implemented to model and optimise waterflooding and enhanced oil recovery (EOR) techniques. However, there is a gap in the application of CRM to analyse physical phenomena in porous media as well as the performance of EOR methods, such as low-salinity water (LSW) flooding. The main purposes of this study were to investigate how changes in time constant, as a CRM parameter, can represent physical phenomena in porous media such as wettability alteration. Moreover, to show CRM is a reliable tool to use for interpretation of LSW process as an EOR method. The results of different experimental/modelling studies in this research showed that in CRM model time constant increases when the wettability alters to a water wetness state, whereby the smallest time constant value is observed for the oil wet medium and the highest is observed for the water wet medium. The cases with a gradual alteration in wettability show an increasing trend with the dilution of the injection water. The core flooding data confirms the observed results of the simulation approach. The increment in time constant values indicates the resistance against displacing fluid, which is due to the wettability alteration of the porous medium, resulting in additional oil production. The observations made during this research illustrate that the time constant parameter can be a powerful tool for comparing different EOR techniques, since it is a good indication of the speed of impact of a particular injection fluid on production.

Abstract Background We hypothesized that the measured expiratory time constant (TauE) could be a bedside parameter for the evaluation of positive end-expiratory pressure (PEEP) settings in mechanically ventilated COVID-19 patients during pressure-controlled ventilation (PCV). Methods A prospective study was conducted including consecutively admitted adults (n = 16) with COVID-19-related ARDS requiring mechanical ventilation. A PEEP titration using PCV with a fixed driving pressure of 14 cmH2O was performed and TauE recorded at each PEEP level (0 to 18 cmH2O) in prone (n = 29) or supine (n = 24) positions. The PEEP setting with the highest TauE (TauEMAX) was considered to represent the best tradeoff between recruitment and overdistention. Results Two groups of patterns were observed in the TauE plots: recruitable (R) (75%) and nonrecruitable (NR) (25%). In the R group, the optimal PEEP and PEEP ranges were 8 ± 3 cmH2O and 6–10 cmH2O for the prone position and 9 ± 3 cmH2O and 7–12 cmH2O for the supine position. In the NR group, the optimal PEEP and PEEP ranges were 4 ± 4 cmH2O and 1–8 cmH2O for the prone position and 5 ± 3 cmH2O and 1–7 cmH2O for the supine position, respectively. The R group showed significantly higher optimal PEEP (p

Direct power smoothing control methods relying on the wind turbine itself have been widely studied to improve wind turbines’ output power quality, and the DC-link voltage control based on the capacitor of the wind power converter is one of them. In this paper, the principle of DC-link capacitor voltage control is studied at first, then an improved time interval DC-link voltage control strategy on the basis of a low-pass filter (LPF) is proposed and compared with existing DC-link voltage power smoothing controls. To further improve the power smoothing effect, the fuzzy logic control is used to adjust the time constant of LPF, and the maximum time constant in the fuzzy logic control is determined through convolution calculation. For the sake of ensuring the system stability, the transfer function of proposed DC-link voltage control is derived to determine proper parameters of voltage loop. The proposed fuzzy logic-based DC-link power smoothing strategy is verified through effective simulation results of the permanent magnet synchronous generator wind energy conversion system (PMSG-WECS).

Copyright of Journal of Mechanical Strength / Jixie Qiangdu is the property of Zhengzhou Research Institute of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fast and slow inhibitory synapses, respectively, induce anti- and in-phase synchronizations, showing different roles of synapse with different time scales. In the present paper, the opposite roles of inhibitory autapses with fast and slow time scales on modulating bursting activities are investigated in a theoretical model, which present a novel viewpoint on the inhibitory autapse and bursting observed in the brain neurons. Firstly, the inhibitory autapses with fast and slow decay time constant are identified to induce enhancement and reduction of bursting activities, respectively, which presents a paradoxical phenomenon and a common phenomenon. Secondly, the bifurcation mechanisms for the paradoxical and common responses are acquired. As autaptic conductance increases, for fast autapse, saddle-node (SN) bifurcation point of the fast subsystem is nearly fixed, while saddle-homoclinic orbit (SH) bifurcation point moves to right to widen the burst region and enhance the bursting activities, while more left shift of SN bifurcation curve than SH bifurcation curve to shorten the burst region and reduce the bursting activities, which is acquired by a novel fast–slow variable dissection method with two slow variables (slow variable C of the model and gating variable of autapse S). Finally, fast and slow dynamics of autaptic current underlying the bifurcation mechanisms are acquired. For the fast autapse, the autaptic current is negative during spike to reduce the spike amplitude to shift the SH point, while it exhibits fast decay to zero between spikes (i.e., node), which cannot influence the SN point. For the slow autapse, the autaptic current exhibits negative value during both the burst and quiescent (between burst) due to slow decay, which induces left shift of both the SN and SH bifurcation curves. The results of the opposite response of bursting to fast and slow autaptic currents present potential functions and diverse dynamics of autapse with different time scales in brain neurons, a novel case of counterintuitive phenomenon related to inhibitory self-feedback, and a novel performance process of analysis method to complex bursting with two slow variables. [ABSTRACT FROM AUTHOR]

This study investigated the dynamic characteristics of thermocouples by using double-pulse laser excitation for dynamic temperature calibration under extreme conditions. An experimental device was constructed for double-pulse laser calibration; the device uses a digital pulse delay trigger to precisely control the double-pulse laser to achieve sub-microsecond dual temperature excitation with adjustable time intervals. The time constants of thermocouples under single-pulse laser excitation and double-pulse laser excitation were evaluated. In addition, the variation trends of thermocouple time constants under different double-pulse laser time intervals were analyzed. The experimental results indicated that the time constant increases and then decreases with the decrease in the time interval of the double-pulse laser. A method for dynamic temperature calibration was established for the evaluation of the dynamic characteristics of temperature sensors. [ABSTRACT FROM AUTHOR]

This paper presents a response time/time constant of III-V material-based interband long wavelength multistage infrared detector optimized for a wavelength of 10.6 µm at 200 K. The device is based on the InAs/InAsSb type-II superlattice with highly doped p+/n+ tunneling junctions among the stages. The detector exhibits a response time of 9.87 ns under zero voltage condition, while for 0.15 V reverse bias, that time decreases to approximately 350 ps. The presented device shows a significant increase in response time, especially for low bias, and for a voltage of −0.2 V, the decrease in the detector’s response time by an order of magnitude was estimated. Higher voltage slightly affects the time constant, and between −0.3 V and −1 V, it varies between 300 and 400 ps. The significant change in the detector’s response time between −0.1 V and −0.2 V probably results from electric field drop over entire absorber region. The optimal operating condition can be reached for −0.15 V, where the time constant reaches approximately 350 ns with peak detectivity at a level of ~3 × 109 Jones.

The novel noninvasive method to diagnose microvascular lesions has been developed􀀃 using time constants obtained from a radial artery pulse (RAPW) and 􀀃 photoplethysmogram (PPG) utilizing the Windkessel model. There are two methods 􀀃 for measuring RAPW: The first is reflectance photoelectric and the second is air conduction. The purpose of this study is to investigate which method was better. Time constants were calculated from each frequency component, with fixtures􀀃 attached to the palm and forearm. Pressure applied to the RAPW sensor was varied 6 􀀃 points. Furthermore, the time constant calculability rate and variation rate calculated􀀃 when the optical and air conduction sensor were used. The maximum value of the 􀀃 calculability rate for the former and latter were 88% and 100%, respectively. The 􀀃 minimum value of variability of the time constant was 18% and 11% for the former􀀃 and latter, respectively. The results demonstrate that air conduction was the superior method. [ABSTRACT FROM AUTHOR]

Impacts of processing, storage, and operation on thin-film perfluorosulfonic acid (PFSA) ionomer coatings used in electrodes of electrochemical devices remains unestablished. In this work, alteration of structure-function relationship in ionomers is achieved via exposure to elevated temperature and humidity (hygrothermal aging). Findings reflect a strong inverse correlation between aging-induced ionomer thin-film domain orientation and water-transport kinetics evaluated from swelling. Impact of aging is shown to be more pronounced on platinum due to interactions with PFSA, as evidenced by greater increase in nanodomain orientation parallel to substrate accompanied by reduced water transport, in contrast to silicon support.

In the present study, experimental investigation of parabolic trough collector is carried out as per ASHRAE 93-1986 standard. In this study, two different case of receiver involving conventional absorber as standard model and optimized secondary optics absorber as proposed model. The heat transfer fluid used for the analysis is distilled water. The important performance parameters such as temperature variation, thermal efficiency, exergy efficiency, and pump work are explored and illustrated. Based on the results, the heating time and cooling time constants obtained for the proposed model are 110 and 115 s, respectively, which shows that the proposed model stabilizes quickly than the standard model. It is observed from the result that the proposed model attained a maximum thermal and exergy efficiency of 73.2 and 48.77%, respectively, which is 14.19 and 9.5% higher than that of the standard model. The electricity generation costs obtained for the proposed model and the standard model are Rs. 3.74/kWh and Rs. 5.71/kWh, respectively. [ABSTRACT FROM AUTHOR]

Background: We hypothesized that the measured expiratory time constant (TauE) could be a bedside parameter for the evaluation of positive end-expiratory pressure (PEEP) settings in mechanically ventilated COVID-19 patients during pressure-controlled ventilation (PCV). Methods: A prospective study was conducted including consecutively admitted adults (n = 16) with COVID-19-related ARDS requiring mechanical ventilation. A PEEP titration using PCV with a fixed driving pressure of 14 cmH2O was performed and TauE recorded at each PEEP level (0 to 18 cmH2O) in prone (n = 29) or supine (n = 24) positions. The PEEP setting with the highest TauE (TauEMAX) was considered to represent the best tradeoff between recruitment and overdistention. Results: Two groups of patterns were observed in the TauE plots: recruitable (R) (75%) and nonrecruitable (NR) (25%). In the R group, the optimal PEEP and PEEP ranges were 8 ± 3 cmH2O and 6–10 cmH2O for the prone position and 9 ± 3 cmH2O and 7–12 cmH2O for the supine position. In the NR group, the optimal PEEP and PEEP ranges were 4 ± 4 cmH2O and 1–8 cmH2O for the prone position and 5 ± 3 cmH2O and 1–7 cmH2O for the supine position, respectively. The R group showed significantly higher optimal PEEP (p < 0.004) and PEEP ranges (p < 0.001) than the NR group. Forty-five percent of measurements resulted in the most optimal PEEP being significantly different between the positions (p < 0.01). Moderate positive correlation has been found between TauE vs CRS at all PEEP levels (r2 = 0.43, p < 0.001). Conclusions: TauE may be a novel method to assess PEEP levels. There was wide variation in patient responses to PEEP, which indicates the need for personalized evaluation. [ABSTRACT FROM AUTHOR]

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Disturbance observer-based control is widely employed in control systems. It demonstrates the ability to estimate intricate disturbances for subsequent measurement, thereby enabling their compensation in the output of existing controllers. Nevertheless, disturbance observer-based control shows limited robustness when utilizing a fixed nominal model. Simultaneously, the fixed time constant of the Q-filter prevents the securement of filtering performance across various flight speed areas. This study aims to enhance robustness in both open- and closed-loop disturbance observer-based control by carefully selecting the Q-filter time constant through a comprehensive transfer function analysis. The transfer function characterizing the quadrotor unmanned aerial vehicle is derived from highly reliable dynamic modeling obtained through wind-tunnel testing, with the nominal model computed by the flight speed. We propose variable disturbance observer-based control by using a nominal model according to flight speed and selecting the Q-filter of disturbance observer-based control by considering the characteristics of the dynamic model, disturbance, and sensor noise. Numerical simulations and flight tests are conducted to compare the controller's performance, focusing specifically on attitude tracking during a round-trip flight with a slung load. [Display omitted] • VDOBC addresses DOBC limitations with a variable nominal model and adaptive Q-filter for robustness. [ABSTRACT FROM AUTHOR]