On-time Duration Research Articles

Prediction and Multiparametric Optimization of the Machined Surface Quality of Tool Steels in Precise Wire Electrical Discharge Machining

This article describes a proposed procedure for multiparametric optimization of the quality of machined surfaces, including mathematical models that can predict the high quality of a precisely machined surface and, at the same time, the high productivity of the process in WEDM of tool steels. The experimental research was carried out using the full DoE factorial design method, which has four technological parameters. The measured output qualitative parameter Surface Roughness (SR) and the output quantitative parameter Material Removal Rate (MRR) were evaluated using the Grey Relational Analysis (GRA) and Analysis of Variance (ANOVA) methods. Multiple Regression Models (MRM) were developed to represent the multiple responses of the investigated tool steels using a regression tool set. The results of the multiparametric optimization revealed a correlation between the input variable parameters of the electrical discharge process, while the favorable results of the observed output-dependent parameters SR and MRR were coupled to the parameters of low peak current I, low value of pulse on-time duration ton, low voltage of discharge U, and high value of pulse off-time duration toff. Based on the multiparametric optimization, key results were obtained that demonstrated the mutual dependence of the observed output process parameters. An optimum SR value of 1.50 μm was obtained with L8-level settings for the input variable parameters I, ton, U, and toff (2 A, 32 μs, 90 V, and 20 μs, respectively) and an MRR value of 12.50 mm3·min−1 was achieved.

Power pattern synthesis of a moving phase center time modulated antenna array using symmetrically and asymmetrically positioned time schemes

The advantages of exploiting the harmonic patterns in a time-modulated linear array (TMLA) is presented in this paper through mathematical validation and also applied for real-world applications like beam scanning. The inherently generated harmonics or sideband radiations (SRs) in TMLAs are normally considered as a loss of power in unwanted direction. The effect of SRs at the multiple harmonic frequencies is mathematically modeled and presented in this paper. Time sequences with symmetrically and asymmetrically oriented pulses are studied (ON-time duration of array element is generally termed as ‘pulse’). The symmetrically oriented non-shifted switching scheme is equivalent to a simple ON–OFF switching, where all the switches connected with array elements are turned ON at the same time. On the other hand, an asymmetrically oriented shifted switching scheme has different switch-ON instants for different elements of an array. Closed-form expressions of radiated power in the main beam and sideband patterns are derived for both cases. The comparison of the shifted and non-shifted pulse is mathematically derived, and the advantages of shifted pulse for exploiting the sidebands are well established. To further discuss the advantages and limitations of these time schemes, phase-centered motion based TMLAs are investigated for electronic beam scanning, and the radiated power by fundamental and sideband patterns are calculated using closed-form equations.

An optimal compact time-modulated circular antenna array synthesis using krill herd optimization

In this paper, an optimal far-field radiation pattern synthesis by using time modulation technique is carried out for a compact circular antenna array (CAA) design using a stochastic optimization method called krill herd (KH) optimization. A compact antenna array is achieved by reducing the inter-element spacing between the array elements, which leads to the miniaturization of the size of the array. On the other hand, an improved far-field radiation characteristic is achieved with a low side lobe level (SLL) and narrow first null beam width (FNBW). A low SLL is an essential requirement to reduce the interference with the other systems operating in the same frequency band. A narrow FNBW is necessary to obtain a high directivity. In time modulation technique, ‘time’ has the most significant role. It is considered the fourth-dimensional parameter, which plays the role of an additional degree of freedom to achieve an improved radiation pattern. The time-modulated antenna array (TMAA) radiates at various harmonic frequencies for the periodic switching time sequence. In this paper, the generation of the radiation pattern at the fundamental/central frequency only is considered. The KH algorithm is a flexible and robust search algorithm. It is applied here to find out the optimum sets of switching on-time duration for each array element and to determine the optimum inter-element separation between two array elements of the 20- and 36-element time-modulated circular antenna array (TMCAA). Particle swarm optimization (PSO) and differential evolution (DE) optimization techniques are also individually applied for the same design purpose to prove the superiority of the KH algorithm–based design. Finally, statistical analysis is performed to ensure the significance of the numerical results.

Diamond Raman oscillator operating at 1178 nm.

In this contribution, we report high-power Raman frequency downconversion based on an Yb-doped fiber amplifier and a linear external diamond Raman cavity. A maximum output power of 136 W with nearly diffraction-limited beam quality was achieved by pumping in quasi-continuous-wave mode with 10% duty cycle and 10 ms on-time duration. For continuous-wave operation, we achieved record average power of 46 W centered at 1178 nm. The emergence of stimulated Brillouin scattering in diamond is further investigated. This technology shows the potential to extend the spectral range of fiber lasers to reach uncommon wavelengths at high power levels.

Correlation of Stroop Effect in Medical Students to Their Performance in Pharmacology National Board of Medical Examiners (NBME) Examination

ObjectiveThe Stroop test is used to assess selective attention in cognitive psychology. Interference between word meaning and ink color in Incongruent Stroop test prolongs reaction time, which involves the brain searching for some collection of the stored information for prompt use. This is called the Stroop effect. Previous studies have reported the strong correlations between the Stroop effect and academic performance. Therefore, we aimed to study the correlation of the Stroop effect in medical students to their performance in pharmacology NBME examination.MethodsFor this study, 40 medical students who completed their pharmacology NBME examination were selected. The Stroop, congruent and incongruent, tests were performed using the EncephalApp Stroop Test (Android/iOS). In Congruent test (Stroop Off), the subjects were asked to select ink color of the hashtag (#) symbols printed in different ink colors (red, blue, and green). In Incongruent test (Stroop On), the subjects were asked to select the ink color of the words RED, BLUE, and GREEN printed in different ink colors, e.g., the word “RED” printed in blue ink had to be selected as blue. Each subject practiced each test for two attempts and 5 attempts of each test were then recorded.The EncephalApp Stroop Test automatically recorded the results of the tests as duration in seconds, which include Congruent Stroop (OffTime duration), Incongruent Stroop (OnTime duration), OffTime plus OnTime duration, OnTime minus OffTime duration. The results of OnTime minus OffTime duration of the Stroop test and pharmacology NBME examination scores were tabulated in Microsoft Excel and descriptive analysis was done. The correlation of the “OnTime minus OffTime duration” to pharmacology NBME examination scores was determined by a Pearson correlation coefficient and regression analysis.ResultsThe correlation coefficient (adjusted r2) of our study was −0.0255 and significance F was 0.862. The “OnTime minus OffTime duration” in medical students was not correlated with the pharmacology NBME examination score (r (38) = 0.0283, p = 0.862). The regression model predicted only 0.08% (R2 = 0.0008) of the pharmacology NBME examination score of medical students.ConclusionThe Stroop effect in medical students is insignificantly correlated with their performance in pharmacology NBME examination. However, correlations of the Stroop effect in medical students with their performance in other subjects and examinations need to be assessed in further studies.Support or Funding InformationThe study was supported by the Trinity Medical Sciences University School of Medicine, St. Vincent and the Grenadines.

Differential evolution to synthesize low sidelobe thinned isophoric time‐modulated planar array with increased directivity

In this article, a novel method for synthesizing rectangular planar array through thinning and time-modulation is proposed. A new differential evolution based approach that generates a rank based population is adopted to find out the optimum element off position for thinning and ontime duration to modulate the antenna elements in time domain. The proposed synthesis method defines a preservative boundary at the array center where the antenna elements are not thinned and time-modulated rather uniformly excited. It is shown that this proposed thinning and time-modulation strategy with an optimum preservative boundary helps to realize low side lobe radiation pattern with increased directivity by controlling less number of optimization variables as compared to traditional approach. It also reduces the feed network complexity specifically for large antenna arrays.

Influence of the On-time on the Ozone Production in Pulsed Dielectric Barrier Discharges

Understanding the production mechanisms of ozone and other reactive species in atmospheric pressure dielectric barrier discharges (DBDs) has become increasingly important for the optimization and commercial success of these plasma devices in emerging applications, such as plasma medicine, plasma agriculture, and plasma catalysis. In many of these applications, input power modulation is exploited as a means to maintain a low gas temperature. Although the chemical pathways leading to ozone production/destruction and their strong temperature dependence are relatively well understood, the effect of the on-time duration on the performance of these modulated DBDs remains largely unexplored. In this study, we use electrical and optical diagnostics, as well as computational methods, to assess the performance of a modulated DBD device. The well-established Lissajous method for measuring the power delivered to the discharge is not suitable for modulated DBDs because the transients generated at the beginning of each pulse become increasingly important in short on-time modulated plasmas. It is shown that for the same input power and modulation duty-cycle, shorter on-time pulses result in significantly enhanced ozone production, despite their operation at slightly higher temperatures. The key underpinning mechanism that causes this counter-intuitive observation is the more efficient net generation rate of ozone during the plasma on-time due to the lower accumulation of NO2 in the discharge volume.

Influence of the voltage waveform’s shape and on-time duration on the dissolved ozone produced by a DBD bubble reactor

In this study we examine both the effect of changing the applied voltage waveform shape and the modulation on-time on the amount of ozone dissolved within a liquid in a dielectric barrier discharges (DBD) bubble reactor. In this device, the discharge forms at the gas–liquid interface allowing for effective transfer of the plasma effluent into the liquid. To produce different voltage waveforms, a multilevel inverter power supply capable of generating arbitrary waveforms without switching-on and switching-off transients has been used. Of the four waveforms used in the study (sinusoidal, sawtooth, square and short-pulse), the square waveform was found to be the most efficient at producing the highest ozone concentration for a fixed peak voltage and average power. To determine the effect of the modulation on-time, the number of cycles during the on-time were increased from 1 up to 1000, adjusting the off-time accordingly to maintain the same duty cycle. Shorter on-time periods were found to be more efficient. Experimental and computational results indicate that the time between subsequent discharges is critical for increased ozone generation efficacy, as this needs to be long enough for ozone produced in one discharge event to diffuse away from the discharge region before the next discharge event occurs, thereby avoiding its partial destruction in the plasma. This insight provides a valuable criterion for the optimization of DBD reactors used in novel biomedical, agricultural and environmental applications.

Performance analysis of pulsed flow control method for radiant slab system

We present a novel pulsed flow control method (PFM) using a two-position valve to regulate the capacity of radiant slab systems. Under PFM, the on-time duration of the valve is short (compared to all prior work, e.g. 4-minute), and fixed, while the off-time varies. We present a novel, open-source, finite difference model that assesses three-dimensional transient slab heat transfer, accounting for the transient heat storage of the pipe fluid. Sensitivity analysis results indicate the dominant factors influencing energy performance of the PFM are: on-time duration; pipe diameter; and spacing. We experimentally validated both the new control strategy and model in full-scale laboratory experiments. Compared with previous intermittent control strategies (with on-time durations over 30 min), at 50% part load the PFM reduces 27% required water flow rate and increases supply to return water temperature differential. Compared with the variable temperature control method, at 50% part load the PFM reduces 24% required water flow rate. The energy performance of PFM is comparable to that of a conventional variable flow rate control. However, it has more accurate capacity control, achieves a more uniform surface temperature distribution, and reduces initial investment by substituting two-position for modulating valves, thus showing promise for engineering applications.

Procedure for Calculating On-Time Duration of the Main Cycle of a Set of Coordinated Traffic Lights

Abstract The task of enhancing efficiency of traffic lights operation demands optimization of the throughput capacity of a regulated street and road network junction including rational and full use of an operation cycle of traffic lights. Oftentimes, the existing calculation system for an operation cycle of traffic lights at intersections does not provide a jam-free and safe route for transport in rush hours. In this article the authors suggest a new calculation methodology for an operation cycle of traffic lights based on the expert calculation which considers the necessity for keeping the possibility of entering a crossing by all vehicles that have arrived to a crossing from each of conflicting directions (including the most loaded one) during one cycle; the use of vehicles slow-down rate called in the traffic rules as “without emergency braking”; the use of phase coefficients at the calculation of the main cycles of the less loaded directions.

Understanding Photoinduced Charge Transfer Dynamics of Single Perylenediimide Dyes in a Polymer Matrix by Bin-Time Dependence of their Fluorescence Blinking Statistics

Fluorescence on–off blinking of single perylenediimide (DMP–PDI) dyes embedded in a disordered matrix of poly(methyl methacrylate) (PMMA) was investigated by single-molecule fluorescence spectroscopy. In particular, we examined the bin-time dependencies of the complementary cumulative distribution functions (cCDF) of the on-time and off-time durations. It appears that intersystem crossing (ISC) within DMP–PDI competes with charge transfer between DMP–PDI and PMMA. The single-molecule and ensemble cCDFs of the on-time and off-time durations (induced by charge transfer) were best described by Weibull functions and log-normal functions, respectively. The dispersive kinetics of the on-time duration were attributed to radical ion pair ISC from triplet charge separation (3CS) state to the corresponding singlet (1CS) state via charge hopping between charge trap sites in PMMA. This process should compete with triplet charge recombination (3CR), which restores the triplet state. On-to-off switching occurs only when 3CS → 1CS ISC overcomes the 3CR process. The resultant Weibull distribution (with A < 1) reflects that the probability of charge hopping rapidly decreases with time. On the other hand, the off-time log-normal kinetics of single-molecules are explained by a Gaussian distribution of activation energies for charge recombination (the so-called Albery model). A simulation study revealed that the ensemble off-time cCDF included power-law kinetics of charge hopping in the polymer matrix.

There and back again: Revisiting the on-time effect

In apparent motion, static stimuli presented successively in shifted locations produce a subjective percept of continuous motion. Reducing stimulus exposure (or on-time) was shown to consistently increase the perceived velocity of apparent motion (Vision Research 29 (1989), 335–347), yet surprisingly little investigation has followed up on the discovery of this illusion. In five experiments, we delineate the boundary conditions of the on-time illusion in order to clarify its underlying mechanisms. Subjects viewed multi-item apparent-motion displays, in which at some point, on-time duration either increased or decreased. Objective velocity remained unchanged, yet participants had to judge whether they perceived the motion to become slower or faster. We observed the on-time illusion during both fast and slow apparent motion. The effect was not modulated by stimulus luminance, thus precluding an energy-summation account of the illusion. It generalized from speed perception to time perception in a temporal bisection task. The illusion was specific to apparent motion, as it did not occur with veridical motion. Finally, the illusion persisted when on-time and off-time were not confounded, that is, when off-time remained constant. These findings are discussed in the framework of current models of motion perception.

Influence of interfacial electron transfer on fluorescence blinking of quantum dots

The fluorescence blinking characteristics of the single CdSe/ZnS core/shell quantum dots (QDs) absorbed on the cover glass surface, indium-tin oxide (ITO) nanoparticles, and polymethyl methacrylate (PMMA) film surface are measured by a laser scanning confocal fluorescence microscopy. It is found that all the distributions of bright state duration time of QDs on the three different interfaces can be described by a truncated power law P(t)∝ t-αexp(-t/μ). The statistical on-time durations of single QDs absorbed on the ITO nanoparticles is shorter than on the glass. In addition, the on-time duration with single QDs absorbed on the PMMA is longer than on the others. These differences can be attributed to the diverse interfacial electron transfers between QD and different materials.

In situ monitoring of a flash light sintering process using silver nano-ink for producing flexible electronics

In this work, a flash light sintering process using silver nano-inks is investigated. A silver nano-ink pattern was printed on a flexible PET (polyethylene terephthalate) substrate using a gravure-offset printing system. The printed silver nano-ink was sintered at room temperature and under ambient conditions using a flash of light from a xenon lamp using an in-house flash light sintering system. In order to monitor the light sintering process, a Wheatstone bridge electrical circuit was devised and changes in the voltage difference of the silver nano-ink were recorded during the sintering process using an oscilloscope. The sheet resistance changes during the sintering process were monitored using the in situ monitoring system devised, under various light conditions (e.g. light energy, on-time and off-time duration, and pulse numbers). The microstructure of the sintered silver film and the interface between the silver film and the PET substrate were observed using a scanning electron microscope, a focused ion beam and an optical microscope. The electrical sheet resistances of the sintered silver films were measured using a four-point probe method. Using the in situ monitoring system devised, the flash light sintering mechanism was studied for each type of light pulse (e.g. evaporation of organic binder followed by the forming of a neck-like junction and its growth, etc). The optimal flash light sintering condition is suggested on the basis of the in situ monitoring results. The optimized flash light sintering process produces a silver film with a lower sheet resistance (0.95 Ω/sq) compared with that of the thermally sintered silver film (2.03 Ω/sq) without damaging the PET substrate or allowing interfacial delamination between the silver film and the PET substrate.

RGFP109, a histone deacetylase inhibitor attenuates l-DOPA-induced dyskinesia in the MPTP-lesioned marmoset: A proof-of-concept study

Backgroundl-3,4-dihydroxyphenylalanine (l-DOPA)-induced dyskinesia (LID) are a complication of chronic dopamine replacement therapy in Parkinson's disease (PD). Recent studies have suggested that the mechanisms underlying development and expression of LID in PD may involve epigenetic changes that include deacetylation of striatal histone proteins. We hypothesised that inhibition of histone deacetylase, the enzyme responsible of histone deacetylation, would alleviate LID. MethodsFour female common marmoset (Callithrix jacchus) were rendered parkinsonian by administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Following stabilisation of the parkinsonian phenotype, marmosets were primed to exhibit dyskinesia with chronic administration of l-DOPA. We then investigated the effects of the brain-penetrant histone deacetylase inhibitor, RGFP109 (30 mg/kg p.o. once daily for 6 days), on LID and l-DOPA anti-parkinsonian efficacy. ResultsRGFP109 had no acute effects on dyskinesia after single or 6 days once-daily treatment (both P > 0.05). However, one week following cessation of RGFP109, dyskinesia and duration of ON-time with disabling dyskinesia were reduced by 37% and 50%, respectively (both P < 0.05), compared to that seen previously with l-DOPA alone. There was no change in anti-parkinsonian actions of, or ON-time duration afforded by, l-DOPA (P > 0.05). ConclusionsHistone deacetylation inhibition may represent a novel approach to reverse established LID in PD and improve quality of the anti-parkinsonian benefit provided by l-DOPA.

A Linear Mixed-Effects Model of Wireless Spectrum Occupancy

We provide regression analysis-based statistical models to explain the usage of wireless spectrum across four mid-size US cities in four frequency bands. Specifically, the variations in spectrum occupancy across space, time, and frequency are investigated and compared between different sites within the city as well as with other cities. By applying the mixed-effects models, several conclusions are drawn that give the occupancy percentage and the ON time duration of the licensed signal transmission as a function of several predictor variables.

Optically stimulated phosphorescence in orthoclase feldspar over the millisecond to second time scale

Abstract In the past, time-resolved IR stimulated luminescence (TR-IRSL) curves from feldspar have mainly been measured over a few hundred μs with the purpose of estimating the lifetimes of the components. In this study, we present the decay form of time-resolved IRSL and IR stimulated phosphorescence (IRSP) from orthoclase feldspar covering over 8 orders of magnitude (50 ns to ∼7 s). A detailed characterisation of the slowly decaying signals (ms to s time scales) from feldspar is undertaken to obtain further insight into the role of re-trapping in both the IR stimulated luminescence (IRSL) and the relatively more stable post-IR IRSL signals. The decay form of the different signals examined here shows a weak dependence on preheat temperature and a strong dependence on stimulation temperature. Interestingly, the IRSP curves show a conspicuous kink of which the position is linearly dependent on the on-time duration. The data on thermal dependence of these signals might suggest that the decay behaviour of the time-resolved IRSL and phosphorescence signals mainly reflect the occupancy of electrons in the band tail states with a significant contribution from the shallow traps. This interpretation is supported by thermoluminescence (TL) curves showing the photo-transfer effect during short IR and post-IR IR stimulations.

Ligand-dependent blinking of zinc-blende CdSe/ZnS core/shell nanocrystals

Blinking of zinc-blende CdSe/ZnS core/shell nanocrystals are studied as a function of surface passivating ligands. Organic-soluble CdSe/ZnS core/shell nanocrystals are prepared by colloidal synthesis free of trioctylphosphine oxide and converted into water-soluble ones by ligand exchange with three different hydrophilic thiols, 2-aminoethanethiol, 3-mercapto-1-propanol, and 3-mercaptopropionic acid. The zinc-blende lattice structure is confirmed by powder X-ray diffraction, the size and shape distributions are visualized by high-resolution transmission electron microscopy, and hydrodynamic size distributions of water-soluble nanocrystals are determined by dynamic light scattering. Ligand-dependent optical properties, such as the absorption and emission spectra as well as the photoluminescence lifetime, are obtained in both solution and glass substrate to characterize the effects of ligand on the bright state of nanocrystals. The time trace of blinking is recorded for single nanocrystals in polymer film. Both on- and off-time distributions are fit to a power law. The off-time exponents are clustered at 1.67+/-0.05, whereas the on-time exponents are scattered in the range of 1.71-2.25. The thiolate conjugation on the surface zinc atom greatly reduces the on-time duration, suggesting that the rate of photoinduced charge separation from the bright (on) to the dark (off) state increases as the number of surface hole-trap states increases.

Biarticular Leg Muscles and Links to Running Economy

Relationships between an index of running economy (VO2 per distance) and the temporal electromyographic characteristics of leg muscles were quantified in female runners. Sixteen women performed a 30-min treadmill run at a speed designed to elicit a hard rating of perceived of exertion. Near the end of the run, oxygen uptake, video, and electromyographic data were collected simultaneously. Measures of muscle on-time durations, and on-time coactivation durations were calculated from the following muscles: gastrocnemius, vastus lateralis, rectus femoris, and biceps femoris. Nonparametric correlations between VO2 per distance and temporal electromyographic data were evaluated. Greater on-time duration of rectus femoris during stance, and greater on-time coactivation duration of rectus femoris-gastrocnemius during stance were significantly associated with more economical runners (i.e., lower VO2 per distance). The coactivation of biarticular leg muscles during stance is clearly linked to running economy and this control strategy may elicit greater elastic energy return.

Study of Fluorescence Enhancement of Colloidal CdSe/ZnS Quantum Dots Bound to Hexadecylamine by Single-Molecule Measurements

Fluorescence enhancement of colloidal CdSe/ZnS quantum dots (QDs) by the binding of hexadecylamine (HDA) ligands was investigated at the single-QD level. The blinking behavior of individual CdSe/ZnS QDs can be dramatically modified by additional HDA ligands. Both the ratio of the mean on/off time lengths and the total number of emitted photons within the on-time duration can be enhanced, by factors of up to 2.8 and 13, respectively. Consequently, the blinking rate can be suppressed down to 18%. The fluorescence decay curve is closer to a single-exponential decay profile and has a longer measured lifetime. These results suggest that HDA ligands can further improve surface passivation.