Dual-exponential Function Research Articles

Level Sets Guided by SoDEF-Fitting Energy for River Channel Detection in SAR Images

To achieve river channel detection in SAR (synthetic aperture radar) images, we developed a level-set-based model (LSBM) guided by a designed data-fitting energy which is called the SoDEF (sum of dual exponential functions)-fitting energy. Firstly, we designed a function by computing the sum of dual exponential functions to substitute for the quadratic function, and used it to construct the data-fitting energy. Secondly, the adaptive area-fitting centers (AFCs) were computed based on two kinds of grayscale characteristics, which are more accurate and more stable. Thirdly, the Dirac function in gradient descent flow was displaced by an edge indicator function to help the evolving level sets stop at the target edges. Moreover, some regularized terms were incorporated into the objective function to guarantee the model’s stability. The river channel detection experiments conducted with real SAR images indicated that the developed model is superior to the related state-of-the-art methods in its detection accuracy and efficiency.

Prediction of the Long-Term Effect of Iron on Methane Yield in an Anaerobic Membrane Bioreactor Using Bayesian Network Meta-Analysis.

A method for predicting the long-term effects of ferric on methane production was developed in an anaerobic membrane bioreactor treating food processing wastewater to provide management tools for maximizing methane recovery using ferric based on a batch test. The results demonstrated the accuracy of the predictions for both batch and long-term continuous operations using a Bayesian network meta-analysis based on the Gompertz model. The prediction bias of methane production for batch and continuous operations was minimized, from 11~19% to less than 0.5%. A biochemical methane potential-based Bayesian network meta-analysis suggested a maximum 2.55% ± 0.42% enhancement for Fe2.25. An anaerobic membrane bioreactor improved the methane yield by 2.27% and loading rate by 4.57% for Fe2.25, operating in the sequenced batch mode. The method allowed for a predictable methane yield enhancement based on the biochemical methane potential. Ferric enhanced the biochemical methane potential in batch tests and the methane yield in a continuously operated reactor by a maximum of 8.20% and 7.61% for Fe2.25, respectively. Copper demonstrated a higher methane (18.91%) and sludge yield (17.22%) in batch but faded in the continuous operation (0.32% of methane yield). The enhancement was primarily due to changing the kinetic patterns for the last period, i.e., increasing the second methane production peak (k71), bringing forward the second peak (λ7, λ8), and prolonging the second period (k62). The dual exponential function demonstrated a better fit in the last three stages (after the first peak), which implied that syntrophic methanogenesis with a ferric shuttle played a primary role in the last three methane production periods, in which long-term effects were sustained, as the Bayesian network meta-analysis predicted.

Experimental Research on Lightning Disturbance Characteristics of 10-kV Fusion Voltage Transformer Intelligent Component Acquisition Port

In the lightning impulse test, the 10 kV fusion voltage transformer intelligent component acquisition port often suffers from functional failure or breakdown. In this paper, experimental measurement and inversion calculation were used to study the electromagnetic disturbance level of smart component acquisition port. During the inversion calculation, the applicability of the dual exponential function model, Heidler function model, and impulse function model as the primary source for describing the lightning impulse device were compared and analyzed. The results show that the double exponential model was used as the calculation source of the primary side lightning waveform, and the inversion calculation results were in good agreement with the actual measurement. In addition, the effects of the primary side lightning voltage peak, wave head, and wave tail parameters on the maximum amplitude of the disturbance waveform calculated by inversion are discussed and analyzed. Based on the analysis results, a sufficient inversion calculation parameter was proposed to estimate the disturbance level of the intelligent component acquisition port. Finally, the measured results were compared and discussed with the IEC 61439 assessment level, and it was suggested that the assessment level of fusion equipment should be modified.

Concentrations and biological half-life of radioactive cesium in epigeic earthworms after the Fukushima Dai-ichi Nuclear Power Plant accident

To understand the long-term behavior of radiocesium in the biological processes of a forest ecosystem, its concentration in Japanese epigeic earthworms (Megascolecidae), litter, and soil, and the ambient dose equivalent rates, were investigated after the Fukushima Dai-ichi Nuclear Power Plant accident. The metabolism of radiocesium in the earthworms was also investigated in the laboratory, and its biological half-life (Tb) was estimated. The concentration of 137Cs in the habitat soil and litter changed from 2014 to 2016, with levels in the litter going from 44.9 Bq/g dw (in 2014) to 45.3 Bq/g dw (2015) and 10.7 Bq/g dw (2016); in soil, these values were 9.79 Bq/g dw, 7.14 Bq/g dw and 18.0 Bq/g dw, respectively. By contrast, no significant changes were observed in the concentrations in the earthworms, which were 4.87 Bq/g fw, 5.30 Bq/g fw and 4.67 Bq/g fw in 2014, 2015, and 2016, respectively. The ambient dose equivalent rates at the sampling site declined significantly over these three years, going from 2.15 μSv/h to 1.68 μSv/h and 1.35 μSv/h, mostly corresponding to physical decay of radiocesium. The majority (95%) of the 137Cs in the earthworms, observed via autoradiography, was concentrated primarily in the intestine. The clearance of 137Cs from the earthworms was described by dual exponential functions: the half-life in the rapid loss due to gut clearance was 0.10 days and a second slower loss due to physiological clearance was 27.4 days.

State of charge modeling of lithium-ion batteries using dual exponential functions

A mathematical model is developed by fitting the discharging curve of LiFePO4 batteries and used to investigate the relationship between the state of charge and the closed-circuit voltage. The proposed mathematical model consists of dual exponential terms and a constant term which can fit the characteristics of dual equivalent RC circuits closely, representing a LiFePO4 battery. One exponential term presents the stable discharging behavior and the other one presents the unstable discharging behavior and the constant term presents the cut-off voltage.

Kinetic study of E′ center formed by radiation with low energy particles in high purity silica

In this paper, a kinetic model for the radiation-induced production of the intrinsic point defect E′ center is proposed. The results show that E′ center concentration increases linearly with dose in low dose regions, and it tends to saturate in high dose regions. Further, it is found that E′ center is dual exponential function of dose, and the saturate state collapses if the second reaction is considered. The theoretical result is in good agreement with the experiment.

A new automated delineation method for SPECT lung scans using adaptive dual‐exponential thresholding

AbstractAn accurate method for delineating lung contours in single photon emission computed tomography (SPECT) is critical to respiratory studies such as pulmonary embolism (PE) and respiratory aerosol deposition. Current delineation methods are not adaptive in nature and may require a priori information on lung volumes. We have developed a dual‐exponential thresholding method that solely requires SPECT scans, and is fast, accurate, and adaptive in nature. A dataset consisted of 90 patients was studied retrospectively. While most were suspected of PE, other pulmonary disorders were also present. SPECT ventilation scans were obtained after inhalation of ∼40 MBq of 99mTc‐Technegas. Examination of the corresponding natural logarithmically transformed histograms revealed dual exponential functions like pattern. Adaptive thresholds were found as the intercept between the two exponential functions. 350 Monte Carlo simulations representative of normally‐ventilated scans with varying counts were used to quantitatively measure and evaluate the method. Our method correctly delineated lung volumes to above 97% agreement for 310 of the 350 Monte Carlo simulations with maximum count values greater than or equal to 31. The 40 low‐count simulations were included purely as extreme cases. For real patient scenario, an experienced physician was called upon to visually delineate a sample of 50 actual patient scans, and these delineated lung volumes were used as gold standard and compared with those delineated using our method. Our results had an average of 96% agreement. © 2007 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 17, 22–27, 2007

Combined depth- and time-resolved autofluorescence spectroscopy of epithelial tissue

A time-resolved confocal fluorescence spectroscopy system is built to measure the fine structure and localized biochemistry of epithelial tissue. It is found that the autofluorescence excited at 405 nm is sensitive to the cellular metabolism and can be used to sense the metabolic status of epithelial tissue. The decay of autofluorescence excited at 405 nm can be accurately fitted with a dual-exponential function consisting of short lifetime (0.4-0.6 ns) and long lifetime (3-4 ns) components. The ratio of the amplitudes of the two components provides information on the fine structure of epithelial tissue. We demonstrate that the combined depth- and time-resolved measurements with single excitation can potentially provide accurate information for the diagnosis of tissue pathology.

Investigation on photoexcited dynamics of IR-140 dye in ethanol by femtosecond supercontinuum-probing technique

Transient absorption and emission spectra of IR-140 dye (5,5'-dichloro-11- diphenylamine-3,3'-diethyl-10,12-ethylene-thiatricarbocyanine-perchlorate) in ethanol have been investigated by using the pump supercontinuum-probing technique of 130 fs time resolution. Excited at a wavelength of 807 nm, two peaks at 820 and 840 nm in the emission spectra were observed. The decay of stimulated emission (SE) at 840 nm can be fitted by a dual-exponential function. Meanwhile, a new transient absorption band ranging from 500 to 650 nm was observed and attributed to the transition between the excited singlet states. Its relaxation process could also be fitted by a dual-exponential function. Both relaxation processes of SE and excited-state absorption were probing wavelength-dependent and included a fast relaxation with a decay time of about several picoseconds and a slow relaxation with decay time longer than 0.1 ns. The prime energy structure was proposed according to the relaxation process and transient spectra of IR-140.

α,α-Dinaphthylpropane: a model for polymer photophysics and a probe for the investigation of macromolecular dynamics?

The time-resolved photophysical behaviour of α,α-dinaphthylpropane (αα-DNP) in iso-octane solution at temperatures greater than 30°C is in good agreement with the predictions of Birks kinetics. At temperatures below 30°C the fluorescence decay behaviour is more complex. This has serious implications for the attempted use of αα-DNP (or indeed any other bichromophoric compound) in attempts to probe macromolecular dynamics if ‘ forced fits’ to dual-exponential functions were to be employed. The complexity of the fluorescence decay behaviour of such a simple model molecule (in which the complication of ‘tacticity’ and/or energy migration effects are obviated) has implications regarding the interpretation of the photophysical behaviour of macromolecules derived from vinyl aromatic monomers.

Block of cardiac sodium channels by amiodarone studied by using Vmax of action potential in single ventricular myocytes.

1. Acute effects of amiodarone on cardiac sodium channels were investigated in ventricular myocytes isolated from guinea-pig hearts, and compared with those of lignocaine. 2. Transmembrane potential was recorded and controlled by whole-cell current-clamp and voltage-clamp respectively through suction pipette electrodes. The maximum upstroke velocity (Vmax) of the action potential was used as a qualitative index of sodium channel availability. 3. In myocytes treated with amiodarone (1 microM) or lignocaine (40 microM), Vmax of reference action potential elicited at 0.03 Hz was decreased by 6-11%, indicating minimal tonic block of sodium channels. 4. Application of a single conditioning depolarization to those myocytes resulted in a significant decrease in Vmax of a subsequent test action potential. The Vmax reduction was enhanced in a single exponential function as the clamp pulse duration was prolonged. Time constants at 0 mV clamp were 25 ms for amiodarone and 122 ms for lignocaine. 5. Vmax recovery of test action potential following a 1000 ms 0 mV clamp was approximated by a dual exponential function. Time constants for the late slow component (tau R) at the resting potential level were 418 ms for amiodarone and 178 ms for lignocaine. tau R values were shortened in a voltage-dependent manner by hyperpolarization during the coupling interval. 6. These findings suggested that amiodarone, like lignocaine, blocks the sodium channel primarily when it is in the inactivated state. Both onset and offset kinetics of the block are very rapid. Such sodium channel blocking characteristics may contribute to its potent antiarrhythmic activity.

Analysis of time-resolved fluorescence anisotropy in lipid-protein systems

The subnanosecond fluorescence and motional dynamics of the tryptophan residue in the bacteriophage M13 coat protein incorporated within pure dioleoylphosphatidylcholine (DOPC) as well as dioleoylphosphatidylcholine/dioleoylphosphatidylglycerol (DOPC/DOPG) and dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol (DMPC/DMPG) bilayers (80/20 w/w) with various L/P ratio have been investigated. The fluorescence decay is decomposed into four components with lifetimes of about 0.5, 2.0, 4.5 and 10.0 ns, respectively. In pure DOPC and DOPC/DOPG lipid bilayers, above the phase transition temperature, the rotational diffusion of the protein molecules contributes to the depolarization and the anisotropy of tryptophan is fitted to a dual exponential function. The longer correlation time, describing the rotational diffusion of the whole protein, shortens with increasing temperature and decreasing protein aggregation number. In DMPC/DMPG lipid bilayers, below the phase transition, the rotational diffusion of the protein is slowed down such that the subnanosecond anisotropy decay of tryptophan in this system reflects only the segmental motion of the tryptophan residue. Because of a heterogeneous microenvironment, the anisotropy decay must be described by three exponentials with a constant term, containing a negative coefficient and a negative decay time constant. From such a decay, the tryptophan residue within the aggregate undergoes a more restricted motion than the one exposed to the lipids. At 20 degrees C, the order parameter of the transition moment of the isolated tryptophan is about 0.9 and that for the exposed one is about 0.5.

Transient decay studies of photophysical processes in aromatic polymers: 2. Investigation of intramolecular excimer formation in copolymers of 1-vinyl naphthalene and methyl acrylate

Transient decay studies of the copolymer system 1-vinyl naphthalene/methyl acrylate using pulsed laser excitation have shown that monomer and excimer decay rates are not described by dual exponential functions. Triple exponential decays are attributed to the existence of emission from two kinetically distinct monomer sites in addition to that of the excimer. Variation of intramolecular chromophore concentration in the copolymers allows adoption of a versatile series of extrapolation procedures to derive individual rate constants in the photophysical reaction scheme governing intramolecular excimer formation. Use of this procedure yields a rate parameter governing excimer formation in which the dependence upon local chromophore concentration within the polymer coil is removed to a degree not possible in studies of homopolymers alone.