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Journal articles on the topic 'Fluctuation'
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1
Treacy, Michael M. J. "Fluctuation Microscopy: What is it?" Microscopy Today 13, no. 5 (September 2005): 20–21. http://dx.doi.org/10.1017/s1551929500053761.
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Fluctuation microscopy is the enigmatic name given to an otherwise straightforward technique for studying medium range order in highly disordered materials. By medium range, we mean atomic ordering at length scales within the range 0.5-2.0 nm, where traditional imaging and diffraction techniques have the most difficulty detecting structural correlations in amorphous materials. Puzzlement over fluctuation microscopy generally arises not because of the "microscopy" part of the name, but because of the "fluctuation" part. What, exactly, is fluctuating? And, why does it fluctuate?The fluctuations are simply the variations in scattering between small sub-volumes within a thin sample. These are usually not timevarying fluctuations (although they could be), but instead they are the position-varying fluctuations in local diffraction.
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Mila, A. L., and X. B. Yang. "Effects of Fluctuating Soil Temperature and Water Potential on Sclerotia Germination and Apothecial Production of Sclerotinia sclerotiorum." Plant Disease 92, no. 1 (January 2008): 78–82. http://dx.doi.org/10.1094/pdis-92-1-0078.
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The effects of fluctuating soil temperature and water potential on sclerotial germination and apothecial production by Sclerotinia sclerotiorum were investigated in growth chamber experiments. In the temperature experiments, temperature fluctuations of 4, 8, 12, and 16°C around a median of 20°C, and a constant of 20°C, were tested. Daily temperature fluctuations of 8°C resulted in highest levels of sclerotial germination and apothecial production. The earliest appearance of apothecia occurred in the 8°C fluctuation treatment, 24 days after the start of the experiment. Sclerotia in the 12°C fluctuation treatment germinated last; its first sclerotium germinated 44 days after experiment initiation. For the soil water potential experiments, constant saturation (approximately –0.001 MPa) and three levels of soil water potential fluctuation from saturation—“low” (–0.03 to –0.04 MPa), “medium” (–0.06 to –0.07 MPa), and “high” (–0.09 to –0.1 MPa)—were tested. Constant saturation yielded the highest number of germinated sclerotia and apothecia. All soil water potential fluctuations were detrimental to sclerotial germination and apothecial production, with sclerotial germination under fluctuating moisture conditions less than a tenth of that occurring under constant saturation. The first sclerotium in the constant saturation treatment germinated in 35 days; however, 76 days were required in the high soil water potential fluctuation treatment.
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Cai, Jian-Cheng, Hao-Jie Chen, Volodymyr Brazhenko, and Yi-Hong Gu. "Study of the Hydrodynamic Unsteady Flow Inside a Centrifugal Fan and Its Downstream Pipe Using Detached Eddy Simulation." Sustainability 13, no. 9 (May 2, 2021): 5113. http://dx.doi.org/10.3390/su13095113.
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The detailed unsteady turbulent flow inside a centrifugal fan and its downstream pipe was studied using detached eddy simulation (DES) at three flowrates, namely, the best efficiency point (BEP), 0.75BEP, and 1.49BEP. Both the mean and fluctuating flow fields were analyzed on the basis of the root-mean-square value as the indication of fluctuating intensity. Results showed that the pressure fluctuation had the minimum value at BEP, but the velocity fluctuation increased with the flowrate. Most regions inside the centrifugal fan underwent large pressure fluctuation with the magnitude of about 10~20% of pref = 0.5 ρu22, where u2 is the blade velocity at the impeller outlet. The pressure fluctuation had a maximum value at the impeller side of the tongue tip rather than the stagnation point, and it decreased rapidly along the outlet pipe with magnitude about 1% of pref after distance of five pipe diameters. The spectra of hydrodynamic pressure showed conspicuous spikes at the blade passing frequency (BPF) in the volute but not in the downstream pipe. At the downstream pipe entrance, pressure fluctuation spectra agreed with experimental results, showing that hydrodynamic pressure fluctuations were dominant; however, the experimental data showed a much slower decreasing rate due to the acoustic fluctuations.
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Sheldon, Kimberly S., Mojgan Padash, Amanda W. Carter, and Katie E. Marshall. "Different amplitudes of temperature fluctuation induce distinct transcriptomic and metabolomic responses in the dung beetle Phanaeus vindex." Journal of Experimental Biology 223, no. 23 (November 2, 2020): jeb233239. http://dx.doi.org/10.1242/jeb.233239.
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ABSTRACTMost studies exploring molecular and physiological responses to temperature have focused on constant temperature treatments. To gain a better understanding of the impact of fluctuating temperatures, we investigated the effects of increased temperature variation on Phanaeus vindex dung beetles across levels of biological organization. Specifically, we hypothesized that increased temperature variation is energetically demanding. We predicted that thermal sensitivity of metabolic rate and energetic reserves would be reduced with increasing fluctuation. To test this, we examined the responses of dung beetles to constant (20°C), low fluctuation (20±5°C), or high fluctuation (20±12°C) temperature treatments using respirometry, assessment of energetic reserves and HPLC-MS-based metabolomics. We found no significant differences in metabolic rate or energetic reserves, suggesting increased fluctuations were not energetically demanding. To understand why there was no effect of increased amplitude of temperature fluctuation on energetics, we assembled and annotated a de novo transcriptome, finding non-overlapping transcriptomic and metabolomic responses of beetles exposed to different fluctuations. We found that 58 metabolites increased in abundance in both fluctuation treatments, but 15 only did so in response to high-amplitude fluctuations. We found that 120 transcripts were significantly upregulated following acclimation to any fluctuation, but 174 were upregulated only in beetles from the high-amplitude fluctuation treatment. Several differentially expressed transcripts were associated with post-translational modifications to histones that support a more open chromatin structure. Our results demonstrate that acclimation to different temperature fluctuations is distinct and may be supported by increasing transcriptional plasticity. Our results indicate for the first time that histone modifications may underlie rapid acclimation to temperature variation.
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Laberge, Gaetan J. H., and Rizwan U. Haq. ""Universality" of Gaussian orthogonal ensemble fluctuations: the two-body random ensemble and shell model spectra." Canadian Journal of Physics 68, no. 3 (March 1, 1990): 301–12. http://dx.doi.org/10.1139/p90-048.
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Starting from an appropriate decomposition of the level density into an average and fluctuating part, we studied the energy level fluctuations of an ensemble defined by two-body random Hamiltonians. A detailed analysis of several spectrally averaged fluctuation measures shows close agreement with the predictions of the Gaussian orthogonal ensemble (GOE). This confirms earlier indications that, except for noninteracting particles, fluctuation measures are insensitive to the rank of the interaction. Further, analysis of spectra obtained from realistic nuclear interactions agrees well with the GOE indicating that specific properties of the Hamiltonian have little or no influence on fluctuations. These results, therefore, strengthen our belief in the "universality" of GOE fluctuations.
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Hatef, Hakimeh, Mahmoud Daneshvar Kakhki, Mohammad Reza Kohansal, Mohammad Bannayan, and Naser Shahnoushi Froshani. "Climate vulnerability index fluctuation: a case of Iran." Journal of Water and Climate Change 10, no. 1 (May 3, 2018): 223–35. http://dx.doi.org/10.2166/wcc.2018.044.
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Abstract Climatic fluctuations have severe effects on water and soil resources and economy as a whole. It is hence important to study the fluctuations of climatic parameters in different regions in order to recognize the source and type of parameter that have led to fluctuating climatic parameters. To achieve this goal, the current study attempts to address the following issues: what are the different sources of fluctuations in climate parameters? Do different regions have the same degree of vulnerability and what is the most fluctuating parameter in each region? To answer these questions, the study suggests climate vulnerability index fluctuation. Calculating the index requires data provided by weather stations, so 115 weather stations were divided into 12 climatic zones based on the availability of data. This index considered permanent and frequent temperature, precipitation, storm and aridity shocks. The results indicated that the maximum rank of index has occurred in hot semi-mountainous and very hot desert. Also, temperature fluctuation was the major factor in five regions, whereas wind fluctuation was the major factor in three regions. Generally, the northern and western parts of the country experienced minimum climatic changes. Moving towards southern regions of the country, more climatic changes were observed.
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Li, Yuepeng, Liuyue Wang, Xun Zou, Jihong Qu, and Gang Bai. "Experimental and Simulation Research on the Process of Nitrogen Migration and Transformation in the Fluctuation Zone of Groundwater Level." Applied Sciences 12, no. 8 (April 8, 2022): 3742. http://dx.doi.org/10.3390/app12083742.
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The fluctuation of groundwater causes a change in the groundwater environment and then affects the migration and transformation of pollutants. To study the influence of water level fluctuations on nitrogen migration and transformation, physical experiments on the nitrogen migration and transformation process in the groundwater level fluctuation zone were carried out. A numerical model of nitrogen migration in the Vadose zone and the saturated zone was constructed by using the software HydrUS-1D. The correlation coefficient and the root mean square error of the model show that the model fits well. The numerical model is used to predict nitrogen migration and transformation in different water level fluctuation scenarios. The results show that, compared with the fluctuating physical experiment scenario, when the fluctuation range of the water level increases by 5 cm, the fluctuation range of the nitrogen concentration in the coarse sand, medium sand and fine sand media increases by 37.52%, 31.40% and 21.14%, respectively. Additionally, when the fluctuation range of the water level decreases by 5 cm, the fluctuation range of the nitrogen concentration in the coarse sand, medium sand and fine sand media decreases by 36.74%, 14.70% and 9.39%, respectively. The fluctuation of nitrogen concentration varies most significantly with the amplitude of water level fluctuations in coarse sand; the change in water level has the most significant impact on the flux of nitrate nitrogen and has little effect on the change in nitrite nitrogen and ammonium nitrogen, and the difference in fine sand is the most obvious, followed by medium sand, and the difference in coarse sand is not great.
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Olszewski, Marcin, and Nikolaj A. Sergeev. "Lineshape of a Stochastic Oscillator with Two State Frequency Modulations." Zeitschrift für Naturforschung A 63, no. 10-11 (November 1, 2008): 688–92. http://dx.doi.org/10.1515/zna-2008-10-1112.
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The transformations of the lineshape with a fluctuating frequency for the Kubo-Anderson oscillator are considered. Assuming that the frequency of the oscillator fluctuates between two values and the rate of this fluctuation is a stochastic function of the time the analytical expression of the lineshape is obtained. It is assumed that the stochastic fluctuations of the potential barrier for the Kubo-Anderson oscillator lead to the stochastic fluctuations of the frequency. The transformations of the lineshape are extremely sensitive to the function, which describes the distributions of the frequency fluctuations. The obtained expression is applied to the different distributions of the fluctuation frequency rate. It is shown that a unusual type of the motional narrowing phenomenon is observed for the log-normal and log-Lorentzian distribution.
9
Wu, Peipeng, Jean-Christophe Comte, Lijuan Zhang, Shuhong Wang, and Bin Chang. "Effect of Surface Water Level Fluctuations on the Performance of Near-Bank Managed Aquifer Recharge from Injection Wells." Water 13, no. 21 (October 27, 2021): 3013. http://dx.doi.org/10.3390/w13213013.
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Managed aquifer recharge operations are often conducted in near-bank areas to regulate water resources or reduce seawater intrusion. Yet little is known about the influence of surface water level fluctuations at different temporal scales on MAR performance. A generalized conceptual model was developed based on an investigation site in Western China as a basis to simulate the response surface water level fluctuations on the water table, artificially recharged water lens (formed by the artificially recharged water), groundwater flow paths and average travel times (which is an important control on how quickly contaminants are flushed out of aquifers), and the discharge of the artificially recharged aquifer during the surface water level fluctuation. The results showed a fluctuating groundwater table in the artificially recharged near-bank aquifer under the influence of surface water level fluctuations. The peak values of the increment of the groundwater table induced by artificial recharge decreased with the increase of the period and amplitude of surface water level fluctuation, but the trough values of the increment of water table increases with that. The penetration depth of surface water into the aquifer with a fluctuating surface water level leads to a decreasing increment of the groundwater table which follows a power law. The fluctuating surface water level leads to dynamic changes of artificially recharged water lens morphology and a thinner artificially recharged water lens. A mixing zone of recharged water and ambient water could be found in the artificially recharged near-bank area, which is expected to lead to modifications in the geochemical conditions in the artificially recharged near-bank aquifer. A longer period of surface water level fluctuation leads to a longer average travel time, but the larger penetration depth of surface water and amplitude lead to a shorter average travel time. The peak discharge of the near-bank aquifer was found to decrease with the period of surface water level fluctuation, but it increases with penetration depth and amplitude. This study is important in providing insights into the performance of near-bank managed aquifer recharge with respect to surface water level fluctuation.
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Koga, Y. "Fluctuations in aqueous methanol, ethanol, and propan-1-ol: amplitude and wavelength of fluctuation." Canadian Journal of Chemistry 77, no. 12 (December 5, 1999): 2039–45. http://dx.doi.org/10.1139/v99-213.
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Density, heat capacity, and isentropic compressibility data for aqueous methanol, ethanol, and propan-1-ol by Benson's group were used to evaluate two kinds of fluctuations; mean-square fluctuation densities; and (mean-square) normalized fluctuations, respectively, in volume, entropy, and cross (entropy/volume) effect. The mean-square fluctuation densitiesprovide measures for the amplitude (intensity) of the fluctuation, while the normalized fluctuations contain information regarding the wavelength (extensity) of the fluctuation. Furthermore, their composition derivatives, the partial molar fluctuationsof alcohols were calculated. These quantities signify the effect of additional solute on the respective fluctuations. These data were interpreted in terms of mixing schemes learned earlier in this laboratory by using the data of excess partial molar enthalpy, entropy, and volume, and the respective alcohol-alcohol interaction functions, i.e., the composition derivatives of partial molar quantities. Key words: aqueous methanol, ethanol, and propan-1-ol;fluctuation density; normalized fluctuation; partial molar fluctuations of alcohol.
11
Nelson, D. A. "Band Radiation From a Fluctuating Medium." Journal of Heat Transfer 111, no. 1 (February 1, 1989): 131–34. http://dx.doi.org/10.1115/1.3250633.
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A simple model of band radiation from a fluctuating medium, which emulates fluctuations in a turbulent diffusion flame, has been studied to determine the relative importance of the many mean and fluctuation parameters. The importance of fluctuations is largely confined to variation in the Planck function, which is strongly dependent upon the mean and variance of the mixture fraction and upon the band fundamental wavenumber.
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Rahav, Saar, and Christopher Jarzynski. "Nonequilibrium fluctuation theorems from equilibrium fluctuations." New Journal of Physics 15, no. 12 (December 20, 2013): 125029. http://dx.doi.org/10.1088/1367-2630/15/12/125029.
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Itto, Yuichi. "Conditional Entropic Approach to Nonequilibrium Complex Systems with Weak Fluctuation Correlation." Entropy 25, no. 4 (March 24, 2023): 556. http://dx.doi.org/10.3390/e25040556.
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A conditional entropic approach is discussed for nonequilibrium complex systems with a weak correlation between spatiotemporally fluctuating quantities on a large time scale. The weak correlation is found to constitute the fluctuation distribution that maximizes the entropy associated with the conditional fluctuations. The approach is illustrated in diffusion phenomenon of proteins inside bacteria. A further possible illustration is also presented for membraneless organelles in embryos and beads in cell extracts, which share common natures of fluctuations in their diffusion.
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Khovanov, Igor, Natalia Khovanova, and Peter McClintock. "Optimal control of fluctuations applied to the suppression of noise-induced failures of chaos stabilization." Izvestiya VUZ. Applied Nonlinear Dynamics 11, no. 3 (December 31, 2003): 46–55. http://dx.doi.org/10.18500/0869-6632-2003-11-3-46-55.
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Double strategy of chaos and fluctuation controls is developed. Noise-induced failures in the stabilization of аn unstable orbit in the one-dimensional logistic mар are considered as large fluctuations from a stable state. The properties of the large fluctuations are examined by determination and analysis of the optimal path and the optimal fluctuational force corresponding to the stabilization failure. The problem of controlling noise-induced large fluctuations is discussed, and methods of control have been developed.
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Shi-yao, Zhu, Zhou Chao, and Wang Cheng. "Experimental Investigation of the Magnetic Fluctuations in a Toroidal Plasma." Zeitschrift für Naturforschung A 48, no. 10 (October 1, 1993): 965–67. http://dx.doi.org/10.1515/zna-1993-1003.
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Abstract This paper presents experimental results on the magnetic field fluctuations in the KT-5C tokamak plasma, including magnetic field fluctuation frequency spectra and the radial profile of the fluctuation amplitudes. These results show that the low frequency components are dominant for the magnetic field fluctuation signals, and that the magnetic field fluctuation levels decrease towards the edge of the plasma. A remarkable influence of the gas puffing level on the amplitude of the magnetic field fluctuations was observed.
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Sakoda, Gen, Hideki Takayasu, and Misako Takayasu. "Tracking Poisson Parameter for Non-Stationary Discontinuous Time Series with Taylor’s Abnormal Fluctuation Scaling." Stats 2, no. 1 (January 23, 2019): 55–69. http://dx.doi.org/10.3390/stats2010005.
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We propose a parameter estimation method for non-stationary Poisson time series with the abnormal fluctuation scaling, known as Taylor’s law. By introducing the effect of Taylor’s fluctuation scaling into the State Space Model with the Particle Filter, the underlying Poisson parameter’s time evolution is estimated correctly from given non-stationary time series data with abnormally large fluctuations. We also developed a discontinuity detection method which enables tracking the Poisson parameter even for time series including sudden discontinuous jumps. As an example of application of this new general method, we analyzed Point-of-Sales data in convenience stores to estimate change of probability of purchase of commodities under fluctuating number of potential customers. The effectiveness of our method for Poisson time series with non-stationarity, large discontinuities and Taylor’s fluctuation scaling is verified by artificial and actual time series.
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Kato, Taro, Takuya Kitamura, Fumiya Maehara, Daigo Uchino, Kazuki Ogawa, Keigo Ikeda, Ayato Endo, Hideaki Kato, Takayoshi Narita, and Mitsuaki Furui. "Calculation of 1/f Fluctuation from Sound Signal and Comfort Evaluation." Applied Sciences 12, no. 19 (September 20, 2022): 9425. http://dx.doi.org/10.3390/app12199425.
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Providing a comfortable sound for users is an important factor for high-value products. Therefore, many studies have investigated pleasant sound levels for developing and manufacturing new products. Notably, sounds containing 1/f fluctuations provide a relaxing effect in humans. There are many studies on the influence of sound signals, including 1/f fluctuations; however, the verification of fluctuations, including sound signals, has not been performed. In this study on fluctuation, the discrete Fourier transform was used to directly calculate the time of the sound signal. We evaluated the duration of music and the 1/f fluctuation via the discrete Fourier transform using the time history of the music data. Furthermore, we investigated the relaxation effect of music containing a 1/f fluctuation. We determined a person’s comfort according to the difference in the calculated fluctuation coefficient by subjectively evaluating the comfort felt by people when listening to music with two different fluctuation coefficients, and we examined the improvement in the fluctuation coefficient and human comfort.
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Sims-Williams, D. B., and D. A. Luck. "Transfer function characterization of pressure signal tubes for the measurement of large amplitude pressure fluctuations." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 221, no. 6 (June 1, 2007): 707–13. http://dx.doi.org/10.1243/0954406jmes582.
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The measurement of fluctuating pressures in gasses is relevant to a wide range of fluid flow applications. The frequency response of pressure measurement systems using remote transducers is usually limited by the response of the connecting tubing. For small fluctuation levels it is well established that the signal distortion can be corrected using a transfer function technique. This work extends the approach to include the more challenging issue of large amplitude fluctuations where the transfer function is strongly dependent on the fluctuation amplitude as well as frequency. The tubing transfer function was found to closely depend on the ratio of the standard deviation of the pressure fluctuation and the absolute pressure ( PSTD/ PABS). An algorithm for correction is described and demonstrated. Levels of PSTD/ PABS of up to 0.6 have been tested and distortions of up to 250 per cent have been corrected to within 5 per cent.
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Okonkwo, Onyinye, Renaud Escudie, Nicolas Bernet, Rahul Mangayil, Aino-Maija Lakaniemi, and Eric Trably. "Bioaugmentation enhances dark fermentative hydrogen production in cultures exposed to short-term temperature fluctuations." Applied Microbiology and Biotechnology 104, no. 1 (November 21, 2019): 439–49. http://dx.doi.org/10.1007/s00253-019-10203-8.
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AbstractHydrogen-producing mixed cultures were subjected to a 48-h downward or upward temperature fluctuation from 55 to 35 or 75 °C. Hydrogen production was monitored during the fluctuations and for three consecutive batch cultivations at 55 °C to evaluate the impact of temperature fluctuations and bioaugmentation with synthetic mixed culture of known H2 producers either during or after the fluctuation. Without augmentation, H2 production was significantly reduced during the downward temperature fluctuation and no H2 was produced during the upward fluctuation. H2 production improved significantly during temperature fluctuation when bioaugmentation was applied to cultures exposed to downward or upward temperatures. However, when bioaugmentation was applied after the fluctuation, i.e., when the cultures were returned to 55 °C, the H2 yields obtained were between 1.6 and 5% higher than when bioaugmentation was applied during the fluctuation. Thus, the results indicate the usefulness of bioaugmentation in process recovery, especially if bioaugmentation time is optimised.
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Artemenko, S. N. "Modification of charge density wave fluctuations by charge perturbations." Journal de Physique IV 12, no. 9 (November 2002): 77–78. http://dx.doi.org/10.1051/jp4:20020359.
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Spectral density of fluctuations of the CDW phase are calculated taking into account electric field induced by phase fluctuations. The approach based upon the fluctuation-dissipation theorem (FDT) combined with equations of linear response of the CDW conductor is used. Fluctuating electric field is found to suppress fluctuations of the phase, while fluctuations of the electric potential are sizeable. This suggests that transition from the CDW to the normal state (which is usually observed well below the mean-field transition temperature) may he provoked by fluctuations of the chemical potential, rather than by destruction of the CDW coherence between conducting chains due to phase fluctuations.
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TAKAGI, K. "A STUDY ON TRANSIT TIME FLUCTUATION, AND CORRELATION BETWEEN LOW FREQUENCY PHASE AND CURRENT OR AMPLITUDE NOISES IN A TRANSISTOR." Fluctuation and Noise Letters 07, no. 04 (December 2007): C69—C74. http://dx.doi.org/10.1142/s0219477507004136.
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The low frequency phase and amplitude or average collector current noises are studied in a bipolar transistor. The transit time fluctuation is calculated from the diffusion coefficient fluctuation in the base. The phase noise is proportional to the base transit time fluctuation of the carriers. We discuss the relation between the phase and amplitude fluctuations and find both fluctuations correlate each other in low frequency. An experimental study is carried out in a bipolar transistor.
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Wang, Rui Hao. "Analysis on the Fluctuation of Wind Power." Applied Mechanics and Materials 733 (February 2015): 199–202. http://dx.doi.org/10.4028/www.scientific.net/amm.733.199.
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This paper is aimed at exploring the characteristic fluctuation of wind power based on samples from a certain wind farm. First, the paper is to analyze fluctuations of wind power at different time scales. According to a sliding difference algorithm to build wind power fluctuations evaluation. Wind power fluctuation index for different time scales are used to fit probability distributions, indicating that the best form of distribution of wind power fluctuations is t location scale distribution. Secondly, considering the wind power has the characteristics of non-linear, non-stationary signal of the data, it fully meets the wavelet neural network analysis of the characteristics of the data. Therefore, select wavelet neural network training and testing so as to make predictions about the future of the total power of wind farm. It points out the differences between different regions covered by the index from the fluctuation characteristics of wind power, thus further understanding the fluctuation characteristics of wind power: Influenced by the time and space distribution and other factors, there is a big difference between the output power fluctuation characteristics of single wind generator and wind farm, which is because of the different wind machine in the field by the wind energy differences, and the wake effect of organic groups, making frequent fluctuations in power distribution; the fluctuation of wind is gentle, i.e. with increasing spatial distribution scale, so gentle effect occurs to wind power fluctuations. Finally, through the analysis of the fluctuation characteristics of power, power factor and analyses the influence of the characteristics of fluctuation, the paper draws a conclusion of the following improvement programs to overcome the adverse effects of wind power fluctuation of power grid operation: the rational allocation of energy storage devices, expanding the coverage area of a wind farm, or improving the design of the windmill, which will make wind farms adapt to different wind directions, thus eliminating the impact of fluctuations on the power grid from the wind farm power output by the energy storage device, and covering the area of large wind farms can adapt to different wind directions, and with power complementary, it has achieved the amount of stable power transmission into the grid.
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Lu, Yi, Hengchi Lei, Kuo Zhou, and Lingkun Ran. "Gravity Wave Characterization of Multiple Convections in the Beijing–Tianjin–Hebei Region." Remote Sensing 15, no. 20 (October 19, 2023): 5024. http://dx.doi.org/10.3390/rs15205024.
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Using high-precision microbarograph data and radar data to analyze the gravity fluctuation characteristics of four convective processes of different intensities that occurred in the Beijing–Tianjin–Hebei region in June 2018, the results show that convective cases are accompanied by gravity fluctuations of different time scales and can be separated from the background field through the wavelet transform. The stronger the convective process, the larger the fluctuation amplitude. As the convection gradually approaches the station, the fluctuation frequency broadens, and smaller period fluctuations are excited. Through Fourier analysis, the longer period of fluctuation is concentrated at about 190 min, and the power spectrum of the short-period fluctuation is weak, with a peak frequency of about 2.04 × 10−4 Hz. The results obtained by wavelet transform are similar to them, but they reflect the characteristics of fluctuation evolution over time: (1) convection-related gravity wave periods are mainly concentrated in three bands: 15–40 min, 40–120 min, and 120–250 min; (2) there may be precursor activity before the occurrence of the convective flow, and the long-period fluctuation occurs about 1–4 h ahead of time; (3) there is a short-period fluctuation in the process of convective system development, and the period range is mainly concentrated at about 40–120 min; strong convective clouds may inspire shorter-period fluctuations. The geometrical relationship between the microbarograph stations shows that the short-period fluctuations of the four convective cases propagate at a speed of 14–37 m/s, and the azimuthal angle is consistent with the convective orientation, which indicates that there is a close relationship between gravity waves and convection.
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Moreno-Casasola, Patricia, John Philip Grime, and M. Luisa Martínez. "A comparative study of the effects of fluctuations in temperature and moisture supply on hard coat dormancy in seeds of coastal tropical legumes in Mexico." Journal of Tropical Ecology 10, no. 1 (February 1994): 67–86. http://dx.doi.org/10.1017/s0266467400007720.
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ABSTRACTThe effect of fluctuations in temperature and moisture supply on hard seeds of nine tropical coastal sand dune legumes, including herbs (Schrankia atiadrivalvis, Macropiilium atropurpureum and Canavalia rosea), and shrubs (Acacia farncsiana, A. macracantha, Mimosa chaetocarpa, Indigoftra sujjruticosa, Crolalaria incana and Chamaecrista chamaecrutoides), has been studied under laboratory and field conditions. Using a fluctuating temperature gradient bar seeds buried in sand were exposed to various amplitudes of diurnal temperature fluctuation over an extended period of time and seed germinability was examined at intervals. Germination percentage increased considerably in most species as a consequence of treatment with marked effects occurring at temperature fluctuations greater than 20°C and becoming detectable after 45 days. In several species the effect of applying wetting and drying cycles was to lower the amplitude of temperature fluctuation necessary to soften the seeds. Species can be grouped into physiological groups on the basis of differences in seed response to temperature fluctuations. It is suggested that these differences may help to explain the mechanisms distinguishing the different colonization patterns observed in tropical sand dune systems.
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SCHMID, FRIEDERIKE. "FLUCTUATIONS IN LIPID BILAYERS: ARE THEY UNDERSTOOD?" Biophysical Reviews and Letters 08, no. 01n02 (June 2013): 1–20. http://dx.doi.org/10.1142/s1793048012300113.
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We review recent computer simulation studies of undulating lipid bilayers. Theoretical interpretations of such fluctuating membranes are most commonly based on generalized Helfrich-type elastic models, with additional contributions of local "protrusions" and/or density fluctuations. Such models provide an excellent basis for describing the fluctuations of tensionless bilayers in the fluid Lαphase at a quantitative level.However, this description is found to fail for membranes in the gel phase and for membranes subject to high tensions. The fluctuations of tilted gel membranes (Lβ′phase) show a signature of the modulated ripple structure Pβ′, which is a nearby phase observed in the pretransition regime between the Lαand Lβ′state. This complicates a quantitative analysis on mesoscopic length scales. In the case of fluid membranes under tension, the large-wavelength fluctuation modes are found to be significantly softer than predicted by theory.In the latter context, we also address the general problem of the relation between frame tension and the fluctuation tension, which has been discussed somewhat controversially in recent years. Simulations of very simple model membranes with fixed area show that the fluctuations should be controlled by the frame tension, and not by the internal tension.
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Wang, Z. G., Y. Q. Sun, and Y. Zheng. "Study of the Dynamical Model for Manufacturing and Materials Market." Key Engineering Materials 693 (May 2016): 1954–59. http://dx.doi.org/10.4028/www.scientific.net/kem.693.1954.
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Econophysics is a new interdiscipline where physics concept and methods are applied to financial analysis. For example, the application of theoretical physics in the modeling of financial markets has aroused wide concern. In the process of random fluctuation of prices in financial markets, many nonlinear dynamical problems are hidden in set coefficients and assumptions, resulting in the invisibility of market price fluctuations and unavailability of hidden benefits in fluctuations. Based on the analysis of price fluctuation mechanism in financial markets, this paper analyzes the characteristics of price fluctuation, and constructs the dynamical model of price fluctuation by means of physics theory, thereby providing a theoretical reference for the control and prevention of transaction risks.
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Yang, Taiji, Siqi Zhuo, and Yongsheng Yang. "“Investor attention fluctuation and stock market volatility: Evidence from China”." PLOS ONE 18, no. 11 (November 27, 2023): e0293825. http://dx.doi.org/10.1371/journal.pone.0293825.
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This paper examines the linkage between Chinese stock market volatility and investor attention fluctuation. In Heterogeneous autoregressive (HAR) model, first, we analyzed the linkage between both decomposed and undecomposed stock market realized volatility and investor attention fluctuations across full-sample and two-year moving window sub-samples. Second, we compare the predictive power of four models in short-, medium-, and long-term volatility forecasting. Empirical results show large positive attention fluctuation amplified Chinese stock market volatility after the outbreak of COVID-19, and negative small attention fluctuation significantly stabilized stock market volatility before COVID-19, and the impact dwindled in after COVID-19. The model incorporating decomposed realized volatility and decomposed attention fluctuation performs better in volatility Forecasting. This research underscores a shift in the dynamics between stock market volatility and investor attention fluctuations, and investor attention fluctuation improves the volatility forecasting accuracy of the Chinese stock market.
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KOIKE, MASAFUMI, and JOE SATO. "EFFECTS OF MATTER DENSITY FLUCTUATION IN LONG BASELINE NEUTRINO OSCILLATION EXPERIMENTS." Modern Physics Letters A 14, no. 19 (June 21, 1999): 1297–302. http://dx.doi.org/10.1142/s0217732399001383.
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The effects of matter density fluctuation in long baseline neutrino oscillation experiments are studied. Effects of short wavelength fluctuations are irrelevant. Effects of long wavelength fluctuations must be checked on a case-by-case basis. As an example we checked the fluctuation effects and showed its irrelevance in a case of K2K experiments.
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Van Liere, Marti J., Eric-Alain D. Ategbo, Jan Hoorweg, Adel P. Den Hartog, and Joseph G. A. J. Hautvast. "The significance of socio-economic characteristics for adult seasonal body-weight fluctuations: a study in north-western Benin." British Journal of Nutrition 72, no. 3 (September 1994): 479–88. http://dx.doi.org/10.1079/bjn19940049.
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Large variations in seasonal body-weight fluctuations have been described for individuals from different households living and working under comparable circumstances. In the present study the relationship between socio-economic household characteristics and seasonal body-weight fluctuations of individual members of rural Beninese households were studied. No significant correlation was found for body-weight fluctuation between the two study years, nor for body-weight fluctuation of men and women belonging to the same household. When comparing dichotomized socio-economic classes for relative body-weight fluctuation of men and women in both study years, no consistent trends were observed for both years nor for both sexes. The distribution of subjects with a consistent high weight fluctuation over the two study years did not differ between socio-economic groups. In conclusion it may be stated that there were no indications that socio-economic characteristics play a determining role in the magnitude of body-weight fluctuation of this study population, despite the large variations observed in the latter. Therefore it is most likely that other factors decide the weight fluctuations of individuals, health and sanitation being the most likely candidates.
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Zhang, Bei Chen, Qing Lian Li, Yuan Wang, and Jian Qiang Zhang. "Analysis of Two-Phase Pressure Drop Fluctuation Characteristics in a Single Mini-Channel." Defect and Diffusion Forum 366 (April 2016): 151–56. http://dx.doi.org/10.4028/www.scientific.net/ddf.366.151.
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Two-phase pressure drop fluctuations during flow boiling in a single mini-channel were experimentally investigated. Degassed water was tested in circular cross section mini-channels with the hydraulic diameter of 1.0 mm at liquid mass fluxes range of 21.19-84.77 kg m-2 s-1 and heat fluxes of 0~155.75 kW m-2. Effects of heat flux and mass flux on pressure drop fluctuations were discussed based on the time and frequency domain analysis of the measured pressure drop. Two types of fluctuations were identified, which are the incipient boiling fluctuation (IBF) and the explosive boiling fluctuation (EBF) respectively. The IBF is a low frequency low amplitude fluctuation, which relates to the bubble dynamics when incipient boiling occurs. It is sensitive to the thermal and flow conditions. With the increase of heat flux and mass flux, the IBF is suppressed. The EBF is a low frequency high amplitude fluctuation, which occurs near the critical heat flux.
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Li, Xixi. "Cascading Propagation Path of Vinyl Chloride Process Risk Based on Complex Network." Academic Journal of Science and Technology 9, no. 2 (February 23, 2024): 149–54. http://dx.doi.org/10.54097/cxw6gf62.
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In the production of vinyl chloride, small parameter fluctuations may lead to large-scale cascade fluctuations, causing serious economic losses and casualties, in order to ensure the safety and stability of production, it is necessary to study the cascade fluctuation propagation path of vinyl chloride production process. In this paper, a complex network model of vinyl chloride production process is constructed based on complex network theory, and the concept of comprehensive degree considering network direction is introduced to identify important nodes in the network: secondly, the fluctuation overload propagation probability and material hazard degree of the edge are used to define the fluctuation overload propagation intensity of the edge; finally, according to the fluctuation overload propagation intensity, the risk propagation path of cascading fluctuations under different overload modes is obtained by using ant colony algorithm, it provides a basis for the prevention of cascade overload and the selection and protection of key monitoring nodes.
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Zhang, Sheng. "Trade Opening and The Real Effective Exchange Rate of the RMB." Frontiers in Business, Economics and Management 11, no. 2 (October 11, 2023): 54–60. http://dx.doi.org/10.54097/fbem.v11i2.12163.
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This paper uses the Redux model and shows that the fluctuation of the RMB under certain fluctuations; then analyzes the effect of the fluctuation of the RMB on the actual effective exchange rate. The study found that trade opening can reduce the fluctuation of the real effective exchange rate of the RMB; the rationalization of industrial structure can also enhance trade opening and restrain the real effective exchange rate fluctuation of the RMB. Meanwhile, the "Belt and Road" initiative intensifies the real effective exchange rate fluctuation of the RMB, possibly due to the change of the "Belt and Road" initiative and implementation in the total industrial structure of import and export. Therefore, all provinces (autonomous regions and municipalities directly under the Central Government) should increase basic research such as science and technology, promote the rationalization of industrial structure, and make the help of the good opportunity of the "Belt and Road" initiative to reduce the real effective exchange rate fluctuations of RMB.
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Dooner, D. B. "Use of Noncircular Gears to Reduce Torque and Speed Fluctuations in Rotating Shafts." Journal of Mechanical Design 119, no. 2 (June 1, 1997): 299–306. http://dx.doi.org/10.1115/1.2826251.
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A methodology is presented where noncircular gears are used to reduce unwanted torque and speed fluctuations that may exist in rotating shafts. A noncircular gear pair is used to drive an auxiliary shaft where a flywheel is mounted, thus creating an auxiliary torque fluctuation. The form of the undesirable torque fluctuation is used to determine a motion specification for the synthesis of a noncircular gear pair. The undesired torque fluctuation and the auxiliary torque fluctuation are added to reduce the net torque fluctuation. Two illustrative examples are included. This approach of torque balancing is compared to the classical method of mounting a flywheel onto the shaft that experiences the unwanted torque fluctuation to reduce its speed variation.
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Li, Ming, and Wei Zhao. "Wild Fluctuations of Random Functions with the Pareto Distribution." Mathematical Problems in Engineering 2013 (2013): 1–3. http://dx.doi.org/10.1155/2013/767502.
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This paper provides the fluctuation analysis of random functions with the Pareto distribution. By the introduced concept of wild fluctuations, we give an alternative way to classify the fluctuations from those with light-tailed distributions. Moreover, the suggested term wildest fluctuation may be used to classify random functions with infinite variance from those with finite variances.
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WOJTKOWSKI, MACIEJ P. "Abstract fluctuation theorem." Ergodic Theory and Dynamical Systems 29, no. 1 (February 2009): 273–79. http://dx.doi.org/10.1017/s0143385708000163.
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AbstractWe formulate an abstract fluctuation theorem which sheds light on mathematical relations between the fluctuation theorems of Bochkov and Kuzovlev [Contribution to the general theory of thermal fluctuations in nonlinear systems. Sov. Phys.–JETP45 (1977), 125] and Jarzynski [Hamiltonian derivation of a detailed fluctuation theorem. J. Stat. Phys.98 (2001), 77–102] on the one hand, and those of Evans and Searles [Equilibrium microstates which generate second law violating steady states. Phys. Rev. E 50 (1994), 1645–1648] and Gallavotti and Cohen [Dynamical ensembles in stationary states. J. Stat. Phys.80 (1995), 931–970] on the other.
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Jia, Dongya, Ratnadeep Mukherjee, and Grégoire Altan-Bonnet. "Fluctuation of cell numbers and kinetics reveals dynamical hematopoiesis." Journal of Immunology 210, no. 1_Supplement (May 1, 2023): 65.10. http://dx.doi.org/10.4049/jimmunol.210.supp.65.10.
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Abstract Fluctuations of multiple blood cell types (B cells, neutrophils, reticulocytes, platelets etc.) have been reported in many hematological disorder and leukemia patients. It remains largely elusive about the mechanisms underlying cell fluctuation. To quantify the dynamics of blood cells, we performed a longitudinal studies of blood profiling using identical healthy mice. We combine a pulse protocol of 5-iodo-20-deoxyuridine (IdU) injections with subsequent analysis by mass cytometry (CyTOF and CyTEK) and mathematical modeling of the cell dynamics. We demonstrate that cell abundance exhibits large fluctuations, and a 10-fold change has been observed for the blood neutrophil numbers in healthy mice. Although individual cell type is fluctuating, different cell types exhibit strong correlation/anti-correlations, such as the anti-correlated cell numbers of B cells and neutrophils. The large fluctuation of cell numbers motivated us to characterize cell kinetics, such as the proliferation rate. Through the IdU pulse experiments, we show that cell proliferation rates also exhibit large variation across identical mice. Strikingly, we observe a broad involvement of cell types in exhibiting strong positive correlations of their proliferation rates. Through mathematical modeling, we show that the burst of B cell proliferation often reduces the plasticity of the hematopoietic system and result in regular oscillatory behaviors of B cells, neutrophil etc., which is consistent with the previous reports. A better understanding of the fluctuation of cell numbers and kinetics can afford a better administration of therapies for blood disorder patients.
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Meng, Tao, Huanchang Wei, Feng Gao, and Huichao Shi. "Measurement of Flow Fluctuation in the Flow Standard Facility Based on Singular Value Decomposition." Sensors 21, no. 20 (October 15, 2021): 6850. http://dx.doi.org/10.3390/s21206850.
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In order to accurately evaluate the flow stability of the flow standard facility, the flow fluctuation in the standard facility needs to be accurately measured. However, the flow fluctuation signal is always superimposed with the fluctuation signal of the measuring flowmeter or measurement system (mainly noise), which leads to inaccurate measurement of the flow fluctuation and even an unreliable evaluation result of the flow stability. In addition, when there are multiple fluctuation sources, flow fluctuations with different frequencies are superimposed together, which is extremely unfavorable for evaluating the impact of flow fluctuation with different single frequencies. In this paper, a new measuring method was proposed to obtain the fluctuation signal and the flow fluctuation based on singular value decomposition (SVD). Simulation experiments on the fluctuation signal (single frequency and multiple frequencies) under different levels of noise were conducted, and simulation results showed that the proposed method could accurately obtain the fluctuation signal and the flow fluctuation, even under high noise. Finally, an experimental platform was set-up based on a water flow standard facility and a flow fluctuation generator, and experiments on the output signal of a venturi flowmeter were carried out. The experiment results showed that the proposed method could effectively obtain the fluctuation signal and accurately measure the flow fluctuation.
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Searles, Debra J., and Denis J. Evans. "Fluctuations Relations for Nonequilibrium Systems." Australian Journal of Chemistry 57, no. 12 (2004): 1119. http://dx.doi.org/10.1071/ch04115.
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Fluctuation relations have been developed over the past decade, which describe the statistical fluctuations in time-averaged properties of many-particle, nonequilibrium systems such as fluids. The fluctuation theorems show how thermodynamic irreversibility emerges from the time-reversible dynamics of the constituent molecules, and are thus of fundamental importance. The relationships also make quantitative predictions on fluctuations in small systems that are monitored over short periods, and these have been verified numerically and experimentally. Fluctuation theorems are thus anticipated to play an important role in the design of nanotechnological devices and understanding of biological processes. These relationships and their importance are summarized.
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Crespo-Miguel, Rodrigo, and Francisco J. Cao-García. "Predictability of Population Fluctuations." Mathematics 10, no. 17 (September 3, 2022): 3176. http://dx.doi.org/10.3390/math10173176.
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Population dynamics is affected by environmental fluctuations (such as climate variations), which have a characteristic correlation time. Strikingly, the time scale of predictability can be larger for the population dynamics than for the underlying environmental fluctuations. Here, we present a general mechanism leading to this increase in predictability. We considered colored environmental fluctuation acting on a population close to equilibrium. In this framework, we derived the temporal auto and cross-correlation functions for the environmental and population fluctuations. We found a general correlation time hierarchy led by the environmental-population correlation time, closely followed by the population autocorrelation time. The increased predictability of the population fluctuations arises as an increase in its autocorrelation and cross-correlation times. These increases are enhanced by the slow damping of the population fluctuations, which has an integrative effect on the impact of correlated environmental fluctuations. Therefore, population fluctuation predictability is enhanced when the damping time of the population fluctuation is larger than the environmental fluctuations. This general mechanism can be quite frequent in nature, and it largely increases the perspectives of making reliable predictions of population fluctuations.
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Liu, J. T. C. "An extended Reynolds analogy for excited wavy instabilities of developing streamwise vortices with applications to scalar mixing intensification." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 463, no. 2083 (May 16, 2007): 1791–813. http://dx.doi.org/10.1098/rspa.2007.1848.
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Studies are presented to elucidate the role of steady streamwise vortex structures, initiated upstream from weak Görtler vortices in the absence of explicit vortex generators, and their excited nonlinear wavy instabilities in the intensification of scalar mixing in a spatially developing mixing region. While steady streamwise vortex flow gives rise to significant mixing enhancement, the excited nonlinear wavy instabilities, which in turn modify the basic three-dimensional streamwise vortices, give rise to further mixing intensification which is quantitatively assessed by a mixedness parameter. Possibility of similarity between the dimensionless streamwise momentum and scalar transport problems leading to an extended Reynolds analogy is sought. This similarity is shown earlier to hold for the steady streamwise vortex flow in the absence of nonlinear wavy instabilities (Liu & Sabry 1991 Proc. R. Soc. A 432 , 1–12). In this paper, the momentum conservation equations for the nonlinear wavy or secondary instabilities together with the advected fluctuation scalar problems are examined in detail. The presence of the streamwise fluctuation pressure gradient, which prevents the similarity, is estimated in terms of the fluctuation dynamical pressure and its relative importance to advective transport. It is found from scaling that the fluctuating streamwise pressure gradient, though not completely negligible, is sufficiently unimportant so as to render similarity between fluctuation streamwise velocity and fluctuation temperature and concentration a distinct possibility. The scalar fluctuations are then inferable from the fluctuation streamwise velocity and that the Reynolds stresses of the nonlinear fluctuations and the scalar fluxes are also similar. The nonlinear instability-modified mean streamwise momentum and the modified mean heat and mass transport problems are also similar, thus providing a complete ‘Reynolds analogy’, rendering possible the interpretation of the scalar mixedness for a gaseous medium for which the Prandtl and Schmidt numbers are near unity. It is found that the nonlinearity of the wavy instability, which induces scalar fluxes modifying the mean scalar transport, further intensifies scalar mixedness over a significant streamwise region which is well above that achieved by the steady, unmodified streamwise vortices alone for the numerical example corresponding to the most amplified wavy-sinuous mode.
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Jia, Xiao-Qi, Bao-Ling Cui, Zu-Chao Zhu, and Yu-Liang Zhang. "Experimental Investigation of Pressure Fluctuations on Inner Wall of a Centrifugal Pump." International Journal of Turbo & Jet-Engines 36, no. 4 (November 18, 2019): 401–10. http://dx.doi.org/10.1515/tjj-2016-0078.
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Abstract Affected by rotor–stator interaction and unstable inner flow, asymmetric pressure distributions and pressure fluctuations cannot be avoided in centrifugal pumps. To study the pressure distributions on volute and front casing walls, dynamic pressure tests are carried out on a centrifugal pump. Frequency spectrum analysis of pressure fluctuation is presented based on Fast Fourier transform and steady pressure distribution is obtained based on time-average method. The results show that amplitudes of pressure fluctuation and blade-passing frequency are sensitive to the flow rate. At low flow rates, high-pressure region and large pressure gradients near the volute tongue are observed, and the main factors contributing to the pressure fluctuation are fluctuations in blade-passing frequency and high-frequency fluctuations. By contrast, at high flow rates, fluctuations of rotating-frequency and low frequencies are the main contributors to pressure fluctuation. Moreover, at low flow rates, pressure near volute tongue increases rapidly at first and thereafter increases slowly, whereas at high flow rates, pressure decreases sharply. Asymmetries are observed in the pressure distributions on both volute and front casing walls. With increasing of flow rate, both asymmetries in the pressure distributions and magnitude of the pressure decrease.
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Ghozali, Ghozali. "Pengaruh Iklim dan Fluktuasi Harga Bawang Merah dan Bawang Putih terhadap Pendapatan Petani (Studi Kasus pada Petani Sayur di Pacet Mojokerto)." JEBDEER: Journal of Entrepreneurship, Business Development and Economic Educations Research 1, no. 1 (December 11, 2017): 35–44. http://dx.doi.org/10.32616/jbr.v1i1.53.
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Many people are involved in the vegetable trade business, the majority of farmers in Pacet plunge in planting shallot and garlic, Along with the number of traders, the majority of demand more and more, and when the harvest price is very low and make the farmers lose, and when the season Rain arrives, farmers in the Pacet region many do not plant, so the scarcity of shallot and garlic price is rising. The purpose of this paper is the influence of climate and price fluctuations simultaneously affect the farmer's income, climate influence and price fluctuations affect partially on the market, the variables that predominantly affect the income level of farmers.
The results showed that climate and fluctuation influence simultaneously to farmer's earnings that is X1 (Climate) and X2 (Price fluctuation) obtained F value count bigger than F table value (4,391> 3,35). Climate and price fluctuation have partial effect to farmer's income t value (3,45> 2,055) with significance level less than 0,05 0.008 and t variable X2 (price fluctuation) bigger than t table (8.561> 2.055) with significance level below 0.05 ie 0.002. And the most dominant variable influencing farmer's income is price fluctuation from SPSS result shows between variable X1 (climate) and variable X2 (price fluctuation) obtained In variable X1, pearson correlation 0,381 <pearson correlation X2 0,081 This means that variable X2 price fluctuations are more influential on farmers' income.
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Tano, K., L. Z. Lee, F. Castaigne, and J. Arul. "Impact of Storage Temperature Fluctuation on Modified-atmosphere Packaging of Fresh Produce." HortScience 30, no. 4 (July 1995): 811D—811. http://dx.doi.org/10.21273/hortsci.30.4.811d.
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Use of modified atmosphere (MA) as an adjunct to low temperature can be effective method for prolonging the shelflife of fresh fruits and vegetables. However, if storage temperature fluctuates, anoxic conditions can result and, consequently, the fresh produce quality can deteriorate rapidly. The objective of this investigation was to evaluate the effects of temperature fluctuation on the atmosphere inside the package and on the quality of packaged produce. Mushrooms (A. bisporus, U3 Sylvan 381) were packaged in rigid containers (4 liters) fitted with diffusion windows to obtain an atmosphere of 5% O2 and 10% CO2 at 4C. Temperature fluctuation had a major impact to the atmosphere inside package. During the first fluctuation sequence, O2 level depleted to 1.5% and CO2 increased to 18%. When the temperature returned to 4C during the next sequence, CO2 level fell back to 10%, but O2 level remained at 1.5%. The quality of mushrooms stored under temperature-fluctuating conditions was severely affected, as indicted by the extent of browning, loss of texture, and level of ethanol in the tissue compared to mushrooms stored at constant temperature. It was clear from this experiment that under temperature fluctuation, even it occurs once, can seriously compromise the benefits of MA packaging and safety of the packaged product. It is thus necessary that MA packaging compensate for the additional permeability required that is caused by storage temperature fluctuations.
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Gong, Can-Sheng, Yan-Zhen Li, Rui-Zhi Yang, Meng-Nan Chen, Hang-Ling Qiu, Jun-Dan Jiang, Xiao-Chun Zheng, and Cai-Zhu Lin. "Impact of Intraoperative Hemodynamic Fluctuation on Postoperative Complications in Patients With Pheochromocytoma and Paraganglioma Surgery." American Journal of Hypertension 35, no. 9 (September 1, 2022): 833–34. http://dx.doi.org/10.1093/ajh/hpac038.
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Abstract Background To identify the effect of hemodynamic fluctuations on severe postoperative complications in patients undergoing surgery for pheochromocytoma and paraganglioma (PPGL). Methods Patients with PPGL confirmed by postoperative pathologic examination in Fujian Provincial Hospital from January 2015 to January 2021 were enrolled. Demographic characteristics, comorbidities, preoperative examinations, preoperative preparation, intraoperative data, and postoperative complications were collected. Receiver operating characteristic curve was used to calculate the cutoff point of intraoperative standard deviation of systolic blood pressure for prediction of severe postoperative complication. According to the cutoff point, patients were divided into fluctuation and nonsevere fluctuation groups. Incidence of postoperative complication, intensive care unit (ICU) admission, length of stay after the operation, and length of ICU stay between the 2 groups was compared. The cumulative incidence and hazard ratio of postoperative complications were evaluated by Kaplan�Meier method and Cox regression analysis. Results A total of 126 patients were included in the study with 41 and 85 cases in the severe fluctuation and nonsevere fluctuation groups, respectively. Compared with the nonsevere fluctuation group, the incidence of postoperative complications (58.5% vs. 16.5%, P < 0.001), ICU admission rate (26.8% vs. 10.6%, P = 0.019), postoperative hospital stay, and ICU stay (P < 0.05) were higher in the severe fluctuation group. The Kaplan–Meier curve showed a higher incidence of postoperative complications in patients with severe blood pressure fluctuations (P < 0.05). The Cox regression analysis also showed that patients in the severe fluctuation group were more susceptible to postoperative complications (hazard ratio = 3.010, 95% confidence interval 1.334–6.806). Conclusions For patients with PPGL, the intraoperative hemodynamic fluctuations are associated with an increased risk of severe postoperative complications.
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Li, Wei. "Analysis of Potential Fluctuation in Flow." Processes 10, no. 10 (October 17, 2022): 2107. http://dx.doi.org/10.3390/pr10102107.
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Understanding the physics of flow instabilities is important for processes in a wide range of engineering applications. Flow instabilities occur at the interfaces between moving fluids. Potential fluctuations are generated at the interfaces between two moving fluids based on the relationship of continuity. Theoretical analysis demonstrated that, in flow instabilities, potential fluctuation exhibits a potential oscillatory wave surface concurrently in the temporal and spatial dimensions. Potential fluctuations already internally exist in flow before flow instabilities begin to develop; these potential fluctuations greatly affect the formation of interpenetrating structures after forces act on the interfaces. Experimental studies supported the theoretical study: Experiments visualizing condensation flows using refrigerant in one smooth tube and one three-dimensional enhanced tube were conducted to show the development of potential fluctuation in spatial dimensions, and an experiment with cooling tower fouling in seven helically ridged tubes and one smooth tube were conducted to show the development of potential fluctuation in the temporal dimension. Both experimental studies confirmed that potential fluctuation was determined by the densities and velocities of the two fluids in the instability as indicated by the relationship of continuity. In addition, the results of numerical simulation in the literature qualitatively confirm the theoretical study. This paper is a first attempt to provide a comprehensive analysis of the potential fluctuation in flow.
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Ghosh, D., A. Deb, M. Mondal, R. Saha, and A. Mondal. "Fluctuation of fluctuations in pionisation: Target excitation dependence." Physics of Particles and Nuclei Letters 12, no. 2 (March 2015): 251–61. http://dx.doi.org/10.1134/s1547477115020132.
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Shiratani, Masaharu, Masahiro Soejima, Hyun Woong Seo, Naho Itagaki, and Kazunori Koga. "Fluctuation of Position and Energy of a Fine Particle in Plasma Nanofabrication." Materials Science Forum 879 (November 2016): 1772–77. http://dx.doi.org/10.4028/www.scientific.net/msf.879.1772.
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We are developing plasma nanofabrication, namely, nanoand micro scale guided assembly using plasmas. We manipulate nanoand micro objects using electrostatic, electromagnetic, ion drag, neutral drag, and optical forces. The accuracy of positioning the objects depends on fluctuation of position and energy of a fine particle (= each object) in plasmas. Here we evaluate such fluctuations and discuss the mechanism behind them. In the first experiment, we grabbed a fine particle in plasma using an optical tweezers. The fine particle moves in a potential well made by the optical tweezers. This is a kind of Brownian motion and the position fluctuation can be caused by neutral molecule collisions, ion collisions, and fluctuation of electrostatic force. Among theses possible causes, fluctuation of electrostatic force may be main one. In the second experiment, we deduced interaction potential between two fine particles during their Coulomb collision. We found that there exist repulsive and attractive forces between them. The repulsive force is a screened Coulomb one, whereas the attractive force is likely a force due to a shadow effect, a non-collective attractive force. Moreover, we noted that there is a fluctuation of the potential, probably due to fluctuation of electrostatic force. These position and potential energy fluctuations may limit the accuracy of guided assembly using plasmas.
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Yang, Yang, Xionghuan Chen, Ling Bai, Yulong Yao, Hui Wang, Leilei Ji, Zhaoming He, Xiangyu Song, and Ling Zhou. "Quantification and investigation of pressure fluctuation intensity in a multistage electric submersible pump." Physics of Fluids 35, no. 3 (March 2023): 035122. http://dx.doi.org/10.1063/5.0136664.
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Pressure fluctuation is an important factor affecting the stability of rotating machinery. Electric submersible pumps (ESPs) are generally arranged in a multistage series structure, and its internal unsteady flow is extremely easy to propagate and develop in the lengthy flow passage, which brings about differences in the characteristics of pressure fluctuations in each stage. In contrast to the conventional method of processing pressure fluctuation signals, we propose a parameter called “energy flow density (EFD)” of pressure pulsation by analogy with the definition of wave intensity, in order to directly quantify the intensity of pressure fluctuations. Here, we study these pressure fluctuation characteristics using a typical three-stage ESP as the research object. We apply theoretical analysis, numerical simulation, and test verification. First, in comparisons between numerical predictions of pressure fluctuation and test results, the period, amplitude, and phase of pulsation curves are highly consistent, verifying the accuracy of the numerical method employed in this paper. Next, the mechanism underlying the pressure fluctuations and the characteristics of inter-stage interference are investigated through flow field analysis. Subsequently, the results of the evaluation of the pressure fluctuations based on EFD processing are compared with those obtained in the conventional way. The results are consistent in terms of characterizing the multistage ESP pressure fluctuation characteristics, but the conventional method does not reflect subtle differences due to inter-stage propagation and coupling. However, the EFD method combines the amplitudes of all signals and provides the intensity of pressure fluctuations directly, which reflects inter-stage differences. Our results provide a theoretical basis for improving the operational stability of ESPs connected in a multistage series and have practical engineering significance.
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Liu, Chuanbo, Shutian Liu, Conglin Dong, Chengqing Yuan, and Xiuqin Bai. "The Reduction in the Deformation of HDPE Composites Using Self-Lubricating Fillers in an Aqueous Environment." Polymers 14, no. 3 (January 21, 2022): 433. http://dx.doi.org/10.3390/polym14030433.
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Reducing the deformation of polymer matrix materials can decrease the fluctuation of coefficient of friction (COF), and friction-induced vibration and its amplitudes. HDPE composites with T-ZnOw as a fixed strengthening filler were modified with the addition of Si3N4 particles at different concentrations. The COFs, wear rates, micro-morphologies, and friction-induced vibrations were obtained by conducting sliding tests against carbon steel balls in an aqueous environment at a low velocity and high load. The mechanism of the reduction in frictional fluctuation due to the addition of Si3N4 particles was revealed through the frictional responses. The results demonstrated that 4 wt% addition of Si3N4 in HDPE can enhance the strain–stress property and improve the lubrication by forming a lubricating film. Therefore, the surface deformation and the fluctuations of COFs and its vibrations were reduced. The aggregation phenomenon and reduced strain–stress response at a high concentration of Si3N4 disrupted the positive fluctuating reduction, and resulted in a rough surface with severe tearing and cracking deformations. Additionally, it led to fluctuating wear behaviors with high COF and vibrations. The results obtained in this study can elucidate the effects of adding Si3N4 particles to enhance lubrication in polymer composites. Additionally, the results provide a new research method for designing and manufacturing polymer-based composites with low friction-induced fluctuations.
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Han, Zefeng, Engang Wang, Zhongxin Zhai, and Zepeng Wang. "An Experiment on Surface Fluctuation of Ga-In-Sn Alloy with a Permanent Magnet Flow Control Mold." Metals 13, no. 10 (September 28, 2023): 1662. http://dx.doi.org/10.3390/met13101662.
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To control well the surface fluctuation of liquid metal in a slab mold, a new type of combined permanent magnets braking system, namely a permanent magnet flow control mold (PMFC-Mold) is proposed by our research group, of which its main feature is that the device can control the flow of molten steel in the mold without additional energy. To observe the fluctuation state of the alloy with the PMFC-Mold, instantaneous surface fluctuations were recorded by a laser level meter and camera. To study the effect of various casting speeds and permanent magnet placement on surface fluctuations, the three measurement points, which were 7, 18, and 36 mm away from the narrow surface of the mold, were selected to record the trend of level fluctuation. Three types of permanent magnet placement were designed by setting the differences between the height center of the permanent magnet and the free surface in the slab mold, which were H1 = 0 mm, H2 = −25 mm, and H3 = −75 mm. The experimental results indicated that with the acceleration of the casting speed, the average height and standard deviation of surface fluctuation at the measurement point increased, but the surface fluctuation pattern remained. When the permanent magnets were arranged at H1 = 0 mm and H2 = −25 mm, the position of the magnetic field was reasonable and the surface fluctuation could be effectively suppressed. In contrast, when the permanent magnets were arranged at H3 = −75 mm, the level fluctuation was intensified.