Journal articles: 'Four Fluctuations'

1

Gonçalves, Sérgio M. C. V., and Ian G. Moss. "Scalar curvature fluctuations on the four-sphere." Physics Letters B 401, no. 3-4 (May 1997): 254–57. http://dx.doi.org/10.1016/s0370-2693(97)00397-3.

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2

Yan-peng, Zhang, Wu Hong-cai, Wang Peng-fei, Li Chuang-she, and Fu Pan-ming. "Phase fluctuations on Raman-enhanced nondegenerate four-wave mixing." Chinese Physics 9, no. 8 (August 2000): 599–605. http://dx.doi.org/10.1088/1009-1963/9/8/009.

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3

Kofman, A. G., A. M. Levine, and Yehiam Prior. "Stochastic fluctuations in four-wave mixing: A unified theory." Physical Review A 37, no. 4 (February 1, 1988): 1248–60. http://dx.doi.org/10.1103/physreva.37.1248.

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4

Bucci, F., C. Castellani, C. Di Castro, and M. Grilli. "Charge fluctuations in the four-band extended Hubbard model." Physical Review B 52, no. 9 (September 1, 1995): 6880–93. http://dx.doi.org/10.1103/physrevb.52.6880.

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5

Zhang, Weiping, and Daniel F. Walls. "Sub-shot-noise intensity fluctuations in four-wave mixing." Physical Review A 41, no. 11 (June 1, 1990): 6385–92. http://dx.doi.org/10.1103/physreva.41.6385.

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6

Min, He Qun, Xiao Yang Huang, and Qi De Zhang. "Pressure Fluctuations and Flow-Induced Vibration Measurements in a Hard Disk Drive under Different Rotation Speeds." Applied Mechanics and Materials 197 (September 2012): 292–96. http://dx.doi.org/10.4028/www.scientific.net/amm.197.292.

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Flow-induced vibration (FIV) of a head gimbals assembly (HGA) in hard disk drives (HDDs) limits the positioning accuracy of magnetic head in the HGA for higher HDD magnetic recording density. The pressure fluctuations characterize turbulent fluctuations exciting the HGA off-track vibration (HGA-OTV). In this paper, experimental studies have been carried out to investigate the spectrum characteristics correspondence between pressure fluctuations around an HGA and the simultaneous HGA-OTV under different HDD rotation speeds. A practical and effective experimental setup has been implemented to enable the simultaneous measurements on both the pressure fluctuation and HGA-OTV signals, where pressure fluctuations are measured with a pressure transducer through a small hole on the HDD top cover and the direct HGA-OTV signals are detected through a laser Doppler vibrometer. Results under conditions of three different HDD rotation speeds of 7200, 9000, 10800 rpm have been investigated and compared. It is shown that the HGA off-track vibration spectra are highly associated with those of the pressure fluctuations in terms of principal peaks in four frequency bands around 1.8 kHz, 2.5-3.5 kHz, 7-7.5 kHz and 11.5-12.5 kHz. With increasing HDD rotation speed, it is shown that the spectrum magnitudes of both the pressure fluctuation and the HGA off-track vibration increase correspondingly, while the principal peak positions in spectra of either pressure fluctuation or the HGA off-track vibration always hold the line. This study demonstrates a causal nexus from the pressure fluctuation to the HGA off-track vibration and suggests the feasibility of controlling the HGA-OTV through suppression of pressure fluctuations around the HGA.

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7

Kume, Tatsuya, Masanori Satoh, Tsuyoshi Suwada, Kazuro Furukawa, and Eiki Okuyama. "Angle Detection Using Gyro Signals Rotating Around Four Orthogonally Aligned Axes." International Journal of Automation Technology 14, no. 1 (January 5, 2020): 52–58. http://dx.doi.org/10.20965/ijat.2020.p0052.

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An angle sensor can be used to evaluate profiles without any shape references. We regard it suitable for evaluating a large profile and consider a gyro as an angle sensor for evaluating a profile larger than 100 m with an accuracy of better than 1 mm. A gyro can evaluate profiles without restrictions in span or direction; however, angles detected by a gyro typically fluctuate unacceptably for our purpose. We demonstrate that periodical reversal measurement by flipping a gyro is effective in reducing the effect of the fluctuation. Then, we rotate the gyro for continuously realizing the reversal, where the angles of the gyro’s rotating axis against the earth’s rotating axis can be derived without being affected by the fluctuation, and can be used as an angle sensor. Here, we consider a new method using gyro signals rotating around four orthogonally aligned axes. This can improve the accuracy of the derived angles by eliminating the effects of the gyro’s scale factor as well as the fluctuations.

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8

Bloom, N. "Fluctuations in uncertainty." Voprosy Ekonomiki, no. 4 (April 20, 2016): 30–55. http://dx.doi.org/10.32609/0042-8736-2016-4-30-55.

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In this essay, the author addresses four questions about uncertainty. First, what are some facts and patterns about economic uncertainty? Both macro and micro uncertainty appear to rise sharply in recessions and fall in booms. Uncertainty also varies heavily across countries - developing countries appear to have about one-third more macro uncertainty than developed countries. Second, why does uncertainty vary during business cycles? Third, do fluctuations in uncertainty affect behavior? Fourth, has higher uncertainty worsened the Great Recession and slowed the recovery? Much of this discussion is based on research on uncertainty from the last five years, reflecting the recent growth of the literature.

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9

Parker, Jonathan A., and Bruce Preston. "Precautionary Saving and Consumption Fluctuations." American Economic Review 95, no. 4 (August 1, 2005): 1119–43. http://dx.doi.org/10.1257/0002828054825556.

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This paper uses the consumption Euler equation to derive a decomposition of consumption growth into four sources. These four sources are new information, and three sources of predictable consumption growth: intertemporal substitution, changes in the preferences for consumption, and incomplete markets for consumption insurance. Using household-level data, we implement this decomposition for the average growth rate of consumption expenditures on nondurable goods in the United States from 1982 to 1997. The economic importance of precautionary saving rivals that of the real interest rate, but the relative importance of each source of movement in the volatility of consumption is not precisely measured.

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10

Hershfield, Selman, and Vinay Ambegaokar. "Resistance fluctuations in a four-probe geometry with infinite leads." Physical Review B 38, no. 12 (October 15, 1988): 7909–12. http://dx.doi.org/10.1103/physrevb.38.7909.

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11

Koolaee, Elaheh, Hamed Mousavi, and Afifeh Abedi. "Fluctuations in Iran-Russia Relations During the Past Four Decades." Iran and the Caucasus 24, no. 2 (June 23, 2020): 216–32. http://dx.doi.org/10.1163/1573384x-20200206.

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Iran-Russia relations are highly affected by the shared interest of the two countries in confronting the influence of the United States in the Middle East, Central Asia and the Caucasus. However, the development of the relationship between the two countries has been hampered by the ongoing legacy of historical antagonism between them, casting doubt and pessimism upon the prospect of more constructive bilateral relations. Two groups of internal and external factors are the main obstacles to the expansion of cooperation between Iran and Russia. First, the lack of economic overlap or affiliation between Iran’s dependent economy and Russia's energy exports, and the state-based nature of both economies, as well as their cultural and social differences. Second, despite the Nuclear Deal, the difficulties in relations between the West, Russia and Iran remain a barrier to the expansion of Iran-Russia cooperation.

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12

Hershfield, Selman. "Resistance fluctuations with magnetic impurities in a four-terminal geometry." Physical Review B 44, no. 7 (August 15, 1991): 3320–23. http://dx.doi.org/10.1103/physrevb.44.3320.

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13

Iida, Shinji, and Axel Müller-Groeling. "Resistance fluctuations in four-lead devices: A statistical scattering approach." Physical Review B 44, no. 15 (October 15, 1991): 8097–106. http://dx.doi.org/10.1103/physrevb.44.8097.

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14

Hershfield, Selman. "Current conservation and resistance fluctuations in a four probe geometry." Annals of Physics 196, no. 1 (November 1989): 12–70. http://dx.doi.org/10.1016/0003-4916(89)90044-4.

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15

Matsui, Naohiro. "11-Year Rainfall and Maize Yield Variation (2003-2013) in Four Northern Districts of Malawi." Journal of Agricultural Science 8, no. 5 (April 13, 2016): 95. http://dx.doi.org/10.5539/jas.v8n5p95.

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<p>Rainfall in the maize cropping season (Oct-Apr) in the four northern districts of Malawi was examined in terms of seasonal fluctuation and spatial distribution, and data spanning 11 years were analyzed. Rainfall fluctuations in the 11-year period differed considerably among the four districts and the Extension Planning Areas (EPAs) showed high coefficients of variance (CVs) (16.9-93.7). The equation with the three-month rainfall (October, February, and April), i.e., Maize yield (kg/ha) in SH = 2.29 + 0.0042 × Oct rainfall – 0.0009 × Feb rainfall + 0.00045 × Apr rainfall (r<sup>2</sup> = 0.41), better explained maize yield in the 2013/14 season than the equation with total rainfall in the cropping season. Rainfall accounted for more than 41% of the total variation in maize yields of smallholder farmers (SHs). Rainfall in April was the most critical factor influencing maize and other crop yields. After the Farm Input Subsidy Programme (FISP) was implemented in 2005/06, maize yield became more dependent on rainfall. CV was higher in maize than in groundnut and sweet potato, indicating that maize is susceptible to rainfall fluctuations, and groundnut and sweet potato should be incorporated in farming as a countermeasure against unpredictable rainfall.</p>

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16

Shastry, B. Sriram, and Boris I. Shraiman. "Raman Scattering in Mott-Hubbard Systems." International Journal of Modern Physics B 05, no. 01n02 (January 1991): 365–88. http://dx.doi.org/10.1142/s0217979291000237.

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We present a theory of Raman Scattering in the Hubbard model. The scattering of light has resonant and non-resonant contributions. The resonant term gives rise to scattering by spin degrees of freedom in the insulating case, for which we derive a general form of the effective scattering Hamiltonian. The later involves four terms with distinct symmetry properties, one of them being the “chiral” spin operator ∑ Si · (Sj×Sk). The corresponding four distinct correlation function can be measured directly in the experiments with different scattering geometries. The nonresonant term contributes to the scattering in the doped case and is shown to probe the fluctuations of the “stress tensor”. This quantity is not conserved and hence its fluctuations at small q inherent in optical experiments, need not be small, in striking contrast with the density fluctuation in usual metals.

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17

HO, CHOON-LIN, BAMBI HU, and HOI-LAI YU. "VECTOR PAIRING AND FLUCTUATION-INDUCED CHERN-SIMONS TERM IN ANYON SUPERCONDUCTIVITY." Modern Physics Letters B 04, no. 18 (October 10, 1990): 1137–41. http://dx.doi.org/10.1142/s0217984990001434.

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Assuming some sorts of vector pairing in high-temperature superconductivity, we show how the topological Chern-Simons term can be generated dynamically due to quantum fluctuations in a BCS-type four-fermion model. This fluctuation-induced Chern-Simons term provides a natural way to incorporate fractional statistics and thus a more direct connection with anyon superconductivity.

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18

Edge, K. A., and B. R. Lipscombe. "The Reduction of Gear Pump Pressure Ripple." Proceedings of the Institution of Mechanical Engineers, Part B: Management and engineering manufacture 201, no. 2 (May 1987): 99–106. http://dx.doi.org/10.1243/pime_proc_1987_201_052_02.

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Pressure fluctuations in a hydraulic system may be substantially reduced by cancelling the flow ripple produced by the pump. This paper describes a secondary flow ripple generating mechanism which introduces an equal and opposite flow fluctuation to that generated by the pump. Tests have shown that the mechanism can virtually cancel four harmonics of pressure ripple but success is dependent on an accurate knowledge of the pump flow fluctuation characteristic. This is best determined experimentally. Similar improvements can be achieved using a mechanism in a motor. This has the additional benefit of reducing torque fluctuations. The reduction in gear pump pressure ripple achieved with the mechanism has been shown to reduce overall airborne noise levels from a hydraulic system by as much as 10 dB, although the airborne noise radiated from the pump casing was not affected.

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19

Bloom, Nicholas. "Fluctuations in Uncertainty." Journal of Economic Perspectives 28, no. 2 (May 1, 2014): 153–76. http://dx.doi.org/10.1257/jep.28.2.153.

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Uncertainty is an amorphous concept. It reflects uncertainty in the minds of consumers, managers, and policymakers about possible futures. It is also a broad concept, including uncertainty over the path of macro phenomena like GDP growth, micro phenomena like the growth rate of firms, and noneconomic events like war and climate change. In this essay, I address four questions about uncertainty. First, what are some facts and patterns about economic uncertainty? Both macro and micro uncertainty appear to rise sharply in recessions and fall in booms. Uncertainty also varies heavily across countries—developing countries appear to have about one-third more macro uncertainty than developed countries. Second, why does uncertainty vary during business cycles? Third, do fluctuations in uncertainty affect behavior? Fourth, has higher uncertainty worsened the Great Recession and slowed the recovery? Much of this discussion is based on research on uncertainty from the last five years, reflecting the recent growth of the literature.

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20

Esmaeelpour, Mina, Rene-Jean Essiambre, Nicolas K. Fontaine, Roland Ryf, Jean Toulouse, Yi Sun, and Robert Lingle. "Power Fluctuations of Intermodal Four-Wave Mixing in Few-Mode Fibers." Journal of Lightwave Technology 35, no. 12 (June 15, 2017): 2429–35. http://dx.doi.org/10.1109/jlt.2017.2660459.

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21

Failache, H., M. Oriá, and A. Lezama. "Degenerate four-wave-mixing intensity noise fluctuations as a spectroscopic tool." Physical Review A 52, no. 1 (July 1, 1995): 699–704. http://dx.doi.org/10.1103/physreva.52.699.

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22

Malek, Abdul. "Temperature Fluctuations in Dusty Fluid Homogeneous Turbulence at Four Point Correlations." American Journal of Applied Mathematics 5, no. 5 (2017): 132. http://dx.doi.org/10.11648/j.ajam.20170505.12.

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23

Schmitt-Grohé, Stephanie. "Comparing Four Models of Aggregate Fluctuations due to Self-Fulfilling Expectations." Journal of Economic Theory 72, no. 1 (January 1997): 96–147. http://dx.doi.org/10.1006/jeth.1996.2195.

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24

Zhang, Weiping, and Daniel F. Walls. "Sub shot-noise intensity fluctuations in a four-wave mixing oscillator." Optics Communications 79, no. 6 (November 1990): 497–508. http://dx.doi.org/10.1016/0030-4018(90)90488-f.

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25

Yang, Hong Xing, Chang Ning Guo, and Bao Shu Shi. "Analysis on Circumferential Clearance of Four-Ball-Pin Constant Velocity Joint." Advanced Materials Research 655-657 (January 2013): 625–29. http://dx.doi.org/10.4028/www.scientific.net/amr.655-657.625.

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By using Matlab, the circumferential clearance changing law with any swing angle and rotating angle of four-ball-pin CVJ was obtained, the results show that, under the same size specification and machining accuracy, four-ball-pin CVJ has a roughly similar vibration amplitude with traditional tripod CVJ, when the CVJ rotates one circle at any swing angle, there are four fluctuations of circumferential angle in four-ball-pin CVJ, but there six fluctuations in tripod CVJ, so the former one fluctuate less and has much more slight impact on the vibration and noise during traveling. These results provide a theoretical basis for development and application of this new structural form of four-ball-pin CVJ.

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26

Chaudhry, Ifra, Raheel Suleman, Adrish Bhatti, and Inam Ullah. "Review: Food price fluctuations and its influence on global food market." ANNALS OF SOCIAL SCIENCES AND PERSPECTIVE 2, no. 1 (June 30, 2021): 21–33. http://dx.doi.org/10.52700/assap.v2i1.33.

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Food price fluctuation is a multifarious problem in the food marketing. Food price fluctuations have a huge effect on the vulnerable. Food security considered at three levels (household, national and international levels). Food supply, safety, physical and financial accessibility, and food utilization are the four pillars of food security. Since 2006-2007, the costs of most food products in Pakistan have risen by more than 100 percent. Consumption patterns, income, market and stockholding are the main causes of increased food prices. Maternal and child nutrition affected due to price fluctuation at individual level. Short term and long-term police are important to improve food productivity by enhancing agricultural system. The main focus of the study is to identify the effects of price fluctuations on poor pregnant women diet specifically in Pakistan and then on the children. If mother is malnourished or micronutrient deficient then child will also be deficient in that specific nutrient and deficiency will run in families. Hence our purpose is to find out these deficiencies in Pakistan and better implementation of policies.

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27

Kawashima, Kenji, Chongho Youn, and Toshiharu Kagawa. "Development of a Nozzle-Flapper-Type Servo Valve Using a Slit Structure." Journal of Fluids Engineering 129, no. 5 (November 6, 2006): 573–78. http://dx.doi.org/10.1115/1.2717617.

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Pneumatic servo valves play a significant role in power transmission and system control using a pressurized gas. When pressurized air passes through servo valves, noise and pressure fluctuations are often experienced at the downstream side, and such fluctuations limit the value’s efficiency. In this paper, a novel four-port nozzle-flapper-type servo valve using a slit structure instead of an orifice plate is proposed. The slit structure maintains a laminar flow condition, and this provides an opportunity for the minimization of the noise and pressure fluctuations. The slit structure is fabricated using etching technology. The flow characteristics of the slit are investigated theoretically and experimentally in order to evaluate the design specifications and characteristics of the valve. The experimental results indicated that the noise level decreased by approximately 15dB and could reduce the pressure fluctuation by 75%, compared with the previous valve. It is felt that the valve is more effective than many current valves.

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28

BARRY, J. H., J. D. COHEN, and M. W. MEISEL. "EXACT SOLUTIONS IN A SPATIALLY ANISOTROPIC QUANTUM SPIN LADDER MODEL HAVING TWO- AND FOUR-SPIN EXCHANGE INTERACTIONS." International Journal of Modern Physics B 23, no. 08 (March 30, 2009): 1981–2019. http://dx.doi.org/10.1142/s0217979209052236.

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We consider a two-leg S=1/2 quantum spin ladder model with two-spin (intra-rung) and four-spin (inter-rung) Heisenberg exchange interactions and a uniform magnetic field. Exact mappings are derived connecting the partition function and correlations in the three-parameter quantum model to those known in a two-parameter Ising chain. The quantum phase diagram of the ladder magnet is determined. Static correlations provide pertinent correlation lengths and underlie spatial fluctuation behaviors at arbitrary temperatures, including quantum fluctuations at absolute zero. Dynamic correlations in zero field are used to obtain an exact solution for the inelastic neutron scattering function Sxx(q, ω) at all temperatures, explicitly yielding the elementary excitation spectrum.

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29

Perez, Jean C., Sofiane Bourouaine, Christopher H. K. Chen, and Nour E. Raouafi. "Applicability of Taylor’s hypothesis during Parker Solar Probe perihelia." Astronomy & Astrophysics 650 (June 2021): A22. http://dx.doi.org/10.1051/0004-6361/202039879.

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We investigate the validity of Taylor’s hypothesis (TH) in the analysis of velocity and magnetic field fluctuations in Alfvénic solar wind streams measured by Parker Solar Probe (PSP) during the first four encounters. The analysis is based on a recent model of the spacetime correlation of magnetohydrodynamic (MHD) turbulence, which has been validated in high-resolution numerical simulations of strong reduced MHD turbulence. We use PSP velocity and magnetic field measurements from 24 h intervals selected from each of the first four encounters. The applicability of TH is investigated by measuring the parameter ϵ = δu0/√2V⊥, which quantifies the ratio between the typical speed of large-scale fluctuations, δu0, and the local perpendicular PSP speed in the solar wind frame, V⊥. TH is expected to be applicable for ϵ ≲ 0.5 when PSP is moving nearly perpendicular to the local magnetic field in the plasma frame, irrespective of the Alfvén Mach number MA = VSW∕VA, where VSW and VA are the local solar wind and Alfvén speed, respectively. For the four selected solar wind intervals, we find that between 10 and 60% of the time, the parameter ϵ is below 0.2 and the sampling angle (between the spacecraft velocity in the plasma frame and the local magnetic field) is greater than 30°. For angles above 30°, the sampling direction is sufficiently oblique to allow one to reconstruct the reduced energy spectrum E(k⊥) of magnetic fluctuations from its measured frequency spectra. The spectral indices determined from power-law fits of the measured frequency spectrum accurately represent the spectral indices associated with the underlying spatial spectrum of turbulent fluctuations in the plasma frame. Aside from a frequency broadening due to large-scale sweeping that requires careful consideration, the spatial spectrum can be recovered to obtain the distribution of fluctuation’s energy across scales in the plasma frame.

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30

Cao, Weidong, Jiayu Mao, and Wei Li. "Analysis of Unsteady Pressure Fluctuation in a Semi-Open Cutting Pump." Energies 13, no. 14 (July 15, 2020): 3657. http://dx.doi.org/10.3390/en13143657.

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In order to understand the pressure fluctuation characteristics of a semi-open cutting pump, the three-dimensional unsteady flow fields were calculated. External and internal flow characteristics of four schemes with different relative angles between the rotary cutter and the impeller were studied. The pressure fluctuations in the lower plate, the upper plate, the clearance between the rotary cutter and the fixed cutter, the first section in volute and nearby parts of the tongue were all analyzed, which are all the places that pressure distributions are greatly affected by the static and dynamic interaction, and at the same time, the force on the impeller was also analyzed. The results show that the fluctuations at different positions change periodically; the main frequency is blade frequency. The amplitude of pressure fluctuation decreases from near the rotating part to far away, from near the tongue to far from the tongue. Due to the influence of both impeller and rotary cutter, the pressure fluctuation on the lower plate is the largest. The pressure fluctuation is affected by flow rate, the larger the flow rate, the greater the pressure fluctuation. The radial and axial forces of the impeller change periodically with time, and the number of wave peaks and wave valleys is the same as the number of blades.

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31

Burridge, H. C., and G. R. Hunt. "The rhythm of fountains: the length and time scales of rise height fluctuations at low and high Froude numbers." Journal of Fluid Mechanics 728 (July 1, 2013): 91–119. http://dx.doi.org/10.1017/jfm.2013.263.

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AbstractThe magnitude and frequency of vertical fluctuations of the top of an axisymmetric miscible Boussinesq fountain forms the focus of this work. We present measurements of these quantities for saline-aqueous fountains in uniform quiescent surroundings. Our results span source Froude numbers $0. 3\leq {\mathrm{Fr} }_{0} \leq 40$ and, thereby, encompass very weak, weak, intermediate and forced classes of fountain. We identify distinct scalings, based on known quantities at the fountain source, for the frequency of fountain height fluctuations which collapse our data within bands of ${\mathrm{Fr} }_{0} $. Notably, our scalings reveal that the (dimensionless) frequency takes a constant value within each band. These results highlight characteristic time scales for the fluctuations which we decompose into a single, physically apparent, length scale and velocity scale within each band. Moreover, within one particular band, spanning source Froude numbers towards the lower end of the full range considered, we identify unexpectedly long-period fluctuations indicating a near balance of inertia and (opposing) buoyancy at the source. Our analysis identifies four distinct classes of fluctuation behaviour (four bands of ${\mathrm{Fr} }_{0} $) and this classification matches well with existing classifications of fountains based on rise heights. As such, we show that an analysis of the behaviour of the fountain top alone, rather than the entire fountain, provides an alternative approach to classifying fountains. The similarity of classifications based on the two different methods confirms that the boundaries between classes mark tangible changes in the physics of fountains. For high ${\mathrm{Fr} }_{0} $ we show that the dominant fluctuations occur at the scale of the largest eddies which can be contained within the fountain near its top. Extending this, we develop a Strouhal number, ${\mathrm{Str} }_{top} $, based on experimental measures of the fountain top, defined such that ${\mathrm{Str} }_{top} = 1$ would suggest the dominant fluctuations are caused by a continual cycle of eddies forming and collapsing at this largest physical scale. For high-${\mathrm{Fr} }_{0} $ fountains we find ${\mathrm{Str} }_{top} \approx 0. 9$.

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32

Johnston, R. J., and C. J. Pattie. "Fluctuating Party Identification in Great Britain: Patterns Revealed by Four Years of a Longitudinal Study." Politics 17, no. 2 (May 1997): 67–77. http://dx.doi.org/10.1111/1467-9256.00036.

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The concept of party identification is widely used in British electoral studies, but its value as a measure of underlying links between voters and parties, irrespective of short-term fluctuations in partisan popularity, has come under increased scrutiny recently Data from the first four waves of a longitudinal study provide evidence of substantial variability in the strength of voters' identification with the three main British political parties, suggesting the need for research into the causes of, and meanings associated with, such fluctuations.

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33

Ye, Lyuzhou, Jérémy R. Rouxel, Daeheum Cho, and Shaul Mukamel. "Imaging electron-density fluctuations by multidimensional X-ray photon-coincidence diffraction." Proceedings of the National Academy of Sciences 116, no. 2 (December 24, 2018): 395–400. http://dx.doi.org/10.1073/pnas.1816730116.

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The ultrafast spontaneous electron-density fluctuation dynamics in molecules is studied theoretically by off-resonant multiple X-ray diffraction events. The time- and wavevector-resolved photon-coincidence signals give an image of electron-density fluctuations expressed through the four-point correlation function of the charge density in momentum space. A Fourier transform of the signal provides a real-space image of the multipoint charge-density correlation functions, which reveal snapshots of the evolving electron density in between the diffraction events. The proposed technique is illustrated by ab initio simulations of the momentum- and real-space inelastic scattering signals from a linear cyanotetracetylene molecule.

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34

Woodward, Guy, Núria Bonada, Lee E. Brown, Russell G. Death, Isabelle Durance, Clare Gray, Sally Hladyz, et al. "The effects of climatic fluctuations and extreme events on running water ecosystems." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1694 (May 19, 2016): 20150274. http://dx.doi.org/10.1098/rstb.2015.0274.

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Most research on the effects of environmental change in freshwaters has focused on incremental changes in average conditions, rather than fluctuations or extreme events such as heatwaves, cold snaps, droughts, floods or wildfires, which may have even more profound consequences. Such events are commonly predicted to increase in frequency, intensity and duration with global climate change, with many systems being exposed to conditions with no recent historical precedent. We propose a mechanistic framework for predicting potential impacts of environmental fluctuations on running-water ecosystems by scaling up effects of fluctuations from individuals to entire ecosystems. This framework requires integration of four key components: effects of the environment on individual metabolism, metabolic and biomechanical constraints on fluctuating species interactions, assembly dynamics of local food webs, and mapping the dynamics of the meta-community onto ecosystem function. We illustrate the framework by developing a mathematical model of environmental fluctuations on dynamically assembling food webs. We highlight (currently limited) empirical evidence for emerging insights and theoretical predictions. For example, widely supported predictions about the effects of environmental fluctuations are: high vulnerability of species with high per capita metabolic demands such as large-bodied ones at the top of food webs; simplification of food web network structure and impaired energetic transfer efficiency; and reduced resilience and top-down relative to bottom-up regulation of food web and ecosystem processes. We conclude by identifying key questions and challenges that need to be addressed to develop more accurate and predictive bio-assessments of the effects of fluctuations, and implications of fluctuations for management practices in an increasingly uncertain world.

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35

Yildirim, Zekeriya, and Mehmet Ivrendi. "Exchange rate fluctuations and macroeconomic performance." Journal of Economic Studies 43, no. 5 (October 10, 2016): 678–98. http://dx.doi.org/10.1108/jes-01-2015-0010.

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Purpose Recent turbulence in global financial markets implies that emerging economies are likely to soon enter a new era with greater pressure for currency depreciation and capital outflows. This will likely bring challenges, including macroeconomic instability and inflationary pressures due to potential rapid depreciation. In this context, certain key questions about emerging economies have become focal points of discussion in political and academic spheres: what are the effects of exchange rate depreciation on economic activity? Does exchange rate depreciation create inflationary pressure? Finding answers to these questions is critical for policymakers and financial market participants. As such, the purpose of this paper is to shed light on these questions and thus provides guidance on mitigating the negative impacts of shocks in four fast-growing emerging economies. Design/methodology/approach The authors use a vector autoregression model with sign restrictions to examine the dynamic effects of exchange rate movements on fundamental macroeconomic indicators for four fast-growing countries, namely, Brazil, Turkey, Russia, and South Africa. Following Berument et al. (2012a), Ncube and Ndou (2013), Bjørnland and Halvorsen (2013), and An et al. (2014), the authors adopt the sign restriction methodology to identify exchange rate shocks alongside other macroeconomic shocks (monetary policy and productivity shocks) leading to exchange rate fluctuations. Findings The results show that exchange rate depreciation typically generates a deep recession and high inflation while improving the trade balance in the four emerging economies. This indicates that depreciation has strong “stagflationary” effects, which are transmitted to the macroeconomy primarily via supply-side channels, especially through the cost of import. Furthermore, the authors find that monetary policy reacts immediately to a domestic currency depreciation in all four emerging countries. Practical implications The results imply that these countries’ monetary policies are not and cannot be neutral to exchange rate shocks. However, in these import-dependent countries, monetary tightening (i.e. rate hikes in response to an exchange rate shock) plays a limited role in mitigating the negative effects of depreciation on inflation and economic activity due to the presence of a dominant supply-side channel. In this framework, policymakers should pay greater attention to structural reforms that aim to reduce import dependency. These reforms may increase the effectiveness of domestic monetary policy in mitigating the negative effects of external shocks. Originality/value This paper provides a useful perspective for policymakers designing economic interventions to mitigate the adverse effects of exchange rate depreciation and to those who borrow or lend in domestic or international financial markets.

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36

Solis, Moisés, Farid Bakir, Sofiane Khelladi, and Ricardo Noguera. "Numerical Study on Pressure Fluctuations Reduction in Centrifugal Pumps: Influence of Radial Gap and Splitter Blades." ISRN Mechanical Engineering 2011 (October 13, 2011): 1–14. http://dx.doi.org/10.5402/2011/479594.

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Numerical study was carried out in four centrifugal pumps to analyze the effects of adding splitters and incrementing the radial gap in order to decrease the pressure fluctuations at the blade passage frequency. It is well known that in this kind of pump, the interactions between the flow leaving the impeller and entering the volute generate fluctuating pressures which propagate toward the inlet and the discharge of the pump. These pulsations are mainly associated to the blade passage frequency presenting high amplitudes near the volute tongue and at impeller discharge. Four configurations were analyzed using numerical simulations; the first is the reference pump which will be optimized and the others are the optimized ones. The numerical modelling was performed at the same flow rate having to vary in some cases the rotational speed to reach the operating point. During the calculations, the pressure signals were recorded by virtual sensors placed at several locations of the pump then they were analyzed and processed by means of the Fast Fourier Transform. The pressure fluctuations were plotted and compared between the four configurations, showing clearly the fact of varying the blades number and the radial gap influence significantly on their reduction.

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Sanidas, Elias. "Four harmonic cycles explain and predict commodity currencies' wide long term fluctuations." Technological Forecasting and Social Change 87 (September 2014): 135–51. http://dx.doi.org/10.1016/j.techfore.2013.11.008.

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Carlson, Lee, and W. C. Schieve. "Chaos and quantum fluctuations in the Hénon-Heiles and four-leg potentials." Physical Review A 40, no. 10 (November 1, 1989): 5896–904. http://dx.doi.org/10.1103/physreva.40.5896.

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Tsuji, Kenichiro, Hideaki Yokota, and Masatoshi Saruwatari. "Influence of dispersion fluctuations on four-wave mixing efficiency in optical fibers." Electronics and Communications in Japan (Part II: Electronics) 85, no. 8 (July 9, 2002): 16–24. http://dx.doi.org/10.1002/ecjb.10032.

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Qiu, Rong-ke, and Zhi-dong Zhang. "Four-sublattice ferrimagnetic systems: I. Quantum fluctuations of spins at zero temperature." physica status solidi (b) 241, no. 1 (January 2004): 189–204. http://dx.doi.org/10.1002/pssb.200301912.

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Mustafa, Shatha, and Dr Faisal Khan. "The Relationship between Accounting Frauds and Economic Fluctuations: A Case of Project Based Organizations in UAE." Journal of Economics and Public Finance 6, no. 1 (February 21, 2020): p87. http://dx.doi.org/10.22158/jepf.v6n1p87.

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Purpose: the purpose of this study is to provide a better understanding of the rate of accounting frauds (misappropriation of assets, fraudulent financial reporting), and how they occur in different business cycles (economic fluctuations). Further, it aims at exploring the relationship between factors influencing the economic fluctuations and the level of accounting frauds. Design/methodology approach: a qualitative research design used semi-structured interviews with a group of internal controllers and external auditors from the big four auditing companies in addition to other Leading and certified audit offices in UAE in order to identify how the factors influencing the GDP fluctuations could affect the degree of accounting frauds.Findings: GDP components that influence economic fluctuations associate with the accounting frauds rate, especially fraudulent financial reporting. Economic factors including the GDP, unemployment and inflation are very important in the steadiness of an economy. The probable drop of GDP, or raise in unemployment level, high rates of inflation are positively influence the occurrences of accounting frauds.Research limitation/implications: There are many ECONOMIC roots of business cycles and economic fluctuations such as variations in trading strategy, warfare, inflation caused by governmental finance or fears. But these represent non-economic data that is hard to be rationalized by economic theory. Typical macroeconomic theory inclines to illuminate business cycles by a number of mistake and emphasis on modifying this mistake either by dynamic strategy or by supporting a separate strategy (Raudino, 2016). Thus, it is very hard to capture all the factors influencing the economic fluctuations. However, most of the studies in the literature considers the GDP as the most important factors, in addition to inflation and unemployment. Practical implication: This study contributes to both economic and accounting research by proving findings from an investigation of the elements modifying the economical fluctuation and how these fluctuations might impact the rate of accounting Frauds (AF), with implications for economists and financiers, shareholders, stakeholders, stockholders and external inspectors of auditing companies an additional visions about the audit risk in PBOs at altered stages of GDP. Originality/value: This study contributes to both economic and accounting research by exploratory research into the GDP fluctuation, inflation, and unemployment and accounting frauds rate.

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MAHATO, MANGAL C., T. P. PAREEK, and A. M. JAYANNAVAR. "ENSLAVING RANDOM FLUCTUATIONS IN NONEQUILIBRIUM SYSTEMS." International Journal of Modern Physics B 10, no. 28 (December 30, 1996): 3857–73. http://dx.doi.org/10.1142/s0217979296002099.

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Several physical models have recently been proposed to obtain unidirectional motion of an overdamped Brownian particle in a periodic system. The asymmetric ratchetlike form of the periodic potential and the presence of correlated nonequilibrium fluctuating forces are considered essential to obtain such a macroscopic motion in homogeneous systems. In the present work, instead, inhomogeneous systems are considered, wherein the friction coefficient and/or temperature could vary in space. We show that unidirectional motion can be obtained even in a symmetric nonratchetlike periodic potential system in the presence of white noise fluctuations. We consider four different cases of system inhomogeneity. We argue that all these different models work under the same basic principle of alteration of relative stability of otherwise locally stable states in the presence of temperature inhomogeneity.

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Ekstam, B., R. Johannesson, and P. Milberg. "The effect of light and number of diurnal temperature fluctuations on germination of Phragmites australis." Seed Science Research 9, no. 2 (February 1999): 165–70. http://dx.doi.org/10.1017/s0960258599000185.

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AbstractSeed germination of the wetland emergent perennial Phragmites australis is stimulated by diurnally fluctuating temperatures. A germination experiment in darkness and light at different temperature regimes showed that P. australis germinated as well in darkness as in light over most of the temperature regimes tested. The germination requirements could partly explain why this species, despite a large annual production of small seeds, does not accumulate a persistent soil seed bank. A second experiment examined the effect of one to four diurnal temperature cycles with amplitude of fluctuations ranging from 0 to 30°C; diurnal mean temperature of 15°C. Germination in the absence of fluctuations was low, and logistic model estimates showed a positive effect of number of temperature cycles which was strongly influenced by amplitude size. For seeds that have fallen on moist ground during the winter, these laboratory results predict that a few large diurnal temperature fluctuations could be sufficient for onset of germination in the subsequently warmer spring period. Seeds that are located under water, however, are predicted to remain ungerminated until the water level falls. Hence, we suggest that the requirement for fluctuating temperature, in addition to being a sensor for ‘exposed’ seed sites, is also effectively acting as a germination timing mechanism.

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Li, Guoping, Eryun Chen, Ailing Yang, Zhibin Xie, and Gaiping Zhao. "Effect of Guide Vanes on Flow and Vibroacoustic in an Axial-Flow Pump." Mathematical Problems in Engineering 2018 (October 30, 2018): 1–11. http://dx.doi.org/10.1155/2018/3095890.

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An effect of guide-vane numbers on pressure fluctuations and structural vibroacoustics induced by unsteady flow is performed by a hybrid numerical method. A 3D flow field is simulated in axial-flow pump with four impeller blades, in which three diffuser models with 5, 7, and 9 vanes are devised to match, respectively. A full scale structural vibroacoustics coupled model is solved using LMS acoustics software. The results show that the blade-passing frequency (BPF) is dominated frequency of the vibration acceleration of pump, which is consistent with frequency spectral characteristics of pressure pulsation. The unsteady pressure fluctuating becomes strong as the flow discharge decreases from 1.0Qv to 0.6Qv, the circumferential unsteady behavior of which is more severe due to flow nonuniformity induced by the suction elbow at partial operation. Generally, the pressure fluctuating increases slightly when the flow discharge increases from 1.0Qv to 1.3Qv. Moreover, pressure fluctuations amplitude on the pump with 9-vane diffuser is small relative to other two models and the vibrating accelerating and radiation sound field at BPF are also slight relatively, which indicates that appropriate guide-vane numbers contribute to suppress pressure fluctuations and vibroacoustics in axial-flow pump. The conclusions in the present paper can provide theoretical guidance for low vibration pump design.

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Phillips, Joseph R., Elie Matar, Kaylena A. Ehgoetz Martens, Glenda M. Halliday, Ahmed A. Moustafa, and Simon J. G. Lewis. "Evaluating the Sustained Attention Response Task to Quantify Cognitive Fluctuations in Dementia With Lewy Bodies." Journal of Geriatric Psychiatry and Neurology 33, no. 6 (October 31, 2019): 333–39. http://dx.doi.org/10.1177/0891988719882093.

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Cognitive fluctuations (CFs) are a core diagnostic feature of dementia with Lewy bodies (DLB). Detection of CF is still mostly based on subjective reports from the patient or informant; more quantitative measures are likely to improve the accuracy for the diagnosis of DLB. The purpose of the current study is to test whether performance on the Sustained Attention Response Task (SART) could distinguish those patients with DLB with and without CF. Twenty-four patients with DLB were tested on the SART and performance was related to scores on the Clinical Assessment of Fluctuations (CAFs) and One Day Fluctuation Assessment Scale (ODFAS). The number of “misses” made was a significant predictor of their fluctuation severity, attentional performance, disorganized thinking, and language production ratings on the ODFAS. However, measures on the SART did not correlate with measures on the CAF scale. In conclusion, these findings suggest that SART is a feasible measure of sustained attention in this population and has clinical and diagnostic relevance to the measurement of CF, particularly those aspects measured by the ODFAS.

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Ho, C. L., B. Hu, and H. L. Yu. "Induced Topological Terms, Hidden Local Symmetry, and Anyon Superconductivity." International Journal of Modern Physics B 05, no. 10 (June 1991): 1763–70. http://dx.doi.org/10.1142/s0217979291001668.

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We show how the topological Chern-Simons term in three dimensions and the θ-term, [Formula: see text] in four dimensions can be dynamically generated due to quantum fluctuations in Nambu-Jona-Lasinio models. These results give a vivid demonstration of hidden local symmetry at work. The fluctuation-induced Chern-Simons term provides a natural way to incorporate fractional statistics and thus a more direct connection with anyon superconductivity. Possible phenomenological implications of this approach in particle physics are also discussed.

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Trnka, Otakar, and Miloslav Hartman. "On the Influence of Fluctuating Flow Rate Upon the Performance and Behaviour of Isothermal Reacting Systems." Collection of Czechoslovak Chemical Communications 63, no. 6 (1998): 881–98. http://dx.doi.org/10.1135/cccc19980881.

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Three simple computational techniques are proposed and employed to demonstrate the effect of fluctuating flow rate of feed on the behaviour and performance of an isothermal, continuous stirred tank reactor (CSTR). A fluidized bed reactor (FBR), in which a non-catalytic gas-solid reaction occurs, is also considered. The influence of amplitude and frequency of gas flow rate fluctuations on reactant concentrations at the exit of the CSTR is shown in four different situations.

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Rankin, Summer K., Edward W. Large, and Philip W. Fink. "Fractal Tempo Fluctuation and Pulse Prediction." Music Perception 26, no. 5 (June 1, 2009): 401–13. http://dx.doi.org/10.1525/mp.2009.26.5.401.

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WE INVESTIGATED PEOPLES' ABILITY TO ADAPT TO THE fluctuating tempi of music performance. In Experiment 1, four pieces from different musical styles were chosen, and performances were recorded from a skilled pianist who was instructed to play with natural expression. Spectral and rescaled range analyses on interbeat interval time-series revealed long-range (1/f type) serial correlations and fractal scaling in each piece. Stimuli for Experiment 2 included two of the performances from Experiment 1, with mechanical versions serving as controls. Participants tapped the beat at ¼¼- and ⅛⅛-note metrical levels, successfully adapting to large tempo fluctuations in both performances. Participants predicted the structured tempo fluctuations, with superior performance at the ¼¼-note level. Thus, listeners may exploit long-range correlations and fractal scaling to predict tempo changes in music.

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Wei, Zhicong, Wei Yang, and Ruofu Xiao. "Pressure Fluctuation and Flow Characteristics in a Two-Stage Double-Suction Centrifugal Pump." Symmetry 11, no. 1 (January 8, 2019): 65. http://dx.doi.org/10.3390/sym11010065.

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Pressure fluctuation is the primary factor that affects the stability of turbomachines. The goal of the present work is to explore the propagation of pressure fluctuations in a two-stage double-suction centrifugal pump. The pressure fluctuation characteristics of each component of a two-stage double-suction centrifugal pump are simulated under four typical flow rates based on the SST k-ω turbulence model. It is shown that the pressure fluctuation frequency at blade passing frequency and its first harmonic is the same at the suction chamber, the leading edge, and the middle of the first-stage impeller, which is different from the rotor–stator interaction. Moreover, the uneven impeller inlet flow distribution will produce fluctuations with rotation frequency and its harmonics at the leading edge of the impellers in both stages. Finally, broadband frequency is found at the trailing edge of the impellers in both stages associated with the first harmonic of the rotation frequency, especially under the part load condition. The large size backflow vortex appears in the blade flow channel leading to the low-pressure zone between the impeller, the tongue, and the start of the partition. That is why the pressure drops significantly twice in one rotation period when the blades pass through the tongue and the start of the partition.

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Farzad, M. H., and M. T. Tavassoly. "Semiclassical behavior of the degenerate four-wave mixing without slowly varying amplitude approximation." Canadian Journal of Physics 81, no. 8 (August 1, 2003): 1037–50. http://dx.doi.org/10.1139/p02-127.

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In this study, a semiclassical version of the degenerate four-wave mixing (DFWM) solution without slowly varying amplitude (SVA) approximation is investigated. The quadrature fluctuations of the output modes exhibit an oscillatory behavior with respect to that of the corresponding SVA modes. Furthermore, the variation of the two quadrature fluctuations of the combined mode, plotted against the normalized coupling constant κL, oscillates. Beyond a certain value of κL, the two quadratures oscillate in opposite directions, which implies that the squeezing effect of DFWM without the SVA approximation oscillates around that of the SVA. In addition, the squeezing effect in DFWM without SVA approximation depends on the refractive index of the medium and increases sharply upon the increase of the latter. This study also shows that the super-Poissonian behavior of the conjugate mode is preserved but is oscillatory. PACS No.: 42.65.Hw

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Journal articles on the topic 'Four Fluctuations'

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