Periodic Phenomena Research Articles

New physics capabilities from the upgraded Thomson scattering diagnostic on MAST

The newly upgraded MAST Thomson scattering (TS) system provides excellent spatial resolution (∼1 cm) at over 130 radial locations across a full plasma diameter, and utilizes eight individual Nd: :YAG laser systems which can be fired sequentially, providing electron temperature and density profiles approximately every 4 ms throughout a plasma discharge. By operating the system in burst mode, whereby the laser separation can be adjusted to within a few microseconds of each other, it is possible to obtain detailed profiles of transient and periodic phenomena such as sawteeth crashes, massive gas injection for disruption mitigation and the temperature perturbations associated with neoclassical tearing mode (NTM) islands. Following Fitzpatrick et al (1995 Phys. Plasmas 2 825), we consider a simplified model in which finite parallel diffusive heat transport can provide a threshold for NTM island growth and demonstrate that the TS derived electron temperature profiles around an island can be used to obtain both the island width and the critical island width below which temperature gradients are maintained across the island, potentially removing the bootstrap current drive for the NTM. Initial results from high beta, neutral beam injection heated discharges on MAST show that the measured island width inferred from the TS data is in good agreement with magnetic estimates of the island width (considering both a cylindrical approximation and using a full field line tracing estimate). The temporal behaviour of the island width obtained from the magnetic diagnostics indicates that for the scenarios considered to date, finite parallel diffusion is likely to play an important role in NTM threshold physics in MAST.

Effect of trapped hydrogen on the induction period of cobalt–tungsten–boron/nickel foam catalyst in catalytic hydrolysis reaction of sodium borohydride

Calcination treatment is an important step in preparation of supported transition metal catalysts that are effective for promoting the hydrolysis reaction of sodium borohydride. We found that calcination treatment of cobalt–tungsten–boron/nickel foam catalysts results in the appearance of an induction period in their first time use, and the duration of which depends on the calcination temperature and atmosphere. Upon reusing the catalysts, the induction period completely disappeared. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and synchronous thermal analyses techniques were employed to study the mechanism underlying the induction period phenomenon. Our study results showed that the appearance/disappearance of the induction period should be correlated with the desorption/reabsorption of hydrogen in the catalysts.

Periodic problems of first order uncertain dynamical systems

It is well known that there are no periodic solutions to fuzzy differential equations in the sense of Hukuhara derivatives, i.e. H-derivatives, so fuzzy differential equations in the sense of H-derivatives cannot be used to describe periodic phenomena in the real world. To overcome this disadvantage, this paper studies periodic problems of first order fuzzy differential equations in the sense of differential inclusions, i.e., periodic problems of first order uncertain dynamical systems, and obtains the existence of periodic solutions for first order uncertain dynamical systems.

Numerical study on a designable linear-resonant multiband single-layer fractal frequency-selective surface

In this paper, the multiband transmission resonant properties of single-layer Minkowski fractal planar frequency-selective surfaces (FSSs) at normal-incidence case were numerically investigated in detail. The self-similar iterative transformational method was proposed to construct the fractal FSSs. Both the finite integration technology and finite element method were used to calculate the magnitudes and phases of transmittances, and then the induced surface current and magnetic energy density distributions were demonstrated to analyze the insight physical picture of the multiband resonant feature. The results indicate that the individual resonant frequencies of our fractal FSSs present a periodical linear-resonant phenomenon and they could be designed easily and precisely just according to the geometrical characteristic of each iteration. With the intriguing resonant properties, the fractal FSS has a potential application in the fields of dual-band or multiband resonance.

Two-body scattering in a trap and a special periodic phenomenon sensitive to the interaction

Two-body scattering of neutral particles in a trap is studied theoretically. The control of the initial state is realized by using optical traps. The collisions inside the trap occur repeatedly; thereby the effect of interaction can be accumulated. Two periodic phenomena with a shorter and a much longer period, respectively, are found. The latter is sensitive to the interaction. Instead of measuring the differential cross section as usually does, the measurement of the longer period and the details of the periodic behavior might be a valid source of information on weak interactions among neutral particles.

Introduction

Introduction

Spectral-decomposition techniques for the identification of periodic and anomalous phenomena in radon time-series

Abstract. Two hourly-sampled time-series of soil-gas radon concentrations of durations of the order of a year have been investigated for periodic and anomalous phenomena. These time-series have been recorded in locations having little or no routine human behaviour and thus are effectively free of significant anthropogenic influences. One measurement site, Sur-Frêtes, is located in the French Alps, with saturated soil conditions; the second site, Syabru-Bensi, is located in Nepal, in a river terrace with unsaturated soil conditions. In such conditions, periodic components with periods ranging from 8 h to 7 days are often weak and intermittent and therefore, even in the presence of stationary forcing, difficult to identify. Two spectral decomposition techniques, Empirical Mode Decomposition (EMD) and Singular Spectrum Analysis (SSA), have been applied to these time series and yield similar results. For Sur-Frêtes, weak diurnal and semi-diurnal components are observed with EMD, while SSA reveals only a diurnal component. In Syabru-Bensi, both EMD and SSA reveal a strong diurnal component and a weaker semi-diurnal component. Tidal components M1 and M2 are also suggested by EMD in Sur-Frêtes, while these frequencies are not observed in Syabru-Bensi. The development of such analytical techniques can help in characterising the multiple physical processes contributing to the surface and subsurface dynamics of soil gases.

Special section on the 13th International Symposium on Flow Visualization

The 13th International Symposium on Flow Visualization (ISFV 13, http://isfv13.univ-fcomte.fr) was held at the Acropolis Convention Center, Nice, France on July 1–4, 2008. The 12th French congress on visualization in fluid mechanics (Fluvisu 12) was jointly held at the same venue. Every 2 years, the ISFV series gathers the international communities of Fluids and Thermal Engineering around the common theme of imagery and optical measurements, including the development of new visualization techniques, visualization of transport phenomena, characterization of fields of velocity, temperature and pressure, and of course, the validation of theoretical models. The ISFV-13 symposium attracted a total of 298 participants from 27 countries and was organized in 40 standard sessions, four invited lectures, and a poster exhibition. The standard sessions included Acoustics, Specific PIV/ PTV, Periodic Phenomena, Aeronautics and Space, High Speed, Multiphase, Turbulence/Vortices, Computer Visualization, Industrial Applications, DGV/DPV, Cavities, Refractometry, Stereo and 3D, Heat and Mass Transfer, BOS/Stereo Schlieren, Walls/Boundaries, Microflows, Combustion, Hybrid/Specific Methods, Coating Sensors, Interferometry, Terrestrial Vehicles, Rotating/Oscillating/ Swirling Flows, Advanced Image Processing, Optical and Electrical Manipulations, Natural Life, Human Life, Earth and Environment, and Art and Learning. In addition, more than 40 posters were displayed throughout the duration of the conference. The special committee of eight internationally recognized researchers (Kyung Chun Kim, Sang Joon Lee, Osamu Mochizuki, Robert Nelson, Jean-Michel Desse, Daniel H. Fruman, Godfrey Mungal, and Kenneth D. Kihm) attended the presentation sessions to invite selected authors to submit their manuscripts for the special section for Experiments in Fluids. A total of 20 conference proceeding papers were solicited, 15 authors responded with manuscript submissions, and seven completed their revisions as finally accepted contributions. This special section begins with a review article on the surface plasmon resonance (SPR) imaging technique as a new far-field visualization tool for near-field transport characterization. The second study presents an experimental study with the use of PIV for the vortex flow characteristics along a sharp-edged delta wing with apex strake. A third study presents the ‘‘Interfacial PIV’’ technique for application in near-wall velocity profile determinations. The fourth study proposes a new PTV image processing algorithm adopted from an ant colony optimization. The next study in this section deals with supersonic flows for characterization of shock wave discontinuities inside a shock tube using nanosecond space discharge. A sixth study presents planar fluorescence imaging for identification of bubbles in an axisymmetric two-phase jet flow. The final paper in this section presents the effect of rim-shroud clearance on flows around a rotating disk. Two International Awards were presented during the plenary session to two international experts for their outstanding contributions to the field of flow visualization: (1) Dr. Juergen Kompenhans, DLR, Germany, Asanuma K. D. Kihm (&) Mechanical, Aerospace, and Biomedical Engineering Department, University of Tennessee, Knoxville, TN 37996, USA e-mail: kkihm@utk.edu

The circular dataimage, a graph for high-resolution circular-spatial data

Vectors and periodic phenomena, e.g. traffic versus time, have direction on a circular scale of 360°. An overview of existing methods for the display of circular-spatial and vectorial-spatial data, such as arrow plots, is given. We introduce the circular dataimage, a new type of graphic for the display of circular-spatial data. It is defined by encoding direction in a spatial display by using colors from a color wheel constructed by connecting three or more two-color gradients with color continuity at the connections. Therefore, image discontinuity from using a single-color gradient, e.g. blue–red, does not occur. High-resolution global views of ocean wind direction are used as a running example throughout the paper. Advantages and disadvantages of circular dataimages compared to arrow plots were obtained from a usability study. Circular dataimages provide for simultaneous recognition of fine structure on a small-scale and large-scale structure on a global scale.

The mechanism of bursting phenomena in Belousov-Zhabotinsky (BZ) chemical reaction with multiple time scales

The dynamics of a typical Belousov-Zhabotinsky (BZ) reaction with multiple time scales is investigated in this paper. Different forms of periodic bursting phenomena, and specially, three types of chaotic bursters with different structures can be obtained, which are in common with the behaviors observed in experiments. The bifurcations connecting the quiescent state and the repetitive spikes are presented to account for the occurrence of the N K oscillations as well as the different forms of chaotic bursters. The mechanism of the period-adding bifurcation sequences is explored to reveal why the length of the periods in the sequences does not change continuously with the continuous variation of the parameters.

Identification of characteristic components in frequency domain from signal singularities

In rotating machinery condition monitoring, identification of characteristic components is fundamental in many engineering applications so as to obtain fault sensitive features for fault detection and diagnosis. This paper proposed a novel method for the identification of characteristic components in frequency domain based on singularity analysis. In this process, Lipschitz exponent function is constructed from the signal through wavelet-based singularity analysis. In order to highlight the periodic phenomena, autocorrelation transform is employed to extract the periodic exponents and Fourier transform is used to map the time-domain information into frequency domain. Case study with rolling element bearing vibration data shows that the proposed has very excellent capability for the identification of characteristic components compared with traditional methods.

A Synthesis Method of Gene Networks Having Cyclic Expression Pattern Sequences by Network Learning

Recently, the synthesis of gene networks having desired functions has become of interest to many researchers and several studies have been done. Synthesis methods of gene networks possessing desired expression pattern sequences are proposed. Periodic phenomena, e.g. circadian rhythm, are the important functions of cells. In this paper, we consider a synthesis problem of gene networks possessing the desired persistent cyclic expression pattern sequences. We have proposed the synthesis method of gene networks possessing the desired expression pattern sequences. Desired cyclic expression pattern sequences can be realized by using the synthesis method. But the behavior may not be persistent. We derive a sufficient condition such that the desired cyclic expression pattern sequences are persistent and propose a synthesis method realizing the persistent desired behavior by network learning.

1501 カルマン渦が誘起する非定常圧力場の感圧塗料計測(OS15-1 先端的熱流体計測法,オーガナイズドセッション)

To understand unsteady flow phenomena around a body, it is important to measure time-resolved surface pressure distributions with high spatial resolution. Pressure Sensitive Paint (PSP) has a capability of providing high-resolution pressure images. In this study, we propose a new PSP technique to obtain time-resolved surface pressure distributions by using conditional sampling of time-series PSP images. To obtain high SNR data, the high-speed camera images are phase-averaged after image acquisition, using a simultaneously-measured pressure transducer data to detect a phase of each image. This method allows us to obtain high SNR images at arbitrary phase of the periodic phenomena using a simplify measurement system and image processing. The effectiveness of the present method was evaluated by applying it to a 3-D square cylinder in low-speed wind tunnel testing. As a result of this experiment, we could obtain time-resolved unsteady pressure images around the square cylinder caused by periodic vortex shedding.

TRIGONOMETRIC PARALLAXES OF MASSIVE STAR-FORMING REGIONS. VII. G9.62+0.20 AND THE EXPANDING 3 kpc ARM

We report a trigonometric parallax of 12 GHz methanol masers associated with the massive star forming region G9.62+0.20, corresponding to a distance of 5.2+-0.6 kpc. With a local standard of rest velocity of about 2 km/s, the region's kinematic distances of 0.5 and 16 kpc differ greatly from the distance derived here. Our measurement of the peculiar motion of the star forming region shows a very large deviation from a circular Galactic orbit: 41 km/s radially outward from the Galactic center and 60 km/s counter to Galactic rotation. The combination of its radial velocity and distance places G9.62+0.20 in the inner region of the Galaxy close to the Expanding Near 3 kpc-Arm, where the bulge/bar potential has strong gravitational influence. We also map the distribution of 12 GHz methanol masers, locate them with respect to a hypercompact H II region, and compare our data with the periodic flare phenomenon reported previously for this source.

Annual rhythms of some physiological parameters in Ovis aries and Capra hircus

The aim of this study was to evaluate the annual variation of some physiological parameters (total lipid, NEFA, phospholipids, triglycerides, creatinine, β-idrossibutirrate, albumin, total protein, total cholesterol, urea, uric acid, glucose, rectal temperature and heart rate) in five female goats and five female sheep housed under natural photoperiod and natural ambient temperature in a 12 m2 sound proof box equipped with 50 × 100 cm opening window, that allowed natural ventilation. ANOVA was used to determine significant differences (p values < 0.05 were considered statistically significant). A trigonometric statistical model was applied to describe the periodic phenomenon analytically, by individuating the main rhythmic parameters according to the single cosinor procedure. Serum total lipid, NEFA, phospholipids, triglycerides, rectal temperature and heart rate, both in sheep and goats, showed an annual rhythm with acrophases in autumn. The results show that sheep and goats present similar annual patterns, probably influenced by various environmental factors.

Foreign Direct Investment Inflows to India

India, without exception, as in case of other developing countries, is eager to prompt its economic growth which compels it to accept and seek assistance of foreign direct investment (FDI). At present, it accounts for 1.25 per cent share of global FDI inflows, 7.18 per cent of Asian inflows and garners more than two third share of FDI inflows to the developing South Asia. Present study traces the history of FDI in India and reveals that actually FDI in India is an evolution since mid-eighteenth century and is an outcome of international and domestic dynamisms. It is not merely a phenomenon of post Independence or post liberalization period. Present study is an effort to examine the growth of FDI inflows to India and some selected representative countries of the developing Asia, through the computation of compound annual growth rates by fitting an exponential function estimated by ordinary least square method. It is detected that during the last three decades, the growth of FDI inflows remained highest in case of India followed by UAE, Turkey and China. What will happen in future is the function of what happened in the past. Believing this, the study has generated the forecasts of FDI inflows to the representative countries of Asia for the period 2009 to 2020, by using Double Exponential Smoothing Model. The adequacy of the model is tested by computing autocorrelation coefficients and Ljung-Box Q statistics. The study revealed that in the ensuing decade, out of all the countries of developing Asia, Saudi Arabia is expected to grow at the fastest pace as far as FDI inflows are concerned. In near future, although the magnitude of FDI inflows may remain highest in case of China but India is expected to leap forward swiftly and attract more than one seventh share of aggregate anticipated inflows to the developing Asia.

How Volatile is ENSO

The El Ninos Southern Oscillations (ENSO) is a periodical phenomenon of climatic interannual variability which could be measured through either the Southern Oscillation Index (SOI) or the Sea Surface Temperature (SST) Index. The main purpose of this paper is to analyze these two indexes in order to capture ENSO volatility. The empirical results show that both the ARMA(1,1)-GARCH(1,1) and ARMA(3,2)-GJR(1,1) models are suitable for modelling ENSO volatility. Moreover, 1998 is a turning point for the volatility of SOI, and the ENSO volatility has became stronger since 1998 which indicates that the ENSO strength has increased.

Ocean tidal cooling effect on summer sea fog over the Okhotsk Sea

Ocean tide is a periodic phenomenon of the rise and fall of the sea level that depends on the bathymetry and positions of the moon and sun relative to the earth. In the Okhotsk Sea, the ocean tide causes strong vertical mixing in the upper ocean, generating rich structures in summer SST with extraordinarily cold patches on Kashevarov Bank, along the Kuril Islands, northeast of the Terpeniya Peninsula, and inside Shelikhov Bay. The present study analyzes and synthesizes a suite of ship‐board and satellite observations, and numerical simulations to investigate the ocean tidal cooling effect on summer sea fog over the Okhotsk Sea. Over the tide‐induced cold patches, atmospheric stability increases, and surface wind weakens markedly possibly through suppressed atmospheric vertical mixing. Our analysis of ship‐board observations reveals frequent sea‐fog occurrence over the cold patches with a maximum exceeding 70% along the Kuril Islands in July–August. Numerical simulations with the Weather Research and Forecasting (WRF) model support that the cold patches cool air temperature, decelerate surface wind, and form a strong surface inversion layer up to 0.5 km high, creating favorable conditions for sea‐fog occurrence. The WRF simulation without the tidal cooling effect reduces sea‐fog occurrence by more than 20% over cold patches, illustrating the importance of SST products for climate models.

RNA interference is a powerful tool for chronobiological study in the cricket

Circadian rhythms are periodic phenomena recurring with a period of about 24 h that are observed in a variety of physiological functions. The rhythms are driven by an endogenous timing system involving the circadian clock. While recent molecular studies promoted understanding the oscillatory mechanism of the clock in model organisms such as Drosophila, its applicability to other insects still remains to be examined. RNA interference (RNAi) becomes a powerful method to dissect the clock and clock-related mechanisms in non-model insects. Crickets are particularly suitable for the application of RNAi, because a single injection of a clock gene dsRNA has long-lasting effects both on mRNA and behavioral rhythms. In this review, we introduce our current approach to the circadian clock as well as photoperiodic time-measurement mechanism in crickets, and describe the effectiveness of nymphal, adult, and parental RNAi in studies of biological timing mechanisms.

Metapopulation dynamics for spatially extended predator–prey interactions

Traditional metapopulation theory classifies a metapopulation as a spatially homogeneous population that persists on neighboring habitat patches. The fate of each population on a habitat patch is a function of a balance between births and deaths via establishment of new populations through migration to neighboring patches. In this study, we expand upon traditional metapopulation models by incorporating spatial heterogeneity into a previously studied two-patch nonlinear ordinary differential equation metapopulation model, in which the growth of a general prey species is logistic and growth of a general predator species displays a Holling type II functional response. The model described in this work assumes that migration by generalist predator and prey populations between habitat patches occurs via a migratory corridor. Thus, persistence of species is a function of local population dynamics and migration between spatially heterogeneous habitat patches. Numerical results generated by our model demonstrate that population densities exhibit periodic plane-wave phenomena, which appear to be functions of differences in migration rates between generalist predator and prey populations. We compare results generated from our model to results generated by similar, but less ecologically realistic work, and to observed population dynamics in natural metapopulations.