Irregular Wave Patterns Research Articles

Development and Performance Evaluation of a Microcontroller Pulsed Magnetic Field Technique for Assisting Cellular Foods Freezing

Cellular foods have a short shelf-life due to the high water content and activity of microorganisms. Their water content is known to be magnetized when they are exposed to electromagnetic field, which is beneficial to their freezing. Although, magnetized water contained in cellular foods benefits freezing, but pulsed magnetic field technique available generates irregular wave patterns that are not promising to modern days freezing market. Therefore, the current study focuses on development and performance evaluation of a microcontroller pulsed magnetic field (MPMF) device for assisting cellular foods freezing. The MPMF technology consists of four main components including the magnetic field treatment chamber (120 mm x 90 mm x 60 mm), four electromagnets, and a step down transformer, a rectifier, capacitors, diodes, and a timer. The technology was operated at a voltage range and current of 2, 5, 7, 9, 11, 13 V, and 2.00, 12.60, 20.70, 28.60, 34.90, 38.60 A, respectively. The performance evaluation carried out on the machine includes magnetic field strengths and wave patterns. The results showed that the magnetic field strength varies between 9.15 to 42.96 T, and the wave patterns obtained were regular and satisfactorily. It is hope that the information on the development and evaluation of MPMF technique for assisting cellular foods freezing will be useful for the food industry

Experimental study of dripping, jetting and drop-off from thin film flows on inclined fibers

Gravity driven film flows on vertical fibers are known to exhibit a variety of flow dynamics including the formation of droplet trains induced by the hydrodynamic (Kapitza) and Plateau–Rayleigh instability mechanisms. Through an experimental study, it is shown how inclination of the fiber from the vertical influences these dynamics. The formation of waves, regime transitions from dripping to jetting regimes, as well as the onset of drop-off in the form of droplet detachment from the fiber are illustrated and described in dependence of the fiber inclination angle and the liquid mass flow rate. Additionally, the influence of fiber diameter and nozzle geometry on regime transitions and the onset of drop-off from the substrate are examined. It is shown that the onset of drop-off is strongly related to the transition from a regime characterized by a regular wave pattern to a regime characterized by an irregular wave pattern. It is also demonstrated that this regime transition depends not only on flow rate and fiber geometry, but also strongly on the inclination angle. Interestingly, a stabilizing effect of increasing the fiber inclination is detected for constant fiber geometry and film flow rate.

Bathymetry Determination From Marine Radar Image Sequences Using the Hilbert Transform

This letter presents an image processing technique based on the theory of the Hilbert transform to determine the coastal bathymetry from marine radar image sequences. Use of the Hilbert transform enables the difficulties and complications of inhomogeneous image analysis to be avoided. In addition, a number of steps and complex computations can be avoided using the numerical algorithm of the Hilbert transform. Because the Hilbert transform is suitable for only monocomponent signals, we first applied the image procedure to decompose the irregular wave patterns into different single wave period images. Analysis of the simulated wave field and radar image sequences demonstrated that there was a high correlation between the estimated depths and reference depths. The causes for errors in the bathymetry estimations are also discussed.

Tricho-Taxonomic Studies for Identification of Wild Boar, <I>Sus Scrofa</I> Linnaeus, 1758 by Dorsal Guard Hairs (Suidae: Artiodactyla: Mammalia)

The macroscopic and microscopic charactersof dorsal guard hairs of Sus scrofaLinnaeus, 1758 were examined using optical light and scanning electron microscopes for species identification. The hair of Sus scrofa is characterised by brown coat with tinged grey colour hairs, the profile is straight, thicker in diameter (109.4 ± 41.1μm) and have distinct microscopic characters such as irregular wave pattern and close margin of cuticular scales, unicellular regular and simple medulla, and circular shape. The micro and macroscopic characters of dorsal guard hairs can be used predator diet analysis as well as in forensic science as an appropriate reference for the species identification.

Wave Characteristics of Falling Film on Inclination Plate at Moderate Reynolds Number

Falling water film on an inclined plane is studied by shadowgraphy. The ranges of inclination angle and the film Reynolds number are, respectively, up to 21° and 60. Water is used as working fluid. The scenario of wave regime evolution is identified as three distinctive regimes, namely, initial quiescent smooth film flow, two-dimensional regular solitary wave pattern riding on film flow, and three-dimensional irregular wave pattern. Three characteristic parameters of two-dimensional solitary wave pattern, namely, inception length, primary pulse spacing, and propagation velocity, are examined, which are significant in engineering applications for estimation of heat and mass transfer on film flow. The present experimental data are well in agreement with the Koizumi correlations, the deviation from which is limited to 20% and 15%, respectively, for primary pulse spacing and propagation velocity. Through the scrutiny of the present experimental observation, it is concluded that wave evolution on film flow at the moderate Reynolds number is controlled by gravity and drag and the Rayleigh-Taylor instability that occurred on the steep front of primary pulse triggers the disintegration of continuous two-dimensional regular solitary wave pattern into three-dimensional irregular wave pattern.

The effect of non-uniform depth on the baroclinic response to wind in elongated basins

We examined the effect of along-thalweg depth variability on the baroclinic response to wind in elongated narrow basins with a sharp thermocline. The effect of depth variability was examined by deriving a modal-based forced model with two density layers and applying the model to a symmetric curved-bottom basin (CB), an asymmetric wedge-shaped basin (with a sloping bottom towards a vertical wall, WB), and a flat-bottom basin (FB). The baroclinic responses of CB, WB, and FB to uniform wind were found to differ in time-scale, number and energy of excited modes, and temporal pattern and along-thalweg structure of baroclinic flow and thermocline deflection. For all bottom profiles that were examined, the fundamental mode was found to dominate the response to spatially-uniform wind. Compared to FB, the asymmetric depth variability in WB increased the number and energy of excited higher modes and localized the interface shear, while the symmetric deviation from flat bottom in CB caused the opposite effects. Linear deviation from uniform wind was found to feed energy into higher baroclinic modes for the symmetric CB, but was found to reduce the energy of higher baroclinic modes for WB when the deviation from uniform wind is comparable to the spatial-average magnitude. Our results can explain the observation of the second baroclinic mode and irregular wave patterns in some lakes and reservoirs. Further, our results suggest that one-dimensional vertical mixed-layer models provide better results for shear entrainment in curved-bottom basins than in wedge-shaped basins.

Electrophysiological Characteristics of Human Colon Circular Muscle

Purpose: Interstitial cells of Cajal (ICC) play a core function in colonic motility as a pacemaker by regulating the slow wave. We intended to investigate the electrophysiological characteristics of the circular smooth muscle in the human colon, especially in Koreans. Methods: Colon tissues were obtained from patients undergoing an elective colectomy for non-obstructive lesions. Tissues were immediately stored in oxygenated Krebs-Ringer’s bicarbonate solution, and conventional microelectrode recordings of the colonic circular muscle were done from muscle cells. Results: The trans-membrane potentials from 100 tissues were recorded. Regular slow-wave patterns were observed in 36 patients, and 64 patients showed irregular wave patterns. In the tissues exhibiting regular slow-wave patterns, 20 tissues were recorded from the proximal colon and 16 from the distal colon. The frequency of the slow wave from the proximal part was significantly higher than that from the distal part. The resting membrane potential, the upstroke amplitude, the spike amplitude, and the maximal rate of rise showed no significant difference between the two parts, but the time to reach half amplitude did show a significant difference between the two parts. No significant differences in parameters were observed based on the patients’ demographics such as sex and age (younger or older than 60). We were able to divide the irregular waves into 3 groups. Irregular slow waves were observed in 35 tissues, irregular slow waves mixed with spike waves were observed in 26 tissues, and spike waves alone were observed in 3 tissues. Conclusion: We analyzed the electrophysiological characteristics of the human colonic circular smooth muscle, especially those of the slow wave originating from ICC of patients who had not been pretreated with drugs.

Non-uniform convergence of finite volume schemes for Riemann problems of ideal magnetohydrodynamics

This paper presents Riemann test problems for ideal magnetohydrodynamics (MHD) finite volume schemes. The test problems place emphasis on the hyperbolic irregularities of the ideal MHD system, namely the occurrence of intermediate shocks and non-unique solutions. We investigate numerical solutions for the test problems obtained by several commonly used methods (Roe, HLLE, central scheme). All methods turned out to show a non-uniform convergence behavior which may be paraphrased as ‘pseudo-convergence’: Initially the methods show convergence towards a wrong solution with irregular wave patterns. Only after heavy grid refinement the methods switch to converge to the true solution. This behavior is most pronounced whenever the solution should be unique but its phase space trajectory lies in the vicinity of that of a non-unique solution. We show detailed grid convergence studies and empirical error analysis. The results may be related to similar results for a 2 × 2 model system and to time dependent investigations of other authors. The non-uniform convergence is expected to be present for any diffusive finite volume method and question the reliability of coarse grid ideal MHD solutions, also in higher space dimensions.

Periodic and irregular wave patterns in an open tubular gel reactor

In an open quasi-one-dimensional Belousov-Zhabotinsky reaction-diffusion system we investigated simple periodic, complex and irregular spatiotemporal concentration patterns emerging under oscillatory boundary conditions. Symmetric (identical) feed concentrations were used at each boundary of a tabular gel reactor and the length of the system was varied. For tubes shorter than 11 mm the intrinsic wavelength is larger than half the length of the tube. In this case regular pairs of pulse waves are generated. When the length of the tube was increased we found more complex spatiotemporal behavior. Small inevitable differences in the oscillation frequencies at the boundaries finally lead to irregular patterns. The Karhunen-Loeve decomposition technique was applied for an analysis of the observed patterns.

Anomalous reflection of a shock wave at a fluid interface

Several wave patterns can be produced by the interaction of a shock wave with a fluid interface. Regular wave patterns have previously been explained by a shock-polar analysis. We focus on an irregular wave pattern that typically occurs when a shock passes from a medium of high to low acoustic impedance. Curvature of either the shock front or contact causes the flow to bifurcate from a locally self-similar quasi-stationary shock diffraction, to an unsteady anomalous reflection. We show that the anomalous reflection wave pattern can be explained with a modified shock-polar analysis in which the geometric node velocity is replaced by a downstream boundary condition. Anomalous reflection is analogous to the transition from a regular to a Mach reflection when the reflected wave is a rarefaction instead of a shock. These bifurcations have been incorporated into a front-tracking code that provides an accurate description of wave interactions. Numerical results for two illustrative cases are described: a planar shock passing over a bubble, and an expanding shock impacting a planar contact.

Snow-Water Equivalent Observation by Pressure Pillow

During the period from 26 November 1976 to 10 May 1977, a continuous observation of snow-water equivalent by the use of surface-mounted type pressure pillow 2. 4 m in diameter, mounted on ground surface. was carried out at Hassaki, Yunotani-mura, Kitauonuma-gun, Niigata-ken, Japan.The inner pressure of this pillow was measured electrically by a pressure sensor consisted of semiconductor gages instead of the standpipe system which was equipped in original pressure pillows. The out-put response was recorded on strip chart of an analog recorder.Snow-water equivalent values obtained by the pressure pillow agreed well with the actual values by a snow sampler with a error less than 10%, especially in the snow melt season. The record of the pressure pillow indicated irregular wave pattern in the daytime of the melt season.

Assessment of Seakeepability

This paper attempts to apply presently available knowledge of ship model behavior in regular waves to the prediction of trends of ship performance in realistic irregular wave patterns. Performance is studied in the terms of tendency to ship water forward and to slam, and of magnitude of heaving accelerations. The variables of particular interest considered are severity of sea, ship speed, ship heading, and hull proportions. It is believed that the trends obtained in this exploratory project should provide the naval architect with some guidance in the selection of basic hull characteristics for one particular type of ship (in this case, the single-screw dry-cargo ship). The results should also be of assistance in planning further systematic research.

Measurement and analysis of the response field of turbulent boundary layer excited panels

Reported here are experimental results 0f the wall pressure covariance on a rigid wall, the dynamic response, and acoustic radiation characteristics of rigidly clamped panels excited by turbulent flow. Statistical techniques are employed. A duct 0f 7·3 × 3·5 in. crosssection was used, with flow speeds up t0 700 ft/sec. Two functional representations 0f the wall pressure covariance in the broad frequency band have been obtained. One representation uses a probability density distribution which fits the experimental cross-correlation distribution but is of limited range of frequency components. The other covariance is constructed from the auto-correlation obtained from the power spectral density with temporal decay in a moving frame of reference, corresponding to a broader range 0f frequency components. The panels tested were 7 × 12 in. made 0f aluminium flush mounted in the wall of a turbulent flow duct. Panel thicknesses were 0·020 0·040 0·060 and 0·080 in. It is found that the modal mean-square displacement, along the flow direction, varies with Mach number and panel thickness. The higher order modes show the effect 0f aerodynamic coincidence corresponding to the maximum displacement amplitude. A similar maximum is indicated by the bending stresses. The broad-band longitudinal space-time correlation 0f the displacement 0f the 0·040 in. panel clearly shows pronounced oblique ridges and valleys which are interpreted as moving waves having the same phase velocity as the convected wall pressure fluctuations. The correlation 0f the 0·080 in. panel shows a more irregular wave pattern with n0 evidence of coincidence. This difference in response between the thickest and the thinnest panel is also manifested in the total mean-square displacement, the total acoustic power radiated, and the modal bending stresses; indicating a transition in power laws for conditions above and below coincidence. The degree of coupling between the structural field and the acoustic field is discussed. It is shown that the modal acoustic impedance is a measurable quantity which increases with modal number, and less significantly with Mach number.

The diffraction of galactic radio waves as a method of investigating the irregular structure of the ionosphere

The amplitudes of the radio waves received from a radio star at two points separated by about 1 km have been studied and compared. The results indicate that the variations of phase and amplitude at one point can be ascribed to the steady drift of an irregular wavepattern over the ground. It is shown how the structure and movement of the wave-pattern can be deduced from the observations. The irregular wave-pattern across the ground can be thought of as a diffraction pattern produced by the passage of the waves through a portion of the ionosphere which imposes irregular changes of phase on it, and it is shown how the ionospheric characteristics can be deduced. The ionospheric irregularities are shown to have a lateral extent of the order 2 to 10 km, and a variation of electron content of about 5 × 10 9 electrons per cm. 2 It is deduced that the irregularities are at a height of about 400 km. They are most pronounced around midnight and exhibit little annual variation. The irregular portion of the ionosphere moves with a steady wind-like motion with a velocity of the order 100 to 300 m/s. The velocity decreases after midnight, and large velocities are associated with periods of magnetic disturbance.