Decrease In Wave Height Research Articles

Wave setup/setdown and longshore current on non-planar beaches

Wave-induced setup/setdown and longshore currents are examined theoretically for non-planar, concave-up beaches. A beach profile in which the still-water-depth is proportional to the horizontal distance offshore raised to the 2 3 power is examined in detail. The total mean-water-depth, which includes the sum of the still-water-depth for this 2 3 power beach profile plus the wave-induced setup/setdown, may be approximated shoreward of the breaker line in a best least-squares sense by a profile that is proportional to the horizontal distance offshore raised to the 1 2 power. The longshore current profile for this non-planar beach is found to differ significantly from that predicted analytically for a planar beach. The longshore current velocity does not vanish at the shoreline as in the planar beach case. In addition, the peak velocities and the total longshore transport of water are found to be less than for the corresponding planar beach cases. For a given concave-up beach profile, the influence of the lateral mixing increases as the wave height decreases.

On the detectability of ocean surface waves by real and synthetic aperture radar

Real and synthetic aperture radars have been used in recent years to image ocean surface waves. Though wavelike patterns are often discernible on radar images, it is still not fully understood how they relate to the actual wave field. The present paper reviews and extends current models on the imaging mechanism. Linear transfer functions that relate the two‐dimensional wave field to the real aperture radar (SLAR) image are calculated by using the two‐scale wave model. It is noted that a description of the imaging process by these transfer functions can only be adequate for low to moderate sea states. Possible other mechanisms that contribute to the visibility of waves by real aperture radar at higher sea states, such as Bragg scattering from spontaneously generated short waves at peaked crests or in wave breaking regions, and Rayleigh scattering from air bubbles entrained in the water and from water droplets thrown into the air by breaking waves, are discussed in a qualitative way. The imaging mechanism for synthetic aperture radars (SAR's) is strongly influenced by wave motions (i.e., by the orbital velocity and acceleration associated with the long waves). The phase velocity of the long waves does not enter into the imaging process. Focusing of ocean wave imagery is attributed to orbital acceleration effects. The orbital motions lead to a degradation in resolution which causes image smear as well as a SAR inherent imaging mechanism called velocity bunching. The parameter range for which velocity bunching is a linear mapping process is calculated. It is shown that linearity holds only for a relative small range of ocean wave parameters: The likelihood that the transfer function is linear increases as the direction of wave propagation approaches the range direction, as the wavelength increases, and as the wave height decreases. Linearity is required for applying simple linear system theory for calculating the ocean wave spectrum from the gray level intensity spectrum of the image. Although, in general, the full ocean wave spectrum cannot be recovered from the SAR image by applying simple linear inversion techniques, it is concluded that for many cases in which the ocean wave spectrum is relatively narrow the dominant wavelength and direction can still be retrieved from the image even when the mapping transfer function is nonlinear. Finally, we compare our theoretical models for the imaging mechanisms with existing SLAR and SAR imagery of ocean waves and conclude that our theoretical models are in agreement with experimental data. In particular, our theory predicts that swell traveling in flight (azimuthal) direction is not detectable by SLAR but is detectable by SAR.

Motions of a Moored Ship Along the Perforated Quay Wall

In recent years, hydraulic functions of perforated quay walls have been studied by many investigators. They have mainly discussed the decrease of wave height reflected from the quay wall. In order ...

Polarographic reduction behaviour of N-benzoylphenylhydroxylamine

The reduction characteristics of N-benzoylphenylhydroxylamine have been examined with the help of DC, normal pulse and derivative pulse polarographic techniques and also cyclic voltammetry. The DC polarograms were found to be of a very steep nature with half-wave potential (El/z) lying in the region of 1270 inV. Due to the steep nature of the polarogram the logarithmic analysis could not be performed accurately for ascertaining the number of electrons involved in the reduction. However, a rough estimate of 3 4 electrons could be made. The slope of the curve obtained by plotting the wave height against drop time and the decrease of the wave height with increasing temperature indicate that the wave is adsorption controlled. The variation of the wave height with mercury pressure rules out the possibility of a kinetic wave. The derivative pulse polarograms were found to be very sharp and narrow. The peak potential (E,) lies at about 1270 mV and the peak halfwidth of 22.5 mV points towards a four electron reduction. The normal pulse polarograms exhibit the appearance of a maximum which is absent in the case of the DC polarograms. The cyclic voltammograms recorded wi tha hanging mercury drop electrode show very sharp and symmetrical peaks indicating a reversible reduction. The electrocapillary curve obtained by plotting the potential with drop time shows a minimum in the descending region at about 1250 mV which is near to the value of Et/2 of BPHA. All these above results clearly indicate that the reduction wave of BPHA is an adsorption controlled wave. The wave is only obtained in a neutral or slighty basic solution (pH7.5), but even in a slighty acidic solution it disappears. This signifies that in all probability the anionic form of BPHA is adsorbed at the electrode surface and causes the appearance of the wave. BPHA is very weak acid having a pK value of 8.30 in aqueous solution. So under the conditions of the experiment the adsorption of the anion is;quite understandable. No polarogram could, however, be recorded above pH 8.0 due to the decomposition of the compound. The solubility of BPHA in water has been reported [2] to be 1.95x 10-3M at 25~ and our studies were made at this concentration, At a lower concentration (4x 10-4M) the derivative pulse polarograms show a broad peak with Ep = l l 0 0 m V . At a concentration of 8x10 a M the peak becomes more or less sharp with Ep = 1180 inV. Addition of a metal ion lead did not, however, alter the nature of the peak obtained with 1.95 x 10-3M BPHA. Thus, it may be concluded that the steep DC polarograms and the sharp and narrow derivative pulse polarograms recorded with 1.95 x 10-3 M BPHA solution occur due to the total coverage of the mercury drop surface with the anionic form of BPHA.

Boundary-Layer Theory for Pressure and Drag of a Wavy Surface

The approximate theory presented, including the effect of the boundary layer, permits a much more accurate determination of pressure and drag of wavy surfaces in subsonic and supersonic flow (for M < 2.0) than is possible with inviscid flow theory. The B.L. (boundary layer) theory shows that the effective wave height and associated pressure decrease and eventually approach zero as the ratio of boundary-layer thickness to wave length increases. In supersonic flow, the decrease in effective wave height due to the boundary layer is accompanied by an aft phase shift in the B.L. wave, further decreasing the pressure drag due to the surface waves. The analysis correlates the theory with the results of surface waviness experiments conducted at the Langley Research Center and includes an estimate of drag contribution due to Gortler vortices generated by multiple waves. Application of the theory to a subsonic wing shows that surface waviness of appreciably smaller magnitude than that commonly found on military aircraft causes a significant detrimental effect on the drag-rise characteristics. Additional experimental research is needed to better evaluate the phase shift in supersonic flow, and the effect of Gortler vortices in both subsonic and supersonic flow.

On a Decrease of the High-frequency Polarographic Wave Height Caused by the Resistance of the Supporting Electrolyte

The wave height of a potential controlled high-frequency (hf) pblar ograph is greatly decreased by the series resistance of the electrolysis system.To clarify this phenomenon the total impedance of the electrolysis system is estimated in the absence of electrode process by measuring and induced hf amplitude (ref.18) and a hf runnMg current.The insertion of the corresponding series resistance from outside had a same effect on the wave height as the change of the sak concentration, Consequently, it was clarified experimentally that the effect of electrolyte concentration on the wave height was mainly due to the solution resistance of supporting electrolyte.A mutual relationship among the wave height, the solution resistance and the induced hf amplitude was investigated for three systems which gave the best typical shape of the hf polarographic wave.From Table 1, it is presumed that the wave height is not merely proportional to the square of the induced hf amplitude as shown in eq. (2), (3). Hence, a new factor xvith regard to the solution resistance should be considered.It is also presumed that the wave height is inversely Proportional to the square of the solution resistanee as show in eq. (2),

Physico-chemical studies on the binding of dyes with surfactants: II. Polarography of surfactant-dye mixtures

The polarographic method has been used to determine the binding of the acidic dyes, congo red and alizarin red S, to cationic surfactants (cetylpyridinium bromide—CPB, and cetyltrimethylammonium bromide—CTMAB) and that of the basic dye, methylene blue, to the anionic surfactant, dioctyl sodium sulphosuccinate (Manoxol OT). The surfactant concentration did not affect the combining ratio of dye to surfactant. Similarly, the pH of the reaction mixture had no influence on the combining ratio of dye to surfactant in the case of alizarin red S. A slight positive shift in E1/2 of methylene blue in the presence of Manoxol OT was realized at higher surfactant concentration. The calibration curve of surfactant concentration vs. decrease in wave height was used to determine the concentration of anionic and cationic surfactants.

薬品のポーラログラフ的研究 (第13報)

Xanthopterin undergoes two-electron reduction to form dihydroxanthopterin and its reduction wave is split into several steps by dissociation of the hydroxyls. The apparent pK' obtained from its wave height-pH curve are 11.25 and 11.9, which are larger than pK 6.84 and 9.46. This is explained as the kinetic current due to recombination reaction of proton. The reduction wave of non-dissociating molecule obtained at pH below 8 is accompanied with an adsorption wave and its wave height is not proportional to the concentration but to mercury pressure, decreasing in an organic solvent. Adsorption phenomenon was also confirmed from AC polarography and electrocapillary curve. From the adsorption wave height, the area of electrode occupied by adsorbed molecule was calculated as 55Å2 and the ring plane was assumed to be oriented parallel to the mercury surface. Transition from alkalinity to acidity results in decrease of total wave height, lowering of the degree of fluores-cence, and increase of oxidation wave observed in rotating platinum electrode. It is assumed from these facts that 2-amino-4, 6-dihydroxypteridine takes the phenoxide form in alkaline medium and about one-half is present as 2-amino-7-hydroxy-7, 8-dihydropteridine-4(3H), 6(5H)-dione in acid medium. Velocity of transition from the former to the latter is proportional to the concentration of hydrogen ion and is calcul-ated as ΔH 11, 000 calories and ΔS -37 calories. Inverse reaction is proportional to [OH-].

Das polarographische Verhalten von Ti(III) und Ti(IV) in Äthylendiamintetraazetat

Ti(III) and Ti(IV) form complexes, at pH values of under 2.5, with ethylene di-amino-tetra-acetate (Y−4) with the probable formula TiY− and TiY, which are reduced reversibly and independantly of pH at the dropping Hg-electrode. Temporary values are given for the dissociation constants. At higher pH values, the electrode processes are irreversible and dependant on Ph. From this fact, and from the decrease in wave height, the presence of complexes containing oxygen and numerous nuclei is concluded.