Destructive Waves Research Articles

An inhomogeneous Landau-like equation

The problem of the mixing of two plasmas is very difficult to solve if the methods of statistical mechanics are used. When both plasmas are homogeneous in space, and the limit of weak coupling is appropriate, the Landau equation describes the motion. An equation, similar to the Landau equation, is developed for the case when one of the plasmas is initially inhomogeneous in space. The equation is a power series in time and involves wave vectors in space. The short-time-after-mixing limit is considered, which restricts the number of wave vectors. A sample problem is presented of the short time development of an infinite-temperature spike interacting with a homogeneous plasma. The spike is found to move very rapidly from the origin owing to the long range of the forces. Extension of the time development past the initial short time requires consideration of destructive wave vectors in addition to the wave vector generation considered here.

Selective cell destruction and precise neurite transection in neuroblastoma cultures with pulsed ultraviolet laser microbeam irradiation: An analysis of mechanisms and transection reliability with light and scanning electron microscopy

Ultraviolet (UV) laser pulses at 337 nm and 12 nsec were used as an effective surgical tool for the elimination of cells and the transection of cellular processes in culture. Analyses of lased neuroblastoma cells with light and scanning electron microscopy show that precise, immediate lesions of 0.5 μm to 2 μm can be produced using either of two techniques: (1) direct laser transections at energy densities above 12 μJ/μm 2; and (2) indirect transections by involving the substrate in the surgery process at energy densities ranging from 1 to 12 μJ/μm 2. The first technique uses cytoplasmic cavitations in the laser focus; the second depends on shock waves created by vaporizing substrate. Damage thresholds have been established for commonly used tissue culture materials and for unpigmented cytoplasm. Thresholds for all plastics tested lie below that of unpigmented cytoplasm making the direct transection technique inapplicable because of the formation of large, destructive shock waves. A reduction of energy densities to the damage thresholds of specific substrate materials allows the production of minute shock waves that create the highly localized damage required for reliable, precise and non-lethal cell surgery in culture.

False paradoxes of superposition in electric and acoustic waves

When acoustic or electromagnetic waves cancel by destructive interference, the wave impedance reflected to the sources of the wave energy changes so that the input power is reduced correspondingly. Because this rather subtle point is not discussed in most instructional treatments of wave physics, misconceptions concerning the apparently ’’missing’’ energy are widespread, as reflected in semipopular science writing. This paper presents an analysis of the cases of destructive and constructive wave interference, and analogous problems for lumped electrical and mechanical systems.

Mate size and breeding success in a monogamous cichlid fish

The patterns of mate size and parental care of a monogamous cichlid fish,Cichlasoma maculicauda, were studied in Gatun Lake, Panama. Males defend territories which serve as courtship and nest sites. Within a population most mates in pairs are of equal size rank. In each pair the male is larger than the female, probably because most mature males are larger than most mature females. Clutch size increases with female body size. Male size affects breeding success in two ways. First, larger males provide nest sites less susceptible to destructive wave action. Second, young of larger males grow faster than young of smaller males. Large males defeat small males in contests for position in feeding areas, and this may provide their young with better feeding conditions. In the laboratory young growth rates increase with food abundance, and at high levels of food surpass those observed in nature. Fast growth of young reduces their vulnerability to predators and should allow parents to breed more often. Young survival rates improve with the size of the parents, so that larger fish raise more offspring at each breeding attempt. These observations suggest why preference for large mates should occur.

Stability of sloping structures in relation to ξ = tanα/√ H/ Lo risk criteria in design

This paper discusses the importance of wave period to the stability of sloping-faced waveprotection structures (permeable and impermeable). A summary of wave breaking, run-up and run-down is given using a one parameter system ξ = tanα/√ H/ L o. The nature of hydrodynamic forces during the time history of flow is analysed and the most destructive wave vs slope combinations are described as a function of ξ. Model test data are presented in connection with the theory. A risk criterion in the design for stability and wave run-up is given using the joint distribution of wave heights and periods. Three case histories are demonstrated which verify the importance of wave period as well as wave height in the design.

Ice Avalanches

Ice Avalanches

Ice Avalanches

Ice Avalanches

Principles and Application of Ultrasonic Spectroscopy in NDE of Adhesive Bonds

Ultrasonic spectroscopy utilizes the principle of construc- tive and destructive wave interferences to obtain information about ultrasound in the frequency domain. For applications in the nondes- tructive evaluation (NDE) of adhesive-bonded structures, destructive interference of the pulsed sound waves at the boundaries of the adhesive bond layer produces spectroscopic signals characteristic of the bond. The bondline thickness can be determined accurately from the fre- quency minima in the spectrum. The width of the antiresonance dips at half-power points and the amplitude of the dips are related to the acoustical properties at the interfaces of the adhesive layer. The amplitude ratio of the RF signals reflected from the boundary surfaces of the adhesive layer in the time domain is also affected by the acous- tic impedance mismatch at the boundaries. A combination of these measurements in the frequency and time domains characterize the adhesive properties between the adherend and the adhesive. The ex- perimental set-up consists of a wide-band pulser/receiver as an energy source, a highly damped piezoelectric sensor serving as the transmitting and receiving transducer, and a digital computer for waveform digitiza- tion and Fourier transform. Single lap-shear adhesive-bond specimens using three types of adhesive systems were used in a correlation study between bond strengul and NDE parameters from the ultrasonic spectroscopy method. An empirical bond strength/NDE parameters relationship established from the correlation study has been justified by analytical calculation. The experimental procedures, analytical derivations of the sound wave interactions in the layered media, and the statistically valid correlation of the bond strength with NDE parameters is presented. obtained by using the ultrasonic spectroscopy technique wlll be presented. The bondline thickness can be measured ac- curately by means of reflected spectra using a known value of the velocity of sound. An anlytical calculation of the sound wave interference in the bondline is presented. This calcula- tion takes into consideration the attenuation in the adhesive and relates the attenuation coefficients to the antiresonances in the frequency spectra. A brief presentation of the experi- mental setup precedes the results obtained on single lap-shear specimens. Discussions on the potentials of the ultrasonic spectroscopy technique and conclusions on the presentation are included. 11. ANALYTICAL CALCULATION For the normal incidence of compressive ultrasonic waves on an attenuating layer, the wave numbers in the media will, in general, be complex. The complex form of the wave numbers was presented by Brekhovskikh (5) as

Tsunami Disaster on the Aquiculture in Miyako Bay, Iwate Prefecture caused by the Tkachi-oki Earthquake

The aquiculture along the Sanriku coast was heavily damaged by destructive high waves, tsunami, especially in Miyako bay, caused by the Tokachi-oki earthquake on May 16th 1968. In Miyako bay, facilities to raise crops (oysters, lavers, wakame and so on) were entirely destructed. They were not only washed away by the waves but were also drifted against lumbers which flowed out from the port to the bay.In spite of such heavy damages, farmers began to restore the destructed facilities and tried to reopen the raising of crops. The main factors which enabled the reconstruction are as follows. 1) Aquiculturists were consisted of small scale farmers, which bears the instability of production caused by natural disasters and by fluctuation of prices. For example, they are engaged in part-time jobs other than aquicultrure, facilities are evenly distributed among them, farms are exchanged every year, and so on. 2) A part of cost necessary to buy new facilities was subsidized by national and prefectural governments but it is not always sufficient. As it is very difficult to protect aquiculture from tsunami under present economic and technical conditions, it is especially important for national and local governments to take reconstruction measures effectively.

The 1953 Suva earthquake and tsunami

Abstract The epicenter of the Suva earthquake of Sept. 14, 1953, (U.S.C. & G.S. data: H = 00h26m36s UT 1812°S,17812°E;M=634; h about 60 kilometers) has been redetermined on the basis of landslide intensity, isoseismic analysis, damage criteria, the bathymetry of the epicentral zone, and by other means. The new epicenter is at 18.2° S, 178.3° E with an estimated probable error of five miles. Employing the new epicenter, P residuals of 15 stations (U.S.C. & G.S. data) were computed, assuming a normal and a 60 kilometer depth of focus. A normal depth of focus was decidedly the most likely. Arrival times of the ensuing tsunami at various points were reconciled to show that the tsunami had an extended source from Suva harbor to Beqa island. The tsunami was clearly caused by the slumping of marine sediments immediately after the earthquake. The direct action of the earthquake produced small waves that served as warnings on Beqa and Kadavu islands. These waves are presumed to have been created by the vibration of the reef against the water. The destructive waves, arriving later, were produced by slumping effects originating on the edge of the marginal shelf. Their observed arrivals are consistent with this mechanism. The bathymetry of the affected area was resurveyed and bottom changes up to 300 feet vertically were found. At a distance of more than 30 miles from the slumps, submarine cables were disrupted and displaced by as much as 13,000 feet. It is inferred that these effects were caused by turbidity currents travelling down a gradient of about 5 per cent for the first 10 miles and nearly flat thereafter.

9.地震による構造物の非線型振動について : その1・構造物力学特性の必然的非線型化過程

For the establishment of the rational aseismic design of structures, it is necessary, at first, to study the following problems qualitatively. That is, what measure we should adopt for the destructive force of the earthquake, what pattern of the seismic wave we should take up for the object of the final aseismic design, and what sort of quantity we should prescribe as the limit value of the final aseismic calculation. Here, we must consider that the seismic waves are irregular and mingled with unstationary waves and that the mechanical character of structures varies inevitably from linear state to nonlinear state when subjected to the destructive seismic wave. Under these considerations we find the most dangerous wave for each structure from various seismic waves assuming the certain measure of the destructive force of the earthquake, and analyze the final nonlinear behavior of structures subjected to such a wave. Mathematically, these problems reduce to simultaneous ordinary second order nonlinear differential equations if structures are assumed to be a mass-system, so that we can solve them graphically by using our improved method induced from the phase-plane-delta method of L.S. Jacobsen. Thus we can reach the following conclusions. 1. The measure of the destructive force of the earthquake should be the constant seismic displacement. 2. The most dangerous pattern of the seismic wave has the period nearly equal to that of each structure under the constant seismic displacement- 3. Horizontal relative displacements of structures should be prescribed as the limit value in final seismic calculation.

衝撃の傳播により起る大阪灣の高潮

衝撃の傳播により起る大阪灣の高潮

衝撃の傳播により起る湖水等の靜振及びその風津浪への應用

衝撃の傳播により起る湖水等の靜振及びその風津浪への應用