Mechanism of high energy absorption by foamed materials-foamed rigid polyurethane and foamed glass

Energy absorbability of foamed rigid materials, polyurethane and glass, was studied under a compressive load. The brittle materials were proved to absorb much energy in a manner similar to ductile materials. A mechanism for such high energy absorption was proposed, based on a fracture model in which crushing of cells initiates at the weakest cell followed by propagation to cells lying in the layer containing the weakest one and lying in a direction perpendicular to the compressive force; then the crushing propagates to another layer under the compressive force after the completion of the first layer crushing. In the period of one layer crushing, the strain energy stored in the period of compression prior to the crushing is temporarily released, and it is stored again in the period of compression after the crushing. The store and release of strain energy is assumed to be repeated until all cell layers are crushed. This mechanism of layer-by-layer crushing allows the cells to absorb strain energy repeatedly, and causes high energy absorption in the brittle foamed material. The calculated energy based on the mechanism agrees well with the observed one.     

Mechanism of production of midsystolic click in a prolapsed mitral valve

In order to examine the production mechanism of the midsystolic click in cases of a midsystolic click and a late systolic murmur, the relationship between the click and the motion of the mitral apparatus was studied by means of ultrasono-cardiotomography and the simultaneous recording of phonocardiograms and ultrasono-cardiograms (UCGs). It was found that the systolic click occurred in exact coincidence with the time at which the hump of the echo of the unusual early systolic anterior motion (early SAM) took its backmost position. This coincidence was found when the click was shifted either by postural changes or inhalation of amyl nitrite. The present ultrasono-cardiotomographic study demonstrated that the echo source of the early SAM could be attributed to the protrusion into the left ventricular outflow tract of the slackened elongated chordae tendineae in systole. The anterior leaflet moved suddenly to the position of maximal prolapse when the slackened chordae tendineae were stretched taut in midsystole. In other words, the midsystolic click occurred when the anterior leaflet prolapsed and the tension exerted on the chordae tendineae was at its maximum.     

Learning behavior of stochastic automata in the last stage of learning

In this paper, a learning behavior of stochastic automata acting in an unknown random environment is considered. Especially, a learning behavior of stochastic automata in the last stage of learning is investigated. Using the theory of Stochastic Stability and Control [9], it is shown that there exists an upper bound of the probability with which stochastic automaton goes back to an unfavorable state within some finite time.     

In situ high temperature TEM observation of interaction between multi-walled carbon nanotube and in situ deposited gold nano-particles

Interaction between multi-walled carbon nanotubes (MWNTs) and deposited gold nano-particles has been dynamically observed in a 200 kV transmission electron microscope (TEM) using a specimen heating holder. Gold particles with diameters of several tens of microns were mixed with MWNTs to mount on the heating element of a specimen heating holder. The gold particles were instantaneously heated to 1373 K to deposit gold nano-particles on the MWNTs from a very short distance. The MWNTs were then heated to 1073 K to observe interaction between the deposited gold nano-particles and MWNTs. Some gold nano-particles drilled through the wall of the MWNT and entered the capillary space of the MWNTs. To characterize the mechanism of the transition of the gold nano-particles into the capillary space of the MWNT, high resolution TEM observation of the deformed wall of MWNT was also carried out.     

The role of pyrophosphate in copper deposition from cupric pyrophosphate solutions

Cathodic polarization characteristics of copper was examined in cupric pyrophosphate solutions of different concentrations and temperatures. The structure and composition of the deposited copper was examined by scanning electron microscopy, X-ray diffraction, electron probe microanalysis and Auger electron spectroscopy. The polarization characteristics implied that the coverage of the electrode by adsorbed pyrophosphate ions decreases with increasing cathodic polarization and it becomes almost zero past a critical potential E_b of about ?0.75 V vs sce. E_b becomes more negative with increasing concentration of free pyrophosphate ions. As expected, pyrophosphate was incorporated at relatively high concentrations (0.05–0.07 wt% as P) in the deposits in the potential region I (E ? E_b) and at lower concentrations (ca. 0.02 wt%) in region II (E < E_b). Smooth deposits with random crystalline orientations were obtained in a part of region I for cd ? ca. 5 mA/cm². The rough deposits obtained outside this showed preferred (220) orientations as could be expected from the orientation theory. The smooth deposition in region I is due to the pyroposphate adsorption which inhibits the ordered deposition of copper.     

Stress intensity factor at a bilaterally-bent crack in the bending problem of thin plate

An infinite plate with an asymmetric bilaterally-bent crack is analyzed as a bending problem of a thin plate. Stress distributions and stress intensity factors are obtained for some angles and length of bent crack. These are obtained for the some Poisson's ratio. Influence of the initial crack width on the stress intensity factor are also investigated. Three loading conditions are taken into consideration: uniform out of plane bending at infinity in the $\text{x}$ and $\text{y}$ directions and uniform out of plane twist. The rational mapping function in the form of a sum of fractional expressions and the complex variable method are used for the analysis.     

Nuclear reactor strategies: Sensitivity analysis of the Häfele — Manne model

In the March issue Professors Häfele and Manne described their linear programming model of the transition from fossil to nuclear fuels. The present authors report on the sensitivity analyses they have performed on this model.