Damage of a steel plate from hypervelocity impact

We presents the results of damage of a carbon steel plate30 mm thick upon its loading by the impact of a steel ball5.55 mm in diameter at a velocity of up to7.4 km/sec. The dimensions of the crater formed and the bending flexure of the spalling layer are in good agreement with the results obtained upon a less intense loading of the target. One more feature of damage, namely, a crack passing through the target at the level of the crater bottom, has been revealed for the first time. Institute of Experimental Physics, Sarov 607200. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 1, pp. 119–121, January–February, 1997.     

Quadricuspid aortic valve: diagnosis by multiple transesophageal echocardiography

The case of a quadricuspid aortic valve diagnosed in adult age is reported. A 67-year-old patient, who had no previous diseases or cardiovascular complaints, presented in the clinic for an embolic occlusion of the left retinal artery. Isolated moderate aortic regurgitation was diagnosed clinically and echocardiographically. For its further evaluation and for seeking embolic sources, multiplane transesophageal echocardiography was performed, which discovered a quadricuspid aortic valve as the cause of aortic regurgitation and major atherosclerotic lesions in the ascending aorta and the aortic arch as possible cause of the embolic event. The fourth, accessory cusp, smaller than the other three, was localized between the non-coronary and left coronary cusp. In the short axis view the quadricuspid aortic valve showed in diastole a "X"-configuration, with a persistent central orifice between the commissures, which was the cause of the regurgitation jet in color Doppler examination, and in the systole a trapezoid opening pattern. In the long-axis view the valve showed a tricuspid closing pattern. The quadricuspid aortic valve can be exactly diagnosed by multiplane transesophageal echocardiography.     

Brachistochrone with friction

The brachistochrone problem is solved under the action of dry and viscous friction. For this purpose, this problem is represented as a problem of choosing a time optimal normal component (control) of the reaction of the support curve, whose shape is to be found. The Okhotsimsky-Pontryagin method of investigation of the functional differential is applied. Necessary optimality conditions that give the solution of the classical brachistochrone problem without friction and provide the corresponding optimal curves with friction are found. Parametric formulas for brachistochrones under the action of dry and viscous frictions are found analytically. Their properties are investigated. Attainability domains are determined. For certain values of the friction coefficients, the results of calculations are presented, which show the shape of the found brachistochrones and the optimal motion time.     

Crossing a small body of water by an insectomorphic robot on a raft

A mathematical model of the action of water on a raft in the case of nonstationary motion is developed. In the linear approximation, the dynamics and stability of the raft motion in the case of a shifted constant load and disturbed initial data are investigated. The motion enabling the robot to cross a body of water in the simple case when the robot imparts an initial push from the shore to the raft is designed. The proposed algorithm was worked out using computer simulation. Given sufficient data about the robot’s motion, numerical results proving the validity of the algorithm are presented.     

A control for an insectomorphic robot in climbing to the top of a vertical corner and in moving on a step ladder

For a six-legged robot, the problem of climbing a roof of a vertical right dihedral corner along its walls and a vertical high shelf with the help of a step ladder is investigated. The motions are realized with the help of the dry friction forces. The motion of the robot is formed by imposing servo-constraints in the form of adaptive step cycles of legs and the required geometric structure of body motion. An asymptotically stable program motion of legs relative to the body and the whole system is implemented by a PD controller. The results of 3D computer simulation of the controlled robot dynamics are presented.     

Effect of limbic structure and striatum damage caused by kainic acid on seizure reactions in animals after intracranial injury

It has been established that hippocampus, enthorhinal cortex, amygdala and substantia nigra (pars reticulata) lesions before head injury lead to a decrease of kainic acid-induced behavioral and electrographic seizure expressions. It can be concluded that after head injury the activation of limbic structures excitability due to excitation of "inputs" to these formations takes place. The obtained data indicate the significant role of nucleus caudatus in activation of posttraumatic brain excitatory mechanisms.     

Design of submerged turbulent jets of gases of different densities

We present results of a theoretical and experimental investigation of submerged gas jets in the range of density variations ( _j/ _e=0.05–10).Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 36, No. 4, pp. 715–720, April, 1979.     

Sets and Uncertainty

Arguments are presented indicating coincidence between the concepts of uncertainty and precision, and also on the undesirability of using the uncertainty propagation law for estimating dispersion. It is possible to estimate the reproducibility without performing an interlaboratory experiment and ways are characterized for estimating the closeness between the actual (or true) value of a measured quantity to the measurement result in the presence of influencing factors.We continue the selection of papers from the seminar “Mathematical methods in providing quality and mutual acceptance in measurement results,” with the start of the selection found in Nos. 4 and 5 for 2005.__________Translated from Izmeritel’naya Tekhnika, No. 6, pp. 20–25, June, 2005.