Effect of desulphurization on the fracture toughness of structural steels at climatic temperatures

The results show that desulphurization of 09G2 and 10KhSND steels by blowing silicocalcium into the ladle and by treatment in the ladle with a synthetic slag with the sulphur content varying from 0.04–0.04 to 0.003–0.005% increases several times the impact toughness, 1.2–1.5 times the critical stress intensity factor, reduces the temperature of transition from ductile to quasibrittle failure, and increases the critical crack opening displacement two to six times in the temperature range 213–293 K. Desulphurization is an important method of increasing the brittle failure resistance of structural steels at reduced temperatures.Translated from Problemy Prochnosti, No. 11, pp. 14–21, November, 1990.     

Dynamics of the uptake of free amino acids in the blood serum of the portal vein during the digestion of isolated krill protein

The rate of absorption of amino acids obtained from isolated krill protein administered to rat stomach was studied. Absorption of casein amino acids was determined for reference purposes. Rats subjected to 48-hour fasting were administered krill isolate and casein in the form of homogenates at a rate 540 mg protein per 100 g bw in 6 ml of distilled water. The concentration of free amino acids in the portal vein was measured after 30 minutes, 1, 3 and 6 hours. The content of amino acids was measured by ion-exchange chromatography with the use of an automatic analyzer of amino acids. The digestion of krill protein proceeds at a high rate. This ensures the maximal augmentation of the concentration of most amino acids in the blood of the portal vein 30 min after isolate administration to the stomach.     

Ultrasonic shock treatment of welded joints

We develop a method of ultrasonic shock treatment of welded joints. It is shown that ultrasonic shock treatment increases the yield stress and microhardness of welded joints and decreases the probability of fatigue fracture. We study the microstructure of welded joints after ultrasonic shock treatment and propose a theory of accumulation of strains in the process of treatment. Institute of Physics of Metals, Ukrainian Academy of Sciences, Kiev; Institut für Metallkunde, University of Stuttgart, Stuttgart, Germany. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 5, pp. 71–74, September–October, 1999.     

Frequency-response equalization in integrated current amplifiers with collector—base cross coupling

It is shown that monolithic current amplifiers with collector-base cross coupling can ensure a single-stage amplification up to 40 dB in the frequency range from 0 to 0.1f_c (wheref _c is the cutoff frequency of the transistors). This is possible if the effect of intrinsic positive feedback and a parasitic low-pass filter is suppressed. The equalization procedure is described.     

Chaotic Negative-Resistance Oscillators with a Multibranch Piecewise-Linear Current—Voltage Characteristic

Chaotic oscillators with a negative-differential-resistance (NDR) subsystem having a multibranch piecewise-linear i–v characteristic (IVC) are considered. The problem of switching between chaotic oscillation regimes by changing the IVC electronically is addressed. New circuit realizations of the NDR subsystem are described in detail. It is shown that they provide highly stable IVCs.