Phosphorus oxynitride: a thermally stable fire retardant additive for polyamide 6 and poly(butylene terephthalate)

The combustion performance of polyamide 6 (PA 6) and poly(butylene terephthalate) (PBT), both fire retarded by phosphorus oxynitride (PON), was studied by oxygen index (OI) and Underwriters Laboratory UL94 tests. It was shown that either PON alone or in combination with different co-additives is efficient in PA 6 and much less active in PBT. Thermogravimetric experiments provided evidence that PON promotes charring in both PA 6 and PBT. The mechanism of the char formation from PA 6 and PBT in the presence of PON was discussed on the basis of IR studies of solid residues produced in the thermal decomposition. The effective fire retardant action of PON in PA 6 is related to the interaction with the polymer to produce char, whereas the less effective activity of PON in PBT is related to the unfavorable acceleration of the evolution of combustible aliphatic fragments.     

Combined Impact of Magnetic Force and Spaceflight Conditions on Escherichia coli Physiology

Changes in bacterial physiology caused by the combined action of the magnetic force and microgravity were studied in Escherichia coli grown using a specially developed device aboard the International Space Station. The morphology and metabolism of E. coli grown under spaceflight (SF) or combined spaceflight and magnetic force (SF + MF) conditions were compared with ground cultivated bacteria grown under standard (control) or magnetic force (MF) conditions. SF, SF + MF, and MF conditions provided the up-regulation of Ag43 auto-transporter and cell auto-aggregation. The magnetic force caused visible clustering of non-sedimenting bacteria that formed matrix-containing aggregates under SF + MF and MF conditions. Cell auto-aggregation was accompanied by up-regulation of glyoxylate shunt enzymes and Vitamin B12 transporter BtuB. Under SF and SF + MF but not MF conditions nutrition and oxygen limitations were manifested by the down-regulation of glycolysis and TCA enzymes and the up-regulation of methylglyoxal bypass. Bacteria grown under combined SF + MF conditions demonstrated superior up-regulation of enzymes of the methylglyoxal bypass and down-regulation of glycolysis and TCA enzymes compared to SF conditions, suggesting that the magnetic force strengthened the effects of microgravity on the bacterial metabolism. This strengthening appeared to be due to magnetic force-dependent bacterial clustering within a small volume that reinforced the effects of the microgravity-driven absence of convectional flows.     

Geometric and elastostatic calibration of robotic manipulator using partial pose measurements

The paper deals with the geometric and elastostatic calibration of robotic manipulator using partial pose measurements, which do not provide the end-effector orientation. The main attention is paid to the efficiency improvement of identification procedure. In contrast to previous works, the developed calibration technique is based on the direct measurements only. To improve the identification accuracy, it is proposed to use several reference points for each manipulator configuration. This allows avoiding the problem of non-homogeneity of the least-square objective, which arises in the classical identification technique with the full pose information (position and orientation). Its efficiency is confirmed by the comparison analysis, which deals with the accuracy evaluation of different identification strategies. The obtained theoretical results have been successfully applied to the geometric and elastostatic calibration of a serial industrial robot employed in a machining work cell for aerospace industry.     

An efficient algorithm for the solution of the general mathematical programming problem

Conclusions As is obvious from these tables, the proposed algorithm allows problem (4), (6) to be solved fairly fast. At the same time, it depends weakly both on the dimensions of the problem and on the required precision of solution. This justifies reliance on the effectiveness of applying auxiliary problems, using nonlinear approximation of the constraints, in iterative methods of nonlinear programming.Translated from Kibernetika, No. 2, pp. 88–91, March–April, 1977.