Electric Resistance Welding of Dissimilar Pipes

Numerous studies have shown that corrosion of the casing outer side is one of the factors that has a negative impact on the accident rate of the casing string and is the reason of loss of tightness and various failures and complications in the well. The article describes a method of electric resistance welding of dissimilar steel bonding, which allows to increase the corrosion resistance of casing strings in elevator sections with an increased exterior aggressiveness. The developed technology solutions for welding conditions are presented. Metallographic studies of welded joints and recommendations for technological welding conditions are given. © 2020 Published under licence by IOP Publishing Ltd

Aesthetic surgery of the lower limbs in current orthopedic practice

Introduction Correction of the shape of the lower extremities for aesthetic puposes has specific features that are associated with the role of the patient in the treatment process and assessment of results. An important element is the relationship between the appearance of the limb and changes in the axes of the skeleton. Aim of study Assessment of many-years of experience in orthopedic correction of the shape of the lower extremities for aesthetic purposes, discussion of possibilities, analysis of problems and search for possible ways to prevent them. Methods The material of the study was 123 patients who underwent aesthetic surgical correction in the period from 2005 to 2020. Their long-term results were followed in the period from 6 months to 11 years. In all cases, operations were performed simultaneously on both limbs. The total number of operations, thus, amounted to 246. The main indication for surgery was the so-called true O-shaped curvature (varus deformity) of the lower extremities. In all cases, the main elements of the operation were osteosynthesis with the Ilizarov apparatus and osteotomy of the tibia. Wires and half-pins were used as transosseous elements. To assess the main reference lines and angles (RLA), X-ray examination of the lower extremities was performed with the capture of the hip and ankle joints. Results and discussion Corrective manipulations in the group of patients led to a change in the position of the main RLA. Before treatment, MAD value was 15 ± 7 mm, after correction MAD = -2 ± 4 mm, before surgery MPTA = 85 ± 40, after correction MPTA = 91 ± 20. Subjective satisfaction was reported in 114 (92.7 %) cases. Subjectively unsatisfactory results were recorded in 4 (3.3 %) cases; objectively unsatisfactory results were detected in 5 (4.1 %) cases. Conclusions Aesthetic surgery of the lower extremities is a part of orthopedic practice and has its specific features due to the goal of realizing the patient's wishes about changing the appearance of the lower extremities indirectly by performing operations on the skeleton. Corrective surgery should be considered as a preventive intervention aimed at preventing the development of gonarthrosis in old age. The key to a good result is a careful selection of candidates for surgery and their compliance, along with a thorough explanation of the principles and features of correction. © 2021. Artemev A.A., Brizhan L.K., Davydov D.V., Bytdaev Z.M., Kashoob Á.M., Shipulin A.A., Gululyan G.G. All rights reserved

On Conditional Density Estimation

With the aim of mitigating the possible problem of negativity in the estimation of the conditional density function, we introduce a so-called re-weighted Nadaraya-Watson (RNW) estimator. The proposed RNW estimator is constructed by a slight modification of the well-known Nadaraya-Watson smoother. With a detailed asymptotic analysis, we demonstrate that the RNW smoother preserves the superior large-sample bias property of the local linear smoother of the conditional density recently proposed in the literature. As a matter of independent statistical interest, the limit distribution of the RNW estimator is also derived