The laparoscopic technique for the treatment of duplex kidney anomaly became popular thanks to the efforts of G. Jordan and B. Winslow, who in 1993 successfully performed the world’s first laparoscopic heminephrectomy in a child. This operation has made its way into the world of surgical methods that have great potential for improving postoperative patient recovery and cosmetics, asserting the progress of pediatric endourology. Since the first report of laparoscopic heminephrectomy, a minimally invasive approach has gained popularity, and in some advanced surgical centers it has completely replaced open surgery in the treatment of urinary tract abnormalities. To date, there are several studies that demonstrate the safety and feasibility of laparoscopic heminephrectomy in children; nevertheless, the use of such an approach in the pediatric population is limited. Other endosurgical techniques for treating duplex kidney anomaly include retroperitoneoscopy, single-port laparoscopy and robotic surgery. The choice of endosurgical heminephrectomy technology is determined in accordance with the patient’s age, possession of technical capabilities and personal experience of the surgeon. In the literature, there is still a relative lack of evidence of the safety and effectiveness of endosurgical operations designed to remove the affected kidney segment in children. The purpose of the scientific review is to analyze the results of laparoscopic heminephrectomy in children and present its strengths and weaknesses, based on data that exist today in modern scientific literature.
Purpose of the study is to develop a matrix method for studying the dynamics of a tractor as a multi-mass spatial system of rigid bodies with an arbitrary arrangement of elastic suspension of bodies on shock absorbers relative to a fixed support surface and the presence of elastic connections between the bodies, made in the form of beam elements. Research methods. The methodological basis of the work is the generalization and analysis of well-known scientific results regarding the dynamics of two-mass systems in resonance modes and the use of a systematic approach. The analytical method and comparative analysis were used to form a scientific problem, determine the goal and formulate the research objectives. When creating empirical models, the main provisions of the theory of stability of systems, methodology of systems analysis and research of operations were used. The results of the study. A wheeled vehicle is presented as an amortized continuous frame type structure with assemblies and assembly units located on it, as well as a methodology for calculating individual block matrices of stiffness and damping coefficients. In this case, it is assumed that a viscous damper can be connected in parallel to each elastic element. In this construction of the stiffness and damping matrix of the block matrix are formed in the same way. Damping matrices are derived from the corresponding matrices by substituting damping constants instead of stiffness constants. To determine the natural frequencies and vibration modes of an undamped system using a PC, the most effective method of diagonalization by successive rotations. This method provides a complete solution to the problem, allowing all frequencies and shapes to be determined simultaneously, and good convergence. Conclusions. The considered method for analyzing and calculating the dynamics and vibration damping of a tractor as a complex mechanical system is based on a matrix record of the problem of spatial vibrations of a system of rigid bodies with elastic bonds. Matrix equations seem to be especially useful in the study of complex tightly coupled systems with the obligatory use of a PC. The presented work provides a complete methodology for calculating a tractor as a complex mechanical system such as a spatial frame with equipment installed on it.
In the work, the unevenness of the translational speed of a crawler with a triangular outline shape and the upper location of the drive wheel is analyzed. It was established that the value of the motion unevenness coefficient is a function of the design parameters of the engine. Of all these parameters, only the height of the location of the driving wheel practically cannot be changed, since it is determined by the dimensions of the tire in the wheel modification. Other structural parameters can change during the development of the engine design and, therefore, be the controlling elements in the system, which causes the unevenness of the translational speed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.