Numerical simulation of the stress-strain state of the dental system

We present mathematical models, computational algorithms and software, which can be used for prediction of results of prosthetic treatment. More interest issue is biomechanics of the periodontal complex because any prosthesis is accompanied by a risk of overloading the supporting elements. Such risk can be avoided by the proper load distribution and prediction of stresses that occur during the use of dentures. We developed the mathematical model of the periodontal complex and its software implementation. This model is based on linear elasticity theory and allows to calculate the stress and strain fields in periodontal ligament and jawbone. The input parameters for the developed model can be divided into two groups. The first group of parameters describes the mechanical properties of periodontal ligament, teeth and jawbone (for example, elasticity of periodontal ligament etc.). The second group characterized the geometric properties of objects: the size of the teeth, their spatial coordinates, the size of periodontal ligament etc. The mechanical properties are the same for almost all, but the input of geometrical data is complicated because of their individual characteristics. In this connection, we develop algorithms and software for processing of images obtained by computed tomography (CT) scanner and for constructing individual digital model of the tooth-periodontal ligament-jawbone system of the patient. Integration of models and algorithms described allows to carry out biomechanical analysis on three-dimensional digital model and to select prosthesis design.Comment: 19 pages, 9 figure

Efficient numerical methods for the Biot poroelasticity system in multilayered domains

In this thesis, the quasi-static Biot poroelasticity system in bounded multilayered domains in one and three dimensions is studied. In more detail, in the one-dimensional case, a finite volume discretization for the Biot system with discontinuous coefficients is derived. The discretization results in a difference scheme with harmonic averaging of the coefficients. Detailed theoretical analysis of the obtained discrete model is performed. Error estimates, which establish convergence rates for both primary as well as flux unknowns are derived. Besides, modified and more accurate discretizations, which can be applied when the interface position coincides with a grid node, are obtained. These discretizations yield second order convergence of the fluxes of the problem. Finally, the solver for the solution of the produced system of linear equations is developed and extensively tested. A number of numerical experiments, which confirm the theoretical considerations are performed. In the three-dimensional case, the finite volume discretization of the system involves construction of special interpolating polynomials in the dual volumes. These polynomials are derived so that they satisfy the same continuity conditions across the interface, as the original system of PDEs. This technique allows to obtain such a difference scheme, which provides accurate computation of the primary as well as of the flux unknowns, including the points adjacent to the interface. Numerical experiments, based on the obtained discretization, show second order convergence for auxiliary problems with known analytical solutions. A multigrid solver, which incorporates the features of the discrete model, is developed in order to solve efficiently the linear system, produced by the finite volume discretization of the three-dimensional problem. The crucial point is to derive problem-dependent restriction and prolongation operators. Such operators are a well-known remedy for the scalar PDEs with discontinuous coefficients. Here, these operators are derived for the system of PDEs, taking into account interdependence of different unknowns within the system. In the derivation, the interpolating polynomials from the finite volume discretization are employed again, linking thus the discretization and the solution processes. The developed multigrid solver is tested on several model problems. Numerical experiments show that, due to the proper problem-dependent intergrid transfer, the multigrid solver is robust with respect to the discontinuities of the coefficients of the system. In the end, the poroelasticity system with discontinuous coefficients is used to model a real problem. The Biot model, describing this problem, is treated numerically, i.e., discretized by the developed finite volume techniques and then solved by the constructed multigrid solver. Physical characteristics of the process, such as displacement of the skeleton, pressure of the fluid, components of the stress tensor, are calculated and then presented at certain cross-sections

Addressing Transplant Tourism Problems and Proposed Solutions: Regulation Instead of Prohibition

Medical tourism, as defined by scholar Glenn Cohen, is the travel of residents of one country to another country for treatment. \u27 Transplant tourism, a type of medical tourism, is traveling abroad to purchase an organ for transplant. Although organ sale is currently illegal in every country except Iran, many countries-such as India, the Philippines, Pakistan, Bangladesh, and Egypt-have thriving black markets for these goods. Organ transplants are often the only effective means of treating end state organ failure, and the demand for transplants is especially high in developed and middle-income countries. Shortages of available donors and organs, however, have caused an increased demand with a limited supply. The Global Observatory on Donation and Transplantation estimates that in 2013, there were 118,000 organs transplanted globally, meeting only 10 percent or less of global needs. This gap in supply and demand has created a black market for underground organ sales where poor and vulnerable individuals sell their organs to brokers, who then resell these organs at higher costs. In 2011, the World Health Organization estimated that global illicit organ sales produced between $600 million and$1.2 billion annually. The market that has emerged is harmful to sellers in many aspects, and sellers are often taken advantage of by brokers\u27 manipulative tactics. This paper will explore the problems associated with black market organ sales and analyze its effects on sellers (i.e., the people selling their organs) and the tourists (i.e., the people who travel abroad for transplantation). Part I will give an overview of how transplant tourism operates, focusing specifically on kidney sales. Part II will address ethical arguments for why transplant tourism is harmful to sellers. Part III will address the international response to this phenomenon and the various international protocols in place. Finally, Part IV will propose regulatory solutions that are aimed at protecting sellers. Since a thriving black market already exists, regulation-instead of outright prohibition-is the best solution for protecting sellers\u27 well-being who are currently unprotected in the market

Influence of operational parameters on characteristics of pneumatic hammers

The paper covers the results of experimental study in influence of temperature and compressed air pressure, pressing force on operational characteristics of puncher. It is shown that increasing the temperature of compressed air the less the initial degree of compression in the back chamber, the more the energy parameters are, but air consumption decreases unequally for different types of puncher. It is stated that increasing the pressing force the air consumption grows up to a definite limit which is the most significant factor in the case of plugger with spring-loaded valve

Modeling of cation diffusion in bifunctional polymers based on cis-tetraphenylcalix[4]resorcinarene

In this study, we report that interaction of the network functional polymers based on cis-tetraphenylcalix[4]resorcinarene with aqueous solutions of electrolytes is controlled by diffusion of ions in a polymeric phase. The nanoreactor effect consisting in sufficiently high rate increase of a cation diffusion flux in bifunctional polymers containing sulfonic acid and phenol ionogenic groups has been found. For steady and non-steady states the solutions of the fundamental differential equation of cation diffusion in bifunctional polymers by means of the spherical layer model are obtained for a variety of initial and boundary conditions with constant diffusion coefficient. The proposed mathematical model explains the nanoreactor effect in bifunctional polymers

Thermal Efficiency of Steel Melting

This paper presents the results of energy consumption measurements at steel foundries using induction and/or electric arc furnace melting. Statistical methods, infrared thermography, and numerical investigations were used for analysis of heat losses. The influence of different melting practices on energy losses was examined. Industrial experiments in isothermal holding of liquid steel in induction furnaces under different power inputs were used for evaluation of the real values of heat losses by radiation from liquid steel and conductivity through lining. Average values and statistical distributions of energy consumptions for melting steel are presented in this article

Пандемия: философский диагноз

The paper examines the event of the pandemic in three aspects: a metaphor of our age, an issue of ethics, a new phase of anthropogenesis. As the metaphor of the era, the pandemic stars as Belikov (A. Chekhov’s The Man in the Case): the form of bio-phobia and socio-phobia, the growing sterility of contacts, socializing over distances, closeness, and the priority of packaging (covers) before the procedures of openness, nudity, fusion. There appears a change in genres: the detective as a genre based on the revelation and removal of a shroud of mystery, the punishment of crime, gives way to the genre of the protectIva (from protegere: to shroud, to pull the veil, to shield). The protective is a genre to avert a catastrophe, protect against crime that has already become a norm, — the experience of survival on edge. There emerges homo tegens, “man who enclothes”, who pulls a veil over everything including himself. The pandemic as an issue of ethics poses a multitude of ethical challenges and choices (between utilitarianism and egalitarianism, the principles of "not doing bad things" and "doing good"). The pandemic as the dawn of a new phase of anthropogenesis demonstrates the transformation of a man climbing and walking upright into a man sitting (in front of the screen) — Homo Sedens. With the development of civilization and the transition to intellectual work and a sedentary lifestyle, sight and hearing gain superiority. These organs are of remote perception, and in this sense, they meet the requirements of social distance and self-isolation that favour the preservation of man as a species. Physical sensitivity and tactility in the culture of Late Modern times have a paradoxical linkage with a change in the concepts of tact and decorum, with the ability to keep a distance, not to impose their views on another person. The author expects the consequence of the pandemic to be the movement of the frontier of civilization deep into the virtual worlds. Globalization is moving from an extroverted stage to an introverted one. The author concludes that when faced with a common danger that does not make national, ethnic, or religious distinctions, humankind becomes a concrete reality that one used to feel vague.Событие пандемии исследуется в трех аспектах: метафора нашей эпохи, проблема этики, новая фаза антропогенеза. Как метафора эпохи пандемия предстает в образе Беликова (А. Чехов «Человек в футляре»): форме биофобии и социофобии, растущей стерильности контактов, общения на расстоянии, закрытости и приоритете упаковок (покрытий) перед процедурами открытости, обнаженности, слияния. Констатируется изменение в жанрах: детектив как жанр, основанный на разоблачении и снятии покровов тайны, наказании преступления, уступает место жанру протектИва (от protegere: закрываться, натягивать покров, заслоняться щитом). Протектив — это жанр предотвращения катастрофы, защиты от преступления, уже ставшего нормой, — опыт выживания на пределе. Возникает homo tegens, «человек облекающий», набрасывающий покровы на все, в том числе и на самого себя. Пандемия как проблема этики ставит множество этических вопросов и выборов (между утилитаризмом и эгалитаризмом, принципами «не делать плохого» и «делать хорошее»). Пандемия как начало новой фазы антропогенеза демонстрирует превращение человека лазающего и прямоходящего в человека сидящего (перед экраном) — Homo Sedens. С развитием цивилизации и с переходом к умственному труду и сидячему образу жизни все больший перевес получают органы зрения и слуха — дистанционные органы восприятия и в этом смысле отвечающие требованиям социальной «дистанции» и «самоизоляции», которые благоприятствуют сохранению человека как вида. Физическая чувствительность и тактильность в культуре Нового времени парадоксально связана с изменением понятий «такт» и «тактичность», с умением соблюдать дистанцию, не навязывать другому человеку своих мнений. Следствие пандемии прогнозируется как передвижение фронтира цивилизации вглубь виртуальных миров. Глобализация переходит из экстравертной стадии в интровертную. Делается вывод о том, что, столкнувшись с общей опасностью, не делающей национальных, этнических, религиозных различий, человечество становится конкретной реальностью, которая раньше ощущалась смутно

Using Automated Inclusion Analysis for Casting Process Improvements

Different industrial melting and ladle practices (deoxidation, slag, refractory types, etc.) used in steel foundries were analyzed and compared using an ASPEX automated inclusion analyzer for study of inclusions. The effects of deoxidation and pouring practices on the size, type and number of inclusions were evaluated for steel foundries equipped with induction and arc melting furnaces, with capacities ranging from 1 to 20 tons. Samples were collected from the furnace, ladle, and castings. Specific rules were developed for classification of inclusions by composition, size distribution and shape. Inclusion statistics, including composition, quantity, shape, and size during cast steel processing from the furnace to the final casting were used for treatment optimization in the foundry ladles

Improvements in Steel Melting Efficiency -- Industrial Trials

Industrial trials were completed to improve energy efficiency in steel melting. First, the benefits of increased chemical energy from an oxyfuel burner and a Co-Jet system in a basic 20 ton electric arc furnace (EAF) were studied. Observations and measurements were made during production before and after the installation of the two systems. The additional chemical energy improved energy efficiency and resulted in increased production. In addition, production using a basic EAF practice was compared to the traditional acid EAF practice. Second, an industrial trial using a 750 lb ladle with a combination of a lightweight alumina castable refractory and a insulating board was compared to a standard alumina castable ladle. The new material also showed a potential for significant energy savings