Parametric identification of mathematical models of coupled conductive-radiative heat transfer

In many practical situations it is impossible to measure directly such characteristics of analyzed materials as thermal and radiation properties. The only way, which can often be used to overcome these difficulties, is indirect measurements. This type of measurements is usually formulated as the solution of inverse heat transfer problems. Such problems are illposed in mathematical sense and their main feature shows itself in the solution instabilities. That is why special regularizing methods are needed to solve them. The experimental methods of identification of the mathematical models of heat transfer based on solving of the inverse problems are one of the modern effective solving manners. The goal of this paper is to estimate thermal and radiation properties of advanced materials using the approach based on inverse methods (as example: thermal conductivityλ(T) , heat capacity C(T) and emissivity ε (T )). New metrology under development is the combination of accurate enough measurements of thermal quantities, which can be experimentally observable under real conditions and accurate data processing, which are based on the solutions of inverse heat transfer problems. In this paper, the development of methods for estimating thermal and radiation characteristics is carried out for thermally stable high temperature materials. Such problems are of great practical importance in the study of properties of materials used as non-destructive surface coating in objects of space engineering, power engineering etc. Also the corresponded optimal experiment design problem is considered. The algorithm is based on the theory of Fisher information matrix

A Study of Anyon Statistics by Breit Hamiltonian Formalism

We study the anyon statistics of a $2 + 1$ dimensional Maxwell-Chern-Simons (MCS) gauge theory by using a systemmetic metheod, the Breit Hamiltonian formalism.Comment: 25 pages, LATE

Pennsylvania Folklife Vol. 18, No. 2

• The Swiss Bank House in Pennsylvania • Trance-Preaching in the United States • The Sleeping Preachers: An Historical Study of the Role of Charisma in Amish Society • A Central Chimney Continental Log House • The German Journalist and the Dunker Love-Feast • Christmas Customs: Folk-Cultural Questionnaire No. 10https://digitalcommons.ursinus.edu/pafolklifemag/1034/thumbnail.jp

Prognostic risk factors for diabetic retinopathy in patients with type 2 diabetes mellitus

Purpose: To establish a relationship of diabetic retinopathy with the presence of lesions of other target organs, disease severity and the requirement for insulin therapy in patients with type 2 diabetes mellitus, and to determine the most significant prognostic markers. Material and Methods: We examined 270 patients (270 eyes) with type 2 diabetes mellitus. They were divided into the diabetic retinopathy group and no-diabetic retinopathy group. The status of diabetic target organs was determined as per endocrinologist’s, cardiologist’s, nephrologist’s, neurologist’s and vascular surgeon’s conclusions. Statistica v6.1 (Statsoft, Tulsa, OK) software was used for statistical analysis. The level of significance р < 0.05 was assumed. Results: Diabetic retinopathy positively correlated with severe diabetes (r = 0.383, p < 0.001), insulin therapy requirement (r = 0.389, p < 0.001), diabetic nephropathy (r = 0.350, p < 0.001), chronic kidney failure (r = 0.390, p < 0.001), and lower-extremity angiopathy (r = 0.312, p < 0.001). In addition, the risk of diabetic retinopathy was high in patients on insulin therapy (odds ratio (OR) 6.1; 95 % СІ 3.40-10.93), patients with diabetic nephropathy (OR 17.34; 95 % СІ 4.94-60.83), chronic kidney failure (OR 6.88; 95 % СІ 3.66-12.94), lower-extremity angiopathy (OR 19.15; 95 % СІ 4.24-86.45), coronary heart disease (OR 2.4; 95 % СІ 1.21-4.76) and essential hypertension (OR 4.29; 95 % СІ 1.22-15.10). The risk of diabetic retinopathy was higher in patients with severe diabetes (OR 5.79, 95% CI 3.26-10.26) as compared to patients with mild to moderate diabetes. Conclusion: The positive associations of diabetic retinopathy with chronic kidney failure, diabetic nephropathy and lower-extremity angiopathy were stronger than the positive associations with other diabetic target organs. In addition, there was a moderate positive correlation of diabetic retinopathy with severe diabetes and insulin therapy requirement. The association of diabetic retinopathy with acute coronary and cerebral events was not significant

Численное моделирование процесса магнитно-импульсной обработки осевого режущего инструмента в ANSYS

The purpose of this study is an analysis of the numerical simulation results of the magnetic-pulsed processing (MPP) of axis cutting tools using ANSYS. Practical recommendations for the choice of optimal MPP modes are developed on the basis of this analysis. The induction current distribution on the surface of a drill placed in an inductor was obtained using the Ansys Electronics Desktop (Maxwell) module. The time realization of the current pulse in the inductor corresponds to the shape of the experimentally measured pulse waveform. The magnetic pulse is generated by the unit MIU-2. According to the calculation, the magnetic field strength reaches the value h0,1 = 1.247 · 107 [A/m] at a depth of 0.1 mm from the drill surface. Two cases of drill positioning in the inductor are considered: full loading of the drill (the drill is installed on the inductor entire length) and half loading of the drill (the cutting edges are situated in the inductor center). The analysis results show that the density of the induction current has the highest value in the grove of the drill at full loading and in the region of cutting during the discharging in the inductor for the MPP cycle and drill cooling during the charging of the capacitor bank for the repeated MPP cycle) using the Ansys Transient Thermal module. The temperature distribution was obtained for the both options for the location of the drill inside the inductor. The result is that for reinforcing the side surface of the cutting tool (cutting band) the full loading option must be used. For reinforcing the cutting edges the half loading option is more efficient.Целью данного исследования является анализ результатов численного моделирования процесса магнитно-импульсной обработки (МИО) осевого режущего инструмента в среде ANSYS и выработка на их основе практических рекомендаций, связанных с выбором режимов МИО. С использованием модуля Ansys Electronics Desktop (Maxwell) получено распределение индукционных токов на поверхности сверла, помещенного в индуктор. Временная реализация импульса тока в индукторе соответствует форме экспериментально измеренного импульса, который генерируется установкой МИУ-2. Рассчитана напряженность магнитного поля, которая на глубине 0,1 мм от поверхности сверла достигает h0,1 = 1,247 · 107 [А/м]. Рассмотрены два случая позиционирования сверла в индукторе: полная загрузка сверла (сверло устанавливается на всю длину индуктора) и половинная загрузка сверла (режущие кромки находятся в центре). Анализ показал, что плотность индукционного тока имеет наибольшую величину в канавке сверла при полной загрузке и в области режущих кромок при половинной загрузке. С использованием модуля Ansys Transient Thermal: выполнено моделирование тепловых процессов для двух основных временных интервалов (нагрев сверла в процессе разряда в индукторе при МИО и остывание сверла во время заряда конденсаторной батареи для повторного цикла МИО). Получено распределение температуры для обоих вариантов расположения сверла внутри индуктора и сделан вывод, что для обработки боковой поверхности режущего инструмента (режущей ленточки) необходимо использовать вариант с полной загрузкой, а для обработки режущих кромок, более эффективной является половинная загрузка

Model of impact of pulsed magnetic field on titanium alloy product

На основе разработанной модели проведен анализ изменений фазового состава, которые происходят в поверхностных слоях заготовки, изготовленной из титанового сплава ТС4, при магнитно-импульсном упрочнении. Результаты анализа были обобщены, сделаны заключения о характерных особенностях обработки магнитно-импульсным упрочнением изделий из титанового слава при помощи плоского индуктора. Based on the developed model, an analysis of the change in a phase composition, which occur in the surface layers of the workpiece made of titanium alloy TC4 during magnetic-pulse hardening, was performed. The results of the analysis were summarized and conclusions about the characteristic features of the processing of MPH titanium alloy product with the help of a flat indicator were made

Modeling of radiative - conductive heat transfer in compositing materials

A layer of composite material is investigated, which is heated one-sidedly with one-dimensional energy transfer accounting for thermal conductivity and radiation. A mathematical model is suggested for non-stationary coefficient thermophysical problem under radiative-conductive heat transfer in a material layer. Temperature dependencies of thermal capacity and thermal conductivity coefficient of composite radio-transparent material have been determined through numerical modeling by solving the coefficient reverse problem of thermal conductivity