МАТЕМАТИЧНЕ МОДЕЛІ ДИНАМІЧНОЇ ВЗАЄМОДІЇ МІЖ КОЛЕСАМИ І РЕЙКОВИМ ШЛЯХОМ

The main goal of this paper is to show how the effects of maximum bending tensions at different locations in the track caused by simultaneous changes of various parameters can be estimated in a rational manner. The dynamics of the vertical interaction between a moving rigid wheel and a flexible railway track is investigated. An asymmetric linear three-dimensional beam structure model of a finite length of the track is suggested. The influence of eight selected track parameters on the dynamic behaviour of the track is investigated. A two-level fractional factorial design method is used in the search for the combination of numerical values of these parameters minimizing themaximum bending tensions.В статье показано влияние моделируемых параметров, которые учитываются рациональным способом с применением фракционного факториала двух уровней на распределение напряжений в различных местах рельсового звена. Представлен анализ вертикальной динамики взаимодействия жесткого колеса с рельсом. С целью минимизации напряжений рельса производится поиск оптимального варианта комбинации множества влияющих параметров с применением метод фракционного факториала двух уровней.У статті показаний вплив моделюючих параметрів, що враховуються раціональним способом, застосовуючи фракційний факторіал двох рівнів, на розподіл напружень у різних місцях рейки. Представлено аналіз вертикальної динаміки взаємодії твердого колеса з рейкою. З метою мінімізації напружень рейки шукається оптимальний варіант комбінації безлічі параметрів із застосуванням методу фракційного факторіала двох рівнів.

Investigation of properties of lubricants in locomotive Diesels

This paper describes experimental investigation of lubricant properties used in locomotive engines. The workbench for experimental investigation is described, which presented theoretical background and technique of the experiment. The results are analyzed and presented graphically. Their interpretation shows the direction for further investigation. Final conclusions of the results are made

Analysis of locomotive wheel sets wearing

Wearing dynamics of traction rolling-stock wheel tyres of diesel locomotives was investigated. Based on research results it is possible to predict wheel-tyre safety margin, to improve maintenance and state periodicity of repair, as well as to use traction rolling-stock repair funds most efficiently

High-Speed Quadratic Electrooptic Nonlinearity in dc-Biased InP

We present experimental data on degenerate four-wave mixing as well as simulation results of fast optical nonlinearities in highly-excited semi-insulating InP under applied dc-field. Hot-electron transport governed enhancement of optical nonlinearity is obtained by applying a dc-field of 10-14 kV/cm at full-modulation depth of a light-interference pattern. The hydrodynamic model, which incorporates both free-carrier and photorefractive nonlinearities is used to explain the experimentally observed features. We show that the enhancement of optical nonlinearity is due to the quadratic electrooptic effect

High-Speed Quadratic Electrooptic Nonlinearity in dc-Biased InP

We present experimental data on degenerate four-wave mixing as well as simulation results of fast optical nonlinearities in highly-excited semiinsulating InP under applied dc-field. Hot-electron transport governed enhancement of optical nonlinearity is obtained by applying a dc-field of 10-14 kV/cm at full-modulation depth of a light-interference pattern. The hydrodynamic model, which incorporates both free-carrier and photorefractive nonlinearities is used to explain the experimentally observed features. We show that the enhancement of optical nonlinearity is due to the quadratic electrooptic effect

High-Speed Quadratic Electrooptic Nonlinearity in dc-Biased InP

We present experimental data on degenerate four-wave mixing as well as simulation results of fast optical nonlinearities in highly-excited semi-insulating InP under applied dc-field. Hot-electron transport governed enhancement of optical nonlinearity is obtained by applying a dc-field of 10-14 kV/cm at full-modulation depth of a light-interference pattern. The hydrodynamic model, which incorporates both free-carrier and photorefractive nonlinearities is used to explain the experimentally observed features. We show that the enhancement of optical nonlinearity is due to the quadratic electrooptic effect

Strong Electric Field Driven Carrier Transport Non-Linearities in n-Type GaAs/AlGaAs Superlattices

Nanosecond pulsed technique was used to study and discriminate strong electric field induced effects in carrier transport in silicon doped GaAs/$Al_{0.3}Ga_{0.7}As$ superlattices at room temperature. The experiment shows that the superlattice can serve as gain media to employ parametric phenomena for microwave amplification

One‐Year Landmark Analysis of the Effect of Beta‐Blocker Dose on Survival After Acute Myocardial Infarction

Background Although beta‐blockers are recommended following myocardial infarction (MI), the benefits of long‐term treatment have not been established. The study's aim was to evaluate beta‐blocker efficacy by dose in 1‐year post‐MI survivors. Methods and Results The OBTAIN (Outcomes of Beta‐Blocker Therapy After Myocardial Infarction) registry included 7057 patients with acute MI, with 6077 one‐year survivors. For this landmark analysis, beta‐blocker dose status was available in 3004 patients and analyzed by use (binary) and dose at 1 year after MI. Doses were classified as no beta‐blocker and >0% to 12.5%, >12.5% to 25%, >25% to 50%, and >50% of target doses used in randomized clinical trials. Age was 63 to 64 years, and approximately two thirds were men. Median follow‐up duration was 1.05 years (interquartile range, 0.98–1.22). When analyzed dichotomously, beta‐blocker therapy was not associated with improved survival. When analyzed by dose, propensity score analysis showed significantly increased mortality in the no–beta‐blocker group (hazard ratio,1.997; 95% CI, 1.118–3.568; P 0% to 12.5% group (hazard ratio, 1.817; 95% CI, 1.094–3.016; P 25% to 50% group (hazard ratio, 1.764; 95% CI, 1.105–2.815; P 12.5% to 25% dose group. The mortality in the full‐dose group was not significantly higher (hazard ratio, 1.196; 95% CI, 0.687–2.083). In subgroup analyses, only history of congestive heart failure demonstrated significant interaction with beta‐blocker effects on survival. Conclusions This analysis suggests that patients treated with >12.5% to 25% of the target dose used in prior randomized clinical trials beyond 1 year after MI may have enhanced survival compared with no beta‐blocker and other beta‐blocker doses. A new paradigm for post‐MI beta‐blocker therapy is needed that addresses which patients should be treated, for how long, and at what dose