MAINTENANCE EXPENSES PREDICTION OF TRANSPORTATION FACILITIES

To predict maintenance expenses of transportation facilities it is necessary to consider conditions of its operation and age as well as drivers proficiency

Generation of second mode solitary waves by the interaction of a first mode soliton with a sill

Results of an experimental and theoretical study of the interaction of a first mode internal solitary wave with a localised bottom topography (sill) are presented. Laboratory experiments have been performed in a 10m long and 0.33m wide channel filled with a stratified fluid. The interface between the two layers (fresh and salt water) is diffuse and has a finite thickness. Soliton-type disturbances of the interface having characteristics of the first baroclinic mode are generated at one channel end. They move along the channel and encounter an underwater obstacle (sill) in the middle of the channel, where they break into reflected and transmitted waves. Two types of internal waves are produced by the interaction: a fast first mode internal soliton and a slower (by a factor of approximately 3) second mode soliton-like wave. A numerical model, based on the two-dimensional Navier-Stokes equations in the Boussinesq approximation, is used tore produce the laboratory experiment. The detailed analysis of the horizontal and vertical structures of transmitted and reflected waves showed that the fast reflected and transmitted waves observed in the experiment can be interpreted as a first mode internal solitary wave whose characteristics are very close to those of the K-dV solitons. It is also demonstrated that the slow speed waves, generated during the interaction behind the first fast wave have vertical and horizontal structures very close to the second mode internal K-dV solitons

Challenges of D=6 N=(1,1) SYM Theory

Maximally supersymmetric Yang-Mills theories have several remarkable properties, among which are the cancellation of UV divergences, factorization of higher loop corrections and possible integrability. Much attention has been attracted to the N=4 D=4 SYM theory. The N=(1,1) D=6 SYM theory possesses similar properties but is nonrenomalizable and serves as a toy model for supergravity. We consider the on-shell four point scattering amplitude and analyze its perturbative expansion within the spin-helicity and superspace formalism. The integrands of the resulting diagrams coincide with those of the N=4 D=4 SYM and obey the dual conformal invariance. Contrary to 4 dimensions, no IR divergences on mass shell appear. We calculate analytically the leading logarithmic asymptotics in all loops. Their summation leads to a Regge trajectory which is calculated exactly. The leading powers of s are calculated up to six loops. Their summation is performed numerically and leads to a smooth function of s. The leading UV divergences are calculated up to 5 loops. The result suggests the geometrical progression which ends up in a finite expression. This leads us to a radical point of view on nonrenormalizable theories.Comment: 11 pages, 2 figures, Late

Internal tides near the Celtic Sea shelf break: A new look at a well known problem

Internal waves generated by tides in the Celtic Sea were investigated on the basis of in situ data collected at the continental slope in July 2012, and theoretically using a weakly nonlinear theory and the Massachusetts Institute of Technology general circulation model. It was found that internal solitary waves generated over the shelf break and propagated seaward did not survive in the course of their evolution. Due to the large bottom steepness they disintegrated locally over the continental slope radiating several wave systems seaward and transforming their energy to higher baroclinic modes. In the open part of the sea, i.e. 120. km away from the shelf break, internal waves were generated by a baroclinic tidal beam which was radiated from the shelf break downward to the abyss. After reflection from the bottom it returned back to the surface where it hit the seasonal pycnocline and generated packets of high-mode internal solitary waves. Another effect that had strong implications for the wave dynamics was internal wave reflection from sharp changes of vertical fluid stratification in the main pycnocline. A large proportion of the tidal beam energy that propagated downward did not reach the bottom but reflected upward from the layered pycnocline and returned back to the surface seasonal pycnocline where it generated some extra higher mode internal wave systems, including internal wave breathers

Generation of secondary internal waves by the interaction of an internal solitary wave with an underwater bank

The generation of secondary internal waves by the interaction of a large-amplitude internal solitary wave with the Dreadnought Bank in the Andaman Sea (6°40′N, 95° 47′E) is shown by analyzing a synthetic aperture radar (SAR) image acquired by the European Remote Sensing satellite ERS-2 and by carrying out model calculations. Although the Dreadnought Bank is quite deep (241 m), the model calculations show that large-amplitude internal solitary waves as encountered in this sea area can overturn and break over the bank and generate secondary internal waves. Comparison of model results with observations clearly demonstrates that the semicircular wave pattern visible on the ERS-2 SAR image centered at the Dreadnought Bank is indeed a sea surface manifestation of a secondary internal wave packet generated by scattering of a large-amplitude internal solitary wave and not by the interaction of the barotropic tidal flux with this underwater obstacle. Copyright 2005 by the American Geophysical Union

Amplification and suppression of internal waves by tides over variable bottom topography

The energy exchange between internal waves and barotropic currents over inclined bottom topography is studied theoretically and in the framework of the numerical model. The energy balance equation derived for a continuously stratified fluid predicts that energy can either be transferred toward or away from the internal wave depending on the direction of propagation of both the wave and current. Four scenarios of wave-flow interaction over the inclined bottom were identified. An internal wave extracts energy from the background tidal flow during its propagation upslope-upstream or downslope-downstream and its amplitude grows. The wave loses energy propagating downslope-upstream or upslope-downstream and reduces in amplitude. This mechanism of suppression or amplification of internal waves by a current over an inclined bottom is verified numerically. When applied to the area of the Knight Inlet sill, a high-resolution fully nonlinear, nonhydrostatic model reproduces the packets of internal waves generated by supercritical tidal flow over the sill. Careful inspection of the wave fields revealed the presence of an irregular wave structure within wave packets - namely, internal waves are not arranged by amplitude. This phenomenon, obtained numerically and observed in situ, is treated in terms of the mechanism of wave-flow interaction: the energy exchange between the tidal current and generated internal waves over the inclined bottom topography is the reason for the absence of traditional rank-ordered waves in the packet

ОБМЕЖЕННЯ СТРУМУ ТРИФАЗНОГО СИЛОВОГО АКТИВНОГО ФІЛЬТРА В УМОВАХ ПЕРЕВАНТАЖЕННЯ ТА КОРОТКОГО ЗАМИКАННЯ

Purpose. The purpose of the work is to develop a method of limiting the maximum allowable level of current of a three-phase active power filter in conditions of overload or short circuit and a system for the implementation of the method. Methodology. For research purposes, the provisions of the pq-theory of instantaneous power, the method of the theory of automatic control in systems with relay controllers, and the methods of simulation in the visual programming environment were used. Results. Both the overloading mode and the short circuit emergency mode, using the proposed solution, do not lead to significant changes in the voltage level on the accumulation capacitor, thus maintaining the stability of the power part of the active power filter. Originality. In the case of temporary overloads of current and short circuits at the network node to which a active power filter is connected, the current's limiting is performed by scaling the current to the level allowed by normal operation of the semiconductor elements of the device, which allows the basic operating algorithm to be implemented in the specified modes. Practical value. The proposed solution can be used as a mean to protect the power part of the device in case of overload, which, in the event of emergencies, and their elimination will automatically restore the normal mode of the device.Мета. Метою роботи є розробка методики обмеження до гранично допустимого рівня струму трифазного силового активного фільтру (САФ) в умовах перевантаження або короткого замикання та системи для реалізації методики. Методика. Для проведення досліджень використовувались положення pq-теорії миттєвої потужності, метод теорії автоматичного управління в системах з релейними регуляторами, методи моделювання в середовищі візуального програмування. Результати. Як режим перевантаження так і аварійний режим короткого замикання, з використанням пропонованого рішення, не призводять до суттєвих змін рівня напруги на накопичуючому конденсаторі, відповідно підтримуючи стабільність роботи силової частини силового активного фільтру. Наукова новизна. При тимчасових перевантаженнях за струмом та коротких замикань у вузлі мережі до якого приєднують силовий активний фільтр, обмеження його струму виконують шляхом масштабування діючого струму до рівня припустимого за умов нормальної роботи напівпровідникових елементів пристрою, що дозволяє в зазначених режимах реалізовувати основний алгоритм роботи. Практичне значення. Запропоноване рішення може бути використаним як засіб захисту силової частини пристрою у разі перевантаження, що, у разі виникнення аварійних ситуацій, та їх усунення забезпечить автоматичне поновлення нормального режиму пристрою