Sewer inspection and comparison of acoustic and CCTV methods

In the UK, the majority of sewer pipe inspections are carried out using closed-circuit television (CCTV) technology. This inspection technology is expensive; given the size of the UK sewer network, this means that only a small sample of network is inspected regularly. Up-to-date condition information on individual sewers is required to minimise sewer network operation failures and, ultimately, to eliminate flooding. There is therefore a need for a quicker and cheaper inspection method. This paper reports on a novel low-cost acoustic sensor system that can be used for the rapid detection of various defects in sewer pipes. It is shown that a large number of pipe defects can be classified and validated against CCTV images by way of visual examination of the acoustical data presented in the form of spectrograms. An overview of the technological principles used by the acoustic inspection method is presented in this paper together with the results of field trial surveys. The new method was tested in operational sewers in Austria and the acoustic inspection results compared with available CCTV reports: 79% of the defects identified by CCTV were also detected using the acoustic technique

Packing of concave polyhedra with continuous rotations using nonlinear optimisation

We study the problem of packing a given collection of arbitrary, in general concave, polyhedra into a cuboid of minimal volume. Continuous rotations and translations of polyhedra are allowed. In addition, minimal allowable distances between polyhedra are taken into account. We derive an exact mathematical model using adjusted radical free quasi phi-functions for concave polyhedra to describe non-overlapping and distance constraints. The model is a nonlinear programming formulation. We develop an efficient solution algorithm, which employs a fast starting point algorithm and a new compaction procedure. The procedure reduces our problem to a sequence of nonlinear programming subproblems of considerably smaller dimension and a smaller number of nonlinear inequalities. The benefit of this approach is borne out by the computational results, which include a comparison with previously published instances and new instances

Relativistic Jets from Accretion Disks

The jets observed to emanate from many compact accreting objects may arise from the twisting of a magnetic field threading a differentially rotating accretion disk which acts to magnetically extract angular momentum and energy from the disk. Two main regimes have been discussed, hydromagnetic jets, which have a significant mass flux and have energy and angular momentum carried by both matter and electromagnetic field and, Poynting jets, where the mass flux is small and energy and angular momentum are carried predominantly by the electromagnetic field. Here, we describe recent theoretical work on the formation of relativistic Poynting jets from magnetized accretion disks. Further, we describe new relativistic, fully-electromagnetic, particle-in-cell simulations of the formation of jets from accretion disks. Analog Z-pinch experiments may help to understand the origin of astrophysical jets.Comment: 7 pages, 3 figures, Proc. of High Energy Density Astrophysics Conf., 200

Optimal clustering of a pair of irregular objects

Cutting and packing problems arise in many fields of applications and theory. When dealing with irregular objects, an important subproblem is the identification of the optimal clustering of two objects. Within this paper we consider a container (rectangle, circle, convex polygon) of variable sizes and two irregular objects bounded by circular arcs and/or line segments, that can be continuously translated and rotated. In addition minimal allowable distances between objects and between each object and the frontier of a container, may be imposed. The objects should be arranged within a container such that a given objective will reach its minimal value. We consider a polynomial function as the objective, which depends on the variable parameters associated with the objects and the container. The paper presents a universal mathematical model and a solution strategy which are based on the concept of phi-functions and provide new benchmark instances of finding the containing region that has either minimal area, perimeter or homothetic coefficient of a given container, as well as finding the convex polygonal hull (or its approximation) of a pair of objects

Layout problems for arc objects in convex domains

We introduce a new methodology for solving layout problems. Our objects and containers are bounded by circular arcs and line segments. We allow continuous object translations and rotations as well as minimal allowable distances between objects. For describing non-overlapping, containment and distance constraints the phi-function technique is used. We provide a general mathematical model as nonlinear programming problem with nonsmooth functions. We propose here the automatic feasible region generator, using phi-trees. The generator allows us to form ready-to-use systems of inequalities with smooth functions in order to apply efficient nonlinear optimisation procedures. We develop an efficient solution algorithm and original solver for layout problems which uses the core representation of inequlities in a sybmol form and provides exact calculation of Jacobian and Hessian matrixes. The search for local minima of NLP-problems is performed by IPOPT algorithm. An essential part of our local optimisation scheme is LORA algorithm that simplifies description of feasible region of the problem and reduces the runtime of local optimisation. It is due to this reduction our strategy can work efficiently with collections of composed objects and search for “good” local-optimal solutions for layout problems in reasonable time.Розглянуто отпимізаційну задачу упаковки довільних об'єктів, обмежених дугами кіл та відрізками прямих в опукіі області. Побудовано математичну модель у вигляді задачі недиференційованої оптимізації, множина реалізацій яко? покриває широкий клас наукових і прикладних задач геометричного проектування. Розроблено методологію розв'язання задач упаковки з урахуванням технологічних обмежень (мінімально допустимі відстані, зони заборони, можливість неперервних трансляцій та обертань об'єктів). Запропоновано генератор простору розв'язків та вирішувач (solver) для автоматичного розв'язання NLP-задач розглянутого класу.Предлагается новая методология решения оптимизационных задач компоновки произвольных объектов в контейнерах, ограниченных дугами окружностей и отрезками прямых. Строится математическая модель в виде задачи нелинейного программирования. Описывается процедура генерации области допустимых решений с применением phi-деревьев, которая позволяет формировать системы неравенств с гладкими функциями. Предлагается эффективный алгоритм поиска локально оптимальных решений.Разработан оригинальный решатель для задач негладкой оптимизации, который использует символьное представление неравенств и обеспечивает точное вычисление элементов матриц Якобиана и Гессиана. Предлагаемая методология эффективна для решения задач компоновки произвольных объектов и позволяет получать «хорошие» локально оптимальные решения за приемлемое время

Shear-Flow Driven Current Filamentation: Two-Dimensional Magnetohydrodynamic Simulations

The process of current filamentation in permanently externally driven, initially globally ideal plasmas is investigated by means of two-dimensional Magnetohydrodynamic (MHD)-simulations. This situation is typical for astrophysical systems like jets, the interstellar and intergalactic medium where the dynamics is dominated by external forces. Two different cases are studied. In one case, the system is ideal permanently and dissipative processes are excluded. In the second case, a system with a current density dependent resistivity is considered. This resistivity is switched on self-consistently in current filaments and allows for local dissipation due to magnetic reconnection. Thus one finds tearing of current filaments and, besides, merging of filaments due to coalescence instabilities. Energy input and dissipation finally balance each other and the system reaches a state of constant magnetic energy in time.Comment: 32 Pages, 13 Figures. accepted, to appear in Physics of Plasmas (049012

Relativistic dynamical polarizability of hydrogen-like atoms

Using the operator representation of the Dirac Coulomb Green function the analytical method in perturbation theory is employed in obtaining solutions of the Dirac equation for a hydrogen-like atom in a time-dependent electric field. The relativistic dynamical polarizability of hydrogen-like atoms is calculated and analysed

Three-dimensional Simulations of Accretion to Stars with Complex Magnetic Fields

Disk accretion to rotating stars with complex magnetic fields is investigated using full three-dimensional magnetohydrodynamic (MHD) simulations. The studied magnetic configurations include superpositions of misaligned dipole and quadrupole fields and off-centre dipoles. The simulations show that when the quadrupole component is comparable to the dipole component, the magnetic field has a complex structure with three major magnetic poles on the surface of the star and three sets of loops of field lines connecting them. A significant amount of matter flows to the quadrupole "belt", forming a ring-like hot spot on the star. If the maximum strength of the magnetic field on the star is fixed, then we observe that the mass accretion rate, the torque on the star, and the area covered by hot spots are several times smaller in the quadrupole-dominant cases than in the pure dipole cases. The influence of the quadrupole component on the shape of the hot spots becomes noticeable when the ratio of the quadrupole and dipole field strengths $B_q/B_d\gtrsim0.5$, and becomes dominant when $B_q/B_d\gtrsim1$. In the case of an off-centre dipole field, most of the matter flows through a one-armed accretion stream, forming a large hot spot on the surface, with a second much smaller secondary spot. The light curves may have simple, sinusoidal shapes, thus mimicking stars with pure dipole fields. Or, they may be complex and unusual. In some cases the light curves may be indicators of a complex field, in particular if the inclination angle is known independently. We also note that in the case of complex fields, magnetospheric gaps are often not empty, and this may be important for the survival of close-in exosolar planets.Comment: 13 pages, 21 figures, accepted for publication in MNRA

Superconducting properties of sulfur-doped iron selenide

The recent discovery of high-temperature superconductivity in single-layer iron selenide has generated significant experimental interest for optimizing the superconducting properties of iron-based superconductors through the lattice modification. For simulating the similar effect by changing the chemical composition due to S doping, we investigate the superconducting properties of high-quality single crystals of FeSe$_{1-x}$S$_{x}$ ($x$=0, 0.04, 0.09, and 0.11) using magnetization, resistivity, the London penetration depth, and low temperature specific heat measurements. We show that the introduction of S to FeSe enhances the superconducting transition temperature $T_{c}$, anisotropy, upper critical field $H_{c2}$, and critical current density $J_{c}$. The upper critical field $H_{c2}(T)$ and its anisotropy are strongly temperature dependent, indicating a multiband superconductivity in this system. Through the measurements and analysis of the London penetration depth $\lambda _{ab}(T)$ and specific heat, we show clear evidence for strong coupling two-gap $s$-wave superconductivity. The temperature-dependence of $\lambda _{ab}(T)$ calculated from the lower critical field and electronic specific heat can be well described by using a two-band model with $s$-wave-like gaps. We find that a $d$-wave and single-gap BCS theory under the weak-coupling approach can not describe our experiments. The change of specific heat induced by the magnetic field can be understood only in terms of multiband superconductivity.Comment: 13 pages, 7 figure

The daily arterial stiffness profile in rheumatoid arthritis patients with and without hypertension

Patients with rheumatoid arthritis (RA) have an increased risk for cardiovascular diseases. To determine their daily arterial stiffness (AS) as an indicator of cardiovascular risk is of unquestionable interest.Objective: to evaluate the features of daily AS in RA patients with or without hypertension.Patients and methods. Twenty-four hour AS monitoring (24-h ASM) was done in 75 women with a valid diagnosis of RA. The patients were randomized into 3 groups: 1) 39 RA patients with hypertension; 2) 24 RA patients without hypertension; 3) 12 RA patients with masked hypertension. A comparison group consisted of 30 hypertensive patients without RA and a control group included 22 apparently healthy women who were age-matched with the patients with RA and those from the comparison group. 24-h ASM readings were studied using a BPlab device with Vasotens software (Russia).Results. All the patients with RA were found to have higher 24-h ASM readings than the controls; and, in the presence of hypertension, these changes were even more pronounced. Group 1 was noted to have higher ambulatory AS index than the comparison group; more than 70% of the patients in Group 2 were observed tohave increased aortic pulse wave velocity when reducing to a blood pressure (BP) of 100 mm Hg. The patients in Groups 1 and 2 had increases in augmentation index, in the latter normalized for a heart rate of 75 beats/min, in the propagation time of a reflected wave when reducing to a BP of 100 mm Hg, and in AS index at night. The patients with RA showed an association between daily AS and major cardiovascular risk factors (hypertension, age, body mass index, menopause duration), RA-specific risk factors (RA duration, erythrocyte sedimentation rate, and C-reactive protein), and psychoemotional status. Conclusion. 24-h ASM revealed that the patients with RA had higher vascular wall stiffness than the individuals in the comparison and control groups. Taking into consideration the pronounced changes in AS not only during the daytime, but also during the night, it is appropriate to perform daily monitoring in patients with RA in order to obtain more objective data