Dynamic compliance of multilayer coatings

The algorithm for calculation of dynamic compliance of multilayer coatings was developed. The compliance modulus and phase lag of coating surface motion vs. the current pressure depend on viscoelastic properties of materials, ratio of wavelength to layer thickness λ/H, and ratio of wave velocity to propagation velocity of shear vibrations in the base layer V / C _t,2 ⁰ Dynamic compliance of the two-layer coating consisting of a thick base layer and thin durable outer layer was calculated. The elasticity modulus of the outer layer ranged up to eight values of elastic modulus of the inner layer; the density of the outer layer either remained equal to the density of the inner layer or increased proportionally to the elastic modulus. Depending on V / C _t,2 ⁰ two scenarios of compliant coating interaction with the turbulent flow were distinguished: resonant and broadband ones. It is shown that the vibration properties of two-layer coatings can be significantly better than the properties of the monolayer coatings. This makes it possible either to increase the coating strength or to work efficiently at lower velocities.     

Dynamic impedances and free-field vibration analysis of pile groups in saturated ground

A three-dimensional (3D) numerical model basing on the thin layer element method and the flexible volume method was established for the computation of dynamic impedances and free-field vibrations of rigidly-capped pile groups embedded in saturated ground. The piles were considered as beams and the saturated ground was represented by Biot?s three-dimensional elastodynamic theory. By recourse to the thin layer element method, Green function of the three dimensional saturated ground was obtained and then verified. The dynamic interaction of the piles and the saturated ground was solved by using the flexible volume method, in which the piles were discretized into three dimensional Euler−Bernoulli beam elements and the dynamic stiffness matrix of saturated ground was formed at the pile−soil interaction nodes by using the Green function. Impedances of the 2×2 pile group and free-field displacement and pore pressure responses caused by harmonic vertical, lateral and rocking forces (moments) applied at the cap center were presented, respectively, for different soil permeability and excitation frequencies. It is found that the soil permeability and the excitation frequency have significant influence on the impedances and the free-field vibration responses.     

Static and cyclic behaviours of multistorey infilled frames with different interface conditions

Results are presented from a study aimed at a deeper understanding of the static and cyclic behaviours of non-integral, partially integral and integral infilled frames. In the first part of the study the load-deflection behaviour, stress distribution and collapse modes under static loads are examined and in the second part the hysteretic characteristics, energy dissipation capacities and degradation properties under cyclic loads are evaluated.     

Dynamic magnification of the galitzin seismograph excited by shock motion of the ground

A reduced dynamic magnification of the first maximum is derived for the seismograph of B. B. Galitzin during shock motion of the ground represented by the expressionAt ³e^– t     

Resilient mounting systems in buildings

The basic elements of resilient mounting systems are described and various measures for quantifying the effect of such systems defined. Using electrical analogue circuits, the calculation of these measures is illustrated. With special reference to resilient mounting systems in buildings, under specified assumptions, improved analogies for system elements are derived, thus arriving finally at a complete electrical analogy of a compound mounting system. Some results of computer calculations, as well as a greatly simplified method suitable for manual computation, are presented.The second section of the paper describes the application to practical problems of the approach developed in the first section.Data from present standards for maximum permissible noise and vibration levels are given in suitable form. Nomograms for calculation of the lowest eigenfrequency of concrete floor fields are also given.     

Visualization of leakage flow in buildings

Leakage flow around a window has been visualized with the aid of holographic interferometry. The experiments were performed during winter.     

Magnetism in singlet ground states

The spin‐gap phenomenon is a key characteristic of high T_c superconducting cuprates, whose experimental results are summarized and discussed in the context of the slave‐boson mean field theory of the extended t–J model. It is seen that there exists satisfactory agreement between theory and experiments in bilayer cuprates. As regards the apparent absence of the spin‐gap in single layer La_2-xSr_xCuO₄ (LSCO), the possible roles played by disorder have been pointed out in view of the recent neutron scattering experiment on other spin singlet systems, the spin‐Peierls CuGeO₃ and two‐leg ladders. This revised version was published online in July 2006 with corrections to the Cover Date.     

Optical-waveguide-based temperature sensor applied in intelligent buildings

We propose an optical-waveguide-based temperature sensor with temperature-sensitive material, and design the corresponding system block for its application in intelligent building. By the change of lateral shift of incident light at total reflection angle caused by temperature effect the environment temperature can be detected with a non-contact method. The accuracies of temperature sensors without and with gold layer are analyzed by simulation results, and the application of their cascade can provide a high accurate measurement result (as small as 0.03 K) even in a large temperature range.     

Wideband FSS for electromagnetic architecture in buildings

Interweaving the elements of a frequency selective surface (FSS) is a technique that allows wideband frequency filtering as well as size reduction. FSS structures using this method are well suited to wireless indoor applications where the operating bands are spread over a wide spectrum. Interwoven square loop slots FSS have been designed, fabricated and measured. The FSS structure to be presented offers transparency at the emergency services band at around 400 MHz and suppresses most of the mobile and wireless bands up to 3 GHz. The size of the unit cell developed is around 3% of the corresponding wavelength, significantly smaller than a half wavelength resonant dipole.     

Load-aware femtocell placement in the commercial buildings

Femtocells are designed to cover small indoor areas. In commercial buildings, femtocell placement and number is one of the most important network issues. In such buildings, another problem is uneven traffic distribution in different spaces, which causes high traffic and low traffic areas. Due to the small coverage areas of femtocells and these high traffic and low traffic areas, some femtocells are overloaded and some femtocells are underloaded. Also, increase in the distance of high-traffic areas from the femtocells, increases the number of resource blocks used. These issues reduce network efficiency. In this article, femtocell placement has been managed in such a way that the traffic load on the femtocells is balanced and is reduced the number of resource blocks used in the building and efficiency is increased. A mathematical model for femtocell placement has been introduced which balancing the femtocell load and reducing the average number of resource blocks used, the conditions of maximum coverage area and minimum femtocell number should also be fulfilled. This challenge has been addressed by using non-dominated sorting genetic algorithm (NSGA-II). An initial population generation algorithm and a selection function are also presented. The assessment results indicate that compared to the latest studies, this newly proposed method reduces the average load on the whole building by 79% and decreases the load variance between the femtocells by 86%.     

Acceptor ground state problems in silicon

The effective mass potential that transforms ordinary acceptors into their associated X-acceptors is directly related to the presence of carbon neighbours. The physical mechanism which leads to carbon's effective potential is shown to be similar to that which leads to the chemical shift of unperturbed acceptor ground states.     

Inhomogenous magnetic ground state in CeAgGa

CeAgGa crystallizes in CeCu₂ Imma structure with Ag and Ga atoms randomly distributed at 8h sites. The magnetic and transport properties of the orthorhombic CeAgGa compound have been obtained from the analysis of ac magnetic susceptibility χ _ac , magnetization M vs. magnetic field, specific heat C and electrical resistivity ρ. The results provide evidence for the formation of a spin-glass state with a freezing temperature T _f = 5.1 K. The randomness in the Ce-Ce magnetic exchange interactions seem to arise from a statistical distribution of Ag and Ga atoms on a crystallographic site of the CeAgGa crystal lattice. The results provide also evidence for the formation of ferromagnetic-like order at the temperature T _C ≈ 3.6 K. Band structure calculations for a disordered system give magnetic moment similar to saturation moment obtained from magnetization measurements, however, its calculated value is insensitive on Ga/Ag off-stoichiometry in the 8h position. Complex behavior of CeAgGa Kondo-lattice compound is discussed in terms of interplaying Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions, Kondo effect and structural disorder.     

Classical ground states in one dimension

We give conditions on an interaction sufficient to guarantee that in one dimension it yield a periodic ground state with one or two particles per unit cell.Research supported in part by NSF Grant MCS 81-01596-A01.     

Trapped antihydrogen in its ground state

Antihydrogen atoms (Hˉ) are confined in an Ioffe trap for 15-1000 s-long enough to ensure that they reach their ground state. Though reproducibility challenges remain in making large numbers of cold antiprotons (pˉ) and positrons (e(+)) interact, 5±1 simultaneously confined ground-state atoms are produced and observed on average, substantially more than previously reported. Increases in the number of simultaneously trapped Hˉ are critical if laser cooling of trapped Hˉ is to be demonstrated and spectroscopic studies at interesting levels of precision are to be carried out.     

Energy scaling law for buildings

Hyperfine Interactions - This paper is an ode to my friend Hendrik. We collaborated on hyperfine interactions from 1962 to 1984, when he was colleague and friend. Since then I have been working on...     

Dynamic Random Networks in Dynamic Populations

We consider a random network evolving in continuous time in which new nodes are born and old may die, and where undirected edges between nodes are created randomly and may also disappear. The node population is Markovian and so is the creation and deletion of edges, given the node population. Each node is equipped with a random social index and the intensity at which a node creates new edges is proportional to the social index, and the neighbour is either chosen uniformly or proportional to its social index in a modification of the model. We derive properties of the network as time and the node population tends to infinity. In particular, the degree-distribution is shown to be a mixed Poisson distribution which may exhibit a heavy tail (e.g. power-law) if the social index distribution has a heavy tail. The limiting results are verified by means of simulations, and the model is fitted to a network of sexual contacts.     

Isotopic sum rules and compliance scheme

It is known that compliance scheme does not provide simple linear isotopic sum rules in λ^?1 similar to the ones in λ in the force constant scheme. The advantage of not having such sum rules in the compliance scheme is discussed in relation to the uniqueness problem of the molecular force field.Incidentally, for the molecules H₂O, D₂O, and HDO, two quadratic relations in terms of the inverse frequency parameters λ^?1 are obtained. These supplement the three obvious product rule relations.     

Wall compliance and violin cavity modes

Violin corpus wall compliance, which has a substantial effect on cavity mode frequencies, was added to Shaw's two-degree-of-freedom (2DOF) network model for A0 ("main air") and A1 (lowest length mode included in "main wood") cavity modes. The 2DOF model predicts a V(-0.25) volume dependence for A0 for rigid violin-shaped cavities, to which a semiempirical compliance correction term, V(-x(c)) (optimization parameter x(c)) consistent with cavity acoustical compliance and violin-based scaling was added. Optimizing x(c) over A0 and A1 frequencies measured for a Hutchins-Schelleng violin octet yielded x(c) approximately 0.08. This markedly improved A0 and A1 frequency predictions to within approximately +/- 10% of experiment over a range of about 4.5:1 in length, 10:1 in f-hole area, 3:1 in top plate thickness, and 128:1 in volume. Compliance is a plausible explanation for A1 falling close to the "main wood" resonance, not increasingly higher for the larger instruments, which were scaled successively shorter compared to the violin for ergonomic and practical reasons. Similarly incorporating compliance for A2 and A4 (lowest lower-/upper-bout modes, respectively) improves frequency predictions within +/-20% over the octet.