C 1-stably ℒ p shadowable homoclinic classes

Let p be a hyperbolic saddle of diffeomorphism f on closed manifold M and H(p, f) be the homoclinic class associated with it. In this article, we introduce the notion of C ¹-stably ? _p shadowing and prove that if f is C ¹-stably ? _p shadowable on a homoclinic class H(p, f) then, H(p, f) has a dominated splitting. Moreover, we prove that if f is C ¹-stably Lipschitz ? _p shadowable on H(p, f) and H(p, f)-germ of f is expansive then the homoclinic class is hyperbolic.     

Determination of ultratrace levels of lead (II) in water samples using a modified carbon paste electrode based on a new podand

A new podand of 1,1′-thiobis(naphthalene-2,1-diyl)bis(2-aminobenzoate) (TNBA) was synthesized and used as a suitable carrier for construction of Pb²⁺ modified carbon paste electrode (CPE). The effects of various plasticizers; 2-nitrophenyloctylether (o-NPOE), dioctyl pththalate (DOP), dibutyl phthalate (DBP) and paraffin oil were studied. The best performance was obtained with a matrix composition of CPE with a DOP/graphite powder/TNBA weight percent ratio of 35/60.5/4.5. The sensor exhibits significantly enhanced selectivity toward Pb²⁺ ion over the concentration range 8.0 × 10^? 8 to 1.0 × 10^? 2 mol L^? 1 with a lower detection limit of 5.0 × 10^? 8 mol L^? 1 and a Nernstian slope of 29.0 ± 0.2 mV decade^? 1 of lead activity. It has a fast response time of 8 s with a working pH range from 3.5 to 7. The interaction between TNBA and Pb²⁺ was studied spectrophotometrically and it exhibits that the stoichiometry of the complex is 1:1 in acetonitrile solution. Finally, the electrode was satisfactorily used as an indicator electrode in complexometric titration of Pb²⁺ with EDTA and in direct determination of lead in various water samples.     

Phase time delay and Hartman effect in a one-dimensional photonic crystal with four-level atomic defect layer

The Hartman effect is revisited using a Gaussian beam incident on a one-dimensional photonic crystal (1DPC) having a defect layer doped with four-level atoms. It is considered that each atom of the defect layer interacts with three driving fields, whereas a Gaussian beam of width w is used as a probe light to study Hartman effect. The atom–field interaction inside the defect layer exhibits electromagnetically induced transparency (EIT). The 1DPC acts as positive index material (PIM) and negative index material (NIM) corresponding to the normal and anomalous dispersion of the defect layer, respectively, via control of the phase associated with the driving fields and probe detuning. The positive and negative Hartman effects are noticed for PIM and NIM, respectively, via control of the relative phase corresponding to the driving fields and probe detuning. The advantage of using four-level EIT system is that a much smaller absorption of the transmitted beam occurs as compared to three-level EIT system corresponding to the anomalous dispersion, leading to negative Hartman effect.     

Neutron transmission measurements of zinc and lead single crystals

Neutron transmission measurements of zinc and lead single crystals have been carried out in a neutron wavelength band from 0.03 to 0.55 nm at different orientations of the crystal with regard to the beam direction. The measurements were performed using both time-of-flight and fixed-angle scattering spectrometers installed in front of the ET-RR-1 reactor horizontal channels. It was found that the position of the observed dips in the neutron transmission measurements corresponded to the reflections from the (hkl) planes of the hexagonal zinc single crystal which was cut along the (002) plane, while in the case of lead, the single crystal was cut perpendicular to the (311) plane. The reflectivity from the (002) plane of zinc was determined using both transmission and reflection methods. The maximum reflectivity was found to be 55% when the zinc crystal was orientated at 45° to the beam direction. The wavelength spread of the observed reflectivity curve was found to be in agreement with the calculated one, taking into consideration the spectrometer's resolution and the crystal mosaic spread.     

High-Precision Determination of the Neutron Coherent Scattering Length

The neutron coherent scattering length b_c has been determined interferometrically to an uncertainty of about 5 × 10⁻⁵ by measuring the nondispersive phase. We propose improving the uncertainty to about 10⁻⁶ by optimizing various parameters of the interferometric experiment. Any uncertainty in the b_c determination arising from possible variations in the constitution of the ambient air can be eliminated by performing the experiment in vacuum. When such uncertainty is attained, it becomes necessary to account for the neutron beam refraction at the sample-ambient interfaces, to infer the correct b_c from the observed phase. The formula for the phase used hitherto is approximate and would significantly overestimate b_c. The refractive index for neutrons can thus be determined to a phenomenal uncertainty of about 10⁻¹².     

A mixed finite element formulation for shells through a reduced Reissner's principle in elastodynamics

Summary The use of Mixed models based in Reissner's principle in statics has been found to lead to some desirable simplifications in Finite Element formulations, in particular in plates and shells. Reduced formulations of Reissner's principle such as the one used by Prato have proved to be even more successful. In this paper, a reduction similar to that of Prato is attempted on a mixed elastodynamic variational principle by Karnopp.

---

Eine gemischte finite Elemente-Formulierung für Schalen durch ein reduziertes Reissnersches Prinzip der Elastodynamik

Zusammenfassung Die Verwendung von gemischten Modellen basiert auf Reissners Prinzip der Statik führt zu erwünschten Vereinfachungen bei der Formulierung von finiten Elementen im speziellen bei Untersuchungen von Platten und Schalen. Reduzierungen des Reissnerschen Prinzips, wie sie von Prato angewendet worden sind, haben sich sogar als noch erfolgreicher erwiesen. In dieser Untersuchung wird eine Reduktion, ähnlich der von Prato, für ein gemischtes elastodynamisches Variationsprinzip nach Karnopp, vorgenommen.

---

Symbol Table A Domain of integration of the Functional. Also area of the triangle - b Second fundamental form of the shell middle surface - C ^ijkl Elastic Constants - E ₁,E ₁ ^* Strain Energy and Co-Energy density - e _ij Elastic strain tensor - f _i Body force density tensor - I _ks Karnopp's functional, specialized to shells - I _ksc Contracted Karnopp's functional, specialized to shells - i, j, k Index 1, 2, 3 - K ₁,K ₁ ^* Kinetic Energy and Co-Energy density - K ^* Kinetic co-energy density for shell - m Moment tensor defined at the mid-surface - n In-plane stress tensor defined at the middle surface - n Qualifier for the boundary normal - p ,p ³ Boundary forces - Prescribed boundary forces - p Shear force tensor defined at the mid-surface - R Position vector of a point in the volume of the shell - r Position vector of a point on the mid-surface - r _i Net impulse density tensor - S _u Portion of the boundary where displacements are preseribed - S Portion of the boundary where forces are prescribed - s Qualifier for the direction tangent to the boundary - t Time variable - t ^ij Stress tensor - u ,u ₃ Mid-surface displacements - Mid-surface velocities - V Volume - v _i Displacement tensor - , Indices. Range 1, 2 - Shear strain tensor for the middle surface - Variation operator - Mid-surface strain tensor - Mid-surface curvature strain tensor - Direction cosine tensor for boundary normal - Mid-surface rotation tensor - Mid-surface angular velocity tensor - _M Strain energy density - _M * Strain co-energy density - _B * Bending strain co-energy density - _TS ^* Transverse shear strain co-energy density - | Covariant differentiation with respect tox , etc - Partial differentiation with respect tox , etc - .(dot) Time differentiation - -(bar) Prescribed quantities     

ECaD: Energy‐efficient routing in flying ad hoc networks

Much progress can be expected in the domain of unmanned aerial vehicle (UAV) communication by the next decade. The cooperation between multiple UAVs in the air exchanging data among themselves can naturally form a flying ad hoc network (FANET). Such networks can be the key support to accomplish several kinds of missions while providing the required assistance to terrestrial networks. However, they are confronted with many challenges and difficulties, which are due to the high mobility of UAVs, the frequent packet losses, and the weak links between UAVs, all affecting the reliability of the data delivery. Furthermore, the unbalanced energy consumption may result in earlier UAV failure and consequently accelerate the decrease of the network lifetime, thus disrupting the overall network. This paper supports the use of the movement information and the residual energy level of each UAV to guarantee a high level of communication stability while predicting a sudden link breakage prior to its occurrence. A robust route discovery process is used to explore routing paths where the balanced energy consumption, the link breakage prediction, and the connectivity degree of the discovered paths are all considered. The performance of the scheme is evaluated through a series of simulations. The outcomes demonstrate the benefits of the proposed scheme in terms of increasing the lifetime of the network, minimizing the number of path failures, and decreasing the packet losses.     

Performance of a Multiple HAP System Employing Multiple Polarization

In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with HAP (High Altitude Platforms) diversity techniques in order to increase the data rates in HAP communication systems. We will also investigate the effects of spatial correlation and mutual coupling between the separate antenna elements on system performance. Simulation results show that although the capacity is degraded by correlation and mutual coupling, we still achieve significant capacity gain compared to the single HAP case. In addition, we evaluate the performance of the system for different separation angles between HAPs, and determine the optimal separation angle that maximizes the total capacity of the system.     

Directed assembly of gold nanorods using aligned electrospun polymer nanofibers for highly efficient SERS substrates

Nonspherical metal nanoparticles are very attractive plasmonic nanostructures owing to the facile tunability of the plasmonic properties and the presence of sharp corners and edges, which act as electromagnetic hot spots for surface enhanced Raman scattering (SERS). However, such anisotropic nanostructures exhibit strong polarization dependence in their plasmonic properties, exhibiting significantly higher SERS intensity in certain orientations. In this paper, we demonstrate a facile strategy to achieve directed assembly of aligned gold nanorods using highly aligned electrospun nanofibers. We believe that the interstices between the nanofibers act as micro-and nanochannels, resulting in hydrodynamic drag forces on the gold nanorods, thus inducing massive alignment of the same on the nanofibers. Apart from exhibiting nearly 50 times higher SERS intensity compared to a planar SERS substrate with randomly oriented nanorods, our results highlight the importance of the orientation of anisotropic nanostructures. Finite difference time domain (FDTD) simulations employed to understand the electromagnetic field distribution around an aligned nanorod array showed excellent agreement with the experimental observations.