Three-dimensional light bullets in a Bragg medium with carbon nanotubes

We present a theoretical study of the propagation of three-dimensional extremely short electromagnetic pulses (a.k.a. light bullets) through a Bragg medium containing an immersed array of carbon nanotubes. We demonstrate the possible stable propagation of such light bullets. In particular, our results suggest these light bullets can carry information about the Bragg medium itself.Comment: To appear in Appl. Phys.

Modified variable phase method for the solution of coupled radial Schrodinger equations

A modified variable phase method for the numerical solution of coupled radial Schrodinger equations, which maintains linear independence for different sets of solution vectors, is suggested. The modification involves rearrangement of coupled equations to avoid the usual numerical instabilities associated with components of the wave function in their classically forbidden regions. The modified method is applied to nuclear structure calculations of halo nuclei within the hyperspherical harmonics approach

Disturbance impulse effects on large umbrella space reflector dynamics

Large umbrella space antennas are essential for communication, monitoring and observation of Earth and space objects. Despite investigations devoted to space antenna dynamics, the disturbance impulse shape effect on the root mean square error of spacecraft antenna reflecting surface has not been studied. This paper overcomes this gap describing disturbance impulse impact on root mean square error of spacecraftantenna reflecting surface relative to paraboloid via nonlinear finite element method. Based on numerical results root mean square dependency on disturbance time for rectangular and sine impulses was calculated. This approach could be applied in studying antenna reflecting surface response on disturbance impulse for different types of perspective large space antennas

Structure and Properties of the Bulk Standard Samples and Cellular Energy Absorbers

The development of additive technology revealed a real prospect of their use for the manufacture of complex shapes. Now, it is possible to produce parts that previously were either very difficult to produce using the subtracting technology and joining technology, or it was not at all feasible. In the manufacture of parts of complex shape, it is necessary to use a supporting structure, which is necessary to place such a way that they can be easily removed. Additionally, they must necessarily be absent in certain places. In this regard, the preparation model can take significant time to satisfy all of these, often conflicting, requirements. In this paper, we show optimization examples of the model preparation with support structures for parts manufactured at the facility EOSINT M270 and used in medicine and engineering. Additional emphasis is on the fact that, during the manufacture of parts, solidification’s modes of massive parts differ from those of the thin-walled portions of parts. The results of the complex studies on the different stainless steels (including martensitic) are described with an emphasis on their structure and mechanical properties. The results of a honeycomb energy absorbers, which are quite seldom produced by the additive technologies, are presented in this chapter

Calculation method for cable-beam shell structures

This paper presents a calculation method suitable for cable-beam shell structures. It is based on both nonlinear finite element and force density methods. The main idea is to define the solution sequence for stress - strain state problem of above mentioned structures by nonlinear finite element method. Every successive solution involves the previous one as an initial estimate in convergent domain. To find an initial estimate for the first solution a force density method is used. The proposed method is tested on a new large space umbrella reflector

On the possibility to fabricate ceramics using fused deposition modeling

The paper presents a uniquely designed device that enables controlled manufacturing of semi-fabricated products from thermoplastic ceramic suspensions by fused deposition modeling. Sintering of the products yields ceramics with high strength and hardness. We use ceramic aluminum oxide (Al2O3) as an example to prove that additive ceramic structures can be produced without noticeable boundaries between layers of the material

Studying a LW-VCSEL-Based Resonant Cavity Enhanced Photodetector and Its Application in Microwave Photonics Circuits

A detailed comparative experimental study was carried out to pursue advanced performances corresponding to the key parameters of two photodetectors based on vertical cavity surface emitting laser (VCSEL) operating in free-running or optically injection locked mode, as well as an inherent pin-photodetector. During the preliminary study, the key static and dynamic parameters were quantitatively determined and the optimal operating modes were derived for the both versions of VCSEL-based photodetectors as separate microwave-photonics circuit elements. Based on them, a final experiment was conducted to evaluate the processing quality, when one of the versions of VCSEL-based photodetectors or a inherent pin-photodetector is implemented as an optical-to-electrical converter for a typical microwave-photonics circuit that processes 120-Mbps 16-position quadrature amplitude modulated signal on the radio frequency carrier of 1–6 GHz. As a result, it was confirmed that better processing quality, i.e. Error Vector Magnitude value of less than 4%, could be obtained by using the free-running VCSEL-based photodetector version

Ultralow-noise terahertz detection by p-n junctions in gapped bilayer graphene

Graphene shows a strong promise for detection of terahertz (THz) radiation due to its high carrier mobility, compatibility with on-chip waveguides and transistors, and small heat capacitance. At the same time, weak reaction of graphene's physical properties on the detected radiation can be traced down to the absence of band gap. Here, we study the effect of electrically-induced band gap on THz detection in graphene bilayer with split-gate p-n junction. We show that gap induction leads to simultaneous increase in current and voltage responsivities. At operating temperatures of ~25 K, the responsivity at 20 meV band gap is from 3 to 20 times larger than that in the gapless state. The maximum voltage responsivity of our devices at 0.13 THz illumination exceeds 50 kV/W, while the noise equivalent power falls down to 36 fW/Hz^0.5. These values set new records for semiconductor-based cryogenic terahertz detectors, and pave the way for efficient and fast terahertz detection

Superhalo of C 22 reexamined

An unusually large value of the C22 matter radius, extracted by Tanaka et al. [Phys. Rev. Lett. 104, 062701 (2010)PRLTAO0031-900710.1103/PhysRevLett.104.062701] from measured reaction cross sections, attracted great attention of scientific community. Since that time, several experimental works related to the C22 nucleus have appeared in the literature. Some of the experimental data, measured with high accuracy, allow us to fix C22 structure more reliably. Two limiting models reproducing C22 nuclear structure within the three-body cluster approach, that allow us to describe all existing experimental data, are presented. The C22 ground state, continuum structure, and geometry are obtained. With fixed C22 wave function, the prediction for the soft dipole mode in C22, which is studied in the process of Coulomb fragmentation, is performed

Modelling large-sized mesh reflector with extended aperture

Offset large-sized deployable mesh reflector with symmetric frontal and rear nets is described in the paper. This reflector involves extended aperture area and reduced framework elements by applying beam elements in the peripheral areas of reflecting surface. Strain-stress analysis is conducted to calculate reflecting surface shape of required accuracy