Brillouin gain spectrum manipulation using multifrequency pump and probe for slope-assisted BOTDA with wider dynamic range

We propose slope assisted Brillouin optical time domain analysis (SA-BOTDA) with virtual Brillouin gain spectrum (BGS) generated by multifrequency pump and probe. The virtual BGS having a wide linear slope region of 100 MHz is easily generated by employing time-to-space spectral shaping technique that has been originally developed for generating short optical pulses. We demonstrate the distribution of virtual BGS realized by using five spectral components of pump and probe.

Stone equipment of the Poludensky complex of the Kedrovy Mys-1 site

The paper deals with the complex analysis of the stone equipment of the Kedrovy Mys-1 site associated with the Poludensky tradition, classical for the Trans-Urals, dated to the Late Neolithic period. On the basis of typologi-cal and functional analyses, aimed at the study of tool shapes and identification of their correlation with the func-tional purpose, specifics of the stone industry of the Poludensky complex have been determined. The tools manu-factured at the site of Kedrovy Mys-1 were produced from the materials from the valley of the river Miass, situated behind the Ilmensky ridge, approximately 20–25 km away from the site. Dominant materials are phtanitoids and sealing-wax green jade; these quality materials were scarce, so that local chalcedonies were used. The stone industry based on the prismatic flaking was aimed at the production of plates as the feedstock for the tools. For the production of tools, preference was given to the medium-width plates, with a little use of small plates. A fea-ture of the complex is represented by the tools indicating the existence of the insert technique, such as plates with the rounded back and face, chamfered tips, “triangle”, and unretouched plates used as knives. Mainly blunting retouching, and sometimes sharpening, was used for the plate processing from the back side. A cutter spalling as the tool shaping technique was used occasionally. No cutters were found. Typologically identified tools are repre-sented by arrow tips, end scrapers, piercers, borers, scrapers on the flakes and nucleus cleavage, chopping tools, abrasives, and a retoucher. Specifics of the Poludensky toolset of the Kedrovy Mys-1 site allows suggestion that during this period of the site the main activity of the population was concerned with food processing — meat cut-ting and catch processing. This is evidenced by the predominance of the knives for meat/fish cutting. The propor-tion of tools used for the production of wooden equipment is quite small, which is probably due to the sampling, although morphologically it is very prominent. In the meantime, the presence of tools for processing of skin, stone, bone, and for repair of ceramics indicates a full cycle of the production activity ensuring efficient adaptation in the lake system environment.

Real-Time Implementation of Robust Loop-Shaping Controller for a VSC HVDC System

Voltage source converter (VSC) based HVDC systems are one of the most promising technologies for high voltage bulk power transmission. The reliability and stability of a VSC-based HVDC system greatly depends on the design of a proper controller for the inner decoupled d-q current loop. One of the major causes of instability in a properly tuned controller is due to system parameter variation. This paper presents the design of a fixed parameter robust controller for the inner decoupled d-q current loop for a VSC-based HVDC system to deal with the uncertainties due to system parameter variations. The method of multiplicative uncertainty is employed in the robust design to model the variations in the system parameters. The robust control design was realized through a graphical procedure known as the loop-shaping technique. The graphical loop shaping technique is a much simpler and more straightforward method compared to the traditional H∞-based algorithms for robust controller design. The designed robust controller was experimentally verified using a real-time hardware in loop (HIL) system and was tested on a VSC HVDC system. The performance of the designed robust controller is compared to that of a traditional PI controller. It has been observed that a classical PI controller is effective for a given operating point, and its performance deteriorates when the operating point changes or when the system parameters change. The studies conducted using real-time hardware in the loop (HIL) system prove that the designed loop-shaping-based robust controller provides very good performance and stability for a wide range of system parameter variations, such as changes in resistance and the inductance of the VSC HVDC system compared to the PI controller tuned using conventional methods.

Arbitrary Pulse Shaping using Nonuniform Spacetime Modulation

This paper introduces and demonstrates a pulse shaping technique based on nonuniform spacetime modulation. This technique allows arbitrary pulse shaping and is in this regard unique, to the knowledge of the authors. Although we restrict here our attention to a 1+1D (1 dimension of time + 1 dimension of space) system, this idea can be extended to 1+2D (and 1+3D) systems, which will feature richer scattering phenomenology given the simultaneous transformations of the temporal vectorial spatial spectra of pulses.

Shape Optimization of an Integrated Mast for RCS Reduction of a Stealth Naval Vessel

In this paper, we analyze the radar cross section (RCS) of an integrated mast and present the optimized mast shape for RCS reduction. The RCS is simulated using commercial electromagnetic (EM) software based on the shooting and bouncing rays (SBR) method and the diffraction fields at the edges are also considered. Threat frequencies, threat regions and cardinal points are first defined considering the operational environments of a naval vessel. We calculate and analyze the RCS of the integrated mast in terms of the threat frequencies, the shapes of the integrated mast and the direction and polarization of the incident waves. The shape of the integrated mast is optimized based on the shaping technique. The optimized mast has low RCS properties in the primary threat sectors except for the exceptional angle regions.