Evaluation and measures to increase performance coefficient of hydrokinetic turbines

In this study was presented the valid equations for energy conversion system from water currents analogous to wind power system. Hydrokinetic technology may be divided into two categories such as horizontal and vertical system. Application of the systems is possible to marine, and river currents. Each system has different performance coefficient. Hydrokinetic energy conversion systems shows lower power coefficient. The existing measures with the purpose of increasing of performance coefficient have been presented. Additional suggestions have been put forward. Future perspectives for application improvement and working fields of different kind have been given.     

Millimeter-wave Ground-based Synthetic Aperture Radar Imaging for Foreign Object Debris Detection: Experimental Studies at Short Ranges

In this paper, millimeter-wave imaging of foreign object debris (FOD)-type objects on the ground is studied with the help of ground-based synthetic aperture radar (GB-SAR) technique. To test the feasibility of detecting runway FODs with this technique, some preliminary experiments are conducted within short antenna-to-target ranges of small imaging patches. An automated stripmap GB-SAR system with stepped-frequency transmission is constructed together with a quasi-monostatic data collection operation. The imaging experiments for various braces and screws are then carried out by using 32–36?GHz and 90–95?GHz frequency bands of the millimeter-wave. Images reconstructed by a matched-filter based algorithm are analyzed to determine the proper system parameters for an efficient imaging and to comprehend the factors against a successful detection. Results demonstrate the capability of GB-SAR imaging in accurately locating these FOD-like targets under near-range operating conditions.     

Game of protocols: Is QUIC ready for prime time streaming?

Quick User Datagram Protocol (UDP) Internet Connections (QUIC) is an experimental and low‐latency transport protocol proposed by Google, which is still being improved and specified in the Internet Engineering Task Force (IETF). The viewer's quality of experience (QoE) in HTTP adaptive streaming (HAS) applications may be improved with the help of QUIC's low‐latency, improved congestion control, and multiplexing features. We measured the streaming performance of QUIC on wireless and cellular networks in order to understand whether the problems that occur when running HTTP over TCP can be reduced by using HTTP over QUIC. The performance of QUIC was tested in the presence of network interface changes caused by the mobility of the viewer. We observed that QUIC resulted in quicker start of media streams, better streaming, and seeking experience, especially during the higher levels of congestion in the network and had a better performance than TCP when the viewer was mobile and switched between the wireless networks. Furthermore, we measured QUIC's performance in an emulated network that had a various amount of losses and delays to evaluate how QUIC's multiplexing feature would be beneficial for HAS applications. We compared the performance of HAS applications using multiplexing video streams with HTTP/1.1 over multiple TCP connections to HTTP/2 over one TCP connection and to QUIC over one UDP connection. To that effect, we observed that QUIC provided better performance than TCP on a network that had large delays. However, QUIC did not provide a significant improvement when the loss rate was large. Finally, we analyzed the performance of the congestion control mechanisms implemented by QUIC and TCP, and tested their ability to provide fairness among streaming clients. We found that QUIC always provided fairness among QUIC flows, but was not always fair to TCP.     

A geographic information system‐based model for economical and eco‐friendly high‐speed railway route determination using analytic hierarchy process and least‐cost‐path analysis

In this study, geographic information system (GIS)‐based network analysis and analytic hierarchy process (AHP) methods were applied to the Erzincan–Trabzon segment of the Turkish high‐speed railway (HSR) project. A new hybrid route, which considers both economic and environmental criteria, was created and compared with three different routes from various preconstruction studies. The route‐generating analysis included the eight parameters (criteria) of slope, geology, soil quality, rivers, protected areas, roads, land cover, and lakes. The optimum route for connecting the port of Trabzon to Turkey's interior via HSR was generated. The weights for determining the route were tested for sensitivity. The study demonstrated the efficiency of GIS and AHP integration in generating optimum routes for HSR projects according to given databases. All these GIS and AHP analyses were applied automatically with our novel GIS extension for determining optimum HSR routes. The final route has preserved cultural and historical structures, environmental integrity. The new hybrid route also decreased construction costs by approximately 12%, and the least‐cost‐path analysis confirmed the environmental efficiency of the route.     

Ferroelectric Based Photonic Crystal Cavity by Liquid Crystal Infiltration

A novel type of two-dimensional photonic crystal is investigated for it optical properties as a core-shell-type ferroelectric nanorod infiltrated with nematic liquid crystals. Using the plane wave expansion method and finite-difference time-domain method, the photonic crystal structure, which is composed of a photonic crystal in a core-shell-type ferroelectric nanorod, is designed for the square lattice and the hexagonal lattice. It has been used 5CB as a photonic crystal core, and LiNbO₃ as a ferroelectric material. The photonic crystal with a core-shell-type LiNbO₃ nanorod infiltrated with nematic liquid crystals is compared with the photonic crystal with solid LiNbO₃ rods and the photonic crystal with hollow LiNbO₃ rods.