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This paper presents an ultra-wideband Phased Array Feed (PAF) based on novel flat bend crossed dipole fed by 50Ohm coaxial line. The PAF is dual-polarized and made from all-metal to minimize Ohmic losses and simplify cryogenic integration. It is optimized for 1-2 GHz band and can be good PAF candidate for the Five hundred meter Aperture Spherical Telescope (FAST) and Qi Tai Telescope (QTT) as well as other radio telescopes.

Visible light communication (VLC) is a promising technology, which can provide both illumination and communication. In order to maximize the data rate and improve the quality of service in the indoor scenarios, it is essential to investigate VLC channels. In this paper, we present analysis for a VLC system considering random distribution of users and the shadow they formed. The detailed process to calculate the area of the shadow is also given. The simulation results show that the shadow can significantly affect the system performance and other parameters such as room size and half power angle also exhibit a negative effect.

Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega-science project to build the largest single dish radio telescope in Guizhou province, Southwest China. The construction of FAST will involve many kinds of analog and digital electrical equipments. The electrical equipments are potential threat to radio observation due to its ElectroMagnetic Interference (EMI) emission. The EMI should be safely shielded when FAST telescope operates. The shielding effectiveness of large shielding enclosures can be tested with two log periodic antennas, signal generator and spectrum analyzer. It is not suitable to test small shielding enclosure for that is not possible to put big antenna and signal generator inside. In this paper, an effective shielding effectiveness measurement system for the small shielding enclosure is introduced. This measurement system uses a frequency synthesizer of Valon Technology as signal generator which can measure the shielding effectiveness no more than 100dB in a frequency range of 23–6000MHz. Some of measurement results of shielding effectiveness are also presented.

After five and a half years construction, the main structure of Five-hundred-meter Aperture Spherical radio Telescope (FAST) has been completed in September 2016. Meanwhile, a Radio Quiet Zone (RQZ) with radius 30 km has also been established. In order to evaluate the Radio Frequency Interference (RFI) influence from the mobile base stations within radius 5 km (the restriction zone of RQZ) around FAST, several measurements have been carried out when these stations were closed temperately. Comparing the RFI measurement results before and after the closure of these stations, the interference has been decreased more than 30 dB. Since November 1 2016, all the mobile base station within the restriction zone of FAST RQZ have be closed permanently to avoid the risk of the receiver saturation due to the interference coming from these stations.

To address the issue of evolutionary data classification, we propose an evolving swarm classification model. It treats each class as an ant colony carrying different type of pheromone. The ant colonies send their members to propagate their unique pheromone on the unlabeled instances, so as to label them for member recruitment. Meanwhile, the unlabeled instances are treated as unlabeled ants, which also have their preferences for joining one of those labeled colonies. We call it homing feedback, and integrate it into the pheromone update process. Afterwards, the natural selection process is carried out to keep a balance between the member recruitment and the ant colony size maintenance. Sufficient experiments demonstrate that our algorithm is effective in the real-world evolutionary classification applications.

Food Traceability is regarded as a critical capability to enable and improve food safety both in public and private sector. However, the market practice to food traceability system (FTS) is not perfect. In lots of cases, the inefficient traceability supply is attributed to the gap of public's demand on higher traceability level and private companies' insufficient supply as expected. The fact is that public sector is less informed about quality and safety attributes of food than private sector, but private sector does not have adequate incentive to cover the gap. In order to explore how to mitigate the gap, this paper reviewed the key concepts and adoption history of FTS, compared the different incentives of each role in the ecosystem to adopt FTS, and analyzed the impacts of those incentives on the system design. Then a conceptual framework is developed to guide the FTS design with insight in the architecture design, functionality collection and business model design. Finally, theoretical and practical implications are discussed and future research opportunities are suggested.

In this paper a improving relay selection scheme based on the coalitional game is designed in the multi-user wireless networks. We firstly analyze the model of mutil-user cooperation networks. Then a brief introduction of the coalition concepts is given. In our strategy, source node and relay nodes constitute a coalition in order to increase the transmission rate and lower the BER of system. One coalition contains only one source. However, the relays that we consider can be the members of different coalitions. So how many coalitions a node is in takes into consideration in the scheme. Finally, we present the simulation results of the relay selection scheme.