Tailoring Accelerating Beams in Phase Space

An appropriate design of wavefront will enable light fields propagating along arbitrary trajectories thus forming accelerating beams in free space. Previous ways of designing such accelerating beams mainly rely on caustic methods, which start from diffraction integrals and only deal with two-dimensional fields. Here we introduce a new perspective to construct accelerating beams in phase space by designing the corresponding Wigner distribution function (WDF). We find such a WDF-based method is capable of providing both the initial field distribution and the angular spectrum in need by projecting the WDF into the real space and the Fourier space respectively. Moreover, this approach applies to the construction of both two- and three-dimensional fields, greatly generalizing previous caustic methods. It may therefore open up a new route to construct highly-tailored accelerating beams and facilitate applications ranging from particle manipulation and trapping to optical routing as well as material processing.Comment: 8 pages, 6 figure

Spiral Transformation for High-Resolution and Efficient Sorting of Optical Vortex Modes

Mode sorting is an essential function for optical multiplexing systems that exploit the orthogonality of the orbital angular momentum mode space. The familiar log-polar optical transformation provides a simple yet efficient approach whose resolution is, however, restricted by a considerable overlap between adjacent modes resulting from the limited excursion of the phase along a complete circle around the optical vortex axis. We propose and experimentally verify a new optical transformation that maps spirals (instead of concentric circles) to parallel lines. As the phase excursion along a spiral in the wave front of an optical vortex is theoretically unlimited, this new optical transformation can separate orbital angular momentum modes with superior resolution while maintaining unity efficiency

A comparative study of the Chinese characters in the Graded list and the EBCL list

This study scrutinizes the Chinese characters in two reference works compiled as part of two projects: the Graded list and the EBCL list. Situated in the character-based theory, the characters compiled in both are examined in depth from the perspective of character complexity, character structure, semantic and phonetic radical transparency, frequency of character and frequency of word formation. The results show that the two lists share similarities in terms of distribution of characters of different structures, level of semantic radical transparency, and frequencies of character and word formation. The character complexity of the Graded list is higher than that of the EBCL, while the level of phonetic radical transparency of the Graded list is lower than that of the EBCL list. With the Graded list, the high demands of character learning need to be borne in mind; this is due to the visual load of character complexity and the pronunciation information provided in phonetic radicals. Against a backdrop of increasing demand for CFL pedagogical materials, the differences and similarities between the two lists analysed and discussed in this study contribute to their pedagogical applications in teaching and learning Chinese characters

Distributed Relay Selection for Heterogeneous UAV Communication Networks Using A Many-to-Many Matching Game Without Substitutability

This paper proposes a distributed multiple relay selection scheme to maximize the satisfaction experiences of unmanned aerial vehicles (UAV) communication networks. The multi-radio and multi-channel (MRMC) UAV communication system is considered in this paper. One source UAV can select one or more relay radios, and each relay radio can be shared by multiple source UAVs equally. Without the center controller, source UAVs with heterogeneous requirements compete for channels dominated by relay radios. In order to optimize the global satisfaction performance, we model the UAV communication network as a many-to-many matching market without substitutability. We design a potential matching approach to address the optimization problem, in which the optimizing of local matching process will lead to the improvement of global matching results. Simulation results show that the proposed distributed matching approach yields good matching performance of satisfaction, which is close to the global optimum result. Moreover, the many-to-many potential matching approach outperforms existing schemes sufficiently in terms of global satisfaction within a reasonable convergence time.Comment: 6 pages, 4 figures, conferenc

Compact and high-performance vortex mode sorter for multi-dimensional multiplexed fiber communication systems

With the amplitude, time, wavelength/frequency, phase, and polarization/spin parameter dimensions of the light wave/photon almost fully utilized in both classical and quantum photonic information systems, orbital angular momentum (OAM) carried by optical vortex modes is regarded as a new modal parameter dimension for further boosting the capacity and performance of the systems. To exploit the OAM mode space for such systems, stringent performance requirements on a pair of OAM mode multiplexer and demultiplexer (also known as mode sorters) must be met. In this work, we implement a newly discovered optical spiral transformation to achieve a low-cross-Talk, wide-opticalbandwidth, polarization-insensitive, compact, and robust OAM mode sorter that realizes the desired bidirectional conversion between seven co-Axial OAM modes carried by a ring-core fiber and seven linearly displaced Gaussian-like modes in parallel single-mode fiber channels. We further apply the device to successfully demonstrate high-spectralefficiency and high-capacity data transmission in a 50-km OAM fiber communication link for the first time, in which a multi-dimensional multiplexing scheme multiplexes eight orbital-spin vortex mode channels with each mode channel simultaneously carrying 10 wavelength-division multiplexing channels, demonstrating the promising potential of both the OAM mode sorter and the multi-dimensional multiplexed OAM fiber systems enabled by the device. Our results pave the way for futureOAM-based multi-dimensional communication systems

Environment-Enhancing Energy - Third Generation Biofuel

Yuanhui Zhang - Professor UI Department of Agricultural and Biological Engineering. Energy consumption and environment have been so far contradictory to each other and have difficulty in coexistence. Some extreme examples have been on the path of rapid development, and in many ways selfdestructive. How can we continue to improve human living conditions with limited energy sources? How can we protect our environment while sustaining our economy? How can we handle the magnitude and the multitude of these challenges? Are you optimistic, or pessimistic, about our future? In this presentation, Professor Zhang offers his perspectives, based on his own research, on the issues of energy and environment, and their implications to our economic development and sustainability. He conducts research in Environment-Enhancing Energy, which first converts organic solids in animal, human and food wastes into biocrude oil via a hydrothermal process (HTP); then grows fast-growing algae in the HTP wastewaters and sequesters carbon dioxide from the atmosphere. Finally, the algae biomass is fed back to the HTP, as a sole feedstock or as an additive, to be converted into additional biocrude oil. This synergistic process is extremely advantageous because it Simultaneously produces energy and improves the environment by improving water quality, sequestering carbon dioxide, and, of no less importance, having the potential to meet the entire national fuel need

Spatial and Temporal Distributions of Dust and Ammonia Concentrations in a Swine Building

Pollutants, especially dust, are rarely uniformly distributed within ventilated air spaces due to non‐uniform flow fields, particle inertia, gravitational settling, and diffusion. Thus, selecting suitable sampling locations for representative sampling is a challenge. The objective of this study was to determine the spatial and temporal distributions of dust and ammonia concentrations(NH3) in a swine building. Results of this study are useful in the design of sampling strategies that require limited sampling locations and in studying pollutant transport. This study was conducted in a commercial swine building in Illinois. The total suspended particulate (TSP) matter and ammonia concentrations were measured at 50 and 30 indoor sampling locations in December and June, respectively. Results showed that the average TSP concentrations ranged from 0.86 to 3.81 mg m‐3 in December and from 0.24 to 1.68 mg m‐3 in June. In December, the dust gradient across the length of the building was more pronounced than along its length. In June, the gradient along the length of the building was more pronounced, resulting in essentially uniform concentration in a cross‐section. The spatial distributions of the TSP concentrations in both December and June were essentially symmetrical about the longitudinal section of the building. The spatial gradient of NH3 concentrations was more pronounced along the length of the building in December, while the spatial distribution was almost uniform in June. These results suggest that the choice of representative sampling locations indoors will vary depending on the air movement in the building, which is dictated by the ventilation scheme

Measurement of Particle Size Distribution in a Swine Building

The majority of the research in animal buildings has been on measured concentrations of contaminants that the workers and animals are exposed to; emission measurements have only gained attention in recent years due to potential federal regulations on air quality emissions from animal feeding operations (AFOs). The contribution of AFOs to ambient PM10 and PM2.5 entails reliable measurement of particle size distribution. The objective of this study was to measure and compare the size distribution of particulate matter (PM) at multiple locations inside and at the exhausts of a wean‐to‐finish commercial swine building. The particle size distribution was measured by collecting total suspended particulate matter on Teflon filters and using Coulter Counter and Horiba LA‐300 analyzers for particle size distribution analyses. Results showed that the mass median diameter (MMD) of swine PM at the exhaust was about 14% lower than the average MMD indoors (26.84 vs. 31.55m), while the geometric standard deviations were about the same (1.85 vs. 1.86). In addition, the average percentage by volume of PM10 indoors was about 8%, while the percentage of PM10 leaving the building was 10%. In terms of the mass concentrations, PM10 indoors ranged from 0.014 to 0.125 mg m‐3, while at the exhaust PM10 ranged from 0.02 to 0.15 mg m‐3. This study will aid in understanding the exposure of workers to particles indoors and in quantifying the contribution of a commercial swine building to emissions of PM10 in the atmosphere