An optimum design and fabrication of lens on luminous uniformity and light extraction of high-power light-emitting diode

The effect of lens inner structure on radiation pattern and light extraction efficiency of light-emitting diode (LED) and the application to artificial light in compact greenhouse is demonstrated. A commercial software package of Trace Pro and one-factor at-a-time (OFAT) method are used to simulate the lens with different inner structure. The optimum parameters of lens inner structure design for the maximum light extraction efficiency and the best uniform luminous are described by the corner radius of curvature, lens width, and lens height, respectively. For a real single LED module, base on the optimum parameters of lens inner structure, the corresponding best luminous uniformity is 62% and corresponding output extraction is 14.11 lm. The maximum uniformity of illumination for LED matrix assembled by LED modules with optimum lens is 88% and corresponding light extraction 1141 lm. In comparison with a commercial artificial light of LED matrix used in agriculture, the high-power LED module with proposed lens inner structure exhibit good improvement in uniformity of illumination and light extraction. This study may provide a practical guideline for design and fabrication of a high-performance lens used in various compact agricultural applications.     

Tomographic implementation of astronomical speckle imaging from bispectra

A bispectral method for astronomical speckle imaging utilizes an average speckle bispectrum of an object to derive its Fourier phase. There has been, however, a problem in conventional bispectral algorithm owing to difficulty in processing bispectral data in a four-dimensional (4D) space. In this paper, we propose an implementation to overcome this problem, where a one-dimensional (1D) object projection is reconstructed from a two-dimensional (2D) average bispectrum of speckle projections, and object projections so obtained at various angles are then tomographically combined into a 2D object image. In this tomographic approach, processes are separable into those for individual projection angles, implying that bispectral data required to be stored at a time are from 4D to 2D and computation time can be substantially reduced by parallelizing angle-by-angle processes. We have performed experiments using simulated and observed data, and have demonstrated the feasibility of the present approach with an achievable accuracy comparable to that of a conventional approach.     

Higher Spin Dirac Operators Between Spaces of Simplicial Monogenics in Two Vector Variables

The higher spin Dirac operator \(\mathcal{Q}_{k,l}\) acting on functions taking values in an irreducible representation space for \(\mathfrak{so}(m)\) with highest weight \((k+\frac{1}{2},l+\frac{1}{2},\frac{1}{2},\ldots,\frac{1}{2})\), with k, l?∈?\(\mathbb{N}\) and \(k\geqslant l\), is constructed. The structure of the kernel space containing homogeneous polynomial solutions is then also studied.     

How can nanobiotechnology oversight advance science and industry: examples from environmental,health, and safety studies of nanoparticles (nano-EHS)

Nanotechnology has great potential to transform science and industry in the fields of energy, material, environment, and medicine. At the same time, more concerns are being raised about the occupational health and safety of nanomaterials in the workplace and the implications of nanotechnology on the environment and living systems. Studies on environmental, health, and safety (EHS) issues of nanomaterials have a strong influence on public acceptance of nanotechnology and, eventually, affect its sustainability. Oversight and regulation by government agencies and non-governmental organizations (NGOs) play significant roles in ensuring responsible and environmentally friendly development of nanotechnology. The EHS studies of nanomaterials can provide data and information to help the development of regulations and guidelines. We present research results on three aspects of EHS studies: physico-chemical characterization and measurement of nanomaterials; emission, exposure, and toxicity of nanomaterials; and control and abatement of nanomaterial releases using filtration technology. Measurement of nanoparticle agglomerates using a newly developed instrument, the Universal NanoParticle Analyzer (UNPA), is discussed. Exposure measurement results for silicon nanoparticles in a pilot scale production plant are presented, as well as exposure measurement and toxicity study of carbon nanotubes (CNTs). Filtration studies of nanoparticle agglomerates are also presented as an example of emission control methods.     

Synthesis and photo physical properties of Au @ Ag (core @ shell) nanoparticles disperse in poly vinyl alcohol matrix

Synthesis of core @ shell (Au @ Ag) nanoparticle with varying silver composition has been carried out in aqueous poly vinyl alcohol (PVA) matrix. Core gold nanoparticle (~15 nm) has been synthesized through seed-mediated growth process. Synthesis of silver shell with increasing thickness (~1–5 nm) has been done by reducing Ag⁺ over the gold sol in the presence of mild reducing ascorbic acid. Characterization of Au @ Ag nanoparticles has been done by UV–Vis, High resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDX) spectroscopic study. The blue shift of surface plasmon resonance (SPR) band with increasing mole fraction of silver has been interpreted due to dampening of core, i.e. Au SPR by Ag. The dependence of nonlinear optical response of spherical core @ shell nanoparticles has been investigated as a function of relative composition of each metal. Simulation of SPR extinction spectra based on quasi-static theory is done. A comparison of our experimental and the simulated extinction spectra using quasi-static theory of nanoshell suggests that our synthesized bimetallic particles have core @ shell structure rather than bimetallic alloy particles.     

Governing nanobiotechnology: lessons from agricultural biotechnology regulation

This article uses lessons from biotechnology to help inform the design of oversight for nanobiotechnology. Those lessons suggest the following: first, oversight needs to be broadly defined, encompassing not just regulatory findings around safety and efficacy, but also public understanding and acceptance of the technology and its products. Second, the intensity of scrutiny and review should reflect not just risks but also perceptions of risk. Finally, a global marketplace argues for uniform standards or commercially practical solutions to differences in standards. One way of designing oversight to achieve these purposes is to think about it in three phases—precaution, prudence, and promotion. Precaution comes early in the technology or product’s development and reflects real and perceived uncertainties. Prudence governs when risks and hazards have been identified, containment approaches established, and benefits broadly defined. Transparency and public participation rise to the fore. The promotional phase moves toward shaping public understanding and acceptance and involves marketing issues rather than safety ones. This flexible, three-phase approach to oversight would have avoided some of the early regulatory problems with agricultural biotechnology. It also would have led to a more risk-adjusted pathway to regulatory approval. Furthermore, it would avoid some of the arbitrary, disruptive marketing issues that have arisen.     

First principles study of the electronic properties of twinned SiC nanowires

The electronic properties of saturated and unsaturated twinned SiC nanowires grown along [111] direction and surrounded by {111} facets are investigated using first-principles calculations with density functional theory and generalized gradient approximation. All the nanowires considered, including saturated and unsaturated ones, exhibit semiconducting characteristics. The saturated nanowires have a direct band gap and the band gap decreases with increasing diameters of the nanowires. The hexagonal (2H) stacking inside the cubic (3C) stacking has no effect on electronic properties of the SiC nanowires. The highest occupied molecular orbitals and the lowest unoccupied molecular orbitals are distributed along the nanowire axis uniformly, which indicates that the twinned SiC nanowires are good candidates in realizing nano-optoelectronic devices.     

Hidden conformal symmetry of self-dual warped AdS<Subscript>3</Subscript> black holes in topological massive gravity

We extend the recently proposal of hidden conformal symmetry to the self-dual warped AdS₃ black holes in topological massive gravity. It is shown that the wave equation of massive scalar field with sufficient small angular momentum can be reproduced by the SL(2, R) Casimir quadratic operator. Due to the periodic identification in the φ direction, it is found that only the left section of hidden conformal symmetry is broken to U(1), while the right section is unbroken, which only gives the left temperature of dual CFT. As a check of the dual CFT conjecture of self-warped AdS₃ black hole, we further compute the Bekenstein–Hawking entropy and absorption cross section and quasinormal modes of scalar field perturbation and show these are just of the forms predicted by the dual CFT.