A Continuously Operating, Flux Locked, Superfluid Interferometer

We report the characteristics of a flux locked, superfluid ⁴He interferometer that can continuously measure time-varying rotation rates. We describe the principles underlying the interferometer, including the dynamics of a superfluid chemical potential battery used to obtain continuous operation. We also discuss noise and drift issues and their possible amelioration.     

A novel biorthogonal wavelet network system for off-angle iris recognition

One important category of non-ideal conditions for iris recognition is off-angle iris images. Practically it is very difficult for images to be captured with no offset. It then becomes necessary to account for off angle information in order to maintain robust performance. A biorthogonal wavelet based iris recognition system, previously designed at our lab, is modified and demonstrated to perform off-angle iris recognition. Biorthogonal wavelet network (BWN) are developed and trained for each class. The non-ideal factors are adjusted by repositioning the BWN. To test, along with the real data, synthetic iris images are generated by using affine and geometric transforms of 0°, 10° and 20^° experimentally collected images. The tests were carried out on the experimentally collected off-angle data and synthetically generated data for angles from 0° to 60^° with a resolution of 5^°. This approach is shown to have less constraints than a transformation based iris recognition approach. Iris images off-angle by up to 42^° for synthetic data and up to 45^° for experimental data are successfully recognized.     

A dual polarized aperture coupled circular patch antenna using a C-shaped coupling slot

The design and development of a dual linearly polarized aperture coupled circular microstrip patch antenna at C-band are presented. The antenna uses a novel configuration of symmetric and asymmetric coupling slots. Variations in isolation between orthogonal feedlines and antenna axial ratio with the position of coupling slots are studied and broadband isolation and axial ratio are achieved. The prototype antenna yields 7.6 dBi peak gain, 70/spl deg/ 3-dB beam width, 25 dB cross-polarization levels and an isolation better than 28 dB between the two ports. With an external quadrature hybrid coupler connected to the two orthogonal feedlines, the antenna yields 3-dB axial ratio bandwidth of more than 30% at 5.8 GHz.     

Role of PbSe Structural Stabilization in Photovoltaic Cells

Semiconductor nanocrystals are promising materials for printed optoelectronic devices, but their high surface areas are susceptible to forming defects that hinder charge carrier transport. Furthermore, correlation of chalcogenide nanocrystal (NC) material properties with solar cell operation is not straightforward due to the disorder often induced into NC films during processing. Here, an improvement in long‐range ordering of PbSe NCs symmetry that results from halide surface passivation is described, and the effects on chemical, optical, and photovoltaic device properties are investigated. Notably, this passivation method leads to a nanometer‐scale rearrangement of PbSe NCs during ligand exchange, improving the long‐range ordering of nanocrystal symmetry entirely with inorganic surface chemistry. Solar cells constructed with a variety of architectures show varying improvement and suggest that triplet formation and ionization, rather than carrier transport, is the limiting factor in singlet fission solar cells. Compared to existing protocols, our synthesis leads to PbSe nanocrystals with surface‐bound chloride ions, reduced sub‐bandgap absorption and robust materials and devices that retain performance characteristics many hours longer than their unpassivated counterparts.     

A novel photogalvanic cell using anthraquinone-2-sulfonate

A photoelectrochemical cell based on the photochemistry of anthraquinone-2-sulfonate (D) has been set up. In the presence of formate at pH 11.0, D on illumination produces D^? or D^2?. In the absence of oxygen, at the platinum electrode the anodic reaction is D^? → D + e, or D^2? → D + 2e, and at the dark electrode the cathodic reaction is O₂ + 2H₂O + 4e → 4OH^?. The open circuit potential of the cell is 500 mV. The short circuit current is 180 μA. The cell has been recycled at least eight times. The efficiency increases with platinized platinum electrode in the dark chamber. The steady current under illumination is 65 μA with the same open circuit voltage of 500 mV. The short circuit current is 250 μA. With a CdS electrode in the illuminated chamber the efficiency is even better. The open circuit voltage is 560 mV. After charging by illumination for 8 h a steady current of 120 μA can be drawn from the cell, with illumination off, for 40 h. The short circuit current is 450 μA. The maximum power output is 4.2 × 10^?6W The cell can be recycled at least four times without any loss in efficiency. Grey deposition on the CdS electrode possibly indicates electrode decomposition.     

Atmospheric microplasma jet: spectroscopic database development and analytical results

This paper presents a developed dielectric-barrier-discharge-based "sniffer" that offers unique characteristics not available from other techniques. It is a portable, highly specific, and sensitive detector that operates at atmospheric pressure. It provides both molecular and elemental information on organic and inorganic gases and particulate aerosols. Measurements were made to electrically characterize the plasma and calculate the energy coupled into the plasma. We created a signature database for diverse chemicals based on the atomic and diatomic emission spectrum that serves to classify the compound and ideally recognize it by composition with the optical emission intensity corresponding to concentration. For some operational regimes and species, emission from OH (A(2)Σ(+)-X(2)Π), CH (A(2)Δ-X(2)Π), and often C(2) (d(3)Π(g)-a(3)Π(u); Swan band system) diatomic radicals is produced. Limits of detection extend to parts per billion (ppb) levels for some species such as decane, 2-decanol, and nitrobenzene. Results are presented for differentiation of classes of organic compounds such as alkanes, aromatics, oxygenates, chlorinated, and nitrogen-containing organic compounds.