Urine nitrification and sewer discharge to realize in-sewer denitrification to simplify sewage treatment in Hong Kong

The chemically enhanced primary treatment works in Hong Kong will be upgraded for biological nitrogen removal. This study proposed a novel approach to waive the upgrading by urine source-separation, onsite nitrification and discharge of nitrified urine into sewers to achieve in-sewer denitrification. Human urine was collected and a lab-scale experiment for full urine nitrification was conducted. The results showed that full nitrification was achieved with alkaline addition. Simulation of nitrified urine discharge into an 8-km pressure main in Hong Kong was conducted with a quasi-2D dynamic sewer model developed from a previously calibrated sewer biofilm model. It was assumed that 70% of the residents' urine was collected and fully nitrified on-site. The simulation results revealed that the proposed approach is effective in removal of nitrogen within the sewer, which decreases ammonia-N at the sewer outlet to a level required for secondary effluent discharge in Hong Kong.     

Parameter control, characterization, and optimization in the fabrication of optical fiber near-field probes

Tip diameter and transmission efficiency of a visible-wavelength near-field optic probe determine both the lateral spatial resolution and experimental utility of the near-field scanning optical microscope. The commonly used tip fabrication technique, laser-heated pulling of fused-silica optical fiber followed by aperture formation through aluminization, is a complex process governed by a large number of parameters. An extensive study of the pulling parameter space has revealed a time-dependent functionality between the various pulling parameters dominated by a photon-based heating mechanism. The photon-based heat source results in a temperature and viscosity dependence that is a complex function of time and fiber diameter. Changing the taper of the optical probe can affect transmission efficiency by an order of magnitude or more.     

Measurement of transient deformations with dual-pulse addition electronic speckle-pattern interferometry

We describe an electronic speckle-pattern interferometry system for analyzing addition fringes generated by the transient deformation of a test object. The system is based on a frequency-doubled twin Nd:YAG laser emitting dual pulses at a TV camera field rate (50 Hz). The main advance has been the automatic, quantitative analysis of dual-pulse addition electronic speckle-pattern interferometry data by the introduction of carrier fringes and the application of Fourier methods. The carrier fringes are introduced between dual pulses by a rotating mirror that tilts the reference beam. The resulting deformation-modulated addition fringes are enhanced with a deviation filter, giving fringe visibility close to that of subtraction fringes. The phase distribution is evaluated with a Fourier-transform method with bandpass filtering. From the wrapped phase distribution, a continuous phase map is reconstructed with an iterative weighted least-squares unwrapper. Preliminary results for a thin plate excited by an acoustic shock show the suitability of the system for the quantitative evaluation of transient deformation fields.     

Unwrapping of Digital Speckle-Pattern Interferometry Phase Maps by use of a Minimum L(0)-Norm Algorithm

The performance of a minimum L(0)-norm unwrapping algorithm is investigated by use of synthetic digital speckle-pattern interferometry (DSPI) wrapped phase maps that simulate experimentally obtained data. This algorithm estimates its own weights to mask inconsistent pixels. Particular features usually included in DSPI wrapped phase distributions, such as shears, speckle noise, fringe cuts, object physical limits, and superimposed phase maps, are analyzed. Some adequate approaches to solving these features are discussed. Finally, it is shown that a complex case in which shears and fringe cuts coexist in the wrapped phase cannot be solved satisfactorily with the minimum L(0)-norm algorithm by itself. To cope with this problem, we propose a new scheme.     

Absorptivity contrast in transillumination imaging of tissue abnormalities

We calculate the time-resolved flux of photons transmitted across an optically turbid slab containing a partially absorbing inclusion. An analytical expression is obtained for the flux at a detector positioned opposite a point source (at a distance equal to the thickness of the slab) when the center of the inclusion lies on the line connecting those points. The calculation employs a discrete-time lattice random-walk model of photon transport. The resulting expression is used to assess the affects of time resolution on the detectability of the inclusion.     

Corneal-tissue absorption coefficients for 193- and 213-nm ultraviolet radiation

The small-signal absorption coefficients of 193- and 213-nm nanosecond laser pulses in bovine corneal tissue have been studied. The absolute reflectance of a planar quartz-cornea interface was measured at various angles of incidence for low-intensity laser irradiation (i.e., pulse fluences 3 orders of magnitude below the ablation threshold). The reflectance-versus-angle data were analyzed by the use of Fresnel theory to estimate the effective complex index of refraction of the tissue. This analysis indicated corneal absorption coefficients of 39,900 ± 9800 cm(-1) at 193 nm and 21,400 ± 4900 cm(-1) at 213 nm.     

On-column solvent exchange for purified preparative fractions

On-column solvent exchange, using many of the principles of solid-phase extraction, has been implemented to significantly reduce evaporation cycle time following reverse-phase preparative HPLC. Additional benefits, such as a reduced potential for salt formation, thermal decomposition, and residual solvent, are also described. Fractions obtained from preparative separations, typically in a large volume of acetonitrile:water, are injected into the preparative HPLC and then eluted in acetonitrile, creating a new fraction in a volatile organic solvent. Minimal modification to the instrument was required, and unattended operation is possible. Acetonitrile evaporation is achieved within 3 h, compared with 17 h for aqueous-based fractions; lower temperatures can be used during the evaporation step; mobile-phase additives, likely to form salts with the target compound if concentrated in the fraction, are removed before evaporation; sample recovery and purity are unaffected.     

WorldView卫星16波段影像光谱特征分类

传统的高分辨率遥感卫星光谱分辨率较低,WorldView卫星在8个可见光G近红外多光谱波段的基础上,新增加的８个短波红外(short wave infrared,SWIR)影像,有助于提高影像提取地物信息能力。分析了WorldView卫星的16波段影像上各种地物的光谱特征和分类性能,提出了新的植被指数、水体指数和建成区指数。实验表明,相比于8波段影像,使用16波段影像分类能够显著提高各类地物特别是裸地、建筑物和道路的分类精度,总体精度提高约5.5％。基于16波段设计的新地物特征指数能更好地避免干扰地物,通过简单阈值提取地物,取得较高的提取精度。