Analysis of singularities from modulus maxima of complex wavelets

Complex-valued wavelets are normally used to measure instantaneous frequencies, while real wavelets are normally used to detect singularities. We prove that the wavelet modulus maxima with a complex-valued wavelet can detect and characterize singularities. This is an extension of the previous wavelet work of Mallat and Hwang on modulus maxima using a real wavelet. With this extension, we can simultaneously detect instantaneous frequencies and singularities from the wavelet modulus maxima of a complex-valued wavelet. Some results of singularity detection with the modulus maxima from a real wavelet and an analytic complex-valued wavelet are compared. We also demonstrate that singularity detection methods can be employed to detect the corners of a planar object.     

Motion Error Compensation Method for Hydrostatic Tables Using Actively Controlled Capillaries

To compensate for the motion errors in hydrostatic tables, a method to actively control the clearance of a bearing corresponding to the amount of error using actively controlled capillaries is introduced in this paper. The design method for an actively controlled capillary that considers the output rate of a piezo actuator and the amount of error that must be corrected is described. The basic characteristics of such a system were tested, such as the maximum controllable range of the error, micro-step response, and available dynamic bandwidth when the capillary was installed in a hydrostatic table. The tests demonstrated that the maximum controllable range was 2.4 /im, the resolution was 27 nm, and the frequency bandwidth was 5.5 Hz. Simultaneous compensation of the linear and angular motion errors using two actively controlled capillaries was also performed for a hydrostatic table driven by a ballscrew and a DC servomotor. An iterative compensation method was applied to improve the compensation characteristics. Experimental results showed that the linear and angular motion errors were improved to 0.12 μm and 0.20 arcsec, which were about 1/15^th and l/6^th of the initial motion errors, respectively. These results confirmed that the proposed compensation method improves the motion accuracy of hydrostatic tables very effectively.     

Separation of whey proteins by anion-exchange membranes

Three strong anion-exchange membranes (CIM QA, Q100 and HiTrap Q) were investigated for the separation of the major proteins, which were contained in whey, such as α-Lactalbumin, BSA and β-Lactoglobulin. Experiments were performed to determine the optimum mobile phase composition for separating the whey proteins using the standard chemicals of the proteins. The mobile phase was buffer A (20 mM piperazine-HCl pH 6.4) and buffer B (buffer A+1 M NaCl) and the linear gradient elution changes of salt concentration were applied. The standard chemicals of the proteins were used to investigate the optimal mobile phase compositions with the three anion-exchange membranes. From the experimental results, it was found that HiTrap Q was the most effective in separating whey proteins.     

Capacity improvement in CDMA downlink with orthogonal code-hopping multiplexing

Orthogonal code-hopping multiplexing (OCHM) is a statistical multiplexing scheme designed to increase the number of allowable downlink channels in code division multiple access (CDMA) systems. OCHM is expected to compensate for a lack of codewords in future communication systems. In CDMA systems including OCHM, system capacity is limited by the number of codewords and power (or interference), and the maximum system capacity is determined by a stronger limitation between them. Call blockings due to power limitation may occur firstly if downlink channels demand large E/sub b//I/sub 0/ values and a high-channel activity. On the other hand, code limitation may occur prior to power limitation in CDMA. The maximum system capacities determined by both code and power limitations must be known, even in OCHM. However, previous studies on OCHM system capacity focused only on increasing the number of multiplexed users with no consideration of the power limitation. In this paper, the overall system capacity of OCHM considering both code and power limitations was evaluated. For this analysis, the transmission chip energy of base station (BS) and inner/outer-cell interference is mathematically derived in a multicell and multiuser environment. The downlink system capacity for OCHM is larger than for orthogonal code division multiplexing (OCDM) as other cell interference (OCI), mean channel activity, and the required E/sub b//I/sub 0/ value decrease.     

Application of computational fluid dynamics analysis for improving performance of commercial scale selective catalytic reduction

The performance of commercial scale selective catalytic reduction (SCR) system is strongly dependant upon the degree of mixing between NH₃ and NOx or NH₃ concentration distribution at the catalyst layer according to the reaction kinetics of SCR catalysts. Insufficient mixing of the reduction agent and NOx mass flow necessitates an uneconomically large catalyst volume and high NH₃ slip to meet the required NOx emission values. The effective methodology which can increase the performance of commercial scale SCR through improving NH₃ concentration distribution at the catalyst layer using computational fluid dynamics (CFD) analysis was suggested and applied to the real operations. The operation results have shown that the performance of commercial SCR was improved from 54.4% to 74.8% as NH₃ concentration deviation at the catalyst layer was reduced from 23.6% to 8.6%. It is established that the increase of NH₃ concentration uniformity at the catalyst layer contributes to improvement of performance of commercial scale SCR.     

Effect of temperature and pressure on permeation,ageing and emissions of elastomers

This article details permeation tests that were performed on sheet samples of elastomers, over a wide range of pressures and temperatures, to study their effects on gas diffusion and solubility. It also explains how ageing is affected by gas permeation, and how the permeation test results can be used as input data for finite element analysis to aid the design of elastomeric components.     

Identification of a reservoir for HIV-1 in patients on highly active antiretroviral therapy

The hypothesis that quiescent CD4+ T lymphocytes carrying proviral DNA provide a reservoir for human immunodeficiency virus-type 1 (HIV-1) in patients on highly active antiretroviral therapy (HAART) was examined. In a study of 22 patients successfully treated with HAART for up to 30 months, replication-competent virus was routinely recovered from resting CD4+ T lymphocytes. The frequency of resting CD4+ T cells harboring latent HIV-1 was low, 0.2 to 16.4 per 10(6) cells, and, in cross-sectional analysis, did not decrease with increasing time on therapy. The recovered viruses generally did not show mutations associated with resistance to the relevant antiretroviral drugs. This reservoir of nonevolving latent virus in resting CD4+ T cells should be considered in deciding whether to terminate treatment in patients who respond to HAART.     

Paediatric upper gastrointestinal endoscopy: a 2-year review

OBJECTIVE: To review the paediatric upper gastrointestinal endoscopy service in a paediatric department in Hong Kong. METHODS: Records of all endoscopies undertaken in this department from May 1995 to January 1996 were retrieved and analysed. RESULTS: The commonest indication for upper endoscopy was dyspepsia with 88% positive histological findings. Helicobacter pylori (H. pylori) was found in 25% of this group of children. CONCLUSION: Paediatric upper gastrointestinal endoscopy service is invaluable in a paediatric department by providing useful diagnostic information which would otherwise be missed.     

Oxidation properties of mesophase pitch prepared by a heterogeneous nucleation method

Mesophase pitches prepared by a heterogeneous nucleation method from various mixtures of coal tar-derived isotropic pitch and petroleum-derived mesophase pitch (MP-P) were oxidatively stabilized, and the dependence of chemical reactivity and stabilization rate on their chemical structure was investigated. The rate and amount of oxygen uptake of the mesophase pitch fibres, revealed by thermogravimetry, increased under given conditions of oxidation with the amount of added MP-P, but the rate of stabilization showed a reverse trend. The lower chemical reactivity of coal tar-derived mesophase pitch (MP-C) appears to induce a slower rate of oxygen uptake, while the higher content of pyridine-insoluble fraction and higher aromaticity of MP-C may result in a lesser content of oxygen being required for stabilization, as compared with MP-P.