Design of resolution testing facility for ultraviolet imager

We present a resolution testing system of ultraviolet （UV） imager. In this system, an UV Czerny-Turner monochromator with a small f-number is designed to get more energy as an UV radiation source, and its stray light is rejected effectively by light traps. And UV diffuser is employed in order to get uniform light distribution on the resolving power test target. We also design a novel UV collimator which makes infinite UV testing targets. It can reduce the difficulty of optical design and the machining cost, and utilize UV energy at maximum extent. This facility has been applied in the imaging quality evaluation of the UV instrument, and the results accord with the theoretical analysis.     

Maintenance policy for multivariate standby/operating units

In this paper the maintenance of multi‐component systems, which may be either in operating condition or in the standby mode is studied. A less than perfect testing procedure to detect failures in the latter case is considered. We focus on the existence of an optimum policy weighing the cost incurred under this policy against the cost derived from an undetected failure. Copyright © 2002 John Wiley & Sons, Ltd.     

Hardness and Elastic Modulus Profiles of Hybrid Coatings

Instrumented-indentation testing (IIT) provided with a continuous stiffness measurement (CSM) technique was employed to measure hardness and elastic modulus profiles of thin organic/inorganic hybrid coatings on glass surfaces. Hybrids were synthesized by the hydrolytic condensation of (3-methacryloxypropyl) trimethoxysilane (MPMS) or vinyltrimethoxysilane (VMS), with 5–30 wt% tetraethoxysilane (TEOS), in the presence of formic acid. Coatings of 600–800 nm on glass substrates were obtained by dip-coating solutions of these hybrids with benzoyl peroxide (BPO) addition, and curing in an oven following a thermal cycle up to 120C. Both hardness and elastic modulus showed a maximum value close to the surface, followed by a plateau and a significant increase at higher penetrations. Hybrids based on MPMS and 20–30 wt% TEOS exhibited a good combination of intrinsic values of hardness (0.50 GPa) and brittle index (0.06–0.07), that makes them suitable for coatings of plastic substrates.     

Effect of ultrasound on oil removal from soils

The soil-flushing method enhanced by ultrasonic waves is a new technique that potentially can become an effective method for in situ remediation of the ground contaminated by NAPL hydrocarbons. This study investigated the effectiveness of ultrasound enhancement in the soil-flushing method for a range of conditions involving soil type, soil density, flushing rate, and sonication power. The study was conducted in the laboratory using specially designed and fabricated equipment. The test results indicated that the rate of contaminant extraction increased considerably with increasing sonication power up to the level where cavitation occurred. The effectiveness of sonication-enhanced soil-flushing can be expressed as a function of (D(10))(2)*i, in which D(10) is the effective grain size, and i is the hydraulic gradient.     

Inferences based on a bivariate distribution with von Mises marginals

There is very little literature concerning modeling the correlation between paired angular observations. We propose a bivariate model with von Mises marginal distributions. An algorithm for generating bivariate angles from this von Mises distribution is given. Maximum likelihood estimation is then addressed. We also develop a likelihood ratio test for independence in paired circular data. Application of the procedures to paired wind directions is illustrated. Employing simulation, using the proposed model, we compare the power of the likelihood ratio test with six existing tests of independence.     

Structural Change Models with an Application in Cryogenic Thermometry

In a linear regression framework, structural change models are proposed for the detection of abrupt changes in parameter values. Two models are discussed: 1) the pure structural change model, where all the components of the parameter are allowed to change and are tested all together, and 2) the partial structural change model, where only some of the parameter β components might change. For an on-line implementation, a sliding window algorithm is introduced. The procedure was successfully applied to phase transition identification in cryogenic thermometry. *Work partially funded under EU SofTools_MetroNet Contact N. G6RT-CT-2001-05061.     

Statistical analysis of queueing systems

This paper provides an overview of the literature on statistical analysis of queueing systems. Topics discussed include: model identification, estimation, hypothesis testing and other related aspects. Not all of these statistical problems are covered in books on queueing theory or stochastic processes. The bibliography is not exhaustive, but comprehensive enough to provide sources from the literature.     

Surface acoustic wave studies of subsurface damage

We have measured the attenuation of surface acoustic waves on polished substrates and correlated the frequency-dependent attenuation with sub-surface damage. The damage was produced in single crystal lithium niobate samples by lapping and polishing with commercially available diamond compound. Surface acoustic wave attenuation on these samples was measured from 100 MHz to 1.5 GHz using interdigital transducers, thus covering depths ranging from 35 μm to 2 μm below the lithium niobate surface     

Parametric multiple regression risk models: Theory and statistical analysis

Parametric multiple regression models for the claim number and the claim amount of an individual risk are introduced allowing explanatory variables to influence the mean claim number (amount). A model for an entire portfolio of risks is established on this basis. Then an extensive and in many cases efficient statistical analysis of this model is presented.