Goodness of fit of small samples to the weibull distribution

Weibull paper is used extensively to estimate the parameters of a population, even when the results may look somewhat suspicious to the eye. In this paper the author suggests a statistical test, gives the limiting values of the test statistic, and goes on to illustrate the use of such a test by analysing some data.     

Intersatellite range monitoring using optical interferometry

We report on an interferometer designed to provide 1-10 nm/square root(Hz) displacement measurement resolution, in the range 0.01 Hz to 1 Hz, while in low Earth orbit. The interferometer comprises two units, each with its own laser and in separate satellites, which would be in the same orbit separated by approximately 50 km. We discuss the requirements on the interferometer subsystem and describe the optical transponder distance measurement, including a phase locking method to generate a heterodyne beat signal between the two lasers. Design, fabrication, and testing of a "flightlike" engineering model interferometer is outlined, and results from environmental and performance tests are reported.     

Modifiable variables affecting interdialytic weight gain include dialysis time,frequency, and dialysate sodium

Interdialytic weight gain (IDWG) is associated with hypertension, left ventricular hypertrophy, and all‐cause mortality. Dialysate sodium concentration may cause diffusion gradients with plasma sodium and influence subsequent IDWG. Dialysis time and frequency may also influence the outcomes of this Na⁺ gradient; these have been overlooked. Our objective was to identify modifiable factors influencing IDWG. We performed a retrospective multivariable regression analyses of data from 86 home hemodialysis patients treated by hemodialysis modalities differing in frequency and session duration to determine factors involved that predict IDWG. Age, diabetic status, and residual renal function did not correlate with IDWG in the univariable analysis. However, using a combination of backwards selection and Akaike information criterion to build our model, we created an equation that predicted IDWG on the basis of serum albumin, age, patient sex, dialysis frequency, and the diffusive balance of sodium, represented by the product of the duration of dialysis and the patient plasma to dialysate Na⁺ gradient. This equation was internally validated using bootstrapping, and externally validated in a temporally distinct patient population. We have created an equation to predict IDWG on the basis of independent factors readily available before a dialysis session. The modifiable factors include dialysis time and frequency, and dialysate sodium. Patient sex, age, and serum albumin are also correlated with IDWG. Further work is required to establish how improvements in IDWG influence cardiovascular and other clinical outcomes.     

Noncontact Photogrammetric Measurement of Vertical Bridge Deflection

This paper reports on the results from a study of vertical deflection measurement of bridges using digital close-range terrestrial photogrammetry (DCRTP). The study consisted of a laboratory and two field exercises. In the laboratory exercise, photogrammetric measurements of a 11.6 m (38 ft) steel beam loaded at midspan were made and compared with dial gauge readings and elastic beam theory. In the first field exercise, the initial camber and dead load deflection of 31.1 m (102 ft) prestressed concrete bridge girders were measured photogrammetrically and compared with level rod and total station readings. A comparison of the photogrammetric measurements with the dead load deflection diagram is also made. In the second field exercise, the vertical deflection of a 14.9 m (49 ft) noncomposite steel girder bridge loaded with two dump trucks was measured. Photogrammetric results are compared with deflections estimated using elastic finite-element analysis, level rod readings, and curvature-based deflection measurements. The paper is concluded with a discussion of work in progress to further improve the accuracy of DCRTP in the field.     

Finite element calculations of the accommodation energy of a misfitting precipitate in an elastic-plastic matrix

The elastic-plastic accommodation energy generated by the formation of a plate-shaped inclusion in an effectively infinite solid is calculated using two-dimensional (2-D) and three-dimensional (3-D) finite element techniques. A typical example of the occurrence of such an inclusion, modeled in detail in this article, is the formation of a zirconium hydride platelet in a zirconium alloy. To verify the finite element models, initial calculations were based on a linear elastic model of the inclusion and the surrounding matrix material, plus elastic-plastic solutions of an isotropically misfitting spherical inclusion expanding within an elastic/perfectly plastic, infinite solid. Good agreement with the corresponding exact analytical results was found. The finite element analysis was used to determine the accommodation energy of isotropically and anisotropically misfitting oblate spheroids contained in an elastic/perfectly plastic medium. Calculations were carried out for oblate spheroids with aspect ratios (semiminor to semimajor axes) of 0.75, 0.5, 0.25, and 0.1. In contrast to the elastic result, the elastic-plastic accommodation energy values increased with decreasing aspect ratio. This result is due to an increase in the hydrostatic component of the stress in the matrix and a consequent loss in ability to decrease the misfit stresses by plastic deformation. Three-dimensional analyses of cuboidal inclusions expanding into infinite elastic and elastic/plastic solids were also performed. The results depended on mesh density, but reasonable values could be obtained at moderate mesh densities.     

Effect of organic loading rate on the biological performance of the thermophilic anaerobic membrane bioreactor treating pulp and paper primary sludge

Clean Technologies and Environmental Policy - Waste-to-energy or value-added products have been increasingly considered in many pulp and paper mills (PPMs) worldwide. However, developing...