Scherk-Type Capillary Graphs

This paper concerns the regularity of a capillary graph (the meniscus profile of liquid in a cylindrical tube) over a corner domain of angle α. By giving an explicit construction of minimal surface solutions previously shown to exist (Indiana Univ. Math. J. 50 (2001), no. 1, 411–441) we clarify two outstanding questions. Solutions are constructed in the case α = π/2 for contact angle data (γ₁, γ₂) = (γ, π − γ) with 0 < γ < π. The solutions given with |γ − π/2| < π/4 are the first known solutions that are not C² up to the corner. This shows that the best known regularity (C^{1, ∈}) is the best possible in some cases. Specific dependence of the H?lder exponent on the contact angle for our examples is given. Solutions with γ = π/4 have continuous, but horizontal, normal vector at the corners in accordance with results of Tam (Pacific J. Math. 124 (1986), 469–482). It is shown that our examples are C^{0, β} up to and including the corner for any β < 1. Solutions with |γ − π/2| > π/4 have a jump discontinuity at the corner. This kind of behavior was suggested by numerical work of Concus and Finn (Microgravity sci. technol. VII/2 (1994), 152–155) and Mittelmann and Zhu (Microgravity sci. technol. IX/1 (1996), 22–27). Our explicit construction, however, allows us to investigate the solutions quantitatively. For example, the trace of these solutions, excluding the jump discontinuity, is C^2/3.     

Recent Developments in Solid-Propellant Binders

Abstract

The complex and important role of the propellant binder in solid-propellant rockets is described. The severe weight problems of space exploratrion cause high propellant performance to be of major concern in a highly competitive field. Binders contribute to performance, not only in terms of fuel value, but by being compatible with energetic components and by providing good mechanical properties. Both sterilization required for planetary landings and compatibility problems of new energetic oxidizers generate new requirements too stringent for existing binders; only binders composed essentially of saturated aliphatic hydrocarbon are predicted to be suitable. Several saturated-binder developments are in progress. The achievements of one of these programs, based on free-radical synthesis, are evaluated against the goals of the new binder.     

Continuous conversion of methanol to higher hydrocarbons at ambient pressure

An iodozincate ionic liquid solvent and catalyst is used to convert methanol continuously to a wide variety of hydrocarbons at atmospheric pressure.     

Signature of twin planes in Mössbauer spectroscopy of cuprate superconductors

One of the four quadrupole doublets (A, B, C, and D) observed in Mössbauer spectra of orthorhombic (Y or RE)₁Ba₂(Cu_1-xFe_x)30_7-δ(δ≈0) samples is identified with Fe dopant replacing a Cu site in twin planes. The site in question, labelled as D, is characterized by a quadrupole splitting Δ_D in the range 1.6±0.1 mm/s. The D-site intensity is found to approach zero when the 1-2-3, material is driven tetragonal, either upon oxygen desorption, upon oxygen loading, or upon increasing the Fe-dopant concentration.     

Compact High-Order Finite Differences for Interface Problems in One Dimension

This paper is concerned with the construction and analysis ofcompact finite difference approximations to the model linearsource problem –(pu')' + qu = f where the functions p,q, and f can have jump discontinuities at a finite number ofpoints. Explicit formulae that give O(h²) O(h³) and O(h⁴) accuracyare derived, and a procedure for computing three-point schemesof any prescribed order of accuracy is presented. A rigoroustruncation and discretization error analysis is offered. Numericalresults are also given.     

Comparison of graphite,aluminum, and TransHab shielding material characteristics in a high-energy neutron field

Space radiation transport models clearly show that low atomic weight materials provide a better shielding protection for interplanetary human missions than high atomic weight materials. These model studies have concentrated on shielding properties against charged particles. A light-weight, inflatable habitat module called TransHab was built and shown to provide adequate protection against micrometeoroid impacts and good shielding properties against charged particle radiation in the International Space Station orbits. An experiment using a tissue equivalent proportional counter, to study the changes in dose and lineal energy spectra with graphite, aluminum, and a TransHab build-up as shielding, was carried out at the Los Alamos Nuclear Science Center neutron facility. It is a continuation of a previous study using regolith and doped polyethylene materials. This paper describes the results and their comparison with the previous study.     

Review of Chemometrics Applied to Spectroscopy: 1985-95, Part 3 — Multi-way Analysis

INTRODUCTION

In this third part of a review on chemometrics in spectroscopy we will describe a recent methodology that has attracted increasing interest in spectroscopy. namely multi-way analysis. The application of multi-way analysis in spectroscopy is still relatively new. hence many methodological improvements are being investigated currently. Part of thls review will also be used to describe the algorithmic improvements gained the last decade.     

Asymptotic behaviour of the ratio of density gradient to electron density for atomic systems

The asymptotic behaviour of the negative ratio of the density gradient to the electron density, q(r), for neutral and singly charged atoms has been investigated. The results show that, for large r, q(r) can approach its limit √8?, where ? is the first ionization potential, from either above or below depending on the specific system considered.