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We revisit an investment experiment that compares the performance of an investor using Bayesian methods for determining portfolio weights with an investor that uses the Monte Carlo based resampling approach advocated in Michaud (1998). Markowitz and Usmen (2003) showed that the Michaud investor always won. However, in the original experiment, the Bayes investor was handicapped because the algorithm that was used to evaluate the predictive distribution of the portfolio provided only a rough approximation. We level the playing field by allowing the Bayes investor to use a more standard algorithm. Our results sharply contrast with those of the original experiment. The final part of our paper proposes a new investment experiment that is much more relevant for the average investor - a one-period ahead asset allocation. We examine in detail why this is the best comparison to make, and why the Bayes investor always wins.

Objective To investigate the presence of inflammatory cytokines and the fibronectin-aggrecan complex (FAC) in persons undergoing surgical treatment for cervical radiculopathy caused by disk herniation. Design Single-center, prospective, consecutive case series. Setting A single large academic institution. Patients A total of 11 patients with radiculopathic pain and magnetic resonance imaging findings positive for disk herniation elected to undergo single-level cervical diskectomy. Methods or Interventions Lavage was performed by needle injection and aspiration upon entering the disk space for fluoroscopic localization before diskectomy. Main Outcome Measurements The lavage fluid was assayed for pH and the FAC, as well as for the cytokines interleukin-6 (IL-6), interferon-γ, monocyte chemotactic protein (MCP), and macrophage inhibitory protein-1β. Results The subjects were 7 women and 4 men with a mean age of 50.6 years (SE 9.7; range, 36-70 years). The mean concentrations (SE; range) in picograms per milliliter were 7.9 (4.4; 0-44) for IL-6, 25.3 (15.5; 0-159) for interferon-γ, 16.1 (11.9; 0-121) for MCP, and 6.1 (2.8; 0-29) for macrophage inhibitory protein-1β. The optical density of the FAC at 450 nm was 0.151 (0.036; 0.1-0.32), and the pH was 6.68 (0.1; 6.10-7.15). Statistically significant correlations were found between MCP and FAC ( P = .036) and between FAC and pH ( P = .008). Conclusions Biochemical analysis of injured cervical intervertebral disks reveals the presence of inflammatory markers such as MCP, fragments of structural matrix proteins such as FAC, and a correlation with pH. Further evaluation of the FAC as a potential diagnostic biomarker or therapeutic target is warranted in the cervical spine.

Equations that describe acoustic oscillations in a Rijke burner have been developed. Eigenvalues giving frequencies and growth rates of acoustic modes can be calculated from these equations. In their most general form, these acoustic equations include the effects of nonuniform gas temperature and entrained, burning particles. In general, analytical solution of the equations is not possible. A computer program has been developed that uses numerical methods to calculate eigenvalues from the general equations. For some limiting cases, analytical solution of the equations is possible. Analytical solutions are presented for three such cases. Eigenvalues predicted by the numerical model compare well to the analytical solutions. The Bailey and McIntosh flame-acoustic interaction models were tested with the computer program. Predicted frequencies and growth rates agreed well with experimental data when heat loss was taken into account. The program matched one experimental frequency and growth rate exactly when a time lag was added to the Bailey model. The McIntosh model did nearly as well without any adjustments. A particle combustion-acoustic interaction model for burning aluminum particles has been developed. This model was also tested in the Rijke burner model. The predictions show qualitative but not quantitative agreement with experimental measurements of particle combustion effects. A mechanism is suggested that may explain the discrepancy.

Thermoacoustic devices related to the Rijke tube are reviewed. Most modern thermoacoustic devices use as a heat source a heated wire or ribbon or a premixed gas flame anchored to a metal gauze, metal tube matrix or porous ceramic frit. Numerous experiments have confirmed that combustion-driven oscillations in tube devices are ‘Rijke tube’ or ‘organ pipe’ oscillations, i.e. frequencies are the same as those in a Rijke tube or organ pipe of the same length and with the same gas temperature distribution. Experiments have also established the validity of Rayleigh's stability criterion for the development of heat-driven acoustic oscillations. Modern mathematical analyses of acoustic oscillations in Rijke-type devices begin with a common basis: equations for mass, momentum and energy conservation. Almost all analyses assume constant hot section temperature. The main difference between analyses is the manner in which the oscillating response of the heat source is modeled. Frequency of oscillation is governed primarily by the acoustic speed of gases in a chamber. Thus, the flame or heater response model used does not significantly effect frequency predictions. However, the flame or heater response model can have a dramatic effect on predicted growth rates. Since flame models influence predicted response of Rijke burners, some work with vibrating flames is also reviewed. Flame response models vary widely, from simple phenomenological models to sophisticated models based on large activation energy asymptotic theory.

SummaryThrough the feeding of certain allergenic compounds to the non-sensitive subject, a state of resistance may be established against subsequent experimental sensitization of the skin by the sa...

The Liang and Beckstead aluminum-particle combustion model has been successfully joined with a detailed chemical-kinetic mechanism. The model has been used to investigate the effect of oxidizer concentration, initial temperature, and pressure on the combustion of steam and micrometer-sized aluminum particles. The results compare well with experimental data investigating the effects of initial temperature and oxidizer concentration on burn time. The simulations and experimental data have opposite trends for the change in burn time as the pressure increased. The calculated flame temperature increases with increasing pressure, initial temperature, and oxidizer concentration. The effects of particle diameter, initial temperature, and pressure on the calculated flame temperature, flame structure, and species profiles were also investigated.

Gas chromatography/mass spectrometry was used to analyze the oxygen evolved from Ba 0.6 K 0.4 BiO 3 , LaCuO 3 and La 1.85 Sr 0.15 CuO 4 upon dissolution in normal and 18 O-enriched acid. From the 18 O/ 16 O ratio we show that the oxide phases are the principal source of evolved oxygen in the copper-containing materials, while more than half of the oxygen is evolved from the solution with Ba 0.6 K 0.4 BiO 3 . The difference may be due to the location of the holes, which appear to be predominantly on the oxygens in the copper-based materials and on the Bi(Bi V) in Ba 0.6 K 0.4 BiO 3 .

An important and not completely resolved question regarding the high temperature superconductors is the relationship between the hole concentration and the transition temperature, T c . We address this question in terms of a proposed “master curve” on a T c versus hole concentration plot. This curve shows a maximum at 90 K at a hole concentration of approximately 0.2–0.22 holes per plane copper for the 1-2-3 type systems. Here we report on hole compensation studies where we selectively substituted Nd, Ca and Zn into the 1-2-3 structure. We used chemical and Hall measurements to determine the hole concentrations and looked at their relationship to the superconducting transition temperatures, T c , in terms of the “master curve”. We show that the T c lowerin g by Zn cannot be attributed to hole concentration changes alone. Although Zn substituted materials appear to be the most obvious examples, we expect that substitutions on the CuO 2 plane are less likely to fit the so-called “master curve” than non Cu-site substitutions such as Nd, Ca, La, etc.

*† ‡ § A multi-phase model for the combustion of ammonium dinitramide (ADN) monopropellant is presented. As part of the work, an in depth study concerning ADN combustion has been undertaken. An extensive literature review has been conducted to extract both experimental data and qualitative theories concerning ADN combustion. Analyses and reviews are presented pertaining to some of the major theories. Based on the literature review a numerical model has also been developed for ADN using the BYU PHASE3 combustion code. The model accurately predicts burning rates, temperature and species profiles, and other combustion characteristics of ADN at pressures preceding the unstable region (20 to 100 atm) of combustion. Burning rates are also predicted in the unstable zone and at higher pressures. Results are discussed and proposed modifications to the present condensed phase model are presented. Nomenclature b = constant in burning rate correlation P = pressure n = pressure exponent

The steady-state combustion of mixtures of RDX/GAP has been modeled using a 1dimensional, three-phase numerical model, with detailed chemical kinetics. Several compositions have been modeled, from 100% RDX/0% GAP to 0% RDX/100% GAP. The approach used in this work has been to first model and validate monopropellant RDX and GAP. These monopropellant kinetic models were then combined to get the pseudopropellant model, thus limiting the uncertainties in model inputs. Based on experimental decomposition studies of RDX and GAP in the literature, a condensed-phase kinetic model consisting of four global reactions has been assembled. The evaporation of RDX is also included. A detailed gas-phase kinetic mechanism has been assembled based on several mechanisms reported in the literature. The gas-phase mechanism consists of 83 species and 534 reactions and has been used previously in modeling several monopropellants and pseudo-propellants. The improvement and validation of this universal gas phase mechanism is one of the main goals of this work. The combustion has been modeled over a pressure range of 1 atm-136 atm (2000 psia), and initial temperatures of 298 ± 50 K. The calculated combustion characteristics include the burning rate, pressure exponent, temperature sensitivity, surface and flame temperatures, temperature and species profiles, and condensed and gas-phase heat releases.

Combustion stability additives like zirconium carbide (ZrC), aluminum oxide (AO o is the angular frequency, ro is the particle relaxation time

This paper reports the effect of ZrO{sub 2} addition on the phase transformation of Bi{sub 2}O{sub 3} studied with powder x-ray diffraction and differential thermal analysis. Samples containing higher than a few mole percent ZrO{sub 2} were obtained as the metastable {beta} phase (tetragonal) at room temperature when they were cooled at 20{degrees}C/min from 800{degrees}C where the {delta} phase (fcc) is stable. When the same samples were cooled at the same rate from 1000{degrees}C, which is above the solidus, they formed the stable {alpha} phase (monoclinic) at room temperature. Evidence for the relatively higher solubility of ZrO{sub 2} in the {delta} phase is discussed to explain this observation.

In spite of the long history of metalized propellants combustion studying there is little systematic data on the effectof propellant formulation on the generation of condensed combustion products. The objective of this work was to study the pressure dependence of the size distribution and neat metal content of sampled combustion products of aluminized propellants with different binders and oxidizers. The formulations with AP and HMX as oxidizers and with butadiene, isoprene and energetic binders were studied. The results obtained help to provide an understanding of the role various components play in determining aluminum agglomeration at the burning surface, and metal combustion far from the surface.

Many improvements have been made to models of RDX combustion in the past few years. The onedimensional model presented in this paper, models the solid, two-phase, and gas regions using complex kinetics and concentration and temperature dependent thermophysical properties. Calculated values agree well with experimentally determined burn rate, ap, melt layer thickness, surface temperature and species concentration profiles. When including laser-assisted burning in the model, a dark zone appeared similar to that seen experimentally. With the laser assisted case, the chemistry controlling the burn rate is significantly different from cases without the laser heat flux. Calculations show that the melt layer thickness is determined primarily by the liquid thermal conductivity and the surface temperature is controlled by the vapor pressure correlation. All other model predictions are relatively insensitive to these parameters. The weakest areas of the model remain the condensed phase decomposition and evaporation/condensation sub-model. Nomenclature A = area (cm) A = pre-exponential rate constant c = heat capacity (erg/g K) C = molar concentration (moles/cm-*) Ea = activation energy (cal/mole) H = molar enthalpy (erg/mole) h = specific enthalpy (erg/g) kk = number of gas phase species rh = mass flow rate (g/s) n = number of bubbles per volume 1 e 13 bubbles/cm^ p = pressure q = rate of progress variable (moles/cm s) rb = burn rate (cm/s) R = universal gas constant s = sticking factor T = temperature (K) u = gas velocity (cm/sec) V = diffusion velocity (cm/sec) W = average molecular weight (g/mole) W = molecular weight (g/mole) W = molar rate of production (moles/cm s) x = distance from 2-phase-gas interface (cm) X = mole fraction Y = mass fraction P = temperature exponent rate constant

The paper presents the development of a fault detection and diagnosis (FDD) system with applications to the Space Shuttle main engine. The FDD utilizes a model-based method with real-time identification and hypothesis testing for actuation, sensor, and performance degradation faults.