An investigation of rotor harmonic noise by the use of small scale wind tunnel models

Noise measurements of small scale helicopter rotor models were compared with noise measurements of full scale helicopters to determine what information about the full scale helicopters could be derived from noise measurements of small scale helicopter models. Comparisons were made of the discrete frequency (rotational) noise for 4 pairs of tests. Areas covered were tip speed effects, isolated rotor, tandem rotor, and main rotor/tail rotor interaction. Results show good comparison of noise trends with configuration and test condition changes, and good comparison of absolute noise measurements with the corrections used except for the isolated rotor case. Noise measurements of the isolated rotor show a great deal of scatter reflecting the fact that the rotor in hover is basically unstable

Transient Moisture Gradient in Fire-Exposed Wood Slab

Improved fire endurance design procedures for heavy timber members may require the input of moisture content-dependent allowable stresses. Therefore, experiments were conducted to characterize the transient moisture gradient in a wood slab subjected to fire on one face. Electrodes and thermocouples embedded within the wood sections monitored moisture and temperature levels at selected locations. Time-moisture content curves indicated an increase in moisture content that appeared to be associated with the vaporization of the bound water in the wood. For the eight slabs tested, the average peak moisture content was 1.26 to 2.00 times greater than the initial moisture content

Replicate Fire Endurance Tests of an Unprotected Wood Joist Floor Assembly

To encourage new developments in building technology, a solid basis for building code requirements is needed. Fire endurance is a code requirement, yet no objective procedure exists for computing a structure's chances of failing (degree of risk) in a fire. However, a model for predicting the fire endurance of part of a structure, a conventional unprotected wood joist floor, is available. The aim of this study was to determine the fire endurance performance of an unprotected wood joist floor for use in the model.Eleven ASTM Standard E 119 floor tests were conducted. All the floors were 2 by 10 Douglas-fir wood joists, sixteen inches on center with 23/32-inch-thick plywood as the floor sheathing. In addition to one trial test, five tests were conducted using a live load of 11.35 lb/ft2. For the other five tests, the live load was 79.2 lb/ft2. Twenty joists were tested for modulus of elasticity and modulus of rupture.The joist population had a mean modulus of rupture of 5.280 lb/in.2 and a mean modulus of elasticity of 1,530,000 lb/in.2. For the five floors loaded to 11.35 lb/ft2, the mean time for initial joist failure was 17.9 min with a coefficient of variation (COV) of 3.7%. For the five floors loaded to 79.2 lb/ft2, the mean time was 6.5 min with a COV of 11.6%. Based on linear interpolation of these results, first joist failure would have occurred in 13.1 min if a 40 lb/ft2 live load had been used, which is the typical live loading specified in the building codes for residential one- and two-family dwellings.As a result of this study, fire-resistance performance of a wood floor is known for a specific population of wood joists with known structural properties. These results can be used to verify and revise the model for predicting fire endurance

The metaphysics of Machian frame-dragging

The paper investigates the kind of dependence relation that best portrays Machian frame-dragging in general relativity. The question is tricky because frame-dragging relates local inertial frames to distant distributions of matter in a time-independent way, thus establishing some sort of non-local link between the two. For this reason, a plain causal interpretation of frame-dragging faces huge challenges. The paper will shed light on the issue by using a generalized structural equation model analysis in terms of manipulationist counterfactuals recently applied in the context of metaphysical enquiry by Schaffer (2016) and Wilson (2017). The verdict of the analysis will be that frame-dragging is best understood in terms of a novel type of dependence relation that is half-way between causation and grounding

Enslaved Phase-Separation Fronts in One-Dimensional Binary Mixtures

Phase-separation fronts leave in their wakes morphologies that are substantially different from the morphologies formed in homogeneous phase-separation. In this paper we focus on fronts in binary mixtures that are enslaved phase-separation fronts, i.e. fronts that follow in the wake of a control-parameter front. In the one-dimensional case, which is the focus of this paper, the formed morphology is deceptively simple: alternating domains of a regular size. However, determining the size of these domains as a function of the front speed and other system parameters is a non-trivial problem. We present an analytical solution for the case where no material is deposited ahead of the front and numerical solutions and scaling arguments for more general cases. Through these enslaved phase-separation fronts large domains can be formed that are practically unattainable in homogeneous one-dimensional phase-separation

Mass modification of D-meson in hot hadronic matter

We evaluate the in-medium $D$ and $\bar D$-meson masses in hot hadronic matter induced by interactions with the light hadron sector described in a chiral SU(3) model. The effective Lagrangian approach is generalized to SU(4) to include charmed mesons. We find that the D-mass drops substantially at finite temperatures and densities, which open the channels of the decay of the charmonium states ($\Psi^\prime$, $\chi_c$, $J/\Psi$) to $D \bar D$ pairs in the thermal medium. The effects of vacuum polarisations from the baryon sector on the medium modification of the $D$-meson mass relative to those obtained in the mean field approximation are investigated. The results of the present work are compared to calculations based on the QCD sum-rule approach, the quark-meson coupling model, chiral perturbation theory, as well as to studies of quarkonium dissociation using heavy quark potential from lattice QCD.Comment: 18 pages including 7 figures, minor revision of the text, figure styles modified, to appear in Phys. Rev.

Granulocyte-targeted therapies for airway diseases

The average respiration rate for an adult is 12–20 breaths per minute, which constantly exposes the lungs to allergens and harmful particles. As a result, respiratory diseases, which includes asthma, chronic obstructive pulmonary disease (COPD) and acute lower respiratory tract infections (LTRI), are a major cause of death worldwide. Although asthma, COPD and LTRI are distinctly different diseases with separate mechanisms of disease progression, they do share a common feature – airway inflammation with intense recruitment and activation of granulocytes and mast cells. Neutrophils, eosinophils, basophils, and mast cells are crucial players in host defense against pathogens and maintenance of lung homeostasis. Upon contact with harmful particles, part of the pulmonary defense mechanism is to recruit these cells into the airways. Despite their protective nature, overactivation or accumulation of granulocytes and mast cells in the lungs results in unwanted chronic airway inflammation and damage. As such, understanding the bright and the dark side of these leukocytes in lung physiology paves the way for the development of therapies targeting this important mechanism of disease. Here we discuss the role of granulocytes in respiratory diseases and summarize therapeutic strategies focused on granulocyte recruitment and activation in the lungs

The heats of formation of the haloacetylenes XCCY [X, Y = H, F, Cl]: basis set limit ab initio results and thermochemical analysis

The heats of formation of haloacetylenes are evaluated using the recent W1 and W2 ab initio computational thermochemistry methods. These calculations involve CCSD and CCSD(T) coupled cluster methods, basis sets of up to spdfgh quality, extrapolations to the one-particle basis set limit, and contributions of inner-shell correlation, scalar relativistic effects, and (where relevant) first-order spin-orbit coupling. The heats of formation determined using W2 theory are: \hof(HCCH) = 54.48 kcal/mol, \hof(HCCF) = 25.15 kcal/mol, \hof(FCCF) = 1.38 kcal/mol, \hof(HCCCl) = 54.83 kcal/mol, \hof(ClCCCl) = 56.21 kcal/mol, and \hof(FCCCl) = 28.47 kcal/mol. Enthalpies of hydrogenation and destabilization energies relative to acetylene were obtained at the W1 level of theory. So doing we find the following destabilization order for acetylenes: FCCF $>$ ClCCF $>$ HCCF $>$ ClCCCl $>$ HCCCl $>$ HCCH. By a combination of W1 theory and isodesmic reactions, we show that the generally accepted heat of formation of 1,2-dichloroethane should be revised to -31.8$\pm$0.6 kcal/mol, in excellent agreement with a very recent critically evaluated review. The performance of compound thermochemistry schemes such as G2, G3, G3X and CBS-QB3 theories has been analyzed.Comment: Mol. Phys., in press (E. R. Davidson issue