Transmission loss predictions for dissipative silencers of arbitrary cross section in the presence of mean flow

A numerical technique is developed for the analysis of dissipative silencers of arbitrary, but axially uniform, cross section. Mean gas flow is included in a central airway which is separated from a bulk reacting porous material by a concentric perforate screen. The analysis begins by employing the finite element method to extract the eigenvalues and associated eigenvectors for a silencer of infinite length. Point collocation is then used to match the expanded acoustic pressure and velocity fields in the silencer chamber to those in the inlet and outlet pipes. Transmission loss predictions are compared with experimental measurements taken for two automotive dissipative silencers with elliptical cross sections. Good agreement between prediction and experiment is observed both without mean flow and for a mean flow Mach number of 0.15. It is demonstrated also that the technique presented offers a considerable reduction in computational expenditure when compared to a three dimensional finite element analysis

Vasotocin receptor expression in the brain and pituitary gland during the ovulatory cycle of the fowl

Vasotocin receptors are members of seven transmembrane spanning G-protein associated receptors. Several isoforms have been recognized in mammals and birds. It has been shown that VT-1 expression occurs primarily in the brain while VT-2 expression occurs mainly in the pituitary. There is no current evidence to support that both VTR-1 and -2 are found in a single tissue. Our goal in this experiment was to see if VT-1 and VT-2 receptor mRNA expression varied in known sites of expression over the period of the ovulatory cycle of broiler breeder hens. In order to study potential changes in VT-1 and VT-2 expression, birds were sacrificed at 3 hour intervals over a 24 hour period. Blood samples were drawn. After cervical dislocation, the brain, pituitary, shell gland, and kidney were removed. Plasma was stored at -20ºC prior to determination of corticosterone levels by radioimmuno assays. Isolated mRNA from the brains and the pituitaries was transferred to nylon membranes for northern slot blot analysis. cDNA for VT-1 and VT-2 was used to make random primed cDNA probes. Corticosterone levels significantly increased at 9 hours post oviposition relative to all other times. Neither VT-1 or VT- 2 expression showed any significant variation over the 24 hour cycle. Based on these results, we conclude that VT-1 and VT-2 steady state mRNA levels do not fluctuate dramatically over the ovulatory cycle of broiler breeder hens. Further work on membrane bound receptors and on circadian variations in membrane bound receptors in the brain and pituitary is currently underway of broiler breeder hens

Quasi-planar steep water waves

A new description for highly nonlinear potential water waves is suggested, where weak 3D effects are included as small corrections to exact 2D equations written in conformal variables. Contrary to the traditional approach, a small parameter in this theory is not the surface slope, but it is the ratio of a typical wave length to a large transversal scale along the second horizontal coordinate. A first-order correction for the Hamiltonian functional is calculated, and the corresponding equations of motion are derived for steep water waves over an arbitrary inhomogeneous quasi-1D bottom profile.Comment: revtex4, 4 pages, no figure

Translatory shock absorber for attitude sensors

A translatory shock absorber is provided for mounting an attitude sensor thereon for isolating a sensor from translatory vibrations. The translatory shock absorber includes a hollow block structure formed as one piece to form a parallelogram. The absorber block structure includes a movable top plate for supporting the attitude sensor and a fixed base plate with opposed side plates interposed between. At the junctions of the side plates, and the base and top plates, there are provided grooves which act as flexible hinges for attenuating translatory vibrations. A damping material is supported on a pedestal which is carried on the base plate between the side plates thereof. The top of the damping material rests against the bottom surface of the top plate for eliminating the resonant peaks of vibration

ELF: The electronic learning facilitator

As the world‐wide computer network becomes ubiquitous, new tools have been developed, such as the World Wide Web (WWW), for the delivery of multimedia hypertext‐based documents. Similarly, there has been an explosion in the amount of email, bulletin boards, and Usenet News available. This has led to a major problem of information overload: we are slowly but surely being overwhelmed by the amount of information available to us

Incorporating vertical travel into non-traditional cross aisles for unit-load warehouse designs

We propose modifications to the travel-time models for non-traditional warehouse layouts, Flying-V Fishbone, by incorporating a vertical travel dimension. The Flying-V model determines a cross aisle intersection for every picking aisle, while the Fishbone model determines a single point where the inserted cross aisle intersects the side of the warehouse. The shape and angle of the cross aisle is unrestricted for the Flying-V layout, while the angle is unrestricted for the Fishbone layout. The resulting non-linear optimization models incorporate Chebychev travel within the picking aisles. We compare both the shape of the aisle and the percent improvement over a traditional warehouse with the results found in previous research that ignores vertical travel. We show that the percent improvement diminishes as the height of the rack increases, with Fishbone maintaining a higher percent improvement over Flying-V. We also show that while the shape of Flying-V can be considerably altered by considering vertical travel, the Fishbone layout often maintains its recommended shape regardless of the height of the rack. We also altered the travel rules for the Flying-V model in order to find simpler designs and obtained near-optimal results. We conclude with recommendations for effective implementation of these two designs

Neutron Star Mergers Are the Dominant Source of the r-process in the Early Evolution of Dwarf Galaxies

There are many candidate sites of the r-process: core-collapse supernovae (including rare magnetorotational core-collapse supernovae), neutron star mergers, and neutron star/black hole mergers. The chemical enrichment of galaxies---specifically dwarf galaxies---helps distinguish between these sources based on the continual build-up of r-process elements. This technique can distinguish between the r-process candidate sites by the clearest observational difference---how quickly these events occur after the stars are created. The existence of several nearby dwarf galaxies allows us to measure robust chemical abundances for galaxies with different star formation histories. Dwarf galaxies are especially useful because simple chemical evolution models can be used to determine the sources of r-process material. We have measured the r-process element barium with Keck/DEIMOS medium-resolution spectroscopy. We present the largest sample of barium abundances (almost 250 stars) in dwarf galaxies ever assembled. We measure [Ba/Fe] as a function of [Fe/H] in this sample and compare with existing [alpha/Fe] measurements. We have found that a large contribution of barium needs to occur at more delayed timescales than core-collapse supernovae in order to explain our observed abundances, namely the significantly more positive trend of the r-process component of [Ba/Fe] vs. [Fe/H] seen for [Fe/H] <~ -1.6 when compared to the [Mg/Fe] vs. [Fe/H] trend. We conclude that neutron star mergers are the most likely source of r-process enrichment in dwarf galaxies at early times.Comment: Accepted to ApJ on 2018 October 2

A generalization of Sperner's lemma

AbstractA brief proof is given of a generalization of Sperner's lemma to certain finite partially ordered sets