Comparative Performance of a Powerplus Vane-type Supercharger and an N.A.C.A. Roots-type Supercharger

This report presents the results of tests of a Power plus supercharger and a comparison of its performance with the performance previously obtained with an N.A.C.A. Roots-type supercharger. The Powerplus supercharger is a positive displacement blower of the vane type having mechanically operated vanes, the movement of which is controlled by slots and eccentrics. The supercharger was tested at a range of pressure differences from 0 to 15 inches of mercury and at speeds from 500 to 2,500 r.p.m. The pressure difference across the supercharger was obtained by throttling the intake of a depression tank which was interposed in the air duct between the supercharger and the Durley orifice box used for measuring the air. The results of these tests show that at low pressure differences and at all speeds the power required by the Powerplus supercharger to compress a definite quantity of air per second is considerably higher than that required by the Roots. At pressure differences from 10 to 14 inches of mercury and at speeds over 2,000 r.p.m. the power requirements of the two superchargers are practically the same. At a pressure difference of 15 inches of mercury or greater and at a speed of 2,500 r.p.m. or greater the performance of the Powerplus supercharger is slightly better than that of the Roots. Because the Powerplus supercharger cannot be operated at a speed greater than 3,000 r.p.m. as compared with 7,000 r.p.m. for the Roots, its capacity is approximately one-half that of the Roots for the same bulk. The Powerplus supercharger is more complicated and less reliable than the Roots supercharger

Preliminary analysis of problem of determining experimental performance of air-cooled turbine III : methods for determining power and efficiency

Suggested formula are given for determining air-cooled turbine-performance characteristics, such as power and efficiency, as functions of certain parameters. These functions, generally being unknown, are determined from experimental data obtained from specific investigations. Special plotting methods for isolating the effect of each parameter are outlined

Preliminary analysis of problem of determining experimental performance of air-cooled turbine I : methods for determining heat-transfer characteristics

In determining the experimental performance of an air-cooled turbine, the heat-transfer characteristics must be evaluated. The suggested formulas that are required to determine these characteristics are presented. The formulas have a form in which dependent parameters are expressed as unknown functions of independent parameters. Methods of experimenting to determine these functions are suggested. In some cases general heat-transfer discussions that lead to the suggested forms of the formulas are given

Relating soil organic matter composition to soil water repellency for soil biopore surfaces different in history from two Bt horizons of a Haplic Luvisol

This study was funded by the “German Research Foundation (DFG),”Bonn, under Grant PAK 888. We thank Timo Kautz and the staff of the Institute of Organic Agriculture in Bonn for assistance with the field work. Thanks to the anonymous reviewers for their helpful comments. We sincerely thank Prof. Dr. MB Kirkham/USA for valuable comments and the final control of the English language.Peer reviewedPostprin

Analyse von Langzeit Düngereffekten auf die Zusammensetzung der organischen Bodensubstanz

Es ist immer noch weitgehend unklar, wie Düngung und Bodenbearbeitung die Zusammensetzung der organischen Bodensubstanz (OBS) beeinflussen. Für diesen Zweck sollte auch getestet werden, ob die Infrarotspektroskopie geeignet ist, derartige Änderungen in der Zusammensetzung der OBS nachzuweisen. Untersucht wurden Böden aus Ap Horizonten von Langzeitfeldexperimenten. Die Proben stammen von lehmigen Böden (Bad Lauchstädt) und lehmigen Sanden (Groß Kreutz, Halle, und Müncheberg). Verglichen wurden die Varianten mit Stallmistdüngung (STM), mineralischem Stickstoff (N), Stallmist plus Mineralstickstoff (STM+N) und eine Variante ohne Dünger (Kontrolle). Mittels Fourier-Transform Infrarot-(FTIR)-Spektroskopie wurde die gesamte OBS sowie die pyrophosphatlösliche (OM-PY) Fraktion der OBS analysiert. Die OBS Zusammensetzung wurde als das Verhältnis zwischen den Absorptionsintensitäten der C=O und C-O-C Banden in den FTIR Spektren charakterisiert. Die OM-PY Fraktion aus den mit Stallmist gedüngten Böden hatte die höchsten Werte des C=O/C-O-C-Verhältnisses. Für alle Böden war die Kationenaustauschkapazität (KAK) von OM-PY aus der STM Variante im Vergleich zu den N Varianten höher. Die Ergebnisse zeigen eine düngungsbedingte Langzeitdynamik in (i) der OBS Zusammensetzung und (ii) in der KAK sowie der potentiellen Benetzbarkeit von OBS und löslichen Fraktionen. Die OM-PY Fraktion könnte genutzt werden, um langfristige Veränderungen in der OBS Zusammensetzung zu identifizieren und zu charakterisieren. Spektren archivierter Bodenproben aus Halle zeigen für die Jahre 1958 und 1994 Variationen im CH/C=O Verhältnis. Um zwischen kurz- und langfristigen Effekten unterscheiden zu können, wären jedoch vergleichende Daten zur jahreszeitlichen Dynamik in der OBS Zusammensetzung erforderlich. Die wichtigste Schlussfolgerung ist, dass eine mineralische Stickstoffdüngung langfristig zu einer relativen Abnahme der C=O Gruppen in der OBS führt, obwohl die OBS Menge, zunimmt

Analysis, Verification, and Application of Equations and Procedures for Design of Exhaust-pipe Shrouds

Investigations were made to develop a simplified method for designing exhaust-pipe shrouds to provide desired or maximum cooling of exhaust installations. Analysis of heat exchange and pressure drop of an adequate exhaust-pipe shroud system requires equations for predicting design temperatures and pressure drop on cooling air side of system. Present experiments derive such equations for usual straight annular exhaust-pipe shroud systems for both parallel flow and counter flow. Equations and methods presented are believed to be applicable under certain conditions to the design of shrouds for tail pipes of jet engines

Measurement of the spatial distribution of mucilage around roots using infrared spectroscopy

Mucilage is a mixture of polysaccharides and some lipids which is secreted by the root tip. It facilitates plant nutrient acquisition, stabilizes aggregates, reduces lubrication during plant growth and may increase rhizosphere water content due to its high water holding capacity. So far there is no method to measure the spatial distribution of mucilage in soil around roots. The aim of this study was to test whether infrared spectroscopy can be applied to quantify gradients of mucilage around roots in soil. The C-H to C-O ratio obtained from infrared spectroscopy measurements is an indicator of soil hydrophobicity. As Mucilage turns hydrophobic after drying we hypothesized that mucilage can be detected by the C-H to C-O ratio measured with infrared spectroscopy. We grew maize plants in rhizoboxes filled with quartz silt. Before measurement the planted containers were dried and the roots were removed from soil. Infrared spectroscopy measurements were conducted with a spatial resolution of 50x50 µm a) radially with increasing distance from the root channel center and b) axially with increasing distance from the root channel tip. In parallel, the contact angle, which also indicates soil hydrophobicity, was quantified in the same locations. Both measurements were additionally conducted on glass slides covered with quartz silt mixed with given concentrations of mucilage. The measurements on the glass slides revealed that the C-H to C-O ratio and the contact angle measurements correlated well with the mucilage concentration in soil. Similarly, the infrared spectroscopy measurements in in the rhizoboxes revealed that radial profiles of mucilage around roots can be quantified: while the C-H to C-O ratio was highest inside the root channels, it decreased to the bulk soil values 0.7 mm in radial direction from the border of the root channel. In axial direction the C-H to C-O ratio did not change significantly, indicating that those compounds causing hydrophobicity of mucilage are not easily degraded by soil microorganisms. We showed that infrared spectroscopy can be applied to measure profiles of mucilage around roots in soil. The radial profiles of mucilage were narrower than those reported for other rhizodeposits which may be explained by the viscosity of mucilage

Menge, Verteilung und Zusammensetzung organischer Bodensubstanz auf Oberflächen von Makroporen in Bt-Horizonten

In strukturierten Unterböden können die Oberflächen von Makroporen (Aggregatränder und Bioporen) in Folge von präferenzieller Verlagerung und Stabilisierungsprozessen mit organischer Bodensubstanz (OBS) angereichert sein. Menge, Verteilung und Zusammensetzung der OBS beeinflussen über die physiko-chemischen Oberflächeneigenschaften der Makroporen den präferenziellen Transport und den Massentransfer zwischen Fließweg und Bodenmatrix. Darüber hinaus führt eine räumlich diskrete Verteilung von OBS auf Oberflächen von Makroporen zu - in Unterböden wenig erforschten - „hot spots“ mit erhöhten Umsatzraten. Die Analyse der OBS-Zusammensetzung gestattet außerdem Rückschlüsse auf die Landnutzung, so deutet z.B. das Auftreten von Benzonitril und Naphtalen (BN+NA) auf Biomasse-Verbrennung hin. Ziel der Arbeit war die Quantifizierung von organischem Kohlenstoff (Corg) und BN+NA auf intakten Makroporen-Oberflächen in Bt-Horizonten von Parabraunerden aus Löss und Geschiebemergel. Die zweidimensionale (2D), mm-skalige Verteilung von Corg und BN+NA auf verschiedenen Makroporen-Typen wurde mittels Diffuse Reflectance Infrared Fourier Transform (DRIFT) Spektroskopie in Kombination mit Corg-Messungen und Pyrolyse-Feldionisation Massenspektrometrie (Py-FIMS) quantitativ beschrieben. Für eine Horizont-bezogene Quantifizierung wurden die Porenverteilungen und Porenraum-Geometrien mit Röntgen-Computertomographie (CT) dreidimensional (3D) analysiert. Erhöhte Gehalte an Corg- und BN+NA korrelierten mit dem Auftreten von Ton-haltigen Kutanen und Porenfüllungen. Die Kombination von 2D- und 3D-Daten zeigte Unterschiede in der räumlichen Verteilung von Corg bzw. OBS sowie von BN+NA in Abhängigkeit der Makroporen-Typen und Standorte bzw. bodenbildenden Substrate. Die Ergebnisse tragen zur genaueren Beschreibung von Stoffumsetzungsprozessen und Stofftransporten in strukturierten Unterböden bei und ermöglichen darüber hinaus Schlüsse auf die Genese von Bt-Horizonten in Parabraunerden

Searches at HERA for Squarks in R-Parity Violating Supersymmetry

A search for squarks in R-parity violating supersymmetry is performed in e^+p collisions at HERA at a centre of mass energy of 300 GeV, using H1 data corresponding to an integrated luminosity of 37 pb^(-1). The direct production of single squarks of any generation in positron-quark fusion via a Yukawa coupling lambda' is considered, taking into account R-parity violating and conserving decays of the squarks. No significant deviation from the Standard Model expectation is found. The results are interpreted in terms of constraints within the Minimal Supersymmetric Standard Model (MSSM), the constrained MSSM and the minimal Supergravity model, and their sensitivity to the model parameters is studied in detail. For a Yukawa coupling of electromagnetic strength, squark masses below 260 GeV are excluded at 95% confidence level in a large part of the parameter space. For a 100 times smaller coupling strength masses up to 182 GeV are excluded.Comment: 32 pages, 14 figures, 3 table

Deep-Inelastic Inclusive ep Scattering at Low x and a Determination of alpha_s

A precise measurement of the inclusive deep-inelastic e^+p scattering cross section is reported in the kinematic range 1.5<= Q^2 <=150 GeV^2 and 3*10^(-5)<= x <=0.2. The data were recorded with the H1 detector at HERA in 1996 and 1997, and correspond to an integrated luminosity of 20 pb^(-1). The double differential cross section, from which the proton structure function F_2(x,Q^2) and the longitudinal structure function F_L(x,Q^2) are extracted, is measured with typically 1% statistical and 3% systematic uncertainties. The measured partial derivative (dF_2(x,Q^2)/dln Q^2)_x is observed to rise continuously towards small x for fixed Q^2. The cross section data are combined with published H1 measurements at high Q^2 for a next-to-leading order DGLAP QCD analysis.The H1 data determine the gluon momentum distribution in the range 3*10^(-4)<= x <=0.1 to within an experimental accuracy of about 3% for Q^2 =20 GeV^2. A fit of the H1 measurements and the mu p data of the BCDMS collaboration allows the strong coupling constant alpha_s and the gluon distribution to be simultaneously determined. A value of alpha _s(M_Z^2)=0.1150+-0.0017 (exp) +0.0009-0.0005 (model) is obtained in NLO, with an additional theoretical uncertainty of about +-0.005, mainly due to the uncertainty of the renormalisation scale.Comment: 68 pages, 24 figures and 18 table