bluuebunny/crossref_metadata_2025 huggingface dataset:
Level of agreement between self‐administered and interviewer‐administered CPQ8–10 and CPQ11–14
Authors: Ramos‐Jorge Maria Letícia , Vieira‐Andrade Raquel G. , Martins‐Júnior Paulo A. , Cordeiro Mabel M. R. , Ramos‐Jorge Joana , Paiva Saul Martins , Marques Leandro S.
Published: November 2011

Ramos‐Jorge ML, Vieira‐Andrade RG, Martins‐Júnior PA, Cordeiro MMR, Ramos‐Jorge J, Paiva SM, Marques LS. Level of agreement between self‐administered and interviewer‐administered CPQ8–10 and CPQ11–14. Community Dent Oral Epidemiol 2011. © 2011 John Wiley & Sons A/S

Abstract –  Objectives:  The aim of the present study was to assess the psychometric properties and level of agreement between the self‐administered and interviewer‐administered Child Perceptions Questionnaire (CPQ) for children between 8 and 10 years of age (CPQ8–10) and between 11 and 14 (CPQ11–14) years of age.

Methods:  A randomized cross‐over study was carried out, involving 180 children (Group 1 – 90 children between 8 and 10; Group 2 – 90 children between 11 and 14 years of age) in the state of Minas Gerais, Brazil. All children completed both administration modes of the CPQ; half of each group received interviewer‐administered mode first [Subgroup A (CPQ8–10n = 45) and Subgroup C (CPQ11–14n = 45)], and the other half performed the self‐administered mode first [Subgroup B (CPQ8–10n = 45) and Subgroup D (CPQ11–14n = 45)]. Test–retest reliability of each mode of administration was tested on 60 children (30 for CPQ8–10; 30 for CPQ11–14), who were not included in the other analyses. The level of agreement between scores on the self‐administered and interviewer‐administered versions of the CPQ8–10 and CPQ11–14 was established using the intraclass correlation coefficient (ICC). The order of presentation of both instruments was tested considering the four subgroups (A, B, C and D). The calculation of effect size proposed by Cohen (1992) was used to test the clinical significance of the findings.

Results:  Both the self‐administered and interviewer‐administered versions of CPQ8–10 and CPQ11–14 demonstrated acceptable psychometric properties. Agreement between the administration modes for the CPQ8–10 and CPQ11–14 was 0.90 and 0.88 (ICC), respectively. With the exception of the functional limitation subscale, the scores of the subscales and overall score on the CPQ8–10 were significantly higher in the group of children who responded to the interviewer‐administered measure first. With the CPQ11–14, statistically significant differences were found only for the emotional well‐being subscale.

Conclusions:  Both administration modes of the CPQ8–10 and CPQ11–14 demonstrated satisfactory psychometric properties and a high level of agreement. Although statistically significant differences were observed for oral symptoms, emotional well‐being and social well‐being, with the first administration of the interviewer‐administered version, the effect of the order of administration had small to medium effects on the CPQ scores.
Skin fragility in obese diabetic mice: possible involvement of elevated oxidative stress and upregulation of matrix metalloproteinases
Authors: Ibuki Ai , Akase Tomoko , Nagase Takashi , Minematsu Takeo , Nakagami Gojiro , Horii Motoko , Sagara Hiroshi , Komeda Takashi , Kobayashi Masayuki , Shimada Tsutomu , Aburada Masaki , Yoshimura Kotaro , Sugama Junko , Sanada Hiromi
Published: November 2011

Abstract:  The purpose of this study was to test the hypothesis that obese diabetic mice exhibit marked skin fragility, which is caused by increased oxidative stress and increased matrix metalloproteinase (MMP) gene expression in the subcutaneous adipose tissue. Scanning electron microscopy of skin samples from Tsumura‐Suzuki obese diabetic (TSOD) mice revealed thinner collagen bundles, and decreased density and convolution of the collagen fibres. Furthermore, skin tensile strength measurements confirmed that the dorsal skin of TSOD mice was more fragile to tensile force than that of non‐obese mice. The mRNA expressions of heme oxygenase 1 (Hmox1), a marker of oxidative stress, Mmp2 and Mmp14 were increased in the adipose tissue of TSOD mice. Antioxidant experiments were subsequently performed to determine whether the changes in collagen fibres and skin fragility were caused by oxidative stress. Strikingly, oral administration of the antioxidant dl‐α‐tocopherol acetate (vitamin E) decreased Hmox1, Mmp2 and Mmp14 mRNA expressions, and improved the skin tensile strength and structure of collagen fibres in TSOD mice. These findings suggest that the skin fragility in TSOD mice is associated with dermal collagen damage and weakened tensile strength, and that oxidative stress and MMP overexpression in the subcutaneous adipose tissue may, at least in part, affect dermal fragility via a paracrine pathway. These observations may contribute to novel clinical interventions, such as dietary supplementation with antioxidants or application of skin cream containing antioxidants, which may overcome skin fragility in obese patients with diabetes.
A heat wave and dispersal cause dominance shift and decrease biomass in experimental metacommunities
Authors: Eggers Sarah Lena , Eriksson Britas Klemens , Matthiessen Birte
Published: November 2011

In experimental metacommunities with marine benthic microalgae, we tested whether heat stress changes effects of connectivity and habitat heterogeneity on metacommunity structure and functioning, by manipulating a simulated heat wave, dispersal frequency and a light intensity gradient. We found that all measures of mean local and regional diversity and community biomass significantly declined after the heat wave and showed no sign of recovery. Additionally, dispersal decreased diversity and increased dominance in both the heat stressed and control communities. Together the heat wave and high dispersal frequency induced a dominance shift by spreading a temperature tolerant but low yielding species from its source patches with low light intensity across the metacommunity, an effect that increased with time. Although different species became dominant at high dispersal frequency with and without the heat wave, the shift towards a temperature tolerant species was not sufficient to maintain total community biomass. Thus, short‐term disturbance may cause longer‐term loss of ecosystem function due to dominance shifts in the composition of communities. This study illustrates the importance of employing multispecies approaches when attempting to predict responses of communities to environmental changes.
Unravelling the role of mate density and sex ratio in competition for pollen
Authors: Bianchi Felix J. J. A. , Cunningham Saul A.
Published: November 2011

Mate density and sex ratio are commonly used concepts in pollination biology, but are not always clearly distinguished. Here we propose that mate density should only capture the number of male‐phase flowers in a defined area and ignore female‐phase flowers. Sex ratio is the ratio of male and female‐phase flowers in a defined area and captures female–female competition. We use a spatially explicit simulation model to quantify the effect of variation in mate density and sex ratio for plant–pollinator systems characterized by combinations of high or low rates of pollen loss and deposition from pollinator to stigma and then assess the size of pollination neighbourhoods. In efficient systems with relatively little pollen loss, female–female competition is of overriding importance. In contrast, in wasteful systems with high pollen loss rates, mate density becomes the dominant factor and sex ratio is no longer consequential. These patterns were observed at both landscape and local scales. Systems with low deposition and low pollen loss rates are associated with large pollination neighbourhoods, which decline with increasing deposition and pollen loss rates. These results show that mate density and sex ratio should carefully be distinguished and highlight the complex way in which pollen loss interacts with deposition rate, which has not previously been appreciated.
Dental injuries with kick‐scooters in 6‐ to 12‐year‐old children
Authors: Baumgartner Elisabeth Nathalie , Krastl Gabriel , Kühl Sebastian , Filippi Andreas
Published: November 2011

Abstract –  Background/Aim: The objective of this study was to investigate the occurrence of injuries, especially dental trauma, in scooter‐related accidents. In addition, children’s habits of wearing protective gear were assessed. Material and Methods: The study was conducted in primary schools in three neighboring towns near Basel, Switzerland, using anonymous multiple‐choice questionnaires completed by parents of schoolchildren. Results: A total of 953 scooter riders were included in the study. The average age was 9.1 years (range 6–12 years). Of riders, 58.3% wore no protective gear, 39.6% wore a helmet, and 2% wore other protective equipment. Twenty‐nine percentage of the children have sustained an accident while riding the scooter, of those injuries, 41.4% affected the lower extremities, 37.0% the upper extremities, 21.6% the head, and 11.2% dental injuries; 20.3% of accidents required medical treatment. Conclusions: Parents, teachers, and doctors should be aware of the dangers involved in scooter riding. Educational measures, especially concerning use of protective gear, should be implemented to reduce the number and severity of injuries caused by this popular recreational activity.
Causal effects of latitude, disturbance and dispersal limitation on richness in a recovering temperate, subtropical and tropical forest
Authors: Leithead Mark , Anand Madhur , Duarte Leandro da S. , D. Pillar Valério
Published: November 2011

Question

Do regional differences in latitude, and local factors of disturbance and distance from mature forest, influence dispersal syndromes, rate of accumulation of species and total richness in a recovering temperate, subtropical and tropical forest?

Location

Temperate old‐growth red pine forest, Canada; subtropical Araucaria Atlantic forest, southern Brazil; tropical Gallery forest, central Brazil.

Methods

We used path analysis to determine causal relationships of regional (latitude) and local (disturbance intensity, distance of recovering site from forest) factors on percentage zoochory, exponent z from species–area relationships and total richness.

Results

Path results showed linear decreases in percentage zoochory, z and richness with increasing latitude. Disturbance and distance from mature forest each reduced richness by similar amounts; however responses of percentage zoochory and z were inconsistent between the two local factors. A second path model, using only the subtropical and tropical forest, greatly increased model significance, yielded insignificant regional effects and strengthened effects of local factors on the three richness responses. Important results from this path model were linear decreases of z (0.1) and percentage zoochory (10%) and a log‐decrease of richness (five‐fold) 100 m from the mature subtropical and tropical forest.

Conclusions

Regional differences in latitude and local effects of dispersal limitation can influence forest richness as strongly as disturbance alone. Isolated, recovering subtropical and tropical forest fragments of southern and central Brazil may therefore be recovering at much slower rates than estimates made from those adjacent to mature forest stands.
The lived experience of a foot burn injury from the perspective of seven Jordanians with diabetes: a hermeneutic phenomenological study
Authors: Abu‐Qamar Maén Zaid , Wilson Anne
Published: November 2011

Poor vision and poor pain sensation expose sufferers of diabetes to foot burn injuries. A phenomenological approach was used to illuminate the lived experience of those with diabetes who sustained foot burn injuries. Face‐to‐face unstructured interviews were conducted with seven patients recruited from health care facilities throughout Jordan. The interviews were digitally recorded, transcribed verbatim into Arabic, checked for accuracy and then analysed using thematic analysis. Our study highlights that household appliances are a major cause of foot burn injuries among the studied population and that culturally specific risk factors predispose Jordanians with diabetes to foot burn injuries, namely ablution for males and cooking activities for females. Participants sought health care when home remedies failed. Inconsistent management practices were identified among health care providers. Culturally specific health education programs should be made to raise patients' awareness towards avoiding possible risks at home.
Queensland Emergency Medicine Research Foundation: Special report
Authors: FitzGerald Gerry , Codd Catrina , Aitken Peter , Sinnott Michael
Published: November 2011

Development of any new profession is dependent on the development of a special body of knowledge that is the domain of the profession. Key to this is research. Following sustained lobbying, the Queensland Government agreed to establish an emergency medicine research fund as part of an Enterprise Bargaining Agreement in 2006. That fund is managed by the Queensland Emergency Medicine Research Foundation. The present article describes the strategic approaches of the Foundation in its first 3 years, the application of research funds, and foreshadows an evaluative framework for determining the strategic value of this investment. The Foundation has developed a range of personnel and project support funding programmes, and competition for funding has increased. Ongoing evaluation will seek to determine the effectiveness of the current funding strategy on improving the effectiveness of research performance. It will also evaluate the clinical and organizational outcomes.
Greenfield run off and flood estimation on small catchments
Authors: Faulkner D.S. , Francis O. , Lamb R.
Published: November 2011

Using evidence from 46 gauged small catchments in the United Kingdom, this paper demonstrates that the methods most commonly used for estimating design flows and greenfield run off rates on small catchments do not perform as well as alternative methods. Their results show larger error and a bias towards underestimation of the median annual flood. In contrast, newer methods from the Flood Estimation Handbook (FEH), when applied to small catchments, tend to have lower error and less bias. The paper investigates the theoretical and empirical support for four methods: Institute of Hydrology Report 124, Agricultural Development and Advisory Service (ADAS) Report 345, the FEH Statistical method and the Revitalised Flood Hydrograph method. It compares the results from all four methods with those from direct analysis of flood peak data and discusses the implications of scaling down flows to the development plot scale.

The paper recommends that the many guidance documents on run off estimation and urban drainage are amended to recommend use of Flood Estimation Handbook methods.
Validation of a Global Rating Scale for Shoulder Arthroscopy: A Pilot Study
Authors: Hoyle Antonia C. , Whelton Christopher , Umaar Rowena , Funk Lennard
Published: November 2011

Background

Reliable, valid, feasible and objective assessment is desirable in all aspects of medical training to allow monitoring of progress and to ensure high standards. At present, no assessment model for shoulder arthroscopy exists that indisputably meets these criteria. The global rating scale (GRS) has been validated as a measure of technical performance in various surgical procedures. We have developed and aim to validate a GRS for shoulder arthroscopy (GRSSA).

Materials and Methods

Using the GRSSA, 13 shoulder surgeons, rated 10 videos of diagnostic shoulder arthroscopy showing different levels of proficiency. Assessments were performed remotely using an online system developed for the study; assessors were blinded to the experience of the surgeon who was performing the arthroscopy. Construct validity was assessed via Cronbach's a and inter-rater reliability was assessed via two-way analysis of variance (ANOVA).

Results

The results suggest good construct validity (high internal consistency of GRSSA categories: Cronbach's a = 0.89 to 0.96). Two-way ANOVA demonstrated a good discriminatory ability of the GRSSA but variability between raters ( p = 0.0002 to 0.01), suggesting a current lack of inter-rater reliability.

Discussion

The GRSSA appears to be a useful tool for the assessment of diagnostic arthroscopic skills and, using our online system, the assessor can be remote to the surgeon who is performing the procedure.
Parametric simulation of drug release from hydrogel-based matrices
Authors: Lamberti Gaetano
Published: November 2011

Objectives

In this work a model recently proposed to describe the drug release from hydrogel-based matrices was applied to describe the fractional drug release from matrices based on hydroxypropylmethylcellulose (HPMC) and diclofenac.

Methods

The model, firstly proposed to describe the behaviour of systems based on HPMC and theophylline and a single set of preparation variables, is based on mass balances and transport phenomena evaluation and it was solved by an FEM-based numerical code. The experimental data on the HPMC–diclofenac matrices, taken from literature, have been obtained by varying the drug loading ratio, the compression force, the powder size of both the drug and the polymer.

Key findings

A good agreement between experimental data and model predictions, as calculated in the present work, was obtained without the use of any adjustable parameters.

Conclusions

The predictive nature of the model has been confirmed, even changing the drug molecule and other preparative parameters.
Nicotine and vascular endothelial dysfunction in female ovariectomized rats: role of estrogen replacement therapy
Authors: El-Seweidy Mohamed M , Mohamed Hoda E , Asker Mervat E , Atteia Hebatallah H
Published: November 2011

Objectives

The protective effects of estrogen replacement therapy (ERT) against oxidative injury and endothelial dysfunction in the aortic tissues induced with nicotine in ovariectomized (OVX) rats were investigated.

Methods

Female rats were divided into a sham-operated group (n = 8) and four groups in which OVX rats received either vehicle (0.1 ml sesame oil, i.m., n = 8), or nicotine (0.1 mg/kg, s.c., n = 8), or estradiol benzoate (0.1 mg/kg, i.m., n = 8), or both nicotine and estradiol benzoate (n = 8) starting at week 5 after the surgery and continuing for the following 6 weeks.

Key findings

ERT was effective in preventing the rise in plasma lipid profile, atherogenic index and the level of induced endothelin-1 (ET-1) in nicotine-treated OVX rats. It also reduced aortic malondialdehyde, hydroxyproline levels, calcium content and caspase-3 expression induced in nicotine-treated OVX rats. ERT increased serum estradiol, high-density lipoprotein cholesterol and nitric oxide levels in nicotine-treated OVX rats. Furthermore, ERT was effective in restoring reduced glutathione and cyclic guanosine monophosphate contents and endothelial nitric oxide synthase expression in aortic tissues of nicotine-treated OVX rats.

Conclusions

Short-term ERT could be a promising therapeutic strategy to minimize nicotine-induced oxidative stress and vascular endothelial dysfunction in menopausal women subjected to environmental smoke.
Ca2+ transients in myenteric glial cells during the colonic migrating motor complex in the isolated murine large intestine
Authors: Broadhead Matthew J. , Bayguinov Peter O. , Okamoto Takanobu , Heredia Dante J. , Smith Terence K.
Published: November 2011

Non‐technical summary  A ganglionated neural plexus, the myenteric plexus, within the colon generates a propagating contraction called the colonic migrating motor complex (CMMC) that underlies faecal pellet propulsion. Neurons in the myenteric plexus are surrounded by a network of enteric glia cells (EGCs), which were traditionally thought to be the glue that held the neurons together. Using imaging techniques, we demonstrate that 36% of EGCs respond with prolonged Ca2+ transients following their activation by excitatory nerve fibres that generate the CMMC, suggesting that EGCs are innervated and are activated during the CMMC.
Regulation and Control of the Thyroid-Pituitary System
Authors: Brown-Grant K.
Published: November 2011

The thyroid-pituitary system of warm-blooded animals does appear to behave as an effective regulatory system in which the controlled variable is the level of free (unbound) thyroid hormone in the plasma. A negative feedback loop illustrating the concept of the free hormone level in plasma acting on the pituitary gland to regulate the secretion of thyroid-stimulating hormone (TSH) is an essential feature of the biologist’s line-and-arrow diagram of this system and some function to express this action appears in any mathematical description of the system. However, the relationship between the rate of secretion of thyroid hormone and the concentration of free hormone in the plasma to which the pituitary is exposed is neither simple nor direct. The animal is a highly complex and variable plant, affecting the distribution and metabolism of thyroid hormone. Any adequate and realistic model of the system must consider the features of the plant in detail. A mathematical formulation of the process of hormone binding to carrier proteins in plasma is presented. Simulation of even a limited aspect of a complex biological system as it exists in real life may provide valuable insight into the overall behavior of the system.
Crack Growth Under Cyclic Compression
Authors: Hubbard R. P.
Published: November 2011

An investigation was made of fatigue crack growth in notched samples of 7075-T6 aluminum alloy which were subjected to cyclic compressive loading. Photoelastic techniques were employed to determine plastic strain distribution in the vicinity of the notch at different load levels. A fracture mechanics model relating crack growth to residual tensile stress at the notch root is proposed. Validity of the model is examined by comparing calculated stress intensity values based on the model with stress intensity values determined from the observed growth rate data.
A Theoretical and Experimental Investigation of a Confined Vortex Oscillator
Authors: Sarpkaya Turgut , Pavlin Cyrille , Phasook Sompong
Published: November 2011

A theoretical and experimental study was carried out in both air and water of the forced and temporally periodic motion that occurs in a double input vortex chamber when two jets of nearly equal momentum impinge along a common tangent. The motion is described in terms of an oscillator that derives its energy from the hydrodynamic instability of the resulting swirling flow and whose frequency is determined by the inertance and capacitance of the system. The experimental data, expressed in terms of the relevant dynamic parameters, are found to be in fair agreement with those predicted theoretically.
An Experimental Investigation of Possible Methods to Reduce Laminar Entry Lengths
Authors: Emery A. F. , Chen C. S.
Published: November 2011

The use of annuli, converging nozzles, and a converging-diverging wall section in round tubes to reduce the laminar entry lengths was studied. Over a very limited range of Reynolds numbers only the largest diameter annuli were partially effective—and then only by yielding a reduction of 20 percent.
Velocity Distributions in Two-Phase Vortex Flow
Authors: Lafferty J. F. , Hammitt F. G. , Cheesewright R.
Published: November 2011

An analytical model is developed to describe gas-jet driven two-phase vortex flow. Utilizing experimental data, the model is used to calculate the velocity distributions of the two phases within an air-water vortex. The computed velocities are in very good agreement with independent measurements and with trends predicted from other investigations of single-phase vortex flow.
Nonlinear Interaction of Two Lifting Bodies in Arbitrary Unsteady Motion
Authors: Giesing J. P.
Published: November 2011

A Method is developed for the exact calculation of the two-dimensional potential flow about two bodies, either or both of which are lifting, in nonlinear-unsteady flight. No restrictions are placed on either the body shapes or their motions. Pressures, forces, moments, and vortex-wake shapes are determined by applying a surface singularity method step by step in time. Calculated results for a variety of flow situations are presented.
Blade Oscillations in One-Stage Axial Turbomachinery
Authors: Lotz M. , Raabe J.
Published: November 2011

Two parallel straight cascades moving against one another with constant velocity are considered within plane incompressible potential flow. The position of the exciting active cascade is assumed upstream as well as downstream of the passive cascade. Free vortex sheets start only from the trailing edge of the passive cascade. Assuming infinite thin blades with small camber, small elongation and harmonic excitement, amplitudes of instationary lift and moment in relation to the corresponding stationary quantities are calculated as a function of pitch ratio of the two cascades, stagger angles of both cascades, and ratio of plate circulation to total circulation. These amplitudes reach up to 20 percent of the corresponding values in stationary flow but do not form a pronounced maximum in case of equal pitches. This effect increases if the vortex sheets from the neighboring passive profiles are neglected; it also increases with increasing pitch-chord ratio and decreasing number of harmonics. A comparison with the theoretical results of Kemps and Sears [15] shows up to 30 percent smaller lift amplitudes. Downstream position of the active cascade increases the amplitudes, especially in the case of increasing angle of attack.
A Study of Cracking During Welding of Aluminum Alloys
Authors: Wells R. L.
Published: November 2011

The objective of this investigation was to establish the factors governing weldability and to determine their effects with sufficient quantitativeness to be able to predict cracking. A test was developed that permits variation of three factors deduced to be important—strain, maximum temperature, and cooling rate—so that welding conditions can be duplicated on a parent-metal specimen. Predictions of cracking during cooling of aluminum alloy panels containing 4.5 and 8 weight percent copper were made from results of this test and observed to be very accurate.
On Fitting With Functional Polynomials
Authors: Zaborsky J. , Flake R. H.
Published: November 2011

A method is introduced for finding a functional polynomial fit of a continuous functional. This method radically reduces the number of measured records required by straightforward techniques for the second-degree approximation.
Transfer Functions and Input Impedances of Pressurized Piping Systems
Authors: Johnson B. L. , Wandling D. E.
Published: November 2011

This paper presents a method to determine the transfer function and input impedance of a pressurized fluid piping system. Distributed parameters are used to arrive at a transfer function of a single line, and then block-diagram feedback methods are used to model the system. The input impedance is derived from the feedback model, and methods are presented for finding the flow and pressure at any point in the system.
Short Endurance Fatigue of Supported, Pressurized Thin Shells
Authors: Hagen O.
Published: November 2011

An analysis of short endurance fatigue of thin walled shells with internal pressure and supported at the outside diameter while subjected to an imposed axial motion, has been investigated in detail. The variations in the number of cycles as a function of material strength, friction coefficient, thin walled shell thickness and internal pressure, were analyzed.
The Inductive Coil Technique for High-Pressure Measurements: An Analysis of Nonhomogeneous Material Environment as a Source of Irreproducibility and Error
Authors: Giardini A. A.
Published: November 2011

Significant sources of error independent of the apparatus are analyzed on the basis of experimental experience and elastic theory. All are mechanical in nature and subject to corrective action. The most serious is found to be self-generating internal pressure differences which result from differential elastic and dimensional values in multicomponent assemblies. High-pressure data on elastic constants, relative critical yield stresses, radial displacements, and ratios of external to internal pressure for various compositional arrangements of pyrophyllite, MgO, NaCl, and AgCl are given in graphical form. Observance of suggested corrective measures can render the inductive coil technique capable of operational accuracies of 2 percent or better in compressibility and resistivity measurements.
Wave Propagation in Viscous Fluid Lines Including Higher Mode Effects
Authors: Gerlach C. R. , Parker J. D.
Published: November 2011

An analytical investigation of the symmetric modes of propagation for a viscous, compressible liquid in a cylindrical conduit is given in the form of an exact solution of the first-order Navier-Stokes equations. Boundary conditions for both rigid and elastic walls are imposed and the resulting characteristic equation is solved for the spatial attenuation-factor and phase velocity for several modes. The near-piston axial velocity profiles are found analytically for the case of a piston oscillating in a semi-infinite pipe and used to obtain the approximate state of shear stress near the piston. Experimental verification of this state of shear stress is made by viewing the action of a birefringent liquid in the neighborhood of an oscillating piston in a plexiglass tube. It is concluded that, in general, disturbances in a viscous fluid line consist of an infinite number of modes of propagation, the excitation of which depends upon the conduit end conditions, with the extent of spatial propagation being highly dependent upon the frequency and upon the type of conduit walls.
Errors Due to a Representation of Source Flow in an Electrical Analogy
Authors: Gibbings J. C.
Published: November 2011

The necessarily finite-size electrode used to represent a source flow in an analog solution is usually circular in shape. The resulting distortion of the true potential map introduces errors in potential which are investigated for an electrode adjacent to a corner. A numerical example is given.
An Ion-Drag Thrust Bearing
Authors: Timko Charles A.
Published: November 2011

A means of pressurizing thrust bearings through the use of ions and high electric fields is investigated theoretically and experimentally. Theoretically, the mechanism is attributed to corona generated like-charged ions. Experimentally, this effect does exist but with other effects present. In both cases, the carrying capacity of the bearing is quite small. Applications of the bearing are rather limited.
Dimensionless Parameter Reliability Analysis and Application to Mechanical Creep
Authors: Simon R.
Published: November 2011

A formal procedure is outlined for establishing a priori functional relationships between the probability-of-success measure of reliability and dimensionless parameter combinations of the pertinent system variables. The latter include the criteria for failure, the expected load and environmental conditions, the statistical distributions in values of the material properties, and the explicit and implicit times. This procedure is illustrated by application to the case of structural element creep assuming a bimodal failure criterion, either exceeding a given critical strain level or rupture. The implications of this analysis in regard to indicating the directions of future research in materials science pertinent to mechanical reliability are briefly discussed.
Optimal Singular Solutions for Linear Multi-Input Systems
Authors: Rohrer R. A. , Sobral M.
Published: November 2011

Linear, stationary systems with multiple inputs when subject to performance indices quadratic in the state variables, but explicitly independent of the control variables, may be optimally governed by singular control. Necessary and sufficient conditions for the optimality of both partially singular control and totally singular control are obtained. Moreover, explicit formulae are presented for both open-loop and linear-feedback implementations of the optimal singular control.
On a Class of Constrained Control, Linear Regulator Problems
Authors: Tchamran A.
Published: November 2011

An optimum control problem which can be solved completely is the linear, time-invariant free-terminal-time, regulator problem with unrestricted control function and a quadratic-type performance index. However, if the control function is constrained, the solution of the regulator problem becomes complicated. In the present work, when the control function |u(t)| ≤ 1, the requirements of the existence of an optimal solution and a method for obtaining this solution are outlined.
Application of the Direct Stiffness Method to Plane Problems Involving Large, Time-Dependent Deformations
Authors: Gerstenkorn G. F. , Kobayashi A. S.
Published: November 2011

The direct stiffness method is used to formulate a numerical procedure for solving plane structural problems involving large, time-dependent deformations and nonhomogeneous, time-dependent material properties. The stiffness matrix in polar coordinates is derived for the state of plane strain. The nonlinear structural response is incrementally linearized by considering the deformation process to be linear within small time increments. The developed procedure is compared numerically with a known solution of creep deformations in a thick-walled cylinder subjected to internal pressure loading and elevated temperature.
Toughness of Warm Worked Martensitic Steels
Authors: Ripling E. J. , Lindberg R. S.
Published: November 2011

The Charpy “V” notch transition temperature of quenched and tempered armor steel was lowered by warm stretching at a temperature just below the initial tempering temperature. The transition temperature was lowered almost linearly with prestrain; and a 30 percent deformation suppressed it approximately 150 deg F. This toughness improvement occurred with no change in hardness, although there was a loss in super-transition temperature shelf height. The initial tensile strength of the steel was only slightly changed, while the yield strength was increased and ductility reduced. The enhanced toughness persisted through retempering after warm working. The added heating did not change the hardness while the supertransition shelf was brought back to its “as-received” level. In addition, the tensile strength, yield strength, elongation, and reduction in area of the warm stretched plus tempered and “as-received” steel were essentially identical, resulting in a net increase in toughness. A severe room temperature toughness loss was produced by compressive prestrains in excess of about 10 percent. Retempering after straining not only delayed this precipitous loss until the strain exceeded 25 percent, but also raised the Charpy energy after small compressions to about 140 percent of its “as-received” values. Step-wise prestraining was found to be as effective as a single straining step in lowering transition temperatures. In a single test series warm working by rolling was compared with stretching. The suppression of the transition temperature was found to be almost identical for the two deformation processes.
Primary Creep Design of Thick Tubes
Authors: Smith E. M.
Published: November 2011

For thick tubes subjected to internal pressure, the estimation of creep-life by the cumulative damage criterion requires knowledge of the time variation of stress and strain at certain critical radii. An approximate method of analysis for primary creep is described which provides the stress and strain data required. The theory is based on a design concept first proposed by Voorhees, et al., and results obtained using the theory with a time-hardening law are presented.
Step Responses of Liquid Lines With Frequency-Dependent Effects of Viscosity
Authors: Brown F. T. , Nelson S. E.
Published: November 2011

Universal step-response plots are given from theoretical considerations for rigid cylindrical lines containing a compressible Newtonian laminar-flow liquid. The pressure and flow step inputs and pressure and flow outputs for semi-infinite lines can, with the principle of superposition, be used to estimate the responses of a network of lines, terminations, and so on, for any transient input. Where possible, analytic expressions were found for these step responses, but in a certain region of each curve complex numerical routines based on the analytic frequency response were necessary. Analytical expressions are based on propagation and characteristic impedance operators published earlier by one of the authors.
An Investigation Into the Performance of Two ISA Metering Nozzles of Finite and Zero Area Ratio
Authors: Soundranayagam S.
Published: November 2011

The flow through two ISA nozzles of area ratio zero and 0.4 was investigated to determine the nature of the flow and its variation with Reynolds number. Separation occurs within the nozzle of zero area ratio, the size of the bubble increasing with decreasing Reynolds number. The predicted discharge coefficient based on a simplified flow model agrees with experiment for large Reynolds numbers. Upstream influences affect the performance of the nozzle of area ratio 0.4. The flows through the two nozzles are not comparable, and potential-flow results cannot be used to explain flow in venturis and nozzles in pipes. The discharge-coefficient curve for area ratio 0.4 shows a distinct hump when based on the head differential measured as for venturis, but no hump when based on the head differential across the corner taps.
Theoretical Solution as a Boundary Value Problem for Externally Pressurized Porous Gas-Bearings
Authors: Mori H. , Yabe H. , Shibayama T.
Published: November 2011

In this paper, an analytical solution is obtained and discussed for externally pressurized porous gas-bearings from a theoretical standpoint in which the flowing condition in bearing clearance is taken into consideration as a boundary value of the three-dimensional flow in porous media. This approach makes it possible to investigate the characteristics of various bearing configurations with consideration of anisotropy of porous material. And it is assumed that the flow in bearing clearance is laminar and fully viscous while the flow in porous media is characterized by Darcy’s law. The theoretical results are found to give more reasonable prediction of porous gas-bearing performance than those in the previous paper [1].
Antiwear and Antifriction Properties of Polyorganosiloxanes and Their Mixtures With Hydrocarbons
Authors: Vinogradov G. V. , Nametkin N. S. , Nossov M. I.
Published: November 2011

The antiwear and antifriction (lubricating) properties of polyorganosiloxanes of various kinds and of their mixtures with hydrocarbons are studied. It is shown that in mixtures with hydrocarbons, polyorganosiloxanes may display a high activity under boundary friction. The conditions under which this activity is brought out are determined. A change in the oxidative activity of the gas phase acts on the lubricity of polyorganosiloxanes in the same direction as on that of mineral oils; this action is weaker as the stability of the polyorganosiloxanes to thermal oxidation increases. Additives highly active in preventing steel seizure in hydrocarbon lubricants are either utterly inactive in polyorganosiloxanes (polymethylphenylsiloxanes) or are much weaker (polyethylsiloxanes). A hypothesis is suggested, attributing this to the difficulty in polyorganosiloxanes of processes occurring which involve chain reactions initiated by free radicals. The mechanism of action of E.P. additives in lubricating media is discussed.
The Critical Temperature of Oil With Point and Line Contact Machines
Authors: Matveevsky R. M.
Published: November 2011

The temperatures on the rubbing surfaces were calculated (just before seizure) for the row tests of different mineral oils (without EP additives), which were carried out by different authors on several testing machines (four-ball machines, crossed-cylinder machine and disk machine) with different sliding speeds. These temperatures for certain oil-metal combinations, evaluated by means of the theoretical formulas (developed by Blok and Jaeger) practically coincide with the values of the critical temperatures of the same oils, obtained by the author directly from experiments with KT-2 four-ball machine (very low)—sliding speed, high contact load, and external heating of the oil and specimens). The influence of the plastic deformation at the area of contact on the value of the critical temperatures for some oil-metal combinations is shown.
Fluid-Temperature Transients in a Dual-Heat-Exchanger System
Authors: Thal-Larsen H. , Loscutoff W. V.
Published: November 2011

A study of fluid-temperature transients in an experimental dual-heat-exchanger system based on a combination of analog simulation and analytical techniques.
The Influence of Finite-Wall Conductance on Load Capacity of the Magnetohydrodynamic Slider Bearing
Authors: Snyder W. T.
Published: November 2011

An analysis is presented which considers the influence of finite-wall conductance on the pressure distribution and load capacity of the magnetohydrodynamic slider bearing. The analysis is based on general external loading conditions with the open-circuit condition being a special case. The load capacity is a linear function of the quantity Φ = Es/V By and the dependence of Φ on the conductivity and thickness of the walls is shown in explicit form. Curves showing the variation of Φ with wall conductance are presented. A numerical example is included which indicates a substantial reduction of load capacity from the case of insulating walls to the case where the wall conductivity is 1 percent of the fluid conductivity.
Rigid Water-Column Theory in Water-Hammer Problems
Authors: Swiecicki Ignacy
Published: November 2011

Equations and charts for solving pressure-rise problems by the rigid water-column theory are presented with an example of their application. These are compared with the elastic water-column theory and the merits of both are discussed.
Yield Behavior of Polycrystalline Niobium
Authors: Huffaker D. C. , Sinclair G. M.
Published: November 2011

The yield behavior of niobium (columbium) has been studied under conditions of different states of stress, temperatures and strain rates, material compositions, and microstructures. Using data gathered in the present investigation as well as that obtained from ten other sources, it is shown that a relationship including the foregoing variables is given by γ˙G=Ae−[ΔH*−V(τG−τiG)]/RT While details of the frequency factor A remain unclear, it appears that it may be treated as a constant over a wide range of temperatures and strain rates. The analysis included in this paper shows that a simple parameter representation of yield behavior of niobium is feasible in terms of pertinent engineering variables.
Velocity Profile Effects on the Discharge Coefficient of Pressure-Differential Meters
Authors: Ferron A. G.
Published: November 2011

Tests performed on a high-differential meter, venturi meter, and orifice indicated changes in the discharge coefficient with changes in upstream velocity distribution. These tests along with those by other investigators lead to the conclusion that all pressure-differential meters are affected by upstream velocity distributions when defined in some characteristic manner. This effect is increased as the beta ratio increases.
Hydraulic Flow in Coupled Parallel Channels of Varying Cross-Sectional Area
Authors: Thorpe J. F.
Published: November 2011

The problem considered is that of flow in the two parallel channels formed by the introduction of a long thin plate into a duct of uniform rectangular cross section. The plate is slightly inclined and does not, in general, span the channel so that transverse flow may occur. The flow is described by applying the one-dimensional approximation. Boundary conditions were established by regarding the stagnation streamline as defining two separate channels upstream of the plate leading edge. The solution was then obtained numerically with an IBM 650 computer. Computed hydraulic parameters were in good agreement with those obtained experimentally.
Stress-Strain Distribution During Transient Heating of a Transversely Anisotropic Material
Authors: Suzuki Bob H. , Frisch J.
Published: November 2011

Four by six-in. transversely anisotropic plates of 1/8 and 1/4-in-thick pyrolytic graphite were subjected to transient heating in an oxyacetylene flame apparatus. At temperatures up to 1500 deg F, the temperature and thermal strain distributions were determined over the length and thickness of the plates. The thermal strains measured with an optical gauge and the analytically determined strains calculated from the three-dimensional thermoelasticity equations for a two-dimensional temperature distribution were found to be in good agreement. The calculated stress distribution indicates that maximum compressive stresses of −1400 psi and −3000 psi were produced in the 1/8-in. and 1/4-in. pyrolytic-graphite plates, respectively.
Elastic-Plastic Deformation of a Single Grooved Flat Plate Under Longitudinal Shear
Authors: Koskinen Michael F.
Published: November 2011

The development of plastic strain is followed from the elastic through the partially plastic to the fully plastic condition for a nonstrainhardening material. Adjacent to the zone of deformation in the fully plastic case is a region of limited plastic deformation. The growth of the plastic zone is compared with predictions based on the elastic-plastic solution for a semi-infinite solid and the elastic solution for a plate. Agreement is good at low stress levels. At high stress levels, a relatively simple semiempirical equation is proposed. Predictions based on elasticity theory alone are shown to be seriously in error.
The Shape of Creep Curves
Authors: Glen J.
Published: November 2011

The scatter of results in long time creep or rupture tests is such that the strongest sample can sustain a stress at least 50 percent higher than the weakest sample. A large part of this scatter is associated with metallurgical variations in steel. Starting with the assumption that a pure metal of given grain size has a clearly defined shape of creep curve at a given stress and temperature, it is shown that strain aging and precipitation phenomena complicate the shape of the creep curve. A number of examples of these phenomena are discussed showing the great importance of strain age hardening in relation to scatter.
A Switching Criterion for Certain Time-Optimal Regulating Systems
Authors: Rang E. R.
Published: November 2011

A rule for computing the initial relay position for time-optimal regulation corresponding to any set of initial conditions without solving the transcendental switching equations is presented. The discussion is restricted to systems represented by ordinary differential equations with constant coefficients with real characteristic roots. The calculation requires the evaluation of an (n − 1)-order surface integral and cannot be considered a practical solution of the problem.
Derived-Rate Increment Stabilization: Its Application to the Attitude Control Problem
Authors: Nicklas J. C. , Vivian H. C.
Published: November 2011

A gyro-free nonlinear attitude control system for a spacecraft is analyzed. On-off jet actuators are used. Hysteresis and a dead zone are intentionally put into the system. Under certain conditions the feedback signal in the control system is proportional to an angular velocity increment of the system. This is called the derived-rate increment feedback signal. The analysis for a single axis of the attitude control system is given in two parts. One part is concerned with the performance of the system in a limit cycle. The other part discusses the convergence to a limit cycle after a disturbance has occurred. Experimental results verify the results of the analysis. Typical results show the performance of the system during convergence to and operation in a limit cycle. Although the technique is described for use in an attitude control system, it can be successfully employed in other applications.