bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluating Parent Empowerment: A Look at the Potential of Social Justice Evaluation in Education
Authors: Cooper Camille Wilson , Christie Christina A.
Published: September 2005

In an effort to improve our nation's underperforming schools, education reformers are designing programs to educate and empower urban school parents. Parent involvement can be critical to a child's academic success, yet the education community still knows very little about the impact of specific parent programs. We evaluated a parent program that was part of a major school-university partnership. A responsive evaluation approach initially guided the design of our qualitative case study evaluation. Our social justice-oriented values, however, prompted us to revise our approach and adhere more closely to a social justice evaluation model. This change caused us to highlight the perspectives of low-income Latina mothers and emphasize the gap between parents’ and educators’ notions of empowerment. In this article, we describe our evaluation and highlight key findings that offer insightful implications for education practitioners, researchers, and evaluators. The findings pertain to the challenge of educators sharing power with urban parents and developing partnerships that are sensitive to the social and cultural factors that affect parents’ values, goals, and modes of participation. We also emphasize the relationship between evaluation theory and practice and point to the potential impact of social justice evaluation in education.
Complications of Therapeutic Plasma Exchange: Experience With 4857 Treatments
Authors: Basic‐Jukic Nikolina , Kes Petar , Glavas‐Boras Snjezana , Brunetta Bruna , Bubic‐Filipi Ljubica , Puretic Zvonimir
Published: September 2005

Abstract:  Plasma exchange (PE) is a technique of extracorporeal blood purification which removes large molecular weight substances from plasma. The Department of Dialysis, Zagreb University Hospital Center's database, which includes data on 509 patients, or 4857 PE treatments, was retrospectively analyzed to test the safety of PE. A total of 231 adverse reactions were recorded (4.75% of treatments). The most common complications were paresthesias (2.7%), hematoma at the puncture site (2.4%), clotting (1.7%), mild to moderate allergic reactions (urticaria; 1.6%) and bleeding (0.06%). True anaphylactoid reactions were recorded in five procedures. The incidence of severe, potentially life‐threatening adverse reactions was 0.12%. The prophylactic use of calcium and potassium was responsible for a low incidence of electrolyte disturbances. There was no lethal outcome associated with PE. When carried out by experienced staff, PE is a relatively safe procedure. The use of fresh frozen plasma is associated with a higher rate of adverse reactions.
Lp(a) apheresis for the treatment of severe CHD patients with Lp(a) hyperlipidemia
Authors: Pokrovsky Sergei , Straube R. , Afanasieva O. , Kukharchuk V. , Konovalov G.
Published: September 2005

Objectives. To demonstrate the effectiveness of the specific lipoprotein(a)[Lp(a)] removal with immunosorption columns for treatment of severe CHD patients with elevated (more than 30 mg/dL) Lp(a) level. Methods. The following inclusion criteria were used for the recruitment of patients: age – under 55; coronary atherosclerosis documented by angiography; Lp(a) greater than 60 mg/dl; normal total and LDL cholesterol; clinically apparent progression of the CHD. Specific removal of Lp(a) from plasma was carried out with immunosorbtion columns ‘Lp(a) Lipopak’ contained specific antibodies against human Lp(a). Results. During last 10 years more than 1200 Lp(a) apheresis procedures have been carried out for ten severe CHD patients with 2–3 vessels disease in Moscow, Russia and Ludenscheid, Germany with Lp(a) Lipopak columns (POCARD Ltd, Russia). The Lp(a) level was reduced on the average on 75–85%, other parameters are practically constant during one procedure and duting all period of treatment. Our experience with Lp(a) Lipopak columns has shown that the specific removal of Lp(a) from the patient's plasma to 30 mg/dL or lower by weekly Lp(a) apheresis resulted in a significant improvement in the patient's health status and quality of life. After numerous Lp(a) apheresis procedures the progression of atherosclerosis was stopped in all cases, while some segments of coronary arteries showed regression of atherosclerotic plaques. Conclusion. We conclude that Lp(a) apheresis could be a very effective therapy for severe CHD patients with elevated Lp(a), and/or Lp(a) and LDL but for whom LDL level could be effectively corrected by lipids lowering drugs.
The pH dependence of NADPH oxidase in human eosinophils
Authors: Morgan Deri , Cherny Vladimir V. , Murphy Ricardo , Katz Ben Z. , DeCoursey Thomas E.
Published: September 2005

NADPH oxidase generates reactive oxygen species that are essential to innate immunity against microbes. Like most enzymes, it is sensitive to pH, although the relative importance of pHo and pHi has not been clearly distinguished. We have taken advantage of the electrogenic nature of NADPH oxidase to determine its pH dependence in patch‐clamped individual human eosinophils using the electron current to indicate enzyme activity. Electron current stimulated by PMA (phorbol myristate acetate) was recorded in both perforated‐patch configuration, using an NH4+ gradient to control pHi, and in excised, inside‐out patches of membrane. No electron current was detected in cells or excised patches from eosinophils from a patient with chronic granulomatous disease. When the pH was varied symmetrically (pHo= pHi) in cells in perforated‐patch configuration, NADPH oxidase‐generated electron current was maximal at pH 7.5, decreasing drastically at higher or lower values. Varying pHo and pHi independently revealed that this pH dependence was entirely due to effects of pHi and that the oxidase is insensitive to pHo. Surprisingly, the electron current in inside‐out patches of membrane was only weakly sensitive to pHi, indicating that the enzyme turnover rate per se is not strongly pH dependent. The most likely interpretation is that assembly or deactivation of the NADPH oxidase complex has one or more pH‐sensitive steps, and that pH‐dependent changes in electron current in intact cells mainly reflect different numbers of active complexes at different pH.
Calcium events in smooth muscles and their interstitial cells; physiological roles of sparks
Authors: Bolton Tom B.
Published: September 2005

The observation of spontaneous sporadic releases of packets of stored calcium made 20 years ago has opened up a number of new concepts in smooth muscle physiology: (1) the calcium release sites are ryanodine and inositol 1,4,5‐trisphosphate (IP3) receptor channels which contribute to cell‐wide increases in [Ca2+]i in response to cell depolarization, activation of IP3‐generating receptors, or other stimuli; (2) changes in [Ca2+]i act back on the cell membrane to activate or modulate K+, Cl− and cation channel activity so affecting contraction, in arterial smooth muscle for example affecting blood pressure; (3) IP3 production is voltage dependent and is believed to contribute to pacemaker potentials and to refractory periods which control the rhythmical motility of many hollow organs. Most smooth muscle tissues contain interstitial cells (ICs) in addition to contractile smooth muscle cells (SMCs). The interactions of these internal mechanisms, and in turn the interactions of SMCs and ICs in various smooth muscle tissues, are major factors in determining the unique physiological profiles of individual smooth muscles.
Vortex-Wake-Blade Interaction in a Shrouded Axial Turbine
Authors: Schlienger J. , Kalfas A. I. , Abhari R. S.
Published: September 2005

This paper presents time-resolved flow field measurements at the exit of the first rotor blade row of a two stage shrouded axial turbine. The observed unsteady interaction mechanism between the secondary flow vortices, the rotor wake and the adjacent blading at the exit plane of the first turbine stage is of prime interest and analyzed in detail. The results indicate that the unsteady secondary flows are primarily dominated by the rotor hub passage vortex and the shed secondary flow field from the upstream stator blade row. The analysis of the results revealed a roll-up mechanism of the rotor wake layer into the rotor indigenous passage vortex close to the hub endwall. This interesting mechanism is described in a flow schematic within this paper. In a second measurement campaign the first stator blade row is clocked by half a blade pitch relative to the second stator in order to shift the relative position of both stator indigenous secondary flow fields. The comparison of the time-resolved data for both clocking cases showed a surprising result. The steady flow profiles for both cases are nearly identical. The analysis of the probe pressure signal indicates a high level of unsteadiness that is due to the periodic occurrence of the shed first stator secondary flow field.
Unsteady Flow Interactions Within the Inlet Cavity of a Turbine Rotor Tip Labyrinth Seal
Authors: Pfau A. , Schlienger J. , Rusch D. , Kalfas A. I. , Abhari R. S.
Published: September 2005

This paper focuses on the flow within the inlet cavity of a turbine rotor tip labyrinth seal of a two stage axial research turbine. Highly resolved, steady and unsteady three-dimensional flow data are presented. The probes used here are a miniature five-hole probe of 0.9 mm head diameter and the novel virtual four sensor fast response aerodynamic probe (FRAP) with a head diameter of 0.84mm. The cavity flow itself is not only a loss producing area due to mixing and vortex stretching, it also adversely affects the following rotor passage through the fluid that is spilled into the main flow. The associated fluctuating mass flow has a relatively low total pressure and results in a negative incidence to the rotor tip blade profile section. The dominating kinematic flow feature in the region between cavity and main flow is a toroidal vortex, which is swirling at high circumferential velocity. It is fed by strong shear and end wall fluid from the pressure side of the stator passage. The static pressure field interaction between the moving rotor leading edges and the stator trailing edges is one driving force of the cavity flow. It forces the toroidal vortex to be stretched in space and time. A comprehensive flow model including the drivers of this toroidal vortex is proposed. This labyrinth seal configuration results in about 1.6% turbine efficiency reduction. This is the first in a series of papers focusing on turbine loss mechanisms in shrouded axial turbines. Additional measurements have been made with variations in seal clearance gap. Initial indications show that variation in the gap has a major effect on flow structures and turbine loss.
Concerning New Methods of the Measurement of Hearing in Man
Authors: Gersuni G. V.
Published: September 2005

It is known that the main quantitative characteristics of hearing in man can be obtained by so-called psychophysical methods. In these methods, the responses to sound stimuli are based upon the use of verbal instructions. This paper gives a description of methods of measurement of hearing based upon the use of other different responses to sound stimuli, worked out by the author and his collaborators. For this purpose, a set of different conditioned responses was used (galvanic skin-reflexes, eye-lid reflexes, electrocortical reactions, etc.). The data obtained by these methods show the following: (1) Absolute auditory thresholds and difference limens for frequency and intensity of pure tones can be measured with the same accuracy by these reactions as by verbal responses. (2) In certain cases, conditioned reflexes subliminal to the verbal responses in the range of 1 to 6 db may be detected. (3) Changes of absolute and differential sensitivity attaining 25 to 30 db, and dependent on the condition under which the reactions take place, can be detected. The presented data of hearing measurements obtained by means of different responses are considered highly characteristic of the process of sound discrimination in man and animals.
Scale Model Factory for Measurement of Partial Enclosures
Authors: Bishop Dwight E. , Hardy Howard C. , Tyzzer Franklin G.
Published: September 2005

A scale model factory was constructed and equipped for evaluating noise reduction methods, in particular partial enclosures described in the next paper. On a 110 scale, the model simulated a factory 80 ft by 60 ft with an 18-ft ceiling. With absorbing sides, the desired simulation of a factory with very large dimensions compared to ceiling height was obtained. The model was constructed of panels either 4 ft by 6 ft or 4 ft by 4 ft, mounted on a steel framework. The sound source was mounted on a rotating disk for ease in making directional patterns of enclosures and a track was provided for making microphone traverses. A stable mechanical sound source with a circular pattern was developed to produce wide-band noise at levels giving a signal-to-noise ratio of 30 to 50 db in the scaled frequency range of 2 to 50 kc (200 to 5000 cps in the prototype). The noise was made by steel balls thrown by a rotating paddle against the inside of a steel cylinder. The measuring system consisted of a special high-frequency condenser microphone, amplifier, and octave band filters. [This work was supported in part by the National Gypsum Company.]
Portable Recorder for Acoustical Measurements
Authors: Kamperman George W.
Published: September 2005

This paper describes the modifications performed on a commercial audio magnetic-tape recorder to convert it into a moderate-cost, portable, field instrument for use in making acoustical measurements such as reverberation time, noise spectra, etc. An Ampex Model 600 recorder was chosen because of inherent features that make it readily adaptable for this purpose. The principal modifications include a precision step attenuator in the recording amplifier, an increase in tape speed from 712 to 15 in./sec, a peak signal overload indicator, a pre-emphasis filter selector, and a second recording channel.
Evaluation of Two Message-Storage Schemes in a Competing Message Situation
Authors: Thompson Paul O. , Webster John C. , Bertsch W.
Published: September 2005

Two schemes of message storage were evaluated in a communications-net simulation. An operator received messages, which frequently overlapped, from talkers on four channels. In a typical test problem, 32 relevant and six irrelevant messages were distributed over a five-minute period. The operator's task was (1) to transcribe message information onto a plotting board and (2) to synthesize a problem solution from this information. In one scheme, Fixed Delay, the operator attempted to hear each message individually by appropriate use of a 9-sec delay alternate circuit in each channel. In the other scheme, Variable Delay, messages were never heard directly; instead, message arrivals were indicated by lights and the operator summoned each message from storage individually. A third arrangement, in which all messages were heard directly as programed, served as a control condition. Performance criteria were speed, accuracy, and the number of repeats the operator had to request. The results for the Fixed Delay and control conditions were roughly equivalent. Under the Variable Delay condition more transcription and synthesis were complete and correct by the end of a programed sequence; only about half as much additional time and a third as many repeats were needed for problem solution.
Intelligibility as a Function of Frequency of Usage
Authors: Rosenzweig Mark R.
Published: September 2005

In two experiments, one in English and the other in French, we have found that the intelligibility of words in the presence of noise is greater, the greater the frequency of usage of the words in the language. The English experiment was done in collaboration with Leo J. Postman. Samples of monosyllabic words were selected at four ranges of frequency in the Thorndike-Lorge count. The words were arranged in seven randomly ordered lists and were recorded with masking noise. The signal-to-noise ratio was increased for each of the successive lists, and the threshold of each word was obtained for each subject. The subjects were 110 native American students at the University of California. The same design was used for the French experiment. Samples of disyllabic words were selected from the count of oral material made for Le Français Elémentaire. The test recording was made by the Centre d'Etudes de Radio-Télévision, and the subjects were 60 native French students at the Sorbonne. The relationship found between the intelligibility and frequency can be applied to the selection of words for intelligibility. The relationship also affords a demonstration of the effects of frequency of exercise upon perception. In both languages, half of the threshold variance is accounted for by frequency of usage.
Preliminary Investigation of the Acoustical Characteristics of Inter-Phonemic Transitions
Authors: Schultz Martin C.
Published: September 2005

The study employed selected vowels, each combined with prevocalic or post-vocalic consonants in consonant-vowel or vowel-consonant syllables. Each combination was recorded non-contextually by several speakers and then tested by listeners for recognizability of phonemes. Oscillograms and sound spectrograms were made of all syllables correctly identified. These were used to obtain several measures of syllabic component duration and formant frequency change during transition. Measures of direction and extent of frequency change during transitions appeared to offer most promise of relationship to known physiological features of articulation and were subjected to more complete analysis. Results of the study indicate the following: (1) for the first two formants, the transitions reflect aspects of tongue placement for the vowel, and place and manner of articulation and voicing characteristics of the consonant; (2) lack of speaker agreement resulted in variations obscuring most aspects of patterning for the third formant. Specific hypotheses were tested within the limits of the experimental procedure and results are reported. Future research trends are suggested.
Second-Order Statistics of Speech
Authors: Kramer Henry P.
Published: September 2005

Preparatory to a numerical investigation of the statistics of speech, current knowledge of the production of speech is presented in such a way as to accentuate its random character. We imagine an individual's speech to be produced in two stages: (a) excitation of the vocal tract and (b) modulation of the vocal tract. We accept the capriciousness of the speaker in exercising at successive junctures his choice of pitch and phoneme. Accordingly we introduce randomness in (a) by supposing excitation to be produced by g[ωt + α(t)] where ω/2π is a mean frequency, g(x) is periodic, and α(t) is a random function with mean zero. The random succession of phonemes is represented by a pseudo-transfer characteristic V (t;f) =  ∑ 13ak(t)f − fk(t), which is thought to vary with time as follows: at each instant tn in a sequence a choice is made of the parameter values ak and fk to be used until the next instant tn+1 in the sequence. Thus, for each f, V(t;f) is a random function. Suppose that α(t) and V(t;f) are independent and stationary. Let ρ(f) be the power spectrum of g(ωt+α(t)). Then, denoting by r(τf) the covariance function for each f of V(t;f), we have the following for the covariance of speech: R(τ) =  ∫ −∞∞ r(τ;f)e2πifτdρ(f). By means of this expression the effect on the covariance of various assumptions about α(t), ak(t), and fk(t) is investigated.
Standards of Sound Insulation in Buildings
Authors: Pickles Alan T.
Published: September 2005

Until recently the standards of sound insulation in buildings were those that resulted from traditional building methods, and often depended on other consideration than protection against noise; i.e., fire resistance, stability, etc. Such “standards” are becoming increasingly unsatisfactory at the present time owing to change of methods and materials of building, also the arrival of new sources of noise, such as radios, aircraft, and automobiles. An opinion survey has recently been carried out in Britain to assess the reaction of occupants in apartments separated by floors having either 40-, 45-, or 50-db sound insulation from each other. The reactions of the occupants to intruding noise in terms of verbal responses such as “disturbance,” “annoyance,” etc., have been related to the physical measurements of sound insulation.
New Light-Weight Acoustical Absorber
Authors: Brüel Per V.
Published: September 2005

As absorbing material, a thin sheet of aluminum or plastic impregnated cardboard perforated with many very small holes is used. The flow resistance is between 20 and 80 g cm−2 sec−1 . By forming a cone of the material a sufficient air volume behind the perforated sheet is achieved and high absorption at low frequency is obtained. The construction of some mechanical fixtures facilitating the assembly of the cone and fixing the assembled cone in the ceiling will be shown. Some practical use of the new type of absorbers, together with measured results of its absorbing characteristics will be shown.
Linguistic Prerequisites for a Speech Writer
Authors: Chao Yuen Ren
Published: September 2005

A speech writer is a device by which the energy of speech sounds causes the formation of a series of discrete visual tokens whose number of types is of the same order as the number of distinctive symbols in a written language. In particular a speech writer can take the form of a typewriter operated by voice to form conventional, or nearly conventional, orthography. The first stage in the construction of a speech writer must be concerned with the conversion of the flow of speech into discrete operations. Such operations have been brought within the realm of possibility by recent developments in analysis and synthesis of speech in terms of formants. The present paper deals primarily with the phonetic and graphic aspects of the response and discrimination required of the dictating person and the machine.
Phonetic Typewriter
Authors: Olson Harry F. , Belar Herbert
Published: September 2005

The important factors involved in the development of a phonetic typewriter are as follows: the particular form in which the words are typed, the means for analyzing the sounds of speech, the identification of the analyzed sounds, the encoding and decoding of the sounds for the operation of the actuating mechanism, and the design of the mechanism for actuating the typewriter. A study has been made of these problems. As a result of this study a simplified model of a phonetic typewriter has been developed incorporating all of these aspects. This model serves to illustrate the principles involved and provides means for further study towards a complete system.
Dynamic Analog of the Vocal Tract
Authors: Rosen George , Stevens Kenneth N. , Heinz John M.
Published: September 2005

A dynamically controllable electrical analog of the vocal tract capable of synthesizing sequences of speech sounds is described. The acoustic transmission line between the glottis and lips in the human vocal tract is realized electrically by eleven electronically controlled variable LC sections plus three fixed sections. Each variable capacitor is realized by means of the Miller effect, and the inductors are saturable reactors. Both elements of each section are controlled by a single voltage in a manner that constrains the LC product to remain constant, and varies the ratio L/C to simulate changes in effective cross-sectional area. The analog can be excited by a buzz source to simulate the glottal tone, by a noise source inserted at various distances from the glottis to simulate the noise of turbulence, or by both together. Thus vowels and most consonants can be produced with equal facility by the dynamic analog. Control voltages are derived from a resistance network in which a series of desired articulatory configurations is stored. A timing arrangement chooses the excitation and articulatory configurations in the proper sequence, and smoothing circuits are used to assure natural transitions from one configuration to the next. Several synthesized syllables are demonstrated by means of recordings. [This work was supported in part by the Air Force Cambridge Research Center under Contract No. AF 19(604)-626.]
Diffusion Properties of Various Irregular Panels
Authors: McKinney Chester M. , Lane Richard N.
Published: September 2005

An experimental study has been made of the angular distribution of scattered sound energy from several types of 8-ft by 8-ft wall panels used in room construction. The measurements were made using pulse type transmission with carrier frequencies from 500 cps to 4000 cps. The various panels studied were flat transite, corrugated transite, triangular splayed panels, panels with rectangular irregularities, and polycylindrical panels. The paper will present some of the experimental data on scattering together with a comparison of data obtained from full scale panels to that reported from model studies.
On the Noise of Jets Operating at Pressure Ratios Greater than the Critical
Authors: Richards E. J.
Published: September 2005

This paper describes a series of investigations aimed at a greater understanding of the fundamental nature of the noise emission from supersonic jets, carried out at the University of Southampton. Both theory and experiment in a shock tube indicate that the noise emitted when a “vortex” interacts with a stationary shock wave in an under-or over-expanded flow from a jet unit is dependent on the strength of the vortex rather than on the strength of the shock wave. The conclusion to be drawn from this, viz., that the shock-turbulence interaction type of noise will exist under all conditions except when the flow is subsonic or correctly expanded through a convergent-divergent nozzle is confirmed in tests on a series of convergent-divergent nozzles. They show that, on each nozzle, there is a noise reduction below the normal noise law of about 7 to 10 db in the region of the design Mach number, but that away from this condition, the noise is not greatly dependent on the design of nozzle used. A further analysis described in the paper emphasizes the serious effect of local temperature fluctuations in addition to turbulence in causing noise emission when passing through stationary shock waves.
Sound-Turbulence Interaction in a Closed Region
Authors: Franken Peter A. , Lyon Richard H. , Ingard Uno
Published: September 2005

Sound can be scattered by turbulence inside a cylindrical resonator. The turbulence is generated by rotating a smaller concentric cylinder at high speeds, and the sound is introduced by forcing the cylinder end plate. The structure of the turbulence has been studied with hot wire anemometers. The cylinder dimensions are such that only axial acoustic modes can occur. The interaction is detected (1) by measuring the lowering in Q value of a mode due to turbulent scattering, and (2) by measuring the equilibrium sound level in the scattered modes. Starting with the Lighthill formulation of the problem, one can obtain expressions for scattered power and relate the theoretical values to the measured quantities. [Supported by Owens-Corning Fiberglas Corporation Fellowship in Acoustics and by Contract NAw-6463 with the National Advisory Committee for Aeronautics.]
Temperature Dependence of Mechanical Tissue Destruction by Ultrasound
Authors: Fry William J.
Published: September 2005

Ultrasonic radiation, under suitably chosen dosage conditions, produces changes in tissue which are not initiated by the increased temperature resulting from acoustic absorption. Such changes, of a selective nature in the tissue components of the central nervous system, have been produced and are currently the subject of a considerable research effort. It is imperative that the physical mechanism of the mechanical action of the sound on the tissue be elucidated. One method of contributing to such an understanding consists in determining the variation in the ultrasonic dosage relations, to realize a given change in the tissue, as a function of the initial temperature of the preparation. Evidence which has resulted in the identification of changes in tissue caused by mechanical (nonthermal) action of the sound will be reviewed and recent data on the temperature dependence of this mechanical action will be presented.
Performance of Magnetostrictive Transducers Made of Aluminum-Iron Alloy or Nickel-Copper Ferrite
Authors: Kikuchi Yoshimitsu
Published: September 2005

Magnetostrictive transducers made of aluminum-iron alloy have almost the same properties as those made of nickel when prepared according to certain specifications. Since more than ten years, transducers of this kind have been successfully used in place of nickel transducers. Some of their performance characteristics will be discussed. We have recently developed magnetostrictive ferrite transducers. An investigation of various kinds of ferrite materials has shown that Ni-Cu ferrite is the most suitable material for transducers over a wide range of frequencies. A few industrial models suitable for mass production have been made and we believe that Ni-Cu ferrites shall prove to be superior to ordinary metallic magnetostrictive transducers, especially in efficiency of transduction and in their lower cost of production. We are now engaged in an investigation of their characteristics under intense excitation in order to determine the limits of the fatigue at high sonic power output.
Vibration Measurement by Interferometer
Authors: Edelman Seymour , Jones Earle , Smith Ernest R.
Published: September 2005

This paper reports continued progress in the work described in our recent paper [J. Acoust. Soc. Am. 27, 728 (1955)] developing methods for calibrating vibration pickups using the wavelength of light as the standard of length. Small amplitudes are measured using a Fizeau-type interferometer illuminated by stroboscopic light to slow or stop the apparent motion of the fringes. Large amplitudes are measured by counting fringes with a photomultiplier.
Magnetic Noise of Polyphase Induction Motors
Authors: Alger P. L. , Erdelyi Edward
Published: September 2005

The demand for quieter machines has led to a general procedure for calculation of sound pressure levels of polyphase induction motors. The origin of the magnetic driving forces which are responsible for the motor noise, and the method of calculating the mechanical response of the motor structure, are described in this paper. A method is developed to calculate the sound pressure levels of the magnetic noise at a specified point near the motor. The paper gives numerical results of calculations, and the corresponding sound pressure levels for a particular 4-pole, 30-horsepower polyphase induction motor of open frame construction under different operating conditions. The agreement is unexpectedly good.
Vibrations of Stators of Large Electrical Machines
Authors: Lübcke Ernst
Published: September 2005

The reciprocal action of magnetic forces between stator and rotor of an electrical machine causes mechanical vibrations of the stator of larger machines. These forces are varying temporarily and three-dimensionally or changing periodically. The magnitude of these vibrations is characterized by the oscillating velocity (Schnelle) v = ξw (where ξ = amplitude, w = angular frequency), and can be measured with piezoelectric acceleration meters of an especially light construction. The vibration of stators of electrical machines equals, in approximation, those of rings. When the total section of the stator is introduced as polar moment of inertia into the calculation of the natural frequency, it is possible to determine the natural frequencies of the vibration forms of higher order. The frequency coefficient, experimentally determined by the measurement of the frequencies of vibration forms of higher order, is introduced in the equation of the natural frequency. Thus it is possible to calculate beforehand the frequencies of natural mechanical vibrations which can be expected in a new machine design. It is shown that, by simplification of the problem, all natural frequencies of a mechanical system with a great number of possible natural frequencies can be obtained by the application of the forces at one point. The amplitude in the form of a natural vibration is dependent on the mode of fixing the stator ring. The investigations are made with a view to getting reliable data for noise control in electrical machines.
Structural Fatigue Due to Jet Noise
Authors: Powell Alan
Published: September 2005

This is a new field concerning the aerodynamicist and acoustician, the vibration specialist, the metallurgist, and the structural designer: each aspect has to be investigated and welded together to form a general picture. Apart from purely scientific interest, a principal result of the work in this field should be guidance to the aircraft designer. The paper briefly considers these various aspects in the light of theoretical and experimental work that has been done or is in progress, and shows how a careful coordination between theoretical and experimental work is necessary, since several aspects appear to be beyond present theoretical methods. Essentially the problem as visualized at present necessitates (1) an experimental study to obtain certain pertinent quantities in the near pressure field of a jet (where “hydrodynamic” turbulent effects are important): the quantities are spectra of space-time correlations which at present are only calculable far from the jet; (2) a theoretical step to estimate the effectiveness of the pressure field in exciting vibration, whose modes and damping are calculable in simple structures (but an experimental approach is necessary for most practical aircraft structures); and (3) finally use has to be made of cumulative damage concepts to estimate the fatigue life under these random vibrations, this step again involving much experimental work.
Pressure Fluctuations in Aerodynamic Boundary Layers
Authors: Dyer Ira
Published: September 2005

Pressure fluctuations in boundary layers of airplanes have been measured by various groups. In one case, the pressure fluctuations were measured by flush-mounting a microphone at the surface of the airplane fuselage. In all other cases, the pressure fluctuations are estimated from sound measurements made inside the fuselage, and measurements or estimations of the sound pressure reduction of the fuselage. This paper reviews and compares these measurements in the light of dimensional analysis, and indicates possible extrapolation methods. Preliminary results indicate that (1) the boundary layer pressure fluctuations can be related to the free-stream dynamic pressure (considering the airplane to be stationary and the air to be moving), (2) the spectra can be related to the free-stream velocity and to an unknown length l, and (3) the length l is a constant for approximately alike airplanes at corresponding positions along the fuselage. The measurements used in this study have been supplied or reported by Convair Division of General Dynamics Corporation, Douglas Aircraft Company, Royal Aircraft Establishment [M. E. Department Test Note No. 562, 1. I. McNaughton], and Wright Air Development Center [Technical Report No. 52-341, O. R. Rogers and R. F. Cook]. L. L. Beranek, E. M. Kerwin, and D. N. Keast have also contributed greatly to this study.
Ultrasonic Absorption of Binary Liquid Mixtures
Authors: Piercy J. E.
Published: September 2005

Recent work has shown that the sound-absorption coefficient of several binary liquid mixtures attains a high value at ultrasonic frequencies in the critical mixing region. In a number of other mixtures, a maximum in the sound absorption has been observed at intermediate concentration which is usually attributed to molecular association. The possibility that these maxima are also caused by critical mixing phenomena is examined. The maximum previously observed for mixtures of butyl-cellosolve and water is shown by new measurements to be associated with critical mixing.
Absorption and Dispersion of Forced Spherical and Cylindrical Waves According to the Navier-Stokes Equations
Authors: Kanwal Ram P.
Published: September 2005

Absorption and dispersion measures for forced spherical and cylindrical infinitesimal waves are calculated exactly within the classical linearized theory of fluids endowed with heat conduction and with both shear and bulk viscosity. A proper treatment of this problem requires a dimensionless standard of length. Two alternatives are considered: (1) the unit of length is fixed as the radius of a given oscillator, (2) the unit of length is the wavelength corresponding to the driving frequency according to the theory of nondissipative fluids. The characteristic equation for a general class of curved waves is shown to be the same as that obtained by Kirchhoff and Langevin for plane waves. The results of Truesdel's exact analysis of this equation are adjusted so as to apply to spherical and cylindrical waves. For the second class of spherical waves, the absorption coefficient per cm is shown always to be less than that for the first class, which was calculated by Kirchhoff. There is a frequency dependent factor which tends to increase the amplitude with the frequency.
Nondestructive Testing: Objectives and Potentialities
Authors: Roth Wilfred
Published: September 2005

Nondestructive testing in the broad sense refers to methods whereby internal characteristics of solid structures can be examined without permanently affecting the structure. Thus, parts that prove to be satisfactory under specified test conditions are not degraded by the test procedures. We are concerned primarily with the question “Will the structure satisfactorily perform its intended function throughout its service life?” Implications of this question as related to the interpretation of the results of nondestructive test methods will be discussed. Elastic waves are presently employed to detect gross internal mechanical defects such as voids, fractures, and impurities. Many internal characteristics that bear on the question of structural performance are not tested by ultrasonic techniques. These include such properties as grain structure and size, variation in elastic moduli, variation in chemical composition, presence of permanent strains, structure of domains, depth of surface treatment produced by hardening procedures, effects of radiation, etc. A discussion of the importance of these additional internal characteristics will be given, and the applicability of ultrasonic procedures to the measurement of these properties will be treated.
Effects of Acoustical Waves on the Annealing of Steels
Authors: Fairbanks H. V.
Published: September 2005

Research in the West Virginia University Engineering Experiment Station in the field of acoustical waves has been concerned primarily with the effect of high-frequency sound waves on the annealing of 0.07 and 1.05% carbon steels. The acoustical waves were produced by means of a bowl-shaped crystal of barium titanate and were coupled to the steel samples through distilled water. The lower end of the sample was placed in the distilled water of the transducer and the upper end was placed in the heat treating furnace. The acoustic frequencies used were 400 and 1000 kc. Examination of the acoustically treated samples of 0.07% carbon steel showed finer grain size and greater hardness than the reference samples which had undergone the same heat treating cycle but with no acoustic treatment. Also the lamellar layers of ferrite and iron carbide making up the pearlite crystals in the 1.05% carbon steel were definitely thicker in the acoustically treated samples than in the untreated samples.
Dynamic Method for Measuring the Constants of Elasticity and Damping in Solids
Authors: Cabarat Robert
Published: September 2005

The dynamic method to be described is based on the possibility of maintaining longitudinal vibrations in a test cylinder by electrostatic action. The frequency and the amplitude of these vibrations may be measured up to temperatures of the order of 800°C. For nonconducting materials a thin conducting layer is applied to the surface of the cylinder, e.g., by silver or by evaporation in vacuo. Such a layer does not change the mechanical properties of the material and permits the maintenance of the vibrations. From the width of the resonance curve of the cylinder, or from the decay of free oscillations the logarithmic decrement of the vibrations may be calculated. Experimental data are given which show the sensitivity of the method and the elasticimeter constructed at the Testing Laboratory of the Conservatoire National des Arts et Métiers is described.
Recent Experiences with the Variables of the Ultrasonic Machining Process
Authors: Goetze Dieter
Published: September 2005

Experimental results are presented which demonstrate the dependence of the ultrasonic machining rate in Ketos tool steel on variables associated with the ultrasonic machining process. These variables include the peak to peak amplitude and the frequency of vibration of the tool tip; the geometric shape of the tool tip; the pressure which is maintained between the tool tip and the work piece; the diameter of the abrasive particles and the ratio of the weight of the abrasive to the weight of the water vehicle used in compounding the slurry. An analysis of the experimental evidence makes it apparent that four constants are of fundamental importance in the ultrasonic machining process. One constant is a number representing the critical fractional part of an abrasive particle which is crowded into a cubic volume having sides equal to the abrasive particle diameter; another constant is the normal distance outward from the perimeter of the tool tip over which abrasive is effectively sucked underneath the tool tip; a third constant is the maximum pressure which a single abrasive particle can withstand; and the fourth constant is the ability of the work piece to translate a unit of pressure delivered by a single abrasive particle into a rate of machining. A phenomenological expression describing the experimental evidence is given in terms of the aforementioned variables and constants. [Work supported in part by the U. S. Air Force.]
Investigation of the Scattering of Sound Waves on Corrugated Surfaces
Authors: Leporsky A. N.
Published: September 2005

Experiments on the scattering of sound waves by models with periodically corrugated frontal surfaces are described. Results of measurements are discussed and compared with existing theories [L. M. Brekhovskikh, Zhur. Eksptl. i Teort. Fiz. 23 (1952); Yu. P. Lysanov, dissertation (1955)]. It is shown that the scattered field resolves into separate spectral beams at the distance R ≈ (4÷6) (DL/λ), where L is the spatial period of corrugation, D the length of corrugated surface, and λ the wavelength of incident sound. The angle of incidence θ0 and the corresponding angles θm of spectra of different orders agree within the experimental error with the theoretical expression sinθm = sinθ0 + mλ/L, where m is the order of a particular spectrum. In the regions of validity of the mentioned theories, the agreement between experimental and computed data for the relative values of sound pressure amplitudes is satisfactory.
Ultrasonic Absorption in Liquids
Authors: Hazzard George W.
Published: September 2005

The Debye-Sears method for measuring ultrasonic absorption is used for various organic liquids at room temperature and at frequencies of 3 to 15 mc/sec. The effect of molecular symmetry on absorption is studied for the pairs benzene, toluene; paraxylene, orthoxylene; and cyclohexane, methyl cyclohexane. The effect of double versus single bond is given for tetrachlorethane versus tetrachloroethylene. The effect of viscosity on absorption is shown to be almost negligible for solutions of polystyrene in either toluene or benzene. Finally, a possible explanation along relaxational lines is suggested.
Acoustic Circulation Effects and the Nonlinear Impedance of Orifices
Authors: Ingård U. , Labate S.
Published: September 2005

In his theory of streaming caused by sound waves, Eckart shows that time independent streams necessarily follow as part of the solution of the complete wave equatoin, taking into account viscosity and second-order terms. His treatment is mainly valid for liquids and it proves that the driving force of the streams is proportional to frequency squared. The effect, therefore, is especially important in the ultrasonic region (crystal winds). However, he suggests that slow streams might also be carried in air at audio frequencies.

Studies of acoustical streaming phenomena around orifices have been made by the use of smoke particles in a 3-in. diameter circular tube. These studies covered a range of orifices from thicknesses of 0.5 mm to 19 mm and diameters of 3.5 mm to 20 mm. The frequency lay between 150 to 1000 c.p.s. Velocities in the orifice cover the range of 0 to 700 cm/sec.

Close studies of the flow patterns have disclosed that there exist four definite regions of flow as the particle velocity in the orifice is increased. These regions have been represented by “phase diagrams.” Photographs of the various flow patterns in each region of the “phase diagram” have been taken for a number of orifices. Under each observed condition, the acoustic impedance of the orifice is determined by a conventional standing-wave measurement in the tube.

It is shown that the nonlinear properties of the acoustic impedance of an orifice is closely connected with the circulation effects. Quantitative check in one of the circulation regions and a good qualitative over-all agreement indicate that the nonlinear properties of the impedance is due to the interaction between the sound field and the circulatory effects.
Transmission of Reverberant Sound through Double Walls
Authors: London Albert
Published: September 2005

The transmission of reverberant sound through a double wall, which consists of two identical single walls coupled by an airspace, is investigated both theoretically and experimentally. A theory is developed which gives good agreement with experiment. In order to compute the transmission loss of a double wall, it is necessary to know the impedance Zw of the single wall. Zw was determined from experiments conducted on the single wall and includes the effects of mass, dissipation, and flexural motion. The treatment shows that it is impossible to get a large improvement in transmission loss for a double wall relative to a single wall under reverberant sound field conditions if the single wall is considered to have only mass reactance. In addition, the customary normal incidence theory is totally inadequate in explaining the behavior of a double wall in a reverberant sound field.

For double walls having air-coupling only, very shallow airspaces can produce appreciable increases in transmission loss over a single wall. An absorbent material when inserted in the airspace produces large improvements only when the mass of the walls is relatively light and has but little effect for heavy walls. Honeycomb or other non-absorbent cellular structures having no cell walls in a direction normal to the wall faces do not result in an increase in transmission loss. Air-coupled walls having no solid sound conducting paths between individual septa are extremely effective sound insulators as compared to conventional double wall constructions. The theory indicates that a large improvement in the transmission loss of a double wall can be obtained by using as components single walls with high internal dissipation.