bluuebunny/crossref_metadata_2025 huggingface dataset:
A direct difference infrared cell for studying the hydration of protein glasses
Authors: P L Poole  , J L Finney
Published: July 2002

A method of obtaining direct difference infrared spectra of protein glasses is described. The cell constructions are given and the procedure for producing protein glasses outlined. The protein glasses are wedged shaped so as to allow easy adjustment of protein amounts in the spectrophotometer beams. The method is used to obtain difference spectra between wet (hydrated) and dry lysozyme glasses.
A miniature rugged and accurate solid electrolyte oxygen sensor
Authors: R M A Kocache  , J Swan  , D F Holman
Published: July 2002

Present sensor designs are critically examined and their commonly encountered problems are assessed. A sensor design is detailed and its performance characteristics are examined showing that the problems have either been eliminated or minimised.
Some aspects of pharmaceutical analysis using high performance liquid chromatography
Authors: M J Cope  , I E Davidson
Published: July 2002

The history and general principles of high performance liquid chromatography are reviewed. Liquid chromatographic theory and the various modes of chromatography are discussed, including adsorption, partition, reversed phase and ion-exchange modes. Equipment used in pharmaceutical analysis is described including pumping systems, mobile phases, sample introduction systems, columns and column fittings, detectors and data handling systems. Applications are reviewed, with particular reference to antibiotic analysis, optical isomer resolution, biopharmaceutical analysis and pharmaceutical production. Future developments are considered, including column technology, detector development, automation and the analysis of biopolymers.
Reliability in instrumentation
Authors: K B Klaassen  , J C L van Peppen
Published: July 2002

Instrument reliability is defined and related to other measures of durability such as MTTF and failure rate. The need for reliability in modern instrumentation is discussed. A quantitative analysis is given of both maintained and nonmaintained instruments. Various measures for improving an instrument's reliability and availability are described, two of which, redundancy and maintenance, are treated in more detail. Illustrations of specific forms of redundancy are taken from the domain of analogue instrumentation. Preventive and corrective maintenance and their effectiveness are discussed.
Optical method of measuring the motility of bull spermatozoa
Authors: F A Glover
Published: July 2002

The apparent group movement of spermatozoa in semen is destroyed by shearing but returns as shearing ceases. The time of return is taken as a measure of motility.
Variable area and pressure difference flowmeters
Authors: J M Hobbs
Published: July 2002

Considers variable area flowmeters and the major types of pressure difference meter such as orifice plates, nozzles and venturi. It outlines the basic fluid mechanics relevant to both types and describes the various meters available, their range of size and common applications. The effects of installation on performance and methods of obtaining traceable calibrations of meters with liquids and gases are discussed. Recent meter developments and future needs are considered.
Design and assessment of monolithic high precision translation mechanisms
Authors: S T Smith  , D G Chetwynd  , D K Bowen
Published: July 2002

Crucial to the success of devices such as the scanning tunnelling microscope is the availability of translation mechanisms of very high precision. Elastic design is a natural approach to this problem and here one family of such devices, mechanisms cut from a monolith and using 'web hinges', is examined in detail. Simple design rules, derived in part from finite-element analysis, are given and manufacturing tolerances considered. It is demonstrated that the drive system can cause significant parasitic motion even in very stiff systems and so a non-contact force transducer utilising a solenoid and permanent magnet is investigated. Experimental investigation confirms that even with very routine, low-cost manufacturing methods the combination of these devices can produce 'slideways' with subnanometer out-of-plane inaccuracies.
An apparatus for accurate measurement of liquid densities over an extended temperature range
Authors: J L Hales
Published: July 2002

An apparatus for accurate measurement of liquid densities, based on the second of two designs due to Beams and Clarke, is described. The sealed sample cell contains a glass float, which can be held magnetically in the midst of the liquid sample by a servo-controlled solenoid. The sample cell is suspended from a conventional balance and weighed with and without activation of the solenoid. Pure water is used to standardize the apparatus. Advantages of the method are listed, and specific design features discussed. The present equipment is used to measure densities from 0·7 to 2·9 g cm−3at temperatures from 20 to 150°C and pressures up to 700 kN m−2. An estimated accuracy to ±50 p.p.m. is attained with a sample of volume 6 cm3. The results of measurements on benzene and hexafluorobenzene are presented.
Sample holder for single crystals of refractory metals
Authors: H E J Schins  , M C Ooms
Published: July 2002

A sample holder for fixing small single crystals of refractory metals is described. The single crystals can be mounted easily and precisely; they can be electron bombarded and show a reliable saturated current profile.
Rapid profile measurements in ion implanted silicon
Authors: S M Davidson
Published: July 2002

Ion beam etching has been used, in conjunction with the Van der Pauw technique, to determine the electrical profiles of implanted dopants in silicon, the profiles being obtained much more rapidly than by using the more usual anodic stripping. The damage produced by the ion beam must be taken into account, and this involves a simple correction to the depth scale. Profiles obtained for 40 kV B+ implanted silicon, annealed at temperatures between 500 and 970 degrees C, are presented and briefly discussed.
Accessory for measurement of highly reproducible local ultraviolet-visible spectra of single crystals
Authors: H Abplanalp  , K Eigenmann  , Hs H Gunthard
Published: July 2002

A set-up is described which allows the measurement of optical spectra of single crystals with local reproducibility within +or-0.2 mm. As an application, the measurement of concentration profiles of coloured transition metal ions in alpha -Al2O3 single crystals is reported.
A low power, high stability, superconducting modulator
Authors: J C Allnutt  , A J Walton
Published: July 2002

A simply constructed high-stability superconducting modulator requiring a power of 3 mW and capable of detecting 5 pV is described.
Method for measuring temperature of crystals during elastic and plastic deformation
Authors: D Ronnpagel  , H Neuhauser
Published: July 2002

A method of measurement developed for the investigation of energy relations during plastic deformation of metal crystals is described. The energy stored in the crystal is obtained from the difference in work expended and energy converted into heat. The heat evolved per unit of time is determined by measuring the crystal temperature during plastic deformation by means of small thermistors. The measuring technique using the thermoelastic effect to obtain the rise of temperature per unit of time at stationary plastic deformation is explained.
Recovery characteristics of a single-shielded self-aspirating thermocouple probe at low pressure levels and subsonic speeds
Authors: C E Willbanks
Published: July 2002

A novel method of measuring the temperature-recovery characteristics of thermocouple probes at low Reynolds number has been developed. Temperature-recovery characteristics were determined experimentally for a thermocouple probe of the single-shielded, self-aspirating type for total pressures of 0.75, 1.0, 3.0, 7.5 and 15 lb in-2 absolute with subsonic flow speeds ranging in Mach number from 0.25 to 1.0. The probe is typical of the type used in turbine engine testing. The total temperature of the air was approximately 670 degrees R for all the tests.
Low-impedance high-voltage pulsers for travelling-wave excitation of high-power UV gas lasers
Authors: H M von Bergmann  , V Hasson
Published: July 2002

The authors describe the design of a simple and novel travelling-wave-type pulsing system suitable for transverse discharge excitation of high-power UV gas lasers. The pulsers have been used to excite high-pressure nitrogen lasers at 337.1 nm with effective inversion lifetimes of <or approximately=1 ns. The beam powers exceed 2 MW.
Fast computation of 3D radon transform via a direct Fourier method.
Authors: Lanzavecchia S , Luigi Bellon P
Published: July 2002

MOTIVATION: Arrays of three-dimensional (3D) data are ubiquitous in structural biology, biomedicine and clinical imaging. The Radon transform can be implied in their manipulation mainly for the solution of the inverse tomographic problem, since experimental data are often collected as projections or as samples of the Radon space. In electron tomography, new applications of the transform may become convenient if a fast and accurate transformation algorithm is adopted. RESULTS: A direct Fourier method (DFM) is proposed to compute the 3D Radon transform from a sampled function with compact support. This paper describes an already known two-step algorithm and illustrates its DFM implementation by coordinate transformations in 2D Fourier space. The algorithm is easily inverted to obtain a density distribution from the Radon transform. The main applications are in the field of electron tomography, especially in processes of angular refinement, since whatever projection of a structure can be retrieved from its Radon transform in a fast and accurate way. The times required to compute a number of projections with use of the Radon transform are compared with those required by other algorithms. Further uses of the Radon transform can be foreseen in applications based on 'projection onto convex sets' (POCS). AVAILABILITY: Software is available free of charge upon request to the authors. CONTACT: salvator@csmtbo.mi.cnr.it
The 26S proteasome of the fission yeast Schizosaccharomyces pombe
Authors: Wilkinson C. R. M. , Penny M. , McGurk G. , Wallace M. , Gordon C.
Published: July 2002

The 26S proteasome is the multiprotein complex that degrades proteins that have been marked for destruction by the ubiquitin pathway. It is made up of two multisubunit complexes, the 20S catalytic core and the 19S regulatory complex. We describe the isolation and characterisation of conditional mutants in the regulatory complex and their use to investigate interactions between different subunits. In addition we have investigated the localisation of the 26S proteasome in fission yeast, by immunofluoresence in fixed cells and live cells using a GFP tagged subunit. Surprisingly we find that in mitotic cells the 26S proteasome occupies a discrete intracellular compartment, the nuclear periphery. EM analysis demonstrates that the complex resides inside the nuclear envelope. During meiosis the localisation showed a more dynamic distribution. In meiosis I the proteasome remained around the nuclear periphery. However, during meiosis II there was a dramatic relocalisation wherebye initially the signal occupied the area between the dividing nuclei. At the end of mitosis the signal dispersed returning to the nuclear periphery upon ascospore formation. This observation implies that the nuclear periphery is a major site of proteolysis in yeast during mitotic growth and raises important questions about the function of the 26S proteasome in protein degradation.
T–cell memory: lessons from Epstein–Barr virus infection in man
Authors: Rickinson A. B. , Callan M. F. C. , Annels N. E.
Published: July 2002

Epstein–Barr virus offers an ideal opportunity to follow the human T–cell response to a virus infection over time from its acute primary phase, as seen in infectious mononucleosis patients, into the memory phase that accompanies life–long virus persistence. Here we review recent evidence on the development and maturation of cytotoxic T–cell memory using this viral system.
A new class of errant DNA polymerases provides candidates for somatic hypermutation
Authors: Tippin Brigette , Goodman Myron F.
Published: July 2002

The mechanism of somatic hypermutation of the immunoglobulin genes remains a mystery after nearly 30 years of intensive research in the field. While many clues to the process have been discovered in terms of the genetic elements required in the immunoglobulin genes, the key enzymatic players that mediate the introduction of mutations into the variable region are unknown. The recent wave of newly discovered eukaryotic DNA polymerases have given a fresh supply of potential candidates and a renewed vigour in the search for the elusive mutator factor governing affinity maturation. In this paper, we discuss the relevant genetic and biochemical evidence known to date regarding both somatic hypermutation and the new DNA polymerases and address how the two fields can be brought together to identify the strongest candidates for further study. In particular we discuss evidence for thein vitrobiochemical misincorporation properties of human Rad30B/Pol ι and how it compares to thein vivosomatic hypermutation spectra.
Orthology between the genomes ofPlasmodium falciparumand rodent malaria parasites: possible practical applications
Authors: Waters A. P.
Published: July 2002

The work of the consortium that has been formed to complete the entire sequence of the genome of a selected clone of the human malaria parasite,Plasmodium falciparum, is almost finished. Already huge tracts of the genome are available as fully assembled chromosomes or large contigs and the work of initial annotation is in an advanced state. Post–genomic research is in one sense the process of furthering the process of annotation, creating biological atlases and preliminary attempts to make global descriptions of gene transcription and proteome analysis are underway. Comparison between significant amounts of genome data from both closely, and more distantly related organisms, can facilitate the identification of genes themselves, coordinately regulated gene expression groups, gene function and genome organization. Models of malaria can fulfil these functions and in addition provide an experimental system wherein predictions can be tested and basic experimental investigations performed within numerous aspects of disease, pathology, parasite–host and parasite–vector interactions. Comparative genomics inPlasmodiumhas already been shown to have informative roles in the completion of annotation and the elucidation of gene function. These roles will be illustrated by example and used as the basis for a discussion of the utility of genome information and malaria models in realizing the desired product ofPlasmodiumgenomics, the development of malaria therapies.
Spectral analysis of full field digital mammography data
Authors: Heine John J. , Velthuizen Robert P.
Published: July 2002

The spectral content of mammograms acquired from using a full field digital mammography (FFDM) system are analyzed. Fourier methods are used to show that the FFDM image power spectra obey an inverse power law; in an average sense, the images may be considered as fields. Two data representations are analyzed and compared (1) the raw data, and (2) the logarithm of the raw data. Two methods are employed to analyze the power spectra (1) a technique based on integrating the Fourier plane with octave ring sectioning developed previously, and (2) an approach based on integrating the Fourier plane using rings of constant width developed for this work. Both methods allow theoretical modeling. Numerical analysis indicates that the effects due to the transformation influence the power spectra measurements in a statistically significant manner in the high frequency range. However, this effect has little influence on the inverse power law estimation for a given image regardless of the data representation or the theoretical analysis approach. The analysis is presented from two points of view (1) each image is treated independently with the results presented as distributions, and (2) for a given representation, the entire image collection is treated as an ensemble with the results presented as expected values. In general, the constant ring width analysis forms the foundation for a spectral comparison method for finding spectral differences, from an image distribution sense, after applying a nonlinear transformation to the data. The work also shows that power law estimation may be influenced due to the presence of noise in the higher frequency range, which is consistent with the known attributes of the detector efficiency. The spectral modeling and inverse power law determinations obtained here are in agreement with that obtained from the analysis of digitized film–screen images presented previously. The form of the power spectrum for a given image is approximately with β∼1.4–1.5.
Anatomy‐based three‐dimensional dose optimization in brachytherapy using multiobjective genetic algorithms
Authors: Lahanas M. , Baltas D. , Zamboglou N.
Published: July 2002

In conventional dose optimization algorithms, in brachytherapy, multiple objectives are expressed in terms of an aggregating function which combines individual objective values into a single utility value, making the problem single objective, prior to optimization. A multiobjective genetic algorithm (MOGA) was developed for dose optimization based on an a posteriori approach, leaving the decision‐making process to a planner and offering a representative trade‐off surface of the various objectives. The MOGA provides a flexible search engine which provides the maximum of information for a decision maker. Tests performed with various treatment plans in brachytherapy have shown that MOGA gives solutions which are superior to those of traditional dose optimization algorithms. Objectives were proposed in terms of the COIN distribution and differential volume histograms, taking into account patient anatomy in the optimization process.
Investigating student understanding of quantum physics: Spontaneous models of conductivity
Authors: Wittmann Michael C. , Steinberg Richard N. , Redish Edward F.
Published: July 2002

Students are taught several models of conductivity, both at the introductory and the advanced level. From early macroscopic models of current flow in circuits, through the discussion of microscopic particle descriptions of electrons flowing in an atomic lattice, to the development of microscopic nonlocalized band diagram descriptions in advanced physics courses, they need to be able to distinguish between commonly used, though sometimes contradictory, physical models. In investigations of student reasoning about models of conduction, we find that students often are unable to account for the existence of free electrons in a conductor and create models that lead to incorrect predictions and responses contradictory to expert descriptions of the physics. We have used these findings as a guide to creating curriculum materials that we show can be effective helping students to apply the different conduction models more effectively.
Equipartition and mean-square responses in large undamped structures
Authors: Weaver Richard L.
Published: July 2002

It is shown that the smoothed spectral energy density at one point in a large complex structure may be approximated in a simple manner as proportional to the frequency-smoothed admittance at the receiver and at the source, and inversely proportional to the global modal density. Thus, the mean-square response may be estimated with little computational burden, knowing only the local properties at source and receiver and the size of the system. The approximate predictions are compared with the results of direct numerical simulations and found to be accurate except in the presence of Anderson localization.
Active vibroacoustic control with multiple local feedback loops
Authors: Elliott Stephen J. , Gardonio Paolo , Sors Thomas C. , Brennan Michael J.
Published: July 2002

When multiple actuators and sensors are used to control the vibration of a panel, or its sound radiation, they are usually positioned so that they couple into specific modes and are all connected together with a centralized control system. This paper investigates the physical effects of having a regular array of actuator and sensor pairs that are connected only by local feedback loops. An array of 4×4 force actuators and velocity sensors is first simulated, for which such a decentralized controller can be shown to be unconditionally stable. Significant reductions in both the kinetic energy of the panel and in its radiated sound power can be obtained for an optimal value of feedback gain, although higher values of feedback gain can induce extra resonances in the system and degrade the performance. A more practical transducer pair, consisting of a piezoelectric actuator and velocity sensor, is also investigated and the simulations suggest that a decentralized controller with this arrangement is also stable over a wide range of feedback gains. The resulting reductions in kinetic energy and sound power are not as great as with the force actuators, due to the extra resonances being more prominent and at lower frequencies, but are still worthwhile. This suggests that an array of independent modular systems, each of which included an actuator, a sensor, and a local feedback control loop, could be a simple and robust method of controlling broadband sound transmission when integrated into a panel.
Modal analysis of Lamb wave generation in elastic plates by liquid wedge transducers
Authors: Jia X.
Published: July 2002

A modal analysis is presented to describe the excitation of Lamb waves in an elastic plate using a liquid wedge transducer. Analytical expression for the displacement of a given mode is derived for the excitation by a uniform bounded beam. In contrast to previous studies, the contribution of the reflected wave is included in the input exciting forces using a perturbation theory. The conversion efficiency, defined as the ratio of the guided mode power to the incident power, is related to a single parameter which depends on the rate of attenuation due to leakage from the guided wave into the liquid wedge. Numerical results relevant to the fundamental Lamb modes are obtained as a function of frequency for various incident beam widths and plate thickness. Using optical interferometric detection, direct measurements of the Lamb modes displacements have been carried out in aluminium plates to verify the theoretical analysis.
Full numerical solution for the far-field and near-field scattering from a fluid-loaded elastic plate with distributed mass or stiffness inhomogeneity
Authors: Cuschieri J. M. , Feit D.
Published: July 2002

The scattering of a plane acoustic wave by a fluid-loaded thin elastic plate of infinite extent with a distributed mass or stiffness inhomogeneity is investigated. This paper is a follow up to previous work done by the same authors on the scattering from a fluid-loaded plate with a distributed mass inhomogeneity. In this paper both stiffness and mass distributed inhomogeneities are considered and a complete description of the full numerical solution is presented. Furthermore, both near-field and far-field scattering results are presented in this paper. The presence of the distributed inhomogeneity modifies the wave number transform of the equation of motion of the fluid-loaded plate to a Fredholm integral equation. This integral equation has singularities at the roots of the dispersion equation. To obtain a complete numerical solution of the Fredholm integral equation, a singularity subtraction technique is used, which is similar in essence to the hybrid analytic/numerical approach for the solution of the scattering from a fluid-loaded elastic plate [J. Acoust. Soc. Am. 95, 1998–2005 (1994)]. The solution to the resulting Fredholm integral equation of the second kind is obtained using the Nyström approximation. The results for the far-field scattering are for an oblique angle of incidence and for monostatic scattering. The results show that mass distributed inhomogeneities are stronger scatterers than distributed stiffness inhomogeneities for frequencies below the critical frequency of the plate. Above the critical frequency, both types of inhomogeneities have similar scattering strengths. Also included are results for different types of inhomogeneity distributions. This work was sponsored by ONR.
New and improved parabolic equation models
Authors: Collins Michael D.
Published: July 2002

The stability of the self starter and the accuracy of the elastic parabolic equation have been improved. The self starter is an initial condition that is generated by applying an operator to the source term [IEEE J. Ocean. Eng. 22, 102–109 (1997)]. Although the self starter is continuous, numerical difficulties can arise for problems involving relatively deep water and/or low bottom attenuation and/or high frequency. This problem has been eliminated by placing the pole of the smoothing operator far from the eigenvalues of the depth separated wave equation. The improved self starter has been incorporated into Version 1.1 of RAM (range-dependent acoustic model), which is available by anonymous ftp from ram.nrl.navy.mil. The elastic parabolic equation accounts for compressional and shear waves in the sediment. Handling a sloping ocean bottom is complicated by the change in the number of dependent variables across the interface. Gradual slopes can be handled accurately by applying a coordinate translation to flatten the ocean bottom interface. Energy is conserved and the adiabatic mode solution is invariant under this mapping. This approach has been incorporated into Version 1.0 of RAMS, which is also available by ftp. [Work supported by ONR.]
The elastodynamic finite integration technique for waves in cylindrical geometries
Authors: Schubert Frank , Peiffer Alexander , Köhler Bernd , Sanderson Terry
Published: July 2002

This paper deals with the elastodynamic finite integration technique for axisymmetric wave propagation in a homogeneous and heterogeneous cylindrical medium (CEFIT). This special variant of a finite difference time domain (FDTD) scheme offers a suitable method to calculate real three-dimensional problems in a two-dimensional staggered grid. In order to test the accuracy of the numerical CEFIT code, problems for which analytical solutions are available are presented. These solutions involve wave propagation in an elastic plate, the scattering of a plane longitudinal wave by a spherical obstacle, and ultrasound generation by a thermoelastic laser source. For the latter problem experimental results are included. The CEFIT code also allows the treatment of more complicated problems. Further possible applications are the investigation of elastic waves generated in an acoustic microscope, the simulation of impact-echo measurements in multi-layer systems, axisymmetric wave propagation in arbitrary bodies of revolution, the calculation of elastic wave fields of longitudinal wave transducers with a circular aperture, and the investigation of multi-layer models for particulates.
A signal detection analysis of auditory-frequency discrimination in the rat
Authors: Talwar Sanjiv K. , Gerstein George L.
Published: July 2002

The frequency-discrimination behavior of rats in a simple go/no-go task was analyzed using the theory of signal detection. Discrimination acuity was studied and the receiver operating characteristic (ROC) was generated in subjects by varying the reinforcement schedule and signal probability. The detectability indices d′, A′, and sensitivity index (SI) and response-bias indices B″ and responsivity index (RI) were used to describe behavior. A′ gave the most suitable psychometric functions while RI best described response-bias behavior. Weber ratios were 6.25%±0.23% at 5 kHz in three subjects. The best method to obtain the ROC was to vary the probability with which subjects were reinforced. The ROC in two subjects demonstrated classical forms; in another subject, the function was asymmetric to the extent that detectability was not independent of response bias. Subjects altered their decision criterion in reporting a signal from trial to trial depending on previous trial events. On any given trial, subjects made a decision in one of several “decision states.” Variables that influenced decision states included previous reinforcement and timeouts. The data indicate that timeouts may not be a useful feature in go/no-go tasks. The identification of multiple-decision states within a single behavioral session is a convenient method to generate the ROC without expressly manipulating experimental conditions.
Recognition of spectrally degraded and frequency-shifted vowels in acoustic and electric hearing
Authors: Fu Qian-Jie , Shannon Robert V.
Published: July 2002

The present study measured the recognition of spectrally degraded and frequency-shifted vowels in both acoustic and electric hearing. Vowel stimuli were passed through 4, 8, or 16 bandpass filters and the temporal envelopes from each filter band were extracted by half-wave rectification and low-pass filtering. The temporal envelopes were used to modulate noise bands which were shifted in frequency relative to the corresponding analysis filters. This manipulation not only degraded the spectral information by discarding within-band spectral detail, but also shifted the tonotopic representation of spectral envelope information. Results from five normal-hearing subjects showed that vowel recognition was sensitive to both spectral resolution and frequency shifting. The effect of a frequency shift did not interact with spectral resolution, suggesting that spectral resolution and spectral shifting are orthogonal in terms of intelligibility. High vowel recognition scores were observed for as few as four bands. Regardless of the number of bands, no significant performance drop was observed for tonotopic shifts equivalent to 3 mm along the basilar membrane, that is, for frequency shifts of 40%–60%. Similar results were obtained from five cochlear implant listeners, when electrode locations were fixed and the spectral location of the analysis filters was shifted. Changes in recognition performance in electrical and acoustic hearing were similar in terms of the relative location of electrodes rather than the absolute location of electrodes, indicating that cochlear implant users may at least partly accommodate to the new patterns of speech sounds after long-time exposure to their normal speech processor.
Dolphin hearing: Relative sensitivity as a function of point of application of a contact sound source in the jaw and head region
Authors: Mo/hl B. , Au W. W. L. , Pawloski J. , Nachtigall P. E.
Published: July 2002

The auditory input area of the dolphin head was investigated in an unrestrained animal trained to beach itself and to accept noninvasive electroencephalograph (EEG) electrodes for the recording of the auditory brain-stem response (ABR). The stimulus was a synthetic dolphin click, transmitted from a piezo-electric transducer and coupled to the skin via a small volume of water. The results conform with earlier experiments on acute preparations that show best auditory sensitivity at the middle of the lower jaw. Minimum latency was found at the rear of the lower jaw. A shaded receiver configuration for the dolphin ear is proposed.
Forced response of sandwich ring with viscoelastic core subjected to traveling loads
Authors: Hu Yuh-Chung , Huang Shyh-Chin
Published: July 2002

The forced vibrations of a three-layer sandwich ring with viscoelastic material (VEM) core subjected to traveling loads are investigated. The VEM layer is added to provide damping, and subsequently to reduce vibration. The derived differential equations contain three displacements, which are one transverse displacement and two tangential displacements of the two face layers. The modal expansion technique then yields the forced solution being characterized of six generalized coordinates for each circumferential wave number n. The closed form solutions to the harmonic traveling point loads are solved and discussed. Examples for various cases are illustrated as well and the influences of the viscoelastic core and the face layers on dynamic response and damping effects are particularly discussed. The results show that a very thin VEM can suppress the vibration very effectively.
Localization by interaural time difference (ITD): Effects of interaural frequency mismatch
Authors: Bonham Ben H. , Lewis Edwin R.
Published: July 2002

A commonly accepted physiological model for lateralization of low-frequency sounds by interaural time delay (ITD) stipulates that binaural comparison neurons receive input from frequency-matched channels from each ear. Here, the effects of hypothetical interaural frequency mismatches on this model are reported. For this study, the cat’s auditory system peripheral to the binaural comparison neurons was represented by a neurophysiologically derived model, and binaural comparison neurons were represented by cross-correlators. The results of the study indicate that, for binaural comparison neurons receiving input from one cochlear channel from each ear, interaural CF mismatches may serve to either augment or diminish the effective difference in ipsilateral and contralateral axonal time delays from the periphery to the binaural comparison neuron. The magnitude of this increase or decrease in the effective time delay difference can be up to 400 μs for CF mismatches of 0.2 octaves or less for binaural neurons with CFs between 250 Hz and 2.5 kHz. For binaural comparison neurons with nominal CFs near 500 Hz, the 25-μs effective time delay difference caused by a 0.012-octave CF mismatch is equal to the ITD previously shown to be behaviorally sufficient for the cat to lateralize a low-frequency sound source.
One-dimensional phenomenological model of hysteresis. II. Applications
Authors: Piquette Jean C. , Forsythe Stephen E.
Published: July 2002

A model of hysteresis is applied to determine material response to multifrequency drives, and to the output control problem. Although as presented in Paper I the model is based on a monofrequency sinusoidal drive, it can readily be generalized. The generalization is based upon the fact, at least for quasistatic drives, that the shape of the hysteresis loop is independent of the shape of the drive waveform used to produce it provided that the drive is characterized by only one wave amplitude. The material response to a given arbitrarily shaped drive can be determined if the drive is first subdivided into single-amplitude regimes or epochs. Each such regime then has associated with it a unique hysteresis loop, which can be determined from the model. Each theoretical loop is generated using a monofrequency sinusoidal drive whose amplitude is equal to the single amplitude contained within the corresponding drive epoch. The material response is then determined by correlating the level of the given drive field (and the sign of its time derivative) with that of the sinusoidal drive used to generate the associated theoretical loop. The response to the arbitrary drive is taken to be equal to the response to the sinusoidal drive at the corresponding drive level and correspondingly signed time derivative. This process is capable of inversion. Thus, not only can the material response be determined for a drive of arbitrary waveshape, but also the drive waveshape required to produce a desired output trajectory can be determined. The procedure is illustrated by determining the drive necessary to produce a monofrequency sinusoidal magnetization response from a biased, prestressed sample of Terfenol D driven at high-amplitude magnetic field.
Objective and subjective evaluations of twenty-three opera houses in Europe, Japan, and the Americas
Authors: Hidaka Takayuki , Beranek Leo L.
Published: July 2002

The room acoustical parameters, reverberation time RT, early decay time EDT, clarity factor C80, bass ratio BR, strength G, interaural cross-correlation coefficient IACC, and initial-time-delay gap ITDG [definitions in Hidaka et al., J. Acoust. Soc. Am. 107, 340–354 (2000) and Beranek, Concert and Opera Halls: How They Sound (Acoustical Society of America, New York, 1996)], were measured in 23 major opera houses under unoccupied conditions in 11 countries: Argentina, Austria, Czech, France, England, Germany, Hungary, Italy, Japan, The Netherlands, and the USA. Questionnaires containing rating scales on the acoustical quality of 24 opera houses were mailed to 67 conductors, 22 of whom responded. The objective measurements were analyzed for reliability and orthogonality, and were related to the subjective responses. Presented are (a) the rankings of 21 opera houses each rated by at least 6 conductors for acoustical quality as heard by them both in the audience areas and in the pit; (b) relations between objective room acoustical parameters and subjective ratings; (c) findings of the most important of the parameters for determining acoustical quality: RT (or EDT), GM, ITDG, [1−IACCE3], texture (appearance of reflectrograms in the first 80–100 ms after arrival of the direct sound), a lower limiting value for BR, and major concern for diffusion and avoidance of destructive characteristics (noise, vibration, echoes, focusing, etc.); (d) the differences between average audience levels with and without enclosed stage sets; and (e) the differences between average levels in audience areas for sounds from the stage and from the pit.
Foliage echoes: A probe into the ecological acoustics of bat echolocation
Authors: Müller Rolf , Kuc Roman
Published: July 2002

The research reported here aims at understanding the biosonar system of bats based on the properties of its natural inputs (ecological acoustics). Echoes from foliages are studied as examples of ubiquitous, natural targets. The echo properties and their qualitative relationship to plant architecture are described. The echoes were found to be profoundly stochastic and in general neither Gaussian nor stationary. Consequently, features useful for discrimination of such target classes will be confined to estimated random process parameters. Several such statistical signal features which are sufficiently invariant to allow a classification of the used example plants were identified: the characteristic exponent and the dispersion of an α-stable model for the amplitude distribution, a crest factor defined as the ratio of maximum squared amplitude and signal energy, the dispersion of the first threshold passage distribution, the structure of the correlation matrix, and a nonstationarity in sound channel gain. Discrimination error probability could be reduced by combining features pairwise. The best combination was the crest factor and the correlation coefficient of a log-linear model of the time-variant sound channel gain; it yielded an estimated Bayes risk of 6.9% for data pooled from different views.
Stable Cycling of Room‐Temperature Sodium‐Sulfur Batteries Based on an In Situ Crosslinked Gel Polymer Electrolyte
Authors: Murugan Saravanakumar , Klostermann Sina V. , Schützendübe Peter , Richter Gunther , Kästner Johannes , Buchmeiser Michael R.
Published: June 2022

High‐temperature sodium‐sulfur battery (HT Na–S) technology has attracted substantial interest in the stationary energy storage sector due to its low cost and high energy density. However, the currently used solid electrolyte (ß‐alumina) is expensive and can only be operated at high temperatures, which compromises safety. On the other hand, liquid electrolytes in room temperature sodium‐sulfur batteries (RT Na–S) are susceptible to dendrite formation and polysulfide shuttle. Consequently, an electrolyte with both solid (shuttle blocking) and liquid (ionic conductivity) properties to overcome the above‐mentioned issues is highly desired. Herein, a high‐performance quasi‐solid state crosslinked gel polymer electrolyte (GPE) prepared in situ using pentaerythritol triacrylate (PETA) exhibiting high ionic conductivity of 2.33 mS cm−1 at 25 °C is presented. The GPE‐based electrolyte shows high stability resulting in a high discharge capacity of >600 mAh gs−1 after 2500 cycles with an average Coulombic efficiency of 99.91%. Density functional theory calculations reveal a weak interaction between the Na+ ions and the oxygen molecules of the PETA moiety, which leads to a facile cation movement. The crosslinked polymer network is tightly connected to the cathode and can confine sulfides, thereby facilitating the conversion process.
Tuning Electronic and Ionic Transport by Carbon‐Based Additives in Polymer Electrolytes for Thermoelectric Applications
Authors: Frank Maximilian , Pflaum Jens
Published: June 2022

Thermoelectric materials utilizing ionic transport open‐up entirely new possibilities for the recuperation of waste heat. Remarkably, solid state electrolytes which have entered the focus of battery research in recent years turn‐out to be promising candidates also for ionic thermoelectrics. Here, the dynamics of ionic transport and thermoelectric properties of a methacrylate based polymer blend in combination with a lithium salt is analyzed. Impedance spectroscopy data indicates the presence of just one transport mechanism irrespective of lithium salt concentration. In contrast, the temperature dependent ionic conductivity increases with salt concentration and can be ascribed to a Vogel–Fulcher–Tammann (VFT) behavior. The obtained Seebeck coefficients of 2 mV K−1 allow for high power outputs while the polymer matrix maintains the temperature gradient by its low thermal conductivity. Adding multi‐walled carbon nanotubes to the polymer matrix allows for variation of the Seebeck coefficient as well as the ionic and electronic conductivities. As a result, a transition between a high temperature VFT regime and a low temperature Arrhenius regime appears at a critical temperature, Tc, shifting upon addition of salt. The observed polarity change in Seebeck voltage at Tc suggests a new mode of thermoelectric operation, which is demonstrated by a proof‐of‐concept mixed electronic‐ionic‐thermoelectric generator.
Mechanistic Understanding and Three‐Dimensional Tuning of Fluid Imbibition in Silica‐Coated Cotton Linter Paper Sheets
Authors: Mikolei Joanna J. , Neuenfeld Lukas , Paech Steffen , Langhans Markus , Biesalski Markus , Meckel Tobias , Andrieu‐Brunsen Annette
Published: June 2022

Paper‐based microfluidic devices are used in point of care diagnostic, sensor technology or lab‐on‐a‐chip devices. Although a number of studies has been reported, only relatively few paper‐based diagnostic tools are available on the market. A remaining challenge is the mechanistic understanding and precise design of capillary flow in paper. Here, silica coatings are applied to control paper wettability, fiber swelling, and thus fluid transport in all three dimensions of a paper sheet via a simple dip‐coating and post‐treatment process. By adjusting the three‐dimensional silica coating distribution, a three‐dimensional asymmetric wettability gradient within the paper sheet is obtained which controls the fluid distribution and imbibition. The correlation between silica coating amount and silica distribution with the resulting fluid behavior is systematically elaborated by analyzing the interaction between fiber and fluid as well as the fiber swelling by applying confocal microscopy. Three different silica‐amount dependent fluid distribution states are demonstrated. These new insights into the mechanism of fluid imbibition using simple silica coatings enable the specific design of different imbibition mechanisms and thus the adjustment of the microfluidic properties in paper‐based microfluidic devices with control over all three spatial dimensions of a paper sheet in one fabrication step.
Sulfur oxidative coupling of methane process development and its modeling via machine learning
Authors: Scabbia Giovanni , Abotaleb Ahmed , Sinopoli Alessandro
Published: June 2022

Sulfur oxidative coupling of methane (SOCM) has seen a significant improvement in catalyst design and performances, but there is still a lack of development at process level. We propose an optimized SOCM process flow diagram, with integrated waste heat recovery system and an efficient separation technique. The outcomes of the simulated process were used to design a data‐driven modeling approach, based on machine learning methods, and to evaluate its interpolation accuracy. The simultaneous multi‐input/multioutput relationship between the different parameters of the SOCM system were determined, revealing the optimum reaction conditions for the maximum benzene, toluene and xylene yield, at the minimum CH4 and H2S recycling rate.
Separation ofCH4/N2by an ultra‐stable metal–organic framework with the highest breakthrough selectivity
Authors: Chang Miao , Wang Fei , Wei Yan , Yang Qingyuan , Wang Jie‐Xin , Liu Dahuan , Chen Jian‐Feng
Published: June 2022

Selectively separating CH4from N2in natural gas purification is extremely important, but challenging. Herein, a copper‐based metal–organic framework (MOF) NKMOF‐8‐Me with inert pore environment was reported for efficient CH4/N2separation. Adsorption results show that this material owns the highest CH4uptake (1.76 mmol/g) and initial adsorption heat (Qst0) of CH4(28.0 kJ/mol) as well as difference inQst0(9.1 kJ/mol) among all materials with good water stability. Breakthrough experiments confirm that this MOF can completely separate the CH4/N2mixture with the highest CH4/N2breakthrough selectivity (7.8) reported so far. Theoretical calculations reveal the separation mechanism is the short average distance between CH4and pore wall, resulting in a stronger adsorption affinity for CH4. In addition, this MOF exhibits highly structural stability and regeneration. These results guarantee this MOF as a promising adsorbent for the recovery of CH4from coalbed methane.
Molecule transfer mechanism in two‐dimensional heterostructured lamellar membranes: The effects of dissolution and diffusion
Authors: Chen Chongchong , Wu Xiaoli , Zhang Jie , Chen Jingjing , Cui Xulin , Li Wenpeng , Wu Wenjia , Wang Jingtao
Published: June 2022

Two‐dimensional lamellar membranes are promising for efficient molecule transfer, while the underlying transfer mechanism is rarely elucidated. Herein, heterostructured nanosheets are prepared by self‐assembling small‐sized hydrophilic cyanuric acid melamine and hydrophobic g‐C3N4 nanosheets. Resultant lamellar membranes show comparable affinity to polar and nonpolar solvents, allowing them to dissolve on membrane surface and diffuse through membrane channels. Results demonstrate that for lamellar membranes with distinct wettability, the permeance difference for polar solvents is originated from dissolution and diffusion processes, while that for nonpolar solvents is stemmed from dissolution process. Accordingly, corresponding equations which are suitable for heterostructured lamellar membranes are established. Importantly, polar solvents are induced to form ordered arrangement in hydrophilic nanodomains and then maintain the ordered state in hydrophobic nanodomains, affording a low‐resistance transfer and high acetonitrile permeance of 1025 L m−2 h−1 bar−1. In contrast, nonpolar solvents with disordered arrangement exhibit lower permeance than that of polar ones.