bluuebunny/crossref_metadata_2025 huggingface dataset:
Rocking Mechanics of Flat-Bottom Cylindrical Shell Model Tanks Subjected to Harmonic Excitation
Authors: Taniguchi Tomoyo
Published: October 2005

The rocking motion of the tanks is complex and not fully understood. Using model tanks that possess concentric rigid-doughnut-shaped bottom plates, this paper tries to clarify its fundamental mechanics through the analog of rocking motion of rigid bodies. Introducing an effective mass for the internal liquid for rocking motion enables the development of a dynamical system including the rocking-bulging interaction motion and the effective mass of liquid for the interaction motion. Since the base shear and uplift displacement observed during shaking tests match well with computed values, the proposed procedure can explain the mechanics of the rocking motion of the model tanks used herein.
Thermally Induced Deflections in Bolted Flanged Connections
Authors: Bouzid Abdel-Hakim , Nechache Akli
Published: October 2005

Pressure vessel joints operating at high temperature are often very difficult to seal. The existing flange design methods do not address thermal effects other than the variation of flange material mechanical properties with temperature. It is possible to include the effects of temperature loading in joint analysis, however, presently very few guidelines exist for this type of analysis. This paper outlines the theoretical analysis used for the determination of the steady state operating temperature and deflections in bolted flange joints. It details the theoretical equations necessary to predict the temperature profiles and thermal expansion difference between the joint components necessary for the evaluation of the load redistribution for the two cases of a flange pair and a flange with a cover plate. The results from the theoretical models are verified by comparison to finite element results.
Plastic Collapse Assessment Method For Unequal Wall Transition Joints in Transmission Pipelines
Authors: Zhu Xian-Kui , Leis Brian N.
Published: October 2005

This paper investigates plastic collapse failure behavior and analytical assessment methods for unequal wall transition joints in transmission pipelines. The objective is to (i) validate the plastic-collapse-based code requirements that were determined by the early lower-strength pipes and (ii) develop an effective method for assessing plastic collapse failure of unequal wall joints involving modern high-strength pipes. Detailed finite element analysis was conducted to evaluate the failure behavior of transition joints and the effects of geometry, including weld taper angle, mismatched diameter and location, and material parameters, including the steel grade, mechanical property, yield-to-tensile strength (Y∕T) ratio, and anisotropy. Numerical results show that the wall-thickness mismatch and tensile-strength mismatch are the two first-order parameters that control the plastic collapse failure behavior of unequal wall transition joints. Based on these first-order parameters, an analytic solution is formulated to predict burst pressure at plastic collapse as a function of the pipe geometry, material tensile and hardening properties for both end-opened and end-capped pipes in reference to the plastic instability and finite strain theory. A plastic collapse criterion and the corresponding plastic collapse assessment diagram (PCAD) are then developed as a function of the wall-thickness mismatch and tensile-strength mismatch conditions to ensure that plastic collapse failure would occur in the thinner wall, with higher strength pipe. General procedures to use PCAD for assessing the plastic collapse failure of unequal wall joints are outlined. Application of PCAD indicates that high-strength pipeline grades with high Y∕T ratios can be safely used beyond current code limitations on the wall-thickness mismatch of transition joints for a wide range of strength mismatch.
Seismic Requalification of an Underground RCC Duct
Authors: Bhargava Kapilesh , Ramesh P. , Ghosh A. K. , Ramanujam S.
Published: October 2005

The present paper deals with the reevaluation of design stresses and assessment of safety margins available for an underground reinforced cement concrete (RCC) duct. For stress analysis, a two-dimensional mathematical model has been adopted to appropriately represent the structure. The structure has been analyzed for both static and seismic loads. The seismic analysis has been carried out for site-specific response spectra. The design checks have been performed using available international standards and, accordingly, the safety margins have been evaluated. The structure has been found to possess sufficient safety margins under all the postulated design loadings. The seismic reassessment methodology conforms to the available international standards.
Target representation of naturalistic echolocation sequences in single unit responses from the inferior colliculus of big brown bats
Authors: Sanderson Mark I. , Simmons James A.
Published: October 2005

Echolocating big brown bats (Eptesicus fuscus) emit trains of frequency-modulated (FM) biosonar signals whose duration, repetition rate, and sweep structure change systematically during interception of prey. When stimulated with a 2.5-s sequence of 54 FM pulse-echo pairs that mimic sounds received during search, approach, and terminal stages of pursuit, single neurons (N=116) in the bat’s inferior colliculus (IC) register the occurrence of a pulse or echo with an average of <1 spike/sound. Individual IC neurons typically respond to only a segment of the search or approach stage of pursuit, with fewer neurons persisting to respond in the terminal stage. Composite peristimulus-time-histogram plots of responses assembled across the whole recorded population of IC neurons depict the delay of echoes and, hence, the existence and distance of the simulated biosonar target, entirely as on-response latencies distributed across time. Correlated changes in pulse duration, repetition rate, and pulse or echo amplitude do modulate the strength of responses (probability of the single spike actually occurring for each sound), but registration of the target itself remains confined exclusively to the latencies of single spikes across cells. Modeling of echo processing in FM biosonar should emphasize spike-time algorithms to explain the content of biosonar images.
Ray-theoretic localization of an impulsive source in a stratified ocean using two hydrophones
Authors: Skarsoulis E. K. , Kalogerakis M. A.
Published: October 2005

A method is presented for passive localization of impulsive acoustic sources in a stratified ocean by measuring relative times of direct and surface-reflected arrivals at two hydrophones. The proposed method is based on ray theory and takes into account the effects of refraction on the geometry of acoustic paths (ray bending) and travel times, generalizing previous approaches based on the homogeneous-ocean assumption (straight-line localization). If the hydrophone depths are known, then the source depth and distance from each hydrophone can be estimated from the three differential arrival times. If in addition the hydrophone separation is known, the bearing of the source can be estimated as well. Apart from the effects on ray geometry and travel times, stratification affects localization by introducing shadow zones and caustics. For source locations in the neighborhood of caustics, the localization problem accepts two solutions, one of which is the true source location and the other one which is an artifact (ghost solution). This ambiguity can be resolved in the case of tracking moving sources since as the source moves away from the caustic only the track corresponding to the true source position will be continued. The present method has been developed primarily for monitoring the dive behavior of sperm whales producing acoustic clicks, yet it is general and can be applied for the localization and tracking of any kind of impulsive acoustic source in the ocean.
Localization of multiple acoustic sources in the shallow ocean
Authors: Neilsen Tracianne B.
Published: October 2005

An iterative, rotated coordinates inversion technique is applied in conjunction with spatial narrowband filters in matrix form to localize multiple acoustic sources in the shallow ocean. When the iterative, rotated coordinates inversion technique is applied to broadband horizontal line array data designed to simulate a group of moving ships, the bearing of the loudest source is quickly identified. Both passband and stop band matrix filters are constructed for an angular sector centered on the identified bearing. Data filtered with the passband filters are used in the inversion to obtain estimates of the remaining source parameters, range, depth, course angle and speed, and prominent environmental parameters. Additional inversions applied to data modified by the stop band filters yield the bearing of the next loudest source. The procedure is repeated until all detectable sources have been localized. Results of applying this strategy to several simulated cases are presented.
Forward masking of amplitude modulation: Basic characteristics
Authors: Wojtczak Magdalena , Viemeister Neal F.
Published: October 2005

In this study we demonstrate an effect for amplitude modulation (AM) that is analogous to forward making of audio frequencies, i.e., the modulation threshold for detection of AM (signal) is raised by preceding AM (masker). In the study we focused on the basic characteristics of the forward-masking effect. Functions representing recovery from AM forward masking measured with a 150-ms 40-Hz masker AM and a 50-ms signal AM of the same rate imposed on the same broadband-noise carrier, showed an exponential decay of forward masking with increasing delay from masker offset. Thresholds remained elevated by more than 2dB over an interval of at least 150ms following the masker. Masked-threshold patterns, measured with a fixed signal rate (20, 40, and 80Hz) and a variable masker rate, showed tuning of the AM forward-masking effect. The tuning was approximately constant across signal modulation rates used and consistent with the idea of modulation-rate selective channels. Combining two equally effective forward maskers of different frequencies did not lead to an increase in forward masking relative to that produced by either component alone. Overall, the results are consistent with modulation-rate selective neural channels that adapt and recover from the adaptation relatively quickly.
Experiments on vibration absorption using energy sinks
Authors: Akay Adnan , Xu Zhaoshun , Carcaterra Antonio , Koç I. Murat
Published: October 2005

This paper presents experiments that demonstrate the concept of energy sinks, which when attached to a vibrating structure can absorb most of its energy. Energy sinks consist of a set of undamped linear oscillators and, in principle, do not require presence of damping in the classical sense. The set of undamped oscillators that make up an energy sink collectively absorb the vibratory energy and retain it in their phase space. Earlier optimization studies by the authors have shown the feasibility of vibration absorption and energy retention by energy sinks if the set of oscillators have a particular frequency distribution. Experimental results presented in this paper support the concept of energy sinks. Different physical realizations of energy sinks demonstrate the significance of frequency distributions and the ability of energy sinks to reduce vibration amplitude of a primary structure to which they are attached.
Numerical simulation of finite amplitude wave propagation in air using a realistic atmospheric absorption model
Authors: Wochner Mark S. , Atchley Anthony A. , Sparrow Victor W.
Published: October 2005

A nonlinear system of fluid dynamic equations is modeled that accounts for the effects of classical absorption, nitrogen and oxygen molecular relaxation, and relative humidity. Total variables rather than acoustic variables are used, which allow for the inclusion of frequency-independent terms. This system of equations is then solved in two dimensions using a fourth-order Runge-Kutta scheme in time and a dispersion-relation-preserving scheme in space. It is shown that the model accurately simulates wave steepening for propagation up to one shock formation distance. For a source amplitude of 157dB re 20μPa, the Fourier component amplitudes of the analytical and computed waveforms differ by 0.21% at most for the first harmonic in a lossless medium and 0.16% at most for the first harmonic in a medium that includes thermoviscous losses. It is shown that the absorption due to classical effects and molecular relaxation demonstrated by the model is within 1% of the analytical model and the computed dispersion due to molecular relaxation of nitrogen and oxygen is within 0.7% over a large frequency range. Furthermore, it is shown that the model can predict the amplification factor at a rigid boundary, which in a nonlinear system will be greater than two, to within 0.015%.
Effect of flow on the drumlike silencer
Authors: Choy Y. S. , Huang Lixi
Published: October 2005

This study examines the effects of a mean flow and turbulent flow excitation on the performance of the recently conceived device which was tested under the no-flow condition [J. Acoust. Soc. Am. 112, 2014–2035 (2002)]. The silencer consists of two cavity-backed membranes lining part of the duct walls. When a certain optimal tension is applied, the silencer gives a broad stopband in the low-frequency regime. Similar performance is predicted for the condition with a mean flow, and tests conducted for flow speeds from 5to15m∕s validated these predictions. The spectrum of transmission loss without flow features three resonance peaks, and the mean flow is found to smooth out all peaks and shift two of them through cross-modal coupling. The silencer was tested in a wind tunnel, and no flow induced flexural instability was found on the membrane in the range of flow speeds tested. Insertion loss measurement was also conducted in a natural ventilation condition where a turbulence intensity of 3% was recorded, and the results were close to those without flow. It is concluded that no noticeable extra sound is produced by the turbulent excitation of the membrane under the optimal tension required by the silencer.
Comparing monaural and interaural temporal windows: Effects of a temporal fringe on sensitivity to intensity differences
Authors: Stellmack Mark A. , Viemeister Neal F. , Byrne Andrew J.
Published: October 2005

In an effort to provide a unifying framework for understanding monaural and binaural processing of intensity differences, an experiment was performed to assess whether temporal weighting functions estimated in two-interval monaural intensity-discrimination tasks could account for data in single-interval interaural intensity-discrimination tasks. In both tasks, stimuli consisted of a 50-ms burst of noise with a 5-ms probe segment at temporal positions ranging between the onset and offset of the overall stimulus. During the probe segment, one monaural interval or binaural channel of each trial contained an intensity increment and the other contained a decrement. Listeners were instructed to choose the interval/channel containing the increment. The pattern of monaural thresholds was roughly symmetrical (an inverted U) across temporal position of the probe but interaural thresholds were substantially higher for a brief time interval following stimulus onset. A two-sided exponential temporal window fit to the monaural data accounted for the interaural data well when combined with a post-onset-weighting function that described greatest weighting of binaural information at stimulus onset. A second experiment showed that the specific procedure used in measuring fringed interaural-intensity-difference-discrimination thresholds affects thresholds as a function of fringe duration and influences the form of the best-fitting post-onset-weighting function.
Development of a multiview time-domain imaging algorithm with a Fermat correction
Authors: Fisher Karl A. , Lehman Sean K. , Chambers Dave H.
Published: October 2005

An imaging algorithm is presented based on the standard assumption that the total scattered field can be separated into an elastic component with monopolelike dependence and an inertial component with dipolelike dependence. The resulting inversion generates two separate image maps corresponding to the monopole and dipole terms of the forward model. The complexity of imaging flaws and defects in layered elastic media is further compounded by the existence of high contrast gradients in either sound speed and/or density from layer to layer. To compensate for these gradients, we have incorporated Fermat’s method of least time into our forward model to determine the appropriate delays between individual source-receiver pairs. Preliminary numerical and experimental results are in good agreement with each other.
On errors in estimating seabed scattering strength from long-range reverberation
Authors: Holland Charles
Published: October 2005

Shallow water acoustic reverberation is sometimes exploited to estimate properties of the seabed. In the process of estimating these properties, the scattering kernel (the dependence of the scattering on incident and scattered angle) is often assumed. That is, the scattering kernel is generally not known a priori. The errors associated with assuming an incorrect scattering kernel are explored and quantified for several types of scattering kernels. Choosing an incorrect scattering kernel can lead to significant errors in the frequency dependence of the estimated scattering strength. Finally, it is shown that the sonar equation approach for obtaining scattering strength from reverberation assumes that the scattering strength is independent of both incident and scattered angle. This assumption appears to be contrary to a large body of evidence that indicates the scattering strength decreases at low grazing angles.
Listening experience with iterated rippled noise alters the perception of ‘pitch’ strength of complex sounds in the chinchilla
Authors: Shofner William P. , Whitmer William M. , Yost William A.
Published: October 2005

Behavioral responses obtained from chinchillas trained to discriminate a cosine-phase harmonic tone complex from wideband noise indicate that the perception of ‘pitch’ strength in chinchillas is largely influenced by periodicity information in the stimulus envelope. The perception of ‘pitch’ strength was examined in chinchillas in a stimulus generalization paradigm after animals had been retrained to discriminate infinitely iterated rippled noise from wideband noise. Retrained chinchillas gave larger behavioral responses to test stimuli having strong fine structure periodicity, but weak envelope periodicity. That is, chinchillas learn to use the information in the fine structure and consequently, their perception of ‘pitch’ strength is altered. Behavioral responses to rippled noises having similar periodicity strengths, but large spectral differences were also tested. Responses to these rippled noises were similar, suggesting a temporal analysis can be used to account for the behavior. Animals were then retested using the cosine-phase harmonic tone complex as the expected signal stimulus. Generalization gradients returned to those obtained originally in the naïve condition, suggesting that chinchillas do not remain “fine structure listeners,” but rather revert back to being “envelope listeners” when the periodicity strength in the envelope of the expected stimulus is high.
Plane wave propagation in generalized multiply connected acoustic filters
Authors: Panigrahi S. N. , Munjal M. L.
Published: October 2005

A generalized algorithm is developed for studying the sound wave propagation in a system of interconnected rigid walled acoustic filter elements. The algorithm is based on the transfer matrix approach of analysis. Interconnection between various elements is represented by a connectivity matrix. Equations of mass velocity continuity and pressure equilibrium at the interconnections are generated using this connectivity matrix and are solved to get the overall transfer matrix of the system. The algorithm used for generalized labeling of the network and computation of transmission loss is discussed. The algorithm is applied to investigate multiply connected automobile mufflers as a network of acoustic elements. Results for some configurations have been compared with those from the finite element model analysis and experiments cited in the literature. A parametric study with respect to some geometric variables is carried out. While the results are illustrated here for a few configurations, the approach holds for all kinds of combinations of acoustic elements with any degree of complexity. The acoustical similarity between apparently different networks is discussed. The approach is flexible to incorporate any other acoustic elements, provided the acoustic variables at the junctions of the element can be related by a transfer matrix a priori.
Micromachined microphones with diffraction-based optical displacement detection
Authors: Hall Neal A. , Bicen Baris , Jeelani M. Kamran , Lee Wook , Qureshi Shakeel , Degertekin F. Levent , Okandan Murat
Published: October 2005

Micromachined microphones with diffraction-based optical displacement detection are introduced. The approach enables interferometric displacement detection sensitivity in a system that can be optoelectronically integrated with a multichip module into mm3 volumes without beamsplitters, focusing optics, or critical alignment problems. Prototype devices fabricated using Sandia National Laboratories’ silicon based SwIFT-Lite™ process are presented and characterized in detail. Integrated electrostatic actuation capabilities of the microphone diaphragm are used to perform dynamic characterization in vacuum and air environments to study the acoustic impedances in an equivalent circuit model of the device. The characterization results are used to predict the thermal mechanical noise spectrum, which is in excellent agreement with measurements performed in an anechoic test chamber. An A weighted displacement noise of 2.4×10−2Å measured from individual prototype 2100μm×2100μm diaphragms demonstrates the potential for achieving precision measurement quality microphone performance from elements 1mm2 in size. The high sensitivity to size ratio coupled with the ability to fabricate elements with precisely matched properties on the same silicon chip may make the approach ideal for realizing high fidelity miniature microphone arrays (sub-cm2 aperture) employing recently developed signal processing algorithms for sound source separation and localization in the audio frequency range.
Temporal analysis of tissue displacement induced by a transient ultrasound radiation force
Authors: Callé Samuel , Remenieras Jean-Pierre , Bou Matar Olivier , Hachemi Melouka Elkateb , Patat Frédéric
Published: October 2005

One of the stress sources that can be used in dynamic elastography imaging methods is the acoustic radiation force. However, displacements of the medium induced by this stress field are generally not fully understood in terms of spatial distribution and temporal evolution. A model has been developed based on the elastodynamic Green’s function describing the different acoustic waves generated by focused ultrasound. The function is composed of three terms: two far-field terms, which correspond to a purely longitudinal compression wave and a purely transverse shear wave, and a coupling near-field term which has a longitudinal component and a transverse component. For propagation distances in the shear wavelength range, the predominant term is the near field term. The displacement duration corresponds to the propagation duration of the shear wave between the farthest source point and the observation point. This time therefore depends on the source size and the local shear modulus of the tissue. Evolution of the displacement/time curve profile, which is directly linked to spatial and temporal source profiles, is computed at different radial distances, for different durations of force applications and different shear elastic coefficients. Experimental results performed with an optical interferometric method in a homogeneous tissue-mimicking phantom agreed with the theoretical profiles.
Technique for the calibration of hydrophones in the frequency range 10 to 600 kHz using a heterodyne interferometer and an acoustically compliant membrane
Authors: Theobald Pete D. , Robinson Stephen P. , Thompson Alex D. , Preston Roy C. , Lepper Paul A. , Yuebing Wang
Published: October 2005

A technique for the calibration of hydrophones using an optical method is presented. In the method, a measurement is made of the acoustic particle velocity in the field of a transducer by use of a thin plastic pellicle that is used to reflect the optical beam of a laser vibrometer, the pellicle being acoustically transparent at the frequency of interest. The hydrophone under test is then substituted for the pellicle, and the hydrophone response to the known acoustic field is measured. A commercially available laser vibrometer is used to undertake the calibrations, and results are presented over a frequency range from 10 to 600 kHz. A comparison is made with the method of three-transducer spherical-wave reciprocity, with agreement of better than 0.5 dB over the majority of the frequency range. The pellicle used is in the form of a narrow strip of thin Mylar©, and a discussion is given of the effect of the properties of the pellicle on the measurement results. The initial results presented here show that the method has the potential to form the basis of a primary standard method, with the calibration traceable to standards of length measurement through the wavelength of the laser light.
Reflection of the s Lamb mode from a flat bottom circular hole
Authors: Diligent O. , Lowe M. J. S.
Published: October 2005

A study of the interaction of the s0 Lamb wave with a flat bottom circular hole in a plate is presented. The majority of the study was performed using a three-dimensional finite element model, representing an area of the plate with a circular flat-bottom hole (33% or 50% of the plate thickness deep). In the first part of the work, the incident s0 wave was specified to be a plane wave. The specular reflection was predicted and showed the importance of several factors: the interference phenomena between reflections from the leading and trailing edges of the hole and secondary reflections, and the decay in amplitude of the reflected wave. Some results of this case are also compared with analytical solutions based on modal superposition. In the second part of the work, the Lamb wave mode is excited by a small circular source. The specular reflection is predicted and compared with experimental results. An assessment is made of the significance of the path lengths, wavelengths, and defect sizes on the reflection characteristics. Good agreement is found between all techniques.
FEEDFORWARD NEURAL NETWORK MODELS FOR HANDLING CLASS OVERLAP AND CLASS IMBALANCE
Authors: KRETZSCHMAR RALF , KARAYIANNIS NICOLAOS B. , EGGIMANN FRITZ
Published: October 2005

This paper proposes a framework for training feedforward neural network models capable of handling class overlap and imbalance by minimizing an error function that compensates for such imperfections of the training set. A special case of the proposed error function can be used for training variance-controlled neural networks (VCNNs), which are developed to handle class overlap by minimizing an error function involving the class-specific variance (CSV) computed at their outputs. Another special case of the proposed error function can be used for training class-balancing neural networks (CBNNs), which are developed to handle class imbalance by relying on class-specific correction (CSC). VCNNs and CBNNs are compared with conventional feedforward neural networks (FFNNs), quantum neural networks (QNNs), and resampling techniques. The properties of VCNNs and CBNNs are illustrated by experiments on artificial data. Various experiments involving real-world data reveal the advantages offered by VCNNs and CBNNs in the presence of class overlap and class imbalance.
THE USE OF GAS-SENSOR ARRAYS TO DIAGNOSE URINARY TRACT INFECTIONS
Authors: KODOGIANNIS VASSILIS , WADGE EDMUND
Published: October 2005

Sensorial analysis based on the utilisation of human senses, is one of the most important and straightforward investigation methods in food and chemical analysis. An electronic nose has been used to detect in vivo Urinary Tract Infections from 45 suspected cases that were sent for analysis in a UK Health Laboratory environment. These samples were analysed by incubation in a volatile generation test tube system for 4–5 h. The volatile production patterns were then analysed using an electronic nose system with 14 conducting polymer sensors. An intelligent model consisting of an odour generation mechanism, rapid volatile delivery and recovery system, and a classifier system based on learning techniques has been considered. The implementation of an Extended Normalised Radial Basis Function network with advanced features for determining its size and parameters and the concept of fusion of multiple classifiers dedicated to specific feature parameters has been also adopted in this study. The proposed scheme achieved a very high classification rate of the testing dataset, demonstrating in this way the efficiency of the proposed scheme compared with other approaches. This study has shown the potential for early detection of microbial contaminants in urine samples using electronic nose technology.
NEURAL NETWORKS FOR THE OPTIMIZATION OF CRUDE OIL BLENDING
Authors: YU WEN , MORALES AMÉRICA
Published: October 2005

Crude oil blending is an important unit in petroleum refining industry. Many blend automation systems use real-time optimizer (RTO), which apply current process information to update the model and predict the optimal operating policy. The key unites of the conventional RTO are on-line analyzers. Sometimes oil fields cannot apply these analyzers. In this paper, we propose an off-line optimization technique to overcome the main drawback of RTO. We use the history data to approximate the output of the on-line analyzers, then the desired optimal inlet flow rates are calculated by the optimization technique. After this off-line optimization, the inlet flow rates are used for on-line control, for example PID control, which forces the flow rate to follow the desired inlet flow rates. Neural networks are applied to model the blending process from the history data. The new optimization is carried out via the neural model. The contributions of this paper are: (1) Stable learning for the discrete-time multilayer neural network is proposed. (2) Sensitivity analysis of the neural optimization is given. (3) Real data of a oil field is used to show effectiveness of the proposed method.
A MULTI-CLUSTERING FUSION SCHEME FOR DATA PARTITIONING
Authors: FROSSYNIOTIS DIMITRIOS S. , PATERITSAS CHRISTOS , STAFYLOPATIS ANDREAS
Published: October 2005

A multi-clustering fusion method is presented based on combining several runs of a clustering algorithm resulting in a common partition. More specifically, the results of several independent runs of the same clustering algorithm are appropriately combined to obtain a distinct partition of the data which is not affected by initialization and overcomes the instabilities of clustering methods. Subsequently, a fusion procedure is applied to the clusters generated during the previous phase to determine the optimal number of clusters in the data set according to some predefined criteria.
WHY PANEL DATA?
Authors: HSIAO CHENG
Published: October 2005

We explain the proliferation of panel data studies in terms of (i) data availability; (ii) the heightened capacity for modeling the complexity of human behavior than a single cross-section or time series data can possibly allow; and (iii) challenging methodology. Advantages and issues of panel data modeling are also discussed.
FRACTIONAL INTEGRATION AT ZERO AND THE CYCLICAL FREQUENCIES IN THE SPECIFICATION OF US PRICES
Authors: GIL-ALANA L. A.
Published: October 2005

In this paper we show that US prices can be specified in terms of a time series model that contains roots simultaneously at zero and the cyclical frequencies. Using a general procedure for testing this type of hypothesis, the results show that the secular component in the US prices is nonstationary, with an order of integration ranging between 0.7 and 1.4. However, the cyclical part seems to be stationary, with the order of integration fluctuating around 0. This implies that shocks affecting the long run component will be highly persistent, while those affecting the cyclical part will disappear quickly.
THE DETERMINANTS OF AGGREGATE IMPORT DEMAND IN BRUNEI DARUSSALAM: AN EMPIRICAL ASSESSMENT USING A COINTEGRATION AND ERROR CORRECTION APPROACH
Authors: NARAYAN PARESH KUMAR , SMYTH RUSSELL
Published: October 2005

This article examines the determinants of aggregate import demand in Brunei Darussalam within a cointegration and error correction framework using the bounds test for cointegration. In addition to the real effective exchange rate and real GDP, in alternative specifications we examine the effect of population growth and world petroleum prices on import demand in Brunei Darussalam. We find that in both the long-run and short-run aggregate imports are inelastic with respect to income and world petroleum prices, but are price-elastic and elastic with respect to population.
A NOTE ON THE FUTURE POPULATION OF SINGAPORE RESIDENTS
Authors: WONG YOKE WAI , BALASOORIYA UDITHA , TAN KHYE CHONG
Published: October 2005

This paper examines the population trends in Singapore over the next 50 years. The component method is employed in the projection calculations. The aging of Singapore's resident population is well-known. The projections show that the Singaporean population will reach a maximum of about 3.63 million in the year 2025 before steadily declining to reach 3.32 million by the year 2050. The population projections were also done in terms of gender and ethnic groups. Dependency ratios, weighted and unweighted were also calculated assuming different retirement ages. Remarks on some policy implications of these projections are provided.
A SOLUTION TO THE COSMOLOGICAL CONSTANT PROBLEM
Authors: TRIAY ROLAND
Published: October 2005

According to general relativity, the present analysis shows on geometrical grounds that the cosmological constant problem is an artifact due to the unfounded link of this fundamental constant to vacuum energy density of quantum fluctuations.
CONSTRAINT ON INTERMEDIATE-RANGE GRAVITY FROM EARTH–SATELLITE AND LUNAR ORBITER MEASUREMENTS, AND LUNAR LASER RANGING
Authors: LI GUANGYU , ZHAO HAIBIN
Published: October 2005

In the experimental tests of gravity, there have been considerable interests in the possibility of intermediate-range gravity. In this paper, we use the earth–satellite measurement of earth gravity, the lunar orbiter measurement of lunar gravity, and lunar laser ranging measurement to constrain the intermediate-range gravity from λ = 1.2 × 107 m –3.8 × 108 m . The limits for this range are α = 10-8–5 × 10-8, which improve previous limits by about one order of magnitude in the range λ = 1.2 × 107 m –3.8 × 108 m .
SYMMETRIES OF LOCALLY ROTATIONALLY SYMMETRIC MODELS
Authors: SHARIF M.
Published: October 2005

Matter collineations of locally rotationally symmetric space–times are considered. These are investigated when the energy–momentum tensor is degenerate. We know that the degenerate case provides infinite dimensional matter collineations in most of the cases. However, an interesting case arises where we obtain proper matter collineations. We also solve the constraint equations for a particular case to obtain some cosmological models.
AN IMPROVED MODEL FOR THE MULTIPLICITY FUNCTION
Authors: DEL POPOLO ANTONINO
Published: October 2005

I compare the numerical multiplicity function given in Ref. 35 with the theoretical multiplicity function obtained by means of the excursion set model and an improved version of the barrier shape obtained in Ref. 7, which implicitly takes account of total angular momentum acquired by the proto-structure during evolution and of a non-zero cosmological constant. I show that the multiplicity function obtained in the present paper is in better agreement with the simulations of Yahagi, Nagashima and Yoshii35 than other previous models16,29–31 and that unlike some previous multiplicity function models16,35 it was obtained from a sound theoretical background.
A DYNAMICAL SYMMETRY OF THE QUASI-SPHERICAL (OR SPHERICAL) COLLAPSE
Authors: DEBNATH UJJAL , CHAKRABORTY SUBENOY , DADHICH NARESH
Published: October 2005

By linearly scaling the initial data set (mass and kinetic energy functions), it is found that the dynamics of quasi-spherical (or spherical) collapse remains invariant for dust or a general (Type I) matter field, provided the comoving radius is also appropriately scaled. This defines a symmetry of the quasi spherical (or spherical) collapse. That is, the linear transformation identifies an equivalence class of data sets which lead to the same end result as well as its evolution all through. In particular, it is shown that the physical parameters, density and shear remain invariant. What the transformation is exhibiting is an interesting scaling relationship between mass, kinetic energy and the size of the collapsing sphere which is respected not only by the initial data set but remarkably also by the dynamics of collapse.
INFLATIONARY UNIVERSE WITH TACHYON FIELD
Authors: PAUL B. C. , PAUL D.
Published: October 2005

We present an inflationary solution of the early universe considering tachyon field. The technique of Zhuravlev and Chervon to obtain inflationary cosmological models without restrictions on a scalar field potential is employed here. We note that like the scalar field, the inflationary solution obtained here with tachyon field does not depend on the potential. However, unlike the scalar field, inflation with the tachyon field is obtained for restricted values of the field to begin with. We present the potential for which one gets inflation. Unlike the scalar field potential, the tachyonic potential is not regular at all values of the field. The solution obtained here with tachyon field is new.
A LITERATURE-BASED INNOVATION OUTPUT ANALYSIS: IMPLICATIONS FOR INNOVATION CAPACITY
Authors: ALEGRE JOAQUÍN , CHIVA RICARDO , LAPIEDRA RAFAEL
Published: October 2005

This study aims to contribute to a better understanding of the innovative profile in products, an analysis of which focuses on the type of product novelty and on the degree of complexity. Spanish ceramic tile producers' innovative profile was analysed by means of an empirical study employing LBIO indicator methodology. Results show that firms that have launched more new products, that is, firms with more experience in product innovation, have a greater capacity for developing novel and complex products.
Secularizing Interreligious Law in Egypt
Authors: Berger Maurits
Published: October 2005

Among the fifteen recognized Muslim, Christian and Jewish communities in contemporary Egypt, nine religious family laws are applicable. There is no civil or secular marriage: the creed of the individual Egyptian determines which family law is applicable. The question as to which law applies when the spouses are of different religions is answered by the so-called interreligious rules that determine which law prevails. According to Egyptian legal doctrine, these interreligious rules are based on Islamic law and, in particular, the prevailing opinion of Hanafi legal doctrine. In this article it will be shown that the legal reforms of 1955 have created substantial changes, not of, but within the framework of Egyptian interreligious law. These developments illustrate how Egyptian law formally adheres to the legacy of Islamic law, but allows for new albeit unobtrusive interpretations of Islamic law that are of a secular rather than religious nature.
The IMPROVE-1 Storm of 1–2 February 2001. Part I: Development of a Forward-Tilted Cold Front and a Warm Occlusion
Authors: Locatelli John D. , Stoelinga Mark T. , Garvert Matthew F. , Hobbs Peter V.
Published: October 2005

Analysis of observations and the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) are used to study the development of a forward-tilted cold front off the coast of Washington State. The vertical velocity associated with the cold front produced a wide cold-frontal rainband. In the early stage of development the midtropospheric baroclinic zone (or upper cold front) moved forward with time over the warm sector to produce a structure similar to a split front. The movement of the upper cold front was due to horizontal transport and frontogenetical propagation. The frontogenetical propagation was produced by a combination of tilting and diabatic frontogenesis, which resulted in a negative/positive couplet of frontogenesis straddling the baroclinic zone.

The lower-tropospheric cold front eventually caught up with the warm front to form a classical warm occlusion. In the initial occluding process the converging frontal zones tilted into a warm-type occlusion configuration due to the presence of a background vertical shear of the horizontal wind component perpendicular to the occluded front. Consequently, as the storm moved over the observing network, the occluded front had the structure of a warm occlusion (tilted forward) in the lower levels. Above the occlusion, the cold front was also tilted forward because it retained its split-front-like structure. Thus, the development of the split front and the warm occlusion were separate processes that occurred in sequence.

Although the MM5 captured the basic forward tilt with time of the cold front, some key aspects of the midtropospheric frontal structure were not well simulated. Because diabatic heating was an important contributor to the maintenance and movement of the upper cold front, it is hypothesized that discrepancies in diabatic heating associated with deficiencies in the model’s explicit microphysical scheme may be responsible for deficiencies in reproducing the structure of the upper cold front.
The 13–14 December 2001 IMPROVE-2 Event. Part I: Synoptic and Mesoscale Evolution and Comparison with a Mesoscale Model Simulation
Authors: Garvert Matthew F. , Colle Brian A. , Mass Clifford F.
Published: October 2005

This paper describes the large-scale synoptic and mesoscale features of a major precipitation event that affected the second Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE-2) study area on 13–14 December 2001. The fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) was used to simulate both the synoptic and mesoscale features of the storm. Extensive model verification was performed utilizing the wealth of observational assets available during the experiment, including in situ aircraft measurements, radiosondes, radar data, and surface observations.

The 13–14 December 2001 storm system was characterized by strong low-level cross-barrier flow, heavy precipitation, and the passage of an intense baroclinic zone. The model realistically simulated the three-dimensional thermodynamic and kinematic fields, the forward-tilted vertical structure of the baroclinic zone, and the associated major precipitation band. Deficiencies in the model simulations included an attenuated low-level jet accompanying the middle-level baroclinic zone and the lack of precipitation associated with the surface front; NOAA P-3 aircraft in situ data indicated that the model required 1.33-km grid spacing to capture realistically the complex mesoscale forcing related to terrain features. Despite the relatively skillful portrayal of mesoscale and synoptic structures, the model overpredicted precipitation in localized areas on the windward slopes and over a broad area to the lee of the Oregon Cascades.
Mesoscale Variability and Drizzle in Southeast Pacific Stratocumulus
Authors: Comstock Kimberly K. , Bretherton Christopher S. , Yuter Sandra E.
Published: October 2005

Observations from the East Pacific Investigation of Climate (EPIC) 2001 field campaign are well suited for exploring the relationships among the diurnal cycle, mesoscale (10–100 km) structure, and precipitation in the stratocumulus region in the southeast Pacific. Meteorological time series and observations from a scanning C-band radar, vertically pointing cloud radar, and ceilometer, as well as satellite data, are used to show that drizzle is associated with increased variability in cloud and boundary layer properties compared to nondrizzling periods. The stratocumulus-topped boundary layer is typically well mixed at night, transitioning to less well mixed in the afternoon, with drizzle most frequently occurring in the early morning. Coherent patches of drizzle, or “cells,” can have large areas with radar reflectivities of greater than 5 dBZ of up to about 100 km2. Individual cells have long lifetimes, up to 2 h, and appear to be replenished by moisture in the boundary layer.
A Method to Improve Prediction of Atmospheric Flow Transitions
Authors: Roebber P. J. , Tsonis A. A.
Published: October 2005

Ensemble prediction has become an indispensable tool in weather forecasting. One of the issues in ensemble prediction is that, regardless of the method, the prediction error does not map well to the underlying physics (i.e., error estimates do not project strongly onto physical structures). This paper is driven by the hypothesis that prediction error includes a deterministic component, which can be isolated and then removed, and that removing the error would enable researchers and forecasters to better map the error to the physics and improve prediction of atmospheric transitions. Here, preliminary experimental evidence is provided that supports this hypothesis. This evidence is provided from results obtained from two low-order but highly chaotic systems, one of which incorporates atmospheric flow transitions. Using neural networks to probe the deterministic component of forecast error, it is shown that the error recovery relates to the underlying type of flow and that it can be used to better forecast transitions in the atmospheric flow using ensemble data. A discussion of methods to extend these ideas to more realistic forecast settings is provided.
Effect of Synoptic Systems on the Variability of the North Atlantic Oscillation
Authors: Löptien Ulrike , Ruprecht Eberhard
Published: October 2005

The North Atlantic Oscillation (NAO) represents the dominant mode of atmospheric variability in the North Atlantic region. In the present study, the role of the synoptic systems (cyclones and anticyclones) in generating the NAO pattern is investigated. To study the intermonthly variations of the NAO, NCEP–NCAR reanalysis data are used, and for the interdecadal variations the results of a 300-yr control integration under present-day conditions of the coupled model ECHAM4/OPYC3 are analyzed. A filtering method is developed for the sea level pressure anomalies. Application of this method to each grid point yields the low-frequency variability in the sea level pressure field that is due to the synoptic systems. The low-frequency variability of the filtered and the original data are in high agreement. This indicates that the low-frequency pressure variability, and with it the variability of the NAO, is essentially caused by the distribution of the synoptic systems. The idea that the distribution of the synoptic systems is the cause of the variation of the NAO is confirmed by high correlation between the latitudinal position of the polar front over the North Atlantic and the NAO index. Since most of the low-frequency variability in sea level pressure can be explained through the distribution of the synoptic systems, the NAO seems to be a reflection of the distribution of the synoptic systems, rather than the source for variations in the cyclone tracks.