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Gamma-Ray Burst (GRB) prompt emission can, for specific conditions, be so powerful and short-pulsed to strongly influence any surrounding plasma. In this paper, we briefly discuss the possibility that a very intense initial burst of radiation produced by GRBs satisfy the intensity and temporal conditions to cause stochastic wake-field particle acceleration in a surrounding plasma of moderate density. We consider a simple but realistic GRB model for which particle wake-field acceleration can first be excited by a very strong low-energy precursor, and then be effective in producing the observed prompt X-ray and gamma-ray GRB emission. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Suzaku Wide-band All-sky Monitor (WAM), realized by large thick anti-coincidence shields of the Hard X-ray Detector (HXD), can be powerful gamma-ray burst (GRB) detector which is sensitive to 50–5000 keV gamma-rays. The WAM is now in a full operational phase, and we have already detected some GRBs simultaneously with other satellites (Swift, Konus-Wind, HETE2 and INTEGRAL SPI/ACS). The most impressive event among detected GRBs is GRB051008, which was detected up to 2 MeV with the WAM. In this paper, we report on the WAM in-flight performance as a GRB monitor from initial three-months operations, focusing on the GRB trigger status and spectral analysis of GRB051008 and GRB051111 combined with Swift. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Swift Ultra-Violet/Optical Telescope (UVOT) has performed extensive follow-up on 71 Swift Burst Alert Telescope triggered gamma-ray bursts (GRBs) in its first ten months of operations. In this paper, we discuss some of the UV and optical properties of UVOT detected afterglows such as XRF 050406, the bright GRB 050525A, the high redshift GRB 050730, the early flaring GRB 050801, and others. We also discuss some of the implications of why 75% of GRB afterglows observed by UVOT in less than one hour are “dark.” © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The GLAST Large Area Telescope (LAT) is the next generation satellite experiment for high-energy gamma-ray astronomy. It is a pair conversion telescope built with a plastic anticoincidence shield, a segmented CsI electromagnetic calorimeter, and the largest silicon strip tracker ever built. It will cover the energy range from 30 MeV to 300 GeV, shedding light on many issues left open by its predecessor EGRET. One of the most exciting science topics is the detection and observation of gamma-ray bursts (GRBs). In this paper we present the work done so far by the GRB LAT science group in studying the performance of the LAT detector to observe GRBs. We report on the simulation framework developed by the group as well as on the science tools dedicated to GRBs data analysis. We present the LAT sensitivity to GRBs obtained with such simulations, and, finally, the general scheme of GRBs detection that will be adopted on orbit. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this paper, we describe a numerical method to model aperture structures and flow paths in single rock fractures based on actual fracture surface geometries and actual fracture permeability. Fracture surfaces were measured using a CCD laser displacement sensor (resolution: 10 μm) with 250 μm square mesh for 100 mm × 150 mm single tensile fractures in granite samples. Fracture permeability was also measured under 10–100 MPa confining pressure conditions. Aperture structures and flow paths were modeled numerically using the actual fracture surface geometries so that the model’s permeability consistent with actual fracture permeability. Channeling flows were clearly observed at all conditions because of heterogeneous aperture structures. The results also suggested that fracture permeability could be overestimated if based on the conventional parallel plate model using an arithmetic mean value of local apertures. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

New method for noncontact measurements of shear elasticity and viscosity variations of soft materials with microstructure is proposed in the report. This method based on the analysis of amplitude-frequency response of a specially designed active tuning fork. A simple theoretical model is developed. Experimental researches were carried out on samples of biological tissues (bovine heart and liver) in vitro. The results demonstrate sensitive of the method to shear elasticity and viscosity changes, which arise in soft tissues under influence of ultrasound. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The quality of the dimuon measurements made by NA60, in proton-nucleus and heavy-ion collisions, is much better than that reached by previous experiments, such as NA38 and NA50. The most important improvement is due to the use of a radiation-tolerant silicon vertex telescope, placed immediately downstream of the target. This allows NA60 to do a high quality measurement of [lowercase_phi_synonym] meson yields and pT distributions. This paper presents results obtained in p-Be, p-In and p-Pb collisions at 400 GeV, from data collected in 2002, and in In-In collisions at 158 AGeV, as a function of centrality, from the 2003 running period. In particular, we show that the inverse mT slope measured in In-In collisions, in the [lowercase_phi_synonym] → μμ decay channel, increases with the number of nucleons participating in the collisions, rather than following a flat trend as seen in the NA50 data collected in the same decay channel but restricted to high pT values. We also show that our measurements seem to agree with the values previously measured by NA49, using [lowercase_phi_synonym] → KK decays, in Pb-Pb and other collision systems. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this paper we present a proof of the Hecke quantum unique ergodicity conjecture for the Berry-Hannay model, a model of quantum mechanics on a two dimensional torus. This conjecture was stated in Z. Rudnick’s lectures at MSRI, Berkeley, 1999 and ECM, Barcelona, 2000. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this paper we introduce a framework that can be used to categorize instructional practices. We then use this framework to identify areas where mainstream Physics Education Research (PER) has embraced alternative ideas and areas where mainstream PER is more traditional. As an example we argue that while PER has embraced the practice of interactivity, it has neglected the practice of student autonomy. This is despite student autonomy being consistent with the goals of PER and being supported by research in other fields. We offer insights and implications based on this analysis. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Despite significant documentation and rigorously controlled conditions, most research involving extraordinary human-generated phenomena (e.g. remote viewing, teleportation, etc.) has focused either upon the observation of the macro-phenomena itself, or cumulative statistical deviation from chance. This paper, however, examines the influences upon and augmentation of ambient gravitational and geomagnetic fields, a previously unobserved and unrecognized concomitant physics phenomenon during activities requiring singular and total concentration. Utilizing simple field measurement instrumentation, original experimental data is presented, discussed, and compared with controlled baselines. Whereas some previous research has examined the influence of ambient fields upon human subjects, published literature is sparse concerning the influence of human subjects specifically upon ambient fields. As well, research that rigorously pursued the study of the effects of indirect human interference on engineering instrumentation did not consider ambient fields for experimental control, perhaps limiting potential theoretical modeling and integration. The presented empirical data demonstrates that gravitational and geomagnetic field augmentation occurring during such all-consuming activity is neither incidental nor subtle and may well be a worthy consideration for modeling frontier scientific theories and expanding current physics paradigms. Insomuch as natural, human-generated phenomena currently stand as the most accessible and repeatable examples of anomalous environmental interactivity, this data and suggested research protocols presented offer exploratory perspectives for observing the underlying scientific principals and physics concepts of ambient field interface as well as potential applications in developing more effective theoretical models for frontier space science. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In relativity, two simultaneous events at two different places are not simultaneous for observers in different Lorentz frames. In the Einstein-Podolsky-Rosen experiment, two simultaneous measurements are taken at two different places. Would they still be simultaneous to observers in moving frames? It is a difficult question, but it is still possible to study this problem in the microscopic world. In the hydrogen atom, the incertainty can be considered to be entirely associated with the groundstate. However, is there an uncertainty associated with the time-separation variable between the proton and electron? This time-separation variable is a forgotten, if not hidden, variable in the present form of quantum mechanics. The first step toward the simultaneity problem is to study the role of this time-separation variable in the Lorentz-covariant world. It is shown possible to study this problem using harmonic oscillators applicable to hadrons which are bound states of quarks. It is also possible to derive consequences that can be tested experimentally. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper makes an attempt to present Quantum Mechanics in simple terms, but without oversimplification. It will be in essence, a comparison of the usual understanding of randomness to the more difficult notion of “quantumness.” The restricted format of this paper will unfortunately force the presentation to be very terse. But perhaps this paper can be seen as a synopsis of the approach I have in mind. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A thermionic cusp gun is proposed for use in a 3 MW second harmonic X-band gyro-TWA with a helically corrugated waveguide interaction region. The passage of an electron beam through a non-adiabatic magnetic field reversal converts part of the electron beam’s axial velocity into axis-encircling transverse velocity. The paper presents the design and simulation of this cusp-based electron gun, yielding a 12 MW, 81.5 A axis-encircling beam with an axial velocity spread Δvz < 15% suitable for use in harmonic gyro-devices. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Supersymmetric U(NC) gauge theory with NF massive hypermultiplets in the fundamental representation admits various BPS solitons like domain walls and their webs. In the first part we show as a review of the previous paper that domain walls are realized as kinky fractional D3-branes interpolating between separated D7-branes. In the second part we discuss brane configurations for domain wall webs. This is a contribution to the conference based on the talk given by MN. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This work is primary interested in the problem of, given the observed data, selecting a single decision (or classification) tree. Although a single decision tree has a high risk to be overfitted, the induced tree is easily interpreted. Researchers have invented various methods such as tree pruning or tree averaging for preventing the induced tree from overfitting (and from underfitting) the data. In this paper, instead of using those conventional approaches, we apply the Bayesian evidence framework of Gull, Skilling and Mackay to a process of selecting a decision tree. We derive a formal function to measure ‘the fitness’ for each decision tree given a set of observed data. Our method, in fact, is analogous to a well-known Bayesian model selection method for interpolating noisy continuous-value data. As in regression problems, given reasonable assumptions, this derived score function automatically quantifies the principle of Ockham’s razor, and hence reasonably deals with the issue of underfitting-overfitting tradeoff. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper proposes a novel method for Blindly Separating unobservable independent component (IC) Signals (BSS) based on the use of a maximum entropy guide (MEG). The paper also includes a formal proof on the convergence of the proposed algorithm using the guiding operator, a new concept in the genetic algorithm (GA) scenario. The Guiding GA (GGA) presented in this work, is able to extract IC with faster rate than the previous ICA algorithms, based on maximum entropy contrast functions, as input space dimension increases. It shows significant accuracy and robustness than the previous approaches in any case. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

In many practical situations it is common to have information about the values of the mean and range of certain population. In these cases it is important to specify the population distribution from the given values of its mean and range. The article by de Alba, Fernández-Durán and Gregorio-Domínguez (2004) includes a bibliography with articles dealing with the case of making inference about the mean and standard deviation of a normal population in terms of the observed sample mean and range. In this paper, the maximum entropy principle is used to specify the population distribution given its mean and range. This problem has the particular difficulty that it is necessary to determine the unknown support of the maximum entropy distribution given its length which is equal to the specified value of the range. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Large production of the cc pairs and high integrated luminosity make the PEP-II B Factory an excellent place for studying the charm hadrons. In this paper, we present a few of the most recent results from the BABAR collaboration in the charm sector. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper reviews the most recent findings of the laboratory experiment which address the local physics of magnetic reconnection, and related physics issues. In particular, physics analysis of the experimental data from Magnetic Reconnection Experiment (MRX) based on the one-fluid MHD and the two-fluid MHD formulations are comparatively highlighted. Major results are: (1) Reduced magnetic reconnection rate measured with externally applied guide field, (2) Experimental verification of Hall MHD effects in the Harris-type neutral sheet, with the width comparable to the ion skin depth, during magnetic reconnection, (3) Recognition of correlation between magnetic turbulence and reconnection rate, and (4) Discussions with regard to scalings for magnetic reconnection observed in MRX, particularly on the transition from the collisional to the collisionless regime. This paper also briefly discusses the basic goals and approaches of the new initiatives to study magnetic reconnection as a part of magnetic self-organization phenomena, a common frontier of both laboratory and space astrophysics research. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

As silicon CMOS technology approaches its limits, new device structures and computational paradigms will be required to replace and augment standard CMOS devices for ULSI circuits. The extreme sensitivity of the electronic properties of these devices to their nanoscale physical properties defines a significant need for precise metrology. This paper provides an overview of the characterization requirements for these technologies. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper reports on the influence of the gate length reduction on the noise performance of strained-Si surface channel MOSFETs for very low power applications. When the gate length is reduced from 100nm to 20nm an increase of the current gain is achieved that nearly doubles the cut-off frequency of the transistor. This is counterbalanced by a deterioration of the noise figure and the noise resistance of the device for low values of the drain current. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The hydroforming process of a double conical tube with the biggest difference of cross-section 75 percent is studied by means of FE simulation in this paper. The effects of loading paths during hydroforming process on the wrinkle shape and failure modes are analyzed. Thickness distribution and strain path of position with the biggest expansion rate on FLD diagram of this workpiece are given. The simulation results show that the part can be formed successfully with the feeding pressure selected in the range from 20 to 25MPa. When the feeding pressure is 23MPa, the preform with desirable wrinkle distribution and plenty storage of materials can be obtained. The maximum of thinning rate by the simulation is about 18.29 percent, which is close to 19.54% that is obtained in experiment. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this paper we investigate the formability of multiphase steels. A new model based on crystal plasticity has been developed to investigate large strain phenomena in multiphase steels. The approach is based on the concept of a unit cell. The unit cell is defined as a globally small region of the sheet that contains all the essential micro-structural and textural features that characterize the sheet. Orientations within the measured texture data are randomly assigned in the mesh/unit cell. In other words, each element of the mesh represents an orientation from the measured texture and the constitutive response at a material point is given by the single crystal constitutive model. This model is employed to construct forming limit diagrams for multiphase steels. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper summarizes and presents the most important results from a research project on FE simulation of hemming carried out at Volvo Cars Body Components and Chalmers University of Technology. In the automotive industry, hemming is used to join two sheet metal panels by bending the flange of the outer panel over the inner one. The final goal of the project was to simulate all of the hemming steps of production parts. In order to make three-dimensional simulations of hemming possible within reasonable simulation times, it is necessary to use shell elements and not solid elements. On the other hand, the radius of curvature of the outer part in the folded area is very small, normally of the same order of magnitude as the sheet thickness. This fact raises the question if shell elements are applicable in FE simulation of hemming. One part of the project was therefore a thorough investigation of the order of magnitude of the errors resulting from the use of shell elements in FE simulation of hemming. Another part of the project was devoted to three-dimensional simulations of the hemming of an automotive hood. The influence on the roll-in from several parameters, such as shell element formulation, adhesives, and anisotropy was studied. Finally, results from a forming simulation were also mapped to the flanging and hemming models in order to study the influence from the stamping of the outer panel on the roll-in. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Advanced High Strength Steels (AHSS) are currently being considered for use in closure and structural panels in the automotive industry because of their high potential for affordable weight reduction and improved performance. AHSS such as dual phase steels are currently being used in some vehicle platforms. From a manufacturing perspective, stretch flanging during stamping is an important deformation mode requiring careful consideration of geometry and the die process. This paper presents some geometric and process guidelines for stretch flanging AHSS. Hole expansion experiments were conducted to determine the failure limit for a sheared edge condition. Effects of punching clearance, prestrain and prior strain path on hole expansion were explored in these experiments. In addition, dynamic explicit FE calculations using LS-DYNA were also conducted for a typical stretch flange by varying some key geometric parameters. The experimental and FEA results were then analyzed to yield process and geometric guidelines to enable successful stretch flanging of AHSS. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Meshfree methods have been well recognized for their capability of delivering high solution accuracy for large strain problems. To make the methods available for manufacturing applications, over the past two years we have further developed the Element-Free-Galerkin-based meshfree shell formulation for better solution accuracy and computation efficiency, and implemented the method into the commercial solver, LS-DYNA. This paper presents the application of the meshfree shell formulation in the study of NUMISHEET 2005 benchmark testing example, that is, forming analysis of an automotive decklid inner panel. Both the physical drawbead geometry and its effective line bead model are considered in the simulations to study the effect of different drawbead modeling schemes on the accuracy of the forming analysis. The meshfree simulations are compared with the best available finite element analysis in terms of solution accuracy. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Nuclear data needs can play an important role for innovative nuclear systems. However, in order to establish priority items, a systematic sensitivity/uncertainty analysis must be performed. Same selected examples will be discussed in this paper. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this paper, I illustrate how the ability to rapidly access the broad range of nuclear data has facilitated my research in fields from searches for double beta decay, to measurements of astrophysical reaction rates, to issues in homeland security. In doing this, I hope to persuade even the skeptics that for the benefit of the broad scientific community, it is imperative that the outstanding work of the nuclear data community continue. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper broadly covers key events and activities from which the Department of Energy Nuclear Criticality Safety Program (NCSP) evolved. The NCSP maintains fundamental infrastructure that supports operational criticality safety programs. This infrastructure includes continued development and maintenance of key calculational tools, differential and integral data measurements, benchmark compilation, development of training resources, hands-on training, and web-based systems to enhance information preservation and dissemination. The NCSP was initiated in response to Defense Nuclear Facilities Safety Board Recommendation 97-2, Criticality Safety, and evolved from a predecessor program, the Nuclear Criticality Predictability Program, that was initiated in response to Defense Nuclear Facilities Safety Board Recommendation 93-2, The Need for Critical Experiment Capability. This paper also discusses the role Dr. Sol Pearlstein played in helping the Department of Energy lay the foundation for a robust and enduring criticality safety infrastructure. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The US Nuclear Data Program maintains and provides easy and free access to several comprehensive databases that assist scientists to sift through and assess the vast quantity of published nuclear structure and decay data. These databases are an invaluable asset for nuclear-science experimentalists and theorists alike, and the recommended values provided for nuclear properties such as decay modes, level energies and lifetimes, and radiation properties can also be of great importance to specialists in other fields such as medicine, geophysics, and reactor design. The Evaluated Nuclear Structure Data File (ENSDF) contains experimental nuclear structure data for all known nuclides, evaluated by the US nuclear data program evaluators in collaboration with a number of international data groups; the Nuclear Science Reference (NSR) database provides complementary bibliographic information; the Experimental Unevaluated Nuclear Data Listing (XUNDL) exists to enable rapid access to experimental nuclear-structure data compiled from the most recent publications (primarily in high-spin physics). This paper presents an overview of the nuclear structure and decay data available through these databases, with emphasis on recent and forthcoming additions to and presentations of the available material. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Interest in nuclear data uncertainties is growing robustly after having languished for several years. Renewed attention to this topic is being motivated by the practical need for assuring that nuclear systems will be safe, reliable, and cost effective, according to the individual requirements of each specific nuclear technology. Furthermore, applications are emerging in certain areas of basic nuclear science, e.g., in astrophysics, where, until recently, attention has focused mainly on understanding basic concepts and physics principles rather than on dealing with detailed quantitative information. The availability of fast computers and the concurrent development of sophisticated software enable nuclear data uncertainty information to be used more effectively than ever before. For example, data uncertainties and associated methodologies play useful roles in advanced data measurement, analysis, and evaluation procedures. Unfortunately, the current inventory of requisite uncertainty information is rather limited when measured against these evolving demands. Consequently, there is a real need to generate more comprehensive and reasonable nuclear data uncertainty information, and to make this available relatively soon in suitable form for use in the computer codes employed for nuclear analyses and the development of advanced nuclear energy systems. This conference contribution discusses several conceptual and technical issues that need to be addressed in meeting this demand during the next few years. The role of data uncertainties in several areas of nuclear science will also be mentioned briefly. Finally, the opportunities that ultimately will be afforded by the availability of more extensive and reasonable uncertainty information, and some technical challenges to master, will also be explored in this paper. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The DSMC method is currently one of the main tools for studying the hypersonic chemically reacting rarefied flows. New models of the DSMC method are permanently developed for a more detailed description of physical and chemical processes in gases. Their implementation into the existing DSMC codes, however, is rather difficult. The promising way of overcoming these difficulties is to develop object-oriented DSMC codes that can be readily modified to include the new models. The present paper deals with the development of the structure of objects of a new object-oriented DSMC code including a database of physicochemical properties of gases. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

It is known that the chemical elements and their isotopes were created by nuclear fusion reactions in the hot interiors of remote and long-vanished stars over many billions of years. The present picture is that all elements from carbon to uranium have been produced entirely within stars during their fiery lifetimes and explosive deaths. The detailed understanding of the origin of the chemical elements and their isotopes combines astrophysics and nuclear physics, and forms what is called nuclear astrophysics. In turn, nuclear reactions are at the heart of nuclear astrophysics: they influence sensitively the nucleosynthesis of the elements in the earliest stages of the universe and in all the objects formed thereafter, and control the associated energy generation, neutrino luminosity, and evolution of stars. A good knowledge of the rates of these fusion reactions is essential to understanding this broad picture. Some of the most important experimental techniques to measure the corresponding cross sections, based both on direct and indirect methods, will be described in this paper. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper describes the use of a Finite Element code for modeling the effects of weak interfaces on the propagation of low order Lamb modes. The variable properties of the interface are modeled by uniform repartitions of compression and shear springs that insure the continuity of the stresses and impose a discontinuity in the displacement field. The method is tested by comparison with measurements that were presented in a previous QNDE conference (B.W.Drinkwater, M.Castaings, and B.Hosten “The interaction of Lamb waves with solid-solid interfaces”, Q.N.D.E. Vol. 22, (2003) 1064–1071). The interface was the contact between a rough elastomer with high internal damping loaded against one surface of a glass plate. Both normal and shear stiffnesses of the interface were quantified from the attenuation of A0 and S0 Lamb waves caused by leakage of energy from the plate into the elastomer and measured at each step of a compressive loading. The FE model is made in the frequency domain, thus allowing the viscoelastic properties of the elastomer to be modeled by using complex moduli as input data. By introducing the interface stiffnesses in the code, the predicted guided waves attenuations are compared to the experimental results to validate the numerical FE method. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper presents the second part of the review of Nonlinear Elastic Wave Spectroscopy (NEWS) in NDE, and describe two different methods of nonlinear NDE that provide not only damage detection but location as well. Nonlinear Wave Modulation Spectroscopy is based on the application of an ultrasonic probe signal modulated by a low frequency vibration. Damage location can be obtained by application of Impulse Modulation Techniques that exploit the modulation of a short pulse reflected from a damage feature (e.g. crack) by low frequency vibration. Nonlinear Time Reversed Acoustic methods provide the means to focus acoustic energy to any point in a solid. In combination, we are applying the focusing properties of TRA and the nonlinear properties of cracks to locate them. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Early detection of corrosion precursor pitting and estimation of its overall dimensions directly affects the required effort and cost associated with repair and maintenance of critical aircraft structural components. The magnitude and phase of a reflected signal from a pitting are directly related to its dimensions. This paper presents a millimeter wave probe and a sizing procedure used to detect and evaluate overall pitting dimensions. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Eddy current testing (ECT) probe consisted of spin-valve giant magneto-resistance (SV-GMR) sensor and meander type exciter coil applied to printed circuited board (PCB) conductor dimension and alignment inspection is proposed in this paper. High-frequency excitation up to 18 MHz is allowed to inspect the thin PCB conductor, less than 10 μm. The proposed ECT probe characteristics and configuration were presented. The inspection results were shown that the proposed ECT probe will provide an accurate inspection. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

With magnetic methods of testing, a magnetic field is induced inside the object being tested and any resulting changes of magnetic flux in the region of interest are observed. In this paper we consider the magnetic field excitation by using an electromagnet yoke, operated by DC and with adjustable distance between the pole-pieces of the yoke. The sensitivity of detection for any portion of a component being tested varies with the distance between the pole pieces and, hence, the choice of the distance is of great importance. Simplified theoretical analysis as well as results of measurements for steel plates are given. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

C-scan data obtained from multifrequency eddy current inspection are smeared representations of true flaws due to finite size of inspection probes. Deconvolution algorithms are commonly used to remove the effect of finite probe size and estimate the true flaw footprint. Single frequency blind deconvolution techniques are insufficient to correctly determine the true flaw footprint since single frequency eddy current inspection does not provide sufficient information about a flaw. This paper proposes a blind deconvolution algorithm that estimates the flaw footprint by using complementary information present across multifrequency eddy current inspection data. Initial results of applying the algorithm to steam generator tubing inspection data indicate the feasibility and robustness of the proposed algorithm. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper introduces a Directional Filter Bank (DFB) for segmentation of C-Scan images from fiber-reinforced composites. The DFB is a two-channel decomposition employing the Quincunx sampling matrix and the Diamond Half Band filter pair. The incident ultrasonic field on a fiber-reinforced composite is backscattered by the fibers leading to the appearance of a characteristic pattern (oriented along the fiber direction) in the C-Scan image. The fiber pattern can cloud the defects, such as delaminations etc, thus making their detection difficult. The DFB is a sub-band coding technique that has been applied to segment the fiber pattern from the defect features in the C-Scan image of the composite. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The energy of ultrasonic guided waves may be focused in pipes by utilizing a partially loaded excitation. This focusing technique is called “natural focusing”, which can be used to improve a defect’s sensitivity to ultrasonic guided waves. However, it is possible that there are a few natural focal points within the inspection range at a particular frequency. Consequently, some defects could be missed. The location of the natural focal points, however, changes with frequency. This phenomenon was theoretically predicted and experimentally confirmed. In this paper, the natural focusing inspection technique is investigated. Although a very limited circumferential length might be covered by a naturally focused profile at a single excitation frequency, the entire cross sectional area of the pipe can be inspected when a range of frequencies is employed. Hence, the natural focusing inspection technique can sufficiently inspect the entire pipe with frequency tuning. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Efficient structural health monitoring using Lamb waves requires a clear understanding of the wave phenomena involved. In this paper wave phenomena are studied by a non-contact detection technique using a modified Laser vibrometer. Collected data are stored in a computer and animated after the measurement. Having already studied the generation and defect interaction of elastic waves in isotropic plates this paper deals with waves in Carbon Fiber Reinforced Plastics (CFRP) as example of an anisotropic material of increasing practical importance. Effects due to acoustic anisotropy and dispersion were found. The interaction of different wave modes with impact flaws is visualized. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The CIVA software developed at the French Atomic Energy Commission for processing and simulating NDT data (ultrasonics, eddy-current) includes tools for simulating the whole inspection of a component in which virtual defects are positioned. In this paper, the Kirchhoff’s approximation is applied and the reciprocity principle predicts the reception by transducers of waves scattered by defects. Simulated results are compared to experimental data for the various problems of the 2004 UT benchmark session. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Motivated by the desire to reduce the time and costs and to improve the accuracy of POD studies, there is an increasing interest in incorporating information from physics-based models of flaw response. This paper will concentrate on the case of internal defects. As compared to surface-breaking fatigue cracks, internal defects, generally inclusions or voids, have a 3-dimensional shape and are hard to simulate in simple fabricated reference samples. Hence, empirical studies pose many problems. This paper will summarize experiences in the development of Model-Assisted POD predictions. After an introduction to some of the fundamental issues, an approach of Model-Assisted POD determination will be introduced, supported by experience obtained in applications to the ultrasonic inspection of aircraft engine components and welds in pipelines. Attention will be paid to the interplay of information provided by the physics-based models and empirical measurements. Of particular importance for internal defects are the effects of flaw morphology and orientation, information that can significantly affect signal strength. Examples will be given regarding how models can be used to understand and quantify these effects. A distinction is noted between the POD that would be obtained in survey and characterization modes, and the importance of models in interpreting multiple pieces of information in the latter case is emphasized. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper describes a joint project by the Naval Research Laboratory (NRL) and Argonne National Laboratory (ANL), in collaboration with the StanFord Linear Accelerator Center (SLAC), to develop a dielectric-loaded accelerator (DLA) test facility powered by a high-power 11.424-GHz magnicon amplifier. The magnicon can presently produce 25 MW of output power in a 250-ns pulse at 10 Hz, and efforts are in progress to increase this to 50 MW. The facility will include a 5 MeV electron injector being developed by the Accelerator Laboratory of Tsinghua University in Beijing, China. The DLA test structures are being developed by ANL, and some have undergone testing at NRL at gradients up to ∼8 MV/m. SLAC is developing a means to combine the two magnicon output arms, and to drive an injector and accelerator with separate control of the power ratio and relative phase. RWBruce Associates, Inc., working with NRL, is developing a means to join short ceramic sections into a continuous accelerator tube by ceramic brazing using an intense millimeter-wave beam. The installation and testing of the first dielectric-loaded test accelerator, including injector, DLA structure, and spectrometer, should take place within the next year. The facility will be used for testing DLA structures using a variety of materials and configurations, and also for testing other X-band accelerator concepts. The initial goal is to produce a compact 20 MeV dielectric-loaded test accelerator. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Acoustic propagation experiments have been carried out in the Florida Straits with a multi-frequency broadband source that transmitted M-sequence pulses over a range of 10 km to a sparse-filled vertical line array. The sound source was cycled in octaves from 100 Hz to 3200 Hz, transmitting each octave for one hour. This paper presents results of matched field inversions of the acoustic field data to estimate geoacoustic model parameters for the experimental site. The inversion is very sensitive to the sediment sound speed at the sea floor. The estimated value of 1560 m/s is consistent with fine-grain calcareous sand material that is considered to represent ground truth for the site. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Rapid Geo-acoustic Characterization (RGC) algorithm was developed to perform geo-acoustic characterization using the interference patterns of surface ships of opportunity in shallow water. It has been applied successfully at low frequencies to synthetic inversion workshop data and at sea in near real-time. The RGC algorithm determines an effective sediment, which matches the slope (waveguide invariant) and spacing (reciprocal of the time -spread) of interference patterns as well as the fall off in range of the received level. In this paper, we evaluate the extension of the algorithm to mid and high-frequency acoustic signals in shallow water. The issues explored are the robustness of the waveguide invariant, time -spread and TL slope at frequencies above 2 kHz. The algorithm will be applied to a synthetic data example with a known bottom in a range-independent environment. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Time-reversal signal processing can be viewed as a form of matched filtering that operates both in time and in space. Acoustic communication represents a promising potential application of the processing. In designing a communications system, constraints are imposed by the available bandwidth and by the geometry of the time-reversal array. In the present paper, the interplay between bandwidth and array geometry is examined. If the bandwidth is large relative to the symbol rate, time-reversal processing can be successful with sparse arrays. If the array is well populated, the required bandwidth can be reduced. Results from experiments and data-driven simulations are presented. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper analyzes the environmental effect and signal processing approaches for frequency-hopped frequency-shift-keyed (FH FSK) underwater acoustic communications based upon data collected in two experiments: the RDS4 experiment near Halifax, Canada and MREA03 experiment near Elba, Italy. The FH FSK signals have a bandwidth of 4 kHz centered at 17 and 20 kHz. The source was lowed at ∼4 knots. The signals were received on a vertical line array anchored to the bottom. The acoustic environments at both sites have the same downward refractive sound speed profiles but very different bottom properties. The multipath spread last ∼20 msec in the MREA03 experiment and is > 1 sec in the RDS4 experiment. The different lengths of multipath delays have a significant effect on the bit error rate (BER) and the appropriate signal processing needed to reduce the BER. We present the data analysis results, the signal processing approaches, including multi-channel beamforming and spatial diversity combining, and discuss the implications for the use of FH-FSK for multi-user communications. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Acoustic detection for active sonars involves identifying target signatures in the presence of environmental effects, such as acoustic scattering from the ocean boundaries and fish. The Naval Research Laboratory has recently developed 3D broadband models that provide physics-based estimates of the dependence of scattering from the sea surface, bubble clouds and near-boundary fish (including boundary-interference effects) on the incident and scattered angles, and physical/biological descriptors of the environment. In this paper, these models and a surface-loss model are used as kernels in reverberation models, which in turn are used to assess the sensitivity at 3.5 kHz of long-range reverberation to environmental variables. It is shown that the acoustic field in shallow water waveguides could be quite sensitive to the values of sea surface (wind speed) and fish (density, size, depth) parameters, and that physics-based models are needed for accurate field characterization. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]