bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Channel Profile Engineering on Hot Carrier Reliability in nMOSFETs with 100 nm Channel Lengths
Authors: Saha Samar K. 
Published: June 2019

ABSTRACTHot-carrier effect was studied for different channel doping profiles in nMOSFET devices with effective channel length near 100 nm using a device simulator. The test structures for device simulation were generated using gate oxide thickness of 3 nm. The channel doping profiles used were abrupt- and graded-retrograde types with low surface and high substrate concentrations, and conventional step profiles with high surface and low substrate concentrations. For accurate device simulation, a hydrodynamic model for semiconductors was used to simulate the non-local transport phenomena in the devices. The simulation results indicate that for ultra-short channel devices, the current drivability and the hot-carrier effects depend on the shape of channel doping profiles. For a given supply voltage, the hot-carrier effects in ultra-short channel devices can be controlled by optimizing the channel doping profiles.
Stress-Recovery Transients in Ultra Thin Oxides on Silicon
Authors: Lundgren Per , Jauhiainen Anders , Ragnarsson Lars-Åke 
Published: June 2019

ABSTRACTThe logarithmic current transients observed after electrical stress of 2 nm thick oxides on silicon show no sign of saturation for times up to 1 Ms. These results contradict the hypothesis that the tunneling distance from oxide defects to an interface is the main source of the dispersive relaxation in our case, and this might very well extend to other cases where such relaxation is observed in MOS devices with thicker oxides.
Effects of Adhesion on the Measurement of Thin Film Mechanical Properties by Nanoindentation
Authors: Tsui T. Y. , Ross C. A. , Pharr G. M. 
Published: June 2019

ABSTRACTExperiments have been performed on soft aluminum films deposited on hard ceramic substrates to explore the influences of interfacial adhesion on mechanical property measurement by nanoindentation. The substrate materials included soda-lime silicate glass, aluminum oxynitride (ALON), and (100) sapphire. Thin films of high purity aluminum were sputtered onto each substrate to a thickness of 500 nm. Because the films were deposited simultaneously, the only major difference in the specimens was the nature of the substrate, which exerts an important influence on film adhesion through interfacial chemistry. Of the substrates examined, aluminum adheres strongly to glass and sapphire, but poorly to ALON. In addition, two different types of aluminum films on sapphire were examined - one with and the other without a 10 nm interlayer of amorphous carbon which significantly reduces film adhesion. Testing revealed important differences in the hardness of the specimens when measured by standard nanoindentation methods. Characterization of the residual hardness impressions by high resolution scanning electron microscopy showed that the hardness differences arise from an influence of interfacial debonding and film delamination on pile-up in the film. Furthermore, when the pile-up is accounted for in contact area determinations, the film hardness is actually independent of the substrate, thus indicating that the hardness differences observed in nanoindentation testing are an artifact of the testing analysis procedure. Results of the experiments are documented and discussed.
Integrated Fiber Optic Sensors For Nondestructive Characterization Of Concrete Structures
Authors: Ansari F. 
Published: June 2019

ABSTRACTIt is possible to monitor the initiation and progress of various mechanical or environmentally induced perturbations in concrete elements by way of fully integrated optical fiber sensors. Geometric adaptability and ease by which optical fibers can be embedded within concrete elements has led to the development of a number of innovative applications for concrete elements. This article is intended for a brief introduction into the theories, principles, and applications of fiber optic sensors as they pertain to applications in concrete.. However, due to the fact that the transduction mechanism in optical fibers is invariant of the materials employed, the principles introduced here also correspond to other structural materials. The only application related differences among various materials pertain to sensitivity and choice of optical fiber sensor types.
A Multiplexed Optical Fiber Sensor System For Distributed Measurement Of Structural Strains
Authors: Ansari F. , Chen Z. , Li Q. 
Published: June 2019

ABSTRACTStructurally integrated optical fiber sensors form the basis for smart structure technology. Over the past decade a variety of sensor configurations have been developed for measurement of strains and deformations in structures. Strains and deformations alter the refractive index and the geometry of the optical fiber material. These changes perturb the intensity, phase, and polarization of the light-wave propagating along the probing fiber. The optical perturbations are detected for the determination of strain. The research presented here describes the development of a new optical fiber sensor system for measurement of structural strains based on white light interferometry. An optical switch provides for multiplexing of strain signals from various locations in the structure. Redundant Bragg grating type fiber optic sensors as well as strain gauges were employed for comparison and verification of strain signals as measured by the new system. The system provides capability for distributed sensing of strains in large structures.
Monitoring Fatigue Damage In Concrete
Authors: Subramaniam Kolluru V. , Popovics John S. , Shah Surendra P. 
Published: June 2019

ABSTRACTRigid airport pavement structures suffer damage from multi-axial high magnitude cyclic stresses resulting from passing heavy aircraft. It is of interest to model the response of plain portland cement concrete to such loading conditions; thus, the sensitive detection and characterization of such damage during the loading process is important. Low strain vibrational resonance frequency measurement offers direct information concerning the global, apparent elastic moduli of the material and preliminary results have shown such measurements are sensitive to the presence of damage in concrete.The work reported here includes the theoretical foundation and experimental results of a non-destructive technique, based on vibrational resonance measurement. The tests are applied to monitor damage imparted to end-mounted hollow concrete cylinders subjected to monotonic and cyclic torsional (bi-axial) loads. An introduction to the concepts of vibration testing and details of mechanical and vibrational test procedures employed are given first. The most significant vibrational modes, of all of the possible modes setup within the specimen, are identified. The frequency value of these significant modes in the concrete specimen are experimentally obtained throughout a controlled cyclic testing procedure to failure. The behavior of these modes is then monitored during
a controlled cyclic testing procedure to failure. Distinctions between the frequency values of the various excited resonance modes are noted. Moreover, effects of the two damage types (monotonic and cyclic) on the frequency values of the modes are studied. Finally, conclusions concerning the applicability of the vibrational resonance techniques for monitoring imparted damage in these concrete specimens are drawn.
A Possible Basis for Nondestructive Characterization of Ropes of Nylon 6
Authors: Jiang H. , Davis M. K. , Eby R. K. , Arsenovic P. 
Published: June 2019

ABSTRACTPhysical properties and structural parameters have been measured for ropes of nylon 6 as a function of the number of use operations. The fractional content of the α crystal form, sound velocity, birefringence, tensile strength and length all increase systematically and significantly with increasing the number of use operations. The fractional content of the γ crystal form and fiber diameter decrease with use. These trends indicate that the measurement of such properties and structural parameters, especially the length, provide a possible basis for establishing a reliable, rapid, and convenient nondestructive characterization method to predict the remaining service life of nylon 6 ropes.
The Use of Thermoelasticity to Evaluate Stress Redistribution and Notch Sensitivity in Ceramic Matrix Composites
Authors: Mackin T. J. , Roberts M. C. 
Published: June 2019

ABSTRACTA new generation of relatively ‘ductile’ CMCs is being developed that expands the general utility of structural ceramic composites. These new materials rely on inelastic mechanisms such as interface failure, matrix cracking, fiber failure and fiber pullout to redistribute stress away from locations of stress concentration.1 The combined effect of these mechanisms can be summarized in three macroscopic damage classifications: Class I damage is the development of a single matrix crack bridged by fibers; Class II damage involves the development of multiple cracks in the matrix; and Class III damage involves the development of a shear damage zone. The operative damage mechanism depends upon the composite constituent properties, while the extent of stress redistribution depends upon the damage mechanism. Recent experiments have identified these damage mechanisms and have also quantified the effect of stress redistribution.2,2,4
Short-Time Fourier Transform of Continuous Wave Doppler Signals
Authors: Wooh Shi-Chang , Wei Coach , Clay Arthur 
Published: June 2019

ABSTRACTA Doppler-based ultrasonic monitoring scheme was introduced to detect discontinuities on the surface of a rapidly moving object. Single-tone, continuous wave (CW) ultrasound was impinged onto the moving surface and the reflected signal was processed by a Short-Time Fourier Transform (STFT) algorithm to identify surface anomalies. By monitoring the peak magnitude of the STFT spectra within a specified window, it was possible to reconstruct a signal representing Doppler frequency shift continuously in the time domain.
Nondestructive Inspection of Thin, Low-Z Samples using Multiplexed Compton Scatter Tomography
Authors: Evans B. L. , Martin J. B. , Burggraf L. W. 
Published: June 2019

ABSTRACTThe viability of a Compton scattering tomography system for nondestructively inspecting thin, low Z samples for corrosion is examined. This technique differs from conventional x-ray backscatter NDI because it does not rely on narrow collimation of source and detectors to examine small volumes in the sample. Instead, photons of a single energy are backscattered from the sample and their scattered energy spectra are measured at multiple detector locations, and these spectra are then used to reconstruct an image of the object. This multiplexed Compton scatter tomography technique interrogates multiple volume elements simultaneously. Thin samples less than 1 cm thick and made of low Z materials are best imaged with gamma rays at or below 100 keV energy. At this energy, Compton line broadening becomes an important resolution limitation. An analytical model has been developed to simulate the signals collected in a demonstration system consisting of an array of planar high-purity germanium detectors. A technique for deconvolving the effects of Compton broadening and detector energy resolution from signals with additive noise is also presented. A filtered backprojection image reconstruction algorithm with similarities to that used in conventional transmission computed tomography is developed. A simulation of a 360–degree inspection gives distortion-free results. In a simulation of a single-sided inspection, a 5 mm × 5 mm corrosion flaw with 50% density is readily identified in 1-cm thick aluminum phantom when the signal to noise ratio in the data exceeds 28.
Emerging Technologies For Nde Of Aging Aircraft Structures
Authors: Green R. E. 
Published: June 2019

ABSTRACTSeveral emerging technologies affording new opportunities for the nondestructive evaluation of aging aircraft structures. Among these technologies are ultrasonic attenuation detection of fatigue and corrosion damage; non-contact ultrasound including laser-laser, laser-EMAT, laser-air, and air-air; laser based acoustic emission source identification; full-field double-pulse holographic imaging; non-linear assessment of adhesive bond quality; x-ray diffraction topographic imaging of the quality of nickel based alloy single crystal turbine blades.
A New Scanning Thermal Microprobe
Authors: Zhang Yongxia , Zhang Yanwei , Blaser Juliana , Sriiram T. S. , Marcus R. B. 
Published: June 2019

ABSTRACTA thermal microprobe has been designed and built for high resolution temperature sensing. The thermal sensor is a thin-film thermocouple junction at the tip of an Atomic Force Microprobe (AFM) silicon probe needle. Only wafer-stage processing steps are used for the fabrication. The thermal response over the range 25–s 4.5–rovolts per degree C and is linear.
Electronic X-Ray Systems For Field Aircraft Inspection
Authors: Gibbs K. M. , Berger H. , Jones T. S. , Davis M. 
Published: June 2019

ABSTRACTSelected electronic, digital x-ray imaging systems and techniques were evaluated as possible replacements for the use of x-ray film at Air Force field aircraft maintenance facilities. Incentives for the introduction of digital systems include the elimination of recurring costs of film, processing, and waste disposal, and the advantages of electronic data analysis, digital signal processing, and the ease of storage, retrieval, and transfer of digital data. Initial experimental evaluations included photostimulable storage phosphors, scintillator-camera systems, flat panel imagers and the reverse geometry method. The technical evaluations were conducted with a test object consisting of typical honeycomb structure containing various faults, line pair gages, and image quality indicators on ¼–inch aluminum. Several electronic systems were capable of meeting most of the technical requirements for x-ray inspection, with system prices attractive for field locations with annual film costs in the range of $15,000 or more. All the electronic methods eliminate processing chemicals and offer advantages in certain applications. However, the storage phosphor systems were particularly well suited for field implementation because of their similarity to film, but without most of the recurring costs and the environmental problems associated with the use of film. These evaluations were conducted under a Small Business Innovation Research (SBIR) Phase I program. More extensive system evaluations are planned as the program continues into an SBIR Phase II project.
Characterization of an Extended Reactive Noble-Metal/III-V Semiconductor Interface: Cu/GaAs(110)
Authors: Joyce J. J. , Weaver J. H. 
Published: June 2019

ABSTRACTWe examine the electronic structure of the Cu/GaAs(110) interface using high resolution synchrotron radiation photoelectron spectroscopy. Analysis of valence band and core level spectra indicate that a reactive, extended interface is formed when Cu is deposited on the cleaved GaAs(110) surface at room temperature. Arsenic 3d core level data show a single reacted component shifted 500 meV to lower binding energy while the Ga 3d core shows a reacted component shifted by 800 meV below the substrate position. Core level attenuation curves indicate preferential As outdiffusion with the As signal at 30% of initial intensity for 100 ML of Cu while the Ga intensity for the same coverage has dropped to 2% of initial intensity. Band bending results show two separate regions of interest with a secondary pinning position 775 meV below the CBM for n-type GaAs. Results are discussed in light of thermodynamic and electronegativity parameters as well as other transition and rare-earth metal GaAs interfaces.
Areas of Need for Future Biomaterials Research
Authors: Lemons J. E. 
Published: June 2019

ABSTRACTClinical treatment modalities have undergone very significant changes over the past 30 years, in part because of the development of new or improved synthetic substances (biomaterials) for the replacement of tissues. Most all aspects of medical care have been directly influenced. It is now possible to obtain biomaterials made from basic metallic, ceramic, carbonitic, or polymeric materials where the substance has been manufactured for a specific biomedical application. In past years, this was not possible and available industrial grade materials were often adapted or modified to accommodate applications in biological environments. These developments, along with the many other advances in both biomedical sciences and clinical applications, have provided an exciting situation with regard to the improvement of existing prostheses and materials or the development of new biomaterials for surgical implant devices. This presentation will summarize eight areas where defined needs for active biomaterials research continues, following an outline theme of: (1) the current clinical situation; (2) specific area of need; and (3) possible improvements through basic science and clinical research.This thematic presentation will consider the following general areas: (1) the minimization of interfacial wear and implant biodegradation with examples of total joint replacements and occlusal surfaces of teeth; (2) adhesives for soft and hard tissues with examples of total joint replacements, cements, cardiovascular and plastic surgery reconstructions; (3) percutaneous devices for orthopaedic, dental, cardiovascular, and general surgery; (4) bone and skin replacements for the treatment of major bone lesions and burns; (5) ligaments and tendons for joint and hand reconstructions; (6) spinal instruments for orthopaedic procedures; (7) conduits of various diameters for general and cardiovascular applications; and (8) valves for cardiovascular and urological procedures.
Fatigue Fracture of Al2O3 Ceramic-to Ceramic Total HIP Replacements
Authors: Walter Adam , Lang W. 
Published: June 2019

ABSTRACTFatigue phenomena of high-density alumina ceramic hip joint endoprosthesis with ceramic-to-ceramic articulating components were analyzed for retrieved ex-vivo objects and for in-vitro tests in hip-joint simulators. Scanning electron microscope investigations were employed. The cyclical compression between ball and cup causes severe shear stresses to form below the bearing surfaces. Locally changing subsurface maxima of contact stresses can generate fatigue cracks starting at subsurface microstructural defects and grain boundaries. The fatigue fractures are regarded as being identified with the tribological surfaces of the simulator specimens and of the ex-vivo prostheses retrieved because of fracture.
Results of a Stemmed Bone Ingrowth HIP Resurfacing Arthroplasty in the Canine
Authors: Kim W. C. , Rechl H. , Amstutz H. C. , Hermens K. , O'Carroll P. F. , Kabo M. 
Published: June 2019

ABSTRACTA stemmed bone ingrowth hip resurfacing arthroplasty designed for use with bone deficient femoral heads raises concerns of stress shielding and is investigated in this study. Ten CoCr bone ingrowth hip resurfacing devices were implanted in five adult canines. Design consisted of a 6mm deep cylindrical cavity with porous beaded surface of 150um pore size and Imm nominal depth. A 3mm diameter smooth CoCr stem was eccentrically fixed to the component for additional fixation with threaded nut at the lateral cortex. Femoral head was reamed for interference fit with hole for the stem placed superiorly. Acrylic fixed polyethylene cups were used for acetabular components. Animals were followed with serial radiographs to sacrifice at 73 to 267 days. After sacrifice microradiographs of ground sections and histologic specimens were evaluated for bone ingrowth, remodeling, and femoral neck attenuation. All specimens showed well ingrown bone at the porous layer. Bone remodeling showed preservation of proximal femoral neck cancellous trabecular pattern and medial cortical support. Resorption of bone at the implant rim and femoral neck thinning were, however, present. Two specimens had neck thinning of 10% or less, four of 10 to 25%, three of 25 to 50%, and one greater than 50%. There was no correlation with time to sacrifice for parameters evaluated. Results indicate preservation of the compressive stresses through the femoral head. Resorption of bone at the rim and femoral neck attenuation, however, indicates load sharing between the implant and bone. Though a lower modulus material such as titanium would decrease load sharing, the geometrical design insures the presence of stress distribution anomalies.
Conductive Polymer Electrodes for Neural Prosthetic Applications
Authors: Foos J. S. , Erker S. M. 
Published: June 2019

ABSTRACTA variety of materials have been evaluated for use as electrodes for neural stimulation. In an effort to maximize the charge density on the electrode surface, faradaic stimulation electrodes have been investigated. Electrodes consisting of thin films of polypyrrole on Pt have been studied in phosphate buffered saline using cyclic voltammetry at 100 mV/s. The electrode capacity diminishes initially but stabilizes after ˜500 cycles. The electrodes were further evaluated in pulsing experiments using constant current, biphasic pulses. In these experiments, significant charge storage was observed only when using pulse widths greater than 5 ms. A modified polypyrrole was prepared using anthraquinone containing electrolyte. This new material is an apparent improvement over the polypyrrole previously studied.
The Small Diameter Vascular Graft - A Challenging Biomaterials Problem
Authors: Hoffman Allan S. , Ratner Buddy D. , Garfinkle Andy , Horbett Thomas A. , Reynolds Larry O. , Hanson Steven R. 
Published: June 2019

ABSTRACTThe surface composition of a biomaterial can have an important influence on biologic responses. In this paper we report on a surface treatment using a gas discharge which deposits a thin fluorocarbon polymer coating onto tie surface of a synthetic vascular graft. The surface chemistry of the graft is significantly changed, while there is no measurable change in porosity, compliance or surface topography. Treatments with tetrafluoroethylene (TFE) gas yield dramatic improvements in both thrombo and emboli-resistance of the graft, based on in vitro measurements and ex vivo shunt tests in a baboon.
Charged Polymers as Osmotic Agents for Peritoneal Dialysis
Authors: Twardowski Zbylut J. , Nolph Karl D. , Khanna Ramesh , Hain Hannelore , Moore Harold , McGary Terry J. 
Published: June 2019

ABSTRACTA sustained ultrafiltration during long-dwell peritoneal dialysis exchanges cannot be achieved with rapidly absorbable small molecular weight substances such as commonly used glucose. Uncharged polymeric substances are absorbed slower, but yield insufficient osmotic driving force because osmolality is inversely proportional to the molecular weight.Charged polymers induce colloid osmotic pressure not only because of the molecules themselves, but also by ions kept in the peritoneal cavity by opposite charges of polymers. In anin vitromodel of peritoneal dialysis, a sustained ultrafiltration has been achieved with several synthetic polymers including polyacrylate, dextran sulfate and polyethylenimine. However, these polymers were locally toxic to the peritoneal membrane when tested in rats and rabbits.Chemically modified gelatin derivatives, such as polygelin, exypolygelatin, and succinylated gelatin are widely used in Europe as plasma substitutes. They are metabolized and have proven to be systemically non-toxic. These gelatin derivative solutions were tested in rat models of peritoneal dialysis. Up to 10% solutions achieved sustained ultrafiltration at the rate proportional to the concentration and no untoward systemic or local effects on the peritoneum were observed. Absorption of gelatin molecules ranged from 40–60% of the infused amounts. The results of the studies indicate that gelatin derivitives have potential for clinical use as osmotic agents in long-dwell peritoneal dialysis exchanges if the absorption rates in humans are markedly lower than in rats.