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Analytical methods for modeling of ultrasonic nondestructive testing of anisotropic media.

Many modern structural materials exhibit anisotropic elastic behavior leading to complicated wave propagation phenomena. To ensure the reliability of ultrasonic nondestructive testing techniques, these material properties as well as the influence of microstructural inhomogeneities and the effects of interfaces on ultrasonic wave propagation have to be taken into account. In this respect, mathematical modeling provides an efficient method of assisting analysis. Two computationally efficient analytical approaches--a Gaussian beam and a point source superposition technique--are presented, which are well-suited for performing ultrasonic wave propagation and scattering simulations for anisotropic media. Results for homogeneous as well as inhomogeneous anisotropic media like composites and weld material are presented.

Journal Article↗

Characterisation of a laser droplet formation process by acoustic emission.

The aim of this article is to describe an application of acoustic emission to characterise a process of laser droplet formation from a metal wire. Laser droplet formation is a crucial process in new laser droplet welding technology, where parts are joined by means of the heat content of a liquid metal droplet deposited onto the parts to be joined. A laser beam is used for heating and melting the wire tip, and for detaching the molten pendant droplet. Depending on the process parameters, three different outcomes of the process can be observed: (1) no droplet formed; (2) a droplet formed but not detached; (3) a droplet formed and detached from the wire. It is shown that AE can be used to monitor the process and to indicate the different process outcomes.

Journal Article↗

Development of an ultrasonic inspection robot using an electromagnetic acoustic transducer for a Lamb wave and an SH-plate wave.

For inspection of a storage tank and pipeline in service, the application of an automatic inspection system (nondestructive inspection robot) is desirable, because manual inspection is difficult to perfectly and exactly perform due to the enormous amount of inspection needed. However, an ultrasonic nondestructive inspection robot with a piezoelectric oscillator needs to touch only the material surface to be directly inspected using a coupling medium. That is, the material surface and the sensor must always be held by constant pressure in the vertical direction on the material side. Actually, it is difficult to overcome these problems; thus an ultrasonic inspection robot could not be widely applied. We then tried to develop an ultrasonic inspection robot with an electromagnetic acoustic transducer (EMAT) which did not require a coupling medium to inspect the circumferential pipe parts. We developed a special EMAT that could transmit and receive alternately a Lamb wave with high sensitivity and a SH-plate wave without influence by the welded part. The method by which the inspection robot turned around the direction of the steel pipe surroundings was executed by observing the tape pasted in the direction of the steel pipe surroundings with an installed CCD camera. In this report, the basic mechanism of this inspection robot and an examination of results are described.

Journal Article↗

Characteristics of large capacity ultrasonic complex vibration sources with stepped complex transverse vibration rods.

Configurations of large capacity ultrasonic complex vibration sources with multiple longitudinal transducers are proposed and studied. The ultrasonic complex vibration systems are effective and essential for new applications in various industries. The complex vibration source of 27 kHz consists of a complex transverse rod with a welding tip (aluminum alloy, stainless steel and titanium alloy), a complex vibration rod with a flange and stepped part for holding the system, a circular longitudinal vibration disk (aluminum alloy) and six bolt-clamped Langevin type PLT transducers. Three transducer pairs are driven simultaneously using three driving systems at phase difference 120 degrees, and almost circular vibration locus is obtained.

Journal Article↗

Configurations of high-frequency ultrasonics complex vibration systems for packaging in microelectronics.

Ultrasonic high-frequency complex vibrations are effective for various ultrasonic high-power applications. Three types of ultrasonic complex vibration system with a welding tip vibrating elliptical to circular locus for packaging in microelectronics were studied. The complex vibration sources are using (1) a longitudinal-torsional vibration converter with diagonal slits that is driven only by a longitudinal vibration source, (2) a complex transverse vibration rod with several stepped parts that is driven by two longitudinal vibration source crossed at a right angle and (3) a longitudinal vibration circular disk and three longitudinal transducers that are installed at the circumference of the disk.

Journal Article↗

Control of complex components with Smart Flexible Phased Arrays.

The inspection is mainly performed in contact with ultrasonic wedge transducers; However, the shape cannot fit the changing geometries of components (butt weld, nozzle, elbow). The variable thickness of the coupling layer, between the wedge and the local surface, leads to beam distortions and losses of sensitivity. Previous studies have shown that these two phenomena contribute to reduce the inspection performances leading to shadow area, split beam.... Flexible phased arrays have been developed to fit the complex profile and improve such controls. The radiating surface is composed with independent piezoelectric elements mechanically assembled and a profilometer, embedded in the transducer, measures the local distortion. The computed shape is used by an algorithm to compute in real-time the adapted delay laws compensating the distortions of 2D or 3D profiles. Those delay laws are transferred to the real-time UT acquisition system, which applies them to the piezoelectric elements. This self-adaptive process preserves, during the scanning, the features of the focused beam (orientation and focal depth) in the specimen. To validate the concept of the Smart Flexible Phased Array Transducer, prototypes have been integrated to detect flaws machined in mock-ups with realistic irregular 2D and 3D shapes. Inspections have been carried out on samples showing the enhancement performances of the "Smart Flexible Phased Array" and validating the mechanical and acoustical behaviors of these probes.

Algorithms↗

3D analysis of interaction of Lamb waves with defects in loaded steel plates.

The objective of the research presented here is the investigation of the interaction of guided waves with welds, defects and other non-uniformities in steel plates loaded by liquid. The investigation has been performed using numerical simulation for 2D and 3D cases by the finite differences method, finite element method and measurement of 3D distributions of acoustic fields. Propagation of the S(0) mode in a steel plate and its interaction with non-uniformities was investigated. It was shown that using the measured leaky wave signals in the water loading of the steel plate and by application of signal processing, the 3D ultrasonic field structure inside and outside of the plate can be reconstructed. The presence of leaky wave signals over the defect caused by the mode conversion of Lamb waves has been proved using the numerical modelling and experimental investigations. The developed signal and data processing enables to visualise dynamics of ultrasonic fields over the plate, and also to estimate spatial positions of defects inside the steel plates.

Journal Article↗

Preliminary clinical experience with the Bard XT coronary stent.

BACKGROUND: The Bard XT stent is a balloon expandable stent with a new design, consisting of discrete zigzag modules welded onto a flexible longitudinal spine. METHODS: To assess the safety and efficacy of this recently introduced coronary stent, we studied 81 patients (107 lesions) who underwent implantation of 108 such stents (66% elective). RESULTS: Primary success in stent delivery was 97.1% and angiographic success was achieved in all cases. Reference segment diameter was 2.69+/-1.4 mm and average lesion length 10.9 mm. Mean minimal luminal diameter before the procedure was 0.79+/-1.11 mm and increased to 2.55+/-1.09 mm after stenting. Diameter stenosis decreased from 76%+/-24% to 9%+/-12%. One Q wave and 1 non-Q-wave myocardial infarction occurred but no other significant complications were observed. At 1-month follow-up, angiographically documented subacute thrombosis occurred in 2 cases at days 1 and 3. Conclusions These preliminary data suggest that the Bard XT stent has a promising design for the safe and effective treatment of coronary lesions, even in the presence of high-risk clinical and unfavorable angiographic characteristics.

Aged↗

Hemodynamic evaluation of the integral monostrut Björk-Shiley prosthesis in the aortic position.

Between May, 1983, and November, 1984, the new integral monostrut Björk-Shiley prosthesis was used for aortic valve replacement in 62 patients. The prosthesis is machined from a solid piece of cobalt alloy and has no welded joints. The traditional U-shaped outlet strut has been replaced by a projecting metal finger that holds the disc in place. The disc opens to 70 degrees and is convexoconcave. Successful transseptal heart catheterization was performed in 23 patients an average of 6 months following operation to evaluate the hemodynamic performance of the prosthesis. The mean peak-to-peak gradient was 7.73 +/- 7.49 mm Hg (+/- standard deviation). In five valves it was 0, and in only three was it higher than 15 mm Hg. Significant peak gradients were directly related to the valve index (valve area/body surface area). Mean systolic gradient at rest was 12.7 +/- 6.27 mm Hg and did not increase after exercise. Effective orifice areas were adequate, and the discharge coefficient ranged from 0.77 for the 21-mm prosthesis to 0.48 for the 29-mm prosthesis. Minimal regurgitation, which was washed out on the next systole, was observed with all sizes of the prosthesis. Disc opening was maximal (70 degrees) in all but one of the observed instances. Longer clinical follow-up is required, but the new integral monostrut Björk-Shiley prosthesis, with its important design changes and excellent hemodynamic performance, appears to be a promising aortic valve substitute.

Adult↗

Paternal occupational exposures and embryo implantation rates after IVF.

OBJECTIVE: To investigate any influence of paternal occupational exposures on implantation rates after IVF. DESIGN: Cohort study of couples who sought IVF treatment. SETTING: University Hospital Utrecht, The Netherlands. PATIENT(S): The study population was composed of 726 couples pursuing IVF treatment. INTERVENTION(S): Only the earliest IVF treatment cycle with ET was selected for the analysis. All couples filled in a generic questionnaire on lifestyle factors and details about their occupation. In addition, more detailed exposure information was obtained for pesticides with use of job-specific questionnaires and a subsequent telephone interview. MAIN OUTCOME MEASURE(S): The implantation rate was defined as the number of gestational sacs seen with ultrasound at 6-7 weeks of pregnancy, divided by the number of embryos replaced. RESULT(S): A significantly reduced implantation rate was seen among couples with male partners working in occupations with presumably high levels of organic solvent exposure. Conversely, paternal pesticide exposure was significantly associated with an increased implantation rate. Paternal exposures to metal dust or fumes and welding fumes were not related to the probability of implantation. CONCLUSION(S): The findings suggested that paternal organic solvent exposure decreased the implantation rate among couples undergoing IVF-ET treatment.

Adult↗

Comparison of tubal surgery with the CO2 laser and the unipolar microelectrode.

The uterine horns of 40 New Zealand White female rabbits were resected and anastomosed to compare microsurgical anastomosis of the horns excised with microscissors, with a laser, and with a microelectrode. The rabbits were divided into four groups. In the first group of ten rabbits, 3 cm of tissue was resected by microscissors from each uterine horn; the cut ends were then anastomosed in one layer with 8-0 Vicryl sutures using the operating microscope. In the second group of ten rabbits, 3 cm of tissue was resected by laser from each uterine horn; the cut ends were then anastomosed in one layer with 8-0 Vicryl. In the third group of ten rabbits, 3 cm of tissue was resected by laser from each uterine horn; the cut ends were then anastomosed by "welding" the tissues with the laser. In the fourth group of ten rabbits, 3 cm of tissue was resected by a microelectrode; the cut ends were then anastomosed in one layer with 8-0 Vicryl sutures using loupe magnification. All the rabbits in the first and fourth groups became pregnant, only four became pregnant in the second group, and none became pregnant in the third group. It is concluded that the CO2 laser beam as used in this study has no place in tubal resection and reconstruction.

Animals↗

Comparative study of different laser systems.

OBJECTIVE: To review lasers, laser physics, laser-tissue interaction, delivery systems, and their clinical applications relevant to gynecology. SETTINGS: Gynecological Service at Massachusetts General Hospital (MGH) and MGH Laser Center. INTERVENTIONS: None. DESIGN: Laser literature review and personal experiences of the authors were used to prepare this manuscript. CONCLUSIONS: Lasers have been used in gynecologic practice for cutting and coagulating purposes. Photodynamic therapy has been used clinically for malignant conditions and is being investigated for dysplastic lesions of the lower genital tract and for endometrial ablation. Laser welding has potential, but further work is required in this field before it finds a clinical application. The main lasers used in gynecology are CO2, neodymium-yttrium aluminum garnet (Nd:YAG), and potassium tatanyl-phosphate-doubled Nd:YAG. Pulsed Ho:YAG laser looks promising, as does diode lasers. Holmium-yttrium aluminum garnet and diode lasers will be soon available commercially. Improvements in delivery systems have increased user friendliness, and more developments in this area are anticipated, for example, a fiber-optic delivery system for CO2 lasers. We believe that enhanced understanding of laser technology will provide unique applications for development in gynecology.

Female↗

Funding options for research: facing the market as well as government.

Parasitology is a challenge. At one level, the structural and genetic complexities of parasites provide ample technical challenges in regard to an understanding of parasite variability and adaptability, epidemiological diversity, drug resistance, etc. The intricacies of host parasite relationships including the immunology of parasitism will continually surprise yet frustrate the vaccine developer and keep the bravest immunoparasitologist busy and creative for decades. As if the technical considerations were not challenging enough, we see difficulties arising in sustaining a research endeavour and preserving a critical mass of researchers through the generation of high-level, long-term funding support. Contributing to this situation is the fact that most parasitic diseases of major impact in humans are largely centred around the rural poor in tropical, less industrially-developed countries and therefore of little or of fickle interest to the strictly commercially oriented. Moreover, the focus in the rural industries has moved away from aspects of on-farm production with lower priority given to studies on even the 'economically-important' parasites of livestock. It is contended that this may change again with pressures and clear marketing advantages to preserving a 'clean and green' image for Australia's primary industries. Overall, the extraordinary technical and conceptual advances in recent times have been tempered by uncertainties in research funding and severe cuts from some traditional sources for both fundamental and strategic/applied research in Parasitology. Several have highlighted the fact that deliverables in terms of new methods of disease control have been sparse and some claims made in the past have certainly been exaggerated. Yet the prospects and achievements at the front end of the long R&D pathway have never been brighter. In this article we examine the merits of a 'portfolio approach' to generating research funds in Parasitology and Science and Technology in Australia more generally, with an emphasis on strategies that, through welding good science with clear, medium-term product objectives, increase research funding opportunities.

Biotechnology↗

Telemetry of forces from proximal femoral replacements and relevance to fixation.

Two proximal femoral replacements were instrumented to enable axial forces to be determined at two sites within the prosthesis: in the main shaft and near the tip of the intramedullary stem. The goal was to measure the changes in force distribution over time, as indicated by the ratio of the two forces. Inductive coupling between a coil worn around the leg and a small implanted coil was used, both to supply power to electronic circuits sealed into a welded cavity in the prosthesis and to telemeter data from the prosthesis. Data from both subjects were recorded over the first two years following surgery. For the first subject, there was an increase in mean shaft force excursions (peak force minus resting force) during level walking from 0.53 x BW after 1 week 2.77 x BW after 23 months. The corresponding mean tip force excursions were 0.13 x BW and 1.74 x BW, respectively. The ratio of mean tip force excursions to shaft force excursions steadily increased over the same period from 25 to 63%. Similar increases over time in the tip/shaft ratio were found during treadmill walking, stair climbing and stair descending. Data from the second subject were obtained for the shaft forces only, and were consistent with those from the first subject. The progressive transfer of axial load from the proximal to the distal part of the IM stem recorded telemetrically, together with radiographic observations, suggested that bone remodelling had taken place together with a less stable interface around the proximal part of the stem. This process evidently began soon after implantation.

Bicycling↗

Trace analysis of airborne 1,6-hexamethylenediisocyanate and the related aminoisocyanate and diamine by glass capillary gas chromatography.

A capillary gas chromatographic method was developed for the analysis of complex air mixtures of 1,6-hexamethylenediisocyanate, 1,6-hexamethyleneaminoisocyanate and 1,6-hexamethylenediamine. The method is based on derivatization in the sampling step of the reactive isocyanate groups to corresponding urethane groups by the alkaline ethanolic solvent and a subsequent derivatization of remaining amino groups to amide groups with heptafluorobutyric acid anhydride. The overall procedure, including sampling, gave a linear response at air concentrations of 3-300 micrograms/m3 for 1,6-hexamethylenediisocyanate with a precision of ca. 4% at 15 micrograms/m3 and a detection limit of ca. 0.2 microgram/m3 using nitrogen selective detection. In a field measurement of air concentrations in welding work on lacquered metal parts at a motor-car workshop, concentrations of 1,6-hexamethylenediisocyanate above 600 micrograms/m3 were found. Also 1,6-hexamethyleneaminoisocyanate and 1,6-hexamethylenediamine were found at concentrations of the order of 15% of the 1,6-hexamethylenediisocyanate concentration.

Air Pollutants↗

Thermal degradation of weldable poly(vinyl chloride) samples at low temperatures.

A study was performed to determine possible emission products during plastic welding that may be responsible for health problems. Thermal degradation of poly(vinyl chloride) samples was carried out at 170 degrees C in a thermal desorption gas chromatography (GC) injector and in a modified impinger in a GC oven, in combination with various analytical techniques, thermogravimetric analysis, capillary GC, GC-mass spectrometry, high-performance liquid chromatography and isotachophoresis. Some of the degradation products found are known to be eye irritants.

Adsorption↗

Tracheobronchial stenting for the treatment of airway obstruction.

PURPOSE: The authors report a 5-year experience of inserting the Palmaz stent into infants and children who had a variety of major airway obstructions. METHODS: From 1992 to 1997, 30 balloon expandable stents (Palmaz) were inserted in the trachea (n = 18) and bronchi (n = 12) of 16 infants, ages 1 week to 26 months (median, 9 months), suffering from three types of serious airway obstruction. In group 1, 10 stents were placed in eight children for tracheal or bronchomalacia. In group II, 11 stents were inserted in four infants for stricture at the site of surgical repair of stenosis. In group III, nine stents were placed to relieve airway compression from enlarged pulmonary arteries associated with severe congenital heart disease in three children and mediastinal lymphangioma in one. Tracheal stents were 30 mm long and were expanded to 8 to 10 mm at placement. Bronchial stents were 12 to 15 mm long and were expanded to 7 to 9 mm. The nonexpanded stents were placed on an inflatable balloon catheter and were inserted into the desired position in the airway through a bronchoscope or endotracheal tube using x-ray control. They were expanded and fixed in place by inflating the balloon to its rated diameter. RESULTS: In group I, granulation tissue developed over the stents in five of eight cases. Obstructing granulations were removed by scraping or balloon compression in three and resulted in earlier than the planned removal in two. Stents have now been removed in six of eight cases. Major airway obstruction has not recurred. In group II, stents have been in place in all cases for 13 to 56 months after insertion, but in one child with three stents, two were removed for obstructive granulations 44 months after insertion. All are well. All group III patients could be extubated after stenting, but two with heart disease died after 3 and 12 months of palliation. During the course of follow-up, stents in the bronchi of two had migrated, and an additional stent was required. Autopsy in one showed full-thickness bronchial erosion but no perforation by the stent. A total 11 of 30 stents have been removed bronchoscopically in seven children without complications. Another child referred here for tracheal stent removal after laser resection of granulations died at attempted removal because the stent was "welded" into the tracheal wall by the inflammatory reaction. Manipulation of the stent completely occluded the airway. CONCLUSIONS: Airway stents can be inserted easily and safely and left in-situ for prolonged periods to relieve major airway obstruction from a variety of causes. Tissue reaction may necessitate bronchoscopic manipulation and early stent removal, and adds to the difficulty of removal.

Bronchial Diseases↗

Methods to preclude aspiration or swallowing of dental appliances.

A technique which precludes the swallowing of dental restorations during fitting and cementation has been described. An alternative technique is to spot-weld a small loop or wire to the finished crown. Dental floss may be attached to the loop. Another method is to attach a piece of unwaxed floss to the completed crown with Eastman adhesive 910. The floss is removed after the restoration is cemented.

Crowns↗