Total Power Level Research Articles

Enhanced methods to get high average power by combining yttrium–aluminum–garnet laser beams and their characteristics in processing materials

We investigated two related topics as the first stage of our research: the characteristics of welding with multiple yttrium–aluminum–garnet (YAG) laser beams transmitted through optical fibers and combined at the focal point; and the study of methods of combining YAG laser beams. Each laser beam must be inclined in such a combined system. The plume and the penetration changed their direction from the vertical direction of the specimen to the parallel one of an irradiated beam, if the peak power or energy of the irradiated YAG laser beam exceeds a threshold value. In the two continuous wave YAG laser beams irradiation the form of plume and welding penetration were the same at the average angle of inclination of the two beams of 15° and at typical total power levels as those with a single and vertically irradiated beam to the specimen surface, but were split above the angle of inclination of 30° and total average power of 3.3 kW. Two keyholes would be formed under the split penetration condition. The three split plumes were observed for irradiation by three combined beams. The second stage of our research was the development of an integration optics based on these experiments, which could focus the laser beams transmitted through optical fibers with a condensing lens. We studied all position welding characteristics using the developed integration optics and obtained the result that the overhead welding has the maximum fusion volume among the three orientations—horizontal, vertical, and overhead position welding. The result will be attributed to the direct reach of laser beam to the unfused bottom metal due to the molten metal being pulled down from around the keyhole by gravity. The integration optics is too heavy and large for an articulated robot to hand it and move with high speed. This difficulty comes from combining laser beams at the exit sides of optical fibers. Then, we developed a new launching optics of laser beams at an entrance side of an optical fiber in order to overcome the disadvantage. The development of the launching optics is described.

The relationship between spectral properties and perceptual evaluation of hypernasality in children with cleft palate—vowel /i/

The purpose of this study was to examine the relationship between spectral characteristics and the perceptual evaluation of hypernasality in speakers with cleft palate. Speech samples from 32 cleft palate patients (average age 9.3 years) and 5 normal subjects (average age 9.4 years) were used in this study. The isolated vowel /i/ produced by each subject was filtered using 16 one-third octave bandpass filters from 200 Hz to 6.3 kHz to obtain a 1/3 octave spectrum. These spectra were normalized using the total power level of the 16 1/3 octave bands. Three sophisticated listeners rated the speech samples using a six-point equal-appearing interval scale. Average spectra obtained from the hypernasal and the normal groups were compared. Spectral characteristics of hypernasality in the vowel /i/ were identified as a rise in power level between the first formant (F1) and the second formant (F2) and a rise in power level of F1. Multiple regression analysis revealed a high correlation (r=0.81) between the averaged perceptual scores and four levels of 1/3 octave bands: the band containing F1, the first, the second, and the fourth bands from F1. [Work supported by NIDR Grant Nos. DE07105 and DE06957.]

Simulation of Loss of the Residual Heat Removal System of BETHSY Integral Test Facility Using CATHARE Thermal-Hydraulic Code

The thermal-hydraulic CATHARE V1.3U code has been used to simulate an International Standard Problem (ISP38) experiment conducted at BETHSY Integral Test Facility located in Grenoble, France. This experiment presents simulation of the loss of residual heat removal system during midloop operation. It involved opening of the pressurizer manway and steam generator outlet plenum manway simultaneously with switching on the heating rod power to simulate the decay heat. The total power level of 138 kW was kept unchanged throughout the test. Mass discharge through both manways led to core boiling and uncovery. The test was stopped when the primary cooling system was filled back to a midloop level. Overall, the code’s prediction and experimental data were found to be in reasonable qualitative agreement. However, the code underestimated the time of the core uncovery and the actuation of the gravity feed injection because of the overprediction of the discharge through the steam generator manway during the initial stage of the transient. This was caused by misestimation of the phase separation effect at the hot leg/surge line tee junction and significant water entrainment into the surge line at the beginning of the test. It was found that the upward tee junction model needs to be refined for the low-pressure transients.

Parametric study of high energy plasmas for electrothermal-chemical propulsion applications

Theoretical calculations are performed with a one-dimensional (1-D), steady state, isothermal computer plasma model to define plasma output parameters for various input electrical energies and capillary radii of relevance to the electrothermal-chemical (ETC) propulsion concept. Three capillaries of 1.92, 4.75, and 7.0 mm radius, and a fixed length of 11.84 cm, were chosen for this study with input currents between 30 and 350 kA. Plasmas are categorized according to their total power and energy levels (based on a 3-ms pulse width) and are compared with respect to their resistance, exit pressure, and core plasma temperature. The input power ranges from 0.17 to 1.89 GW, for input energies from 0.49 to 5.80 MJ, which is considered suitable coverage for ETC ignition through ETC enhanced propulsion concepts. The study shows that the range of resistance, pressure, and temperature are 12.8-195 m/spl Omega/, 19.8-2000 MPa, and 2.9-13.5 eV, respectively, for the chosen capillary geometry. Flow conditions for plasma calculations include choked (no pressure boundary) and unchoked (450-MPa pressure boundary) for some calculations. Results from the computational model and interpretations from the perspective of capillary implementation into ETC propulsion concepts are also included.

Operating characteristics of a 100 kV, 100 kW plasma ion implantation facility

Plasma ion implantation of gaseous ion species is conducted in two different operating modes corresponding to two different gas pressure regimes, a low-pressure mode (1.33 × 10-3 -1.33 × 10-2Pa (10-5 -10-4Torr)) and a high-pressure mode (1.33 × 10-2 -0.133 Pa (10-4 -10-3Torr)). In the low-pressure operating mode, the plasma production and ion implantation processes are decoupled, i.e. a part to be implanted is immersed in a separately generated nitrogen plasma and then independently pulse biased to -100 kV to implant ions. The current-pulse waveform continuously decays from an initial high-current-spike value (300 A) to a low relatively steady-state value (30 A). A wide dynamic range of operation is possible in this mode. Pulse durations can extend from 10 to 50 us and frequencies can range from 100 to 1000 Hz. Total power levels of 100 kW have been demonstrated. In the high-pressure operating mode, the plasma production and ion implantation processes are coupled, i.e. the part is immersed in a gas, and the voltage used to pulse bias the part both initiates and sustains the plasma production process, as well as implanting ions. The current-pulse waveform increases during the initial part of the pulse duration and can attain a near-steady value of 150 A at 100 kV. The higher near-steady-state pulsed current of the high-pressure mode potentially allows faster implantation of parts as well as a smaller more conformal plasma sheath compared with the low-pressure mode. However, the dynamic range in this mode differs from the low-pressure mode. At 100 kV, pulse durations are limited to less than 5 μs at a frequency of less than 100 Hz. In this paper, we present the operating characteristics for both operating modes, as well as their implications for faster treatment and more conformal implants of complex-shaped parts.

Plasma antioxidant depletion after cardiopulmonary bypass in operations for congenital heart disease

We describe the use of two in vitro tests to characterize plasma antioxidant capacity at the time of cardiac bypass in operations for congenital heart disease in 30 patients aged 3 days to 16 years (average 4.4 +/- 0.9 years [standard error]). Bypass and crossclamp time, circuit volume, and type of operation were recorded for each patient. First, a test of plasma radical antioxidant power measured chain breaking (secondary) antioxidant capacity of plasma to prevent oxidation of linoleic acid in vitro. Second, overall ability of plasma to prevent lipid peroxidation was assessed by a classic test of plasma inhibition of malondialdehyde formation in a beef brain homogenate. Plasma total radical antioxidant power level at baseline was 0.74 +/- 0.03 mumol/ml plasma, which decreased to 0.15 +/- 0.05 mumol/ml plasma after bypass (p < 0.001) and 0.26 +/- 0.08 mumol/ml plasma with recovery (n = 18, p < 0.001). Analysis of variance of postbypass total radical antioxidant power value showed age (p = 0.0002, r = 0.63) and bypass time (p = 0.009, r = 0.4677) to be significant factors. Pump prime volume in milliliters per kilogram and preoperative hemoglobin value were not significant factors. Beef brain malondialdehyde formation in vitro was limited 92% +/- 3% by normal plasma before operation versus 53% +/- 5% after operation (p < 0.001) and 51% +/- 5% at recovery after arrival in the pediatric intensive care unit (p < 0.001). Analysis of variance of the changes from before to after operation showed age p = 0.0015, r = 0.55) and bypass time (p = 0.033, r = 0.39) to be significant factors. Thus antioxidant capacity of plasma is significantly diminished after cardiopulmonary bypass in children. Young patient age and long duration of cardiopulmonary bypass are identified as factors that correlate positively with depletion of antioxidant capacity with bypass.

Dependence of spectral power of EEG rhythms on menstrual cycle phases in women suffering from epilepsy

The effect of menstrual cycle on EEG parameters is investigated in norm, in epilepsy becoming acute in menstrual and perimenstrual periods (catamenial), and in epilepsy whose exacerbation is not connected with menstrual cycle. The ten dencies to the decrease of spectral power in cycle luteal phase in healthy women and women suffering from epilepsy are mentioned. The primary role of spectrum low-frequency components and total power level in neurodynamics of catamenial epilepsy is shown.

ETUDE DU BRUIT ENGENDRÉ PAR L'IMPACT D'UN JET SUPERSONIQUE CHAUD SUR UN OBSTACLE

This document presents experimental works on supersonic hot jet impingement noise which have been done in an anechoic wind tunnel. Far field noise directivity measurements were done for a supersonic jet impingement on an axisymmetric obstacle. Source localizations with focused microphone arrays were realized simultaneously. Introduction of a board in a jet increases the sound pressure level upstream of the board. The localizations with focused microphone arrays show that the predominant sources of noise are located near the impingement region. However, this apparition of sound sources does not amount to a large increase of the total sound power level

Perspectives on variable‐period/polarizing insertion devices in synchrotron radiation science and technology: Recent developments at SSRL (abstract)

Insertion devices that are tuned by electrical period variation, in contrast to the conventional method of mechanically varying the field strength, offer a number of advantages for the successful development of the next generation of higher‐brightness storage rings and associated experimental techniques [R. Tatchyn, Nucl. Instrum. Methods A 275, 430 (1989); J. Appl. Phys. 65, 4107 (1989); R. Tatchyn and T. Cremer, IEEE Trans. Mag. 26, 3102 (1990)]. for example, due to the inherently low total output power levels of variable‐period devices, their use can do more to relax power loading constraints on beamline optics at existing and future facilities than many of the alternative approaches explored in recent years, such as, e.g., gallium‐cooled optics, multilayer premonochromator structures, or adaptive/deformable optics. With regard to machine optics, variable‐period structures can be operated without varying the tune of the host machine lattice, enabling the design and flexible operation of ultralarge, yet...

A ray tracing approach to underwater reverberation modeling

Abstract : The effects of multiple boundary returns and non-isovelocity conditions were incorporated into a time-varying representation of underwater reverberation measured at the moving source. The research focused on the development of the time-varying power gain and frequency spectra of scattering functions, which have been shown to characterize the reverberation from an underwater environment. A sound velocity profile, which may consist of up to fifty depth-velocity point pairs, has been introduced. The ocean has been assumed to be horizontally stratified, and each stratification to be represented by a constant velocity gradient. Acoustic beam effects, backscattering coefficients, reflection loss factors, and a varying absorption coefficient have been considered. All reverberant returns have been assumed to arrive at the receiver along the same raypath that was traversed from the source to the backscattering element. Two examples are presented for comparison of the spectra and total power levels of the modified scattering function with those of the original model. One focuses on the inclusion of multiple boundary returns only. The total power curve from the revised model was observed to decay more slowly than that of the original model because of the added boundary returns. The other emphasizes the propagation effects of a non-isovelocity profile. In this scenario, the emergence of a surface shadow zone was observed, as well as the formation of a caustic near the axis of source motion.

Performance of a directly water-cooled silicon crystal for use in high-power synchrotron radiation applications

Results of measurements made using the multipole wiggler at beamline 16 of Photon Factory are reported. Double crystal rocking curves, Si(111) and Si(333) topographs, and thermal maps of the cooled-crystal surface were measured at total incident power levels up to 1600 W and power densities up to 0.7 W/mm2, for two different crystal designs. Significant crystal deformation occurred in the form of surface curvature for both designs. Finite element calculations provided a preview of the experimental results and proved very valuable in interpretation of the measurements.

Ureteral Stenting During Extracorporeal Shock Wave Lithotripsy: Help or Hindrance?

We retrospectively reviewed the outcome of extracorporeal shock wave lithotripsy in patients with renal calculi less than 3cm. in size who were treated at a large multi-user lithotripsy center. Patients in whom indwelling ureteral stents were placed before lithotripsy treatment were subjected to higher levels of total power (shocks times voltage), yet the rate free of stones did not differ from those treated without a stent. In addition, the patients with internal ureteral stents experienced a significantly higher incidence of urinary urgency (43 versus 25 per cent) and hematuria (40 versus 23 per cent) than nonstented patients, respectively (p less than 0.05). Also, the duration of bladder discomfort was longer for stented patients (26 versus 13 per cent) as was the duration of urinary frequency (31 versus 16 per cent), compared to nonstented patients (p less than 0.05).The results suggest that use of an indwelling ureteral stent may not contribute to a higher rate free of stones for the treatment of small to medium sized renal calculi and, in fact, it may make the treatment more uncomfortable for the patient than performing lithotripsy without ureteral stenting. Of course, in selected cases (solitary kidney, large stone burden and aid in stone localization) ureteral stenting has a useful adjunctive role in extracorporeal shock wave lithotripsy.

Sound power level and directivity pattern determination of a space shuttle solid rocket booster

The sound power level and directivity pattern of sound were determined for a space shuttle solid rocket booster motor during a horizontal test firing at the Morton Thiokol Wasatch Test Facility in Utah. Six Bruel & Kjaer type 2230 precision sound level meters were placed at 60‐deg intervals around the rocket motor at a distance of 1000 ft, except the location directly behind the nozzle (2600 ft). These analyzers were used to determine the overall sound‐pressure level, between 20 and 20 000 Hz, at each of the six locations during the test. Two Cetec‐Ivie model IE‐30A audio spectrum analyzers were used to determine the shape of the spectrum at a one‐third octave band resolution. The equipment was turned on approximately 2 h prior to the scheduled test and was unattended during the test. Various adjustments were made to the data to account for topographic and atmospheric effects. The sound produced was predominantly low frequency, and the directivity pattern exhibited major acoustic lobes 60 deg to both sides of the line of fire. A total overall sound power level of 196 dB was determined. [Work funded by NASA Stennis Space Center, Mississippi.]

Technical note: Comparison of film density, stoichiometry, optical and electrical properties of thin metal oxide films produced by reactive d.c. magnetron sputtering and electron beam evaporation techniques

Multilayer thin metal oxide films are used in the fabrication of some electro-optic devices. Many of these devices are produced by reactively sputtering metals or by evaporating the metal oxide. To design and engineer such devices, a thorough knowledge of the physical properties of these films is essential. One can then relate these properties to the conditions under which the films were made. Critical parameters in the fabrication process are then identified and the process is not only better controlled but can also be optimized for the end product required. In this study, film thicknesses varied from 20 nm to 360 nm and were determined by a surface profiling technique. The film density and stoichiometry were then determined by Rutherford backscattering measurements. The reactively sputtered metal oxide films were made between base argon pressures of 2.5 and 20 mTorr, oxygen partial pressures of 1% and 65% of the total pressure and direct current magnetron power levels of 2 and 6 kW. Significant enhancements to deposition rates and variation in physical properties were accomplished with non-standard gas flow geometries. Comparable metal oxide films were made with electron beam evaporation. Optical properties of the films were determined from transmission and reflection measurements from 380 nm to 780 nm. The index of refraction and absorption as a function of wavelength were deduced from these data. The index of refraction exhibits a surprising, significant and changing structure with deposition parameters and film thickness. The resistivities of the sputtered films vary greatly with process parameters. The values of film resistivity and index of refraction can be altered in a controlled manner by subsequent in-line substrate heating in an enriched O2 atmosphere. TaxOy films will be used as typical examples to illustrate the above phenomena.

Effect of Satellite Transponder Nonlinearity on Uplink Thermal Noise*

The satellite transponder nonlinearity causes the uplink thermal noise to be suppressed relative to the carriers. It also causes the uplink thermal noise to interact with the carriers to generate intermodulation products. For the single carrier access where-one FM-TV carrier, one FM-FDM carrier or one TDMA-PSK carrier operating at or very close to saturation, the net effect is an improvement in the carrier to uplink thermal noise ratio (C/N)u of, about 2.2 to 3.5 dB. When there are two or more carriers accessing the transponder at the same time, the net effect is reversed. For a typical dual TV operation, it results in a degradation in (C/N)u of 0.5 to 0.7 dB when the total carrier input power level is 1 dB IPBO and is negligible when the total carrier input power level is 3 dB IPBO or lower; and for a typical multiple SCPC carrier access, due to the backoff operation, it is negligible.

Jet Engine Integrated Generator

The paper presented discusses the design of a permanent magnet (PM) excited synchronous generator to be integrated into a modern jet engine. The electrical machine is to replace the mechanical accessory power drive system; thus all secondary power supplied from the engine to the aircraft is supplied by the electrical generator. The generator is also to double as starter motor for the engine, a job which can easily be handled at the required total secondary power level. It has been found that an integrated generator is technically feasible. It is heavier than its conventional counterpart, but offers significant reliability and maintenance benefits. This paper describes part of the work done for a study to investigate the feasibility of integrating a PM generator into a jet engine. IR Force and industry have recognized the potential value of integrating secondary-power-generation devices and engine accessory components into the basic engine structure. The objective of this design approach is to minimize the propulsion system envelope. Provided that a suitable configuration can be defined, the propulsion system should then provide improved installed performance, in two respects: drag will be reduced, and reliability will be improved by eliminating the complex mechanical secondary-power- generating equipment and accessory drive system. A program was undertaken to study the practicality of an integrated jet engine generator and its potential benefits. Experience with conventional aircraft alternators had proven that only solid rotor type electrical machines such as a per- manent magnet (PM) machine would meet the stringent reliability and maintainability requirements which would allow the integration of the alternator into an engine. The program encompassed a detailed study and design effort to determine applicability, location, and configuration of the engine structure. This paper describes the tradeoff and design studies un- dertaken to obtain an electrical machine design suitable for the application. The major goals were to achieve high reliability, low maintenance, and low life cycle costs for the electrical system. These goals can best be served by PM ex- cited electrical machines, since their rotors have a reliability potential which is higher than that for industrial induction motors and only surpassed by solid rotor machines. The PM generator is part of a variable speed constant- frequency-generating system which consists of the high frequency generator and a cycloconverter. The cycloconverter allows power flow in both directions. Thus the cycloconverter generator system is also capable of operating as an elec- tronically commutated motor-drive to start the engine. The cycloconverter will provide for all electrical controls, in- cluding frequency and voltage control, since an ac-PM machine does not allow for a simple reliable voltage control within the machine itself.

Rotating Blades Radio Interference in a Helicopter-Borne CW Doppler Radar

Radio interference generated in a helicopter-borne continuous wave (CW) Doppler radar system due to the rotating blades is analyzed. This problem has been previously treated for the case of pulse Doppler radar systems with very narrow (near zero) beamwidth. In this case the strong interference component returning directly from the blades (with no ground reflection) need not be considered as it reaches the receiver when it is still blinded. In the case of a CW Doppler radar, however, this interference component must be included. Numerical calculations show that the total blade interference power level, dominated by the direct component, is higher than that of the direct ground clutter in the radar clutter region. It decreases approximately as (f - fo)-4 in the radar clear region. It stays, however, well above the thermal noise level which might cause false alarm and degrade the radar performance.

Single-photon optical heterodyning

Optical heterodyning has been observed at the single-photon level by recording the sinusoidal variation in the probability for detection of a photoelectron from a photomultiplier tube illuminated with a FM laser and a local oscillator laser. The single-photon character of the heterodyne process was demonstrated by observation of beat signals at total power levels down to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6 \times 10^{-15}</tex> W where the spacing between photons emitted from the source laser was <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim40 000</tex> times greater than their transit time through the apparatus.

Simple and reliable subsonic HF chemical laser with 40 W power output (16 W DF)

The design and performance of a transverse flow subsonic chemical laser with a total power output of 40 W for HF and 16 W for DF are presented. Laser operation has been observed in the wavelength range 2.6–3.0 μ for HF and 3.6–4.0 μ for DF resulting from v=2−1 and 1−0 transitions of the HF molecule and from v=3−2, 2−1, and 1−0 transitions of DF. The range of the participating rotational states in the emission spectra can be controlled to some extent by a variation of the gas temperature in the optical cavity region. The observed total power levels correspond to an electrical efficiency of 1.3% for HF and 0.9% for DF.

Sound power level determination for large steam turbine generators

A technique is presented for calculating the approximate total sound power level (PWL) of large steam turbine-generators as well as the PWL of individual turbine-generator components. A near field approximation is used which is similar in structure to the new IEEE test code 85. Modifications are introduced in the test code procedure to reduce the effect of component flanking noise, and noise contributed by extraneous sources. The overall turbine room PWL is also calculated by a reverberant field technique and compared to PWL as calculated by free field methods. Measurements were made around ten large steam turbine generator units ranging in name plate rating from 390 to 1050 MVA. PWL's of turbine-generators were found to increase by approximately 3.5db for each doubling of unit rated MVA. PWL's calculated from indoor near field approximation show a 3 dbA increase over PWL's of outdoor units of equivalent rating. This difference is an indication of the need for further development of methods for determining sound power level.