Low Scatter Research Articles

Ultrasonic tightening control of a screw joint: A comparison of the clamp force accuracy from different tightening methods

Clamp force and its accuracy are investigated using torque, angle, gradient, and clamp force/elongation control. Phosphated, lightly oiled M14 and M10 bolts are tightened. A PowerMACS 4000 system with a QST62-350CT nutrunner is used in the experimental setup. An ultrasonic signal processing unit using a piezoelectric sensor fitted to the socket is used for signal generation and processing when evaluating clamp force. The ultrasonic clamp force control is based on a novel method for assuring correct echo and high repeatability measurements in the tightening system. Torque and angle are extracted from the tool control system. During the experiments a load cell is used to measure the clamp force in the joint. Combined head and thread friction is calculated at final torque and clamp force. The results show that the lowest scatter (3 s) in clamp force, approximately 2.9% can be obtained using ultrasonic clamp force control and the highest, approximately 18% when using torque control. The results are also compared to tightening factors described in VDI2230.

MEASUREMENT OF GALAXY CLUSTER INTEGRATED COMPTONIZATION AND MASS SCALING RELATIONS WITH THE SOUTH POLE TELESCOPE

We describe a method for measuring the integrated Comptonization (YSZ) of clusters of galaxies from measurements of the Sunyaev-Zel'dovich (SZ) effect in multiple frequency bands and use this method to characterize a sample of galaxy clusters detected in South Pole Telescope (SPT) data. We test this method on simulated cluster observations and verify that it can accurately recover cluster parameters with negligible bias. In realistic simulations of an SPT-like survey, with realizations of cosmic microwave background anisotropy, point sources, and atmosphere and instrumental noise at typical SPT-SZ survey levels, we find that YSZ is most accurately determined in an aperture comparable to the SPT beam size. We demonstrate the utility of this method to measure YSZ and to constrain mass scaling relations using X-ray mass estimates for a sample of 18 galaxy clusters from the SPT-SZ survey. Measuring YSZ within a 0.75' radius aperture, we find an intrinsic log-normal scatter of 21+/-11% in YSZ at a fixed mass. Measuring YSZ within a 0.3 Mpc projected radius (equivalent to 0.75' at the survey median redshift z = 0.6), we find a scatter of 26+/-9%. Prior to this study, the SPT observable found to have the lowest scatter with mass was cluster detection significance. We demonstrate, from both simulations and SPT observed clusters, that YSZ measured within an aperture comparable to the SPT beam size is equivalent, in terms of scatter with cluster mass, to SPT cluster detection significance.

Airborne measurements of CO2 column absorption and range using a pulsed direct-detection integrated path differential absorption lidar

We report on airborne CO(2) column absorption measurements made in 2009 with a pulsed direct-detection lidar operating at 1572.33 nm and utilizing the integrated path differential absorption technique. We demonstrated these at different altitudes from an aircraft in July and August in flights over four locations in the central and eastern United States. The results show clear CO(2) line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. The lidar measurement statistics were also calculated for each flight as a function of altitude. The optical depth varied nearly linearly with altitude, consistent with calculations based on atmospheric models. The scatter in the optical depth measurements varied with aircraft altitude as expected, and the median measurement precisions for the column varied from 0.9 to 1.2 ppm. The altitude range with the lowest scatter was 8-10 km, and the majority of measurements for the column within it had precisions between 0.2 and 0.9 ppm.

Fingerprints of the hierarchical building-up of the structure on the gas kinematics of galaxies

Recent observational and theoretical works have suggested that the Tully-Fisher Relation might be generalised to include dispersion-dominated systems by combining the rotation and dispersion velocity in the definition of the kinematical indicator. Mergers and interactions have been pointed out as responsible of driving turbulent and disordered gas kinematics, which could generate Tully-Fisher Relation outliers. We intend to investigate the gas kinematics of galaxies by using a simulated sample which includes both, gas disc-dominated and spheroid-dominated systems. Cosmological hydrodynamical simulations which include a multiphase model and physically-motivated Supernova feedback were performed in order to follow the evolution of galaxies as they are assembled. Both the baryonic and stellar Tully-Fisher relations for gas disc-dominated systems are tight while, as more dispersion-dominated systems are included, the scatter increases. We found a clear correlation between $\sigma / V_{\rm rot}$ and morphology, with dispersion-dominated systems exhibiting the larger values ($> 0.7$). Mergers and interactions can affect the rotation curves directly or indirectly inducing a scatter in the Tully-Fisher Relation larger than the simulated evolution since $z \sim 3$. Kinematical indicators which combine rotation velocity and dispersion velocity can reduce the scatter in the baryonic and the stellar mass-velocity relations. Our findings also show that the lowest scatter in both relations is obtained if the velocity indicators are measured at the maximum of the rotation curve. Moreover, the rotation velocity estimated at the maximum of the gas rotation curve is found to be the best proxy for the potential well regardless of morphology.

Discussion of “thermodynamics of liquid Al-Na alloys determined by using CaF2 solid electrolyte”

Discussion of “thermodynamics of liquid Al-Na alloys determined by using CaF2 solid electrolyte”

Influence of pressurization on flexural strength distributions of PMMA-based bone cements.

Flexural strength distributions of standard viscosity and low viscosity bone cements based on Polymethylmethacrylate were obtained by testing the materials in four-point bending according to the ISO 5833 protocol. The cement dough was poured into a mold and was allowed to cure at atmospheric pressure. An additional set of specimens of the standard viscosity cement was prepared under pressure while the cement dough was polymerizing in the mold. Following preparation, test specimens were stored in a 37 degrees C water bath for 48 h. The two-parameter Weibull model, which was used to analyze the data, gave a good representation of the fracture loads distribution. Low viscosity cement displayed a higher mean flexural strength and a slightly lower data scatter than standard viscosity cement. The mean flexural strength of the cement increased about 60% when pressure was applied compared with the same material cured at atmospheric pressure. The Weibull modulus, m, characterizes the scattering in the measured values of strength. For the cement prepared at atmospheric pressure the m value was 8.6 while for the cement cured under pressure it was 12.3, which reveals a reduction in the data scatter. The cement tested in four-point bending displayed lower mean flexural strength compared with the cement tested in three-point bending. The influence of the load type upon the mean flexural strength was satisfactory predicted by Weibull model.

Correlation between substrate preparation technique and scatter observed from optical coatings

We present experimental evidence of the dependence of coating scatter on a substrate preparation technique for fused silica substrates. Samples included conventionally polished, superpolished, andfloat-polished substrates. We used scatterometry and total internal reflection microscopy to investigate the effects of substrate preparation on the performance of zirconium oxide thin films. Results indicate that scatter from coatings dominates the scatter signature of the coated optic. They also demonstrate that substrate preparation can affect the level of scatter produced in optical coatings. In addition it is observed that the substrates with the lowest scatter do not necessarily result in the coatings with the lowest scatter.

Chemical Vapor Deposition of Epmtaxial BaTiO3 Films for Frequency Doubling Devices

AbstractFerroelectric materials such as BaTiO3 are notable for their nonlinear optical and electrical properties. Optical frequency doubling in thin films integrated with compact semiconductor laser pumped solid state lasers is an attractive candidate for high efficiency generation of blue light. Chemical vapor deposition (CVD) using a single liquid source has been used to grow BaTiO3 films on MgO. X-ray diffraction in the pole figure configuration indicates the films to be epitaxial, and rocking curves had FWHM ≈ 0.7°. An optical scatterometer (λ = 633 nm.) has been used to identify deposition conditions that result in the lowest scatter losses. This paper describes these results as well as waveguide designs to enhance the second harmonic generation efficiency in epitaxial BaTiO3 films on MgO.