Results 1 - 10 of 140799
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[en] The effects of linear and nonlinear friction on the seiche's motion in the Adriatic sea have been studied through a perturbative and numerical method. A roughness has been introduced to study the interaction with nonlinear friction term. (author)
[en] When completed, the National Ignition Facility (NIF) will provide laser energies in the Mega-joule range. Successful pulse amplification to these extremely high levels requires that all small optics, found earlier in the beamline, have stringent surface and laser fluence requirements. In addition, they must operate reliably for 30 years constituting hundreds of thousands of shots. As part of the first four beamlines, spherical and aspherical lenses were required for the beam relaying telescopes. The magneto-rheological technique allows for faster and more accurate finishing of aspheres. The spherical and aspherical lenses were final figured using both conventional-pitch polishing processes for high quality laser optics and the magneto-rheological finishing process. The purpose of this paper is to compare the surface properties between these two finishing processes. Some lenses were set aside from production for evaluation. The surface roughness in the mid-frequency range was measured and the scatter was studied. Laser damage testing at 1064 nm (3-ns pulse width) was performed on surfaces in both the uncoated and coated condition.
[en] Simulation results of roughening of nanocomposite materials during both isotropic and anisotropic etching processes based on the level set method are presented. It is clearly shown that the presence of two phases with different etching rates affects the development of surface roughness and that some roughness characteristics obey simple scaling laws. In addition, certain scaling laws that describe the time dependence of the root mean square (rms) roughness w for various etching processes and different characteristics of the nanocomposite materials are determined.
[en] The invention relates to an improvement of a chamber for gas etching, ion etching or vapor coating surfaces. The improvement refers to the type of movable specimen holder within the chamber. This allows the specimen to be moved without damaging the vacuum. As a consequence, the specimen can be observed under the microscope either periodically or continuously. Even remote control is possible (in hot cells). (GSC)
[de]Die Erfindung betrifft eine Verbesserung an einer Kammer, in der Gasaetzung, Ionenaetzung oder die Bedampfung einer Oberflaeche durchgefuehrt wird. Die Verbesserung bezieht sich auf die Art der beweglichen Probenhalterung innerhalb der Kammer. Sie erlaubt es, die Probe zu bewegen, ohne dass das Vakuum verletzt wird. Die Probe kann daher periodisch oder dauernd unter mikroskopischer Beobachtung stehen, auch Fernbedienung (in kurzen Zellen) ist moeglich. (GSC)
[en] Vibratory finishing belongs to the wider group of near ubiquitous mass finishing processes. Components are typically bulk finished in a fluidised media bed and applications vary from performance critical polishing, to cosmetic surface preparation. The established model of surface topography development has been one of initial rapid change during a ‘transient’ process phase, with subsequent slowing and a final ‘steady state’ phase in which surface character is uniform with no dependence on process duration or initial surface finish. Recent reassessment of the steady state phase has suggested that its surface roughness oscillates with process duration about a mean value and redefines it as the ‘equilibrium’ phase. Though this new model is considered to incorporate the existing model as a special case, it is argued that it represents a fundamental shift in the process mechanics. In addition, it is argued that the new findings have potential relevance to a much wider group of stochastic processes. Thus, the current paper seeks to clarify the underlying development process by investigating the nature of the end phase surface and testing these models by examining new and existing data. Results show no statistical evidence to support any periodic oscillations in the end phase surface and a number of issues with the oscillating model are noted. In addition, it is suggested that there is no clear physical mechanism to underpin the oscillating model and that the saturating model is sufficient to describe all the presented data. In conclusion a qualitative description of the end phase topography and its dynamic but temporally uniform character is given. The idea of ‘process bandwidth’ relating to the range of surface-media interactions is introduced to help describe some of the behavioural and control aspects of this stochastic process and the surface topography it produces. (paper)
[en] Magnetic trapping potentials for atoms on atom chips are determined by the current flow in the chip wires. By modifying the shape of the conductor we can realize specialized current flow patterns and therefore microdesign the trapping potentials. We have demonstrated this by nano-machining an atom chip using the focused ion beam technique. We built a trap, a barrier, and using a Bose-Einstein Condensate as a probe we showed that by polishing the conductor edge the potential roughness on the selected wire can be reduced. Furthermore, we give different other designs and discuss the creation of a one-dimensional magnetic lattice on an atom chip
[en] Roughness of channel surfaces, both deterministic and random, is known to affect the fluid flow behavior in micro/nanoscale fluidic devices. This has relevance particularly for applications involving non-Newtonian fluids, such as in biomedical lab-on-chip devices. While several studies have investigated effects of relative large, deterministic surface structures on fluid flow, the effect of random roughness on microfluidic flow remains relatively unexplored. In this study, the effects of processing conditions for wet etching of glass including etching time and etching orientation on centre-line average (Ra) and the autocorrelation length (ACL) were investigated. Statistical distribution of the roughness was also studied. Results indicated that ACL can be tailored in the range of 1–4 µm by changing etching time in horizontal etching while Ra was found to increase weakly with etching time in all three etching orientations. Analysis of the experimental data using the Kolmogorov–Smirnov goodness-of-fit hypothesis test shows that the glass surface roughness does not follow a Gaussian distribution, as is typically assumed in the literature. Instead, the T location-scale distribution fits the roughness data with 1.11% error. These results provide promising insights into tailoring surface roughness for improving microfluidic devices.
[en] Low temperature scanning laser microscopy (LTSLM) can be used for a two-dimensional display of bolometric response arising from the localized excitation of a sample by the focused laser beam. In this study, the distribution of critical temperature (Tc) and critical current density (Jc) in YBCO coated conductor were analyzed using LTSLM. For improving the temperature stability, we have modified the system into a double-shielding type. Through the modification, the temperature stability was successfully improved from ±10 mK to ±2 mK. The superconducting properties of YBCO coated conductors were measured for the sample of a narrow bridge type using wet etching process. The spatial non-uniformity of the ac voltage response, δV(x), which is proportional to ∂ρ(x, JB)/ δT in the transition temperature region could be observed and displayed in a two-dimensional image.