Mikrotechnik für Raumfahrtanwendungen

This contribution describes the preparation, based upon a chemically amplified novolak resist (CAR), electron beam lithography, and ECR plasma etching, of structures with a high aspect ratio (10∶1) and lateral dimensions in the sub-micrometer range (150nm–300nm) which may serve as collector surfaces for sub-μm dust particles in a space experiment.     

The handwriting problem [man-machine motion analogy in robotics]

Two approaches are proposed to model and control a human-like motion of robot arms. The first, which is based on the concept of distributed positioning (DP), is suggested as a good model of arm motion in the phase where fatigue does not appear. The prescribed motion of the end-effector is distributed to a redundant number of arm joints in accordance to their acceleration capabilities. For the phase where fatigue appears, the concept of virtual fatigue is proposed. This artificial variable, which is based on robot dynamics, emulates the progress of biological fatigue. The human handwriting task is chosen for the simulation. The DP concept is tested first by modeling nonfatigued motion. The justification of the usual inclination of letters is presented, and the relation between the inclination, legibility, and a secondary objective (finger involvement, energy consumption, motor thermal load) is discussed. It is found that, for some prescribed level of legibility, the individual optima of all the secondary cost functions are quite near to each other. Writing in the presence of fatigue is also analyzed, applying the method of the so-called "virtual fatigue".     

Modeling Robot “Psycho-Physical” State and Reactions – A New Option in Human–Robot Communication Part 2: Modeling and Simulation

This part of the paper examines numerically the possibility of modeling robot fatigue being representative of a human psychophysical state that can be applied to robots. Temperatures of driving motors are suggested as analogs to fatigue in muscles. Simulation of robot behavior is performed on a typical human task, namely handwriting. Three phases of task execution, characteristic for humans, are observed, i.e. regular motion, reconfiguration after symptoms of fatigue, and degeneration caused by the too long, hard work.     

Motion in human and machine: A virtual fatigue approach

Achieving human-like behavior of a robot is a key issue of the paper. Redundancy in the inverse kinematics problem is resolved using a biological analogue. It is shown that by means of "virtual fatigue" functions, it is possible to generate robot movements similar to movements of a human arm subject to muscle fatigue. Analytic method enabling control of robot motions in a human-like fashion is described. An example of an anthropomorphic robot arm performing a screw-driving task illustrates the method.     

Morphology and structure of bainite plates in the β’ phase of an Ag-45 at. pct Cd alloy

The morphology and structure of bainite plates which formed in the ordered bcc β’ phase of a Ag-45 at. pct Cd alloy at temperatures 160 to 300°C were studied by X-ray diffraction and transmission electron microscopy. Initially, the plates formed with a 3R stacking fault modulation of the fcc structure and contained a high density of random stacking faults. The stacking faults annealed out during a prolonged isothermal treatment, the structure gradually changing to a regular fcc. The orientation relationship between the bcc matrix and the fcc bainite was as follows: [1•11]_b 0.7 deg from [0•11]_f, [110]_b 1.1 deg from [l00]_f and [011]_b 4.3 deg from the stacking fault plane pole [111]_f. The habit plane of the bainite plates, determined by two surface trace analysis, was close to (3, 11, 12)_b. The surface relief of the plates, examined by interference microscopy, was in the form of a simple tilt indicating an invariant plane strain transformation. The features of the transformation agreed with the predictions of the Bowles-MacKenzie theory of martensite formation. It was concluded that the morphology, structure and other characteristics of the freshly formed bainite plates were consistent with their formation by a thermally activated martensitic process. formerly Research Associate, Department of Metallurgy, University of British Columbia, Vancouver, B.C., Canada.     

Resolving subchip-spaced multipath components in CDMA communicationsystems

A method is developed for resolving channel multipath components for direct-sequence code-division multiple-access (DS-CDMA) communication systems. Components which are spaced closer than a chip interval of the DS signature sequence are separable by the presented technique. The method is based on the constrained iterative deconvolution which uses the method of projection onto convex sets (POCS). A novel POCS constraint is derived which takes advantage of the noise covariance modified by a matched filter at the front end of the receiver. Simulation results for m-sequences and BPSK modulation are presented     

Analysis of complex grounding systems consisting of foundationgrounding systems with external grids

Results of an extensive research, conducted using a technique developed to calculate the grounding resistance of a complex grounding system consisting of a foundation grounding system with an external grid, buried in two-layer soil, are presented and discussed. It is shown that connecting a foundation grounding system to the already existing external grid provides only a small reduction of the overall grounding system resistance compared to the resistance of the external grid alone. A number of tables related to the most frequent cases of soil-concrete structures are given for practical assessment of the grounding resistance of such complex grounding systems     

Advanced patterning techniques for nanodevice fabrication

The key elements in the fabrication of future devices are lithography and pattern transfer. The continuous advances in miniaturization and increasing integration densities are a direct result of improved lithographic resolution and overlay accuracy. Electron beam direct write and e-beam projection lithography are potential candidates for the mass production of microelectronic devices with critical dimensions below 100 nm. To realize these nanometer patterns by this technology, the performance of exposure tools and resist materials should be increased. In this paper, the method of direct write e-beam lithography is demonstrated and critical issues are discussed.     

Predicting turbulent friction factors of non-newtonian fluids in noncircular ducts

On the basis of limited experimental data it appears that the procedure developed by Jones for predicting turbulent friction factors for Newtonian fluids in rectangular and concentric annular ducts may be extended to purely viscous non-Newtonian fluid in noncircular ducts using the Reynolds number introduced by Kozicki.