A methodology for systemic‐structural analysis and design of manual‐based manufacturing operations

The main objective of this study was to develop a method for systemic‐structural analysis and design of manufacturing assembly operations based on the activity theory. The “activity” was defined as behavior distinctively specific to workers, associated with mobilizations and realization of conscious manufacturing goals. The fundamental units of analysis of activity are actions that are both motor and mental. Activity is considered as a complicated structure of actions that are logically ordered in space and time. Each action is comprised of different operations. The building blocks of motor actions are motions. The building blocks of cognitive actions are mental operations. Activity integrates not merely cognitive and behavioral components, but the energy components as well. The proposed methodology is illustrated using an example of two manufacturing assembly operations. © 2001 John Wiley and Sons, Inc.     

Human perception of robot safe speed and idle time

Operators and users of robotic systems perform tasks which require close proximity to dangerous moving parts. Two experiments were performed to assess human perception of safe robot arm speed and idling times. Experiment 1 was designed to determine the maximum safe speed of robots. Subjects were asked to adjust the robot speeds. Perceived safe speeds were indicated for two different types of robots. Experiment 2 was designed to determine safe programmed idle time of robots. Subjects were asked to enter the robot work envelope when a programmed idle was perceived to be caused by a malfunction. Safe idle times were reported for two different robot speeds during operational cycles.     

Fatigue strength of welded joints in austenitic Cr-Ni steels

Abstract

High quality corrosion resistant Cr-Ni steels are used in many branches of industry. Constructors are faced with the problem of correctly dimensioning statically and dynamically loaded parts, but have little data available for dynamically loaded welded constructions of high alloy austenitic steels. To close this gap fatigue strength tests were carried out on three different steels and five different welded joints.     

Late psychosocial improvement in a case of severe head injury with bilateral fronto-orbital lesions.

Describes the results of a 19-yr follow-up study of a head-injured female patient. At age 17 yrs, the S sustained a blunt head trauma with bilateral fronto-orbital lesions verified by late regional cerebral blood flow. The S presented an extreme state of regression for many months after injury. During the first posttraumatic years no behavioral disorders were reported, but after the 5th yr lack of control, including sexual disinhibition, and lack of motivation became severe problems. More than 10 yrs after the accident, a partner applied a simple program of behavioral modification to the S. After 2 yrs of rigid training, an unexpected improvement in psychosocial adaptation took place. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Non-hydrothermal synthesis of copper-, zinc- and copper-zinc hydrosilicates

Cu/SiO₂, Zn/SiO₂ and Cu-Zn/SiO₂ samples have been prepared by the homogeneous deposition-precipitation method. The samples were analyzed by thermal analysis, X-ray diffraction and infrared spectroscopy after various heat treatments and compared with data obtained for several minerals. It has been shown that interaction between the components occurs through formation of hydrosilicates. Copper-silica system at a Cu:Si ratio ≤ 1, gives rise to a hydrosilicate stable up to a calcination temperature of 930 K resembling the mineral Chrisocolla; at higher ratios a hydroxonitrate (gerhardite type) is also formed. Zinc-silica interaction produces two hydrosilicates such as a well crystallized Hemimorphite at Zn:Si = 2 and highly dispersed Zincsilite at Zn:Si ≤ 0.75, both stable up to 1073 K. The Zincsilite structure consists of three layered sheets (an octahedral layer sandwiched by two tetrahedral ones) like the Stevensite mineral group. For the copper-zinc-silica system no copper hydrosilicate is formed. Copper merely enters the Zincsilite structure independenly of the applied (Cu + Zn):Si ratio. Resulting layered copper-zinc hydrosilicate may be described by formula Zn_x-yCu_y(Zn_3-x–zCu_z–y▪_x)[Si₄O₁₀](OH)₂.nH₂O, where Zn_3-x-zCu_z-y– ions are located in octahedral sites, Zn_x-yCu_y–ions in the interlayer; ▪_x are vacancies in the layers. Copper and zinc in excess of the Zincsilite ratio of Me:Si = 0.75, gives rise to copper and copper-zinc hydroxonitrates. Received: 7 November 2000 / Reviewed: 23 January 20001 / Accepted: 23 January 2001     

Modeling and analysis of communication systems based oncomputational methods for Markov chains

The authors describe a computational approach for modeling and analyzing modern communication systems based on numerical methods for Markov chains. Advanced direct and iterative procedures for the calculation of the stationary distribution of a homogeneous discrete- or continuous-time Markov chain with finite state space are presented. They are implemented in a convenient software tool called MACOM for interactive modeling and performance evaluation of communication systems. MACOM provides the user with a predefined markovian model world describing modern telecommunication networks with adaptive routing schemes and advanced congestion-control mechanisms. The versatility of these algorithms is illustrated by their application to Markovian queuing models derived from telecommunications networks     

Bistatic TerraSAR-X/F-SAR Spaceborne–Airborne SAR Experiment: Description, Data Processing, and Results

We report about the first X-band spaceborne–airborne bistatic synthetic aperture radar (SAR) experiment, conducted early November 2007, using the German satellite TerraSAR-X as transmitter and the German Aerospace Center's (DLR) new airborne radar system F-SAR as receiver. The importance of the experiment resides in both its pioneering character and its potential to serve as a test bed for the validation of nonstationary bistatic acquisitions, novel calibration and synchronization algorithms, and advanced imaging techniques. Due to the independent operation of the transmitter and receiver, an accurate synchronization procedure was needed during processing to make high-resolution imaging feasible. Precise phase-preserving bistatic focusing can only be achieved if time and phase synchronization exist. The synchronization approach, based on the evaluation of the range histories of several reference targets, was verified through a separate analysis of the range and Doppler contributions. After successful synchronization, nonstationary focusing was performed using a bistatic backprojection algorithm. During the campaign, stand-alone TerraSAR-X monostatic as well as interoperated TerraSAR-X/F-SAR bistatic data sets were recorded. As expected, the bistatic image shows a space-variant behavior in spatial resolution and in signal-to-noise ratio. Due to the selected configuration, the bistatic image outperforms its monostatic counterpart in almost the complete imaged scene. A detailed comparison between monostatic and bistatic images is given, illustrating the complementarity of both measurements in terms of backscatter and Doppler information. The results are of fundamental importance for the development of future nonsynchronized bistatic SAR systems.      

2‐Acetyl‐4,6,8,10,12‐Pentanitro‐Hexaazaisowurtzitane (PNAIW) Preparation and Properties

2‐Acetyl‐4,6,8,10,12‐pentanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (PNAIW) is formed in the last step of nitration of acetyl isowurtzitane derivatives. The amount of the PNAIW formed depends on the conditions of the nitration reaction (temperature, time, and nitrating mixture used) and on the type of the starting acetyl intermediate. The highest PNAIW yields (30 %) were obtained by nitrating 2,6,8,12‐tetraacetylhexaazaisowurtzitane (TAIW) at 60 °C for half an hour using HNO₃/H₂SO₄ nitrating mixture. HPLC, NMR, FTIR, and DSC measurements were used in the study and their results are reported.