Measurements of the equivalent dose in aircraft with TLDS

For measurements of the equivalent dose of the mixed radiation fields in aircraft many different measuring devices are usually necessary for consideration of the different components of the radiation field. The possibility is discussed of using thermoluminescence dosemeters (TLDS) for determination of absorbed dose and average LET of this complex radiation field in aircraft. The HTR method, developed for determination of the equivalent dose in spacecraft, enables the measurement of the average LET in addition to the absorbed dose. Furthermore, a rem counter based on TLDs and a modified pair method (TLD-600, TLD-700) was used for determination of the absorbed dose due to the neutron component. Using small TLD crystals it is possible to obtain the depth distribution of absorbed dose and average LET by exposing TLDs in Bonner spheres with different diameters. The results indicate that the standards for determination of the effective dose may not be applicable in these mixed radiation fields in aircraft.     

Monitoring of toxic compounds in air using a handheld rectilinear ion trap mass spectrometer

A miniature, handheld mass spectrometer, based on the rectilinear ion trap mass analyzer, has been applied to air monitoring for traces of toxic compounds. The instrument is battery-operated, hand-portable, and rugged. We anticipate its use in public safety, industrial hygiene, and environmental monitoring. Gaseous samples of nine toxic industrial compounds, phosgene, ethylene oxide, sulfur dioxide, acrylonitrile, cyanogen chloride, hydrogen cyanide, acrolein, formaldehyde, and ethyl parathion, were tested. A sorption trap inlet was constructed to serve as the interface between atmosphere and the vacuum chamber of the mass spectrometer. After selective collection of analytes on the sorbent bed, the sorbent tube was evacuated and then heated to desorb analyte into the instrument. Sampling, detection, identification, and quantitation of all compounds were readily achieved in times of less than 2 min, with detection limits ranging from 800 parts per trillion to 3 parts per million depending on the analyte. For all but one analyte, detection limits were well below (3.5-130 times below) permissible exposure limits. A linear dynamic range of 1-2 orders of magnitude was obtained over the concentration ranges studied (sub-ppbv to ppmv) for all analytes.     

Detection of ozone on Saturn's satellites Rhea and Dione

The satellites Rhea and Dione orbit within the magnetosphere of Saturn, where they are exposed to particle irradiation from trapped ions. A similar situation applies to the galilean moons Europa, Ganymede and Callisto, which reside within Jupiter's radiation belts. All of these satellites have surfaces rich in water ice. Laboratory studies of the interaction of charged-particle radiation with water ice predicted the tenuous oxygen atmospheres recently found on Europa and Ganymede. However, theoretical investigations did not anticipate the trapping of significantly larger quantities of O2 within the surface ice. The accumulation of detectable abundances of O3, produced by the action of ultraviolet or charged-particle radiation on O2, was also not predicted before being observed on Ganymede. Here we report the identification of O3 in spectra of the saturnian satellites Rhea and Dione. The presence of trapped O3 is thus no longer unique to Ganymede, suggesting that special circumstances may not be required for its production.     

Einfluss und Bedeutung chemischer Entmischungen auf mechanische Eigenschaften thixogeformter Bauteile

Chemical Segregation Effect on Mechanical Properties of Thioxo Formed Components Thixoforming is a near net shape forming process of semi solid billets with a stiffness, which is comparable to “butter”. Advantages of conventional forming and casting processes can be combined due to this modern forming process technology. The objective of this investigation is to identify the effect of local chemical segregation regarding the microstructure and mechanical properties in various parts of a component. Different components and component regions – with diverse cross‐sections and flow lengths – have been tested. Tensile, charpy and fatigue tests are completed by metallography and local chemical analysis. The investigation was focused on AlSi7Mg0.3 and AlSi6Cu3 aluminium casting alloys. It can be confirmed, that chemical composition of the raw material and segregation are important effects on mechanical properties of components. Chemical segregation can be caused by abrupt changes in cross‐section. The inhomogeneity verified by chemical analysis and metallography are important effects on mechanical properties of Thixoforming components. In future the counteract between metal structure and processing steps regarding mechanical properties of components must be examined more intensively. The aim is to create a fundamental understanding of the relationship between the structure, chemical composition, homogeneity and characteristics of aluminium materials.     

Architecture and circuit design of a 6-GOPS signal processor forQAM demodulator applications

A QAM processor for applications in QAM demodulators with baud rates of up to 60 Mbaud and modulation schemes of up to 1024 QAM has been implemented on a single chip. The chip performs 11-tap complex-valued adaptive time-domain equalization and the complete digital base-band signal processing of high-capacity QAM demodulators. This includes frequency-domain slope equalization and the digital parts of the timing and carrier recovery as well as the gain and offset control for the A-to-D converters. The equalizer can be operated in baud spaced and half-baud spaced mode and can also be applied for cross-polarization interference cancellation. The computational power of the QAM processor exceeds 6 giga-multiply-accumulate operations per second. Fabricated in an 1.0-μm CMOS technology on a silicon area of 185 mm² this 800 K-transistor chip demonstrates the potential of such low-cost technologies. The maximum clock frequency under worst-case conditions is 60 MHz. The corresponding power dissipation is 4.2 W     

A low cost multichip packaging technology for monolithic microwaveintegrated circuits

This paper describes a multichip module technology based on highly impermeable liquid crystal polymers (LCPs) to interconnect and package monolithic microwave integrated circuits (MMICs). Because of the low moisture permeability of the LCPs, the packages can be made hermetic without heavy expensive housings can be two to four times lighter and one-fifth the cost of conventional ceramic based transmit/receive (T/R) modules. The LCP material has a low dielectric constant (2.65) and low-loss tangent and is manufacturable using high volume, large-area processing methods that provide very reliable high-performance circuits at low cost. Using flip-chip bonded MMICs attached to a high thermal conductivity, low coefficient of thermal expansion substrate, this innovative technology can meet a variety of commercial, military, and NASA requirements     

Embedding of Dedicated High-Performance ASICs into Reconfigurable Systems Providing Additional Multimedia Functionality

The computational power required in many multimedia applications is well beyond the capabilities of today's multimedia systems. Therefore, the embedding of additional high-performance accelerator multimedia components into these systems is most decisive. This paper presents the embedding of multimedia components into computer systems using reconfigurable coprocessor boards. The goal of those reconfigurable platforms which can be adapted to several applications and which include programmable digital signal processors, control and memory devices as well as dedicated multimedia ASICs is worked out. On the way to such a platform four ASICs for image and text processing are presented. The embedding of these components into a computing system using a CardBus-based coprocessor board is shown. Such a reconfigurable coprocessor board is an important intermediate stage on the way to future hybrid reconfigurable systems on chip.     

Data driven search organization for continuous speech recognition

The authors describe an architecture and search organization for continuous speech recognition. The recognition module is part of the Siemens-Philips-Ipo project on continuous speech recognition and understanding (SPICOS) system for the understanding of database queries spoken in natural language. The goal of this project is a man-machine dialogue system that is able to understand fluently spoken German sentences and thus to provide voice access to a database. The recognition strategy is based on Bayes decision rule and attempts to find the best interpretation of the input speech data in terms of knowledge sources such as a language model, pronunciation lexicon, and inventory of subword units. The implementation of the search has been tested on a continuous speech database comprising up to 4000 words for each of several speakers. The efficiency and robustness of the search organization have been checked and evaluated along many dimensions, such as different speakers, phoneme models, and language models     

Structural and optical characterization of InP/GalnP islands grown by solid-source MBE

We report on the growth of InP/GalnP islands on GaAs substrates by solidsource molecular beam epitaxy. It is shown by reflection high energy electron diffraction and atomic force microscopy that a rapid change from a twodimensional to a three-dimensional growth mode occurs at about nominally 1.5 monolayers (MLs) InP. Transmission electron microscopy measurements demonstrate the coherent incorporation of InP islands in an GalnP matrix for nominally 2.5 MLs InP. The energy of the InP photoluminescence (PL) shifts to lower energies (100 meV) when the growth interruption time between the island and cap layer growth is increased from 1 to 300 s in case of nominally 3 MLs InP. Simultaneously, an increase of the PL linewidth is observed from 30 to 60 meV. Room temperature photoreflectance measurements on samples with various InP thickness have been performed. Compared to PL measurements, an additional feature in the photoreflectance spectra is observed for samples with more than 7 MLs InP, which is attributed to a transition between excited electron and hole states of the islands.