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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 48 (1989), S. 437-443 
    ISSN: 1432-0630
    Keywords: 85.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Computer studies have been made on the high frequency characteristics of symmetrically doped flat profile double drift region (DDR) InP and GaAs impatts in the mm-wave (60–100 GHz) frequency band. The spatial distribution of high frequency negative resistance and reactance in the depletion layer of DDR devices and their admittance properties have been investigated. The results indicate that DDR InP impatts should have higher drift zone voltage drop, higher negative resistance and higher negative conductance compared to their GaAs counterparts designed for the same range of mm-wave frequencies. Furthermore, the negative resistance peak is larger in magnitude for InP impatts compared to that for GaAs impatts. It is thus observed that DDR InP impatts should be superior to their GaAs counterparts as regards mm-wave power generation with high conversion efficiency.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0630
    Keywords: 85.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract High-frequency analysis has been carried out to predict the rf performance of 〈111〉, 〈110〉 and 〈100〉 oriented p + nn +, n + pp + (single drift region) and n + npp + (double drift region) GaAs IMPATT diodes for opertion at 35 and 60 GHz. The microwave performance is observed to be highly sensitive to crystal orientation in case of p + nn + and n + npp + diodes whereas orientation of the substrate has negligible effect on n + pp + avalanche diodes. The calculation shows that 〈111〉 oriented GaAs IMPATT diode would provide the largest magnitude of negative resistance and negative conductance for both SDR p + nn + and DDR n + npp + diodes which indicates that high microwave power with high conversion efficiency can be realised from these 〈111〉 oriented GaAs devices. This result can be explained from the experimental data of electron and hole ionization rates for different orientations in GaAs.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0630
    Keywords: 85.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The effect of mobile space charge on avalanche zone width and conversion efficiency of single drift region (SDR) indium phosphide impatts at 12 and 60 GHz has been investigated. The results show thatp +nn+ InP diodes have a narrower avalanche zone and a higher conversion efficiency compared ton +pp+ diodes for both the frequencies at normal operating current densities. The expansion of avalanche zone and efficiency degradation at high current levels are more pronounced inp +nn+ at 12 GHz and inn +pp+ at 60 GHz.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0630
    Keywords: 85.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A generalized small-signal computer simulation of double avalanche region (DAR) n +-p-v-n-p + Si and InP IMPATT diodes has been carried out for different frequencies and current densities taking both drift and diffusion of charge carriers into account. The simulation results show that both symmetrically and asymmetrically doped devices based on Si and InP exhibit discrete negative conductance frequency bands separated by positive conductance frequency bands. The magnitudes of both negative conductance and negative resistance of InP devices are larger than those of Si devices in case of symmetrical and asymmetrical diodes. Further, the negative resistance profiles in the depletion layer of these diodes exhibit a single peak in the middle of the drift layer in contrast to double peaks in double drift region diodes.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-2959
    Keywords: risk assessment ; chlorinated compound ; environmental ; marine ; exposure ; aquatic toxicity ; monitoring ; trichloroethylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This risk assessment on trichloroethylene (TRI) was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 19 studies for fish, 30 studies for invertebrates and 14 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a PNEC value of 150 µg/l. Most of the available monitoring data apply to rivers and estuaries and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.1 µg TRI/l water and a worst case PEC of 3.5 µg TRI/l water. The calculated PEC/PNEC ratios give a safety margin of 40 to 1,500 between the predicted no effect concentration and the exposure concentration. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern for food chain accumulation is expected.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-2959
    Keywords: risk assessment ; chlorinated compound ; environmental ; marine ; exposure ; aquatic toxicity ; monitoring ; chloroform
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This risk assessment on chloroform was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 23 studies for fish, 17 studies for invertebrates and 10 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a typical PNEC value of 72 µg/l. Due to limitations of the studies evaluated, a worst PNEC of 1 µg/l could also be used. Most of the available monitoring data apply to rivers and estuaries and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.2 µg chloroform per litre of water and a worst case PEC of 5 to 11.5 µg chloroform per litre of water. The calculated PEC/PNEC ratios give a safety margin of 6 to 360 between the predicted no effect concentration and the exposure concentrations. A worst case ratio, however, points to a potential risk for sensitive species. Refinement of the assessment is necessary by looking for more data. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern is expected for food chain accumulation.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-2959
    Keywords: risk assessment ; chlorinated compound ; environmental ; marine ; exposure ; aquatic toxicity ; monitoring ; tetrachloroethylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This risk assessment on tetrachloroethylene (PER) was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 18 studies for fish, 13 studies for invertebrates and 8 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a PNEC value of 51 µg/l. Most of the available monitoring data apply to rivers and estuary waters and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.2 µg PER/l water and a worst case PEC of 2.5 µg PER/l water. The calculated PEC/PNEC ratios give a safety margin of 20 to 250 between the predicted no effect concentration and the exposure concentration. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern is expected for food chain accumulation.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-2959
    Keywords: risk assessment ; chlorinated compound ; marine ; environmental ; exposure ; aquatic toxicity ; monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This risk assessment on 1,1,2-trichloroethane (T112) was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 22 studies for fish, 45 studies for invertebrates and 9 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a PNEC value of 300 µg/l. Most of the available monitoring data apply to rivers and estuaries and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.01 µg T112/l water and a worst case PEC of 5 µg T112/l water. The calculated PEC/PNEC ratios give a safety margin of 60 to 30,000 between the predicted no effect concentration and the exposure concentration. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern is expected for food chain accumulation.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-2959
    Keywords: risk assessment ; chlorinated compound ; environmental ; marine ; exposure ; aquatic toxicity ; monitoring ; 1,2-dichloroethane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This risk assessment on 1,2-dichloroethane (EDC) was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 21 studies for fish, 17 studies for invertebrates and 7 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a PNEC value of 1100 µg/l. Most of the available monitoring data apply to rivers and estuaries and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.5 µg EDC/l and a worst case PEC of 6.4 µg EDC/l. The calculated PEC/PNEC ratios give a safety margin of 170 to 2200 between the predicted no effect concentration and the exposure concentration. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern is expected for food chain accumulation.
    Type of Medium: Electronic Resource
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