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  • 1
    ISSN: 1432-1882
    Keywords: Key words:Virtual worlds – Embodiments – Avatars – Clones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. This paper explores the issue of user embodiment within collaborative virtual environments. By user embodiment we mean the provision of users with appropriate body images so as to represent them to others and also to themselves. By collaborative virtual environments we mean multi-user virtual reality systems which explicitly support cooperative work (although we argue that the results of our exploration may also be applied to other kinds of collaborative system). The main part of the paper identifies a list of embodiment design issues grouped by the general themes of personal representation, conveying activity, embodiment in heterogeneous systems, embodiment of agents, and ethical issues. These issues are illustrated with examples from our own DIVE and MASSIVE collaborative virtual environments. The paper also uses this set of issues as an analytical framework for comparing a number of other communication technologies.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Risk analysis 15 (1995), S. 0 
    ISSN: 1539-6924
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Several major epidemiological studies have reported significant mortality rates (SMRs) for both rare cancers (soft tissue sarcoma, non-Hodgkin's, lymphoma, liver) and the more common cancers (lung, colon, etc), all allegedly caused by TCDD. In this paper, we use the potency of TCDD in animals to establish a plausible worst case cancer risk and ask whether its likely that TCDD is responsible for the epidemiological findings assuming the animal carcinogenic potency is applicable to the conditions of human exposure. Two new features of the technique are the use of measured TCDD blood levels in both animals and humans for dose scale-up and the calculation of an integrated life-time exposure for the exposed workers using measured blood levels. On the basis of the stated assumptions it appears unlikely that any of the major epidemiological studies, with the possible exception of the NIOSH study(1)have adequate power to detect the common cancers potentially caused by TCDD.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 489-491 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate quantum efficiency limitations in InGaAsP/InP multiquantum-well (MQW) laser diodes emitting at 1.5 μm. At room temperature, the internal differential efficiency above threshold is found to be reduced mainly by increasing Auger recombination and spontaneous emission within the quantum wells. These carrier loss increments are commonly assumed negligible due to MQW carrier density clamping. Even with clamped average carrier density, increasing nonuniformity of the quantum well carrier population leads to enhanced losses. We analyze these loss enhancements using an advanced laser simulation software. Excellent agreement between measurements and simulations is obtained. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2637-2638 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A vertical directional coupler fabricated using wafer fusion is demonstrated with a very short coupling length of 62 μm. The optical propagation loss introduced by the fused layer is investigated. An excess loss of 1.1 dB/cm at 1.55 μm was measured for waveguides which incorporate a fused junction near the core region. Fused vertical couplers make it possible to realize three-dimensional waveguide structures and compact switching arrays and they solve some of the topology problems of large switch arrays. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2084-2086 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the measurements of nonlinearity effects on analog transmission of long wavelength vertical-cavity surface-emitting lasers. The experiments involved measuring single-mode fiber-optic transmissions of microwave signals (100–1000 MHz) at 1.54 μm to characterize the dynamic range, intermodulation distortion and frequency response. Spur free dynamic ranges up to 69 dB were demonstrated. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2508-2510 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The authors demonstrate p-i-n traveling wave photodetectors utilizing low-temperature-grown GaAs as the absorption layer. The electro-optically measured impulse response was found to exhibit a pulsewidth of 1.1 ps full width at half maximum, corresponding to a −3 dB bandwidth of 370 GHz with an external quantum efficiency of 8% at 800 nm. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 303-305 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the fabrication of a near-infrared avalanche photodetector with a gain-bandwidth product of over 300 GHz. The detector uses a Si multiplication layer and an InGaAs absorption layer. A 3 dB bandwidth of over 9 GHz was measured for current gains as high as 35. Photocurrent measurements using 1.3 μm light indicate a quantum efficiency for the detector of 0.60, near the limit expected based on the absorber thickness. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 471-472 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a novel long wavelength(1.55 μm) vertical cavity laser using a current constricting AlAs oxidation layer. The devices exhibit record low room temperature continuous wave (cw) threshold current(1.3 mA) and highest cw operating temperature reported for long wavelength VCLs(39 °C). Wafer fusion is used to combined seven strain compensated InGaAsP wells between two Al(Ga)As/GaAs quarter wave mirrors. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2630-2632 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The first vertical-cavity surface-emitting laser diodes operating continuous-wave at room temperature at 1.54 μm emission wavelength are analyzed using a comprehensive numerical simulation procedure. These lasers employ strain-compensated InGaAsP multi-quantum wells sandwiched between GaAs/AlGaAs mirrors that are double-fused on the InP spacer layers at both sides. The model includes finite element electro-thermal simulation, transfer-matrix optical analysis, and k⋅p band structure calculations. Internal laser parameters are obtained by fitting experimental data at different heat sink temperatures. Intervalence band absorption is found to be the dominating loss mechanism that restricts cw operation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3558-3560 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe the use of flared waveguide diode lasers for obtaining increased output power under mode-locked operation. The flared waveguide expands the optical mode from a narrow region which gives a single lateral optical mode, to a wider multimode region for higher pulse saturation energy. Flared gain and flared absorber section geometry devices are compared to devices with conventional uniform waveguides. Using flared gain section devices, improvements in both pulse energy (6.8 pJ) and pulsewidth (3.3 ps) were measured compared to uniform waveguide devices. Peak powers of over 2 W are obtained, which, to our knowledge, is the highest peak power obtained directly from mode-locked single stripe diode lasers. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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