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  • 1
    Electronic Resource
    Electronic Resource
    Mirror-image calibrator for resonant perturbation method in surface resistance measurements of high Tc superconducting thin films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3092-3096 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In surface resistance measurement of high Tc superconducting (HTS) thin films, the conventional resonant perturbation methods have large uncertainties, because their calibrators usually have much larger surface resistance than HTS thin films. This article describes a new type of calibrator, mirror-image calibrator: when the open end of a dielectric resonator is connected to its mirror image, the resonant frequency and quality factor of the resonator are equal to those of the dielectric resonator when its open end is shorted by a perfect conductor. This principle is applied to modify the dielectric resonator method in surface resistance measurement of HTS thin films. The structures of the dielectric resonator for surface resistance measurement (Rs probe) and its mirror-image calibrator are explained in detail. Comparison is made between the present technique and the conventional perturbation technique, and results show that the accuracy and sensitivity of the resonant perturbation method are greatly improved by using the mirror-image calibrator. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149893
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  • 2
    Electronic Resource
    Electronic Resource
    A time-resolved current method for the investigation of charging ability of insulators under electron beam irradiation (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7123-7128 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the present article, a convenient method for the direct measurement of the displacement current caused by electron trapping is developed to measure the trapped charge in insulators under electron beam irradiation from a scanning electron microscope. The trapping process during electron beam irradiation can be directly observed by this method. By using the conservation of current, a macroscopic formula is derived to describe our observation. The derived formula relates the measured current to the radiated beam energy, current, radiation-induced conductivity, and electron penetration depth of a sample. Experiments have been performed on polymethymethacrylate samples in which the samples are irradiated with electron beams of fixed beam energy as well as fixed beam current. The results are as predicted in theory. An agate sample is found to be unable to trap charge due to the small electron penetration depth and large radiation-induced conductivity of the sample. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361427
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  • 3
    Electronic Resource
    Electronic Resource
    Variation of the relative permittivity of charged dielectrics (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 317-319 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The variation of the relative permittivity of charged dielectrics with trapped charge density has been investigated by a time-resolved current method, in conjunction with a mirror image method employing a scanning electron microscope. The calculation is made by a mathematical expression derived from classical electromagnetic theory. It is found that the relative permittivity of the charged area in the polymethylmethacrylate sample increases with the trapped charge density and saturates at a certain value of the trapped charge density. These observations have been discussed by analogy with the dielectric saturation occurring at a high applied external electric field. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120723
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of charge distribution volume in electron irradiated insulators by scanning electron microscope (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3714-3718 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The scanning electron microscope mirror image method is developed to measure the charge distribution volume in insulators. An electrostatic potential expression is derived by assuming the dipolar approximation and hemispheroid distribution. Dielectric samples with different relative permittivities are employed in charging experiments to justify our approach. The proposed method is employed to measure the radius of the charge distribution volume in polymethylmethacrylate samples irradiated by electron beams with energy ranging from 25 to 39 keV. Experimental results achieved are in good agreement with those obtained through the use of other experimental techniques and Monte Carlo simulation. The strength of the present method is in its ability to quantitatively give the total trapped charge and its distribution in the electron irradiated insulators in a single experiment. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359950
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of conjugated bonds on the charging of insulating polymers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2414-2418 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Different densities of conjugated bonds, which affect the polarization states necessary in forming polarons, are generated by stretching polymers at various rates. An investigation of the charging of the stretched high-impact polystyrene and high-density polyethylene by using a scanning electron microscope technique is made. The experimental results reveal that polymer charging is related to electron trapping as polarons at the polarized sites of the polymeric chains, confirming the recent interpretation of charging behavior in insulating materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357590
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  • 6
    Electronic Resource
    Electronic Resource
    Dielectric polarization relaxation measurement in α-SiO2 by means of a scanning electron microscope technique (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1250-1255 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A scanning electron microscope is used as a tool to study dielectric relaxation processes in α-SiO2 by measuring the leakage current in the sample surrounded by a metallic aperture. A transient time (tt) of the order of a few seconds appears before the steady-state current is established. The time dependence of the trapping rate is found to follow a power law and to be related to relaxation processes of a dielectric under electrical and thermal stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354928
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  • 7
    Electronic Resource
    Electronic Resource
    Microwave dielectric resonance of a fluoride glass (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 8219-8221 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dielectric properties of a fluorozirconate glass are investigated in the frequency range from 0.5 to 13.5 GHz using a microwave vector network analyzer. A prominent dielectric resonance is observed around 7.0 GHz. The resonance may be due to a fundamental interunit vibrational mode of the basic structural ZrFn polyhedral units of the fluorozirconate glass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357028
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of impurity concentration on dielectric loss in Zn-doped InP at microwave X-band frequencies (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7444-7447 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microwave dielectric measurements have been performed on various Zn-doped InP crystals using a vector network analyzer. There are two kinds of dielectric response in Zn-doped InP crystals depending on their Zn concentration. The general dielectric response in InP in the microwave frequency region is dielectric relaxation, which is related to the dipolar species formed from the ionized substitutional ZnIn−. The other dielectric response of InP crystals doped with a higher Zn concentration is dielectric loss. The crystal doped with Zn to a concentration of 2.14×1018 cm−3 shows a strong dielectric loss at 11 GHz, but no dielectric loss peaks are found in crystals doped with a lower Zn concentration of 4.36×1017 cm−3. The dipolar species, which gives rise to the dielectric loss in Zn-doped InP crystals, is believed to be a result of vacancy complex defects of neutral substitutional ZnIn and two P vacancies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356638
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  • 9
    Electronic Resource
    Electronic Resource
    The physiology of tiller death in grasses. 2. Causes of tiller death in a grass sward (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 33 (1978), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The causes of tiller death in a 2-year-old perennial ryegrass sward were examined between April and August 1977. Physiological causes accounted for most tiller deaths and grazing by slugs and rodents was more important than the damage caused by stem-boring larvae. Tillers which died were mainly small and vegetative, although some flowering tillers died prematurely. Low nutrient status delayed but did not prevent tiller death.Using 14CO2 it was shown that small tillers fixed relatively less radiocarbon than did larger tillers and they did not receive much support for their carbon economy. Selective defoliation showed that in April defoliated tillers imported radiocarbon from undefoliated tillers but that in July at anthesis an undefoliated reproductive tiller retained most of the carbon it fixed, despite its vascular association with defoliated tillers. It appears that much of the tiller death during the period April-August is due to the failure of the more favourably placed tillers to support other tillers which are heavily shaded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1978.tb00821.x
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  • 10
    Electronic Resource
    Electronic Resource
    The physiology of tiller death in grasses. (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 33 (1978), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A reproducible method of causing tiller death on individual ryegrass (Lolium perenne L., cv. S23) plants is described. This was achieved by subjecting whole plants grown previously for 7 weeks in full light (100%) and full nutrient (100%) to either light stress (17.5% or 2.5%) or nutrient stress (10% or 0%) or various combinations of light and nutrient stress. Detailed records were made of tiller appearance, position and weight, and the probability of tiller death was calculated. Analysis of each plant indicated that the smallest tiller, which was often, but not always the youngest, was the most vulnerable when the whole plant was stressed. Tiller position was relatively unimportant in determining survival. The results are discussed in relation to tiller mortality in natural populations and crop communities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1978.tb00820.x
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