scholarly journals Short period phosphorescence and electron traps

1945 ◽  
Vol 184 (999) ◽  
pp. 408-433 ◽  
Keyword(s):  
Exponential Decay ◽  
Low Temperatures ◽  
Decay Curve ◽  
Optical Transition ◽  
Excited Electron ◽  
Decay Process ◽  
Effect Of Temperature ◽  
Temperature Dependent ◽  
Experimental Proof ◽  
Short Period

The decay of phosphorescence of various types is measured during the first few milliseconds of the process. Phosphorescence with exponential decay occurs when luminescence is due to an optical transition of a type normally forbidden. Experimental proof of this is provided by a study of the ruby. A further study is made of the effect of temperature on exponential decays. Some phosphors give complex decays in which a temperature-dependent decay process due to thermally metastable states or traps is superimposed on the exponential decay. An experimental separation of these decay processes is described for the case of ZnS-Mn. It had been believed that in hyperbolic decays, characteristic of ZnS-Cu and ZnS-Ag, the time constant of the process was due to the time that an excited electron spent in moving through the phosphor. The experiments described here show, however, that this type of decay is due primarily to the time electrons spend in traps; therefore the bimolecular theory of phosphorescence is largely rejected. The main experimental results show the temperature dependence of the decay curve and the correlation between the decay curve and the amount of light energy which may be stored in traps in the phosphor at low temperatures. An explanation is given of the change of shape of the decay curve with temperature.

Transmission Coefficients for Tunneling of Electrons and Holes in Biased Ga1−xAlxAs–GaAs–Ga1−xAlxAs Triple Barriers Semiconductor Heterostructures

2008 ◽  
Author(s):  
A. M. Elabsy ◽  
H. G. Abdelwahed
Keyword(s):  
Applied Voltage ◽  
Low Temperatures ◽  
Semiconductor Heterostructures ◽  
Effect Of Temperature ◽  
Temperature Dependent ◽  
Material Parameters ◽  
Transmission Coefficients ◽  
Effective Masses ◽  
Resonant Transmission ◽  
Double Wells

In this work we calculate the transmission coefficients for tunneling of electrons and holes through biased triple barriers (double-wells) semiconductor heterostructures (TBSH’s), composed of Ga1−xAlxAs–GaAs–Ga1−xAlxAs with x = 0.45. The calculations are based on the effective mass theory that employs the spatial effective masses and the temperature dependent of the material parameters that constitute the heterostructure. The transverse motions of carriers are also considered. In the analysis the Airy’s function formalism is taken into account. It is found that, the resonant transmission energies for both electrons and holes are decreased by enhancing the applied voltage. Also, the total resonant transmission energies for the tunneling carriers are deviated toward higher energies, as the temperature is increased. Therefore, these devices should be operated at low temperatures. Furthermore, the present work shows a discrepancy in resonant transmission energies with those reported ones, due to ignoring the effect of temperature.

scholarly journals Potential for the Postharvest Biological Control of Phthorimaea operculella (Lepidoptera, Gelechiidae) by Blattisocius tarsalis (Mesostigmata, Blattisociidae)

Agronomy ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 288
Author(s):  
Jorge Gavara ◽  
Ana Piedra-Buena ◽  
Estrella Hernandez-Suarez ◽  
Manuel Gamez ◽  
Tomas Cabello ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Storage Conditions ◽  
Control Agent ◽  
Phthorimaea Operculella ◽  
Effect Of Temperature ◽  
Potato Storage ◽  
Release Rates ◽  
Blattisocius Tarsalis ◽  
Predatory Capacity ◽  
Pest Density

Phthorimaea operculella is one of the most important pests causing damage to stored potatoes. In this work, the effect of temperature (at 10, 20 and 30 °C) on the predation of pest eggs by Blattisocius tarsalis was studied in the laboratory. In addition, the effect of three predatory release rates on two pest densities was studied under microcosm conditions. The results showed that B. tarsalis maintains its predatory capacity at low temperatures (10 °C), obtaining an efficiency of 49.66 ± 5.06% compared to the control. In turn, at 20 °C, a maximum efficacy of 78.17 ± 4.77% was achieved, very similar to that presented at 30 °C (75.57 ± 4.34%). Under microcosm conditions and at low pest density (10 eggs/container), the mortality due to the mite was 96.97 ± 3.03%, 81.82 ± 8.84%, and 84.85 ± 8.30%, respectively, for the three predatory release rates (5, 10 or 20 mites/container). At the high infestation level, the pest control ranged from 61.54 ± 9.21% to 92.31 ± 2.74%, depending on the predatory release rate. The results obtained show that B. tarsalis could be a relevant control agent against P. operculella under non-refrigerated potato storage conditions, as well as in the first stages of their storage under refrigerated conditions.

MAGNETIC BEHAVIOUR OF UPdAl, UCuGa AND UCuSn

1993 ◽  
Vol 07 (01n03) ◽  
pp. 850-854 ◽  
Author(s):  
V.H. TRAN ◽  
R. TROĆ
Keyword(s):  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Low Temperatures ◽  
Magnetic Behaviour ◽  
Type Structure ◽  
Complex Structures ◽  
Temperature Dependent ◽  
Antiferromagnetic Ordering

Magnetic susceptibility and electrical resistivity have been measured on UCuGa, UCu1+xSn1−x, (x=0 and 0.1), and UPdAl. The first two compounds, crystallizing in the hexagonal CaIn2-type structure, show at low temperatures an antiferromagnetic ordering probably with complex structures. UPdAl, which adopts the orthorhombic TiNiSi-type structure, was found to be a weakly temperature-dependent paramagnet down to 4.2 K.

The effect of temperature-dependent thermal parameters in thermal models of subduction zones

2021 ◽  
Author(s):  
Iris van Zelst ◽  
Timothy J. Craig ◽  
Cedric Thieulot
Keyword(s):  
Subduction Zones ◽  
Thermal Parameters ◽  
Dislocation Creep ◽  
Seismogenic Zone ◽  
Effect Of Temperature ◽  
Temperature Dependent ◽  
Thermal Models ◽  
Intermediate Depth ◽  
Dehydration Reactions ◽  
Model Setup

<p>The thermal structure of subduction zones plays an important role in the seismicity that occurs there with e.g., the downdip limit of the seismogenic zone associated with particular isotherms (350 °C - 450 °C) and intermediate-depth seismicity linked to dehydration reactions that occur at specific temperatures and pressures. Therefore, accurate thermal models of subduction zones that include the complexities found in laboratory studies are necessary. One of the often-ignored effects in models is the temperature-dependence of the thermal parameters such as the thermal conductivity, heat capacity, and density.<span> </span></p><p>Here, we build upon the model setup presented by Van Keken et al., 2008 by including temperature-dependent thermal parameters to an otherwise clearly constrained, simple model setup of a subducting plate. We consider a fixed kinematic slab dipping at 45° and a stationary overriding plate with a dynamic mantle wedge. Such a simple setup allows us to isolate the effect of temperature-dependent thermal parameters. We add a more complex plate cooling model for the oceanic plate for consistency with the thermal parameters.<span> </span></p><p>We test the effect of temperature-dependent thermal parameters on models with different rheologies, such as an isoviscous wedge, diffusion and dislocation creep. We find that slab temperatures can change by up to 65 °C which affects the location of isotherm depths. The downdip limit of the seismogenic zone defined by e.g., the 350 °C isotherm shifts by approximately 4 km, thereby increasing the maximum possible rupture area of the seismogenic zone. Similarly, the 600 °C isotherm is shifted approximately 30 km deeper, affecting the depth at which dehydration reactions and hence intermediate-depth seismicity occurs. Our results therefore show that temperature-dependent thermal parameters in thermal models of subduction zones cannot be ignored when studying subduction-related seismicity.<span> </span></p>

The Effect of Temperature Dependent Yield Strength on Upper Bounds for Creep Ratcheting

2006 ◽  
Author(s):  
Timothy E. McGreevy ◽  
Frederick A. Leckie ◽  
Peter Carter ◽  
Douglas L. Marriott
Keyword(s):  
Yield Strength ◽  
Upper Bounds ◽  
Effect Of Temperature ◽  
Strain Accumulation ◽  
Core Concept ◽  
Temperature Dependent ◽  
Inelastic Analysis ◽  
Asme Code ◽  
Inelastic Design ◽  
Very High

The Bree model and the elastic core concept have been used as the foundation for the simplified inelastic design analysis methods in the ASME Code for the design of components at elevated temperature for nearly three decades. The methodology provides upper bounds for creep strain accumulation and a physical basis for ascertaining if a structure under primary and secondary loading will behave elastically, plastically, shakedown, or ratchet. Comparisons of the method with inelastic analysis results have demonstrated its conservatism in stainless steel at temperatures representative of those in LMBR applications. The upper bounds on creep accumulation are revisited for very high temperatures representative of VHTR applications, where the yield strength of the material is strongly dependent upon temperature. The effect of the variation in yield strength on the evolution of the core stress is illustrated, and is shown to extend the shakedown regions, and affects the location of the boundaries between shakedown, ratcheting, and plasticity.

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