The impact of automation on NBS noise temperature measurements

1986 ◽  
Vol 74 (1) ◽  
pp. 117-120 ◽  
Author(s):  
D.F. Wait
Keyword(s):  
Noise Temperature ◽  
Temperature Measurements ◽  
The Impact

Detection and evaluation of self-heating effects in n+nn+AlxGa1-xAs devices by noise temperature measurements

1995 ◽  
Vol 10 (4) ◽  
pp. 515-522 ◽  
Author(s):  
M De Murcia ◽  
E Richard ◽  
J M Perraudin ◽  
A Boyer ◽  
A Benvenuti ◽  
...  
Keyword(s):  
Noise Temperature ◽  
Temperature Measurements ◽  
Self Heating ◽  
Heating Effects

Temperature measurements at an implosion focus

1982 ◽  
Vol 384 (1786) ◽  
pp. 217-231 ◽  
Keyword(s):  
Detonation Wave ◽  
Focal Point ◽  
Strong Shock ◽  
Black Body ◽  
Temperature Measurements ◽  
Gaseous Detonation ◽  
Photographic Film ◽  
Random Choice Method ◽  
Visible Wavelength Range ◽  
The Impact

Spectroscopic temperature measurements were made at the focal point of imploding shock waves in the UTIAS implosion chamber, which has a 20 cm diameter hemispherical cavity. The chamber was filled with a stoichiometric H 2 -O 2 gas mixture at different initial pressures (1.4-6.9 MPa). The mixture was ignited at the origin by an exploding wire generating an outgoing detonation wave, which reflected at the chamber wall as an imploding shock wave (gas runs). Experiments with an explosive shell of pentaerythritol tetranitrate (PETN: C 5 H 8 N 4 O 12 ) placed at the hemispherical wall were also conducted. The shell was detonated by the impact of the reflected gaseous detonation wave at its surface, an intense implosion wave being generated thereby (explosive run). The temperatures were measured at the implosion focus by using a medium quartz Hilger spectrograph with an eight-photocell polychromator attachment over the visible wavelength range. The measured radiation intensity distributions were fitted to black-body curves. The temperatures were 10000-13000 K, for gas runs, and 15000-17000 K, for explosive runs. The continuous spectra from photographic film and the measured emissivities, which were very close to unity, confirmed that the plasma was a black body. Numerical studies with the random choice method and classical strong-shock theory were used to analyse the flows in the entire range of the implosion process. They provided much information on the entire implosion process within the restriction of a perfect-gas assumption, which was found to be reasonable as a first step in this kind of analysis. The experimental data were com­pared with the analytical results. For both gas and explosive runs, the temperatures were lower than the calculated values and reasonable explanations are given for this deviation.

scholarly journals Assessing the impact of Argo floats temperature measurements on the numerical weather prediction forecast skill

2019 ◽  
Vol 20 (2) ◽  
pp. 331 ◽  
Author(s):  
GEORGE VARLAS ◽  
PETROS KATSAFADOS ◽  
GERASIMOS KORRES ◽  
ANASTASIOS PAPADOPOULOS
Keyword(s):  
Boundary Conditions ◽  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Lower Boundary ◽  
Forecast Skill ◽  
Temperature Measurements ◽  
Precipitation Forecast ◽  
Numerical Weather ◽  
Argo Floats ◽  
The Impact

The forecast skill of numerical weather prediction (NWP) models relies, among other factors such as the prediction itself and the assimilation scheme, on the accuracy of the observations utilized in the assimilation systems for the production of initial and boundary conditions. One of the most crucial parameters in weather forecasting is the sea surface temperature (SST). In the majority of NWP models, the initial and lower boundary conditions involve gridded (SST) analyses which consist of data obtained by buoys, ships and satellites. The main aim of this study is to integrate Argo temperature measurements in gridded SST analyses and to assess their impact on the forecast skill of a limited area atmospheric model. Argo floats are “state-of-the-art” oceanographic instruments producing high-quality temperature profiles for the ice-free ocean. In this study, Argo temperatures are incorporated into gridded SST fields without applying any smoothing method in order to directly assess the impact of Argo temperatures on numerical weather prediction. Their impact is assessed under intense weather cyclonic conditions at the Mediterranean Sea by performing two sensitivity simulations either incorporating or not Argo temperatures into gridded SST fields used in the generation of the initial and lower boundary conditions. The results indicate that the inclusion of Argo-measured near-surface temperatures in the lower boundary condition modifies the surface heat fluxes, thus affecting mean sea level pressure and precipitation. In particular, an overall improvement of the precipitation forecast skill up to 3% has been demonstrated. Moreover, the incorporation of Argo temperatures affects the simulated track and intensity of the cyclone over the Balkan Peninsula.

scholarly journals Impact of Flow Unsteadiness on Steady-State Gas-Path Stagnation Temperature Measurements

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Clare Bonham ◽  
Mark Brend ◽  
Adrian Spencer ◽  
Katsu Tanimizu ◽  
Dylan Wise
Keyword(s):  
Steady State ◽  
Unsteady Flows ◽  
Temperature Measurements ◽  
Conductive Heat ◽  
Calibration Data ◽  
Measured Temperature ◽  
Stagnation Temperature ◽  
Post Test ◽  
Mach Numbers ◽  
The Impact

Steady-state stagnation temperature probes are used during gas turbine engine testing as a means of characterizing turbomachinery component performance. The probes are located in the high-velocity gas-path, where temperature recovery and heat transfer effects cause a shortfall between the measured temperature and the flow stagnation temperature. To improve accuracy, the measurement shortfall is corrected post-test using data acquired at representative Mach numbers in a steady aerodynamic calibration facility. However, probes installed in engines are typically subject to unsteady flows, which are characterized by periodic variations in Mach number and temperature caused by the wakes shed from upstream blades. The present work examines the impact of this periodic unsteadiness on stagnation temperature measurements by translating probes between jets with dissimilar Mach numbers. For conventional Kiel probes in unsteady flows, a greater temperature measurement shortfall is recorded compared to equivalent steady flows, which is related to greater conductive heat loss from the temperature sensor. This result is important for the application of post-test corrections, since an incorrect value will be applied using steady calibration data. A new probe design with low susceptibility to conductive heat losses is therefore developed, which is shown to deliver the same performance in both steady and unsteady flows. Measurements from this device can successfully be corrected using steady aerodynamic calibration data, resulting in improved stagnation temperature accuracy compared to conventional probe designs. This is essential for resolving in-engine component performance to better than ±0.5% across all component pressure ratios.

scholarly journals The representation of solar cycle signals in stratospheric ozone – Part 1: A comparison of satellite observations

2016 ◽  
Author(s):  
A. Maycock ◽  
K. Matthes ◽  
S. Tegtmeier ◽  
R. Thiéblemont ◽  
L. Hood
Keyword(s):  
Solar Cycle ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
Satellite Observations ◽  
Solar Variability ◽  
Temperature Measurements ◽  
Climate Response ◽  
Mixing Ratio ◽  
Substantial Impact ◽  
The Impact

Abstract. The impact of changes in incoming solar ultraviolet irradiance on stratospheric ozone forms an important part of the climate response to solar variability. To realistically simulate the climate response to solar variability using climate models, a minimum requirement is that they should include a solar cycle ozone component that has a realistic amplitude and structure, and which varies with season. For climate models that do not include interactive ozone chemistry, this component must be derived from observations and/or chemistry–climate model simulations and included in an externally prescribed ozone database that also includes the effects of all major external forcings. Part 1 of this two part study presents the solar-ozone responses in a number of updated satellite datasets for the period 1984–2004, including the Stratospheric Aerosol and Gas Experiment (SAGE) II version 6.2 and version 7.0 data, and the Solar Backscatter Ultraviolet Instrument (SBUV) version 8.0 and version 8.6 data. A number of combined datasets, which have extended SAGE II using more recent satellite measurements, are also analysed for the period 1984–2011. It is shown that SAGE II derived solar-ozone signals are sensitive to the independent temperature measurements used to convert ozone number density to mixing ratio units. A change in these temperature measurements in the recent SAGE II v7.0 data leads to substantial differences in the mixing ratio solar-ozone response compared to the previous v6.2, particularly in the tropical upper stratosphere. We also show that alternate satellite ozone datasets have issues (e.g., sparse spatial and temporal sampling, low vertical resolution, and shortness of measurement record), and that the methods of accounting for instrument offsets and drifts in merged satellite datasets can have a substantial impact on the solar cycle signal in ozone. For example, the magnitude of the solar-ozone response varies by around a factor of two across different versions of the SBUV VN8.6 record, which appears to be due to the methods used to combine the separate SBUV timeseries. These factors make it difficult to extract more than an annual-mean solar-ozone response from the available satellite observations. It is therefore unlikely that satellite ozone measurements alone can be applied to estimate the necessary solar cycle ozone component of the prescribed ozone database for future coupled model intercomparison projects (e.g., CMIP6).

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