THE ENERGY OF ALPHA PARTICLES FROM U234, U238, AND Th232

1957 ◽  
Vol 35 (3) ◽  
pp. 258-270 ◽  
Author(s):  
B. G. Harvey ◽  
H. G. Jackson ◽  
T. A. Eastwood ◽  
G. C. Hanna
Keyword(s):  
Standard Deviation ◽  
High Resolution ◽  
Ionization Chamber ◽  
Pulse Generator ◽  
Low Noise ◽  
Alpha Particles ◽  
Pulse Rise Time ◽  
Long Term Stability ◽  
Two Parameter

The α-particle energies of U234, U238, and Th232 have been measured with a grid ionization chamber. The electronic equipment was designed to provide low noise, high resolution, and good long term stability. Ra226, Em222, Po218, Po214, and Po210 were used as energy standards. An investigation was made of the corrections to the measurements due to variation in pulse rise-time, source thickness, and imperfect shielding of the collector by the grid. It was found that the experimentally observed resolution was satisfactorily accounted for by the combination of these factors and the noise and ionization straggling.Alpha particle pulse heights were measured in terms of the output of a precision pulse generator. The corrected pulse heights were related to the energies of the standard sources by a two-parameter least squares calculation; the standard deviation was never greater than 5 kev. On extrapolating to zero ionization the line so obtained intercepted the energy axis at 83 kev. The α-particle energies deduced using this line were: U234 4.768 ± 0.003, U238 4.195 ± 0.005, Th232 4.007 ± 0.005 Mev.

scholarly journals British Museum Natural Radiocarbon Measurements VI

Radiocarbon ◽  
1969 ◽  
Vol 11 (2) ◽  
pp. 278-294 ◽  
Author(s):  
Harold Barker ◽  
Richard Burleigh ◽  
Nigel Meeks
Keyword(s):  
Liquid Scintillation Counting ◽  
Liquid Scintillation ◽  
British Museum ◽  
Low Noise ◽  
Scintillation Counting ◽  
Statistical Accuracy ◽  
Liquid Scintillation Spectrometer ◽  
Long Term Stability ◽  
Replicate Measurements

Dates listed below are based on measurements made up to May 1968, and cover a period during which the technique of gas proportional counting using CO2 was gradually replaced by liquid scintillation counting using benzene. The gas counting measurements were carried out by the method and techniques previously described (Barker and Mackey, 1968) the only modifications being the replacement of some old electronic units by more stable solid-state equipment; proportional counting results are indicated in the text by (P) at the end of the relevant sample descriptions. Liquid scintillation counting, which is now the preferred method in this laboratory, is carried out using a Packard Tri-Carb liquid scintillation spectrometer model 3315/AES fitted with selected low-noise quartz-faced photomultipliers. Normally 3 ml of benzene is prepared from each sample. This is dissolved in 12 ml of scintillation grade toluene containing 5 gm/liter of scintillator (PPO) and the solution is measured in a standard low-potassium glass vial at a temperature of 0°C. Photomultiplier E.H.T., amplifier, and channel width settings are optimized for C14, and measurements are carried out at ca. 65% efficiency of detection for C14 to eliminate interference from any tritium which may be present in the benzene. Under these circumstances the background is approx. 8.6 cpm and the modern (95% Aox) is approx. 24.0 cpm. Samples are counted in groups of 3 to 5 together with background and modern reference samples and are measured for at least one week, the instrument being set to cycle at 100 min intervals. In this period, the counts accumulated are such that the background is always measured to a statistical accuracy of better than 1% and most other samples to a higher accuracy than this. Background and modern counts used in the calculation of each result are only those relevant to the period of measurement of that particular sample. Statistical analysis of groups of replicate measurements made under these conditions over a very long period of time has demonstrated the excellent long-term stability of the equipment and indicates that the technique is quite capable of achieving results of very high statistical accuracy when required.

scholarly journals Determination of St. George Basilica Tower Historical Inclination from Contemporary Photograph

2011 ◽  
Vol 6 ◽  
pp. 212-219
Author(s):  
Bronislav Koska
Keyword(s):  
Standard Deviation ◽  
Visual Information ◽  
Bundle Adjustment ◽  
Long Term Stability ◽  
The North ◽  
Research Activities ◽  
Geometrical Information ◽  
Historical Photographs

A large amount of photographic material has been accumulated from the photography emerge in the nineteenth century. The most photographs record portraits, urbanistic complex, significant architecture and others important objects in the photography inception. Historical photographs recorded a huge amount of information, which can be use for various research activities. Photograph visual information is sufficient in many cases, but accurate geometrical information must be acquired from it in specific situations. It is the case of long-term stability monitoring of buildings in the Prague Castle area see [1]. For static analysis in the monitoring project, it is necessary to determine accurately specific geometrical parameter – mutual angle of St. George Basilica towers in the north-south direction before the reconstruction started in 1888. The angle standard deviation must be solved as well. The task demanded using of photogrammetric methods. Own implementation of general bundle adjustment had to be created to fulfill determination of reliable standard deviation of the angle, because standard photogrammetric software does not have all the necessary options.

scholarly journals NO2 and NH3 Sensing Characteristics of Inkjet Printing Graphene Gas Sensors

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3379 ◽  
Author(s):  
Caterina Travan ◽  
Alexander Bergmann
Keyword(s):  
Gas Sensors ◽  
Inkjet Printing ◽  
High Mobility ◽  
High Sensitivity ◽  
Low Noise ◽  
Manufacturing Method ◽  
Long Term Stability ◽  
Wide Range ◽  
Ideal Technique

Graphene is a good candidate for filling the market requirements for cheap, high sensitivity, robust towards contamination, low noise, and low power consumption gas sensors, thanks to its unique properties, i.e., large surface, high mobility, and long-term stability. Inkjet printing is a cheap additive manufacturing method allowing fast, relatively precise and contactless deposition of a wide range of materials; it can be considered therefore the ideal technique for fast deposition of graphene films on thin substrates. In this paper, the sensitivity of graphene-based chemiresistor gas sensors, fabricated through inkjet printing, is investigated using different concentrations of graphene in the inks. Samples have been produced and characterized in terms of response towards humidity, nitrogen dioxide, and ammonia. The presented results highlight the importance of tuning the layer thickness and achieving good film homogeneity in order to maximize the sensitivity of the sensor.

scholarly journals A 23-Year Retrospective Blind Check of Accuracy of the Copenhagen Radiocarbon Dating System

Radiocarbon ◽  
1999 ◽  
Vol 41 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Kaare L Rasmussen ◽  
Henrik Tauber ◽  
Niels Bonde ◽  
Kjeld Christensen ◽  
Páll Theodórsson
Keyword(s):  
Standard Deviation ◽  
Tree Rings ◽  
Radiocarbon Dating ◽  
Average Difference ◽  
Blind Test ◽  
Term Stability ◽  
Long Term Stability ◽  
Measuring Accuracy ◽  
Sample Age

A 23-yr record of the measuring accuracy of the Copenhagen radiocarbon dating laboratory has retrospectively been provided through a true blind test. A total of 92 samples of oak from old tree trunks were dated in the period 1971 to 1993 and their dendrochronological age determined independently. The 14C activity of the dendrochronological samples measured in the Copenhagen radiocarbon laboratory was compared to the activity of the tree rings of the same age measured by Stuiver and Pearson (1993) for calibration purposes. The average difference was found to be 54 ± 72 14C yr. The results further indicate that the actual standard deviation is only 7% higher than that quoted by the laboratory. The investigation has shown a long-term stability of laboratory accuracy with no systematic laboratory variations either with respect to sample age or to the time of measurement from 1971 to 1993.

scholarly journals Merging ground-based sunshine duration observations with satellite cloud and aerosol retrievals to produce high-resolution long-term surface solar radiation over China

2021 ◽  
Vol 13 (3) ◽  
pp. 907-922
Author(s):  
Fei Feng ◽  
Kaicun Wang
Keyword(s):  
Standard Deviation ◽  
High Resolution ◽  
Solar Radiation ◽  
Spatial Resolution ◽  
Sunshine Duration ◽  
Ordinary Least Squares ◽  
Cloud Fraction ◽  
Surface Solar Radiation ◽  
The Impact

Abstract. Although great progress has been made in estimating surface solar radiation (Rs) from meteorological observations, satellite retrieval, and reanalysis, getting best-estimated long-term variations in Rs are sorely needed for climate studies. It has been shown that Rs data derived from sunshine duration (SunDu) can provide reliable long-term variability, but such data are available at sparsely distributed weather stations. Here, we merge SunDu-derived Rs with satellite-derived cloud fraction and aerosol optical depth (AOD) to generate high-spatial-resolution (0.1∘) Rs over China from 2000 to 2017. The geographically weighted regression (GWR) and ordinary least-squares regression (OLS) merging methods are compared, and GWR is found to perform better. Based on the SunDu-derived Rs from 97 meteorological observation stations, which are co-located with those that direct Rs measurement sites, the GWR incorporated with satellite cloud fraction and AOD data produces monthly Rs with R2=0.97 and standard deviation =11.14 W m−2, while GWR driven by only cloud fraction produces similar results with R2=0.97 and standard deviation =11.41 W m−2. This similarity is because SunDu-derived Rs has included the impact of aerosols. This finding can help to build long-term Rs variations based on cloud data, such as Advanced Very High Resolution Radiometer (AVHRR) cloud retrievals, especially before 2000, when satellite AOD retrievals are not unavailable. The merged Rs product at a spatial resolution of 0.1∘ in this study can be downloaded at https://doi.org/10.1594/PANGAEA.921847 (Feng and Wang, 2020).

scholarly journals A study to assess the long-term stability of the ionization chamber reference system in the LNMRI

2018 ◽  
Vol 975 ◽  
pp. 012059
Author(s):  
O L Trindade Filho ◽  
D A Conceição ◽  
C J da Silva ◽  
J U Delgado ◽  
A E de Oliveira ◽  
...  
Keyword(s):  
Reference System ◽  
Ionization Chamber ◽  
Term Stability ◽  
Long Term Stability

Structural characterization of free-standing gallium arsenide coiled membranes produced by micromachining

1999 ◽  
Vol 32 (1) ◽  
pp. 60-64
Author(s):  
Krishan Lal ◽  
S. Niranjana N. Goswami ◽  
J. Miao ◽  
H. L. Hartnagel
Keyword(s):  
High Resolution ◽  
Beam Width ◽  
Thin Strip ◽  
X Ray Diffraction ◽  
Free Standing ◽  
X Ray ◽  
Long Term Stability ◽  
Diffraction Peaks

High-resolution X-ray diffraction techniques have been employed successfully to evaluate crystalline quality and long-term stability of coiled membranes. The process of fabrication involves photolithography, implantation by 2 MeV N^{2+} ions inn-type GaAs substrates, followed by selective etching. A five-crystal X-ray diffractometer was employed in (+, −, +) setting with an Mo Kα1exploring beam for high-resolution X-ray diffractometry and topography experiments. The exploring-beam width was reduced to illuminate different segments of the coiled membrane. Diffraction curves recorded from the bulk crystal surrounding the sensor had a half width of 26 arcseconds, whereas the half widths from sensor segments were in the range ∼58 to ∼166 arcseconds. Different segments (particularly vertical ones) were identified from the observed angular separations between different diffraction peaks as well as from the shape of the diffraction peaks. It was found that different segments of the sensor were tilted with respect to one another and the tilt angles were in the range 15–212 arcseconds. High-resolution X-ray diffraction topographs recorded from (5\bar 11) and (400) diffracting planes revealed that the sides of the trough below the membrane created by etching are not vertical, but tapered. Also, there is a thin strip of crystal freely hanging over the tapered regions as a result of underetching. The surface of the cavity is uneven. The structural perfection of different membrane segments could also be ascertained from the contrast in topographs.

scholarly journals A Nanoindentation Approach for Time-Dependent Evaluation of Surface Free Energy in Micro- and Nano-Structured Titanium

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 287
Author(s):  
Serena De Santis ◽  
Edoardo Rossi ◽  
Marco Sebastiani ◽  
Simona Sennato ◽  
Edoardo Bemporad ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Free Energy ◽  
High Resolution ◽  
Sample Preparation ◽  
Surface Free Energy ◽  
Time Dependent ◽  
Long Term Stability ◽  
Titanium Surfaces ◽  
Non Destructive

Surface free energy (SFE) of titanium surfaces plays a significant role in tissue engineering, as it affects the effectiveness and long-term stability of both active coatings and functionalization and the establishment of strong bonds to the newly growing bone. A new contact–mechanics methodology based on high-resolution non-destructive elastic contacting nanoindentation is applied here to study SFE of micro- and nano-structured titanium surfaces, right after their preparation and as a function of exposure to air. The effectiveness of different surface treatments in enhancing SFE is assessed. A time-dependent decay of SFE within a few hours is observed, with kinetics related to the sample preparation. The fast, non-destructive method adopted allowed for SFE measurements in very hydrophilic conditions, establishing a reliable comparison between surfaces with different properties.

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