SU-FF-T-01: Effective Source Distance and Virtual Source Location for MLC Based Electron Radiotherapy

2007 ◽  
Vol 34 (6Part7) ◽  
pp. 2400-2401 ◽  
Author(s):  
P Tynan ◽  
S Stathakis ◽  
C Esquivel ◽  
C Shi ◽  
N Papanikolaou
Keyword(s):  
Source Location ◽  
Virtual Source ◽  
Source Distance ◽  
Electron Radiotherapy ◽  
Effective Source

scholarly journals Shift of effective lightning areas during pre to post period of solar cycle minimum of 2008-2009 as determined from Schumann resonance studies at Agra, India

2015 ◽  
Vol 57 (6) ◽  
Author(s):  
Birbal Singh ◽  
Devbrat Pundhir
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Seasonal Variations ◽  
Thunderstorm Activity ◽  
Schumann Resonance ◽  
Cycle Minimum ◽  
Source Distance ◽  
Imaging Sensor ◽  
Post Period ◽  
Effective Source

<p>Employing a set of 3-component search coil magnetometer, Schumann resonance studies have been in progress at Agra (Geograph. lat. 27.2°N, long. 78°E), India since 01 April, 2007. We have analysed the data for two periods; first from 01 April, 2007 to 31 March, 2008 (period-I), and then from 01 March, 2011 to 29 February, 2012 (period-II) which correspond to pre and post periods of solar cycle minimum of 2008-2009. From the diurnal variation of first mode intensity and frequency, we study the seasonal variations of global thunderstorm activity, effective source distance and level of lightning during both the periods. We show that world thunderstorm activity shifts to summer in the northern hemisphere as the effective source distance approaches close to the observer, and the level of intense lightning shifts from the month of July, 2007 in period-I to August, 2011 in period-II. This is supported by Lightning Imaging Sensor (LIS) satellite data also. A possible explanation in terms of increasing solar activity is suggested.</p>

Imaging the Subsurface with Ambient Noise Autocorrelations

2020 ◽  
Vol 91 (2A) ◽  
pp. 930-935 ◽  
Author(s):  
Robert W. Clayton
Keyword(s):  
Los Angeles ◽  
Lower Crust ◽  
Ambient Noise ◽  
Virtual Source ◽  
Source Time Function ◽  
San Bernardino ◽  
Reflection Image ◽  
Zero Offset ◽  
First Time ◽  
Effective Source

Abstract Autocorrelations created by stacks of near-offset traces from virtual source gathers are used to form an image of the deeper subsurface. We minimize the masking effects of the effective source time function by subtracting the survey-wide average autocorrelation from each trace. The result is a zero-offset reflection image of the subsurface generated by ambient noise correlation. The technique can be particularly useful for imaging the mid and lower crust, in which traditional seismic methods have penetration problems. We show examples from a one-component 3D survey and a three-component 2D profile. The 3D example shows the crust in the transition zone between the continent and the Inner Borderland in the Los Angeles, California, area, and for the first time, shows an image of the lower crust. The 2D profile provides both a P image and an S image of the basement interface in the San Bernardino basin in southern California.

scholarly journals Angle-Based Virtual Source Location Representation for Spatial Audio Coding

ETRI Journal ◽  
2006 ◽  
Vol 28 (2) ◽  
pp. 219-222 ◽  
Author(s):  
Seungkwon Beack ◽  
Jeongil Seo ◽  
Hangil Moon ◽  
Kyeongok Kang ◽  
Minsoo Hahn
Keyword(s):  
Source Location ◽  
Audio Coding ◽  
Spatial Audio ◽  
Virtual Source ◽  
Spatial Audio Coding

Virtual Real Source: Source signature estimation using seismic interferometry

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. Q57-Q68 ◽  
Author(s):  
Jyoti Behura ◽  
Roel Snieder
Keyword(s):  
Waveform Inversion ◽  
Seismic Source ◽  
Normal Derivative ◽  
Source Location ◽  
Seismic Interferometry ◽  
Virtual Source ◽  
Data Set ◽  
The North ◽  
Zero Offset ◽  
Streamer Data

Knowledge of the seismic source signature is crucial in numerousproblems in exploration seismology, especially in full-waveform inversion. However, existing methods of source signature estimation like statistical methods and well-log-based methods suffer from several drawbacks arising from assumptions such as whiteness of the reflectivity series and the minimum-phase character of the wavelet. Also, estimation of the source signature using wave-theoretical methods requires the recording of the wavefield and its normal derivative or additional recordings above the receiver surface which are not always available. We introduce a method, called the Virtual Real Source, of extracting the source signature based on the theory of seismic interferometry, also known as the virtual source method. This method is independent of the assumptions and drawbacks of the above-mentioned methods. The only requirement for the method of Virtual Real Source is to have a virtual source location coincide with the physical shot position whose source signature is desired. The virtual source location does not necessarily have to be a zero-offset receiver because one can use interpolation for it. The source signature is extracted by deconvolving the real recording at a receiver from the virtual source recording. Through modeling examples, we show that Virtual Real Source produces accurate source signatures even for complicated subsurface structures and source signatures, and is robust in the presence of noise. Source signature of every shot in a survey can be extracted reliably as long as the source signatures have similar amplitude spectra. The phase spectrum of the source signature is always extracted accurately even if it varies randomly from one shot to another. The Virtual Real Source applied on a 2D streamer data set from the North Viking Graben in the North Sea extracts all the airgun signatures with the main pulse and the bubble oscillation.

Development of a conical anode Fe-gun for low voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 978-979
Author(s):  
T. Miyokawa ◽  
S. Norioka ◽  
S. Goto
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Low Voltage ◽  
Irradiation Damage ◽  
Cold Cathode ◽  
Virtual Source ◽  
Source Position ◽  
Electrostatic Lens ◽  
Electrostatic Lenses ◽  
Wide Range

Field emission SEMs (FE-SEMs) are becoming popular due to their high resolution needs. In the field of semiconductor product, it is demanded to use the low accelerating voltage FE-SEM to avoid the electron irradiation damage and the electron charging up on samples. However the accelerating voltage of usual SEM with FE-gun is limited until 1 kV, which is not enough small for the present demands, because the virtual source goes far from the tip in lower accelerating voltages. This virtual source position depends on the shape of the electrostatic lens. So, we investigated several types of electrostatic lenses to be applicable to the lower accelerating voltage. In the result, it is found a field emission gun with a conical anode is effectively applied for a wide range of low accelerating voltages.A field emission gun usually consists of a field emission tip (cold cathode) and the Butler type electrostatic lens.

Using the secondary electrons (SE) of SEM with NIST‘s MONSEL-II program to obtain improved linewidth measurements and slope angles of line edges on a MMIC GaAs device

1996 ◽  
Vol 54 ◽  
pp. 944-945
Author(s):  
Richard G. Sartore
Keyword(s):  
Integrated Circuits ◽  
Plasma Etching ◽  
Microwave Integrated Circuits ◽  
Monolithic Microwave Integrated Circuits ◽  
Thick Gold ◽  
Gaas Devices ◽  
Source Distance ◽  
Margin Of Error ◽  
Dimensional Measurements ◽  
Barrier Metal

In the evaluation of GaAs devices from the MMIC (Monolithic Microwave Integrated Circuits) program for Army applications, there was a requirement to obtain accurate linewidth measurements on the nominal 0.5 micrometer gate lengths used to fabricate these devices. Preliminary measurements indicated a significant variation (typically 10 % to 30% but could be more) in the critical dimensional measurements of the gate length, gate to source distance and gate to drain distance. Passivation introduced a margin of error, which was removed by plasma etching. Additionally, the high aspect ratio (4-5) of the thick gold (Au) conductors also introduced measurement difficulties. The final measurements were performed after the thick gold conductor was removed and only the barrier metal remained, which was approximately 250 nanometer thick platinum on GaAs substrate. The thickness was measured using the penetration voltage method. Linescan of the secondary electron signal as it scans across the gate is shown in Figure 1.

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