Seasonal and interannual variation in vegetation composition: Implications for survey design and data interpretation

2014 ◽  
Vol 39 (7) ◽  
pp. 755-766 ◽  
Author(s):  
Nick L. Schultz ◽  
Nick Reid ◽  
Greg Lodge ◽  
John T. Hunter
Geophysics ◽  
1999 ◽  
Vol 64 (3) ◽  
pp. 732-738 ◽  
Author(s):  
James E. Reid ◽  
James C. Macnae

The depth at which the amplitude of the frequency‐domain electromagnetic fields due to dipole and square loop sources over a homogeneous half‐space fall to 1/e of their value at the surface is compared to the conventional plane‐wave skin depth. The skin depth due to a local source depends on the transmitter frequency, half‐space conductivity, transmitter altitude, and transmitter‐receiver offset, and may range from a fraction of to more than twice the plane‐wave skin depth. Unlike the plane‐wave skin depth, the “local‐source skin depth” is different for electric and magnetic fields, and may be nonunique for some transmitter geometries and field components. For all transmitter geometries, however, the local‐source skin depth approaches the plane‐wave skin depth as the transmitter altitude and/or receiver offset increase. The concept of the local‐source skin depth has direct application to survey design and data interpretation. A theoretical example demonstrates that it is possible to predict, for a given survey geometry and frequency range, whether or not an electromagnetic sounding can detect a conductive basement below a thick overburden layer.


Geophysics ◽  
2006 ◽  
Vol 71 (3) ◽  
pp. G73-G81
Author(s):  
Jiuping Chen ◽  
Douglas W. Oldenburg

Magnetometric resistivity (MMR) is an electromagnetic (EM) exploration method that has been used successfully to investigate electrical-resistivity structures below the sea-floor. Apparent resistivity, derived from the observed azimuthal component of the magnetic field, often is used as an approximation to the resistivity of a layered earth. Two commonly used formulas to compute the apparent resistivity have their own limitations and are invalid for a deep-sea experiment. In this paper, we derive an apparent-resistivity formula based upon the magnetic field resulting from a semi-infinite electrode buried in a 1D layered earth. This new formula can be applied to both shallow and deep marine MMR surveys. In addition, we address the effects that arise from the transmitter-receiver (Tx-Rx) depth difference and the choice of the normalized range (the radial distance between transmitter and receiver, divided by the thickness of seawater) on data interpretation and survey design. The performance of the new formula is shown by processing synthetic and field data.


Geophysics ◽  
2002 ◽  
Vol 67 (5) ◽  
pp. 1348-1363 ◽  
Author(s):  
Robert R. Stewart ◽  
James E. Gaiser ◽  
R. James Brown ◽  
Don C. Lawton

Multicomponent seismic recording (measurement with vertical‐ and horizontal‐component geophones and possibly a hydrophone or microphone) captures the seismic wavefield more completely than conventional single‐element techniques. In the last several years, multicomponent surveying has developed rapidly, allowing creation of converted‐wave or P‐S images. These make use of downgoing P‐waves that convert on reflection at their deepest point of penetration to upcoming S‐waves. Survey design for acquiring P‐S data is similar to that for P‐waves, but must take into account subsurface VP/VS values and the asymmetric P‐S ray path. P‐S surveys use conventional sources, but require several times more recording channels per receiving location. Some special processes for P‐S analysis include anisotropic rotations, S‐wave receiver statics, asymmetric and anisotropic binning, nonhyperbolic velocity analysis and NMO correction, P‐S to P‐P time transformation, P‐S dip moveout, prestack migration with two velocities and wavefields, and stacking velocity and reflectivity inversion for S‐wave velocities. Current P‐S sections are approaching (and in some cases exceeding) the quality of conventional P‐P seismic data. Interpretation of P‐S sections uses full elastic ray tracing, synthetic seismograms, correlation with P‐wave sections, and depth migration. Development of the P‐S method has taken about 20 years, but has now become commercially viable.


Author(s):  
H.A. Cohen ◽  
T.W. Jeng ◽  
W. Chiu

This tutorial will discuss the methodology of low dose electron diffraction and imaging of crystalline biological objects, the problems of data interpretation for two-dimensional projected density maps of glucose embedded protein crystals, the factors to be considered in combining tilt data from three-dimensional crystals, and finally, the prospects of achieving a high resolution three-dimensional density map of a biological crystal. This methodology will be illustrated using two proteins under investigation in our laboratory, the T4 DNA helix destabilizing protein gp32*I and the crotoxin complex crystal.


2005 ◽  
Vol 18 (4) ◽  
pp. 327-340 ◽  
Author(s):  
Graham J. Pierce ◽  
Alain F. Zuur ◽  
Jennifer M. Smith ◽  
M. Begoña Santos ◽  
Nick Bailey ◽  
...  

2018 ◽  
Vol 8 (1) ◽  
pp. 01-07
Author(s):  
Alfred Eboh

Background: The hawking of wares by children has been a serious issue confronting the Nigerian society. Children hawk in some of the most horrible conditions conceivable, where they face a serious risk of injury, chronic illness, kidnapping, rape or death. Objective: The focus of this study was to assess the perceived effects of street hawking on the well-being of children in Anyigba, Dekina Local Government Area of Kogi State. Methods: The population of this study consists of parents of the street hawkers in Anyigba while cross-sectional survey design was used through the purposive sampling technique to choose the sample size of one hundred and sixty-two (162) respondents. The validated structured questionnaire and In-Depth Interviews (IDIs) served as the instruments for the data collection respectively. The hypotheses were tested using Chi-Square at a predetermined 0.05 level of significance. The quantitative data were analysed with the aid of the SPSS (version 20). Results: The results indicated among others that street hawking had significant social implications and physical consequences on children's moral behaviour as well as health status in the study area. Conclusion: The study, therefore, concluded that the government of Kogi State should carry out an enlightenment campaign through the media and religious institutions on the negative consequences of street hawking are recommended as panacea. Also, the child right act instrument and its implementation should be strengthened in order to curb street hawking in the study area.


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