On: “Gravity vertical gradient measurements for the detection of small geologic and anthropogenic forms” by Zbigniew J. Fajklewicz (GEOPHYSICS, October 1976, p. 1016–1030)

Geophysics ◽  
1977 ◽  
Vol 42 (5) ◽  
pp. 1066-1067
Author(s):  
Avner A. Arzi
Keyword(s):  
Ground Surface ◽  
Vertical Gradient ◽  
Powerful Method ◽  
Gravity Measurements ◽  
The Difference ◽  
Gradient Measurements ◽  
Tower Height

Microgravimetry is indeed a powerful method for the detection of many small geologic and anthropogenic bodies (Arzi, 1975). Fajklewicz essentially advocates a particular procedure for microgravimetric surveys. Whereas gravity measurements are usually performed at the ground surface, Fajklewicz simultaneously performs measurements also at a surface situated 3 m above ground, using a portable tower. His data are presented as a map of the difference between the bottom and the top measurements. This difference (which may be measured in gradient units after being divided by the tower height) is called the Gravity Tower Vertical Gradient (GTVG). Similar procedures have been occasionally employed for various purposes (Thyssen‐Bornemisza, 1976). My main comments on the paper by Fajklewicz are as follows.

GRADIENT MEASUREMENTS IN AEROMAGNETIC SURVEYING

Geophysics ◽  
1965 ◽  
Vol 30 (5) ◽  
pp. 891-902 ◽  
Author(s):  
Peter Hood
Keyword(s):  
Optical Pumping ◽  
Vertical Gradient ◽  
Horizontal Distance ◽  
Total Field ◽  
Highly Sensitive ◽  
Geophysical Information ◽  
The Difference ◽  
Gradient Measurements ◽  
First Vertical Derivative ◽  
Depth Of Burial

The recent development of highly sensitive magnetometers, such as the optical‐pumping varieties, has made feasible the measurement of the first vertical derivative of the total field (∂ΔT/∂h) in aeromagnetic surveys. This is accomplished by using two sensitive magnetometer heads separated by a constant vertical distance, and recording the difference in outputs. The effect of diurnal is thus eliminated in the resultant differential output, and this is an especially desirable feature in northern Canada where the diurnal variation is usually much greater than is found in more southerly magnetic latitudes. Moreover, steeply dipping geological contacts in high‐magnetic latitudes are outlined by the resultant zero‐gradient contour. It is also possible to obtain the depth of burial of the contact from the graph of (∂ΔT/∂h) versus (x∂ΔT/∂x) where x is the horizontal distance measured from the contact. Similar quantitative interpretations may be made for the point pole and dipole. The data reduction necessary to produce a vertical‐gradient map is much simpler than with the total‐field case because no datum levelling is necessary. Since the aircraft track will be available from the main compilation it is only necessary to plot the resultant vertical‐gradient values on the track map and contour. Thus, two maps will be obtained for little more than the price of one but with a greatly increased gain in geophysical information concerning the geometry of the causative bodies. Actually, a first‐derivative map is difficult (and therefore costly) to produce by any other means. The measurement of the vertical gradient would appear to be the main advantage to using hundredth‐gamma magnetometers in aeromagnetic surveys, since those types presently in service are sensitive enough for the effective delineation of total‐field anomalies.

GRAVITY VERTICAL GRADIENT MEASUREMENTS FOR THE DETECTION OF SMALL GEOLOGIC AND ANTHROPOGENIC FORMS

Geophysics ◽  
1976 ◽  
Vol 41 (5) ◽  
pp. 1016-1030 ◽  
Author(s):  
Zbigniew J. Fajklewicz
Keyword(s):  
Detailed Analysis ◽  
Research Work ◽  
Vertical Gradient ◽  
Industrial Applications ◽  
New Method ◽  
Topographic Correction ◽  
Engineering Problems ◽  
Mine Workings ◽  
The Difference ◽  
Gradient Measurements

The gravity tower vertical gradient has been applied to the solution of a number of important geologic, mining, and engineering problems, particularly to the search for and investigation of geologic structures and the detection of caverns and old mine workings. The effective application of the method depends upon recognizing the difference between the theoretical gravity vertical gradient [Formula: see text] and the gradient [Formula: see text] measured by means of a tower and gravimeter. The former is a derivative of the function g, the latter its differential quotient. Consequently, the differences between [Formula: see text] and [Formula: see text] in the same point may attain high values. Thus, e.g., for a sphere with a radius of 1 m, a density of 2.0 gm/cc and the depth of occurrence of its center equaling 1.2 m, the difference of the theoretical absolute amplitudes [Formula: see text] Eötvös units. Application of the method of the gravity tower vertical gradient on an industrial scale was possible due to the introduction of (1) a new design of the measuring tower, (2) detailed analysis of errors, and (3) a new method of calculating the topographic correction of the gravity vertical gradient. The paper sums up the results of five years of research work and industrial applications. During that period several thousand measurements of the gravity vertical gradient were made.

Experimental and Numerical Study on Grinding Temperature during Surface Grinding with Different Cooling Methods

2009 ◽  
Vol 416 ◽  
pp. 514-518 ◽  
Author(s):  
Qing Long An ◽  
Yu Can Fu ◽  
Jiu Hua Xu
Keyword(s):  
Numerical Study ◽  
Specific Energy Consumption ◽  
Ground Surface ◽  
Numerical Results ◽  
Surface Grinding ◽  
Grinding Temperature ◽  
Air Jet ◽  
The Difference ◽  
High Specific Energy ◽  
Cooling Methods

Grinding, characterized by its high specific energy consumption, may generate high grinding zone temperature. These can cause thermal damage to the ground surface and poor surface integrity, especially in the grinding of difficult-to-machine materials. In this paper, experimental and fem study on grinding temperature during surface grinding of Ti-6Al-4V with different cooling methods. A comparison between the experimental and numerical results is made. It is indicated that the difference between experimental and numerical results is below 15% and the numerical results can be considered reliable. Grinding temperature can be more effectively reduced with CPMJ than that with cold air jet and flood cooling method.

Experimental Research on ELID Grinding and Cutting Performance of Nano Cemented Carbide Cutters

2005 ◽  
Vol 291-292 ◽  
pp. 115-120 ◽  
Author(s):  
Fei Hu Zhang ◽  
J.C. Gui ◽  
Yi Zhi Liu ◽  
Hua Li Zhang
Keyword(s):  
Cutting Speed ◽  
Ground Surface ◽  
High Hardness ◽  
Cemented Carbide ◽  
Carbide Tool ◽  
Elid Grinding ◽  
Fine Grain ◽  
Cemented Carbide Tool ◽  
The Difference ◽  
Ground Surface Roughness

Nano cemented carbide is a new style cutter material. Because its grain size is very small, it is superior to common cemented carbide in properties, such as high hardness, fracture toughness, flexural strength and higher abrasion resistance. As a cutter material, nano cemented carbide has wide use. In this paper, nano cemented carbide tool was ground with ELID technology, and the cutting properties of nano cemented carbide were studied, and the difference in cutting properties among the ultra-fine grain, common cemented carbide and nano cemented carbide was analyzed under the same condition. Results imply that the ground surface roughness of nano cemented carbide is obviously lower than that of common cemented carbide, and the tool life of nano cemented carbide is 5-7 times longer than that of common cemented carbide at low cutting speed.

GWAS as the Detective to Find Genetic Contribution in Diseases

2018 ◽  
pp. 466-476
Author(s):  
Simanti Bhattacharya ◽  
Amit Das
Keyword(s):  
Genome Wide Association Study ◽  
Genome Mapping ◽  
Disease Onset ◽  
Genome Wide Association ◽  
Powerful Method ◽  
Disease Phenotype ◽  
Genome Wide ◽  
The Difference ◽  
Complex Scenario ◽  
Near Future

Genome Wide Association Study (GWAS) is a powerful method to understand the complex association of variant in gene and disease phenotype. With the approach of GWAS the traditional 'one gene to one disease' belief has been taken to another dimension where a rather complex scenario of many possible causal agent (polymorphisms) behind disease onset is explicitly explored. it also gives the liberty to monitor the difference at each point of DNA for each individual in the sample. GWAS is powered with genome mapping projects and depends on stringent statistical analysis that detects the association of polymorphisms to disease phenotype after comparing the samples collected from afflicted and un-afflicted population. However, this method also has its own limitations. But with careful experiment design and unbiased analysis this GWAS, in near future, will become a new edge technology to decipher the disease mechanism so that effective therapeutics, tailored for specific cases can be developed.

Regional differences in pleural lymphatic albumin concentration in sheep

1987 ◽  
Vol 252 (1) ◽  
pp. H64-H70 ◽  
Author(s):  
K. H. Albertine ◽  
E. L. Schultz ◽  
J. P. Wiener-Kronish ◽  
N. C. Staub
Keyword(s):  
Hydrostatic Pressure ◽  
Regional Differences ◽  
Left Lung ◽  
Vertical Gradient ◽  
Dark Field ◽  
Vertical Position ◽  
Albumin Concentration ◽  
The Difference ◽  
Field Reflectance ◽  
Vertical Height

We used quantitative reflectance autoradiography to compare the concentration of albumin in visceral pleural lymphatics at the cranial and caudal ends of the sheep's lung in the vertical (60 degrees head-up) and horizontal (supine) positions. Twelve to fourteen hours after injecting 125I-albumin intravenously we placed four anesthetized sheep in the vertical position to establish a microvascular hydrostatic pressure gradient along the vertical height of the lung. We placed two anesthetized sheep in the horizontal position. Four hours later, we fixed the left lung and removed visceral pleural tissue blocks from the cranial and caudal ends, separated by a 15-cm distance, along the costovertebral margin. We measured the silver grain density in the pleural lymphatic autoradiograms by dark-field reflectance microspectrophotometry. In the vertical position, the lymph albumin concentration at the cranial end (top) of the lung averaged 2.5 +/- 0.4 g/dl compared with the caudal end (bottom), which averaged 1.8 +/- 0.3 g/dl. The difference (42% greater at the top than the bottom) is significant (P less than 0.05). The computed gradient in perimicrovascular interstitial albumin osmotic pressure was 0.26 +/- 0.13 cmH2O/cm lung height. There were no differences between the cranial and caudal lymphatic groups in the two horizontal sheep. We conclude that in the sheep lung there is a gradient in perimicrovascular albumin concentration due to the vertical gradient in microvascular hydrostatic pressure.

Regional lung water and hematocrit determined by positron emission tomography

1985 ◽  
Vol 59 (3) ◽  
pp. 860-868 ◽  
Author(s):  
D. P. Schuster ◽  
M. A. Mintun ◽  
M. A. Green ◽  
M. M. Ter-Pogossian
Keyword(s):  
Positron Emission Tomography ◽  
Regional Distribution ◽  
Vertical Gradient ◽  
Emission Tomography ◽  
Lung Water ◽  
Average Value ◽  
Positron Emission ◽  
Significant Difference ◽  
Regional Basis ◽  
The Difference

We have measured with positron emission tomography (PET) the regional distribution of extravascular lung water (EVLW) and hematocrit (HctL) in normal supine dogs. H2(15)O and C15O were used as total lung water (TLW) and intravascular water (IVW) compartment labels, respectively. An additional plasma volume label (68Ga-transferrin) was used to determine regional HctL. EVLW was calculated as the difference between TLW and IVW. In 13 dogs, EVLW was relatively constant along a gravity-dependent vertical gradient, although values in the most anterior regions were statistically less (P less than 0.05) than those in more posterior ones. The average value for EVLW (13 dogs) was 14.4 +/- 2.5 ml H2O/100 ml lung. When EVLW was compared with IVW on a regional basis, the EVLW/IVW ratio decreased significantly in a gravity-dependent direction from 1.95 +/- 0.28 to 0.88 +/- 0.18. In 7 dogs, no significant difference between HctL and systemic hematocrit (average ratio 1.01 +/- 0.08) was found nor was any significant variation of HctL within the lung detected. Thus, in contrast to gravimetric techniques, a hematocrit correction does not appear to be necessary when regional EVLW is studied by PET.

The calculation of deflexions of the vertical from gravity anomalies

1950 ◽  
Vol 204 (1078) ◽  
pp. 374-395 ◽  
Keyword(s):  
Gravity Data ◽  
Gravity Anomalies ◽  
Sources Of Error ◽  
Free Air ◽  
Gravity Measurements ◽  
Standard Deviations ◽  
The Difference ◽  
Different Sources

The theory of the application of gravity measurements to geodetic calculations is discussed, and the errors involved in calculating deflexions of the vertical are estimated. If the gravity data are given as free air anomalies from Jeffreys’s (1948) formula, so thdt the second and third harmonics of gravity are assumed known, the orders of magnitude of the standard deviations of the different sources of error are the following: Single deflexion: neglect of gravity outside 20° 1" Difference of deflexions: neglect of gravity outside 5° 0"·5 Calculation of effects of gravity from 0º·05 to 5° 0"·1 Calculation of effects of gravity within 0º·05 between 0"·1 and 0"·5 Estimates of the deflexions are made for Greenwich, Herstmonceux, Southampton and Bayeux, and the difference between Greenwich and Southampton is compared with the astronomical and geodetic amplitudes.

On: “Gravity vertical gradient measurements for the detection of small geologic and anthropogenic forms” by Z. J. Fajklewicz (GEOPHYSICS, October 1976, p. 1016–1030)

Geophysics ◽  
1977 ◽  
Vol 42 (4) ◽  
pp. 872-873
Author(s):  
Stephen Thyssen‐Bornemisza
Keyword(s):  
Research Work ◽  
Vertical Gradient ◽  
Gravity Gradient ◽  
Wind Gust ◽  
Near Surface ◽  
New Methods ◽  
Vertical Gravity Gradient ◽  
Surface Variation ◽  
Gradient Measurements ◽  
Vertical Gravity

In his paper, Fajklewicz discusses the improvement of vertical gravity gradient measurements arising from a very stable tower apparently not affected by wind gust vibration and climatic changes. Further, the lower plate where the gravity meter is resting can be changed in position to avoid possible disturbances from surface and near‐surface variation, and new methods for correcting and interpreting observed gradients over the vertical interval of about 3 m are presented. Some 1000 field stations were observed, including research work and industrial application.

Effects of terrain on borehole gravity data

Geophysics ◽  
1980 ◽  
Vol 45 (2) ◽  
pp. 234-243 ◽  
Author(s):  
J. R Hearst ◽  
J. W. Schmoker ◽  
R. C. Carlson
Keyword(s):  
Gravity Data ◽  
Radial Distance ◽  
Ground Surface ◽  
Absolute Maximum ◽  
Near Surface ◽  
Free Air ◽  
Gravity Measurements ◽  
Terrain Elevation ◽  
Lower Magnitude ◽  
Terrain Features

The effect of terrain on gravity measurements in a borehole and on formation density derived from borehole gravity data is studied as a function of depth in the well, terrain elevation, terrain inclination, and radial distance to the terrain feature. The vertical attraction of gravity [Formula: see text] in a borehole resulting from a terrain element is small at the surface and reaches an absolute maximum at a depth of about one and one‐half times the radial distance to the terrain element, then decreases at greater depths. The effect of terrain on calculated formation density is proportional to the vertical derivative of [Formula: see text] and is maximum at the surface, passes through zero where |[Formula: see text]| is greatest, and reaches a second extremum of opposite sign to the first and of much lower magnitude. Accuracy criteria for borehole‐gravity terrain corrections show that elevation accuracy requirements are most stringent for a combination of nearby terrain features and near‐surface gravity stations. Sensitivity to terrain inclination is also greatest for this combination. The measurement of the free‐air gradient of gravity, commonly made’slightly above the ground surface, is extremely sensitive to topographic irregularities within about 300m of the measurement point. The effect of terrain features 21.9 to 166.7 km from the well [Hammer’s (1939) zone M through Hayford‐Bowie’s (1912) zone O] on calculated formation density is nearly constant with depth. At these distances, the terrain correction will be equivalent to a dc shift of about [Formula: see text] of average elevation above or below the correction datum. The effect of topography beyond 166.7 km is not likely to exceed [Formula: see text].

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