Threshold depth

GWQMN (mm H20) Threshold depth of water in the shallow aquifer required for return flow to occur. Groundwater flow to the reach is allowed only if the depth of water in the shallow aquifer is equal to or greater than GWQMN. 

An effect of type B (Figure 14-2) does not become manifest until a certain threshold depth is reached then it manifests itself and increases in intensity with increasing depth, as does type A. But, after stabilizing at some maximum value for a while, the... 

Benson R. H. (1972) Ostracodes as indicators of threshold depth in the Mediterranean during the Pliocene. In The Mediterranean Sea A Natural Sedimentation Laboratory (ed. D. J. Stanley), pp. 63-73. Dowden, Hutchinson Ross, Inc., Stroudsburg, PA. 

The HMI automatically displays the shaft coarse depth scale based on the top and bottom shaft limits. As the shaft is deepened through the sinking process, the bottom shaft limit will increase, and there will be several threshold depths where the shaft scaling will be changed to incorporate the additional depth. The algorithm is set up so that on average at least 75% of the coarse depth indicator is used to display the shaft level positions. 

IV.2. Dewetting Transition The cocoon is stable only if AF < 0, F = 0 defines a threshold depth he... 

Automatic setting of threshold of the depth of detected cracks... 

Let us consider the calculation of sensitivity threshold in the case when the cracks are revealing by PT method. Constant distance H between crack s walls along the whole defect s depth is assumed for the simplicity. The calculation procedure depends on the dispersity of dry developer s powder [1]. Simple formula has to be used in the case when developer s effective radius of pores IC, which depends mainly on average particle s size, is smaller than crack s width H. One can use formula (1) when Re is small enough being less than the value corresponding maximum sensitivity (0,25 - 1 pm). For example. Re = 0,25 pm in the case when fine-dispersed magnesia oxide powder is used as the developer. In this case minimum crack s width H that can be detected at prescribed depth lo is calculated as... 

One more obvious example illustrates strong influence of particle s sedimentation upon the sensitivity threshold. Assume that we have to ensure the detection of the cracks with the depth 10 > 2 mm in the case when the same product family indicated above is applied and h = 20 pm. The calculation using formula (1) shows that in the absence of sedimentation only the cracks with the width H > 2 pm could be detected. But when the effect of sedimentation results in the reduction of the value of developer layer thickness from h = 20 pm to h = 8 pm, then the cracks of substantially smaller width H > 0,17 pm can be revealed at the same length lo = 2 mm. Therefore we can state that due to the sedimentation of developer s particles the sensitivity threshold has changed being 12 times smaller. Similar results were obtained using formula (2) for larger particles of the developers such as kaolin powder. 

The depth profiling of the Cu-Ag-Si samples was performed with the laser beam focused on to the sample surface to the spot of approximately 30-40 pm. To obtain the best depth resolution the laser fluence was maintained near the 1 J cm level, close to the threshold of the LIBS detection scheme. The intensity profiles of Cu and Ag emission lines are shown in Fig. 4.43. The individual layers of Cu and Ag were defi-... 

With the downhole power available and the signal detection threshold at surface, Figure 4-254b gives the maximum depth that can be reached by the technique as a function of frequency. Assuming that phase-shift keying is used with two cycles per bit, in a 10 fi m area (such as the Rocky mountains) a depth of 2 km (6,000 ft) could be reached while transmitting 7 bits/s. 

Downhole Shocks Measurements. An accelerometer in the MWD telemetry tool measures transverse accelerations, or shocks, that may be damaging for the bottomhole assemblies. When acceleration exceeds a certain threshold, the event is signaled to the surface as being a shock. These events versus time or depth are displayed as shock count. This information is used as a warning against excessive downhole vibrations and to alert the driller to change the rpm or weight on the bit [106]. 

Local surface structure and coordination numbers of neighbouring atoms can be extracted from the analysis of extended X-ray absorption fine structures (EXAFS). The essential feature of the method22 is the excitation of a core-hole by monoenergetic photons modulation of the absorption cross-section with energy above the excitation threshold provides information on the distances between neighbouring atoms. A more surface-sensitive version (SEXAFS) monitors the photoemitted or Auger electrons, where the electron escape depth is small ( 1 nm) and discriminates in favour of surface atoms over those within the bulk solid. Model compounds, where bond distances and atomic environments are known, are required as standards. 

Here, L total is the depth of the etched hole per pulse and is assumed to be the sum of photochemical and photothermal contributions, Tphoto and Thermal, respectively 0Ceff is the effective photon absorption coefficient of the medium and can vary with laser emission characteristics, e g., photon density Fis the incident laser fluence Fth is the medium s threshold fluence A and F are the effective frequency factor with units of pm/pulse and the effective activation energy with units of J/cm2, respectively, for the zeroth-order thermal rate constant F0, comparable in magnitude to Fth, is important only at low fluences.64 Equation (5) is obtained after assuming that the polymer temperature T in the laser-exposed region of mass mp and the thermal rate constant k are given, respectively, as... 

From a knowledge of the absorption coefficient aeff and the threshold fluence Fth, the value of the photochemical contribution to the etch rate, Fph0to> can calculated and subtracted from the measured hole depth for any given fluence. The difference, which according to this model is the thermal etch rate Fthermai will be modeled by Eq. (5) by rewriting it as... 

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