Threshold detection

The detection of all abnormal indication based on a detection threshold. 

For each tube, the analyst carefully examines the complete eddy current record. Any indication above the detection threshold that did not lead to a confirmed computer diagnostic is manually examined. 

Odors are characterized by quaUty and intensity. Descriptive quaUties such as sour, sweet, pungent, fishy, and spicy are commonly used. Intensity is deterrnined by how much the concentration of the odoriferous substance exceeds its detection threshold (the concentration at which most people can detect an odor). Odor intensity is approximately proportional to the logarithm of the concentration. However, several factors affect the abiUty of an individual to detect an odor the sensitivity of a subject s olfactory system, the presence of other masking odors, and olfactory fatigue (ie, reduced olfactory sensitivity during continued exposure to the odorous substance). In addition, the average person s sensitivity to odor decreases with age. 

Generalizations. Several generalizations can be made regarding taste (16,26). A substance must be in water solution, eg, the Hquid bathing the tongue (sahva), to have taste. Water solubiUty is the first requirement of the taste stimulus (12). The typical stimuli are concentrated aqueous solution in contrast with the Hpid-soluble substances which act as stimuli for olfaction (22). Many taste substances are hydrophilic, nonvolatile molecules (15). Taste detection thresholds for lipophilic molecules tend to be lower than those of their hydrophilic counterparts (16). 

The odor detection-threshold values of organic compounds, water, and mineral oil have been determined by different investigators (Table 2 and 3) and may vary by as much as 1000, depending on the test methods, because human senses are not invariable in their sensitivity. Human senses are subject to adaption, ie, reduced sensitivity after prolonged response to a stimulus, and habituation, ie, reduced attention to monotonous stimulation. The values give approximate magnitudes and are significant when the same techiriques for evaluation are used. Since 1952, the chemistry of odorous materials has been the subject of intense research (43). Many new compounds have been identified in natural products (37—40,42,44—50) and find use in flavors. 

Table 2. Odor Detection Threshold Levels in Water and Mineral Oil, ppm...

Table 3. Odor Detection Thresholds of Organic Compounds ...

Odors are measured by their intensity. The threshold value of one odor to another, however, can vary greatly. Detection threshold is the minimum physical intensity necessary for detection by a subject where the person is not required to identify the stimulus, but just detect the existence of the stimulus. Accordingly, threshold deterrninations are used to evaluate the effectiveness of different treatments and to estabflsh the level of odor control necessary to make a product acceptable (8). Concentration can also produce different odors for the same matenal. For example, indole (qv) in low concentrations has the smell of jasmine and a low threshold of perception. In high concentrations, it has a strong odor of feces and CX-naphthyl amine as well as a considerably higher threshold of perception. 

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. 

Using the probable detection threshold achievable and a gas kick model applied to a typical 10,000-ft drill hole, an early alarm provided by MWD systems decreases significantly the amount of gas to be circulated as compared to using conventional methods of kick detection. 

The maximum ground-level concentration calculated on a 10-minute basis for no nuisance should therefore be equal to the detection threshold, i.e. 

Food colorants play an important role in quality perception. Color is often the first notable characteristic of a food and it influences the expectations of consumers buying the product and also influences food handlers who make quality-related decisions, for example, during visual inspections." More specifically, color predetermines our expectations and perceptions of flavor and taste. " Color is interrelated with flavor intensity (detection threshold), with sweetness and salinity sensations, and also with our susceptibilities to and preferences for products. For example, consumers perceived a strongly red-colored strawberry-flavored drink to be sweeter than a less colored version, and yellow was associated with lemon and pink with grapefruit, but by reversing the colors, flavor perception changed." If food color is not appealing, consumers will not enjoy the flavor and texture of the food. ... 

The plant sample in lane 6 is also positive for the transgene of interest. Because the band for the effect gene (middle band) is typically fainter than the band for the selectable marker gene (bottom band), it appears that for lane 6, the PCR product amplitication for the effect gene is below the assay detection threshold. Because the selectable marker is clearly present and the PCR amplitication worked, lane 6 can be interpreted as a positive result for the transgene of interest. 

An ingenious whole-cell mechanism-based assay using an antisense fabF RNA was developed to increase the detection threshold to FabH/F inhibitors in S. aureus. A range of new natural products was thus... 

Fig. 9.1. Spectrum of the energetic electrons in the collimated beam as obtained in the experiment described in [16]. Black dots represent the experimental data. Also shown is the detection threshold of the electron spectrometer. The solid line is the spectrum of the electrons in the collimated beam as obtained from the PIC simulation...

In the CEN procedure, the European odor unit per cubic meter, ou m-3 is used. The odor concentration at the detection threshold is defined as equal to 1 ou m-3. 

Figure 12 shows the appropriately calculated detection threshold in the pure noise situation (12 a). This homogeneous noise model with unknown noise power was the motivation to develop CA-CFAR. The... 

A simple quantitative comparison between different CFAR procedures in pure clutter and noise situations, which is the most important situation, can be calculated using the average detection threshold (ADT)... 

An established system for odour detection threshold measurements Guideline for olfactometric measurements in the Netherlands. Comparison with Western European guidelines... 

AN ESTABLISHED SYSTEM FOR ODOUR DETECTION THRESHOLD MEASUREMENTS... 

Often the number of dilutions to detection threshold, D (dimensionless) is combined with the rate, F (m3 s 1) at which malodorous air is discharged or escapes from the building or process plant to derive the odour emission rate, E (m3 s1 ) where E=DF. Information on the odour strength in terms of D or the odour emission rate, E, can be used in various ways ... 

It is known that odour detection thresholds measured by different types of olfactometer can vary substantially. Not unreasonably, there are well-intentioned calls for standardisation of odour measurements , possibly as the basis for odour emission regulations, and so it might be useful to express some cautionary views. 

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