One-point measurement

Maron, Samuel H.. Determination of intrinsic viscosity from one-point measurements. Journal of Applied Polymer Science 5,15 (1961) 282-284. 

DERIVATION OF MEMBRANE-RETENTION PERMEABILITY EQUATIONS (ONE-POINT MEASUREMENTS, PHYSICAL SINKS, IONIZATION SINKS, BINDING SINKS, DOUBLE SINKS)... 

A method was proposed to obtain the kinetic rate constant at a fixed temperature with a one-point measurement. This method is comparable to gas-chromato-graphic concentration measurements and can in principle be executed with a convenient gas-chromatograph equipped with a flame ionization detector (FID) [37]. The background of this method is introduced in the following. 

Integral exposure Quarterly TLD 4-8 TLD elements are used for one point measurement... 

The test with the flow cup is a one-point measurement and only gives a viscosity value that is determined under the given measurement conditions. In the short capillary, no stationary laminar flow profile can be build up, since the inlet and acceleration part is often greater than the viscous part. Because of the undefined flow form in the short capillary, further parameters cannot be determined. Even though flow cups are still a widely used method for the determination of a characteristic efflux time for example for coating compounds. 

Nevertheless, Brookfield viscosimeters are the widely used devices for quality management they are a fast and cheap alternative for conducting one-point measurements. In addition to this, many companies use special stirring systems that are custom tailored for a specific application. However, for the determination of the intrinsic viscosity or an exact viscosity devices like the Brookfield viscosimeter are not appropriate. 

In many engineering applications the relation between the average velocity in a pipe and the maximum velocity is useful, since in some cases only the at the center point of the tube is measured. Hence, from only one point measurement this relationship between and u can be used to determine In Fig. 2.10-2 experimentally measured values of are plotted as a function of the Reynolds numbers... 

Progress curves will vary depending on medium pH, temperature, ionic strength, polarity, substrate type, and enzyme and coenzyme concentration, among many others. Too often, researchers use one-point measurements to... 

Time lag observed Eudiometer, special vessel Inverse buret, hand shaking Pressure measured Horisontal manometer Asotometer with Hg Van Slyke apparatus Eudiometer hand shaking Pressure method Special apparatus Like (30), but only one point measured Inverse buret No leveling device... 

To date many paint manufacturers use one-point measurement for measurement of paint consistency. This can be carried out, for example, with a simple Brookfield viscometer using one spindle at a given rpm. This one-point measurement can be misleading [49]. To illustrate this point let us consider three systems, namely Newtonian, Bingham plastic and pseudoplastic with thixotropy as illustrated in Fig. 4.27. At a specific shear rate, all the three systems show the same apparent viscosity although their flow behavior (using the full shear-stress curves) is significantly different [49]. These systems will show entirely different behavior on application at the shear rate at which the apparent viscosity is the same. A study of the flow curves indicates that the Newtonian system will flow at extremely low shear rates, whereas the plastic and thixotropic systems will show reluctance to do so because of their yield values. This is clearly reflected in the final film properties. Once the yield value is overcome, the... 

The PIV method is a fairly new technique, capable of simultaneous velocity measurements at many points in a plane. This gives information on large scale structures, vorticity, etc. which is very difficult or impossible to obtain from one-point measuring techniques. 

For a larger size non-uniformity, for example, variation within the batch of internal mixers may appear as a pressure oscillation observed by a pressure-tap at the chamber wall of a mixer [13]. It may also appear as an oscillation of the mixing torque (see Table 3.1 [24]). However, before using these oscillations as a measure of degree of nonuniformity, an independent check by actual sampling of the contents must be done, because the oscillation is also related to the way in which the compound is moved around the mixer. For the batch-to-batch variation, previously mentioned two-point measurements of moduli may be used. If the requirement is not very critical, even a one-point measurement may be adequate. 

The flash point measures the tendency of a petroleum material to form a flammable mixture with air. It is one of the properties to be considered when evaluating the flammability of a petroleum cut. 

Using the theorem that the sufficiency condition for mathematical correctness in 3D-reconstruction is fulfilled if all planes intersecting the object have to intersect the source-trajectory at least in one point [8], it is possible to generalise Feldkamp s method. Using projection data measured after changing the sotuce-trajectory from circular to spiral focus orbit it is possible to reconstruct the sample volume in a better way with the Wang algorithm [9]. 

One of the advantages of the Verlet integrator is that it is time reversible and symplectic[30, 31, 32]. Reversibility means that in the absence of numerical round off error, if the trajectory is run for many time steps, say nAt, and the velocities are then reversed, the trajectory will retrace its path and after nAt more time steps it will land back where it started. An integrator can be viewed as a mapping from one point in phase apace to another. If this mapping is applied to a measurable point set of states at on(> time, it will... 

Quantitative Analysis Using the Method of Standard Additions Because of the difficulty of maintaining a constant matrix for samples and standards, many quantitative potentiometric methods use the method of standard additions. A sample of volume, Vx) and analyte concentration, Cx, is transferred to a sample cell, and the potential, (ficell)x) measured. A standard addition is made by adding a small volume, Vs) of a standard containing a known concentration of analyte, Cs, to the sample, and the potential, (ficell)s) measured. Provided that Vs is significantly smaller than Vx, the change in sample matrix is ignored, and the analyte s activity coefficient remains constant. Example 11.7 shows how a one-point standard addition can be used to determine the concentration of an analyte. 

The concentration of Ca + in a sample of sea water is determined using a Ca ion-selective electrode and a one-point standard addition. A 10.00-mL sample is transferred to a 100-mL volumetric flask and diluted to volume. A 50.00-mL aliquot of sample is placed in a beaker with the Ca ion-selective electrode and a reference electrode, and the potential is measured as -0.05290 V. A 1.00-mL aliquot of a 5.00 X 10 M standard solution of Ca + is added, and a potential of -0.04417 V is measured. What is the concentration of Ca + in the sample of sea water ... 

The concentration of NO3 in a water sample is determined by a one-point standard addition using an N03 ion-selective electrode. A 25.00-mL sample is placed in a beaker, and a potential of -t0.102 V is measured. A 1.00-mL aliquot of a 200.0 ppm standard solution of N03 is added, after which the potential is found to be -t0.089 V. Report the concentration of N03 in parts per million. 

In Example 13.1 the initial concentration of analyte is determined by measuring the amount of unreacted analyte at a fixed time. Sometimes it is more convenient to measure the concentration of a reagent reacting with the analyte or the concentration of one of the reaction s products. The one-point fixed-time integral method can still be applied if the stoichiometry is known between the analyte and the species being monitored. For example, if the concentration of the product in the reaction... 

The one-point fixed-time integral method has the advantage of simplicity since only a single measurement is needed to determine the analyte s initial concentration. As with any method relying on a single determination, however, a... 

An alternative to a fixed-time method is a variable-time method, in which we measure the time required for a reaction to proceed by a fixed amount. In this case the analyte s initial concentration is determined by the elapsed time, Af, with a higher concentration of analyte producing a smaller Af. For this reason variabletime integral methods are appropriate when the relationship between the detector s response and the concentration of analyte is not linear or is unknown. In the one-point variable-time integral method, the time needed to cause a desired change in concentration is measured from the start of the reaction. With the two-point variable-time integral method, the time required to effect a change in concentration is measured. 

Sensitivity The sensitivity for a one-point fixed-time integral method of analysis is improved by making measurements under conditions in which the concentration of the monitored species is larger rather than smaller. When the analyte s concentration, or the concentration of any other reactant, is monitored, measurements are best made early in the reaction before its concentration has substantially decreased. On the other hand, when a product is used to monitor the reaction, measurements are more appropriately made at longer times. For a two-point fixed-time integral method, sensitivity is improved by increasing the difference between times t and f2. As discussed earlier, the sensitivity of a rate method improves when using the initial rate. 

An array ion collector (detector) consists of a large number of miniature electron multiplier elements arranged side by side along a plane. Point ion collectors gather and detect ions sequentially (all ions are focused at one point one after another), but array collectors gather and detect all ions simultaneously (all ions are focused onto the array elements at the same time). Array detectors are particularly useful for situations in which ionization occurs within a very short space of time, as with some ionization sources, or in which only trace quantities of a substance are available. For these very short time scales, only the array collector can measure a whole spectrum or part of a spectrum satisfactorily in the time available. 

This frequency is a measure of the vibration rate of the electrons relative to the ions which are considered stationary. Eor tme plasma behavior, plasma frequency, COp, must exceed the particle-coUision rate, This plays a central role in the interactions of electromagnetic waves with plasmas. The frequencies of electron plasma waves depend on the plasma frequency and the thermal electron velocity. They propagate in plasmas because the presence of the plasma oscillation at any one point is communicated to nearby regions by the thermal motion. The frequencies of ion plasma waves, also called ion acoustic or plasma sound waves, depend on the electron and ion temperatures as well as on the ion mass. Both electron and ion waves, ie, electrostatic waves, are longitudinal in nature that is, they consist of compressions and rarefactions (areas of lower density, eg, the area between two compression waves) along the direction of motion. 

The wrinkle recovery angle provides a measure of the degree of chemical modification. This is calculated by blending a small sample and measuring the recovery to the flat configuration (180°). Whereas the untreated cotton recovers approximately 90°, the cross-linked cotton sample recovers 120—140°. If this is measured on dry fabric, it is termed conditional wrinkle recovery angle if on wet fabric, it is termed wet wrinkle recovery. At one point, wet wrinkle recovery was important, particularly in Europe. In the United States, the widespread use of clothes dryers has made conditional wrinkle recovery important. 

The remarkable theoretical predictions mentioned above are even more difficult to verify by experimental measurements in the case of electrical conductivity. Ideally, one has to solve two experimental problems. First, one has to realize a four-point measurement on an individual nanotube. That means four contacts on a sample with typical dimensions of the order of a nm... 

For example, the type test of a laboratory fume hood includes determination of the concentration at various points across the opening of the hodd by using various tracer source locations inside the hood. The commissioning test could concentrate on the measurements taken at one point in the opening with one source location. 

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