Noise long-time

For the determination of the dynamic detector noise it is necessary to equilibrate the whole HPLC system for at least 30 min according to the conditions described in the autosampler test. The recording unit is set to 0.5-1.5 X 10 AU and the detector signal is recorded during 10 min. The detector noise is determined graphically (peak-to-peak) and documented. Note that this is only a test of short-time noise. A possible drift (long-time noise) is not included. 

Specific heat capacities and their change with temperature can thus be directly measured and recorded. The baseline has a repeatability (long-time noise) of 20 p.W. The specific heat capacities and reaction enthalpies can be measured with... 

The detector noise is defined as the maximum amplitude of the combined short and long term noise, measured in millivolts, over a period of fifteen minutes. If a column 4.5 mm i.d. is employed, a flow rate of 1 ml/min is appropriate. The flow rate should be adjusted appropriately for columns of different diameters. The value for the detector noise should be obtained by constructing parallel lines embracing the maximum excursions of the recorder trace over the defined time period as shown in figure 4. The distance between the parallel lines measured in millivolts is taken as the noise level. 

Relatively long time-constants of 1 to 60 s are used in order to minimize the noise inherent in c.d. spectra. Thus, the scanning rate is low, and as c.d. instruments tend to drift with time, they should be calibrated daily, and baselines should be measured for each sample. 

K. Kulpa, Z. Czekala, M. Smolarczyk, Long-Time-Integration Surveillance Noise Radar , First International Workshop On The Noise Radar Technology (NRTW 2002), Yalta, Crimea, Ukraine, September 18-20, 2002, pp. 238-243. 

Check the intensity and the age of the lamps before carrying out the performance tests. Lamps that have been in use for a long time usually have a high noise level and unstable energy output. 

Although all physical processes are, of course, of limited duration there are many situations in which this limitation is not of practical interest. When studying the noise in an electronic device one normally is not interested in effects connected with the switching on and off. A description in which the duration does not enter is then simpler and more appropriate. One is thus led to examining sets of dots whose density does not tend to zero for t - + oo. Such sets cannot be described in terms of the Qs, because the normalization condition (1.3) requires Qs to vanish at infinity. It is true that this shortcoming can be overcome by introducing a fictitious long time interval T, but that burdens the equations with an irrelevant quantity. The description in terms of the / , however, carries over without additional artifice. 

Remark. The white noise limit is not sufficiently defined by just saying rc 0. We have to construct a sequence of processes which in this limit reduce to Gaussian white noise. For that purpose take a long time interval (0, T) and a Poisson distribution of time points Ta in it with density v. To each Ta attach a random number ca they are independent and identically distributed, with zero mean. Consider the process... 

The chronocoulometric method offers some advantages over the chronoamperometric method, (a) The measured signal grows with time and hence the later part of the transient, that corresponds better with theory, suffers less from instrumental inaccuracy, (b) The act of integration smoothes random noise in the current signal and hence also improves the accuracy, (c) Even the long-time approximation, eqn. (37b), contains... 

Time-dependent correlation functions have been familiar for a long time in the theory of noise and stochastic processes. In recent years they have become very useful in many areas of statistical physics and spectroscopy. Correlation functions provide a concise method for expressing the degree to which two dynamical properties are correlated over a period of time. 

For gas or ions, FET sensors response speed is not the main prerequisite because of the relatively long time constants associated with chemical measurements. However, the ON-OFF conductance ratio, as well as the transconductance IJ Vg should be maximized. As far as noise is concerned, attention shold be paid to reducing both the noise-equivalent input current zn and voltage vn generators of the sensor. In fact, the total rms input noise for unity bandwidth of such a device can be expressed in a first approximation as (Motchenbacher and Fitchen, 1973)... 

Data acquisition is straightforward, while digital noise filtering can improve long-time data [87]... 

Another problem is the ease with which a DSC apparatus degrades. Briefly, after it is used for a long time, it begins to produce noise, such that no definite DSC curve can be obtained. This may be attributable to the contamination of cell holders by gas from samples. The authors have conducted experiments with sealed cells by passing nitrogen gas through them, but contamination and its related noise production could not be avoided. For a time, a DTA apparatus considered less prone to contamination was borrowed from Nippon Kayaku Co., Ltd. and used for investigative purposes. 

We have been living here for a long time. When it starts to get warm, we immediately come out here for the entire time. We live here, well that is, we breathe the air. You yourself know the condition [of the air] in the city There is dust, it is humid, noisy. And when you go from the dacha to the city—you cannot sleep at night for an entire week. It is impossible to sleep because of the noise, the cars. . . impossible. But here—here you sleep like the dead [tut spish kak ubytii]. It is marvelous. . . The forest is your own. 

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