Delayed Generation Time

Define the six factors of K ff and typical values, the multiplication factor for an infinite reactor, criticality, subcriticality, supercriticality, reactivity, neutron lifetime with representative values, prompt generation time with representative values, and delayed generation time with representative values,... 

Delayed generation time, t, is the weighted average of the mean generation times of the six delayed neutron precursors. 

Generation time determines reactor period or startup rate. The shorter the generation time, the shorter the period and greater the startup rate for a positive reactivity addition. Prompt generation time, 1 x 1x10 sec. Delayed generation time,... 

When time-dependent signals are to be measured by a photomultiplier, the time sensitivity is usually limited by the inhomogeneous transit time. The transit time is the time taken by electrons generated in the cathode to arrive at the anode. If all of the emitted electrons had the same transit time, then the current induced in the anode would display the same time dependence as the incoming light, but delayed in time. However, not all of the electrons have the same transit time. This produces some uncertainty in the time taken by electrons to arrive at the anode. There are two main causes of this dispersion ... 

Nanosecond Absorption Spectroscopy Absorption apparatus, 226, 131 apparatus, 226, 152 detectors, 226, 126 detector systems, 226, 125 excitation source, 226, 121 global analysis, 226, 146, 155 heme proteins, 226, 142 kinetic applications, 226, 134 monochromators/spectrographs, 226, 125 multiphoton effects, 226, 141 nanosecond time-resolved recombination, 226, 141 overview, 226, 119, 147 probe source, 226, 124 quantum yields, 226, 139 rhodopsin, 226, 158 sample holders, 226, 133 singular value decomposition, 226, 146, 155 spectral dynamics, 226, 136 time delay generators, 226, 130. 

The first-generation sulfonylureas are not frequently used in the modem management of diabetes mellitus because of their relatively low specificity of action, delay in time of onset, occasional long duration of action, and a variety of side effects. They also tend to have more adverse drug interactions than the second-generation sulfonylureas. They are occasionally used in patients who have achieved previous adequate control with these agents. 

Two trigger pulses, one to fire the flash and one to fire the photomultiplier gate, are obtained from a General Radio time-delay generator operating with a repetition rate of 40 per sec. The sequence of events is as follows ... 

The temporal resolution of both methods is limited by the risetime of the IR detectors and preamplifiers, rather than the delay generators (for CS work) or transient recorders (SS) used to acquire the data, and is typically a few hundred nanoseconds. For experiments at low total pressure the time between gas-kinetic collisions is considerably longer, for example, approximately 8 /is for self-collisions of HF at lOmTorr. Nascent rotational and vibrational distributions of excited fragments following photodissociation can thus be obtained from spectra taken at several microseconds delay, subject to adequate SNR at the low pressures used. For products of chemical reactions, the risetime of the IR emission will depend upon the rate constant, and even for a reaction that proceeds at the gas-kinetic rate the intensity may not reach its maximum for tens of microseconds. Although the products may only have suffered one or two collisions, and the vibrational distribution is still the initial one, rotational distributions may be partially relaxed. 

The residence time was determined for our neutron counter by measuring the time intervals between beta start signals and neutron stop signals. With a residence half-time of 11 ms and a coincidence resolving time of 40 ms. 92 of the true coincidence events were included. The fraction of true events not detected does not influence the present results because we normalize the Pn measurements to a known Pn value measured under identical conditions. The coincidence rate was measured by a simple overlap coincidence module where the beta pulse Input was stretched to 40 ms by a gate and delay generator. To measure the accidental coincidence rate, the same beta pulse was sent to a second coincidence module and overlapped with neutron pulses which had been delayed 45 ms. After correcting each coincidence rate for deadtime effects, the difference was the true coincidence rate. 

Figure 1. Experimental system used in the time resolved absorption measurements. (EL=excimer laser, KrF, 248nm DG=delay generator OMA=optical multichannel analyser MC=monochromator and gated diode array detector C=cell X=xenon flash lamp L=lenses )...

Electric equipment for time delay generation or time interval measurement ... 

The time sequence of the ablation pulse, the ionization pulse, and the recording of TOF signals by the detector is shown in the lower part of Figure 9.1. Spectra were recorded for various time intervals between the ablation and ionization pulses. These time intervals are called delay times as stated in Section 9.2 (see Figure 9.1). The timings of all the instruments were controlled by delay generators (Stanford Research Systems DG535). 

The previous discussions of the signal are nicely illustrated by an extremely simple model analysis using real fields and signals for two Lorenzian resonances at frequencies a and b. The sample is irradiated with two very short pulses whose spectra are flat. The real generated field from the sample is the real part of Eq. (21) or Eq. (33) with T set equal to zero for convenience since is in any case a multiplicative factor. In time-domain interferometry, this is measured directly along the indicated time axes as described above. In spectral interferometry the real generated field along with a real local oscillator field, delayed by time d, is dispersed (i.e., Fourier-transformed) by a monochromator, then squared by the detection to yield a spectrum on the array detector at each value of t ... 

Comparing recovery time interval to generation time, we find that exposure to the EEC of acephate resulted in a delay of >1 generation time interval only for the oriental fruit fly (Table 5.2). Therefore, results of this exercise show that these 3 closely related species exhibited differences in life history traits and susceptibility to acephate, which resulted in very different outcomes at the population level. The quotient method correctly indicated that acephate posed a hazard only to the oriental fruit fly. However, sublethal effects were not considered in this model and the range of effects (7-week recovery) versus no delay in the Mediterranean fly could not be predicted by the quotient method. 

Fig. 17. Hydrodynamic and viscoplastic models for pore collapse, (a) Hydrodynamic collapse is much faster. Heat is generated when the upstream surface impacts the downstream surface. A pressure spike is generated by hydrodynamic focusing, (b) Viscoplastic collapse occurs more slowly, behind shock front. Heat is generated by viscoplastic work. Both collapse processes break up and attenuate the shock front, and generate time-delayed shocklets. Reproduced from ref. [120].

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