Response spectra

Figure 14.13 Typical broad band floor response spectra showing the floor acceleration at different damping levels...

Figure 14.14 Displacement response spectra of the Koyna (India), Chamoli (India) and EL Centro (USA) earthquakes...

Seismie analysis is carried out for all important engineering structures such as dams, bridges and nuclear power plants. For regions where these are to be located the likely expectations of an earthquake as well as the extent of its magnitude must be assessed on the basis of the seismic history and the earthquake records of the region (Figures 14.12 to Figure 14.16). Based on these and other factors such as soil stratification, site dependent response spectra are determined. These are the RRS for equipment mounted... 

The following are the main parameters that must be considered to arrive at the most appropriate response spectra ... 

An RRS is normally constructed for several levels of critical dampings as illustrated in Figure 14.13. The most appropriate of these is then chosen for the purpose of testing. Any of the above response spectra can be developed into a time history of the earthquake, similar to that in Figure 14,12(b),... 

Hydro projects, dams, bridges, naval equipment and any installations that aie prone to continuous shocks and vibrations also require their primary and secondary systems to have a better design and operational ability to withstand seismic effects or other ground/surface vibrations. No specific tests are presently prescribed for such applications. But response spectra can be established even for such locations and the primary and secondary systems analysed mathematically or laboratory tested. 

Proof testing This is conducted when the seismic requirements in the form of floor response spectra (FRS) or required response spectra (RRS) have been pre-determined, and consequently test response spectra (TRS) have been established. This test will verify whether the test object can withstand an earthquake, of this magnitude and characteristics. 

Normally the user provides the nature of a probable earthquake in the form of RRS, i.e. acceleration characteristic curves, period versus spectral acceleration, such as those in Figure 14.18. The first objective is to generate a signal which should be able to produce a time history, on a shake table, whose response spectra match those of the RRS. 

The critical items may then be checked for the required response spectra (RRS) as discussed above. 

In Section 14.6 we have provided a brief account of such disturbances as well as the recommended tests and procedures to verify the suitability of critical enclosures and bus systems for locations that are earthquake-prone. For this the user is required to provide the manufacturer with the intensity of seismic effects at site of the installation in the form of response spectra (RS). (See Section 14.6.)... 

Fig. 2. Empirical and theoretical response spectra of a TEOS-TiN-Al stack using the reflectometry. The TiN and TEOS thicknesses are 250 and 10,000 A, respectively. The empirical and theoretical curves are matched within a tolerance.

Comparison of Oxide Thickness Measurement on TiN/Al Substrate with the TiN Thickness Fixed and as a Variable in the Response Spectra Simulation... 

Figure 4. Transient response spectra of the activation process over pretreated silver powder at 800 torr for step inputs of oxygen and ethylene.

Table I. Response spectra of gustatory receptor cells in Pieris brassicae larvae (7,8).

In addition to the sensilla styloconica, lepidopterous larvae possess gustatory sensilla on the maxillary palps. Eight basiconic sensilla are located on top of each palpus (see Figure 1). Five of them possess a terminal pore, and for that reason these sensilla might be considered as contact chemoreceptors. The remaining three show numerous small perforations all over the cuticle, which indicates an olfactory function (.8). The response spectra of these sensilla are, however, still obscure. 

Different insect species posses different gustatory receptor cells, their response spectra being adapted to the perception of chemical components distributed in their host plant species (9 ). Taste perception in P. brassicae larvae forms a representative example for phytophagous insects, which are able to discriminate a number of compounds like sugars, amino acids, salts, and secondary plant substances acting as feeding inhibitors or feeding incitants (3,6,, 10). 

The density of antennal sensilla in males rises sharply away from the basal segment for about 1 cm then declines over the next 4 cm to the tip of the antenna (Schaller, 1978 Hosl, 1990). The two receptor cells that are tuned to each of the two periplanones are housed within the same sensillum, the basiconic single-walled type , along with two other cells that respond to terpenes and alcohols (Boeckh and Ernst, 1987). However, unlike the highly specialized receptor cells of male moths, the periplanone-A and periplanone-B cells have overlapping response spectra to these two compounds. Also, it is not known how responsiveness of pheromone-sensitive sensilla to food odorants (terpenes and alcohols) affects behavior of the male cockroach. 

By combining the results of several methods (dynamic mechanical, dielectric, NMR, etc.), it is usually possible to determine quite reliably the structural units whose motions give rise to secondary relaxations. If dynamic mechanical measurements alone are employed, the usual procedure is that the chemical constitution is systematically altered and correlated with the dynamic mechanical response spectra, i.e. with the temperature-dependence of the G" and G moduli. If the presence of a certain group in polymers is marked by the formation of a loss peak characterized by a certain temperature position, size and shape etc., then the conclusion may be drawn that the motional units responsible for the secondary relaxation are identical or related with that group. Naturally, the relations obtained in this way are empirical and qualitative. 

Dynamic mechanical response spectra of elastin145 (insoluble protein of vessels and ligaments), poly(ethylene terephthalate)141 and polycarbonate based on Bisphenol A (4,4 -dihydroxydiphenylmethane)141 show that incorporated water brings about enlargement of the existing secondary loss peak and its displacement toward lower temperatures. In conformity with the latter result, the activation energy of the relaxation process of elastin decreases. So far, no detailed data on this type of relaxation have been collected so that the copartidpation of water in the molecular motion cannot be specified more accurately. 

Most conspicuous modifications of the dynamic mechanical response spectra of PHEMA and related polymers are brought about by incorporation of low-molecular weight compounds (Fig. 13). Along with alterations of parameters (temperature, height, shape) of the peaks characteristic of a dry polymer, usually a new diluent peak appears. (The relaxation patterns of various polymethacrylates are not modified by diluents in a unique way but several modes can be distinguished as mentioned before.) A remarkable feature... 

With the exception of local main-chain motions, the above-mentioned types of molecular motions have been investigated on a series of hydrophilic polymethacrylates and polyacrylates by means of dynamic mechanical measurements carried out with a torsional pendulum. For this purpose, the constitution of polymethacrylates was systematically altered and correlated with the dynamic mechanical response spectra. It was established for a series of copolymers of poly(2-hydroxyethyl methacrylate) that the temperature of the y relaxation (140 K 1 Hz), assigned to the motion of 2-hydroxyethyl... 

A tungsten electrode inserted at the sensillum base records action potentials fired by two neurons, which can be reliably separated based on amplitude and shape of spikes. Neuron A fires the large spike and responds to stimulation with ethyl acetate. Neuron B (small spikes labeled with dots) does not respond to this odorant. For odor stimulation, air was expelled from a 5 ml syringe laden with 20 pi of odorant, diluted 10-2 in paraffin oil. B The palp carries six classes of ORN with different response spectra. They are consistently housed together as stereotypical pairs in three functional types of sensilla. 

All the response spectra were taken in standardized solutions, with the electrode potential under potentiostatic control at +0.2V vs SCE. 

As approximate fits to spectra, oscillator models often miss essential details in the physics of the material response. Spectra of real samples reveal the consequences of composition, structure, doping, oxidation or reduction, multiplicity of phases, contaminant or introduced charges, etc., on electronic structure. These consequences from sample preparation can qualitatively affect intermolecular forces. To the extent possible, the best procedure is to use the best spectral data collected on the actual materials used in force measurement or materials designed for particular force properties. Given the present progress in spectroscopy, such coupling of spectra and forces may soon become routine. 

In Figure 1 the FR spectra were recorded at 523K excepted A-zeolite (423K). However frequency-responses were well detectable for various zeolite structure of different Si/Al ratios over a wide tenq)erature range of 373-723K The FR spectra showed differencies which were of the different types of zeolites. The appearance of a peak at -lOHz was a conunon feature of all samples. The response spectra of ammonia in various zeolite structures can be associated to adsorption/desorption processes on acidic sites because ... 

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