Support Excitation Research Articles

Water Photolysis by UV Irradiation of Rhodium Loaded Strontium Titanate Catalysts. Relation between Catalytic Activity and Nature of the Deposit from Combined Photolysis and ESCA Studies

AbstractPhotochemical water splitting (H2O → H2 + 1/2O2) has been shown to occur on UV irradiation of aqueous suspensions of strontium titanate, modified by surface photodeposition of rhodium species.7 Further improvement of the catalytic materials has now been achieved, using thermal deposition techniques. The most active material, prepared by heating rhodium chloride impregnated SrTiO3 powder at 500°C in air, allowed one to produce appreciable quantities of (H2 + 1/2O2) gas and to reach high turnover numbers on the catalytic material. The photolysis efficiency presents a strong pH dependence with an optimum around pH ∼ 14 and increases markedly when the wavelength of the light decreases from 400 to 300 nm. The amount of rhodium deposited also has a marked effect with an optimum at about 0.2–0.3% Rh by weight. ESCA studies have provided information about the nature of the catalytic deposit and about its relation to the activity of the materials. Catalytic efficiency and mechanistic aspects are discussed. The oxidation state of the rhodium species has a drastic influence: whereas SrTiO3 loaded with reduced rhodium shows no catalytic activity, the efficiency increases on progressive oxidation of the deposited metal to surface rhodium(III) species, as detected by ESCA. The photoactive step may involve both band‐gap excitation of the semi‐conductor support and direct UV excitation of the deposited Rh(III) species.

Comparison of multiple support excitation solution techniques for piping systems

Design and analysis of nuclear power plant piping systems exposed to a variety of dynamic loads often require multiple support excitation analysis by modal or direct time integration methods. Both methods have recently been implemented in the computer program KWUROHR for static and dynamic analysis of piping systems, following the previous implementation of the multiple support excitation response spectrum method (see papers K6/15 and K6/15a of the SMiRT-4 Conference). The results of multiple support excitation response spectrum analyses can be examined by carrying out the equivalent time history analyses which do not distort the time phase relationship between the excitations at different support points. A frequent point of discussion is multiple versus single support excitation. A single support excitation analysis is computationally straightforward and tends to be on the conservative side, as the numerical results show. A multiple support excitation analysis, however, does not incur much more additional computer cost than the expenditure for an initial static solution involving three times the number, L, of excitation levels, i.e. 3 L static load cases. The results are more realistic than those from a single support excitation analysis. A number of typical nuclear plant piping systems have been analyzed using single and multiple support excitation algorithms for: (1) the response spectrum method, (2) the modal time history method via the Wilson, Newmark and Goldberg integration operators and (3) the direct time history method via the Wilson integration operator. Characteristic results are presented to compare the computational quality of all three methods.

Dynamic response of the bridge girders of E.O.T. Cranes due to dissimilar rail joints

Though every care is taken at the time of laying rails for the E.O.T. Crane travel, the track is usually found to be imperfect. These imperfect rail joints produce greater dynamic deflections in the E.O.T. Crane bridge girders. Earlier investigations mainly deal with simultaneous similar type of joints. Joints of the dissimilar type occuring simultaneously produce dynamic deflections of high magnitudes and need to be avoided. Considering the bridge girder as a beam of constant flexural rigidity, the effects of dissimilar type of joints occuring simultaneously are studied by considering them as support excitation functions acting on either side of the bridge girder.

Identification of a one‐dimensional model for a soil‐layer–bedrock system during an earthquake

AbstractThe propriety of adopting a multi‐degree‐of‐freedom lumped mass–spring–dampers system driven by white noise support excitation as a one‐dimensional model for a soil‐layer–bedrock system during an earthquake is investigated by means of statistical system identification of the model with noisy measurement of the earthquake ground velocity. The present discussion also suggests that this model may not be applicable to all observed earthquake records, since the model itself depends on the statistical nature of the earthquake motion. For appropriate earthquake records, the system identification procedure may be accomplished; then dynamical properties of the soil‐layer and the power spectral density for white noise excitation acting upon the bedrock can be estimated as shown in a numerical example.

Seismic response analysis of structural system subjected to multiple support excitation

In the seismic analysis of a multiply supported structural system subjected to nonuniform excitations at each support point, the single response spectrum, the time history, and the multiple response spectrum are the three commonly employed methods. In the present paper the three methods are developed, evaluated, and the limitations and advantages of each method assessed. A numerical example has been carried out for a typical piping system. Considerably smaller responses have been predicted by the time history method than that by the single response spectrum method. This is mainly due to the fact that the phase and amplitude relations between the support excitations are faithfully retained in the time history method. The multiple response spectrum prediction has been observed to compare favorably with the time history method prediction. Based on the present evaluation, the multiple response spectrum method is the most efficient method for seismic response analysis of structural systems subjected to multiple support excitation.

Industry standard for B-Series CMOS : D. Blandford. Microelectron. Reliab.16, 449 (1977)

We propose in this paper the support excitation scheme for analyzing transient structural responses of electronic components subjected to JEDEC board-level drop test conditions. Equations of motion of the board-level test vehicle are derived based on coordinate transformations that translate the input acceleration pulse into the effective support excitation load on the test vehicle. In this way, modeling of the drop table along with calculations for the impact force on the drop table through contact methodologies can be omitted. Furthermore, either an explicit or an implicit solver works for the numerical model. Compared with the conventional numerical treatment for board-level drop tests, this novel methodology provides computationally economical solutions. With the support excitation scheme implemented, numerical studies are carried out to investigate efficiencies of implicit and explicit time integration schemes, solution accuracies with respect to the mesh density of the test board, and effects of drop orientations as well as structural damping on transient structural responses of a board-level chip-scale package subjected to the JEDEC drop test condition.

An analysis of diffusion process control : P. S. Gwozdz. Solid St. Technol. p. 71 (November 1977)

We propose in this paper the support excitation scheme for analyzing transient structural responses of electronic components subjected to JEDEC board-level drop test conditions. Equations of motion of the board-level test vehicle are derived based on coordinate transformations that translate the input acceleration pulse into the effective support excitation load on the test vehicle. In this way, modeling of the drop table along with calculations for the impact force on the drop table through contact methodologies can be omitted. Furthermore, either an explicit or an implicit solver works for the numerical model. Compared with the conventional numerical treatment for board-level drop tests, this novel methodology provides computationally economical solutions. With the support excitation scheme implemented, numerical studies are carried out to investigate efficiencies of implicit and explicit time integration schemes, solution accuracies with respect to the mesh density of the test board, and effects of drop orientations as well as structural damping on transient structural responses of a board-level chip-scale package subjected to the JEDEC drop test condition.

Modern physics brings semiconductor technology to a turning point : M. Lassus and J-P. Founaud. Microelectron. Reliab.16, 367 (1977)

We propose in this paper the support excitation scheme for analyzing transient structural responses of electronic components subjected to JEDEC board-level drop test conditions. Equations of motion of the board-level test vehicle are derived based on coordinate transformations that translate the input acceleration pulse into the effective support excitation load on the test vehicle. In this way, modeling of the drop table along with calculations for the impact force on the drop table through contact methodologies can be omitted. Furthermore, either an explicit or an implicit solver works for the numerical model. Compared with the conventional numerical treatment for board-level drop tests, this novel methodology provides computationally economical solutions. With the support excitation scheme implemented, numerical studies are carried out to investigate efficiencies of implicit and explicit time integration schemes, solution accuracies with respect to the mesh density of the test board, and effects of drop orientations as well as structural damping on transient structural responses of a board-level chip-scale package subjected to the JEDEC drop test condition.

Harmonic non-linear response of beck's column to a lateral excitation

The non-linear response of a column with a follower force (Beck's column) subjected to a distributed periodic lateral excitation, or to a support excitation, is determined. An analytical solution for the response amplitude in terms of the loading and system parameters is obtained by a perturbation analysis of the differential equations of motion. Non-linear inertia and non-linear curvature terms are taken into account in the formulation of the differential equations.

Experimental behavior of thin circular arches subjected to forced excitation

Experimental evidence is presented to verify the steady-state solution for a thin circular arch, pinned at the ends, and subjected to symmetrical and unsymmetrical support excitation. The steady-state solutions consist of a series of the free modes of vibration. It is shown how these solutions are developed when both supports of the arch are moving simultaneously and in phase with one another. The unsymmetrical case, where only one support is moving, is also considered.

On the zero shift problem of a vertical pendulum

The effect of the vibration transmitted through pendulum support on the accuracy of a pendulum used as a vertical reference is examined. Based upon the method of equivalent linearization of Kryloff and Bogoliuboff together with a perturbation scheme, the average angular displacement of a vertical pendulum is obtained in terms of the functional averages involving support excitations. It is shown that the method leads to general and simple formulas for estimating the zero shift and, in the case of random support excitations, second-moment properties. The analysis is valid for both heavily damped and weakly damped systems. The zero shifts due to several types of deterministic and random excitations are computed. Methods of minimizing the zero shift are considered for these cases.