Transient Analysis Technique Research Articles

A new figure of merit and methodology for quantitatively determining defect resolution capabilities in deep level transient spectroscopy analysis

This article provides guidelines for accurately comparing the defect resolution capabilities of different deep level transient spectroscopy (DLTS) analysis techniques. Additionally, guidelines for choosing measurement parameters such as the proper weighting times and temperature range in order to achieve maximum energy resolution are presented. The modulation function method is compared to the correlation method of linear predictive modeling (CMLPM) transient analysis technique, and conventional DLTS spectrum methods. It is found that for extremely high signal to noise ratio transients (high trap concentration), the modulation function method is superior to all other methods. As the signal to noise ratio is reduced to a more practical range, CMLPM resolves closely spaced defect levels better than any other method examined. For very low signal to noise ratios, the effects of noise can only be overcome by the inherent averaging present in the more conventional DLTS spectrum analyses. To demonstrate the applicability of this figure of merit, a discussion of the resolution problems involved in distinguishing between simultaneously present Ti and Mo impurities in Si is also presented. Finally, CMLPM is also found to be superior to the inverse laplace transform technique.

Dynamics and probabilistic fatigue analysis schemes for high-speed press machines

The dynamic behavior of a connecting rod (CR) is relatively more complicated than other major moving parts in a high-speed press machine. For various analysis and design reasons, the lumping mass method is traditionally used in an attempt to represent the original CR dynamically equivalently, but this representation of CR is usually inaccurate. This inaccuracy may eventually lead to undesirable dynamic unbalancing and associated vibration problems. In that concern, an ingenious varied-mass lumping method (VLM) fused with percussion concept is developed here to integrate the dynamics analysis and design of press machines in a highly mutually beneficial sense. The ramhead reactive force due to workpieces will eventually transmit to the press frame through CR, crankshaft and its center bearing. This wavy, yet periodic forcing function can be conveniently obtained by the above VLM scheme. Then, the fatigue survivability at particular points can be calculated with the aid of finite element method, transient analysis techniques, peak range pairing, S-N fatigue curves and/or family of S-N-P curves for material used.

A class of hierarchical queueing networks and their analysis

Queueing networks are an adequate model type for the analysis of complex system behavior. Most of the more realistic models are rather complex and do not fall into the easy solvable class of product form networks. Those models have to be analyzed by numerical solution of the underlying Markov chain and/or approximation techniques including simulation. In this paper a class of hierarchically structured queueing networks is considered and it is shown that the hierarchical model structure is directly reflected in the state space and the generator matrix of the underlying Markov chain. Iterative solution techniques for stationary and transient analysis can be modified to make use of the model structure and allow an efficient numerical analysis of large, up to now not solvable queueing networks.

Carbon pathways for the partial oxidation of methane

The partial oxidation of methane to formaldehyde was studied at 1-atm pressure using a 2% V[sub 2]O[sub 5]/SiO[sub 2] catalyst with molecular oxygen as an oxidant. As methane conversion increased, formaldehyde selectivity decreased rapidly while CO[sub x] selectivity increased, indicating that formaldehyde was a primary product of the reaction, while CO[sub x] formation occurred apparently in large part by secondary reaction. Using steady-state isotopic transient kinetic analysis technique, carbon transients were obtained by switching from [sup 12]CH[sub 4] to [sup 13]CH[sub 4] at steady state, permitting the determination of surface residence times and surface concentrations of various carbon-containing intermediates. It was possible to observe detectable reversible chemisorption of methane on the catalyst studied and other reference oxides only at conditions where significant reaction took place. For the partial oxidation of methane over the 2% V[sub 2]O[sub 5]/SiO[sub 2] catalyst, it was found that HCHO and CO did not exhibit significant reversible readsorption under the reaction conditions used. It is suggested that the formation of CO involves a sequential pathway wherein an irreversible readsorption of HCHO is involved. A carbon pathway consistent with the observations is proposed. It is speculated that different types of sites involved in the formation of HCHO,more » CO and C[sub 2]H[sub 6] may correspond to vanadium oxide species in different redox states. 30 refs., 6 figs., 5 tabs.« less

Application of mass balance of kick fluid in well control

A material balance equation of kick fluid in the annulus is derived. This equation can be used to determine the pressure head of the kick, whether or not the kick is intermittent or a continuous slug, the volume (or length) of the kick, the rate of rise of the kick fluid, the maximum casing pressure that will be encountered during the well control operation and the annular pressure as the kick reaches critical points of interest such as the casing seat. When integrated with transient surface shut-in drill stem test analysis techniques, pertinent formation characteristics can be evaluated. These can be useful for optimizing the planning, design and drilling of subsequent wells within the particular field. The model requires a minimum of assumptions and it is dynamic as it is based on the well control process. With speedy and accurate acquisition of the kick data, well control can become more efficient. The major limitations of the model include possible leakages in the flow system and high gas solubility in the drilling fluid. The procedure for the application is discussed and examples of a gas kick and a saltwater kick illustrate the applicability of the model.

A nystagmus strategy to linearize the vestibulo-ocular reflex

This paper addresses two important aspects of the vestibulo-ocular reflex (VOR). First, the linear range of ocular responses is much more extensive than expected from the characteristics of central pathways (CNS), and this is shown to result directly from early convergence of 'fast' and 'slow' premotor signals in the central processes, associated with significant and intermittent changes in functional connectivity (effective structural modulation). Second, the presence of such structural modulation implies that responses must be analyzed using transient analysis techniques, rather than previous steady state approaches, in order to properly evaluate reflex dynamics. Simulation results with a recent model of the VOR are used to illustrate the arguments. Relying on known inter-connections between saccadic burst circuits in the brainstem, and the ocular premotor areas of the vestibular nuclei, a viable strategy for the timing of nystagmus events is proposed. The strategy easily reproduces the characteristic changes in vestibular nystagmus with the amplitude of head velocities, and with the frequency of passive head oscillation.

Assessment of Transient Analysis Techniques for Rotor Stability Testing

Assessment of Transient Analysis Techniques for Rotor Stability Testing

A Direct Integration Technique for the Transient Analysis of Rotating Shafts

The continuous space discrete time Riccati transfer matrix method is a new direct integration technique for transient analysis of structural members. This method is applied to rotating shafts with bearing systems containing masses. Numerical results are given for a rotor with isotropic bearings.

Recovered Transient Load Analysis for Payload Structural Systems

A recovered transient analysis technique is proposed wherein the results of a previous launch vehicle/payload system can be used to obtain the information on a new payload structure to be launched by an identical launch vehicle. The advantage of the proposed method is that the complete analysis can be performed within the payload organization with the same accuracy as that of a full scale, multiorganizational loads analysis. Also, the flight measured interface accelerations can be used as the forcing functions for more realistic representations of the dynamic environments.

Finite element procedures for fluid-structure interactions and application to liquid storage tanks

Most of the failures of large tanks after severe earthquakes are suspected to have resulted from the dynamic buckling caused by overturning moments of seismically induced liquid inertia and surface slosh waves. In this paper, a nonlinear finite element method is presented which can treated the structural behavior of the tanks in conjunction with fluid, including the dynamics and buckling. Both the formulation and computer implementation aspects are presented. The areas upon which attention is focused are: the mixed Lagrangian-Eulerian kinematical description for modeling fluid subdomains in fluid-structure interaction problems, the finite rotation effects in numerical integration of rate constitutive equations arising in large-deformation analysis and the implicit-explicit finite element techniques for transient analysis. All these nonlinear methodologies have been integrated into a finite element computer code [47]. A number of physically important buckling and dynamic analyses of tanks are being investigated. Various other fluid structure phenomena such as the stability of off-shore structures can be analyzed with this computer program. The proposed nonlinear finite-element procedures can serve as a basis for future developments of various other fluid-structure phenomena such as the transient motion of submerged or partially submerged structures.

A Direct Integration Technique for the Transient Analysis of Rotating Shafts

The Continuous Space Discrete Time Riccati Transfer Matrix Method is a new direct integration technique for transient analysis of structural members. This method is applied to rotating shafts with bearing systems containing masses. Numerical results are given for a rotor with isotropic bearings.

Scattering of acoustic waves from randomly rough surfaces

Measurements have been made of sound scattered in the specular direction by fixed rough surfaces. The surfaces used were physical realizations of computer generated topographies which corresponded to Gaussian distributions in height to within specified limits. The RMS heights and correlation lengths of the two selected surfaces are 0.124 and 0.74 cm for the coarser surface and 0.021 and 0.305 cm for the finer surface. Each surface was milled into both brass and aluminum blocks. Measurements were made in water using 0.5‐, 1.0‐ and 2.25‐MHz transducers. Transient pulse analysis techniques were used to provide information about the scattered pulse over a wide range of frequencies. The dependence of the scattered return on incident angle, the sound speed in and density of the scattering material, the RMS height and the number of correlation lengths insonified is investigated. Comparisons are made with several theoretical models including a multiple scattering model. The scattered field is also illustrated by means of schlieren visualization.

Numerical study of dynamic crack growth by the finite element method

Recent developments in numerical techniques for dynamic transient stress analysis have ensured that realistic models can now be employed in crack propagation studies. In this paper transient dynamic finite element solutions are undertaken for both double cantilever beam (DCB) and pipeline problems with propagation of the crack being permitted. Standard parabolic isoparametric elements are employed for spatial discretization with an explicit (central difference) scheme being employed for time integration. Both critical stress and energy balance crack propagation criteria are considered.

Spectral analysis of Doppler ultrasonic decompression data

Several aspects of spectral analysis of bubble transients in Doppler ultrasonic decompression data are discussed. The computation of energy density spectra, using fast Fourier transform techniques for analyzing bubble transients, is described. Spectral analysis of data from probes implanted within animals, using a conventional Fourier analyzer, provided good visual indications of bubble events and interesting changes in spectral structure. A new transient spectral analysis technique that is suitable for quantitative real-time monitoring of small decompression bubbles is described. In a feasibility study using data from an implanted probe, an increase of 900% in bubble signal/noise ratio was observed.

A Study of the Anodization of Niobium Using the Method of Open‐Circuit Transients in Aqueous and Nonaqueous Solutions

The anodic oxidation of niobium in glacial acetic acid‐sodium tetraborate solution and in aqueous boric acid‐sodium tetraborate solution has been studied over a potential range of 74V using the open‐circuit transient analysis technique. The results indicate that the relationship between the formation current density, , and the formation potential, , is of the form where and are parameters resulting from data analysis. was found to be a linear function of the formation voltage. The quantity, θ, was found to be essentially equal to zero, a result which agrees with results previously reported for vanadium and molybdenum. Attempts were made to correlate the results with film structure.

Recovery Improvement Study of the Gray Sand Reservoir

A study was performed to determine the optimum economic number and location of new wells necessary to maximize wet gas production subject to a 17-year estimated remaining gas plant life. The study uses an unsteady-state, single-phase, two-dimensional gas model, coupled with transient test analysis techniques, to provide a basis for the recovery improvement projections. projections. Introduction This study was performed to determine the optimum economic number and location of new wells necessary to maximize wet gas production subject to a 17-year estimated remaining gas plant life. The produced gas contains approximately 60 bbl of liquid per MMscf; this liquid currently provides incremental income over and above that derived from the dry gas contract. Since field separation is considerably less efficient (9 bbl/MMscf) than that which the plant provides, it is desirable to improve or at least sustain provides, it is desirable to improve or at least sustain production while the plant is still available. production while the plant is still available. The saturation pressure for the gas in this reservoir is 1,900 psia. Over the range of pressures encountered in this study, liquid condensation is considered to be a wellbore phenomenon. Due to this fact, the reservoir study utilizes an unsteady-state, single-phase, two-dimensional gas model. Coupled with the modeling approach, transient test analysis techniques are used to provide a basis for the recovery improvement projections. The development of the pressure history projections. The development of the pressure history match, production well controls, and prediction rules are discussed. Utilizing economic indicators, the comparison of various alternative development cases is considered. The resulting direction taken following the study is described and conclusions as to its effectiveness are drawn. The model is similar to those described by Burns et al. and Henderson et al. This model is a single-phase, unsteady-state, two-dimensional gas model for multiwell systems. The pressure variable has been converted to real gas potential to linearize partially the equation of flow. After the model was pressure history matched using reservoir production data, a trial and error approach was used to provide new well locations. Analysis of buildup tests became an integral part of the history match and the production-prediction phase of the reservoir modeling production-prediction phase of the reservoir modeling study. After several prediction runs were made with various new well locations, economic calculations were made to determine which case was best. Although this is not an optimization in the truest sense of the word, the method did provide a "best case" situation. Field History The Gray sand reservoir is located in the Cotton Valley field, Webster Parish, La. It is operated by the Cotton Valley Operating Committee (CVOC). Major owners of this field are Hunt Oil Co., Ceja Corp., Bodcaw Co., Mobil Oil Corp., and Marathon Oil Co. The Gray sand, which is a member of the Lou-Ark group of upper Jurassic age, is encountered at depths ranging from 10,379 to 10,816 ft subsea. The Gray sand was discovered in 1944 with the drilling of the CVOC Gray No. 1. Eleven wells have been drilled through the Gray sand, resulting in eight producers and three dry holes. There are presently producers and three dry holes. There are presently seven wells producing from the Gray sand. To date, the cumulative production has been 87.6 Bscf. P. 28

Pulse Tests and Other Early Transient Pressure Analyses for In-Situ Estimation of Vertical Permeability

Abstract Formation vertical permeability is often the dominant influence in water or gas coning into a well, in gravity drainage of high-relief reservoirs, and in interlayer crossflow in secondary recovery projects. The advantages of either conducting a projects. The advantages of either conducting a pulse test or analyzing the early transient pressure pulse test or analyzing the early transient pressure response of a constant-rate test compared with previous techniques are simplicity of interpretation, previous techniques are simplicity of interpretation, short duration of test, and minimum interference from conditions some distance from the test well. The pulse test has a further advantage over the constant-rate test in that the rate does not have to be kept constant during the short flow period. Presented are the development of the theory and the curves of the dimensionless response time used in interpreting field data obtained by these techniques. The vertical permeability is determined with the pulse test from the time to the maximum pressure response and with the constant-rate test pressure response and with the constant-rate test from the extrapolated time to zero pressure response from the inflection point. Applications of the techniques to layered systems and to an oil zone with underlying water are demonstrated with results of numerical simulations. The vertical-permeability pulse test has been used to estimate the vertical permeability of a low-permeability zone in the Fahud field, Oman. Introduction The formation vertical permeability is often a dominant influence in reservoir recovery processes with vertical fluid flow such as water or gas coning, gravity drainage of high-relief reservoirs, the rising steam process, and displacement by water or gas in a heterogeneous formation. How reliably numerical reservoir simulators can predict the recovery performance of these processes depends upon how performance of these processes depends upon how accurately the significant reservoir parameters are estimated. Furthermore, in simulating a reservoir in two dimensions, the validity of the assumption of vertical equilibrium is based on the value of the vertical permeability. With the previously mentioned recovery processes, the reservoir cannot be modeled as a homogeneous reservoir with a single fluid. A well that has fluid coning or that is producing by gravity drainage will often have a fluid contact intersecting the well and thus dividing the reservoir into zones of differing mobility and compressibility. Reservoir stratification on a microscopic scale will result in a vertical permeability that is less than the horizontal permeability that is less than the horizontal permeability; but stratification on a macroscopic permeability; but stratification on a macroscopic scale will divide the reservoir into zones of differing permeabilities. Thus the design and interpretation permeabilities. Thus the design and interpretation of a vertical-permeability test for most practical reservoir situations will require that the reservoir zonation be represented. Transient pressure techniques for estimating in-situ vertical permeability have been introduced by Burns and by Prats. Both techniques require injection or production at a constant rate from a short perforated interval and measurement of the pressure response at another perforated interval pressure response at another perforated interval that is isolated from the first by a packer. The interpretation technique of Burns required a computer-generated type curve or a single-phase numerical reservoir simulator. This type-curve approach is applicable for an anisotropic, homogeneous, infinite reservoir model, and the numerical simulator with a regression analysis program is needed for finite or layered reservoir models. The technique presented by Prats did not require a computer program because the result of the analysis was presented on a single graph. The horizontal and vertical permeabilities could be estimated from the slope and the intercept of the pressure response and, the appropriate value from the graph. The method of Prats was based on an infinite, anisotropic, Prats was based on an infinite, anisotropic, homogeneous reservoir model.The pulse test and early transient analysis techniques presented here were developed to provide a simple means of interpretation for layered provide a simple means of interpretation for layered systems.

A Study of the Anodic Oxidation of Vanadium

The anodic oxidation of vanadium in acetic acid‐sodium tetraborate solutions containing small amounts of water has been studied over a potential range of 100V using the open‐circuit transient analysis technique. An anodic layer which showed bright uniform interference colors was found to grow on the metal surface. Results of these experiments indicate that the dependence of the oxidation current density, , on the formation potential, , is expressible in the form exp , where and are parameters determined from the data analysis. The parameter is found to depend on the applied current density, while the parameter varies directly with the formation potential during galvanostatic oxidation. A result in this form implies that the electric field in the oxide is a function of the applied current density. These results show similarities to results previously obtained by others for the anodic oxidation of bismuth, tantalum, and iron.

The Stimulation Treatment Pressure Record An Overlooked Formation Evaluation Tool

Pressure transient analyses of stimulation treatment pressure records Pressure transient analyses of stimulation treatment pressure records give formation permeability and show the condition of the formation around the wellbore both before and after treatment. Introduction Much has been written in recent years about transient testing theory and its application in understanding well behavior. The literature illustrates various special transient analysis techniques and their interpretations; however, in the past, one important source of transient data has been overlooked. This source is the stimulation treatment pressure record. On every well that is stimulated by a service company, a treatment report giving pertinent well data, materials and volumes, and pumping times is prepared, and a copy is presented to the oil company representative. In nearly every case, the treating pressures are recorded by either a strip chart or a circular clock recorder. Either the original pressure chart or a copy is given to the customer if he requests it. During the treatment, fluids are injected into the well, causing a pressure response that is recorded at the wellhead. At times the injection may be stopped for mixing of fluids. These injection pressure buildups and fall-offs during the treatment can be calculated and interpreted to determine the condition of the wellbore and the formation transmissibility. The engineer can check the validity of the result by calculating expected production before and after the treatment and comparing with the actual well production. Statement of Theory and Definitions In the analysis of drawdown pressures at a constant well production rate in an infinite reservoir, the point source solution is used. This equation is also valid for describing the behavior of a well in a bounded reservoir prior to the occurrence of any boundary effects. Except for the sign of the production rate, q, the same transient equation applies to well pressure buildup at a constant injection rate. Although this is well known mathematically, it has not been used in actual testing in our experience because of the supposed problem of holding a constant injection rate and because of possible filtering at the formation face in the wellbore. possible filtering at the formation face in the wellbore. In actual practice, though, as we will see later, these problems are not a real handicap in most wells particularly problems are not a real handicap in most wells particularly during early injection times. All the same equations developed for constant rate drawdown can be applied to constant injection rate buildup. An advantage of using a constant injection rate buildup test is that the liquid injected is not as compressible as most produced fluids; therefore, the wellbore unloading factor found in producing wells is not significant in an injection test. producing wells is not significant in an injection test. The following approximate equations (Eqs. 2 and 3) are well known and apply when tdw = (0.000264kt/ccrw2) greater than 100. JPT P. 951

A Discussion on the Transient Analysis of Coaxial Cables Considering High-Frequency Losses

The physical processes of HF loss are discussed. Two cases in transient analysis for coaxial cables are presented; the first considers skin effect in plated conductors while the second is an analysis based upon an attenuation approximation of the form (frequency) ^m , 0 . A graphical transient analysis technique is described which allows one to easily analyze cables whose losses are due to a combination of physical processes. Generalized curves based upon the (frequency) ^m approximation are presented by which the transient response of a cable can be rapidly evaluated for purposes of engineering design.