Practical Design Criteria Research Articles

The implementation of tribological principles in an expert-system (“PRECEPT”) for the selection of metallic materials, surface treatments and coatings in engineering design

Many of the component failures occurring in service can be avoided or delayed by better incorporation of tribological principles into engineering design. However, the concept of tribology has not yet penetrated successfully into industry in general and there remains an urgent need for the provision of practical tribology design criteria and the transference of tribology knowledge to engineering designers. Knowledge-based computer systems offer great potential for effecting tribology knowledge transfer and promoting improved design practice. Here we report the development and implementation of eight wear design rules in an expert system for assisting the selection of metallic materials, surface treatments and coatings during the initial stages of engineering design. These rules, which are intended principally for engineering designers involved with fine mechanical constructions operating at temperatures at or close to room temperature, allow the tribological reliability of a candidate design to be assessed on the basis of the most likely wear-related problems that can arise in service.

Random process simulation of strong ground motion

The state-of-art of random process simulation model research of strong ground motion are analysed and the shortcomings of previous models is pointed out in this paper. Based on these, a random process model of ground motion with color spectrum on bedrock is presented which can give expression to the recent results in engineering seismology and near-field seismology and simulate the practioal spectrum function of strong ground motion as well. Moreover, the presented model can solve the incompatible problem between the horizontal model and the rotational model, and it is easy to determine the model parameters and to set up a practical design criterion of random seismic motion by use of the basic parameters used in the present aseismic design.

Periodic Thermal Deformation of Large Seal Ring.

Oil film seals of large diameter sometimes show low-frequency whirling of the deformation mode of a floating seal ring whose rotation is constrained by a stopper pin. Cyclic change of deformation and oil film temperature may cause fatigue damage of the seal ring after long-term operation. We present a theory for the mechanisms of deformation and its whirling, the results of which agree well with those of measurements, and which provides a practical design criterion to prevent this phenomenon.

Proposed criteria to accommodate severe accidents in containment design

Criteria for LWR containment designs developed a generation ago are no longer adequate. Recent research has improved knowledge about severe accidents but this has not been synthesized into practical design criteria. The beginning of such a synthesis, a set of accident surrogates which could be used for design, is proposed.

Design considerations for tubular reactors with highly exothermic reactions

AbstractPractical guidelines are required for the design and operation of complicated catalytic packed‐bed reactors. Primary among design considerations is the avoidance of operating regions of high parametric sensitivity, in which small changes in operating conditions can lead to thermal runaway in the reactor. Existing criteria for predicting these regions rely on complex mathematical formulations for differential sensitivity between input and output variables. The present work centers on the development of practical design criteria for avoiding reactor instability and temperature sensitivity in multitubular packed‐bed reactors. A set of simple guidelines is proposed for the sizing of reactors and proper selection of operating conditions. The implications of these open‐loop sensitivities for a controlled reactor are investigated. It is shown through simulation studies that violation of the proposed criteria leads to control problems and difficulty in operating at the design point.

Equivalence between preamplified direct detection and heterodyne receivers

The interrelationship of heterodyne receivers and preamplified direct-detection receivers is explained. The authors compare the performances of the two lightwave receiver schemes, taking into account all of the essential functional blocks needed in a real receiver. This includes analysis of the laser phase noise, the limiting noise processes, the optical and electrical carrier wave filters, the nonlinear demodulation functions, and the baseband filters. Even with these realistic effects included, the two receivers have mathematically equivalent performance under certain conditions, which are rigorously identified. It is shown that this is a general result which is independent of the modulation format used. The established equivalence suggests that the analytical and practical design criteria used for one scheme can also be used for the other.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Practical design criteria for a dynamic ratio imaging system

Problems encountered and solutions devised during the construction of a productive Ca 2+-imaging system are discussed. Many of these relate to the rapid and interactive nature of experiments on cytosolic Ca 2+. The emphasis on accurate photometric quantitation of dynamically changing images contrasts with that of most image-processing software packages, which concentrate either on leisurely massage of static images or on descriptions of lateral motions of objects without concern for their brightnesses. Particularly important goals for Ca 2+-imaging include real-time ratioing, psychophysically effective display formats, ease of experiment annotation, mass storage of image sequences, automated extraction of time courses and population statistics, aids to presenting images for seminars and publications, and program modifiability.

Practical design criteria for photovoltaic systems

In 1975 the Commission of the European Communities (CEC) began a programme on 'Non-nuclear non-fossil' fuels and part of this involved research into PV. In 1979 a programme was started which involved building 15 large PV systems ranging in size from 30 to 300 kWp. The aim of this programme was to gain practical design and operational experience with systems at European latitudes and with European climates. The authors review the design and operation of one of these PV systems and highlight some of the practical design criteria associated with PV systems.

The design of sigma-delta modulation analog-to-digital converters

The author examines the practical design criteria for implementing oversampled analog/digital converters based on second-order sigma-delta ( Sigma Delta ) modulation. Behavioral models that include representation of various circuit impairments are established for each of the functional building blocks comprising a second-order Sigma 2gD modulator. Extensive simulations based on these models are then used to establish the major design criteria for each of the building blocks. As an example, these criteria are applied to the design of a modulator that has been integrated in a 3- mu m CMOS technology. An experimental prototype operates from a single 5-V supply, dissipates 12 mW, occupies an area of 0.77 mm/sup 2/, and has achieved a measured dynamic range of 89 dB.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Coplanar Waveguides for MMIC Applications: Effect of Upper Shielding, Conductor Backing, Finite-Extent Ground Planes, and Line-to-Line Coupling

Parasitic effects occurring in actual realizations of coplanar waveguides (CPW) for microwave integrated circuits on GaAs substrates, such as the influence of an upper shield, conductor backing, finite-extent ground planes, and line-to-line coupling, are discussed and evaluated. CAD-oriented analytical expressions are obtained for the electrical quasi-TEM parameters of the relevant waveguiding structures by means of exact or approximate conformal mapping techniques. Differences in electrical behavior with respect to ideal CPW's are highlighted, and practical design criteria are obtained for keeping cover height, ground-plane width, and line-to-line spacing effects to a minimum.

Infiltration Rates for Separate Sewage Collection Systems

Factors that influence infiltration rates for separate sewage collection systems are reviewed. Practical design and construction criteria that minimise infiltration and appropriate design infiltration rates adopted in 1960's are enunciated. Measured infiltration rates for typical catchments substantiate the design rates.

Some Considerations on the Design of Adaptive Digital Filters Equipped with the Sign Algorithm

In this paper we present some tools that can be helpful in design of adaptive digital filters operating with so-called sign algorithm. Although theoretical results with respect to convergence behavior of such filters are available, it may be hard to derive practical design criteria from them. We introduce a new type of design graph, which characterizes convergence pretty well and which we call the elephant's ear, due to its typical shape. We also consider some effects of non-Gaussian statistics of received signal and show how preceding analysis can be extended to include effects of dithering. Finally, we pay attention to digital word lengths required in a finite precision implementation. The subject of this paper is restricted to adaptive digital echo cancellers (EC), but results can be generalized to include other adaptive filters like decision feedback equalizers (DFE) or combinations of EC and DFE.

Safety Checking Formats for Limit States Design

The growing need for a unified approach to structural design for different construction materials and technologies is met by the limit states design approach. Several standards-writing committees currently are considering how best to implement practical limit states design criteria. This paper examines the relative advantages of several approaches proposed for this purpose, with regard to their ability to provide desired levels of reliability for all probable design situations. The choice of an appropriate approach is found to depend on fundamental characteristics of structural behavior, and thus might not be the same for different construction materials.

Research status and needs for shear tests on large-scale reinforced concrete containment elements

Reinforced concrete containments at nuclear power plants are designed to resist forces caused by internal pressure, gravity, and severe earthquakes. The size, shape, and possible stress states in containments produce unique problems for design and construction. A lack of experimental data on the capacity of reinforced concrete to transfer shear stresses while subjected to biaxial tension has led to cumbersome if not impractical design criteria. Research programs recently conducted at the Construction Technology Laboratories and at Cornell University indicate that design criteria for tangential, peripheral, and radial shear are conservative. This paper discusses results from recent research and presents tentative changes for shear design provisions of the current United States code for containment structures. Areas where information is still lacking to fully verify new design provisions are discussed. Needs for further experimental research on large-scale specimens to develop economical, practical, and reliable design criteria for resisting shear forces in containment are identified.

Threshold conditions for laser-initiated plasma shutters

The characteristics of laser-initiated plasma shutters used for retropulse isolation in high-power CO2 laser-fusion systems are discussed. Initiation of the plasma breakdown is shown to depend on the fluence that is incident on the edge of the iris which is employed in these shutters. A relatively simple model for the ignition process has been verified for a range of pulse durations (0.7–60 ns) and iris diameters (100–800 mm). This model provides practical design criteria for sizing plasma isolators for a variety of applications.

Practical views on the design and construction of mound breakwaters

The design section of this paper is an abstract of Report No. 7, 1979 by the Institute of Port and Ocean Engineering, The Norwegian Institute of Technology (IPOE). It is written in continuation of an article on “Common Reasons for Breakdown of Rubble Mound Breakwaters” published in this Journal. It discusses details of breakdown, block and blocklayer hydrodynamics, how to improve resistance to damage, the development of damages and how to describe damages in practical terms. Practical design criteria, laboratory procedures and data needed for design are mentioned and finally practical construction procedures and equipment to be used to build a mound with structural characteristics as close as possible to the one tested in the laboratory. The construction section summarizes a number of practical experiences on construction of rubble mound breakwaters with special reference to conditions in Norway, particularly its northern “top”.

Design graphs for the intrinsic alpha cut-off parameters ωα, ωTandmof bipolar transistors

Design graphs are developed for the intrinsic alpha cut-off frequencies ωα, and ωT, and for the excess phase m of bipolar transistors. The Kroemer equation giving the base transport factor in single-diffused transistors (constant aiding field in the base) is extended to cover double-diffused transistors (constant aiding and retarding fields in the base). The base retarding held is found to have an important degradation effect on the cut-off frequencies: a 2 kT/q retarding voltage extended along 20% of the base width diminishes ωα,to about half the value corresponding to a single-diffused transistor. A practical design criterion is given for optimizing the impurity-concentration profiles of double-diffused transistors.

LAKE SHORE PROTECTION AGAINST WIND‐GENERATED WAVES1

ABSTRACT: A method is reported for estimating the height of wind waves in any lake for a given wind condition. Maximum wind speeds from five climatological stations in and around Ilinois for the period of 1950–1972 were analyzed and the maximum wind speed for various durations and return periods were presented. Statistical analysis of wind wave data collected from Carlyle Lake indicated the Rayleigh distribution fitted the wave height distribution reasonably well and that the nondimensional energy spectra followed the (f/fm)‐5 rule in the equilibrium range of frequencies. From a consideration of various forces and physical properties of riprap particles and water, a relationship was developed to estimate the stable weight of riprap particles. A practical design criteria is proposed to stabilize lake shores against wind waves.

Design of a Viscoelastic Dynamic Absorber for Machine Tool Applications

The design equations are developed for a viscoelastic dynamic absorber in uniaxial compression. The dependence of mechanical properties of the absorber on frequency, temperature, and preload are developed through an extension of the thermorheologically simple theory of linear viscoelasticity. An approximation of the exact boundary value problem is made in order to develop practical design criteria for the size and shape of the absorber element. The results of the experimental program for the constitutive equation are included. A dynamic absorber is designed to control a self-excited lathe chatter problem and a significant improvement is demonstrated.

Risk-Based Evaluation of Design Criteria

The development of risk-based structural design criteria is described. The analysis of design uncertainties arising from the statistical nature of some variables and incomplete information regarding others is examined. The risk of unfavorable performance commensurate with the level of uncertainty is shown to provide a consistent measure of design safety and thus furnish a systematic means for comparing design alternatives. Current design provisions for reinforced concrete beams are appraised in terms of their underlying uncertainties and risks. It is shown that practical risk-based design criteria can be prescribed without unreasonable increase in design code complexity.