Non-standard Design Research Articles

Denil Fishways of Varying Geometry

This paper presents the results of an extensive laboratory study aimed at improving the design of Denil fishways. For the standard design of the simple Denil, an equation has been developed between the dimensionless discharge Q* and the relative depth of flow d/b for d/b as large as 5.5. The normalized velocity distributions in the centerplane of the Denil were found to have certain shapes depending upon the d/b ratio. For the nonstandard designs of the Denil fishway, based on the results of about 660 experiments, a method has been found to predict not only the relation between Q* and d/b but also the normalized velocity profiles in the centerplane of the Denil. The coefficient of friction between the central stream in the Denil and the circulating water on the sides as well as the bottom has been evaluated along with the equivalent Manning's n for the Denil fishway. These results are believed to be important in extending the depth range of the standard Denils as well as making changes to the standard Den...

Timing of Multi-Gigahertz Rapid Single Flux Quantum Digital Circuits

Rapid Single Flux Quantum (RSFQ) logic is a digital circuit technology based on superconductors that has emerged as a possible alternative to advanced semiconductor technologies for large scale ultra-high speed, very low power digital applications. Timing of RSFQ circuits at frequencies of tens to hundreds of gigahertz is a challenging and still unresolved problem. Despite the many fundamental differences between RSFQ and semi- conductor logic at the device and at the circuit level, timing of large scale digital circuits in both technologies is principally governed by the same rules and constraints. Therefore, RSFQ offers a new perspective on the timing of ultra-high speed digital circuits. This paper is intended as a comprehensive review of RSFQ timing, from the viewpoint of the principles, concepts, and language developed for semiconductor VLSI. It includes RSFQ clocking schemes, both synchronous and asynchronous, which have been adapted from semiconductor design methodologies as well as those developed specifically for RSFQ logic. The primary features of these synchronization schemes, including timing equations, are presented and compared. In many circuit topologies of current medium to large scale RSFQ circuits, single-phase synchronous clocking outperforms asynchronous schemes in speed, device/area overhead, and simplicity of the design procedure. Synchronous clocking of RSFQ circuits at multigigahertz frequencies requires the application of non-standard design techniques such as pipelined clocking and intentional non-zero clock skew. Even with these techniques, there exist difficulties which arise from the deleterious effects of process variations on circuit yield and performance. As a result, alternative synchronization techniques, including but not limited to asynchronous timing, should be considered for certain circuit topologies. A synchronous two-phase clocking scheme for RSFQ circuits of arbitrary complexity is introduced, which for critical circuit topologies offers advantages over previous synchronous and asynchronous schemes.

Simulation of Initially Slackened and Stiffened Structures by Virtual Distortions∗

ABSTRACT Variational principles and computational methods for analysis of initially slackened and stiffened structures are discussed. The simulation of clearances or internal dry fraction in structural elements by virtual (eigen) distortions is applied. Considerations presented are used in the problem of nonstandard design of structural settings, with clearances or friction in the structural joints, for load capacity maximization.

Overview of Coast Guard Plan Review for High-Tech Ship Design

The competitive nature of the marine industry has compelled ship and drill rig owners to expect vessel designs which operate more efficiently and are less expensive to build. Designers have abandoned the "old reliable" rule based designs of the 1960's and 1970's in favor of state-of-the-art, high-tech approaches to reduce design unknowns. Analysis techniques include six-degree-of-freedom motion simulation, finite-element structural analysis, fatigue and fracture mechanics techniques, structural and component reliabilities, and electronic on-board monitoring systems. At the Coast Guard Marine Safety Center, where construction plans are reviewed and approved, evaluating the safety of these designs is not an easy task! Unlike the rule-based designs, there are no "cookbook" formulas for double-checking the designer's calculations. An acceptable level of safety must be established and the design approach must be proven for its application to be accepted. Unfortunately, the level of safety that is built into "the rules" is not completely clear, so "acceptable" becomes difficult to establish. This paper discusses the requirements and capabilities of the Coast Guard commercial vessel plan review program and proposes an alternative plan submittal procedure for nonstandard designs.

An Evaluation of Spline Functions for use in Cam Design

This paper shows how spline functions can be employed for kinematic motion specification in cam design. The polynomial spline is introduced as a special case of a continuous piecewise function. Cubic and quintic splines are derived and their properties are discussed in the cam design context. It is shown how standard cam laws can be approximated extremely accurately with a small number of points and appropriate boundary conditions. The modified sinusoidal acceleration cam law is used as an example. The application of quintic splines to non-standard and special motions is discussed. The algebraic and B-spline representations of spline functions are compared. The former is considered preferable in this context and a list of useful algorithms is given. The real power of the spline function, in particular the algebraic quintic spline, is its simplicity, ease of computation and adaptability to non-standard design problems. The use of parametrized, deficient and exponential splines is proposed for specific applications.

Reconstruction algorithms for nonstandard CT scanner designs.

Data collected by a CT scanner provide estimates of line integrals of the X-ray attenuation distribution in a cross section of the human body. The lines along which integrals are collected are determined by the positions of the source-detector pairs during the data collection. Since only the lines are important (and not the positions of the source and the detector on the line), essentially the same data may be collected by scanners of very different design. In this article we illustrate that in certain situations the problem of reconstruction from data collected by a CT scanner of a new (and nonstandard) design can be "reduced" to the problem of reconstruction from data collected by a CT scanner for which the problem has already been solved. The "reduction" involves identifying values of free parameters in the old design (such as the radius of the circle in which the source rotates), which would make the geometry of data collection essentially identical to that of the proposed new design. Since reconstruction algorithms for the old design already exist, they can be applied without any change to the data collected by the new scanner. In other words, the problem of finding a reconstruction algorithm for a nonstandard mode of data collection can sometimes be solved by describing a (virtual) machine of standard design whose reconstruction algorithms are immediately applicable to the data collected by the nonstandard machine. The method is demonstrated on a recently proposed concept for transforming a radiotherapy simulator into a CT scanner.

Factor Screening in Computer Simulation

In many simulation models, only a few input variables have a significant effect on the output. By identi fying those variables in some reasonable way, we could undoubtedly make the model simpler, more effi cient, cheaper to run, and easier to analyze. Factor screening methods attempt to identify the more important variables. The most effective methods, however, require more computer runs than are normally reasonable or affordable. Thus screening must usually be based on nonstandard designs not customarily dis cussed in standard statistical references. In this paper, we review and discuss the major classes of factor screening designs. We pay partic ular attention to two strategies that are useful when there are more factors than available runs. The first of these is group-screening, in which fac tors are grouped and tested in a multistage proce dure ; the other is based on a combination of random balance and Plackett-Burman designs. Unfortunately, the performance of a screening strategy is difficult to measure; the modeler must consider both how much it costs and how accurately it classifies factors. An artificial example illustrates the tradeoffs that the modeler must make.

Design criteria for pole-changing windings

A set of rational criteria are identified for assessing the merits of pole-changing windings for cage induction motors, in terms of capacity and performance of the two speed settings. It is shown that a change-pole setting is simply a nonstandard design that differs from the standard design essentially in respect of flux density and winding factor. In terms of these two quantities, relative performance indexes are derived that are pure numerics, with unity for the standard machine. Optimum coil spans are obtained for the familiar 1:2 pole, changing winding. Other criteria are the quality of the winding in terms of balance and m.m.f.harmonics, and the size of the controller. The uses of the main criteria are illustrated by application to some existing designs. Earlier criteria are surveyed and shown to be either incomplete or incorrect. The new criteria form a logical basis on which meaningful comparison can be made, not only between pole. changing machines and standard machines, but also between different designs of two-speed machine for a given pole combination.

Non-Standard Designs

Non-Standard Designs