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The joint velocity jump for redundant robots in the presence of locked-joint failures is discussed in this paper. First, the analytical formula of the optimal joint velocity with minimum jump is derived, and its specific expressions for both all joint failure and certain single joint failure are presented. Then, the jump difference between the minimum jump solution and the least-norm velocity solution is mathematically analyzed, and the influence factors on this difference are also discussed. Based on this formula, a new fault tolerant algorithm with the minimum jump is proposed. Finally, simulation examples are implemented with a planar 3R robot and a 4R spatial robot, and an experimental study is also done. Study results indicate that the new algorithm proposed in this paper is well suited for real time implementation, and can further reduce the joint velocity jump thereby improving the motion stability of redundant robots in fault tolerant operations. Also, the fewer the possible failed joints are, the more obvious the effect of this new algorithm becomes. [DOI: 10.1115/1.2943302]

Two types of uncertainty exist in engineering. Aleatory uncertainty comes from inherent variations while epistemic uncertainty derives from ignorance or incomplete information. The former is usually modeled by the probability theory and has been widely researched. The latter can be modeled by the probability theory or nonprobability theories and is much more difficult to deal with. In this work, the effects of both types of uncertainty are quantified with belief and plausibility measures (lower and upper probabilities) in the context of the evidence theory. Input parameters with aleatory uncertainty are modeled with probability distributions by the probability theory. Input parameters with epistemic uncertainty are modeled with basic probability assignments by the evidence theory. A computational method is developed to compute belief and plausibility measures for blackbox performance functions. The proposed method involves the nested probabilistic analysis and interval analysis. To handle black-box functions, we employ the first order reliability method for probabilistic analysis and nonlinear optimization for interval analysis. Two example problems are presented to demonstrate the proposed, method. [DOI: 10.1115/1.2943295]

This paper presents a mathematical framework to properly account for uncertainty in wind resource assessment and wind energy production estimation. A meteorological tower based wind measurement campaign is considered exclusively, in which measurecorrelate-predict is used to estimate the long-term wind resource. The evaluation of a wind resource and the subsequent estimation of the annual energy production (AEP) is a highly uncertain process. Uncertainty arises at all points in the process, from measuring the wind speed to the uncertainty in a power curve. A proper assessment of uncertainty is critical for judging the feasibility and risk of a potential wind energy development. The approach in this paper provides a framework for an accurate and objective accounting of uncertainty and, therefore, better decision making when assessing a potential wind energy site. It does not investigate the values of individual uncertainty sources. Three major aspects of site assessment uncertainty are presented here. First, a method is presented for combining uncertainty that arises in assessing the wind resource. Second, methods for handling uncertainty sources in wind turbine power output and energy losses are presented. Third, a new method for estimating the overall AEP uncertainty when using a Weibull distribution is presented. While it is commonly assumed that the uncertainty in the wind resource should be scaled by a factor between 2 and 3 to yield the uncertainty in the AEP, this work demonstrates that this assumption is an oversimplification and also presents a closed form solution for the sensitivity factors of the Weibull parameters. [DOI: 10.1115/1.2931499]

Layout of temporary construction facilities (objects) is an important activity during the planning process of construction projects. The construction area layout is a complex problem whose solution requires the use of analytical models. Existing popular models employ genetic algorithms that have proven to be useful tools in generating near optimal site layouts. This paper presents an alternative approach based on mathematical optimization that offers several important features and generates a global optimal solution. The construction area consists of an unavailable area that includes existing facilities (sites) and available area in which the objects can be located. The available area is divided into regions that are formulated using binary variables. The locations of the objects are determined by optimizing an objective function subject to a variety of physical and functional constraints. The objective function minimizes the total weighted distance between the objects and the sites as well as among the objects (if desired). The distance can be expressed as Euclidean or Manhattan distance. Constraints that ensure objects do not overlap are developed. The new approach, which considers a continuous space in locating the objects simultaneously, offers such capabilities as accommodating object adjacency constraints, facility proximity constraints, object--region constraints, flexible orientation of objects, visibility constraints, and nonrectangular objects, regions, and construction areas. Application of the model is illustrated using two examples involving single and multiple objects. The proposed model is efficient and easy to apply, and as such should be of interest to construction engineers and practitioners. DOI: 10.1061/(ASCE)0733-9364(2008)134:8(653) CE Database subject headings: Construction sites; Construction management; Optimization models.

Reliable estimates of reference evapotranspiration ([ET.sub.0]) are key elements for efficient water resource management, and estimating [ET.sub.0], based on 'Class 'A' pan evaporation' data is common in arid climates. A pan coefficient ([K.sub.p]), which depends on the distance (or fetch) of green vegetation or fallow soil around the pan (F), wind run (U), and relative humidity (RH), is used to convert from pan evaporation to [ET.sub.0]. Several researchers have developed models for estimating [K.sub.p] values for pans surrounded by green vegetated fetch, but there is only one equation to estimate [K.sub.p], values for dry fetch conditions. The equation is complex, so the objective of this research was to develop a new simple equation to estimate [K.sub.p] under fallow soil fetch conditions. The new [K.sub.p] equation and the more complex equation were compared with tabular values published by the United Nations Food and Agriculture Organization. The new equation performed slightly better at matching the tabular [K.sub.p] values than the complex equation. The equation derivation and evaluation are presented. DOI: 10.1061/(ASCE)0733-9437(2008)134:4(425) CE Database subject headings: Coefficients; Evaporation; Evapotranspiration; Water resources; Water management.

A series of detailed laboratory measurements were made under steady-state flow conditions through a 0.914-m (3-ft) Cutthroat flume in an attempt to more accurately define transition submergence for four standard throat widths. It was found that the change from free to submerged flow, and vice versa, is gradual and that there is no easily observable transition point. The gradual transition between the flow regimes suggested a new calibration approach in which a single equation could more elegantly and more accurately fit the laboratory measurements, eschewing the need for separate tree- and submerged-flow equations, and obviating the need to define transition submergence. Such an equation was found, providing greater calibration accuracy up to 95% submergence in 0.914-In Cutthroat flumes. DOI: 10.1061/(ASCE)0733-9437(2008)134:4(521) CE Database subject headings: Flumes; Calibration; Measurement; Submerged flow; Steady flow.

Although the Darcy-Weisbach equation combined with the Colebrook-White semitheoretical formula for calculating the friction coefficient is a highly accurate generalized pipe-water flow resistance equation, most users prefer the use of simple, explicit power law form formulas. Because of their simplicity (despite their limitations) the purely empirical power formulas of Hazen-Williams and Manning remain the most popular pipe flow resistance equations used in routine hydraulic engineering applications. In this paper, a new simple power law form formula is derived to approximate the generalized Darcy-Weisbach combined with the Colebrook-White equation. The two main pipe flow parameters, such as the discharge (or velocity) and the diameter, appeared explicitly in the proposed formula. The suggested power-form formula compared with the Darcy-Weisbach and Coolbrook-White equation yields a maximum relative error of about [+ or -] 4.5%. The power-form suggested formula is dimensionally homogeneous and its accuracy is sufficient for practical engineering applications. A correction factor is introduced for the variation of kinematic viscosity with temperature. The usefulness of the formula is demonstrated in an application concerning the optimal design of a delivery pipeline with pumping. The power form of the friction formula facilitates the formulation of the problem leading to the derivation of a simple equation from which the economic diameter is explicitly calculated. DOI: 10.1061/(ASCE)0733-9437(2008)134:4(454) CE Database subject headings: Friction: Turbulent flow; Hydraulic roughness; Pipe networks; Pipe flow.

This investigation deals with some exact solutions of the equations governing the steady plane motions of an incompressible third grade fluid by using complex variables and complex functions. Some of the solutions admit, as particular cases, all the solutions of Moro et al. [1990, 'Steady Flows of a Third Grade Fluid by Transformation Methods,' ZAMM, 70(3), pp. 189-198] [DOI: 10.1115/1.2928407] Keywords: vorticity function, third grade fluid, stream function

Analytical analysis of fluid flow in an annular microchannel subjected to uniform wall injection at various Reynolds numbers is presented. The classical Navier-Stokes equations are used in the present study. Mathematically, using an appropriate change of variable, Navier-Stokes equations are transformed to a set of nonlinear ordinary differential equations. The governing equations are analytically solved using series solution method. Some analytical results are given for the prediction of velocity profiles and pressure distributions in annular microchannels. The agreement between the computational fluid dynamics and the analytical predictions is very good. However, the analytical results are valid in a limited range of radius ratios and needs more study. Keywords: laminar and incompressible fluid flow, annular microchannel, Navier-Stokes equations, analytical method

A novel structured grid approach which provides an efficient way of treating a class of complex geometries is proposed. The incompressible Navier-Stokes equations are formulated in a two-dimensional, generalized curvilinear coordinate system complemented by a third quasi-curvilinear coordinate. By keeping all two-dimensional planes defined by constant third coordinate values parallel to one another, the proposed approach significantly reduces the memory requirement in fully three-dimensional geometries, and makes the computation more cost effective. The formulation can be easily adapted to an existing flow solver based on a two-dimensional generalized coordinate system coupled with a Cartesian third direction, with only a small increase in computational cost. The feasibility and efficiency of the present method have been assessed in a simulation of flow over a tapered cylinder. [DOI: 10.1115/1.2354533]

The classical Foster's reactance theorem is generalized to complex frequency functions. The result sheds light on the stability of complex polynomials, which is of interest in the system theory and applied mathematics. In Assertion 1, a novel method for the generation and the analysis of a Complex Reactance Function (CRF) is presented. Assertion 2 deals with the expansion and synthesis of CRF. Assertion 3 relates this note to a more basic problem of stability and applied mathematics. Assertion 4 gives an example of application by focusing on the two-dimensional homogeneous reactance functions.

Constant coefficient one-dimensional linear hyperbolic systems of partial differential equations (PDEs) are often used for description of fluid-structure interaction (FSI) phenomena during transient conditions in piping systems. In the past, these systems of equations have been numerically solved with method of characteristics (MOCs). The MOC method is actually the most efficient and accurate method for description of the single-phase transient in the cold liquid where the constant coefficient mathematical model describes phenomenon with sufficient accuracy. In energy production systems where hot pressurized liquid is used for heat transfer between the heat source and the steam generator, more complex and nonlinear mathematical models are needed to describe transient flow and these models cannot be solved with MOC method because the models are not constant. In addition, the MOC method can be used for pipes having discontinuities like elbows, geometrical changes, material properties changes, etc., but only with some extra numerical modeling. An interesting alternative is explicit characteristic upwind numerical method, known as Godunov's method that is frequently used for nonlinear systems or systems where properties change with position. In the present study, applicability of the Godunov's method for the FSI analyses is tested with eight first order PDEs mathematical model. The conventional linear mathematical model is improved with convective term that makes the system nonlinear and additional terms that enable simulations of the FSI in arbitrarily shaped piping systems located in a plane. Two PDEs describe pressure waves in the single-phase fluid and six PDEs describe axial, lateral, and rotational stress waves in the pipe. The applied system of equations has stiff source terms. This numerical problem is solved introducing implicit iterations. The proposed model is verified with a rod impact experiment that is carried out on single-elbow pipe hanging on wires. Godunov's method is found as a very promising numerical method for simulations of the FSI problems. [DOI: 10.1115/1.2937758] Keywords: fluid-structure interaction, single-phase flow, water hammer, nonlinear system, Godunov's method

In this paper, a 6R linkage suitable as a building block for the construction of large deployable structures is presented. First, we report the possibility of construct an extended 5R Myard linkage by combining two complimentary Bennett linkages. Unlike the original 5R Myard linkage (also called Myard's 'number 1' linkage), the angle of twists in the Bennett linkages is not necessary to be [pi]/2. Then we show that a 6R linkage can be produced by merging two extended Myard linkages together and removing the common links. The closure equations for the 6R linkage are derived and its motion characteristics are discussed. Moreover, we demonstrate that a number of such 6R linkages can be assembled together to form a large-scale deployable structure, which opens to a flat profile. [DOI: 10.111511.2885506] Keywords: Bennett linkage, Myard 5R linkage, 6R linkage, closure equation