bluuebunny/crossref_metadata_2025 huggingface dataset:
Incorporating Physiological and Biochemical Mechanisms into Pharmacokinetic–Pharmacodynamic Models: A Conceptual Framework*
Authors: Dahl Svein G. , Aarons Leon , Gundert‐Remy Ursula , Karlsson Mats O. , Schneider Yves‐Jacques , Steimer Jean‐Louis , Trocóniz Iñaki F.
Published: July 2009

Abstract: The aim of this conceptual framework paper is to contribute to the further development of the modelling of effects of drugs or toxic agents by an approach which is based on the underlying physiology and pathology of the biological processes. In general, modelling of data has the purpose (1) to describe experimental data, (2a) to reduce the amount of data resulting from an experiment, e.g. a clinical trial and (2b) to obtain the most relevant parameters, (3) to test hypotheses and (4) to make predictions within the boundaries of experimental conditions, e.g. range of doses tested (interpolation) and out of the boundaries of the experimental conditions, e.g. to extrapolate from animal data to the situation in man. Describing the drug/xenobiotic‐target interaction and the chain of biological events following the interaction is the first step to build a biologically based model. This is an approach to represent the underlying biological mechanisms in qualitative and also quantitative terms, thus being inherently connected in many aspects to systems biology. As the systems biology models may contain variables in the order of hundreds connected with differential equations, it is obvious that it is in most cases not possible to assign values to the variables resulting from experimental data. Reduction techniques may be used to create a manageable model which, however, captures the biologically meaningful events in qualitative and quantitative terms. Until now, some success has been obtained by applying empirical pharmacokinetic/pharmacodynamic models which describe direct and indirect relationships between the xenobiotic molecule and the effect, including tolerance. Some of the models may have physiological components built in the structure of the model and use parameter estimates from published data. In recent years, some progress toward semi‐mechanistic models has been made, examples being chemotherapy‐induced myelosuppression and glucose‐endogenous insulin‐antidiabetic drug interactions. We see a way forward by employing approaches to bridge the gap between systems biology and physiologically based kinetic and dynamic models. To be useful for decision making, the ‘bridging’ model should have a well founded mechanistic basis, but being reduced to the extent that its parameters can be deduced from experimental data, however capturing the biological/clinical essential details so that meaningful predictions and extrapolations can be made.
Coupled Aquifer‐Borehole Simulation
Authors: Clemo Tom
Published: July 2009

A model coupling fluid hydraulics in a borehole with fluid flow in an aquifer is developed in this paper. Conservation of momentum is used to create a one‐dimensional steady‐state model of vertical flow in an open borehole combined with radially symmetric flow in an aquifer and with inflow to the well through the wellbore screen. Both laminar and turbulent wellbore conditions are treated. The influence of inflow through the wellbore screen on vertical flow in the wellbore is included, using a relation developed bySiwoń (1987). The influence of inflow reduces the predicted vertical variation in head up to 15% compared to a calculation of head losses due to fluid acceleration and the conventional Colebrook‐White formulation of friction losses in a circular pipe. The wellbore flow model is embedded into the MODFLOW‐2000 ground water flow code. The nonlinear conservation of momentum equations are iteratively linearized to calculate the conductance terms for vertical flow in the wellbore. The resulting simulations agree favorably with previously published results when the model is adjusted to meet the assumptions of the previous coupled models.
An Analytical Method to Determine Ground Water Supply Well Network Designs
Authors: MacMillan Gordon James
Published: July 2009

An analytical method is provided where the ground water practitioner can quickly determine the size (number of wells) and spacing of a well network capable of meeting a known ground water demand. In order to apply the method, two new parameters are derived that relate theoretical drawdown to the maximum drawdown that is achievable without mining the aquifer. The size of a well network is shown to be proportional to the ground water demand and inversely proportional to the transmissivity and available head. The spacing between wells in a supply well network is shown to be most sensitive to a derived parameter rHA/3, which is related to the available head and the propagation of drawdown away from a theoretical well if the total ground water demand was applied to that well. The method can be used to quickly determine the required spacing between wells in well networks of various sizes that are completed in confined aquifers with no leakance.
Development of Chinese Agriculture since WTO Accession
Authors: Carter Colin A. , Zhong Funing , Zhu Jing
Published: July 2009

Development of Chinese Agriculture since WTO Accession

This article discusses the main agricultural impacts of China’s WTO accession and the associated challenges. We elaborate on four issues – agricultural production and trade, food security and self‐sufficiency, farmers’ incomes, and rural land reform. After more than seven years of WTO accession, the value of China’s agricultural production and trade has increased and China has turned into a net importer of agricultural products. Globally, China now ranks as the fifth largest agricultural exporter and fourth largest agricultural importer. Although considerable resource shifts have taken place from land‐intensive towards labour‐intensive agricultural products in both production and trade, this transfer remains well below the potential due to trade barriers facing China’s exports of labour‐intensive agricultural products. Farmers’ incomes increased after WTO entry, with a growing off‐farm portion linked closely with world economic cycles. Rural land reform to improve economies of scale will require complementary policy aimed at a fully integrated labour and housing market, as well as a unified education and social welfare system for all of China’s society. We argue that WTO accession has impacted China’s agriculture in a positive fashion and has improved the efficiency of the sector, but accession has also given rise to new agricultural policy challenges.
Early Childhood Nutrition Increases Adult Wages Adäquate Ernährung in der frühen Kindheit führt zu höheren Einkommen im Erwachsenenalter La participation à des programmes de nutrition des très jeunes enfants accroît les salaires à l’âge adulte
Authors: Hoddinott John
Published: July 2009

Early Childhood Nutrition Increases Adult Wages

A study in Guatemala presents the first direct evidence of the effects of early childhood nutrition programs on adult economic productivity and incomes. The research shows that feeding young children a caloric, micronutrient‐enriched nutritional supplement leads to significant increases in wage rates for men as adults. Boys who received the supplement in the first two years of life earned on average 46 per cent higher wages as adults. Boys who received the supplement in their first three years earned 37 per cent higher wages on average. Those who first received the supplement after age three did not gain any economic benefits as adults. The study demonstrates that early childhood nutrition is not only crucial for the physical growth of children, but is also a long‐term driver of economic growth and a wise economic investment. The study also provides compelling evidence that the first two years of life are the window of opportunity when nutrition programs have an enormous impact on a child’s development, with life‐long benefits. The study was conducted by the International Food Policy Research Institute in collaboration with researchers from Emory University, the Institute of Nutrition in Central America and Panama, the University of Pennsylvania, and Middlebury College.
Politics of Anti‐Terrorism Policy in Southeast Asia: A Comparative Study of the Philippines and Indonesia
Authors: Lee Dong‐Yoon
Published: July 2009

The purpose of this study is to explore the current status of terrorism and the process of promoting anti‐terrorism policies in Southeast Asia, and to search for fundamental differences manifested in diverse policies of the countries in the region. Amidst the growing fear of terrorism in the international community, this research particularly focuses on the comparison of the terrorism situations and anti‐terrorism policies in the Philippines and Indonesia. The 9/11 terrorist attack in 2001 was a moment that triggered a worldwide international anti‐terrorism cooperation in response to the increasing terrorist threat. In Southeast Asia, however, policies and measures to prevent terror, initiated by the ASEAN, were relatively weak. In particular, the Philippines and Indonesia – which both held presidential elections in 2004 – sought different policy lines due to the different domestic situations and dynamics of political relations, in spite of an equal amount of pressure from the international community. In the Philippines, the Muslim minority‐group‐led separatist movement and armed combats were regarded as threatening elements that caused nation‐wide political unrest. Moreover, strong support on anti‐terrorism in cooperation with the USA operated as a tool that consolidated the political status of the Arroyo administration. Meanwhile, an Islam‐oriented Indonesia interpreted international pressure for strong anti‐terrorism policies as suppression of Islam, and Indonesia faced strong resistance from domestic opposition parties and Islamic political groups, which in turn resulted in a relatively ambiguous anti‐terrorism policy.
The transition from fetal growth restriction to accelerated postnatal growth: a potential role for insulin signalling in skeletal muscle
Authors: Muhlhausler B. S. , Duffield J. A. , Ozanne S. E. , Pilgrim C. , Turner N. , Morrison J. L. , McMillen I. C.
Published: July 2009

A world‐wide series of epidemiological and experimental studies have demonstrated that there is an association between being small at birth, accelerated growth in early postnatal life and the emergence of insulin resistance in adult life. The aim of this study was to investigate why accelerated growth occurs in postnatal life after in utero growth restriction. Samples of quadriceps muscle were collected at ∼140 days gestation (term ∼150 days gestation) from normally grown fetal lambs (Control, n= 7) and from growth restricted fetal lambs (placentally restricted: PR, n= 8) and from Control (n= 14) and PR (n= 9) lambs at 21 days after birth. The abundance of the insulin and IGF1 receptor protein was higher in the quadriceps muscle of the PR fetus, but there was a lower abundance of the insulin signalling molecule PKCζ, and GLUT4 protein in the PR group. At 21 days of postnatal age, insulin receptor abundance remained higher in the muscle of the PR lamb, and there was also an up‐regulation of the insulin signalling molecules, PI3Kinase p85, Akt1 and Akt2 and of the GLUT4 protein in the PR group. Fetal growth restriction therefore results in an increased abundance of the insulin receptor in skeletal muscle, which persists after birth when it is associated with an upregulation of insulin signalling molecules and the glucose transporter, GLUT4. These data provide evidence that the origins of the accelerated growth experienced by the small baby after birth lie in the adaptive response of the growth restricted fetus to its low placental substrate supply.
The molecular architecture of the arachidonate‐regulated Ca2+‐selective ARC channel is a pentameric assembly of Orai1 and Orai3 subunits
Authors: Mignen Olivier , Thompson Jill L. , Shuttleworth Trevor J.
Published: July 2009

The activation of Ca2+ entry is a critical component of agonist‐induced cytosolic Ca2+ signals in non‐excitable cells. Although a variety of different channels may be involved in such entry, the recent identification of the STIM and Orai proteins has focused attention on the channels in which these proteins play a key role. To date, two distinct highly Ca2+‐selective STIM1‐regulated and Orai‐based channels have been identified – the store‐operated CRAC channels and the store‐independent arachidonic acid activated ARC channels. In contrast to the CRAC channels, where the channel pore is composed of only Orai1 subunits, both Orai1 and Orai3 subunits are essential components of the ARC channel pore. Using an approach involving the co‐expression of a dominant‐negative Orai1 monomer along with different preassembled concatenated Orai1 constructs, we recently demonstrated that the functional CRAC channel pore is formed by a homotetrameric assembly of Orai1 subunits. Here, we use a similar approach to demonstrate that the functional ARC channel pore is a heteropentameric assembly of three Orai1 subunits and two Orai3 subunits. Expression of concatenated pentameric constructs with this stoichiometry results in the appearance of large currents that display all the key biophysical and pharmacological features of the endogenous ARC channels. They also replicate the essential regulatory characteristics of native ARC channels including specific activation by low concentrations of arachidonic acid, complete independence of store depletion, and an absolute requirement for the pool of STIM1 that constitutively resides in the plasma membrane.
Calcium‐activated chloride currents in olfactory sensory neurons from mice lacking bestrophin‐2
Authors: Pifferi Simone , Dibattista Michele , Sagheddu Claudia , Boccaccio Anna , Al Qteishat Ahmed , Ghirardi Filippo , Tirindelli Roberto , Menini Anna
Published: July 2009

Olfactory sensory neurons use a chloride‐based signal amplification mechanism to detect odorants. The binding of odorants to receptors in the cilia of olfactory sensory neurons activates a transduction cascade that involves the opening of cyclic nucleotide‐gated channels and the entry of Ca2+ into the cilia. Ca2+ activates a Cl− current that produces an efflux of Cl− ions and amplifies the depolarization. The molecular identity of Ca2+‐activated Cl− channels is still elusive, although some bestrophins have been shown to function as Ca2+‐activated Cl− channels when expressed in heterologous systems. In the olfactory epithelium, bestrophin‐2 (Best2) has been indicated as a candidate for being a molecular component of the olfactory Ca2+‐activated Cl− channel. In this study, we have analysed mice lacking Best2. We compared the electrophysiological responses of the olfactory epithelium to odorant stimulation, as well as the properties of Ca2+‐activated Cl− currents in wild‐type (WT) and knockout (KO) mice for Best2. Our results confirm that Best2 is expressed in the cilia of olfactory sensory neurons, while odorant responses and Ca2+‐activated Cl− currents were not significantly different between WT and KO mice. Thus, Best2 does not appear to be the main molecular component of the olfactory channel. Further studies are required to determine the function of Best2 in the cilia of olfactory sensory neurons.
Optimal Observer Design With Specified Eigenvalues for Time-Invariant Linear System
Authors: Kung F. C. , Yeh Y. M.
Published: July 2009

The elements of the observer matrix are determined to meet the specified eigenvalues, distinct and multiple, and at the same time, the measure of quadratic estimate error expressed in block pulse functions is minimized. It is relatively simple as compared to other design methods for optimal observers.
Modal Cost Analysis for Linear Matrix-Second-Order Systems
Authors: Skelton R. E. , Hughes P. C.
Published: July 2009

Reduced models and reduced controllers for systems governed by matrix-second-order differential equations are obtained by retaining those modes which make the largest contributions to quadratic control objectives. Such contributions, expressed in terms of modal data, are called “modal costs” and when used as mode truncation criteria, allow the statement of the specific control objectives to influence the early model reduction from very high order models which are available, for example, from finite element methods. The relative importance of damping, frequency and eigenvector in the mode truncation decisions are made explicit for each of these control objectives: attitude control, vibration suppression and figure control. The paper also shows that using Modal Cost Analysis (MCA) on the closed loop modes of the optimally controlled system allows the construction of reduced control policies which feedback only those closed loop modal coordinates which are most critical to the quadratic control performance criterion. In this way, the modes which should be controlled (and hence the modes which must be observable by choice of measurements), are deduced from truncations of the optimal controller.
A Modified Volterra Series Representation for a Class of Single-Valued, Continuous Nonlinear Systems
Authors: Parker G. A. , Moore E. L.
Published: July 2009

A modification is presented to the Volterra functional series representation of the response from a cascaded linear-nonlinear-linear system in which the nonlinear element is single-valued, separable, and continuous. The particular advantage of this approach is that the dynamic effects represented in the convolution terms are independent of the bias or mean level of the input signal to the system. The effects of bias and element gain are included in a weighting coefficient βi (m) to each term in the series, with the first term representing the small signal gain of the system. The special case of pseudo-random input signals to the nonlinear system model is also examined using the modified functional series. It is concluded that the three-level sequence is particularly useful in producing a truncation in the modified cross-correlation series representation of the system.
An Active and Passive Steering Controller Study of Rubber-Tired Automated Guideway Transit Vehicles
Authors: Kwak Y. K. , Smith C. C.
Published: July 2009

A comparative study of an active and passive steering controller of a rubber-tired Automated Guideway Transit (AGT) vehicle excited by random guideway irregularities is discussed. The thirteen-degree-of-freedom vehicle model, which was previously developed for passively steered rubber-tired AGT vehicles, is modified to facilitate the coupling of the vehicle to an active steering controller. Vehicle performance with the active steering controller, as well as the passive one, is evaluated in terms of root mean square (rms) values of the system outputs of interest. For the same level of the average rms tracking error, a two-sensor proportional active steering controller can improve the ride quality (about 12 percent reduction in lateral rms acceleration) compared to the present passive steering controller for a typical AGT vehicle with random guideway irregularity inputs.
An Optimal Preview Control for Linear Systems
Authors: MacAdam C. C.
Published: July 2009

A technique for synthesizing closed-loop control of linear time-invariant systems during tracking of previewed inputs is presented. The derived control is directly dependent upon the properties of the controlled system and is obtained by minimization of a defined previewed output error.
A Geometric Series Approach for Approximation of Transition Matrices in Quadratic Synthesis
Authors: Shieh L. S. , Wai W. B. , Yates R. E.
Published: July 2009

A geometric-series approach is used to approximate the exponentials of Hamiltonian matrices for quadratic synthesis problems. The approximants of the discretized transition matrices are then used to construct piecewise-constant gains and piecewise-time varying gains for approximating a time-varying optimal gain and a time-varying Kalman gain. The proposed method is more accurate and computationally faster than those existing methods which use the Walsh function approach and the block-pulse function approach.
Lateral Dynamics of a Rail Transit Vehicle: A Comparison of Experimental and Theoretical Results
Authors: Young J. A. , AppaRao T. A. P. S.
Published: July 2009

A subway rail vehicle was tested on tangent and curved track sections to provide dynamics data for validation of theoretical models. Tests were done with three combinations of primary suspension and wheel profiles which were selected using a simplified truck stability/curving trade off analysis. The test results of one configuration are compared with two lateral dynamic models. Experimental frequency and damping results are compared with the predictions of a linear Lateral Stability model for a number of vehicle speeds. The measured time histories of vehicle responses on a spiral and a 122 m (400 ft) radius curve are compared with the results obtained from a Curve Entry Dynamics model. The agreement between theory and experiment varied from good to poor depending on the parameter being compared. The discrepancies between theory and experiment can be attributed to four major sources: limitations of models, errors in vehicle parameters used in obtaining theoretical results, measurement errors and data analysis limitations.
One Engineering Concept of Dynamic Control of Manipulators
Authors: Vukobratovic´ M. , Stokic´ D.
Published: July 2009

In the stage of nominal regimes, programmed (nominal) control is synthesized taking into account coupling among degrees of freedom under nominal conditions. Thus, in the stage of perturbed regimes the influence of coupling among the d.o.f. is reduced if practical stability of the system in the finite regions of the state space is under consideration. In this paper, global control in the form of force feedback is introduced. The problem of global system stability is also considered. In order to discuss different aspects of the application of decentralized and global control to industrial manipulators, numerical examples are presented.
Hybrid Position/Force Control of Manipulators
Authors: Raibert M. H. , Craig J. J.
Published: July 2009

A new conceptually simple approach to controlling compliant motions of a robot manipulator is presented. The “hybrid” technique described combines force and torque information with positional data to satisfy simultaneous position and force trajectory constraints specified in a convenient task related coordinate system. Analysis, simulation, and experiments are used to evaluate the controller’s ability to execute trajectories using feedback from a force sensing wrist and from position sensors found in the manipulator joints. The results show that the method achieves stable, accurate control of force and position trajectories for a variety of test conditions.
Control of Force Distribution in Robotic Mechanisms Containing Closed Kinematic Chains
Authors: Orin D. E. , Oh S. Y.
Published: July 2009

Control of the force distribution in locomotion and manipulation systems containing closed kinematic chains is an important problem since many tasks such as walking or grasping depend upon it. The basic problem is to solve for the input joint torques for a particular system trajectory and is usually underspecified. As such, linear programming has been used to obtain a solution which optimizes a weighted combination of energy consumption and load balancings. Inequality constraints on the maximum actuator torques and reaction forces at the tip of each chain of the system are imposed, in addition to equality constraints which specify movement in a desired system trajectory. An example is given in which the joint torques to drive a hexapod locomotion vehicle in a tripod gait are computed.
The Bilinear, Modal State Equations for Age-Dependent Growth Control
Authors: Brewer J. W.
Published: July 2009

There have been previous attempts to model biological processes as bilinear systems [4,9,10]. In these early studies any member of a population was taken to be quite like any other so that the variation of fertility and susceptibility to mortality with age was ignored. In this paper, however, the age-dependent nature of biological growth [5] is accounted for. The modal (eigenfunction) analysis of the basic partial differential equation of age-dependent growth is shown to result in a system of bilinear equations. (The basic mathematical model is a non-self-adjoint operator with a discrete spectrum and the modes are coupled by the control term.) The impulse control of a truncated version of this system of equations is then discussed. It is anticipated that the results presented here will aid planning for optimal amounts of pesticides to agro-ecosystems or for optimal amounts of drugs (or radiations) to unwanted cell populations.
Development of an Electrofluidic Rate Sensor
Authors: Abbott C. L. , Tippetts T. B.
Published: July 2009

This paper is a report on an effort to develop electrofluidic rate sensors (EFRS) using laminar jet angular rate sensors (LJARS) to sense angular rate and laminar proportional amplifiers (LPA) to amplify the rate signal. Two different bandwidth LJARS (80 Hz and 40 Hz) are matched with fluidic amplifiers, pressure transducers, and constant Reynolds number (NR) power supplies to yield target accuracies of 0.25 percent of full scale output. The fluidic components use air as the working fluid.
Developments in Power Fluidics for Application in Nuclear Plant
Authors: Tippetts J. R. , Priestman G. H. , Thompson D.
Published: July 2009

Fluidic systems have been developed for handling toxic and corrosive fluids in U.K. nuclear plant. Recent work carried out in the CEFT department in collaboration with UKAEA, Risley, which has led to the installation of plant hardware is described. The systems include: single and double-acting pumps with no-moving-part driving units, experiments on multistage pumps and the effect of temperature on pumping rate, fluidic control of mixer-settlers, and pulse-columns. Also described are applications in ventilation plant control and the effect of argon controlling air in a vortex amplifier.
A Proportional Piezoelectric Electro-Fluidic Pneumatic Value Design
Authors: Taft C. K. , Herrick B. M.
Published: July 2009

The development of a proportional electro-fluidic pneumatic valve is presented. The first stage of the valve consists of a piezoelectric bender element of bimorph construction centered between two nozzles. The bimorph is deformed by an electrical input signal. This, in turn, causes a change in pressure at the output of the nozzles, which will then be amplified to a usable level using cascaded laminar proportional amplifiers. A mathematical model of the valve’s behavior is discussed and verified with experimental measurements.
Experimental Results in the Modeling and Control of a Small Furnace
Authors: Baheti R. S. , Mohler R. R.
Published: July 2009

A dynamic model is developed to control the temperature of a specimen in a laboratory furnace. The control variables are the power input to the furnace and the rate of airflow inside the chamber. For a constant airflow input, the furnace can be represented by a linear model and a static gain dependent on the sample temperature. The power input to the furnace is perturbed with a pseudorandom binary sequence and the model parameters are estimated from the input-output measurements. The controller parameters are selected to minimize the variance in the sample temperature.
Dynamics of Mechanisms and Machine Systems in Accelerating Reference Frames
Authors: Allen R. R.
Published: July 2009

Matrix equations of motion are derived for a general machine system in an accelerating reference frame. These equations are highly-nonlinear in the displacements of inertial elements and describe the dynamics of large motions. This analysis permits study of dynamic interactions between the moving elements of a machine and the motion of the machine body. The latter may undergo general translation and rotation as a result of internal and external forces. Power-conserving transformations relating inertial, kinematic, and generalized velocities provide a highly formal procedure for kinematic and dynamic analyses and produce explicit equations in generalized variables which are efficient for numerical solution. The theory is applied to study a machine with a four-bar linkage and driveshaft elasticity mounted on a spring-damper suspension. In this example, torsional oscillations in the drive are compared to those obtained with the machine body fixed in inertial space.
Estimating Reachable Sets
Authors: Grantham W. J.
Published: July 2009

Two methods are presented for investigating reachable sets for nonlinear control systems. One method, based on a reachability maximum principle, lacks appropriate boundary conditions if the reachable set is not closed. The main result of the paper is an approximate method employing a Lyapunov-type function and an associated optimization problem, both involving a parameter vector. For each value of the parameter vector the resulting estimate for the reachable set (and the intersection of all such estimates) is guaranteed to contain the actual reachable set. The method is applicable to systems of any dimension and does not require integration of the equations of motion.
Advances in Nonlinear Wheel/Rail Force Prediction Methods and Their Validation
Authors: Elkins J. A. , Eickhoff B. M.
Published: July 2009

Improvements have been made to the nonlinear wheel / rail force prediction method of Elkins and Gostling. These improvements are described, along with the experimental equipment used in order to provide input data for the predictions, and to validate them. A further series of curving tests, using a Laboratory Coach equipped with bogies having variable suspension parameters, has been carried out, and shown to give excellent agreement with the improved theory. The prediction method is now used on a regular basis within British Rail, and its use for vehicle design is considered, together with planned extensions to cover calculation of wheel and rail wear and dynamic behavior of railway vehicles on curve and switch entry.
Guaranteed Avoidance Control and Holding Control
Authors: Schmitendorf W. E. , Barmish B. R. , Elenbogen B. S.
Published: July 2009

This paper considers the problem of steering the state of a system, in the presence of disturbances, so that it avoids a specified subset of the state space. This subset is called the avoidance set and the problem is called the avoidance control problem. An avoidance control is a control which guarantees that the system does not enter the avoidance set regardless of the disturbance. A necessary condition and a sufficient condition for the existence of an avoidance control are given when the disturbance is subject to magnitude constraints. Closely related to the avoidance problem is the holding problem which is concerned with guaranteeing that the state of the system remains within a specified set. We also reinterpret our conditions for the existence of an avoidance control within the context of the holding problem.
General Scheme for Automatic Control of Continuous Bending of Beams
Authors: Trostmann E. , Hansen N. E. , Cook G.
Published: July 2009

The paper addresses the problem of automating the process of continuous bending of metal beams. The history of previous efforts along these lines is presented and a comparison of this problem with that of numerical control in metal cutting is made. A mathematical model of the bending process suitable for a control system is presented. The uncertainties due to springback and the stochastic nature of bending properties of the beam material are discussed. The needs for parameter identification and output prediction are described. A block diagram for a closed-loop system to control this process is introduced. Results are presented which demonstrate that it is possible to bend to desired curvature if the springback characteristics are known. It is concluded that automatic control of this process is feasible making possible continuous bending of beams into arbitrary desired shapes.
A Method for Optimal Synthesis of Manipulation Robot Trajectories
Authors: Vukobratovic´ M. , Kirc´anski M.
Published: July 2009

Manipulation robots belong to a class of complex, nonlinear dynamic systems. In addition, they are subjected to the constraints resulting from work-space obstacles, kinematical and physical characteristics of the mechanism itself and the actuators. Therefore, the application of optimal control theory (in energy or time optimization) leads to substantial practical difficulties, so that significant simplifications are usually performed, either in model complexity or by neglecting the existing constraints. In this paper the problem of obtaining such an optimization method, which would take into account the complete system dynamics and all the constraints is considered. The only method found to be suitable for such a complex optimization should be based on dynamic programming. In this paper an algorithm for determining optimal velocity distribution for a given manipulator tip trajectory is elaborated in detail. Practical application of the developed procedure is in off-line calculation of nominal input generalized forces (programmed control) of a nonredundant manipulator, by which the minimum of consumed energy is ensured. This is specially important for high speed motions as well as handling of heavy loads.
Errors in Cross-Correlation Peak Location
Authors: Lassahn G. D. , Baker A. G.
Published: July 2009

A method for determining the uncertainty in the location of a cross-correlation peak is derived and two examples are examined. When a cross-correlation peak location is used in transit time flowmeters as a measurement technique for fluid-flow velocity, turbulence in the fluid increases the peak location uncertainty. This effect is examined for two models of turbulence. Also examined is the bias or shift in the peak location due to time response or filter mismatch.
Efficient Dynamic Computer Simulation of Robotic Mechanisms
Authors: Walker M. W. , Orin D. E.
Published: July 2009

The Newton-Euler formulation of the equations of motion of an open-loop kinematic chain is used within a dynamic computer simulation of a robotic mechanism. Four different methods are presented for obtaining the joint variable accelerations given the joint positions, velocities, and input torques or forces. Each of these methods was programmed in FORTRAN and then executed on a CYBER 175 digital computer. This paper contains a comparison of the computational complexity of these methods and the execution time of the programs which implement them.
Verification of a Transit Vehicle’s Curving Behavior and Projected Wheel/Rail Wear Performance
Authors: Elkins J. A. , Allen R. A.
Published: July 2009

A test program was undertaken at the Transportation Test Center in Pueblo, Colorado, to investigate whether modifications to the truck design, particularly a reduction of the primary yaw stiffness, would reduce wheel and rail wear on a new rapid transit system. The test program examined the behavior of the trucks during the negotiation of a number of curves typical of those encountered in revenue service. Test results compared favorably with predictions from a mathematical model of the truck’s curving behavior and, subsequently, the model was used to evaluate a number of truck parameter variations. Results show that the reduction in primary yaw stiffness produced a large improvement in curving performance. This paper also quantifies the effects of axle misalignment and discusses the need for experimental data to relate a wear index to wheel and rail wear.
Proposition for an Unambiguous Vector Bond Graph Notation
Authors: Breedveld P. C.
Published: July 2009

Notation and definitions of vector bonds and multiport elements are proposed. Multiport element arrays and junction arrays are introduced as well as the direct sum of vector bonds. The usefulness of these concepts is demonstrated by some examples: the lumped representation of distributed parameter systems, the representation of a 3-D mechanical system (coordinate transformations) and of a nonisothermal chemical reaction.
Multivariable PID Controller for Unidentified Plant
Authors: Thompson S.
Published: July 2009

A procedure is presented for designing multivariable controllers for unidentified plant. It is assumed that the open-loop plant is stable and its response to step inputs are basically nonoscillatory. For such plant, no mathematical model is required in order to generate multivariable I, PI, or PID controllers. Method of tuning the controllers are also presented and demonstrated, first on a low order linear distillation column model, and finally on a high order, nonlinear, once-through boiler model typical of the type used in nuclear power plant simulation studies.
A Semi-Empirical Moisture Transport Model for On-Line Optimal Lumber Drying Control
Authors: Lessard R. A. , Limbert D. E. , Pokoski J. L. , Hill J. L.
Published: July 2009

Green lumber is often dried in climatically controlled kilns to prepare it for commercial use. Optimization of the kiln drying schedule (air temperature and humidity) to minimize drying costs requires a mathematical model of the drying lumber. A model that will predict moisture content distribution within the lumber when drying from 80 percent to 6 percent adequately enough for control purposes does not exist at this time. Graphical results from this study have demonstrated that a non-linear regression method for on-line optimizing of the model diffusion coefficient function provides an effective predicting model. Thus a simplified version of an available diffusion model can function in an optimal process control system.
Spectral Analysis of Freight Car Truck Lateral Response
Authors: Sweet L. M. , Karmel A.
Published: July 2009

This paper summarizes methods used to quantify the lateral response of freight car trucks to random track irregularity inputs. Spectral analysis is applied to the results of an extensive series of experiments using a one-fifth scale model of a truck and half carbody, in which all inertial, friction, creep, and stiffness forces are dynamically scaled. The repeatability and confidence limits for estimates of the spectral densities of track inputs and truck response variables are determined. The influence of forward velocity, truck internal friction, and axle load on the dominant truck response modes is presented. Cross spectral methods are used to reference signals to the true track centerline, and to compute lateral response transfer functions and coherence levels. The low levels of coherence between track inputs and freight car truck/carbody response indicate that linear transfer functions do not represent the response adequately, and that measured output spectra are superior to transfer functions for comparison of truck configurations.
Quasi-Direct Adaptive Control for Nonminimum Phase Systems
Authors: Lozano Leal R. , Landau I. D.
Published: July 2009

An adaptive control algorithm applicable to nonminimum phase, discrete, linear, time invariant systems is presented. This algorithm does not require solving a Bezout identity at each sampling step by incorporating two different identification algorithms. The first one identifies the plant’s parameters and provides them to the second one which in turn identifies the controller’s parameters. Independent tracking and regulation objectives are achieved in the limit with bounded plant input and output for a range of initial plant parameters estimates.
Closed-Loop Shape Control of a Roll-Bending Process
Authors: Hardt D. E. , Roberts M. A. , Stelson K. A.
Published: July 2009

This paper describes a shape control system for a three roll bending process. The objective of this process is to impart a desired curvature to a workpiece at each point along the length of the part. Since final part shape is determined by the shape to which the workpiece is loaded and the amount of elastic springback, and since the latter is a strong function of the material properties of the workpiece, a truly closed-loop controller must account for these properties to insure consistent process performance. The scheme presented here accomplishes shape control by measuring both the loaded shape, the loading moment, and the effective beam rigidity of the material in real-time. As a result, a very accurate prediction of unloaded curvature can be made and an unloaded curvature control system can be designed. A series of experiments were performed to test this scheme by bending thin sheets of different materials to constant radii, specifying only the desired radius. The results indicate that the controller responds to the different material properties and produces accurate shapes regardless of variability in these properties.
Ellipsoidal Set-Theoretic Control Synthesis
Authors: Usoro P. B. , Schweppe F. C. , Wormley D. N. , Gould L. A.
Published: July 2009

A Set-Theoretic approach to solving control problems is presented for systems with control and state constraints which are subjected to input disturbances. The input disturbance is modeled as an unknown-but-bounded process. The constraints on the states and controls are treated explicitly. The primary objective is to construct a control system that uses only available control effort to insure nonviolation of the prespecified state constraints in the presence of the input disturbance. Since the constraints are treated directly, this technique yields a design that satisfies the constraints. The effectiveness of Set-Theoretic control synthesis is evaluated by means of an example and by comparison with a specific Linear-Quadratic Control design procedure.
Signal Validation for Nuclear Power Plants
Authors: Deckert J. C. , Fisher J. L. , Laning D. B. , Ray A.
Published: July 2009

A signal validation methodology to improve the reliability of the information displayed to the operator of a nuclear power plant is presented. The general design methodology is developed and then applied to the steam generator and feedwater subsystem of a typical pressurized water reactor. Using steady-state and transient simulations of this subsystem, including realistic additive sensor noise, the developed algorithm successfully isolates a variety of injected sensor faults and demonstrates its inherent capability to isolate common-mode sensor failures and plant component failures.
Measurement Errors in Closed-Loop Frequency Response Estimates
Authors: Davall P. W. , Nikiforuk P. N.
Published: July 2009

The sampling distributions associated with frequency response estimates of single input, single output closed-loop systems are derived for the case where both the output and feedback signal measurements are subject to added noise. This work is an extension of that done by Goodman [1-3] and Akaike [4, 5] on open-loop systems. Conditions for response estimate bias are investigated and approximate distributions for the power spectra estimates of the added noise terms are derived.
New Results on Optimal Joint Parameter and State Estimation of Linear Stochastic Systems
Authors: Salut G. , Aguilar-Martin J. , Lefebvre S.
Published: July 2009

In this paper a complete presentation of a new canonical representation of multiinput, multioutput linear stochastic systems is given. Its equivalence with operator form directly linked with ARMA processes as well as with classical state space representation is given, and a transfer matrix interpretation is developed in an example. The importance of the new representation is mainly in the fact that in the joint state and parameters estimation problem, all unknown parameters appear linearly when an input-output record is available. Moreover, if noises are Gaussian and their statistics are known, a conditionally time varying Kalman-Bucy type filter gives the recursive optimal estimation of parameters and state. Historical comments and remarks about the adaptive version of this algorithm are given. Finally an illustrative low order example is described.
Stability and Curving Mechanics of Rail Vehicles
Authors: Bell C. E. , Horak D. , Hedrick J. K.
Published: July 2009

This paper presents a unified treatment of stability and curving mechanics of steel wheel/steel rail vehicles utilizing low order, predominantly linear models. The analysis is applicable to both conventional and self-steering radial passenger trucks. A six degree of freedom truck model is utilized to illustrate the various instability modes that can occur due to the destabilizing influence of a wheelset. It is shown that the individual wheelset mode, the rigid truck mode and the carbody mode are of academic interest only, while the elastically coupled wheelset mode is the one which limits the performance of intercity trucks. Carbody resonance can occur but is controlled by relatively small amounts of damping in the secondary lateral suspension. A four degree of freedom steady-state curving model is used to investigate the influence of shear and bending stiffness on both off and on-flange curving performance. It is shown that a low bending stiffness provides superior on and off-flange curving and that the selection of the shear stiffness depends upon the severity of the curves to be negotiated. A low shear stiffness improves the ability of the truck to stay off the flange while a high shear stiffness results in a “floating” truck which flanges earlier but results in the lowest flange forces and angle of attack once flange contact occurs.
A Comparison of the Stability and Curving Performance of Radial and Conventional Rail Vehicle Trucks
Authors: Horak D. , Bell C. E. , Hedrick J. K.
Published: July 2009

This paper compares the lateral stability and steady-state curving performance of radial and conventional rail vehicle trucks. The radial truck has two unique features, it allows direct elastic coupling between the wheelsets and it allows greater total truck shear stiffness for a given bending stiffness. It is shown that the first property allows the radial truck to achieve up to a 40 percent higher critical speed than the conventional truck for equivalent truck total shear and bending stiffness since the direct coupling between the wheelsets allows decoupling of the truck mass from the hunting wheelset masses. The second feature, i.e., greater shear stiffness capability, allows the radial truck to have improved wear properties during the negotiation of tight curves. It is shown that the high shear stiffness property combined with a low bending stiffness reduces the lateral flange force and wheelset angle of attack during flange contact. It is concluded that for routes where the majority of curves are less than 4 deg (greater than 400 m radius) the truck optimized for off-flange performance should have intermediate values of shear stiffness, bending stiffness, and conicity. On the other hand, for routes where the majority of curves are greater than 4 deg, the truck optimized for on-flange performance should have a high shear stiffness and low values of bending stiffness and conicity.
Longitudinal Instability in Braked Landing Gear
Authors: Allen R. R. , O’Massey R. C.
Published: July 2009

An instability in the form of a self-excited, bounded longitudinal oscillation may occur in aircraft landing gear when one or more wheels lock due to excessive braking. The instability usually appears at ground speeds below 40 knots (20 m/s) and results from interaction between structural elasticity and the nonlinear characteristics of tire-runway friction. A nonlinear mathematical model is developed to study the dynamics of this divergence in a braked, dual tire landing gear. Analytical methods are presented to determine critical ground speeds in terms of runway friction characteristics and to predict the amplitude of steady-state oscillations. The effect of design variables on longitudinal stability is evaluated and design guidelines are presented which insure reduction of the severity of this divergent dynamic behavior.