Unknown Physical Parameters Research Articles

Donor‐Substituted 1,1,4,4‐Tetracyanobutadienes (TCBDs): New Chromophores with Efficient Intramolecular Charge‐Transfer Interactions by Atom‐Economic Synthesis

A wide variety of monomeric and oligomeric, donor-substituted 1,1,4,4-tetracyanobutadienes (TCBDs) have been synthesized by [2+2] cycloaddition between tetracyanoethylene (TNCE) and donor-substituted alkynes, followed by electrocyclic ring opening of the initially formed cyclobutenes. Reaction yields are often nearly quantitative but can be affected by the electron-donating power and steric demands of the alkyne substituents. The intramolecular charge-transfer (CT) interactions between the donor and TCBD acceptor moieties were comprehensively investigated by X-ray crystallography, electrochemistry, UV-visible spectroscopy, and theoretical calculations. Despite the nonplanarity of the new chromophores, which have a substantial twist between the two dicyanovinyl planes, efficient intramolecular CT interactions are observed, and the crystal structures demonstrate a high quinoid character in strong donor substituents, such as N,N-dimethylanilino (DMA) rings. The maxima of the CT bands shift bathochromically upon reduction of the amount of conjugative coupling between strong donor and acceptor moieties. Each TCBD moiety undergoes two reversible, one-electron reduction steps. Thus, a tri-TCBD derivative with a 1,3,5-trisubstituted benzene core shows six reversible reduction steps within an exceptionally narrow potential range of 1.0 V. The first reduction potential E(red,1) is strongly influenced by the donor substitution: introduction of more donor moieties causes an increasingly twisted TCBD structure, a fact that results in the elevation of the LUMO level and, consequently, a more difficult first reduction. The potentials are also strongly influenced by the nature of the donor residues and the extent of donor-acceptor coupling. A careful comparison of electrochemical data and the correlation with UV-visible spectra made it possible to estimate unknown physical parameters such as the E(red,1) of unsubstituted TCBD (-0.31 V vs Fc+/Fc) as well as the maxima of highly broadened CT bands. Donor-substituted TCBDs are stable molecules and can be sublimed without decomposition. With their high third-order optical nonlinearities, as revealed in preliminary measurements, they should become interesting chromophores for ultra-thin film formation by vapor deposition techniques and have applications in opto-electronic devices.

Erratum: Gravitational waves from inspiraling compact binaries: Energy flux to third post-Newtonian order [Phys. Rev. D65, 064005 (2002)

The multipolar-post-Minkowskian approach to gravitational radiation is applied to the problem of the generation of waves by the compact binary inspiral. We investigate specifically the third post-Newtonian (3PN) approximation in the total energy flux. The new results are the computation of the mass quadrupole moment of the binary to the 3PN order, and the current quadrupole and mass octupole to the 2PN order. Wave tails and tails of tails in the far zone are included up to the 3.5PN order. The recently derived 3PN equations of binary motion are used to compute the time-derivatives of the moments. We find perfect agreement to the 3.5PN order with perturbation calculations of black holes in the test-mass limit for one body. Technical inputs in our computation include a model of point particles for describing the compact objects, and the Hadamard self-field regularization. Because of a physical incompleteness of the Hadamard regularization at the 3PN order, the energy flux depends on one unknown physical parameter, which is a combination of a parameter \lambda in the equations of motion, and a new parameter \theta coming from the quadrupole moment.

Experimental verification for detection of damage of sensor-arrayed truss domes using afocusing strategy

A damage detection scheme using a focusing strategy, developed for the purpose ofmaintaining structural integrity of truss domes during their service life, that estimates thelocation and extent of damage on the basis of vibration monitoring and systemidentification is presented. The main idea of the focusing strategy is to reduce the numberof unknown physical parameters as much as possible by shifting from global tolocal damage detection gradually. The scheme is divided into three stages: global,intermediate and local damage detection. In the global damage detection, the centralconcern is whether the damage occurs in the superstructure or substructure. Inthe intermediate damage detection, possible damaged regions are located in thesuperstructure. In the local damage detection, damaged members or joints are located inthe damaged regions. Finally, the extent of member, joint or support damageis quantified in terms of member stiffness reduction ratios. Depending on thedamage detection levels, different probing forces are used and different damageindices are defined. To verify the overall damage detection scheme, a series ofshaking table, vibration generator and impact hammer tests have been carried outfor a small-scale experimental model. On the basis of the damage identificationresults, the effectiveness and limitations of the proposed scheme are discussed.

Data compression for estimation of the physical parameters of stable and unstable linear systems

A two-stage method for the identification of physical system parameters from experimental data is presented. The first stage compresses the data as an empirical model which encapsulates the data content at frequencies of interest. The second stage then uses data extracted from the empirical model of the first stage within a nonlinear estimation scheme to estimate the unknown physical parameters. Furthermore, the paper proposes use of exponential data weighting in the identification of partially unknown, unstable systems so that they can be treated in the same framework as stable systems. Experimental data are used to demonstrate the efficacy of the proposed approach.

AN ADAPTIVE PRESSURE CONTROLLER DESIGN OF HYDRAULIC SERVO SYSTEM WITH DEAD ZONE

This paper develops a design of adaptive pressure controller for hydraulic servo valve with unknown dead zone. In general to reduce leakage flow, the servo valves adopt positive lap structures. This makes dead zone larger and is obstacle for precise positioning control. To compensate of such dead zone and unknown physical parameters of system, adaptive control strategy is examined for simple pressure control system. First it is assumed that only the flow gain of servo valve can be known by experiment and the adaptive controller is designed. This controller is examined on water hydraulic servo system which has larger leakage and positive lap for lower viscosity of tap water. The experimental results show that the better tracking performance is obtained comparing with PI or conventional adaptive controller without dead zone compensation. Then the controller is extended for unknown flow gain case.

Robust and adaptive path following for underactuated autonomous underwater vehicles

This paper proposes a nonlinear robust adaptive control strategy to force a six degrees of freedom underactuated underwater vehicle with only four actuators to follow a predefined path at a desired speed despite of the presence of environmental disturbances and vehicle’s unknown physical parameters. The proposed controller is designed using Lyapunov’s direct method, the popular backstepping and parameter projection techniques. The closed loop path following errors can be made arbitrarily small. Interestingly, it is shown that our developed control strategy is easily extendible to situations of practical importance such as parking and point-to-point navigation. Numerical simulations are provided to illustrate the effectiveness of the proposed methodology.

A Methodology for Estimation of Mass Transfer Parameters in a Detailed Chromatography Model Based on Frontal Experiments

A methodology for estimation of the unknown physical parameters in a detailed model for chromatographic processes is proposed. The model describes the concentration of the solute in the mobile phase and considers external/internal mass transfer resistance. The external volume and its mixing effect are also considered. The unknown model parameters estimated are the bed void, the axial dispersion coefficient, the liquid film mass transfer coefficient, the effective diffusion coefficient and the apparent bead porosity. All the parameters in the model were subsequently determined in three classes of experiments, the external mixing behaviour, the mobile phase behaviour and the stationary phase behaviour. The estimates are based on the sum of the least squares of the residuals between the experimental breakthrough curves and the model response. The methodology is exemplified by frontal experiments with lysozyme, bovine serum albumin and immuno globulin γ on a well-defined column set-up. When the mixing properties in the external volume had to be accounted for, to avoid adding broadening behaviour to the dispersion coefficient, the film mass transfer coefficient and the diffusion coefficient were also investigated. The results show that it is possible to estimate the unknown parameters using the proposed methodology.

Controle de robôs manipuladores em modo dual adaptativo/robusto

Considera-se o problema de rastreamento de trajetórias para robôs manipuladores com parâmetros físicos incertos e sob a ação de distúrbios de amplitude limitada. Descreve-se um algoritmo de controle de modo dual adaptativo/robusto que garante desempenho transitório exponencial com relação a um domínio residual arbitrariamente pequeno e com atenuação arbitrária de distúrbios. Na ausência destes, o controlador mostra-se capaz de rastrear assintoticamente a trajetória desejada.

Gravitational waves from inspiraling compact binaries: Energy flux to third post-Newtonian order

The multipolar-post-Minkowskian approach to gravitational radiation is applied to the problem of the generation of waves by the compact binary inspiral. We investigate specifically the third post-Newtonian (3PN) approximation in the total energy flux. The new results are the computation of the mass quadrupole moment of the binary to the 3PN order, and the current quadrupole and mass octupole to the 2PN order. Wave tails and tails of tails in the far zone are included up to the 3.5PN order. The recently derived 3PN equations of binary motion are used to compute the time derivatives of the moments. We find perfect agreement to the 3.5PN order with perturbation calculations of black holes in the test-mass limit for one body. Technical inputs in our computation include a model of point particles for describing the compact objects, and the Hadamard self-field regularization. Because of a physical incompleteness of the Hadamard regularization at the 3PN order, the energy flux depends on one unknown physical parameter, which is a combination of a parameter \ensuremath{\lambda} in the equations of motion, and a new parameter \ensuremath{\theta} coming from the quadrupole moment.

Searching for Ammonia in Grain Mantles toward Massive Young Stellar Objects

We present a study of the mid-infrared spectral regions of 17 objects observed with the Short-Wavelength Spectrometer on the Infrared Space Observatory (ISO SWS) in a search for the presence of the elusive NH3 solid-state absorption features at 2.96 and 9.0 μm. We compare the 3 μm profile with laboratory spectra of pure water and water/ammonia mixtures from the Leiden Molecular Astrophysics database. We determine that the shape of the 3 μm water feature alone does not present conclusive evidence of the presence or lack of NH3 ice on dust grain mantles because of the large number of unknown physical parameters that influence the 3 μm water profile: grain size distribution, grain shape, mantle composition, thermal history, and geometrical effects. In the 9 μm region, the presence of NH3 is characterized by a sudden change in slope at 8.5 μm and a peak at 9.0 μm within the silicate profile. Of the 16 silicate features studied, four show evidence of a 9 μm ammonia feature, including the previously reported detections in ground-based observations of NGC 7538 IRS 9, and SWS observations of W33 A. Upper limits are found for the remaining objects. Why NH3, which is an abundant gas-phase molecule in cold, dense cores, is not apparently present in significant amounts on most grain mantles, where it is expected to freeze out, is currently a mystery.

On Robustness of a Stabilization Method Based on Generalized Canonical Transformations

This paper studies the robustness analysis of feedback systems for two-wheeled vehicle systems which are designed based on generalized canonical transformations. Firstly the relation between the design parameter in the stabilization procedure and the sensitivity against external disturbances is discussed. Secondly a sufficient condition for the robust stability against unknown physical parameter variations is derived. Finally the effectiveness of our method is demonstrated by experiments.

Bayesian surrogates for integrating numerical, analytical, and experimental data: application to inverse heat transfer in wearable computers

Wearable computers are portable electronics worn on the body. The increasing thermal challenges facing these compact electronics systems have motivated new cooling strategies such as transient thermal management with thermal storage materials. The ability of building models to assess quickly the effect of different design parameters is critical for effectively incorporating innovative thermal strategies into new products. System models that enable design space exploration are built from different information sources such as numerical simulations, physical experiments, analytical solutions and heuristics. These models, called surrogates, are nonlinear, adaptive, and suitable for system responses where limited information is available and few realizations of experiments or numerical simulations are feasible. This paper applies a Bayesian surrogate framework to estimate values for unknown physical parameters of an embedded electronics system. Physical experiments and numerical simulations are performed on an embedded electronics prototype system of a wearable computer. Numerical models for the experimental prototype, which involve five and three unknown parameters, are implemented with and without thermal contact resistances. Through the use of orthogonal arrays and optimal sampling, an efficient exploration of the parameter space is performed to determine thermal conductivities, thermal contact resistances and heat transfer coefficients. Surrogate models are built that combine information obtained from numerical simulations, experimental model measurements and a thermal resistance network. The integration of several information sources reduces the number of large-scale numerical simulations needed to find reliable estimates of the system parameters. For the embedded electronics case, the use of prior information from the thermal resistance network model reduces significantly the computational effort required to investigate the solution space.

Identification of Unknown Physical Parameters of Cantilevered Beam Using its Vibration Data.

In this paper, an efficient computer algorithm is proposed for identifying the unknown spatially invariant/varying parameter values such as flexural stiffness and both air and structural damping coefficients of a class of mechanically flexible cantilevered beams, using dynamic data measured on its vibration in a non-destructive manner. First, the mathematical model of the cantilevered beam is given by an Euler-Bernoulli type partial differential equation and the identification problem is formulated as one of the inverse problems by minimizing the quadratic error functional between mathematical model and measurement data with respect to model parameters. Then, the identification algorithm is developed by introducing finite approximations both to the modeled partial differential equation and the unknown parameter profiles using Galerkin method and basis functions. Finally, the efficacy of the proposed identification algorithm is examined for two kinds of beams-one is spatially uniform and the other is nonuniform in its shape by simulations and experiments.

Rosetta lander in situ characterization of a comet nucleus

Rosetta is one of the cornerstone missions within the science program “Horizon 2000” of the European Space Agency (ESA). Its objective is the characterization of comet Wirtanen, which will be reached after 9 years of cruise in the year 2012. As comets are believed to be the most primitive bodies in our planetary system, having preserved material from the early stages of its formation, the Rosetta mission shall result in a better understanding of the formation of the solar system. The Rosetta Lander, part of the Rosetta payload, is contributed to the mission by an international consortium of research institutes. It will perform in situ measurements on the surface of the comet nucleus. The science objectives of the Rosetta Lander can be comprised by: • • determination of the composition of cometary near surface matter: bulk elemental abundances, isotopes, minerals, ices, carbonaceous compounds, organics volatiles -in dependance on time and insolation. • • measurement of physical parameters — mechanical strength, density, sound speed, electrical permittivity, heat conductivity and temperature. • • investigation of topology, surface structure including colour and albedo, near surface structure (strategraphy) and internal structure. • • the comets interaction with solar wind. The payload of the Rosetta Lander consists of nine instruments with a total mass of about 20kg. The Rosetta Lander system with an overall mass of about 85kg consists of a light weight structure of carbonfibre material, solar cells to provide power, a thermal control system securing operation without the use of radiactive heaters, a telecommunications system, using the orbiter as relay to Earth and a central computer, serving all subsystems and the payload. The lander will be ejected from the main spacecraft after selection of an adequate landing area from an orbit, about 1–5km above the surface of the nucleus. The actual descent strategy is highly depending on the (yet unknown) physical parameters of P/Wirtanen (like mass, shape and rotation period). Thus, a flexible landing concept, which allows the setting of the landing parameters interactively during the mission is required. Landing will take place on a tripod that includes a device that dissipates most of the impact energy and allows rotation of the main structure. At impact, a hold-down thruster and the shot of an anchoring harpoon will avoid rebound from the surface.

Decentralized Adaptive and Nonadaptive Position/Force Controllers for Redundant Manipulators in Cooperations

This paper addresses the problem of controlling positions and forces of multiple redundant manipulators cooperatively handling an ob ject in a decentralized manner while optimizing a performance in dex. The authors propose one adaptive and two nonadaptive de centralized controllers. The adaptive controller is able to cope with unknown or uncertain physical parameters of the system. The Lya punov approach proves that this controller not only yields asymp totic convergence of the position and force errors but also opti mizes the specified performance index. To improve the transition performance, besides the nonadaptive version of the controller, an implicit decentralized force controller with exponential stability is developed. The controllers realize the force and position controls simultaneously by using coupled force and position signals. The coupled signals distinguish these methods from traditional hybrid controllers in which decoupling of the signals is a must. The de centralized architectures of all the controllers must be emphasized. In detail, the joint input for each robot is designed in its own state space; thus, no coordinator exists, and the computation cost is less expensive than that of centralized controllers designed in the state space of the whole system.

Semiquantitative subplantation model for low energy ion interactions with surfaces. II. Ion beam deposition of carbon and carbon nitride

The semiquantitative subplantation model developed in article I of this series [J. Vac. Sci. Technol. A 16, 444 (1998)] is applied to model experimental data for the systems of C+ and N+ ion interactions with graphite, the deposition of diamondlike carbon (DLC) films from C+ ions, and the deposition of carbon nitride (CxNy) films from C+ and N+ ions. The success of the model is based on its ability to provide semiquantitative interpretations of the physical phenomena underlying experimental data from several sources that had previously been interpreted only qualitatively. These phenomena include the effects of ion kinetic energy, ion beam fluence, substrate temperature, radiation enhanced diffusion, penetration thresholds, displacement thresholds, substrate density, and bonding sites. The model allows one to draw previously unexpected conclusions about the interaction mechanisms and to establish quantitative estimates for some previously unknown physical parameters. The results indicate that there is a value of the C+ and N+ ion penetration threshold, ∼7 to 8 eV, which is applicable to graphite, CxNy, and DLC surfaces. The production of sp3 bonded structures is determined by a balance between the beneficial effects (subsurface deposition, enhanced diffusion, densification) and the deleterious effects (damage) of energetic particle beams.

ゴム人工筋６自由度パラレルリンクマニピュレータの積分型確率ファジィ制御

A robust control approach is described for controlling the position and orientation of a six-DOF parallel link manipulator, in which one prismatic link consists of a rubber muscle actuator, so that the controlled object contains several nonlinear factors. The position of the link is also assumed to be measured by using a linear potentiometer. As a result, the associated measurement system contains some measurement noises. The control system is construted using a stochastic fuzzy controller with an integlator so as to remove a tracking error. To design the feedback gains of the stochastic fuzzy controller, a mmn-max control strategy is adopted to the systems, with unknown physical parameters. The effectiveness of the proposed method is illustrated by using some actual experiments.

Identification of Vibration Parameters for Motor Vehicles

SUMMARY Identification of the vibration parameters of motor vehicles, as well as of dynamic systems in general, represents a complex problem. Many experimental-theoretical procedures have been proposed in order to solve the problem but there is no generally accepted method. The development of a method for the identification of the vibration parameters of motor vehicles is described in this paper. The identification of the unknown parameters is achieved by the use of experimental data applied to an vibration model with a known structure but unknown physical parameters. The methods of nonlinear programming are employed in the computations. The elastic and damping elements, including the tyres, are also by assumption nonlinear. Verification of the reliability of the method is carried out by using two vibration models of the vehicle - one with known and the other with unknown values of the vibration parameters.

Approaching the inverse problem of parameter estimation in groundwater models by means of artificial neural networks

Mathematical models are widely used to simulate the behaviour of groundwater systems under various physical conditions. The development of these models requires that the system state evolution be predicted by solving appropriate governing equations. This also requires that the values of the parameters imbedded in the models be accurately determined. Since the hydraulic and water quality parameters are in general not directly measurable, their estimation must be obtained by solving the so called inverse parameter identification problem which amounts to determining the unknown physical parameters by fitting observed histories of the system states. In this paper we investigate the feasibility of solving the inverse problem by using artificial neural networks. These computational tools have the ability to learn complex input-output relationships and have a very advantageous property of generalization. To demonstrate the approach, a simple case study is considered consisting of an analytic model of contaminant transport due to a point source in stationary flow field. The model is used to simulate the behaviour of the groundwater systems for different values of the dispersion coefficient. A set of supervised, multilayered, feedforward neural networks are then trained to predict the values of the parameter corresponding to given concentration histories.

Strain effect on electronic and optical properties of GaN/AlGaN quantum-well lasers

In order to clarify the strain effect on the GaN-based lasers and to give the important guideline on their device design, the subband structure and the optical gains of strained wurtzite GaN/AlGaN quantum wells are theoretically investigated on the basis of k⋅p theory. First-principles band calculations are used for deriving the unknown physical parameters. It is found that neither compressive nor tensile biaxial strains in the c plane are so effective on the reduction of the threshold carrier density as conventional zinc-blende lasers and that the uniaxial strain in the c plane is very useful for reducing it. The relation between the uniaxial strain’s direction and the optical polarization is also clarified. As a result, we suggest that the uniaxial strain in the c plane is one of the preferable approaches for the efficient improvement of the GaN-based lasers performance.