bluuebunny/crossref_metadata_2025_split huggingface dataset:
APPROXIMATION PROPERTIES OF TP MODEL FORMS AND ITS CONSEQUENCES TO TPDC DESIGN FRAMEWORK
Authors: Tikk Domonkos , Baranyi Péter , Patton Ron J. 
Published: September 2010

ABSTRACTTensor Product Distributed Compensation (TPDC) is a recently established controller design framework, that links TP model transformation and Parallel Distributed Compensation (PDC) framework. TP model transformation converts different models to a common representational form: the TP model form. The primary aim of this paper is to investigate the approximation capabilities of TP model forms, because the universal applicability of TPDC framework strongly relies on it. We point out that the set of functions that can be approximated arbitrarily well by TP forms with bounded number of components lies no‐where dense in the set of continuous functions. Consequently, in a class of control problems this property necessitates the usage of tradeoff techniques between the accuracy and the complexity of the TP form, which is easily feasible within the TPDC framework unlike in analytic models.
ADAPTIVE FUZZY‐BASED MIXED H2/H∞ TRACKING CONTROL DESIGN IN UNCERTAIN ROBOTIC SYSTEMS
Authors: Tseng Chung‐Shi , Jan Rong‐Maw 
Published: September 2010

ABSTRACTIn this study, an adaptive fuzzy‐based mixed H2/H∞ tracking control design is developed in robotic systems under unknown or uncertain plant parameters and external disturbances. The mixed H2/H∞ control design has the advantage of both H2 optimal control performance and H∞ robust control performance and the fuzzy adaptive control scheme is used to compensate for the plant uncertainties. By virtue of the skew‐symmetric property in the robotic systems and adequate choice of state variable transformation, sufficient conditions are developed for the adaptive fuzzy‐based mixed H2/H∞ tracking control problems in terms of a pair of coupled algebraic equations instead of a pair of coupled differential equations. The proposed methods are simple and the coupled algebraic equations can be solved analytically. Simulation results indicate that the desired performance of the proposed adaptive fuzzy‐based mixed H2/H∞ tracking control schemes for the uncertain robotic systems can be achieved.
ANALYSIS AND DESIGN OF FEEDBACK CONTROL SYSTEMS WITH TRACKING ERRORS SQUARE
Authors: Tsay Tain‐Sou 
Published: September 2010

ABSTRACTIn this study, a command tracking error square control scheme is first proposed for analysis and design of feedback control systems. One of the tracking errors is low‐pass filtered and used in the feedback loop for gain adaptation; the other is used in the forward loop for command tracking control. The overall systems are nonlinear feedback systems, and can be reconfigured to an automatic gain control (AGC) loop with command tracking error input. The stability and robustness of the controlled systems are verified by time response, frequency response, and large parameter variation testing with a simple illustrating example and are finally applied to a complicated electro‐hydraulic velocity servo system with large load disturbance.
A ROBUST SENSOR FAULT TOLERANT CONTROL SCHEME IMPLEMENTED ON A CRANE
Authors: Tan Chee Pin , Edwards Christopher 
Published: September 2010

ABSTRACTThis paper presents a sensor fault tolerant control scheme applied to a crane system. Sensor faults affect the system's performance in the closed‐loop when the faulty sensor readings are used to generate the control input. In this paper, the measured outputs are separated into potentially faulty and nonfaulty components, and the latter are injected into a linear observer to reconstruct the faults. The reconstruction is subtracted from the faulty sensors to form a compensated ‘virtual sensor’ and this signal is then used to generate the control input. A design method for the observer is also presented in which the reconstruction signal is made as insensitive as possible to any uncertainties or nonlinearities present in the system. Good results have been obtained; with reduced performance degradation during faulty conditions.
DISCRETE‐TIME OBSERVER‐BASED OUTPUT TRACKING CONTROLLER DESIGN FOR NONMINIMUM PHASE SYSTEMS WITH PERTURBATIONS
Authors: Chang Jeang‐Lin 
Published: September 2010

ABSTRACTIn this paper, an observer‐based output tracking controller for an SISO nonminimum phase discrete‐time system is proposed. When the disturbances between two consecutive sampling instances do not vary significantly, the observer algorithm can simultaneously estimate the system states and the unknown perturbation, and can render the estimation errors of system states and perturbation constrained in a small bounded region. The control law, including a feedforward term and a feedback input, can make the tracking error constrained in a small bounded region with guaranteed system stability. A numerical example is presented to demonstrate the applicability of the proposed control scheme.
PARAMETRIC SOLUTIONS TO THE GENERALIZED SYLVESTER MATRIX EQUATION AX ‐ XF = BY AND THE REGULATOR EQUATION AX ‐ XF = BY + R
Authors: Zhou Bin , Duan Guang‐Ren 
Published: September 2010

ABSTRACTIn this paper, explicit parametric solutions to the generalized Sylvester matrix equation AX ‐ XF = BY and the regulator matrix equation AX ‐ XF = BY + R are proposed without any transformation and factorization. The proposed solutions are presented in terms of the Krylov matrix of matrix pair (A, B), a symmetric operator and the generalized observability matrix of matrix pair (Z, F) where Z is an arbitrary matrix and is used to denote the degree of freedom in the solution. Due to its elegant form and convenient computation, these proposed solutions will play an important role in solving and analyzing these types of equations in control systems theory.
Blood–brain‐barrier disruption in chronic canine hypothyroidism
Authors: Pancotto Theresa , Rossmeisl John H. , Panciera David L. , Zimmerman Kurt L. 
Published: September 2010

Background:Central nervous system (CNS) manifestations of hypothyroidism have been associated with cerebrovascular complications. Reports of cerebrospinal fluid (CSF) abnormalities are rare in hypothyroid dogs.Objective:The aim of this study was to determine if chronic hypothyroidism causes blood–brain‐barrier (BBB) abnormalities that are detectable using indirect CSF biomarkers.Methods:The study included 18 normal, euthyroid, female mixed‐breed dogs. Hypothyroidism was induced by131iodine administration in 9 dogs; 9 served as untreated controls. Evaluations included physical and neurologic examination, complete CSF analysis, serum and CSF protein electrophoresis, measurement of plasma vascular endothelial growth factor (VEGF) and serum S‐100B concentrations, and calculation of CSF albumin quota (AQ) and were conducted at baseline and 6, 12, and 18 months after induction of hypothyroidism. Data were analyzed using repeated measures ANOVA.Results:At baseline, differences between groups were not detected for any variable. Throughout the study, controls dogs remained free of neurologic disease and had test variables that remained within reference intervals. Two hypothyroid dogs developed CNS signs during the study, and evidence of cerebrovascular disease was found at necropsy. At 12 and 18 months, the CSF total protein, VEGF, S‐100B, and fractional albumin concentrations, and AQ were significantly higher (P<.04) in hypothyroid dogs than controls. Among test variables assayed in serum or plasma, the only significant difference was a higher S‐100B concentration in hypothyroid dogs (P=.003) at 18 months.Conclusions:BBB integrity is disrupted in chronic hypothyroidism. Significant increases in CSF concentrations of VEGF and S100‐B in hypothyroid dogs indicate dysfunction in both endothelial and glial elements of the BBB.
Classification, location and legitimacy of web-based suppliers of Viagra to the UK
Authors: Gallagher Cathal T , Chapman Laura E 
Published: September 2010

Abstract

Objectives
To categorise online suppliers of Viagra based on their legal status, and to quantify the suppliers within each category.

Methods
Google was used to search for websites offering to sell or supply either proprietary Viagra tablets or generic versions containing sildenafil citrate. Relevant websites were classified as falling into one of three categories, which were further subclassified. Simple descriptive statistics were calculated.

Key findings
The number of relevant sites found within the first 100 Google hits, following the removal of mirror and affiliate sites, was 44. Only 6.8% of sites identified were legitimate online pharmacies. Some 34.1% of sites offered to sell Viagra to patients in the UK without any form of medical consultation. Whether or not the online consultation offered by 59.1% of sites had to be completed in order to make a purchase could not be confirmed. The location of only three pharmacies could be ascertained; the remainder made various claims as to their location, which could not be verified.

Conclusions
We have been unable to verify that the questionnaires used for online consultations are scrutinised by any healthcare practitioners to determine the appropriateness of the treatment sought. This represents a serious safety concern for UK residents who procure drugs for erectile dysfunction on the internet.
Empirical beam hardening correction (EBHC) for CT
Authors: Kyriakou Yiannis , Meyer Esther , Prell Daniel , Kachelrieß Marc 
Published: September 2010

Purpose:Due to x‐ray beam polychromaticity and scattered radiation, attenuation measurements tend to be underestimated. Cupping and beam hardening artifacts become apparent in the reconstructed CT images. If only one material such as water, for example, is present, these artifacts can be reduced by precorrecting the rawdata. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to obtain new rawdata. Typically, the forward projection must correctly model the beam polychromaticity and account for all physical effects, including the energy dependence of the assumed materials in the patient, the detector response, and others. We propose a new algorithm that does not require any knowledge about spectra or attenuation coefficients and that does not need to be calibrated. The proposed method corrects beam hardening in single energy CT data.Methods:The onlya priori knowledge entering EBHC is the segmentation of the object into different materials. Materials other than water are segmented from the original image, e.g., by using simple thresholding. Then, a (monochromatic) forward projection of these other materials is performed. The measured rawdata and the forward projected material‐specific rawdata are monomially combined (e.g., multiplied or squared) and reconstructed to yield a set of correction volumes. These are then linearly combined and added to the original volume. The combination weights are determined to maximize the flatness of the new and corrected volume. EBHC is evaluated using data acquired with a modern cone‐beam dual‐source spiral CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany), with a modern dual‐source micro‐CT scanner (TomoScope Synergy Twin, CT Imaging GmbH, Erlangen, Germany), and with a modern C‐arm CT scanner (Axiom Artis dTA, Siemens Healthcare, Forchheim, Germany). A large variety of phantom, small animal, and patient data were used to demonstrate the data and system independence of EBHC.Results:Although no physics apart from the initial segmentation procedure enter the correction process, beam hardening artifacts were significantly reduced by EBHC. The image quality for clinical CT, micro‐CT, and C‐arm CT was highly improved. Only in the case of C‐arm CT, where high scatter levels and calibration errors occur, the relative improvement was smaller.Conclusions:The empirical beam hardening correction is an interesting alternative to conventional iterative higher order beam hardening correction algorithms. It does not tend to over‐ or undercorrect the data. Apart from the segmentation step, EBHC does not require assumptions on the spectra or on the type of material involved. Potentially, it can therefore be applied to any CT image.
Differentiation between diamagnetic and paramagnetic cerebral lesions based on magnetic susceptibility mapping
Authors: Schweser Ferdinand , Deistung Andreas , Lehr Berengar W. , Reichenbach Jürgen R. 
Published: September 2010

Purpose:Identification of calcifications and hemorrhages is essential for the etiological diagnosis of cerebral lesions. The purpose of this work was to develop a robust method for characterization of para‐ and diamagnetic intracerebral lesions based on clinical gradient‐echo magnetic resonance phase data acquired at 1.5 Tesla.Methods:The magnetic susceptibility distribution of biological tissue produces a distinct magnetic field pattern, which is directly reflected in gradient‐echo magnetic resonance phase images. Compared to brain parenchyma, iron‐laden tissues are more paramagnetic, whereas mineralized tissues usually possess more diamagnetic susceptibilities. Magnetic resonance phase data were inverted to the underlying susceptibility distribution utilizing additional geometrical information about the lesions, which was obtained from the gradient‐echo magnitude signal void corresponding to the lesions. Clinical magnetic resonance exams of three patients with multiple brain lesions (total ) were processed and evaluated. For one patient, the results were validated by an additionally available computed tomography scan. Numerical simulations were conducted to evaluate the robustness of the method.Results:The obtained susceptibility maps showed impressive delineation of lesions, vessels, and potentially iron‐laden tissue. Compensation of the nonlocal field perturbations was clearly discernable on the susceptibility maps. In all cases, discrimination of para‐ from diamagnetic lesions was achieved and the results were confirmed by the additional computed tomography. The numerical simulations demonstrated that robust determination of the total magnetic moment of lesions is possible. Thus, the proposed method is able to yield quantitative values for the minimum magnetic susceptibility of lesions.Conclusions:A method has been developed for noninvasive, semiautomatic characterization of brain lesions based on magnetic resonance imaging data. Initial clinical results demonstrated that the proposed technique can be applied to diagnosis of lesions with calcifications or hemorrhages. If confirmed by larger studies, it bears the potential to obviate the need for confirmation with computed tomography.
A new method to combine 3D reconstruction volumes for multiple parallel circular cone beam orbits
Authors: Baek Jongduk , Pelc Norbert J. 
Published: September 2010

Purpose:This article presents a new reconstruction method for 3D imaging using a multiple 360° circular orbit cone beam CT system, specifically a way to combine 3D volumes reconstructed with each orbit. The main goal is to improve the noise performance in the combined image while avoiding cone beam artifacts.Methods:The cone beam projection data of each orbit are reconstructed using the FDK algorithm. When at least a portion of the total volume can be reconstructed by more than one source, the proposed combination method combines these overlap regions using weighted averaging in frequency space. The local exactness and the noise performance of the combination method were tested with computer simulations of a Defrise phantom, aFORBILD head phantom, and uniform noise in the raw data.Results:A noiseless simulation showed that the local exactness of the reconstructed volume from the source with the smallest tilt angle was preserved in the combined image. A noise simulation demonstrated that the combination method improved the noise performance compared to a single orbit reconstruction.Conclusions:In CT systems which have overlap volumes that can be reconstructed with data from more than one orbit and in which the spatial frequency content of each reconstruction can be calculated, the proposed method offers improved noise performance while keeping the local exactness of data from the source with the smallest tilt angle.
Measuring output factors of small fields formed by collimator jaws and multileaf collimator using plastic scintillation detectors
Authors: Klein David M. , Tailor Ramesh C. , Archambault Louis , Wang Lilie , Therriault‐Proulx Francois , Beddar A. Sam 
Published: September 2010

Purpose:As the practice of using high‐energy photon beams to create therapeutic radiation fields of subcentimeter dimensions (as in intensity‐modulated radiotherapy or stereotactic radiosurgery) grows, so too does the need for accurate verification of beam output at these small fields in which standard practices of dose verification break down. This study investigates small‐field output factors measured using a small plastic scintillation detector (PSD), as well as aionization chamber. Specifically, output factors were measured with both detectors using small fields that were defined by either the X‐Y collimator jaws or the multileaf collimator (MLC).Methods:A PSD of 0.5 mm diameter and 2 mm length was irradiated with 6 and 18 MV linac beams. The PSD was positioned vertically at a source‐to‐axis distance of 100 cm, at 10 cm depth in a water phantom, and irradiated with fields ranging in size fromto. The field sizes were defined either by the collimator jaws alone or by a MLC alone. The MLC fields were constructed in two ways: with the closed leaves (i.e., those leaves that were not opened to define the square field) meeting at either the field center line or at a 4 cm offset from the center line. Scintillation light was recorded using a CCD camera and an estimation of error in the median‐filtered signals was made using the bootstrapping technique. Measurements were made using a CC01 ionization chamber under conditions identical to those used for the PSD.Results:Output factors measured by the PSD showed close agreement with those measured using the ionization chamber for field sizes ofand above. At smaller field sizes, the PSD obtained output factors as much as 15% higher than those found using the ionization chamber byjaw‐defined fields. Output factors measured with no offset of the closed MLC leaves were as much as 20% higher than those measured using a 4 cm leaf offset.Conclusions:The authors’ results suggest that PSDs provide a useful and possibly superior alternative to existing dosimetry systems for small fields, as they are inherently less susceptible to volume‐averaging and perturbation effects than larger, air‐filled ionization chambers. Therefore, PSDs may provide more accurate small‐field output factor determination, regardless of the collimation mechanism.
Hyperpolarized MRS surface coil: Design and signal‐to‐noise ratio estimation
Authors: Giovannetti Giulio , Frijia Francesca , Menichetti Luca , Milanesi Matteo , Ardenkjaer‐Larsen Jan Henrik , De Marchi Daniele , Hartwig Valentina , Positano Vincenzo , Landini Luigi , Lombardi Massimo , Santarelli Maria Filomena 
Published: September 2010

Purpose:Hyperpolarized carbon‐13 magnetic resonance spectroscopy is a novel and powerful tool for exploring the metabolic state of tissue, but a number of technological problems still limit this technology and need innovative solutions. In particular, the low molar concentration of derivate metabolites give rise to low signal‐to‐noise ratio (SNR), which makes the design and development of dedicated RF coils a task of fundamental importance. In this article, the authors describe the simulation and the design of a dedicated surface coil for cardiac metabolism assessment in pig models.Methods:A SNR model for a circular loop is presented and applied to the design of a coil which guarantees the desired field‐of‐view and provides high SNR with a good penetration in deep sample regions. The coil resistance was calculated from Ohm's law and the magnetic field pattern was calculated using Biot–Savart law, while the sample induced resistance was calculated using a numerical finite‐difference time‐domain algorithm. Successively, a prototype of the coil was built and tested on the workbench and by acquisition of MR data.Results:The comparison of SNR‐vs‐depth profiles between the theoretical SNR model and the experimental SNR extracted from the phantom chemical shift image (CSI) showed the accuracy of the authors’ model. Moreover, the authors demonstrated the use of the coil for the acquisition of a CSI of a hyperpolarized pyruvate phantom.Conclusions:The results demonstrated the design trade‐offs to successfully design a dedicated coil for cardiac imaging in the pig with hyperpolarized by developing a SNR model which allows the prediction of the coil performance. This approach can be employed for deriving SNR formulations for coil with more complex geometries.
EASY-HIT: HIV Full-Replication Technology for Broad Discovery of Multiple Classes of HIV Inhibitors
Authors: Kremb Stephan , Helfer Markus , Heller Werner , Hoffmann Dieter , Wolff Horst , Kleinschmidt Andrea , Cepok Sabine , Hemmer Bernhard , Durner Jörg , Brack-Werner Ruth 
Published: September 2010

ABSTRACT

HIV replication assays are important tools for HIV drug discovery efforts. Here, we present a full HIV replication system (EASY-HIT) for the identification and analysis of HIV inhibitors. This technology is based on adherently growing HIV-susceptible cells, with a stable fluorescent reporter gene activated by HIV Tat and Rev. A fluorescence-based assay was designed that measures HIV infection by two parameters relating to the early and the late phases of HIV replication, respectively. Validation of the assay with a panel of nine reference inhibitors yielded effective inhibitory concentrations consistent with published data and allowed discrimination between inhibitors of early and late phases of HIV replication. Finer resolution of the effects of reference drugs on different steps of HIV replication was achieved in secondary time-of-addition assays. The EASY-HIT assay yielded high
Z
′ scores (>0.9) and signal stabilities, confirming its robustness. Screening of the LOPAC
1280
library identified 10 compounds (0.8%), of which eight were known to inhibit HIV, validating the suitability of this assay for screening applications. Studies evaluating anti-HIV activities of natural products with the EASY-HIT technology led to the identification of three novel inhibitory compounds that apparently act at different steps of HIV-1 replication. Furthermore, we demonstrate successful evaluation of plant extracts for HIV-inhibitory activities, suggesting application of this technology for the surveillance of biological extracts with anti-HIV activities. We conclude that the EASY-HIT technology is a versatile tool for the discovery and characterization of HIV inhibitors.