bluuebunny/crossref_metadata_2025 huggingface dataset:
Administrative reform in Jamaica: A component of structural adjustment
Authors: Kitchen Richard
Published: July 2007

Jamaica is currently undergoing a major innovative administrative reform programme (ARP). The impetus for the ARP stems from the realization that weak public administration (as prevailed in Jamaica) is a major obstacle to the implementation of economic reforms. The ARP thus became a significant plank of the World Bank's structural adjustment lending to Jamaica. The Jamaican programme is probably the leading and most ambitious attempt at administrative reform in the Third World, and the experiences and lessons learnt can be applied to the many developing countries which are contemplating or implementing similar programmes. The Jamaican experience indicates that the most important ingredients for success are political commitment at the highest level, a determined external agency, a carefully designed but flexible participatory programme which learns as it progresses, and good communication of the reform proposals. Administrative reform is a long‐term process, and it would be dangerous to pitch expectations too high.
Effect of rubbers on the flame retardancy of EVA/ultrafine fully vulcanized powdered rubber/nanomagnesium hydroxide ternary composites
Authors: Gui Hua , Zhang Xiaohong , Dong Weifu , Gao Jianming , Song Zhihai , Lai Jinmei , Liu Yiqun , Huang Fan , Qiao Jinliang , Wang Qingguo
Published: July 2007

Two flame retardant ternary composites of ethylene‐vinyl acetate copolymer (EVA)/ultrafine fully vulcanized powdered rubber (UFPR)/nanomagnesium hydroxide (MH) were studied in this article. It has been found that carboxyl acrylonitrile butadiene UFPR (CNB‐UFPR) and acrylonitrile butadiene UFPR (NB‐UFPR) have different effect on the flame retardancy of related materials when they are used together with nano‐MH. CNB‐UFPR is in favor of lowering the material's heat release rate during its combustion, while NB‐UFPR benefits the material on the resistance to ignition. Observation on the microstructure of the composites by transmission electron micrograph revealed that the aforementioned two ternary composites have quite different morphology. EVA/CNB‐UFPR/nano‐MH composite exhibits partial encapsulation structure, while EVA/NB‐UFPR/nano‐MH composite has full separation structure. POLYM. COMPOS., 28:479–483, 2007. © 2007 Society of Plastics Engineers
Synthesis and asymmetric polymerization of (S)‐N‐maleoyl‐L‐leucine propargyl ester
Authors: Gao Huajing , Isobe Yukio , Onimura Kenjiro , Oishi Tsutomu
Published: July 2007

A kind of N‐substituted maleimide (RMI), chiral (S)‐N‐maleoyl‐L‐leucine propargyl ester ((S)‐PLMI) with a specific rotation of [α]435 = −27.5° was successfully synthesized from maleic anhydride, L‐leucine, and propargyl alcohol. (S)‐PLMI was polymerized by three polymerization methods to obtain the corresponding optically active polymers. Asymmetric anionic, radical, and transition‐metal‐catalyzed polymerizations were carried out using organometal/chiral ligands, 2,2′‐azobisisobutyronitrile (AIBN) and (bicyclo [2,2,1]hepta‐2,5‐diene) chloro rhodium (I) dimer ([Rh(nbd) Cl]2), respectively. Poly((S)‐PLMI) obtained by [Rh(nbd)Cl]2 in DMF showed the highest specific rotation of −280.6°. Chiroptical properties and structures of the polymers obtained were investigated by GPC, CD, IR, and NMR measurements. Two types of poly((S)‐PLMI)‐bonded‐silica gels as the chiral stationary phase (CSP) were prepared for high‐performance liquid chromatography (HPLC). Their optical resolution abilities were also elucidated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3722–3738, 2007
Kinetics of radical copolymerization of [1‐(fluoromethyl)vinyl]benzene with chlorotrifluoroethylene
Authors: Kostov G. , Tredwell M. , Gouverneur V. , Ameduri B.
Published: July 2007

The synthesis of [1‐(fluoromethyl)vinyl]benzene (or α‐(fluoromethyl)styrene, FMB) and its radical copolymerization with chlorotrifluorethylene (CTFE), initiated by tert‐butyl peroxypivalate (TBPPi) are presented. The allyl monomer [H2C = C(CH2F)C6H5] was obtained by electrophilic fluorodesilylation of trimethyl(2‐phenylprop‐2‐en‐1‐yl)silane in 93% yield. A series of seven copolymerization reactions were carried out starting from initial [CTFE]0/([FMB]0 + [CTFE]0) molar ratios ranging from 19.6 to 90.0 mol %. The molar compositions of the obtained poly(CTFE‐co‐FMB) copolymers were assessed by means of 19F nuclear magnetic resonance spectroscopy. Statistic copolymers were produced with molar masses ranging between 13,800 and 25,600 g/mol. From the Kelen and Tudos method, the kinetics of the copolymerization led to the determination of the reactivity ratios, ri, of both comonomers (rCTFE = 0.4 ± 0.2 and rFMB = 3.7 ± 1.8 at 74 °C) showing that FMB is more reactive than CTFE as well as other halogenated or nonhalogenated monomers involved in the radical copolymerization with CTFE. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3843–3850, 2007
Substance P analogs containing α,α‐dialkylated amino acids with potent anticancer activity
Authors: Prasad Sudhanand , Mathur Archna , Jaggi Manu , Singh Anu T. , Mukherjee Rama
Published: July 2007

Six analogs (peptides 1–6) of the potent substance P (SP) derivative known as ‘Antagonist D’ were synthesized by substituting constrained amino acids Aib or Acp (cycloleucine, 1‐amino cyclopentane carboxylic acid) at different positions in the Antagonist D sequence: D‐Arg1‐Pro2‐Lys3‐Pro4‐D‐Phe5‐Gln6‐D‐Trp7‐Phe8‐D‐Trp9‐Leu10‐Leu11‐NH2. In the preliminary in vitro antiproliferative screening of the analogs on different human cancer cell lines by 3–(4,5–dimethylthiazol–2–yl)–2,5–diphenyltetrazolium bromide (MTT) assay, peptide 1 was found to be the most active. Further, peptide 1 was butanoylated (analog 5) or octanoylated (analog 6) at the N‐terminus. SP analogs 1, 5, and 6 were evaluated in vivo in a xenograft model of human primary colon tumor (PTC) cell line in athymic nude mice and were found to cause tumor regression. This study investigates if the use of the constrained amino acids Aib and Acp in the designed SP analogs can retain the in vitro and in vivo anticancer activities, which could be useful in cancer therapy and drug targeting. Further, the strategy of incorporation of Aib or Acp in biologically active peptides can be exploited in determining the receptor‐bound conformation and in transforming these bioactive peptides into pharmacologically useful drugs. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.
First‐ and second order Raman scattering in Sb and Bi at high pressure
Authors: Olijnyk H. , Nakano S. , Takemura K.
Published: July 2007

Sb and Bi were investigated by high‐pressure Raman spectroscopy in their low pressure phases. One‐ and two‐phonon spectra were measured in the stability field of the A7 structure. The optical zone‐centre modes of monoclinic Bi‐II were obtained for the first time and have been monitored over an extended pressure range. The pressure response of the observed phonon modes, which is qualitatively similar for both substances, is discussed within the context of the anisotropic bonding properties and their gradual lowering under compression. At ambient conditions in both substances the contributions to the temperature shift of both Raman modes due to thermal expansion are much smaller than the explicit contributions. In contrast to Bi‐I, there is evidence that in Sb‐I both phonon–phonon‐ and electron–phonon interactions significantly increase with the application of pressure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Area selective growth of GaAs by migration‐enhanced epitaxy
Authors: Horikoshi Y. , Uehara T. , Iwai T. , Yoshiba I.
Published: July 2007

Application of migration‐enhanced deposition sequence to area selective growth of GaAs and other III–V compound semiconductors makes it possible to achieve well‐defined area selective growth even using solid source molecular beam epitaxy. Successful growth of small disks and other structures has been performed on SiO2 masked (111)A and (111)B substrates at temperatures around 590 °C. General rule for facets formation suggests that the facet angle is quite sensitive to the V/III flax ratio as well as the substrate orientation. To create vertical $ \bar 1 $ facets around the structures at relatively low V/III flux ratios, (111)A substrates is much more preferable to (111)B substrate. However, high density of hillocks emerges on the structures grown on (111)A substrate. It is found that the hillocks are caused by the stacking faults. The density of hillocks has been dramatically reduced by depositing As in the Ga deposition period. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Boson Green's functions treatment of three‐layer ferrimagnetic superlattice [Comment on “Magnon energy gap and the magnetically structural symmetry in a three‐layer ferrimagnetic superlattice”, phys. stat. sol. (b) 243, No. 8, 1983–1995 (2006)]
Authors: Kapor D. , Pantić M. , Škrinjar M. , Pavkov M. , Radošević S. , Rutonjski M.
Published: July 2007

A magnetic superlattice with three‐layer (plane) unit cell was treated within the boson formalism. The energies were derived using Green's functions formalism, and it is shown that previous calculations did not take into account the principal demand that excitation energies should be positive, so many previous conclusions should be re‐examined. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bonded semiconductor interfaces with twist and tilt rotation: TEM analysis supported by molecular dynamics structure modelling
Authors: Wilhelm T. , Kuhlmann V. , Scheerschmidt K.
Published: July 2007

Regular dislocation networks have been created by hydrophobic wafer direct bonding of (001) oriented Si wafers. The dislocation densities depend on the (arbitrary) rotational misorientation of the wafers in [001] (twist) and the miscut (tilt). The interfaces have been studied by transmission electron microscopy. Additionally, molecular dynamics simulations have been used to study the system. The simulation of arbitrary angles and multiple misorientations prevents the use of periodic boundary conditions and necessitates the calculation of large cells with up to 500 000 atoms. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preface: phys. stat. sol. (c) 4/8
Authors: Leipner Hartmut S. , Kittler Martin
Published: July 2007

This issue of physica status solidi – Proceedings contains papers presented as oral and poster contribu‐tions at the International Conference on Extended Defects in Semiconductors (EDS 2006) held in Halle, Germany, on 17–22 September 2006. The event was organized by the Martin‐Luther‐Universität Halle–Wittenberg, the Max‐Planck‐Institut für Mikrostrukturphysik Halle, and the Fraunhofer‐Institut für Werkstoffmechanik Halle. The EDS conference series was inaugurated in Hünfeld (Germany) and followed by conferences in Poland, France, Great Britain, Germany, and Russia. The EDS 2006 is the direct follower of the conferences of 2002 held in Bologna (Italy) and 2004 in Chernogolovka (Russia). Although there were some difficulties in numbering the EDS conferences, we followed the scheme in‐troduced at the conference in Brighton 2000 and define our meeting as EDS13. In order to appreciate the 1200th anniversary of the city of Halle in 2006, we selected the famous five towers of the market square as the conference logo. The dislocation expert, however, will recognize a dislocation line, pinned by glide obstacles.

The aim of the conference was to provide a forum on the current state of art of investigation and modeling of extended defects in semiconductors in order to achieve a deeper understanding of lattice imperfections, their interaction, and their role in the development of semiconductor technology. The following main topics were covered: Structure of defects, defect imaging, structure modelling, electronic structure of extended defects, mechanical properties and dislocation dynamics, interaction between different kinds of defects, structure of strained layers, compliant substrates, wafer bonding, defects in thin films and interfaces, interface structures, role of extended defects in devices, utilizing of defects for devices, wide band gap materials (SiC, diamond, ZnO, III–V nitrides), defects in solar cell materials and photovoltaic devices, embedded semiconductor nanoparticles, and quantum‐dot‐like “extended defects”.

As a new topic, we introduced a crossover between extended defects and nanostructures in semiconductors. We think that the comparison of experiments and the theoretical description of extended defects and nanostructures in semiconductors may give exciting new insights into the understanding of dimensionally confined systems in general. This approach will certainly be extended in the next EDS conference to be held in Poitiers, France, in 2008.

We dedicate this proceedings volume to our friend and colleague Jürgen Schreiber, who suddenly passed away during the preparation of this conference. His cathodoluminescence studies on dislocations in semiconductors will be a lasting contribution to the defect community.

Halle, January 2007
Graphical weibull analysis of repairable systems
Authors: Hurtler Gisela
Published: July 2007

A graphical method is given for the analysis of repairable systems failing according to a Weilbull process. The integrated hazard rate is plotted in a logarithmic co‐ordinate system. If the process is of Weibull type the observed data will be located around a straight line. The plot provides estimates of the parameters. The graphical procedure is completed by confidence bands and variation bands built either around the observed failure numbers at fixed time or vice versa.
Reliability analysis techniques for mechanical systems
Authors: Bernstein N.
Published: July 2007

This paper discusses the application of known system reliability analysis techniques and identifies problems encountered in the practical implementation of these methods, revealing that no single technique is sufficient or even feasible in the case of complex mechanical systems. A new functional analysis method as well as a (new) criticality quantitative approach and failure mechanism analysis are presented and used to analyse an aircraft fuel system. A rigorous and detailed FMECA is still required. Besides its main function it will supply much of the valuable information for many other techniques.
How pulsed operation affects aluminium bond wires
Authors: Fredriksson Gunnel
Published: July 2007

Aluminium bond wires are exposed to pulsed current with varying duty cycles, pulse widths and current amplitudes. How these parameters influence the temperature rise in the wire and what it takes to damage or break it are studied. There are two possible failure modes. One is burn‐out due to high current amplitude, the other is metallurgical flexure fatigue at the bond heel. Both failure modes are described. The thermal time constant of the wire is determined for different wire lengths. SEM studies of wires during pulsing are made to see structural changes in the wire when it heats. The bond wire may suffer from damage, which affects the reliability, but it may still function electrically.
Production reliability in flexible manufacturing systems
Authors: Khodabandehloo K. , Sayles R. S.
Published: July 2007

A typical flexible manufacturing system, Westland Helicopters' sheet metal detail manufacturing complex, has been analysed for reliability. The techniques of fault tree analysis and event tree analysis are presented and their applicability to this study investigated. Event tree analysis has been found to be a more effective method for analysing manufacturing systems. The failure states of the system have been identified from the construction of an event tree which considers random hardware faults that influence production. Failure rate data have been used to quantify the critical production failure states in terms of machine failures. Estimates are made of the system's MTTF and percentage availability using typical MTTR figures. The probability that a selected production route fails to complete the manufacture of a set of parts is also evaluated. A dependency of systems reliability on the production demand has been discovered, and a possible method for modelling and assessing the reliability of systems capable of producing several products is proposed.
Optimization of product and process design for quality and cost
Authors: Phadke M. S. , Dehnad K.
Published: July 2007

Robust product and process design is an important technique for achieving high quality at low cost. It involves making the product's function much less sensitive to various sources of noise such as manufacturing variation, environmental variation and deterioration. This is a problem in optimization involving minimization of the mean square loss resulting from the deviation of the product's function from its target. Here we show that the optimization can be carried out in two steps: first maximize a quantity called signal‐to‐noise ratio (S/N) and then bring the performance on target by special adjustment parameters. The two‐step procedure works for a wide variety of product functions and makes the optimization process more efficient and practical compared to the direct minimization of the quadratic loss function.
High‐performance, low‐cost analog data processing and control using a 16‐bit single‐board microcomputer
Authors: Huang M. , Driels M.
Published: July 2007

In this article, the implementation of a microcomputer‐based control system using a low‐cost 16‐bit single‐board microcomputer combined with a general‐purpose data acquisition board is described. It is intended that this combination forms a suitable basis of a control system for the type of complex sensor systems currently associated with modern industrial robots. The technique of interfacing a 16‐bit microcomputer to a peripheral environment which has essentially an 8‐bit architecture is presented. The result is a high‐performance, low‐cost analog data processing and control system. A novel timing device with both software‐ and hardware‐configurable features has been developed so that an accurate interval timer for use with sample data systems is also available. To demonstrate the potential use of the system, an illustrative example of real‐time adaptive process control is described.
Nonadaptive dynamic control for manipulation robots: Centralized or decentralized control
Authors: Vukobratović Miomir , Stokić Dragan
Published: July 2007

Different concepts for dynamic control of manipulation robots are presented. Principles for the synthesis of optimal control, optimal regulator, “inverse problem” technique, force feedback, decoupled control, and decentralized control are considered. An attempt is made to provide a comparative analysis of all the stated control algorithms and to point out the advantage of decentralized control concept.
Generalized algorithm for computing the 4‐3‐4 N‐axis robotic trajectory
Authors: Shahinpoor M. , Abdel‐Rahman S. Z.
Published: July 2007

A generalized inversion technique and algorithm is presented for the purpose of computing the 9n coefficients pertaining to the three segments—i.e., liftoff, transitory, and setdown—of a motion trajectory of an n‐axis robot manipulator. The technique and the computer program presented is general enough to be immediately applicable to an n‐axis robot manipulator if only the desired initial and final position, velocity, acceleration, as well as the intermediate “via” positions are given. A number of examples are presented for a wide spectrum of these constraint conditions on the desired motion trajectories.
A generic multirobot control experimental system
Authors: Maimon Oded Z.
Published: July 2007

This article describes a generic experimental system that implemented the activity controller theory. The controller has the ability to coordinate any number of robots (and other automated machines) and to respond to the random arrival of components, so as to efficiently assemble various mixes of products. The work also briefly presents the structure of the coordination system, and a solution frame to the dynamic collision avoidance problem. The computer‐controlled experimental system is used to simultaneously operate two robots sharing tasks and auxiliary devices in an assembly cell.
Movement coordination for single‐track robot systems
Authors: Kim Chul E. , Langston Michael A.
Published: July 2007

We consider problems associated with the coordination of movement within a multiple‐robot system in which all motion is restricted to a single track. Our objective is to minimize the reconfiguration time, that is, the total time required to move a collection of robots from an initial to a goal configuration. We show that various models give rise to a wide range of problem complexities. For these problems we design and analyze optimization and approximation strategies.
Nonlinear repetitive control with application to trajectory control of manipulators
Authors: Omata Tohru , Hara Shinji , Nakano Michio
Published: July 2007

In this article, a new control scheme named repetitive control is proposed for a class of nonlinear systems described by x(t) = Ax(t) + Bu(t) + n(x(t)) and y(t) = Cx(t), in which the controlled variables follow periodic reference commands. The stability condition is derived by applying the passivity theorem. We show how to apply the repetitive control scheme to the trajectory control of a manipulator. A simple repetitive control scheme is developed for the trajectory control of a manipulator by using nonlinear compensation and feedbacks of position and velocity signals. Experimental results for a three link manipulator verify that the proposed repetitive control reduces the tracking error to a very low level.
Hypersurfaces of special configurations of serial manipulators and related concepts. part II: Passive joints, configurations, component manifolds and some applications
Authors: Soylu Resit , Duffy Joseph
Published: July 2007

In this article the novel concepts of passive/active joints, component/subcomponent manifolds of the HSC, configurations/subconfigurations and their applications are presented. The article also contains a theorem which predicts the existence of passive joints and a synthesis procedure for passive joints. The concepts introduced here and in Part I are illustrated by way of examples which include three existing industrial manipulators.
Interaction dynamics of multiple mobile robots with simple navigation strategies
Authors: Wang P. K. C.
Published: July 2007

The global dynamic behavior of multiple interacting autonomous mobile robots with simple navigation strategies is studied. Here, the effective spatial domain of each robot is taken to be a closed ball about its mass center. It is assumed that each robot has a specified cone of visibility such that interaction with other robots takes place only when they enter its visibility cone. Based on a particle model for the robots, various simple homing and collision‐avoidance navigation strategies are derived first. Then, an analysis of the dynamical behavior of the interacting robots in unbounded spatial domains is made. The article concludes with the results of computer simulation studies of two or more interacting robots.
A computationally efficient method for manipulator dynamic analysis
Authors: Song Shin‐Min , Lin Yueh‐Jaw
Published: July 2007

A computationally efficient method for manipulator dynamic analysis is presented. This method adopts two schemes to improve the computational efficiency. First, it takes the advantage of the following geometric feature of most manipulators: For the first three‐degree‐of‐freedom (DOF) mechanism (positioning mechanism), all the links are moving in a principal plane that is rotating about the base axis with respect to the ground. With this geometry, only three equations of motion per link, two equations for the forces in the principal plane and one equation for the moments which are perpendicular to the principal plane, are needed for the inverse dynamic analysis of the first three‐DOF motion. Thus, the number of equations can be reduced to half. Second, this method adopts longitudinal and transverse force components at certain joints in the formulation of equations of motion. This eliminates the need of a simultaneous solution of many equations, which is necessary in conventional Newton‐Euler method. Hence, this method is more computationally efficient than the many existing dynamic analysis methods. Two examples, one is closed‐chain type and the other is open‐chain type, are used as illustrations.
A simple and efficient computational approach for the forward dynamics of elastic robots
Authors: Serna Miguel Angel , Bayo Eduardo
Published: July 2007

A simple and efficient Lagrangian formulation is presented for the forward dynamic analysis of elastic robots. The proposed method formulates the equations of motion with respect to a floating frame that follows the rigid motion of the links. By virtue of the proposed formulation the constraint conditions are inserted in the Hamilton's principle by means of a penalty formulation rather than by the classical Lagrange's multiplier technique. As a consequence, the number of equations that define the behavior of the robot does not increase. The numerical implementation of the new method is very simple and always leads to the solution of positive definite matrices. A series of elastic robots are analyzed and the results demonstrate the capabilities of the new formulation for the forward dynamics.
Integrated distributed sensing and active vibration suppression of flexible manipulators using distributed piezoelectrics
Authors: Tzou H. S.
Published: July 2007

Structural oscillation of flexible robot manipulators would severely hamper their operation accuracy and precision. This article presents an integrated distributed sensor and active distributed vibration actuator design for elastic or flexible robot structures. The proposed distributed sensor and actuator is a layer, or multilayer of piezoelectric material directly attached on the flexible component needed to be monitored and controlled. The integrated piezoelectric sensor/actuator can monitor the oscillation as well as actively and directly constrain the undesirable oscillation of the flexible robot manipulators by direct/converse piezoelectric effects, respectively. A general theory on the distributed sensing and active vibration control using the piezoelectric elements is first proposed. An equivalent finite element formulation is also developed. A physical model with distributed sensor/actuator is tested in laboratory; and a finite element model with the piezoelectric actuator is simulated. The distributed sensing and control effectiveness are studied.
Kinematics of robot manipulators via line transformations
Authors: Kim Jung‐Ha , Kumar Vijay R.
Published: July 2007

Robot kinematics is an extensively researched subject and several well developed techniques for the analysis of robot manipulators and spatial mechanisms exist. Most of these methods are based on point transformations. However, far less research is in evidence for line transformations. Lines and screws are more fundamental to velocity analysis and hence line transformations are believed to be better suited for the kinematic and static analysis of manipulators. In this article, the kinematics for serial chain manipulators using line transformations is investigated. Dual number quaternions are used as spatial transformation operators since they allow compact representation of both rotations and translations. Further, the symbolic computation of the direct and inverse kinematics equations using dual number quaternions is described.
Nuclear sample management using a plutonium dissolution robotic system
Authors: Hollen Robert M.
Published: July 2007

At Los Alamos National Laboratory, a unique sample management robotic system has been developed that automates plutonium metal acid dissolutions, the aliquoting of resulting solutions to be analyzed using several analytical chemistry methods, and automates the barcode labeling of the solution containment vial providing positive solution identification. This system is based upon a commercial laboratory robot from Zymark, Inc. that has been enhanced by the addition of custom robotic workstations engineered and fabricated at our facility. This system will significantly reduce personnel radiation exposure and eliminate the redundancy of each analytical area producing separate dissolved plutonium solutions, which are used in chemical analyses.
Teleoperated equipment for emergency response applications at the savannah river site
Authors: Fogle Robert F. , Heckendorn Frank M.
Published: July 2007

The Robotics Development Group (RDG) of the Westinghouse Savannah River Company (WSRC) is developing an array of teleoperated vehicles and support equipment to be used in emergency response applications. Teleoperators have been used to monitor and map radiation areas, perform decontamination tasks, and handle radioactive material. Other possible scenarios include video surveillance, remote sensing, and fire fighting. The primary justification for developing teleoperated vehicles and support hardware is to eliminate or significantly reduce personnel exposure to radioactive or other hazardous activities. This article discusses past, present, and future applications that use teleoperated equipment and current development work on several mobile teleoperators at the U.S. Department of Energy's (DoE) Savannah River Site (SRS).
Applications of automated sampling systems in British nuclear reprocessing plants
Authors: Welch P. J.
Published: July 2007

This article describes the design and development of a fully automated sampling system currently entering service at the British Nuclear Fuels reprocessing complex at Sellafield in the United Kingdom. Novel features of the system are described and the benefits resulting from automation of the sampling system are highlighted.
Path feasibility and modification
Authors: Young Kuu‐Young , Wu Chi‐Haur
Published: July 2007

Kinematic feasibility of a planned robot path is restrained by the kinematic constraints of the robot executing the task, such as workspace, configuration, and singularity. Since these kinematic constraints can be described utilizing the geometry of the given robot, corresponding regions within the robot workspace can be expressed in geometrical representation. Consequently, geometric information can be derived from the planned path and the geometric boundaries of these regions. Then, by utilizing the geometric information and proper modification strategies, a Cartesian robot path that is kinematically infeasible can be modified according to different task requirements. To demonstrate the proposed feasibility and modification schemes, simulations for a 6R robot manipulator are executed.
Model for robot motion performance
Authors: Wygant Robert M. , White Bob E.
Published: July 2007

Experimental studies were conducted on the Prab Model E, General Electric P‐50, and Cincinnati T3 robots to develop a model to predict performance times for motions in the X, Y, and Z axes. Based on this analysis, it was determined that some robots have a definite point where the programmed velocity does not affect the time to move from one point to another.
Design of robust PD‐type control laws for robotic manipulators with parametric uncertainties
Authors: Shahruz S. M. , Langari G. , Tomizuka M.
Published: July 2007

In this article, design of a simple robust control law that achieves desired positions and orientations for robotic manipulators with parametric uncertainties is studied. A discontinuous control law is proposed, which consists of a high‐gain linear proportional plus derivative (PD) term and additional terms that compensate for the effect of gravitation. The stability of the robotic system under the proposed control law is proved by LaSalle's stability theorem. Furthermore, by the theory of singularly perturbed systems, it is shown that if the proportional and derivative gain matrices are diagonal with large positive elements then the system is decoupled into a set of first‐order linear systems. Simulation results are presented to illustrate the application of the proposed control law to a two‐link robotic manipulator.
Dynamic analysis and determination of the joint characteristics of parallel‐drive robot manipulators
Authors: Chen C. C. , Yeh M. K. , Sung C. K.
Published: July 2007

This article presents a theoretical and experimental study on structural dynamic response and determination of the joint characteristics of a five degree‐of‐freedom industrial robot manipulator with a parallel‐drive mechanism. The joints were modeled as a linear spring in parallel with a viscous damper while the link members were assumed to be rigid in this study. The dynamic equations of motion of the robot manipulator were derived using the principle of virtual work. Based on these equations, the complex structural characteristics of the manipulator were simplified by carefully arranging the manipulator in proper arm configurations to avoid coupling effects among joints. Hence, the joint stiffness and damping ratio of each joint were determined experimentally. Meanwhile, the dynamic responses of the robot manipulator were also investigated. Good correlation between computer simulations and experimental results was achieved. From the experimental study, an additional troublesome flexural mode of about 10 Hz that tends to dominate the whole dynamic response and influence the positioning accuracy of the manipulator was found due to the weakness of the structural member at the base rotation joint, which was not modeled in the dynamic equations. The results of this study will be useful in providing a basis for improving the design of mechanical components and the articulating members of industrial robot manipulators.
Path planning in the presence of obstacles based on task requirements
Authors: Wu Tzung‐Hsien , Young Kuu‐Young
Published: July 2007

We propose a novel and efficient scheme for planning a kinematically feasible path in the presence of obstacles according to task requirements. By employing geometrical analysis, we derive expressions to describe the relationship between the planned path, kinematic constraints, and obstacles in the robot workspace. The freedom available according to task requirements is then utilized to modify the infeasible portions of the planned path. We use a 6R (revolute) wrist‐partitioned type of robot manipulator and a spherical obstacle as a case study to demonstrate the proposed scheme. We then extend our results to general wrist‐partitioned types of robot manipulators and arbitrarily‐shaped or multiple obstacles. © 1994 John Wiley & Sons, Inc.
Efficient quadrature multichannel processor algorithms for MCD applications
Authors: Corden I. R. , Carrasco R. A.
Published: July 2007

The forthcoming third generation of satellites incorporating multichannel demodulator (MCD) processors, and the needs apparent within aviation systems, induce the requirement for efficient band processing algorithms with specific regard to the quadrature processing arrangement.

This paper presents a coherent z‐domain formulation of the pertinent digital transmultiplexer algorithms for the on‐board processing (OBP) scenario, with a view to establishing a set of desirable algorithmic properties suitable for the preferred complex oriented quadrature processing algorithms. Stemming from the principles set forth, an ensemble of new algorithms based upon mixes of Hilbert transforming and real transform algorithms is presented, wherein the established concepts relating to the telephone network transmultiplexer algorithms are able to be exploited in certain cases. Further, the computational load of one of the methods is lower than that of a known prominent OBP related technique. The computational necessities of the various algorithms are laid down for comparative purposes in addition to the mathematical descriptions.
On‐board baseband switch development using A high speed optical ring
Authors: Pontano B. A. , Redman W. A. , Inukai T. , Razdan R. , Paul D. K.
Published: July 2007

This paper presents work performed at COMSAT Laboratories to develop a prototype on‐board baseband switch. The switch design is modular to accommodate different service types, and the architecture features a high‐speed optical ring operating at 1 Gb/s to route input (up‐link) channels to output (down‐link) channels. The switch is inherently a packet switch, but can process either circuit‐switched or packet‐switched traffic. If the traffic arrives at the satellite in a circuit‐switched mode, the input processor packetizes it and passes it on to the switch. The main advantage of the packet approach lies in its simplified control structure. Details of the switch architecture and design, and the status of its implementation, are presented.
Efficient modulation techniques for satellite telemetry—receiver design and performance evaluation
Authors: Luise M. , Reggiannini R. , Vitetta G. M.
Published: July 2007

In this paper we address the design of the data demodulator for high‐efficiency satellite communications suited for telemetry applications. We choose Gaussian minimum shift keying as the modulation format and analyse its relative merits with respect to the more traditional filtered offset quadrature phase‐shift keying scheme, when applied to medium‐to‐high data rate telemetry. Our study encompasses both geostationary orbits and the more challenging low earth orbit scenarios, and investigates the acquisition and tracking performance of the receiver with the aid of computer simulations. In particular, we present design criteria leading to the development of efficient, low‐complexity schemes for symbol timing and carrier phase/frequency recovery and we analyse the impact of these synchronization algorithms on the system performance. Next, we discuss the demodulator performance degradation when the transmitted signal is passed through on‐board solid‐state or travelling‐wave‐tube power amplifiers. The paper is concluded by a comparative analysis of the above modulation schemes, with special emphasis on their power and spectral efficiency.
An assessment of the efficiency performance of linearization schemes in the Australian mobilesat system
Authors: Wilkinson T. A.
Published: July 2007

The efficiency of class C type amplifiers with digital predistortion linearizers is discussed. It is shown, by simulation with the AUSSAT MOBILESAT modulation schemes as examples, that the maximum efficiency from such a linearizer amplifier combination is significantly reduced for non‐constant envelope modulation schemes on that achievable with constant envelope schemes. This aspect is often neglected when linearizer performance with such amplifers is discussed. The results are generally applicable to Cartesian feedback linearization also.
Performance of a satellite modem transmitting convolutionally and differentially encoded 8PSK signals
Authors: Clark A. P. , Cheung S. W.
Published: July 2007

The paper studies a digital satellite modem for mobile systems. The modem transmits a convolutionally and differentially encoded eight‐phase‐shift‐keyed (CDE8PSK) signal over a satellite link and employs a near‐maximum‐likelihood decoder at the receiver. The signal can tolerate phase ambiguities that are multiples of 4 radians, which normally result from the carrier recovery loop at the receiver. However, the carrier recovery loop is not considered here. The high‐power amplifier (HPA) at the earth‐station transmitter may introduce non‐linear distortion to the CDE8PSK signal, and predistortion may or may not be used. Several different earth‐stations are assumed to have simultaneous access to a given transponder on the satellite, in an arrangement of frequency division multiple access, but the satellite transponder is assumed to be linear. Thus the CDE8PSK signals that occupy the immediately adjacent frequency bands can introduce adjacent‐channel interference (ACI) to the desired CDE8PSK signal. Extensive computer‐simulation tests have been carried out to evaluate the effects of non‐linear distortion with predistortion, in the presence of ACI, on the tolerance of the modem to additive white Gaussian noise. Four different bandwidths of the transmitted signal are considered, together with three different arrangements of the demodulator. The predistorter operates on the baseband signal at the input to the modulator and assumes a prior knowledge of the HPA characteristics. In all simulation tests, an equivalent baseband model of the transmission system is used, and the results are used to determine the preferred modem design.
The application of a bistatic intersystem interference model to radio systems co‐ordination and satellite systems optimization
Authors: McGuinness R.
Published: July 2007

This paper presents results from a new theoretical model to estimate bistatic rain scatter interference between terrestrial radio relay systems and earth‐satellite systems operating at the same frequency. The current model used by the CCIR was developed in the early 1970s when system packing density was low and the large earth‐station antennas allowed the consideration of narrow beam approximations. This resulted in a small common volume of intersection of the two beams and large circular contours. The recent increase in microwave communications traffic and the improvements in technology have meant that very small aperture terminals (VSATs) can be employed, and hence the model must allow for the consideration of sidelobes, low gain antennas and non‐uniform rain cells intersecting much larger common volumes. Aspects of the new model are discussed and different assumptions made by the CCIR model are examined. Results from the new model show that the contours are smaller and non‐circular and result in much smaller co‐ordination areas.
Improving FH and FH/PN spread spectrum communications through PN M‐ary phase sequences and signal editing
Authors: Ng W. H. , Ungar J. L.
Published: July 2007

Pseudo‐noise (PN) or direct sequence (DS) modulation, frequency hopping (FH) and their combination (i.e. the hybrid FH/PN approach) are common spread spectrum (SS) communications techniques used to achieve anti‐jamming (AJ) and/or low probability of intercept (LPI). This study investigates the following FH and FH/PN related issues: (i) derive and apply M‐ary phases of PN sequences to increase the AJ and transmission efficiency, (ii) use of erasure channel to reduce received errors and unreliable data, (iii) employ error correction coding and signal editing (SE) to improve communication surviv‐ability, and (iv) adopt surface acoustic wave (SAW) devices to simplify the synchronization procedure in PN correlation. A special example is also given to illustrate the potential AJ improvement when an SS communications system employs both concatenated coding and concatenated SE techniques.
A frequency scanning satellite system for land mobile communications
Authors: Russo P. , D'Ippolito A. , Ruggieri M. , Volpicella N. , Scialino G. , Vatta S. , Jones T.
Published: July 2007

A frequency scanning system for mobile applications has been assessed for a European mission at L‐band. Feasibility evaluations, electrical design and analysis have been performed for both the antenna and the entire repeater. Efforts have also been made to solve accommodation, thermal and mechanical problems, so as to demonstrate the actual feasibility of the frequency scanning concept in user‐oriented applications. The very promising results obtained are presented in this paper.
A multi‐carrier demodulator architecture for SMS/IBS
Authors: Barton S. K. , Al‐Jalili Y. O.
Published: July 2007

This paper describes a multi‐carrier demodulator (MCD) architecture which is capable of demodulating a mixture of signals of different data rates, such as are found in present day transparent transponders. No extra restrictions are placed on the signal transmission rates, bandwidths, channel spacings, frequency stabilities, independent timing, etc. beyond what is already specified by INTELSAT and EUTELSAT. The only exception to this is that no signal should straddle the centre frequency of the existing 72 MHz bandwidth transponders. The system is a refinement of the ‘frequency domain’ filtering approach described in References 7 and 8. The main improvement is in performing the symbol timing recovery in the frquency domain before converting to the time domain. This leads to reductions in computational complexity in both the timing recovery and the frequency to time conversion process. All of these functions can be performed by standard DSP processors. Only the initial time to frequency domain transform requires ASIC technology.
An engineering approach for site shielding calculations
Authors: Van Dooren G. A. J. , Herben M. H. A. J.
Published: July 2007

In this paper, two models to approximately calculate the field distribution in the vicinity of a perfectly conducting finite width screen are discussed. The first model is based on the geometrical theory of diffraction (GTD), and is simplified such that the magnitude of the individual ray contributions can be easily calculated. The second model is based on a graphical approach. Coefficients that are representative for the dimensions of the obstacle and the relative position of the observation point are used together with standardized equations to calculate the field strength in the shadow region behind the screen. Also a modification of the current CCIR procedure for knife‐edge diffraction is proposed, such that it can be applied to a finite width screen.

Results of all models are compared with more accurate and complex results from a model based on the uniform theory of diffraction (UTD). All models proposed are simple to apply and present an essential extension to currently available engineering models. It is found that the GTD model has the best performance with respect to the UTD approach. The graphical method, however, is more user friendly than the GTD model, because fewer intermediate results need to be calculated. Moreover, the use of this method yields a field‐strength distribution for the whole shadow region of the obstacle instead of the field at just a single point. Further, it is found that the modified CCIR approach can also be used with good accuracy.

The models discussed answer some questions formulated by the CCIR concerning site shielding, and extend the currently available engineering models for this interference reduction technique.
A co‐designed coding, modulation and equalization scheme for the transmission of 155‐52 Mbit/s data over a 72 MHz intelsat transponder. Part 2: Equalization
Authors: Peile R. E. , Rajput S. A. , Welch L. R.
Published: July 2007

This paper reports on the application of co‐designed coding, modulation and equalization techiques to an INTELSAT requirement for transmitting 155‐52 Mbit/s data over a 72 MHz satellite channel. A specific solution as regards coding, modulation and equalization is proposed and analysed that differs from ‘standard’ concatenation in that the inner decoder integrates equalization, modulation and coding. In Part 2, a novel technique for integrating decision feedback equalization into the inner decoder is described. The gains in integrating the coding and equalization are shown to be significant for channels that need equalizing.