bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Commercial Heat Setting on the Structure and Properties of Polyester Carpet Yarn
Authors: Cullerton D.L. , Ellison M.S. , Aspland J.R. 
Published: March 2007

Polyester carpet yarn is heat set during the production process in order to impart structural stability. Although batch (autoclave) and continuous (Superba TVP and Suessen GVA ) heat setting methods are used, the continuous processes are prevalent and constitute a greater part of this study. Commercial heat setting equipment and settings are used here because previous works were the results of laboratory studies. The primary technique applied in this study to determine the microstructural features of polyester is x-ray diffraction. Crystallization and crystallite melting temperatures from differential thermal analysis ( DTA ) and colorimetric determinations of initial rates of dyeing are also measured to provide additional data for interpreting the results, and tensile properties of the yarns are reported as well. X-ray and DTA results indicate no significant increases in the degree of crystallinity of yarns heat set by the Superba TVP method, while crystallinity increases with in creasing temperature for samples heat set by the Suessen GVA method. Crystal size increases for samples heat set by either of the continuous methods. Although x-ray determined crystallinity measures are significantly different at different levels of tem perature and dwell time, there are no significant differences in heat of fusion values obtained from DTA with changes in heat setting temperatures and dwell times. Te nacity, percent elongation, and work to break increase as a result of heat setting for samples set using the Superba TVP, autoclave, or Suessen GVA equipment, while the initial modulus decreases compared to a non-heat set sample.
Polyurea RIM-A Versatile High Performance Material
Authors: Grigsby R.A. , Dominguez R.J.G. 
Published: March 2007

Polyurethane elastomers were the first products to find wide commercial use in the RIM process. Recently, the advent of a new chain extender, diethyltolu enediamine (DETDA), provided another class of commercially useful RIM elas tomers. These materials are best classified as polyurethane/urea elastomers. We have been working on the next logical step in this evolution: amine- terminated polyether resins with amine chain extenders. These are best classi fied as polyurea elastomers. Amine-terminated polyether resins, or polyether polyamines, can replace the polyol in a RIM formulation. These materials are much more reactive than pol yols, and their composition can be varied more easily than conventional RIM polyols. Thus, these products can be tailored to meet the performance require ments of a particular end use more easily than polyols. The use of amine-terminated polyether products in RIM applications brings a new dimension to the RIM process. Depending on the choice of amine termi nated polyether amine, one can formulate systems covering a broad range of properties from elastomeric materials to rigid materials. Elastomeric materials are made by having a small amount of hard segment in a block-copolymer in conjunction with a polyether diamine. These elasto meric materials can be more closely tailored to meet a specific physical prop erty by either adjusting the formulation or by adjusting the density of the polymer. Very rigid materials can also be made by increasing the amount of hard seg ment in the block-copolymer in conjunction with a polyether triamine. High levels of an aromatic diamine chain extender can be used with the polyether triamine.
Fracture Mechanism Study of Flake Glass Filled RIM Urethane Systems
Authors: Yang P.C. , Lee W.M. 
Published: March 2007

Impact resistance in reaction injection molding (RIM) polyurethanes is desired in automotive applications such as fascia and exterior body panels. In these applications, flake glass is usually added to control thermal expansion and contraction, which adversely affects the impact damage resistance of the composite. It is, therefore, important to investigate and understand the impact failure modes involved in the loss of this damage resistance. The present study examines the major mechanisms of fracture initiation under a variety of loading conditions. Four distinct modes of crack initiation, namely: (1) debonding at the glass/matrix interface, (2) tensile cracking in the matrix, (3) multiple glass breakages in the central region of glass flake, and (4) matrix cracking and fibrillation at the edge surface of glass flake, have been identified. These fracture modes are discussed with respect to existing elastic stress analysis theory involving short glass fiber. This fracture mechanism study is carried out with the aid of a model glass filled system. The failure modes in the model system are followed by optical microscopy. The results are then compared to a real system which is impact tested and studied by scanning electron microscopy.
High-Performance PUR Elastomers with Aromatic Diamines
Authors: Kleimann Helmut 
Published: March 2007

Solid polyurethane elastomers produced by the casting method are used mainly in technical applications. They bridge the gap between soft rubber grades and hard thermoplastics without losing their excellent elastomeric properties. Current sales and consumption figures confirm the excellent future prospects of these products. The elastomers are produced from modified isocyanates and crosslinking agents. Amine crosslinking agents play a particularly vital role here: they are largely responsible for the processing characteristics of the systems and deter mine many of the final properties of the end products. While looking for suitable amines, we discovered two aromatic diamines capable of either retarding or accelerating the reactivity of the systems. Various ways of formulating systems are demonstrated in the light of these characteristics, and the properties of the end products are discussed. New processing methods should permit cost-effective production and open up new fields of application.
The suggestibility of children in interview studies
Authors: Moston Stephen 
Published: March 2007

Eyewitness researchers have long argued that children's testimony is unreliable because of their excessive suggestibility. The present study is an examination of two factors thought to explain some of the apparent suggestibility of children: (1) the emphasis placed on giving a classifiable answer to every question asked; (2) the effects of repeated questioning within an interview. A total of 72 children, from three age groups (6, 8 and 10 years) was questioned about a staged event they had witnessed earlier. It was found that telling children that they could say 'Don't know' to questions increased the number of such responses, but with no effect on the overall proportion of correct or incorrect responses. Even subjects who had not been instructed in the use of this response were prepared to say 'Don't know' to the experimenter's questions. Repeated questioning resulted in a decrease in the number of correct responses given, but had no effect on the number of incorrect re sponses.
A. Supervised Correspondence Instruction as an Integral Part of the High School Program
Authors: Broady K.O. 
Published: March 2007

ASSUME now—on the basis of the evidence only partially presented in Chapter I—that we can safely assign a pupil to supervised correspondence study for certain purposes: that he will be well taught. What, then, are the administrative uses to which this good, new tool may be put? You have seen a few of them listed al ready, but in this chapter let's take a more detailed look at the possibilities that have revealed themselves.
The High School We Need
Authors: Wiles Kimball , Patterson Franklin 
Published: March 2007

UNIVERSAL education should be provided for all youth through the high-school years. The educational system should enable youth to secure the type of experiences which develop the personal, social, and vocational competencies needed in our society. Various community agencies should be available to serve the educational needs of youth. A suitable program should be provided by the secondary school for all youth assigned to it through the legal authority of the community. Each youth should be free to select his vocational goals and pursue an educational program leading to these goals.1
Analysis of Multifingered Hands
Authors: Kerr Jeffrey , Roth Bernard 
Published: March 2007

This paper discusses three fundamental problems relating to grasping and manipulating objects within an articulated, multifingered hand: determining how hard to squeeze an ob ject in order to ensure a secure grasp, determining the finger- joint motions required to produce a desired motion of the object, and determining the workspace of the hand. Squeezing the object, or the application of internal grasp forces, is reduced to a linear programming problem which considers friction and joint torque limit constraints. The relationship between the finger-joint motions and the motion of the object, for the case of pure rolling between the finger tips and the object, is formulated as a set of differential equa tions. The total workspace for a hand is determinedfor spe cial cases of planar and spatial hands.
Manipulator Inverse Kinematics for Untimed End-Effector Trajectories With Ordinary Singularities
Authors: Kieffer Jon 
Published: March 2007

This article addresses the following inverse kinematics problem: given an untimed spatial end-effector trajectory, determine joint trajectories that are consistent with its execution. An algorithm for the continuous iterative solution of this problem for six-degree-of-freedom manipulators of arbitrary structure is presented. The main idea of this algorithm is that it converges with equal ease at both regular configurations and certain ( "or dinary ") singularities. Ordinary singularities (herein defined) depend on the given end-effector trajectory, as well as the ma nipulator configuration, and represent "dead points" where the end effector (but not the manipulator) must pause during trajectory execution. The algorithm is based on the predictor-corrector method of path following using (1) a newly developed second-order predictor, (2) a first-order Newton method corrector, and (3) the idea of including the end effector's position (along its trajec tory) as a dependent (rather than independent) variable in the formulation. Both the predictor and the corrector are derived from Taylor series expansion of the 4 x 4 matrix equation of closure and require only the solution of linear systems of equations. Examples are given that demonstrate the algorithm's ability to pass through ordinary singularities to determine alternate joint trajectories for the same end-effector trajectory. These examples also show how ordinary singularities can be included in manipulator motions that are similar to a boxer's jab or a runner's kick.
Self-Tuning Control of a Two-Link Manipulator With a Flexible Forearm
Authors: Koivo A.J. , Lee K.S. 
Published: March 2007

The control of the motion of a two-link manipulator with a flex ible forearm is studied. The first link is rigid, and the second link has a flexible part as an extension of a rigid part. The motion of the manipulator takes place on a horizontal plane. The dynamics of the two-link manipulator with a flexible fore arm are determined in Lagrange's formulation. The positions of specified points on the flexible forearm are obtained from the strain gauge measurements and the positions of the joint vari ables. The inputs are applied to the actuators of the revolute first joint and the prismatic link. For the controller design, a time series multivariate model of the autoregressive exogenous (ARX) type is used to describe the input/output relation. The discounted least squares method is used to estimate the parameters of the time series model. A self-tuning controller is so designed that the positions of the specified points on the flexible forearm track the given trajectory points. The controller operates on the Cartesian coordinates, which specify the positions of the chosen points on the flexible forearm. Simulation results as well as laboratory experiments on a Stanford/JPL arm controlled by a self-tuning controller are presented to illustrate the approach.
Randomization in Robot Tasks
Authors: Erdmann Michael 
Published: March 2007

This article explores the role of randomization in the solution of robot manipulation tasks. Randomization refers to the ran dom selection and execution of an action from a collection of possible actions. The intention is that this collection contains some actions that are useful for making progress toward ac complishing a task, but that the precise identity of these useful actions is unknown. Randomization offers one approach for ensuring progress in a probabilistic sense. An example of randomization is given by the strategy of shaking a bin containing a part in order to orient the part in a desired stable state with some high probability. Another exam ple consists of using reliable sensory information to bring two parts close together, then relying on short random motions to actually mate the two parts once the part motions lie below the available sensing resolution. Further examples include tapping parts that are tightly wedged, twirling gears before trying to mesh them, and vibrating parts to facilitate a mating operation. Randomization is also useful for mobile robot navigation and as a means of guiding the design process. Randomization is useful in three basic ways. First, random ization can increase the class of solvable tasks. This is because a randomized strategy need not guarantee task success with certainty in a specific number of steps, relying instead on re peated execution of the randomizing actions to accomplish the task in an expected sense. Second. randomization can reduce a strategy's knowledge requirements. This is because randomiza tion can tolerate and circumvent local failures, thereby making a strategy less sensitive to task details. Third, randomization can simplify the planning and execution process. This is be cause a randomized solution may be able to ignore precise prediction of special case scenarios, instead simply ensuring eventual accomplishment of the task independent of the actual scenarios encountered.
Two-Handed Assembly Sequencing
Authors: Wilson Randall H. , Kavraki Lydia , Latombe Jean-Claude , Lozano-Pérez Tomás 
Published: March 2007

This article considers the computational complexity of automat ically determining assembly sequences for mechanical products. Specifically, we address the partitioning problem: given an assembly of rigid parts, identify a proper subassembly that can be removed as a rigid object without disturbing the rest of the assembly. We examine the complexity of the partition ing problem under various types of relative motions allowed for the subassemblies. We show that when arbitrary motions are allowed to separate the two subassemblies, partitioning is NP-complete. We then describe a general framework for reasoning about assembly motions called the interference diagram. In its most general form the interference diagram yields an exponential- time algorithm to partition an assembly. However, two special cases of the interference diagram studied in this article yield polynomial-time sequencing algorithms. The first case occurs when assembly motions are restricted to single translations. The second case considers infinitesimal rigid motions in translation and rotation and yields a superset of all feasible partitionings. These two algorithms have important practical applications in assembly planning.
Stabilization of Flexible One-Link Arm Position: Stability Domains in the Space of Feedback Gains
Authors: Formal'sky A.M. , Lavrovsky E.K. 
Published: March 2007

A one-link flexible arm with a load at the end is considered. The arm can be rotated around its hub in a horizontal plane. This rotation is actuated by a DC motor. The dynamics of a controlled flexible arm are described by an infinite-dimensional mathematical model, which contains the Bernoulli-Euler beam equation, equations of the actuator motion and boundary con ditions. The control voltage fed to the motor is a linear com bination of arm angular position, integral, rotation speed, arm deformations, tip position, and velocity. The principal goal of the article is to find linear feedback gains such that the desired arm position is asymptotically sta ble. This problem of stability arises when an elastic manipula tor is designed. We have analytically described the boundaries of the domains of asymptotic stability in the space of feedback gains and constructed these domains in different cases. It is shown that the stability domains for a flexible arm belong to and are less than the corresponding domains for a rigid arm. We have shown that under feedback on tip position and veloc ity, the one-link flexible manipulator is unstable if damping is small.
Quantitative Evaluation of the Exploration Strategies of a Mobile Robot
Authors: Lee David , Recce Michael 
Published: March 2007

This article describes an experimental investigation into the map-building and exploration capabilities of a mobile robot. Two types of map are used: a set of line and point features, and a grid-based free-space map. Potential features are ex tracted from sonar range readings and classed as "confirmed" if detected repeatedly. The free-space map is derived from the set of confirmed features. A distance-transform algorithm is then used to plan paths on this map. The confirmed features are used by a Kalman filter to estimate the robot's position relative to known objects. This research places exceptional stress on the need for practical experimentation and quantitative, statistical evaluation of the results. For this to be possible, it is essential to have a clearly defined measure of map quality. A novel metric is defined that predicts the effectiveness of the robot if it were to use the map to execute a set of test tasks. Exploration strategies are tested experimentally in a range of environments and starting positions. The results are eval uated and compared statistically. The tested strategies range from those that are totally reactive, such as wall-following, to those that use the developing map to focus attention on the un examined parts of the environment. The most promising results are observed from hybrid exploration strategies that combine the robustness of reactive navigation and the directive power of map-based strategies.
Forward Dynamics, Elimination Methods, and Formulation Stiffness in Robot Simulation
Authors: Ascher Uri M. , Pai Dinesh K. , Cloutier Benoit P. 
Published: March 2007

The numerical simulation problem of tree-structured multi body systems, such as robot manipulators, is usually treated as two separate problems: 1) the forward dynamics problem for computing system accelerations, and 2) the numerical integra tion problem for advancing the state in time. The interaction of these two problems can be important, and has led to new conclusions about the overall efficiency of multibody simula tion algorithms (Cloutier, Pai, and Ascher 1995). In particular, the fastest forward dynamics methods are not necessarily the most numerically stable, and in ill-conditioned cases may slow down popular adaptive step-size integration methods. This phenomenon is called formulation stiffness. In this article, we first unify the derivation of both the com posite rigid-body method (Walker and Orin 1982) and the articulated-body method (Featherstone 1983, 1987) as two elimination methods for solving the same linear system, with the articulated-body method taking advantage of sparsity. Then the numerical instability phenomenon for the composite rigid- body method is explained as a cancellation error that can be avoided, or at least minimized, when using an appropriate version of the articulated-body method. Specifically, we show that a variant of the articulated-body method is better suited to deal with certain types of ill-conditioning than the composite rigid-body method. The unified derivation also clarifies the un derlying linear algebra of forward dynamics algorithms, and is therefore of interest in its own right.
Dispatch I. Amongst 'Our Selves'
Authors: Silverman Marilyn 
Published: March 2007

Dispatches is a Critique forum where contributors can comment on issues which do not necessarily fall within the scope of a scholarly article. The first Dispatch in this issue concerns hiring practices; the second concerns ethnocidal practices. Both are awkward pieces, the first revealing the drab—if still compelling—politics of recruitment and reproduction of the anthropological workforce; it also shows distress ingly clearly the kind of manipulation of ethnic stereotypes which anthro pologists frequently claim as one of the main objects of their critical ire. The second dispatch reveals some of the realpolitik aspects of 'research in exotic places', in this case the State's alliance with private mining enterprise in convincing Indian groups that their interests are best represented by a cynical and criminal fraternity. We encourage readers to avail themselves of the Dispatches section of Critique.
Domesticity, Feminism, and Friendship: Female Aristocratic Culture and Marriage in England, 1660-1760
Authors: Brown Irene Q. 
Published: March 2007

Domesticity, the careful, self-conscious cultivation of affection and mutuality in the family, has usuallv been recognized only in its Victorian and sub sequent modes. This essay identifies an earlier Enlightenment form of domesticity, based on rational friendship, the equal capacity for reason in both sexes, and a dis tinctive view of death and Christian spirituality. Focusing on English aristocratic widows, the author explores rational friendship and its corollaries—the legitimacy of marriage refusal, socially unequal intermar riage, and the single life. She introduces a new paradigm of sociality and sexuality, and interprets some demographic changes and issues of family affect. She concludes that rational domesticity promoted emotional interdependence beyond the nuclear family, especially among siblings, but also among other kin and non kin. Enlightenment domesticity had a far-reaching effect on family culture in a modernizing society because of its emphasis on reason, choice, egalitarian moral responsibility, and hetersocial as well as homosocial friendships.
Assessment of Cigarettes of Reduced Ignition Power and Their Role to Reduce Fire Risks of Upholstered Seating, Mattresses, and Bed Assembies
Authors: Paul K.T. 
Published: March 2007

In the UK, the flammability of domestic upholstered furniture is regulated by a cigarette composite test and flame ignition tests for components. In the USA, cigarettes of reduced ignition power have been suggested as a means of complementing the voluntary UFAC Code for cigarette resistant seating. This type of cigarette may be defined by the NIST mock-up and cigarette smouldering propensity tests that were developed from empirical correlations with seating tests. The NIST tests have been criticised by the Cigarette Ignition Propensity Joint Venture, (CIPJV, see note) which examined the effect of variations of con ditions and materials on results. Part 1 of this paper deals with the determination of the ignition power of se lected commercial cigarettes that included popular and slender filter-tipped cigarettes and the untipped cigarettes used for standard tests. Part 2 deals with the cigarette testing of seating, Part 3 with mattresses, Part 4 with bed assem blies, and Part 5 assesses the role of cigarettes of reduced ignition power in re ducing the fire risks of upholstery composites.