bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel polylactide/vermiculite nanocomposites by in situ intercalative polymerization. I. Preparation, characterization, and properties
Authors: Zhang Jian Hua , Zhuang Wei , Zhang Qiang , Liu Baolei , Wang Wei , Hu Bai Xing , Shen Jian 
Published: July 2007

AbstractPolylactide (PLA)/vermiculite nanocomposites were prepared by in situ intercalative polymerization of L,L‐lactide (LLA) in the presence of organomodified vermiculite (VMT). The d‐spacings of both the organomodified VMT and the exfoliated nanocomposites were investigated by X‐ray diffraction (XRD) analysis, and the morphology of exfoliated nanocomposites was examined by transmission electron microscopy (TEM). Thermogravimetric analysis (TGA) indicated that there is some enhancement in degradation behavior between the nanocomposites and the PLA matrix. Dynamic mechanical analysis (DMA) confirmed the constraint effect of exfoliated VMT layers on PLA chains, which is beneficial to the increased storage and loss modulus and increased glass transition temperature. The tensile strength showed that the exfoliated nanocomposites are reinforced and toughened by the addition of nanometer‐size vermiculite layers. POLYM. COMPOS., 28:545–550, 2007. © 2007 Society of Plastics Engineers
Effect of matrix molecular weight on the dispersion of nanoclay in unmodified high density polyethylene
Authors: Chu David , Nguyen Quang , Baird Donald G. 
Published: July 2007

AbstractThe effect that polymer molecular weight has on the dispersion of relatively polar montmorillonite (MMT) in nonpolar, unmodified high density polyethylene (HDPE) was examined. Polymer layered silicate (PLS) nanocomposites were prepared via melt compounding in a single screw extruder using three unmodified HDPE matrices of differing molecular weight and organically modified MMT (organoclay) in concentrations ranging from 2 to 8 wt%. The weight average molecular weights (MW) of the HDPE matrices used ranged from 87,000 to 460,000 g/mol. X‐ray diffraction (XRD), tensile testing, dynamic mechanical thermal analysis (DMTA), and dynamic rheometry were performed on these nanocomposites. Nanocomposites generated from the high molecular weight (HMW) HDPE matrix exhibited increased intercalation of the MMT as shown by XRD and greater improvements in the Young's modulus when compared with nanocomposites generated from the low (LMW) and middle molecular weight (MMW) matrices. DMTA measurements carried out in torsion showed that the increase in shear modulus of the HMW nanocomposites was not as great as that of the LMW and MMW counterparts as observed from a lower percentage enhancement in the storage modulus (G′) and estimated heat distortion temperature (HDT). This was attributed to the higher degree of mechanical anisotropy in the HMW nanocomposites. POLYM. COMPOS., 28:499–511, 2007. © 2007 Society of Plastics Engineers
Structure–function relationship studies of PTH(1–11) analogues containing sterically hindered dipeptide mimetics
Authors: Fiori Nereo , Caporale Andrea , Schievano Elisabetta , Mammi Stefano , Geyer Armin , Tremmel Peter , Wittelsberger Angela , Woznica Iwona , Chorev Michael , Peggion Evaristo 
Published: July 2007

AbstractThe N‐terminal 1–34 fragment of parathyroid hormone (PTH) is fully active in vitro and in vivo and reproduces all biological responses characteristic of the native intact PTH. In order to develop safer and non‐parenteral PTH‐like bone anabolic agents, we have studied the effect of introducing conformationally constrained dipeptide mimetics into the N‐terminal portion of PTH in an effort to generate miniaturized PTH‐mimetics. To this end, we have synthesized and conformationally and biologically characterized PTH(1–11) analogues containing 3R‐carboxy‐6S‐amino‐7,5‐bicyclic thiazolidinlactam (7,5‐bTL), a rigidified dipeptide mimetic unit. The wild type sequence of PTH(1–11) is H‐Ser‐Val‐Ser‐Glu‐Ile‐Gln‐Leu‐Met‐His‐Asn‐Leu‐NH2. The following pseudo‐undecapeptides were prepared: [Ala1, 7,5‐bTL3, 4, Nle8, Arg11]hPTH(1–11)NH2 (I); [Ala1, 7,5‐bTL6, 7, Nle8, Arg11]hPTH(1–11)NH2 (II); [Ala1, Nle8, 7,5‐bTL9, 10, Arg11]hPTH(1–11)NH2 (III). In aqueous solution containing 20% TFE, only analogue I exhibited the typical CD pattern of the α‐helical conformation. NMR experiments and molecular dynamics calculations located the α‐helical stretch in the sequence Ile5‐His9. The dipeptide mimetic unit 7,5‐bTL induces a type III β‐turn, occupying the positions i − 1 and i of the turn. Analogue II exhibited an equilibrium between a type I β‐turn and an α‐helix, and analogue III did not show any ordered structure. Biological tests revealed poor activity for all analogues (EC50 > 0.1 mM). Apparently, the relative side‐chain orientation of Val2, Ile5 and Met8 can be critical for effective analogue‐receptor interaction. Considering helicity as an essential property to obtain active PTH agonists, one must decorate the correctly positioned dipeptide mimetic azabicycloalkane scaffold with substitutions corresponding to the displaced amino acids. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.
Development of GaInNAsSb alloys: Growth, band structure, optical properties and applications
Authors: Harris James S. , Kudrawiec R. , Yuen H. B. , Bank S. R. , Bae H. P. , Wistey M. A. , Jackrel D. , Pickett E. R. , Sarmiento T. , Goddard L. L. , Lordi V. , Gugov T. 
Published: July 2007

AbstractIn the past few years, GaInNAsSb has been found to be a potentially superior material to both GaInNAs and InGaAsP for communications wavelength laser applications. It has been observed that due to the surfactant role of antimony during epitaxy, higher quality material can be grown over the entire 1.2–1.6 µm range on GaAs substrates. In addition, it has been discovered that antimony in GaInNAsSb also works as a constituent that significantly modifies the valence band. These findings motivated a systematic study of GaInNAsSb alloys with widely varying compositions. Our recent progress in growth and materials development of GaInNAsSb alloys and our fabrication of 1.5–1.6 µm lasers are discussed in this paper. We review our recent studies of the conduction band offset in (Ga,In) (N,As,Sb)/GaAs quantum wells and discuss the growth challenges of GaInNAsSb alloys. Finally, we report record setting long wavelength edge emitting lasers and the first monolithic VCSELs operating at 1.5 μm based on GaInNAsSb QWs grown on GaAs. Successful development of GaInNAsSb alloys for lasers has led to a much broader range of potential applications for this material including: solar cells, electroabsorption modulators, saturable absorbers and far infrared optoelectronic devices and these are also briefly discussed in this paper. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exploring reliability data
Authors: Bendell A. , Walls L. A. 
Published: July 2007

AbstractDespite the recent revolution in statistical thinking and methodology. practical reliability analysis and assessment remains almost exclusively based on a black‐box approach employing parametric statistical techniques and significance tests. Such practice, which is largely automatic for the industrial practitioner, implicity involves a large number of physically unreasonable assumptions that in practice are rarely met. Extensive investigation of reliability source data indicates a variety of differing data structures, which contradict the assumptions implicit in the usual methodology. As well as these, lack of homogeneity in the data, due, for instance, to multiple failure modes or misdefinition of environment, is commonly overlooked by the standard methodology.In this paper we argue the case for exploring reliability data.The pattern revealed by such exploration of a data set provides intrinsic information which helps to reinforce and reinterpret the engineering knowledge about the physical nature of the technological system to which the data refers. Employed in this way, the data analyst and the reliability engineer are partners in an iterative process aimed towards the greater understanding of the system and the process of failure. Despite current standard practice, the authors believe it to be critical that the structure of data analysismustreflect the structure in the failure data. Although standard methodology provides an easy and repeatable analysis, the authors' experience indicates that it is rarely an appropriate one. It is ironic that whereas methods to analyse the data structures commonly found in reliability data have been available for some time, the insistence about the standard black‐box approach has prevented the identification of such ‘abnormal’ features in reliability data and the application of these approaches. We discuss simple graphical procedures to investigate the structure of reliability data, as well as more formal testing procedures which assist in decision‐making methodology. Partial reviews of such methods have appeared previously and a more detailed development of the exploration approach and of the appropriate analysis it implies will be dealt with elsewhere. Here, our aim is to argue the case for the reliability analyst toLOOK AT THE DATA.and to analyse it accordingly.
The rationale of reliability prediction
Authors: Harris L. N. 
Published: July 2007

AbstractThis paper is the first of what is intended to be a series of papers which investigate the foundations of reliability theory, particularly when applied to the prediction process. It will contrast current reliability practice against those practices common in normal science and engineering. The claim will be made that in general the prediction process as used in reliability, when stripped of the mathematical embellishments, is no more than simple enumeration: a method long held by the philosophers of science to be unreliable and in general a poor basis on which to make predictions.This initial paper rejects the statistical method as being an insufficient basis for making predictions and claims that it is incapable of logically supporting its conclusions. Although no evidence is provided to substantiate this claim, a number of scientific methods, both of historical and present day importance, are briefly reviewed with which one can contrast the statistical method.
Reliability of plastic‐encapsulated integrated circuits in moisture environments
Authors: Gallace L. , Rosenfield M. 
Published: July 2007

AbstractAn overview of the factors affecting the reliability of plastic‐encapsulated ICs in moisture environments is presented. Particular attention is given to the moisture‐related failure mechanism EMA (electrolytic metal attack). The package design and process steps and techniques developed at RCA (through identification of the proper analytical models, thorough engineering programs, and by the statistical design of experiments) are detailed. Particular attention was paid to eliminating chlorides and their sources. The nature and state of ongoing plastic‐package moisture‐resistance programmes and future expectations are described.
Burn–in models and ttt‐transforms
Authors: Bergman Bo , Klefsjou Bengt 
Published: July 2007

AbstractThe total time on test (TTT) concept has proved to be a very useful tool in many reliability applications. In this paper we illustrate the usefulness of the TTT‐transform, a certain functional of the survival function, and an empirical counterpart called the TTT‐plot when analysing some different burn‐in models for both repairable and non‐repairable units.
Mechanical reliability by design
Authors: Carter A. D. S. 
Published: July 2007

AbstractWith distributed loads and strengths the condition of minimum whole life cost defines uniquely the safety margin (or factor of safety) that must be used. Established empirical factors used in current deterministic design are not then relevant. It is postulated that computer‐aided design packages should incorporate a simultaneous optimization of the safety margin and maintenance policy in place of these factors, since once the design is finalized the whole life cost is finalized. The full development of stochastic CAD methods is seen as the next essential step to advance design techniques.
Reliability indicators
Authors: Jensen Finn , Møltoft Jørgen 
Published: July 2007

AbstractThis is a review paper. It describes the state‐of‐the‐art of the research on reliability indicators for either electronic or mechanical components. Typical component failure patterns are presented and discussed. The concept of component screening using reliability indicators is then outlined. The paper sketches a theoretical approach to the problem of detecting flaws in components. The approach is based on an old concept of energy imbalance in flawed objects.
Proportional hazards modelling in reliability analysis—an application to brake discs on high speed trains
Authors: Bendell A. , Walley M. , Wightman D. W. , Wood L. M. 
Published: July 2007

AbstractThere has been much recent interest in the reliability field in the application of proportional hazards modelling. A number of practitioners and academics have recently been advocating its use and reviewing the basic theory. The technique is, however, in the early stages of application in reliability studies, and apparently no satisfactory examples of its application to reliability data are to be found in the open literature. An implication is that the enormous potential of this approach for reliability analysis, as well as the particular shortcomings and difficulties of applying it in this field are not well understood in the reliability community as a whole.In this article we discuss the application of the method to the reliability analysis of the brake discs on British Railways high speed trains. The need for such an approach arose owing to the paucity of current reliability analysis methods for the problem in hand. The proportional hazards methodology provided an effective means of exploratory analysis and the application of the method provided an explanation for a previously unresolved discrepancy between the statistical and metallurgical analyses. As a result of its use, the effects of the underlying failure mechanism and the various design and operating variables and their interactions are better understood, and British Rail's maintenance policy has been changed accordingly. On the basis of experience of this and similar applications, the potential for application of proportional hazards modelling in reliability, and the likely benefits to be obtained, are discussed.
A review of the ‘taguchi methods’ for off‐line quality control
Authors: Basso L. , Winterbottom A , Wynn H. P. 
Published: July 2007

AbstractThe Taguchi methods have recently become popular in the U.S.A following a realization of their importance in Japanese quality design. This review is an initial attempt to extract the important ideas while drawing on the ‘Western’ experience with response surface methodology and experimental design.
Fatigue analysis for crack initiation
Authors: Yen Charles C. S. 
Published: July 2007

AbstractFor the prediction of life leading to fatigue crack initiation, a method for performing a cycle‐by‐cycle local stress analysis at the stress concentration area of a structural component was developed. Elastoplastic stress‐strain values along the hysteresis loop are traced for each load reversal in making the life prediction calculations. In this manner, the load sequence effect and the residual stress due to local yielding are inherently included.Neuber's rule and a linear rule were used with this method and compared. The results of life prediction were compared with test results. The use of the linear rule provided more accurate predictions than using other alternatives, including Miner's rule.
Acceleration and time to fail
Authors: Hale P. W. 
Published: July 2007

AbstractA physical model of the growth of chemically related failures in electronic components is developed. This model is used to demonstrate that time to failure is as much a function of the component geometry as it is of the activation energy of the reaction. Further interpretation suggests that for any specified failure mechanism the acceleration achieved in a high temperature stress environment will appear to be a variable. Finally, using a simulation technique, a statistical distribution of the times to fail can be generated which resembles very closely the classical exponential failure curve.
Application of the weibull proportional hazards model to aircraft and marine engine failure data
Authors: Jardine A. K. S. , Anderson P. M. , Mann D. S. 
Published: July 2007

AbstractThe environment in which an equipment operates and associated diagnostic variables, such as metal particle level in engine oil, are factors that can influence an equipment's failure time. These factors can be incorporated into concomitant variable models such as the proportional hazards model (PHM), which has been widely used in medical research but not in engineering reliability. A Weibull PHM is applied to both aircraft engine failure data and marine gas turbine failure data. Examination of the residuals shows a good fit of the Weibull proportional hazards model to the data.
Causes and effects of spacecraft failures
Authors: Hecht Myron , Fiorentino Eugene 
Published: July 2007

AbstractIn a study conducted for the USAF Rome Air Development Center to improve reliability prediction for spacecraft approximately 2600 incident reports on 300 spacecraft (representing 100 programmes) that were launched between the early 1960s and January 1984 were analysed. The causes of the spacecraft failures and the severity of the observed effects are examined.The classification of causes is explained in detail and examples of each type of failure are provided. Differences in the relative frequency of certain causes between pre‐1977 missions and later ones are analysed and some significant trends are identified. The association of spacecraft subsystems with the major causes of failure is investigated. Finally, the severity of the failure effects due to the identified cause categories is discussed. A significant finding is that a large fraction of the incidents is due to design and environmental causes rather than to random failures.
The role of data transformation in taguchi analysis
Authors: Logothetis N. 
Published: July 2007

AbstractThis paper reports on the usefulness of data transformation in a proper application of the ‘Taguchi method’ for off‐line quality control. With the joint aim of establishing a meaningful measure of performance variability and reducing the risk of incorrectly assuming no interactions in the performance model, a simple method of choosing appropriate data transformations is presented. This provides the basis for a suggested general procedure for carrying out Taguchi analyses. The technique is assessed by considering how it performs on data taken from previously published applications of the Taguchi method.
Reliability prediction: A constructive critique of MIL‐HDBK‐217E
Authors: Blanks Henry S. 
Published: July 2007

AbstractMIL‐HDBK‐217E is based on some major fallacies and oversimplifications. These include the assumption of constant failure rate, the assumed independence of the Pi factors, the oversimplification of temperature dependence, the neglect of process yield and screening fall‐out as determinants in the categorization of quality grade and the absence of manufacturing date information. These weaknesses are discussed and some recommendations made.
Detecting lack of control in a new, untried process
Authors: Murray Ian , Oakland John S. 
Published: July 2007

AbstractIn his original work on the use of control charts, Shewhart distinguished between a long running known process and a new, untried process. In the latter case, the control limits are obtained from the sample data. If the process variability increases during the sampling period, the control limits will widen, reducing the sensitivity of the standard deviation and range charts and producing charts which are in control for out‐of‐control situations. Simulations were produced to investigate this problem through the eyes of the operator. Cusum procedures were used to provide the operator with a means of controlling process variability which is more sensitive to change than the control chart alone. The method was applied to data taken from an industrial situation.
Reliability predictions for integrated circuits from test structure data
Authors: Kleppmann W. G. 
Published: July 2007

AbstractFor the prediction of product reliability from test structure data the observed times to failure have to be fitted to an assumed probability distribution and extrapolated to small failure probabilities. And the probability distribution for the (small) test structure size has to be extrapolated to the corresponding distribution for the (larger) product size.With respect to the probability distribution it is shown that even in the ‘defect’ dominated case, extreme value distributions do not have to apply. This leads to considerable extrapolation uncertainties.For the size extrapolation of test structure data to the product the degree of dependence between times to failure of substructures on the same chip is of crucial importance. It can change the predicted reliability by orders of magnitude. A model describing this dependence is given and analyses yielding the required information are suggested.
Bettering operation of Robots by learning
Authors: Arimoto Suguru , Kawamura Sadao , Miyazaki Fumio 
Published: July 2007

AbstractThis article proposes a betterment process for the operation of a mechanical robot in a sense that it betters the next operation of a robot by using the previous operation's data. The process has an iterative learning structure such that the (k + 1)th input to joint actuators consists of the kth input plus an error increment composed of the derivative difference between the kth motion trajectory and the given desired motion trajectory. The convergence of the process to the desired motion trajectory is assured under some reasonable conditions. Numerical results by computer simulation are presented to show the effectiveness of the proposed learning scheme.
Computational requirements of customized Newton‐Euler algorithms
Authors: Khosla Pradeep K. , Neuman Charles P. 
Published: July 2007

AbstractTo reduce the computational requirements of the Newton‐Euler (N‐E) algorithm for real‐time applications, we customize the algorithm for specific manipulator designs. We analyze the computational requirements of the algorithm for designs incorporating practical kinematic and dynamic parameter simplifications. We illustrate our approach by customizing the N‐E algorithm for the CMU direct drive arm II (DD Arm II). Our customized algorithm reduces the computational requirements of the general‐purpose N‐E algorithm by 56 percent. We describe the hardware implementation of our customized algorithm on a Marinco array processor. Our prototype computes in 1.2 ms the inverse dynamic torques for each trajectory set‐point.
The specification of distributed sensing and control
Authors: Henderson Tom , Hansen Chuck , Bhanu Bir 
Published: July 2007

AbstractLogical Sensor System Specification (LSS) has been introduced as a convenient means for specifying multi‐sensor systems and their implementations. In this article we demonstrate how control issues can be handled in the context of LSS. In particular, the Logical Sensor Specification is extended to include a control mechanism which permits control information to (1) flow from more centralized processing to more peripheral processes, and (2) be generated locally in the logical sensor by means of a micro‐expert system specific to the interface represented by the given logical sensor. Examples are given including a proposed scheme for controlling the Utah/MIT dextrous hand.