bluuebunny/crossref_metadata_2025 huggingface dataset:
Silicone rubber/graphite nanosheet electrically conducting nanocomposite with a low percolation threshold
Authors: Chen Ling , Lu Liang , Wu Dajun , Chen Guohua
Published: July 2007

A novel electrically conductive nanocomposite was successfully fabricated by dispersing homogeneously conductive graphite nanosheets (GN) in an insulating silicone rubber (SR) matrix. GN were prepared by powdering expanded graphite with sonication in aqueous alcoholic solution. The particular geometry of GN 30–80 nm in thickness with high aspect ratio contributes to the advantage of forming the conducting network, so that the percolation threshold of SR/GN nanocomposite is about 0.009, much lower than that of composites with conventional graphite. The SR/GN nanocomposite presents a remarkable piezoresistive behavior under much low pressure, related to the low elastic modulus of the composite. The elastic modulus of the nanocomposite with various GN content and at the different speed of compression was discussed. POLYM. COMPOS., 28:493–498, 2007. © 2007 Society of Plastics Engineers
Flame retardancy and toughening of high impact polystyrene
Authors: Cui Wenguang , Guo Fen , Chen Jianfeng
Published: July 2007

Flame retardant high impact polystyrene (HIPS) was prepared by melt blending HIPS, nano‐modified aluminum trihydrate (nano‐CG‐ATH), red phosphorus masterbatch (RPM), and modified polyphenylene oxide (MPPO). Styrene‐butadiene‐styrene (SBS) was used as a toughener in this research. The effects of nano‐CG‐ATH, RPM, MPPO, and SBS on properties of HIPS composites were studied by combustion test, mechanical tests, and thermogravimetric analysis. The morphologies of fracture surfaces and char layers were characterized through scanning electron microscopy (SEM). The HIPS/nano‐CG‐ATH/RPM/MPPO (60/6/9/25) composite and its combustion residues at various temperatures were characterized by Fourier transform infrared (FTIR) spectra analysis. The results showed that the UL‐94 rating of the HIPS/nano‐CG‐ATH/RPM/MPPO (60/6/9/25) composite reached V‐0 and its char layer after flame test was integrated, but its impact strength was low. Addition of SBS improved its impact property and did not influence its thermal and flame retardant properties but lowered its tensile strength and flexural modulus to some extent. The FTIR spectra confirmed that the POC group was present in the charred substance. POLYM. COMPOS., 28:551–559, 2007. © 2007 Society of Plastics Engineers
National surveillance of herbal dietary supplement exposures: the poison control center experience
Authors: Gryzlak Brian M. , Wallace Robert B. , Zimmerman M. Bridget , Nisly Nicole L.
Published: July 2007

Purpose

The purpose of this report is to characterize reports to poison control centers (PCCs) involving two widely used herbal dietary supplements (HDSs), Echinacea, and St. John's wort (SJW).

Methods

We purchased data from the American Association of Poison Control Center's (AAPCC) toxic exposure surveillance system (TESS®) on reports made to PCCs in 2001 involving Echinacea or SJW. Analyses were limited to those cases in which Echinacea or SJW were the only associated products, and in which these HDSs were deemed primary to observed adverse effects. Descriptive statistics were generated for selected demographic and exposure‐related variables.

Results

During 2001, PCCs were contacted regarding 406 exposures involving Echinacea and 356 exposures involving SJW. Most of the reported exposures for both HDSs occurred among children 5 years and younger, and the majority of exposures were coded as unintentional. For both HDSs, exposures among patients ≥20 years old were more likely to be associated with adverse effects. Intentional exposures accounted for 21% of SJW cases and 3% of Echinacea cases, with 13% of SJW exposures reported as ‘suspected suicidal’.

Conclusions

TESS® represents a potentially important means of assessing and characterizing HDS‐related adverse effects. Detailed studies validating the clinical events and outcomes of a sample of exposures reported to TESS® might offer substantial insights into adverse events (AEs) that could be systematically studied with other, established pharmacoepidemiological study designs. Copyright © 2007 John Wiley & Sons, Ltd.
Polymerization of β‐pinene with Schiff‐base nickel complexes catalyst: Synthesis of relatively high molecular weight poly(β‐pinene) at high temperature with high productivity
Authors: Yu Peng , Li An‐Long , Liang Hui , Lu Jiang
Published: July 2007

A series of easily accessible and stable Schiff‐base nickel complexes (complex 1–4) in conjunction with methylaluminoxane (MAO) were employed for the synthesis of relatively high molecular weight β‐pinene polymers at high temperature with high productivity. The ligand structure of the complex had a substantial effect on the polymerization in terms of the productivity and the molecular weight. With complex 4 in the presence of MAO, high molecular weight polymers of β‐pinene (Mn ∼ 10,900) were obtained at 40 °C with an extremely high productivity up to 1.25 × 107 g polyβ‐pinene/mol of Ni. 1H NMR analyses showed that the obtained β‐pinene polymer was structurally identical to that formed by conventional cationic Lewis acid initiators. The polymerization was presumably initiated by the nickel cation formed by the reaction of the schiff‐base nickel complex and MAO, while the propagation proceeded in a manner typical for a conventional carbocationic polymerization process. Direct evidence for the carbocationic polymerization was offered by the fact that quenching of the polymerization with methanol at a low monomer conversion resulted in incorporation of a methoxyl end group into the polymer chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3739–3746, 2007
Synthesis and characterization of polyimide‐polysiloxane segmented copolymers for fuel cell applications
Authors: Zou Lijun , Anthamatten Mitchell
Published: July 2007

Sulfonated polyimides exhibit high strength, good film‐forming ability, chemical resistance, and, in their hydrated state, relatively high proton conductivity. Here we report the one‐pot synthesis of sulfonated polyimide‐polysiloxane segmented copolymers through the reaction of a dianhydride with a mixture of three diamines: a nonionic aromatic diamine (4,4′‐oxydianiline), a sulfonated diamine (4,4′‐diamino‐2,2′‐biphenyldisulfonic acid), and a telechelic diamino polysiloxane. Copolymer compositions were evaluated using 1H NMR and size‐exclusion chromatography. The presence of ion‐containing diamines in the reaction mixture inhibited stoichiometric incorporation of hydrophobic siloxane segments. Siloxane segments were found to lower the thermal stability of the polyimide host. Copolymers with and without siloxane segments were cast into free‐standing films. Equilibrium water sorption studies of cast films show that, for the compositions studied here, the presence of siloxane segments does not interfere with water swelling, suggesting that a microphase‐segregated morphology may exist. TEM and SAXS analyses show evidence of phase‐segregation in sulfonated polyimides and reveal that siloxane segments strongly affect ionic clustering. However, proton conductivity only changes slightly when polysiloxane segments are incorporated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3747–3758, 2007
Synergistic effects in hybrid free radical/cationic photopolymerizations
Authors: Crivello James V.
Published: July 2007

Multifunctional alkyl glycidyl ether and oxetane monomers are usually deemed to be poorly reactive and are consequently of limited use for high speed photocuring applications. However, these monomers can be made to undergo exceedingly rapid exothermic photopolymerization when combined with a multifunctional acrylate monomer and a corresponding free radical photoinitiator. Under optimum UV irradiation conditions, these hybrid photopolymerizations take place rapidly and substantially without an induction period. A mechanism was proposed on the basis of thermal acceleration of the cationic ring‐opening polymerizations induced by the fast exothermic free radical acrylate photopolymerization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3759–3769, 2007
Synthesis of grafted poly(p‐phenyleneethynylene) with energy donor–acceptor architecture via atom transfer radical polymerization: Towards nonaggregating and hole‐facilitating light‐emitting material
Authors: Pu Kan‐Yi , Chen Yi , Qi Xiao‐Ying , Qin Chun‐Yang , Chen Qing‐Quan , Wang Hong‐Yu , Deng Yun , Fan Qu‐Li , Huang Yan‐Qin , Liu Shu‐Juan , Wei Wei , Peng Bo , Huang Wei
Published: July 2007

In this contribution, we demonstrate a new effective methodology for constructing highly efficient and durable poly(p‐phenyleneethynylene) (PPE) containing emissive material with nonaggregating and hole‐facilitating properties through the introduction of hole‐transporting blocks into the PPE system as the grafting coils as well as building the energy donor–acceptor architecture between the grafting coils and the PPE backbone. Poly(2‐(carbazol‐9‐yl)ethyl methacrylate) (PCzEMA), herein, is chosen as the hole‐transporting blocks, and incorporated into the PPE system as the grafting coils via atom transfer radical polymerization. The chemical structure of the resultant copolymer, PPE‐g‐PCzEMA, was characterized by NMR and gel permeation chromatography, showing that the desirable copolymer was obtained with the narrow polydispersity. The increased thermal stability of PPE‐g‐PCzEMA was confirmed by thermogravimetric analysis and differential scanning calorimetry along with its macroinitiator. The optoelectronic properties of this copolymer were studied in detail by ultraviolet‐visible absorption, photoluminescence emission and excitation spectra, and cyclic voltammogram (CV). The results indicate that PPE‐g‐PCzEMA exhibits the solid‐state luminescent property dominated by individual lumophores, and also the energy transfer process from the PCzEMA blocks to the PPE backbone with a relatively higher energy transfer efficiency in the solid‐state compared to that of the solution state. Additionally, the hole‐injection property is greatly facilitated due to the presence of PCzEMA, as confirmed by CV profiles. All these data indicate that PPE‐g‐PCzEMA is a good candidate for use in optoelectronic devices. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3776–3787, 2007
Interaction of ACTH synthetic fragments with rat adrenal cortex membranes
Authors: Kovalitskaya Yulia A. , Zolotarev Yury A. , Kolobov Alexander A. , Sadovnikov Vladimir B. , Yurovsky Vladimir V. , Navolotskaya Elena V.
Published: July 2007

Synthetic peptide, corresponding to the amino acid sequence 11–24 of human adrenocorticotropic hormone (ACTH), was labeled with tritium (specific activity of 22 Ci/mmol). [3H]ACTH (11–24) was found to bind to rat adrenal cortex membranes with high affinity and specificity (Kd = 1.8 ± 0.1 nM). Twenty nine fragments of ACTH (11–24) have been synthesized and their ability to inhibit the specific binding of [3H]ACTH (11–24) to adrenocortical membranes has been investigated. Unlabeled fragment ACTH 15–18 (KKRR) was found to replace in a concentration‐dependent manner [3H]ACTH (11–24) in the receptor–ligand complex (Ki = 2.3 ± 0.2 nM). ACTH (15–18) was labeled with tritium (specific activity of 20 Ci/mmol). [3H]ACTH (15–18) was found to bind to rat adrenal cortex membranes with high affinity (Kd = 2.1 ± 0.1 nM). The specific binding of [3H]ACTH (15–18) was inhibited by unlabeled ACTH (11–24) (Ki = 2.2 ± 0.1 nM). ACTH (15–18) at the concentration range of 1–1000 nM did not affect the adenylate cyclase activity in adrenocortical membranes. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.
Assimilating GPS radio occultation measurements with two‐dimensional bending angle observation operators
Authors: Healy S. B. , Eyre J. R. , Hamrud M. , Thépaut J.‐N.
Published: July 2007

Four‐dimensional variational (4D‐Var) assimilation forecast impact experiments were conducted with CHAMP radio occultation measurements from 1st June to 31st July 2004. The CHAMP bending angles were assimilated with one‐dimensional (1D) and two‐dimensional (2D) bending angle observation operators, enabling the potential benefits of the latter to be investigated. Two computationally affordable 2D bending angle observation operators were considered. The first can be viewed as a straightforward generalisation of the 1D operator. The second is based on a fourth order Runge–Kutta solution of the differential equations defining the ray‐path through the refracting atmosphere.

It is demonstrated that the computational cost of the 2D bending angle operators is not prohibitive and that they improve the root‐mean‐square of the observed minus background (O‐B) bending angle departures by around 5% in the lower‐troposphere of the northern and southern hemispheres. The O‐B distributions in the tropical lower‐troposphere are biased low, but the first‐guess departure quality control procedure removes ∼2–3% of the observations and this reduces the bias by around 20%. The assimilation of the CHAMP measurements with both the 1D and 2D operators improves the analysis and forecast fit to radiosonde temperature measurements in the southern hemisphere on the 300, 200, 100 and 50 hPa levels, over the day‐1 to day‐5 forecast range. The forecast scores in the lower‐troposphere for geopotential height and relative humidity are generally neutral, but there is a small improvement in the anomaly correlation of the 500 hPa geopotential height field in the southern hemisphere, over the day‐1 to day‐2 forecast range. However, there are no clear, statistically significant differences between the 1D and 2D experiments for this two‐month period. Copyright © 2007 Royal Meteorological Society
Activation energies and the arrhenius equation
Authors: Jensen Finn
Published: July 2007

This paper examines the current use of the Arrhenius equation and the activation energies associated with integrated circuits. A short introduction to the Arrhenius equation is given and it is shown how activation energies may be computed from experimental data.

The paper next addresses the following basic question: is it reasonable to extrapolate from high‐temperature laboratory life‐tests down to use conditions using the Arrhenius equation? The paper shows that the answer to this question in general must be an emphatic no. It is not the validity of the Arrhenius equation as such that is questioned, but its indiscriminate use by reliability practitioners across the electronics industry.

This is not a scientific paper, and no ‘proofs’ are given. The discussion is based on ‘typical’ integrated circuits using published data on the temperature dependence of the hazard rate of such circuits. The paper serves as a warning against thinking that ‘well established practices’ are necessarily scientifically sound.
Effectiveness of formal reliability programmes
Authors: O'Connor Patrick D. T.
Published: July 2007

The development of complex yet highly reliable systems is one of the greatest technical and management challenges of our time. Because such systems are often developed and manufactured for official agencies, and to their specifications, it is necessary to impose controls that will ensure achievement of a performance parameter which is neither predictable nor measurable during development. Since failure is a stochastic process, statistical and actuarial techniques have been developed, but these have been emphasized too much in official reliability programmes.
Electrostatic discharge: mechanisms, protection techniques and effects on integrated circuit reliability
Authors: Avery L. R.
Published: July 2007

Electrostatic discharge (ESD) was once considered a problem only for unprotected, insulated‐gate field‐effect transistors, but the ever shrinking geometries of all semiconductor devices have made them vulnerable to this phenomenon. ESD models and on‐chip device protection techniques are reviewed, together with current evidence concerning latent defects and their effect on device reliability. A brief discussion on the importance of ESD controls in the assembly environment is also included, with an emphasis on realistic cost‐effective measures. Finally, the impact of continued scaling on ESD vulnerability and protection structure limitations, are examined.
Reliability in communications satellites
Authors: Mancino Vincent J. , Slusark Walter J.
Published: July 2007

The reliability of complex communications satellites is discussed as well as the elements necessary to ensure the specified life. Some of these elements are novel to commercial communications satellites, and generally are found only in military satellites having very exacting reliability requirements. Also treated are some of the changes that have been implemented within the last decade to enhance reliability and increase the life of space communications satellites.
Traffic signal equipment procurement based on cost of ownership and community cost
Authors: Blanks H. S.
Published: July 2007

The principles of cost of ownership have been applied to the development of a system of traffic signal equipment procurement in which the failure cost includes the cost to the community arising from increased accident rate and traffic disruption due to malfunctioning equipment.

The paper first summarizes some of the principles and guidelines of LCC procurement. It then gives the cost‐of‐ownership equation which has been developed for the comparative tender assessment of traffic signal equipment. It explains the categorization of signal malfunction modes according to their hazard‐creation and traffic‐disruption severities, providing a matrix of 5 × 5 hazard/disruption categories, and gives the derivation of the corresponding community cost rates. It discusses the proposed method of implementation of the system, including a warranty/guarantee plan intended to overcome the problem of MTBF prediction inaccuracy and to provide incentive for MTBF improvement. The paper concludes with a discussion of the savings which can be achieved through use of the system and of its cost effectiveness.

The system was developed for the Department of Main Roads, New South Wales.
Vlsi yield management and prediction
Authors: Ferris‐Prabhu A. V.
Published: July 2007

This paper presents a practical method for managing and predicting the yield of VLSI products, in a manner that will provide insight, with a minimum of mathematical complexity, into the sensitivity of the yield to the different quantities which limit it. The yield equation is cast into a form which makes evident the contributions of its constituent terms and the formulation is developed in a manner that permits its ready application to yield characterization, diagnostics and prediction. An illustrative example is presented that integrates the concepts and methods developed.
In defence of numerical techniquesgl
Authors: Benz Glen E.
Published: July 2007

The purpose of this article is to say a few kind words for numerical techniques, which have become the object of some undeserved criticism. Probability information is part of decision‐making, be it intuitive or analytical. In this age of the personal computer we do not have to go to great lengths to quantify this information, so why not do it? The failure to rescue hostages in Iran is a dramatic example that reliance on intuition can have bad results. On the side of numerical techniques, three examples of successful and practical applications are described. It is concluded that ‘the numbers game’ contributes worthwhile support to decision‐making and should continue to co‐exist with ‘shirt‐sleeve’ efforts to improve products and policies.
Stress test development on a processor system
Authors: Venn Keith
Published: July 2007

Thermal cycling and vibration tests were carried out on an intermediate processor family of machines to investigate the benefits of controlled stressing as a means of screening manufacturing defects, and to provide data for return on investment calculations. Major items to be considered were

(a) low cost of test programme

(b) complete unit to be stressed (complex interactions between subassemblies)

(c) relatively low expected failure rate

(d) limited field reporting.

Stress techniques used were mild thermal cycling and pseudo‐random vibration.

Analysis of field data from the stressed population showed an overall reliability improvement of 24 per cent during the first 30 days of customer operation.
A new approach to reliability prediction is needed
Authors: Florescu Radu A.
Published: July 2007

This paper starts from the main objections regarding MIL‐HDBK‐217 and the BELLCORE method for reliability prediction, objections asserting that these methods are approximate, complicated and unconvincing. To support these assertions, and by applying techniques specific to reliability theory, the author has developed a reliability model which is plausible for certain elements of technical systems. The existence of such a model, which in practice is useless because the failure rate expression is too complicated, proves clearly the inefficiency of classical methods.
Electrostatic pulse breakdown in nmos devices
Authors: Amerasekera E. A. , Campbell D. S.
Published: July 2007

The electrostatic discharge (ESD) sensitivity of small dimension n‐channel metal oxide semiconductor (NMOS) field effect transistors (FETs) has been investigated. NMOS FETs of varying dimensions and a constant gate oxide thickness of 400® were each subjected to a single ESD voltage pulse of between 50 and 250V at temperatures between 25 and 200°C. Over 4000 devices were used, all resident on a single 3 inch silicon wafer. The object of the experiment was to determine the dependence of device ESD sensitivity on temperature, voltage and device dimensions as well as to investigate the mechanisms that cause oxide breakdown as a result of ESD damage.

No temperature dependence of device ESD sensitivity was observed within the range of the experiment. A significant voltage dependence was observed, with degradation accounting for over 80 per cent of devices at 250V. A cumulative ESD effect was observed, whereby the degradation of device performance was found to increase with the number of applied pulses. Analysis of the breakdown characteristics revealed that the cause of damage was oxide breakdown. Application of the ESD pulse appears to lead to oxide breakdown through impact ionization within the oxide, the very short duration of the pulse not being favourable to processes involving electron trapping unless these traps are already present in the oxide.
Use of liquid‐crystal thermography for defect location on semiconductor devices
Authors: Beck F.
Published: July 2007

Hot‐spot detection, a thermographic technique with liquid crystals, marks hot regions on a surface. The use of this highly sensitive method in failure analysis of integrated devices allows the detection of points on a chip where electrical power is converted into heat. Points such as these are often indicative of a fault, e.g. a leakage path or an increase in transfer resistance. The technique is based on the birefringence of a liquid crystal (LC) in the anisotropic state below the clearing temperature (Tc). Above this temperature, in the isotropic state, the effect disappears. The device under test, covered with the LC, is observed below the clearing point in polarized light with a crossed polarizer and analyser. Owing to the optical rotation of the anisotropic LC the image is bright. At hot spots the LC changes to the isotropic state and a dark spot is produced. A decisive factor for the thermal resolution of the technique is the precise temperature adjustment of the tested device. With lateral resolution of some tenths of a μ‐m it is still possible to detect current paths with dissipation of 50 to 500μW. The sensitivity can be increased further. Square‐wave pulses of selectable voltage, frequency and duty cycle are used to drive the test item. Four examples from failure analysis demonstrate the possibilities of using hot‐spot thermography, the main features of which are speed, uncomplicated handling and depth of information.
Cathode ray tube bleed resistor reliability—a case study
Authors: Hale Peter , Mactaggart Iain , Shaw Martin
Published: July 2007

This paper describes, and gives a mathematical analysis of, the performance of two makes of CRT bleed resistors which exhibit markedly different characteristics under heat soak conditions. By examining the observed resistance changes with temperature, and relating these to the Arrhenius equation, the reaction activation energies can be determined.

Further analysis of the power consumption characteristics of the resistors leads to the establishment of resistance‐time curves for both makes of resistor. These indicate very different conclusions than might otherwise have been drawn from initial test data. Finally the Monte Carlo' simulation technique is used to determine the most likely survival characteristics in a field situation, and a quantitative assessment of the reliability of CRTs using these bleed resistors is given.

The construction of the resistor body is common to both makes and comprises a resistor substrate enclosed within an overcoat which is in turn encapsulated in epoxy. One make (type A) is a glass thick film structure, whereas the other is a polymer thick film system.
Optimum replacement of deteriorating and inadequate equipment
Authors: Blanks H. S. , Tordon M. J.
Published: July 2007

Determination of the optimum equipment replacement policy and time is of great economic importance. After a brief survey of the models which have been used for decision making, the paper looks at methods for detecting and quantifying growth of failure frequency (peril rate) in repairable equipment. It examines the trend detection methods of Laplace and Mann when the peril rate varies as a power of equipment age and also applies them to some actual field failure data. An economic model is developed, based on total discounted future cost and providing for ongoing future technological growth. The cost comprises not only the conventional cost of ownership, but also the shortfall between an equipment's achieved benefit and that which would be achieved by an ideal equipment in the same demand environment. The inclusion of this shortfall, called incapacity cost', enables the replacement decision to be based not only on the deterioration of equipment but also on its performance inadequacy and on the availability of technological improvement in present and future challengers.

The formulation of the cost model is such that for both a single‐replacement finite planning horizon and an infinite horizon the total discounted future cost is readily computed for a range of alternative replacement times and the optimum replacement programme thereby determined. The sensitivity of total cost to the replacement times and the sensitivity of the optimum times to the variability of assumed input data are easily examined.

The application of the model to traffic signal equipment is described. In this application the total cost is shared between the nominal owner of the equipment and the community.
Economic models and process quality control
Authors: Montgomery Douglas C. , Storer Robert H.
Published: July 2007

Quality is an important business strategy in the economic and technological environment of today. To achieve high product quality, it is important to take explicit account of the cost of quality, and to use this cost as another management control. A new direction for achieving a cost‐effective quality management system is to design statistical process controls so as to directly incorporate quality costs. This paper discusses the major approaches to the economic design of statistical process controls, and compares several different model formulations. The practical implication of these techniques is stressed. In particular, two economic models of the chart are presented: a full economic model requiring a user‐specified process and nine cost parameters, and a semi‐economic model using five user‐specified parameters. Both of these could serve as approaches to reducing the total cost of process control. Because of its simplicity in application the semi‐economic model should gain greater acceptance by practitioners for the design of process control techniques.
Simplified markov techniques for some stand‐by redundant systems
Authors: Hamilton R. , Bazovsky Sr I. ,
Published: July 2007

The simplified techniques presented in this paper are the result of a study* of specific stand‐by system configurations comprised of combinations of two different types of non‐repairable operating parts. Failed parts of either type are replaced with stand‐by parts of just one of the two types. All parts have constant failure rates. The simplified transition probability diagram technique centres on the transition probability diagram and is here applied to one of seven system configurations of the original study. To validate the transition probability diagram technique an expanded Markov flow graph is used. Both of these simplified techniques offer advantages over other, existing techniques. A single, general mean time to failure (MTTF) equation is obtained for all the configurations analysed. The developed techniques were used in the analysis of an actual electrical system design project.
Goodness of fit of small samples to the weibull distribution
Authors: Leitch R. D.
Published: July 2007

Weibull paper is used extensively to estimate the parameters of a population, even when the results may look somewhat suspicious to the eye. In this paper the author suggests a statistical test, gives the limiting values of the test statistic, and goes on to illustrate the use of such a test by analysing some data.
Functional screens for electronic reliability
Authors: Ganter William A.
Published: July 2007

This paper describes a class of reliability screens for use in the manufacturing process of electronic products which are directly related to the funcationality of the product being produced. The field reliability that was attained from using functional screening on an example product is presented. Because of the exceptionally low failure occurrence now possible in today's products, some simple alternative reliability monitoring statistics based on the binomial are suggested. Implications of this improved reliability on the effectiveness of screening methods is discussed, and the notion of field failures as screening escapes is introduced. Then some reasons to experiment with functional stress screens in place of a total reliance on the more traditional environmental stress screens are presented. Finally, the characteristics of functional screens are presented. Careful experimentation using appropriate statistical analysis in developing and comparing screening approaches is emphasized throughout this paper.
(LCCs) R & M Implications of leadless chip carriers
Authors: Fox H. E.
Published: July 2007

The current state‐of‐the‐art regarding LCCs is reviewed in terms of published papers concerning LCC applications, device reliability and attachment techniques. Reliability uncertainties relating to environment, size and attachment geometry are identified. An extensive bibliography is included.
Application of a multi‐model approach to estimating residual software faults and time between failures
Authors: Bowen John B.
Published: July 2007

This paper reports the results of applying a multi‐model interactive computer program called SMERFS (statistical modelling and estimation of reliability functions for software) to a large air defence system project. SMERFS includes four fault‐count models and four time‐between‐failure models which were applied at the compilation unit and computer software configuration item level. The four fault‐count models yielded reasonable results supported by acceptable fits for nine of the ten compilation units. The four time‐between‐failure models yielded reasonable results with acceptable fits for all compilation units. A validation of the SMERFS results was attempted by truncating the latter developmental data from the input data, and by using the latter data in lieu of operational data. With the exception of one fault‐count model, no models accurately predicted the simulated operational data.
The influence of climatic conditions on the reliability of electronic components in telephone exchanges
Authors: Lelievre A. , Goarin R.
Published: July 2007

This paper shows the significant influence of climatic conditions on the reliability of components in telephone exchanges. The great number of observations made enabled numerous data to be collected. Sophisticated data processing was used using data analysis methods, in particular factor analysis. Prominence was thus given to the various parameters affecting the reliability of components (temperature, hygrometry, location of the board, air conditioning process…). A physical analysis of the failure of components complemented the statistical study. It resulted in taking practical measures to improve the field reliability of French telecommunication equipment.
Quality assurance technologies for vlsi manufacturing
Authors: Kohoutek Henry J.
Published: July 2007

Considering the fundamental aims of VLSI Manufacturing and objectives of the Quality Assurance and Quality Control programs, three technologies, namely Dimensional Metrology, Material Analysis, and Statistical Methods of Process Control, emerge as key to success. The bewildering array of methods, instrumentation alternatives, and process states and variables to be controlled, make Quality Assurance and control activities as complex as the VLSI manufacturing itself, and demand a long‐term commitment by all management, engineering, and work force teams involved.
Load‐strength modelling of mechanics and electronics
Authors: Loll Valter
Published: July 2007

The basic conditions for using the load‐strength theory is listed. The use of the theory as a modelling tool—a way of thinking, is discussed. The theory is used to explain differences and similarities in failure patterns of mechanics and electronics. Further, real data is shown for load‐strength in an electronic system.
Development of stress screens
Authors: Hobbs Gregg K.
Published: July 2007

Development of stress screens is discussed including selection of stimuli appropriate to the defect types sought, selection of screen levels and then finally proof of screen tests.
Considerations in the use of optimal preventive maintenance policies
Authors: Zaino Nicholas A.
Published: July 2007

Designing products which require maintenance always involves compromises between reliability and maintainability. Both scheduled and preventive maintenance (PM) should be considered in the design phases of a product so that the design can include features to ease the maintenance task. In addition, many design decisions based on Failure Modes and Effects Criticality Analysis (FMECA), Pareto criticality rankings, etc., could and should be strongly influenced by the potential for using preventive maintenance. A component that has a major negative impact on system reliability (because of its life distribution) could become much less consequential if appropriate PM policies are implemented. This paper describes the use of an easy‐to‐implement analysis procedure to assist a designer or systems analyst in making the reliability/maintainability tradeoff.
Quality assurance education and training in the U.K.
Authors: Oakland John S. , Grayson Ric
Published: July 2007

This paper deals with the part that education and training plays in the achievement of quality.

The initial section examines the role of the Government sponsored Directory of Quality Training and Education in the U.K. and the aims of the National Quality Campaign. It assesses how successful the courses outlined in the Directory might be in providing sufficient stimulus for a change in attitude towards quality within industry particulraly with regard to satisfying the identified aims of the campaign. The conclusions that are drawn as a result indicate that there are several problems that need to be resolved before progress can be assured.

The final section details what progress has already been made in the pursuit of improved quality and looks at various alternative methods of education and training that have been proposed to aid the process of change.
Purple plague: Eliminated or just forgotten?
Authors: Footner P. K. , Richards B. P. , Yates R. B.
Published: July 2007

The reappearance of ‘purple plague’ as a reliability and failure risk in current IC devices has led to renewed interest in the precise failure mechanisms and eventual failure mode. These are outlined and illustrated with examples of recent failures in plastic encapsulated integrated circuits, hermetically sealed integrated circuits and hybrids. The reasons for the reappearance of this type of failure are discussed, and it is shown that the problem may be expected to increase in future generation devices.
Influence of quality of manufacture on electronic equipment and system reliability
Authors: Ender Urs , Gerling Wolfgang
Published: July 2007

For electronic equipment and systems a correspondance of predominant faults is observed during the electrical test phases at board and at system level prior to use, and during subsequent application of the system. Relationships are expected based on the common causes of these faults. Such faults might be those that have escaped detection during electrical testing, faults that induce secondary latent defects on parts, or original latent defects incorporated in the installed components. Causes and effects are discussed.

Measures have been taken over several years to improve the manufacturing quality of electronic equipment following these aspects. It is shown, by practical experience with an electronic communication system, that an improvement of manufacturing quality by a factor of 5 has increased system reliability by about the same degree.

This noticeable effect of the manufacturing quality of printed circuit board assemblies on the reliability of the system and on the failure rates of installed components is not considered by usual reliability prediction models. The observed failure rates of components are low when compared to values of prediction models, even including those component types contributing to focal points of failure with the achieved level of reliability.
Off‐line quality control and ill‐designed data
Authors: Logothetis N.
Published: July 2007

‘Bad’ data resulting from ill‐designed experiments or in‐production/after‐production monitoring require a careful use of proper statistical techniques for their analysis. Prior exploration of the available data is of paramout importance especially if we wish to apply off‐line quality control techniques such as the Taguchi method. A stepwise approach is proposed involving data analysis and straightforward significance tests, which can ensure statistically valid and useful conclusions.
Component reliability assessment and assurance using a new step‐stress test
Authors: Aagesen Svend M. , Stevenson John L.
Published: July 2007

Several features of accelerated reliability testing are surveyed in this paper. A new technique for the practical evaluation of reliability under thermally induced acceleration is introduced. This procedure is termed the reverse‐step‐stress test, and involves a decrease in applied stress after some pre‐specified failure criterion has been met within a fixed sample of components. An analysis is presented which confirms that the reverse‐step‐stress test can reveal failures having low activation energies that would not be detectable in conventional constant‐stress, high temperature testing.
The organization of a study of the field failure of electronic components
Authors: Campbell D. S. , Hayes J. A. , Hetherington D. R.
Published: July 2007

This paper describes the organization that has been evolved for the collection and analysis of field failure data. A summary breakdown is given of the data collection organization, the Data Format and the methodology of Data Analysis.

Preliminary studies show the system is working.

The concept of superpopulation has been established in order to judge the relative importance of data as it is accumulated.
Recognizing the optimum burn‐in period
Authors: Shaw Martin
Published: July 2007

It is generally accepted within the reliability discipline that component failures occur when the strength of the component ie less than the stresses imposed. Due to the unavoidable variations in processing and materials, it will not be unusul to find component or product strength distributions that are bimodal in nature, consisting of a mixture of two Weibull distributions (i.e. weak and strong component distributions).

This paper presents an analysis of both field performance and burn‐in data collated over a period of time on one particular type of display unit which clearly exhibits some form of bimodality.

The text also explains in detail the manner in which optimum burn‐in duration can be computed via a Weibull plotting technique or by applying the sequential burn‐in procedure.
Fatigue reliability assessment of offshore structures
Authors: Kam J. C. P.
Published: July 2007

Substantial laboratory and field experience has indicated that, owing to the large number of wave stress cyles experienced by offshore steel structures, fatigue cracking should be the main consideration of structural reliability assessment.

This paper presents the latest implementation of probabilistic fracture mechanics modelling for fatigue reliability analysis of the most common offshore structural component, the welded tubular joints. Coupled with the recent findings in inspection reliability, effective maintenance and integrity monitoring policies can be formulated.

Examples of many practical situations have been analysed to illustrate the applications of the methodology.
A managerial tool for process capability analysis
Authors: Holmes Donald S. , Mergen A. Erhan
Published: July 2007

Measures of process capability are usually presented in straight numerical form. In this paper we present a technique which displays process capability measures graphically. We call this technique a Z‐Cp chart. It is a very simple and practical descriptive statistics tool which allows managers to see graphically how the different product lines are performing or how a given process is doing over time.
Accounting for maintenance in a computer memory reliability prediction model
Authors: Miller Jeffrey E. , Hecht Hebert , Morris Seymour
Published: July 2007

This paper reviews the benefit of periodic maintenance for improving the reliability of computer memory protected by error detection and correction (EDAC), and presents a new memory reliability model that accounts for such maintenance. Mean time to failure (MTTF) has been the traditional figure of merit for assessing the benefit of memory maintenance. This paper proposes failure probability calculated at maintenance intervals as a more meaningful figure of merit for periodically maintained systems and presents examples using the new model.
Parameter tolerance design for electrical circuits
Authors: Ilumoka A. , Spence R.
Published: July 2007

Realistic circuit design requires that unavoidable tolerances on component parameters be taken into account, particularly in situations where a circuit is to be mass‐produced. Since specifications are normally imposed on circuit performance, parameter tolerances can have the undesirable effect of reducing manufacturing yield (i.e. the percentage of circuits which meet specifications) to values below unity, thereby effectively increasing circuit cost.

Approaches have been developed to electrical circuit design which incorporate aspects of parameter tolerance variations at the various stages of design, thus enabling tolerance effects to be assessed and minimized. There are two principal approaches: statistical and deterministic. The first uses probabilistic techniques to predict variations in circuit performance, whereas the second uses deterministic (i.e. non‐stochastic) methods. Within each group, three types of problems are important: first, the maximization of yield, secondly, the minimization of circuit unit cost and, thirdly, the minimization of performance variability. This paper discusses some important advances in the statistical approach to tolerance design. Monte Carlo analysis is almost invariably an important component of the procedure: random fluctuations in parameter values are simulated according to some probability density function and inserted into a computer circuit simulation program which computes corresponding circuit performance variations. The procedure — also referred to as tolerance analysis — not only allows the designer to predict expected performance fluctuations but also presents him with information regarding the relative location of acceptable and non‐acceptable circuits in component parameter space. The Monte Carlo method can handle without difficult any number of component parameters and performance functions; moreover, statistical dependence among parameters is readily handled.

The algorithm presented here is experimentally validated through successful design of practical circuits and is applicable to both discrete and integrated circuits. Strategies which ensure computational efficiency of the methods are discussed and a cost/benefit analysis carried out for a typical circuit.
A methodology for planning experiments in robust product and process design
Authors: Shoemaker Anne C. , Kacker Raghu N.
Published: July 2007

Robust design is an important method for improving product manufacturability and life, and for increasing manufacturing process stability and yield. In 1980 Genichi Taguchi introduced his approach to using statistically planned experiments in robust product and process design to U.S. industry. Since then, the robust design problem and Taguchi's approach to solving it has received much attention from product designers, manufacturers, statisticians and quality professionals. Although most agree on the importance of the robust design problem, controversy over some of the specific methods used to solve the problem has made this an active research area.

Although the answers are not all in yet, the importance of the problem has led to development of a four‐step methodology for implementing robust design. The steps are (1) formulate the problem by stating objectives and then listing and classifying product or process variables, (2) plan an experiment to study these variables, (3) identify improved settings of controllable variables from the experiment's results and (4) confirm the improvement in a small follow‐up experiment.

This paper presents a methodology for the problem formulation and experiment planning steps. We give practical guidelines for making key decisions in these two steps, including choice of response characteristics, and specification of interactions and test levels for variables. We describe how orthogonal arrays and interaction graphs can be used to simplify the process of planning an experiment. We also compare the experiment planning strategies we are recommending to those of Taguchi and to more traditional approaches.