Long term analysis of citation counts at the micro-level

Analysis over a 13 year period of citation counts to research papers in pursuit of a new scientific hypothesis on the mechanism of action of oestrogen hormones, which therefore could be defined at the micro-level, revealed that during a period of expansion of the field there was an overall fall in mean citation counts, even to papers bywith hindsight still successful groups. This fall appeared to be related to a relatively greater increase in the number of papers to be cited than in the number of citing papers.     

Development of a comprehensiveness of Rasch measurement application scale

A large number of papers and technical reports are published every year describing researches where Rasch models are used. It has been observed, however, that not all the authors describe the application of the Rasch measurement with the same thoroughness. Some authors may leave behind important bits of information e.g. they may fail to investigate the person or item fit or may even fail to discuss the reliability of measurement. As a result, editorial guidelines have been published in order to suggest an informal minimum of thoroughness with which the authors may describe the application of Rasch measurement in their papers. This study presents stages for the development of a scale to investigate the comprehensiveness with which individual papers describe the application of Rasch models in practical settings. The scale is used to evaluate how comprehensively the papers published by the Journal of Applied Measurement present the application of Rasch models.     

随机多孔碳纤维纸的非线性面外压缩本构模型

多孔碳纤维纸由随机分布的碳纤维构成,常用于燃料电池、发热材料等先进结构,其主要服役状态为面外压缩。碳纤维纸的压缩应变对其力学、热学、电学性能均有显著影响,因此迫切需要揭示其面外压缩本构关系。该文针对碳纤维纸微结构随机多孔的特点,提出了2种非线性面外压缩本构模型,分别是考虑赫兹接触影响的对数型模型和考虑孔隙率和单胞尺寸的幂函数型模型。基于3种商品化碳纤维纸的应力-应变实验数据,将该文提出的两种模型与传统的线性模型进行分析对比,并讨论了有、无额外有机物对碳纤维纸力学性能的影响。结果表明：碳纤维纸中的额外有机物对其应力-应变关系有比较明显的影响,全面考虑接触变形、弯曲变形与孔隙率变化的对数型本构模型具有较好的鲁棒性,适用范围较广;幂函数型本构模型能够较准确地预测有机物含量较低的碳纤维纸的应力-应变关系;传统的线性本构模型对各种碳纤维纸的预测均有较大的误差,该文提出的两种非线性本构模型对碳纤维纸具有较好的适用性,可以反映碳纤维纸的非线性应力-应变关系。     

An improved modified Weibull distribution applied to predict the reliability evolution of an aircraft lock mechanism

A new improved modified Weibull distribution (IMW), which consists of two tandem failure models is proposed in this paper. The order statistics, moment estimate and maximum likelihood estimate of the new distribution are investigated. The distribution is flexible for modeling the three phases of the modified bathtub-shaped hazard function. The modified distribution allows for enhanced statistical simulation. The new distribution is analyzed and applied to two sets of known lifetime data to demonstrate the advantages of the model. To verify the practical engineering applications of the model, reliability evolution test data for an aircraft door lock mechanism are analyzed and fitted. Based on the obtained trends of the lock hook angle and lock hook distance, we predict the evolutionary data for numerous mechanism samples, thus reducing the test cost. By considering the subdistribution and removing one parameter, the fitting effect is improved over that of the traditional distribution model.     

Superstring theory: Information transfer in an emerging field

This paper traced an individual paper through the literature as it garnered citations. This paper was chosen because of its seminal nature in a highly controversial area of theoretical physics. The distribution of citations was tested against models suggested byPrice andKuhn as well as compared to other studies which also examined benchmark papers. The results indicate that the paper chosen behaved in a significantly different way from most of the prior models. The suggestion is made that further study of this and papers like it will add much to the theory of information transfer in science.     

Long‐term Reliability Prediction of 935 nm LEDs Using Failure Laws and Low Acceleration Factor Ageing Tests

Numerous papers have already reported various results on electrical and optical performances of GaAs‐based materials for optoelectronic applications. Other papers have proposed some methodologies for a classical estimation of reliability of GaAs compounds using life testing methods on a few thousand samples over 10 000 hours of testing. In contrast, fewer papers have studied the complete relation between degradation laws in relation to failure mechanisms and the estimation of lifetime distribution using accelerated ageing tests considering a short test duration, low acceleration factor and analytical extrapolation. In this paper, we report the results for commercial InGaAs/GaAs 935 nm packaged light emitting diodes (LEDs) using electrical and optical measurements versus ageing time. Cumulative failure distributions are calculated using degradation laws and process distribution data of optical power. A complete methodology is described proposing an accurate reliability model from experimental determination of the failure mechanisms (defect diffusion) for this technology. Electrical and optical characterizations are used with temperature dependence, short‐duration accelerated tests (less than 1500 h) with an increase in bias current (up to 50%), a small number of samples (less than 20) and weak acceleration factors (up to 240). Copyright © 2005 John Wiley & Sons, Ltd.     

Models for citation behavior

The number of citations of journal papers is an important measure of the impact of research. Thus, the modeling of citation behavior needs attention. Burrell, Egghe, Rousseau and others pioneered this type of modeling. Several models have been proposed for the citation distribution. In this note, we derive the most comprehensive collection of formulas for the citation distribution, covering some 17 flexible families. The corresponding estimation procedures are also derived by the method of moments. We feel that this work could serve as a useful reference for the modeling of citation behavior.     

A hypergraph model for representing scientific output

Representation and analysis of publication data in the form of a network has become a common method of illustrating and evaluating the scientific output of a group or of a scientific field. Co-authorship networks also reveal patterns and collaboration practices. In this paper we propose the use of a hypergraph model—a generalized network—to represent publication data by considering papers as hypergraph nodes. Hyperedges, connecting the nodes, represent the authors connecting all their papers. We show that this representation is more straightforward than other authorship network models. Using the hypergraph model we propose a collaboration measure of an author that reflects the influence of that author over the collaborations of its co-authors. We illustrate the introduced concepts by analyzing publishing data of computer scientists and mathematicians in Romania over a 10 year period.     

Probabilities for encountering genius,basic, ordinary or insignificant papers based on the cumulative n<Superscript>th</Superscript> citation distribution

This article calculates probabilities for the occurrence of different types of papers such as genius papers, basic papers, ordinary papers or insignificant papers. The basis of these calculations are the formulae for the cumulative n^th citation distribution, being the cumulative distribution of times at which articles receive their n^th(n = 1,2,3,...) citation. These formulae (proved in previous papers) are extended to allow for different aging rates of the papers. These new results are then used to define different importance classes of papers according to the different values of n, in function of time t. Examples are given in case of a classification into four parts: genius papers, basic papers, ordinary papers and (almost) insignificant papers. The fact that, in these examples, the size of each class is inversely related to the importance of the journals in this class is proved in a general mathematical context in which we have an arbitrary number of classes and where the threshold values of n in each class are defined according to the natural law of Weber-Fechner.     

Endogeneity of store attributes in heterogeneous store-level sales response models

Retailing firms as a rule decide on store attributes (e.g., store size) considering an assessment of future sales of these stores. Typically, managers allocate better or more equipment to stores for which they expect higher sales. Models which ignore the fact that this behavior leads to endogeneity overestimate effects of these attributes. Managers, who base decisions on such models, loose profits by installing more (or more costly) equipment. The number of papers studying store-level sales response models accounting for endogeneity appears to be very limited. We consider potential endogeneity of store attributes in the sales response function by an instrumental variable approach. We also allow for heterogeneity across stores by assuming that store-level coefficients are generated by a finite mixture distribution. Models are estimated by a Markov chain Monte Carlo simulation technique which combines two Gibbs sampling algorithms. In the empirical study both heterogeneity and endogeneity turn out to influence estimates. For a cross section of more than 1,000 gas stations credible intervals of differences of coefficients are computed between models ignoring and models considering endogeneity. These intervals indicate that models which ignore endogeneity overestimate the effects of two store attributes on sales. We also discuss managerial implications of these endogeneity biases.     

Semantic word shifts in a scientific domain

Understanding semantic word shifts in scientific domains is essential for facilitating interdisciplinary communication. Using a data set of published papers in the field of information retrieval (IR), this paper studies the semantic shifts of words in IR based on mining per-word topic distribution over time. We propose that semantic word shifts not only occur over time, but also over topics. The shifts are examined from two perspectives, the topic-level and the context-level. According to the over-time word-topic distribution, stable words and unstable words are recognized. The diverging and converging trends in the unstable type reveal characteristics of the topic evolution process. The context-level shifts are further detected by similarities between word vectors. Our work associates semantic word shifts with the evolving of topics, which facilitates a better understanding of semantic word shifts from both topics and contexts.     

Influence of proceedings papers on citation impact in seven sub-fields of sustainable energy research 2005–2011

This paper analyses the following seven sub-fields of Sustainable Energy Research with respect to the influence of proceedings papers on citation patterns across citing and cited document types, overall sub-field and document type impacts and citedness: the Wind Power, Renewable Energy, Solar and Wave Energy, Geo-thermal, Bio-fuel and Bio-mass energy sub-fields. The analyses cover peer reviewed research and review articles as well as two kinds of proceeding papers from conferences published 2005–2009 in (a) book series or volumes and (b) special journal issues excluding meeting abstracts cited 2005–2011 through Web of Science. Central findings are: The distribution across document types of cited versus citing documents is highly asymmetric. Predominantly proceedings papers from both proceeding volumes as well as published in journals cite research articles (60–76 %). Largely, journal-based proceedings papers are cited rather than papers published in book series or volumes and have field impacts corresponding to research articles. With decreasing proceedings paper dominance in research fields the ratio of proceeding paper volumes over journal-based proceedings papers decreases significantly and the percentage of proceedings papers in journals citing journal-based proceedings papers over all publications citing journal-based proceedings papers decreases significantly (from 26.3 % in Wind Power to 4 % in Bio Fuel). Further, the segment of all kinds of proceedings papers (the combined proceedings paper types) citing all proceedings papers over all publications citing all kinds of proceedings papers decreases significantly (from 36.1 % in Wind Power to 11.3 % in Bio Fuel). Simultaneously the field citedness increases across the seven research fields. The distribution of citations from review articles shows that novel knowledge essentially derives directly from research articles (53–72 %)—to a much less extent from proceedings publications published in journals (9–13 %).     

A discussion of results from models simulating crack tip reinforcement: Fully bridged situation

Against the background of the need to understand the mechanics of toughening for various types of advanced material, several recent papers have analysed crack models in which the crack faces are bridged by a continuous distribution of springs. This paper addresses the full bridging situation, and shows how results for the linear elastic (hardening) case can, after appropriate modification, be used for the case where the springs have a linear softening law.     

The research guarantors of scientific papers and the output counting: a promising new approach

We propose a method for selecting the research guarantor when papers are co-authored. The method is simply based on identifying the corresponding author. The method is here applied to global scientific output based on the SCOPUS database in order to build a new output distribution by country. This new distribution is then compared with previous output distributions by country but which were based on whole or fractional counting, not only for the total output but also for the excellence output (papers belonging to the 10 % most cited papers). The comparison allows one to examine the effect of the different methodological approaches on the scientific performance indicators assigned to countries. In some cases, there was a very large variation in scientific performance between the total output (whole counting) and output as research guarantor. The research guarantor approach is especially interesting when used with the excellence output where the quantity of excellent papers is also a quality indicator. The impact of excellent papers naturally has less variability as they are all top-cited papers.     

The use of deciles of the citation impact to evaluate different fields of research in Israel

One often uses the average citation impact factor in order to perform international comparisons between the levels of scientific performance within given disciplines. In averaging over all (or all cited) papers one may gives undue weight to papers with few citations while, in fact, the standing of a country within a given field would be better assessed by looking only at the “successful” papers in that discipline. The present papers suggests that one should do so by averaging citations only over the ten (or twenty) percent of the most cited papers in a discipline and use these in order to establish a ranking between countries. The case of Israel is used as an illustration of this approach.     

Rapid prototyping and rapid manufacturing in medicine and dentistry

The fundamentals and latest developments of Rapid Prototyping (RP) and Rapid Manufacturing (RM) technologies and the application of most common biomaterials such as titanium and titanium alloy (Ti6Al4V) are discussed in this paper. The issues while fabricating pre-surgical models, scaffolds for cell growth and tissue engineering and concerning fabrication of medical implants and dental prostheses are addressed. Major resources related to RP/RM technology, biocompatible materials and RP/RM applications in medicine and dentistry are reviewed. A large number of papers published in leading journals are searched.

Besides the titanium and titanium alloys which were established as bio-compatible materials over five decades ago, other biocompatible materials such as cobalt-chromium and PEEK have also been increasingly used in medical implants and dental prosthesis fabrication. For over a decade RP technologies such as Selective Laser Sintering (SLS) and Selective Laser Melting (SLM) along with the Fused Depositing Modelling (FDM) are predominantly employed in the fabrication of implants, prostheses and scaffolds. Recently Electron Beam Melting (EBM) has been successfully employed for fabrication of medical implants and dental prostheses with complex features. In dentistry crown restoration, the use of thin copings of Ti6Al4V made by the EBM process is an emerging trend. This review is based upon the findings published in highly cited papers during the last two decades. However the major breakthrough in the field of RP/RM for medical implants and dental prostheses took place in the last decade. The fabrication of medical implants and prostheses and biological models have three distinct characteristics: low volume, complex shapes and they are highly customised. These characteristics make them suitable to be made by RM technologies even on a commercial scale. Finally, current status and methodology and their limitations as well as future directions are discussed.     

On the influence of growth on obsolescence

In many papers, the influence of growth on obsolescence is studied but a formal model for such an influence has not been constructed. In this paper, we develop such a model and find different results for the synchronous and for the diachronous study. We prove that, in the synchronous case, an increase of growth implies an increase of the obsolescence, while, in the diachronous case, exactly the opposite mechanism is found. Exact proofs are given, based on the exponential models for growth as well as obsolescence. We leave open a more general theory.     

Exploratory mapping of theoretical landscapes through word use in abstracts

We present a case study of how scientometric tools can reveal the structure of scientific theory in a discipline. Specifically, we analyze the patterns of word use in the discipline of cognitive science using latent semantic analysis, a well-known semantic model, in the abstracts of over a thousand academic papers relevant to these theories. Our results show that it is possible to link these theories with specific statistical distributions of words in the abstracts of papers that espouse these theories. We show that theories have different patterns of word use, and that the similarity relationships with each other are intuitive and informative. Moreover, we show that it is possible to predict fairly accurately the theory of a paper by constructing a model of the theories based on their distribution of word use. These results may open new avenues for the application of scientometric tools on theoretical divides.     

在污染环境中个体的持续生存与绝灭

近年来,国内外许多学者对环境污染下种群的持续生存与绝灭进行了大量的研究。但是,有关污染环境中非自治个体生长模型的研究刚刚起步,有关这方面的文章还很少见到。本文对具有毒素影响的非自治个体生长模型进行了研究,给出了个体持续生存与绝灭的一些充分条件。     

Is technology becoming science?

Citation and referencing data from recent biotechnology patents and bioscience papers is used to show that the bibliometric properties in these two realms are quite similar. Specifically, it is shown that the time distribution of references from both patents and papers are similar, with peak citing at two to four years prior to publication or issue. This is shown to hold for patents citing patents, for papers citing papers, and for patents citing papers. Furthermore, it is shown that there is a very skewed distribution of cited material in both patents and papers, with a relatively small number of highly cited patents and papers, and a relatively large number of documents which are cited only once or twice, or not at all. Finally, it is shown that there is a substantial amount of citation from biotechnology patents to the central scientific literature. We conclude from this that science and technology are far more closely linked today than is normally perceived, and that, in fact, the division between leading edge biotechnology and modern bioscience has alsmot completely disappeared.