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The expression ‘half‐life’, borrowed from physics, has appeared quite frequently in the literature on documentation since 1960, when an article by Burton and Kebler on The ‘half‐life’ of some scientific and technical literatures was published, although it had certainly been used previously. Burton and Kebler point out that literature becomes obsolescent rather than disintegrating (as in its original meaning), so that ‘half‐life’ means ‘half the active life’, and this is commonly understood as meaning the time during which one‐half of the currently active literature was published. Numerous studies have been carried out, mainly by the analysis of citations, to establish obsolescence rates of the literature of different subjects. Bourne points out that different studies have given widely different results, so that many of the ‘half‐life’ figures reported are not valid beyond the particular sample of literature or users surveyed; certainly they cannot be used as accurate measures for discriminating between different subject‐fields.

The main purpose of the present study is to examine the availability and persistence of URL citations in two LIS open access journals. It also intended to calculate the half‐life period of URL citations cited in journal articles.

A total of 2,890 URL citations cited in 689 research articles published in LIS journals spanning a period of 14 years (1996‐2009) were extracted. In order to check the accessibility of URL citations, W3C link checker was used. After the initial check, inactive URL citations were listed. Domains and HTTP errors associated with inactive URL citations were identified for further analysis. The half‐life period was calculated using the formula t(h)=[t ln(0.5)]/[ln W(t)−ln W(0)].

The research findings indicated that 57.61 percent (397 of 689) of articles have URL citations and percentage of URL citations increased from 5.98 percent in 1996 to 27.79 percent in 2009. It was found that 26.08 percent of all citations were not accessible during the time of testing and the majority of errors were due to HTTP 404 error code (not found). The domains.net and.gov were more stable compared to the domains.com/.co,.org, and.edu. The half‐life was computed to be approximately 11.5 years, which compares favorably against earlier research works.

This is a comprehensive study on the availability and persistence of URL citations cited in LIS journals articles spanning a period of 14 years. The findings of the study will be helpful to authors, publishers and editorial staff to improve existing URL citation conventions and to promote URL use to ensure that URL citations are accessible in future.

Symbols for concepts like ‘half life’, ‘impact factor’, ‘normalised impact factor’ and ‘immediacy index’ are proposed and formulas for the determination of their values are provided. The features of the concepts are also highlighted.

The aim of this study is to compare the situation of internet resource citations in scientific articles of the journals of Shahid Beheshti University of Medical Sciences from 2005‐2009.

The research method is an analytical survey with webometrics and citation analysis. The internet was used as a tool for accessing articles. They are separately analyzed on the basis of journal name and publication year. The analysis is done using MATLAB and Excel software.

A total of 717 articles from seven journals during five years were reviewed. Of 13,448 citations extracted, 120 internet references were found. The final results indicated that the sum of web citations is less than 1 per cent of total citations and only 52 per cent of internet citations in studied journal articles are available. The average half‐life for the medical journals is estimated to be 1.02 years.

To increase the rate of URLs availability, publishers should oblige authors to utilize online archives such as WebCite to preserve expected information for all of the citations referred to in their articles.

This research would be valuable since it is the first that studies stability and persistence of URL domains of medical journals published in Shahid Beheshti University of Medical Sciences according to type of domain names and file extensions. Moreover, this is the first time that the half‐life for medical universities web citations is calculated.

The purpose of this paper is to observe the colour and thermal stability of natural red dye consisting of anthocyanin with addition of different aqueous acids and applied as coating films.

The natural red dye was extracted from Hibiscus sabdariffa L. (roselle) flowers and mixed with 1 per cent hydrochloric acid, 5 per cent acetic acid, 5 per cent citric acid and 5 per cent oxalic acid. All the dye samples were exposed to heat and UV-B to observe the colour stability by calculating the half-life and rate of reaction. In coating film application, each of the dye samples was mixed with 25 wt% of poly(vinyl alcohol) (PVA) and applied on to a glass substrate. The coating samples’ colour stability was observed by using CIE L*a*b* colour space coordinates. The coating films’ weight loss stability against temperature was observed by using thermogravimetric analysis.

Addition of hydrochloric acid enhances the thermal and UV stability of the anthocyanin natural dye. This can be observed from the calculation of the half-life of the dye. The half-life values for the thermal and UV stability studies were 1,155 hours and 210 hours, respectively. In coating films, the sample with addition of acetic acid showed the highest colour stability with colour difference (ΔE*) value 8.95.

The coating films developed in this work are not suitable to be applied on metal substrates due to the presence of water, which can contribute to the corrosion formation.

The coating films developed in this work are suitable for washable coating application. In other words, they are non-permanent coatings applied on a glass substrate.

Development of water-based coatings from PVA binder with anthocyanin colourant is introduced in this study.

Terminology and parameters for describing the relation between figures for the use of library literature and for its age are discussed. Unless a correction for growth is applied, half‐life fails a simple test of suitability, as do Brookes's ageing and utility factors. Results based on cumulated data have other important disadvantages. Relative ‘use‐per‐item’ figures are satisfactory. The need to relate terminology more closely to the facts they represent is stressed: item‐consultation decay rate, and 50% consultation probability age are suggested and defined. In the context of citation studies, item‐citation decay rate and 50% citation probability age are equivalent and avoid similar objections. In data from NRLSI, item‐consultation decay rates are only approximately exponential. Different rates are demonstrated for updating and basic searches, for academic and other types of readers, and for types of literature. For some historical searches negative decay rates were found in the NRLSI and BML.

Condition-based maintenance (CBM) has become a central maintenance approach because it performs more efficient diagnoses and prognoses based on equipment health condition compared to time-based methods. CBM models greatly inform maintenance decisions. This research examines three CBM fault prognostics models: logical analysis of data (LAD), artificial neural networks (ANNs) and proportional hazard models (PHM). A methodology, which involves data pre-processing, formulating the models and analyzing model outputs, is developed to apply and compare these models. The methodology is applied on NASA’s Turbofan Engine Degradation data set and the structural health monitoring (SHM) data set from a Nova Scotia Bridge. Results are evaluated using three metrics: error, half-life error and a cost score. This paper concludes that the LAD and feedforward ANN models compares favorably to the PHM model. However, the feedback ANN does not compare favorably, and its predictions show much larger variance than the predictions from the other three methods. Based on these conclusions, the purpose of this paper is to provide recommendations on the appropriate situations in which to apply these three prognostics models.

LAD, ANNs and PHM methods are adopted to perform prognostics and to calculate the mean residual life (MRL) of eqipment using NASA’s Turbofan Engine Degradation data set and the SHM data set from a Nova Scotia Bridge. Statistical testing was used to evaluate the statistical differences between the approaches based on these metrics. By considering the differences in these metrics between the models, it was possible to draw conclusions about how the models perform in specific cases.

Results were evaluated using three metrics: error, half-life error and a cost score. It was concluded that the LAD and feedforward ANN models compares favorably to the PHM model. However, the feedback ANN does not compare favorably and its predictions show much larger variance than the predictions from the other three methods. Overall the models predict failure after it has already occurred (negative error) when the residual life is large and vice versa.

It was concluded that a good CBM prognostics model for practical implications can be determined based on three main considerations: accuracy, run time and data type. When accuracy is a main concern, as in the case where impacts of failure are large, LAD and feedforward neural network are preferred. The preference changes when run time is considered. If data can be easily collected and updating the model is performed often, the ANNs and LAD are preferred. On the other hand, if CM data are not easily obtainable and existing data are not representative of the population’s behavior, data type comes into play. In this case, PHM is preferred.

Previous research in the literature performed reviews of multiple independent studies on CBM techniques performed on different data sets. They concluded that it is typically harder to implement artificial intelligence models, because of difficulties in data procurement, but these approaches offer improved performance as compared to more traditional model-based and statistical approaches. In this research, the authors further investigate and compare the performance and results from two major artificial intelligence models, namely, ANNs and LAD, and one pioneer statistical model, PHM over the same two real life prognostics data sets. Such in-depth comparison and review of major CBM techniques was missing in current literature of CBM field.

The purpose of the paper is to investigate the causal relationships and speed of adjustment of stock prices to changes in macroeconomic information (MEI) in Ghana from 1996 to 2018 using monthly data. The paper seeks to conduct the investigation at individual MEI level rather than the composite MEI.

Quantitative approach was used in this paper. Monthly data span of 1996–2018 was used. The delay and half-life technique was used to determine the speed with which the information resulting from the changes in the macroeconomic are evident in the stock price. Thereafter, Toda–Yamamoto Granger no-causality approach was used to examine the causal relationship amongst variables.

The paper revealed that although the market adjustment to MEI has improved, the speed is till slow. The exchange rate exhibited the slowest speed in respect of the market reaction while the market reaction to money supply was the fastest. Toda–Yamamoto Granger no-causality estimation also revealed a bi-directional causality between MEI (gross domestic product, interest rate and money supply) and stock price and uni-directional relationship flowing from MEI (the exchange rate and foreign direct investment) to stock price. The paper also found no causality between inflation and stock price.

The findings although revealed improved level of market efficiency in comparison with the earlier data, the speed of adjustment is still undesirable. Rigorous approach should be adopted for the implementation of major reforms such as alternative market so as to increase the number of share listing and to increase the scope of investors' participation to enhancing trading volume and marketability and ultimately speed up information diffusion.

The practical implication of the low level of information processing rate of Ghana Stock Exchange (averagely more than a month) is that astute investors and market analysts could employ MEI to outperform the market prior to their infusion onto the stock market.

This study is one of the few studies in the Ghanaian literature that has extended the investigation of the speed of adjustment beyond composite or aggregate macroeconomic level estimation to estimation at individual variable level. This contribution is very relevant since each macroeconomic variable has unique characteristics and require specific policy framework, it is important to consider the speed of adjustment from the perspective of each of the individual variables.

The aim of this chapter is to explore whether price dynamics is homogenous across Emerging Europe. We employ dynamic panel estimation techniques (including the Pooled Mean Group estimator of Pesaran, Smith, and Shin) over the 2003–2013 period and use Germany, and respectively, the European Union (EU) as the references. Results highlight some heterogeneity across the Emerging Europe members in terms of price convergence speed. Findings are robust across different specifications.