Читать книгу A Guide to the Scientific Career - Группа авторов - Страница 91

In an effort to address the shortcomings of the h‐index, several modifications and extensions of this index have been proposed. At least 37 h‐index variants (a.k.a. h‐type indicators or h‐index related indices) are found in literature (see Panaretos and Malesios 2009; Bornmann et al. 2011; Schreiber et al. 2012; Zhang 2013). Of course, various authorities favor certain indicators over others. Each of these indicators are intended to address one or more of the limitations presented by the original h‐index. For example, some of the h‐index variants are no longer robust to the number of excess citations of the highly cited articles in the h‐core (Jin 2006), meaning that excess citations can actually have an affect on the ranking. Other h‐related indices weigh the paper's contribution toward the index based on the number of authors (Schreiber 2008a). In a multilevel meta‐analysis, Bornmann et al. (2011) noted that “some h‐index variants have a relatively low correlation with the h‐index” and “can make a non‐redundant contribution to the h‐index.” These variants are primarily included in the modified impact index (Sypsa and Hatzakis 2009) and the m‐index (Bornmann et al. 2008).⁹

Table 9.1 Describing some of the popular h‐type indicators. Among the vast literature on h‐index variants, we single out the g‐index, the A‐index, the R‐index, the h _w ‐index, and the h _m ‐index. Alonso et al. (2010) proposed the use of the geometric mean of the h‐ and g‐indices, which they called the hg‐index, as a remedy to the high sensitivity of the g‐index to single highly cited papers. Despite the fact that h‐index variants fix some of the problems of the h‐index (e.g. the problem of the h‐index being robust to the number of citations of the h‐core's highly cited articles), there are situations where the features of the new index itself constitute a drawback. For example, some h‐index variants are influenced by the presence of one highly cited paper (Alonso et al. 2010; Costas and Bordons 2008). The g‐index specifically is limited by its extreme sensitivity to highly cited papers in a scientist's portfolio (Costas and Bordons 2008).

Table 9.1 List of h‐type indices and their descriptions.

Indicators	Definition/significance	References
w‐index	The highest number w of articles that each received 10w or more citations.	Wu (2010)
h2‐index	The highest number h(2) of articles that received at least [h(2)]2 citations.	Kosmulski (2006)
h‐index	The highest number h of articles that each received h or more citations.	Hirsch (2005)
f‐index	The highest number of articles that received f or more citations on average, where the average is calculated as the harmonic mean.	Tol (2009)
t‐index	The highest number of articles that received t or more citations on average, where the average is calculated as the geometric mean.	Tol (2009)
ħ‐index	The square root of half of the total number of citations.	Miller (2006)
s‐index	Measures the deviation from a uniform citation record.	Silagadze (2010)
h T‐index	The sum of weights of the ith citation to the rth paper.	Anderson et al. (2008)
x‐index	Maximum of the product of rank and citation frequency.	Kosmulski (2007)
A‐index	Average number of citations received by the articles in the h‐core.	Jin (2006)
g‐index	The highest number g of articles that together received g 2 or more citations.	Egghe (2006c)
m‐index	The median number of citations received by the articles in the h‐core.	Bornmann et al. (2008)
h w‐index	The square root of the total number S w of citations received by the highest number of articles that each received S w/h or more citations.	Egghe and Rousseau (2008)
R‐index	The square root of the total number of citations received by the articles in the h‐core.	Jin et al. (2007)
π‐index	The one‐hundredth of the total number of citations received by top square root of the total number of papers (“elite set of papers”).	Vinkler (2009)
e‐index	Reflects excess citations of the h‐core that are ignored by the h‐index.	Zhang (2009)
hg‐index	The geometric mean of the h‐ and g‐indices. hg‐index =	Alonso et al. (2010)

Attempts have been made to classify all of the proposed indices. Schreiber et al. (2012) suggested a classification system based on two dimensions of scientific performance: quality and quantity. This classification system considers that some indices have a stronger tendency than the rest to measure the quantity of research output, while other indices (g‐, A‐, and R‐indices) have a stronger tendency to characterize the quality of research output. It is suggested that two complementary indices, for example, h‐ and A‐indices, should be used in the scientometric analysis of an individual researcher's productivity and impact (Schreiber et al. 2011).