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Un modello di soluto polarizzabile per migliorare la procedura di stima delle cariche parziali
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
I sistemi terrazzati: un patrimonio, un rischio.
No full textTerraced systems: heritage and risk -
Artificial terracing is a “complex system of transforming
steep slopes to create cultivatable areas
through the conservation of land resources and the use
and optimal management of water resources”. The
results of this transformation can be seen in the
extremely varied and complex landscapes qualified as
World Heritage sites (Cinque Terre): probably the only
case of a natural landscape achieving this status.
In actual fact, terracing is much more than just a scenic
resource regarding which a great number of papers and
essays have been written and its value is indisputable:
despite being anthropogenic, terracing is, above all, an
integral element of the morphogenetic system, namely
of the series of processes that generate the shapes of the
earth’s surface.
As soon as a rock comes into contact with the
atmosphere, it is subjected to a series of physical and
chemical processes and agents that modify its status,
transforming its original properties. Firstly, the rock is
weathered and debris is gradually generated: this
brought to the formation of broken material formed
by small pieces of varying size. This debris can then be
transported for small or great distance depending on
its position in space. If the debris is in an area where
the morphology is gentle, featuring low gradients, it
will most probably not move a great distance from its
original position (autochthonous debris). On the other
hand, if the mass of debris sits on a steep slope, it can
travel for long distances (allochthonous debris),
depending on the factors described below.
So let’s take into consideration a natural slope, i.e. that
portion of the earth’s surface that runs between a
watershed and a valley floor. It is characterized by
geometric parameters, such as: exposure, gradient and
length of the slope. By exposure we mean how the
“face” of the slope is oriented with respect to the path
of the sun; the gradient is the angle formed between
the slope and the horizontal plane; and the length is the distance from the watershed to the valley floor.
These three parameters, when inserted in the context
of erosion processes, determine how mountain ranges
evolve. At latitudes where water is the main modelling
agent, its erosive power usually increases as the
gradient and length of the slope increase. The increase
in the erosive power of unchannellized water means
that the material produced as a result of rocks
weathering is unable to stay where it is and is instead
carried away by the water (and by the ever-present
force of gravity). There is another piece that has to be
added to the puzzle: if a certain amount of organic
material – whether of animal or plant origin – is added
to the mass of debris, we get a product that goes by the
name of soil, which is the raw material required for
farming. The soil-forming process is called pedogenesis
(pedogenetic process). The more organic material is
added and the greater the mass of debris, with the
addition of water and a favourable climate, the richer
(more fertile) the resulting soil will be.
In order to develop, the pedogenetic process
nonetheless needs a stable geomorphologic environment,
which implies a low gradient of the slopes.
Indeed, it is the gradient that increase the velocity of
surface water , and hence the strength required to
move the debris. Consequently, steep slopes prevent
the pedogenetic process from being completed with
the result that no or a very poor and not fertile soil
develops, making it inhospitable for agricultural
purposes.
This, in brief, is the morphological situation typical of
the areas involved in the alpter project: hilly or
mountainous areas, hence featuring quite steep
gradients, with few flat areas and little soil avalaible for
agricultural practices.
The need for slopes that are compatible with soil
formation led the old farmers to “build” their own flat
ground. Thus they resorted to terracing, which, as we mentioned earlier, is a “complex system of transforming
steep slopes to create cultivatable areas
through the conservation of land resources and the use
and optimal management of water resources”. Terraced
hillsides, though, interact with the morphogenetic
system. This interaction mainly lies in the forced
immobilizing of large amounts of material by means of
dry stone walls or terrace steps (calculate approx. 1 cu
m of earth for every linear metre of dry stone wall).
Looking at the interaction of terracing in terms of
interaction with the morphogenetic system, we see that
it can have feedback – like any anthropogenic action
on the land – leading to positive and/or negative
effects. Terracing has both effects: positive in that it
limits the erosive action of water washing away soil and
debris, encourages pedogenesis, contributes to the
overall stabilization of evolution in sloping areas and
helps optimize the regimes of rivers and streams; and negative because it actually robs the erosion cycle of
material, limiting the amount of debris that could
contribute to the formation of alluvial plains or, in the
case of coastal areas, possibly compounding the
shrinking beach problem as less material is carried to
the sea.
However, we should not forget that terracing is an
anthropogenic process, i.e. it is the work of man. Ever
since man appeared on the Earth, he has interacted
increasingly with the modelling processes shaping the
earth’s surface. This increase has been and continues to
be directly proportional to the technical skill and
technology that man manages to bring into play.
Human intervention of any kind must be kept efficient
and this is particularly true in the case of work like
terraces, which – despite being brilliant in concept –
are actually fragile unless their structure is kept intact.
As a matter of fact, the terraced system’s constituent
parts, retaining works and, above all, water control
elements need constant attention.
Indeed, in those areas where changed social conditions
have led to the migration from countryside to urban
areas, risk factors linked to the increase of the erosion
rate become an actual problem, with the result that
hill- and mountainsides tend to revert to the original
conditions of slopes described earlier. Water washing
away debris, once its flow is no longer regulated, and
retaining works that are left unattended have a part to
play in causing areas of instability. The more extensive
the portion of abandoned land and the longer it has
been abandoned, the more important are the
instability processes affecting areas. The balance, which
has been skilfully maintained for so many years,
quickly reaches a breaking point. To make matters
worse, on the one hand the expertise required to
maintain the terraced hillsides efficiently is practically
extinct in today’s society and, on the other, with regard
to the type of agriculture (appropriately called “heroic”), there is no economic basis to encourage
wide-ranging repair work. In a best case scenario,
repairs are limited to restoring very small portions of
land that are mainly devited for often high-quality
niche production. This neglect of the terracing is seen,
as will be illustrated in the following sections, even
where reconstruction measures have been attempted
but prove incompatible with the structure of the area
both in terms of the scenery and, from a functional
point of view.
As we have mentioned, terracing is found mainly on
steeper slopes. Nonetheless, it is not unusual to see
terracing in privileged locations on hillsides made up
of loose deposits driven by gravity, bedrock debris,
ancient stabilized landslide deposits etc. that have built
up to a certain thickness. In most cases, the grain size
features of these deposits are ideal for the ground to be
exploited for agricultural purposes since they mostly
feature:
– a matrix that is not too fine and incorporates stone
fragments in a diversity of sizes;
– chips that are tens of centimetres in diameter;
– blocks that can be used to build retaining walls or
rural buildings associated with the farming practices;
– erratic boulders, on occasion, which can measure
several cubic metres.
In the areas investigated by the project, moreover, it is
not unusual to find terracing built on stabilized
landslide deposits (Fig. 2), namely based on landslides
that occurred in the ancient past where the gradient -
which is usually less steep than in the surrounding
areas - allows a kind of terrace to be built that is wider
and not as high.
The extent of the change on the landscape, both from
an aesthetic point of view and in terms of the whole
hillside’s drainage system, is radical. The drainage
element is essential to maintain these structures since
the moment they are neglected/no longer used, the environment tends to revert to its original form,
progressively hiding the “irregularities” constituted by
the terracing (blake et al., 2003; gisotti, 2003).
When farming is discontinued, it leads to the loss of
land qualities due to the humic/clay complex, which is
rich in organic substances. As a result, the particles of
loose earth with a sandy matrix tend to slip easily
through the gaps between the elements of the wall
holding up the embankment (brancucci et al., 2001).
The surface water that seeps into the subsurface flows
toward a medium whose permeability has been
reduced, starting a failure process that affects the wall
and, consequently, the terrace (masetti et al., 2005).
The eventual failure of part of the terrace can develop
a preferential path for runoff, which becomes less and
less controllable and increasingly erosive. Consequently,
a chain reaction can ensue undermining the
whole hillside system, to the point where its stability is
compromised (Fig. 3).
From a geomorphologic point of view, the most
interesting aspect of the problem arising from the
abandoned use of terraced slopes is precisely this one,
implying, the ways in which the landscape reverts to its
original situation, preceded by the structures’ various
stages of deterioration. Based on observations, the
deterioration phenomena can be classified as:
a) internal phenomena, depending on the walls’
construction features:
– phenomena depending on defects in the wall’s
construction, such as incorrect sizing of the wall or
incorrect arrangement of the stones the actual wall is
built with;
– phenomena depending on the walls’ “natural”
deterioration processes.
b) external phenomena, not depending on the walls’ construction features (Fig. 4). – of natural origin;
– induced by human activity.
As far as deterioration generated by natural factors that
do not depend on the walls’ structure is concerned, the
following phenomena have been pointed out:
– failure of elements at the top of the wall (Fig. 5) due to
surface water runoff (when the top of the wall is built
with small-sized elements);
– partial failure of the wall due to loss of stability as a
result of a progressive increase of strain induced in the
median part of the wall by backfill pressure.
– base of the wall shifts, probably due to the force
exerted by the backfill (this phenomenon can be
accentuated by incorrect building of wall foundations
as well as by the action of animals).
As far as deterioration induced by human activity is
concerned, we basically refer to the practice of
abandoning farming and, consequently, to the neglect
of terrace maintenance, without which terraces easily
loss their benefic effects on slope stability.
The maintenance consists of a series of small, neverending
operations such as pulling out weeds; clearing
stones from the cultivated land; tidying up and
repairing dry stone walls; and cleaning drainage
channels. The absence of these operations triggers the
collapse of the whole hydrogeological control system
constituted by the terracing.
At the beginning the irrigation ditches and water
collection channels become clogged (Fig. 6): grass,
stones and earth prevent rain from flowing into the
proper channels, meaning that water runs over the
whole surface of the terrace, which is made less
permeable due to the overgrown grass that is left
unmown and the weeds that suffocate the crops. The
hillside, which is divided into a succession of terraces,
ends up interrupting the water’s flow with drops and
obstacles, causing it to become turbulent and even more erosive than a laminar flow of water over even
slopes (see cemagref, 1988).
In any case this subdivision of the causes of
deterioration into natural and anthropogenic causes
must be considered as a theoretical schematization
only, which we can gather from the very meaning of
terracing, i.e. the artificial shaping (therefore, decided
by man) of an area that would otherwise not be
farming friendly. Consequently, man is the main
engine behind the “birth”, “survival” and “death” of his
creation.
1. types of dry stone wall deterioration
In a terraced environment that is being neglected,
various kinds of failure can arise: the erosive action of
water can result in the undermining of the foot of the
wall retaining the terraced strips, which can then
topple. Water is free to seep into the terraces in an
uncontrolled and ever more violent way, generating
high pore-water pressure on the walls, which start to
bulge and then leading to actual landslides.
Moreover, landslides and bulging walls can be caused
by uncontrolled groundwater, or by a lack of
maintenance on walls. The structure of the walls is
weakened by frost or by the thrust of tree roots allowed
to grow unchecked, thus triggering the failure of parts
of the walls, starting with the top stones, which creates
openings for water to flow through.
It is common to see parts of wall that have collapsed,
leaving a clear small scarp in the part of the backfill
previously retained by the wall, and a downhil area
where the rest of the wall have been accumulated
mixed with the and slipped soil.
When a landslide occurs, an opening is created that
causes an increase in water flow rate when it rains. As
a result, the next wall down is in greater danger of succumbing to deterioration itself and this eventually
leads to trails of wreckage that can be clearly seen on
hillsides that are being neglected1.
The wall-less earth banks, on the other hand, begin to
fail when the drainage channel system is abandoned:
water runs unchannelized along the banks where the
grass is no longer mown, potentially causing small
landslides as a result of erosion induced by the surface
runoff.
Terraces failure triggers a domino effect: from the top
down, with the slippage of a terraced strip high up the
slope eventually affecting all the strips downhill; or
from the bottom up, with the collapse of a strip of land
inducing instability in the wall above it, which no
longer has foot protection.
The urbanization of valley floors is a trait common to
many terraced valleys: the morphologic situation has
forced almost the entire population to cram into the only existing flat or almost flat areas, meaning the
danger associated with the deterioration of the terraces
lying above densely-populated areas is considerable.
The abandonment of crops is generally followed by the
hillside’s renaturalization as spontaneous vegetation
(often weeds) takes over. This phase, which can vary in
length depending on the location’s characteristics,
presages the appearance of various shrubby pioneer
species, which will develop and give rise to complex
associations, until the wood is fully reinstated.
Nonetheless, we should bear in mind that the
transition from cultivated to revegetated goes through a
period of extreme dangerousness, especially considering
the fire risk, which is typical of the stage during
which terraces are abandoned and the terraced
structures deteriorate.
Analysing how these renaturalization phenomena
occur and how the growth of suitable species to
consolidate the earth might be fostered is a rather
interesting, albeit extremely complex, matter. Nonetheless,
even supposing that wood growth restores
stability to the hillside, this entails losing the
agricultural land and cultural heritage offered by the
terraced systems, which is not to be underestimated.
2. abandonment, visual conflict
and disarray on the landscape
So-called semi-abandonment seems to be almost as
frequent in terraced areas as the abandonment problem.
We frequently come across non-traditional farming
techniques that fail to use the terrace structure correctly,
from the point of view of function. Rubbish, such as
bed frames by way of fencing and bathtubs for
collecting rainwater, is often used in the farming of
terraced strips, thus employing fewer financial resources
and less energy. The visual conflict caused by these forms of “sub-farming” on the landscape is no less
serious than the risk of hillside instability resulting from
lack of maintenance, which the terraces really needed.
Greenhouse farming deserves its own special mention.
If built without the necessary precautions, greenhouses
can cause serious damages. Even when the hillside is
not completely transformed by a series of concretereinforced
terraces, during heavy rains, the waterproof
surface of the greenhouses still causes a surficial runoff
dangerous for the terracing itself as well as the people
living below. Moreover, the large amounts of chemical
fertilizers, weed killers and insecticides used must be
suitably removed from the terraced land so as not to
pollute the area downhill or contaminate the aquifers.
From the point of view of landscape ecology,
greenhouse farming can be seen as an industry for all
intents and purposes2. What’s more, when it comes to
how the landscape is perceived, greenhouses stand out
as rigid, messy volumes that are certainly not a joy to
behold, unlike a terraced hillside planted with vines or
olive trees.
The loss of knowledge of the terracing culture also has
a considerable effect on what consolidation systems are
chosen: replacing dry stone walls with reinforced
concrete walls with no outlet for water, without
allowing for drainage, can lead to even more serious failures
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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