621 research outputs found
CONSTRUCTION OF A PRECISE GROWTH MODEL TO PREDICT THE NDIVIDUAL STEM VOLUME OF Alstonia macrophylla WALL. EX G. DON
In order to reduce the pressure on existing Natural Forests in Sri Lanka,Forest Department promoted growing timber species as plantations and inhome gardens. Among the suggested species Alstonia macrophylla(Hawarinuga) has recently become popular due to its fast growth rate, ease ofestablishment and timber value. There are about 1913 ha extent of Alstoniamacrophylla plantations at the end of the year 1998 maintained by the ForestDepartment of Sri Lanka. However, this figure must be higher than thatbecause many other private organizations are establishing Alstoniamacrophylla plantations in the wet zone in large scale. This species is alsogrown in home gardens, alleys and borders as non-blocks (non-plantations).However, at present there is no method at present for estimating the stemvolume of this species, which is considered as the most important variable incommercial forestry. Therefore a mathematical model was constructed in thisstudy to predict the individual stem volume of Alstonia macrophylla treesgrown in plantations.Since Alstonia macrophylla is widely found in wet zone of Sri Lanka, studysites were selected from Galle (two even-aged plantations from Pituwala andWattehena Beats) districts. The ages of these plantations were 19 and 16respectively. Ten 0.02 ha circular plots with slope correction were randomlylaid out for each plantation, in order to measure the necessary parametersfrom the individual trees. Diameter at breast height (dbh), total height andheight to the crown base of all the trees inside the plots were measured.Newton's formula was used in this research because it is the most accuratemethod. In order to calculate the volume using the Newton's formula, thestem of each tree was hypothetically divided into 4 -5 sections. Then thebottom, mid and top diameters and section lengths were measured usingSpeigal Relascope and Blume Leiss Altimeter respectively. The final sectionof the tree was assumed as a cone and only the bottom diameter and heightwere used in that particular section. The total volume of each section wasestimated by adding the section volumes calculated using Newton's formulato the volume of the final section.First a theoretical model structure was developed using the relationship ofform factor with volume, height and area at the base. Regression analysis wasused to fit the data into the model. Untransformed as well as transformedcombinations of all variables were tested. In this procedure the combinedvariable (basal area * tree height) was always kept as the first explanatoryvariable. After trying with many combinations of selected variables withvolume, final model was selected using its compatibility with the real world,R2 values, and residual distributions, model bias value and modelingefficiency. The selected models at the preliminary stage indicated very highperformance and insignificant bias. In order to select a final one, the abovemodels were validated with a new set of data. The final selected model in thisstudy to predict the individual stem volume with insignificant bias ofAlstonia macrophylla is; --.jv= 0.659 log BA *Ht + 0.00404 ...fer h
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Impact assessment and adaptation to climate change of plantations in Sri Lanka
This report documents the work undertaken by the IRI, FECT, NRMS and University of
Peradeniya as part of the overall project. Separate reports were prepared by the Tea
Research Institute, Coconut Research Institute and the Department of Meteorology in Sri
Lanka. The work at IRI, FECT and NRMS has proceeded satisfactorily. The work was in
the domain of climate and climate change, crop-climate impact analysis and contributions
to synthesis. We have contributed significantly in terms of research output and in
capacity building, which were the goals of the AIACC project
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Multiparticle azimuthal correlations for extracting event-by-event elliptic and triangular flow in Au + Au collisions at sNN =200 GeV
We present measurements of elliptic and triangular azimuthal anisotropy of charged particles detected at forward rapidity 1<|η|<3 in Au + Au collisions at sNN=200 GeV, as a function of centrality. The multiparticle cumulant technique is used to obtain the elliptic flow coefficients v2{2},v2{4},v2{6}, and v2{8}, and triangular flow coefficients v3{2} and v3{4}. Using the small-variance limit, we estimate the mean and variance of the event-by-event v2 distribution from v2{2} and v2{4}. In a complementary analysis, we also use a folding procedure to study the distributions of v2 and v3 directly, extracting both the mean and variance. Implications for initial geometrical fluctuations and their translation into the final-state momentum distributions are discussed
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Pseudorapidity Dependence of Particle Production and Elliptic Flow in Asymmetric Nuclear Collisions of p+Al, p+Au, d+Au, and ^{3}He+Au at sqrt[s_{NN}]=200 GeV.
Asymmetric nuclear collisions of p+Al, p+Au, d+Au, and ^{3}He+Au at sqrt[s_{NN}]=200 GeV provide an excellent laboratory for understanding particle production, as well as exploring interactions among these particles after their initial creation in the collision. We present measurements of charged hadron production dN_{ch}/dη in all such collision systems over a broad pseudorapidity range and as a function of collision multiplicity. A simple wounded quark model is remarkably successful at describing the full data set. We also measure the elliptic flow v_{2} over a similarly broad pseudorapidity range. These measurements provide key constraints on models of particle emission and their translation into flow
Nuclear dependence of the transverse single-spin asymmetry in the production of charged hadrons at forward rapidity in polarized , Al, and Au collisions at GeV
We report on the nuclear dependence of transverse single-spin asymmetries
(TSSAs) in the production of positively-charged hadrons in polarized
, Al and Au collisions at
GeV. The measurements have been performed at forward
rapidity () over the range of GeV and
. We observed a positive asymmetry for
positively-charged hadrons in \polpp collisions, and a significantly reduced
asymmetry in + collisions. These results reveal a nuclear
dependence of charged hadron in a regime where perturbative techniques
are relevant. These results provide new opportunities to use \polpA collisions
as a tool to investigate the rich phenomena behind TSSAs in hadronic collisions
and to use TSSA as a new handle in studying small-system collisions.Comment: 303 authors from 66 institutions, 9 pages, 2 figures, 1 table. v1 is
version accepted for publication in Physical Review Letters. Plain text data
tables for the points plotted in figures for this and previous PHENIX
publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Nuclear dependence of the transverse-single-spin asymmetry for forward neutron production in polarized collisions at GeV
During 2015 the Relativistic Heavy Ion Collider (RHIC) provided collisions of
transversely polarized protons with Au and Al nuclei for the first time,
enabling the exploration of transverse-single-spin asymmetries with heavy
nuclei. Large single-spin asymmetries in very forward neutron production have
been previously observed in transversely polarized collisions at
RHIC, and the existing theoretical framework that was successful in describing
the single-spin asymmetry in collisions predicts only a moderate
atomic-mass-number () dependence. In contrast, the asymmetries observed at
RHIC in collisions showed a surprisingly strong dependence in
inclusive forward neutron production. The observed asymmetry in Al
collisions is much smaller, while the asymmetry in Au collisions is a
factor of three larger in absolute value and of opposite sign. The interplay of
different neutron production mechanisms is discussed as a possible explanation
of the observed dependence.Comment: 315 authors, 8 pages, 4 figures, 1 table. v2 is version accepted for
publication in Phys. Rev. Lett. Plain text data tables for the points plotted
in figures for this and previous PHENIX publications are (or will be)
publicly available at http://www.phenix.bnl.gov/papers.htm
Measurements of double-helicity asymmetries in inclusive production in longitudinally polarized collisions at GeV
We report the double helicity asymmetry, , in inclusive
production at forward rapidity as a function of transverse momentum
and rapidity . The data analyzed were taken during
GeV longitudinally polarized collisions at the Relativistic Heavy Ion
Collider (RHIC) in the 2013 run using the PHENIX detector. At this collision
energy, particles are predominantly produced through gluon-gluon
scatterings, thus is sensitive to the gluon polarization
inside the proton. We measured by detecting the decay
daughter muon pairs within the PHENIX muon spectrometers in the
rapidity range . In this kinematic range, we measured the
to be ~(stat)~~(syst). The
can be expressed to be proportional to the product of the
gluon polarization distributions at two distinct ranges of Bjorken : one at
moderate range where recent RHIC data of jet and
double helicity spin asymmetries have shown evidence for significant gluon
polarization, and the other one covering the poorly known small- region . Thus our new results could be used to further
constrain the gluon polarization for .Comment: 335 authors, 10 pages, 4 figures, 3 tables, 2013 data. Version
accepted for publication by Phys. Rev. D. Plain text data tables for the
points plotted in figures for this and previous PHENIX publications are (or
will be) publicly available at http://www.phenix.bnl.gov/papers.htm
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