673 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
SCREENING OF WOODY AND SHRUB LEGUMES FOR AGRO-FORESTRY SYSTEMS BASED ON BIOMASS PRODUCTION, N YIELD AND BIOLOGICAL N2 FIXING CAPACITY
A field study was carried out to identify the suitable tree species for agrolorcstry systemsbased on their biomass production. N yield and Nrfixing capacity at the ExportAgriculture Research Station. Matalc for a period of 9 months. I'N isotope dilutionmethod was used for the assessment or the proportion of N2 derived through fixation (Pfix).Gl iricidi« spiurn (g+iric idia). Calliandra calothvrsus (calliandru). Lcucacna leucoccpha!a(lcucacna). Ervthrina suhumhrancc (Erythrina). Albizia [alraturi« (Albicia) and AI'(/Iiamangium (acacia) were used as N2-fixing species and SCIII/a siamea (siamca), SCI/I/aspettabilis (Spcctnhilis). both are non-nodulating legumes. and Michaella chantpaca(michalia) were used as non Ny-fixing reference species.Total dry matter yield of non Ns-Iixing reference crop spcctabilis was significantly (pO.05)higher than all the species. Among the fixing species. Calliandra produced the highestbiomass though the value is not significantly (p~O.O.'i) different from gliricidia, lcucacnaand siamca. Acacia and michaclia recorded the lowest yields.Highest leaf. twigs and root NIl,) was found in crythrina and the highest trunk N% wasassociated with gliricidia. Leaf NIYr,of spcctahilis was less than that of gliricidin andcrythrinu but total N yield of spcctabilis was the highest due to high biomass production.Among the six fixing species highest N yield was found with calliandra and the value isover two fold higher than that for gliricidia. Acacia and michaclia recorded the lowest nyields.Highest Pfix values for whole plant was found with alhizia followed by g liricidia,cnlliandra. crythrina, lcuccana and acacia. The trend is common for the values based onall the three reference crops. Total Ns-fix iug capacity 01" calliandra recorded the highestvalue followed by lcucacnn, gliricidia, albizia. crythrina, and acacia. Ny-Iixing valuescalculated based on siamea and spcctabilis revealed N-fixing species calliandra, lcucacnaand gliricidia have thc capacity to fix 19.51-23.11. 15.77-19.79 and 13.IO-l4.42g Nplant I. The values equivalent to 1<)5-231. 15X-19X and 13l-l44kg of N ha').S. spcctabilis. C calothyrsus, L. leucocephala and G. sepium produced higher biomassand higher N yields over the others. Total N fixing capacity of C calothvrsus. L.leucoccphal« and G. septum were superior to the other species. However, wheremaintenance of soil N status is considered further studies arc recommended to evaluate thelitter quality and N transferring ability before a firm recommendation is made.
Goal Commitment And Competition As Drivers For Group Productivity In Business Process Modeling
Many studies have looked at the factors that control the productivity of collaborative work. We claim that goal commitment and competition have a strong impact on group productivity in collaborative modelling. To substantiate this claim we first take a look at existing factor models to identify the factors that potentially mediate the effect on group productivity. We then investigate the relation between the factors with the help of controlled field experiments in five different organisations. We confirm the theoretical results with the help of structured equation modelling
Nanopore surface coating delivers nanopore size and shape through conductance-based sizing
The performance of nanopore single-molecule sensing elements depends intimately on their physical dimensions and surface chemical properties. These factors underpin the dependence of the nanopore ionic conductance on electrolyte concentration, yet the measured, or modeled, dependence only partially illuminates the details of geometry and surface chemistry. Using the electrolyte-dependent conductance data before and after selective surface functionalization of solid-state nanopores, however, introduces more degrees of freedom and improves the performance of conductance-based nanopore characterizations. Sets of representative nanopore profiles were used to generate conductance data, and the nanopore shape and exact dimensions were identified, through conductance alone, by orders-of-magnitude 3 reductions in the geometry optimization metrics. The optimization framework could similarly be used to evaluate the nanopore surface coating thickness
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
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
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
meson production in Au collisions at GeV
The PHENIX experiment has measured meson production in Au
collisions at GeV using the dimuon and dielectron decay
channels. The meson is measured in the forward (backward) -going
(Au-going) direction, () in the transverse-momentum
() range from 1--7 GeV/, and at midrapidity in the
range below 7 GeV/. The meson invariant yields and
nuclear-modification factors as a function of , rapidity, and centrality
are reported. An enhancement of meson production is observed in the
Au-going direction, while suppression is seen in the -going direction, and
no modification is observed at midrapidity relative to the yield in
collisions scaled by the number of binary collisions. Similar behavior was
previously observed for inclusive charged hadrons and open heavy flavor
indicating similar cold-nuclear-matter effects.Comment: 484 authors, 16 pages, 12 figures, 6 tables. v1 is the version
accepted for publication in Phys. Rev. C. Data tables for the points plotted
in the figures are given in the paper itsel
- …