29 research outputs found
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A Simple Decision - and How to Get There
Combinations of 7 remarkably similar factors have led to the (partial)
failure of recent efforts to address five global or national crises. The paper
analyzes the global financial crisis, climate change, the US health care
crisis, the blue fin tuna collapse in the Atlantic Ocean and the collapse of
fish stocks in Yemen and West Africa from the optics of (i) the strategy of
politics, (ii) the role of science and economics, (iii) the effect of (dis-)
information and communications, (iv) the role of leadership, (v)
weaknesses of institutions and (vi) a variable rest factor, including the
nature of opposition. Final decisions balancing the long-term future impact
of maintaining the status-quo (or worse) for millions or even billions of
stakeholders against the short-term benefits for far fewer stakeholders,
favoring the latter, suggest that neither science nor economic
considerations largely determined the final outcome, but that a more
complex vector of factors was at work. To better manage this vector in
fisheries, a Fisheries Authority may be more suitable than existing
Ministries and Departments. The author suggests that to improve the
chances of success of future local and regional fisheries management: (i) a
global pilot program be created with some external donor assistance -
establishing Fisheries Authorities in developed and developing countries to
demonstrate more effective sector management; and (ii) BA and MA
programs be created at two highly rated universities in developed and
developing countries to educate future fisheries managers in critical
subjects that impact decision making
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PFS = ECY + SEP
The inability to find a solution – acceptable to sufficient stakeholders to achieve political agreement - to effectively adjust fisheries resources management systems and sector policies lies at the heart of most overexploitation tragedies. For developing countries the application of a technological approach - focusing on rights, maximizing single, economic or biological objectives - is largely irrelevant. To successfully introduce necessary changes in their sector policies and resources management systems, they require operational analysis of politically feasible solutions to create the political critical mass to support adjustment and a roadmap to move the political processes. This paper explains what caused operational ‘politics’ to be ignored in the past, what analytical tools exist and it provides an example of the scope of potential benefits of such political analysis. The paper discusses the Politically Feasible Solution (PFS), the outcome of political processes and decisions – analyzed in advance - that better satisfies a larger number of stakeholders compared to the without analysis scenario. To create multi-stakeholder consensus, such political analysis may use parameters that combine the multiple interests of key stakeholder groups into a single variable. Joining scientific, commercial and public finance objectives, the Effective Commercial Yield (ECY) would enable the fleet to: (a) compete effectively in international markets, and (b) provide a share of the resource rent to the public sector. The Socio-economic and Environmental Program (SEP) combines the multiple objectives of small-scale fishermen for meaningful employment with those of environmental protection and biodiversity interests
Modeling the sorption dynamics of NaH using a reactive force field
We have parametrized a reactive force field for NaH, ReaxFFNaH, against a training set of ab initio derived data. To ascertain that ReaxFFNaH is properly parametrized, a comparison between ab initio heats of formation of small representative NaH clusters with ReaxFFNaH was done. The results and trend of ReaxFFNaH are found to be consistent with ab initio values. Further validation includes comparing the equations of state of condensed phases of Na and NaH as calculated from ab initio and ReaxFFNaH. There is a good match between the two results, showing that ReaxFFNaH is correctly parametrized by the ab initio training set. ReaxFFNaH has been used to study the dynamics of hydrogen desorption in NaH particles. We find that ReaxFFNaH properly describes the surface molecular hydrogen charge transfer during the abstraction process. Results on heat of desorption versus cluster size shows that there is a strong dependence on the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. To gain more insight into the structural transformations of NaH during thermal decomposition, we performed a heating run in a molecular dynamics simulation. These runs exhibit a series of drops in potential energy, associated with cluster fragmentation and desorption of molecular hydrogen. This is consistent with experimental evidence that NaH dissociates at its melting point into smaller fragments
Predictions of melting, crystallization, and local atomic arrangements of aluminum clusters using a reactive force field
A parametrized reactive force field model for aluminum ReaxFFAl has been developed based on density functional theory (DFT) data. A comparison has been made between DFT and ReaxFFAl outputs to ascertain whether ReaxFFAl is properly parametrized and to check if the output of the latter has correlation with DFT results. Further checks include comparing the equations of state of condensed phases of Al as calculated from DFT and ReaxFFAl. There is a good match between the two results, again showing that ReaxFFAl is correctly parametrized as per the DFT input. Simulated annealing has been performed on aluminum clusters Aln using ReaxFFAl to find the stable isomers of the clusters. A plot of stability function versus cluster size shows the existence of highly stable clusters (magic clusters). Quantum mechanically these magic clusters arise due to the complete filling of the orbital shells. However, since force fields do not care about electrons but work on the assumption of validity of Born–Oppenheimer approximation, the magic clusters are therefore correlated with high structural symmetry. There is a rapid decline in surface energy contribution due to the triangulated nature of the surface atoms leading to higher coordination number. The bulk binding energy is computed to be 76.8 kcal/mol. This gives confidence in the suitability of ReaxFF for studying and understanding the underlying dynamics in aluminum clusters. In the quantification of the growth of cluster it is seen that as the size of the clusters increase there is preference for the coexistence of fcc/hcp orders at the expense of simple icosahedral ordering, although there is some contribution from distorted icosahedral ordering. It is found that even for aluminum clusters with 512 atoms distorted icosahedral ordering exists. For clusters with N≥256 atoms fcc ordering dominates, which implies that at this point we are already on the threshold of bulklike bonding
Parametrization of a reactive force field for aluminum hydride
A reactive force field, REAXFF, for aluminum hydride has been developed based on density functional theory (DFT) derived data. REAXFF_(AlH_3) is used to study the dynamics governing hydrogen desorption in AlH_3. During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by REAXFF_(AlH_3). Results on heat of desorption versus cluster size show that there is a strong dependence of the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. In the gas phase, it was observed that small alane clusters agglomerated into a bigger cluster. After agglomeration molecular hydrogen was desorbed from the structure. This thermodynamically driven spontaneous agglomeration followed by desorption of molecular hydrogen provides a mechanism on how mobile alane clusters can facilitate the mass transport of aluminum atoms during the thermal decomposition of NaAlH_4
Modeling of Hydrogen Storage Materials: A Reactive Force Field for NaH
Parameterization of a reactive force field for NaH is done using ab initio derived data. The parameterized force field(ReaxFFNaH) is used to study the dynamics governing hydrogen desorption in NaH. During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by the parameterized force field. To gain more insight into the mechanism governing structural transformation of NaH during thermal decomposition a heating run in a molecular dynamics simulation is done. The result shows that a clear signature of hydrogen desorption is the fall in potential energy surface during heating
Multiscale modeling of interaction of alane clusters on Al(111) surfaces: A reactive force field and infrared absorption spectroscopy approach
We have used reactive force field (ReaxFF) to investigate the mechanism of interaction of alanes on Al(111) surface. Our simulations show that, on the Al(111) surface, alanes oligomerize into larger alanes. In addition, from our simulations, adsorption of atomic hydrogen on Al(111) surface leads to the formation of alanes via H-induced etching of aluminum atoms from the surface. The alanes then agglomerate at the step edges forming stringlike conformations. The identification of these stringlike intermediates as a precursor to the bulk hydride phase allows us to explain the loss of resolution in surface IR experiments with increasing hydrogen coverage on single crystal Al(111) surface. This is in excellent agreement with the experimental works of Go et al. [ E. Go, K. Thuermer, and J. E. Reutt-Robey, Surf. Sci. 437, 377 (1999) ]. The mobility of alanes molecules has been studied using molecular dynamics and it is found that the migration energy barrier of Al_(2)H_6 is 2.99 kcal/mol while the prefactor is D_0 = 2.82 × 10^(−3) cm^2/s. We further investigated the interaction between an alane and an aluminum vacancy using classical molecular dynamics simulations. We found that a vacancy acts as a trap for alane, and eventually fractionates/annihilates it. These results show that ReaxFF can be used, in conjunction with ab initio methods, to study complex reactions on surfaces at both ambient and elevated temperature conditions