A Simultaneous Deterministic Perturbation Actor-Critic Algorithm with an Application to Optimal Mortgage Refinancing

Wedevelopasimulation-based,two-timescale actorcritic algorithm for infinite horizon Markov decision processes with finite state and action spaces, with a discounted reward criterion. The algorithm is of the gradient ascent type and performs a search in the space of stationary randomized policies. The algorithm uses certain simultaneous deterministic perturbation stochastic approximation (SDPSA) gradient estimates for enhanced performance. We show an application of our algorithm on a problem of mortgage refinancing. Our algorithm obtains the optimal refinancing strategies in a computationally efficient manner

Current Status of Superheat Spray Modeling With NCC

An understanding of liquid fuel behavior at superheat conditions is identified to be a topic of importance in the design of modern supersonic engines. As a part of the NASA's supersonics project office initiative on high altitude emissions, we have undertaken an effort to assess the accuracy of various existing CFD models used in the modeling of superheated sprays. As a part of this investigation, we have completed the implementation of a modeling approach into the national combustion code (NCC), and then applied it to investigate the following three cases: (1) the validation of a flashing jet generated by the sudden release of pressurized R134A from a cylindrical nozzle, (2) the differences between two superheat vaporization models were studied based on both hot and cold flow calculations of a Parker-Hannifin pressure swirl atomizer, (3) the spray characteristics generated by a single-element LDI (Lean Direct Injector) experiment were studied to investigate the differences between superheat and non-superheat conditions. Further details can be found in the paper

Spinor two-point functions and Peierls bracket in de Sitter space

This paper studies spinor two-point functions for spin-1/2 and spin-3/2 fields in maximally symmetric spaces such as de Sitter spacetime, by using intrinsic geometric objects. The Feynman, positive- and negative-frequency Green functions are then obtained for these cases, from which we eventually display the supercommutator and the Peierls bracket under such a setting in two-component-spinor language.Comment: 22 pages, Latex. In the final version, the presentation has been improve

Experiencing space–time: the stretched lifeworlds of migrant workers in India

In the relatively rare instances when the spatialities of temporary migrant work, workers’ journeys, and labour-market negotiations have been the subject of scholarly attention, there has been little work that integrates time into the analysis. Building on a case study of low-paid and insecure migrant manual workers in the context of rapid economic growth in India, we examine both material and subjective dimensions of these workers’ spatiotemporal experiences. What does it mean to live life stretched out, multiplyattached to places across national space? What kinds of place attachments emerge for people temporarily sojourning in, rather than moving to, new places to reside and work? Our analysis of the spatiotemporalities of migrant workers’ experiences in India suggests that, over time, this group of workers use their own agency to seek to avoid the experience of humiliation and indignity in employment relations. Like David Harvey, we argue that money needs to be integrated into such analysis, along with space and time. The paper sheds light on processes of exclusion, inequality and diff erentiation, unequal power geometries, and social topographies that contrast with neoliberalist narratives of ‘Indian shining

Photodegradation of methyl red by advanced and homogeneous photo-​Fenton's processes: A comparative study and kinetic approach

The degrdn. of methyl red (MR)​, an azo dye, was carried out by the homogeneous photo-​Fenton's process (HPFP) and the advanced photo-​Fenton's process (APFP) using sym. peroxides such as hydrogen peroxide and ammonium persulfate (APS) as oxidants. The APFP showed higher efficiency than their homogeneous counterparts even at high dye concns. due to the faster redn. of Fe3+ to Fe2+ ions on the iron surface. H2O2 proved to be a better oxidant for both the processes. However, APS efficiently inhibited the pptn. of iron oxy hydroxides at higher dosage of iron powder compared to H2O2 by providing excess acidity to the reaction medium. The rate const. for the kinetics of decolorisation by various oxidn. processes is of the order: Fe0/H2O2/UV > Fe0/H2O2/dark > Fe0/APS​/UV > Fe2+/H2O2/UV > Fe0/UV > Fe0/APS​/dark > Fe0/dark ≈ H2O2/UV > Fe2+/APS​/UV > APS​/UV > Fe2+/H2O2/dark > Fe2+/APS​/dark ≈ Fe2+/UV. The degrdn. reaction was followed by UV-​visible and GC-​MS spectroscopic techniques. Based on the intermediates obtained, probable degrdn. mechanisms have been proposed. It was found that the initial mechanism in the APFP involves the redn. of azo groups to amines while in the case of HPFP it leads to the formation of hydroxylated products due to the oxidn. of azo groups

Coral bleaching: causes, consequences and mitigation

The coral reefs are distributed in the tropical regions and cover less than one percent of the earth’s surface, but provide habitat for many species in the marine realm. The majority of reef building corals are found in tropical and subtropical waters and typically occur between 30° N and 30° S latitudes (Fig. 1). Coral reefs are greatly valued due for their beauty, biodiversity it encompasses and the products and services they provide to human society. The coral reefs are made of calcium carbonate secreted as skeletal material by the coral polyp. Coral polyps live in association with intracellular algae (zooxanthellae), which provide additional nutrition to the coral in its life processes. The association of coral polyp with zooxanthellae, restrict its distribution in waters up to the depth of 100 meters where sunlight would be available for the photosynthetic zooxanthellae. The worldwide of zooxanthellate corals in the different distribution eco-regions is a unique underwater ecosystem and provides annual net economic benefit around 30 billion dollars (Buddemeier et al., 2004 Pew Center on Global Climate Change, 44p). However, coral reefs are most vulnerable to Climate Change due to the stenothermic nature of coral polyps

Magnetic and Thermodynamic Properties of the Collective Paramagnet-Spin Liquid Pyrochlore Tb2Ti2O7

In a recent letter [Phys. Rev. Lett. {\bf 82}, 1012 (1999)] it was found that the Tb$^{3+}$ magnetic moments in the Tb$_2$Ti$_2$O$_7$ pyrochlore lattice of corner-sharing tetrahedra remain in a {\it collective paramagnetic} state down to 70mK. In this paper we present results from d.c. magnetic susceptibility, specific heat data, inelastic neutron scattering measurements, and crystal field calculations that strongly suggest that (1) the Tb$^{3+}$ ions in Tb$_2$Ti$_2$O$_7$ possess a moment of approximatively 5$\mu_{\rm B}$, and (2) the ground state $g-$tensor is extremely anisotropic below a temperature of $O(10^0)$K, with Ising-like Tb$^{3+}$ magnetic moments confined to point along a local cubic $$diagonal (e.g. towards the middle of the tetrahedron). Such a very large easy-axis Ising like anisotropy along a$$ direction dramatically reduces the frustration otherwise present in a Heisenberg pyrochlore antiferromagnet. The results presented herein underpin the conceptual difficulty in understanding the microscopic mechanism(s) responsible for Tb$_2$Ti$_2$O$_7$ failing to develop long-range order at a temperature of the order of the paramagnetic Curie-Weiss temperature $\theta_{\rm CW} \approx -10^1$K. We suggest that dipolar interactions and extra perturbative exchange coupling(s)beyond nearest-neighbors may be responsible for the lack of ordering of Tb$_2$Ti$_2$O$_7$.Comment: 8 POSTSCRIPT figures included. Submitted to Physical Review B. Contact: [email protected]

Finite-element analysis of corner cracks in rectangular bars

Stress intensity factors for a wide range of quarter-elliptical corner cracks in rectangular bars are presented. Cracked configurations were subjected to remote tension, in-plane bending, or out-of-plane bending. Results were compared with other numerical results for a quarter-circular corner crack configuration. The present results along the interior of the crack generally agreed within 3 percent with those from the literature. Some larger differences (3 to 13 percent) were observed near the intersection of the crack front and the free surfaces in the boundary layer region. Analyses were performed to study the effect of mesh refinement in the boundary layer region and the influence of Poisson's ratio on the distribution of stress-intensity factors

Photometric Titration of Se(IV) with Fe(II)*

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Comprehensive Income Options: A Detriment To Transparency

The Financial Accounting Standards Board (FASB) in 1997 compromised its belief that comprehensive income (CI) should be listed either in a combined statement of net income and CI or in a separate statement of CI and allowed corporations to choose using the statement of changes in stockholders’ equity (SCSE).  Of course, the latter option implies just as Jordan and Clark (2002) suggest, that CI is not a measure of financial performance.  Studies incorporating professional analysts by Hirst and Hopkins (1998) and a study of nonprofessional investors by Maines and McDaniel (2000) both conclude that format presentation matters and behaviors can be affected.  We believe that FASB should revisit the format structure of CI and eliminate the SCSE option, which was their initial intent before they compromised with corporate managers in 1997.  In addition, we believe that all items of other comprehensive income (OCI) – foreign currency translation adjustment, pension value adjustments and adjustment to securities-for-sale should be presented on an after-tax basis only in order to prevent investors from being forced to comb through the footnotes