1,354,561 research outputs found
Impulse Control in Finance: Numerical Methods and Viscosity Solutions
No full textThe goal of this thesis is to provide efficient and provably convergent numerical methods for solving partial differential equations (PDEs) coming from impulse control problems motivated by finance. Impulses, which are controlled jumps in a stochastic process, are used to model realistic features in financial problems which cannot be captured by ordinary stochastic controls. In this thesis, we consider two distinct cases of impulse control: one in which impulses can occur at any time and one in which they occur only at “fixed” (i.e., nonrandom and noncontrollable) times.
The first case is used to model features in finance such as fixed transaction costs, liquidity risk, execution delay, etc. In this case, the corresponding PDEs are HamiltonJacobi-Bellman quasi-variational inequalities (HJBQVIs). Other than in certain special cases, the numerical schemes that come from the discretization of HJBQVIs take the form of complicated nonlinear matrix equations also known as Bellman problems. We prove that a policy iteration algorithm can be used to compute their solutions. In order to do so, we employ the theory of weakly chained diagonally dominant (w.c.d.d.) matrices. As a byproduct of our analysis, we obtain some new results regarding a particular family of Markov decision processes which can be thought of as impulse control problems on a discrete state space and the relationship between w.c.d.d. matrices and M-matrices. Since HJBQVIs are nonlocal PDEs, we are unable to directly use the seminal result of Barles and Souganidis (concerning the convergence of monotone, stable, and consistent numerical schemes to the viscosity solution) to prove the convergence of our schemes. We address this issue by extending the work of Barles and Souganidis to nonlocal PDEs in a manner general enough to apply to HJBQVIs. We apply our schemes to compute the solutions of various classical problems from finance concerning optimal control of the exchange rate, optimal consumption with fixed and proportional transaction costs, and guaranteed minimum withdrawal benefits in variable annuities.
The second case of impulse control, involving impulses occurring at fixed times, is frequently used in pricing and hedging insurance contracts. In this case, the impulses correspond to regular anniversaries (e.g., monthly, yearly, etc.) at which the holder of the contract can perform certain actions (e.g., lapse the contract). The corresponding pricing equations are a sequence of linear PDEs coupled by nonlinear constraints corresponding to the impulses. For these problems, our focus is on speeding up the computation associated with the nonlinear constraints by means of a control reduction. We apply our results to price guaranteed lifelong withdrawal benefits in variable annuities
Geochronology and Petrology of the Early Carboniferous Misho Mafic Complex (NW Iran), and Implications for the Melt Evolution of Paleo-Tethyan Rifting in Western Cimmeria
No full textWe report new petrological, geochemical and geochronological data from the Misho Mafic Complex (NWIran), which represents a significant component of the West Cimmerian domain in Paleo-Tethys. The Misho Mafic Complex (MMC) mainly consists of gabbros crosscut by abundant basaltic dykes and the overlying basaltic sheeted dyke complex. Gabbros are intrusive into the Precambrian continental basement representing the northern margin of Gondwana. The U–Pb zircon age of a leucogabbro dyke reveals that the igneous emplacement age of theMMC is 356.7±3.4 Ma(Early Carboniferous). The gabbros and basaltic dykes are represented by (1) a subgroup
of rocks showing normal mid-ocean ridge basalt (N-MORB) affinity, and (2) another subgroup of rocks displaying plume-type MORB (P-MORB) affinity. These subgroups of rocks are coeval. The N-MORB rocks have almost flat N-MORB normalized incompatible element patterns, low Th/Yb, Ta/Yb, Zr/Y ratios, and high Zr/Nb ratios. The P-MORB rocks show significant OIB-type trace element signatures, such as enrichments in Th, Ta, Nb and light rare earth elements (LREE) with respect to N-MORB composition, high Th/Yb, Ta/Yb, Zr/Y ratios, and low Zr/Nb ratios. Petrogenetic modeling suggests that N-MORB rocks were generated by ~13% partial melting of a depletedMORB mantle (DMM) source,whereas P-MORB rocks were generated by ~4–6% partialmelting of a DMM source metasomatized by variable proportions of OIB-type (plume-type) enriched components. The mantle melting for both N-MORBs and P-MORBs appears to have started initially deep in the garnet-facies mantle,
and then shifted to shallowlevels in the spinel-facies mantle where it experienced higher degrees of melting.
The MMC collectively formed as a product of interaction between a depleted MORB-type asthenosphere and plume-typematerial. Itsmafic–ultramafic rocks represent an early Carboniferous magmatic event developed during the continental break-up of the northern edge of Gondwana that led to the opening of Paleo-Tethys, that was
originally triggered by a mantle plume. This model is consistent with well-documented late Devonian–early Carboniferous mantle plume activity to the east, along the Paleo-Tethys margins in central-eastern Asia, and suggests that the initial rift-drift tectonics of Paleo-Tethys was strongly affected by plume-related magmatism and associated lithospheric weakening at a regional scale
Clinopyroxene compositions of the gabbros from Misho mountains in Northwestern Iran
No full textThe Misho Mts are located in the the East Azerbaijan province (NW Iran) and are bounded both in the north and the south by two dextral, oblique-strike slip Cenozoic fault systems that are responsible of the uplifting of the Precambrian to Triassic formations as a major positive flower structurehas. This mafic complex probably is a part of paleotethyan suture zone[1]. Field evidences indicate that the mafic plutonic rocks are intruded into the basement rocks of the infracambrian Kahar formation through sharp contacts. U-Pb method dating for gabbroes confirms Carboniferous age. They mainly consist of cumulate and isotropic gabbro with rare layers of dunite, pyroxenite, troctolite and anorthosite. In all magmatic varieties, the crystallization order is: (olivine) plagioclase - clinopyroxene - Fe-Ti-oxides. Gabbros display N-MORB normalized incompatible element
pattern with elemental concentration decreasing from Th to Yb. The
rocks show rather variable Mg#, most likely reflecting different, progressive degrees of fractionation. The pyroxenes in gabbros and
diabases are mostly ca-clinopyroxene. The results of EMP analysese
of clinoproxenes show that Pyroxens have diopside to augite compositions with subalkaline properties. The partial melting model of depleted MORB mantle (DMM) source[2] is shown for gabbros. Low Si, Ti, Al, Na and heigh Si in CPXs show these gabbros relation with MORBs. Low Ti and heigh Mg in CPXs are reasons for these gabbros source from pre- depleted oceanic lithosphere in within plate setting. The mantle melting originating all rock-types starts deep in the garnet-facies mantle and continues at shallow levels in the spinel-facies mantle. The Misho mafic complex is made of gabbros and sheeted dykes showing basically two magmatic affinities: N-MORB and P-MORB. The Misho mafic complex, together with the host continental
rocks, represents a part of paleotethyan ocean
Electrochemical Sensors in the Food Sector: a Review
No full textIn a world that is becoming increasingly concerned with health, safety, and the sustainability of food supply chains, the control and assurance of food quality have become of utmost importance. This review examines the application and potential of electrochemical sensors in the dynamic field of food science to meet these expanding demands. The article introduces electrochemical sensors and describes their operational mechanics and the components contributing to their function. A summary of the most prevalent electrochemical methods outlines the diverse food analysis techniques available. The review shifts to discussing the food science applications of these sensors, highlighting their crucial role in detecting compounds in food samples like meat, fish, juice, and milk for contemporary quality control. This paper showcases electrochemical sensors' utility in food analysis, underscoring their significance as powerful, efficient tools for maintaining food safety and how they could transform our approach to global food quality control and assurance
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Variations on the Author
No full text“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
No full textWe 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
No full textWe 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
Author, publisher and bookseller : a tripartite synergy in Nigerian book industry
No full textThis work is about the roles of Author, Publisher and Bookseller in Book development in
Nigeria. The paper started by delving into the history of Book Publishing in Nigeria after
which it proceeded by defining who an author, a publisher, and a bookseller is and
expatiated on the indispensable roles of these key actors in Nigerian Book Industry and in
the emerging Information Society. Furthermore, the various constraints to book
development were identified while the paper advised on how the Book Industry can be
further promoted in Nigeria. However, the paper concluded and made recommendations
on how the Book sector can help in enhancing scholarship in the country
The Thursday Murder Club: Launching a megabrand author - a publishing case study
No full textIn 2020, the Christmas book charts in the UK made headlines: Barack Obama’s eagerly awaited autobiography, The Promised Land, was beaten to the top spot by The Thursday Murder Club by Richard Osman, a debut cosy crime novel set in a retirement village. Not only did Osman’s book beat the former US president’s expected bestseller, it also broke records, becoming the fastest-selling debut crime novel of all time. Although Osman has a certain level of fame in the UK from his TV appearances on shows such as Pointless, his celebrity status does not entirely explain the novel’s huge sales. This article tracks the acquisition, publication, and promotion journey of The Thursday Murder Club in order to understand the industry and cultural context of its success and to interrogate the role of celebrity in the creation of author brands. The findings suggest that the unexpected scale of the success of the book owed to a number of factors, including in-depth editing by the novel’s agent, editor, and author to tighten up the plot, an extensive and strategic promotional campaign, the pandemic (which drove interest in the book’s genre and themes), and the quality of the writing. We find that the book’s success was accentuated by Osman’s celebrity status rather than being entirely reliant on it. This research adds to the growing scholarship on celebrity authorship by means of an in-depth case study and provides insight into the processes behind publishing a ‘celebrity’ book and launching a megabrand author
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