4,116 research outputs found

    Inverse Methods: a Powerful Tool for Evaluating Aerosol Data, Exemplified on Cases With Relevance for the Atmosphere and the Aerosol Climate Effect

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    For a complete description of a given aerosol, more than one parameter is necessary, e.g. parameters concerning size distribution, chemical composition, and particle morphology. On the other hand, most instruments measuring aerosol properties are sensitive mostly to one parameter, but cross-sensitive to others. These cross-sensitivities are often eliminated by assumptions during data evaluation, inducing systematic uncertainties in the results. The use of assumptions can be reduced by combining the information of several instruments on the same aerosol and using inverse methods for interpretation of the data. The presentation focuses on two application examples of these methods. The first example concerns a size distribution inversion algorithm that combines data from several instruments into one size distribution. The second example deals with an algorithm that retrieves the aerosol asymmetry parameter (with respect to particle scattering) from measurements of the aerosol absorption and spectral scattering and hemispheric backscattering coefficients, thereby providing a set of parameters that completely describes an aerosol with respect to its direct climate effect

    Some aspects of the ecology of the leatherback turtle Dermochelys coriacea at Laguna Jalova, Costa Rica

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    The ecology and reproductive biology of the leatherback turtle (Dennochelys coriacea) was studied on a high-energy nesting beach near Laguna Jalova, Costa Rica, between 28 March and 8 June 1985. The peak of nesting was between 15 April and 21 May. Leatherbacks here measured an average 146.6 cm straightline standard carapace length and laid an average 81.57 eggs. The eggs measured a mean 52.12 mm diameter and weighed an average of 85.01 g. Significant positive relationships were found between the carapace lengths of nesters and their clutch sizes and average diameter and weight of eggs. The total clutch weighed between 4.02 and 13.39 kg, and yolkless eggs accounted for an average 12.4% of this weight. The majority of nesters dug shallow (<24 cm) body pits and spent an average 81 minutes at the nest site. A significant number of c1utcbes were laid below the berm crest. In a hatchery 42.2% of the eggs hatched, while in natural nests 70.2% hatched. The average hatchling carapace length was 59.8 mm and weight was 44.6 g. The longevity of leatherback tracks and nests on the beach was affected by weather. One nester was recaptured about one year later off the coast of Mississippi, U.S.A. Egg poaching was intense on some sections of the Costa Rican coast. Four aerial surveys in four different months provided the basis for comparing density of nesting on seven sectors of the Caribbean coast of Costa Rica. The beach at Jalova is heavily used by green turtles (Chelonia mydJJs) after the leatherback nesting season. The role of the Parque Nacional Tortuguero in conserving the leatherback and green turtle is discussed.(PDF file contains 20 pages.

    Stochastic solutions of Stefan problems

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    This work deals with the one-dimensional Stefan problem with a general time-dependent boundary condition at the fixed boundary. Stochastic solutions are obtained using discrete random walks, and the results are compared with analytic formulae when they exist, otherwise with numerical solutions from a finite difference method. The innovative part is to model the moving boundary with a random walk method. The results show statistical convergence for many random walkers when Δx→0\Delta x \rightarrow 0. Stochastic methods are very competitive in large domains in higher dimensions and has the advantages of generality and ease of implementation. The stochastic method suffers from that longer execution times are required for increased accuracy. Since the code is easily adapted for parallel computing, it is possible to speed up the calculations. Regarding applications for Stefan problems, they have historically been used to model the dynamics of melting ice, and we give such an example here where the fixed boundary condition follows data from observed day temperatures at \"{O}rebro airport. Nowadays, there are a large range of examples of applications, such as climate models, the diffusion of lithium-ions in lithium-ion batteries and modelling steam chambers for petroleum extraction.Comment: Submitted as Proceedings to Stochastic Processes and Algebraic Structures (SPAS) 201

    What Does Homesteading Mean for Us? Better Living Now in Many Ways: Part I

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    Objekti kÀÀnde varieerumine eesti keele da-infinitiiviga konstruktsioonides

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    VĂ€itekirja elektrooniline versioon ei sisalda publikatsiooneProbleemi kirjeldus. Reeglid, mis kirjeldavad tĂ€is- ja osasihitise vastandust eesti keeles, kehtivad kĂŒllaltki jĂ€rjekindlalt, kui sihitis kuulub finiitse verbivormi juurde, mitte aga siis, kui sihitis laiendab infiniitset verbivormi. Kui finiitlauses on keelekasutajal enamasti lihtne otsustada, kas sĂŒndmus on mĂ”eldud kestva vĂ”i lĂ”petatuna, ja sihitise kÀÀne valitakse sellest tĂ”lgendusest tulenevalt (vrd kĂŒpsetas Ă”unakooki ja kĂŒpsetas Ă”unakoogi), siis nĂ€iteks da-infinitiivi puhul on mĂ”testus palju hĂ€gusam: kas tahan kĂŒpsetada Ă”unakooki vĂ”i tahan kĂŒpsetada Ă”unakoogi? MĂ”lemad variandid on vĂ”imalikud. See aga ei tĂ€henda, et sihitise kÀÀnde valik oleks juhuslik; isegi kui puudub selge reegel, mille jĂ€rgi saab sobivaima kÀÀnde valida, on igal lausel mĂ”ned olulised sĂŒntaktilis-semantilised tunnused, mis suunavad valikut, soodustades ĂŒhe vĂ”i teise kÀÀnde kasutust. Doktoritöö keskendub objekti kÀÀndevalikule da-infinitiivi puhul, mis on kĂ”ige laiema kasutusalaga infiniitne verbivorm eesti keeles. Uurimuse ĂŒks pĂ”hieesmĂ€rk oli vĂ€lja selgitada da-infinitiivi konstruktsioonides esineva sihitise kÀÀnde valikut mĂ”jutavad tegurid ning nende omavahelised suhted, vaadeldes lauseid, milles sihitise kÀÀnde seletamiseks ei piisa objekti vormivahelduse pĂ”hireeglitest. Lisaks oli eesmĂ€rgiks vĂ”rrelda erinevaid da-infinitiiviga konstruktsioone, et nĂ€ha, kuivĂ”rd sarnased on neis sihitise kÀÀnet mĂ”jutavate tegurite kimbud: kas kĂ”igis konstruktsioonides ilmnevad samad tendentsid? Tulemus ja kasutegur. Sihitise kÀÀnde varieerumine da-infinitiiviga konstruktsioonides on tihedalt seotud sĂ”najĂ€rjega ning sellega, kas lauses kirjeldatakse korduvat vĂ”i ĂŒhekordset sĂŒndmust; osasihitis on sagedasem korduvate sĂŒndmuste puhul ning siis, kui sihitis eelneb da-infinitiivile. Lisaks vĂ”ivad mĂ”ju avaldada leksikaalsed elemendid, mis ei kuulu da-infinitiiviga fraasi (vrd nĂ€iteks verbe tahtma ja otsustama; tahtis osta autot on palju vastuvĂ”etavam kui otsustas osta autot). Doktoritöö nĂ€itab, et tegeliku keelekasutuse selgitamiseks ei piisa „reeglitest“, tegemist on konstruktsioonidele omaste, sageli erinevate tendentsidega, kusjuures mĂ”nes konstruktsioonis kasutatakse sihitise kÀÀndeid ĂŒsna ebajĂ€rjekindlalt. Sellise varieerumise seletamiseks tuleb keelekasutust vaadelda kui omavahel vastandlike motivatsioonide vĂ”istluse tulemust, kus on argumendid nii tĂ€is- kui ka osasihitise kasutamise poolt, kuid igas konkreetses lauses vĂ”ib ainult ĂŒks kÀÀne peale jÀÀda. Uurimistulemused on huvipakkuvad rahvusvahelise keeleteaduse jaoks ning annavad olulist infot eesti keele uurimise, keeleĂ”ppe jm rakenduste jaoks.Research question. The rules describing the alternation between total and partial objects in Estonian do not apply with nearly the same regularity in daÂŹ-infinitive constructions as they do in finite clauses. In finite clauses, it is generally easy for the speaker to decide whether he/she conceptualizes an event as continuous or completed, and to choose the appropriate object case accordingly (partial object for continuous activity, total object for completed events). With da-infinitives, however, things are much less clear: does tahan kĂŒpsetada koogi/kooki (‘I want to bake a cake’) mean “I want to bake a cake (and achieve the result)” or “I want to be engaged in the activity of baking a cake”? Both are possible. However, this does not mean that the choice of object case is random; even if there is no clear rule to follow, every sentence has some essential syntactic-semantic features which push the language user in the direction of either the partial or total object. One primary aim of the thesis was to identify the factors influencing the choice of object case in da-infinitive constructions and their relative importance, looking at sentences where the standard rules for object case do not provide a sufficient explanation. In addition, the thesis compares various da-infinitive constructions, to see how similar or different they are with respect to which factors influence object case: can the same patterns be observed in all da-infinitive constructions? Results and contribution of the thesis. Object case variation in da-infinitive constructions is closely tied to word order and whether the sentence describes a repeating or non-repeating situation; the partial object is more common in the case of repeating situations and OV word order (where the object precedes the infinitive form). Moreover, different constructions feature different lexical elements, which are not part of the non-finite clause but nevertheless can exert a substantial influence on the form of the object modifying the infinitive. The thesis demonstrates that the “rules” for object case are not sufficient to explain actual language usage, as in several da-infinitive constructions object case usage is quite inconsistent. To explain such variation, it is helpful to view language usage as the product of competing motivations, with some factors supporting the use of the partial object and others the total object. The research results will be of interest to the international linguistics community and can also be applied in the teaching of Estonian as a foreign language
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