CONICET Digital
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El repositorio digital DSpace captura, almacena, indexa, preserva y distribuye materiales de investigación en formato digital.Sun, 23 Sep 2018 19:45:09 GMT2018-09-23T19:45:09ZInfluence of background size, luminance and eccentricity on different adaptation mechanisms
http://hdl.handle.net/11336/60700
Influence of background size, luminance and eccentricity on different adaptation mechanisms
Gloriani, Alejandro H.; Matesanz, Beatriz M.; Barrionuevo, Pablo Alejandro; Arranz, Isabel; Issolio, Luis Alberto; Mar, Santiago; Aparicio, Juan A.
Mechanisms of light adaptation have been traditionally explained with reference to psychophysical experimentation. However, the neural substrata involved in those mechanisms remain to be elucidated. Our study analyzed links between psychophysical measurements and retinal physiological evidence with consideration for the phenomena of rod-cone interactions, photon noise, and spatial summation. Threshold test luminances were obtained with steady background fields at mesopic and photopic light levels (i.e., 0.06-110 cd/m2) for retinal eccentricities from 0° to 15° using three combinations of background/test field sizes (i.e., 10°/2°, 10°/0.45°, and 1°/0.45°). A two-channel Maxwellian view optical system was employed to eliminate pupil effects on the measured thresholds. A model based on visual mechanisms that were described in the literature was optimized to fit the measured luminance thresholds in all experimental conditions. Our results can be described by a combination of visual mechanisms. We determined how spatial summation changed with eccentricity and how subtractive adaptation changed with eccentricity and background field size. According to our model, photon noise plays a significant role to explain contrast detection thresholds measured with the 1/0.45° background/test size combination at mesopic luminances and at off-axis eccentricities. In these conditions, our data reflect the presence of rod-cone interaction for eccentricities between 6° and 9° and luminances between 0.6 and 5 cd/m2. In spite of the increasing noise effects with eccentricity, results also show that the visual system tends to maintain a constant signal-to-noise ratio in the off-axis detection task over the whole mesopic range.
Mon, 01 Aug 2016 00:00:00 GMThttp://hdl.handle.net/11336/607002016-08-01T00:00:00ZEffect of steel fibers on static and blast response of high strength concrete
http://hdl.handle.net/11336/60699
Effect of steel fibers on static and blast response of high strength concrete
Luccioni, Bibiana Maria; Isla, Federico Ignacio; Codina, Ramon Humberto; Ambrosini, Ricardo Daniel; Zerbino, Raul Luis; Giaccio, Graciela Marta; Torrijos, Maria Celeste
The advantages of High Strength Fiber Reinforced Concrete (HSFRC) in static behavior highlighted by many researchers suggest it is a promising material to withstand dynamic loads. However, available experimental results regarding blast performance of HSFRC structural elements are still limited. The results of exploratory series of tests using a high strength concrete, over 100 MPa compressive strength, reinforced with long hooked-end steel fibers are presented in this paper. The results of static characterization tests performed on prisms and slabs and the results of blast tests on slabs are presented and analyzed. The improvements found in static flexure response with different fibers contents are compared with those found under blast loads. The effects of fibers controlling cracking, scabbing and spalling under close-in explosions are also addressed.
Fri, 01 Sep 2017 00:00:00 GMThttp://hdl.handle.net/11336/606992017-09-01T00:00:00ZSemisimple varieties of implication zroupoids
http://hdl.handle.net/11336/60698
Semisimple varieties of implication zroupoids
Cornejo, Juan Manuel; Sankappanavar, Hanamantagouda P.
It is a well known fact that Boolean algebras can be defined using only implication and a constant. In fact, in 1934, Bernstein (Trans Am Math Soc 36:876–884, 1934) gave a system of axioms for Boolean algebras in terms of implication only. Though his original axioms were not equational, a quick look at his axioms would reveal that if one adds a constant, then it is not hard to translate his system of axioms into an equational one. Recently, in 2012, the second author of this paper extended this modified Bernstein’s theorem to De Morgan algebras (see Sankappanavar, Sci Math Jpn 75(1):21–50, 2012). Indeed, it is shown in Sankappanavar (Sci Math Jpn 75(1):21–50, 2012) that the varieties of De Morgan algebras, Kleene algebras, and Boolean algebras are term-equivalent, respectively, to the varieties, DM, KL, and BA whose defining axioms use only the implication → and the constant 0. The fact that the identity, herein called (I), occurs as one of the two axioms in the definition of each of the varieties DM, KL and BA motivated the second author of this paper to introduce, and investigate, the variety I of implication zroupoids, generalizing De Morgan algebras. These investigations are continued by the authors of the present paper in Cornejo and Sankappanavar (Implication zroupoids I, 2015), wherein several new subvarieties of I are introduced and their relationships with each other and with the varieties studied in Sankappanavar (Sci Math Jpn 75(1):21–50, 2012) are explored. The present paper is a continuation of Sankappanavar (Sci Math Jpn 75(1):21–50, 2012) and Cornejo and Sankappanavar (Implication zroupoids I, 2015). The main purpose of this paper is to determine the simple algebras in I. It is shown that there are exactly five (nontrivial) simple algebras in I. From this description we deduce that the semisimple subvarieties of I are precisely the subvarieties of the variety generated by these simple I-zroupoids and that they are locally finite. It also follows that the lattice of semisimple subvarieties of I is isomorphic to the direct product of a 4-element Boolean lattice and a 4-element chain.
Mon, 01 Aug 2016 00:00:00 GMThttp://hdl.handle.net/11336/606982016-08-01T00:00:00ZOn derived algebras and subvarieties of implication zroupoids
http://hdl.handle.net/11336/60697
On derived algebras and subvarieties of implication zroupoids
Cornejo, Juan Manuel; Sankappanavar, Hanamantagouda P.
In 2012, the second author introduced and studied in Sankappanavar (Sci Math Jpn 75(1):21–50, 2012) the variety I of algebras, called implication zroupoids, that generalize De Morgan algebras. An algebra A= ⟨ A, → , 0 ⟩ , where → is binary and 0 is a constant, is called an implication zroupoid (I-zroupoid, for short) if A satisfies: (x→y)→z≈[(z′→x)→(y→z)′]′ and 0 ′ ′≈ 0 , where x′: = x→ 0. The present authors devoted the papers, Cornejo and Sankappanavar (Alegbra Univers, 2016a; Stud Log 104(3):417–453, 2016b. doi:10.1007/s11225-015-9646-8; and Soft Comput: 20:3139–3151, 2016c. doi:10.1007/s00500-015-1950-8), to the investigation of the structure of the lattice of subvarieties of I, and to making further contributions to the theory of implication zroupoids. This paper investigates the structure of the derived algebras Am: = ⟨ A, ∧ , 0 ⟩ and Amj: = ⟨ A, ∧ , ∨ , 0 ⟩ of A∈ I, where x∧y:=(x→y′)′ and x∨y:=(x′∧y as well as the lattice of subvarieties of I. The varieties I2 , 0, RD, SRD, C, CP, A, MC, and CLD are defined relative to I, respectively, by: (I2 , 0) x′ ′≈ x, (RD) (x→ y) → z≈ (x→ z) → (y→ z) , (SRD) (x→ y) → z≈ (z→ x) → (y→ z) , (C) x→ y≈ y→ x, (CP) x→ y′≈ y→ x′, (A) (x→ y) → z≈ x→ (y→ z) , (MC) x∧ y≈ y∧ x, (CLD) x→ (y→ z) ≈ (x→ z) → (y→ x). The purpose of this paper is two-fold. Firstly, we show that, for each A∈ I, Am is a semigroup. From this result, we deduce that, for A∈ I2 , 0∩ MC, the derived algebra Amj is a distributive bisemilattice and is also a Birkhoff system. Secondly, we show that CLD⊂ SRD⊂ RD and C⊂CP∩A∩MC∩CLD, both of which are much stronger results than were announced in Sankappanavar (Sci Math Jpn 75(1):21–50, 2012).
Fri, 01 Dec 2017 00:00:00 GMThttp://hdl.handle.net/11336/606972017-12-01T00:00:00Z