Avaliação e reforço sísmico de estruturas de betão armado

Apresenta-se um programa experimental que incluiu o ensaio em escala real de dois pórticos de betão armado representativos da construção no sul da Europa com 40/50 anos, com necessi-dade de reabilitação sísmica. São feitas algumas considerações sobre o comportamento experi-mental das estruturas, que foram ensaiadas sem qualquer intervenção, posteriormente reparadas e novamente ensaiadas considerando diferentes técnicas de reforço sísmico

Electron Spin Resonance G Shift In Gd5 Si4, Gd5 Ge4, And Gd5.09 Ge2.03 Si1.88

Gd5 Si4, Gd5 Ge4, and Gd5.09 Ge2.03 Si1.88 compounds were studied by electron spin resonance. The arc-melted samples were initially characterized by optical metallography, x-ray diffraction, and static magnetization measurements. The electron spin resonance results show a negative paramagnetic g shift for Gd5 Si4 and Gd5.09 Ge2.03 Si1.88, and a smaller positive one for Gd5 Ge4. The values of the exchange parameter (j) between the localized Gd-4f spins and the conduction electrons are obtained from the g shifts. These values are positive and of the same order of magnitude for Gd5 Si4 and Gd5.09 Ge2.03 Si1.88, and negative one order of magnitude smaller for Gd5 Ge4. The electron spin resonance data were interpreted considering the strongly bottlenecked solution of the coupled Bloch-Hasegawa equations. © 2006 The American Physical Society.7314Pecharsky, V.K., Gschneidner Jr., K.A., (1997) Phys. Rev. Lett., 78, p. 4494. , PRLTAO 0031-9007 10.1103/PhysRevLett.78.4494Pecharsky, V.K., Gschneidner Jr., K.A., (1997) J. Alloys Compd., 260, p. 98. , JALCEU 0925-8388 10.1016/S0925-8388(97)00143-6Choe, W., Pecharsky, V.K., Pecharsky, A.O., Gschneidner Jr., K.A., Young Jr., V.G., Miller, G.J., (2000) Phys. Rev. Lett., 84, p. 4617. , PRLTAO 0031-9007 10.1103/PhysRevLett.84.4617Levin, E.M., Pecharsky, V.K., Gschneidner Jr., K.A., (2000) Phys. Rev. B, 62, p. 14625. , PRBMDO 0163-1829 10.1103/PhysRevB.62.R14625Szade, J., Skorek, G., (1999) J. Magn. Magn. Mater., 196-197, p. 699. , JMMMDC 0304-8853Levin, E.M., Pecharsky, V.K., Gschneidner Jr., K.A., (1999) Phys. Rev. B, 60, p. 7993. , PRBMDO 0163-1829 10.1103/PhysRevB.60.7993Harmon, B.N., Antonov, V.N., (2002) J. Appl. Phys., 91, p. 9815. , JAPIAU 0021-8979 10.1063/1.1461896Levin, E.M., Pecharsky, V.K., Gschneidner Jr., K.A., Miller, G.J., (2001) Phys. Rev. B, 64, p. 235103. , PRBMDO 0163-1829 10.1103/PhysRevB.64.235103Skorek, G., Deniszczyk, J., Szade, J., (2002) J. Phys.: Condens. Matter, 14, p. 7273. , JCOMEL 0953-8984 10.1088/0953-8984/14/30/316Samolyuk, G.D., Antropov, V.P., (2002) J. Appl. Phys., 91, p. 8540. , JAPIAU 0021-8979 10.1063/1.1455614Pecharsky, V.K., Samolyuk, G.D., Antropov, V.P., Pecharsky, A.O., Gschneidner Jr., K.A., (2003) Solid State Chem., 171, p. 57. , 29CBA6Pires, M.J.M., Magnus Carvalho G, A., Gama, S., Da Silva, E.C., Coelho, A.A., Mansanares, A.M., (2005) Phys. Rev. B, 72, p. 224435. , PRBMDO 0163-1829 10.1103/PhysRevB.72.224435Gama, S., Alves, C.S., Coelho, A.A., Ribeiro, C.A., Persiano, A.I.C., Silva, D., (2004) J. Magn. Magn. Mater., 272-276, p. 848. , JMMMDC 0304-8853Usenko, N.I., Ivanov, M.I., Berezutski, V.V., Polotska, R.I., (1998) J. Alloys Compd., 266, p. 186. , JALCEU 0925-8388Zipper, E., (1982) J. Phys. F: Met. Phys., 12, p. 3123. , JPFMAT 0305-4608Glaunsinger, W.S., (1976) J. Phys. Chem. Solids, 37, p. 51. , JPCSAW 0022-3697 10.1016/0022-3697(76)90179-7Kaczmarska, K., (1996) J. Alloys Compd., 240, p. 88. , JALCEU 0925-8388Barnes, S.E., (1981) Adv. Phys., 30, p. 801. , ADPHAH 0001-8732 10.1080/00018738100101447Taylor, R.H., Coles, B.R., (1975) J. Phys. F: Met. Phys., 5, p. 121. , JPFMAT 0305-4608 10.1088/0305-4608/5/1/017Kaczmarska, K., Kwapulińska, E., Lebarski, A., Zipper, E., Chelkowski, A., (1985) J. Magn. Magn. Mater., 50, p. 101. , JMMMDC 0304-8853Schütz, G., Knülle, M., Wienke, R., Wilhelm, W., Wagner, W., Kienle, P., Frahm, R., (1988) Z. Phys. B: Condens. Matter, 73, p. 67. , ZPCMDN. 0722-3277. 10.1007/BF01312156Kim, J.W., Lee, Y., Wermeille, D., Sieve, B., Tan, L., Bud'Ko, S.L., Law, S., Goldman, A.I., (2005) Phys. Rev. B, 72, p. 064403. , PRBMDO 0163-1829 10.1103/PhysRevB.72.064403Lee, Y., Kim, J.W., Goldman, A.I., Harmon, B.N., (2005) J. Appl. Phys., 97, pp. 10A311. , JAPIAU 0021-8979 10.1063/1.185221

Electron Spin Resonance And Magnetic Characterization Of The Gd5.09 Ge2.03 Si1.88

Electron spin resonance was applied on samples of Gd5.09 Ge2.03 Si1.88. The results are discussed under the scope of magnetization measurements, optical metallography, and wavelength dispersive spectroscopy. Polycrystalline arc-melted samples submitted to different heat treatments were investigated. The correlation of the electron spin resonance and magnetization results permitted a characterization of the present phases and their transitions. Two coexisting phases in the temperature range between two phase transitions have been identified and associated to distinct crystallographic phases. Additionally, the magnetic moment at high temperatures has been estimated from the measured effective g factor. A peak value of 21.5 J kg K for the magnetocaloric effect was obtained for a sample heat treated at 1500°C for 16 h. © 2005 The American Physical Society.7222Morellon, L., Algarabel, P.A., Ibarra, M.R., Blasco, J., Garcia-Landa, B., Arnold, Z., Albertini, F., (1998) Phys. Rev. B, 58, p. 14721. , PRBMDO 0163-1829 10.1103/PhysRevB.58.R14721Levin, E.M., Pecharsky, V.K., Gschneidner Jr., K.A., (1999) Phys. Rev. B, 60, p. 7993. , PRBMDO 0163-1829 10.1103/PhysRevB.60.7993Levin, E.M., Pecharsky, V.K., Gschneidner Jr., K.A., (2000) Phys. Rev. B, 62, p. 14625. , PRBMDO 0163-1829 10.1103/PhysRevB.62.R14625Pecharsky, A.O., Gschneidner Jr., K.A., Pecharsky, V.K., (2003) J. Magn. Magn. Mater., 267, p. 60. , JMMMDC 0304-8853 10.1016/S0304-8853(03)00305-6Gama, S., Alves, C.S., Coelho, A.A., Ribeiro, C.A., Persiano, A.I.C., Silva, D., (2004) J. Magn. Magn. Mater., 272-276, p. 848. , JMMMDC 0304-8853Pecharsky, V.K., Gschneidner Jr., K.A., (1997) Phys. Rev. Lett., 78, p. 4494. , PRLTAO 0031-9007 10.1103/PhysRevLett.78.4494Szade, J., Skorek, G., (1999) J. Magn. Magn. Mater., 196-197, p. 699. , JMMMDC 0304-8853Magnus Carvalho, G.A., Nascimento, F.C., Alves, C.S., Doce, T.S., Gama, S., Cardoso, L.P., Coelho, A.A., (2005), Influence of the processing parameters on structural and magnetic properties of the Gd5.09 Ge2.03 Si1.88 compound," presented at the First International Conference on Magnetic Refrigeration at Room Temperature, Montreux, Switzerland, 27-30 SeptemberPoole, C.P., (1967) Electron Spin Resonance: A Comprehensive Treatise on Experimental Techniques, pp. 814-822. , 1st ed. (J. Wiley, New YorkAbragam, A., Bleaney, B., (1986) Electron Paramagnetic Resonance of Transition Ions, p. 335. , 1st ed. (Dover Publications, New YorkTaylor, R.H., Coles, B.R., (1975) J. Phys. F: Met. Phys., 5, p. 121. , JPFMAT 0305-4608 10.1088/0305-4608/5/1/017Stoppels, D., Sawatzky, G.A., (1978) Phys. Rev. B, 18, p. 157. , PLRBAQ 0556-2805 10.1103/PhysRevB.18.157Samolyuk, G.D., Antropov, V.P., (2002) J. Appl. Phys., 91, p. 8540. , JAPIAU 0021-8979 10.1063/1.1455614Von Ranke, P.J., De Oliveira, N.A., Gama, S., (2004) J. Magn. Magn. Mater., 277, p. 78. , JMMMDC 0304-8853 10.1016/j.jmmm.2003.10.013Von Ranke, P.J., De Oliveira, N.A., Mello, C., Carvalho, A.M., Gama, S., (2005) Phys. Rev. B, 71, p. 054410. , PRBMDO 0163-1829 10.1103/PhysRevB.71.054410Zipper, E., Kaczmarska, K., Kwapulinska, E., Pichet, J., (1984) J. Magn. Magn. Mater., 40, p. 259. , JMMMDC 0304-8853Heimann, J., Kaczmarska, K., Kwapulinska, E., Slebarski, A., Chelkowski, A., (1982) J. Magn. Magn. Mater., 27, p. 187. , JMMMDC 0304-885

Acoustic Detection Of The Magnetocaloric Effect: Application To Gd And Gd5.09 Ge2.03 Si1.88

In this paper we present a simple method for the determination of the total magnetocaloric effect based on the acoustic detection of the adiabatic temperature rise caused by the application of an ac magnetic field of small amplitude. The continuous scanning of a superimposed dc magnetic field allows, by numerical integration, the determination of large temperature variations caused by magnetic field steps from zero to tens of kOe. Absolute values of temperature rise are easily acquired after the calibration of the microphone signal using an appropriate reference sample. Once the calibration is done, no further information about the sample's thermal properties is necessary since the measured signal is directly proportional to the temperature variation. Measurements were made in Gd and Gd5.09 Ge2.03 Si1.88 samples in the temperature range from 240 to 320 K. The technique shows to be suitable for the investigation of materials undergoing both purely magnetic phase transitions, as in the case of Gd, and magnetic-crystallographic first-order ones, as observed for Gd5.09 Ge2.03 Si1.88. Besides the ability to determine the temperature variation due to a large magnetic field step through the continuous scanning of the magnetic field, the technique is also very suitable for measuring the magnetocaloric effect under very small magnetic field steps since it has sensitivity below millikelvin. Moreover, it is able to detect temperature variations in very small amount of sample, leading to its potential application in magnetocaloric thin films. © 2009 The American Physical Society.8013Foldeaki, M., Schnelle, W., Gmelin, E., Benard, P., Koszegi, B., Giguere, A., Chahine, R., Bose, T.K., (1997) J. Appl. Phys., 82, p. 309. , 10.1063/1.365813Pecharsky, V.K., Gschneidner, Jr.K.A., (1999) J. Appl. Phys., 86, p. 565. , 10.1063/1.370767Gopal, B.R., Chahine, R., Bose, T.K., (1997) Rev. Sci. Instrum., 68, p. 1818. , 10.1063/1.1147999Pecharsky, V.K., Gschneidner, Jr.K.A., (1999) J. Magn. Magn. Mater., 200, p. 44. , 10.1016/S0304-8853(99)00397-2Pecharsky, V.K., Gschneidner, Jr.K.A., (1997) Phys. Rev. Lett., 78, p. 4494. , 10.1103/PhysRevLett.78.4494Otowski, W., Glorieux, C., Hofman, R., Thoen, J., (1993) Thermochim. Acta, 218, p. 123. , 10.1016/0040-6031(93)80416-8Gopal, B.R., Chahine, R., Földeàki, M., Bose, T.K., (1995) Rev. Sci. Instrum., 66, p. 232. , 10.1063/1.1145264Rosencwaig, A., Gersho, A., (1976) J. Appl. Phys., 47, p. 64. , 10.1063/1.322296Pecharsky, V.K., Gschneidner, Jr.K.A., (2001) Adv. Mater., 13, p. 683. , 10.1002/1521-4095(200105)13:93.0.CO;2-OVon Ranke, P.J., De Oliveira, N.A., Gama, S., (2004) J. Magn. Magn. Mater., 277, p. 78. , 10.1016/j.jmmm.2003.10.013Carvalho, A.M.G., Alves, C.S., Campos, A., Coelho, A.A., Gama, S., Gandra, F.C.G., Von Ranke, P.J., Oliveira, N.A., (2005) J. Appl. Phys., 97, pp. 10M320. , 10.1063/1.1860932Pecharsky, A.O., Gschneidner, Jr.K.A., Pecharsky, V.K., (2003) J. Magn. Magn. Mater., 267, p. 60. , 10.1016/S0304-8853(03)00305-6Gama, S., Alves, C.S., Coelho, A.A., Ribeiro, C.A., Persiano, A.I.C., Silva, D., (2004) J. Magn. Magn. Mater., 272-276, p. 848. , 10.1016/j.jmmm.2003.12.1260Pires, M.J.M., Carvalho, A.M.G., Gama, S., Da Silva, E.C., Coelho, A.A., Mansanares, A.M., (2005) Phys. Rev. B, 72, p. 224435. , 10.1103/PhysRevB.72.224435Glorieux, C., Thoen, J., Bednarz, G., White, M.A., Geldart, D.J.W., (1995) Phys. Rev. B, 52, p. 12770. , 10.1103/PhysRevB.52.12770Bednarz, G., Geldart, D.J.W., White, M.A., (1993) Phys. Rev. B, 47, p. 14247. , 10.1103/PhysRevB.47.14247Yu. Dan'Kov, S., Tishin, A.M., Pecharsky, V.K., Gschneidner, Jr.K.A., (1998) Phys. Rev. B, 57, p. 3478. , 10.1103/PhysRevB.57.3478Glorieux, C., Caerels, J., Thoen, J., (1996) J. Appl. Phys., 80, p. 3412. , 10.1063/1.363208Pecharsky, V.K., Gschneidner, Jr.K.A., (1999) J. Appl. Phys., 86, p. 6315. , 10.1063/1.371734Giguere, A., Foldeaki, M., Ravi Gopal, B., Chahine, R., Bose, T.K., Frydman, A., Barclay, J.A., (1999) Phys. Rev. Lett., 83, p. 2262. , 10.1103/PhysRevLett.83.2262Yue, M., Zhang, J., Zeng, H., Chen, H., Liu, X.B., (2006) J. Appl. Phys., 99, pp. 08Q104. , 10.1063/1.2158971Tocado, L., Palacios, E., Burriel, R., (2006) J. Therm Anal. Calorim., 84, p. 213. , 10.1007/s10973-005-7180-zGschneidner, Jr.K.A., Pecharsky, V.K., Brück, E., Duijn, H.G.M., Levin, E.M., (2000) Phys. Rev. Lett., 85, p. 4190. , 10.1103/PhysRevLett.85.419

Effect of partial soil wetting on transpiration, vegetative growth and root system of young orange trees

The wetted area fraction is a factor critical to the success of drip irrigation. This study aimed to evaluate the effect of partial soil wetting on transpiration, vegetative growth and root system of young orange trees. The experiment was carried out in a greenhouse where plants were grown in 0.5 m3boxes internally divided into compartments. The wetting of 12 % of soil area was tested on two types of soil cultivated with ‘Valencia’ orange trees grafted onto Rangpur lime and ‘Swingle’ citrumelo rootstocks. Transpiration was determined in 40 plants. Water extraction and root density were evaluated in the compartments. Transpiration is reduced by restriction in wetted soil area, and such reduction is influenced by the number of days after the beginning of partial irrigation, atmospheric evaporative demand and plant phenological stage. Mean transpiration of plants with partial irrigation was equivalent to 84 % of the mean transpiration of plants with 100 % of wetted soil area in the period studied. However, after 156 days of imposing partial irrigation there was no difference in transpiration between treatments. Plant acclimation was caused by an increase in root concentration in the irrigated area. After a period of acclimation, if the entire root system is wetted, soil water extraction becomes proportional to the percentage of wetted area after a short period of time. Despite the reduction in transpiration, there was no difference between treatments with 12 % and 100 % of wetted soil area in terms of vegetative growth