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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Thin film resistance to hydrofluoric acid etch with applications in monolithic microelectronic/MEMS integration

McKenzie, Todd G. 01 December 2003 (has links)
No description available.
22

Effect of HA-coating and HF etching on experemental zirconia implant evaluation using in vivo rabbit model

Huang, Sung-En January 2010 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / The objective of this study was to evaluate the in vivo performance of the hydroxyapatite (HA) coating and hydrofluoric acid (HF) etching zirconia (ZrO) implants and to compare the result with titanium (Ti) implants treated in a similar manner. A total of four different implant types were tested in this study. Threaded zirconia implants with HA coating (Test 1) and zirconia implants with HF-treated surfaces (Test 2) were used to compare to the same size of titanium implants treated in identical fashion (control 1 and control 2). All implants measured about 3.5 mm at the thread diameter and 7.0 mm in total length. Each rabbit received two zirconia and two titanium implants treated in the same manner (either HA-coated or HF-etched). The samples were implanted into the rabbit tibias and retrieved at 6 weeks. Upon retrieval, 24 specimens (6 samples for each group) were fixed and dehydrated. The samples were then embedded undecalcified in PMMA for histomorphometry to quantify the bone-to-implant contact (BIC). Another 24 samples were kept in 0.9% saline and were evaluated using removal torque (RT) analysis to assess the strength of the implant-to-bone interface. The histomorphometric examination demonstrated direct bone-to-implant contact for all four groups. HA particle separation from the implants surface was seen in a majority of the HA-coated samples. No signs of inflammation or foreign body reaction were found during examination. Due to the HA particle smear contamination in the ZrO-HA group, no data was collected in this group. The mean BIC at the first three threads of the Ti-HA, Ti-HF and ZrO-HF were 57.78±18.22%, 46.41±14.55% and 47.41±14.05%, respectively. No statistically significant difference was found pair-wise among these three groups. When comparing the BIC data with the machined-surface implants, a statistically significant difference was found between the Ti-HA versus Ti implant group and the Ti-HF versus Ti implant group. The mean bone area (BA) at the first three threads for Ti-HA, Ti-HF and ZrO-HF showed statistically significant difference (p<0.05) between the ZrO-HF and Ti-HA groups, favoring the ZrO-HF group. The value of the peak removal force could only be collected from the Ti-HA group during the removal torque test. The mean RT value for the Ti-HA group was 24.39±2.58 Ncm. When comparing the RT result with our pilot study using machined-surface implants, the Ti-HA group showed statistically significant (p<0.05) higher values than the machined-surface Ti implants. The result of this study proves the in vivo biocompatibility of all four implant types tested. In the three measurable implant groups, the histomorphologic analysis showed comparable osseointegration properties in this animal model.
23

Effect of Hydrofluoric Acid Etching Followed by Unfilled Resin Application on the Biaxial Flexural Strength of a Glass-based Ceramic

Posritong, Sumana, 1974- January 2012 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Background: Numerous studies have reported the use of hydrofluoric (HF) acid as one of the most effective methods for the achievement of a durable bond between glass-based ceramics and resin cements. Nevertheless, there is little information available regarding the potential deleterious effect on the ceramic mechanical strength. Objectives: (1) to investigate the effect of HF acid etching regimens on the biaxial flexural strength of a low-fusing nanofluorapatite glass-ceramic (IPS e.max ZirPress, Ivoclar Vivadent), (2) to study the ability of an unfilled resin (UR) to restore the initial (i.e., before etching) mechanical strength, and (3) to evaluate the effect of HF acid etching on the ceramic surface morphology before and after UR treatment via scanning electron microscopy (SEM). Methods: One hundred and forty-four disc-shaped (15 ± 1 mm in diameter and 0.8 ± 0.1 mm in thickness) IPS e.max ZirPress specimens were allocated into 12 groups, as follows: G1-control (no etching), G2-30 s, G3-60 s, G4-90 s, G5-120 s, G6- 60 + 60 s. Meanwhile, groups (G7- G12) were treated in the same fashion as G1-G6, but followed by silane and UR applications. Surface morphology evaluation of non-etched and etched IPS e.max ZirPress (G1-G12) was carried out by scanning electron microscopy (SEM). The flexural strength was determined by biaxial testing as described in ISO 6872. Statistics were performed using two-way ANOVA and the Sidak multiple comparisons (α = 0.05). In addition, the Weibull statistics were estimated. Results: A significant effect of etching time (p=0.0290) on biaxial flexural strength was observed. Indeed, G4 led to a significantly (p=0.0392) higher flexural strength than G1. Correspondingly, G10 revealed a considerably higher flexural strength than G7 (p=0.0392). Furthermore, biaxial flexural strength was significantly higher for G7 – G12 than for G1 – G6 (p<0.0001). For G1 – G6, G4 showed the highest Weibull characteristic strength while the lowest Weibull characteristic strength was seen in G6. In G7 – G12, the highest Weibull characteristic strength was presented in G10 whereas G7 had the lowest. Finally, the SEM data revealed that the HF acid etching affected the surface of IPS e.max ZirPress by generating pores and irregularities and more importantly that the UR was able to penetrate into the ceramic microstructure. Conclusion: Within the limitations of this study, HF acid etching time did not show a damaging effect on the biaxial flexural strength of the IPS e.max ZirPress ceramic. Moreover, the ceramic biaxial flexural strength could be enhanced after UR treatment.
24

Interface Formation Between High Dielectric Permittivity Films and III-V Compound Semiconductors using HF Chemistries and Atomic Layer Deposition

Lie, Fee Li January 2011 (has links)
In-based III-V compound semiconductors have higher electron mobilities than either Si or Ge and direct band gaps. These properties could enable the fabrication of low power, high-speed n-channel metal oxide semiconductor field effect transistors (MOSFETs) and optoelectronics combining MOS technology with photonics. Since thermal and native oxides formed on III-V surfaces exhibit large current leakage and high densities of trap states, a key to incorporating these materials into advanced devices is the development of processing steps that form stable interfaces with dielectric layers. In this thesis, a processing flow consisting of native oxide removal using HF chemistries and deposition of high dielectric permittivity films using atomic layer deposition was investigated. Understanding the reaction mechanisms of these processes could provide the means of controlling composition and structure, yielding a desired electronic behavior. Quantitative X-ray photoelectron spectroscopy analysis of surfaces was coupled with electrical measurements on MOS capacitors of the interface quality in order to understand the nature of high-k/III-V interface defects and their repair. Ex situ liquid phase HF etching removed InSb, InAs, and InGaAs(100) native oxides and produced an Sb- or As-enriched surface, which oxidized when exposed to air. A 5 to 22 °A thick As- and Sb-rich residual oxide was left on the surface after etching and < 5 min of air exposure. The results showed that group V enrichment originated from the reduction of group V oxides by protons in the solution and the preferential reaction of HF with the group III atom of the substrate. A sub-atmospheric in situ gas phase HF/H2O process removed native oxide from InSb, InAs, and InGaAs(100) surfaces, producing an In or Ga fluoride-rich sacrificial layer. A 50 to 90% oxide removal was achieved and a 10 to 25 °A-thick overlayer consisting of mainly In and Ga fluorides was produced. The composition and morphology of the sacrificial layer were controlled by the partial pressure of H2O as well as the ratio of HF to H2O used. Water played a critical role in the process by directly participating in the etching reaction and promoting the desorption of fluoride etching products. Accumulation of thick fluoride layer at high HF to water partial pressure ratios prevented adsorption and diffusion of etchant to the buried residual oxide. When oxide was removed, HF preferentially reacted with In or Ga atoms from the substrate, enriching the surface with group III fluorides and producing approximately one monolayer of elemental group V atoms at the interface. Interface reactions occurred during atomic layer deposition of Al2O3, in which trimethylaluminum (TMA) removed surface oxides and fluorides. Chemically sharp InSb/Al2O3 and InGaAs/Al2O3 interfaces were achieved for gas phase HF-etched InSb and liquid phase HF-etched InGaAs. A ligand transfer mechanism promotes nucleation of Al2O3 and removal of III-V atoms from the sacrificial oxide and fluoride layers as volatile trimethyl indium, gallium, arsenic, and antimony. These reactions have been explained by the relative bond strength of surface and precursor metal atoms with O and F. Interaction of a InSb(100) surface with TiCl4 as a model for metal halide ALD precursors showed that similar ligand transfer reactions occured. Adsorbed chlorine from the dissociative adsorption of TiCl4 on the InSb surface at elevated temperature, however, preferentially etched In atoms from the substrate and produced a roughened surface. The quality of InGaAs/Al2O3 interfaces prepared by solvent cleaning and liquid phase HF were assesed electrically using capacitance-voltage and conductance measurements. Surface recombination velocity (SRV) values were extracted from the measurements to represent the net effect of interface defects, which includes defect density and capture cross section. The InGaAs/Al2O3 interface prepared by solvent cleaning consisted of interfacial native oxides while that etched in liquid phase HF consisted of submonolayer arsenic oxide. The two chemically contrasting interfaces, however, gave similar SRV values of 34.4±3.7 and 28.9±13.4 cm/s for native oxide and liquid phase HF prepared samples, respectively. This suggests that the presence or absence of oxides was not the only determining factor. Post Al2O3 deposition annealing in forming gas and NH3 ambient significantly improved the electrical quality for both surfaces, as shown by SRV values between 1 to 4 cm/s which is comparable to that of an ideal H-terminated Si surface. XPS analysis showed that the contribution from elemental As and Ga2O3 at the interface of both surfaces increased after annealing in forming gas and NH3, likely due to thermal or hydrogen-induced reaction between interfacial As oxide and Ga atoms in the substrate. There was no correlation between the atomic coverages of interfacial elemental As and oxides to the SRV values. High activity defects at III-V/Al2O3 interfaces are associated with interfacial dangling bonds which were passivated thermally and chemically by annealing in forming gas and NH3.
25

Energy absorption and vibrational heating in molecules following intense laser excitation.

McNair, Ronald Erwin January 1977 (has links)
Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Physics. / Microfiche copy available in Archives and Science. / Includes bibliographical references. / Ph.D.
26

DIFERENTES CONCENTRAÇÕES DE ÁCIDO FLUORÍDRICO E SEU EFEITO NA RESISTÊNCIA FLEXURAL DE UMA CERÂMICA VÍTREA À BASE DE DISSILICATO DE LÍTIO / HYDROFLUORIC ACID AND IT IS EFFECT ON THE FLEXURAL STRENGTH OF A LITHIUM DISILICATE- BASED GLASS CERAMIC

Prochnow, Catina 08 July 2015 (has links)
Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / This study aimed to evaluate the effect of different hydrfluoric acid (HF) concentrations on the flexural strength of a lithium disilicate based glass ceramic. Ceramic bar-specimens (14x4x1.2mm) were produced from ceramic blocks (e.max CAD, Ivoclar Vivadent), according to ISO 6872. The ceramic bars were randomly divided into 5 groups (n=23): SC (control) without treatment, HF1, HF3, HF5 e HF10 conditioned for 20 s with different acid concentrations: 1%, 3%, 5% e 10%, respectively. The etched ceramic surfaces were evaluated in a scanning electron microscope (SEM) and atomic force microscope (AFM). The roughness of treated surfaces was measured and the specimens were submitted to the 3-point flexural strength testing. Data were analyzed using 1-way ANOVA, Tukey‟s test (α=0.05), Pearson correlation and Weibull analyzis (modulus and characteristic strength). No statistical difference was found amoung groups for roughness and flexural strength, and the correlation between the data roughness and flexural strength was not statistically significance. The structural reliability (Weibull modulus) was similar among the tested groups, however, HF1 presented characteristic strength greater than HF10. The conditioning with different HF concentrations did not affect the surface roughness anfd flexural strength to a lithium disilicate based glass ceramic, when compared to untreated ceramic, regardless of the HF concentration used. / Este estudo teve como objetivo avaliar o efeito de diferentes concentrações de ácido fluorídrico (HF) na resistência flexural de uma cerâmica vítrea à base de dissilicato de lítio. Espécimes cerâmicos na forma de barra (14x4x1,2mm) foram produzidos a partir de blocos cerâmicos (e.max CAD, Ivoclar Vivadent), conforme a ISO 6872. As barras cerâmicas foram aleatoriamente divididas em 5 grupos (n=23): SC (controle) sem tratamento, HF1, HF3, HF5 e HF10 - condicionadas por 20 s com diferentes concentrações de ácido: 1%, 3%, 5% e 10%, respectivamente. As superfícies condicionadas foram avaliadas em microscópio eletrônico de varredura (MEV) e microscópio de força atômica (MFA). A rugosidade das superfícies tratadas foi aferida e os espécimes foram submetidos ao teste de resistência flexural (3 pontos). Os dados foram analisados utilizando ANOVA 1-fator, Teste de Tukey (α=0.05), Correlação de Pearson e análise de Weibull (módulo e resistência característica σₒ). Nenhuma diferença estatística foi encontrada entre os grupos para rugosidade e resistência flexural, da mesma forma que a correlação entre os dados de rugosidade e resistência flexural não teve significância estatística. A confiabilidade estrutural (modulo de Weilbull) foi semelhante entre os grupos testados, entretanto, HF1 apresentou resistência característica maior que HF10. O condicionamento com diferentes concentrações de HF não afetou a rugosidade superficial e a resistência flexural de uma cerâmica vítrea à base de dissilicato de lítio, quando comparada à cerâmica não tratada, independente da concentração de HF utilizada.
27

Efeito da neutralização e remoção sônica do precipitado do ácido fluorídrico na resistência à fratura de coroas cerâmicas

Zogheib, Lucas Villaça [UNESP] 06 July 2010 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:35:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-07-06Bitstream added on 2014-06-13T21:07:04Z : No. of bitstreams: 1 zogheib_lv_dr_sjc.pdf: 837093 bytes, checksum: 4dc61b2def9629ca9d60de96c6bceb65 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Testou-se o efeito de diferentes formas de tratamento da superfície cerâmica após condicionamento com ácido hidrofluorídrico (HF) na resistência à fratura de coroas cerâmicas à base de dissilicato de lítio. Quarenta terceiros molares humanos receberam um preparo convencional para coroa total. Após escaneamento digital dos preparos, blocos cerâmicos foram usinados pelo sistema CAD/CAM para obtenção das coroas. A espessura da película de cimento das coroas ao preparo foi verificada com silicone de adição. As coroas foram distribuídas nos 4 grupos conforme o tratamento da superfície cerâmica (n=10): (HF)- HF à 4.9% por 20s + spray ar-água por 30s; (HFN)– HF + agente neutralizador por 5 min (N); (HFU) – HF + banho sônico por 5 min (U); e (HFNU)– HF + N + U. Após aplicação de uma camada de silano (60s), as coroas foram cimentadas com cimento resinoso dual. Uma carga compressiva de 1000Kg foi aplicada no centro da face oclusal da coroa com velocidade de 1 mm/min até a fratura. Os dados foram analisados por ANOVA e Tukey (α=0,05). A carga média de fratura (Kgf) foi: HF = 169,92 ± 21,37; HFN = 187,34 ± 34,79; HFU = 166,63 ± 40,22 e HFNU = 175,26 ± 40,22. O tratamento da superfície cerâmica após condicionamento ácido não influenciou significativamente (p>0.05) na resistência à fratura das coroas cerâmicas testadas, sugerindo que é desnecessário qualquer tratamento adicional para remoção de resíduos após o uso de HF e lavagem com jato de água-ar / The effect of different ceramic surface post hydrofluoric acid (HF) etching cleaning protocols in the fracture strength of lithium dissilicate glass ceramic crowns were evaluated. Forty maxillary third human molars received a conventional full preparation. Crowns were obtained from the digital scanning of the preparations and CAD/CAM blocks machining. Crown cement film thickness was evaluated with vinyl polysiloxane. The crowns were allocated in 4 groups according to the ceramic surface treatment (n=10): (HF)- 4.9% HF for 20s + water spray for 30s; (HFN)- HF + neutralizing agent for 5 min (N); (HFU) -: HF+ sonic bath for 5 min (U) and (HFNU): HF + N + U. After a silane coat (60s), crowns were cemented with dual cure cement. A compressive load of 1000Kg was applied in the occlusal surface center at crosshead speed of 1mm/min until the fracture. Data were analyzed by one-way ANOVA and Tukey tests (α = 0.05). Fracture strength mean for each group was (Kgf): HF = 169.92 ± 21.37; HFN = 187.34 ± 34.79; HFU = 166.63 ± 40.22 e HFNU = 175.26 ± 40.22. There was no statistical difference as the surface treatment (p>0.05) suggesting that it is not necessary any additional ceramic surface treatment in order to remove debris after using of HF and air-water spray rinsing
28

Estudo da sorpcao de plutonio em coluna de alumina no sistema acido nitrico-acido fluoridrico.Aplicacao a recuperacao de plutonio de soluções do tratamento do combustivel nuclear irradiado

ARAUJO, JOSE A. de 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:24:46Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:10Z (GMT). No. of bitstreams: 1 00782.pdf: 1670811 bytes, checksum: bd77b95f1c55b0ee73feddb77b4bba3a (MD5) / Tese (Doutoramento) / IEA/T / Instituto de Energia Atomica
29

Efeito do tratamento da superfície, ciclagem térmica e fadiga mecânica na resitência de união entre uma cerâmica reforçada por dissilicato de lítio e em cimento resinoso / Effect of surface treatments, thermocycling and loading on the bond between a ceramic and a resin cement

Guarda, Guilherme Bottene, 1987- 18 August 2018 (has links)
Orientadores: Lourenço Correr Sobrinho, Mário Alexandre Coelho Sinhoreti / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-18T00:18:54Z (GMT). No. of bitstreams: 1 Guarda_GuilhermeBottene_M.pdf: 2504078 bytes, checksum: 72f1d754db2ac04524c40271b35d7366 (MD5) Previous issue date: 2011 / Resumo: O objetivo neste estudo foi investigar o efeito de diferentes tratamentos de superfície, fadiga mecânica e termociclagem na resistência da união à microtração da cerâmica IPS e.max (Ivoclar) e do cimento resinoso de ativação dupla. Métodos: 18 blocos de cerâmica (10 mm de comprimento x 7 mm de largura x 3 mm de espessura) foram confeccionados e divididos em 6 grupos (n=3): Grupos 1, 2 e 3 - jateamento por 5 segundos com partículas de óxido de alumínio de 50?m; Grupos 4, 5 e 6 - condicionamento com acido hidrofluorídrico à 10% por 20 segundos. O silano Rely X Ceramic Primer foi aplicado sobre todos os espécimes e seco por 5 minutos. Após, os blocos de cerâmica foram unidos à blocos de compósito restaurador Tetric N-Ceram (Ivoclar-Vivadent) com cimento resinoso RelyX ARC (3M ESPE), sob carga estática de 500 gf por 2 minutos. O excesso de cimento foi removido com micropincel e fotoativado por 160 segundos (40 s cada face) com um aparelho de LED (UltraLume 5, Ultradent). Os espécimes dos grupos 1 e 4 foram armazenados em água destilada a 37°C por 24 h. Nos grupos 2 e 5, os espécimes foram submetidos a 3.000 ciclos térmicos entre 5°C e 55°C. Para os grupos 3 e 6, os espécimes foram submetidos ao ensaio de fadiga mecânica por 100.000 ciclos com 2 Hz. Os espécimes foram seccionados perpendiculares a área de união para obtenção de palitos com área seccional de 1mm2 (25 palitos por grupo) e submetidos ao ensaio de resistência de união à microtração em máquina de teste universal (EZ Test - Shimadzu) com velocidade de 0,5 mm/min. Foi utilizado para verificar o padrão de fratura uma lupa estereoscópica (Olympus) com aumento de 40x. Os dados foram submetidos à Análise de Variância de 2 fatores e ao teste de Tukey (p<0,05). Os valores de resistência de união à microtração (MPa) foram: 26,9 ± 6,9, 22,2 ± 7,8 e 21,2 ± 9,1 para os Grupos 1 a 3 e 35,0 ± 9,6, 24,3 ± 8,9 e 23,9 ± 6,3 para os Grupos 4 a 6. O grupo controle submetido ao teste de fadiga e termociclado mostrou predominância de padrão de fratura adesiva para o tratamento de superfície com acido hidrofluorídrico a 10% e padrões adesiva e mista para tratamento de superfície com 50um de oxido de alumínio. Concluindo a fadiga e a termociclagem diminuíram significantemente a resistência de união à microtração para ambos os tratamentos de superfície das cerâmicas comparada ao grupo controle. Condicionamento com acido hidrofluorídrico a 10% aumentou a resistência de união à microtração para o grupo controle / Abstract: The aim of this study was to investigate the effect of surface treatments, mechanic fatigue and thermocycling tested on the microtensile bond strength of the ceramic IPS e.max Press (Ivoclar Vivadent) luted with dual-cured resin cement. Eighteen ceramic bars (10mm length x 7mm width x 3.0mm thickness) were fabricated, and divided into 6 groups (n=3): Groups 1, 2 and 3 - air particle abraded for 5 s with 50?m aluminum oxide particles; Groups 4, 5 and 6 - acid etched with 10% hydrofluoric acid for 20 s. Coupling agent silane was applied on to all bond surface specimens and allowed to dry for 5 s and the ceramic bars were bonded to a block of composite resin Tetric N-Ceram (Ivoclar-Vivadent) with Rely X ARC (3M ESPE) resin cement and placed under a 500 g static load for 2 min. The cement excess was removed with a disposable microbrush and 40 s light-activation (four activations) were performed using a LED curing unit (UltraLume LED 5, Ultradent). The specimens of the groups 1 and 4 were stored in distilled water at 37°C for 24 hours, groups 2 and 5 were submitted to 3,000 thermocycles between 5°C and 55°C and groups 3 and 6 submitted to a fatigue test for 100,000 cycles with 2 HZ. Specimens were sectioned perpendicular to the bonding area to obtain 1mm2 sectional area beams (25 beams per group) and submitted to a microtensile bond strength test in a universal testing machine (EZ Test - Shimadzu), at a crosshead speed of 0.5mm/min. The fracture specimens were observed under optical microscopy (Olympus) at a 40x magnification. Data were submitted to ANOVA and Tukey's test (p?0.05). Results: The microtensile bond strength values (MPa) were: 26.9 ± 6.9, 22.2 ± 7.8 and 21.2 ± 9.1 for G1-G3 and 35.0 ± 9.6, 24.3 ± 8.9 and 23.9 ± 6.3 for G4-G6. The control group, fatigue tested and thermocycled groups showed a predominance of failure adhesive for surface treatment with 10% hydrofluoric acid and adhesive and mixed for surface treatment with 50 ?m Al2O3. In conclusion the fatigue and thermocycling decreased significantly the microtensile bond strength for both ceramic surface treatments compared to control groups. Etching with 10% hydrofluoric acid increased the microtensile bond strength for the control group / Mestrado / Materiais Dentarios / Mestre em Materiais Dentários
30

Estudo da sorpcao de plutonio em coluna de alumina no sistema acido nitrico-acido fluoridrico.Aplicacao a recuperacao de plutonio de soluções do tratamento do combustivel nuclear irradiado

ARAUJO, JOSE A. de 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:24:46Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:10Z (GMT). No. of bitstreams: 1 00782.pdf: 1670811 bytes, checksum: bd77b95f1c55b0ee73feddb77b4bba3a (MD5) / Tese (Doutoramento) / IEA/T / Instituto de Energia Atomica

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