5,876 research outputs found
Damage formation on fused silica illuminated with ultraviolet-infrared femtosecond pulse pairs
No full textCitation: Yu, X., Chang, Z., Corkum, P. B., & Lei, S. (2015). Damage formation on fused silica illuminated with ultraviolet-infrared femtosecond pulse pairs. Proceedings of SPIE. doi:10.1117/12.2182633We investigate damage formation on the surface of fused silica by two femtosecond laser pulses, a tightly focused 266 nm (UV) pulse followed by a loosely focused 800 nm (IR) pulse. We show that the damage size is determined by the UV pulse, and only a small fraction of the normal UV damage threshold energy is needed to cause damage when combined with the properly delayed IR pulse. Our results, analyzed with a rate equation model, suggest that the UV pulse generates seed electrons through multiphoton absorption and the IR pulse utilizes these electrons to cause damage by avalanche ionization. By tuning such parameters like pulse energy, time delay, IR pulse duration and polarization, we further demonstrate that damage profile can be controlled. Copyright © 2015 SPIE
Dataset for the paper "Climate model bias indicates higher projected future temperature extremes"
No full text<div>
<div>This repository holds data and scripts used to produce the paper entitled:</div>
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<div>"Climate model bias indicates higher projected future temperature extremes"</div>
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<div>by Lei Duan, Lyssa M. Freese, Govindasamy Bala, and Ken Caldeira.</div>
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<div>The paper is currently submitted for peer review.</div>
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<div>Any questions regarding the data and paper could be sent to the corresponding author: Lei Duan ([email protected])</div>
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Lei nº 12.846, de 2013: mudanças e perspectivas na responsabilização da pessoa jurídica
No full textTCC(graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Jurídicas. Direito.Este trabalho propõe-se a, inicialmente, analisar os motivos que levaram à elaboração da Lei nº 12.846, de 2013, assim como os princípios de direito constitucional e administrativo que servirão como sua base legitimadora e fundamentarão sua atuação. Posteriormente a tal análise, elaborar-se-á, a partir do rito processual administrativo previsto na Lei nº 9.784, de 1999, a estrutura processual e a sequência dos procedimentos que as pessoas jurídicas de direito privado que forem investigadas a partir da Lei nº 12.846 serão sujeitas, com destaque aos pontos em que o novo diploma legal diverge ou acrescenta no previsto pela Lei processual, assim como suas semelhanças e peculiaridades quando comparado a outros corpos normativos similares. Após, será realizado estudo relativo ao instituto da responsabilidade objetiva previsto na Lei nº 12.846, sua evolução histórica e as consequências de sua aplicação na seara administrativa. A matéria de análise subsequente tratará das possíveis sanções a serem aplicadas contra as pessoas jurídicas de direito privado condenadas em processo administrativo, as previsões aplicáveis frente a seus gestores, além das possibilidades de responsabilização judicial elencadas na nova Lei. Em seguida será exposta ponderação no tocante a Acordos de Leniência, sua aplicação no direito brasileiro e suas perspectivas frente à Lei nº 12.846, onde esta possibilidade de acordo vêm prevista. No capítulo final deste trabalho serão analisados os programas de Compliance, que cada vez mais ganham importância no cenário econômico internacional e passam a receber grande impulso a partir das previsões contidas na nova Lei. Também neste bloco serão elencadas críticas e análises que vem sendo elaboradas por profissionais do ramo jurídico frente à nova Lei, contrapostas pela leitura do autor dos dispositivos contestados.This paper proposes to initially analyze the reasons that led to the drafting of Law No. 12.846, of 2013, as well as the principles of constitutional and administrative framework will serve as a legitimizing basis and will base its operations right. Subsequent to this analysis, will be drawn up, from the administrative procedural rite under Law No. 9.784, of 1999, the procedural structure and sequence of procedures that legal entities of private law which are investigated from the Law No. 12.846 will be subject, highlighting the points where the new law differs or adds predicted by the procedural law, as well as their similarities and peculiarities when compared to similar regulatory bodies. After, will be held on the institute's strict liability under Law No. 12.846, its historical evolution and study the consequences of its application in administrative harvest. The subsequent analysis focuses on the field of the possible sanctions to be applied against legal persons of private law convicted in an administrative proceeding, the predictions apply against their managers, the possibilities of judicial accountability listed in the new law. Next will be exposed weighting in respect of the leniency agreements, their implementation in Brazilian law and its prospects ahead to Law No. 12,846, where this possibility according come provided. In the final chapter of this work the Compliance programs, which increasingly gain importance in the international economic scenario and started to receive major boost from the forecasts contained in the new law also in this block will be analyzed and critical analysis that has been developed will be listed by professionals in the legal branch opposite the new law, opposing the reading of the author of the disputed devices
Thermally assisted high efficiency ductile machining of nanocrystalline hydroxyapatite: a numerical study
No full textThis study investigates the role of thermal assistance and tool geometry on ductile regime machining of a nanocrystalline (nano-HAP) bioceramic using numerical simulation. AdvantEdge FEM Version 5.9 is used to conduct the simulation of orthogonal machining of the nano-HAP material. Thermal boundary conditions are specified to approximate laser preheating of the work material. The effects of operating conditions (preheat temperature, rake angle, and edge radius) on critical depth of cut, cutting force, and thrust force are investigated. Based on the pressure-based criterion for ductile regime machining (DRM), the dependence of critical depth of cut on preheating temperature is examined. It is found that for different combinations of rake angle and edge radius, the critical depth of cut increases as thermal boundary temperature increases. In addition, it is concluded that using higher thermal boundary temperature for smaller negative or 0° rake angle, we can achieve the comparable critical depth of cut obtained by using a higher negative rake angle, which usually generates higher thrust force and consequently deteriorates the dimensional accuracy of finished parts
Nanofiltration and sensing of picomolar chemical residues in aqueous solution using an optical porous resonator in a microelectrofluidic channel
No full textFor the first time the use a porous microresonator placed in a microelectrofluidic system for integrated functions of nano filtration and sensing of small biomolecules and chemical analytes in extremely dilute solution was proposed and investigated. As an example, aminoglycosides in drug residues in food and livestock products were considered as the trace chemical analyte. The filtration process of the charged analyte in aqueous solution driven by an applied electrical field and the accompanied optical whispering-gallery modes in the resonator are modeled. The dynamic process of adsorption and desorption of the analyte onto the porous matrix is studied. The analyte deposition inside the porous structure will alter the material refractive index of the resonator, and thus, induce optical resonance frequency shift. By measuring the optical frequency shift, the analyte concentration as well as the absorption/desorption process can be analyzed. Through an intensive numerical study, a correlation between the frequency shift and the analyte concentration and the applied electrical voltage gradient was obtained. It reveals a linear relationship between the resonance frequency shift and the analyte concentration. The applied electrical voltage enhances substantially the filtration capability and the magnitude of the optical frequency shift, pushing the porous resonator-based sensor to function at the extremely dilute picomolar concentration level for small bio/chemical molecules down to the sub-nanometer scale. Moreover, use of the second-order whispering-gallery mode is found to provide better sensitivity as compared with the first-order mode.Peer reviewed
An exploratory study of multiple identities in East Asian American women who are attracted to women
No full textThis exploratory study examined the experiences of East Asian American women who are romantically or sexually attracted to women (EAAWAW). EAAWAW was selected as the most inclusive term for women self-identifying as lesbian, gay, queer, and bisexual. EAAWAW have previously been studied as a population that experiences unique challenges due to their multiple minority status. They have to navigate situations in which one or more of their minority statuses related to their gender, sexual orientation, and ethnicity are stigmatized, which might lead to psychological stress. Three main research questions were addressed in this study: 1) What are the challenges that EAAWAW face with regard to their sexual identity, gender, and ethnicity? 2) How do they deal with these challenges? Specifically, how might they utilize multiple self-aspects to manage stigma and stress associated with being attracted to women, East Asian, and female? 3) How do EAAWAW conceptualize themselves with regard to their identity and how does their self-concept vary across contexts? A qualitative analysis of nine semi-structured, in-depth interviews was completed using a grounded theory approach. Participants ranged in age from 25 to 65 and were all residing in the United States. The interview data were analyzed to uncover qualitative themes. These included the range of identities and roles with which EAAWAW identify, multiple minority stress, invisibility, conflict between sexual orientation and family and East Asian values, freedom from societal norms, positive discrimination, benevolent prejudice, social support, identity management, and cognitive reframes. Overall, despite the stigma- related challenges that EAAWAW experience, the individuals interviewed in this study demonstrated much resilience and a variety of coping strategies that allowed them to move between communities and manage their multiple identities. These findings are discussed as well as their important implications for EAAWAW, their families, mental health professionals, and the communities to which EAAWAW belong. The study suggests that these groups would benefit from an increased understanding of the nature of multiple minority stress as well as the variety of cognitive, interpersonal, and identity management strategies available to EAAWAW as they navigate different communities and contexts in their personal and professional lives.Psy. D.Includes bibliographical referencesby Diana Lei Lei On
Fabricating nanostructures on fused silica using femtosecond infrared pulses combined with sub-nanojoule ultraviolet pulses
No full textCircular craters with diameters of 500 nm are fabricated on the surface of fused silica by femtosecond ultraviolet–infrared (UV–IR) pulse trains with 0.8 nJ UV pulse energy. UV damage thresholds at different IR energies and UV–IR delays are measured. Diameters and depths of the ablated craters can be modified by adding the IR pulse and varying the UV–IR delays. These results demonstrate the feasibility of nanomachining using short wavelength lasers with pulse energy far below normal damage thresholds
Friction and wear behavior of WS2/Zr self-lubricating soft coatings in dry sliding against 40Cr hardened steel balls
No full textWS[subscript 2] and WS[subscript 2]/Zr self-lubricating soft coatings were produced by medium-frequency magnetron sputtering, multi-arc ion plating and ion beam assisted deposition technique on the cemented carbide YT15 (WC+15%TiC+6%Co) substrates. Microstructural and fundamental properties of these coatings were examined. Sliding wear tests against 40Cr hardened steel using a ball-on-disk tribometer method were carried out with these coated materials. The friction coefficient and wear rates were measured with various applied loads and sliding speeds. The wear surface features of the coatings were examined using SEM. The results showed that the WS-1 specimen (with WS[subscript 2]/Zr composite coating) has higher hardness and coating/substrate critical load compared with that of the WS-2 specimen (only with WS2 coating). The friction coefficient of WS-1 specimen increases with the increase in applied load, and is quite insensitive to the sliding speed. The wear rate of the WS-1 specimen is almost constant under different applied loads and sliding speeds. The WS-1 specimen shows the smallest friction coefficient and wear rate among all the specimens tested under the same conditions. The WS-1 specimen exhibits improved friction behavior to that of the WS-2 specimen, and the antiwear lifetime of the WS2 coatings can be prolonged through adding Zr additives. The self-lubricating and wear mechanism of the WS[subscript 2]/Zr coating was also found from the sliding wear tests
Periodic and uniform nanogratings formed on cemented carbide by femtosecond laser scanning
No full textPeriodic and uniform nanogratings are fabricated by femtosecond laser scanning on cemented carbide. Specifically, three experiments are designed to study the influence of single pulse energy, scanning speed, and scanning spacing on the period and the uniformity of the formed nanogratings. The results show that the sample with single pulse energy of 2 μJ, scanning speed of 1000 μm/s, and scanning spacing of 5 μm shows the best quality of nanogratings among all the tested samples at different processing parameters. The uniformity of the nanogratings is largely determined by single pulse energy, scanning speed, and scanning spacing. Single pulse energy and scanning speed significantly affect the period of the nanogratings, whereas the period of the nanogratings maintains a fixed value under different scanning spacings. The period of the nanogratings increases gradually with the decrease of the single pulse energy and the increase of the scanning speed, respectively
A study on laser-fiber coupling efficiency and ablation rate in femtosecond laser deep microdrilling
No full textLaser microdrilling is a common micromachining operation in many industrial applications. This paper presents a new laser microdrilling technique in which a hollow-core fiber is employed to transmit femtosecond laser pulses to the target position. The coupling efficiency between the laser and the fiber is investigated and found to be strongly related to pulse energy and pulse duration. A parametric study on the ablation rate indicates that in microdrilling of a stainless steel (type 303), the operating parameters including pulse energy, pulse duration, sample thickness, focal length and sample-fiber distance can affect the ablation rate. The experimental results show that the new technique developed in this study is feasible to conduct microdrilling of holes with high aspect ratio
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