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Listas de cabeçalhos de assunto e tesauros: discussões e iniciativas à luz da justiça social e equidade
(Universidade Federal de São Carlos, 2023-04-14) Silva, Fabíola Rubim; Dal'Evedove, Paula Regina; https://lattes.cnpq.br/1170937498266968; https://lattes.cnpq.br/3470862820521303
The research aimed to describe initiatives for creating and updating subject headings list and thesaurus considering justice and social equity, based on literature on the sociocultural dimension of the Organization of Knowledge. To achieve this objective, three specific objectives were proposed: to map scientific discussions on subject headings list and thesaurus in the sociocultural dimension of the Organization of Knowledge, to present these discussions and highlight initiatives focused on justice and social equity based on the available literature. The research, of an applied nature, adopts a qualitative approach, making use of systematic literature mapping as a methodological procedure to achieve the established objectives. The study identifies discussions on the representation of different social groups in subject headings list and thesaurus. Criticisms are identified regarding the structure and terminology used in traditional systems, which reflect a historical privilege for a masculine, Euro-American, heterosexual, white, and Christian perspective. The mapped recommendations highlight collaboration with communities to promote fair and equitable representation and propose the implementation of local changes to incorporate terms used by people to refer to themselves, include terms representative of local culture and minority social groups, and use friendly and democratic language. Regarding initiatives, the research identifies 27 initiatives for creating and updating subject headings list and thesaurus focused on social justice and equity. Eight initiatives for gender, eight for indigenous groups, five for queer groups, five for race and ethnicity, and one for diverse groups are identified. The research identifies successful initiatives for creating and updating subject headings list and thesaurus to promote social justice and equity, especially those focused on indigenous communities. However, limited access to some of these systems is considered a barrier to expanding the reach of initiatives. The research concludes by defending the incorporation of institutionalized mechanisms for requesting and monitoring the revision of terms, aiming at transparency and accountability of institutions in promoting inclusion and diversity in SOC.
Desenvolvimento de um amplificador de áudio de alto desempenho utilizando realimentação negativa global
(Universidade Federal de São Carlos, 2023-04-14) Ferreira, Roni Henrique Cardoso; De Francisco, Carlos Alberto; https://lattes.cnpq.br/1246572405382250; https://orcid.org/0000-0001-6472-5957; https://orcid.org/0000-0002-1847-8251
This paper proposes the development of a high-performance audio amplifier with global feedback. The proposed topology is based on "A design methodology for audio amplifiers with no global negative feedback: proposal and validation" Visintin et al. (2022) in order to compare the approaches of amplifiers with and without global negative feedback. A 50W power amplifier is designed and built. In this project example, three stages are used with field effect transistors operating with a symmetrical voltage of ±55V. The practical results obtained satisfied the design requirements, such as: Slew Rate above 1.13V/us (4.2V/us), upper cutoff frequency above 40kHz (250kHz), THD+N below 0, 5% (0.0296%). In this way, it was possible to develop an amplifier with global negative feedback and the objective of this work was achieved.
Projeto, montagem e teste de um subwoofer ativo
(Universidade Federal de São Carlos, 2023-04-14) Silva, Wellngton Corrêa de Faria; De Francisco, Carlos Alberto; https://lattes.cnpq.br/1246572405382250; https://orcid.org/0000-0001-6472-5957
The present work describes in detail the development and construction of an active bass reproduction system "subwoofer". For this, it uses a TPA3255 integrated circuit. This class D amplifier has two outputs that are applied to each of the two 4 Ω coils of the BRAVOX-P12X-D4 loudspeaker, which has a nominal power of 220 WRMS. In addition, the system has adjustment features (volume control, phase inversion and adjustable low-pass filter) and protection (against overvoltage, overcurrent and filters). All circuits were mounted on printed circuit boards and their operation was evaluated through performance measurements. A comparison of the costs involved in the project in relation to the commercialized models was also carried out.
Análise de um amplificador de áudio padrão
(Universidade Federal de São Carlos, 2023-04-14) Boldrin, Vinícius José; De Francisco, Carlos Alberto; https://lattes.cnpq.br/1246572405382250; https://orcid.org/0000-0001-6472-5957; https://lattes.cnpq.br/9540694539079697
This work analyzes and assembles the 50W "Blameless" audio amplifier designed by Douglas Self in his book. The three stages of the amplifier, the feedback loop, and the mechanisms used to minimize distortion were studied. Only components available domestically were used, leading to modifications of some components from the original design. The prototype proved to be in line with Self's vision, demonstrating satisfactory performance in terms of distortion.