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RISS 인기검색어
- 검색키워드
- 저자 : João Paulo Martins (검색결과 5 건)
- 무료
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Integration of Forming Operations on Hybrid Additive Manufacturing Systems Based on Fusion Welding
João P. M. Pragana,Valentino A. M. Cristino,Ivo M. F. Bragança,Carlos M. A. Silva,Paulo A. F. Martins 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.7 No.3
This paper is focused on the integration of metal forming operations in hybrid systems that combine additive manufacturing (AM) by gas metal wire arc and subtractive manufacturing by machining. The investigation is carried out in AISI 316L stainless steel wire and draws from tensile testing to incremental sheet forming of truncated conical shapes. Commercial sheets from the same material are utilized for comparison purposes. Thickness measurements, digital image correlation (DIC), circle grid analysis (CGA) and microstructural and scanning electron microscopy (SEM) observations are carried out to understand how diff erent is the mechanical behaviour of the deposited metal from that of commercial metal sheets and how signifi cant is the infl uence of the deposited metal microstructure on its overall formability. Results confi rm that integration of metal forming operations in hybrid AM routes is feasible despite the formability of deposited metal being smaller than that of the commercial metal sheets due to the strong anisotropy induced by the dendritic based microstructure of the deposited metal. Incremental forming of two deposited parts also allows concluding that integration of metal forming operations in hybrid AM systems is a step towards green and sustainable manufacturing by extending their fi eld of applicability to the fabrication of complex ready-to-use parts requiring combination of diff erent processes.
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Hybrid Wire-Arc Additive Manufacturing of Conformal Cooling Channels: A Feasibility Study
João P. M. Pragana,Ivo M. F. Bragança,Carlos M. A. Silva,Paulo A. F. Martins 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.1
This paper investigates the feasibility of hybridizing wire-arc additive manufacturing with metal forming to create conformal cooling channels in moulds for hot material processing. An axisymmetric mould is used as a prototype test case and plastic deformation by flaring of the additively deposited inner tubular element is utilized to create the overhangs for connecting with the outer tubular element that are needed to fabricate the cooling channels. Finite element modelling of plastic deformation by flaring of the additively deposited material is carried out to identify the different modes of deformation and to determine the maximum allowable radius of the overhangs. Results show that the proposed hybridization of wire-arc additive manufacturing with plastic deformation by flaring adds flexibility to the design and fabrication of conformal channels in the as-built mould by eliminating the use of support structures and avoiding the use of complex deposition strategies. Finishing of the functional surfaces of the as-built mould by turning ensures the required accuracy and surface quality.
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Bruno Augusto Alves Martins,Marcelo de Melo Andrade Coura,Romulo Medeiros de Almeida,Natascha Mourão Moreira,João Batista de Sousa,Paulo Gonçalves de Oliveira 대한대장항문학회 2017 Annals of Coloproctolgy Vol.33 No.3
Transanal endoscopic microsurgery is considered a safe, appropriate, and minimally invasive approach, and complications after endoscopic microsurgery are rare. We report a case of sepsis and pneumoretroperitoneum after resection of a rectal lateral spreading tumor. The patient presented with rectal mucous discharge. Colonoscopy revealed a rectal lateral spreading tumor. The patient underwent an endoscopic transanal resection of the lesion. He presented with sepsis of the abdominal focus, and imaging tests revealed pneumoretroperitoneum. A new surgical intervention was performed with a loop colostomy. Despite the existence of other reports on pneumoretroperitoneum after transanal endoscopic microsurgery, what draws attention to this case is the association with sepsis.
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Beatriz Sona Cardoso,Mariana Brito da Cruz,Joana Faria Marques,João Carlos Roque,João Paulo Martins,Rodrigo Cordeiro Malheiro,António Duarte da Mata 대한치과보철학회 2024 The Journal of Advanced Prosthodontics Vol.16 No.2
Purpose. The aim of this study was to evaluate the influence of different 3D dental resins, using a manufacturer recommended printer and a third-party printer, on cellular responses of human gingival cells. Materials and Methods. Three NextDent resins (Denture 3D+, C&B MFH and Crowntec) were used to produce specimens on printers NextDent 5100 (groups ND, NC and NT, respectively) and Phrozen Sonic Mini 4K (groups PD, PC and PT, respectively). Human gingival fibroblasts were cultured and biocompatibility was evaluated on days 1, 3 and 7. IL-6 and IL-8 concentrations were evaluated at 3 days using ELISA. Surface roughness was evaluated by a contact profilometer. SEM and fluorescence micrographs were analyzed at days 1 and 7. Statistical analyses were performed using SPSS and mean differences were tested using ANOVA and post-hoc Tukey tests (P < .05). Results. There was an increase in cellular viability after 7 days in groups PC and PT, when compared to group PD. ND group resulted in higher concentration of IL-6 when compared to PT group. SEM and fluorescence micrographs showed less adhesion and thinner morphology of fibroblasts from group PD. No significant differences were found regarding surface roughness. Conclusion. The use of different printers or resins did not seem to influence surface roughness. NextDent 5100 and Phrozen Sonic Mini 4K produced resins with similar cellular responses in human gingival fibroblasts. However, Denture 3D+ resin resulted in significantly lower biocompatibility, when compared to C&B MFH and Crowntec resins. Further testing is required to support its long-term use, required for complete dentures.
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Paulo R. Barbosa,Samira S. Valvassori,Celso L. Bordignon Jr.,Virginia D. Kappel,M?rcio R. Martins,Elaine C. Gavioli,Jo?o Quevedo,Fl?vio H. Reginatto 한국식품영양과학회 2008 Journal of medicinal food Vol.11 No.2
Several species of Passiflorahave been employed widely as a folk medicine because of sedative and tran-quillizer activities. In this study, we evaluate the effects on anxiety and memory process of two popularly used Passifloraspecies. To this aim, male Wistar rats (weighing 250300 g) were intraperitoneally injected with the aqueous extract of Pas-siflora alataor Passiflora edulis(25, 50, 100, or 150 mg/kg; single injection) 30 minutes prior to the elevated plus-maze test,inhibitory avoidance test, or habituation to an open-field apparatus. The effects of both species of Passiflorawere comparedwith that of diazepam (1 mg/kg), a standard anxiolytic drug. Our findings revealed that, similar to diazepam, the treatmentwith P. alata(100 and 150 mg/kg) and P. edulis(50, 100, and 150 mg/kg) induced anxiolytic-like effects in rats. Memorywas not affected by the treatment with any dose of P. alataor P. edulis, but diazepam disrupted memory process in rats. Phy-tochemical analysis showed that the content of flavonoids of the aqueous extract of P. edulisis almost twice that of P. alata.These differences in contents of flavonoids could explain the lower active doses of the aqueous extract of P. edulisin induc-ing anxiolytic-like effects compared to P. alata. In conclusion, our findings suggest that, distinct from diazepam, the aque-ous extract of both species of Passiflorainduced anxiolytic-like effects in rats without disrupting memory process.
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