Development and production of a CNC machined 420 stainless steel reinforced with Cu by hot pressing

Multi-material structures make it possible to obtain effective solutions to engineering problems by combining the benefits of different materials to meet the requirements of different working conditions. The aim of this multifunctional 420 stainless steel-copper structure is to create a hybrid solution in which copper acts as heat-transfer enhancer (through cooling channels) while maintaining the required mechanical properties of the steel matrix. This work focuses on a combined engineering process consisting of CNC machining through holes on a 420 stainless steel surface substrate and subsequent filling with copper by hot pressing. The influence of the copper filling on the physical, chemical, microstructural, mechanical, and thermal properties of this multi-material solution was analysed. The machined area (5% of the total surface area) consisted of nine holes with a diameter of approximately 1 mm. The multi-material samples showed high densification, homogeneous microstructures, and a well-defined and sharp interface between the two materials. The microhardness values measured for the 420 stainless steel and copper were 759 and 57 HV, respectively, and the thermal conductivity of the multi-material was ≅ 59% higher than the 420 stainless steel (39.74 and 16.40 W/m K, respectively).This work is supported by FCT (Fundação para a Ciência e a Tecnologia) through the grant SFRH/BD/147460/2019 and the reference projects UIDB/04436/2020 and UIDP/04436/2020, UIDB/00285/2020, and LA/P/0112/2020. Additionally, this work is co-financed by FEDER, through the Competitiveness and Internationalization Operational Program (POCI), in the projects Add. Additive and MoedINOV, with the references POCI-01-0247-FEDER-024533 and POCI-01-0247-FEDER-033361, respectively

3D Multi-Material Laser Powder Bed Fusion: a disruptive approach to design/manufacture unparalleled multi-functional solutions

[Excerpt] Engineering has been so far a mono-dimension tool where components are mono-material, dense unoptimized and designed for one or two requirements, due to processes’ limitations. Traditional components diverge entirely from lightweight and multi-material nature structures endowed with a high level of multi-functionality. [...]This work was supported by FCT national funds, under the national support to R&D units grant, through the reference projects UIDB/04436/2020 and UIDP/04436/2020

On the Levi-Civita solutions with cosmological constant

The main properties of the Levi-Civita solutions with the cosmological constant are studied. In particular, it is found that some of the solutions need to be extended beyond certain hypersurfaces in order to have geodesically complete spacetimes. Some extensions are considered and found to give rise to black hole structure but with plane symmetry. All the spacetimes that are not geodesically complete are Petrov type D, while in general the spacetimes are Petrov type I.Comment: Typed in Revtex, including two figures. To appear in Phys. Rev.

DXA assessment

Accurate assessment of body composition is an important issue among athletes. Different methodologies generate controversial results, leading to a deep uncertainty on individual exercise prescriptions. Thus, this study aims to identify the differences between field methods, such as bioelectrical impedance (BIA) and skinfold assessment, with a clinical method, highly accurate, dual-energy X-ray absorptiometry (DXA), among elite young football players. Thirty-eight male football players with a mean (sd) age of 16.7 (0.87) years, involved in the Portuguese national competition of U16 (n = 13) and U19 (n = 25), were evaluated and objective measures of body composition, muscle strength and football skills were collected by trained specialists. Body composition was assessed using BIA (Tanita BC-418, Tanita Corp., Tokyo, Japan), in agreement with all the evaluation premises. Additionally, all athletes were evaluated using the clinical method DXA (Hologic Inc., Waltham, MA, USA). Among the U19 athletes, three skinfold sites (SKF) were assessed: chest, abdomin and thigh. The Spearman correlation coefficients and the mean difference between methods were calculated. The agreement between both methods was analyzed using Bland-Altman plots. Among the evaluated athletes, lower mean values of body fat % were found using BIA as a method of body composition assessment compared with DXA (12.05 vs. 15.58 for U16; 11.97 vs. 14.16 for U19). Despite the moderate correlation between methods (r = 0.33) to estimate the percentage of total fat, the median of the difference (DXA vs. BIA) was relevant in clinical terms, with 2.90% and 1.47% for U16 and U19 athletes, respectively. Stronger correlations were found between the sum of the SKF and DXA fat estimation (r = 0.68). The Bland-Altman plots showed a clear underestimation in the evaluations using the BIA, namely among athletes with better body composition profiles (8%?12% of fat). Using BIA, an underestimation of body fat assessment was observed among 94.5% of the athletes with less than 12% body fat mass. Among the evaluated athletes, fat mass was underestimated at a median value of 2.21% using BIA in comparison with DXA. The sum of the SKF showed a stronger correlation with the reference method (DXA) (r = 0.68) than BIA.D915-7373-ED16 | Cesar LeaoN/

Conductive polysaccharides-based proton-exchange membranes for fuel cell applications: the case of bacterial cellulose and fucoidan

Conductive natural-based separators for application in polymer electrolyte fuel cells (PEFCs) were fabricated by combining a bacterial polysaccharide, i.e. bacterial cellulose (BC), and an algae sulphated polysaccharide, i.e. fucoidan (Fuc). The diffusion of fucoidan aqueous solution containing a natural-based cross-linker, viz. tannic acid, into the wet BC nanofibrous three-dimensional network, followed by thermal cross-linking, originated fully bio-based proton exchange membranes (PEMs). The PEMs present thermal-oxidative stability in the range of 180-200 °C and good dynamic mechanical performance (storage modulus ≥ 460 MPa). Additionally, the BC/Fuc membranes exhibit protonic conductivity that increases with increasing relative humidity (RH), which is a typical feature for numerous water-mediated proton conductors. The traditional Arrhenius-type plots demonstrate a linear behaviour with a maximum protonic conductivity of 1.6 mS cm-1 at 94 °C and 98 % RH. The results showed that these fully bio-based conductive membranes have potential as eco-friendly alternatives to other PEMs for application in PEFCs.publishe

Energy partition and methane production in sheep fed with Andropogon Gayanus hays in three different ages

Foi realizado estudo para descrever a partição da energia e produção de metano por ovinos alimentados com fenos do capim Andropogon gayanus colhidos aos 56, 84 e 112 dias de crescimento. Utilizou-se a metodologia da calorimetria indireta para mensuração das perdas de energia e para a determinação da energia digestível (ED), metabolizável (EM) e líquida (EL). O delineamento experimental foi inteiramente casualizado, sendo constituído de três tratamentos e seis repetições. As médias foram comparadas pelo teste Studant-Newman- Keuls (SNK) ao nível de 5% de significância. O feno, cujo material foi colhido aos 56 dias, resultou em maior (P<0,05) consumo de energia digestível (CED) em relação aos materiais fenados com 84 e 112 dias de rebrote. As perdas diárias de energia através da urina, do metano e do incremento calórico não apresentaram diferença (P>0,05) entre os tratamentos. O feno contendo material colhido aos 56 dias apresentou valor de digestibilidade aparente da energia bruta (DAEB) superior (P0,05) entre si. O feno colhido as 56 dias apresentou maior valor de energia digestível e energia metabolizavél em relação aos demais fenos que não diferiram entre si (P>0,05). A produção de metano não variou (P>0,05) entre os tratamentos estudados.A study was conducted to describe the energy partition and methane production by sheep fed grass hay of Andropogon gayanus harvested at 56, 84 and 112 days of growth. We used the methodology of indirect calorimetry to measure energy losses and to determine the digestible energy (DE), metabolizable (ME) and liquid (EL). The experimental design was completely randomized, consisting of three treatments and six replications. Means were compared by Studant -Newman -Keuls (SNK) test at 5 % significance level. Hays was collected at 56 days, resulted in higher (P &lt; 0.05) digestible energy intake (DEI) in relation to hays 84 and 112 days of regrowth. The daily energy losses through urine, methane and heat increment did not differ (P&gt; 0.05) between treatments. Hay containing material collected at 56 days showed apparent digestibility of the gross energy value higher ( P &lt; 0.5) to the other treatments did not differ ( P&gt; 0.05 ) between them. Hay harvested the 56 days had higher digestible energy and metabolizable energy value compared to other hays that did not differ (P&gt; 0.05). The methane production did not change (P&gt; 0.05) between the treatments.Facultad de Ciencias Agrarias y Forestale

Evaluation of hays produced with Andropogon gayanus grass at different ages using semi - automated in vitro gas production technique

Objetivou-se avaliar o feno da Andropogon gayanus pela técnica in vitro semi-automática de produção de gases. O delineamento estatístico adotado foi o de blocos ao acaso com parcelas subdivididas, sendo as três idades de corte (56, 84 e 112 dias) as parcelas, os inóculos ruminais os blocos, e os tempos de leitura de produção de gases as sub-parcelas. A degradabilidade da matéria seca foi medida nos tempos de 6,12, 24, 48 e 96 horas. As maiores produções (p>0,05) acumuladas de gases foram obtidas com os fenos colhidos aos 56 e 84 dias com 195,1 e 189,4 mL/g de MS respectivamente. Dentre as três idades avaliadas, recomenda-se o feno colhido aos 56 dias de crescimento.In this study were utilized Andropogon gayanus hays produced at different ages of growth (56, 84 and 112 days) for assay of degradability of in vitro dry matter using semi-automated in vitro gas production technique. The statistical design was randomized blocks with split plots. The ages of growth were parcels and degradation time (6, 12, 24, 48 and 96 hours) were subparcels, with five blocks. The observed results indicated that the best hay of A. gayanus are obtained from plants cutted in between 56 days of growth.Facultad de Ciencias Agrarias y Forestale

Energy partition and methane production in sheep fed with Andropogon Gayanus hays in three different ages

Foi realizado estudo para descrever a partição da energia e produção de metano por ovinos alimentados com fenos do capim Andropogon gayanus colhidos aos 56, 84 e 112 dias de crescimento. Utilizou-se a metodologia da calorimetria indireta para mensuração das perdas de energia e para a determinação da energia digestível (ED), metabolizável (EM) e líquida (EL). O delineamento experimental foi inteiramente casualizado, sendo constituído de três tratamentos e seis repetições. As médias foram comparadas pelo teste Studant-Newman- Keuls (SNK) ao nível de 5% de significância. O feno, cujo material foi colhido aos 56 dias, resultou em maior (P<0,05) consumo de energia digestível (CED) em relação aos materiais fenados com 84 e 112 dias de rebrote. As perdas diárias de energia através da urina, do metano e do incremento calórico não apresentaram diferença (P>0,05) entre os tratamentos. O feno contendo material colhido aos 56 dias apresentou valor de digestibilidade aparente da energia bruta (DAEB) superior (P0,05) entre si. O feno colhido as 56 dias apresentou maior valor de energia digestível e energia metabolizavél em relação aos demais fenos que não diferiram entre si (P>0,05). A produção de metano não variou (P>0,05) entre os tratamentos estudados.A study was conducted to describe the energy partition and methane production by sheep fed grass hay of Andropogon gayanus harvested at 56, 84 and 112 days of growth. We used the methodology of indirect calorimetry to measure energy losses and to determine the digestible energy (DE), metabolizable (ME) and liquid (EL). The experimental design was completely randomized, consisting of three treatments and six replications. Means were compared by Studant -Newman -Keuls (SNK) test at 5 % significance level. Hays was collected at 56 days, resulted in higher (P &lt; 0.05) digestible energy intake (DEI) in relation to hays 84 and 112 days of regrowth. The daily energy losses through urine, methane and heat increment did not differ (P&gt; 0.05) between treatments. Hay containing material collected at 56 days showed apparent digestibility of the gross energy value higher ( P &lt; 0.5) to the other treatments did not differ ( P&gt; 0.05 ) between them. Hay harvested the 56 days had higher digestible energy and metabolizable energy value compared to other hays that did not differ (P&gt; 0.05). The methane production did not change (P&gt; 0.05) between the treatments.Facultad de Ciencias Agrarias y Forestale

Evaluation of hays produced with Andropogon gayanus grass at different ages using semi - automated in vitro gas production technique

Objetivou-se avaliar o feno da Andropogon gayanus pela técnica in vitro semi-automática de produção de gases. O delineamento estatístico adotado foi o de blocos ao acaso com parcelas subdivididas, sendo as três idades de corte (56, 84 e 112 dias) as parcelas, os inóculos ruminais os blocos, e os tempos de leitura de produção de gases as sub-parcelas. A degradabilidade da matéria seca foi medida nos tempos de 6,12, 24, 48 e 96 horas. As maiores produções (p>0,05) acumuladas de gases foram obtidas com os fenos colhidos aos 56 e 84 dias com 195,1 e 189,4 mL/g de MS respectivamente. Dentre as três idades avaliadas, recomenda-se o feno colhido aos 56 dias de crescimento.In this study were utilized Andropogon gayanus hays produced at different ages of growth (56, 84 and 112 days) for assay of degradability of in vitro dry matter using semi-automated in vitro gas production technique. The statistical design was randomized blocks with split plots. The ages of growth were parcels and degradation time (6, 12, 24, 48 and 96 hours) were subparcels, with five blocks. The observed results indicated that the best hay of A. gayanus are obtained from plants cutted in between 56 days of growth.Facultad de Ciencias Agrarias y Forestale

Evaluation of hays produced with Andropogon gayanus grass at different ages using semi - automated in vitro gas production technique

Objetivou-se avaliar o feno da Andropogon gayanus pela técnica in vitro semi-automática de produção de gases. O delineamento estatístico adotado foi o de blocos ao acaso com parcelas subdivididas, sendo as três idades de corte (56, 84 e 112 dias) as parcelas, os inóculos ruminais os blocos, e os tempos de leitura de produção de gases as sub-parcelas. A degradabilidade da matéria seca foi medida nos tempos de 6,12, 24, 48 e 96 horas. As maiores produções (p>0,05) acumuladas de gases foram obtidas com os fenos colhidos aos 56 e 84 dias com 195,1 e 189,4 mL/g de MS respectivamente. Dentre as três idades avaliadas, recomenda-se o feno colhido aos 56 dias de crescimento.In this study were utilized Andropogon gayanus hays produced at different ages of growth (56, 84 and 112 days) for assay of degradability of in vitro dry matter using semi-automated in vitro gas production technique. The statistical design was randomized blocks with split plots. The ages of growth were parcels and degradation time (6, 12, 24, 48 and 96 hours) were subparcels, with five blocks. The observed results indicated that the best hay of A. gayanus are obtained from plants cutted in between 56 days of growth.Facultad de Ciencias Agrarias y Forestale