Mechanical Behavior Associated with Metallurgical Aspects of Friction Stir Welded Al-Li Alloy Exposed to Exfoliation Corrosion Test

Open Access articleThis research aims to investigate the effect of the exfoliation corrosion exposure time on the mechanical properties, the strength and elongation, of friction stir welded Al-Li alloy type 2195-T8. The exfoliation corrosion test was performed using the exfoliation corrosion (EXCO) solution, based on ASTM G34. The samples were exposed to different exposure times 24, 48, 96, 192 and 384 hours. The results showed that both the strength and elongation of the welded specimens - exposed to the exfoliation corrosion tests - were reduced. For example, the samples that were exposed to 384 hrs, their initial tensile strength and elongation were reduced by 13% and 17% respectively. The degradation process due to the exfoliation corrosion on the tensile strength was divided into three stages: fast (0-96 hrs: 443.7 MPa-416.3 MPa, the degraded rate was 0.29 MPa/h), steady (96-192 hrs: 416.3 MPa-413.4 MPa, the degraded rate was 0.03 MPa/h) and medium rate (192-384 hrs: 413.4 MPa-386.7 MPa, the degraded rate was 0.14 MPa/h). For the elongation, in general, the reduction was similar to the style of strength, but with different rates. The TEM images showed that this degradation was due to the dissolution of T1 (Al2CuLi) and S´ (Al2CuMg) phase. Also, the corrosion products and their role of adherence on the surface of the tested specimens were investigated. An empirical equation p-t (mechanical properties-exposure time) was established to calculate the effect of exposure corrosion time on the performance of welded specimens

Hubungan Tingkat Pendidikan Dan Tanggung Jawab Lingkungan Dengan Partisipasi Pemeliharaan Kesehatan Lingkungan

The Objective of the research is to determine the relationship between the level of education the community Bojong Rawa village and environmental responsibility with the participation of the health maintenance environment. The method which is used in this research is the correlation associative quantitative approach of 60 people a total sample. Data were collected through questionnaires. Analysis of data to test the hypothesis of research is used the regression analysis. The research concluded that; First, there is a positive relationship between the level of education with the participation of the health maintenance environment with the correllation coefficient of  0, 86 at  = 0, 05 on  = 39, 71 + 3, 191 X1 the regression equation. Second, have a positive relationship between environmental responsibility and participation of the healthmaintenance environment with the correlation  regression equation. Third, there is a positive relationship between the level of education and environmental responsibility together with the participation of the health maintenance environment with multiple  correlation coefficient () of () with coefficients of determination of 96 %. The double regression equation   = - 0, 7 + - 0, 64 + 1, 13

Assessment of fish populations and habitat on Oculina Bank, a deep-sea coral marine protected area off eastern Florida

A portion of the Oculina Bank located off eastern Florida is a marine protected area (MPA) preserved for its dense populations of the ivory tree coral (Oculina varicosa), which provides important habitat for fish. Surveys of fish assemblages and benthic habitat were conducted inside and outside the MPA in 2003 and 2005 by using remotely operated vehicle video transects and digital still imagery. Fish species composition, biodiversity, and grouper densities were used to determine whether O. varicosa forms an essential habitat compared to other structure-forming habitats and to examine the effectiveness of the MPA. Multivariate analyses indicated no differences in fish assemblages or biodiversity among hardbottom habitat types and grouper densities were highest among the most complex habitats; however the higher densities were not exclusive to coral habitat. Therefore, we conclude that O. varicosa was functionally equivalent to other hardbottom habitats. Even though fish assemblages were not different among management areas, biodiversity and grouper densities were higher inside the MPA compared to outside. The percentage of intact coral was also higher inside the MPA. These results provide initial evidence demonstrating effectiveness of the MPA for restoring reef fish and their habitat. This is the first study to compare reef fish populations on O. varicosa with other structure-forming reef habitats and also the first to examine the effectiveness of the MPA for restoring fish populations and live reef cover

EFEK PENAMBAHAN SERAT POLYPROPYLENE TERHADAP KUAT TEKAN DAN MODULUS ELASTISITAS SELF COMPACTING MORTAR (SCM)

Pada dinding pracetak penggunaan fiber reinforced sebagai lapis kulit dinding sandwich dengan metode self-compacting mortar (SCM) akan sangat tepat digunakan karena akan lebih mudah dan cepat dalam proses produksi panel dinding pracetak. Penelitian ini bertujuan untuk mengetahui nilai kuat tekan dan modulus elastisitas pada self-compacting mortar (SCM) dengan penambahan serat polypropylene. Penambahan serat polypropylene dalam adukan self-compacting mortar (SCM) diberikan dalam 4 (empat) variasi, yaitu: 0 kg/m3; 0,5 kg/m3; 1 kg/m3; 1,5 kg/m3 serat polypropylene. Adukan mortar ditetapkan dengan perbandingan volume: 1 semen dan 5 pasir, f.a.s 0,9 dan sikamen NN 1,2 dari berat semen. Pengujian yang dilakukan pada kuat tekan dan modulus elastisitas dilakukan setelah mortar berumur 28 hari. Data untuk setiap variasi campuran serat diperoleh dari 3 (tiga) benda uji silinder berukuran 15 x 30 cm. Dari hasil penelitian didapatkan kuat tekan silinder mortar dengan penambahan serat polypropylene 0 kg/m3; 0,5 kg/m3; 1 kg/m3;dan 1,5 kg/m3 Berturut turut adalah 12,44 MPa; 10,40 MPa; 12,23 MPa; 9,48 MPa. Dan besarnya nilai modulus elastisitas dengan campuran 0 kg/m3; 0,5 kg/m3; 1 kg/m3; 1,5 kg/m3serat polypropylene. Berturut turut sebesar 9959,53MPa; 8650,95MPa; 10080,19 MPa; dan 8074,94 MPa