Analisa Sifat Mekanik Dan Struktur Mikro Pada Proses Friction Stir Welding Alumunium 5052

Friction stir welding (FSW) adalah proses penyambungan material dengan kondisi solid state atau logam tidakmeleleh saat di lakukan penyambungan. Metoda ini digunakan agar karakteristik dari logam induk tidak banyakberubah. Proses ini banyak digunakan untuk material khususnya alumunium yang biasanya harus di heattreatment terlebih dahulu sebelum dilakukan pengelasan, metoda FSW ditemukan oleh W.Thomas dari TheWelding Institute (TWI). Proses FSW dilakukan pada alumunium seri 5052 T0 dengan bentuk sambungan tumpulsebanyak 9 pelat. Parameter yang divariasikan adalah design bentuk pin dengan bentuk segitiga ulir, silinder ulirdan kerucut ulir. Selanjutnya dilakukan pengujian yang meliputi pengamatan uji radiografi, uji tarik, uji keras danpemeriksaan metalografi. Hasil penelitian bahwa dengan variasi bentuk pin segitiga ulir, silinder ulir dan kerucutulir menyebabkan nilai kekerasan dan kekuatan tarik meningkat serta terjadi penurunan pada pin segitiga ulir.Dari variasi ini hasil kekerasan dan kekuatan tarik tertinggi terdapat pada silinder ulir sebesar 38.27 HV dan120.442 MP

Hot moments in the Antarctic due to climate warming?

Climate warming is severely affecting maritime Antarctica, causing accelerated glacier retreat and thus leading to an ongoing exposure of once ice- covered land. This initiates a succession of plant and soil development. Nevertheless, the temporal dynamics and controlling factors of these processes, like C and N status of soils and the effect of root exudation are widely unknown under these harsh climatic conditions. Topsoil samples from three different sites of a chronological soil sequence in the forefront of a retreating glacier of the Fildes Peninsula, King George Island, were collected and incubated at 2 °C for three weeks. To mimic the influence of C and N containing root exudates (primers) on the mineralization of soil C, we added 13C labeled glucose or alanine and compared CO2 evolution in comparison to samples without C and N addition. Soil microbes covered up to 90% of their C demand for anabolic functions with the added C-sources in the case of late soil successions while it was only 50% for the young soils. These findings were independent of the form of primer. Both primers increased the mineralization of soil carbon in the young soils as compared to the control. For the later stages of soil development, we found negative priming which was strongest for the latest stage. These results give evidence for a clear shift in the microbial community of the three investigated sites. While sites with initial soil formation seem to be dominated by k-strategists with low turnover rates that rather use complex C-sources, a significant number of r-strategists in the soils of the older sites uses simple C-substrates very efficiently. As this leads to a relative decrease in SOM mineralization for the late stages of soil development, it is questionable if higher plants can improve their nutrition by stimulating free living soil microbes with root exudates or if they rather have to rely on mycorrhiza

Faktor-faktor yang Memengaruhi Anggota Organisasi Kepemudaan Alumni Budi Mulia (Album-medan) terhadap Donor Darah di Pmi Medan Tahun 2012

Many factor affecting the members of youth organizations Budi Mulia (Album- Medan) to donate blood in medan red cross 2012. The importance of the availability of blood is to meet the need for blood transfusions that could occur anytime such as for accident victims, cesarean section and for patients with blood diseases such as hemophilia and thalassemia. Therefore, it is very important to know what are the factors that could affect members of youth organization such as ALBUM-Medan to donate their blood. The purpose of this study was aimed to determine the factors that affect members of youth organization ALBUM-Medan to donate blood. The factors were characteristics, sources of information, knowledge, social capital, attitude, reference groups, intentions and actions of members of youth organization ALBUM-Medan to donate blood at Medan Red Cross in 2012. This research used descriptive quantitative. The number of respondents in this study amounted to 62 people with total sampling as the sampling technique, where the respondent was a person who members of youth organizations ALBUM-Medan that register in 2009-2011. The results are presented in frequency distribution table. This is the result of the research, 33,9 % is 18th years old, 59,7% is male. The catagorized of youth's sources of information is medium or 71,0%. The catagorized of youth's knowledge is medium or 67,7%. And for the catagorized of the social capital is medium or 50,0%. The attitude of the responden considered good or 88,7%. The intention of the respondents considered good or 67,7% and for the youth's action considered bad or 88,7%

Understanding the formation of biogenic secondary organic aerosol from ?-pinene in smog chamber studies: role of organic peroxy radicals

International audienceThis study focusses on the description of the nucleation process observed during the ozone reaction of the biogenic monoterpene ?-pinene in smog chambers. Therefore, a detailed aerosol dynamics model (UHMA) was extended by a tropospheric chemistry module and a detailed description of the first steps of organic nucleation. We assume secondary ozonides to act as nucleation initiating molecules, which are subsequently activated by reactions with organic peroxy radicals (RO2). With this set-up the observed particle size distributions of an exemplary experiment in Valencia was reproduced, when only the long-lived organic compounds like carboxylic acids and carbonyl compounds are detected by the available aerosol size distribution instruments. Our results indicate that fragile or reactive species might get destroyed because of weak bond breakage during the size classification. This assumption would imply a serious detection problem in nucleation studies to be solved

Estimation and Validation of Oceanic Mass Circulation from the GRACE Mission

Since the launch of the Gravity Recovery And Climate Experiment (GRACE) in March 2002, the Earth's surface mass variations have been monitored with unprecedented accuracy and resolution. Compared to the classical spherical harmonic solutions, global high-resolution mascon solutions allows the retrieval of mass variations with higher spatial and temporal sampling (2 degrees and 10 days). We present here the validation of the GRACE global mascon solutions by comparing mass estimates to a set of about 100 ocean bottom pressure (OSP) records, and show that the forward modelling of continental hydrology prior to the inversion of the K-band range rate data allows better estimates of ocean mass variations. We also validate our GRACE results to OSP variations modelled by different state-of-the-art ocean general circulation models, including ECCO (Estimating the Circulation and Climate of the Ocean) and operational and reanalysis from the MERCATOR project

Physical modelling to remove hydrological effects at local and regional scale: application to the 100-m hydrostatic inclinometer in Sainte-Croix-aux-Mines (France)

International audienceNew inclinometers devoted to hydrological studies were set up in the Vosges Mountains (France). Two orthogonal 100-meter base hydrostatic inclinometers were installed in December 2004 as well as a hydrometeorological monitoring system for the 100-km² hydrological unit around the inclinometer. As inclinometers are very sensitive to environmental influences, this observatory is a test site to confront hydrological modelling and geodetic observations. Physical modelling to remove hydrological effects without calibrating on geodetic data is tested on these instruments. Specifically, two deformation processes are most important: fluid pressure variations in nearby hydraulically active fractures and surface loading at regional scale

An Iterated Global Mascon Solution with Focus on Land Ice Mass Evolution

Land ice mass evolution is determined from a new GRACE global mascon solution. The solution is estimated directly from the reduction of the inter-satellite K-band range rate observations taking into account the full noise covariance, and formally iterating the solution. The new solution increases signal recovery while reducing the GRACE KBRR observation residuals. The mascons are estimated with 10-day and 1-arc-degree equal area sampling, applying anisotropic constraints for enhanced temporal and spatial resolution of the recovered land ice signal. The details of the solution are presented including error and resolution analysis. An Ensemble Empirical Mode Decomposition (EEMD) adaptive filter is applied to the mascon solution time series to compute timing of balance seasons and annual mass balances. The details and causes of the spatial and temporal variability of the land ice regions studied are discussed