Pengaruh Bentuk Badan Profil Baja Ringan Terhadap Kuat Tekan

Adanya produk baja ringan (cold formed steel) yang dipakai sebagai material struktur memberikan gagasan untuk melakukan inovasi yaitu, penggunaan material baja ringan pada struktur utama bangunan. Akibat dari penggunaan pelat yang tipis ini, pengaruh tekuk lokal pada badan dan flens penampang akan menjadi lebih signifikan dibanding baja biasa. Namun karena penggunaan pelat yang sangat tipis dan metode pembentukan dengan penggilingan dingin, maka penampang dapat digiling dalam berbagai bentuk yang lebih optimal. Untuk menaikkan kuat tekan penampang, kecenderungan untuk mengalami tekuk dapat dikurangi salah satunya dengan memodifikasi bentuk geometri penampang dengan menggunakan pengaku memanjang, atau biasa disebut pengaku tengah (Intermediate stiffner).Penelitian dilakukan terhadap profil kanal C dengan tiga bentuk modifikasi bentuk badan profil dimana mutu baja ringan mengikuti standar Australia (AS1397) yaitu G550 yang diaplikasikan pada seluruh profil yang akan dianalisis. Selanjutnya dilakukan pemodelan finite element dengan program Ansys Mechanical APDL. Analisis linear buckling (eigen buckling) digunakan untuk memperoleh besarnya beban kritis tekuk profil dan mode keruntuhan struktur. Setelah diperoleh besar beban kritis tekuk, maka hasil tersebut dibandingkan antara profil kanal C tanpa modifikasi badan profil (C1) dengan profil kanal C yang dimodifikasi bentuk badan profilnya (C2, C3 dan C4).Dari analisis eigen buckling dengan finite element model diketahui bahwa dengan memodifikasi bentuk badan profil dapat mereduksi tekuk lokal yang terjadi pada badan profil sehingga dapat meningkatkan kemampuan tekan. Persentase peningkatan beban kritis yang terjadi pada short column sebesar 1.46%-2.16%, untuk intermediate column sebesar 0.08%-1% dan untuk long column sebesar 0.1%-0.12%. Peningkatan beban kritis terbesar terjadi pada profil C3 untuk semua angka rasio kelangsingan yang dianalisis

Biomarkers in monitoring - a review

Årsliste 2006Biological effects are increasingly used to monitor impacts of contaminants in marine ecosystems. Biomarkers have been defined as ”biochemical, cellular, physiological or behavioural variations in the tissue or body fluids or at the level of whole organism that provide evidence of exposure to chemical pollutants, and may also indicate a toxic effect”. The biomarkers reviewed here were PAH bile metabolites, cytochrome P4501A, glutathione S-transferase, markers for DNA damage (adducts, alkaline unwinding, Comet assay), micronucleus formation, peroxisomal proliferation, acetyl cholinesterase inhibition, metallothionein, vitellogenin and delta-aminolevulinic acid dehydratase. Focus for the review was dose-response relationships, confounding factors, links to population effects, baseline values, assessment criteria and quality assurance for the relevant biomarker. Whereas correlative links to population-relevant effects have been found for some biomarkers, e.g. biomarkers for DNA damage, most biomarkers are generally more useful as markers for possible impacts elsewhere in ecosystems.OL

Autoionization of the Ca 2 p

The decay of the photon-excited $2p^53s^23p^63d4s^2$ core resonances of atomic Ca has been studied by electron spectroscopy and by multiconfiguration calculations of the autoionization rates. Strong correlation effects give rise to complicated line structures that are mostly due to the autoionization of the resonances into the $3p^43d4s^2εl, 3p^43d4p^2εl$, and $3p^43d3εl$ continua. The breakdown of the spectator model, which is caused by the collapse of the 3d orbital, manifests itself in the dramatic differences between the spectra excited via the two resonances split by the spin-orbit and 2p-3d interactions

Biomarkers in Natural Fish Populations Indicate Adverse Biological Effects of Offshore Oil Production

Despite the growing awareness of the necessity of a sustainable development, the global economy continues to depend largely on the consumption of non-renewable energy resources. One such energy resource is fossil oil extracted from the seabed at offshore oil platforms. This type of oil production causes continuous environmental pollution from drilling waste, discharge of large amounts of produced water, and accidental spills.Samples from natural populations of haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua) in two North Sea areas with extensive oil production were investigated. Exposure to and uptake of polycyclic aromatic hydrocarbons (PAHs) were demonstrated, and biomarker analyses revealed adverse biological effects, including induction of biotransformation enzymes, oxidative stress, altered fatty acid composition, and genotoxicity. Genotoxicity was reflected by a hepatic DNA adduct pattern typical for exposure to a mixture of PAHs. Control material was collected from a North Sea area without oil production and from remote Icelandic waters. The difference between the two control areas indicates significant background pollution in the North Sea.It is most remarkable to obtain biomarker responses in natural fish populations in the open sea that are similar to the biomarker responses in fish from highly polluted areas close to a point source. Risk assessment of various threats to the marine fish populations in the North Sea, such as overfishing, global warming, and eutrophication, should also take into account the ecologically relevant impact of offshore oil production

A charge transfer analysis of the resonant 2p3p3p Auger spectra of CaF2

A theoretical description is given of the 2p3p3p (= L2,3M2,3M2,3) resonant Auger spectra in CaF2. Using a charge-transfer multiplet analysis, it is shown that the 2p3p3p Auger spectra excited at the 2p x-ray absorption edge show a large variation if one scans through the edge and excites the different symetry states. A detailed comparison is made with experiment. The origins of the symmetry effects on the resonance are analyzed and the full charge-transfer multiplet theory is approximated using crystal-field and atomic multiplet calculations. The analysis shows that the Auger spectra of CaF2 are dominated by the resonance channel, with little contribution of the normal Auger channel. The differences with other recently used analysis are discussed

NaK photoabsorption and resonant KLL Auger spectra in naf and NaCl

The nature of Na Is photoabsorption in NaF and NaCl is investigated using the resonant Auger decay of Na Is core excitations. The appearance of new peaks in Auger spectra, when the energy of excitation coincides with the photoabsorption thresholds, shows that the core excitons are created in the threshold region of the Na 1s photoabsorption spectrum. The core excitons around 1074.2 eV originate from the dipole-forbidden 1s(-1)3s final state, the population of which is made possible by the symmetry disruption at the photoabsorption site. Another core exciton, excited at photon energies of 1076.8 eV in NaF and 1076.3 eV in NaCl, originates from 1s(-1)3p states similar to atoms of Ne and Na. Resonant Auger spectra show also that in NaCl the first sharp photoabsorption maximum at 1076.6 eV has only partially excitonic character