Numerical simulation of sheet metal forming processes and localized deformation phenomena for FCC polycrystals

Une formulation par éléments finis pour les polycristaux, basée sur l'hypothèse de Taylor pour un matériau sensible au taux de déformation, a été appliquée pour analyser la mise en forme des métaux et les phénomènes de localisation. Cette formulation s'applique aux problèmes de conditions aux limites non homogènes des métaux polycristallins sous grandes déformations. Elle tient également compte des textures initiales ainsi que des anisotropies induites par la déformation causée par l'évolution de la texture. Des codes d'éléments finis bases sur les hypothèses de déformations planes et de contraintes planes incorporant des algorithmes de calcul parallèle ont été élaborés. En utilisant les codes d'éléments finis établis, les instabilités et les phénomènes de localisation dans l'alliage d'aluminium AA3004-H19 sous tension ont alors été étudiés. Les effets de divers paramètres tels que la texture initiale et son évolution, l'écrouissage, la sensibilité au taux de déformation du matériau, la direction du chargement, la sensibilité du maillage, les imperfections géométriques et les conditions limites sur la formation des déformations locales ont été traités. Un critère d'instabilité a été défini pour la striction et la formation des bandes de cisaillement. Le comportement à grandes déformations pour l'alliage d'aluminium AA3004-H19, sous cisaillement simple, a aussi été simule numériquement en utilisant les codes d'éléments finis. Les effets des directions du cisaillement sur les courbes de contrainte-déformation et les morphologies des déformations ont été étudiés. L'initiation et la propagation des bandes de cisaillement ont aussi été examinées en détail. Finalement, l'emboutissage profond des alliages d'aluminium AA6111-T4 et AA5754-0 a été modélisé en utilisant à la fois Ie modèle polycristallin et un modèle phénoménologique où seulement la zone de « flange » a été analysée. Les effets de ces textures ont été examines et les résultats obtenus ont été comparés avec les données expérimentales.Abstract: In this thesis, finite element analyses based on a rate-dependent Taylor-type polycrystal model have been developed to simulate sheet metal forming processes and localized deformation phenomena. This formulation can be applied to nonhomogeneous boundary-value problems for FCC polycrystals subjected to large deformations. The analysis inherently accounts for initial textures as well as deformation-induced anisotropies due to texture evolution. Both plane strain and plane stress finite element (FE) codes incorporating parallel computing algorithms have been developed so that simulations could be performed for applications requiring fairly large numbers of elements. Using the finite element codes which have been developed, instability and localization phenomena for the rolled aluminum sheet alloy AA3004-H19 under tension have been studied. The effects of various parameters on the formation of localized deformation bands have been investigated. These include initial texture and its evolution, strain hardening, material strain-rate sensitivity, loading direction, mesh sensitivity, geometric imperfections, and boundary conditions. Instability criteria have been defined for both necking and shear banding. The large strain behaviour of the rolled aluminum sheet alloy AA3004-H19 under planar simple shear has also been simulated numerically using both the plane strain and the plane stress polycrystal FE codes. The effects of the shearing direction on the overall shear stress--shear deformation curves and deformation patterns have been investigated. The initiation and propagation of shear bands have been studied in detail. Finally, the plane strain FE code was employed to simulate earing during the deep drawing of the rolled aluminum sheet alloys AA6111-T4 and AA5754-0. Simulations based on both the polycrystal model and a phenomenological constitutive law were performed where only the flange area of the sheet was analyzed. The effects of these textures were examined, and comparisons were made with experimental data

AlxGa1-xN-based avalanche photodiodes with high reproducible avalanche gain

Cataloged from PDF version of article.The authors report high performance solar-blind photodetectors with reproducible avalanche gain as high as 1560 under ultraviolet illumination. The solar-blind photodetectors have a sharp cutoff around 276 nm. The dark currents of the 40 m diameter devices are measured to be lower than 8 fA for bias voltages up to 20 V. The responsivity of the photodetectors is 0.13 A/W at 272 nm under 20 V reverse bias. The thermally limited detectivity is calculated as D*=1.4 1014 cm Hz1/2 W−1 for a 40 m diameter device

General expression for the dielectronic recombination cross section of polarized ions with polarized electrons

A general expression for the differential cross section of dielectronic recombination (DR) of polarized electrons and polarized ions is derived by using usual atomic theory methods and is represented in the form of multiple expansions over spherical tensors. The ways of the application of the general expressions suitable for the specific experimental conditions are outlined by deriving asymmetry parameters of angular distribution of DR radiation in the case of nonpolarized and polarized ions and electrons.Comment: 4 page

Comparison of the accelerated and classic vaccination schedules against Hepatitis B: three-week Hepatitis B vaccination schedule provides immediate and protective immunity

BACKGROUND: Hepatitis B virus infection although preventable by vaccination remains an important health issue throughout the world due to its morbidity, mortality and economical losses. Early seroprotection is desirable for people at high risk of exposure. The aim of this study was to determine whether three-week hepatitis B vaccination (on days 0, 10 and 21) provide seroprotection or not. METHODS: The 120 subjects enrolled into the study were divided into two groups and vaccinated by the classic (months 0, 1, and 2) or the accelerated (days 0, 10, and 21) schedules and antibody response determined on days 30, 60, and 90 and, if below 10 mIU/ml(-1), again on day 180. For each individual in the classic group (B) three subjects were enrolled in the accelerated group (A). Recombinant hepatitis B vaccine (Gen-Hevac B, Pasteur) was given as 20 micrograms intramuscular injections via the deltoid muscle. A booster dose on day 365 was administered for each group. Family members of hepatitis B carriers and volunteer health personnel were enrolled into group A. To the B group only volunteers who wanted vaccination against hepatitis B were included. RESULTS: After three doses of vaccine, Anti-HBs titers reached protective levels in both groups. The number of vaccinees with seroprotective levels of Anti-HBs (≥10 mIU/ml(-1)) on day 30 was 53 (58.9%) in group A and 9 (30.0%) in group B (p < 0.05). On day 60, there was no difference between group A and B, with response rates of 84.4% (n = 76) and 80.0% (n = 24) respectively (p > 0.05). On day 90 there was no difference between group B and group A; with 26 (86.7%) and 79 (87.7%) responders respectively. In both groups those with Anti-HBs levels <10 mIU/ml(-1 )attained protective levels by day 180. CONCLUSION: In this study, the three-week vaccination provided protective antibody titers within a shorter time compared to the classic schedule. Therefore, in order to provide rapid antibody production against hepatitis B virus, the accelerated vaccination schedule seems to be a good preference

PENGAMATAN POST-MORTEM KUALITAS KULIT KAMBING DI KOTA MANADO

Kulit ternak merupakan hasil ikutan ternak yang memiliki nilai ekonomis sebagai bahan baku utama berbagai produk industri kulit. Kualitas kuli tsegar dapat mengalami penurunan pada saat ternak masih hidup maupun setelah lepas dari tubuh ternak. Penyembelihan ternak kambing di Kota Manado cukup banyak namun belum memperhatikan kualitas kulitnya. Penelitian ini bertujuan untuk mengetahui seberapa jauh kualitas post-mortem kulit kambing di Kota Manado. Pengambilan data dilakukan di tempat pemotongan hewan pasar bersehati Kota Manado menggunakan metode observasi terhadap beberapa variabel yaitu cacat irisan, cacat penyakit kulit, dan cacat flek darah. Pengambilan sampel melalui purposive sampling serta penyajian data menggunakan statistik deskriptif. Hasil pengamatan menunjukkan bahwa cacat pada kulit kambing post mortem yang terbanyak adalah cacat irisan dan cacat penyakit kulit (± 60%) dan cacat flek darah paling sedikit (± 13,3%). Cacat yang ditemui terbanyak pada daerah D (daerah badan)

Organic Electrochemical Transistors

Organic electrochemical transistors (OECTs) leverage ion injection from an electrolyte into an organic semiconductor film to yield compelling advances in biological interfacing, printed logic circuitry and neuromorphic devices. Their defining characteristic is the coupling between electronic and ionic charges within the volume of an organic film. In this review we discuss the mechanism of operation and the materials that are being used, overview the various form factors, fabrication technologies and proposed applications, and take a critical look at the future of OECT research and development

The effect of overt and subclinical hypothyroidism on the development of non-dipper blood pressure

Introduction: &prime;Non-dippers&prime; are individuals without the anticipated nocturnal decrease in blood pressure. An increased incidence of target organ damage and a worse outcome in terms of cardiovascular events have been reported in this group of people. The pathogenesis of non-dipper hypertension is not clear at present. We aimed to investigate the effects of overt and subclinical hypothyroidism on the development of a non-dipper blood pressure pattern via 24-hour ambulatory blood pressure monitoring. Material and methods: 109 normotensive patients with overt and subclinical hypothyroidism were evaluated, and 95 of these patients without reverse dipping and masked hypertension were included in the study. The control group consisted of 75 gender- and age-matched, normotensive, euthyroid healthy individuals. Results: Median serum TSH levels were 7.61 and 1.59 mUmL in patient and control groups, respectively. The number of non-dippers according to systolic, diastolic and mean blood pressure was significantly higher in the patients with hypothyroidism compared to the control group. In linear regression analysis, TSH had a negative effect on the night/day ratio of the systolic, diastolic and mean blood pressures. Conclusion: Despite the fact that the effect of hypothyroidism on non-dipper blood pressure pattern is not known, the present study has revealed that elevated TSH levels are likely to increase the risk of non-dipping in normotensive patients with either overt or subclinical hypothyroidism. (Pol J Endocrinol 2012; 63 (2): 97&#8211;103)Wstęp: U osób określanych jako non-dippers nie występuje fizjologiczne obniżenie ciśnienia tętniczego w godzinach nocnych. Jak wynika z doniesień, w tej grupie chorych częściej dochodzi do zmian narządowych i zdarzeń sercowo-naczyniowych. Patogenezy nadciśnienia tętniczego typu non-dipper dotychczas nie wyjaśniono. Celem autorów było zbadanie wpływu jawnej i subklinicznej niedoczynności tarczycy na rozwój profilu dobowej zmienności ciśnienia tętniczego typu non-dipper metodą całodobowego automatycznego pomiaru ciśnienia tętniczego. Materiał i metody: Spośród 109 chorych z prawidłowym ciśnieniem i z jawną lub subkliniczną niedoczynnością tarczycy do analizy włączono 95 osób, u których nie występował nocny wzrost ciśnienia tętniczego (reverse dipping) ani utajone nadciśnienie tętnicze. Grupa kontrolna składała się z 75 zdrowych osób z prawidłowym ciśnieniem tętniczym i prawidłową czynnością tarczycy odpowiednio dobranych pod względem płci i wieku. Wyniki: Mediany stężeń TSH w surowicy w grupach badanej i kontrolnej wynosiły odpowiednio 7,61 i 1,59 mUml. Liczba osób, u których nie występował nocny spadek wartości skurczowego, rozkurczowego i średniego ciśnienia tętniczego, był istotnie wyższy w grupie chorych z niedoczynnością tarczycy niż w grupie kontrolnej. W analizie regresji liniowej wykazano istnienie odwrotnej zależności między stężeniem TSH a stosunkiem między nocnymi i dziennymi wartościami ciśnienia skurczowego, rozkurczowego i średniego ciśnienia tętniczego. Wnioski: Mimo że nie wiadomo, jaki jest mechanizm oddziaływania niedoczynności tarczycy na rozwój dobowego profilu ciśnienia tętniczego typu non-dipper, w niniejszym badaniu wykazano, że podwyższone stężenie TSH może zwiększać ryzyko wystąpienia takiego profilu ciśnienia tętniczego u osób z prawidłowym ciśnieniem tętniczym i jawną lub subkliniczną niedoczynnością tarczycy. (Endokrynol Pol 2012; 63 (2): 97&#8211;103

Pengamatan Post-mortem Kualitas Kulit Kambing Di Kota Manado

Kulit ternak merupakan hasil ikutan ternak yang memiliki nilai ekonomis sebagai bahan baku utama berbagai produk industri kulit. Kualitas kuli tsegar dapat mengalami penurunan pada saat ternak masih hidup maupun setelah lepas dari tubuh ternak. Penyembelihan ternak kambing di Kota Manado cukup banyak namun belum memperhatikan kualitas kulitnya. Penelitian ini bertujuan untuk mengetahui seberapa jauh kualitas post-mortem kulit kambing di Kota Manado. Pengambilan data dilakukan di tempat pemotongan hewan pasar bersehati Kota Manado menggunakan metode observasi terhadap beberapa variabel yaitu cacat irisan, cacat penyakit kulit, dan cacat flek darah. Pengambilan sampel melalui purposive sampling serta penyajian data menggunakan statistik deskriptif. Hasil pengamatan menunjukkan bahwa cacat pada kulit kambing post mortem yang terbanyak adalah cacat irisan dan cacat penyakit kulit (± 60%) dan cacat flek darah paling sedikit (± 13,3%). Cacat yang ditemui terbanyak pada daerah D (daerah badan)