Verbesserung des Schwingungsrißkorrosionsverhaltens von Stahlproben durch Beschichtung

Improvement of the corrosion fatigue behavior of steels by paint-coating Paint-coatings have been used extensively to prevent corrosion of steel. In order to investigate the influence of an anticorrosive paint on the corrosion fatigue strength of steel, specimens of SAE 4135 in a quenched and tempered state, and in salt bath nitrocarburized state, on the one hand, and specimens of the steel SAE 5115 in a salt bath carburized state, on the other hand, were subjected to comparative rotating bending fatigue tests in inert media and in aqueous 5 pct NaCl. The results demonstrate that the 5 pct NaCl environment is reducing fatigue life drastically, but the painting treatment, however, was found to improve significantly the corrosion fatigue life. Regarding the beneficial effect of the painting treatment on the corrosion fatigue behavior, a superiority of the nitrocarburized variant in contrast to the other variants was ascertained.     

Superlattice barrier 1528-nm vertical-cavity laser with 85/spl deg/C continuous-wave operation

We report 85/spl deg/C continuous-wave electrically pumped operation of a 1528-nm vertical-cavity laser. An InP-InGaAsP active region was wafer bonded to the GaAs-AlGaAs mirrors, with a superlattice barrier to reduce the defect density in the active region.     

Starch from the Sago (Metroxylon sagu) Palm Tree—Properties,Prospects, and Challenges as a New Industrial Source for Food and Other Uses

ABSTRACT: The common industrial starches are typically derived from cereals (corn, wheat, rice, sorghum), tubers (potato, sweet potato), roots (cassava), and legumes (mung bean, green pea). Sago (Metroxylon sagu Rottb.) starch is perhaps the only example of commercial starch derived from another source, the stem of palm (sago palm). Sago palm has the ability to thrive in the harsh swampy peat environment of certain areas. It is estimated that there are about 2 million ha of natural sago palm forests and about 0.14 million ha of planted sago palm at present, out of a total swamp area of about 20 million ha in Asia and the Pacific Region, most of which are under‐ or nonutilized. Growing in a suitable environment with organized farming practices, sago palm could have a yield potential of up to 25 tons of starch per hectare per year. Sago starch yield per unit area could be about 3 to 4 times higher than that of rice, corn, or wheat, and about 17 times higher than that of cassava. Compared to the common industrial starches, however, sago starch has been somewhat neglected and relatively less attention has been devoted to the sago palm and its starch. Nevertheless, a number of studies have been published covering various aspects of sago starch such as molecular structure, physicochemical and functional properties, chemical/physical modifications, and quality issues. This article is intended to piece together the accumulated knowledge and highlight some pertinent information related to sago palm and sago starch studies.     

Sulfonated polyaniline–titanium dioxide nanocomposites synthesized by one-pot UV-curable polymerization method

Sulfonated polyaniline–titanium dioxide (SPAni–TiO₂) hybrid composites have been synthesized by using a new strategy in one-pot system of UV-cured polymerization method. Aqueous solution of aniline and orthoanilinic acid comonomers, a free-radical oxidant and titania precursor were irradiated by UV rays. Hydrolysis and reprecipitation of the titania precursor in aqueous aniline and orthoanilic acid lead to the formation of titanium dioxide particles which in turn catalyze oxidation of comonomers to sulfonated polyaniline. The resultant SPAni–TiO₂ composites were characterized by using different spectroscopy analyses like X-ray diffraction, UV–visible (UV–vis) and infrared spectroscopy. The UV–vis absorption bands revealed that SPAni–TiO₂ nanocomposites are optically active and the blue-shifted peaks due to the presence of titania within the SPAni matrix. Scanning electron microscopy and transmission electron microscopy of the nanocomposite showed a uniform size distribution with spherical and granular morphology. Thermogravimetric analysis revealed that the SPAni–TiO₂ composites have a good thermal stability than the pristine SPAni.     

Equilibrium Reconstruction of Anisotropic Pressure Profile in the Levitated Dipole Experiment

The Levitated Dipole Experiment (LDX) is an innovative confinement concept that uses an internal superconducting dipole field to confine plasma. Plasma equilibrium is calculated by a least-squares fit of an anisotropic pressure model to magnetic measurements constrained by X-ray images. Reconstructions have been done for different heating schemes using two-frequency electron cyclotron heating at 2.45 and 6.4 GHz. Results show that a maximum local β ∼ 20% has been achieved using two frequency heating at a combined full power of 5 kW. Analysis of the reconstruction results shows that the magnetic sensors are sensitive primarily to changes in the plasma dipole moment. This is partly due to the fact that the dipole current decreases as the plasma current increases (as required by flux conservation through the superconducting dipole) and the magnetic sensors detect the sum of these changes. This paper will present details of the reconstruction procedure and describe how new magnetic sensors will aid in resolving the pressure profile more accurately.     

Effects of Plasticizers,Antioxidants and Burning Rate Modifiers on Aging Performance of the HTPB/HMDI Composite Solid Propellant

The effects of plasticizers,antioxidants and burning rate modifiers on the aging performance of the composite solid propellant based on hydroxyl-terminated polybutadiene(HTPB)/hexamethylene diisocyanate(HMDI)were explored by apply-ing an accelerated aging program for 90 day at 70 ℃. The HTPB propellant matrix with the diisooctyl sebacate(DOS)as plasti-cizers and diisooctyl azelate(DOZ), antioxidants as N,N ′-Diphenyl-p-phenylenediamine(AO) and 2,2′-methylenebis(4-methyl-6-tert-butylphenol)(cyanox 2246)and burning rate modifiers as barium ferrite(BF),copper chromites(CC)and fer-ric oxide(FO)were varied. Results show that sample(S1)which based on DOS decreases the stress value and increases the strain value which considered to be an excellent start for aging program. Sample(S3)containing AO presents the higher resis-tance to oxidation showing the better performance that reflects on increasing the shelf life of the composite solid propellant mo-tor. Sample(S5)which based on BF enhances the ballistic performance among over the other tested two samples. The accelerat-ed aging program allowed us to estimate the motor in-service lifetime.     

Asymptotic Distortion Performance of Source-Channel Diversity over Multihop and Relay Channels

A key challenge in the design of real-time wireless multimedia systems is the presence of fading coupled with strict delay constraints. A very effective answer to this problem is the use of diversity achieving techniques to overcome the fading nature of the wireless channels caused by the mobility of the nodes. The mobility of the nodes gives rise to the need of cooperation among the nodes to enhance the system performance. This paper focuses on comparing systems that exhibit diversity of three forms: source coding diversity, channel coding diversity, and user cooperation diversity implemented through multihop or relay channels with amplify-and-forward or decode-and-forward protocols. Commonly used in multimedia communications, performance is measured in terms of the distortion exponent, which measures the rate of decay of the end-to-end distortion at asymptotically high signal-to-noise ratio (SNR). For the case of repetition coding at the relay nodes, we prove that having more relays is not always beneficial. For the general case of having a large number of relays that can help the source using repetition coding, the optimum number of relay nodes that maximizes the distortion exponent is determined in this paper. This optimum number of relay nodes will depend on the system bandwidth as well as the channel quality. The derived result shows a trade-off between the quality (resolution) of the source encoder and the amount of cooperation (number of relay nodes). Also, the performances of the channel coding diversity-based scheme and the source coding diversity-based scheme are compared. The results show that for both relay and multihop channels, channel coding diversity provides the best performance, followed by the source coding diversity.     

Unusual Features of the Unusual Ribosomal Elongation Factor EF4 (LepA)

Bacteria, mitochondria, and chloroplasts contain the highly conserved elongation factor EF4; they have in common that the intracellular ionic strength can change dramatically, in contrast to that of archaea and eukaryotic cytoplasm, where EF4 is absent. This factor has the unique function of back-translocating ribosomes, viz., it exerts the opposite function as EF-G. Under unfavorable growth conditions which increase the intracellular ionic strength, such as high salts, low pH, or low temperature, wild-type cells effectively overgrow strains lacking the EF4 gene lepA. Under these conditions most of EF4 is present in the cytoplasm, and only small amounts in the membrane fraction; the opposite is true under optimal conditions, indicating that the membrane is a storage organ for EF4. This factor tunes bacteria for fitness at high ionic strength by (i) improving the active fraction by reactivating unscheduled stalled ribosomes, and (ii) increasing significantly the rate of protein synthesis.