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      • KCI등재

        An improved Corten-Dolan’s model based on damage and stress state effects

        Huiying Gao,Hong-Zhong Huang,Zhiqiang Lv,Fang-Jun Zuo,Hai-Kun Wang 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.8

        The value of exponent d in Corten-Dolan’s model is generally considered to be a constant. Nonetheless, the results predicted on thebasis of this statement deviate significantly from the real values. In consideration of the effects of damage and stress state on fatigue lifeprediction, Corten-Dolan’s model is improved by redefining the exponent d used in the traditional model. The improved model performsbetter than the traditional one with respect to the demonstration of a fatigue failure mechanism. Predictions of fatigue life on thebasis of investigations into three metallic specimens indicate that the errors caused by the improved model are significantly smaller thanthose induced by the traditional model. Meanwhile, predictions derived according to the improved model fall into a narrower dispersionzone than those made as per Miner’s rule and the traditional model. This finding suggests that the proposed model improves the life predictionaccuracy of the other two models. The predictions obtained using the improved Corten-Dolan’s model differ slightly from thosederived according to a model proposed in previous literature; a few life predictions obtained on the basis of the former are more accuratethan those derived according to the latter. Therefore, the improved model proposed in this paper is proven to be rational and reliable giventhe proven validity of the existing model. Therefore, the improved model can be feasibly and credibly applied to damage accumulationand fatigue life prediction to some extent.

      • KCI등재

        Lifetime prediction for turbine discs based on a modified Walker strain model

        Zhiqiang Lv,Hong-Zhong Huang,Huiying Gao,Fang-Jun Zuo,Hai-Kun Wang 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.10

        We created three-dimensional models of turbine disc and blades of a type of aero-engine according to their geometries. Extant studies show that low cycle fatigue is the main failure mechanism of turbine disc. By using a non-linear elastic-plasticfinite element method, the static stress and strain state of the critically high stress regions, which can lead to operational failures,are determined. On the basis of stress-strain relation, a modified Walker strain life prediction model is proposed with norequired knowledge on the mean stress correction. Then the predicted life data from the modified Walker strain model arecompared with the testing results. After the verification, the modified Walker strain life prediction model and Miner’s rule wereapplied to predict the lifetime of the turbine disc under various operating conditions.

      • KCI등재

        Immobilization of Acetobacter sp. CGMCC 8142 for Efficient Biocatalysis of 1, 3-propanediol to 3-hydroxypropionic Acid

        Jun Li,Hong Zong,Bin Zhuge,Xinyao Lu,Huiying Fang,Jin Sun 한국생물공학회 2016 Biotechnology and Bioprocess Engineering Vol.21 No.4

        3-hydroxypropionic acid (3-HP) is an important chemical platform organic in material industry, daily chemical industry and biomedicine field due to its numerous valuable derivatives. However, no mature methods have been established in the synthesis industry for direct large scale production. The bacterium Acetobacter sp. CGMCC 8142 with high efficiency of alcohols oxidation property was immobilized for biosynthesis of 3-HP from 1, 3- propanediol (1, 3-PDO). Parameter values in mass transfer modeling indicated that mass transfer of immobilized biocatalysts affected the oxidation reaction (the internal effectiveness factor ηi < 1) but was not the rate-limiting step if Thiele modulus 1 > ϕ > 0.3. The optimal immobilization conditions for 3-HP biocatalysis was sodium alginate 40 g/L, gel beads diameter 1 mm, cross-linkage time 2 h and 0.1mM FeCl2. Immobilized cells showed promising substrate tolerance, pH stability, thermal stability and storability. After 5 cycles of reaction, 3-HP molar yield of immobilized beads was retained to 80.26%, and 66.95 g/L 3-HP were produced from 70 g/L 1, 3-PDO. The biocatalysis process of immobilized cells introduced in this study may provide an economical and efficiency alternative route for practical production of 3-HP.

      • KCI등재

        Protoplast Preparation and Polyethylene Glycol (PEG)-mediated Transformation of Candida glycerinogenes

        Cheng Zhang,Hong Zong,Bin Zhuge,Xinyao Lu,Huiying Fang,Jiali Zhu,Jian Zhuge 한국생물공학회 2016 Biotechnology and Bioprocess Engineering Vol.21 No.1

        The regeneration of Candida glycerinogenes protoplasts is a major step following genetic manipulations such as fusion and DNA-mediated transformation. An investigation of protoplast formation and cytological examination was used to gain further insight into the loss of protoplast viability in osmotically stabilized support media. Protoplasts with the highest regeneration frequency (98.6% protoplasts/mL) were isolated, using lysozyme dissolved in 1M sorbitol osmoticum. The commercial enzyme preparations, osmotic stabilisers, and growth phase were effective in raising the protoplast yield. Sodium chloride was effective for protoplast preparation; however, sugars and sugar alcohols were better for protoplast regeneration. Sorbitol at a concentration of 1 M was used in regeneration agar for further studies. Regeneration of colonies from protoplasts was maximal (11 ~ 15%) when protoplasts were incorporated in cooled agar containing 0.5% glucose, supplemented with 1M sorbitol as osmotic stabilizer. C. glycerinogenes strain was highly sensitive to zeocin, so transformation of protoplasts and PEG-mediated was achieved with an improved transformation system, using plasmid pURGAP-gfp containing zeocin gene driven by a PCgGAP promoter from C. glycerinogenes to express gfp gene and be transformed into the 5.8S rDNA site of C. glycerinogenes in order to test the system for studying the yeast osmoregulation. We developed an efficient method for transformation of C. glycerinogenes, and parameters involved in transformation efficiency were optimized. Expressions of gfp at different levels were conducted under osmotic stress containing NaCl, KCl, sorbitol or glycerol for the recombinant strains. These improved procedures for protoplast isolation, regeneration and transformation proved to be useful applications in genetic studies for other Candida species and industrial yeast.

      • KCI등재

        Determining the Walker exponent and developing a modified Smith-Watson-Topper parameter model

        Zhiqiang Lv,Hong-Zhong Huang,Hai-Kun Wang,Huiying Gao,Fang-Jun Zuo 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.3

        Mean stress effects significantly influence the fatigue life of components. In general, tensile mean stresses are known to reduce the fatigue life of components, whereas compressive mean stresses are known to increase it. To date, various methods that account for mean stress effects have been studied. In this research, considering the high accuracy of mean stress correction and the difficulty in obtaining the material parameter of the Walker method, a practical method is proposed to describe the material parameter of this method. The test data of various materials are then used to verify the proposed practical method. Furthermore, by applying the Walker material parameter and the Smith-Watson-Topper (SWT) parameter, a modified strain-life model is developed to consider sensitivity to mean stress of materials. In addition, three sets of experimental fatigue data from super alloy GH4133, aluminum alloy 7075-T651, and carbon steel are used to estimate the accuracy of the proposed model. A comparison is also made between the SWT parameter method and the proposed strainlife model. The proposed strain-life model provides more accurate life prediction results than the SWT parameter method.

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