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  • Author: Xu Zhao x
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Peiqi Liu, Liming Zhang, Siyuan Xu, Zhixiang Duan, Zuzhi Chen and Wenjing Zhao

Abstract

The structure of wellbore and coupling is connected by thread, it is the position where fatigue failure accidents are happened in gas storage well, and the make-up torque of thread is the key factor that influences the mechanical properties of this structure. In this pa- per, a finite element method was established to discuss the calculation method of make-up torque and the influence law on the stress of coupling in the gas storage well. Results show that the make-up torque cannot be simply ignored due to its great impact on internal stress distribution of gas storage well. Experimental results showed the correctness of the model. Under the action of the make-up torque, the overall stress level inside the wellbore is higher than the external coupling. However the maximum stress exists in the external coupling. The overall stress grad- ually increases with the increase of interference rotation number (abbr. RN) between coupling and wellbore, but the overall distribution trend is almost the same. The first thread on the left of the connection part is the area where fatigue failure is most likely to occur. The make-up torque between threads increases linearly with the increase of RN between cou- pling and wellbore.

Open access

Hui-Min Hou, Guo-Hai Dong, Tiao-Jian Xu, Yun-Peng Zhao and Chun-Wei Bi

Abstract

Investigation of the embedded chains in soil starts to play an important role in understanding the structural performance of mooring system, when the embedded anchors will be employed to sustain large loads with the gradually growth of installation depth of offshore aquaculture farm. The aim of this study is to investigate the dynamic response of mooring line considering the influence of embedded chains in clay soil for net cage system. Lumped-mass method is used to establish the numerical model for evaluating the performance of mooring line with embedded chains. To validate the numerical model, comparisons of numerical results with the analytical formulas and the experimental data are conducted. A good agreement of the profile and the tension response is obtained. Then, the effect of embedded chains on the static and dynamic response of mooring line is evaluated, and the dynamic behavior of mooring system considering embedded chains for net cage system is investigated. The results indicate that the soil resistance on embedded chains should be included to predict the mooring line development and the load on the embedded anchors in the numerical simulations. An appropriate safety factor should be included if employing the simplified model Case C at the initial design phase. And the effect of embedded chains on the holding capacity of embedded anchors in single-point mooring system for single net cage cannot be negligible during the design and operation phases. Consequently, it is profound to take into account the interaction of embedded chains and soil for accurately predicting the reliability of mooring system for fish cage.

Open access

Ming-hui Li, Yao Xie, Yao Lu, Guo-hua Qiu, Lu Zhang, Ge Shen, Li-wei Zhuang, Ju-long Hu, Jian-ping Dong, Cai-qin Mu, Lei-ping Hu, Li-jun Chen, Xing-hong Li, Min Yang, Yun-zhong Wu, Hui Zhao, Shu-jing Song, Jun Cheng and Dao-zhen Xu

Abstract

Objective To investigate the effects of individualised treatment with peginterferon alpha-2a (40 kD) plus ribavirin in Chinese patients with CHC.

Methods Total of 297 consecutive Chinese patients were enrolled, including 250 naïve cases and 47 cases who were previously treated. Treatment duration was determined according to viral genotypes, prior treatment history and viral responses at week 4, 12 and 24.

Results Totally, 235 patients (79.1%) completed treatment and 186 (87.3%) achieved SVR. And 219 out of 289 (75.8%) patients achieved HCV RNA negative at week 4 (RVR) and 259 of 276 (93.8%) at week 12. Among the 164 patients with RVR who completed follow-up, 158 (96.3%) achieved SVR. Patients with RVR had lower baseline viral loads than patients without RVR (P = 0.034). The positive predictive value (PPV) of RVR for SVR was 90.7% (OR 2.10 vs. non-RVR, 95% CI: 0.50 - 8.7). Similar outcomes were observed among patients with HCV undetectable at week 12.

Conclusions Complete viral suppression by week 4 is associated with a high rate of treatment success in treatment naïve and experienced patients receiving individualized CHC therapy.