Efficient Fault Tree Analysis of Complex Fault Tolerant Multiple-Phased Systems

Fault tolerant multiple phased systems (FTMPS), i.e., systems whose critical components are independently replicated and whose operational life can be partitioned in a set of disjoint periods, are called 'phases'. Because of their deployment in critical applications, their reliability analysis is a task of primary relevance to validate the designs. Fault tree analysis based on binary decision diagram (BDD) is one of the most commonly used techniques for FTMPS reliability analysis. To utilize the technique the fault tree structure of FTMPS needs to be converted into the corresponding BDD format. Our research work shows that the system BDD generation algorithms presented in the literature are too inefficient to be used for industrial complex FTPMS because of the problems, such as variable ordering and combination of large BDDs. This paper presents a more efficient approach consisting of a flatting pre-processing technique, a proved efficient ordering heuristic and a bottom-up generation algorithm. The approach tries to combine share-variable BDDs by complex combination operation firstly and then combine no-share-variable BDDs using simple combination operation, thus to alvoid the intensive computations caused by large BDD combination operations. An example FTMPS is analyzed to illustrate the advantages of our approach.

Variations in the Microstructure and Properties of Mn-Ti Multiple-phase Steel with High Strength under Different Tempering Temperatures

There are few relevant researches on coils by tempering,and the variations of microstructure and properties of steel coil during the tempering process also remain unclear.By using thermo-mechanical control process（TMCP）technology,Mn-Ti typical HSLA steel coils with yield strength of 920 MPa are produced on the 2250 hot rolling production line.Then,the samples are taken from the coils and tempered at the temperatures of 220℃,350℃,and 620℃respectively.After tempering the strength,ductility and toughness of samples are tested,and meanwhile microstructures are investigated.Precipitates initially emerge inside the ferrite laths and the density of the dislocation drops.Then,the lath-shaped ferrites begin to gather,and the retained austenite films start to decompose.Finally,the retained austenite films are completely decomposed into coarse and short rod-shape precipitates composed of C and Ti compounds.The yield strength increases with increasing tempering temperature due to the pinning effect of the precipitates,and the dislocation density decreases.The yield strength is highest when the steel is tempered at 220℃because of pinning of the precipitates to dislocations.The total elongation increases in all samples because of the development of ferrites during tempering.The tensile strength and impact absorbed energy decline because the effect of impeding crack propagation weakens as the retained austenite films completely decompose and the precipitates coarsen.This paper clarifies the influence of different tempering temperatures on phase transformation characteristics and process of Mn-Ti typical multiphase steels,as well as its resulting performance variation rules.

Effect of multiple-phase regional intra-arterial infusion chemotherapy on patients with resectable pancreatic head adenocarcinoma

Background Regional intra-arterial infusion chemotherapy （RIAC） has been more valuable to improve prognosis and quality of life of patients with inoperable pancreatic adenocarcinomas, and adjuvant RIAC plays an important role in prolonging survival and reducing risk of liver metastasis after radical resection of pancreatic cancer, but the effect of preoperative or multiple-phase RIAC （preoperative combined with postoperative RIAC） for resectable pancreatic cancers has not been investigated. In this prospective study, the effect of multiple-phase RIAC for patients with resectable pancreatic head adenocarcinoma was evaluated, and its safety and validity comparing with postoperative RIAC were also assessed. Methods Patients with resectable pancreatic head cancer were randomly assigned to two groups. Patients in group A （n=-50） were treated with new therapeutic mode of extended pancreaticoduodenectomy combined with multiple-phase RIAC, and those in group B （n=-50） were treated with extended pancreaticoduodenectomy combined with postoperative RIAC in the same period. The feasibility, compliance and efficiency of the new therapeutic mode were evaluated by tumor size, serum tumor markers, clinical benefit response （CBR）, surgical complications, mortality and toxicity of RIAC. The disease-free survival time, median survival time, incidence of liver metastasis, survival rate at 1, 2, 3 and 5 years were also observed. Life curves were generated by the Kaplan-Meier method. Results The pain relief rate and CBR in group A was 80% and 84% respectively. Serum tumor markers decreased obviously and tumors size decreased in 26% of patients after preoperative RIAC in group A. No more surgical complications, mortality or severe systemic side effects were observed in group A compared with group B. The incidence of liver metastasis in group A was 34% which was lower than 50% in group B. The disease-free survival time and median survival time in group A were 15.5 months and 18 months respectively. The 1-, 2-, 3- and 5-year survival rates were 54.87%, 34.94%, 24.51% and 12.25% respectively. There was no significant difference of survival time or survival rates between two groups. Conclusions Multiple-phase RIAC is effective in combined therapy of resectable pancreatic head carcinomas by enhancing inhibition of tumor growth and reduction of liver metastasis, without negative effect on patients＇ safety or surgical procedure.