Mechanical properties of gas hydrate-bearing sediments during hydrate dissociation

The changes in the mechanical properties of gas hydrate-bearing sediments(GHBS) induced by gas hydrate(GH) dissociation are essential to the evaluation of GH exploration and stratum instabilities. Previous studies present substantial mechanical data and constitutive models for GHBS at a given GH saturation under the non-dissociated condition. In this paper, GHBS was formed by the gas saturated method, GH was dissociated by depressurization until the GH saturation reached different dissociation degrees. The stress–strain curves were measured using triaxial tests at a same pore gas pressure and different confining pressures. The results show that the shear strength decreases progressively by 30%–90% of the initial value with GH dissociation, and the modulus decreases by 50% –75%. Simplified relationships for the modulus, cohesion, and internal friction angle with GH dissociated saturation were presented.

Al-Mg-Si-Mn-Fe系合金均匀化过程中的显微组织演化:数值模拟与实验结果对比（英文）

通过数值模拟和实验相结合的方法,对Al-Mg-Si-Mn-Fe(AA6xxx)系合金均匀化过程中的显微组织演化进行研究。所应用的数学模型是结合CALPHAD及基于AA3xxx(Al-Mn-Fe-Si)系合金均匀化热处理而开发的。而后对此模型进行修正,以使得其应用拓展到更为复杂的AA6xxx系合金。该热处理模型可以预测包括溶质元素分布、初生相类型与比例、以及弥散相密度和尺寸分布在内的关键显微组织的演化。实验方面,对3种不同锰含量的AA6xxx系合金进行均匀化热处理。应用扫描电子显微镜、EPMA、XRD和电阻率等实验手段对所得均匀化组织进行多角度表征。预测结果与实验表征的对比表明,数学模型可以较为准确地反映均匀化过程中显微组织的演化。

RELIABILITY ANALYSIS FOR AN AERO ENGINE TURBINE DISK UNDER LOW CYCLE FATIGUE CONDITION

Reliability analysis methods based on the linear damage accumulation law (LDAL) and load-life interference model are studied in this paper. According to the equal probability rule, the equivalent loads are derived, and the reliability analysis method based on load-life interference model and recurrence formula is constructed. In conjunction with finite element analysis (FEA) program, the reliability of an aero engine turbine disk under low cycle fatigue (LCF) condition has been analyzed. The results show the turbine disk is safety and the above reliability analysis methods are feasible.

RANDOM-FUZZY SAFETY ANALYSIS FOR AN AERO ENGINE TURBINE DISK

A numerical simulation method is presented for the random-fuzzy safety analysis of an aero engine disk. Based on the equivalent transformation from a fuzzy variable to a random variable, the equivalent random Probability Density Functions(PDFs) are got from their corresponding Fuzzy Possibility Distributions(FPDs) for the fuzzy variables. In that case the perfect numerical simulation method for the random uncertainty is employed to solve the fuzzy uncertainty. For the complex structure such as the aero engine disk with implicit relationship between the input basic variable and the response variable, the equivalent PDFs of the input basic variables are delivered simultaneously to the response variable by an empirical PDF, which is simulated by Finite Element Method(FEM). Then, in view of the fuzzy application requirement occurring in engineering usually, the reliability definition and calculation are discussed for the aero engine disk with multiple fuzzy failure modes. On the other hand, through the inverse transformation of the fuzzy variable to the random variable, the FPDs of the response variables can be calculated from their empirical PDFs as well.

Determination of the number of ψ' events at BES Ⅲ

The number of φ＇ events accumulated by the BESIII experiment from March 3 through April 14, 2009, is determined by counting inclusive hadronic events. The result is 106.41×（1.00±0.81%）×10^6. The error is systematic dominant; the statistical error is negligible.

Measurement of the integrated luminosities of the data taken by BESⅢ at √s=3.650 and 3.773 GeV

Data sets were collected with the BESⅢ detector at the BEPCⅡ collider at the center-of-mass energy of √s=3.650 GeV during May 2009 and at √s=3.773 GeV from January 2010 to May 2011. By analyzing the large angle Bhabha scattering events, the integrated luminosities of the two data sets are measured to be （44.49±0.02±0.44） pb-1 and （2916.94±0.18±29.17） pb-1, respectively, where the first error is statistical and the second error is systematic.

Investigation on Collision of Si^(2+)with H from Intermediate to High Projectile Energies

Total and state-selective charge transfer,ionization and stripping cross sections due to the collision of Si^(2+)ion with atomic hydrogen are investigated using the classical-trajectory Monte-Carlo(CTMC)method in the collision energy from 1 keV/amu to 10 MeV/amu.Total electron capture rate coefficient is obtained in the temperature range from 105 Ko to 108 Ko.Comparison with the data available shows that our CTMC results are reliable.The behaviors for these cross sections varying with the projectile energy are analyzed.A classical physical picture is presented to explain the reason behind the behaviors.

Evidence for e^+e^-→γχ_(c1,2) at center-of-mass energies from 4.009 to 4.360 GeV

Using data samples collected at center-of-mass energies of √s=4.009, 4.230, 4.260, and 4.360 GeV with the BES0 detector operating at the BEPC/ collider, we perform a search for the process e＋e-→γχc,j （J =0, 1, 2） and find evidence for e＋e-→γχc1 and e＋e-→γχc2 with statistical significances of 3.0σ and 3.4σ, respectively. The Born cross sections σB（e＋e-→γχc,j）, as well as their upper limits at the 90% con dence level （C.L.） are determined at each center-of-mass energy.

China’s participation in the international RRT for I_(c) measurement of superconducting cables organized by IEC/TC90

Currently,IEC/TC90 is working on standardizing the method for measuring critical current(Ic)in superconducting cables.At the end of 2020,an international round robin test(RRT)was organized,in which five Chinese institutions participated,and four accomplished the test.The electric-field versus current(E-I)curves obtained by each institution are highly repeatable.Those obtained by different institutions are nearly identical after appropriate curve averaging,indicating high reproducibility,except the last participant's inner core curves.The discrepancy was later determined to be the result of sample cable damage.After excluding highly deviated data,it is determined that the maximum relative standard uncertainty in I_(c) is 0.7%,and the maximum relative standard uncertainty in n-value is 12.8%.The I_(c)values are comparable to Japan's domestic RRT results,but the n-values are significantly different.The test results support the DC four-terminal method as a recommended test method,with a target relative uncertainty of less than 2%for the Ic value.