[en] This thesis aims to study low-energy strong interaction effects of open-charm mesons. Our studies are based on the chiral Lagrangian supplemented by constraints from the heavy-quark spin symmetry. The pseudoscalar and vector open-charm-meson masses are calculated up to next-to-next-to-next leading order (N³LO) corrections. Different assumptions on the counting rules are investigated. It is illustrated that a chiral expansion uniformly converges rapidly up to Goldstone boson masses as heavy as the kaon masses if formulated in terms of physical meson masses. First estimates of the relevant low-energy parameters are extracted from lattice QCD data on the quark mass dependence of the D meson masses. Such low-energy parameters are of crucial importance for the low-energy interaction of the Goldstone bosons with the D mesons.

[en] Thymic epithelial tumors including thymomas and thymic carcinomas have well-known heterogeneous oncologic behaviors and variable histologic features. They show variable and unpredictable evolutions ranging from an indolent non-invasive feature to a highly infiltrative and metastasising one. Currently, CT is a common and efficient imaging method for assessing thymic epithelial tumors. CT evaluation is the main reference for preoperative clinic staging and histological classification. CT features of subtypes of thymic epithelial tumors on the basis of the World Health Organization classification provide the foundation for the diagnosis and predicting prognosis. (authors)

[en] This work illustrates a quantitative uncertainty analysis of CTF, one thermal-hydraulics sub-channel code for nuclear engineering applications. Like many other thermal-hydraulics codes, large uncertainties of CTF stem from the inaccuracy of parameters in the empirical correlations. However, many previous uncertainty analyses of CTF are based on the inexact parameter distributions described by the 'expert opinions', which are generally overestimations. To resolve these issues, inverse uncertainty quantification (IUQ) is conducted to determine the parameter uncertainties. IUQ is a process of quantifying the uncertainties of physical model parameters given relevant experimental measurements. In this study, the OECD/NRC BWR Full-size Fine-Mesh Bundle Tests (BFBT) benchmark steady-state void fraction data is used as the prior knowledge and Bayesian inference is implemented to formulate the IUQ problem. Two Markov Chain Monte Carlo (MCMC) sampling techniques, the adaptive Metropolis-Hasting with global scaling algorithm and the adaptive Metropolis-Hasting with component-wise scaling algorithm, are implemented and investigated to explore the posterior probability density functions. Once the framework is established, approximate 100000 runs of CTF are needed which is a big computational burden. Gaussian process regression (GPR) is therefore introduced to construct the surrogate model for CTF, which can significantly reduce the simulation time and make the Bayesian inference possible. The outcomes contain the posterior distributions of 7 physical model parameters that are crucial to the BFBT experiment. Results of IUQ can be used for the forward uncertainty propagation and validation analysis. The results also show that two MCMC algorithms take the advantages of self-adaptive method, capable of inferring the posterior distribution of model parameters with arbitrary form of prior information. These two MCMC algorithms give consistent results and the posterior accepted samples of each model parameter are then fitted to the classic distribution. (author)

[en] This paper studies the direct simulation method of neutron space-time kinetics, based on the RMC developed by Reactor Engineering Analysis Lab (REAL), Department of Engineering Physics, Tsinghua University. A comb sampling method that adjusts the neutron history numbers is developed to control the computational cost of the Monte Carlo algorithm, and is verified by the TRACY-r61 case. A method based on precursor forced decay and roulette is developed to reduce the variance of precursor simulation, and is verified by a single group point reactor model. The simulation process of absorption reaction and fission reaction was modified to smoothen the number of neutrons in each counting time box. Furthermore, after the critical calculation module is added, the code is verified by the case 16A. The results show that the simulation of the code reaches good precision. (author)

[en] Highlights: • Dandelion-like PtPd heterogeneous structure was fabricated by using HDPCl. • DPtPdNC with open structure provide abundant electrochemical active sites. • DPtPdNC show superior catalytic activity for ethanol oxidation and high stability. - Abstract: We successfully synthesized a dandelion-like PtPd heterogeneous structure via a facile one-pot hydrothermal route by reducing Na_2PdCl_4 and H_2PtCl_6 with ascorbic acid in the presence of hexadecylpyridinium chloride monohydrate. Hexadecylpyridinium chloride monohydrate acted as the shape-directing agent, which is critical to the reproducible formation of dandelion-like PtPd nanoclusters (DPtPdNC). The prepared DPtPdNC with an average diameter of 40 nm composed of dozens of branched arm assembled by Pt and Pd heterogeneous nanoseeds. DPtPdNC had a strong electron-electron interaction. What's more, there were numerous nanoscale steps, kinks and edges in DPtPdNC open channel structure. As a result, an optimized DPtPdNC made by fine-tuning ratio of the Pt (7%) and Pd (93%) showed hugely active surface sites and a superior electrocatalytic performance for ethanol oxidation was well as a long durability

[en] CTF (Coolant Boiling in Rod Arrays-Two Fluid) is a new sub-channel thermal/hydraulic simulation code developed by CASL (The Consortium for Advanced Simulation of Light Water Reactors) and PSU (Pennsylvania State University). It can solve steady or transient-state problems efficiently for both single assembly and full-core reactor. Thus, this code solves the computational efficiency and memory consumption problems effectively. First, CTF computes the BEAVRS benchmark in parallel with the domain decomposition technology. The power data which CTF uses are calculated by RMC(a Monte Carlo code for reactor core analysis). After calculating for 268 s, we get detailed fuel pin temperature, water temp and density output results. Accordingly, the efficiency and reliability of CTF is verified. On this basic work of CTF calculation for BEAVRS benchmark,the coupling between RMC and CTS for full-core problem will achieved soon. (authors)

[en] We propose an extended Nambu-Jona-Lasinio model to include heavy mesons with heavy quark symmetry. The quark current-current interaction is generalized to include the heavy quark currents. In order to comply with the heavy quark spin symmetry at the heavy quark limit, the dependence of the quark mass on the interaction strength is introduced. The light and heavy pseudo-scalar and vector mesons, their masses and the weak decay constants are calculated in the unified frame. (authors)

[en] The Reactor Monte Carlo code RMC, developed by REAL group, at Tsinghua University, has a function of kinetic calculation. RMC has participated in C5G7-TD transient benchmark calculation to further optimize its kinetic algorithm, and also to validate its results. The C5G7-TD benchmark consists of 6 sets of cases, 28 subcases in total, where the movement or moderator density variation of the control rods is adopted in these cases to introduce the reactivity change. To decrease the oscillation in Monte Carlo calculation, 1 million particles was used in the calculation, and non-uniform time steps were applied to reduce the calculation cost. Except for those cases with different specifications, the power profiles calculated by RMC are in good agreement with those of n TRACER. (authors)

[en] The position of the magnetic dipole can be estimated by measuring the magnetic field of the magnetic dipole and processing the measurement information. The main problem in locating a ferromagnetic target is to eliminate the interference of the geomagnetic field. In recent years, there has been a lot of research to eliminate geomagnetic interference by processing measurement results. For an object with an alternating current signal, the interference of geomagnetic field can be eliminated through a simple band-pass filter. However, there are still other causes of localization errors. The measurement error of the sensor has different effects on different positioning systems. This paper compares the influence of measurement error on localization systems with different structures. The simulation results show that when the measurement error is at a reasonable level, some localization systems perform better than others. (paper)

[en] Highlights: • The adjoint flux weighted predictor-corrector quasi-static Monte Carlo method is proposed. • The algorithm of the method is developed and implemented. • A fitting method to eliminate the statistical error in transient Monte Carlo calculations is used and effective. • The method is validated and tested using several typical cases of the C5G7-TD benchmark. Reactor safety analyses require high-fidelity numerical solutions of transient neutron transport problems. A predictor–corrector quasi-static (PCQS) method based on the Monte Carlo (MC) simulation is developed and implemented into the Reactor Monte Carlo code (RMC). This method used a hybrid stochastic-deterministic scheme utilizing point kinetic equation formalism to solve transient problems without geometric and energy spectrum approximations and to offer accurate kinetic parameters as well. The PCQS MC method and the RMC code are verified here for the C5G7-TD transient benchmark sub-critical cases. The computational time of this method is only about 1% of that for the quasi-static DMC method. The RMC results agree within about 1% with results of the SUHAM and nTRACER codes for the TD2-1, TD4-4 and TD1-3 cases. The denoising method based on polynomial fittings used here improves the results for these cases.