Quantitative model checking of continuous-time Markov chains against timed automata specifications

We study the following problem: given a continuous-time Markov chain (CTMC) C, and a linear real-time property provided as a deterministic timed automaton (DTA) A, what is the probability of the set of paths of C that are\ud accepted by A (C satisfies A)? It is shown that this set of paths is measurable and computing its probability can be reduced to computing the reachability probability in a piecewise deterministic Markov process (PDP). The reachability probability is characterized as the least solution of a system of integral equations and is shown to be approximated by solving a system of partial differential equations. For the special case of single-clock DTA, the system of integral equations can be transformed into a system of linear equations where the coefficients are solutions of ordinary differential equations

CHARACTERIZING ANAEROBIC BIODEGRADATION OF GASOLINE WITH LOW MOLECULAR WEIGHT ORGANIC ACID ANIONS AND PHOSPHATE AMENDMENT

Bioremediation is a feasible method to clean up petroleum hydrocarbons (PHC) contaminated soil. But bioremediation is often limited by nutrient bioavailability, PHC bioaccessibility, microbial activity and environmental factors. It was hypothesized low molecular weight organic acid anions (LMOAA) can enhance PHC biodegradation by increasing PHC bioavailability, increasing phosphorus (P) bioavailability, or stimulating hydrocarbon degrader community. A microcosm study and a field study were conducted to evaluate this hypothesis. In the microcosm study, 10-100 mM citrate increased petroleum hydrocarbon bioavailability to enhance in situ anaerobic gasoline degradation. Lower citrate addition, 1.0 mM and 1.75 mM, accelerated ex situ biodegradation for benzene and gasoline respectively, probably through changing P bioavailability. In the field, two large bore injectors were constructed in a gasoline contaminated cold region calcareous site, for in situ biostimulation solution delivery. Two biostimulation solutions were applied. The first solution containing 11 mM MgSO4, 1 mM H3PO4, and 0.08 mM HNO3 (phosphate amendment) stimulated the site for about 4 months. Then, 10 mM citric acid was incorporated into the existing biostimulation solution (phosphate and citrate amendment) for another 8 months. Dissolved P in groundwater and bioavailable organic P in soil were increased after citrate addition, which corresponded to the decrease for benzene, toluene, ethylbenzene, and xylene (BTEX) in groundwater and F1-BTEX (C6-C10 with BTEX subtracted) decrease in soil. Citrate addition also increased benzoate degradation N (bzdN, encoding ATP-dependent benzoyl-CoA reductase subunit N) gene prevalence and culturable anaerobic PHC degraders population in soil. After applying phosphate amendment, the bacterial community structure changed in both soil and groundwater. However, the influence of citrate on microbial community differed between soil and groundwater. Citrate selectively stimulated anaerobic hydrocarbon degraders in groundwater, and reversed soil bacterial community structure, which corresponded to the rebounded adsorbed phosphate. In addition, a method trapping 13CO2 produced from 13C-labelled contaminates was developed and successfully assessed PHC mineralization rate using the cavity ring-down spectrometry. This research highlights the positive effect of LMOAA on anaerobic PHC biodegradation through increasing PHC/P bioavailability and stimulating PHC degraders

On the complexity of computing maximum entropy for Markovian Models

We investigate the complexity of computing entropy of various Markovian models including Markov Chains (MCs), Interval Markov Chains (IMCs) and Markov Decision Processes (MDPs). We consider both entropy and entropy rate for general MCs, and study two algorithmic questions, i.e., entropy approximation problem and entropy threshold problem. The former asks for an approximation of the entropy/entropy rate within a given precision, whereas the latter aims to decide whether they exceed a given threshold. We give polynomial-time algorithms for the approximation problem, and show the threshold problem is in P CH3 (hence in PSPACE) and in P assuming some number-theoretic conjectures. Furthermore, we study both questions for IMCs and MDPs where we aim to maximise the entropy/entropy rate among an infinite family of MCs associated with the given model. We give various conditional decidability results for the threshold problem, and show the approximation problem is solvable in polynomial-time via convex programming

Research on The Issue of Payments in The Cross-Border E-Commerce

Cross-border e-commerce is the combination of “Internet+” International Trade, which shorten the distance between products and market in time and space, and promote trade development. While cross-border payment services play an important role in cross-border e-commerce, once the payment services is not successful, it means we are unable to make a deal, so, it pushes the completion of cross-border e-commerce transactions. This paper researches the concept of cross-border e-commerce and cross-border payment, and develops a model to describe current situation of China’s cross-border payment business, summarizes the domestic and foreign cross-border e-commerce platform to solve cross-border payments service solutions. Finally, we analyze the opportunities and challenges of Xi\u27an city facing e-commerce cross-border payment, and proposes solutions