Linear Tabulated Resolution Based on Prolog Control Strategy

Infinite loops and redundant computations are long recognized open problems in Prolog. Two ways have been explored to resolve these problems: loop checking and tabling. Loop checking can cut infinite loops, but it cannot be both sound and complete even for function-free logic programs. Tabling seems to be an effective way to resolve infinite loops and redundant computations. However, existing tabulated resolutions, such as OLDT-resolution, SLG- resolution, and Tabulated SLS-resolution, are non-linear because they rely on the solution-lookup mode in formulating tabling. The principal disadvantage of non-linear resolutions is that they cannot be implemented using a simple stack-based memory structure like that in Prolog. Moreover, some strictly sequential operators such as cuts may not be handled as easily as in Prolog. In this paper, we propose a hybrid method to resolve infinite loops and redundant computations. We combine the ideas of loop checking and tabling to establish a linear tabulated resolution called TP-resolution. TP-resolution has two distinctive features: (1) It makes linear tabulated derivations in the same way as Prolog except that infinite loops are broken and redundant computations are reduced. It handles cuts as effectively as Prolog. (2) It is sound and complete for positive logic programs with the bounded-term-size property. The underlying algorithm can be implemented by an extension to any existing Prolog abstract machines such as WAM or ATOAM.Comment: To appear as the first accepted paper in Theory and Practice of Logic Programming (http://www.cwi.nl/projects/alp/TPLP

A γ\gamma-ray Quasi-Periodic modulation in the Blazar PKS 0301−-243?

We report a nominally high-confidence $\gamma$-ray quasi-periodic modulation in the blazar PKS 0301$-$243. For this target, we analyze its \emph{Fermi}-LAT Pass 8 data covering from 2008 August to 2017 May. Two techniques, i.e., the maximum likelihood optimization and the exposure-weighted aperture photometry, are used to build the $\gamma$-ray light curves. Then both the Lomb-Scargle Periodogram and the Weighted Wavelet Z-transform are applied to the light curves to search for period signals. A quasi-periodicity with a period of $2.1\pm0.3$ yr appears at the significance level of $\sim5\sigma$, although it should be noted that this putative quasi-period variability is seen in a data set barely four times longer. We speculate that this $\gamma$-ray quasi-periodic modulation might be evidence of a binary supermassive black hole.Comment: 9 pages, 8 figures; Accepted for publication in Ap

compiling answer set programs into event-driven action rules

Artificial Intelligence Journal; Pacific Institute of the Mathematical Sciences (PIMS); Assocation of Logic Programming (ALP); Simon Fraser University; University of CalabriaThis paper presents a compilation scheme, called ASP2AR, for translating ASP into event-driven action rules. For an ASP program, the generated program maintains a partial answer set as a pair of sets of tuples (called IN and OUT) and propagates updates to these sets using action rules. To facilitate propagation, we encode each set as a finite-domain variable and treat additions of tuples into a set as events handled by action rules. Like GASP and ASPeRiX, ASP2AR requires no prior grounding of programs. The preliminary experimental results show that ASP2AR is an order of magnitude faster than GASP and is much faster than Clasp on benchmarks that require heavy grounding. © 2011 Springer-Verlag Berlin Heidelberg

Implementation of a Linear Tabling Mechanism

Delaying-based tabling mechanisms, such as the one adopted in XSB, are non-linear in the sense that the computation state of delayed calls has to be preserved. In this paper, we present the implementation of a linear tabling mechanism. The key idea is to let a call execute from the backtracking point of a former variant call if such a call exists. The linear tabling mechanism has the following advantages over non-linear ones: (1) it is relatively easy to implement; (2) it imposes no overhead on standard Prolog programs; and (3) the cut operator works as for standard Prolog programs and thus it is possible to use the cut operator to express negation-as-failure and conditionals in tabled programs. The weakness of the linear mechanism is the necessity of re-computation for computing x-points. However, we have found that re-computation can be avoided for a large portion of calls of directly-recursive tabled predicates. We have implemented the linear tabling mechanism in B-P..

Fabrication of Nano Capacitor and its Electrical Properties

用逐层组装法在阳极氧化铝模板的纳米孔内制备纳米电容器,其组成为电化学聚合PPy/电沉积TiO2多孔隔膜/化学聚合PPy.该纳米电容器显示了典型的电化学超电容性质,且具有良好的充放电性能.A step-by-step assembling method was developed for preparing nano capacitors using anodic aluminum oxide (AAO) membrane as templates. The nano capacitor consisted of three parts: electrochemically polymerized PPy electrode/ el ectrochemically precipitated porous TiO_(2) separator / chemically polymerized PPy electrode, and demonstrated the charge/discharge behavior as a typical electrochemical supercapacitor with good cyclic ability.作者联系地址：复旦大学化学系,复旦大学化学系,复旦大学化学系,复旦大学化学系 上海200433 ,上海200433 ,上海200433 ,上海200433Author's Address: Department of Chemistry, Fudan University, Shanghai 200433,Chin

The Effectiveness of National Expanded Program on Immunization With Hepatitis A Vaccines in the Chinese Mainland: Interrupted Time-Series Analysis

BackgroundThe high prevalence of hepatitis A delivered a blow to public health decades ago. The World Health Organization (WHO) set a goal to eliminate viral hepatitis including hepatitis A by 2030. In 2008, hepatitis A vaccines were integrated into the Expanded Program on Immunization (EPI) in China to alleviate the burden of hepatitis A, although the effectiveness of the EPI has not been well investigated. ObjectiveWe aimed to evaluate the intervention effect at both provincial and national levels on the incidence of hepatitis A in the Chinese mainland from 2005 to 2019. MethodsBased on the monthly reported number of hepatitis A cases from 2005 to 2019 in each provincial-level administrative division, we adopted generalized additive models with an interrupted time-series design to estimate province-specific effects of the EPI on the incidence of hepatitis A among the target population (children aged 2-9 years) from 2005 to 2019. We then pooled province-specific effect estimates using random-effects meta-analyses. We also assessed the effect among the nontarget population and the whole population. ResultsA total of 98,275 hepatitis A cases among children aged 2-9 years were reported in the Chinese mainland from 2005 to 2019, with an average annual incidence of 5.33 cases per 100,000 persons. Nationally, the EPI decreased the hepatitis A incidence by 80.77% (excess risk [ER] –80.77%, 95% CI –85.86% to –72.92%) during the study period, guarding an annual average of 28.52 (95% empirical CI [eCI] 27.37-29.00) cases per 100,000 persons among the target children against hepatitis A. Western China saw a more significant effect of the EPI on the decrease in the incidence of hepatitis A among the target children. A greater number of target children were protected from onset in Northwest and Southwest China, with an excess incidence rate of –129.72 (95% eCI –135.67 to –117.86) and –66.61 (95% eCI –67.63 to –64.22) cases per 100,000 persons on average, respectively. Intervention effects among nontarget (ER –32.88%, 95% CI –39.76% to –25.21%) and whole populations (ER –31.97%, 95% CI –39.61% to –23.37%) were relatively small. ConclusionsThe EPI has presented a lasting positive effect on the containment of hepatitis A in the target population in China. The EPI’s effect on the target children also provided a degree of indirect protection for unvaccinated individuals. The continuous surveillance of hepatitis A and the maintenance of mass vaccination should shore up the accomplishment in the decline of hepatitis A incidence to ultimately achieve the goal set by the WHO