快速关联规则挖掘算法

关联规则挖掘是数据挖掘及知识发现领域的重要研究内容之一,其核心任务是挖掘数据库中的频繁项集。Apriori及其改良算法是频繁项集挖掘的有效算法。在类Apriori的算法中,它们都采用哈希树来存储频繁项集的候补项集以便快速计算其支持度。该文在仔细分析这些算法所存在的效率瓶颈的基础上,提出了另一个有效的改进算法。所提算法通过利用一个一维数组替代已有算法中的复杂的哈希树来达到改善它们效率瓶颈的目的。通过多个实验评估,该文所提算法的挖掘效率很高,比Apriori及其改良算法要快2到5倍。     

Drawing slicing graphs with face areas

We consider orthogonal drawings of a plane graph G$G$ with specified face areas. For a natural number k$k$, a k$k$-gonal drawing of G$G$ is an orthogonal drawing such that the boundary of G$G$ is drawn as a rectangle and each inner face is drawn as a polygon with at most k$k$ corners whose area is equal to the specified value. In this paper, we show that every slicing graph G$G$ with a slicing tree T$T$ and a set of specified face areas admits a 10-gonal drawing D$D$ such that the boundary of each slicing subgraph that appears in T$T$ is also drawn as a polygon with at most 10 corners. Such a drawing D$D$ can be found in linear time.     

Automated Verification of Functional Correctness of Race-Free GPU Programs

We study an automated verification method for functional correctness of parallel programs running on graphics processing units (GPUs). Our method is based on Kojima and Igarashi’s Hoare logic for GPU programs. Our algorithm generates verification conditions (VCs) from a program annotated by specifications and loop invariants, and passes them to off-the-shelf SMT solvers. It is often impossible, however, to solve naively generated VCs in reasonable time. A main difficulty stems from quantifiers over threads due to the parallel nature of GPU programs. To overcome this difficulty, we additionally apply several transformations to simplify VCs before calling SMT solvers. Our implementation successfully verifies correctness of several GPU programs, including matrix multiplication optimized by using shared memory. In contrast to many existing verification tools for GPU programs, our verifier succeeds in verifying fully parameterized programs: parameters such as the number of threads and the sizes of matrices are all symbolic. We empirically confirm that our simplification heuristics is highly effective for improving efficiency of the verification procedure.     

Alcohol electrooxidation at Pt‐Ru sputter‐deposited electrode

The use of various alcohols including methanol has been considered as the fuel of direct alcohol fuel cells (DAFCs). Thus far, the Pt alloys have mainly been studied as anode electrocatalysts for DAFCs. Pt itself is poisoned by chemical species produced during the alcohol oxidation. There exist many reports that the addition of Ru is effective for alcohol oxidation. In this work, we prepared a Pt‐Ru co‐sputtered electrode by changing the Ru content, sputtering time, and Ar pressure for the sputtering. By using the prepared electrocatalysts, relationships between sputtering conditions and electrocatalytic activity were measured for some alcohols. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(2): 14–21, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20594     

Identification of melanoma‐specific serological markers using proteomic analyses

The discovery of novel melanoma markers for not only early detection but also monitoring disease status is promising to improve the clinical outcome of patients. In the present study, we performed proteomic comparative analysis of plasma proteins between healthy volunteers and melanoma patients using NanoLC and MALDI‐TOF‐MS. As a result, we were successful in identifying nine proteins that were specifically expressed in melanoma plasma compared with healthy plasma, most of which had not previously been identified as plasma markers of melanoma. The mRNA expression levels of four proteins [pro‐platelet basic protein precursor (PPBP), serum amyloid A2 (SAA2), complement factor H‐related protein 1 precursor (FHR1), inter‐alpha‐trypsin inhibitor heavy chain H4 precursor (IAIH4)] were prominently up‐regulated in several melanoma cell lines compared with melanocytes. Moreover, two proteins (PPBP, SAA) were shown to be expressed in tumor specimens from melanoma patients. In the survival time analysis regarding melanoma patients, the semi‐quantified plasma PPBP levels were statistically negatively correlated with the survival time. Most interestingly, the significant survival benefit was seen in low PBPP level group (< index 20) versus high level (≥ index 20) group. The results suggest that PPBP might be a novel promising serological marker and a prognostic factor specific to melanomas.     

An adaptive and reliable system based on interdependence between agents

A multiagent system (MAS) has recently gained public attention as a technique to solve competition and cooperation in distributed systems. However, MAS's vulnerability due to the propagation of failures prevents its application to a large‐scale system. This paper proposes a general composition technique to improve its reliability easily applied to the existent MAS. The proposed system monitors messages between agents to detect undesirable behaviors (failures). Collecting related information, the system generates global information of interdependence between agents and expresses it in a graph. This interdependence graph enables us to detect or predict undesirable behaviors. This paper also shows that the system can optimize performance of MAS and improve adaptively its reliability under complicated and dynamic environment by applying the global information acquired from analysis of the interdependence graph to a replication system. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 62–68, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20517     

Thermal design of a closed cabinet with a heat exchanger for inner air cooling

This paper describes a thermal design and simulation method of a closed cabinet with a heat exchanger for inner air cooling. In the controller system that we used for this research, the cabinet is equipped to be outdoors, and the cabinet is sealed to prevent the introduction of dust. Because this system dissipated 630 W in total, it suffered from a problem that the inner air temperature of the cabinet was raised over 30 K. Thus, we installed a heat pipe and heat exchanger in the cabinet, and we also changed the air flow path to realize the best performance of heat exchange according to the results from thermal and fluid simulations using a macroscopic model of heat exchanger to reduce the computational load. We found that the inner air temperature rise was reduced below 15 K, and the measured results were in good agreement with the simulation. © 2001 Scripta Technica, Heat Trans Asian Res, 30(4): 267–279, 2001     

Removal of dilute benzene using a zeolite-hybrid plasma reactor

The decomposition of benzene was carried out using a plasma reactor packed with a mixture of BaTiO₃ and zeolite pellets, the zeolite-hybrid reactor. The reactor performance was characterized by measuring CO_x formed during plasma discharge and CO_x adsorbed on the solid surface, The decomposition efficiency of benzene in the hybrid reactor was 1.4-2.1× higher than that in a conventional plasma reactor packed with BaTiO₃ alone. Benzene existing outside a zeolite crystalline pore was found to decompose more easily than that inside a zeolite pore. In addition, the presence of zeolites suppressed the formation of NO_x     

Oxidation of carbon black over various Pt/MOx/SiC catalysts

Catalytic activities of various Pt/MO_x/SiC systems for carbon oxidation under simulated diesel exhaust gas were investigated in temperature-programmed reactions. When Pt/MO_x (MO_x=TiO₂, ZrO₂, Al₂O₃) was loaded onto silicon carbide (SiC), the oxidation activities became higher than those of Pt/MO_x alone or other Pt/MO_x/SiC systems (MO_x=Ta₂O₅, WO₃, Nb₂O₅, SnO₂, SiO₂, CeO₂, MoO₃, V₂O₅). Among them, Pt/TiO₂/SiC exhibited the highest activity. We discuss the activity of MO_x=TiO₂, ZrO₂, and Al₂O₃ in connection with NO oxidation activity, adsorption of sulfate onto the support, Pt dispersion, and specific surface area of the catalyst. Furthermore, we investigated the catalytic performance of Pt/TiO₂/SiC in more detail under isothermal conditions and in a staged arrangement.     

High sensitive detection of sulfuric compounds using electrochemical impedance

Attention has been focused recently on the harmful effects and malodor of sulfuric compounds; therefore, various laws have been enacted to regulate environmental concentration and use of most sulfuric compounds. In order to avoid sulfuric malodor, a reasonable, easy, sensitive, and selective measuring method to detect sulfuric compounds is required. In this research, we adopted the specific adsorption of sulfuric compounds to a metal surface as a sensing principle. It was suggested that polarization is an important factor of molecular recognition from results obtained by quartz crystal microbalance (QCM), ellipsometry, and stripping voltammetry (SV). Therefore, we used cyclic surface polarization impedance (cSPI), based on electrochemical impedance spectroscopy (EIS) under the dynamic control of an electrode potential and a constant phase element (CPE) impedance, as a detecting method for sulfuric compounds. As a result, we could detect three sulfuric compounds, hydrogen sulfide, methyl mercaptan, and dimethyl sulfide, with this method at sub ppb levels and discriminate the three sulfuric compounds. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.