On the Effectiveness of Log Representation for Log-based Anomaly Detection

Logs are an essential source of information for people to understand the running status of a software system. Due to the evolving modern software architecture and maintenance methods, more research efforts have been devoted to automated log analysis. In particular, machine learning (ML) has been widely used in log analysis tasks. In ML-based log analysis tasks, converting textual log data into numerical feature vectors is a critical and indispensable step. However, the impact of using different log representation techniques on the performance of the downstream models is not clear, which limits researchers and practitioners' opportunities of choosing the optimal log representation techniques in their automated log analysis workflows. Therefore, this work investigates and compares the commonly adopted log representation techniques from previous log analysis research. Particularly, we select six log representation techniques and evaluate them with seven ML models and four public log datasets (i.e., HDFS, BGL, Spirit and Thunderbird) in the context of log-based anomaly detection. We also examine the impacts of the log parsing process and the different feature aggregation approaches when they are employed with log representation techniques. From the experiments, we provide some heuristic guidelines for future researchers and developers to follow when designing an automated log analysis workflow. We believe our comprehensive comparison of log representation techniques can help researchers and practitioners better understand the characteristics of different log representation techniques and provide them with guidance for selecting the most suitable ones for their ML-based log analysis workflow.Comment: Accepted by Journal of Empirical Software Engineering (EMSE

Self-doping effect in confined copper selenide semiconducting quantum dots for efficient photoelectrocatalytic oxygen evolution

Self-doping can not only suppress the photogenerated charge recombination of semiconducting quantum dots by self-introducing trapping states within the bandgap, but also provide high-density catalytic active sites as the consequence of abundant non-saturated bonds associated with the defects. Here, we successfully prepared semiconducting copper selenide (CuSe) confined quantum dots with abundant vacancies and systematically investigated their photoelectrochemical characteristics. Photoluminescence characterizations reveal that the presence of vacancies reduces the emission intensity dramatically, indicating a low recombination rate of photogenerated charge carriers due to the self-introduced trapping states within the bandgap. In addition, the ultra-low charge transfer resistance measured by electrochemical impedance spectroscopy implies the efficient charge transfer of CuSe semiconducting quantum dots-based photoelectrocatalysts, which is guaranteed by the high conductivity of their confined structure as revealed by room-temperature electrical transport measurements. Such high conductivity and low photogenerated charge carriers recombination rate, combined with high-density active sites and confined structure, guaranteeing the remarkable photoelectrocatalytic performance and stability as manifested by photoelectrocatalysis characterizations. This work promotes the development of semiconducting quantum dots-based photoelectrocatalysis and demonstrates CuSe semiconducting quantum confined catalysts as an advanced photoelectrocatalysts for oxygen evolution reaction

Cluster-Like Headache Secondary to Anamnesis of Sphenoid Ridge Meningioma: A Case Report and Literature Review

Cluster headache is generally considered to be a primary headache; secondary cluster-like headache is quite rare, while cluster-like headache secondary to meningioma is even rarer. Here, we describe an unusual case with cluster-like headache 2.5 years after sphenoid ridge meningioma surgery. The cluster-like headache and meningioma were on the same side, and even at the same position. Furthermore, the cluster-like headache lasted for 6 months. In addition, the patient did not respond well to conventional treatments for cluster headache, such as oxygen inhalation, carbamazepine, and tramadol. Brain magnetic resonance imaging demonstrated a softening lesion, glial hyperplasia, and localized thickening and enhancement of the dura in the left frontal-temporal lobe. However, positron-emission computed tomography showed reduced metabolism in the left frontal-temporal lobe. Although the possibility of a primary headache cannot be completely eliminated, the association between cluster-like headache and probable tumor recurrence or postoperative changes should be considered

Genome-wide analysis of WRKY gene family in Cucumis sativus

<p>Abstract</p> <p>Background</p> <p>WRKY proteins are a large family of transcriptional regulators in higher plant. They are involved in many biological processes, such as plant development, metabolism, and responses to biotic and abiotic stresses. Prior to the present study, only one full-length cucumber WRKY protein had been reported. The recent publication of the draft genome sequence of cucumber allowed us to conduct a genome-wide search for cucumber WRKY proteins, and to compare these positively identified proteins with their homologs in model plants, such as <it>Arabidopsis</it>.</p> <p>Results</p> <p>We identified a total of 55 WRKY genes in the cucumber genome. According to structural features of their encoded proteins, the cucumber WRKY (<it>CsWRKY</it>) genes were classified into three groups (group 1-3). Analysis of expression profiles of <it>CsWRKY </it>genes indicated that 48 WRKY genes display differential expression either in their transcript abundance or in their expression patterns under normal growth conditions, and 23 WRKY genes were differentially expressed in response to at least one abiotic stresses (cold, drought or salinity). The expression profile of stress-inducible <it>CsWRKY </it>genes were correlated with those of their putative <it>Arabidopsis WRKY (AtWRKY) </it>orthologs, except for the group 3 WRKY genes. Interestingly, duplicated group 3 <it>AtWRKY </it>genes appear to have been under positive selection pressure during evolution. In contrast, there was no evidence of recent gene duplication or positive selection pressure among <it>CsWRKY </it>group 3 genes, which may have led to the expressional divergence of group 3 orthologs.</p> <p>Conclusions</p> <p>Fifty-five WRKY genes were identified in cucumber and the structure of their encoded proteins, their expression, and their evolution were examined. Considering that there has been extensive expansion of group 3 WRKY genes in angiosperms, the occurrence of different evolutionary events could explain the functional divergence of these genes.</p

Effect of annealing process on the surface roughness in multiple Al implanted4H-SiC

A P-layer can be formed on a SiC wafer surface by using multiple Al ion implantations and post-implantation annealing in a low pressure CVD reactor. The Al depth profile was almost box shaped with a height of1×1019cm-3 and a depth of550 nm. Three different annealing processes were developed to protect the wafer surface. Variations in RMS roughness have been measured and compared with each other. The implanted SiC, annealed with a carbon cap, maintains a high-quality surface with an RMS roughness as low as3.8 nm. Macrosteps and terraces were found in the SiC surface, which annealed by the other two processes(protect in Ar/protect with SiC capped wafer in Ar). The RMS roughness is12.2 nm and6.6 nm, respectively.?2011 Chinese Institute of Electronics

High-quality homoepitaxial layers grown on4H-SiC at a high growth rate by vertical LPCVD

High quality, homoepitaxial layers of4H-SiC were grown on off-oriented4H-SiC(0001) Si planes in a vertical low-pressure hot-wall CVD system(LPCVD) by using trichlorosilane(TCS) as a silicon precursor source together with ethylene(C2H4) as a carbon precursor source. The growth rate of25-30μm/h has been achieved at lower temperatures between1500 and1530°C. The surface roughness and crystalline quality of50μm thick epitaxial layers(grown for2 h) did not deteriorate compared with the corresponding results of thinner layers(grown for30 min). The background doping concentration was reduced to2.13×1015× cm-3. The effect of the C/Si ratio in the gas phase on growth rate and quality of the epi-layers was investigated.?2011 Chinese Institute of Electronics