Comparing Code Similarity Using Information Retrieval Techniques and Deep Learning

コード片の類似性判定法はソフトウェア工学における重要な基礎技術であり，コードクローン検出やコード片検索などで使用される．コード片の類似性判定法では，構文的な類似性だけでなく，処理内容の意味的な類似性も判定することが重要である．我々の先行研究では，情報検索技術に基づくベクトル表現とコサイン類似度を組み合わせた類似性判定法を用いていた．この手法は処理内容の意味的な類似性を高速に判定できる一方で，検出漏れが多い課題がある．また近年，深層学習を用いた類似性判定法が提案されている．この手法は意味的な類似性を高い精度で判定できる反面，実行速度が遅い課題がある．そこで本研究では，判定精度と実行速度の二つの観点で情報検索技術に基づくベクトル表現と深層学習の効果的な組み合わせを調査する．調査の結果，情報検索技術の一種であるLSI (Latent Semantic Indexing)と深層学習モデルの組み合わせが判定精度の面で最も高い値となった．またこの組み合わせは実行速度が最も速いことも確認した．横井, 一輝, 崔, 恩瀞, 吉田, 則裕, et al. 情報検索技術と深層学習を用いたコード片類似性判定法の比較調査. 電子情報通信学会論文誌D 情報・システム J106-D, 231 (2023); https://doi.org/10.14923/transinfj.2022pdp0009

Electrode montage for transcranial direct current stimulation governs its effect on symptoms and functionality in schizophrenia

BackgroundsPatients with schizophrenia suffer from cognitive impairment that worsens real-world functional outcomes. We previously reported that multi-session transcranial direct current stimulation (tDCS) delivered to the left dorsolateral prefrontal cortex (DLPFC) improved daily living skills, while stimulation on the left superior temporal sulcus (STS) enhanced performance on a test of social cognition in these patients. To examine the region-dependent influence of tDCS on daily-living skills, neurocognition, and psychotic symptoms, this study compared effects of anodal stimulation targeting either of these two brain areas in patients with schizophrenia.MethodsData were collected from open-label, single-arm trials with anodal electrodes placed over the left DLPFC (N = 28) or STS (N = 15). Daily-living skills, neurocognition, and psychotic symptoms were measured with the UCSD performance-based skills assessment-brief (UPSA-B), Brief Assessment of Cognition in Schizophrenia (BACS), and Positive and Negative Syndrome Scale (PANSS), respectively. After baseline evaluation, tDCS (2 mA × 20 min) were delivered two times per day for 5 consecutive days. One month after the final stimulation, clinical assessments were repeated.ResultsPerformance on the UPSA-B was significantly improved in patients who received anodal tDCS at the left DLPFC (d = 0.70, p < 0.001), while this effect was absent in patients with anodal electrodes placed on the left STS (d = 0.02, p = 0.939). Significant improvement was also observed for scores on the BACS with anodal tDCS delivered to the DLPFC (d = 0.49, p < 0.001); however, such neurocognitive enhancement was absent when the STS was stimulated (d = 0.05, p = 0.646). Both methods of anodal stimulation showed a significant improvement of General Psychopathology scores on the PANSS (DLPFC, d = 0.50, p = 0.027; STS, d = 0.44, p = 0.001).ConclusionThese results indicate the importance of selecting brain regions as a target for tDCS according to clinical features of individual patients. Anodal stimulation of the left DLPFC may be advantageous in improving higher level functional outcomes in patients with schizophrenia.Trial registrationThese studies were registered within the University hospital Medical Information Network Clinical Trials Registry [(24), UMIN000015953], and the Japan Registry of Clinical Trials [(28), jRCTs032180026]

Design Analysis of a Novel Synchronous Generator for Wind Power Generation

A novel synchronous generator is proposed for wind power generation. The field flux is generated by the half-wave rectified excitation method. The generator does not require slip rings and brushes for field power supply, as well as permanent magnets. In this paper, the excitation method is explained, and then, the basic characteristics are calculated using the finite element method analysis. Furthermore, the generator is designed for increasing the output power and efficiency

Quantification of Large Deformation with Punching in Dual Phase Steel and Change of its Microstructure : Part I: Proposal of the Quantification Technique of the Punching Damage of the Dual Phase Steel

Dual Phase (DP) steel is used in automotive body parts for weight saving and crashworthiness, however there is an issue of DP steel in low stretch flange ability evaluated by hole expanding tests. In order to improve stretch flange ability of DP steel, it is important to estimate the damage of punching quantitatively and to clarify the change of microstructure before and after punching because the hole expansion ratio is decided in the ductility remained after pre-strain equivalent to punching. Therefore we tried to measure the damage of punching by unique techniques of Electron Backscatter Diffraction (EBSD), nano-indentation and micro-tensile testing and to observe fracture surface by Scanning Transmission Electron Microscope (STEM). Average EBSD-Kernel Average Misorientation (KAM) value and pre-strain damage have strong correlation, thus average KAM value can become the index of the damage. The nanohardness and tensile strength using micrometer-sized specimens increased with increasing average KAM value in the ferritic phase as approaching the punching edge. A shear type fracture occurred without necking in the specimen cut out in the area of the edge. The ultrafine-grained ferritic microstructure was observed in the sample cut out in the same area with STEM. It seems that the ductility loss of the punched DP steel was probably attributed to localized strain into the ultrafine-grained ferritic microstructure

情報検索技術と深層学習を用いたコード片類似性判定法の比較調査

横井, 一輝, 崔, 恩瀞, 吉田, 則裕, et al. 情報検索技術と深層学習を用いたコード片類似性判定法の比較調査. 電子情報通信学会論文誌D 情報・システム J106-D, 231 (2023); https://doi.org/10.14923/transinfj.2022pdp0009.コード片の類似性判定法はソフトウェア工学における重要な基礎技術であり，コードクローン検出やコード片検索などで使用される．コード片の類似性判定法では，構文的な類似性だけでなく，処理内容の意味的な類似性も判定することが重要である．我々の先行研究では，情報検索技術に基づくベクトル表現とコサイン類似度を組み合わせた類似性判定法を用いていた．この手法は処理内容の意味的な類似性を高速に判定できる一方で，検出漏れが多い課題がある．また近年，深層学習を用いた類似性判定法が提案されている．この手法は意味的な類似性を高い精度で判定できる反面，実行速度が遅い課題がある．そこで本研究では，判定精度と実行速度の二つの観点で情報検索技術に基づくベクトル表現と深層学習の効果的な組み合わせを調査する．調査の結果，情報検索技術の一種であるLSI (Latent Semantic Indexing)と深層学習モデルの組み合わせが判定精度の面で最も高い値となった．またこの組み合わせは実行速度が最も速いことも確認した