溶体化処理された面心立方構造を有するNi-Cr合金における水素脆化抵抗の支配因子

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溶体化処理された面心立方構造を有するNi-Cr合金における水素脆化抵抗の支配因子

Tohoku University博士（工学）要約のみthesi

Finding the Missing Link between Corporate Social Responsibility and Firm Competitiveness through Social Capital: A Business Ecosystem Perspective

There are existing studies that successfully show the impact of corporate social responsibility (CSR) on firms’ financial performance. However, limited attention is paid to its impact on the business ecosystem. CSR could be seen as an investment for building a sustainable business ecosystem, which enhances the competitiveness of this system’s members. In that context, this study apprehends and captures the virtuous cycle of firm competitiveness. On analyzing data from interviews with seven firms, the study offers four propositions identifying the structure of the virtuous cycle linking CSR activities to firm competitiveness through the accumulation of social capital within business ecosystems. Based on those propositions, the study offers new insights into CSR research for academics and strategic planning guidelines for managers that integrate social and economic values for a sustainable business ecosystem and firm competitiveness

Active Contour Models

Active contour models have been widely applied to image segmentation and analysis. It has been successfully used in contour detection for object recognition, computer vision, computer graphics, and biomedical image processing such as X-ray, MRI and Ultrasound images. The energy-minimizing active contour models or snakes were developed by Kass, Witkin and Terzopoulos in 1987. Snakes are curves defined in the image domain that can move under the influence of internal forces within the curve itself and external forces derived from the image data. Snakes perform well on certain types of images (such as well-defined, convex shapes). There have been several improvements proposed to the original snake or active contour model. These improvements include balloon snakes, adaptive snakes, and GVF snakes. In this project, I reviewed and implemented their algorithms as well as the original snake model. GCBAC (Graph Cut Based Active Contour) is one of alternative solutions to the object extraction problem. Although the GCBAC belongs to family of active contour models, it differs fundamentally from original active contours. In this project, I also review and implement the GCBAC algorithm as well

Understanding co-speech gestures in-the-wild

Co-speech gestures play a vital role in non-verbal communication. In this paper, we introduce a new framework for co-speech gesture understanding in the wild. Specifically, we propose three new tasks and benchmarks to evaluate a model’s capability to comprehend gesture-speech-text associations: (i) gesture based retrieval, (ii) gesture word spotting, and (iii) active speaker detection using gestures. We present a new approach that learns a tri-modal video-gesture-speech-text representation to solve these tasks. By leveraging a combination of global phrase contrastive loss and local gesture-word coupling loss, we demonstrate that a strong gesture representation can be learned in a weakly supervised manner from videos in the wild. Our learned representations outperform previous methods, including large vision-language models (VLMs). Further analysis reveals that speech and text modalities capture distinct gesture related signals, underscoring the advantages of learning a shared tri-modal embedding space

Experimental Study: Enhancing Voice Spoofing Detection Models with wav2vec 2.0

Conventional spoofing detection systems have heavily relied on the use of handcrafted features derived from speech data. However, a notable shift has recently emerged towards the direct utilization of raw speech waveforms, as demonstrated by methods like SincNet filters. This shift underscores the demand for more sophisticated audio sample features. Moreover, the success of deep learning models, particularly those utilizing large pretrained wav2vec 2.0 as a featurization front-end, highlights the importance of refined feature encoders. In response, this research assessed the representational capability of wav2vec 2.0 as an audio feature extractor, modifying the size of its pretrained Transformer layers through two key adjustments: (1) selecting a subset of layers starting from the leftmost one and (2) fine-tuning a portion of the selected layers from the rightmost one. We complemented this analysis with five spoofing detection back-end models, with a primary focus on AASIST, enabling us to pinpoint the optimal configuration for the selection and fine-tuning process. In contrast to conventional handcrafted features, our investigation identified several spoofing detection systems that achieve state-of-the-art performance in the ASVspoof 2019 LA dataset. This comprehensive exploration offers valuable insights into feature selection strategies, advancing the field of spoofing detection.Comment: 5 page

강체와 열탄성적 접촉하에 있는 사각블럭의 불안정성에 대한 유한요소해석

두 물체의 접촉면 사이의 정상상태의 열전달은 열변형을 일으키고 그결과 나타나는 접촉압력의 변화는 열접촉저항 및 열전달을 변화시켜 전체 시스템을 불안정하게 할 수 있다. 섭동법에 의한 이론적 해석방법은 단순한 시스템에 대하여는 가능하지만 유한한 길이의 기하학적 형상을 가진 시스템에 대하여는 매우 어려워진다. 본논문에서는 강체와 열탄성적 접촉을 하고있는 사각블럭의 안정성을 판정하기위해 시간에 따라 지수적으로 변화하는 변수분리 형태의 섭동을 가정하여 지배방정식들을 유한요소식화 하였다. 그 결과 지수증가율에 대한 선형 고유치 문제를 얻을 수 있으며, 시스템은 모든 고유치가 음의 실수부를 가질때 안정하다. 수치적인 해석결과를 강체인 벽과 열탄성적인 접촉을 하고 있는 스트립의 이론적 해석결과와 비교하여 제안한 유한요소법의 타당성을 보였다.The steady-state conduction of heat across an interface between two contacting bodies can become unstable as a result of the interaction between thermoelastic distortion and a pressure-dependent thermal contact resistance. Analytical solutions for the stability boundary have been obtained for simple systems using perturbation methods, but become prohibitively complex for finite geometries. This paper presents a finite element formulation of the perturbation method, in which the linearity of the governing equations is exploited to obtain separated-variable solutions for the perturbation with exponential variation in time. The problem is thus reduced to a linear eigenvalue problem with the exponential growth rate appearing as the eigenvalue. Stability of the system requires that all eigenvalues have negative real part. The method is tested against an analytical solution of the two-dimensional problem of a strip in contact with a rigid wall. Excellent results are obtained for the stability boundary even with a relatively coarse discretization.The steady-state conduction of heat across an interface between two contacting bodies can become unstable as a result of the interaction between thermoelastic distortion and a pressure-dependent thermal contact resistance. Analytical solutions for the stability boundary have been obtained for simple systems using perturbation methods, but become prohibitively complex for finite geometries. This paper presents a finite element formulation of the perturbation method, in which the linearity of the governing equations is exploited to obtain separated-variable solutions for the perturbation with exponential variation in time. The problem is thus reduced to a linear eigenvalue problem with the exponential growth rate appearing as the eigenvalue. Stability of the system requires that all eigenvalues have negative real part. The method is tested against an analytical solution of the two-dimensional problem of a strip in contact with a rigid wall. Excellent results are obtained for the stability boundary even with a relatively coarse discretization

Thermoelastic contact stability: Analytical and numerical methods.

When heat is conducted across an interface between two dissimilar materials, thermoelastic distortion affects the contact pressure distribution. The existence of a pressure-sensitive thermal contact resistance at the interface can cause such systems to be unstable in the steady-state. Stability analysis for thermoelastic contact has been previously conducted for one-dimensional and simple two-dimensional geometries. However, nothing is known for the two-dimensional systems with finite geometry. This thesis extends the scope of stability analysis to more complex thermoelastic contact systems of finite geometry by a linear perturbation method. Thermoelastic stability is investigated analytically for a layer on the half-plane, which has a finite dimension normal to the contact plane. It is found that, unlike the two contacting half-planes, the stability criterion is not necessarily determined by the perturbational temperature with the largest wavelength. A simple system involving a finite contact area is the semi-infinite strip contacting a rigid wall, for which the stability analysis is done analytically using a series representation of the solution. Due to the symmetry of the problem, the perturbation can be classified into symmetric and anti-symmetric modes, the stability boundary being determined by the first symmetric mode. The complexity of the problem, especially when an analytical method is adopted, motivates the development of a finite element method to reduce the stability problem to a linear algebraic eigenvalue problem. This method is tested against the one-dimensional system of two contacting rods, for which an analytical stability analysis is available. The numerical method is extended to a two-dimensional problem of a rectangular block in thermoelastic contact with a rigid wall, which is a typical problem with finite geometry. As the ratio of the dimension of the body normal to the contact surface to the contact dimension becomes small, the perturbation mode which determines the stability boundary becomes more wavy at the contact boundary and the stability boundary increases monotonically.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103519/1/9319664.pdfDescription of 9319664.pdf : Restricted to UM users only