Feasibility study to control fiber distribution for enhancement of composite properties via three-dimensional printing

The distribution of fibers in the composite (which takes into account both their locations and orientations) is one of the important factors that affect the mechanical properties of FRCs. However, this parameter depends on various factors during composite fabrication, and controlling the distribution of fibers in the produced material represents a significant challenge. In this study, the applicability of three-dimensional (3D) printing technique for controlling fiber distributions was evaluated. The fibers fabricated using a 3D printer were placed inside a mold to produce cementitious composites. Three-point bending tests were conducted and the results of the experiment were discussed.     

Enhanced Charge Injection Properties of Organic Field‐Effect Transistor by Molecular Implantation Doping

Organic semiconductors (OSCs) have been widely studied due to their merits such as mechanical flexibility, solution processability, and large‐area fabrication. However, OSC devices still have to overcome contact resistance issues for better performances. Because of the Schottky contact at the metal–OSC interfaces, a non‐ideal transfer curve feature often appears in the low‐drain voltage region. To improve the contact properties of OSCs, there have been several methods reported, including interface treatment by self‐assembled monolayers and introducing charge injection layers. Here, a selective contact doping of 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F₄‐TCNQ) by solid‐state diffusion in poly(2,5‐bis(3‐hexadecylthiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT) to enhance carrier injection in bottom‐gate PBTTT organic field‐effect transistors (OFETs) is demonstrated. Furthermore, the effect of post‐doping treatment on diffusion of F₄‐TCNQ molecules in order to improve the device stability is investigated. In addition, the application of the doping technique to the low‐voltage operation of PBTTT OFETs with high‐k gate dielectrics demonstrated a potential for designing scalable and low‐power organic devices by utilizing doping of conjugated polymers.     

Improvement of Ni-Cermet performance of protonic ceramic fuel cells by catalyst

Generally, the NiO composite anode becomes porous after reduction. To infiltrate additional catalysts such as Pd into the NiO-composite anode before reducing NiO to Ni, a porous NiO composite anode for protonic ceramic fuel cells (PCFCs) was fabricated in this study. The porous NiO composite was fabricated by adding graphite as a pore former along with CuO as a sintering agent. The addition of graphite increased the porosity of the NiO composite anode but resulted in poor sinterability, which was addressed by adding CuO as a sintering agent to the NiO composite anode. The Pd catalyst was added to the NiO-composite anode before reducing NiO to Ni. The composite anode for PCFC with three components, namely Ni, protonic ceramics, and a Pd catalyst, was obtained by reducing NiO to Ni during the measurement. The addition of the Pd catalyst improved the anode performance in methane fuel and hydrogen fuel by enhancing the catalytic activity for the electrochemical reaction on the surface.     

Hybrid Segmentation Scheme for Skin Features Extraction Using Dermoscopy Images

Objective and quantitative assessment of skin conditions is essential for cosmeceutical studies and research on skin aging and skin regeneration. Various handcraft-based image processing methods have been proposed to evaluate skin conditions objectively, but they have unavoidable disadvantages when used to analyze skin features accurately. This study proposes a hybrid segmentation scheme consisting of Deeplab v3+ with an Inception-ResNet-v2 backbone, LightGBM, and morphological processing (MP) to overcome the shortcomings of handcraft-based approaches. First, we apply Deeplab v3+ with an Inception-ResNet-v2 backbone for pixel segmentation of skin wrinkles and cells. Then, LightGBM and MP are used to enhance the pixel segmentation quality. Finally, we determine several skin features based on the results of wrinkle and cell segmentation. Our proposed segmentation scheme achieved a mean accuracy of 0.854, mean of intersection over union of 0.749, and mean boundary F1 score of 0.852, which achieved 1.1%, 6.7%, and 14.8% improvement over the panoptic-based semantic segmentation method, respectively.     

Hydroelastic vibration of the bottom plate of the cylindrical tank coupled with sloshing

Journal of Mechanical Science and Technology - This study is concerned with the hydroelastic vibration of the flexible bottom plate of a cylindrical tank coupled with sloshing. The cylindrical tank...     

Fretting cracking behavior of nub of last-stage blade for steam turbine

Journal of Mechanical Science and Technology - Nub-and-sleeve of last-stage blade for steam turbine is a part-span damper. The nub is vulnerable to fretting cracking since it is in contact with the...     

Assessment of two-parameter mixed models for large eddy simulations of transitional and turbulent flows

In the present study, improved two-parameter mixed models for large eddy simulations are proposed based on previous two-parameter mixed models of Salvetti and Banerjee [1] and Horiuti [2]. The subgrid-scale (SGS) stress in our models is decomposed into the modified Leonard stress, modified cross stress and modified SGS Reynolds stress terms. Although the modified Leonard stress term is explicitly calculated based on the scale-similarity, the modified cross stress term is built using an extension of the filtered Bardina model proposed by Horiuti [3] for better predictions of the interaction between resolved and unresolved scales (i.e., energy exchange). The modified SGS Reynolds stress is modeled by the dynamic Smagorinsky model or by a dynamic global model, leading to two unknown model coefficients for the modified cross stress and the modified SGS Reynolds stress terms. In order to demonstrate the reliability of the proposed SGS models, large eddy simulations of two types of flows (i.e., a fully developed turbulent channel flow and a transitional boundary layer flow) are performed. It is shown that the modified cross stress term makes an important contribution to the accurate predictions of such flows because the emergence of negative SGS dissipation (backward scatter) by the modified cross stress term decreases the excessive positive SGS dissipation (forward scatter). A direct comparison of the turbulent statistics with those from previous SGS models shows that the proposed SGS models result in better prediction performance both in transitional and turbulent flows.

     

A numerical study on an infinite linear elastic Bernoulli-Euler beam on a viscoelastic foundation subjected to harmonic line loads

Journal of Mechanical Science and Technology - This paper presents a numerical study on the low-amplitude responses of an infinite Bernoulli-Euler beam resting on a viscoelastic foundation...     

A resilient buffer allocation scheme in active queue management: a stochastic cooperative game theoretic approach

During the last decade, a plentiful number of active queue management schemes have been proposed, but their main objectives are simply allocating the buffer resource to all flows evenly, or protecting responsive flows from being degraded by unresponsive flows. However, the sending rates of the responsive flows can be determined diversely, and not all unresponsive flows have aggressively high sending rates. Furthermore, it is rational to reserve a portion of the buffer resource for certain privileged traffic. Grounded by these evidences, in this paper, we present a resilient active queue management algorithm, named Prior‐Core‐based Buffer Allocation considering diverse congestion control algorithms, fair‐unresponsive flows, and some privileged traffic. Our approach is based on stochastic cooperative game theory, where the payoffs yielded by cooperation are described by random variables, and the core is defined only over the distribution of these random payoffs; the core in this situation is called the prior‐core. As a result, it is shown that our buffer allocation, yielded by the prior‐core, achieves completely fair allocation for those flows whose requirement does not exceed the fair‐share regardless of the responsiveness, whereas aggressive flows are restricted according to availability of the buffer; all these are verified through ns‐2 simulation experiments. Copyright © 2014 John Wiley & Sons, Ltd.     

Distributed deep learning platform for pedestrian detection on IT convergence environment

The Journal of Supercomputing - IT technology and traditional industries have been combined recently, resulting in IT convergence technology in various fields. Through convergence with the...