Chang‐Kyu Hwang  Jong Min Kim  Sehoon Hwang  Joo‐Hyung Kim  Chang Hyun Sung  Byung‐Moo Moon  Keun Hwa Chae  Jitendra Pal Singh  Seung‐Hoon Kim  Seung Soon Jang  Seung Woo Lee  Hyung Chul Ham  Seunghee Han  Jin Young Kim 《Advanced Materials Interfaces》2020,7(2)

The exploitation of state‐of‐the‐art Pt/C electrocatalysts for polymer electrolyte membrane fuel cells (PEMFCs) is mostly limited, due to high Pt loading and durability issues caused by electrochemical instability of the carbon support in high potential regimes. In this study, the authors report that high‐compressive 3D Pt nanostructured thin films can considerably increase the catalytic activity and electrochemical durability of electrocatalysts under PEMFC device operating conditions. The nanostructure fabrication relies on the dealloying or selective leaching of solid alloys of Pt–C binary film to produce a residual 3D nanoporous thin‐film structure. A very rich structural behavior from the dealloying is shown, in which stress relief plays a governing role; the films possess a 3D structure of randomly interpenetrating ligaments and hierarchical pores with sizes between less than 50 nm and several tens of micrometers. In addition, a significant change is observed in the average lattice constant (1.55% compressive strain), which can tune the structural and electronic states of catalytic sites for enhancing the activity of the Pt electrocatalysts. Electrochemical performance of the fabricated porous strained Pt thin‐film electrocatalysts in both half‐cell and single‐cell analyses has demonstrated activity and durability superior to benchmark carbon support Pt catalysts.  相似文献   

    

Dahee Jin  Joonam Park  Myung‐Hyun Ryou  Yong Min Lee 《Advanced Materials Interfaces》2020,7(8)

Li dendrite formation deteriorates cyclability and poses a safety hazard, hindering the widespread use of Li metal as the ultimate anode material for post‐Li‐ion batteries. Hence, the underlying reasons of this phenomenon and ways to suppress it have been extensively investigated, which has resulted in the establishment of corresponding theoretical models and their practical applications. Herein, several representative models (e.g., the Chazalviel model) of Li dendrite growth are explained, and the key technologies of structure‐controlled framework and Li metal usage allowing to realize low local current densities and improved electrochemical performance are covered with the practical (dis)advantages due to material characteristics, electrode and cell design, and even manufacturing processes. In particular, the use of Li metal powder and patterned Li metal is discussed in conjunction with corresponding applications (e.g., protection layers, functional additives, and salts in the electrolyte) and advantages.  相似文献   

    

Ji‐Hyun Oh  Chung Hee Park 《Advanced Materials Interfaces》2020,7(10)

Superhydrophobic fabrics suffer from issues, such as poor breathability, surface color and handle changes, and toxicity because of additional chemical coating. Therefore, to resolve these issues, colorful fluorine‐free superhydrophobic polyester fabrics are prepared by controlling the conditions of a conventional disperse dyeing process. Alkaline hydrolysis, a pretreatment process in the dyeing process, is modified to create nanocraters on the surface of microrough polyester fabric. Then, the hydrolyzed polyester fabric is dyed with two different dyestuffs accompanied by thermal aging to lower the surface energy. The developed polyester fabrics become superhydrophobic and show the static contact angles over 160° and the shedding angles below 10°. Furthermore, the superhydrophobic polyester fabric exhibits improved color fastness as well as water vapor transmission rate and air permeability, while the handle properties of the alkaline‐hydrolyzed polyester fabric remain unchanged after dyeing and thermal aging. Finally, the self‐cleaning ability of the developed fabric is demonstrated by perfectly removing silicon carbide particles from its surface. Therefore, the developed fluorine‐free and superhydrophobic polyester fabric not only has color but also is nontoxic and environmentally friendly and can be readily recycled as it has no coated chemical to be removed. Thus, it has great potential for practical applications.  相似文献   

    

Ye Jin Park  Hye Min Seo  Jin Yong Lee  Kyounghee Shin  Jin Woong Kim 《Advanced Materials Interfaces》2020,7(15)

Herein, a temperature‐responsive nanoemulsion film (NEF) system is introduced with spinodal decomposition for in situ thermoset curing. The NEFs, fabricated by alternate layering of nanoemulsion droplets with bacterial cellulose nanofibrils (BCFs) and polyelectrolytes through the layer‐by‐layer (LbL) deposition, show ≈32% increase in Young's modulus compared with those fabricated with polyelectrolytes only. It is determined that such reinforcement stemmed from the presence of BCFs that form fibrillary layers in the NEF matrix. The BCF‐reinforced NEFs show the unprecedented spinodal decomposition behavior; nanoemulsion droplets uniformly dispersed in the NEF network and readily interdiffused to produce microscale oil domains with controlled phase separation rate as well as oil domain size. The insight gained from the thin film‐based microphase separation behavior confirms that NEFs layered with epoxy resin nanoemulsions are materials with promising temperature‐responsive in situ thermoset curing performance.  相似文献   

    

Tedrick Thomas Salim Lew  Volodymyr B. Koman  Pavlo Gordiichuk  Minkyung Park  Michael S. Strano 《Advanced Materials Technologies》2020,5(3)

Plants are naturally abundant and display high sensitivity to ecological factors to thrive in diverse environmental conditions. As sessile organisms, they have evolved complex, internal, and interplant signaling pathways with distinct structures to promptly adjust to the constantly changing environment. In the past five years, the unique ways in which they exchange information with and function in the environment have inspired an emerging field of plant nanobionics, which describes the interface between living plants and nanotechnology to impart the former with novel and useful functions. The structural merits of plant organs and organelles have also inspired the creation of plant‐derived structures through biointerfacing with nanoparticles containing electronic and optical properties. Here, the emerging applications and vision of plant nanobionics are highlighted together with related plant‐inspired materials in potentially replacing the myriad devices in the everyday lives stamped out of plastic, containing circuit boards and consuming power from the electrical grid. Applications in environmental sensing, communication devices, and energy harvesting and conversion are comprehensively discussed.  相似文献   

    

Chun Su Park  Chester J. Van Tyne  Seok-Jae Lee  Taekyung Lee  Ji Hoon Kim  Young Hoon Moon 《国际钢铁研究》2020,91(1)

  相似文献   

  总被引：1，自引：0，他引：1  

Jaechan Lim  Hun‐Seok Kim  Hyung‐Min Park 《国际强度与非线性控制杂志
》2020,30(2):636-651

In this paper, we propose a new framework of particle filtering that adopts the minimax strategy. In the approach, we minimize a maximized risk, and the process of the risk maximization is reflected when computing the weights of particles. This scheme results in the significantly reduced variance of the weights of particles that enables the robustness against the degeneracy problem, and we can obtain improved quality of particles. The proposed approach is robust against environmentally adverse scenarios, particularly when the state of a target is highly maneuvering. Furthermore, we can reduce the computational complexity by avoiding the computation of a complex joint probability density function. We investigate the new method by comparing its performance to that of standard particle filtering and verify its effectiveness through experiments. The employed strategy can be adopted for any other variants of particle filtering to enhance tracking performance.  相似文献   

    

Jun Chen  Ju H. Park  Shengyuan Xu  Xian‐Ming Zhang 《国际强度与非线性控制杂志
》2020,30(12):4779-4788

This article is concerned with the problem of stability analysis of discrete‐time systems with time‐varying delay. Unlike previous articles concentrating on the improvement of summation inequalities, this article constructs a novel augmented Lyapunov‐Krasovskii (L‐K) functional by fully considering the coupling information among state‐related vectors. Based on the newly developed L‐K functional, a more relaxed stability criterion is derived by exploring the interest of existing inequalities. Three numerical examples are given to demonstrate the effectiveness of the proposed method.  相似文献   

    

Jungyoon Kim  Jangwoon Park  Jaehyun Park 《人机工程学与制造业中的人性因素》2020,30(5):321-328

Many studies have demonstrated the strong relationships between physiological responses and driving stress, but they have done little to build a model that could be used to identify a driver's stress accurately in real time. The objective of this study is to develop a model that accurately classifies driving stress by monitoring physiological responses—specifically galvanic skin response (GSR). GSR data were collected from nine drivers with licenses obtained in the US in real road driving situations with two stress conditions—rest period (low stress) and highway or city driving (high stress). The validation drive was performed by one driver with licenses obtained in South Korea in real long‐term road driving situations with two stress conditions—rural area (low stress) and highway or highway under construction (high stress). Those two conditions were used to build a binary logistic regression model to classify low stress or high stress based on a driver's measured hand GSR. The overall classification accuracy of the developed model was found to be 85.3%, and the accuracy of cross validation, with a testing dataset, was found to be 83.2%. A simple logit model was developed to identify drivers' stress by incorporating their GSR data. The developed model can be embedded in a wearable device equipped with GSR sensors for drivers to detect their stress level in real time.  相似文献   

    

Laxmikant Minz  Seong‐Ook Park 《国际射频与微波计算机辅助工程杂志》2020,30(6)

Wireless power transfer has been the field of research for many decades, and with technological advancement and increase in wireless mobile devices, the future of wireless power transfer technology is very promising. The major requirement of wireless power transfer is an efficient and compact antenna array with high gain and flawless scanning performance. In this article, a 4 × 8 element array is proposed with a gain of 18 dB and scanning capability of ±45^° in azimuth and elevation plane at 5.8 GHz. The overall size of the array is 100 mm × 200 mm. The element separation in the array is only 0.48 λ. There was strong mutual coupling due to smaller separation, which has been minimized with the application of via‐fence around the antenna element. A dual feed circularly polarized annular slot‐ring antenna is proposed and analyzed with via‐fence to develop an array of 4 × 8 elements. The antenna array reflection coefficient obtained is less than 20 dB for different scan angles and the gain of the array obtained is also within 2 dB for ±45^° scan angles.  相似文献