• Progress in Superconductivity and Cryogenics
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• v.25 no.1
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• pp.1-5
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• 2023

The study of two-dimensional electron systems with extraordinarily low levels of disorder was, for a long time, the exclusive privilege of the epitaxial thin film research community. However, the successful isolation of graphene by mechanical exfoliation has truly disrupted this field. Furthermore, the assembly of heterostructures consisting of several layers of different 2D materials in arbitrary order by exploiting van der Waals forces has been a game-changer in the field of low-dimensional physics. This technique can be generalized to the large class of strictly 2D materials and offers unprecedented parameters to play with in order to tune electronic and other properties. It has led to a paradigm shift in the field of 2D condensed matter physics with bright prospects. In this review article, we discuss three device fabrication techniques towards high mobility devices: suspended structures, dry transfer, and pick-up transfer methods. We also address state-of-the-art device structures, which are fabricated by the van der Waals pick-up transfer method. Finally, we briefly introduce correlated ground states in the fractional quantum Hall regime.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2003.05a
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• pp.643-647
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• 2003

Direct methanol fuel cells (DMFC) employing proton exchange polymer electrolyte have recently gained considerable interest because of their attractiveness as the power source for electronic devices or vehicular applications. However, it suffers from the fuel crossover and its impact on cathode operation and the consequent penalty in system energy efficiency. Efforts to circumvent the methanol crossover in DMFC have been made basically along three different strategies.(Omitted)

• Applied Chemistry
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• v.16 no.1
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• pp.73-76
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• 2012

Due to the developments of communications equipment and electronic devices, lithium ion secondary battery usage is growing. Along with demand increasing, the amount of scrap has been steadily increasing. In this study, method of cobalt recovery using organic eco-friendly is proposed. Sulfuric acid, Malic acid, Citric acid at reflux device had good cobalt leaching efficiency. And Sulfuric acid, Malic acid at the autoclave increased cobalt leaching efficiency.

• Journal of Powder Materials
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• v.31 no.1
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• pp.57-76
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• 2024

Recent advancements in electronic devices and wireless communication technologies, particularly the rise of 5G, have raised concerns about the escalating electromagnetic pollution and its potential adverse impacts on human health and electronics. As a result, the demand for effective electromagnetic interference (EMI) shielding materials has grown significantly. Traditional materials face limitations in providing optimal solutions owing to inadequacy and low performance due to small thickness. MXene-based composite materials have emerged as promising candidates in this context owing to their exceptional electrical properties, high conductivity, and superior EMI shielding efficiency across a broad frequency range. This review examines the recent developments and advantages of MXene-based composite materials in EMI shielding applications, emphasizing their potential to address the challenges posed by electromagnetic pollution and to foster advancements in modern electronics systems and vital technologies.

• Journal of Sensor Science and Technology
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• v.33 no.1
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• pp.12-17
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• 2024

Floating inverter amplifiers (FIAs) have recently garnered considerable attention owing to their high energy efficiency and inherent resilience to input common-mode voltages and process-voltage-temperature variations. Since the voltage gain of a simple FIA is low, it is typically cascaded or cascoded to achieve a higher voltage gain. However, cascading poses stability concerns in closed-loop applications, while cascoding limits the output swing. This study introduces a gain-enhanced FIA that features cross-coupled body biasing. Through simulations, it is demonstrated that the proposed FIA designed using a 28-nm complementary metal-oxide-semiconductor technology with a 1-V power supply can achieve a high voltage gain (> 90 dB) suitable for dynamic open-loop applications. The proposed FIA can also be used as a closed-loop amplifier by adjusting the amount of positive feedback due to the cross-coupled body biasing. The capability of achieving a high gain with minimum-length devices makes the proposed FIA a promising candidate for low-power, high-speed sensor interface systems.

• Journal of the Korean Chemical Society
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• v.68 no.2
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• pp.87-92
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• 2024

The commercialization of rechargeable metal-air batteries is extremely desirable but designing stable oxygen reduction reaction (ORR) catalysts with non-noble metal still has faced challenges to replace platinum-based catalysts. The nonnoble metal catalysts for ORR were prepared to improve the catalytic performance and stability by the thermal decomposition of ZIF-8 with optimum cobalt loading. The porous carbon was obtained by the calcination of ZIF-8 and different loading amounts of Co nanoparticles were anchored onto porous carbon forming a Co/PC catalyst. Co/PC composite shows a significant increase in the ORR value of current and stability (500 h) due to the good electronic conductive PCN support and optimum cobalt metal loading. The significantly improved catalytic performance is ascribed to the chemical structure, synergistic effects, porous carbon networks, and rich active sites. This method develops a new pathway for a highly active and advantageous catalyst for electrochemical devices.

• International Journal of Computer Science & Network Security
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• v.24 no.1
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• pp.107-118
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• 2024

With the seamless growth of the technology, network usage requirements are expanding day by day. The majority of electronic devices are capable of communication, which strongly requires a secure and reliable network. Network-based intrusion detection systems (NIDS) is a new method for preventing and alerting computers and networks from attacks. Machine Learning is an emerging field that provides a variety of ways to implement effective network intrusion detection systems (NIDS). Bagging and Boosting are two ensemble ML techniques, renowned for better performance in the learning and classification process. In this paper, the study provides a detailed literature review of the past work done and proposed a novel ensemble approach to develop a NIDS system based on the voting method using bagging and boosting ensemble techniques. The test results demonstrate that the ensemble of bagging and boosting through voting exhibits the highest classification accuracy of 99.98% and a minimum false positive rate (FPR) on both datasets. Although the model building time is average which can be a tradeoff by processor speed.

• Current Optics and Photonics
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• v.8 no.4
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• pp.399-405
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• 2024

In this paper, an optical modulator based on monolayer graphene and triple-layer black phosphorus (BP) heterojunction in the optical communication band range is designed. The influences of geometric parameters, chemical potential, BP orientation and dispersion on the fundamental mode of this modulator were determined in detail by the finite-difference time-domain (FDTD) method. Using appropriate geometric parameter settings, the extinction ratio of this proposed modulator is 0.166 dB, while the modulator with a working length of 3 ㎛ can realize a 0.498 dB modulation depth. The 3-dB bandwidth of this modulator could achieve up to 2.65 GHz with 27.23 fJ/bit energy consumption. The extinction ratio and bandwidth of the proposed modulator increased by 66% and 120.83%, respectively, compared to the monolayer graphene-based ridge-type waveguide modulator. Energy consumption was reduced by 97.28%, compared to a double-layer graphene-based modulator.

• Journal of the Korean Society of Visualization
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• v.22 no.2
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• pp.96-103
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• 2024

As micro-electronic devices are getting miniaturized, technology that can manage the temperature of confined area is required. On these demands, microchannel heat exchanger is suggested as promising solution. However, due to laminar flow created inside the microchannel with high Reynolds number suppresses diffusion based natural convection, leads to low heat transfer performance of microchannel. This paper shows how acoustic streaming flow enhances the heat transfer performance inside the microchannel without using additional structure or nanoparticle inside the straight microchannel and fluid numerically. Various parameters, such as Reynolds number (Re), initial displacement (ξ) was adopted to evaluate the influence of acoustic streaming flow. The results showed that acoustic streaming flow can disturb the thermal boundary, by creating the micro-vortex inside the straight-microchannel and enhance the heat transfer performance.

• Archives of Metallurgy and Materials
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• v.64 no.3
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• pp.913-916
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• 2019

For the reliable applications of silver nanowires, AgNW, which is used as a conductive transparent film in electronic devices, the isothermal degradation behaviors of AgNW films with and without overcoating were investigated. Accelerated isothermal degradation was performed as a function of temperature, time, and atmosphere. Electrical resistance and optical transmittance were measured and correlated with the microstructural damages, such as formation of oxide particles and fragmentations of AgNW, which were quantitatively determined from the scanning electron micrographs. The overcoating retarded the formation of oxide particles and subsequent fragmentations as well as resulting degradation in electrical resistance without affecting the optical transmittance.