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71.
Hyung-Jong Kim Myuhng Joo Kim Yoonjeong Kim Hyun Cheol Jeong 《Simulation Modelling Practice and Theory》2009,17(4):569-584
At the present time the VoIP (Voice over Internet Protocol) service is generally accepted as an alternative for people seeking cheaper means to make a phone call. Users of VoIP service may fall anywhere along a spectrum between types at two extremes: one of which is an ordinary caller who doesn’t use the telephone for commercial purposes, while the other is a person who generates spam calls for commercial purposes. The focus of this paper concerns modeling of spam callers’ behavior to calculate the SPIT (Spam over Internet Telephony) level for management of the quality of service. From the perspective of a VoIP service provider’s view, spam callers are also a type of customer and sometimes they are valuable for increasing revenue. However, if a service provider does not manage spam calls, it can harm their business, because ordinary users might not receive phone calls using the phone numbers of the VoIP service. Thus, there is a trade-off between revenues and usability in managing spam calls in the VoIP service. This work presents a model of spam caller’s behavior using the DEVS (Discrete Event System Specification) formalism. The DEVS formalism is applicable as a model of behavior, by defining the state and state transition of the target of the model. In our model, we use six main parameters to define the states and state transitions. Each state is represented by a number which indicates the SPIT level of a caller. If the value is 1.0 then the caller is more similar to a spam caller. Based on the model definition, we constructed a SPIT level Calculation UI (User Interface) that is used to manage spam calls to improve VoIP service quality. 相似文献
72.
In this article, the method for increasing dynamic stability of quadruped robot is proposed. Previous researches on dynamic
walking of quadruped robots have used only walking pattern called central pattern generator (CPG). In this research, different
from walking generation with only CPG, a instinctive stability measure called landing accordance ratio, is proposed and used
for increasing dynamic stability. In addition, dynamic balance control and control to adjust walking trajectory for increasing
dynamic stability measure is also proposed. Proposed methods are verified with dynamic simulation and a large number of experiments
with quadruped robot platform. 相似文献
73.
Hwan Seong Moon Jae Suk Lee Sung Wook Han Jong Wan Park Jae Hak Lee Seung Kee Yang Hyung Ho Park 《Journal of Materials Science》1994,29(6):1545-1548
Tantalum oxide film formation by plasma-enhanced chemical vapour deposition (PECVD) using TaCl5 as a source material was examined. The effects of deposition temperature on the formation, structure and electric properties of the Ta2O5 film were investigated for Al/Ta2O5/ p-Si (MTS) capacitors. The deposition rate and refractive index increased with increasing deposition temperature. It was found that the structure of Ta2O5 deposited by PECVD was amorphous as-deposited. However, crystalline -Ta2O5 of hexagonal structure was formed by a 700 °C, 1 h heat treatment in argon. Capacitance and relative dielectric constant of the PECVD Ta2O5 were found to be 2.54 fF m–2 and 23.5, respectively. The PECVD films obtained in this study have higher dielectric constants and remarkably better general film characteristics than those obtained by other deposition methods. 相似文献
74.
Seung Gyo Jeong Jin Young Oh Lin Hao Jian Liu Woo Seok Choi 《Advanced functional materials》2023,33(38):2301770
Unexpected, yet useful functionalities emerge when two or more materials merge coherently. Artificial oxide superlattices realize atomic and crystal structures that are not available in nature, thus providing controllable correlated quantum phenomena. This review focuses on 4d and 5d perovskite oxide superlattices, in which the spin–orbit coupling plays a significant role compared with conventional 3d oxide superlattices. Modulations in crystal structures with octahedral distortion, phonon engineering, electronic structures, spin orderings, and dimensionality control are discussed for 4d oxide superlattices. Atomic and magnetic structures, Jeff = 1/2 pseudospin and charge fluctuations, and the integration of topology and correlation are discussed for 5d oxide superlattices. This review provides insights into how correlated quantum phenomena arise from the deliberate design of superlattice structures that give birth to novel functionalities. 相似文献
75.
Seonho Kim Ho Kyun Jung Puji Lestari Handayani Taehoon Kim Byung Mun Jung U Hyeok Choi 《Advanced functional materials》2023,33(13):2210916
For the development of all-solid-state lithium metal batteries (LMBs), a high-porous silica aerogel (SA)-reinforced single-Li+ conducting nanocomposite polymer electrolyte (NPE) is prepared via two-step selective functionalization. The mesoporous SA is introduced as a mechanical framework for NPE as well as a channel for fast lithium cation migration. Two types of monomers containing weak-binding imide anions and Li+ cations are synthesized and used to prepare NPEs, where these monomers are grafted in SA to produce SA-based NPEs (SANPEs) as ionomer-in-framework. This hybrid SANPE exhibits high ionic conductivities (≈10−3 S cm−1), high modulus (≈105 Pa), high lithium transference number (0.84), and wide electrochemical window (>4.8 V). The resultant SANPE in the lithium symmetric cell possesses long-term cyclic stability without short-circuiting over 800 h under 0.2 mA cm−2. Furthermore, the LiFePO4|SANPE|Li solid-state batteries present a high discharge capacity of 167 mAh g−1 at 0.1 C, good rate capability up to 1 C, wide operating temperatures (from −10 to 40 °C), and a stable cycling performance with 97% capacity retention and 100% coulombic efficiency after 75 cycles at 1 C and 25 °C. The SANPE demonstrates a new design principle for solid-state electrolytes, allowing for a perfect complex between inorganic silica and organic polymer, for high-energy-density LMBs. 相似文献
76.
Dohyung Kim Hyeonsu Bang Hyoung Won Baac Jongmin Lee Phuoc Loc Truong Bum Ho Jeong Tamilselvan Appadurai Kyu Kwan Park Donghyeok Heo Vu Binh Nam Hocheon Yoo Kyeounghak Kim Daeho Lee Jong Hwan Ko Hui Joon Park 《Advanced functional materials》2023,33(14):2213064
Reversible metal-filamentary mechanism has been widely investigated to design an analog resistive switching memory (RSM) for neuromorphic hardware-implementation. However, uncontrollable filament-formation, inducing its reliability issues, has been a fundamental challenge. Here, an analog RSM with 3D ion transport channels that can provide unprecedentedly high reliability and robustness is demonstrated. This architecture is realized by a laser-assisted photo-thermochemical process, compatible with the back-end-of-line process and even applicable to a flexible format. These superior characteristics also lead to the proposal of a practical adaptive learning rule for hardware neural networks that can significantly simplify the voltage pulse application methodology even with high computing accuracy. A neural network, which can perform the biological tissue classification task using the ultrasound signals, is designed, and the simulation results confirm that this practical adaptive learning rule is efficient enough to classify these weak and complicated signals with high accuracy (97%). Furthermore, the proposed RSM can work as a diffusive-memristor at the opposite voltage polarity, exhibiting extremely stable threshold switching characteristics. In this mode, several crucial operations in biological nervous systems, such as Ca2+ dynamics and nonlinear integrate-and-fire functions of neurons, are successfully emulated. This reconfigurability is also exceedingly beneficial for decreasing the complexity of systems—requiring both drift- and diffusive-memristors. 相似文献
77.
A Novel and Facile Route to Synthesize Atomic‐Layered MoS2 Film for Large‐Area Electronics 下载免费PDF全文
Stephen Boandoh Soo Ho Choi Ji‐Hoon Park So Young Park Seungho Bang Mun Seok Jeong Joo Song Lee Hyeong Jin Kim Woochul Yang Jae‐Young Choi Soo Min Kim Ki Kang Kim 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(39)
High‐quality and large‐area molybdenum disulfide (MoS2) thin film is highly desirable for applications in large‐area electronics. However, there remains a challenge in attaining MoS2 film of reasonable crystallinity due to the absence of appropriate choice and control of precursors, as well as choice of suitable growth substrates. Herein, a novel and facile route is reported for synthesizing few‐layered MoS2 film with new precursors via chemical vapor deposition. Prior to growth, an aqueous solution of sodium molybdate as the molybdenum precursor is spun onto the growth substrate and dimethyl disulfide as the liquid sulfur precursor is supplied with a bubbling system during growth. To supplement the limiting effect of Mo (sodium molybdate), a supplementary Mo is supplied by dissolving molybdenum hexacarbonyl (Mo(CO)6) in the liquid sulfur precursor delivered by the bubbler. By precisely controlling the amounts of precursors and hydrogen flow, full coverage of MoS2 film is readily achievable in 20 min. Large‐area MoS2 field effect transistors (FETs) fabricated with a conventional photolithography have a carrier mobility as high as 18.9 cm2 V?1 s?1, which is the highest reported for bottom‐gated MoS2‐FETs fabricated via photolithography with an on/off ratio of ≈105 at room temperature. 相似文献
78.
Solar Cells: Multidimensional Anodized Titanium Foam Photoelectrode for Efficient Utilization of Photons in Mesoscopic Solar Cells (Small 34/2017) 下载免费PDF全文
79.
Ji Chan Park Shin Wook Kang Jeong-Chul Kim Jae In Kwon Sanha Jang Geun Bae Rhim Mijong Kim Dong Hyun Chun Ho-Tae Lee Heon Jung Hyunjoon Song Jung-II Yang 《Nano Research》2017,(3):1044-1055
A cobalt-silica hybrid nanocatalyst bearing small cobalt particles of diameter ~5 nm was prepared through a hydrothermal reaction and hydrogen reduction.The resulting material showed very high CO conversion (>82%) and high hydrocarbon productivity (~1.0 gHc·g-1cat,·h-11) with high activity (~8.5 x 10-5 molco·g-1Co·S-1) in the Fischer-Tropsch synthesis reaction. 相似文献
80.
High‐Performance Integrated Perovskite and Organic Solar Cells with Enhanced Fill Factors and Near‐Infrared Harvesting 下载免费PDF全文