• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.5
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• pp.1303-1315
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• 2012

In the draft of the IEEE 802.11s standard, a tree topology is established by the proactive tree-building mode of the Hybrid Wireless Mesh Protocol (HWMP). It is used for cases in which the root station (e.g., gateway) is an end point of the majority of the data connections. In the tree topology, the root or central stations (e.g., parent stations) are connected to the other stations (e.g., leaves) that are one level lower than the central station. Such mesh stations are likely to suffer heavily from contention in bottleneck links when the network has a high traffic load. Moreover, the dependence of the network on such stations is a point of vulnerability. A failure of the central station (e.g., a crash or simply going into sleep mode to save energy) can cripple the whole network in the tree topology. This causes performance degradation for end-to-end transmissions. In a connected mesh topology where the stations having two or more radio links between them are connected in such a way that if a failure subsists in any of the links, the other link could provide the redundancy to the network. We propose a scheme to utilize this characteristic by organizing the network into concentric tiers around the root mesh station. The tier structure facilitates path recovery and congestion control. The resulting mode is referred to as Tier-based Proactive Path Selection Mode (TPPSM). The performance of TPPSM is compared with the proactive tree mode of HWMP. Simulation results show that TPPSM has better performance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.11
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• pp.1071-1077
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• 2012

Low frequency noises(up to about 200 Hz) such as booming are mainly caused by particular modes, and in general the solutions may be found based on mode controls where conventional methods such as FEM can be used. However, at higher frequencies between 0.3~1 kHz, as the number of modes rapidly increases, radiation characteristics from structures, performances of damping sheets and sound packages may be more crucial rather than particular modes, and consequently the conventional FEM may be less practical in dealing with this kinds of structure-borne problems. In this context, so-called 'mid-frequency simulation model' based on FE-SEA hybrid method is studied and validated to reduce noise in this frequency region. Energy transmission loss(i.e. air borne noise) is also studied. A dash panel component is chosen for this study, which is an important path that transmits both structure-borne and air borne energies into the cavity. Design modifications including structural modifications, attachment of damping sheets and application of different sound packages are taken into account and the corresponding noise characteristics are experimentally identified. It is found that the dash member behaves as a noise path. The damping sheet and sound packages have similar influences on both sound radiation and transmission loss. The comparison between experiments and simulations shows that this model could be used to predict the tendency of noise improvement.

• Journal of Information Processing Systems
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• v.16 no.5
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• pp.1196-1213
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• 2020

There is a growing interest in the development of smart environments through predicting the behaviors of inhabitants of smart spaces in the recent past. Various smart services are deployed in modern smart cities to facilitate residents and city administration. Prediction algorithms are broadly used in the smart fields in order to well equip the smart services for the future demands. Hence, an accurate prediction technology plays a vital role in the smart services. In this paper, we take out an extensive survey of smart spaces such as smart homes, smart farms and smart cars and smart applications such as smart health and smart energy. Our extensive survey is based on more than 400 articles and the final list of research studies included in this survey consist of 134 research papers selected using Google Scholar database for period of 2008 to 2018. In this survey, we highlight the role of prediction algorithms in each sub-domain of smart Internet of Things (IoT) environments. We also discuss the main algorithms which play pivotal role in a particular IoT subfield and effectiveness of these algorithms. The conducted survey provides an efficient way to analyze and have a quick understanding of state of the art work in the targeted domain. To the best of our knowledge, this is the very first survey paper on main categories of prediction algorithms covering statistical, heuristic and hybrid approaches for smart environments.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.73-73
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• 2012

Modern technology-driven society largely relies on hybrid electric vehicles or electric vehicles for eco-friendly transportation and the use of high technology devices. Lithium rechargeable batteries are the most promising power sources because of its high energy density but still have a challenge. Graphite is the most widely used anode material in the field of lithium rechargeable batteries due to its many advantages such as good cyclic performances, and high charge/discharge efficiency in the initial cycle. However, it has an important safety issue associated with the dendritic lithium growth on the anode surface at high charging current because the conventional graphite approaches almost 0 V vs $Li/Li^+$ at the end of lithium insertion. Therefore, a fundamental solution is to use an electrochemical redox couple with higher equilibrium potentials, which suppresses lithium metal formation on the anode surface. Among the candidates, $Li_4Ti_5O_{12}$ is a very interesting intercalation compound with safe operation, high rate capability, no volume change, and excellent cycleability. But the insulating character of $Li_4Ti_5O_{12}$ has raised concerns about its electrochemical performance. The initial insulating character associated with Ti4+ in $Li_4Ti_5O_{12}$ limits the electronic transfer between particles and to the external circuit, thereby worsening its high rate performance. In order to overcome these weak points, several alternative synthetic methods are highly required. Hence, in this presentation, novel ways using a synergetic strategy based on 1D architecture and surface coating will be introduced to enhance the kinetic property of Ti-based electrode. In addition, first-principle calculation will prove its significance to design Ti-based electrode for the most optimized electrochemical performance.

• Bulletin of the Korean Chemical Society
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• v.29 no.7
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• pp.1335-1343
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• 2008

Theoretical studies on the un-catalyzed and catalyzed aminations of ketene with $NH_3$ and $(NH_3)_2$, respectively, were studied using MP2 and hybrid density functional theory of B3LYP at the 6-31+G(d,p) and 6- 311+G(3df,2p) basis sets in the gas phase and in benzene and acetonitrile solvents. In the gas phase reaction, the un-catalyzed mechanism was the same as those previously reported by others. The catalyzed mechanism, however, was more complicated than expected requiring three transition states for the complete description of the C=O addition pathways. In the un-catalyzed amination, rate determining step was the breakdown of enol amide but in the catalyzed reaction, it was changed to the formation of enol amide, which was contradictory to the previous findings. Starting from the gas-phase structures, all structures were re-optimized using the CPCM method in solvent medium. In a high dielectric medium, acetonitrile, a zwitterions formed from the reaction of $CH_2$=C=O with $(NH_3)_2$, I(d), exists as a genuine minimum but other zwitterions, I(m) in acetonitrile and I(d) in benzene become unstable when ZPE corrected energies are used. Structural and energetic changes induced by solvation were considered in detail. Lowering of the activation energy by introducing additional $NH_3$ molecule amounted to ca. −20 $\sim$ −25 kcal/mol, which made catalyzed reaction more facile than un-catalyzed one.

• Journal of the Korean Magnetics Society
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• v.22 no.6
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• pp.221-227
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• 2012

High performance permanent magnets have become the subject of considerable attention because of the potential applications in the traction motors of hybrid and electric vehicles and wind generators. Nd-Fe-B magnets have attracted considerable interest due to a large maximum energy product. However, Nd-Fe-B magnet cannot be used in high temperature (${\sim}200^{\circ}C$) applications due to the thermal degradation of coercivity. Therefore, the development of high coercivity Nd-Fe-B permanent magnet is a challenging issue. In case of high coercivity Nd-Fe-B permanent magnet, an increment in the intrinsic coercivity can be easily achieved by substituting Nd atoms with Dy or Tb atoms. However, these heavy rare-earth elements are known to cause a decrease in remanence due to the antiferromagnetic coupling between Dy and Fe atoms. In addition, Dy is relatively expensive and being limited in quantity. Hence, a new technology that can increase the coercivity of Nd-Fe-B sintered magnet using only a small amount, or even, no amount of heavy rare-earth elements is being investigated. This article describes the research trend in reducing the heavy rare-earth elements in Nd-Fe-B magnets.

• Food Science of Animal Resources
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• v.35 no.5
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• pp.692-702
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• 2015

Lactobacillus mucosae is a natural resident of the gastrointestinal tract of humans and animals and a potential probiotic bacterium. To understand the global protein expression profile and metabolic features of L. mucosae LM1 in the early stationary phase, the QExactive^TM Hybrid Quadrupole-Orbitrap Mass Spectrometer was used. Characterization of the intracellular proteome identified 842 proteins, accounting for approximately 35% of the 2,404 protein-coding sequences in the complete genome of L. mucosae LM1. Proteome quantification using QExactive^TM Orbitrap MS detected 19 highly abundant proteins (> 1.0% of the intracellular proteome), including CysK (cysteine synthase, 5.41%) and EF-Tu (elongation factor Tu, 4.91%), which are involved in cell survival against environmental stresses. Metabolic pathway annotation of LM1 proteome using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database showed that half of the proteins expressed are important for basic metabolic and biosynthetic processes, and the other half might be structurally important or involved in basic cellular processes. In addition, glycogen biosynthesis was activated in the early stationary phase, which is important for energy storage and maintenance. The proteogenomic data presented in this study provide a suitable reference to understand the protein expression pattern of lactobacilli in standard conditions

• Journal of KIISE:Information Networking
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• v.30 no.2
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• pp.155-166
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• 2003

Mobile computing becomes a new issue of researches in computing due to the advances of mobile equipment and the connection with Internet. In mobile environment, there are many constraints such as limited bandwidth, intermittent disconnection, limited battery life, and so on. By these reasons, broadcasting has been generally used to disseminate data efficiently by the mobile applications. This paper proposes an adaptive broadcasting method which logically divides broadcast channel into the periodic broadcast channel and the on-demand broadcast channel and dynamically assigns the bandwidths of both channel. The former disseminates data that are selected based on both the popularity and the size of each datum, the latter disseminates data that are selected based on the requests of mobile clients. When selecting data to be disseminated, the proposed broadcasting method considers the mobility of a mobile client and also considers the size of each datum by using SF(size factor) proposed in this paper. This paper also evaluates the proposed broadcasting method by measuring the energy expenditure of mobile client in experiments.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.3021-3024
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• 2009

$Zn_2Ti_{1-x}Fe_xO_4\;(0\;{\leq}\;x\;{\leq}\;0.7)$ photocatalysts were synthesized by polymerized complex (PC) method and investigated for its physico-chemical as well as optical properties. $Zn_2Ti_{1-x}Fe_xO_4$ can absorb not only UV light but also visible light region due to doping of Fe in the Ti site of $Zn_2TiO_4$ lattice because of the band transition from Fe 3d to the Fe 3d + Ti3d hybrid orbital. The photocatalytic activity of Fe doped $Zn_2TiO_4$ samples for hydrogen production under UV light irradiation decreased with an increase in Fe concentration in $Zn_2TiO_4$. Consequently, there exists an optimized concentration of iron for improved photocatalytic activity under visible light (${\lambda}{\leq}$420 nm)

• Journal of IKEEE
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• v.15 no.4
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• pp.324-329
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• 2011

In recent years, the performance and functions of portable devices has increased. so it requires more power efficiency and energy density while using the battery for a long time. therefore Battery pack which are made up from several battery cells in series in order to achieve higher operating voltage is being used. when using a Li-ion battery, we need a protection circuit to protect from overcharge, over discharge, high temperature and over current. Also, when using battery pack, we need to Cell voltage balancing circuit that each cell in tune with the balancing. In this paper, the proposed IC is applicable by mobile devices as well as E-bike, hybrid vehicles, electric vehicles, and is expected to contribute to the development of domestic PMIC.