• Journal of applied mathematics & informatics
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• v.39 no.3_4
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• pp.381-403
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• 2021

Consider the three-dimensional system of difference equations $x_{n+1}=\frac{{\prod_{j=0}^{k}}z_n-3j}{{\prod_{j=1}^{k}}x_n-(3j-1)\;\(a_n+b_n{\prod_{j=0}^{k}}z_n-3j\)}$, $y_{n+1}=\frac{{\prod_{j=0}^{k}}x_n-3j}{{\prod_{j=1}^{k}}y_n-(3j-1)\;\(c_n+d_n{\prod_{j=0}^{k}}x_n-3j\)}$, $z_{n+1}=\frac{{\prod_{j=0}^{k}}y_n-3j}{{\prod_{j=1}^{k}}z_n-(3j-1)\;\(e_n+f_n{\prod_{j=0}^{k}}y_n-3j\)}$, n ∈ ℕ₀, where k ∈ ℕ₀, the sequences $(a_n)_{n{\in}{\mathbb{N}}_0$, $(b_n)_{n{\in}{\mathbb{N}}_0$, $(c_n)_{n{\in}{\mathbb{N}}_0$, $(d_n)_{n{\in}{\mathbb{N}}_0$, $(e_n)_{n{\in}{\mathbb{N}}_0$, $(f_n)_{n{\in}{\mathbb{N}}_0$ and the initial values x_-3k, x_-3k+1, …, x₀, y_-3k, y_-3k+1, …, y₀, z_-3k, z_-3k+1, …, z₀ are real numbers. In this work, we give explicit formulas for the well defined solutions of the above system. Also, the forbidden set of solution of the system is found. For the constant case, a result on the existence of periodic solutions is provided and the asymptotic behavior of the solutions is investigated in detail.

• Journal of Korea Multimedia Society
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• v.20 no.8
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• pp.1369-1378
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• 2017

Pub/Sub (Publish/Subscribe) paradigm is a simple and easy to use model for interconnecting applications in a distributed environment. In general, subscribers register their interests in a topic or a pattern of events and then asynchronously receive events matching their interest, regardless of the events' publisher. In order to build a low latency lightweight pub/sub system for Internet of Things (IoT) services, we propose a GQSFPS (Group Quorum System-based Fog Pub/Sub) system that is a core component in the event-driven service oriented architecture framework for IoT services. The GQSFPS organizes multiple installed pub/sub brokers in the fog servers into a group quorum based P2P (peer-to-peer) topology for the efficient searching and the low latency accessing of events. Therefore, the events of IoT are cached on the basis of group quorum, and the delay-sensitive IoT applications of edge devices can effectively access the cached events from group quorum fog servers in low latency. The performance of the proposed GQSFPS is evaluated through an analytical model, and is compared to the GQPS (grid quorum-based pud/sub system).

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.9
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• pp.846-852
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• 2013

In this paper, the authors propose a new approach to control problem of the marine vessels which are moored or controlled by actuators. The vessel control problem in the specified area is called a DPS (Dynamic Positioning System). The main objective of this paper is to obtain more useful control design method for DPS. In this problem, a complicate fact is control allocation which is a numerical method for distributing the control signal to the controlled system. For this, many results have been given and verified by other researchers using two individual processes. It means that the controller design and control allocation design process are carried out individually. In this paper, the authors give more sophisticated design solution on this issue. In which the controller design and control allocation problem are unified by a robust controller design problem. In other word, the stability of the closed-loop system, control performance and allocation problem are unified by an LMI (Linear Matrix Inequality) constraint based on $H_2/H_{\infty}$ mixed design framework. The usefulness of proposed approach is verified by simulation with a supply vessel model and found works well.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.639-642
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• 2009

The research was performed to find out the optimum firing condition for the $SnO_2-TiO_2-V_2O_5$ system yellow pigment. The pigment based on $SnO_2-V_2O_5$ system showed very intense yellow color and it was used widely in ceramics industry. Synthesized pigment, with partial substitutions of $SnO_2\;by\;TiO_2$, was fired at $1300{^{\circ}C}$ soaking 1h and it showed bright yellow color. $SnO_2-TiO_2-V_2O_5$ system was very more intensive changes in yellow color by colorimetric value $b^*$ than $SnO_2-V_2O_5$ system. Synthesized yellow pigments were characterized by X-ray diffraction (XRD), FT-IR, and UV-vis spectroscopy. The best composition for yellow pigment was 93:7:0.5(mole%) for $SnO_2-V_2O_5-TiO_2$. The measurement of CIE $L^*a^*b^*$ of pigment was $L^*(78.82),\;a^*(-4.88)\;and\;b^*$(59.25).

• Journal of Korean Society of Water and Wastewater
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• v.12 no.3
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• pp.55-64
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• 1998

The degradation efficiency of chlorophenolic compounds in $TiO_2/H_2O_2$ combined system was compared with that of in $TiO_2$ sole system. As a result, the addition of hydrogen peroxide in photocatalytic oxidation reaction greatly enhanced the degradation efficiency of chlorophenolic compounds due to the availability of the hydroxyl radical formed on the $TiO_2$ surface. The hydrogen peroxide under UV illumination produces hydroxyl radicals that appear to be another source of hydroxyl radical formation. These results indicated the $TiO_2/H_2O_2$ combined system shows higher degradation efficiency than the $TiO_2$ sole system. Compared to another oxidation reaction, hydrogen peroxide assisted photocatalytic oxidation is more promising in practical aspect.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.272-280
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• 1999

A cycle analysis was achieved to predict the characteristics by comprehensive modeling and simulation of an air-cooled, double-effect absorption system using a new $H_2O/LiBr+HO(CH_2)_3OH$ solution. The simulation results showed that the new working fluid may provide the crystallization limit 8% higher than the conventional $H_2O/LiBr$ solution. With a crystallization margin of 3wt%(weight%), the optimal solution distribution ratio was found in the range of 36 to 40%. Variation of cooling air Inlet temperature has a sensitive effect on the cooling COP and corrosion problem. The simulation of heat exchangers with UA value revealed that the absorber and the evaporator are relatively important for an air-cooled system compared with the condenser and the low temperature generator. The effect of cooling air flow rate, circulation weak solution flow rate and chilled water inlet temperature were also examined. The new working fluid may provide the COP approximately 5% higher than the conventional $H_2O/LiBr$ solution.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.2
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• pp.141-146
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• 2020

Thermoelectric Bi₂Te₃ thin films were synthesized by a co-sputtering method at 300℃. A Fe dopant was considered to enhance the thermoelectric properties of the system. The Seebeck coefficient of the Fe-doped films increased whereas the electrical conductivity decreased. As a result, the power factor of the system increased owing to the enhanced Seebeck coefficient. Grain growth inhibition was detected in the Fe-doped system, which produced more grain boundaries in the Fe-doped films than in the undoped system. The increased grain boundary scattering was deemed to be effective for a reduced thermal conductivity. This is advantageous for the preparation of high-performance thermoelectric films.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.694-700
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• 2008

Proton conducting oxides based on the $BaCe_{0.9}M_{0.1}O_{3-{\delta}}$ (M = La, AL) were tested for the alternative electrolyte materials of fuel cell. The power density for single cell of Air |Pt| $BaCe_{0.9}M_{0.1}O_{3-{\delta}}$ |Pt| $H_2(3%H_2O)$ system was maximum $0.04W/cm^2$ at $1000^{\circ}C$. In this system, proton transport number was proved to depend on the lattice parameters and the distortion of $CeO_6$ octahedral as a function of the ionic radii of acceptor ions. This proton conducting oxide system requires developing the new electrode materials for application.

• Textile Coloration and Finishing
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• v.32 no.3
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• pp.158-166
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• 2020

Self-cleaning fabric is a fabric having a function of decotamination via photodecomposition of photocatalyst or wash-off of contaminants on the superhydrophobic surface. TiO₂ is the main photocatalyst for this purpose, but it only functions under UV light which is only a little portion of sunlight, compared to visible light. In this regard, this study aims to investigate Fe-doped TiO₂ for improved photodecomposition from visible light sensitization to apply self-cleaning finishing of PET fabrics. Moreover, the Fe-doped TiO₂ treated PET fabric was further treated with hexadecyltrimethoxysilane to provide superhydrophobicity on the PET fabrics. As a result of this dual treatment, the prepared fabric exhibited excellent photodecomposition of methylene blue with 96.96% in 12h under sunlight and superhydrophobicity with water contact angle of 166.5° and roll-off angle of 7°. This suggested that the excellent self-cleaning functions can be privided to PET fabric via Fe-doped TiO₂ and hexadecyltrimethoxysilane treatment.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.359-362
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• 2003

In PDP(Plasma Display Panel), sub-field method is used to implement gray scale. Each sub-field has different periods. And Every gray level has information of which sub-field has to be displayed. This is called sub-field mapping. There are several sub-field mapping values in some gray levels. So, it is possible to select best choice in this paper, we propose new sub field mapping method using a fuzzy inference system to select best sub-field mapping values in accordance with input image and environment temperature. In order to implement fuzzy system, we used MATLAB fuzzy inference editor.