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Search Results: 1 - 10 of 45007 matches for " Dong Kyoo Kim "
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Tone-Independent Orthogonalizing Lattice Equalization for Insufficient Cyclic-Prefix OFDM Transmissions
Dong Kyoo Kim,Yang Sun Lee
International Journal of Distributed Sensor Networks , 2013, DOI: 10.1155/2013/281895
Abstract: Tone-independent orthogonalizing lattice per tone equalizer (TOL-PTEQ) is introduced and its convergence is analyzed. Cyclic-prefix redundancy, one of the major drawbacks of orthogonal frequency division multiplexing (OFDM), can be reduced by TOL-PTEQ. Fast convergence and low computational complexity of TOL-PTEQ are also suitable properties for packet-based wireless communications and detections in which OFDM is widely deployed for their modulation technique. 1. Introduction PTEQ was originally proposed for optimizing bit rate of discrete-multitone (DMT) modem in wired communications such as digital subscriber lines (DSLs), where SNR of each tone can be independently maximized [1–4]. In these literatures, computational complexity is a major issue because they should cover a large number of tones, for example, DMTs with 512, 1024, or 2048 tones. Several types of stochastic-gradient algorithms for PTEQ have been proposed to reduce the computational complexity [1, 2]. But convergence rate is considered as a minor issue for DSLs because various DSLs have long training sequences in their initial set-up process. Wireless broadband communication technology is becoming more important for pervasive healthcare solutions as healthcare applications [5–7] are extending their coverage up to global scale as shown in Figure 1 [8]. According to [8], researches on more fast and reliable wireless infrastructures are conducted in order to improve the healthcare services in remote location. Candidate wireless technologies are as follows: IEEE 802.11x, IEEE 802.16x, ETSI HiperLAN, ETSI HiperMAN, and so on. A common feature of the candidates is that they use OFDM as their modulation method which is the promising technology because it is easy to handle the multipath channel problem by using fast Fourier transform. It is also widely utilized for multiple-access method, say OFDMA. It gives multiuser diversity taking advantage of channel frequency selectivity and good scalability over wide range of bandwidth that is achieved just by adjusting FFT size, where FFT stands for fast Fourier transform [9]. OFDM can also be utilized in the field of radar technologies as shown in Figure 2, where the multitone technique can be applied to enhance the radar scanning performance [10]. In this case, various OFDM technologies are essential to the multitone based radar systems. As shown in Figure 2, the radar transmits and receives the radar signal through the antennas. The received signal contains various reflection signals generated by the interfaces between two different layers. To obtain
Stochastic Design of Enhanced Network Management Architecture and Algorithmic Implementations  [PDF]
Song-Kyoo Kim
American Journal of Operations Research (AJOR) , 2013, DOI: 10.4236/ajor.2013.31A008

The paper is focused on available server management in Internet connected network environments. The local backup servers are hooked up by LAN and replace broken main server immediately and several different types of backup servers are also considered. The remote backup servers are hooked up by VPN (Virtual Private Network) with high-speed optical network. A Virtual Private Network (VPN) is a way to use a public network infrastructure and hooks up long-distance servers within a single network infrastructure. The remote backup servers also replace broken main severs immediately under the different conditions with local backups. When the system performs a mandatory routine maintenance of main and local backup servers, auxiliary servers from other location are being used for backups during idle periods. Analytically tractable results are obtained by using several mathematical techniques and the results are demonstrated in the framework of optimized networked server allocation problems. The operational workflow give the guidelines for the actual implementations.

Lean Practice Case for Improving Service Operations of Donuts Company  [PDF]
Song-Kyoo Kim
Journal of Service Science and Management (JSSM) , 2013, DOI: 10.4236/jssm.2013.63026

The study is based on a data set which has been corrected by the service company and analyzed using Lean Thinking tools. It provides the application of Lean Service into the actual service company. The project is intended to provide a pragmatic view of Lean application. It indicates some of the key practical factors to watch for when considering implementation aspects at each stage of the journey. Both value identification and service quality improvement were applied. The paper explores and clarifies Lean by showing how the process can be supported to add incremental value. The paper demonstrates how Lean methods can be adapted into real-world situations by applying Lean tools to the actual company. So, companies of different service industries can also learn and adapt the Lean approach more effectively.

Enhanced Stochastic Methodology for Combined Architecture of E-Commerce and Security Networks
Song-Kyoo Kim
Mathematical Problems in Engineering , 2009, DOI: 10.1155/2009/691680
Abstract: This paper deals with network architecture which is a combination of electronic commerce and security systems in the typical Internet ecosystems. The e-commerce model that is typically known as online shopping can be considered as a multichannel queueing system. In the other hand, stochastic security system is designed for improving the reliability and availability of the e-commerce system. The security system in this paper deals with a complex system that consists of main unreliable servers, backups, and repair facilities to repair the broken servers. The results are applied for analyzing the current Internet ecosystem, and the mathematical methods can be also applied to the various areas such as human resources, manufacturing processes, and military operations. The solution presents the analytical solutions of the combined architecture of two queueing systems, and these tractable results are used for demonstration in the framework of optimization problems.
Extensive Methodologies for Design of User Experience by Systematic Innovations
Song-Kyoo Kim
International Journal of Social Science and Humanity , 2013, DOI: 10.7763/ijssh.2013.v3.204
Abstract: The paper deals Systematic Innovation method adaptations for revealing the universal framework design of user experience enhancement. User Experience is the way a person feels about using a product, system or services. The key idea of the enhanced user experience is behavior analysis based on the typical statistical data that can be gathering during the regular user operations. The proposed new user interface enhancing framework is targeted to give general guidelines of simpler user experiences design.
Analytic Hierarchy Process Expansion for Innovation Performance Measurement Framework
Song-Kyoo Kim
Journal of Engineering , 2013, DOI: 10.1155/2013/632845
Abstract: Innovation is a top strategic priority for the majority of companies. The need for innovation becomes more and more evident in the current corporate world, and the purpose of innovation is to create business value. The Analytic Hierarchy Process (AHP) is a structured technique for organizing and analyzing complex decisions. This paper is targeting the framework design of the innovation performance criteria and provides the general guidelines to evaluate the relationship between the criteria by using AHP expansion. 1. Introduction Innovation is a top strategic priority for the majority of companies. The need for innovation becomes more and more evident in the current corporate world, and the purpose of innovation is to create business value. Western companies in particular are facing high competition due to the continuous globalization. This brings focus on making innovation more comprehensive in order to be effectively able to manage and improve it. The value of innovation can take many different forms, such as incremental improvements to existing products, the creation of entirely new products and services, or reducing costs. Enterprise is driven to survive and to grow, and in a rapidly changing market the only way to do either is to innovate effectively. But most companies are failing to keep pace in a critical part of the equation: metrics and measurement. It may be called innovation uncertainty principle as many of the ways that companies might want to measure innovation can significantly impede the innovation process, because innovation involves a venture into the unknown, and if we try to pin these unknowns down too fast we may make them harder to recognize and realize. The Analytic Hierarchy Process (AHP) is a structured technique for organizing and analyzing complex decisions: selecting among competing alternatives in a multiobjective environment, the allocation of scarce resources, and forecasting. Although it has wide applicability, the axiomatic foundation of the AHP carefully delimits the scope of the problem environment. Based on mathematics and psychology, it was developed by Thomas L. Saaty in the 1970s and is quite often referred to as the Saaty method. The method is mathematically simple calculations but the very practical tool. There is the homogeneity axiom states that the elements being compared should not differ by too much in the property being compared [1–3]. If this is not the case, large errors in judgment could occur. When constructing a hierarchy of objectives, one should attempt to arrange elements in clusters, so that they
Explicit Design of Innovation Performance Metrics by Using Analytic Hierarchy Process Expansion
Song-Kyoo Kim
International Journal of Mathematics and Mathematical Sciences , 2014, DOI: 10.1155/2014/125950
Abstract: The paper presents the explicit and objective measurement method for innovation performances by using the extensive version of Analytic Hierarchy Process (AHP). A hierarchical framework is constructed for the innovation performance criteria and giving the guideline for innovation performance of companies. By applying AHP Expansion framework, the innovation performance measurement factors can be prioritized and descending-order rank list of the performance factors can be made in order to select the best strategies to improve the innovativeness of companies. This new framework of innovation measurement is targeted for implementation at the actual analysis for innovation competitiveness of companies and expected to provide the milestones of measuring the innovation more effectively. 1. Introduction Current corporate world understands that innovation is more evident and creating business value is the purpose of innovation. Global companies are focused on making innovation more understandable to be able to manage and improve their business because the companies are facing high competition because of endless globalization. The value of innovation can be considered in many different forms. Regardless of company size, modern companies are driven to survive and to grow. Finding the solution for the rapidly changing market which is to innovative effectively is the way to survive. But most of companies fail to sustain their innovativeness because they miss the critical parts of the equation: metrics and measurements. Innovation uncertainty principle means that the procedure to measure innovation of the company may interrupt the innovation process because innovation by itself involves venture for the unknown factors, and the company could make the unknown factors harder to realize or recognize if the company tries to pin these unknowns down too fast [1]. The criteria to measure the innovation are the critical issue and several researches [2–7] suggest the framework of innovation metric criteria. Innovation can be viewed as having three distinct approaches. There are many alternatives for choosing the innovation metrics but three distinct approaches are appropriate approaches [2–5]. All three components should be measured thoroughly. The practical ways of measuring innovation differ highly from the metrics suggested by theory, through highly unbalanced and seemingly random metrics. There is a need for a framework on how to select which innovation metrics that an organization should use. The aim of creating this framework is to show that despite small changes of the
The coexistence of charge density wave and superconductivity in Pt-based layered superconductors : SrPt$_2$As$_2$ and LaPt$_2$Si$_2$
Sooran Kim,Kyoo Kim,B. I. Min
Physics , 2014, DOI: 10.1038/srep15052
Abstract: The intriguing coexistence of the charge density wave (CDW) and superconductivity in SrPt$_2$As$_2$ and LaPt$_2$Si$_2$ has been investigated based on the {\it ab initio} density functional theory band structure and phonon calculations. We have found that the local split distortions Pt atoms in the [As-Pt-As] layers play an essential role in driving the five-fold supercell CDW instability as well as the phonon softening instability in SrPt$_2$As$_2$. By contrast, the CDW and phonon softening instabilities in LaPt$_2$Si$_2$ occur without split distortions of Pt atoms, indicating that the driving mechanisms of the CDW in SrPt$_2$As$_2$ and LaPt$_2$Si$_2$ are different. We have found that the CDW instability for the former arises from the Fermi surface nesting, while, for the latter, from the saddle point scattering. The phonon calculations, however, suggest that the CDW and the superconductivity coexist in [{\it X}-Pt-{\it X}] layers ({\it X} = As or Si) for both cases.
Universal metastability of the low-spin state in Co$^{2+}$ systems: non-Mott type pressure-induced spin-state transition in CoCl$_{2}$
Bongjae Kim,Kyoo Kim,B. I. Min
Physics , 2014, DOI: 10.1103/PhysRevB.89.115131
Abstract: We have investigated the pressure-induced spin-state transition in Co$^{2+}$ systems in terms of a competition between the Hund's exchange energy ($J$) and the crystal-field splitting ($\Delta_{CF}$). First, we show the universal metastability of the low-spin state in octahedrally coordinated Co$^{2+}$ systems. Then we present the strategy to search for a Co$^{2+}$ system, for which the mechanism of spin-state and metal-insulator transitions is governed not by the Mott physics but by $J$ vs. $\Delta_{CF}$ physics. Using CoCl$_{2}$ as a prototypical Co$^{2+}$ system, we have demonstrated the pressure-induced spin-state transition from high-spin to low-spin, which is accompanied with insulator-to-metal and antiferromagnetic to half-metallic ferromagnetic transitions. Combined with metastable character of Co$^{2+}$ and the high compressibility nature of CoCl$_{2}$, the transition pressure as low as 27 GPa can be identified on the basis of $J$ vs. $\Delta_{CF}$ physics.
Structural instability and the Mott-Peierls transition in a half-metallic hollandite : K$_{2}$Cr$_{8}$O$_{16}$
Sooran Kim,Kyoo Kim,B. I. Min
Physics , 2014, DOI: 10.1103/PhysRevB.90.045124
Abstract: In order to explore the driving mechanism of the concomitant metal-insulator and structural transitions in quasi-one-dimensional hollandite K$_{2}$Cr$_{8}$O$_{16}$, electronic structures and phonon properties are investigated by employing the {\it ab initio} density functional theory (DFT) calculations. We have found that the imaginary phonon frequency reflecting the structural instability appears only in the DFT+$U$ ($U$: Coulomb correlation) calculation, which indicates that the Coulomb correlation plays an essential role in the structural transition. The lattice displacements of the softened phonon at X explain the observed lattice distortions in K$_{2}$Cr$_{8}$O$_{16}$ perfectly well, suggesting the Peierls distortion vector {\bf Q} of X (0, 0, 1/2). The combined study of electronic and phonon properties reveals that half-metallic K$_{2}$Cr$_{8}$O$_{16}$, upon cooling, undergoes the correlation-assisted Peierls transition to become a Mott-Peierls ferromagnetic insulator at low temperature.
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