• Journal of Welding and Joining
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• v.16 no.4
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• pp.109-116
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• 1998

The three-dimensional profile of a solder fillet is predicted by minimizing the surface tension and gravity energies of the solder joint using finite element modeling. Geometric complexity stemming from the inclined plane of the gullwing lead is resolved by employing three element types. These element types are used to describe the joint profile formed on the vertical, inclined and interfacial planes. The predicted solder joint profiles show good agreements with the experimental data provided that the solder volume is adjusted considering the wicking effects. Effects of the pad length, inclined lead angle and solder volume on joint profiles are also investigated.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.5
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• pp.53-59
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• 2009

In this paper, we describe the problems which can happen during multi-tasking process in the Windows operating system (OS) environment. To cope with the problems, multiple-windows manager program is proposed in this paper. If we use the proposed multiple-windows manager program with three virtual screen, we can obtain the effect like using four Windows OS and thus we can improve the tardy speed and the high complexity for multi-tasking process.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.758-764
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• 2018

Digital documents such as patents, scholarly papers and research reports have author keywords which summarize the topics of documents. Different documents are likely to describe the same topic if they share the same keywords. Document clustering aims at clustering documents to similar topics with an unsupervised learning method. However, it is difficult to apply to a large amount of documents event though the document clustering is utilized to in various data analysis due to computational complexity. In this case, we can cluster and connect massive documents using keywords efficiently. Existing bottom-up hierarchical clustering requires huge computation and time complexity for clustering a large number of keywords. This paper proposes an inverted index based bottom-up clustering for keywords and analyzes the results of clustering with massive keywords extracted from scholarly papers and research reports.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.651-656
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• 2002

In general, the most important problem in slope stability analysis is that there is no definite way to describe the natural three-dimensional Joint network. Therefore, the many approaches were tried to anlayze the slope stability. Numerical modeling approach is one of the branch to resolve the complexity of natural system. UDEC, FLAC, and SWEDGE are widely used commercial code for the purpose on stability analysis. For the purpose on the more appropriate application of these kind of code, however, three-dimensional distribution of joint network must be identified in more explicit way. Remaining problem is to definitely describe the three dimensional network of joint and bedding, but it is almost impossible in practical sense. Three dimensional joint generation method with random number generation and the results of generation to UDEC have been applied to settle the refered problems in field site. However, this approach also has a important problem, and it is that joint network is generated only once. This problem lead to the limitation on the application to field case, in practical sense. To get rid of this limitation, Monte Carlo Simulation is proposed in this study 1) statistical analysis of input values and definition of the applied system with statistical parameter, 2) instead of the consideration of generated network as a real system, generated system is just taken as one reliable system, 3) present the design parameters, through the statistical analysis of ouput values Results of this study are not only the probability of failure, but also area of failure block, shear strength, normal strength and failure pattern, and all of these results are described in statistical parameters. The results of this study, shear strength, failure area, pattern etc, can provide the direct basement on the design, cutoff angle, support pattern, support strength and etc.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.2
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• pp.453-459
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• 2017

Users tend to check in and post their statuses in location-based social networks (LBSNs) to describe that their interests are related to a point-of-interest (POI). While previous studies on discovering area-of-interests (AOIs) were conducted mostly on the basis of density-based clustering methods with the collection of geo-tagged photos from LBSNs, we focus on estimating a POI boundary, which corresponds to only one cluster containing its POI center. Using geo-tagged tweets recorded from Twitter users, this paper introduces a density-based low-complexity two-phase method to estimate a POI boundary by finding a suitable radius reachable from the POI center. We estimate a boundary of the POI as the convex hull of selected geo-tags through our two-phase density-based estimation, where each phase proceeds with different sizes of radius increment. It is shown that our method outperforms the conventional density-based clustering method in terms of computational complexity.

• Journal of the Korean Society of Systems Engineering
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• v.12 no.2
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• pp.59-67
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• 2016

Recently, the increased complexity of systems has made systems engineering necessary. It is very useful for system designers to understand the whole context of the concerned system based on systems engineering. A system model can be used to describe the outcome of a system design. A system model describes the system from the viewpoint of the stakeholder's needs using the mutually exclusive and collectively exhaustive principle. A system model can be used to smoothly design a large and complicated system based on the systems engineering development process. Many companies and countries are attempting to apply model-based systems engineering, and the significance of the system model quality is increasing as system models are referenced during system development. In this paper, we propose a quality assessment method for ontology which is one of system models by focusing on the system development process. First, in this process, a system developer should explicitly show the relationship between viewpoints. Then, the system developer should select dependent rather than independent viewpoints. With dependent viewpoints, each viewpoint used to describe the system has some logical relationship. The set of viewpoints makes it possible to show, not only tangible and physical system parts, but also conceptual system parts. In this paper, we develop an ontological system model of a Japanese weather observation system. By comparing some ontological system models, we verify the effectiveness of explicitly describing the relationships between viewpoints and select dependent viewpoints.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1911-1932
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• 2013

Orthogonal frequency-division multiplexing (OFDM) has become a popular modulation scheme for wireless protocols because of its spectral efficiency and robustness against multipath interference. Although the components of various OFDM protocols are functionally similar, they remain distinct because of the characteristics of the environment. Recently, graphics processing units (GPUs) have been used to accelerate the signal processing of the physical layer (PHY) because of their great computational power, high development efficiency, and flexibility. In this paper, we describe the implementation of parameterized baseband modules using GPUs for two different OFDM protocols, namely, 802.11a and 802.16. First, we introduce various modules in the modulator/demodulator parts of the transmitter and receiver and analyze the computational complexity of each module. We then describe the integration of the GPU-based baseband modules of the two protocols using the parameterized method. GPU-based implementations are addressed to explain how to accelerate the baseband processing to archive real-time throughput. Finally, the performance results of each signal processing module are evaluated and analyzed. The experiments show that the GPU-based 802.11a and 802.16 PHY meet the real-time requirement and demonstrate good bit error ratio (BER) performance. The performance comparison indicates that our GPU-based implemented modules have better flexibility and throughput to the current ones.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.4
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• pp.43-57
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• 2006

When building a software system out of software components, the composition is not simple because of the complexity caused by diverse versions, digital signatures, static type information, and off-the-shelf components from various vendors. Well-established linking policies are one of the best solutions to solve the complexity problem at linking time. Secure Linking (SL) enables users to specify their linking policies which can be enforced at link time. Secure Linking framework is a framework based on a higher-order logic in order to help build a SL system. This paper shows that the Secure Linking logic is expressive enough to describe a real-world component composition system, the linking protocol of.NET. The paper also demonstrates the advantage of the logic-based linking framework by discussing the weakness of the code signing protocol in.NET which was found while we encoded the assembly linking system of.NET.

• Journal of the Korean Electrochemical Society
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• v.23 no.4
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• pp.81-89
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• 2020

To understand the performance of the electrochemical device, the analysis of the mechanism of ionic conduction is important. However, due to the ionic interaction in the electrolyte and the complexity of the electrolyte structure, a clear analysis method of the ion conduction mechanism has not been proposed. Instead, a variety of mathematical models have been devised to explain the mechanism of ion conduction, and this review introduces the Arrhenius and Vogel-Tammann-Fulcher (VTF) model. In general, the above two mathematical models are used to describe the temperature dependence of the transport properties of electrolytes such as ionic conductivity, diffusion coefficient, and viscosity, and a suitable model can be determined through the linearity of the graph consisting of the logarithm of the moving property and the reciprocal of the temperature. Currently, many electrolyte studies are evaluating the suitability of the above two models for electrolytes by varying the composition and temperature range, and the ion conduction mechanism analysis and activation energy calculation are in progress. However, since there are no models that can accurately describe the transport properties of electrolytes, new models and improvement of existing models are needed.

• Journal of Korean Society of Transportation
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• v.27 no.6
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• pp.129-137
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• 2009

Operation of intelligent transport systems technologies in transportation networks and more detailed analysis give rise to necessity of dynamic traffic analysis model. Existing static models describe network state in average. on the contrary, dynamic traffic analysis model can describe the time-dependent network state. In this study, a dynamic traffic model for the expressway system using FTMS data is developed. Time-dependent origin-destination trip tables for nationwide expressway network are constructed using TCS data. Computation complexity is critical issue in modeling nationwide network for dynamic simulation. A subarea analysis model is developed which converts the nationwide O-D trip tables into subarea O-D trip tables. The applicability of the proposed model is tested under various scenario. This study can be viewed as a starting point of developing deployable dynamic traffic analysis model. The proposed model needs to be expanded to include arterial as well without critical computation burden.