• Journal of Internet Computing and Services
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• v.17 no.1
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• pp.109-118
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• 2016

As Internet technology further develops, a social networking service (SNS) also develops. But most studies on SNS are not appropriate for business purposes since they mainly focus on personal characteristics. Unlike previous studies, however, this study tries to understand the effect of SNS on performance in the perspective of business. As the result of analysis, SNSE(Social Networking Service Engagement) appears to have positive effect on TMC(Transactive Memory Capability) and PER(Performance), and TMC also seems to affect PER. On the assumption that there should be some parameters between SNSE and PER that earlier studies did not consider, this study has proved that a new way of memories, or TMC, forms the bridge between SNS and PER. It also found out that the time spent on SNS is positively controlled when SNSE affects TMC. These results are different from those of the previous studies arguing that SNS has nothing to do with PER.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.1
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• pp.10-15
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• 2015

This paper proposes the parallel implementation of a self-similarity based image SR (super-resolution) algorithm using OpenCL. The SR algorithm requires tremendous computations to search for a similar patch. This becomes a bottleneck for the real-time conversion from a FHD image to UHD. Therefore, it is imperative to accelerate the processing speed of SR algorithms. For parallelization, the SR process is divided into several kernels, and memory optimization is performed. In addition, two GPUs are used for further acceleration. The experimental results shows that a GPGPU implementation can speed up over 140 times compared to a single-core CPU. Furthermore, it was confirmed experimentally that utilizing two GPUs can speed up the execution time proportionally, up to 277 times.

• Journal of Korea Multimedia Society
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• v.15 no.5
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• pp.632-638
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• 2012

A smartphone is one of the best candidate devices on which context based services can be provided because a smartphone has considerably powerful computing ability and large memory capacity and it is a personal belonging. One of the most important factors of context is the moving status of the smartphone. For example, if the smartphone is not moving and the user is in an exhibition room then we can conclude that the user is watching an exhibit. This paper proposes an algorithm of determining the moving status of a smartphone for the first time. Our test results showed that the proposed algorithm is 100% correct.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.2
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• pp.327-334
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• 2016

Contrary to the common belief, DRAM which is used for the main memory of various computing devices retains its content even though it is powered-off. Especially, the data-retaining time can increase if DRAM is cooled down. The Cold Boot Attack, a kind of side-channel attacks, tries to recover the sensitive information such as the cryptographic key from the powered-off DRAM. This paper proposes a new algorithm which recovers the AES key under the symmetric-decay cold-boot-attack model. In particular, the proposed algorithm uses the strategy of reducing the size of the candidate key space by testing the randomness of the extracted AES key bit stream.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.4
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• pp.642-648
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• 2006

In this paper, I have proposed a secure dynamic ID allocation protocol using mutual authentication on the RFID tag. Currently, there are many security protocols focused on the low-price RFID tag. The conventional low-price tags have limitation of computing power and rewritability of memory. The proposed secure dynamic ID allocation protocol targets to the high-performance RFID tags which have more powerful performance than conventional low-price tag by allocating a dynamic ID to RFID using mutual authentication based on symmetric encryption algorithm. This protocol can be used as a partial solution for ID tracing and forgery.

• Journal of the Korean Magnetics Society
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• v.1 no.2
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• pp.79-84
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• 1991

A variational approach employing localized functional is presented to solve alternating magnetic field problems with open boundary. The functional used in the approach consists of the domain integral of finite element region only and the boundary integral of the interfacial boundary between the finite and infinite element regions. The boundary integral is obtained by transforming the infinite domain integral for the infinite element region into the interfacial boundary integral. The proposed algorithm is then applied to a simple two-dimensional problem where the analytic solutions are available. It is shown that the algorithm makes it possible to yield good agreements between the numerical and analytic solutions. and that it requires less computer storage memory and computation time than the conventional finite element method due to the reduction of the computing region.

• Computational Structural Engineering
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• v.8 no.2
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• pp.123-132
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• 1995

Genetic Algorithms(GA), which are based on the theory of natural evolution, have been evaluated highly for their robust performances. Traditional GA has mostly used binary code for representing design variable. The binary code GA has many difficulties to solve optimization problems with continuous design variables because of its large computer core memory size, inefficiency of its computing time, and its bad performance on local search. In this paper, a real code GA is proposed for dealing with the above problems. So, new crossover and mutation processes of GA are developed to use continuous design variables directly. The results of read code GA are compared with those of binary code GA for several single and multiple objective optimization problems. As a result of comparisons, it is found that the performance of the real code GA is better than that of the binary code GA, and concluded that the real code GA developed here can be used for the general optimization problem.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.120-124
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• 2007

Helicopters and rotary-wing vehicles encounter a wide variety of complex aerodynamic phenomena and these phenomena present substantial challenges for computational fluid dynamics(CFD) models. This investigation presents the rotor aerodynamic analysis items for the helicopter development and variety aerodynamic analysis methods to provide the better solution to researchers and helicopter developers between aerodynamic problems and numerical aerodynamic analysis methods. The numerical methods to make an analysis of helicopter rotor are as below - CFD Modelling : actuator disk model, BET model, fully rotor model,... - Grid : sliding mesh, chimera mesh / structure mesh, unstructure mesh,... - etc. : panel method periodic boundary, quasi-steady simulation, incompressible,... The choice of CFD methodology and the numerical resolution for the overall problem have been driven mostly by available computer speed and memory at any point in time. The combination of the knowledge of aerodynamic analysis items, available computing power and choice of CFD methods now allows the solution of a number of important rotorcraft aerodynamics design problems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.2
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• pp.723-743
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• 2016

Indoor positioning is considered an enabler for a variety of applications, the demand for an indoor positioning service has also been accelerated. That is because that people spend most of their time indoor environment. Meanwhile, the smartphone integrated powerful camera is an efficient platform for navigation and positioning. However, for high accuracy indoor positioning by using a smartphone, there are two constraints that includes: (1) limited computational and memory resources of smartphone; (2) users' moving in large buildings. To address those issues, this paper uses the TC-OFDM for calculating the coarse positioning information includes horizontal and altitude information for assisting smartphone camera-based positioning. Moreover, a unified representation model of image features under variety of scenarios whose name is FAST-SURF is established for computing the fine location. Finally, an optimization marginalized particle filter is proposed for fusing the positioning information from TC-OFDM and images. The experimental result shows that the wide location detection accuracy is 0.823 m (1σ) at horizontal and 0.5 m at vertical. Comparing to the WiFi-based and ibeacon-based positioning methods, our method is powerful while being easy to be deployed and optimized.

• The KSFM Journal of Fluid Machinery
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• v.15 no.5
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• pp.11-19
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• 2012

The main function of fuel cell manifold is to render reactants distribution as uniform as possible into a fuel cell stack. The purpose of this study is to numerically investigate the effects of stack manifold design on reactants distribution within a fuel cell stack. Four manifold designs with different manifold entrance shapes (expansion or diffuser) and different values of the extra width between the cell outer channel and manifold side wall are considered and applied to the fuel cell stack consisting of 50 cells. Since the fuel cell stack geometry involves several millions of grid points for numerical calculations, a parallel computing methodology is employed to substantially reduce the computational time and overcome the memory requirement. The numerical simulations are carried out and calculated results clearly demonstrate that both the manifold entrance shape and extra width have a substantial influence on manifold performance, controlling the degree of flow separation and entrance length for fully developed flow in the manifold channel. Finally, we suggest the optimum design of fuel cell manifold based on the simulation results.