• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.6
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• pp.13-25
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• 2005

In these days, there are various uses of Linux such as small embedded systems, routers, and huge servers, because Linux gives several advantages to system developers by allowing to use the open source code of the Linux kernel. On the other hand, the open source nature of the Linux kernel gives a bad influence on system security. If someone wants to exploit Linux-based systems, the attacker can easily do it by finding vulnerabilities of their Linux kernel sources. There are many kinds of existing methods for lading source-level vulnerabilities of softwares, but they are not suitable for finding source-level vulnerabilities of the Linux kernel which has an enormous amount of source code. In this paper, we propose the Onion mechanism as a methodology of finding source-level vulnerabilities of Linux kernel variables. The Onion mechanism is made up of two steps. The Int step is to select variables that may be vulnerable by using pattern matching mechanism and the second step is to inspect vulnerability of each selected variable by constructing and analyzing the system call trees. We also evaluate our proposed methodology by applying it to two well-known source-level vulnerabilities.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.6
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• pp.703-714
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• 2001

In C language, a local buffer overflow in stack can destroy control information stored near the buffer. In case the buffer overflow is used maliciously to overwrite the stored return address, the system is exposed to serious security vulnerabilities. This paper analyzes the process of buffer overflow hacking and methodologies to avoid the attacks in details. And it proposes a device of static buffer overflow detection by using function summary and tracking information flow of buffer domain at assembly source code level(SASS, Static Assembly Source code Scanner) and then show the feasibility and validity of it by implementing a prototype in Pentium based Linux environment.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.431-436
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• 2010

Recently, several open source codes for computational fluid dynamics (CFD) have been emerged and are spreading fast. Our group has chosen OpenFOAM as a platform to develop our own in-house code. In this paper, we would like to share the information on the codes and what we have experienced so far. We introduce several features of OpenFOAM, which include the performance compared with commercial packages, estimation for current user population and our own prospect for future improvement in performance and growth in user population. In addition, we briefly introduce our experience gained in embedding the level set method into the OpenFOAM.

• Journal of computational fluids engineering
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• v.15 no.3
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• pp.46-53
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• 2010

Recently, several open source codes for computational fluid dynamics (CFD) have been introduced and are spreading fast. Our group has chosen the OpenFOAM as a platform to develop our own in-house code. In this brief review, we would like to share the information on the codes and what we have experienced so far. We introduce several features of OpenFOAM, which include the performance compared with commercial packages, estimation for current user population, and our own prospect for future improvement in performance and growth in user population. In addition, we briefly introduce our experience gained in embedding the level set method into the OpenFOAM.

• Journal of the Korea Computer Industry Society
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• v.3 no.8
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• pp.963-980
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• 2002

Software reengineering is making various research for solutions against problem of maintain existing systems. Reengineering has a meaning of development of software on exizting systems through the reverse engineering auf forward engineering. Most of the important concepts used in reengineering is composition that is restructuring of the existing objects. Is there a compiler that can compile a program written in a traditional procedural language (like C or Pascal) and generate a Java bytecode, rather than an executable code that runs oかy on the machine it was compiled (such as an a.out file on a Unix machine)\ulcorner This type of compiler may be very handy for today's computing environment of heterogeneous networks. In this paper we present a software system that does this job at the binary-to-binary level. It takes the compiled binary code of a procedural language and translates it into Java bytecode. To do this, we first translate into an assembler code called Jasmin [7] that is a human-readable representation of Java bytecode. Then the Jasmin assembler converts it into real Java bytecode. The system is not a compiler because it does not start at the source level. We believe this kind of translator is even more useful than a compiler because most of the executable code that is available for sharing does not come with source programs. Of course, it works only if the format of the executable binary code is known. This translation process consists of three major stages: (1) analysis stage that identifies the language constructs in the given binary code, (2) initialization stage where variables and objects are located, classified, and initialized, and (3) mapping stage that maps the given binary code into a Jasmin assembler code that is then converted to Java bytecode.

• Journal of Korea Multimedia Society
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• v.19 no.10
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• pp.1792-1807
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• 2016

Android application is vulnerable to reverse engineering attack. And by this, it is easy to extract significant module from source code and repackage it. To prevent this problem, dynamic class loading technique, which is able to exclude running code from distributed source code and is able to load running code dynamically during runtime can be used. Recently, this technique was adapted on variety of fields and applications like updating pre-loaded android application, preventing from repacking malicious application, etc. Despite the fact that this technique is used on variety of fields and applications, there is fundamental lack on the study of potential weakness or related secure coding. This paper would deal with potential weaknesses during the implementation of dynamic class loading technique with analysing related international/domestic standard of weaknesses and suggest a secure way for the implementation of dynamic class loading technique. Finally, we believe that this technique described here could increase the level of trust by decreasing the weakness related to dynamic class loading technique.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.43-54
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• 2016

In the present paper, development of the three-dimensional (3D) computational code based on Galerkin finite element method (GFEM) for solving the multigroup forward/adjoint diffusion equation in both rectangular and hexagonal geometries is reported. Linear approximation of shape functions in the GFEM with unstructured tetrahedron elements is used in the calculation. Both criticality and fixed source calculations may be performed using the developed GFEM-3D computational code. An acceptable level of accuracy at a low computational cost is the main advantage of applying the unstructured tetrahedron elements. The unstructured tetrahedron elements generated with Gambit software are used in the GFEM-3D computational code through a developed interface. The forward/adjoint multiplication factor, forward/adjoint flux distribution, and power distribution in the reactor core are calculated using the power iteration method. Criticality calculations are benchmarked against the valid solution of the neutron diffusion equation for International Atomic Energy Agency (IAEA)-3D and Water-Water Energetic Reactor (VVER)-1000 reactor cores. In addition, validation of the calculations against the $P_1$ approximation of the transport theory is investigated in relation to the liquid metal fast breeder reactor benchmark problem. The neutron fixed source calculations are benchmarked through a comparison with the results obtained from similar computational codes. Finally, an analysis of the sensitivity of calculations to the number of elements is performed.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.504-507
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• 2009

The purpose of this work is to predict the low frequency aero-acoustic noise generated from the horizontal axis wind turbine, NREL Phase VI using large eddy simulation and Ffowcs-Williams and Hawkings model provided in the commercial code, FLUENT. Calculated aerodynamic performances such as shaft torque and power are compared with experimentally measured value. Performance results show a good agreement with experimental data within about 0.8%. If the distance by two times is changed from 32D to 64D toward the downstream region, sound pressure level is reduced by about 6.4dB.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.40-49
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• 2016

In this paper, we present a symbol-level iterative source-channel decoding (ISCD) algorithm for reliable transmission of variable-length codes (VLCs). Firstly, an improved source a posteriori probability (APP) decoding approach is proposed for packetized variable-length encoded Markov sources. Also proposed is a recursive implementation based on a three-dimensional joint trellis for symbol decoding of binary convolutional codes. APP channel decoding on this joint trellis is realized by modification of the Bahl-Cocke-Jelinek-Raviv algorithm and adaptation to the non-stationary VLC trellis. Simulation results indicate that the proposed ISCD scheme allows to exchange between its constituent decoders the symbol-level extrinsic information and achieves high robustness against channel noises.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.13-30
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• 2019

This paper presents the recent improvements in the DeCART code for HTGR analysis. A new 190-group DeCART cross-section library based on ENDF/B-VII.0 was generated using the KAERI library processing system for HTGR. Two methods for the eigen-mode adjoint flux calculation were implemented. An azimuthal angle discretization method based on the Gaussian quadrature was implemented to reduce the error from the azimuthal angle discretization. A two-level parallelization using MPI and OpenMP was adopted for massive parallel computations. A quadratic depletion solver was implemented to reduce the error involved in the Gd depletion. A module to generate equivalent group constants was implemented for the nodal codes. The capabilities of the DeCART code were improved for geometry handling including an approximate treatment of a cylindrical outer boundary, an explicit border model, the R-G-B checker-board model, and a super-cell model for a hexagonal geometry. The newly improved and implemented functionalities were verified against various numerical benchmarks such as OECD/MHTGR-350 benchmark phase III problems, two-dimensional high temperature gas cooled reactor benchmark problems derived from the MHTGR-350 reference design, and numerical benchmark problems based on the compact nuclear power source experiment by comparing the DeCART solutions with the Monte-Carlo reference solutions obtained using the McCARD code.