• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.3
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• pp.493-501
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• 2020

For the obfuscation of Flow Analysis on the Android operating system, the size of the Flow Graph can be large enough to make analysis difficult. To this end, a library in the form of aar was implemented so that it could be inserted into the application in the form of an external library. The library is designed to have up to five child nodes from the entry point in the dummy code, and for each depth has 2n+1 numbers of methods from 100 to 900 for each node, so it consists of a total of 2,500 entry points. In addition, entry points consist of a total of 150 views in XML, each of which is connected via asynchronous interface. Thus, the process of creating a Inter-procedural Control Flow Graph has a maximum of 14,175E+11 additional cases. As a result of applying this to application, the Inter Procedure Control Flow Analysis too generates an average of 10,931 edges and 3,015 nodes with an average graph size increase of 36.64%. In addition, in the APK analyzing process showed that up to average 76.33MB of overhead, but only 0.88MB of execution overhead in the user's ART environment.

• Journal of Yeungnam Medical Science
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• v.39 no.4
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• pp.344-346
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• 2022

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly spread worldwide, leading the World Health Organization to declare coronavirus disease 2019 (COVID-19) a pandemic. To curb the unchecked spread of SARS-CoV-2 infection, most countries have enforced travel restrictions. However, it is debatable whether such restrictions are effective in containing infections and preventing pandemics. Rather, they may negatively impact economies and diplomatic relationships. Each government should conduct an extensive and appropriate analysis of its national economy, diplomatic status, and COVID-19 preparedness to decide whether it is best to restrict entering travelers. Even if travelers from other countries are allowed entry, extensive contact tracing is required to prevent the spread of COVID-19. In addition, governments can implement "travel bubbles," which allow the quarantine-free flow of people among countries with relatively low levels of community transmission. An accurate evaluation of the benefits and losses due to entry restrictions during the COVID-19 pandemic would be helpful in determining whether entry restrictions are an effective measure to reduce the spread of infection in future pandemics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.53-54
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• 2006

• Journal of Internet Computing and Services
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• v.22 no.2
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• pp.11-17
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• 2021

Software-defined networking provides a programmable and flexible way to manage the network by separating the control plane from data plane. However, the limited switch memory restricts the number of flow entries in the flow table used to forward packets. This leads to flow table overflow and flow entry reinstallation, which severely degrade the network performance. Therefore, this paper proposes a comprehensive policy for timely eviction of inactive flow entries to optimally maintain flow tables usage. In particular, statistics of user datagram protocol flow entries are periodically sampled to enable the inactive entries to be evicted early. Through traffic-based experiments, we found that the proposed system reduces the number of overflow occurrences and flow entries reinstallation compared to the random and FIFO policies.

• Journal of Ocean Engineering and Technology
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• v.25 no.4
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• pp.36-41
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• 2011

In the present paper, a direct forcing/fictitious domain (DF/FD) level set method is proposed to simulate the FSI (fluid-solid interaction) in two-phase flow. The main idea is to combine the direct-forcing/fictitious domain (DF/FD) method with the level set method in the Cartesian coordinates. The DF/FD method is a non-Lagrange-multiplier version of a distributed Lagrange multiplier/fictitious domain (DLM/FD) method. This method does not sacrifice the accuracy and robustness by employing a discrete ${\delta}$ (Dirac delta) function to transfer quantities between the Eulerian nodes and Lagrangian points explicitly as the immersed boundary method. The advantages of this approach are the simple concept, easy implementation, and utilization of the original governing equation without modification. Simulations of various water-entry problems have been conducted to validate the capability and accuracy of the present method in solving the FSI in two-phase flow. Consequently, the present results are found to be in good agreement with those of previous studies.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.115-118
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• 2008

Many theoretical and experimental studies have been conducted to investigate elements of the hydrodynamic process, such as variations in liquid film thickness or air core diameter. From these studies, some theoretical relationships have been established through an approximated analytical solution of flow hydrodynamics in a swirl nozzle. However, experimental studies on elements such as internal flow have not produced conclusive results. In this study, the variations and stability of the internal flow were examined by visualizing the air core and measuring the liquid film thickness.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.725-730
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• 1987

An experimental study of the air flow through inlet pipe of reciprocating two-cycle engine was investigated under motored condition. Measurements of the two components of velocity, velocity fluctuation, and the other behavior of inlet flow have been obtained by laser Doppler anemometer system. The research engine comprised the cylinder head of a two-cycle engine which mounted on optical spacer with measuring window and glass inlet entry for laser anemometer measurement. A dual beam laser Doppler anemometer was used with conventional forward scattered method and comprised argon-ion laser, frequency shifter with Bragg cell module, and the signal processor. Measurements of mean velocity fluctuation of inlet flow for different engine speeds, measuring positions, and the changes in cylinder volume are investigated. The results presented show that the changes in engine speed is shown to be strongly influenced on the mean velocity of inlet air. The effect of measuring position and cylinder volume on the inlet velocity was also investigated for the inlet port entry and is shown to be small compared to the engine speed.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.190-201
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• 1998

The numerical methodology for computing the impact forces of the water entry bodies has been developed. The present method assumed the impact occurs within a very short time interval and the viscous effects do not have time enough to play a significant role in the impact forces, that is, the flow around a water-entry object was assumed as an inviscid potential flow and is solved by the source panel method. The elements fully submerged into the water are routinely treated, but the elements intersected with the effective planar free surface are redefined and reorganized to be amendable to the source panel method. To validate the present code, it has been applied to disk and ogive model and compared with experimental data. Good agreement has been obtained.

• Advances in aircraft and spacecraft science
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• v.2 no.2
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• pp.109-124
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• 2015

This paper deals with the aerodynamic and aerothermodynamic trade-off analysis of a hypersonic flying test bed. Such vehicle will have to be launched with an expendable launcher and shall re-enter the Earth atmosphere allowing to perform several experiments on critical re-entry phenomena. The demonstrator under study is a re-entry space glider characterized by a relatively simple vehicle architecture able to validate hypersonic aerothermodynamic design database and passenger experiments, including thermal shield and hot structures. A summary review of the aerodynamic characteristics of two flying test bed concepts, compliant with a phase-A design level, has been provided hereinafter. Several design results, based both on engineering approach and computational fluid dynamics, are reported and discussed in the paper.

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.78.2-78.2
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• 2008