• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3121-3131
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• 2014

Vulnerabilities related to memory have been known as major threats to the security of a computer system. Actually, the number of attacks using memory vulnerability has been increased. Accordingly, various memory protection mechanisms have been studied and implemented on operating system while new attack techniques bypassing the protection systems have been developed. Especially, buffer overflow attacks have been developed as Return-Oriented Programing(ROP) and Jump-Oriented Programming(JOP) called Code Re-used attack to bypass the memory protection mechanism. Thus, in this paper, I analyzed code re-use attack techniques emerged recently among attacks related to memory, as well as analyzed various detection mechanisms proposed previously. Based on the results of the analyses, a mechanism that could detect various code re-use attacks on a binary level was proposed. In addition, it was verified through experiments that the proposed mechanism could detect code re-use attacks effectively.

• Journal of Wetlands Research
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• v.15 no.1
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• pp.149-157
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• 2013

The weirs built so far are mainly overflow type weirs overflowing to the upstream. Main advantages of overflow type weirs are, effective water resources management and easy design, construction and maintenance due to many accumulated studies. However, due to the special feature of the overflow type weir where water overflows through the upstream of the weir, the silt coming from the upstream is not discharged to the downstream of the weir. This increases the river bed and reduces the reservoir capacity, and as a result, the weir loses its function. A underflow type weir with a water gate has been implemented in order to solve such sediment deposit and weir maintenance problems. However due to the design problem of recently constructed underflow type weirs, the river bed of the downstream of a weir has been scoured. And this leds to a structural problem. In this study, the flow characteristics of overflow type weirs and underflow type weir, hydraulic jump length analysis depending on change of water depth and the amount of specific energy loss generated per unit length depending on a weir type have been compared and analyzed, for the effective design and management of the weirs. The experiment results show that, when identical upstream conditions of underflow type weir and an overflow type weir were maintained, the hydraulic jump length was up to twice longer with Fr(Froude number) 3.5 of the hydraulic jump length at the underflow type weir, and the hydraulic jump length gradually decreased as the downstream water depth increased. The comparative analysis result of the amount of specific energy loss generated per unit length showed that the amount of energy loss per unit length was twice higher for an overlfow type weir than a underflow type weir. Therefore, in case of a underflow type facility, an additional energy reduction facility is determined to be necessary for safety of water construction structures.

• Proceedings of the IEEK Conference
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• 2001.06c
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• pp.63-66
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• 2001

In this paper, We propose the new interconnection network which is designed to edge numbering labeling using postorder traversal which can reduce diameter when it has same node number with Hypercube, which can reduce total node numbers considering node degree and diameter on Fibonacci trees and its jump sequence of circulant is Fibonacci numbers. It has a simple (shortest oath)routing algorithm, diameter, node degree. It has a spaning subtree which is Fibonacci tree and it is embedded to Fibonacci tree. It is compared with Hypercube. We improve diameter compared with Hypercube.

• Journal of the Korean Data and Information Science Society
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• v.18 no.3
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• pp.669-678
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• 2007

An algorithm to detect the number of discontinuity points of the variance function in regression model is proposed. The proposed algorithm is based on the left and right one-sided kernel estimators of the second moment function and test statistics of the existence of a discontinuity point coming from the asymptotic distribution of the estimated jump size. The finite sample performance is illustrated by simulated example.

• Journal of the Korean Mathematical Society
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• v.56 no.4
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• pp.935-946
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• 2019

Hawkes process is a self-exciting simple point process with clustering effect whose jump rate depends on its entire past history. We consider Hawkes processes with uniform immigrants which is a special case of the Hawkes processes with renewal immigrants. We study the limit theorems for Hawkes processes with uniform immigrants. In particular, we obtain a law of large number, a central limit theorem, and a large deviation principle.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.255-260
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• 2015

Flash evaporation phenomenon is affected by temperature, pressure and water level in the open chamber and Baffle etc. In this study, PIV experiments were conducted to ensured the flow Characteristics in the open chamber, and optimum baffle location and baffle height. Baffle had a considerable effect on the recirculation flow, hydraulic jump and the flow characteristics in the Open chamber, and influence of Reynolds number was insignificant. The optimum baffle height was about h/H=1.5. and optimum baffle location was x/H=1.5 from the inlet of open chamber.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.26 no.2
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• pp.108-120
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• 2022

We considered qualitative behaviour of the generalization of Einstein's model of Brownian motion when the key parameter of the time interval of free jump degenerates. Fluids will be characterised by number of particles per unit volume (density of fluid) at point of observation. Degeneration of the phenomenon manifests in two scenarios: a) flow of the fluid, which is highly dispersing like a non-dense gas and b) flow of fluid far away from the source of flow, when the velocity of the flow is incomparably smaller than the gradient of the density. First, we will show that both types of flows can be modeled using the Einstein paradigm. We will investigate the question: What features will particle flow exhibit if the time interval of the free jump is inverse proportional to the density and its gradient ? We will show that in this scenario, the flow exhibits localization property, namely: if at some moment of time t₀ in the region, the gradient of the density or density itself is equal to zero, then for some T during time interval [t₀, t₀ + T] there is no flow in the region. This directly links to Barenblatt's finite speed of propagation property for the degenerate equation. The method of the proof is very different from Barenblatt's method and based on the application of Ladyzhenskaya - De Giorgi iterative scheme and Vespri - Tedeev technique. From PDE point of view it assumed that solution exists in appropriate Sobolev type of space.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.5
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• pp.61-68
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• 1992

Knock phenomenon is an abnormal combustion originated from autoignition of unburned gas in the end-gas region during the later stage of combustion process and it accompanys a high pitched metallic noise. Engine Knock is accompanied with a vibration of engine cylinder and when it is severe, it can cause major engine demage. Engine Knock is characterized in terms of knock crank angle, knock pressure, pressure jump and knock intensity. In this study, a 4-cylinder spark ignition engine was used for experiment and eighty consecutive cycles were analyzed statistically. The purpose of this study is to characterize spark ignition engine knock as a function of ignition timing and fuel research octane number. The result of this study can be summerized as follows. Knock occurrence angle approached TDC as ignition timing is advanced. Pressure and knock intensity gradually increased as spark timing is advanced. Mean knock occurence angle gradually approached TDC as fuel research octane number is decreased for identical spark timing. Knock intensity increased linearly as RON is decreased.

• Journal of the Korean Data and Information Science Society
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• v.23 no.2
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• pp.309-315
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• 2012

The purpose of this study was to examine the comparison of physique with physical fitness according to TBS (Talented-Educational in Sport) program by H University in 2009-2011. For this study, 668 elementary students (2009: 297, 2010: 194, 2011: 177 or 1st: 506, 2nd: 104, 3rd: 58) were collected who aged 7 to 13 living in Seoul and Gyeonggi area. The subjects were measured on physique variables (5) and physical fitness variables (7). Mean comparisons (ANOVA) were conducted for each gender in order to compare the mean differences among attendance number. For association analysis, Pearson correlation coefficient was used to find association between the physique and physical fitness variables. Some physical fitness variables (sit up, half squat jump, side step, standing long jump, flexibility in male children; sit up, half squat jump, side step in female children) increased significantly in the attendance number but the physique variables did not. The results show that TES program was effective on the physical fitness variables (muscle endurance & agility) in sports talent children.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.178-181
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• 2011

Recently, micro shock tube is being extensively used in various fields of engineering applications. The flow characteristics occurring in the micro shock tube may be significantly different from that of conventional macro shock tube due to very low Reynolds number and Knudsen number effects which are, in general, manifested in such flows of rarefied gas, solid-gas two-phase, etc. In these situations, Navier-Stokes equations cannot properly predict the micro shock tube flow. In the present study, a two-dimensional CFD method has been applied to simulate the micro shock tube, with slip velocity and temperature jump boundary conditions. The effects of wall thermal conditions on the unsteady flow in the micro shock tube were also investigated. The unsteady behaviors of shock wave and contact discontinuity were, in detail, analyzed. The results obtained show much more attenuation of shock wave, compared with macro-shock tubes.