• Spatial Information Research
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• v.20 no.1
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• pp.9-18
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• 2012

South Korea has many landslides caused by heavy rains during summer time recently and the landslides continue to cause damages in many places. These landslides occur repeatedly each year, and the frequency of landslides is expected to increase in the coming future due to dramatic global climate change. In Korea, 81.5% of the population is living in urban areas and about 1,055 million people are living in Seoul. In 2011, the landslide that occurred in Seocho-dong killed 18 people and about 9% of Seoul's area is under the same land conditions as Seocho-dong. Even the size of landslide occurred in a city is small, but it is more likely to cause a big disaster because of a greater population density in the city. So far, the effort has been made to identify landslide vulnerability and causes, but now, the new dem and arises for the prediction study about the areal extent of disaster area in case of landslides. In this study, the diffusion model of the landslide disaster area was established based on Cellular Automata(CA) to analyze the physical diffusion forms of landslide. This study compared the accuracy with the Seocho-dong landslide case, which occurred in July 2011, applying the SCIDDICA model and the CAESAR model. The SCIDDICA model involves the following variables, such as the movement rules and the topographical obstacles, and the CAESAR model is also applied to this process to simulate the changes of deposition and erosion.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.9
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• pp.854-864
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• 2016

The use of small drone platform has become a popular topic in these days but its application for SAR operation has been little known due to the burden of the payload implementation. Drone platforms are distinguished from the conventional UAV system by the increased vulnerability to the turbulences, control-errors and poor motion stability. Consequently, sophisticated motion compensation may be required to guarantee the successful acquisition of high quality SAR imagery. Extremely limited power and mass budgets may prevent the use of additional hardwares for motion compensation and the difficulty of SAR focusing is further aggravated. In this paper, we have carried out a feasibility study of mico-SAR drone operation. We present the image acquisition results from the preliminary flight tests and a quality assessment is followed on the experimental SAR images. The in-flight motion errors derived from the unique drone movements are investigated and attempts have been made to compensate for the geometrical and phase errors caused by motions against the nominal trajectory. Finally, the successful operation of drone SAR system is validated through the focussed SAR images taken over test sites.

• Journal of Korean Neurosurgical Society
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• v.54 no.2
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• pp.93-99
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• 2013

Objective : Neurologic complications during carotid artery stenting (CAS) are usually associated with distal embolic event. These embolic incident during CAS are highly associated with the carotid plaque instability. The current study was undertaken to identify the angiographic characteristics of carotid plaque vulnerability, which was represented as filling defect in the cerebral protection filters during CAS. Methods : A total of 107 patients underwent CAS with use of a distal protection filter. Angiographic carotid plaque surface morphology was classified as smooth, irregular, and ulcerated. To determine predictable factors of filling defect in the protection filters, 11 variables were retrospectively analyzed which might influence filling defect in the protection filters during CAS. Results : Filling defects during CAS were presented in the 33 cerebral protection filters. In multivariate analysis, angiographic ulceration [odds ratio (OR), 6.60; 95% confidence interval (CI) : 2.24, 19.4; p=0.001], higher stenosis degree (OR, 1.06; 95% CI : 1.00, 1.12; p=0.039), and coexistent thrombus (OR, 7.58; 95% CI : 1.69, 34.05; p=0.08) were highly associated with filling defect in the cerebral protection devices during CAS. Among several variables, angiographic surface ulceration was the only significant factor associated with flow stagnation during CAS (OR, 4.11; 95% CI : 1.33, 12.72; p=0.014). Conclusion : Plaque surface morphology on carotid angiography can be a highly sensitive marker of plaque instability during CAS. The independent risk factors for filling defect in the filter devices during CAS were plaque ulceration, stenosis degree, and coexistent thrombus.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.3
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• pp.257-268
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• 2018

We have studied the damage mechanism of a metallic thin plate by the highly energetic fragments generated from high explosive(HE) warhead. The penetration process has presumed that the velocity of a fragment is in the range of 350 m/s to 3353 m/s, the thickness of Aluminum 2024 target plate is in the range of 1 mm~6.3 mm thick. The mass of fragment with hemisphere nose shape is in the range of 0.32 g to 16 g. The analytical solution for penetration process has been derived by using the report of the project THOR. The results of analysis implied that the closed forms by an exponentially decay function well fit the change of the ballistic limit velocity, loss velocity and loss mass of fragment as the mass of fragment and the thickness of target plate increase.

• The KIPS Transactions:PartC
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• v.14C no.1 s.111
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• pp.27-38
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• 2007

IPv6 has appeared for solving the address exhaustion of IPv4 and for guaranteeing the problems of security and QoS. It occurs the unexpected new attacks of IPv6 as well as the existing attacks of IPv4 because of the increasing address space to 128bits and the address hierarchies for efficient network management and additions of the new messages between nodes and routers like neighbor discovery and auto address configuration for the various comfortable services. For the successful transition from IPv4 to IPv6, we should get the secure compatibility between IPv4 hosts or routers working based on secure and systematic policy and IPv6. Network manager should design security technologies for efficient management in IPv4/IPv6 co-existence network and IPv6 network and security management framework designation. In this paper, we inspected the characteristics of IPv4 and IPv6, study on security requirement for efficient security management of various attacks, protocol, service in IPv4/IPv6 co-existence and IPv6 network, and finally suggest integrated solution about security vulnerability of IPv6 network in considering of analysis of IPv6 system, host and application, IPv6 characteristics, modified CGA(MCGA).

• The KIPS Transactions:PartC
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• v.17C no.1
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• pp.1-14
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• 2010

IEEE 802.15.4[1] has been standardized for the physical layer and MAC layer of LR-PANs(Low Rate-Wireless Personal Area Networks) as a technology for operations with low power on sensor networks. The standardization is applied to the variety of applications in the shortrange wireless communication with limited output and performance, for example wireless sensor or virtual wire, but it includes vulnerabilities for various attacks because of the lack of security researches. In this paper, we analyze the vulnerabilities against the denial of sleep attacks on the MAC layer of IEEE 802.15.4, and propose a detection mechanism against it. In results, we analyzed the possibilities of denial of sleep attacks by the modification of superframe, the modification of CW(Contention Window), the process of channel scan or PAN association, and so on. Moreover, we comprehended that some of these attacks can mount even though the standardized security services such as encryption or authentication are performed. In addition to, we model for denial of sleep attacks by Beacon/Association Request messages, and propose a detection mechanism against them. This detection mechanism utilizes the management table consisting of the interval and node ID of request messages, and signal strength. In simulation results, we can show the effect of attacks, the detection possibility and performance superiorities of proposed mechanism.

• Korean Journal of Psychosomatic Medicine
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• v.15 no.1
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• pp.22-28
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• 2007

The pregnancy and postpartum period appear to be a time of heightened vulnerability for the development of major depression in some women. Postpartum depression affects 10% of women within a few weeks immediately postpartum. Postpartum depression is associated with disturbances in the mother-infant relationship, which in turn have an adverse impact on the course of child cognitive and emotional development. Depression during pregnancy is also common, although it has been relatively neglected. Psychopathological symptoms during pregnancy have physiological consequences for the fetus. Understanding the aetiology of perinatal depression requires integrating of multiple psychosocial and biological risk factors. The treatment of depressed pregnant women requires skilled decision making by psychiatrists. Risk-benefit analysis is appropriate method for intervention fur depression in pregnancy. Effective treatments for depression in pregnancy include psychotherapy, antidepressant medication and electroconvulsive therapy. In treatment of postpartum depression, the biological, psychological, and social interventions are included. Prescribing antidepressants(such as fluoxetine), estrogen in severe and chronic cases, and counselling can be effective for improving maternal mood and aspects of infant outcome. Ongoing research is directed to further elucidating neurohormonal and psychosocial contributions to depression during pregnancy or postpartum. Screening for risk factors and symptoms for depression need to be incorporated into antenatal and pediatric clinics.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.12
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• pp.904-912
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• 2019

We have studied the numerical analysis about the fragment ejection velocity and spray angle when the High Explosive warhead detonated at proximity distance at an aircraft. To study the physical quantities about the warhead components is very important to assessment the vulnerability of aircraft. Generally, the physical quantities about the components of a warhead such as the mass, length, diameter and charge to mass ratio are unknown. Therefore, it is required to estimate the physical quantities by using physical continuities of similar threats. The empirical formulas to understand the dependence among charge to mass ratio, length and diameter ratio were driven by using the physical parameters of similar threatening such as terrier, sparrow. As a result, we confirmed that the dead mass ratio was closed to 20% of warhead mass since the metal case of the proximity threat acts as a simple carrier. This implies that the effective length and diameter of High Explosive Compound is smaller than the length and diameter of warhead, and become a key to understand the large ejection gradient velocity and small spray angle of fragments within 6 degree.

• Journal of Internet Computing and Services
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• v.20 no.6
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• pp.105-117
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• 2019

Bitcoin, which can be classified as a cryptocurrency, has attracted attention from various industries because it is an innovative digital currency and the beginning of a Blockchain system. However, as the research on Bitcoin progressed, several security vulnerabilities and possible attacks were analyzed. Among them, the security problem caused by the transparency of the Blockchain database prevents the Blockchain system from being applied to various fields. This vulnerability is further classified as the weak anonymity of participating nodes and privacy problem due to disclosure of transaction details. In recent years, several countermeasures have been developed against these vulnerabilities. In this paper, we first describe the main features of the public and private Blockchain, and explain privacy, unlinkability and anonymity. And, three public Blockchain platforms, Dash, Zcash and Monero which are derived from Bitcoin, and Hyperledger Fabric which is a private Blockchain platform, are examined. And we analyze the operating principles of the protocols applied on each platform. In addition, we classify the applied technologies into anonymity and privacy protection in detail, analyze the advantages and disadvantages, and compare the features and relative performance of the platforms based on the computational speed of the applied cryptographic mechanisms.

• Journal of Broadcast Engineering
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• v.22 no.3
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• pp.350-365
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• 2017

Steganography is a technique for secret data communication, which is not perceived by third person between a receiver and a transmitter. It has been developed for thousands of years for the transmission of military, diplomatic or business information. The development of digital media and communication has led to the development of steganography techniques in modern times. Technic of image steganography include the LSB, which fixes the number of embedded bits into a pixel, and PVD, which exploits the difference value in the neighboring pixel pairs. In the case of PVD image steganography, a large amount of information is embedded fluidly by difference value in neighboring pixel pairs and the designed range table. However, since the secret information in order is embedded, if an error of the number of embedded bits occurs in a certain pixel pair, all subsequent information will be destroyed. In this paper, we proposes the method, which improve the vulnerability of PVD property about external attack or various noise and extract secret information. Experimental process is comparison analysis about stego-image, which embedded various noise. PVD shows that it is not possible to preserve secret information at all about noise, but it was possible to robustly extract secret information for partial noise of stego-image in case of the proposed PVD image steganography with locally-fixed number of embedding bits.