• Convergence Security Journal
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• v.14 no.4
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• pp.3-8
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• 2014

Wireless Ad hoc Network is threatened from many types of attacks because of its open structure, dynamic topology and the absence of infrastructure. Attacks by malicious nodes inside the network destroy communication path and discard packet. The damage is quite large and detecting attacks are difficult. In this paper, we proposed attack detection technique using secure authentication infrastructure for efficient detection and prevention of internal attack nodes. Cluster structure is used in the proposed method so that each nodes act as a certificate authority and the public key is issued in cluster head through trust evaluation of nodes. Symmetric Key is shared for integrity of data between the nodes and the structure which adds authentication message to the RREQ packet is used. ns-2 simulator is used to evaluate performance of proposed method and excellent performance can be performed through the experiment.

• Journal of Advanced Navigation Technology
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• v.22 no.5
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• pp.415-419
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• 2018

This paper predicts and measures the C/N ratio of a beacon signal transmitted from geostationary orbit satellite KorSat 5A ($113^{\circ}E$) at a ground station located in Kimpo. Based on the ground stations, we compared the rain attenuation of the zone K of ITU-R and the rain attenuation which analyzed the domestic weather information. In ITU-R, the Korean rainfall characteristics are classified into zone K, but forecasting the rainfall intensity and attenuation of three adjacent cities based on the cumulative rainfall data per minute from 2013 to 2017. The calculation of rainfall path and attenuation is based on ITU-R recommendations. The change of the C/N according to the rainfall amount was confirmed through the 2 week satellite beacon signal C/N measurement. The predicted critical C/N was decreased to 12 dB at $A_{0.3}$. During the experiment, it was confirmed that it decreased up to 8 dB according to the concentrated rainfall.

• The Journal of Korean Physical Therapy
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• v.20 no.2
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• pp.1-10
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• 2008

Purpose: This study examines the effects of elastic band of resistance exercise for balance control of the elderly. Methods: Thirty of eighty participants in experiment subjects who demonstrated balance-impairment through the use of primary screening tests including the one leg standing test (OLST), functional reach test (FRT) and timed up and go (TUG) were selected as subjects. Fifteen subjects that underwent muscle-strengthening exercise using an elastic band were selected as the exercise group and fifteen subjects were selected as a control group. Subjects undertook a home-based exercise program three times per week for 9 weeks. Muscle strength, functional assessment and a balance test were quantitatively measured before and after the exercise regimen. Results: After muscle strengthening exercises, changes in maximal voluntary isometric contraction (MVIC) showed a significant increase in all of the lower extremity muscles of the exercise group subjects. There were statistically significant differences between the exercise and control groups for changes in the OLST, FRT and TUG, which are functional assessments of balance ability, and changes of the unit path length and circumference area, measurement items of quantitative analysis. In addition, from examining correlations between MVIC, balance ability, it was found that an increase of muscle strength in the hip joint group of muscles among the lower extremity muscles had greater improvement in correlation with balance ability in this elderly population. Conclusion: Resistance exercise using elastic bands had significant effects on muscle strengthening in elderly subjects, with a resultant increase of lower extremity muscle strength with significant improvement of balance ability.

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.271-280
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• 2007

This paper presents the results of an experimental study to evaluate the redundancy in two plate-girder bridges, which are generally classified as non-redundant load path structures. The study was performed at a time when one of the two girders was damaged. The bottom lateral bracing was considered the experimental variable, and two 1/5-scale bridge specimens of simple span with and without a lateral bracing system were fabricated. Loading tests were first performed on the intact specimens without a cracked girder, within an elastic range. Thereafter, the ultimate loading tests were conducted on the damaged specimens with an induced crack at the center of a girder. The test results showed that the cross beams and the concrete deck redistributed some of the load to the uncracked girder, but the lateral bracing system played an important role in improving the redundancy during the damage and was also effective for load redistribution even when the bridge was intact.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.6
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• pp.297-301
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• 2006

In the present work, we investigate the characteristics of new composition material, chalcogenide $Ge_1Se_1Te_2$ material in order to overcome the problems of conventional PRAM devices. The Tc of $Ge_1Se_1Te_2$ bulk was measured $231.503^{\circ}C$ with DSC analysis. For static DC test mode, at low voltage, two different resistances are observed. depending on the crystalline state of the phase-change resistor. In the first sweep, the as-deposited amorphous $Ge_1Se_1Te_2$ showed very high resistance. However when it reached the threshold voltage(about 11.8 V), the electrical resistance of device was drastically reduced through the formation of an electrically conducting path. The phase transition between the low conductive amorphous state and the high conductive crystal]me state was caused by the set and reset pulses respectively which fed through electrical signal. Set pulse has 4.3 V. 200 ns. then sample resistance is $80\sim100{\Omega}$. Reset pulse has 8.6 V 80 ns, then the sample resistance is $50{\sim}100K{\Omega}$. For such high resistance ratio of $R_{reset}/R_{set}$, we can expect high sensing margin reading the recorded data. We have confirmed that phase change properties of $Ge_1Se_1Te_2$ materials are closely related with the structure through the experiment of self-heating layers.

• Journal of the Korean Society for Marine Environment & Energy
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• v.4 no.1
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• pp.38-46
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• 2001

To assess the oil-containment effectiveness of tandem oil fences placed in currents, the movement of oil droplets in the fore and aft region of the fences is investigated by experimental and numerical methods. The effect of the flexibility of the fence skirt of single fence on the fence effectiveness is also investigated. Laboratory experiment is conducted to trace the path of a spherical solid particle of equivalent density to an oil droplet which was released in a uniform stream ahead of a model oil fence. Depending upon the releasing position and the flow condition there, it was observed that the particle floated up to the free surface, collided with the fence, or escaped below the fence. By analyzing the droplet trajectories, a numerical method is developed to predict the region ahead of the fore fence where an oil droplet initiating its motion eventually escapes beneath the fence. The effect of the relative sizes of the drafts of the fore and aft fences, the fence separation, and the bottom depth of the sea bed on the effectiveness of tandem fences is investigated using the numerically obtained trajectories of oil droplets.

• IE interfaces
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• v.24 no.1
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• pp.1-7
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• 2011

The purpose of this research was to develop an integrated interface for the usability test of systems or products in the design process. It is capable of automatically creating GOMS models which can predict human task performances. It can generate GOMS models to be interacted with the prototype interfaces. It can also effectively manage various design information and various usability test results to be implemented into the new product and/or system design. Thus we can perform usability test for products or system prototypes more effectively and also reduce time and effort required for this test. For usability tests, we established an integrated interface based on GOMS model by the LabVIEW program. We constructed the system that the linkage to GOMS model is available. Using this integrated interface, the menu structure of mobile phone can be constructed easily. User can design a depth and a breath that he want. The size of button and the label of the button is changable. The path to the goal can be defined by the user. Using a designed menu structure, the experiment could be performed. The results of GOMS model and the actual time are presented. Besides, values of operators of GOMS model can be defined as the value that user wants. Using the integrated interface that we developed, the optimal menu structure deducted. The menu structure that user wants can be established easily. The optimal layout and button size can be decided by comparison of numerous menu structures. User can choose the method of usability test among GOMS model and empirical data. Using this integrated interface, the time and costs can be saved and the optimal menu structure can be found easily.

• The KIPS Transactions:PartA
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• v.9A no.2
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• pp.207-216
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• 2002

This paper present a design and implementation of a distributed audio, Video stream service framework based on CORBA for efficient processing and control of audio/video stream. We design software components which support processing, control and transmission of audio/video streams as distributed objects. For optimization of stream transmission performance, we separate the transmission path of control data and media data. Distributed objects are defined by IDL and implemented using JAVA. And device dependent facilities like media capturing, playing and communication channels are implemented using JMF (Java Media Framework) components. We show a connection establishment and control procedure of streams communication. And for evaluation, we implement a test system and experiment a system performance. Our experiments show that test system has somewhat longer connection latency time compared to TCP connection establishment, but has optimized media transmission time compared to CORBA IIOP. Also test system show acceptable service quality of media transmission.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.2
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• pp.136-141
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• 2021

Heating cables, widely used in office buildings, factories, streets and railways, deteriorate in electrical insulation during operation. The insulation deterioration of heating cables leads to electric discharges that can cause electrical fires. With this background, this paper dealt with a condition monitoring technique for heating cables by the analysis of discharge signals to prevent electrical fires. Insulation deterioration was simulated using an arc generator specified in UL1699 under AC operation, and the characteristic and propagation of discharge signals were analyzed on a 100 meter-long heating cable. Discharge signals produced by insulation deterioration were detected as a voltage pulse because they are as small as a few mV and they are attenuated through propagation path. The frequency spectrum of discharge signals mainly existed in the range from 70 kHz to 110 kHz, and the maximum attenuation of the signal was 84.8% at 100 meters away from the discharge point. Based on the experimental results, a monitoring device, which is composed of a high pass filter with the cut-off frequency of 70 kHz, a comparator, a wave shaper and a microprocessor, was designed and fabricated. Also, an algorithm was designed to discriminate the discharge signal in the presence of noise, compared with the pulse repetition period and the number of pulse counts per 100ms. In the experiment, the result showed that the prototype monitoring device could detect and discriminate the discharge signals produced at every discharge point on a heating cable.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.2
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• pp.201-211
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• 2022

According to the recent change in the cybersecurity paradigm, research on anomaly detection methods using machine learning and deep learning techniques, which are AI implementation technologies, is increasing. In this study, a comparative study on data preprocessing techniques that can improve the anomaly detection performance of a GRU (Gated Recurrent Unit) neural network-based intrusion detection model using NGIDS-DS (Next Generation IDS Dataset), an open dataset, was conducted. In addition, in order to solve the class imbalance problem according to the ratio of normal data and attack data, the detection performance according to the oversampling ratio was compared and analyzed using the oversampling technique applied with DCGAN (Deep Convolutional Generative Adversarial Networks). As a result of the experiment, the method preprocessed using the Doc2Vec algorithm for system call feature and process execution path feature showed good performance, and in the case of oversampling performance, when DCGAN was used, improved detection performance was shown.