• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.2
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• pp.33-48
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• 2018

In this paper, we characterise the joint interference alignment and power allocation strategies for a K-user multicell multiple-input multiple-output (MIMO) Gaussian interference channel. We consider a MIMO interference channel with a blind interference alignment through staggered antenna switching on the receiver. We explore the power allocation and the feasibility condition for cooperative cell-edge (CE) mobile users (MUs) by assuming that the channel state information is unknown. The new insight behind the transmission strategy of the proposed scheme is premeditated (randomly generated transmission strategy) and partial cooperative CE MUs, where the transmitter is equipped with a conventional antenna, the receiver is equipped with a reconfigurable multimode antenna (staggered antenna switching pattern), and the receiver switches between preset T modes. Our proposed scheme assists and aligns the desired and interference signals to cancel the common interference signals, since the received signal must have a corresponding independent signal subspace. The sum capacity for a K-user multicell MIMO Gaussian interference channel with reconfigurable multimode antennas is completely characterised.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.10
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• pp.915-921
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• 2017

Recently, studies to reduce vibration and noise of automobiles have been actively conducted. However, previous studies did not concentrate on the optimization of the mount system with passive or active mounts. This study analytically studies an active mounting system with three active structural paths between source and receiver and the feasibility has been verified. Active mounting system has a coupled structure of piezoelectric stack actuators and passive mounts. A dynamic model of the whole system is prepared and the control force and phase of the stack actuators in each path are determined to target full isolation of each path. Its performance on vibration attenuation is investigated and based on it, optimized combinations of passive and active paths for the best attenuation are presented.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.1
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• pp.20-26
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• 2005

Ultrasonic guided waves have been widely employed for long range inspection of structures such as plates, rods and pipes. There are numerous modes with different wave velocities, and the appropriate mode selection is one of key techniques in the application of guided waves. In the present work, phase tuning by an array transducer was applied to generate ultrasonic guided waves. For this purpose, 8-channel ultrasonic pulser/receiver and their controller which enables sequential activation of each channels with given time delay were developed. Eight transducers were fabricated in order to generate guided waves by using an array transducer. The selective tuning of wave mode can be achieved by changing the interval between elements of an array transducer.

• Journal of KIISE
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• v.43 no.2
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• pp.212-221
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• 2016

Android apps suffer from intent vulnerabilities in that they abnormally stop execution when Android components such as, activity, service, and broadcast receiver, take malformed intents. This paper proposes a method to prevent intent vulnerabilities by allowing programmers to write a specification on intents that a component expects to have, and by checking intents against the specification in runtime. By declaring intent specifications, we can solve the problem that one may miss writing conditional statements, which check the validity of intents, or one may mix those statements with another regular code, so making it difficult to maintain them. We perform an experiment by applying the proposed method to 7 Android apps, and confirm that many of abnormal termination of the apps because of malformed intents can be avoided by the intent specification based runtime assertion.

• The Journal of the Acoustical Society of Korea
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• v.36 no.4
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• pp.238-246
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• 2017

High frequency ultrasound imaging typically suffers from low sensitivity due to the small aperture of high frequency transducers and shallow imaging depth due to the frequency-dependent attenuation of ultrasound. These limitations should be overcome to obtain high-frequency, high- resolution ultrasound images. One practical solution to the problems is a high-performance signal receiver capable of detecting a very small signal and amplifying the signal with minimal electronic noise addition. This paper reports a recently developed low-noise, wideband ultrasound receiver for high-frequency, high-resolution ultrasound imaging. The developed receiver has an amplification gain of up to 73 dB and a variable amplification gain range of 48 dB over an operating frequency of 80 MHz. Also, it has an amplification gain flatness of ${\pm}1dB$. Due to these high performances, the developed receiver has a signal-to-noise ratio of at least 8.4 dB and a contrast-to-noise ratio of at least 3.7 dB higher than commercial receivers.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.5
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• pp.1145-1157
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• 2012

Google Android employs a security model based on application permissions to control accesses to system resources and components of other applications from a potentially malicious program. But, this model has security vulnerabilities due to lack of user comprehension and excessive permission requests by 3rd party applications. Broadcast intent message is widely used as a primary means of communication among internal application components. However, this mechanism has also potential security problems because it has no security policy related with it. In this paper, we first present security breach scenarios caused by inappropriate use of application permissions and broadcast intent messages. We then analyze and compare usage patterns of application permissions and broadcast intent message for popular applications on Android market and malwares, respectively. The analysis results show that there exists a characteristic set for application permissions and broadcast intent receiver that are requested by typical malwares. Based on the results, we propose a scheme to detect applications that are suspected as malicious and notify the result to users at installation time.