• Proceedings of the Korea Information Processing Society Conference
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• 2019.05a
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• pp.170-173
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• 2019

Windows는 UAC(User Account Control)를 통해 사용자의 동의를 얻은 프로세스에게만 관리자 권한을 부여한다. 관리자 권한을 부여받은 프로세스는 시스템 파일 변경, 환경 변수 변경 등 표준 권한을 가진 프로세스가 수행하지 못하는 작업을 수행할 수 있다. 일부 악성코드들은 사용자 동의 없이 관리자 권한을 획득하기 위해 UAC Bypass 기법을 이용한다. 그러나 UACMe에 공개된 56개의 UAC Bypass 기법 중 20개의 기법에 대한 보안 패치가 현재까지 이루어지지 않고 있다. 따라서 본 논문에서는 현재 Windows 시스템의 UAC Bypass에 대한 안전성 수준을 분석하기 위해 시스템 디렉터리 내부 82개의 프로그램을 대상으로 UAC Bypass가 가능한 DLL Hijacking 취약점을 분석한다. 또한 UAC Bypass에 악용 가능한 50개의 신규 취약점을 발견하고 악용 시나리오에 따른 공격가능성을 보인다.

• Journal of Microbiology and Biotechnology
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• v.21 no.7
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• pp.739-745
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• 2011

During the production of grape wine, the formation of thick leathery pellicle/bacterial cellulose (BC) at the airliquid interface was due to the bacterium, which was isolated and identified as Gluconacetobacter hansenii UAC09. Cultural conditions for bacterial cellulose production from G. hansenii UAC09 were optimized by central composite rotatable experimental design. To economize the BC production, coffee cherry husk (CCH) extract and corn steep liquor (CSL) were used as less expensive sources of carbon and nitrogen, respectively. CCH and CSL are byproducts from the coffee processing and starch processing industry, respectively. The interactions between pH (4.5-8.5), CSL (2-10%), alcohol (0.5-2%), acetic acid (0.5-2%), and water dilution rate to CCH ratio (1:1 to 1:5) were studied using response surface methodology. The optimum conditions for maximum BC production were pH (6.64), CSL (10%), alcohol (0.5%), acetic acid (1.13%), and water to CCH ratio (1:1). After 2 weeks of fermentation, the amount of BC produced was 6.24 g/l. This yield was comparable to the predicted value of 6.09 g/l. This is the first report on the optimization of the fermentation medium by RSM using CCH extract as the carbon source for BC production by G. hansenii UAC09.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.8
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• pp.1465-1471
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• 2007

The electro-magnetic wave propagates through the air in the terrestrial communications, but the acoustic wave propagates through the seawater in the underwater acoustic communication(UAC). It makes the differences between the UAC link and the well hon air communication links. In this paper, we have studied path loss, absorption and ambient noise of the ocean as a medium for UAC. We have analyzed the absorption coefficient and ambient noise level of the coastal area of South Korea and suggested a strategy for the selection of the frequency band by considering the absorption coefficient and ambient noise level. Also, we present an illustrative example of a link budget for the QPSK UAC system which has carrier frequency 25kHz, bit rate 10kbps, range 1km and BER $10^{-3}$ in the shallow water environment with an ideal AWGN assumption.

• Journal of information and communication convergence engineering
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• v.8 no.1
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• pp.6-12
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• 2010

In this paper a cross layer protocol, referred to as an underwater ad-hoc communication (UAC) protocol, is proposed for underwater acoustic networks (UANets). An underwater node (UN), which tries to transfer data to another UN or a buoy in ad-hoc manner, can access channel as well as determine routing path by employing the UAC protocol. The channel access, route determination, and reliable data transfer are designed being adaptive to underwater environments. In addition, we propose both UN and packet architectures in order to efficiently implement the UAC protocol for UANets.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.12
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• pp.2151-2156
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• 2006

Beamforming for underwater acoustic communication (UAC) is affected by the broadband feature of UAC signal, which has relatively low currier frequency as compared to the signal bandwidth. The narrow-band assumption does not hold good in UAC. In this paper, we discuss a broadband FIR beamformer for UAC using the baseband equivalent way signal model. We consider the broadband FIR beamformer for QPSK UAC with carrier frequency 25kHz and symbol rate 5kHz. Array geometry is a uniform linear way with 8 omni-directional elements and sensor spacing is the half of the carrier wavelength. The simulation results show that the broadband n beamformer achieves nearly optimum signal to interference and noise ratio (SINR) and outperforms the conventional narrowband beamformer by SINR 0.5dB when two-tap FIR filter is employed at each sensor and the inter-tap delay is a quarter of the symbol interval. The broadband FIR beamformer performance is more degraded as the FIR filter length is increased above a certain value. If the inter-tap delay is not greater than half of the symbol period, SINR performance does not depend on the inter-tap delay. More training period is required when the inter-tap delay is same as the symbol period.

• The Journal of the Acoustical Society of Korea
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• v.26 no.3E
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• pp.97-103
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• 2007

We propose a combined STBC (Space Time Block Coding) and AMC (Adaptive Modulation and Coding) in the underwater multipath communication channel. Performance of UAC (underwater acoustic communication) in shallow water is degraded by complicated multipath and reverberation. For this reason, and considering the variability of the ocean channel, we combined STBC and AMC techniques, which are the spatial diversity in a multi-sensor communication system. BER (Bit error rate) of combined STBC and AMC is improved by 5dB when we compare with the BER of a single sensor based system. The proposed system shows a 3dB improvement when we compare it with the BER of the single sensor based system applying the AMC technique only.

• Journal of the Korea Society for Simulation
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• v.25 no.3
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• pp.15-28
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• 2016

It is necessary to analyze underwater acoustics channel(UAC) modeling and simulation for underwater weapon system development and acquisition. In order to analyze UAC, there are underwater acoustics propagation numerical analysis models(Ray theory, Parabolic equation, Normal-mode, Wavenumber integration). However, If these models are used for multiple frequency signal analysis, they are inaccurate to calculate result of analysis effectiveness and restricted for signal processing and analysis. In this paper, to overcome this problem, we propose simple/multiple frequency signal analysis model of the Pseudospectral Time-Domain Method synthetic environment UAC applied to underwater environment noise model as like as realistic underwater environment. In order to confirm the validation of the model, we performed the 9 scenarios simulation(4 scenarios of single frequency signal, 4 scenarios of multiple frequency signal, 1 scenario of single/multiple frequency signal like submarine radiated noise) for validation and confirmed the validation of this model through the simulation model.

• The Journal of the Acoustical Society of Korea
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• v.33 no.1
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• pp.48-53
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• 2014

The underwater acoustic communication (UAC) is characterized by doubly spread channel. It is included in the time-variant doppler shift and delay-time spreads due to multiple paths. To compensate such distorted signals, various techniques including time-reversal processing, spatial diversity, phase estimator, and equalizer are being applied. In this paper, a spatial filter based on the beamforming is proposed as a method to mitigate such inter-symbol interferences that are generated in time-varying multipath channels. The proposed technique realizes coherent communications by steering the direction of the desired signals and improves the performance of UAC by increasing the signal-to-interference plus noise ratio using the array gain.

• The Korean Journal of Food And Nutrition
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• v.22 no.4
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• pp.479-484
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• 2009

This study investigated the characteristics of baking bread and cookies supplemented with taurine and the effect of taurine addition on BAC(blood alcohol concentrations) and UAC(urine alcohol concentrations). Healthy male college students were divided into two groups, the control and the taurine group. Bread was baked with the addition of 0, 2, 4 and 6% taurine and baked with the addition 0, 3 and 6% taurine. The bread containing 2% taurine showed the fastest fermentation among the 4 groups. Fermentation and oven-spring of breads baked with a taurine concentration greater than 4% of taurine disturbed. In some areas of the sensory test, the taurine supplemented bread had higher scores than the control bread. We served 6 g of taurine supplemented cookies with 1,000 $m{\ell}$ of beer to 8 students in the taurine group. After 2 hours of drinking beer, the BAC and UAC of the taurine group were found to be lower than the control group. But no difference was found in the alcohol excretion of their urine. From this study we concluded that the taurine has an effect on the detoxication of alcohol, which reduces the BAC.

• The KIPS Transactions:PartC
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• v.15C no.3
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• pp.141-148
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• 2008

Windows Vista published by Microsoft provides more powerful security mechanisms than previous Windows operating systems. In the forensics point of view, new security mechanisms make it more difficult to get data related to the criminals in a storage device. In this paper, we analyze BitLocker introduced as an new security mechanism in Windows Vista. Also, compared to the previous Windows operating systems, the changes and security issues of UAC and EFS in Windows Vista are discussed in the forensics point of view. Futhermore, we discuss other characteristics of Windows Vista useful for forensic examinations.