• 한국컴퓨터정보학회논문지
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• 제26권6호
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• pp.9-17
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• 2021

본 논문에서는 기존 네트워크의 물리적인 구조 및 구성을 변경하지 않고 네트워크 보안을 도입할 수 있는 방안으로 "Man In The Middle Attack" 공격 기법을 역이용함으로, Single Ethernet Interface만으로 가상 네트워크 오버레이를 형성하여 논리적인 In-line Mode를 구현하여 외부의 공격으로부터 네트워크를 보호하는 초소형 네트워크 보안 센서와 클라우드서비스를 통한 통합관제 방안을 제안한다. 실험 결과, Single Ethernet Interface만으로 가상 네트워크 오버레이를 형성하여 논리적인 In-line Mode를 구현할 수 있었으며, Network IDS/IPS, Anti-Virus, Network Access Control, Firewall 등을 구현할 수 있었고, 초소형 네트워크보안센서를 클라우드서비스에서 통합관제하는 것이 가능했다. 본 논문의 제안시스템으로 저비용으로 고성능의 네트워크 보안을 기대하는 중소기업에 도움이 되고 또한, IoT 및 Embedded System 분야에 안전·신뢰성을 갖춘 네트워크 보안환경을 제공할 수 있다.

• Smart Structures and Systems
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• 제23권6호
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• pp.653-667
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• 2019

Using cross-ties to connect cables together when forming a cable network is regarded as an efficient method of mitigating cable vibrations. Cross-ties have been extended and fixed on bridge decks or towers in some engineering applications. However, the dynamics of this kind of system need to be further studied, and the effects of extending cross-links to bridge decks/towers on the modal response of the system should be assessed in detail. In this paper, a system of two cables connected by an inter-supported cross-link with another lower cross-link extended to the ground is proposed and analyzed. The characteristic equation of the system is derived, and some limiting solutions in closed form of the system are derived. Roots of cable system with special configurations are also discussed, attention being given to the case when the two cables are identical. A predictable mode behavior was found when the stiffness of inter-connection cross-link and the cross-link extended to the ground were the same. The vector of mode energy distribution and the degree of mode localization index are proposed so as to distinguish global and local modes. The change of mode behaviors is further discussed in the case when the two cables are not identical. Effects of cross-link stiffness, cross-link location, mass-tension ratio, cable length ratio and frequency ratio on $1^{st}$ mode frequency and mode shape are addressed.

• 생물정신의학
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• 제24권2호
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• pp.68-74
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• 2017

Objectives It is well known that problem drinking is associated with alterations of brain structures and functions. Brain functions related to alcohol consumption can be determined by the resting state functional connectivity in various resting state networks (RSNs). This study aims to ascertain the alcohol effect on the structures forming predetermined RSNs by assessing their cortical thickness. Methods Twenty-six abstinent male patients with alcohol dependence and the same number of age-matched healthy control were recruited from an inpatient mental hospital and community. All participants underwent a 3T MRI scan. Averaged cortical thickness of areas constituting 7 RSNs were determined by using FreeSurfer with Yeo atlas derived from cortical parcellation estimated by intrinsic functional connectivity. Results There were significant group differences of mean cortical thicknesses (Cohen's d, corrected p) in ventral attention (1.01, < 0.01), dorsal attention (0.93, 0.01), somatomotor (0.90, 0.01), and visual (0.88, 0.02) networks. We could not find significant group differences in the default mode network. There were also significant group differences of gray matter volumes corrected by head size across the all networks. However, there were no group differences of surface area in each network. Conclusions There are differences in degree and pattern of structural recovery after abstinence across areas forming RSNs. Considering the previous observation that group differences of functional connectivity were significant only in networks related to task-positive networks such as dorsal attention and cognitive control networks, we can explain recovery pattern of cognition and emotion related to the default mode network and the mechanisms for craving and relapse associated with task-positive networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권3호
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• pp.958-979
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• 2023

Due to laws, regulations, privacy, etc., between 70-90 percent of providers do not share medical data, forming a "data island". It is essential to collaborate across multiple institutions without sharing patient data. Most existing methods adopt distributed learning and centralized federal architecture to solve this problem, but there are problems of resource heterogeneity and data heterogeneity in the practical application process. This paper proposes a collaborative deep learning modelling method based on the blockchain network. The training process uses encryption parameters to replace the original remote source data transmission to protect privacy. Hyperledger Fabric blockchain is adopted to realize that the parties are not restricted by the third-party authoritative verification end. To a certain extent, the distrust and single point of failure caused by the centralized system are avoided. The aggregation algorithm uses the FedProx algorithm to solve the problem of device heterogeneity and data heterogeneity. The experiments show that the maximum improvement of segmentation accuracy in the collaborative training mode proposed in this paper is 11.179% compared to local training. In the sequential training mode, the average accuracy improvement is greater than 7%. In the parallel training mode, the average accuracy improvement is greater than 8%. The experimental results show that the model proposed in this paper can solve the current problem of centralized modelling of multicenter data. In particular, it provides ideas to solve privacy protection and break "data silos", and protects all data.

• Smart Structures and Systems
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• 제12권3_4호
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• pp.345-361
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• 2013

Locating and assessing the severity of damage in large or complex structures is one of the most challenging problems in the field of civil engineering. Considering that the wavelet packet transform (WPT) has the ability to clearly reflect the damage characteristics of structural response signals and the artificial neural network (ANN) is capable of learning in an unsupervised manner and of forming new classes when the structural exhibits change, this paper investigates a multi-stage structural damage diagnosis method by using the WPT and ANN based on "energy-damage" theory, in which, the wavelet packet component energies are first extracted to be damage sensitive feature and then adopted as input into an improved back propagation (BP) neural network model for damage diagnosis in a step by step mode. To validate the efficacy of the presented approach of the damage diagnosis, the benchmark structure of the American Society of Civil Engineers (ASCE) is employed in the case study. The results of damage diagnosis indicate that the method herein is computationally efficient and is able to detect the existence of different damage patterns in the simulated experiment where minor, moderate and severe damages corresponds to involving in the loss of stiffness on braces or the removal bracing in various combinations.

• 천문학회보
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• 제42권1호
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• pp.46.1-46.1
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• 2017

Class I methanol masers are found to be good tracers of the interaction between outflows from massive young stellar objects with their surrounding media. Although polarization observations of Class II methanol masers have been able to provide information about magnetic fi elds close to the central (proto)stars, polarization observations of Class I methanol masers are rare, especially at 44 and 95GHz. We present the results of linear polarization observations of 39 Class I methanol maser sources at 44 and 95GHz. These two lines are observed simultaneously with one of the 21m Korean VLBI Network telescopes in single-dish mode. Approximately 60% of the observed sources have fractional polarizations of a few percent in at least one transition. This is the fi rst reported detection of linear polarization of the 44GHz methanol maser. We also observed 7 targets with the KVN in VLBI mode. We will present its preliminary results, too.

• Geomechanics and Engineering
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• 제30권3호
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• pp.281-291
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• 2022

Complex rock masses include various joint planes, bedding planes and other weak structural planes. The existence of these structural planes affects the mechanical properties, deformation rules and failure modes of jointed rock masses. To study the influence of the parameters of a nonpersistent joint network on the mechanical properties and failure modes of jointed rock masses, synthetic rock mass (SRM) technology based on discrete elements is introduced. The results show that as the size of the joints in the rock mass increases, the compressive strength and the discreteness of the rock mass first increase and then decrease. Among them, the joints that are characterized by "small but many" joints and "large and clustered" joints have the most significant impact on the strength of the rock mass. With the increase in joint density in the rock mass, the compressive strength of rock mass decreases monotonically, but the rate of decrease gradually decreases. With the increase in the joint dip angle in rock mass, the strength of the rock mass first decreases and then increases, forming a U-shaped change rule. In the analysis of the failure mode and deformation of a jointed rock mass, the type of plastic zone formed after rock mass failure is closely related to the macroscopic displacement deformation of the rock mass and the parameters of the joints, which generally shows that the location and density of the joints greatly affect the failure mode and displacement degree of the jointed rock mass. The instability mechanism of jointed surrounding rock is revealed.

• 융합신호처리학회논문지
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• 제14권1호
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• pp.39-44
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• 2013

본 논문에서는 멀티암(multi-arm) 스파이럴 안테나용 디지털 위상천이기(digital phase-shifter)를 힐버트 변환(Hillbert transform)을 이용하여 설계하였다. 힐버트 변환은 입력신호에 포함된 모든 주파수 성분을 $90^{\circ}$ 위상천이 시키며, 퓨리에 변환(Fourier transform)과 역퓨리에 변환(Inverse FIT)을 통해 구현된다. 디지털 위상천이기는 ADC(Analog-digital converter)로 샘플링된 입력신호에 힐버트 변환을 적용하여 위상차가 $90^{\circ}$인 두 신호를 생성하고, 이 두 신호를 이용하여 입력신호의 위상을 천이위상만큼 천이시키게 한다. 힐버트 변환 기반의 디지털 위상천이기는 Xilinx사의 System generator로 설계되었고, 입력 잡음, FFT 포인트 수, 샘플링 주기, 입력신호의 초기위상 및 천이 위상각 등에 따른 위상천이 성능을 시뮬레이션 하였으며, Matlab 결과와 비교하여 일치함을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제7권5호
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• pp.331-334
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• 1986

The crystal structure of thiamin tetrahydrofurfuryl disulfide, one of the ring-opened derivatives of thiamin, has been determined by the X-ray diffraction methods. The crystal is monoclinic with cell dimensions of a = 8.704 (1), b = 11.207 (2), c = 21.260 (3) ${\AA}$ and ${\beta}$ = 92.44 (2)$^{circ}$, space group P2$_{1}$/c and Z = 4. The structure was solved by direct methods and refined to R = 0.076 for 1252 observed reflections measured on a diffractometer. The molecule assumes a folded conformation in which the pyrimidine and the tetrahydrofurfuryl rings are on the same side of the ethylenic plane. The pyrimidinyl, N-formyl and ethylenic planes are mutually perpendicular to each other and the N(3)-C(4) bond retains a single bond character. The structure is stabilized by an intramolecular N(4'${\alpha})-H{\cdots}O(2{\alpha}$) hydrogen bond. The molecules are connected via N(4'${\alpha}$)-H{\cdots}(N3')$ and O(5${\gamma})-H{\cdots}(N1')$ hydrogen bonds, forming a two-dimensional hydrogen-bonding network. The tetrahydrofurfuryl ring is dynamically disordered. The overall conformation as well as the packing mode is very similar to that of thiamin propyl disulfide.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2005년도 ISMP
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• pp.201-212
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• 2005

[ $Epoxy/BaTiO_3$ ] composite embedded capacitor films (ECFs) were newly designed fur high dielectric constant and low tolerance (less than ${\pm}15\%$) embedded capacitor fabrication for organic substrates. In terms of material formulation, ECFs are composed of specially formulated epoxy resin and latent curing agent, and in terms of coating process, a comma roll coating method is used for uniform film thickness in large area. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ composite ECF is measured with MIM capacitor at 100 kHz using LCR meter. Dielectric constant of $BaTiO_3$ ECF is bigger than that of $SrTiO_3$ ECF, and it is due to difference of permittivity of $BaTiO_3\;and\;SrTiO_3$ particles. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ ECF in high frequency range $(0.5\~10GHz)$ is measured using cavity resonance method. In order to estimate dielectric constant, the reflection coefficient is measured with a network analyzer. Dielectric constant is calculated by observing the frequencies of the resonant cavity modes. About both powders, calculated dielectric constants in this frequency range are about 3/4 of the dielectric constants at 1 MHz. This difference is due to the decrease of the dielectric constant of epoxy matrix. For $BaTiO_3$ ECF, there is the dielectric relaxation at $5\~9GHz$. It is due to changing of polarization mode of $BaTiO_3$ powder. In the case of $SrTiO_3$ ECF, there is no relaxation up to 10GHz. Alternative material for embedded capacitor fabrication is $epoxy/BaTiO_3$ composite embedded capacitor paste (ECP). It uses similar materials formulation like ECF and a screen printing method for film coating. The screen printing method has the advantage of forming capacitor partially in desired part. But the screen printing makes surface irregularity during mask peel-off, Surface flatness is significantly improved by adding some additives and by applying pressure during curing. As a result, dielectric layer with improved thickness uniformity is successfully demonstrated. Using $epoxy/BaTiO_3$ composite ECP, dielectric constant of 63 and specific capacitance of 5.1nF/cm2 were achieved.