• 한국정보통신학회논문지
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• 제25권8호
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• pp.1019-1025
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• 2021

경력단절여성들의 재취업을 위한 교육 훈련 등의 지원정책이 이루어지고 있으나, 효과적으로 취업과 연계되지 않고 있다. 또한, 고학력 경력단절여성의 경우에는 재취업을 위하여 이전 경력을 수정하거나 새로운 경력을 계획해야 하는 등 재진입이 어려운 상황이다. 기존 선행연구들에서는 취업기회가 높은 유망 직종 등 재취업을 위한 근본적인 문제를 해결하기 위한 연구가 부족하였다. 따라서 경력단절여성들을 위한 교육과정 개발 시 교육 대상자의 연령 및 학력별로 취업에 도움이 되는 교육직종을 선별할 필요성이 있다. 본 연구는 경력단절여성들의 직업훈련 교육 데이터를 활용하여 연령 및 학력별로 취업률이 높은 교육직종을 분석하였다.

• 시스템엔지니어링학술지
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• 제14권2호
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• pp.73-82
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• 2018

In this work, a hardware based cryptographic module for the cyber security of nuclear power plant is developed using a system engineering approach. Nuclear power plants are isolated from the Internet, but as shown in the case of Iran, Man-in-the-middle attacks (MITM) could be a threat to the safety of the nuclear facilities. This FPGA-based module does not have an operating system and it provides protection as a firewall and mitigates the cyber threats. The encryption equipment consists of an encryption module, a decryption module, and interfaces for communication between modules and systems. The Advanced Encryption Standard (AES)-128, which is formally approved as top level by U.S. National Security Agency for cryptographic algorithms, is adopted. The development of the cyber security module is implemented in two main phases: reverse engineering and re-engineering. In the reverse engineering phase, the cyber security plan and system requirements are analyzed, and the AES algorithm is decomposed into functional units. In the re-engineering phase, we model the logical architecture using Vitech CORE9 software and simulate it with the Enhanced Functional Flow Block Diagram (EFFBD), which confirms the performance improvements of the hardware-based cryptographic module as compared to software based cryptography. Following this, the Hardware description language (HDL) code is developed and tested to verify the integrity of the code. Then, the developed code is implemented on the FPGA and connected to the personal computer through Recommended Standard (RS)-232 communication to perform validation of the developed component. For the future work, the developed FPGA based encryption equipment will be verified and validated in its expected operating environment by connecting it to the Advanced power reactor (APR)-1400 simulator.

• 한국항공우주학회지
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• 제48권5호
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• pp.323-334
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• 2020

경계층 천이는 극초음속 비행체의 열공력 성능에 직접적인 영향을 미치기 때문에, 성능 해석과 설계를 위해 천이지점의 정확한 예측 능력이 필수적으로 요구된다. 본 연구에서는 극초음속 경계층 천이 예측을 위한 γ-Re_θt 모델을 개선하고 검증하였다. 천이 시작 위치 결정에 영향을 주는 간헐도 수송방정식 생성항의 계수를 압축성 경계층 상사해를 기반으로 마하수와 벽면온도, 자유류 정체온도 등에 대한 함수 형태로 구성하고 적용하였다. 기본 모델의 Re_θc와 F_length 상관관계식에 마하수에 따른 천이 시작 운동량두께 레이놀즈수와 천이구간의 길이 변화를 반영할 수 있도록 마하수에 대한 관계식을 추가로 결정하여 적용하였다. 실용적인 사용을 고려하여 제안 모델을 상용 CFD 코드에 적용하였으며, 검증을 위해 모델을 사용하여 극초음속 평판과 원뿔 경계층 해석을 수행하였다. 실험 결과와의 비교를 통해 마하수와 단위 레이놀즈수 변화에 대한 개선된 예측성능을 확인하였다.

• 한국정보통신학회논문지
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• 제21권10호
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• pp.1999-2007
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• 2017

본 논문에서는, 해상에서 가용한 LTE, 초단파(VHF), 단파(HF) 통신 서비스 중에서 네트워크 환경에 따라서 최적의 통신 대역을 결정하는 멀티대역 네트워크 선택기 (MNS: Multi-band Network Selection) 시스템을 리눅스 기반의 소프트웨어로 구현한다. 구현된 소프트웨어는 네트워크 인터페이스, MNS 서버, 사용자 GUI로 구성된다. 2조의 MNS 시스템을 구축하여 구현된 MNS 시스템의 기능을 실내 시험을 통하여 검증한다. 이를 위하여, ITU-R M.1842-1 Annex1과 Annex4를 각각 준수하는 2종의 VHF 통신 링크는 소프트웨어적으로 에뮬레이션하고, HF 통신은 한 MNS 시스템의 송신(수신)을 다른 MNS의 수신(송신)에 직접 연결하여 실내 기능 검증이 가능하도록 한다. LTE, 초단파, 단파 각 통신 링크의 인위적인 단절 또는 재연결에 따른 구현된 MNS의 단절 없는 해상 통신 서비스 기능을 검증한다. 구현된 MNS 시스템은 e-navigation 등과 같은 다양한 해상 통신 서비스에 활용 가능하다.

• Wind and Structures
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• 제14권5호
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• pp.465-480
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• 2011

In this paper, a stabilized large eddy simulation technique is developed to predict turbulent flow with high Reynolds number. Streamline Upwind Petrov-Galerkin (SUPG) stabilized method and three-step technique are both implemented for the finite element formulation of Smagorinsky sub-grid scale (SGS) model. Temporal discretization is performed using three-step technique with viscous term treated implicitly. And the pressure is computed from Poisson equation derived from the incompressible condition. Then two numerical examples of turbulent flow with high Reynolds number are discussed. One is lid driven flow at Re = $10^5$ in a triangular cavity, the other is turbulent flow past a square cylinder at Re = 22000. Results show that the present technique can effectively suppress the instabilities of turbulent flow caused by traditional FEM and well predict the unsteady flow even with coarse mesh.

• Communications for Statistical Applications and Methods
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• 제22권6호
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• pp.575-587
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• 2015

The development in data collection techniques results in high dimensional data sets, where discrimination is an important and commonly encountered problem that are crucial to resolve when high dimensional data is heterogeneous (non-common variance covariance structure for classes). An example of this is to classify microbial habitat preferences based on codon/bi-codon usage. Habitat preference is important to study for evolutionary genetic relationships and may help industry produce specific enzymes. Most classification procedures assume homogeneity (common variance covariance structure for all classes), which is not guaranteed in most high dimensional data sets. We have introduced regularized elimination in partial least square coupled with QDA (rePLS-QDA) for the parsimonious variable selection and classification of high dimensional heterogeneous data sets based on recently introduced regularized elimination for variable selection in partial least square (rePLS) and heterogeneous classification procedure quadratic discriminant analysis (QDA). A comparison of proposed and existing methods is conducted over the simulated data set; in addition, the proposed procedure is implemented to classify microbial habitat preferences by their codon/bi-codon usage. Five bacterial habitats (Aquatic, Host Associated, Multiple, Specialized and Terrestrial) are modeled. The classification accuracy of each habitat is satisfactory and ranges from 89.1% to 100% on test data. Interesting codon/bi-codons usage, their mutual interactions influential for respective habitat preference are identified. The proposed method also produced results that concurred with known biological characteristics that will help researchers better understand divergence of species.

• Earthquakes and Structures
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• 제10권2호
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• pp.409-428
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• 2016

To realise the full benefits of a self-centering seismic resilient system, the designer must ensure that the entire structure does indeed re-center following an earthquake. The idealised flag-shaped hysteresis response that is often used to define the cyclic behaviour of self-centering concrete systems seldom exists and the residual drift of a building subjected to an earthquake is dependent on the realistic cyclic hysteresis response as well as the dynamic loading history. Current methods that are used to ensure that re-centering is achieved during the design of self-centering concrete systems are presented, and a series of cyclic analyses are used to demonstrate the flaws in these current procedures, even when idealised hysteresis models were used. Furthermore, results are presented for 350 time-history analyses that were performed to investigate the expected residual drift of an example self-centering concrete wall system during an earthquake. Based upon the results of these time-history analyses it was concluded that due to dynamic shake-down the residual drifts at the conclusion of the ground motion were significantly less than the maximum possible residual drifts that were observed from the cyclic hysteresis response, and were below acceptable residual drift performance limits established for seismic resilient structures. To estimate the effect of the dynamic shakedown, a residual drift ratio was defined that can be implemented during the design process to ensure that residual drift performance targets are achieved for self-centering concrete wall systems.

• 대한의용생체공학회:의공학회지
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• 제30권4호
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• pp.279-287
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• 2009

Magnetic resonance electrical impedance tomography (MREIT) is a new medical imaging modality providing cross-sectional images of a conductivity distribution inside an electrically conducting object. MREIT has rapidly progressed in its theory, algorithm and experimental technique and now reached the stage of in vivo animal and human experiments. Conductivity image reconstructions in MREIT require various steps of carefully implemented numerical computations. To facilitate MREIT research, there is a pressing need for an MREIT software package with an efficient user interface. In this paper, we present an example of such a software, called CoReHA which stands for conductivity reconstructor using harmonic algorithms. It offers various computational tools including preprocessing of MREIT data, identification of boundary geometry, electrode modeling, meshing and implementation of the finite element method. Conductivity image reconstruction methods based on the harmonic $B_z$ algorithm are used to produce cross-sectional conductivity images. After summarizing basics of MREIT theory and experimental method, we describe technical details of each data processing task for conductivity image reconstructions. We pay attention to pitfalls and cautions in their numerical implementations. The presented software will be useful to researchers in the field of MREIT for simulation as well as experimental studies.

• Journal of Communications and Networks
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• 제12권2호
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• pp.174-180
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• 2010

Automatic Repeat reQuest (ARQ) is a very effective technique against transmission error at the medium access control (MAC) layer. An erroneous MAC protocol data unit can be typically retransmitted within a given limit. In order to improve the IP-level performance, which directly affects the user-perceived quality-of-service (QoS), we propose a new truncated ARQ strategy, called MAC service data unit-based ARQ (S-ARQ), where the finite number of opportunities for retransmissions are shared by multiple fragments out of an IP datagram. We describe how SARQ can be implemented in a practical system, and then propose another variant of S-ARQ employing a functionality called early detection of failure. Basically, we evaluate the performance of SARQ in two different manners. First, assuming i.i.d. error process, we analyze both the probability of the delivery failure and the average delay of IP datagram. Then, we assess the performance of S-ARQ via simulation over a 2-state Markov channel.

• 한국전산유체공학회지
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• 제17권1호
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• pp.44-53
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• 2012

Immersed boundary method(IBM) is a numerical scheme proposed to simulate flow field around complex objectives using simple Cartesian grid system. In the previous studies, the IBM has mostly been implemented to fractional step method based Navier-Stokes solvers. In this study, we implement the IBM to an incompressible Navier-Stokes solver which uses SIMPLE algorithm. The weight coefficients of the bi-linear and quadratic interpolation equations were formulated by using only geometric information of boundary to reconstruct velocities near IB. Flow around 2D circular cylinder at Re=40 and 100 was solved by using these formulations. It was found that the pressure buildup was not observed even when the bi-linear interpolation was adopted. The use of quadratic interpolation made the predicted aerodynamic forces in good agreement with those of previous studies. For an analysis of moving boundary, we smulated an oscillating circular cylinder with Re=100 and KC(Keulegan-Carpenter) number of 5. The predicted flow fields were compared with experimental data and they also showed good agreements.