• 한국컴퓨터정보학회논문지
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• 제23권1호
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• pp.57-66
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• 2018

It is known that a single-key and a related-key attacks on AES-128 are possible for at most 7 and 8 rounds, respectively. The security of CMAC, a typical block-cipher-based MAC algorithm, has very high possibility of inheriting the security of the underlying block cipher. Since the attacks on the underlying block cipher can be applied directly to the first block of CMAC, the current security margin is not sufficient compared to what the designers of AES claimed. In this paper, we consider HMAC-DM-AES-128 as an alternative to CMAC-AES-128 and analyze its security for reduced rounds of AES-128. For 2-round AES-128, HMAC-DM-AES-128 requires the precomputation phase time complexity of $2^{97}$ AES, the online phase time complexity of $2^{98.68}$ AES and the data complexity of $2^{98}$ blocks. Our work is meaningful in the point that it is the first security analysis of MAC based on hash modes of AES.

• 한국산학기술학회논문지
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• 제13권11호
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• pp.5487-5495
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• 2012

무선 센서 네트워크 환경에서 클러스터키 등의 보안키를 적용하기 위한 중요한 고려 사항은 보안키 갱신이 안전하게 이루어져야 하고, 보안키 갱신 시 요구되는 시간과 비용이 적어야 한다는 점이다. 각 센서 노드는 제한된 에너지를 보유하기 때문에 보안키 갱신에 소모되는 에너지가 클 경우 전체 네트워크 수명에 많은 영향을 준다. 따라서 안전하고 에너지 효율적인 보안키 관리 방법이 요구된다. 본 논문에서는 그룹을 기반으로 한 에너지 효율적인 클러스터키 관리 방안을 제안한다. 제안하는 방법에서 대규모 센서 네트워크에서 안전하고 효율적인 키 관리를 위해 5개의 보안키를 사용하고, 섹터, 클러스터 및 그룹 수준의 보안 적합도를 관리하여 보안키 갱신 주기 및 보안에 사용되는 다항식의 차수를 차별화시킨다. 실험을 통해 이전의 보안키 관리 기법보다 네트워크 에너지 효율성이 향상됨을 입증한다.

• Structural Engineering and Mechanics
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• 제56권4호
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• pp.549-567
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• 2015

A first-order moment method (FORM) reliability analysis is commonly used for structural stability analysis. It requires the values and partial derivatives of the performance to function with respect to the random variables for the design. These calculations can be cumbersome when the performance functions are implicit. A Gaussian process (GP)-based response surface is adopted in this study to approximate the limit state function. By using a trained GP model, a large number of values and partial derivatives of the performance functions can be obtained for conventional reliability analysis with a FORM, thereby reducing the number of stability analysis calculations. This dynamic renewed knowledge source can provide great assistance in improving the predictive capacity of GP during the iterative process, particularly from the view of machine learning. An iterative algorithm is therefore proposed to improve the precision of GP approximation around the design point by constantly adding new design points to the initial training set. Examples are provided to illustrate the GP-based response surface for both structural and non-structural reliability analyses. The results show that the proposed approach is applicable to structural reliability analyses that involve implicit performance functions and structural response evaluations that entail time-consuming finite element analyses.

• Asian Pacific Journal of Cancer Prevention
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• 제15권24호
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• pp.10739-10743
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• 2015

The present study aimed at evaluating and comparing the diagnostic performance of B-mode ultrasound (US), elastography score (ES), and strain ratio (SR) for the differentiation of breast lesions. This retrospective study enrolled 431 lesions from 417 in-hospital patients. All patients were examined with both conventional ultrasound and elastography. Two experienced radiologists reviewed ultrasound and elasticity images. The histopathologic result obtained from ultrasound-guided core biopsy or operation excisions were used as the reference standard. Pathologic examination revealed 276 malignant lesions (64%) and 155 benign lesions (36%). A cut-off point of 4.15 (area under the curve, 0.891) allowed significant differentiation of malignant and benign lesions. ROC (receiver-operating characteristic) curves showed a higher value for combination of B-mode ultrasound and elastography for the diagnosis of breast lesions. Conventional ultrasound combined elastography showed high sensitivity, specificity, and accuracy for group II lesions (10mm${\leq}20mm$). Elastography combined with conventional ultrasound show high specificity and accuracy for differentiation of benign and malignant breast lesions. Elastography is particularly important for the diagnosis of BI-RADS 4 and small breast lesions.

• 호남수학학술지
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• 제39권4호
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• pp.617-635
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• 2017

By applying a classical approach for scalar rational interpolation problem, certain type of minimal interpolation problem for rational matrix functions is solved. It is shown that an appropriately defined matrix plays a key role in solving the minimal problem.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제13권2호
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• pp.103-108
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• 2009

We present the thoughts behind a course combining the subjects of differential equations and infinite series. The key point is how to connect the two topics in a course with a natural flow.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2004년도 춘계공동학술대회 논문집
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• pp.56-59
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• 2004

• Journal of applied mathematics & informatics
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• 제19권1_2호
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• pp.147-149
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• 2005

Recently, there are some empirical Bayes procedures using NA samples. We point out a key equality which may not hold for NA samples. Thus, the results of those empirical Bayes procedures based on NA samples are dubious

• International Journal of Stem Cells
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• 제15권3호
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• pp.247-257
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• 2022

Background and Objectives: Although human-induced pluripotent stem cells (hiPSC) can be efficiently differentiated into cardiomyocytes (CMs), the heterogeneity of the hiPSC-CMs hampers their applications in research and regenerative medicine. Retinoic acid (RA)-mediated signaling pathway has been proved indispensable in cardiac development and differentiation of hiPSC toward atrial CMs. This study was aimed to test whether RA signaling pathway can be manipulated to direct the differentiation into sinoatrial node (SAN) CMs. Methods and Results: Using the well-characterized GiWi protocol that cardiomyocytes are generated from hiPSC via temporal modulation of Wnt signaling pathway by small molecules, RA signaling pathway was manipulated during the differentiation of hiPSC-CMs on day 5 post-differentiation, a crucial time point equivalent to the transition from cardiac mesoderm to cardiac progenitor cells in cardiac development. The resultant CMs were characterized at mRNA, protein and electrophysiology levels by a combination of qPCR, immunofluorescence, flow cytometry, and whole-cell patch clamp. The results showed that activation of the RA signaling pathway biased the differentiation of atrial CMs, whereas inhibition of the signaling pathway biased the differentiation of sinoatrial node-like cells (SANLCs). Conclusions: Our study not only provides a novel and simple strategy to enrich SANLCs but also improves our understanding of the importance of RA signaling in the differentiation of hiPSC-CMs.

• Steel and Composite Structures
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• 제21권5호
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• pp.1145-1156
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• 2016

To study the effects of foam core density and face-sheet thickness on the mechanical properties and failure modes of aluminum foam sandwich (AFS) beam, especially when the aluminum foam core is made in aluminum alloy and the face sheet thickness is less than 1.5 mm, three-point bending tests were investigated experimentally by using WDW-50E electronic universal tensile testing machine. Load-displacement curves were recorded to understand the mechanical response and photographs were taken to capture the deformation process of the composite structures. Results demonstrated that when foam core was combined with face-sheet thickness of 0.8 mm, its carrying capacity improved with the increase of core density. But when the thickness of face-sheet increased from 0.8 mm to 1.2 mm, result was opposite. For AFS with the same core density, their carrying capacity increased with the face-sheet thickness, but failure modes of thin face-sheet AFS were completely different from the thick face-sheet AFS. There were three failure modes in the present research: yield damage of both core and bottom face-sheet (Failure mode I), yield damage of foam core (Failure mode II), debonding between the adhesive interface (Failure mode III).