• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.91-97
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• 2022

The wettability and rheological properties of solder paste with the size of the solder powder were evaluated. To formulate the solder paste, three types of solder powder were used: T4 (20~28 ㎛), T5 (15~25 ㎛), and T6 (5~15 ㎛). The viscosities of the T4, T5, and T6 solder pastes at 10 RPM were 155, 263, and 418 Pa·s, respectively. After 7 days, the viscosity of the T4 solder paste slightly increased by 2.6% and that of T5 was increased by 20.6%. The viscosity of the T6 solder paste after 7 days could not be measured due to high viscosity. The viscosity variation with solder particle size also affected on the printability of the solder. In the case of the T4 solder paste, printability, slump, bridging, and soldering properties were excellent. On the other hand, T5 showed slight dewetting and solder ball defects. Especially, T6, which the smallest powder size, showed poor printability and dewetting at the edge of solder.

• Journal of Adhesion and Interface
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• v.23 no.2
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• pp.44-52
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• 2022

Epoxy resin has the disadvantage of being easily destroyed by instantaneous impact due to its high crosslinking density despite its high glass transition temperature (T_g) and excellent properties. To compensate for this, in this study, polyol was synthesized by ring opening polymerization of propylene glycol (PPG) diamine, Jeffamine D 2000 and propylene carbonate, and urethane modified epoxy was synthesized using this. The properties of the synthesized urethane modified epoxy were confirmed by FT-IR, H-NMR. To confirm the degree of improvement in impact resistance as an adhesive, a urethane modified epoxy adhesive was prepared by mixing a digylcidyl ether bisphenol A (DGEBA) with curing agent and curing accelerator. Properties test of urethane modified epoxy were shear strength, tensile strength and impact strength. As a result, excellent results were obtained in all test when the ratio of DGEBA : urethane modified epoxy was 8:2.

• Journal of Korea Water Resources Association
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• v.51 no.12
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• pp.1217-1227
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• 2018

This paper aims to evaluate the applicability of dam inflow prediction model using recurrent neural network theory. To achieve this goal, the Artificial Neural Network (ANN) model and the Elman Recurrent Neural Network(RNN) model were applied to hydro-meteorological data sets for the Soyanggang dam and the Chungju dam basin during dam operation period. For the model training, inflow, rainfall, temperature, sunshine duration, wind speed were used as input data and daily inflow of dam for 10 days were used for output data. The verification was carried out through dam inflow prediction between July, 2016 and June, 2018. The results showed that there was no significant difference in prediction performance between ANN model and the Elman RNN model in the Soyanggang dam basin but the prediction results of the Elman RNN model are comparatively superior to those of the ANN model in the Chungju dam basin. Consequently, the Elman RNN prediction performance is expected to be similar to or better than the ANN model. The prediction performance of Elman RNN was notable during the low dam inflow period. The performance of the multiple hidden layer structure of Elman RNN looks more effective in prediction than that of a single hidden layer structure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.71-80
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• 2007

Because of the characteristics relating to high tensile ductility, High Performance Fiber Reinforced Cementitious Composites (HPFRCC) are studied to be adopted in repair and retrofit of buildings. A series of three shear wall specimens was tested under constant axial stress and reversed cyclic lateral loading in order to evaluate the seismic retrofit that had been proposed for the shear wall with the opening. The retrofit involved the use of newly developed ECC and MDF(Macro Defect Free), both of which are sprayed through the high pressure pump, over the entire face of the wall. The results indicate that two difference types of retrofitting strategy make the different effects of a rise in the strength and ductility of each specimen.

• Korean Journal of Remote Sensing
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• v.18 no.2
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• pp.81-90
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• 2002

We carried out accuracy assessment for DEM extraction from the KOMPSAT-1 EOC stereo images over Daejeon and Nonsan in Korea. DEM generation divided into two parts. One is camera modeling and the other stereo matching. We used Orun & Natarajan's(1994) model and Gupta & Hartley's(1997) model in the camera modeling step and checked the possibility using Orun & Natarajan and Gupta & Hartley's models in EOC stereo pairs. For stereo matching, we used an algorithms developed in-house for SPOT images and showed that this algorithm could work with EOC images. Using these algorithms, DEMs were successfully generated from EOC images. The comparison of DEM from EOC Images with a DEM from SPOT Images showed that EOC could be used for high-accuracy DEM generation.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2022.06a
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• pp.246-249
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• 2022

최근 들어 세계적으로 크게 관심을 받는 메타버스 및 몰입형(가상현실, 확장현실, 및 라이트필드) 콘텐츠 서비스의 응용 범위를 확대하기 위해서는 3D 객체의 실시간 전송을 위한 압축 기술이 필요하다. ISO/IEC 23090 MPEG-I Part 5 로 2021 년 표준화 완료된 V-PCC (Video-based Point Cloud Compression)는 이러한 산업계의 관심 및 필요에 의해서 국제 표준화된 동적 3D 포인트 클라우드 객체 부호화 기술이다. V-PCC 기술의 압축 성능은 기존 산업계 기술에 비해 매우 우수하나, 부호화기의 연산 복잡도가 매우 높다는 단점을 가지고 있다. 본 논문에서는 V-PCC 부호화기에서 가장 높은 연산 복잡도를 갖는 법선 추정 알고리즘의 결합 고속화 기법을 제안한다. 법선 추정은 2 개의 알고리즘으로 구성되어 있다. 첫번째는 "방향을 무시하는 법선 추정 알고리즘(normal estimation)"이고, 두번째는 첫번째 알고리즘에서 추정된 법선들을 대상으로 하는 "법선 방향 추정 알고리즘(normal orientation)"이다. 본 논문에서 제안하는 고속화 기법은 2 개 알고리즘을 결합하여 첫번째 법선 추정 알고리즘에서 획득한 부가 정보를 두번째 법선 방향 추정 알고리즘에서 활용함으로써 연산량을 대폭 줄이고, 또한 법선 방향 추정 알고리즘 내의 우선순위 큐 자료구조를 변경하여 추가적인 고속화를 달성한다. 7 개 테스트 영상에 대한 실험 결과, 압축 효율 저하 없이 법선 방향 추정 알고리즘의 속도를 평균 89.2% 향상시킬 수 있다.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.71-71
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• 2022

들깨는 잎은 채소, 종자는 기름과 향신료로 이용하는 특용작물로 국립농업과학원 농업유전자원센터에는 국가등록 3,066자원을 보유하고 있다. 들깨 유전자원의 보존기간과 방법에 따라 종자 활력의 차이가 어떻게 변화했는지 알아보기 위해 농업유전자원센터 보존 중인 들깨 유전자원의 발아율을 조사하였다. 온도는 4도, -18도, 밀폐용기 보관하여 보존한 들깨 종자를 10년 보존 후 발아조사를 수행하였다. 발아환경은 페트리디쉬에 거름종이를 깔아 멸균수로 수분을 공급하고, 종자를 50립씩 2반복 치상 후 20도에서 7일, 14일에 조사하였다. 4도에서 보존한 들깨 577자원은 발아율이 85%이상인 자원이 184자원으로 나타났다. -18도에서 보존한 들깨 725자원은 발아율이 85%이상이 자원이 329자원으로 나타났다. 세계적으로 식물유전자원은행에서 양호한 발아율의 기준으로 85%를 사용하는데, 4도 보존 들깨 유전자원들은 조사한 자원의 32%가 양호하였고, -18도 보존 자원들은 45%가 발아 기준을 만족하였다. 들깨유전자원을 10년 주기로 발아율을 조사한 결과 -18도 보존 종자의 발아율이 4도 보존 종자보다 기준발아율이 13% 우수하였으나 두 처리 모두 85% 기준발아율을 만족하는 자원이 50%이하로 나타났다. 본 연구결과는 들깨유전자원을 4도, -18도에서 장기 보존할 때에 종자 활력 예측 및 활력 모니터링 연구에 도움이 될 것이다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.164-171
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• 2008

Adaptive equalizers are inevitable schemes in digital communication systems for compensating the transmission channel distortion. Additionally, to obtain the required BER(Bit Error Rate), the adaptive algorithms appropriate to the mobile communication channels are required. In this paper, we propose the NPDFE (Noise-Predictive Decision Feedback Equalizer) for communication systems performance improvement in mobile communication channels. The performance of the proposed NPDFE with QPSK (Quadrature Phase Shift Keying) is simulated under AWGN (Additive White Gaussian Noise), Ricean fading, ETSI (European Telecommunications Standards Institute) fading, and Rayleigh fading channels. The equalizers used in simulations are a LE (Linear Equalizer), a DFE (Decision Feedback Equalizer), and a NPDFE. Moreover, the equalizer performance criterion of the QPSK is the BER.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.6
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• pp.59-69
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• 2002

Many Linear attacks have introduced after M. Matsui suggested Linear Cryptanalysis in 1993. The one of them is the method suggested by B. Kaliski and M. Robshaw. It was a new method using multiple linear approximations to attack for block ciphers. It requires less known plaintexts than that of Linear Cryptanalysis(LC) by Matsui, but it has a problem. In this paper, we will introduce the new method using multiple linear approximation that can solve the problem. Using the new method, the requirements of the known plaintexts is 5(1.25) times as small as the requirements in LC on 8(16) round DES with a success rate of 95%(86%) respectively. We can also adopt A Chosen Plaintext Linear Attack suggested by L. R. Knudsen and J. E. Mathiassen and then our attack requires about $2^{40.6}$ chosen plaintexts to recover 15 key bits with 86% success rate. We believe that the results in this paper contain the fastest attack on the DES full round reported so far in the open literature.

• Analytical Science and Technology
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• v.19 no.3
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• pp.194-202
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• 2006

In this work, extraction and purification of the possible whitening agents from the Chinese plants; Chrysanthemum morifolium Ramat (xizang cai ju hua), Rhodiola sachalinensis, and Terminalia chebula Retzius have been described. The chopped leaves of Chrysanthemum morifolium Ramat and Terminalia chebula Retzius were added to water and ethyl ether, respectively. Components were separated on a GS310 column ($21.5{\times}500mm$ i.d., $10-15{\mu}m$) and concentrated into four or three portions. The chopped leaves of Rhodiola salientness were added to methanol and separated and concentrated on a column ($C_{18}$ column, $3.9^{\circ}$�F8;300 mm i.d., $15{\mu}m$) into two parts. The whitening effects of extracts were examined by in-vitro melanin production assay, in melana and B16 cells at a concentration of $10{\mu}g/ml$. The ethyl acetate layer of Chrysanthemum morifolium Ramat showed 92% melanin inhibitory at $200{\mu}g/ml$, the extract of Rhodiola sachalinensis showed a whitening effect of about 60% melanin inhibitory, which was more efficient than the whitening effect of arbutin (45.6%). The methanol extract of Terminalia chebula Retzius inhibited melanin expression by 90% at $100{\mu}g/ml$; however, it was toxic to B16 melanoma cells.